1 . /////////////////////////////////////////////////////////////////////////////
2 . This is the primary source of the Exim Manual. It is an xfpt document that is
3 . converted into DocBook XML for subsequent conversion into printable and online
4 . formats. The markup used herein is "standard" xfpt markup, with some extras.
5 . The markup is summarized in a file called Markup.txt.
7 . WARNING: When you use the .new macro, make sure it appears *before* any
8 . adjacent index items; otherwise you get an empty "paragraph" which causes
9 . unwanted vertical space.
10 . /////////////////////////////////////////////////////////////////////////////
15 . /////////////////////////////////////////////////////////////////////////////
16 . This outputs the standard DocBook boilerplate.
17 . /////////////////////////////////////////////////////////////////////////////
21 . /////////////////////////////////////////////////////////////////////////////
22 . These lines are processing instructions for the Simple DocBook Processor that
23 . Philip Hazel has developed as a less cumbersome way of making PostScript and
24 . PDFs than using xmlto and fop. They will be ignored by all other XML
26 . /////////////////////////////////////////////////////////////////////////////
30 foot_right_recto="&chaptertitle; (&chapternumber;)"
31 foot_right_verso="&chaptertitle; (&chapternumber;)"
32 toc_chapter_blanks="yes,yes"
33 table_warn_overflow="overprint"
37 . /////////////////////////////////////////////////////////////////////////////
38 . This generates the outermost <book> element that wraps the entire document.
39 . /////////////////////////////////////////////////////////////////////////////
43 . /////////////////////////////////////////////////////////////////////////////
44 . These definitions set some parameters and save some typing.
45 . Update the Copyright year (only) when changing content.
46 . /////////////////////////////////////////////////////////////////////////////
48 .set previousversion "4.96"
49 .include ./local_params
51 .set ACL "access control lists (ACLs)"
52 .set I " "
54 .set drivernamemax "64"
60 . /////////////////////////////////////////////////////////////////////////////
61 . Additional xfpt markup used by this document, over and above the default
62 . provided in the xfpt library.
63 . /////////////////////////////////////////////////////////////////////////////
65 . --- Override the &$ flag to automatically insert a $ with the variable name.
67 .flag &$ $& "<varname>$" "</varname>"
69 . --- Short flags for daggers in option headings. They will always be inside
70 . --- an italic string, but we want the daggers to be in Roman.
72 .flag &!! "</emphasis>†<emphasis>"
73 .flag &!? "</emphasis>‡<emphasis>"
75 . --- A macro for an Exim option definition heading, generating a one-line
76 . --- table with four columns. For cases when the option name is given with
77 . --- a space, so that it can be split, a fifth argument is used for the
87 .itable all 0 0 4 8* left 6* center 6* center 6* right
88 .row "&%$1%&" "Use: &'$2'&" "Type: &'$3'&" "Default: &'$4'&"
92 . --- A macro for the common 2-column tables. The width of the first column
93 . --- is suitable for the many tables at the start of the main options chapter;
94 . --- a small number of other 2-column tables override it.
96 .macro table2 196pt 254pt
97 .itable none 0 0 2 $1 left $2 left
101 . --- A macro for a plain variable, including the .vitem and .vindex
107 . --- A macro for a "tainted" marker, done as a one-element table
109 .itable none 0 0 1 10pt left
114 . --- A macro for a tainted variable, adding a taint-marker
120 . --- A macro for a cmdline option, including a .oindex
121 . --- 1st arg is the option name, undecorated (we do that here).
122 . --- 2nd arg, optional, text (decorated as needed) to be appended to the name
124 .vitem &%$1%&$=2+&~$2+
128 . --- A macro that generates .row, but puts &I; at the start of the first
129 . --- argument, thus indenting it. Assume a minimum of two arguments, and
130 . --- allow up to four arguments, which is as many as we'll ever need.
134 .row "&I;$1" "$2" "$3" "$4"
138 .row "&I;$1" "$2" "$3"
146 . --- Macros for option, variable, and concept index entries. For a "range"
147 . --- style of entry, use .scindex for the start and .ecindex for the end. The
148 . --- first argument of .scindex and the only argument of .ecindex must be the
149 . --- ID that ties them together.
150 . --- The index entry points to the most-recent chapter head, section or subsection
151 . --- head, or list-item.
154 &<indexterm role="concept">&
155 &<primary>&$1&</primary>&
157 &<secondary>&$2&</secondary>&
163 &<indexterm role="concept" id="$1" class="startofrange">&
164 &<primary>&$2&</primary>&
166 &<secondary>&$3&</secondary>&
172 &<indexterm role="concept" startref="$1" class="endofrange"/>&
176 &<indexterm role="option">&
177 &<primary>&$1&</primary>&
179 &<secondary>&$2&</secondary>&
184 . --- The index entry points to the most-recent chapter head, section or subsection
185 . --- head, or varlist item.
188 &<indexterm role="variable">&
189 &<primary>&$1&</primary>&
191 &<secondary>&$2&</secondary>&
197 .echo "** Don't use .index; use .cindex or .oindex or .vindex"
201 . use this for a concept-index entry for a header line
203 .cindex "&'$1'& header line"
204 .cindex "header lines" $1
206 . ////////////////////////////////////////////////////////////////////////////
209 . ////////////////////////////////////////////////////////////////////////////
210 . The <bookinfo> element is removed from the XML before processing for ASCII
212 . ////////////////////////////////////////////////////////////////////////////
216 <title>Specification of the Exim Mail Transfer Agent</title>
217 <titleabbrev>The Exim MTA</titleabbrev>
221 <author><firstname>Exim</firstname><surname>Maintainers</surname></author>
222 <authorinitials>EM</authorinitials>
223 <revhistory><revision>
225 <authorinitials>EM</authorinitials>
226 </revision></revhistory>
229 </year><holder>The Exim Maintainers</holder></copyright>
234 . /////////////////////////////////////////////////////////////////////////////
235 . These implement index entries of the form "x, see y" and "x, see also y".
236 . However, the DocBook DTD doesn't allow <indexterm> entries
237 . at the top level, so we have to put the .chapter directive first.
238 . /////////////////////////////////////////////////////////////////////////////
240 .chapter "Introduction" "CHID1"
244 <indexterm role="$2">
245 <primary>$3</primary>
247 <secondary>$5</secondary>
249 <$1><emphasis>$4</emphasis></$1>
254 . NB: for the 4-arg variant the ordering is awkward
256 .seeother see "$1" "$2" "$3" "$4"
259 .seeother seealso "$1" "$2" "$3" "$4"
262 .see variable "<emphasis>$1</emphasis>, <emphasis>$2</emphasis>, etc." "numerical variables"
263 .see concept address rewriting rewriting
264 .see concept "Bounce Address Tag Validation" BATV
265 .see concept "Client SMTP Authorization" CSA
266 .see concept "CR character" "carriage return"
267 .see concept CRL "certificate revocation list"
268 .seealso concept de-tainting "tainted data"
269 .see concept delivery "bounce message" "failure report"
270 .see concept dialup "intermittently connected hosts"
271 .see concept exiscan "content scanning"
272 .see concept fallover fallback
273 .see concept filter "Sieve filter" Sieve
274 .see concept headers "header lines"
275 .see concept ident "RFC 1413"
276 .see concept "LF character" "linefeed"
277 .seealso concept maximum limit
278 .see concept monitor "Exim monitor"
279 .see concept "no_<emphasis>xxx</emphasis>" "entry for xxx"
280 .see concept NUL "binary zero"
281 .see concept "passwd file" "/etc/passwd"
282 .see concept "process id" pid
283 .see concept RBL "DNS list"
284 .see concept redirection "address redirection"
285 .see concept "return path" "envelope sender"
286 .see concept scanning "content scanning"
288 .see concept string expansion expansion
289 .see concept "top bit" "8-bit characters"
290 .see concept variables "expansion, variables"
291 .see concept "zero, binary" "binary zero"
294 . /////////////////////////////////////////////////////////////////////////////
295 . This is the real start of the first chapter. See the comment above as to why
296 . we can't have the .chapter line here.
297 . chapter "Introduction"
298 . /////////////////////////////////////////////////////////////////////////////
300 Exim is a mail transfer agent (MTA) for hosts that are running Unix or
301 Unix-like operating systems. It was designed on the assumption that it would be
302 run on hosts that are permanently connected to the Internet. However, it can be
303 used on intermittently connected hosts with suitable configuration adjustments.
305 Configuration files currently exist for the following operating systems: AIX,
306 BSD/OS (aka BSDI), Darwin (Mac OS X), DGUX, Dragonfly, FreeBSD, GNU/Hurd,
307 GNU/Linux, HI-OSF (Hitachi), HI-UX, HP-UX, IRIX, MIPS RISCOS, NetBSD, OpenBSD,
308 OpenUNIX, QNX, SCO, SCO SVR4.2 (aka UNIX-SV), Solaris (aka SunOS5), SunOS4,
309 Tru64-Unix (formerly Digital UNIX, formerly DEC-OSF1), Ultrix, and UnixWare.
310 Some of these operating systems are no longer current and cannot easily be
311 tested, so the configuration files may no longer work in practice.
313 There are also configuration files for compiling Exim in the Cygwin environment
314 that can be installed on systems running Windows. However, this document does
315 not contain any information about running Exim in the Cygwin environment.
317 The terms and conditions for the use and distribution of Exim are contained in
318 the file &_NOTICE_&. Exim is distributed under the terms of the GNU General
319 Public Licence, a copy of which may be found in the file &_LICENCE_&.
321 The use, supply, or promotion of Exim for the purpose of sending bulk,
322 unsolicited electronic mail is incompatible with the basic aims of Exim,
323 which revolve around the free provision of a service that enhances the quality
324 of personal communications. The author of Exim regards indiscriminate
325 mass-mailing as an antisocial, irresponsible abuse of the Internet.
327 Exim owes a great deal to Smail 3 and its author, Ron Karr. Without the
328 experience of running and working on the Smail 3 code, I could never have
329 contemplated starting to write a new MTA. Many of the ideas and user interfaces
330 were originally taken from Smail 3, though the actual code of Exim is entirely
331 new, and has developed far beyond the initial concept.
333 Many people, both in Cambridge and around the world, have contributed to the
334 development and the testing of Exim, and to porting it to various operating
335 systems. I am grateful to them all. The distribution now contains a file called
336 &_ACKNOWLEDGMENTS_&, in which I have started recording the names of
340 .section "Exim documentation" "SECID1"
341 . Keep this example change bar when updating the documentation!
344 .cindex "documentation"
345 This edition of the Exim specification applies to version &version() of Exim.
346 Substantive changes from the &previousversion; edition are marked in some
347 renditions of this document; this paragraph is so marked if the rendition is
348 capable of showing a change indicator.
351 This document is very much a reference manual; it is not a tutorial. The reader
352 is expected to have some familiarity with the SMTP mail transfer protocol and
353 with general Unix system administration. Although there are some discussions
354 and examples in places, the information is mostly organized in a way that makes
355 it easy to look up, rather than in a natural order for sequential reading.
356 Furthermore, this manual aims to cover every aspect of Exim in detail, including
357 a number of rarely-used, special-purpose features that are unlikely to be of
360 .cindex "books about Exim"
361 An &"easier"& discussion of Exim which provides more in-depth explanatory,
362 introductory, and tutorial material can be found in a book entitled &'The Exim
363 SMTP Mail Server'& (second edition, 2007), published by UIT Cambridge
364 (&url(https://www.uit.co.uk/exim-book/)).
366 The book also contains a chapter that gives a general introduction to SMTP and
367 Internet mail. Inevitably, however, the book is unlikely to be fully up-to-date
368 with the latest release of Exim. (Note that the earlier book about Exim,
369 published by O'Reilly, covers Exim 3, and many things have changed in Exim 4.)
371 .cindex "Debian" "information sources"
372 If you are using a Debian distribution of Exim, you will find information about
373 Debian-specific features in the file
374 &_/usr/share/doc/exim4-base/README.Debian_&.
375 The command &(man update-exim.conf)& is another source of Debian-specific
378 .cindex "&_doc/NewStuff_&"
379 .cindex "&_doc/ChangeLog_&"
381 As Exim develops, there may be features in newer versions that have not
382 yet made it into this document, which is updated only when the most significant
383 digit of the fractional part of the version number changes. Specifications of
384 new features that are not yet in this manual are placed in the file
385 &_doc/NewStuff_& in the Exim distribution.
387 Some features may be classified as &"experimental"&. These may change
388 incompatibly while they are developing, or even be withdrawn. For this reason,
389 they are not documented in this manual. Information about experimental features
390 can be found in the file &_doc/experimental.txt_&.
392 All changes to Exim (whether new features, bug fixes, or other kinds of
393 change) are noted briefly in the file called &_doc/ChangeLog_&.
395 .cindex "&_doc/spec.txt_&"
396 This specification itself is available as an ASCII file in &_doc/spec.txt_& so
397 that it can easily be searched with a text editor. Other files in the &_doc_&
401 .row &_OptionLists.txt_& "list of all options in alphabetical order"
402 .row &_dbm.discuss.txt_& "discussion about DBM libraries"
403 .row &_exim.8_& "a man page of Exim's command line options"
404 .row &_experimental.txt_& "documentation of experimental features"
405 .row &_filter.txt_& "specification of the filter language"
406 .row &_Exim3.upgrade_& "upgrade notes from release 2 to release 3"
407 .row &_Exim4.upgrade_& "upgrade notes from release 3 to release 4"
408 .row &_openssl.txt_& "installing a current OpenSSL release"
411 The main specification and the specification of the filtering language are also
412 available in other formats (HTML, PostScript, PDF, and Texinfo). Section
413 &<<SECTavail>>& below tells you how to get hold of these.
417 .section "FTP site and websites" "SECID2"
420 The primary site for Exim source distributions is the &%exim.org%& FTP site,
421 available over HTTPS, HTTP and FTP. These services, and the &%exim.org%&
422 website, are hosted at the University of Cambridge.
426 As well as Exim distribution tar files, the Exim website contains a number of
427 differently formatted versions of the documentation. A recent addition to the
428 online information is the Exim wiki (&url(https://wiki.exim.org)),
429 which contains what used to be a separate FAQ, as well as various other
430 examples, tips, and know-how that have been contributed by Exim users.
431 The wiki site should always redirect to the correct place, which is currently
432 provided by GitHub, and is open to editing by anyone with a GitHub account.
435 An Exim Bugzilla exists at &url(https://bugs.exim.org). You can use
436 this to report bugs, and also to add items to the wish list. Please search
437 first to check that you are not duplicating a previous entry.
438 Please do not ask for configuration help in the bug-tracker.
441 .section "Mailing lists" "SECID3"
442 .cindex "mailing lists" "for Exim users"
443 The following Exim mailing lists exist:
446 .row &'exim-announce@exim.org'& "Moderated, low volume announcements list"
447 .row &'exim-users@exim.org'& "General discussion list"
448 .row &'exim-dev@exim.org'& "Discussion of bugs, enhancements, etc."
449 .row &'exim-cvs@exim.org'& "Automated commit messages from the VCS"
452 You can subscribe to these lists, change your existing subscriptions, and view
453 or search the archives via the mailing lists link on the Exim home page.
454 .cindex "Debian" "mailing list for"
455 If you are using a Debian distribution of Exim, you may wish to subscribe to
456 the Debian-specific mailing list &'pkg-exim4-users@lists.alioth.debian.org'&
459 &url(https://alioth-lists.debian.net/cgi-bin/mailman/listinfo/pkg-exim4-users)
461 Please ask Debian-specific questions on that list and not on the general Exim
464 .section "Bug reports" "SECID5"
465 .cindex "bug reports"
466 .cindex "reporting bugs"
467 Reports of obvious bugs can be emailed to &'bugs@exim.org'& or reported
468 via the Bugzilla (&url(https://bugs.exim.org)). However, if you are unsure
469 whether some behaviour is a bug or not, the best thing to do is to post a
470 message to the &'exim-dev'& mailing list and have it discussed.
474 .section "Where to find the Exim distribution" "SECTavail"
476 .cindex "HTTPS download site"
477 .cindex "distribution" "FTP site"
478 .cindex "distribution" "https site"
479 The master distribution site for the Exim distribution is
481 &url(https://downloads.exim.org/)
483 The service is available over HTTPS, HTTP and FTP.
484 We encourage people to migrate to HTTPS.
486 The content served at &url(https://downloads.exim.org/) is identical to the
487 content served at &url(https://ftp.exim.org/pub/exim) and
488 &url(ftp://ftp.exim.org/pub/exim).
490 If accessing via a hostname containing &'ftp'&, then the file references that
491 follow are relative to the &_exim_& directories at these sites.
492 If accessing via the hostname &'downloads'& then the subdirectories described
493 here are top-level directories.
495 There are now quite a number of independent mirror sites around
496 the world. Those that I know about are listed in the file called &_Mirrors_&.
498 Within the top exim directory there are subdirectories called &_exim3_& (for
499 previous Exim 3 distributions), &_exim4_& (for the latest Exim 4
500 distributions), and &_Testing_& for testing versions. In the &_exim4_&
501 subdirectory, the current release can always be found in files called
505 &_exim-n.nn.tar.bz2_&
507 where &'n.nn'& is the highest such version number in the directory. The three
508 files contain identical data; the only difference is the type of compression.
509 The &_.xz_& file is usually the smallest, while the &_.gz_& file is the
510 most portable to old systems.
512 .cindex "distribution" "signing details"
513 .cindex "distribution" "public key"
514 .cindex "public key for signed distribution"
515 The distributions will be PGP signed by an individual key of the Release
516 Coordinator. This key will have a uid containing an email address in the
517 &'exim.org'& domain and will have signatures from other people, including
518 other Exim maintainers. We expect that the key will be in the "strong set" of
519 PGP keys. There should be a trust path to that key from the Exim Maintainer's
520 PGP keys, a version of which can be found in the release directory in the file
521 &_Exim-Maintainers-Keyring.asc_&. All keys used will be available in public keyserver pools,
522 such as &'pool.sks-keyservers.net'&.
524 At the time of the last update, releases were being made by Jeremy Harris and signed
525 with key &'0xBCE58C8CE41F32DF'&. Other recent keys used for signing are those
526 of Heiko Schlittermann, &'0x26101B62F69376CE'&,
527 and of Phil Pennock, &'0x4D1E900E14C1CC04'&.
529 The signatures for the tar bundles are in:
531 &_exim-n.nn.tar.xz.asc_&
532 &_exim-n.nn.tar.gz.asc_&
533 &_exim-n.nn.tar.bz2.asc_&
535 For each released version, the log of changes is made available in a
536 separate file in the directory &_ChangeLogs_& so that it is possible to
537 find out what has changed without having to download the entire distribution.
539 .cindex "documentation" "available formats"
540 The main distribution contains ASCII versions of this specification and other
541 documentation; other formats of the documents are available in separate files
542 inside the &_exim4_& directory of the FTP site:
544 &_exim-html-n.nn.tar.gz_&
545 &_exim-pdf-n.nn.tar.gz_&
546 &_exim-postscript-n.nn.tar.gz_&
547 &_exim-texinfo-n.nn.tar.gz_&
549 These tar files contain only the &_doc_& directory, not the complete
550 distribution, and are also available in &_.bz2_& and &_.xz_& forms.
553 .section "Limitations" "SECID6"
555 .cindex "limitations of Exim"
556 .cindex "bang paths" "not handled by Exim"
557 Exim is designed for use as an Internet MTA, and therefore handles addresses in
558 RFC 2822 domain format only. It cannot handle UUCP &"bang paths"&, though
559 simple two-component bang paths can be converted by a straightforward rewriting
560 configuration. This restriction does not prevent Exim from being interfaced to
561 UUCP as a transport mechanism, provided that domain addresses are used.
563 .cindex "domainless addresses"
564 .cindex "address" "without domain"
565 Exim insists that every address it handles has a domain attached. For incoming
566 local messages, domainless addresses are automatically qualified with a
567 configured domain value. Configuration options specify from which remote
568 systems unqualified addresses are acceptable. These are then qualified on
571 .cindex "transport" "external"
572 .cindex "external transports"
573 The only external transport mechanisms that are currently implemented are SMTP
574 and LMTP over a TCP/IP network (including support for IPv6). However, a pipe
575 transport is available, and there are facilities for writing messages to files
576 and pipes, optionally in &'batched SMTP'& format; these facilities can be used
577 to send messages to other transport mechanisms such as UUCP, provided they can
578 handle domain-style addresses. Batched SMTP input is also catered for.
580 Exim is not designed for storing mail for dial-in hosts. When the volumes of
581 such mail are large, it is better to get the messages &"delivered"& into files
582 (that is, off Exim's queue) and subsequently passed on to the dial-in hosts by
585 Although Exim does have basic facilities for scanning incoming messages, these
586 are not comprehensive enough to do full virus or spam scanning. Such operations
587 are best carried out using additional specialized software packages. If you
588 compile Exim with the content-scanning extension, straightforward interfaces to
589 a number of common scanners are provided.
593 .section "Runtime configuration" "SECID7"
594 Exim's runtime configuration is held in a single text file that is divided
595 into a number of sections. The entries in this file consist of keywords and
596 values, in the style of Smail 3 configuration files. A default configuration
597 file which is suitable for simple online installations is provided in the
598 distribution, and is described in chapter &<<CHAPdefconfil>>& below.
601 .section "Calling interface" "SECID8"
602 .cindex "Sendmail compatibility" "command line interface"
603 Like many MTAs, Exim has adopted the Sendmail command line interface so that it
604 can be a straight replacement for &_/usr/lib/sendmail_& or
605 &_/usr/sbin/sendmail_& when sending mail, but you do not need to know anything
606 about Sendmail in order to run Exim. For actions other than sending messages,
607 Sendmail-compatible options also exist, but those that produce output (for
608 example, &%-bp%&, which lists the messages in the queue) do so in Exim's own
609 format. There are also some additional options that are compatible with Smail
610 3, and some further options that are new to Exim. Chapter &<<CHAPcommandline>>&
611 documents all Exim's command line options. This information is automatically
612 made into the man page that forms part of the Exim distribution.
614 Control of messages in the queue can be done via certain privileged command
615 line options. There is also an optional monitor program called &'eximon'&,
616 which displays current information in an X window, and which contains a menu
617 interface to Exim's command line administration options.
621 .section "Terminology" "SECID9"
622 .cindex "terminology definitions"
623 .cindex "body of message" "definition of"
624 The &'body'& of a message is the actual data that the sender wants to transmit.
625 It is the last part of a message and is separated from the &'header'& (see
626 below) by a blank line.
628 .cindex "bounce message" "definition of"
629 When a message cannot be delivered, it is normally returned to the sender in a
630 delivery failure message or a &"non-delivery report"& (NDR). The term
631 &'bounce'& is commonly used for this action, and the error reports are often
632 called &'bounce messages'&. This is a convenient shorthand for &"delivery
633 failure error report"&. Such messages have an empty sender address in the
634 message's &'envelope'& (see below) to ensure that they cannot themselves give
635 rise to further bounce messages.
637 The term &'default'& appears frequently in this manual. It is used to qualify a
638 value which is used in the absence of any setting in the configuration. It may
639 also qualify an action which is taken unless a configuration setting specifies
642 The term &'defer'& is used when the delivery of a message to a specific
643 destination cannot immediately take place for some reason (a remote host may be
644 down, or a user's local mailbox may be full). Such deliveries are &'deferred'&
647 The word &'domain'& is sometimes used to mean all but the first component of a
648 host's name. It is &'not'& used in that sense here, where it normally refers to
649 the part of an email address following the @ sign.
651 .cindex "envelope, definition of"
652 .cindex "sender" "definition of"
653 A message in transit has an associated &'envelope'&, as well as a header and a
654 body. The envelope contains a sender address (to which bounce messages should
655 be delivered), and any number of recipient addresses. References to the
656 sender or the recipients of a message usually mean the addresses in the
657 envelope. An MTA uses these addresses for delivery, and for returning bounce
658 messages, not the addresses that appear in the header lines.
660 .cindex "message" "header, definition of"
661 .cindex "header section" "definition of"
662 The &'header'& of a message is the first part of a message's text, consisting
663 of a number of lines, each of which has a name such as &'From:'&, &'To:'&,
664 &'Subject:'&, etc. Long header lines can be split over several text lines by
665 indenting the continuations. The header is separated from the body by a blank
668 .cindex "local part" "definition of"
669 .cindex "domain" "definition of"
670 The term &'local part'&, which is taken from RFC 2822, is used to refer to the
671 part of an email address that precedes the @ sign. The part that follows the
672 @ sign is called the &'domain'& or &'mail domain'&.
674 .cindex "local delivery" "definition of"
675 .cindex "remote delivery, definition of"
676 The terms &'local delivery'& and &'remote delivery'& are used to distinguish
677 delivery to a file or a pipe on the local host from delivery by SMTP over
678 TCP/IP to another host. As far as Exim is concerned, all hosts other than the
679 host it is running on are &'remote'&.
681 .cindex "return path" "definition of"
682 &'Return path'& is another name that is used for the sender address in a
685 .cindex "queue" "definition of"
686 The term &'queue'& is used to refer to the set of messages awaiting delivery
687 because this term is in widespread use in the context of MTAs. However, in
688 Exim's case, the reality is more like a pool than a queue, because there is
689 normally no ordering of waiting messages.
691 .cindex "queue runner" "definition of"
692 The term &'queue runner'& is used to describe a process that scans the queue
693 and attempts to deliver those messages whose retry times have come. This term
694 is used by other MTAs and also relates to the command &%runq%&, but in Exim
695 the waiting messages are normally processed in an unpredictable order.
697 .cindex "spool directory" "definition of"
698 The term &'spool directory'& is used for a directory in which Exim keeps the
699 messages in its queue &-- that is, those that it is in the process of
700 delivering. This should not be confused with the directory in which local
701 mailboxes are stored, which is called a &"spool directory"& by some people. In
702 the Exim documentation, &"spool"& is always used in the first sense.
709 . ////////////////////////////////////////////////////////////////////////////
710 . ////////////////////////////////////////////////////////////////////////////
712 .chapter "Incorporated code" "CHID2"
713 .cindex "incorporated code"
714 .cindex "regular expressions" "library"
717 A number of pieces of external code are included in the Exim distribution.
720 Regular expressions are supported in the main Exim program and in the
721 Exim monitor using the freely-distributable PCRE2 library, copyright
722 © University of Cambridge. The source to PCRE2 is not longer shipped with
723 Exim, so you will need to use the version of PCRE2 shipped with your system,
724 or obtain and install the full version of the library from
725 &url(https://github.com/PhilipHazel/pcre2/releases).
727 .cindex "cdb" "acknowledgment"
728 Support for the cdb (Constant DataBase) lookup method is provided by code
729 contributed by Nigel Metheringham of (at the time he contributed it) Planet
730 Online Ltd. The implementation is completely contained within the code of Exim.
731 It does not link against an external cdb library. The code contains the
732 following statements:
735 Copyright © 1998 Nigel Metheringham, Planet Online Ltd
737 This program is free software; you can redistribute it and/or modify it under
738 the terms of the GNU General Public License as published by the Free Software
739 Foundation; either version 2 of the License, or (at your option) any later
741 This code implements Dan Bernstein's Constant DataBase (cdb) spec. Information,
742 the spec and sample code for cdb can be obtained from
743 &url(https://cr.yp.to/cdb.html). This implementation borrows
744 some code from Dan Bernstein's implementation (which has no license
745 restrictions applied to it).
748 .cindex "SPA authentication"
749 .cindex "Samba project"
750 .cindex "Microsoft Secure Password Authentication"
751 Client support for Microsoft's &'Secure Password Authentication'& is provided
752 by code contributed by Marc Prud'hommeaux. Server support was contributed by
753 Tom Kistner. This includes code taken from the Samba project, which is released
757 .cindex "&'pwcheck'& daemon"
758 .cindex "&'pwauthd'& daemon"
759 Support for calling the Cyrus &'pwcheck'& and &'saslauthd'& daemons is provided
760 by code taken from the Cyrus-SASL library and adapted by Alexander S.
761 Sabourenkov. The permission notice appears below, in accordance with the
762 conditions expressed therein.
765 Copyright © 2001 Carnegie Mellon University. All rights reserved.
767 Redistribution and use in source and binary forms, with or without
768 modification, are permitted provided that the following conditions
772 Redistributions of source code must retain the above copyright
773 notice, this list of conditions and the following disclaimer.
775 Redistributions in binary form must reproduce the above copyright
776 notice, this list of conditions and the following disclaimer in
777 the documentation and/or other materials provided with the
780 The name &"Carnegie Mellon University"& must not be used to
781 endorse or promote products derived from this software without
782 prior written permission. For permission or any other legal
783 details, please contact
785 Office of Technology Transfer
786 Carnegie Mellon University
788 Pittsburgh, PA 15213-3890
789 (412) 268-4387, fax: (412) 268-7395
790 tech-transfer@andrew.cmu.edu
793 Redistributions of any form whatsoever must retain the following
796 &"This product includes software developed by Computing Services
797 at Carnegie Mellon University (&url(https://www.cmu.edu/computing/)."&
799 CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
800 THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
801 AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
802 FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
803 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
804 AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
805 OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
810 .cindex "Exim monitor" "acknowledgment"
813 The Exim Monitor program, which is an X-Window application, includes
814 modified versions of the Athena StripChart and TextPop widgets.
815 This code is copyright by DEC and MIT, and their permission notice appears
816 below, in accordance with the conditions expressed therein.
819 Copyright 1987, 1988 by Digital Equipment Corporation, Maynard, Massachusetts,
820 and the Massachusetts Institute of Technology, Cambridge, Massachusetts.
824 Permission to use, copy, modify, and distribute this software and its
825 documentation for any purpose and without fee is hereby granted,
826 provided that the above copyright notice appear in all copies and that
827 both that copyright notice and this permission notice appear in
828 supporting documentation, and that the names of Digital or MIT not be
829 used in advertising or publicity pertaining to distribution of the
830 software without specific, written prior permission.
832 DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
833 ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
834 DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
835 ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
836 WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
837 ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
842 .cindex "opendmarc" "acknowledgment"
843 The DMARC implementation uses the OpenDMARC library which is Copyrighted by
844 The Trusted Domain Project. Portions of Exim source which use OpenDMARC
845 derived code are indicated in the respective source files. The full OpenDMARC
846 license is provided in the LICENSE.opendmarc file contained in the distributed
850 Many people have contributed code fragments, some large, some small, that were
851 not covered by any specific license requirements. It is assumed that the
852 contributors are happy to see their code incorporated into Exim under the GPL.
859 . ////////////////////////////////////////////////////////////////////////////
860 . ////////////////////////////////////////////////////////////////////////////
862 .chapter "How Exim receives and delivers mail" "CHID11" &&&
863 "Receiving and delivering mail"
866 .section "Overall philosophy" "SECID10"
867 .cindex "design philosophy"
868 Exim is designed to work efficiently on systems that are permanently connected
869 to the Internet and are handling a general mix of mail. In such circumstances,
870 most messages can be delivered immediately. Consequently, Exim does not
871 maintain independent queues of messages for specific domains or hosts, though
872 it does try to send several messages in a single SMTP connection after a host
873 has been down, and it also maintains per-host retry information.
876 .section "Policy control" "SECID11"
877 .cindex "policy control" "overview"
878 Policy controls are now an important feature of MTAs that are connected to the
879 Internet. Perhaps their most important job is to stop MTAs from being abused as
880 &"open relays"& by misguided individuals who send out vast amounts of
881 unsolicited junk and want to disguise its source. Exim provides flexible
882 facilities for specifying policy controls on incoming mail:
885 .cindex "&ACL;" "introduction"
886 Exim 4 (unlike previous versions of Exim) implements policy controls on
887 incoming mail by means of &'Access Control Lists'& (ACLs). Each list is a
888 series of statements that may either grant or deny access. ACLs can be used at
889 several places in the SMTP dialogue while receiving a message from a remote
890 host. However, the most common places are after each RCPT command, and at the
891 very end of the message. The sysadmin can specify conditions for accepting or
892 rejecting individual recipients or the entire message, respectively, at these
893 two points (see chapter &<<CHAPACL>>&). Denial of access results in an SMTP
896 An ACL is also available for locally generated, non-SMTP messages. In this
897 case, the only available actions are to accept or deny the entire message.
899 When Exim is compiled with the content-scanning extension, facilities are
900 provided in the ACL mechanism for passing the message to external virus and/or
901 spam scanning software. The result of such a scan is passed back to the ACL,
902 which can then use it to decide what to do with the message.
904 When a message has been received, either from a remote host or from the local
905 host, but before the final acknowledgment has been sent, a locally supplied C
906 function called &[local_scan()]& can be run to inspect the message and decide
907 whether to accept it or not (see chapter &<<CHAPlocalscan>>&). If the message
908 is accepted, the list of recipients can be modified by the function.
910 Using the &[local_scan()]& mechanism is another way of calling external scanner
911 software. The &%SA-Exim%& add-on package works this way. It does not require
912 Exim to be compiled with the content-scanning extension.
914 After a message has been accepted, a further checking mechanism is available in
915 the form of the &'system filter'& (see chapter &<<CHAPsystemfilter>>&). This
916 runs at the start of every delivery process.
921 .section "User filters" "SECID12"
922 .cindex "filter" "introduction"
923 .cindex "Sieve filter"
924 In a conventional Exim configuration, users are able to run private filters by
925 setting up appropriate &_.forward_& files in their home directories. See
926 chapter &<<CHAPredirect>>& (about the &(redirect)& router) for the
927 configuration needed to support this, and the separate document entitled
928 &'Exim's interfaces to mail filtering'& for user details. Two different kinds
929 of filtering are available:
932 Sieve filters are written in the standard filtering language that is defined
935 Exim filters are written in a syntax that is unique to Exim, but which is more
936 powerful than Sieve, which it pre-dates.
939 User filters are run as part of the routing process, described below.
943 .section "Message identification" "SECTmessiden"
944 .cindex "message ids" "details of format"
945 .cindex "format" "of message id"
946 .cindex "id of message"
951 Every message handled by Exim is given a &'message id'& which is sixteen
952 characters long. It is divided into three parts, separated by hyphens, for
953 example &`16VDhn-0001bo-D3`&. Each part is a sequence of letters and digits,
954 normally encoding numbers in base 62. However, in the Darwin operating
955 system (Mac OS X) and when Exim is compiled to run under Cygwin, base 36
956 (avoiding the use of lower case letters) is used instead, because the message
957 id is used to construct filenames, and the names of files in those systems are
958 not always case-sensitive.
960 .cindex "pid (process id)" "re-use of"
961 The detail of the contents of the message id have changed as Exim has evolved.
962 Earlier versions relied on the operating system not re-using a process id (pid)
963 within one second. On modern operating systems, this assumption can no longer
964 be made, so the algorithm had to be changed. To retain backward compatibility,
965 the format of the message id was retained, which is why the following rules are
969 The first six characters of the message id are the time at which the message
970 started to be received, to a granularity of one second. That is, this field
971 contains the number of seconds since the start of the epoch (the normal Unix
972 way of representing the date and time of day).
974 After the first hyphen, the next six characters are the id of the process that
975 received the message.
977 There are two different possibilities for the final two characters:
979 .oindex "&%localhost_number%&"
980 If &%localhost_number%& is not set, this value is the fractional part of the
981 time of reception, normally in units of 1/2000 of a second, but for systems
982 that must use base 36 instead of base 62 (because of case-insensitive file
983 systems), the units are 1/1000 of a second.
985 If &%localhost_number%& is set, it is multiplied by 200 (100) and added to
986 the fractional part of the time, which in this case is in units of 1/200
991 After a message has been received, Exim waits for the clock to tick at the
992 appropriate resolution before proceeding, so that if another message is
993 received by the same process, or by another process with the same (re-used)
994 pid, it is guaranteed that the time will be different. In most cases, the clock
995 will already have ticked while the message was being received.
998 .section "Receiving mail" "SECID13"
999 .cindex "receiving mail"
1000 .cindex "message" "reception"
1001 The only way Exim can receive mail from another host is using SMTP over
1002 TCP/IP, in which case the sender and recipient addresses are transferred using
1003 SMTP commands. However, from a locally running process (such as a user's MUA),
1004 there are several possibilities:
1007 If the process runs Exim with the &%-bm%& option, the message is read
1008 non-interactively (usually via a pipe), with the recipients taken from the
1009 command line, or from the body of the message if &%-t%& is also used.
1011 If the process runs Exim with the &%-bS%& option, the message is also read
1012 non-interactively, but in this case the recipients are listed at the start of
1013 the message in a series of SMTP RCPT commands, terminated by a DATA
1014 command. This is called &"batch SMTP"& format,
1015 but it isn't really SMTP. The SMTP commands are just another way of passing
1016 envelope addresses in a non-interactive submission.
1018 If the process runs Exim with the &%-bs%& option, the message is read
1019 interactively, using the SMTP protocol. A two-way pipe is normally used for
1020 passing data between the local process and the Exim process.
1021 This is &"real"& SMTP and is handled in the same way as SMTP over TCP/IP. For
1022 example, the ACLs for SMTP commands are used for this form of submission.
1024 A local process may also make a TCP/IP call to the host's loopback address
1025 (127.0.0.1) or any other of its IP addresses. When receiving messages, Exim
1026 does not treat the loopback address specially. It treats all such connections
1027 in the same way as connections from other hosts.
1031 .cindex "message sender, constructed by Exim"
1032 .cindex "sender" "constructed by Exim"
1033 In the three cases that do not involve TCP/IP, the sender address is
1034 constructed from the login name of the user that called Exim and a default
1035 qualification domain (which can be set by the &%qualify_domain%& configuration
1036 option). For local or batch SMTP, a sender address that is passed using the
1037 SMTP MAIL command is ignored. However, the system administrator may allow
1038 certain users (&"trusted users"&) to specify a different sender addresses
1039 unconditionally, or all users to specify certain forms of different sender
1040 address. The &%-f%& option or the SMTP MAIL command is used to specify these
1041 different addresses. See section &<<SECTtrustedadmin>>& for details of trusted
1042 users, and the &%untrusted_set_sender%& option for a way of allowing untrusted
1043 users to change sender addresses.
1045 Messages received by either of the non-interactive mechanisms are subject to
1046 checking by the non-SMTP ACL if one is defined. Messages received using SMTP
1047 (either over TCP/IP or interacting with a local process) can be checked by a
1048 number of ACLs that operate at different times during the SMTP session. Either
1049 individual recipients or the entire message can be rejected if local policy
1050 requirements are not met. The &[local_scan()]& function (see chapter
1051 &<<CHAPlocalscan>>&) is run for all incoming messages.
1053 Exim can be configured not to start a delivery process when a message is
1054 received; this can be unconditional, or depend on the number of incoming SMTP
1055 connections or the system load. In these situations, new messages wait on the
1056 queue until a queue runner process picks them up. However, in standard
1057 configurations under normal conditions, delivery is started as soon as a
1058 message is received.
1064 .section "Handling an incoming message" "SECID14"
1065 .cindex "spool directory" "files that hold a message"
1066 .cindex "file" "how a message is held"
1067 When Exim accepts a message, it writes two files in its spool directory. The
1068 first contains the envelope information, the current status of the message, and
1069 the header lines, and the second contains the body of the message. The names of
1070 the two spool files consist of the message id, followed by &`-H`& for the
1071 file containing the envelope and header, and &`-D`& for the data file.
1073 .cindex "spool directory" "&_input_& sub-directory"
1074 By default, all these message files are held in a single directory called
1075 &_input_& inside the general Exim spool directory. Some operating systems do
1076 not perform very well if the number of files in a directory gets large; to
1077 improve performance in such cases, the &%split_spool_directory%& option can be
1078 used. This causes Exim to split up the input files into 62 sub-directories
1079 whose names are single letters or digits. When this is done, the queue is
1080 processed one sub-directory at a time instead of all at once, which can improve
1081 overall performance even when there are not enough files in each directory to
1082 affect file system performance.
1084 The envelope information consists of the address of the message's sender and
1085 the addresses of the recipients. This information is entirely separate from
1086 any addresses contained in the header lines. The status of the message includes
1087 a list of recipients who have already received the message. The format of the
1088 first spool file is described in chapter &<<CHAPspool>>&.
1090 .cindex "rewriting" "addresses"
1091 Address rewriting that is specified in the rewrite section of the configuration
1092 (see chapter &<<CHAPrewrite>>&) is done once and for all on incoming addresses,
1093 both in the header lines and the envelope, at the time the message is accepted.
1094 If during the course of delivery additional addresses are generated (for
1095 example, via aliasing), these new addresses are rewritten as soon as they are
1096 generated. At the time a message is actually delivered (transported) further
1097 rewriting can take place; because this is a transport option, it can be
1098 different for different forms of delivery. It is also possible to specify the
1099 addition or removal of certain header lines at the time the message is
1100 delivered (see chapters &<<CHAProutergeneric>>& and
1101 &<<CHAPtransportgeneric>>&).
1105 .section "Life of a message" "SECID15"
1106 .cindex "message" "life of"
1107 .cindex "message" "frozen"
1108 A message remains in the spool directory until it is completely delivered to
1109 its recipients or to an error address, or until it is deleted by an
1110 administrator or by the user who originally created it. In cases when delivery
1111 cannot proceed &-- for example when a message can neither be delivered to its
1112 recipients nor returned to its sender, the message is marked &"frozen"& on the
1113 spool, and no more deliveries are attempted.
1115 .cindex "frozen messages" "thawing"
1116 .cindex "message" "thawing frozen"
1117 An administrator can &"thaw"& such messages when the problem has been
1118 corrected, and can also freeze individual messages by hand if necessary. In
1119 addition, an administrator can force a delivery error, causing a bounce message
1122 .oindex "&%timeout_frozen_after%&"
1123 .oindex "&%ignore_bounce_errors_after%&"
1124 There are options called &%ignore_bounce_errors_after%& and
1125 &%timeout_frozen_after%&, which discard frozen messages after a certain time.
1126 The first applies only to frozen bounces, the second to all frozen messages.
1128 .cindex "message" "log file for"
1129 .cindex "log" "file for each message"
1130 While Exim is working on a message, it writes information about each delivery
1131 attempt to its main log file. This includes successful, unsuccessful, and
1132 delayed deliveries for each recipient (see chapter &<<CHAPlog>>&). The log
1133 lines are also written to a separate &'message log'& file for each message.
1134 These logs are solely for the benefit of the administrator and are normally
1135 deleted along with the spool files when processing of a message is complete.
1136 The use of individual message logs can be disabled by setting
1137 &%no_message_logs%&; this might give an improvement in performance on very busy
1140 .cindex "journal file"
1141 .cindex "file" "journal"
1142 All the information Exim itself needs to set up a delivery is kept in the first
1143 spool file, along with the header lines. When a successful delivery occurs, the
1144 address is immediately written at the end of a journal file, whose name is the
1145 message id followed by &`-J`&. At the end of a delivery run, if there are some
1146 addresses left to be tried again later, the first spool file (the &`-H`& file)
1147 is updated to indicate which these are, and the journal file is then deleted.
1148 Updating the spool file is done by writing a new file and renaming it, to
1149 minimize the possibility of data loss.
1151 Should the system or Exim crash after a successful delivery but before
1152 the spool file has been updated, the journal is left lying around. The next
1153 time Exim attempts to deliver the message, it reads the journal file and
1154 updates the spool file before proceeding. This minimizes the chances of double
1155 deliveries caused by crashes.
1159 .section "Processing an address for delivery" "SECTprocaddress"
1160 .cindex "drivers" "definition of"
1161 .cindex "router" "definition of"
1162 .cindex "transport" "definition of"
1163 The main delivery processing elements of Exim are called &'routers'& and
1164 &'transports'&, and collectively these are known as &'drivers'&. Code for a
1165 number of them is provided in the source distribution, and compile-time options
1166 specify which ones are included in the binary. Runtime options specify which
1167 ones are actually used for delivering messages.
1169 .cindex "drivers" "instance definition"
1170 Each driver that is specified in the runtime configuration is an &'instance'&
1171 of that particular driver type. Multiple instances are allowed; for example,
1172 you can set up several different &(smtp)& transports, each with different
1173 option values that might specify different ports or different timeouts. Each
1174 instance has its own identifying name. In what follows we will normally use the
1175 instance name when discussing one particular instance (that is, one specific
1176 configuration of the driver), and the generic driver name when discussing
1177 the driver's features in general.
1179 A &'router'& is a driver that operates on an address, either determining how
1180 its delivery should happen, by assigning it to a specific transport, or
1181 converting the address into one or more new addresses (for example, via an
1182 alias file). A router may also explicitly choose to fail an address, causing it
1185 A &'transport'& is a driver that transmits a copy of the message from Exim's
1186 spool to some destination. There are two kinds of transport: for a &'local'&
1187 transport, the destination is a file or a pipe on the local host, whereas for a
1188 &'remote'& transport the destination is some other host. A message is passed
1189 to a specific transport as a result of successful routing. If a message has
1190 several recipients, it may be passed to a number of different transports.
1192 .cindex "preconditions" "definition of"
1193 An address is processed by passing it to each configured router instance in
1194 turn, subject to certain preconditions, until a router accepts the address or
1195 specifies that it should be bounced. We will describe this process in more
1196 detail shortly. First, as a simple example, we consider how each recipient
1197 address in a message is processed in a small configuration of three routers.
1199 To make this a more concrete example, it is described in terms of some actual
1200 routers, but remember, this is only an example. You can configure Exim's
1201 routers in many different ways, and there may be any number of routers in a
1204 The first router that is specified in a configuration is often one that handles
1205 addresses in domains that are not recognized specifically by the local host.
1206 Typically these are addresses for arbitrary domains on the Internet. A precondition
1207 is set up which looks for the special domains known to the host (for example,
1208 its own domain name), and the router is run for addresses that do &'not'&
1209 match. Typically, this is a router that looks up domains in the DNS in order to
1210 find the hosts to which this address routes. If it succeeds, the address is
1211 assigned to a suitable SMTP transport; if it does not succeed, the router is
1212 configured to fail the address.
1214 The second router is reached only when the domain is recognized as one that
1215 &"belongs"& to the local host. This router does redirection &-- also known as
1216 aliasing and forwarding. When it generates one or more new addresses from the
1217 original, each of them is routed independently from the start. Otherwise, the
1218 router may cause an address to fail, or it may simply decline to handle the
1219 address, in which case the address is passed to the next router.
1221 The final router in many configurations is one that checks to see if the
1222 address belongs to a local mailbox. The precondition may involve a check to
1223 see if the local part is the name of a login account, or it may look up the
1224 local part in a file or a database. If its preconditions are not met, or if
1225 the router declines, we have reached the end of the routers. When this happens,
1226 the address is bounced.
1230 .section "Processing an address for verification" "SECID16"
1231 .cindex "router" "for verification"
1232 .cindex "verifying address" "overview"
1233 As well as being used to decide how to deliver to an address, Exim's routers
1234 are also used for &'address verification'&. Verification can be requested as
1235 one of the checks to be performed in an ACL for incoming messages, on both
1236 sender and recipient addresses, and it can be tested using the &%-bv%& and
1237 &%-bvs%& command line options.
1239 When an address is being verified, the routers are run in &"verify mode"&. This
1240 does not affect the way the routers work, but it is a state that can be
1241 detected. By this means, a router can be skipped or made to behave differently
1242 when verifying. A common example is a configuration in which the first router
1243 sends all messages to a message-scanning program unless they have been
1244 previously scanned. Thus, the first router accepts all addresses without any
1245 checking, making it useless for verifying. Normally, the &%no_verify%& option
1246 would be set for such a router, causing it to be skipped in verify mode.
1251 .section "Running an individual router" "SECTrunindrou"
1252 .cindex "router" "running details"
1253 .cindex "preconditions" "checking"
1254 .cindex "router" "result of running"
1255 As explained in the example above, a number of preconditions are checked before
1256 running a router. If any are not met, the router is skipped, and the address is
1257 passed to the next router. When all the preconditions on a router &'are'& met,
1258 the router is run. What happens next depends on the outcome, which is one of
1262 &'accept'&: The router accepts the address, and either assigns it to a
1263 transport or generates one or more &"child"& addresses. Processing the
1264 original address ceases
1265 .oindex "&%unseen%&"
1266 unless the &%unseen%& option is set on the router. This option
1267 can be used to set up multiple deliveries with different routing (for example,
1268 for keeping archive copies of messages). When &%unseen%& is set, the address is
1269 passed to the next router. Normally, however, an &'accept'& return marks the
1272 Any child addresses generated by the router are processed independently,
1273 starting with the first router by default. It is possible to change this by
1274 setting the &%redirect_router%& option to specify which router to start at for
1275 child addresses. Unlike &%pass_router%& (see below) the router specified by
1276 &%redirect_router%& may be anywhere in the router configuration.
1278 &'pass'&: The router recognizes the address, but cannot handle it itself. It
1279 requests that the address be passed to another router. By default, the address
1280 is passed to the next router, but this can be changed by setting the
1281 &%pass_router%& option. However, (unlike &%redirect_router%&) the named router
1282 must be below the current router (to avoid loops).
1284 &'decline'&: The router declines to accept the address because it does not
1285 recognize it at all. By default, the address is passed to the next router, but
1286 this can be prevented by setting the &%no_more%& option. When &%no_more%& is
1287 set, all the remaining routers are skipped. In effect, &%no_more%& converts
1288 &'decline'& into &'fail'&.
1290 &'fail'&: The router determines that the address should fail, and queues it for
1291 the generation of a bounce message. There is no further processing of the
1292 original address unless &%unseen%& is set on the router.
1294 &'defer'&: The router cannot handle the address at the present time. (A
1295 database may be offline, or a DNS lookup may have timed out.) No further
1296 processing of the address happens in this delivery attempt. It is tried again
1297 next time the message is considered for delivery.
1299 &'error'&: There is some error in the router (for example, a syntax error in
1300 its configuration). The action is as for defer.
1303 If an address reaches the end of the routers without having been accepted by
1304 any of them, it is bounced as unrouteable. The default error message in this
1305 situation is &"unrouteable address"&, but you can set your own message by
1306 making use of the &%cannot_route_message%& option. This can be set for any
1307 router; the value from the last router that &"saw"& the address is used.
1309 Sometimes while routing you want to fail a delivery when some conditions are
1310 met but others are not, instead of passing the address on for further routing.
1311 You can do this by having a second router that explicitly fails the delivery
1312 when the relevant conditions are met. The &(redirect)& router has a &"fail"&
1313 facility for this purpose.
1316 .section "Duplicate addresses" "SECID17"
1317 .cindex "case of local parts"
1318 .cindex "address duplicate, discarding"
1319 .cindex "duplicate addresses"
1320 Once routing is complete, Exim scans the addresses that are assigned to local
1321 and remote transports and discards any duplicates that it finds. During this
1322 check, local parts are treated case-sensitively. This happens only when
1323 actually delivering a message; when testing routers with &%-bt%&, all the
1324 routed addresses are shown.
1328 .section "Router preconditions" "SECTrouprecon"
1329 .cindex "router" "preconditions, order of processing"
1330 .cindex "preconditions" "order of processing"
1331 The preconditions that are tested for each router are listed below, in the
1332 order in which they are tested. The individual configuration options are
1333 described in more detail in chapter &<<CHAProutergeneric>>&.
1336 .cindex affix "router precondition"
1337 The &%local_part_prefix%& and &%local_part_suffix%& options can specify that
1338 the local parts handled by the router may or must have certain prefixes and/or
1339 suffixes. If a mandatory affix (prefix or suffix) is not present, the router is
1340 skipped. These conditions are tested first. When an affix is present, it is
1341 removed from the local part before further processing, including the evaluation
1342 of any other conditions.
1344 Routers can be designated for use only when not verifying an address, that is,
1345 only when routing it for delivery (or testing its delivery routing). If the
1346 &%verify%& option is set false, the router is skipped when Exim is verifying an
1348 Setting the &%verify%& option actually sets two options, &%verify_sender%& and
1349 &%verify_recipient%&, which independently control the use of the router for
1350 sender and recipient verification. You can set these options directly if
1351 you want a router to be used for only one type of verification.
1352 Note that cutthrough delivery is classed as a recipient verification for this purpose.
1354 If the &%address_test%& option is set false, the router is skipped when Exim is
1355 run with the &%-bt%& option to test an address routing. This can be helpful
1356 when the first router sends all new messages to a scanner of some sort; it
1357 makes it possible to use &%-bt%& to test subsequent delivery routing without
1358 having to simulate the effect of the scanner.
1360 Routers can be designated for use only when verifying an address, as
1361 opposed to routing it for delivery. The &%verify_only%& option controls this.
1362 Again, cutthrough delivery counts as a verification.
1364 Individual routers can be explicitly skipped when running the routers to
1365 check an address given in the SMTP EXPN command (see the &%expn%& option).
1368 If the &%domains%& option is set, the domain of the address must be in the set
1369 of domains that it defines.
1370 .cindex "tainted data" "de-tainting"
1371 .cindex "de-tainting" "using router domains option"
1372 A match verifies the variable &$domain$& (which carries tainted data)
1373 and assigns an untainted value to the &$domain_data$& variable.
1374 Such an untainted value is often needed in the transport.
1375 For specifics of the matching operation and the resulting untainted value,
1376 refer to section &<<SECTdomainlist>>&.
1378 When an untainted value is wanted, use this option
1379 rather than the generic &%condition%& option.
1382 .vindex "&$local_part_prefix$&"
1383 .vindex "&$local_part_prefix_v$&"
1384 .vindex "&$local_part$&"
1385 .vindex "&$local_part_suffix$&"
1386 .vindex "&$local_part_suffix_v$&"
1387 .cindex affix "router precondition"
1388 If the &%local_parts%& option is set, the local part of the address must be in
1389 the set of local parts that it defines.
1390 A match verifies the variable &$local_part$& (which carries tainted data)
1391 and assigns an untainted value to the &$local_part_data$& variable.
1392 Such an untainted value is often needed in the transport.
1393 For specifics of the matching operation and the resulting untainted value,
1394 refer to section &<<SECTlocparlis>>&.
1396 When an untainted value is wanted, use this option
1397 rather than the generic &%condition%& option.
1399 If &%local_part_prefix%& or
1400 &%local_part_suffix%& is in use, the prefix or suffix is removed from the local
1401 part before this check. If you want to do precondition tests on local parts
1402 that include affixes, you can do so by using a &%condition%& option (see below)
1403 that uses the variables &$local_part$&, &$local_part_prefix$&,
1404 &$local_part_prefix_v$&, &$local_part_suffix$&
1405 and &$local_part_suffix_v$& as necessary.
1408 .vindex "&$local_user_uid$&"
1409 .vindex "&$local_user_gid$&"
1411 If the &%check_local_user%& option is set, the local part must be the name of
1412 an account on the local host. If this check succeeds, the uid and gid of the
1413 local user are placed in &$local_user_uid$& and &$local_user_gid$& and the
1414 user's home directory is placed in &$home$&; these values can be used in the
1415 remaining preconditions.
1418 If the &%router_home_directory%& option is set, it is expanded at this point,
1419 because it overrides the value of &$home$&. If this expansion were left till
1420 later, the value of &$home$& as set by &%check_local_user%& would be used in
1421 subsequent tests. Having two different values of &$home$& in the same router
1422 could lead to confusion.
1425 If the &%senders%& option is set, the envelope sender address must be in the
1426 set of addresses that it defines.
1429 If the &%require_files%& option is set, the existence or non-existence of
1430 specified files is tested.
1433 .cindex "customizing" "precondition"
1434 If the &%condition%& option is set, it is evaluated and tested. This option
1435 uses an expanded string to allow you to set up your own custom preconditions.
1436 Expanded strings are described in chapter &<<CHAPexpand>>&.
1438 Note that while using
1439 this option for address matching technically works,
1440 it does not set any de-tainted values.
1441 Such values are often needed, either for router-specific options or
1442 for transport options.
1443 Using the &%domains%& and &%local_parts%& options is usually the most
1444 convenient way to obtain them.
1448 Note that &%require_files%& comes near the end of the list, so you cannot use
1449 it to check for the existence of a file in which to lookup up a domain, local
1450 part, or sender. However, as these options are all expanded, you can use the
1451 &%exists%& expansion condition to make such tests within each condition. The
1452 &%require_files%& option is intended for checking files that the router may be
1453 going to use internally, or which are needed by a specific transport (for
1454 example, &_.procmailrc_&).
1458 .section "Delivery in detail" "SECID18"
1459 .cindex "delivery" "in detail"
1460 When a message is to be delivered, the sequence of events is as follows:
1463 If a system-wide filter file is specified, the message is passed to it. The
1464 filter may add recipients to the message, replace the recipients, discard the
1465 message, cause a new message to be generated, or cause the message delivery to
1466 fail. The format of the system filter file is the same as for Exim user filter
1467 files, described in the separate document entitled &'Exim's interfaces to mail
1469 .cindex "Sieve filter" "not available for system filter"
1470 (&*Note*&: Sieve cannot be used for system filter files.)
1472 Some additional features are available in system filters &-- see chapter
1473 &<<CHAPsystemfilter>>& for details. Note that a message is passed to the system
1474 filter only once per delivery attempt, however many recipients it has. However,
1475 if there are several delivery attempts because one or more addresses could not
1476 be immediately delivered, the system filter is run each time. The filter
1477 condition &%first_delivery%& can be used to detect the first run of the system
1480 Each recipient address is offered to each configured router, in turn, subject to
1481 its preconditions, until one is able to handle it. If no router can handle the
1482 address, that is, if they all decline, the address is failed. Because routers
1483 can be targeted at particular domains, several locally handled domains can be
1484 processed entirely independently of each other.
1486 .cindex "routing" "loops in"
1487 .cindex "loop" "while routing"
1488 A router that accepts an address may assign it to a local or a remote
1489 transport. However, the transport is not run at this time. Instead, the address
1490 is placed on a list for the particular transport, which will be run later.
1491 Alternatively, the router may generate one or more new addresses (typically
1492 from alias, forward, or filter files). New addresses are fed back into this
1493 process from the top, but in order to avoid loops, a router ignores any address
1494 which has an identically-named ancestor that was processed by itself.
1496 When all the routing has been done, addresses that have been successfully
1497 handled are passed to their assigned transports. When local transports are
1498 doing real local deliveries, they handle only one address at a time, but if a
1499 local transport is being used as a pseudo-remote transport (for example, to
1500 collect batched SMTP messages for transmission by some other means) multiple
1501 addresses can be handled. Remote transports can always handle more than one
1502 address at a time, but can be configured not to do so, or to restrict multiple
1503 addresses to the same domain.
1505 Each local delivery to a file or a pipe runs in a separate process under a
1506 non-privileged uid, and these deliveries are run one at a time. Remote
1507 deliveries also run in separate processes, normally under a uid that is private
1508 to Exim (&"the Exim user"&), but in this case, several remote deliveries can be
1509 run in parallel. The maximum number of simultaneous remote deliveries for any
1510 one message is set by the &%remote_max_parallel%& option.
1511 The order in which deliveries are done is not defined, except that all local
1512 deliveries happen before any remote deliveries.
1514 .cindex "queue runner"
1515 When it encounters a local delivery during a queue run, Exim checks its retry
1516 database to see if there has been a previous temporary delivery failure for the
1517 address before running the local transport. If there was a previous failure,
1518 Exim does not attempt a new delivery until the retry time for the address is
1519 reached. However, this happens only for delivery attempts that are part of a
1520 queue run. Local deliveries are always attempted when delivery immediately
1521 follows message reception, even if retry times are set for them. This makes for
1522 better behaviour if one particular message is causing problems (for example,
1523 causing quota overflow, or provoking an error in a filter file).
1525 .cindex "delivery" "retry in remote transports"
1526 Remote transports do their own retry handling, since an address may be
1527 deliverable to one of a number of hosts, each of which may have a different
1528 retry time. If there have been previous temporary failures and no host has
1529 reached its retry time, no delivery is attempted, whether in a queue run or
1530 not. See chapter &<<CHAPretry>>& for details of retry strategies.
1532 If there were any permanent errors, a bounce message is returned to an
1533 appropriate address (the sender in the common case), with details of the error
1534 for each failing address. Exim can be configured to send copies of bounce
1535 messages to other addresses.
1537 .cindex "delivery" "deferral"
1538 If one or more addresses suffered a temporary failure, the message is left on
1539 the queue, to be tried again later. Delivery of these addresses is said to be
1542 When all the recipient addresses have either been delivered or bounced,
1543 handling of the message is complete. The spool files and message log are
1544 deleted, though the message log can optionally be preserved if required.
1550 .section "Retry mechanism" "SECID19"
1551 .cindex "delivery" "retry mechanism"
1552 .cindex "retry" "description of mechanism"
1553 .cindex "queue runner"
1554 Exim's mechanism for retrying messages that fail to get delivered at the first
1555 attempt is the queue runner process. You must either run an Exim daemon that
1556 uses the &%-q%& option with a time interval to start queue runners at regular
1557 intervals or use some other means (such as &'cron'&) to start them. If you do
1558 not arrange for queue runners to be run, messages that fail temporarily at the
1559 first attempt will remain in your queue forever. A queue runner process works
1560 its way through the queue, one message at a time, trying each delivery that has
1561 passed its retry time.
1562 You can run several queue runners at once.
1564 Exim uses a set of configured rules to determine when next to retry the failing
1565 address (see chapter &<<CHAPretry>>&). These rules also specify when Exim
1566 should give up trying to deliver to the address, at which point it generates a
1567 bounce message. If no retry rules are set for a particular host, address, and
1568 error combination, no retries are attempted, and temporary errors are treated
1573 .subsection "Temporary delivery failure" SECID20
1574 .cindex "delivery" "temporary failure"
1575 There are many reasons why a message may not be immediately deliverable to a
1576 particular address. Failure to connect to a remote machine (because it, or the
1577 connection to it, is down) is one of the most common. Temporary failures may be
1578 detected during routing as well as during the transport stage of delivery.
1579 Local deliveries may be delayed if NFS files are unavailable, or if a mailbox
1580 is on a file system where the user is over quota. Exim can be configured to
1581 impose its own quotas on local mailboxes; where system quotas are set they will
1584 If a host is unreachable for a period of time, a number of messages may be
1585 waiting for it by the time it recovers, and sending them in a single SMTP
1586 connection is clearly beneficial. Whenever a delivery to a remote host is
1588 .cindex "hints database" "deferred deliveries"
1589 Exim makes a note in its hints database, and whenever a successful
1590 SMTP delivery has happened, it looks to see if any other messages are waiting
1591 for the same host. If any are found, they are sent over the same SMTP
1592 connection, subject to a configuration limit as to the maximum number in any
1597 .subsection "Permanent delivery failure" SECID21
1598 .cindex "delivery" "permanent failure"
1599 .cindex "bounce message" "when generated"
1600 When a message cannot be delivered to some or all of its intended recipients, a
1601 bounce message is generated. Temporary delivery failures turn into permanent
1602 errors when their timeout expires. All the addresses that fail in a given
1603 delivery attempt are listed in a single message. If the original message has
1604 many recipients, it is possible for some addresses to fail in one delivery
1605 attempt and others to fail subsequently, giving rise to more than one bounce
1606 message. The wording of bounce messages can be customized by the administrator.
1607 See chapter &<<CHAPemsgcust>>& for details.
1609 .cindex "&'X-Failed-Recipients:'& header line"
1610 Bounce messages contain an &'X-Failed-Recipients:'& header line that lists the
1611 failed addresses, for the benefit of programs that try to analyse such messages
1614 .cindex "bounce message" "recipient of"
1615 A bounce message is normally sent to the sender of the original message, as
1616 obtained from the message's envelope. For incoming SMTP messages, this is the
1617 address given in the MAIL command. However, when an address is expanded via a
1618 forward or alias file, an alternative address can be specified for delivery
1619 failures of the generated addresses. For a mailing list expansion (see section
1620 &<<SECTmailinglists>>&) it is common to direct bounce messages to the manager
1625 .subsection "Failures to deliver bounce messages" SECID22
1626 .cindex "bounce message" "failure to deliver"
1627 If a bounce message (either locally generated or received from a remote host)
1628 itself suffers a permanent delivery failure, the message is left in the queue,
1629 but it is frozen, awaiting the attention of an administrator. There are options
1630 that can be used to make Exim discard such failed messages, or to keep them
1631 for only a short time (see &%timeout_frozen_after%& and
1632 &%ignore_bounce_errors_after%&).
1638 . ////////////////////////////////////////////////////////////////////////////
1639 . ////////////////////////////////////////////////////////////////////////////
1641 .chapter "Building and installing Exim" "CHID3"
1642 .scindex IIDbuex "building Exim"
1644 .section "Unpacking" "SECID23"
1645 Exim is distributed as a gzipped or bzipped tar file which, when unpacked,
1646 creates a directory with the name of the current release (for example,
1647 &_exim-&version()_&) into which the following files are placed:
1650 .irow &_ACKNOWLEDGMENTS_& "contains some acknowledgments"
1651 .irow &_CHANGES_& "contains a reference to where changes are &&&
1653 .irow &_LICENCE_& "the GNU General Public Licence"
1654 .irow &_Makefile_& "top-level make file"
1655 .irow &_NOTICE_& "conditions for the use of Exim"
1656 .irow &_README_& "list of files, directories and simple build &&&
1660 Other files whose names begin with &_README_& may also be present. The
1661 following subdirectories are created:
1664 .irow &_Local_& "an empty directory for local configuration files"
1665 .irow &_OS_& "OS-specific files"
1666 .irow &_doc_& "documentation files"
1667 .irow &_exim_monitor_& "source files for the Exim monitor"
1668 .irow &_scripts_& "scripts used in the build process"
1669 .irow &_src_& "remaining source files"
1670 .irow &_util_& "independent utilities"
1673 The main utility programs are contained in the &_src_& directory and are built
1674 with the Exim binary. The &_util_& directory contains a few optional scripts
1675 that may be useful to some sites.
1678 .section "Multiple machine architectures and operating systems" "SECID24"
1679 .cindex "building Exim" "multiple OS/architectures"
1680 The building process for Exim is arranged to make it easy to build binaries for
1681 a number of different architectures and operating systems from the same set of
1682 source files. Compilation does not take place in the &_src_& directory.
1683 Instead, a &'build directory'& is created for each architecture and operating
1685 .cindex "symbolic link" "to build directory"
1686 Symbolic links to the sources are installed in this directory, which is where
1687 the actual building takes place. In most cases, Exim can discover the machine
1688 architecture and operating system for itself, but the defaults can be
1689 overridden if necessary.
1690 .cindex compiler requirements
1691 .cindex compiler version
1692 A C99-capable compiler will be required for the build.
1695 .section "PCRE2 library" "SECTpcre"
1696 .cindex "PCRE2 library"
1697 Exim no longer has an embedded regular-expression library as the vast majority of
1698 modern systems include PCRE2 as a system library, although you may need to
1699 install the PCRE2 package or the PCRE2 development package for your operating
1700 system. If your system has a normal PCRE2 installation the Exim build
1701 process will need no further configuration. If the library or the
1702 headers are in an unusual location you will need to either set the PCRE2_LIBS
1703 and INCLUDE directives appropriately,
1704 or set PCRE2_CONFIG=yes to use the installed &(pcre-config)& command.
1705 If your operating system has no
1706 PCRE2 support then you will need to obtain and build the current PCRE2
1707 from &url(https://github.com/PhilipHazel/pcre2/releases).
1708 More information on PCRE2 is available at &url(https://www.pcre.org/).
1710 .section "DBM libraries" "SECTdb"
1711 .cindex "DBM libraries" "discussion of"
1712 .cindex "hints database" "DBM files used for"
1713 Even if you do not use any DBM files in your configuration, Exim still needs a
1714 DBM library in order to operate, because it uses indexed files for its hints
1715 databases. Unfortunately, there are a number of DBM libraries in existence, and
1716 different operating systems often have different ones installed.
1718 .cindex "Solaris" "DBM library for"
1719 .cindex "IRIX, DBM library for"
1720 .cindex "BSD, DBM library for"
1721 .cindex "Linux, DBM library for"
1722 If you are using Solaris, IRIX, one of the modern BSD systems, or a modern
1723 Linux distribution, the DBM configuration should happen automatically, and you
1724 may be able to ignore this section. Otherwise, you may have to learn more than
1725 you would like about DBM libraries from what follows.
1727 .cindex "&'ndbm'& DBM library"
1728 Licensed versions of Unix normally contain a library of DBM functions operating
1729 via the &'ndbm'& interface, and this is what Exim expects by default. Free
1730 versions of Unix seem to vary in what they contain as standard. In particular,
1731 some early versions of Linux have no default DBM library, and different
1732 distributors have chosen to bundle different libraries with their packaged
1733 versions. However, the more recent releases seem to have standardized on the
1734 Berkeley DB library.
1736 Different DBM libraries have different conventions for naming the files they
1737 use. When a program opens a file called &_dbmfile_&, there are several
1741 A traditional &'ndbm'& implementation, such as that supplied as part of
1742 Solaris, operates on two files called &_dbmfile.dir_& and &_dbmfile.pag_&.
1744 .cindex "&'gdbm'& DBM library"
1745 The GNU library, &'gdbm'&, operates on a single file. If used via its &'ndbm'&
1746 compatibility interface it makes two different hard links to it with names
1747 &_dbmfile.dir_& and &_dbmfile.pag_&, but if used via its native interface, the
1748 filename is used unmodified.
1750 .cindex "Berkeley DB library"
1751 The Berkeley DB package, if called via its &'ndbm'& compatibility interface,
1752 operates on a single file called &_dbmfile.db_&, but otherwise looks to the
1753 programmer exactly the same as the traditional &'ndbm'& implementation.
1755 If the Berkeley package is used in its native mode, it operates on a single
1756 file called &_dbmfile_&; the programmer's interface is somewhat different to
1757 the traditional &'ndbm'& interface.
1759 To complicate things further, there are several very different versions of the
1760 Berkeley DB package. Version 1.85 was stable for a very long time, releases
1761 2.&'x'& and 3.&'x'& were current for a while,
1762 but the latest versions when Exim last revamped support were numbered 5.&'x'&.
1763 Maintenance of some of the earlier releases has ceased,
1764 and Exim no longer supports versions before 3.&'x'&.
1765 All versions of Berkeley DB could be obtained from
1766 &url(http://www.sleepycat.com/), which is now a redirect to their new owner's
1767 page with far newer versions listed.
1768 It is probably wise to plan to move your storage configurations away from
1769 Berkeley DB format, as today there are smaller and simpler alternatives more
1770 suited to Exim's usage model.
1772 .cindex "&'tdb'& DBM library"
1773 Yet another DBM library, called &'tdb'&, is available from
1774 &url(https://sourceforge.net/projects/tdb/files/). It has its own interface, and also
1775 operates on a single file.
1779 .cindex "DBM libraries" "configuration for building"
1780 Exim and its utilities can be compiled to use any of these interfaces. In order
1781 to use any version of the Berkeley DB package in native mode, you must set
1782 USE_DB in an appropriate configuration file (typically
1783 &_Local/Makefile_&). For example:
1787 Similarly, for gdbm you set USE_GDBM, and for tdb you set USE_TDB. An
1788 error is diagnosed if you set more than one of these.
1789 You can set USE_NDBM if needed to override an operating system default.
1791 At the lowest level, the build-time configuration sets none of these options,
1792 thereby assuming an interface of type (1). However, some operating system
1793 configuration files (for example, those for the BSD operating systems and
1794 Linux) assume type (4) by setting USE_DB as their default, and the
1795 configuration files for Cygwin set USE_GDBM. Anything you set in
1796 &_Local/Makefile_&, however, overrides these system defaults.
1798 As well as setting USE_DB, USE_GDBM, or USE_TDB, it may also be
1799 necessary to set DBMLIB, to cause inclusion of the appropriate library, as
1800 in one of these lines:
1804 DBMLIB = -lgdbm -lgdbm_compat
1806 The last of those was for a Linux having GDBM provide emulated NDBM facilities.
1807 Settings like that will work if the DBM library is installed in the standard
1808 place. Sometimes it is not, and the library's header file may also not be in
1809 the default path. You may need to set INCLUDE to specify where the header
1810 file is, and to specify the path to the library more fully in DBMLIB, as in
1813 INCLUDE=-I/usr/local/include/db-4.1
1814 DBMLIB=/usr/local/lib/db-4.1/libdb.a
1816 There is further detailed discussion about the various DBM libraries in the
1817 file &_doc/dbm.discuss.txt_& in the Exim distribution.
1821 .section "Pre-building configuration" "SECID25"
1822 .cindex "building Exim" "pre-building configuration"
1823 .cindex "configuration for building Exim"
1824 .cindex "&_Local/Makefile_&"
1825 .cindex "&_src/EDITME_&"
1826 Before building Exim, a local configuration file that specifies options
1827 independent of any operating system has to be created with the name
1828 &_Local/Makefile_&. A template for this file is supplied as the file
1829 &_src/EDITME_&, and it contains full descriptions of all the option settings
1830 therein. These descriptions are therefore not repeated here. If you are
1831 building Exim for the first time, the simplest thing to do is to copy
1832 &_src/EDITME_& to &_Local/Makefile_&, then read it and edit it appropriately.
1834 There are three settings that you must supply, because Exim will not build
1835 without them. They are the location of the runtime configuration file
1836 (CONFIGURE_FILE), the directory in which Exim binaries will be installed
1837 (BIN_DIRECTORY), and the identity of the Exim user (EXIM_USER and
1838 maybe EXIM_GROUP as well). The value of CONFIGURE_FILE can in fact be
1839 a colon-separated list of filenames; Exim uses the first of them that exists.
1841 There are a few other parameters that can be specified either at build time or
1842 at runtime, to enable the same binary to be used on a number of different
1843 machines. However, if the locations of Exim's spool directory and log file
1844 directory (if not within the spool directory) are fixed, it is recommended that
1845 you specify them in &_Local/Makefile_& instead of at runtime, so that errors
1846 detected early in Exim's execution (such as a malformed configuration file) can
1849 .cindex "content scanning" "specifying at build time"
1850 Exim's interfaces for calling virus and spam scanning software directly from
1851 access control lists are not compiled by default. If you want to include these
1852 facilities, you need to set
1854 WITH_CONTENT_SCAN=yes
1856 in your &_Local/Makefile_&. For details of the facilities themselves, see
1857 chapter &<<CHAPexiscan>>&.
1860 .cindex "&_Local/eximon.conf_&"
1861 .cindex "&_exim_monitor/EDITME_&"
1862 If you are going to build the Exim monitor, a similar configuration process is
1863 required. The file &_exim_monitor/EDITME_& must be edited appropriately for
1864 your installation and saved under the name &_Local/eximon.conf_&. If you are
1865 happy with the default settings described in &_exim_monitor/EDITME_&,
1866 &_Local/eximon.conf_& can be empty, but it must exist.
1868 This is all the configuration that is needed in straightforward cases for known
1869 operating systems. However, the building process is set up so that it is easy
1870 to override options that are set by default or by operating-system-specific
1871 configuration files, for example, to change the C compiler, which
1872 defaults to &%gcc%&. See section &<<SECToverride>>& below for details of how to
1877 .section "Support for iconv()" "SECID26"
1878 .cindex "&[iconv()]& support"
1880 The contents of header lines in messages may be encoded according to the rules
1881 described RFC 2047. This makes it possible to transmit characters that are not
1882 in the ASCII character set, and to label them as being in a particular
1883 character set. When Exim is inspecting header lines by means of the &%$h_%&
1884 mechanism, it decodes them, and translates them into a specified character set
1885 (default is set at build time). The translation is possible only if the operating system
1886 supports the &[iconv()]& function.
1888 However, some of the operating systems that supply &[iconv()]& do not support
1889 very many conversions. The GNU &%libiconv%& library (available from
1890 &url(https://www.gnu.org/software/libiconv/)) can be installed on such
1891 systems to remedy this deficiency, as well as on systems that do not supply
1892 &[iconv()]& at all. After installing &%libiconv%&, you should add
1896 to your &_Local/Makefile_& and rebuild Exim.
1900 .section "Including TLS/SSL encryption support" "SECTinctlsssl"
1901 .cindex "TLS" "including support for TLS"
1902 .cindex "encryption" "including support for"
1903 .cindex "OpenSSL" "building Exim with"
1904 .cindex "GnuTLS" "building Exim with"
1905 Exim is usually built to support encrypted SMTP connections, using the STARTTLS
1906 command as per RFC 2487. It can also support clients that expect to
1907 start a TLS session immediately on connection to a non-standard port (see the
1908 &%tls_on_connect_ports%& runtime option and the &%-tls-on-connect%& command
1911 If you want to build Exim with TLS support, you must first install either the
1912 OpenSSL or GnuTLS library. There is no cryptographic code in Exim itself for
1915 If you do not want TLS support you should set
1919 in &_Local/Makefile_&.
1921 If OpenSSL is installed, you should set
1924 TLS_LIBS=-lssl -lcrypto
1926 in &_Local/Makefile_&. You may also need to specify the locations of the
1927 OpenSSL library and include files. For example:
1930 TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto
1931 TLS_INCLUDE=-I/usr/local/openssl/include/
1933 .cindex "pkg-config" "OpenSSL"
1934 If you have &'pkg-config'& available, then instead you can just use:
1937 USE_OPENSSL_PC=openssl
1939 .cindex "USE_GNUTLS"
1940 If GnuTLS is installed, you should set
1943 TLS_LIBS=-lgnutls -ltasn1 -lgcrypt
1945 in &_Local/Makefile_&, and again you may need to specify the locations of the
1946 library and include files. For example:
1949 TLS_LIBS=-L/usr/gnu/lib -lgnutls -ltasn1 -lgcrypt
1950 TLS_INCLUDE=-I/usr/gnu/include
1952 .cindex "pkg-config" "GnuTLS"
1953 If you have &'pkg-config'& available, then instead you can just use:
1956 USE_GNUTLS_PC=gnutls
1959 You do not need to set TLS_INCLUDE if the relevant directory is already
1960 specified in INCLUDE. Details of how to configure Exim to make use of TLS are
1961 given in chapter &<<CHAPTLS>>&.
1966 .section "Use of tcpwrappers" "SECID27"
1968 .cindex "tcpwrappers, building Exim to support"
1969 .cindex "USE_TCP_WRAPPERS"
1970 .cindex "TCP_WRAPPERS_DAEMON_NAME"
1971 .cindex "tcp_wrappers_daemon_name"
1972 Exim can be linked with the &'tcpwrappers'& library in order to check incoming
1973 SMTP calls using the &'tcpwrappers'& control files. This may be a convenient
1974 alternative to Exim's own checking facilities for installations that are
1975 already making use of &'tcpwrappers'& for other purposes. To do this, you
1976 should set USE_TCP_WRAPPERS in &_Local/Makefile_&, arrange for the file
1977 &_tcpd.h_& to be available at compile time, and also ensure that the library
1978 &_libwrap.a_& is available at link time, typically by including &%-lwrap%& in
1979 EXTRALIBS_EXIM. For example, if &'tcpwrappers'& is installed in &_/usr/local_&,
1982 USE_TCP_WRAPPERS=yes
1983 CFLAGS=-O -I/usr/local/include
1984 EXTRALIBS_EXIM=-L/usr/local/lib -lwrap
1986 in &_Local/Makefile_&. The daemon name to use in the &'tcpwrappers'& control
1987 files is &"exim"&. For example, the line
1989 exim : LOCAL 192.168.1. .friendly.domain.example
1991 in your &_/etc/hosts.allow_& file allows connections from the local host, from
1992 the subnet 192.168.1.0/24, and from all hosts in &'friendly.domain.example'&.
1993 All other connections are denied. The daemon name used by &'tcpwrappers'&
1994 can be changed at build time by setting TCP_WRAPPERS_DAEMON_NAME in
1995 &_Local/Makefile_&, or by setting tcp_wrappers_daemon_name in the
1996 configure file. Consult the &'tcpwrappers'& documentation for
2000 .section "Including support for IPv6" "SECID28"
2001 .cindex "IPv6" "including support for"
2002 Exim contains code for use on systems that have IPv6 support. Setting
2003 &`HAVE_IPV6=YES`& in &_Local/Makefile_& causes the IPv6 code to be included;
2004 it may also be necessary to set IPV6_INCLUDE and IPV6_LIBS on systems
2005 where the IPv6 support is not fully integrated into the normal include and
2008 Two different types of DNS record for handling IPv6 addresses have been
2009 defined. AAAA records (analogous to A records for IPv4) are in use, and are
2010 currently seen as the mainstream. Another record type called A6 was proposed
2011 as better than AAAA because it had more flexibility. However, it was felt to be
2012 over-complex, and its status was reduced to &"experimental"&.
2014 have a compile option for including A6 record support but this has now been
2019 .section "Dynamically loaded lookup module support" "SECTdynamicmodules"
2020 .cindex "lookup modules"
2021 .cindex "dynamic modules"
2022 .cindex ".so building"
2023 On some platforms, Exim supports not compiling all lookup types directly into
2024 the main binary, instead putting some into external modules which can be loaded
2026 This permits packagers to build Exim with support for lookups with extensive
2027 library dependencies without requiring all users to install all of those
2029 Most, but not all, lookup types can be built this way.
2031 Set &`LOOKUP_MODULE_DIR`& to the directory into which the modules will be
2032 installed; Exim will only load modules from that directory, as a security
2033 measure. You will need to set &`CFLAGS_DYNAMIC`& if not already defined
2034 for your OS; see &_OS/Makefile-Linux_& for an example.
2035 Some other requirements for adjusting &`EXTRALIBS`& may also be necessary,
2036 see &_src/EDITME_& for details.
2038 Then, for each module to be loaded dynamically, define the relevant
2039 &`LOOKUP_`&<&'lookup_type'&> flags to have the value "2" instead of "yes".
2040 For example, this will build in lsearch but load sqlite and mysql support
2049 .section "The building process" "SECID29"
2050 .cindex "build directory"
2051 Once &_Local/Makefile_& (and &_Local/eximon.conf_&, if required) have been
2052 created, run &'make'& at the top level. It determines the architecture and
2053 operating system types, and creates a build directory if one does not exist.
2054 For example, on a Sun system running Solaris 8, the directory
2055 &_build-SunOS5-5.8-sparc_& is created.
2056 .cindex "symbolic link" "to source files"
2057 Symbolic links to relevant source files are installed in the build directory.
2059 If this is the first time &'make'& has been run, it calls a script that builds
2060 a make file inside the build directory, using the configuration files from the
2061 &_Local_& directory. The new make file is then passed to another instance of
2062 &'make'&. This does the real work, building a number of utility scripts, and
2063 then compiling and linking the binaries for the Exim monitor (if configured), a
2064 number of utility programs, and finally Exim itself. The command &`make
2065 makefile`& can be used to force a rebuild of the make file in the build
2066 directory, should this ever be necessary.
2068 If you have problems building Exim, check for any comments there may be in the
2069 &_README_& file concerning your operating system, and also take a look at the
2070 FAQ, where some common problems are covered.
2074 .section 'Output from &"make"&' "SECID283"
2075 The output produced by the &'make'& process for compile lines is often very
2076 unreadable, because these lines can be very long. For this reason, the normal
2077 output is suppressed by default, and instead output similar to that which
2078 appears when compiling the 2.6 Linux kernel is generated: just a short line for
2079 each module that is being compiled or linked. However, it is still possible to
2080 get the full output, by calling &'make'& like this:
2084 The value of FULLECHO defaults to &"@"&, the flag character that suppresses
2085 command reflection in &'make'&. When you ask for the full output, it is
2086 given in addition to the short output.
2090 .section "Overriding build-time options for Exim" "SECToverride"
2091 .cindex "build-time options, overriding"
2092 The main make file that is created at the beginning of the building process
2093 consists of the concatenation of a number of files which set configuration
2094 values, followed by a fixed set of &'make'& instructions. If a value is set
2095 more than once, the last setting overrides any previous ones. This provides a
2096 convenient way of overriding defaults. The files that are concatenated are, in
2099 &_OS/Makefile-Default_&
2100 &_OS/Makefile-_&<&'ostype'&>
2102 &_Local/Makefile-_&<&'ostype'&>
2103 &_Local/Makefile-_&<&'archtype'&>
2104 &_Local/Makefile-_&<&'ostype'&>-<&'archtype'&>
2105 &_OS/Makefile-Base_&
2107 .cindex "&_Local/Makefile_&"
2108 .cindex "building Exim" "operating system type"
2109 .cindex "building Exim" "architecture type"
2110 where <&'ostype'&> is the operating system type and <&'archtype'&> is the
2111 architecture type. &_Local/Makefile_& is required to exist, and the building
2112 process fails if it is absent. The other three &_Local_& files are optional,
2113 and are often not needed.
2115 The values used for <&'ostype'&> and <&'archtype'&> are obtained from scripts
2116 called &_scripts/os-type_& and &_scripts/arch-type_& respectively. If either of
2117 the environment variables EXIM_OSTYPE or EXIM_ARCHTYPE is set, their
2118 values are used, thereby providing a means of forcing particular settings.
2119 Otherwise, the scripts try to get values from the &%uname%& command. If this
2120 fails, the shell variables OSTYPE and ARCHTYPE are inspected. A number
2121 of &'ad hoc'& transformations are then applied, to produce the standard names
2122 that Exim expects. You can run these scripts directly from the shell in order
2123 to find out what values are being used on your system.
2126 &_OS/Makefile-Default_& contains comments about the variables that are set
2127 therein. Some (but not all) are mentioned below. If there is something that
2128 needs changing, review the contents of this file and the contents of the make
2129 file for your operating system (&_OS/Makefile-<ostype>_&) to see what the
2133 .cindex "building Exim" "overriding default settings"
2134 If you need to change any of the values that are set in &_OS/Makefile-Default_&
2135 or in &_OS/Makefile-<ostype>_&, or to add any new definitions, you do not
2136 need to change the original files. Instead, you should make the changes by
2137 putting the new values in an appropriate &_Local_& file. For example,
2138 .cindex "Tru64-Unix build-time settings"
2139 when building Exim in many releases of the Tru64-Unix (formerly Digital UNIX,
2140 formerly DEC-OSF1) operating system, it is necessary to specify that the C
2141 compiler is called &'cc'& rather than &'gcc'&. Also, the compiler must be
2142 called with the option &%-std1%&, to make it recognize some of the features of
2143 Standard C that Exim uses. (Most other compilers recognize Standard C by
2144 default.) To do this, you should create a file called &_Local/Makefile-OSF1_&
2145 containing the lines
2150 If you are compiling for just one operating system, it may be easier to put
2151 these lines directly into &_Local/Makefile_&.
2153 Keeping all your local configuration settings separate from the distributed
2154 files makes it easy to transfer them to new versions of Exim simply by copying
2155 the contents of the &_Local_& directory.
2158 .cindex "NIS lookup type" "including support for"
2159 .cindex "NIS+ lookup type" "including support for"
2160 .cindex "LDAP" "including support for"
2161 .cindex "lookup" "inclusion in binary"
2162 Exim contains support for doing LDAP, NIS, NIS+, and other kinds of file
2163 lookup, but not all systems have these components installed, so the default is
2164 not to include the relevant code in the binary. All the different kinds of file
2165 and database lookup that Exim supports are implemented as separate code modules
2166 which are included only if the relevant compile-time options are set. In the
2167 case of LDAP, NIS, and NIS+, the settings for &_Local/Makefile_& are:
2173 and similar settings apply to the other lookup types. They are all listed in
2174 &_src/EDITME_&. In many cases the relevant include files and interface
2175 libraries need to be installed before compiling Exim.
2176 .cindex "cdb" "including support for"
2177 However, there are some optional lookup types (such as cdb) for which
2178 the code is entirely contained within Exim, and no external include
2179 files or libraries are required. When a lookup type is not included in the
2180 binary, attempts to configure Exim to use it cause runtime configuration
2183 .cindex "pkg-config" "lookups"
2184 .cindex "pkg-config" "authenticators"
2185 Many systems now use a tool called &'pkg-config'& to encapsulate information
2186 about how to compile against a library; Exim has some initial support for
2187 being able to use pkg-config for lookups and authenticators. For any given
2188 makefile variable which starts &`LOOKUP_`& or &`AUTH_`&, you can add a new
2189 variable with the &`_PC`& suffix in the name and assign as the value the
2190 name of the package to be queried. The results of querying via the
2191 &'pkg-config'& command will be added to the appropriate Makefile variables
2192 with &`+=`& directives, so your version of &'make'& will need to support that
2193 syntax. For instance:
2196 LOOKUP_SQLITE_PC=sqlite3
2198 AUTH_GSASL_PC=libgsasl
2199 AUTH_HEIMDAL_GSSAPI=yes
2200 AUTH_HEIMDAL_GSSAPI_PC=heimdal-gssapi
2203 .cindex "Perl" "including support for"
2204 Exim can be linked with an embedded Perl interpreter, allowing Perl
2205 subroutines to be called during string expansion. To enable this facility,
2209 must be defined in &_Local/Makefile_&. Details of this facility are given in
2210 chapter &<<CHAPperl>>&.
2212 .cindex "X11 libraries, location of"
2213 The location of the X11 libraries is something that varies a lot between
2214 operating systems, and there may be different versions of X11 to cope
2215 with. Exim itself makes no use of X11, but if you are compiling the Exim
2216 monitor, the X11 libraries must be available.
2217 The following three variables are set in &_OS/Makefile-Default_&:
2220 XINCLUDE=-I$(X11)/include
2221 XLFLAGS=-L$(X11)/lib
2223 These are overridden in some of the operating-system configuration files. For
2224 example, in &_OS/Makefile-SunOS5_& there is
2227 XINCLUDE=-I$(X11)/include
2228 XLFLAGS=-L$(X11)/lib -R$(X11)/lib
2230 If you need to override the default setting for your operating system, place a
2231 definition of all three of these variables into your
2232 &_Local/Makefile-<ostype>_& file.
2235 If you need to add any extra libraries to the link steps, these can be put in a
2236 variable called EXTRALIBS, which appears in all the link commands, but by
2237 default is not defined. In contrast, EXTRALIBS_EXIM is used only on the
2238 command for linking the main Exim binary, and not for any associated utilities.
2240 .cindex "DBM libraries" "configuration for building"
2241 There is also DBMLIB, which appears in the link commands for binaries that
2242 use DBM functions (see also section &<<SECTdb>>&). Finally, there is
2243 EXTRALIBS_EXIMON, which appears only in the link step for the Exim monitor
2244 binary, and which can be used, for example, to include additional X11
2247 .cindex "configuration file" "editing"
2248 The make file copes with rebuilding Exim correctly if any of the configuration
2249 files are edited. However, if an optional configuration file is deleted, it is
2250 necessary to touch the associated non-optional file (that is,
2251 &_Local/Makefile_& or &_Local/eximon.conf_&) before rebuilding.
2254 .section "OS-specific header files" "SECID30"
2256 .cindex "building Exim" "OS-specific C header files"
2257 The &_OS_& directory contains a number of files with names of the form
2258 &_os.h-<ostype>_&. These are system-specific C header files that should not
2259 normally need to be changed. There is a list of macro settings that are
2260 recognized in the file &_OS/os.configuring_&, which should be consulted if you
2261 are porting Exim to a new operating system.
2265 .section "Overriding build-time options for the monitor" "SECID31"
2266 .cindex "building Eximon"
2267 A similar process is used for overriding things when building the Exim monitor,
2268 where the files that are involved are
2270 &_OS/eximon.conf-Default_&
2271 &_OS/eximon.conf-_&<&'ostype'&>
2272 &_Local/eximon.conf_&
2273 &_Local/eximon.conf-_&<&'ostype'&>
2274 &_Local/eximon.conf-_&<&'archtype'&>
2275 &_Local/eximon.conf-_&<&'ostype'&>-<&'archtype'&>
2277 .cindex "&_Local/eximon.conf_&"
2278 As with Exim itself, the final three files need not exist, and in this case the
2279 &_OS/eximon.conf-<ostype>_& file is also optional. The default values in
2280 &_OS/eximon.conf-Default_& can be overridden dynamically by setting environment
2281 variables of the same name, preceded by EXIMON_. For example, setting
2282 EXIMON_LOG_DEPTH in the environment overrides the value of
2283 LOG_DEPTH at runtime.
2287 .section "Installing Exim binaries and scripts" "SECID32"
2288 .cindex "installing Exim"
2289 .cindex "BIN_DIRECTORY"
2290 The command &`make install`& runs the &(exim_install)& script with no
2291 arguments. The script copies binaries and utility scripts into the directory
2292 whose name is specified by the BIN_DIRECTORY setting in &_Local/Makefile_&.
2293 .cindex "setuid" "installing Exim with"
2294 The install script copies files only if they are newer than the files they are
2295 going to replace. The Exim binary is required to be owned by root and have the
2296 &'setuid'& bit set, for normal configurations. Therefore, you must run &`make
2297 install`& as root so that it can set up the Exim binary in this way. However, in
2298 some special situations (for example, if a host is doing no local deliveries)
2299 it may be possible to run Exim without making the binary setuid root (see
2300 chapter &<<CHAPsecurity>>& for details).
2302 .cindex "CONFIGURE_FILE"
2303 Exim's runtime configuration file is named by the CONFIGURE_FILE setting
2304 in &_Local/Makefile_&. If this names a single file, and the file does not
2305 exist, the default configuration file &_src/configure.default_& is copied there
2306 by the installation script. If a runtime configuration file already exists, it
2307 is left alone. If CONFIGURE_FILE is a colon-separated list, naming several
2308 alternative files, no default is installed.
2310 .cindex "system aliases file"
2311 .cindex "&_/etc/aliases_&"
2312 One change is made to the default configuration file when it is installed: the
2313 default configuration contains a router that references a system aliases file.
2314 The path to this file is set to the value specified by
2315 SYSTEM_ALIASES_FILE in &_Local/Makefile_& (&_/etc/aliases_& by default).
2316 If the system aliases file does not exist, the installation script creates it,
2317 and outputs a comment to the user.
2319 The created file contains no aliases, but it does contain comments about the
2320 aliases a site should normally have. Mail aliases have traditionally been
2321 kept in &_/etc/aliases_&. However, some operating systems are now using
2322 &_/etc/mail/aliases_&. You should check if yours is one of these, and change
2323 Exim's configuration if necessary.
2325 The default configuration uses the local host's name as the only local domain,
2326 and is set up to do local deliveries into the shared directory &_/var/mail_&,
2327 running as the local user. System aliases and &_.forward_& files in users' home
2328 directories are supported, but no NIS or NIS+ support is configured. Domains
2329 other than the name of the local host are routed using the DNS, with delivery
2332 It is possible to install Exim for special purposes (such as building a binary
2333 distribution) in a private part of the file system. You can do this by a
2336 make DESTDIR=/some/directory/ install
2338 This has the effect of pre-pending the specified directory to all the file
2339 paths, except the name of the system aliases file that appears in the default
2340 configuration. (If a default alias file is created, its name &'is'& modified.)
2341 For backwards compatibility, ROOT is used if DESTDIR is not set,
2342 but this usage is deprecated.
2344 .cindex "installing Exim" "what is not installed"
2345 Running &'make install'& does not copy the Exim 4 conversion script
2346 &'convert4r4'&. You will probably run this only once if you are
2347 upgrading from Exim 3. None of the documentation files in the &_doc_&
2348 directory are copied, except for the info files when you have set
2349 INFO_DIRECTORY, as described in section &<<SECTinsinfdoc>>& below.
2351 For the utility programs, old versions are renamed by adding the suffix &_.O_&
2352 to their names. The Exim binary itself, however, is handled differently. It is
2353 installed under a name that includes the version number and the compile number,
2354 for example, &_exim-&version()-1_&. The script then arranges for a symbolic link
2355 called &_exim_& to point to the binary. If you are updating a previous version
2356 of Exim, the script takes care to ensure that the name &_exim_& is never absent
2357 from the directory (as seen by other processes).
2359 .cindex "installing Exim" "testing the script"
2360 If you want to see what the &'make install'& will do before running it for
2361 real, you can pass the &%-n%& option to the installation script by this
2364 make INSTALL_ARG=-n install
2366 The contents of the variable INSTALL_ARG are passed to the installation
2367 script. You do not need to be root to run this test. Alternatively, you can run
2368 the installation script directly, but this must be from within the build
2369 directory. For example, from the top-level Exim directory you could use this
2372 (cd build-SunOS5-5.5.1-sparc; ../scripts/exim_install -n)
2374 .cindex "installing Exim" "install script options"
2375 There are two other options that can be supplied to the installation script.
2378 &%-no_chown%& bypasses the call to change the owner of the installed binary
2379 to root, and the call to make it a setuid binary.
2381 &%-no_symlink%& bypasses the setting up of the symbolic link &_exim_& to the
2385 INSTALL_ARG can be used to pass these options to the script. For example:
2387 make INSTALL_ARG=-no_symlink install
2389 The installation script can also be given arguments specifying which files are
2390 to be copied. For example, to install just the Exim binary, and nothing else,
2391 without creating the symbolic link, you could use:
2393 make INSTALL_ARG='-no_symlink exim' install
2398 .section "Installing info documentation" "SECTinsinfdoc"
2399 .cindex "installing Exim" "&'info'& documentation"
2400 Not all systems use the GNU &'info'& system for documentation, and for this
2401 reason, the Texinfo source of Exim's documentation is not included in the main
2402 distribution. Instead it is available separately from the FTP site (see section
2405 If you have defined INFO_DIRECTORY in &_Local/Makefile_& and the Texinfo
2406 source of the documentation is found in the source tree, running &`make
2407 install`& automatically builds the info files and installs them.
2411 .section "Setting up the spool directory" "SECID33"
2412 .cindex "spool directory" "creating"
2413 When it starts up, Exim tries to create its spool directory if it does not
2414 exist. The Exim uid and gid are used for the owner and group of the spool
2415 directory. Sub-directories are automatically created in the spool directory as
2421 .section "Testing" "SECID34"
2422 .cindex "testing" "installation"
2423 Having installed Exim, you can check that the runtime configuration file is
2424 syntactically valid by running the following command, which assumes that the
2425 Exim binary directory is within your PATH environment variable:
2429 If there are any errors in the configuration file, Exim outputs error messages.
2430 Otherwise it outputs the version number and build date,
2431 the DBM library that is being used, and information about which drivers and
2432 other optional code modules are included in the binary.
2433 Some simple routing tests can be done by using the address testing option. For
2436 &`exim -bt`& <&'local username'&>
2438 should verify that it recognizes a local mailbox, and
2440 &`exim -bt`& <&'remote address'&>
2442 a remote one. Then try getting it to deliver mail, both locally and remotely.
2443 This can be done by passing messages directly to Exim, without going through a
2444 user agent. For example:
2446 exim -v postmaster@your.domain.example
2447 From: user@your.domain.example
2448 To: postmaster@your.domain.example
2449 Subject: Testing Exim
2451 This is a test message.
2454 The &%-v%& option causes Exim to output some verification of what it is doing.
2455 In this case you should see copies of three log lines, one for the message's
2456 arrival, one for its delivery, and one containing &"Completed"&.
2458 .cindex "delivery" "problems with"
2459 If you encounter problems, look at Exim's log files (&'mainlog'& and
2460 &'paniclog'&) to see if there is any relevant information there. Another source
2461 of information is running Exim with debugging turned on, by specifying the
2462 &%-d%& option. If a message is stuck on Exim's spool, you can force a delivery
2463 with debugging turned on by a command of the form
2465 &`exim -d -M`& <&'exim-message-id'&>
2467 You must be root or an &"admin user"& in order to do this. The &%-d%& option
2468 produces rather a lot of output, but you can cut this down to specific areas.
2469 For example, if you use &%-d-all+route%& only the debugging information
2470 relevant to routing is included. (See the &%-d%& option in chapter
2471 &<<CHAPcommandline>>& for more details.)
2473 .cindex '&"sticky"& bit'
2474 .cindex "lock files"
2475 One specific problem that has shown up on some sites is the inability to do
2476 local deliveries into a shared mailbox directory, because it does not have the
2477 &"sticky bit"& set on it. By default, Exim tries to create a lock file before
2478 writing to a mailbox file, and if it cannot create the lock file, the delivery
2479 is deferred. You can get round this either by setting the &"sticky bit"& on the
2480 directory, or by setting a specific group for local deliveries and allowing
2481 that group to create files in the directory (see the comments above the
2482 &(local_delivery)& transport in the default configuration file). Another
2483 approach is to configure Exim not to use lock files, but just to rely on
2484 &[fcntl()]& locking instead. However, you should do this only if all user
2485 agents also use &[fcntl()]& locking. For further discussion of locking issues,
2486 see chapter &<<CHAPappendfile>>&.
2488 One thing that cannot be tested on a system that is already running an MTA is
2489 the receipt of incoming SMTP mail on the standard SMTP port. However, the
2490 &%-oX%& option can be used to run an Exim daemon that listens on some other
2491 port, or &'inetd'& can be used to do this. The &%-bh%& option and the
2492 &'exim_checkaccess'& utility can be used to check out policy controls on
2495 Testing a new version on a system that is already running Exim can most easily
2496 be done by building a binary with a different CONFIGURE_FILE setting. From
2497 within the runtime configuration, all other file and directory names
2498 that Exim uses can be altered, in order to keep it entirely clear of the
2502 .section "Replacing another MTA with Exim" "SECID35"
2503 .cindex "replacing another MTA"
2504 Building and installing Exim for the first time does not of itself put it in
2505 general use. The name by which the system's MTA is called by mail user agents
2506 is either &_/usr/sbin/sendmail_&, or &_/usr/lib/sendmail_& (depending on the
2507 operating system), and it is necessary to make this name point to the &'exim'&
2508 binary in order to get the user agents to pass messages to Exim. This is
2509 normally done by renaming any existing file and making &_/usr/sbin/sendmail_&
2510 or &_/usr/lib/sendmail_&
2511 .cindex "symbolic link" "to &'exim'& binary"
2512 a symbolic link to the &'exim'& binary. It is a good idea to remove any setuid
2513 privilege and executable status from the old MTA. It is then necessary to stop
2514 and restart the mailer daemon, if one is running.
2516 .cindex "FreeBSD, MTA indirection"
2517 .cindex "&_/etc/mail/mailer.conf_&"
2518 Some operating systems have introduced alternative ways of switching MTAs. For
2519 example, if you are running FreeBSD, you need to edit the file
2520 &_/etc/mail/mailer.conf_& instead of setting up a symbolic link as just
2521 described. A typical example of the contents of this file for running Exim is
2524 sendmail /usr/exim/bin/exim
2525 send-mail /usr/exim/bin/exim
2526 mailq /usr/exim/bin/exim -bp
2527 newaliases /usr/bin/true
2529 Once you have set up the symbolic link, or edited &_/etc/mail/mailer.conf_&,
2530 your Exim installation is &"live"&. Check it by sending a message from your
2531 favourite user agent.
2533 You should consider what to tell your users about the change of MTA. Exim may
2534 have different capabilities to what was previously running, and there are
2535 various operational differences such as the text of messages produced by
2536 command line options and in bounce messages. If you allow your users to make
2537 use of Exim's filtering capabilities, you should make the document entitled
2538 &'Exim's interface to mail filtering'& available to them.
2542 .section "Running the daemon" SECTdaemonLaunch
2543 The most common command line for launching the Exim daemon looks like
2547 This starts a daemon which
2549 listens for incoming smtp connections, launching handler processes for
2552 starts a queue-runner process every five minutes, to inspect queued messages
2553 and run delivery attempts on any that have arrived at their retry time
2555 Should a queue run take longer than the time between queue-runner starts,
2556 they will run in parallel.
2557 Numbers of jobs of the various types are subject to policy controls
2558 defined in the configuration.
2561 .section "Upgrading Exim" "SECID36"
2562 .cindex "upgrading Exim"
2563 If you are already running Exim on your host, building and installing a new
2564 version automatically makes it available to MUAs, or any other programs that
2565 call the MTA directly. However, if you are running an Exim daemon, you do need
2566 .cindex restart "on HUP signal"
2567 .cindex signal "HUP, to restart"
2568 to send it a HUP signal, to make it re-execute itself, and thereby pick up the
2569 new binary. You do not need to stop processing mail in order to install a new
2570 version of Exim. The install script does not modify an existing runtime
2576 .section "Stopping the Exim daemon on Solaris" "SECID37"
2577 .cindex "Solaris" "stopping Exim on"
2578 The standard command for stopping the mailer daemon on Solaris is
2580 /etc/init.d/sendmail stop
2582 If &_/usr/lib/sendmail_& has been turned into a symbolic link, this script
2583 fails to stop Exim because it uses the command &'ps -e'& and greps the output
2584 for the text &"sendmail"&; this is not present because the actual program name
2585 (that is, &"exim"&) is given by the &'ps'& command with these options. A
2586 solution is to replace the line that finds the process id with something like
2588 pid=`cat /var/spool/exim/exim-daemon.pid`
2590 to obtain the daemon's pid directly from the file that Exim saves it in.
2592 Note, however, that stopping the daemon does not &"stop Exim"&. Messages can
2593 still be received from local processes, and if automatic delivery is configured
2594 (the normal case), deliveries will still occur.
2599 . ////////////////////////////////////////////////////////////////////////////
2600 . ////////////////////////////////////////////////////////////////////////////
2602 .chapter "The Exim command line" "CHAPcommandline"
2603 .scindex IIDclo1 "command line" "options"
2604 .scindex IIDclo2 "options" "command line"
2605 Exim's command line takes the standard Unix form of a sequence of options,
2606 each starting with a hyphen character, followed by a number of arguments. The
2607 options are compatible with the main options of Sendmail, and there are also
2608 some additional options, some of which are compatible with Smail 3. Certain
2609 combinations of options do not make sense, and provoke an error if used.
2610 The form of the arguments depends on which options are set.
2613 .section "Setting options by program name" "SECID38"
2615 If Exim is called under the name &'mailq'&, it behaves as if the option &%-bp%&
2616 were present before any other options.
2617 The &%-bp%& option requests a listing of the contents of the mail queue on the
2619 This feature is for compatibility with some systems that contain a command of
2620 that name in one of the standard libraries, symbolically linked to
2621 &_/usr/sbin/sendmail_& or &_/usr/lib/sendmail_&.
2624 If Exim is called under the name &'rsmtp'& it behaves as if the option &%-bS%&
2625 were present before any other options, for compatibility with Smail. The
2626 &%-bS%& option is used for reading in a number of messages in batched SMTP
2630 If Exim is called under the name &'rmail'& it behaves as if the &%-i%& and
2631 &%-oee%& options were present before any other options, for compatibility with
2632 Smail. The name &'rmail'& is used as an interface by some UUCP systems.
2635 .cindex "queue runner"
2636 If Exim is called under the name &'runq'& it behaves as if the option &%-q%&
2637 were present before any other options, for compatibility with Smail. The &%-q%&
2638 option causes a single queue runner process to be started.
2640 .cindex "&'newaliases'&"
2641 .cindex "alias file" "building"
2642 .cindex "Sendmail compatibility" "calling Exim as &'newaliases'&"
2643 If Exim is called under the name &'newaliases'& it behaves as if the option
2644 &%-bi%& were present before any other options, for compatibility with Sendmail.
2645 This option is used for rebuilding Sendmail's alias file. Exim does not have
2646 the concept of a single alias file, but can be configured to run a given
2647 command if called with the &%-bi%& option.
2650 .section "Trusted and admin users" "SECTtrustedadmin"
2651 Some Exim options are available only to &'trusted users'& and others are
2652 available only to &'admin users'&. In the description below, the phrases &"Exim
2653 user"& and &"Exim group"& mean the user and group defined by EXIM_USER and
2654 EXIM_GROUP in &_Local/Makefile_& or set by the &%exim_user%& and
2655 &%exim_group%& options. These do not necessarily have to use the name &"exim"&.
2658 .cindex "trusted users" "definition of"
2659 .cindex "user" "trusted definition of"
2660 The trusted users are root, the Exim user, any user listed in the
2661 &%trusted_users%& configuration option, and any user whose current group or any
2662 supplementary group is one of those listed in the &%trusted_groups%&
2663 configuration option. Note that the Exim group is not automatically trusted.
2665 .cindex '&"From"& line'
2666 .cindex "envelope from"
2667 .cindex "envelope sender"
2668 Trusted users are always permitted to use the &%-f%& option or a leading
2669 &"From&~"& line to specify the envelope sender of a message that is passed to
2670 Exim through the local interface (see the &%-bm%& and &%-f%& options below).
2671 See the &%untrusted_set_sender%& option for a way of permitting non-trusted
2672 users to set envelope senders.
2676 For a trusted user, there is never any check on the contents of the &'From:'&
2677 header line, and a &'Sender:'& line is never added. Furthermore, any existing
2678 &'Sender:'& line in incoming local (non-TCP/IP) messages is not removed.
2680 Trusted users may also specify a host name, host address, interface address,
2681 protocol name, ident value, and authentication data when submitting a message
2682 locally. Thus, they are able to insert messages into Exim's queue locally that
2683 have the characteristics of messages received from a remote host. Untrusted
2684 users may in some circumstances use &%-f%&, but can never set the other values
2685 that are available to trusted users.
2687 .cindex "user" "admin definition of"
2688 .cindex "admin user" "definition of"
2689 The admin users are root, the Exim user, and any user that is a member of the
2690 Exim group or of any group listed in the &%admin_groups%& configuration option.
2691 The current group does not have to be one of these groups.
2693 Admin users are permitted to list the queue, and to carry out certain
2694 operations on messages, for example, to force delivery failures. It is also
2695 necessary to be an admin user in order to see the full information provided by
2696 the Exim monitor, and full debugging output.
2698 By default, the use of the &%-M%&, &%-q%&, &%-R%&, and &%-S%& options to cause
2699 Exim to attempt delivery of messages on its queue is restricted to admin users.
2700 However, this restriction can be relaxed by setting the &%prod_requires_admin%&
2701 option false (that is, specifying &%no_prod_requires_admin%&).
2703 Similarly, the use of the &%-bp%& option to list all the messages in the queue
2704 is restricted to admin users unless &%queue_list_requires_admin%& is set
2709 &*Warning*&: If you configure your system so that admin users are able to
2710 edit Exim's configuration file, you are giving those users an easy way of
2711 getting root. There is further discussion of this issue at the start of chapter
2717 .section "Command line options" "SECID39"
2718 Exim's command line options are described in alphabetical order below. If none
2719 of the options that specifies a specific action (such as starting the daemon or
2720 a queue runner, or testing an address, or receiving a message in a specific
2721 format, or listing the queue) are present, and there is at least one argument
2722 on the command line, &%-bm%& (accept a local message on the standard input,
2723 with the arguments specifying the recipients) is assumed. Otherwise, Exim
2724 outputs a brief message about itself and exits.
2726 . ////////////////////////////////////////////////////////////////////////////
2727 . Insert a stylized XML comment here, to identify the start of the command line
2728 . options. This is for the benefit of the Perl script that automatically
2729 . creates a man page for the options.
2730 . ////////////////////////////////////////////////////////////////////////////
2733 <!-- === Start of command line options === -->
2739 .cindex "options" "command line; terminating"
2740 This is a pseudo-option whose only purpose is to terminate the options and
2741 therefore to cause subsequent command line items to be treated as arguments
2742 rather than options, even if they begin with hyphens.
2745 This option causes Exim to output a few sentences stating what it is.
2746 The same output is generated if the Exim binary is called with no options and
2750 This option is an alias for &%-bV%& and causes version information to be
2757 These options are used by Sendmail for selecting configuration files and are
2760 .cmdopt -B <&'type'&>
2762 .cindex "8-bit characters"
2763 .cindex "Sendmail compatibility" "8-bit characters"
2764 This is a Sendmail option for selecting 7 or 8 bit processing. Exim is 8-bit
2765 clean; it ignores this option.
2769 .cindex "SMTP" "listener"
2770 .cindex "queue runner"
2771 This option runs Exim as a daemon, awaiting incoming SMTP connections. Usually
2772 the &%-bd%& option is combined with the &%-q%&<&'time'&> option, to specify
2773 that the daemon should also initiate periodic queue runs.
2775 The &%-bd%& option can be used only by an admin user. If either of the &%-d%&
2776 (debugging) or &%-v%& (verifying) options are set, the daemon does not
2777 disconnect from the controlling terminal. When running this way, it can be
2778 stopped by pressing ctrl-C.
2780 By default, Exim listens for incoming connections to the standard SMTP port on
2781 all the host's running interfaces. However, it is possible to listen on other
2782 ports, on multiple ports, and only on specific interfaces. Chapter
2783 &<<CHAPinterfaces>>& contains a description of the options that control this.
2785 When a listening daemon
2786 .cindex "daemon" "process id (pid)"
2787 .cindex "pid (process id)" "of daemon"
2788 is started without the use of &%-oX%& (that is, without overriding the normal
2789 configuration), it writes its process id to a file called &_exim-daemon.pid_&
2790 in Exim's spool directory. This location can be overridden by setting
2791 PID_FILE_PATH in &_Local/Makefile_&. The file is written while Exim is still
2794 When &%-oX%& is used on the command line to start a listening daemon, the
2795 process id is not written to the normal pid file path. However, &%-oP%& can be
2796 used to specify a path on the command line if a pid file is required.
2800 .cindex restart "on HUP signal"
2801 .cindex signal "HUP, to restart"
2802 .cindex "daemon" "restarting"
2803 .cindex signal "to reload configuration"
2804 .cindex daemon "reload configuration"
2805 .cindex reload configuration
2806 can be used to cause the daemon to re-execute itself. This should be done
2807 whenever Exim's configuration file, or any file that is incorporated into it by
2808 means of the &%.include%& facility, is changed, and also whenever a new version
2809 of Exim is installed. It is not necessary to do this when other files that are
2810 referenced from the configuration (for example, alias files) are changed,
2811 because these are reread each time they are used.
2814 This option has the same effect as &%-bd%& except that it never disconnects
2815 from the controlling terminal, even when no debugging is specified.
2818 .cindex "testing" "string expansion"
2819 .cindex "expansion" "testing"
2820 Run Exim in expansion testing mode. Exim discards its root privilege, to
2821 prevent ordinary users from using this mode to read otherwise inaccessible
2822 files. If no arguments are given, Exim runs interactively, prompting for lines
2823 of data. Otherwise, it processes each argument in turn.
2825 If Exim was built with USE_READLINE=yes in &_Local/Makefile_&, it tries
2826 to load the &%libreadline%& library dynamically whenever the &%-be%& option is
2827 used without command line arguments. If successful, it uses the &[readline()]&
2828 function, which provides extensive line-editing facilities, for reading the
2829 test data. A line history is supported.
2831 Long expansion expressions can be split over several lines by using backslash
2832 continuations. As in Exim's runtime configuration, white space at the start of
2833 continuation lines is ignored. Each argument or data line is passed through the
2834 string expansion mechanism, and the result is output. Variable values from the
2835 configuration file (for example, &$qualify_domain$&) are available, but no
2836 message-specific values (such as &$message_exim_id$&) are set, because no message
2837 is being processed (but see &%-bem%& and &%-Mset%&).
2839 &*Note*&: If you use this mechanism to test lookups, and you change the data
2840 files or databases you are using, you must exit and restart Exim before trying
2841 the same lookup again. Otherwise, because each Exim process caches the results
2842 of lookups, you will just get the same result as before.
2844 Macro processing is done on lines before string-expansion: new macros can be
2845 defined and macros will be expanded.
2846 Because macros in the config file are often used for secrets, those are only
2847 available to admin users.
2850 The word &"set"& at the start of a line, followed by a single space,
2851 is recognised specially as defining a value for a variable.
2852 The syntax is otherwise the same as the ACL modifier &"set ="&.
2855 .cmdopt -bem <&'filename'&>
2856 .cindex "testing" "string expansion"
2857 .cindex "expansion" "testing"
2858 This option operates like &%-be%& except that it must be followed by the name
2859 of a file. For example:
2861 exim -bem /tmp/testmessage
2863 The file is read as a message (as if receiving a locally-submitted non-SMTP
2864 message) before any of the test expansions are done. Thus, message-specific
2865 variables such as &$message_size$& and &$header_from:$& are available. However,
2866 no &'Received:'& header is added to the message. If the &%-t%& option is set,
2867 recipients are read from the headers in the normal way, and are shown in the
2868 &$recipients$& variable. Note that recipients cannot be given on the command
2869 line, because further arguments are taken as strings to expand (just like
2872 .cmdopt -bF <&'filename'&>
2873 .cindex "system filter" "testing"
2874 .cindex "testing" "system filter"
2875 This option is the same as &%-bf%& except that it assumes that the filter being
2876 tested is a system filter. The additional commands that are available only in
2877 system filters are recognized.
2879 .cmdopt -bf <&'filename'&>
2880 .cindex "filter" "testing"
2881 .cindex "testing" "filter file"
2882 .cindex "forward file" "testing"
2883 .cindex "testing" "forward file"
2884 .cindex "Sieve filter" "testing"
2885 This option runs Exim in user filter testing mode; the file is the filter file
2886 to be tested, and a test message must be supplied on the standard input. If
2887 there are no message-dependent tests in the filter, an empty file can be
2890 If you want to test a system filter file, use &%-bF%& instead of &%-bf%&. You
2891 can use both &%-bF%& and &%-bf%& on the same command, in order to test a system
2892 filter and a user filter in the same run. For example:
2894 exim -bF /system/filter -bf /user/filter </test/message
2896 This is helpful when the system filter adds header lines or sets filter
2897 variables that are used by the user filter.
2899 If the test filter file does not begin with one of the special lines
2904 it is taken to be a normal &_.forward_& file, and is tested for validity under
2905 that interpretation. See sections &<<SECTitenonfilred>>& to
2906 &<<SECTspecitredli>>& for a description of the possible contents of non-filter
2909 The result of an Exim command that uses &%-bf%&, provided no errors are
2910 detected, is a list of the actions that Exim would try to take if presented
2911 with the message for real. More details of filter testing are given in the
2912 separate document entitled &'Exim's interfaces to mail filtering'&.
2914 When testing a filter file,
2915 .cindex "&""From""& line"
2916 .cindex "envelope from"
2917 .cindex "envelope sender"
2918 .oindex "&%-f%&" "for filter testing"
2919 the envelope sender can be set by the &%-f%& option,
2920 or by a &"From&~"& line at the start of the test message. Various parameters
2921 that would normally be taken from the envelope recipient address of the message
2922 can be set by means of additional command line options (see the next four
2925 .cmdopt -bfd <&'domain'&>
2926 .vindex "&$qualify_domain$&"
2927 This sets the domain of the recipient address when a filter file is being
2928 tested by means of the &%-bf%& option. The default is the value of
2931 .cmdopt -bfl <&'local&~part'&>
2932 This sets the local part of the recipient address when a filter file is being
2933 tested by means of the &%-bf%& option. The default is the username of the
2934 process that calls Exim. A local part should be specified with any prefix or
2935 suffix stripped, because that is how it appears to the filter when a message is
2936 actually being delivered.
2938 .cmdopt -bfp <&'prefix'&>
2939 .cindex affix "filter testing"
2940 This sets the prefix of the local part of the recipient address when a filter
2941 file is being tested by means of the &%-bf%& option. The default is an empty
2944 .cmdopt -bfs <&'suffix'&>
2945 .cindex affix "filter testing"
2946 This sets the suffix of the local part of the recipient address when a filter
2947 file is being tested by means of the &%-bf%& option. The default is an empty
2950 .cmdopt -bh <&'IP&~address'&>
2951 .cindex "testing" "incoming SMTP"
2952 .cindex "SMTP" "testing incoming"
2953 .cindex "testing" "relay control"
2954 .cindex "relaying" "testing configuration"
2955 .cindex "policy control" "testing"
2956 .cindex "debugging" "&%-bh%& option"
2957 This option runs a fake SMTP session as if from the given IP address, using the
2958 standard input and output. The IP address may include a port number at the end,
2959 after a full stop. For example:
2961 exim -bh 10.9.8.7.1234
2962 exim -bh fe80::a00:20ff:fe86:a061.5678
2964 When an IPv6 address is given, it is converted into canonical form. In the case
2965 of the second example above, the value of &$sender_host_address$& after
2966 conversion to the canonical form is
2967 &`fe80:0000:0000:0a00:20ff:fe86:a061.5678`&.
2969 Comments as to what is going on are written to the standard error file. These
2970 include lines beginning with &"LOG"& for anything that would have been logged.
2971 This facility is provided for testing configuration options for incoming
2972 messages, to make sure they implement the required policy. For example, you can
2973 test your relay controls using &%-bh%&.
2977 You can test features of the configuration that rely on ident (RFC 1413)
2978 information by using the &%-oMt%& option. However, Exim cannot actually perform
2979 an ident callout when testing using &%-bh%& because there is no incoming SMTP
2982 &*Warning 2*&: Address verification callouts (see section &<<SECTcallver>>&)
2983 are also skipped when testing using &%-bh%&. If you want these callouts to
2984 occur, use &%-bhc%& instead.
2986 Messages supplied during the testing session are discarded, and nothing is
2987 written to any of the real log files. There may be pauses when DNS (and other)
2988 lookups are taking place, and of course these may time out. The &%-oMi%& option
2989 can be used to specify a specific IP interface and port if this is important,
2990 and &%-oMaa%& and &%-oMai%& can be used to set parameters as if the SMTP
2991 session were authenticated.
2993 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%& whose
2994 output just states whether a given recipient address from a given host is
2995 acceptable or not. See section &<<SECTcheckaccess>>&.
2997 Features such as authentication and encryption, where the client input is not
2998 plain text, cannot easily be tested with &%-bh%&. Instead, you should use a
2999 specialized SMTP test program such as
3000 &url(https://www.jetmore.org/john/code/swaks/,swaks).
3002 .cmdopt -bhc <&'IP&~address'&>
3003 This option operates in the same way as &%-bh%&, except that address
3004 verification callouts are performed if required. This includes consulting and
3005 updating the callout cache database.
3008 .cindex "alias file" "building"
3009 .cindex "building alias file"
3010 .cindex "Sendmail compatibility" "&%-bi%& option"
3011 Sendmail interprets the &%-bi%& option as a request to rebuild its alias file.
3012 Exim does not have the concept of a single alias file, and so it cannot mimic
3013 this behaviour. However, calls to &_/usr/lib/sendmail_& with the &%-bi%& option
3014 tend to appear in various scripts such as NIS make files, so the option must be
3017 If &%-bi%& is encountered, the command specified by the &%bi_command%&
3018 configuration option is run, under the uid and gid of the caller of Exim. If
3019 the &%-oA%& option is used, its value is passed to the command as an argument.
3020 The command set by &%bi_command%& may not contain arguments. The command can
3021 use the &'exim_dbmbuild'& utility, or some other means, to rebuild alias files
3022 if this is required. If the &%bi_command%& option is not set, calling Exim with
3025 . // Keep :help first, then the rest in alphabetical order
3027 .cindex "querying exim information"
3028 We shall provide various options starting &`-bI:`& for querying Exim for
3029 information. The output of many of these will be intended for machine
3030 consumption. This one is not. The &%-bI:help%& option asks Exim for a
3031 synopsis of supported options beginning &`-bI:`&. Use of any of these
3032 options shall cause Exim to exit after producing the requested output.
3035 .cindex "DSCP" "values"
3036 This option causes Exim to emit an alphabetically sorted list of all
3037 recognised DSCP names.
3040 .cindex "Sieve filter" "capabilities"
3041 This option causes Exim to emit an alphabetically sorted list of all supported
3042 Sieve protocol extensions on stdout, one per line. This is anticipated to be
3043 useful for ManageSieve (RFC 5804) implementations, in providing that protocol's
3044 &`SIEVE`& capability response line. As the precise list may depend upon
3045 compile-time build options, which this option will adapt to, this is the only
3046 way to guarantee a correct response.
3049 .cindex "local message reception"
3050 This option runs an Exim receiving process that accepts an incoming,
3051 locally-generated message on the standard input. The recipients are given as the
3052 command arguments (except when &%-t%& is also present &-- see below). Each
3053 argument can be a comma-separated list of RFC 2822 addresses. This is the
3054 default option for selecting the overall action of an Exim call; it is assumed
3055 if no other conflicting option is present.
3057 If any addresses in the message are unqualified (have no domain), they are
3058 qualified by the values of the &%qualify_domain%& or &%qualify_recipient%&
3059 options, as appropriate. The &%-bnq%& option (see below) provides a way of
3060 suppressing this for special cases.
3062 Policy checks on the contents of local messages can be enforced by means of
3063 the non-SMTP ACL. See chapter &<<CHAPACL>>& for details.
3065 .cindex "return code" "for &%-bm%&"
3066 The return code is zero if the message is successfully accepted. Otherwise, the
3067 action is controlled by the &%-oe%&&'x'& option setting &-- see below.
3070 .cindex "message" "format"
3071 .cindex "format" "message"
3072 .cindex "&""From""& line"
3073 .cindex "UUCP" "&""From""& line"
3074 .cindex "Sendmail compatibility" "&""From""& line"
3075 of the message must be as defined in RFC 2822, except that, for
3076 compatibility with Sendmail and Smail, a line in one of the forms
3078 From sender Fri Jan 5 12:55 GMT 1997
3079 From sender Fri, 5 Jan 97 12:55:01
3081 (with the weekday optional, and possibly with additional text after the date)
3082 is permitted to appear at the start of the message. There appears to be no
3083 authoritative specification of the format of this line. Exim recognizes it by
3084 matching against the regular expression defined by the &%uucp_from_pattern%&
3085 option, which can be changed if necessary.
3087 .oindex "&%-f%&" "overriding &""From""& line"
3088 The specified sender is treated as if it were given as the argument to the
3089 &%-f%& option, but if a &%-f%& option is also present, its argument is used in
3090 preference to the address taken from the message. The caller of Exim must be a
3091 trusted user for the sender of a message to be set in this way.
3093 .cmdopt -bmalware <&'filename'&>
3094 .cindex "testing", "malware"
3095 .cindex "malware scan test"
3096 This debugging option causes Exim to scan the given file or directory
3097 (depending on the used scanner interface),
3098 using the malware scanning framework. The option of &%av_scanner%& influences
3099 this option, so if &%av_scanner%&'s value is dependent upon an expansion then
3100 the expansion should have defaults which apply to this invocation. ACLs are
3101 not invoked, so if &%av_scanner%& references an ACL variable then that variable
3102 will never be populated and &%-bmalware%& will fail.
3104 Exim will have changed working directory before resolving the filename, so
3105 using fully qualified pathnames is advisable. Exim will be running as the Exim
3106 user when it tries to open the file, rather than as the invoking user.
3107 This option requires admin privileges.
3109 The &%-bmalware%& option will not be extended to be more generally useful,
3110 there are better tools for file-scanning. This option exists to help
3111 administrators verify their Exim and AV scanner configuration.
3114 .cindex "address qualification, suppressing"
3115 By default, Exim automatically qualifies unqualified addresses (those
3116 without domains) that appear in messages that are submitted locally (that
3117 is, not over TCP/IP). This qualification applies both to addresses in
3118 envelopes, and addresses in header lines. Sender addresses are qualified using
3119 &%qualify_domain%&, and recipient addresses using &%qualify_recipient%& (which
3120 defaults to the value of &%qualify_domain%&).
3122 Sometimes, qualification is not wanted. For example, if &%-bS%& (batch SMTP) is
3123 being used to re-submit messages that originally came from remote hosts after
3124 content scanning, you probably do not want to qualify unqualified addresses in
3125 header lines. (Such lines will be present only if you have not enabled a header
3126 syntax check in the appropriate ACL.)
3128 The &%-bnq%& option suppresses all qualification of unqualified addresses in
3129 messages that originate on the local host. When this is used, unqualified
3130 addresses in the envelope provoke errors (causing message rejection) and
3131 unqualified addresses in header lines are left alone.
3135 .cindex "configuration options" "extracting"
3136 .cindex "options" "configuration &-- extracting"
3137 If this option is given with no arguments, it causes the values of all Exim's
3138 main configuration options to be written to the standard output. The values
3139 of one or more specific options can be requested by giving their names as
3140 arguments, for example:
3142 exim -bP qualify_domain hold_domains
3144 .cindex "hiding configuration option values"
3145 .cindex "configuration options" "hiding value of"
3146 .cindex "options" "hiding value of"
3147 However, any option setting that is preceded by the word &"hide"& in the
3148 configuration file is not shown in full, except to an admin user. For other
3149 users, the output is as in this example:
3151 mysql_servers = <value not displayable>
3153 If &%config%& is given as an argument, the config is
3154 output, as it was parsed, any include file resolved, any comment removed.
3156 If &%config_file%& is given as an argument, the name of the runtime
3157 configuration file is output. (&%configure_file%& works too, for
3158 backward compatibility.)
3159 If a list of configuration files was supplied, the value that is output here
3160 is the name of the file that was actually used.
3162 .cindex "options" "hiding name of"
3163 If the &%-n%& flag is given, then for most modes of &%-bP%& operation the
3164 name will not be output.
3166 .cindex "daemon" "process id (pid)"
3167 .cindex "pid (process id)" "of daemon"
3168 If &%log_file_path%& or &%pid_file_path%& are given, the names of the
3169 directories where log files and daemon pid files are written are output,
3170 respectively. If these values are unset, log files are written in a
3171 sub-directory of the spool directory called &%log%&, and the pid file is
3172 written directly into the spool directory.
3174 If &%-bP%& is followed by a name preceded by &`+`&, for example,
3176 exim -bP +local_domains
3178 it searches for a matching named list of any type (domain, host, address, or
3179 local part) and outputs what it finds.
3181 .cindex "options" "router &-- extracting"
3182 .cindex "options" "transport &-- extracting"
3183 .cindex "options" "authenticator &-- extracting"
3184 If one of the words &%router%&, &%transport%&, or &%authenticator%& is given,
3185 followed by the name of an appropriate driver instance, the option settings for
3186 that driver are output. For example:
3188 exim -bP transport local_delivery
3190 The generic driver options are output first, followed by the driver's private
3191 options. A list of the names of drivers of a particular type can be obtained by
3192 using one of the words &%router_list%&, &%transport_list%&, or
3193 &%authenticator_list%&, and a complete list of all drivers with their option
3194 settings can be obtained by using &%routers%&, &%transports%&, or
3197 .cindex "environment"
3198 If &%environment%& is given as an argument, the set of environment
3199 variables is output, line by line. Using the &%-n%& flag suppresses the value of the
3202 .cindex "options" "macro &-- extracting"
3203 If invoked by an admin user, then &%macro%&, &%macro_list%& and &%macros%&
3204 are available, similarly to the drivers. Because macros are sometimes used
3205 for storing passwords, this option is restricted.
3206 The output format is one item per line.
3207 For the "-bP macro <name>" form, if no such macro is found
3208 the exit status will be nonzero.
3211 .cindex "queue" "listing messages in"
3212 .cindex "listing" "messages in the queue"
3213 This option requests a listing of the contents of the mail queue on the
3214 standard output. If the &%-bp%& option is followed by a list of message ids,
3215 just those messages are listed. By default, this option can be used only by an
3216 admin user. However, the &%queue_list_requires_admin%& option can be set false
3217 to allow any user to see the queue.
3219 Each message in the queue is displayed as in the following example:
3221 25m 2.9K 0t5C6f-0000c8-00 <alice@wonderland.fict.example>
3222 red.king@looking-glass.fict.example
3225 .cindex "message" "size in queue listing"
3226 .cindex "size" "of message"
3227 The first line contains the length of time the message has been in the queue
3228 (in this case 25 minutes), the size of the message (2.9K), the unique local
3229 identifier for the message, and the message sender, as contained in the
3230 envelope. For bounce messages, the sender address is empty, and appears as
3231 &"<>"&. If the message was submitted locally by an untrusted user who overrode
3232 the default sender address, the user's login name is shown in parentheses
3233 before the sender address.
3235 .cindex "frozen messages" "in queue listing"
3236 If the message is frozen (attempts to deliver it are suspended) then the text
3237 &"*** frozen ***"& is displayed at the end of this line.
3239 The recipients of the message (taken from the envelope, not the headers) are
3240 displayed on subsequent lines. Those addresses to which the message has already
3241 been delivered are marked with the letter D. If an original address gets
3242 expanded into several addresses via an alias or forward file, the original is
3243 displayed with a D only when deliveries for all of its child addresses are
3248 This option operates like &%-bp%&, but in addition it shows delivered addresses
3249 that were generated from the original top level address(es) in each message by
3250 alias or forwarding operations. These addresses are flagged with &"+D"& instead
3255 .cindex "queue" "count of messages on"
3256 This option counts the number of messages in the queue, and writes the total
3257 to the standard output. It is restricted to admin users, unless
3258 &%queue_list_requires_admin%& is set false.
3262 This option operates like &%-bp%&, but the output is not sorted into
3263 chronological order of message arrival. This can speed it up when there are
3264 lots of messages in the queue, and is particularly useful if the output is
3265 going to be post-processed in a way that doesn't need the sorting.
3268 This option is a combination of &%-bpr%& and &%-bpa%&.
3271 This option is a combination of &%-bpr%& and &%-bpu%&.
3275 This option operates like &%-bp%& but shows only undelivered top-level
3276 addresses for each message displayed. Addresses generated by aliasing or
3277 forwarding are not shown, unless the message was deferred after processing by a
3278 router with the &%one_time%& option set.
3282 .cindex "testing" "retry configuration"
3283 .cindex "retry" "configuration testing"
3284 This option is for testing retry rules, and it must be followed by up to three
3285 arguments. It causes Exim to look for a retry rule that matches the values
3286 and to write it to the standard output. For example:
3288 exim -brt bach.comp.mus.example
3289 Retry rule: *.comp.mus.example F,2h,15m; F,4d,30m;
3291 See chapter &<<CHAPretry>>& for a description of Exim's retry rules. The first
3292 argument, which is required, can be a complete address in the form
3293 &'local_part@domain'&, or it can be just a domain name. If the second argument
3294 contains a dot, it is interpreted as an optional second domain name; if no
3295 retry rule is found for the first argument, the second is tried. This ties in
3296 with Exim's behaviour when looking for retry rules for remote hosts &-- if no
3297 rule is found that matches the host, one that matches the mail domain is
3298 sought. Finally, an argument that is the name of a specific delivery error, as
3299 used in setting up retry rules, can be given. For example:
3301 exim -brt haydn.comp.mus.example quota_3d
3302 Retry rule: *@haydn.comp.mus.example quota_3d F,1h,15m
3306 .cindex "testing" "rewriting"
3307 .cindex "rewriting" "testing"
3308 This option is for testing address rewriting rules, and it must be followed by
3309 a single argument, consisting of either a local part without a domain, or a
3310 complete address with a fully qualified domain. Exim outputs how this address
3311 would be rewritten for each possible place it might appear. See chapter
3312 &<<CHAPrewrite>>& for further details.
3315 .cindex "SMTP" "batched incoming"
3316 .cindex "batched SMTP input"
3317 This option is used for batched SMTP input, which is an alternative interface
3318 for non-interactive local message submission. A number of messages can be
3319 submitted in a single run. However, despite its name, this is not really SMTP
3320 input. Exim reads each message's envelope from SMTP commands on the standard
3321 input, but generates no responses. If the caller is trusted, or
3322 &%untrusted_set_sender%& is set, the senders in the SMTP MAIL commands are
3323 believed; otherwise the sender is always the caller of Exim.
3325 The message itself is read from the standard input, in SMTP format (leading
3326 dots doubled), terminated by a line containing just a single dot. An error is
3327 provoked if the terminating dot is missing. A further message may then follow.
3329 As for other local message submissions, the contents of incoming batch SMTP
3330 messages can be checked using the non-SMTP ACL (see chapter &<<CHAPACL>>&).
3331 Unqualified addresses are automatically qualified using &%qualify_domain%& and
3332 &%qualify_recipient%&, as appropriate, unless the &%-bnq%& option is used.
3334 Some other SMTP commands are recognized in the input. HELO and EHLO act
3335 as RSET; VRFY, EXPN, ETRN, and HELP act as NOOP;
3336 QUIT quits, ignoring the rest of the standard input.
3338 .cindex "return code" "for &%-bS%&"
3339 If any error is encountered, reports are written to the standard output and
3340 error streams, and Exim gives up immediately. The return code is 0 if no error
3341 was detected; it is 1 if one or more messages were accepted before the error
3342 was detected; otherwise it is 2.
3344 More details of input using batched SMTP are given in section
3345 &<<SECTincomingbatchedSMTP>>&.
3348 .cindex "SMTP" "local input"
3349 .cindex "local SMTP input"
3350 This option causes Exim to accept one or more messages by reading SMTP commands
3351 on the standard input, and producing SMTP replies on the standard output. SMTP
3352 policy controls, as defined in ACLs (see chapter &<<CHAPACL>>&) are applied.
3353 Some user agents use this interface as a way of passing locally-generated
3354 messages to the MTA.
3357 .cindex "sender" "source of"
3358 this usage, if the caller of Exim is trusted, or &%untrusted_set_sender%& is
3359 set, the senders of messages are taken from the SMTP MAIL commands.
3360 Otherwise the content of these commands is ignored and the sender is set up as
3361 the calling user. Unqualified addresses are automatically qualified using
3362 &%qualify_domain%& and &%qualify_recipient%&, as appropriate, unless the
3363 &%-bnq%& option is used.
3367 &%-bs%& option is also used to run Exim from &'inetd'&, as an alternative to
3368 using a listening daemon. Exim can distinguish the two cases by checking
3369 whether the standard input is a TCP/IP socket. When Exim is called from
3370 &'inetd'&, the source of the mail is assumed to be remote, and the comments
3371 above concerning senders and qualification do not apply. In this situation,
3372 Exim behaves in exactly the same way as it does when receiving a message via
3373 the listening daemon.
3376 .cindex "testing" "addresses"
3377 .cindex "address" "testing"
3378 This option runs Exim in address testing mode, in which each argument is taken
3379 as a recipient address to be tested for deliverability. The results are
3380 written to the standard output. If a test fails, and the caller is not an admin
3381 user, no details of the failure are output, because these might contain
3382 sensitive information such as usernames and passwords for database lookups.
3384 If no arguments are given, Exim runs in an interactive manner, prompting with a
3385 right angle bracket for addresses to be tested.
3387 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3388 &[readline()]& function, because it is running as &'root'& and there are
3391 Each address is handled as if it were the recipient address of a message
3392 (compare the &%-bv%& option). It is passed to the routers and the result is
3393 written to the standard output. However, any router that has
3394 &%no_address_test%& set is bypassed. This can make &%-bt%& easier to use for
3395 genuine routing tests if your first router passes everything to a scanner
3398 .cindex "return code" "for &%-bt%&"
3399 The return code is 2 if any address failed outright; it is 1 if no address
3400 failed outright but at least one could not be resolved for some reason. Return
3401 code 0 is given only when all addresses succeed.
3403 .cindex "duplicate addresses"
3404 &*Note*&: When actually delivering a message, Exim removes duplicate recipient
3405 addresses after routing is complete, so that only one delivery takes place.
3406 This does not happen when testing with &%-bt%&; the full results of routing are
3409 &*Warning*&: &%-bt%& can only do relatively simple testing. If any of the
3410 routers in the configuration makes any tests on the sender address of a
3412 .oindex "&%-f%&" "for address testing"
3413 you can use the &%-f%& option to set an appropriate sender when running
3414 &%-bt%& tests. Without it, the sender is assumed to be the calling user at the
3415 default qualifying domain. However, if you have set up (for example) routers
3416 whose behaviour depends on the contents of an incoming message, you cannot test
3417 those conditions using &%-bt%&. The &%-N%& option provides a possible way of
3421 .cindex "version number of Exim"
3422 This option causes Exim to write the current version number, compilation
3423 number, and compilation date of the &'exim'& binary to the standard output.
3424 It also lists the DBM library that is being used, the optional modules (such as
3425 specific lookup types), the drivers that are included in the binary, and the
3426 name of the runtime configuration file that is in use.
3428 As part of its operation, &%-bV%& causes Exim to read and syntax check its
3429 configuration file. However, this is a static check only. It cannot check
3430 values that are to be expanded. For example, although a misspelt ACL verb is
3431 detected, an error in the verb's arguments is not. You cannot rely on &%-bV%&
3432 alone to discover (for example) all the typos in the configuration; some
3433 realistic testing is needed. The &%-bh%& and &%-N%& options provide more
3434 dynamic testing facilities.
3437 .cindex "verifying address" "using &%-bv%&"
3438 .cindex "address" "verification"
3439 This option runs Exim in address verification mode, in which each argument is
3440 taken as a recipient address to be verified by the routers. (This does
3441 not involve any verification callouts). During normal operation, verification
3442 happens mostly as a consequence processing a &%verify%& condition in an ACL
3443 (see chapter &<<CHAPACL>>&). If you want to test an entire ACL, possibly
3444 including callouts, see the &%-bh%& and &%-bhc%& options.
3446 If verification fails, and the caller is not an admin user, no details of the
3447 failure are output, because these might contain sensitive information such as
3448 usernames and passwords for database lookups.
3450 If no arguments are given, Exim runs in an interactive manner, prompting with a
3451 right angle bracket for addresses to be verified.
3453 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3454 &[readline()]& function, because it is running as &'exim'& and there are
3457 Verification differs from address testing (the &%-bt%& option) in that routers
3458 that have &%no_verify%& set are skipped, and if the address is accepted by a
3459 router that has &%fail_verify%& set, verification fails. The address is
3460 verified as a recipient if &%-bv%& is used; to test verification for a sender
3461 address, &%-bvs%& should be used.
3463 If the &%-v%& option is not set, the output consists of a single line for each
3464 address, stating whether it was verified or not, and giving a reason in the
3465 latter case. Without &%-v%&, generating more than one address by redirection
3466 causes verification to end successfully, without considering the generated
3467 addresses. However, if just one address is generated, processing continues,
3468 and the generated address must verify successfully for the overall verification
3471 When &%-v%& is set, more details are given of how the address has been handled,
3472 and in the case of address redirection, all the generated addresses are also
3473 considered. Verification may succeed for some and fail for others.
3476 .cindex "return code" "for &%-bv%&"
3477 return code is 2 if any address failed outright; it is 1 if no address
3478 failed outright but at least one could not be resolved for some reason. Return
3479 code 0 is given only when all addresses succeed.
3481 If any of the routers in the configuration makes any tests on the sender
3482 address of a message, you should use the &%-f%& option to set an appropriate
3483 sender when running &%-bv%& tests. Without it, the sender is assumed to be the
3484 calling user at the default qualifying domain.
3487 This option acts like &%-bv%&, but verifies the address as a sender rather
3488 than a recipient address. This affects any rewriting and qualification that
3494 .cindex "inetd" "wait mode"
3495 This option runs Exim as a daemon, awaiting incoming SMTP connections,
3496 similarly to the &%-bd%& option. All port specifications on the command-line
3497 and in the configuration file are ignored. Queue-running may not be specified.
3499 In this mode, Exim expects to be passed a socket as fd 0 (stdin) which is
3500 listening for connections. This permits the system to start up and have
3501 inetd (or equivalent) listen on the SMTP ports, starting an Exim daemon for
3502 each port only when the first connection is received.
3504 If the option is given as &%-bw%&<&'time'&> then the time is a timeout, after
3505 which the daemon will exit, which should cause inetd to listen once more.
3507 .cmdopt -C <&'filelist'&>
3508 .cindex "configuration file" "alternate"
3509 .cindex "CONFIGURE_FILE"
3510 .cindex "alternate configuration file"
3511 This option causes Exim to find the runtime configuration file from the given
3512 list instead of from the list specified by the CONFIGURE_FILE
3513 compile-time setting. Usually, the list will consist of just a single filename,
3514 but it can be a colon-separated list of names. In this case, the first
3515 file that exists is used. Failure to open an existing file stops Exim from
3516 proceeding any further along the list, and an error is generated.
3518 When this option is used by a caller other than root, and the list is different
3519 from the compiled-in list, Exim gives up its root privilege immediately, and
3520 runs with the real and effective uid and gid set to those of the caller.
3521 However, if a TRUSTED_CONFIG_LIST file is defined in &_Local/Makefile_&, that
3522 file contains a list of full pathnames, one per line, for configuration files
3523 which are trusted. Root privilege is retained for any configuration file so
3524 listed, as long as the caller is the Exim user (or the user specified in the
3525 CONFIGURE_OWNER option, if any), and as long as the configuration file is
3526 not writeable by inappropriate users or groups.
3528 Leaving TRUSTED_CONFIG_LIST unset precludes the possibility of testing a
3529 configuration using &%-C%& right through message reception and delivery,
3530 even if the caller is root. The reception works, but by that time, Exim is
3531 running as the Exim user, so when it re-executes to regain privilege for the
3532 delivery, the use of &%-C%& causes privilege to be lost. However, root can
3533 test reception and delivery using two separate commands (one to put a message
3534 in the queue, using &%-odq%&, and another to do the delivery, using &%-M%&).
3536 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
3537 prefix string with which any file named in a &%-C%& command line option
3538 must start. In addition, the filename must not contain the sequence &`/../`&.
3539 However, if the value of the &%-C%& option is identical to the value of
3540 CONFIGURE_FILE in &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as
3541 usual. There is no default setting for ALT_CONFIG_PREFIX; when it is
3542 unset, any filename can be used with &%-C%&.
3544 ALT_CONFIG_PREFIX can be used to confine alternative configuration files
3545 to a directory to which only root has access. This prevents someone who has
3546 broken into the Exim account from running a privileged Exim with an arbitrary
3549 The &%-C%& facility is useful for ensuring that configuration files are
3550 syntactically correct, but cannot be used for test deliveries, unless the
3551 caller is privileged, or unless it is an exotic configuration that does not
3552 require privilege. No check is made on the owner or group of the files
3553 specified by this option.
3556 .vitem &%-D%&<&'macro'&>=<&'value'&>
3558 .cindex "macro" "setting on command line"
3559 This option can be used to override macro definitions in the configuration file
3560 (see section &<<SECTmacrodefs>>&). However, like &%-C%&, if it is used by an
3561 unprivileged caller, it causes Exim to give up its root privilege.
3562 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
3563 completely disabled, and its use causes an immediate error exit.
3565 If WHITELIST_D_MACROS is defined in &_Local/Makefile_& then it should be a
3566 colon-separated list of macros which are considered safe and, if &%-D%& only
3567 supplies macros from this list, and the values are acceptable, then Exim will
3568 not give up root privilege if the caller is root, the Exim run-time user, or
3569 the CONFIGURE_OWNER, if set. This is a transition mechanism and is expected
3570 to be removed in the future. Acceptable values for the macros satisfy the
3571 regexp: &`^[A-Za-z0-9_/.-]*$`&
3573 The entire option (including equals sign if present) must all be within one
3574 command line item. &%-D%& can be used to set the value of a macro to the empty
3575 string, in which case the equals sign is optional. These two commands are
3581 To include spaces in a macro definition item, quotes must be used. If you use
3582 quotes, spaces are permitted around the macro name and the equals sign. For
3585 exim '-D ABC = something' ...
3587 &%-D%& may be repeated up to 10 times on a command line.
3588 Only macro names up to 22 letters long can be set.
3591 .vitem &%-d%&<&'debug&~options'&>
3593 .cindex "debugging" "list of selectors"
3594 .cindex "debugging" "&%-d%& option"
3595 This option causes debugging information to be written to the standard
3596 error stream. It is restricted to admin users because debugging output may show
3597 database queries that contain password information. Also, the details of users'
3598 filter files should be protected. If a non-admin user uses &%-d%&, Exim
3599 writes an error message to the standard error stream and exits with a non-zero
3602 When &%-d%& is used, &%-v%& is assumed. If &%-d%& is given on its own, a lot of
3603 standard debugging data is output. This can be reduced, or increased to include
3604 some more rarely needed information, by directly following &%-d%& with a string
3605 made up of names preceded by plus or minus characters. These add or remove sets
3606 of debugging data, respectively. For example, &%-d+filter%& adds filter
3607 debugging, whereas &%-d-all+filter%& selects only filter debugging. Note that
3608 no spaces are allowed in the debug setting. The available debugging categories
3610 .itable none 0 0 2 20* left 80* left
3611 .irow acl "ACL interpretation"
3612 .irow auth "authenticators"
3613 .irow deliver "general delivery logic"
3614 .irow dns "DNS lookups (see also resolver)"
3615 .irow dnsbl "DNS black list (aka RBL) code"
3616 .irow exec "arguments for &[execv()]& calls"
3617 .irow expand "detailed debugging for string expansions"
3618 .irow filter "filter handling"
3619 .irow hints_lookup "hints data lookups"
3620 .irow host_lookup "all types of name-to-IP address handling"
3621 .irow ident "ident lookup"
3622 .irow interface "lists of local interfaces"
3623 .irow lists "matching things in lists"
3624 .irow load "system load checks"
3625 .irow local_scan "can be used by &[local_scan()]& (see chapter &&&
3626 &<<CHAPlocalscan>>&)"
3627 .irow lookup "general lookup code and all lookups"
3628 .irow memory "memory handling"
3629 .irow noutf8 "modifier: avoid UTF-8 line-drawing"
3630 .irow pid "modifier: add pid to debug output lines"
3631 .irow process_info "setting info for the process log"
3632 .irow queue_run "queue runs"
3633 .irow receive "general message reception logic"
3634 .irow resolver "turn on the DNS resolver's debugging output"
3635 .irow retry "retry handling"
3636 .irow rewrite "address rewriting""
3637 .irow route "address routing"
3638 .irow timestamp "modifier: add timestamp to debug output lines"
3639 .irow tls "TLS logic"
3640 .irow transport "transports"
3641 .irow uid "changes of uid/gid and looking up uid/gid"
3642 .irow verify "address verification logic"
3643 .irow all "almost all of the above (see below), and also &%-v%&"
3645 The &`all`& option excludes &`memory`& when used as &`+all`&, but includes it
3646 for &`-all`&. The reason for this is that &`+all`& is something that people
3647 tend to use when generating debug output for Exim maintainers. If &`+memory`&
3648 is included, an awful lot of output that is very rarely of interest is
3649 generated, so it now has to be explicitly requested. However, &`-all`& does
3650 turn everything off.
3652 .cindex "resolver, debugging output"
3653 .cindex "DNS resolver, debugging output"
3654 The &`resolver`& option produces output only if the DNS resolver was compiled
3655 with DEBUG enabled. This is not the case in some operating systems. Also,
3656 unfortunately, debugging output from the DNS resolver is written to stdout
3659 The default (&%-d%& with no argument) omits &`expand`&, &`filter`&,
3660 &`interface`&, &`load`&, &`memory`&, &`pid`&, &`resolver`&, and &`timestamp`&.
3661 However, the &`pid`& selector is forced when debugging is turned on for a
3662 daemon, which then passes it on to any re-executed Exims. Exim also
3663 automatically adds the pid to debug lines when several remote deliveries are
3666 The &`timestamp`& selector causes the current time to be inserted at the start
3667 of all debug output lines. This can be useful when trying to track down delays
3670 .cindex debugging "UTF-8 in"
3671 .cindex UTF-8 "in debug output"
3672 The &`noutf8`& selector disables the use of
3673 UTF-8 line-drawing characters to group related information.
3674 When disabled. ascii-art is used instead.
3675 Using the &`+all`& option does not set this modifier,
3677 If the &%debug_print%& option is set in any driver, it produces output whenever
3678 any debugging is selected, or if &%-v%& is used.
3680 .vitem &%-dd%&<&'debug&~options'&>
3682 This option behaves exactly like &%-d%& except when used on a command that
3683 starts a daemon process. In that case, debugging is turned off for the
3684 subprocesses that the daemon creates. Thus, it is useful for monitoring the
3685 behaviour of the daemon without creating as much output as full debugging does.
3688 This is an obsolete option that is now a no-op. It used to affect the way Exim
3689 handled CR and LF characters in incoming messages. What happens now is
3690 described in section &<<SECTlineendings>>&.
3693 .cindex "bounce message" "generating"
3694 This option specifies that an incoming message is a locally-generated delivery
3695 failure report. It is used internally by Exim when handling delivery failures
3696 and is not intended for external use. Its only effect is to stop Exim
3697 generating certain messages to the postmaster, as otherwise message cascades
3698 could occur in some situations. As part of the same option, a message id may
3699 follow the characters &%-E%&. If it does, the log entry for the receipt of the
3700 new message contains the id, following &"R="&, as a cross-reference.
3703 .oindex "&%-e%&&'x'&"
3704 There are a number of Sendmail options starting with &%-oe%& which seem to be
3705 called by various programs without the leading &%o%& in the option. For
3706 example, the &%vacation%& program uses &%-eq%&. Exim treats all options of the
3707 form &%-e%&&'x'& as synonymous with the corresponding &%-oe%&&'x'& options.
3709 .cmdopt -F <&'string'&>
3710 .cindex "sender" "name"
3711 .cindex "name" "of sender"
3712 This option sets the sender's full name for use when a locally-generated
3713 message is being accepted. In the absence of this option, the user's &'gecos'&
3714 entry from the password data is used. As users are generally permitted to alter
3715 their &'gecos'& entries, no security considerations are involved. White space
3716 between &%-F%& and the <&'string'&> is optional.
3718 .cmdopt -f <&'address'&>
3719 .cindex "sender" "address"
3720 .cindex "address" "sender"
3721 .cindex "trusted users"
3722 .cindex "envelope from"
3723 .cindex "envelope sender"
3724 .cindex "user" "trusted"
3725 This option sets the address of the envelope sender of a locally-generated
3726 message (also known as the return path). The option can normally be used only
3727 by a trusted user, but &%untrusted_set_sender%& can be set to allow untrusted
3730 Processes running as root or the Exim user are always trusted. Other
3731 trusted users are defined by the &%trusted_users%& or &%trusted_groups%&
3732 options. In the absence of &%-f%&, or if the caller is not trusted, the sender
3733 of a local message is set to the caller's login name at the default qualify
3736 There is one exception to the restriction on the use of &%-f%&: an empty sender
3737 can be specified by any user, trusted or not, to create a message that can
3738 never provoke a bounce. An empty sender can be specified either as an empty
3739 string, or as a pair of angle brackets with nothing between them, as in these
3740 examples of shell commands:
3742 exim -f '<>' user@domain
3743 exim -f "" user@domain
3745 In addition, the use of &%-f%& is not restricted when testing a filter file
3746 with &%-bf%& or when testing or verifying addresses using the &%-bt%& or
3749 Allowing untrusted users to change the sender address does not of itself make
3750 it possible to send anonymous mail. Exim still checks that the &'From:'& header
3751 refers to the local user, and if it does not, it adds a &'Sender:'& header,
3752 though this can be overridden by setting &%no_local_from_check%&.
3755 .cindex "&""From""& line"
3756 space between &%-f%& and the <&'address'&> is optional (that is, they can be
3757 given as two arguments or one combined argument). The sender of a
3758 locally-generated message can also be set (when permitted) by an initial
3759 &"From&~"& line in the message &-- see the description of &%-bm%& above &-- but
3760 if &%-f%& is also present, it overrides &"From&~"&.
3763 .cindex "submission fixups, suppressing (command-line)"
3764 This option is equivalent to an ACL applying:
3766 control = suppress_local_fixups
3768 for every message received. Note that Sendmail will complain about such
3769 bad formatting, where Exim silently just does not fix it up. This may change
3772 As this affects audit information, the caller must be a trusted user to use
3775 .cmdopt -h <&'number'&>
3776 .cindex "Sendmail compatibility" "&%-h%& option ignored"
3777 This option is accepted for compatibility with Sendmail, but has no effect. (In
3778 Sendmail it overrides the &"hop count"& obtained by counting &'Received:'&
3782 .cindex "Solaris" "&'mail'& command"
3783 .cindex "dot" "in incoming non-SMTP message"
3784 This option, which has the same effect as &%-oi%&, specifies that a dot on a
3785 line by itself should not terminate an incoming, non-SMTP message.
3786 Solaris 2.4 (SunOS 5.4) Sendmail has a similar &%-i%& processing option
3787 &url(https://docs.oracle.com/cd/E19457-01/801-6680-1M/801-6680-1M.pdf),
3788 p. 1M-529), and therefore a &%-oi%& command line option, which both are used
3789 by its &'mailx'& command.
3791 .cmdopt -L <&'tag'&>
3792 .cindex "syslog" "process name; set with flag"
3793 This option is equivalent to setting &%syslog_processname%& in the config
3794 file and setting &%log_file_path%& to &`syslog`&.
3795 Its use is restricted to administrators. The configuration file has to be
3796 read and parsed, to determine access rights, before this is set and takes
3797 effect, so early configuration file errors will not honour this flag.
3799 The tag should not be longer than 32 characters.
3801 .cmdopt -M <&'message&~id'&>&~<&'message&~id'&>&~...
3802 .cindex "forcing delivery"
3803 .cindex "delivery" "forcing attempt"
3804 .cindex "frozen messages" "forcing delivery"
3805 This option requests Exim to run a delivery attempt on each message in turn. If
3806 any of the messages are frozen, they are automatically thawed before the
3807 delivery attempt. The settings of &%queue_domains%&, &%queue_smtp_domains%&,
3808 and &%hold_domains%& are ignored.
3811 .cindex "hints database" "overriding retry hints"
3812 hints for any of the addresses are overridden &-- Exim tries to deliver even if
3813 the normal retry time has not yet been reached. This option requires the caller
3814 to be an admin user. However, there is an option called &%prod_requires_admin%&
3815 which can be set false to relax this restriction (and also the same requirement
3816 for the &%-q%&, &%-R%&, and &%-S%& options).
3818 The deliveries happen synchronously, that is, the original Exim process does
3819 not terminate until all the delivery attempts have finished. No output is
3820 produced unless there is a serious error. If you want to see what is happening,
3821 use the &%-v%& option as well, or inspect Exim's main log.
3823 .cmdopt -Mar <&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3824 .cindex "message" "adding recipients"
3825 .cindex "recipient" "adding"
3826 This option requests Exim to add the addresses to the list of recipients of the
3827 message (&"ar"& for &"add recipients"&). The first argument must be a message
3828 id, and the remaining ones must be email addresses. However, if the message is
3829 active (in the middle of a delivery attempt), it is not altered. This option
3830 can be used only by an admin user.
3832 .vitem "&%-MC%&&~<&'transport'&>&~<&'hostname'&>&&&
3834 &~<&'sequence&~number'&>&&&
3835 &~<&'message&~id'&>"
3837 .cindex "SMTP" "passed connection"
3838 .cindex "SMTP" "multiple deliveries"
3839 .cindex "multiple SMTP deliveries"
3840 This option is not intended for use by external callers. It is used internally
3841 by Exim to invoke another instance of itself to deliver a waiting message using
3842 an existing SMTP connection, which is passed as the standard input. Details are
3843 given in chapter &<<CHAPSMTP>>&. This must be the final option, and the caller
3844 must be root or the Exim user in order to use it.
3847 This option is not intended for use by external callers. It is used internally
3848 by Exim in conjunction with the &%-MC%& option. It signifies that the
3849 connection to the remote host has been authenticated.
3852 This option is not intended for use by external callers. It is used internally
3853 by Exim in conjunction with the &%-MC%& option. It signifies that the
3854 remote host supports the ESMTP &_DSN_& extension.
3857 This option is not intended for use by external callers. It is used internally
3858 by Exim in conjunction with the &%-d%& option
3859 to pass on an information string on the purpose of the process.
3861 .cmdopt -MCG <&'queue&~name'&>
3862 This option is not intended for use by external callers. It is used internally
3863 by Exim in conjunction with the &%-MC%& option. It signifies that an
3864 alternate queue is used, named by the following argument.
3867 This option is not intended for use by external callers. It is used internally
3868 by Exim in conjunction with the &%-MC%& option. It signifies that a
3869 remote host supports the ESMTP &_CHUNKING_& extension.
3872 This option is not intended for use by external callers. It is used internally
3873 by Exim in conjunction with the &%-MC%& option. It signifies that the server to
3874 which Exim is connected advertised limits on numbers of mails, recipients or
3876 The limits are given by the following three arguments.
3879 This option is not intended for use by external callers. It is used internally
3880 by Exim in conjunction with the &%-MC%& option. It signifies that the server to
3881 which Exim is connected supports pipelining.
3884 This option is not intended for use by external callers. It is used internally
3885 by Exim in conjunction with the &%-MC%& option. It signifies that the connection
3886 t a remote server is via a SOCKS proxy, using addresses and ports given by
3887 the following four arguments.
3889 .cmdopt -MCQ <&'process&~id'&>&~<&'pipe&~fd'&>
3890 This option is not intended for use by external callers. It is used internally
3891 by Exim in conjunction with the &%-MC%& option when the original delivery was
3892 started by a queue runner. It passes on the process id of the queue runner,
3893 together with the file descriptor number of an open pipe. Closure of the pipe
3894 signals the final completion of the sequence of processes that are passing
3895 messages through the same SMTP connection.
3897 .cmdopt -MCq <&'recipient&~address'&>&~<&'size'&>
3898 This option is not intended for use by external callers. It is used internally
3899 by Exim to implement quota checking for local users.
3902 This option is not intended for use by external callers. It is used internally
3903 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3904 ESMTP SIZE option should be used on messages delivered down the existing
3908 This option is not intended for use by external callers. It is used internally
3909 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3910 host to which Exim is connected supports TLS encryption.
3912 .vitem &%-MCr%&&~<&'SNI'&> &&&
3916 These options are not intended for use by external callers. It is used internally
3917 by Exim in conjunction with the &%-MCt%& option, and passes on the fact that
3918 a TLS Server Name Indication was sent as part of the channel establishment.
3919 The argument gives the SNI string.
3920 The "r" variant indicates a DANE-verified connection.
3922 .cmdopt -MCt <&'IP&~address'&>&~<&'port'&>&~<&'cipher'&>
3923 This option is not intended for use by external callers. It is used internally
3924 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3925 connection is being proxied by a parent process for handling TLS encryption.
3926 The arguments give the local address and port being proxied, and the TLS cipher.
3928 .cmdopt -Mc <&'message&~id'&>&~<&'message&~id'&>&~...
3929 .cindex "hints database" "not overridden by &%-Mc%&"
3930 .cindex "delivery" "manually started &-- not forced"
3931 This option requests Exim to run a delivery attempt on each message, in turn,
3932 but unlike the &%-M%& option, it does check for retry hints, and respects any
3933 that are found. This option is not very useful to external callers. It is
3934 provided mainly for internal use by Exim when it needs to re-invoke itself in
3935 order to regain root privilege for a delivery (see chapter &<<CHAPsecurity>>&).
3936 However, &%-Mc%& can be useful when testing, in order to run a delivery that
3937 respects retry times and other options such as &%hold_domains%& that are
3938 overridden when &%-M%& is used. Such a delivery does not count as a queue run.
3939 If you want to run a specific delivery as if in a queue run, you should use
3940 &%-q%& with a message id argument. A distinction between queue run deliveries
3941 and other deliveries is made in one or two places.
3943 .cmdopt -Mes <&'message&~id'&>&~<&'address'&>
3944 .cindex "message" "changing sender"
3945 .cindex "sender" "changing"
3946 This option requests Exim to change the sender address in the message to the
3947 given address, which must be a fully qualified address or &"<>"& (&"es"& for
3948 &"edit sender"&). There must be exactly two arguments. The first argument must
3949 be a message id, and the second one an email address. However, if the message
3950 is active (in the middle of a delivery attempt), its status is not altered.
3951 This option can be used only by an admin user.
3953 .cmdopt -Mf <&'message&~id'&>&~<&'message&~id'&>&~...
3954 .cindex "freezing messages"
3955 .cindex "message" "manually freezing"
3956 This option requests Exim to mark each listed message as &"frozen"&. This
3957 prevents any delivery attempts taking place until the message is &"thawed"&,
3958 either manually or as a result of the &%auto_thaw%& configuration option.
3959 However, if any of the messages are active (in the middle of a delivery
3960 attempt), their status is not altered. This option can be used only by an admin
3963 .cmdopt -Mg <&'message&~id'&>&~<&'message&~id'&>&~...
3964 .cindex "giving up on messages"
3965 .cindex "message" "abandoning delivery attempts"
3966 .cindex "delivery" "abandoning further attempts"
3967 This option requests Exim to give up trying to deliver the listed messages,
3968 including any that are frozen. However, if any of the messages are active,
3969 their status is not altered. For non-bounce messages, a delivery error message
3970 is sent to the sender, containing the text &"cancelled by administrator"&.
3971 Bounce messages are just discarded. This option can be used only by an admin
3974 .cmdopt -MG <&'queue&~name'&>&~<&'message&~id'&>&~<&'message&~id'&>&~...
3976 .cindex "named queues" "moving messages"
3977 .cindex "queue" "moving messages"
3978 This option requests that each listed message be moved from its current
3979 queue to the given named queue.
3980 The destination queue name argument is required, but can be an empty
3981 string to define the default queue.
3982 If the messages are not currently located in the default queue,
3983 a &%-qG<name>%& option will be required to define the source queue.
3985 .cmdopt -Mmad <&'message&~id'&>&~<&'message&~id'&>&~...
3986 .cindex "delivery" "cancelling all"
3987 This option requests Exim to mark all the recipient addresses in the messages
3988 as already delivered (&"mad"& for &"mark all delivered"&). However, if any
3989 message is active (in the middle of a delivery attempt), its status is not
3990 altered. This option can be used only by an admin user.
3992 .cmdopt -Mmd <&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3993 .cindex "delivery" "cancelling by address"
3994 .cindex "recipient" "removing"
3995 .cindex "removing recipients"
3996 This option requests Exim to mark the given addresses as already delivered
3997 (&"md"& for &"mark delivered"&). The first argument must be a message id, and
3998 the remaining ones must be email addresses. These are matched to recipient
3999 addresses in the message in a case-sensitive manner. If the message is active
4000 (in the middle of a delivery attempt), its status is not altered. This option
4001 can be used only by an admin user.
4003 .cmdopt -Mrm <&'message&~id'&>&~<&'message&~id'&>&~...
4004 .cindex "removing messages"
4005 .cindex "abandoning mail"
4006 .cindex "message" "manually discarding"
4007 This option requests Exim to remove the given messages from the queue. No
4008 bounce messages are sent; each message is simply forgotten. However, if any of
4009 the messages are active, their status is not altered. This option can be used
4010 only by an admin user or by the user who originally caused the message to be
4011 placed in the queue.
4016 . .cindex REQUIRETLS
4017 . This option is used to request REQUIRETLS processing on the message.
4018 . It is used internally by Exim in conjunction with -E when generating
4022 .cmdopt -Mset <&'message&~id'&>
4023 .cindex "testing" "string expansion"
4024 .cindex "expansion" "testing"
4025 This option is useful only in conjunction with &%-be%& (that is, when testing
4026 string expansions). Exim loads the given message from its spool before doing
4027 the test expansions, thus setting message-specific variables such as
4028 &$message_size$& and the header variables. The &$recipients$& variable is made
4029 available. This feature is provided to make it easier to test expansions that
4030 make use of these variables. However, this option can be used only by an admin
4031 user. See also &%-bem%&.
4033 .cmdopt -Mt <&'message&~id'&>&~<&'message&~id'&>&~...
4034 .cindex "thawing messages"
4035 .cindex "unfreezing messages"
4036 .cindex "frozen messages" "thawing"
4037 .cindex "message" "thawing frozen"
4038 This option requests Exim to &"thaw"& any of the listed messages that are
4039 &"frozen"&, so that delivery attempts can resume. However, if any of the
4040 messages are active, their status is not altered. This option can be used only
4043 .cmdopt -Mvb <&'message&~id'&>
4044 .cindex "listing" "message body"
4045 .cindex "message" "listing body of"
4046 This option causes the contents of the message body (-D) spool file to be
4047 written to the standard output. This option can be used only by an admin user.
4049 .cmdopt -Mvc <&'message&~id'&>
4050 .cindex "message" "listing in RFC 2822 format"
4051 .cindex "listing" "message in RFC 2822 format"
4052 This option causes a copy of the complete message (header lines plus body) to
4053 be written to the standard output in RFC 2822 format. This option can be used
4054 only by an admin user.
4056 .cmdopt -Mvh <&'message&~id'&>
4057 .cindex "listing" "message headers"
4058 .cindex "header lines" "listing"
4059 .cindex "message" "listing header lines"
4060 This option causes the contents of the message headers (-H) spool file to be
4061 written to the standard output. This option can be used only by an admin user.
4063 .cmdopt -Mvl <&'message&~id'&>
4064 .cindex "listing" "message log"
4065 .cindex "message" "listing message log"
4066 This option causes the contents of the message log spool file to be written to
4067 the standard output. This option can be used only by an admin user.
4070 This is a synonym for &%-om%& that is accepted by Sendmail
4071 (&url(https://docs.oracle.com/cd/E19457-01/801-6680-1M/801-6680-1M.pdf)
4072 p. 1M-258), so Exim treats it that way too.
4075 .cindex "debugging" "&%-N%& option"
4076 .cindex "debugging" "suppressing delivery"
4077 This is a debugging option that inhibits delivery of a message at the transport
4078 level. It implies &%-v%&. Exim goes through many of the motions of delivery &--
4079 it just doesn't actually transport the message, but instead behaves as if it
4080 had successfully done so. However, it does not make any updates to the retry
4081 database, and the log entries for deliveries are flagged with &"*>"& rather
4084 Because &%-N%& discards any message to which it applies, only root or the Exim
4085 user are allowed to use it with &%-bd%&, &%-q%&, &%-R%& or &%-M%&. In other
4086 words, an ordinary user can use it only when supplying an incoming message to
4087 which it will apply. Although transportation never fails when &%-N%& is set, an
4088 address may be deferred because of a configuration problem on a transport, or a
4089 routing problem. Once &%-N%& has been used for a delivery attempt, it sticks to
4090 the message, and applies to any subsequent delivery attempts that may happen
4094 This option is interpreted by Sendmail to mean &"no aliasing"&.
4095 For normal modes of operation, it is ignored by Exim.
4096 When combined with &%-bP%& it makes the output more terse (suppresses
4097 option names, environment values and config pretty printing).
4099 .cmdopt -O <&'data'&>
4100 This option is interpreted by Sendmail to mean &`set option`&. It is ignored by
4103 .cmdopt -oA <&'file&~name'&>
4104 .cindex "Sendmail compatibility" "&%-oA%& option"
4105 This option is used by Sendmail in conjunction with &%-bi%& to specify an
4106 alternative alias filename. Exim handles &%-bi%& differently; see the
4110 .cindex "SMTP" "passed connection"
4111 .cindex "SMTP" "multiple deliveries"
4112 .cindex "multiple SMTP deliveries"
4113 This is a debugging option which limits the maximum number of messages that can
4114 be delivered down one SMTP connection, overriding the value set in any &(smtp)&
4115 transport. If <&'n'&> is omitted, the limit is set to 1.
4118 .cindex "background delivery"
4119 .cindex "delivery" "in the background"
4120 This option applies to all modes in which Exim accepts incoming messages,
4121 including the listening daemon. It requests &"background"& delivery of such
4122 messages, which means that the accepting process automatically starts a
4123 delivery process for each message received, but does not wait for the delivery
4124 processes to finish.
4126 When all the messages have been received, the reception process exits,
4127 leaving the delivery processes to finish in their own time. The standard output
4128 and error streams are closed at the start of each delivery process.
4129 This is the default action if none of the &%-od%& options are present.
4131 If one of the queueing options in the configuration file
4132 (&%queue_only%& or &%queue_only_file%&, for example) is in effect, &%-odb%&
4133 overrides it if &%queue_only_override%& is set true, which is the default
4134 setting. If &%queue_only_override%& is set false, &%-odb%& has no effect.
4137 .cindex "foreground delivery"
4138 .cindex "delivery" "in the foreground"
4139 This option requests &"foreground"& (synchronous) delivery when Exim has
4140 accepted a locally-generated message. (For the daemon it is exactly the same as
4141 &%-odb%&.) A delivery process is automatically started to deliver the message,
4142 and Exim waits for it to complete before proceeding.
4144 The original Exim reception process does not finish until the delivery
4145 process for the final message has ended. The standard error stream is left open
4148 However, like &%-odb%&, this option has no effect if &%queue_only_override%& is
4149 false and one of the queueing options in the configuration file is in effect.
4151 If there is a temporary delivery error during foreground delivery, the
4152 message is left in the queue for later delivery, and the original reception
4153 process exits. See chapter &<<CHAPnonqueueing>>& for a way of setting up a
4154 restricted configuration that never queues messages.
4158 This option is synonymous with &%-odf%&. It is provided for compatibility with
4162 .cindex "non-immediate delivery"
4163 .cindex "delivery" "suppressing immediate"
4164 .cindex "queueing incoming messages"
4165 This option applies to all modes in which Exim accepts incoming messages,
4166 including the listening daemon. It specifies that the accepting process should
4167 not automatically start a delivery process for each message received. Messages
4168 are placed in the queue, and remain there until a subsequent queue runner
4169 process encounters them. There are several configuration options (such as
4170 &%queue_only%&) that can be used to queue incoming messages under certain
4171 conditions. This option overrides all of them and also &%-odqs%&. It always
4175 .cindex "SMTP" "delaying delivery"
4176 .cindex "first pass routing"
4177 This option is a hybrid between &%-odb%&/&%-odi%& and &%-odq%&.
4178 However, like &%-odb%& and &%-odi%&, this option has no effect if
4179 &%queue_only_override%& is false and one of the queueing options in the
4180 configuration file is in effect.
4182 When &%-odqs%& does operate, a delivery process is started for each incoming
4183 message, in the background by default, but in the foreground if &%-odi%& is
4184 also present. The recipient addresses are routed, and local deliveries are done
4185 in the normal way. However, if any SMTP deliveries are required, they are not
4186 done at this time, so the message remains in the queue until a subsequent queue
4187 runner process encounters it. Because routing was done, Exim knows which
4188 messages are waiting for which hosts, and so a number of messages for the same
4189 host can be sent in a single SMTP connection. The &%queue_smtp_domains%&
4190 configuration option has the same effect for specific domains. See also the
4194 .cindex "error" "reporting"
4195 If an error is detected while a non-SMTP message is being received (for
4196 example, a malformed address), the error is reported to the sender in a mail
4199 .cindex "return code" "for &%-oee%&"
4201 this error message is successfully sent, the Exim receiving process
4202 exits with a return code of zero. If not, the return code is 2 if the problem
4203 is that the original message has no recipients, or 1 for any other error.
4204 This is the default &%-oe%&&'x'& option if Exim is called as &'rmail'&.
4207 .cindex "error" "reporting"
4208 .cindex "return code" "for &%-oem%&"
4209 This is the same as &%-oee%&, except that Exim always exits with a non-zero
4210 return code, whether or not the error message was successfully sent.
4211 This is the default &%-oe%&&'x'& option, unless Exim is called as &'rmail'&.
4214 .cindex "error" "reporting"
4215 If an error is detected while a non-SMTP message is being received, the
4216 error is reported by writing a message to the standard error file (stderr).
4217 .cindex "return code" "for &%-oep%&"
4218 The return code is 1 for all errors.
4221 .cindex "error" "reporting"
4222 This option is supported for compatibility with Sendmail, but has the same
4226 .cindex "error" "reporting"
4227 This option is supported for compatibility with Sendmail, but has the same
4231 .cindex "dot" "in incoming non-SMTP message"
4232 This option, which has the same effect as &%-i%&, specifies that a dot on a
4233 line by itself should not terminate an incoming, non-SMTP message. Otherwise, a
4234 single dot does terminate, though Exim does no special processing for other
4235 lines that start with a dot. This option is set by default if Exim is called as
4236 &'rmail'&. See also &%-ti%&.
4239 This option is treated as synonymous with &%-oi%&.
4241 .cmdopt -oMa <&'host&~address'&>
4242 .cindex "sender" "host address, specifying for local message"
4243 A number of options starting with &%-oM%& can be used to set values associated
4244 with remote hosts on locally-submitted messages (that is, messages not received
4245 over TCP/IP). These options can be used by any caller in conjunction with the
4246 &%-bh%&, &%-be%&, &%-bf%&, &%-bF%&, &%-bt%&, or &%-bv%& testing options. In
4247 other circumstances, they are ignored unless the caller is trusted.
4249 The &%-oMa%& option sets the sender host address. This may include a port
4250 number at the end, after a full stop (period). For example:
4252 exim -bs -oMa 10.9.8.7.1234
4254 An alternative syntax is to enclose the IP address in square brackets,
4255 followed by a colon and the port number:
4257 exim -bs -oMa [10.9.8.7]:1234
4259 The IP address is placed in the &$sender_host_address$& variable, and the
4260 port, if present, in &$sender_host_port$&. If both &%-oMa%& and &%-bh%&
4261 are present on the command line, the sender host IP address is taken from
4262 whichever one is last.
4264 .cmdopt -oMaa <&'name'&>
4265 .cindex "authentication" "name, specifying for local message"
4266 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMaa%&
4267 option sets the value of &$sender_host_authenticated$& (the authenticator
4268 name). See chapter &<<CHAPSMTPAUTH>>& for a discussion of SMTP authentication.
4269 This option can be used with &%-bh%& and &%-bs%& to set up an
4270 authenticated SMTP session without actually using the SMTP AUTH command.
4272 .cmdopt -oMai <&'string'&>
4273 .cindex "authentication" "id, specifying for local message"
4274 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMai%&
4275 option sets the value of &$authenticated_id$& (the id that was authenticated).
4276 This overrides the default value (the caller's login id, except with &%-bh%&,
4277 where there is no default) for messages from local sources. See chapter
4278 &<<CHAPSMTPAUTH>>& for a discussion of authenticated ids.
4280 .cmdopt -oMas <&'address'&>
4281 .cindex "authentication" "sender, specifying for local message"
4282 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMas%&
4283 option sets the authenticated sender value in &$authenticated_sender$&. It
4284 overrides the sender address that is created from the caller's login id for
4285 messages from local sources, except when &%-bh%& is used, when there is no
4286 default. For both &%-bh%& and &%-bs%&, an authenticated sender that is
4287 specified on a MAIL command overrides this value. See chapter
4288 &<<CHAPSMTPAUTH>>& for a discussion of authenticated senders.
4290 .cmdopt -oMi <&'interface&~address'&>
4291 .cindex "interface" "address, specifying for local message"
4292 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMi%&
4293 option sets the IP interface address value. A port number may be included,
4294 using the same syntax as for &%-oMa%&. The interface address is placed in
4295 &$received_ip_address$& and the port number, if present, in &$received_port$&.
4297 .cmdopt -oMm <&'message&~reference'&>
4298 .cindex "message reference" "message reference, specifying for local message"
4299 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMm%&
4300 option sets the message reference, e.g. message-id, and is logged during
4301 delivery. This is useful when some kind of audit trail is required to tie
4302 messages together. The format of the message reference is checked and will
4303 abort if the format is invalid. The option will only be accepted if exim is
4304 running in trusted mode, not as any regular user.
4306 The best example of a message reference is when Exim sends a bounce message.
4307 The message reference is the message-id of the original message for which Exim
4308 is sending the bounce.
4310 .cmdopt -oMr <&'protocol&~name'&>
4311 .cindex "protocol, specifying for local message"
4312 .vindex "&$received_protocol$&"
4313 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMr%&
4314 option sets the received protocol value that is stored in
4315 &$received_protocol$&. However, it does not apply (and is ignored) when &%-bh%&
4316 or &%-bs%& is used. For &%-bh%&, the protocol is forced to one of the standard
4317 SMTP protocol names (see the description of &$received_protocol$& in section
4318 &<<SECTexpvar>>&). For &%-bs%&, the protocol is always &"local-"& followed by
4319 one of those same names. For &%-bS%& (batched SMTP) however, the protocol can
4320 be set by &%-oMr%&. Repeated use of this option is not supported.
4322 .cmdopt -oMs <&'host&~name'&>
4323 .cindex "sender" "host name, specifying for local message"
4324 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMs%&
4325 option sets the sender host name in &$sender_host_name$&. When this option is
4326 present, Exim does not attempt to look up a host name from an IP address; it
4327 uses the name it is given.
4329 .cmdopt -oMt <&'ident&~string'&>
4330 .cindex "sender" "ident string, specifying for local message"
4331 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMt%&
4332 option sets the sender ident value in &$sender_ident$&. The default setting for
4333 local callers is the login id of the calling process, except when &%-bh%& is
4334 used, when there is no default.
4337 .cindex "Sendmail compatibility" "&%-om%& option ignored"
4338 In Sendmail, this option means &"me too"&, indicating that the sender of a
4339 message should receive a copy of the message if the sender appears in an alias
4340 expansion. Exim always does this, so the option does nothing.
4343 .cindex "Sendmail compatibility" "&%-oo%& option ignored"
4344 This option is ignored. In Sendmail it specifies &"old style headers"&,
4345 whatever that means.
4347 .cmdopt -oP <&'path'&>
4348 .cindex "pid (process id)" "of daemon"
4349 .cindex "daemon" "process id (pid)"
4350 This option is useful only in conjunction with &%-bd%& or &%-q%& with a time
4351 value. The option specifies the file to which the process id of the daemon is
4352 written. When &%-oX%& is used with &%-bd%&, or when &%-q%& with a time is used
4353 without &%-bd%&, this is the only way of causing Exim to write a pid file,
4354 because in those cases, the normal pid file is not used.
4357 .cindex "pid (process id)" "of daemon"
4358 .cindex "daemon" "process id (pid)"
4359 This option is not intended for general use.
4360 The daemon uses it when terminating due to a SIGTEM, possibly in
4361 combination with &%-oP%&&~<&'path'&>.
4362 It causes the pid file to be removed.
4364 .cmdopt -or <&'time'&>
4365 .cindex "timeout" "for non-SMTP input"
4366 This option sets a timeout value for incoming non-SMTP messages. If it is not
4367 set, Exim will wait forever for the standard input. The value can also be set
4368 by the &%receive_timeout%& option. The format used for specifying times is
4369 described in section &<<SECTtimeformat>>&.
4371 .cmdopt -os <&'time'&>
4372 .cindex "timeout" "for SMTP input"
4373 .cindex "SMTP" "input timeout"
4374 This option sets a timeout value for incoming SMTP messages. The timeout
4375 applies to each SMTP command and block of data. The value can also be set by
4376 the &%smtp_receive_timeout%& option; it defaults to 5 minutes. The format used
4377 for specifying times is described in section &<<SECTtimeformat>>&.
4380 This option has exactly the same effect as &%-v%&.
4382 .cmdopt -oX <&'number&~or&~string'&>
4383 .cindex "TCP/IP" "setting listening ports"
4384 .cindex "TCP/IP" "setting listening interfaces"
4385 .cindex "port" "receiving TCP/IP"
4386 This option is relevant only when the &%-bd%& (start listening daemon) option
4387 is also given. It controls which ports and interfaces the daemon uses. Details
4388 of the syntax, and how it interacts with configuration file options, are given
4389 in chapter &<<CHAPinterfaces>>&. When &%-oX%& is used to start a daemon, no pid
4390 file is written unless &%-oP%& is also present to specify a pid filename.
4393 .cindex "daemon notifier socket"
4394 This option controls the creation of an inter-process communications endpoint
4396 It is only relevant when the &%-bd%& (start listening daemon) option is also
4398 Normally the daemon creates this socket, unless a &%-oX%& and &*no*& &%-oP%&
4399 option is also present.
4400 If this option is given then the socket will not be created. This could be
4401 required if the system is running multiple daemons.
4403 The socket is currently used for
4405 fast ramp-up of queue runner processes
4407 obtaining a current queue size
4411 .cindex "Perl" "starting the interpreter"
4412 This option applies when an embedded Perl interpreter is linked with Exim (see
4413 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4414 option, forcing the starting of the interpreter to be delayed until it is
4418 .cindex "Perl" "starting the interpreter"
4419 This option applies when an embedded Perl interpreter is linked with Exim (see
4420 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4421 option, forcing the starting of the interpreter to occur as soon as Exim is
4424 .vitem &%-p%&<&'rval'&>:<&'sval'&>
4426 For compatibility with Sendmail, this option is equivalent to
4428 &`-oMr`& <&'rval'&> &`-oMs`& <&'sval'&>
4430 It sets the incoming protocol and host name (for trusted callers). The
4431 host name and its colon can be omitted when only the protocol is to be set.
4432 Note the Exim already has two private options, &%-pd%& and &%-ps%&, that refer
4433 to embedded Perl. It is therefore impossible to set a protocol value of &`d`&
4434 or &`s`& using this option (but that does not seem a real limitation).
4435 Repeated use of this option is not supported.
4438 .cindex "queue runner" "starting manually"
4439 This option is normally restricted to admin users. However, there is a
4440 configuration option called &%prod_requires_admin%& which can be set false to
4441 relax this restriction (and also the same requirement for the &%-M%&, &%-R%&,
4442 and &%-S%& options).
4444 .cindex "queue runner" "description of operation"
4445 If other commandline options do not specify an action,
4446 the &%-q%& option starts one queue runner process. This scans the queue of
4447 waiting messages, and runs a delivery process for each one in turn. It waits
4448 for each delivery process to finish before starting the next one. A delivery
4449 process may not actually do any deliveries if the retry times for the addresses
4450 have not been reached. Use &%-qf%& (see below) if you want to override this.
4453 .cindex "SMTP" "passed connection"
4454 .cindex "SMTP" "multiple deliveries"
4455 .cindex "multiple SMTP deliveries"
4456 the delivery process spawns other processes to deliver other messages down
4457 passed SMTP connections, the queue runner waits for these to finish before
4460 When all the queued messages have been considered, the original queue runner
4461 process terminates. In other words, a single pass is made over the waiting
4462 mail, one message at a time. Use &%-q%& with a time (see below) if you want
4463 this to be repeated periodically.
4465 Exim processes the waiting messages in an unpredictable order. It isn't very
4466 random, but it is likely to be different each time, which is all that matters.
4467 If one particular message screws up a remote MTA, other messages to the same
4468 MTA have a chance of getting through if they get tried first.
4470 It is possible to cause the messages to be processed in lexical message id
4471 order, which is essentially the order in which they arrived, by setting the
4472 &%queue_run_in_order%& option, but this is not recommended for normal use.
4474 .vitem &%-q%&<&'qflags'&>
4475 The &%-q%& option may be followed by one or more flag letters that change its
4476 behaviour. They are all optional, but if more than one is present, they must
4477 appear in the correct order. Each flag is described in a separate item below.
4481 .cindex "queue" "double scanning"
4482 .cindex "queue" "routing"
4483 .cindex "routing" "whole queue before delivery"
4484 .cindex "first pass routing"
4485 .cindex "queue runner" "two phase"
4486 An option starting with &%-qq%& requests a two-stage queue run. In the first
4487 stage, the queue is scanned as if the &%queue_smtp_domains%& option matched
4488 every domain. Addresses are routed, local deliveries happen, but no remote
4491 Performance will be best if the &%queue_run_in_order%& option is false.
4492 If that is so and the &%queue_fast_ramp%& option is true then
4493 in the first phase of the run,
4494 once a threshold number of messages are routed for a given host,
4495 a delivery process is forked in parallel with the rest of the scan.
4497 .cindex "hints database" "remembering routing"
4498 The hints database that remembers which messages are waiting for specific hosts
4499 is updated, as if delivery to those hosts had been deferred. After this is
4500 complete, a second, normal queue scan happens, with routing and delivery taking
4501 place as normal. Messages that are routed to the same host should mostly be
4502 delivered down a single SMTP
4503 .cindex "SMTP" "passed connection"
4504 .cindex "SMTP" "multiple deliveries"
4505 .cindex "multiple SMTP deliveries"
4506 connection because of the hints that were set up during the first queue scan.
4507 This option may be useful for hosts that are connected to the Internet
4510 .vitem &%-q[q]i...%&
4512 .cindex "queue" "initial delivery"
4513 If the &'i'& flag is present, the queue runner runs delivery processes only for
4514 those messages that haven't previously been tried. (&'i'& stands for &"initial
4515 delivery"&.) This can be helpful if you are putting messages in the queue using
4516 &%-odq%& and want a queue runner just to process the new messages.
4518 .vitem &%-q[q][i]f...%&
4520 .cindex "queue" "forcing delivery"
4521 .cindex "delivery" "forcing in queue run"
4522 If one &'f'& flag is present, a delivery attempt is forced for each non-frozen
4523 message, whereas without &'f'& only those non-frozen addresses that have passed
4524 their retry times are tried.
4526 .vitem &%-q[q][i]ff...%&
4528 .cindex "frozen messages" "forcing delivery"
4529 If &'ff'& is present, a delivery attempt is forced for every message, whether
4532 .vitem &%-q[q][i][f[f]]l%&
4534 .cindex "queue" "local deliveries only"
4535 The &'l'& (the letter &"ell"&) flag specifies that only local deliveries are to
4536 be done. If a message requires any remote deliveries, it remains in the queue
4539 .vitem &%-q[q][i][f[f]][l][G<name>[/<time>]]]%&
4542 .cindex "named queues" "deliver from"
4543 .cindex "queue" "delivering specific messages"
4544 If the &'G'& flag and a name is present, the queue runner operates on the
4545 queue with the given name rather than the default queue.
4546 The name should not contain a &'/'& character.
4547 For a periodic queue run (see below)
4548 append to the name a slash and a time value.
4550 If other commandline options specify an action, a &'-qG<name>'& option
4551 will specify a queue to operate on.
4554 exim -bp -qGquarantine
4556 exim -qGoffpeak -Rf @special.domain.example
4559 .vitem &%-q%&<&'qflags'&>&~<&'start&~id'&>&~<&'end&~id'&>
4560 When scanning the queue, Exim can be made to skip over messages whose ids are
4561 lexically less than a given value by following the &%-q%& option with a
4562 starting message id. For example:
4564 exim -q 0t5C6f-0000c8-00
4566 Messages that arrived earlier than &`0t5C6f-0000c8-00`& are not inspected. If a
4567 second message id is given, messages whose ids are lexically greater than it
4568 are also skipped. If the same id is given twice, for example,
4570 exim -q 0t5C6f-0000c8-00 0t5C6f-0000c8-00
4572 just one delivery process is started, for that message. This differs from
4573 &%-M%& in that retry data is respected, and it also differs from &%-Mc%& in
4574 that it counts as a delivery from a queue run. Note that the selection
4575 mechanism does not affect the order in which the messages are scanned. There
4576 are also other ways of selecting specific sets of messages for delivery in a
4577 queue run &-- see &%-R%& and &%-S%&.
4579 .vitem &%-q%&<&'qflags'&><&'time'&>
4580 .cindex "queue runner" "starting periodically"
4581 .cindex "periodic queue running"
4582 When a time value is present, the &%-q%& option causes Exim to run as a daemon,
4583 starting a queue runner process at intervals specified by the given time value
4584 (whose format is described in section &<<SECTtimeformat>>&). This form of the
4585 &%-q%& option is commonly combined with the &%-bd%& option, in which case a
4586 single daemon process handles both functions. A common way of starting up a
4587 combined daemon at system boot time is to use a command such as
4589 /usr/exim/bin/exim -bd -q30m
4591 Such a daemon listens for incoming SMTP calls, and also starts a queue runner
4592 process every 30 minutes.
4594 When a daemon is started by &%-q%& with a time value, but without &%-bd%&, no
4595 pid file is written unless one is explicitly requested by the &%-oP%& option.
4597 .vitem &%-qR%&<&'rsflags'&>&~<&'string'&>
4599 This option is synonymous with &%-R%&. It is provided for Sendmail
4602 .vitem &%-qS%&<&'rsflags'&>&~<&'string'&>
4604 This option is synonymous with &%-S%&.
4606 .vitem &%-R%&<&'rsflags'&>&~<&'string'&>
4608 .cindex "queue runner" "for specific recipients"
4609 .cindex "delivery" "to given domain"
4610 .cindex "domain" "delivery to"
4611 The <&'rsflags'&> may be empty, in which case the white space before the string
4612 is optional, unless the string is &'f'&, &'ff'&, &'r'&, &'rf'&, or &'rff'&,
4613 which are the possible values for <&'rsflags'&>. White space is required if
4614 <&'rsflags'&> is not empty.
4616 This option is similar to &%-q%& with no time value, that is, it causes Exim to
4617 perform a single queue run, except that, when scanning the messages on the
4618 queue, Exim processes only those that have at least one undelivered recipient
4619 address containing the given string, which is checked in a case-independent
4620 way. If the <&'rsflags'&> start with &'r'&, <&'string'&> is interpreted as a
4621 regular expression; otherwise it is a literal string.
4623 If you want to do periodic queue runs for messages with specific recipients,
4624 you can combine &%-R%& with &%-q%& and a time value. For example:
4626 exim -q25m -R @special.domain.example
4628 This example does a queue run for messages with recipients in the given domain
4629 every 25 minutes. Any additional flags that are specified with &%-q%& are
4630 applied to each queue run.
4632 Once a message is selected for delivery by this mechanism, all its addresses
4633 are processed. For the first selected message, Exim overrides any retry
4634 information and forces a delivery attempt for each undelivered address. This
4635 means that if delivery of any address in the first message is successful, any
4636 existing retry information is deleted, and so delivery attempts for that
4637 address in subsequently selected messages (which are processed without forcing)
4638 will run. However, if delivery of any address does not succeed, the retry
4639 information is updated, and in subsequently selected messages, the failing
4640 address will be skipped.
4642 .cindex "frozen messages" "forcing delivery"
4643 If the <&'rsflags'&> contain &'f'& or &'ff'&, the delivery forcing applies to
4644 all selected messages, not just the first; frozen messages are included when
4647 The &%-R%& option makes it straightforward to initiate delivery of all messages
4648 to a given domain after a host has been down for some time. When the SMTP
4649 command ETRN is accepted by its ACL (see chapter &<<CHAPACL>>&), its default
4650 effect is to run Exim with the &%-R%& option, but it can be configured to run
4651 an arbitrary command instead.
4654 This is a documented (for Sendmail) obsolete alternative name for &%-f%&.
4656 .vitem &%-S%&<&'rsflags'&>&~<&'string'&>
4658 .cindex "delivery" "from given sender"
4659 .cindex "queue runner" "for specific senders"
4660 This option acts like &%-R%& except that it checks the string against each
4661 message's sender instead of against the recipients. If &%-R%& is also set, both
4662 conditions must be met for a message to be selected. If either of the options
4663 has &'f'& or &'ff'& in its flags, the associated action is taken.
4665 .cmdopt -Tqt <&'times'&>
4666 This is an option that is exclusively for use by the Exim testing suite. It is not
4667 recognized when Exim is run normally. It allows for the setting up of explicit
4668 &"queue times"& so that various warning/retry features can be tested.
4671 .cindex "recipient" "extracting from header lines"
4675 When Exim is receiving a locally-generated, non-SMTP message on its standard
4676 input, the &%-t%& option causes the recipients of the message to be obtained
4677 from the &'To:'&, &'Cc:'&, and &'Bcc:'& header lines in the message instead of
4678 from the command arguments. The addresses are extracted before any rewriting
4679 takes place and the &'Bcc:'& header line, if present, is then removed.
4681 .cindex "Sendmail compatibility" "&%-t%& option"
4682 If the command has any arguments, they specify addresses to which the message
4683 is &'not'& to be delivered. That is, the argument addresses are removed from
4684 the recipients list obtained from the headers. This is compatible with Smail 3
4685 and in accordance with the documented behaviour of several versions of
4686 Sendmail, as described in man pages on a number of operating systems (e.g.
4687 Solaris 8, IRIX 6.5, HP-UX 11). However, some versions of Sendmail &'add'&
4688 argument addresses to those obtained from the headers, and the O'Reilly
4689 Sendmail book documents it that way. Exim can be made to add argument addresses
4690 instead of subtracting them by setting the option
4691 &%extract_addresses_remove_arguments%& false.
4693 .cindex "&%Resent-%& header lines" "with &%-t%&"
4694 If there are any &%Resent-%& header lines in the message, Exim extracts
4695 recipients from all &'Resent-To:'&, &'Resent-Cc:'&, and &'Resent-Bcc:'& header
4696 lines instead of from &'To:'&, &'Cc:'&, and &'Bcc:'&. This is for compatibility
4697 with Sendmail and other MTAs. (Prior to release 4.20, Exim gave an error if
4698 &%-t%& was used in conjunction with &%Resent-%& header lines.)
4700 RFC 2822 talks about different sets of &%Resent-%& header lines (for when a
4701 message is resent several times). The RFC also specifies that they should be
4702 added at the front of the message, and separated by &'Received:'& lines. It is
4703 not at all clear how &%-t%& should operate in the present of multiple sets,
4704 nor indeed exactly what constitutes a &"set"&.
4705 In practice, it seems that MUAs do not follow the RFC. The &%Resent-%& lines
4706 are often added at the end of the header, and if a message is resent more than
4707 once, it is common for the original set of &%Resent-%& headers to be renamed as
4708 &%X-Resent-%& when a new set is added. This removes any possible ambiguity.
4711 This option is exactly equivalent to &%-t%& &%-i%&. It is provided for
4712 compatibility with Sendmail.
4714 .cmdopt -tls-on-connect
4715 .cindex "TLS" "use without STARTTLS"
4716 .cindex "TLS" "automatic start"
4717 This option is available when Exim is compiled with TLS support. It forces all
4718 incoming SMTP connections to behave as if the incoming port is listed in the
4719 &%tls_on_connect_ports%& option. See section &<<SECTsupobssmt>>& and chapter
4720 &<<CHAPTLS>>& for further details.
4724 .cindex "Sendmail compatibility" "&%-U%& option ignored"
4725 Sendmail uses this option for &"initial message submission"&, and its
4726 documentation states that in future releases, it may complain about
4727 syntactically invalid messages rather than fixing them when this flag is not
4728 set. Exim ignores this option.
4731 This option causes Exim to write information to the standard error stream,
4732 describing what it is doing. In particular, it shows the log lines for
4733 receiving and delivering a message, and if an SMTP connection is made, the SMTP
4734 dialogue is shown. Some of the log lines shown may not actually be written to
4735 the log if the setting of &%log_selector%& discards them. Any relevant
4736 selectors are shown with each log line. If none are shown, the logging is
4740 AIX uses &%-x%& for a private purpose (&"mail from a local mail program has
4741 National Language Support extended characters in the body of the mail item"&).
4742 It sets &%-x%& when calling the MTA from its &%mail%& command. Exim ignores
4745 .cmdopt -X <&'logfile'&>
4746 This option is interpreted by Sendmail to cause debug information to be sent
4747 to the named file. It is ignored by Exim.
4749 .cmdopt -z <&'log-line'&>
4750 This option writes its argument to Exim's logfile.
4751 Use is restricted to administrators; the intent is for operational notes.
4752 Quotes should be used to maintain a multi-word item as a single argument,
4760 . ////////////////////////////////////////////////////////////////////////////
4761 . Insert a stylized DocBook comment here, to identify the end of the command
4762 . line options. This is for the benefit of the Perl script that automatically
4763 . creates a man page for the options.
4764 . ////////////////////////////////////////////////////////////////////////////
4767 <!-- === End of command line options === -->
4774 . ////////////////////////////////////////////////////////////////////////////
4775 . ////////////////////////////////////////////////////////////////////////////
4778 .chapter "The Exim runtime configuration file" "CHAPconf" &&&
4779 "The runtime configuration file"
4781 .cindex "runtime configuration"
4782 .cindex "configuration file" "general description"
4783 .cindex "CONFIGURE_FILE"
4784 .cindex "configuration file" "errors in"
4785 .cindex "error" "in configuration file"
4786 .cindex "return code" "for bad configuration"
4787 Exim uses a single runtime configuration file that is read whenever an Exim
4788 binary is executed. Note that in normal operation, this happens frequently,
4789 because Exim is designed to operate in a distributed manner, without central
4792 If a syntax error is detected while reading the configuration file, Exim
4793 writes a message on the standard error, and exits with a non-zero return code.
4794 The message is also written to the panic log. &*Note*&: Only simple syntax
4795 errors can be detected at this time. The values of any expanded options are
4796 not checked until the expansion happens, even when the expansion does not
4797 actually alter the string.
4799 The name of the configuration file is compiled into the binary for security
4800 reasons, and is specified by the CONFIGURE_FILE compilation option. In
4801 most configurations, this specifies a single file. However, it is permitted to
4802 give a colon-separated list of filenames, in which case Exim uses the first
4803 existing file in the list.
4806 .cindex "EXIM_GROUP"
4807 .cindex "CONFIGURE_OWNER"
4808 .cindex "CONFIGURE_GROUP"
4809 .cindex "configuration file" "ownership"
4810 .cindex "ownership" "configuration file"
4811 The runtime configuration file must be owned by root or by the user that is
4812 specified at compile time by the CONFIGURE_OWNER option (if set). The
4813 configuration file must not be world-writeable, or group-writeable unless its
4814 group is the root group or the one specified at compile time by the
4815 CONFIGURE_GROUP option.
4817 &*Warning*&: In a conventional configuration, where the Exim binary is setuid
4818 to root, anybody who is able to edit the runtime configuration file has an
4819 easy way to run commands as root. If you specify a user or group in the
4820 CONFIGURE_OWNER or CONFIGURE_GROUP options, then that user and/or any users
4821 who are members of that group will trivially be able to obtain root privileges.
4823 Up to Exim version 4.72, the runtime configuration file was also permitted to
4824 be writeable by the Exim user and/or group. That has been changed in Exim 4.73
4825 since it offered a simple privilege escalation for any attacker who managed to
4826 compromise the Exim user account.
4828 A default configuration file, which will work correctly in simple situations,
4829 is provided in the file &_src/configure.default_&. If CONFIGURE_FILE
4830 defines just one filename, the installation process copies the default
4831 configuration to a new file of that name if it did not previously exist. If
4832 CONFIGURE_FILE is a list, no default is automatically installed. Chapter
4833 &<<CHAPdefconfil>>& is a &"walk-through"& discussion of the default
4838 .section "Using a different configuration file" "SECID40"
4839 .cindex "configuration file" "alternate"
4840 A one-off alternate configuration can be specified by the &%-C%& command line
4841 option, which may specify a single file or a list of files. However, when
4842 &%-C%& is used, Exim gives up its root privilege, unless called by root (or
4843 unless the argument for &%-C%& is identical to the built-in value from
4844 CONFIGURE_FILE), or is listed in the TRUSTED_CONFIG_LIST file and the caller
4845 is the Exim user or the user specified in the CONFIGURE_OWNER setting. &%-C%&
4846 is useful mainly for checking the syntax of configuration files before
4847 installing them. No owner or group checks are done on a configuration file
4848 specified by &%-C%&, if root privilege has been dropped.
4850 Even the Exim user is not trusted to specify an arbitrary configuration file
4851 with the &%-C%& option to be used with root privileges, unless that file is
4852 listed in the TRUSTED_CONFIG_LIST file. This locks out the possibility of
4853 testing a configuration using &%-C%& right through message reception and
4854 delivery, even if the caller is root. The reception works, but by that time,
4855 Exim is running as the Exim user, so when it re-execs to regain privilege for
4856 the delivery, the use of &%-C%& causes privilege to be lost. However, root
4857 can test reception and delivery using two separate commands (one to put a
4858 message in the queue, using &%-odq%&, and another to do the delivery, using
4861 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
4862 prefix string with which any file named in a &%-C%& command line option must
4863 start. In addition, the filename must not contain the sequence &"&`/../`&"&.
4864 There is no default setting for ALT_CONFIG_PREFIX; when it is unset, any
4865 filename can be used with &%-C%&.
4867 One-off changes to a configuration can be specified by the &%-D%& command line
4868 option, which defines and overrides values for macros used inside the
4869 configuration file. However, like &%-C%&, the use of this option by a
4870 non-privileged user causes Exim to discard its root privilege.
4871 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
4872 completely disabled, and its use causes an immediate error exit.
4874 The WHITELIST_D_MACROS option in &_Local/Makefile_& permits the binary builder
4875 to declare certain macro names trusted, such that root privilege will not
4876 necessarily be discarded.
4877 WHITELIST_D_MACROS defines a colon-separated list of macros which are
4878 considered safe and, if &%-D%& only supplies macros from this list, and the
4879 values are acceptable, then Exim will not give up root privilege if the caller
4880 is root, the Exim run-time user, or the CONFIGURE_OWNER, if set. This is a
4881 transition mechanism and is expected to be removed in the future. Acceptable
4882 values for the macros satisfy the regexp: &`^[A-Za-z0-9_/.-]*$`&
4884 Some sites may wish to use the same Exim binary on different machines that
4885 share a file system, but to use different configuration files on each machine.
4886 If CONFIGURE_FILE_USE_NODE is defined in &_Local/Makefile_&, Exim first
4887 looks for a file whose name is the configuration filename followed by a dot
4888 and the machine's node name, as obtained from the &[uname()]& function. If this
4889 file does not exist, the standard name is tried. This processing occurs for
4890 each filename in the list given by CONFIGURE_FILE or &%-C%&.
4892 In some esoteric situations different versions of Exim may be run under
4893 different effective uids and the CONFIGURE_FILE_USE_EUID is defined to
4894 help with this. See the comments in &_src/EDITME_& for details.
4898 .section "Configuration file format" "SECTconffilfor"
4899 .cindex "configuration file" "format of"
4900 .cindex "format" "configuration file"
4901 Exim's configuration file is divided into a number of different parts. General
4902 option settings must always appear at the start of the file. The other parts
4903 are all optional, and may appear in any order. Each part other than the first
4904 is introduced by the word &"begin"& followed by at least one literal
4905 space, and the name of the part. The optional parts are:
4908 &'ACL'&: Access control lists for controlling incoming SMTP mail (see chapter
4911 .cindex "AUTH" "configuration"
4912 &'authenticators'&: Configuration settings for the authenticator drivers. These
4913 are concerned with the SMTP AUTH command (see chapter &<<CHAPSMTPAUTH>>&).
4915 &'routers'&: Configuration settings for the router drivers. Routers process
4916 addresses and determine how the message is to be delivered (see chapters
4917 &<<CHAProutergeneric>>&&--&<<CHAPredirect>>&).
4919 &'transports'&: Configuration settings for the transport drivers. Transports
4920 define mechanisms for copying messages to destinations (see chapters
4921 &<<CHAPtransportgeneric>>&&--&<<CHAPsmtptrans>>&).
4923 &'retry'&: Retry rules, for use when a message cannot be delivered immediately.
4924 If there is no retry section, or if it is empty (that is, no retry rules are
4925 defined), Exim will not retry deliveries. In this situation, temporary errors
4926 are treated the same as permanent errors. Retry rules are discussed in chapter
4929 &'rewrite'&: Global address rewriting rules, for use when a message arrives and
4930 when new addresses are generated during delivery. Rewriting is discussed in
4931 chapter &<<CHAPrewrite>>&.
4933 &'local_scan'&: Private options for the &[local_scan()]& function. If you
4934 want to use this feature, you must set
4936 LOCAL_SCAN_HAS_OPTIONS=yes
4938 in &_Local/Makefile_& before building Exim. Details of the &[local_scan()]&
4939 facility are given in chapter &<<CHAPlocalscan>>&.
4942 .cindex "configuration file" "leading white space in"
4943 .cindex "configuration file" "trailing white space in"
4944 .cindex "white space" "in configuration file"
4945 Leading and trailing white space in configuration lines is always ignored.
4947 Blank lines in the file, and lines starting with a # character (ignoring
4948 leading white space) are treated as comments and are ignored. &*Note*&: A
4949 # character other than at the beginning of a line is not treated specially,
4950 and does not introduce a comment.
4952 Any non-comment line can be continued by ending it with a backslash. Note that
4953 the general rule for white space means that trailing white space after the
4954 backslash and leading white space at the start of continuation
4955 lines is ignored. Comment lines beginning with # (but not empty lines) may
4956 appear in the middle of a sequence of continuation lines.
4958 A convenient way to create a configuration file is to start from the
4959 default, which is supplied in &_src/configure.default_&, and add, delete, or
4960 change settings as required.
4962 The ACLs, retry rules, and rewriting rules have their own syntax which is
4963 described in chapters &<<CHAPACL>>&, &<<CHAPretry>>&, and &<<CHAPrewrite>>&,
4964 respectively. The other parts of the configuration file have some syntactic
4965 items in common, and these are described below, from section &<<SECTcos>>&
4966 onwards. Before that, the inclusion, macro, and conditional facilities are
4971 .section "File inclusions in the configuration file" "SECID41"
4972 .cindex "inclusions in configuration file"
4973 .cindex "configuration file" "including other files"
4974 .cindex "&`.include`& in configuration file"
4975 .cindex "&`.include_if_exists`& in configuration file"
4976 You can include other files inside Exim's runtime configuration file by
4979 &`.include`& <&'filename'&>
4980 &`.include_if_exists`& <&'filename'&>
4982 on a line by itself. Double quotes round the filename are optional. If you use
4983 the first form, a configuration error occurs if the file does not exist; the
4984 second form does nothing for non-existent files.
4985 The first form allows a relative name. It is resolved relative to
4986 the directory of the including file. For the second form an absolute filename
4989 Includes may be nested to any depth, but remember that Exim reads its
4990 configuration file often, so it is a good idea to keep them to a minimum.
4991 If you change the contents of an included file, you must HUP the daemon,
4992 because an included file is read only when the configuration itself is read.
4994 The processing of inclusions happens early, at a physical line level, so, like
4995 comment lines, an inclusion can be used in the middle of an option setting,
4998 hosts_lookup = a.b.c \
5001 Include processing happens after macro processing (see below). Its effect is to
5002 process the lines of the included file as if they occurred inline where the
5007 .section "Macros in the configuration file" "SECTmacrodefs"
5008 .cindex "macro" "description of"
5009 .cindex "configuration file" "macros"
5010 If a line in the main part of the configuration (that is, before the first
5011 &"begin"& line) begins with an upper case letter, it is taken as a macro
5012 definition, and must be of the form
5014 <&'name'&> = <&'rest of line'&>
5016 The name must consist of letters, digits, and underscores, and need not all be
5017 in upper case, though that is recommended. The rest of the line, including any
5018 continuations, is the replacement text, and has leading and trailing white
5019 space removed. Quotes are not removed. The replacement text can never end with
5020 a backslash character, but this doesn't seem to be a serious limitation.
5022 Macros may also be defined between router, transport, authenticator, or ACL
5023 definitions. They may not, however, be defined within an individual driver or
5024 ACL, or in the &%local_scan%&, retry, or rewrite sections of the configuration.
5026 .section "Macro substitution" "SECID42"
5027 Once a macro is defined, all subsequent lines in the file (and any included
5028 files) are scanned for the macro name; if there are several macros, the line is
5029 scanned for each, in turn, in the order in which the macros are defined. The
5030 replacement text is not re-scanned for the current macro, though it is scanned
5031 for subsequently defined macros. For this reason, a macro name may not contain
5032 the name of a previously defined macro as a substring. You could, for example,
5035 &`ABCD_XYZ = `&<&'something'&>
5036 &`ABCD = `&<&'something else'&>
5038 but putting the definitions in the opposite order would provoke a configuration
5039 error. Macro expansion is applied to individual physical lines from the file,
5040 before checking for line continuation or file inclusion (see above). If a line
5041 consists solely of a macro name, and the expansion of the macro is empty, the
5042 line is ignored. A macro at the start of a line may turn the line into a
5043 comment line or a &`.include`& line.
5046 .section "Redefining macros" "SECID43"
5047 Once defined, the value of a macro can be redefined later in the configuration
5048 (or in an included file). Redefinition is specified by using &'=='& instead of
5053 MAC == updated value
5055 Redefinition does not alter the order in which the macros are applied to the
5056 subsequent lines of the configuration file. It is still the same order in which
5057 the macros were originally defined. All that changes is the macro's value.
5058 Redefinition makes it possible to accumulate values. For example:
5062 MAC == MAC and something added
5064 This can be helpful in situations where the configuration file is built
5065 from a number of other files.
5067 .section "Overriding macro values" "SECID44"
5068 The values set for macros in the configuration file can be overridden by the
5069 &%-D%& command line option, but Exim gives up its root privilege when &%-D%& is
5070 used, unless called by root or the Exim user. A definition on the command line
5071 using the &%-D%& option causes all definitions and redefinitions within the
5076 .section "Example of macro usage" "SECID45"
5077 As an example of macro usage, consider a configuration where aliases are looked
5078 up in a MySQL database. It helps to keep the file less cluttered if long
5079 strings such as SQL statements are defined separately as macros, for example:
5081 ALIAS_QUERY = select mailbox from user where \
5082 login='${quote_mysql:$local_part}';
5084 This can then be used in a &(redirect)& router setting like this:
5086 data = ${lookup mysql{ALIAS_QUERY}}
5088 In earlier versions of Exim macros were sometimes used for domain, host, or
5089 address lists. In Exim 4 these are handled better by named lists &-- see
5090 section &<<SECTnamedlists>>&.
5093 .section "Builtin macros" "SECTbuiltinmacros"
5094 Exim defines some macros depending on facilities available, which may
5095 differ due to build-time definitions and from one release to another.
5096 All of these macros start with an underscore.
5097 They can be used to conditionally include parts of a configuration
5100 The following classes of macros are defined:
5102 &` _HAVE_* `& build-time defines
5103 &` _DRIVER_ROUTER_* `& router drivers
5104 &` _DRIVER_TRANSPORT_* `& transport drivers
5105 &` _DRIVER_AUTHENTICATOR_* `& authenticator drivers
5106 &` _LOG_* `& log_selector values
5107 &` _OPT_MAIN_* `& main config options
5108 &` _OPT_ROUTERS_* `& generic router options
5109 &` _OPT_TRANSPORTS_* `& generic transport options
5110 &` _OPT_AUTHENTICATORS_* `& generic authenticator options
5111 &` _OPT_ROUTER_*_* `& private router options
5112 &` _OPT_TRANSPORT_*_* `& private transport options
5113 &` _OPT_AUTHENTICATOR_*_* `& private authenticator options
5116 Use an &"exim -bP macros"& command to get the list of macros.
5119 .section "Conditional skips in the configuration file" "SECID46"
5120 .cindex "configuration file" "conditional skips"
5121 .cindex "&`.ifdef`&"
5122 You can use the directives &`.ifdef`&, &`.ifndef`&, &`.elifdef`&,
5123 &`.elifndef`&, &`.else`&, and &`.endif`& to dynamically include or exclude
5124 portions of the configuration file. The processing happens whenever the file is
5125 read (that is, when an Exim binary starts to run).
5127 The implementation is very simple. Instances of the first four directives must
5128 be followed by text that includes the names of one or macros. The condition
5129 that is tested is whether or not any macro substitution has taken place in the
5133 message_size_limit = 50M
5135 message_size_limit = 100M
5138 sets a message size limit of 50M if the macro &`AAA`& is defined
5139 (or &`A`& or &`AA`&), and 100M
5140 otherwise. If there is more than one macro named on the line, the condition
5141 is true if any of them are defined. That is, it is an &"or"& condition. To
5142 obtain an &"and"& condition, you need to use nested &`.ifdef`&s.
5144 Although you can use a macro expansion to generate one of these directives,
5145 it is not very useful, because the condition &"there was a macro substitution
5146 in this line"& will always be true.
5148 Text following &`.else`& and &`.endif`& is ignored, and can be used as comment
5149 to clarify complicated nestings.
5153 .section "Common option syntax" "SECTcos"
5154 .cindex "common option syntax"
5155 .cindex "syntax of common options"
5156 .cindex "configuration file" "common option syntax"
5157 For the main set of options, driver options, and &[local_scan()]& options,
5158 each setting is on a line by itself, and starts with a name consisting of
5159 lower-case letters and underscores. Many options require a data value, and in
5160 these cases the name must be followed by an equals sign (with optional white
5161 space) and then the value. For example:
5163 qualify_domain = mydomain.example.com
5165 .cindex "hiding configuration option values"
5166 .cindex "configuration options" "hiding value of"
5167 .cindex "options" "hiding value of"
5168 Some option settings may contain sensitive data, for example, passwords for
5169 accessing databases. To stop non-admin users from using the &%-bP%& command
5170 line option to read these values, you can precede the option settings with the
5171 word &"hide"&. For example:
5173 hide mysql_servers = localhost/users/admin/secret-password
5175 For non-admin users, such options are displayed like this:
5177 mysql_servers = <value not displayable>
5179 If &"hide"& is used on a driver option, it hides the value of that option on
5180 all instances of the same driver.
5182 The following sections describe the syntax used for the different data types
5183 that are found in option settings.
5186 .section "Boolean options" "SECID47"
5187 .cindex "format" "boolean"
5188 .cindex "boolean configuration values"
5189 .oindex "&%no_%&&'xxx'&"
5190 .oindex "&%not_%&&'xxx'&"
5191 Options whose type is given as boolean are on/off switches. There are two
5192 different ways of specifying such options: with and without a data value. If
5193 the option name is specified on its own without data, the switch is turned on;
5194 if it is preceded by &"no_"& or &"not_"& the switch is turned off. However,
5195 boolean options may be followed by an equals sign and one of the words
5196 &"true"&, &"false"&, &"yes"&, or &"no"&, as an alternative syntax. For example,
5197 the following two settings have exactly the same effect:
5202 The following two lines also have the same (opposite) effect:
5207 You can use whichever syntax you prefer.
5212 .section "Integer values" "SECID48"
5213 .cindex "integer configuration values"
5214 .cindex "format" "integer"
5215 If an option's type is given as &"integer"&, the value can be given in decimal,
5216 hexadecimal, or octal. If it starts with a digit greater than zero, a decimal
5217 number is assumed. Otherwise, it is treated as an octal number unless it starts
5218 with the characters &"0x"&, in which case the remainder is interpreted as a
5221 If an integer value is followed by the letter K, it is multiplied by 1024; if
5222 it is followed by the letter M, it is multiplied by 1024x1024;
5223 if by the letter G, 1024x1024x1024.
5225 of integer option settings are output, values which are an exact multiple of
5226 1024 or 1024x1024 are sometimes, but not always, printed using the letters K
5227 and M. The printing style is independent of the actual input format that was
5231 .section "Octal integer values" "SECID49"
5232 .cindex "integer format"
5233 .cindex "format" "octal integer"
5234 If an option's type is given as &"octal integer"&, its value is always
5235 interpreted as an octal number, whether or not it starts with the digit zero.
5236 Such options are always output in octal.
5239 .section "Fixed point numbers" "SECID50"
5240 .cindex "fixed point configuration values"
5241 .cindex "format" "fixed point"
5242 If an option's type is given as &"fixed-point"&, its value must be a decimal
5243 integer, optionally followed by a decimal point and up to three further digits.
5247 .section "Time intervals" "SECTtimeformat"
5248 .cindex "time interval" "specifying in configuration"
5249 .cindex "format" "time interval"
5250 A time interval is specified as a sequence of numbers, each followed by one of
5251 the following letters, with no intervening white space:
5261 For example, &"3h50m"& specifies 3 hours and 50 minutes. The values of time
5262 intervals are output in the same format. Exim does not restrict the values; it
5263 is perfectly acceptable, for example, to specify &"90m"& instead of &"1h30m"&.
5267 .section "String values" "SECTstrings"
5268 .cindex "string" "format of configuration values"
5269 .cindex "format" "string"
5270 If an option's type is specified as &"string"&, the value can be specified with
5271 or without double-quotes. If it does not start with a double-quote, the value
5272 consists of the remainder of the line plus any continuation lines, starting at
5273 the first character after any leading white space, with trailing white space
5274 removed, and with no interpretation of the characters in the string. Because
5275 Exim removes comment lines (those beginning with #) at an early stage, they can
5276 appear in the middle of a multi-line string. The following two settings are
5277 therefore equivalent:
5279 trusted_users = uucp:mail
5280 trusted_users = uucp:\
5281 # This comment line is ignored
5284 .cindex "string" "quoted"
5285 .cindex "escape characters in quoted strings"
5286 If a string does start with a double-quote, it must end with a closing
5287 double-quote, and any backslash characters other than those used for line
5288 continuation are interpreted as escape characters, as follows:
5291 .irow &`\\`& "single backslash"
5292 .irow &`\n`& "newline"
5293 .irow &`\r`& "carriage return"
5295 .irow "&`\`&<&'octal digits'&>" "up to 3 octal digits specify one character"
5296 .irow "&`\x`&<&'hex digits'&>" "up to 2 hexadecimal digits specify one &&&
5300 If a backslash is followed by some other character, including a double-quote
5301 character, that character replaces the pair.
5303 Quoting is necessary only if you want to make use of the backslash escapes to
5304 insert special characters, or if you need to specify a value with leading or
5305 trailing spaces. These cases are rare, so quoting is almost never needed in
5306 current versions of Exim. In versions of Exim before 3.14, quoting was required
5307 in order to continue lines, so you may come across older configuration files
5308 and examples that apparently quote unnecessarily.
5311 .section "Expanded strings" "SECID51"
5312 .cindex "expansion" "definition of"
5313 Some strings in the configuration file are subjected to &'string expansion'&,
5314 by which means various parts of the string may be changed according to the
5315 circumstances (see chapter &<<CHAPexpand>>&). The input syntax for such strings
5316 is as just described; in particular, the handling of backslashes in quoted
5317 strings is done as part of the input process, before expansion takes place.
5318 However, backslash is also an escape character for the expander, so any
5319 backslashes that are required for that reason must be doubled if they are
5320 within a quoted configuration string.
5323 .section "User and group names" "SECID52"
5324 .cindex "user name" "format of"
5325 .cindex "format" "user name"
5326 .cindex "groups" "name format"
5327 .cindex "format" "group name"
5328 User and group names are specified as strings, using the syntax described
5329 above, but the strings are interpreted specially. A user or group name must
5330 either consist entirely of digits, or be a name that can be looked up using the
5331 &[getpwnam()]& or &[getgrnam()]& function, as appropriate.
5334 .section "List construction" "SECTlistconstruct"
5335 .cindex "list" "syntax of in configuration"
5336 .cindex "format" "list item in configuration"
5337 .cindex "string" "list, definition of"
5338 The data for some configuration options is a list of items, with colon as the
5339 default separator. Many of these options are shown with type &"string list"& in
5340 the descriptions later in this document. Others are listed as &"domain list"&,
5341 &"host list"&, &"address list"&, or &"local part list"&. Syntactically, they
5342 are all the same; however, those other than &"string list"& are subject to
5343 particular kinds of interpretation, as described in chapter
5344 &<<CHAPdomhosaddlists>>&.
5346 In all these cases, the entire list is treated as a single string as far as the
5347 input syntax is concerned. The &%trusted_users%& setting in section
5348 &<<SECTstrings>>& above is an example. If a colon is actually needed in an item
5349 in a list, it must be entered as two colons. Leading and trailing white space
5350 on each item in a list is ignored. This makes it possible to include items that
5351 start with a colon, and in particular, certain forms of IPv6 address. For
5354 local_interfaces = 127.0.0.1 : ::::1
5356 contains two IP addresses, the IPv4 address 127.0.0.1 and the IPv6 address ::1.
5358 &*Note*&: Although leading and trailing white space is ignored in individual
5359 list items, it is not ignored when parsing the list. The spaces around the first
5360 colon in the example above are necessary. If they were not there, the list would
5361 be interpreted as the two items 127.0.0.1:: and 1.
5363 .section "Changing list separators" "SECTlistsepchange"
5364 .cindex "list separator" "changing"
5365 .cindex "IPv6" "addresses in lists"
5366 Doubling colons in IPv6 addresses is an unwelcome chore, so a mechanism was
5367 introduced to allow the separator character to be changed. If a list begins
5368 with a left angle bracket, followed by any punctuation character, that
5369 character is used instead of colon as the list separator. For example, the list
5370 above can be rewritten to use a semicolon separator like this:
5372 local_interfaces = <; 127.0.0.1 ; ::1
5374 This facility applies to all lists, with the exception of the list in
5375 &%log_file_path%&. It is recommended that the use of non-colon separators be
5376 confined to circumstances where they really are needed.
5378 .cindex "list separator" "newline as"
5379 .cindex "newline" "as list separator"
5380 It is also possible to use newline and other control characters (those with
5381 code values less than 32, plus DEL) as separators in lists. Such separators
5382 must be provided literally at the time the list is processed. For options that
5383 are string-expanded, you can write the separator using a normal escape
5384 sequence. This will be processed by the expander before the string is
5385 interpreted as a list. For example, if a newline-separated list of domains is
5386 generated by a lookup, you can process it directly by a line such as this:
5388 domains = <\n ${lookup mysql{.....}}
5390 This avoids having to change the list separator in such data. You are unlikely
5391 to want to use a control character as a separator in an option that is not
5392 expanded, because the value is literal text. However, it can be done by giving
5393 the value in quotes. For example:
5395 local_interfaces = "<\n 127.0.0.1 \n ::1"
5397 Unlike printing character separators, which can be included in list items by
5398 doubling, it is not possible to include a control character as data when it is
5399 set as the separator. Two such characters in succession are interpreted as
5400 enclosing an empty list item.
5404 .section "Empty items in lists" "SECTempitelis"
5405 .cindex "list" "empty item in"
5406 An empty item at the end of a list is always ignored. In other words, trailing
5407 separator characters are ignored. Thus, the list in
5409 senders = user@domain :
5411 contains only a single item. If you want to include an empty string as one item
5412 in a list, it must not be the last item. For example, this list contains three
5413 items, the second of which is empty:
5415 senders = user1@domain : : user2@domain
5417 &*Note*&: There must be white space between the two colons, as otherwise they
5418 are interpreted as representing a single colon data character (and the list
5419 would then contain just one item). If you want to specify a list that contains
5420 just one, empty item, you can do it as in this example:
5424 In this case, the first item is empty, and the second is discarded because it
5425 is at the end of the list.
5430 .section "Format of driver configurations" "SECTfordricon"
5431 .cindex "drivers" "configuration format"
5432 There are separate parts in the configuration for defining routers, transports,
5433 and authenticators. In each part, you are defining a number of driver
5434 instances, each with its own set of options. Each driver instance is defined by
5435 a sequence of lines like this:
5437 <&'instance name'&>:
5442 In the following example, the instance name is &(localuser)&, and it is
5443 followed by three options settings:
5448 transport = local_delivery
5450 For each driver instance, you specify which Exim code module it uses &-- by the
5451 setting of the &%driver%& option &-- and (optionally) some configuration
5452 settings. For example, in the case of transports, if you want a transport to
5453 deliver with SMTP you would use the &(smtp)& driver; if you want to deliver to
5454 a local file you would use the &(appendfile)& driver. Each of the drivers is
5455 described in detail in its own separate chapter later in this manual.
5457 You can have several routers, transports, or authenticators that are based on
5458 the same underlying driver (each must have a different instance name).
5460 The order in which routers are defined is important, because addresses are
5461 passed to individual routers one by one, in order. The order in which
5462 transports are defined does not matter at all. The order in which
5463 authenticators are defined is used only when Exim, as a client, is searching
5464 them to find one that matches an authentication mechanism offered by the
5467 .cindex "generic options"
5468 .cindex "options" "generic &-- definition of"
5469 Within a driver instance definition, there are two kinds of option: &'generic'&
5470 and &'private'&. The generic options are those that apply to all drivers of the
5471 same type (that is, all routers, all transports or all authenticators). The
5472 &%driver%& option is a generic option that must appear in every definition.
5473 .cindex "private options"
5474 The private options are special for each driver, and none need appear, because
5475 they all have default values.
5477 The options may appear in any order, except that the &%driver%& option must
5478 precede any private options, since these depend on the particular driver. For
5479 this reason, it is recommended that &%driver%& always be the first option.
5481 Driver instance names, which are used for reference in log entries and
5482 elsewhere, can be any sequence of letters, digits, and underscores (starting
5483 with a letter) and must be unique among drivers of the same type. A router and
5484 a transport (for example) can each have the same name, but no two router
5485 instances can have the same name. The name of a driver instance should not be
5486 confused with the name of the underlying driver module. For example, the
5487 configuration lines:
5492 create an instance of the &(smtp)& transport driver whose name is
5493 &(remote_smtp)&. The same driver code can be used more than once, with
5494 different instance names and different option settings each time. A second
5495 instance of the &(smtp)& transport, with different options, might be defined
5501 command_timeout = 10s
5503 The names &(remote_smtp)& and &(special_smtp)& would be used to reference
5504 these transport instances from routers, and these names would appear in log
5507 Comment lines may be present in the middle of driver specifications. The full
5508 list of option settings for any particular driver instance, including all the
5509 defaulted values, can be extracted by making use of the &%-bP%& command line
5517 . ////////////////////////////////////////////////////////////////////////////
5518 . ////////////////////////////////////////////////////////////////////////////
5520 .chapter "The default configuration file" "CHAPdefconfil"
5521 .scindex IIDconfiwal "configuration file" "default &""walk through""&"
5522 .cindex "default" "configuration file &""walk through""&"
5523 The default configuration file supplied with Exim as &_src/configure.default_&
5524 is sufficient for a host with simple mail requirements. As an introduction to
5525 the way Exim is configured, this chapter &"walks through"& the default
5526 configuration, giving brief explanations of the settings. Detailed descriptions
5527 of the options are given in subsequent chapters. The default configuration file
5528 itself contains extensive comments about ways you might want to modify the
5529 initial settings. However, note that there are many options that are not
5530 mentioned at all in the default configuration.
5534 .section "Macros" "SECTdefconfmacros"
5535 All macros should be defined before any options.
5537 One macro is specified, but commented out, in the default configuration:
5539 # ROUTER_SMARTHOST=MAIL.HOSTNAME.FOR.CENTRAL.SERVER.EXAMPLE
5541 If all off-site mail is expected to be delivered to a "smarthost", then set the
5542 hostname here and uncomment the macro. This will affect which router is used
5543 later on. If this is left commented out, then Exim will perform direct-to-MX
5544 deliveries using a &(dnslookup)& router.
5546 In addition to macros defined here, Exim includes a number of built-in macros
5547 to enable configuration to be guarded by a binary built with support for a
5548 given feature. See section &<<SECTbuiltinmacros>>& for more details.
5551 .section "Main configuration settings" "SECTdefconfmain"
5552 The main (global) configuration option settings section must always come first
5553 in the file, after the macros.
5554 The first thing you'll see in the file, after some initial comments, is the line
5556 # primary_hostname =
5558 This is a commented-out setting of the &%primary_hostname%& option. Exim needs
5559 to know the official, fully qualified name of your host, and this is where you
5560 can specify it. However, in most cases you do not need to set this option. When
5561 it is unset, Exim uses the &[uname()]& system function to obtain the host name.
5563 The first three non-comment configuration lines are as follows:
5565 domainlist local_domains = @
5566 domainlist relay_to_domains =
5567 hostlist relay_from_hosts = 127.0.0.1
5569 These are not, in fact, option settings. They are definitions of two named
5570 domain lists and one named host list. Exim allows you to give names to lists of
5571 domains, hosts, and email addresses, in order to make it easier to manage the
5572 configuration file (see section &<<SECTnamedlists>>&).
5574 The first line defines a domain list called &'local_domains'&; this is used
5575 later in the configuration to identify domains that are to be delivered
5578 .cindex "@ in a domain list"
5579 There is just one item in this list, the string &"@"&. This is a special form
5580 of entry which means &"the name of the local host"&. Thus, if the local host is
5581 called &'a.host.example'&, mail to &'any.user@a.host.example'& is expected to
5582 be delivered locally. Because the local host's name is referenced indirectly,
5583 the same configuration file can be used on different hosts.
5585 The second line defines a domain list called &'relay_to_domains'&, but the
5586 list itself is empty. Later in the configuration we will come to the part that
5587 controls mail relaying through the local host; it allows relaying to any
5588 domains in this list. By default, therefore, no relaying on the basis of a mail
5589 domain is permitted.
5591 The third line defines a host list called &'relay_from_hosts'&. This list is
5592 used later in the configuration to permit relaying from any host or IP address
5593 that matches the list. The default contains just the IP address of the IPv4
5594 loopback interface, which means that processes on the local host are able to
5595 submit mail for relaying by sending it over TCP/IP to that interface. No other
5596 hosts are permitted to submit messages for relaying.
5598 Just to be sure there's no misunderstanding: at this point in the configuration
5599 we aren't actually setting up any controls. We are just defining some domains
5600 and hosts that will be used in the controls that are specified later.
5602 The next two configuration lines are genuine option settings:
5604 acl_smtp_rcpt = acl_check_rcpt
5605 acl_smtp_data = acl_check_data
5607 These options specify &'Access Control Lists'& (ACLs) that are to be used
5608 during an incoming SMTP session for every recipient of a message (every RCPT
5609 command), and after the contents of the message have been received,
5610 respectively. The names of the lists are &'acl_check_rcpt'& and
5611 &'acl_check_data'&, and we will come to their definitions below, in the ACL
5612 section of the configuration. The RCPT ACL controls which recipients are
5613 accepted for an incoming message &-- if a configuration does not provide an ACL
5614 to check recipients, no SMTP mail can be accepted. The DATA ACL allows the
5615 contents of a message to be checked.
5617 Two commented-out option settings are next:
5619 # av_scanner = clamd:/tmp/clamd
5620 # spamd_address = 127.0.0.1 783
5622 These are example settings that can be used when Exim is compiled with the
5623 content-scanning extension. The first specifies the interface to the virus
5624 scanner, and the second specifies the interface to SpamAssassin. Further
5625 details are given in chapter &<<CHAPexiscan>>&.
5627 Three more commented-out option settings follow:
5629 # tls_advertise_hosts = *
5630 # tls_certificate = /etc/ssl/exim.crt
5631 # tls_privatekey = /etc/ssl/exim.pem
5633 These are example settings that can be used when Exim is compiled with
5634 support for TLS (aka SSL) as described in section &<<SECTinctlsssl>>&. The
5635 first one specifies the list of clients that are allowed to use TLS when
5636 connecting to this server; in this case, the wildcard means all clients. The
5637 other options specify where Exim should find its TLS certificate and private
5638 key, which together prove the server's identity to any clients that connect.
5639 More details are given in chapter &<<CHAPTLS>>&.
5641 Another two commented-out option settings follow:
5643 # daemon_smtp_ports = 25 : 465 : 587
5644 # tls_on_connect_ports = 465
5646 .cindex "port" "465 and 587"
5647 .cindex "port" "for message submission"
5648 .cindex "message" "submission, ports for"
5649 .cindex "submissions protocol"
5650 .cindex "smtps protocol"
5651 .cindex "ssmtp protocol"
5652 .cindex "SMTP" "submissions protocol"
5653 .cindex "SMTP" "ssmtp protocol"
5654 .cindex "SMTP" "smtps protocol"
5655 These options provide better support for roaming users who wish to use this
5656 server for message submission. They are not much use unless you have turned on
5657 TLS (as described in the previous paragraph) and authentication (about which
5658 more in section &<<SECTdefconfauth>>&).
5659 Mail submission from mail clients (MUAs) should be separate from inbound mail
5660 to your domain (MX delivery) for various good reasons (eg, ability to impose
5661 much saner TLS protocol and ciphersuite requirements without unintended
5663 RFC 6409 (previously 4409) specifies use of port 587 for SMTP Submission,
5664 which uses STARTTLS, so this is the &"submission"& port.
5665 RFC 8314 specifies use of port 465 as the &"submissions"& protocol,
5666 which should be used in preference to 587.
5667 You should also consider deploying SRV records to help clients find
5669 Older names for &"submissions"& are &"smtps"& and &"ssmtp"&.
5671 Two more commented-out options settings follow:
5674 # qualify_recipient =
5676 The first of these specifies a domain that Exim uses when it constructs a
5677 complete email address from a local login name. This is often needed when Exim
5678 receives a message from a local process. If you do not set &%qualify_domain%&,
5679 the value of &%primary_hostname%& is used. If you set both of these options,
5680 you can have different qualification domains for sender and recipient
5681 addresses. If you set only the first one, its value is used in both cases.
5683 .cindex "domain literal" "recognizing format"
5684 The following line must be uncommented if you want Exim to recognize
5685 addresses of the form &'user@[10.11.12.13]'& that is, with a &"domain literal"&
5686 (an IP address within square brackets) instead of a named domain.
5688 # allow_domain_literals
5690 The RFCs still require this form, but many people think that in the modern
5691 Internet it makes little sense to permit mail to be sent to specific hosts by
5692 quoting their IP addresses. This ancient format has been used by people who
5693 try to abuse hosts by using them for unwanted relaying. However, some
5694 people believe there are circumstances (for example, messages addressed to
5695 &'postmaster'&) where domain literals are still useful.
5697 The next configuration line is a kind of trigger guard:
5701 It specifies that no delivery must ever be run as the root user. The normal
5702 convention is to set up &'root'& as an alias for the system administrator. This
5703 setting is a guard against slips in the configuration.
5704 The list of users specified by &%never_users%& is not, however, the complete
5705 list; the build-time configuration in &_Local/Makefile_& has an option called
5706 FIXED_NEVER_USERS specifying a list that cannot be overridden. The
5707 contents of &%never_users%& are added to this list. By default
5708 FIXED_NEVER_USERS also specifies root.
5710 When a remote host connects to Exim in order to send mail, the only information
5711 Exim has about the host's identity is its IP address. The next configuration
5716 specifies that Exim should do a reverse DNS lookup on all incoming connections,
5717 in order to get a host name. This improves the quality of the logging
5718 information, but if you feel it is too expensive, you can remove it entirely,
5719 or restrict the lookup to hosts on &"nearby"& networks.
5720 Note that it is not always possible to find a host name from an IP address,
5721 because not all DNS reverse zones are maintained, and sometimes DNS servers are
5724 The next two lines are concerned with &'ident'& callbacks, as defined by RFC
5725 1413 (hence their names):
5728 rfc1413_query_timeout = 0s
5730 These settings cause Exim to avoid ident callbacks for all incoming SMTP calls.
5731 Few hosts offer RFC1413 service these days; calls have to be
5732 terminated by a timeout and this needlessly delays the startup
5733 of an incoming SMTP connection.
5734 If you have hosts for which you trust RFC1413 and need this
5735 information, you can change this.
5737 This line enables an efficiency SMTP option. It is negotiated by clients
5738 and not expected to cause problems but can be disabled if needed.
5743 When Exim receives messages over SMTP connections, it expects all addresses to
5744 be fully qualified with a domain, as required by the SMTP definition. However,
5745 if you are running a server to which simple clients submit messages, you may
5746 find that they send unqualified addresses. The two commented-out options:
5748 # sender_unqualified_hosts =
5749 # recipient_unqualified_hosts =
5751 show how you can specify hosts that are permitted to send unqualified sender
5752 and recipient addresses, respectively.
5754 The &%log_selector%& option is used to increase the detail of logging
5757 log_selector = +smtp_protocol_error +smtp_syntax_error \
5758 +tls_certificate_verified
5761 The &%percent_hack_domains%& option is also commented out:
5763 # percent_hack_domains =
5765 It provides a list of domains for which the &"percent hack"& is to operate.
5766 This is an almost obsolete form of explicit email routing. If you do not know
5767 anything about it, you can safely ignore this topic.
5769 The next two settings in the main part of the default configuration are
5770 concerned with messages that have been &"frozen"& on Exim's queue. When a
5771 message is frozen, Exim no longer continues to try to deliver it. Freezing
5772 occurs when a bounce message encounters a permanent failure because the sender
5773 address of the original message that caused the bounce is invalid, so the
5774 bounce cannot be delivered. This is probably the most common case, but there
5775 are also other conditions that cause freezing, and frozen messages are not
5776 always bounce messages.
5778 ignore_bounce_errors_after = 2d
5779 timeout_frozen_after = 7d
5781 The first of these options specifies that failing bounce messages are to be
5782 discarded after 2 days in the queue. The second specifies that any frozen
5783 message (whether a bounce message or not) is to be timed out (and discarded)
5784 after a week. In this configuration, the first setting ensures that no failing
5785 bounce message ever lasts a week.
5787 Exim queues it's messages in a spool directory. If you expect to have
5788 large queues, you may consider using this option. It splits the spool
5789 directory into subdirectories to avoid file system degradation from
5790 many files in a single directory, resulting in better performance.
5791 Manual manipulation of queued messages becomes more complex (though fortunately
5794 # split_spool_directory = true
5797 In an ideal world everybody follows the standards. For non-ASCII
5798 messages RFC 2047 is a standard, allowing a maximum line length of 76
5799 characters. Exim adheres that standard and won't process messages which
5800 violate this standard. (Even ${rfc2047:...} expansions will fail.)
5801 In particular, the Exim maintainers have had multiple reports of
5802 problems from Russian administrators of issues until they disable this
5803 check, because of some popular, yet buggy, mail composition software.
5805 # check_rfc2047_length = false
5808 If you need to be strictly RFC compliant you may wish to disable the
5809 8BITMIME advertisement. Use this, if you exchange mails with systems
5810 that are not 8-bit clean.
5812 # accept_8bitmime = false
5815 Libraries you use may depend on specific environment settings. This
5816 imposes a security risk (e.g. PATH). There are two lists:
5817 &%keep_environment%& for the variables to import as they are, and
5818 &%add_environment%& for variables we want to set to a fixed value.
5819 Note that TZ is handled separately, by the &%timezone%& runtime
5820 option and by the TIMEZONE_DEFAULT buildtime option.
5822 # keep_environment = ^LDAP
5823 # add_environment = PATH=/usr/bin::/bin
5827 .section "ACL configuration" "SECID54"
5828 .cindex "default" "ACLs"
5829 .cindex "&ACL;" "default configuration"
5830 In the default configuration, the ACL section follows the main configuration.
5831 It starts with the line
5835 and it contains the definitions of two ACLs, called &'acl_check_rcpt'& and
5836 &'acl_check_data'&, that were referenced in the settings of &%acl_smtp_rcpt%&
5837 and &%acl_smtp_data%& above.
5839 .cindex "RCPT" "ACL for"
5840 The first ACL is used for every RCPT command in an incoming SMTP message. Each
5841 RCPT command specifies one of the message's recipients. The ACL statements
5842 are considered in order, until the recipient address is either accepted or
5843 rejected. The RCPT command is then accepted or rejected, according to the
5844 result of the ACL processing.
5848 This line, consisting of a name terminated by a colon, marks the start of the
5853 This ACL statement accepts the recipient if the sending host matches the list.
5854 But what does that strange list mean? It doesn't actually contain any host
5855 names or IP addresses. The presence of the colon puts an empty item in the
5856 list; Exim matches this only if the incoming message did not come from a remote
5857 host, because in that case, the remote hostname is empty. The colon is
5858 important. Without it, the list itself is empty, and can never match anything.
5860 What this statement is doing is to accept unconditionally all recipients in
5861 messages that are submitted by SMTP from local processes using the standard
5862 input and output (that is, not using TCP/IP). A number of MUAs operate in this
5865 deny domains = +local_domains
5866 local_parts = ^[.] : ^.*[@%!/|]
5867 message = Restricted characters in address
5869 deny domains = !+local_domains
5870 local_parts = ^[./|] : ^.*[@%!] : ^.*/\\.\\./
5871 message = Restricted characters in address
5873 These statements are concerned with local parts that contain any of the
5874 characters &"@"&, &"%"&, &"!"&, &"/"&, &"|"&, or dots in unusual places.
5875 Although these characters are entirely legal in local parts (in the case of
5876 &"@"& and leading dots, only if correctly quoted), they do not commonly occur
5877 in Internet mail addresses.
5879 The first three have in the past been associated with explicitly routed
5880 addresses (percent is still sometimes used &-- see the &%percent_hack_domains%&
5881 option). Addresses containing these characters are regularly tried by spammers
5882 in an attempt to bypass relaying restrictions, and also by open relay testing
5883 programs. Unless you really need them it is safest to reject these characters
5884 at this early stage. This configuration is heavy-handed in rejecting these
5885 characters for all messages it accepts from remote hosts. This is a deliberate
5886 policy of being as safe as possible.
5888 The first rule above is stricter, and is applied to messages that are addressed
5889 to one of the local domains handled by this host. This is implemented by the
5890 first condition, which restricts it to domains that are listed in the
5891 &'local_domains'& domain list. The &"+"& character is used to indicate a
5892 reference to a named list. In this configuration, there is just one domain in
5893 &'local_domains'&, but in general there may be many.
5895 The second condition on the first statement uses two regular expressions to
5896 block local parts that begin with a dot or contain &"@"&, &"%"&, &"!"&, &"/"&,
5897 or &"|"&. If you have local accounts that include these characters, you will
5898 have to modify this rule.
5900 Empty components (two dots in a row) are not valid in RFC 2822, but Exim
5901 allows them because they have been encountered in practice. (Consider the
5902 common convention of local parts constructed as
5903 &"&'first-initial.second-initial.family-name'&"& when applied to someone like
5904 the author of Exim, who has no second initial.) However, a local part starting
5905 with a dot or containing &"/../"& can cause trouble if it is used as part of a
5906 filename (for example, for a mailing list). This is also true for local parts
5907 that contain slashes. A pipe symbol can also be troublesome if the local part
5908 is incorporated unthinkingly into a shell command line.
5910 The second rule above applies to all other domains, and is less strict. This
5911 allows your own users to send outgoing messages to sites that use slashes
5912 and vertical bars in their local parts. It blocks local parts that begin
5913 with a dot, slash, or vertical bar, but allows these characters within the
5914 local part. However, the sequence &"/../"& is barred. The use of &"@"&, &"%"&,
5915 and &"!"& is blocked, as before. The motivation here is to prevent your users
5916 (or your users' viruses) from mounting certain kinds of attack on remote sites.
5918 accept local_parts = postmaster
5919 domains = +local_domains
5921 This statement, which has two conditions, accepts an incoming address if the
5922 local part is &'postmaster'& and the domain is one of those listed in the
5923 &'local_domains'& domain list. The &"+"& character is used to indicate a
5924 reference to a named list. In this configuration, there is just one domain in
5925 &'local_domains'&, but in general there may be many.
5927 The presence of this statement means that mail to postmaster is never blocked
5928 by any of the subsequent tests. This can be helpful while sorting out problems
5929 in cases where the subsequent tests are incorrectly denying access.
5931 require verify = sender
5933 This statement requires the sender address to be verified before any subsequent
5934 ACL statement can be used. If verification fails, the incoming recipient
5935 address is refused. Verification consists of trying to route the address, to
5936 see if a bounce message could be delivered to it. In the case of remote
5937 addresses, basic verification checks only the domain, but &'callouts'& can be
5938 used for more verification if required. Section &<<SECTaddressverification>>&
5939 discusses the details of address verification.
5941 accept hosts = +relay_from_hosts
5942 control = submission
5944 This statement accepts the address if the message is coming from one of the
5945 hosts that are defined as being allowed to relay through this host. Recipient
5946 verification is omitted here, because in many cases the clients are dumb MUAs
5947 that do not cope well with SMTP error responses. For the same reason, the
5948 second line specifies &"submission mode"& for messages that are accepted. This
5949 is described in detail in section &<<SECTsubmodnon>>&; it causes Exim to fix
5950 messages that are deficient in some way, for example, because they lack a
5951 &'Date:'& header line. If you are actually relaying out from MTAs, you should
5952 probably add recipient verification here, and disable submission mode.
5954 accept authenticated = *
5955 control = submission
5957 This statement accepts the address if the client host has authenticated itself.
5958 Submission mode is again specified, on the grounds that such messages are most
5959 likely to come from MUAs. The default configuration does not define any
5960 authenticators, though it does include some nearly complete commented-out
5961 examples described in &<<SECTdefconfauth>>&. This means that no client can in
5962 fact authenticate until you complete the authenticator definitions.
5964 require message = relay not permitted
5965 domains = +local_domains : +relay_to_domains
5967 This statement rejects the address if its domain is neither a local domain nor
5968 one of the domains for which this host is a relay.
5970 require verify = recipient
5972 This statement requires the recipient address to be verified; if verification
5973 fails, the address is rejected.
5975 # deny dnslists = black.list.example
5976 # message = rejected because $sender_host_address \
5977 # is in a black list at $dnslist_domain\n\
5980 # warn dnslists = black.list.example
5981 # add_header = X-Warning: $sender_host_address is in \
5982 # a black list at $dnslist_domain
5983 # log_message = found in $dnslist_domain
5985 These commented-out lines are examples of how you could configure Exim to check
5986 sending hosts against a DNS black list. The first statement rejects messages
5987 from blacklisted hosts, whereas the second just inserts a warning header
5990 # require verify = csa
5992 This commented-out line is an example of how you could turn on client SMTP
5993 authorization (CSA) checking. Such checks do DNS lookups for special SRV
5998 The final statement in the first ACL unconditionally accepts any recipient
5999 address that has successfully passed all the previous tests.
6003 This line marks the start of the second ACL, and names it. Most of the contents
6004 of this ACL are commented out:
6007 # message = This message contains a virus \
6010 These lines are examples of how to arrange for messages to be scanned for
6011 viruses when Exim has been compiled with the content-scanning extension, and a
6012 suitable virus scanner is installed. If the message is found to contain a
6013 virus, it is rejected with the given custom error message.
6015 # warn spam = nobody
6016 # message = X-Spam_score: $spam_score\n\
6017 # X-Spam_score_int: $spam_score_int\n\
6018 # X-Spam_bar: $spam_bar\n\
6019 # X-Spam_report: $spam_report
6021 These lines are an example of how to arrange for messages to be scanned by
6022 SpamAssassin when Exim has been compiled with the content-scanning extension,
6023 and SpamAssassin has been installed. The SpamAssassin check is run with
6024 &`nobody`& as its user parameter, and the results are added to the message as a
6025 series of extra header line. In this case, the message is not rejected,
6026 whatever the spam score.
6030 This final line in the DATA ACL accepts the message unconditionally.
6033 .section "Router configuration" "SECID55"
6034 .cindex "default" "routers"
6035 .cindex "routers" "default"
6036 The router configuration comes next in the default configuration, introduced
6041 Routers are the modules in Exim that make decisions about where to send
6042 messages. An address is passed to each router, in turn, until it is either
6043 accepted, or failed. This means that the order in which you define the routers
6044 matters. Each router is fully described in its own chapter later in this
6045 manual. Here we give only brief overviews.
6048 # driver = ipliteral
6049 # domains = !+local_domains
6050 # transport = remote_smtp
6052 .cindex "domain literal" "default router"
6053 This router is commented out because the majority of sites do not want to
6054 support domain literal addresses (those of the form &'user@[10.9.8.7]'&). If
6055 you uncomment this router, you also need to uncomment the setting of
6056 &%allow_domain_literals%& in the main part of the configuration.
6058 Which router is used next depends upon whether or not the ROUTER_SMARTHOST
6059 macro has been defined, per
6061 .ifdef ROUTER_SMARTHOST
6070 If ROUTER_SMARTHOST has been defined, either at the top of the file or on the
6071 command-line, then we route all non-local mail to that smarthost; otherwise, we'll
6072 perform DNS lookups for direct-to-MX lookup. Any mail which is to a local domain will
6073 skip these routers because of the &%domains%& option.
6077 driver = manualroute
6078 domains = ! +local_domains
6079 transport = smarthost_smtp
6080 route_data = ROUTER_SMARTHOST
6081 ignore_target_hosts = <; 0.0.0.0 ; 127.0.0.0/8 ; ::1
6084 This router only handles mail which is not to any local domains; this is
6085 specified by the line
6087 domains = ! +local_domains
6089 The &%domains%& option lists the domains to which this router applies, but the
6090 exclamation mark is a negation sign, so the router is used only for domains
6091 that are not in the domain list called &'local_domains'& (which was defined at
6092 the start of the configuration). The plus sign before &'local_domains'&
6093 indicates that it is referring to a named list. Addresses in other domains are
6094 passed on to the following routers.
6096 The name of the router driver is &(manualroute)& because we are manually
6097 specifying how mail should be routed onwards, instead of using DNS MX.
6098 While the name of this router instance is arbitrary, the &%driver%& option must
6099 be one of the driver modules that is in the Exim binary.
6101 With no pre-conditions other than &%domains%&, all mail for non-local domains
6102 will be handled by this router, and the &%no_more%& setting will ensure that no
6103 other routers will be used for messages matching the pre-conditions. See
6104 &<<SECTrouprecon>>& for more on how the pre-conditions apply. For messages which
6105 are handled by this router, we provide a hostname to deliver to in &%route_data%&
6106 and the macro supplies the value; the address is then queued for the
6107 &(smarthost_smtp)& transport.
6112 domains = ! +local_domains
6113 transport = remote_smtp
6114 ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
6117 The &%domains%& option behaves as per smarthost, above.
6119 The name of the router driver is &(dnslookup)&,
6120 and is specified by the &%driver%& option. Do not be confused by the fact that
6121 the name of this router instance is the same as the name of the driver. The
6122 instance name is arbitrary, but the name set in the &%driver%& option must be
6123 one of the driver modules that is in the Exim binary.
6125 The &(dnslookup)& router routes addresses by looking up their domains in the
6126 DNS in order to obtain a list of hosts to which the address is routed. If the
6127 router succeeds, the address is queued for the &(remote_smtp)& transport, as
6128 specified by the &%transport%& option. If the router does not find the domain
6129 in the DNS, no further routers are tried because of the &%no_more%& setting, so
6130 the address fails and is bounced.
6132 The &%ignore_target_hosts%& option specifies a list of IP addresses that are to
6133 be entirely ignored. This option is present because a number of cases have been
6134 encountered where MX records in the DNS point to host names
6135 whose IP addresses are 0.0.0.0 or are in the 127 subnet (typically 127.0.0.1).
6136 Completely ignoring these IP addresses causes Exim to fail to route the
6137 email address, so it bounces. Otherwise, Exim would log a routing problem, and
6138 continue to try to deliver the message periodically until the address timed
6145 data = ${lookup{$local_part}lsearch{/etc/aliases}}
6147 file_transport = address_file
6148 pipe_transport = address_pipe
6150 Control reaches this and subsequent routers only for addresses in the local
6151 domains. This router checks to see whether the local part is defined as an
6152 alias in the &_/etc/aliases_& file, and if so, redirects it according to the
6153 data that it looks up from that file. If no data is found for the local part,
6154 the value of the &%data%& option is empty, causing the address to be passed to
6157 &_/etc/aliases_& is a conventional name for the system aliases file that is
6158 often used. That is why it is referenced by from the default configuration
6159 file. However, you can change this by setting SYSTEM_ALIASES_FILE in
6160 &_Local/Makefile_& before building Exim.
6165 # local_part_suffix = +* : -*
6166 # local_part_suffix_optional
6167 file = $home/.forward
6172 file_transport = address_file
6173 pipe_transport = address_pipe
6174 reply_transport = address_reply
6176 This is the most complicated router in the default configuration. It is another
6177 redirection router, but this time it is looking for forwarding data set up by
6178 individual users. The &%check_local_user%& setting specifies a check that the
6179 local part of the address is the login name of a local user. If it is not, the
6180 router is skipped. The two commented options that follow &%check_local_user%&,
6183 # local_part_suffix = +* : -*
6184 # local_part_suffix_optional
6186 .vindex "&$local_part_suffix$&"
6187 show how you can specify the recognition of local part suffixes. If the first
6188 is uncommented, a suffix beginning with either a plus or a minus sign, followed
6189 by any sequence of characters, is removed from the local part and placed in the
6190 variable &$local_part_suffix$&. The second suffix option specifies that the
6191 presence of a suffix in the local part is optional. When a suffix is present,
6192 the check for a local login uses the local part with the suffix removed.
6194 When a local user account is found, the file called &_.forward_& in the user's
6195 home directory is consulted. If it does not exist, or is empty, the router
6196 declines. Otherwise, the contents of &_.forward_& are interpreted as
6197 redirection data (see chapter &<<CHAPredirect>>& for more details).
6199 .cindex "Sieve filter" "enabling in default router"
6200 Traditional &_.forward_& files contain just a list of addresses, pipes, or
6201 files. Exim supports this by default. However, if &%allow_filter%& is set (it
6202 is commented out by default), the contents of the file are interpreted as a set
6203 of Exim or Sieve filtering instructions, provided the file begins with &"#Exim
6204 filter"& or &"#Sieve filter"&, respectively. User filtering is discussed in the
6205 separate document entitled &'Exim's interfaces to mail filtering'&.
6207 The &%no_verify%& and &%no_expn%& options mean that this router is skipped when
6208 verifying addresses, or when running as a consequence of an SMTP EXPN command.
6209 There are two reasons for doing this:
6212 Whether or not a local user has a &_.forward_& file is not really relevant when
6213 checking an address for validity; it makes sense not to waste resources doing
6216 More importantly, when Exim is verifying addresses or handling an EXPN
6217 command during an SMTP session, it is running as the Exim user, not as root.
6218 The group is the Exim group, and no additional groups are set up.
6219 It may therefore not be possible for Exim to read users' &_.forward_& files at
6223 The setting of &%check_ancestor%& prevents the router from generating a new
6224 address that is the same as any previous address that was redirected. (This
6225 works round a problem concerning a bad interaction between aliasing and
6226 forwarding &-- see section &<<SECTredlocmai>>&).
6228 The final three option settings specify the transports that are to be used when
6229 forwarding generates a direct delivery to a file, or to a pipe, or sets up an
6230 auto-reply, respectively. For example, if a &_.forward_& file contains
6232 a.nother@elsewhere.example, /home/spqr/archive
6234 the delivery to &_/home/spqr/archive_& is done by running the &%address_file%&
6240 # local_part_suffix = +* : -*
6241 # local_part_suffix_optional
6242 transport = local_delivery
6244 The final router sets up delivery into local mailboxes, provided that the local
6245 part is the name of a local login, by accepting the address and assigning it to
6246 the &(local_delivery)& transport. Otherwise, we have reached the end of the
6247 routers, so the address is bounced. The commented suffix settings fulfil the
6248 same purpose as they do for the &(userforward)& router.
6251 .section "Transport configuration" "SECID56"
6252 .cindex "default" "transports"
6253 .cindex "transports" "default"
6254 Transports define mechanisms for actually delivering messages. They operate
6255 only when referenced from routers, so the order in which they are defined does
6256 not matter. The transports section of the configuration starts with
6260 Two remote transports and four local transports are defined.
6264 message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}
6269 This transport is used for delivering messages over SMTP connections.
6270 The list of remote hosts comes from the router.
6271 The &%message_size_limit%& usage is a hack to avoid sending on messages
6272 with over-long lines.
6274 The &%hosts_try_prdr%& option enables an efficiency SMTP option. It is
6275 negotiated between client and server and not expected to cause problems
6276 but can be disabled if needed. The built-in macro _HAVE_PRDR guards the
6277 use of the &%hosts_try_prdr%& configuration option.
6279 The other remote transport is used when delivering to a specific smarthost
6280 with whom there must be some kind of existing relationship, instead of the
6281 usual federated system.
6286 message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}
6290 # Comment out any of these which you have to, then file a Support
6291 # request with your smarthost provider to get things fixed:
6292 hosts_require_tls = *
6293 tls_verify_hosts = *
6294 # As long as tls_verify_hosts is enabled, this this will have no effect,
6295 # but if you have to comment it out then this will at least log whether
6296 # you succeed or not:
6297 tls_try_verify_hosts = *
6299 # The SNI name should match the name which we'll expect to verify;
6300 # many mail systems don't use SNI and this doesn't matter, but if it does,
6301 # we need to send a name which the remote site will recognize.
6302 # This _should_ be the name which the smarthost operators specified as
6303 # the hostname for sending your mail to.
6304 tls_sni = ROUTER_SMARTHOST
6306 .ifdef _HAVE_OPENSSL
6307 tls_require_ciphers = HIGH:!aNULL:@STRENGTH
6310 tls_require_ciphers = SECURE192:-VERS-SSL3.0:-VERS-TLS1.0:-VERS-TLS1.1
6317 After the same &%message_size_limit%& hack, we then specify that this Transport
6318 can handle messages to multiple domains in one run. The assumption here is
6319 that you're routing all non-local mail to the same place and that place is
6320 happy to take all messages from you as quickly as possible.
6321 All other options depend upon built-in macros; if Exim was built without TLS support
6322 then no other options are defined.
6323 If TLS is available, then we configure "stronger than default" TLS ciphersuites
6324 and versions using the &%tls_require_ciphers%& option, where the value to be
6325 used depends upon the library providing TLS.
6326 Beyond that, the options adopt the stance that you should have TLS support available
6327 from your smarthost on today's Internet, so we turn on requiring TLS for the
6328 mail to be delivered, and requiring that the certificate be valid, and match
6329 the expected hostname. The &%tls_sni%& option can be used by service providers
6330 to select an appropriate certificate to present to you and here we re-use the
6331 ROUTER_SMARTHOST macro, because that is unaffected by CNAMEs present in DNS.
6332 You want to specify the hostname which you'll expect to validate for, and that
6333 should not be subject to insecure tampering via DNS results.
6335 For the &%hosts_try_prdr%& option see the previous transport.
6337 All other options are defaulted.
6341 file = /var/mail/$local_part_data
6348 This &(appendfile)& transport is used for local delivery to user mailboxes in
6349 traditional BSD mailbox format.
6351 We prefer to avoid using &$local_part$& directly to define the mailbox filename,
6352 as it is provided by a potential bad actor.
6353 Instead we use &$local_part_data$&,
6354 the result of looking up &$local_part$& in the user database
6355 (done by using &%check_local_user%& in the the router).
6357 By default &(appendfile)& runs under the uid and gid of the
6358 local user, which requires the sticky bit to be set on the &_/var/mail_&
6359 directory. Some systems use the alternative approach of running mail deliveries
6360 under a particular group instead of using the sticky bit. The commented options
6361 show how this can be done.
6363 Exim adds three headers to the message as it delivers it: &'Delivery-date:'&,
6364 &'Envelope-to:'& and &'Return-path:'&. This action is requested by the three
6365 similarly-named options above.
6371 This transport is used for handling deliveries to pipes that are generated by
6372 redirection (aliasing or users' &_.forward_& files). The &%return_output%&
6373 option specifies that any output on stdout or stderr generated by the pipe is to
6374 be returned to the sender.
6382 This transport is used for handling deliveries to files that are generated by
6383 redirection. The name of the file is not specified in this instance of
6384 &(appendfile)&, because it comes from the &(redirect)& router.
6389 This transport is used for handling automatic replies generated by users'
6394 .section "Default retry rule" "SECID57"
6395 .cindex "retry" "default rule"
6396 .cindex "default" "retry rule"
6397 The retry section of the configuration file contains rules which affect the way
6398 Exim retries deliveries that cannot be completed at the first attempt. It is
6399 introduced by the line
6403 In the default configuration, there is just one rule, which applies to all
6406 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
6408 This causes any temporarily failing address to be retried every 15 minutes for
6409 2 hours, then at intervals starting at one hour and increasing by a factor of
6410 1.5 until 16 hours have passed, then every 6 hours up to 4 days. If an address
6411 is not delivered after 4 days of temporary failure, it is bounced. The time is
6412 measured from first failure, not from the time the message was received.
6414 If the retry section is removed from the configuration, or is empty (that is,
6415 if no retry rules are defined), Exim will not retry deliveries. This turns
6416 temporary errors into permanent errors.
6419 .section "Rewriting configuration" "SECID58"
6420 The rewriting section of the configuration, introduced by
6424 contains rules for rewriting addresses in messages as they arrive. There are no
6425 rewriting rules in the default configuration file.
6429 .section "Authenticators configuration" "SECTdefconfauth"
6430 .cindex "AUTH" "configuration"
6431 The authenticators section of the configuration, introduced by
6433 begin authenticators
6435 defines mechanisms for the use of the SMTP AUTH command. The default
6436 configuration file contains two commented-out example authenticators
6437 which support plaintext username/password authentication using the
6438 standard PLAIN mechanism and the traditional but non-standard LOGIN
6439 mechanism, with Exim acting as the server. PLAIN and LOGIN are enough
6440 to support most MUA software.
6442 The example PLAIN authenticator looks like this:
6445 # driver = plaintext
6446 # server_set_id = $auth2
6447 # server_prompts = :
6448 # server_condition = Authentication is not yet configured
6449 # server_advertise_condition = ${if def:tls_in_cipher }
6451 And the example LOGIN authenticator looks like this:
6454 # driver = plaintext
6455 # server_set_id = $auth1
6456 # server_prompts = <| Username: | Password:
6457 # server_condition = Authentication is not yet configured
6458 # server_advertise_condition = ${if def:tls_in_cipher }
6461 The &%server_set_id%& option makes Exim remember the authenticated username
6462 in &$authenticated_id$&, which can be used later in ACLs or routers. The
6463 &%server_prompts%& option configures the &(plaintext)& authenticator so
6464 that it implements the details of the specific authentication mechanism,
6465 i.e. PLAIN or LOGIN. The &%server_advertise_condition%& setting controls
6466 when Exim offers authentication to clients; in the examples, this is only
6467 when TLS or SSL has been started, so to enable the authenticators you also
6468 need to add support for TLS as described in section &<<SECTdefconfmain>>&.
6470 The &%server_condition%& setting defines how to verify that the username and
6471 password are correct. In the examples it just produces an error message.
6472 To make the authenticators work, you can use a string expansion
6473 expression like one of the examples in chapter &<<CHAPplaintext>>&.
6475 Beware that the sequence of the parameters to PLAIN and LOGIN differ; the
6476 usercode and password are in different positions.
6477 Chapter &<<CHAPplaintext>>& covers both.
6479 .ecindex IIDconfiwal
6483 . ////////////////////////////////////////////////////////////////////////////
6484 . ////////////////////////////////////////////////////////////////////////////
6486 .chapter "Regular expressions" "CHAPregexp"
6488 .cindex "regular expressions" "library"
6490 Exim supports the use of regular expressions in many of its options. It
6491 uses the PCRE2 regular expression library; this provides regular expression
6492 matching that is compatible with Perl 5. The syntax and semantics of
6493 regular expressions is discussed in
6494 online Perl manpages, in
6495 many Perl reference books, and also in
6496 Jeffrey Friedl's &'Mastering Regular Expressions'&, which is published by
6497 O'Reilly (see &url(http://www.oreilly.com/catalog/regex2/)).
6498 . --- the http: URL here redirects to another page with the ISBN in the URL
6499 . --- where trying to use https: just redirects back to http:, so sticking
6500 . --- to the old URL for now. 2018-09-07.
6502 The documentation for the syntax and semantics of the regular expressions that
6503 are supported by PCRE2 is included in the PCRE2 distribution, and no further
6504 description is included here. The PCRE2 functions are called from Exim using
6505 the default option settings (that is, with no PCRE2 options set), except that
6506 the PCRE2_CASELESS option is set when the matching is required to be
6509 In most cases, when a regular expression is required in an Exim configuration,
6510 it has to start with a circumflex, in order to distinguish it from plain text
6511 or an &"ends with"& wildcard. In this example of a configuration setting, the
6512 second item in the colon-separated list is a regular expression.
6514 domains = a.b.c : ^\\d{3} : *.y.z : ...
6516 The doubling of the backslash is required because of string expansion that
6517 precedes interpretation &-- see section &<<SECTlittext>>& for more discussion
6518 of this issue, and a way of avoiding the need for doubling backslashes. The
6519 regular expression that is eventually used in this example contains just one
6520 backslash. The circumflex is included in the regular expression, and has the
6521 normal effect of &"anchoring"& it to the start of the string that is being
6524 There are, however, two cases where a circumflex is not required for the
6525 recognition of a regular expression: these are the &%match%& condition in a
6526 string expansion, and the &%matches%& condition in an Exim filter file. In
6527 these cases, the relevant string is always treated as a regular expression; if
6528 it does not start with a circumflex, the expression is not anchored, and can
6529 match anywhere in the subject string.
6531 In all cases, if you want a regular expression to match at the end of a string,
6532 you must code the $ metacharacter to indicate this. For example:
6534 domains = ^\\d{3}\\.example
6536 matches the domain &'123.example'&, but it also matches &'123.example.com'&.
6539 domains = ^\\d{3}\\.example\$
6541 if you want &'example'& to be the top-level domain. The backslash before the
6542 $ is needed because string expansion also interprets dollar characters.
6546 . ////////////////////////////////////////////////////////////////////////////
6547 . ////////////////////////////////////////////////////////////////////////////
6549 .chapter "File and database lookups" "CHAPfdlookup"
6550 .scindex IIDfidalo1 "file" "lookups"
6551 .scindex IIDfidalo2 "database" "lookups"
6552 .cindex "lookup" "description of"
6553 Exim can be configured to look up data in files or databases as it processes
6554 messages. Two different kinds of syntax are used:
6557 A string that is to be expanded may contain explicit lookup requests. These
6558 cause parts of the string to be replaced by data that is obtained from the
6559 lookup. Lookups of this type are conditional expansion items. Different results
6560 can be defined for the cases of lookup success and failure. See chapter
6561 &<<CHAPexpand>>&, where string expansions are described in detail.
6562 The key for the lookup is &*specified*& as part of the string to be expanded.
6564 Lists of domains, hosts, and email addresses can contain lookup requests as a
6565 way of avoiding excessively long linear lists. In this case, the data that is
6566 returned by the lookup is often (but not always) discarded; whether the lookup
6567 succeeds or fails is what really counts. These kinds of list are described in
6568 chapter &<<CHAPdomhosaddlists>>&.
6569 Depending on the lookup type (see below)
6570 the key for the lookup may need to be &*specified*& as above
6571 or may be &*implicit*&,
6572 given by the context in which the list is being checked.
6575 String expansions, lists, and lookups interact with each other in such a way
6576 that there is no order in which to describe any one of them that does not
6577 involve references to the others. Each of these three chapters makes more sense
6578 if you have read the other two first. If you are reading this for the first
6579 time, be aware that some of it will make a lot more sense after you have read
6580 chapters &<<CHAPdomhosaddlists>>& and &<<CHAPexpand>>&.
6582 .section "Examples of different lookup syntax" "SECID60"
6583 It is easy to confuse the two different kinds of lookup, especially as the
6584 lists that may contain the second kind are always expanded before being
6585 processed as lists. Therefore, they may also contain lookups of the first kind.
6586 Be careful to distinguish between the following two examples:
6588 domains = ${lookup{$sender_host_address}lsearch{/some/file}}
6589 domains = lsearch;/some/file
6592 The first uses a string expansion, the result of which must be a domain list.
6593 The key for an expansion-style lookup must be given explicitly.
6594 No strings have been specified for a successful or a failing lookup; the
6595 defaults in this case are the looked-up data and an empty string, respectively.
6596 The expansion takes place before the string is processed as a list, and the
6597 file that is searched could contain lines like this:
6599 192.168.3.4: domain1:domain2:...
6600 192.168.1.9: domain3:domain4:...
6602 When the lookup succeeds, the result of the expansion is a list of domains (and
6603 possibly other types of item that are allowed in domain lists).
6604 .cindex "tainted data" "de-tainting"
6605 .cindex "de-tainting" "using a lookup expansion""
6606 The result of the expansion is not tainted.
6609 In the second example, the lookup is a single item in a domain list. It causes
6610 Exim to use a lookup to see if the domain that is being processed can be found
6612 The file could contains lines like this:
6617 Any data that follows the keys is not relevant when checking that the domain
6618 matches the list item.
6620 The key for a list-style lookup is implicit, from the lookup context, if
6621 the lookup is a single-key type (see below).
6622 For query-style lookup types the query must be given explicitly.
6625 It is possible, though no doubt confusing, to use both kinds of lookup at once.
6626 Consider a file containing lines like this:
6628 192.168.5.6: lsearch;/another/file
6630 If the value of &$sender_host_address$& is 192.168.5.6, expansion of the
6631 first &%domains%& setting above generates the second setting, which therefore
6632 causes a second lookup to occur.
6634 The lookup type may optionally be followed by a comma
6635 and a comma-separated list of options.
6636 Each option is a &"name=value"& pair.
6637 Whether an option is meaningful depends on the lookup type.
6639 All lookups support the option &"cache=no_rd"&.
6640 If this is given then the cache that Exim manages for lookup results
6641 is not checked before doing the lookup.
6642 The result of the lookup is still written to the cache.
6644 The rest of this chapter describes the different lookup types that are
6645 available. Any of them can be used in any part of the configuration where a
6646 lookup is permitted.
6649 .section "Lookup types" "SECID61"
6650 .cindex "lookup" "types of"
6651 .cindex "single-key lookup" "definition of"
6652 Two different types of data lookup are implemented:
6655 The &'single-key'& type requires the specification of a file in which to look,
6656 and a single key to search for. The key must be a non-empty string for the
6657 lookup to succeed. The lookup type determines how the file is searched.
6658 .cindex "tainted data" "single-key lookups"
6659 The file string may not be tainted.
6661 .cindex "tainted data" "de-tainting"
6662 .cindex "de-tainting" "using a single-key lookup"
6663 All single-key lookups support the option &"ret=key"&.
6664 If this is given and the lookup
6665 (either underlying implementation or cached value)
6666 returns data, the result is replaced with a non-tainted
6667 version of the lookup key.
6670 .cindex "query-style lookup" "definition of"
6671 The &'query-style'& type accepts a generalized database query. No particular
6672 key value is assumed by Exim for query-style lookups. You can use whichever
6673 Exim variables you need to construct the database query.
6674 .cindex "tainted data" "quoting for lookups"
6675 If tainted data is used in the query then it should be quuted by
6676 using the &*${quote_*&<&'lookup-type'&>&*:*&<&'string'&>&*}*& expansion operator
6677 appropriate for the lookup.
6680 The code for each lookup type is in a separate source file that is included in
6681 the binary of Exim only if the corresponding compile-time option is set. The
6682 default settings in &_src/EDITME_& are:
6687 which means that only linear searching and DBM lookups are included by default.
6688 For some types of lookup (e.g. SQL databases), you need to install appropriate
6689 libraries and header files before building Exim.
6694 .section "Single-key lookup types" "SECTsinglekeylookups"
6695 .cindex "lookup" "single-key types"
6696 .cindex "single-key lookup" "list of types"
6697 The following single-key lookup types are implemented:
6700 .cindex "cdb" "description of"
6701 .cindex "lookup" "cdb"
6702 .cindex "binary zero" "in lookup key"
6703 &(cdb)&: The given file is searched as a Constant DataBase file, using the key
6704 string without a terminating binary zero. The cdb format is designed for
6705 indexed files that are read frequently and never updated, except by total
6706 re-creation. As such, it is particularly suitable for large files containing
6707 aliases or other indexed data referenced by an MTA. Information about cdb and
6708 tools for building the files can be found in several places:
6710 &url(https://cr.yp.to/cdb.html)
6711 &url(https://www.corpit.ru/mjt/tinycdb.html)
6712 &url(https://packages.debian.org/stable/utils/freecdb)
6713 &url(https://github.com/philpennock/cdbtools) (in Go)
6715 A cdb distribution is not needed in order to build Exim with cdb support,
6716 because the code for reading cdb files is included directly in Exim itself.
6717 However, no means of building or testing cdb files is provided with Exim, so
6718 you need to obtain a cdb distribution in order to do this.
6720 .cindex "DBM" "lookup type"
6721 .cindex "lookup" "dbm"
6722 .cindex "binary zero" "in lookup key"
6723 &(dbm)&: Calls to DBM library functions are used to extract data from the given
6724 DBM file by looking up the record with the given key. A terminating binary
6725 zero is included in the key that is passed to the DBM library. See section
6726 &<<SECTdb>>& for a discussion of DBM libraries.
6728 .cindex "Berkeley DB library" "file format"
6729 For all versions of Berkeley DB, Exim uses the DB_HASH style of database
6730 when building DBM files using the &%exim_dbmbuild%& utility. However, when
6731 using Berkeley DB versions 3 or 4, it opens existing databases for reading with
6732 the DB_UNKNOWN option. This enables it to handle any of the types of database
6733 that the library supports, and can be useful for accessing DBM files created by
6734 other applications. (For earlier DB versions, DB_HASH is always used.)
6736 .cindex "lookup" "dbmjz"
6737 .cindex "lookup" "dbm &-- embedded NULs"
6739 .cindex "dbmjz lookup type"
6740 &(dbmjz)&: This is the same as &(dbm)&, except that the lookup key is
6741 interpreted as an Exim list; the elements of the list are joined together with
6742 ASCII NUL characters to form the lookup key. An example usage would be to
6743 authenticate incoming SMTP calls using the passwords from Cyrus SASL's
6744 &_/etc/sasldb2_& file with the &(gsasl)& authenticator or Exim's own
6745 &(cram_md5)& authenticator.
6747 .cindex "lookup" "dbmnz"
6748 .cindex "lookup" "dbm &-- terminating zero"
6749 .cindex "binary zero" "in lookup key"
6751 .cindex "&_/etc/userdbshadow.dat_&"
6752 .cindex "dbmnz lookup type"
6753 &(dbmnz)&: This is the same as &(dbm)&, except that a terminating binary zero
6754 is not included in the key that is passed to the DBM library. You may need this
6755 if you want to look up data in files that are created by or shared with some
6756 other application that does not use terminating zeros. For example, you need to
6757 use &(dbmnz)& rather than &(dbm)& if you want to authenticate incoming SMTP
6758 calls using the passwords from Courier's &_/etc/userdbshadow.dat_& file. Exim's
6759 utility program for creating DBM files (&'exim_dbmbuild'&) includes the zeros
6760 by default, but has an option to omit them (see section &<<SECTdbmbuild>>&).
6762 .cindex "lookup" "dsearch"
6763 .cindex "dsearch lookup type"
6764 &(dsearch)&: The given file must be an
6766 directory path; this is searched for an entry
6767 whose name is the key by calling the &[lstat()]& function.
6769 contain any forward slash characters.
6770 If &[lstat()]& succeeds then so does the lookup.
6771 .cindex "tainted data" "dsearch result"
6772 The result is regarded as untainted.
6774 Options for the lookup can be given by appending them after the word "dsearch",
6775 separated by a comma. Options, if present, are a comma-separated list having
6776 each element starting with a tag name and an equals.
6778 Two options are supported, for the return value and for filtering match
6780 The "ret" option requests an alternate result value of
6781 the entire path for the entry. Example:
6783 ${lookup {passwd} dsearch,ret=full {/etc}}
6785 The default result is just the requested entry.
6786 The "filter" option requests that only directory entries of a given type
6787 are matched. The match value is one of "file", "dir" or "subdir" (the latter
6788 not matching "." or ".."). Example:
6790 ${lookup {passwd} dsearch,filter=file {/etc}}
6792 The default matching is for any entry type, including directories
6795 An example of how this
6796 lookup can be used to support virtual domains is given in section
6797 &<<SECTvirtualdomains>>&.
6799 .cindex "lookup" "iplsearch"
6800 .cindex "iplsearch lookup type"
6801 &(iplsearch)&: The given file is a text file containing keys and data. A key is
6802 terminated by a colon or white space or the end of the line. The keys in the
6803 file must be IP addresses, or IP addresses with CIDR masks. Keys that involve
6804 IPv6 addresses must be enclosed in quotes to prevent the first internal colon
6805 being interpreted as a key terminator. For example:
6807 1.2.3.4: data for 1.2.3.4
6808 192.168.0.0/16: data for 192.168.0.0/16
6809 "abcd::cdab": data for abcd::cdab
6810 "abcd:abcd::/32" data for abcd:abcd::/32
6812 The key for an &(iplsearch)& lookup must be an IP address (without a mask). The
6813 file is searched linearly, using the CIDR masks where present, until a matching
6814 key is found. The first key that matches is used; there is no attempt to find a
6815 &"best"& match. Apart from the way the keys are matched, the processing for
6816 &(iplsearch)& is the same as for &(lsearch)&.
6818 &*Warning 1*&: Unlike most other single-key lookup types, a file of data for
6819 &(iplsearch)& can &'not'& be turned into a DBM or cdb file, because those
6820 lookup types support only literal keys.
6822 &*Warning 2*&: In a host list, you must always use &(net-iplsearch)& so that
6823 the implicit key is the host's IP address rather than its name (see section
6824 &<<SECThoslispatsikey>>&).
6826 &*Warning 3*&: Do not use an IPv4-mapped IPv6 address for a key; use the
6827 IPv4, in dotted-quad form. (Exim converts IPv4-mapped IPv6 addresses to this
6828 notation before executing the lookup.)
6830 One option is supported, "ret=full", to request the return of the entire line
6831 rather than omitting the key portion.
6832 Note however that the key portion will have been de-quoted.
6836 .cindex json "lookup type"
6837 .cindex JSON expansions
6838 &(json)&: The given file is a text file with a JSON structure.
6839 An element of the structure is extracted, defined by the search key.
6840 The key is a list of subelement selectors
6841 (colon-separated by default but changeable in the usual way)
6842 which are applied in turn to select smaller and smaller portions
6843 of the JSON structure.
6844 If a selector is numeric, it must apply to a JSON array; the (zero-based)
6845 nunbered array element is selected.
6846 Otherwise it must apply to a JSON object; the named element is selected.
6847 The final resulting element can be a simple JSON type or a JSON object
6848 or array; for the latter two a string-representation of the JSON
6850 For elements of type string, the returned value is de-quoted.
6856 .cindex database lmdb
6857 &(lmdb)&: The given file is an LMDB database.
6858 LMDB is a memory-mapped key-value store,
6859 with API modeled loosely on that of BerkeleyDB.
6860 See &url(https://symas.com/products/lightning-memory-mapped-database/)
6861 for the feature set and operation modes.
6863 Exim provides read-only access via the LMDB C library.
6864 The library can be obtained from &url(https://github.com/LMDB/lmdb)
6865 or your operating system package repository.
6866 To enable LMDB support in Exim set LOOKUP_LMDB=yes in &_Local/Makefile_&.
6868 You will need to separately create the LMDB database file,
6869 possibly using the &"mdb_load"& utility.
6873 .cindex "linear search"
6874 .cindex "lookup" "lsearch"
6875 .cindex "lsearch lookup type"
6876 .cindex "case sensitivity" "in lsearch lookup"
6877 &(lsearch)&: The given file is a text file that is searched linearly for a
6878 line beginning with the search key, terminated by a colon or white space or the
6879 end of the line. The search is case-insensitive; that is, upper and lower case
6880 letters are treated as the same. The first occurrence of the key that is found
6881 in the file is used.
6883 White space between the key and the colon is permitted. The remainder of the
6884 line, with leading and trailing white space removed, is the data. This can be
6885 continued onto subsequent lines by starting them with any amount of white
6886 space, but only a single space character is included in the data at such a
6887 junction. If the data begins with a colon, the key must be terminated by a
6892 Empty lines and lines beginning with # are ignored, even if they occur in the
6893 middle of an item. This is the traditional textual format of alias files. Note
6894 that the keys in an &(lsearch)& file are literal strings. There is no
6895 wildcarding of any kind.
6897 .cindex "lookup" "lsearch &-- colons in keys"
6898 .cindex "white space" "in lsearch key"
6899 In most &(lsearch)& files, keys are not required to contain colons or #
6900 characters, or white space. However, if you need this feature, it is available.
6901 If a key begins with a doublequote character, it is terminated only by a
6902 matching quote (or end of line), and the normal escaping rules apply to its
6903 contents (see section &<<SECTstrings>>&). An optional colon is permitted after
6904 quoted keys (exactly as for unquoted keys). There is no special handling of
6905 quotes for the data part of an &(lsearch)& line.
6908 .cindex "NIS lookup type"
6909 .cindex "lookup" "NIS"
6910 .cindex "binary zero" "in lookup key"
6911 &(nis)&: The given file is the name of a NIS map, and a NIS lookup is done with
6912 the given key, without a terminating binary zero. There is a variant called
6913 &(nis0)& which does include the terminating binary zero in the key. This is
6914 reportedly needed for Sun-style alias files. Exim does not recognize NIS
6915 aliases; the full map names must be used.
6918 .cindex "wildlsearch lookup type"
6919 .cindex "lookup" "wildlsearch"
6920 .cindex "nwildlsearch lookup type"
6921 .cindex "lookup" "nwildlsearch"
6922 &(wildlsearch)& or &(nwildlsearch)&: These search a file linearly, like
6923 &(lsearch)&, but instead of being interpreted as a literal string, each key in
6924 the file may be wildcarded. The difference between these two lookup types is
6925 that for &(wildlsearch)&, each key in the file is string-expanded before being
6926 used, whereas for &(nwildlsearch)&, no expansion takes place.
6928 .cindex "case sensitivity" "in (n)wildlsearch lookup"
6929 Like &(lsearch)&, the testing is done case-insensitively. However, keys in the
6930 file that are regular expressions can be made case-sensitive by the use of
6931 &`(-i)`& within the pattern. The following forms of wildcard are recognized:
6933 . ==== As this is a nested list, any displays it contains must be indented
6934 . ==== as otherwise they are too far to the left.
6937 The string may begin with an asterisk to mean &"ends with"&. For example:
6939 *.a.b.c data for anything.a.b.c
6940 *fish data for anythingfish
6943 The string may begin with a circumflex to indicate a regular expression. For
6944 example, for &(wildlsearch)&:
6946 ^\N\d+\.a\.b\N data for <digits>.a.b
6948 Note the use of &`\N`& to disable expansion of the contents of the regular
6949 expression. If you are using &(nwildlsearch)&, where the keys are not
6950 string-expanded, the equivalent entry is:
6952 ^\d+\.a\.b data for <digits>.a.b
6954 The case-insensitive flag is set at the start of compiling the regular
6955 expression, but it can be turned off by using &`(-i)`& at an appropriate point.
6956 For example, to make the entire pattern case-sensitive:
6958 ^(?-i)\d+\.a\.b data for <digits>.a.b
6961 If the regular expression contains white space or colon characters, you must
6962 either quote it (see &(lsearch)& above), or represent these characters in other
6963 ways. For example, &`\s`& can be used for white space and &`\x3A`& for a
6964 colon. This may be easier than quoting, because if you quote, you have to
6965 escape all the backslashes inside the quotes.
6967 &*Note*&: It is not possible to capture substrings in a regular expression
6968 match for later use, because the results of all lookups are cached. If a lookup
6969 is repeated, the result is taken from the cache, and no actual pattern matching
6970 takes place. The values of all the numeric variables are unset after a
6971 &((n)wildlsearch)& match.
6974 Although I cannot see it being of much use, the general matching function that
6975 is used to implement &((n)wildlsearch)& means that the string may begin with a
6976 lookup name terminated by a semicolon, and followed by lookup data. For
6979 cdb;/some/file data for keys that match the file
6981 The data that is obtained from the nested lookup is discarded.
6984 Keys that do not match any of these patterns are interpreted literally. The
6985 continuation rules for the data are the same as for &(lsearch)&, and keys may
6986 be followed by optional colons.
6988 &*Warning*&: Unlike most other single-key lookup types, a file of data for
6989 &((n)wildlsearch)& can &'not'& be turned into a DBM or cdb file, because those
6990 lookup types support only literal keys.
6993 .cindex "spf lookup type"
6994 .cindex "lookup" "spf"
6995 &(spf)&: If Exim is built with SPF support, manual lookups can be done
6996 (as opposed to the standard ACL condition method).
6997 For details see section &<<SECSPF>>&.
7001 .section "Query-style lookup types" "SECTquerystylelookups"
7002 .cindex "lookup" "query-style types"
7003 .cindex "query-style lookup" "list of types"
7004 The supported query-style lookup types are listed below. Further details about
7005 many of them are given in later sections.
7008 .cindex "DNS" "as a lookup type"
7009 .cindex "lookup" "DNS"
7010 &(dnsdb)&: This does a DNS search for one or more records whose domain names
7011 are given in the supplied query. The resulting data is the contents of the
7012 records. See section &<<SECTdnsdb>>&.
7014 .cindex "InterBase lookup type"
7015 .cindex "lookup" "InterBase"
7016 &(ibase)&: This does a lookup in an InterBase database.
7018 .cindex "LDAP" "lookup type"
7019 .cindex "lookup" "LDAP"
7020 &(ldap)&: This does an LDAP lookup using a query in the form of a URL, and
7021 returns attributes from a single entry. There is a variant called &(ldapm)&
7022 that permits values from multiple entries to be returned. A third variant
7023 called &(ldapdn)& returns the Distinguished Name of a single entry instead of
7024 any attribute values. See section &<<SECTldap>>&.
7026 .cindex "MySQL" "lookup type"
7027 .cindex "lookup" "MySQL"
7028 &(mysql)&: The format of the query is an SQL statement that is passed to a
7029 MySQL database. See section &<<SECTsql>>&.
7031 .cindex "NIS+ lookup type"
7032 .cindex "lookup" "NIS+"
7033 &(nisplus)&: This does a NIS+ lookup using a query that can specify the name of
7034 the field to be returned. See section &<<SECTnisplus>>&.
7036 .cindex "Oracle" "lookup type"
7037 .cindex "lookup" "Oracle"
7038 &(oracle)&: The format of the query is an SQL statement that is passed to an
7039 Oracle database. See section &<<SECTsql>>&.
7041 .cindex "lookup" "passwd"
7042 .cindex "passwd lookup type"
7043 .cindex "&_/etc/passwd_&"
7044 &(passwd)& is a query-style lookup with queries that are just user names. The
7045 lookup calls &[getpwnam()]& to interrogate the system password data, and on
7046 success, the result string is the same as you would get from an &(lsearch)&
7047 lookup on a traditional &_/etc/passwd file_&, though with &`*`& for the
7048 password value. For example:
7050 *:42:42:King Rat:/home/kr:/bin/bash
7053 .cindex "PostgreSQL lookup type"
7054 .cindex "lookup" "PostgreSQL"
7055 &(pgsql)&: The format of the query is an SQL statement that is passed to a
7056 PostgreSQL database. See section &<<SECTsql>>&.
7059 .cindex "Redis lookup type"
7060 .cindex lookup Redis
7061 &(redis)&: The format of the query is either a simple get or simple set,
7062 passed to a Redis database. See section &<<SECTsql>>&.
7065 .cindex "sqlite lookup type"
7066 .cindex "lookup" "sqlite"
7067 &(sqlite)&: The format of the query is
7068 an SQL statement that is passed to an SQLite database. See section &<<SECTsqlite>>&.
7071 &(testdb)&: This is a lookup type that is used for testing Exim. It is
7072 not likely to be useful in normal operation.
7074 .cindex "whoson lookup type"
7075 .cindex "lookup" "whoson"
7076 . --- still http:-only, 2018-09-07
7077 &(whoson)&: &'Whoson'& (&url(http://whoson.sourceforge.net)) is a protocol that
7078 allows a server to check whether a particular (dynamically allocated) IP
7079 address is currently allocated to a known (trusted) user and, optionally, to
7080 obtain the identity of the said user. For SMTP servers, &'Whoson'& was popular
7081 at one time for &"POP before SMTP"& authentication, but that approach has been
7082 superseded by SMTP authentication. In Exim, &'Whoson'& can be used to implement
7083 &"POP before SMTP"& checking using ACL statements such as
7085 require condition = \
7086 ${lookup whoson {$sender_host_address}{yes}{no}}
7088 The query consists of a single IP address. The value returned is the name of
7089 the authenticated user, which is stored in the variable &$value$&. However, in
7090 this example, the data in &$value$& is not used; the result of the lookup is
7091 one of the fixed strings &"yes"& or &"no"&.
7096 .section "Temporary errors in lookups" "SECID63"
7097 .cindex "lookup" "temporary error in"
7098 Lookup functions can return temporary error codes if the lookup cannot be
7099 completed. For example, an SQL or LDAP database might be unavailable. For this
7100 reason, it is not advisable to use a lookup that might do this for critical
7101 options such as a list of local domains.
7103 When a lookup cannot be completed in a router or transport, delivery
7104 of the message (to the relevant address) is deferred, as for any other
7105 temporary error. In other circumstances Exim may assume the lookup has failed,
7106 or may give up altogether.
7110 .section "Default values in single-key lookups" "SECTdefaultvaluelookups"
7111 .cindex "wildcard lookups"
7112 .cindex "lookup" "default values"
7113 .cindex "lookup" "wildcard"
7114 .cindex "lookup" "* added to type"
7115 .cindex "default" "in single-key lookups"
7116 In this context, a &"default value"& is a value specified by the administrator
7117 that is to be used if a lookup fails.
7119 &*Note:*& This section applies only to single-key lookups. For query-style
7120 lookups, the facilities of the query language must be used. An attempt to
7121 specify a default for a query-style lookup provokes an error.
7123 If &"*"& is added to a single-key lookup type (for example, &%lsearch*%&)
7124 and the initial lookup fails, the key &"*"& is looked up in the file to
7125 provide a default value. See also the section on partial matching below.
7127 .cindex "*@ with single-key lookup"
7128 .cindex "lookup" "*@ added to type"
7129 .cindex "alias file" "per-domain default"
7130 Alternatively, if &"*@"& is added to a single-key lookup type (for example
7131 &%dbm*@%&) then, if the initial lookup fails and the key contains an @
7132 character, a second lookup is done with everything before the last @ replaced
7133 by *. This makes it possible to provide per-domain defaults in alias files
7134 that include the domains in the keys. If the second lookup fails (or doesn't
7135 take place because there is no @ in the key), &"*"& is looked up.
7136 For example, a &(redirect)& router might contain:
7138 data = ${lookup{$local_part@$domain}lsearch*@{/etc/mix-aliases}}
7140 Suppose the address that is being processed is &'jane@eyre.example'&. Exim
7141 looks up these keys, in this order:
7147 The data is taken from whichever key it finds first. &*Note*&: In an
7148 &(lsearch)& file, this does not mean the first of these keys in the file. A
7149 complete scan is done for each key, and only if it is not found at all does
7150 Exim move on to try the next key.
7154 .section "Partial matching in single-key lookups" "SECTpartiallookup"
7155 .cindex "partial matching"
7156 .cindex "wildcard lookups"
7157 .cindex "lookup" "partial matching"
7158 .cindex "lookup" "wildcard"
7159 .cindex "asterisk" "in search type"
7160 The normal operation of a single-key lookup is to search the file for an exact
7161 match with the given key. However, in a number of situations where domains are
7162 being looked up, it is useful to be able to do partial matching. In this case,
7163 information in the file that has a key starting with &"*."& is matched by any
7164 domain that ends with the components that follow the full stop. For example, if
7165 a key in a DBM file is
7167 *.dates.fict.example
7169 then when partial matching is enabled this is matched by (amongst others)
7170 &'2001.dates.fict.example'& and &'1984.dates.fict.example'&. It is also matched
7171 by &'dates.fict.example'&, if that does not appear as a separate key in the
7174 &*Note*&: Partial matching is not available for query-style lookups. It is
7175 also not available for any lookup items in address lists (see section
7176 &<<SECTaddresslist>>&).
7178 Partial matching is implemented by doing a series of separate lookups using
7179 keys constructed by modifying the original subject key. This means that it can
7180 be used with any of the single-key lookup types, provided that
7181 partial matching keys
7182 beginning with a special prefix (default &"*."&) are included in the data file.
7183 Keys in the file that do not begin with the prefix are matched only by
7184 unmodified subject keys when partial matching is in use.
7186 Partial matching is requested by adding the string &"partial-"& to the front of
7187 the name of a single-key lookup type, for example, &%partial-dbm%&. When this
7188 is done, the subject key is first looked up unmodified; if that fails, &"*."&
7189 is added at the start of the subject key, and it is looked up again. If that
7190 fails, further lookups are tried with dot-separated components removed from the
7191 start of the subject key, one-by-one, and &"*."& added on the front of what
7194 A minimum number of two non-* components are required. This can be adjusted
7195 by including a number before the hyphen in the search type. For example,
7196 &%partial3-lsearch%& specifies a minimum of three non-* components in the
7197 modified keys. Omitting the number is equivalent to &"partial2-"&. If the
7198 subject key is &'2250.dates.fict.example'& then the following keys are looked
7199 up when the minimum number of non-* components is two:
7201 2250.dates.fict.example
7202 *.2250.dates.fict.example
7203 *.dates.fict.example
7206 As soon as one key in the sequence is successfully looked up, the lookup
7209 .cindex "lookup" "partial matching &-- changing prefix"
7210 .cindex "prefix" "for partial matching"
7211 The use of &"*."& as the partial matching prefix is a default that can be
7212 changed. The motivation for this feature is to allow Exim to operate with file
7213 formats that are used by other MTAs. A different prefix can be supplied in
7214 parentheses instead of the hyphen after &"partial"&. For example:
7216 domains = partial(.)lsearch;/some/file
7218 In this example, if the domain is &'a.b.c'&, the sequence of lookups is
7219 &`a.b.c`&, &`.a.b.c`&, and &`.b.c`& (the default minimum of 2 non-wild
7220 components is unchanged). The prefix may consist of any punctuation characters
7221 other than a closing parenthesis. It may be empty, for example:
7223 domains = partial1()cdb;/some/file
7225 For this example, if the domain is &'a.b.c'&, the sequence of lookups is
7226 &`a.b.c`&, &`b.c`&, and &`c`&.
7228 If &"partial0"& is specified, what happens at the end (when the lookup with
7229 just one non-wild component has failed, and the original key is shortened right
7230 down to the null string) depends on the prefix:
7233 If the prefix has zero length, the whole lookup fails.
7235 If the prefix has length 1, a lookup for just the prefix is done. For
7236 example, the final lookup for &"partial0(.)"& is for &`.`& alone.
7238 Otherwise, if the prefix ends in a dot, the dot is removed, and the
7239 remainder is looked up. With the default prefix, therefore, the final lookup is
7240 for &"*"& on its own.
7242 Otherwise, the whole prefix is looked up.
7246 If the search type ends in &"*"& or &"*@"& (see section
7247 &<<SECTdefaultvaluelookups>>& above), the search for an ultimate default that
7248 this implies happens after all partial lookups have failed. If &"partial0"& is
7249 specified, adding &"*"& to the search type has no effect with the default
7250 prefix, because the &"*"& key is already included in the sequence of partial
7251 lookups. However, there might be a use for lookup types such as
7252 &"partial0(.)lsearch*"&.
7254 The use of &"*"& in lookup partial matching differs from its use as a wildcard
7255 in domain lists and the like. Partial matching works only in terms of
7256 dot-separated components; a key such as &`*fict.example`&
7257 in a database file is useless, because the asterisk in a partial matching
7258 subject key is always followed by a dot.
7263 .section "Lookup caching" "SECID64"
7264 .cindex "lookup" "caching"
7265 .cindex "caching" "lookup data"
7266 Exim caches all lookup results in order to avoid needless repetition of
7267 lookups. However, because (apart from the daemon) Exim operates as a collection
7268 of independent, short-lived processes, this caching applies only within a
7269 single Exim process. There is no inter-process lookup caching facility.
7271 If an option &"cache=no_rd"& is used on the lookup then
7272 the cache is only written to, cached data is not used for the operation
7273 and a real lookup is done.
7275 For single-key lookups, Exim keeps the relevant files open in case there is
7276 another lookup that needs them. In some types of configuration this can lead to
7277 many files being kept open for messages with many recipients. To avoid hitting
7278 the operating system limit on the number of simultaneously open files, Exim
7279 closes the least recently used file when it needs to open more files than its
7280 own internal limit, which can be changed via the &%lookup_open_max%& option.
7282 The single-key lookup files are closed and the lookup caches are flushed at
7283 strategic points during delivery &-- for example, after all routing is
7289 .section "Quoting lookup data" "SECID65"
7290 .cindex "lookup" "quoting"
7291 .cindex "quoting" "in lookups"
7292 When data from an incoming message is included in a query-style lookup, there
7293 is the possibility of special characters in the data messing up the syntax of
7294 the query. For example, a NIS+ query that contains
7298 will be broken if the local part happens to contain a closing square bracket.
7299 For NIS+, data can be enclosed in double quotes like this:
7301 [name="$local_part"]
7303 but this still leaves the problem of a double quote in the data. The rule for
7304 NIS+ is that double quotes must be doubled. Other lookup types have different
7305 rules, and to cope with the differing requirements, an expansion operator
7306 of the following form is provided:
7308 ${quote_<lookup-type>:<string>}
7310 For example, the safest way to write the NIS+ query is
7312 [name="${quote_nisplus:$local_part}"]
7314 See chapter &<<CHAPexpand>>& for full coverage of string expansions. The quote
7315 operator can be used for all lookup types, but has no effect for single-key
7316 lookups, since no quoting is ever needed in their key strings.
7321 .section "More about dnsdb" "SECTdnsdb"
7322 .cindex "dnsdb lookup"
7323 .cindex "lookup" "dnsdb"
7324 .cindex "DNS" "as a lookup type"
7325 The &(dnsdb)& lookup type uses the DNS as its database. A simple query consists
7326 of a record type and a domain name, separated by an equals sign. For example,
7327 an expansion string could contain:
7329 ${lookup dnsdb{mx=a.b.example}{$value}fail}
7331 If the lookup succeeds, the result is placed in &$value$&, which in this case
7332 is used on its own as the result. If the lookup does not succeed, the
7333 &`fail`& keyword causes a &'forced expansion failure'& &-- see section
7334 &<<SECTforexpfai>>& for an explanation of what this means.
7336 The supported DNS record types are A, CNAME, MX, NS, PTR, SOA, SPF, SRV, TLSA
7337 and TXT, and, when Exim is compiled with IPv6 support, AAAA.
7338 If no type is given, TXT is assumed.
7340 For any record type, if multiple records are found, the data is returned as a
7341 concatenation, with newline as the default separator. The order, of course,
7342 depends on the DNS resolver. You can specify a different separator character
7343 between multiple records by putting a right angle-bracket followed immediately
7344 by the new separator at the start of the query. For example:
7346 ${lookup dnsdb{>: a=host1.example}}
7348 It is permitted to specify a space as the separator character. Further
7349 white space is ignored.
7350 For lookup types that return multiple fields per record,
7351 an alternate field separator can be specified using a comma after the main
7352 separator character, followed immediately by the field separator.
7354 .cindex "PTR record" "in &(dnsdb)& lookup"
7355 When the type is PTR,
7356 the data can be an IP address, written as normal; inversion and the addition of
7357 &%in-addr.arpa%& or &%ip6.arpa%& happens automatically. For example:
7359 ${lookup dnsdb{ptr=192.168.4.5}{$value}fail}
7361 If the data for a PTR record is not a syntactically valid IP address, it is not
7362 altered and nothing is added.
7364 .cindex "MX record" "in &(dnsdb)& lookup"
7365 .cindex "SRV record" "in &(dnsdb)& lookup"
7366 For an MX lookup, both the preference value and the host name are returned for
7367 each record, separated by a space. For an SRV lookup, the priority, weight,
7368 port, and host name are returned for each record, separated by spaces.
7369 The field separator can be modified as above.
7371 .cindex "TXT record" "in &(dnsdb)& lookup"
7372 .cindex "SPF record" "in &(dnsdb)& lookup"
7373 For TXT records with multiple items of data, only the first item is returned,
7374 unless a field separator is specified.
7375 To concatenate items without a separator, use a semicolon instead.
7377 default behaviour is to concatenate multiple items without using a separator.
7379 ${lookup dnsdb{>\n,: txt=a.b.example}}
7380 ${lookup dnsdb{>\n; txt=a.b.example}}
7381 ${lookup dnsdb{spf=example.org}}
7383 It is permitted to specify a space as the separator character. Further
7384 white space is ignored.
7386 .cindex "SOA record" "in &(dnsdb)& lookup"
7387 For an SOA lookup, while no result is obtained the lookup is redone with
7388 successively more leading components dropped from the given domain.
7389 Only the primary-nameserver field is returned unless a field separator is
7392 ${lookup dnsdb{>:,; soa=a.b.example.com}}
7395 .subsection "Dnsdb lookup modifiers" SECTdnsdb_mod
7396 .cindex "dnsdb modifiers"
7397 .cindex "modifiers" "dnsdb"
7398 .cindex "options" "dnsdb"
7399 Modifiers for &(dnsdb)& lookups are given by optional keywords,
7400 each followed by a comma,
7401 that may appear before the record type.
7403 The &(dnsdb)& lookup fails only if all the DNS lookups fail. If there is a
7404 temporary DNS error for any of them, the behaviour is controlled by
7405 a defer-option modifier.
7406 The possible keywords are
7407 &"defer_strict"&, &"defer_never"&, and &"defer_lax"&.
7408 With &"strict"& behaviour, any temporary DNS error causes the
7409 whole lookup to defer. With &"never"& behaviour, a temporary DNS error is
7410 ignored, and the behaviour is as if the DNS lookup failed to find anything.
7411 With &"lax"& behaviour, all the queries are attempted, but a temporary DNS
7412 error causes the whole lookup to defer only if none of the other lookups
7413 succeed. The default is &"lax"&, so the following lookups are equivalent:
7415 ${lookup dnsdb{defer_lax,a=one.host.com:two.host.com}}
7416 ${lookup dnsdb{a=one.host.com:two.host.com}}
7418 Thus, in the default case, as long as at least one of the DNS lookups
7419 yields some data, the lookup succeeds.
7421 .cindex "DNSSEC" "dns lookup"
7422 Use of &(DNSSEC)& is controlled by a dnssec modifier.
7423 The possible keywords are
7424 &"dnssec_strict"&, &"dnssec_lax"&, and &"dnssec_never"&.
7425 With &"strict"& or &"lax"& DNSSEC information is requested
7427 With &"strict"& a response from the DNS resolver that
7428 is not labelled as authenticated data
7429 is treated as equivalent to a temporary DNS error.
7430 The default is &"lax"&.
7432 See also the &$lookup_dnssec_authenticated$& variable.
7434 .cindex timeout "dns lookup"
7435 .cindex "DNS" timeout
7436 Timeout for the dnsdb lookup can be controlled by a retrans modifier.
7437 The form is &"retrans_VAL"& where VAL is an Exim time specification
7439 The default value is set by the main configuration option &%dns_retrans%&.
7441 Retries for the dnsdb lookup can be controlled by a retry modifier.
7442 The form if &"retry_VAL"& where VAL is an integer.
7443 The default count is set by the main configuration option &%dns_retry%&.
7445 .cindex caching "of dns lookup"
7446 .cindex TTL "of dns lookup"
7448 Dnsdb lookup results are cached within a single process (and its children).
7449 The cache entry lifetime is limited to the smallest time-to-live (TTL)
7450 value of the set of returned DNS records.
7453 .subsection "Pseudo dnsdb record types" SECID66
7454 .cindex "MX record" "in &(dnsdb)& lookup"
7455 By default, both the preference value and the host name are returned for
7456 each MX record, separated by a space. If you want only host names, you can use
7457 the pseudo-type MXH:
7459 ${lookup dnsdb{mxh=a.b.example}}
7461 In this case, the preference values are omitted, and just the host names are
7464 .cindex "name server for enclosing domain"
7465 Another pseudo-type is ZNS (for &"zone NS"&). It performs a lookup for NS
7466 records on the given domain, but if none are found, it removes the first
7467 component of the domain name, and tries again. This process continues until NS
7468 records are found or there are no more components left (or there is a DNS
7469 error). In other words, it may return the name servers for a top-level domain,
7470 but it never returns the root name servers. If there are no NS records for the
7471 top-level domain, the lookup fails. Consider these examples:
7473 ${lookup dnsdb{zns=xxx.quercite.com}}
7474 ${lookup dnsdb{zns=xxx.edu}}
7476 Assuming that in each case there are no NS records for the full domain name,
7477 the first returns the name servers for &%quercite.com%&, and the second returns
7478 the name servers for &%edu%&.
7480 You should be careful about how you use this lookup because, unless the
7481 top-level domain does not exist, the lookup always returns some host names. The
7482 sort of use to which this might be put is for seeing if the name servers for a
7483 given domain are on a blacklist. You can probably assume that the name servers
7484 for the high-level domains such as &%com%& or &%co.uk%& are not going to be on
7487 .cindex "CSA" "in &(dnsdb)& lookup"
7488 A third pseudo-type is CSA (Client SMTP Authorization). This looks up SRV
7489 records according to the CSA rules, which are described in section
7490 &<<SECTverifyCSA>>&. Although &(dnsdb)& supports SRV lookups directly, this is
7491 not sufficient because of the extra parent domain search behaviour of CSA. The
7492 result of a successful lookup such as:
7494 ${lookup dnsdb {csa=$sender_helo_name}}
7496 has two space-separated fields: an authorization code and a target host name.
7497 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
7498 authorization required but absent, or &"?"& for unknown.
7500 .cindex "A+" "in &(dnsdb)& lookup"
7501 The pseudo-type A+ performs an AAAA
7502 and then an A lookup. All results are returned; defer processing
7503 (see below) is handled separately for each lookup. Example:
7505 ${lookup dnsdb {>; a+=$sender_helo_name}}
7509 .subsection "Multiple dnsdb lookups" SECID67
7510 In the previous sections, &(dnsdb)& lookups for a single domain are described.
7511 However, you can specify a list of domains or IP addresses in a single
7512 &(dnsdb)& lookup. The list is specified in the normal Exim way, with colon as
7513 the default separator, but with the ability to change this. For example:
7515 ${lookup dnsdb{one.domain.com:two.domain.com}}
7516 ${lookup dnsdb{a=one.host.com:two.host.com}}
7517 ${lookup dnsdb{ptr = <; 1.2.3.4 ; 4.5.6.8}}
7519 In order to retain backwards compatibility, there is one special case: if
7520 the lookup type is PTR and no change of separator is specified, Exim looks
7521 to see if the rest of the string is precisely one IPv6 address. In this
7522 case, it does not treat it as a list.
7524 The data from each lookup is concatenated, with newline separators by default,
7525 in the same way that multiple DNS records for a single item are handled. A
7526 different separator can be specified, as described above.
7531 .section "More about LDAP" "SECTldap"
7532 .cindex "LDAP" "lookup, more about"
7533 .cindex "lookup" "LDAP"
7534 .cindex "Solaris" "LDAP"
7535 The original LDAP implementation came from the University of Michigan; this has
7536 become &"Open LDAP"&, and there are now two different releases. Another
7537 implementation comes from Netscape, and Solaris 7 and subsequent releases
7538 contain inbuilt LDAP support. Unfortunately, though these are all compatible at
7539 the lookup function level, their error handling is different. For this reason
7540 it is necessary to set a compile-time variable when building Exim with LDAP, to
7541 indicate which LDAP library is in use. One of the following should appear in
7542 your &_Local/Makefile_&:
7544 LDAP_LIB_TYPE=UMICHIGAN
7545 LDAP_LIB_TYPE=OPENLDAP1
7546 LDAP_LIB_TYPE=OPENLDAP2
7547 LDAP_LIB_TYPE=NETSCAPE
7548 LDAP_LIB_TYPE=SOLARIS
7550 If LDAP_LIB_TYPE is not set, Exim assumes &`OPENLDAP1`&, which has the
7551 same interface as the University of Michigan version.
7553 There are three LDAP lookup types in Exim. These behave slightly differently in
7554 the way they handle the results of a query:
7557 &(ldap)& requires the result to contain just one entry; if there are more, it
7560 &(ldapdn)& also requires the result to contain just one entry, but it is the
7561 Distinguished Name that is returned rather than any attribute values.
7563 &(ldapm)& permits the result to contain more than one entry; the attributes
7564 from all of them are returned.
7568 For &(ldap)& and &(ldapm)&, if a query finds only entries with no attributes,
7569 Exim behaves as if the entry did not exist, and the lookup fails. The format of
7570 the data returned by a successful lookup is described in the next section.
7571 First we explain how LDAP queries are coded.
7574 .subsection "Format of LDAP queries" SECTforldaque
7575 .cindex "LDAP" "query format"
7576 An LDAP query takes the form of a URL as defined in RFC 2255. For example, in
7577 the configuration of a &(redirect)& router one might have this setting:
7579 data = ${lookup ldap \
7580 {ldap:///cn=$local_part,o=University%20of%20Cambridge,\
7581 c=UK?mailbox?base?}}
7583 .cindex "LDAP" "with TLS"
7584 The URL may begin with &`ldap`& or &`ldaps`& if your LDAP library supports
7585 secure (encrypted) LDAP connections. The second of these ensures that an
7586 encrypted TLS connection is used.
7588 With sufficiently modern LDAP libraries, Exim supports forcing TLS over regular
7589 LDAP connections, rather than the SSL-on-connect &`ldaps`&.
7590 See the &%ldap_start_tls%& option.
7592 Starting with Exim 4.83, the initialization of LDAP with TLS is more tightly
7593 controlled. Every part of the TLS configuration can be configured by settings in
7594 &_exim.conf_&. Depending on the version of the client libraries installed on
7595 your system, some of the initialization may have required setting options in
7596 &_/etc/ldap.conf_& or &_~/.ldaprc_& to get TLS working with self-signed
7597 certificates. This revealed a nuance where the current UID that exim was
7598 running as could affect which config files it read. With Exim 4.83, these
7599 methods become optional, only taking effect if not specifically set in
7603 .subsection "LDAP quoting" SECID68
7604 .cindex "LDAP" "quoting"
7605 Two levels of quoting are required in LDAP queries, the first for LDAP itself
7606 and the second because the LDAP query is represented as a URL. Furthermore,
7607 within an LDAP query, two different kinds of quoting are required. For this
7608 reason, there are two different LDAP-specific quoting operators.
7610 The &%quote_ldap%& operator is designed for use on strings that are part of
7611 filter specifications. Conceptually, it first does the following conversions on
7619 in accordance with RFC 2254. The resulting string is then quoted according
7620 to the rules for URLs, that is, all non-alphanumeric characters except
7624 are converted to their hex values, preceded by a percent sign. For example:
7626 ${quote_ldap: a(bc)*, a<yz>; }
7630 %20a%5C28bc%5C29%5C2A%2C%20a%3Cyz%3E%3B%20
7632 Removing the URL quoting, this is (with a leading and a trailing space):
7634 a\28bc\29\2A, a<yz>;
7636 The &%quote_ldap_dn%& operator is designed for use on strings that are part of
7637 base DN specifications in queries. Conceptually, it first converts the string
7638 by inserting a backslash in front of any of the following characters:
7642 It also inserts a backslash before any leading spaces or # characters, and
7643 before any trailing spaces. (These rules are in RFC 2253.) The resulting string
7644 is then quoted according to the rules for URLs. For example:
7646 ${quote_ldap_dn: a(bc)*, a<yz>; }
7650 %5C%20a(bc)*%5C%2C%20a%5C%3Cyz%5C%3E%5C%3B%5C%20
7652 Removing the URL quoting, this is (with a trailing space):
7654 \ a(bc)*\, a\<yz\>\;\
7656 There are some further comments about quoting in the section on LDAP
7657 authentication below.
7660 .subsection "LDAP connections" SECID69
7661 .cindex "LDAP" "connections"
7662 The connection to an LDAP server may either be over TCP/IP, or, when OpenLDAP
7663 is in use, via a Unix domain socket. The example given above does not specify
7664 an LDAP server. A server that is reached by TCP/IP can be specified in a query
7667 ldap://<hostname>:<port>/...
7669 If the port (and preceding colon) are omitted, the standard LDAP port (389) is
7670 used. When no server is specified in a query, a list of default servers is
7671 taken from the &%ldap_default_servers%& configuration option. This supplies a
7672 colon-separated list of servers which are tried in turn until one successfully
7673 handles a query, or there is a serious error. Successful handling either
7674 returns the requested data, or indicates that it does not exist. Serious errors
7675 are syntactical, or multiple values when only a single value is expected.
7676 Errors which cause the next server to be tried are connection failures, bind
7677 failures, and timeouts.
7679 For each server name in the list, a port number can be given. The standard way
7680 of specifying a host and port is to use a colon separator (RFC 1738). Because
7681 &%ldap_default_servers%& is a colon-separated list, such colons have to be
7682 doubled. For example
7684 ldap_default_servers = ldap1.example.com::145:ldap2.example.com
7686 If &%ldap_default_servers%& is unset, a URL with no server name is passed
7687 to the LDAP library with no server name, and the library's default (normally
7688 the local host) is used.
7690 If you are using the OpenLDAP library, you can connect to an LDAP server using
7691 a Unix domain socket instead of a TCP/IP connection. This is specified by using
7692 &`ldapi`& instead of &`ldap`& in LDAP queries. What follows here applies only
7693 to OpenLDAP. If Exim is compiled with a different LDAP library, this feature is
7696 For this type of connection, instead of a host name for the server, a pathname
7697 for the socket is required, and the port number is not relevant. The pathname
7698 can be specified either as an item in &%ldap_default_servers%&, or inline in
7699 the query. In the former case, you can have settings such as
7701 ldap_default_servers = /tmp/ldap.sock : backup.ldap.your.domain
7703 When the pathname is given in the query, you have to escape the slashes as
7704 &`%2F`& to fit in with the LDAP URL syntax. For example:
7706 ${lookup ldap {ldapi://%2Ftmp%2Fldap.sock/o=...
7708 When Exim processes an LDAP lookup and finds that the &"hostname"& is really
7709 a pathname, it uses the Unix domain socket code, even if the query actually
7710 specifies &`ldap`& or &`ldaps`&. In particular, no encryption is used for a
7711 socket connection. This behaviour means that you can use a setting of
7712 &%ldap_default_servers%& such as in the example above with traditional &`ldap`&
7713 or &`ldaps`& queries, and it will work. First, Exim tries a connection via
7714 the Unix domain socket; if that fails, it tries a TCP/IP connection to the
7717 If an explicit &`ldapi`& type is given in a query when a host name is
7718 specified, an error is diagnosed. However, if there are more items in
7719 &%ldap_default_servers%&, they are tried. In other words:
7722 Using a pathname with &`ldap`& or &`ldaps`& forces the use of the Unix domain
7725 Using &`ldapi`& with a host name causes an error.
7729 Using &`ldapi`& with no host or path in the query, and no setting of
7730 &%ldap_default_servers%&, does whatever the library does by default.
7734 .subsection "LDAP authentication and control information" SECID70
7735 .cindex "LDAP" "authentication"
7736 The LDAP URL syntax provides no way of passing authentication and other control
7737 information to the server. To make this possible, the URL in an LDAP query may
7738 be preceded by any number of <&'name'&>=<&'value'&> settings, separated by
7739 spaces. If a value contains spaces it must be enclosed in double quotes, and
7740 when double quotes are used, backslash is interpreted in the usual way inside
7741 them. The following names are recognized:
7742 .itable none 0 0 2 20* left 80* left
7743 .irow DEREFERENCE "set the dereferencing parameter"
7744 .irow NETTIME "set a timeout for a network operation"
7745 .irow USER "set the DN, for authenticating the LDAP bind"
7746 .irow PASS "set the password, likewise"
7747 .irow REFERRALS "set the referrals parameter"
7748 .irow SERVERS "set alternate server list for this query only"
7749 .irow SIZE "set the limit for the number of entries returned"
7750 .irow TIME "set the maximum waiting time for a query"
7752 The value of the DEREFERENCE parameter must be one of the words &"never"&,
7753 &"searching"&, &"finding"&, or &"always"&. The value of the REFERRALS parameter
7754 must be &"follow"& (the default) or &"nofollow"&. The latter stops the LDAP
7755 library from trying to follow referrals issued by the LDAP server.
7757 .cindex LDAP timeout
7758 .cindex timeout "LDAP lookup"
7759 The name CONNECT is an obsolete name for NETTIME, retained for
7760 backwards compatibility. This timeout (specified as a number of seconds) is
7761 enforced from the client end for operations that can be carried out over a
7762 network. Specifically, it applies to network connections and calls to the
7763 &'ldap_result()'& function. If the value is greater than zero, it is used if
7764 LDAP_OPT_NETWORK_TIMEOUT is defined in the LDAP headers (OpenLDAP), or
7765 if LDAP_X_OPT_CONNECT_TIMEOUT is defined in the LDAP headers (Netscape
7766 SDK 4.1). A value of zero forces an explicit setting of &"no timeout"& for
7767 Netscape SDK; for OpenLDAP no action is taken.
7769 The TIME parameter (also a number of seconds) is passed to the server to
7770 set a server-side limit on the time taken to complete a search.
7772 The SERVERS parameter allows you to specify an alternate list of ldap servers
7773 to use for an individual lookup. The global &%ldap_default_servers%& option provides a
7774 default list of ldap servers, and a single lookup can specify a single ldap
7775 server to use. But when you need to do a lookup with a list of servers that is
7776 different than the default list (maybe different order, maybe a completely
7777 different set of servers), the SERVERS parameter allows you to specify this
7778 alternate list (colon-separated).
7780 Here is an example of an LDAP query in an Exim lookup that uses some of these
7781 values. This is a single line, folded to fit on the page:
7784 {user="cn=manager,o=University of Cambridge,c=UK" pass=secret
7785 ldap:///o=University%20of%20Cambridge,c=UK?sn?sub?(cn=foo)}
7788 The encoding of spaces as &`%20`& is a URL thing which should not be done for
7789 any of the auxiliary data. Exim configuration settings that include lookups
7790 which contain password information should be preceded by &"hide"& to prevent
7791 non-admin users from using the &%-bP%& option to see their values.
7793 The auxiliary data items may be given in any order. The default is no
7794 connection timeout (the system timeout is used), no user or password, no limit
7795 on the number of entries returned, and no time limit on queries.
7797 When a DN is quoted in the USER= setting for LDAP authentication, Exim
7798 removes any URL quoting that it may contain before passing it LDAP. Apparently
7799 some libraries do this for themselves, but some do not. Removing the URL
7800 quoting has two advantages:
7803 It makes it possible to use the same &%quote_ldap_dn%& expansion for USER=
7804 DNs as with DNs inside actual queries.
7806 It permits spaces inside USER= DNs.
7809 For example, a setting such as
7811 USER=cn=${quote_ldap_dn:$1}
7813 should work even if &$1$& contains spaces.
7815 Expanded data for the PASS= value should be quoted using the &%quote%&
7816 expansion operator, rather than the LDAP quote operators. The only reason this
7817 field needs quoting is to ensure that it conforms to the Exim syntax, which
7818 does not allow unquoted spaces. For example:
7822 The LDAP authentication mechanism can be used to check passwords as part of
7823 SMTP authentication. See the &%ldapauth%& expansion string condition in chapter
7828 .subsection "Format of data returned by LDAP" SECID71
7829 .cindex "LDAP" "returned data formats"
7830 The &(ldapdn)& lookup type returns the Distinguished Name from a single entry
7831 as a sequence of values, for example
7833 cn=manager,o=University of Cambridge,c=UK
7835 The &(ldap)& lookup type generates an error if more than one entry matches the
7836 search filter, whereas &(ldapm)& permits this case, and inserts a newline in
7837 the result between the data from different entries. It is possible for multiple
7838 values to be returned for both &(ldap)& and &(ldapm)&, but in the former case
7839 you know that whatever values are returned all came from a single entry in the
7842 In the common case where you specify a single attribute in your LDAP query, the
7843 result is not quoted, and does not contain the attribute name. If the attribute
7844 has multiple values, they are separated by commas. Any comma that is
7845 part of an attribute's value is doubled.
7847 If you specify multiple attributes, the result contains space-separated, quoted
7848 strings, each preceded by the attribute name and an equals sign. Within the
7849 quotes, the quote character, backslash, and newline are escaped with
7850 backslashes, and commas are used to separate multiple values for the attribute.
7851 Any commas in attribute values are doubled
7852 (permitting treatment of the values as a comma-separated list).
7853 Apart from the escaping, the string within quotes takes the same form as the
7854 output when a single attribute is requested. Specifying no attributes is the
7855 same as specifying all of an entry's attributes.
7857 Here are some examples of the output format. The first line of each pair is an
7858 LDAP query, and the second is the data that is returned. The attribute called
7859 &%attr1%& has two values, one of them with an embedded comma, whereas
7860 &%attr2%& has only one value. Both attributes are derived from &%attr%&
7861 (they have SUP &%attr%& in their schema definitions).
7864 ldap:///o=base?attr1?sub?(uid=fred)
7867 ldap:///o=base?attr2?sub?(uid=fred)
7870 ldap:///o=base?attr?sub?(uid=fred)
7871 value1.1,value1,,2,value two
7873 ldap:///o=base?attr1,attr2?sub?(uid=fred)
7874 attr1="value1.1,value1,,2" attr2="value two"
7876 ldap:///o=base??sub?(uid=fred)
7877 objectClass="top" attr1="value1.1,value1,,2" attr2="value two"
7880 make use of Exim's &%-be%& option to run expansion tests and thereby check the
7881 results of LDAP lookups.
7882 The &%extract%& operator in string expansions can be used to pick out
7883 individual fields from data that consists of &'key'&=&'value'& pairs.
7884 The &%listextract%& operator should be used to pick out individual values
7885 of attributes, even when only a single value is expected.
7886 The doubling of embedded commas allows you to use the returned data as a
7887 comma separated list (using the "<," syntax for changing the input list separator).
7892 .section "More about NIS+" "SECTnisplus"
7893 .cindex "NIS+ lookup type"
7894 .cindex "lookup" "NIS+"
7895 NIS+ queries consist of a NIS+ &'indexed name'& followed by an optional colon
7896 and field name. If this is given, the result of a successful query is the
7897 contents of the named field; otherwise the result consists of a concatenation
7898 of &'field-name=field-value'& pairs, separated by spaces. Empty values and
7899 values containing spaces are quoted. For example, the query
7901 [name=mg1456],passwd.org_dir
7903 might return the string
7905 name=mg1456 passwd="" uid=999 gid=999 gcos="Martin Guerre"
7906 home=/home/mg1456 shell=/bin/bash shadow=""
7908 (split over two lines here to fit on the page), whereas
7910 [name=mg1456],passwd.org_dir:gcos
7916 with no quotes. A NIS+ lookup fails if NIS+ returns more than one table entry
7917 for the given indexed key. The effect of the &%quote_nisplus%& expansion
7918 operator is to double any quote characters within the text.
7922 .section "SQL lookups" "SECTsql"
7923 .cindex "SQL lookup types"
7924 .cindex "MySQL" "lookup type"
7925 .cindex "PostgreSQL lookup type"
7926 .cindex "lookup" "MySQL"
7927 .cindex "lookup" "PostgreSQL"
7928 .cindex "Oracle" "lookup type"
7929 .cindex "lookup" "Oracle"
7930 .cindex "InterBase lookup type"
7931 .cindex "lookup" "InterBase"
7932 .cindex "Redis lookup type"
7933 .cindex lookup Redis
7934 Exim can support lookups in InterBase, MySQL, Oracle, PostgreSQL, Redis,
7936 databases. Queries for these databases contain SQL statements, so an example
7939 ${lookup mysql{select mailbox from users where id='userx'}\
7942 If the result of the query contains more than one field, the data for each
7943 field in the row is returned, preceded by its name, so the result of
7945 ${lookup pgsql{select home,name from users where id='userx'}\
7950 home=/home/userx name="Mister X"
7952 Empty values and values containing spaces are double quoted, with embedded
7953 quotes escaped by a backslash. If the result of the query contains just one
7954 field, the value is passed back verbatim, without a field name, for example:
7958 If the result of the query yields more than one row, it is all concatenated,
7959 with a newline between the data for each row.
7962 .subsection "More about MySQL, PostgreSQL, Oracle, InterBase, and Redis" SECID72
7963 .cindex "MySQL" "lookup type"
7964 .cindex "PostgreSQL lookup type"
7965 .cindex "lookup" "MySQL"
7966 .cindex "lookup" "PostgreSQL"
7967 .cindex "Oracle" "lookup type"
7968 .cindex "lookup" "Oracle"
7969 .cindex "InterBase lookup type"
7970 .cindex "lookup" "InterBase"
7971 .cindex "Redis lookup type"
7972 .cindex lookup Redis
7973 If any MySQL, PostgreSQL, Oracle, InterBase or Redis lookups are used, the
7974 &%mysql_servers%&, &%pgsql_servers%&, &%oracle_servers%&, &%ibase_servers%&,
7975 or &%redis_servers%&
7976 option (as appropriate) must be set to a colon-separated list of server
7978 .oindex &%mysql_servers%&
7979 .oindex &%pgsql_servers%&
7980 .oindex &%oracle_servers%&
7981 .oindex &%ibase_servers%&
7982 .oindex &%redis_servers%&
7983 (For MySQL and PostgreSQL, the global option need not be set if all
7984 queries contain their own server information &-- see section
7985 &<<SECTspeserque>>&.)
7987 each item in the list is a slash-separated list of four
7988 items: host name, database name, user name, and password. In the case of
7989 Oracle, the host name field is used for the &"service name"&, and the database
7990 name field is not used and should be empty. For example:
7992 hide oracle_servers = oracle.plc.example//userx/abcdwxyz
7994 Because password data is sensitive, you should always precede the setting with
7995 &"hide"&, to prevent non-admin users from obtaining the setting via the &%-bP%&
7996 option. Here is an example where two MySQL servers are listed:
7998 hide mysql_servers = localhost/users/root/secret:\
7999 otherhost/users/root/othersecret
8001 For MySQL and PostgreSQL, a host may be specified as <&'name'&>:<&'port'&> but
8002 because this is a colon-separated list, the colon has to be doubled. For each
8003 query, these parameter groups are tried in order until a connection is made and
8004 a query is successfully processed. The result of a query may be that no data is
8005 found, but that is still a successful query. In other words, the list of
8006 servers provides a backup facility, not a list of different places to look.
8008 For Redis the global option need not be specified if all queries contain their
8009 own server information &-- see section &<<SECTspeserque>>&.
8010 If specified, the option must be set to a colon-separated list of server
8012 Each item in the list is a slash-separated list of three items:
8013 host, database number, and password.
8015 The host is required and may be either an IPv4 address and optional
8016 port number (separated by a colon, which needs doubling due to the
8017 higher-level list), or a Unix socket pathname enclosed in parentheses
8019 The database number is optional; if present that number is selected in the backend
8021 The password is optional; if present it is used to authenticate to the backend
8024 The &%quote_mysql%&, &%quote_pgsql%&, and &%quote_oracle%& expansion operators
8025 convert newline, tab, carriage return, and backspace to \n, \t, \r, and \b
8026 respectively, and the characters single-quote, double-quote, and backslash
8027 itself are escaped with backslashes.
8029 The &%quote_redis%& expansion operator
8030 escapes whitespace and backslash characters with a backslash.
8032 .subsection "Specifying the server in the query" SECTspeserque
8033 For MySQL, PostgreSQL and Redis lookups (but not currently for Oracle and InterBase),
8034 it is possible to specify a list of servers with an individual query. This is
8035 done by appending a comma-separated option to the query type:
8037 &`,servers=`&&'server1:server2:server3:...'&
8039 Each item in the list may take one of two forms:
8041 If it contains no slashes it is assumed to be just a host name. The appropriate
8042 global option (&%mysql_servers%& or &%pgsql_servers%&) is searched for a host
8043 of the same name, and the remaining parameters (database, user, password) are
8046 If it contains any slashes, it is taken as a complete parameter set.
8048 The list of servers is used in exactly the same way as the global list.
8049 Once a connection to a server has happened and a query has been
8050 successfully executed, processing of the lookup ceases.
8052 This feature is intended for use in master/slave situations where updates
8053 are occurring and you want to update the master rather than a slave. If the
8054 master is in the list as a backup for reading, you might have a global setting
8057 mysql_servers = slave1/db/name/pw:\
8061 In an updating lookup, you could then write:
8063 ${lookup mysql,servers=master {UPDATE ...} }
8065 That query would then be sent only to the master server. If, on the other hand,
8066 the master is not to be used for reading, and so is not present in the global
8067 option, you can still update it by a query of this form:
8069 ${lookup pgsql,servers=master/db/name/pw {UPDATE ...} }
8072 An older syntax places the servers specification before the query,
8073 semicolon separated:
8075 ${lookup mysql{servers=master; UPDATE ...} }
8077 The new version avoids potential issues with tainted
8078 arguments in the query, for explicit expansion.
8079 &*Note*&: server specifications in list-style lookups are still problematic.
8082 .subsection "Special MySQL features" SECID73
8083 For MySQL, an empty host name or the use of &"localhost"& in &%mysql_servers%&
8084 causes a connection to the server on the local host by means of a Unix domain
8085 socket. An alternate socket can be specified in parentheses.
8086 An option group name for MySQL option files can be specified in square brackets;
8087 the default value is &"exim"&.
8088 The full syntax of each item in &%mysql_servers%& is:
8090 <&'hostname'&>::<&'port'&>(<&'socket name'&>)[<&'option group'&>]/&&&
8091 <&'database'&>/<&'user'&>/<&'password'&>
8093 Any of the four sub-parts of the first field can be omitted. For normal use on
8094 the local host it can be left blank or set to just &"localhost"&.
8096 No database need be supplied &-- but if it is absent here, it must be given in
8099 If a MySQL query is issued that does not request any data (an insert, update,
8100 or delete command), the result of the lookup is the number of rows affected.
8102 &*Warning*&: This can be misleading. If an update does not actually change
8103 anything (for example, setting a field to the value it already has), the result
8104 is zero because no rows are affected.
8107 .subsection "Special PostgreSQL features" SECID74
8108 PostgreSQL lookups can also use Unix domain socket connections to the database.
8109 This is usually faster and costs less CPU time than a TCP/IP connection.
8110 However it can be used only if the mail server runs on the same machine as the
8111 database server. A configuration line for PostgreSQL via Unix domain sockets
8114 hide pgsql_servers = (/tmp/.s.PGSQL.5432)/db/user/password : ...
8116 In other words, instead of supplying a host name, a path to the socket is
8117 given. The path name is enclosed in parentheses so that its slashes aren't
8118 visually confused with the delimiters for the other server parameters.
8120 If a PostgreSQL query is issued that does not request any data (an insert,
8121 update, or delete command), the result of the lookup is the number of rows
8124 .subsection "More about SQLite" SECTsqlite
8125 .cindex "lookup" "SQLite"
8126 .cindex "sqlite lookup type"
8127 SQLite is different to the other SQL lookups because a filename is required in
8128 addition to the SQL query. An SQLite database is a single file, and there is no
8129 daemon as in the other SQL databases.
8131 .oindex &%sqlite_dbfile%&
8132 There are two ways of
8133 specifying the file.
8134 The first is is by using the &%sqlite_dbfile%& main option.
8135 The second, which allows separate files for each query,
8136 is to use an option appended, comma-separated, to the &"sqlite"&
8137 lookup type word. The option is the word &"file"&, then an equals,
8139 The filename in this case cannot contain whitespace or open-brace charachters.
8141 A deprecated method is available, prefixing the query with the filename
8142 separated by white space.
8144 .cindex "tainted data" "sqlite file"
8145 the query cannot use any tainted values, as that taints
8146 the entire query including the filename - resulting in a refusal to open
8149 In all the above cases the filename must be an absolute path.
8151 Here is a lookup expansion example:
8153 sqlite_dbfile = /some/thing/sqlitedb
8155 ${lookup sqlite {select name from aliases where id='userx';}}
8157 In a list, the syntax is similar. For example:
8159 domainlist relay_to_domains = sqlite;\
8160 select * from relays where ip='$sender_host_address';
8162 The only character affected by the &%quote_sqlite%& operator is a single
8163 quote, which it doubles.
8165 .cindex timeout SQLite
8166 .cindex sqlite "lookup timeout"
8167 The SQLite library handles multiple simultaneous accesses to the database
8168 internally. Multiple readers are permitted, but only one process can
8169 update at once. Attempts to access the database while it is being updated
8170 are rejected after a timeout period, during which the SQLite library
8171 waits for the lock to be released. In Exim, the default timeout is set
8172 to 5 seconds, but it can be changed by means of the &%sqlite_lock_timeout%&
8175 .subsection "More about Redis" SECTredis
8176 .cindex "lookup" "Redis"
8177 .cindex "redis lookup type"
8178 Redis is a non-SQL database. Commands are simple get and set.
8181 ${lookup redis{set keyname ${quote_redis:objvalue plus}}}
8182 ${lookup redis{get keyname}}
8185 As of release 4.91, "lightweight" support for Redis Cluster is available.
8186 Requires &%redis_servers%& list to contain all the servers in the cluster, all
8187 of which must be reachable from the running exim instance. If the cluster has
8188 master/slave replication, the list must contain all the master and slave
8191 When the Redis Cluster returns a "MOVED" response to a query, Exim does not
8192 immediately follow the redirection but treats the response as a DEFER, moving on
8193 to the next server in the &%redis_servers%& list until the correct server is
8200 . ////////////////////////////////////////////////////////////////////////////
8201 . ////////////////////////////////////////////////////////////////////////////
8203 .chapter "Domain, host, address, and local part lists" &&&
8204 "CHAPdomhosaddlists" &&&
8205 "Domain, host, and address lists"
8206 .scindex IIDdohoadli "lists of domains; hosts; etc."
8207 A number of Exim configuration options contain lists of domains, hosts,
8208 email addresses, or local parts. For example, the &%hold_domains%& option
8209 contains a list of domains whose delivery is currently suspended. These lists
8210 are also used as data in ACL statements (see chapter &<<CHAPACL>>&), and as
8211 arguments to expansion conditions such as &%match_domain%&.
8213 Each item in one of these lists is a pattern to be matched against a domain,
8214 host, email address, or local part, respectively. In the sections below, the
8215 different types of pattern for each case are described, but first we cover some
8216 general facilities that apply to all four kinds of list.
8218 Note that other parts of Exim use a &'string list'& which does not
8219 support all the complexity available in
8220 domain, host, address and local part lists.
8224 .section "Results of list checking" SECTlistresults
8225 The primary result of doing a list check is a truth value.
8226 In some contexts additional information is stored
8227 about the list element that matched:
8230 A &%hosts%& ACL condition
8231 will store a result in the &$host_data$& variable.
8233 A &%local_parts%& router option or &%local_parts%& ACL condition
8234 will store a result in the &$local_part_data$& variable.
8236 A &%domains%& router option or &%domains%& ACL condition
8237 will store a result in the &$domain_data$& variable.
8239 A &%senders%& router option or &%senders%& ACL condition
8240 will store a result in the &$sender_data$& variable.
8242 A &%recipients%& ACL condition
8243 will store a result in the &$recipient_data$& variable.
8246 The detail of the additional information depends on the
8247 type of match and is given below as the &*value*& information.
8252 .section "Expansion of lists" "SECTlistexpand"
8253 .cindex "expansion" "of lists"
8254 Each list is expanded as a single string before it is used.
8256 &'Exception: the router headers_remove option, where list-item
8257 splitting is done before string-expansion.'&
8260 expansion must be a list, possibly containing empty items, which is split up
8261 into separate items for matching. By default, colon is the separator character,
8262 but this can be varied if necessary. See sections &<<SECTlistconstruct>>& and
8263 &<<SECTempitelis>>& for details of the list syntax; the second of these
8264 discusses the way to specify empty list items.
8267 If the string expansion is forced to fail, Exim behaves as if the item it is
8268 testing (domain, host, address, or local part) is not in the list. Other
8269 expansion failures cause temporary errors.
8271 If an item in a list is a regular expression, backslashes, dollars and possibly
8272 other special characters in the expression must be protected against
8273 misinterpretation by the string expander. The easiest way to do this is to use
8274 the &`\N`& expansion feature to indicate that the contents of the regular
8275 expression should not be expanded. For example, in an ACL you might have:
8277 deny senders = \N^\d{8}\w@.*\.baddomain\.example$\N : \
8278 ${lookup{$domain}lsearch{/badsenders/bydomain}}
8280 The first item is a regular expression that is protected from expansion by
8281 &`\N`&, whereas the second uses the expansion to obtain a list of unwanted
8282 senders based on the receiving domain.
8287 .subsection "Negated items in lists" SECID76
8288 .cindex "list" "negation"
8289 .cindex "negation" "in lists"
8290 Items in a list may be positive or negative. Negative items are indicated by a
8291 leading exclamation mark, which may be followed by optional white space. A list
8292 defines a set of items (domains, etc). When Exim processes one of these lists,
8293 it is trying to find out whether a domain, host, address, or local part
8294 (respectively) is in the set that is defined by the list. It works like this:
8296 The list is scanned from left to right. If a positive item is matched, the
8297 subject that is being checked is in the set; if a negative item is matched, the
8298 subject is not in the set. If the end of the list is reached without the
8299 subject having matched any of the patterns, it is in the set if the last item
8300 was a negative one, but not if it was a positive one. For example, the list in
8302 domainlist relay_to_domains = !a.b.c : *.b.c
8304 matches any domain ending in &'.b.c'& except for &'a.b.c'&. Domains that match
8305 neither &'a.b.c'& nor &'*.b.c'& do not match, because the last item in the
8306 list is positive. However, if the setting were
8308 domainlist relay_to_domains = !a.b.c
8310 then all domains other than &'a.b.c'& would match because the last item in the
8311 list is negative. In other words, a list that ends with a negative item behaves
8312 as if it had an extra item &`:*`& on the end.
8314 Another way of thinking about positive and negative items in lists is to read
8315 the connector as &"or"& after a positive item and as &"and"& after a negative
8320 .subsection "File names in lists" SECTfilnamlis
8321 .cindex "list" "filename in"
8322 If an item in a domain, host, address, or local part list is an absolute
8323 filename (beginning with a slash character), each line of the file is read and
8324 processed as if it were an independent item in the list, except that further
8325 filenames are not allowed,
8326 and no expansion of the data from the file takes place.
8327 Empty lines in the file are ignored, and the file may also contain comment
8331 For domain and host lists, if a # character appears anywhere in a line of the
8332 file, it and all following characters are ignored.
8334 Because local parts may legitimately contain # characters, a comment in an
8335 address list or local part list file is recognized only if # is preceded by
8336 white space or the start of the line. For example:
8338 not#comment@x.y.z # but this is a comment
8342 Putting a filename in a list has the same effect as inserting each line of the
8343 file as an item in the list (blank lines and comments excepted). However, there
8344 is one important difference: the file is read each time the list is processed,
8345 so if its contents vary over time, Exim's behaviour changes.
8347 If a filename is preceded by an exclamation mark, the sense of any match
8348 within the file is inverted. For example, if
8350 hold_domains = !/etc/nohold-domains
8352 and the file contains the lines
8357 then &'a.b.c'& is in the set of domains defined by &%hold_domains%&, whereas
8358 any domain matching &`*.b.c`& is not.
8362 .subsection "An lsearch file is not an out-of-line list" SECID77
8363 As will be described in the sections that follow, lookups can be used in lists
8364 to provide indexed methods of checking list membership. There has been some
8365 confusion about the way &(lsearch)& lookups work in lists. Because
8366 an &(lsearch)& file contains plain text and is scanned sequentially, it is
8367 sometimes thought that it is allowed to contain wild cards and other kinds of
8368 non-constant pattern. This is not the case. The keys in an &(lsearch)& file are
8369 always fixed strings, just as for any other single-key lookup type.
8371 If you want to use a file to contain wild-card patterns that form part of a
8372 list, just give the filename on its own, without a search type, as described
8373 in the previous section. You could also use the &(wildlsearch)& or
8374 &(nwildlsearch)&, but there is no advantage in doing this.
8379 .subsection "Named lists" SECTnamedlists
8380 .cindex "named lists"
8381 .cindex "list" "named"
8382 A list of domains, hosts, email addresses, or local parts can be given a name
8383 which is then used to refer to the list elsewhere in the configuration. This is
8384 particularly convenient if the same list is required in several different
8385 places. It also allows lists to be given meaningful names, which can improve
8386 the readability of the configuration. For example, it is conventional to define
8387 a domain list called &'local_domains'& for all the domains that are handled
8388 locally on a host, using a configuration line such as
8390 domainlist local_domains = localhost:my.dom.example
8392 Named lists are referenced by giving their name preceded by a plus sign, so,
8393 for example, a router that is intended to handle local domains would be
8394 configured with the line
8396 domains = +local_domains
8398 The first router in a configuration is often one that handles all domains
8399 except the local ones, using a configuration with a negated item like this:
8403 domains = ! +local_domains
8404 transport = remote_smtp
8407 The four kinds of named list are created by configuration lines starting with
8408 the words &%domainlist%&, &%hostlist%&, &%addresslist%&, or &%localpartlist%&,
8409 respectively. Then there follows the name that you are defining, followed by an
8410 equals sign and the list itself. For example:
8412 hostlist relay_from_hosts = 192.168.23.0/24 : my.friend.example
8413 addresslist bad_senders = cdb;/etc/badsenders
8415 A named list may refer to other named lists:
8417 domainlist dom1 = first.example : second.example
8418 domainlist dom2 = +dom1 : third.example
8419 domainlist dom3 = fourth.example : +dom2 : fifth.example
8421 &*Warning*&: If the last item in a referenced list is a negative one, the
8422 effect may not be what you intended, because the negation does not propagate
8423 out to the higher level. For example, consider:
8425 domainlist dom1 = !a.b
8426 domainlist dom2 = +dom1 : *.b
8428 The second list specifies &"either in the &%dom1%& list or &'*.b'&"&. The first
8429 list specifies just &"not &'a.b'&"&, so the domain &'x.y'& matches it. That
8430 means it matches the second list as well. The effect is not the same as
8432 domainlist dom2 = !a.b : *.b
8434 where &'x.y'& does not match. It's best to avoid negation altogether in
8435 referenced lists if you can.
8437 .cindex "hiding named list values"
8438 .cindex "named lists" "hiding value of"
8439 Some named list definitions may contain sensitive data, for example, passwords for
8440 accessing databases. To stop non-admin users from using the &%-bP%& command
8441 line option to read these values, you can precede the definition with the
8442 word &"hide"&. For example:
8444 hide domainlist filter_for_domains = ldap;PASS=secret ldap::/// ...
8448 Named lists may have a performance advantage. When Exim is routing an
8449 address or checking an incoming message, it caches the result of tests on named
8450 lists. So, if you have a setting such as
8452 domains = +local_domains
8454 on several of your routers
8455 or in several ACL statements,
8456 the actual test is done only for the first one. However, the caching works only
8457 if there are no expansions within the list itself or any sublists that it
8458 references. In other words, caching happens only for lists that are known to be
8459 the same each time they are referenced.
8461 By default, there may be up to 16 named lists of each type. This limit can be
8462 extended by changing a compile-time variable. The use of domain and host lists
8463 is recommended for concepts such as local domains, relay domains, and relay
8464 hosts. The default configuration is set up like this.
8468 .subsection "Named lists compared with macros" SECID78
8469 .cindex "list" "named compared with macro"
8470 .cindex "macro" "compared with named list"
8471 At first sight, named lists might seem to be no different from macros in the
8472 configuration file. However, macros are just textual substitutions. If you
8475 ALIST = host1 : host2
8476 auth_advertise_hosts = !ALIST
8478 it probably won't do what you want, because that is exactly the same as
8480 auth_advertise_hosts = !host1 : host2
8482 Notice that the second host name is not negated. However, if you use a host
8485 hostlist alist = host1 : host2
8486 auth_advertise_hosts = ! +alist
8488 the negation applies to the whole list, and so that is equivalent to
8490 auth_advertise_hosts = !host1 : !host2
8494 .subsection "Named list caching" SECID79
8495 .cindex "list" "caching of named"
8496 .cindex "caching" "named lists"
8497 While processing a message, Exim caches the result of checking a named list if
8498 it is sure that the list is the same each time. In practice, this means that
8499 the cache operates only if the list contains no $ characters, which guarantees
8500 that it will not change when it is expanded. Sometimes, however, you may have
8501 an expanded list that you know will be the same each time within a given
8502 message. For example:
8504 domainlist special_domains = \
8505 ${lookup{$sender_host_address}cdb{/some/file}}
8507 This provides a list of domains that depends only on the sending host's IP
8508 address. If this domain list is referenced a number of times (for example,
8509 in several ACL lines, or in several routers) the result of the check is not
8510 cached by default, because Exim does not know that it is going to be the
8511 same list each time.
8513 By appending &`_cache`& to &`domainlist`& you can tell Exim to go ahead and
8514 cache the result anyway. For example:
8516 domainlist_cache special_domains = ${lookup{...
8518 If you do this, you should be absolutely sure that caching is going to do
8519 the right thing in all cases. When in doubt, leave it out.
8523 .section "Domain lists" "SECTdomainlist"
8524 .cindex "domain list" "patterns for"
8525 .cindex "list" "domain list"
8526 Domain lists contain patterns that are to be matched against a mail domain.
8527 The following types of item may appear in domain lists:
8530 .cindex "primary host name"
8531 .cindex "host name" "matched in domain list"
8532 .oindex "&%primary_hostname%&"
8533 .cindex "domain list" "matching primary host name"
8534 .cindex "@ in a domain list"
8535 If a pattern consists of a single @ character, it matches the local host name,
8536 as set by the &%primary_hostname%& option (or defaulted). This makes it
8537 possible to use the same configuration file on several different hosts that
8538 differ only in their names.
8540 The value for a match will be the primary host name.
8544 .cindex "@[] in a domain list"
8545 .cindex "domain list" "matching local IP interfaces"
8546 .cindex "domain literal"
8547 If a pattern consists of the string &`@[]`& it matches an IP address enclosed
8548 in square brackets (as in an email address that contains a domain literal), but
8549 only if that IP address is recognized as local for email routing purposes. The
8550 &%local_interfaces%& and &%extra_local_interfaces%& options can be used to
8551 control which of a host's several IP addresses are treated as local.
8552 In today's Internet, the use of domain literals is controversial;
8553 see the &%allow_domain_literals%& main option.
8555 The value for a match will be the string &`@[]`&.
8560 .cindex "@mx_primary"
8561 .cindex "@mx_secondary"
8562 .cindex "domain list" "matching MX pointers to local host"
8563 If a pattern consists of the string &`@mx_any`& it matches any domain that
8564 has an MX record pointing to the local host or to any host that is listed in
8565 .oindex "&%hosts_treat_as_local%&"
8566 &%hosts_treat_as_local%&. The items &`@mx_primary`& and &`@mx_secondary`&
8567 are similar, except that the first matches only when a primary MX target is the
8568 local host, and the second only when no primary MX target is the local host,
8569 but a secondary MX target is. &"Primary"& means an MX record with the lowest
8570 preference value &-- there may of course be more than one of them.
8572 The MX lookup that takes place when matching a pattern of this type is
8573 performed with the resolver options for widening names turned off. Thus, for
8574 example, a single-component domain will &'not'& be expanded by adding the
8575 resolver's default domain. See the &%qualify_single%& and &%search_parents%&
8576 options of the &(dnslookup)& router for a discussion of domain widening.
8578 Sometimes you may want to ignore certain IP addresses when using one of these
8579 patterns. You can specify this by following the pattern with &`/ignore=`&<&'ip
8580 list'&>, where <&'ip list'&> is a list of IP addresses. These addresses are
8581 ignored when processing the pattern (compare the &%ignore_target_hosts%& option
8582 on a router). For example:
8584 domains = @mx_any/ignore=127.0.0.1
8586 This example matches any domain that has an MX record pointing to one of
8587 the local host's IP addresses other than 127.0.0.1.
8589 The list of IP addresses is in fact processed by the same code that processes
8590 host lists, so it may contain CIDR-coded network specifications and it may also
8591 contain negative items.
8593 Because the list of IP addresses is a sublist within a domain list, you have to
8594 be careful about delimiters if there is more than one address. Like any other
8595 list, the default delimiter can be changed. Thus, you might have:
8597 domains = @mx_any/ignore=<;127.0.0.1;0.0.0.0 : \
8598 an.other.domain : ...
8600 so that the sublist uses semicolons for delimiters. When IPv6 addresses are
8601 involved, it is easiest to change the delimiter for the main list as well:
8603 domains = <? @mx_any/ignore=<;127.0.0.1;::1 ? \
8604 an.other.domain ? ...
8606 The value for a match will be the list element string (starting &`@mx_`&).
8610 .cindex "asterisk" "in domain list"
8611 .cindex "domain list" "asterisk in"
8612 .cindex "domain list" "matching &""ends with""&"
8613 If a pattern starts with an asterisk, the remaining characters of the pattern
8614 are compared with the terminating characters of the domain. The use of &"*"& in
8615 domain lists differs from its use in partial matching lookups. In a domain
8616 list, the character following the asterisk need not be a dot, whereas partial
8617 matching works only in terms of dot-separated components. For example, a domain
8618 list item such as &`*key.ex`& matches &'donkey.ex'& as well as
8621 The value for a match will be the list element string (starting with the asterisk).
8622 Additionally, &$0$& will be set to the matched string
8623 and &$1$& to the variable portion which the asterisk matched.
8626 .cindex "regular expressions" "in domain list"
8627 .cindex "domain list" "matching regular expression"
8628 If a pattern starts with a circumflex character, it is treated as a regular
8629 expression, and matched against the domain using a regular expression matching
8630 function. The circumflex is treated as part of the regular expression.
8631 Email domains are case-independent, so this regular expression match is by
8632 default case-independent, but you can make it case-dependent by starting it
8633 with &`(?-i)`&. References to descriptions of the syntax of regular expressions
8634 are given in chapter &<<CHAPregexp>>&.
8636 &*Warning*&: Because domain lists are expanded before being processed, you
8637 must escape any backslash and dollar characters in the regular expression, or
8638 use the special &`\N`& sequence (see chapter &<<CHAPexpand>>&) to specify that
8639 it is not to be expanded (unless you really do want to build a regular
8640 expression by expansion, of course).
8642 The value for a match will be the list element string (starting with the circumflex).
8643 Additionally, &$0$& will be set to the string matching the regular expression,
8644 and &$1$& (onwards) to any submatches identified by parentheses.
8649 .cindex "lookup" "in domain list"
8650 .cindex "domain list" "matching by lookup"
8651 If a pattern starts with the name of a single-key lookup type followed by a
8652 semicolon (for example, &"dbm;"& or &"lsearch;"&), the remainder of the pattern
8653 must be a filename in a suitable format for the lookup type. For example, for
8654 &"cdb;"& it must be an absolute path:
8656 domains = cdb;/etc/mail/local_domains.cdb
8658 The appropriate type of lookup is done on the file using the domain name as the
8659 key. In most cases, the value resulting from the lookup is not used; Exim is interested
8660 only in whether or not the key is present in the file. However, when a lookup
8661 is used for the &%domains%& option on a router
8662 or a &%domains%& condition in an ACL statement, the value is preserved in the
8663 &$domain_data$& variable and can be referred to in other router options or
8664 other statements in the same ACL.
8665 .cindex "tainted data" "de-tainting"
8666 .cindex "de-tainting" "using ACL domains condition"
8667 The value will be untainted.
8669 &*Note*&: If the data result of the lookup (as opposed to the key)
8670 is empty, then this empty value is stored in &$domain_data$&.
8671 The option to return the key for the lookup, as the value,
8672 may be what is wanted.
8676 Any of the single-key lookup type names may be preceded by
8677 &`partial`&<&'n'&>&`-`&, where the <&'n'&> is optional, for example,
8679 domains = partial-dbm;/partial/domains
8681 This causes partial matching logic to be invoked; a description of how this
8682 works is given in section &<<SECTpartiallookup>>&.
8685 .cindex "asterisk" "in lookup type"
8686 Any of the single-key lookup types may be followed by an asterisk. This causes
8687 a default lookup for a key consisting of a single asterisk to be done if the
8688 original lookup fails. This is not a useful feature when using a domain list to
8689 select particular domains (because any domain would match), but it might have
8690 value if the result of the lookup is being used via the &$domain_data$&
8694 If the pattern starts with the name of a query-style lookup type followed by a
8695 semicolon (for example, &"nisplus;"& or &"ldap;"&), the remainder of the
8696 pattern must be an appropriate query for the lookup type, as described in
8697 chapter &<<CHAPfdlookup>>&. For example:
8699 hold_domains = mysql;select domain from holdlist \
8700 where domain = '${quote_mysql:$domain}';
8702 In most cases, the value resulting from the lookup is not used (so for an SQL query, for
8703 example, it doesn't matter what field you select). Exim is interested only in
8704 whether or not the query succeeds. However, when a lookup is used for the
8705 &%domains%& option on a router, the value is preserved in the &$domain_data$&
8706 variable and can be referred to in other options.
8707 .cindex "tainted data" "de-tainting"
8708 .cindex "de-tainting" "using router domains option"
8709 The value will be untainted.
8712 If the pattern starts with the name of a lookup type
8713 of either kind (single-key or query-style) it may be
8714 followed by a comma and options,
8715 The options are lookup-type specific and consist of a comma-separated list.
8716 Each item starts with a tag and and equals "=" sign.
8719 .cindex "domain list" "matching literal domain name"
8720 If none of the above cases apply, a caseless textual comparison is made
8721 between the pattern and the domain.
8723 The value for a match will be the list element string.
8724 .cindex "tainted data" "de-tainting"
8725 Note that this is commonly untainted
8726 (depending on the way the list was created).
8727 Specifically, explicit text in the configuration file in not tainted.
8728 This is a useful way of obtaining an untainted equivalent to
8729 the domain, for later operations.
8731 However if the list (including one-element lists)
8732 is created by expanding a variable containing tainted data,
8733 it is tainted and so will the match value be.
8737 Here is an example that uses several different kinds of pattern:
8739 domainlist funny_domains = \
8742 *.foundation.fict.example : \
8743 \N^[1-2]\d{3}\.fict\.example$\N : \
8744 partial-dbm;/opt/data/penguin/book : \
8745 nis;domains.byname : \
8746 nisplus;[name=$domain,status=local],domains.org_dir
8748 There are obvious processing trade-offs among the various matching modes. Using
8749 an asterisk is faster than a regular expression, and listing a few names
8750 explicitly probably is too. The use of a file or database lookup is expensive,
8751 but may be the only option if hundreds of names are required. Because the
8752 patterns are tested in order, it makes sense to put the most commonly matched
8757 .section "Host lists" "SECThostlist"
8758 .cindex "host list" "patterns in"
8759 .cindex "list" "host list"
8760 Host lists are used to control what remote hosts are allowed to do. For
8761 example, some hosts may be allowed to use the local host as a relay, and some
8762 may be permitted to use the SMTP ETRN command. Hosts can be identified in
8763 two different ways, by name or by IP address. In a host list, some types of
8764 pattern are matched to a host name, and some are matched to an IP address.
8765 You need to be particularly careful with this when single-key lookups are
8766 involved, to ensure that the right value is being used as the key.
8769 .subsection "Special host list patterns" SECID80
8770 .cindex "empty item in hosts list"
8771 .cindex "host list" "empty string in"
8772 If a host list item is the empty string, it matches only when no remote host is
8773 involved. This is the case when a message is being received from a local
8774 process using SMTP on the standard input, that is, when a TCP/IP connection is
8777 .cindex "asterisk" "in host list"
8778 The special pattern &"*"& in a host list matches any host or no host. Neither
8779 the IP address nor the name is actually inspected.
8783 .subsection "Host list patterns that match by IP address" SECThoslispatip
8784 .cindex "host list" "matching IP addresses"
8785 If an IPv4 host calls an IPv6 host and the call is accepted on an IPv6 socket,
8786 the incoming address actually appears in the IPv6 host as
8787 &`::ffff:`&<&'v4address'&>. When such an address is tested against a host
8788 list, it is converted into a traditional IPv4 address first. (Not all operating
8789 systems accept IPv4 calls on IPv6 sockets, as there have been some security
8792 The following types of pattern in a host list check the remote host by
8793 inspecting its IP address:
8796 If the pattern is a plain domain name (not a regular expression, not starting
8797 with *, not a lookup of any kind), Exim calls the operating system function
8798 to find the associated IP address(es). Exim uses the newer
8799 &[getipnodebyname()]& function when available, otherwise &[gethostbyname()]&.
8800 This typically causes a forward DNS lookup of the name. The result is compared
8801 with the IP address of the subject host.
8803 If there is a temporary problem (such as a DNS timeout) with the host name
8804 lookup, a temporary error occurs. For example, if the list is being used in an
8805 ACL condition, the ACL gives a &"defer"& response, usually leading to a
8806 temporary SMTP error code. If no IP address can be found for the host name,
8807 what happens is described in section &<<SECTbehipnot>>& below.
8810 .cindex "@ in a host list"
8811 If the pattern is &"@"&, the primary host name is substituted and used as a
8812 domain name, as just described.
8815 If the pattern is an IP address, it is matched against the IP address of the
8816 subject host. IPv4 addresses are given in the normal &"dotted-quad"& notation.
8817 IPv6 addresses can be given in colon-separated format, but the colons have to
8818 be doubled so as not to be taken as item separators when the default list
8819 separator is used. IPv6 addresses are recognized even when Exim is compiled
8820 without IPv6 support. This means that if they appear in a host list on an
8821 IPv4-only host, Exim will not treat them as host names. They are just addresses
8822 that can never match a client host.
8825 .cindex "@[] in a host list"
8826 If the pattern is &"@[]"&, it matches the IP address of any IP interface on
8827 the local host. For example, if the local host is an IPv4 host with one
8828 interface address 10.45.23.56, these two ACL statements have the same effect:
8830 accept hosts = 127.0.0.1 : 10.45.23.56
8834 .cindex "CIDR notation"
8835 If the pattern is an IP address followed by a slash and a mask length, for
8840 , it is matched against the IP address of the subject
8841 host under the given mask. This allows an entire network of hosts to be
8842 included (or excluded) by a single item. The mask uses CIDR notation; it
8843 specifies the number of address bits that must match, starting from the most
8844 significant end of the address.
8846 &*Note*&: The mask is &'not'& a count of addresses, nor is it the high number
8847 of a range of addresses. It is the number of bits in the network portion of the
8848 address. The above example specifies a 24-bit netmask, so it matches all 256
8849 addresses in the 10.11.42.0 network. An item such as
8853 matches just two addresses, 192.168.23.236 and 192.168.23.237. A mask value of
8854 32 for an IPv4 address is the same as no mask at all; just a single address
8857 Here is another example which shows an IPv4 and an IPv6 network:
8859 recipient_unqualified_hosts = 192.168.0.0/16: \
8860 3ffe::ffff::836f::::/48
8862 The doubling of list separator characters applies only when these items
8863 appear inline in a host list. It is not required when indirecting via a file.
8866 recipient_unqualified_hosts = /opt/exim/unqualnets
8868 could make use of a file containing
8873 to have exactly the same effect as the previous example. When listing IPv6
8874 addresses inline, it is usually more convenient to use the facility for
8875 changing separator characters. This list contains the same two networks:
8877 recipient_unqualified_hosts = <; 172.16.0.0/12; \
8880 The separator is changed to semicolon by the leading &"<;"& at the start of the
8886 .subsection "Host list patterns for single-key lookups by host address" &&&
8888 .cindex "host list" "lookup of IP address"
8889 When a host is to be identified by a single-key lookup of its complete IP
8890 address, the pattern takes this form:
8892 &`net-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
8896 hosts_lookup = net-cdb;/hosts-by-ip.db
8898 The text form of the IP address of the subject host is used as the lookup key.
8899 IPv6 addresses are converted to an unabbreviated form, using lower case
8900 letters, with dots as separators because colon is the key terminator in
8901 &(lsearch)& files. [Colons can in fact be used in keys in &(lsearch)& files by
8902 quoting the keys, but this is a facility that was added later.] The data
8903 returned by the lookup is not used.
8905 .cindex "IP address" "masking"
8906 .cindex "host list" "masked IP address"
8907 Single-key lookups can also be performed using masked IP addresses, using
8908 patterns of this form:
8910 &`net<`&&'number'&&`>-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
8914 net24-dbm;/networks.db
8916 The IP address of the subject host is masked using <&'number'&> as the mask
8917 length. A textual string is constructed from the masked value, followed by the
8918 mask, and this is used as the lookup key. For example, if the host's IP address
8919 is 192.168.34.6, the key that is looked up for the above example is
8920 &"192.168.34.0/24"&.
8922 When an IPv6 address is converted to a string, dots are normally used instead
8923 of colons, so that keys in &(lsearch)& files need not contain colons (which
8924 terminate &(lsearch)& keys). This was implemented some time before the ability
8925 to quote keys was made available in &(lsearch)& files. However, the more
8926 recently implemented &(iplsearch)& files do require colons in IPv6 keys
8927 (notated using the quoting facility) so as to distinguish them from IPv4 keys.
8928 For this reason, when the lookup type is &(iplsearch)&, IPv6 addresses are
8929 converted using colons and not dots.
8930 In all cases except IPv4-mapped IPv6, full, unabbreviated IPv6
8931 addresses are always used.
8932 The latter are converted to IPv4 addresses, in dotted-quad form.
8934 Ideally, it would be nice to tidy up this anomalous situation by changing to
8935 colons in all cases, given that quoting is now available for &(lsearch)&.
8936 However, this would be an incompatible change that might break some existing
8939 &*Warning*&: Specifying &%net32-%& (for an IPv4 address) or &%net128-%& (for an
8940 IPv6 address) is not the same as specifying just &%net-%& without a number. In
8941 the former case the key strings include the mask value, whereas in the latter
8942 case the IP address is used on its own.
8946 .subsection "Host list patterns that match by host name" SECThoslispatnam
8947 .cindex "host" "lookup failures"
8948 .cindex "unknown host name"
8949 .cindex "host list" "matching host name"
8950 There are several types of pattern that require Exim to know the name of the
8951 remote host. These are either wildcard patterns or lookups by name. (If a
8952 complete hostname is given without any wildcarding, it is used to find an IP
8953 address to match against, as described in section &<<SECThoslispatip>>&
8956 If the remote host name is not already known when Exim encounters one of these
8957 patterns, it has to be found from the IP address.
8958 Although many sites on the Internet are conscientious about maintaining reverse
8959 DNS data for their hosts, there are also many that do not do this.
8960 Consequently, a name cannot always be found, and this may lead to unwanted
8961 effects. Take care when configuring host lists with wildcarded name patterns.
8962 Consider what will happen if a name cannot be found.
8964 Because of the problems of determining host names from IP addresses, matching
8965 against host names is not as common as matching against IP addresses.
8967 By default, in order to find a host name, Exim first does a reverse DNS lookup;
8968 if no name is found in the DNS, the system function (&[gethostbyaddr()]& or
8969 &[getipnodebyaddr()]& if available) is tried. The order in which these lookups
8970 are done can be changed by setting the &%host_lookup_order%& option. For
8971 security, once Exim has found one or more names, it looks up the IP addresses
8972 for these names and compares them with the IP address that it started with.
8973 Only those names whose IP addresses match are accepted. Any other names are
8974 discarded. If no names are left, Exim behaves as if the host name cannot be
8975 found. In the most common case there is only one name and one IP address.
8977 There are some options that control what happens if a host name cannot be
8978 found. These are described in section &<<SECTbehipnot>>& below.
8980 .cindex "host" "alias for"
8981 .cindex "alias for host"
8982 As a result of aliasing, hosts may have more than one name. When processing any
8983 of the following types of pattern, all the host's names are checked:
8986 .cindex "asterisk" "in host list"
8987 If a pattern starts with &"*"& the remainder of the item must match the end of
8988 the host name. For example, &`*.b.c`& matches all hosts whose names end in
8989 &'.b.c'&. This special simple form is provided because this is a very common
8990 requirement. Other kinds of wildcarding require the use of a regular
8993 .cindex "regular expressions" "in host list"
8994 .cindex "host list" "regular expression in"
8995 If the item starts with &"^"& it is taken to be a regular expression which is
8996 matched against the host name. Host names are case-independent, so this regular
8997 expression match is by default case-independent, but you can make it
8998 case-dependent by starting it with &`(?-i)`&. References to descriptions of the
8999 syntax of regular expressions are given in chapter &<<CHAPregexp>>&. For
9004 is a regular expression that matches either of the two hosts &'a.c.d'& or
9005 &'b.c.d'&. When a regular expression is used in a host list, you must take care
9006 that backslash and dollar characters are not misinterpreted as part of the
9007 string expansion. The simplest way to do this is to use &`\N`& to mark that
9008 part of the string as non-expandable. For example:
9010 sender_unqualified_hosts = \N^(a|b)\.c\.d$\N : ....
9012 &*Warning*&: If you want to match a complete host name, you must include the
9013 &`$`& terminating metacharacter in the regular expression, as in the above
9014 example. Without it, a match at the start of the host name is all that is
9021 .subsection "Behaviour when an IP address or name cannot be found" SECTbehipnot
9022 .cindex "host" "lookup failures, permanent"
9023 While processing a host list, Exim may need to look up an IP address from a
9024 name (see section &<<SECThoslispatip>>&), or it may need to look up a host name
9025 from an IP address (see section &<<SECThoslispatnam>>&). In either case, the
9026 behaviour when it fails to find the information it is seeking is the same.
9028 &*Note*&: This section applies to permanent lookup failures. It does &'not'&
9029 apply to temporary DNS errors, whose handling is described in the next section.
9031 .cindex "&`+include_unknown`&"
9032 .cindex "&`+ignore_unknown`&"
9033 Exim parses a host list from left to right. If it encounters a permanent
9034 lookup failure in any item in the host list before it has found a match,
9035 Exim treats it as a failure and the default behavior is as if the host
9036 does not match the list. This may not always be what you want to happen.
9037 To change Exim's behaviour, the special items &`+include_unknown`& or
9038 &`+ignore_unknown`& may appear in the list (at top level &-- they are
9039 not recognized in an indirected file).
9042 If any item that follows &`+include_unknown`& requires information that
9043 cannot found, Exim behaves as if the host does match the list. For example,
9045 host_reject_connection = +include_unknown:*.enemy.ex
9047 rejects connections from any host whose name matches &`*.enemy.ex`&, and also
9048 any hosts whose name it cannot find.
9051 If any item that follows &`+ignore_unknown`& requires information that cannot
9052 be found, Exim ignores that item and proceeds to the rest of the list. For
9055 accept hosts = +ignore_unknown : friend.example : \
9058 accepts from any host whose name is &'friend.example'& and from 192.168.4.5,
9059 whether or not its host name can be found. Without &`+ignore_unknown`&, if no
9060 name can be found for 192.168.4.5, it is rejected.
9063 Both &`+include_unknown`& and &`+ignore_unknown`& may appear in the same
9064 list. The effect of each one lasts until the next, or until the end of the
9067 .subsection "Mixing wildcarded host names and addresses in host lists" &&&
9069 .cindex "host list" "mixing names and addresses in"
9071 This section explains the host/ip processing logic with the same concepts
9072 as the previous section, but specifically addresses what happens when a
9073 wildcarded hostname is one of the items in the hostlist.
9076 If you have name lookups or wildcarded host names and
9077 IP addresses in the same host list, you should normally put the IP
9078 addresses first. For example, in an ACL you could have:
9080 accept hosts = 10.9.8.7 : *.friend.example
9082 The reason you normally would order it this way lies in the
9083 left-to-right way that Exim processes lists. It can test IP addresses
9084 without doing any DNS lookups, but when it reaches an item that requires
9085 a host name, it fails if it cannot find a host name to compare with the
9086 pattern. If the above list is given in the opposite order, the
9087 &%accept%& statement fails for a host whose name cannot be found, even
9088 if its IP address is 10.9.8.7.
9091 If you really do want to do the name check first, and still recognize the IP
9092 address, you can rewrite the ACL like this:
9094 accept hosts = *.friend.example
9095 accept hosts = 10.9.8.7
9097 If the first &%accept%& fails, Exim goes on to try the second one. See chapter
9098 &<<CHAPACL>>& for details of ACLs. Alternatively, you can use
9099 &`+ignore_unknown`&, which was discussed in depth in the first example in
9104 .subsection "Temporary DNS errors when looking up host information" &&&
9106 .cindex "host" "lookup failures, temporary"
9107 .cindex "&`+include_defer`&"
9108 .cindex "&`+ignore_defer`&"
9109 A temporary DNS lookup failure normally causes a defer action (except when
9110 &%dns_again_means_nonexist%& converts it into a permanent error). However,
9111 host lists can include &`+ignore_defer`& and &`+include_defer`&, analogous to
9112 &`+ignore_unknown`& and &`+include_unknown`&, as described in the previous
9113 section. These options should be used with care, probably only in non-critical
9114 host lists such as whitelists.
9118 .subsection "Host list patterns for single-key lookups by host name" &&&
9120 .cindex "unknown host name"
9121 .cindex "host list" "matching host name"
9122 If a pattern is of the form
9124 <&'single-key-search-type'&>;<&'search-data'&>
9128 dbm;/host/accept/list
9130 a single-key lookup is performed, using the host name as its key. If the
9131 lookup succeeds, the host matches the item. The actual data that is looked up
9134 &*Reminder*&: With this kind of pattern, you must have host &'names'& as
9135 keys in the file, not IP addresses. If you want to do lookups based on IP
9136 addresses, you must precede the search type with &"net-"& (see section
9137 &<<SECThoslispatsikey>>&). There is, however, no reason why you could not use
9138 two items in the same list, one doing an address lookup and one doing a name
9139 lookup, both using the same file.
9143 .subsection "Host list patterns for query-style lookups" SECID81
9144 If a pattern is of the form
9146 <&'query-style-search-type'&>;<&'query'&>
9148 the query is obeyed, and if it succeeds, the host matches the item. The actual
9149 data that is looked up is not used. The variables &$sender_host_address$& and
9150 &$sender_host_name$& can be used in the query. For example:
9152 hosts_lookup = pgsql;\
9153 select ip from hostlist where ip='$sender_host_address'
9155 The value of &$sender_host_address$& for an IPv6 address contains colons. You
9156 can use the &%sg%& expansion item to change this if you need to. If you want to
9157 use masked IP addresses in database queries, you can use the &%mask%& expansion
9160 If the query contains a reference to &$sender_host_name$&, Exim automatically
9161 looks up the host name if it has not already done so. (See section
9162 &<<SECThoslispatnam>>& for comments on finding host names.)
9164 Historical note: prior to release 4.30, Exim would always attempt to find a
9165 host name before running the query, unless the search type was preceded by
9166 &`net-`&. This is no longer the case. For backwards compatibility, &`net-`& is
9167 still recognized for query-style lookups, but its presence or absence has no
9168 effect. (Of course, for single-key lookups, &`net-`& &'is'& important.
9169 See section &<<SECThoslispatsikey>>&.)
9175 .section "Address lists" "SECTaddresslist"
9176 .cindex "list" "address list"
9177 .cindex "address list" "empty item"
9178 .cindex "address list" "patterns"
9179 Address lists contain patterns that are matched against mail addresses. There
9180 is one special case to be considered: the sender address of a bounce message is
9181 always empty. You can test for this by providing an empty item in an address
9182 list. For example, you can set up a router to process bounce messages by
9183 using this option setting:
9187 The presence of the colon creates an empty item. If you do not provide any
9188 data, the list is empty and matches nothing. The empty sender can also be
9189 detected by a regular expression that matches an empty string,
9190 and by a query-style lookup that succeeds when &$sender_address$& is empty.
9192 Non-empty items in an address list can be straightforward email addresses. For
9195 senders = jbc@askone.example : hs@anacreon.example
9197 A certain amount of wildcarding is permitted. If a pattern contains an @
9198 character, but is not a regular expression and does not begin with a
9199 semicolon-terminated lookup type (described below), the local part of the
9200 subject address is compared with the local part of the pattern, which may start
9201 with an asterisk. If the local parts match, the domain is checked in exactly
9202 the same way as for a pattern in a domain list. For example, the domain can be
9203 wildcarded, refer to a named list, or be a lookup:
9205 deny senders = *@*.spamming.site:\
9206 *@+hostile_domains:\
9207 bozo@partial-lsearch;/list/of/dodgy/sites:\
9208 *@dbm;/bad/domains.db
9210 .cindex "local part" "starting with !"
9211 .cindex "address list" "local part starting with !"
9212 If a local part that begins with an exclamation mark is required, it has to be
9213 specified using a regular expression, because otherwise the exclamation mark is
9214 treated as a sign of negation, as is standard in lists.
9216 If a non-empty pattern that is not a regular expression or a lookup does not
9217 contain an @ character, it is matched against the domain part of the subject
9218 address. The only two formats that are recognized this way are a literal
9219 domain, or a domain pattern that starts with *. In both these cases, the effect
9220 is the same as if &`*@`& preceded the pattern. For example:
9222 deny senders = enemy.domain : *.enemy.domain
9225 The following kinds of more complicated address list pattern can match any
9226 address, including the empty address that is characteristic of bounce message
9230 .cindex "regular expressions" "in address list"
9231 .cindex "address list" "regular expression in"
9232 If (after expansion) a pattern starts with &"^"&, a regular expression match is
9233 done against the complete address, with the pattern as the regular expression.
9234 You must take care that backslash and dollar characters are not misinterpreted
9235 as part of the string expansion. The simplest way to do this is to use &`\N`&
9236 to mark that part of the string as non-expandable. For example:
9238 deny senders = \N^.*this.*@example\.com$\N : \
9239 \N^\d{8}.+@spamhaus.example$\N : ...
9241 The &`\N`& sequences are removed by the expansion, so these items do indeed
9242 start with &"^"& by the time they are being interpreted as address patterns.
9245 .cindex "address list" "lookup for complete address"
9246 Complete addresses can be looked up by using a pattern that starts with a
9247 lookup type terminated by a semicolon, followed by the data for the lookup. For
9250 deny senders = cdb;/etc/blocked.senders : \
9251 mysql;select address from blocked where \
9252 address='${quote_mysql:$sender_address}'
9254 Both query-style and single-key lookup types can be used. For a single-key
9255 lookup type, Exim uses the complete address as the key. However, empty keys are
9256 not supported for single-key lookups, so a match against the empty address
9257 always fails. This restriction does not apply to query-style lookups.
9259 Partial matching for single-key lookups (section &<<SECTpartiallookup>>&)
9260 cannot be used, and is ignored if specified, with an entry being written to the
9262 .cindex "*@ with single-key lookup"
9263 However, you can configure lookup defaults, as described in section
9264 &<<SECTdefaultvaluelookups>>&, but this is useful only for the &"*@"& type of
9265 default. For example, with this lookup:
9267 accept senders = lsearch*@;/some/file
9269 the file could contains lines like this:
9271 user1@domain1.example
9274 and for the sender address &'nimrod@jaeger.example'&, the sequence of keys
9277 nimrod@jaeger.example
9281 &*Warning 1*&: Do not include a line keyed by &"*"& in the file, because that
9282 would mean that every address matches, thus rendering the test useless.
9284 &*Warning 2*&: Do not confuse these two kinds of item:
9286 deny recipients = dbm*@;/some/file
9287 deny recipients = *@dbm;/some/file
9289 The first does a whole address lookup, with defaulting, as just described,
9290 because it starts with a lookup type. The second matches the local part and
9291 domain independently, as described in a bullet point below.
9295 The following kinds of address list pattern can match only non-empty addresses.
9296 If the subject address is empty, a match against any of these pattern types
9301 .cindex "@@ with single-key lookup"
9302 .cindex "address list" "@@ lookup type"
9303 .cindex "address list" "split local part and domain"
9304 If a pattern starts with &"@@"& followed by a single-key lookup item
9305 (for example, &`@@lsearch;/some/file`&), the address that is being checked is
9306 split into a local part and a domain. The domain is looked up in the file. If
9307 it is not found, there is no match. If it is found, the data that is looked up
9308 from the file is treated as a colon-separated list of local part patterns, each
9309 of which is matched against the subject local part in turn.
9311 .cindex "asterisk" "in address list"
9312 The lookup may be a partial one, and/or one involving a search for a default
9313 keyed by &"*"& (see section &<<SECTdefaultvaluelookups>>&). The local part
9314 patterns that are looked up can be regular expressions or begin with &"*"&, or
9315 even be further lookups. They may also be independently negated. For example,
9318 deny senders = @@dbm;/etc/reject-by-domain
9320 the data from which the DBM file is built could contain lines like
9322 baddomain.com: !postmaster : *
9324 to reject all senders except &%postmaster%& from that domain.
9326 .cindex "local part" "starting with !"
9327 If a local part that actually begins with an exclamation mark is required, it
9328 has to be specified using a regular expression. In &(lsearch)& files, an entry
9329 may be split over several lines by indenting the second and subsequent lines,
9330 but the separating colon must still be included at line breaks. White space
9331 surrounding the colons is ignored. For example:
9333 aol.com: spammer1 : spammer2 : ^[0-9]+$ :
9336 As in all colon-separated lists in Exim, a colon can be included in an item by
9339 If the last item in the list starts with a right angle-bracket, the remainder
9340 of the item is taken as a new key to look up in order to obtain a continuation
9341 list of local parts. The new key can be any sequence of characters. Thus one
9342 might have entries like
9344 aol.com: spammer1 : spammer 2 : >*
9345 xyz.com: spammer3 : >*
9348 in a file that was searched with &%@@dbm*%&, to specify a match for 8-digit
9349 local parts for all domains, in addition to the specific local parts listed for
9350 each domain. Of course, using this feature costs another lookup each time a
9351 chain is followed, but the effort needed to maintain the data is reduced.
9353 .cindex "loop" "in lookups"
9354 It is possible to construct loops using this facility, and in order to catch
9355 them, the chains may be no more than fifty items long.
9358 The @@<&'lookup'&> style of item can also be used with a query-style
9359 lookup, but in this case, the chaining facility is not available. The lookup
9360 can only return a single list of local parts.
9363 &*Warning*&: There is an important difference between the address list items
9364 in these two examples:
9367 senders = *@+my_list
9369 In the first one, &`my_list`& is a named address list, whereas in the second
9370 example it is a named domain list.
9375 .subsection "Case of letters in address lists" SECTcasletadd
9376 .cindex "case of local parts"
9377 .cindex "address list" "case forcing"
9378 .cindex "case forcing in address lists"
9379 Domains in email addresses are always handled caselessly, but for local parts
9380 case may be significant on some systems (see &%caseful_local_part%& for how
9381 Exim deals with this when routing addresses). However, RFC 2505 (&'Anti-Spam
9382 Recommendations for SMTP MTAs'&) suggests that matching of addresses to
9383 blocking lists should be done in a case-independent manner. Since most address
9384 lists in Exim are used for this kind of control, Exim attempts to do this by
9387 The domain portion of an address is always lowercased before matching it to an
9388 address list. The local part is lowercased by default, and any string
9389 comparisons that take place are done caselessly. This means that the data in
9390 the address list itself, in files included as plain filenames, and in any file
9391 that is looked up using the &"@@"& mechanism, can be in any case. However, the
9392 keys in files that are looked up by a search type other than &(lsearch)& (which
9393 works caselessly) must be in lower case, because these lookups are not
9396 .cindex "&`+caseful`&"
9397 To allow for the possibility of caseful address list matching, if an item in
9398 an address list is the string &"+caseful"&, the original case of the local
9399 part is restored for any comparisons that follow, and string comparisons are no
9400 longer case-independent. This does not affect the domain, which remains in
9401 lower case. However, although independent matches on the domain alone are still
9402 performed caselessly, regular expressions that match against an entire address
9403 become case-sensitive after &"+caseful"& has been seen.
9407 .section "Local part lists" "SECTlocparlis"
9408 .cindex "list" "local part list"
9409 .cindex "local part" "list"
9410 These behave in the same way as domain and host lists, with the following
9413 Case-sensitivity in local part lists is handled in the same way as for address
9414 lists, as just described. The &"+caseful"& item can be used if required. In a
9415 setting of the &%local_parts%& option in a router with &%caseful_local_part%&
9416 set false, the subject is lowercased and the matching is initially
9417 case-insensitive. In this case, &"+caseful"& will restore case-sensitive
9418 matching in the local part list, but not elsewhere in the router. If
9419 &%caseful_local_part%& is set true in a router, matching in the &%local_parts%&
9420 option is case-sensitive from the start.
9422 If a local part list is indirected to a file (see section &<<SECTfilnamlis>>&),
9423 comments are handled in the same way as address lists &-- they are recognized
9424 only if the # is preceded by white space or the start of the line.
9425 Otherwise, local part lists are matched in the same way as domain lists, except
9426 that the special items that refer to the local host (&`@`&, &`@[]`&,
9427 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`&) are not recognized.
9428 Refer to section &<<SECTdomainlist>>& for details of the other available item
9430 .ecindex IIDdohoadli
9435 . ////////////////////////////////////////////////////////////////////////////
9436 . ////////////////////////////////////////////////////////////////////////////
9438 .chapter "String expansions" "CHAPexpand"
9439 .scindex IIDstrexp "expansion" "of strings"
9440 Many strings in Exim's runtime configuration are expanded before use. Some of
9441 them are expanded every time they are used; others are expanded only once.
9443 When a string is being expanded it is copied verbatim from left to right except
9444 .cindex expansion "string concatenation"
9445 when a dollar or backslash character is encountered. A dollar specifies the
9446 start of a portion of the string that is interpreted and replaced as described
9447 below in section &<<SECTexpansionitems>>& onwards. Backslash is used as an
9448 escape character, as described in the following section.
9450 Whether a string is expanded depends upon the context. Usually this is solely
9451 dependent upon the option for which a value is sought; in this documentation,
9452 options for which string expansion is performed are marked with † after
9453 the data type. ACL rules always expand strings. A couple of expansion
9454 conditions do not expand some of the brace-delimited branches, for security
9456 .cindex "tainted data" expansion
9457 .cindex "tainted data" definition
9458 .cindex expansion "tainted data"
9459 and expansion of data deriving from the sender (&"tainted data"&)
9460 is not permitted (including acessing a file using a tainted name).
9462 Common ways of obtaining untainted equivalents of variables with
9464 .cindex "tainted data" "de-tainting"
9465 come down to using the tainted value as a lookup key in a trusted database.
9466 This database could be the filesystem structure,
9467 or the password file,
9468 or accessed via a DBMS.
9469 Specific methods are indexed under &"de-tainting"&.
9473 .section "Literal text in expanded strings" "SECTlittext"
9474 .cindex "expansion" "including literal text"
9475 An uninterpreted dollar can be included in an expanded string by putting a
9476 backslash in front of it. A backslash can be used to prevent any special
9477 character being treated specially in an expansion, including backslash itself.
9478 If the string appears in quotes in the configuration file, two backslashes are
9479 required because the quotes themselves cause interpretation of backslashes when
9480 the string is read in (see section &<<SECTstrings>>&).
9482 .cindex "expansion" "non-expandable substrings"
9483 A portion of the string can specified as non-expandable by placing it between
9484 two occurrences of &`\N`&. This is particularly useful for protecting regular
9485 expressions, which often contain backslashes and dollar signs. For example:
9487 deny senders = \N^\d{8}[a-z]@some\.site\.example$\N
9489 On encountering the first &`\N`&, the expander copies subsequent characters
9490 without interpretation until it reaches the next &`\N`& or the end of the
9495 .section "Character escape sequences in expanded strings" "SECID82"
9496 .cindex "expansion" "escape sequences"
9497 A backslash followed by one of the letters &"n"&, &"r"&, or &"t"& in an
9498 expanded string is recognized as an escape sequence for the character newline,
9499 carriage return, or tab, respectively. A backslash followed by up to three
9500 octal digits is recognized as an octal encoding for a single character, and a
9501 backslash followed by &"x"& and up to two hexadecimal digits is a hexadecimal
9504 These escape sequences are also recognized in quoted strings when they are read
9505 in. Their interpretation in expansions as well is useful for unquoted strings,
9506 and for other cases such as looked-up strings that are then expanded.
9509 .section "Testing string expansions" "SECID83"
9510 .cindex "expansion" "testing"
9511 .cindex "testing" "string expansion"
9513 Many expansions can be tested by calling Exim with the &%-be%& option. This
9514 takes the command arguments, or lines from the standard input if there are no
9515 arguments, runs them through the string expansion code, and writes the results
9516 to the standard output. Variables based on configuration values are set up, but
9517 since no message is being processed, variables such as &$local_part$& have no
9518 value. Nevertheless the &%-be%& option can be useful for checking out file and
9519 database lookups, and the use of expansion operators such as &%sg%&, &%substr%&
9523 When reading lines from the standard input,
9524 macros can be defined and ACL variables can be set.
9528 set acl_m_myvar = bar
9530 Such macros and variables can then be used in later input lines.
9533 Exim gives up its root privilege when it is called with the &%-be%& option, and
9534 instead runs under the uid and gid it was called with, to prevent users from
9535 using &%-be%& for reading files to which they do not have access.
9538 If you want to test expansions that include variables whose values are taken
9539 from a message, there are two other options that can be used. The &%-bem%&
9540 option is like &%-be%& except that it is followed by a filename. The file is
9541 read as a message before doing the test expansions. For example:
9543 exim -bem /tmp/test.message '$h_subject:'
9545 The &%-Mset%& option is used in conjunction with &%-be%& and is followed by an
9546 Exim message identifier. For example:
9548 exim -be -Mset 1GrA8W-0004WS-LQ '$recipients'
9550 This loads the message from Exim's spool before doing the test expansions, and
9551 is therefore restricted to admin users.
9554 .section "Forced expansion failure" "SECTforexpfai"
9555 .cindex "expansion" "forced failure"
9556 A number of expansions that are described in the following section have
9557 alternative &"true"& and &"false"& substrings, enclosed in brace characters
9558 (which are sometimes called &"curly brackets"&). Which of the two strings is
9559 used depends on some condition that is evaluated as part of the expansion. If,
9560 instead of a &"false"& substring, the word &"fail"& is used (not in braces),
9561 the entire string expansion fails in a way that can be detected by the code
9562 that requested the expansion. This is called &"forced expansion failure"&, and
9563 its consequences depend on the circumstances. In some cases it is no different
9564 from any other expansion failure, but in others a different action may be
9565 taken. Such variations are mentioned in the documentation of the option that is
9571 .section "Expansion items" "SECTexpansionitems"
9572 The following items are recognized in expanded strings. White space may be used
9573 between sub-items that are keywords or substrings enclosed in braces inside an
9574 outer set of braces, to improve readability. &*Warning*&: Within braces,
9575 white space is significant.
9578 .vitem &*$*&<&'variable&~name'&>&~or&~&*${*&<&'variable&~name'&>&*}*&
9579 .cindex "expansion" "variables"
9580 Substitute the contents of the named variable, for example:
9585 The second form can be used to separate the name from subsequent alphanumeric
9586 characters. This form (using braces) is available only for variables; it does
9587 &'not'& apply to message headers. The names of the variables are given in
9588 section &<<SECTexpvar>>& below. If the name of a non-existent variable is
9589 given, the expansion fails.
9591 .vitem &*${*&<&'op'&>&*:*&<&'string'&>&*}*&
9592 .cindex "expansion" "operators"
9593 The string is first itself expanded, and then the operation specified by
9594 <&'op'&> is applied to it. For example:
9598 The string starts with the first character after the colon, which may be
9599 leading white space. A list of operators is given in section &<<SECTexpop>>&
9600 below. The operator notation is used for simple expansion items that have just
9601 one argument, because it reduces the number of braces and therefore makes the
9602 string easier to understand.
9604 .vitem &*$bheader_*&<&'header&~name'&>&*:*&&~or&~&*$bh_*&<&'header&~name'&>&*:*&
9605 This item inserts &"basic"& header lines. It is described with the &%header%&
9606 expansion item below.
9609 .vitem "&*${acl{*&<&'name'&>&*}{*&<&'arg'&>&*}...}*&"
9610 .cindex "expansion" "calling an acl"
9611 .cindex "&%acl%&" "call from expansion"
9612 The name and zero to nine argument strings are first expanded separately. The expanded
9613 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
9614 Any unused are made empty. The variable &$acl_narg$& is set to the number of
9615 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
9616 and may use the variables; if another acl expansion is used the values
9617 are restored after it returns. If the ACL sets
9618 a value using a "message =" modifier and returns accept or deny, the value becomes
9619 the result of the expansion.
9620 If no message is set and the ACL returns accept or deny
9621 the expansion result is an empty string.
9622 If the ACL returns defer the result is a forced-fail. Otherwise the expansion fails.
9625 .vitem "&*${authresults{*&<&'authserv-id'&>&*}}*&"
9626 .cindex authentication "results header"
9627 .chindex Authentication-Results:
9628 .cindex authentication "expansion item"
9629 This item returns a string suitable for insertion as an
9630 &'Authentication-Results:'&
9632 The given <&'authserv-id'&> is included in the result; typically this
9633 will be a domain name identifying the system performing the authentications.
9634 Methods that might be present in the result include:
9643 Example use (as an ACL modifier):
9645 add_header = :at_start:${authresults {$primary_hostname}}
9647 This is safe even if no authentication results are available.
9650 .vitem "&*${certextract{*&<&'field'&>&*}{*&<&'certificate'&>&*}&&&
9651 {*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9652 .cindex "expansion" "extracting certificate fields"
9653 .cindex "&%certextract%&" "certificate fields"
9654 .cindex "certificate" "extracting fields"
9655 The <&'certificate'&> must be a variable of type certificate.
9656 The field name is expanded and used to retrieve the relevant field from
9657 the certificate. Supported fields are:
9661 &`subject `& RFC4514 DN
9662 &`issuer `& RFC4514 DN
9667 &`subj_altname `& tagged list
9671 If the field is found,
9672 <&'string2'&> is expanded, and replaces the whole item;
9673 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
9674 variable &$value$& contains the value that has been extracted. Afterwards, it
9675 is restored to any previous value it might have had.
9677 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
9678 key is not found. If {<&'string2'&>} is also omitted, the value that was
9681 Some field names take optional modifiers, appended and separated by commas.
9683 The field selectors marked as "RFC4514" above
9684 output a Distinguished Name string which is
9686 parseable by Exim as a comma-separated tagged list
9687 (the exceptions being elements containing commas).
9688 RDN elements of a single type may be selected by
9689 a modifier of the type label; if so the expansion
9690 result is a list (newline-separated by default).
9691 The separator may be changed by another modifier of
9692 a right angle-bracket followed immediately by the new separator.
9693 Recognised RDN type labels include "CN", "O", "OU" and "DC".
9695 The field selectors marked as "time" above
9696 take an optional modifier of "int"
9697 for which the result is the number of seconds since epoch.
9698 Otherwise the result is a human-readable string
9699 in the timezone selected by the main "timezone" option.
9701 The field selectors marked as "list" above return a list,
9702 newline-separated by default,
9703 (embedded separator characters in elements are doubled).
9704 The separator may be changed by a modifier of
9705 a right angle-bracket followed immediately by the new separator.
9707 The field selectors marked as "tagged" above
9708 prefix each list element with a type string and an equals sign.
9709 Elements of only one type may be selected by a modifier
9710 which is one of "dns", "uri" or "mail";
9711 if so the element tags are omitted.
9713 If not otherwise noted field values are presented in human-readable form.
9715 .vitem "&*${dlfunc{*&<&'file'&>&*}{*&<&'function'&>&*}{*&<&'arg'&>&*}&&&
9716 {*&<&'arg'&>&*}...}*&"
9718 This expansion dynamically loads and then calls a locally-written C function.
9719 This functionality is available only if Exim is compiled with
9723 set in &_Local/Makefile_&. Once loaded, Exim remembers the dynamically loaded
9724 object so that it doesn't reload the same object file in the same Exim process
9725 (but of course Exim does start new processes frequently).
9727 There may be from zero to eight arguments to the function.
9730 a local function that is to be called in this way,
9731 first &_DLFUNC_IMPL_& should be defined,
9732 and second &_local_scan.h_& should be included.
9733 The Exim variables and functions that are defined by that API
9734 are also available for dynamically loaded functions. The function itself
9735 must have the following type:
9737 int dlfunction(uschar **yield, int argc, uschar *argv[])
9739 Where &`uschar`& is a typedef for &`unsigned char`& in &_local_scan.h_&. The
9740 function should return one of the following values:
9742 &`OK`&: Success. The string that is placed in the variable &'yield'& is put
9743 into the expanded string that is being built.
9745 &`FAIL`&: A non-forced expansion failure occurs, with the error message taken
9746 from &'yield'&, if it is set.
9748 &`FAIL_FORCED`&: A forced expansion failure occurs, with the error message
9749 taken from &'yield'& if it is set.
9751 &`ERROR`&: Same as &`FAIL`&, except that a panic log entry is written.
9753 When compiling a function that is to be used in this way with gcc,
9754 you need to add &%-shared%& to the gcc command. Also, in the Exim build-time
9755 configuration, you must add &%-export-dynamic%& to EXTRALIBS.
9758 .vitem "&*${env{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&"
9759 .cindex "expansion" "extracting value from environment"
9760 .cindex "environment" "values from"
9761 The key is first expanded separately, and leading and trailing white space
9763 This is then searched for as a name in the environment.
9764 If a variable is found then its value is placed in &$value$&
9765 and <&'string1'&> is expanded, otherwise <&'string2'&> is expanded.
9767 Instead of {<&'string2'&>} the word &"fail"& (not in curly brackets) can
9768 appear, for example:
9770 ${env{USER}{$value} fail }
9772 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9773 {<&'string1'&>} must be present for &"fail"& to be recognized.
9775 If {<&'string2'&>} is omitted an empty string is substituted on
9777 If {<&'string1'&>} is omitted the search result is substituted on
9780 The environment is adjusted by the &%keep_environment%& and
9781 &%add_environment%& main section options.
9784 .vitem "&*${extract{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9785 {*&<&'string3'&>&*}}*&"
9786 .cindex "expansion" "extracting substrings by key"
9787 .cindex "&%extract%&" "substrings by key"
9788 The key and <&'string1'&> are first expanded separately. Leading and trailing
9789 white space is removed from the key (but not from any of the strings). The key
9790 must not be empty and must not consist entirely of digits.
9791 The expanded <&'string1'&> must be of the form:
9793 <&'key1'&> = <&'value1'&> <&'key2'&> = <&'value2'&> ...
9796 where the equals signs and spaces (but not both) are optional. If any of the
9797 values contain white space, they must be enclosed in double quotes, and any
9798 values that are enclosed in double quotes are subject to escape processing as
9799 described in section &<<SECTstrings>>&. The expanded <&'string1'&> is searched
9800 for the value that corresponds to the key. The search is case-insensitive. If
9801 the key is found, <&'string2'&> is expanded, and replaces the whole item;
9802 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
9803 variable &$value$& contains the value that has been extracted. Afterwards, it
9804 is restored to any previous value it might have had.
9806 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
9807 key is not found. If {<&'string2'&>} is also omitted, the value that was
9808 extracted is used. Thus, for example, these two expansions are identical, and
9811 ${extract{gid}{uid=1984 gid=2001}}
9812 ${extract{gid}{uid=1984 gid=2001}{$value}}
9814 Instead of {<&'string3'&>} the word &"fail"& (not in curly brackets) can
9815 appear, for example:
9817 ${extract{Z}{A=... B=...}{$value} fail }
9819 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9820 {<&'string2'&>} must be present for &"fail"& to be recognized.
9822 .vitem "&*${extract json{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9823 {*&<&'string3'&>&*}}*&" &&&
9824 "&*${extract jsons{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9825 {*&<&'string3'&>&*}}*&"
9826 .cindex "expansion" "extracting from JSON object"
9827 .cindex JSON expansions
9828 The key and <&'string1'&> are first expanded separately. Leading and trailing
9829 white space is removed from the key (but not from any of the strings). The key
9830 must not be empty and must not consist entirely of digits.
9831 The expanded <&'string1'&> must be of the form:
9833 { <&'"key1"'&> : <&'value1'&> , <&'"key2"'&> , <&'value2'&> ... }
9836 The braces, commas and colons, and the quoting of the member name are required;
9837 the spaces are optional.
9838 Matching of the key against the member names is done case-sensitively.
9839 For the &"json"& variant,
9840 if a returned value is a JSON string, it retains its leading and
9842 For the &"jsons"& variant, which is intended for use with JSON strings, the
9843 leading and trailing quotes are removed from the returned value.
9844 . XXX should be a UTF-8 compare
9846 The results of matching are handled as above.
9849 .vitem "&*${extract{*&<&'number'&>&*}{*&<&'separators'&>&*}&&&
9850 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9851 .cindex "expansion" "extracting substrings by number"
9852 .cindex "&%extract%&" "substrings by number"
9853 The <&'number'&> argument must consist entirely of decimal digits,
9854 apart from leading and trailing white space, which is ignored.
9855 This is what distinguishes this form of &%extract%& from the previous kind. It
9856 behaves in the same way, except that, instead of extracting a named field, it
9857 extracts from <&'string1'&> the field whose number is given as the first
9858 argument. You can use &$value$& in <&'string2'&> or &`fail`& instead of
9859 <&'string3'&> as before.
9861 The fields in the string are separated by any one of the characters in the
9862 separator string. These may include space or tab characters.
9863 The first field is numbered one. If the number is negative, the fields are
9864 counted from the end of the string, with the rightmost one numbered -1. If the
9865 number given is zero, the entire string is returned. If the modulus of the
9866 number is greater than the number of fields in the string, the result is the
9867 expansion of <&'string3'&>, or the empty string if <&'string3'&> is not
9868 provided. For example:
9870 ${extract{2}{:}{x:42:99:& Mailer::/bin/bash}}
9874 ${extract{-4}{:}{x:42:99:& Mailer::/bin/bash}}
9876 yields &"99"&. Two successive separators mean that the field between them is
9877 empty (for example, the fifth field above).
9880 .vitem "&*${extract json {*&<&'number'&>&*}}&&&
9881 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&" &&&
9882 "&*${extract jsons{*&<&'number'&>&*}}&&&
9883 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9884 .cindex "expansion" "extracting from JSON array"
9885 .cindex JSON expansions
9886 The <&'number'&> argument must consist entirely of decimal digits,
9887 apart from leading and trailing white space, which is ignored.
9889 Field selection and result handling is as above;
9890 there is no choice of field separator.
9891 For the &"json"& variant,
9892 if a returned value is a JSON string, it retains its leading and
9894 For the &"jsons"& variant, which is intended for use with JSON strings, the
9895 leading and trailing quotes are removed from the returned value.
9898 .vitem &*${filter{*&<&'string'&>&*}{*&<&'condition'&>&*}}*&
9899 .cindex "list" "selecting by condition"
9900 .cindex "expansion" "selecting from list by condition"
9902 After expansion, <&'string'&> is interpreted as a list, colon-separated by
9903 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
9905 in this list, its value is place in &$item$&, and then the condition is
9906 evaluated. If the condition is true, &$item$& is added to the output as an
9907 item in a new list; if the condition is false, the item is discarded. The
9908 separator used for the output list is the same as the one used for the
9909 input, but a separator setting is not included in the output. For example:
9911 ${filter{a:b:c}{!eq{$item}{b}}}
9913 yields &`a:c`&. At the end of the expansion, the value of &$item$& is restored
9914 to what it was before. See also the &%map%& and &%reduce%& expansion items.
9917 .vitem &*${hash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9918 .cindex "hash function" "textual"
9919 .cindex "expansion" "textual hash"
9920 This is a textual hashing function, and was the first to be implemented in
9921 early versions of Exim. In current releases, there are other hashing functions
9922 (numeric, MD5, and SHA-1), which are described below.
9924 The first two strings, after expansion, must be numbers. Call them <&'m'&> and
9925 <&'n'&>. If you are using fixed values for these numbers, that is, if
9926 <&'string1'&> and <&'string2'&> do not change when they are expanded, you can
9927 use the simpler operator notation that avoids some of the braces:
9929 ${hash_<n>_<m>:<string>}
9931 The second number is optional (in both notations). If <&'n'&> is greater than
9932 or equal to the length of the string, the expansion item returns the string.
9933 Otherwise it computes a new string of length <&'n'&> by applying a hashing
9934 function to the string. The new string consists of characters taken from the
9935 first <&'m'&> characters of the string
9937 abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQWRSTUVWXYZ0123456789
9939 If <&'m'&> is not present the value 26 is used, so that only lower case
9940 letters appear. For example:
9942 &`$hash{3}{monty}} `& yields &`jmg`&
9943 &`$hash{5}{monty}} `& yields &`monty`&
9944 &`$hash{4}{62}{monty python}}`& yields &`fbWx`&
9947 .vitem "&*$header_*&<&'header&~name'&>&*:*&&~or&~&&&
9948 &*$h_*&<&'header&~name'&>&*:*&" &&&
9949 "&*$bheader_*&<&'header&~name'&>&*:*&&~or&~&&&
9950 &*$bh_*&<&'header&~name'&>&*:*&" &&&
9951 "&*$lheader_*&<&'header&~name'&>&*:*&&~or&~&&&
9952 &*$lh_*&<&'header&~name'&>&*:*&" &&&
9953 "&*$rheader_*&<&'header&~name'&>&*:*&&~or&~&&&
9954 &*$rh_*&<&'header&~name'&>&*:*&"
9955 .cindex "expansion" "header insertion"
9956 .vindex "&$header_$&"
9957 .vindex "&$bheader_$&"
9958 .vindex "&$lheader_$&"
9959 .vindex "&$rheader_$&"
9960 .cindex "header lines" "in expansion strings"
9961 .cindex "header lines" "character sets"
9962 .cindex "header lines" "decoding"
9963 Substitute the contents of the named message header line, for example
9967 The newline that terminates a header line is not included in the expansion, but
9968 internal newlines (caused by splitting the header line over several physical
9969 lines) may be present.
9971 The difference between the four pairs of expansions is in the way
9972 the data in the header line is interpreted.
9975 .cindex "white space" "in header lines"
9976 &%rheader%& gives the original &"raw"& content of the header line, with no
9977 processing at all, and without the removal of leading and trailing white space.
9980 .cindex "list" "of header lines"
9981 &%lheader%& gives a colon-separated list, one element per header when there
9982 are multiple headers with a given name.
9983 Any embedded colon characters within an element are doubled, so normal Exim
9984 list-processing facilities can be used.
9985 The terminating newline of each element is removed; in other respects
9986 the content is &"raw"&.
9989 .cindex "base64 encoding" "in header lines"
9990 &%bheader%& removes leading and trailing white space, and then decodes base64
9991 or quoted-printable MIME &"words"& within the header text, but does no
9992 character set translation. If decoding of what looks superficially like a MIME
9993 &"word"& fails, the raw string is returned. If decoding
9994 .cindex "binary zero" "in header line"
9995 produces a binary zero character, it is replaced by a question mark &-- this is
9996 what Exim does for binary zeros that are actually received in header lines.
9999 &%header%& tries to translate the string as decoded by &%bheader%& to a
10000 standard character set. This is an attempt to produce the same string as would
10001 be displayed on a user's MUA. If translation fails, the &%bheader%& string is
10002 returned. Translation is attempted only on operating systems that support the
10003 &[iconv()]& function. This is indicated by the compile-time macro HAVE_ICONV in
10004 a system Makefile or in &_Local/Makefile_&.
10007 In a filter file, the target character set for &%header%& can be specified by a
10008 command of the following form:
10010 headers charset "UTF-8"
10012 This command affects all references to &$h_$& (or &$header_$&) expansions in
10013 subsequently obeyed filter commands. In the absence of this command, the target
10014 character set in a filter is taken from the setting of the &%headers_charset%&
10015 option in the runtime configuration. The value of this option defaults to the
10016 value of HEADERS_CHARSET in &_Local/Makefile_&. The ultimate default is
10019 Header names follow the syntax of RFC 2822, which states that they may contain
10020 any printing characters except space and colon. Consequently, curly brackets
10021 &'do not'& terminate header names, and should not be used to enclose them as
10022 if they were variables. Attempting to do so causes a syntax error.
10024 Only header lines that are common to all copies of a message are visible to
10025 this mechanism. These are the original header lines that are received with the
10026 message, and any that are added by an ACL statement or by a system
10027 filter. Header lines that are added to a particular copy of a message by a
10028 router or transport are not accessible.
10030 For incoming SMTP messages, no header lines are visible in
10031 ACLs that are obeyed before the data phase completes,
10032 because the header structure is not set up until the message is received.
10033 They are visible in DKIM, PRDR and DATA ACLs.
10034 Header lines that are added in a RCPT ACL (for example)
10035 are saved until the message's incoming header lines are available, at which
10036 point they are added.
10037 When any of the above ACLs are
10038 running, however, header lines added by earlier ACLs are visible.
10040 Upper case and lower case letters are synonymous in header names. If the
10041 following character is white space, the terminating colon may be omitted, but
10042 this is not recommended, because you may then forget it when it is needed. When
10043 white space terminates the header name, this white space is included in the
10044 expanded string. If the message does not contain the given header, the
10045 expansion item is replaced by an empty string. (See the &%def%& condition in
10046 section &<<SECTexpcond>>& for a means of testing for the existence of a
10049 If there is more than one header with the same name, they are all concatenated
10050 to form the substitution string, up to a maximum length of 64K. Unless
10051 &%rheader%& is being used, leading and trailing white space is removed from
10052 each header before concatenation, and a completely empty header is ignored. A
10053 newline character is then inserted between non-empty headers, but there is no
10054 newline at the very end. For the &%header%& and &%bheader%& expansion, for
10055 those headers that contain lists of addresses, a comma is also inserted at the
10056 junctions between headers. This does not happen for the &%rheader%& expansion.
10058 .cindex "tainted data" "message headers"
10059 When the headers are from an incoming message,
10060 the result of expanding any of these variables is tainted.
10063 .vitem &*${hmac{*&<&'hashname'&>&*}{*&<&'secret'&>&*}{*&<&'string'&>&*}}*&
10064 .cindex "expansion" "hmac hashing"
10066 This function uses cryptographic hashing (either MD5 or SHA-1) to convert a
10067 shared secret and some text into a message authentication code, as specified in
10068 RFC 2104. This differs from &`${md5:secret_text...}`& or
10069 &`${sha1:secret_text...}`& in that the hmac step adds a signature to the
10070 cryptographic hash, allowing for authentication that is not possible with MD5
10071 or SHA-1 alone. The hash name must expand to either &`md5`& or &`sha1`& at
10072 present. For example:
10074 ${hmac{md5}{somesecret}{$primary_hostname $tod_log}}
10076 For the hostname &'mail.example.com'& and time 2002-10-17 11:30:59, this
10079 dd97e3ba5d1a61b5006108f8c8252953
10081 As an example of how this might be used, you might put in the main part of
10082 an Exim configuration:
10084 SPAMSCAN_SECRET=cohgheeLei2thahw
10086 In a router or a transport you could then have:
10089 X-Spam-Scanned: ${primary_hostname} ${message_exim_id} \
10090 ${hmac{md5}{SPAMSCAN_SECRET}\
10091 {${primary_hostname},${message_exim_id},$h_message-id:}}
10093 Then given a message, you can check where it was scanned by looking at the
10094 &'X-Spam-Scanned:'& header line. If you know the secret, you can check that
10095 this header line is authentic by recomputing the authentication code from the
10096 host name, message ID and the &'Message-id:'& header line. This can be done
10097 using Exim's &%-be%& option, or by other means, for example, by using the
10098 &'hmac_md5_hex()'& function in Perl.
10101 .vitem &*${if&~*&<&'condition'&>&*&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
10102 .cindex "expansion" "conditional"
10103 .cindex "&%if%&, expansion item"
10104 If <&'condition'&> is true, <&'string1'&> is expanded and replaces the whole
10105 item; otherwise <&'string2'&> is used. The available conditions are described
10106 in section &<<SECTexpcond>>& below. For example:
10108 ${if eq {$local_part}{postmaster} {yes}{no} }
10110 The second string need not be present; if it is not and the condition is not
10111 true, the item is replaced with nothing. Alternatively, the word &"fail"& may
10112 be present instead of the second string (without any curly brackets). In this
10113 case, the expansion is forced to fail if the condition is not true (see section
10114 &<<SECTforexpfai>>&).
10116 If both strings are omitted, the result is the string &`true`& if the condition
10117 is true, and the empty string if the condition is false. This makes it less
10118 cumbersome to write custom ACL and router conditions. For example, instead of
10120 condition = ${if >{$acl_m4}{3}{true}{false}}
10124 condition = ${if >{$acl_m4}{3}}
10129 .vitem &*${imapfolder{*&<&'foldername'&>&*}}*&
10130 .cindex expansion "imap folder"
10131 .cindex "&%imapfolder%& expansion item"
10132 This item converts a (possibly multilevel, or with non-ASCII characters)
10133 folder specification to a Maildir name for filesystem use.
10134 For information on internationalisation support see &<<SECTi18nMDA>>&.
10138 .vitem &*${length{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
10139 .cindex "expansion" "string truncation"
10140 .cindex "&%length%& expansion item"
10141 The &%length%& item is used to extract the initial portion of a string. Both
10142 strings are expanded, and the first one must yield a number, <&'n'&>, say. If
10143 you are using a fixed value for the number, that is, if <&'string1'&> does not
10144 change when expanded, you can use the simpler operator notation that avoids
10145 some of the braces:
10147 ${length_<n>:<string>}
10149 The result of this item is either the first <&'n'&> bytes or the whole
10150 of <&'string2'&>, whichever is the shorter. Do not confuse &%length%& with
10151 &%strlen%&, which gives the length of a string.
10152 All measurement is done in bytes and is not UTF-8 aware.
10155 .vitem "&*${listextract{*&<&'number'&>&*}&&&
10156 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
10157 .cindex "expansion" "extracting list elements by number"
10158 .cindex "&%listextract%&" "extract list elements by number"
10159 .cindex "list" "extracting elements by number"
10160 The <&'number'&> argument must consist entirely of decimal digits,
10161 apart from an optional leading minus,
10162 and leading and trailing white space (which is ignored).
10164 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
10165 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10167 The first field of the list is numbered one.
10168 If the number is negative, the fields are
10169 counted from the end of the list, with the rightmost one numbered -1.
10170 The numbered element of the list is extracted and placed in &$value$&,
10171 then <&'string2'&> is expanded as the result.
10173 If the modulus of the
10174 number is zero or greater than the number of fields in the string,
10175 the result is the expansion of <&'string3'&>.
10179 ${listextract{2}{x:42:99}}
10183 ${listextract{-3}{<, x,42,99,& Mailer,,/bin/bash}{result: $value}}
10185 yields &"result: 42"&.
10187 If {<&'string3'&>} is omitted, an empty string is used for string3.
10188 If {<&'string2'&>} is also omitted, the value that was
10190 You can use &`fail`& instead of {<&'string3'&>} as in a string extract.
10193 .vitem &*${listquote{*&<&'separator'&>&*}{*&<&'string'&>&*}}*&
10194 .cindex quoting "for list"
10195 .cindex list quoting
10196 This item doubles any occurrence of the separator character
10197 in the given string.
10198 An empty string is replaced with a single space.
10199 This converts the string into a safe form for use as a list element,
10200 in a list using the given separator.
10203 .vitem "&*${lookup&~{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&&
10204 {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&" &&&
10205 "&*${lookup&~*&<&'search&~type'&>&*&~{*&<&'query'&>&*}&~&&&
10206 {*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
10207 .cindex "expansion" "lookup in"
10208 .cindex "file" "lookups"
10209 .cindex "lookup" "in expanded string"
10210 The two forms of lookup item specify data lookups in files and databases, as
10211 discussed in chapter &<<CHAPfdlookup>>&. The first form is used for single-key
10212 lookups, and the second is used for query-style lookups. The <&'key'&>,
10213 <&'file'&>, and <&'query'&> strings are expanded before use.
10215 If there is any white space in a lookup item which is part of a filter command,
10216 a retry or rewrite rule, a routing rule for the &(manualroute)& router, or any
10217 other place where white space is significant, the lookup item must be enclosed
10218 in double quotes. The use of data lookups in users' filter files may be locked
10219 out by the system administrator.
10221 .vindex "&$value$&"
10222 If the lookup succeeds, <&'string1'&> is expanded and replaces the entire item.
10223 During its expansion, the variable &$value$& contains the data returned by the
10224 lookup. Afterwards it reverts to the value it had previously (at the outer
10225 level it is empty). If the lookup fails, <&'string2'&> is expanded and replaces
10226 the entire item. If {<&'string2'&>} is omitted, the replacement is the empty
10227 string on failure. If <&'string2'&> is provided, it can itself be a nested
10228 lookup, thus providing a mechanism for looking up a default value when the
10229 original lookup fails.
10231 If a nested lookup is used as part of <&'string1'&>, &$value$& contains the
10232 data for the outer lookup while the parameters of the second lookup are
10233 expanded, and also while <&'string2'&> of the second lookup is expanded, should
10234 the second lookup fail. Instead of {<&'string2'&>} the word &"fail"& can
10235 appear, and in this case, if the lookup fails, the entire expansion is forced
10236 to fail (see section &<<SECTforexpfai>>&). If both {<&'string1'&>} and
10237 {<&'string2'&>} are omitted, the result is the looked up value in the case of a
10238 successful lookup, and nothing in the case of failure.
10240 For single-key lookups, the string &"partial"& is permitted to precede the
10241 search type in order to do partial matching, and * or *@ may follow a search
10242 type to request default lookups if the key does not match (see sections
10243 &<<SECTdefaultvaluelookups>>& and &<<SECTpartiallookup>>& for details).
10245 .cindex "numerical variables (&$1$& &$2$& etc)" "in lookup expansion"
10246 If a partial search is used, the variables &$1$& and &$2$& contain the wild
10247 and non-wild parts of the key during the expansion of the replacement text.
10248 They return to their previous values at the end of the lookup item.
10250 This example looks up the postmaster alias in the conventional alias file:
10252 ${lookup {postmaster} lsearch {/etc/aliases} {$value}}
10254 This example uses NIS+ to look up the full name of the user corresponding to
10255 the local part of an address, forcing the expansion to fail if it is not found:
10257 ${lookup nisplus {[name=$local_part],passwd.org_dir:gcos} \
10262 .vitem &*${map{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
10263 .cindex "expansion" "list creation"
10265 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
10266 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10268 in this list, its value is place in &$item$&, and then <&'string2'&> is
10269 expanded and added to the output as an item in a new list. The separator used
10270 for the output list is the same as the one used for the input, but a separator
10271 setting is not included in the output. For example:
10273 ${map{a:b:c}{[$item]}} ${map{<- x-y-z}{($item)}}
10275 expands to &`[a]:[b]:[c] (x)-(y)-(z)`&. At the end of the expansion, the
10276 value of &$item$& is restored to what it was before. See also the &%filter%&
10277 and &%reduce%& expansion items.
10279 .vitem &*${nhash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10280 .cindex "expansion" "numeric hash"
10281 .cindex "hash function" "numeric"
10282 The three strings are expanded; the first two must yield numbers. Call them
10283 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
10284 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
10285 can use the simpler operator notation that avoids some of the braces:
10287 ${nhash_<n>_<m>:<string>}
10289 The second number is optional (in both notations). If there is only one number,
10290 the result is a number in the range 0&--<&'n'&>-1. Otherwise, the string is
10291 processed by a div/mod hash function that returns two numbers, separated by a
10292 slash, in the ranges 0 to <&'n'&>-1 and 0 to <&'m'&>-1, respectively. For
10295 ${nhash{8}{64}{supercalifragilisticexpialidocious}}
10297 returns the string &"6/33"&.
10301 .vitem &*${perl{*&<&'subroutine'&>&*}{*&<&'arg'&>&*}{*&<&'arg'&>&*}...}*&
10302 .cindex "Perl" "use in expanded string"
10303 .cindex "expansion" "calling Perl from"
10304 This item is available only if Exim has been built to include an embedded Perl
10305 interpreter. The subroutine name and the arguments are first separately
10306 expanded, and then the Perl subroutine is called with those arguments. No
10307 additional arguments need be given; the maximum number permitted, including the
10308 name of the subroutine, is nine.
10310 The return value of the subroutine is inserted into the expanded string, unless
10311 the return value is &%undef%&. In that case, the entire expansion is
10312 forced to fail, in the same way as an explicit &"fail"& on a lookup item
10313 does (see section &<<SECTforexpfai>>&). Whatever you return is evaluated
10314 in a scalar context, thus the return value is a scalar. For example, if you
10315 return a Perl vector, the return value is the size of the vector,
10318 If the subroutine exits by calling Perl's &%die%& function, the expansion fails
10319 with the error message that was passed to &%die%&. More details of the embedded
10320 Perl facility are given in chapter &<<CHAPperl>>&.
10322 The &(redirect)& router has an option called &%forbid_filter_perl%& which locks
10323 out the use of this expansion item in filter files.
10326 .vitem &*${prvs{*&<&'address'&>&*}{*&<&'secret'&>&*}{*&<&'keynumber'&>&*}}*&
10327 .cindex "&%prvs%& expansion item"
10328 The first argument is a complete email address and the second is secret
10329 keystring. The third argument, specifying a key number, is optional. If absent,
10330 it defaults to 0. The result of the expansion is a prvs-signed email address,
10331 to be typically used with the &%return_path%& option on an &(smtp)& transport
10332 as part of a bounce address tag validation (BATV) scheme. For more discussion
10333 and an example, see section &<<SECTverifyPRVS>>&.
10335 .vitem "&*${prvscheck{*&<&'address'&>&*}{*&<&'secret'&>&*}&&&
10336 {*&<&'string'&>&*}}*&"
10337 .cindex "&%prvscheck%& expansion item"
10338 This expansion item is the complement of the &%prvs%& item. It is used for
10339 checking prvs-signed addresses. If the expansion of the first argument does not
10340 yield a syntactically valid prvs-signed address, the whole item expands to the
10341 empty string. When the first argument does expand to a syntactically valid
10342 prvs-signed address, the second argument is expanded, with the prvs-decoded
10343 version of the address and the key number extracted from the address in the
10344 variables &$prvscheck_address$& and &$prvscheck_keynum$&, respectively.
10346 These two variables can be used in the expansion of the second argument to
10347 retrieve the secret. The validity of the prvs-signed address is then checked
10348 against the secret. The result is stored in the variable &$prvscheck_result$&,
10349 which is empty for failure or &"1"& for success.
10351 The third argument is optional; if it is missing, it defaults to an empty
10352 string. This argument is now expanded. If the result is an empty string, the
10353 result of the expansion is the decoded version of the address. This is the case
10354 whether or not the signature was valid. Otherwise, the result of the expansion
10355 is the expansion of the third argument.
10357 All three variables can be used in the expansion of the third argument.
10358 However, once the expansion is complete, only &$prvscheck_result$& remains set.
10359 For more discussion and an example, see section &<<SECTverifyPRVS>>&.
10361 .vitem &*${readfile{*&<&'file&~name'&>&*}{*&<&'eol&~string'&>&*}}*&
10362 .cindex "expansion" "inserting an entire file"
10363 .cindex "file" "inserting into expansion"
10364 .cindex "&%readfile%& expansion item"
10365 The filename and end-of-line (eol) string are first expanded separately. The file is
10366 then read, and its contents replace the entire item. All newline characters in
10367 the file are replaced by the end-of-line string if it is present. Otherwise,
10368 newlines are left in the string.
10369 String expansion is not applied to the contents of the file. If you want this,
10370 you must wrap the item in an &%expand%& operator. If the file cannot be read,
10371 the string expansion fails.
10373 The &(redirect)& router has an option called &%forbid_filter_readfile%& which
10374 locks out the use of this expansion item in filter files.
10378 .vitem "&*${readsocket{*&<&'name'&>&*}{*&<&'request'&>&*}&&&
10379 {*&<&'options'&>&*}{*&<&'eol&~string'&>&*}{*&<&'fail&~string'&>&*}}*&"
10380 .cindex "expansion" "inserting from a socket"
10381 .cindex "socket, use of in expansion"
10382 .cindex "&%readsocket%& expansion item"
10383 This item inserts data from a Unix domain or TCP socket into the expanded
10384 string. The minimal way of using it uses just two arguments, as in these
10387 ${readsocket{/socket/name}{request string}}
10388 ${readsocket{inet:some.host:1234}{request string}}
10390 For a Unix domain socket, the first substring must be the path to the socket.
10391 For an Internet socket, the first substring must contain &`inet:`& followed by
10392 a host name or IP address, followed by a colon and a port, which can be a
10393 number or the name of a TCP port in &_/etc/services_&. An IP address may
10394 optionally be enclosed in square brackets. This is best for IPv6 addresses. For
10397 ${readsocket{inet:[::1]:1234}{request string}}
10399 Only a single host name may be given, but if looking it up yields more than
10400 one IP address, they are each tried in turn until a connection is made. For
10401 both kinds of socket, Exim makes a connection, writes the request string
10402 (unless it is an empty string; no terminating NUL is ever sent)
10403 and reads from the socket until an end-of-file
10404 is read. A timeout of 5 seconds is applied. Additional, optional arguments
10405 extend what can be done. Firstly, you can vary the timeout. For example:
10407 ${readsocket{/socket/name}{request string}{3s}}
10410 The third argument is a list of options, of which the first element is the timeout
10411 and must be present if any options are given.
10412 Further elements are options of form &'name=value'&.
10415 ${readsocket{/socket/name}{request string}{3s:shutdown=no}}
10418 The following option names are recognised:
10421 Defines if the result data can be cached for use by a later identical
10422 request in the same process.
10423 Values are &"yes"& or &"no"& (the default).
10424 If not, all cached results for this connection specification
10425 will be invalidated.
10429 Defines whether or not a write-shutdown is done on the connection after
10430 sending the request. Values are &"yes"& (the default) or &"no"&
10431 (preferred, eg. by some webservers).
10435 Controls the use of TLS on the connection.
10436 Values are &"yes"& or &"no"& (the default).
10437 If it is enabled, a shutdown as described above is never done.
10441 A fourth argument allows you to change any newlines that are in the data
10442 that is read, in the same way as for &%readfile%& (see above). This example
10443 turns them into spaces:
10445 ${readsocket{inet:127.0.0.1:3294}{request string}{3s}{ }}
10447 As with all expansions, the substrings are expanded before the processing
10448 happens. Errors in these sub-expansions cause the expansion to fail. In
10449 addition, the following errors can occur:
10452 Failure to create a socket file descriptor;
10454 Failure to connect the socket;
10456 Failure to write the request string;
10458 Timeout on reading from the socket.
10461 By default, any of these errors causes the expansion to fail. However, if
10462 you supply a fifth substring, it is expanded and used when any of the above
10463 errors occurs. For example:
10465 ${readsocket{/socket/name}{request string}{3s}{\n}\
10468 You can test for the existence of a Unix domain socket by wrapping this
10469 expansion in &`${if exists`&, but there is a race condition between that test
10470 and the actual opening of the socket, so it is safer to use the fifth argument
10471 if you want to be absolutely sure of avoiding an expansion error for a
10472 non-existent Unix domain socket, or a failure to connect to an Internet socket.
10474 The &(redirect)& router has an option called &%forbid_filter_readsocket%& which
10475 locks out the use of this expansion item in filter files.
10478 .vitem &*${reduce{*&<&'string1'&>}{<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10479 .cindex "expansion" "reducing a list to a scalar"
10480 .cindex "list" "reducing to a scalar"
10481 .vindex "&$value$&"
10483 This operation reduces a list to a single, scalar string. After expansion,
10484 <&'string1'&> is interpreted as a list, colon-separated by default, but the
10485 separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10486 Then <&'string2'&> is expanded and
10487 assigned to the &$value$& variable. After this, each item in the <&'string1'&>
10488 list is assigned to &$item$&, in turn, and <&'string3'&> is expanded for each of
10489 them. The result of that expansion is assigned to &$value$& before the next
10490 iteration. When the end of the list is reached, the final value of &$value$& is
10491 added to the expansion output. The &%reduce%& expansion item can be used in a
10492 number of ways. For example, to add up a list of numbers:
10494 ${reduce {<, 1,2,3}{0}{${eval:$value+$item}}}
10496 The result of that expansion would be &`6`&. The maximum of a list of numbers
10499 ${reduce {3:0:9:4:6}{0}{${if >{$item}{$value}{$item}{$value}}}}
10501 At the end of a &*reduce*& expansion, the values of &$item$& and &$value$& are
10502 restored to what they were before. See also the &%filter%& and &%map%&
10505 .vitem &*$rheader_*&<&'header&~name'&>&*:*&&~or&~&*$rh_*&<&'header&~name'&>&*:*&
10506 This item inserts &"raw"& header lines. It is described with the &%header%&
10507 expansion item in section &<<SECTexpansionitems>>& above.
10509 .vitem "&*${run <&'options'&> {*&<&'command&~arg&~list'&>&*}{*&<&'string1'&>&*}&&&
10510 {*&<&'string2'&>&*}}*&"
10511 .cindex "expansion" "running a command"
10512 .cindex "&%run%& expansion item"
10513 This item runs an external command, as a subprocess.
10514 One option is supported after the word &'run'&, comma-separated.
10516 If the option &'preexpand'& is not used,
10517 the command string is split into individual arguments by spaces
10518 and then each argument is expanded.
10519 Then the command is run
10520 in a separate process, but under the same uid and gid. As in other command
10521 executions from Exim, a shell is not used by default. If the command requires
10522 a shell, you must explicitly code it.
10523 The command name may not be tainted, but the remaining arguments can be.
10525 &*Note*&: if tainted arguments are used, they are supplied by a
10526 potential attacker;
10527 a careful assessment for security vulnerabilities should be done.
10529 If the option &'preexpand'& is used,
10530 the command and its arguments are first expanded as one string. The result is
10531 split apart into individual arguments by spaces, and then the command is run
10533 Since the arguments are split by spaces, when there is a variable expansion
10534 which has an empty result, it will cause the situation that the argument will
10535 simply be omitted when the program is actually executed by Exim. If the
10536 script/program requires a specific number of arguments and the expanded
10537 variable could possibly result in this empty expansion, the variable must be
10538 quoted. This is more difficult if the expanded variable itself could result
10539 in a string containing quotes, because it would interfere with the quotes
10540 around the command arguments. A possible guard against this is to wrap the
10541 variable in the &%sg%& operator to change any quote marks to some other
10543 Neither the command nor any argument may be tainted.
10545 The standard input for the command exists, but is empty. The standard output
10546 and standard error are set to the same file descriptor.
10547 .cindex "return code" "from &%run%& expansion"
10548 .vindex "&$value$&"
10549 If the command succeeds (gives a zero return code) <&'string1'&> is expanded
10550 and replaces the entire item; during this expansion, the standard output/error
10551 from the command is in the variable &$value$&. If the command fails,
10552 <&'string2'&>, if present, is expanded and used. Once again, during the
10553 expansion, the standard output/error from the command is in the variable
10556 If <&'string2'&> is absent, the result is empty. Alternatively, <&'string2'&>
10557 can be the word &"fail"& (not in braces) to force expansion failure if the
10558 command does not succeed. If both strings are omitted, the result is contents
10559 of the standard output/error on success, and nothing on failure.
10561 .vindex "&$run_in_acl$&"
10562 The standard output/error of the command is put in the variable &$value$&.
10563 In this ACL example, the output of a command is logged for the admin to
10566 warn condition = ${run{/usr/bin/id}{yes}{no}}
10567 log_message = Output of id: $value
10569 If the command requires shell idioms, such as the > redirect operator, the
10570 shell must be invoked directly, such as with:
10572 ${run{/bin/bash -c "/usr/bin/id >/tmp/id"}{yes}{yes}}
10575 .vindex "&$runrc$&"
10576 The return code from the command is put in the variable &$runrc$&, and this
10577 remains set afterwards, so in a filter file you can do things like this:
10579 if "${run{x y z}{}}$runrc" is 1 then ...
10580 elif $runrc is 2 then ...
10584 If execution of the command fails (for example, the command does not exist),
10585 the return code is 127 &-- the same code that shells use for non-existent
10588 &*Warning*&: In a router or transport, you cannot assume the order in which
10589 option values are expanded, except for those preconditions whose order of
10590 testing is documented. Therefore, you cannot reliably expect to set &$runrc$&
10591 by the expansion of one option, and use it in another.
10593 The &(redirect)& router has an option called &%forbid_filter_run%& which locks
10594 out the use of this expansion item in filter files.
10597 .vitem &*${sg{*&<&'subject'&>&*}{*&<&'regex'&>&*}{*&<&'replacement'&>&*}}*&
10598 .cindex "expansion" "string substitution"
10599 .cindex "&%sg%& expansion item"
10600 This item works like Perl's substitution operator (s) with the global (/g)
10601 option; hence its name. However, unlike the Perl equivalent, Exim does not
10602 modify the subject string; instead it returns the modified string for insertion
10603 into the overall expansion. The item takes three arguments: the subject string,
10604 a regular expression, and a substitution string. For example:
10606 ${sg{abcdefabcdef}{abc}{xyz}}
10608 yields &"xyzdefxyzdef"&. Because all three arguments are expanded before use,
10609 if any $, } or \ characters are required in the regular expression or in the
10610 substitution string, they have to be escaped. For example:
10612 ${sg{abcdef}{^(...)(...)\$}{\$2\$1}}
10614 yields &"defabc"&, and
10616 ${sg{1=A 4=D 3=C}{\N(\d+)=\N}{K\$1=}}
10618 yields &"K1=A K4=D K3=C"&. Note the use of &`\N`& to protect the contents of
10619 the regular expression from string expansion.
10621 The regular expression is compiled in 8-bit mode, working against bytes
10622 rather than any Unicode-aware character handling.
10625 .vitem &*${sort{*&<&'string'&>&*}{*&<&'comparator'&>&*}{*&<&'extractor'&>&*}}*&
10626 .cindex sorting "a list"
10627 .cindex list sorting
10628 .cindex expansion "list sorting"
10629 After expansion, <&'string'&> is interpreted as a list, colon-separated by
10630 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10631 The <&'comparator'&> argument is interpreted as the operator
10632 of a two-argument expansion condition.
10633 The numeric operators plus ge, gt, le, lt (and ~i variants) are supported.
10634 The comparison should return true when applied to two values
10635 if the first value should sort before the second value.
10636 The <&'extractor'&> expansion is applied repeatedly to elements of the list,
10637 the element being placed in &$item$&,
10638 to give values for comparison.
10640 The item result is a sorted list,
10641 with the original list separator,
10642 of the list elements (in full) of the original.
10646 ${sort{3:2:1:4}{<}{$item}}
10648 sorts a list of numbers, and
10650 ${sort {${lookup dnsdb{>:,,mx=example.com}}} {<} {${listextract{1}{<,$item}}}}
10652 will sort an MX lookup into priority order.
10656 .vitem &*${srs_encode&~{*&<&'secret'&>&*}{*&<&'return&~path'&>&*}{*&<&'original&~domain'&>&*}}*&
10657 SRS encoding. See SECT &<<SECTSRS>>& for details.
10661 .vitem &*${substr{*&<&'start'&>&*}{*&<&'len'&>&*}{*&<&'subject'&>&*}}*&
10662 .cindex "&%substr%& expansion item"
10663 .cindex "substring extraction"
10664 .cindex "expansion" "substring extraction"
10665 The three strings are expanded; the first two must yield numbers. Call them
10666 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
10667 if <&'start'&> and <&'len'&> do not change when they are expanded, you
10668 can use the simpler operator notation that avoids some of the braces:
10670 ${substr_<n>_<m>:<subject>}
10672 The second number is optional (in both notations).
10673 If it is absent in the simpler format, the preceding underscore must also be
10676 The &%substr%& item can be used to extract more general substrings than
10677 &%length%&. The first number, <&'n'&>, is a starting offset, and <&'m'&> is the
10678 length required. For example
10680 ${substr{3}{2}{$local_part}}
10682 If the starting offset is greater than the string length the result is the
10683 null string; if the length plus starting offset is greater than the string
10684 length, the result is the right-hand part of the string, starting from the
10685 given offset. The first byte (character) in the string has offset zero.
10687 The &%substr%& expansion item can take negative offset values to count
10688 from the right-hand end of its operand. The last byte (character) is offset -1,
10689 the second-last is offset -2, and so on. Thus, for example,
10691 ${substr{-5}{2}{1234567}}
10693 yields &"34"&. If the absolute value of a negative offset is greater than the
10694 length of the string, the substring starts at the beginning of the string, and
10695 the length is reduced by the amount of overshoot. Thus, for example,
10697 ${substr{-5}{2}{12}}
10699 yields an empty string, but
10701 ${substr{-3}{2}{12}}
10705 When the second number is omitted from &%substr%&, the remainder of the string
10706 is taken if the offset is positive. If it is negative, all bytes (characters) in the
10707 string preceding the offset point are taken. For example, an offset of -1 and
10708 no length, as in these semantically identical examples:
10711 ${substr{-1}{abcde}}
10713 yields all but the last character of the string, that is, &"abcd"&.
10715 All measurement is done in bytes and is not UTF-8 aware.
10719 .vitem "&*${tr{*&<&'subject'&>&*}{*&<&'characters'&>&*}&&&
10720 {*&<&'replacements'&>&*}}*&"
10721 .cindex "expansion" "character translation"
10722 .cindex "&%tr%& expansion item"
10723 This item does single-character (in bytes) translation on its subject string. The second
10724 argument is a list of characters to be translated in the subject string. Each
10725 matching character is replaced by the corresponding character from the
10726 replacement list. For example
10728 ${tr{abcdea}{ac}{13}}
10730 yields &`1b3de1`&. If there are duplicates in the second character string, the
10731 last occurrence is used. If the third string is shorter than the second, its
10732 last character is replicated. However, if it is empty, no translation takes
10735 All character handling is done in bytes and is not UTF-8 aware.
10741 .section "Expansion operators" "SECTexpop"
10742 .cindex "expansion" "operators"
10743 For expansion items that perform transformations on a single argument string,
10744 the &"operator"& notation is used because it is simpler and uses fewer braces.
10745 The substring is first expanded before the operation is applied to it. The
10746 following operations can be performed:
10749 .vitem &*${address:*&<&'string'&>&*}*&
10750 .cindex "expansion" "RFC 2822 address handling"
10751 .cindex "&%address%& expansion item"
10752 The string is interpreted as an RFC 2822 address, as it might appear in a
10753 header line, and the effective address is extracted from it. If the string does
10754 not parse successfully, the result is empty.
10756 The parsing correctly handles SMTPUTF8 Unicode in the string.
10759 .vitem &*${addresses:*&<&'string'&>&*}*&
10760 .cindex "expansion" "RFC 2822 address handling"
10761 .cindex "&%addresses%& expansion item"
10762 The string (after expansion) is interpreted as a list of addresses in RFC
10763 2822 format, such as can be found in a &'To:'& or &'Cc:'& header line. The
10764 operative address (&'local-part@domain'&) is extracted from each item, and the
10765 result of the expansion is a colon-separated list, with appropriate
10766 doubling of colons should any happen to be present in the email addresses.
10767 Syntactically invalid RFC2822 address items are omitted from the output.
10769 It is possible to specify a character other than colon for the output
10770 separator by starting the string with > followed by the new separator
10771 character. For example:
10773 ${addresses:>& Chief <ceo@up.stairs>, sec@base.ment (dogsbody)}
10775 expands to &`ceo@up.stairs&&sec@base.ment`&. The string is expanded
10776 first, so if the expanded string starts with >, it may change the output
10777 separator unintentionally. This can be avoided by setting the output
10778 separator explicitly:
10780 ${addresses:>:$h_from:}
10783 Compare the &%address%& (singular)
10784 expansion item, which extracts the working address from a single RFC2822
10785 address. See the &%filter%&, &%map%&, and &%reduce%& items for ways of
10788 To clarify "list of addresses in RFC 2822 format" mentioned above, Exim follows
10789 a strict interpretation of header line formatting. Exim parses the bare,
10790 unquoted portion of an email address and if it finds a comma, treats it as an
10791 email address separator. For the example header line:
10793 From: =?iso-8859-2?Q?Last=2C_First?= <user@example.com>
10795 The first example below demonstrates that Q-encoded email addresses are parsed
10796 properly if it is given the raw header (in this example, &`$rheader_from:`&).
10797 It does not see the comma because it's still encoded as "=2C". The second
10798 example below is passed the contents of &`$header_from:`&, meaning it gets
10799 de-mimed. Exim sees the decoded "," so it treats it as &*two*& email addresses.
10800 The third example shows that the presence of a comma is skipped when it is
10801 quoted. The fourth example shows SMTPUTF8 handling.
10803 # exim -be '${addresses:From: \
10804 =?iso-8859-2?Q?Last=2C_First?= <user@example.com>}'
10806 # exim -be '${addresses:From: Last, First <user@example.com>}'
10807 Last:user@example.com
10808 # exim -be '${addresses:From: "Last, First" <user@example.com>}'
10810 # exim -be '${addresses:フィル <フィリップ@example.jp>}'
10814 .vitem &*${base32:*&<&'digits'&>&*}*&
10815 .cindex "&%base32%& expansion item"
10816 .cindex "expansion" "conversion to base 32"
10817 The string must consist entirely of decimal digits. The number is converted to
10818 base 32 and output as a (empty, for zero) string of characters.
10819 Only lowercase letters are used.
10821 .vitem &*${base32d:*&<&'base-32&~digits'&>&*}*&
10822 .cindex "&%base32d%& expansion item"
10823 .cindex "expansion" "conversion to base 32"
10824 The string must consist entirely of base-32 digits.
10825 The number is converted to decimal and output as a string.
10827 .vitem &*${base62:*&<&'digits'&>&*}*&
10828 .cindex "&%base62%& expansion item"
10829 .cindex "expansion" "conversion to base 62"
10830 The string must consist entirely of decimal digits. The number is converted to
10831 base 62 and output as a string of six characters, including leading zeros. In
10832 the few operating environments where Exim uses base 36 instead of base 62 for
10833 its message identifiers (because those systems do not have case-sensitive
10834 filenames), base 36 is used by this operator, despite its name. &*Note*&: Just
10835 to be absolutely clear: this is &'not'& base64 encoding.
10837 .vitem &*${base62d:*&<&'base-62&~digits'&>&*}*&
10838 .cindex "&%base62d%& expansion item"
10839 .cindex "expansion" "conversion to base 62"
10840 The string must consist entirely of base-62 digits, or, in operating
10841 environments where Exim uses base 36 instead of base 62 for its message
10842 identifiers, base-36 digits. The number is converted to decimal and output as a
10845 .vitem &*${base64:*&<&'string'&>&*}*&
10846 .cindex "expansion" "base64 encoding"
10847 .cindex "base64 encoding" "in string expansion"
10848 .cindex "&%base64%& expansion item"
10849 .cindex certificate "base64 of DER"
10850 This operator converts a string into one that is base64 encoded.
10852 If the string is a single variable of type certificate,
10853 returns the base64 encoding of the DER form of the certificate.
10856 .vitem &*${base64d:*&<&'string'&>&*}*&
10857 .cindex "expansion" "base64 decoding"
10858 .cindex "base64 decoding" "in string expansion"
10859 .cindex "&%base64d%& expansion item"
10860 This operator converts a base64-encoded string into the un-coded form.
10863 .vitem &*${domain:*&<&'string'&>&*}*&
10864 .cindex "domain" "extraction"
10865 .cindex "expansion" "domain extraction"
10866 The string is interpreted as an RFC 2822 address and the domain is extracted
10867 from it. If the string does not parse successfully, the result is empty.
10870 .vitem &*${escape:*&<&'string'&>&*}*&
10871 .cindex "expansion" "escaping non-printing characters"
10872 .cindex "&%escape%& expansion item"
10873 If the string contains any non-printing characters, they are converted to
10874 escape sequences starting with a backslash. Whether characters with the most
10875 significant bit set (so-called &"8-bit characters"&) count as printing or not
10876 is controlled by the &%print_topbitchars%& option.
10878 .vitem &*${escape8bit:*&<&'string'&>&*}*&
10879 .cindex "expansion" "escaping 8-bit characters"
10880 .cindex "&%escape8bit%& expansion item"
10881 If the string contains any characters with the most significant bit set,
10882 they are converted to escape sequences starting with a backslash.
10883 Backslashes and DEL characters are also converted.
10886 .vitem &*${eval:*&<&'string'&>&*}*&&~and&~&*${eval10:*&<&'string'&>&*}*&
10887 .cindex "expansion" "expression evaluation"
10888 .cindex "expansion" "arithmetic expression"
10889 .cindex "&%eval%& expansion item"
10890 These items supports simple arithmetic and bitwise logical operations in
10891 expansion strings. The string (after expansion) must be a conventional
10892 arithmetic expression, but it is limited to basic arithmetic operators, bitwise
10893 logical operators, and parentheses. All operations are carried out using
10894 integer arithmetic. The operator priorities are as follows (the same as in the
10895 C programming language):
10897 .irow &'highest:'& "not (~), negate (-)"
10898 .irow "" "multiply (*), divide (/), remainder (%)"
10899 .irow "" "plus (+), minus (-)"
10900 .irow "" "shift-left (<<), shift-right (>>)"
10901 .irow "" "and (&&)"
10903 .irow &'lowest:'& "or (|)"
10905 Binary operators with the same priority are evaluated from left to right. White
10906 space is permitted before or after operators.
10908 For &%eval%&, numbers may be decimal, octal (starting with &"0"&) or
10909 hexadecimal (starting with &"0x"&). For &%eval10%&, all numbers are taken as
10910 decimal, even if they start with a leading zero; hexadecimal numbers are not
10911 permitted. This can be useful when processing numbers extracted from dates or
10912 times, which often do have leading zeros.
10914 A number may be followed by &"K"&, &"M"& or &"G"& to multiply it by 1024, 1024*1024
10916 respectively. Negative numbers are supported. The result of the computation is
10917 a decimal representation of the answer (without &"K"&, &"M"& or &"G"&). For example:
10920 &`${eval:1+1} `& yields 2
10921 &`${eval:1+2*3} `& yields 7
10922 &`${eval:(1+2)*3} `& yields 9
10923 &`${eval:2+42%5} `& yields 4
10924 &`${eval:0xc&5} `& yields 4
10925 &`${eval:0xc|5} `& yields 13
10926 &`${eval:0xc^5} `& yields 9
10927 &`${eval:0xc>>1} `& yields 6
10928 &`${eval:0xc<<1} `& yields 24
10929 &`${eval:~255&0x1234} `& yields 4608
10930 &`${eval:-(~255&0x1234)} `& yields -4608
10933 As a more realistic example, in an ACL you might have
10937 {>{$rcpt_count}{10}} \
10940 {$recipients_count} \
10941 {${eval:$rcpt_count/2}} \
10944 message = Too many bad recipients
10946 The condition is true if there have been more than 10 RCPT commands and
10947 fewer than half of them have resulted in a valid recipient.
10950 .vitem &*${expand:*&<&'string'&>&*}*&
10951 .cindex "expansion" "re-expansion of substring"
10952 The &%expand%& operator causes a string to be expanded for a second time. For
10955 ${expand:${lookup{$domain}dbm{/some/file}{$value}}}
10957 first looks up a string in a file while expanding the operand for &%expand%&,
10958 and then re-expands what it has found.
10961 .vitem &*${from_utf8:*&<&'string'&>&*}*&
10963 .cindex "UTF-8" "conversion from"
10964 .cindex "expansion" "UTF-8 conversion"
10965 .cindex "&%from_utf8%& expansion item"
10966 The world is slowly moving towards Unicode, although there are no standards for
10967 email yet. However, other applications (including some databases) are starting
10968 to store data in Unicode, using UTF-8 encoding. This operator converts from a
10969 UTF-8 string to an ISO-8859-1 string. UTF-8 code values greater than 255 are
10970 converted to underscores. The input must be a valid UTF-8 string. If it is not,
10971 the result is an undefined sequence of bytes.
10973 Unicode code points with values less than 256 are compatible with ASCII and
10974 ISO-8859-1 (also known as Latin-1).
10975 For example, character 169 is the copyright symbol in both cases, though the
10976 way it is encoded is different. In UTF-8, more than one byte is needed for
10977 characters with code values greater than 127, whereas ISO-8859-1 is a
10978 single-byte encoding (but thereby limited to 256 characters). This makes
10979 translation from UTF-8 to ISO-8859-1 straightforward.
10982 .vitem &*${hash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
10983 .cindex "hash function" "textual"
10984 .cindex "expansion" "textual hash"
10985 The &%hash%& operator is a simpler interface to the hashing function that can
10986 be used when the two parameters are fixed numbers (as opposed to strings that
10987 change when expanded). The effect is the same as
10989 ${hash{<n>}{<m>}{<string>}}
10991 See the description of the general &%hash%& item above for details. The
10992 abbreviation &%h%& can be used when &%hash%& is used as an operator.
10996 .vitem &*${hex2b64:*&<&'hexstring'&>&*}*&
10997 .cindex "base64 encoding" "conversion from hex"
10998 .cindex "expansion" "hex to base64"
10999 .cindex "&%hex2b64%& expansion item"
11000 This operator converts a hex string into one that is base64 encoded. This can
11001 be useful for processing the output of the various hashing functions.
11005 .vitem &*${hexquote:*&<&'string'&>&*}*&
11006 .cindex "quoting" "hex-encoded unprintable characters"
11007 .cindex "&%hexquote%& expansion item"
11008 This operator converts non-printable characters in a string into a hex
11009 escape form. Byte values between 33 (!) and 126 (~) inclusive are left
11010 as is, and other byte values are converted to &`\xNN`&, for example, a
11011 byte value 127 is converted to &`\x7f`&.
11014 .vitem &*${ipv6denorm:*&<&'string'&>&*}*&
11015 .cindex "&%ipv6denorm%& expansion item"
11016 .cindex "IP address" normalisation
11017 This expands an IPv6 address to a full eight-element colon-separated set
11018 of hex digits including leading zeroes.
11019 A trailing ipv4-style dotted-decimal set is converted to hex.
11020 Pure IPv4 addresses are converted to IPv4-mapped IPv6.
11022 .vitem &*${ipv6norm:*&<&'string'&>&*}*&
11023 .cindex "&%ipv6norm%& expansion item"
11024 .cindex "IP address" normalisation
11025 .cindex "IP address" "canonical form"
11026 This converts an IPv6 address to canonical form.
11027 Leading zeroes of groups are omitted, and the longest
11028 set of zero-valued groups is replaced with a double colon.
11029 A trailing ipv4-style dotted-decimal set is converted to hex.
11030 Pure IPv4 addresses are converted to IPv4-mapped IPv6.
11033 .vitem &*${lc:*&<&'string'&>&*}*&
11034 .cindex "case forcing in strings"
11035 .cindex "string" "case forcing"
11036 .cindex "lower casing"
11037 .cindex "expansion" "case forcing"
11038 .cindex "&%lc%& expansion item"
11039 This forces the letters in the string into lower-case, for example:
11043 Case is defined per the system C locale.
11045 .vitem &*${length_*&<&'number'&>&*:*&<&'string'&>&*}*&
11046 .cindex "expansion" "string truncation"
11047 .cindex "&%length%& expansion item"
11048 The &%length%& operator is a simpler interface to the &%length%& function that
11049 can be used when the parameter is a fixed number (as opposed to a string that
11050 changes when expanded). The effect is the same as
11052 ${length{<number>}{<string>}}
11054 See the description of the general &%length%& item above for details. Note that
11055 &%length%& is not the same as &%strlen%&. The abbreviation &%l%& can be used
11056 when &%length%& is used as an operator.
11057 All measurement is done in bytes and is not UTF-8 aware.
11060 .vitem &*${listcount:*&<&'string'&>&*}*&
11061 .cindex "expansion" "list item count"
11062 .cindex "list" "item count"
11063 .cindex "list" "count of items"
11064 .cindex "&%listcount%& expansion item"
11065 The string is interpreted as a list and the number of items is returned.
11068 .vitem &*${listnamed:*&<&'name'&>&*}*&&~and&~&*${listnamed_*&<&'type'&>&*:*&<&'name'&>&*}*&
11069 .cindex "expansion" "named list"
11070 .cindex "&%listnamed%& expansion item"
11071 The name is interpreted as a named list and the content of the list is returned,
11072 expanding any referenced lists, re-quoting as needed for colon-separation.
11073 If the optional type is given it must be one of "a", "d", "h" or "l"
11074 and selects address-, domain-, host- or localpart- lists to search among respectively.
11075 Otherwise all types are searched in an undefined order and the first
11076 matching list is returned.
11077 &*Note*&: Neither string-expansion of lists referenced by named-list syntax elements,
11078 nor expansion of lookup elements, is done by the &%listnamed%& operator.
11081 .vitem &*${local_part:*&<&'string'&>&*}*&
11082 .cindex "expansion" "local part extraction"
11083 .cindex "&%local_part%& expansion item"
11084 The string is interpreted as an RFC 2822 address and the local part is
11085 extracted from it. If the string does not parse successfully, the result is
11087 The parsing correctly handles SMTPUTF8 Unicode in the string.
11090 .vitem &*${mask:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*& &&&
11091 &*${mask_n:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*&
11092 .cindex "masked IP address"
11093 .cindex "IP address" "masking"
11094 .cindex "CIDR notation"
11095 .cindex "expansion" "IP address masking"
11096 .cindex "&%mask%& expansion item"
11097 If the form of the string to be operated on is not an IP address followed by a
11098 slash and an integer (that is, a network address in CIDR notation), the
11099 expansion fails. Otherwise, this operator converts the IP address to binary,
11100 masks off the least significant bits according to the bit count, and converts
11101 the result back to text, with mask appended. For example,
11103 ${mask:10.111.131.206/28}
11105 returns the string &"10.111.131.192/28"&.
11107 Since this operation is expected to
11108 be mostly used for looking up masked addresses in files, the
11111 address uses dots to separate components instead of colons, because colon
11112 terminates a key string in lsearch files. So, for example,
11114 ${mask:3ffe:ffff:836f:0a00:000a:0800:200a:c031/99}
11118 3ffe.ffff.836f.0a00.000a.0800.2000.0000/99
11120 If the optional form &*mask_n*& is used, IPv6 address result are instead
11121 returned in normailsed form, using colons and with zero-compression.
11122 Letters in IPv6 addresses are always output in lower case.
11125 .vitem &*${md5:*&<&'string'&>&*}*&
11127 .cindex "expansion" "MD5 hash"
11128 .cindex certificate fingerprint
11129 .cindex "&%md5%& expansion item"
11130 The &%md5%& operator computes the MD5 hash value of the string, and returns it
11131 as a 32-digit hexadecimal number, in which any letters are in lower case.
11133 If the string is a single variable of type certificate,
11134 returns the MD5 hash fingerprint of the certificate.
11137 .vitem &*${nhash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
11138 .cindex "expansion" "numeric hash"
11139 .cindex "hash function" "numeric"
11140 The &%nhash%& operator is a simpler interface to the numeric hashing function
11141 that can be used when the two parameters are fixed numbers (as opposed to
11142 strings that change when expanded). The effect is the same as
11144 ${nhash{<n>}{<m>}{<string>}}
11146 See the description of the general &%nhash%& item above for details.
11149 .vitem &*${quote:*&<&'string'&>&*}*&
11150 .cindex "quoting" "in string expansions"
11151 .cindex "expansion" "quoting"
11152 .cindex "&%quote%& expansion item"
11153 The &%quote%& operator puts its argument into double quotes if it
11154 is an empty string or
11155 contains anything other than letters, digits, underscores, dots, and hyphens.
11156 Any occurrences of double quotes and backslashes are escaped with a backslash.
11157 Newlines and carriage returns are converted to &`\n`& and &`\r`&,
11158 respectively For example,
11166 The place where this is useful is when the argument is a substitution from a
11167 variable or a message header.
11169 .vitem &*${quote_local_part:*&<&'string'&>&*}*&
11170 .cindex "&%quote_local_part%& expansion item"
11171 This operator is like &%quote%&, except that it quotes the string only if
11172 required to do so by the rules of RFC 2822 for quoting local parts. For
11173 example, a plus sign would not cause quoting (but it would for &%quote%&).
11174 If you are creating a new email address from the contents of &$local_part$&
11175 (or any other unknown data), you should always use this operator.
11177 This quoting determination is not SMTPUTF8-aware, thus quoting non-ASCII data
11178 will likely use the quoting form.
11179 Thus &'${quote_local_part:フィル}'& will always become &'"フィル"'&.
11182 .vitem &*${quote_*&<&'lookup-type'&>&*:*&<&'string'&>&*}*&
11183 .cindex "quoting" "lookup-specific"
11184 This operator applies lookup-specific quoting rules to the string. Each
11185 query-style lookup type has its own quoting rules which are described with
11186 the lookups in chapter &<<CHAPfdlookup>>&. For example,
11188 ${quote_ldap:two * two}
11194 For single-key lookup types, no quoting is ever necessary and this operator
11195 yields an unchanged string.
11198 .vitem &*${randint:*&<&'n'&>&*}*&
11199 .cindex "random number"
11200 This operator returns a somewhat random number which is less than the
11201 supplied number and is at least 0. The quality of this randomness depends
11202 on how Exim was built; the values are not suitable for keying material.
11203 If Exim is linked against OpenSSL then RAND_pseudo_bytes() is used.
11204 If Exim is linked against GnuTLS then gnutls_rnd(GNUTLS_RND_NONCE) is used,
11205 for versions of GnuTLS with that function.
11206 Otherwise, the implementation may be arc4random(), random() seeded by
11207 srandomdev() or srandom(), or a custom implementation even weaker than
11211 .vitem &*${reverse_ip:*&<&'ipaddr'&>&*}*&
11212 .cindex "expansion" "IP address"
11213 This operator reverses an IP address; for IPv4 addresses, the result is in
11214 dotted-quad decimal form, while for IPv6 addresses the result is in
11215 dotted-nibble hexadecimal form. In both cases, this is the "natural" form
11216 for DNS. For example,
11218 ${reverse_ip:192.0.2.4}
11219 ${reverse_ip:2001:0db8:c42:9:1:abcd:192.0.2.127}
11224 f.7.2.0.0.0.0.c.d.c.b.a.1.0.0.0.9.0.0.0.2.4.c.0.8.b.d.0.1.0.0.2
11228 .vitem &*${rfc2047:*&<&'string'&>&*}*&
11229 .cindex "expansion" "RFC 2047"
11230 .cindex "RFC 2047" "expansion operator"
11231 .cindex "&%rfc2047%& expansion item"
11232 This operator encodes text according to the rules of RFC 2047. This is an
11233 encoding that is used in header lines to encode non-ASCII characters. It is
11234 assumed that the input string is in the encoding specified by the
11235 &%headers_charset%& option, which gets its default at build time. If the string
11236 contains only characters in the range 33&--126, and no instances of the
11239 ? = ( ) < > @ , ; : \ " . [ ] _
11241 it is not modified. Otherwise, the result is the RFC 2047 encoding of the
11242 string, using as many &"encoded words"& as necessary to encode all the
11246 .vitem &*${rfc2047d:*&<&'string'&>&*}*&
11247 .cindex "expansion" "RFC 2047"
11248 .cindex "RFC 2047" "decoding"
11249 .cindex "&%rfc2047d%& expansion item"
11250 This operator decodes strings that are encoded as per RFC 2047. Binary zero
11251 bytes are replaced by question marks. Characters are converted into the
11252 character set defined by &%headers_charset%&. Overlong RFC 2047 &"words"& are
11253 not recognized unless &%check_rfc2047_length%& is set false.
11255 &*Note*&: If you use &%$header%&_&'xxx'&&*:*& (or &%$h%&_&'xxx'&&*:*&) to
11256 access a header line, RFC 2047 decoding is done automatically. You do not need
11257 to use this operator as well.
11261 .vitem &*${rxquote:*&<&'string'&>&*}*&
11262 .cindex "quoting" "in regular expressions"
11263 .cindex "regular expressions" "quoting"
11264 .cindex "&%rxquote%& expansion item"
11265 The &%rxquote%& operator inserts a backslash before any non-alphanumeric
11266 characters in its argument. This is useful when substituting the values of
11267 variables or headers inside regular expressions.
11270 .vitem &*${sha1:*&<&'string'&>&*}*&
11271 .cindex "SHA-1 hash"
11272 .cindex "expansion" "SHA-1 hashing"
11273 .cindex certificate fingerprint
11274 .cindex "&%sha1%& expansion item"
11275 The &%sha1%& operator computes the SHA-1 hash value of the string, and returns
11276 it as a 40-digit hexadecimal number, in which any letters are in upper case.
11278 If the string is a single variable of type certificate,
11279 returns the SHA-1 hash fingerprint of the certificate.
11282 .vitem &*${sha256:*&<&'string'&>&*}*& &&&
11283 &*${sha2:*&<&'string'&>&*}*& &&&
11284 &*${sha2_<n>:*&<&'string'&>&*}*&
11285 .cindex "SHA-256 hash"
11286 .cindex "SHA-2 hash"
11287 .cindex certificate fingerprint
11288 .cindex "expansion" "SHA-256 hashing"
11289 .cindex "&%sha256%& expansion item"
11290 .cindex "&%sha2%& expansion item"
11291 The &%sha256%& operator computes the SHA-256 hash value of the string
11293 it as a 64-digit hexadecimal number, in which any letters are in upper case.
11295 If the string is a single variable of type certificate,
11296 returns the SHA-256 hash fingerprint of the certificate.
11298 The operator can also be spelled &%sha2%& and does the same as &%sha256%&
11299 (except for certificates, which are not supported).
11300 Finally, if an underbar
11301 and a number is appended it specifies the output length, selecting a
11302 member of the SHA-2 family of hash functions.
11303 Values of 256, 384 and 512 are accepted, with 256 being the default.
11306 .vitem &*${sha3:*&<&'string'&>&*}*& &&&
11307 &*${sha3_<n>:*&<&'string'&>&*}*&
11308 .cindex "SHA3 hash"
11309 .cindex "expansion" "SHA3 hashing"
11310 .cindex "&%sha3%& expansion item"
11311 The &%sha3%& operator computes the SHA3-256 hash value of the string
11313 it as a 64-digit hexadecimal number, in which any letters are in upper case.
11315 If a number is appended, separated by an underbar, it specifies
11316 the output length. Values of 224, 256, 384 and 512 are accepted;
11317 with 256 being the default.
11319 The &%sha3%& expansion item is only supported if Exim has been
11320 compiled with GnuTLS 3.5.0 or later,
11321 or OpenSSL 1.1.1 or later.
11322 The macro "_CRYPTO_HASH_SHA3" will be defined if it is supported.
11325 .vitem &*${stat:*&<&'string'&>&*}*&
11326 .cindex "expansion" "statting a file"
11327 .cindex "file" "extracting characteristics"
11328 .cindex "&%stat%& expansion item"
11329 The string, after expansion, must be a file path. A call to the &[stat()]&
11330 function is made for this path. If &[stat()]& fails, an error occurs and the
11331 expansion fails. If it succeeds, the data from the stat replaces the item, as a
11332 series of <&'name'&>=<&'value'&> pairs, where the values are all numerical,
11333 except for the value of &"smode"&. The names are: &"mode"& (giving the mode as
11334 a 4-digit octal number), &"smode"& (giving the mode in symbolic format as a
11335 10-character string, as for the &'ls'& command), &"inode"&, &"device"&,
11336 &"links"&, &"uid"&, &"gid"&, &"size"&, &"atime"&, &"mtime"&, and &"ctime"&. You
11337 can extract individual fields using the &%extract%& expansion item.
11339 The use of the &%stat%& expansion in users' filter files can be locked out by
11340 the system administrator. &*Warning*&: The file size may be incorrect on 32-bit
11341 systems for files larger than 2GB.
11343 .vitem &*${str2b64:*&<&'string'&>&*}*&
11344 .cindex "&%str2b64%& expansion item"
11345 Now deprecated, a synonym for the &%base64%& expansion operator.
11349 .vitem &*${strlen:*&<&'string'&>&*}*&
11350 .cindex "expansion" "string length"
11351 .cindex "string" "length in expansion"
11352 .cindex "&%strlen%& expansion item"
11353 The item is replaced by the length of the expanded string, expressed as a
11354 decimal number. &*Note*&: Do not confuse &%strlen%& with &%length%&.
11355 All measurement is done in bytes and is not UTF-8 aware.
11358 .vitem &*${substr_*&<&'start'&>&*_*&<&'length'&>&*:*&<&'string'&>&*}*&
11359 .cindex "&%substr%& expansion item"
11360 .cindex "substring extraction"
11361 .cindex "expansion" "substring expansion"
11362 The &%substr%& operator is a simpler interface to the &%substr%& function that
11363 can be used when the two parameters are fixed numbers (as opposed to strings
11364 that change when expanded). The effect is the same as
11366 ${substr{<start>}{<length>}{<string>}}
11368 See the description of the general &%substr%& item above for details. The
11369 abbreviation &%s%& can be used when &%substr%& is used as an operator.
11370 All measurement is done in bytes and is not UTF-8 aware.
11372 .vitem &*${time_eval:*&<&'string'&>&*}*&
11373 .cindex "&%time_eval%& expansion item"
11374 .cindex "time interval" "decoding"
11375 This item converts an Exim time interval such as &`2d4h5m`& into a number of
11378 .vitem &*${time_interval:*&<&'string'&>&*}*&
11379 .cindex "&%time_interval%& expansion item"
11380 .cindex "time interval" "formatting"
11381 The argument (after sub-expansion) must be a sequence of decimal digits that
11382 represents an interval of time as a number of seconds. It is converted into a
11383 number of larger units and output in Exim's normal time format, for example,
11386 .vitem &*${uc:*&<&'string'&>&*}*&
11387 .cindex "case forcing in strings"
11388 .cindex "string" "case forcing"
11389 .cindex "upper casing"
11390 .cindex "expansion" "case forcing"
11391 .cindex "&%uc%& expansion item"
11392 This forces the letters in the string into upper-case.
11393 Case is defined per the system C locale.
11395 .vitem &*${utf8clean:*&<&'string'&>&*}*&
11396 .cindex "correction of invalid utf-8 sequences in strings"
11397 .cindex "utf-8" "utf-8 sequences"
11398 .cindex "incorrect utf-8"
11399 .cindex "expansion" "utf-8 forcing"
11400 .cindex "&%utf8clean%& expansion item"
11401 This replaces any invalid utf-8 sequence in the string by the character &`?`&.
11402 In versions of Exim before 4.92, this did not correctly do so for a truncated
11403 final codepoint's encoding, and the character would be silently dropped.
11404 If you must handle detection of this scenario across both sets of Exim behavior,
11405 the complexity will depend upon the task.
11406 For instance, to detect if the first character is multibyte and a 1-byte
11407 extraction can be successfully used as a path component (as is common for
11408 dividing up delivery folders), you might use:
11410 condition = ${if inlist{${utf8clean:${length_1:$local_part}}}{:?}{yes}{no}}
11412 (which will false-positive if the first character of the local part is a
11413 literal question mark).
11415 .vitem "&*${utf8_domain_to_alabel:*&<&'string'&>&*}*&" &&&
11416 "&*${utf8_domain_from_alabel:*&<&'string'&>&*}*&" &&&
11417 "&*${utf8_localpart_to_alabel:*&<&'string'&>&*}*&" &&&
11418 "&*${utf8_localpart_from_alabel:*&<&'string'&>&*}*&"
11419 .cindex expansion UTF-8
11420 .cindex UTF-8 expansion
11422 .cindex internationalisation
11423 .cindex "&%utf8_domain_to_alabel%& expansion item"
11424 .cindex "&%utf8_domain_from_alabel%& expansion item"
11425 .cindex "&%utf8_localpart_to_alabel%& expansion item"
11426 .cindex "&%utf8_localpart_from_alabel%& expansion item"
11427 These convert EAI mail name components between UTF-8 and a-label forms.
11428 For information on internationalisation support see &<<SECTi18nMTA>>&.
11436 .section "Expansion conditions" "SECTexpcond"
11437 .scindex IIDexpcond "expansion" "conditions"
11438 The following conditions are available for testing by the &%${if%& construct
11439 while expanding strings:
11442 .vitem &*!*&<&'condition'&>
11443 .cindex "expansion" "negating a condition"
11444 .cindex "negation" "in expansion condition"
11445 Preceding any condition with an exclamation mark negates the result of the
11448 .vitem <&'symbolic&~operator'&>&~&*{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11449 .cindex "numeric comparison"
11450 .cindex "expansion" "numeric comparison"
11451 There are a number of symbolic operators for doing numeric comparisons. They
11453 .itable none 0 0 2 10* left 90* left
11455 .irow "== " "equal"
11456 .irow "> " "greater"
11457 .irow ">= " "greater or equal"
11459 .irow "<= " "less or equal"
11463 ${if >{$message_size}{10M} ...
11465 Note that the general negation operator provides for inequality testing. The
11466 two strings must take the form of optionally signed decimal integers,
11467 optionally followed by one of the letters &"K"&, &"M"& or &"G"& (in either upper or
11468 lower case), signifying multiplication by 1024, 1024*1024 or 1024*1024*1024, respectively.
11469 As a special case, the numerical value of an empty string is taken as
11472 In all cases, a relative comparator OP is testing if <&'string1'&> OP
11473 <&'string2'&>; the above example is checking if &$message_size$& is larger than
11474 10M, not if 10M is larger than &$message_size$&.
11477 .vitem &*acl&~{{*&<&'name'&>&*}{*&<&'arg1'&>&*}&&&
11478 {*&<&'arg2'&>&*}...}*&
11479 .cindex "expansion" "calling an acl"
11480 .cindex "&%acl%&" "expansion condition"
11481 The name and zero to nine argument strings are first expanded separately. The expanded
11482 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
11483 Any unused are made empty. The variable &$acl_narg$& is set to the number of
11484 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
11485 and may use the variables; if another acl expansion is used the values
11486 are restored after it returns. If the ACL sets
11487 a value using a "message =" modifier the variable $value becomes
11488 the result of the expansion, otherwise it is empty.
11489 If the ACL returns accept the condition is true; if deny, false.
11490 If the ACL returns defer the result is a forced-fail.
11492 .vitem &*bool&~{*&<&'string'&>&*}*&
11493 .cindex "expansion" "boolean parsing"
11494 .cindex "&%bool%& expansion condition"
11495 This condition turns a string holding a true or false representation into
11496 a boolean state. It parses &"true"&, &"false"&, &"yes"& and &"no"&
11497 (case-insensitively); also integer numbers map to true if non-zero,
11499 An empty string is treated as false.
11500 Leading and trailing whitespace is ignored;
11501 thus a string consisting only of whitespace is false.
11502 All other string values will result in expansion failure.
11504 When combined with ACL variables, this expansion condition will let you
11505 make decisions in one place and act on those decisions in another place.
11508 ${if bool{$acl_m_privileged_sender} ...
11512 .vitem &*bool_lax&~{*&<&'string'&>&*}*&
11513 .cindex "expansion" "boolean parsing"
11514 .cindex "&%bool_lax%& expansion condition"
11515 Like &%bool%&, this condition turns a string into a boolean state. But
11516 where &%bool%& accepts a strict set of strings, &%bool_lax%& uses the same
11517 loose definition that the Router &%condition%& option uses. The empty string
11518 and the values &"false"&, &"no"& and &"0"& map to false, all others map to
11519 true. Leading and trailing whitespace is ignored.
11521 Note that where &"bool{00}"& is false, &"bool_lax{00}"& is true.
11523 .vitem &*crypteq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11524 .cindex "expansion" "encrypted comparison"
11525 .cindex "encrypted strings, comparing"
11526 .cindex "&%crypteq%& expansion condition"
11527 This condition is included in the Exim binary if it is built to support any
11528 authentication mechanisms (see chapter &<<CHAPSMTPAUTH>>&). Otherwise, it is
11529 necessary to define SUPPORT_CRYPTEQ in &_Local/Makefile_& to get &%crypteq%&
11530 included in the binary.
11532 The &%crypteq%& condition has two arguments. The first is encrypted and
11533 compared against the second, which is already encrypted. The second string may
11534 be in the LDAP form for storing encrypted strings, which starts with the
11535 encryption type in curly brackets, followed by the data. If the second string
11536 does not begin with &"{"& it is assumed to be encrypted with &[crypt()]& or
11537 &[crypt16()]& (see below), since such strings cannot begin with &"{"&.
11538 Typically this will be a field from a password file. An example of an encrypted
11539 string in LDAP form is:
11541 {md5}CY9rzUYh03PK3k6DJie09g==
11543 If such a string appears directly in an expansion, the curly brackets have to
11544 be quoted, because they are part of the expansion syntax. For example:
11546 ${if crypteq {test}{\{md5\}CY9rzUYh03PK3k6DJie09g==}{yes}{no}}
11548 The following encryption types (whose names are matched case-independently) are
11553 .cindex "base64 encoding" "in encrypted password"
11554 &%{md5}%& computes the MD5 digest of the first string, and expresses this as
11555 printable characters to compare with the remainder of the second string. If the
11556 length of the comparison string is 24, Exim assumes that it is base64 encoded
11557 (as in the above example). If the length is 32, Exim assumes that it is a
11558 hexadecimal encoding of the MD5 digest. If the length not 24 or 32, the
11562 .cindex "SHA-1 hash"
11563 &%{sha1}%& computes the SHA-1 digest of the first string, and expresses this as
11564 printable characters to compare with the remainder of the second string. If the
11565 length of the comparison string is 28, Exim assumes that it is base64 encoded.
11566 If the length is 40, Exim assumes that it is a hexadecimal encoding of the
11567 SHA-1 digest. If the length is not 28 or 40, the comparison fails.
11570 .cindex "&[crypt()]&"
11571 &%{crypt}%& calls the &[crypt()]& function, which traditionally used to use
11572 only the first eight characters of the password. However, in modern operating
11573 systems this is no longer true, and in many cases the entire password is used,
11574 whatever its length.
11577 .cindex "&[crypt16()]&"
11578 &%{crypt16}%& calls the &[crypt16()]& function, which was originally created to
11579 use up to 16 characters of the password in some operating systems. Again, in
11580 modern operating systems, more characters may be used.
11582 Exim has its own version of &[crypt16()]&, which is just a double call to
11583 &[crypt()]&. For operating systems that have their own version, setting
11584 HAVE_CRYPT16 in &_Local/Makefile_& when building Exim causes it to use the
11585 operating system version instead of its own. This option is set by default in
11586 the OS-dependent &_Makefile_& for those operating systems that are known to
11587 support &[crypt16()]&.
11589 Some years after Exim's &[crypt16()]& was implemented, a user discovered that
11590 it was not using the same algorithm as some operating systems' versions. It
11591 turns out that as well as &[crypt16()]& there is a function called
11592 &[bigcrypt()]& in some operating systems. This may or may not use the same
11593 algorithm, and both of them may be different to Exim's built-in &[crypt16()]&.
11595 However, since there is now a move away from the traditional &[crypt()]&
11596 functions towards using SHA1 and other algorithms, tidying up this area of
11597 Exim is seen as very low priority.
11599 If you do not put a encryption type (in curly brackets) in a &%crypteq%&
11600 comparison, the default is usually either &`{crypt}`& or &`{crypt16}`&, as
11601 determined by the setting of DEFAULT_CRYPT in &_Local/Makefile_&. The default
11602 default is &`{crypt}`&. Whatever the default, you can always use either
11603 function by specifying it explicitly in curly brackets.
11605 .vitem &*def:*&<&'variable&~name'&>
11606 .cindex "expansion" "checking for empty variable"
11607 .cindex "&%def%& expansion condition"
11608 The &%def%& condition must be followed by the name of one of the expansion
11609 variables defined in section &<<SECTexpvar>>&. The condition is true if the
11610 variable does not contain the empty string. For example:
11612 ${if def:sender_ident {from $sender_ident}}
11614 Note that the variable name is given without a leading &%$%& character. If the
11615 variable does not exist, the expansion fails.
11617 .vitem "&*def:header_*&<&'header&~name'&>&*:*&&~&~or&~&&&
11618 &~&*def:h_*&<&'header&~name'&>&*:*&"
11619 .cindex "expansion" "checking header line existence"
11620 This condition is true if a message is being processed and the named header
11621 exists in the message. For example,
11623 ${if def:header_reply-to:{$h_reply-to:}{$h_from:}}
11625 &*Note*&: No &%$%& appears before &%header_%& or &%h_%& in the condition, and
11626 the header name must be terminated by a colon if white space does not follow.
11628 .vitem &*eq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11629 &*eqi&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11630 .cindex "string" "comparison"
11631 .cindex "expansion" "string comparison"
11632 .cindex "&%eq%& expansion condition"
11633 .cindex "&%eqi%& expansion condition"
11634 The two substrings are first expanded. The condition is true if the two
11635 resulting strings are identical. For &%eq%& the comparison includes the case of
11636 letters, whereas for &%eqi%& the comparison is case-independent, where
11637 case is defined per the system C locale.
11639 .vitem &*exists&~{*&<&'file&~name'&>&*}*&
11640 .cindex "expansion" "file existence test"
11641 .cindex "file" "existence test"
11642 .cindex "&%exists%&, expansion condition"
11643 The substring is first expanded and then interpreted as an absolute path. The
11644 condition is true if the named file (or directory) exists. The existence test
11645 is done by calling the &[stat()]& function. The use of the &%exists%& test in
11646 users' filter files may be locked out by the system administrator.
11648 &*Note:*& Testing a path using this condition is not a sufficient way of
11650 Consider using a dsearch lookup.
11652 .vitem &*first_delivery*&
11653 .cindex "delivery" "first"
11654 .cindex "first delivery"
11655 .cindex "expansion" "first delivery test"
11656 .cindex "&%first_delivery%& expansion condition"
11657 This condition, which has no data, is true during a message's first delivery
11658 attempt. It is false during any subsequent delivery attempts.
11661 .vitem "&*forall{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&" &&&
11662 "&*forany{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&"
11663 .cindex "list" "iterative conditions"
11664 .cindex "expansion" "&*forall*& condition"
11665 .cindex "expansion" "&*forany*& condition"
11667 These conditions iterate over a list. The first argument is expanded to form
11668 the list. By default, the list separator is a colon, but it can be changed by
11669 the normal method (&<<SECTlistsepchange>>&).
11670 The second argument is interpreted as a condition that is to
11671 be applied to each item in the list in turn. During the interpretation of the
11672 condition, the current list item is placed in a variable called &$item$&.
11674 For &*forany*&, interpretation stops if the condition is true for any item, and
11675 the result of the whole condition is true. If the condition is false for all
11676 items in the list, the overall condition is false.
11678 For &*forall*&, interpretation stops if the condition is false for any item,
11679 and the result of the whole condition is false. If the condition is true for
11680 all items in the list, the overall condition is true.
11682 Note that negation of &*forany*& means that the condition must be false for all
11683 items for the overall condition to succeed, and negation of &*forall*& means
11684 that the condition must be false for at least one item. In this example, the
11685 list separator is changed to a comma:
11687 ${if forany{<, $recipients}{match{$item}{^user3@}}{yes}{no}}
11689 The value of &$item$& is saved and restored while &%forany%& or &%forall%& is
11690 being processed, to enable these expansion items to be nested.
11692 To scan a named list, expand it with the &*listnamed*& operator.
11694 .vitem "&*forall_json{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
11695 "&*forany_json{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
11696 "&*forall_jsons{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
11697 "&*forany_jsons{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&"
11698 .cindex JSON "iterative conditions"
11699 .cindex JSON expansions
11700 .cindex expansion "&*forall_json*& condition"
11701 .cindex expansion "&*forany_json*& condition"
11702 .cindex expansion "&*forall_jsons*& condition"
11703 .cindex expansion "&*forany_jsons*& condition"
11704 As for the above, except that the first argument must, after expansion,
11706 The array separator is not changeable.
11707 For the &"jsons"& variants the elements are expected to be JSON strings
11708 and have their quotes removed before the evaluation of the condition.
11712 .vitem &*ge&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11713 &*gei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11714 .cindex "string" "comparison"
11715 .cindex "expansion" "string comparison"
11716 .cindex "&%ge%& expansion condition"
11717 .cindex "&%gei%& expansion condition"
11718 The two substrings are first expanded. The condition is true if the first
11719 string is lexically greater than or equal to the second string. For &%ge%& the
11720 comparison includes the case of letters, whereas for &%gei%& the comparison is
11722 Case and collation order are defined per the system C locale.
11724 .vitem &*gt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11725 &*gti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11726 .cindex "string" "comparison"
11727 .cindex "expansion" "string comparison"
11728 .cindex "&%gt%& expansion condition"
11729 .cindex "&%gti%& expansion condition"
11730 The two substrings are first expanded. The condition is true if the first
11731 string is lexically greater than the second string. For &%gt%& the comparison
11732 includes the case of letters, whereas for &%gti%& the comparison is
11734 Case and collation order are defined per the system C locale.
11737 .vitem &*inbound_srs&~{*&<&'local&~part'&>&*}{*&<&'secret'&>&*}*&
11738 SRS decode. See SECT &<<SECTSRS>>& for details.
11741 .vitem &*inlist&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11742 &*inlisti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11743 .cindex "string" "comparison"
11744 .cindex "list" "iterative conditions"
11745 Both strings are expanded; the second string is treated as a list of simple
11746 strings; if the first string is a member of the second, then the condition
11748 For the case-independent &%inlisti%& condition, case is defined per the system C locale.
11750 These are simpler to use versions of the more powerful &*forany*& condition.
11751 Examples, and the &*forany*& equivalents:
11753 ${if inlist{needle}{foo:needle:bar}}
11754 ${if forany{foo:needle:bar}{eq{$item}{needle}}}
11755 ${if inlisti{Needle}{fOo:NeeDLE:bAr}}
11756 ${if forany{fOo:NeeDLE:bAr}{eqi{$item}{Needle}}}
11759 The variable &$value$& will be set for a successful match and can be
11760 used in the success clause of an &%if%& expansion item using the condition.
11761 .cindex "tainted data" "de-tainting"
11762 .cindex "de-tainting" "using an inlist expansion condition"
11763 It will have the same taint status as the list; expansions such as
11765 ${if inlist {$h_mycode:} {0 : 1 : 42} {$value}}
11767 can be used for de-tainting.
11768 Any previous &$value$& is restored after the if.
11771 .vitem &*isip&~{*&<&'string'&>&*}*& &&&
11772 &*isip4&~{*&<&'string'&>&*}*& &&&
11773 &*isip6&~{*&<&'string'&>&*}*&
11774 .cindex "IP address" "testing string format"
11775 .cindex "string" "testing for IP address"
11776 .cindex "&%isip%& expansion condition"
11777 .cindex "&%isip4%& expansion condition"
11778 .cindex "&%isip6%& expansion condition"
11779 The substring is first expanded, and then tested to see if it has the form of
11780 an IP address. Both IPv4 and IPv6 addresses are valid for &%isip%&, whereas
11781 &%isip4%& and &%isip6%& test specifically for IPv4 or IPv6 addresses.
11783 For an IPv4 address, the test is for four dot-separated components, each of
11784 which consists of from one to three digits. For an IPv6 address, up to eight
11785 colon-separated components are permitted, each containing from one to four
11786 hexadecimal digits. There may be fewer than eight components if an empty
11787 component (adjacent colons) is present. Only one empty component is permitted.
11789 &*Note*&: The checks used to be just on the form of the address; actual numerical
11790 values were not considered. Thus, for example, 999.999.999.999 passed the IPv4
11792 This is no longer the case.
11794 The main use of these tests is to distinguish between IP addresses and
11795 host names, or between IPv4 and IPv6 addresses. For example, you could use
11797 ${if isip4{$sender_host_address}...
11799 to test which IP version an incoming SMTP connection is using.
11801 .vitem &*ldapauth&~{*&<&'ldap&~query'&>&*}*&
11802 .cindex "LDAP" "use for authentication"
11803 .cindex "expansion" "LDAP authentication test"
11804 .cindex "&%ldapauth%& expansion condition"
11805 This condition supports user authentication using LDAP. See section
11806 &<<SECTldap>>& for details of how to use LDAP in lookups and the syntax of
11807 queries. For this use, the query must contain a user name and password. The
11808 query itself is not used, and can be empty. The condition is true if the
11809 password is not empty, and the user name and password are accepted by the LDAP
11810 server. An empty password is rejected without calling LDAP because LDAP binds
11811 with an empty password are considered anonymous regardless of the username, and
11812 will succeed in most configurations. See chapter &<<CHAPSMTPAUTH>>& for details
11813 of SMTP authentication, and chapter &<<CHAPplaintext>>& for an example of how
11817 .vitem &*le&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11818 &*lei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11819 .cindex "string" "comparison"
11820 .cindex "expansion" "string comparison"
11821 .cindex "&%le%& expansion condition"
11822 .cindex "&%lei%& expansion condition"
11823 The two substrings are first expanded. The condition is true if the first
11824 string is lexically less than or equal to the second string. For &%le%& the
11825 comparison includes the case of letters, whereas for &%lei%& the comparison is
11827 Case and collation order are defined per the system C locale.
11829 .vitem &*lt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11830 &*lti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11831 .cindex "string" "comparison"
11832 .cindex "expansion" "string comparison"
11833 .cindex "&%lt%& expansion condition"
11834 .cindex "&%lti%& expansion condition"
11835 The two substrings are first expanded. The condition is true if the first
11836 string is lexically less than the second string. For &%lt%& the comparison
11837 includes the case of letters, whereas for &%lti%& the comparison is
11839 Case and collation order are defined per the system C locale.
11842 .vitem &*match&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11843 .cindex "expansion" "regular expression comparison"
11844 .cindex "regular expressions" "match in expanded string"
11845 .cindex "&%match%& expansion condition"
11846 The two substrings are first expanded. The second is then treated as a regular
11847 expression and applied to the first. Because of the pre-expansion, if the
11848 regular expression contains dollar, or backslash characters, they must be
11849 escaped. Care must also be taken if the regular expression contains braces
11850 (curly brackets). A closing brace must be escaped so that it is not taken as a
11851 premature termination of <&'string2'&>. The easiest approach is to use the
11852 &`\N`& feature to disable expansion of the regular expression.
11855 ${if match {$local_part}{\N^\d{3}\N} ...
11857 If the whole expansion string is in double quotes, further escaping of
11858 backslashes is also required.
11860 The condition is true if the regular expression match succeeds.
11861 The regular expression is not required to begin with a circumflex
11862 metacharacter, but if there is no circumflex, the expression is not anchored,
11863 and it may match anywhere in the subject, not just at the start. If you want
11864 the pattern to match at the end of the subject, you must include the &`$`&
11865 metacharacter at an appropriate point.
11866 All character handling is done in bytes and is not UTF-8 aware,
11867 but we might change this in a future Exim release.
11869 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%if%& expansion"
11870 At the start of an &%if%& expansion the values of the numeric variable
11871 substitutions &$1$& etc. are remembered. Obeying a &%match%& condition that
11872 succeeds causes them to be reset to the substrings of that condition and they
11873 will have these values during the expansion of the success string. At the end
11874 of the &%if%& expansion, the previous values are restored. After testing a
11875 combination of conditions using &%or%&, the subsequent values of the numeric
11876 variables are those of the condition that succeeded.
11878 .vitem &*match_address&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11879 .cindex "&%match_address%& expansion condition"
11880 See &*match_local_part*&.
11882 .vitem &*match_domain&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11883 .cindex "&%match_domain%& expansion condition"
11884 See &*match_local_part*&.
11886 .vitem &*match_ip&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11887 .cindex "&%match_ip%& expansion condition"
11888 This condition matches an IP address to a list of IP address patterns. It must
11889 be followed by two argument strings. The first (after expansion) must be an IP
11890 address or an empty string. The second (not expanded) is a restricted host
11891 list that can match only an IP address, not a host name. For example:
11893 ${if match_ip{$sender_host_address}{1.2.3.4:5.6.7.8}{...}{...}}
11895 The specific types of host list item that are permitted in the list are:
11898 An IP address, optionally with a CIDR mask.
11900 A single asterisk, which matches any IP address.
11902 An empty item, which matches only if the IP address is empty. This could be
11903 useful for testing for a locally submitted message or one from specific hosts
11904 in a single test such as
11905 . ==== As this is a nested list, any displays it contains must be indented
11906 . ==== as otherwise they are too far to the left. This comment applies to
11907 . ==== the use of xmlto plus fop. There's no problem when formatting with
11908 . ==== sdop, with or without the extra indent.
11910 ${if match_ip{$sender_host_address}{:4.3.2.1:...}{...}{...}}
11912 where the first item in the list is the empty string.
11914 The item @[] matches any of the local host's interface addresses.
11916 Single-key lookups are assumed to be like &"net-"& style lookups in host lists,
11917 even if &`net-`& is not specified. There is never any attempt to turn the IP
11918 address into a host name. The most common type of linear search for
11919 &*match_ip*& is likely to be &*iplsearch*&, in which the file can contain CIDR
11920 masks. For example:
11922 ${if match_ip{$sender_host_address}{iplsearch;/some/file}...
11924 It is of course possible to use other kinds of lookup, and in such a case, you
11925 do need to specify the &`net-`& prefix if you want to specify a specific
11926 address mask, for example:
11928 ${if match_ip{$sender_host_address}{net24-dbm;/some/file}...
11930 However, unless you are combining a &%match_ip%& condition with others, it is
11931 just as easy to use the fact that a lookup is itself a condition, and write:
11933 ${lookup{${mask:$sender_host_address/24}}dbm{/a/file}...
11937 Note that <&'string2'&> is not itself subject to string expansion, unless
11938 Exim was built with the EXPAND_LISTMATCH_RHS option.
11940 Consult section &<<SECThoslispatip>>& for further details of these patterns.
11942 .vitem &*match_local_part&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11943 .cindex "domain list" "in expansion condition"
11944 .cindex "address list" "in expansion condition"
11945 .cindex "local part" "list, in expansion condition"
11946 .cindex "&%match_local_part%& expansion condition"
11947 This condition, together with &%match_address%& and &%match_domain%&, make it
11948 possible to test domain, address, and local part lists within expansions. Each
11949 condition requires two arguments: an item and a list to match. A trivial
11952 ${if match_domain{a.b.c}{x.y.z:a.b.c:p.q.r}{yes}{no}}
11954 In each case, the second argument may contain any of the allowable items for a
11955 list of the appropriate type. Also, because the second argument
11956 is a standard form of list, it is possible to refer to a named list.
11957 Thus, you can use conditions like this:
11959 ${if match_domain{$domain}{+local_domains}{...
11961 .cindex "&`+caseful`&"
11962 For address lists, the matching starts off caselessly, but the &`+caseful`&
11963 item can be used, as in all address lists, to cause subsequent items to
11964 have their local parts matched casefully. Domains are always matched
11967 The variable &$value$& will be set for a successful match and can be
11968 used in the success clause of an &%if%& expansion item using the condition.
11969 .cindex "tainted data" "de-tainting"
11970 .cindex "de-tainting" "using a match_local_part expansion condition"
11971 It will have the same taint status as the list; expansions such as
11973 ${if match_local_part {$local_part} {alice : bill : charlotte : dave} {$value}}
11975 can be used for de-tainting.
11976 Any previous &$value$& is restored after the if.
11978 Note that <&'string2'&> is not itself subject to string expansion, unless
11979 Exim was built with the EXPAND_LISTMATCH_RHS option.
11981 &*Note*&: Host lists are &'not'& supported in this way. This is because
11982 hosts have two identities: a name and an IP address, and it is not clear
11983 how to specify cleanly how such a test would work. However, IP addresses can be
11984 matched using &%match_ip%&.
11986 .vitem &*pam&~{*&<&'string1'&>&*:*&<&'string2'&>&*:...}*&
11987 .cindex "PAM authentication"
11988 .cindex "AUTH" "with PAM"
11989 .cindex "Solaris" "PAM support"
11990 .cindex "expansion" "PAM authentication test"
11991 .cindex "&%pam%& expansion condition"
11992 &'Pluggable Authentication Modules'&
11993 (&url(https://mirrors.edge.kernel.org/pub/linux/libs/pam/)) are a facility that is
11994 available in Solaris
11995 and in some GNU/Linux distributions.
11996 The Exim support, which is intended for use in conjunction with
11997 the SMTP AUTH command, is available only if Exim is compiled with
12001 in &_Local/Makefile_&. You probably need to add &%-lpam%& to EXTRALIBS, and
12002 in some releases of GNU/Linux &%-ldl%& is also needed.
12004 The argument string is first expanded, and the result must be a
12005 colon-separated list of strings. Leading and trailing white space is ignored.
12006 The PAM module is initialized with the service name &"exim"& and the user name
12007 taken from the first item in the colon-separated data string (<&'string1'&>).
12008 The remaining items in the data string are passed over in response to requests
12009 from the authentication function. In the simple case there will only be one
12010 request, for a password, so the data consists of just two strings.
12012 There can be problems if any of the strings are permitted to contain colon
12013 characters. In the usual way, these have to be doubled to avoid being taken as
12015 The &%listquote%& expansion item can be used for this.
12016 For example, the configuration
12017 of a LOGIN authenticator might contain this setting:
12019 server_condition = ${if pam{$auth1:${listquote{:}{$auth2}}}}
12021 In some operating systems, PAM authentication can be done only from a process
12022 running as root. Since Exim is running as the Exim user when receiving
12023 messages, this means that PAM cannot be used directly in those systems.
12024 . --- 2018-09-07: the pam_exim modified variant has gone, removed claims re using Exim via that
12027 .vitem &*pwcheck&~{*&<&'string1'&>&*:*&<&'string2'&>&*}*&
12028 .cindex "&'pwcheck'& daemon"
12030 .cindex "expansion" "&'pwcheck'& authentication test"
12031 .cindex "&%pwcheck%& expansion condition"
12032 This condition supports user authentication using the Cyrus &'pwcheck'& daemon.
12033 This is one way of making it possible for passwords to be checked by a process
12034 that is not running as root. &*Note*&: The use of &'pwcheck'& is now
12035 deprecated. Its replacement is &'saslauthd'& (see below).
12037 The pwcheck support is not included in Exim by default. You need to specify
12038 the location of the pwcheck daemon's socket in &_Local/Makefile_& before
12039 building Exim. For example:
12041 CYRUS_PWCHECK_SOCKET=/var/pwcheck/pwcheck
12043 You do not need to install the full Cyrus software suite in order to use
12044 the pwcheck daemon. You can compile and install just the daemon alone
12045 from the Cyrus SASL library. Ensure that &'exim'& is the only user that has
12046 access to the &_/var/pwcheck_& directory.
12048 The &%pwcheck%& condition takes one argument, which must be the user name and
12049 password, separated by a colon. For example, in a LOGIN authenticator
12050 configuration, you might have this:
12052 server_condition = ${if pwcheck{$auth1:$auth2}}
12054 Again, for a PLAIN authenticator configuration, this would be:
12056 server_condition = ${if pwcheck{$auth2:$auth3}}
12058 .vitem &*queue_running*&
12059 .cindex "queue runner" "detecting when delivering from"
12060 .cindex "expansion" "queue runner test"
12061 .cindex "&%queue_running%& expansion condition"
12062 This condition, which has no data, is true during delivery attempts that are
12063 initiated by queue runner processes, and false otherwise.
12066 .vitem &*radius&~{*&<&'authentication&~string'&>&*}*&
12068 .cindex "expansion" "Radius authentication"
12069 .cindex "&%radius%& expansion condition"
12070 Radius authentication (RFC 2865) is supported in a similar way to PAM. You must
12071 set RADIUS_CONFIG_FILE in &_Local/Makefile_& to specify the location of
12072 the Radius client configuration file in order to build Exim with Radius
12075 With just that one setting, Exim expects to be linked with the &%radiusclient%&
12076 library, using the original API. If you are using release 0.4.0 or later of
12077 this library, you need to set
12079 RADIUS_LIB_TYPE=RADIUSCLIENTNEW
12081 in &_Local/Makefile_& when building Exim. You can also link Exim with the
12082 &%libradius%& library that comes with FreeBSD. To do this, set
12084 RADIUS_LIB_TYPE=RADLIB
12086 in &_Local/Makefile_&, in addition to setting RADIUS_CONFIGURE_FILE.
12087 You may also have to supply a suitable setting in EXTRALIBS so that the
12088 Radius library can be found when Exim is linked.
12090 The string specified by RADIUS_CONFIG_FILE is expanded and passed to the
12091 Radius client library, which calls the Radius server. The condition is true if
12092 the authentication is successful. For example:
12094 server_condition = ${if radius{<arguments>}}
12098 .vitem "&*saslauthd&~{{*&<&'user'&>&*}{*&<&'password'&>&*}&&&
12099 {*&<&'service'&>&*}{*&<&'realm'&>&*}}*&"
12100 .cindex "&'saslauthd'& daemon"
12102 .cindex "expansion" "&'saslauthd'& authentication test"
12103 .cindex "&%saslauthd%& expansion condition"
12104 This condition supports user authentication using the Cyrus &'saslauthd'&
12105 daemon. This replaces the older &'pwcheck'& daemon, which is now deprecated.
12106 Using this daemon is one way of making it possible for passwords to be checked
12107 by a process that is not running as root.
12109 The saslauthd support is not included in Exim by default. You need to specify
12110 the location of the saslauthd daemon's socket in &_Local/Makefile_& before
12111 building Exim. For example:
12113 CYRUS_SASLAUTHD_SOCKET=/var/state/saslauthd/mux
12115 You do not need to install the full Cyrus software suite in order to use
12116 the saslauthd daemon. You can compile and install just the daemon alone
12117 from the Cyrus SASL library.
12119 Up to four arguments can be supplied to the &%saslauthd%& condition, but only
12120 two are mandatory. For example:
12122 server_condition = ${if saslauthd{{$auth1}{$auth2}}}
12124 The service and the realm are optional (which is why the arguments are enclosed
12125 in their own set of braces). For details of the meaning of the service and
12126 realm, and how to run the daemon, consult the Cyrus documentation.
12131 .section "Combining expansion conditions" "SECID84"
12132 .cindex "expansion" "combining conditions"
12133 Several conditions can be tested at once by combining them using the &%and%&
12134 and &%or%& combination conditions. Note that &%and%& and &%or%& are complete
12135 conditions on their own, and precede their lists of sub-conditions. Each
12136 sub-condition must be enclosed in braces within the overall braces that contain
12137 the list. No repetition of &%if%& is used.
12141 .vitem &*or&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
12142 .cindex "&""or""& expansion condition"
12143 .cindex "expansion" "&""or""& of conditions"
12144 The sub-conditions are evaluated from left to right. The condition is true if
12145 any one of the sub-conditions is true.
12148 ${if or {{eq{$local_part}{spqr}}{eq{$domain}{testing.com}}}...
12150 When a true sub-condition is found, the following ones are parsed but not
12151 evaluated. If there are several &"match"& sub-conditions the values of the
12152 numeric variables afterwards are taken from the first one that succeeds.
12154 .vitem &*and&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
12155 .cindex "&""and""& expansion condition"
12156 .cindex "expansion" "&""and""& of conditions"
12157 The sub-conditions are evaluated from left to right. The condition is true if
12158 all of the sub-conditions are true. If there are several &"match"&
12159 sub-conditions, the values of the numeric variables afterwards are taken from
12160 the last one. When a false sub-condition is found, the following ones are
12161 parsed but not evaluated.
12163 .ecindex IIDexpcond
12168 .section "Expansion variables" "SECTexpvar"
12169 .cindex "expansion" "variables, list of"
12170 This section contains an alphabetical list of all the expansion variables. Some
12171 of them are available only when Exim is compiled with specific options such as
12172 support for TLS or the content scanning extension.
12173 .cindex "tainted data"
12174 Variables marked as &'tainted'& are likely to carry data supplied by
12175 a potential attacker.
12176 Variables without such marking may also, depending on how their
12177 values are created.
12178 Such variables should not be further expanded,
12180 or used as command-line arguments for external commands.
12183 .vitem "&$0$&, &$1$&, etc"
12184 .cindex "numerical variables (&$1$& &$2$& etc)"
12185 When a &%match%& expansion condition succeeds, these variables contain the
12186 captured substrings identified by the regular expression during subsequent
12187 processing of the success string of the containing &%if%& expansion item.
12188 In the expansion condition case
12189 they do not retain their values afterwards; in fact, their previous
12190 values are restored at the end of processing an &%if%& item. The numerical
12191 variables may also be set externally by some other matching process which
12192 precedes the expansion of the string. For example, the commands available in
12193 Exim filter files include an &%if%& command with its own regular expression
12194 matching condition.
12195 If the subject string was tainted then any captured substring will also be.
12197 .vitem "&$acl_arg1$&, &$acl_arg2$&, etc"
12198 Within an acl condition, expansion condition or expansion item
12199 any arguments are copied to these variables,
12200 any unused variables being made empty.
12202 .vitem "&$acl_c...$&"
12203 Values can be placed in these variables by the &%set%& modifier in an ACL. They
12204 can be given any name that starts with &$acl_c$& and is at least six characters
12205 long, but the sixth character must be either a digit or an underscore. For
12206 example: &$acl_c5$&, &$acl_c_mycount$&. The values of the &$acl_c...$&
12207 variables persist throughout the lifetime of an SMTP connection. They can be
12208 used to pass information between ACLs and between different invocations of the
12209 same ACL. When a message is received, the values of these variables are saved
12210 with the message, and can be accessed by filters, routers, and transports
12211 during subsequent delivery.
12213 .vitem "&$acl_m...$&"
12214 These variables are like the &$acl_c...$& variables, except that their values
12215 are reset after a message has been received. Thus, if several messages are
12216 received in one SMTP connection, &$acl_m...$& values are not passed on from one
12217 message to the next, as &$acl_c...$& values are. The &$acl_m...$& variables are
12218 also reset by MAIL, RSET, EHLO, HELO, and after starting a TLS session. When a
12219 message is received, the values of these variables are saved with the message,
12220 and can be accessed by filters, routers, and transports during subsequent
12223 .vitem &$acl_narg$&
12224 Within an acl condition, expansion condition or expansion item
12225 this variable has the number of arguments.
12227 .vitem &$acl_verify_message$&
12228 .vindex "&$acl_verify_message$&"
12229 After an address verification has failed, this variable contains the failure
12230 message. It retains its value for use in subsequent modifiers of the verb.
12231 The message can be preserved by coding like this:
12233 warn !verify = sender
12234 set acl_m0 = $acl_verify_message
12236 You can use &$acl_verify_message$& during the expansion of the &%message%& or
12237 &%log_message%& modifiers, to include information about the verification
12239 &*Note*&: The variable is cleared at the end of processing the ACL verb.
12241 .vitem &$address_data$&
12242 .vindex "&$address_data$&"
12243 This variable is set by means of the &%address_data%& option in routers. The
12244 value then remains with the address while it is processed by subsequent routers
12245 and eventually a transport. If the transport is handling multiple addresses,
12246 the value from the first address is used. See chapter &<<CHAProutergeneric>>&
12247 for more details. &*Note*&: The contents of &$address_data$& are visible in
12250 If &$address_data$& is set when the routers are called from an ACL to verify
12251 a recipient address, the final value is still in the variable for subsequent
12252 conditions and modifiers of the ACL statement. If routing the address caused it
12253 to be redirected to just one address, the child address is also routed as part
12254 of the verification, and in this case the final value of &$address_data$& is
12255 from the child's routing.
12257 If &$address_data$& is set when the routers are called from an ACL to verify a
12258 sender address, the final value is also preserved, but this time in
12259 &$sender_address_data$&, to distinguish it from data from a recipient
12262 In both cases (recipient and sender verification), the value does not persist
12263 after the end of the current ACL statement. If you want to preserve
12264 these values for longer, you can save them in ACL variables.
12266 .vitem &$address_file$&
12267 .vindex "&$address_file$&"
12268 When, as a result of aliasing, forwarding, or filtering, a message is directed
12269 to a specific file, this variable holds the name of the file when the transport
12270 is running. At other times, the variable is empty. For example, using the
12271 default configuration, if user &%r2d2%& has a &_.forward_& file containing
12273 /home/r2d2/savemail
12275 then when the &(address_file)& transport is running, &$address_file$&
12276 contains the text string &`/home/r2d2/savemail`&.
12277 .cindex "Sieve filter" "value of &$address_file$&"
12278 For Sieve filters, the value may be &"inbox"& or a relative folder name. It is
12279 then up to the transport configuration to generate an appropriate absolute path
12280 to the relevant file.
12282 .vitem &$address_pipe$&
12283 .vindex "&$address_pipe$&"
12284 When, as a result of aliasing or forwarding, a message is directed to a pipe,
12285 this variable holds the pipe command when the transport is running.
12287 .vitem "&$auth1$& &-- &$auth4$&"
12288 .vindex "&$auth1$&, &$auth2$&, etc"
12289 These variables are used in SMTP authenticators (see chapters
12290 &<<CHAPplaintext>>&&--&<<CHAPtlsauth>>&). Elsewhere, they are empty.
12292 .vitem &$authenticated_id$&
12293 .cindex "authentication" "id"
12294 .vindex "&$authenticated_id$&"
12295 When a server successfully authenticates a client it may be configured to
12296 preserve some of the authentication information in the variable
12297 &$authenticated_id$& (see chapter &<<CHAPSMTPAUTH>>&). For example, a
12298 user/password authenticator configuration might preserve the user name for use
12299 in the routers. Note that this is not the same information that is saved in
12300 &$sender_host_authenticated$&.
12302 When a message is submitted locally (that is, not over a TCP connection)
12303 the value of &$authenticated_id$& is normally the login name of the calling
12304 process. However, a trusted user can override this by means of the &%-oMai%&
12305 command line option.
12306 This second case also sets up information used by the
12307 &$authresults$& expansion item.
12309 .vitem &$authenticated_fail_id$&
12310 .cindex "authentication" "fail" "id"
12311 .vindex "&$authenticated_fail_id$&"
12312 When an authentication attempt fails, the variable &$authenticated_fail_id$&
12313 will contain the failed authentication id. If more than one authentication
12314 id is attempted, it will contain only the last one. The variable is
12315 available for processing in the ACL's, generally the quit or notquit ACL.
12316 A message to a local recipient could still be accepted without requiring
12317 authentication, which means this variable could also be visible in all of
12321 .tvar &$authenticated_sender$&
12322 .cindex "sender" "authenticated"
12323 .cindex "authentication" "sender"
12324 .cindex "AUTH" "on MAIL command"
12325 When acting as a server, Exim takes note of the AUTH= parameter on an incoming
12326 SMTP MAIL command if it believes the sender is sufficiently trusted, as
12327 described in section &<<SECTauthparamail>>&. Unless the data is the string
12328 &"<>"&, it is set as the authenticated sender of the message, and the value is
12329 available during delivery in the &$authenticated_sender$& variable. If the
12330 sender is not trusted, Exim accepts the syntax of AUTH=, but ignores the data.
12332 .vindex "&$qualify_domain$&"
12333 When a message is submitted locally (that is, not over a TCP connection), the
12334 value of &$authenticated_sender$& is an address constructed from the login
12335 name of the calling process and &$qualify_domain$&, except that a trusted user
12336 can override this by means of the &%-oMas%& command line option.
12339 .vitem &$authentication_failed$&
12340 .cindex "authentication" "failure"
12341 .vindex "&$authentication_failed$&"
12342 This variable is set to &"1"& in an Exim server if a client issues an AUTH
12343 command that does not succeed. Otherwise it is set to &"0"&. This makes it
12344 possible to distinguish between &"did not try to authenticate"&
12345 (&$sender_host_authenticated$& is empty and &$authentication_failed$& is set to
12346 &"0"&) and &"tried to authenticate but failed"& (&$sender_host_authenticated$&
12347 is empty and &$authentication_failed$& is set to &"1"&).
12348 Failure includes cancellation of a authentication attempt,
12349 and any negative response to an AUTH command,
12350 (including, for example, an attempt to use an undefined mechanism).
12352 .vitem &$av_failed$&
12353 .cindex "content scanning" "AV scanner failure"
12354 This variable is available when Exim is compiled with the content-scanning
12355 extension. It is set to &"0"& by default, but will be set to &"1"& if any
12356 problem occurs with the virus scanner (specified by &%av_scanner%&) during
12357 the ACL malware condition.
12359 .vitem &$body_linecount$&
12360 .cindex "message body" "line count"
12361 .cindex "body of message" "line count"
12362 .vindex "&$body_linecount$&"
12363 When a message is being received or delivered, this variable contains the
12364 number of lines in the message's body. See also &$message_linecount$&.
12366 .vitem &$body_zerocount$&
12367 .cindex "message body" "binary zero count"
12368 .cindex "body of message" "binary zero count"
12369 .cindex "binary zero" "in message body"
12370 .vindex "&$body_zerocount$&"
12371 When a message is being received or delivered, this variable contains the
12372 number of binary zero bytes (ASCII NULs) in the message's body.
12374 .vitem &$bounce_recipient$&
12375 .vindex "&$bounce_recipient$&"
12376 This is set to the recipient address of a bounce message while Exim is creating
12377 it. It is useful if a customized bounce message text file is in use (see
12378 chapter &<<CHAPemsgcust>>&).
12380 .vitem &$bounce_return_size_limit$&
12381 .vindex "&$bounce_return_size_limit$&"
12382 This contains the value set in the &%bounce_return_size_limit%& option, rounded
12383 up to a multiple of 1000. It is useful when a customized error message text
12384 file is in use (see chapter &<<CHAPemsgcust>>&).
12386 .vitem &$caller_gid$&
12387 .cindex "gid (group id)" "caller"
12388 .vindex "&$caller_gid$&"
12389 The real group id under which the process that called Exim was running. This is
12390 not the same as the group id of the originator of a message (see
12391 &$originator_gid$&). If Exim re-execs itself, this variable in the new
12392 incarnation normally contains the Exim gid.
12394 .vitem &$caller_uid$&
12395 .cindex "uid (user id)" "caller"
12396 .vindex "&$caller_uid$&"
12397 The real user id under which the process that called Exim was running. This is
12398 not the same as the user id of the originator of a message (see
12399 &$originator_uid$&). If Exim re-execs itself, this variable in the new
12400 incarnation normally contains the Exim uid.
12402 .vitem &$callout_address$&
12403 .vindex "&$callout_address$&"
12404 After a callout for verification, spamd or malware daemon service, the
12405 address that was connected to.
12407 .vitem &$compile_number$&
12408 .vindex "&$compile_number$&"
12409 The building process for Exim keeps a count of the number
12410 of times it has been compiled. This serves to distinguish different
12411 compilations of the same version of Exim.
12413 .vitem &$config_dir$&
12414 .vindex "&$config_dir$&"
12415 The directory name of the main configuration file. That is, the content of
12416 &$config_file$& with the last component stripped. The value does not
12417 contain the trailing slash. If &$config_file$& does not contain a slash,
12418 &$config_dir$& is ".".
12420 .vitem &$config_file$&
12421 .vindex "&$config_file$&"
12422 The name of the main configuration file Exim is using.
12424 .vitem &$dkim_verify_status$&
12425 Results of DKIM verification.
12426 For details see section &<<SECDKIMVFY>>&.
12428 .vitem &$dkim_cur_signer$& &&&
12429 &$dkim_verify_reason$& &&&
12430 &$dkim_domain$& &&&
12431 &$dkim_identity$& &&&
12432 &$dkim_selector$& &&&
12434 &$dkim_canon_body$& &&&
12435 &$dkim_canon_headers$& &&&
12436 &$dkim_copiedheaders$& &&&
12437 &$dkim_bodylength$& &&&
12438 &$dkim_created$& &&&
12439 &$dkim_expires$& &&&
12440 &$dkim_headernames$& &&&
12441 &$dkim_key_testing$& &&&
12442 &$dkim_key_nosubdomains$& &&&
12443 &$dkim_key_srvtype$& &&&
12444 &$dkim_key_granularity$& &&&
12445 &$dkim_key_notes$& &&&
12446 &$dkim_key_length$&
12447 These variables are only available within the DKIM ACL.
12448 For details see section &<<SECDKIMVFY>>&.
12450 .vitem &$dkim_signers$&
12451 .vindex &$dkim_signers$&
12452 When a message has been received this variable contains
12453 a colon-separated list of signer domains and identities for the message.
12454 For details see section &<<SECDKIMVFY>>&.
12456 .vitem &$dmarc_domain_policy$& &&&
12457 &$dmarc_status$& &&&
12458 &$dmarc_status_text$& &&&
12459 &$dmarc_used_domains$&
12460 Results of DMARC verification.
12461 For details see section &<<SECDMARC>>&.
12463 .vitem &$dnslist_domain$& &&&
12464 &$dnslist_matched$& &&&
12465 &$dnslist_text$& &&&
12467 .vindex "&$dnslist_domain$&"
12468 .vindex "&$dnslist_matched$&"
12469 .vindex "&$dnslist_text$&"
12470 .vindex "&$dnslist_value$&"
12471 .cindex "black list (DNS)"
12472 When a DNS (black) list lookup succeeds, these variables are set to contain
12473 the following data from the lookup: the list's domain name, the key that was
12474 looked up, the contents of any associated TXT record, and the value from the
12475 main A record. See section &<<SECID204>>& for more details.
12478 When an address is being routed, or delivered on its own, this variable
12479 contains the domain. Uppercase letters in the domain are converted into lower
12480 case for &$domain$&.
12482 Global address rewriting happens when a message is received, so the value of
12483 &$domain$& during routing and delivery is the value after rewriting. &$domain$&
12484 is set during user filtering, but not during system filtering, because a
12485 message may have many recipients and the system filter is called just once.
12487 When more than one address is being delivered at once (for example, several
12488 RCPT commands in one SMTP delivery), &$domain$& is set only if they all
12489 have the same domain. Transports can be restricted to handling only one domain
12490 at a time if the value of &$domain$& is required at transport time &-- this is
12491 the default for local transports. For further details of the environment in
12492 which local transports are run, see chapter &<<CHAPenvironment>>&.
12494 .oindex "&%delay_warning_condition%&"
12495 At the end of a delivery, if all deferred addresses have the same domain, it is
12496 set in &$domain$& during the expansion of &%delay_warning_condition%&.
12498 The &$domain$& variable is also used in some other circumstances:
12501 When an ACL is running for a RCPT command, &$domain$& contains the domain of
12502 the recipient address. The domain of the &'sender'& address is in
12503 &$sender_address_domain$& at both MAIL time and at RCPT time. &$domain$& is not
12504 normally set during the running of the MAIL ACL. However, if the sender address
12505 is verified with a callout during the MAIL ACL, the sender domain is placed in
12506 &$domain$& during the expansions of &%hosts%&, &%interface%&, and &%port%& in
12507 the &(smtp)& transport.
12510 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
12511 &$domain$& contains the domain portion of the address that is being rewritten;
12512 it can be used in the expansion of the replacement address, for example, to
12513 rewrite domains by file lookup.
12516 With one important exception, whenever a domain list is being scanned,
12517 &$domain$& contains the subject domain. &*Exception*&: When a domain list in
12518 a &%sender_domains%& condition in an ACL is being processed, the subject domain
12519 is in &$sender_address_domain$& and not in &$domain$&. It works this way so
12520 that, in a RCPT ACL, the sender domain list can be dependent on the
12521 recipient domain (which is what is in &$domain$& at this time).
12524 .cindex "ETRN" "value of &$domain$&"
12525 .oindex "&%smtp_etrn_command%&"
12526 When the &%smtp_etrn_command%& option is being expanded, &$domain$& contains
12527 the complete argument of the ETRN command (see section &<<SECTETRN>>&).
12530 .cindex "tainted data"
12531 If the origin of the data is an incoming message,
12532 the result of expanding this variable is tainted and may not
12533 be further expanded or used as a filename.
12534 When an untainted version is needed, one should be obtained from
12535 looking up the value in a local (therefore trusted) database.
12536 Often &$domain_data$& is usable in this role.
12539 .vitem &$domain_data$&
12540 .vindex "&$domain_data$&"
12541 When the &%domains%& condition on a router
12544 against a list, the match value is copied to &$domain_data$&.
12545 This is an enhancement over previous versions of Exim, when it only
12546 applied to the data read by a lookup.
12547 For details on match values see section &<<SECTlistresults>>& et. al.
12549 If the router routes the
12550 address to a transport, the value is available in that transport. If the
12551 transport is handling multiple addresses, the value from the first address is
12554 &$domain_data$& set in an ACL is available during
12555 the rest of the ACL statement.
12557 .vitem &$exim_gid$&
12558 .vindex "&$exim_gid$&"
12559 This variable contains the numerical value of the Exim group id.
12561 .vitem &$exim_path$&
12562 .vindex "&$exim_path$&"
12563 This variable contains the path to the Exim binary.
12565 .vitem &$exim_uid$&
12566 .vindex "&$exim_uid$&"
12567 This variable contains the numerical value of the Exim user id.
12569 .vitem &$exim_version$&
12570 .vindex "&$exim_version$&"
12571 This variable contains the version string of the Exim build.
12572 The first character is a major version number, currently 4.
12573 Then after a dot, the next group of digits is a minor version number.
12574 There may be other characters following the minor version.
12575 This value may be overridden by the &%exim_version%& main config option.
12577 .vitem &$header_$&<&'name'&>
12579 This is not strictly an expansion variable. It is expansion syntax for
12580 inserting the message header line with the given name. Note that the name must
12581 be terminated by colon or white space, because it may contain a wide variety of
12582 characters. Note also that braces must &'not'& be used.
12583 See the full description in section &<<SECTexpansionitems>>& above.
12585 .vitem &$headers_added$&
12586 .vindex "&$headers_added$&"
12587 Within an ACL this variable contains the headers added so far by
12588 the ACL modifier add_header (section &<<SECTaddheadacl>>&).
12589 The headers are a newline-separated list.
12593 When the &%check_local_user%& option is set for a router, the user's home
12594 directory is placed in &$home$& when the check succeeds. In particular, this
12595 means it is set during the running of users' filter files. A router may also
12596 explicitly set a home directory for use by a transport; this can be overridden
12597 by a setting on the transport itself.
12599 When running a filter test via the &%-bf%& option, &$home$& is set to the value
12600 of the environment variable HOME, which is subject to the
12601 &%keep_environment%& and &%add_environment%& main config options.
12605 If a router assigns an address to a transport (any transport), and passes a
12606 list of hosts with the address, the value of &$host$& when the transport starts
12607 to run is the name of the first host on the list. Note that this applies both
12608 to local and remote transports.
12610 .cindex "transport" "filter"
12611 .cindex "filter" "transport filter"
12612 For the &(smtp)& transport, if there is more than one host, the value of
12613 &$host$& changes as the transport works its way through the list. In
12614 particular, when the &(smtp)& transport is expanding its options for encryption
12615 using TLS, or for specifying a transport filter (see chapter
12616 &<<CHAPtransportgeneric>>&), &$host$& contains the name of the host to which it
12619 When used in the client part of an authenticator configuration (see chapter
12620 &<<CHAPSMTPAUTH>>&), &$host$& contains the name of the server to which the
12621 client is connected.
12624 .vitem &$host_address$&
12625 .vindex "&$host_address$&"
12626 This variable is set to the remote host's IP address whenever &$host$& is set
12627 for a remote connection. It is also set to the IP address that is being checked
12628 when the &%ignore_target_hosts%& option is being processed.
12630 .vitem &$host_data$&
12631 .vindex "&$host_data$&"
12632 If a &%hosts%& condition in an ACL is satisfied by means of a lookup, the
12633 result of the lookup is made available in the &$host_data$& variable. This
12634 allows you, for example, to do things like this:
12636 deny hosts = net-lsearch;/some/file
12637 message = $host_data
12640 .vitem &$host_lookup_deferred$&
12641 .cindex "host name" "lookup, failure of"
12642 .vindex "&$host_lookup_deferred$&"
12643 This variable normally contains &"0"&, as does &$host_lookup_failed$&. When a
12644 message comes from a remote host and there is an attempt to look up the host's
12645 name from its IP address, and the attempt is not successful, one of these
12646 variables is set to &"1"&.
12649 If the lookup receives a definite negative response (for example, a DNS lookup
12650 succeeded, but no records were found), &$host_lookup_failed$& is set to &"1"&.
12653 If there is any kind of problem during the lookup, such that Exim cannot
12654 tell whether or not the host name is defined (for example, a timeout for a DNS
12655 lookup), &$host_lookup_deferred$& is set to &"1"&.
12658 Looking up a host's name from its IP address consists of more than just a
12659 single reverse lookup. Exim checks that a forward lookup of at least one of the
12660 names it receives from a reverse lookup yields the original IP address. If this
12661 is not the case, Exim does not accept the looked up name(s), and
12662 &$host_lookup_failed$& is set to &"1"&. Thus, being able to find a name from an
12663 IP address (for example, the existence of a PTR record in the DNS) is not
12664 sufficient on its own for the success of a host name lookup. If the reverse
12665 lookup succeeds, but there is a lookup problem such as a timeout when checking
12666 the result, the name is not accepted, and &$host_lookup_deferred$& is set to
12667 &"1"&. See also &$sender_host_name$&.
12669 .cindex authentication "expansion item"
12670 Performing these checks sets up information used by the
12671 &%authresults%& expansion item.
12674 .vitem &$host_lookup_failed$&
12675 .vindex "&$host_lookup_failed$&"
12676 See &$host_lookup_deferred$&.
12678 .vitem &$host_port$&
12679 .vindex "&$host_port$&"
12680 This variable is set to the remote host's TCP port whenever &$host$& is set
12681 for an outbound connection.
12683 .vitem &$initial_cwd$&
12684 .vindex "&$initial_cwd$&
12685 This variable contains the full path name of the initial working
12686 directory of the current Exim process. This may differ from the current
12687 working directory, as Exim changes this to "/" during early startup, and
12688 to &$spool_directory$& later.
12691 .vindex "&$inode$&"
12692 The only time this variable is set is while expanding the &%directory_file%&
12693 option in the &(appendfile)& transport. The variable contains the inode number
12694 of the temporary file which is about to be renamed. It can be used to construct
12695 a unique name for the file.
12697 .vitem &$interface_address$& &&&
12699 .vindex "&$interface_address$&"
12700 .vindex "&$interface_port$&"
12701 These are obsolete names for &$received_ip_address$& and &$received_port$&.
12705 This variable is used during the expansion of &*forall*& and &*forany*&
12706 conditions (see section &<<SECTexpcond>>&), and &*filter*&, &*map*&, and
12707 &*reduce*& items (see section &<<SECTexpcond>>&). In other circumstances, it is
12711 .vindex "&$ldap_dn$&"
12712 This variable, which is available only when Exim is compiled with LDAP support,
12713 contains the DN from the last entry in the most recently successful LDAP
12716 .vitem &$load_average$&
12717 .vindex "&$load_average$&"
12718 This variable contains the system load average, multiplied by 1000 so that it
12719 is an integer. For example, if the load average is 0.21, the value of the
12720 variable is 210. The value is recomputed every time the variable is referenced.
12722 .tvar &$local_part$&
12723 When an address is being routed, or delivered on its own, this
12724 variable contains the local part. When a number of addresses are being
12725 delivered together (for example, multiple RCPT commands in an SMTP
12726 session), &$local_part$& is not set.
12728 Global address rewriting happens when a message is received, so the value of
12729 &$local_part$& during routing and delivery is the value after rewriting.
12730 &$local_part$& is set during user filtering, but not during system filtering,
12731 because a message may have many recipients and the system filter is called just
12734 .cindex "tainted data"
12735 If the origin of the data is an incoming message,
12736 the result of expanding this variable is tainted and
12737 may not be further expanded or used as a filename.
12739 &*Warning*&: the content of this variable is usually provided by a potential
12741 Consider carefully the implications of using it unvalidated as a name
12743 This presents issues for users' &_.forward_& and filter files.
12744 For traditional full user accounts, use &%check_local_users%& and the
12745 &$local_part_data$& variable rather than this one.
12746 For virtual users, store a suitable pathname component in the database
12747 which is used for account name validation, and use that retrieved value
12748 rather than this variable.
12749 Often &$local_part_data$& is usable in this role.
12750 If needed, use a router &%address_data%& or &%set%& option for
12751 the retrieved data.
12753 When a message is being delivered to a file, pipe, or autoreply transport as a
12754 result of aliasing or forwarding, &$local_part$& is set to the local part of
12755 the parent address, not to the filename or command (see &$address_file$& and
12758 When an ACL is running for a RCPT command, &$local_part$& contains the
12759 local part of the recipient address.
12761 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
12762 &$local_part$& contains the local part of the address that is being rewritten;
12763 it can be used in the expansion of the replacement address, for example.
12765 In all cases, all quoting is removed from the local part. For example, for both
12768 "abc:xyz"@test.example
12769 abc\:xyz@test.example
12771 the value of &$local_part$& is
12775 If you use &$local_part$& to create another address, you should always wrap it
12776 inside a quoting operator. For example, in a &(redirect)& router you could
12779 data = ${quote_local_part:$local_part}@new.domain.example
12781 &*Note*&: The value of &$local_part$& is normally lower cased. If you want
12782 to process local parts in a case-dependent manner in a router, you can set the
12783 &%caseful_local_part%& option (see chapter &<<CHAProutergeneric>>&).
12785 .vitem &$local_part_data$&
12786 .vindex "&$local_part_data$&"
12787 When the &%local_parts%& condition on a router or ACL
12788 matches a local part list
12789 the match value is copied to &$local_part_data$&.
12790 This is an enhancement over previous versions of Exim, when it only
12791 applied to the data read by a lookup.
12792 For details on match values see section &<<SECTlistresults>>& et. al.
12794 The &%check_local_user%& router option also sets this variable.
12796 .vindex &$local_part_prefix$& &&&
12797 &$local_part_prefix_v$& &&&
12798 &$local_part_suffix$& &&&
12799 &$local_part_suffix_v$&
12800 .cindex affix variables
12801 If a local part prefix or suffix has been recognized, it is not included in the
12802 value of &$local_part$& during routing and subsequent delivery. The values of
12803 any prefix or suffix are in &$local_part_prefix$& and
12804 &$local_part_suffix$&, respectively.
12805 .cindex "tainted data"
12806 If the specification did not include a wildcard then
12807 the affix variable value is not tainted.
12809 If the affix specification included a wildcard then the portion of
12810 the affix matched by the wildcard is in
12811 &$local_part_prefix_v$& or &$local_part_suffix_v$& as appropriate,
12812 and both the whole and varying values are tainted.
12814 .vitem &$local_scan_data$&
12815 .vindex "&$local_scan_data$&"
12816 This variable contains the text returned by the &[local_scan()]& function when
12817 a message is received. See chapter &<<CHAPlocalscan>>& for more details.
12819 .vitem &$local_user_gid$&
12820 .vindex "&$local_user_gid$&"
12821 See &$local_user_uid$&.
12823 .vitem &$local_user_uid$&
12824 .vindex "&$local_user_uid$&"
12825 This variable and &$local_user_gid$& are set to the uid and gid after the
12826 &%check_local_user%& router precondition succeeds. This means that their values
12827 are available for the remaining preconditions (&%senders%&, &%require_files%&,
12828 and &%condition%&), for the &%address_data%& expansion, and for any
12829 router-specific expansions. At all other times, the values in these variables
12830 are &`(uid_t)(-1)`& and &`(gid_t)(-1)`&, respectively.
12832 .vitem &$localhost_number$&
12833 .vindex "&$localhost_number$&"
12834 This contains the expanded value of the
12835 &%localhost_number%& option. The expansion happens after the main options have
12838 .vitem &$log_inodes$&
12839 .vindex "&$log_inodes$&"
12840 The number of free inodes in the disk partition where Exim's
12841 log files are being written. The value is recalculated whenever the variable is
12842 referenced. If the relevant file system does not have the concept of inodes,
12843 the value of is -1. See also the &%check_log_inodes%& option.
12845 .vitem &$log_space$&
12846 .vindex "&$log_space$&"
12847 The amount of free space (as a number of kilobytes) in the disk
12848 partition where Exim's log files are being written. The value is recalculated
12849 whenever the variable is referenced. If the operating system does not have the
12850 ability to find the amount of free space (only true for experimental systems),
12851 the space value is -1. See also the &%check_log_space%& option.
12854 .vitem &$lookup_dnssec_authenticated$&
12855 .vindex "&$lookup_dnssec_authenticated$&"
12856 This variable is set after a DNS lookup done by
12857 a dnsdb lookup expansion, dnslookup router or smtp transport.
12858 .cindex "DNS" "DNSSEC"
12859 It will be empty if &(DNSSEC)& was not requested,
12860 &"no"& if the result was not labelled as authenticated data
12861 and &"yes"& if it was.
12862 Results that are labelled as authoritative answer that match
12863 the &%dns_trust_aa%& configuration variable count also
12864 as authenticated data.
12866 .vitem &$mailstore_basename$&
12867 .vindex "&$mailstore_basename$&"
12868 This variable is set only when doing deliveries in &"mailstore"& format in the
12869 &(appendfile)& transport. During the expansion of the &%mailstore_prefix%&,
12870 &%mailstore_suffix%&, &%message_prefix%&, and &%message_suffix%& options, it
12871 contains the basename of the files that are being written, that is, the name
12872 without the &".tmp"&, &".env"&, or &".msg"& suffix. At all other times, this
12875 .vitem &$malware_name$&
12876 .vindex "&$malware_name$&"
12877 This variable is available when Exim is compiled with the
12878 content-scanning extension. It is set to the name of the virus that was found
12879 when the ACL &%malware%& condition is true (see section &<<SECTscanvirus>>&).
12881 .vitem &$max_received_linelength$&
12882 .vindex "&$max_received_linelength$&"
12883 .cindex "maximum" "line length"
12884 .cindex "line length" "maximum"
12885 This variable contains the number of bytes in the longest line that was
12886 received as part of the message, not counting the line termination
12888 It is not valid if the &%spool_wireformat%& option is used.
12890 .vitem &$message_age$&
12891 .cindex "message" "age of"
12892 .vindex "&$message_age$&"
12893 This variable is set at the start of a delivery attempt to contain the number
12894 of seconds since the message was received. It does not change during a single
12897 .tvar &$message_body$&
12898 .cindex "body of message" "expansion variable"
12899 .cindex "message body" "in expansion"
12900 .cindex "binary zero" "in message body"
12901 .oindex "&%message_body_visible%&"
12902 This variable contains the initial portion of a message's body while it is
12903 being delivered, and is intended mainly for use in filter files. The maximum
12904 number of characters of the body that are put into the variable is set by the
12905 &%message_body_visible%& configuration option; the default is 500.
12907 .oindex "&%message_body_newlines%&"
12908 By default, newlines are converted into spaces in &$message_body$&, to make it
12909 easier to search for phrases that might be split over a line break. However,
12910 this can be disabled by setting &%message_body_newlines%& to be true. Binary
12911 zeros are always converted into spaces.
12913 .tvar &$message_body_end$&
12914 .cindex "body of message" "expansion variable"
12915 .cindex "message body" "in expansion"
12916 This variable contains the final portion of a message's
12917 body while it is being delivered. The format and maximum size are as for
12920 .vitem &$message_body_size$&
12921 .cindex "body of message" "size"
12922 .cindex "message body" "size"
12923 .vindex "&$message_body_size$&"
12924 When a message is being delivered, this variable contains the size of the body
12925 in bytes. The count starts from the character after the blank line that
12926 separates the body from the header. Newlines are included in the count. See
12927 also &$message_size$&, &$body_linecount$&, and &$body_zerocount$&.
12929 If the spool file is wireformat
12930 (see the &%spool_wireformat%& main option)
12931 the CRLF line-terminators are included in the count.
12933 .vitem &$message_exim_id$&
12934 .vindex "&$message_exim_id$&"
12935 When a message is being received or delivered, this variable contains the
12936 unique message id that is generated and used by Exim to identify the message.
12937 An id is not created for a message until after its header has been successfully
12938 received. &*Note*&: This is &'not'& the contents of the &'Message-ID:'& header
12939 line; it is the local id that Exim assigns to the message, for example:
12940 &`1BXTIK-0001yO-VA`&.
12942 .tvar &$message_headers$&
12943 This variable contains a concatenation of all the header lines when a message
12944 is being processed, except for lines added by routers or transports. The header
12945 lines are separated by newline characters. Their contents are decoded in the
12946 same way as a header line that is inserted by &%bheader%&.
12948 .tvar &$message_headers_raw$&
12949 This variable is like &$message_headers$& except that no processing of the
12950 contents of header lines is done.
12952 .vitem &$message_id$&
12953 This is an old name for &$message_exim_id$&. It is now deprecated.
12955 .vitem &$message_linecount$&
12956 .vindex "&$message_linecount$&"
12957 This variable contains the total number of lines in the header and body of the
12958 message. Compare &$body_linecount$&, which is the count for the body only.
12959 During the DATA and content-scanning ACLs, &$message_linecount$& contains the
12960 number of lines received. Before delivery happens (that is, before filters,
12961 routers, and transports run) the count is increased to include the
12962 &'Received:'& header line that Exim standardly adds, and also any other header
12963 lines that are added by ACLs. The blank line that separates the message header
12964 from the body is not counted.
12966 As with the special case of &$message_size$&, during the expansion of the
12967 appendfile transport's maildir_tag option in maildir format, the value of
12968 &$message_linecount$& is the precise size of the number of newlines in the
12969 file that has been written (minus one for the blank line between the
12970 header and the body).
12972 Here is an example of the use of this variable in a DATA ACL:
12975 ${if <{250}{${eval:$message_linecount - $body_linecount}}}
12976 message = Too many lines in message header
12978 In the MAIL and RCPT ACLs, the value is zero because at that stage the
12979 message has not yet been received.
12981 This variable is not valid if the &%spool_wireformat%& option is used.
12983 .vitem &$message_size$&
12984 .cindex "size" "of message"
12985 .cindex "message" "size"
12986 .vindex "&$message_size$&"
12987 When a message is being processed, this variable contains its size in bytes. In
12988 most cases, the size includes those headers that were received with the
12989 message, but not those (such as &'Envelope-to:'&) that are added to individual
12990 deliveries as they are written. However, there is one special case: during the
12991 expansion of the &%maildir_tag%& option in the &(appendfile)& transport while
12992 doing a delivery in maildir format, the value of &$message_size$& is the
12993 precise size of the file that has been written. See also
12994 &$message_body_size$&, &$body_linecount$&, and &$body_zerocount$&.
12996 .cindex "RCPT" "value of &$message_size$&"
12997 While running a per message ACL (mail/rcpt/predata), &$message_size$&
12998 contains the size supplied on the MAIL command, or -1 if no size was given. The
12999 value may not, of course, be truthful.
13001 .vitem &$mime_anomaly_level$& &&&
13002 &$mime_anomaly_text$& &&&
13003 &$mime_boundary$& &&&
13004 &$mime_charset$& &&&
13005 &$mime_content_description$& &&&
13006 &$mime_content_disposition$& &&&
13007 &$mime_content_id$& &&&
13008 &$mime_content_size$& &&&
13009 &$mime_content_transfer_encoding$& &&&
13010 &$mime_content_type$& &&&
13011 &$mime_decoded_filename$& &&&
13012 &$mime_filename$& &&&
13013 &$mime_is_coverletter$& &&&
13014 &$mime_is_multipart$& &&&
13015 &$mime_is_rfc822$& &&&
13016 &$mime_part_count$&
13017 A number of variables whose names start with &$mime$& are
13018 available when Exim is compiled with the content-scanning extension. For
13019 details, see section &<<SECTscanmimepart>>&.
13021 .vitem "&$n0$& &-- &$n9$&"
13022 These variables are counters that can be incremented by means
13023 of the &%add%& command in filter files.
13025 .tvar &$original_domain$&
13026 .vindex "&$domain$&"
13027 When a top-level address is being processed for delivery, this contains the
13028 same value as &$domain$&. However, if a &"child"& address (for example,
13029 generated by an alias, forward, or filter file) is being processed, this
13030 variable contains the domain of the original address (lower cased). This
13031 differs from &$parent_domain$& only when there is more than one level of
13032 aliasing or forwarding. When more than one address is being delivered in a
13033 single transport run, &$original_domain$& is not set.
13035 If a new address is created by means of a &%deliver%& command in a system
13036 filter, it is set up with an artificial &"parent"& address. This has the local
13037 part &'system-filter'& and the default qualify domain.
13039 .tvar &$original_local_part$&
13040 .vindex "&$local_part$&"
13041 When a top-level address is being processed for delivery, this contains the
13042 same value as &$local_part$&, unless a prefix or suffix was removed from the
13043 local part, because &$original_local_part$& always contains the full local
13044 part. When a &"child"& address (for example, generated by an alias, forward, or
13045 filter file) is being processed, this variable contains the full local part of
13046 the original address.
13048 If the router that did the redirection processed the local part
13049 case-insensitively, the value in &$original_local_part$& is in lower case.
13050 This variable differs from &$parent_local_part$& only when there is more than
13051 one level of aliasing or forwarding. When more than one address is being
13052 delivered in a single transport run, &$original_local_part$& is not set.
13054 If a new address is created by means of a &%deliver%& command in a system
13055 filter, it is set up with an artificial &"parent"& address. This has the local
13056 part &'system-filter'& and the default qualify domain.
13058 .vitem &$originator_gid$&
13059 .cindex "gid (group id)" "of originating user"
13060 .cindex "sender" "gid"
13061 .vindex "&$caller_gid$&"
13062 .vindex "&$originator_gid$&"
13063 This variable contains the value of &$caller_gid$& that was set when the
13064 message was received. For messages received via the command line, this is the
13065 gid of the sending user. For messages received by SMTP over TCP/IP, this is
13066 normally the gid of the Exim user.
13068 .vitem &$originator_uid$&
13069 .cindex "uid (user id)" "of originating user"
13070 .cindex "sender" "uid"
13071 .vindex "&$caller_uid$&"
13072 .vindex "&$originator_uid$&"
13073 The value of &$caller_uid$& that was set when the message was received. For
13074 messages received via the command line, this is the uid of the sending user.
13075 For messages received by SMTP over TCP/IP, this is normally the uid of the Exim
13078 .tvar &$parent_domain$&
13079 This variable is similar to &$original_domain$& (see
13080 above), except that it refers to the immediately preceding parent address.
13082 .tvar &$parent_local_part$&
13083 This variable is similar to &$original_local_part$&
13084 (see above), except that it refers to the immediately preceding parent address.
13087 .cindex "pid (process id)" "of current process"
13089 This variable contains the current process id.
13091 .vitem &$pipe_addresses$&
13092 .cindex "filter" "transport filter"
13093 .cindex "transport" "filter"
13094 .vindex "&$pipe_addresses$&"
13095 This is not an expansion variable, but is mentioned here because the string
13096 &`$pipe_addresses`& is handled specially in the command specification for the
13097 &(pipe)& transport (chapter &<<CHAPpipetransport>>&) and in transport filters
13098 (described under &%transport_filter%& in chapter &<<CHAPtransportgeneric>>&).
13099 It cannot be used in general expansion strings, and provokes an &"unknown
13100 variable"& error if encountered.
13101 &*Note*&: This value permits data supplied by a potential attacker to
13102 be used in the command for a &(pipe)& transport.
13103 Such configurations should be carefully assessed for security vulnerbilities.
13105 .vitem &$primary_hostname$&
13106 .vindex "&$primary_hostname$&"
13107 This variable contains the value set by &%primary_hostname%& in the
13108 configuration file, or read by the &[uname()]& function. If &[uname()]& returns
13109 a single-component name, Exim calls &[gethostbyname()]& (or
13110 &[getipnodebyname()]& where available) in an attempt to acquire a fully
13111 qualified host name. See also &$smtp_active_hostname$&.
13114 .vitem &$proxy_external_address$& &&&
13115 &$proxy_external_port$& &&&
13116 &$proxy_local_address$& &&&
13117 &$proxy_local_port$& &&&
13119 These variables are only available when built with Proxy Protocol
13121 For details see chapter &<<SECTproxyInbound>>&.
13123 .vitem &$prdr_requested$&
13124 .cindex "PRDR" "variable for"
13125 This variable is set to &"yes"& if PRDR was requested by the client for the
13126 current message, otherwise &"no"&.
13128 .vitem &$prvscheck_address$& &&&
13129 &$prvscheck_keynum$& &&&
13130 &$prvscheck_result$&
13131 These variables are used in conjunction with the &%prvscheck%& expansion item,
13132 which is described in sections &<<SECTexpansionitems>>& and
13133 &<<SECTverifyPRVS>>&.
13135 .vitem &$qualify_domain$&
13136 .vindex "&$qualify_domain$&"
13137 The value set for the &%qualify_domain%& option in the configuration file.
13139 .vitem &$qualify_recipient$&
13140 .vindex "&$qualify_recipient$&"
13141 The value set for the &%qualify_recipient%& option in the configuration file,
13142 or if not set, the value of &$qualify_domain$&.
13144 .vitem &$queue_name$&
13145 .vindex &$queue_name$&
13146 .cindex "named queues" variable
13147 .cindex queues named
13148 The name of the spool queue in use; empty for the default queue.
13150 .vitem &$queue_size$&
13151 .vindex "&$queue_size$&"
13152 .cindex "queue" "size of"
13153 .cindex "spool" "number of messages"
13154 This variable contains the number of messages queued.
13155 It is evaluated on demand, but no more often than once every minute.
13156 If there is no daemon notifier socket open, the value will be
13161 .cindex router variables
13162 Values can be placed in these variables by the &%set%& option of a router.
13163 They can be given any name that starts with &$r_$&.
13164 The values persist for the address being handled through subsequent routers
13165 and the eventual transport.
13167 .vitem &$rcpt_count$&
13168 .vindex "&$rcpt_count$&"
13169 When a message is being received by SMTP, this variable contains the number of
13170 RCPT commands received for the current message. If this variable is used in a
13171 RCPT ACL, its value includes the current command.
13173 .vitem &$rcpt_defer_count$&
13174 .vindex "&$rcpt_defer_count$&"
13175 .cindex "4&'xx'& responses" "count of"
13176 When a message is being received by SMTP, this variable contains the number of
13177 RCPT commands in the current message that have previously been rejected with a
13178 temporary (4&'xx'&) response.
13180 .vitem &$rcpt_fail_count$&
13181 .vindex "&$rcpt_fail_count$&"
13182 When a message is being received by SMTP, this variable contains the number of
13183 RCPT commands in the current message that have previously been rejected with a
13184 permanent (5&'xx'&) response.
13186 .vitem &$received_count$&
13187 .vindex "&$received_count$&"
13188 This variable contains the number of &'Received:'& header lines in the message,
13189 including the one added by Exim (so its value is always greater than zero). It
13190 is available in the DATA ACL, the non-SMTP ACL, and while routing and
13193 .tvar &$received_for$&
13194 If there is only a single recipient address in an incoming message, this
13195 variable contains that address when the &'Received:'& header line is being
13196 built. The value is copied after recipient rewriting has happened, but before
13197 the &[local_scan()]& function is run.
13199 .vitem &$received_ip_address$& &&&
13201 .vindex "&$received_ip_address$&"
13202 .vindex "&$received_port$&"
13203 As soon as an Exim server starts processing an incoming TCP/IP connection, these
13204 variables are set to the address and port on the local IP interface.
13205 (The remote IP address and port are in
13206 &$sender_host_address$& and &$sender_host_port$&.) When testing with &%-bh%&,
13207 the port value is -1 unless it has been set using the &%-oMi%& command line
13210 As well as being useful in ACLs (including the &"connect"& ACL), these variable
13211 could be used, for example, to make the filename for a TLS certificate depend
13212 on which interface and/or port is being used for the incoming connection. The
13213 values of &$received_ip_address$& and &$received_port$& are saved with any
13214 messages that are received, thus making these variables available at delivery
13216 For outbound connections see &$sending_ip_address$&.
13218 .vitem &$received_protocol$&
13219 .vindex "&$received_protocol$&"
13220 When a message is being processed, this variable contains the name of the
13221 protocol by which it was received. Most of the names used by Exim are defined
13222 by RFCs 821, 2821, and 3848. They start with &"smtp"& (the client used HELO) or
13223 &"esmtp"& (the client used EHLO). This can be followed by &"s"& for secure
13224 (encrypted) and/or &"a"& for authenticated. Thus, for example, if the protocol
13225 is set to &"esmtpsa"&, the message was received over an encrypted SMTP
13226 connection and the client was successfully authenticated.
13228 Exim uses the protocol name &"smtps"& for the case when encryption is
13229 automatically set up on connection without the use of STARTTLS (see
13230 &%tls_on_connect_ports%&), and the client uses HELO to initiate the
13231 encrypted SMTP session. The name &"smtps"& is also used for the rare situation
13232 where the client initially uses EHLO, sets up an encrypted connection using
13233 STARTTLS, and then uses HELO afterwards.
13235 The &%-oMr%& option provides a way of specifying a custom protocol name for
13236 messages that are injected locally by trusted callers. This is commonly used to
13237 identify messages that are being re-injected after some kind of scanning.
13239 .vitem &$received_time$&
13240 .vindex "&$received_time$&"
13241 This variable contains the date and time when the current message was received,
13242 as a number of seconds since the start of the Unix epoch.
13244 .vitem &$recipient_data$&
13245 .vindex "&$recipient_data$&"
13246 This variable is set after an indexing lookup success in an ACL &%recipients%&
13247 condition. It contains the data from the lookup, and the value remains set
13248 until the next &%recipients%& test. Thus, you can do things like this:
13250 &`require recipients = cdb*@;/some/file`&
13251 &`deny `&&'some further test involving'& &`$recipient_data`&
13253 &*Warning*&: This variable is set only when a lookup is used as an indexing
13254 method in the address list, using the semicolon syntax as in the example above.
13255 The variable is not set for a lookup that is used as part of the string
13256 expansion that all such lists undergo before being interpreted.
13258 .vitem &$recipient_verify_failure$&
13259 .vindex "&$recipient_verify_failure$&"
13260 In an ACL, when a recipient verification fails, this variable contains
13261 information about the failure. It is set to one of the following words:
13264 &"qualify"&: The address was unqualified (no domain), and the message
13265 was neither local nor came from an exempted host.
13268 &"route"&: Routing failed.
13271 &"mail"&: Routing succeeded, and a callout was attempted; rejection occurred at
13272 or before the MAIL command (that is, on initial connection, HELO, or
13276 &"recipient"&: The RCPT command in a callout was rejected.
13279 &"postmaster"&: The postmaster check in a callout was rejected.
13282 The main use of this variable is expected to be to distinguish between
13283 rejections of MAIL and rejections of RCPT.
13285 .tvar &$recipients$&
13286 This variable contains a list of envelope recipients for a message. A comma and
13287 a space separate the addresses in the replacement text. However, the variable
13288 is not generally available, to prevent exposure of Bcc recipients in
13289 unprivileged users' filter files. You can use &$recipients$& only in these
13293 In a system filter file.
13295 In the ACLs associated with the DATA command and with non-SMTP messages, that
13296 is, the ACLs defined by &%acl_smtp_predata%&, &%acl_smtp_data%&,
13297 &%acl_smtp_mime%&, &%acl_not_smtp_start%&, &%acl_not_smtp%&, and
13298 &%acl_not_smtp_mime%&.
13300 From within a &[local_scan()]& function.
13304 .vitem &$recipients_count$&
13305 .vindex "&$recipients_count$&"
13306 When a message is being processed, this variable contains the number of
13307 envelope recipients that came with the message. Duplicates are not excluded
13308 from the count. While a message is being received over SMTP, the number
13309 increases for each accepted recipient. It can be referenced in an ACL.
13312 .vitem &$regex_match_string$&
13313 .vindex "&$regex_match_string$&"
13314 This variable is set to contain the matching regular expression after a
13315 &%regex%& ACL condition has matched (see section &<<SECTscanregex>>&).
13317 .vitem "&$regex1$&, &$regex2$&, etc"
13318 .cindex "regex submatch variables (&$1regex$& &$2regex$& etc)"
13319 When a &%regex%& or &%mime_regex%& ACL condition succeeds,
13320 these variables contain the
13321 captured substrings identified by the regular expression.
13322 If the subject string was tainted then so will any captured substring.
13325 .tvar &$reply_address$&
13326 When a message is being processed, this variable contains the contents of the
13327 &'Reply-To:'& header line if one exists and it is not empty, or otherwise the
13328 contents of the &'From:'& header line. Apart from the removal of leading
13329 white space, the value is not processed in any way. In particular, no RFC 2047
13330 decoding or character code translation takes place.
13332 .vitem &$return_path$&
13333 .vindex "&$return_path$&"
13334 When a message is being delivered, this variable contains the return path &--
13335 the sender field that will be sent as part of the envelope. It is not enclosed
13336 in <> characters. At the start of routing an address, &$return_path$& has the
13337 same value as &$sender_address$&, but if, for example, an incoming message to a
13338 mailing list has been expanded by a router which specifies a different address
13339 for bounce messages, &$return_path$& subsequently contains the new bounce
13340 address, whereas &$sender_address$& always contains the original sender address
13341 that was received with the message. In other words, &$sender_address$& contains
13342 the incoming envelope sender, and &$return_path$& contains the outgoing
13345 .vitem &$return_size_limit$&
13346 .vindex "&$return_size_limit$&"
13347 This is an obsolete name for &$bounce_return_size_limit$&.
13349 .vitem &$router_name$&
13350 .cindex "router" "name"
13351 .cindex "name" "of router"
13352 .vindex "&$router_name$&"
13353 During the running of a router this variable contains its name.
13356 .cindex "return code" "from &%run%& expansion"
13357 .vindex "&$runrc$&"
13358 This variable contains the return code from a command that is run by the
13359 &%${run...}%& expansion item. &*Warning*&: In a router or transport, you cannot
13360 assume the order in which option values are expanded, except for those
13361 preconditions whose order of testing is documented. Therefore, you cannot
13362 reliably expect to set &$runrc$& by the expansion of one option, and use it in
13365 .vitem &$self_hostname$&
13366 .oindex "&%self%&" "value of host name"
13367 .vindex "&$self_hostname$&"
13368 When an address is routed to a supposedly remote host that turns out to be the
13369 local host, what happens is controlled by the &%self%& generic router option.
13370 One of its values causes the address to be passed to another router. When this
13371 happens, &$self_hostname$& is set to the name of the local host that the
13372 original router encountered. In other circumstances its contents are null.
13374 .tvar &$sender_address$&
13375 When a message is being processed, this variable contains the sender's address
13376 that was received in the message's envelope. The case of letters in the address
13377 is retained, in both the local part and the domain. For bounce messages, the
13378 value of this variable is the empty string. See also &$return_path$&.
13380 .vitem &$sender_address_data$&
13381 .vindex "&$address_data$&"
13382 .vindex "&$sender_address_data$&"
13383 If &$address_data$& is set when the routers are called from an ACL to verify a
13384 sender address, the final value is preserved in &$sender_address_data$&, to
13385 distinguish it from data from a recipient address. The value does not persist
13386 after the end of the current ACL statement. If you want to preserve it for
13387 longer, you can save it in an ACL variable.
13389 .tvar &$sender_address_domain$&
13390 The domain portion of &$sender_address$&.
13392 .tvar &$sender_address_local_part$&
13393 The local part portion of &$sender_address$&.
13395 .vitem &$sender_data$&
13396 .vindex "&$sender_data$&"
13397 This variable is set after a lookup success in an ACL &%senders%& condition or
13398 in a router &%senders%& option. It contains the data from the lookup, and the
13399 value remains set until the next &%senders%& test. Thus, you can do things like
13402 &`require senders = cdb*@;/some/file`&
13403 &`deny `&&'some further test involving'& &`$sender_data`&
13405 &*Warning*&: This variable is set only when a lookup is used as an indexing
13406 method in the address list, using the semicolon syntax as in the example above.
13407 The variable is not set for a lookup that is used as part of the string
13408 expansion that all such lists undergo before being interpreted.
13410 .vitem &$sender_fullhost$&
13411 .vindex "&$sender_fullhost$&"
13412 When a message is received from a remote host, this variable contains the host
13413 name and IP address in a single string. It ends with the IP address in square
13414 brackets, followed by a colon and a port number if the logging of ports is
13415 enabled. The format of the rest of the string depends on whether the host
13416 issued a HELO or EHLO SMTP command, and whether the host name was verified by
13417 looking up its IP address. (Looking up the IP address can be forced by the
13418 &%host_lookup%& option, independent of verification.) A plain host name at the
13419 start of the string is a verified host name; if this is not present,
13420 verification either failed or was not requested. A host name in parentheses is
13421 the argument of a HELO or EHLO command. This is omitted if it is identical to
13422 the verified host name or to the host's IP address in square brackets.
13424 .vitem &$sender_helo_dnssec$&
13425 .vindex "&$sender_helo_dnssec$&"
13426 This boolean variable is true if a successful HELO verification was
13427 .cindex "DNS" "DNSSEC"
13428 done using DNS information the resolver library stated was authenticated data.
13430 .tvar &$sender_helo_name$&
13431 When a message is received from a remote host that has issued a HELO or EHLO
13432 command, the argument of that command is placed in this variable. It is also
13433 set if HELO or EHLO is used when a message is received using SMTP locally via
13434 the &%-bs%& or &%-bS%& options.
13436 .vitem &$sender_host_address$&
13437 .vindex "&$sender_host_address$&"
13438 When a message is received from a remote host using SMTP,
13439 this variable contains that
13440 host's IP address. For locally non-SMTP submitted messages, it is empty.
13442 .vitem &$sender_host_authenticated$&
13443 .vindex "&$sender_host_authenticated$&"
13444 This variable contains the name (not the public name) of the authenticator
13445 driver that successfully authenticated the client from which the message was
13446 received. It is empty if there was no successful authentication. See also
13447 &$authenticated_id$&.
13449 .vitem &$sender_host_dnssec$&
13450 .vindex "&$sender_host_dnssec$&"
13451 If an attempt to populate &$sender_host_name$& has been made
13452 (by reference, &%hosts_lookup%& or
13453 otherwise) then this boolean will have been set true if, and only if, the
13454 resolver library states that both
13455 the reverse and forward DNS were authenticated data. At all
13456 other times, this variable is false.
13458 .cindex "DNS" "DNSSEC"
13459 It is likely that you will need to coerce DNSSEC support on in the resolver
13460 library, by setting:
13465 In addition, on Linux with glibc 2.31 or newer the resolver library will
13466 default to stripping out a successful validation status.
13467 This will break a previously working Exim installation.
13468 Provided that you do trust the resolver (ie, is on localhost) you can tell
13469 glibc to pass through any successful validation with a new option in
13470 &_/etc/resolv.conf_&:
13475 Exim does not perform DNSSEC validation itself, instead leaving that to a
13476 validating resolver (e.g. unbound, or bind with suitable configuration).
13478 If you have changed &%host_lookup_order%& so that &`bydns`& is not the first
13479 mechanism in the list, then this variable will be false.
13481 This requires that your system resolver library support EDNS0 (and that
13482 DNSSEC flags exist in the system headers). If the resolver silently drops
13483 all EDNS0 options, then this will have no effect. OpenBSD's asr resolver
13484 is known to currently ignore EDNS0, documented in CAVEATS of asr_run(3).
13487 .tvar &$sender_host_name$&
13488 When a message is received from a remote host, this variable contains the
13489 host's name as obtained by looking up its IP address. For messages received by
13490 other means, this variable is empty.
13492 .vindex "&$host_lookup_failed$&"
13493 If the host name has not previously been looked up, a reference to
13494 &$sender_host_name$& triggers a lookup (for messages from remote hosts).
13495 A looked up name is accepted only if it leads back to the original IP address
13496 via a forward lookup. If either the reverse or the forward lookup fails to find
13497 any data, or if the forward lookup does not yield the original IP address,
13498 &$sender_host_name$& remains empty, and &$host_lookup_failed$& is set to &"1"&.
13500 .vindex "&$host_lookup_deferred$&"
13501 However, if either of the lookups cannot be completed (for example, there is a
13502 DNS timeout), &$host_lookup_deferred$& is set to &"1"&, and
13503 &$host_lookup_failed$& remains set to &"0"&.
13505 Once &$host_lookup_failed$& is set to &"1"&, Exim does not try to look up the
13506 host name again if there is a subsequent reference to &$sender_host_name$&
13507 in the same Exim process, but it does try again if &$host_lookup_deferred$&
13510 Exim does not automatically look up every calling host's name. If you want
13511 maximum efficiency, you should arrange your configuration so that it avoids
13512 these lookups altogether. The lookup happens only if one or more of the
13513 following are true:
13516 A string containing &$sender_host_name$& is expanded.
13518 The calling host matches the list in &%host_lookup%&. In the default
13519 configuration, this option is set to *, so it must be changed if lookups are
13520 to be avoided. (In the code, the default for &%host_lookup%& is unset.)
13522 Exim needs the host name in order to test an item in a host list. The items
13523 that require this are described in sections &<<SECThoslispatnam>>& and
13524 &<<SECThoslispatnamsk>>&.
13526 The calling host matches &%helo_try_verify_hosts%& or &%helo_verify_hosts%&.
13527 In this case, the host name is required to compare with the name quoted in any
13528 EHLO or HELO commands that the client issues.
13530 The remote host issues a EHLO or HELO command that quotes one of the
13531 domains in &%helo_lookup_domains%&. The default value of this option is
13532 . ==== As this is a nested list, any displays it contains must be indented
13533 . ==== as otherwise they are too far to the left.
13535 helo_lookup_domains = @ : @[]
13537 which causes a lookup if a remote host (incorrectly) gives the server's name or
13538 IP address in an EHLO or HELO command.
13542 .vitem &$sender_host_port$&
13543 .vindex "&$sender_host_port$&"
13544 When a message is received from a remote host, this variable contains the port
13545 number that was used on the remote host.
13547 .vitem &$sender_ident$&
13548 .vindex "&$sender_ident$&"
13549 When a message is received from a remote host, this variable contains the
13550 identification received in response to an RFC 1413 request. When a message has
13551 been received locally, this variable contains the login name of the user that
13554 .vitem &$sender_rate_$&&'xxx'&
13555 A number of variables whose names begin &$sender_rate_$& are set as part of the
13556 &%ratelimit%& ACL condition. Details are given in section
13557 &<<SECTratelimiting>>&.
13559 .vitem &$sender_rcvhost$&
13560 .cindex "DNS" "reverse lookup"
13561 .cindex "reverse DNS lookup"
13562 .vindex "&$sender_rcvhost$&"
13563 This is provided specifically for use in &'Received:'& headers. It starts with
13564 either the verified host name (as obtained from a reverse DNS lookup) or, if
13565 there is no verified host name, the IP address in square brackets. After that
13566 there may be text in parentheses. When the first item is a verified host name,
13567 the first thing in the parentheses is the IP address in square brackets,
13568 followed by a colon and a port number if port logging is enabled. When the
13569 first item is an IP address, the port is recorded as &"port=&'xxxx'&"& inside
13572 There may also be items of the form &"helo=&'xxxx'&"& if HELO or EHLO
13573 was used and its argument was not identical to the real host name or IP
13574 address, and &"ident=&'xxxx'&"& if an RFC 1413 ident string is available. If
13575 all three items are present in the parentheses, a newline and tab are inserted
13576 into the string, to improve the formatting of the &'Received:'& header.
13578 .vitem &$sender_verify_failure$&
13579 .vindex "&$sender_verify_failure$&"
13580 In an ACL, when a sender verification fails, this variable contains information
13581 about the failure. The details are the same as for
13582 &$recipient_verify_failure$&.
13584 .vitem &$sending_ip_address$&
13585 .vindex "&$sending_ip_address$&"
13586 This variable is set whenever an outgoing SMTP connection to another host has
13587 been set up. It contains the IP address of the local interface that is being
13588 used. This is useful if a host that has more than one IP address wants to take
13589 on different personalities depending on which one is being used. For incoming
13590 connections, see &$received_ip_address$&.
13592 .vitem &$sending_port$&
13593 .vindex "&$sending_port$&"
13594 This variable is set whenever an outgoing SMTP connection to another host has
13595 been set up. It contains the local port that is being used. For incoming
13596 connections, see &$received_port$&.
13598 .vitem &$smtp_active_hostname$&
13599 .vindex "&$smtp_active_hostname$&"
13600 During an incoming SMTP session, this variable contains the value of the active
13601 host name, as specified by the &%smtp_active_hostname%& option. The value of
13602 &$smtp_active_hostname$& is saved with any message that is received, so its
13603 value can be consulted during routing and delivery.
13605 .tvar &$smtp_command$&
13606 During the processing of an incoming SMTP command, this variable contains the
13607 entire command. This makes it possible to distinguish between HELO and EHLO in
13608 the HELO ACL, and also to distinguish between commands such as these:
13613 For a MAIL command, extra parameters such as SIZE can be inspected. For a RCPT
13614 command, the address in &$smtp_command$& is the original address before any
13615 rewriting, whereas the values in &$local_part$& and &$domain$& are taken from
13616 the address after SMTP-time rewriting.
13618 .tvar &$smtp_command_argument$&
13619 .cindex "SMTP" "command, argument for"
13620 While an ACL is running to check an SMTP command, this variable contains the
13621 argument, that is, the text that follows the command name, with leading white
13622 space removed. Following the introduction of &$smtp_command$&, this variable is
13623 somewhat redundant, but is retained for backwards compatibility.
13625 .vitem &$smtp_command_history$&
13626 .cindex SMTP "command history"
13627 .vindex "&$smtp_command_history$&"
13628 A comma-separated list (with no whitespace) of the most-recent SMTP commands
13629 received, in time-order left to right. Only a limited number of commands
13632 .vitem &$smtp_count_at_connection_start$&
13633 .vindex "&$smtp_count_at_connection_start$&"
13634 This variable is set greater than zero only in processes spawned by the Exim
13635 daemon for handling incoming SMTP connections. The name is deliberately long,
13636 in order to emphasize what the contents are. When the daemon accepts a new
13637 connection, it increments this variable. A copy of the variable is passed to
13638 the child process that handles the connection, but its value is fixed, and
13639 never changes. It is only an approximation of how many incoming connections
13640 there actually are, because many other connections may come and go while a
13641 single connection is being processed. When a child process terminates, the
13642 daemon decrements its copy of the variable.
13644 .vitem "&$sn0$& &-- &$sn9$&"
13645 These variables are copies of the values of the &$n0$& &-- &$n9$& accumulators
13646 that were current at the end of the system filter file. This allows a system
13647 filter file to set values that can be tested in users' filter files. For
13648 example, a system filter could set a value indicating how likely it is that a
13649 message is junk mail.
13651 .vitem &$spam_score$& &&&
13652 &$spam_score_int$& &&&
13654 &$spam_report$& &&&
13656 A number of variables whose names start with &$spam$& are available when Exim
13657 is compiled with the content-scanning extension. For details, see section
13658 &<<SECTscanspamass>>&.
13660 .vitem &$spf_header_comment$& &&&
13661 &$spf_received$& &&&
13663 &$spf_result_guessed$& &&&
13664 &$spf_smtp_comment$&
13665 These variables are only available if Exim is built with SPF support.
13666 For details see section &<<SECSPF>>&.
13668 .vitem &$spool_directory$&
13669 .vindex "&$spool_directory$&"
13670 The name of Exim's spool directory.
13672 .vitem &$spool_inodes$&
13673 .vindex "&$spool_inodes$&"
13674 The number of free inodes in the disk partition where Exim's spool files are
13675 being written. The value is recalculated whenever the variable is referenced.
13676 If the relevant file system does not have the concept of inodes, the value of
13677 is -1. See also the &%check_spool_inodes%& option.
13679 .vitem &$spool_space$&
13680 .vindex "&$spool_space$&"
13681 The amount of free space (as a number of kilobytes) in the disk partition where
13682 Exim's spool files are being written. The value is recalculated whenever the
13683 variable is referenced. If the operating system does not have the ability to
13684 find the amount of free space (only true for experimental systems), the space
13685 value is -1. For example, to check in an ACL that there is at least 50
13686 megabytes free on the spool, you could write:
13688 condition = ${if > {$spool_space}{50000}}
13690 See also the &%check_spool_space%& option.
13693 .vitem &$thisaddress$&
13694 .vindex "&$thisaddress$&"
13695 This variable is set only during the processing of the &%foranyaddress%&
13696 command in a filter file. Its use is explained in the description of that
13697 command, which can be found in the separate document entitled &'Exim's
13698 interfaces to mail filtering'&.
13700 .vitem &$tls_in_bits$&
13701 .vindex "&$tls_in_bits$&"
13702 Contains an approximation of the TLS cipher's bit-strength
13703 on the inbound connection; the meaning of
13704 this depends upon the TLS implementation used.
13705 If TLS has not been negotiated, the value will be 0.
13706 The value of this is automatically fed into the Cyrus SASL authenticator
13707 when acting as a server, to specify the "external SSF" (a SASL term).
13709 The deprecated &$tls_bits$& variable refers to the inbound side
13710 except when used in the context of an outbound SMTP delivery, when it refers to
13713 .vitem &$tls_out_bits$&
13714 .vindex "&$tls_out_bits$&"
13715 Contains an approximation of the TLS cipher's bit-strength
13716 on an outbound SMTP connection; the meaning of
13717 this depends upon the TLS implementation used.
13718 If TLS has not been negotiated, the value will be 0.
13720 .vitem &$tls_in_ourcert$&
13721 .vindex "&$tls_in_ourcert$&"
13722 .cindex certificate variables
13723 This variable refers to the certificate presented to the peer of an
13724 inbound connection when the message was received.
13725 It is only useful as the argument of a
13726 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13727 or a &%def%& condition.
13729 &*Note*&: Under versions of OpenSSL preceding 1.1.1,
13730 when a list of more than one
13731 file is used for &%tls_certificate%&, this variable is not reliable.
13732 The macro "_TLS_BAD_MULTICERT_IN_OURCERT" will be defined for those versions.
13734 .vitem &$tls_in_peercert$&
13735 .vindex "&$tls_in_peercert$&"
13736 This variable refers to the certificate presented by the peer of an
13737 inbound connection when the message was received.
13738 It is only useful as the argument of a
13739 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13740 or a &%def%& condition.
13741 If certificate verification fails it may refer to a failing chain element
13742 which is not the leaf.
13744 .vitem &$tls_out_ourcert$&
13745 .vindex "&$tls_out_ourcert$&"
13746 This variable refers to the certificate presented to the peer of an
13747 outbound connection. It is only useful as the argument of a
13748 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13749 or a &%def%& condition.
13751 .vitem &$tls_out_peercert$&
13752 .vindex "&$tls_out_peercert$&"
13753 This variable refers to the certificate presented by the peer of an
13754 outbound connection. It is only useful as the argument of a
13755 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13756 or a &%def%& condition.
13757 If certificate verification fails it may refer to a failing chain element
13758 which is not the leaf.
13760 .vitem &$tls_in_certificate_verified$&
13761 .vindex "&$tls_in_certificate_verified$&"
13762 This variable is set to &"1"& if a TLS certificate was verified when the
13763 message was received, and &"0"& otherwise.
13765 The deprecated &$tls_certificate_verified$& variable refers to the inbound side
13766 except when used in the context of an outbound SMTP delivery, when it refers to
13769 .vitem &$tls_out_certificate_verified$&
13770 .vindex "&$tls_out_certificate_verified$&"
13771 This variable is set to &"1"& if a TLS certificate was verified when an
13772 outbound SMTP connection was made,
13773 and &"0"& otherwise.
13775 .vitem &$tls_in_cipher$&
13776 .vindex "&$tls_in_cipher$&"
13777 .vindex "&$tls_cipher$&"
13778 When a message is received from a remote host over an encrypted SMTP
13779 connection, this variable is set to the cipher suite that was negotiated, for
13780 example DES-CBC3-SHA. In other circumstances, in particular, for message
13781 received over unencrypted connections, the variable is empty. Testing
13782 &$tls_in_cipher$& for emptiness is one way of distinguishing between encrypted and
13783 non-encrypted connections during ACL processing.
13785 The deprecated &$tls_cipher$& variable is the same as &$tls_in_cipher$& during message reception,
13786 but in the context of an outward SMTP delivery taking place via the &(smtp)& transport
13787 becomes the same as &$tls_out_cipher$&.
13789 .vitem &$tls_in_cipher_std$&
13790 .vindex "&$tls_in_cipher_std$&"
13791 As above, but returning the RFC standard name for the cipher suite.
13793 .vitem &$tls_out_cipher$&
13794 .vindex "&$tls_out_cipher$&"
13796 cleared before any outgoing SMTP connection is made,
13797 and then set to the outgoing cipher suite if one is negotiated. See chapter
13798 &<<CHAPTLS>>& for details of TLS support and chapter &<<CHAPsmtptrans>>& for
13799 details of the &(smtp)& transport.
13801 .vitem &$tls_out_cipher_std$&
13802 .vindex "&$tls_out_cipher_std$&"
13803 As above, but returning the RFC standard name for the cipher suite.
13805 .vitem &$tls_out_dane$&
13806 .vindex &$tls_out_dane$&
13807 DANE active status. See section &<<SECDANE>>&.
13809 .vitem &$tls_in_ocsp$&
13810 .vindex "&$tls_in_ocsp$&"
13811 When a message is received from a remote client connection
13812 the result of any OCSP request from the client is encoded in this variable:
13814 0 OCSP proof was not requested (default value)
13815 1 No response to request
13816 2 Response not verified
13817 3 Verification failed
13818 4 Verification succeeded
13821 .vitem &$tls_out_ocsp$&
13822 .vindex "&$tls_out_ocsp$&"
13823 When a message is sent to a remote host connection
13824 the result of any OCSP request made is encoded in this variable.
13825 See &$tls_in_ocsp$& for values.
13827 .vitem &$tls_in_peerdn$&
13828 .vindex "&$tls_in_peerdn$&"
13829 .vindex "&$tls_peerdn$&"
13830 .cindex certificate "extracting fields"
13831 When a message is received from a remote host over an encrypted SMTP
13832 connection, and Exim is configured to request a certificate from the client,
13833 the value of the Distinguished Name of the certificate is made available in the
13834 &$tls_in_peerdn$& during subsequent processing.
13835 If certificate verification fails it may refer to a failing chain element
13836 which is not the leaf.
13838 The deprecated &$tls_peerdn$& variable refers to the inbound side
13839 except when used in the context of an outbound SMTP delivery, when it refers to
13842 .vitem &$tls_out_peerdn$&
13843 .vindex "&$tls_out_peerdn$&"
13844 When a message is being delivered to a remote host over an encrypted SMTP
13845 connection, and Exim is configured to request a certificate from the server,
13846 the value of the Distinguished Name of the certificate is made available in the
13847 &$tls_out_peerdn$& during subsequent processing.
13848 If certificate verification fails it may refer to a failing chain element
13849 which is not the leaf.
13852 .vitem &$tls_in_resumption$& &&&
13853 &$tls_out_resumption$&
13854 .vindex &$tls_in_resumption$&
13855 .vindex &$tls_out_resumption$&
13856 .cindex TLS resumption
13857 Observability for TLS session resumption. See &<<SECTresumption>>& for details.
13860 .tvar &$tls_in_sni$&
13861 .vindex "&$tls_sni$&"
13862 .cindex "TLS" "Server Name Indication"
13864 .cindex SNI "observability on server"
13865 When a TLS session is being established, if the client sends the Server
13866 Name Indication extension, the value will be placed in this variable.
13867 If the variable appears in &%tls_certificate%& then this option and
13868 some others, described in &<<SECTtlssni>>&,
13869 will be re-expanded early in the TLS session, to permit
13870 a different certificate to be presented (and optionally a different key to be
13871 used) to the client, based upon the value of the SNI extension.
13873 The deprecated &$tls_sni$& variable refers to the inbound side
13874 except when used in the context of an outbound SMTP delivery, when it refers to
13877 .vitem &$tls_out_sni$&
13878 .vindex "&$tls_out_sni$&"
13879 .cindex "TLS" "Server Name Indication"
13881 .cindex SNI "observability in client"
13883 SMTP deliveries, this variable reflects the value of the &%tls_sni%& option on
13886 .vitem &$tls_out_tlsa_usage$&
13887 .vindex &$tls_out_tlsa_usage$&
13888 Bitfield of TLSA record types found. See section &<<SECDANE>>&.
13890 .vitem &$tls_in_ver$&
13891 .vindex "&$tls_in_ver$&"
13892 When a message is received from a remote host over an encrypted SMTP connection
13893 this variable is set to the protocol version, eg &'TLS1.2'&.
13895 .vitem &$tls_out_ver$&
13896 .vindex "&$tls_out_ver$&"
13897 When a message is being delivered to a remote host over an encrypted SMTP connection
13898 this variable is set to the protocol version.
13901 .vitem &$tod_bsdinbox$&
13902 .vindex "&$tod_bsdinbox$&"
13903 The time of day and the date, in the format required for BSD-style mailbox
13904 files, for example: Thu Oct 17 17:14:09 1995.
13906 .vitem &$tod_epoch$&
13907 .vindex "&$tod_epoch$&"
13908 The time and date as a number of seconds since the start of the Unix epoch.
13910 .vitem &$tod_epoch_l$&
13911 .vindex "&$tod_epoch_l$&"
13912 The time and date as a number of microseconds since the start of the Unix epoch.
13914 .vitem &$tod_full$&
13915 .vindex "&$tod_full$&"
13916 A full version of the time and date, for example: Wed, 16 Oct 1995 09:51:40
13917 +0100. The timezone is always given as a numerical offset from UTC, with
13918 positive values used for timezones that are ahead (east) of UTC, and negative
13919 values for those that are behind (west).
13922 .vindex "&$tod_log$&"
13923 The time and date in the format used for writing Exim's log files, for example:
13924 1995-10-12 15:32:29, but without a timezone.
13926 .vitem &$tod_logfile$&
13927 .vindex "&$tod_logfile$&"
13928 This variable contains the date in the format yyyymmdd. This is the format that
13929 is used for datestamping log files when &%log_file_path%& contains the &`%D`&
13932 .vitem &$tod_zone$&
13933 .vindex "&$tod_zone$&"
13934 This variable contains the numerical value of the local timezone, for example:
13937 .vitem &$tod_zulu$&
13938 .vindex "&$tod_zulu$&"
13939 This variable contains the UTC date and time in &"Zulu"& format, as specified
13940 by ISO 8601, for example: 20030221154023Z.
13942 .vitem &$transport_name$&
13943 .cindex "transport" "name"
13944 .cindex "name" "of transport"
13945 .vindex "&$transport_name$&"
13946 During the running of a transport, this variable contains its name.
13949 .vindex "&$value$&"
13950 This variable contains the result of an expansion lookup, extraction operation,
13951 or external command, as described above. It is also used during a
13952 &*reduce*& expansion.
13954 .vitem &$verify_mode$&
13955 .vindex "&$verify_mode$&"
13956 While a router or transport is being run in verify mode or for cutthrough delivery,
13957 contains "S" for sender-verification or "R" for recipient-verification.
13960 .vitem &$version_number$&
13961 .vindex "&$version_number$&"
13962 The version number of Exim. Same as &$exim_version$&, may be overridden
13963 by the &%exim_version%& main config option.
13965 .vitem &$warn_message_delay$&
13966 .vindex "&$warn_message_delay$&"
13967 This variable is set only during the creation of a message warning about a
13968 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
13970 .vitem &$warn_message_recipients$&
13971 .vindex "&$warn_message_recipients$&"
13972 This variable is set only during the creation of a message warning about a
13973 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
13979 . ////////////////////////////////////////////////////////////////////////////
13980 . ////////////////////////////////////////////////////////////////////////////
13982 .chapter "Embedded Perl" "CHAPperl"
13983 .scindex IIDperl "Perl" "calling from Exim"
13984 Exim can be built to include an embedded Perl interpreter. When this is done,
13985 Perl subroutines can be called as part of the string expansion process. To make
13986 use of the Perl support, you need version 5.004 or later of Perl installed on
13987 your system. To include the embedded interpreter in the Exim binary, include
13992 in your &_Local/Makefile_& and then build Exim in the normal way.
13995 .section "Setting up so Perl can be used" "SECID85"
13996 .oindex "&%perl_startup%&"
13997 Access to Perl subroutines is via a global configuration option called
13998 &%perl_startup%& and an expansion string operator &%${perl ...}%&. If there is
13999 no &%perl_startup%& option in the Exim configuration file then no Perl
14000 interpreter is started and there is almost no overhead for Exim (since none of
14001 the Perl library will be paged in unless used). If there is a &%perl_startup%&
14002 option then the associated value is taken to be Perl code which is executed in
14003 a newly created Perl interpreter.
14005 The value of &%perl_startup%& is not expanded in the Exim sense, so you do not
14006 need backslashes before any characters to escape special meanings. The option
14007 should usually be something like
14009 perl_startup = do '/etc/exim.pl'
14011 where &_/etc/exim.pl_& is Perl code which defines any subroutines you want to
14012 use from Exim. Exim can be configured either to start up a Perl interpreter as
14013 soon as it is entered, or to wait until the first time it is needed. Starting
14014 the interpreter at the beginning ensures that it is done while Exim still has
14015 its setuid privilege, but can impose an unnecessary overhead if Perl is not in
14016 fact used in a particular run. Also, note that this does not mean that Exim is
14017 necessarily running as root when Perl is called at a later time. By default,
14018 the interpreter is started only when it is needed, but this can be changed in
14022 .oindex "&%perl_at_start%&"
14023 Setting &%perl_at_start%& (a boolean option) in the configuration requests
14024 a startup when Exim is entered.
14026 The command line option &%-ps%& also requests a startup when Exim is entered,
14027 overriding the setting of &%perl_at_start%&.
14030 There is also a command line option &%-pd%& (for delay) which suppresses the
14031 initial startup, even if &%perl_at_start%& is set.
14034 .oindex "&%perl_taintmode%&"
14035 .cindex "Perl" "taintmode"
14036 To provide more security executing Perl code via the embedded Perl
14037 interpreter, the &%perl_taintmode%& option can be set. This enables the
14038 taint mode of the Perl interpreter. You are encouraged to set this
14039 option to a true value. To avoid breaking existing installations, it
14042 &*Note*&: This is entirely separate from Exim's tainted-data tracking.
14045 .section "Calling Perl subroutines" "SECID86"
14046 When the configuration file includes a &%perl_startup%& option you can make use
14047 of the string expansion item to call the Perl subroutines that are defined
14048 by the &%perl_startup%& code. The operator is used in any of the following
14052 ${perl{foo}{argument}}
14053 ${perl{foo}{argument1}{argument2} ... }
14055 which calls the subroutine &%foo%& with the given arguments. A maximum of eight
14056 arguments may be passed. Passing more than this results in an expansion failure
14057 with an error message of the form
14059 Too many arguments passed to Perl subroutine "foo" (max is 8)
14061 The return value of the Perl subroutine is evaluated in a scalar context before
14062 it is passed back to Exim to be inserted into the expanded string. If the
14063 return value is &'undef'&, the expansion is forced to fail in the same way as
14064 an explicit &"fail"& on an &%if%& or &%lookup%& item. If the subroutine aborts
14065 by obeying Perl's &%die%& function, the expansion fails with the error message
14066 that was passed to &%die%&.
14069 .section "Calling Exim functions from Perl" "SECID87"
14070 Within any Perl code called from Exim, the function &'Exim::expand_string()'&
14071 is available to call back into Exim's string expansion function. For example,
14074 my $lp = Exim::expand_string('$local_part');
14076 makes the current Exim &$local_part$& available in the Perl variable &$lp$&.
14077 Note those are single quotes and not double quotes to protect against
14078 &$local_part$& being interpolated as a Perl variable.
14080 If the string expansion is forced to fail by a &"fail"& item, the result of
14081 &'Exim::expand_string()'& is &%undef%&. If there is a syntax error in the
14082 expansion string, the Perl call from the original expansion string fails with
14083 an appropriate error message, in the same way as if &%die%& were used.
14085 .cindex "debugging" "from embedded Perl"
14086 .cindex "log" "writing from embedded Perl"
14087 Two other Exim functions are available for use from within Perl code.
14088 &'Exim::debug_write()'& writes a string to the standard error stream if Exim's
14089 debugging is enabled. If you want a newline at the end, you must supply it.
14090 &'Exim::log_write()'& writes a string to Exim's main log, adding a leading
14091 timestamp. In this case, you should not supply a terminating newline.
14094 .section "Use of standard output and error by Perl" "SECID88"
14095 .cindex "Perl" "standard output and error"
14096 You should not write to the standard error or output streams from within your
14097 Perl code, as it is not defined how these are set up. In versions of Exim
14098 before 4.50, it is possible for the standard output or error to refer to the
14099 SMTP connection during message reception via the daemon. Writing to this stream
14100 is certain to cause chaos. From Exim 4.50 onwards, the standard output and
14101 error streams are connected to &_/dev/null_& in the daemon. The chaos is
14102 avoided, but the output is lost.
14104 .cindex "Perl" "use of &%warn%&"
14105 The Perl &%warn%& statement writes to the standard error stream by default.
14106 Calls to &%warn%& may be embedded in Perl modules that you use, but over which
14107 you have no control. When Exim starts up the Perl interpreter, it arranges for
14108 output from the &%warn%& statement to be written to the Exim main log. You can
14109 change this by including appropriate Perl magic somewhere in your Perl code.
14110 For example, to discard &%warn%& output completely, you need this:
14112 $SIG{__WARN__} = sub { };
14114 Whenever a &%warn%& is obeyed, the anonymous subroutine is called. In this
14115 example, the code for the subroutine is empty, so it does nothing, but you can
14116 include any Perl code that you like. The text of the &%warn%& message is passed
14117 as the first subroutine argument.
14121 . ////////////////////////////////////////////////////////////////////////////
14122 . ////////////////////////////////////////////////////////////////////////////
14124 .chapter "Starting the daemon and the use of network interfaces" &&&
14125 "CHAPinterfaces" &&&
14126 "Starting the daemon"
14127 .cindex "daemon" "starting"
14128 .cindex "interface" "listening"
14129 .cindex "network interface"
14130 .cindex "interface" "network"
14131 .cindex "IP address" "for listening"
14132 .cindex "daemon" "listening IP addresses"
14133 .cindex "TCP/IP" "setting listening interfaces"
14134 .cindex "TCP/IP" "setting listening ports"
14135 A host that is connected to a TCP/IP network may have one or more physical
14136 hardware network interfaces. Each of these interfaces may be configured as one
14137 or more &"logical"& interfaces, which are the entities that a program actually
14138 works with. Each of these logical interfaces is associated with an IP address.
14139 In addition, TCP/IP software supports &"loopback"& interfaces (127.0.0.1 in
14140 IPv4 and ::1 in IPv6), which do not use any physical hardware. Exim requires
14141 knowledge about the host's interfaces for use in three different circumstances:
14144 When a listening daemon is started, Exim needs to know which interfaces
14145 and ports to listen on.
14147 When Exim is routing an address, it needs to know which IP addresses
14148 are associated with local interfaces. This is required for the correct
14149 processing of MX lists by removing the local host and others with the
14150 same or higher priority values. Also, Exim needs to detect cases
14151 when an address is routed to an IP address that in fact belongs to the
14152 local host. Unless the &%self%& router option or the &%allow_localhost%&
14153 option of the smtp transport is set (as appropriate), this is treated
14154 as an error situation.
14156 When Exim connects to a remote host, it may need to know which interface to use
14157 for the outgoing connection.
14161 Exim's default behaviour is likely to be appropriate in the vast majority
14162 of cases. If your host has only one interface, and you want all its IP
14163 addresses to be treated in the same way, and you are using only the
14164 standard SMTP port, you should not need to take any special action. The
14165 rest of this chapter does not apply to you.
14167 In a more complicated situation you may want to listen only on certain
14168 interfaces, or on different ports, and for this reason there are a number of
14169 options that can be used to influence Exim's behaviour. The rest of this
14170 chapter describes how they operate.
14172 When a message is received over TCP/IP, the interface and port that were
14173 actually used are set in &$received_ip_address$& and &$received_port$&.
14177 .section "Starting a listening daemon" "SECID89"
14178 When a listening daemon is started (by means of the &%-bd%& command line
14179 option), the interfaces and ports on which it listens are controlled by the
14183 &%daemon_smtp_ports%& contains a list of default ports
14185 (For backward compatibility, this option can also be specified in the singular.)
14187 &%local_interfaces%& contains list of interface IP addresses on which to
14188 listen. Each item may optionally also specify a port.
14191 The default list separator in both cases is a colon, but this can be changed as
14192 described in section &<<SECTlistsepchange>>&. When IPv6 addresses are involved,
14193 it is usually best to change the separator to avoid having to double all the
14194 colons. For example:
14196 local_interfaces = <; 127.0.0.1 ; \
14199 3ffe:ffff:836f::fe86:a061
14201 There are two different formats for specifying a port along with an IP address
14202 in &%local_interfaces%&:
14205 The port is added onto the address with a dot separator. For example, to listen
14206 on port 1234 on two different IP addresses:
14208 local_interfaces = <; 192.168.23.65.1234 ; \
14209 3ffe:ffff:836f::fe86:a061.1234
14212 The IP address is enclosed in square brackets, and the port is added
14213 with a colon separator, for example:
14215 local_interfaces = <; [192.168.23.65]:1234 ; \
14216 [3ffe:ffff:836f::fe86:a061]:1234
14220 When a port is not specified, the value of &%daemon_smtp_ports%& is used. The
14221 default setting contains just one port:
14223 daemon_smtp_ports = smtp
14225 If more than one port is listed, each interface that does not have its own port
14226 specified listens on all of them. Ports that are listed in
14227 &%daemon_smtp_ports%& can be identified either by name (defined in
14228 &_/etc/services_&) or by number. However, when ports are given with individual
14229 IP addresses in &%local_interfaces%&, only numbers (not names) can be used.
14233 .section "Special IP listening addresses" "SECID90"
14234 The addresses 0.0.0.0 and ::0 are treated specially. They are interpreted
14235 as &"all IPv4 interfaces"& and &"all IPv6 interfaces"&, respectively. In each
14236 case, Exim tells the TCP/IP stack to &"listen on all IPv&'x'& interfaces"&
14237 instead of setting up separate listening sockets for each interface. The
14238 default value of &%local_interfaces%& is
14240 local_interfaces = 0.0.0.0
14242 when Exim is built without IPv6 support; otherwise it is:
14244 local_interfaces = <; ::0 ; 0.0.0.0
14246 Thus, by default, Exim listens on all available interfaces, on the SMTP port.
14250 .section "Overriding local_interfaces and daemon_smtp_ports" "SECID91"
14251 The &%-oX%& command line option can be used to override the values of
14252 &%daemon_smtp_ports%& and/or &%local_interfaces%& for a particular daemon
14253 instance. Another way of doing this would be to use macros and the &%-D%&
14254 option. However, &%-oX%& can be used by any admin user, whereas modification of
14255 the runtime configuration by &%-D%& is allowed only when the caller is root or
14258 The value of &%-oX%& is a list of items. The default colon separator can be
14259 changed in the usual way (&<<SECTlistsepchange>>&) if required.
14260 If there are any items that do not
14261 contain dots or colons (that is, are not IP addresses), the value of
14262 &%daemon_smtp_ports%& is replaced by the list of those items. If there are any
14263 items that do contain dots or colons, the value of &%local_interfaces%& is
14264 replaced by those items. Thus, for example,
14268 overrides &%daemon_smtp_ports%&, but leaves &%local_interfaces%& unchanged,
14271 -oX 192.168.34.5.1125
14273 overrides &%local_interfaces%&, leaving &%daemon_smtp_ports%& unchanged.
14274 (However, since &%local_interfaces%& now contains no items without ports, the
14275 value of &%daemon_smtp_ports%& is no longer relevant in this example.)
14279 .section "Support for the submissions (aka SSMTP or SMTPS) protocol" "SECTsupobssmt"
14280 .cindex "submissions protocol"
14281 .cindex "ssmtp protocol"
14282 .cindex "smtps protocol"
14283 .cindex "SMTP" "ssmtp protocol"
14284 .cindex "SMTP" "smtps protocol"
14285 Exim supports the use of TLS-on-connect, used by mail clients in the
14286 &"submissions"& protocol, historically also known as SMTPS or SSMTP.
14287 For some years, IETF Standards Track documents only blessed the
14288 STARTTLS-based Submission service (port 587) while common practice was to support
14289 the same feature set on port 465, but using TLS-on-connect.
14290 If your installation needs to provide service to mail clients
14291 (Mail User Agents, MUAs) then you should provide service on both the 587 and
14294 If the &%tls_on_connect_ports%& option is set to a list of port numbers or
14295 service names, connections to those ports must first establish TLS, before
14296 proceeding to the application layer use of the SMTP protocol.
14298 The common use of this option is expected to be
14300 tls_on_connect_ports = 465
14303 There is also a command line option &%-tls-on-connect%&, which forces all ports
14304 to behave in this way when a daemon is started.
14306 &*Warning*&: Setting &%tls_on_connect_ports%& does not of itself cause the
14307 daemon to listen on those ports. You must still specify them in
14308 &%daemon_smtp_ports%&, &%local_interfaces%&, or the &%-oX%& option. (This is
14309 because &%tls_on_connect_ports%& applies to &%inetd%& connections as well as to
14310 connections via the daemon.)
14315 .section "IPv6 address scopes" "SECID92"
14316 .cindex "IPv6" "address scopes"
14317 IPv6 addresses have &"scopes"&, and a host with multiple hardware interfaces
14318 can, in principle, have the same link-local IPv6 address on different
14319 interfaces. Thus, additional information is needed, over and above the IP
14320 address, to distinguish individual interfaces. A convention of using a
14321 percent sign followed by something (often the interface name) has been
14322 adopted in some cases, leading to addresses like this:
14324 fe80::202:b3ff:fe03:45c1%eth0
14326 To accommodate this usage, a percent sign followed by an arbitrary string is
14327 allowed at the end of an IPv6 address. By default, Exim calls &[getaddrinfo()]&
14328 to convert a textual IPv6 address for actual use. This function recognizes the
14329 percent convention in operating systems that support it, and it processes the
14330 address appropriately. Unfortunately, some older libraries have problems with
14331 &[getaddrinfo()]&. If
14333 IPV6_USE_INET_PTON=yes
14335 is set in &_Local/Makefile_& (or an OS-dependent Makefile) when Exim is built,
14336 Exim uses &'inet_pton()'& to convert a textual IPv6 address for actual use,
14337 instead of &[getaddrinfo()]&. (Before version 4.14, it always used this
14338 function.) Of course, this means that the additional functionality of
14339 &[getaddrinfo()]& &-- recognizing scoped addresses &-- is lost.
14341 .section "Disabling IPv6" "SECID93"
14342 .cindex "IPv6" "disabling"
14343 Sometimes it happens that an Exim binary that was compiled with IPv6 support is
14344 run on a host whose kernel does not support IPv6. The binary will fall back to
14345 using IPv4, but it may waste resources looking up AAAA records, and trying to
14346 connect to IPv6 addresses, causing delays to mail delivery. If you set the
14347 .oindex "&%disable_ipv6%&"
14348 &%disable_ipv6%& option true, even if the Exim binary has IPv6 support, no IPv6
14349 activities take place. AAAA records are never looked up, and any IPv6 addresses
14350 that are listed in &%local_interfaces%&, data for the &(manualroute)& router,
14351 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
14352 to handle IPv6 literal addresses.
14354 On the other hand, when IPv6 is in use, there may be times when you want to
14355 disable it for certain hosts or domains. You can use the &%dns_ipv4_lookup%&
14356 option to globally suppress the lookup of AAAA records for specified domains,
14357 and you can use the &%ignore_target_hosts%& generic router option to ignore
14358 IPv6 addresses in an individual router.
14362 .section "Examples of starting a listening daemon" "SECID94"
14363 The default case in an IPv6 environment is
14365 daemon_smtp_ports = smtp
14366 local_interfaces = <; ::0 ; 0.0.0.0
14368 This specifies listening on the smtp port on all IPv6 and IPv4 interfaces.
14369 Either one or two sockets may be used, depending on the characteristics of
14370 the TCP/IP stack. (This is complicated and messy; for more information,
14371 read the comments in the &_daemon.c_& source file.)
14373 To specify listening on ports 25 and 26 on all interfaces:
14375 daemon_smtp_ports = 25 : 26
14377 (leaving &%local_interfaces%& at the default setting) or, more explicitly:
14379 local_interfaces = <; ::0.25 ; ::0.26 \
14380 0.0.0.0.25 ; 0.0.0.0.26
14382 To listen on the default port on all IPv4 interfaces, and on port 26 on the
14383 IPv4 loopback address only:
14385 local_interfaces = 0.0.0.0 : 127.0.0.1.26
14387 To specify listening on the default port on specific interfaces only:
14389 local_interfaces = 10.0.0.67 : 192.168.34.67
14391 &*Warning*&: Such a setting excludes listening on the loopback interfaces.
14395 .section "Recognizing the local host" "SECTreclocipadd"
14396 The &%local_interfaces%& option is also used when Exim needs to determine
14397 whether or not an IP address refers to the local host. That is, the IP
14398 addresses of all the interfaces on which a daemon is listening are always
14401 For this usage, port numbers in &%local_interfaces%& are ignored. If either of
14402 the items 0.0.0.0 or ::0 are encountered, Exim gets a complete list of
14403 available interfaces from the operating system, and extracts the relevant
14404 (that is, IPv4 or IPv6) addresses to use for checking.
14406 Some systems set up large numbers of virtual interfaces in order to provide
14407 many virtual web servers. In this situation, you may want to listen for
14408 email on only a few of the available interfaces, but nevertheless treat all
14409 interfaces as local when routing. You can do this by setting
14410 &%extra_local_interfaces%& to a list of IP addresses, possibly including the
14411 &"all"& wildcard values. These addresses are recognized as local, but are not
14412 used for listening. Consider this example:
14414 local_interfaces = <; 127.0.0.1 ; ::1 ; \
14416 3ffe:2101:12:1:a00:20ff:fe86:a061
14418 extra_local_interfaces = <; ::0 ; 0.0.0.0
14420 The daemon listens on the loopback interfaces and just one IPv4 and one IPv6
14421 address, but all available interface addresses are treated as local when
14424 In some environments the local host name may be in an MX list, but with an IP
14425 address that is not assigned to any local interface. In other cases it may be
14426 desirable to treat other host names as if they referred to the local host. Both
14427 these cases can be handled by setting the &%hosts_treat_as_local%& option.
14428 This contains host names rather than IP addresses. When a host is referenced
14429 during routing, either via an MX record or directly, it is treated as the local
14430 host if its name matches &%hosts_treat_as_local%&, or if any of its IP
14431 addresses match &%local_interfaces%& or &%extra_local_interfaces%&.
14435 .section "Delivering to a remote host" "SECID95"
14436 Delivery to a remote host is handled by the smtp transport. By default, it
14437 allows the system's TCP/IP functions to choose which interface to use (if
14438 there is more than one) when connecting to a remote host. However, the
14439 &%interface%& option can be set to specify which interface is used. See the
14440 description of the smtp transport in chapter &<<CHAPsmtptrans>>& for more
14446 . ////////////////////////////////////////////////////////////////////////////
14447 . ////////////////////////////////////////////////////////////////////////////
14449 .chapter "Main configuration" "CHAPmainconfig"
14450 .scindex IIDconfima "configuration file" "main section"
14451 .scindex IIDmaiconf "main configuration"
14452 The first part of the runtime configuration file contains three types of item:
14455 Macro definitions: These lines start with an upper case letter. See section
14456 &<<SECTmacrodefs>>& for details of macro processing.
14458 Named list definitions: These lines start with one of the words &"domainlist"&,
14459 &"hostlist"&, &"addresslist"&, or &"localpartlist"&. Their use is described in
14460 section &<<SECTnamedlists>>&.
14462 Main configuration settings: Each setting occupies one line of the file
14463 (with possible continuations). If any setting is preceded by the word
14464 &"hide"&, the &%-bP%& command line option displays its value to admin users
14465 only. See section &<<SECTcos>>& for a description of the syntax of these option
14469 This chapter specifies all the main configuration options, along with their
14470 types and default values. For ease of finding a particular option, they appear
14471 in alphabetical order in section &<<SECTalomo>>& below. However, because there
14472 are now so many options, they are first listed briefly in functional groups, as
14473 an aid to finding the name of the option you are looking for. Some options are
14474 listed in more than one group.
14476 .section "Miscellaneous" "SECID96"
14478 .row &%add_environment%& "environment variables"
14479 .row &%bi_command%& "to run for &%-bi%& command line option"
14480 .row &%debug_store%& "do extra internal checks"
14481 .row &%disable_ipv6%& "do no IPv6 processing"
14482 .row &%keep_environment%& "environment variables"
14483 .row &%keep_malformed%& "for broken files &-- should not happen"
14484 .row &%localhost_number%& "for unique message ids in clusters"
14485 .row &%message_body_newlines%& "retain newlines in &$message_body$&"
14486 .row &%message_body_visible%& "how much to show in &$message_body$&"
14487 .row &%mua_wrapper%& "run in &""MUA wrapper""& mode"
14488 .row &%print_topbitchars%& "top-bit characters are printing"
14489 .row &%spool_wireformat%& "use wire-format spool data files when possible"
14490 .row &%timezone%& "force time zone"
14494 .section "Exim parameters" "SECID97"
14496 .row &%exim_group%& "override compiled-in value"
14497 .row &%exim_path%& "override compiled-in value"
14498 .row &%exim_user%& "override compiled-in value"
14499 .row &%primary_hostname%& "default from &[uname()]&"
14500 .row &%split_spool_directory%& "use multiple directories"
14501 .row &%spool_directory%& "override compiled-in value"
14506 .section "Privilege controls" "SECID98"
14508 .row &%admin_groups%& "groups that are Exim admin users"
14509 .row &%commandline_checks_require_admin%& "require admin for various checks"
14510 .row &%deliver_drop_privilege%& "drop root for delivery processes"
14511 .row &%local_from_check%& "insert &'Sender:'& if necessary"
14512 .row &%local_from_prefix%& "for testing &'From:'& for local sender"
14513 .row &%local_from_suffix%& "for testing &'From:'& for local sender"
14514 .row &%local_sender_retain%& "keep &'Sender:'& from untrusted user"
14515 .row &%never_users%& "do not run deliveries as these"
14516 .row &%prod_requires_admin%& "forced delivery requires admin user"
14517 .row &%queue_list_requires_admin%& "queue listing requires admin user"
14518 .row &%trusted_groups%& "groups that are trusted"
14519 .row &%trusted_users%& "users that are trusted"
14524 .section "Logging" "SECID99"
14526 .row &%event_action%& "custom logging"
14527 .row &%hosts_connection_nolog%& "exemption from connect logging"
14528 .row &%log_file_path%& "override compiled-in value"
14529 .row &%log_selector%& "set/unset optional logging"
14530 .row &%log_timezone%& "add timezone to log lines"
14531 .row &%message_logs%& "create per-message logs"
14532 .row &%preserve_message_logs%& "after message completion"
14533 .row &%panic_coredump%& "request coredump on fatal errors"
14534 .row &%process_log_path%& "for SIGUSR1 and &'exiwhat'&"
14535 .row &%slow_lookup_log%& "control logging of slow DNS lookups"
14536 .row &%syslog_duplication%& "controls duplicate log lines on syslog"
14537 .row &%syslog_facility%& "set syslog &""facility""& field"
14538 .row &%syslog_pid%& "pid in syslog lines"
14539 .row &%syslog_processname%& "set syslog &""ident""& field"
14540 .row &%syslog_timestamp%& "timestamp syslog lines"
14541 .row &%write_rejectlog%& "control use of message log"
14546 .section "Frozen messages" "SECID100"
14548 .row &%auto_thaw%& "sets time for retrying frozen messages"
14549 .row &%freeze_tell%& "send message when freezing"
14550 .row &%move_frozen_messages%& "to another directory"
14551 .row &%timeout_frozen_after%& "keep frozen messages only so long"
14556 .section "Data lookups" "SECID101"
14558 .row &%ibase_servers%& "InterBase servers"
14559 .row &%ldap_ca_cert_dir%& "dir of CA certs to verify LDAP server's"
14560 .row &%ldap_ca_cert_file%& "file of CA certs to verify LDAP server's"
14561 .row &%ldap_cert_file%& "client cert file for LDAP"
14562 .row &%ldap_cert_key%& "client key file for LDAP"
14563 .row &%ldap_cipher_suite%& "TLS negotiation preference control"
14564 .row &%ldap_default_servers%& "used if no server in query"
14565 .row &%ldap_require_cert%& "action to take without LDAP server cert"
14566 .row &%ldap_start_tls%& "require TLS within LDAP"
14567 .row &%ldap_version%& "set protocol version"
14568 .row &%lookup_open_max%& "lookup files held open"
14569 .row &%mysql_servers%& "default MySQL servers"
14570 .row &%oracle_servers%& "Oracle servers"
14571 .row &%pgsql_servers%& "default PostgreSQL servers"
14572 .row &%sqlite_lock_timeout%& "as it says"
14577 .section "Message ids" "SECID102"
14579 .row &%message_id_header_domain%& "used to build &'Message-ID:'& header"
14580 .row &%message_id_header_text%& "ditto"
14585 .section "Embedded Perl Startup" "SECID103"
14587 .row &%perl_at_start%& "always start the interpreter"
14588 .row &%perl_startup%& "code to obey when starting Perl"
14589 .row &%perl_taintmode%& "enable taint mode in Perl"
14594 .section "Daemon" "SECID104"
14596 .row &%daemon_smtp_ports%& "default ports"
14597 .row &%daemon_startup_retries%& "number of times to retry"
14598 .row &%daemon_startup_sleep%& "time to sleep between tries"
14599 .row &%extra_local_interfaces%& "not necessarily listened on"
14600 .row &%local_interfaces%& "on which to listen, with optional ports"
14601 .row &%notifier_socket%& "override compiled-in value"
14602 .row &%pid_file_path%& "override compiled-in value"
14603 .row &%queue_run_max%& "maximum simultaneous queue runners"
14604 .row &%smtp_backlog_monitor%& "level to log listen backlog"
14609 .section "Resource control" "SECID105"
14611 .row &%check_log_inodes%& "before accepting a message"
14612 .row &%check_log_space%& "before accepting a message"
14613 .row &%check_spool_inodes%& "before accepting a message"
14614 .row &%check_spool_space%& "before accepting a message"
14615 .row &%deliver_queue_load_max%& "no queue deliveries if load high"
14616 .row &%queue_only_load%& "queue incoming if load high"
14617 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
14618 .row &%queue_run_max%& "maximum simultaneous queue runners"
14619 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
14620 .row &%smtp_accept_max%& "simultaneous incoming connections"
14621 .row &%smtp_accept_max_nonmail%& "non-mail commands"
14622 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
14623 .row &%smtp_accept_max_per_connection%& "messages per connection"
14624 .row &%smtp_accept_max_per_host%& "connections from one host"
14625 .row &%smtp_accept_queue%& "queue mail if more connections"
14626 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
14628 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
14629 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
14630 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
14631 .row &%smtp_load_reserve%& "SMTP from reserved hosts if load high"
14632 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
14637 .section "Policy controls" "SECID106"
14639 .row &%acl_not_smtp%& "ACL for non-SMTP messages"
14640 .row &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
14641 .row &%acl_not_smtp_start%& "ACL for start of non-SMTP message"
14642 .row &%acl_smtp_auth%& "ACL for AUTH"
14643 .row &%acl_smtp_connect%& "ACL for connection"
14644 .row &%acl_smtp_data%& "ACL for DATA"
14645 .row &%acl_smtp_data_prdr%& "ACL for DATA, per-recipient"
14646 .row &%acl_smtp_dkim%& "ACL for DKIM verification"
14647 .row &%acl_smtp_etrn%& "ACL for ETRN"
14648 .row &%acl_smtp_expn%& "ACL for EXPN"
14649 .row &%acl_smtp_helo%& "ACL for EHLO or HELO"
14650 .row &%acl_smtp_mail%& "ACL for MAIL"
14651 .row &%acl_smtp_mailauth%& "ACL for AUTH on MAIL command"
14652 .row &%acl_smtp_mime%& "ACL for MIME parts"
14653 .row &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
14654 .row &%acl_smtp_predata%& "ACL for start of data"
14655 .row &%acl_smtp_quit%& "ACL for QUIT"
14656 .row &%acl_smtp_rcpt%& "ACL for RCPT"
14657 .row &%acl_smtp_starttls%& "ACL for STARTTLS"
14658 .row &%acl_smtp_vrfy%& "ACL for VRFY"
14659 .row &%av_scanner%& "specify virus scanner"
14660 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
14662 .row &%dns_cname_loops%& "follow CNAMEs returned by resolver"
14663 .row &%dns_csa_search_limit%& "control CSA parent search depth"
14664 .row &%dns_csa_use_reverse%& "en/disable CSA IP reverse search"
14665 .row &%header_maxsize%& "total size of message header"
14666 .row &%header_line_maxsize%& "individual header line limit"
14667 .row &%helo_accept_junk_hosts%& "allow syntactic junk from these hosts"
14668 .row &%helo_allow_chars%& "allow illegal chars in HELO names"
14669 .row &%helo_lookup_domains%& "lookup hostname for these HELO names"
14670 .row &%helo_try_verify_hosts%& "HELO soft-checked for these hosts"
14671 .row &%helo_verify_hosts%& "HELO hard-checked for these hosts"
14672 .row &%host_lookup%& "host name looked up for these hosts"
14673 .row &%host_lookup_order%& "order of DNS and local name lookups"
14674 .row &%hosts_proxy%& "use proxy protocol for these hosts"
14675 .row &%host_reject_connection%& "reject connection from these hosts"
14676 .row &%hosts_treat_as_local%& "useful in some cluster configurations"
14677 .row &%local_scan_timeout%& "timeout for &[local_scan()]&"
14678 .row &%message_size_limit%& "for all messages"
14679 .row &%percent_hack_domains%& "recognize %-hack for these domains"
14680 .row &%proxy_protocol_timeout%& "timeout for proxy protocol negotiation"
14681 .row &%spamd_address%& "set interface to SpamAssassin"
14682 .row &%strict_acl_vars%& "object to unset ACL variables"
14683 .row &%spf_smtp_comment_template%& "template for &$spf_smtp_comment$&"
14688 .section "Callout cache" "SECID107"
14690 .row &%callout_domain_negative_expire%& "timeout for negative domain cache &&&
14692 .row &%callout_domain_positive_expire%& "timeout for positive domain cache &&&
14694 .row &%callout_negative_expire%& "timeout for negative address cache item"
14695 .row &%callout_positive_expire%& "timeout for positive address cache item"
14696 .row &%callout_random_local_part%& "string to use for &""random""& testing"
14701 .section "TLS" "SECID108"
14703 .row &%gnutls_compat_mode%& "use GnuTLS compatibility mode"
14704 .row &%gnutls_allow_auto_pkcs11%& "allow GnuTLS to autoload PKCS11 modules"
14705 .row &%hosts_require_alpn%& "mandatory ALPN"
14706 .row &%hosts_require_helo%& "mandatory HELO/EHLO"
14707 .row &%openssl_options%& "adjust OpenSSL compatibility options"
14708 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
14709 .row &%tls_alpn%& "acceptable protocol names"
14710 .row &%tls_certificate%& "location of server certificate"
14711 .row &%tls_crl%& "certificate revocation list"
14712 .row &%tls_dh_max_bits%& "clamp D-H bit count suggestion"
14713 .row &%tls_dhparam%& "DH parameters for server"
14714 .row &%tls_eccurve%& "EC curve selection for server"
14715 .row &%tls_ocsp_file%& "location of server certificate status proof"
14716 .row &%tls_on_connect_ports%& "specify SSMTP (SMTPS) ports"
14717 .row &%tls_privatekey%& "location of server private key"
14718 .row &%tls_remember_esmtp%& "don't reset after starting TLS"
14719 .row &%tls_require_ciphers%& "specify acceptable ciphers"
14720 .row &%tls_try_verify_hosts%& "try to verify client certificate"
14721 .row &%tls_verify_certificates%& "expected client certificates"
14722 .row &%tls_verify_hosts%& "insist on client certificate verify"
14727 .section "Local user handling" "SECID109"
14729 .row &%finduser_retries%& "useful in NIS environments"
14730 .row &%gecos_name%& "used when creating &'Sender:'&"
14731 .row &%gecos_pattern%& "ditto"
14732 .row &%max_username_length%& "for systems that truncate"
14733 .row &%unknown_login%& "used when no login name found"
14734 .row &%unknown_username%& "ditto"
14735 .row &%uucp_from_pattern%& "for recognizing &""From ""& lines"
14736 .row &%uucp_from_sender%& "ditto"
14741 .section "All incoming messages (SMTP and non-SMTP)" "SECID110"
14743 .row &%header_maxsize%& "total size of message header"
14744 .row &%header_line_maxsize%& "individual header line limit"
14745 .row &%message_size_limit%& "applies to all messages"
14746 .row &%percent_hack_domains%& "recognize %-hack for these domains"
14747 .row &%received_header_text%& "expanded to make &'Received:'&"
14748 .row &%received_headers_max%& "for mail loop detection"
14749 .row &%recipients_max%& "limit per message"
14750 .row &%recipients_max_reject%& "permanently reject excess recipients"
14756 .section "Non-SMTP incoming messages" "SECID111"
14758 .row &%receive_timeout%& "for non-SMTP messages"
14765 .section "Incoming SMTP messages" "SECID112"
14766 See also the &'Policy controls'& section above.
14769 .row &%dkim_verify_hashes%& "DKIM hash methods accepted for signatures"
14770 .row &%dkim_verify_keytypes%& "DKIM key types accepted for signatures"
14771 .row &%dkim_verify_min_keysizes%& "DKIM key sizes accepted for signatures"
14772 .row &%dkim_verify_signers%& "DKIM domains for which DKIM ACL is run"
14773 .row &%dmarc_forensic_sender%& "DMARC sender for report messages"
14774 .row &%dmarc_history_file%& "DMARC results log"
14775 .row &%dmarc_tld_file%& "DMARC toplevel domains file"
14776 .row &%host_lookup%& "host name looked up for these hosts"
14777 .row &%host_lookup_order%& "order of DNS and local name lookups"
14778 .row &%recipient_unqualified_hosts%& "may send unqualified recipients"
14779 .row &%rfc1413_hosts%& "make ident calls to these hosts"
14780 .row &%rfc1413_query_timeout%& "zero disables ident calls"
14781 .row &%sender_unqualified_hosts%& "may send unqualified senders"
14782 .row &%smtp_accept_keepalive%& "some TCP/IP magic"
14783 .row &%smtp_accept_max%& "simultaneous incoming connections"
14784 .row &%smtp_accept_max_nonmail%& "non-mail commands"
14785 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
14786 .row &%smtp_accept_max_per_connection%& "messages per connection"
14787 .row &%smtp_accept_max_per_host%& "connections from one host"
14788 .row &%smtp_accept_queue%& "queue mail if more connections"
14789 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
14791 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
14792 .row &%smtp_active_hostname%& "host name to use in messages"
14793 .row &%smtp_banner%& "text for welcome banner"
14794 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
14795 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
14796 .row &%smtp_enforce_sync%& "of SMTP command/responses"
14797 .row &%smtp_etrn_command%& "what to run for ETRN"
14798 .row &%smtp_etrn_serialize%& "only one at once"
14799 .row &%smtp_load_reserve%& "only reserve hosts if this load"
14800 .row &%smtp_max_unknown_commands%& "before dropping connection"
14801 .row &%smtp_ratelimit_hosts%& "apply ratelimiting to these hosts"
14802 .row &%smtp_ratelimit_mail%& "ratelimit for MAIL commands"
14803 .row &%smtp_ratelimit_rcpt%& "ratelimit for RCPT commands"
14804 .row &%smtp_receive_timeout%& "per command or data line"
14805 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
14806 .row &%smtp_return_error_details%& "give detail on rejections"
14811 .section "SMTP extensions" "SECID113"
14813 .row &%accept_8bitmime%& "advertise 8BITMIME"
14814 .row &%auth_advertise_hosts%& "advertise AUTH to these hosts"
14815 .row &%chunking_advertise_hosts%& "advertise CHUNKING to these hosts"
14816 .row &%dsn_advertise_hosts%& "advertise DSN extensions to these hosts"
14817 .row &%ignore_fromline_hosts%& "allow &""From ""& from these hosts"
14818 .row &%ignore_fromline_local%& "allow &""From ""& from local SMTP"
14819 .row &%pipelining_advertise_hosts%& "advertise pipelining to these hosts"
14820 .row &%pipelining_connect_advertise_hosts%& "advertise pipelining to these hosts"
14821 .row &%prdr_enable%& "advertise PRDR to all hosts"
14822 .row &%smtputf8_advertise_hosts%& "advertise SMTPUTF8 to these hosts"
14823 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
14828 .section "Processing messages" "SECID114"
14830 .row &%allow_domain_literals%& "recognize domain literal syntax"
14831 .row &%allow_mx_to_ip%& "allow MX to point to IP address"
14832 .row &%allow_utf8_domains%& "in addresses"
14833 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
14835 .row &%delivery_date_remove%& "from incoming messages"
14836 .row &%envelope_to_remove%& "from incoming messages"
14837 .row &%extract_addresses_remove_arguments%& "affects &%-t%& processing"
14838 .row &%headers_charset%& "default for translations"
14839 .row &%qualify_domain%& "default for senders"
14840 .row &%qualify_recipient%& "default for recipients"
14841 .row &%return_path_remove%& "from incoming messages"
14842 .row &%strip_excess_angle_brackets%& "in addresses"
14843 .row &%strip_trailing_dot%& "at end of addresses"
14844 .row &%untrusted_set_sender%& "untrusted can set envelope sender"
14849 .section "System filter" "SECID115"
14851 .row &%system_filter%& "locate system filter"
14852 .row &%system_filter_directory_transport%& "transport for delivery to a &&&
14854 .row &%system_filter_file_transport%& "transport for delivery to a file"
14855 .row &%system_filter_group%& "group for filter running"
14856 .row &%system_filter_pipe_transport%& "transport for delivery to a pipe"
14857 .row &%system_filter_reply_transport%& "transport for autoreply delivery"
14858 .row &%system_filter_user%& "user for filter running"
14863 .section "Routing and delivery" "SECID116"
14865 .row &%disable_ipv6%& "do no IPv6 processing"
14866 .row &%dns_again_means_nonexist%& "for broken domains"
14867 .row &%dns_check_names_pattern%& "pre-DNS syntax check"
14868 .row &%dns_dnssec_ok%& "parameter for resolver"
14869 .row &%dns_ipv4_lookup%& "only v4 lookup for these domains"
14870 .row &%dns_retrans%& "parameter for resolver"
14871 .row &%dns_retry%& "parameter for resolver"
14872 .row &%dns_trust_aa%& "DNS zones trusted as authentic"
14873 .row &%dns_use_edns0%& "parameter for resolver"
14874 .row &%hold_domains%& "hold delivery for these domains"
14875 .row &%local_interfaces%& "for routing checks"
14876 .row &%queue_domains%& "no immediate delivery for these"
14877 .row &%queue_fast_ramp%& "parallel delivery with 2-phase queue run"
14878 .row &%queue_only%& "no immediate delivery at all"
14879 .row &%queue_only_file%& "no immediate delivery if file exists"
14880 .row &%queue_only_load%& "no immediate delivery if load is high"
14881 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
14882 .row &%queue_only_override%& "allow command line to override"
14883 .row &%queue_run_in_order%& "order of arrival"
14884 .row &%queue_run_max%& "of simultaneous queue runners"
14885 .row &%queue_smtp_domains%& "no immediate SMTP delivery for these"
14886 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
14887 .row &%remote_sort_domains%& "order of remote deliveries"
14888 .row &%retry_data_expire%& "timeout for retry data"
14889 .row &%retry_interval_max%& "safety net for retry rules"
14894 .section "Bounce and warning messages" "SECID117"
14896 .row &%bounce_message_file%& "content of bounce"
14897 .row &%bounce_message_text%& "content of bounce"
14898 .row &%bounce_return_body%& "include body if returning message"
14899 .row &%bounce_return_linesize_limit%& "limit on returned message line length"
14900 .row &%bounce_return_message%& "include original message in bounce"
14901 .row &%bounce_return_size_limit%& "limit on returned message"
14902 .row &%bounce_sender_authentication%& "send authenticated sender with bounce"
14903 .row &%dsn_from%& "set &'From:'& contents in bounces"
14904 .row &%errors_copy%& "copy bounce messages"
14905 .row &%errors_reply_to%& "&'Reply-to:'& in bounces"
14906 .row &%delay_warning%& "time schedule"
14907 .row &%delay_warning_condition%& "condition for warning messages"
14908 .row &%ignore_bounce_errors_after%& "discard undeliverable bounces"
14909 .row &%smtp_return_error_details%& "give detail on rejections"
14910 .row &%warn_message_file%& "content of warning message"
14915 .section "Alphabetical list of main options" "SECTalomo"
14916 Those options that undergo string expansion before use are marked with
14919 .option accept_8bitmime main boolean true
14921 .cindex "8-bit characters"
14922 .cindex "log" "selectors"
14923 .cindex "log" "8BITMIME"
14924 .cindex "ESMTP extensions" 8BITMIME
14925 This option causes Exim to send 8BITMIME in its response to an SMTP
14926 EHLO command, and to accept the BODY= parameter on MAIL commands.
14927 However, though Exim is 8-bit clean, it is not a protocol converter, and it
14928 takes no steps to do anything special with messages received by this route.
14930 Historically Exim kept this option off by default, but the maintainers
14931 feel that in today's Internet, this causes more problems than it solves.
14932 It now defaults to true.
14933 A more detailed analysis of the issues is provided by Dan Bernstein:
14935 &url(https://cr.yp.to/smtp/8bitmime.html)
14938 To log received 8BITMIME status use
14940 log_selector = +8bitmime
14943 .option acl_not_smtp main string&!! unset
14944 .cindex "&ACL;" "for non-SMTP messages"
14945 .cindex "non-SMTP messages" "ACLs for"
14946 This option defines the ACL that is run when a non-SMTP message has been
14947 read and is on the point of being accepted. See chapter &<<CHAPACL>>& for
14950 .option acl_not_smtp_mime main string&!! unset
14951 This option defines the ACL that is run for individual MIME parts of non-SMTP
14952 messages. It operates in exactly the same way as &%acl_smtp_mime%& operates for
14955 .option acl_not_smtp_start main string&!! unset
14956 .cindex "&ACL;" "at start of non-SMTP message"
14957 .cindex "non-SMTP messages" "ACLs for"
14958 This option defines the ACL that is run before Exim starts reading a
14959 non-SMTP message. See chapter &<<CHAPACL>>& for further details.
14961 .option acl_smtp_auth main string&!! unset
14962 .cindex "&ACL;" "setting up for SMTP commands"
14963 .cindex "AUTH" "ACL for"
14964 This option defines the ACL that is run when an SMTP AUTH command is
14965 received. See chapter &<<CHAPACL>>& for further details.
14967 .option acl_smtp_connect main string&!! unset
14968 .cindex "&ACL;" "on SMTP connection"
14969 This option defines the ACL that is run when an SMTP connection is received.
14970 See chapter &<<CHAPACL>>& for further details.
14972 .option acl_smtp_data main string&!! unset
14973 .cindex "DATA" "ACL for"
14974 This option defines the ACL that is run after an SMTP DATA command has been
14975 processed and the message itself has been received, but before the final
14976 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
14978 .option acl_smtp_data_prdr main string&!! accept
14979 .cindex "PRDR" "ACL for"
14980 .cindex "DATA" "PRDR ACL for"
14981 .cindex "&ACL;" "PRDR-related"
14982 .cindex "&ACL;" "per-user data processing"
14983 This option defines the ACL that,
14984 if the PRDR feature has been negotiated,
14985 is run for each recipient after an SMTP DATA command has been
14986 processed and the message itself has been received, but before the
14987 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
14989 .option acl_smtp_dkim main string&!! unset
14990 .cindex DKIM "ACL for"
14991 This option defines the ACL that is run for each DKIM signature
14992 (by default, or as specified in the dkim_verify_signers option)
14993 of a received message.
14994 See section &<<SECDKIMVFY>>& for further details.
14996 .option acl_smtp_etrn main string&!! unset
14997 .cindex "ETRN" "ACL for"
14998 This option defines the ACL that is run when an SMTP ETRN command is
14999 received. See chapter &<<CHAPACL>>& for further details.
15001 .option acl_smtp_expn main string&!! unset
15002 .cindex "EXPN" "ACL for"
15003 This option defines the ACL that is run when an SMTP EXPN command is
15004 received. See chapter &<<CHAPACL>>& for further details.
15006 .option acl_smtp_helo main string&!! unset
15007 .cindex "EHLO" "ACL for"
15008 .cindex "HELO" "ACL for"
15009 This option defines the ACL that is run when an SMTP EHLO or HELO
15010 command is received. See chapter &<<CHAPACL>>& for further details.
15013 .option acl_smtp_mail main string&!! unset
15014 .cindex "MAIL" "ACL for"
15015 This option defines the ACL that is run when an SMTP MAIL command is
15016 received. See chapter &<<CHAPACL>>& for further details.
15018 .option acl_smtp_mailauth main string&!! unset
15019 .cindex "AUTH" "on MAIL command"
15020 This option defines the ACL that is run when there is an AUTH parameter on
15021 a MAIL command. See chapter &<<CHAPACL>>& for details of ACLs, and chapter
15022 &<<CHAPSMTPAUTH>>& for details of authentication.
15024 .option acl_smtp_mime main string&!! unset
15025 .cindex "MIME content scanning" "ACL for"
15026 This option is available when Exim is built with the content-scanning
15027 extension. It defines the ACL that is run for each MIME part in a message. See
15028 section &<<SECTscanmimepart>>& for details.
15030 .option acl_smtp_notquit main string&!! unset
15031 .cindex "not-QUIT, ACL for"
15032 This option defines the ACL that is run when an SMTP session
15033 ends without a QUIT command being received.
15034 See chapter &<<CHAPACL>>& for further details.
15036 .option acl_smtp_predata main string&!! unset
15037 This option defines the ACL that is run when an SMTP DATA command is
15038 received, before the message itself is received. See chapter &<<CHAPACL>>& for
15041 .option acl_smtp_quit main string&!! unset
15042 .cindex "QUIT, ACL for"
15043 This option defines the ACL that is run when an SMTP QUIT command is
15044 received. See chapter &<<CHAPACL>>& for further details.
15046 .option acl_smtp_rcpt main string&!! unset
15047 .cindex "RCPT" "ACL for"
15048 This option defines the ACL that is run when an SMTP RCPT command is
15049 received. See chapter &<<CHAPACL>>& for further details.
15051 .option acl_smtp_starttls main string&!! unset
15052 .cindex "STARTTLS, ACL for"
15053 This option defines the ACL that is run when an SMTP STARTTLS command is
15054 received. See chapter &<<CHAPACL>>& for further details.
15056 .option acl_smtp_vrfy main string&!! unset
15057 .cindex "VRFY" "ACL for"
15058 This option defines the ACL that is run when an SMTP VRFY command is
15059 received. See chapter &<<CHAPACL>>& for further details.
15061 .option add_environment main "string list" empty
15062 .cindex "environment" "set values"
15063 This option adds individual environment variables that the
15064 currently linked libraries and programs in child processes may use.
15065 Each list element should be of the form &"name=value"&.
15067 See &<<SECTpipeenv>>& for the environment of &(pipe)& transports.
15069 .option admin_groups main "string list&!!" unset
15070 .cindex "admin user"
15071 This option is expanded just once, at the start of Exim's processing. If the
15072 current group or any of the supplementary groups of an Exim caller is in this
15073 colon-separated list, the caller has admin privileges. If all your system
15074 programmers are in a specific group, for example, you can give them all Exim
15075 admin privileges by putting that group in &%admin_groups%&. However, this does
15076 not permit them to read Exim's spool files (whose group owner is the Exim gid).
15077 To permit this, you have to add individuals to the Exim group.
15079 .option allow_domain_literals main boolean false
15080 .cindex "domain literal"
15081 If this option is set, the RFC 2822 domain literal format is permitted in
15082 email addresses. The option is not set by default, because the domain literal
15083 format is not normally required these days, and few people know about it. It
15084 has, however, been exploited by mail abusers.
15086 Unfortunately, it seems that some DNS black list maintainers are using this
15087 format to report black listing to postmasters. If you want to accept messages
15088 addressed to your hosts by IP address, you need to set
15089 &%allow_domain_literals%& true, and also to add &`@[]`& to the list of local
15090 domains (defined in the named domain list &%local_domains%& in the default
15091 configuration). This &"magic string"& matches the domain literal form of all
15092 the local host's IP addresses.
15094 .option allow_mx_to_ip main boolean false
15095 .cindex "MX record" "pointing to IP address"
15096 It appears that more and more DNS zone administrators are breaking the rules
15097 and putting domain names that look like IP addresses on the right hand side of
15098 MX records. Exim follows the rules and rejects this, giving an error message
15099 that explains the misconfiguration. However, some other MTAs support this
15100 practice, so to avoid &"Why can't Exim do this?"& complaints,
15101 &%allow_mx_to_ip%& exists, in order to enable this heinous activity. It is not
15102 recommended, except when you have no other choice.
15104 .option allow_utf8_domains main boolean false
15105 .cindex "domain" "UTF-8 characters in"
15106 .cindex "UTF-8" "in domain name"
15107 Lots of discussion is going on about internationalized domain names. One
15108 camp is strongly in favour of just using UTF-8 characters, and it seems
15109 that at least two other MTAs permit this.
15110 This option allows Exim users to experiment if they wish.
15112 If it is set true, Exim's domain parsing function allows valid
15113 UTF-8 multicharacters to appear in domain name components, in addition to
15114 letters, digits, and hyphens.
15116 If Exim is built with internationalization support
15117 and the SMTPUTF8 ESMTP option is in use (see chapter &<<CHAPi18n>>&)
15118 this option can be left as default.
15120 if you want to look up such domain names in the DNS, you must also
15121 adjust the value of &%dns_check_names_pattern%& to match the extended form. A
15122 suitable setting is:
15124 dns_check_names_pattern = (?i)^(?>(?(1)\.|())[a-z0-9\xc0-\xff]\
15125 (?>[-a-z0-9\x80-\xff]*[a-z0-9\x80-\xbf])?)+$
15127 Alternatively, you can just disable this feature by setting
15129 dns_check_names_pattern =
15131 That is, set the option to an empty string so that no check is done.
15134 .option auth_advertise_hosts main "host list&!!" *
15135 .cindex "authentication" "advertising"
15136 .cindex "AUTH" "advertising"
15137 .cindex "ESMTP extensions" AUTH
15138 If any server authentication mechanisms are configured, Exim advertises them in
15139 response to an EHLO command only if the calling host matches this list.
15140 Otherwise, Exim does not advertise AUTH.
15141 Exim does not accept AUTH commands from clients to which it has not
15142 advertised the availability of AUTH. The advertising of individual
15143 authentication mechanisms can be controlled by the use of the
15144 &%server_advertise_condition%& generic authenticator option on the individual
15145 authenticators. See chapter &<<CHAPSMTPAUTH>>& for further details.
15147 Certain mail clients (for example, Netscape) require the user to provide a name
15148 and password for authentication if AUTH is advertised, even though it may
15149 not be needed (the host may accept messages from hosts on its local LAN without
15150 authentication, for example). The &%auth_advertise_hosts%& option can be used
15151 to make these clients more friendly by excluding them from the set of hosts to
15152 which Exim advertises AUTH.
15154 .cindex "AUTH" "advertising when encrypted"
15155 If you want to advertise the availability of AUTH only when the connection
15156 is encrypted using TLS, you can make use of the fact that the value of this
15157 option is expanded, with a setting like this:
15159 auth_advertise_hosts = ${if eq{$tls_in_cipher}{}{}{*}}
15161 .vindex "&$tls_in_cipher$&"
15162 If &$tls_in_cipher$& is empty, the session is not encrypted, and the result of
15163 the expansion is empty, thus matching no hosts. Otherwise, the result of the
15164 expansion is *, which matches all hosts.
15167 .option auto_thaw main time 0s
15168 .cindex "thawing messages"
15169 .cindex "unfreezing messages"
15170 If this option is set to a time greater than zero, a queue runner will try a
15171 new delivery attempt on any frozen message, other than a bounce message, if
15172 this much time has passed since it was frozen. This may result in the message
15173 being re-frozen if nothing has changed since the last attempt. It is a way of
15174 saying &"keep on trying, even though there are big problems"&.
15176 &*Note*&: This is an old option, which predates &%timeout_frozen_after%& and
15177 &%ignore_bounce_errors_after%&. It is retained for compatibility, but it is not
15178 thought to be very useful any more, and its use should probably be avoided.
15181 .option av_scanner main string "see below"
15182 This option is available if Exim is built with the content-scanning extension.
15183 It specifies which anti-virus scanner to use. The default value is:
15185 sophie:/var/run/sophie
15187 If the value of &%av_scanner%& starts with a dollar character, it is expanded
15188 before use. See section &<<SECTscanvirus>>& for further details.
15191 .option bi_command main string unset
15193 This option supplies the name of a command that is run when Exim is called with
15194 the &%-bi%& option (see chapter &<<CHAPcommandline>>&). The string value is
15195 just the command name, it is not a complete command line. If an argument is
15196 required, it must come from the &%-oA%& command line option.
15199 .option bounce_message_file main string&!! unset
15200 .cindex "bounce message" "customizing"
15201 .cindex "customizing" "bounce message"
15202 This option defines a template file containing paragraphs of text to be used
15203 for constructing bounce messages. Details of the file's contents are given in
15204 chapter &<<CHAPemsgcust>>&.
15205 .cindex bounce_message_file "tainted data"
15206 The option is expanded to give the file path, which must be
15207 absolute and untainted.
15208 See also &%warn_message_file%&.
15211 .option bounce_message_text main string unset
15212 When this option is set, its contents are included in the default bounce
15213 message immediately after &"This message was created automatically by mail
15214 delivery software."& It is not used if &%bounce_message_file%& is set.
15216 .option bounce_return_body main boolean true
15217 .cindex "bounce message" "including body"
15218 This option controls whether the body of an incoming message is included in a
15219 bounce message when &%bounce_return_message%& is true. The default setting
15220 causes the entire message, both header and body, to be returned (subject to the
15221 value of &%bounce_return_size_limit%&). If this option is false, only the
15222 message header is included. In the case of a non-SMTP message containing an
15223 error that is detected during reception, only those header lines preceding the
15224 point at which the error was detected are returned.
15225 .cindex "bounce message" "including original"
15227 .option bounce_return_linesize_limit main integer 998
15228 .cindex "size" "of bounce lines, limit"
15229 .cindex "bounce message" "line length limit"
15230 .cindex "limit" "bounce message line length"
15231 This option sets a limit in bytes on the line length of messages
15232 that are returned to senders due to delivery problems,
15233 when &%bounce_return_message%& is true.
15234 The default value corresponds to RFC limits.
15235 If the message being returned has lines longer than this value it is
15236 treated as if the &%bounce_return_size_limit%& (below) restriction was exceeded.
15238 The option also applies to bounces returned when an error is detected
15239 during reception of a message.
15240 In this case lines from the original are truncated.
15242 The option does not apply to messages generated by an &(autoreply)& transport.
15245 .option bounce_return_message main boolean true
15246 If this option is set false, none of the original message is included in
15247 bounce messages generated by Exim. See also &%bounce_return_size_limit%& and
15248 &%bounce_return_body%&.
15251 .option bounce_return_size_limit main integer 100K
15252 .cindex "size" "of bounce, limit"
15253 .cindex "bounce message" "size limit"
15254 .cindex "limit" "bounce message size"
15255 This option sets a limit in bytes on the size of messages that are returned to
15256 senders as part of bounce messages when &%bounce_return_message%& is true. The
15257 limit should be less than the value of the global &%message_size_limit%& and of
15258 any &%message_size_limit%& settings on transports, to allow for the bounce text
15259 that Exim generates. If this option is set to zero there is no limit.
15261 When the body of any message that is to be included in a bounce message is
15262 greater than the limit, it is truncated, and a comment pointing this out is
15263 added at the top. The actual cutoff may be greater than the value given, owing
15264 to the use of buffering for transferring the message in chunks (typically 8K in
15265 size). The idea is to save bandwidth on those undeliverable 15-megabyte
15268 .option bounce_sender_authentication main string unset
15269 .cindex "bounce message" "sender authentication"
15270 .cindex "authentication" "bounce message"
15271 .cindex "AUTH" "on bounce message"
15272 This option provides an authenticated sender address that is sent with any
15273 bounce messages generated by Exim that are sent over an authenticated SMTP
15274 connection. A typical setting might be:
15276 bounce_sender_authentication = mailer-daemon@my.domain.example
15278 which would cause bounce messages to be sent using the SMTP command:
15280 MAIL FROM:<> AUTH=mailer-daemon@my.domain.example
15282 The value of &%bounce_sender_authentication%& must always be a complete email
15285 .option callout_domain_negative_expire main time 3h
15286 .cindex "caching" "callout timeouts"
15287 .cindex "callout" "caching timeouts"
15288 This option specifies the expiry time for negative callout cache data for a
15289 domain. See section &<<SECTcallver>>& for details of callout verification, and
15290 section &<<SECTcallvercache>>& for details of the caching.
15293 .option callout_domain_positive_expire main time 7d
15294 This option specifies the expiry time for positive callout cache data for a
15295 domain. See section &<<SECTcallver>>& for details of callout verification, and
15296 section &<<SECTcallvercache>>& for details of the caching.
15299 .option callout_negative_expire main time 2h
15300 This option specifies the expiry time for negative callout cache data for an
15301 address. See section &<<SECTcallver>>& for details of callout verification, and
15302 section &<<SECTcallvercache>>& for details of the caching.
15305 .option callout_positive_expire main time 24h
15306 This option specifies the expiry time for positive callout cache data for an
15307 address. See section &<<SECTcallver>>& for details of callout verification, and
15308 section &<<SECTcallvercache>>& for details of the caching.
15311 .option callout_random_local_part main string&!! "see below"
15312 This option defines the &"random"& local part that can be used as part of
15313 callout verification. The default value is
15315 $primary_hostname-$tod_epoch-testing
15317 See section &<<CALLaddparcall>>& for details of how this value is used.
15320 .option check_log_inodes main integer 100
15321 See &%check_spool_space%& below.
15324 .option check_log_space main integer 10M
15325 See &%check_spool_space%& below.
15327 .oindex "&%check_rfc2047_length%&"
15328 .cindex "RFC 2047" "disabling length check"
15329 .option check_rfc2047_length main boolean true
15330 RFC 2047 defines a way of encoding non-ASCII characters in headers using a
15331 system of &"encoded words"&. The RFC specifies a maximum length for an encoded
15332 word; strings to be encoded that exceed this length are supposed to use
15333 multiple encoded words. By default, Exim does not recognize encoded words that
15334 exceed the maximum length. However, it seems that some software, in violation
15335 of the RFC, generates overlong encoded words. If &%check_rfc2047_length%& is
15336 set false, Exim recognizes encoded words of any length.
15339 .option check_spool_inodes main integer 100
15340 See &%check_spool_space%& below.
15343 .option check_spool_space main integer 10M
15344 .cindex "checking disk space"
15345 .cindex "disk space, checking"
15346 .cindex "spool directory" "checking space"
15347 The four &%check_...%& options allow for checking of disk resources before a
15348 message is accepted.
15350 .vindex "&$log_inodes$&"
15351 .vindex "&$log_space$&"
15352 .vindex "&$spool_inodes$&"
15353 .vindex "&$spool_space$&"
15354 When any of these options are nonzero, they apply to all incoming messages. If you
15355 want to apply different checks to different kinds of message, you can do so by
15356 testing the variables &$log_inodes$&, &$log_space$&, &$spool_inodes$&, and
15357 &$spool_space$& in an ACL with appropriate additional conditions.
15360 &%check_spool_space%& and &%check_spool_inodes%& check the spool partition if
15361 either value is greater than zero, for example:
15363 check_spool_space = 100M
15364 check_spool_inodes = 100
15366 The spool partition is the one that contains the directory defined by
15367 SPOOL_DIRECTORY in &_Local/Makefile_&. It is used for holding messages in
15370 &%check_log_space%& and &%check_log_inodes%& check the partition in which log
15371 files are written if either is greater than zero. These should be set only if
15372 &%log_file_path%& and &%spool_directory%& refer to different partitions.
15374 If there is less space or fewer inodes than requested, Exim refuses to accept
15375 incoming mail. In the case of SMTP input this is done by giving a 452 temporary
15376 error response to the MAIL command. If ESMTP is in use and there was a
15377 SIZE parameter on the MAIL command, its value is added to the
15378 &%check_spool_space%& value, and the check is performed even if
15379 &%check_spool_space%& is zero, unless &%no_smtp_check_spool_space%& is set.
15381 The values for &%check_spool_space%& and &%check_log_space%& are held as a
15382 number of kilobytes (though specified in bytes).
15383 If a non-multiple of 1024 is specified, it is rounded up.
15385 For non-SMTP input and for batched SMTP input, the test is done at start-up; on
15386 failure a message is written to stderr and Exim exits with a non-zero code, as
15387 it obviously cannot send an error message of any kind.
15389 There is a slight performance penalty for these checks.
15390 Versions of Exim preceding 4.88 had these disabled by default;
15391 high-rate installations confident they will never run out of resources
15392 may wish to deliberately disable them.
15394 .option chunking_advertise_hosts main "host list&!!" *
15395 .cindex CHUNKING advertisement
15396 .cindex "RFC 3030" "CHUNKING"
15397 .cindex "ESMTP extensions" CHUNKING
15398 The CHUNKING extension (RFC3030) will be advertised in the EHLO message to
15400 Hosts may use the BDAT command as an alternate to DATA.
15402 .option commandline_checks_require_admin main boolean &`false`&
15403 .cindex "restricting access to features"
15404 This option restricts various basic checking features to require an
15405 administrative user.
15406 This affects most of the &%-b*%& options, such as &%-be%&.
15408 .option debug_store main boolean &`false`&
15409 .cindex debugging "memory corruption"
15410 .cindex memory debugging
15411 This option, when true, enables extra checking in Exim's internal memory
15412 management. For use when a memory corruption issue is being investigated,
15413 it should normally be left as default.
15415 .option daemon_smtp_ports main string &`smtp`&
15416 .cindex "port" "for daemon"
15417 .cindex "TCP/IP" "setting listening ports"
15418 This option specifies one or more default SMTP ports on which the Exim daemon
15419 listens. See chapter &<<CHAPinterfaces>>& for details of how it is used. For
15420 backward compatibility, &%daemon_smtp_port%& (singular) is a synonym.
15422 .option daemon_startup_retries main integer 9
15423 .cindex "daemon startup, retrying"
15424 This option, along with &%daemon_startup_sleep%&, controls the retrying done by
15425 the daemon at startup when it cannot immediately bind a listening socket
15426 (typically because the socket is already in use): &%daemon_startup_retries%&
15427 defines the number of retries after the first failure, and
15428 &%daemon_startup_sleep%& defines the length of time to wait between retries.
15430 .option daemon_startup_sleep main time 30s
15431 See &%daemon_startup_retries%&.
15433 .option delay_warning main "time list" 24h
15434 .cindex "warning of delay"
15435 .cindex "delay warning, specifying"
15436 .cindex "queue" "delay warning"
15437 When a message is delayed, Exim sends a warning message to the sender at
15438 intervals specified by this option. The data is a colon-separated list of times
15439 after which to send warning messages. If the value of the option is an empty
15440 string or a zero time, no warnings are sent. Up to 10 times may be given. If a
15441 message has been in the queue for longer than the last time, the last interval
15442 between the times is used to compute subsequent warning times. For example,
15445 delay_warning = 4h:8h:24h
15447 the first message is sent after 4 hours, the second after 8 hours, and
15448 the third one after 24 hours. After that, messages are sent every 16 hours,
15449 because that is the interval between the last two times on the list. If you set
15450 just one time, it specifies the repeat interval. For example, with:
15454 messages are repeated every six hours. To stop warnings after a given time, set
15455 a very large time at the end of the list. For example:
15457 delay_warning = 2h:12h:99d
15459 Note that the option is only evaluated at the time a delivery attempt fails,
15460 which depends on retry and queue-runner configuration.
15461 Typically retries will be configured more frequently than warning messages.
15463 .option delay_warning_condition main string&!! "see below"
15464 .vindex "&$domain$&"
15465 The string is expanded at the time a warning message might be sent. If all the
15466 deferred addresses have the same domain, it is set in &$domain$& during the
15467 expansion. Otherwise &$domain$& is empty. If the result of the expansion is a
15468 forced failure, an empty string, or a string matching any of &"0"&, &"no"& or
15469 &"false"& (the comparison being done caselessly) then the warning message is
15470 not sent. The default is:
15472 delay_warning_condition = ${if or {\
15473 { !eq{$h_list-id:$h_list-post:$h_list-subscribe:}{} }\
15474 { match{$h_precedence:}{(?i)bulk|list|junk} }\
15475 { match{$h_auto-submitted:}{(?i)auto-generated|auto-replied} }\
15478 This suppresses the sending of warnings for messages that contain &'List-ID:'&,
15479 &'List-Post:'&, or &'List-Subscribe:'& headers, or have &"bulk"&, &"list"& or
15480 &"junk"& in a &'Precedence:'& header, or have &"auto-generated"& or
15481 &"auto-replied"& in an &'Auto-Submitted:'& header.
15483 .option deliver_drop_privilege main boolean false
15484 .cindex "unprivileged delivery"
15485 .cindex "delivery" "unprivileged"
15486 If this option is set true, Exim drops its root privilege at the start of a
15487 delivery process, and runs as the Exim user throughout. This severely restricts
15488 the kinds of local delivery that are possible, but is viable in certain types
15489 of configuration. There is a discussion about the use of root privilege in
15490 chapter &<<CHAPsecurity>>&.
15492 .option deliver_queue_load_max main fixed-point unset
15493 .cindex "load average"
15494 .cindex "queue runner" "abandoning"
15495 When this option is set, a queue run is abandoned if the system load average
15496 becomes greater than the value of the option. The option has no effect on
15497 ancient operating systems on which Exim cannot determine the load average.
15498 See also &%queue_only_load%& and &%smtp_load_reserve%&.
15501 .option delivery_date_remove main boolean true
15502 .cindex "&'Delivery-date:'& header line"
15503 Exim's transports have an option for adding a &'Delivery-date:'& header to a
15504 message when it is delivered, in exactly the same way as &'Return-path:'& is
15505 handled. &'Delivery-date:'& records the actual time of delivery. Such headers
15506 should not be present in incoming messages, and this option causes them to be
15507 removed at the time the message is received, to avoid any problems that might
15508 occur when a delivered message is subsequently sent on to some other recipient.
15510 .option disable_fsync main boolean false
15511 .cindex "&[fsync()]&, disabling"
15512 This option is available only if Exim was built with the compile-time option
15513 ENABLE_DISABLE_FSYNC. When this is not set, a reference to &%disable_fsync%& in
15514 a runtime configuration generates an &"unknown option"& error. You should not
15515 build Exim with ENABLE_DISABLE_FSYNC or set &%disable_fsync%& unless you
15516 really, really, really understand what you are doing. &'No pre-compiled
15517 distributions of Exim should ever make this option available.'&
15519 When &%disable_fsync%& is set true, Exim no longer calls &[fsync()]& to force
15520 updated files' data to be written to disc before continuing. Unexpected events
15521 such as crashes and power outages may cause data to be lost or scrambled.
15522 Here be Dragons. &*Beware.*&
15525 .option disable_ipv6 main boolean false
15526 .cindex "IPv6" "disabling"
15527 If this option is set true, even if the Exim binary has IPv6 support, no IPv6
15528 activities take place. AAAA records are never looked up, and any IPv6 addresses
15529 that are listed in &%local_interfaces%&, data for the &%manualroute%& router,
15530 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
15531 to handle IPv6 literal addresses.
15534 .option dkim_verify_hashes main "string list" "sha256 : sha512"
15535 .cindex DKIM "selecting signature algorithms"
15536 This option gives a list of hash types which are acceptable in signatures,
15537 and an order of processing.
15538 Signatures with algorithms not in the list will be ignored.
15540 Acceptable values include:
15547 Note that the acceptance of sha1 violates RFC 8301.
15549 .option dkim_verify_keytypes main "string list" "ed25519 : rsa"
15550 This option gives a list of key types which are acceptable in signatures,
15551 and an order of processing.
15552 Signatures with algorithms not in the list will be ignored.
15555 .option dkim_verify_min_keysizes main "string list" "rsa=1024 ed25519=250"
15556 This option gives a list of key sizes which are acceptable in signatures.
15557 The list is keyed by the algorithm type for the key; the values are in bits.
15558 Signatures with keys smaller than given by this option will fail verification.
15560 The default enforces the RFC 8301 minimum key size for RSA signatures.
15562 .option dkim_verify_minimal main boolean false
15563 If set to true, verification of signatures will terminate after the
15566 .option dkim_verify_signers main "domain list&!!" $dkim_signers
15567 .cindex DKIM "controlling calls to the ACL"
15568 This option gives a list of DKIM domains for which the DKIM ACL is run.
15569 It is expanded after the message is received; by default it runs
15570 the ACL once for each signature in the message.
15571 See section &<<SECDKIMVFY>>&.
15574 .option dmarc_forensic_sender main string&!! unset
15575 .option dmarc_history_file main string unset
15576 .option dmarc_tld_file main string unset
15577 .cindex DMARC "main section options"
15578 These options control DMARC processing.
15579 See section &<<SECDMARC>>& for details.
15582 .option dns_again_means_nonexist main "domain list&!!" unset
15583 .cindex "DNS" "&""try again""& response; overriding"
15584 DNS lookups give a &"try again"& response for the DNS errors
15585 &"non-authoritative host not found"& and &"SERVERFAIL"&. This can cause Exim to
15586 keep trying to deliver a message, or to give repeated temporary errors to
15587 incoming mail. Sometimes the effect is caused by a badly set up name server and
15588 may persist for a long time. If a domain which exhibits this problem matches
15589 anything in &%dns_again_means_nonexist%&, it is treated as if it did not exist.
15590 This option should be used with care. You can make it apply to reverse lookups
15591 by a setting such as this:
15593 dns_again_means_nonexist = *.in-addr.arpa
15595 This option applies to all DNS lookups that Exim does. It also applies when the
15596 &[gethostbyname()]& or &[getipnodebyname()]& functions give temporary errors,
15597 since these are most likely to be caused by DNS lookup problems. The
15598 &(dnslookup)& router has some options of its own for controlling what happens
15599 when lookups for MX or SRV records give temporary errors. These more specific
15600 options are applied after this global option.
15602 .option dns_check_names_pattern main string "see below"
15603 .cindex "DNS" "pre-check of name syntax"
15604 When this option is set to a non-empty string, it causes Exim to check domain
15605 names for characters that are not allowed in host names before handing them to
15606 the DNS resolver, because some resolvers give temporary errors for names that
15607 contain unusual characters. If a domain name contains any unwanted characters,
15608 a &"not found"& result is forced, and the resolver is not called. The check is
15609 done by matching the domain name against a regular expression, which is the
15610 value of this option. The default pattern is
15612 dns_check_names_pattern = \
15613 (?i)^(?>(?(1)\.|())[^\W_](?>[a-z0-9/-]*[^\W_])?)+$
15615 which permits only letters, digits, slashes, and hyphens in components, but
15616 they must start and end with a letter or digit. Slashes are not, in fact,
15617 permitted in host names, but they are found in certain NS records (which can be
15618 accessed in Exim by using a &%dnsdb%& lookup). If you set
15619 &%allow_utf8_domains%&, you must modify this pattern, or set the option to an
15622 .option dns_csa_search_limit main integer 5
15623 This option controls the depth of parental searching for CSA SRV records in the
15624 DNS, as described in more detail in section &<<SECTverifyCSA>>&.
15626 .option dns_csa_use_reverse main boolean true
15627 This option controls whether or not an IP address, given as a CSA domain, is
15628 reversed and looked up in the reverse DNS, as described in more detail in
15629 section &<<SECTverifyCSA>>&.
15631 .option dns_cname_loops main integer 1
15632 .cindex DNS "CNAME following"
15633 This option controls the following of CNAME chains, needed if the resolver does
15634 not do it internally.
15635 As of 2018 most should, and the default can be left.
15636 If you have an ancient one, a value of 10 is likely needed.
15638 The default value of one CNAME-follow is needed
15639 thanks to the observed return for an MX request,
15640 given no MX presence but a CNAME to an A, of the CNAME.
15643 .option dns_dnssec_ok main integer -1
15644 .cindex "DNS" "resolver options"
15645 .cindex "DNS" "DNSSEC"
15646 If this option is set to a non-negative number then Exim will initialise the
15647 DNS resolver library to either use or not use DNSSEC, overriding the system
15648 default. A value of 0 coerces DNSSEC off, a value of 1 coerces DNSSEC on.
15650 If the resolver library does not support DNSSEC then this option has no effect.
15652 On Linux with glibc 2.31 or newer this is insufficient, the resolver library
15653 will default to stripping out a successful validation status.
15654 This will break a previously working Exim installation.
15655 Provided that you do trust the resolver (ie, is on localhost) you can tell
15656 glibc to pass through any successful validation with a new option in
15657 &_/etc/resolv.conf_&:
15663 .option dns_ipv4_lookup main "domain list&!!" unset
15664 .cindex "IPv6" "DNS lookup for AAAA records"
15665 .cindex "DNS" "IPv6 lookup for AAAA records"
15666 .cindex DNS "IPv6 disabling"
15667 When Exim is compiled with IPv6 support and &%disable_ipv6%& is not set, it
15668 looks for IPv6 address records (AAAA records) as well as IPv4 address records
15669 (A records) when trying to find IP addresses for hosts, unless the host's
15670 domain matches this list.
15672 This is a fudge to help with name servers that give big delays or otherwise do
15673 not work for the AAAA record type. In due course, when the world's name
15674 servers have all been upgraded, there should be no need for this option.
15675 Note that all lookups, including those done for verification, are affected;
15676 this will result in verify failure for IPv6 connections or ones using names
15677 only valid for IPv6 addresses.
15680 .option dns_retrans main time 0s
15681 .cindex "DNS" "resolver options"
15682 .cindex timeout "dns lookup"
15683 .cindex "DNS" timeout
15684 The options &%dns_retrans%& and &%dns_retry%& can be used to set the
15685 retransmission and retry parameters for DNS lookups. Values of zero (the
15686 defaults) leave the system default settings unchanged. The first value is the
15687 time between retries, and the second is the number of retries. It isn't
15688 totally clear exactly how these settings affect the total time a DNS lookup may
15689 take. I haven't found any documentation about timeouts on DNS lookups; these
15690 parameter values are available in the external resolver interface structure,
15691 but nowhere does it seem to describe how they are used or what you might want
15693 See also the &%slow_lookup_log%& option.
15696 .option dns_retry main integer 0
15697 See &%dns_retrans%& above.
15700 .option dns_trust_aa main "domain list&!!" unset
15701 .cindex "DNS" "resolver options"
15702 .cindex "DNS" "DNSSEC"
15703 If this option is set then lookup results marked with the AA bit
15704 (Authoritative Answer) are trusted the same way as if they were
15705 DNSSEC-verified. The authority section's name of the answer must
15706 match with this expanded domain list.
15708 Use this option only if you talk directly to a resolver that is
15709 authoritative for some zones and does not set the AD (Authentic Data)
15710 bit in the answer. Some DNS servers may have an configuration option to
15711 mark the answers from their own zones as verified (they set the AD bit).
15712 Others do not have this option. It is considered as poor practice using
15713 a resolver that is an authoritative server for some zones.
15715 Use this option only if you really have to (e.g. if you want
15716 to use DANE for remote delivery to a server that is listed in the DNS
15717 zones that your resolver is authoritative for).
15719 If the DNS answer packet has the AA bit set and contains resource record
15720 in the answer section, the name of the first NS record appearing in the
15721 authority section is compared against the list. If the answer packet is
15722 authoritative but the answer section is empty, the name of the first SOA
15723 record in the authoritative section is used instead.
15725 .cindex "DNS" "resolver options"
15726 .option dns_use_edns0 main integer -1
15727 .cindex "DNS" "resolver options"
15728 .cindex "DNS" "EDNS0"
15729 .cindex "DNS" "OpenBSD
15730 If this option is set to a non-negative number then Exim will initialise the
15731 DNS resolver library to either use or not use EDNS0 extensions, overriding
15732 the system default. A value of 0 coerces EDNS0 off, a value of 1 coerces EDNS0
15735 If the resolver library does not support EDNS0 then this option has no effect.
15737 OpenBSD's asr resolver routines are known to ignore the EDNS0 option; this
15738 means that DNSSEC will not work with Exim on that platform either, unless Exim
15739 is linked against an alternative DNS client library.
15742 .option drop_cr main boolean false
15743 This is an obsolete option that is now a no-op. It used to affect the way Exim
15744 handled CR and LF characters in incoming messages. What happens now is
15745 described in section &<<SECTlineendings>>&.
15747 .option dsn_advertise_hosts main "host list&!!" unset
15748 .cindex "bounce messages" "success"
15749 .cindex "DSN" "success"
15750 .cindex "Delivery Status Notification" "success"
15751 .cindex "ESMTP extensions" DSN
15752 DSN extensions (RFC3461) will be advertised in the EHLO message to,
15753 and accepted from, these hosts.
15754 Hosts may use the NOTIFY and ORCPT options on RCPT TO commands,
15755 and RET and ENVID options on MAIL FROM commands.
15756 A NOTIFY=SUCCESS option requests success-DSN messages.
15757 A NOTIFY= option with no argument requests that no delay or failure DSNs
15759 &*Note*&: Supplying success-DSN messages has been criticised
15760 on privacy grounds; it can leak details of internal forwarding.
15762 .option dsn_from main "string&!!" "see below"
15763 .cindex "&'From:'& header line" "in bounces"
15764 .cindex "bounce messages" "&'From:'& line, specifying"
15765 This option can be used to vary the contents of &'From:'& header lines in
15766 bounces and other automatically generated messages (&"Delivery Status
15767 Notifications"& &-- hence the name of the option). The default setting is:
15769 dsn_from = Mail Delivery System <Mailer-Daemon@$qualify_domain>
15771 The value is expanded every time it is needed. If the expansion fails, a
15772 panic is logged, and the default value is used.
15774 .option envelope_to_remove main boolean true
15775 .cindex "&'Envelope-to:'& header line"
15776 Exim's transports have an option for adding an &'Envelope-to:'& header to a
15777 message when it is delivered, in exactly the same way as &'Return-path:'& is
15778 handled. &'Envelope-to:'& records the original recipient address from the
15779 message's envelope that caused the delivery to happen. Such headers should not
15780 be present in incoming messages, and this option causes them to be removed at
15781 the time the message is received, to avoid any problems that might occur when a
15782 delivered message is subsequently sent on to some other recipient.
15785 .option errors_copy main "string list&!!" unset
15786 .cindex "bounce message" "copy to other address"
15787 .cindex "copy of bounce message"
15788 Setting this option causes Exim to send bcc copies of bounce messages that it
15789 generates to other addresses. &*Note*&: This does not apply to bounce messages
15790 coming from elsewhere. The value of the option is a colon-separated list of
15791 items. Each item consists of a pattern, terminated by white space, followed by
15792 a comma-separated list of email addresses. If a pattern contains spaces, it
15793 must be enclosed in double quotes.
15795 Each pattern is processed in the same way as a single item in an address list
15796 (see section &<<SECTaddresslist>>&). When a pattern matches the recipient of
15797 the bounce message, the message is copied to the addresses on the list. The
15798 items are scanned in order, and once a matching one is found, no further items
15799 are examined. For example:
15801 errors_copy = spqr@mydomain postmaster@mydomain.example :\
15802 rqps@mydomain hostmaster@mydomain.example,\
15803 postmaster@mydomain.example
15805 .vindex "&$domain$&"
15806 .vindex "&$local_part$&"
15807 The address list is expanded before use. The expansion variables &$local_part$&
15808 and &$domain$& are set from the original recipient of the error message, and if
15809 there was any wildcard matching in the pattern, the expansion
15810 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%errors_copy%&"
15811 variables &$0$&, &$1$&, etc. are set in the normal way.
15814 .option errors_reply_to main string unset
15815 .cindex "bounce message" "&'Reply-to:'& in"
15816 By default, Exim's bounce and delivery warning messages contain the header line
15818 &`From: Mail Delivery System <Mailer-Daemon@`&&'qualify-domain'&&`>`&
15820 .oindex &%quota_warn_message%&
15821 where &'qualify-domain'& is the value of the &%qualify_domain%& option.
15822 A warning message that is generated by the &%quota_warn_message%& option in an
15823 &(appendfile)& transport may contain its own &'From:'& header line that
15824 overrides the default.
15826 Experience shows that people reply to bounce messages. If the
15827 &%errors_reply_to%& option is set, a &'Reply-To:'& header is added to bounce
15828 and warning messages. For example:
15830 errors_reply_to = postmaster@my.domain.example
15832 The value of the option is not expanded. It must specify a valid RFC 2822
15833 address. However, if a warning message that is generated by the
15834 &%quota_warn_message%& option in an &(appendfile)& transport contain its
15835 own &'Reply-To:'& header line, the value of the &%errors_reply_to%& option is
15839 .option event_action main string&!! unset
15841 This option declares a string to be expanded for Exim's events mechanism.
15842 For details see chapter &<<CHAPevents>>&.
15845 .option exim_group main string "compile-time configured"
15846 .cindex "gid (group id)" "Exim's own"
15847 .cindex "Exim group"
15848 This option changes the gid under which Exim runs when it gives up root
15849 privilege. The default value is compiled into the binary. The value of this
15850 option is used only when &%exim_user%& is also set. Unless it consists entirely
15851 of digits, the string is looked up using &[getgrnam()]&, and failure causes a
15852 configuration error. See chapter &<<CHAPsecurity>>& for a discussion of
15856 .option exim_path main string "see below"
15857 .cindex "Exim binary, path name"
15858 This option specifies the path name of the Exim binary, which is used when Exim
15859 needs to re-exec itself. The default is set up to point to the file &'exim'& in
15860 the directory configured at compile time by the BIN_DIRECTORY setting. It
15861 is necessary to change &%exim_path%& if, exceptionally, Exim is run from some
15863 &*Warning*&: Do not use a macro to define the value of this option, because
15864 you will break those Exim utilities that scan the configuration file to find
15865 where the binary is. (They then use the &%-bP%& option to extract option
15866 settings such as the value of &%spool_directory%&.)
15869 .option exim_user main string "compile-time configured"
15870 .cindex "uid (user id)" "Exim's own"
15871 .cindex "Exim user"
15872 This option changes the uid under which Exim runs when it gives up root
15873 privilege. The default value is compiled into the binary. Ownership of the run
15874 time configuration file and the use of the &%-C%& and &%-D%& command line
15875 options is checked against the values in the binary, not what is set here.
15877 Unless it consists entirely of digits, the string is looked up using
15878 &[getpwnam()]&, and failure causes a configuration error. If &%exim_group%& is
15879 not also supplied, the gid is taken from the result of &[getpwnam()]& if it is
15880 used. See chapter &<<CHAPsecurity>>& for a discussion of security issues.
15883 .option exim_version main string "current version"
15884 .cindex "Exim version"
15885 .cindex customizing "version number"
15886 .cindex "version number of Exim" override
15887 This option overrides the &$version_number$&/&$exim_version$& that Exim reports in
15888 various places. Use with care; this may fool stupid security scanners.
15891 .option extra_local_interfaces main "string list" unset
15892 This option defines network interfaces that are to be considered local when
15893 routing, but which are not used for listening by the daemon. See section
15894 &<<SECTreclocipadd>>& for details.
15897 . Allow this long option name to split; give it unsplit as a fifth argument
15898 . for the automatic .oindex that is generated by .option.
15900 .option "extract_addresses_remove_arguments" main boolean true &&&
15901 extract_addresses_remove_arguments
15903 .cindex "command line" "addresses with &%-t%&"
15904 .cindex "Sendmail compatibility" "&%-t%& option"
15905 According to some Sendmail documentation (Sun, IRIX, HP-UX), if any addresses
15906 are present on the command line when the &%-t%& option is used to build an
15907 envelope from a message's &'To:'&, &'Cc:'& and &'Bcc:'& headers, the command
15908 line addresses are removed from the recipients list. This is also how Smail
15909 behaves. However, other Sendmail documentation (the O'Reilly book) states that
15910 command line addresses are added to those obtained from the header lines. When
15911 &%extract_addresses_remove_arguments%& is true (the default), Exim subtracts
15912 argument headers. If it is set false, Exim adds rather than removes argument
15916 .option finduser_retries main integer 0
15917 .cindex "NIS, retrying user lookups"
15918 On systems running NIS or other schemes in which user and group information is
15919 distributed from a remote system, there can be times when &[getpwnam()]& and
15920 related functions fail, even when given valid data, because things time out.
15921 Unfortunately these failures cannot be distinguished from genuine &"not found"&
15922 errors. If &%finduser_retries%& is set greater than zero, Exim will try that
15923 many extra times to find a user or a group, waiting for one second between
15926 .cindex "&_/etc/passwd_&" "multiple reading of"
15927 You should not set this option greater than zero if your user information is in
15928 a traditional &_/etc/passwd_& file, because it will cause Exim needlessly to
15929 search the file multiple times for non-existent users, and also cause delay.
15933 .option freeze_tell main "string list, comma separated" unset
15934 .cindex "freezing messages" "sending a message when freezing"
15935 On encountering certain errors, or when configured to do so in a system filter,
15936 ACL, or special router, Exim freezes a message. This means that no further
15937 delivery attempts take place until an administrator thaws the message, or the
15938 &%auto_thaw%&, &%ignore_bounce_errors_after%&, or &%timeout_frozen_after%&
15939 feature cause it to be processed. If &%freeze_tell%& is set, Exim generates a
15940 warning message whenever it freezes something, unless the message it is
15941 freezing is a locally-generated bounce message. (Without this exception there
15942 is the possibility of looping.) The warning message is sent to the addresses
15943 supplied as the comma-separated value of this option. If several of the
15944 message's addresses cause freezing, only a single message is sent. If the
15945 freezing was automatic, the reason(s) for freezing can be found in the message
15946 log. If you configure freezing in a filter or ACL, you must arrange for any
15947 logging that you require.
15950 .option gecos_name main string&!! unset
15952 .cindex "&""gecos""& field, parsing"
15953 Some operating systems, notably HP-UX, use the &"gecos"& field in the system
15954 password file to hold other information in addition to users' real names. Exim
15955 looks up this field for use when it is creating &'Sender:'& or &'From:'&
15956 headers. If either &%gecos_pattern%& or &%gecos_name%& are unset, the contents
15957 of the field are used unchanged, except that, if an ampersand is encountered,
15958 it is replaced by the user's login name with the first character forced to
15959 upper case, since this is a convention that is observed on many systems.
15961 When these options are set, &%gecos_pattern%& is treated as a regular
15962 expression that is to be applied to the field (again with && replaced by the
15963 login name), and if it matches, &%gecos_name%& is expanded and used as the
15966 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%gecos_name%&"
15967 Numeric variables such as &$1$&, &$2$&, etc. can be used in the expansion to
15968 pick up sub-fields that were matched by the pattern. In HP-UX, where the user's
15969 name terminates at the first comma, the following can be used:
15971 gecos_pattern = ([^,]*)
15975 .option gecos_pattern main string unset
15976 See &%gecos_name%& above.
15979 .option gnutls_compat_mode main boolean unset
15980 This option controls whether GnuTLS is used in compatibility mode in an Exim
15981 server. This reduces security slightly, but improves interworking with older
15982 implementations of TLS.
15985 .option gnutls_allow_auto_pkcs11 main boolean unset
15986 This option will let GnuTLS (2.12.0 or later) autoload PKCS11 modules with
15987 the p11-kit configuration files in &_/etc/pkcs11/modules/_&.
15990 &url(https://www.gnutls.org/manual/gnutls.html#Smart-cards-and-HSMs)
15995 .option headers_charset main string "see below"
15996 This option sets a default character set for translating from encoded MIME
15997 &"words"& in header lines, when referenced by an &$h_xxx$& expansion item. The
15998 default is the value of HEADERS_CHARSET in &_Local/Makefile_&. The
15999 ultimate default is ISO-8859-1. For more details see the description of header
16000 insertions in section &<<SECTexpansionitems>>&.
16004 .option header_maxsize main integer "see below"
16005 .cindex "header section" "maximum size of"
16006 .cindex "limit" "size of message header section"
16007 This option controls the overall maximum size of a message's header
16008 section. The default is the value of HEADER_MAXSIZE in
16009 &_Local/Makefile_&; the default for that is 1M. Messages with larger header
16010 sections are rejected.
16013 .option header_line_maxsize main integer 0
16014 .cindex "header lines" "maximum size of"
16015 .cindex "limit" "size of one header line"
16016 This option limits the length of any individual header line in a message, after
16017 all the continuations have been joined together. Messages with individual
16018 header lines that are longer than the limit are rejected. The default value of
16019 zero means &"no limit"&.
16024 .option helo_accept_junk_hosts main "host list&!!" unset
16025 .cindex "HELO" "accepting junk data"
16026 .cindex "EHLO" "accepting junk data"
16027 Exim checks the syntax of HELO and EHLO commands for incoming SMTP
16028 mail, and gives an error response for invalid data. Unfortunately, there are
16029 some SMTP clients that send syntactic junk. They can be accommodated by setting
16030 this option. Note that this is a syntax check only. See &%helo_verify_hosts%&
16031 if you want to do semantic checking.
16032 See also &%helo_allow_chars%& for a way of extending the permitted character
16036 .option helo_allow_chars main string unset
16037 .cindex "HELO" "underscores in"
16038 .cindex "EHLO" "underscores in"
16039 .cindex "underscore in EHLO/HELO"
16040 This option can be set to a string of rogue characters that are permitted in
16041 all EHLO and HELO names in addition to the standard letters, digits,
16042 hyphens, and dots. If you really must allow underscores, you can set
16044 helo_allow_chars = _
16046 Note that the value is one string, not a list.
16049 .option helo_lookup_domains main "domain list&!!" &`@:@[]`&
16050 .cindex "HELO" "forcing reverse lookup"
16051 .cindex "EHLO" "forcing reverse lookup"
16052 If the domain given by a client in a HELO or EHLO command matches this
16053 list, a reverse lookup is done in order to establish the host's true name. The
16054 default forces a lookup if the client host gives the server's name or any of
16055 its IP addresses (in brackets), something that broken clients have been seen to
16059 .option helo_try_verify_hosts main "host list&!!" unset
16060 .cindex "HELO verifying" "optional"
16061 .cindex "EHLO" "verifying, optional"
16062 By default, Exim just checks the syntax of HELO and EHLO commands (see
16063 &%helo_accept_junk_hosts%& and &%helo_allow_chars%&). However, some sites like
16064 to do more extensive checking of the data supplied by these commands. The ACL
16065 condition &`verify = helo`& is provided to make this possible.
16066 Formerly, it was necessary also to set this option (&%helo_try_verify_hosts%&)
16067 to force the check to occur. From release 4.53 onwards, this is no longer
16068 necessary. If the check has not been done before &`verify = helo`& is
16069 encountered, it is done at that time. Consequently, this option is obsolete.
16070 Its specification is retained here for backwards compatibility.
16072 When an EHLO or HELO command is received, if the calling host matches
16073 &%helo_try_verify_hosts%&, Exim checks that the host name given in the HELO or
16074 EHLO command either:
16077 is an IP literal matching the calling address of the host, or
16079 .cindex "DNS" "reverse lookup"
16080 .cindex "reverse DNS lookup"
16081 matches the host name that Exim obtains by doing a reverse lookup of the
16082 calling host address, or
16084 when looked up in DNS yields the calling host address.
16087 However, the EHLO or HELO command is not rejected if any of the checks
16088 fail. Processing continues, but the result of the check is remembered, and can
16089 be detected later in an ACL by the &`verify = helo`& condition.
16091 If DNS was used for successful verification, the variable
16092 .cindex "DNS" "DNSSEC"
16093 &$helo_verify_dnssec$& records the DNSSEC status of the lookups.
16095 .option helo_verify_hosts main "host list&!!" unset
16096 .cindex "HELO verifying" "mandatory"
16097 .cindex "EHLO" "verifying, mandatory"
16098 Like &%helo_try_verify_hosts%&, this option is obsolete, and retained only for
16099 backwards compatibility. For hosts that match this option, Exim checks the host
16100 name given in the HELO or EHLO in the same way as for
16101 &%helo_try_verify_hosts%&. If the check fails, the HELO or EHLO command is
16102 rejected with a 550 error, and entries are written to the main and reject logs.
16103 If a MAIL command is received before EHLO or HELO, it is rejected with a 503
16106 .option hold_domains main "domain list&!!" unset
16107 .cindex "domain" "delaying delivery"
16108 .cindex "delivery" "delaying certain domains"
16109 This option allows mail for particular domains to be held in the queue
16110 manually. The option is overridden if a message delivery is forced with the
16111 &%-M%&, &%-qf%&, &%-Rf%& or &%-Sf%& options, and also while testing or
16112 verifying addresses using &%-bt%& or &%-bv%&. Otherwise, if a domain matches an
16113 item in &%hold_domains%&, no routing or delivery for that address is done, and
16114 it is deferred every time the message is looked at.
16116 This option is intended as a temporary operational measure for delaying the
16117 delivery of mail while some problem is being sorted out, or some new
16118 configuration tested. If you just want to delay the processing of some
16119 domains until a queue run occurs, you should use &%queue_domains%& or
16120 &%queue_smtp_domains%&, not &%hold_domains%&.
16122 A setting of &%hold_domains%& does not override Exim's code for removing
16123 messages from the queue if they have been there longer than the longest retry
16124 time in any retry rule. If you want to hold messages for longer than the normal
16125 retry times, insert a dummy retry rule with a long retry time.
16128 .option host_lookup main "host list&!!" unset
16129 .cindex "host name" "lookup, forcing"
16130 Exim does not look up the name of a calling host from its IP address unless it
16131 is required to compare against some host list, or the host matches
16132 &%helo_try_verify_hosts%& or &%helo_verify_hosts%&, or the host matches this
16133 option (which normally contains IP addresses rather than host names). The
16134 default configuration file contains
16138 which causes a lookup to happen for all hosts. If the expense of these lookups
16139 is felt to be too great, the setting can be changed or removed.
16141 After a successful reverse lookup, Exim does a forward lookup on the name it
16142 has obtained, to verify that it yields the IP address that it started with. If
16143 this check fails, Exim behaves as if the name lookup failed.
16145 .vindex "&$host_lookup_failed$&"
16146 .vindex "&$sender_host_name$&"
16147 After any kind of failure, the host name (in &$sender_host_name$&) remains
16148 unset, and &$host_lookup_failed$& is set to the string &"1"&. See also
16149 &%dns_again_means_nonexist%&, &%helo_lookup_domains%&, and
16150 &`verify = reverse_host_lookup`& in ACLs.
16153 .option host_lookup_order main "string list" &`bydns:byaddr`&
16154 This option specifies the order of different lookup methods when Exim is trying
16155 to find a host name from an IP address. The default is to do a DNS lookup
16156 first, and then to try a local lookup (using &[gethostbyaddr()]& or equivalent)
16157 if that fails. You can change the order of these lookups, or omit one entirely,
16160 &*Warning*&: The &"byaddr"& method does not always yield aliases when there are
16161 multiple PTR records in the DNS and the IP address is not listed in
16162 &_/etc/hosts_&. Different operating systems give different results in this
16163 case. That is why the default tries a DNS lookup first.
16167 .option host_reject_connection main "host list&!!" unset
16168 .cindex "host" "rejecting connections from"
16169 If this option is set, incoming SMTP calls from the hosts listed are rejected
16170 as soon as the connection is made.
16171 This option is obsolete, and retained only for backward compatibility, because
16172 nowadays the ACL specified by &%acl_smtp_connect%& can also reject incoming
16173 connections immediately.
16175 The ability to give an immediate rejection (either by this option or using an
16176 ACL) is provided for use in unusual cases. Many hosts will just try again,
16177 sometimes without much delay. Normally, it is better to use an ACL to reject
16178 incoming messages at a later stage, such as after RCPT commands. See
16179 chapter &<<CHAPACL>>&.
16182 .option hosts_connection_nolog main "host list&!!" unset
16183 .cindex "host" "not logging connections from"
16184 This option defines a list of hosts for which connection logging does not
16185 happen, even though the &%smtp_connection%& log selector is set. For example,
16186 you might want not to log SMTP connections from local processes, or from
16187 127.0.0.1, or from your local LAN. This option is consulted in the main loop of
16188 the daemon; you should therefore strive to restrict its value to a short inline
16189 list of IP addresses and networks. To disable logging SMTP connections from
16190 local processes, you must create a host list with an empty item. For example:
16192 hosts_connection_nolog = :
16195 The hosts affected by this option also do not log "no MAIL in SMTP connection"
16196 lines, as may commonly be produced by a monitoring system.
16200 .option hosts_require_alpn main "host list&!!" unset
16201 .cindex ALPN "require negotiation in server"
16203 .cindex TLS "Application Layer Protocol Names"
16204 If the TLS library supports ALPN
16205 then a successful negotiation of ALPN will be required for any client
16206 matching the list, for TLS to be used.
16207 See also the &%tls_alpn%& option.
16209 &*Note*&: prevention of fallback to in-clear connection is not
16210 managed by this option, and should be done separately.
16213 .option hosts_require_helo main "host list&!!" *
16214 .cindex "HELO/EHLO" requiring
16215 Exim will require an accepted HELO or EHLO command from a host matching
16216 this list, before accepting a MAIL command.
16219 .option hosts_proxy main "host list&!!" unset
16220 .cindex proxy "proxy protocol"
16221 This option enables use of Proxy Protocol proxies for incoming
16222 connections. For details see section &<<SECTproxyInbound>>&.
16225 .option hosts_treat_as_local main "domain list&!!" unset
16226 .cindex "local host" "domains treated as"
16227 .cindex "host" "treated as local"
16228 If this option is set, any host names that match the domain list are treated as
16229 if they were the local host when Exim is scanning host lists obtained from MX
16231 or other sources. Note that the value of this option is a domain list, not a
16232 host list, because it is always used to check host names, not IP addresses.
16234 This option also applies when Exim is matching the special items
16235 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`& in a domain list (see
16236 section &<<SECTdomainlist>>&), and when checking the &%hosts%& option in the
16237 &(smtp)& transport for the local host (see the &%allow_localhost%& option in
16238 that transport). See also &%local_interfaces%&, &%extra_local_interfaces%&, and
16239 chapter &<<CHAPinterfaces>>&, which contains a discussion about local network
16240 interfaces and recognizing the local host.
16243 .option ibase_servers main "string list" unset
16244 .cindex "InterBase" "server list"
16245 This option provides a list of InterBase servers and associated connection data,
16246 to be used in conjunction with &(ibase)& lookups (see section &<<SECID72>>&).
16247 The option is available only if Exim has been built with InterBase support.
16251 .option ignore_bounce_errors_after main time 10w
16252 .cindex "bounce message" "discarding"
16253 .cindex "discarding bounce message"
16254 This option affects the processing of bounce messages that cannot be delivered,
16255 that is, those that suffer a permanent delivery failure. (Bounce messages that
16256 suffer temporary delivery failures are of course retried in the usual way.)
16258 After a permanent delivery failure, bounce messages are frozen,
16259 because there is no sender to whom they can be returned. When a frozen bounce
16260 message has been in the queue for more than the given time, it is unfrozen at
16261 the next queue run, and a further delivery is attempted. If delivery fails
16262 again, the bounce message is discarded. This makes it possible to keep failed
16263 bounce messages around for a shorter time than the normal maximum retry time
16264 for frozen messages. For example,
16266 ignore_bounce_errors_after = 12h
16268 retries failed bounce message deliveries after 12 hours, discarding any further
16269 failures. If the value of this option is set to a zero time period, bounce
16270 failures are discarded immediately. Setting a very long time (as in the default
16271 value) has the effect of disabling this option. For ways of automatically
16272 dealing with other kinds of frozen message, see &%auto_thaw%& and
16273 &%timeout_frozen_after%&.
16276 .option ignore_fromline_hosts main "host list&!!" unset
16277 .cindex "&""From""& line"
16278 .cindex "UUCP" "&""From""& line"
16279 Some broken SMTP clients insist on sending a UUCP-like &"From&~"& line before
16280 the headers of a message. By default this is treated as the start of the
16281 message's body, which means that any following headers are not recognized as
16282 such. Exim can be made to ignore it by setting &%ignore_fromline_hosts%& to
16283 match those hosts that insist on sending it. If the sender is actually a local
16284 process rather than a remote host, and is using &%-bs%& to inject the messages,
16285 &%ignore_fromline_local%& must be set to achieve this effect.
16288 .option ignore_fromline_local main boolean false
16289 See &%ignore_fromline_hosts%& above.
16291 .option keep_environment main "string list" unset
16292 .cindex "environment" "values from"
16293 This option contains a string list of environment variables to keep.
16294 You have to trust these variables or you have to be sure that
16295 these variables do not impose any security risk. Keep in mind that
16296 during the startup phase Exim is running with an effective UID 0 in most
16297 installations. As the default value is an empty list, the default
16298 environment for using libraries, running embedded Perl code, or running
16299 external binaries is empty, and does not not even contain PATH or HOME.
16301 Actually the list is interpreted as a list of patterns
16302 (&<<SECTlistexpand>>&), except that it is not expanded first.
16304 WARNING: Macro substitution is still done first, so having a macro
16305 FOO and having FOO_HOME in your &%keep_environment%& option may have
16306 unexpected results. You may work around this using a regular expression
16307 that does not match the macro name: ^[F]OO_HOME$.
16309 Current versions of Exim issue a warning during startup if you do not mention
16310 &%keep_environment%& in your runtime configuration file and if your
16311 current environment is not empty. Future versions may not issue that warning
16314 See the &%add_environment%& main config option for a way to set
16315 environment variables to a fixed value. The environment for &(pipe)&
16316 transports is handled separately, see section &<<SECTpipeenv>>& for
16320 .option keep_malformed main time 4d
16321 This option specifies the length of time to keep messages whose spool files
16322 have been corrupted in some way. This should, of course, never happen. At the
16323 next attempt to deliver such a message, it gets removed. The incident is
16327 .option ldap_ca_cert_dir main string unset
16328 .cindex "LDAP", "TLS CA certificate directory"
16329 .cindex certificate "directory for LDAP"
16330 This option indicates which directory contains CA certificates for verifying
16331 a TLS certificate presented by an LDAP server.
16332 While Exim does not provide a default value, your SSL library may.
16333 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
16334 and constrained to be a directory.
16337 .option ldap_ca_cert_file main string unset
16338 .cindex "LDAP", "TLS CA certificate file"
16339 .cindex certificate "file for LDAP"
16340 This option indicates which file contains CA certificates for verifying
16341 a TLS certificate presented by an LDAP server.
16342 While Exim does not provide a default value, your SSL library may.
16343 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
16344 and constrained to be a file.
16347 .option ldap_cert_file main string unset
16348 .cindex "LDAP" "TLS client certificate file"
16349 .cindex certificate "file for LDAP"
16350 This option indicates which file contains an TLS client certificate which
16351 Exim should present to the LDAP server during TLS negotiation.
16352 Should be used together with &%ldap_cert_key%&.
16355 .option ldap_cert_key main string unset
16356 .cindex "LDAP" "TLS client key file"
16357 .cindex certificate "key for LDAP"
16358 This option indicates which file contains the secret/private key to use
16359 to prove identity to the LDAP server during TLS negotiation.
16360 Should be used together with &%ldap_cert_file%&, which contains the
16361 identity to be proven.
16364 .option ldap_cipher_suite main string unset
16365 .cindex "LDAP" "TLS cipher suite"
16366 This controls the TLS cipher-suite negotiation during TLS negotiation with
16367 the LDAP server. See &<<SECTreqciphssl>>& for more details of the format of
16368 cipher-suite options with OpenSSL (as used by LDAP client libraries).
16371 .option ldap_default_servers main "string list" unset
16372 .cindex "LDAP" "default servers"
16373 This option provides a list of LDAP servers which are tried in turn when an
16374 LDAP query does not contain a server. See section &<<SECTforldaque>>& for
16375 details of LDAP queries. This option is available only when Exim has been built
16379 .option ldap_require_cert main string unset.
16380 .cindex "LDAP" "policy for LDAP server TLS cert presentation"
16381 This should be one of the values "hard", "demand", "allow", "try" or "never".
16382 A value other than one of these is interpreted as "never".
16383 See the entry "TLS_REQCERT" in your system man page for ldap.conf(5).
16384 Although Exim does not set a default, the LDAP library probably defaults
16388 .option ldap_start_tls main boolean false
16389 .cindex "LDAP" "whether or not to negotiate TLS"
16390 If set, Exim will attempt to negotiate TLS with the LDAP server when
16391 connecting on a regular LDAP port. This is the LDAP equivalent of SMTP's
16392 "STARTTLS". This is distinct from using "ldaps", which is the LDAP form
16394 In the event of failure to negotiate TLS, the action taken is controlled
16395 by &%ldap_require_cert%&.
16396 This option is ignored for &`ldapi`& connections.
16399 .option ldap_version main integer unset
16400 .cindex "LDAP" "protocol version, forcing"
16401 This option can be used to force Exim to set a specific protocol version for
16402 LDAP. If it option is unset, it is shown by the &%-bP%& command line option as
16403 -1. When this is the case, the default is 3 if LDAP_VERSION3 is defined in
16404 the LDAP headers; otherwise it is 2. This option is available only when Exim
16405 has been built with LDAP support.
16409 .option local_from_check main boolean true
16410 .cindex "&'Sender:'& header line" "disabling addition of"
16411 .cindex "&'From:'& header line" "disabling checking of"
16412 When a message is submitted locally (that is, not over a TCP/IP connection) by
16413 an untrusted user, Exim removes any existing &'Sender:'& header line, and
16414 checks that the &'From:'& header line matches the login of the calling user and
16415 the domain specified by &%qualify_domain%&.
16417 &*Note*&: An unqualified address (no domain) in the &'From:'& header in a
16418 locally submitted message is automatically qualified by Exim, unless the
16419 &%-bnq%& command line option is used.
16421 You can use &%local_from_prefix%& and &%local_from_suffix%& to permit affixes
16422 on the local part. If the &'From:'& header line does not match, Exim adds a
16423 &'Sender:'& header with an address constructed from the calling user's login
16424 and the default qualify domain.
16426 If &%local_from_check%& is set false, the &'From:'& header check is disabled,
16427 and no &'Sender:'& header is ever added. If, in addition, you want to retain
16428 &'Sender:'& header lines supplied by untrusted users, you must also set
16429 &%local_sender_retain%& to be true.
16431 .cindex "envelope from"
16432 .cindex "envelope sender"
16433 These options affect only the header lines in the message. The envelope sender
16434 is still forced to be the login id at the qualify domain unless
16435 &%untrusted_set_sender%& permits the user to supply an envelope sender.
16437 For messages received over TCP/IP, an ACL can specify &"submission mode"& to
16438 request similar header line checking. See section &<<SECTthesenhea>>&, which
16439 has more details about &'Sender:'& processing.
16444 .option local_from_prefix main string unset
16445 When Exim checks the &'From:'& header line of locally submitted messages for
16446 matching the login id (see &%local_from_check%& above), it can be configured to
16447 ignore certain prefixes and suffixes in the local part of the address. This is
16448 done by setting &%local_from_prefix%& and/or &%local_from_suffix%& to
16449 appropriate lists, in the same form as the &%local_part_prefix%& and
16450 &%local_part_suffix%& router options (see chapter &<<CHAProutergeneric>>&). For
16453 local_from_prefix = *-
16455 is set, a &'From:'& line containing
16457 From: anything-user@your.domain.example
16459 will not cause a &'Sender:'& header to be added if &'user@your.domain.example'&
16460 matches the actual sender address that is constructed from the login name and
16464 .option local_from_suffix main string unset
16465 See &%local_from_prefix%& above.
16468 .option local_interfaces main "string list" "see below"
16469 This option controls which network interfaces are used by the daemon for
16470 listening; they are also used to identify the local host when routing. Chapter
16471 &<<CHAPinterfaces>>& contains a full description of this option and the related
16472 options &%daemon_smtp_ports%&, &%extra_local_interfaces%&,
16473 &%hosts_treat_as_local%&, and &%tls_on_connect_ports%&. The default value for
16474 &%local_interfaces%& is
16476 local_interfaces = 0.0.0.0
16478 when Exim is built without IPv6 support; otherwise it is
16480 local_interfaces = <; ::0 ; 0.0.0.0
16483 .option local_scan_timeout main time 5m
16484 .cindex "timeout" "for &[local_scan()]& function"
16485 .cindex "&[local_scan()]& function" "timeout"
16486 This timeout applies to the &[local_scan()]& function (see chapter
16487 &<<CHAPlocalscan>>&). Zero means &"no timeout"&. If the timeout is exceeded,
16488 the incoming message is rejected with a temporary error if it is an SMTP
16489 message. For a non-SMTP message, the message is dropped and Exim ends with a
16490 non-zero code. The incident is logged on the main and reject logs.
16494 .option local_sender_retain main boolean false
16495 .cindex "&'Sender:'& header line" "retaining from local submission"
16496 When a message is submitted locally (that is, not over a TCP/IP connection) by
16497 an untrusted user, Exim removes any existing &'Sender:'& header line. If you
16498 do not want this to happen, you must set &%local_sender_retain%&, and you must
16499 also set &%local_from_check%& to be false (Exim will complain if you do not).
16500 See also the ACL modifier &`control = suppress_local_fixups`&. Section
16501 &<<SECTthesenhea>>& has more details about &'Sender:'& processing.
16506 .option localhost_number main string&!! unset
16507 .cindex "host" "locally unique number for"
16508 .cindex "message ids" "with multiple hosts"
16509 .vindex "&$localhost_number$&"
16510 Exim's message ids are normally unique only within the local host. If
16511 uniqueness among a set of hosts is required, each host must set a different
16512 value for the &%localhost_number%& option. The string is expanded immediately
16513 after reading the configuration file (so that a number can be computed from the
16514 host name, for example) and the result of the expansion must be a number in the
16515 range 0&--16 (or 0&--10 on operating systems with case-insensitive file
16516 systems). This is available in subsequent string expansions via the variable
16517 &$localhost_number$&. When &%localhost_number is set%&, the final two
16518 characters of the message id, instead of just being a fractional part of the
16519 time, are computed from the time and the local host number as described in
16520 section &<<SECTmessiden>>&.
16524 .option log_file_path main "string list&!!" "set at compile time"
16525 .cindex "log" "file path for"
16526 This option sets the path which is used to determine the names of Exim's log
16527 files, or indicates that logging is to be to syslog, or both. It is expanded
16528 when Exim is entered, so it can, for example, contain a reference to the host
16529 name. If no specific path is set for the log files at compile or runtime,
16530 or if the option is unset at runtime (i.e. &`log_file_path = `&)
16531 they are written in a sub-directory called &_log_& in Exim's spool directory.
16532 A path must start with a slash.
16533 To send to syslog, use the word &"syslog"&.
16534 Chapter &<<CHAPlog>>& contains further details about Exim's logging, and
16535 section &<<SECTwhelogwri>>& describes how the contents of &%log_file_path%& are
16536 used. If this string is fixed at your installation (contains no expansion
16537 variables) it is recommended that you do not set this option in the
16538 configuration file, but instead supply the path using LOG_FILE_PATH in
16539 &_Local/Makefile_& so that it is available to Exim for logging errors detected
16540 early on &-- in particular, failure to read the configuration file.
16543 .option log_selector main string unset
16544 .cindex "log" "selectors"
16545 This option can be used to reduce or increase the number of things that Exim
16546 writes to its log files. Its argument is made up of names preceded by plus or
16547 minus characters. For example:
16549 log_selector = +arguments -retry_defer
16551 A list of possible names and what they control is given in the chapter on
16552 logging, in section &<<SECTlogselector>>&.
16555 .option log_timezone main boolean false
16556 .cindex "log" "timezone for entries"
16557 .vindex "&$tod_log$&"
16558 .vindex "&$tod_zone$&"
16559 By default, the timestamps on log lines are in local time without the
16560 timezone. This means that if your timezone changes twice a year, the timestamps
16561 in log lines are ambiguous for an hour when the clocks go back. One way of
16562 avoiding this problem is to set the timezone to UTC. An alternative is to set
16563 &%log_timezone%& true. This turns on the addition of the timezone offset to
16564 timestamps in log lines. Turning on this option can add quite a lot to the size
16565 of log files because each line is extended by 6 characters. Note that the
16566 &$tod_log$& variable contains the log timestamp without the zone, but there is
16567 another variable called &$tod_zone$& that contains just the timezone offset.
16570 .option lookup_open_max main integer 25
16571 .cindex "too many open files"
16572 .cindex "open files, too many"
16573 .cindex "file" "too many open"
16574 .cindex "lookup" "maximum open files"
16575 .cindex "limit" "open files for lookups"
16576 This option limits the number of simultaneously open files for single-key
16577 lookups that use regular files (that is, &(lsearch)&, &(dbm)&, and &(cdb)&).
16578 Exim normally keeps these files open during routing, because often the same
16579 file is required several times. If the limit is reached, Exim closes the least
16580 recently used file. Note that if you are using the &'ndbm'& library, it
16581 actually opens two files for each logical DBM database, though it still counts
16582 as one for the purposes of &%lookup_open_max%&. If you are getting &"too many
16583 open files"& errors with NDBM, you need to reduce the value of
16584 &%lookup_open_max%&.
16587 .option max_username_length main integer 0
16588 .cindex "length of login name"
16589 .cindex "user name" "maximum length"
16590 .cindex "limit" "user name length"
16591 Some operating systems are broken in that they truncate long arguments to
16592 &[getpwnam()]& to eight characters, instead of returning &"no such user"&. If
16593 this option is set greater than zero, any attempt to call &[getpwnam()]& with
16594 an argument that is longer behaves as if &[getpwnam()]& failed.
16597 .option message_body_newlines main bool false
16598 .cindex "message body" "newlines in variables"
16599 .cindex "newline" "in message body variables"
16600 .vindex "&$message_body$&"
16601 .vindex "&$message_body_end$&"
16602 By default, newlines in the message body are replaced by spaces when setting
16603 the &$message_body$& and &$message_body_end$& expansion variables. If this
16604 option is set true, this no longer happens.
16607 .option message_body_visible main integer 500
16608 .cindex "body of message" "visible size"
16609 .cindex "message body" "visible size"
16610 .vindex "&$message_body$&"
16611 .vindex "&$message_body_end$&"
16612 This option specifies how much of a message's body is to be included in the
16613 &$message_body$& and &$message_body_end$& expansion variables.
16616 .option message_id_header_domain main string&!! unset
16617 .cindex "&'Message-ID:'& header line"
16618 If this option is set, the string is expanded and used as the right hand side
16619 (domain) of the &'Message-ID:'& header that Exim creates if a
16620 locally-originated incoming message does not have one. &"Locally-originated"&
16621 means &"not received over TCP/IP."&
16622 Otherwise, the primary host name is used.
16623 Only letters, digits, dot and hyphen are accepted; any other characters are
16624 replaced by hyphens. If the expansion is forced to fail, or if the result is an
16625 empty string, the option is ignored.
16628 .option message_id_header_text main string&!! unset
16629 If this variable is set, the string is expanded and used to augment the text of
16630 the &'Message-id:'& header that Exim creates if a locally-originated incoming
16631 message does not have one. The text of this header is required by RFC 2822 to
16632 take the form of an address. By default, Exim uses its internal message id as
16633 the local part, and the primary host name as the domain. If this option is set,
16634 it is expanded, and provided the expansion is not forced to fail, and does not
16635 yield an empty string, the result is inserted into the header immediately
16636 before the @, separated from the internal message id by a dot. Any characters
16637 that are illegal in an address are automatically converted into hyphens. This
16638 means that variables such as &$tod_log$& can be used, because the spaces and
16639 colons will become hyphens.
16642 .option message_logs main boolean true
16643 .cindex "message logs" "disabling"
16644 .cindex "log" "message log; disabling"
16645 If this option is turned off, per-message log files are not created in the
16646 &_msglog_& spool sub-directory. This reduces the amount of disk I/O required by
16647 Exim, by reducing the number of files involved in handling a message from a
16648 minimum of four (header spool file, body spool file, delivery journal, and
16649 per-message log) to three. The other major I/O activity is Exim's main log,
16650 which is not affected by this option.
16653 .option message_size_limit main string&!! 50M
16654 .cindex "message" "size limit"
16655 .cindex "limit" "message size"
16656 .cindex "size" "of message, limit"
16657 This option limits the maximum size of message that Exim will process. The
16658 value is expanded for each incoming connection so, for example, it can be made
16659 to depend on the IP address of the remote host for messages arriving via
16660 TCP/IP. After expansion, the value must be a sequence of decimal digits,
16661 optionally followed by K or M.
16663 .cindex "SIZE" "ESMTP extension, advertising"
16664 .cindex "ESMTP extensions" SIZE
16665 If nonzero the value will be advertised as a parameter to the ESMTP SIZE
16666 service extension keyword.
16668 &*Note*&: This limit cannot be made to depend on a message's sender or any
16669 other properties of an individual message, because it has to be advertised in
16670 the server's response to EHLO. String expansion failure causes a temporary
16671 error. A value of zero means no limit, but its use is not recommended. See also
16672 &%bounce_return_size_limit%&.
16674 Incoming SMTP messages are failed with a 552 error if the limit is
16675 exceeded; locally-generated messages either get a stderr message or a delivery
16676 failure message to the sender, depending on the &%-oe%& setting. Rejection of
16677 an oversized message is logged in both the main and the reject logs. See also
16678 the generic transport option &%message_size_limit%&, which limits the size of
16679 message that an individual transport can process.
16681 If you use a virus-scanner and set this option to to a value larger than the
16682 maximum size that your virus-scanner is configured to support, you may get
16683 failures triggered by large mails. The right size to configure for the
16684 virus-scanner depends upon what data is passed and the options in use but it's
16685 probably safest to just set it to a little larger than this value. E.g., with a
16686 default Exim message size of 50M and a default ClamAV StreamMaxLength of 10M,
16687 some problems may result.
16689 A value of 0 will disable size limit checking; Exim will still advertise the
16690 SIZE extension in an EHLO response, but without a limit, so as to permit
16691 SMTP clients to still indicate the message size along with the MAIL verb.
16694 .option move_frozen_messages main boolean false
16695 .cindex "frozen messages" "moving"
16696 This option, which is available only if Exim has been built with the setting
16698 SUPPORT_MOVE_FROZEN_MESSAGES=yes
16700 in &_Local/Makefile_&, causes frozen messages and their message logs to be
16701 moved from the &_input_& and &_msglog_& directories on the spool to &_Finput_&
16702 and &_Fmsglog_&, respectively. There is currently no support in Exim or the
16703 standard utilities for handling such moved messages, and they do not show up in
16704 lists generated by &%-bp%& or by the Exim monitor.
16707 .option mua_wrapper main boolean false
16708 Setting this option true causes Exim to run in a very restrictive mode in which
16709 it passes messages synchronously to a smart host. Chapter &<<CHAPnonqueueing>>&
16710 contains a full description of this facility.
16714 .option mysql_servers main "string list" unset
16715 .cindex "MySQL" "server list"
16716 This option provides a list of MySQL servers and associated connection data, to
16717 be used in conjunction with &(mysql)& lookups (see section &<<SECID72>>&). The
16718 option is available only if Exim has been built with MySQL support.
16721 .option never_users main "string list&!!" unset
16722 This option is expanded just once, at the start of Exim's processing. Local
16723 message deliveries are normally run in processes that are setuid to the
16724 recipient, and remote deliveries are normally run under Exim's own uid and gid.
16725 It is usually desirable to prevent any deliveries from running as root, as a
16728 When Exim is built, an option called FIXED_NEVER_USERS can be set to a
16729 list of users that must not be used for local deliveries. This list is fixed in
16730 the binary and cannot be overridden by the configuration file. By default, it
16731 contains just the single user name &"root"&. The &%never_users%& runtime option
16732 can be used to add more users to the fixed list.
16734 If a message is to be delivered as one of the users on the fixed list or the
16735 &%never_users%& list, an error occurs, and delivery is deferred. A common
16738 never_users = root:daemon:bin
16740 Including root is redundant if it is also on the fixed list, but it does no
16741 harm. This option overrides the &%pipe_as_creator%& option of the &(pipe)&
16745 .option notifier_socket main string "$spool_directory/exim_daemon_notify"
16746 This option gives the name for a unix-domain socket on which the daemon
16747 listens for work and information-requests.
16748 Only installations running multiple daemons sharing a spool directory
16749 should need to modify the default.
16751 The option is expanded before use.
16752 If the platform supports Linux-style abstract socket names, the result
16753 is used with a nul byte prefixed.
16755 it should be a full path name and use a directory accessible
16758 If this option is set as empty,
16759 or the command line &%-oY%& option is used, or
16760 the command line uses a &%-oX%& option and does not use &%-oP%&,
16761 then a notifier socket is not created.
16764 .option openssl_options main "string list" "+no_sslv2 +no_sslv3 +single_dh_use +no_ticket +no_renegotiation"
16765 .cindex "OpenSSL "compatibility options"
16766 This option allows an administrator to adjust the SSL options applied
16767 by OpenSSL to connections. It is given as a space-separated list of items,
16768 each one to be +added or -subtracted from the current value.
16770 This option is only available if Exim is built against OpenSSL. The values
16771 available for this option vary according to the age of your OpenSSL install.
16772 The &"all"& value controls a subset of flags which are available, typically
16773 the bug workaround options. The &'SSL_CTX_set_options'& man page will
16774 list the values known on your system and Exim should support all the
16775 &"bug workaround"& options and many of the &"modifying"& options. The Exim
16776 names lose the leading &"SSL_OP_"& and are lower-cased.
16778 Note that adjusting the options can have severe impact upon the security of
16779 SSL as used by Exim. It is possible to disable safety checks and shoot
16780 yourself in the foot in various unpleasant ways. This option should not be
16781 adjusted lightly. An unrecognised item will be detected at startup, by
16782 invoking Exim with the &%-bV%& flag.
16784 The option affects Exim operating both as a server and as a client.
16786 Historical note: prior to release 4.80, Exim defaulted this value to
16787 "+dont_insert_empty_fragments", which may still be needed for compatibility
16788 with some clients, but which lowers security by increasing exposure to
16789 some now infamous attacks.
16793 # Make both old MS and old Eudora happy:
16794 openssl_options = -all +microsoft_big_sslv3_buffer \
16795 +dont_insert_empty_fragments
16797 # Disable older protocol versions:
16798 openssl_options = +no_sslv2 +no_sslv3
16801 Possible options may include:
16805 &`allow_unsafe_legacy_renegotiation`&
16807 &`cipher_server_preference`&
16809 &`dont_insert_empty_fragments`&
16813 &`legacy_server_connect`&
16815 &`microsoft_big_sslv3_buffer`&
16817 &`microsoft_sess_id_bug`&
16819 &`msie_sslv2_rsa_padding`&
16821 &`netscape_challenge_bug`&
16823 &`netscape_reuse_cipher_change_bug`&
16827 &`no_session_resumption_on_renegotiation`&
16841 &`safari_ecdhe_ecdsa_bug`&
16845 &`single_ecdh_use`&
16847 &`ssleay_080_client_dh_bug`&
16849 &`sslref2_reuse_cert_type_bug`&
16851 &`tls_block_padding_bug`&
16855 &`tls_rollback_bug`&
16858 As an aside, the &`safari_ecdhe_ecdsa_bug`& item is a misnomer and affects
16859 all clients connecting using the MacOS SecureTransport TLS facility prior
16860 to MacOS 10.8.4, including email clients. If you see old MacOS clients failing
16861 to negotiate TLS then this option value might help, provided that your OpenSSL
16862 release is new enough to contain this work-around. This may be a situation
16863 where you have to upgrade OpenSSL to get buggy clients working.
16866 .option oracle_servers main "string list" unset
16867 .cindex "Oracle" "server list"
16868 This option provides a list of Oracle servers and associated connection data,
16869 to be used in conjunction with &(oracle)& lookups (see section &<<SECID72>>&).
16870 The option is available only if Exim has been built with Oracle support.
16874 .option panic_coredump main boolean false
16875 This option is rarely needed but can help for some debugging investigations.
16876 If set, when an internal error is detected by Exim which is sufficient
16877 to terminate the process
16878 (all such are logged in the paniclog)
16879 then a coredump is requested.
16881 Note that most systems require additional administrative configuration
16882 to permit write a core file for a setuid program, which is Exim's
16883 common installed configuration.
16886 .option percent_hack_domains main "domain list&!!" unset
16887 .cindex "&""percent hack""&"
16888 .cindex "source routing" "in email address"
16889 .cindex "address" "source-routed"
16890 The &"percent hack"& is the convention whereby a local part containing a
16891 percent sign is re-interpreted as a new email address, with the percent
16892 replaced by @. This is sometimes called &"source routing"&, though that term is
16893 also applied to RFC 2822 addresses that begin with an @ character. If this
16894 option is set, Exim implements the percent facility for those domains listed,
16895 but no others. This happens before an incoming SMTP address is tested against
16898 &*Warning*&: The &"percent hack"& has often been abused by people who are
16899 trying to get round relaying restrictions. For this reason, it is best avoided
16900 if at all possible. Unfortunately, a number of less security-conscious MTAs
16901 implement it unconditionally. If you are running Exim on a gateway host, and
16902 routing mail through to internal MTAs without processing the local parts, it is
16903 a good idea to reject recipient addresses with percent characters in their
16904 local parts. Exim's default configuration does this.
16907 .option perl_at_start main boolean false
16909 This option is available only when Exim is built with an embedded Perl
16910 interpreter. See chapter &<<CHAPperl>>& for details of its use.
16913 .option perl_startup main string unset
16915 This option is available only when Exim is built with an embedded Perl
16916 interpreter. See chapter &<<CHAPperl>>& for details of its use.
16918 .option perl_taintmode main boolean false
16920 This option enables the taint mode of the embedded Perl interpreter.
16923 .option pgsql_servers main "string list" unset
16924 .cindex "PostgreSQL lookup type" "server list"
16925 This option provides a list of PostgreSQL servers and associated connection
16926 data, to be used in conjunction with &(pgsql)& lookups (see section
16927 &<<SECID72>>&). The option is available only if Exim has been built with
16928 PostgreSQL support.
16931 .option pid_file_path main string&!! "set at compile time"
16932 .cindex "daemon" "pid file path"
16933 .cindex "pid file, path for"
16934 This option sets the name of the file to which the Exim daemon writes its
16935 process id. The string is expanded, so it can contain, for example, references
16938 pid_file_path = /var/log/$primary_hostname/exim.pid
16940 If no path is set, the pid is written to the file &_exim-daemon.pid_& in Exim's
16942 The value set by the option can be overridden by the &%-oP%& command line
16943 option. A pid file is not written if a &"non-standard"& daemon is run by means
16944 of the &%-oX%& option, unless a path is explicitly supplied by &%-oP%&.
16947 .option pipelining_advertise_hosts main "host list&!!" *
16948 .cindex "PIPELINING" "suppressing advertising"
16949 .cindex "ESMTP extensions" PIPELINING
16950 This option can be used to suppress the advertisement of the SMTP
16951 PIPELINING extension to specific hosts. See also the &*no_pipelining*&
16952 control in section &<<SECTcontrols>>&. When PIPELINING is not advertised and
16953 &%smtp_enforce_sync%& is true, an Exim server enforces strict synchronization
16954 for each SMTP command and response. When PIPELINING is advertised, Exim assumes
16955 that clients will use it; &"out of order"& commands that are &"expected"& do
16956 not count as protocol errors (see &%smtp_max_synprot_errors%&).
16958 .option pipelining_connect_advertise_hosts main "host list&!!" *
16959 .cindex "pipelining" "early connection"
16960 .cindex "pipelining" PIPECONNECT
16961 .cindex "ESMTP extensions" PIPECONNECT
16962 If Exim is built without the DISABLE_PIPE_CONNECT build option
16963 this option controls which hosts the facility is advertised to
16964 and from which pipeline early-connection (before MAIL) SMTP
16965 commands are acceptable.
16966 When used, the pipelining saves on roundtrip times.
16968 See also the &%hosts_pipe_connect%& smtp transport option.
16970 The SMTP service extension keyword advertised is &"PIPECONNECT"&;
16971 it permits the client to pipeline
16972 TCP connection and hello command (inclear phase),
16973 or TLS-establishment and hello command (encrypted phase),
16974 on later connections to the same host.
16977 .option prdr_enable main boolean false
16978 .cindex "PRDR" "enabling on server"
16979 .cindex "ESMTP extensions" PRDR
16980 This option can be used to enable the Per-Recipient Data Response extension
16981 to SMTP, defined by Eric Hall.
16982 If the option is set, PRDR is advertised by Exim when operating as a server.
16983 If the client requests PRDR, and more than one recipient, for a message
16984 an additional ACL is called for each recipient after the message content
16985 is received. See section &<<SECTPRDRACL>>&.
16987 .option preserve_message_logs main boolean false
16988 .cindex "message logs" "preserving"
16989 If this option is set, message log files are not deleted when messages are
16990 completed. Instead, they are moved to a sub-directory of the spool directory
16991 called &_msglog.OLD_&, where they remain available for statistical or debugging
16992 purposes. This is a dangerous option to set on systems with any appreciable
16993 volume of mail. Use with care!
16996 .option primary_hostname main string "see below"
16997 .cindex "name" "of local host"
16998 .cindex "host" "name of local"
16999 .cindex "local host" "name of"
17000 .vindex "&$primary_hostname$&"
17001 This specifies the name of the current host. It is used in the default EHLO or
17002 HELO command for outgoing SMTP messages (changeable via the &%helo_data%&
17003 option in the &(smtp)& transport), and as the default for &%qualify_domain%&.
17004 The value is also used by default in some SMTP response messages from an Exim
17005 server. This can be changed dynamically by setting &%smtp_active_hostname%&.
17007 If &%primary_hostname%& is not set, Exim calls &[uname()]& to find the host
17008 name. If this fails, Exim panics and dies. If the name returned by &[uname()]&
17009 contains only one component, Exim passes it to &[gethostbyname()]& (or
17010 &[getipnodebyname()]& when available) in order to obtain the fully qualified
17011 version. The variable &$primary_hostname$& contains the host name, whether set
17012 explicitly by this option, or defaulted.
17015 .option print_topbitchars main boolean false
17016 .cindex "printing characters"
17017 .cindex "8-bit characters"
17018 By default, Exim considers only those characters whose codes lie in the range
17019 32&--126 to be printing characters. In a number of circumstances (for example,
17020 when writing log entries) non-printing characters are converted into escape
17021 sequences, primarily to avoid messing up the layout. If &%print_topbitchars%&
17022 is set, code values of 128 and above are also considered to be printing
17025 This option also affects the header syntax checks performed by the
17026 &(autoreply)& transport, and whether Exim uses RFC 2047 encoding of
17027 the user's full name when constructing From: and Sender: addresses (as
17028 described in section &<<SECTconstr>>&). Setting this option can cause
17029 Exim to generate eight bit message headers that do not conform to the
17033 .option process_log_path main string unset
17034 .cindex "process log path"
17035 .cindex "log" "process log"
17036 .cindex "&'exiwhat'&"
17037 This option sets the name of the file to which an Exim process writes its
17038 &"process log"& when sent a USR1 signal. This is used by the &'exiwhat'&
17039 utility script. If this option is unset, the file called &_exim-process.info_&
17040 in Exim's spool directory is used. The ability to specify the name explicitly
17041 can be useful in environments where two different Exims are running, using
17042 different spool directories.
17045 .option prod_requires_admin main boolean true
17046 .cindex "restricting access to features"
17050 The &%-M%&, &%-R%&, and &%-q%& command-line options require the caller to be an
17051 admin user unless &%prod_requires_admin%& is set false. See also
17052 &%queue_list_requires_admin%& and &%commandline_checks_require_admin%&.
17055 .option proxy_protocol_timeout main time 3s
17056 .cindex proxy "proxy protocol"
17057 This option sets the timeout for proxy protocol negotiation.
17058 For details see section &<<SECTproxyInbound>>&.
17061 .option qualify_domain main string "see below"
17062 .cindex "domain" "for qualifying addresses"
17063 .cindex "address" "qualification"
17064 This option specifies the domain name that is added to any envelope sender
17065 addresses that do not have a domain qualification. It also applies to
17066 recipient addresses if &%qualify_recipient%& is not set. Unqualified addresses
17067 are accepted by default only for locally-generated messages. Qualification is
17068 also applied to addresses in header lines such as &'From:'& and &'To:'& for
17069 locally-generated messages, unless the &%-bnq%& command line option is used.
17071 Messages from external sources must always contain fully qualified addresses,
17072 unless the sending host matches &%sender_unqualified_hosts%& or
17073 &%recipient_unqualified_hosts%& (as appropriate), in which case incoming
17074 addresses are qualified with &%qualify_domain%& or &%qualify_recipient%& as
17075 necessary. Internally, Exim always works with fully qualified envelope
17076 addresses. If &%qualify_domain%& is not set, it defaults to the
17077 &%primary_hostname%& value.
17080 .option qualify_recipient main string "see below"
17081 This option allows you to specify a different domain for qualifying recipient
17082 addresses to the one that is used for senders. See &%qualify_domain%& above.
17086 .option queue_domains main "domain list&!!" unset
17087 .cindex "domain" "specifying non-immediate delivery"
17088 .cindex "queueing incoming messages"
17089 .cindex "message" "queueing certain domains"
17090 This option lists domains for which immediate delivery is not required.
17091 A delivery process is started whenever a message is received, but only those
17092 domains that do not match are processed. All other deliveries wait until the
17093 next queue run. See also &%hold_domains%& and &%queue_smtp_domains%&.
17096 .option queue_fast_ramp main boolean true
17097 .cindex "queue runner" "two phase"
17098 .cindex "queue" "double scanning"
17099 If set to true, two-phase queue runs, initiated using &%-qq%& on the
17100 command line, may start parallel delivery processes during their first
17101 phase. This will be done when a threshold number of messages have been
17102 routed for a single host.
17105 .option queue_list_requires_admin main boolean true
17106 .cindex "restricting access to features"
17108 The &%-bp%& command-line option, which lists the messages that are on the
17109 queue, requires the caller to be an admin user unless
17110 &%queue_list_requires_admin%& is set false.
17111 See also &%prod_requires_admin%& and &%commandline_checks_require_admin%&.
17114 .option queue_only main boolean false
17115 .cindex "queueing incoming messages"
17116 .cindex "message" "queueing unconditionally"
17117 If &%queue_only%& is set, a delivery process is not automatically started
17118 whenever a message is received. Instead, the message waits in the queue for the
17119 next queue run. Even if &%queue_only%& is false, incoming messages may not get
17120 delivered immediately when certain conditions (such as heavy load) occur.
17122 The &%-odq%& command line has the same effect as &%queue_only%&. The &%-odb%&
17123 and &%-odi%& command line options override &%queue_only%& unless
17124 &%queue_only_override%& is set false. See also &%queue_only_file%&,
17125 &%queue_only_load%&, and &%smtp_accept_queue%&.
17128 .option queue_only_file main string unset
17129 .cindex "queueing incoming messages"
17130 .cindex "message" "queueing by file existence"
17131 This option can be set to a colon-separated list of absolute path names, each
17132 one optionally preceded by &"smtp"&. When Exim is receiving a message,
17133 it tests for the existence of each listed path using a call to &[stat()]&. For
17134 each path that exists, the corresponding queueing option is set.
17135 For paths with no prefix, &%queue_only%& is set; for paths prefixed by
17136 &"smtp"&, &%queue_smtp_domains%& is set to match all domains. So, for example,
17138 queue_only_file = smtp/some/file
17140 causes Exim to behave as if &%queue_smtp_domains%& were set to &"*"& whenever
17141 &_/some/file_& exists.
17144 .option queue_only_load main fixed-point unset
17145 .cindex "load average"
17146 .cindex "queueing incoming messages"
17147 .cindex "message" "queueing by load"
17148 If the system load average is higher than this value, incoming messages from
17149 all sources are queued, and no automatic deliveries are started. If this
17150 happens during local or remote SMTP input, all subsequent messages received on
17151 the same SMTP connection are queued by default, whatever happens to the load in
17152 the meantime, but this can be changed by setting &%queue_only_load_latch%&
17155 Deliveries will subsequently be performed by queue runner processes. This
17156 option has no effect on ancient operating systems on which Exim cannot
17157 determine the load average. See also &%deliver_queue_load_max%& and
17158 &%smtp_load_reserve%&.
17161 .option queue_only_load_latch main boolean true
17162 .cindex "load average" "re-evaluating per message"
17163 When this option is true (the default), once one message has been queued
17164 because the load average is higher than the value set by &%queue_only_load%&,
17165 all subsequent messages received on the same SMTP connection are also queued.
17166 This is a deliberate choice; even though the load average may fall below the
17167 threshold, it doesn't seem right to deliver later messages on the same
17168 connection when not delivering earlier ones. However, there are special
17169 circumstances such as very long-lived connections from scanning appliances
17170 where this is not the best strategy. In such cases, &%queue_only_load_latch%&
17171 should be set false. This causes the value of the load average to be
17172 re-evaluated for each message.
17175 .option queue_only_override main boolean true
17176 .cindex "queueing incoming messages"
17177 When this option is true, the &%-od%&&'x'& command line options override the
17178 setting of &%queue_only%& or &%queue_only_file%& in the configuration file. If
17179 &%queue_only_override%& is set false, the &%-od%&&'x'& options cannot be used
17180 to override; they are accepted, but ignored.
17183 .option queue_run_in_order main boolean false
17184 .cindex "queue runner" "processing messages in order"
17185 If this option is set, queue runs happen in order of message arrival instead of
17186 in an arbitrary order. For this to happen, a complete list of the entire queue
17187 must be set up before the deliveries start. When the queue is all held in a
17188 single directory (the default), a single list is created for both the ordered
17189 and the non-ordered cases. However, if &%split_spool_directory%& is set, a
17190 single list is not created when &%queue_run_in_order%& is false. In this case,
17191 the sub-directories are processed one at a time (in a random order), and this
17192 avoids setting up one huge list for the whole queue. Thus, setting
17193 &%queue_run_in_order%& with &%split_spool_directory%& may degrade performance
17194 when the queue is large, because of the extra work in setting up the single,
17195 large list. In most situations, &%queue_run_in_order%& should not be set.
17199 .option queue_run_max main integer&!! 5
17200 .cindex "queue runner" "maximum number of"
17201 This controls the maximum number of queue runner processes that an Exim daemon
17202 can run simultaneously. This does not mean that it starts them all at once,
17203 but rather that if the maximum number are still running when the time comes to
17204 start another one, it refrains from starting another one. This can happen with
17205 very large queues and/or very sluggish deliveries. This option does not,
17206 however, interlock with other processes, so additional queue runners can be
17207 started by other means, or by killing and restarting the daemon.
17209 Setting this option to zero does not suppress queue runs; rather, it disables
17210 the limit, allowing any number of simultaneous queue runner processes to be
17211 run. If you do not want queue runs to occur, omit the &%-q%&&'xx'& setting on
17212 the daemon's command line.
17214 .cindex queues named
17215 .cindex "named queues" "resource limit"
17216 To set limits for different named queues use
17217 an expansion depending on the &$queue_name$& variable.
17219 .option queue_smtp_domains main "domain list&!!" unset
17220 .cindex "queueing incoming messages"
17221 .cindex "message" "queueing remote deliveries"
17222 .cindex "first pass routing"
17223 When this option is set, a delivery process is started whenever a message is
17224 received, routing is performed, and local deliveries take place.
17225 However, if any SMTP deliveries are required for domains that match
17226 &%queue_smtp_domains%&, they are not immediately delivered, but instead the
17227 message waits in the queue for the next queue run. Since routing of the message
17228 has taken place, Exim knows to which remote hosts it must be delivered, and so
17229 when the queue run happens, multiple messages for the same host are delivered
17230 over a single SMTP connection. The &%-odqs%& command line option causes all
17231 SMTP deliveries to be queued in this way, and is equivalent to setting
17232 &%queue_smtp_domains%& to &"*"&. See also &%hold_domains%& and
17236 .option receive_timeout main time 0s
17237 .cindex "timeout" "for non-SMTP input"
17238 This option sets the timeout for accepting a non-SMTP message, that is, the
17239 maximum time that Exim waits when reading a message on the standard input. If
17240 the value is zero, it will wait forever. This setting is overridden by the
17241 &%-or%& command line option. The timeout for incoming SMTP messages is
17242 controlled by &%smtp_receive_timeout%&.
17244 .option received_header_text main string&!! "see below"
17245 .cindex "customizing" "&'Received:'& header"
17246 .cindex "&'Received:'& header line" "customizing"
17247 This string defines the contents of the &'Received:'& message header that is
17248 added to each message, except for the timestamp, which is automatically added
17249 on at the end (preceded by a semicolon). The string is expanded each time it is
17250 used. If the expansion yields an empty string, no &'Received:'& header line is
17251 added to the message. Otherwise, the string should start with the text
17252 &"Received:"& and conform to the RFC 2822 specification for &'Received:'&
17254 The default setting is:
17257 received_header_text = Received: \
17258 ${if def:sender_rcvhost {from $sender_rcvhost\n\t}\
17259 {${if def:sender_ident \
17260 {from ${quote_local_part:$sender_ident} }}\
17261 ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\
17262 by $primary_hostname \
17263 ${if def:received_protocol {with $received_protocol }}\
17264 ${if def:tls_in_ver { ($tls_in_ver)}}\
17265 ${if def:tls_in_cipher_std { tls $tls_in_cipher_std\n\t}}\
17266 (Exim $version_number)\n\t\
17267 ${if def:sender_address \
17268 {(envelope-from <$sender_address>)\n\t}}\
17269 id $message_exim_id\
17270 ${if def:received_for {\n\tfor $received_for}}
17273 The references to the TLS version and cipher are
17274 omitted when Exim is built without TLS
17275 support. The use of conditional expansions ensures that this works for both
17276 locally generated messages and messages received from remote hosts, giving
17277 header lines such as the following:
17279 Received: from scrooge.carol.example ([192.168.12.25] ident=root)
17280 by marley.carol.example with esmtp (Exim 4.00)
17281 (envelope-from <bob@carol.example>)
17282 id 16IOWa-00019l-00
17283 for chas@dickens.example; Tue, 25 Dec 2001 14:43:44 +0000
17284 Received: by scrooge.carol.example with local (Exim 4.00)
17285 id 16IOWW-000083-00; Tue, 25 Dec 2001 14:43:41 +0000
17287 Until the body of the message has been received, the timestamp is the time when
17288 the message started to be received. Once the body has arrived, and all policy
17289 checks have taken place, the timestamp is updated to the time at which the
17290 message was accepted.
17293 .option received_headers_max main integer 30
17294 .cindex "loop" "prevention"
17295 .cindex "mail loop prevention"
17296 .cindex "&'Received:'& header line" "counting"
17297 When a message is to be delivered, the number of &'Received:'& headers is
17298 counted, and if it is greater than this parameter, a mail loop is assumed to
17299 have occurred, the delivery is abandoned, and an error message is generated.
17300 This applies to both local and remote deliveries.
17303 .option recipient_unqualified_hosts main "host list&!!" unset
17304 .cindex "unqualified addresses"
17305 .cindex "host" "unqualified addresses from"
17306 This option lists those hosts from which Exim is prepared to accept unqualified
17307 recipient addresses in message envelopes. The addresses are made fully
17308 qualified by the addition of the &%qualify_recipient%& value. This option also
17309 affects message header lines. Exim does not reject unqualified recipient
17310 addresses in headers, but it qualifies them only if the message came from a
17311 host that matches &%recipient_unqualified_hosts%&,
17312 or if the message was submitted locally (not using TCP/IP), and the &%-bnq%&
17313 option was not set.
17316 .option recipients_max main integer 50000
17317 .cindex "limit" "number of recipients"
17318 .cindex "recipient" "maximum number"
17319 If this option is set greater than zero, it specifies the maximum number of
17320 original recipients for any message. Additional recipients that are generated
17321 by aliasing or forwarding do not count. SMTP messages get a 452 response for
17322 all recipients over the limit; earlier recipients are delivered as normal.
17323 Non-SMTP messages with too many recipients are failed, and no deliveries are
17326 .cindex "RCPT" "maximum number of incoming"
17327 &*Note*&: The RFCs specify that an SMTP server should accept at least 100
17328 RCPT commands in a single message.
17331 .option recipients_max_reject main boolean false
17332 If this option is set true, Exim rejects SMTP messages containing too many
17333 recipients by giving 552 errors to the surplus RCPT commands, and a 554
17334 error to the eventual DATA command. Otherwise (the default) it gives a 452
17335 error to the surplus RCPT commands and accepts the message on behalf of the
17336 initial set of recipients. The remote server should then re-send the message
17337 for the remaining recipients at a later time.
17340 .option remote_max_parallel main integer 4
17341 .cindex "delivery" "parallelism for remote"
17342 This option controls parallel delivery of one message to a number of remote
17343 hosts. If the value is less than 2, parallel delivery is disabled, and Exim
17344 does all the remote deliveries for a message one by one. Otherwise, if a single
17345 message has to be delivered to more than one remote host, or if several copies
17346 have to be sent to the same remote host, up to &%remote_max_parallel%&
17347 deliveries are done simultaneously. If more than &%remote_max_parallel%&
17348 deliveries are required, the maximum number of processes are started, and as
17349 each one finishes, another is begun. The order of starting processes is the
17350 same as if sequential delivery were being done, and can be controlled by the
17351 &%remote_sort_domains%& option. If parallel delivery takes place while running
17352 with debugging turned on, the debugging output from each delivery process is
17353 tagged with its process id.
17355 This option controls only the maximum number of parallel deliveries for one
17356 message in one Exim delivery process. Because Exim has no central queue
17357 manager, there is no way of controlling the total number of simultaneous
17358 deliveries if the configuration allows a delivery attempt as soon as a message
17361 See also the &%max_parallel%& generic transport option,
17362 and the &%serialize_hosts%& smtp transport option.
17364 .cindex "number of deliveries"
17365 .cindex "delivery" "maximum number of"
17366 If you want to control the total number of deliveries on the system, you
17367 need to set the &%queue_only%& option. This ensures that all incoming messages
17368 are added to the queue without starting a delivery process. Then set up an Exim
17369 daemon to start queue runner processes at appropriate intervals (probably
17370 fairly often, for example, every minute), and limit the total number of queue
17371 runners by setting the &%queue_run_max%& parameter. Because each queue runner
17372 delivers only one message at a time, the maximum number of deliveries that can
17373 then take place at once is &%queue_run_max%& multiplied by
17374 &%remote_max_parallel%&.
17376 If it is purely remote deliveries you want to control, use
17377 &%queue_smtp_domains%& instead of &%queue_only%&. This has the added benefit of
17378 doing the SMTP routing before queueing, so that several messages for the same
17379 host will eventually get delivered down the same connection.
17382 .option remote_sort_domains main "domain list&!!" unset
17383 .cindex "sorting remote deliveries"
17384 .cindex "delivery" "sorting remote"
17385 When there are a number of remote deliveries for a message, they are sorted by
17386 domain into the order given by this list. For example,
17388 remote_sort_domains = *.cam.ac.uk:*.uk
17390 would attempt to deliver to all addresses in the &'cam.ac.uk'& domain first,
17391 then to those in the &%uk%& domain, then to any others.
17394 .option retry_data_expire main time 7d
17395 .cindex "hints database" "data expiry"
17396 This option sets a &"use before"& time on retry information in Exim's hints
17397 database. Any older retry data is ignored. This means that, for example, once a
17398 host has not been tried for 7 days, Exim behaves as if it has no knowledge of
17402 .option retry_interval_max main time 24h
17403 .cindex "retry" "limit on interval"
17404 .cindex "limit" "on retry interval"
17405 Chapter &<<CHAPretry>>& describes Exim's mechanisms for controlling the
17406 intervals between delivery attempts for messages that cannot be delivered
17407 straight away. This option sets an overall limit to the length of time between
17408 retries. It cannot be set greater than 24 hours; any attempt to do so forces
17412 .option return_path_remove main boolean true
17413 .cindex "&'Return-path:'& header line" "removing"
17414 RFC 2821, section 4.4, states that an SMTP server must insert a
17415 &'Return-path:'& header line into a message when it makes a &"final delivery"&.
17416 The &'Return-path:'& header preserves the sender address as received in the
17417 MAIL command. This description implies that this header should not be present
17418 in an incoming message. If &%return_path_remove%& is true, any existing
17419 &'Return-path:'& headers are removed from messages at the time they are
17420 received. Exim's transports have options for adding &'Return-path:'& headers at
17421 the time of delivery. They are normally used only for final local deliveries.
17424 .option return_size_limit main integer 100K
17425 This option is an obsolete synonym for &%bounce_return_size_limit%&.
17428 .option rfc1413_hosts main "host list&!!" @[]
17430 .cindex "host" "for RFC 1413 calls"
17431 RFC 1413 identification calls are made to any client host which matches
17432 an item in the list.
17433 The default value specifies just this host, being any local interface
17436 .option rfc1413_query_timeout main time 0s
17437 .cindex "RFC 1413" "query timeout"
17438 .cindex "timeout" "for RFC 1413 call"
17439 This sets the timeout on RFC 1413 identification calls. If it is set to zero,
17440 no RFC 1413 calls are ever made.
17443 .option sender_unqualified_hosts main "host list&!!" unset
17444 .cindex "unqualified addresses"
17445 .cindex "host" "unqualified addresses from"
17446 This option lists those hosts from which Exim is prepared to accept unqualified
17447 sender addresses. The addresses are made fully qualified by the addition of
17448 &%qualify_domain%&. This option also affects message header lines. Exim does
17449 not reject unqualified addresses in headers that contain sender addresses, but
17450 it qualifies them only if the message came from a host that matches
17451 &%sender_unqualified_hosts%&, or if the message was submitted locally (not
17452 using TCP/IP), and the &%-bnq%& option was not set.
17455 .option slow_lookup_log main integer 0
17456 .cindex "logging" "slow lookups"
17457 .cindex "dns" "logging slow lookups"
17458 This option controls logging of slow lookups.
17459 If the value is nonzero it is taken as a number of milliseconds
17460 and lookups taking longer than this are logged.
17461 Currently this applies only to DNS lookups.
17465 .option smtp_accept_keepalive main boolean true
17466 .cindex "keepalive" "on incoming connection"
17467 This option controls the setting of the SO_KEEPALIVE option on incoming
17468 TCP/IP socket connections. When set, it causes the kernel to probe idle
17469 connections periodically, by sending packets with &"old"& sequence numbers. The
17470 other end of the connection should send an acknowledgment if the connection is
17471 still okay or a reset if the connection has been aborted. The reason for doing
17472 this is that it has the beneficial effect of freeing up certain types of
17473 connection that can get stuck when the remote host is disconnected without
17474 tidying up the TCP/IP call properly. The keepalive mechanism takes several
17475 hours to detect unreachable hosts.
17479 .option smtp_accept_max main integer 20
17480 .cindex "limit" "incoming SMTP connections"
17481 .cindex "SMTP" "incoming connection count"
17483 This option specifies the maximum number of simultaneous incoming SMTP calls
17484 that Exim will accept. It applies only to the listening daemon; there is no
17485 control (in Exim) when incoming SMTP is being handled by &'inetd'&. If the
17486 value is set to zero, no limit is applied. However, it is required to be
17487 non-zero if either &%smtp_accept_max_per_host%& or &%smtp_accept_queue%& is
17488 set. See also &%smtp_accept_reserve%& and &%smtp_load_reserve%&.
17490 A new SMTP connection is immediately rejected if the &%smtp_accept_max%& limit
17491 has been reached. If not, Exim first checks &%smtp_accept_max_per_host%&. If
17492 that limit has not been reached for the client host, &%smtp_accept_reserve%&
17493 and &%smtp_load_reserve%& are then checked before accepting the connection.
17496 .option smtp_accept_max_nonmail main integer 10
17497 .cindex "limit" "non-mail SMTP commands"
17498 .cindex "SMTP" "limiting non-mail commands"
17499 Exim counts the number of &"non-mail"& commands in an SMTP session, and drops
17500 the connection if there are too many. This option defines &"too many"&. The
17501 check catches some denial-of-service attacks, repeated failing AUTHs, or a mad
17502 client looping sending EHLO, for example. The check is applied only if the
17503 client host matches &%smtp_accept_max_nonmail_hosts%&.
17505 When a new message is expected, one occurrence of RSET is not counted. This
17506 allows a client to send one RSET between messages (this is not necessary,
17507 but some clients do it). Exim also allows one uncounted occurrence of HELO
17508 or EHLO, and one occurrence of STARTTLS between messages. After
17509 starting up a TLS session, another EHLO is expected, and so it too is not
17510 counted. The first occurrence of AUTH in a connection, or immediately
17511 following STARTTLS is not counted. Otherwise, all commands other than
17512 MAIL, RCPT, DATA, and QUIT are counted.
17515 .option smtp_accept_max_nonmail_hosts main "host list&!!" *
17516 You can control which hosts are subject to the &%smtp_accept_max_nonmail%&
17517 check by setting this option. The default value makes it apply to all hosts. By
17518 changing the value, you can exclude any badly-behaved hosts that you have to
17522 . Allow this long option name to split; give it unsplit as a fifth argument
17523 . for the automatic .oindex that is generated by .option.
17524 . We insert " &~&~" which is both pretty nasty visually and results in
17525 . non-searchable text. HowItWorks.txt mentions an option for inserting
17526 . zero-width-space, which would be nicer visually and results in (at least)
17527 . html that Firefox will split on when it's forced to reflow (rather than
17528 . inserting a horizontal scrollbar). However, the text is still not
17529 . searchable. NM changed this occurrence for bug 1197 to no longer allow
17530 . the option name to split.
17532 .option "smtp_accept_max_per_connection" main integer&!! 1000 &&&
17533 smtp_accept_max_per_connection
17534 .cindex "SMTP" "limiting incoming message count"
17535 .cindex "limit" "messages per SMTP connection"
17536 The value of this option limits the number of MAIL commands that Exim is
17537 prepared to accept over a single SMTP connection, whether or not each command
17538 results in the transfer of a message. After the limit is reached, a 421
17539 response is given to subsequent MAIL commands. This limit is a safety
17540 precaution against a client that goes mad (incidents of this type have been
17542 The option is expanded after the HELO or EHLO is received
17543 and may depend on values available at that time.
17544 An empty or zero value after expansion removes the limit.
17547 .option smtp_accept_max_per_host main string&!! unset
17548 .cindex "limit" "SMTP connections from one host"
17549 .cindex "host" "limiting SMTP connections from"
17550 This option restricts the number of simultaneous IP connections from a single
17551 host (strictly, from a single IP address) to the Exim daemon. The option is
17552 expanded, to enable different limits to be applied to different hosts by
17553 reference to &$sender_host_address$&. Once the limit is reached, additional
17554 connection attempts from the same host are rejected with error code 421. This
17555 is entirely independent of &%smtp_accept_reserve%&. The option's default value
17556 of zero imposes no limit. If this option is set greater than zero, it is
17557 required that &%smtp_accept_max%& be non-zero.
17559 &*Warning*&: When setting this option you should not use any expansion
17560 constructions that take an appreciable amount of time. The expansion and test
17561 happen in the main daemon loop, in order to reject additional connections
17562 without forking additional processes (otherwise a denial-of-service attack
17563 could cause a vast number or processes to be created). While the daemon is
17564 doing this processing, it cannot accept any other incoming connections.
17568 .option smtp_accept_queue main integer 0
17569 .cindex "SMTP" "incoming connection count"
17570 .cindex "queueing incoming messages"
17571 .cindex "message" "queueing by SMTP connection count"
17572 If the number of simultaneous incoming SMTP connections being handled via the
17573 listening daemon exceeds this value, messages received by SMTP are just placed
17574 in the queue; no delivery processes are started automatically. The count is
17575 fixed at the start of an SMTP connection. It cannot be updated in the
17576 subprocess that receives messages, and so the queueing or not queueing applies
17577 to all messages received in the same connection.
17579 A value of zero implies no limit, and clearly any non-zero value is useful only
17580 if it is less than the &%smtp_accept_max%& value (unless that is zero). See
17581 also &%queue_only%&, &%queue_only_load%&, &%queue_smtp_domains%&, and the
17582 various &%-od%&&'x'& command line options.
17585 . See the comment on smtp_accept_max_per_connection
17587 .option "smtp_accept_queue_per_connection" main integer 10 &&&
17588 smtp_accept_queue_per_connection
17589 .cindex "queueing incoming messages"
17590 .cindex "message" "queueing by message count"
17591 This option limits the number of delivery processes that Exim starts
17592 automatically when receiving messages via SMTP, whether via the daemon or by
17593 the use of &%-bs%& or &%-bS%&. If the value of the option is greater than zero,
17594 and the number of messages received in a single SMTP session exceeds this
17595 number, subsequent messages are placed in the queue, but no delivery processes
17596 are started. This helps to limit the number of Exim processes when a server
17597 restarts after downtime and there is a lot of mail waiting for it on other
17598 systems. On large systems, the default should probably be increased, and on
17599 dial-in client systems it should probably be set to zero (that is, disabled).
17602 .option smtp_accept_reserve main integer 0
17603 .cindex "SMTP" "incoming call count"
17604 .cindex "host" "reserved"
17605 When &%smtp_accept_max%& is set greater than zero, this option specifies a
17606 number of SMTP connections that are reserved for connections from the hosts
17607 that are specified in &%smtp_reserve_hosts%&. The value set in
17608 &%smtp_accept_max%& includes this reserve pool. The specified hosts are not
17609 restricted to this number of connections; the option specifies a minimum number
17610 of connection slots for them, not a maximum. It is a guarantee that this group
17611 of hosts can always get at least &%smtp_accept_reserve%& connections. However,
17612 the limit specified by &%smtp_accept_max_per_host%& is still applied to each
17615 For example, if &%smtp_accept_max%& is set to 50 and &%smtp_accept_reserve%& is
17616 set to 5, once there are 45 active connections (from any hosts), new
17617 connections are accepted only from hosts listed in &%smtp_reserve_hosts%&,
17618 provided the other criteria for acceptance are met.
17621 .option smtp_active_hostname main string&!! unset
17622 .cindex "host" "name in SMTP responses"
17623 .cindex "SMTP" "host name in responses"
17624 .vindex "&$primary_hostname$&"
17625 This option is provided for multi-homed servers that want to masquerade as
17626 several different hosts. At the start of an incoming SMTP connection, its value
17627 is expanded and used instead of the value of &$primary_hostname$& in SMTP
17628 responses. For example, it is used as domain name in the response to an
17629 incoming HELO or EHLO command.
17631 .vindex "&$smtp_active_hostname$&"
17632 The active hostname is placed in the &$smtp_active_hostname$& variable, which
17633 is saved with any messages that are received. It is therefore available for use
17634 in routers and transports when the message is later delivered.
17636 If this option is unset, or if its expansion is forced to fail, or if the
17637 expansion results in an empty string, the value of &$primary_hostname$& is
17638 used. Other expansion failures cause a message to be written to the main and
17639 panic logs, and the SMTP command receives a temporary error. Typically, the
17640 value of &%smtp_active_hostname%& depends on the incoming interface address.
17643 smtp_active_hostname = ${if eq{$received_ip_address}{10.0.0.1}\
17644 {cox.mydomain}{box.mydomain}}
17647 Although &$smtp_active_hostname$& is primarily concerned with incoming
17648 messages, it is also used as the default for HELO commands in callout
17649 verification if there is no remote transport from which to obtain a
17650 &%helo_data%& value.
17652 .option smtp_backlog_monitor main integer 0
17653 .cindex "connection backlog" monitoring
17654 If this option is set to greater than zero, and the backlog of available
17655 TCP connections on a socket listening for SMTP is larger than it, a line
17656 is logged giving the value and the socket address and port.
17657 The value is retrived jsut before an accept call.
17658 This facility is only available on Linux.
17660 .option smtp_banner main string&!! "see below"
17661 .cindex "SMTP" "welcome banner"
17662 .cindex "banner for SMTP"
17663 .cindex "welcome banner for SMTP"
17664 .cindex "customizing" "SMTP banner"
17665 This string, which is expanded every time it is used, is output as the initial
17666 positive response to an SMTP connection. The default setting is:
17668 smtp_banner = $smtp_active_hostname ESMTP Exim \
17669 $version_number $tod_full
17671 Failure to expand the string causes a panic error. If you want to create a
17672 multiline response to the initial SMTP connection, use &"\n"& in the string at
17673 appropriate points, but not at the end. Note that the 220 code is not included
17674 in this string. Exim adds it automatically (several times in the case of a
17675 multiline response).
17678 .option smtp_check_spool_space main boolean true
17679 .cindex "checking disk space"
17680 .cindex "disk space, checking"
17681 .cindex "spool directory" "checking space"
17682 When this option is set, if an incoming SMTP session encounters the SIZE
17683 option on a MAIL command, it checks that there is enough space in the
17684 spool directory's partition to accept a message of that size, while still
17685 leaving free the amount specified by &%check_spool_space%& (even if that value
17686 is zero). If there isn't enough space, a temporary error code is returned.
17689 .option smtp_connect_backlog main integer 20
17690 .cindex "connection backlog" "set maximum"
17691 .cindex "SMTP" "connection backlog"
17692 .cindex "backlog of connections"
17693 This option specifies a maximum number of waiting SMTP connections. Exim passes
17694 this value to the TCP/IP system when it sets up its listener. Once this number
17695 of connections are waiting for the daemon's attention, subsequent connection
17696 attempts are refused at the TCP/IP level. At least, that is what the manuals
17697 say; in some circumstances such connection attempts have been observed to time
17698 out instead. For large systems it is probably a good idea to increase the
17699 value (to 50, say). It also gives some protection against denial-of-service
17700 attacks by SYN flooding.
17703 .option smtp_enforce_sync main boolean true
17704 .cindex "SMTP" "synchronization checking"
17705 .cindex "synchronization checking in SMTP"
17706 The SMTP protocol specification requires the client to wait for a response from
17707 the server at certain points in the dialogue. Without PIPELINING these
17708 synchronization points are after every command; with PIPELINING they are
17709 fewer, but they still exist.
17711 Some spamming sites send out a complete set of SMTP commands without waiting
17712 for any response. Exim protects against this by rejecting a message if the
17713 client has sent further input when it should not have. The error response &"554
17714 SMTP synchronization error"& is sent, and the connection is dropped. Testing
17715 for this error cannot be perfect because of transmission delays (unexpected
17716 input may be on its way but not yet received when Exim checks). However, it
17717 does detect many instances.
17719 The check can be globally disabled by setting &%smtp_enforce_sync%& false.
17720 If you want to disable the check selectively (for example, only for certain
17721 hosts), you can do so by an appropriate use of a &%control%& modifier in an ACL
17722 (see section &<<SECTcontrols>>&). See also &%pipelining_advertise_hosts%&.
17726 .option smtp_etrn_command main string&!! unset
17727 .cindex "ETRN" "command to be run"
17728 .cindex "ESMTP extensions" ETRN
17729 .vindex "&$domain$&"
17730 If this option is set, the given command is run whenever an SMTP ETRN
17731 command is received from a host that is permitted to issue such commands (see
17732 chapter &<<CHAPACL>>&). The string is split up into separate arguments which
17733 are independently expanded. The expansion variable &$domain$& is set to the
17734 argument of the ETRN command, and no syntax checking is done on it. For
17737 smtp_etrn_command = /etc/etrn_command $domain \
17738 $sender_host_address
17740 If the option is not set, the argument for the ETRN command must
17741 be a &'#'& followed by an address string.
17742 In this case an &'exim -R <string>'& command is used;
17743 if the ETRN ACL has set up a named-queue then &'-MCG <queue>'& is appended.
17745 A new process is created to run the command, but Exim does not wait for it to
17746 complete. Consequently, its status cannot be checked. If the command cannot be
17747 run, a line is written to the panic log, but the ETRN caller still receives
17748 a 250 success response. Exim is normally running under its own uid when
17749 receiving SMTP, so it is not possible for it to change the uid before running
17753 .option smtp_etrn_serialize main boolean true
17754 .cindex "ETRN" "serializing"
17755 When this option is set, it prevents the simultaneous execution of more than
17756 one identical command as a result of ETRN in an SMTP connection. See
17757 section &<<SECTETRN>>& for details.
17760 .option smtp_load_reserve main fixed-point unset
17761 .cindex "load average"
17762 If the system load average ever gets higher than this, incoming SMTP calls are
17763 accepted only from those hosts that match an entry in &%smtp_reserve_hosts%&.
17764 If &%smtp_reserve_hosts%& is not set, no incoming SMTP calls are accepted when
17765 the load is over the limit. The option has no effect on ancient operating
17766 systems on which Exim cannot determine the load average. See also
17767 &%deliver_queue_load_max%& and &%queue_only_load%&.
17771 .option smtp_max_synprot_errors main integer 3
17772 .cindex "SMTP" "limiting syntax and protocol errors"
17773 .cindex "limit" "SMTP syntax and protocol errors"
17774 Exim rejects SMTP commands that contain syntax or protocol errors. In
17775 particular, a syntactically invalid email address, as in this command:
17777 RCPT TO:<abc xyz@a.b.c>
17779 causes immediate rejection of the command, before any other tests are done.
17780 (The ACL cannot be run if there is no valid address to set up for it.) An
17781 example of a protocol error is receiving RCPT before MAIL. If there are
17782 too many syntax or protocol errors in one SMTP session, the connection is
17783 dropped. The limit is set by this option.
17785 .cindex "PIPELINING" "expected errors"
17786 When the PIPELINING extension to SMTP is in use, some protocol errors are
17787 &"expected"&, for instance, a RCPT command after a rejected MAIL command.
17788 Exim assumes that PIPELINING will be used if it advertises it (see
17789 &%pipelining_advertise_hosts%&), and in this situation, &"expected"& errors do
17790 not count towards the limit.
17794 .option smtp_max_unknown_commands main integer 3
17795 .cindex "SMTP" "limiting unknown commands"
17796 .cindex "limit" "unknown SMTP commands"
17797 If there are too many unrecognized commands in an incoming SMTP session, an
17798 Exim server drops the connection. This is a defence against some kinds of abuse
17801 into making connections to SMTP ports; in these circumstances, a number of
17802 non-SMTP command lines are sent first.
17806 .option smtp_ratelimit_hosts main "host list&!!" unset
17807 .cindex "SMTP" "rate limiting"
17808 .cindex "limit" "rate of message arrival"
17809 .cindex "RCPT" "rate limiting"
17810 Some sites find it helpful to be able to limit the rate at which certain hosts
17811 can send them messages, and the rate at which an individual message can specify
17814 Exim has two rate-limiting facilities. This section describes the older
17815 facility, which can limit rates within a single connection. The newer
17816 &%ratelimit%& ACL condition can limit rates across all connections. See section
17817 &<<SECTratelimiting>>& for details of the newer facility.
17819 When a host matches &%smtp_ratelimit_hosts%&, the values of
17820 &%smtp_ratelimit_mail%& and &%smtp_ratelimit_rcpt%& are used to control the
17821 rate of acceptance of MAIL and RCPT commands in a single SMTP session,
17822 respectively. Each option, if set, must contain a set of four comma-separated
17826 A threshold, before which there is no rate limiting.
17828 An initial time delay. Unlike other times in Exim, numbers with decimal
17829 fractional parts are allowed here.
17831 A factor by which to increase the delay each time.
17833 A maximum value for the delay. This should normally be less than 5 minutes,
17834 because after that time, the client is liable to timeout the SMTP command.
17837 For example, these settings have been used successfully at the site which
17838 first suggested this feature, for controlling mail from their customers:
17840 smtp_ratelimit_mail = 2,0.5s,1.05,4m
17841 smtp_ratelimit_rcpt = 4,0.25s,1.015,4m
17843 The first setting specifies delays that are applied to MAIL commands after
17844 two have been received over a single connection. The initial delay is 0.5
17845 seconds, increasing by a factor of 1.05 each time. The second setting applies
17846 delays to RCPT commands when more than four occur in a single message.
17849 .option smtp_ratelimit_mail main string unset
17850 See &%smtp_ratelimit_hosts%& above.
17853 .option smtp_ratelimit_rcpt main string unset
17854 See &%smtp_ratelimit_hosts%& above.
17857 .option smtp_receive_timeout main time&!! 5m
17858 .cindex "timeout" "for SMTP input"
17859 .cindex "SMTP" "input timeout"
17860 This sets a timeout value for SMTP reception. It applies to all forms of SMTP
17861 input, including batch SMTP. If a line of input (either an SMTP command or a
17862 data line) is not received within this time, the SMTP connection is dropped and
17863 the message is abandoned.
17864 A line is written to the log containing one of the following messages:
17866 SMTP command timeout on connection from...
17867 SMTP data timeout on connection from...
17869 The former means that Exim was expecting to read an SMTP command; the latter
17870 means that it was in the DATA phase, reading the contents of a message.
17872 If the first character of the option is a &"$"& the option is
17873 expanded before use and may depend on
17874 &$sender_host_name$&, &$sender_host_address$& and &$sender_host_port$&.
17878 The value set by this option can be overridden by the
17879 &%-os%& command-line option. A setting of zero time disables the timeout, but
17880 this should never be used for SMTP over TCP/IP. (It can be useful in some cases
17881 of local input using &%-bs%& or &%-bS%&.) For non-SMTP input, the reception
17882 timeout is controlled by &%receive_timeout%& and &%-or%&.
17885 .option smtp_reserve_hosts main "host list&!!" unset
17886 This option defines hosts for which SMTP connections are reserved; see
17887 &%smtp_accept_reserve%& and &%smtp_load_reserve%& above.
17890 .option smtp_return_error_details main boolean false
17891 .cindex "SMTP" "details policy failures"
17892 .cindex "policy control" "rejection, returning details"
17893 In the default state, Exim uses bland messages such as
17894 &"Administrative prohibition"& when it rejects SMTP commands for policy
17895 reasons. Many sysadmins like this because it gives away little information
17896 to spammers. However, some other sysadmins who are applying strict checking
17897 policies want to give out much fuller information about failures. Setting
17898 &%smtp_return_error_details%& true causes Exim to be more forthcoming. For
17899 example, instead of &"Administrative prohibition"&, it might give:
17901 550-Rejected after DATA: '>' missing at end of address:
17902 550 failing address in "From" header is: <user@dom.ain
17906 .option smtputf8_advertise_hosts main "host list&!!" *
17907 .cindex "SMTPUTF8" "ESMTP extension, advertising"
17908 .cindex "ESMTP extensions" SMTPUTF8
17909 When Exim is built with support for internationalised mail names,
17910 the availability thereof is advertised in
17911 response to EHLO only to those client hosts that match this option. See
17912 chapter &<<CHAPi18n>>& for details of Exim's support for internationalisation.
17915 .option spamd_address main string "127.0.0.1 783"
17916 This option is available when Exim is compiled with the content-scanning
17917 extension. It specifies how Exim connects to SpamAssassin's &%spamd%& daemon.
17918 See section &<<SECTscanspamass>>& for more details.
17922 .option spf_guess main string "v=spf1 a/24 mx/24 ptr ?all"
17923 This option is available when Exim is compiled with SPF support.
17924 See section &<<SECSPF>>& for more details.
17926 .option spf_smtp_comment_template main string&!! "Please%_see%_http://www.open-spf.org/Why"
17927 This option is available when Exim is compiled with SPF support. It
17928 allows the customisation of the SMTP comment that the SPF library
17929 generates. You are strongly encouraged to link to your own explanative
17930 site. The template must not contain spaces. If you need spaces in the
17931 output, use the proper placeholder. If libspf2 can not parse the
17932 template, it uses a built-in default broken link. The following placeholders
17933 (along with Exim variables (but see below)) are allowed in the template:
17937 &*%{L}*&: Envelope sender's local part.
17939 &*%{S}*&: Envelope sender.
17941 &*%{O}*&: Envelope sender's domain.
17943 &*%{D}*&: Current(?) domain.
17945 &*%{I}*&: SMTP client Ip.
17947 &*%{C}*&: SMTP client pretty IP.
17949 &*%{T}*&: Epoch time (UTC).
17951 &*%{P}*&: SMTP client domain name.
17953 &*%{V}*&: IP version.
17955 &*%{H}*&: EHLO/HELO domain.
17957 &*%{R}*&: Receiving domain.
17959 The capitalized placeholders do proper URL encoding, if you use them
17960 lowercased, no encoding takes place. This list was compiled from the
17963 A note on using Exim variables: As
17964 currently the SPF library is initialized before the SMTP EHLO phase,
17965 the variables useful for expansion are quite limited.
17968 .option split_spool_directory main boolean false
17969 .cindex "multiple spool directories"
17970 .cindex "spool directory" "split"
17971 .cindex "directories, multiple"
17972 If this option is set, it causes Exim to split its input directory into 62
17973 subdirectories, each with a single alphanumeric character as its name. The
17974 sixth character of the message id is used to allocate messages to
17975 subdirectories; this is the least significant base-62 digit of the time of
17976 arrival of the message.
17978 Splitting up the spool in this way may provide better performance on systems
17979 where there are long mail queues, by reducing the number of files in any one
17980 directory. The msglog directory is also split up in a similar way to the input
17981 directory; however, if &%preserve_message_logs%& is set, all old msglog files
17982 are still placed in the single directory &_msglog.OLD_&.
17984 It is not necessary to take any special action for existing messages when
17985 changing &%split_spool_directory%&. Exim notices messages that are in the
17986 &"wrong"& place, and continues to process them. If the option is turned off
17987 after a period of being on, the subdirectories will eventually empty and be
17988 automatically deleted.
17990 When &%split_spool_directory%& is set, the behaviour of queue runner processes
17991 changes. Instead of creating a list of all messages in the queue, and then
17992 trying to deliver each one, in turn, it constructs a list of those in one
17993 sub-directory and tries to deliver them, before moving on to the next
17994 sub-directory. The sub-directories are processed in a random order. This
17995 spreads out the scanning of the input directories, and uses less memory. It is
17996 particularly beneficial when there are lots of messages in the queue. However,
17997 if &%queue_run_in_order%& is set, none of this new processing happens. The
17998 entire queue has to be scanned and sorted before any deliveries can start.
18001 .option spool_directory main string&!! "set at compile time"
18002 .cindex "spool directory" "path to"
18003 This defines the directory in which Exim keeps its spool, that is, the messages
18004 it is waiting to deliver. The default value is taken from the compile-time
18005 configuration setting, if there is one. If not, this option must be set. The
18006 string is expanded, so it can contain, for example, a reference to
18007 &$primary_hostname$&.
18009 If the spool directory name is fixed on your installation, it is recommended
18010 that you set it at build time rather than from this option, particularly if the
18011 log files are being written to the spool directory (see &%log_file_path%&).
18012 Otherwise log files cannot be used for errors that are detected early on, such
18013 as failures in the configuration file.
18015 By using this option to override the compiled-in path, it is possible to run
18016 tests of Exim without using the standard spool.
18018 .option spool_wireformat main boolean false
18019 .cindex "spool directory" "file formats"
18020 If this option is set, Exim may for some messages use an alternative format
18021 for data-files in the spool which matches the wire format.
18022 Doing this permits more efficient message reception and transmission.
18023 Currently it is only done for messages received using the ESMTP CHUNKING
18026 The following variables will not have useful values:
18028 $max_received_linelength
18033 Users of the local_scan() API (see &<<CHAPlocalscan>>&),
18034 and any external programs which are passed a reference to a message data file
18035 (except via the &"regex"&, &"malware"& or &"spam"&) ACL conditions)
18036 will need to be aware of the different formats potentially available.
18038 Using any of the ACL conditions noted will negate the reception benefit
18039 (as a Unix-mbox-format file is constructed for them).
18040 The transmission benefit is maintained.
18042 .option sqlite_lock_timeout main time 5s
18043 .cindex "sqlite lookup type" "lock timeout"
18044 This option controls the timeout that the &(sqlite)& lookup uses when trying to
18045 access an SQLite database. See section &<<SECTsqlite>>& for more details.
18047 .option strict_acl_vars main boolean false
18048 .cindex "&ACL;" "variables, handling unset"
18049 This option controls what happens if a syntactically valid but undefined ACL
18050 variable is referenced. If it is false (the default), an empty string
18051 is substituted; if it is true, an error is generated. See section
18052 &<<SECTaclvariables>>& for details of ACL variables.
18054 .option strip_excess_angle_brackets main boolean false
18055 .cindex "angle brackets, excess"
18056 If this option is set, redundant pairs of angle brackets round &"route-addr"&
18057 items in addresses are stripped. For example, &'<<xxx@a.b.c.d>>'& is
18058 treated as &'<xxx@a.b.c.d>'&. If this is in the envelope and the message is
18059 passed on to another MTA, the excess angle brackets are not passed on. If this
18060 option is not set, multiple pairs of angle brackets cause a syntax error.
18063 .option strip_trailing_dot main boolean false
18064 .cindex "trailing dot on domain"
18065 .cindex "dot" "trailing on domain"
18066 If this option is set, a trailing dot at the end of a domain in an address is
18067 ignored. If this is in the envelope and the message is passed on to another
18068 MTA, the dot is not passed on. If this option is not set, a dot at the end of a
18069 domain causes a syntax error.
18070 However, addresses in header lines are checked only when an ACL requests header
18074 .option syslog_duplication main boolean true
18075 .cindex "syslog" "duplicate log lines; suppressing"
18076 When Exim is logging to syslog, it writes the log lines for its three
18077 separate logs at different syslog priorities so that they can in principle
18078 be separated on the logging hosts. Some installations do not require this
18079 separation, and in those cases, the duplication of certain log lines is a
18080 nuisance. If &%syslog_duplication%& is set false, only one copy of any
18081 particular log line is written to syslog. For lines that normally go to
18082 both the main log and the reject log, the reject log version (possibly
18083 containing message header lines) is written, at LOG_NOTICE priority.
18084 Lines that normally go to both the main and the panic log are written at
18085 the LOG_ALERT priority.
18088 .option syslog_facility main string unset
18089 .cindex "syslog" "facility; setting"
18090 This option sets the syslog &"facility"& name, used when Exim is logging to
18091 syslog. The value must be one of the strings &"mail"&, &"user"&, &"news"&,
18092 &"uucp"&, &"daemon"&, or &"local&'x'&"& where &'x'& is a digit between 0 and 7.
18093 If this option is unset, &"mail"& is used. See chapter &<<CHAPlog>>& for
18094 details of Exim's logging.
18097 .option syslog_pid main boolean true
18098 .cindex "syslog" "pid"
18099 If &%syslog_pid%& is set false, the PID on Exim's log lines are
18100 omitted when these lines are sent to syslog. (Syslog normally prefixes
18101 the log lines with the PID of the logging process automatically.) You need
18102 to enable the &`+pid`& log selector item, if you want Exim to write it's PID
18103 into the logs.) See chapter &<<CHAPlog>>& for details of Exim's logging.
18107 .option syslog_processname main string &`exim`&
18108 .cindex "syslog" "process name; setting"
18109 This option sets the syslog &"ident"& name, used when Exim is logging to
18110 syslog. The value must be no longer than 32 characters. See chapter
18111 &<<CHAPlog>>& for details of Exim's logging.
18115 .option syslog_timestamp main boolean true
18116 .cindex "syslog" "timestamps"
18117 .cindex timestamps syslog
18118 If &%syslog_timestamp%& is set false, the timestamps on Exim's log lines are
18119 omitted when these lines are sent to syslog. See chapter &<<CHAPlog>>& for
18120 details of Exim's logging.
18123 .option system_filter main string&!! unset
18124 .cindex "filter" "system filter"
18125 .cindex "system filter" "specifying"
18126 .cindex "Sieve filter" "not available for system filter"
18127 This option specifies an Exim filter file that is applied to all messages at
18128 the start of each delivery attempt, before any routing is done. System filters
18129 must be Exim filters; they cannot be Sieve filters. If the system filter
18130 generates any deliveries to files or pipes, or any new mail messages, the
18131 appropriate &%system_filter_..._transport%& option(s) must be set, to define
18132 which transports are to be used. Details of this facility are given in chapter
18133 &<<CHAPsystemfilter>>&.
18134 A forced expansion failure results in no filter operation.
18137 .option system_filter_directory_transport main string&!! unset
18138 .vindex "&$address_file$&"
18139 This sets the name of the transport driver that is to be used when the
18140 &%save%& command in a system message filter specifies a path ending in &"/"&,
18141 implying delivery of each message into a separate file in some directory.
18142 During the delivery, the variable &$address_file$& contains the path name.
18145 .option system_filter_file_transport main string&!! unset
18146 .cindex "file" "transport for system filter"
18147 This sets the name of the transport driver that is to be used when the &%save%&
18148 command in a system message filter specifies a path not ending in &"/"&. During
18149 the delivery, the variable &$address_file$& contains the path name.
18151 .option system_filter_group main string unset
18152 .cindex "gid (group id)" "system filter"
18153 This option is used only when &%system_filter_user%& is also set. It sets the
18154 gid under which the system filter is run, overriding any gid that is associated
18155 with the user. The value may be numerical or symbolic.
18157 .option system_filter_pipe_transport main string&!! unset
18158 .cindex "&(pipe)& transport" "for system filter"
18159 .vindex "&$address_pipe$&"
18160 This specifies the transport driver that is to be used when a &%pipe%& command
18161 is used in a system filter. During the delivery, the variable &$address_pipe$&
18162 contains the pipe command.
18165 .option system_filter_reply_transport main string&!! unset
18166 .cindex "&(autoreply)& transport" "for system filter"
18167 This specifies the transport driver that is to be used when a &%mail%& command
18168 is used in a system filter.
18171 .option system_filter_user main string unset
18172 .cindex "uid (user id)" "system filter"
18173 If this option is set to root, the system filter is run in the main Exim
18174 delivery process, as root. Otherwise, the system filter runs in a separate
18175 process, as the given user, defaulting to the Exim run-time user.
18176 Unless the string consists entirely of digits, it
18177 is looked up in the password data. Failure to find the named user causes a
18178 configuration error. The gid is either taken from the password data, or
18179 specified by &%system_filter_group%&. When the uid is specified numerically,
18180 &%system_filter_group%& is required to be set.
18182 If the system filter generates any pipe, file, or reply deliveries, the uid
18183 under which the filter is run is used when transporting them, unless a
18184 transport option overrides.
18187 .option tcp_nodelay main boolean true
18188 .cindex "daemon" "TCP_NODELAY on sockets"
18189 .cindex "Nagle algorithm"
18190 .cindex "TCP_NODELAY on listening sockets"
18191 If this option is set false, it stops the Exim daemon setting the
18192 TCP_NODELAY option on its listening sockets. Setting TCP_NODELAY
18193 turns off the &"Nagle algorithm"&, which is a way of improving network
18194 performance in interactive (character-by-character) situations. Turning it off
18195 should improve Exim's performance a bit, so that is what happens by default.
18196 However, it appears that some broken clients cannot cope, and time out. Hence
18197 this option. It affects only those sockets that are set up for listening by the
18198 daemon. Sockets created by the smtp transport for delivering mail always set
18202 .option timeout_frozen_after main time 0s
18203 .cindex "frozen messages" "timing out"
18204 .cindex "timeout" "frozen messages"
18205 If &%timeout_frozen_after%& is set to a time greater than zero, a frozen
18206 message of any kind that has been in the queue for longer than the given time
18207 is automatically cancelled at the next queue run. If the frozen message is a
18208 bounce message, it is just discarded; otherwise, a bounce is sent to the
18209 sender, in a similar manner to cancellation by the &%-Mg%& command line option.
18210 If you want to timeout frozen bounce messages earlier than other kinds of
18211 frozen message, see &%ignore_bounce_errors_after%&.
18213 &*Note:*& the default value of zero means no timeouts; with this setting,
18214 frozen messages remain in the queue forever (except for any frozen bounce
18215 messages that are released by &%ignore_bounce_errors_after%&).
18218 .option timezone main string unset
18219 .cindex "timezone, setting"
18220 .cindex "environment" "values from"
18221 The value of &%timezone%& is used to set the environment variable TZ while
18222 running Exim (if it is different on entry). This ensures that all timestamps
18223 created by Exim are in the required timezone. If you want all your timestamps
18224 to be in UTC (aka GMT) you should set
18228 The default value is taken from TIMEZONE_DEFAULT in &_Local/Makefile_&,
18229 or, if that is not set, from the value of the TZ environment variable when Exim
18230 is built. If &%timezone%& is set to the empty string, either at build or run
18231 time, any existing TZ variable is removed from the environment when Exim
18232 runs. This is appropriate behaviour for obtaining wall-clock time on some, but
18233 unfortunately not all, operating systems.
18236 .option tls_advertise_hosts main "host list&!!" *
18237 .cindex "TLS" "advertising"
18238 .cindex "encryption" "on SMTP connection"
18239 .cindex "SMTP" "encrypted connection"
18240 .cindex "ESMTP extensions" STARTTLS
18241 When Exim is built with support for TLS encrypted connections, the availability
18242 of the STARTTLS command to set up an encrypted session is advertised in
18243 response to EHLO only to those client hosts that match this option. See
18244 chapter &<<CHAPTLS>>& for details of Exim's support for TLS.
18245 Note that the default value requires that a certificate be supplied
18246 using the &%tls_certificate%& option. If TLS support for incoming connections
18247 is not required the &%tls_advertise_hosts%& option should be set empty.
18250 .option tls_alpn main "string list&!!" "smtp : esmtp"
18251 .cindex TLS "Application Layer Protocol Names"
18253 .cindex ALPN "set acceptable names for server"
18254 If this option is set,
18255 the TLS library supports ALPN,
18256 and the client offers either more than
18257 ALPN name or a name which does not match the list,
18258 the TLS connection is declined.
18261 .option tls_certificate main "string list&!!" unset
18262 .cindex "TLS" "server certificate; location of"
18263 .cindex "certificate" "server, location of"
18264 The value of this option is expanded, and must then be a list of absolute paths to
18265 files which contain the server's certificates (in PEM format).
18266 Commonly only one file is needed.
18267 The server's private key is also
18268 assumed to be in this file if &%tls_privatekey%& is unset. See chapter
18269 &<<CHAPTLS>>& for further details.
18271 &*Note*&: The certificates defined by this option are used only when Exim is
18272 receiving incoming messages as a server. If you want to supply certificates for
18273 use when sending messages as a client, you must set the &%tls_certificate%&
18274 option in the relevant &(smtp)& transport.
18276 &*Note*&: If you use filenames based on IP addresses, change the list
18277 separator in the usual way (&<<SECTlistsepchange>>&) to avoid confusion under IPv6.
18279 &*Note*&: Under versions of OpenSSL preceding 1.1.1,
18280 when a list of more than one
18281 file is used, the &$tls_in_ourcert$& variable is unreliable.
18282 The macro "_TLS_BAD_MULTICERT_IN_OURCERT" will be defined for those versions.
18284 .cindex SNI "selecting server certificate based on"
18285 If the option contains &$tls_out_sni$& and Exim is built against OpenSSL, then
18286 if the OpenSSL build supports TLS extensions and the TLS client sends the
18287 Server Name Indication extension, then this option and others documented in
18288 &<<SECTtlssni>>& will be re-expanded.
18290 If this option is unset or empty a self-signed certificate will be
18292 Under Linux this is generated at daemon startup; on other platforms it will be
18293 generated fresh for every connection.
18295 .option tls_crl main string&!! unset
18296 .cindex "TLS" "server certificate revocation list"
18297 .cindex "certificate" "revocation list for server"
18298 This option specifies a certificate revocation list. The expanded value must
18299 be the name of a file that contains CRLs in PEM format.
18301 Under OpenSSL the option can specify a directory with CRL files.
18303 &*Note:*& Under OpenSSL the option must, if given, supply a CRL
18304 for each signing element of the certificate chain (i.e. all but the leaf).
18305 For the file variant this can be multiple PEM blocks in the one file.
18307 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
18310 .option tls_dh_max_bits main integer 2236
18311 .cindex "TLS" "D-H bit count"
18312 The number of bits used for Diffie-Hellman key-exchange may be suggested by
18313 the chosen TLS library. That value might prove to be too high for
18314 interoperability. This option provides a maximum clamp on the value
18315 suggested, trading off security for interoperability.
18317 The value must be at least 1024.
18319 The value 2236 was chosen because, at time of adding the option, it was the
18320 hard-coded maximum value supported by the NSS cryptographic library, as used
18321 by Thunderbird, while GnuTLS was suggesting 2432 bits as normal.
18323 If you prefer more security and are willing to break some clients, raise this
18326 Note that the value passed to GnuTLS for *generating* a new prime may be a
18327 little less than this figure, because GnuTLS is inexact and may produce a
18328 larger prime than requested.
18331 .option tls_dhparam main string&!! unset
18332 .cindex "TLS" "D-H parameters for server"
18333 The value of this option is expanded and indicates the source of DH parameters
18334 to be used by Exim.
18336 &*Note: The Exim Maintainers strongly recommend using a filename with site-generated
18337 local DH parameters*&, which has been supported across all versions of Exim. The
18338 other specific constants available are a fallback so that even when
18339 "unconfigured", Exim can offer Perfect Forward Secrecy in older ciphersuites in TLS.
18341 If &%tls_dhparam%& is a filename starting with a &`/`&,
18342 then it names a file from which DH
18343 parameters should be loaded. If the file exists, it should hold a PEM-encoded
18344 PKCS#3 representation of the DH prime. If the file does not exist, for
18345 OpenSSL it is an error. For GnuTLS, Exim will attempt to create the file and
18346 fill it with a generated DH prime. For OpenSSL, if the DH bit-count from
18347 loading the file is greater than &%tls_dh_max_bits%& then it will be ignored,
18348 and treated as though the &%tls_dhparam%& were set to "none".
18350 If this option expands to the string "none", then no DH parameters will be
18353 If this option expands to the string "historic" and Exim is using GnuTLS, then
18354 Exim will attempt to load a file from inside the spool directory. If the file
18355 does not exist, Exim will attempt to create it.
18356 See section &<<SECTgnutlsparam>>& for further details.
18358 If Exim is using OpenSSL and this option is empty or unset, then Exim will load
18359 a default DH prime; the default is Exim-specific but lacks verifiable provenance.
18361 In older versions of Exim the default was the 2048 bit prime described in section
18362 2.2 of RFC 5114, "2048-bit MODP Group with 224-bit Prime Order Subgroup", which
18363 in IKE is assigned number 23.
18365 Otherwise, the option must expand to the name used by Exim for any of a number
18366 of DH primes specified in RFC 2409, RFC 3526, RFC 5114, RFC 7919, or from other
18367 sources. As names, Exim uses a standard specified name, else "ike" followed by
18368 the number used by IKE, or "default" which corresponds to
18369 &`exim.dev.20160529.3`&.
18371 The available standard primes are:
18372 &`ffdhe2048`&, &`ffdhe3072`&, &`ffdhe4096`&, &`ffdhe6144`&, &`ffdhe8192`&,
18373 &`ike1`&, &`ike2`&, &`ike5`&,
18374 &`ike14`&, &`ike15`&, &`ike16`&, &`ike17`&, &`ike18`&,
18375 &`ike22`&, &`ike23`& and &`ike24`&.
18377 The available additional primes are:
18378 &`exim.dev.20160529.1`&, &`exim.dev.20160529.2`& and &`exim.dev.20160529.3`&.
18380 Some of these will be too small to be accepted by clients.
18381 Some may be too large to be accepted by clients.
18382 The open cryptographic community has suspicions about the integrity of some
18383 of the later IKE values, which led into RFC7919 providing new fixed constants
18384 (the "ffdhe" identifiers).
18386 At this point, all of the "ike" values should be considered obsolete;
18387 they are still in Exim to avoid breaking unusual configurations, but are
18388 candidates for removal the next time we have backwards-incompatible changes.
18389 Two of them in particular (&`ike1`& and &`ike22`&) are called out by RFC 8247
18390 as MUST NOT use for IPSEC, and two more (&`ike23`& and &`ike24`&) as
18392 Because of this, Exim regards them as deprecated; if either of the first pair
18393 are used, warnings will be logged in the paniclog, and if any are used then
18394 warnings will be logged in the mainlog.
18395 All four will be removed in a future Exim release.
18397 The TLS protocol does not negotiate an acceptable size for this; clients tend
18398 to hard-drop connections if what is offered by the server is unacceptable,
18399 whether too large or too small, and there's no provision for the client to
18400 tell the server what these constraints are. Thus, as a server operator, you
18401 need to make an educated guess as to what is most likely to work for your
18404 Some known size constraints suggest that a bit-size in the range 2048 to 2236
18405 is most likely to maximise interoperability. The upper bound comes from
18406 applications using the Mozilla Network Security Services (NSS) library, which
18407 used to set its &`DH_MAX_P_BITS`& upper-bound to 2236. This affects many
18408 mail user agents (MUAs). The lower bound comes from Debian installs of Exim4
18409 prior to the 4.80 release, as Debian used to patch Exim to raise the minimum
18410 acceptable bound from 1024 to 2048.
18413 .option tls_eccurve main string&!! &`auto`&
18414 .cindex TLS "EC cryptography"
18415 This option selects a EC curve for use by Exim when used with OpenSSL.
18416 It has no effect when Exim is used with GnuTLS.
18418 After expansion it must contain a valid EC curve parameter, such as
18419 &`prime256v1`&, &`secp384r1`&, or &`P-512`&. Consult your OpenSSL manual
18420 for valid selections.
18422 For OpenSSL versions before (and not including) 1.0.2, the string
18423 &`auto`& selects &`prime256v1`&. For more recent OpenSSL versions
18424 &`auto`& tells the library to choose.
18426 If the option expands to an empty string, no EC curves will be enabled.
18429 .option tls_ocsp_file main string&!! unset
18430 .cindex TLS "certificate status"
18431 .cindex TLS "OCSP proof file"
18433 must if set expand to the absolute path to a file which contains a current
18434 status proof for the server's certificate, as obtained from the
18435 Certificate Authority.
18437 Usable for GnuTLS 3.4.4 or 3.3.17 or OpenSSL 1.1.0 (or later).
18438 The macro "_HAVE_TLS_OCSP" will be defined for those versions.
18440 For OpenSSL 1.1.0 or later, and
18441 for GnuTLS 3.5.6 or later the expanded value of this option can be a list
18442 of files, to match a list given for the &%tls_certificate%& option.
18443 The ordering of the two lists must match.
18444 The macro "_HAVE_TLS_OCSP_LIST" will be defined for those versions.
18446 The file(s) should be in DER format,
18447 except for GnuTLS 3.6.3 or later
18449 when an optional filetype prefix can be used.
18450 The prefix must be one of "DER" or "PEM", followed by
18451 a single space. If one is used it sets the format for subsequent
18452 files in the list; the initial format is DER.
18453 If multiple proofs are wanted, for multiple chain elements
18454 (this only works under TLS1.3)
18455 they must be coded as a combined OCSP response.
18457 Although GnuTLS will accept PEM files with multiple separate
18458 PEM blobs (ie. separate OCSP responses), it sends them in the
18459 TLS Certificate record interleaved with the certificates of the chain;
18460 although a GnuTLS client is happy with that, an OpenSSL client is not.
18462 .option tls_on_connect_ports main "string list" unset
18465 This option specifies a list of incoming SSMTP (aka SMTPS) ports that should
18466 operate the SSMTP (SMTPS) protocol, where a TLS session is immediately
18467 set up without waiting for the client to issue a STARTTLS command. For
18468 further details, see section &<<SECTsupobssmt>>&.
18472 .option tls_privatekey main "string list&!!" unset
18473 .cindex "TLS" "server private key; location of"
18474 The value of this option is expanded, and must then be a list of absolute paths to
18475 files which contains the server's private keys.
18476 If this option is unset, or if
18477 the expansion is forced to fail, or the result is an empty string, the private
18478 key is assumed to be in the same file as the server's certificates. See chapter
18479 &<<CHAPTLS>>& for further details.
18481 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
18484 .option tls_remember_esmtp main boolean false
18485 .cindex "TLS" "esmtp state; remembering"
18486 .cindex "TLS" "broken clients"
18487 If this option is set true, Exim violates the RFCs by remembering that it is in
18488 &"esmtp"& state after successfully negotiating a TLS session. This provides
18489 support for broken clients that fail to send a new EHLO after starting a
18493 .option tls_require_ciphers main string&!! unset
18494 .cindex "TLS" "requiring specific ciphers"
18495 .cindex "cipher" "requiring specific"
18496 This option controls which ciphers can be used for incoming TLS connections.
18497 The &(smtp)& transport has an option of the same name for controlling outgoing
18498 connections. This option is expanded for each connection, so can be varied for
18499 different clients if required. The value of this option must be a list of
18500 permitted cipher suites. The OpenSSL and GnuTLS libraries handle cipher control
18501 in somewhat different ways. If GnuTLS is being used, the client controls the
18502 preference order of the available ciphers. Details are given in sections
18503 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
18506 .option tls_resumption_hosts main "host list&!!" unset
18507 .cindex TLS resumption
18508 This option controls which connections to offer the TLS resumption feature.
18509 See &<<SECTresumption>>& for details.
18512 .option tls_try_verify_hosts main "host list&!!" unset
18513 .cindex "TLS" "client certificate verification"
18514 .cindex "certificate" "verification of client"
18515 See &%tls_verify_hosts%& below.
18518 .option tls_verify_certificates main string&!! system
18519 .cindex "TLS" "client certificate verification"
18520 .cindex "certificate" "verification of client"
18521 The value of this option is expanded, and must then be either the
18523 or the absolute path to
18524 a file or directory containing permitted certificates for clients that
18525 match &%tls_verify_hosts%& or &%tls_try_verify_hosts%&.
18527 The "system" value for the option will use a
18528 system default location compiled into the SSL library.
18529 This is not available for GnuTLS versions preceding 3.0.20,
18530 and will be taken as empty; an explicit location
18533 The use of a directory for the option value is not available for GnuTLS versions
18534 preceding 3.3.6 and a single file must be used.
18536 With OpenSSL the certificates specified
18538 either by file or directory
18539 are added to those given by the system default location.
18541 These certificates should be for the certificate authorities trusted, rather
18542 than the public cert of individual clients. With both OpenSSL and GnuTLS, if
18543 the value is a file then the certificates are sent by Exim as a server to
18544 connecting clients, defining the list of accepted certificate authorities.
18545 Thus the values defined should be considered public data. To avoid this,
18546 use the explicit directory version. (If your peer is Exim up to 4.85,
18547 using GnuTLS, you may need to send the CAs (thus using the file
18548 variant). Otherwise the peer doesn't send its certificate.)
18550 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
18552 A forced expansion failure or setting to an empty string is equivalent to
18556 .option tls_verify_hosts main "host list&!!" unset
18557 .cindex "TLS" "client certificate verification"
18558 .cindex "certificate" "verification of client"
18559 This option, along with &%tls_try_verify_hosts%&, controls the checking of
18560 certificates from clients. The expected certificates are defined by
18561 &%tls_verify_certificates%&, which must be set. A configuration error occurs if
18562 either &%tls_verify_hosts%& or &%tls_try_verify_hosts%& is set and
18563 &%tls_verify_certificates%& is not set.
18565 Any client that matches &%tls_verify_hosts%& is constrained by
18566 &%tls_verify_certificates%&. When the client initiates a TLS session, it must
18567 present one of the listed certificates. If it does not, the connection is
18569 &*Warning*&: Including a host in &%tls_verify_hosts%& does not require
18570 the host to use TLS. It can still send SMTP commands through unencrypted
18571 connections. Forcing a client to use TLS has to be done separately using an
18572 ACL to reject inappropriate commands when the connection is not encrypted.
18574 A weaker form of checking is provided by &%tls_try_verify_hosts%&. If a client
18575 matches this option (but not &%tls_verify_hosts%&), Exim requests a
18576 certificate and checks it against &%tls_verify_certificates%&, but does not
18577 abort the connection if there is no certificate or if it does not match. This
18578 state can be detected in an ACL, which makes it possible to implement policies
18579 such as &"accept for relay only if a verified certificate has been received,
18580 but accept for local delivery if encrypted, even without a verified
18583 Client hosts that match neither of these lists are not asked to present
18587 .option trusted_groups main "string list&!!" unset
18588 .cindex "trusted groups"
18589 .cindex "groups" "trusted"
18590 This option is expanded just once, at the start of Exim's processing. If this
18591 option is set, any process that is running in one of the listed groups, or
18592 which has one of them as a supplementary group, is trusted. The groups can be
18593 specified numerically or by name. See section &<<SECTtrustedadmin>>& for
18594 details of what trusted callers are permitted to do. If neither
18595 &%trusted_groups%& nor &%trusted_users%& is set, only root and the Exim user
18598 .option trusted_users main "string list&!!" unset
18599 .cindex "trusted users"
18600 .cindex "user" "trusted"
18601 This option is expanded just once, at the start of Exim's processing. If this
18602 option is set, any process that is running as one of the listed users is
18603 trusted. The users can be specified numerically or by name. See section
18604 &<<SECTtrustedadmin>>& for details of what trusted callers are permitted to do.
18605 If neither &%trusted_groups%& nor &%trusted_users%& is set, only root and the
18606 Exim user are trusted.
18608 .option unknown_login main string&!! unset
18609 .cindex "uid (user id)" "unknown caller"
18610 .vindex "&$caller_uid$&"
18611 This is a specialized feature for use in unusual configurations. By default, if
18612 the uid of the caller of Exim cannot be looked up using &[getpwuid()]&, Exim
18613 gives up. The &%unknown_login%& option can be used to set a login name to be
18614 used in this circumstance. It is expanded, so values like &%user$caller_uid%&
18615 can be set. When &%unknown_login%& is used, the value of &%unknown_username%&
18616 is used for the user's real name (gecos field), unless this has been set by the
18619 .option unknown_username main string unset
18620 See &%unknown_login%&.
18622 .option untrusted_set_sender main "address list&!!" unset
18623 .cindex "trusted users"
18624 .cindex "sender" "setting by untrusted user"
18625 .cindex "untrusted user setting sender"
18626 .cindex "user" "untrusted setting sender"
18627 .cindex "envelope from"
18628 .cindex "envelope sender"
18629 When an untrusted user submits a message to Exim using the standard input, Exim
18630 normally creates an envelope sender address from the user's login and the
18631 default qualification domain. Data from the &%-f%& option (for setting envelope
18632 senders on non-SMTP messages) or the SMTP MAIL command (if &%-bs%& or &%-bS%&
18633 is used) is ignored.
18635 However, untrusted users are permitted to set an empty envelope sender address,
18636 to declare that a message should never generate any bounces. For example:
18638 exim -f '<>' user@domain.example
18640 .vindex "&$sender_ident$&"
18641 The &%untrusted_set_sender%& option allows you to permit untrusted users to set
18642 other envelope sender addresses in a controlled way. When it is set, untrusted
18643 users are allowed to set envelope sender addresses that match any of the
18644 patterns in the list. Like all address lists, the string is expanded. The
18645 identity of the user is in &$sender_ident$&, so you can, for example, restrict
18646 users to setting senders that start with their login ids
18647 followed by a hyphen
18648 by a setting like this:
18650 untrusted_set_sender = ^$sender_ident-
18652 If you want to allow untrusted users to set envelope sender addresses without
18653 restriction, you can use
18655 untrusted_set_sender = *
18657 The &%untrusted_set_sender%& option applies to all forms of local input, but
18658 only to the setting of the envelope sender. It does not permit untrusted users
18659 to use the other options which trusted user can use to override message
18660 parameters. Furthermore, it does not stop Exim from removing an existing
18661 &'Sender:'& header in the message, or from adding a &'Sender:'& header if
18662 necessary. See &%local_sender_retain%& and &%local_from_check%& for ways of
18663 overriding these actions. The handling of the &'Sender:'& header is also
18664 described in section &<<SECTthesenhea>>&.
18666 The log line for a message's arrival shows the envelope sender following
18667 &"<="&. For local messages, the user's login always follows, after &"U="&. In
18668 &%-bp%& displays, and in the Exim monitor, if an untrusted user sets an
18669 envelope sender address, the user's login is shown in parentheses after the
18673 .option uucp_from_pattern main string "see below"
18674 .cindex "&""From""& line"
18675 .cindex "UUCP" "&""From""& line"
18676 Some applications that pass messages to an MTA via a command line interface use
18677 an initial line starting with &"From&~"& to pass the envelope sender. In
18678 particular, this is used by UUCP software. Exim recognizes such a line by means
18679 of a regular expression that is set in &%uucp_from_pattern%&. When the pattern
18680 matches, the sender address is constructed by expanding the contents of
18681 &%uucp_from_sender%&, provided that the caller of Exim is a trusted user. The
18682 default pattern recognizes lines in the following two forms:
18684 From ph10 Fri Jan 5 12:35 GMT 1996
18685 From ph10 Fri, 7 Jan 97 14:00:00 GMT
18687 The pattern can be seen by running
18689 exim -bP uucp_from_pattern
18691 It checks only up to the hours and minutes, and allows for a 2-digit or 4-digit
18692 year in the second case. The first word after &"From&~"& is matched in the
18693 regular expression by a parenthesized subpattern. The default value for
18694 &%uucp_from_sender%& is &"$1"&, which therefore just uses this first word
18695 (&"ph10"& in the example above) as the message's sender. See also
18696 &%ignore_fromline_hosts%&.
18699 .option uucp_from_sender main string&!! &`$1`&
18700 See &%uucp_from_pattern%& above.
18703 .option warn_message_file main string&!! unset
18704 .cindex "warning of delay" "customizing the message"
18705 .cindex "customizing" "warning message"
18706 This option defines a template file containing paragraphs of text to be used
18707 for constructing the warning message which is sent by Exim when a message has
18708 been in the queue for a specified amount of time, as specified by
18709 &%delay_warning%&. Details of the file's contents are given in chapter
18710 &<<CHAPemsgcust>>&.
18711 .cindex warn_message_file "tainted data"
18712 The option is expanded to give the file path, which must be
18713 absolute and untainted.
18714 See also &%bounce_message_file%&.
18717 .option write_rejectlog main boolean true
18718 .cindex "reject log" "disabling"
18719 If this option is set false, Exim no longer writes anything to the reject log.
18720 See chapter &<<CHAPlog>>& for details of what Exim writes to its logs.
18721 .ecindex IIDconfima
18722 .ecindex IIDmaiconf
18727 . ////////////////////////////////////////////////////////////////////////////
18728 . ////////////////////////////////////////////////////////////////////////////
18730 .chapter "Generic options for routers" "CHAProutergeneric"
18731 .scindex IIDgenoprou1 "options" "generic; for routers"
18732 .scindex IIDgenoprou2 "generic options" "router"
18733 This chapter describes the generic options that apply to all routers.
18734 Those that are preconditions are marked with ‡ in the &"use"& field.
18736 For a general description of how a router operates, see sections
18737 &<<SECTrunindrou>>& and &<<SECTrouprecon>>&. The latter specifies the order in
18738 which the preconditions are tested. The order of expansion of the options that
18739 provide data for a transport is: &%errors_to%&, &%headers_add%&,
18740 &%headers_remove%&, &%transport%&.
18742 The name of a router is limited to be &drivernamemax; ASCII characters long;
18743 prior to Exim 4.95 names would be silently truncated at this length, but now
18747 .option address_data routers string&!! unset
18748 .cindex "router" "data attached to address"
18749 The string is expanded just before the router is run, that is, after all the
18750 precondition tests have succeeded. If the expansion is forced to fail, the
18751 router declines, the value of &%address_data%& remains unchanged, and the
18752 &%more%& option controls what happens next. Other expansion failures cause
18753 delivery of the address to be deferred.
18755 .vindex "&$address_data$&"
18756 When the expansion succeeds, the value is retained with the address, and can be
18757 accessed using the variable &$address_data$& in the current router, subsequent
18758 routers, and the eventual transport.
18760 &*Warning*&: If the current or any subsequent router is a &(redirect)& router
18761 that runs a user's filter file, the contents of &$address_data$& are accessible
18762 in the filter. This is not normally a problem, because such data is usually
18763 either not confidential or it &"belongs"& to the current user, but if you do
18764 put confidential data into &$address_data$& you need to remember this point.
18766 Even if the router declines or passes, the value of &$address_data$& remains
18767 with the address, though it can be changed by another &%address_data%& setting
18768 on a subsequent router. If a router generates child addresses, the value of
18769 &$address_data$& propagates to them. This also applies to the special kind of
18770 &"child"& that is generated by a router with the &%unseen%& option.
18772 The idea of &%address_data%& is that you can use it to look up a lot of data
18773 for the address once, and then pick out parts of the data later. For example,
18774 you could use a single LDAP lookup to return a string of the form
18776 uid=1234 gid=5678 mailbox=/mail/xyz forward=/home/xyz/.forward
18778 In the transport you could pick out the mailbox by a setting such as
18780 file = ${extract{mailbox}{$address_data}}
18782 This makes the configuration file less messy, and also reduces the number of
18783 lookups (though Exim does cache lookups).
18785 See also the &%set%& option below.
18787 .vindex "&$sender_address_data$&"
18788 .vindex "&$address_data$&"
18789 The &%address_data%& facility is also useful as a means of passing information
18790 from one router to another, and from a router to a transport. In addition, if
18791 &$address_data$& is set by a router when verifying a recipient address from an
18792 ACL, it remains available for use in the rest of the ACL statement. After
18793 verifying a sender, the value is transferred to &$sender_address_data$&.
18797 .option address_test routers&!? boolean true
18799 .cindex "router" "skipping when address testing"
18800 If this option is set false, the router is skipped when routing is being tested
18801 by means of the &%-bt%& command line option. This can be a convenience when
18802 your first router sends messages to an external scanner, because it saves you
18803 having to set the &"already scanned"& indicator when testing real address
18808 .option cannot_route_message routers string&!! unset
18809 .cindex "router" "customizing &""cannot route""& message"
18810 .cindex "customizing" "&""cannot route""& message"
18811 This option specifies a text message that is used when an address cannot be
18812 routed because Exim has run out of routers. The default message is
18813 &"Unrouteable address"&. This option is useful only on routers that have
18814 &%more%& set false, or on the very last router in a configuration, because the
18815 value that is used is taken from the last router that is considered. This
18816 includes a router that is skipped because its preconditions are not met, as
18817 well as a router that declines. For example, using the default configuration,
18820 cannot_route_message = Remote domain not found in DNS
18822 on the first router, which is a &(dnslookup)& router with &%more%& set false,
18825 cannot_route_message = Unknown local user
18827 on the final router that checks for local users. If string expansion fails for
18828 this option, the default message is used. Unless the expansion failure was
18829 explicitly forced, a message about the failure is written to the main and panic
18830 logs, in addition to the normal message about the routing failure.
18833 .option caseful_local_part routers boolean false
18834 .cindex "case of local parts"
18835 .cindex "router" "case of local parts"
18836 By default, routers handle the local parts of addresses in a case-insensitive
18837 manner, though the actual case is preserved for transmission with the message.
18838 If you want the case of letters to be significant in a router, you must set
18839 this option true. For individual router options that contain address or local
18840 part lists (for example, &%local_parts%&), case-sensitive matching can be
18841 turned on by &"+caseful"& as a list item. See section &<<SECTcasletadd>>& for
18844 .vindex "&$local_part$&"
18845 .vindex "&$original_local_part$&"
18846 .vindex "&$parent_local_part$&"
18847 The value of the &$local_part$& variable is forced to lower case while a
18848 router is running unless &%caseful_local_part%& is set. When a router assigns
18849 an address to a transport, the value of &$local_part$& when the transport runs
18850 is the same as it was in the router. Similarly, when a router generates child
18851 addresses by aliasing or forwarding, the values of &$original_local_part$&
18852 and &$parent_local_part$& are those that were used by the redirecting router.
18854 This option applies to the processing of an address by a router. When a
18855 recipient address is being processed in an ACL, there is a separate &%control%&
18856 modifier that can be used to specify case-sensitive processing within the ACL
18857 (see section &<<SECTcontrols>>&).
18861 .option check_local_user routers&!? boolean false
18862 .cindex "local user, checking in router"
18863 .cindex "router" "checking for local user"
18864 .cindex "&_/etc/passwd_&"
18866 When this option is true, Exim checks that the local part of the recipient
18867 address (with affixes removed if relevant) is the name of an account on the
18868 local system. The check is done by calling the &[getpwnam()]& function rather
18869 than trying to read &_/etc/passwd_& directly. This means that other methods of
18870 holding password data (such as NIS) are supported. If the local part is a local
18872 .cindex "tainted data" "de-tainting"
18873 .cindex "de-tainting" "using router check_local_user option"
18874 &$local_part_data$& is set to an untainted version of the local part and
18875 &$home$& is set from the password data. The latter can be tested in other
18876 preconditions that are evaluated after this one (the order of evaluation is
18877 given in section &<<SECTrouprecon>>&). However, the value of &$home$& can be
18878 overridden by &%router_home_directory%&. If the local part is not a local user,
18879 the router is skipped.
18881 If you want to check that the local part is either the name of a local user
18882 or matches something else, you cannot combine &%check_local_user%& with a
18883 setting of &%local_parts%&, because that specifies the logical &'and'& of the
18884 two conditions. However, you can use a &(passwd)& lookup in a &%local_parts%&
18885 setting to achieve this. For example:
18887 local_parts = passwd;$local_part : lsearch;/etc/other/users
18889 Note, however, that the side effects of &%check_local_user%& (such as setting
18890 up a home directory) do not occur when a &(passwd)& lookup is used in a
18891 &%local_parts%& (or any other) precondition.
18895 .option condition routers&!? string&!! unset
18896 .cindex "router" "customized precondition"
18897 This option specifies a general precondition test that has to succeed for the
18898 router to be called. The &%condition%& option is the last precondition to be
18899 evaluated (see section &<<SECTrouprecon>>&). The string is expanded, and if the
18900 result is a forced failure, or an empty string, or one of the strings &"0"& or
18901 &"no"& or &"false"& (checked without regard to the case of the letters), the
18902 router is skipped, and the address is offered to the next one.
18904 If the result is any other value, the router is run (as this is the last
18905 precondition to be evaluated, all the other preconditions must be true).
18907 This option is unusual in that multiple &%condition%& options may be present.
18908 All &%condition%& options must succeed.
18910 The &%condition%& option provides a means of applying custom conditions to the
18911 running of routers. Note that in the case of a simple conditional expansion,
18912 the default expansion values are exactly what is wanted. For example:
18914 condition = ${if >{$message_age}{600}}
18916 Because of the default behaviour of the string expansion, this is equivalent to
18918 condition = ${if >{$message_age}{600}{true}{}}
18921 A multiple condition example, which succeeds:
18923 condition = ${if >{$message_age}{600}}
18924 condition = ${if !eq{${lc:$local_part}}{postmaster}}
18928 If the expansion fails (other than forced failure) delivery is deferred. Some
18929 of the other precondition options are common special cases that could in fact
18930 be specified using &%condition%&.
18932 Historical note: We have &%condition%& on ACLs and on Routers. Routers
18933 are far older, and use one set of semantics. ACLs are newer and when
18934 they were created, the ACL &%condition%& process was given far stricter
18935 parse semantics. The &%bool{}%& expansion condition uses the same rules as
18936 ACLs. The &%bool_lax{}%& expansion condition uses the same rules as
18937 Routers. More pointedly, the &%bool_lax{}%& was written to match the existing
18938 Router rules processing behavior.
18940 This is best illustrated in an example:
18942 # If used in an ACL condition will fail with a syntax error, but
18943 # in a router condition any extra characters are treated as a string
18945 $ exim -be '${if eq {${lc:GOOGLE.com}} {google.com}} {yes} {no}}'
18948 $ exim -be '${if eq {${lc:WHOIS.com}} {google.com}} {yes} {no}}'
18951 In each example above, the &%if%& statement actually ends after
18952 &"{google.com}}"&. Since no true or false braces were defined, the
18953 default &%if%& behavior is to return a boolean true or a null answer
18954 (which evaluates to false). The rest of the line is then treated as a
18955 string. So the first example resulted in the boolean answer &"true"&
18956 with the string &" {yes} {no}}"& appended to it. The second example
18957 resulted in the null output (indicating false) with the string
18958 &" {yes} {no}}"& appended to it.
18960 In fact you can put excess forward braces in too. In the router
18961 &%condition%&, Exim's parser only looks for &"{"& symbols when they
18962 mean something, like after a &"$"& or when required as part of a
18963 conditional. But otherwise &"{"& and &"}"& are treated as ordinary
18966 Thus, in a Router, the above expansion strings will both always evaluate
18967 true, as the result of expansion is a non-empty string which doesn't
18968 match an explicit false value. This can be tricky to debug. By
18969 contrast, in an ACL either of those strings will always result in an
18970 expansion error because the result doesn't look sufficiently boolean.
18973 .option debug_print routers string&!! unset
18974 .cindex "testing" "variables in drivers"
18975 If this option is set and debugging is enabled (see the &%-d%& command line
18976 option) or in address-testing mode (see the &%-bt%& command line option),
18977 the string is expanded and included in the debugging output.
18978 If expansion of the string fails, the error message is written to the debugging
18979 output, and Exim carries on processing.
18980 This option is provided to help with checking out the values of variables and
18981 so on when debugging router configurations. For example, if a &%condition%&
18982 option appears not to be working, &%debug_print%& can be used to output the
18983 variables it references. The output happens after checks for &%domains%&,
18984 &%local_parts%&, and &%check_local_user%& but before any other preconditions
18985 are tested. A newline is added to the text if it does not end with one.
18986 The variable &$router_name$& contains the name of the router.
18990 .option disable_logging routers boolean false
18991 If this option is set true, nothing is logged for any routing errors
18992 or for any deliveries caused by this router. You should not set this option
18993 unless you really, really know what you are doing. See also the generic
18994 transport option of the same name.
18996 .option dnssec_request_domains routers "domain list&!!" *
18997 .cindex "MX record" "security"
18998 .cindex "DNSSEC" "MX lookup"
18999 .cindex "security" "MX lookup"
19000 .cindex "DNS" "DNSSEC"
19001 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
19002 the DNSSEC request bit set.
19003 This applies to all of the SRV, MX, AAAA, A lookup sequence.
19005 .option dnssec_require_domains routers "domain list&!!" unset
19006 .cindex "MX record" "security"
19007 .cindex "DNSSEC" "MX lookup"
19008 .cindex "security" "MX lookup"
19009 .cindex "DNS" "DNSSEC"
19010 DNS lookups for domains matching &%dnssec_require_domains%& will be done with
19011 the DNSSEC request bit set. Any returns not having the Authenticated Data bit
19012 (AD bit) set will be ignored and logged as a host-lookup failure.
19013 This applies to all of the SRV, MX, AAAA, A lookup sequence.
19016 .option domains routers&!? "domain list&!!" unset
19017 .cindex "router" "restricting to specific domains"
19018 .vindex "&$domain_data$&"
19019 If this option is set, the router is skipped unless the current domain matches
19020 the list. If the match is achieved by means of a file lookup, the data that the
19021 lookup returned for the domain is placed in &$domain_data$& for use in string
19022 expansions of the driver's private options and in the transport.
19023 See section &<<SECTrouprecon>>& for
19024 a list of the order in which preconditions are evaluated.
19028 .option driver routers string unset
19029 This option must always be set. It specifies which of the available routers is
19033 .option dsn_lasthop routers boolean false
19034 .cindex "DSN" "success"
19035 .cindex "Delivery Status Notification" "success"
19036 If this option is set true, and extended DSN (RFC3461) processing is in effect,
19037 Exim will not pass on DSN requests to downstream DSN-aware hosts but will
19038 instead send a success DSN as if the next hop does not support DSN.
19039 Not effective on redirect routers.
19043 .option errors_to routers string&!! unset
19044 .cindex "envelope from"
19045 .cindex "envelope sender"
19046 .cindex "router" "changing address for errors"
19047 If a router successfully handles an address, it may assign the address to a
19048 transport for delivery or it may generate child addresses. In both cases, if
19049 there is a delivery problem during later processing, the resulting bounce
19050 message is sent to the address that results from expanding this string,
19051 provided that the address verifies successfully. The &%errors_to%& option is
19052 expanded before &%headers_add%&, &%headers_remove%&, and &%transport%&.
19054 The &%errors_to%& setting associated with an address can be overridden if it
19055 subsequently passes through other routers that have their own &%errors_to%&
19056 settings, or if the message is delivered by a transport with a &%return_path%&
19059 If &%errors_to%& is unset, or the expansion is forced to fail, or the result of
19060 the expansion fails to verify, the errors address associated with the incoming
19061 address is used. At top level, this is the envelope sender. A non-forced
19062 expansion failure causes delivery to be deferred.
19064 If an address for which &%errors_to%& has been set ends up being delivered over
19065 SMTP, the envelope sender for that delivery is the &%errors_to%& value, so that
19066 any bounces that are generated by other MTAs on the delivery route are also
19067 sent there. You can set &%errors_to%& to the empty string by either of these
19073 An expansion item that yields an empty string has the same effect. If you do
19074 this, a locally detected delivery error for addresses processed by this router
19075 no longer gives rise to a bounce message; the error is discarded. If the
19076 address is delivered to a remote host, the return path is set to &`<>`&, unless
19077 overridden by the &%return_path%& option on the transport.
19079 .vindex "&$address_data$&"
19080 If for some reason you want to discard local errors, but use a non-empty
19081 MAIL command for remote delivery, you can preserve the original return
19082 path in &$address_data$& in the router, and reinstate it in the transport by
19083 setting &%return_path%&.
19085 The most common use of &%errors_to%& is to direct mailing list bounces to the
19086 manager of the list, as described in section &<<SECTmailinglists>>&, or to
19087 implement VERP (Variable Envelope Return Paths) (see section &<<SECTverp>>&).
19091 .option expn routers&!? boolean true
19092 .cindex "address" "testing"
19093 .cindex "testing" "addresses"
19094 .cindex "EXPN" "router skipping"
19095 .cindex "router" "skipping for EXPN"
19096 If this option is turned off, the router is skipped when testing an address
19097 as a result of processing an SMTP EXPN command. You might, for example,
19098 want to turn it off on a router for users' &_.forward_& files, while leaving it
19099 on for the system alias file.
19100 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19103 The use of the SMTP EXPN command is controlled by an ACL (see chapter
19104 &<<CHAPACL>>&). When Exim is running an EXPN command, it is similar to testing
19105 an address with &%-bt%&. Compare VRFY, whose counterpart is &%-bv%&.
19109 .option fail_verify routers boolean false
19110 .cindex "router" "forcing verification failure"
19111 Setting this option has the effect of setting both &%fail_verify_sender%& and
19112 &%fail_verify_recipient%& to the same value.
19116 .option fail_verify_recipient routers boolean false
19117 If this option is true and an address is accepted by this router when
19118 verifying a recipient, verification fails.
19122 .option fail_verify_sender routers boolean false
19123 If this option is true and an address is accepted by this router when
19124 verifying a sender, verification fails.
19128 .option fallback_hosts routers "string list" unset
19129 .cindex "router" "fallback hosts"
19130 .cindex "fallback" "hosts specified on router"
19131 String expansion is not applied to this option. The argument must be a
19132 colon-separated list of host names or IP addresses. The list separator can be
19133 changed (see section &<<SECTlistsepchange>>&), and a port can be specified with
19134 each name or address. In fact, the format of each item is exactly the same as
19135 defined for the list of hosts in a &(manualroute)& router (see section
19136 &<<SECTformatonehostitem>>&).
19138 If a router queues an address for a remote transport, this host list is
19139 associated with the address, and used instead of the transport's fallback host
19140 list. If &%hosts_randomize%& is set on the transport, the order of the list is
19141 randomized for each use. See the &%fallback_hosts%& option of the &(smtp)&
19142 transport for further details.
19145 .option group routers string&!! "see below"
19146 .cindex "gid (group id)" "local delivery"
19147 .cindex "local transports" "uid and gid"
19148 .cindex "transport" "local"
19149 .cindex "router" "setting group"
19150 When a router queues an address for a transport, and the transport does not
19151 specify a group, the group given here is used when running the delivery
19153 The group may be specified numerically or by name. If expansion fails, the
19154 error is logged and delivery is deferred.
19155 The default is unset, unless &%check_local_user%& is set, when the default
19156 is taken from the password information. See also &%initgroups%& and &%user%&
19157 and the discussion in chapter &<<CHAPenvironment>>&.
19161 .option headers_add routers list&!! unset
19162 .cindex "header lines" "adding"
19163 .cindex "router" "adding header lines"
19164 This option specifies a list of text headers,
19165 newline-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
19166 that is associated with any addresses that are accepted by the router.
19167 Each item is separately expanded, at routing time. However, this
19168 option has no effect when an address is just being verified. The way in which
19169 the text is used to add header lines at transport time is described in section
19170 &<<SECTheadersaddrem>>&. New header lines are not actually added until the
19171 message is in the process of being transported. This means that references to
19172 header lines in string expansions in the transport's configuration do not
19173 &"see"& the added header lines.
19175 The &%headers_add%& option is expanded after &%errors_to%&, but before
19176 &%headers_remove%& and &%transport%&. If an item is empty, or if
19177 an item expansion is forced to fail, the item has no effect. Other expansion
19178 failures are treated as configuration errors.
19180 Unlike most options, &%headers_add%& can be specified multiple times
19181 for a router; all listed headers are added.
19183 &*Warning 1*&: The &%headers_add%& option cannot be used for a &(redirect)&
19184 router that has the &%one_time%& option set.
19186 .cindex "duplicate addresses"
19187 .oindex "&%unseen%&"
19188 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
19189 additions are deleted when the address is passed on to subsequent routers.
19190 For a &%redirect%& router, if a generated address is the same as the incoming
19191 address, this can lead to duplicate addresses with different header
19192 modifications. Exim does not do duplicate deliveries (except, in certain
19193 circumstances, to pipes -- see section &<<SECTdupaddr>>&), but it is undefined
19194 which of the duplicates is discarded, so this ambiguous situation should be
19195 avoided. The &%repeat_use%& option of the &%redirect%& router may be of help.
19199 .option headers_remove routers list&!! unset
19200 .cindex "header lines" "removing"
19201 .cindex "router" "removing header lines"
19202 This option specifies a list of text headers,
19203 colon-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
19204 that is associated with any addresses that are accepted by the router.
19205 However, the option has no effect when an address is just being verified.
19206 Each list item is separately expanded, at transport time.
19207 If an item ends in *, it will match any header with the given prefix.
19209 the text is used to remove header lines at transport time is described in
19210 section &<<SECTheadersaddrem>>&. Header lines are not actually removed until
19211 the message is in the process of being transported. This means that references
19212 to header lines in string expansions in the transport's configuration still
19213 &"see"& the original header lines.
19215 The &%headers_remove%& option is handled after &%errors_to%& and
19216 &%headers_add%&, but before &%transport%&. If an item expansion is forced to fail,
19217 the item has no effect. Other expansion failures are treated as configuration
19220 Unlike most options, &%headers_remove%& can be specified multiple times
19221 for a router; all listed headers are removed.
19223 &*Warning 1*&: The &%headers_remove%& option cannot be used for a &(redirect)&
19224 router that has the &%one_time%& option set.
19226 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
19227 removal requests are deleted when the address is passed on to subsequent
19228 routers, and this can lead to problems with duplicates -- see the similar
19229 warning for &%headers_add%& above.
19231 &*Warning 3*&: Because of the separate expansion of the list items,
19232 items that contain a list separator must have it doubled.
19233 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
19237 .option ignore_target_hosts routers "host list&!!" unset
19238 .cindex "IP address" "discarding"
19239 .cindex "router" "discarding IP addresses"
19240 Although this option is a host list, it should normally contain IP address
19241 entries rather than names. If any host that is looked up by the router has an
19242 IP address that matches an item in this list, Exim behaves as if that IP
19243 address did not exist. This option allows you to cope with rogue DNS entries
19246 remote.domain.example. A 127.0.0.1
19250 ignore_target_hosts = 127.0.0.1
19252 on the relevant router. If all the hosts found by a &(dnslookup)& router are
19253 discarded in this way, the router declines. In a conventional configuration, an
19254 attempt to mail to such a domain would normally provoke the &"unrouteable
19255 domain"& error, and an attempt to verify an address in the domain would fail.
19256 Similarly, if &%ignore_target_hosts%& is set on an &(ipliteral)& router, the
19257 router declines if presented with one of the listed addresses.
19259 You can use this option to disable the use of IPv4 or IPv6 for mail delivery by
19260 means of the first or the second of the following settings, respectively:
19262 ignore_target_hosts = 0.0.0.0/0
19263 ignore_target_hosts = <; 0::0/0
19265 The pattern in the first line matches all IPv4 addresses, whereas the pattern
19266 in the second line matches all IPv6 addresses.
19268 This option may also be useful for ignoring link-local and site-local IPv6
19269 addresses. Because, like all host lists, the value of &%ignore_target_hosts%&
19270 is expanded before use as a list, it is possible to make it dependent on the
19271 domain that is being routed.
19273 .vindex "&$host_address$&"
19274 During its expansion, &$host_address$& is set to the IP address that is being
19277 .option initgroups routers boolean false
19278 .cindex "additional groups"
19279 .cindex "groups" "additional"
19280 .cindex "local transports" "uid and gid"
19281 .cindex "transport" "local"
19282 If the router queues an address for a transport, and this option is true, and
19283 the uid supplied by the router is not overridden by the transport, the
19284 &[initgroups()]& function is called when running the transport to ensure that
19285 any additional groups associated with the uid are set up. See also &%group%&
19286 and &%user%& and the discussion in chapter &<<CHAPenvironment>>&.
19290 .option local_part_prefix routers&!? "string list" unset
19291 .cindex affix "router precondition"
19292 .cindex "router" "prefix for local part"
19293 .cindex "prefix" "for local part, used in router"
19294 If this option is set, the router is skipped unless the local part starts with
19295 one of the given strings, or &%local_part_prefix_optional%& is true. See
19296 section &<<SECTrouprecon>>& for a list of the order in which preconditions are
19299 The list is scanned from left to right, and the first prefix that matches is
19300 used. A limited form of wildcard is available; if the prefix begins with an
19301 asterisk, it matches the longest possible sequence of arbitrary characters at
19302 the start of the local part. An asterisk should therefore always be followed by
19303 some character that does not occur in normal local parts.
19304 .cindex "multiple mailboxes"
19305 .cindex "mailbox" "multiple"
19306 Wildcarding can be used to set up multiple user mailboxes, as described in
19307 section &<<SECTmulbox>>&.
19309 .vindex "&$local_part$&"
19310 .vindex "&$local_part_prefix$&"
19311 During the testing of the &%local_parts%& option, and while the router is
19312 running, the prefix is removed from the local part, and is available in the
19313 expansion variable &$local_part_prefix$&. When a message is being delivered, if
19314 the router accepts the address, this remains true during subsequent delivery by
19315 a transport. In particular, the local part that is transmitted in the RCPT
19316 command for LMTP, SMTP, and BSMTP deliveries has the prefix removed by default.
19317 This behaviour can be overridden by setting &%rcpt_include_affixes%& true on
19318 the relevant transport.
19320 .vindex &$local_part_prefix_v$&
19321 If wildcarding (above) was used then the part of the prefix matching the
19322 wildcard is available in &$local_part_prefix_v$&.
19324 When an address is being verified, &%local_part_prefix%& affects only the
19325 behaviour of the router. If the callout feature of verification is in use, this
19326 means that the full address, including the prefix, will be used during the
19329 The prefix facility is commonly used to handle local parts of the form
19330 &%owner-something%&. Another common use is to support local parts of the form
19331 &%real-username%& to bypass a user's &_.forward_& file &-- helpful when trying
19332 to tell a user their forwarding is broken &-- by placing a router like this one
19333 immediately before the router that handles &_.forward_& files:
19337 local_part_prefix = real-
19339 transport = local_delivery
19341 For security, it would probably be a good idea to restrict the use of this
19342 router to locally-generated messages, using a condition such as this:
19344 condition = ${if match {$sender_host_address}\
19345 {\N^(|127\.0\.0\.1)$\N}}
19348 If both &%local_part_prefix%& and &%local_part_suffix%& are set for a router,
19349 both conditions must be met if not optional. Care must be taken if wildcards
19350 are used in both a prefix and a suffix on the same router. Different
19351 separator characters must be used to avoid ambiguity.
19354 .option local_part_prefix_optional routers boolean false
19355 See &%local_part_prefix%& above.
19359 .option local_part_suffix routers&!? "string list" unset
19360 .cindex "router" "suffix for local part"
19361 .cindex "suffix for local part" "used in router"
19362 This option operates in the same way as &%local_part_prefix%&, except that the
19363 local part must end (rather than start) with the given string, the
19364 &%local_part_suffix_optional%& option determines whether the suffix is
19365 mandatory, and the wildcard * character, if present, must be the last
19366 character of the suffix. This option facility is commonly used to handle local
19367 parts of the form &%something-request%& and multiple user mailboxes of the form
19371 .option local_part_suffix_optional routers boolean false
19372 See &%local_part_suffix%& above.
19376 .option local_parts routers&!? "local part list&!!" unset
19377 .cindex "router" "restricting to specific local parts"
19378 .cindex "local part" "checking in router"
19379 The router is run only if the local part of the address matches the list.
19380 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19382 section &<<SECTlocparlis>>& for a discussion of local part lists. Because the
19383 string is expanded, it is possible to make it depend on the domain, for
19386 local_parts = dbm;/usr/local/specials/$domain_data
19388 .vindex "&$local_part_data$&"
19389 If the match is achieved by a lookup, the data that the lookup returned
19390 for the local part is placed in the variable &$local_part_data$& for use in
19391 expansions of the router's private options or in the transport.
19392 You might use this option, for
19393 example, if you have a large number of local virtual domains, and you want to
19394 send all postmaster mail to the same place without having to set up an alias in
19395 each virtual domain:
19399 local_parts = postmaster
19400 data = postmaster@real.domain.example
19404 .option log_as_local routers boolean "see below"
19405 .cindex "log" "delivery line"
19406 .cindex "delivery" "log line format"
19407 Exim has two logging styles for delivery, the idea being to make local
19408 deliveries stand out more visibly from remote ones. In the &"local"& style, the
19409 recipient address is given just as the local part, without a domain. The use of
19410 this style is controlled by this option. It defaults to true for the &(accept)&
19411 router, and false for all the others. This option applies only when a
19412 router assigns an address to a transport. It has no effect on routers that
19413 redirect addresses.
19417 .option more routers boolean&!! true
19418 The result of string expansion for this option must be a valid boolean value,
19419 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
19420 result causes an error, and delivery is deferred. If the expansion is forced to
19421 fail, the default value for the option (true) is used. Other failures cause
19422 delivery to be deferred.
19424 If this option is set false, and the router declines to handle the address, no
19425 further routers are tried, routing fails, and the address is bounced.
19427 However, if the router explicitly passes an address to the following router by
19428 means of the setting
19432 or otherwise, the setting of &%more%& is ignored. Also, the setting of &%more%&
19433 does not affect the behaviour if one of the precondition tests fails. In that
19434 case, the address is always passed to the next router.
19436 Note that &%address_data%& is not considered to be a precondition. If its
19437 expansion is forced to fail, the router declines, and the value of &%more%&
19438 controls what happens next.
19441 .option pass_on_timeout routers boolean false
19442 .cindex "timeout" "of router"
19443 .cindex "router" "timeout"
19444 If a router times out during a host lookup, it normally causes deferral of the
19445 address. If &%pass_on_timeout%& is set, the address is passed on to the next
19446 router, overriding &%no_more%&. This may be helpful for systems that are
19447 intermittently connected to the Internet, or those that want to pass to a smart
19448 host any messages that cannot immediately be delivered.
19450 There are occasional other temporary errors that can occur while doing DNS
19451 lookups. They are treated in the same way as a timeout, and this option
19452 applies to all of them.
19456 .option pass_router routers string unset
19457 .cindex "router" "go to after &""pass""&"
19458 Routers that recognize the generic &%self%& option (&(dnslookup)&,
19459 &(ipliteral)&, and &(manualroute)&) are able to return &"pass"&, forcing
19460 routing to continue, and overriding a false setting of &%more%&. When one of
19461 these routers returns &"pass"&, the address is normally handed on to the next
19462 router in sequence. This can be changed by setting &%pass_router%& to the name
19463 of another router. However (unlike &%redirect_router%&) the named router must
19464 be below the current router, to avoid loops. Note that this option applies only
19465 to the special case of &"pass"&. It does not apply when a router returns
19466 &"decline"& because it cannot handle an address.
19470 .option redirect_router routers string unset
19471 .cindex "router" "start at after redirection"
19472 Sometimes an administrator knows that it is pointless to reprocess addresses
19473 generated from alias or forward files with the same router again. For
19474 example, if an alias file translates real names into login ids there is no
19475 point searching the alias file a second time, especially if it is a large file.
19477 The &%redirect_router%& option can be set to the name of any router instance.
19478 It causes the routing of any generated addresses to start at the named router
19479 instead of at the first router. This option has no effect if the router in
19480 which it is set does not generate new addresses.
19484 .option require_files routers&!? "string list&!!" unset
19485 .cindex "file" "requiring for router"
19486 .cindex "router" "requiring file existence"
19487 This option provides a general mechanism for predicating the running of a
19488 router on the existence or non-existence of certain files or directories.
19489 Before running a router, as one of its precondition tests, Exim works its way
19490 through the &%require_files%& list, expanding each item separately.
19492 Because the list is split before expansion, any colons in expansion items must
19493 be doubled, or the facility for using a different list separator must be used
19494 (&<<SECTlistsepchange>>&).
19495 If any expansion is forced to fail, the item is ignored. Other expansion
19496 failures cause routing of the address to be deferred.
19498 If any expanded string is empty, it is ignored. Otherwise, except as described
19499 below, each string must be a fully qualified file path, optionally preceded by
19500 &"!"&. The paths are passed to the &[stat()]& function to test for the
19501 existence of the files or directories. The router is skipped if any paths not
19502 preceded by &"!"& do not exist, or if any paths preceded by &"!"& do exist.
19505 If &[stat()]& cannot determine whether a file exists or not, delivery of
19506 the message is deferred. This can happen when NFS-mounted filesystems are
19509 This option is checked after the &%domains%&, &%local_parts%&, and &%senders%&
19510 options, so you cannot use it to check for the existence of a file in which to
19511 look up a domain, local part, or sender. (See section &<<SECTrouprecon>>& for a
19512 full list of the order in which preconditions are evaluated.) However, as
19513 these options are all expanded, you can use the &%exists%& expansion condition
19514 to make such tests. The &%require_files%& option is intended for checking files
19515 that the router may be going to use internally, or which are needed by a
19516 transport (e.g., &_.procmailrc_&).
19518 During delivery, the &[stat()]& function is run as root, but there is a
19519 facility for some checking of the accessibility of a file by another user.
19520 This is not a proper permissions check, but just a &"rough"& check that
19521 operates as follows:
19523 If an item in a &%require_files%& list does not contain any forward slash
19524 characters, it is taken to be the user (and optional group, separated by a
19525 comma) to be checked for subsequent files in the list. If no group is specified
19526 but the user is specified symbolically, the gid associated with the uid is
19529 require_files = mail:/some/file
19530 require_files = $local_part_data:$home/.procmailrc
19532 If a user or group name in a &%require_files%& list does not exist, the
19533 &%require_files%& condition fails.
19535 Exim performs the check by scanning along the components of the file path, and
19536 checking the access for the given uid and gid. It checks for &"x"& access on
19537 directories, and &"r"& access on the final file. Note that this means that file
19538 access control lists, if the operating system has them, are ignored.
19540 &*Warning 1*&: When the router is being run to verify addresses for an
19541 incoming SMTP message, Exim is not running as root, but under its own uid. This
19542 may affect the result of a &%require_files%& check. In particular, &[stat()]&
19543 may yield the error EACCES (&"Permission denied"&). This means that the Exim
19544 user is not permitted to read one of the directories on the file's path.
19546 &*Warning 2*&: Even when Exim is running as root while delivering a message,
19547 &[stat()]& can yield EACCES for a file in an NFS directory that is mounted
19548 without root access. In this case, if a check for access by a particular user
19549 is requested, Exim creates a subprocess that runs as that user, and tries the
19550 check again in that process.
19552 The default action for handling an unresolved EACCES is to consider it to
19553 be caused by a configuration error, and routing is deferred because the
19554 existence or non-existence of the file cannot be determined. However, in some
19555 circumstances it may be desirable to treat this condition as if the file did
19556 not exist. If the filename (or the exclamation mark that precedes the filename
19557 for non-existence) is preceded by a plus sign, the EACCES error is treated
19558 as if the file did not exist. For example:
19560 require_files = +/some/file
19562 If the router is not an essential part of verification (for example, it
19563 handles users' &_.forward_& files), another solution is to set the &%verify%&
19564 option false so that the router is skipped when verifying.
19568 .option retry_use_local_part routers boolean "see below"
19569 .cindex "hints database" "retry keys"
19570 .cindex "local part" "in retry keys"
19571 When a delivery suffers a temporary routing failure, a retry record is created
19572 in Exim's hints database. For addresses whose routing depends only on the
19573 domain, the key for the retry record should not involve the local part, but for
19574 other addresses, both the domain and the local part should be included.
19575 Usually, remote routing is of the former kind, and local routing is of the
19578 This option controls whether the local part is used to form the key for retry
19579 hints for addresses that suffer temporary errors while being handled by this
19580 router. The default value is true for any router that has any of
19581 &%check_local_user%&,
19584 &%local_part_prefix%&,
19585 &%local_part_suffix%&,
19588 set, and false otherwise. Note that this option does not apply to hints keys
19589 for transport delays; they are controlled by a generic transport option of the
19592 Failing to set this option when it is needed
19593 (because a remote router handles only some of the local-parts for a domain)
19594 can result in incorrect error messages being generated.
19596 The setting of &%retry_use_local_part%& applies only to the router on which it
19597 appears. If the router generates child addresses, they are routed
19598 independently; this setting does not become attached to them.
19602 .option router_home_directory routers string&!! unset
19603 .cindex "router" "home directory for"
19604 .cindex "home directory" "for router"
19606 This option sets a home directory for use while the router is running. (Compare
19607 &%transport_home_directory%&, which sets a home directory for later
19608 transporting.) In particular, if used on a &(redirect)& router, this option
19609 sets a value for &$home$& while a filter is running. The value is expanded;
19610 forced expansion failure causes the option to be ignored &-- other failures
19611 cause the router to defer.
19613 Expansion of &%router_home_directory%& happens immediately after the
19614 &%check_local_user%& test (if configured), before any further expansions take
19616 (See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19618 While the router is running, &%router_home_directory%& overrides the value of
19619 &$home$& that came from &%check_local_user%&.
19621 When a router accepts an address and assigns it to a local transport (including
19622 the cases when a &(redirect)& router generates a pipe, file, or autoreply
19623 delivery), the home directory setting for the transport is taken from the first
19624 of these values that is set:
19627 The &%home_directory%& option on the transport;
19629 The &%transport_home_directory%& option on the router;
19631 The password data if &%check_local_user%& is set on the router;
19633 The &%router_home_directory%& option on the router.
19636 In other words, &%router_home_directory%& overrides the password data for the
19637 router, but not for the transport.
19641 .option self routers string freeze
19642 .cindex "MX record" "pointing to local host"
19643 .cindex "local host" "MX pointing to"
19644 This option applies to those routers that use a recipient address to find a
19645 list of remote hosts. Currently, these are the &(dnslookup)&, &(ipliteral)&,
19646 and &(manualroute)& routers.
19647 Certain configurations of the &(queryprogram)& router can also specify a list
19649 Usually such routers are configured to send the message to a remote host via an
19650 &(smtp)& transport. The &%self%& option specifies what happens when the first
19651 host on the list turns out to be the local host.
19652 The way in which Exim checks for the local host is described in section
19653 &<<SECTreclocipadd>>&.
19655 Normally this situation indicates either an error in Exim's configuration (for
19656 example, the router should be configured not to process this domain), or an
19657 error in the DNS (for example, the MX should not point to this host). For this
19658 reason, the default action is to log the incident, defer the address, and
19659 freeze the message. The following alternatives are provided for use in special
19664 Delivery of the message is tried again later, but the message is not frozen.
19666 .vitem "&%reroute%&: <&'domain'&>"
19667 The domain is changed to the given domain, and the address is passed back to
19668 be reprocessed by the routers. No rewriting of headers takes place. This
19669 behaviour is essentially a redirection.
19671 .vitem "&%reroute: rewrite:%& <&'domain'&>"
19672 The domain is changed to the given domain, and the address is passed back to be
19673 reprocessed by the routers. Any headers that contain the original domain are
19678 .vindex "&$self_hostname$&"
19679 The router passes the address to the next router, or to the router named in the
19680 &%pass_router%& option if it is set. This overrides &%no_more%&. During
19681 subsequent routing and delivery, the variable &$self_hostname$& contains the
19682 name of the local host that the router encountered. This can be used to
19683 distinguish between different cases for hosts with multiple names. The
19689 ensures that only those addresses that routed to the local host are passed on.
19690 Without &%no_more%&, addresses that were declined for other reasons would also
19691 be passed to the next router.
19694 Delivery fails and an error report is generated.
19697 .cindex "local host" "sending to"
19698 The anomaly is ignored and the address is queued for the transport. This
19699 setting should be used with extreme caution. For an &(smtp)& transport, it
19700 makes sense only in cases where the program that is listening on the SMTP port
19701 is not this version of Exim. That is, it must be some other MTA, or Exim with a
19702 different configuration file that handles the domain in another way.
19707 .option senders routers&!? "address list&!!" unset
19708 .cindex "router" "checking senders"
19709 If this option is set, the router is skipped unless the message's sender
19710 address matches something on the list.
19711 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19714 There are issues concerning verification when the running of routers is
19715 dependent on the sender. When Exim is verifying the address in an &%errors_to%&
19716 setting, it sets the sender to the null string. When using the &%-bt%& option
19717 to check a configuration file, it is necessary also to use the &%-f%& option to
19718 set an appropriate sender. For incoming mail, the sender is unset when
19719 verifying the sender, but is available when verifying any recipients. If the
19720 SMTP VRFY command is enabled, it must be used after MAIL if the sender address
19724 .option set routers "string list" unset
19725 .cindex router variables
19726 This option may be used multiple times on a router;
19727 because of this the list aspect is mostly irrelevant.
19728 The list separator is a semicolon but can be changed in the
19731 Each list-element given must be of the form &"name = value"&
19732 and the names used must start with the string &"r_"&.
19733 Values containing a list-separator should have them doubled.
19734 When a router runs, the strings are evaluated in order,
19735 to create variables which are added to the set associated with
19737 This is done immediately after all the preconditions, before the
19738 evaluation of the &%address_data%& option.
19739 The variable is set with the expansion of the value.
19740 The variables can be used by the router options
19741 (not including any preconditions)
19742 and by the transport.
19743 Later definitions of a given named variable will override former ones.
19744 Variable use is via the usual &$r_...$& syntax.
19746 This is similar to the &%address_data%& option, except that
19747 many independent variables can be used, with choice of naming.
19750 .option translate_ip_address routers string&!! unset
19751 .cindex "IP address" "translating"
19752 .cindex "packet radio"
19753 .cindex "router" "IP address translation"
19754 There exist some rare networking situations (for example, packet radio) where
19755 it is helpful to be able to translate IP addresses generated by normal routing
19756 mechanisms into other IP addresses, thus performing a kind of manual IP
19757 routing. This should be done only if the normal IP routing of the TCP/IP stack
19758 is inadequate or broken. Because this is an extremely uncommon requirement, the
19759 code to support this option is not included in the Exim binary unless
19760 SUPPORT_TRANSLATE_IP_ADDRESS=yes is set in &_Local/Makefile_&.
19762 .vindex "&$host_address$&"
19763 The &%translate_ip_address%& string is expanded for every IP address generated
19764 by the router, with the generated address set in &$host_address$&. If the
19765 expansion is forced to fail, no action is taken.
19766 For any other expansion error, delivery of the message is deferred.
19767 If the result of the expansion is an IP address, that replaces the original
19768 address; otherwise the result is assumed to be a host name &-- this is looked
19769 up using &[gethostbyname()]& (or &[getipnodebyname()]& when available) to
19770 produce one or more replacement IP addresses. For example, to subvert all IP
19771 addresses in some specific networks, this could be added to a router:
19773 translate_ip_address = \
19774 ${lookup{${mask:$host_address/26}}lsearch{/some/file}\
19777 The file would contain lines like
19779 10.2.3.128/26 some.host
19780 10.8.4.34/26 10.44.8.15
19782 You should not make use of this facility unless you really understand what you
19787 .option transport routers string&!! unset
19788 This option specifies the transport to be used when a router accepts an address
19789 and sets it up for delivery. A transport is never needed if a router is used
19790 only for verification. The value of the option is expanded at routing time,
19791 after the expansion of &%errors_to%&, &%headers_add%&, and &%headers_remove%&,
19792 and result must be the name of one of the configured transports. If it is not,
19793 delivery is deferred.
19795 The &%transport%& option is not used by the &(redirect)& router, but it does
19796 have some private options that set up transports for pipe and file deliveries
19797 (see chapter &<<CHAPredirect>>&).
19801 .option transport_current_directory routers string&!! unset
19802 .cindex "current directory for local transport"
19803 This option associates a current directory with any address that is routed
19804 to a local transport. This can happen either because a transport is
19805 explicitly configured for the router, or because it generates a delivery to a
19806 file or a pipe. During the delivery process (that is, at transport time), this
19807 option string is expanded and is set as the current directory, unless
19808 overridden by a setting on the transport.
19809 If the expansion fails for any reason, including forced failure, an error is
19810 logged, and delivery is deferred.
19811 See chapter &<<CHAPenvironment>>& for details of the local delivery
19817 .option transport_home_directory routers string&!! "see below"
19818 .cindex "home directory" "for local transport"
19819 This option associates a home directory with any address that is routed to a
19820 local transport. This can happen either because a transport is explicitly
19821 configured for the router, or because it generates a delivery to a file or a
19822 pipe. During the delivery process (that is, at transport time), the option
19823 string is expanded and is set as the home directory, unless overridden by a
19824 setting of &%home_directory%& on the transport.
19825 If the expansion fails for any reason, including forced failure, an error is
19826 logged, and delivery is deferred.
19828 If the transport does not specify a home directory, and
19829 &%transport_home_directory%& is not set for the router, the home directory for
19830 the transport is taken from the password data if &%check_local_user%& is set for
19831 the router. Otherwise it is taken from &%router_home_directory%& if that option
19832 is set; if not, no home directory is set for the transport.
19834 See chapter &<<CHAPenvironment>>& for further details of the local delivery
19840 .option unseen routers boolean&!! false
19841 .cindex "router" "carrying on after success"
19842 The result of string expansion for this option must be a valid boolean value,
19843 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
19844 result causes an error, and delivery is deferred. If the expansion is forced to
19845 fail, the default value for the option (false) is used. Other failures cause
19846 delivery to be deferred.
19848 When this option is set true, routing does not cease if the router accepts the
19849 address. Instead, a copy of the incoming address is passed to the next router,
19850 overriding a false setting of &%more%&. There is little point in setting
19851 &%more%& false if &%unseen%& is always true, but it may be useful in cases when
19852 the value of &%unseen%& contains expansion items (and therefore, presumably, is
19853 sometimes true and sometimes false).
19855 .cindex "copy of message (&%unseen%& option)"
19856 Setting the &%unseen%& option has a similar effect to the &%unseen%& command
19857 qualifier in filter files. It can be used to cause copies of messages to be
19858 delivered to some other destination, while also carrying out a normal delivery.
19859 In effect, the current address is made into a &"parent"& that has two children
19860 &-- one that is delivered as specified by this router, and a clone that goes on
19861 to be routed further. For this reason, &%unseen%& may not be combined with the
19862 &%one_time%& option in a &(redirect)& router.
19864 &*Warning*&: Header lines added to the address (or specified for removal) by
19865 this router or by previous routers affect the &"unseen"& copy of the message
19866 only. The clone that continues to be processed by further routers starts with
19867 no added headers and none specified for removal. For a &%redirect%& router, if
19868 a generated address is the same as the incoming address, this can lead to
19869 duplicate addresses with different header modifications. Exim does not do
19870 duplicate deliveries (except, in certain circumstances, to pipes -- see section
19871 &<<SECTdupaddr>>&), but it is undefined which of the duplicates is discarded,
19872 so this ambiguous situation should be avoided. The &%repeat_use%& option of the
19873 &%redirect%& router may be of help.
19875 Unlike the handling of header modifications, any data that was set by the
19876 &%address_data%& option in the current or previous routers &'is'& passed on to
19877 subsequent routers.
19880 .option user routers string&!! "see below"
19881 .cindex "uid (user id)" "local delivery"
19882 .cindex "local transports" "uid and gid"
19883 .cindex "transport" "local"
19884 .cindex "router" "user for filter processing"
19885 .cindex "filter" "user for processing"
19886 When a router queues an address for a transport, and the transport does not
19887 specify a user, the user given here is used when running the delivery process.
19888 The user may be specified numerically or by name. If expansion fails, the
19889 error is logged and delivery is deferred.
19890 This user is also used by the &(redirect)& router when running a filter file.
19891 The default is unset, except when &%check_local_user%& is set. In this case,
19892 the default is taken from the password information. If the user is specified as
19893 a name, and &%group%& is not set, the group associated with the user is used.
19894 See also &%initgroups%& and &%group%& and the discussion in chapter
19895 &<<CHAPenvironment>>&.
19899 .option verify routers&!? boolean true
19900 Setting this option has the effect of setting &%verify_sender%& and
19901 &%verify_recipient%& to the same value.
19904 .option verify_only routers&!? boolean false
19905 .cindex "EXPN" "with &%verify_only%&"
19907 .cindex "router" "used only when verifying"
19908 If this option is set, the router is used only when verifying an address,
19909 delivering in cutthrough mode or
19910 testing with the &%-bv%& option, not when actually doing a delivery, testing
19911 with the &%-bt%& option, or running the SMTP EXPN command. It can be further
19912 restricted to verifying only senders or recipients by means of
19913 &%verify_sender%& and &%verify_recipient%&.
19915 &*Warning*&: When the router is being run to verify addresses for an incoming
19916 SMTP message, Exim is not running as root, but under its own uid. If the router
19917 accesses any files, you need to make sure that they are accessible to the Exim
19921 .option verify_recipient routers&!? boolean true
19922 If this option is false, the router is skipped when verifying recipient
19924 delivering in cutthrough mode
19925 or testing recipient verification using &%-bv%&.
19926 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19928 See also the &$verify_mode$& variable.
19931 .option verify_sender routers&!? boolean true
19932 If this option is false, the router is skipped when verifying sender addresses
19933 or testing sender verification using &%-bvs%&.
19934 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19936 See also the &$verify_mode$& variable.
19937 .ecindex IIDgenoprou1
19938 .ecindex IIDgenoprou2
19945 . ////////////////////////////////////////////////////////////////////////////
19946 . ////////////////////////////////////////////////////////////////////////////
19948 .chapter "The accept router" "CHID4"
19949 .cindex "&(accept)& router"
19950 .cindex "routers" "&(accept)&"
19951 The &(accept)& router has no private options of its own. Unless it is being
19952 used purely for verification (see &%verify_only%&) a transport is required to
19953 be defined by the generic &%transport%& option. If the preconditions that are
19954 specified by generic options are met, the router accepts the address and queues
19955 it for the given transport. The most common use of this router is for setting
19956 up deliveries to local mailboxes. For example:
19960 domains = mydomain.example
19962 transport = local_delivery
19964 The &%domains%& condition in this example checks the domain of the address, and
19965 &%check_local_user%& checks that the local part is the login of a local user.
19966 When both preconditions are met, the &(accept)& router runs, and queues the
19967 address for the &(local_delivery)& transport.
19974 . ////////////////////////////////////////////////////////////////////////////
19975 . ////////////////////////////////////////////////////////////////////////////
19977 .chapter "The dnslookup router" "CHAPdnslookup"
19978 .scindex IIDdnsrou1 "&(dnslookup)& router"
19979 .scindex IIDdnsrou2 "routers" "&(dnslookup)&"
19980 The &(dnslookup)& router looks up the hosts that handle mail for the
19981 recipient's domain in the DNS. A transport must always be set for this router,
19982 unless &%verify_only%& is set.
19984 If SRV support is configured (see &%check_srv%& below), Exim first searches for
19985 SRV records. If none are found, or if SRV support is not configured,
19986 MX records are looked up. If no MX records exist, address records are sought.
19987 However, &%mx_domains%& can be set to disable the direct use of address
19990 MX records of equal priority are sorted by Exim into a random order. Exim then
19991 looks for address records for the host names obtained from MX or SRV records.
19992 When a host has more than one IP address, they are sorted into a random order,
19993 except that IPv6 addresses are sorted before IPv4 addresses. If all the
19994 IP addresses found are discarded by a setting of the &%ignore_target_hosts%&
19995 generic option, the router declines.
19997 Unless they have the highest priority (lowest MX value), MX records that point
19998 to the local host, or to any host name that matches &%hosts_treat_as_local%&,
19999 are discarded, together with any other MX records of equal or lower priority.
20001 .cindex "MX record" "pointing to local host"
20002 .cindex "local host" "MX pointing to"
20003 .oindex "&%self%&" "in &(dnslookup)& router"
20004 If the host pointed to by the highest priority MX record, or looked up as an
20005 address record, is the local host, or matches &%hosts_treat_as_local%&, what
20006 happens is controlled by the generic &%self%& option.
20009 .section "Problems with DNS lookups" "SECTprowitdnsloo"
20010 There have been problems with DNS servers when SRV records are looked up.
20011 Some misbehaving servers return a DNS error or timeout when a non-existent
20012 SRV record is sought. Similar problems have in the past been reported for
20013 MX records. The global &%dns_again_means_nonexist%& option can help with this
20014 problem, but it is heavy-handed because it is a global option.
20016 For this reason, there are two options, &%srv_fail_domains%& and
20017 &%mx_fail_domains%&, that control what happens when a DNS lookup in a
20018 &(dnslookup)& router results in a DNS failure or a &"try again"& response. If
20019 an attempt to look up an SRV or MX record causes one of these results, and the
20020 domain matches the relevant list, Exim behaves as if the DNS had responded &"no
20021 such record"&. In the case of an SRV lookup, this means that the router
20022 proceeds to look for MX records; in the case of an MX lookup, it proceeds to
20023 look for A or AAAA records, unless the domain matches &%mx_domains%&, in which
20024 case routing fails.
20027 .section "Declining addresses by dnslookup" "SECTdnslookupdecline"
20028 .cindex "&(dnslookup)& router" "declines"
20029 There are a few cases where a &(dnslookup)& router will decline to accept
20030 an address; if such a router is expected to handle "all remaining non-local
20031 domains", then it is important to set &%no_more%&.
20033 The router will defer rather than decline if the domain
20034 is found in the &%fail_defer_domains%& router option.
20036 Reasons for a &(dnslookup)& router to decline currently include:
20038 The domain does not exist in DNS
20040 The domain exists but the MX record's host part is just "."; this is a common
20041 convention (borrowed from SRV) used to indicate that there is no such service
20042 for this domain and to not fall back to trying A/AAAA records.
20044 Ditto, but for SRV records, when &%check_srv%& is set on this router.
20046 MX record points to a non-existent host.
20048 MX record points to an IP address and the main section option
20049 &%allow_mx_to_ip%& is not set.
20051 MX records exist and point to valid hosts, but all hosts resolve only to
20052 addresses blocked by the &%ignore_target_hosts%& generic option on this router.
20054 The domain is not syntactically valid (see also &%allow_utf8_domains%& and
20055 &%dns_check_names_pattern%& for handling one variant of this)
20057 &%check_secondary_mx%& is set on this router but the local host can
20058 not be found in the MX records (see below)
20064 .section "Private options for dnslookup" "SECID118"
20065 .cindex "options" "&(dnslookup)& router"
20066 The private options for the &(dnslookup)& router are as follows:
20068 .option check_secondary_mx dnslookup boolean false
20069 .cindex "MX record" "checking for secondary"
20070 If this option is set, the router declines unless the local host is found in
20071 (and removed from) the list of hosts obtained by MX lookup. This can be used to
20072 process domains for which the local host is a secondary mail exchanger
20073 differently to other domains. The way in which Exim decides whether a host is
20074 the local host is described in section &<<SECTreclocipadd>>&.
20077 .option check_srv dnslookup string&!! unset
20078 .cindex "SRV record" "enabling use of"
20079 The &(dnslookup)& router supports the use of SRV records (see RFC 2782) in
20080 addition to MX and address records. The support is disabled by default. To
20081 enable SRV support, set the &%check_srv%& option to the name of the service
20082 required. For example,
20086 looks for SRV records that refer to the normal smtp service. The option is
20087 expanded, so the service name can vary from message to message or address
20088 to address. This might be helpful if SRV records are being used for a
20089 submission service. If the expansion is forced to fail, the &%check_srv%&
20090 option is ignored, and the router proceeds to look for MX records in the
20093 When the expansion succeeds, the router searches first for SRV records for
20094 the given service (it assumes TCP protocol). A single SRV record with a
20095 host name that consists of just a single dot indicates &"no such service for
20096 this domain"&; if this is encountered, the router declines. If other kinds of
20097 SRV record are found, they are used to construct a host list for delivery
20098 according to the rules of RFC 2782. MX records are not sought in this case.
20100 When no SRV records are found, MX records (and address records) are sought in
20101 the traditional way. In other words, SRV records take precedence over MX
20102 records, just as MX records take precedence over address records. Note that
20103 this behaviour is not sanctioned by RFC 2782, though a previous draft RFC
20104 defined it. It is apparently believed that MX records are sufficient for email
20105 and that SRV records should not be used for this purpose. However, SRV records
20106 have an additional &"weight"& feature which some people might find useful when
20107 trying to split an SMTP load between hosts of different power.
20109 See section &<<SECTprowitdnsloo>>& above for a discussion of Exim's behaviour
20110 when there is a DNS lookup error.
20115 .option fail_defer_domains dnslookup "domain list&!!" unset
20116 .cindex "MX record" "not found"
20117 DNS lookups for domains matching &%fail_defer_domains%&
20118 which find no matching record will cause the router to defer
20119 rather than the default behaviour of decline.
20120 This maybe be useful for queueing messages for a newly created
20121 domain while the DNS configuration is not ready.
20122 However, it will result in any message with mistyped domains
20126 .option ipv4_only "string&!!" unset
20127 .cindex IPv6 disabling
20128 .cindex DNS "IPv6 disabling"
20129 The string is expanded, and if the result is anything but a forced failure,
20130 or an empty string, or one of the strings “0” or “no” or “false”
20131 (checked without regard to the case of the letters),
20132 only A records are used.
20134 .option ipv4_prefer "string&!!" unset
20135 .cindex IPv4 preference
20136 .cindex DNS "IPv4 preference"
20137 The string is expanded, and if the result is anything but a forced failure,
20138 or an empty string, or one of the strings “0” or “no” or “false”
20139 (checked without regard to the case of the letters),
20140 A records are sorted before AAAA records (inverting the default).
20142 .option mx_domains dnslookup "domain list&!!" unset
20143 .cindex "MX record" "required to exist"
20144 .cindex "SRV record" "required to exist"
20145 A domain that matches &%mx_domains%& is required to have either an MX or an SRV
20146 record in order to be recognized. (The name of this option could be improved.)
20147 For example, if all the mail hosts in &'fict.example'& are known to have MX
20148 records, except for those in &'discworld.fict.example'&, you could use this
20151 mx_domains = ! *.discworld.fict.example : *.fict.example
20153 This specifies that messages addressed to a domain that matches the list but
20154 has no MX record should be bounced immediately instead of being routed using
20155 the address record.
20158 .option mx_fail_domains dnslookup "domain list&!!" unset
20159 If the DNS lookup for MX records for one of the domains in this list causes a
20160 DNS lookup error, Exim behaves as if no MX records were found. See section
20161 &<<SECTprowitdnsloo>>& for more discussion.
20166 .option qualify_single dnslookup boolean true
20167 .cindex "DNS" "resolver options"
20168 .cindex "DNS" "qualifying single-component names"
20169 When this option is true, the resolver option RES_DEFNAMES is set for DNS
20170 lookups. Typically, but not standardly, this causes the resolver to qualify
20171 single-component names with the default domain. For example, on a machine
20172 called &'dictionary.ref.example'&, the domain &'thesaurus'& would be changed to
20173 &'thesaurus.ref.example'& inside the resolver. For details of what your
20174 resolver actually does, consult your man pages for &'resolver'& and
20179 .option rewrite_headers dnslookup boolean true
20180 .cindex "rewriting" "header lines"
20181 .cindex "header lines" "rewriting"
20182 If the domain name in the address that is being processed is not fully
20183 qualified, it may be expanded to its full form by a DNS lookup. For example, if
20184 an address is specified as &'dormouse@teaparty'&, the domain might be
20185 expanded to &'teaparty.wonderland.fict.example'&. Domain expansion can also
20186 occur as a result of setting the &%widen_domains%& option. If
20187 &%rewrite_headers%& is true, all occurrences of the abbreviated domain name in
20188 any &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-to:'&, &'Sender:'&, and &'To:'&
20189 header lines of the message are rewritten with the full domain name.
20191 This option should be turned off only when it is known that no message is
20192 ever going to be sent outside an environment where the abbreviation makes
20195 When an MX record is looked up in the DNS and matches a wildcard record, name
20196 servers normally return a record containing the name that has been looked up,
20197 making it impossible to detect whether a wildcard was present or not. However,
20198 some name servers have recently been seen to return the wildcard entry. If the
20199 name returned by a DNS lookup begins with an asterisk, it is not used for
20203 .option same_domain_copy_routing dnslookup boolean false
20204 .cindex "address" "copying routing"
20205 Addresses with the same domain are normally routed by the &(dnslookup)& router
20206 to the same list of hosts. However, this cannot be presumed, because the router
20207 options and preconditions may refer to the local part of the address. By
20208 default, therefore, Exim routes each address in a message independently. DNS
20209 servers run caches, so repeated DNS lookups are not normally expensive, and in
20210 any case, personal messages rarely have more than a few recipients.
20212 If you are running mailing lists with large numbers of subscribers at the same
20213 domain, and you are using a &(dnslookup)& router which is independent of the
20214 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
20215 lookups for identical domains in one message. In this case, when &(dnslookup)&
20216 routes an address to a remote transport, any other unrouted addresses in the
20217 message that have the same domain are automatically given the same routing
20218 without processing them independently,
20219 provided the following conditions are met:
20222 No router that processed the address specified &%headers_add%& or
20223 &%headers_remove%&.
20225 The router did not change the address in any way, for example, by &"widening"&
20232 .option search_parents dnslookup boolean false
20233 .cindex "DNS" "resolver options"
20234 When this option is true, the resolver option RES_DNSRCH is set for DNS
20235 lookups. This is different from the &%qualify_single%& option in that it
20236 applies to domains containing dots. Typically, but not standardly, it causes
20237 the resolver to search for the name in the current domain and in parent
20238 domains. For example, on a machine in the &'fict.example'& domain, if looking
20239 up &'teaparty.wonderland'& failed, the resolver would try
20240 &'teaparty.wonderland.fict.example'&. For details of what your resolver
20241 actually does, consult your man pages for &'resolver'& and &'resolv.conf'&.
20243 Setting this option true can cause problems in domains that have a wildcard MX
20244 record, because any domain that does not have its own MX record matches the
20249 .option srv_fail_domains dnslookup "domain list&!!" unset
20250 If the DNS lookup for SRV records for one of the domains in this list causes a
20251 DNS lookup error, Exim behaves as if no SRV records were found. See section
20252 &<<SECTprowitdnsloo>>& for more discussion.
20257 .option widen_domains dnslookup "string list" unset
20258 .cindex "domain" "partial; widening"
20259 If a DNS lookup fails and this option is set, each of its strings in turn is
20260 added onto the end of the domain, and the lookup is tried again. For example,
20263 widen_domains = fict.example:ref.example
20265 is set and a lookup of &'klingon.dictionary'& fails,
20266 &'klingon.dictionary.fict.example'& is looked up, and if this fails,
20267 &'klingon.dictionary.ref.example'& is tried. Note that the &%qualify_single%&
20268 and &%search_parents%& options can cause some widening to be undertaken inside
20269 the DNS resolver. &%widen_domains%& is not applied to sender addresses
20270 when verifying, unless &%rewrite_headers%& is false (not the default).
20273 .section "Effect of qualify_single and search_parents" "SECID119"
20274 When a domain from an envelope recipient is changed by the resolver as a result
20275 of the &%qualify_single%& or &%search_parents%& options, Exim rewrites the
20276 corresponding address in the message's header lines unless &%rewrite_headers%&
20277 is set false. Exim then re-routes the address, using the full domain.
20279 These two options affect only the DNS lookup that takes place inside the router
20280 for the domain of the address that is being routed. They do not affect lookups
20281 such as that implied by
20285 that may happen while processing a router precondition before the router is
20286 entered. No widening ever takes place for these lookups.
20287 .ecindex IIDdnsrou1
20288 .ecindex IIDdnsrou2
20298 . ////////////////////////////////////////////////////////////////////////////
20299 . ////////////////////////////////////////////////////////////////////////////
20301 .chapter "The ipliteral router" "CHID5"
20302 .cindex "&(ipliteral)& router"
20303 .cindex "domain literal" "routing"
20304 .cindex "routers" "&(ipliteral)&"
20305 This router has no private options. Unless it is being used purely for
20306 verification (see &%verify_only%&) a transport is required to be defined by the
20307 generic &%transport%& option. The router accepts the address if its domain part
20308 takes the form of an RFC 2822 domain literal. For example, the &(ipliteral)&
20309 router handles the address
20313 by setting up delivery to the host with that IP address. IPv4 domain literals
20314 consist of an IPv4 address enclosed in square brackets. IPv6 domain literals
20315 are similar, but the address is preceded by &`ipv6:`&. For example:
20317 postmaster@[ipv6:fe80::a00:20ff:fe86:a061.5678]
20319 Exim allows &`ipv4:`& before IPv4 addresses, for consistency, and on the
20320 grounds that sooner or later somebody will try it.
20322 .oindex "&%self%&" "in &(ipliteral)& router"
20323 If the IP address matches something in &%ignore_target_hosts%&, the router
20324 declines. If an IP literal turns out to refer to the local host, the generic
20325 &%self%& option determines what happens.
20327 The RFCs require support for domain literals; however, their use is
20328 controversial in today's Internet. If you want to use this router, you must
20329 also set the main configuration option &%allow_domain_literals%&. Otherwise,
20330 Exim will not recognize the domain literal syntax in addresses.
20334 . ////////////////////////////////////////////////////////////////////////////
20335 . ////////////////////////////////////////////////////////////////////////////
20337 .chapter "The iplookup router" "CHID6"
20338 .cindex "&(iplookup)& router"
20339 .cindex "routers" "&(iplookup)&"
20340 The &(iplookup)& router was written to fulfil a specific requirement in
20341 Cambridge University (which in fact no longer exists). For this reason, it is
20342 not included in the binary of Exim by default. If you want to include it, you
20345 ROUTER_IPLOOKUP=yes
20347 in your &_Local/Makefile_& configuration file.
20349 The &(iplookup)& router routes an address by sending it over a TCP or UDP
20350 connection to one or more specific hosts. The host can then return the same or
20351 a different address &-- in effect rewriting the recipient address in the
20352 message's envelope. The new address is then passed on to subsequent routers. If
20353 this process fails, the address can be passed on to other routers, or delivery
20354 can be deferred. Since &(iplookup)& is just a rewriting router, a transport
20355 must not be specified for it.
20357 .cindex "options" "&(iplookup)& router"
20358 .option hosts iplookup string unset
20359 This option must be supplied. Its value is a colon-separated list of host
20360 names. The hosts are looked up using &[gethostbyname()]&
20361 (or &[getipnodebyname()]& when available)
20362 and are tried in order until one responds to the query. If none respond, what
20363 happens is controlled by &%optional%&.
20366 .option optional iplookup boolean false
20367 If &%optional%& is true, if no response is obtained from any host, the address
20368 is passed to the next router, overriding &%no_more%&. If &%optional%& is false,
20369 delivery to the address is deferred.
20372 .option port iplookup integer 0
20373 .cindex "port" "&(iplookup)& router"
20374 This option must be supplied. It specifies the port number for the TCP or UDP
20378 .option protocol iplookup string udp
20379 This option can be set to &"udp"& or &"tcp"& to specify which of the two
20380 protocols is to be used.
20383 .option query iplookup string&!! "see below"
20384 This defines the content of the query that is sent to the remote hosts. The
20387 $local_part@$domain $local_part@$domain
20389 The repetition serves as a way of checking that a response is to the correct
20390 query in the default case (see &%response_pattern%& below).
20393 .option reroute iplookup string&!! unset
20394 If this option is not set, the rerouted address is precisely the byte string
20395 returned by the remote host, up to the first white space, if any. If set, the
20396 string is expanded to form the rerouted address. It can include parts matched
20397 in the response by &%response_pattern%& by means of numeric variables such as
20398 &$1$&, &$2$&, etc. The variable &$0$& refers to the entire input string,
20399 whether or not a pattern is in use. In all cases, the rerouted address must end
20400 up in the form &'local_part@domain'&.
20403 .option response_pattern iplookup string unset
20404 This option can be set to a regular expression that is applied to the string
20405 returned from the remote host. If the pattern does not match the response, the
20406 router declines. If &%response_pattern%& is not set, no checking of the
20407 response is done, unless the query was defaulted, in which case there is a
20408 check that the text returned after the first white space is the original
20409 address. This checks that the answer that has been received is in response to
20410 the correct question. For example, if the response is just a new domain, the
20411 following could be used:
20413 response_pattern = ^([^@]+)$
20414 reroute = $local_part@$1
20417 .option timeout iplookup time 5s
20418 This specifies the amount of time to wait for a response from the remote
20419 machine. The same timeout is used for the &[connect()]& function for a TCP
20420 call. It does not apply to UDP.
20425 . ////////////////////////////////////////////////////////////////////////////
20426 . ////////////////////////////////////////////////////////////////////////////
20428 .chapter "The manualroute router" "CHID7"
20429 .scindex IIDmanrou1 "&(manualroute)& router"
20430 .scindex IIDmanrou2 "routers" "&(manualroute)&"
20431 .cindex "domain" "manually routing"
20432 The &(manualroute)& router is so-called because it provides a way of manually
20433 routing an address according to its domain. It is mainly used when you want to
20434 route addresses to remote hosts according to your own rules, bypassing the
20435 normal DNS routing that looks up MX records. However, &(manualroute)& can also
20436 route to local transports, a facility that may be useful if you want to save
20437 messages for dial-in hosts in local files.
20439 The &(manualroute)& router compares a list of domain patterns with the domain
20440 it is trying to route. If there is no match, the router declines. Each pattern
20441 has associated with it a list of hosts and some other optional data, which may
20442 include a transport. The combination of a pattern and its data is called a
20443 &"routing rule"&. For patterns that do not have an associated transport, the
20444 generic &%transport%& option must specify a transport, unless the router is
20445 being used purely for verification (see &%verify_only%&).
20448 In the case of verification, matching the domain pattern is sufficient for the
20449 router to accept the address. When actually routing an address for delivery,
20450 an address that matches a domain pattern is queued for the associated
20451 transport. If the transport is not a local one, a host list must be associated
20452 with the pattern; IP addresses are looked up for the hosts, and these are
20453 passed to the transport along with the mail address. For local transports, a
20454 host list is optional. If it is present, it is passed in &$host$& as a single
20457 The list of routing rules can be provided as an inline string in
20458 &%route_list%&, or the data can be obtained by looking up the domain in a file
20459 or database by setting &%route_data%&. Only one of these settings may appear in
20460 any one instance of &(manualroute)&. The format of routing rules is described
20461 below, following the list of private options.
20464 .section "Private options for manualroute" "SECTprioptman"
20466 .cindex "options" "&(manualroute)& router"
20467 The private options for the &(manualroute)& router are as follows:
20469 .option host_all_ignored manualroute string defer
20470 See &%host_find_failed%&.
20472 .option host_find_failed manualroute string freeze
20473 This option controls what happens when &(manualroute)& tries to find an IP
20474 address for a host, and the host does not exist. The option can be set to one
20475 of the following values:
20484 The default (&"freeze"&) assumes that this state is a serious configuration
20485 error. The difference between &"pass"& and &"decline"& is that the former
20486 forces the address to be passed to the next router (or the router defined by
20489 overriding &%no_more%&, whereas the latter passes the address to the next
20490 router only if &%more%& is true.
20492 The value &"ignore"& causes Exim to completely ignore a host whose IP address
20493 cannot be found. If all the hosts in the list are ignored, the behaviour is
20494 controlled by the &%host_all_ignored%& option. This takes the same values
20495 as &%host_find_failed%&, except that it cannot be set to &"ignore"&.
20497 The &%host_find_failed%& option applies only to a definite &"does not exist"&
20498 state; if a host lookup gets a temporary error, delivery is deferred unless the
20499 generic &%pass_on_timeout%& option is set.
20502 .option hosts_randomize manualroute boolean false
20503 .cindex "randomized host list"
20504 .cindex "host" "list of; randomized"
20505 If this option is set, the order of the items in a host list in a routing rule
20506 is randomized each time the list is used, unless an option in the routing rule
20507 overrides (see below). Randomizing the order of a host list can be used to do
20508 crude load sharing. However, if more than one mail address is routed by the
20509 same router to the same host list, the host lists are considered to be the same
20510 (even though they may be randomized into different orders) for the purpose of
20511 deciding whether to batch the deliveries into a single SMTP transaction.
20513 When &%hosts_randomize%& is true, a host list may be split
20514 into groups whose order is separately randomized. This makes it possible to
20515 set up MX-like behaviour. The boundaries between groups are indicated by an
20516 item that is just &`+`& in the host list. For example:
20518 route_list = * host1:host2:host3:+:host4:host5
20520 The order of the first three hosts and the order of the last two hosts is
20521 randomized for each use, but the first three always end up before the last two.
20522 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored. If a
20523 randomized host list is passed to an &(smtp)& transport that also has
20524 &%hosts_randomize set%&, the list is not re-randomized.
20527 .option route_data manualroute string&!! unset
20528 If this option is set, it must expand to yield the data part of a routing rule.
20529 Typically, the expansion string includes a lookup based on the domain. For
20532 route_data = ${lookup{$domain}dbm{/etc/routes}}
20534 If the expansion is forced to fail, or the result is an empty string, the
20535 router declines. Other kinds of expansion failure cause delivery to be
20539 .option route_list manualroute "string list" unset
20540 This string is a list of routing rules, in the form defined below. Note that,
20541 unlike most string lists, the items are separated by semicolons. This is so
20542 that they may contain colon-separated host lists.
20545 .option same_domain_copy_routing manualroute boolean false
20546 .cindex "address" "copying routing"
20547 Addresses with the same domain are normally routed by the &(manualroute)&
20548 router to the same list of hosts. However, this cannot be presumed, because the
20549 router options and preconditions may refer to the local part of the address. By
20550 default, therefore, Exim routes each address in a message independently. DNS
20551 servers run caches, so repeated DNS lookups are not normally expensive, and in
20552 any case, personal messages rarely have more than a few recipients.
20554 If you are running mailing lists with large numbers of subscribers at the same
20555 domain, and you are using a &(manualroute)& router which is independent of the
20556 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
20557 lookups for identical domains in one message. In this case, when
20558 &(manualroute)& routes an address to a remote transport, any other unrouted
20559 addresses in the message that have the same domain are automatically given the
20560 same routing without processing them independently. However, this is only done
20561 if &%headers_add%& and &%headers_remove%& are unset.
20566 .section "Routing rules in route_list" "SECID120"
20567 The value of &%route_list%& is a string consisting of a sequence of routing
20568 rules, separated by semicolons. If a semicolon is needed in a rule, it can be
20569 entered as two semicolons. Alternatively, the list separator can be changed as
20570 described (for colon-separated lists) in section &<<SECTlistconstruct>>&.
20571 Empty rules are ignored. The format of each rule is
20573 <&'domain pattern'&> <&'list of hosts'&> <&'options'&>
20575 The following example contains two rules, each with a simple domain pattern and
20579 dict.ref.example mail-1.ref.example:mail-2.ref.example ; \
20580 thes.ref.example mail-3.ref.example:mail-4.ref.example
20582 The three parts of a rule are separated by white space. The pattern and the
20583 list of hosts can be enclosed in quotes if necessary, and if they are, the
20584 usual quoting rules apply. Each rule in a &%route_list%& must start with a
20585 single domain pattern, which is the only mandatory item in the rule. The
20586 pattern is in the same format as one item in a domain list (see section
20587 &<<SECTdomainlist>>&),
20588 except that it may not be the name of an interpolated file.
20589 That is, it may be wildcarded, or a regular expression, or a file or database
20590 lookup (with semicolons doubled, because of the use of semicolon as a separator
20591 in a &%route_list%&).
20593 The rules in &%route_list%& are searched in order until one of the patterns
20594 matches the domain that is being routed. The list of hosts and then options are
20595 then used as described below. If there is no match, the router declines. When
20596 &%route_list%& is set, &%route_data%& must not be set.
20600 .section "Routing rules in route_data" "SECID121"
20601 The use of &%route_list%& is convenient when there are only a small number of
20602 routing rules. For larger numbers, it is easier to use a file or database to
20603 hold the routing information, and use the &%route_data%& option instead.
20604 The value of &%route_data%& is a list of hosts, followed by (optional) options.
20605 Most commonly, &%route_data%& is set as a string that contains an
20606 expansion lookup. For example, suppose we place two routing rules in a file
20609 dict.ref.example: mail-1.ref.example:mail-2.ref.example
20610 thes.ref.example: mail-3.ref.example:mail-4.ref.example
20612 This data can be accessed by setting
20614 route_data = ${lookup{$domain}lsearch{/the/file/name}}
20616 Failure of the lookup results in an empty string, causing the router to
20617 decline. However, you do not have to use a lookup in &%route_data%&. The only
20618 requirement is that the result of expanding the string is a list of hosts,
20619 possibly followed by options, separated by white space. The list of hosts must
20620 be enclosed in quotes if it contains white space.
20625 .section "Format of the list of hosts" "SECID122"
20626 A list of hosts, whether obtained via &%route_data%& or &%route_list%&, is
20627 always separately expanded before use. If the expansion fails, the router
20628 declines. The result of the expansion must be a colon-separated list of names
20629 and/or IP addresses, optionally also including ports.
20630 If the list is written with spaces, it must be protected with quotes.
20631 The format of each item
20632 in the list is described in the next section. The list separator can be changed
20633 as described in section &<<SECTlistsepchange>>&.
20635 If the list of hosts was obtained from a &%route_list%& item, the following
20636 variables are set during its expansion:
20639 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(manualroute)& router"
20640 If the domain was matched against a regular expression, the numeric variables
20641 &$1$&, &$2$&, etc. may be set. For example:
20643 route_list = ^domain(\d+) host-$1.text.example
20646 &$0$& is always set to the entire domain.
20648 &$1$& is also set when partial matching is done in a file lookup.
20651 .vindex "&$value$&"
20652 If the pattern that matched the domain was a lookup item, the data that was
20653 looked up is available in the expansion variable &$value$&. For example:
20655 route_list = lsearch;;/some/file.routes $value
20659 Note the doubling of the semicolon in the pattern that is necessary because
20660 semicolon is the default route list separator.
20664 .section "Format of one host item" "SECTformatonehostitem"
20665 Each item in the list of hosts can be either a host name or an IP address,
20666 optionally with an attached port number, or it can be a single "+"
20667 (see &%hosts_randomize%&).
20668 When no port is given, an IP address
20669 is not enclosed in brackets. When a port is specified, it overrides the port
20670 specification on the transport. The port is separated from the name or address
20671 by a colon. This leads to some complications:
20674 Because colon is the default separator for the list of hosts, either
20675 the colon that specifies a port must be doubled, or the list separator must
20676 be changed. The following two examples have the same effect:
20678 route_list = * "host1.tld::1225 : host2.tld::1226"
20679 route_list = * "<+ host1.tld:1225 + host2.tld:1226"
20682 When IPv6 addresses are involved, it gets worse, because they contain
20683 colons of their own. To make this case easier, it is permitted to
20684 enclose an IP address (either v4 or v6) in square brackets if a port
20685 number follows. For example:
20687 route_list = * "</ [10.1.1.1]:1225 / [::1]:1226"
20691 .section "How the list of hosts is used" "SECThostshowused"
20692 When an address is routed to an &(smtp)& transport by &(manualroute)&, each of
20693 the hosts is tried, in the order specified, when carrying out the SMTP
20694 delivery. However, the order can be changed by setting the &%hosts_randomize%&
20695 option, either on the router (see section &<<SECTprioptman>>& above), or on the
20698 Hosts may be listed by name or by IP address. An unadorned name in the list of
20699 hosts is interpreted as a host name. A name that is followed by &`/MX`& is
20700 interpreted as an indirection to a sublist of hosts obtained by looking up MX
20701 records in the DNS. For example:
20703 route_list = * x.y.z:p.q.r/MX:e.f.g
20705 If this feature is used with a port specifier, the port must come last. For
20708 route_list = * dom1.tld/mx::1225
20710 If the &%hosts_randomize%& option is set, the order of the items in the list is
20711 randomized before any lookups are done. Exim then scans the list; for any name
20712 that is not followed by &`/MX`& it looks up an IP address. If this turns out to
20713 be an interface on the local host and the item is not the first in the list,
20714 Exim discards it and any subsequent items. If it is the first item, what
20715 happens is controlled by the
20716 .oindex "&%self%&" "in &(manualroute)& router"
20717 &%self%& option of the router.
20719 A name on the list that is followed by &`/MX`& is replaced with the list of
20720 hosts obtained by looking up MX records for the name. This is always a DNS
20721 lookup; the &%bydns%& and &%byname%& options (see section &<<SECThowoptused>>&
20722 below) are not relevant here. The order of these hosts is determined by the
20723 preference values in the MX records, according to the usual rules. Because
20724 randomizing happens before the MX lookup, it does not affect the order that is
20725 defined by MX preferences.
20727 If the local host is present in the sublist obtained from MX records, but is
20728 not the most preferred host in that list, it and any equally or less
20729 preferred hosts are removed before the sublist is inserted into the main list.
20731 If the local host is the most preferred host in the MX list, what happens
20732 depends on where in the original list of hosts the &`/MX`& item appears. If it
20733 is not the first item (that is, there are previous hosts in the main list),
20734 Exim discards this name and any subsequent items in the main list.
20736 If the MX item is first in the list of hosts, and the local host is the
20737 most preferred host, what happens is controlled by the &%self%& option of the
20740 DNS failures when lookup up the MX records are treated in the same way as DNS
20741 failures when looking up IP addresses: &%pass_on_timeout%& and
20742 &%host_find_failed%& are used when relevant.
20744 The generic &%ignore_target_hosts%& option applies to all hosts in the list,
20745 whether obtained from an MX lookup or not.
20749 .section "How the options are used" "SECThowoptused"
20750 The options are a sequence of words, space-separated.
20751 One of the words can be the name of a transport; this overrides the
20752 &%transport%& option on the router for this particular routing rule only. The
20753 other words (if present) control randomization of the list of hosts on a
20754 per-rule basis, and how the IP addresses of the hosts are to be found when
20755 routing to a remote transport. These options are as follows:
20758 &%randomize%&: randomize the order of the hosts in this list, overriding the
20759 setting of &%hosts_randomize%& for this routing rule only.
20761 &%no_randomize%&: do not randomize the order of the hosts in this list,
20762 overriding the setting of &%hosts_randomize%& for this routing rule only.
20764 &%byname%&: use &[getipnodebyname()]& (&[gethostbyname()]& on older systems) to
20765 find IP addresses. This function may ultimately cause a DNS lookup, but it may
20766 also look in &_/etc/hosts_& or other sources of information.
20768 &%bydns%&: look up address records for the hosts directly in the DNS; fail if
20769 no address records are found. If there is a temporary DNS error (such as a
20770 timeout), delivery is deferred.
20772 &%ipv4_only%&: in direct DNS lookups, look up only A records.
20774 &%ipv4_prefer%&: in direct DNS lookups, sort A records before AAAA records.
20779 route_list = domain1 host1:host2:host3 randomize bydns;\
20780 domain2 host4:host5
20782 If neither &%byname%& nor &%bydns%& is given, Exim behaves as follows: First, a
20783 DNS lookup is done. If this yields anything other than HOST_NOT_FOUND, that
20784 result is used. Otherwise, Exim goes on to try a call to &[getipnodebyname()]&
20785 or &[gethostbyname()]&, and the result of the lookup is the result of that
20788 &*Warning*&: It has been discovered that on some systems, if a DNS lookup
20789 called via &[getipnodebyname()]& times out, HOST_NOT_FOUND is returned
20790 instead of TRY_AGAIN. That is why the default action is to try a DNS
20791 lookup first. Only if that gives a definite &"no such host"& is the local
20794 &*Compatibility*&: From Exim 4.85 until fixed for 4.90, there was an
20795 inadvertent constraint that a transport name as an option had to be the last
20800 If no IP address for a host can be found, what happens is controlled by the
20801 &%host_find_failed%& option.
20804 When an address is routed to a local transport, IP addresses are not looked up.
20805 The host list is passed to the transport in the &$host$& variable.
20809 .section "Manualroute examples" "SECID123"
20810 In some of the examples that follow, the presence of the &%remote_smtp%&
20811 transport, as defined in the default configuration file, is assumed:
20814 .cindex "smart host" "example router"
20815 The &(manualroute)& router can be used to forward all external mail to a
20816 &'smart host'&. If you have set up, in the main part of the configuration, a
20817 named domain list that contains your local domains, for example:
20819 domainlist local_domains = my.domain.example
20821 You can arrange for all other domains to be routed to a smart host by making
20822 your first router something like this:
20825 driver = manualroute
20826 domains = !+local_domains
20827 transport = remote_smtp
20828 route_list = * smarthost.ref.example
20830 This causes all non-local addresses to be sent to the single host
20831 &'smarthost.ref.example'&. If a colon-separated list of smart hosts is given,
20832 they are tried in order
20833 (but you can use &%hosts_randomize%& to vary the order each time).
20834 Another way of configuring the same thing is this:
20837 driver = manualroute
20838 transport = remote_smtp
20839 route_list = !+local_domains smarthost.ref.example
20841 There is no difference in behaviour between these two routers as they stand.
20842 However, they behave differently if &%no_more%& is added to them. In the first
20843 example, the router is skipped if the domain does not match the &%domains%&
20844 precondition; the following router is always tried. If the router runs, it
20845 always matches the domain and so can never decline. Therefore, &%no_more%&
20846 would have no effect. In the second case, the router is never skipped; it
20847 always runs. However, if it doesn't match the domain, it declines. In this case
20848 &%no_more%& would prevent subsequent routers from running.
20851 .cindex "mail hub example"
20852 A &'mail hub'& is a host which receives mail for a number of domains via MX
20853 records in the DNS and delivers it via its own private routing mechanism. Often
20854 the final destinations are behind a firewall, with the mail hub being the one
20855 machine that can connect to machines both inside and outside the firewall. The
20856 &(manualroute)& router is usually used on a mail hub to route incoming messages
20857 to the correct hosts. For a small number of domains, the routing can be inline,
20858 using the &%route_list%& option, but for a larger number a file or database
20859 lookup is easier to manage.
20861 If the domain names are in fact the names of the machines to which the mail is
20862 to be sent by the mail hub, the configuration can be quite simple. For
20866 driver = manualroute
20867 transport = remote_smtp
20868 route_list = *.rhodes.tvs.example $domain
20870 This configuration routes domains that match &`*.rhodes.tvs.example`& to hosts
20871 whose names are the same as the mail domains. A similar approach can be taken
20872 if the host name can be obtained from the domain name by a string manipulation
20873 that the expansion facilities can handle. Otherwise, a lookup based on the
20874 domain can be used to find the host:
20877 driver = manualroute
20878 transport = remote_smtp
20879 route_data = ${lookup {$domain} cdb {/internal/host/routes}}
20881 The result of the lookup must be the name or IP address of the host (or
20882 hosts) to which the address is to be routed. If the lookup fails, the route
20883 data is empty, causing the router to decline. The address then passes to the
20887 .cindex "batched SMTP output example"
20888 .cindex "SMTP" "batched outgoing; example"
20889 You can use &(manualroute)& to deliver messages to pipes or files in batched
20890 SMTP format for onward transportation by some other means. This is one way of
20891 storing mail for a dial-up host when it is not connected. The route list entry
20892 can be as simple as a single domain name in a configuration like this:
20895 driver = manualroute
20896 transport = batchsmtp_appendfile
20897 route_list = saved.domain.example
20899 though often a pattern is used to pick up more than one domain. If there are
20900 several domains or groups of domains with different transport requirements,
20901 different transports can be listed in the routing information:
20904 driver = manualroute
20906 *.saved.domain1.example $domain batch_appendfile; \
20907 *.saved.domain2.example \
20908 ${lookup{$domain}dbm{/domain2/hosts}{$value}fail} \
20911 .vindex "&$domain$&"
20913 The first of these just passes the domain in the &$host$& variable, which
20914 doesn't achieve much (since it is also in &$domain$&), but the second does a
20915 file lookup to find a value to pass, causing the router to decline to handle
20916 the address if the lookup fails.
20919 .cindex "UUCP" "example of router for"
20920 Routing mail directly to UUCP software is a specific case of the use of
20921 &(manualroute)& in a gateway to another mail environment. This is an example of
20922 one way it can be done:
20928 command = /usr/local/bin/uux -r - \
20929 ${substr_-5:$host}!rmail ${local_part}
20930 return_fail_output = true
20935 driver = manualroute
20937 ${lookup{$domain}lsearch{/usr/local/exim/uucphosts}}
20939 The file &_/usr/local/exim/uucphosts_& contains entries like
20941 darksite.ethereal.example: darksite.UUCP
20943 It can be set up more simply without adding and removing &".UUCP"& but this way
20944 makes clear the distinction between the domain name
20945 &'darksite.ethereal.example'& and the UUCP host name &'darksite'&.
20947 .ecindex IIDmanrou1
20948 .ecindex IIDmanrou2
20957 . ////////////////////////////////////////////////////////////////////////////
20958 . ////////////////////////////////////////////////////////////////////////////
20960 .chapter "The queryprogram router" "CHAPdriverlast"
20961 .scindex IIDquerou1 "&(queryprogram)& router"
20962 .scindex IIDquerou2 "routers" "&(queryprogram)&"
20963 .cindex "routing" "by external program"
20964 The &(queryprogram)& router routes an address by running an external command
20965 and acting on its output. This is an expensive way to route, and is intended
20966 mainly for use in lightly-loaded systems, or for performing experiments.
20967 However, if it is possible to use the precondition options (&%domains%&,
20968 &%local_parts%&, etc) to skip this router for most addresses, it could sensibly
20969 be used in special cases, even on a busy host. There are the following private
20971 .cindex "options" "&(queryprogram)& router"
20973 .option command queryprogram string&!! unset
20974 This option must be set. It specifies the command that is to be run. The
20975 command is split up into a command name and arguments, and then each is
20976 expanded separately (exactly as for a &(pipe)& transport, described in chapter
20977 &<<CHAPpipetransport>>&).
20980 .option command_group queryprogram string unset
20981 .cindex "gid (group id)" "in &(queryprogram)& router"
20982 This option specifies a gid to be set when running the command while routing an
20983 address for deliver. It must be set if &%command_user%& specifies a numerical
20984 uid. If it begins with a digit, it is interpreted as the numerical value of the
20985 gid. Otherwise it is looked up using &[getgrnam()]&.
20988 .option command_user queryprogram string unset
20989 .cindex "uid (user id)" "for &(queryprogram)&"
20990 This option must be set. It specifies the uid which is set when running the
20991 command while routing an address for delivery. If the value begins with a digit,
20992 it is interpreted as the numerical value of the uid. Otherwise, it is looked up
20993 using &[getpwnam()]& to obtain a value for the uid and, if &%command_group%& is
20994 not set, a value for the gid also.
20996 &*Warning:*& Changing uid and gid is possible only when Exim is running as
20997 root, which it does during a normal delivery in a conventional configuration.
20998 However, when an address is being verified during message reception, Exim is
20999 usually running as the Exim user, not as root. If the &(queryprogram)& router
21000 is called from a non-root process, Exim cannot change uid or gid before running
21001 the command. In this circumstance the command runs under the current uid and
21005 .option current_directory queryprogram string /
21006 This option specifies an absolute path which is made the current directory
21007 before running the command.
21010 .option timeout queryprogram time 1h
21011 If the command does not complete within the timeout period, its process group
21012 is killed and the message is frozen. A value of zero time specifies no
21016 The standard output of the command is connected to a pipe, which is read when
21017 the command terminates. It should consist of a single line of output,
21018 containing up to five fields, separated by white space. The maximum length of
21019 the line is 1023 characters. Longer lines are silently truncated. The first
21020 field is one of the following words (case-insensitive):
21023 &'Accept'&: routing succeeded; the remaining fields specify what to do (see
21026 &'Decline'&: the router declines; pass the address to the next router, unless
21027 &%no_more%& is set.
21029 &'Fail'&: routing failed; do not pass the address to any more routers. Any
21030 subsequent text on the line is an error message. If the router is run as part
21031 of address verification during an incoming SMTP message, the message is
21032 included in the SMTP response.
21034 &'Defer'&: routing could not be completed at this time; try again later. Any
21035 subsequent text on the line is an error message which is logged. It is not
21036 included in any SMTP response.
21038 &'Freeze'&: the same as &'defer'&, except that the message is frozen.
21040 &'Pass'&: pass the address to the next router (or the router specified by
21041 &%pass_router%&), overriding &%no_more%&.
21043 &'Redirect'&: the message is redirected. The remainder of the line is a list of
21044 new addresses, which are routed independently, starting with the first router,
21045 or the router specified by &%redirect_router%&, if set.
21048 When the first word is &'accept'&, the remainder of the line consists of a
21049 number of keyed data values, as follows (split into two lines here, to fit on
21052 ACCEPT TRANSPORT=<transport> HOSTS=<list of hosts>
21053 LOOKUP=byname|bydns DATA=<text>
21055 The data items can be given in any order, and all are optional. If no transport
21056 is included, the transport specified by the generic &%transport%& option is
21057 used. The list of hosts and the lookup type are needed only if the transport is
21058 an &(smtp)& transport that does not itself supply a list of hosts.
21060 The format of the list of hosts is the same as for the &(manualroute)& router.
21061 As well as host names and IP addresses with optional port numbers, as described
21062 in section &<<SECTformatonehostitem>>&, it may contain names followed by
21063 &`/MX`& to specify sublists of hosts that are obtained by looking up MX records
21064 (see section &<<SECThostshowused>>&).
21066 If the lookup type is not specified, Exim behaves as follows when trying to
21067 find an IP address for each host: First, a DNS lookup is done. If this yields
21068 anything other than HOST_NOT_FOUND, that result is used. Otherwise, Exim
21069 goes on to try a call to &[getipnodebyname()]& or &[gethostbyname()]&, and the
21070 result of the lookup is the result of that call.
21072 .vindex "&$address_data$&"
21073 If the DATA field is set, its value is placed in the &$address_data$&
21074 variable. For example, this return line
21076 accept hosts=x1.y.example:x2.y.example data="rule1"
21078 routes the address to the default transport, passing a list of two hosts. When
21079 the transport runs, the string &"rule1"& is in &$address_data$&.
21080 .ecindex IIDquerou1
21081 .ecindex IIDquerou2
21086 . ////////////////////////////////////////////////////////////////////////////
21087 . ////////////////////////////////////////////////////////////////////////////
21089 .chapter "The redirect router" "CHAPredirect"
21090 .scindex IIDredrou1 "&(redirect)& router"
21091 .scindex IIDredrou2 "routers" "&(redirect)&"
21092 .cindex "alias file" "in a &(redirect)& router"
21093 .cindex "address redirection" "&(redirect)& router"
21094 The &(redirect)& router handles several kinds of address redirection. Its most
21095 common uses are for resolving local part aliases from a central alias file
21096 (usually called &_/etc/aliases_&) and for handling users' personal &_.forward_&
21097 files, but it has many other potential uses. The incoming address can be
21098 redirected in several different ways:
21101 It can be replaced by one or more new addresses which are themselves routed
21104 It can be routed to be delivered to a given file or directory.
21106 It can be routed to be delivered to a specified pipe command.
21108 It can cause an automatic reply to be generated.
21110 It can be forced to fail, optionally with a custom error message.
21112 It can be temporarily deferred, optionally with a custom message.
21114 It can be discarded.
21117 The generic &%transport%& option must not be set for &(redirect)& routers.
21118 However, there are some private options which define transports for delivery to
21119 files and pipes, and for generating autoreplies. See the &%file_transport%&,
21120 &%pipe_transport%& and &%reply_transport%& descriptions below.
21122 If success DSNs have been requested
21123 .cindex "DSN" "success"
21124 .cindex "Delivery Status Notification" "success"
21125 redirection triggers one and the DSN options are not passed any further.
21129 .section "Redirection data" "SECID124"
21130 The router operates by interpreting a text string which it obtains either by
21131 expanding the contents of the &%data%& option, or by reading the entire
21132 contents of a file whose name is given in the &%file%& option. These two
21133 options are mutually exclusive. The first is commonly used for handling system
21134 aliases, in a configuration like this:
21138 data = ${lookup{$local_part}lsearch{/etc/aliases}}
21140 If the lookup fails, the expanded string in this example is empty. When the
21141 expansion of &%data%& results in an empty string, the router declines. A forced
21142 expansion failure also causes the router to decline; other expansion failures
21143 cause delivery to be deferred.
21145 A configuration using &%file%& is commonly used for handling users'
21146 &_.forward_& files, like this:
21151 file = $home/.forward
21154 If the file does not exist, or causes no action to be taken (for example, it is
21155 empty or consists only of comments), the router declines. &*Warning*&: This
21156 is not the case when the file contains syntactically valid items that happen to
21157 yield empty addresses, for example, items containing only RFC 2822 address
21160 .cindex "tainted data" "in filenames"
21161 .cindex redirect "tainted data"
21162 Tainted data may not be used for a filename.
21164 &*Warning*&: It is unwise to use &$local_part$& or &$domain$&
21165 directly for redirection,
21166 as they are provided by a potential attacker.
21167 In the examples above, &$local_part$& is used for looking up data held locally
21168 on the system, and not used directly (the second example derives &$home$& via
21169 the passsword file or database, using &$local_part$&).
21173 .section "Forward files and address verification" "SECID125"
21174 .cindex "address redirection" "while verifying"
21175 It is usual to set &%no_verify%& on &(redirect)& routers which handle users'
21176 &_.forward_& files, as in the example above. There are two reasons for this:
21179 When Exim is receiving an incoming SMTP message from a remote host, it is
21180 running under the Exim uid, not as root. Exim is unable to change uid to read
21181 the file as the user, and it may not be able to read it as the Exim user. So in
21182 practice the router may not be able to operate.
21184 However, even when the router can operate, the existence of a &_.forward_& file
21185 is unimportant when verifying an address. What should be checked is whether the
21186 local part is a valid user name or not. Cutting out the redirection processing
21187 saves some resources.
21195 .section "Interpreting redirection data" "SECID126"
21196 .cindex "Sieve filter" "specifying in redirection data"
21197 .cindex "filter" "specifying in redirection data"
21198 The contents of the data string, whether obtained from &%data%& or &%file%&,
21199 can be interpreted in two different ways:
21202 If the &%allow_filter%& option is set true, and the data begins with the text
21203 &"#Exim filter"& or &"#Sieve filter"&, it is interpreted as a list of
21204 &'filtering'& instructions in the form of an Exim or Sieve filter file,
21205 respectively. Details of the syntax and semantics of filter files are described
21206 in a separate document entitled &'Exim's interfaces to mail filtering'&; this
21207 document is intended for use by end users.
21209 Otherwise, the data must be a comma-separated list of redirection items, as
21210 described in the next section.
21213 When a message is redirected to a file (a &"mail folder"&), the filename given
21214 in a non-filter redirection list must always be an absolute path. A filter may
21215 generate a relative path &-- how this is handled depends on the transport's
21216 configuration. See section &<<SECTfildiropt>>& for a discussion of this issue
21217 for the &(appendfile)& transport.
21221 .section "Items in a non-filter redirection list" "SECTitenonfilred"
21222 .cindex "address redirection" "non-filter list items"
21223 When the redirection data is not an Exim or Sieve filter, for example, if it
21224 comes from a conventional alias or forward file, it consists of a list of
21225 addresses, filenames, pipe commands, or certain special items (see section
21226 &<<SECTspecitredli>>& below). The special items can be individually enabled or
21227 disabled by means of options whose names begin with &%allow_%& or &%forbid_%&,
21228 depending on their default values. The items in the list are separated by
21229 commas or newlines.
21230 If a comma is required in an item, the entire item must be enclosed in double
21233 Lines starting with a # character are comments, and are ignored, and # may
21234 also appear following a comma, in which case everything between the # and the
21235 next newline character is ignored.
21237 If an item is entirely enclosed in double quotes, these are removed. Otherwise
21238 double quotes are retained because some forms of mail address require their use
21239 (but never to enclose the entire address). In the following description,
21240 &"item"& refers to what remains after any surrounding double quotes have been
21243 .vindex "&$local_part$&"
21244 &*Warning*&: If you use an Exim expansion to construct a redirection address,
21245 and the expansion contains a reference to &$local_part$&, you should make use
21246 of the &%quote_local_part%& expansion operator, in case the local part contains
21247 special characters. For example, to redirect all mail for the domain
21248 &'obsolete.example'&, retaining the existing local part, you could use this
21251 data = ${quote_local_part:$local_part}@newdomain.example
21255 .section "Redirecting to a local mailbox" "SECTredlocmai"
21256 .cindex "routing" "loops in"
21257 .cindex "loop" "while routing, avoidance of"
21258 .cindex "address redirection" "to local mailbox"
21259 A redirection item may safely be the same as the address currently under
21260 consideration. This does not cause a routing loop, because a router is
21261 automatically skipped if any ancestor of the address that is being processed
21262 is the same as the current address and was processed by the current router.
21263 Such an address is therefore passed to the following routers, so it is handled
21264 as if there were no redirection. When making this loop-avoidance test, the
21265 complete local part, including any prefix or suffix, is used.
21267 .cindex "address redirection" "local part without domain"
21268 Specifying the same local part without a domain is a common usage in personal
21269 filter files when the user wants to have messages delivered to the local
21270 mailbox and also forwarded elsewhere. For example, the user whose login is
21271 &'cleo'& might have a &_.forward_& file containing this:
21273 cleo, cleopatra@egypt.example
21275 .cindex "backslash in alias file"
21276 .cindex "alias file" "backslash in"
21277 For compatibility with other MTAs, such unqualified local parts may be
21278 preceded by &"\"&, but this is not a requirement for loop prevention. However,
21279 it does make a difference if more than one domain is being handled
21282 If an item begins with &"\"& and the rest of the item parses as a valid RFC
21283 2822 address that does not include a domain, the item is qualified using the
21284 domain of the incoming address. In the absence of a leading &"\"&, unqualified
21285 addresses are qualified using the value in &%qualify_recipient%&, but you can
21286 force the incoming domain to be used by setting &%qualify_preserve_domain%&.
21288 Care must be taken if there are alias names for local users.
21289 Consider an MTA handling a single local domain where the system alias file
21294 Now suppose that Sam (whose login id is &'spqr'&) wants to save copies of
21295 messages in the local mailbox, and also forward copies elsewhere. He creates
21298 Sam.Reman, spqr@reme.elsewhere.example
21300 With these settings, an incoming message addressed to &'Sam.Reman'& fails. The
21301 &(redirect)& router for system aliases does not process &'Sam.Reman'& the
21302 second time round, because it has previously routed it,
21303 and the following routers presumably cannot handle the alias. The forward file
21304 should really contain
21306 spqr, spqr@reme.elsewhere.example
21308 but because this is such a common error, the &%check_ancestor%& option (see
21309 below) exists to provide a way to get round it. This is normally set on a
21310 &(redirect)& router that is handling users' &_.forward_& files.
21314 .section "Special items in redirection lists" "SECTspecitredli"
21315 In addition to addresses, the following types of item may appear in redirection
21316 lists (that is, in non-filter redirection data):
21319 .cindex "pipe" "in redirection list"
21320 .cindex "address redirection" "to pipe"
21321 An item is treated as a pipe command if it begins with &"|"& and does not parse
21322 as a valid RFC 2822 address that includes a domain. A transport for running the
21323 command must be specified by the &%pipe_transport%& option.
21324 Normally, either the router or the transport specifies a user and a group under
21325 which to run the delivery. The default is to use the Exim user and group.
21327 Single or double quotes can be used for enclosing the individual arguments of
21328 the pipe command; no interpretation of escapes is done for single quotes. If
21329 the command contains a comma character, it is necessary to put the whole item
21330 in double quotes, for example:
21332 "|/some/command ready,steady,go"
21334 since items in redirection lists are terminated by commas. Do not, however,
21335 quote just the command. An item such as
21337 |"/some/command ready,steady,go"
21339 is interpreted as a pipe with a rather strange command name, and no arguments.
21341 Note that the above example assumes that the text comes from a lookup source
21342 of some sort, so that the quotes are part of the data. If composing a
21343 redirect router with a &%data%& option directly specifying this command, the
21344 quotes will be used by the configuration parser to define the extent of one
21345 string, but will not be passed down into the redirect router itself. There
21346 are two main approaches to get around this: escape quotes to be part of the
21347 data itself, or avoid using this mechanism and instead create a custom
21348 transport with the &%command%& option set and reference that transport from
21349 an &%accept%& router.
21352 .cindex "file" "in redirection list"
21353 .cindex "address redirection" "to file"
21354 An item is interpreted as a path name if it begins with &"/"& and does not
21355 parse as a valid RFC 2822 address that includes a domain. For example,
21357 /home/world/minbari
21359 is treated as a filename, but
21361 /s=molari/o=babylon/@x400gate.way
21363 is treated as an address. For a filename, a transport must be specified using
21364 the &%file_transport%& option. However, if the generated path name ends with a
21365 forward slash character, it is interpreted as a directory name rather than a
21366 filename, and &%directory_transport%& is used instead.
21368 Normally, either the router or the transport specifies a user and a group under
21369 which to run the delivery. The default is to use the Exim user and group.
21371 .cindex "&_/dev/null_&"
21372 However, if a redirection item is the path &_/dev/null_&, delivery to it is
21373 bypassed at a high level, and the log entry shows &"**bypassed**"&
21374 instead of a transport name. In this case the user and group are not used.
21377 .cindex "included address list"
21378 .cindex "address redirection" "included external list"
21379 If an item is of the form
21381 :include:<path name>
21383 a list of further items is taken from the given file and included at that
21384 point. &*Note*&: Such a file can not be a filter file; it is just an
21385 out-of-line addition to the list. The items in the included list are separated
21386 by commas or newlines and are not subject to expansion. If this is the first
21387 item in an alias list in an &(lsearch)& file, a colon must be used to terminate
21388 the alias name. This example is incorrect:
21390 list1 :include:/opt/lists/list1
21392 It must be given as
21394 list1: :include:/opt/lists/list1
21396 .cindex "tainted data" "in filenames"
21397 .cindex redirect "tainted data"
21398 Tainted data may not be used for a filename.
21400 .cindex "address redirection" "to black hole"
21401 .cindex "delivery" "discard"
21402 .cindex "delivery" "blackhole"
21403 .cindex "black hole"
21404 .cindex "abandoning mail"
21405 Sometimes you want to throw away mail to a particular local part. Making the
21406 &%data%& option expand to an empty string does not work, because that causes
21407 the router to decline. Instead, the alias item
21411 can be used. It does what its name implies. No delivery is
21412 done, and no error message is generated. This has the same effect as specifying
21413 &_/dev/null_& as a destination, but it can be independently disabled.
21415 &*Warning*&: If &':blackhole:'& appears anywhere in a redirection list, no
21416 delivery is done for the original local part, even if other redirection items
21417 are present. If you are generating a multi-item list (for example, by reading a
21418 database) and need the ability to provide a no-op item, you must use
21422 .cindex "delivery" "forcing failure"
21423 .cindex "delivery" "forcing deferral"
21424 .cindex "failing delivery" "forcing"
21425 .cindex "deferred delivery, forcing"
21426 .cindex "customizing" "failure message"
21427 An attempt to deliver a particular address can be deferred or forced to fail by
21428 redirection items of the form
21433 respectively. When a redirection list contains such an item, it applies
21434 to the entire redirection; any other items in the list are ignored. Any
21435 text following &':fail:'& or &':defer:'& is placed in the error text
21436 associated with the failure. For example, an alias file might contain:
21438 X.Employee: :fail: Gone away, no forwarding address
21440 In the case of an address that is being verified from an ACL or as the subject
21442 .cindex "VRFY" "error text, display of"
21443 VRFY command, the text is included in the SMTP error response by
21445 .cindex "EXPN" "error text, display of"
21446 The text is not included in the response to an EXPN command. In non-SMTP cases
21447 the text is included in the error message that Exim generates.
21449 .cindex "SMTP" "error codes"
21450 By default for verify, Exim sends a 451 SMTP code for a &':defer:'&, and 550 for
21451 &':fail:'&. However, if the message starts with three digits followed by a
21452 space, optionally followed by an extended code of the form &'n.n.n'&, also
21453 followed by a space, and the very first digit is the same as the default error
21454 code, the code from the message is used instead. If the very first digit is
21455 incorrect, a panic error is logged, and the default code is used. You can
21456 suppress the use of the supplied code in a redirect router by setting the
21457 &%forbid_smtp_code%& option true. In this case, any SMTP code is quietly
21460 .vindex "&$acl_verify_message$&"
21461 In an ACL, an explicitly provided message overrides the default, but the
21462 default message is available in the variable &$acl_verify_message$& and can
21463 therefore be included in a custom message if this is desired.
21465 Normally the error text is the rest of the redirection list &-- a comma does
21466 not terminate it &-- but a newline does act as a terminator. Newlines are not
21467 normally present in alias expansions. In &(lsearch)& lookups they are removed
21468 as part of the continuation process, but they may exist in other kinds of
21469 lookup and in &':include:'& files.
21471 During routing for message delivery (as opposed to verification), a redirection
21472 containing &':fail:'& causes an immediate failure of the incoming address,
21473 whereas &':defer:'& causes the message to remain in the queue so that a
21474 subsequent delivery attempt can happen at a later time. If an address is
21475 deferred for too long, it will ultimately fail, because the normal retry
21479 .cindex "alias file" "exception to default"
21480 Sometimes it is useful to use a single-key search type with a default (see
21481 chapter &<<CHAPfdlookup>>&) to look up aliases. However, there may be a need
21482 for exceptions to the default. These can be handled by aliasing them to
21483 &':unknown:'&. This differs from &':fail:'& in that it causes the &(redirect)&
21484 router to decline, whereas &':fail:'& forces routing to fail. A lookup which
21485 results in an empty redirection list has the same effect.
21489 .section "Duplicate addresses" "SECTdupaddr"
21490 .cindex "duplicate addresses"
21491 .cindex "address duplicate, discarding"
21492 .cindex "pipe" "duplicated"
21493 Exim removes duplicate addresses from the list to which it is delivering, so as
21494 to deliver just one copy to each address. This does not apply to deliveries
21495 routed to pipes by different immediate parent addresses, but an indirect
21496 aliasing scheme of the type
21498 pipe: |/some/command $local_part
21502 does not work with a message that is addressed to both local parts, because
21503 when the second is aliased to the intermediate local part &"pipe"& it gets
21504 discarded as being the same as a previously handled address. However, a scheme
21507 localpart1: |/some/command $local_part
21508 localpart2: |/some/command $local_part
21510 does result in two different pipe deliveries, because the immediate parents of
21511 the pipes are distinct.
21515 .section "Repeated redirection expansion" "SECID128"
21516 .cindex "repeated redirection expansion"
21517 .cindex "address redirection" "repeated for each delivery attempt"
21518 When a message cannot be delivered to all of its recipients immediately,
21519 leading to two or more delivery attempts, redirection expansion is carried out
21520 afresh each time for those addresses whose children were not all previously
21521 delivered. If redirection is being used as a mailing list, this can lead to new
21522 members of the list receiving copies of old messages. The &%one_time%& option
21523 can be used to avoid this.
21526 .section "Errors in redirection lists" "SECID129"
21527 .cindex "address redirection" "errors"
21528 If &%skip_syntax_errors%& is set, a malformed address that causes a parsing
21529 error is skipped, and an entry is written to the main log. This may be useful
21530 for mailing lists that are automatically managed. Otherwise, if an error is
21531 detected while generating the list of new addresses, the original address is
21532 deferred. See also &%syntax_errors_to%&.
21536 .section "Private options for the redirect router" "SECID130"
21538 .cindex "options" "&(redirect)& router"
21539 The private options for the &(redirect)& router are as follows:
21542 .option allow_defer redirect boolean false
21543 Setting this option allows the use of &':defer:'& in non-filter redirection
21544 data, or the &%defer%& command in an Exim filter file.
21547 .option allow_fail redirect boolean false
21548 .cindex "failing delivery" "from filter"
21549 If this option is true, the &':fail:'& item can be used in a redirection list,
21550 and the &%fail%& command may be used in an Exim filter file.
21553 .option allow_filter redirect boolean false
21554 .cindex "filter" "enabling use of"
21555 .cindex "Sieve filter" "enabling use of"
21556 Setting this option allows Exim to interpret redirection data that starts with
21557 &"#Exim filter"& or &"#Sieve filter"& as a set of filtering instructions. There
21558 are some features of Exim filter files that some administrators may wish to
21559 lock out; see the &%forbid_filter_%&&'xxx'& options below.
21561 It is also possible to lock out Exim filters or Sieve filters while allowing
21562 the other type; see &%forbid_exim_filter%& and &%forbid_sieve_filter%&.
21565 The filter is run using the uid and gid set by the generic &%user%& and
21566 &%group%& options. These take their defaults from the password data if
21567 &%check_local_user%& is set, so in the normal case of users' personal filter
21568 files, the filter is run as the relevant user. When &%allow_filter%& is set
21569 true, Exim insists that either &%check_local_user%& or &%user%& is set.
21573 .option allow_freeze redirect boolean false
21574 .cindex "freezing messages" "allowing in filter"
21575 Setting this option allows the use of the &%freeze%& command in an Exim filter.
21576 This command is more normally encountered in system filters, and is disabled by
21577 default for redirection filters because it isn't something you usually want to
21578 let ordinary users do.
21582 .option check_ancestor redirect boolean false
21583 This option is concerned with handling generated addresses that are the same
21584 as some address in the list of redirection ancestors of the current address.
21585 Although it is turned off by default in the code, it is set in the default
21586 configuration file for handling users' &_.forward_& files. It is recommended
21587 for this use of the &(redirect)& router.
21589 When &%check_ancestor%& is set, if a generated address (including the domain)
21590 is the same as any ancestor of the current address, it is replaced by a copy of
21591 the current address. This helps in the case where local part A is aliased to B,
21592 and B has a &_.forward_& file pointing back to A. For example, within a single
21593 domain, the local part &"Joe.Bloggs"& is aliased to &"jb"& and
21594 &_&~jb/.forward_& contains:
21596 \Joe.Bloggs, <other item(s)>
21598 Without the &%check_ancestor%& setting, either local part (&"jb"& or
21599 &"joe.bloggs"&) gets processed once by each router and so ends up as it was
21600 originally. If &"jb"& is the real mailbox name, mail to &"jb"& gets delivered
21601 (having been turned into &"joe.bloggs"& by the &_.forward_& file and back to
21602 &"jb"& by the alias), but mail to &"joe.bloggs"& fails. Setting
21603 &%check_ancestor%& on the &(redirect)& router that handles the &_.forward_&
21604 file prevents it from turning &"jb"& back into &"joe.bloggs"& when that was the
21605 original address. See also the &%repeat_use%& option below.
21608 .option check_group redirect boolean "see below"
21609 When the &%file%& option is used, the group owner of the file is checked only
21610 when this option is set. The permitted groups are those listed in the
21611 &%owngroups%& option, together with the user's default group if
21612 &%check_local_user%& is set. If the file has the wrong group, routing is
21613 deferred. The default setting for this option is true if &%check_local_user%&
21614 is set and the &%modemask%& option permits the group write bit, or if the
21615 &%owngroups%& option is set. Otherwise it is false, and no group check occurs.
21619 .option check_owner redirect boolean "see below"
21620 When the &%file%& option is used, the owner of the file is checked only when
21621 this option is set. If &%check_local_user%& is set, the local user is
21622 permitted; otherwise the owner must be one of those listed in the &%owners%&
21623 option. The default value for this option is true if &%check_local_user%& or
21624 &%owners%& is set. Otherwise the default is false, and no owner check occurs.
21627 .option data redirect string&!! unset
21628 This option is mutually exclusive with &%file%&. One or other of them must be
21629 set, but not both. The contents of &%data%& are expanded, and then used as the
21630 list of forwarding items, or as a set of filtering instructions. If the
21631 expansion is forced to fail, or the result is an empty string or a string that
21632 has no effect (consists entirely of comments), the router declines.
21634 When filtering instructions are used, the string must begin with &"#Exim
21635 filter"&, and all comments in the string, including this initial one, must be
21636 terminated with newline characters. For example:
21638 data = #Exim filter\n\
21639 if $h_to: contains Exim then save $home/mail/exim endif
21641 If you are reading the data from a database where newlines cannot be included,
21642 you can use the &${sg}$& expansion item to turn the escape string of your
21643 choice into a newline.
21646 .option directory_transport redirect string&!! unset
21647 A &(redirect)& router sets up a direct delivery to a directory when a path name
21648 ending with a slash is specified as a new &"address"&. The transport used is
21649 specified by this option, which, after expansion, must be the name of a
21650 configured transport. This should normally be an &(appendfile)& transport.
21653 .option file redirect string&!! unset
21654 This option specifies the name of a file that contains the redirection data. It
21655 is mutually exclusive with the &%data%& option. The string is expanded before
21656 use; if the expansion is forced to fail, the router declines. Other expansion
21657 failures cause delivery to be deferred. The result of a successful expansion
21658 must be an absolute path. The entire file is read and used as the redirection
21659 data. If the data is an empty string or a string that has no effect (consists
21660 entirely of comments), the router declines.
21662 .cindex "NFS" "checking for file existence"
21663 If the attempt to open the file fails with a &"does not exist"& error, Exim
21664 runs a check on the containing directory,
21665 unless &%ignore_enotdir%& is true (see below).
21666 If the directory does not appear to exist, delivery is deferred. This can
21667 happen when users' &_.forward_& files are in NFS-mounted directories, and there
21668 is a mount problem. If the containing directory does exist, but the file does
21669 not, the router declines.
21672 .option file_transport redirect string&!! unset
21673 .vindex "&$address_file$&"
21674 A &(redirect)& router sets up a direct delivery to a file when a path name not
21675 ending in a slash is specified as a new &"address"&. The transport used is
21676 specified by this option, which, after expansion, must be the name of a
21677 configured transport. This should normally be an &(appendfile)& transport. When
21678 it is running, the filename is in &$address_file$&.
21681 .option filter_prepend_home redirect boolean true
21682 When this option is true, if a &(save)& command in an Exim filter specifies a
21683 relative path, and &$home$& is defined, it is automatically prepended to the
21684 relative path. If this option is set false, this action does not happen. The
21685 relative path is then passed to the transport unmodified.
21688 .option forbid_blackhole redirect boolean false
21689 .cindex "restricting access to features"
21690 .cindex "filter" "locking out certain features"
21691 If this option is true, the &':blackhole:'& item may not appear in a
21695 .option forbid_exim_filter redirect boolean false
21696 .cindex "restricting access to features"
21697 .cindex "filter" "locking out certain features"
21698 If this option is set true, only Sieve filters are permitted when
21699 &%allow_filter%& is true.
21704 .option forbid_file redirect boolean false
21705 .cindex "restricting access to features"
21706 .cindex "delivery" "to file; forbidding"
21707 .cindex "filter" "locking out certain features"
21708 .cindex "Sieve filter" "forbidding delivery to a file"
21709 .cindex "Sieve filter" "&""keep""& facility; disabling"
21710 If this option is true, this router may not generate a new address that
21711 specifies delivery to a local file or directory, either from a filter or from a
21712 conventional forward file. This option is forced to be true if &%one_time%& is
21713 set. It applies to Sieve filters as well as to Exim filters, but if true, it
21714 locks out the Sieve's &"keep"& facility.
21717 .option forbid_filter_dlfunc redirect boolean false
21718 .cindex "restricting access to features"
21719 .cindex "filter" "locking out certain features"
21720 If this option is true, string expansions in Exim filters are not allowed to
21721 make use of the &%dlfunc%& expansion facility to run dynamically loaded
21724 .option forbid_filter_existstest redirect boolean false
21725 .cindex "restricting access to features"
21726 .cindex "filter" "locking out certain features"
21727 .cindex "expansion" "statting a file"
21728 If this option is true, string expansions in Exim filters are not allowed to
21729 make use of the &%exists%& condition or the &%stat%& expansion item.
21731 .option forbid_filter_logwrite redirect boolean false
21732 .cindex "restricting access to features"
21733 .cindex "filter" "locking out certain features"
21734 If this option is true, use of the logging facility in Exim filters is not
21735 permitted. Logging is in any case available only if the filter is being run
21736 under some unprivileged uid (which is normally the case for ordinary users'
21737 &_.forward_& files).
21740 .option forbid_filter_lookup redirect boolean false
21741 .cindex "restricting access to features"
21742 .cindex "filter" "locking out certain features"
21743 If this option is true, string expansions in Exim filter files are not allowed
21744 to make use of &%lookup%& items.
21747 .option forbid_filter_perl redirect boolean false
21748 .cindex "restricting access to features"
21749 .cindex "filter" "locking out certain features"
21750 This option has an effect only if Exim is built with embedded Perl support. If
21751 it is true, string expansions in Exim filter files are not allowed to make use
21752 of the embedded Perl support.
21755 .option forbid_filter_readfile redirect boolean false
21756 .cindex "restricting access to features"
21757 .cindex "filter" "locking out certain features"
21758 If this option is true, string expansions in Exim filter files are not allowed
21759 to make use of &%readfile%& items.
21762 .option forbid_filter_readsocket redirect boolean false
21763 .cindex "restricting access to features"
21764 .cindex "filter" "locking out certain features"
21765 If this option is true, string expansions in Exim filter files are not allowed
21766 to make use of &%readsocket%& items.
21769 .option forbid_filter_reply redirect boolean false
21770 .cindex "restricting access to features"
21771 .cindex "filter" "locking out certain features"
21772 If this option is true, this router may not generate an automatic reply
21773 message. Automatic replies can be generated only from Exim or Sieve filter
21774 files, not from traditional forward files. This option is forced to be true if
21775 &%one_time%& is set.
21778 .option forbid_filter_run redirect boolean false
21779 .cindex "restricting access to features"
21780 .cindex "filter" "locking out certain features"
21781 If this option is true, string expansions in Exim filter files are not allowed
21782 to make use of &%run%& items.
21785 .option forbid_include redirect boolean false
21786 .cindex "restricting access to features"
21787 .cindex "filter" "locking out certain features"
21788 If this option is true, items of the form
21790 :include:<path name>
21792 are not permitted in non-filter redirection lists.
21795 .option forbid_pipe redirect boolean false
21796 .cindex "restricting access to features"
21797 .cindex "filter" "locking out certain features"
21798 .cindex "delivery" "to pipe; forbidding"
21799 If this option is true, this router may not generate a new address which
21800 specifies delivery to a pipe, either from an Exim filter or from a conventional
21801 forward file. This option is forced to be true if &%one_time%& is set.
21804 .option forbid_sieve_filter redirect boolean false
21805 .cindex "restricting access to features"
21806 .cindex "filter" "locking out certain features"
21807 If this option is set true, only Exim filters are permitted when
21808 &%allow_filter%& is true.
21811 .cindex "SMTP" "error codes"
21812 .option forbid_smtp_code redirect boolean false
21813 If this option is set true, any SMTP error codes that are present at the start
21814 of messages specified for &`:defer:`& or &`:fail:`& are quietly ignored, and
21815 the default codes (451 and 550, respectively) are always used.
21820 .option hide_child_in_errmsg redirect boolean false
21821 .cindex "bounce message" "redirection details; suppressing"
21822 If this option is true, it prevents Exim from quoting a child address if it
21823 generates a bounce or delay message for it. Instead it says &"an address
21824 generated from <&'the top level address'&>"&. Of course, this applies only to
21825 bounces generated locally. If a message is forwarded to another host, &'its'&
21826 bounce may well quote the generated address.
21829 .option ignore_eacces redirect boolean false
21831 If this option is set and an attempt to open a redirection file yields the
21832 EACCES error (permission denied), the &(redirect)& router behaves as if the
21833 file did not exist.
21836 .option ignore_enotdir redirect boolean false
21838 If this option is set and an attempt to open a redirection file yields the
21839 ENOTDIR error (something on the path is not a directory), the &(redirect)&
21840 router behaves as if the file did not exist.
21842 Setting &%ignore_enotdir%& has another effect as well: When a &(redirect)&
21843 router that has the &%file%& option set discovers that the file does not exist
21844 (the ENOENT error), it tries to &[stat()]& the parent directory, as a check
21845 against unmounted NFS directories. If the parent can not be statted, delivery
21846 is deferred. However, it seems wrong to do this check when &%ignore_enotdir%&
21847 is set, because that option tells Exim to ignore &"something on the path is not
21848 a directory"& (the ENOTDIR error). This is a confusing area, because it seems
21849 that some operating systems give ENOENT where others give ENOTDIR.
21853 .option include_directory redirect string unset
21854 If this option is set, the path names of any &':include:'& items in a
21855 redirection list must start with this directory.
21858 .option modemask redirect "octal integer" 022
21859 This specifies mode bits which must not be set for a file specified by the
21860 &%file%& option. If any of the forbidden bits are set, delivery is deferred.
21863 .option one_time redirect boolean false
21864 .cindex "one-time aliasing/forwarding expansion"
21865 .cindex "alias file" "one-time expansion"
21866 .cindex "forward file" "one-time expansion"
21867 .cindex "mailing lists" "one-time expansion"
21868 .cindex "address redirection" "one-time expansion"
21869 Sometimes the fact that Exim re-evaluates aliases and reprocesses redirection
21870 files each time it tries to deliver a message causes a problem when one or more
21871 of the generated addresses fails be delivered at the first attempt. The problem
21872 is not one of duplicate delivery &-- Exim is clever enough to handle that &--
21873 but of what happens when the redirection list changes during the time that the
21874 message is on Exim's queue. This is particularly true in the case of mailing
21875 lists, where new subscribers might receive copies of messages that were posted
21876 before they subscribed.
21878 If &%one_time%& is set and any addresses generated by the router fail to
21879 deliver at the first attempt, the failing addresses are added to the message as
21880 &"top level"& addresses, and the parent address that generated them is marked
21881 &"delivered"&. Thus, redirection does not happen again at the next delivery
21884 &*Warning 1*&: Any header line addition or removal that is specified by this
21885 router would be lost if delivery did not succeed at the first attempt. For this
21886 reason, the &%headers_add%& and &%headers_remove%& generic options are not
21887 permitted when &%one_time%& is set.
21889 &*Warning 2*&: To ensure that the router generates only addresses (as opposed
21890 to pipe or file deliveries or auto-replies) &%forbid_file%&, &%forbid_pipe%&,
21891 and &%forbid_filter_reply%& are forced to be true when &%one_time%& is set.
21893 &*Warning 3*&: The &%unseen%& generic router option may not be set with
21896 The original top-level address is remembered with each of the generated
21897 addresses, and is output in any log messages. However, any intermediate parent
21898 addresses are not recorded. This makes a difference to the log only if
21899 &%all_parents%& log selector is set. It is expected that &%one_time%& will
21900 typically be used for mailing lists, where there is normally just one level of
21904 .option owners redirect "string list" unset
21905 .cindex "ownership" "alias file"
21906 .cindex "ownership" "forward file"
21907 .cindex "alias file" "ownership"
21908 .cindex "forward file" "ownership"
21909 This specifies a list of permitted owners for the file specified by &%file%&.
21910 This list is in addition to the local user when &%check_local_user%& is set.
21911 See &%check_owner%& above.
21914 .option owngroups redirect "string list" unset
21915 This specifies a list of permitted groups for the file specified by &%file%&.
21916 The list is in addition to the local user's primary group when
21917 &%check_local_user%& is set. See &%check_group%& above.
21920 .option pipe_transport redirect string&!! unset
21921 .vindex "&$address_pipe$&"
21922 A &(redirect)& router sets up a direct delivery to a pipe when a string
21923 starting with a vertical bar character is specified as a new &"address"&. The
21924 transport used is specified by this option, which, after expansion, must be the
21925 name of a configured transport. This should normally be a &(pipe)& transport.
21926 When the transport is run, the pipe command is in &$address_pipe$&.
21929 .option qualify_domain redirect string&!! unset
21930 .vindex "&$qualify_recipient$&"
21931 If this option is set, and an unqualified address (one without a domain) is
21932 generated, and that address would normally be qualified by the global setting
21933 in &%qualify_recipient%&, it is instead qualified with the domain specified by
21934 expanding this string. If the expansion fails, the router declines. If you want
21935 to revert to the default, you can have the expansion generate
21936 &$qualify_recipient$&.
21938 This option applies to all unqualified addresses generated by Exim filters,
21939 but for traditional &_.forward_& files, it applies only to addresses that are
21940 not preceded by a backslash. Sieve filters cannot generate unqualified
21943 .option qualify_preserve_domain redirect boolean false
21944 .cindex "domain" "in redirection; preserving"
21945 .cindex "preserving domain in redirection"
21946 .cindex "address redirection" "domain; preserving"
21947 If this option is set, the router's local &%qualify_domain%& option must not be
21948 set (a configuration error occurs if it is). If an unqualified address (one
21949 without a domain) is generated, it is qualified with the domain of the parent
21950 address (the immediately preceding ancestor) instead of the global
21951 &%qualify_recipient%& value. In the case of a traditional &_.forward_& file,
21952 this applies whether or not the address is preceded by a backslash.
21955 .option repeat_use redirect boolean true
21956 If this option is set false, the router is skipped for a child address that has
21957 any ancestor that was routed by this router. This test happens before any of
21958 the other preconditions are tested. Exim's default anti-looping rules skip
21959 only when the ancestor is the same as the current address. See also
21960 &%check_ancestor%& above and the generic &%redirect_router%& option.
21963 .option reply_transport redirect string&!! unset
21964 A &(redirect)& router sets up an automatic reply when a &%mail%& or
21965 &%vacation%& command is used in a filter file. The transport used is specified
21966 by this option, which, after expansion, must be the name of a configured
21967 transport. This should normally be an &(autoreply)& transport. Other transports
21968 are unlikely to do anything sensible or useful.
21971 .option rewrite redirect boolean true
21972 .cindex "address redirection" "disabling rewriting"
21973 If this option is set false, addresses generated by the router are not
21974 subject to address rewriting. Otherwise, they are treated like new addresses
21975 and are rewritten according to the global rewriting rules.
21978 .option sieve_subaddress redirect string&!! unset
21979 The value of this option is passed to a Sieve filter to specify the
21980 :subaddress part of an address.
21982 .option sieve_useraddress redirect string&!! unset
21983 The value of this option is passed to a Sieve filter to specify the :user part
21984 of an address. However, if it is unset, the entire original local part
21985 (including any prefix or suffix) is used for :user.
21988 .option sieve_vacation_directory redirect string&!! unset
21989 .cindex "Sieve filter" "vacation directory"
21990 To enable the &"vacation"& extension for Sieve filters, you must set
21991 &%sieve_vacation_directory%& to the directory where vacation databases are held
21992 (do not put anything else in that directory), and ensure that the
21993 &%reply_transport%& option refers to an &(autoreply)& transport. Each user
21994 needs their own directory; Exim will create it if necessary.
21998 .option skip_syntax_errors redirect boolean false
21999 .cindex "forward file" "broken"
22000 .cindex "address redirection" "broken files"
22001 .cindex "alias file" "broken"
22002 .cindex "broken alias or forward files"
22003 .cindex "ignoring faulty addresses"
22004 .cindex "skipping faulty addresses"
22005 .cindex "error" "skipping bad syntax"
22006 If &%skip_syntax_errors%& is set, syntactically malformed addresses in
22007 non-filter redirection data are skipped, and each failing address is logged. If
22008 &%syntax_errors_to%& is set, a message is sent to the address it defines,
22009 giving details of the failures. If &%syntax_errors_text%& is set, its contents
22010 are expanded and placed at the head of the error message generated by
22011 &%syntax_errors_to%&. Usually it is appropriate to set &%syntax_errors_to%& to
22012 be the same address as the generic &%errors_to%& option. The
22013 &%skip_syntax_errors%& option is often used when handling mailing lists.
22015 If all the addresses in a redirection list are skipped because of syntax
22016 errors, the router declines to handle the original address, and it is passed to
22017 the following routers.
22019 If &%skip_syntax_errors%& is set when an Exim filter is interpreted, any syntax
22020 error in the filter causes filtering to be abandoned without any action being
22021 taken. The incident is logged, and the router declines to handle the address,
22022 so it is passed to the following routers.
22024 .cindex "Sieve filter" "syntax errors in"
22025 Syntax errors in a Sieve filter file cause the &"keep"& action to occur. This
22026 action is specified by RFC 3028. The values of &%skip_syntax_errors%&,
22027 &%syntax_errors_to%&, and &%syntax_errors_text%& are not used.
22029 &%skip_syntax_errors%& can be used to specify that errors in users' forward
22030 lists or filter files should not prevent delivery. The &%syntax_errors_to%&
22031 option, used with an address that does not get redirected, can be used to
22032 notify users of these errors, by means of a router like this:
22038 file = $home/.forward
22039 file_transport = address_file
22040 pipe_transport = address_pipe
22041 reply_transport = address_reply
22044 syntax_errors_to = real-$local_part@$domain
22045 syntax_errors_text = \
22046 This is an automatically generated message. An error has\n\
22047 been found in your .forward file. Details of the error are\n\
22048 reported below. While this error persists, you will receive\n\
22049 a copy of this message for every message that is addressed\n\
22050 to you. If your .forward file is a filter file, or if it is\n\
22051 a non-filter file containing no valid forwarding addresses,\n\
22052 a copy of each incoming message will be put in your normal\n\
22053 mailbox. If a non-filter file contains at least one valid\n\
22054 forwarding address, forwarding to the valid addresses will\n\
22055 happen, and those will be the only deliveries that occur.
22057 You also need a router to ensure that local addresses that are prefixed by
22058 &`real-`& are recognized, but not forwarded or filtered. For example, you could
22059 put this immediately before the &(userforward)& router:
22064 local_part_prefix = real-
22065 transport = local_delivery
22067 For security, it would probably be a good idea to restrict the use of this
22068 router to locally-generated messages, using a condition such as this:
22070 condition = ${if match {$sender_host_address}\
22071 {\N^(|127\.0\.0\.1)$\N}}
22075 .option syntax_errors_text redirect string&!! unset
22076 See &%skip_syntax_errors%& above.
22079 .option syntax_errors_to redirect string unset
22080 See &%skip_syntax_errors%& above.
22081 .ecindex IIDredrou1
22082 .ecindex IIDredrou2
22089 . ////////////////////////////////////////////////////////////////////////////
22090 . ////////////////////////////////////////////////////////////////////////////
22092 .chapter "Environment for running local transports" "CHAPenvironment" &&&
22093 "Environment for local transports"
22094 .scindex IIDenvlotra1 "local transports" "environment for"
22095 .scindex IIDenvlotra2 "environment" "local transports"
22096 .scindex IIDenvlotra3 "transport" "local; environment for"
22097 Local transports handle deliveries to files and pipes. (The &(autoreply)&
22098 transport can be thought of as similar to a pipe.) Exim always runs transports
22099 in subprocesses, under specified uids and gids. Typical deliveries to local
22100 mailboxes run under the uid and gid of the local user.
22102 Exim also sets a specific current directory while running the transport; for
22103 some transports a home directory setting is also relevant. The &(pipe)&
22104 transport is the only one that sets up environment variables; see section
22105 &<<SECTpipeenv>>& for details.
22107 The values used for the uid, gid, and the directories may come from several
22108 different places. In many cases, the router that handles the address associates
22109 settings with that address as a result of its &%check_local_user%&, &%group%&,
22110 or &%user%& options. However, values may also be given in the transport's own
22111 configuration, and these override anything that comes from the router.
22115 .section "Concurrent deliveries" "SECID131"
22116 .cindex "concurrent deliveries"
22117 .cindex "simultaneous deliveries"
22118 If two different messages for the same local recipient arrive more or less
22119 simultaneously, the two delivery processes are likely to run concurrently. When
22120 the &(appendfile)& transport is used to write to a file, Exim applies locking
22121 rules to stop concurrent processes from writing to the same file at the same
22124 However, when you use a &(pipe)& transport, it is up to you to arrange any
22125 locking that is needed. Here is a silly example:
22129 command = /bin/sh -c 'cat >>/some/file'
22131 This is supposed to write the message at the end of the file. However, if two
22132 messages arrive at the same time, the file will be scrambled. You can use the
22133 &%exim_lock%& utility program (see section &<<SECTmailboxmaint>>&) to lock a
22134 file using the same algorithm that Exim itself uses.
22139 .section "Uids and gids" "SECTenvuidgid"
22140 .cindex "local transports" "uid and gid"
22141 .cindex "transport" "local; uid and gid"
22142 All transports have the options &%group%& and &%user%&. If &%group%& is set, it
22143 overrides any group that the router set in the address, even if &%user%& is not
22144 set for the transport. This makes it possible, for example, to run local mail
22145 delivery under the uid of the recipient (set by the router), but in a special
22146 group (set by the transport). For example:
22149 # User/group are set by check_local_user in this router
22153 transport = group_delivery
22156 # This transport overrides the group
22158 driver = appendfile
22159 file = /var/spool/mail/$local_part_data
22162 If &%user%& is set for a transport, its value overrides what is set in the
22163 address by the router. If &%user%& is non-numeric and &%group%& is not set, the
22164 gid associated with the user is used. If &%user%& is numeric, &%group%& must be
22167 .oindex "&%initgroups%&"
22168 When the uid is taken from the transport's configuration, the &[initgroups()]&
22169 function is called for the groups associated with that uid if the
22170 &%initgroups%& option is set for the transport. When the uid is not specified
22171 by the transport, but is associated with the address by a router, the option
22172 for calling &[initgroups()]& is taken from the router configuration.
22174 .cindex "&(pipe)& transport" "uid for"
22175 The &(pipe)& transport contains the special option &%pipe_as_creator%&. If this
22176 is set and &%user%& is not set, the uid of the process that called Exim to
22177 receive the message is used, and if &%group%& is not set, the corresponding
22178 original gid is also used.
22180 This is the detailed preference order for obtaining a gid; the first of the
22181 following that is set is used:
22184 A &%group%& setting of the transport;
22186 A &%group%& setting of the router;
22188 A gid associated with a user setting of the router, either as a result of
22189 &%check_local_user%& or an explicit non-numeric &%user%& setting;
22191 The group associated with a non-numeric &%user%& setting of the transport;
22193 In a &(pipe)& transport, the creator's gid if &%deliver_as_creator%& is set and
22194 the uid is the creator's uid;
22196 The Exim gid if the Exim uid is being used as a default.
22199 If, for example, the user is specified numerically on the router and there are
22200 no group settings, no gid is available. In this situation, an error occurs.
22201 This is different for the uid, for which there always is an ultimate default.
22202 The first of the following that is set is used:
22205 A &%user%& setting of the transport;
22207 In a &(pipe)& transport, the creator's uid if &%deliver_as_creator%& is set;
22209 A &%user%& setting of the router;
22211 A &%check_local_user%& setting of the router;
22216 Of course, an error will still occur if the uid that is chosen is on the
22217 &%never_users%& list.
22223 .section "Current and home directories" "SECID132"
22224 .cindex "current directory for local transport"
22225 .cindex "home directory" "for local transport"
22226 .cindex "transport" "local; home directory for"
22227 .cindex "transport" "local; current directory for"
22228 Routers may set current and home directories for local transports by means of
22229 the &%transport_current_directory%& and &%transport_home_directory%& options.
22230 However, if the transport's &%current_directory%& or &%home_directory%& options
22231 are set, they override the router's values. In detail, the home directory
22232 for a local transport is taken from the first of these values that is set:
22235 The &%home_directory%& option on the transport;
22237 The &%transport_home_directory%& option on the router;
22239 The password data if &%check_local_user%& is set on the router;
22241 The &%router_home_directory%& option on the router.
22244 The current directory is taken from the first of these values that is set:
22247 The &%current_directory%& option on the transport;
22249 The &%transport_current_directory%& option on the router.
22253 If neither the router nor the transport sets a current directory, Exim uses the
22254 value of the home directory, if it is set. Otherwise it sets the current
22255 directory to &_/_& before running a local transport.
22259 .section "Expansion variables derived from the address" "SECID133"
22260 .vindex "&$domain$&"
22261 .vindex "&$local_part$&"
22262 .vindex "&$original_domain$&"
22263 Normally a local delivery is handling a single address, and in that case the
22264 variables such as &$domain$& and &$local_part$& are set during local
22265 deliveries. However, in some circumstances more than one address may be handled
22266 at once (for example, while writing batch SMTP for onward transmission by some
22267 other means). In this case, the variables associated with the local part are
22268 never set, &$domain$& is set only if all the addresses have the same domain,
22269 and &$original_domain$& is never set.
22270 .ecindex IIDenvlotra1
22271 .ecindex IIDenvlotra2
22272 .ecindex IIDenvlotra3
22280 . ////////////////////////////////////////////////////////////////////////////
22281 . ////////////////////////////////////////////////////////////////////////////
22283 .chapter "Generic options for transports" "CHAPtransportgeneric"
22284 .scindex IIDgenoptra1 "generic options" "transport"
22285 .scindex IIDgenoptra2 "options" "generic; for transports"
22286 .scindex IIDgenoptra3 "transport" "generic options for"
22287 The name of a transport is limited to be &drivernamemax; ASCII characters long;
22288 prior to Exim 4.95 names would be silently truncated at this length, but now
22291 The following generic options apply to all transports:
22294 .option body_only transports boolean false
22295 .cindex "transport" "body only"
22296 .cindex "message" "transporting body only"
22297 .cindex "body of message" "transporting"
22298 If this option is set, the message's headers are not transported. It is
22299 mutually exclusive with &%headers_only%&. If it is used with the &(appendfile)&
22300 or &(pipe)& transports, the settings of &%message_prefix%& and
22301 &%message_suffix%& should be checked, because this option does not
22302 automatically suppress them.
22305 .option current_directory transports string&!! unset
22306 .cindex "transport" "current directory for"
22307 This specifies the current directory that is to be set while running the
22308 transport, overriding any value that may have been set by the router.
22309 If the expansion fails for any reason, including forced failure, an error is
22310 logged, and delivery is deferred.
22313 .option disable_logging transports boolean false
22314 If this option is set true, nothing is logged for any
22315 deliveries by the transport or for any
22316 transport errors. You should not set this option unless you really, really know
22317 what you are doing.
22320 .option debug_print transports string&!! unset
22321 .cindex "testing" "variables in drivers"
22322 If this option is set and debugging is enabled (see the &%-d%& command line
22323 option), the string is expanded and included in the debugging output when the
22325 If expansion of the string fails, the error message is written to the debugging
22326 output, and Exim carries on processing.
22327 This facility is provided to help with checking out the values of variables and
22328 so on when debugging driver configurations. For example, if a &%headers_add%&
22329 option is not working properly, &%debug_print%& could be used to output the
22330 variables it references. A newline is added to the text if it does not end with
22332 The variables &$transport_name$& and &$router_name$& contain the name of the
22333 transport and the router that called it.
22335 .option delivery_date_add transports boolean false
22336 .cindex "&'Delivery-date:'& header line"
22337 If this option is true, a &'Delivery-date:'& header is added to the message.
22338 This gives the actual time the delivery was made. As this is not a standard
22339 header, Exim has a configuration option (&%delivery_date_remove%&) which
22340 requests its removal from incoming messages, so that delivered messages can
22341 safely be resent to other recipients.
22344 .option driver transports string unset
22345 This specifies which of the available transport drivers is to be used.
22346 There is no default, and this option must be set for every transport.
22349 .option envelope_to_add transports boolean false
22350 .cindex "&'Envelope-to:'& header line"
22351 If this option is true, an &'Envelope-to:'& header is added to the message.
22352 This gives the original address(es) in the incoming envelope that caused this
22353 delivery to happen. More than one address may be present if the transport is
22354 configured to handle several addresses at once, or if more than one original
22355 address was redirected to the same final address. As this is not a standard
22356 header, Exim has a configuration option (&%envelope_to_remove%&) which requests
22357 its removal from incoming messages, so that delivered messages can safely be
22358 resent to other recipients.
22360 &*Note:*& If used on a transport handling multiple recipients
22361 (the smtp transport unless &%rcpt_max%& is 1, the appendfile, pipe or lmtp
22362 transport if &%batch_max%& is greater than 1)
22363 then information about Bcc recipients will be leaked.
22364 Doing so is generally not advised.
22367 .option event_action transports string&!! unset
22369 This option declares a string to be expanded for Exim's events mechanism.
22370 For details see chapter &<<CHAPevents>>&.
22373 .option group transports string&!! "Exim group"
22374 .cindex "transport" "group; specifying"
22375 This option specifies a gid for running the transport process, overriding any
22376 value that the router supplies, and also overriding any value associated with
22377 &%user%& (see below).
22380 .option headers_add transports list&!! unset
22381 .cindex "header lines" "adding in transport"
22382 .cindex "transport" "header lines; adding"
22383 This option specifies a list of text headers,
22384 newline-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
22385 which are (separately) expanded and added to the header
22386 portion of a message as it is transported, as described in section
22387 &<<SECTheadersaddrem>>&. Additional header lines can also be specified by
22388 routers. If the result of the expansion is an empty string, or if the expansion
22389 is forced to fail, no action is taken. Other expansion failures are treated as
22390 errors and cause the delivery to be deferred.
22392 Unlike most options, &%headers_add%& can be specified multiple times
22393 for a transport; all listed headers are added.
22396 .option headers_only transports boolean false
22397 .cindex "transport" "header lines only"
22398 .cindex "message" "transporting headers only"
22399 .cindex "header lines" "transporting"
22400 If this option is set, the message's body is not transported. It is mutually
22401 exclusive with &%body_only%&. If it is used with the &(appendfile)& or &(pipe)&
22402 transports, the settings of &%message_prefix%& and &%message_suffix%& should be
22403 checked, since this option does not automatically suppress them.
22406 .option headers_remove transports list&!! unset
22407 .cindex "header lines" "removing"
22408 .cindex "transport" "header lines; removing"
22409 This option specifies a list of text headers,
22410 colon-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
22411 to be removed from the message.
22412 However, the option has no effect when an address is just being verified.
22413 Each list item is separately expanded.
22414 If the result of the expansion is an empty string, or if the expansion
22415 is forced to fail, no action is taken. Other expansion failures are treated as
22416 errors and cause the delivery to be deferred.
22417 If an item ends in *, it will match any header with the given prefix.
22419 Matching headers are omitted from the message as it is transported, as described
22420 in section &<<SECTheadersaddrem>>&. Header removal can also be specified by
22423 Unlike most options, &%headers_remove%& can be specified multiple times
22424 for a transport; all listed headers are removed.
22426 &*Warning*&: Because of the separate expansion of the list items,
22427 items that contain a list separator must have it doubled.
22428 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
22432 .option headers_rewrite transports string unset
22433 .cindex "transport" "header lines; rewriting"
22434 .cindex "rewriting" "at transport time"
22435 This option allows addresses in header lines to be rewritten at transport time,
22436 that is, as the message is being copied to its destination. The contents of the
22437 option are a colon-separated list of rewriting rules. Each rule is in exactly
22438 the same form as one of the general rewriting rules that are applied when a
22439 message is received. These are described in chapter &<<CHAPrewrite>>&. For
22442 headers_rewrite = a@b c@d f : \
22445 changes &'a@b'& into &'c@d'& in &'From:'& header lines, and &'x@y'& into
22446 &'w@z'& in all address-bearing header lines. The rules are applied to the
22447 header lines just before they are written out at transport time, so they affect
22448 only those copies of the message that pass through the transport. However, only
22449 the message's original header lines, and any that were added by a system
22450 filter, are rewritten. If a router or transport adds header lines, they are not
22451 affected by this option. These rewriting rules are &'not'& applied to the
22452 envelope. You can change the return path using &%return_path%&, but you cannot
22453 change envelope recipients at this time.
22456 .option home_directory transports string&!! unset
22457 .cindex "transport" "home directory for"
22459 This option specifies a home directory setting for a local transport,
22460 overriding any value that may be set by the router. The home directory is
22461 placed in &$home$& while expanding the transport's private options. It is also
22462 used as the current directory if no current directory is set by the
22463 &%current_directory%& option on the transport or the
22464 &%transport_current_directory%& option on the router. If the expansion fails
22465 for any reason, including forced failure, an error is logged, and delivery is
22469 .option initgroups transports boolean false
22470 .cindex "additional groups"
22471 .cindex "groups" "additional"
22472 .cindex "transport" "group; additional"
22473 If this option is true and the uid for the delivery process is provided by the
22474 transport, the &[initgroups()]& function is called when running the transport
22475 to ensure that any additional groups associated with the uid are set up.
22478 .option max_parallel transports integer&!! unset
22479 .cindex limit "transport parallelism"
22480 .cindex transport "parallel processes"
22481 .cindex transport "concurrency limit"
22482 .cindex "delivery" "parallelism for transport"
22483 If this option is set and expands to an integer greater than zero
22484 it limits the number of concurrent runs of the transport.
22485 The control does not apply to shadow transports.
22487 .cindex "hints database" "transport concurrency control"
22488 Exim implements this control by means of a hints database in which a record is
22489 incremented whenever a transport process is being created. The record
22490 is decremented and possibly removed when the process terminates.
22491 Obviously there is scope for
22492 records to get left lying around if there is a system or program crash. To
22493 guard against this, Exim ignores any records that are more than six hours old.
22495 If you use this option, you should also arrange to delete the
22496 relevant hints database whenever your system reboots. The names of the files
22497 start with &_misc_& and they are kept in the &_spool/db_& directory. There
22498 may be one or two files, depending on the type of DBM in use. The same files
22499 are used for ETRN and smtp transport serialization.
22502 .option message_size_limit transports string&!! 0
22503 .cindex "limit" "message size per transport"
22504 .cindex "size" "of message, limit"
22505 .cindex "transport" "message size; limiting"
22506 This option controls the size of messages passed through the transport. It is
22507 expanded before use; the result of the expansion must be a sequence of decimal
22508 digits, optionally followed by K or M. If the expansion fails for any reason,
22509 including forced failure, or if the result is not of the required form,
22510 delivery is deferred. If the value is greater than zero and the size of a
22511 message exceeds this limit, the address is failed. If there is any chance that
22512 the resulting bounce message could be routed to the same transport, you should
22513 ensure that &%return_size_limit%& is less than the transport's
22514 &%message_size_limit%&, as otherwise the bounce message will fail to get
22519 .option rcpt_include_affixes transports boolean false
22520 .cindex "prefix" "for local part, including in envelope"
22521 .cindex "suffix for local part" "including in envelope"
22522 .cindex "local part" "prefix"
22523 .cindex "local part" "suffix"
22524 When this option is false (the default), and an address that has had any
22525 affixes (prefixes or suffixes) removed from the local part is delivered by any
22526 form of SMTP or LMTP, the affixes are not included. For example, if a router
22529 local_part_prefix = *-
22531 routes the address &'abc-xyz@some.domain'& to an SMTP transport, the envelope
22534 RCPT TO:<xyz@some.domain>
22536 This is also the case when an ACL-time callout is being used to verify a
22537 recipient address. However, if &%rcpt_include_affixes%& is set true, the
22538 whole local part is included in the RCPT command. This option applies to BSMTP
22539 deliveries by the &(appendfile)& and &(pipe)& transports as well as to the
22540 &(lmtp)& and &(smtp)& transports.
22543 .option retry_use_local_part transports boolean "see below"
22544 .cindex "hints database" "retry keys"
22545 When a delivery suffers a temporary failure, a retry record is created
22546 in Exim's hints database. For remote deliveries, the key for the retry record
22547 is based on the name and/or IP address of the failing remote host. For local
22548 deliveries, the key is normally the entire address, including both the local
22549 part and the domain. This is suitable for most common cases of local delivery
22550 temporary failure &-- for example, exceeding a mailbox quota should delay only
22551 deliveries to that mailbox, not to the whole domain.
22553 However, in some special cases you may want to treat a temporary local delivery
22554 as a failure associated with the domain, and not with a particular local part.
22555 (For example, if you are storing all mail for some domain in files.) You can do
22556 this by setting &%retry_use_local_part%& false.
22558 For all the local transports, its default value is true. For remote transports,
22559 the default value is false for tidiness, but changing the value has no effect
22560 on a remote transport in the current implementation.
22563 .option return_path transports string&!! unset
22564 .cindex "envelope sender"
22565 .cindex "envelope from"
22566 .cindex "transport" "return path; changing"
22567 .cindex "return path" "changing in transport"
22568 If this option is set, the string is expanded at transport time and replaces
22569 the existing return path (envelope sender) value in the copy of the message
22570 that is being delivered. An empty return path is permitted. This feature is
22571 designed for remote deliveries, where the value of this option is used in the
22572 SMTP MAIL command. If you set &%return_path%& for a local transport, the
22573 only effect is to change the address that is placed in the &'Return-path:'&
22574 header line, if one is added to the message (see the next option).
22576 &*Note:*& A changed return path is not logged unless you add
22577 &%return_path_on_delivery%& to the log selector.
22579 .vindex "&$return_path$&"
22580 The expansion can refer to the existing value via &$return_path$&. This is
22581 either the message's envelope sender, or an address set by the
22582 &%errors_to%& option on a router. If the expansion is forced to fail, no
22583 replacement occurs; if it fails for another reason, delivery is deferred. This
22584 option can be used to support VERP (Variable Envelope Return Paths) &-- see
22585 section &<<SECTverp>>&.
22587 &*Note*&: If a delivery error is detected locally, including the case when a
22588 remote server rejects a message at SMTP time, the bounce message is not sent to
22589 the value of this option. It is sent to the previously set errors address.
22590 This defaults to the incoming sender address, but can be changed by setting
22591 &%errors_to%& in a router.
22595 .option return_path_add transports boolean false
22596 .chindex Return-path:
22597 If this option is true, a &'Return-path:'& header is added to the message.
22598 Although the return path is normally available in the prefix line of BSD
22599 mailboxes, this is commonly not displayed by MUAs, and so the user does not
22600 have easy access to it.
22602 RFC 2821 states that the &'Return-path:'& header is added to a message &"when
22603 the delivery SMTP server makes the final delivery"&. This implies that this
22604 header should not be present in incoming messages. Exim has a configuration
22605 option, &%return_path_remove%&, which requests removal of this header from
22606 incoming messages, so that delivered messages can safely be resent to other
22610 .option shadow_condition transports string&!! unset
22611 See &%shadow_transport%& below.
22614 .option shadow_transport transports string unset
22615 .cindex "shadow transport"
22616 .cindex "transport" "shadow"
22617 A local transport may set the &%shadow_transport%& option to the name of
22618 another local transport. Shadow remote transports are not supported.
22620 Whenever a delivery to the main transport succeeds, and either
22621 &%shadow_condition%& is unset, or its expansion does not result in the empty
22622 string or one of the strings &"0"& or &"no"& or &"false"&, the message is also
22623 passed to the shadow transport, with the same delivery address or addresses. If
22624 expansion fails, no action is taken except that non-forced expansion failures
22625 cause a log line to be written.
22627 The result of the shadow transport is discarded and does not affect the
22628 subsequent processing of the message. Only a single level of shadowing is
22629 provided; the &%shadow_transport%& option is ignored on any transport when it
22630 is running as a shadow. Options concerned with output from pipes are also
22631 ignored. The log line for the successful delivery has an item added on the end,
22634 ST=<shadow transport name>
22636 If the shadow transport did not succeed, the error message is put in
22637 parentheses afterwards. Shadow transports can be used for a number of different
22638 purposes, including keeping more detailed log information than Exim normally
22639 provides, and implementing automatic acknowledgment policies based on message
22640 headers that some sites insist on.
22643 .option transport_filter transports string&!! unset
22644 .cindex "transport" "filter"
22645 .cindex "filter" "transport filter"
22646 This option sets up a filtering (in the Unix shell sense) process for messages
22647 at transport time. It should not be confused with mail filtering as set up by
22648 individual users or via a system filter.
22649 If unset, or expanding to an empty string, no filtering is done.
22651 When the message is about to be written out, the command specified by
22652 &%transport_filter%& is started up in a separate, parallel process, and
22653 the entire message, including the header lines, is passed to it on its standard
22654 input (this in fact is done from a third process, to avoid deadlock). The
22655 command must be specified as an absolute path.
22657 The lines of the message that are written to the transport filter are
22658 terminated by newline (&"\n"&). The message is passed to the filter before any
22659 SMTP-specific processing, such as turning &"\n"& into &"\r\n"& and escaping
22660 lines beginning with a dot, and also before any processing implied by the
22661 settings of &%check_string%& and &%escape_string%& in the &(appendfile)& or
22662 &(pipe)& transports.
22664 The standard error for the filter process is set to the same destination as its
22665 standard output; this is read and written to the message's ultimate
22666 destination. The process that writes the message to the filter, the
22667 filter itself, and the original process that reads the result and delivers it
22668 are all run in parallel, like a shell pipeline.
22670 The filter can perform any transformations it likes, but of course should take
22671 care not to break RFC 2822 syntax. Exim does not check the result, except to
22672 test for a final newline when SMTP is in use. All messages transmitted over
22673 SMTP must end with a newline, so Exim supplies one if it is missing.
22675 .cindex "content scanning" "per user"
22676 A transport filter can be used to provide content-scanning on a per-user basis
22677 at delivery time if the only required effect of the scan is to modify the
22678 message. For example, a content scan could insert a new header line containing
22679 a spam score. This could be interpreted by a filter in the user's MUA. It is
22680 not possible to discard a message at this stage.
22682 .cindex "SIZE" "ESMTP extension"
22683 A problem might arise if the filter increases the size of a message that is
22684 being sent down an SMTP connection. If the receiving SMTP server has indicated
22685 support for the SIZE parameter, Exim will have sent the size of the message
22686 at the start of the SMTP session. If what is actually sent is substantially
22687 more, the server might reject the message. This can be worked round by setting
22688 the &%size_addition%& option on the &(smtp)& transport, either to allow for
22689 additions to the message, or to disable the use of SIZE altogether.
22691 .vindex "&$pipe_addresses$&"
22692 The value of the &%transport_filter%& option is the command string for starting
22693 the filter, which is run directly from Exim, not under a shell. The string is
22694 parsed by Exim in the same way as a command string for the &(pipe)& transport:
22695 Exim breaks it up into arguments and then expands each argument separately (see
22696 section &<<SECThowcommandrun>>&). Any kind of expansion failure causes delivery
22697 to be deferred. The special argument &$pipe_addresses$& is replaced by a number
22698 of arguments, one for each address that applies to this delivery. (This isn't
22699 an ideal name for this feature here, but as it was already implemented for the
22700 &(pipe)& transport, it seemed sensible not to change it.)
22703 .vindex "&$host_address$&"
22704 The expansion variables &$host$& and &$host_address$& are available when the
22705 transport is a remote one. They contain the name and IP address of the host to
22706 which the message is being sent. For example:
22707 . used to have $sender_address in this cmdline, but it's tainted
22709 transport_filter = /some/directory/transport-filter.pl \
22710 $host $host_address $pipe_addresses
22713 Two problems arise if you want to use more complicated expansion items to
22714 generate transport filter commands, both of which due to the fact that the
22715 command is split up &'before'& expansion.
22717 If an expansion item contains white space, you must quote it, so that it is all
22718 part of the same command item. If the entire option setting is one such
22719 expansion item, you have to take care what kind of quoting you use. For
22722 transport_filter = '/bin/cmd${if eq{$host}{a.b.c}{1}{2}}'
22724 This runs the command &(/bin/cmd1)& if the host name is &'a.b.c'&, and
22725 &(/bin/cmd2)& otherwise. If double quotes had been used, they would have been
22726 stripped by Exim when it read the option's value. When the value is used, if
22727 the single quotes were missing, the line would be split into two items,
22728 &`/bin/cmd${if`& and &`eq{$host}{a.b.c}{1}{2}`&, and an error would occur when
22729 Exim tried to expand the first one.
22731 Except for the special case of &$pipe_addresses$& that is mentioned above, an
22732 expansion cannot generate multiple arguments, or a command name followed by
22733 arguments. Consider this example:
22735 transport_filter = ${lookup{$host}lsearch{/a/file}\
22736 {$value}{/bin/cat}}
22738 The result of the lookup is interpreted as the name of the command, even
22739 if it contains white space. The simplest way round this is to use a shell:
22741 transport_filter = /bin/sh -c ${lookup{$host}lsearch{/a/file}\
22742 {$value}{/bin/cat}}
22746 The filter process is run under the same uid and gid as the normal delivery.
22747 For remote deliveries this is the Exim uid/gid by default. The command should
22748 normally yield a zero return code. Transport filters are not supposed to fail.
22749 A non-zero code is taken to mean that the transport filter encountered some
22750 serious problem. Delivery of the message is deferred; the message remains on
22751 the queue and is tried again later. It is not possible to cause a message to be
22752 bounced from a transport filter.
22754 If a transport filter is set on an autoreply transport, the original message is
22755 passed through the filter as it is being copied into the newly generated
22756 message, which happens if the &%return_message%& option is set.
22759 .option transport_filter_timeout transports time 5m
22760 .cindex "transport" "filter, timeout"
22761 When Exim is reading the output of a transport filter, it applies a timeout
22762 that can be set by this option. Exceeding the timeout is normally treated as a
22763 temporary delivery failure. However, if a transport filter is used with a
22764 &(pipe)& transport, a timeout in the transport filter is treated in the same
22765 way as a timeout in the pipe command itself. By default, a timeout is a hard
22766 error, but if the &(pipe)& transport's &%timeout_defer%& option is set true, it
22767 becomes a temporary error.
22770 .option user transports string&!! "Exim user"
22771 .cindex "uid (user id)" "local delivery"
22772 .cindex "transport" "user, specifying"
22773 This option specifies the user under whose uid the delivery process is to be
22774 run, overriding any uid that may have been set by the router. If the user is
22775 given as a name, the uid is looked up from the password data, and the
22776 associated group is taken as the value of the gid to be used if the &%group%&
22779 For deliveries that use local transports, a user and group are normally
22780 specified explicitly or implicitly (for example, as a result of
22781 &%check_local_user%&) by the router or transport.
22783 .cindex "hints database" "access by remote transport"
22784 For remote transports, you should leave this option unset unless you really are
22785 sure you know what you are doing. When a remote transport is running, it needs
22786 to be able to access Exim's hints databases, because each host may have its own
22788 .ecindex IIDgenoptra1
22789 .ecindex IIDgenoptra2
22790 .ecindex IIDgenoptra3
22797 . ////////////////////////////////////////////////////////////////////////////
22798 . ////////////////////////////////////////////////////////////////////////////
22800 .chapter "Address batching in local transports" "CHAPbatching" &&&
22802 .cindex "transport" "local; address batching in"
22803 The only remote transport (&(smtp)&) is normally configured to handle more than
22804 one address at a time, so that when several addresses are routed to the same
22805 remote host, just one copy of the message is sent. Local transports, however,
22806 normally handle one address at a time. That is, a separate instance of the
22807 transport is run for each address that is routed to the transport. A separate
22808 copy of the message is delivered each time.
22810 .cindex "batched local delivery"
22811 .oindex "&%batch_max%&"
22812 .oindex "&%batch_id%&"
22813 In special cases, it may be desirable to handle several addresses at once in a
22814 local transport, for example:
22817 In an &(appendfile)& transport, when storing messages in files for later
22818 delivery by some other means, a single copy of the message with multiple
22819 recipients saves space.
22821 In an &(lmtp)& transport, when delivering over &"local SMTP"& to some process,
22822 a single copy saves time, and is the normal way LMTP is expected to work.
22824 In a &(pipe)& transport, when passing the message
22825 to a scanner program or
22826 to some other delivery mechanism such as UUCP, multiple recipients may be
22830 These three local transports all have the same options for controlling multiple
22831 (&"batched"&) deliveries, namely &%batch_max%& and &%batch_id%&. To save
22832 repeating the information for each transport, these options are described here.
22834 The &%batch_max%& option specifies the maximum number of addresses that can be
22835 delivered together in a single run of the transport. Its default value is one
22836 (no batching). When more than one address is routed to a transport that has a
22837 &%batch_max%& value greater than one, the addresses are delivered in a batch
22838 (that is, in a single run of the transport with multiple recipients), subject
22839 to certain conditions:
22842 .vindex "&$local_part$&"
22843 If any of the transport's options contain a reference to &$local_part$&, no
22844 batching is possible.
22846 .vindex "&$domain$&"
22847 If any of the transport's options contain a reference to &$domain$&, only
22848 addresses with the same domain are batched.
22850 .cindex "customizing" "batching condition"
22851 If &%batch_id%& is set, it is expanded for each address, and only those
22852 addresses with the same expanded value are batched. This allows you to specify
22853 customized batching conditions. Failure of the expansion for any reason,
22854 including forced failure, disables batching, but it does not stop the delivery
22857 Batched addresses must also have the same errors address (where to send
22858 delivery errors), the same header additions and removals, the same user and
22859 group for the transport, and if a host list is present, the first host must
22863 In the case of the &(appendfile)& and &(pipe)& transports, batching applies
22864 both when the file or pipe command is specified in the transport, and when it
22865 is specified by a &(redirect)& router, but all the batched addresses must of
22866 course be routed to the same file or pipe command. These two transports have an
22867 option called &%use_bsmtp%&, which causes them to deliver the message in
22868 &"batched SMTP"& format, with the envelope represented as SMTP commands. The
22869 &%check_string%& and &%escape_string%& options are forced to the values
22872 escape_string = ".."
22874 when batched SMTP is in use. A full description of the batch SMTP mechanism is
22875 given in section &<<SECTbatchSMTP>>&. The &(lmtp)& transport does not have a
22876 &%use_bsmtp%& option, because it always delivers using the SMTP protocol.
22878 .cindex "&'Envelope-to:'& header line"
22879 If the generic &%envelope_to_add%& option is set for a batching transport, the
22880 &'Envelope-to:'& header that is added to the message contains all the addresses
22881 that are being processed together. If you are using a batching &(appendfile)&
22882 transport without &%use_bsmtp%&, the only way to preserve the recipient
22883 addresses is to set the &%envelope_to_add%& option.
22885 .cindex "&(pipe)& transport" "with multiple addresses"
22886 .vindex "&$pipe_addresses$&"
22887 If you are using a &(pipe)& transport without BSMTP, and setting the
22888 transport's &%command%& option, you can include &$pipe_addresses$& as part of
22889 the command. This is not a true variable; it is a bit of magic that causes each
22890 of the recipient addresses to be inserted into the command as a separate
22891 argument. This provides a way of accessing all the addresses that are being
22892 delivered in the batch. &*Note:*& This is not possible for pipe commands that
22893 are specified by a &(redirect)& router.
22898 . ////////////////////////////////////////////////////////////////////////////
22899 . ////////////////////////////////////////////////////////////////////////////
22901 .chapter "The appendfile transport" "CHAPappendfile"
22902 .scindex IIDapptra1 "&(appendfile)& transport"
22903 .scindex IIDapptra2 "transports" "&(appendfile)&"
22904 .cindex "directory creation"
22905 .cindex "creating directories"
22906 The &(appendfile)& transport delivers a message by appending it to an existing
22907 file, or by creating an entirely new file in a specified directory. Single
22908 files to which messages are appended can be in the traditional Unix mailbox
22909 format, or optionally in the MBX format supported by the Pine MUA and
22910 University of Washington IMAP daemon, &'inter alia'&. When each message is
22911 being delivered as a separate file, &"maildir"& format can optionally be used
22912 to give added protection against failures that happen part-way through the
22913 delivery. A third form of separate-file delivery known as &"mailstore"& is also
22914 supported. For all file formats, Exim attempts to create as many levels of
22915 directory as necessary, provided that &%create_directory%& is set.
22917 The code for the optional formats is not included in the Exim binary by
22918 default. It is necessary to set SUPPORT_MBX, SUPPORT_MAILDIR and/or
22919 SUPPORT_MAILSTORE in &_Local/Makefile_& to have the appropriate code
22922 .cindex "quota" "system"
22923 Exim recognizes system quota errors, and generates an appropriate message. Exim
22924 also supports its own quota control within the transport, for use when the
22925 system facility is unavailable or cannot be used for some reason.
22927 If there is an error while appending to a file (for example, quota exceeded or
22928 partition filled), Exim attempts to reset the file's length and last
22929 modification time back to what they were before. If there is an error while
22930 creating an entirely new file, the new file is removed.
22932 Before appending to a file, a number of security checks are made, and the
22933 file is locked. A detailed description is given below, after the list of
22936 The &(appendfile)& transport is most commonly used for local deliveries to
22937 users' mailboxes. However, it can also be used as a pseudo-remote transport for
22938 putting messages into files for remote delivery by some means other than Exim.
22939 &"Batch SMTP"& format is often used in this case (see the &%use_bsmtp%&
22944 .section "The file and directory options" "SECTfildiropt"
22945 The &%file%& option specifies a single file, to which the message is appended;
22946 the &%directory%& option specifies a directory, in which a new file containing
22947 the message is created. Only one of these two options can be set, and for
22948 normal deliveries to mailboxes, one of them &'must'& be set.
22950 .vindex "&$address_file$&"
22951 .vindex "&$local_part$&"
22952 However, &(appendfile)& is also used for delivering messages to files or
22953 directories whose names (or parts of names) are obtained from alias,
22954 forwarding, or filtering operations (for example, a &%save%& command in a
22955 user's Exim filter). When such a transport is running, &$local_part$& contains
22956 the local part that was aliased or forwarded, and &$address_file$& contains the
22957 name (or partial name) of the file or directory generated by the redirection
22958 operation. There are two cases:
22961 If neither &%file%& nor &%directory%& is set, the redirection operation
22962 must specify an absolute path (one that begins with &`/`&). This is the most
22963 common case when users with local accounts use filtering to sort mail into
22964 different folders. See for example, the &(address_file)& transport in the
22965 default configuration. If the path ends with a slash, it is assumed to be the
22966 name of a directory. A delivery to a directory can also be forced by setting
22967 &%maildir_format%& or &%mailstore_format%&.
22969 If &%file%& or &%directory%& is set for a delivery from a redirection, it is
22970 used to determine the file or directory name for the delivery. Normally, the
22971 contents of &$address_file$& are used in some way in the string expansion.
22973 If the &%create_file%& option is set to a path which
22974 matches (see the option definition below for details)
22975 a file or directory name
22976 for the delivery, that name becomes de-tainted.
22978 .cindex "tainted data" "in filenames"
22979 .cindex appendfile "tainted data"
22980 Tainted data may not be used for a file or directory name.
22981 This means that, for instance, &$local_part$& cannot be used directly
22982 as a component of a path. It can however be used as the key for a lookup
22983 which returns a path (or component).
22986 .cindex "Sieve filter" "configuring &(appendfile)&"
22987 .cindex "Sieve filter" "relative mailbox path handling"
22988 As an example of the second case, consider an environment where users do not
22989 have home directories. They may be permitted to use Exim filter commands of the
22994 or Sieve filter commands of the form:
22996 require "fileinto";
22997 fileinto "folder23";
22999 In this situation, the expansion of &%file%& or &%directory%& in the transport
23000 must transform the relative path into an appropriate absolute filename. In the
23001 case of Sieve filters, the name &'inbox'& must be handled. It is the name that
23002 is used as a result of a &"keep"& action in the filter. This example shows one
23003 way of handling this requirement:
23005 file = ${if eq{$address_file}{inbox} \
23006 {/var/mail/$local_part_data} \
23007 {${if eq{${substr_0_1:$address_file}}{/} \
23009 {$home/mail/$address_file} \
23013 With this setting of &%file%&, &'inbox'& refers to the standard mailbox
23014 location, absolute paths are used without change, and other folders are in the
23015 &_mail_& directory within the home directory.
23017 &*Note 1*&: While processing an Exim filter, a relative path such as
23018 &_folder23_& is turned into an absolute path if a home directory is known to
23019 the router. In particular, this is the case if &%check_local_user%& is set. If
23020 you want to prevent this happening at routing time, you can set
23021 &%router_home_directory%& empty. This forces the router to pass the relative
23022 path to the transport.
23024 &*Note 2*&: An absolute path in &$address_file$& is not treated specially;
23025 the &%file%& or &%directory%& option is still used if it is set.
23030 .section "Private options for appendfile" "SECID134"
23031 .cindex "options" "&(appendfile)& transport"
23035 .option allow_fifo appendfile boolean false
23036 .cindex "fifo (named pipe)"
23037 .cindex "named pipe (fifo)"
23038 .cindex "pipe" "named (fifo)"
23039 Setting this option permits delivery to named pipes (FIFOs) as well as to
23040 regular files. If no process is reading the named pipe at delivery time, the
23041 delivery is deferred.
23044 .option allow_symlink appendfile boolean false
23045 .cindex "symbolic link" "to mailbox"
23046 .cindex "mailbox" "symbolic link"
23047 By default, &(appendfile)& will not deliver if the path name for the file is
23048 that of a symbolic link. Setting this option relaxes that constraint, but there
23049 are security issues involved in the use of symbolic links. Be sure you know
23050 what you are doing if you set this. Details of exactly what this option affects
23051 are included in the discussion which follows this list of options.
23054 .option batch_id appendfile string&!! unset
23055 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
23056 However, batching is automatically disabled for &(appendfile)& deliveries that
23057 happen as a result of forwarding or aliasing or other redirection directly to a
23061 .option batch_max appendfile integer 1
23062 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
23065 .option check_group appendfile boolean false
23066 When this option is set, the group owner of the file defined by the &%file%&
23067 option is checked to see that it is the same as the group under which the
23068 delivery process is running. The default setting is false because the default
23069 file mode is 0600, which means that the group is irrelevant.
23072 .option check_owner appendfile boolean true
23073 When this option is set, the owner of the file defined by the &%file%& option
23074 is checked to ensure that it is the same as the user under which the delivery
23075 process is running.
23078 .option check_string appendfile string "see below"
23079 .cindex "&""From""& line"
23080 As &(appendfile)& writes the message, the start of each line is tested for
23081 matching &%check_string%&, and if it does, the initial matching characters are
23082 replaced by the contents of &%escape_string%&. The value of &%check_string%& is
23083 a literal string, not a regular expression, and the case of any letters it
23084 contains is significant.
23086 If &%use_bsmtp%& is set the values of &%check_string%& and &%escape_string%&
23087 are forced to &"."& and &".."& respectively, and any settings in the
23088 configuration are ignored. Otherwise, they default to &"From&~"& and
23089 &">From&~"& when the &%file%& option is set, and unset when any of the
23090 &%directory%&, &%maildir%&, or &%mailstore%& options are set.
23092 The default settings, along with &%message_prefix%& and &%message_suffix%&, are
23093 suitable for traditional &"BSD"& mailboxes, where a line beginning with
23094 &"From&~"& indicates the start of a new message. All four options need changing
23095 if another format is used. For example, to deliver to mailboxes in MMDF format:
23096 .cindex "MMDF format mailbox"
23097 .cindex "mailbox" "MMDF format"
23099 check_string = "\1\1\1\1\n"
23100 escape_string = "\1\1\1\1 \n"
23101 message_prefix = "\1\1\1\1\n"
23102 message_suffix = "\1\1\1\1\n"
23104 .option create_directory appendfile boolean true
23105 .cindex "directory creation"
23106 When this option is true, Exim attempts to create any missing superior
23107 directories for the file that it is about to write. A created directory's mode
23108 is given by the &%directory_mode%& option.
23110 The group ownership of a newly created directory is highly dependent on the
23111 operating system (and possibly the file system) that is being used. For
23112 example, in Solaris, if the parent directory has the setgid bit set, its group
23113 is propagated to the child; if not, the currently set group is used. However,
23114 in FreeBSD, the parent's group is always used.
23118 .option create_file appendfile string anywhere
23119 This option constrains the location of files and directories that are created
23120 by this transport. It applies to files defined by the &%file%& option and
23121 directories defined by the &%directory%& option. In the case of maildir
23122 delivery, it applies to the top level directory, not the maildir directories
23125 The option must be set to one of the words &"anywhere"&, &"inhome"&, or
23126 &"belowhome"&, or to an absolute path.
23128 In the second and third cases, a home directory must have been
23129 set for the transport, and the file or directory being created must
23131 The "belowhome" checking additionally checks for attempts to use "../"
23132 to evade the testing.
23133 This option is not useful when an explicit filename is
23134 given for normal mailbox deliveries. It is intended for the case when filenames
23135 are generated from users' &_.forward_& files. These are usually handled
23136 by an &(appendfile)& transport called &%address_file%&. See also
23137 &%file_must_exist%&.
23139 In the fourth case,
23140 the value given for this option must be an absolute path for an
23141 existing directory.
23142 The value is used for checking instead of a home directory;
23143 checking is done in "belowhome" mode.
23145 .cindex "tainted data" "de-tainting"
23146 .cindex "de-tainting" "using appendfile create_file option"
23147 If "belowhome" checking is used, the file or directory path
23148 becomes de-tainted.
23151 .option directory appendfile string&!! unset
23152 This option is mutually exclusive with the &%file%& option, but one of &%file%&
23153 or &%directory%& must be set, unless the delivery is the direct result of a
23154 redirection (see section &<<SECTfildiropt>>&).
23156 When &%directory%& is set, the string is expanded, and the message is delivered
23157 into a new file or files in or below the given directory, instead of being
23158 appended to a single mailbox file. A number of different formats are provided
23159 (see &%maildir_format%& and &%mailstore_format%&), and see section
23160 &<<SECTopdir>>& for further details of this form of delivery.
23162 The result of expansion must not be tainted, unless the &%create_file%& option
23166 .option directory_file appendfile string&!! "see below"
23168 .vindex "&$inode$&"
23169 When &%directory%& is set, but neither &%maildir_format%& nor
23170 &%mailstore_format%& is set, &(appendfile)& delivers each message into a file
23171 whose name is obtained by expanding this string. The default value is:
23173 q${base62:$tod_epoch}-$inode
23175 This generates a unique name from the current time, in base 62 form, and the
23176 inode of the file. The variable &$inode$& is available only when expanding this
23180 .option directory_mode appendfile "octal integer" 0700
23181 If &(appendfile)& creates any directories as a result of the
23182 &%create_directory%& option, their mode is specified by this option.
23185 .option escape_string appendfile string "see description"
23186 See &%check_string%& above.
23189 .option file appendfile string&!! unset
23190 This option is mutually exclusive with the &%directory%& option, but one of
23191 &%file%& or &%directory%& must be set, unless the delivery is the direct result
23192 of a redirection (see section &<<SECTfildiropt>>&). The &%file%& option
23193 specifies a single file, to which the message is appended. One or more of
23194 &%use_fcntl_lock%&, &%use_flock_lock%&, or &%use_lockfile%& must be set with
23197 The result of expansion must not be tainted, unless the &%create_file%& option
23200 .cindex "NFS" "lock file"
23201 .cindex "locking files"
23202 .cindex "lock files"
23203 If you are using more than one host to deliver over NFS into the same
23204 mailboxes, you should always use lock files.
23206 The string value is expanded for each delivery, and must yield an absolute
23207 path. The most common settings of this option are variations on one of these
23210 file = /var/spool/mail/$local_part_data
23211 file = /home/$local_part_data/inbox
23214 .cindex "&""sticky""& bit"
23215 In the first example, all deliveries are done into the same directory. If Exim
23216 is configured to use lock files (see &%use_lockfile%& below) it must be able to
23217 create a file in the directory, so the &"sticky"& bit must be turned on for
23218 deliveries to be possible, or alternatively the &%group%& option can be used to
23219 run the delivery under a group id which has write access to the directory.
23223 .option file_format appendfile string unset
23224 .cindex "file" "mailbox; checking existing format"
23225 This option requests the transport to check the format of an existing file
23226 before adding to it. The check consists of matching a specific string at the
23227 start of the file. The value of the option consists of an even number of
23228 colon-separated strings. The first of each pair is the test string, and the
23229 second is the name of a transport. If the transport associated with a matched
23230 string is not the current transport, control is passed over to the other
23231 transport. For example, suppose the standard &(local_delivery)& transport has
23234 file_format = "From : local_delivery :\
23235 \1\1\1\1\n : local_mmdf_delivery"
23237 Mailboxes that begin with &"From"& are still handled by this transport, but if
23238 a mailbox begins with four binary ones followed by a newline, control is passed
23239 to a transport called &%local_mmdf_delivery%&, which presumably is configured
23240 to do the delivery in MMDF format. If a mailbox does not exist or is empty, it
23241 is assumed to match the current transport. If the start of a mailbox doesn't
23242 match any string, or if the transport named for a given string is not defined,
23243 delivery is deferred.
23246 .option file_must_exist appendfile boolean false
23247 If this option is true, the file specified by the &%file%& option must exist.
23248 A temporary error occurs if it does not, causing delivery to be deferred.
23249 If this option is false, the file is created if it does not exist.
23252 .option lock_fcntl_timeout appendfile time 0s
23253 .cindex "timeout" "mailbox locking"
23254 .cindex "mailbox" "locking, blocking and non-blocking"
23255 .cindex "locking files"
23256 By default, the &(appendfile)& transport uses non-blocking calls to &[fcntl()]&
23257 when locking an open mailbox file. If the call fails, the delivery process
23258 sleeps for &%lock_interval%& and tries again, up to &%lock_retries%& times.
23259 Non-blocking calls are used so that the file is not kept open during the wait
23260 for the lock; the reason for this is to make it as safe as possible for
23261 deliveries over NFS in the case when processes might be accessing an NFS
23262 mailbox without using a lock file. This should not be done, but
23263 misunderstandings and hence misconfigurations are not unknown.
23265 On a busy system, however, the performance of a non-blocking lock approach is
23266 not as good as using a blocking lock with a timeout. In this case, the waiting
23267 is done inside the system call, and Exim's delivery process acquires the lock
23268 and can proceed as soon as the previous lock holder releases it.
23270 If &%lock_fcntl_timeout%& is set to a non-zero time, blocking locks, with that
23271 timeout, are used. There may still be some retrying: the maximum number of
23274 (lock_retries * lock_interval) / lock_fcntl_timeout
23276 rounded up to the next whole number. In other words, the total time during
23277 which &(appendfile)& is trying to get a lock is roughly the same, unless
23278 &%lock_fcntl_timeout%& is set very large.
23280 You should consider setting this option if you are getting a lot of delayed
23281 local deliveries because of errors of the form
23283 failed to lock mailbox /some/file (fcntl)
23286 .option lock_flock_timeout appendfile time 0s
23287 This timeout applies to file locking when using &[flock()]& (see
23288 &%use_flock%&); the timeout operates in a similar manner to
23289 &%lock_fcntl_timeout%&.
23292 .option lock_interval appendfile time 3s
23293 This specifies the time to wait between attempts to lock the file. See below
23294 for details of locking.
23297 .option lock_retries appendfile integer 10
23298 This specifies the maximum number of attempts to lock the file. A value of zero
23299 is treated as 1. See below for details of locking.
23302 .option lockfile_mode appendfile "octal integer" 0600
23303 This specifies the mode of the created lock file, when a lock file is being
23304 used (see &%use_lockfile%& and &%use_mbx_lock%&).
23307 .option lockfile_timeout appendfile time 30m
23308 .cindex "timeout" "mailbox locking"
23309 When a lock file is being used (see &%use_lockfile%&), if a lock file already
23310 exists and is older than this value, it is assumed to have been left behind by
23311 accident, and Exim attempts to remove it.
23314 .option mailbox_filecount appendfile string&!! unset
23315 .cindex "mailbox" "specifying size of"
23316 .cindex "size" "of mailbox"
23317 If this option is set, it is expanded, and the result is taken as the current
23318 number of files in the mailbox. It must be a decimal number, optionally
23319 followed by K or M. This provides a way of obtaining this information from an
23320 external source that maintains the data.
23323 .option mailbox_size appendfile string&!! unset
23324 .cindex "mailbox" "specifying size of"
23325 .cindex "size" "of mailbox"
23326 If this option is set, it is expanded, and the result is taken as the current
23327 size the mailbox. It must be a decimal number, optionally followed by K or M.
23328 This provides a way of obtaining this information from an external source that
23329 maintains the data. This is likely to be helpful for maildir deliveries where
23330 it is computationally expensive to compute the size of a mailbox.
23334 .option maildir_format appendfile boolean false
23335 .cindex "maildir format" "specifying"
23336 If this option is set with the &%directory%& option, the delivery is into a new
23337 file, in the &"maildir"& format that is used by other mail software. When the
23338 transport is activated directly from a &(redirect)& router (for example, the
23339 &(address_file)& transport in the default configuration), setting
23340 &%maildir_format%& causes the path received from the router to be treated as a
23341 directory, whether or not it ends with &`/`&. This option is available only if
23342 SUPPORT_MAILDIR is present in &_Local/Makefile_&. See section
23343 &<<SECTmaildirdelivery>>& below for further details.
23346 .option maildir_quota_directory_regex appendfile string "See below"
23347 .cindex "maildir format" "quota; directories included in"
23348 .cindex "quota" "maildir; directories included in"
23349 This option is relevant only when &%maildir_use_size_file%& is set. It defines
23350 a regular expression for specifying directories, relative to the quota
23351 directory (see &%quota_directory%&), that should be included in the quota
23352 calculation. The default value is:
23354 maildir_quota_directory_regex = ^(?:cur|new|\..*)$
23356 This includes the &_cur_& and &_new_& directories, and any maildir++ folders
23357 (directories whose names begin with a dot). If you want to exclude the
23359 folder from the count (as some sites do), you need to change this setting to
23361 maildir_quota_directory_regex = ^(?:cur|new|\.(?!Trash).*)$
23363 This uses a negative lookahead in the regular expression to exclude the
23364 directory whose name is &_.Trash_&. When a directory is excluded from quota
23365 calculations, quota processing is bypassed for any messages that are delivered
23366 directly into that directory.
23369 .option maildir_retries appendfile integer 10
23370 This option specifies the number of times to retry when writing a file in
23371 &"maildir"& format. See section &<<SECTmaildirdelivery>>& below.
23374 .option maildir_tag appendfile string&!! unset
23375 This option applies only to deliveries in maildir format, and is described in
23376 section &<<SECTmaildirdelivery>>& below.
23379 .option maildir_use_size_file appendfile&!! boolean false
23380 .cindex "maildir format" "&_maildirsize_& file"
23381 The result of string expansion for this option must be a valid boolean value.
23382 If it is true, it enables support for &_maildirsize_& files. Exim
23383 creates a &_maildirsize_& file in a maildir if one does not exist, taking the
23384 quota from the &%quota%& option of the transport. If &%quota%& is unset, the
23385 value is zero. See &%maildir_quota_directory_regex%& above and section
23386 &<<SECTmaildirdelivery>>& below for further details.
23388 .option maildirfolder_create_regex appendfile string unset
23389 .cindex "maildir format" "&_maildirfolder_& file"
23390 .cindex "&_maildirfolder_&, creating"
23391 The value of this option is a regular expression. If it is unset, it has no
23392 effect. Otherwise, before a maildir delivery takes place, the pattern is
23393 matched against the name of the maildir directory, that is, the directory
23394 containing the &_new_& and &_tmp_& subdirectories that will be used for the
23395 delivery. If there is a match, Exim checks for the existence of a file called
23396 &_maildirfolder_& in the directory, and creates it if it does not exist.
23397 See section &<<SECTmaildirdelivery>>& for more details.
23400 .option mailstore_format appendfile boolean false
23401 .cindex "mailstore format" "specifying"
23402 If this option is set with the &%directory%& option, the delivery is into two
23403 new files in &"mailstore"& format. The option is available only if
23404 SUPPORT_MAILSTORE is present in &_Local/Makefile_&. See section &<<SECTopdir>>&
23405 below for further details.
23408 .option mailstore_prefix appendfile string&!! unset
23409 This option applies only to deliveries in mailstore format, and is described in
23410 section &<<SECTopdir>>& below.
23413 .option mailstore_suffix appendfile string&!! unset
23414 This option applies only to deliveries in mailstore format, and is described in
23415 section &<<SECTopdir>>& below.
23418 .option mbx_format appendfile boolean false
23419 .cindex "locking files"
23420 .cindex "file" "locking"
23421 .cindex "file" "MBX format"
23422 .cindex "MBX format, specifying"
23423 This option is available only if Exim has been compiled with SUPPORT_MBX
23424 set in &_Local/Makefile_&. If &%mbx_format%& is set with the &%file%& option,
23425 the message is appended to the mailbox file in MBX format instead of
23426 traditional Unix format. This format is supported by Pine4 and its associated
23427 IMAP and POP daemons, by means of the &'c-client'& library that they all use.
23429 &*Note*&: The &%message_prefix%& and &%message_suffix%& options are not
23430 automatically changed by the use of &%mbx_format%&. They should normally be set
23431 empty when using MBX format, so this option almost always appears in this
23438 If none of the locking options are mentioned in the configuration,
23439 &%use_mbx_lock%& is assumed and the other locking options default to false. It
23440 is possible to specify the other kinds of locking with &%mbx_format%&, but
23441 &%use_fcntl_lock%& and &%use_mbx_lock%& are mutually exclusive. MBX locking
23442 interworks with &'c-client'&, providing for shared access to the mailbox. It
23443 should not be used if any program that does not use this form of locking is
23444 going to access the mailbox, nor should it be used if the mailbox file is NFS
23445 mounted, because it works only when the mailbox is accessed from a single host.
23447 If you set &%use_fcntl_lock%& with an MBX-format mailbox, you cannot use
23448 the standard version of &'c-client'&, because as long as it has a mailbox open
23449 (this means for the whole of a Pine or IMAP session), Exim will not be able to
23450 append messages to it.
23453 .option message_prefix appendfile string&!! "see below"
23454 .cindex "&""From""& line"
23455 The string specified here is expanded and output at the start of every message.
23456 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
23457 in which case it is:
23459 message_prefix = "From ${if def:return_path{$return_path}\
23460 {MAILER-DAEMON}} $tod_bsdinbox\n"
23462 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
23463 &`\n`& to &`\r\n`& in &%message_prefix%&.
23465 .option message_suffix appendfile string&!! "see below"
23466 The string specified here is expanded and output at the end of every message.
23467 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
23468 in which case it is a single newline character. The suffix can be suppressed by
23473 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
23474 &`\n`& to &`\r\n`& in &%message_suffix%&.
23476 .option mode appendfile "octal integer" 0600
23477 If the output file is created, it is given this mode. If it already exists and
23478 has wider permissions, they are reduced to this mode. If it has narrower
23479 permissions, an error occurs unless &%mode_fail_narrower%& is false. However,
23480 if the delivery is the result of a &%save%& command in a filter file specifying
23481 a particular mode, the mode of the output file is always forced to take that
23482 value, and this option is ignored.
23485 .option mode_fail_narrower appendfile boolean true
23486 This option applies in the case when an existing mailbox file has a narrower
23487 mode than that specified by the &%mode%& option. If &%mode_fail_narrower%& is
23488 true, the delivery is deferred (&"mailbox has the wrong mode"&); otherwise Exim
23489 continues with the delivery attempt, using the existing mode of the file.
23492 .option notify_comsat appendfile boolean false
23493 If this option is true, the &'comsat'& daemon is notified after every
23494 successful delivery to a user mailbox. This is the daemon that notifies logged
23495 on users about incoming mail.
23498 .option quota appendfile string&!! unset
23499 .cindex "quota" "imposed by Exim"
23500 This option imposes a limit on the size of the file to which Exim is appending,
23501 or to the total space used in the directory tree when the &%directory%& option
23502 is set. In the latter case, computation of the space used is expensive, because
23503 all the files in the directory (and any sub-directories) have to be
23504 individually inspected and their sizes summed. (See &%quota_size_regex%& and
23505 &%maildir_use_size_file%& for ways to avoid this in environments where users
23506 have no shell access to their mailboxes).
23508 As there is no interlock against two simultaneous deliveries into a
23509 multi-file mailbox, it is possible for the quota to be overrun in this case.
23510 For single-file mailboxes, of course, an interlock is a necessity.
23512 A file's size is taken as its &'used'& value. Because of blocking effects, this
23513 may be a lot less than the actual amount of disk space allocated to the file.
23514 If the sizes of a number of files are being added up, the rounding effect can
23515 become quite noticeable, especially on systems that have large block sizes.
23516 Nevertheless, it seems best to stick to the &'used'& figure, because this is
23517 the obvious value which users understand most easily.
23519 The value of the option is expanded, and must then be a numerical value
23520 (decimal point allowed), optionally followed by one of the letters K, M, or G,
23521 for kilobytes, megabytes, or gigabytes, optionally followed by a slash
23522 and further option modifiers. If Exim is running on a system with
23523 large file support (Linux and FreeBSD have this), mailboxes larger than 2G can
23526 The option modifier &%no_check%& can be used to force delivery even if the over
23527 quota condition is met. The quota gets updated as usual.
23529 &*Note*&: A value of zero is interpreted as &"no quota"&.
23531 The expansion happens while Exim is running as root, before it changes uid for
23532 the delivery. This means that files that are inaccessible to the end user can
23533 be used to hold quota values that are looked up in the expansion. When delivery
23534 fails because this quota is exceeded, the handling of the error is as for
23535 system quota failures.
23537 By default, Exim's quota checking mimics system quotas, and restricts the
23538 mailbox to the specified maximum size, though the value is not accurate to the
23539 last byte, owing to separator lines and additional headers that may get added
23540 during message delivery. When a mailbox is nearly full, large messages may get
23541 refused even though small ones are accepted, because the size of the current
23542 message is added to the quota when the check is made. This behaviour can be
23543 changed by setting &%quota_is_inclusive%& false. When this is done, the check
23544 for exceeding the quota does not include the current message. Thus, deliveries
23545 continue until the quota has been exceeded; thereafter, no further messages are
23546 delivered. See also &%quota_warn_threshold%&.
23549 .option quota_directory appendfile string&!! unset
23550 This option defines the directory to check for quota purposes when delivering
23551 into individual files. The default is the delivery directory, or, if a file
23552 called &_maildirfolder_& exists in a maildir directory, the parent of the
23553 delivery directory.
23556 .option quota_filecount appendfile string&!! 0
23557 This option applies when the &%directory%& option is set. It limits the total
23558 number of files in the directory (compare the inode limit in system quotas). It
23559 can only be used if &%quota%& is also set. The value is expanded; an expansion
23560 failure causes delivery to be deferred. A value of zero is interpreted as
23563 The option modifier &%no_check%& can be used to force delivery even if the over
23564 quota condition is met. The quota gets updated as usual.
23566 .option quota_is_inclusive appendfile boolean true
23567 See &%quota%& above.
23570 .option quota_size_regex appendfile string unset
23571 This option applies when one of the delivery modes that writes a separate file
23572 for each message is being used. When Exim wants to find the size of one of
23573 these files in order to test the quota, it first checks &%quota_size_regex%&.
23574 If this is set to a regular expression that matches the filename, and it
23575 captures one string, that string is interpreted as a representation of the
23576 file's size. The value of &%quota_size_regex%& is not expanded.
23578 This feature is useful only when users have no shell access to their mailboxes
23579 &-- otherwise they could defeat the quota simply by renaming the files. This
23580 facility can be used with maildir deliveries, by setting &%maildir_tag%& to add
23581 the file length to the filename. For example:
23583 maildir_tag = ,S=$message_size
23584 quota_size_regex = ,S=(\d+)
23586 An alternative to &$message_size$& is &$message_linecount$&, which contains the
23587 number of lines in the message.
23589 The regular expression should not assume that the length is at the end of the
23590 filename (even though &%maildir_tag%& puts it there) because maildir MUAs
23591 sometimes add other information onto the ends of message filenames.
23593 Section &<<SECID136>>& contains further information.
23595 This option should not be used when other message-handling software
23596 may duplicate messages by making hardlinks to the files. When that is done Exim
23597 will count the message size once for each filename, in contrast with the actual
23598 disk usage. When the option is not set, calculating total usage requires
23599 a system-call per file to get the size; the number of links is then available also
23600 as is used to adjust the effective size.
23603 .option quota_warn_message appendfile string&!! "see below"
23604 See below for the use of this option. If it is not set when
23605 &%quota_warn_threshold%& is set, it defaults to
23607 quota_warn_message = "\
23608 To: $local_part@$domain\n\
23609 Subject: Your mailbox\n\n\
23610 This message is automatically created \
23611 by mail delivery software.\n\n\
23612 The size of your mailbox has exceeded \
23613 a warning threshold that is\n\
23614 set by the system administrator.\n"
23618 .option quota_warn_threshold appendfile string&!! 0
23619 .cindex "quota" "warning threshold"
23620 .cindex "mailbox" "size warning"
23621 .cindex "size" "of mailbox"
23622 This option is expanded in the same way as &%quota%& (see above). If the
23623 resulting value is greater than zero, and delivery of the message causes the
23624 size of the file or total space in the directory tree to cross the given
23625 threshold, a warning message is sent. If &%quota%& is also set, the threshold
23626 may be specified as a percentage of it by following the value with a percent
23630 quota_warn_threshold = 75%
23632 If &%quota%& is not set, a setting of &%quota_warn_threshold%& that ends with a
23633 percent sign is ignored.
23635 The warning message itself is specified by the &%quota_warn_message%& option,
23636 and it must start with a &'To:'& header line containing the recipient(s) of the
23637 warning message. These do not necessarily have to include the recipient(s) of
23638 the original message. A &'Subject:'& line should also normally be supplied. You
23639 can include any other header lines that you want. If you do not include a
23640 &'From:'& line, the default is:
23642 From: Mail Delivery System <mailer-daemon@$qualify_domain_sender>
23644 .oindex &%errors_reply_to%&
23645 If you supply a &'Reply-To:'& line, it overrides the global &%errors_reply_to%&
23648 The &%quota%& option does not have to be set in order to use this option; they
23649 are independent of one another except when the threshold is specified as a
23653 .option use_bsmtp appendfile boolean false
23654 .cindex "envelope from"
23655 .cindex "envelope sender"
23656 If this option is set true, &(appendfile)& writes messages in &"batch SMTP"&
23657 format, with the envelope sender and recipient(s) included as SMTP commands. If
23658 you want to include a leading HELO command with such messages, you can do
23659 so by setting the &%message_prefix%& option. See section &<<SECTbatchSMTP>>&
23660 for details of batch SMTP.
23663 .option use_crlf appendfile boolean false
23664 .cindex "carriage return"
23666 This option causes lines to be terminated with the two-character CRLF sequence
23667 (carriage return, linefeed) instead of just a linefeed character. In the case
23668 of batched SMTP, the byte sequence written to the file is then an exact image
23669 of what would be sent down a real SMTP connection.
23671 &*Note:*& The contents of the &%message_prefix%& and &%message_suffix%& options
23672 (which are used to supply the traditional &"From&~"& and blank line separators
23673 in Berkeley-style mailboxes) are written verbatim, so must contain their own
23674 carriage return characters if these are needed. In cases where these options
23675 have non-empty defaults, the values end with a single linefeed, so they must be
23676 changed to end with &`\r\n`& if &%use_crlf%& is set.
23679 .option use_fcntl_lock appendfile boolean "see below"
23680 This option controls the use of the &[fcntl()]& function to lock a file for
23681 exclusive use when a message is being appended. It is set by default unless
23682 &%use_flock_lock%& is set. Otherwise, it should be turned off only if you know
23683 that all your MUAs use lock file locking. When both &%use_fcntl_lock%& and
23684 &%use_flock_lock%& are unset, &%use_lockfile%& must be set.
23687 .option use_flock_lock appendfile boolean false
23688 This option is provided to support the use of &[flock()]& for file locking, for
23689 the few situations where it is needed. Most modern operating systems support
23690 &[fcntl()]& and &[lockf()]& locking, and these two functions interwork with
23691 each other. Exim uses &[fcntl()]& locking by default.
23693 This option is required only if you are using an operating system where
23694 &[flock()]& is used by programs that access mailboxes (typically MUAs), and
23695 where &[flock()]& does not correctly interwork with &[fcntl()]&. You can use
23696 both &[fcntl()]& and &[flock()]& locking simultaneously if you want.
23698 .cindex "Solaris" "&[flock()]& support"
23699 Not all operating systems provide &[flock()]&. Some versions of Solaris do not
23700 have it (and some, I think, provide a not quite right version built on top of
23701 &[lockf()]&). If the OS does not have &[flock()]&, Exim will be built without
23702 the ability to use it, and any attempt to do so will cause a configuration
23705 &*Warning*&: &[flock()]& locks do not work on NFS files (unless &[flock()]&
23706 is just being mapped onto &[fcntl()]& by the OS).
23709 .option use_lockfile appendfile boolean "see below"
23710 If this option is turned off, Exim does not attempt to create a lock file when
23711 appending to a mailbox file. In this situation, the only locking is by
23712 &[fcntl()]&. You should only turn &%use_lockfile%& off if you are absolutely
23713 sure that every MUA that is ever going to look at your users' mailboxes uses
23714 &[fcntl()]& rather than a lock file, and even then only when you are not
23715 delivering over NFS from more than one host.
23717 .cindex "NFS" "lock file"
23718 In order to append to an NFS file safely from more than one host, it is
23719 necessary to take out a lock &'before'& opening the file, and the lock file
23720 achieves this. Otherwise, even with &[fcntl()]& locking, there is a risk of
23723 The &%use_lockfile%& option is set by default unless &%use_mbx_lock%& is set.
23724 It is not possible to turn both &%use_lockfile%& and &%use_fcntl_lock%& off,
23725 except when &%mbx_format%& is set.
23728 .option use_mbx_lock appendfile boolean "see below"
23729 This option is available only if Exim has been compiled with SUPPORT_MBX
23730 set in &_Local/Makefile_&. Setting the option specifies that special MBX
23731 locking rules be used. It is set by default if &%mbx_format%& is set and none
23732 of the locking options are mentioned in the configuration. The locking rules
23733 are the same as are used by the &'c-client'& library that underlies Pine and
23734 the IMAP4 and POP daemons that come with it (see the discussion below). The
23735 rules allow for shared access to the mailbox. However, this kind of locking
23736 does not work when the mailbox is NFS mounted.
23738 You can set &%use_mbx_lock%& with either (or both) of &%use_fcntl_lock%& and
23739 &%use_flock_lock%& to control what kind of locking is used in implementing the
23740 MBX locking rules. The default is to use &[fcntl()]& if &%use_mbx_lock%& is set
23741 without &%use_fcntl_lock%& or &%use_flock_lock%&.
23746 .section "Operational details for appending" "SECTopappend"
23747 .cindex "appending to a file"
23748 .cindex "file" "appending"
23749 Before appending to a file, the following preparations are made:
23752 If the name of the file is &_/dev/null_&, no action is taken, and a success
23756 .cindex "directory creation"
23757 If any directories on the file's path are missing, Exim creates them if the
23758 &%create_directory%& option is set. A created directory's mode is given by the
23759 &%directory_mode%& option.
23762 If &%file_format%& is set, the format of an existing file is checked. If this
23763 indicates that a different transport should be used, control is passed to that
23767 .cindex "file" "locking"
23768 .cindex "locking files"
23769 .cindex "NFS" "lock file"
23770 If &%use_lockfile%& is set, a lock file is built in a way that will work
23771 reliably over NFS, as follows:
23774 Create a &"hitching post"& file whose name is that of the lock file with the
23775 current time, primary host name, and process id added, by opening for writing
23776 as a new file. If this fails with an access error, delivery is deferred.
23778 Close the hitching post file, and hard link it to the lock filename.
23780 If the call to &[link()]& succeeds, creation of the lock file has succeeded.
23781 Unlink the hitching post name.
23783 Otherwise, use &[stat()]& to get information about the hitching post file, and
23784 then unlink hitching post name. If the number of links is exactly two, creation
23785 of the lock file succeeded but something (for example, an NFS server crash and
23786 restart) caused this fact not to be communicated to the &[link()]& call.
23788 If creation of the lock file failed, wait for &%lock_interval%& and try again,
23789 up to &%lock_retries%& times. However, since any program that writes to a
23790 mailbox should complete its task very quickly, it is reasonable to time out old
23791 lock files that are normally the result of user agent and system crashes. If an
23792 existing lock file is older than &%lockfile_timeout%& Exim attempts to unlink
23793 it before trying again.
23797 A call is made to &[lstat()]& to discover whether the main file exists, and if
23798 so, what its characteristics are. If &[lstat()]& fails for any reason other
23799 than non-existence, delivery is deferred.
23802 .cindex "symbolic link" "to mailbox"
23803 .cindex "mailbox" "symbolic link"
23804 If the file does exist and is a symbolic link, delivery is deferred, unless the
23805 &%allow_symlink%& option is set, in which case the ownership of the link is
23806 checked, and then &[stat()]& is called to find out about the real file, which
23807 is then subjected to the checks below. The check on the top-level link
23808 ownership prevents one user creating a link for another's mailbox in a sticky
23809 directory, though allowing symbolic links in this case is definitely not a good
23810 idea. If there is a chain of symbolic links, the intermediate ones are not
23814 If the file already exists but is not a regular file, or if the file's owner
23815 and group (if the group is being checked &-- see &%check_group%& above) are
23816 different from the user and group under which the delivery is running,
23817 delivery is deferred.
23820 If the file's permissions are more generous than specified, they are reduced.
23821 If they are insufficient, delivery is deferred, unless &%mode_fail_narrower%&
23822 is set false, in which case the delivery is tried using the existing
23826 The file's inode number is saved, and the file is then opened for appending.
23827 If this fails because the file has vanished, &(appendfile)& behaves as if it
23828 hadn't existed (see below). For any other failures, delivery is deferred.
23831 If the file is opened successfully, check that the inode number hasn't
23832 changed, that it is still a regular file, and that the owner and permissions
23833 have not changed. If anything is wrong, defer delivery and freeze the message.
23836 If the file did not exist originally, defer delivery if the &%file_must_exist%&
23837 option is set. Otherwise, check that the file is being created in a permitted
23838 directory if the &%create_file%& option is set (deferring on failure), and then
23839 open for writing as a new file, with the O_EXCL and O_CREAT options,
23840 except when dealing with a symbolic link (the &%allow_symlink%& option must be
23841 set). In this case, which can happen if the link points to a non-existent file,
23842 the file is opened for writing using O_CREAT but not O_EXCL, because
23843 that prevents link following.
23846 .cindex "loop" "while file testing"
23847 If opening fails because the file exists, obey the tests given above for
23848 existing files. However, to avoid looping in a situation where the file is
23849 being continuously created and destroyed, the exists/not-exists loop is broken
23850 after 10 repetitions, and the message is then frozen.
23853 If opening fails with any other error, defer delivery.
23856 .cindex "file" "locking"
23857 .cindex "locking files"
23858 Once the file is open, unless both &%use_fcntl_lock%& and &%use_flock_lock%&
23859 are false, it is locked using &[fcntl()]& or &[flock()]& or both. If
23860 &%use_mbx_lock%& is false, an exclusive lock is requested in each case.
23861 However, if &%use_mbx_lock%& is true, Exim takes out a shared lock on the open
23862 file, and an exclusive lock on the file whose name is
23864 /tmp/.<device-number>.<inode-number>
23866 using the device and inode numbers of the open mailbox file, in accordance with
23867 the MBX locking rules. This file is created with a mode that is specified by
23868 the &%lockfile_mode%& option.
23870 If Exim fails to lock the file, there are two possible courses of action,
23871 depending on the value of the locking timeout. This is obtained from
23872 &%lock_fcntl_timeout%& or &%lock_flock_timeout%&, as appropriate.
23874 If the timeout value is zero, the file is closed, Exim waits for
23875 &%lock_interval%&, and then goes back and re-opens the file as above and tries
23876 to lock it again. This happens up to &%lock_retries%& times, after which the
23877 delivery is deferred.
23879 If the timeout has a value greater than zero, blocking calls to &[fcntl()]& or
23880 &[flock()]& are used (with the given timeout), so there has already been some
23881 waiting involved by the time locking fails. Nevertheless, Exim does not give up
23882 immediately. It retries up to
23884 (lock_retries * lock_interval) / <timeout>
23886 times (rounded up).
23889 At the end of delivery, Exim closes the file (which releases the &[fcntl()]&
23890 and/or &[flock()]& locks) and then deletes the lock file if one was created.
23893 .section "Operational details for delivery to a new file" "SECTopdir"
23894 .cindex "delivery" "to single file"
23895 .cindex "&""From""& line"
23896 When the &%directory%& option is set instead of &%file%&, each message is
23897 delivered into a newly-created file or set of files. When &(appendfile)& is
23898 activated directly from a &(redirect)& router, neither &%file%& nor
23899 &%directory%& is normally set, because the path for delivery is supplied by the
23900 router. (See for example, the &(address_file)& transport in the default
23901 configuration.) In this case, delivery is to a new file if either the path name
23902 ends in &`/`&, or the &%maildir_format%& or &%mailstore_format%& option is set.
23904 No locking is required while writing the message to a new file, so the various
23905 locking options of the transport are ignored. The &"From"& line that by default
23906 separates messages in a single file is not normally needed, nor is the escaping
23907 of message lines that start with &"From"&, and there is no need to ensure a
23908 newline at the end of each message. Consequently, the default values for
23909 &%check_string%&, &%message_prefix%&, and &%message_suffix%& are all unset when
23910 any of &%directory%&, &%maildir_format%&, or &%mailstore_format%& is set.
23912 If Exim is required to check a &%quota%& setting, it adds up the sizes of all
23913 the files in the delivery directory by default. However, you can specify a
23914 different directory by setting &%quota_directory%&. Also, for maildir
23915 deliveries (see below) the &_maildirfolder_& convention is honoured.
23918 .cindex "maildir format"
23919 .cindex "mailstore format"
23920 There are three different ways in which delivery to individual files can be
23921 done, controlled by the settings of the &%maildir_format%& and
23922 &%mailstore_format%& options. Note that code to support maildir or mailstore
23923 formats is not included in the binary unless SUPPORT_MAILDIR or
23924 SUPPORT_MAILSTORE, respectively, is set in &_Local/Makefile_&.
23926 .cindex "directory creation"
23927 In all three cases an attempt is made to create the directory and any necessary
23928 sub-directories if they do not exist, provided that the &%create_directory%&
23929 option is set (the default). The location of a created directory can be
23930 constrained by setting &%create_file%&. A created directory's mode is given by
23931 the &%directory_mode%& option. If creation fails, or if the
23932 &%create_directory%& option is not set when creation is required, delivery is
23937 .section "Maildir delivery" "SECTmaildirdelivery"
23938 .cindex "maildir format" "description of"
23939 If the &%maildir_format%& option is true, Exim delivers each message by writing
23940 it to a file whose name is &_tmp/<stime>.H<mtime>P<pid>.<host>_& in the
23941 directory that is defined by the &%directory%& option (the &"delivery
23942 directory"&). If the delivery is successful, the file is renamed into the
23943 &_new_& subdirectory.
23945 In the filename, <&'stime'&> is the current time of day in seconds, and
23946 <&'mtime'&> is the microsecond fraction of the time. After a maildir delivery,
23947 Exim checks that the time-of-day clock has moved on by at least one microsecond
23948 before terminating the delivery process. This guarantees uniqueness for the
23949 filename. However, as a precaution, Exim calls &[stat()]& for the file before
23950 opening it. If any response other than ENOENT (does not exist) is given,
23951 Exim waits 2 seconds and tries again, up to &%maildir_retries%& times.
23953 Before Exim carries out a maildir delivery, it ensures that subdirectories
23954 called &_new_&, &_cur_&, and &_tmp_& exist in the delivery directory. If they
23955 do not exist, Exim tries to create them and any superior directories in their
23956 path, subject to the &%create_directory%& and &%create_file%& options. If the
23957 &%maildirfolder_create_regex%& option is set, and the regular expression it
23958 contains matches the delivery directory, Exim also ensures that a file called
23959 &_maildirfolder_& exists in the delivery directory. If a missing directory or
23960 &_maildirfolder_& file cannot be created, delivery is deferred.
23962 These features make it possible to use Exim to create all the necessary files
23963 and directories in a maildir mailbox, including subdirectories for maildir++
23964 folders. Consider this example:
23966 maildir_format = true
23967 directory = /var/mail/$local_part_data\
23968 ${if eq{$local_part_suffix}{}{}\
23969 {/.${substr_1:$local_part_suffix}}}
23970 maildirfolder_create_regex = /\.[^/]+$
23972 If &$local_part_suffix$& is empty (there was no suffix for the local part),
23973 delivery is into a toplevel maildir with a name like &_/var/mail/pimbo_& (for
23974 the user called &'pimbo'&). The pattern in &%maildirfolder_create_regex%& does
23975 not match this name, so Exim will not look for or create the file
23976 &_/var/mail/pimbo/maildirfolder_&, though it will create
23977 &_/var/mail/pimbo/{cur,new,tmp}_& if necessary.
23979 However, if &$local_part_suffix$& contains &`-eximusers`& (for example),
23980 delivery is into the maildir++ folder &_/var/mail/pimbo/.eximusers_&, which
23981 does match &%maildirfolder_create_regex%&. In this case, Exim will create
23982 &_/var/mail/pimbo/.eximusers/maildirfolder_& as well as the three maildir
23983 directories &_/var/mail/pimbo/.eximusers/{cur,new,tmp}_&.
23985 &*Warning:*& Take care when setting &%maildirfolder_create_regex%& that it does
23986 not inadvertently match the toplevel maildir directory, because a
23987 &_maildirfolder_& file at top level would completely break quota calculations.
23989 .cindex "quota" "in maildir delivery"
23990 .cindex "maildir++"
23991 If Exim is required to check a &%quota%& setting before a maildir delivery, and
23992 &%quota_directory%& is not set, it looks for a file called &_maildirfolder_& in
23993 the maildir directory (alongside &_new_&, &_cur_&, &_tmp_&). If this exists,
23994 Exim assumes the directory is a maildir++ folder directory, which is one level
23995 down from the user's top level mailbox directory. This causes it to start at
23996 the parent directory instead of the current directory when calculating the
23997 amount of space used.
23999 One problem with delivering into a multi-file mailbox is that it is
24000 computationally expensive to compute the size of the mailbox for quota
24001 checking. Various approaches have been taken to reduce the amount of work
24002 needed. The next two sections describe two of them. A third alternative is to
24003 use some external process for maintaining the size data, and use the expansion
24004 of the &%mailbox_size%& option as a way of importing it into Exim.
24009 .section "Using tags to record message sizes" "SECID135"
24010 If &%maildir_tag%& is set, the string is expanded for each delivery.
24011 When the maildir file is renamed into the &_new_& sub-directory, the
24012 tag is added to its name. However, if adding the tag takes the length of the
24013 name to the point where the test &[stat()]& call fails with ENAMETOOLONG,
24014 the tag is dropped and the maildir file is created with no tag.
24017 .vindex "&$message_size$&"
24018 Tags can be used to encode the size of files in their names; see
24019 &%quota_size_regex%& above for an example. The expansion of &%maildir_tag%&
24020 happens after the message has been written. The value of the &$message_size$&
24021 variable is set to the number of bytes actually written. If the expansion is
24022 forced to fail, the tag is ignored, but a non-forced failure causes delivery to
24023 be deferred. The expanded tag may contain any printing characters except &"/"&.
24024 Non-printing characters in the string are ignored; if the resulting string is
24025 empty, it is ignored. If it starts with an alphanumeric character, a leading
24026 colon is inserted; this default has not proven to be the path that popular
24027 maildir implementations have chosen (but changing it in Exim would break
24028 backwards compatibility).
24030 For one common implementation, you might set:
24032 maildir_tag = ,S=${message_size}
24034 but you should check the documentation of the other software to be sure.
24036 It is advisable to also set &%quota_size_regex%& when setting &%maildir_tag%&
24037 as this allows Exim to extract the size from your tag, instead of having to
24038 &[stat()]& each message file.
24041 .section "Using a maildirsize file" "SECID136"
24042 .cindex "quota" "in maildir delivery"
24043 .cindex "maildir format" "&_maildirsize_& file"
24044 If &%maildir_use_size_file%& is true, Exim implements the maildir++ rules for
24045 storing quota and message size information in a file called &_maildirsize_&
24046 within the toplevel maildir directory. If this file does not exist, Exim
24047 creates it, setting the quota from the &%quota%& option of the transport. If
24048 the maildir directory itself does not exist, it is created before any attempt
24049 to write a &_maildirsize_& file.
24051 The &_maildirsize_& file is used to hold information about the sizes of
24052 messages in the maildir, thus speeding up quota calculations. The quota value
24053 in the file is just a cache; if the quota is changed in the transport, the new
24054 value overrides the cached value when the next message is delivered. The cache
24055 is maintained for the benefit of other programs that access the maildir and
24056 need to know the quota.
24058 If the &%quota%& option in the transport is unset or zero, the &_maildirsize_&
24059 file is maintained (with a zero quota setting), but no quota is imposed.
24061 A regular expression is available for controlling which directories in the
24062 maildir participate in quota calculations when a &_maildirsizefile_& is in use.
24063 See the description of the &%maildir_quota_directory_regex%& option above for
24067 .section "Mailstore delivery" "SECID137"
24068 .cindex "mailstore format" "description of"
24069 If the &%mailstore_format%& option is true, each message is written as two
24070 files in the given directory. A unique base name is constructed from the
24071 message id and the current delivery process, and the files that are written use
24072 this base name plus the suffixes &_.env_& and &_.msg_&. The &_.env_& file
24073 contains the message's envelope, and the &_.msg_& file contains the message
24074 itself. The base name is placed in the variable &$mailstore_basename$&.
24076 During delivery, the envelope is first written to a file with the suffix
24077 &_.tmp_&. The &_.msg_& file is then written, and when it is complete, the
24078 &_.tmp_& file is renamed as the &_.env_& file. Programs that access messages in
24079 mailstore format should wait for the presence of both a &_.msg_& and a &_.env_&
24080 file before accessing either of them. An alternative approach is to wait for
24081 the absence of a &_.tmp_& file.
24083 The envelope file starts with any text defined by the &%mailstore_prefix%&
24084 option, expanded and terminated by a newline if there isn't one. Then follows
24085 the sender address on one line, then all the recipient addresses, one per line.
24086 There can be more than one recipient only if the &%batch_max%& option is set
24087 greater than one. Finally, &%mailstore_suffix%& is expanded and the result
24088 appended to the file, followed by a newline if it does not end with one.
24090 If expansion of &%mailstore_prefix%& or &%mailstore_suffix%& ends with a forced
24091 failure, it is ignored. Other expansion errors are treated as serious
24092 configuration errors, and delivery is deferred. The variable
24093 &$mailstore_basename$& is available for use during these expansions.
24096 .section "Non-special new file delivery" "SECID138"
24097 If neither &%maildir_format%& nor &%mailstore_format%& is set, a single new
24098 file is created directly in the named directory. For example, when delivering
24099 messages into files in batched SMTP format for later delivery to some host (see
24100 section &<<SECTbatchSMTP>>&), a setting such as
24102 directory = /var/bsmtp/$host
24104 might be used. A message is written to a file with a temporary name, which is
24105 then renamed when the delivery is complete. The final name is obtained by
24106 expanding the contents of the &%directory_file%& option.
24107 .ecindex IIDapptra1
24108 .ecindex IIDapptra2
24115 . ////////////////////////////////////////////////////////////////////////////
24116 . ////////////////////////////////////////////////////////////////////////////
24118 .chapter "The autoreply transport" "CHID8"
24119 .scindex IIDauttra1 "transports" "&(autoreply)&"
24120 .scindex IIDauttra2 "&(autoreply)& transport"
24121 The &(autoreply)& transport is not a true transport in that it does not cause
24122 the message to be transmitted. Instead, it generates a new mail message as an
24123 automatic reply to the incoming message. &'References:'& and
24124 &'Auto-Submitted:'& header lines are included. These are constructed according
24125 to the rules in RFCs 2822 and 3834, respectively.
24127 If the router that passes the message to this transport does not have the
24128 &%unseen%& option set, the original message (for the current recipient) is not
24129 delivered anywhere. However, when the &%unseen%& option is set on the router
24130 that passes the message to this transport, routing of the address continues, so
24131 another router can set up a normal message delivery.
24134 The &(autoreply)& transport is usually run as the result of mail filtering, a
24135 &"vacation"& message being the standard example. However, it can also be run
24136 directly from a router like any other transport. To reduce the possibility of
24137 message cascades, messages created by the &(autoreply)& transport always have
24138 empty envelope sender addresses, like bounce messages.
24140 The parameters of the message to be sent can be specified in the configuration
24141 by options described below. However, these are used only when the address
24142 passed to the transport does not contain its own reply information. When the
24143 transport is run as a consequence of a
24145 or &%vacation%& command in a filter file, the parameters of the message are
24146 supplied by the filter, and passed with the address. The transport's options
24147 that define the message are then ignored (so they are not usually set in this
24148 case). The message is specified entirely by the filter or by the transport; it
24149 is never built from a mixture of options. However, the &%file_optional%&,
24150 &%mode%&, and &%return_message%& options apply in all cases.
24152 &(Autoreply)& is implemented as a local transport. When used as a result of a
24153 command in a user's filter file, &(autoreply)& normally runs under the uid and
24154 gid of the user, and with appropriate current and home directories (see chapter
24155 &<<CHAPenvironment>>&).
24157 There is a subtle difference between routing a message to a &(pipe)& transport
24158 that generates some text to be returned to the sender, and routing it to an
24159 &(autoreply)& transport. This difference is noticeable only if more than one
24160 address from the same message is so handled. In the case of a pipe, the
24161 separate outputs from the different addresses are gathered up and returned to
24162 the sender in a single message, whereas if &(autoreply)& is used, a separate
24163 message is generated for each address that is passed to it.
24165 Non-printing characters are not permitted in the header lines generated for the
24166 message that &(autoreply)& creates, with the exception of newlines that are
24167 immediately followed by white space. If any non-printing characters are found,
24168 the transport defers.
24169 Whether characters with the top bit set count as printing characters or not is
24170 controlled by the &%print_topbitchars%& global option.
24172 If any of the generic options for manipulating headers (for example,
24173 &%headers_add%&) are set on an &(autoreply)& transport, they apply to the copy
24174 of the original message that is included in the generated message when
24175 &%return_message%& is set. They do not apply to the generated message itself.
24177 .vindex "&$sender_address$&"
24178 If the &(autoreply)& transport receives return code 2 from Exim when it submits
24179 the message, indicating that there were no recipients, it does not treat this
24180 as an error. This means that autoreplies sent to &$sender_address$& when this
24181 is empty (because the incoming message is a bounce message) do not cause
24182 problems. They are just discarded.
24186 .section "Private options for autoreply" "SECID139"
24187 .cindex "options" "&(autoreply)& transport"
24189 .option bcc autoreply string&!! unset
24190 This specifies the addresses that are to receive &"blind carbon copies"& of the
24191 message when the message is specified by the transport.
24194 .option cc autoreply string&!! unset
24195 This specifies recipients of the message and the contents of the &'Cc:'& header
24196 when the message is specified by the transport.
24199 .option file autoreply string&!! unset
24200 The contents of the file are sent as the body of the message when the message
24201 is specified by the transport. If both &%file%& and &%text%& are set, the text
24202 string comes first.
24205 .option file_expand autoreply boolean false
24206 If this is set, the contents of the file named by the &%file%& option are
24207 subjected to string expansion as they are added to the message.
24210 .option file_optional autoreply boolean false
24211 If this option is true, no error is generated if the file named by the &%file%&
24212 option or passed with the address does not exist or cannot be read.
24215 .option from autoreply string&!! unset
24216 This specifies the contents of the &'From:'& header when the message is
24217 specified by the transport.
24220 .option headers autoreply string&!! unset
24221 This specifies additional RFC 2822 headers that are to be added to the message
24222 when the message is specified by the transport. Several can be given by using
24223 &"\n"& to separate them. There is no check on the format.
24226 .option log autoreply string&!! unset
24227 This option names a file in which a record of every message sent is logged when
24228 the message is specified by the transport.
24231 .option mode autoreply "octal integer" 0600
24232 If either the log file or the &"once"& file has to be created, this mode is
24236 .option never_mail autoreply "address list&!!" unset
24237 If any run of the transport creates a message with a recipient that matches any
24238 item in the list, that recipient is quietly discarded. If all recipients are
24239 discarded, no message is created. This applies both when the recipients are
24240 generated by a filter and when they are specified in the transport.
24244 .option once autoreply string&!! unset
24245 This option names a file or DBM database in which a record of each &'To:'&
24246 recipient is kept when the message is specified by the transport. &*Note*&:
24247 This does not apply to &'Cc:'& or &'Bcc:'& recipients.
24249 If &%once%& is unset, or is set to an empty string, the message is always sent.
24250 By default, if &%once%& is set to a non-empty filename, the message
24251 is not sent if a potential recipient is already listed in the database.
24252 However, if the &%once_repeat%& option specifies a time greater than zero, the
24253 message is sent if that much time has elapsed since a message was last sent to
24254 this recipient. A setting of zero time for &%once_repeat%& (the default)
24255 prevents a message from being sent a second time &-- in this case, zero means
24258 If &%once_file_size%& is zero, a DBM database is used to remember recipients,
24259 and it is allowed to grow as large as necessary. If &%once_file_size%& is set
24260 greater than zero, it changes the way Exim implements the &%once%& option.
24261 Instead of using a DBM file to record every recipient it sends to, it uses a
24262 regular file, whose size will never get larger than the given value.
24264 In the file, Exim keeps a linear list of recipient addresses and the times at
24265 which they were sent messages. If the file is full when a new address needs to
24266 be added, the oldest address is dropped. If &%once_repeat%& is not set, this
24267 means that a given recipient may receive multiple messages, but at
24268 unpredictable intervals that depend on the rate of turnover of addresses in the
24269 file. If &%once_repeat%& is set, it specifies a maximum time between repeats.
24272 .option once_file_size autoreply integer 0
24273 See &%once%& above.
24276 .option once_repeat autoreply time&!! 0s
24277 See &%once%& above.
24278 After expansion, the value of this option must be a valid time value.
24281 .option reply_to autoreply string&!! unset
24282 This specifies the contents of the &'Reply-To:'& header when the message is
24283 specified by the transport.
24286 .option return_message autoreply boolean false
24287 If this is set, a copy of the original message is returned with the new
24288 message, subject to the maximum size set in the &%return_size_limit%& global
24289 configuration option.
24292 .option subject autoreply string&!! unset
24293 This specifies the contents of the &'Subject:'& header when the message is
24294 specified by the transport. It is tempting to quote the original subject in
24295 automatic responses. For example:
24297 subject = Re: $h_subject:
24299 There is a danger in doing this, however. It may allow a third party to
24300 subscribe your users to an opt-in mailing list, provided that the list accepts
24301 bounce messages as subscription confirmations. Well-managed lists require a
24302 non-bounce message to confirm a subscription, so the danger is relatively
24307 .option text autoreply string&!! unset
24308 This specifies a single string to be used as the body of the message when the
24309 message is specified by the transport. If both &%text%& and &%file%& are set,
24310 the text comes first.
24313 .option to autoreply string&!! unset
24314 This specifies recipients of the message and the contents of the &'To:'& header
24315 when the message is specified by the transport.
24316 .ecindex IIDauttra1
24317 .ecindex IIDauttra2
24322 . ////////////////////////////////////////////////////////////////////////////
24323 . ////////////////////////////////////////////////////////////////////////////
24325 .chapter "The lmtp transport" "CHAPLMTP"
24326 .cindex "transports" "&(lmtp)&"
24327 .cindex "&(lmtp)& transport"
24328 .cindex "LMTP" "over a pipe"
24329 .cindex "LMTP" "over a socket"
24330 The &(lmtp)& transport runs the LMTP protocol (RFC 2033) over a pipe to a
24332 or by interacting with a Unix domain socket.
24333 This transport is something of a cross between the &(pipe)& and &(smtp)&
24334 transports. Exim also has support for using LMTP over TCP/IP; this is
24335 implemented as an option for the &(smtp)& transport. Because LMTP is expected
24336 to be of minority interest, the default build-time configure in &_src/EDITME_&
24337 has it commented out. You need to ensure that
24341 .cindex "options" "&(lmtp)& transport"
24342 is present in your &_Local/Makefile_& in order to have the &(lmtp)& transport
24343 included in the Exim binary. The private options of the &(lmtp)& transport are
24346 .option batch_id lmtp string&!! unset
24347 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
24350 .option batch_max lmtp integer 1
24351 This limits the number of addresses that can be handled in a single delivery.
24352 Most LMTP servers can handle several addresses at once, so it is normally a
24353 good idea to increase this value. See the description of local delivery
24354 batching in chapter &<<CHAPbatching>>&.
24357 .option command lmtp string&!! unset
24358 This option must be set if &%socket%& is not set. The string is a command which
24359 is run in a separate process. It is split up into a command name and list of
24360 arguments, each of which is separately expanded (so expansion cannot change the
24361 number of arguments). The command is run directly, not via a shell. The message
24362 is passed to the new process using the standard input and output to operate the
24365 .option ignore_quota lmtp boolean false
24366 .cindex "LMTP" "ignoring quota errors"
24367 If this option is set true, the string &`IGNOREQUOTA`& is added to RCPT
24368 commands, provided that the LMTP server has advertised support for IGNOREQUOTA
24369 in its response to the LHLO command.
24371 .option socket lmtp string&!! unset
24372 This option must be set if &%command%& is not set. The result of expansion must
24373 be the name of a Unix domain socket. The transport connects to the socket and
24374 delivers the message to it using the LMTP protocol.
24377 .option timeout lmtp time 5m
24378 The transport is aborted if the created process or Unix domain socket does not
24379 respond to LMTP commands or message input within this timeout. Delivery
24380 is deferred, and will be tried again later. Here is an example of a typical
24385 command = /some/local/lmtp/delivery/program
24389 This delivers up to 20 addresses at a time, in a mixture of domains if
24390 necessary, running as the user &'exim'&.
24394 . ////////////////////////////////////////////////////////////////////////////
24395 . ////////////////////////////////////////////////////////////////////////////
24397 .chapter "The pipe transport" "CHAPpipetransport"
24398 .scindex IIDpiptra1 "transports" "&(pipe)&"
24399 .scindex IIDpiptra2 "&(pipe)& transport"
24400 The &(pipe)& transport is used to deliver messages via a pipe to a command
24401 running in another process. One example is the use of &(pipe)& as a
24402 pseudo-remote transport for passing messages to some other delivery mechanism
24403 (such as UUCP). Another is the use by individual users to automatically process
24404 their incoming messages. The &(pipe)& transport can be used in one of the
24408 .vindex "&$local_part$&"
24409 A router routes one address to a transport in the normal way, and the
24410 transport is configured as a &(pipe)& transport. In this case, &$local_part$&
24411 contains the local part of the address (as usual), and the command that is run
24412 is specified by the &%command%& option on the transport.
24414 .vindex "&$pipe_addresses$&"
24415 If the &%batch_max%& option is set greater than 1 (the default is 1), the
24416 transport can handle more than one address in a single run. In this case, when
24417 more than one address is routed to the transport, &$local_part$& is not set
24418 (because it is not unique). However, the pseudo-variable &$pipe_addresses$&
24419 (described in section &<<SECThowcommandrun>>& below) contains all the addresses
24420 that are routed to the transport.
24422 .vindex "&$address_pipe$&"
24423 A router redirects an address directly to a pipe command (for example, from an
24424 alias or forward file). In this case, &$address_pipe$& contains the text of the
24425 pipe command, and the &%command%& option on the transport is ignored unless
24426 &%force_command%& is set. If only one address is being transported
24427 (&%batch_max%& is not greater than one, or only one address was redirected to
24428 this pipe command), &$local_part$& contains the local part that was redirected.
24432 The &(pipe)& transport is a non-interactive delivery method. Exim can also
24433 deliver messages over pipes using the LMTP interactive protocol. This is
24434 implemented by the &(lmtp)& transport.
24436 In the case when &(pipe)& is run as a consequence of an entry in a local user's
24437 &_.forward_& file, the command runs under the uid and gid of that user. In
24438 other cases, the uid and gid have to be specified explicitly, either on the
24439 transport or on the router that handles the address. Current and &"home"&
24440 directories are also controllable. See chapter &<<CHAPenvironment>>& for
24441 details of the local delivery environment and chapter &<<CHAPbatching>>&
24442 for a discussion of local delivery batching.
24444 .cindex "tainted data" "in pipe command"
24445 .cindex pipe "tainted data"
24446 Tainted data may not be used for the command name.
24449 .section "Concurrent delivery" "SECID140"
24450 If two messages arrive at almost the same time, and both are routed to a pipe
24451 delivery, the two pipe transports may be run concurrently. You must ensure that
24452 any pipe commands you set up are robust against this happening. If the commands
24453 write to a file, the &%exim_lock%& utility might be of use.
24454 Alternatively the &%max_parallel%& option could be used with a value
24455 of "1" to enforce serialization.
24460 .section "Returned status and data" "SECID141"
24461 .cindex "&(pipe)& transport" "returned data"
24462 If the command exits with a non-zero return code, the delivery is deemed to
24463 have failed, unless either the &%ignore_status%& option is set (in which case
24464 the return code is treated as zero), or the return code is one of those listed
24465 in the &%temp_errors%& option, which are interpreted as meaning &"try again
24466 later"&. In this case, delivery is deferred. Details of a permanent failure are
24467 logged, but are not included in the bounce message, which merely contains
24468 &"local delivery failed"&.
24470 If the command exits on a signal and the &%freeze_signal%& option is set then
24471 the message will be frozen in the queue. If that option is not set, a bounce
24472 will be sent as normal.
24474 If the return code is greater than 128 and the command being run is a shell
24475 script, it normally means that the script was terminated by a signal whose
24476 value is the return code minus 128. The &%freeze_signal%& option does not
24477 apply in this case.
24479 If Exim is unable to run the command (that is, if &[execve()]& fails), the
24480 return code is set to 127. This is the value that a shell returns if it is
24481 asked to run a non-existent command. The wording for the log line suggests that
24482 a non-existent command may be the problem.
24484 The &%return_output%& option can affect the result of a pipe delivery. If it is
24485 set and the command produces any output on its standard output or standard
24486 error streams, the command is considered to have failed, even if it gave a zero
24487 return code or if &%ignore_status%& is set. The output from the command is
24488 included as part of the bounce message. The &%return_fail_output%& option is
24489 similar, except that output is returned only when the command exits with a
24490 failure return code, that is, a value other than zero or a code that matches
24495 .section "How the command is run" "SECThowcommandrun"
24496 .cindex "&(pipe)& transport" "path for command"
24497 The command line is (by default) broken down into a command name and arguments
24498 by the &(pipe)& transport itself. The &%allow_commands%& and
24499 &%restrict_to_path%& options can be used to restrict the commands that may be
24502 .cindex "quoting" "in pipe command"
24503 Unquoted arguments are delimited by white space. If an argument appears in
24504 double quotes, backslash is interpreted as an escape character in the usual
24505 way. If an argument appears in single quotes, no escaping is done.
24507 String expansion is applied to the command line except when it comes from a
24508 traditional &_.forward_& file (commands from a filter file are expanded). The
24509 expansion is applied to each argument in turn rather than to the whole line.
24510 For this reason, any string expansion item that contains white space must be
24511 quoted so as to be contained within a single argument. A setting such as
24513 command = /some/path ${if eq{$local_part}{postmaster}{xx}{yy}}
24515 will not work, because the expansion item gets split between several
24516 arguments. You have to write
24518 command = /some/path "${if eq{$local_part}{postmaster}{xx}{yy}}"
24520 to ensure that it is all in one argument. The expansion is done in this way,
24521 argument by argument, so that the number of arguments cannot be changed as a
24522 result of expansion, and quotes or backslashes in inserted variables do not
24523 interact with external quoting. However, this leads to problems if you want to
24524 generate multiple arguments (or the command name plus arguments) from a single
24525 expansion. In this situation, the simplest solution is to use a shell. For
24528 command = /bin/sh -c ${lookup{$local_part}lsearch{/some/file}}
24531 .cindex "transport" "filter"
24532 .cindex "filter" "transport filter"
24533 .vindex "&$pipe_addresses$&"
24534 Special handling takes place when an argument consists of precisely the text
24535 &`$pipe_addresses`& (no quotes).
24536 This is not a general expansion variable; the only
24537 place this string is recognized is when it appears as an argument for a pipe or
24538 transport filter command. It causes each address that is being handled to be
24539 inserted in the argument list at that point &'as a separate argument'&. This
24540 avoids any problems with spaces or shell metacharacters, and is of use when a
24541 &(pipe)& transport is handling groups of addresses in a batch.
24543 If &%force_command%& is enabled on the transport, special handling takes place
24544 for an argument that consists of precisely the text &`$address_pipe`&. It
24545 is handled similarly to &$pipe_addresses$& above. It is expanded and each
24546 argument is inserted in the argument list at that point
24547 &'as a separate argument'&. The &`$address_pipe`& item does not need to be
24548 the only item in the argument; in fact, if it were then &%force_command%&
24549 should behave as a no-op. Rather, it should be used to adjust the command
24550 run while preserving the argument vector separation.
24552 After splitting up into arguments and expansion, the resulting command is run
24553 in a subprocess directly from the transport, &'not'& under a shell. The
24554 message that is being delivered is supplied on the standard input, and the
24555 standard output and standard error are both connected to a single pipe that is
24556 read by Exim. The &%max_output%& option controls how much output the command
24557 may produce, and the &%return_output%& and &%return_fail_output%& options
24558 control what is done with it.
24560 Not running the command under a shell (by default) lessens the security risks
24561 in cases when a command from a user's filter file is built out of data that was
24562 taken from an incoming message. If a shell is required, it can of course be
24563 explicitly specified as the command to be run. However, there are circumstances
24564 where existing commands (for example, in &_.forward_& files) expect to be run
24565 under a shell and cannot easily be modified. To allow for these cases, there is
24566 an option called &%use_shell%&, which changes the way the &(pipe)& transport
24567 works. Instead of breaking up the command line as just described, it expands it
24568 as a single string and passes the result to &_/bin/sh_&. The
24569 &%restrict_to_path%& option and the &$pipe_addresses$& facility cannot be used
24570 with &%use_shell%&, and the whole mechanism is inherently less secure.
24574 .section "Environment variables" "SECTpipeenv"
24575 .cindex "&(pipe)& transport" "environment for command"
24576 .cindex "environment" "&(pipe)& transport"
24577 The environment variables listed below are set up when the command is invoked.
24578 This list is a compromise for maximum compatibility with other MTAs. Note that
24579 the &%environment%& option can be used to add additional variables to this
24580 environment. The environment for the &(pipe)& transport is not subject
24581 to the &%add_environment%& and &%keep_environment%& main config options.
24582 &*Note*&: Using enviroment variables loses track of tainted data.
24583 Writers of &(pipe)& transport commands should be wary of data supplied
24584 by potential attackers.
24586 &`DOMAIN `& the domain of the address
24587 &`HOME `& the home directory, if set
24588 &`HOST `& the host name when called from a router (see below)
24589 &`LOCAL_PART `& see below
24590 &`LOCAL_PART_PREFIX `& see below
24591 &`LOCAL_PART_SUFFIX `& see below
24592 &`LOGNAME `& see below
24593 &`MESSAGE_ID `& Exim's local ID for the message
24594 &`PATH `& as specified by the &%path%& option below
24595 &`QUALIFY_DOMAIN `& the sender qualification domain
24596 &`RECIPIENT `& the complete recipient address
24597 &`SENDER `& the sender of the message (empty if a bounce)
24598 &`SHELL `& &`/bin/sh`&
24599 &`TZ `& the value of the &%timezone%& option, if set
24600 &`USER `& see below
24602 When a &(pipe)& transport is called directly from (for example) an &(accept)&
24603 router, LOCAL_PART is set to the local part of the address. When it is
24604 called as a result of a forward or alias expansion, LOCAL_PART is set to
24605 the local part of the address that was expanded. In both cases, any affixes are
24606 removed from the local part, and made available in LOCAL_PART_PREFIX and
24607 LOCAL_PART_SUFFIX, respectively. LOGNAME and USER are set to the
24608 same value as LOCAL_PART for compatibility with other MTAs.
24611 HOST is set only when a &(pipe)& transport is called from a router that
24612 associates hosts with an address, typically when using &(pipe)& as a
24613 pseudo-remote transport. HOST is set to the first host name specified by
24617 If the transport's generic &%home_directory%& option is set, its value is used
24618 for the HOME environment variable. Otherwise, a home directory may be set
24619 by the router's &%transport_home_directory%& option, which defaults to the
24620 user's home directory if &%check_local_user%& is set.
24623 .section "Private options for pipe" "SECID142"
24624 .cindex "options" "&(pipe)& transport"
24628 .option allow_commands pipe "string list&!!" unset
24629 .cindex "&(pipe)& transport" "permitted commands"
24630 The string is expanded, and is then interpreted as a colon-separated list of
24631 permitted commands. If &%restrict_to_path%& is not set, the only commands
24632 permitted are those in the &%allow_commands%& list. They need not be absolute
24633 paths; the &%path%& option is still used for relative paths. If
24634 &%restrict_to_path%& is set with &%allow_commands%&, the command must either be
24635 in the &%allow_commands%& list, or a name without any slashes that is found on
24636 the path. In other words, if neither &%allow_commands%& nor
24637 &%restrict_to_path%& is set, there is no restriction on the command, but
24638 otherwise only commands that are permitted by one or the other are allowed. For
24641 allow_commands = /usr/bin/vacation
24643 and &%restrict_to_path%& is not set, the only permitted command is
24644 &_/usr/bin/vacation_&. The &%allow_commands%& option may not be set if
24645 &%use_shell%& is set.
24648 .option batch_id pipe string&!! unset
24649 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
24652 .option batch_max pipe integer 1
24653 This limits the number of addresses that can be handled in a single delivery.
24654 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
24657 .option check_string pipe string unset
24658 As &(pipe)& writes the message, the start of each line is tested for matching
24659 &%check_string%&, and if it does, the initial matching characters are replaced
24660 by the contents of &%escape_string%&, provided both are set. The value of
24661 &%check_string%& is a literal string, not a regular expression, and the case of
24662 any letters it contains is significant. When &%use_bsmtp%& is set, the contents
24663 of &%check_string%& and &%escape_string%& are forced to values that implement
24664 the SMTP escaping protocol. Any settings made in the configuration file are
24668 .option command pipe string&!! unset
24669 This option need not be set when &(pipe)& is being used to deliver to pipes
24670 obtained directly from address redirections. In other cases, the option must be
24671 set, to provide a command to be run. It need not yield an absolute path (see
24672 the &%path%& option below). The command is split up into separate arguments by
24673 Exim, and each argument is separately expanded, as described in section
24674 &<<SECThowcommandrun>>& above.
24676 .cindex "tainted data"
24677 No part of the resulting command may be tainted.
24680 .option environment pipe string&!! unset
24681 .cindex "&(pipe)& transport" "environment for command"
24682 .cindex "environment" "&(pipe)& transport"
24683 This option is used to add additional variables to the environment in which the
24684 command runs (see section &<<SECTpipeenv>>& for the default list). Its value is
24685 a string which is expanded, and then interpreted as a colon-separated list of
24686 environment settings of the form <&'name'&>=<&'value'&>.
24689 .option escape_string pipe string unset
24690 See &%check_string%& above.
24693 .option freeze_exec_fail pipe boolean false
24694 .cindex "exec failure"
24695 .cindex "failure of exec"
24696 .cindex "&(pipe)& transport" "failure of exec"
24697 Failure to exec the command in a pipe transport is by default treated like
24698 any other failure while running the command. However, if &%freeze_exec_fail%&
24699 is set, failure to exec is treated specially, and causes the message to be
24700 frozen, whatever the setting of &%ignore_status%&.
24703 .option freeze_signal pipe boolean false
24704 .cindex "signal exit"
24705 .cindex "&(pipe)& transport", "signal exit"
24706 Normally if the process run by a command in a pipe transport exits on a signal,
24707 a bounce message is sent. If &%freeze_signal%& is set, the message will be
24708 frozen in Exim's queue instead.
24711 .option force_command pipe boolean false
24712 .cindex "force command"
24713 .cindex "&(pipe)& transport", "force command"
24714 Normally when a router redirects an address directly to a pipe command
24715 the &%command%& option on the transport is ignored. If &%force_command%&
24716 is set, the &%command%& option will used. This is especially
24717 useful for forcing a wrapper or additional argument to be added to the
24718 command. For example:
24720 command = /usr/bin/remote_exec myhost -- $address_pipe
24724 Note that &$address_pipe$& is handled specially in &%command%& when
24725 &%force_command%& is set, expanding out to the original argument vector as
24726 separate items, similarly to a Unix shell &`"$@"`& construct.
24729 .option ignore_status pipe boolean false
24730 If this option is true, the status returned by the subprocess that is set up to
24731 run the command is ignored, and Exim behaves as if zero had been returned.
24732 Otherwise, a non-zero status or termination by signal causes an error return
24733 from the transport unless the status value is one of those listed in
24734 &%temp_errors%&; these cause the delivery to be deferred and tried again later.
24736 &*Note*&: This option does not apply to timeouts, which do not return a status.
24737 See the &%timeout_defer%& option for how timeouts are handled.
24740 .option log_defer_output pipe boolean false
24741 .cindex "&(pipe)& transport" "logging output"
24742 If this option is set, and the status returned by the command is
24743 one of the codes listed in &%temp_errors%& (that is, delivery was deferred),
24744 and any output was produced on stdout or stderr, the first line of it is
24745 written to the main log.
24748 .option log_fail_output pipe boolean false
24749 If this option is set, and the command returns any output on stdout or
24750 stderr, and also ends with a return code that is neither zero nor one of
24751 the return codes listed in &%temp_errors%& (that is, the delivery
24752 failed), the first line of output is written to the main log. This
24753 option and &%log_output%& are mutually exclusive. Only one of them may
24757 .option log_output pipe boolean false
24758 If this option is set and the command returns any output on stdout or
24759 stderr, the first line of output is written to the main log, whatever
24760 the return code. This option and &%log_fail_output%& are mutually
24761 exclusive. Only one of them may be set.
24764 .option max_output pipe integer 20K
24765 This specifies the maximum amount of output that the command may produce on its
24766 standard output and standard error file combined. If the limit is exceeded, the
24767 process running the command is killed. This is intended as a safety measure to
24768 catch runaway processes. The limit is applied independently of the settings of
24769 the options that control what is done with such output (for example,
24770 &%return_output%&). Because of buffering effects, the amount of output may
24771 exceed the limit by a small amount before Exim notices.
24774 .option message_prefix pipe string&!! "see below"
24775 The string specified here is expanded and output at the start of every message.
24776 The default is unset if &%use_bsmtp%& is set. Otherwise it is
24779 From ${if def:return_path{$return_path}{MAILER-DAEMON}}\
24783 .cindex "&%tmail%&"
24784 .cindex "&""From""& line"
24785 This is required by the commonly used &_/usr/bin/vacation_& program.
24786 However, it must &'not'& be present if delivery is to the Cyrus IMAP server,
24787 or to the &%tmail%& local delivery agent. The prefix can be suppressed by
24792 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
24793 &`\n`& to &`\r\n`& in &%message_prefix%&.
24796 .option message_suffix pipe string&!! "see below"
24797 The string specified here is expanded and output at the end of every message.
24798 The default is unset if &%use_bsmtp%& is set. Otherwise it is a single newline.
24799 The suffix can be suppressed by setting
24803 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
24804 &`\n`& to &`\r\n`& in &%message_suffix%&.
24807 .option path pipe string&!! "/bin:/usr/bin"
24808 This option is expanded and
24809 specifies the string that is set up in the PATH environment
24810 variable of the subprocess.
24811 If the &%command%& option does not yield an absolute path name, the command is
24812 sought in the PATH directories, in the usual way. &*Warning*&: This does not
24813 apply to a command specified as a transport filter.
24816 .option permit_coredump pipe boolean false
24817 Normally Exim inhibits core-dumps during delivery. If you have a need to get
24818 a core-dump of a pipe command, enable this command. This enables core-dumps
24819 during delivery and affects both the Exim binary and the pipe command run.
24820 It is recommended that this option remain off unless and until you have a need
24821 for it and that this only be enabled when needed, as the risk of excessive
24822 resource consumption can be quite high. Note also that Exim is typically
24823 installed as a setuid binary and most operating systems will inhibit coredumps
24824 of these by default, so further OS-specific action may be required.
24827 .option pipe_as_creator pipe boolean false
24828 .cindex "uid (user id)" "local delivery"
24829 If the generic &%user%& option is not set and this option is true, the delivery
24830 process is run under the uid that was in force when Exim was originally called
24831 to accept the message. If the group id is not otherwise set (via the generic
24832 &%group%& option), the gid that was in force when Exim was originally called to
24833 accept the message is used.
24836 .option restrict_to_path pipe boolean false
24837 When this option is set, any command name not listed in &%allow_commands%& must
24838 contain no slashes. The command is searched for only in the directories listed
24839 in the &%path%& option. This option is intended for use in the case when a pipe
24840 command has been generated from a user's &_.forward_& file. This is usually
24841 handled by a &(pipe)& transport called &%address_pipe%&.
24844 .option return_fail_output pipe boolean false
24845 If this option is true, and the command produced any output and ended with a
24846 return code other than zero or one of the codes listed in &%temp_errors%& (that
24847 is, the delivery failed), the output is returned in the bounce message.
24848 However, if the message has a null sender (that is, it is itself a bounce
24849 message), output from the command is discarded. This option and
24850 &%return_output%& are mutually exclusive. Only one of them may be set.
24854 .option return_output pipe boolean false
24855 If this option is true, and the command produced any output, the delivery is
24856 deemed to have failed whatever the return code from the command, and the output
24857 is returned in the bounce message. Otherwise, the output is just discarded.
24858 However, if the message has a null sender (that is, it is a bounce message),
24859 output from the command is always discarded, whatever the setting of this
24860 option. This option and &%return_fail_output%& are mutually exclusive. Only one
24861 of them may be set.
24865 .option temp_errors pipe "string list" "see below"
24866 .cindex "&(pipe)& transport" "temporary failure"
24867 This option contains either a colon-separated list of numbers, or a single
24868 asterisk. If &%ignore_status%& is false
24869 and &%return_output%& is not set,
24870 and the command exits with a non-zero return code, the failure is treated as
24871 temporary and the delivery is deferred if the return code matches one of the
24872 numbers, or if the setting is a single asterisk. Otherwise, non-zero return
24873 codes are treated as permanent errors. The default setting contains the codes
24874 defined by EX_TEMPFAIL and EX_CANTCREAT in &_sysexits.h_&. If Exim is
24875 compiled on a system that does not define these macros, it assumes values of 75
24876 and 73, respectively.
24879 .option timeout pipe time 1h
24880 If the command fails to complete within this time, it is killed. This normally
24881 causes the delivery to fail (but see &%timeout_defer%&). A zero time interval
24882 specifies no timeout. In order to ensure that any subprocesses created by the
24883 command are also killed, Exim makes the initial process a process group leader,
24884 and kills the whole process group on a timeout. However, this can be defeated
24885 if one of the processes starts a new process group.
24887 .option timeout_defer pipe boolean false
24888 A timeout in a &(pipe)& transport, either in the command that the transport
24889 runs, or in a transport filter that is associated with it, is by default
24890 treated as a hard error, and the delivery fails. However, if &%timeout_defer%&
24891 is set true, both kinds of timeout become temporary errors, causing the
24892 delivery to be deferred.
24894 .option umask pipe "octal integer" 022
24895 This specifies the umask setting for the subprocess that runs the command.
24898 .option use_bsmtp pipe boolean false
24899 .cindex "envelope sender"
24900 If this option is set true, the &(pipe)& transport writes messages in &"batch
24901 SMTP"& format, with the envelope sender and recipient(s) included as SMTP
24902 commands. If you want to include a leading HELO command with such messages,
24903 you can do so by setting the &%message_prefix%& option. See section
24904 &<<SECTbatchSMTP>>& for details of batch SMTP.
24906 .option use_classresources pipe boolean false
24907 .cindex "class resources (BSD)"
24908 This option is available only when Exim is running on FreeBSD, NetBSD, or
24909 BSD/OS. If it is set true, the &[setclassresources()]& function is used to set
24910 resource limits when a &(pipe)& transport is run to perform a delivery. The
24911 limits for the uid under which the pipe is to run are obtained from the login
24915 .option use_crlf pipe boolean false
24916 .cindex "carriage return"
24918 This option causes lines to be terminated with the two-character CRLF sequence
24919 (carriage return, linefeed) instead of just a linefeed character. In the case
24920 of batched SMTP, the byte sequence written to the pipe is then an exact image
24921 of what would be sent down a real SMTP connection.
24923 The contents of the &%message_prefix%& and &%message_suffix%& options are
24924 written verbatim, so must contain their own carriage return characters if these
24925 are needed. When &%use_bsmtp%& is not set, the default values for both
24926 &%message_prefix%& and &%message_suffix%& end with a single linefeed, so their
24927 values must be changed to end with &`\r\n`& if &%use_crlf%& is set.
24930 .option use_shell pipe boolean false
24931 .vindex "&$pipe_addresses$&"
24932 If this option is set, it causes the command to be passed to &_/bin/sh_&
24933 instead of being run directly from the transport, as described in section
24934 &<<SECThowcommandrun>>&. This is less secure, but is needed in some situations
24935 where the command is expected to be run under a shell and cannot easily be
24936 modified. The &%allow_commands%& and &%restrict_to_path%& options, and the
24937 &`$pipe_addresses`& facility are incompatible with &%use_shell%&. The
24938 command is expanded as a single string, and handed to &_/bin/sh_& as data for
24943 .section "Using an external local delivery agent" "SECID143"
24944 .cindex "local delivery" "using an external agent"
24945 .cindex "&'procmail'&"
24946 .cindex "external local delivery"
24947 .cindex "delivery" "&'procmail'&"
24948 .cindex "delivery" "by external agent"
24949 The &(pipe)& transport can be used to pass all messages that require local
24950 delivery to a separate local delivery agent such as &%procmail%&. When doing
24951 this, care must be taken to ensure that the pipe is run under an appropriate
24952 uid and gid. In some configurations one wants this to be a uid that is trusted
24953 by the delivery agent to supply the correct sender of the message. It may be
24954 necessary to recompile or reconfigure the delivery agent so that it trusts an
24955 appropriate user. The following is an example transport and router
24956 configuration for &%procmail%&:
24961 command = /usr/local/bin/procmail -d $local_part_data
24965 check_string = "From "
24966 escape_string = ">From "
24968 user = $local_part_data
24975 transport = procmail_pipe
24977 In this example, the pipe is run as the local user, but with the group set to
24978 &'mail'&. An alternative is to run the pipe as a specific user such as &'mail'&
24979 or &'exim'&, but in this case you must arrange for &%procmail%& to trust that
24980 user to supply a correct sender address. If you do not specify either a
24981 &%group%& or a &%user%& option, the pipe command is run as the local user. The
24982 home directory is the user's home directory by default.
24984 &*Note*&: The command that the pipe transport runs does &'not'& begin with
24988 as shown in some &%procmail%& documentation, because Exim does not by default
24989 use a shell to run pipe commands.
24992 The next example shows a transport and a router for a system where local
24993 deliveries are handled by the Cyrus IMAP server.
24994 . Used to have R: local_part_suffix = .* + T: -m $local_part_suffix_v
24995 . but that suffix is tainted so cannot be used in a command arg
24996 . Really, you'd want to use a lookup for acceptable suffixes to do real detainting
24999 local_delivery_cyrus:
25001 command = /usr/cyrus/bin/deliver \
25002 -- $local_part_data
25014 transport = local_delivery_cyrus
25016 Note the unsetting of &%message_prefix%& and &%message_suffix%&, and the use of
25017 &%return_output%& to cause any text written by Cyrus to be returned to the
25019 .ecindex IIDpiptra1
25020 .ecindex IIDpiptra2
25023 . ////////////////////////////////////////////////////////////////////////////
25024 . ////////////////////////////////////////////////////////////////////////////
25026 .chapter "The smtp transport" "CHAPsmtptrans"
25027 .scindex IIDsmttra1 "transports" "&(smtp)&"
25028 .scindex IIDsmttra2 "&(smtp)& transport"
25029 The &(smtp)& transport delivers messages over TCP/IP connections using the SMTP
25030 or LMTP protocol. The list of hosts to try can either be taken from the address
25031 that is being processed (having been set up by the router), or specified
25032 explicitly for the transport. Timeout and retry processing (see chapter
25033 &<<CHAPretry>>&) is applied to each IP address independently.
25036 .section "Multiple messages on a single connection" "SECID144"
25037 The sending of multiple messages over a single TCP/IP connection can arise in
25041 If a message contains more than &%max_rcpt%& (see below) addresses that are
25042 routed to the same host, more than one copy of the message has to be sent to
25043 that host. In this situation, multiple copies may be sent in a single run of
25044 the &(smtp)& transport over a single TCP/IP connection. (What Exim actually
25045 does when it has too many addresses to send in one message also depends on the
25046 value of the global &%remote_max_parallel%& option. Details are given in
25047 section &<<SECToutSMTPTCP>>&.)
25049 .cindex "hints database" "remembering routing"
25050 When a message has been successfully delivered over a TCP/IP connection, Exim
25051 looks in its hints database to see if there are any other messages awaiting a
25052 connection to the same host. If there are, a new delivery process is started
25053 for one of them, and the current TCP/IP connection is passed on to it. The new
25054 process may in turn send multiple copies and possibly create yet another
25059 For each copy sent over the same TCP/IP connection, a sequence counter is
25060 incremented, and if it ever gets to the value of &%connection_max_messages%&,
25061 no further messages are sent over that connection.
25065 .section "Use of the $host and $host_address variables" "SECID145"
25067 .vindex "&$host_address$&"
25068 At the start of a run of the &(smtp)& transport, the values of &$host$& and
25069 &$host_address$& are the name and IP address of the first host on the host list
25070 passed by the router. However, when the transport is about to connect to a
25071 specific host, and while it is connected to that host, &$host$& and
25072 &$host_address$& are set to the values for that host. These are the values
25073 that are in force when the &%helo_data%&, &%hosts_try_auth%&, &%interface%&,
25074 &%serialize_hosts%&, and the various TLS options are expanded.
25077 .section "Use of $tls_cipher and $tls_peerdn" "usecippeer"
25078 .vindex &$tls_bits$&
25079 .vindex &$tls_cipher$&
25080 .vindex &$tls_peerdn$&
25081 .vindex &$tls_sni$&
25082 At the start of a run of the &(smtp)& transport, the values of &$tls_bits$&,
25083 &$tls_cipher$&, &$tls_peerdn$& and &$tls_sni$&
25084 are the values that were set when the message was received.
25085 These are the values that are used for options that are expanded before any
25086 SMTP connections are made. Just before each connection is made, these four
25087 variables are emptied. If TLS is subsequently started, they are set to the
25088 appropriate values for the outgoing connection, and these are the values that
25089 are in force when any authenticators are run and when the
25090 &%authenticated_sender%& option is expanded.
25092 These variables are deprecated in favour of &$tls_in_cipher$& et. al.
25093 and will be removed in a future release.
25096 .section "Private options for smtp" "SECID146"
25097 .cindex "options" "&(smtp)& transport"
25098 The private options of the &(smtp)& transport are as follows:
25101 .option address_retry_include_sender smtp boolean true
25102 .cindex "4&'xx'& responses" "retrying after"
25103 When an address is delayed because of a 4&'xx'& response to a RCPT command, it
25104 is the combination of sender and recipient that is delayed in subsequent queue
25105 runs until the retry time is reached. You can delay the recipient without
25106 reference to the sender (which is what earlier versions of Exim did), by
25107 setting &%address_retry_include_sender%& false. However, this can lead to
25108 problems with servers that regularly issue 4&'xx'& responses to RCPT commands.
25110 .option allow_localhost smtp boolean false
25111 .cindex "local host" "sending to"
25112 .cindex "fallback" "hosts specified on transport"
25113 When a host specified in &%hosts%& or &%fallback_hosts%& (see below) turns out
25114 to be the local host, or is listed in &%hosts_treat_as_local%&, delivery is
25115 deferred by default. However, if &%allow_localhost%& is set, Exim goes on to do
25116 the delivery anyway. This should be used only in special cases when the
25117 configuration ensures that no looping will result (for example, a differently
25118 configured Exim is listening on the port to which the message is sent).
25121 .option authenticated_sender smtp string&!! unset
25123 When Exim has authenticated as a client, or if &%authenticated_sender_force%&
25124 is true, this option sets a value for the AUTH= item on outgoing MAIL commands,
25125 overriding any existing authenticated sender value. If the string expansion is
25126 forced to fail, the option is ignored. Other expansion failures cause delivery
25127 to be deferred. If the result of expansion is an empty string, that is also
25130 The expansion happens after the outgoing connection has been made and TLS
25131 started, if required. This means that the &$host$&, &$host_address$&,
25132 &$tls_out_cipher$&, and &$tls_out_peerdn$& variables are set according to the
25133 particular connection.
25135 If the SMTP session is not authenticated, the expansion of
25136 &%authenticated_sender%& still happens (and can cause the delivery to be
25137 deferred if it fails), but no AUTH= item is added to MAIL commands
25138 unless &%authenticated_sender_force%& is true.
25140 This option allows you to use the &(smtp)& transport in LMTP mode to
25141 deliver mail to Cyrus IMAP and provide the proper local part as the
25142 &"authenticated sender"&, via a setting such as:
25144 authenticated_sender = $local_part
25146 This removes the need for IMAP subfolders to be assigned special ACLs to
25147 allow direct delivery to those subfolders.
25149 Because of expected uses such as that just described for Cyrus (when no
25150 domain is involved), there is no checking on the syntax of the provided
25154 .option authenticated_sender_force smtp boolean false
25155 If this option is set true, the &%authenticated_sender%& option's value
25156 is used for the AUTH= item on outgoing MAIL commands, even if Exim has not
25157 authenticated as a client.
25160 .option command_timeout smtp time 5m
25161 .cindex timeout "smtp transport command"
25162 This sets a timeout for receiving a response to an SMTP command that has been
25163 sent out. It is also used when waiting for the initial banner line from the
25164 remote host. Its value must not be zero.
25167 .option connect_timeout smtp time 5m
25168 .cindex timeout "smtp transport connect"
25169 This sets a timeout for the &[connect()]& function, which sets up a TCP/IP call
25170 to a remote host. A setting of zero allows the system timeout (typically
25171 several minutes) to act. To have any effect, the value of this option must be
25172 less than the system timeout. However, it has been observed that on some
25173 systems there is no system timeout, which is why the default value for this
25174 option is 5 minutes, a value recommended by RFC 1123.
25177 .option connection_max_messages smtp integer 500
25178 .cindex "SMTP" "passed connection"
25179 .cindex "SMTP" "multiple deliveries"
25180 .cindex "multiple SMTP deliveries"
25181 This controls the maximum number of separate message deliveries that are sent
25182 over a single TCP/IP connection. If the value is zero, there is no limit.
25183 For testing purposes, this value can be overridden by the &%-oB%& command line
25187 .option dane_require_tls_ciphers smtp string&!! unset
25188 .cindex "TLS" "requiring specific ciphers for DANE"
25189 .cindex "cipher" "requiring specific"
25190 .cindex DANE "TLS ciphers"
25191 This option may be used to override &%tls_require_ciphers%& for connections
25192 where DANE has been determined to be in effect.
25193 If not set, then &%tls_require_ciphers%& will be used.
25194 Normal SMTP delivery is not able to make strong demands of TLS cipher
25195 configuration, because delivery will fall back to plaintext. Once DANE has
25196 been determined to be in effect, there is no plaintext fallback and making the
25197 TLS cipherlist configuration stronger will increase security, rather than
25198 counter-intuitively decreasing it.
25199 If the option expands to be empty or is forced to fail, then it will
25200 be treated as unset and &%tls_require_ciphers%& will be used instead.
25203 .option data_timeout smtp time 5m
25204 .cindex timeout "for transmitted SMTP data blocks"
25205 This sets a timeout for the transmission of each block in the data portion of
25206 the message. As a result, the overall timeout for a message depends on the size
25207 of the message. Its value must not be zero. See also &%final_timeout%&.
25210 .option dkim_canon smtp string&!! unset
25211 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25212 .option dkim_domain smtp "string list&!!" unset
25213 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25214 .option dkim_hash smtp string&!! sha256
25215 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25216 .option dkim_identity smtp string&!! unset
25217 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25218 .option dkim_private_key smtp string&!! unset
25219 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25220 .option dkim_selector smtp string&!! unset
25221 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25222 .option dkim_strict smtp string&!! unset
25223 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25224 .option dkim_sign_headers smtp string&!! "per RFC"
25225 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25226 .option dkim_timestamps smtp string&!! unset
25227 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25230 .option delay_after_cutoff smtp boolean true
25231 .cindex "final cutoff" "retries, controlling"
25232 .cindex retry "final cutoff"
25233 This option controls what happens when all remote IP addresses for a given
25234 domain have been inaccessible for so long that they have passed their retry
25237 In the default state, if the next retry time has not been reached for any of
25238 them, the address is bounced without trying any deliveries. In other words,
25239 Exim delays retrying an IP address after the final cutoff time until a new
25240 retry time is reached, and can therefore bounce an address without ever trying
25241 a delivery, when machines have been down for a long time. Some people are
25242 unhappy at this prospect, so...
25244 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
25245 addresses are past their final cutoff time, Exim tries to deliver to those
25246 IP addresses that have not been tried since the message arrived. If there are
25247 none, of if they all fail, the address is bounced. In other words, it does not
25248 delay when a new message arrives, but immediately tries those expired IP
25249 addresses that haven't been tried since the message arrived. If there is a
25250 continuous stream of messages for the dead hosts, unsetting
25251 &%delay_after_cutoff%& means that there will be many more attempts to deliver
25255 .option dns_qualify_single smtp boolean true
25256 If the &%hosts%& or &%fallback_hosts%& option is being used,
25257 and the &%gethostbyname%& option is false,
25258 the RES_DEFNAMES resolver option is set. See the &%qualify_single%& option
25259 in chapter &<<CHAPdnslookup>>& for more details.
25262 .option dns_search_parents smtp boolean false
25263 If the &%hosts%& or &%fallback_hosts%& option is being used, and the
25264 &%gethostbyname%& option is false, the RES_DNSRCH resolver option is set.
25265 See the &%search_parents%& option in chapter &<<CHAPdnslookup>>& for more
25269 .option dnssec_request_domains smtp "domain list&!!" *
25270 .cindex "MX record" "security"
25271 .cindex "DNSSEC" "MX lookup"
25272 .cindex "security" "MX lookup"
25273 .cindex "DNS" "DNSSEC"
25274 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
25275 the DNSSEC request bit set. Setting this transport option is only useful if the
25276 transport overrides or sets the host names. See the &%dnssec_request_domains%&
25281 .option dnssec_require_domains smtp "domain list&!!" unset
25282 .cindex "MX record" "security"
25283 .cindex "DNSSEC" "MX lookup"
25284 .cindex "security" "MX lookup"
25285 .cindex "DNS" "DNSSEC"
25286 DNS lookups for domains matching &%dnssec_require_domains%& will be done with
25287 the DNSSEC request bit set. Setting this transport option is only
25288 useful if the transport overrides or sets the host names. See the
25289 &%dnssec_require_domains%& router option.
25293 .option dscp smtp string&!! unset
25294 .cindex "DCSP" "outbound"
25295 This option causes the DSCP value associated with a socket to be set to one
25296 of a number of fixed strings or to numeric value.
25297 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
25298 Common values include &`throughput`&, &`mincost`&, and on newer systems
25299 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
25301 The outbound packets from Exim will be marked with this value in the header
25302 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
25303 that these values will have any effect, not be stripped by networking
25304 equipment, or do much of anything without cooperation with your Network
25305 Engineer and those of all network operators between the source and destination.
25308 .option fallback_hosts smtp "string list" unset
25309 .cindex "fallback" "hosts specified on transport"
25310 String expansion is not applied to this option. The argument must be a
25311 colon-separated list of host names or IP addresses, optionally also including
25312 port numbers, though the separator can be changed, as described in section
25313 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
25314 item in a &%route_list%& setting for the &(manualroute)& router, as described
25315 in section &<<SECTformatonehostitem>>&.
25317 Fallback hosts can also be specified on routers, which associate them with the
25318 addresses they process. As for the &%hosts%& option without &%hosts_override%&,
25319 &%fallback_hosts%& specified on the transport is used only if the address does
25320 not have its own associated fallback host list. Unlike &%hosts%&, a setting of
25321 &%fallback_hosts%& on an address is not overridden by &%hosts_override%&.
25322 However, &%hosts_randomize%& does apply to fallback host lists.
25324 If Exim is unable to deliver to any of the hosts for a particular address, and
25325 the errors are not permanent rejections, the address is put on a separate
25326 transport queue with its host list replaced by the fallback hosts, unless the
25327 address was routed via MX records and the current host was in the original MX
25328 list. In that situation, the fallback host list is not used.
25330 Once normal deliveries are complete, the fallback queue is delivered by
25331 re-running the same transports with the new host lists. If several failing
25332 addresses have the same fallback hosts (and &%max_rcpt%& permits it), a single
25333 copy of the message is sent.
25335 The resolution of the host names on the fallback list is controlled by the
25336 &%gethostbyname%& option, as for the &%hosts%& option. Fallback hosts apply
25337 both to cases when the host list comes with the address and when it is taken
25338 from &%hosts%&. This option provides a &"use a smart host only if delivery
25342 .option final_timeout smtp time 10m
25343 .cindex timeout "for transmitted SMTP data accept"
25344 This is the timeout that applies while waiting for the response to the final
25345 line containing just &"."& that terminates a message. Its value must not be
25348 .option gethostbyname smtp boolean false
25349 If this option is true when the &%hosts%& and/or &%fallback_hosts%& options are
25350 being used, names are looked up using &[gethostbyname()]&
25351 (or &[getipnodebyname()]& when available)
25352 instead of using the DNS. Of course, that function may in fact use the DNS, but
25353 it may also consult other sources of information such as &_/etc/hosts_&.
25355 .option gnutls_compat_mode smtp boolean unset
25356 This option controls whether GnuTLS is used in compatibility mode in an Exim
25357 server. This reduces security slightly, but improves interworking with older
25358 implementations of TLS.
25360 .option helo_data smtp string&!! "see below"
25361 .cindex "HELO" "argument, setting"
25362 .cindex "EHLO" "argument, setting"
25363 .cindex "LHLO argument setting"
25364 The value of this option is expanded after a connection to a another host has
25365 been set up. The result is used as the argument for the EHLO, HELO, or LHLO
25366 command that starts the outgoing SMTP or LMTP session. The default value of the
25371 During the expansion, the variables &$host$& and &$host_address$& are set to
25372 the identity of the remote host, and the variables &$sending_ip_address$& and
25373 &$sending_port$& are set to the local IP address and port number that are being
25374 used. These variables can be used to generate different values for different
25375 servers or different local IP addresses. For example, if you want the string
25376 that is used for &%helo_data%& to be obtained by a DNS lookup of the outgoing
25377 interface address, you could use this:
25379 helo_data = ${lookup dnsdb{ptr=$sending_ip_address} \
25380 {${listextract{1}{<\n $value}}} \
25381 {$primary_hostname}}
25383 The use of &%helo_data%& applies both to sending messages and when doing
25386 .option host_name_extract smtp "string list&!!" "see below"
25387 .cindex "load balancer" "hosts behind"
25388 .cindex TLS resumption
25389 Some mail-accepting sites
25390 (notably Microsoft)
25391 operate many servers behind a network load-balancer. When this is done,
25392 with separated TLS session caches, TLS session resuption becomes problematic.
25393 It will only succeed when the same server happens to be selected by the
25394 load-balancer, matching the session stored in the client's cache.
25396 Exim can pull out a server name, if there is one, from the response to the
25397 client's SMTP EHLO command.
25398 The default value of this option:
25400 ${if and { {match {$host} {.outlook.com\$}} \
25401 {match {$item} {\N^250-([\w.]+)\s\N}} \
25404 suffices for one known case.
25405 During the expansion of this option the &$item$& variable will have the
25406 server's EHLO response.
25407 The result of the option expansion is included in the key used to store and
25408 retrieve the TLS session, for session resumption.
25410 Operators of high-load sites may wish to evaluate their logs for indications
25411 of other destination sites operating load-balancers, and develop a suitable
25412 expression for this option.
25413 The smtp:ehlo event and the &$tls_out_resumption$& variable
25414 will be useful for such work.
25416 .option hosts smtp "string list&!!" unset
25417 Hosts are associated with an address by a router such as &(dnslookup)&, which
25418 finds the hosts by looking up the address domain in the DNS, or by
25419 &(manualroute)&, which has lists of hosts in its configuration. However,
25420 email addresses can be passed to the &(smtp)& transport by any router, and not
25421 all of them can provide an associated list of hosts.
25423 The &%hosts%& option specifies a list of hosts to be used if the address being
25424 processed does not have any hosts associated with it. The hosts specified by
25425 &%hosts%& are also used, whether or not the address has its own hosts, if
25426 &%hosts_override%& is set.
25428 The string is first expanded, before being interpreted as a colon-separated
25429 list of host names or IP addresses, possibly including port numbers. The
25430 separator may be changed to something other than colon, as described in section
25431 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
25432 item in a &%route_list%& setting for the &(manualroute)& router, as described
25433 in section &<<SECTformatonehostitem>>&. However, note that the &`/MX`& facility
25434 of the &(manualroute)& router is not available here.
25436 If the expansion fails, delivery is deferred. Unless the failure was caused by
25437 the inability to complete a lookup, the error is logged to the panic log as
25438 well as the main log. Host names are looked up either by searching directly for
25439 address records in the DNS or by calling &[gethostbyname()]& (or
25440 &[getipnodebyname()]& when available), depending on the setting of the
25441 &%gethostbyname%& option. When Exim is compiled with IPv6 support, if a host
25442 that is looked up in the DNS has both IPv4 and IPv6 addresses, both types of
25445 During delivery, the hosts are tried in order, subject to their retry status,
25446 unless &%hosts_randomize%& is set.
25449 .option hosts_avoid_esmtp smtp "host list&!!" unset
25450 .cindex "ESMTP, avoiding use of"
25451 .cindex "HELO" "forcing use of"
25452 .cindex "EHLO" "avoiding use of"
25453 .cindex "PIPELINING" "avoiding the use of"
25454 This option is for use with broken hosts that announce ESMTP facilities (for
25455 example, PIPELINING) and then fail to implement them properly. When a host
25456 matches &%hosts_avoid_esmtp%&, Exim sends HELO rather than EHLO at the
25457 start of the SMTP session. This means that it cannot use any of the ESMTP
25458 facilities such as AUTH, PIPELINING, SIZE, and STARTTLS.
25461 .option hosts_avoid_pipelining smtp "host list&!!" unset
25462 .cindex "PIPELINING" "avoiding the use of"
25463 .cindex "ESMTP extensions" PIPELINING
25464 Exim will not use the ESMTP PIPELINING extension when delivering to any host
25465 that matches this list, even if the server host advertises PIPELINING support.
25467 .option hosts_pipe_connect smtp "host list&!!" unset
25468 .cindex "pipelining" "early connection"
25469 .cindex "pipelining" PIPECONNECT
25470 If Exim is built with the SUPPORT_PIPE_CONNECT build option
25471 this option controls which to hosts the facility watched for
25472 and recorded, and used for subsequent connections.
25474 The retry hints database is used for the record,
25475 and records are subject to the &%retry_data_expire%& option.
25476 When used, the pipelining saves on roundtrip times.
25477 It also turns SMTP into a client-first protocol
25478 so combines well with TCP Fast Open.
25480 See also the &%pipelining_connect_advertise_hosts%& main option.
25483 When the facility is used, if the transport &%interface%& option is unset
25484 the &%helo_data%& option
25485 will be expanded before the &$sending_ip_address$& variable
25487 A check is made for the use of that variable, without the
25488 presence of a &"def:"& test on it, but suitably complex coding
25489 can avoid the check and produce unexpected results.
25490 You have been warned.
25493 .option hosts_avoid_tls smtp "host list&!!" unset
25494 .cindex "TLS" "avoiding for certain hosts"
25495 Exim will not try to start a TLS session when delivering to any host that
25496 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
25498 .option hosts_verify_avoid_tls smtp "host list&!!" unset
25499 .cindex "TLS" "avoiding for certain hosts"
25500 Exim will not try to start a TLS session for a verify callout,
25501 or when delivering in cutthrough mode,
25502 to any host that matches this list.
25505 .option hosts_max_try smtp integer 5
25506 .cindex "host" "maximum number to try"
25507 .cindex "limit" "number of hosts tried"
25508 .cindex "limit" "number of MX tried"
25509 .cindex "MX record" "maximum tried"
25510 This option limits the number of IP addresses that are tried for any one
25511 delivery in cases where there are temporary delivery errors. Section
25512 &<<SECTvalhosmax>>& describes in detail how the value of this option is used.
25515 .option hosts_max_try_hardlimit smtp integer 50
25516 This is an additional check on the maximum number of IP addresses that Exim
25517 tries for any one delivery. Section &<<SECTvalhosmax>>& describes its use and
25522 .option hosts_nopass_tls smtp "host list&!!" unset
25523 .cindex "TLS" "passing connection"
25524 .cindex "multiple SMTP deliveries"
25525 .cindex "TLS" "multiple message deliveries"
25526 For any host that matches this list, a connection on which a TLS session has
25527 been started will not be passed to a new delivery process for sending another
25528 message on the same connection. See section &<<SECTmulmessam>>& for an
25529 explanation of when this might be needed.
25531 .option hosts_noproxy_tls smtp "host list&!!" unset
25532 .cindex "TLS" "passing connection"
25533 .cindex "multiple SMTP deliveries"
25534 .cindex "TLS" "multiple message deliveries"
25535 For any host that matches this list, a TLS session which has
25536 been started will not be passed to a new delivery process for sending another
25537 message on the same session.
25539 The traditional implementation closes down TLS and re-starts it in the new
25540 process, on the same open TCP connection, for each successive message
25541 sent. If permitted by this option a pipe to to the new process is set up
25542 instead, and the original process maintains the TLS connection and proxies
25543 the SMTP connection from and to the new process and any subsequents.
25544 The new process has no access to TLS information, so cannot include it in
25549 .option hosts_override smtp boolean false
25550 If this option is set and the &%hosts%& option is also set, any hosts that are
25551 attached to the address are ignored, and instead the hosts specified by the
25552 &%hosts%& option are always used. This option does not apply to
25553 &%fallback_hosts%&.
25556 .option hosts_randomize smtp boolean false
25557 .cindex "randomized host list"
25558 .cindex "host" "list of; randomized"
25559 .cindex "fallback" "randomized hosts"
25560 If this option is set, and either the list of hosts is taken from the
25561 &%hosts%& or the &%fallback_hosts%& option, or the hosts supplied by the router
25562 were not obtained from MX records (this includes fallback hosts from the
25563 router), and were not randomized by the router, the order of trying the hosts
25564 is randomized each time the transport runs. Randomizing the order of a host
25565 list can be used to do crude load sharing.
25567 When &%hosts_randomize%& is true, a host list may be split into groups whose
25568 order is separately randomized. This makes it possible to set up MX-like
25569 behaviour. The boundaries between groups are indicated by an item that is just
25570 &`+`& in the host list. For example:
25572 hosts = host1:host2:host3:+:host4:host5
25574 The order of the first three hosts and the order of the last two hosts is
25575 randomized for each use, but the first three always end up before the last two.
25576 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored.
25578 .option hosts_require_auth smtp "host list&!!" unset
25579 .cindex "authentication" "required by client"
25580 This option provides a list of servers for which authentication must succeed
25581 before Exim will try to transfer a message. If authentication fails for
25582 servers which are not in this list, Exim tries to send unauthenticated. If
25583 authentication fails for one of these servers, delivery is deferred. This
25584 temporary error is detectable in the retry rules, so it can be turned into a
25585 hard failure if required. See also &%hosts_try_auth%&, and chapter
25586 &<<CHAPSMTPAUTH>>& for details of authentication.
25589 .option hosts_request_ocsp smtp "host list&!!" *
25590 .cindex "TLS" "requiring for certain servers"
25591 Exim will request a Certificate Status on a
25592 TLS session for any host that matches this list.
25593 &%tls_verify_certificates%& should also be set for the transport.
25595 .option hosts_require_alpn smtp "host list&!!" unset
25596 .cindex ALPN "require negotiation in client"
25598 .cindex TLS "Application Layer Protocol Names"
25599 If the TLS library supports ALPN
25600 then a successful negotiation of ALPN will be required for any host
25601 matching the list, for TLS to be used.
25602 See also the &%tls_alpn%& option.
25604 &*Note*&: prevention of fallback to in-clear connection is not
25605 managed by this option; see &%hosts_require_tls%&.
25607 .option hosts_require_dane smtp "host list&!!" unset
25608 .cindex DANE "transport options"
25609 .cindex DANE "requiring for certain servers"
25610 If built with DANE support, Exim will require that a DNSSEC-validated
25611 TLSA record is present for any host matching the list,
25612 and that a DANE-verified TLS connection is made.
25613 There will be no fallback to in-clear communication.
25614 See the &%dnssec_request_domains%& router and transport options.
25615 See section &<<SECDANE>>&.
25617 .option hosts_require_ocsp smtp "host list&!!" unset
25618 .cindex "TLS" "requiring for certain servers"
25619 Exim will request, and check for a valid Certificate Status being given, on a
25620 TLS session for any host that matches this list.
25621 &%tls_verify_certificates%& should also be set for the transport.
25623 .option hosts_require_tls smtp "host list&!!" unset
25624 .cindex "TLS" "requiring for certain servers"
25625 Exim will insist on using a TLS session when delivering to any host that
25626 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
25627 &*Note*&: This option affects outgoing mail only. To insist on TLS for
25628 incoming messages, use an appropriate ACL.
25630 .option hosts_try_auth smtp "host list&!!" unset
25631 .cindex "authentication" "optional in client"
25632 This option provides a list of servers to which, provided they announce
25633 authentication support, Exim will attempt to authenticate as a client when it
25634 connects. If authentication fails
25635 and &%hosts_require_auth%& permits,
25636 Exim will try to transfer the message unauthenticated.
25637 See also chapter &<<CHAPSMTPAUTH>>& for details of authentication.
25639 .option hosts_try_chunking smtp "host list&!!" *
25640 .cindex CHUNKING "enabling, in client"
25641 .cindex BDAT "SMTP command"
25642 .cindex "RFC 3030" "CHUNKING"
25643 This option provides a list of servers to which, provided they announce
25644 CHUNKING support, Exim will attempt to use BDAT commands rather than DATA.
25645 Unless DKIM signing is being done,
25646 BDAT will not be used in conjunction with a transport filter.
25648 .option hosts_try_dane smtp "host list&!!" *
25649 .cindex DANE "transport options"
25650 .cindex DANE "attempting for certain servers"
25651 If built with DANE support, Exim will look up a
25652 TLSA record for any host matching the list,
25653 If one is found and that lookup was DNSSEC-validated,
25654 then Exim requires that a DANE-verified TLS connection is made for that host;
25655 there will be no fallback to in-clear communication.
25656 See the &%dnssec_request_domains%& router and transport options.
25657 See section &<<SECDANE>>&.
25659 .option hosts_try_fastopen smtp "host list&!!" *
25660 .cindex "fast open, TCP" "enabling, in client"
25661 .cindex "TCP Fast Open" "enabling, in client"
25662 .cindex "RFC 7413" "TCP Fast Open"
25663 This option provides a list of servers to which, provided
25664 the facility is supported by this system, Exim will attempt to
25665 perform a TCP Fast Open.
25666 No data is sent on the SYN segment but, if the remote server also
25667 supports the facility, it can send its SMTP banner immediately after
25668 the SYN,ACK segment. This can save up to one round-trip time.
25670 The facility is only active for previously-contacted servers,
25671 as the initiator must present a cookie in the SYN segment.
25673 On (at least some) current Linux distributions the facility must be enabled
25674 in the kernel by the sysadmin before the support is usable.
25675 There is no option for control of the server side; if the system supports
25676 it it is always enabled. Note that lengthy operations in the connect ACL,
25677 such as DNSBL lookups, will still delay the emission of the SMTP banner.
25679 .option hosts_try_prdr smtp "host list&!!" *
25680 .cindex "PRDR" "enabling, optional in client"
25681 .cindex "ESMTP extensions" PRDR
25682 This option provides a list of servers to which, provided they announce
25683 PRDR support, Exim will attempt to negotiate PRDR
25684 for multi-recipient messages.
25685 The option can usually be left as default.
25687 .option interface smtp "string list&!!" unset
25688 .cindex "bind IP address"
25689 .cindex "IP address" "binding"
25691 .vindex "&$host_address$&"
25692 This option specifies which interface to bind to when making an outgoing SMTP
25693 call. The value is an IP address, not an interface name such as
25694 &`eth0`&. Do not confuse this with the interface address that was used when a
25695 message was received, which is in &$received_ip_address$&, formerly known as
25696 &$interface_address$&. The name was changed to minimize confusion with the
25697 outgoing interface address. There is no variable that contains an outgoing
25698 interface address because, unless it is set by this option, its value is
25701 During the expansion of the &%interface%& option the variables &$host$& and
25702 &$host_address$& refer to the host to which a connection is about to be made
25703 during the expansion of the string. Forced expansion failure, or an empty
25704 string result causes the option to be ignored. Otherwise, after expansion, the
25705 string must be a list of IP addresses, colon-separated by default, but the
25706 separator can be changed in the usual way (&<<SECTlistsepchange>>&).
25709 interface = <; 192.168.123.123 ; 3ffe:ffff:836f::fe86:a061
25711 The first interface of the correct type (IPv4 or IPv6) is used for the outgoing
25712 connection. If none of them are the correct type, the option is ignored. If
25713 &%interface%& is not set, or is ignored, the system's IP functions choose which
25714 interface to use if the host has more than one.
25717 .option keepalive smtp boolean true
25718 .cindex "keepalive" "on outgoing connection"
25719 This option controls the setting of SO_KEEPALIVE on outgoing TCP/IP socket
25720 connections. When set, it causes the kernel to probe idle connections
25721 periodically, by sending packets with &"old"& sequence numbers. The other end
25722 of the connection should send a acknowledgment if the connection is still okay
25723 or a reset if the connection has been aborted. The reason for doing this is
25724 that it has the beneficial effect of freeing up certain types of connection
25725 that can get stuck when the remote host is disconnected without tidying up the
25726 TCP/IP call properly. The keepalive mechanism takes several hours to detect
25730 .option lmtp_ignore_quota smtp boolean false
25731 .cindex "LMTP" "ignoring quota errors"
25732 If this option is set true when the &%protocol%& option is set to &"lmtp"&, the
25733 string &`IGNOREQUOTA`& is added to RCPT commands, provided that the LMTP server
25734 has advertised support for IGNOREQUOTA in its response to the LHLO command.
25736 .option max_rcpt smtp integer 100
25737 .cindex "RCPT" "maximum number of outgoing"
25738 This option limits the number of RCPT commands that are sent in a single
25739 SMTP message transaction. Each set of addresses is treated independently, and
25740 so can cause parallel connections to the same host if &%remote_max_parallel%&
25741 permits this. A value setting of zero disables the limit.
25744 .option message_linelength_limit smtp integer 998
25745 .cindex "line length" limit
25746 This option sets the maximum line length, in bytes, that the transport
25747 will send. Any messages with lines exceeding the given value
25748 will fail and a failure-DSN ("bounce") message will if possible be returned
25750 The default value is that defined by the SMTP standards.
25752 It is generally wise to also check in the data ACL so that messages
25753 received via SMTP can be refused without producing a bounce.
25756 .option multi_domain smtp boolean&!! true
25757 .vindex "&$domain$&"
25758 When this option is set, the &(smtp)& transport can handle a number of
25759 addresses containing a mixture of different domains provided they all resolve
25760 to the same list of hosts. Turning the option off restricts the transport to
25761 handling only one domain at a time. This is useful if you want to use
25762 &$domain$& in an expansion for the transport, because it is set only when there
25763 is a single domain involved in a remote delivery.
25765 It is expanded per-address and can depend on any of
25766 &$address_data$&, &$domain_data$&, &$local_part_data$&,
25767 &$host$&, &$host_address$& and &$host_port$&.
25769 If the connection is DANE-enabled then this option is ignored;
25770 only messages having the domain used for the DANE TLSA lookup are
25771 sent on the connection.
25773 .option port smtp string&!! "see below"
25774 .cindex "port" "sending TCP/IP"
25775 .cindex "TCP/IP" "setting outgoing port"
25776 This option specifies the TCP/IP port on the server to which Exim connects.
25777 &*Note:*& Do not confuse this with the port that was used when a message was
25778 received, which is in &$received_port$&, formerly known as &$interface_port$&.
25779 The name was changed to minimize confusion with the outgoing port. There is no
25780 variable that contains an outgoing port.
25782 If the value of this option begins with a digit it is taken as a port number;
25783 otherwise it is looked up using &[getservbyname()]&. The default value is
25785 but if &%protocol%& is set to &"lmtp"& the default is &"lmtp"&
25786 and if &%protocol%& is set to &"smtps"& the default is &"smtps"&.
25787 If the expansion fails, or if a port number cannot be found, delivery
25790 Note that at least one Linux distribution has been seen failing
25791 to put &"smtps"& in its &"/etc/services"& file, resulting is such deferrals.
25795 .option protocol smtp string smtp
25796 .cindex "LMTP" "over TCP/IP"
25797 .cindex "ssmtp protocol" "outbound"
25798 .cindex "TLS" "SSL-on-connect outbound"
25800 If this option is set to &"lmtp"& instead of &"smtp"&, the default value for
25801 the &%port%& option changes to &"lmtp"&, and the transport operates the LMTP
25802 protocol (RFC 2033) instead of SMTP. This protocol is sometimes used for local
25803 deliveries into closed message stores. Exim also has support for running LMTP
25804 over a pipe to a local process &-- see chapter &<<CHAPLMTP>>&.
25806 If this option is set to &"smtps"&, the default value for the &%port%& option
25807 changes to &"smtps"&, and the transport initiates TLS immediately after
25808 connecting, as an outbound SSL-on-connect, instead of using STARTTLS to upgrade.
25809 The Internet standards bodies used to strongly discourage use of this mode,
25810 but as of RFC 8314 it is preferred over STARTTLS for message submission
25811 (as distinct from MTA-MTA communication).
25814 .option retry_include_ip_address smtp boolean&!! true
25815 Exim normally includes both the host name and the IP address in the key it
25816 constructs for indexing retry data after a temporary delivery failure. This
25817 means that when one of several IP addresses for a host is failing, it gets
25818 tried periodically (controlled by the retry rules), but use of the other IP
25819 addresses is not affected.
25821 However, in some dialup environments hosts are assigned a different IP address
25822 each time they connect. In this situation the use of the IP address as part of
25823 the retry key leads to undesirable behaviour. Setting this option false causes
25824 Exim to use only the host name.
25825 Since it is expanded it can be made to depend on the host or domain.
25828 .option serialize_hosts smtp "host list&!!" unset
25829 .cindex "serializing connections"
25830 .cindex "host" "serializing connections"
25831 Because Exim operates in a distributed manner, if several messages for the same
25832 host arrive at around the same time, more than one simultaneous connection to
25833 the remote host can occur. This is not usually a problem except when there is a
25834 slow link between the hosts. In that situation it may be helpful to restrict
25835 Exim to one connection at a time. This can be done by setting
25836 &%serialize_hosts%& to match the relevant hosts.
25838 .cindex "hints database" "serializing deliveries to a host"
25839 Exim implements serialization by means of a hints database in which a record is
25840 written whenever a process connects to one of the restricted hosts. The record
25841 is deleted when the connection is completed. Obviously there is scope for
25842 records to get left lying around if there is a system or program crash. To
25843 guard against this, Exim ignores any records that are more than six hours old.
25845 If you set up this kind of serialization, you should also arrange to delete the
25846 relevant hints database whenever your system reboots. The names of the files
25847 start with &_misc_& and they are kept in the &_spool/db_& directory. There
25848 may be one or two files, depending on the type of DBM in use. The same files
25849 are used for ETRN serialization.
25851 See also the &%max_parallel%& generic transport option.
25854 .option size_addition smtp integer 1024
25855 .cindex "SIZE" "ESMTP extension"
25856 .cindex "message" "size issue for transport filter"
25857 .cindex "size" "of message"
25858 .cindex "transport" "filter"
25859 .cindex "filter" "transport filter"
25860 If a remote SMTP server indicates that it supports the SIZE option of the
25861 MAIL command, Exim uses this to pass over the message size at the start of
25862 an SMTP transaction. It adds the value of &%size_addition%& to the value it
25863 sends, to allow for headers and other text that may be added during delivery by
25864 configuration options or in a transport filter. It may be necessary to increase
25865 this if a lot of text is added to messages.
25867 Alternatively, if the value of &%size_addition%& is set negative, it disables
25868 the use of the SIZE option altogether.
25871 .option socks_proxy smtp string&!! unset
25872 .cindex proxy SOCKS
25873 This option enables use of SOCKS proxies for connections made by the
25874 transport. For details see section &<<SECTproxySOCKS>>&.
25877 .option tls_alpn smtp string&!! unset
25878 .cindex TLS "Application Layer Protocol Names"
25880 .cindex ALPN "set name in client"
25881 If this option is set
25882 and the TLS library supports ALPN,
25883 the value given is used.
25885 As of writing no value has been standardised for email use.
25886 The authors suggest using &"smtp"&.
25890 .option tls_certificate smtp string&!! unset
25891 .cindex "TLS" "client certificate, location of"
25892 .cindex "certificate" "client, location of"
25894 .vindex "&$host_address$&"
25895 The value of this option must be the absolute path to a file which contains the
25896 client's certificate, for possible use when sending a message over an encrypted
25897 connection. The values of &$host$& and &$host_address$& are set to the name and
25898 address of the server during the expansion. See chapter &<<CHAPTLS>>& for
25901 &*Note*&: This option must be set if you want Exim to be able to use a TLS
25902 certificate when sending messages as a client. The global option of the same
25903 name specifies the certificate for Exim as a server; it is not automatically
25904 assumed that the same certificate should be used when Exim is operating as a
25908 .option tls_crl smtp string&!! unset
25909 .cindex "TLS" "client certificate revocation list"
25910 .cindex "certificate" "revocation list for client"
25911 This option specifies a certificate revocation list. The expanded value must
25912 be the name of a file that contains a CRL in PEM format.
25915 .option tls_dh_min_bits smtp integer 1024
25916 .cindex "TLS" "Diffie-Hellman minimum acceptable size"
25917 When establishing a TLS session, if a ciphersuite which uses Diffie-Hellman
25918 key agreement is negotiated, the server will provide a large prime number
25919 for use. This option establishes the minimum acceptable size of that number.
25920 If the parameter offered by the server is too small, then the TLS handshake
25923 Only supported when using GnuTLS.
25926 .option tls_privatekey smtp string&!! unset
25927 .cindex "TLS" "client private key, location of"
25929 .vindex "&$host_address$&"
25930 The value of this option must be the absolute path to a file which contains the
25931 client's private key. This is used when sending a message over an encrypted
25932 connection using a client certificate. The values of &$host$& and
25933 &$host_address$& are set to the name and address of the server during the
25934 expansion. If this option is unset, or the expansion is forced to fail, or the
25935 result is an empty string, the private key is assumed to be in the same file as
25936 the certificate. See chapter &<<CHAPTLS>>& for details of TLS.
25939 .option tls_require_ciphers smtp string&!! unset
25940 .cindex "TLS" "requiring specific ciphers"
25941 .cindex "cipher" "requiring specific"
25943 .vindex "&$host_address$&"
25944 The value of this option must be a list of permitted cipher suites, for use
25945 when setting up an outgoing encrypted connection. (There is a global option of
25946 the same name for controlling incoming connections.) The values of &$host$& and
25947 &$host_address$& are set to the name and address of the server during the
25948 expansion. See chapter &<<CHAPTLS>>& for details of TLS; note that this option
25949 is used in different ways by OpenSSL and GnuTLS (see sections
25950 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&). For GnuTLS, the order of the
25951 ciphers is a preference order.
25954 .option tls_resumption_hosts smtp "host list&!!" unset
25955 .cindex TLS resumption
25956 This option controls which connections to use the TLS resumption feature.
25957 See &<<SECTresumption>>& for details.
25961 .option tls_sni smtp string&!! unset
25962 .cindex "TLS" "Server Name Indication"
25964 .cindex SNI "setting in client"
25965 .vindex "&$tls_sni$&"
25966 If this option is set
25967 and the connection is not DANE-validated
25968 then it sets the $tls_out_sni variable and causes any
25969 TLS session to pass this value as the Server Name Indication extension to
25970 the remote side, which can be used by the remote side to select an appropriate
25971 certificate and private key for the session.
25973 See &<<SECTtlssni>>& for more information.
25975 Note that for OpenSSL, this feature requires a build of OpenSSL that supports
25981 .option tls_tempfail_tryclear smtp boolean true
25982 .cindex "4&'xx'& responses" "to STARTTLS"
25983 When the server host is not in &%hosts_require_tls%&, and there is a problem in
25984 setting up a TLS session, this option determines whether or not Exim should try
25985 to deliver the message unencrypted. If it is set false, delivery to the
25986 current host is deferred; if there are other hosts, they are tried. If this
25987 option is set true, Exim attempts to deliver unencrypted after a 4&'xx'&
25988 response to STARTTLS. Also, if STARTTLS is accepted, but the subsequent
25989 TLS negotiation fails, Exim closes the current connection (because it is in an
25990 unknown state), opens a new one to the same host, and then tries the delivery
25994 .option tls_try_verify_hosts smtp "host list&!!" *
25995 .cindex "TLS" "server certificate verification"
25996 .cindex "certificate" "verification of server"
25997 This option gives a list of hosts for which, on encrypted connections,
25998 certificate verification will be tried but need not succeed.
25999 The &%tls_verify_certificates%& option must also be set.
26000 Note that unless the host is in this list
26001 TLS connections will be denied to hosts using self-signed certificates
26002 when &%tls_verify_certificates%& is matched.
26003 The &$tls_out_certificate_verified$& variable is set when
26004 certificate verification succeeds.
26007 .option tls_verify_cert_hostnames smtp "host list&!!" *
26008 .cindex "TLS" "server certificate hostname verification"
26009 .cindex "certificate" "verification of server"
26010 This option give a list of hosts for which,
26011 while verifying the server certificate,
26012 checks will be included on the host name
26013 (note that this will generally be the result of a DNS MX lookup)
26014 versus Subject and Subject-Alternate-Name fields. Wildcard names are permitted
26015 limited to being the initial component of a 3-or-more component FQDN.
26017 There is no equivalent checking on client certificates.
26020 .option tls_verify_certificates smtp string&!! system
26021 .cindex "TLS" "server certificate verification"
26022 .cindex "certificate" "verification of server"
26024 .vindex "&$host_address$&"
26025 The value of this option must be either the
26027 or the absolute path to
26028 a file or directory containing permitted certificates for servers,
26029 for use when setting up an encrypted connection.
26031 The "system" value for the option will use a location compiled into the SSL library.
26032 This is not available for GnuTLS versions preceding 3.0.20; a value of "system"
26033 is taken as empty and an explicit location
26036 The use of a directory for the option value is not available for GnuTLS versions
26037 preceding 3.3.6 and a single file must be used.
26039 With OpenSSL the certificates specified
26041 either by file or directory
26042 are added to those given by the system default location.
26044 The values of &$host$& and
26045 &$host_address$& are set to the name and address of the server during the
26046 expansion of this option. See chapter &<<CHAPTLS>>& for details of TLS.
26048 For back-compatibility,
26049 if neither tls_verify_hosts nor tls_try_verify_hosts are set
26050 (a single-colon empty list counts as being set)
26051 and certificate verification fails the TLS connection is closed.
26054 .option tls_verify_hosts smtp "host list&!!" unset
26055 .cindex "TLS" "server certificate verification"
26056 .cindex "certificate" "verification of server"
26057 This option gives a list of hosts for which, on encrypted connections,
26058 certificate verification must succeed.
26059 The &%tls_verify_certificates%& option must also be set.
26060 If both this option and &%tls_try_verify_hosts%& are unset
26061 operation is as if this option selected all hosts.
26062 &*Warning*&: Including a host in &%tls_verify_hosts%& does not require
26063 that connections use TLS.
26064 Fallback to in-clear communication will be done unless restricted by
26065 the &%hosts_require_tls%& option.
26067 .option utf8_downconvert smtp integer&!! -1
26068 .cindex utf8 "address downconversion"
26069 .cindex i18n "utf8 address downconversion"
26070 If built with internationalization support,
26071 this option controls conversion of UTF-8 in message envelope addresses
26073 If, after expansion, the value is 1, 0, or -1 then this value overrides
26074 any value previously set for the message. Otherwise, any previously
26075 set value is used. To permit use of a previous value,
26076 set this option to an empty string.
26077 For details on the values see section &<<SECTi18nMTA>>&.
26082 .section "How the limits for the number of hosts to try are used" &&&
26084 .cindex "host" "maximum number to try"
26085 .cindex "limit" "hosts; maximum number tried"
26086 There are two options that are concerned with the number of hosts that are
26087 tried when an SMTP delivery takes place. They are &%hosts_max_try%& and
26088 &%hosts_max_try_hardlimit%&.
26091 The &%hosts_max_try%& option limits the number of hosts that are tried
26092 for a single delivery. However, despite the term &"host"& in its name, the
26093 option actually applies to each IP address independently. In other words, a
26094 multihomed host is treated as several independent hosts, just as it is for
26097 Many of the larger ISPs have multiple MX records which often point to
26098 multihomed hosts. As a result, a list of a dozen or more IP addresses may be
26099 created as a result of routing one of these domains.
26101 Trying every single IP address on such a long list does not seem sensible; if
26102 several at the top of the list fail, it is reasonable to assume there is some
26103 problem that is likely to affect all of them. Roughly speaking, the value of
26104 &%hosts_max_try%& is the maximum number that are tried before deferring the
26105 delivery. However, the logic cannot be quite that simple.
26107 Firstly, IP addresses that are skipped because their retry times have not
26108 arrived do not count, and in addition, addresses that are past their retry
26109 limits are also not counted, even when they are tried. This means that when
26110 some IP addresses are past their retry limits, more than the value of
26111 &%hosts_max_retry%& may be tried. The reason for this behaviour is to ensure
26112 that all IP addresses are considered before timing out an email address (but
26113 see below for an exception).
26115 Secondly, when the &%hosts_max_try%& limit is reached, Exim looks down the host
26116 list to see if there is a subsequent host with a different (higher valued) MX.
26117 If there is, that host is considered next, and the current IP address is used
26118 but not counted. This behaviour helps in the case of a domain with a retry rule
26119 that hardly ever delays any hosts, as is now explained:
26121 Consider the case of a long list of hosts with one MX value, and a few with a
26122 higher MX value. If &%hosts_max_try%& is small (the default is 5) only a few
26123 hosts at the top of the list are tried at first. With the default retry rule,
26124 which specifies increasing retry times, the higher MX hosts are eventually
26125 tried when those at the top of the list are skipped because they have not
26126 reached their retry times.
26128 However, it is common practice to put a fixed short retry time on domains for
26129 large ISPs, on the grounds that their servers are rarely down for very long.
26130 Unfortunately, these are exactly the domains that tend to resolve to long lists
26131 of hosts. The short retry time means that the lowest MX hosts are tried every
26132 time. The attempts may be in a different order because of random sorting, but
26133 without the special MX check, the higher MX hosts would never be tried until
26134 all the lower MX hosts had timed out (which might be several days), because
26135 there are always some lower MX hosts that have reached their retry times. With
26136 the special check, Exim considers at least one IP address from each MX value at
26137 every delivery attempt, even if the &%hosts_max_try%& limit has already been
26140 The above logic means that &%hosts_max_try%& is not a hard limit, and in
26141 particular, Exim normally eventually tries all the IP addresses before timing
26142 out an email address. When &%hosts_max_try%& was implemented, this seemed a
26143 reasonable thing to do. Recently, however, some lunatic DNS configurations have
26144 been set up with hundreds of IP addresses for some domains. It can
26145 take a very long time indeed for an address to time out in these cases.
26147 The &%hosts_max_try_hardlimit%& option was added to help with this problem.
26148 Exim never tries more than this number of IP addresses; if it hits this limit
26149 and they are all timed out, the email address is bounced, even though not all
26150 possible IP addresses have been tried.
26151 .ecindex IIDsmttra1
26152 .ecindex IIDsmttra2
26158 . ////////////////////////////////////////////////////////////////////////////
26159 . ////////////////////////////////////////////////////////////////////////////
26161 .chapter "Address rewriting" "CHAPrewrite"
26162 .scindex IIDaddrew "rewriting" "addresses"
26163 There are some circumstances in which Exim automatically rewrites domains in
26164 addresses. The two most common are when an address is given without a domain
26165 (referred to as an &"unqualified address"&) or when an address contains an
26166 abbreviated domain that is expanded by DNS lookup.
26168 Unqualified envelope addresses are accepted only for locally submitted
26169 messages, or for messages that are received from hosts matching
26170 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
26171 appropriate. Unqualified addresses in header lines are qualified if they are in
26172 locally submitted messages, or messages from hosts that are permitted to send
26173 unqualified envelope addresses. Otherwise, unqualified addresses in header
26174 lines are neither qualified nor rewritten.
26176 One situation in which Exim does &'not'& automatically rewrite a domain is
26177 when it is the name of a CNAME record in the DNS. The older RFCs suggest that
26178 such a domain should be rewritten using the &"canonical"& name, and some MTAs
26179 do this. The new RFCs do not contain this suggestion.
26182 .section "Explicitly configured address rewriting" "SECID147"
26183 This chapter describes the rewriting rules that can be used in the
26184 main rewrite section of the configuration file, and also in the generic
26185 &%headers_rewrite%& option that can be set on any transport.
26187 Some people believe that configured address rewriting is a Mortal Sin.
26188 Others believe that life is not possible without it. Exim provides the
26189 facility; you do not have to use it.
26191 The main rewriting rules that appear in the &"rewrite"& section of the
26192 configuration file are applied to addresses in incoming messages, both envelope
26193 addresses and addresses in header lines. Each rule specifies the types of
26194 address to which it applies.
26196 Whether or not addresses in header lines are rewritten depends on the origin of
26197 the headers and the type of rewriting. Global rewriting, that is, rewriting
26198 rules from the rewrite section of the configuration file, is applied only to
26199 those headers that were received with the message. Header lines that are added
26200 by ACLs or by a system filter or by individual routers or transports (which
26201 are specific to individual recipient addresses) are not rewritten by the global
26204 Rewriting at transport time, by means of the &%headers_rewrite%& option,
26205 applies all headers except those added by routers and transports. That is, as
26206 well as the headers that were received with the message, it also applies to
26207 headers that were added by an ACL or a system filter.
26210 In general, rewriting addresses from your own system or domain has some
26211 legitimacy. Rewriting other addresses should be done only with great care and
26212 in special circumstances. The author of Exim believes that rewriting should be
26213 used sparingly, and mainly for &"regularizing"& addresses in your own domains.
26214 Although it can sometimes be used as a routing tool, this is very strongly
26217 There are two commonly encountered circumstances where rewriting is used, as
26218 illustrated by these examples:
26221 The company whose domain is &'hitch.fict.example'& has a number of hosts that
26222 exchange mail with each other behind a firewall, but there is only a single
26223 gateway to the outer world. The gateway rewrites &'*.hitch.fict.example'& as
26224 &'hitch.fict.example'& when sending mail off-site.
26226 A host rewrites the local parts of its own users so that, for example,
26227 &'fp42@hitch.fict.example'& becomes &'Ford.Prefect@hitch.fict.example'&.
26232 .section "When does rewriting happen?" "SECID148"
26233 .cindex "rewriting" "timing of"
26234 .cindex "&ACL;" "rewriting addresses in"
26235 Configured address rewriting can take place at several different stages of a
26236 message's processing.
26238 .vindex "&$sender_address$&"
26239 At the start of an ACL for MAIL, the sender address may have been rewritten
26240 by a special SMTP-time rewrite rule (see section &<<SSECTrewriteS>>&), but no
26241 ordinary rewrite rules have yet been applied. If, however, the sender address
26242 is verified in the ACL, it is rewritten before verification, and remains
26243 rewritten thereafter. The subsequent value of &$sender_address$& is the
26244 rewritten address. This also applies if sender verification happens in a
26245 RCPT ACL. Otherwise, when the sender address is not verified, it is
26246 rewritten as soon as a message's header lines have been received.
26248 .vindex "&$domain$&"
26249 .vindex "&$local_part$&"
26250 Similarly, at the start of an ACL for RCPT, the current recipient's address
26251 may have been rewritten by a special SMTP-time rewrite rule, but no ordinary
26252 rewrite rules have yet been applied to it. However, the behaviour is different
26253 from the sender address when a recipient is verified. The address is rewritten
26254 for the verification, but the rewriting is not remembered at this stage. The
26255 value of &$local_part$& and &$domain$& after verification are always the same
26256 as they were before (that is, they contain the unrewritten &-- except for
26257 SMTP-time rewriting &-- address).
26259 As soon as a message's header lines have been received, all the envelope
26260 recipient addresses are permanently rewritten, and rewriting is also applied to
26261 the addresses in the header lines (if configured). This happens before adding
26262 any header lines that were specified in MAIL or RCPT ACLs, and
26263 .cindex "&[local_scan()]& function" "address rewriting; timing of"
26264 before the DATA ACL and &[local_scan()]& functions are run.
26266 When an address is being routed, either for delivery or for verification,
26267 rewriting is applied immediately to child addresses that are generated by
26268 redirection, unless &%no_rewrite%& is set on the router.
26270 .cindex "envelope from"
26271 .cindex "envelope sender" "rewriting at transport time"
26272 .cindex "rewriting" "at transport time"
26273 .cindex "header lines" "rewriting at transport time"
26274 At transport time, additional rewriting of addresses in header lines can be
26275 specified by setting the generic &%headers_rewrite%& option on a transport.
26276 This option contains rules that are identical in form to those in the rewrite
26277 section of the configuration file. They are applied to the original message
26278 header lines and any that were added by ACLs or a system filter. They are not
26279 applied to header lines that are added by routers or the transport.
26281 The outgoing envelope sender can be rewritten by means of the &%return_path%&
26282 transport option. However, it is not possible to rewrite envelope recipients at
26288 .section "Testing the rewriting rules that apply on input" "SECID149"
26289 .cindex "rewriting" "testing"
26290 .cindex "testing" "rewriting"
26291 Exim's input rewriting configuration appears in a part of the runtime
26292 configuration file headed by &"begin rewrite"&. It can be tested by the
26293 &%-brw%& command line option. This takes an address (which can be a full RFC
26294 2822 address) as its argument. The output is a list of how the address would be
26295 transformed by the rewriting rules for each of the different places it might
26296 appear in an incoming message, that is, for each different header and for the
26297 envelope sender and recipient fields. For example,
26299 exim -brw ph10@exim.workshop.example
26301 might produce the output
26303 sender: Philip.Hazel@exim.workshop.example
26304 from: Philip.Hazel@exim.workshop.example
26305 to: ph10@exim.workshop.example
26306 cc: ph10@exim.workshop.example
26307 bcc: ph10@exim.workshop.example
26308 reply-to: Philip.Hazel@exim.workshop.example
26309 env-from: Philip.Hazel@exim.workshop.example
26310 env-to: ph10@exim.workshop.example
26312 which shows that rewriting has been set up for that address when used in any of
26313 the source fields, but not when it appears as a recipient address. At the
26314 present time, there is no equivalent way of testing rewriting rules that are
26315 set for a particular transport.
26318 .section "Rewriting rules" "SECID150"
26319 .cindex "rewriting" "rules"
26320 The rewrite section of the configuration file consists of lines of rewriting
26323 <&'source pattern'&> <&'replacement'&> <&'flags'&>
26325 Rewriting rules that are specified for the &%headers_rewrite%& generic
26326 transport option are given as a colon-separated list. Each item in the list
26327 takes the same form as a line in the main rewriting configuration (except that
26328 any colons must be doubled, of course).
26330 The formats of source patterns and replacement strings are described below.
26331 Each is terminated by white space, unless enclosed in double quotes, in which
26332 case normal quoting conventions apply inside the quotes. The flags are single
26333 characters which may appear in any order. Spaces and tabs between them are
26336 For each address that could potentially be rewritten, the rules are scanned in
26337 order, and replacements for the address from earlier rules can themselves be
26338 replaced by later rules (but see the &"q"& and &"R"& flags).
26340 The order in which addresses are rewritten is undefined, may change between
26341 releases, and must not be relied on, with one exception: when a message is
26342 received, the envelope sender is always rewritten first, before any header
26343 lines are rewritten. For example, the replacement string for a rewrite of an
26344 address in &'To:'& must not assume that the message's address in &'From:'& has
26345 (or has not) already been rewritten. However, a rewrite of &'From:'& may assume
26346 that the envelope sender has already been rewritten.
26348 .vindex "&$domain$&"
26349 .vindex "&$local_part$&"
26350 The variables &$local_part$& and &$domain$& can be used in the replacement
26351 string to refer to the address that is being rewritten. Note that lookup-driven
26352 rewriting can be done by a rule of the form
26356 where the lookup key uses &$1$& and &$2$& or &$local_part$& and &$domain$& to
26357 refer to the address that is being rewritten.
26360 .section "Rewriting patterns" "SECID151"
26361 .cindex "rewriting" "patterns"
26362 .cindex "address list" "in a rewriting pattern"
26363 The source pattern in a rewriting rule is any item which may appear in an
26364 address list (see section &<<SECTaddresslist>>&). It is in fact processed as a
26365 single-item address list, which means that it is expanded before being tested
26366 against the address. As always, if you use a regular expression as a pattern,
26367 you must take care to escape dollar and backslash characters, or use the &`\N`&
26368 facility to suppress string expansion within the regular expression.
26370 Domains in patterns should be given in lower case. Local parts in patterns are
26371 case-sensitive. If you want to do case-insensitive matching of local parts, you
26372 can use a regular expression that starts with &`^(?i)`&.
26374 .cindex "numerical variables (&$1$& &$2$& etc)" "in rewriting rules"
26375 After matching, the numerical variables &$1$&, &$2$&, etc. may be set,
26376 depending on the type of match which occurred. These can be used in the
26377 replacement string to insert portions of the incoming address. &$0$& always
26378 refers to the complete incoming address. When a regular expression is used, the
26379 numerical variables are set from its capturing subexpressions. For other types
26380 of pattern they are set as follows:
26383 If a local part or domain starts with an asterisk, the numerical variables
26384 refer to the character strings matched by asterisks, with &$1$& associated with
26385 the first asterisk, and &$2$& with the second, if present. For example, if the
26388 *queen@*.fict.example
26390 is matched against the address &'hearts-queen@wonderland.fict.example'& then
26392 $0 = hearts-queen@wonderland.fict.example
26396 Note that if the local part does not start with an asterisk, but the domain
26397 does, it is &$1$& that contains the wild part of the domain.
26400 If the domain part of the pattern is a partial lookup, the wild and fixed parts
26401 of the domain are placed in the next available numerical variables. Suppose,
26402 for example, that the address &'foo@bar.baz.example'& is processed by a
26403 rewriting rule of the form
26405 &`*@partial-dbm;/some/dbm/file`& <&'replacement string'&>
26407 and the key in the file that matches the domain is &`*.baz.example`&. Then
26413 If the address &'foo@baz.example'& is looked up, this matches the same
26414 wildcard file entry, and in this case &$2$& is set to the empty string, but
26415 &$3$& is still set to &'baz.example'&. If a non-wild key is matched in a
26416 partial lookup, &$2$& is again set to the empty string and &$3$& is set to the
26417 whole domain. For non-partial domain lookups, no numerical variables are set.
26421 .section "Rewriting replacements" "SECID152"
26422 .cindex "rewriting" "replacements"
26423 If the replacement string for a rule is a single asterisk, addresses that
26424 match the pattern and the flags are &'not'& rewritten, and no subsequent
26425 rewriting rules are scanned. For example,
26427 hatta@lookingglass.fict.example * f
26429 specifies that &'hatta@lookingglass.fict.example'& is never to be rewritten in
26432 .vindex "&$domain$&"
26433 .vindex "&$local_part$&"
26434 If the replacement string is not a single asterisk, it is expanded, and must
26435 yield a fully qualified address. Within the expansion, the variables
26436 &$local_part$& and &$domain$& refer to the address that is being rewritten.
26437 Any letters they contain retain their original case &-- they are not lower
26438 cased. The numerical variables are set up according to the type of pattern that
26439 matched the address, as described above. If the expansion is forced to fail by
26440 the presence of &"fail"& in a conditional or lookup item, rewriting by the
26441 current rule is abandoned, but subsequent rules may take effect. Any other
26442 expansion failure causes the entire rewriting operation to be abandoned, and an
26443 entry written to the panic log.
26447 .subsection "Rewriting flags" "SSECID153"
26448 There are three different kinds of flag that may appear on rewriting rules:
26451 Flags that specify which headers and envelope addresses to rewrite: E, F, T, b,
26454 A flag that specifies rewriting at SMTP time: S.
26456 Flags that control the rewriting process: Q, q, R, w.
26459 For rules that are part of the &%headers_rewrite%& generic transport option,
26460 E, F, T, and S are not permitted.
26464 .subsection "Flags specifying which headers and envelope addresses to rewrite" &&&
26466 .cindex rewriting flags
26467 If none of the following flag letters, nor the &"S"& flag (see section
26468 &<<SSECTrewriteS>>&) are present, a main rewriting rule applies to all headers
26469 and to both the sender and recipient fields of the envelope, whereas a
26470 transport-time rewriting rule just applies to all headers. Otherwise, the
26471 rewriting rule is skipped unless the relevant addresses are being processed.
26473 &`E`& rewrite all envelope fields
26474 &`F`& rewrite the envelope From field
26475 &`T`& rewrite the envelope To field
26476 &`b`& rewrite the &'Bcc:'& header
26477 &`c`& rewrite the &'Cc:'& header
26478 &`f`& rewrite the &'From:'& header
26479 &`h`& rewrite all headers
26480 &`r`& rewrite the &'Reply-To:'& header
26481 &`s`& rewrite the &'Sender:'& header
26482 &`t`& rewrite the &'To:'& header
26484 "All headers" means all of the headers listed above that can be selected
26485 individually, plus their &'Resent-'& versions. It does not include
26486 other headers such as &'Subject:'& etc.
26488 You should be particularly careful about rewriting &'Sender:'& headers, and
26489 restrict this to special known cases in your own domains.
26492 .subsection "The SMTP-time rewriting flag" SSECTrewriteS
26493 .cindex SMTP "rewriting malformed addresses"
26494 .cindex RCPT "rewriting argument of"
26495 .cindex MAIL "rewriting argument of"
26496 The rewrite flag &"S"& specifies a rewrite of incoming envelope addresses at
26497 SMTP time, as soon as an address is received in a MAIL or RCPT command, and
26498 before any other processing; even before syntax checking. The pattern is
26499 required to be a regular expression, and it is matched against the whole of the
26500 data for the command, including any surrounding angle brackets.
26502 .vindex "&$domain$&"
26503 .vindex "&$local_part$&"
26504 This form of rewrite rule allows for the handling of addresses that are not
26505 compliant with RFCs 2821 and 2822 (for example, &"bang paths"& in batched SMTP
26506 input). Because the input is not required to be a syntactically valid address,
26507 the variables &$local_part$& and &$domain$& are not available during the
26508 expansion of the replacement string. The result of rewriting replaces the
26509 original address in the MAIL or RCPT command.
26512 .subsection "Flags controlling the rewriting process" SSECID155
26513 There are four flags which control the way the rewriting process works. These
26514 take effect only when a rule is invoked, that is, when the address is of the
26515 correct type (matches the flags) and matches the pattern:
26518 If the &"Q"& flag is set on a rule, the rewritten address is permitted to be an
26519 unqualified local part. It is qualified with &%qualify_recipient%&. In the
26520 absence of &"Q"& the rewritten address must always include a domain.
26522 If the &"q"& flag is set on a rule, no further rewriting rules are considered,
26523 even if no rewriting actually takes place because of a &"fail"& in the
26524 expansion. The &"q"& flag is not effective if the address is of the wrong type
26525 (does not match the flags) or does not match the pattern.
26527 The &"R"& flag causes a successful rewriting rule to be re-applied to the new
26528 address, up to ten times. It can be combined with the &"q"& flag, to stop
26529 rewriting once it fails to match (after at least one successful rewrite).
26531 .cindex "rewriting" "whole addresses"
26532 When an address in a header is rewritten, the rewriting normally applies only
26533 to the working part of the address, with any comments and RFC 2822 &"phrase"&
26534 left unchanged. For example, rewriting might change
26536 From: Ford Prefect <fp42@restaurant.hitch.fict.example>
26540 From: Ford Prefect <prefectf@hitch.fict.example>
26543 Sometimes there is a need to replace the whole address item, and this can be
26544 done by adding the flag letter &"w"& to a rule. If this is set on a rule that
26545 causes an address in a header line to be rewritten, the entire address is
26546 replaced, not just the working part. The replacement must be a complete RFC
26547 2822 address, including the angle brackets if necessary. If text outside angle
26548 brackets contains a character whose value is greater than 126 or less than 32
26549 (except for tab), the text is encoded according to RFC 2047. The character set
26550 is taken from &%headers_charset%&, which gets its default at build time.
26552 When the &"w"& flag is set on a rule that causes an envelope address to be
26553 rewritten, all but the working part of the replacement address is discarded.
26557 .section "Rewriting examples" "SECID156"
26558 Here is an example of the two common rewriting paradigms:
26560 *@*.hitch.fict.example $1@hitch.fict.example
26561 *@hitch.fict.example ${lookup{$1}dbm{/etc/realnames}\
26562 {$value}fail}@hitch.fict.example bctfrF
26564 Note the use of &"fail"& in the lookup expansion in the second rule, forcing
26565 the string expansion to fail if the lookup does not succeed. In this context it
26566 has the effect of leaving the original address unchanged, but Exim goes on to
26567 consider subsequent rewriting rules, if any, because the &"q"& flag is not
26568 present in that rule. An alternative to &"fail"& would be to supply &$1$&
26569 explicitly, which would cause the rewritten address to be the same as before,
26570 at the cost of a small bit of processing. Not supplying either of these is an
26571 error, since the rewritten address would then contain no local part.
26573 The first example above replaces the domain with a superior, more general
26574 domain. This may not be desirable for certain local parts. If the rule
26576 root@*.hitch.fict.example *
26578 were inserted before the first rule, rewriting would be suppressed for the
26579 local part &'root'& at any domain ending in &'hitch.fict.example'&.
26581 Rewriting can be made conditional on a number of tests, by making use of
26582 &${if$& in the expansion item. For example, to apply a rewriting rule only to
26583 messages that originate outside the local host:
26585 *@*.hitch.fict.example "${if !eq {$sender_host_address}{}\
26586 {$1@hitch.fict.example}fail}"
26588 The replacement string is quoted in this example because it contains white
26591 .cindex "rewriting" "bang paths"
26592 .cindex "bang paths" "rewriting"
26593 Exim does not handle addresses in the form of &"bang paths"&. If it sees such
26594 an address it treats it as an unqualified local part which it qualifies with
26595 the local qualification domain (if the source of the message is local or if the
26596 remote host is permitted to send unqualified addresses). Rewriting can
26597 sometimes be used to handle simple bang paths with a fixed number of
26598 components. For example, the rule
26600 \N^([^!]+)!(.*)@your.domain.example$\N $2@$1
26602 rewrites a two-component bang path &'host.name!user'& as the domain address
26603 &'user@host.name'&. However, there is a security implication in using this as
26604 a global rewriting rule for envelope addresses. It can provide a backdoor
26605 method for using your system as a relay, because the incoming addresses appear
26606 to be local. If the bang path addresses are received via SMTP, it is safer to
26607 use the &"S"& flag to rewrite them as they are received, so that relay checking
26608 can be done on the rewritten addresses.
26615 . ////////////////////////////////////////////////////////////////////////////
26616 . ////////////////////////////////////////////////////////////////////////////
26618 .chapter "Retry configuration" "CHAPretry"
26619 .scindex IIDretconf1 "retry" "configuration, description of"
26620 .scindex IIDregconf2 "configuration file" "retry section"
26621 The &"retry"& section of the runtime configuration file contains a list of
26622 retry rules that control how often Exim tries to deliver messages that cannot
26623 be delivered at the first attempt. If there are no retry rules (the section is
26624 empty or not present), there are no retries. In this situation, temporary
26625 errors are treated as permanent. The default configuration contains a single,
26626 general-purpose retry rule (see section &<<SECID57>>&). The &%-brt%& command
26627 line option can be used to test which retry rule will be used for a given
26628 address, domain and error.
26630 The most common cause of retries is temporary failure to deliver to a remote
26631 host because the host is down, or inaccessible because of a network problem.
26632 Exim's retry processing in this case is applied on a per-host (strictly, per IP
26633 address) basis, not on a per-message basis. Thus, if one message has recently
26634 been delayed, delivery of a new message to the same host is not immediately
26635 tried, but waits for the host's retry time to arrive. If the &%retry_defer%&
26636 log selector is set, the message
26637 .cindex "retry" "time not reached"
26638 &"retry time not reached"& is written to the main log whenever a delivery is
26639 skipped for this reason. Section &<<SECToutSMTPerr>>& contains more details of
26640 the handling of errors during remote deliveries.
26642 Retry processing applies to routing as well as to delivering, except as covered
26643 in the next paragraph. The retry rules do not distinguish between these
26644 actions. It is not possible, for example, to specify different behaviour for
26645 failures to route the domain &'snark.fict.example'& and failures to deliver to
26646 the host &'snark.fict.example'&. I didn't think anyone would ever need this
26647 added complication, so did not implement it. However, although they share the
26648 same retry rule, the actual retry times for routing and transporting a given
26649 domain are maintained independently.
26651 When a delivery is not part of a queue run (typically an immediate delivery on
26652 receipt of a message), the routers are always run, and local deliveries are
26653 always attempted, even if retry times are set for them. This makes for better
26654 behaviour if one particular message is causing problems (for example, causing
26655 quota overflow, or provoking an error in a filter file). If such a delivery
26656 suffers a temporary failure, the retry data is updated as normal, and
26657 subsequent delivery attempts from queue runs occur only when the retry time for
26658 the local address is reached.
26660 .section "Changing retry rules" "SECID157"
26661 If you change the retry rules in your configuration, you should consider
26662 whether or not to delete the retry data that is stored in Exim's spool area in
26663 files with names like &_db/retry_&. Deleting any of Exim's hints files is
26664 always safe; that is why they are called &"hints"&.
26666 The hints retry data contains suggested retry times based on the previous
26667 rules. In the case of a long-running problem with a remote host, it might
26668 record the fact that the host has timed out. If your new rules increase the
26669 timeout time for such a host, you should definitely remove the old retry data
26670 and let Exim recreate it, based on the new rules. Otherwise Exim might bounce
26671 messages that it should now be retaining.
26675 .section "Format of retry rules" "SECID158"
26676 .cindex "retry" "rules"
26677 Each retry rule occupies one line and consists of three or four parts,
26678 separated by white space: a pattern, an error name, an optional list of sender
26679 addresses, and a list of retry parameters. The pattern and sender lists must be
26680 enclosed in double quotes if they contain white space. The rules are searched
26681 in order until one is found where the pattern, error name, and sender list (if
26682 present) match the failing host or address, the error that occurred, and the
26683 message's sender, respectively.
26686 The pattern is any single item that may appear in an address list (see section
26687 &<<SECTaddresslist>>&). It is in fact processed as a one-item address list,
26688 which means that it is expanded before being tested against the address that
26689 has been delayed. A negated address list item is permitted. Address
26690 list processing treats a plain domain name as if it were preceded by &"*@"&,
26691 which makes it possible for many retry rules to start with just a domain. For
26694 lookingglass.fict.example * F,24h,30m;
26696 provides a rule for any address in the &'lookingglass.fict.example'& domain,
26699 alice@lookingglass.fict.example * F,24h,30m;
26701 applies only to temporary failures involving the local part &%alice%&.
26702 In practice, almost all rules start with a domain name pattern without a local
26705 .cindex "regular expressions" "in retry rules"
26706 &*Warning*&: If you use a regular expression in a retry rule pattern, it
26707 must match a complete address, not just a domain, because that is how regular
26708 expressions work in address lists.
26710 &`^\Nxyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Wrong%&
26711 &`^\N[^@]+@xyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Right%&
26715 .section "Choosing which retry rule to use for address errors" "SECID159"
26716 When Exim is looking for a retry rule after a routing attempt has failed (for
26717 example, after a DNS timeout), each line in the retry configuration is tested
26718 against the complete address only if &%retry_use_local_part%& is set for the
26719 router. Otherwise, only the domain is used, except when matching against a
26720 regular expression, when the local part of the address is replaced with &"*"&.
26721 A domain on its own can match a domain pattern, or a pattern that starts with
26722 &"*@"&. By default, &%retry_use_local_part%& is true for routers where
26723 &%check_local_user%& is true, and false for other routers.
26725 Similarly, when Exim is looking for a retry rule after a local delivery has
26726 failed (for example, after a mailbox full error), each line in the retry
26727 configuration is tested against the complete address only if
26728 &%retry_use_local_part%& is set for the transport (it defaults true for all
26731 .cindex "4&'xx'& responses" "retry rules for"
26732 However, when Exim is looking for a retry rule after a remote delivery attempt
26733 suffers an address error (a 4&'xx'& SMTP response for a recipient address), the
26734 whole address is always used as the key when searching the retry rules. The
26735 rule that is found is used to create a retry time for the combination of the
26736 failing address and the message's sender. It is the combination of sender and
26737 recipient that is delayed in subsequent queue runs until its retry time is
26738 reached. You can delay the recipient without regard to the sender by setting
26739 &%address_retry_include_sender%& false in the &(smtp)& transport but this can
26740 lead to problems with servers that regularly issue 4&'xx'& responses to RCPT
26745 .section "Choosing which retry rule to use for host and message errors" &&&
26747 For a temporary error that is not related to an individual address (for
26748 example, a connection timeout), each line in the retry configuration is checked
26749 twice. First, the name of the remote host is used as a domain name (preceded by
26750 &"*@"& when matching a regular expression). If this does not match the line,
26751 the domain from the email address is tried in a similar fashion. For example,
26752 suppose the MX records for &'a.b.c.example'& are
26754 a.b.c.example MX 5 x.y.z.example
26758 and the retry rules are
26760 p.q.r.example * F,24h,30m;
26761 a.b.c.example * F,4d,45m;
26763 and a delivery to the host &'x.y.z.example'& suffers a connection failure. The
26764 first rule matches neither the host nor the domain, so Exim looks at the second
26765 rule. This does not match the host, but it does match the domain, so it is used
26766 to calculate the retry time for the host &'x.y.z.example'&. Meanwhile, Exim
26767 tries to deliver to &'p.q.r.example'&. If this also suffers a host error, the
26768 first retry rule is used, because it matches the host.
26770 In other words, temporary failures to deliver to host &'p.q.r.example'& use the
26771 first rule to determine retry times, but for all the other hosts for the domain
26772 &'a.b.c.example'&, the second rule is used. The second rule is also used if
26773 routing to &'a.b.c.example'& suffers a temporary failure.
26775 &*Note*&: The host name is used when matching the patterns, not its IP address.
26776 However, if a message is routed directly to an IP address without the use of a
26777 host name, for example, if a &(manualroute)& router contains a setting such as:
26779 route_list = *.a.example 192.168.34.23
26781 then the &"host name"& that is used when searching for a retry rule is the
26782 textual form of the IP address.
26784 .section "Retry rules for specific errors" "SECID161"
26785 .cindex "retry" "specific errors; specifying"
26786 The second field in a retry rule is the name of a particular error, or an
26787 asterisk, which matches any error. The errors that can be tested for are:
26790 .vitem &%auth_failed%&
26791 Authentication failed when trying to send to a host in the
26792 &%hosts_require_auth%& list in an &(smtp)& transport.
26794 .vitem &%data_4xx%&
26795 A 4&'xx'& error was received for an outgoing DATA command, either immediately
26796 after the command, or after sending the message's data.
26798 .vitem &%mail_4xx%&
26799 A 4&'xx'& error was received for an outgoing MAIL command.
26801 .vitem &%rcpt_4xx%&
26802 A 4&'xx'& error was received for an outgoing RCPT command.
26805 For the three 4&'xx'& errors, either the first or both of the x's can be given
26806 as specific digits, for example: &`mail_45x`& or &`rcpt_436`&. For example, to
26807 recognize 452 errors given to RCPT commands for addresses in a certain domain,
26808 and have retries every ten minutes with a one-hour timeout, you could set up a
26809 retry rule of this form:
26811 the.domain.name rcpt_452 F,1h,10m
26813 These errors apply to both outgoing SMTP (the &(smtp)& transport) and outgoing
26814 LMTP (either the &(lmtp)& transport, or the &(smtp)& transport in LMTP mode).
26817 .vitem &%lost_connection%&
26818 A server unexpectedly closed the SMTP connection. There may, of course,
26819 legitimate reasons for this (host died, network died), but if it repeats a lot
26820 for the same host, it indicates something odd.
26823 A DNS lookup for a host failed.
26824 Note that a &%dnslookup%& router will need to have matched
26825 its &%fail_defer_domains%& option for this retry type to be usable.
26826 Also note that a &%manualroute%& router will probably need
26827 its &%host_find_failed%& option set to &%defer%&.
26829 .vitem &%refused_MX%&
26830 A connection to a host obtained from an MX record was refused.
26832 .vitem &%refused_A%&
26833 A connection to a host not obtained from an MX record was refused.
26836 A connection was refused.
26838 .vitem &%timeout_connect_MX%&
26839 A connection attempt to a host obtained from an MX record timed out.
26841 .vitem &%timeout_connect_A%&
26842 A connection attempt to a host not obtained from an MX record timed out.
26844 .vitem &%timeout_connect%&
26845 A connection attempt timed out.
26847 .vitem &%timeout_MX%&
26848 There was a timeout while connecting or during an SMTP session with a host
26849 obtained from an MX record.
26851 .vitem &%timeout_A%&
26852 There was a timeout while connecting or during an SMTP session with a host not
26853 obtained from an MX record.
26856 There was a timeout while connecting or during an SMTP session.
26858 .vitem &%tls_required%&
26859 The server was required to use TLS (it matched &%hosts_require_tls%& in the
26860 &(smtp)& transport), but either did not offer TLS, or it responded with 4&'xx'&
26861 to STARTTLS, or there was a problem setting up the TLS connection.
26864 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
26867 .vitem &%quota_%&<&'time'&>
26868 .cindex "quota" "error testing in retry rule"
26869 .cindex "retry" "quota error testing"
26870 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
26871 transport, and the mailbox has not been accessed for <&'time'&>. For example,
26872 &'quota_4d'& applies to a quota error when the mailbox has not been accessed
26876 .cindex "mailbox" "time of last read"
26877 The idea of &%quota_%&<&'time'&> is to make it possible to have shorter
26878 timeouts when the mailbox is full and is not being read by its owner. Ideally,
26879 it should be based on the last time that the user accessed the mailbox.
26880 However, it is not always possible to determine this. Exim uses the following
26884 If the mailbox is a single file, the time of last access (the &"atime"&) is
26885 used. As no new messages are being delivered (because the mailbox is over
26886 quota), Exim does not access the file, so this is the time of last user access.
26888 .cindex "maildir format" "time of last read"
26889 For a maildir delivery, the time of last modification of the &_new_&
26890 subdirectory is used. As the mailbox is over quota, no new files are created in
26891 the &_new_& subdirectory, because no new messages are being delivered. Any
26892 change to the &_new_& subdirectory is therefore assumed to be the result of an
26893 MUA moving a new message to the &_cur_& directory when it is first read. The
26894 time that is used is therefore the last time that the user read a new message.
26896 For other kinds of multi-file mailbox, the time of last access cannot be
26897 obtained, so a retry rule that uses this type of error field is never matched.
26900 The quota errors apply both to system-enforced quotas and to Exim's own quota
26901 mechanism in the &(appendfile)& transport. The &'quota'& error also applies
26902 when a local delivery is deferred because a partition is full (the ENOSPC
26907 .section "Retry rules for specified senders" "SECID162"
26908 .cindex "retry" "rules; sender-specific"
26909 You can specify retry rules that apply only when the failing message has a
26910 specific sender. In particular, this can be used to define retry rules that
26911 apply only to bounce messages. The third item in a retry rule can be of this
26914 &`senders=`&<&'address list'&>
26916 The retry timings themselves are then the fourth item. For example:
26918 * rcpt_4xx senders=: F,1h,30m
26920 matches recipient 4&'xx'& errors for bounce messages sent to any address at any
26921 host. If the address list contains white space, it must be enclosed in quotes.
26924 a.domain rcpt_452 senders="xb.dom : yc.dom" G,8h,10m,1.5
26926 &*Warning*&: This facility can be unhelpful if it is used for host errors
26927 (which do not depend on the recipient). The reason is that the sender is used
26928 only to match the retry rule. Once the rule has been found for a host error,
26929 its contents are used to set a retry time for the host, and this will apply to
26930 all messages, not just those with specific senders.
26932 When testing retry rules using &%-brt%&, you can supply a sender using the
26933 &%-f%& command line option, like this:
26935 exim -f "" -brt user@dom.ain
26937 If you do not set &%-f%& with &%-brt%&, a retry rule that contains a senders
26938 list is never matched.
26944 .section "Retry parameters" "SECID163"
26945 .cindex "retry" "parameters in rules"
26946 The third (or fourth, if a senders list is present) field in a retry rule is a
26947 sequence of retry parameter sets, separated by semicolons. Each set consists of
26949 <&'letter'&>,<&'cutoff time'&>,<&'arguments'&>
26951 The letter identifies the algorithm for computing a new retry time; the cutoff
26952 time is the time beyond which this algorithm no longer applies, and the
26953 arguments vary the algorithm's action. The cutoff time is measured from the
26954 time that the first failure for the domain (combined with the local part if
26955 relevant) was detected, not from the time the message was received.
26957 .cindex "retry" "algorithms"
26958 .cindex "retry" "fixed intervals"
26959 .cindex "retry" "increasing intervals"
26960 .cindex "retry" "random intervals"
26961 The available algorithms are:
26964 &'F'&: retry at fixed intervals. There is a single time parameter specifying
26967 &'G'&: retry at geometrically increasing intervals. The first argument
26968 specifies a starting value for the interval, and the second a multiplier, which
26969 is used to increase the size of the interval at each retry.
26971 &'H'&: retry at randomized intervals. The arguments are as for &'G'&. For each
26972 retry, the previous interval is multiplied by the factor in order to get a
26973 maximum for the next interval. The minimum interval is the first argument of
26974 the parameter, and an actual interval is chosen randomly between them. Such a
26975 rule has been found to be helpful in cluster configurations when all the
26976 members of the cluster restart at once, and may therefore synchronize their
26977 queue processing times.
26980 When computing the next retry time, the algorithm definitions are scanned in
26981 order until one whose cutoff time has not yet passed is reached. This is then
26982 used to compute a new retry time that is later than the current time. In the
26983 case of fixed interval retries, this simply means adding the interval to the
26984 current time. For geometrically increasing intervals, retry intervals are
26985 computed from the rule's parameters until one that is greater than the previous
26986 interval is found. The main configuration variable
26987 .cindex "limit" "retry interval"
26988 .cindex "retry" "interval, maximum"
26989 .oindex "&%retry_interval_max%&"
26990 &%retry_interval_max%& limits the maximum interval between retries. It
26991 cannot be set greater than &`24h`&, which is its default value.
26993 A single remote domain may have a number of hosts associated with it, and each
26994 host may have more than one IP address. Retry algorithms are selected on the
26995 basis of the domain name, but are applied to each IP address independently. If,
26996 for example, a host has two IP addresses and one is unusable, Exim will
26997 generate retry times for it and will not try to use it until its next retry
26998 time comes. Thus the good IP address is likely to be tried first most of the
27001 .cindex "hints database" "use for retrying"
27002 Retry times are hints rather than promises. Exim does not make any attempt to
27003 run deliveries exactly at the computed times. Instead, a queue runner process
27004 starts delivery processes for delayed messages periodically, and these attempt
27005 new deliveries only for those addresses that have passed their next retry time.
27006 If a new message arrives for a deferred address, an immediate delivery attempt
27007 occurs only if the address has passed its retry time. In the absence of new
27008 messages, the minimum time between retries is the interval between queue runner
27009 processes. There is not much point in setting retry times of five minutes if
27010 your queue runners happen only once an hour, unless there are a significant
27011 number of incoming messages (which might be the case on a system that is
27012 sending everything to a smart host, for example).
27014 The data in the retry hints database can be inspected by using the
27015 &'exim_dumpdb'& or &'exim_fixdb'& utility programs (see chapter
27016 &<<CHAPutils>>&). The latter utility can also be used to change the data. The
27017 &'exinext'& utility script can be used to find out what the next retry times
27018 are for the hosts associated with a particular mail domain, and also for local
27019 deliveries that have been deferred.
27022 .section "Retry rule examples" "SECID164"
27023 Here are some example retry rules:
27025 alice@wonderland.fict.example quota_5d F,7d,3h
27026 wonderland.fict.example quota_5d
27027 wonderland.fict.example * F,1h,15m; G,2d,1h,2;
27028 lookingglass.fict.example * F,24h,30m;
27029 * refused_A F,2h,20m;
27030 * * F,2h,15m; G,16h,1h,1.5; F,5d,8h
27032 The first rule sets up special handling for mail to
27033 &'alice@wonderland.fict.example'& when there is an over-quota error and the
27034 mailbox has not been read for at least 5 days. Retries continue every three
27035 hours for 7 days. The second rule handles over-quota errors for all other local
27036 parts at &'wonderland.fict.example'&; the absence of a local part has the same
27037 effect as supplying &"*@"&. As no retry algorithms are supplied, messages that
27038 fail are bounced immediately if the mailbox has not been read for at least 5
27041 The third rule handles all other errors at &'wonderland.fict.example'&; retries
27042 happen every 15 minutes for an hour, then with geometrically increasing
27043 intervals until two days have passed since a delivery first failed. After the
27044 first hour there is a delay of one hour, then two hours, then four hours, and
27045 so on (this is a rather extreme example).
27047 The fourth rule controls retries for the domain &'lookingglass.fict.example'&.
27048 They happen every 30 minutes for 24 hours only. The remaining two rules handle
27049 all other domains, with special action for connection refusal from hosts that
27050 were not obtained from an MX record.
27052 The final rule in a retry configuration should always have asterisks in the
27053 first two fields so as to provide a general catch-all for any addresses that do
27054 not have their own special handling. This example tries every 15 minutes for 2
27055 hours, then with intervals starting at one hour and increasing by a factor of
27056 1.5 up to 16 hours, then every 8 hours up to 5 days.
27060 .section "Timeout of retry data" "SECID165"
27061 .cindex "timeout" "of retry data"
27062 .oindex "&%retry_data_expire%&"
27063 .cindex "hints database" "data expiry"
27064 .cindex "retry" "timeout of data"
27065 Exim timestamps the data that it writes to its retry hints database. When it
27066 consults the data during a delivery it ignores any that is older than the value
27067 set in &%retry_data_expire%& (default 7 days). If, for example, a host hasn't
27068 been tried for 7 days, Exim will try to deliver to it immediately a message
27069 arrives, and if that fails, it will calculate a retry time as if it were
27070 failing for the first time.
27072 This improves the behaviour for messages routed to rarely-used hosts such as MX
27073 backups. If such a host was down at one time, and happens to be down again when
27074 Exim tries a month later, using the old retry data would imply that it had been
27075 down all the time, which is not a justified assumption.
27077 If a host really is permanently dead, this behaviour causes a burst of retries
27078 every now and again, but only if messages routed to it are rare. If there is a
27079 message at least once every 7 days the retry data never expires.
27084 .section "Long-term failures" "SECID166"
27085 .cindex "delivery failure, long-term"
27086 .cindex "retry" "after long-term failure"
27087 Special processing happens when an email address has been failing for so long
27088 that the cutoff time for the last algorithm is reached. For example, using the
27089 default retry rule:
27091 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
27093 the cutoff time is four days. Reaching the retry cutoff is independent of how
27094 long any specific message has been failing; it is the length of continuous
27095 failure for the recipient address that counts.
27097 When the cutoff time is reached for a local delivery, or for all the IP
27098 addresses associated with a remote delivery, a subsequent delivery failure
27099 causes Exim to give up on the address, and a bounce message is generated.
27100 In order to cater for new messages that use the failing address, a next retry
27101 time is still computed from the final algorithm, and is used as follows:
27103 For local deliveries, one delivery attempt is always made for any subsequent
27104 messages. If this delivery fails, the address fails immediately. The
27105 post-cutoff retry time is not used.
27107 .cindex "final cutoff" "retries, controlling"
27108 .cindex retry "final cutoff"
27109 If the delivery is remote, there are two possibilities, controlled by the
27110 .oindex "&%delay_after_cutoff%&"
27111 &%delay_after_cutoff%& option of the &(smtp)& transport. The option is true by
27112 default. Until the post-cutoff retry time for one of the IP addresses,
27113 as set by the &%retry_data_expire%& option, is
27114 reached, the failing email address is bounced immediately, without a delivery
27115 attempt taking place. After that time, one new delivery attempt is made to
27116 those IP addresses that are past their retry times, and if that still fails,
27117 the address is bounced and new retry times are computed.
27119 In other words, when all the hosts for a given email address have been failing
27120 for a long time, Exim bounces rather then defers until one of the hosts' retry
27121 times is reached. Then it tries once, and bounces if that attempt fails. This
27122 behaviour ensures that few resources are wasted in repeatedly trying to deliver
27123 to a broken destination, but if the host does recover, Exim will eventually
27126 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
27127 addresses are past their final cutoff time, Exim tries to deliver to those IP
27128 addresses that have not been tried since the message arrived. If there are
27129 no suitable IP addresses, or if they all fail, the address is bounced. In other
27130 words, it does not delay when a new message arrives, but tries the expired
27131 addresses immediately, unless they have been tried since the message arrived.
27132 If there is a continuous stream of messages for the failing domains, setting
27133 &%delay_after_cutoff%& false means that there will be many more attempts to
27134 deliver to permanently failing IP addresses than when &%delay_after_cutoff%& is
27137 .section "Deliveries that work intermittently" "SECID167"
27138 .cindex "retry" "intermittently working deliveries"
27139 Some additional logic is needed to cope with cases where a host is
27140 intermittently available, or when a message has some attribute that prevents
27141 its delivery when others to the same address get through. In this situation,
27142 because some messages are successfully delivered, the &"retry clock"& for the
27143 host or address keeps getting reset by the successful deliveries, and so
27144 failing messages remain in the queue for ever because the cutoff time is never
27147 Two exceptional actions are applied to prevent this happening. The first
27148 applies to errors that are related to a message rather than a remote host.
27149 Section &<<SECToutSMTPerr>>& has a discussion of the different kinds of error;
27150 examples of message-related errors are 4&'xx'& responses to MAIL or DATA
27151 commands, and quota failures. For this type of error, if a message's arrival
27152 time is earlier than the &"first failed"& time for the error, the earlier time
27153 is used when scanning the retry rules to decide when to try next and when to
27154 time out the address.
27156 The exceptional second action applies in all cases. If a message has been on
27157 the queue for longer than the cutoff time of any applicable retry rule for a
27158 given address, a delivery is attempted for that address, even if it is not yet
27159 time, and if this delivery fails, the address is timed out. A new retry time is
27160 not computed in this case, so that other messages for the same address are
27161 considered immediately.
27162 .ecindex IIDretconf1
27163 .ecindex IIDregconf2
27170 . ////////////////////////////////////////////////////////////////////////////
27171 . ////////////////////////////////////////////////////////////////////////////
27173 .chapter "SMTP authentication" "CHAPSMTPAUTH"
27174 .scindex IIDauthconf1 "SMTP" "authentication configuration"
27175 .scindex IIDauthconf2 "authentication"
27176 The &"authenticators"& section of Exim's runtime configuration is concerned
27177 with SMTP authentication. This facility is an extension to the SMTP protocol,
27178 described in RFC 2554, which allows a client SMTP host to authenticate itself
27179 to a server. This is a common way for a server to recognize clients that are
27180 permitted to use it as a relay. SMTP authentication is not of relevance to the
27181 transfer of mail between servers that have no managerial connection with each
27184 The name of an authenticator is limited to be &drivernamemax; ASCII characters long;
27185 prior to Exim 4.95 names would be silently truncated at this length, but now
27188 .cindex "AUTH" "description of"
27189 .cindex "ESMTP extensions" AUTH
27190 Very briefly, the way SMTP authentication works is as follows:
27193 The server advertises a number of authentication &'mechanisms'& in response to
27194 the client's EHLO command.
27196 The client issues an AUTH command, naming a specific mechanism. The command
27197 may, optionally, contain some authentication data.
27199 The server may issue one or more &'challenges'&, to which the client must send
27200 appropriate responses. In simple authentication mechanisms, the challenges are
27201 just prompts for user names and passwords. The server does not have to issue
27202 any challenges &-- in some mechanisms the relevant data may all be transmitted
27203 with the AUTH command.
27205 The server either accepts or denies authentication.
27207 If authentication succeeds, the client may optionally make use of the AUTH
27208 option on the MAIL command to pass an authenticated sender in subsequent
27209 mail transactions. Authentication lasts for the remainder of the SMTP
27212 If authentication fails, the client may give up, or it may try a different
27213 authentication mechanism, or it may try transferring mail over the
27214 unauthenticated connection.
27217 If you are setting up a client, and want to know which authentication
27218 mechanisms the server supports, you can use Telnet to connect to port 25 (the
27219 SMTP port) on the server, and issue an EHLO command. The response to this
27220 includes the list of supported mechanisms. For example:
27222 &`$ `&&*&`telnet server.example 25`&*&
27223 &`Trying 192.168.34.25...`&
27224 &`Connected to server.example.`&
27225 &`Escape character is '^]'.`&
27226 &`220 server.example ESMTP Exim 4.20 ...`&
27227 &*&`ehlo client.example`&*&
27228 &`250-server.example Hello client.example [10.8.4.5]`&
27229 &`250-SIZE 52428800`&
27234 The second-last line of this example output shows that the server supports
27235 authentication using the PLAIN mechanism. In Exim, the different authentication
27236 mechanisms are configured by specifying &'authenticator'& drivers. Like the
27237 routers and transports, which authenticators are included in the binary is
27238 controlled by build-time definitions. The following are currently available,
27239 included by setting
27242 AUTH_CYRUS_SASL=yes
27246 AUTH_HEIMDAL_GSSAPI=yes
27251 in &_Local/Makefile_&, respectively. The first of these supports the CRAM-MD5
27252 authentication mechanism (RFC 2195), and the second provides an interface to
27253 the Cyrus SASL authentication library.
27254 The third is an interface to Dovecot's authentication system, delegating the
27255 work via a socket interface.
27256 The fourth provides for negotiation of authentication done via non-SMTP means,
27257 as defined by RFC 4422 Appendix A.
27258 The fifth provides an interface to the GNU SASL authentication library, which
27259 provides mechanisms but typically not data sources.
27260 The sixth provides direct access to Heimdal GSSAPI, geared for Kerberos, but
27261 supporting setting a server keytab.
27262 The seventh can be configured to support
27263 the PLAIN authentication mechanism (RFC 2595) or the LOGIN mechanism, which is
27264 not formally documented, but used by several MUAs.
27265 The eighth authenticator
27266 supports Microsoft's &'Secure Password Authentication'& mechanism.
27267 The last is an Exim authenticator but not an SMTP one;
27268 instead it can use information from a TLS negotiation.
27270 The authenticators are configured using the same syntax as other drivers (see
27271 section &<<SECTfordricon>>&). If no authenticators are required, no
27272 authentication section need be present in the configuration file. Each
27273 authenticator can in principle have both server and client functions. When Exim
27274 is receiving SMTP mail, it is acting as a server; when it is sending out
27275 messages over SMTP, it is acting as a client. Authenticator configuration
27276 options are provided for use in both these circumstances.
27278 To make it clear which options apply to which situation, the prefixes
27279 &%server_%& and &%client_%& are used on option names that are specific to
27280 either the server or the client function, respectively. Server and client
27281 functions are disabled if none of their options are set. If an authenticator is
27282 to be used for both server and client functions, a single definition, using
27283 both sets of options, is required. For example:
27287 public_name = CRAM-MD5
27288 server_secret = ${if eq{$auth1}{ph10}{secret1}fail}
27290 client_secret = secret2
27292 The &%server_%& option is used when Exim is acting as a server, and the
27293 &%client_%& options when it is acting as a client.
27295 Descriptions of the individual authenticators are given in subsequent chapters.
27296 The remainder of this chapter covers the generic options for the
27297 authenticators, followed by general discussion of the way authentication works
27300 &*Beware:*& the meaning of &$auth1$&, &$auth2$&, ... varies on a per-driver and
27301 per-mechanism basis. Please read carefully to determine which variables hold
27302 account labels such as usercodes and which hold passwords or other
27303 authenticating data.
27305 Note that some mechanisms support two different identifiers for accounts: the
27306 &'authentication id'& and the &'authorization id'&. The contractions &'authn'&
27307 and &'authz'& are commonly encountered. The American spelling is standard here.
27308 Conceptually, authentication data such as passwords are tied to the identifier
27309 used to authenticate; servers may have rules to permit one user to act as a
27310 second user, so that after login the session is treated as though that second
27311 user had logged in. That second user is the &'authorization id'&. A robust
27312 configuration might confirm that the &'authz'& field is empty or matches the
27313 &'authn'& field. Often this is just ignored. The &'authn'& can be considered
27314 as verified data, the &'authz'& as an unverified request which the server might
27317 A &'realm'& is a text string, typically a domain name, presented by a server
27318 to a client to help it select an account and credentials to use. In some
27319 mechanisms, the client and server provably agree on the realm, but clients
27320 typically can not treat the realm as secure data to be blindly trusted.
27324 .section "Generic options for authenticators" "SECID168"
27325 .cindex "authentication" "generic options"
27326 .cindex "options" "generic; for authenticators"
27328 .option client_condition authenticators string&!! unset
27329 When Exim is authenticating as a client, it skips any authenticator whose
27330 &%client_condition%& expansion yields &"0"&, &"no"&, or &"false"&. This can be
27331 used, for example, to skip plain text authenticators when the connection is not
27332 encrypted by a setting such as:
27334 client_condition = ${if !eq{$tls_out_cipher}{}}
27338 .option client_set_id authenticators string&!! unset
27339 When client authentication succeeds, this condition is expanded; the
27340 result is used in the log lines for outbound messages.
27341 Typically it will be the user name used for authentication.
27344 .option driver authenticators string unset
27345 This option must always be set. It specifies which of the available
27346 authenticators is to be used.
27349 .option public_name authenticators string unset
27350 This option specifies the name of the authentication mechanism that the driver
27351 implements, and by which it is known to the outside world. These names should
27352 contain only upper case letters, digits, underscores, and hyphens (RFC 2222),
27353 but Exim in fact matches them caselessly. If &%public_name%& is not set, it
27354 defaults to the driver's instance name.
27357 .option server_advertise_condition authenticators string&!! unset
27358 When a server is about to advertise an authentication mechanism, the condition
27359 is expanded. If it yields the empty string, &"0"&, &"no"&, or &"false"&, the
27360 mechanism is not advertised.
27361 If the expansion fails, the mechanism is not advertised. If the failure was not
27362 forced, and was not caused by a lookup defer, the incident is logged.
27363 See section &<<SECTauthexiser>>& below for further discussion.
27366 .option server_condition authenticators string&!! unset
27367 This option must be set for a &%plaintext%& server authenticator, where it
27368 is used directly to control authentication. See section &<<SECTplainserver>>&
27371 For the &(gsasl)& authenticator, this option is required for various
27372 mechanisms; see chapter &<<CHAPgsasl>>& for details.
27374 For the other authenticators, &%server_condition%& can be used as an additional
27375 authentication or authorization mechanism that is applied after the other
27376 authenticator conditions succeed. If it is set, it is expanded when the
27377 authenticator would otherwise return a success code. If the expansion is forced
27378 to fail, authentication fails. Any other expansion failure causes a temporary
27379 error code to be returned. If the result of a successful expansion is an empty
27380 string, &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
27381 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds. For any
27382 other result, a temporary error code is returned, with the expanded string as
27386 .option server_debug_print authenticators string&!! unset
27387 If this option is set and authentication debugging is enabled (see the &%-d%&
27388 command line option), the string is expanded and included in the debugging
27389 output when the authenticator is run as a server. This can help with checking
27390 out the values of variables.
27391 If expansion of the string fails, the error message is written to the debugging
27392 output, and Exim carries on processing.
27395 .option server_set_id authenticators string&!! unset
27396 .vindex "&$authenticated_id$&"
27397 .vindex "&$authenticated_fail_id$&"
27398 When an Exim server successfully authenticates a client, this string is
27399 expanded using data from the authentication, and preserved for any incoming
27400 messages in the variable &$authenticated_id$&. It is also included in the log
27401 lines for incoming messages. For example, a user/password authenticator
27402 configuration might preserve the user name that was used to authenticate, and
27403 refer to it subsequently during delivery of the message.
27404 On a failing authentication the expansion result is instead saved in
27405 the &$authenticated_fail_id$& variable.
27406 If expansion fails, the option is ignored.
27409 .option server_mail_auth_condition authenticators string&!! unset
27410 This option allows a server to discard authenticated sender addresses supplied
27411 as part of MAIL commands in SMTP connections that are authenticated by the
27412 driver on which &%server_mail_auth_condition%& is set. The option is not used
27413 as part of the authentication process; instead its (unexpanded) value is
27414 remembered for later use.
27415 How it is used is described in the following section.
27421 .section "The AUTH parameter on MAIL commands" "SECTauthparamail"
27422 .cindex "authentication" "sender; authenticated"
27423 .cindex "AUTH" "on MAIL command"
27424 When a client supplied an AUTH= item on a MAIL command, Exim applies
27425 the following checks before accepting it as the authenticated sender of the
27429 If the connection is not using extended SMTP (that is, HELO was used rather
27430 than EHLO), the use of AUTH= is a syntax error.
27432 If the value of the AUTH= parameter is &"<>"&, it is ignored.
27434 .vindex "&$authenticated_sender$&"
27435 If &%acl_smtp_mailauth%& is defined, the ACL it specifies is run. While it is
27436 running, the value of &$authenticated_sender$& is set to the value obtained
27437 from the AUTH= parameter. If the ACL does not yield &"accept"&, the value of
27438 &$authenticated_sender$& is deleted. The &%acl_smtp_mailauth%& ACL may not
27439 return &"drop"& or &"discard"&. If it defers, a temporary error code (451) is
27440 given for the MAIL command.
27442 If &%acl_smtp_mailauth%& is not defined, the value of the AUTH= parameter
27443 is accepted and placed in &$authenticated_sender$& only if the client has
27446 If the AUTH= value was accepted by either of the two previous rules, and
27447 the client has authenticated, and the authenticator has a setting for the
27448 &%server_mail_auth_condition%&, the condition is checked at this point. The
27449 valued that was saved from the authenticator is expanded. If the expansion
27450 fails, or yields an empty string, &"0"&, &"no"&, or &"false"&, the value of
27451 &$authenticated_sender$& is deleted. If the expansion yields any other value,
27452 the value of &$authenticated_sender$& is retained and passed on with the
27457 When &$authenticated_sender$& is set for a message, it is passed on to other
27458 hosts to which Exim authenticates as a client. Do not confuse this value with
27459 &$authenticated_id$&, which is a string obtained from the authentication
27460 process, and which is not usually a complete email address.
27462 .vindex "&$sender_address$&"
27463 Whenever an AUTH= value is ignored, the incident is logged. The ACL for
27464 MAIL, if defined, is run after AUTH= is accepted or ignored. It can
27465 therefore make use of &$authenticated_sender$&. The converse is not true: the
27466 value of &$sender_address$& is not yet set up when the &%acl_smtp_mailauth%&
27471 .section "Authentication on an Exim server" "SECTauthexiser"
27472 .cindex "authentication" "on an Exim server"
27473 When Exim receives an EHLO command, it advertises the public names of those
27474 authenticators that are configured as servers, subject to the following
27478 The client host must match &%auth_advertise_hosts%& (default *).
27480 If the &%server_advertise_condition%& option is set, its expansion must not
27481 yield the empty string, &"0"&, &"no"&, or &"false"&.
27484 The order in which the authenticators are defined controls the order in which
27485 the mechanisms are advertised.
27487 Some mail clients (for example, some versions of Netscape) require the user to
27488 provide a name and password for authentication whenever AUTH is advertised,
27489 even though authentication may not in fact be needed (for example, Exim may be
27490 set up to allow unconditional relaying from the client by an IP address check).
27491 You can make such clients more friendly by not advertising AUTH to them.
27492 For example, if clients on the 10.9.8.0/24 network are permitted (by the ACL
27493 that runs for RCPT) to relay without authentication, you should set
27495 auth_advertise_hosts = ! 10.9.8.0/24
27497 so that no authentication mechanisms are advertised to them.
27499 The &%server_advertise_condition%& controls the advertisement of individual
27500 authentication mechanisms. For example, it can be used to restrict the
27501 advertisement of a particular mechanism to encrypted connections, by a setting
27504 server_advertise_condition = ${if eq{$tls_in_cipher}{}{no}{yes}}
27506 .vindex "&$tls_in_cipher$&"
27507 If the session is encrypted, &$tls_in_cipher$& is not empty, and so the expansion
27508 yields &"yes"&, which allows the advertisement to happen.
27510 When an Exim server receives an AUTH command from a client, it rejects it
27511 immediately if AUTH was not advertised in response to an earlier EHLO
27512 command. This is the case if
27515 The client host does not match &%auth_advertise_hosts%&; or
27517 No authenticators are configured with server options; or
27519 Expansion of &%server_advertise_condition%& blocked the advertising of all the
27520 server authenticators.
27524 Otherwise, Exim runs the ACL specified by &%acl_smtp_auth%& in order
27525 to decide whether to accept the command. If &%acl_smtp_auth%& is not set,
27526 AUTH is accepted from any client host.
27528 If AUTH is not rejected by the ACL, Exim searches its configuration for a
27529 server authentication mechanism that was advertised in response to EHLO and
27530 that matches the one named in the AUTH command. If it finds one, it runs
27531 the appropriate authentication protocol, and authentication either succeeds or
27532 fails. If there is no matching advertised mechanism, the AUTH command is
27533 rejected with a 504 error.
27535 .vindex "&$received_protocol$&"
27536 .vindex "&$sender_host_authenticated$&"
27537 When a message is received from an authenticated host, the value of
27538 &$received_protocol$& is set to &"esmtpa"& or &"esmtpsa"& instead of &"esmtp"&
27539 or &"esmtps"&, and &$sender_host_authenticated$& contains the name (not the
27540 public name) of the authenticator driver that successfully authenticated the
27541 client from which the message was received. This variable is empty if there was
27542 no successful authentication.
27544 .cindex authentication "expansion item"
27545 Successful authentication sets up information used by the
27546 &%authresults%& expansion item.
27549 .cindex authentication "failure event, server"
27550 If an authenticator is run and does not succeed,
27551 an event (see &<<CHAPevents>>&) of type "auth:fail" is raised.
27552 While the event is being processed the variables
27553 &$sender_host_authenticated$& (with the authenticator name)
27554 and &$authenticated_fail_id$& (as set by the authenticator &%server_set_id%& option)
27556 If the event is serviced and a string is returned then the string will be logged
27557 instead of the default log line.
27558 See <<CHAPevents>> for details on events.
27562 .section "Testing server authentication" "SECID169"
27563 .cindex "authentication" "testing a server"
27564 .cindex "AUTH" "testing a server"
27565 .cindex "base64 encoding" "creating authentication test data"
27566 Exim's &%-bh%& option can be useful for testing server authentication
27567 configurations. The data for the AUTH command has to be sent using base64
27568 encoding. A quick way to produce such data for testing is the following Perl
27572 printf ("%s", encode_base64(eval "\"$ARGV[0]\""));
27574 .cindex "binary zero" "in authentication data"
27575 This interprets its argument as a Perl string, and then encodes it. The
27576 interpretation as a Perl string allows binary zeros, which are required for
27577 some kinds of authentication, to be included in the data. For example, a
27578 command line to run this script on such data might be
27580 encode '\0user\0password'
27582 Note the use of single quotes to prevent the shell interpreting the
27583 backslashes, so that they can be interpreted by Perl to specify characters
27584 whose code value is zero.
27586 &*Warning 1*&: If either of the user or password strings starts with an octal
27587 digit, you must use three zeros instead of one after the leading backslash. If
27588 you do not, the octal digit that starts your string will be incorrectly
27589 interpreted as part of the code for the first character.
27591 &*Warning 2*&: If there are characters in the strings that Perl interprets
27592 specially, you must use a Perl escape to prevent them being misinterpreted. For
27593 example, a command such as
27595 encode '\0user@domain.com\0pas$$word'
27597 gives an incorrect answer because of the unescaped &"@"& and &"$"& characters.
27599 If you have the &%mimencode%& command installed, another way to produce
27600 base64-encoded strings is to run the command
27602 echo -e -n `\0user\0password' | mimencode
27604 The &%-e%& option of &%echo%& enables the interpretation of backslash escapes
27605 in the argument, and the &%-n%& option specifies no newline at the end of its
27606 output. However, not all versions of &%echo%& recognize these options, so you
27607 should check your version before relying on this suggestion.
27611 .section "Authentication by an Exim client" "SECID170"
27612 .cindex "authentication" "on an Exim client"
27613 The &(smtp)& transport has two options called &%hosts_require_auth%& and
27614 &%hosts_try_auth%&. When the &(smtp)& transport connects to a server that
27615 announces support for authentication, and the host matches an entry in either
27616 of these options, Exim (as a client) tries to authenticate as follows:
27619 For each authenticator that is configured as a client, in the order in which
27620 they are defined in the configuration, it searches the authentication
27621 mechanisms announced by the server for one whose name matches the public name
27622 of the authenticator.
27625 .vindex "&$host_address$&"
27626 When it finds one that matches, it runs the authenticator's client code. The
27627 variables &$host$& and &$host_address$& are available for any string expansions
27628 that the client might do. They are set to the server's name and IP address. If
27629 any expansion is forced to fail, the authentication attempt is abandoned, and
27630 Exim moves on to the next authenticator. Otherwise an expansion failure causes
27631 delivery to be deferred.
27633 If the result of the authentication attempt is a temporary error or a timeout,
27634 Exim abandons trying to send the message to the host for the moment. It will
27635 try again later. If there are any backup hosts available, they are tried in the
27640 .cindex authentication "failure event, client"
27641 If the response to authentication is a permanent error (5&'xx'& code),
27642 an event (see &<<CHAPevents>>&) of type "auth:fail" is raised.
27643 While the event is being processed the variable
27644 &$sender_host_authenticated$& (with the authenticator name)
27646 If the event is serviced and a string is returned then the string will be logged.
27647 See <<CHAPevents>> for details on events.
27651 If the response to authentication is a permanent error (5&'xx'& code), Exim
27652 carries on searching the list of authenticators and tries another one if
27653 possible. If all authentication attempts give permanent errors, or if there are
27654 no attempts because no mechanisms match (or option expansions force failure),
27655 what happens depends on whether the host matches &%hosts_require_auth%& or
27656 &%hosts_try_auth%&. In the first case, a temporary error is generated, and
27657 delivery is deferred. The error can be detected in the retry rules, and thereby
27658 turned into a permanent error if you wish. In the second case, Exim tries to
27659 deliver the message unauthenticated.
27662 Note that the hostlist test for whether to do authentication can be
27663 confused if name-IP lookups change between the time the peer is decided
27664 upon and the time that the transport runs. For example, with a manualroute
27665 router given a host name, and with DNS "round-robin" used by that name: if
27666 the local resolver cache times out between the router and the transport
27667 running, the transport may get an IP for the name for its authentication
27668 check which does not match the connection peer IP.
27669 No authentication will then be done, despite the names being identical.
27671 For such cases use a separate transport which always authenticates.
27673 .cindex "AUTH" "on MAIL command"
27674 When Exim has authenticated itself to a remote server, it adds the AUTH
27675 parameter to the MAIL commands it sends, if it has an authenticated sender for
27676 the message. If the message came from a remote host, the authenticated sender
27677 is the one that was receiving on an incoming MAIL command, provided that the
27678 incoming connection was authenticated and the &%server_mail_auth%& condition
27679 allowed the authenticated sender to be retained. If a local process calls Exim
27680 to send a message, the sender address that is built from the login name and
27681 &%qualify_domain%& is treated as authenticated. However, if the
27682 &%authenticated_sender%& option is set on the &(smtp)& transport, it overrides
27683 the authenticated sender that was received with the message.
27684 .ecindex IIDauthconf1
27685 .ecindex IIDauthconf2
27692 . ////////////////////////////////////////////////////////////////////////////
27693 . ////////////////////////////////////////////////////////////////////////////
27695 .chapter "The plaintext authenticator" "CHAPplaintext"
27696 .scindex IIDplaiauth1 "&(plaintext)& authenticator"
27697 .scindex IIDplaiauth2 "authenticators" "&(plaintext)&"
27698 The &(plaintext)& authenticator can be configured to support the PLAIN and
27699 LOGIN authentication mechanisms, both of which transfer authentication data as
27700 plain (unencrypted) text (though base64 encoded). The use of plain text is a
27701 security risk; you are strongly advised to insist on the use of SMTP encryption
27702 (see chapter &<<CHAPTLS>>&) if you use the PLAIN or LOGIN mechanisms. If you do
27703 use unencrypted plain text, you should not use the same passwords for SMTP
27704 connections as you do for login accounts.
27706 .section "Avoiding cleartext use" "SECTplain_TLS"
27707 The following generic option settings will disable &(plaintext)& authenticators when
27708 TLS is not being used:
27710 server_advertise_condition = ${if def:tls_in_cipher }
27711 client_condition = ${if def:tls_out_cipher}
27714 &*Note*&: a plaintext SMTP AUTH done inside TLS is not vulnerable to casual snooping,
27715 but is still vulnerable to a Man In The Middle attack unless certificates
27716 (including their names) have been properly verified.
27718 .section "Plaintext server options" "SECID171"
27719 .cindex "options" "&(plaintext)& authenticator (server)"
27720 When configured as a server, &(plaintext)& uses the following options:
27722 .option server_condition authenticators string&!! unset
27723 This is actually a global authentication option, but it must be set in order to
27724 configure the &(plaintext)& driver as a server. Its use is described below.
27726 .option server_prompts plaintext "string list&!!" unset
27727 The contents of this option, after expansion, must be a colon-separated list of
27728 prompt strings. If expansion fails, a temporary authentication rejection is
27731 .section "Using plaintext in a server" "SECTplainserver"
27732 .cindex "AUTH" "in &(plaintext)& authenticator"
27733 .cindex "binary zero" "in &(plaintext)& authenticator"
27734 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
27735 "in &(plaintext)& authenticator"
27736 .vindex "&$auth1$&, &$auth2$&, etc"
27737 .cindex "base64 encoding" "in &(plaintext)& authenticator"
27739 When running as a server, &(plaintext)& performs the authentication test by
27740 expanding a string. The data sent by the client with the AUTH command, or in
27741 response to subsequent prompts, is base64 encoded, and so may contain any byte
27742 values when decoded. If any data is supplied with the command, it is treated as
27743 a list of strings, separated by NULs (binary zeros), the first three of which
27744 are placed in the expansion variables &$auth1$&, &$auth2$&, and &$auth3$&
27745 (neither LOGIN nor PLAIN uses more than three strings).
27747 For compatibility with previous releases of Exim, the values are also placed in
27748 the expansion variables &$1$&, &$2$&, and &$3$&. However, the use of these
27749 variables for this purpose is now deprecated, as it can lead to confusion in
27750 string expansions that also use them for other things.
27752 If there are more strings in &%server_prompts%& than the number of strings
27753 supplied with the AUTH command, the remaining prompts are used to obtain more
27754 data. Each response from the client may be a list of NUL-separated strings.
27756 .vindex "&$authenticated_id$&"
27757 Once a sufficient number of data strings have been received,
27758 &%server_condition%& is expanded. If the expansion is forced to fail,
27759 authentication fails. Any other expansion failure causes a temporary error code
27760 to be returned. If the result of a successful expansion is an empty string,
27761 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
27762 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
27763 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
27764 For any other result, a temporary error code is returned, with the expanded
27765 string as the error text.
27767 &*Warning*&: If you use a lookup in the expansion to find the user's
27768 password, be sure to make the authentication fail if the user is unknown.
27769 There are good and bad examples at the end of the next section.
27773 .section "The PLAIN authentication mechanism" "SECID172"
27774 .cindex "PLAIN authentication mechanism"
27775 .cindex authentication PLAIN
27776 .cindex "binary zero" "in &(plaintext)& authenticator"
27777 The PLAIN authentication mechanism (RFC 2595) specifies that three strings be
27778 sent as one item of data (that is, one combined string containing two NUL
27779 separators). The data is sent either as part of the AUTH command, or
27780 subsequently in response to an empty prompt from the server.
27782 The second and third strings are a user name and a corresponding password.
27783 Using a single fixed user name and password as an example, this could be
27784 configured as follows:
27788 public_name = PLAIN
27790 server_condition = \
27791 ${if and {{eq{$auth2}{username}}{eq{$auth3}{mysecret}}}}
27792 server_set_id = $auth2
27794 Note that the default result strings from &%if%& (&"true"& or an empty string)
27795 are exactly what we want here, so they need not be specified. Obviously, if the
27796 password contains expansion-significant characters such as dollar, backslash,
27797 or closing brace, they have to be escaped.
27799 The &%server_prompts%& setting specifies a single, empty prompt (empty items at
27800 the end of a string list are ignored). If all the data comes as part of the
27801 AUTH command, as is commonly the case, the prompt is not used. This
27802 authenticator is advertised in the response to EHLO as
27806 and a client host can authenticate itself by sending the command
27808 AUTH PLAIN AHVzZXJuYW1lAG15c2VjcmV0
27810 As this contains three strings (more than the number of prompts), no further
27811 data is required from the client. Alternatively, the client may just send
27815 to initiate authentication, in which case the server replies with an empty
27816 prompt. The client must respond with the combined data string.
27818 The data string is base64 encoded, as required by the RFC. This example,
27819 when decoded, is <&'NUL'&>&`username`&<&'NUL'&>&`mysecret`&, where <&'NUL'&>
27820 represents a zero byte. This is split up into three strings, the first of which
27821 is empty. The &%server_condition%& option in the authenticator checks that the
27822 second two are &`username`& and &`mysecret`& respectively.
27824 Having just one fixed user name and password, as in this example, is not very
27825 realistic, though for a small organization with only a handful of
27826 authenticating clients it could make sense.
27828 A more sophisticated instance of this authenticator could use the user name in
27829 &$auth2$& to look up a password in a file or database, and maybe do an encrypted
27830 comparison (see &%crypteq%& in chapter &<<CHAPexpand>>&). Here is a example of
27831 this approach, where the passwords are looked up in a DBM file. &*Warning*&:
27832 This is an incorrect example:
27834 server_condition = \
27835 ${if eq{$auth3}{${lookup{$auth2}dbm{/etc/authpwd}}}}
27837 The expansion uses the user name (&$auth2$&) as the key to look up a password,
27838 which it then compares to the supplied password (&$auth3$&). Why is this example
27839 incorrect? It works fine for existing users, but consider what happens if a
27840 non-existent user name is given. The lookup fails, but as no success/failure
27841 strings are given for the lookup, it yields an empty string. Thus, to defeat
27842 the authentication, all a client has to do is to supply a non-existent user
27843 name and an empty password. The correct way of writing this test is:
27845 server_condition = ${lookup{$auth2}dbm{/etc/authpwd}\
27846 {${if eq{$value}{$auth3}}} {false}}
27848 In this case, if the lookup succeeds, the result is checked; if the lookup
27849 fails, &"false"& is returned and authentication fails. If &%crypteq%& is being
27850 used instead of &%eq%&, the first example is in fact safe, because &%crypteq%&
27851 always fails if its second argument is empty. However, the second way of
27852 writing the test makes the logic clearer.
27855 .section "The LOGIN authentication mechanism" "SECID173"
27856 .cindex "LOGIN authentication mechanism"
27857 .cindex authentication LOGIN
27858 The LOGIN authentication mechanism is not documented in any RFC, but is in use
27859 in a number of programs. No data is sent with the AUTH command. Instead, a
27860 user name and password are supplied separately, in response to prompts. The
27861 plaintext authenticator can be configured to support this as in this example:
27865 public_name = LOGIN
27866 server_prompts = User Name : Password
27867 server_condition = \
27868 ${if and {{eq{$auth1}{username}}{eq{$auth2}{mysecret}}}}
27869 server_set_id = $auth1
27871 Because of the way plaintext operates, this authenticator accepts data supplied
27872 with the AUTH command (in contravention of the specification of LOGIN), but
27873 if the client does not supply it (as is the case for LOGIN clients), the prompt
27874 strings are used to obtain two data items.
27876 Some clients are very particular about the precise text of the prompts. For
27877 example, Outlook Express is reported to recognize only &"Username:"& and
27878 &"Password:"&. Here is an example of a LOGIN authenticator that uses those
27879 strings. It uses the &%ldapauth%& expansion condition to check the user
27880 name and password by binding to an LDAP server:
27884 public_name = LOGIN
27885 server_prompts = Username:: : Password::
27886 server_condition = ${if and{{ \
27889 user="uid=${quote_ldap_dn:$auth1},ou=people,o=example.org" \
27890 pass=${quote:$auth2} \
27891 ldap://ldap.example.org/} }} }
27892 server_set_id = uid=$auth1,ou=people,o=example.org
27894 We have to check that the username is not empty before using it, because LDAP
27895 does not permit empty DN components. We must also use the &%quote_ldap_dn%&
27896 operator to correctly quote the DN for authentication. However, the basic
27897 &%quote%& operator, rather than any of the LDAP quoting operators, is the
27898 correct one to use for the password, because quoting is needed only to make
27899 the password conform to the Exim syntax. At the LDAP level, the password is an
27900 uninterpreted string.
27903 .section "Support for different kinds of authentication" "SECID174"
27904 A number of string expansion features are provided for the purpose of
27905 interfacing to different ways of user authentication. These include checking
27906 traditionally encrypted passwords from &_/etc/passwd_& (or equivalent), PAM,
27907 Radius, &%ldapauth%&, &'pwcheck'&, and &'saslauthd'&. For details see section
27913 .section "Using plaintext in a client" "SECID175"
27914 .cindex "options" "&(plaintext)& authenticator (client)"
27915 The &(plaintext)& authenticator has two client options:
27917 .option client_ignore_invalid_base64 plaintext boolean false
27918 If the client receives a server prompt that is not a valid base64 string,
27919 authentication is abandoned by default. However, if this option is set true,
27920 the error in the challenge is ignored and the client sends the response as
27923 .option client_send plaintext string&!! unset
27924 The string is a colon-separated list of authentication data strings. Each
27925 string is independently expanded before being sent to the server. The first
27926 string is sent with the AUTH command; any more strings are sent in response
27927 to prompts from the server. Before each string is expanded, the value of the
27928 most recent prompt is placed in the next &$auth$&<&'n'&> variable, starting
27929 with &$auth1$& for the first prompt. Up to three prompts are stored in this
27930 way. Thus, the prompt that is received in response to sending the first string
27931 (with the AUTH command) can be used in the expansion of the second string, and
27932 so on. If an invalid base64 string is received when
27933 &%client_ignore_invalid_base64%& is set, an empty string is put in the
27934 &$auth$&<&'n'&> variable.
27936 &*Note*&: You cannot use expansion to create multiple strings, because
27937 splitting takes priority and happens first.
27939 Because the PLAIN authentication mechanism requires NUL (binary zero) bytes in
27940 the data, further processing is applied to each string before it is sent. If
27941 there are any single circumflex characters in the string, they are converted to
27942 NULs. Should an actual circumflex be required as data, it must be doubled in
27945 This is an example of a client configuration that implements the PLAIN
27946 authentication mechanism with a fixed user name and password:
27950 public_name = PLAIN
27951 client_send = ^username^mysecret
27953 The lack of colons means that the entire text is sent with the AUTH
27954 command, with the circumflex characters converted to NULs.
27955 Note that due to the ambiguity of parsing three consectutive circumflex characters
27956 there is no way to provide a password having a leading circumflex.
27960 that uses the LOGIN mechanism is:
27964 public_name = LOGIN
27965 client_send = : username : mysecret
27967 The initial colon means that the first string is empty, so no data is sent with
27968 the AUTH command itself. The remaining strings are sent in response to
27970 .ecindex IIDplaiauth1
27971 .ecindex IIDplaiauth2
27976 . ////////////////////////////////////////////////////////////////////////////
27977 . ////////////////////////////////////////////////////////////////////////////
27979 .chapter "The cram_md5 authenticator" "CHID9"
27980 .scindex IIDcramauth1 "&(cram_md5)& authenticator"
27981 .scindex IIDcramauth2 "authenticators" "&(cram_md5)&"
27982 .cindex "CRAM-MD5 authentication mechanism"
27983 .cindex authentication CRAM-MD5
27984 The CRAM-MD5 authentication mechanism is described in RFC 2195. The server
27985 sends a challenge string to the client, and the response consists of a user
27986 name and the CRAM-MD5 digest of the challenge string combined with a secret
27987 string (password) which is known to both server and client. Thus, the secret
27988 is not sent over the network as plain text, which makes this authenticator more
27989 secure than &(plaintext)&. However, the downside is that the secret has to be
27990 available in plain text at either end.
27993 .section "Using cram_md5 as a server" "SECID176"
27994 .cindex "options" "&(cram_md5)& authenticator (server)"
27995 This authenticator has one server option, which must be set to configure the
27996 authenticator as a server:
27998 .option server_secret cram_md5 string&!! unset
27999 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(cram_md5)& authenticator"
28000 When the server receives the client's response, the user name is placed in
28001 the expansion variable &$auth1$&, and &%server_secret%& is expanded to
28002 obtain the password for that user. The server then computes the CRAM-MD5 digest
28003 that the client should have sent, and checks that it received the correct
28004 string. If the expansion of &%server_secret%& is forced to fail, authentication
28005 fails. If the expansion fails for some other reason, a temporary error code is
28006 returned to the client.
28008 For compatibility with previous releases of Exim, the user name is also placed
28009 in &$1$&. However, the use of this variables for this purpose is now
28010 deprecated, as it can lead to confusion in string expansions that also use
28011 numeric variables for other things.
28013 For example, the following authenticator checks that the user name given by the
28014 client is &"ph10"&, and if so, uses &"secret"& as the password. For any other
28015 user name, authentication fails.
28019 public_name = CRAM-MD5
28020 server_secret = ${if eq{$auth1}{ph10}{secret}fail}
28021 server_set_id = $auth1
28023 .vindex "&$authenticated_id$&"
28024 If authentication succeeds, the setting of &%server_set_id%& preserves the user
28025 name in &$authenticated_id$&. A more typical configuration might look up the
28026 secret string in a file, using the user name as the key. For example:
28030 public_name = CRAM-MD5
28031 server_secret = ${lookup{$auth1}lsearch{/etc/authpwd}\
28033 server_set_id = $auth1
28035 Note that this expansion explicitly forces failure if the lookup fails
28036 because &$auth1$& contains an unknown user name.
28038 As another example, if you wish to re-use a Cyrus SASL sasldb2 file without
28039 using the relevant libraries, you need to know the realm to specify in the
28040 lookup and then ask for the &"userPassword"& attribute for that user in that
28045 public_name = CRAM-MD5
28046 server_secret = ${lookup{$auth1:mail.example.org:userPassword}\
28047 dbmjz{/etc/sasldb2}{$value}fail}
28048 server_set_id = $auth1
28051 .section "Using cram_md5 as a client" "SECID177"
28052 .cindex "options" "&(cram_md5)& authenticator (client)"
28053 When used as a client, the &(cram_md5)& authenticator has two options:
28057 .option client_name cram_md5 string&!! "the primary host name"
28058 This string is expanded, and the result used as the user name data when
28059 computing the response to the server's challenge.
28062 .option client_secret cram_md5 string&!! unset
28063 This option must be set for the authenticator to work as a client. Its value is
28064 expanded and the result used as the secret string when computing the response.
28068 .vindex "&$host_address$&"
28069 Different user names and secrets can be used for different servers by referring
28070 to &$host$& or &$host_address$& in the options. Forced failure of either
28071 expansion string is treated as an indication that this authenticator is not
28072 prepared to handle this case. Exim moves on to the next configured client
28073 authenticator. Any other expansion failure causes Exim to give up trying to
28074 send the message to the current server.
28076 A simple example configuration of a &(cram_md5)& authenticator, using fixed
28081 public_name = CRAM-MD5
28083 client_secret = secret
28085 .ecindex IIDcramauth1
28086 .ecindex IIDcramauth2
28090 . ////////////////////////////////////////////////////////////////////////////
28091 . ////////////////////////////////////////////////////////////////////////////
28093 .chapter "The cyrus_sasl authenticator" "CHID10"
28094 .scindex IIDcyrauth1 "&(cyrus_sasl)& authenticator"
28095 .scindex IIDcyrauth2 "authenticators" "&(cyrus_sasl)&"
28096 .cindex "Cyrus" "SASL library"
28098 The code for this authenticator was provided by Matthew Byng-Maddick while
28099 at A L Digital Ltd.
28101 The &(cyrus_sasl)& authenticator provides server support for the Cyrus SASL
28102 library implementation of the RFC 2222 (&"Simple Authentication and Security
28103 Layer"&). This library supports a number of authentication mechanisms,
28104 including PLAIN and LOGIN, but also several others that Exim does not support
28105 directly. In particular, there is support for Kerberos authentication.
28107 The &(cyrus_sasl)& authenticator provides a gatewaying mechanism directly to
28108 the Cyrus interface, so if your Cyrus library can do, for example, CRAM-MD5,
28109 then so can the &(cyrus_sasl)& authenticator. By default it uses the public
28110 name of the driver to determine which mechanism to support.
28112 Where access to some kind of secret file is required, for example, in GSSAPI
28113 or CRAM-MD5, it is worth noting that the authenticator runs as the Exim
28114 user, and that the Cyrus SASL library has no way of escalating privileges
28115 by default. You may also find you need to set environment variables,
28116 depending on the driver you are using.
28118 The application name provided by Exim is &"exim"&, so various SASL options may
28119 be set in &_exim.conf_& in your SASL directory. If you are using GSSAPI for
28120 Kerberos, note that because of limitations in the GSSAPI interface,
28121 changing the server keytab might need to be communicated down to the Kerberos
28122 layer independently. The mechanism for doing so is dependent upon the Kerberos
28125 For example, for older releases of Heimdal, the environment variable KRB5_KTNAME
28126 may be set to point to an alternative keytab file. Exim will pass this
28127 variable through from its own inherited environment when started as root or the
28128 Exim user. The keytab file needs to be readable by the Exim user.
28129 With newer releases of Heimdal, a setuid Exim may cause Heimdal to discard the
28130 environment variable. In practice, for those releases, the Cyrus authenticator
28131 is not a suitable interface for GSSAPI (Kerberos) support. Instead, consider
28132 the &(heimdal_gssapi)& authenticator, described in chapter &<<CHAPheimdalgss>>&
28135 .section "Using cyrus_sasl as a server" "SECID178"
28136 The &(cyrus_sasl)& authenticator has four private options. It puts the username
28137 (on a successful authentication) into &$auth1$&. For compatibility with
28138 previous releases of Exim, the username is also placed in &$1$&. However, the
28139 use of this variable for this purpose is now deprecated, as it can lead to
28140 confusion in string expansions that also use numeric variables for other
28144 .option server_hostname cyrus_sasl string&!! "see below"
28145 This option selects the hostname that is used when communicating with the
28146 library. The default value is &`$primary_hostname`&. It is up to the underlying
28147 SASL plug-in what it does with this data.
28150 .option server_mech cyrus_sasl string "see below"
28151 This option selects the authentication mechanism this driver should use. The
28152 default is the value of the generic &%public_name%& option. This option allows
28153 you to use a different underlying mechanism from the advertised name. For
28157 driver = cyrus_sasl
28158 public_name = X-ANYTHING
28159 server_mech = CRAM-MD5
28160 server_set_id = $auth1
28163 .option server_realm cyrus_sasl string&!! unset
28164 This specifies the SASL realm that the server claims to be in.
28167 .option server_service cyrus_sasl string &`smtp`&
28168 This is the SASL service that the server claims to implement.
28171 For straightforward cases, you do not need to set any of the authenticator's
28172 private options. All you need to do is to specify an appropriate mechanism as
28173 the public name. Thus, if you have a SASL library that supports CRAM-MD5 and
28174 PLAIN, you could have two authenticators as follows:
28177 driver = cyrus_sasl
28178 public_name = CRAM-MD5
28179 server_set_id = $auth1
28182 driver = cyrus_sasl
28183 public_name = PLAIN
28184 server_set_id = $auth2
28186 Cyrus SASL does implement the LOGIN authentication method, even though it is
28187 not a standard method. It is disabled by default in the source distribution,
28188 but it is present in many binary distributions.
28189 .ecindex IIDcyrauth1
28190 .ecindex IIDcyrauth2
28195 . ////////////////////////////////////////////////////////////////////////////
28196 . ////////////////////////////////////////////////////////////////////////////
28197 .chapter "The dovecot authenticator" "CHAPdovecot"
28198 .scindex IIDdcotauth1 "&(dovecot)& authenticator"
28199 .scindex IIDdcotauth2 "authenticators" "&(dovecot)&"
28200 This authenticator is an interface to the authentication facility of the
28201 Dovecot 2 POP/IMAP server, which can support a number of authentication methods.
28202 Note that Dovecot must be configured to use auth-client not auth-userdb.
28203 If you are using Dovecot to authenticate POP/IMAP clients, it might be helpful
28204 to use the same mechanisms for SMTP authentication. This is a server
28205 authenticator only. There is only one option:
28207 .option server_socket dovecot string unset
28209 This option must specify the UNIX socket that is the interface to Dovecot
28210 authentication. The &%public_name%& option must specify an authentication
28211 mechanism that Dovecot is configured to support. You can have several
28212 authenticators for different mechanisms. For example:
28216 public_name = PLAIN
28217 server_socket = /var/run/dovecot/auth-client
28218 server_set_id = $auth1
28223 server_socket = /var/run/dovecot/auth-client
28224 server_set_id = $auth1
28226 If the SMTP connection is encrypted, or if &$sender_host_address$& is equal to
28227 &$received_ip_address$& (that is, the connection is local), the &"secured"&
28228 option is passed in the Dovecot authentication command. If, for a TLS
28229 connection, a client certificate has been verified, the &"valid-client-cert"&
28230 option is passed. When authentication succeeds, the identity of the user
28231 who authenticated is placed in &$auth1$&.
28233 The Dovecot configuration to match the above will look
28236 conf.d/10-master.conf :-
28241 unix_listener auth-client {
28248 conf.d/10-auth.conf :-
28250 auth_mechanisms = plain login ntlm
28253 .ecindex IIDdcotauth1
28254 .ecindex IIDdcotauth2
28257 . ////////////////////////////////////////////////////////////////////////////
28258 . ////////////////////////////////////////////////////////////////////////////
28259 .chapter "The gsasl authenticator" "CHAPgsasl"
28260 .scindex IIDgsaslauth1 "&(gsasl)& authenticator"
28261 .scindex IIDgsaslauth2 "authenticators" "&(gsasl)&"
28262 .cindex "authentication" "GNU SASL"
28263 .cindex "authentication" "SASL"
28264 .cindex "authentication" "EXTERNAL"
28265 .cindex "authentication" "ANONYMOUS"
28266 .cindex "authentication" "PLAIN"
28267 .cindex "authentication" "LOGIN"
28268 .cindex "authentication" "DIGEST-MD5"
28269 .cindex "authentication" "CRAM-MD5"
28270 .cindex "authentication" "SCRAM family"
28271 The &(gsasl)& authenticator provides integration for the GNU SASL
28272 library and the mechanisms it provides. This is new as of the 4.80 release
28273 and there are a few areas where the library does not let Exim smoothly
28274 scale to handle future authentication mechanisms, so no guarantee can be
28275 made that any particular new authentication mechanism will be supported
28276 without code changes in Exim.
28278 The library is expected to add support in an upcoming
28279 realease for the SCRAM-SHA-256 method.
28280 The macro _HAVE_AUTH_GSASL_SCRAM_SHA_256 will be defined
28283 To see the list of mechanisms supported by the library run Exim with "auth" debug
28284 enabled and look for a line containing "GNU SASL supports".
28285 Note however that some may not have been tested from Exim.
28288 .option client_authz gsasl string&!! unset
28289 This option can be used to supply an &'authorization id'&
28290 which is different to the &'authentication_id'& provided
28291 by &%client_username%& option.
28292 If unset or (after expansion) empty it is not used,
28293 which is the common case.
28295 .option client_channelbinding gsasl boolean false
28296 See &%server_channelbinding%& below.
28298 .option client_password gsasl string&!! unset
28299 This option is exapanded before use, and should result in
28300 the password to be used, in clear.
28302 .option client_username gsasl string&!! unset
28303 This option is exapanded before use, and should result in
28304 the account name to be used.
28307 .option client_spassword gsasl string&!! unset
28308 This option is only supported for library versions 1.9.1 and greater.
28309 The macro _HAVE_AUTH_GSASL_SCRAM_S_KEY will be defined when this is so.
28311 If a SCRAM mechanism is being used and this option is set
28312 and correctly sized
28313 it is used in preference to &%client_password%&.
28314 The value after expansion should be
28315 a 40 (for SHA-1) or 64 (for SHA-256) character string
28316 with the PBKDF2-prepared password, hex-encoded.
28318 Note that this value will depend on the salt and iteration-count
28319 supplied by the server.
28320 The option is expanded before use.
28321 During the expansion &$auth1$& is set with the client username,
28322 &$auth2$& with the iteration count, and
28323 &$auth3$& with the salt.
28325 The intent of this option
28326 is to support clients that can cache thes salted password
28327 to save on recalculation costs.
28328 The cache lookup should return an unusable value
28329 (eg. an empty string)
28330 if the salt or iteration count has changed
28332 If the authentication succeeds then the above variables are set,
28333 .vindex "&$auth4$&"
28334 plus the calculated salted password value value in &$auth4$&,
28335 during the expansion of the &%client_set_id%& option.
28336 A side-effect of this expansion can be used to prime the cache.
28339 .option server_channelbinding gsasl boolean false
28340 Some authentication mechanisms are able to use external context at both ends
28341 of the session to bind the authentication to that context, and fail the
28342 authentication process if that context differs. Specifically, some TLS
28343 ciphersuites can provide identifying information about the cryptographic
28346 This should have meant that certificate identity and verification becomes a
28347 non-issue, as a man-in-the-middle attack will cause the correct client and
28348 server to see different identifiers and authentication will fail.
28351 only usable by mechanisms which support "channel binding"; at time of
28352 writing, that's the SCRAM family.
28353 When using this feature the "-PLUS" variants of the method names need to be used.
28355 This defaults off to ensure smooth upgrade across Exim releases, in case
28356 this option causes some clients to start failing. Some future release
28357 of Exim might have switched the default to be true.
28359 . However, Channel Binding in TLS has proven to be vulnerable in current versions.
28360 . Do not plan to rely upon this feature for security, ever, without consulting
28361 . with a subject matter expert (a cryptographic engineer).
28363 This option was deprecated in previous releases due to doubts over
28364 the "Triple Handshake" vulnerability.
28365 Exim takes suitable precausions (requiring Extended Master Secret if TLS
28366 Session Resumption was used) for safety.
28369 .option server_hostname gsasl string&!! "see below"
28370 This option selects the hostname that is used when communicating with the
28371 library. The default value is &`$primary_hostname`&.
28372 Some mechanisms will use this data.
28375 .option server_mech gsasl string "see below"
28376 This option selects the authentication mechanism this driver should use. The
28377 default is the value of the generic &%public_name%& option. This option allows
28378 you to use a different underlying mechanism from the advertised name. For
28383 public_name = X-ANYTHING
28384 server_mech = CRAM-MD5
28385 server_set_id = $auth1
28389 .option server_password gsasl string&!! unset
28390 Various mechanisms need access to the cleartext password on the server, so
28391 that proof-of-possession can be demonstrated on the wire, without sending
28392 the password itself.
28394 The data available for lookup varies per mechanism.
28395 In all cases, &$auth1$& is set to the &'authentication id'&.
28396 The &$auth2$& variable will always be the &'authorization id'& (&'authz'&)
28397 if available, else the empty string.
28398 The &$auth3$& variable will always be the &'realm'& if available,
28399 else the empty string.
28401 A forced failure will cause authentication to defer.
28403 If using this option, it may make sense to set the &%server_condition%&
28404 option to be simply "true".
28407 .option server_realm gsasl string&!! unset
28408 This specifies the SASL realm that the server claims to be in.
28409 Some mechanisms will use this data.
28412 .option server_scram_iter gsasl string&!! 4096
28413 This option provides data for the SCRAM family of mechanisms.
28414 The &$auth1$&, &$auth2$& and &$auth3$& variables are available
28415 when this option is expanded.
28417 The result of expansion should be a decimal number,
28418 and represents both a lower-bound on the security, and
28419 a compute cost factor imposed on the client
28420 (if it does not cache results, or the server changes
28421 either the iteration count or the salt).
28422 A minimum value of 4096 is required by the standards
28423 for all current SCRAM mechanism variants.
28425 .option server_scram_salt gsasl string&!! unset
28426 This option provides data for the SCRAM family of mechanisms.
28427 The &$auth1$&, &$auth2$& and &$auth3$& variables are available
28428 when this option is expanded.
28429 The value should be a base64-encoded string,
28430 of random data typically 4-to-16 bytes long.
28431 If unset or empty after expansion the library will provides a value for the
28432 protocol conversation.
28435 .option server_key gsasl string&!! unset
28436 .option server_skey gsasl string&!! unset
28437 These options can be used for the SCRAM family of mechanisms
28438 to provide stored information related to a password,
28439 the storage of which is preferable to plaintext.
28441 &%server_key%& is the value defined in the SCRAM standards as ServerKey;
28442 &%server_skey%& is StoredKey.
28444 They are only available for version 1.9.0 (or later) of the gsasl library.
28445 When this is so, the macros
28446 _OPT_AUTHENTICATOR_GSASL_SERVER_KEY
28447 and _HAVE_AUTH_GSASL_SCRAM_S_KEY
28450 The &$authN$& variables are available when these options are expanded.
28452 If set, the results of expansion should for each
28453 should be a 28 (for SHA-1) or 44 (for SHA-256) character string
28454 of base64-coded data, and will be used in preference to the
28455 &%server_password%& option.
28456 If unset or not of the right length, &%server_password%& will be used.
28458 The libgsasl library release includes a utility &'gsasl'& which can be used
28459 to generate these values.
28462 .option server_service gsasl string &`smtp`&
28463 This is the SASL service that the server claims to implement.
28464 Some mechanisms will use this data.
28467 .section "&(gsasl)& auth variables" "SECTgsaslauthvar"
28468 .vindex "&$auth1$&, &$auth2$&, etc"
28469 These may be set when evaluating specific options, as detailed above.
28470 They will also be set when evaluating &%server_condition%&.
28472 Unless otherwise stated below, the &(gsasl)& integration will use the following
28473 meanings for these variables:
28476 .vindex "&$auth1$&"
28477 &$auth1$&: the &'authentication id'&
28479 .vindex "&$auth2$&"
28480 &$auth2$&: the &'authorization id'&
28482 .vindex "&$auth3$&"
28483 &$auth3$&: the &'realm'&
28486 On a per-mechanism basis:
28489 .cindex "authentication" "EXTERNAL"
28490 EXTERNAL: only &$auth1$& is set, to the possibly empty &'authorization id'&;
28491 the &%server_condition%& option must be present.
28493 .cindex "authentication" "ANONYMOUS"
28494 ANONYMOUS: only &$auth1$& is set, to the possibly empty &'anonymous token'&;
28495 the &%server_condition%& option must be present.
28497 .cindex "authentication" "GSSAPI"
28498 GSSAPI: &$auth1$& will be set to the &'GSSAPI Display Name'&;
28499 &$auth2$& will be set to the &'authorization id'&,
28500 the &%server_condition%& option must be present.
28503 An &'anonymous token'& is something passed along as an unauthenticated
28504 identifier; this is analogous to FTP anonymous authentication passing an
28505 email address, or software-identifier@, as the "password".
28508 An example showing the password having the realm specified in the callback
28509 and demonstrating a Cyrus SASL to GSASL migration approach is:
28511 gsasl_cyrusless_crammd5:
28513 public_name = CRAM-MD5
28514 server_realm = imap.example.org
28515 server_password = ${lookup{$auth1:$auth3:userPassword}\
28516 dbmjz{/etc/sasldb2}{$value}fail}
28517 server_set_id = ${quote:$auth1}
28518 server_condition = yes
28522 . ////////////////////////////////////////////////////////////////////////////
28523 . ////////////////////////////////////////////////////////////////////////////
28525 .chapter "The heimdal_gssapi authenticator" "CHAPheimdalgss"
28526 .scindex IIDheimdalgssauth1 "&(heimdal_gssapi)& authenticator"
28527 .scindex IIDheimdalgssauth2 "authenticators" "&(heimdal_gssapi)&"
28528 .cindex "authentication" "GSSAPI"
28529 .cindex "authentication" "Kerberos"
28530 The &(heimdal_gssapi)& authenticator provides server integration for the
28531 Heimdal GSSAPI/Kerberos library, permitting Exim to set a keytab pathname
28534 .option server_hostname heimdal_gssapi string&!! "see below"
28535 This option selects the hostname that is used, with &%server_service%&,
28536 for constructing the GSS server name, as a &'GSS_C_NT_HOSTBASED_SERVICE'&
28537 identifier. The default value is &`$primary_hostname`&.
28539 .option server_keytab heimdal_gssapi string&!! unset
28540 If set, then Heimdal will not use the system default keytab (typically
28541 &_/etc/krb5.keytab_&) but instead the pathname given in this option.
28542 The value should be a pathname, with no &"file:"& prefix.
28544 .option server_service heimdal_gssapi string&!! "smtp"
28545 This option specifies the service identifier used, in conjunction with
28546 &%server_hostname%&, for building the identifier for finding credentials
28550 .section "&(heimdal_gssapi)& auth variables" "SECTheimdalgssauthvar"
28551 Beware that these variables will typically include a realm, thus will appear
28552 to be roughly like an email address already. The &'authzid'& in &$auth2$& is
28553 not verified, so a malicious client can set it to anything.
28555 The &$auth1$& field should be safely trustable as a value from the Key
28556 Distribution Center. Note that these are not quite email addresses.
28557 Each identifier is for a role, and so the left-hand-side may include a
28558 role suffix. For instance, &"joe/admin@EXAMPLE.ORG"&.
28560 .vindex "&$auth1$&, &$auth2$&, etc"
28562 .vindex "&$auth1$&"
28563 &$auth1$&: the &'authentication id'&, set to the GSS Display Name.
28565 .vindex "&$auth2$&"
28566 &$auth2$&: the &'authorization id'&, sent within SASL encapsulation after
28567 authentication. If that was empty, this will also be set to the
28572 . ////////////////////////////////////////////////////////////////////////////
28573 . ////////////////////////////////////////////////////////////////////////////
28575 .chapter "The spa authenticator" "CHAPspa"
28576 .scindex IIDspaauth1 "&(spa)& authenticator"
28577 .scindex IIDspaauth2 "authenticators" "&(spa)&"
28578 .cindex "authentication" "Microsoft Secure Password"
28579 .cindex "authentication" "NTLM"
28580 .cindex "Microsoft Secure Password Authentication"
28581 .cindex "NTLM authentication"
28582 The &(spa)& authenticator provides client support for Microsoft's &'Secure
28583 Password Authentication'& mechanism,
28584 which is also sometimes known as NTLM (NT LanMan). The code for client side of
28585 this authenticator was contributed by Marc Prud'hommeaux, and much of it is
28586 taken from the Samba project (&url(https://www.samba.org/)). The code for the
28587 server side was subsequently contributed by Tom Kistner. The mechanism works as
28591 After the AUTH command has been accepted, the client sends an SPA
28592 authentication request based on the user name and optional domain.
28594 The server sends back a challenge.
28596 The client builds a challenge response which makes use of the user's password
28597 and sends it to the server, which then accepts or rejects it.
28600 Encryption is used to protect the password in transit.
28604 .section "Using spa as a server" "SECID179"
28605 .cindex "options" "&(spa)& authenticator (server)"
28606 The &(spa)& authenticator has just one server option:
28608 .option server_password spa string&!! unset
28609 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(spa)& authenticator"
28610 This option is expanded, and the result must be the cleartext password for the
28611 authenticating user, whose name is at this point in &$auth1$&. For
28612 compatibility with previous releases of Exim, the user name is also placed in
28613 &$1$&. However, the use of this variable for this purpose is now deprecated, as
28614 it can lead to confusion in string expansions that also use numeric variables
28615 for other things. For example:
28620 server_password = \
28621 ${lookup{$auth1}lsearch{/etc/exim/spa_clearpass}{$value}fail}
28623 If the expansion is forced to fail, authentication fails. Any other expansion
28624 failure causes a temporary error code to be returned.
28630 .section "Using spa as a client" "SECID180"
28631 .cindex "options" "&(spa)& authenticator (client)"
28632 The &(spa)& authenticator has the following client options:
28636 .option client_domain spa string&!! unset
28637 This option specifies an optional domain for the authentication.
28640 .option client_password spa string&!! unset
28641 This option specifies the user's password, and must be set.
28644 .option client_username spa string&!! unset
28645 This option specifies the user name, and must be set. Here is an example of a
28646 configuration of this authenticator for use with the mail servers at
28652 client_username = msn/msn_username
28653 client_password = msn_plaintext_password
28654 client_domain = DOMAIN_OR_UNSET
28656 .ecindex IIDspaauth1
28657 .ecindex IIDspaauth2
28663 . ////////////////////////////////////////////////////////////////////////////
28664 . ////////////////////////////////////////////////////////////////////////////
28666 .chapter "The external authenticator" "CHAPexternauth"
28667 .scindex IIDexternauth1 "&(external)& authenticator"
28668 .scindex IIDexternauth2 "authenticators" "&(external)&"
28669 .cindex "authentication" "Client Certificate"
28670 .cindex "authentication" "X509"
28671 .cindex "Certificate-based authentication"
28672 The &(external)& authenticator provides support for
28673 authentication based on non-SMTP information.
28674 The specification is in RFC 4422 Appendix A
28675 (&url(https://tools.ietf.org/html/rfc4422)).
28676 It is only a transport and negotiation mechanism;
28677 the process of authentication is entirely controlled
28678 by the server configuration.
28680 The client presents an identity in-clear.
28681 It is probably wise for a server to only advertise,
28682 and for clients to only attempt,
28683 this authentication method on a secure (eg. under TLS) connection.
28685 One possible use, compatible with the
28686 K-9 Mail Android client (&url(https://k9mail.github.io/)),
28687 is for using X509 client certificates.
28689 It thus overlaps in function with the TLS authenticator
28690 (see &<<CHAPtlsauth>>&)
28691 but is a full SMTP SASL authenticator
28692 rather than being implicit for TLS-connection carried
28693 client certificates only.
28695 The examples and discussion in this chapter assume that
28696 client-certificate authentication is being done.
28698 The client must present a certificate,
28699 for which it must have been requested via the
28700 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& main options
28701 (see &<<CHAPTLS>>&).
28702 For authentication to be effective the certificate should be
28703 verifiable against a trust-anchor certificate known to the server.
28705 .section "External options" "SECTexternsoptions"
28706 .cindex "options" "&(external)& authenticator (server)"
28707 The &(external)& authenticator has two server options:
28709 .option server_param2 external string&!! unset
28710 .option server_param3 external string&!! unset
28711 .cindex "variables (&$auth1$& &$auth2$& etc)" "in &(external)& authenticator"
28712 These options are expanded before the &%server_condition%& option
28713 and the result are placed in &$auth2$& and &$auth3$& resectively.
28714 If the expansion is forced to fail, authentication fails. Any other expansion
28715 failure causes a temporary error code to be returned.
28717 They can be used to clarify the coding of a complex &%server_condition%&.
28719 .section "Using external in a server" "SECTexternserver"
28720 .cindex "AUTH" "in &(external)& authenticator"
28721 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
28722 "in &(external)& authenticator"
28723 .vindex "&$auth1$&, &$auth2$&, etc"
28724 .cindex "base64 encoding" "in &(external)& authenticator"
28726 When running as a server, &(external)& performs the authentication test by
28727 expanding a string. The data sent by the client with the AUTH command, or in
28728 response to subsequent prompts, is base64 encoded, and so may contain any byte
28729 values when decoded. The decoded value is treated as
28730 an identity for authentication and
28731 placed in the expansion variable &$auth1$&.
28733 For compatibility with previous releases of Exim, the value is also placed in
28734 the expansion variable &$1$&. However, the use of this
28735 variable for this purpose is now deprecated, as it can lead to confusion in
28736 string expansions that also use them for other things.
28738 .vindex "&$authenticated_id$&"
28739 Once an identity has been received,
28740 &%server_condition%& is expanded. If the expansion is forced to fail,
28741 authentication fails. Any other expansion failure causes a temporary error code
28742 to be returned. If the result of a successful expansion is an empty string,
28743 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
28744 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
28745 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
28746 For any other result, a temporary error code is returned, with the expanded
28747 string as the error text.
28751 ext_ccert_san_mail:
28753 public_name = EXTERNAL
28755 server_advertise_condition = $tls_in_certificate_verified
28756 server_param2 = ${certextract {subj_altname,mail,>:} \
28757 {$tls_in_peercert}}
28758 server_condition = ${if forany {$auth2} \
28759 {eq {$item}{$auth1}}}
28760 server_set_id = $auth1
28762 This accepts a client certificate that is verifiable against any
28763 of your configured trust-anchors
28764 (which usually means the full set of public CAs)
28765 and which has a mail-SAN matching the claimed identity sent by the client.
28767 &*Note*&: up to TLS1.2, the client cert is on the wire in-clear, including the SAN.
28768 The account name is therefore guessable by an opponent.
28769 TLS 1.3 protects both server and client certificates, and is not vulnerable
28773 .section "Using external in a client" "SECTexternclient"
28774 .cindex "options" "&(external)& authenticator (client)"
28775 The &(external)& authenticator has one client option:
28777 .option client_send external string&!! unset
28778 This option is expanded and sent with the AUTH command as the
28779 identity being asserted.
28785 public_name = EXTERNAL
28787 client_condition = ${if !eq{$tls_out_cipher}{}}
28788 client_send = myaccount@smarthost.example.net
28792 .ecindex IIDexternauth1
28793 .ecindex IIDexternauth2
28799 . ////////////////////////////////////////////////////////////////////////////
28800 . ////////////////////////////////////////////////////////////////////////////
28802 .chapter "The tls authenticator" "CHAPtlsauth"
28803 .scindex IIDtlsauth1 "&(tls)& authenticator"
28804 .scindex IIDtlsauth2 "authenticators" "&(tls)&"
28805 .cindex "authentication" "Client Certificate"
28806 .cindex "authentication" "X509"
28807 .cindex "Certificate-based authentication"
28808 The &(tls)& authenticator provides server support for
28809 authentication based on client certificates.
28811 It is not an SMTP authentication mechanism and is not
28812 advertised by the server as part of the SMTP EHLO response.
28813 It is an Exim authenticator in the sense that it affects
28814 the protocol element of the log line, can be tested for
28815 by the &%authenticated%& ACL condition, and can set
28816 the &$authenticated_id$& variable.
28818 The client must present a verifiable certificate,
28819 for which it must have been requested via the
28820 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& main options
28821 (see &<<CHAPTLS>>&).
28823 If an authenticator of this type is configured it is
28824 run before any SMTP-level communication is done,
28825 and can authenticate the connection.
28826 If it does, SMTP authentication is not offered.
28828 A maximum of one authenticator of this type may be present.
28831 .cindex "options" "&(tls)& authenticator (server)"
28832 The &(tls)& authenticator has three server options:
28834 .option server_param1 tls string&!! unset
28835 .cindex "variables (&$auth1$& &$auth2$& etc)" "in &(tls)& authenticator"
28836 This option is expanded after the TLS negotiation and
28837 the result is placed in &$auth1$&.
28838 If the expansion is forced to fail, authentication fails. Any other expansion
28839 failure causes a temporary error code to be returned.
28841 .option server_param2 tls string&!! unset
28842 .option server_param3 tls string&!! unset
28843 As above, for &$auth2$& and &$auth3$&.
28845 &%server_param1%& may also be spelled &%server_param%&.
28852 server_param1 = ${certextract {subj_altname,mail,>:} \
28853 {$tls_in_peercert}}
28854 server_condition = ${if and { {eq{$tls_in_certificate_verified}{1}} \
28857 {${lookup ldap{ldap:///\
28858 mailname=${quote_ldap_dn:${lc:$item}},\
28859 ou=users,LDAP_DC?mailid} {$value}{0} \
28861 server_set_id = ${if = {1}{${listcount:$auth1}} {$auth1}{}}
28863 This accepts a client certificate that is verifiable against any
28864 of your configured trust-anchors
28865 (which usually means the full set of public CAs)
28866 and which has a SAN with a good account name.
28868 Note that, up to TLS1.2, the client cert is on the wire in-clear, including the SAN,
28869 The account name is therefore guessable by an opponent.
28870 TLS 1.3 protects both server and client certificates, and is not vulnerable
28872 Likewise, a traditional plaintext SMTP AUTH done inside TLS is not.
28874 . An alternative might use
28876 . server_param1 = ${sha256:$tls_in_peercert}
28878 . to require one of a set of specific certs that define a given account
28879 . (the verification is still required, but mostly irrelevant).
28880 . This would help for per-device use.
28882 . However, for the future we really need support for checking a
28883 . user cert in LDAP - which probably wants a base-64 DER.
28885 .ecindex IIDtlsauth1
28886 .ecindex IIDtlsauth2
28889 Note that because authentication is traditionally an SMTP operation,
28890 the &%authenticated%& ACL condition cannot be used in
28891 a connect- or helo-ACL.
28895 . ////////////////////////////////////////////////////////////////////////////
28896 . ////////////////////////////////////////////////////////////////////////////
28898 .chapter "Encrypted SMTP connections using TLS/SSL" "CHAPTLS" &&&
28899 "Encrypted SMTP connections"
28900 .scindex IIDencsmtp1 "encryption" "on SMTP connection"
28901 .scindex IIDencsmtp2 "SMTP" "encryption"
28902 .cindex "TLS" "on SMTP connection"
28905 Support for TLS (Transport Layer Security), formerly known as SSL (Secure
28906 Sockets Layer), is implemented by making use of the OpenSSL library or the
28907 GnuTLS library (Exim requires GnuTLS release 1.0 or later). There is no
28908 cryptographic code in the Exim distribution itself for implementing TLS. In
28909 order to use this feature you must install OpenSSL or GnuTLS, and then build a
28910 version of Exim that includes TLS support (see section &<<SECTinctlsssl>>&).
28911 You also need to understand the basic concepts of encryption at a managerial
28912 level, and in particular, the way that public keys, private keys, and
28913 certificates are used.
28915 RFC 3207 defines how SMTP connections can make use of encryption. Once a
28916 connection is established, the client issues a STARTTLS command. If the
28917 server accepts this, the client and the server negotiate an encryption
28918 mechanism. If the negotiation succeeds, the data that subsequently passes
28919 between them is encrypted.
28921 Exim's ACLs can detect whether the current SMTP session is encrypted or not,
28922 and if so, what cipher suite is in use, whether the client supplied a
28923 certificate, and whether or not that certificate was verified. This makes it
28924 possible for an Exim server to deny or accept certain commands based on the
28927 &*Warning*&: Certain types of firewall and certain anti-virus products can
28928 disrupt TLS connections. You need to turn off SMTP scanning for these products
28929 in order to get TLS to work.
28933 .section "Support for the &""submissions""& (aka &""ssmtp""& and &""smtps""&) protocol" &&&
28935 .cindex "submissions protocol"
28936 .cindex "ssmtp protocol"
28937 .cindex "smtps protocol"
28938 .cindex "SMTP" "submissions protocol"
28939 .cindex "SMTP" "ssmtp protocol"
28940 .cindex "SMTP" "smtps protocol"
28941 The history of port numbers for TLS in SMTP is a little messy and has been
28942 contentious. As of RFC 8314, the common practice of using the historically
28943 allocated port 465 for "email submission but with TLS immediately upon connect
28944 instead of using STARTTLS" is officially blessed by the IETF, and recommended
28945 by them in preference to STARTTLS.
28947 The name originally assigned to the port was &"ssmtp"& or &"smtps"&, but as
28948 clarity emerged over the dual roles of SMTP, for MX delivery and Email
28949 Submission, nomenclature has shifted. The modern name is now &"submissions"&.
28951 This approach was, for a while, officially abandoned when encrypted SMTP was
28952 standardized, but many clients kept using it, even as the TCP port number was
28953 reassigned for other use.
28954 Thus you may encounter guidance claiming that you shouldn't enable use of
28956 In practice, a number of mail-clients have only ever supported submissions,
28957 not submission with STARTTLS upgrade.
28958 Ideally, offer both submission (587) and submissions (465) service.
28960 Exim supports TLS-on-connect by means of the &%tls_on_connect_ports%&
28961 global option. Its value must be a list of port numbers;
28962 the most common use is expected to be:
28964 tls_on_connect_ports = 465
28966 The port numbers specified by this option apply to all SMTP connections, both
28967 via the daemon and via &'inetd'&. You still need to specify all the ports that
28968 the daemon uses (by setting &%daemon_smtp_ports%& or &%local_interfaces%& or
28969 the &%-oX%& command line option) because &%tls_on_connect_ports%& does not add
28970 an extra port &-- rather, it specifies different behaviour on a port that is
28973 There is also a &%-tls-on-connect%& command line option. This overrides
28974 &%tls_on_connect_ports%&; it forces the TLS-only behaviour for all ports.
28981 .section "OpenSSL vs GnuTLS" "SECTopenvsgnu"
28982 .cindex "TLS" "OpenSSL &'vs'& GnuTLS"
28983 TLS is supported in Exim using either the OpenSSL or GnuTLS library.
28984 To build Exim to use OpenSSL you need to set
28990 To build Exim to use GnuTLS, you need to set
28996 You must also set TLS_LIBS and TLS_INCLUDE appropriately, so that the
28997 include files and libraries for GnuTLS can be found.
28999 There are some differences in usage when using GnuTLS instead of OpenSSL:
29002 The &%tls_verify_certificates%& option
29003 cannot be the path of a directory
29004 for GnuTLS versions before 3.3.6
29005 (for later versions, or OpenSSL, it can be either).
29007 The default value for &%tls_dhparam%& differs for historical reasons.
29009 .vindex "&$tls_in_peerdn$&"
29010 .vindex "&$tls_out_peerdn$&"
29011 Distinguished Name (DN) strings reported by the OpenSSL library use a slash for
29012 separating fields; GnuTLS uses commas, in accordance with RFC 2253. This
29013 affects the value of the &$tls_in_peerdn$& and &$tls_out_peerdn$& variables.
29015 OpenSSL identifies cipher suites using hyphens as separators, for example:
29016 DES-CBC3-SHA. GnuTLS historically used underscores, for example:
29017 RSA_ARCFOUR_SHA. What is more, OpenSSL complains if underscores are present
29018 in a cipher list. To make life simpler, Exim changes underscores to hyphens
29019 for OpenSSL and passes the string unchanged to GnuTLS (expecting the library
29020 to handle its own older variants) when processing lists of cipher suites in the
29021 &%tls_require_ciphers%& options (the global option and the &(smtp)& transport
29024 The &%tls_require_ciphers%& options operate differently, as described in the
29025 sections &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
29027 The &%tls_dh_min_bits%& SMTP transport option is only honoured by GnuTLS.
29028 When using OpenSSL, this option is ignored.
29029 (If an API is found to let OpenSSL be configured in this way,
29030 let the Exim Maintainers know and we'll likely use it).
29032 With GnuTLS, if an explicit list is used for the &%tls_privatekey%& main option
29033 main option, it must be ordered to match the &%tls_certificate%& list.
29035 Some other recently added features may only be available in one or the other.
29036 This should be documented with the feature. If the documentation does not
29037 explicitly state that the feature is infeasible in the other TLS
29038 implementation, then patches are welcome.
29040 The output from "exim -bV" will show which (if any) support was included
29042 Also, the macro "_HAVE_OPENSSL" or "_HAVE_GNUTLS" will be defined.
29046 .section "GnuTLS parameter computation" "SECTgnutlsparam"
29047 This section only applies if &%tls_dhparam%& is set to &`historic`& or to
29048 an explicit path; if the latter, then the text about generation still applies,
29049 but not the chosen filename.
29050 By default, as of Exim 4.80 a hard-coded D-H prime is used.
29051 See the documentation of &%tls_dhparam%& for more information.
29053 GnuTLS uses D-H parameters that may take a substantial amount of time
29054 to compute. It is unreasonable to re-compute them for every TLS session.
29055 Therefore, Exim keeps this data in a file in its spool directory, called
29056 &_gnutls-params-NNNN_& for some value of NNNN, corresponding to the number
29058 The file is owned by the Exim user and is readable only by
29059 its owner. Every Exim process that start up GnuTLS reads the D-H
29060 parameters from this file. If the file does not exist, the first Exim process
29061 that needs it computes the data and writes it to a temporary file which is
29062 renamed once it is complete. It does not matter if several Exim processes do
29063 this simultaneously (apart from wasting a few resources). Once a file is in
29064 place, new Exim processes immediately start using it.
29066 For maximum security, the parameters that are stored in this file should be
29067 recalculated periodically, the frequency depending on your paranoia level.
29068 If you are avoiding using the fixed D-H primes published in RFCs, then you
29069 are concerned about some advanced attacks and will wish to do this; if you do
29070 not regenerate then you might as well stick to the standard primes.
29072 Arranging this is easy in principle; just delete the file when you want new
29073 values to be computed. However, there may be a problem. The calculation of new
29074 parameters needs random numbers, and these are obtained from &_/dev/random_&.
29075 If the system is not very active, &_/dev/random_& may delay returning data
29076 until enough randomness (entropy) is available. This may cause Exim to hang for
29077 a substantial amount of time, causing timeouts on incoming connections.
29079 The solution is to generate the parameters externally to Exim. They are stored
29080 in &_gnutls-params-N_& in PEM format, which means that they can be
29081 generated externally using the &(certtool)& command that is part of GnuTLS.
29083 To replace the parameters with new ones, instead of deleting the file
29084 and letting Exim re-create it, you can generate new parameters using
29085 &(certtool)& and, when this has been done, replace Exim's cache file by
29086 renaming. The relevant commands are something like this:
29089 [ look for file; assume gnutls-params-2236 is the most recent ]
29092 # chown exim:exim new-params
29093 # chmod 0600 new-params
29094 # certtool --generate-dh-params --bits 2236 >>new-params
29095 # openssl dhparam -noout -text -in new-params | head
29096 [ check the first line, make sure it's not more than 2236;
29097 if it is, then go back to the start ("rm") and repeat
29098 until the size generated is at most the size requested ]
29099 # chmod 0400 new-params
29100 # mv new-params gnutls-params-2236
29102 If Exim never has to generate the parameters itself, the possibility of
29103 stalling is removed.
29105 The filename changed in Exim 4.80, to gain the -bits suffix. The value which
29106 Exim will choose depends upon the version of GnuTLS in use. For older GnuTLS,
29107 the value remains hard-coded in Exim as 1024. As of GnuTLS 2.12.x, there is
29108 a way for Exim to ask for the "normal" number of bits for D-H public-key usage,
29109 and Exim does so. This attempt to remove Exim from TLS policy decisions
29110 failed, as GnuTLS 2.12 returns a value higher than the current hard-coded limit
29111 of the NSS library. Thus Exim gains the &%tls_dh_max_bits%& global option,
29112 which applies to all D-H usage, client or server. If the value returned by
29113 GnuTLS is greater than &%tls_dh_max_bits%& then the value will be clamped down
29114 to &%tls_dh_max_bits%&. The default value has been set at the current NSS
29115 limit, which is still much higher than Exim historically used.
29117 The filename and bits used will change as the GnuTLS maintainers change the
29118 value for their parameter &`GNUTLS_SEC_PARAM_NORMAL`&, as clamped by
29119 &%tls_dh_max_bits%&. At the time of writing (mid 2012), GnuTLS 2.12 recommends
29120 2432 bits, while NSS is limited to 2236 bits.
29122 In fact, the requested value will be *lower* than &%tls_dh_max_bits%&, to
29123 increase the chance of the generated prime actually being within acceptable
29124 bounds, as GnuTLS has been observed to overshoot. Note the check step in the
29125 procedure above. There is no sane procedure available to Exim to double-check
29126 the size of the generated prime, so it might still be too large.
29129 .section "Requiring specific ciphers in OpenSSL" "SECTreqciphssl"
29130 .cindex "TLS" "requiring specific ciphers (OpenSSL)"
29131 .oindex "&%tls_require_ciphers%&" "OpenSSL"
29132 There is a function in the OpenSSL library that can be passed a list of cipher
29133 suites before the cipher negotiation takes place. This specifies which ciphers
29134 are acceptable for TLS versions prior to 1.3.
29135 The list is colon separated and may contain names like
29136 DES-CBC3-SHA. Exim passes the expanded value of &%tls_require_ciphers%&
29137 directly to this function call.
29138 Many systems will install the OpenSSL manual-pages, so you may have
29139 &'ciphers(1)'& available to you.
29140 The following quotation from the OpenSSL
29141 documentation specifies what forms of item are allowed in the cipher string:
29144 It can consist of a single cipher suite such as RC4-SHA.
29146 It can represent a list of cipher suites containing a certain algorithm,
29147 or cipher suites of a certain type. For example SHA1 represents all
29148 ciphers suites using the digest algorithm SHA1 and SSLv3 represents all
29151 Lists of cipher suites can be combined in a single cipher string using
29152 the + character. This is used as a logical and operation. For example
29153 SHA1+DES represents all cipher suites containing the SHA1 and the DES
29157 Each cipher string can be optionally preceded by one of the characters &`!`&,
29160 If &`!`& is used, the ciphers are permanently deleted from the list. The
29161 ciphers deleted can never reappear in the list even if they are explicitly
29164 If &`-`& is used, the ciphers are deleted from the list, but some or all
29165 of the ciphers can be added again by later options.
29167 If &`+`& is used, the ciphers are moved to the end of the list. This
29168 option does not add any new ciphers; it just moves matching existing ones.
29171 If none of these characters is present, the string is interpreted as
29172 a list of ciphers to be appended to the current preference list. If the list
29173 includes any ciphers already present they will be ignored: that is, they will
29174 not be moved to the end of the list.
29177 The OpenSSL &'ciphers(1)'& command may be used to test the results of a given
29180 # note single-quotes to get ! past any shell history expansion
29181 $ openssl ciphers 'HIGH:!MD5:!SHA1'
29184 This example will let the library defaults be permitted on the MX port, where
29185 there's probably no identity verification anyway, but ups the ante on the
29186 submission ports where the administrator might have some influence on the
29187 choice of clients used:
29189 # OpenSSL variant; see man ciphers(1)
29190 tls_require_ciphers = ${if =={$received_port}{25}\
29195 This example will prefer ECDSA-authenticated ciphers over RSA ones:
29197 tls_require_ciphers = ECDSA:RSA:!COMPLEMENTOFDEFAULT
29200 For TLS version 1.3 the control available is less fine-grained
29201 and Exim does not provide access to it at present.
29202 The value of the &%tls_require_ciphers%& option is ignored when
29203 TLS version 1.3 is negotiated.
29205 As of writing the library default cipher suite list for TLSv1.3 is
29207 TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256
29211 .section "Requiring specific ciphers or other parameters in GnuTLS" &&&
29213 .cindex "GnuTLS" "specifying parameters for"
29214 .cindex "TLS" "specifying ciphers (GnuTLS)"
29215 .cindex "TLS" "specifying key exchange methods (GnuTLS)"
29216 .cindex "TLS" "specifying MAC algorithms (GnuTLS)"
29217 .cindex "TLS" "specifying protocols (GnuTLS)"
29218 .cindex "TLS" "specifying priority string (GnuTLS)"
29219 .oindex "&%tls_require_ciphers%&" "GnuTLS"
29220 The GnuTLS library allows the caller to provide a "priority string", documented
29221 as part of the &[gnutls_priority_init]& function. This is very similar to the
29222 ciphersuite specification in OpenSSL.
29224 The &%tls_require_ciphers%& option is treated as the GnuTLS priority string
29225 and controls both protocols and ciphers.
29227 The &%tls_require_ciphers%& option is available both as an global option,
29228 controlling how Exim behaves as a server, and also as an option of the
29229 &(smtp)& transport, controlling how Exim behaves as a client. In both cases
29230 the value is string expanded. The resulting string is not an Exim list and
29231 the string is given to the GnuTLS library, so that Exim does not need to be
29232 aware of future feature enhancements of GnuTLS.
29234 Documentation of the strings accepted may be found in the GnuTLS manual, under
29235 "Priority strings". This is online as
29236 &url(https://www.gnutls.org/manual/html_node/Priority-Strings.html),
29237 but beware that this relates to GnuTLS 3, which may be newer than the version
29238 installed on your system. If you are using GnuTLS 3,
29239 then the example code
29240 &url(https://www.gnutls.org/manual/gnutls.html#Listing-the-ciphersuites-in-a-priority-string)
29241 on that site can be used to test a given string.
29245 # Disable older versions of protocols
29246 tls_require_ciphers = NORMAL:%LATEST_RECORD_VERSION:-VERS-SSL3.0
29249 Prior to Exim 4.80, an older API of GnuTLS was used, and Exim supported three
29250 additional options, "&%gnutls_require_kx%&", "&%gnutls_require_mac%&" and
29251 "&%gnutls_require_protocols%&". &%tls_require_ciphers%& was an Exim list.
29253 This example will let the library defaults be permitted on the MX port, where
29254 there's probably no identity verification anyway, and lowers security further
29255 by increasing compatibility; but this ups the ante on the submission ports
29256 where the administrator might have some influence on the choice of clients
29260 tls_require_ciphers = ${if =={$received_port}{25}\
29266 .section "Configuring an Exim server to use TLS" "SECID182"
29267 .cindex "TLS" "configuring an Exim server"
29268 .cindex "ESMTP extensions" STARTTLS
29269 When Exim has been built with TLS support, it advertises the availability of
29270 the STARTTLS command to client hosts that match &%tls_advertise_hosts%&,
29271 but not to any others. The default value of this option is *, which means
29272 that STARTTLS is always advertised. Set it to blank to never advertise;
29273 this is reasonable for systems that want to use TLS only as a client.
29275 If STARTTLS is to be used you
29276 need to set some other options in order to make TLS available.
29278 If a client issues a STARTTLS command and there is some configuration
29279 problem in the server, the command is rejected with a 454 error. If the client
29280 persists in trying to issue SMTP commands, all except QUIT are rejected
29283 554 Security failure
29285 If a STARTTLS command is issued within an existing TLS session, it is
29286 rejected with a 554 error code.
29288 To enable TLS operations on a server, the &%tls_advertise_hosts%& option
29289 must be set to match some hosts. The default is * which matches all hosts.
29291 If this is all you do, TLS encryption will be enabled but not authentication -
29292 meaning that the peer has no assurance it is actually you he is talking to.
29293 You gain protection from a passive sniffer listening on the wire but not
29294 from someone able to intercept the communication.
29296 Further protection requires some further configuration at the server end.
29298 To make TLS work you need to set, in the server,
29300 tls_certificate = /some/file/name
29301 tls_privatekey = /some/file/name
29303 These options are, in fact, expanded strings, so you can make them depend on
29304 the identity of the client that is connected if you wish. The first file
29305 contains the server's X509 certificate, and the second contains the private key
29306 that goes with it. These files need to be
29307 PEM format and readable by the Exim user, and must
29308 always be given as full path names.
29309 The key must not be password-protected.
29310 They can be the same file if both the
29311 certificate and the key are contained within it. If &%tls_privatekey%& is not
29312 set, or if its expansion is forced to fail or results in an empty string, this
29313 is assumed to be the case. The certificate file may also contain intermediate
29314 certificates that need to be sent to the client to enable it to authenticate
29315 the server's certificate.
29317 For dual-stack (eg. RSA and ECDSA) configurations, these options can be
29318 colon-separated lists of file paths. Ciphers using given authentication
29319 algorithms require the presence of a suitable certificate to supply the
29320 public-key. The server selects among the certificates to present to the
29321 client depending on the selected cipher, hence the priority ordering for
29322 ciphers will affect which certificate is used.
29324 If you do not understand about certificates and keys, please try to find a
29325 source of this background information, which is not Exim-specific. (There are a
29326 few comments below in section &<<SECTcerandall>>&.)
29328 &*Note*&: These options do not apply when Exim is operating as a client &--
29329 they apply only in the case of a server. If you need to use a certificate in an
29330 Exim client, you must set the options of the same names in an &(smtp)&
29333 With just these options, an Exim server will be able to use TLS. It does not
29334 require the client to have a certificate (but see below for how to insist on
29335 this). There is one other option that may be needed in other situations. If
29337 tls_dhparam = /some/file/name
29339 is set, the SSL library is initialized for the use of Diffie-Hellman ciphers
29340 with the parameters contained in the file.
29341 Set this to &`none`& to disable use of DH entirely, by making no prime
29346 This may also be set to a string identifying a standard prime to be used for
29347 DH; if it is set to &`default`& or, for OpenSSL, is unset, then the prime
29348 used is &`ike23`&. There are a few standard primes available, see the
29349 documentation for &%tls_dhparam%& for the complete list.
29355 for a way of generating file data.
29357 The strings supplied for these three options are expanded every time a client
29358 host connects. It is therefore possible to use different certificates and keys
29359 for different hosts, if you so wish, by making use of the client's IP address
29360 in &$sender_host_address$& to control the expansion. If a string expansion is
29361 forced to fail, Exim behaves as if the option is not set.
29363 .cindex "cipher" "logging"
29364 .cindex "log" "TLS cipher"
29365 .vindex "&$tls_in_cipher$&"
29366 The variable &$tls_in_cipher$& is set to the cipher suite that was negotiated for
29367 an incoming TLS connection. It is included in the &'Received:'& header of an
29368 incoming message (by default &-- you can, of course, change this), and it is
29369 also included in the log line that records a message's arrival, keyed by
29370 &"X="&, unless the &%tls_cipher%& log selector is turned off. The &%encrypted%&
29371 condition can be used to test for specific cipher suites in ACLs.
29373 Once TLS has been established, the ACLs that run for subsequent SMTP commands
29374 can check the name of the cipher suite and vary their actions accordingly. The
29375 cipher suite names vary, depending on which TLS library is being used. For
29376 example, OpenSSL uses the name DES-CBC3-SHA for the cipher suite which in other
29377 contexts is known as TLS_RSA_WITH_3DES_EDE_CBC_SHA. Check the OpenSSL or GnuTLS
29378 documentation for more details.
29380 For outgoing SMTP deliveries, &$tls_out_cipher$& is used and logged
29381 (again depending on the &%tls_cipher%& log selector).
29384 .subsection "Requesting and verifying client certificates" SECID183
29385 .cindex "certificate" "verification of client"
29386 .cindex "TLS" "client certificate verification"
29387 If you want an Exim server to request a certificate when negotiating a TLS
29388 session with a client, you must set either &%tls_verify_hosts%& or
29389 &%tls_try_verify_hosts%&. You can, of course, set either of them to * to
29390 apply to all TLS connections. For any host that matches one of these options,
29391 Exim requests a certificate as part of the setup of the TLS session. The
29392 contents of the certificate are verified by comparing it with a list of
29393 expected trust-anchors or certificates.
29394 These may be the system default set (depending on library version),
29395 an explicit file or,
29396 depending on library version, a directory, identified by
29397 &%tls_verify_certificates%&.
29399 A file can contain multiple certificates, concatenated end to end. If a
29402 each certificate must be in a separate file, with a name (or a symbolic link)
29403 of the form <&'hash'&>.0, where <&'hash'&> is a hash value constructed from the
29404 certificate. You can compute the relevant hash by running the command
29406 openssl x509 -hash -noout -in /cert/file
29408 where &_/cert/file_& contains a single certificate.
29410 There is no checking of names of the client against the certificate
29411 Subject Name or Subject Alternate Names.
29413 The difference between &%tls_verify_hosts%& and &%tls_try_verify_hosts%& is
29414 what happens if the client does not supply a certificate, or if the certificate
29415 does not match any of the certificates in the collection named by
29416 &%tls_verify_certificates%&. If the client matches &%tls_verify_hosts%&, the
29417 attempt to set up a TLS session is aborted, and the incoming connection is
29418 dropped. If the client matches &%tls_try_verify_hosts%&, the (encrypted) SMTP
29419 session continues. ACLs that run for subsequent SMTP commands can detect the
29420 fact that no certificate was verified, and vary their actions accordingly. For
29421 example, you can insist on a certificate before accepting a message for
29422 relaying, but not when the message is destined for local delivery.
29424 .vindex "&$tls_in_peerdn$&"
29425 When a client supplies a certificate (whether it verifies or not), the value of
29426 the Distinguished Name of the certificate is made available in the variable
29427 &$tls_in_peerdn$& during subsequent processing of the message.
29429 .cindex "log" "distinguished name"
29430 Because it is often a long text string, it is not included in the log line or
29431 &'Received:'& header by default. You can arrange for it to be logged, keyed by
29432 &"DN="&, by setting the &%tls_peerdn%& log selector, and you can use
29433 &%received_header_text%& to change the &'Received:'& header. When no
29434 certificate is supplied, &$tls_in_peerdn$& is empty.
29437 .section "Revoked certificates" "SECID184"
29438 .cindex "TLS" "revoked certificates"
29439 .cindex "revocation list"
29440 .cindex "certificate" "revocation list"
29441 .cindex "OCSP" "stapling"
29442 Certificate issuing authorities issue Certificate Revocation Lists (CRLs) when
29443 certificates are revoked. If you have such a list, you can pass it to an Exim
29444 server using the global option called &%tls_crl%& and to an Exim client using
29445 an identically named option for the &(smtp)& transport. In each case, the value
29446 of the option is expanded and must then be the name of a file that contains a
29448 The downside is that clients have to periodically re-download a potentially huge
29449 file from every certificate authority they know of.
29451 The way with most moving parts at query time is Online Certificate
29452 Status Protocol (OCSP), where the client verifies the certificate
29453 against an OCSP server run by the CA. This lets the CA track all
29454 usage of the certs. It requires running software with access to the
29455 private key of the CA, to sign the responses to the OCSP queries. OCSP
29456 is based on HTTP and can be proxied accordingly.
29458 The only widespread OCSP server implementation (known to this writer)
29459 comes as part of OpenSSL and aborts on an invalid request, such as
29460 connecting to the port and then disconnecting. This requires
29461 re-entering the passphrase each time some random client does this.
29463 The third way is OCSP Stapling; in this, the server using a certificate
29464 issued by the CA periodically requests an OCSP proof of validity from
29465 the OCSP server, then serves it up inline as part of the TLS
29466 negotiation. This approach adds no extra round trips, does not let the
29467 CA track users, scales well with number of certs issued by the CA and is
29468 resilient to temporary OCSP server failures, as long as the server
29469 starts retrying to fetch an OCSP proof some time before its current
29470 proof expires. The downside is that it requires server support.
29472 Unless Exim is built with the support disabled,
29473 or with GnuTLS earlier than version 3.3.16 / 3.4.8
29474 support for OCSP stapling is included.
29476 There is a global option called &%tls_ocsp_file%&.
29477 The file specified therein is expected to be in DER format, and contain
29478 an OCSP proof. Exim will serve it as part of the TLS handshake. This
29479 option will be re-expanded for SNI, if the &%tls_certificate%& option
29480 contains &`tls_in_sni`&, as per other TLS options.
29482 Exim does not at this time implement any support for fetching a new OCSP
29483 proof. The burden is on the administrator to handle this, outside of
29484 Exim. The file specified should be replaced atomically, so that the
29485 contents are always valid. Exim will expand the &%tls_ocsp_file%& option
29486 on each connection, so a new file will be handled transparently on the
29489 When built with OpenSSL Exim will check for a valid next update timestamp
29490 in the OCSP proof; if not present, or if the proof has expired, it will be
29493 For the client to be able to verify the stapled OCSP the server must
29494 also supply, in its stapled information, any intermediate
29495 certificates for the chain leading to the OCSP proof from the signer
29496 of the server certificate. There may be zero or one such. These
29497 intermediate certificates should be added to the server OCSP stapling
29498 file named by &%tls_ocsp_file%&.
29500 Note that the proof only covers the terminal server certificate,
29501 not any of the chain from CA to it.
29503 There is no current way to staple a proof for a client certificate.
29506 A helper script "ocsp_fetch.pl" for fetching a proof from a CA
29507 OCSP server is supplied. The server URL may be included in the
29508 server certificate, if the CA is helpful.
29510 One failure mode seen was the OCSP Signer cert expiring before the end
29511 of validity of the OCSP proof. The checking done by Exim/OpenSSL
29512 noted this as invalid overall, but the re-fetch script did not.
29516 .section "Caching of static server configuration items" "SECTserverTLScache"
29517 .cindex certificate caching
29518 .cindex privatekey caching
29519 .cindex crl caching
29520 .cindex ocsp caching
29521 .cindex ciphers caching
29522 .cindex "CA bundle" caching
29523 .cindex "certificate authorities" caching
29524 .cindex tls_certificate caching
29525 .cindex tls_privatekey caching
29526 .cindex tls_crl caching
29527 .cindex tls_ocsp_file caching
29528 .cindex tls_require_ciphers caching
29529 .cindex tls_verify_certificate caching
29530 .cindex caching certificate
29531 .cindex caching privatekey
29532 .cindex caching crl
29533 .cindex caching ocsp
29534 .cindex caching ciphers
29535 .cindex caching "certificate authorities
29536 If any of the main configuration options &%tls_certificate%&, &%tls_privatekey%&,
29537 &%tls_crl%& and &%tls_ocsp_file%& have values with no
29538 expandable elements,
29539 then the associated information is loaded at daemon startup.
29540 It is made available
29541 to child processes forked for handling received SMTP connections.
29543 This caching is currently only supported under Linux and FreeBSD.
29545 If caching is not possible, for example if an item has to be dependent
29546 on the peer host so contains a &$sender_host_name$& expansion, the load
29547 of the associated information is done at the startup of the TLS connection.
29549 The cache is invalidated and reloaded after any changes to the directories
29550 containing files specified by these options.
29552 The information specified by the main option &%tls_verify_certificates%&
29553 is similarly cached so long as it specifies files explicitly
29554 or (under GnuTLS) is the string &"system,cache"&.
29555 The latter case is not automatically invalidated;
29556 it is the operator's responsibility to arrange for a daemon restart
29557 any time the system certificate authority bundle is updated.
29558 A HUP signal is sufficient for this.
29559 The value &"system"& results in no caching under GnuTLS.
29561 The macro _HAVE_TLS_CA_CACHE will be defined if the suffix for "system"
29562 is acceptable in configurations for the Exim executavble.
29564 Caching of the system Certificate Authorities bundle can
29565 save siginificant time and processing on every TLS connection
29571 .section "Configuring an Exim client to use TLS" "SECTclientTLS"
29572 .cindex "cipher" "logging"
29573 .cindex "log" "TLS cipher"
29574 .cindex "log" "distinguished name"
29575 .cindex "TLS" "configuring an Exim client"
29576 The &%tls_cipher%& and &%tls_peerdn%& log selectors apply to outgoing SMTP
29577 deliveries as well as to incoming, the latter one causing logging of the
29578 server certificate's DN. The remaining client configuration for TLS is all
29579 within the &(smtp)& transport.
29581 .cindex "ESMTP extensions" STARTTLS
29582 It is not necessary to set any options to have TLS work in the &(smtp)&
29583 transport. If Exim is built with TLS support, and TLS is advertised by a
29584 server, the &(smtp)& transport always tries to start a TLS session. However,
29585 this can be prevented by setting &%hosts_avoid_tls%& (an option of the
29586 transport) to a list of server hosts for which TLS should not be used.
29588 If you do not want Exim to attempt to send messages unencrypted when an attempt
29589 to set up an encrypted connection fails in any way, you can set
29590 &%hosts_require_tls%& to a list of hosts for which encryption is mandatory. For
29591 those hosts, delivery is always deferred if an encrypted connection cannot be
29592 set up. If there are any other hosts for the address, they are tried in the
29595 When the server host is not in &%hosts_require_tls%&, Exim may try to deliver
29596 the message unencrypted. It always does this if the response to STARTTLS is
29597 a 5&'xx'& code. For a temporary error code, or for a failure to negotiate a TLS
29598 session after a success response code, what happens is controlled by the
29599 &%tls_tempfail_tryclear%& option of the &(smtp)& transport. If it is false,
29600 delivery to this host is deferred, and other hosts (if available) are tried. If
29601 it is true, Exim attempts to deliver unencrypted after a 4&'xx'& response to
29602 STARTTLS, and if STARTTLS is accepted, but the subsequent TLS
29603 negotiation fails, Exim closes the current connection (because it is in an
29604 unknown state), opens a new one to the same host, and then tries the delivery
29607 The &%tls_certificate%& and &%tls_privatekey%& options of the &(smtp)&
29608 transport provide the client with a certificate, which is passed to the server
29610 This is an optional thing for TLS connections, although either end
29612 If the server is Exim, it will request a certificate only if
29613 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client.
29615 &*Note*&: Do not use a certificate which has the OCSP-must-staple extension,
29616 for client use (they are usable for server use).
29617 As the TLS protocol has no means for the client to staple before TLS 1.3 it will result
29618 in failed connections.
29620 If the &%tls_verify_certificates%& option is set on the &(smtp)& transport, it
29621 specifies a collection of expected server certificates.
29623 the system default set (depending on library version),
29625 or (depending on library version) a directory.
29626 The client verifies the server's certificate
29627 against this collection, taking into account any revoked certificates that are
29628 in the list defined by &%tls_crl%&.
29629 Failure to verify fails the TLS connection unless either of the
29630 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& options are set.
29632 The &%tls_verify_hosts%& and &%tls_try_verify_hosts%& options restrict
29633 certificate verification to the listed servers. Verification either must
29634 or need not succeed respectively.
29636 The &%tls_verify_cert_hostnames%& option lists hosts for which additional
29637 name checks are made on the server certificate.
29638 The match against this list is, as per other Exim usage, the
29639 IP for the host. That is most closely associated with the
29640 name on the DNS A (or AAAA) record for the host.
29641 However, the name that needs to be in the certificate
29642 is the one at the head of any CNAME chain leading to the A record.
29643 The option defaults to always checking.
29645 The &(smtp)& transport has two OCSP-related options:
29646 &%hosts_require_ocsp%&; a host-list for which a Certificate Status
29647 is requested and required for the connection to proceed. The default
29649 &%hosts_request_ocsp%&; a host-list for which (additionally)
29650 a Certificate Status is requested (but not necessarily verified). The default
29651 value is "*" meaning that requests are made unless configured
29654 The host(s) should also be in &%hosts_require_tls%&, and
29655 &%tls_verify_certificates%& configured for the transport,
29656 for OCSP to be relevant.
29659 &%tls_require_ciphers%& is set on the &(smtp)& transport, it must contain a
29660 list of permitted cipher suites. If either of these checks fails, delivery to
29661 the current host is abandoned, and the &(smtp)& transport tries to deliver to
29662 alternative hosts, if any.
29665 These options must be set in the &(smtp)& transport for Exim to use TLS when it
29666 is operating as a client. Exim does not assume that a server certificate (set
29667 by the global options of the same name) should also be used when operating as a
29671 .vindex "&$host_address$&"
29672 All the TLS options in the &(smtp)& transport are expanded before use, with
29673 &$host$& and &$host_address$& containing the name and address of the server to
29674 which the client is connected. Forced failure of an expansion causes Exim to
29675 behave as if the relevant option were unset.
29677 .vindex &$tls_out_bits$&
29678 .vindex &$tls_out_cipher$&
29679 .vindex &$tls_out_peerdn$&
29680 .vindex &$tls_out_sni$&
29681 Before an SMTP connection is established, the
29682 &$tls_out_bits$&, &$tls_out_cipher$&, &$tls_out_peerdn$& and &$tls_out_sni$&
29683 variables are emptied. (Until the first connection, they contain the values
29684 that were set when the message was received.) If STARTTLS is subsequently
29685 successfully obeyed, these variables are set to the relevant values for the
29686 outgoing connection.
29690 .subsection "Caching of static client configuration items" SECTclientTLScache
29691 .cindex certificate caching
29692 .cindex privatekey caching
29693 .cindex crl caching
29694 .cindex ciphers caching
29695 .cindex "CA bundle" caching
29696 .cindex "certificate authorities" caching
29697 .cindex tls_certificate caching
29698 .cindex tls_privatekey caching
29699 .cindex tls_crl caching
29700 .cindex tls_require_ciphers caching
29701 .cindex tls_verify_certificate caching
29702 .cindex caching certificate
29703 .cindex caching privatekey
29704 .cindex caching crl
29705 .cindex caching ciphers
29706 .cindex caching "certificate authorities
29707 If any of the transport configuration options &%tls_certificate%&, &%tls_privatekey%&
29708 and &%tls_crl%& have values with no
29709 expandable elements,
29710 then the associated information is loaded per smtp transport
29711 at daemon startup, at the start of a queue run, or on a
29712 command-line specified message delivery.
29713 It is made available
29714 to child processes forked for handling making SMTP connections.
29716 This caching is currently only supported under Linux.
29718 If caching is not possible, the load
29719 of the associated information is done at the startup of the TLS connection.
29721 The cache is invalidated in the daemon
29722 and reloaded after any changes to the directories
29723 containing files specified by these options.
29725 The information specified by the main option &%tls_verify_certificates%&
29726 is similarly cached so long as it specifies files explicitly
29727 or (under GnuTLS) is the string &"system,cache"&.
29728 The latter case is not automatically invaludated;
29729 it is the operator's responsibility to arrange for a daemon restart
29730 any time the system certificate authority bundle is updated.
29731 A HUP signal is sufficient for this.
29732 The value &"system"& results in no caching under GnuTLS.
29734 The macro _HAVE_TLS_CA_CACHE will be defined if the suffix for "system"
29735 is acceptable in configurations for the Exim executavble.
29737 Caching of the system Certificate Authorities bundle can
29738 save siginificant time and processing on every TLS connection
29744 .section "Use of TLS Server Name Indication" "SECTtlssni"
29745 .cindex "TLS" "Server Name Indication"
29748 .vindex "&$tls_in_sni$&"
29749 .oindex "&%tls_in_sni%&"
29750 With TLS1.0 or above, there is an extension mechanism by which extra
29751 information can be included at various points in the protocol. One of these
29752 extensions, documented in RFC 6066 (and before that RFC 4366) is
29753 &"Server Name Indication"&, commonly &"SNI"&. This extension is sent by the
29754 client in the initial handshake, so that the server can examine the servername
29755 within and possibly choose to use different certificates and keys (and more)
29758 This is analogous to HTTP's &"Host:"& header, and is the main mechanism by
29759 which HTTPS-enabled web-sites can be virtual-hosted, many sites to one IP
29762 With SMTP to MX, there are the same problems here as in choosing the identity
29763 against which to validate a certificate: you can't rely on insecure DNS to
29764 provide the identity which you then cryptographically verify. So this will
29765 be of limited use in that environment.
29767 With SMTP to Submission, there is a well-defined hostname which clients are
29768 connecting to and can validate certificates against. Thus clients &*can*&
29769 choose to include this information in the TLS negotiation. If this becomes
29770 wide-spread, then hosters can choose to present different certificates to
29771 different clients. Or even negotiate different cipher suites.
29773 The &%tls_sni%& option on an SMTP transport is an expanded string; the result,
29774 if not empty, will be sent on a TLS session as part of the handshake. There's
29775 nothing more to it. Choosing a sensible value not derived insecurely is the
29776 only point of caution. The &$tls_out_sni$& variable will be set to this string
29777 for the lifetime of the client connection (including during authentication).
29779 If DANE validated the connection attempt then the value of the &%tls_sni%& option
29780 is forced to the name of the destination host, after any MX- or CNAME-following.
29782 Except during SMTP client sessions, if &$tls_in_sni$& is set then it is a string
29783 received from a client.
29784 It can be logged with the &%log_selector%& item &`+tls_sni`&.
29786 If the string &`tls_in_sni`& appears in the main section's &%tls_certificate%&
29787 option (prior to expansion) then the following options will be re-expanded
29788 during TLS session handshake, to permit alternative values to be chosen:
29791 &%tls_certificate%&
29797 &%tls_verify_certificates%&
29802 Great care should be taken to deal with matters of case, various injection
29803 attacks in the string (&`../`& or SQL), and ensuring that a valid filename
29804 can always be referenced; it is important to remember that &$tls_in_sni$& is
29805 arbitrary unverified data provided prior to authentication.
29806 Further, the initial certificate is loaded before SNI has arrived, so
29807 an expansion for &%tls_certificate%& must have a default which is used
29808 when &$tls_in_sni$& is empty.
29810 The Exim developers are proceeding cautiously and so far no other TLS options
29813 When Exim is built against OpenSSL, OpenSSL must have been built with support
29814 for TLS Extensions. This holds true for OpenSSL 1.0.0+ and 0.9.8+ with
29815 enable-tlsext in EXTRACONFIGURE. If you invoke &(openssl s_client -h)& and
29816 see &`-servername`& in the output, then OpenSSL has support.
29818 When Exim is built against GnuTLS, SNI support is available as of GnuTLS
29819 0.5.10. (Its presence predates the current API which Exim uses, so if Exim
29820 built, then you have SNI support).
29823 .cindex ALPN "general information"
29824 .cindex TLS "Application Layer Protocol Names"
29825 There is a TLS feature related to SNI
29826 called Application Layer Protocol Name (ALPN).
29827 This is intended to declare, or select, what protocol layer will be using a TLS
29829 The client for the connection proposes a set of protocol names, and
29830 the server responds with a selected one.
29831 It is not, as of 2021, commonly used for SMTP connections.
29832 However, to guard against misirected or malicious use of web clients
29833 (which often do use ALPN) against MTA ports, Exim by default check that
29834 there is no incompatible ALPN specified by a client for a TLS connection.
29835 If there is, the connection is rejected.
29837 As a client Exim does not supply ALPN by default.
29838 The behaviour of both client and server can be configured using the options
29839 &%tls_alpn%& and &%hosts_require_alpn%&.
29840 There are no variables providing observability.
29841 Some feature-specific logging may appear on denied connections, but this
29842 depends on the behavious of the peer
29843 (not all peers can send a feature-specific TLS Alert).
29845 This feature is available when Exim is built with
29846 OpenSSL 1.1.0 or later or GnuTLS 3.2.0 or later;
29847 the macro _HAVE_TLS_ALPN will be defined when this is so.
29851 .section "Multiple messages on the same encrypted TCP/IP connection" &&&
29853 .cindex "multiple SMTP deliveries with TLS"
29854 .cindex "TLS" "multiple message deliveries"
29855 Exim sends multiple messages down the same TCP/IP connection by starting up
29856 an entirely new delivery process for each message, passing the socket from
29857 one process to the next. This implementation does not fit well with the use
29858 of TLS, because there is quite a lot of state information associated with a TLS
29859 connection, not just a socket identification. Passing all the state information
29860 to a new process is not feasible. Consequently, for sending using TLS Exim
29861 starts an additional proxy process for handling the encryption, piping the
29862 unencrypted data stream from and to the delivery processes.
29864 An older mode of operation can be enabled on a per-host basis by the
29865 &%hosts_noproxy_tls%& option on the &(smtp)& transport. If the host matches
29866 this list the proxy process described above is not used; instead Exim
29867 shuts down an existing TLS session being run by the delivery process
29868 before passing the socket to a new process. The new process may then
29869 try to start a new TLS session, and if successful, may try to re-authenticate
29870 if AUTH is in use, before sending the next message.
29872 The RFC is not clear as to whether or not an SMTP session continues in clear
29873 after TLS has been shut down, or whether TLS may be restarted again later, as
29874 just described. However, if the server is Exim, this shutdown and
29875 reinitialization works. It is not known which (if any) other servers operate
29876 successfully if the client closes a TLS session and continues with unencrypted
29877 SMTP, but there are certainly some that do not work. For such servers, Exim
29878 should not pass the socket to another process, because the failure of the
29879 subsequent attempt to use it would cause Exim to record a temporary host error,
29880 and delay other deliveries to that host.
29882 To test for this case, Exim sends an EHLO command to the server after
29883 closing down the TLS session. If this fails in any way, the connection is
29884 closed instead of being passed to a new delivery process, but no retry
29885 information is recorded.
29887 There is also a manual override; you can set &%hosts_nopass_tls%& on the
29888 &(smtp)& transport to match those hosts for which Exim should not pass
29889 connections to new processes if TLS has been used.
29894 .section "Certificates and all that" "SECTcerandall"
29895 .cindex "certificate" "references to discussion"
29896 In order to understand fully how TLS works, you need to know about
29897 certificates, certificate signing, and certificate authorities.
29898 This is a large topic and an introductory guide is unsuitable for the Exim
29899 reference manual, so instead we provide pointers to existing documentation.
29901 The Apache web-server was for a long time the canonical guide, so their
29902 documentation is a good place to start; their SSL module's Introduction
29903 document is currently at
29905 &url(https://httpd.apache.org/docs/current/ssl/ssl_intro.html)
29907 and their FAQ is at
29909 &url(https://httpd.apache.org/docs/current/ssl/ssl_faq.html)
29912 Eric Rescorla's book, &'SSL and TLS'&, published by Addison-Wesley (ISBN
29913 0-201-61598-3) in 2001, contains both introductory and more in-depth
29915 More recently Ivan Ristić's book &'Bulletproof SSL and TLS'&,
29916 published by Feisty Duck (ISBN 978-1907117046) in 2013 is good.
29917 Ivan is the author of the popular TLS testing tools at
29918 &url(https://www.ssllabs.com/).
29921 .subsection "Certificate chains" SECID186
29922 A file named by &%tls_certificate%& may contain more than one
29923 certificate. This is useful in the case where the certificate that is being
29924 sent is validated by an intermediate certificate which the other end does
29925 not have. Multiple certificates must be in the correct order in the file.
29926 First the host's certificate itself, then the first intermediate
29927 certificate to validate the issuer of the host certificate, then the next
29928 intermediate certificate to validate the issuer of the first intermediate
29929 certificate, and so on, until finally (optionally) the root certificate.
29930 The root certificate must already be trusted by the recipient for
29931 validation to succeed, of course, but if it's not preinstalled, sending the
29932 root certificate along with the rest makes it available for the user to
29933 install if the receiving end is a client MUA that can interact with a user.
29935 Note that certificates using MD5 are unlikely to work on today's Internet;
29936 even if your libraries allow loading them for use in Exim when acting as a
29937 server, increasingly clients will not accept such certificates. The error
29938 diagnostics in such a case can be frustratingly vague.
29942 .subsection "Self-signed certificates" SECID187
29943 .cindex "certificate" "self-signed"
29944 You can create a self-signed certificate using the &'req'& command provided
29945 with OpenSSL, like this:
29946 . ==== Do not shorten the duration here without reading and considering
29947 . ==== the text below. Please leave it at 9999 days.
29949 openssl req -x509 -newkey rsa:1024 -keyout file1 -out file2 \
29952 &_file1_& and &_file2_& can be the same file; the key and the certificate are
29953 delimited and so can be identified independently. The &%-days%& option
29954 specifies a period for which the certificate is valid. The &%-nodes%& option is
29955 important: if you do not set it, the key is encrypted with a passphrase
29956 that you are prompted for, and any use that is made of the key causes more
29957 prompting for the passphrase. This is not helpful if you are going to use
29958 this certificate and key in an MTA, where prompting is not possible.
29960 . ==== I expect to still be working 26 years from now. The less technical
29961 . ==== debt I create, in terms of storing up trouble for my later years, the
29962 . ==== happier I will be then. We really have reached the point where we
29963 . ==== should start, at the very least, provoking thought and making folks
29964 . ==== pause before proceeding, instead of leaving all the fixes until two
29965 . ==== years before 2^31 seconds after the 1970 Unix epoch.
29967 NB: we are now past the point where 9999 days takes us past the 32-bit Unix
29968 epoch. If your system uses unsigned time_t (most do) and is 32-bit, then
29969 the above command might produce a date in the past. Think carefully about
29970 the lifetime of the systems you're deploying, and either reduce the duration
29971 of the certificate or reconsider your platform deployment. (At time of
29972 writing, reducing the duration is the most likely choice, but the inexorable
29973 progression of time takes us steadily towards an era where this will not
29974 be a sensible resolution).
29976 A self-signed certificate made in this way is sufficient for testing, and
29977 may be adequate for all your requirements if you are mainly interested in
29978 encrypting transfers, and not in secure identification.
29980 However, many clients require that the certificate presented by the server be a
29981 user (also called &"leaf"& or &"site"&) certificate, and not a self-signed
29982 certificate. In this situation, the self-signed certificate described above
29983 must be installed on the client host as a trusted root &'certification
29984 authority'& (CA), and the certificate used by Exim must be a user certificate
29985 signed with that self-signed certificate.
29987 For information on creating self-signed CA certificates and using them to sign
29988 user certificates, see the &'General implementation overview'& chapter of the
29989 Open-source PKI book, available online at
29990 &url(https://sourceforge.net/projects/ospkibook/).
29991 .ecindex IIDencsmtp1
29992 .ecindex IIDencsmtp2
29995 .section "TLS Resumption" "SECTresumption"
29996 .cindex TLS resumption
29997 TLS Session Resumption for TLS 1.2 and TLS 1.3 connections can be used (defined
29998 in RFC 5077 for 1.2). The support for this requires GnuTLS 3.6.3 or OpenSSL 1.1.1
30001 Session resumption (this is the "stateless" variant) involves the server sending
30002 a "session ticket" to the client on one connection, which can be stored by the
30003 client and used for a later session. The ticket contains sufficient state for
30004 the server to reconstruct the TLS session, avoiding some expensive crypto
30005 calculation and (on TLS1.2) one full packet roundtrip time.
30008 Operational cost/benefit:
30010 The extra data being transmitted costs a minor amount, and the client has
30011 extra costs in storing and retrieving the data.
30013 In the Exim/Gnutls implementation the extra cost on an initial connection
30014 which is TLS1.2 over a loopback path is about 6ms on 2017-laptop class hardware.
30015 The saved cost on a subsequent connection is about 4ms; three or more
30016 connections become a net win. On longer network paths, two or more
30017 connections will have an average lower startup time thanks to the one
30018 saved packet roundtrip. TLS1.3 will save the crypto cpu costs but not any
30021 .cindex "hints database" tls
30022 Since a new hints DB is used on the TLS client,
30023 the hints DB maintenance should be updated to additionally handle "tls".
30028 The session ticket is encrypted, but is obviously an additional security
30029 vulnarability surface. An attacker able to decrypt it would have access
30030 all connections using the resumed session.
30031 The session ticket encryption key is not committed to storage by the server
30032 and is rotated regularly (OpenSSL: 1hr, and one previous key is used for
30033 overlap; GnuTLS 6hr but does not specify any overlap).
30034 Tickets have limited lifetime (2hr, and new ones issued after 1hr under
30035 OpenSSL. GnuTLS 2hr, appears to not do overlap).
30037 There is a question-mark over the security of the Diffie-Helman parameters
30038 used for session negotiation.
30043 The &%log_selector%& "tls_resumption" appends an asterisk to the tls_cipher "X="
30046 The variables &$tls_in_resumption$& and &$tls_out_resumption$&
30047 have bits 0-4 indicating respectively
30048 support built, client requested ticket, client offered session,
30049 server issued ticket, resume used. A suitable decode list is provided
30050 in the builtin macro _RESUME_DECODE for in &%listextract%& expansions.
30055 The &%tls_resumption_hosts%& main option specifies a hostlist for which
30056 exim, operating as a server, will offer resumption to clients.
30057 Current best practice is to not offer the feature to MUA connection.
30058 Commonly this can be done like this:
30060 tls_resumption_hosts = ${if inlist {$received_port}{587:465} {:}{*}}
30062 If the peer host matches the list after expansion then resumption
30063 is offered and/or accepted.
30065 The &%tls_resumption_hosts%& smtp transport option performs the
30066 equivalent function for operation as a client.
30067 If the peer host matches the list after expansion then resumption
30068 is attempted (if a stored session is available) or the information
30069 stored (if supplied by the peer).
30075 In a resumed session:
30077 The variables &$tls_{in,out}_cipher$& will have values different
30078 to the original (under GnuTLS).
30080 The variables &$tls_{in,out}_ocsp$& will be "not requested" or "no response",
30081 and the &%hosts_require_ocsp%& smtp trasnport option will fail.
30082 . XXX need to do something with that hosts_require_ocsp
30088 .section DANE "SECDANE"
30090 DNS-based Authentication of Named Entities, as applied to SMTP over TLS, provides assurance to a client that
30091 it is actually talking to the server it wants to rather than some attacker operating a Man In The Middle (MITM)
30092 operation. The latter can terminate the TLS connection you make, and make another one to the server (so both
30093 you and the server still think you have an encrypted connection) and, if one of the "well known" set of
30094 Certificate Authorities has been suborned - something which *has* been seen already (2014), a verifiable
30095 certificate (if you're using normal root CAs, eg. the Mozilla set, as your trust anchors).
30097 What DANE does is replace the CAs with the DNS as the trust anchor. The assurance is limited to a) the possibility
30098 that the DNS has been suborned, b) mistakes made by the admins of the target server. The attack surface presented
30099 by (a) is thought to be smaller than that of the set of root CAs.
30101 It also allows the server to declare (implicitly) that connections to it should use TLS. An MITM could simply
30102 fail to pass on a server's STARTTLS.
30104 DANE scales better than having to maintain (and communicate via side-channel) copies of server certificates
30105 for every possible target server. It also scales (slightly) better than having to maintain on an SMTP
30106 client a copy of the standard CAs bundle. It also means not having to pay a CA for certificates.
30108 DANE requires a server operator to do three things: 1) run DNSSEC. This provides assurance to clients
30109 that DNS lookups they do for the server have not been tampered with. The domain MX record applying
30110 to this server, its A record, its TLSA record and any associated CNAME records must all be covered by
30112 2) add TLSA DNS records. These say what the server certificate for a TLS connection should be.
30113 3) offer a server certificate, or certificate chain, in TLS connections which is is anchored by one of the TLSA records.
30115 There are no changes to Exim specific to server-side operation of DANE.
30116 Support for client-side operation of DANE can be included at compile time by defining SUPPORT_DANE=yes
30117 in &_Local/Makefile_&.
30118 If it has been included, the macro "_HAVE_DANE" will be defined.
30120 A TLSA record consist of 4 fields, the "Certificate Usage", the
30121 "Selector", the "Matching type", and the "Certificate Association Data".
30122 For a detailed description of the TLSA record see
30123 &url(https://tools.ietf.org/html/rfc7671#page-5,RFC 7671).
30125 The TLSA record for the server may have "Certificate Usage" (1st) field of DANE-TA(2) or DANE-EE(3).
30126 These are the "Trust Anchor" and "End Entity" variants.
30127 The latter specifies the End Entity directly, i.e. the certificate involved is that of the server
30128 (and if only DANE-EE is used then it should be the sole one transmitted during the TLS handshake);
30129 this is appropriate for a single system, using a self-signed certificate.
30130 DANE-TA usage is effectively declaring a specific CA to be used; this might be a private CA or a public,
30132 A private CA at simplest is just a self-signed certificate (with certain
30133 attributes) which is used to sign server certificates, but running one securely
30134 does require careful arrangement.
30135 With DANE-TA, as implemented in Exim and commonly in other MTAs,
30136 the server TLS handshake must transmit the entire certificate chain from CA to server-certificate.
30137 DANE-TA is commonly used for several services and/or servers, each having a TLSA query-domain CNAME record,
30138 all of which point to a single TLSA record.
30139 DANE-TA and DANE-EE can both be used together.
30141 Our recommendation is to use DANE with a certificate from a public CA,
30142 because this enables a variety of strategies for remote clients to verify
30144 You can then publish information both via DANE and another technology,
30145 "MTA-STS", described below.
30147 When you use DANE-TA to publish trust anchor information, you ask entities
30148 outside your administrative control to trust the Certificate Authority for
30149 connections to you.
30150 If using a private CA then you should expect others to still apply the
30151 technical criteria they'd use for a public CA to your certificates.
30152 In particular, you should probably try to follow current best practices for CA
30153 operation around hash algorithms and key sizes.
30154 Do not expect other organizations to lower their security expectations just
30155 because a particular profile might be reasonable for your own internal use.
30157 When this text was last updated, this in practice means to avoid use of SHA-1
30158 and MD5; if using RSA to use key sizes of at least 2048 bits (and no larger
30159 than 4096, for interoperability); to use keyUsage fields correctly; to use
30160 random serial numbers.
30161 The list of requirements is subject to change as best practices evolve.
30162 If you're not already using a private CA, or it doesn't meet these
30163 requirements, then we encourage you to avoid all these issues and use a public
30164 CA such as &url(https://letsencrypt.org/,Let's Encrypt) instead.
30166 The TLSA record should have a "Selector" (2nd) field of SPKI(1) and
30167 a "Matching Type" (3rd) field of SHA2-512(2).
30169 For the "Certificate Authority Data" (4th) field, commands like
30172 openssl x509 -pubkey -noout <certificate.pem \
30173 | openssl rsa -outform der -pubin 2>/dev/null \
30178 are workable to create a hash of the certificate's public key.
30180 An example TLSA record for DANE-EE(3), SPKI(1), and SHA-512 (2) looks like
30183 _25._tcp.mail.example.com. TLSA 3 1 2 8BA8A336E...
30186 At the time of writing, &url(https://www.huque.com/bin/gen_tlsa)
30187 is useful for quickly generating TLSA records.
30190 For use with the DANE-TA model, server certificates must have a correct name (SubjectName or SubjectAltName).
30192 The Certificate issued by the CA published in the DANE-TA model should be
30193 issued using a strong hash algorithm.
30194 Exim, and importantly various other MTAs sending to you, will not
30195 re-enable hash algorithms which have been disabled by default in TLS
30197 This means no MD5 and no SHA-1. SHA2-256 is the minimum for reliable
30198 interoperability (and probably the maximum too, in 2018).
30200 The use of OCSP-stapling should be considered, allowing for fast revocation of certificates (which would otherwise
30201 be limited by the DNS TTL on the TLSA records). However, this is likely to only be usable with DANE-TA. NOTE: the
30202 default of requesting OCSP for all hosts is modified iff DANE is in use, to:
30205 hosts_request_ocsp = ${if or { {= {0}{$tls_out_tlsa_usage}} \
30206 {= {4}{$tls_out_tlsa_usage}} } \
30210 The (new) variable &$tls_out_tlsa_usage$& is a bitfield with numbered bits set for TLSA record usage codes.
30211 The zero above means DANE was not in use, the four means that only DANE-TA usage TLSA records were
30212 found. If the definition of &%hosts_request_ocsp%& includes the
30213 string "tls_out_tlsa_usage", they are re-expanded in time to
30214 control the OCSP request.
30216 This modification of hosts_request_ocsp is only done if it has the default value of "*". Admins who change it, and
30217 those who use &%hosts_require_ocsp%&, should consider the interaction with DANE in their OCSP settings.
30220 For client-side DANE there are three new smtp transport options, &%hosts_try_dane%&, &%hosts_require_dane%&
30221 and &%dane_require_tls_ciphers%&.
30222 The &"require"& variant will result in failure if the target host is not
30223 DNSSEC-secured. To get DNSSEC-secured hostname resolution, use
30224 the &%dnssec_request_domains%& router or transport option.
30226 DANE will only be usable if the target host has DNSSEC-secured MX, A and TLSA records.
30228 A TLSA lookup will be done if either of the above options match and the host-lookup succeeded using DNSSEC.
30229 If a TLSA lookup is done and succeeds, a DANE-verified TLS connection
30230 will be required for the host. If it does not, the host will not
30231 be used; there is no fallback to non-DANE or non-TLS.
30233 If DANE is requested and usable, then the TLS cipher list configuration
30234 prefers to use the option &%dane_require_tls_ciphers%& and falls
30235 back to &%tls_require_ciphers%& only if that is unset.
30236 This lets you configure "decent crypto" for DANE and "better than nothing
30237 crypto" as the default. Note though that while GnuTLS lets the string control
30238 which versions of TLS/SSL will be negotiated, OpenSSL does not and you're
30239 limited to ciphersuite constraints.
30241 If DANE is requested and useable (see above) the following transport options are ignored:
30245 tls_try_verify_hosts
30246 tls_verify_certificates
30248 tls_verify_cert_hostnames
30252 If DANE is not usable, whether requested or not, and CA-anchored
30253 verification evaluation is wanted, the above variables should be set appropriately.
30255 The router and transport option &%dnssec_request_domains%& must not be
30256 set to &"never"&, and &%dnssec_require_domains%& is ignored.
30258 If verification was successful using DANE then the "CV" item in the delivery log line will show as "CV=dane".
30260 There is a new variable &$tls_out_dane$& which will have "yes" if
30261 verification succeeded using DANE and "no" otherwise (only useful
30262 in combination with events; see &<<CHAPevents>>&),
30263 and a new variable &$tls_out_tlsa_usage$& (detailed above).
30265 .cindex DANE reporting
30266 An event (see &<<CHAPevents>>&) of type "dane:fail" will be raised on failures
30267 to achieve DANE-verified connection, if one was either requested and offered, or
30268 required. This is intended to support TLS-reporting as defined in
30269 &url(https://tools.ietf.org/html/draft-ietf-uta-smtp-tlsrpt-17).
30270 The &$event_data$& will be one of the Result Types defined in
30271 Section 4.3 of that document.
30273 Under GnuTLS, DANE is only supported from version 3.0.0 onwards.
30275 DANE is specified in published RFCs and decouples certificate authority trust
30276 selection from a "race to the bottom" of "you must trust everything for mail
30277 to get through". There is an alternative technology called MTA-STS, which
30278 instead publishes MX trust anchor information on an HTTPS website. At the
30279 time this text was last updated, MTA-STS was still a draft, not yet an RFC.
30280 Exim has no support for MTA-STS as a client, but Exim mail server operators
30281 can choose to publish information describing their TLS configuration using
30282 MTA-STS to let those clients who do use that protocol derive trust
30285 The MTA-STS design requires a certificate from a public Certificate Authority
30286 which is recognized by clients sending to you.
30287 That selection of which CAs are trusted by others is outside your control.
30289 The most interoperable course of action is probably to use
30290 &url(https://letsencrypt.org/,Let's Encrypt), with automated certificate
30291 renewal; to publish the anchor information in DNSSEC-secured DNS via TLSA
30292 records for DANE clients (such as Exim and Postfix) and to publish anchor
30293 information for MTA-STS as well. This is what is done for the &'exim.org'&
30294 domain itself (with caveats around occasionally broken MTA-STS because of
30295 incompatible specification changes prior to reaching RFC status).
30299 . ////////////////////////////////////////////////////////////////////////////
30300 . ////////////////////////////////////////////////////////////////////////////
30302 .chapter "Access control lists" "CHAPACL"
30303 .scindex IIDacl "&ACL;" "description"
30304 .cindex "control of incoming mail"
30305 .cindex "message" "controlling incoming"
30306 .cindex "policy control" "access control lists"
30307 Access Control Lists (ACLs) are defined in a separate section of the runtime
30308 configuration file, headed by &"begin acl"&. Each ACL definition starts with a
30309 name, terminated by a colon. Here is a complete ACL section that contains just
30310 one very small ACL:
30314 accept hosts = one.host.only
30316 You can have as many lists as you like in the ACL section, and the order in
30317 which they appear does not matter. The lists are self-terminating.
30319 The majority of ACLs are used to control Exim's behaviour when it receives
30320 certain SMTP commands. This applies both to incoming TCP/IP connections, and
30321 when a local process submits a message using SMTP by specifying the &%-bs%&
30322 option. The most common use is for controlling which recipients are accepted
30323 in incoming messages. In addition, you can define an ACL that is used to check
30324 local non-SMTP messages. The default configuration file contains an example of
30325 a realistic ACL for checking RCPT commands. This is discussed in chapter
30326 &<<CHAPdefconfil>>&.
30329 .section "Testing ACLs" "SECID188"
30330 The &%-bh%& command line option provides a way of testing your ACL
30331 configuration locally by running a fake SMTP session with which you interact.
30334 .section "Specifying when ACLs are used" "SECID189"
30335 .cindex "&ACL;" "options for specifying"
30336 In order to cause an ACL to be used, you have to name it in one of the relevant
30337 options in the main part of the configuration. These options are:
30338 .cindex "AUTH" "ACL for"
30339 .cindex "DATA" "ACLs for"
30340 .cindex "ETRN" "ACL for"
30341 .cindex "EXPN" "ACL for"
30342 .cindex "HELO" "ACL for"
30343 .cindex "EHLO" "ACL for"
30344 .cindex "DKIM" "ACL for"
30345 .cindex "MAIL" "ACL for"
30346 .cindex "QUIT, ACL for"
30347 .cindex "RCPT" "ACL for"
30348 .cindex "STARTTLS, ACL for"
30349 .cindex "VRFY" "ACL for"
30350 .cindex "SMTP" "connection, ACL for"
30351 .cindex "non-SMTP messages" "ACLs for"
30352 .cindex "MIME content scanning" "ACL for"
30353 .cindex "PRDR" "ACL for"
30356 .irow &%acl_not_smtp%& "ACL for non-SMTP messages"
30357 .irow &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
30358 .irow &%acl_not_smtp_start%& "ACL at start of non-SMTP message"
30359 .irow &%acl_smtp_auth%& "ACL for AUTH"
30360 .irow &%acl_smtp_connect%& "ACL for start of SMTP connection"
30361 .irow &%acl_smtp_data%& "ACL after DATA is complete"
30362 .irow &%acl_smtp_data_prdr%& "ACL for each recipient, after DATA is complete"
30363 .irow &%acl_smtp_dkim%& "ACL for each DKIM signer"
30364 .irow &%acl_smtp_etrn%& "ACL for ETRN"
30365 .irow &%acl_smtp_expn%& "ACL for EXPN"
30366 .irow &%acl_smtp_helo%& "ACL for HELO or EHLO"
30367 .irow &%acl_smtp_mail%& "ACL for MAIL"
30368 .irow &%acl_smtp_mailauth%& "ACL for the AUTH parameter of MAIL"
30369 .irow &%acl_smtp_mime%& "ACL for content-scanning MIME parts"
30370 .irow &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
30371 .irow &%acl_smtp_predata%& "ACL at start of DATA command"
30372 .irow &%acl_smtp_quit%& "ACL for QUIT"
30373 .irow &%acl_smtp_rcpt%& "ACL for RCPT"
30374 .irow &%acl_smtp_starttls%& "ACL for STARTTLS"
30375 .irow &%acl_smtp_vrfy%& "ACL for VRFY"
30378 For example, if you set
30380 acl_smtp_rcpt = small_acl
30382 the little ACL defined above is used whenever Exim receives a RCPT command
30383 in an SMTP dialogue. The majority of policy tests on incoming messages can be
30384 done when RCPT commands arrive. A rejection of RCPT should cause the
30385 sending MTA to give up on the recipient address contained in the RCPT
30386 command, whereas rejection at other times may cause the client MTA to keep on
30387 trying to deliver the message. It is therefore recommended that you do as much
30388 testing as possible at RCPT time.
30391 .subsection "The non-SMTP ACLs" SECID190
30392 .cindex "non-SMTP messages" "ACLs for"
30393 The non-SMTP ACLs apply to all non-interactive incoming messages, that is, they
30394 apply to batched SMTP as well as to non-SMTP messages. (Batched SMTP is not
30395 really SMTP.) Many of the ACL conditions (for example, host tests, and tests on
30396 the state of the SMTP connection such as encryption and authentication) are not
30397 relevant and are forbidden in these ACLs. However, the sender and recipients
30398 are known, so the &%senders%& and &%sender_domains%& conditions and the
30399 &$sender_address$& and &$recipients$& variables can be used. Variables such as
30400 &$authenticated_sender$& are also available. You can specify added header lines
30401 in any of these ACLs.
30403 The &%acl_not_smtp_start%& ACL is run right at the start of receiving a
30404 non-SMTP message, before any of the message has been read. (This is the
30405 analogue of the &%acl_smtp_predata%& ACL for SMTP input.) In the case of
30406 batched SMTP input, it runs after the DATA command has been reached. The
30407 result of this ACL is ignored; it cannot be used to reject a message. If you
30408 really need to, you could set a value in an ACL variable here and reject based
30409 on that in the &%acl_not_smtp%& ACL. However, this ACL can be used to set
30410 controls, and in particular, it can be used to set
30412 control = suppress_local_fixups
30414 This cannot be used in the other non-SMTP ACLs because by the time they are
30415 run, it is too late.
30417 The &%acl_not_smtp_mime%& ACL is available only when Exim is compiled with the
30418 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
30420 The &%acl_not_smtp%& ACL is run just before the &[local_scan()]& function. Any
30421 kind of rejection is treated as permanent, because there is no way of sending a
30422 temporary error for these kinds of message.
30425 .subsection "The SMTP connect ACL" SECID191
30426 .cindex "SMTP" "connection, ACL for"
30427 .oindex &%smtp_banner%&
30428 The ACL test specified by &%acl_smtp_connect%& happens at the start of an SMTP
30429 session, after the test specified by &%host_reject_connection%& (which is now
30430 an anomaly) and any TCP Wrappers testing (if configured). If the connection is
30431 accepted by an &%accept%& verb that has a &%message%& modifier, the contents of
30432 the message override the banner message that is otherwise specified by the
30433 &%smtp_banner%& option.
30435 For tls-on-connect connections, the ACL is run after the TLS connection
30436 is accepted (however, &%host_reject_connection%& is tested before).
30439 .subsection "The EHLO/HELO ACL" SECID192
30440 .cindex "EHLO" "ACL for"
30441 .cindex "HELO" "ACL for"
30442 The ACL test specified by &%acl_smtp_helo%& happens when the client issues an
30443 EHLO or HELO command, after the tests specified by &%helo_accept_junk_hosts%&,
30444 &%helo_allow_chars%&, &%helo_verify_hosts%&, and &%helo_try_verify_hosts%&.
30445 Note that a client may issue more than one EHLO or HELO command in an SMTP
30446 session, and indeed is required to issue a new EHLO or HELO after successfully
30447 setting up encryption following a STARTTLS command.
30449 Note also that a deny neither forces the client to go away nor means that
30450 mail will be refused on the connection. Consider checking for
30451 &$sender_helo_name$& being defined in a MAIL or RCPT ACL to do that.
30453 If the command is accepted by an &%accept%& verb that has a &%message%&
30454 modifier, the message may not contain more than one line (it will be truncated
30455 at the first newline and a panic logged if it does). Such a message cannot
30456 affect the EHLO options that are listed on the second and subsequent lines of
30460 .subsection "The DATA ACLs" SECID193
30461 .cindex "DATA" "ACLs for"
30462 Two ACLs are associated with the DATA command, because it is two-stage
30463 command, with two responses being sent to the client.
30464 When the DATA command is received, the ACL defined by &%acl_smtp_predata%&
30465 is obeyed. This gives you control after all the RCPT commands, but before
30466 the message itself is received. It offers the opportunity to give a negative
30467 response to the DATA command before the data is transmitted. Header lines
30468 added by MAIL or RCPT ACLs are not visible at this time, but any that
30469 are defined here are visible when the &%acl_smtp_data%& ACL is run.
30471 You cannot test the contents of the message, for example, to verify addresses
30472 in the headers, at RCPT time or when the DATA command is received. Such
30473 tests have to appear in the ACL that is run after the message itself has been
30474 received, before the final response to the DATA command is sent. This is
30475 the ACL specified by &%acl_smtp_data%&, which is the second ACL that is
30476 associated with the DATA command.
30478 .cindex CHUNKING "BDAT command"
30479 .cindex BDAT "SMTP command"
30480 .cindex "RFC 3030" CHUNKING
30481 If CHUNKING was advertised and a BDAT command sequence is received,
30482 the &%acl_smtp_predata%& ACL is not run.
30483 . XXX why not? It should be possible, for the first BDAT.
30484 The &%acl_smtp_data%& is run after the last BDAT command and all of
30485 the data specified is received.
30487 For both of these ACLs, it is not possible to reject individual recipients. An
30488 error response rejects the entire message. Unfortunately, it is known that some
30489 MTAs do not treat hard (5&'xx'&) responses to the DATA command (either
30490 before or after the data) correctly &-- they keep the message on their queues
30491 and try again later, but that is their problem, though it does waste some of
30494 The &%acl_smtp_data%& ACL is run after
30495 the &%acl_smtp_data_prdr%&,
30496 the &%acl_smtp_dkim%&
30497 and the &%acl_smtp_mime%& ACLs.
30499 .subsection "The SMTP DKIM ACL" SECTDKIMACL
30500 The &%acl_smtp_dkim%& ACL is available only when Exim is compiled with DKIM support
30501 enabled (which is the default).
30503 The ACL test specified by &%acl_smtp_dkim%& happens after a message has been
30504 received, and is executed for each DKIM signature found in a message. If not
30505 otherwise specified, the default action is to accept.
30507 This ACL is evaluated before &%acl_smtp_mime%& and &%acl_smtp_data%&.
30509 For details on the operation of DKIM, see section &<<SECDKIM>>&.
30512 .subsection "The SMTP MIME ACL" SECID194
30513 The &%acl_smtp_mime%& option is available only when Exim is compiled with the
30514 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
30516 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
30519 .subsection "The SMTP PRDR ACL" SECTPRDRACL
30520 .cindex "PRDR" "ACL for"
30521 .oindex "&%prdr_enable%&"
30522 The &%acl_smtp_data_prdr%& ACL is available only when Exim is compiled
30523 with PRDR support enabled (which is the default).
30524 It becomes active only when the PRDR feature is negotiated between
30525 client and server for a message, and more than one recipient
30528 The ACL test specified by &%acl_smtp_data_prdr%& happens after a message
30529 has been received, and is executed once for each recipient of the message
30530 with &$local_part$& and &$domain$& valid.
30531 The test may accept, defer or deny for individual recipients.
30532 The &%acl_smtp_data%& will still be called after this ACL and
30533 can reject the message overall, even if this ACL has accepted it
30534 for some or all recipients.
30536 PRDR may be used to support per-user content filtering. Without it
30537 one must defer any recipient after the first that has a different
30538 content-filter configuration. With PRDR, the RCPT-time check
30539 .cindex "PRDR" "variable for"
30540 for this can be disabled when the variable &$prdr_requested$&
30542 Any required difference in behaviour of the main DATA-time
30543 ACL should however depend on the PRDR-time ACL having run, as Exim
30544 will avoid doing so in some situations (e.g. single-recipient mails).
30546 See also the &%prdr_enable%& global option
30547 and the &%hosts_try_prdr%& smtp transport option.
30549 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
30550 If the ACL is not defined, processing completes as if
30551 the feature was not requested by the client.
30553 .subsection "The QUIT ACL" SECTQUITACL
30554 .cindex "QUIT, ACL for"
30555 The ACL for the SMTP QUIT command is anomalous, in that the outcome of the ACL
30556 does not affect the response code to QUIT, which is always 221. Thus, the ACL
30557 does not in fact control any access.
30558 For this reason, it may only accept
30559 or warn as its final result.
30561 This ACL can be used for tasks such as custom logging at the end of an SMTP
30562 session. For example, you can use ACL variables in other ACLs to count
30563 messages, recipients, etc., and log the totals at QUIT time using one or
30564 more &%logwrite%& modifiers on a &%warn%& verb.
30566 &*Warning*&: Only the &$acl_c$&&'x'& variables can be used for this, because
30567 the &$acl_m$&&'x'& variables are reset at the end of each incoming message.
30569 You do not need to have a final &%accept%&, but if you do, you can use a
30570 &%message%& modifier to specify custom text that is sent as part of the 221
30573 This ACL is run only for a &"normal"& QUIT. For certain kinds of disastrous
30574 failure (for example, failure to open a log file, or when Exim is bombing out
30575 because it has detected an unrecoverable error), all SMTP commands from the
30576 client are given temporary error responses until QUIT is received or the
30577 connection is closed. In these special cases, the QUIT ACL does not run.
30580 .subsection "The not-QUIT ACL" SECTNOTQUITACL
30581 .vindex &$acl_smtp_notquit$&
30582 The not-QUIT ACL, specified by &%acl_smtp_notquit%&, is run in most cases when
30583 an SMTP session ends without sending QUIT. However, when Exim itself is in bad
30584 trouble, such as being unable to write to its log files, this ACL is not run,
30585 because it might try to do things (such as write to log files) that make the
30586 situation even worse.
30588 Like the QUIT ACL, this ACL is provided to make it possible to do customized
30589 logging or to gather statistics, and its outcome is ignored. The &%delay%&
30590 modifier is forbidden in this ACL, and the only permitted verbs are &%accept%&
30593 .vindex &$smtp_notquit_reason$&
30594 When the not-QUIT ACL is running, the variable &$smtp_notquit_reason$& is set
30595 to a string that indicates the reason for the termination of the SMTP
30596 connection. The possible values are:
30598 .irow &`acl-drop`& "Another ACL issued a &%drop%& command"
30599 .irow &`bad-commands`& "Too many unknown or non-mail commands"
30600 .irow &`command-timeout`& "Timeout while reading SMTP commands"
30601 .irow &`connection-lost`& "The SMTP connection has been lost"
30602 .irow &`data-timeout`& "Timeout while reading message data"
30603 .irow &`local-scan-error`& "The &[local_scan()]& function crashed"
30604 .irow &`local-scan-timeout`& "The &[local_scan()]& function timed out"
30605 .irow &`signal-exit`& "SIGTERM or SIGINT"
30606 .irow &`synchronization-error`& "SMTP synchronization error"
30607 .irow &`tls-failed`& "TLS failed to start"
30609 In most cases when an SMTP connection is closed without having received QUIT,
30610 Exim sends an SMTP response message before actually closing the connection.
30611 With the exception of the &`acl-drop`& case, the default message can be
30612 overridden by the &%message%& modifier in the not-QUIT ACL. In the case of a
30613 &%drop%& verb in another ACL, it is the message from the other ACL that is
30617 .section "Finding an ACL to use" "SECID195"
30618 .cindex "&ACL;" "finding which to use"
30619 The value of an &%acl_smtp_%&&'xxx'& option is expanded before use, so
30620 you can use different ACLs in different circumstances. For example,
30622 acl_smtp_rcpt = ${if ={25}{$interface_port} \
30623 {acl_check_rcpt} {acl_check_rcpt_submit} }
30625 In the default configuration file there are some example settings for
30626 providing an RFC 4409 message &"submission"& service on port 587 and
30627 an RFC 8314 &"submissions"& service on port 465. You can use a string
30628 expansion like this to choose an ACL for MUAs on these ports which is
30629 more appropriate for this purpose than the default ACL on port 25.
30631 The expanded string does not have to be the name of an ACL in the
30632 configuration file; there are other possibilities. Having expanded the
30633 string, Exim searches for an ACL as follows:
30636 If the string begins with a slash, Exim uses it as a filename, and reads its
30637 contents as an ACL. The lines are processed in the same way as lines in the
30638 Exim configuration file. In particular, continuation lines are supported, blank
30639 lines are ignored, as are lines whose first non-whitespace character is &"#"&.
30640 If the file does not exist or cannot be read, an error occurs (typically
30641 causing a temporary failure of whatever caused the ACL to be run). For example:
30643 acl_smtp_data = /etc/acls/\
30644 ${lookup{$sender_host_address}lsearch\
30645 {/etc/acllist}{$value}{default}}
30647 This looks up an ACL file to use on the basis of the host's IP address, falling
30648 back to a default if the lookup fails. If an ACL is successfully read from a
30649 file, it is retained in memory for the duration of the Exim process, so that it
30650 can be re-used without having to re-read the file.
30652 If the string does not start with a slash, and does not contain any spaces,
30653 Exim searches the ACL section of the configuration for an ACL whose name
30654 matches the string.
30656 If no named ACL is found, or if the string contains spaces, Exim parses
30657 the string as an inline ACL. This can save typing in cases where you just
30658 want to have something like
30660 acl_smtp_vrfy = accept
30662 in order to allow free use of the VRFY command. Such a string may contain
30663 newlines; it is processed in the same way as an ACL that is read from a file.
30669 .section "ACL return codes" "SECID196"
30670 .cindex "&ACL;" "return codes"
30671 Except for the QUIT ACL, which does not affect the SMTP return code (see
30672 section &<<SECTQUITACL>>& above), the result of running an ACL is either
30673 &"accept"& or &"deny"&, or, if some test cannot be completed (for example, if a
30674 database is down), &"defer"&. These results cause 2&'xx'&, 5&'xx'&, and 4&'xx'&
30675 return codes, respectively, to be used in the SMTP dialogue. A fourth return,
30676 &"error"&, occurs when there is an error such as invalid syntax in the ACL.
30677 This also causes a 4&'xx'& return code.
30679 For the non-SMTP ACL, &"defer"& and &"error"& are treated in the same way as
30680 &"deny"&, because there is no mechanism for passing temporary errors to the
30681 submitters of non-SMTP messages.
30684 ACLs that are relevant to message reception may also return &"discard"&. This
30685 has the effect of &"accept"&, but causes either the entire message or an
30686 individual recipient address to be discarded. In other words, it is a
30687 blackholing facility. Use it with care.
30689 If the ACL for MAIL returns &"discard"&, all recipients are discarded, and no
30690 ACL is run for subsequent RCPT commands. The effect of &"discard"& in a
30691 RCPT ACL is to discard just the one recipient address. If there are no
30692 recipients left when the message's data is received, the DATA ACL is not
30693 run. A &"discard"& return from the DATA or the non-SMTP ACL discards all the
30694 remaining recipients. The &"discard"& return is not permitted for the
30695 &%acl_smtp_predata%& ACL.
30697 If the ACL for VRFY returns &"accept"&, a recipient verify (without callout)
30698 is done on the address and the result determines the SMTP response.
30701 .cindex "&[local_scan()]& function" "when all recipients discarded"
30702 The &[local_scan()]& function is always run, even if there are no remaining
30703 recipients; it may create new recipients.
30707 .section "Unset ACL options" "SECID197"
30708 .cindex "&ACL;" "unset options"
30709 The default actions when any of the &%acl_%&&'xxx'& options are unset are not
30710 all the same. &*Note*&: These defaults apply only when the relevant ACL is
30711 not defined at all. For any defined ACL, the default action when control
30712 reaches the end of the ACL statements is &"deny"&.
30714 For &%acl_smtp_quit%& and &%acl_not_smtp_start%& there is no default because
30715 these two are ACLs that are used only for their side effects. They cannot be
30716 used to accept or reject anything.
30718 For &%acl_not_smtp%&, &%acl_smtp_auth%&, &%acl_smtp_connect%&,
30719 &%acl_smtp_data%&, &%acl_smtp_helo%&, &%acl_smtp_mail%&, &%acl_smtp_mailauth%&,
30720 &%acl_smtp_mime%&, &%acl_smtp_predata%&, and &%acl_smtp_starttls%&, the action
30721 when the ACL is not defined is &"accept"&.
30723 For the others (&%acl_smtp_etrn%&, &%acl_smtp_expn%&, &%acl_smtp_rcpt%&, and
30724 &%acl_smtp_vrfy%&), the action when the ACL is not defined is &"deny"&.
30725 This means that &%acl_smtp_rcpt%& must be defined in order to receive any
30726 messages over an SMTP connection. For an example, see the ACL in the default
30727 configuration file.
30732 .section "Data for message ACLs" "SECID198"
30733 .cindex "&ACL;" "data for message ACL"
30735 .vindex &$local_part$&
30736 .vindex &$sender_address$&
30737 .vindex &$sender_host_address$&
30738 .vindex &$smtp_command$&
30739 When a MAIL or RCPT ACL, or either of the DATA ACLs, is running, the variables
30740 that contain information about the host and the message's sender (for example,
30741 &$sender_host_address$& and &$sender_address$&) are set, and can be used in ACL
30742 statements. In the case of RCPT (but not MAIL or DATA), &$domain$& and
30743 &$local_part$& are set from the argument address. The entire SMTP command
30744 is available in &$smtp_command$&.
30746 When an ACL for the AUTH parameter of MAIL is running, the variables that
30747 contain information about the host are set, but &$sender_address$& is not yet
30748 set. Section &<<SECTauthparamail>>& contains a discussion of this parameter and
30751 .vindex "&$message_size$&"
30752 The &$message_size$& variable is set to the value of the SIZE parameter on
30753 the MAIL command at MAIL, RCPT and pre-data time, or to -1 if
30754 that parameter is not given. The value is updated to the true message size by
30755 the time the final DATA ACL is run (after the message data has been
30758 .vindex "&$rcpt_count$&"
30759 .vindex "&$recipients_count$&"
30760 The &$rcpt_count$& variable increases by one for each RCPT command received.
30761 The &$recipients_count$& variable increases by one each time a RCPT command is
30762 accepted, so while an ACL for RCPT is being processed, it contains the number
30763 of previously accepted recipients. At DATA time (for both the DATA ACLs),
30764 &$rcpt_count$& contains the total number of RCPT commands, and
30765 &$recipients_count$& contains the total number of accepted recipients.
30771 .section "Data for non-message ACLs" "SECTdatfornon"
30772 .cindex "&ACL;" "data for non-message ACL"
30773 .vindex &$smtp_command_argument$&
30774 .vindex &$smtp_command$&
30775 When an ACL is being run for AUTH, EHLO, ETRN, EXPN, HELO, STARTTLS, or VRFY,
30776 the remainder of the SMTP command line is placed in &$smtp_command_argument$&,
30777 and the entire SMTP command is available in &$smtp_command$&.
30778 These variables can be tested using a &%condition%& condition. For example,
30779 here is an ACL for use with AUTH, which insists that either the session is
30780 encrypted, or the CRAM-MD5 authentication method is used. In other words, it
30781 does not permit authentication methods that use cleartext passwords on
30782 unencrypted connections.
30785 accept encrypted = *
30786 accept condition = ${if eq{${uc:$smtp_command_argument}}\
30788 deny message = TLS encryption or CRAM-MD5 required
30790 (Another way of applying this restriction is to arrange for the authenticators
30791 that use cleartext passwords not to be advertised when the connection is not
30792 encrypted. You can use the generic &%server_advertise_condition%& authenticator
30793 option to do this.)
30797 .section "Format of an ACL" "SECID199"
30798 .cindex "&ACL;" "format of"
30799 .cindex "&ACL;" "verbs, definition of"
30800 An individual ACL consists of a number of statements. Each statement starts
30801 with a verb, optionally followed by a number of conditions and &"modifiers"&.
30802 Modifiers can change the way the verb operates, define error and log messages,
30803 set variables, insert delays, and vary the processing of accepted messages.
30805 If all the conditions are met, the verb is obeyed. The same condition may be
30806 used (with different arguments) more than once in the same statement. This
30807 provides a means of specifying an &"and"& conjunction between conditions. For
30810 deny dnslists = list1.example
30811 dnslists = list2.example
30813 If there are no conditions, the verb is always obeyed. Exim stops evaluating
30814 the conditions and modifiers when it reaches a condition that fails. What
30815 happens then depends on the verb (and in one case, on a special modifier). Not
30816 all the conditions make sense at every testing point. For example, you cannot
30817 test a sender address in the ACL that is run for a VRFY command.
30820 .section "ACL verbs" "SECID200"
30821 The ACL verbs are as follows:
30824 .cindex "&%accept%& ACL verb"
30825 &%accept%&: If all the conditions are met, the ACL returns &"accept"&. If any
30826 of the conditions are not met, what happens depends on whether &%endpass%&
30827 appears among the conditions (for syntax see below). If the failing condition
30828 is before &%endpass%&, control is passed to the next ACL statement; if it is
30829 after &%endpass%&, the ACL returns &"deny"&. Consider this statement, used to
30830 check a RCPT command:
30832 accept domains = +local_domains
30836 If the recipient domain does not match the &%domains%& condition, control
30837 passes to the next statement. If it does match, the recipient is verified, and
30838 the command is accepted if verification succeeds. However, if verification
30839 fails, the ACL yields &"deny"&, because the failing condition is after
30842 The &%endpass%& feature has turned out to be confusing to many people, so its
30843 use is not recommended nowadays. It is always possible to rewrite an ACL so
30844 that &%endpass%& is not needed, and it is no longer used in the default
30847 .cindex "&%message%& ACL modifier" "with &%accept%&"
30848 If a &%message%& modifier appears on an &%accept%& statement, its action
30849 depends on whether or not &%endpass%& is present. In the absence of &%endpass%&
30850 (when an &%accept%& verb either accepts or passes control to the next
30851 statement), &%message%& can be used to vary the message that is sent when an
30852 SMTP command is accepted. For example, in a RCPT ACL you could have:
30854 &`accept `&<&'some conditions'&>
30855 &` message = OK, I will allow you through today`&
30857 You can specify an SMTP response code, optionally followed by an &"extended
30858 response code"& at the start of the message, but the first digit must be the
30859 same as would be sent by default, which is 2 for an &%accept%& verb.
30861 If &%endpass%& is present in an &%accept%& statement, &%message%& specifies
30862 an error message that is used when access is denied. This behaviour is retained
30863 for backward compatibility, but current &"best practice"& is to avoid the use
30868 .cindex "&%defer%& ACL verb"
30869 &%defer%&: If all the conditions are true, the ACL returns &"defer"& which, in
30870 an SMTP session, causes a 4&'xx'& response to be given. For a non-SMTP ACL,
30871 &%defer%& is the same as &%deny%&, because there is no way of sending a
30872 temporary error. For a RCPT command, &%defer%& is much the same as using a
30873 &(redirect)& router and &`:defer:`& while verifying, but the &%defer%& verb can
30874 be used in any ACL, and even for a recipient it might be a simpler approach.
30878 .cindex "&%deny%& ACL verb"
30879 &%deny%&: If all the conditions are met, the ACL returns &"deny"&. If any of
30880 the conditions are not met, control is passed to the next ACL statement. For
30883 deny dnslists = blackholes.mail-abuse.org
30885 rejects commands from hosts that are on a DNS black list.
30889 .cindex "&%discard%& ACL verb"
30890 &%discard%&: This verb behaves like &%accept%&, except that it returns
30891 &"discard"& from the ACL instead of &"accept"&. It is permitted only on ACLs
30892 that are concerned with receiving messages. When all the conditions are true,
30893 the sending entity receives a &"success"& response. However, &%discard%& causes
30894 recipients to be discarded. If it is used in an ACL for RCPT, just the one
30895 recipient is discarded; if used for MAIL, DATA or in the non-SMTP ACL, all the
30896 message's recipients are discarded. Recipients that are discarded before DATA
30897 do not appear in the log line when the &%received_recipients%& log selector is set.
30899 If the &%log_message%& modifier is set when &%discard%& operates,
30900 its contents are added to the line that is automatically written to the log.
30901 The &%message%& modifier operates exactly as it does for &%accept%&.
30905 .cindex "&%drop%& ACL verb"
30906 &%drop%&: This verb behaves like &%deny%&, except that an SMTP connection is
30907 forcibly closed after the 5&'xx'& error message has been sent. For example:
30909 drop condition = ${if > {$rcpt_count}{20}}
30910 message = I don't take more than 20 RCPTs
30912 There is no difference between &%deny%& and &%drop%& for the connect-time ACL.
30913 The connection is always dropped after sending a 550 response.
30916 .cindex "&%require%& ACL verb"
30917 &%require%&: If all the conditions are met, control is passed to the next ACL
30918 statement. If any of the conditions are not met, the ACL returns &"deny"&. For
30919 example, when checking a RCPT command,
30921 require message = Sender did not verify
30924 passes control to subsequent statements only if the message's sender can be
30925 verified. Otherwise, it rejects the command. Note the positioning of the
30926 &%message%& modifier, before the &%verify%& condition. The reason for this is
30927 discussed in section &<<SECTcondmodproc>>&.
30930 .cindex "&%warn%& ACL verb"
30931 &%warn%&: If all the conditions are true, a line specified by the
30932 &%log_message%& modifier is written to Exim's main log. Control always passes
30933 to the next ACL statement. If any condition is false, the log line is not
30934 written. If an identical log line is requested several times in the same
30935 message, only one copy is actually written to the log. If you want to force
30936 duplicates to be written, use the &%logwrite%& modifier instead.
30938 If &%log_message%& is not present, a &%warn%& verb just checks its conditions
30939 and obeys any &"immediate"& modifiers (such as &%control%&, &%set%&,
30940 &%logwrite%&, &%add_header%&, and &%remove_header%&) that appear before the
30941 first failing condition. There is more about adding header lines in section
30942 &<<SECTaddheadacl>>&.
30944 If any condition on a &%warn%& statement cannot be completed (that is, there is
30945 some sort of defer), the log line specified by &%log_message%& is not written.
30946 This does not include the case of a forced failure from a lookup, which
30947 is considered to be a successful completion. After a defer, no further
30948 conditions or modifiers in the &%warn%& statement are processed. The incident
30949 is logged, and the ACL continues to be processed, from the next statement
30953 .vindex "&$acl_verify_message$&"
30954 When one of the &%warn%& conditions is an address verification that fails, the
30955 text of the verification failure message is in &$acl_verify_message$&. If you
30956 want this logged, you must set it up explicitly. For example:
30958 warn !verify = sender
30959 log_message = sender verify failed: $acl_verify_message
30963 At the end of each ACL there is an implicit unconditional &%deny%&.
30965 As you can see from the examples above, the conditions and modifiers are
30966 written one to a line, with the first one on the same line as the verb, and
30967 subsequent ones on following lines. If you have a very long condition, you can
30968 continue it onto several physical lines by the usual backslash continuation
30969 mechanism. It is conventional to align the conditions vertically.
30973 .section "ACL variables" "SECTaclvariables"
30974 .cindex "&ACL;" "variables"
30975 There are some special variables that can be set during ACL processing. They
30976 can be used to pass information between different ACLs, different invocations
30977 of the same ACL in the same SMTP connection, and between ACLs and the routers,
30978 transports, and filters that are used to deliver a message. The names of these
30979 variables must begin with &$acl_c$& or &$acl_m$&, followed either by a digit or
30980 an underscore, but the remainder of the name can be any sequence of
30981 alphanumeric characters and underscores that you choose. There is no limit on
30982 the number of ACL variables. The two sets act as follows:
30984 The values of those variables whose names begin with &$acl_c$& persist
30985 throughout an SMTP connection. They are never reset. Thus, a value that is set
30986 while receiving one message is still available when receiving the next message
30987 on the same SMTP connection.
30989 The values of those variables whose names begin with &$acl_m$& persist only
30990 while a message is being received. They are reset afterwards. They are also
30991 reset by MAIL, RSET, EHLO, HELO, and after starting up a TLS session.
30994 When a message is accepted, the current values of all the ACL variables are
30995 preserved with the message and are subsequently made available at delivery
30996 time. The ACL variables are set by a modifier called &%set%&. For example:
30998 accept hosts = whatever
30999 set acl_m4 = some value
31000 accept authenticated = *
31001 set acl_c_auth = yes
31003 &*Note*&: A leading dollar sign is not used when naming a variable that is to
31004 be set. If you want to set a variable without taking any action, you can use a
31005 &%warn%& verb without any other modifiers or conditions.
31007 .oindex &%strict_acl_vars%&
31008 What happens if a syntactically valid but undefined ACL variable is
31009 referenced depends on the setting of the &%strict_acl_vars%& option. If it is
31010 false (the default), an empty string is substituted; if it is true, an
31011 error is generated.
31013 Versions of Exim before 4.64 have a limited set of numbered variables, but
31014 their names are compatible, so there is no problem with upgrading.
31017 .section "Condition and modifier processing" "SECTcondmodproc"
31018 .cindex "&ACL;" "conditions; processing"
31019 .cindex "&ACL;" "modifiers; processing"
31020 An exclamation mark preceding a condition negates its result. For example:
31022 deny domains = *.dom.example
31023 !verify = recipient
31025 causes the ACL to return &"deny"& if the recipient domain ends in
31026 &'dom.example'& and the recipient address cannot be verified. Sometimes
31027 negation can be used on the right-hand side of a condition. For example, these
31028 two statements are equivalent:
31030 deny hosts = !192.168.3.4
31031 deny !hosts = 192.168.3.4
31033 However, for many conditions (&%verify%& being a good example), only left-hand
31034 side negation of the whole condition is possible.
31036 The arguments of conditions and modifiers are expanded. A forced failure
31037 of an expansion causes a condition to be ignored, that is, it behaves as if the
31038 condition is true. Consider these two statements:
31040 accept senders = ${lookup{$host_name}lsearch\
31041 {/some/file}{$value}fail}
31042 accept senders = ${lookup{$host_name}lsearch\
31043 {/some/file}{$value}{}}
31045 Each attempts to look up a list of acceptable senders. If the lookup succeeds,
31046 the returned list is searched, but if the lookup fails the behaviour is
31047 different in the two cases. The &%fail%& in the first statement causes the
31048 condition to be ignored, leaving no further conditions. The &%accept%& verb
31049 therefore succeeds. The second statement, however, generates an empty list when
31050 the lookup fails. No sender can match an empty list, so the condition fails,
31051 and therefore the &%accept%& also fails.
31053 ACL modifiers appear mixed in with conditions in ACL statements. Some of them
31054 specify actions that are taken as the conditions for a statement are checked;
31055 others specify text for messages that are used when access is denied or a
31056 warning is generated. The &%control%& modifier affects the way an incoming
31057 message is handled.
31059 The positioning of the modifiers in an ACL statement is important, because the
31060 processing of a verb ceases as soon as its outcome is known. Only those
31061 modifiers that have already been encountered will take effect. For example,
31062 consider this use of the &%message%& modifier:
31064 require message = Can't verify sender
31066 message = Can't verify recipient
31068 message = This message cannot be used
31070 If sender verification fails, Exim knows that the result of the statement is
31071 &"deny"&, so it goes no further. The first &%message%& modifier has been seen,
31072 so its text is used as the error message. If sender verification succeeds, but
31073 recipient verification fails, the second message is used. If recipient
31074 verification succeeds, the third message becomes &"current"&, but is never used
31075 because there are no more conditions to cause failure.
31077 For the &%deny%& verb, on the other hand, it is always the last &%message%&
31078 modifier that is used, because all the conditions must be true for rejection to
31079 happen. Specifying more than one &%message%& modifier does not make sense, and
31080 the message can even be specified after all the conditions. For example:
31083 !senders = *@my.domain.example
31084 message = Invalid sender from client host
31086 The &"deny"& result does not happen until the end of the statement is reached,
31087 by which time Exim has set up the message.
31091 .section "ACL modifiers" "SECTACLmodi"
31092 .cindex "&ACL;" "modifiers; list of"
31093 The ACL modifiers are as follows:
31096 .vitem &*add_header*&&~=&~<&'text'&>
31097 This modifier specifies one or more header lines that are to be added to an
31098 incoming message, assuming, of course, that the message is ultimately
31099 accepted. For details, see section &<<SECTaddheadacl>>&.
31101 .vitem &*continue*&&~=&~<&'text'&>
31102 .cindex "&%continue%& ACL modifier"
31103 .cindex "database" "updating in ACL"
31104 This modifier does nothing of itself, and processing of the ACL always
31105 continues with the next condition or modifier. The value of &%continue%& is in
31106 the side effects of expanding its argument. Typically this could be used to
31107 update a database. It is really just a syntactic tidiness, to avoid having to
31108 write rather ugly lines like this:
31110 &`condition = ${if eq{0}{`&<&'some expansion'&>&`}{true}{true}}`&
31112 Instead, all you need is
31114 &`continue = `&<&'some expansion'&>
31117 .vitem &*control*&&~=&~<&'text'&>
31118 .cindex "&%control%& ACL modifier"
31119 This modifier affects the subsequent processing of the SMTP connection or of an
31120 incoming message that is accepted. The effect of the first type of control
31121 lasts for the duration of the connection, whereas the effect of the second type
31122 lasts only until the current message has been received. The message-specific
31123 controls always apply to the whole message, not to individual recipients,
31124 even if the &%control%& modifier appears in a RCPT ACL.
31126 As there are now quite a few controls that can be applied, they are described
31127 separately in section &<<SECTcontrols>>&. The &%control%& modifier can be used
31128 in several different ways. For example:
31130 . ==== As this is a nested list, any displays it contains must be indented
31131 . ==== as otherwise they are too far to the left. That comment applies only
31132 . ==== when xmlto and fop are used; formatting with sdop gets it right either
31136 It can be at the end of an &%accept%& statement:
31138 accept ...some conditions
31141 In this case, the control is applied when this statement yields &"accept"&, in
31142 other words, when the conditions are all true.
31145 It can be in the middle of an &%accept%& statement:
31147 accept ...some conditions...
31149 ...some more conditions...
31151 If the first set of conditions are true, the control is applied, even if the
31152 statement does not accept because one of the second set of conditions is false.
31153 In this case, some subsequent statement must yield &"accept"& for the control
31157 It can be used with &%warn%& to apply the control, leaving the
31158 decision about accepting or denying to a subsequent verb. For
31161 warn ...some conditions...
31165 This example of &%warn%& does not contain &%message%&, &%log_message%&, or
31166 &%logwrite%&, so it does not add anything to the message and does not write a
31170 If you want to apply a control unconditionally, you can use it with a
31171 &%require%& verb. For example:
31173 require control = no_multiline_responses
31177 .vitem &*delay*&&~=&~<&'time'&>
31178 .cindex "&%delay%& ACL modifier"
31180 This modifier may appear in any ACL except notquit. It causes Exim to wait for
31181 the time interval before proceeding. However, when testing Exim using the
31182 &%-bh%& option, the delay is not actually imposed (an appropriate message is
31183 output instead). The time is given in the usual Exim notation, and the delay
31184 happens as soon as the modifier is processed. In an SMTP session, pending
31185 output is flushed before the delay is imposed.
31187 Like &%control%&, &%delay%& can be used with &%accept%& or &%deny%&, for
31190 deny ...some conditions...
31193 The delay happens if all the conditions are true, before the statement returns
31194 &"deny"&. Compare this with:
31197 ...some conditions...
31199 which waits for 30s before processing the conditions. The &%delay%& modifier
31200 can also be used with &%warn%& and together with &%control%&:
31202 warn ...some conditions...
31208 If &%delay%& is encountered when the SMTP PIPELINING extension is in use,
31209 responses to several commands are no longer buffered and sent in one packet (as
31210 they would normally be) because all output is flushed before imposing the
31211 delay. This optimization is disabled so that a number of small delays do not
31212 appear to the client as one large aggregated delay that might provoke an
31213 unwanted timeout. You can, however, disable output flushing for &%delay%& by
31214 using a &%control%& modifier to set &%no_delay_flush%&.
31218 .cindex "&%endpass%& ACL modifier"
31219 This modifier, which has no argument, is recognized only in &%accept%& and
31220 &%discard%& statements. It marks the boundary between the conditions whose
31221 failure causes control to pass to the next statement, and the conditions whose
31222 failure causes the ACL to return &"deny"&. This concept has proved to be
31223 confusing to some people, so the use of &%endpass%& is no longer recommended as
31224 &"best practice"&. See the description of &%accept%& above for more details.
31227 .vitem &*log_message*&&~=&~<&'text'&>
31228 .cindex "&%log_message%& ACL modifier"
31229 This modifier sets up a message that is used as part of the log message if the
31230 ACL denies access or a &%warn%& statement's conditions are true. For example:
31232 require log_message = wrong cipher suite $tls_in_cipher
31233 encrypted = DES-CBC3-SHA
31235 &%log_message%& is also used when recipients are discarded by &%discard%&. For
31238 &`discard `&<&'some conditions'&>
31239 &` log_message = Discarded $local_part@$domain because...`&
31241 When access is denied, &%log_message%& adds to any underlying error message
31242 that may exist because of a condition failure. For example, while verifying a
31243 recipient address, a &':fail:'& redirection might have already set up a
31246 The message may be defined before the conditions to which it applies, because
31247 the string expansion does not happen until Exim decides that access is to be
31248 denied. This means that any variables that are set by the condition are
31249 available for inclusion in the message. For example, the &$dnslist_$&<&'xxx'&>
31250 variables are set after a DNS black list lookup succeeds. If the expansion of
31251 &%log_message%& fails, or if the result is an empty string, the modifier is
31254 .vindex "&$acl_verify_message$&"
31255 If you want to use a &%warn%& statement to log the result of an address
31256 verification, you can use &$acl_verify_message$& to include the verification
31259 If &%log_message%& is used with a &%warn%& statement, &"Warning:"& is added to
31260 the start of the logged message. If the same warning log message is requested
31261 more than once while receiving a single email message, only one copy is
31262 actually logged. If you want to log multiple copies, use &%logwrite%& instead
31263 of &%log_message%&. In the absence of &%log_message%& and &%logwrite%&, nothing
31264 is logged for a successful &%warn%& statement.
31266 If &%log_message%& is not present and there is no underlying error message (for
31267 example, from the failure of address verification), but &%message%& is present,
31268 the &%message%& text is used for logging rejections. However, if any text for
31269 logging contains newlines, only the first line is logged. In the absence of
31270 both &%log_message%& and &%message%&, a default built-in message is used for
31271 logging rejections.
31274 .vitem "&*log_reject_target*&&~=&~<&'log name list'&>"
31275 .cindex "&%log_reject_target%& ACL modifier"
31276 .cindex "logging in ACL" "specifying which log"
31277 This modifier makes it possible to specify which logs are used for messages
31278 about ACL rejections. Its argument is a colon-separated list of words that can
31279 be &"main"&, &"reject"&, or &"panic"&. The default is &`main:reject`&. The list
31280 may be empty, in which case a rejection is not logged at all. For example, this
31281 ACL fragment writes no logging information when access is denied:
31283 &`deny `&<&'some conditions'&>
31284 &` log_reject_target =`&
31286 This modifier can be used in SMTP and non-SMTP ACLs. It applies to both
31287 permanent and temporary rejections. Its effect lasts for the rest of the
31291 .vitem &*logwrite*&&~=&~<&'text'&>
31292 .cindex "&%logwrite%& ACL modifier"
31293 .cindex "logging in ACL" "immediate"
31294 This modifier writes a message to a log file as soon as it is encountered when
31295 processing an ACL. (Compare &%log_message%&, which, except in the case of
31296 &%warn%& and &%discard%&, is used only if the ACL statement denies
31297 access.) The &%logwrite%& modifier can be used to log special incidents in
31300 &`accept `&<&'some special conditions'&>
31301 &` control = freeze`&
31302 &` logwrite = froze message because ...`&
31304 By default, the message is written to the main log. However, it may begin
31305 with a colon, followed by a comma-separated list of log names, and then
31306 another colon, to specify exactly which logs are to be written. For
31309 logwrite = :main,reject: text for main and reject logs
31310 logwrite = :panic: text for panic log only
31314 .vitem &*message*&&~=&~<&'text'&>
31315 .cindex "&%message%& ACL modifier"
31316 This modifier sets up a text string that is expanded and used as a response
31317 message when an ACL statement terminates the ACL with an &"accept"&, &"deny"&,
31318 or &"defer"& response. (In the case of the &%accept%& and &%discard%& verbs,
31319 there is some complication if &%endpass%& is involved; see the description of
31320 &%accept%& for details.)
31322 The expansion of the message happens at the time Exim decides that the ACL is
31323 to end, not at the time it processes &%message%&. If the expansion fails, or
31324 generates an empty string, the modifier is ignored. Here is an example where
31325 &%message%& must be specified first, because the ACL ends with a rejection if
31326 the &%hosts%& condition fails:
31328 require message = Host not recognized
31331 (Once a condition has failed, no further conditions or modifiers are
31334 .cindex "SMTP" "error codes"
31335 .oindex "&%smtp_banner%&
31336 For ACLs that are triggered by SMTP commands, the message is returned as part
31337 of the SMTP response. The use of &%message%& with &%accept%& (or &%discard%&)
31338 is meaningful only for SMTP, as no message is returned when a non-SMTP message
31339 is accepted. In the case of the connect ACL, accepting with a message modifier
31340 overrides the value of &%smtp_banner%&. For the EHLO/HELO ACL, a customized
31341 accept message may not contain more than one line (otherwise it will be
31342 truncated at the first newline and a panic logged), and it cannot affect the
31345 When SMTP is involved, the message may begin with an overriding response code,
31346 consisting of three digits optionally followed by an &"extended response code"&
31347 of the form &'n.n.n'&, each code being followed by a space. For example:
31349 deny message = 599 1.2.3 Host not welcome
31350 hosts = 192.168.34.0/24
31352 The first digit of the supplied response code must be the same as would be sent
31353 by default. A panic occurs if it is not. Exim uses a 550 code when it denies
31354 access, but for the predata ACL, note that the default success code is 354, not
31357 Notwithstanding the previous paragraph, for the QUIT ACL, unlike the others,
31358 the message modifier cannot override the 221 response code.
31360 The text in a &%message%& modifier is literal; any quotes are taken as
31361 literals, but because the string is expanded, backslash escapes are processed
31362 anyway. If the message contains newlines, this gives rise to a multi-line SMTP
31365 .vindex "&$acl_verify_message$&"
31366 While the text is being expanded, the &$acl_verify_message$& variable
31367 contains any message previously set.
31368 Afterwards, &$acl_verify_message$& is cleared.
31370 If &%message%& is used on a statement that verifies an address, the message
31371 specified overrides any message that is generated by the verification process.
31372 However, the original message is available in the variable
31373 &$acl_verify_message$&, so you can incorporate it into your message if you
31374 wish. In particular, if you want the text from &%:fail:%& items in &(redirect)&
31375 routers to be passed back as part of the SMTP response, you should either not
31376 use a &%message%& modifier, or make use of &$acl_verify_message$&.
31378 For compatibility with previous releases of Exim, a &%message%& modifier that
31379 is used with a &%warn%& verb behaves in a similar way to the &%add_header%&
31380 modifier, but this usage is now deprecated. However, &%message%& acts only when
31381 all the conditions are true, wherever it appears in an ACL command, whereas
31382 &%add_header%& acts as soon as it is encountered. If &%message%& is used with
31383 &%warn%& in an ACL that is not concerned with receiving a message, it has no
31387 .vitem &*queue*&&~=&~<&'text'&>
31388 .cindex "&%queue%& ACL modifier"
31389 .cindex "named queues" "selecting in ACL"
31390 This modifier specifies the use of a named queue for spool files
31392 It can only be used before the message is received (i.e. not in
31394 This could be used, for example, for known high-volume burst sources
31395 of traffic, or for quarantine of messages.
31396 Separate queue-runner processes will be needed for named queues.
31397 If the text after expansion is empty, the default queue is used.
31400 .vitem &*remove_header*&&~=&~<&'text'&>
31401 This modifier specifies one or more header names in a colon-separated list
31402 that are to be removed from an incoming message, assuming, of course, that
31403 the message is ultimately accepted. For details, see section &<<SECTremoveheadacl>>&.
31406 .vitem &*set*&&~<&'acl_name'&>&~=&~<&'value'&>
31407 .cindex "&%set%& ACL modifier"
31408 This modifier puts a value into one of the ACL variables (see section
31409 &<<SECTaclvariables>>&).
31412 .vitem &*udpsend*&&~=&~<&'parameters'&>
31413 .cindex "UDP communications"
31414 This modifier sends a UDP packet, for purposes such as statistics
31415 collection or behaviour monitoring. The parameters are expanded, and
31416 the result of the expansion must be a colon-separated list consisting
31417 of a destination server, port number, and the packet contents. The
31418 server can be specified as a host name or IPv4 or IPv6 address. The
31419 separator can be changed with the usual angle bracket syntax. For
31420 example, you might want to collect information on which hosts connect
31423 udpsend = <; 2001:dB8::dead:beef ; 1234 ;\
31424 $tod_zulu $sender_host_address
31431 .section "Use of the control modifier" "SECTcontrols"
31432 .cindex "&%control%& ACL modifier"
31433 The &%control%& modifier supports the following settings:
31436 .vitem &*control&~=&~allow_auth_unadvertised*&
31437 This modifier allows a client host to use the SMTP AUTH command even when it
31438 has not been advertised in response to EHLO. Furthermore, because there are
31439 apparently some really broken clients that do this, Exim will accept AUTH after
31440 HELO (rather than EHLO) when this control is set. It should be used only if you
31441 really need it, and you should limit its use to those broken clients that do
31442 not work without it. For example:
31444 warn hosts = 192.168.34.25
31445 control = allow_auth_unadvertised
31447 Normally, when an Exim server receives an AUTH command, it checks the name of
31448 the authentication mechanism that is given in the command to ensure that it
31449 matches an advertised mechanism. When this control is set, the check that a
31450 mechanism has been advertised is bypassed. Any configured mechanism can be used
31451 by the client. This control is permitted only in the connection and HELO ACLs.
31454 .vitem &*control&~=&~caseful_local_part*& &&&
31455 &*control&~=&~caselower_local_part*&
31456 .cindex "&ACL;" "case of local part in"
31457 .cindex "case of local parts"
31458 .vindex "&$local_part$&"
31459 These two controls are permitted only in the ACL specified by &%acl_smtp_rcpt%&
31460 (that is, during RCPT processing). By default, the contents of &$local_part$&
31461 are lower cased before ACL processing. If &"caseful_local_part"& is specified,
31462 any uppercase letters in the original local part are restored in &$local_part$&
31463 for the rest of the ACL, or until a control that sets &"caselower_local_part"&
31466 These controls affect only the current recipient. Moreover, they apply only to
31467 local part handling that takes place directly in the ACL (for example, as a key
31468 in lookups). If a test to verify the recipient is obeyed, the case-related
31469 handling of the local part during the verification is controlled by the router
31470 configuration (see the &%caseful_local_part%& generic router option).
31472 This facility could be used, for example, to add a spam score to local parts
31473 containing upper case letters. For example, using &$acl_m4$& to accumulate the
31476 warn control = caseful_local_part
31477 set acl_m4 = ${eval:\
31479 ${if match{$local_part}{[A-Z]}{1}{0}}\
31481 control = caselower_local_part
31483 Notice that we put back the lower cased version afterwards, assuming that
31484 is what is wanted for subsequent tests.
31487 .vitem &*control&~=&~cutthrough_delivery/*&<&'options'&>
31488 .cindex "&ACL;" "cutthrough routing"
31489 .cindex "cutthrough" "requesting"
31490 This option requests delivery be attempted while the item is being received.
31492 The option is usable in the RCPT ACL.
31493 If enabled for a message received via smtp and routed to an smtp transport,
31494 and only one transport, interface, destination host and port combination
31495 is used for all recipients of the message,
31496 then the delivery connection is made while the receiving connection is open
31497 and data is copied from one to the other.
31499 An attempt to set this option for any recipient but the first
31500 for a mail will be quietly ignored.
31501 If a recipient-verify callout
31503 connection is subsequently
31504 requested in the same ACL it is held open and used for
31505 any subsequent recipients and the data,
31506 otherwise one is made after the initial RCPT ACL completes.
31508 Note that routers are used in verify mode,
31509 and cannot depend on content of received headers.
31510 Note also that headers cannot be
31511 modified by any of the post-data ACLs (DATA, MIME and DKIM).
31512 Headers may be modified by routers (subject to the above) and transports.
31513 The &'Received-By:'& header is generated as soon as the body reception starts,
31514 rather than the traditional time after the full message is received;
31515 this will affect the timestamp.
31517 All the usual ACLs are called; if one results in the message being
31518 rejected, all effort spent in delivery (including the costs on
31519 the ultimate destination) will be wasted.
31520 Note that in the case of data-time ACLs this includes the entire
31523 Cutthrough delivery is not supported via transport-filters or when DKIM signing
31524 of outgoing messages is done, because it sends data to the ultimate destination
31525 before the entire message has been received from the source.
31526 It is not supported for messages received with the SMTP PRDR
31530 Should the ultimate destination system positively accept or reject the mail,
31531 a corresponding indication is given to the source system and nothing is queued.
31532 If the item is successfully delivered in cutthrough mode
31533 the delivery log lines are tagged with ">>" rather than "=>" and appear
31534 before the acceptance "<=" line.
31536 If there is a temporary error the item is queued for later delivery in the
31538 This behaviour can be adjusted by appending the option &*defer=*&<&'value'&>
31539 to the control; the default value is &"spool"& and the alternate value
31540 &"pass"& copies an SMTP defer response from the target back to the initiator
31541 and does not queue the message.
31542 Note that this is independent of any recipient verify conditions in the ACL.
31544 Delivery in this mode avoids the generation of a bounce mail to a
31546 sender when the destination system is doing content-scan based rejection.
31549 .vitem &*control&~=&~debug/*&<&'options'&>
31550 .cindex "&ACL;" "enabling debug logging"
31551 .cindex "debugging" "enabling from an ACL"
31552 This control turns on debug logging, almost as though Exim had been invoked
31553 with &`-d`&, with the output going to a new logfile in the usual logs directory,
31554 by default called &'debuglog'&.
31556 Logging set up by the control will be maintained across spool residency.
31558 Options are a slash-separated list.
31559 If an option takes an argument, the option name and argument are separated by
31560 an equals character.
31561 Several options are supported:
31563 tag=<&'suffix'&> The filename can be adjusted with thise option.
31564 The argument, which may access any variables already defined,
31565 is appended to the default name.
31567 opts=<&'debug&~options'&> The argument specififes what is to be logged,
31568 using the same values as the &`-d`& command-line option.
31570 stop Logging started with this control may be
31571 stopped by using this option.
31573 kill Logging started with this control may be
31574 stopped by using this option.
31575 Additionally the debug file will be removed,
31576 providing one means for speculative debug tracing.
31578 pretrigger=<&'size'&> This option specifies a memory buffuer to be used
31579 for pre-trigger debug capture.
31580 Debug lines are recorded in the buffer until
31581 and if) a trigger occurs; at which time they are
31582 dumped to the debug file. Newer lines displace the
31583 oldest if the buffer is full. After a trigger,
31584 immediate writes to file are done as normal.
31586 trigger=<&'reason'&> This option selects cause for the pretrigger buffer
31587 see above) to be copied to file. A reason of $*now*
31588 take effect immediately; one of &*paniclog*& triggers
31589 on a write to the panic log.
31592 Some examples (which depend on variables that don't exist in all
31596 control = debug/tag=.$sender_host_address
31597 control = debug/opts=+expand+acl
31598 control = debug/tag=.$message_exim_id/opts=+expand
31599 control = debug/kill
31600 control = debug/opts=+all/pretrigger=1024/trigger=paniclog
31601 control = debug/trigger=now
31605 .vitem &*control&~=&~dkim_disable_verify*&
31606 .cindex "disable DKIM verify"
31607 .cindex "DKIM" "disable verify"
31608 This control turns off DKIM verification processing entirely. For details on
31609 the operation and configuration of DKIM, see section &<<SECDKIM>>&.
31612 .vitem &*control&~=&~dmarc_disable_verify*&
31613 .cindex "disable DMARC verify"
31614 .cindex "DMARC" "disable verify"
31615 This control turns off DMARC verification processing entirely. For details on
31616 the operation and configuration of DMARC, see section &<<SECDMARC>>&.
31619 .vitem &*control&~=&~dscp/*&<&'value'&>
31620 .cindex "&ACL;" "setting DSCP value"
31621 .cindex "DSCP" "inbound"
31622 This option causes the DSCP value associated with the socket for the inbound
31623 connection to be adjusted to a given value, given as one of a number of fixed
31624 strings or to numeric value.
31625 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
31626 Common values include &`throughput`&, &`mincost`&, and on newer systems
31627 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
31629 The outbound packets from Exim will be marked with this value in the header
31630 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
31631 that these values will have any effect, not be stripped by networking
31632 equipment, or do much of anything without cooperation with your Network
31633 Engineer and those of all network operators between the source and destination.
31636 .vitem &*control&~=&~enforce_sync*& &&&
31637 &*control&~=&~no_enforce_sync*&
31638 .cindex "SMTP" "synchronization checking"
31639 .cindex "synchronization checking in SMTP"
31640 These controls make it possible to be selective about when SMTP synchronization
31641 is enforced. The global option &%smtp_enforce_sync%& specifies the initial
31642 state of the switch (it is true by default). See the description of this option
31643 in chapter &<<CHAPmainconfig>>& for details of SMTP synchronization checking.
31645 The effect of these two controls lasts for the remainder of the SMTP
31646 connection. They can appear in any ACL except the one for the non-SMTP
31647 messages. The most straightforward place to put them is in the ACL defined by
31648 &%acl_smtp_connect%&, which is run at the start of an incoming SMTP connection,
31649 before the first synchronization check. The expected use is to turn off the
31650 synchronization checks for badly-behaved hosts that you nevertheless need to
31654 .vitem &*control&~=&~fakedefer/*&<&'message'&>
31655 .cindex "fake defer"
31656 .cindex "defer, fake"
31657 This control works in exactly the same way as &%fakereject%& (described below)
31658 except that it causes an SMTP 450 response after the message data instead of a
31659 550 response. You must take care when using &%fakedefer%& because it causes the
31660 messages to be duplicated when the sender retries. Therefore, you should not
31661 use &%fakedefer%& if the message is to be delivered normally.
31663 .vitem &*control&~=&~fakereject/*&<&'message'&>
31664 .cindex "fake rejection"
31665 .cindex "rejection, fake"
31666 This control is permitted only for the MAIL, RCPT, and DATA ACLs, in other
31667 words, only when an SMTP message is being received. If Exim accepts the
31668 message, instead the final 250 response, a 550 rejection message is sent.
31669 However, Exim proceeds to deliver the message as normal. The control applies
31670 only to the current message, not to any subsequent ones that may be received in
31671 the same SMTP connection.
31673 The text for the 550 response is taken from the &%control%& modifier. If no
31674 message is supplied, the following is used:
31676 550-Your message has been rejected but is being
31677 550-kept for evaluation.
31678 550-If it was a legitimate message, it may still be
31679 550 delivered to the target recipient(s).
31681 This facility should be used with extreme caution.
31683 .vitem &*control&~=&~freeze*&
31684 .cindex "frozen messages" "forcing in ACL"
31685 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
31686 other words, only when a message is being received. If the message is accepted,
31687 it is placed on Exim's queue and frozen. The control applies only to the
31688 current message, not to any subsequent ones that may be received in the same
31691 This modifier can optionally be followed by &`/no_tell`&. If the global option
31692 &%freeze_tell%& is set, it is ignored for the current message (that is, nobody
31693 is told about the freezing), provided all the &*control=freeze*& modifiers that
31694 are obeyed for the current message have the &`/no_tell`& option.
31696 .vitem &*control&~=&~no_delay_flush*&
31697 .cindex "SMTP" "output flushing, disabling for delay"
31698 Exim normally flushes SMTP output before implementing a delay in an ACL, to
31699 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
31700 use. This control, as long as it is encountered before the &%delay%& modifier,
31701 disables such output flushing.
31703 .vitem &*control&~=&~no_callout_flush*&
31704 .cindex "SMTP" "output flushing, disabling for callout"
31705 Exim normally flushes SMTP output before performing a callout in an ACL, to
31706 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
31707 use. This control, as long as it is encountered before the &%verify%& condition
31708 that causes the callout, disables such output flushing.
31710 .vitem &*control&~=&~no_mbox_unspool*&
31711 This control is available when Exim is compiled with the content scanning
31712 extension. Content scanning may require a copy of the current message, or parts
31713 of it, to be written in &"mbox format"& to a spool file, for passing to a virus
31714 or spam scanner. Normally, such copies are deleted when they are no longer
31715 needed. If this control is set, the copies are not deleted. The control applies
31716 only to the current message, not to any subsequent ones that may be received in
31717 the same SMTP connection. It is provided for debugging purposes and is unlikely
31718 to be useful in production.
31720 .vitem &*control&~=&~no_multiline_responses*&
31721 .cindex "multiline responses, suppressing"
31722 This control is permitted for any ACL except the one for non-SMTP messages.
31723 It seems that there are broken clients in use that cannot handle multiline
31724 SMTP responses, despite the fact that RFC 821 defined them over 20 years ago.
31726 If this control is set, multiline SMTP responses from ACL rejections are
31727 suppressed. One way of doing this would have been to put out these responses as
31728 one long line. However, RFC 2821 specifies a maximum of 512 bytes per response
31729 (&"use multiline responses for more"& it says &-- ha!), and some of the
31730 responses might get close to that. So this facility, which is after all only a
31731 sop to broken clients, is implemented by doing two very easy things:
31734 Extra information that is normally output as part of a rejection caused by
31735 sender verification failure is omitted. Only the final line (typically &"sender
31736 verification failed"&) is sent.
31738 If a &%message%& modifier supplies a multiline response, only the first
31742 The setting of the switch can, of course, be made conditional on the
31743 calling host. Its effect lasts until the end of the SMTP connection.
31745 .vitem &*control&~=&~no_pipelining*&
31746 .cindex "PIPELINING" "suppressing advertising"
31747 .cindex "ESMTP extensions" PIPELINING
31748 This control turns off the advertising of the PIPELINING extension to SMTP in
31749 the current session. To be useful, it must be obeyed before Exim sends its
31750 response to an EHLO command. Therefore, it should normally appear in an ACL
31751 controlled by &%acl_smtp_connect%& or &%acl_smtp_helo%&. See also
31752 &%pipelining_advertise_hosts%&.
31754 .vitem &*control&~=&~queue/*&<&'options'&>* &&&
31755 &*control&~=&~queue_only*&
31756 .oindex "&%queue%&"
31757 .oindex "&%queue_only%&"
31758 .cindex "queueing incoming messages"
31759 .cindex queueing "forcing in ACL"
31760 .cindex "first pass routing"
31761 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
31762 other words, only when a message is being received. If the message is accepted,
31763 it is placed on Exim's queue and left there for delivery by a subsequent queue
31765 If used with no options set,
31766 no immediate delivery process is started. In other words, it has the
31767 effect as the &%queue_only%& global option or &'-odq'& command-line option.
31769 If the &'first_pass_route'& option is given then
31770 the behaviour is like the command-line &'-oqds'& option;
31771 a delivery process is started which stops short of making
31772 any SMTP delivery. The benefit is that the hints database will be updated for
31773 the message being waiting for a specific host, and a later queue run will be
31774 able to send all such messages on a single connection.
31776 The control only applies to the current message, not to any subsequent ones that
31777 may be received in the same SMTP connection.
31779 .vitem &*control&~=&~submission/*&<&'options'&>
31780 .cindex "message" "submission"
31781 .cindex "submission mode"
31782 This control is permitted only for the MAIL, RCPT, and start of data ACLs (the
31783 latter is the one defined by &%acl_smtp_predata%&). Setting it tells Exim that
31784 the current message is a submission from a local MUA. In this case, Exim
31785 operates in &"submission mode"&, and applies certain fixups to the message if
31786 necessary. For example, it adds a &'Date:'& header line if one is not present.
31787 This control is not permitted in the &%acl_smtp_data%& ACL, because that is too
31788 late (the message has already been created).
31790 Chapter &<<CHAPmsgproc>>& describes the processing that Exim applies to
31791 messages. Section &<<SECTsubmodnon>>& covers the processing that happens in
31792 submission mode; the available options for this control are described there.
31793 The control applies only to the current message, not to any subsequent ones
31794 that may be received in the same SMTP connection.
31796 .vitem &*control&~=&~suppress_local_fixups*&
31797 .cindex "submission fixups, suppressing"
31798 This control applies to locally submitted (non TCP/IP) messages, and is the
31799 complement of &`control = submission`&. It disables the fixups that are
31800 normally applied to locally-submitted messages. Specifically:
31803 Any &'Sender:'& header line is left alone (in this respect, it is a
31804 dynamic version of &%local_sender_retain%&).
31806 No &'Message-ID:'&, &'From:'&, or &'Date:'& header lines are added.
31808 There is no check that &'From:'& corresponds to the actual sender.
31811 This control may be useful when a remotely-originated message is accepted,
31812 passed to some scanning program, and then re-submitted for delivery. It can be
31813 used only in the &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
31814 and &%acl_not_smtp_start%& ACLs, because it has to be set before the message's
31817 &*Note:*& This control applies only to the current message, not to any others
31818 that are being submitted at the same time using &%-bs%& or &%-bS%&.
31820 .vitem &*control&~=&~utf8_downconvert*&
31821 This control enables conversion of UTF-8 in message envelope addresses
31823 For details see section &<<SECTi18nMTA>>&.
31827 .section "Summary of message fixup control" "SECTsummesfix"
31828 All four possibilities for message fixups can be specified:
31831 Locally submitted, fixups applied: the default.
31833 Locally submitted, no fixups applied: use
31834 &`control = suppress_local_fixups`&.
31836 Remotely submitted, no fixups applied: the default.
31838 Remotely submitted, fixups applied: use &`control = submission`&.
31843 .section "Adding header lines in ACLs" "SECTaddheadacl"
31844 .cindex "header lines" "adding in an ACL"
31845 .cindex "header lines" "position of added lines"
31846 .cindex "&%add_header%& ACL modifier"
31847 The &%add_header%& modifier can be used to add one or more extra header lines
31848 to an incoming message, as in this example:
31850 warn dnslists = sbl.spamhaus.org : \
31851 dialup.mail-abuse.org
31852 add_header = X-blacklisted-at: $dnslist_domain
31854 The &%add_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
31855 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
31856 receiving a message). The message must ultimately be accepted for
31857 &%add_header%& to have any significant effect. You can use &%add_header%& with
31858 any ACL verb, including &%deny%& (though this is potentially useful only in a
31861 Headers will not be added to the message if the modifier is used in
31862 DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing.
31864 Leading and trailing newlines are removed from
31865 the data for the &%add_header%& modifier; if it then
31866 contains one or more newlines that
31867 are not followed by a space or a tab, it is assumed to contain multiple header
31868 lines. Each one is checked for valid syntax; &`X-ACL-Warn:`& is added to the
31869 front of any line that is not a valid header line.
31871 Added header lines are accumulated during the MAIL, RCPT, and predata ACLs.
31872 They are added to the message before processing the DATA and MIME ACLs.
31873 However, if an identical header line is requested more than once, only one copy
31874 is actually added to the message. Further header lines may be accumulated
31875 during the DATA and MIME ACLs, after which they are added to the message, again
31876 with duplicates suppressed. Thus, it is possible to add two identical header
31877 lines to an SMTP message, but only if one is added before DATA and one after.
31878 In the case of non-SMTP messages, new headers are accumulated during the
31879 non-SMTP ACLs, and are added to the message after all the ACLs have run. If a
31880 message is rejected after DATA or by the non-SMTP ACL, all added header lines
31881 are included in the entry that is written to the reject log.
31883 .cindex "header lines" "added; visibility of"
31884 Header lines are not visible in string expansions
31886 until they are added to the
31887 message. It follows that header lines defined in the MAIL, RCPT, and predata
31888 ACLs are not visible until the DATA ACL and MIME ACLs are run. Similarly,
31889 header lines that are added by the DATA or MIME ACLs are not visible in those
31890 ACLs. Because of this restriction, you cannot use header lines as a way of
31891 passing data between (for example) the MAIL and RCPT ACLs. If you want to do
31892 this, you can use ACL variables, as described in section
31893 &<<SECTaclvariables>>&.
31895 The list of headers yet to be added is given by the &%$headers_added%& variable.
31897 The &%add_header%& modifier acts immediately as it is encountered during the
31898 processing of an ACL. Notice the difference between these two cases:
31900 &`accept add_header = ADDED: some text`&
31901 &` `&<&'some condition'&>
31903 &`accept `&<&'some condition'&>
31904 &` add_header = ADDED: some text`&
31906 In the first case, the header line is always added, whether or not the
31907 condition is true. In the second case, the header line is added only if the
31908 condition is true. Multiple occurrences of &%add_header%& may occur in the same
31909 ACL statement. All those that are encountered before a condition fails are
31912 .cindex "&%warn%& ACL verb"
31913 For compatibility with previous versions of Exim, a &%message%& modifier for a
31914 &%warn%& verb acts in the same way as &%add_header%&, except that it takes
31915 effect only if all the conditions are true, even if it appears before some of
31916 them. Furthermore, only the last occurrence of &%message%& is honoured. This
31917 usage of &%message%& is now deprecated. If both &%add_header%& and &%message%&
31918 are present on a &%warn%& verb, both are processed according to their
31921 By default, new header lines are added to a message at the end of the existing
31922 header lines. However, you can specify that any particular header line should
31923 be added right at the start (before all the &'Received:'& lines), immediately
31924 after the first block of &'Received:'& lines, or immediately before any line
31925 that is not a &'Received:'& or &'Resent-something:'& header.
31927 This is done by specifying &":at_start:"&, &":after_received:"&, or
31928 &":at_start_rfc:"& (or, for completeness, &":at_end:"&) before the text of the
31929 header line, respectively. (Header text cannot start with a colon, as there has
31930 to be a header name first.) For example:
31932 warn add_header = \
31933 :after_received:X-My-Header: something or other...
31935 If more than one header line is supplied in a single &%add_header%& modifier,
31936 each one is treated independently and can therefore be placed differently. If
31937 you add more than one line at the start, or after the Received: block, they end
31938 up in reverse order.
31940 &*Warning*&: This facility currently applies only to header lines that are
31941 added in an ACL. It does NOT work for header lines that are added in a
31942 system filter or in a router or transport.
31946 .section "Removing header lines in ACLs" "SECTremoveheadacl"
31947 .cindex "header lines" "removing in an ACL"
31948 .cindex "header lines" "position of removed lines"
31949 .cindex "&%remove_header%& ACL modifier"
31950 The &%remove_header%& modifier can be used to remove one or more header lines
31951 from an incoming message, as in this example:
31953 warn message = Remove internal headers
31954 remove_header = x-route-mail1 : x-route-mail2
31956 The &%remove_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
31957 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
31958 receiving a message). The message must ultimately be accepted for
31959 &%remove_header%& to have any significant effect. You can use &%remove_header%&
31960 with any ACL verb, including &%deny%&, though this is really not useful for
31961 any verb that doesn't result in a delivered message.
31963 Headers will not be removed from the message if the modifier is used in
31964 DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing.
31966 More than one header can be removed at the same time by using a colon separated
31967 list of header names. The header matching is case insensitive. Wildcards are
31968 not permitted, nor is list expansion performed, so you cannot use hostlists to
31969 create a list of headers, however both connection and message variable expansion
31970 are performed (&%$acl_c_*%& and &%$acl_m_*%&), illustrated in this example:
31972 warn hosts = +internal_hosts
31973 set acl_c_ihdrs = x-route-mail1 : x-route-mail2
31974 warn message = Remove internal headers
31975 remove_header = $acl_c_ihdrs
31977 Header names for removal are accumulated during the MAIL, RCPT, and predata ACLs.
31978 Matching header lines are removed from the message before processing the DATA and MIME ACLs.
31979 If multiple header lines match, all are removed.
31980 There is no harm in attempting to remove the same header twice nor in removing
31981 a non-existent header. Further header lines to be removed may be accumulated
31982 during the DATA and MIME ACLs, after which they are removed from the message,
31983 if present. In the case of non-SMTP messages, headers to be removed are
31984 accumulated during the non-SMTP ACLs, and are removed from the message after
31985 all the ACLs have run. If a message is rejected after DATA or by the non-SMTP
31986 ACL, there really is no effect because there is no logging of what headers
31987 would have been removed.
31989 .cindex "header lines" "removed; visibility of"
31990 Header lines are not visible in string expansions until the DATA phase when it
31991 is received. Any header lines removed in the MAIL, RCPT, and predata ACLs are
31992 not visible in the DATA ACL and MIME ACLs. Similarly, header lines that are
31993 removed by the DATA or MIME ACLs are still visible in those ACLs. Because of
31994 this restriction, you cannot use header lines as a way of controlling data
31995 passed between (for example) the MAIL and RCPT ACLs. If you want to do this,
31996 you should instead use ACL variables, as described in section
31997 &<<SECTaclvariables>>&.
31999 The &%remove_header%& modifier acts immediately as it is encountered during the
32000 processing of an ACL. Notice the difference between these two cases:
32002 &`accept remove_header = X-Internal`&
32003 &` `&<&'some condition'&>
32005 &`accept `&<&'some condition'&>
32006 &` remove_header = X-Internal`&
32008 In the first case, the header line is always removed, whether or not the
32009 condition is true. In the second case, the header line is removed only if the
32010 condition is true. Multiple occurrences of &%remove_header%& may occur in the
32011 same ACL statement. All those that are encountered before a condition fails
32014 &*Warning*&: This facility currently applies only to header lines that are
32015 present during ACL processing. It does NOT remove header lines that are added
32016 in a system filter or in a router or transport.
32021 .section "ACL conditions" "SECTaclconditions"
32022 .cindex "&ACL;" "conditions; list of"
32023 Some of the conditions listed in this section are available only when Exim is
32024 compiled with the content-scanning extension. They are included here briefly
32025 for completeness. More detailed descriptions can be found in the discussion on
32026 content scanning in chapter &<<CHAPexiscan>>&.
32028 Not all conditions are relevant in all circumstances. For example, testing
32029 senders and recipients does not make sense in an ACL that is being run as the
32030 result of the arrival of an ETRN command, and checks on message headers can be
32031 done only in the ACLs specified by &%acl_smtp_data%& and &%acl_not_smtp%&. You
32032 can use the same condition (with different parameters) more than once in the
32033 same ACL statement. This provides a way of specifying an &"and"& conjunction.
32034 The conditions are as follows:
32038 .vitem &*acl&~=&~*&<&'name&~of&~acl&~or&~ACL&~string&~or&~file&~name&~'&>
32039 .cindex "&ACL;" "nested"
32040 .cindex "&ACL;" "indirect"
32041 .cindex "&ACL;" "arguments"
32042 .cindex "&%acl%& ACL condition"
32043 The possible values of the argument are the same as for the
32044 &%acl_smtp_%&&'xxx'& options. The named or inline ACL is run. If it returns
32045 &"accept"& the condition is true; if it returns &"deny"& the condition is
32046 false. If it returns &"defer"&, the current ACL returns &"defer"& unless the
32047 condition is on a &%warn%& verb. In that case, a &"defer"& return makes the
32048 condition false. This means that further processing of the &%warn%& verb
32049 ceases, but processing of the ACL continues.
32051 If the argument is a named ACL, up to nine space-separated optional values
32052 can be appended; they appear within the called ACL in $acl_arg1 to $acl_arg9,
32053 and $acl_narg is set to the count of values.
32054 Previous values of these variables are restored after the call returns.
32055 The name and values are expanded separately.
32056 Note that spaces in complex expansions which are used as arguments
32057 will act as argument separators.
32059 If the nested &%acl%& returns &"drop"& and the outer condition denies access,
32060 the connection is dropped. If it returns &"discard"&, the verb must be
32061 &%accept%& or &%discard%&, and the action is taken immediately &-- no further
32062 conditions are tested.
32064 ACLs may be nested up to 20 deep; the limit exists purely to catch runaway
32065 loops. This condition allows you to use different ACLs in different
32066 circumstances. For example, different ACLs can be used to handle RCPT commands
32067 for different local users or different local domains.
32069 .vitem &*authenticated&~=&~*&<&'string&~list'&>
32070 .cindex "&%authenticated%& ACL condition"
32071 .cindex "authentication" "ACL checking"
32072 .cindex "&ACL;" "testing for authentication"
32073 If the SMTP connection is not authenticated, the condition is false. Otherwise,
32074 the name of the authenticator is tested against the list. To test for
32075 authentication by any authenticator, you can set
32080 .vitem &*condition&~=&~*&<&'string'&>
32081 .cindex "&%condition%& ACL condition"
32082 .cindex "customizing" "ACL condition"
32083 .cindex "&ACL;" "customized test"
32084 .cindex "&ACL;" "testing, customized"
32085 This feature allows you to make up custom conditions. If the result of
32086 expanding the string is an empty string, the number zero, or one of the strings
32087 &"no"& or &"false"&, the condition is false. If the result is any non-zero
32088 number, or one of the strings &"yes"& or &"true"&, the condition is true. For
32089 any other value, some error is assumed to have occurred, and the ACL returns
32090 &"defer"&. However, if the expansion is forced to fail, the condition is
32091 ignored. The effect is to treat it as true, whether it is positive or
32094 .vitem &*decode&~=&~*&<&'location'&>
32095 .cindex "&%decode%& ACL condition"
32096 This condition is available only when Exim is compiled with the
32097 content-scanning extension, and it is allowed only in the ACL defined by
32098 &%acl_smtp_mime%&. It causes the current MIME part to be decoded into a file.
32099 If all goes well, the condition is true. It is false only if there are
32100 problems such as a syntax error or a memory shortage. For more details, see
32101 chapter &<<CHAPexiscan>>&.
32103 .vitem &*dnslists&~=&~*&<&'list&~of&~domain&~names&~and&~other&~data'&>
32104 .cindex "&%dnslists%& ACL condition"
32105 .cindex "DNS list" "in ACL"
32106 .cindex "black list (DNS)"
32107 .cindex "&ACL;" "testing a DNS list"
32108 This condition checks for entries in DNS black lists. These are also known as
32109 &"RBL lists"&, after the original Realtime Blackhole List, but note that the
32110 use of the lists at &'mail-abuse.org'& now carries a charge. There are too many
32111 different variants of this condition to describe briefly here. See sections
32112 &<<SECTmorednslists>>&&--&<<SECTmorednslistslast>>& for details.
32114 .vitem &*domains&~=&~*&<&'domain&~list'&>
32115 .cindex "&%domains%& ACL condition"
32116 .cindex "domain" "ACL checking"
32117 .cindex "&ACL;" "testing a recipient domain"
32118 .vindex "&$domain_data$&"
32119 This condition is relevant only in a RCPT ACL. It checks that the domain
32120 of the recipient address is in the domain list. If percent-hack processing is
32121 enabled, it is done before this test is done. If the check succeeds with a
32122 lookup, the result of the lookup is placed in &$domain_data$& until the next
32125 &*Note carefully*& (because many people seem to fall foul of this): you cannot
32126 use &%domains%& in a DATA ACL.
32129 .vitem &*encrypted&~=&~*&<&'string&~list'&>
32130 .cindex "&%encrypted%& ACL condition"
32131 .cindex "encryption" "checking in an ACL"
32132 .cindex "&ACL;" "testing for encryption"
32133 If the SMTP connection is not encrypted, the condition is false. Otherwise, the
32134 name of the cipher suite in use is tested against the list. To test for
32135 encryption without testing for any specific cipher suite(s), set
32141 .vitem &*hosts&~=&~*&<&'host&~list'&>
32142 .cindex "&%hosts%& ACL condition"
32143 .cindex "host" "ACL checking"
32144 .cindex "&ACL;" "testing the client host"
32145 This condition tests that the calling host matches the host list. If you have
32146 name lookups or wildcarded host names and IP addresses in the same host list,
32147 you should normally put the IP addresses first. For example, you could have:
32149 accept hosts = 10.9.8.7 : dbm;/etc/friendly/hosts
32151 The lookup in this example uses the host name for its key. This is implied by
32152 the lookup type &"dbm"&. (For a host address lookup you would use &"net-dbm"&
32153 and it wouldn't matter which way round you had these two items.)
32155 The reason for the problem with host names lies in the left-to-right way that
32156 Exim processes lists. It can test IP addresses without doing any DNS lookups,
32157 but when it reaches an item that requires a host name, it fails if it cannot
32158 find a host name to compare with the pattern. If the above list is given in the
32159 opposite order, the &%accept%& statement fails for a host whose name cannot be
32160 found, even if its IP address is 10.9.8.7.
32162 If you really do want to do the name check first, and still recognize the IP
32163 address even if the name lookup fails, you can rewrite the ACL like this:
32165 accept hosts = dbm;/etc/friendly/hosts
32166 accept hosts = 10.9.8.7
32168 The default action on failing to find the host name is to assume that the host
32169 is not in the list, so the first &%accept%& statement fails. The second
32170 statement can then check the IP address.
32172 .vindex "&$host_data$&"
32173 If a &%hosts%& condition is satisfied by means of a lookup, the result
32174 of the lookup is made available in the &$host_data$& variable. This
32175 allows you, for example, to set up a statement like this:
32177 deny hosts = net-lsearch;/some/file
32178 message = $host_data
32180 which gives a custom error message for each denied host.
32182 .vitem &*local_parts&~=&~*&<&'local&~part&~list'&>
32183 .cindex "&%local_parts%& ACL condition"
32184 .cindex "local part" "ACL checking"
32185 .cindex "&ACL;" "testing a local part"
32186 .vindex "&$local_part_data$&"
32187 This condition is relevant only in a RCPT ACL. It checks that the local
32188 part of the recipient address is in the list. If percent-hack processing is
32189 enabled, it is done before this test. If the check succeeds with a lookup, the
32190 result of the lookup is placed in &$local_part_data$&, which remains set until
32191 the next &%local_parts%& test.
32193 .vitem &*malware&~=&~*&<&'option'&>
32194 .cindex "&%malware%& ACL condition"
32195 .cindex "&ACL;" "virus scanning"
32196 .cindex "&ACL;" "scanning for viruses"
32197 This condition is available only when Exim is compiled with the
32198 content-scanning extension
32199 and only after a DATA command.
32200 It causes the incoming message to be scanned for
32201 viruses. For details, see chapter &<<CHAPexiscan>>&.
32203 .vitem &*mime_regex&~=&~*&<&'list&~of&~regular&~expressions'&>
32204 .cindex "&%mime_regex%& ACL condition"
32205 .cindex "&ACL;" "testing by regex matching"
32206 This condition is available only when Exim is compiled with the
32207 content-scanning extension, and it is allowed only in the ACL defined by
32208 &%acl_smtp_mime%&. It causes the current MIME part to be scanned for a match
32209 with any of the regular expressions. For details, see chapter
32212 .vitem &*ratelimit&~=&~*&<&'parameters'&>
32213 .cindex "rate limiting"
32214 This condition can be used to limit the rate at which a user or host submits
32215 messages. Details are given in section &<<SECTratelimiting>>&.
32217 .vitem &*recipients&~=&~*&<&'address&~list'&>
32218 .cindex "&%recipients%& ACL condition"
32219 .cindex "recipient" "ACL checking"
32220 .cindex "&ACL;" "testing a recipient"
32221 This condition is relevant only in a RCPT ACL. It checks the entire
32222 recipient address against a list of recipients.
32224 .vitem &*regex&~=&~*&<&'list&~of&~regular&~expressions'&>
32225 .cindex "&%regex%& ACL condition"
32226 .cindex "&ACL;" "testing by regex matching"
32227 This condition is available only when Exim is compiled with the
32228 content-scanning extension, and is available only in the DATA, MIME, and
32229 non-SMTP ACLs. It causes the incoming message to be scanned for a match with
32230 any of the regular expressions. For details, see chapter &<<CHAPexiscan>>&.
32232 .vitem &*seen&~=&~*&<&'parameters'&>
32233 .cindex "&%seen%& ACL condition"
32234 This condition can be used to test if a situation has been previously met,
32235 for example for greylisting.
32236 Details are given in section &<<SECTseen>>&.
32238 .vitem &*sender_domains&~=&~*&<&'domain&~list'&>
32239 .cindex "&%sender_domains%& ACL condition"
32240 .cindex "sender" "ACL checking"
32241 .cindex "&ACL;" "testing a sender domain"
32242 .vindex "&$domain$&"
32243 .vindex "&$sender_address_domain$&"
32244 This condition tests the domain of the sender of the message against the given
32245 domain list. &*Note*&: The domain of the sender address is in
32246 &$sender_address_domain$&. It is &'not'& put in &$domain$& during the testing
32247 of this condition. This is an exception to the general rule for testing domain
32248 lists. It is done this way so that, if this condition is used in an ACL for a
32249 RCPT command, the recipient's domain (which is in &$domain$&) can be used to
32250 influence the sender checking.
32252 &*Warning*&: It is a bad idea to use this condition on its own as a control on
32253 relaying, because sender addresses are easily, and commonly, forged.
32255 .vitem &*senders&~=&~*&<&'address&~list'&>
32256 .cindex "&%senders%& ACL condition"
32257 .cindex "sender" "ACL checking"
32258 .cindex "&ACL;" "testing a sender"
32259 This condition tests the sender of the message against the given list. To test
32260 for a bounce message, which has an empty sender, set
32264 &*Warning*&: It is a bad idea to use this condition on its own as a control on
32265 relaying, because sender addresses are easily, and commonly, forged.
32267 .vitem &*spam&~=&~*&<&'username'&>
32268 .cindex "&%spam%& ACL condition"
32269 .cindex "&ACL;" "scanning for spam"
32270 This condition is available only when Exim is compiled with the
32271 content-scanning extension. It causes the incoming message to be scanned by
32272 SpamAssassin. For details, see chapter &<<CHAPexiscan>>&.
32274 .vitem &*verify&~=&~certificate*&
32275 .cindex "&%verify%& ACL condition"
32276 .cindex "TLS" "client certificate verification"
32277 .cindex "certificate" "verification of client"
32278 .cindex "&ACL;" "certificate verification"
32279 .cindex "&ACL;" "testing a TLS certificate"
32280 This condition is true in an SMTP session if the session is encrypted, and a
32281 certificate was received from the client, and the certificate was verified. The
32282 server requests a certificate only if the client matches &%tls_verify_hosts%&
32283 or &%tls_try_verify_hosts%& (see chapter &<<CHAPTLS>>&).
32285 .vitem &*verify&~=&~csa*&
32286 .cindex "CSA verification"
32287 This condition checks whether the sending host (the client) is authorized to
32288 send email. Details of how this works are given in section
32289 &<<SECTverifyCSA>>&.
32291 .vitem &*verify&~=&~header_names_ascii*&
32292 .cindex "&%verify%& ACL condition"
32293 .cindex "&ACL;" "verifying header names only ASCII"
32294 .cindex "header lines" "verifying header names only ASCII"
32295 .cindex "verifying" "header names only ASCII"
32296 This condition is relevant only in an ACL that is run after a message has been
32298 This usually means an ACL specified by &%acl_smtp_data%& or &%acl_not_smtp%&.
32299 It checks all header names (not the content) to make sure
32300 there are no non-ASCII characters, also excluding control characters. The
32301 allowable characters are decimal ASCII values 33 through 126.
32303 Exim itself will handle headers with non-ASCII characters, but it can cause
32304 problems for downstream applications, so this option will allow their
32305 detection and rejection in the DATA ACL's.
32307 .vitem &*verify&~=&~header_sender/*&<&'options'&>
32308 .cindex "&%verify%& ACL condition"
32309 .cindex "&ACL;" "verifying sender in the header"
32310 .cindex "header lines" "verifying the sender in"
32311 .cindex "sender" "verifying in header"
32312 .cindex "verifying" "sender in header"
32313 This condition is relevant only in an ACL that is run after a message has been
32314 received, that is, in an ACL specified by &%acl_smtp_data%& or
32315 &%acl_not_smtp%&. It checks that there is a verifiable address in at least one
32316 of the &'Sender:'&, &'Reply-To:'&, or &'From:'& header lines. Such an address
32317 is loosely thought of as a &"sender"& address (hence the name of the test).
32318 However, an address that appears in one of these headers need not be an address
32319 that accepts bounce messages; only sender addresses in envelopes are required
32320 to accept bounces. Therefore, if you use the callout option on this check, you
32321 might want to arrange for a non-empty address in the MAIL command.
32323 Details of address verification and the options are given later, starting at
32324 section &<<SECTaddressverification>>& (callouts are described in section
32325 &<<SECTcallver>>&). You can combine this condition with the &%senders%&
32326 condition to restrict it to bounce messages only:
32329 !verify = header_sender
32330 message = A valid sender header is required for bounces
32333 .vitem &*verify&~=&~header_syntax*&
32334 .cindex "&%verify%& ACL condition"
32335 .cindex "&ACL;" "verifying header syntax"
32336 .cindex "header lines" "verifying syntax"
32337 .cindex "verifying" "header syntax"
32338 This condition is relevant only in an ACL that is run after a message has been
32339 received, that is, in an ACL specified by &%acl_smtp_data%& or
32340 &%acl_not_smtp%&. It checks the syntax of all header lines that can contain
32341 lists of addresses (&'Sender:'&, &'From:'&, &'Reply-To:'&, &'To:'&, &'Cc:'&,
32342 and &'Bcc:'&), returning true if there are no problems.
32343 Unqualified addresses (local parts without domains) are
32344 permitted only in locally generated messages and from hosts that match
32345 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
32348 Note that this condition is a syntax check only. However, a common spamming
32349 ploy used to be to send syntactically invalid headers such as
32353 and this condition can be used to reject such messages, though they are not as
32354 common as they used to be.
32356 .vitem &*verify&~=&~helo*&
32357 .cindex "&%verify%& ACL condition"
32358 .cindex "&ACL;" "verifying HELO/EHLO"
32359 .cindex "HELO" "verifying"
32360 .cindex "EHLO" "verifying"
32361 .cindex "verifying" "EHLO"
32362 .cindex "verifying" "HELO"
32363 This condition is true if a HELO or EHLO command has been received from the
32364 client host, and its contents have been verified. If there has been no previous
32365 attempt to verify the HELO/EHLO contents, it is carried out when this
32366 condition is encountered. See the description of the &%helo_verify_hosts%& and
32367 &%helo_try_verify_hosts%& options for details of how to request verification
32368 independently of this condition, and for detail of the verification.
32370 For SMTP input that does not come over TCP/IP (the &%-bs%& command line
32371 option), this condition is always true.
32374 .vitem &*verify&~=&~not_blind/*&<&'options'&>
32375 .cindex "verifying" "not blind"
32376 .cindex "bcc recipients, verifying none"
32377 This condition checks that there are no blind (bcc) recipients in the message.
32378 Every envelope recipient must appear either in a &'To:'& header line or in a
32379 &'Cc:'& header line for this condition to be true. Local parts are checked
32380 case-sensitively; domains are checked case-insensitively. If &'Resent-To:'& or
32381 &'Resent-Cc:'& header lines exist, they are also checked. This condition can be
32382 used only in a DATA or non-SMTP ACL.
32384 There is one possible option, &`case_insensitive`&. If this is present then
32385 local parts are checked case-insensitively.
32387 There are, of course, many legitimate messages that make use of blind (bcc)
32388 recipients. This check should not be used on its own for blocking messages.
32391 .vitem &*verify&~=&~recipient/*&<&'options'&>
32392 .cindex "&%verify%& ACL condition"
32393 .cindex "&ACL;" "verifying recipient"
32394 .cindex "recipient" "verifying"
32395 .cindex "verifying" "recipient"
32396 .vindex "&$address_data$&"
32397 This condition is relevant only after a RCPT command. It verifies the current
32398 recipient. Details of address verification are given later, starting at section
32399 &<<SECTaddressverification>>&. After a recipient has been verified, the value
32400 of &$address_data$& is the last value that was set while routing the address.
32401 This applies even if the verification fails. When an address that is being
32402 verified is redirected to a single address, verification continues with the new
32403 address, and in that case, the subsequent value of &$address_data$& is the
32404 value for the child address.
32406 .vitem &*verify&~=&~reverse_host_lookup/*&<&'options'&>
32407 .cindex "&%verify%& ACL condition"
32408 .cindex "&ACL;" "verifying host reverse lookup"
32409 .cindex "host" "verifying reverse lookup"
32410 This condition ensures that a verified host name has been looked up from the IP
32411 address of the client host. (This may have happened already if the host name
32412 was needed for checking a host list, or if the host matched &%host_lookup%&.)
32413 Verification ensures that the host name obtained from a reverse DNS lookup, or
32414 one of its aliases, does, when it is itself looked up in the DNS, yield the
32415 original IP address.
32417 There is one possible option, &`defer_ok`&. If this is present and a
32418 DNS operation returns a temporary error, the verify condition succeeds.
32420 If this condition is used for a locally generated message (that is, when there
32421 is no client host involved), it always succeeds.
32423 .vitem &*verify&~=&~sender/*&<&'options'&>
32424 .cindex "&%verify%& ACL condition"
32425 .cindex "&ACL;" "verifying sender"
32426 .cindex "sender" "verifying"
32427 .cindex "verifying" "sender"
32428 This condition is relevant only after a MAIL or RCPT command, or after a
32429 message has been received (the &%acl_smtp_data%& or &%acl_not_smtp%& ACLs). If
32430 the message's sender is empty (that is, this is a bounce message), the
32431 condition is true. Otherwise, the sender address is verified.
32433 .vindex "&$address_data$&"
32434 .vindex "&$sender_address_data$&"
32435 If there is data in the &$address_data$& variable at the end of routing, its
32436 value is placed in &$sender_address_data$& at the end of verification. This
32437 value can be used in subsequent conditions and modifiers in the same ACL
32438 statement. It does not persist after the end of the current statement. If you
32439 want to preserve the value for longer, you can save it in an ACL variable.
32441 Details of verification are given later, starting at section
32442 &<<SECTaddressverification>>&. Exim caches the result of sender verification,
32443 to avoid doing it more than once per message.
32445 .vitem &*verify&~=&~sender=*&<&'address'&>&*/*&<&'options'&>
32446 .cindex "&%verify%& ACL condition"
32447 This is a variation of the previous option, in which a modified address is
32448 verified as a sender.
32450 Note that '/' is legal in local-parts; if the address may have such
32451 (eg. is generated from the received message)
32452 they must be protected from the options parsing by doubling:
32454 verify = sender=${listquote{/}{${address:$h_sender:}}}
32460 .section "Using DNS lists" "SECTmorednslists"
32461 .cindex "DNS list" "in ACL"
32462 .cindex "black list (DNS)"
32463 .cindex "&ACL;" "testing a DNS list"
32464 In its simplest form, the &%dnslists%& condition tests whether the calling host
32465 is on at least one of a number of DNS lists by looking up the inverted IP
32466 address in one or more DNS domains. (Note that DNS list domains are not mail
32467 domains, so the &`+`& syntax for named lists doesn't work - it is used for
32468 special options instead.) For example, if the calling host's IP
32469 address is 192.168.62.43, and the ACL statement is
32471 deny dnslists = blackholes.mail-abuse.org : \
32472 dialups.mail-abuse.org
32474 the following records are looked up:
32476 43.62.168.192.blackholes.mail-abuse.org
32477 43.62.168.192.dialups.mail-abuse.org
32479 As soon as Exim finds an existing DNS record, processing of the list stops.
32480 Thus, multiple entries on the list provide an &"or"& conjunction. If you want
32481 to test that a host is on more than one list (an &"and"& conjunction), you can
32482 use two separate conditions:
32484 deny dnslists = blackholes.mail-abuse.org
32485 dnslists = dialups.mail-abuse.org
32487 If a DNS lookup times out or otherwise fails to give a decisive answer, Exim
32488 behaves as if the host does not match the list item, that is, as if the DNS
32489 record does not exist. If there are further items in the DNS list, they are
32492 This is usually the required action when &%dnslists%& is used with &%deny%&
32493 (which is the most common usage), because it prevents a DNS failure from
32494 blocking mail. However, you can change this behaviour by putting one of the
32495 following special items in the list:
32496 .itable none 0 0 2 25* left 75* left
32497 .irow "+include_unknown" "behave as if the item is on the list"
32498 .irow "+exclude_unknown" "behave as if the item is not on the list (default)"
32499 .irow "+defer_unknown " "give a temporary error"
32501 .cindex "&`+include_unknown`&"
32502 .cindex "&`+exclude_unknown`&"
32503 .cindex "&`+defer_unknown`&"
32504 Each of these applies to any subsequent items on the list. For example:
32506 deny dnslists = +defer_unknown : foo.bar.example
32508 Testing the list of domains stops as soon as a match is found. If you want to
32509 warn for one list and block for another, you can use two different statements:
32511 deny dnslists = blackholes.mail-abuse.org
32512 warn dnslists = dialups.mail-abuse.org
32513 message = X-Warn: sending host is on dialups list
32515 .cindex caching "of dns lookup"
32517 DNS list lookups are cached by Exim for the duration of the SMTP session
32518 (but limited by the DNS return TTL value),
32519 so a lookup based on the IP address is done at most once for any incoming
32520 connection (assuming long-enough TTL).
32521 Exim does not share information between multiple incoming
32522 connections (but your local name server cache should be active).
32524 There are a number of DNS lists to choose from, some commercial, some free,
32525 or free for small deployments. An overview can be found at
32526 &url(https://en.wikipedia.org/wiki/Comparison_of_DNS_blacklists).
32530 .subsection "Specifying the IP address for a DNS list lookup" SECID201
32531 .cindex "DNS list" "keyed by explicit IP address"
32532 By default, the IP address that is used in a DNS list lookup is the IP address
32533 of the calling host. However, you can specify another IP address by listing it
32534 after the domain name, introduced by a slash. For example:
32536 deny dnslists = black.list.tld/192.168.1.2
32538 This feature is not very helpful with explicit IP addresses; it is intended for
32539 use with IP addresses that are looked up, for example, the IP addresses of the
32540 MX hosts or nameservers of an email sender address. For an example, see section
32541 &<<SECTmulkeyfor>>& below.
32546 .subsection "DNS lists keyed on domain names" SECID202
32547 .cindex "DNS list" "keyed by domain name"
32548 There are some lists that are keyed on domain names rather than inverted IP
32549 addresses (see, e.g., the &'domain based zones'& link at
32550 &url(http://www.rfc-ignorant.org/)). No reversing of components is used
32551 with these lists. You can change the name that is looked up in a DNS list by
32552 listing it after the domain name, introduced by a slash. For example,
32554 deny dnslists = dsn.rfc-ignorant.org/$sender_address_domain
32555 message = Sender's domain is listed at $dnslist_domain
32557 This particular example is useful only in ACLs that are obeyed after the
32558 RCPT or DATA commands, when a sender address is available. If (for
32559 example) the message's sender is &'user@tld.example'& the name that is looked
32560 up by this example is
32562 tld.example.dsn.rfc-ignorant.org
32564 A single &%dnslists%& condition can contain entries for both names and IP
32565 addresses. For example:
32567 deny dnslists = sbl.spamhaus.org : \
32568 dsn.rfc-ignorant.org/$sender_address_domain
32570 The first item checks the sending host's IP address; the second checks a domain
32571 name. The whole condition is true if either of the DNS lookups succeeds.
32576 .subsection "Multiple explicit keys for a DNS list" SECTmulkeyfor
32577 .cindex "DNS list" "multiple keys for"
32578 The syntax described above for looking up explicitly-defined values (either
32579 names or IP addresses) in a DNS blacklist is a simplification. After the domain
32580 name for the DNS list, what follows the slash can in fact be a list of items.
32581 As with all lists in Exim, the default separator is a colon. However, because
32582 this is a sublist within the list of DNS blacklist domains, it is necessary
32583 either to double the separators like this:
32585 dnslists = black.list.tld/name.1::name.2
32587 or to change the separator character, like this:
32589 dnslists = black.list.tld/<;name.1;name.2
32591 If an item in the list is an IP address, it is inverted before the DNS
32592 blacklist domain is appended. If it is not an IP address, no inversion
32593 occurs. Consider this condition:
32595 dnslists = black.list.tld/<;192.168.1.2;a.domain
32597 The DNS lookups that occur are:
32599 2.1.168.192.black.list.tld
32600 a.domain.black.list.tld
32602 Once a DNS record has been found (that matches a specific IP return
32603 address, if specified &-- see section &<<SECTaddmatcon>>&), no further lookups
32604 are done. If there is a temporary DNS error, the rest of the sublist of domains
32605 or IP addresses is tried. A temporary error for the whole dnslists item occurs
32606 only if no other DNS lookup in this sublist succeeds. In other words, a
32607 successful lookup for any of the items in the sublist overrides a temporary
32608 error for a previous item.
32610 The ability to supply a list of items after the slash is in some sense just a
32611 syntactic convenience. These two examples have the same effect:
32613 dnslists = black.list.tld/a.domain : black.list.tld/b.domain
32614 dnslists = black.list.tld/a.domain::b.domain
32616 However, when the data for the list is obtained from a lookup, the second form
32617 is usually much more convenient. Consider this example:
32619 deny dnslists = sbl.spamhaus.org/<|${lookup dnsdb {>|a=<|\
32620 ${lookup dnsdb {>|mxh=\
32621 $sender_address_domain} }} }
32622 message = The mail servers for the domain \
32623 $sender_address_domain \
32624 are listed at $dnslist_domain ($dnslist_value); \
32627 Note the use of &`>|`& in the dnsdb lookup to specify the separator for
32628 multiple DNS records. The inner dnsdb lookup produces a list of MX hosts
32629 and the outer dnsdb lookup finds the IP addresses for these hosts. The result
32630 of expanding the condition might be something like this:
32632 dnslists = sbl.spamhaus.org/<|192.168.2.3|192.168.5.6|...
32634 Thus, this example checks whether or not the IP addresses of the sender
32635 domain's mail servers are on the Spamhaus black list.
32637 The key that was used for a successful DNS list lookup is put into the variable
32638 &$dnslist_matched$& (see section &<<SECID204>>&).
32643 .subsection "Data returned by DNS lists" SECID203
32644 .cindex "DNS list" "data returned from"
32645 DNS lists are constructed using address records in the DNS. The original RBL
32646 just used the address 127.0.0.1 on the right hand side of each record, but the
32647 RBL+ list and some other lists use a number of values with different meanings.
32648 The values used on the RBL+ list are:
32649 .itable none 0 0 2 20* left 80* left
32650 .irow 127.1.0.1 "RBL"
32651 .irow 127.1.0.2 "DUL"
32652 .irow 127.1.0.3 "DUL and RBL"
32653 .irow 127.1.0.4 "RSS"
32654 .irow 127.1.0.5 "RSS and RBL"
32655 .irow 127.1.0.6 "RSS and DUL"
32656 .irow 127.1.0.7 "RSS and DUL and RBL"
32658 Section &<<SECTaddmatcon>>& below describes how you can distinguish between
32659 different values. Some DNS lists may return more than one address record;
32660 see section &<<SECThanmuldnsrec>>& for details of how they are checked.
32662 Values returned by a properly running DBSBL should be in the 127.0.0.0/8
32663 range. If a DNSBL operator loses control of the domain, lookups on it
32664 may start returning other addresses. Because of this, Exim now ignores
32665 returned values outside the 127/8 region.
32668 .subsection "Variables set from DNS lists" SECID204
32669 .cindex "expansion" "variables, set from DNS list"
32670 .cindex "DNS list" "variables set from"
32671 .vindex "&$dnslist_domain$&"
32672 .vindex "&$dnslist_matched$&"
32673 .vindex "&$dnslist_text$&"
32674 .vindex "&$dnslist_value$&"
32675 When an entry is found in a DNS list, the variable &$dnslist_domain$& contains
32676 the name of the overall domain that matched (for example,
32677 &`spamhaus.example`&), &$dnslist_matched$& contains the key within that domain
32678 (for example, &`192.168.5.3`&), and &$dnslist_value$& contains the data from
32679 the DNS record. When the key is an IP address, it is not reversed in
32680 &$dnslist_matched$& (though it is, of course, in the actual lookup). In simple
32681 cases, for example:
32683 deny dnslists = spamhaus.example
32685 the key is also available in another variable (in this case,
32686 &$sender_host_address$&). In more complicated cases, however, this is not true.
32687 For example, using a data lookup (as described in section &<<SECTmulkeyfor>>&)
32688 might generate a dnslists lookup like this:
32690 deny dnslists = spamhaus.example/<|192.168.1.2|192.168.6.7|...
32692 If this condition succeeds, the value in &$dnslist_matched$& might be
32693 &`192.168.6.7`& (for example).
32695 If more than one address record is returned by the DNS lookup, all the IP
32696 addresses are included in &$dnslist_value$&, separated by commas and spaces.
32697 The variable &$dnslist_text$& contains the contents of any associated TXT
32698 record. For lists such as RBL+ the TXT record for a merged entry is often not
32699 very meaningful. See section &<<SECTmordetinf>>& for a way of obtaining more
32702 You can use the DNS list variables in &%message%& or &%log_message%& modifiers
32703 &-- even if these appear before the condition in the ACL, they are not
32704 expanded until after it has failed. For example:
32706 deny hosts = !+local_networks
32707 message = $sender_host_address is listed \
32709 dnslists = rbl-plus.mail-abuse.example
32714 .subsection "Additional matching conditions for DNS lists" SECTaddmatcon
32715 .cindex "DNS list" "matching specific returned data"
32716 You can add an equals sign and an IP address after a &%dnslists%& domain name
32717 in order to restrict its action to DNS records with a matching right hand side.
32720 deny dnslists = rblplus.mail-abuse.org=127.0.0.2
32722 rejects only those hosts that yield 127.0.0.2. Without this additional data,
32723 any address record is considered to be a match. For the moment, we assume
32724 that the DNS lookup returns just one record. Section &<<SECThanmuldnsrec>>&
32725 describes how multiple records are handled.
32727 More than one IP address may be given for checking, using a comma as a
32728 separator. These are alternatives &-- if any one of them matches, the
32729 &%dnslists%& condition is true. For example:
32731 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
32733 If you want to specify a constraining address list and also specify names or IP
32734 addresses to be looked up, the constraining address list must be specified
32735 first. For example:
32737 deny dnslists = dsn.rfc-ignorant.org\
32738 =127.0.0.2/$sender_address_domain
32741 If the character &`&&`& is used instead of &`=`&, the comparison for each
32742 listed IP address is done by a bitwise &"and"& instead of by an equality test.
32743 In other words, the listed addresses are used as bit masks. The comparison is
32744 true if all the bits in the mask are present in the address that is being
32745 tested. For example:
32747 dnslists = a.b.c&0.0.0.3
32749 matches if the address is &'x.x.x.'&3, &'x.x.x.'&7, &'x.x.x.'&11, etc. If you
32750 want to test whether one bit or another bit is present (as opposed to both
32751 being present), you must use multiple values. For example:
32753 dnslists = a.b.c&0.0.0.1,0.0.0.2
32755 matches if the final component of the address is an odd number or two times
32760 .subsection "Negated DNS matching conditions" SECID205
32761 You can supply a negative list of IP addresses as part of a &%dnslists%&
32764 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
32766 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
32767 IP address yielded by the list is either 127.0.0.2 or 127.0.0.3"&,
32769 deny dnslists = a.b.c!=127.0.0.2,127.0.0.3
32771 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
32772 IP address yielded by the list is not 127.0.0.2 and not 127.0.0.3"&. In other
32773 words, the result of the test is inverted if an exclamation mark appears before
32774 the &`=`& (or the &`&&`&) sign.
32776 &*Note*&: This kind of negation is not the same as negation in a domain,
32777 host, or address list (which is why the syntax is different).
32779 If you are using just one list, the negation syntax does not gain you much. The
32780 previous example is precisely equivalent to
32782 deny dnslists = a.b.c
32783 !dnslists = a.b.c=127.0.0.2,127.0.0.3
32785 However, if you are using multiple lists, the negation syntax is clearer.
32786 Consider this example:
32788 deny dnslists = sbl.spamhaus.org : \
32790 dnsbl.njabl.org!=127.0.0.3 : \
32793 Using only positive lists, this would have to be:
32795 deny dnslists = sbl.spamhaus.org : \
32797 deny dnslists = dnsbl.njabl.org
32798 !dnslists = dnsbl.njabl.org=127.0.0.3
32799 deny dnslists = relays.ordb.org
32801 which is less clear, and harder to maintain.
32803 Negation can also be used with a bitwise-and restriction.
32804 The dnslists condition with only be trus if a result is returned
32805 by the lookup which, anded with the restriction, is all zeroes.
32808 deny dnslists = zen.spamhaus.org!&0.255.255.0
32814 .subsection "Handling multiple DNS records from a DNS list" SECThanmuldnsrec
32815 A DNS lookup for a &%dnslists%& condition may return more than one DNS record,
32816 thereby providing more than one IP address. When an item in a &%dnslists%& list
32817 is followed by &`=`& or &`&&`& and a list of IP addresses, in order to restrict
32818 the match to specific results from the DNS lookup, there are two ways in which
32819 the checking can be handled. For example, consider the condition:
32821 dnslists = a.b.c=127.0.0.1
32823 What happens if the DNS lookup for the incoming IP address yields both
32824 127.0.0.1 and 127.0.0.2 by means of two separate DNS records? Is the
32825 condition true because at least one given value was found, or is it false
32826 because at least one of the found values was not listed? And how does this
32827 affect negated conditions? Both possibilities are provided for with the help of
32828 additional separators &`==`& and &`=&&`&.
32831 If &`=`& or &`&&`& is used, the condition is true if any one of the looked up
32832 IP addresses matches one of the listed addresses. For the example above, the
32833 condition is true because 127.0.0.1 matches.
32835 If &`==`& or &`=&&`& is used, the condition is true only if every one of the
32836 looked up IP addresses matches one of the listed addresses. If the condition is
32839 dnslists = a.b.c==127.0.0.1
32841 and the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
32842 false because 127.0.0.2 is not listed. You would need to have:
32844 dnslists = a.b.c==127.0.0.1,127.0.0.2
32846 for the condition to be true.
32849 When &`!`& is used to negate IP address matching, it inverts the result, giving
32850 the precise opposite of the behaviour above. Thus:
32852 If &`!=`& or &`!&&`& is used, the condition is true if none of the looked up IP
32853 addresses matches one of the listed addresses. Consider:
32855 dnslists = a.b.c!&0.0.0.1
32857 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
32858 false because 127.0.0.1 matches.
32860 If &`!==`& or &`!=&&`& is used, the condition is true if there is at least one
32861 looked up IP address that does not match. Consider:
32863 dnslists = a.b.c!=&0.0.0.1
32865 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
32866 true, because 127.0.0.2 does not match. You would need to have:
32868 dnslists = a.b.c!=&0.0.0.1,0.0.0.2
32870 for the condition to be false.
32872 When the DNS lookup yields only a single IP address, there is no difference
32873 between &`=`& and &`==`& and between &`&&`& and &`=&&`&.
32878 .subsection "Detailed information from merged DNS lists" SECTmordetinf
32879 .cindex "DNS list" "information from merged"
32880 When the facility for restricting the matching IP values in a DNS list is used,
32881 the text from the TXT record that is set in &$dnslist_text$& may not reflect
32882 the true reason for rejection. This happens when lists are merged and the IP
32883 address in the A record is used to distinguish them; unfortunately there is
32884 only one TXT record. One way round this is not to use merged lists, but that
32885 can be inefficient because it requires multiple DNS lookups where one would do
32886 in the vast majority of cases when the host of interest is not on any of the
32889 A less inefficient way of solving this problem is available. If
32890 two domain names, comma-separated, are given, the second is used first to
32891 do an initial check, making use of any IP value restrictions that are set.
32892 If there is a match, the first domain is used, without any IP value
32893 restrictions, to get the TXT record. As a byproduct of this, there is also
32894 a check that the IP being tested is indeed on the first list. The first
32895 domain is the one that is put in &$dnslist_domain$&. For example:
32898 sbl.spamhaus.org,sbl-xbl.spamhaus.org=127.0.0.2 : \
32899 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
32901 rejected because $sender_host_address is blacklisted \
32902 at $dnslist_domain\n$dnslist_text
32904 For the first blacklist item, this starts by doing a lookup in
32905 &'sbl-xbl.spamhaus.org'& and testing for a 127.0.0.2 return. If there is a
32906 match, it then looks in &'sbl.spamhaus.org'&, without checking the return
32907 value, and as long as something is found, it looks for the corresponding TXT
32908 record. If there is no match in &'sbl-xbl.spamhaus.org'&, nothing more is done.
32909 The second blacklist item is processed similarly.
32911 If you are interested in more than one merged list, the same list must be
32912 given several times, but because the results of the DNS lookups are cached,
32913 the DNS calls themselves are not repeated. For example:
32916 http.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.2 : \
32917 socks.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.3 : \
32918 misc.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.4 : \
32919 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
32921 In this case there is one lookup in &'dnsbl.sorbs.net'&, and if none of the IP
32922 values matches (or if no record is found), this is the only lookup that is
32923 done. Only if there is a match is one of the more specific lists consulted.
32927 .subsection "DNS lists and IPv6" SECTmorednslistslast
32928 .cindex "IPv6" "DNS black lists"
32929 .cindex "DNS list" "IPv6 usage"
32930 If Exim is asked to do a dnslist lookup for an IPv6 address, it inverts it
32931 nibble by nibble. For example, if the calling host's IP address is
32932 3ffe:ffff:836f:0a00:000a:0800:200a:c031, Exim might look up
32934 1.3.0.c.a.0.0.2.0.0.8.0.a.0.0.0.0.0.a.0.f.6.3.8.
32935 f.f.f.f.e.f.f.3.blackholes.mail-abuse.org
32937 (split over two lines here to fit on the page). Unfortunately, some of the DNS
32938 lists contain wildcard records, intended for IPv4, that interact badly with
32939 IPv6. For example, the DNS entry
32941 *.3.some.list.example. A 127.0.0.1
32943 is probably intended to put the entire 3.0.0.0/8 IPv4 network on the list.
32944 Unfortunately, it also matches the entire 3::/4 IPv6 network.
32946 You can exclude IPv6 addresses from DNS lookups by making use of a suitable
32947 &%condition%& condition, as in this example:
32949 deny condition = ${if isip4{$sender_host_address}}
32950 dnslists = some.list.example
32953 If an explicit key is being used for a DNS lookup and it may be an IPv6
32954 address you should specify alternate list separators for both the outer
32955 (DNS list name) list and inner (lookup keys) list:
32957 dnslists = <; dnsbl.example.com/<|$acl_m_addrslist
32961 .section "Previously seen user and hosts" "SECTseen"
32962 .cindex "&%seen%& ACL condition"
32963 .cindex greylisting
32964 The &%seen%& ACL condition can be used to test whether a
32965 situation has been previously met.
32966 It uses a hints database to record a timestamp against a key.
32967 host. The syntax of the condition is:
32969 &`seen =`& <&'optional flag'&><&'time interval'&> &`/`& <&'options'&>
32974 defer seen = -5m / key=${sender_host_address}_$local_part@$domain
32976 in a RCPT ACL will implement simple greylisting.
32978 The parameters for the condition are
32979 a possible minus sign,
32981 then, slash-separated, a list of options.
32982 The interval is taken as an offset before the current time,
32983 and used for the test.
32984 If the interval is preceded by a minus sign then the condition returns
32985 whether a record is found which is before the test time.
32986 Otherwise, the condition returns whether one is found which is since the
32989 Options are read in order with later ones overriding earlier ones.
32991 The default key is &$sender_host_address$&.
32992 An explicit key can be set using a &%key=value%& option.
32994 If a &%readonly%& option is given then
32995 no record create or update is done.
32996 If a &%write%& option is given then
32997 a record create or update is always done.
32998 An update is done if the test is for &"since"&.
32999 If none of those hold and there was no existing record,
33000 a record is created.
33002 Creates and updates are marked with the current time.
33004 Finally, a &"before"& test which succeeds, and for which the record
33005 is old enough, will be refreshed with a timestamp of the test time.
33006 This can prevent tidying of the database from removing the entry.
33007 The interval for this is, by default, 10 days.
33008 An explicit interval can be set using a
33009 &%refresh=value%& option.
33011 Note that &"seen"& should be added to the list of hints databases
33012 for maintenance if this ACL condition is used.
33015 .section "Rate limiting incoming messages" "SECTratelimiting"
33016 .cindex "rate limiting" "client sending"
33017 .cindex "limiting client sending rates"
33018 .oindex "&%smtp_ratelimit_*%&"
33019 The &%ratelimit%& ACL condition can be used to measure and control the rate at
33020 which clients can send email. This is more powerful than the
33021 &%smtp_ratelimit_*%& options, because those options control the rate of
33022 commands in a single SMTP session only, whereas the &%ratelimit%& condition
33023 works across all connections (concurrent and sequential) from the same client
33024 host. The syntax of the &%ratelimit%& condition is:
33026 &`ratelimit =`& <&'m'&> &`/`& <&'p'&> &`/`& <&'options'&> &`/`& <&'key'&>
33028 If the average client sending rate is less than &'m'& messages per time
33029 period &'p'& then the condition is false; otherwise it is true.
33031 As a side-effect, the &%ratelimit%& condition sets the expansion variable
33032 &$sender_rate$& to the client's computed rate, &$sender_rate_limit$& to the
33033 configured value of &'m'&, and &$sender_rate_period$& to the configured value
33036 The parameter &'p'& is the smoothing time constant, in the form of an Exim
33037 time interval, for example, &`8h`& for eight hours. A larger time constant
33038 means that it takes Exim longer to forget a client's past behaviour. The
33039 parameter &'m'& is the maximum number of messages that a client is permitted to
33040 send in each time interval. It also specifies the number of messages permitted
33041 in a fast burst. By increasing both &'m'& and &'p'& but keeping &'m/p'&
33042 constant, you can allow a client to send more messages in a burst without
33043 changing its long-term sending rate limit. Conversely, if &'m'& and &'p'& are
33044 both small, messages must be sent at an even rate.
33046 There is a script in &_util/ratelimit.pl_& which extracts sending rates from
33047 log files, to assist with choosing appropriate settings for &'m'& and &'p'&
33048 when deploying the &%ratelimit%& ACL condition. The script prints usage
33049 instructions when it is run with no arguments.
33051 The key is used to look up the data for calculating the client's average
33052 sending rate. This data is stored in Exim's spool directory, alongside the
33053 retry and other hints databases. The default key is &$sender_host_address$&,
33054 which means Exim computes the sending rate of each client host IP address.
33055 By changing the key you can change how Exim identifies clients for the purpose
33056 of ratelimiting. For example, to limit the sending rate of each authenticated
33057 user, independent of the computer they are sending from, set the key to
33058 &$authenticated_id$&. You must ensure that the lookup key is meaningful; for
33059 example, &$authenticated_id$& is only meaningful if the client has
33060 authenticated (which you can check with the &%authenticated%& ACL condition).
33062 The lookup key does not have to identify clients: If you want to limit the
33063 rate at which a recipient receives messages, you can use the key
33064 &`$local_part@$domain`& with the &%per_rcpt%& option (see below) in a RCPT
33067 Each &%ratelimit%& condition can have up to four options. A &%per_*%& option
33068 specifies what Exim measures the rate of, for example, messages or recipients
33069 or bytes. You can adjust the measurement using the &%unique=%& and/or
33070 &%count=%& options. You can also control when Exim updates the recorded rate
33071 using a &%strict%&, &%leaky%&, or &%readonly%& option. The options are
33072 separated by a slash, like the other parameters. They may appear in any order.
33074 Internally, Exim appends the smoothing constant &'p'& onto the lookup key with
33075 any options that alter the meaning of the stored data. The limit &'m'& is not
33076 stored, so you can alter the configured maximum rate and Exim will still
33077 remember clients' past behaviour. If you change the &%per_*%& mode or add or
33078 remove the &%unique=%& option, the lookup key changes so Exim will forget past
33079 behaviour. The lookup key is not affected by changes to the update mode and
33080 the &%count=%& option.
33083 .subsection "Ratelimit options for what is being measured" ratoptmea
33084 .cindex "rate limiting" "per_* options"
33085 The &%per_conn%& option limits the client's connection rate. It is not
33086 normally used in the &%acl_not_smtp%&, &%acl_not_smtp_mime%&, or
33087 &%acl_not_smtp_start%& ACLs.
33089 The &%per_mail%& option limits the client's rate of sending messages. This is
33090 the default if none of the &%per_*%& options is specified. It can be used in
33091 &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&, &%acl_smtp_mime%&,
33092 &%acl_smtp_data%&, or &%acl_not_smtp%&.
33094 The &%per_byte%& option limits the sender's email bandwidth. It can be used in
33095 the same ACLs as the &%per_mail%& option, though it is best to use this option
33096 in the &%acl_smtp_mime%&, &%acl_smtp_data%& or &%acl_not_smtp%& ACLs; if it is
33097 used in an earlier ACL, Exim relies on the SIZE parameter given by the client
33098 in its MAIL command, which may be inaccurate or completely missing. You can
33099 follow the limit &'m'& in the configuration with K, M, or G to specify limits
33100 in kilobytes, megabytes, or gigabytes, respectively.
33102 The &%per_rcpt%& option causes Exim to limit the rate at which recipients are
33103 accepted. It can be used in the &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
33104 &%acl_smtp_mime%&, or &%acl_smtp_data%& ACLs. In
33105 &%acl_smtp_rcpt%& the rate is updated one recipient at a time; in the other
33106 ACLs the rate is updated with the total (accepted) recipient count in one go. Note that
33107 in either case the rate limiting engine will see a message with many
33108 recipients as a large high-speed burst.
33110 The &%per_addr%& option is like the &%per_rcpt%& option, except it counts the
33111 number of different recipients that the client has sent messages to in the
33112 last time period. That is, if the client repeatedly sends messages to the same
33113 recipient, its measured rate is not increased. This option can only be used in
33116 The &%per_cmd%& option causes Exim to recompute the rate every time the
33117 condition is processed. This can be used to limit the rate of any SMTP
33118 command. If it is used in multiple ACLs it can limit the aggregate rate of
33119 multiple different commands.
33121 The &%count=%& option can be used to alter how much Exim adds to the client's
33122 measured rate. For example, the &%per_byte%& option is equivalent to
33123 &`per_mail/count=$message_size`&. If there is no &%count=%& option, Exim
33124 increases the measured rate by one (except for the &%per_rcpt%& option in ACLs
33125 other than &%acl_smtp_rcpt%&). The count does not have to be an integer.
33127 The &%unique=%& option is described in section &<<ratoptuniq>>& below.
33130 .subsection "Ratelimit update modes" ratoptupd
33131 .cindex "rate limiting" "reading data without updating"
33132 You can specify one of three options with the &%ratelimit%& condition to
33133 control when its database is updated. This section describes the &%readonly%&
33134 mode, and the next section describes the &%strict%& and &%leaky%& modes.
33136 If the &%ratelimit%& condition is used in &%readonly%& mode, Exim looks up a
33137 previously-computed rate to check against the limit.
33139 For example, you can test the client's sending rate and deny it access (when
33140 it is too fast) in the connect ACL. If the client passes this check then it
33141 can go on to send a message, in which case its recorded rate will be updated
33142 in the MAIL ACL. Subsequent connections from the same client will check this
33146 deny ratelimit = 100 / 5m / readonly
33147 log_message = RATE CHECK: $sender_rate/$sender_rate_period \
33148 (max $sender_rate_limit)
33151 warn ratelimit = 100 / 5m / strict
33152 log_message = RATE UPDATE: $sender_rate/$sender_rate_period \
33153 (max $sender_rate_limit)
33156 If Exim encounters multiple &%ratelimit%& conditions with the same key when
33157 processing a message then it may increase the client's measured rate more than
33158 it should. For example, this will happen if you check the &%per_rcpt%& option
33159 in both &%acl_smtp_rcpt%& and &%acl_smtp_data%&. However it's OK to check the
33160 same &%ratelimit%& condition multiple times in the same ACL. You can avoid any
33161 multiple update problems by using the &%readonly%& option on later ratelimit
33164 The &%per_*%& options described above do not make sense in some ACLs. If you
33165 use a &%per_*%& option in an ACL where it is not normally permitted then the
33166 update mode defaults to &%readonly%& and you cannot specify the &%strict%& or
33167 &%leaky%& modes. In other ACLs the default update mode is &%leaky%& (see the
33168 next section) so you must specify the &%readonly%& option explicitly.
33171 .subsection "Ratelimit options for handling fast clients" ratoptfast
33172 .cindex "rate limiting" "strict and leaky modes"
33173 If a client's average rate is greater than the maximum, the rate limiting
33174 engine can react in two possible ways, depending on the presence of the
33175 &%strict%& or &%leaky%& update modes. This is independent of the other
33176 counter-measures (such as rejecting the message) that may be specified by the
33179 The &%leaky%& (default) option means that the client's recorded rate is not
33180 updated if it is above the limit. The effect of this is that Exim measures the
33181 client's average rate of successfully sent email,
33182 up to the given limit.
33183 This is appropriate if the countermeasure when the condition is true
33184 consists of refusing the message, and
33185 is generally the better choice if you have clients that retry automatically.
33186 If the action when true is anything more complex then this option is
33187 likely not what is wanted.
33189 The &%strict%& option means that the client's recorded rate is always
33190 updated. The effect of this is that Exim measures the client's average rate
33191 of attempts to send email, which can be much higher than the maximum it is
33192 actually allowed. If the client is over the limit it may be subjected to
33193 counter-measures by the ACL. It must slow down and allow sufficient time to
33194 pass that its computed rate falls below the maximum before it can send email
33195 again. The time (the number of smoothing periods) it must wait and not
33196 attempt to send mail can be calculated with this formula:
33198 ln(peakrate/maxrate)
33202 .subsection "Limiting the rate of different events" ratoptuniq
33203 .cindex "rate limiting" "counting unique events"
33204 The &%ratelimit%& &%unique=%& option controls a mechanism for counting the
33205 rate of different events. For example, the &%per_addr%& option uses this
33206 mechanism to count the number of different recipients that the client has
33207 sent messages to in the last time period; it is equivalent to
33208 &`per_rcpt/unique=$local_part@$domain`&. You could use this feature to
33209 measure the rate that a client uses different sender addresses with the
33210 options &`per_mail/unique=$sender_address`&.
33212 For each &%ratelimit%& key Exim stores the set of &%unique=%& values that it
33213 has seen for that key. The whole set is thrown away when it is older than the
33214 rate smoothing period &'p'&, so each different event is counted at most once
33215 per period. In the &%leaky%& update mode, an event that causes the client to
33216 go over the limit is not added to the set, in the same way that the client's
33217 recorded rate is not updated in the same situation.
33219 When you combine the &%unique=%& and &%readonly%& options, the specific
33220 &%unique=%& value is ignored, and Exim just retrieves the client's stored
33223 The &%unique=%& mechanism needs more space in the ratelimit database than the
33224 other &%ratelimit%& options in order to store the event set. The number of
33225 unique values is potentially as large as the rate limit, so the extra space
33226 required increases with larger limits.
33228 The uniqueification is not perfect: there is a small probability that Exim
33229 will think a new event has happened before. If the sender's rate is less than
33230 the limit, Exim should be more than 99.9% correct. However in &%strict%& mode
33231 the measured rate can go above the limit, in which case Exim may under-count
33232 events by a significant margin. Fortunately, if the rate is high enough (2.7
33233 times the limit) that the false positive rate goes above 9%, then Exim will
33234 throw away the over-full event set before the measured rate falls below the
33235 limit. Therefore the only harm should be that exceptionally high sending rates
33236 are logged incorrectly; any countermeasures you configure will be as effective
33240 .subsection "Using rate limiting" useratlim
33241 Exim's other ACL facilities are used to define what counter-measures are taken
33242 when the rate limit is exceeded. This might be anything from logging a warning
33243 (for example, while measuring existing sending rates in order to define
33244 policy), through time delays to slow down fast senders, up to rejecting the
33245 message. For example:
33247 # Log all senders' rates
33248 warn ratelimit = 0 / 1h / strict
33249 log_message = Sender rate $sender_rate / $sender_rate_period
33251 # Slow down fast senders; note the need to truncate $sender_rate
33252 # at the decimal point.
33253 warn ratelimit = 100 / 1h / per_rcpt / strict
33254 delay = ${eval: ${sg{$sender_rate}{[.].*}{}} - \
33255 $sender_rate_limit }s
33257 # Keep authenticated users under control
33258 deny authenticated = *
33259 ratelimit = 100 / 1d / strict / $authenticated_id
33261 # System-wide rate limit
33262 defer ratelimit = 10 / 1s / $primary_hostname
33263 message = Sorry, too busy. Try again later.
33265 # Restrict incoming rate from each host, with a default
33266 # set using a macro and special cases looked up in a table.
33267 defer ratelimit = ${lookup {$sender_host_address} \
33268 cdb {DB/ratelimits.cdb} \
33269 {$value} {RATELIMIT} }
33270 message = Sender rate exceeds $sender_rate_limit \
33271 messages per $sender_rate_period
33273 &*Warning*&: If you have a busy server with a lot of &%ratelimit%& tests,
33274 especially with the &%per_rcpt%& option, you may suffer from a performance
33275 bottleneck caused by locking on the ratelimit hints database. Apart from
33276 making your ACLs less complicated, you can reduce the problem by using a
33277 RAM disk for Exim's hints directory (usually &_/var/spool/exim/db/_&). However
33278 this means that Exim will lose its hints data after a reboot (including retry
33279 hints, the callout cache, and ratelimit data).
33283 .section "Address verification" "SECTaddressverification"
33284 .cindex "verifying address" "options for"
33285 .cindex "policy control" "address verification"
33286 Several of the &%verify%& conditions described in section
33287 &<<SECTaclconditions>>& cause addresses to be verified. Section
33288 &<<SECTsenaddver>>& discusses the reporting of sender verification failures.
33289 The verification conditions can be followed by options that modify the
33290 verification process. The options are separated from the keyword and from each
33291 other by slashes, and some of them contain parameters. For example:
33293 verify = sender/callout
33294 verify = recipient/defer_ok/callout=10s,defer_ok
33296 The first stage of address verification, which always happens, is to run the
33297 address through the routers, in &"verify mode"&. Routers can detect the
33298 difference between verification and routing for delivery, and their actions can
33299 be varied by a number of generic options such as &%verify%& and &%verify_only%&
33300 (see chapter &<<CHAProutergeneric>>&). If routing fails, verification fails.
33301 The available options are as follows:
33304 If the &%callout%& option is specified, successful routing to one or more
33305 remote hosts is followed by a &"callout"& to those hosts as an additional
33306 check. Callouts and their sub-options are discussed in the next section.
33308 If there is a defer error while doing verification routing, the ACL
33309 normally returns &"defer"&. However, if you include &%defer_ok%& in the
33310 options, the condition is forced to be true instead. Note that this is a main
33311 verification option as well as a suboption for callouts.
33313 The &%no_details%& option is covered in section &<<SECTsenaddver>>&, which
33314 discusses the reporting of sender address verification failures.
33316 The &%success_on_redirect%& option causes verification always to succeed
33317 immediately after a successful redirection. By default, if a redirection
33318 generates just one address, that address is also verified. See further
33319 discussion in section &<<SECTredirwhilveri>>&.
33321 If the &%quota%& option is specified for recipient verify,
33322 successful routing to an appendfile transport is followed by a call into
33323 the transport to evaluate the quota status for the recipient.
33324 No actual delivery is done, but verification will succeed if the quota
33325 is sufficient for the message (if the sender gave a message size) or
33326 not already exceeded (otherwise).
33329 .cindex "verifying address" "differentiating failures"
33330 .vindex "&$recipient_verify_failure$&"
33331 .vindex "&$sender_verify_failure$&"
33332 .vindex "&$acl_verify_message$&"
33333 After an address verification failure, &$acl_verify_message$& contains the
33334 error message that is associated with the failure. It can be preserved by
33337 warn !verify = sender
33338 set acl_m0 = $acl_verify_message
33340 If you are writing your own custom rejection message or log message when
33341 denying access, you can use this variable to include information about the
33342 verification failure.
33343 This variable is cleared at the end of processing the ACL verb.
33345 In addition, &$sender_verify_failure$& or &$recipient_verify_failure$& (as
33346 appropriate) contains one of the following words:
33349 &%qualify%&: The address was unqualified (no domain), and the message
33350 was neither local nor came from an exempted host.
33352 &%route%&: Routing failed.
33354 &%mail%&: Routing succeeded, and a callout was attempted; rejection
33355 occurred at or before the MAIL command (that is, on initial
33356 connection, HELO, or MAIL).
33358 &%recipient%&: The RCPT command in a callout was rejected.
33360 &%postmaster%&: The postmaster check in a callout was rejected.
33362 &%quota%&: The quota check for a local recipient did non pass.
33365 The main use of these variables is expected to be to distinguish between
33366 rejections of MAIL and rejections of RCPT in callouts.
33368 The above variables may also be set after a &*successful*&
33369 address verification to:
33372 &%random%&: A random local-part callout succeeded
33378 .section "Callout verification" "SECTcallver"
33379 .cindex "verifying address" "by callout"
33380 .cindex "callout" "verification"
33381 .cindex "SMTP" "callout verification"
33382 For non-local addresses, routing verifies the domain, but is unable to do any
33383 checking of the local part. There are situations where some means of verifying
33384 the local part is desirable. One way this can be done is to make an SMTP
33385 &'callback'& to a delivery host for the sender address or a &'callforward'& to
33386 a subsequent host for a recipient address, to see if the host accepts the
33387 address. We use the term &'callout'& to cover both cases. Note that for a
33388 sender address, the callback is not to the client host that is trying to
33389 deliver the message, but to one of the hosts that accepts incoming mail for the
33392 Exim does not do callouts by default. If you want them to happen, you must
33393 request them by setting appropriate options on the &%verify%& condition, as
33394 described below. This facility should be used with care, because it can add a
33395 lot of resource usage to the cost of verifying an address. However, Exim does
33396 cache the results of callouts, which helps to reduce the cost. Details of
33397 caching are in section &<<SECTcallvercache>>&.
33399 Recipient callouts are usually used only between hosts that are controlled by
33400 the same administration. For example, a corporate gateway host could use
33401 callouts to check for valid recipients on an internal mailserver. A successful
33402 callout does not guarantee that a real delivery to the address would succeed;
33403 on the other hand, a failing callout does guarantee that a delivery would fail.
33405 If the &%callout%& option is present on a condition that verifies an address, a
33406 second stage of verification occurs if the address is successfully routed to
33407 one or more remote hosts. The usual case is routing by a &(dnslookup)& or a
33408 &(manualroute)& router, where the router specifies the hosts. However, if a
33409 router that does not set up hosts routes to an &(smtp)& transport with a
33410 &%hosts%& setting, the transport's hosts are used. If an &(smtp)& transport has
33411 &%hosts_override%& set, its hosts are always used, whether or not the router
33412 supplies a host list.
33413 Callouts are only supported on &(smtp)& transports.
33415 The port that is used is taken from the transport, if it is specified and is a
33416 remote transport. (For routers that do verification only, no transport need be
33417 specified.) Otherwise, the default SMTP port is used. If a remote transport
33418 specifies an outgoing interface, this is used; otherwise the interface is not
33419 specified. Likewise, the text that is used for the HELO command is taken from
33420 the transport's &%helo_data%& option; if there is no transport, the value of
33421 &$smtp_active_hostname$& is used.
33423 For a sender callout check, Exim makes SMTP connections to the remote hosts, to
33424 test whether a bounce message could be delivered to the sender address. The
33425 following SMTP commands are sent:
33427 &`HELO `&<&'local host name'&>
33429 &`RCPT TO:`&<&'the address to be tested'&>
33432 LHLO is used instead of HELO if the transport's &%protocol%& option is
33435 The callout may use EHLO, AUTH and/or STARTTLS given appropriate option
33438 A recipient callout check is similar. By default, it also uses an empty address
33439 for the sender. This default is chosen because most hosts do not make use of
33440 the sender address when verifying a recipient. Using the same address means
33441 that a single cache entry can be used for each recipient. Some sites, however,
33442 do make use of the sender address when verifying. These are catered for by the
33443 &%use_sender%& and &%use_postmaster%& options, described in the next section.
33445 If the response to the RCPT command is a 2&'xx'& code, the verification
33446 succeeds. If it is 5&'xx'&, the verification fails. For any other condition,
33447 Exim tries the next host, if any. If there is a problem with all the remote
33448 hosts, the ACL yields &"defer"&, unless the &%defer_ok%& parameter of the
33449 &%callout%& option is given, in which case the condition is forced to succeed.
33451 .cindex "SMTP" "output flushing, disabling for callout"
33452 A callout may take a little time. For this reason, Exim normally flushes SMTP
33453 output before performing a callout in an ACL, to avoid unexpected timeouts in
33454 clients when the SMTP PIPELINING extension is in use. The flushing can be
33455 disabled by using a &%control%& modifier to set &%no_callout_flush%&.
33457 .cindex "tainted data" "de-tainting"
33458 .cindex "de-tainting" "using recipient verify"
33459 A recipient callout which gets a 2&'xx'& code
33460 will assign untainted values to the
33461 &$domain_data$& and &$local_part_data$& variables,
33462 corresponding to the domain and local parts of the recipient address.
33467 .subsection "Additional parameters for callouts" CALLaddparcall
33468 .cindex "callout" "additional parameters for"
33469 The &%callout%& option can be followed by an equals sign and a number of
33470 optional parameters, separated by commas. For example:
33472 verify = recipient/callout=10s,defer_ok
33474 The old syntax, which had &%callout_defer_ok%& and &%check_postmaster%& as
33475 separate verify options, is retained for backwards compatibility, but is now
33476 deprecated. The additional parameters for &%callout%& are as follows:
33480 .vitem <&'a&~time&~interval'&>
33481 .cindex "callout" "timeout, specifying"
33482 This specifies the timeout that applies for the callout attempt to each host.
33485 verify = sender/callout=5s
33487 The default is 30 seconds. The timeout is used for each response from the
33488 remote host. It is also used for the initial connection, unless overridden by
33489 the &%connect%& parameter.
33492 .vitem &*connect&~=&~*&<&'time&~interval'&>
33493 .cindex "callout" "connection timeout, specifying"
33494 This parameter makes it possible to set a different (usually smaller) timeout
33495 for making the SMTP connection. For example:
33497 verify = sender/callout=5s,connect=1s
33499 If not specified, this timeout defaults to the general timeout value.
33501 .vitem &*defer_ok*&
33502 .cindex "callout" "defer, action on"
33503 When this parameter is present, failure to contact any host, or any other kind
33504 of temporary error, is treated as success by the ACL. However, the cache is not
33505 updated in this circumstance.
33507 .vitem &*fullpostmaster*&
33508 .cindex "callout" "full postmaster check"
33509 This operates like the &%postmaster%& option (see below), but if the check for
33510 &'postmaster@domain'& fails, it tries just &'postmaster'&, without a domain, in
33511 accordance with the specification in RFC 2821. The RFC states that the
33512 unqualified address &'postmaster'& should be accepted.
33515 .vitem &*mailfrom&~=&~*&<&'email&~address'&>
33516 .cindex "callout" "sender when verifying header"
33517 When verifying addresses in header lines using the &%header_sender%&
33518 verification option, Exim behaves by default as if the addresses are envelope
33519 sender addresses from a message. Callout verification therefore tests to see
33520 whether a bounce message could be delivered, by using an empty address in the
33521 MAIL command. However, it is arguable that these addresses might never be used
33522 as envelope senders, and could therefore justifiably reject bounce messages
33523 (empty senders). The &%mailfrom%& callout parameter allows you to specify what
33524 address to use in the MAIL command. For example:
33526 require verify = header_sender/callout=mailfrom=abcd@x.y.z
33528 This parameter is available only for the &%header_sender%& verification option.
33531 .vitem &*maxwait&~=&~*&<&'time&~interval'&>
33532 .cindex "callout" "overall timeout, specifying"
33533 This parameter sets an overall timeout for performing a callout verification.
33536 verify = sender/callout=5s,maxwait=30s
33538 This timeout defaults to four times the callout timeout for individual SMTP
33539 commands. The overall timeout applies when there is more than one host that can
33540 be tried. The timeout is checked before trying the next host. This prevents
33541 very long delays if there are a large number of hosts and all are timing out
33542 (for example, when network connections are timing out).
33545 .vitem &*no_cache*&
33546 .cindex "callout" "cache, suppressing"
33547 .cindex "caching callout, suppressing"
33548 When this parameter is given, the callout cache is neither read nor updated.
33550 .vitem &*postmaster*&
33551 .cindex "callout" "postmaster; checking"
33552 When this parameter is set, a successful callout check is followed by a similar
33553 check for the local part &'postmaster'& at the same domain. If this address is
33554 rejected, the callout fails (but see &%fullpostmaster%& above). The result of
33555 the postmaster check is recorded in a cache record; if it is a failure, this is
33556 used to fail subsequent callouts for the domain without a connection being
33557 made, until the cache record expires.
33559 .vitem &*postmaster_mailfrom&~=&~*&<&'email&~address'&>
33560 The postmaster check uses an empty sender in the MAIL command by default.
33561 You can use this parameter to do a postmaster check using a different address.
33564 require verify = sender/callout=postmaster_mailfrom=abc@x.y.z
33566 If both &%postmaster%& and &%postmaster_mailfrom%& are present, the rightmost
33567 one overrides. The &%postmaster%& parameter is equivalent to this example:
33569 require verify = sender/callout=postmaster_mailfrom=
33571 &*Warning*&: The caching arrangements for postmaster checking do not take
33572 account of the sender address. It is assumed that either the empty address or
33573 a fixed non-empty address will be used. All that Exim remembers is that the
33574 postmaster check for the domain succeeded or failed.
33578 .cindex "callout" "&""random""& check"
33579 When this parameter is set, before doing the normal callout check, Exim does a
33580 check for a &"random"& local part at the same domain. The local part is not
33581 really random &-- it is defined by the expansion of the option
33582 &%callout_random_local_part%&, which defaults to
33584 $primary_hostname-$tod_epoch-testing
33586 The idea here is to try to determine whether the remote host accepts all local
33587 parts without checking. If it does, there is no point in doing callouts for
33588 specific local parts. If the &"random"& check succeeds, the result is saved in
33589 a cache record, and used to force the current and subsequent callout checks to
33590 succeed without a connection being made, until the cache record expires.
33592 .vitem &*use_postmaster*&
33593 .cindex "callout" "sender for recipient check"
33594 This parameter applies to recipient callouts only. For example:
33596 deny !verify = recipient/callout=use_postmaster
33598 .vindex "&$qualify_domain$&"
33599 It causes a non-empty postmaster address to be used in the MAIL command when
33600 performing the callout for the recipient, and also for a &"random"& check if
33601 that is configured. The local part of the address is &`postmaster`& and the
33602 domain is the contents of &$qualify_domain$&.
33604 .vitem &*use_sender*&
33605 This option applies to recipient callouts only. For example:
33607 require verify = recipient/callout=use_sender
33609 It causes the message's actual sender address to be used in the MAIL
33610 command when performing the callout, instead of an empty address. There is no
33611 need to use this option unless you know that the called hosts make use of the
33612 sender when checking recipients. If used indiscriminately, it reduces the
33613 usefulness of callout caching.
33616 This option applies to recipient callouts only. For example:
33618 require verify = recipient/callout=use_sender,hold
33620 It causes the connection to be held open and used for any further recipients
33621 and for eventual delivery (should that be done quickly).
33622 Doing this saves on TCP and SMTP startup costs, and TLS costs also
33623 when that is used for the connections.
33624 The advantage is only gained if there are no callout cache hits
33625 (which could be enforced by the no_cache option),
33626 if the use_sender option is used,
33627 if neither the random nor the use_postmaster option is used,
33628 and if no other callouts intervene.
33631 If you use any of the parameters that set a non-empty sender for the MAIL
33632 command (&%mailfrom%&, &%postmaster_mailfrom%&, &%use_postmaster%&, or
33633 &%use_sender%&), you should think about possible loops. Recipient checking is
33634 usually done between two hosts that are under the same management, and the host
33635 that receives the callouts is not normally configured to do callouts itself.
33636 Therefore, it is normally safe to use &%use_postmaster%& or &%use_sender%& in
33637 these circumstances.
33639 However, if you use a non-empty sender address for a callout to an arbitrary
33640 host, there is the likelihood that the remote host will itself initiate a
33641 callout check back to your host. As it is checking what appears to be a message
33642 sender, it is likely to use an empty address in MAIL, thus avoiding a
33643 callout loop. However, to be on the safe side it would be best to set up your
33644 own ACLs so that they do not do sender verification checks when the recipient
33645 is the address you use for header sender or postmaster callout checking.
33647 Another issue to think about when using non-empty senders for callouts is
33648 caching. When you set &%mailfrom%& or &%use_sender%&, the cache record is keyed
33649 by the sender/recipient combination; thus, for any given recipient, many more
33650 actual callouts are performed than when an empty sender or postmaster is used.
33655 .subsection "Callout caching" SECTcallvercache
33656 .cindex "hints database" "callout cache"
33657 .cindex "callout" "cache, description of"
33658 .cindex "caching" "callout"
33659 Exim caches the results of callouts in order to reduce the amount of resources
33660 used, unless you specify the &%no_cache%& parameter with the &%callout%&
33661 option. A hints database called &"callout"& is used for the cache. Two
33662 different record types are used: one records the result of a callout check for
33663 a specific address, and the other records information that applies to the
33664 entire domain (for example, that it accepts the local part &'postmaster'&).
33666 When an original callout fails, a detailed SMTP error message is given about
33667 the failure. However, for subsequent failures that use the cache data, this message
33670 The expiry times for negative and positive address cache records are
33671 independent, and can be set by the global options &%callout_negative_expire%&
33672 (default 2h) and &%callout_positive_expire%& (default 24h), respectively.
33674 If a host gives a negative response to an SMTP connection, or rejects any
33675 commands up to and including
33679 (but not including the MAIL command with a non-empty address),
33680 any callout attempt is bound to fail. Exim remembers such failures in a
33681 domain cache record, which it uses to fail callouts for the domain without
33682 making new connections, until the domain record times out. There are two
33683 separate expiry times for domain cache records:
33684 &%callout_domain_negative_expire%& (default 3h) and
33685 &%callout_domain_positive_expire%& (default 7d).
33687 Domain records expire when the negative expiry time is reached if callouts
33688 cannot be made for the domain, or if the postmaster check failed.
33689 Otherwise, they expire when the positive expiry time is reached. This
33690 ensures that, for example, a host that stops accepting &"random"& local parts
33691 will eventually be noticed.
33693 The callout caching mechanism is based on the domain of the address that is
33694 being tested. If the domain routes to several hosts, it is assumed that their
33695 behaviour will be the same.
33699 .section "Quota caching" "SECTquotacache"
33700 .cindex "hints database" "quota cache"
33701 .cindex "quota" "cache, description of"
33702 .cindex "caching" "quota"
33703 Exim caches the results of quota verification
33704 in order to reduce the amount of resources used.
33705 The &"callout"& hints database is used.
33707 The default cache periods are five minutes for a positive (good) result
33708 and one hour for a negative result.
33709 To change the periods the &%quota%& option can be followed by an equals sign
33710 and a number of optional paramemters, separated by commas.
33713 verify = recipient/quota=cachepos=1h,cacheneg=1d
33715 Possible parameters are:
33717 .vitem &*cachepos&~=&~*&<&'time&~interval'&>
33718 .cindex "quota cache" "positive entry expiry, specifying"
33719 Set the lifetime for a positive cache entry.
33720 A value of zero seconds is legitimate.
33722 .vitem &*cacheneg&~=&~*&<&'time&~interval'&>
33723 .cindex "quota cache" "negative entry expiry, specifying"
33724 As above, for a negative entry.
33726 .vitem &*no_cache*&
33727 Set both positive and negative lifetimes to zero.
33729 .section "Sender address verification reporting" "SECTsenaddver"
33730 .cindex "verifying" "suppressing error details"
33731 See section &<<SECTaddressverification>>& for a general discussion of
33732 verification. When sender verification fails in an ACL, the details of the
33733 failure are given as additional output lines before the 550 response to the
33734 relevant SMTP command (RCPT or DATA). For example, if sender callout is in use,
33737 MAIL FROM:<xyz@abc.example>
33739 RCPT TO:<pqr@def.example>
33740 550-Verification failed for <xyz@abc.example>
33741 550-Called: 192.168.34.43
33742 550-Sent: RCPT TO:<xyz@abc.example>
33743 550-Response: 550 Unknown local part xyz in <xyz@abc.example>
33744 550 Sender verification failed
33746 If more than one RCPT command fails in the same way, the details are given
33747 only for the first of them. However, some administrators do not want to send
33748 out this much information. You can suppress the details by adding
33749 &`/no_details`& to the ACL statement that requests sender verification. For
33752 verify = sender/no_details
33755 .section "Redirection while verifying" "SECTredirwhilveri"
33756 .cindex "verifying" "redirection while"
33757 .cindex "address redirection" "while verifying"
33758 A dilemma arises when a local address is redirected by aliasing or forwarding
33759 during verification: should the generated addresses themselves be verified,
33760 or should the successful expansion of the original address be enough to verify
33761 it? By default, Exim takes the following pragmatic approach:
33764 When an incoming address is redirected to just one child address, verification
33765 continues with the child address, and if that fails to verify, the original
33766 verification also fails.
33768 When an incoming address is redirected to more than one child address,
33769 verification does not continue. A success result is returned.
33772 This seems the most reasonable behaviour for the common use of aliasing as a
33773 way of redirecting different local parts to the same mailbox. It means, for
33774 example, that a pair of alias entries of the form
33777 aw123: :fail: Gone away, no forwarding address
33779 work as expected, with both local parts causing verification failure. When a
33780 redirection generates more than one address, the behaviour is more like a
33781 mailing list, where the existence of the alias itself is sufficient for
33782 verification to succeed.
33784 It is possible, however, to change the default behaviour so that all successful
33785 redirections count as successful verifications, however many new addresses are
33786 generated. This is specified by the &%success_on_redirect%& verification
33787 option. For example:
33789 require verify = recipient/success_on_redirect/callout=10s
33791 In this example, verification succeeds if a router generates a new address, and
33792 the callout does not occur, because no address was routed to a remote host.
33794 When verification is being tested via the &%-bv%& option, the treatment of
33795 redirections is as just described, unless the &%-v%& or any debugging option is
33796 also specified. In that case, full verification is done for every generated
33797 address and a report is output for each of them.
33801 .section "Client SMTP authorization (CSA)" "SECTverifyCSA"
33802 .cindex "CSA" "verifying"
33803 Client SMTP Authorization is a system that allows a site to advertise
33804 which machines are and are not permitted to send email. This is done by placing
33805 special SRV records in the DNS; these are looked up using the client's HELO
33806 domain. At the time of writing, CSA is still an Internet Draft. Client SMTP
33807 Authorization checks in Exim are performed by the ACL condition:
33811 This fails if the client is not authorized. If there is a DNS problem, or if no
33812 valid CSA SRV record is found, or if the client is authorized, the condition
33813 succeeds. These three cases can be distinguished using the expansion variable
33814 &$csa_status$&, which can take one of the values &"fail"&, &"defer"&,
33815 &"unknown"&, or &"ok"&. The condition does not itself defer because that would
33816 be likely to cause problems for legitimate email.
33818 The error messages produced by the CSA code include slightly more
33819 detail. If &$csa_status$& is &"defer"&, this may be because of problems
33820 looking up the CSA SRV record, or problems looking up the CSA target
33821 address record. There are four reasons for &$csa_status$& being &"fail"&:
33824 The client's host name is explicitly not authorized.
33826 The client's IP address does not match any of the CSA target IP addresses.
33828 The client's host name is authorized but it has no valid target IP addresses
33829 (for example, the target's addresses are IPv6 and the client is using IPv4).
33831 The client's host name has no CSA SRV record but a parent domain has asserted
33832 that all subdomains must be explicitly authorized.
33835 The &%csa%& verification condition can take an argument which is the domain to
33836 use for the DNS query. The default is:
33838 verify = csa/$sender_helo_name
33840 This implementation includes an extension to CSA. If the query domain
33841 is an address literal such as [192.0.2.95], or if it is a bare IP
33842 address, Exim searches for CSA SRV records in the reverse DNS as if
33843 the HELO domain was (for example) &'95.2.0.192.in-addr.arpa'&. Therefore it is
33846 verify = csa/$sender_host_address
33848 In fact, this is the check that Exim performs if the client does not say HELO.
33849 This extension can be turned off by setting the main configuration option
33850 &%dns_csa_use_reverse%& to be false.
33852 If a CSA SRV record is not found for the domain itself, a search
33853 is performed through its parent domains for a record which might be
33854 making assertions about subdomains. The maximum depth of this search is limited
33855 using the main configuration option &%dns_csa_search_limit%&, which is 5 by
33856 default. Exim does not look for CSA SRV records in a top level domain, so the
33857 default settings handle HELO domains as long as seven
33858 (&'hostname.five.four.three.two.one.com'&). This encompasses the vast majority
33859 of legitimate HELO domains.
33861 The &'dnsdb'& lookup also has support for CSA. Although &'dnsdb'& also supports
33862 direct SRV lookups, this is not sufficient because of the extra parent domain
33863 search behaviour of CSA, and (as with PTR lookups) &'dnsdb'& also turns IP
33864 addresses into lookups in the reverse DNS space. The result of a successful
33867 ${lookup dnsdb {csa=$sender_helo_name}}
33869 has two space-separated fields: an authorization code and a target host name.
33870 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
33871 authorization required but absent, or &"?"& for unknown.
33876 .section "Bounce address tag validation" "SECTverifyPRVS"
33877 .cindex "BATV, verifying"
33878 Bounce address tag validation (BATV) is a scheme whereby the envelope senders
33879 of outgoing messages have a cryptographic, timestamped &"tag"& added to them.
33880 Genuine incoming bounce messages should therefore always be addressed to
33881 recipients that have a valid tag. This scheme is a way of detecting unwanted
33882 bounce messages caused by sender address forgeries (often called &"collateral
33883 spam"&), because the recipients of such messages do not include valid tags.
33885 There are two expansion items to help with the implementation of the BATV
33886 &"prvs"& (private signature) scheme in an Exim configuration. This scheme signs
33887 the original envelope sender address by using a simple key to add a hash of the
33888 address and some time-based randomizing information. The &%prvs%& expansion
33889 item creates a signed address, and the &%prvscheck%& expansion item checks one.
33890 The syntax of these expansion items is described in section
33891 &<<SECTexpansionitems>>&.
33892 The validity period on signed addresses is seven days.
33894 As an example, suppose the secret per-address keys are stored in an MySQL
33895 database. A query to look up the key for an address could be defined as a macro
33898 PRVSCHECK_SQL = ${lookup mysql{SELECT secret FROM batv_prvs \
33899 WHERE sender='${quote_mysql:$prvscheck_address}'\
33902 Suppose also that the senders who make use of BATV are defined by an address
33903 list called &%batv_senders%&. Then, in the ACL for RCPT commands, you could
33906 # Bounces: drop unsigned addresses for BATV senders
33908 recipients = +batv_senders
33909 message = This address does not send an unsigned reverse path
33911 # Bounces: In case of prvs-signed address, check signature.
33913 condition = ${prvscheck {$local_part@$domain}\
33914 {PRVSCHECK_SQL}{1}}
33915 !condition = $prvscheck_result
33916 message = Invalid reverse path signature.
33918 The first statement rejects recipients for bounce messages that are addressed
33919 to plain BATV sender addresses, because it is known that BATV senders do not
33920 send out messages with plain sender addresses. The second statement rejects
33921 recipients that are prvs-signed, but with invalid signatures (either because
33922 the key is wrong, or the signature has timed out).
33924 A non-prvs-signed address is not rejected by the second statement, because the
33925 &%prvscheck%& expansion yields an empty string if its first argument is not a
33926 prvs-signed address, thus causing the &%condition%& condition to be false. If
33927 the first argument is a syntactically valid prvs-signed address, the yield is
33928 the third string (in this case &"1"&), whether or not the cryptographic and
33929 timeout checks succeed. The &$prvscheck_result$& variable contains the result
33930 of the checks (empty for failure, &"1"& for success).
33932 There is one more issue you must consider when implementing prvs-signing:
33933 you have to ensure that the routers accept prvs-signed addresses and
33934 deliver them correctly. The easiest way to handle this is to use a &(redirect)&
33935 router to remove the signature with a configuration along these lines:
33939 data = ${prvscheck {$local_part@$domain}{PRVSCHECK_SQL}}
33941 This works because, if the third argument of &%prvscheck%& is empty, the result
33942 of the expansion of a prvs-signed address is the decoded value of the original
33943 address. This router should probably be the first of your routers that handles
33946 To create BATV-signed addresses in the first place, a transport of this form
33949 external_smtp_batv:
33951 return_path = ${prvs {$return_path} \
33952 {${lookup mysql{SELECT \
33953 secret FROM batv_prvs WHERE \
33954 sender='${quote_mysql:$sender_address}'} \
33957 If no key can be found for the existing return path, no signing takes place.
33961 .section "Using an ACL to control relaying" "SECTrelaycontrol"
33962 .cindex "&ACL;" "relay control"
33963 .cindex "relaying" "control by ACL"
33964 .cindex "policy control" "relay control"
33965 An MTA is said to &'relay'& a message if it receives it from some host and
33966 delivers it directly to another host as a result of a remote address contained
33967 within it. Redirecting a local address via an alias or forward file and then
33968 passing the message on to another host is not relaying,
33969 .cindex "&""percent hack""&"
33970 but a redirection as a result of the &"percent hack"& is.
33972 Two kinds of relaying exist, which are termed &"incoming"& and &"outgoing"&.
33973 A host which is acting as a gateway or an MX backup is concerned with incoming
33974 relaying from arbitrary hosts to a specific set of domains. On the other hand,
33975 a host which is acting as a smart host for a number of clients is concerned
33976 with outgoing relaying from those clients to the Internet at large. Often the
33977 same host is fulfilling both functions,
33979 . as illustrated in the diagram below,
33981 but in principle these two kinds of relaying are entirely independent. What is
33982 not wanted is the transmission of mail from arbitrary remote hosts through your
33983 system to arbitrary domains.
33986 You can implement relay control by means of suitable statements in the ACL that
33987 runs for each RCPT command. For convenience, it is often easiest to use
33988 Exim's named list facility to define the domains and hosts involved. For
33989 example, suppose you want to do the following:
33992 Deliver a number of domains to mailboxes on the local host (or process them
33993 locally in some other way). Let's say these are &'my.dom1.example'& and
33994 &'my.dom2.example'&.
33996 Relay mail for a number of other domains for which you are the secondary MX.
33997 These might be &'friend1.example'& and &'friend2.example'&.
33999 Relay mail from the hosts on your local LAN, to whatever domains are involved.
34000 Suppose your LAN is 192.168.45.0/24.
34004 In the main part of the configuration, you put the following definitions:
34006 domainlist local_domains = my.dom1.example : my.dom2.example
34007 domainlist relay_to_domains = friend1.example : friend2.example
34008 hostlist relay_from_hosts = 192.168.45.0/24
34010 Now you can use these definitions in the ACL that is run for every RCPT
34014 accept domains = +local_domains : +relay_to_domains
34015 accept hosts = +relay_from_hosts
34017 The first statement accepts any RCPT command that contains an address in
34018 the local or relay domains. For any other domain, control passes to the second
34019 statement, which accepts the command only if it comes from one of the relay
34020 hosts. In practice, you will probably want to make your ACL more sophisticated
34021 than this, for example, by including sender and recipient verification. The
34022 default configuration includes a more comprehensive example, which is described
34023 in chapter &<<CHAPdefconfil>>&.
34027 .section "Checking a relay configuration" "SECTcheralcon"
34028 .cindex "relaying" "checking control of"
34029 You can check the relay characteristics of your configuration in the same way
34030 that you can test any ACL behaviour for an incoming SMTP connection, by using
34031 the &%-bh%& option to run a fake SMTP session with which you interact.
34036 . ////////////////////////////////////////////////////////////////////////////
34037 . ////////////////////////////////////////////////////////////////////////////
34039 .chapter "Content scanning at ACL time" "CHAPexiscan"
34040 .scindex IIDcosca "content scanning" "at ACL time"
34041 The extension of Exim to include content scanning at ACL time, formerly known
34042 as &"exiscan"&, was originally implemented as a patch by Tom Kistner. The code
34043 was integrated into the main source for Exim release 4.50, and Tom continues to
34044 maintain it. Most of the wording of this chapter is taken from Tom's
34047 It is also possible to scan the content of messages at other times. The
34048 &[local_scan()]& function (see chapter &<<CHAPlocalscan>>&) allows for content
34049 scanning after all the ACLs have run. A transport filter can be used to scan
34050 messages at delivery time (see the &%transport_filter%& option, described in
34051 chapter &<<CHAPtransportgeneric>>&).
34053 If you want to include the ACL-time content-scanning features when you compile
34054 Exim, you need to arrange for WITH_CONTENT_SCAN to be defined in your
34055 &_Local/Makefile_&. When you do that, the Exim binary is built with:
34058 Two additional ACLs (&%acl_smtp_mime%& and &%acl_not_smtp_mime%&) that are run
34059 for all MIME parts for SMTP and non-SMTP messages, respectively.
34061 Additional ACL conditions and modifiers: &%decode%&, &%malware%&,
34062 &%mime_regex%&, &%regex%&, and &%spam%&. These can be used in the ACL that is
34063 run at the end of message reception (the &%acl_smtp_data%& ACL).
34065 An additional control feature (&"no_mbox_unspool"&) that saves spooled copies
34066 of messages, or parts of messages, for debugging purposes.
34068 Additional expansion variables that are set in the new ACL and by the new
34071 Two new main configuration options: &%av_scanner%& and &%spamd_address%&.
34074 Content-scanning is continually evolving, and new features are still being
34075 added. While such features are still unstable and liable to incompatible
34076 changes, they are made available in Exim by setting options whose names begin
34077 EXPERIMENTAL_ in &_Local/Makefile_&. Such features are not documented in
34078 this manual. You can find out about them by reading the file called
34079 &_doc/experimental.txt_&.
34081 All the content-scanning facilities work on a MBOX copy of the message that is
34082 temporarily created in a file called:
34084 <&'spool_directory'&>&`/scan/`&<&'message_id'&>/<&'message_id'&>&`.eml`&
34086 The &_.eml_& extension is a friendly hint to virus scanners that they can
34087 expect an MBOX-like structure inside that file. The file is created when the
34088 first content scanning facility is called. Subsequent calls to content
34089 scanning conditions open the same file again. The directory is recursively
34090 removed when the &%acl_smtp_data%& ACL has finished running, unless
34092 control = no_mbox_unspool
34094 has been encountered. When the MIME ACL decodes files, they are put into the
34095 same directory by default.
34099 .section "Scanning for viruses" "SECTscanvirus"
34100 .cindex "virus scanning"
34101 .cindex "content scanning" "for viruses"
34102 .cindex "content scanning" "the &%malware%& condition"
34103 The &%malware%& ACL condition lets you connect virus scanner software to Exim.
34104 It supports a &"generic"& interface to scanners called via the shell, and
34105 specialized interfaces for &"daemon"& type virus scanners, which are resident
34106 in memory and thus are much faster.
34108 Since message data needs to have arrived,
34109 the condition may be only called in ACL defined by
34111 &%acl_smtp_data_prdr%&,
34112 &%acl_smtp_mime%& or
34115 A timeout of 2 minutes is applied to a scanner call (by default);
34116 if it expires then a defer action is taken.
34118 .oindex "&%av_scanner%&"
34119 You can set the &%av_scanner%& option in the main part of the configuration
34120 to specify which scanner to use, together with any additional options that
34121 are needed. The basic syntax is as follows:
34123 &`av_scanner = <`&&'scanner-type'&&`>:<`&&'option1'&&`>:<`&&'option2'&&`>:[...]`&
34125 If you do not set &%av_scanner%&, it defaults to
34127 av_scanner = sophie:/var/run/sophie
34129 If the value of &%av_scanner%& starts with a dollar character, it is expanded
34131 The usual list-parsing of the content (see &<<SECTlistconstruct>>&) applies.
34132 The following scanner types are supported in this release,
34133 though individual ones can be included or not at build time:
34137 .cindex "virus scanners" "avast"
34138 This is the scanner daemon of Avast. It has been tested with Avast Core
34139 Security (currently at version 2.2.0).
34140 You can get a trial version at &url(https://www.avast.com) or for Linux
34141 at &url(https://www.avast.com/linux-server-antivirus).
34142 This scanner type takes one option,
34143 which can be either a full path to a UNIX socket,
34144 or host and port specifiers separated by white space.
34145 The host may be a name or an IP address; the port is either a
34146 single number or a pair of numbers with a dash between.
34147 A list of options may follow. These options are interpreted on the
34148 Exim's side of the malware scanner, or are given on separate lines to
34149 the daemon as options before the main scan command.
34151 .cindex &`pass_unscanned`& "avast"
34152 If &`pass_unscanned`&
34153 is set, any files the Avast scanner can't scan (e.g.
34154 decompression bombs, or invalid archives) are considered clean. Use with
34159 av_scanner = avast:/var/run/avast/scan.sock:FLAGS -fullfiles:SENSITIVITY -pup
34160 av_scanner = avast:/var/run/avast/scan.sock:pass_unscanned:FLAGS -fullfiles:SENSITIVITY -pup
34161 av_scanner = avast:192.168.2.22 5036
34163 If you omit the argument, the default path
34164 &_/var/run/avast/scan.sock_&
34166 If you use a remote host,
34167 you need to make Exim's spool directory available to it,
34168 as the scanner is passed a file path, not file contents.
34169 For information about available commands and their options you may use
34171 $ socat UNIX:/var/run/avast/scan.sock STDIO:
34177 If the scanner returns a temporary failure (e.g. license issues, or
34178 permission problems), the message is deferred and a paniclog entry is
34179 written. The usual &`defer_ok`& option is available.
34181 .vitem &%aveserver%&
34182 .cindex "virus scanners" "Kaspersky"
34183 This is the scanner daemon of Kaspersky Version 5. You can get a trial version
34184 at &url(https://www.kaspersky.com/). This scanner type takes one option,
34185 which is the path to the daemon's UNIX socket. The default is shown in this
34188 av_scanner = aveserver:/var/run/aveserver
34193 .cindex "virus scanners" "clamd"
34194 This daemon-type scanner is GPL and free. You can get it at
34195 &url(https://www.clamav.net/). Some older versions of clamd do not seem to
34196 unpack MIME containers, so it used to be recommended to unpack MIME attachments
34197 in the MIME ACL. This is no longer believed to be necessary.
34199 The options are a list of server specifiers, which may be
34200 a UNIX socket specification,
34201 a TCP socket specification,
34202 or a (global) option.
34204 A socket specification consists of a space-separated list.
34205 For a Unix socket the first element is a full path for the socket,
34206 for a TCP socket the first element is the IP address
34207 and the second a port number,
34208 Any further elements are per-server (non-global) options.
34209 These per-server options are supported:
34211 retry=<timespec> Retry on connect fail
34214 The &`retry`& option specifies a time after which a single retry for
34215 a failed connect is made. The default is to not retry.
34217 If a Unix socket file is specified, only one server is supported.
34221 av_scanner = clamd:/opt/clamd/socket
34222 av_scanner = clamd:192.0.2.3 1234
34223 av_scanner = clamd:192.0.2.3 1234:local
34224 av_scanner = clamd:192.0.2.3 1234 retry=10s
34225 av_scanner = clamd:192.0.2.3 1234 : 192.0.2.4 1234
34227 If the value of av_scanner points to a UNIX socket file or contains the
34229 option, then the ClamAV interface will pass a filename containing the data
34230 to be scanned, which should normally result in less I/O happening and be
34231 more efficient. Normally in the TCP case, the data is streamed to ClamAV as
34232 Exim does not assume that there is a common filesystem with the remote host.
34234 The final example shows that multiple TCP targets can be specified. Exim will
34235 randomly use one for each incoming email (i.e. it load balances them). Note
34236 that only TCP targets may be used if specifying a list of scanners; a UNIX
34237 socket cannot be mixed in with TCP targets. If one of the servers becomes
34238 unavailable, Exim will try the remaining one(s) until it finds one that works.
34239 When a clamd server becomes unreachable, Exim will log a message. Exim does
34240 not keep track of scanner state between multiple messages, and the scanner
34241 selection is random, so the message will get logged in the mainlog for each
34242 email that the down scanner gets chosen first (message wrapped to be readable):
34244 2013-10-09 14:30:39 1VTumd-0000Y8-BQ malware acl condition:
34245 clamd: connection to localhost, port 3310 failed
34246 (Connection refused)
34249 If the option is unset, the default is &_/tmp/clamd_&. Thanks to David Saez for
34250 contributing the code for this scanner.
34253 .cindex "virus scanners" "command line interface"
34254 This is the keyword for the generic command line scanner interface. It can be
34255 used to attach virus scanners that are invoked from the shell. This scanner
34256 type takes 3 mandatory options:
34259 The full path and name of the scanner binary, with all command line options,
34260 and a placeholder (&`%s`&) for the directory to scan.
34263 A regular expression to match against the STDOUT and STDERR output of the
34264 virus scanner. If the expression matches, a virus was found. You must make
34265 absolutely sure that this expression matches on &"virus found"&. This is called
34266 the &"trigger"& expression.
34269 Another regular expression, containing exactly one pair of parentheses, to
34270 match the name of the virus found in the scanners output. This is called the
34271 &"name"& expression.
34274 For example, Sophos Sweep reports a virus on a line like this:
34276 Virus 'W32/Magistr-B' found in file ./those.bat
34278 For the trigger expression, we can match the phrase &"found in file"&. For the
34279 name expression, we want to extract the W32/Magistr-B string, so we can match
34280 for the single quotes left and right of it. Altogether, this makes the
34281 configuration setting:
34283 av_scanner = cmdline:\
34284 /path/to/sweep -ss -all -rec -archive %s:\
34285 found in file:'(.+)'
34288 .cindex "virus scanners" "DrWeb"
34289 The DrWeb daemon scanner (&url(https://www.sald.ru/)) interface
34291 either a full path to a UNIX socket,
34292 or host and port specifiers separated by white space.
34293 The host may be a name or an IP address; the port is either a
34294 single number or a pair of numbers with a dash between.
34297 av_scanner = drweb:/var/run/drwebd.sock
34298 av_scanner = drweb:192.168.2.20 31337
34300 If you omit the argument, the default path &_/usr/local/drweb/run/drwebd.sock_&
34301 is used. Thanks to Alex Miller for contributing the code for this scanner.
34304 .cindex "virus scanners" "f-protd"
34305 The f-protd scanner is accessed via HTTP over TCP.
34306 One argument is taken, being a space-separated hostname and port number
34310 av_scanner = f-protd:localhost 10200-10204
34312 If you omit the argument, the default values shown above are used.
34314 .vitem &%f-prot6d%&
34315 .cindex "virus scanners" "f-prot6d"
34316 The f-prot6d scanner is accessed using the FPSCAND protocol over TCP.
34317 One argument is taken, being a space-separated hostname and port number.
34320 av_scanner = f-prot6d:localhost 10200
34322 If you omit the argument, the default values show above are used.
34325 .cindex "virus scanners" "F-Secure"
34326 The F-Secure daemon scanner (&url(https://www.f-secure.com/)) takes one
34327 argument which is the path to a UNIX socket. For example:
34329 av_scanner = fsecure:/path/to/.fsav
34331 If no argument is given, the default is &_/var/run/.fsav_&. Thanks to Johan
34332 Thelmen for contributing the code for this scanner.
34334 .vitem &%kavdaemon%&
34335 .cindex "virus scanners" "Kaspersky"
34336 This is the scanner daemon of Kaspersky Version 4. This version of the
34337 Kaspersky scanner is outdated. Please upgrade (see &%aveserver%& above). This
34338 scanner type takes one option, which is the path to the daemon's UNIX socket.
34341 av_scanner = kavdaemon:/opt/AVP/AvpCtl
34343 The default path is &_/var/run/AvpCtl_&.
34346 .cindex "virus scanners" "mksd"
34347 This was a daemon type scanner that is aimed mainly at Polish users,
34348 though some documentation was available in English.
34349 The history can be shown at &url(https://en.wikipedia.org/wiki/Mks_vir)
34350 and this appears to be a candidate for removal from Exim, unless
34351 we are informed of other virus scanners which use the same protocol
34353 The only option for this scanner type is
34354 the maximum number of processes used simultaneously to scan the attachments,
34355 provided that mksd has
34356 been run with at least the same number of child processes. For example:
34358 av_scanner = mksd:2
34360 You can safely omit this option (the default value is 1).
34363 .cindex "virus scanners" "simple socket-connected"
34364 This is a general-purpose way of talking to simple scanner daemons
34365 running on the local machine.
34366 There are four options:
34367 an address (which may be an IP address and port, or the path of a Unix socket),
34368 a commandline to send (may include a single %s which will be replaced with
34369 the path to the mail file to be scanned),
34370 an RE to trigger on from the returned data,
34371 and an RE to extract malware_name from the returned data.
34374 av_scanner = sock:127.0.0.1 6001:%s:(SPAM|VIRUS):(.*)$
34376 Note that surrounding whitespace is stripped from each option, meaning
34377 there is no way to specify a trailing newline.
34378 The socket specifier and both regular-expressions are required.
34379 Default for the commandline is &_%s\n_& (note this does have a trailing newline);
34380 specify an empty element to get this.
34383 .cindex "virus scanners" "Sophos and Sophie"
34384 Sophie is a daemon that uses Sophos' &%libsavi%& library to scan for viruses.
34385 You can get Sophie at &url(http://sophie.sourceforge.net/). The only option
34386 for this scanner type is the path to the UNIX socket that Sophie uses for
34387 client communication. For example:
34389 av_scanner = sophie:/tmp/sophie
34391 The default path is &_/var/run/sophie_&, so if you are using this, you can omit
34395 When &%av_scanner%& is correctly set, you can use the &%malware%& condition in
34396 the DATA ACL. &*Note*&: You cannot use the &%malware%& condition in the MIME
34399 The &%av_scanner%& option is expanded each time &%malware%& is called. This
34400 makes it possible to use different scanners. See further below for an example.
34401 The &%malware%& condition caches its results, so when you use it multiple times
34402 for the same message, the actual scanning process is only carried out once.
34403 However, using expandable items in &%av_scanner%& disables this caching, in
34404 which case each use of the &%malware%& condition causes a new scan of the
34407 The &%malware%& condition takes a right-hand argument that is expanded before
34408 use and taken as a list, slash-separated by default.
34409 The first element can then be one of
34412 &"true"&, &"*"&, or &"1"&, in which case the message is scanned for viruses.
34413 The condition succeeds if a virus was found, and fail otherwise. This is the
34416 &"false"& or &"0"& or an empty string, in which case no scanning is done and
34417 the condition fails immediately.
34419 A regular expression, in which case the message is scanned for viruses. The
34420 condition succeeds if a virus is found and its name matches the regular
34421 expression. This allows you to take special actions on certain types of virus.
34422 Note that &"/"& characters in the RE must be doubled due to the list-processing,
34423 unless the separator is changed (in the usual way &<<SECTlistsepchange>>&).
34426 You can append a &`defer_ok`& element to the &%malware%& argument list to accept
34427 messages even if there is a problem with the virus scanner.
34428 Otherwise, such a problem causes the ACL to defer.
34430 You can append a &`tmo=<val>`& element to the &%malware%& argument list to
34431 specify a non-default timeout. The default is two minutes.
34434 malware = * / defer_ok / tmo=10s
34436 A timeout causes the ACL to defer.
34438 .vindex "&$callout_address$&"
34439 When a connection is made to the scanner the expansion variable &$callout_address$&
34440 is set to record the actual address used.
34442 .vindex "&$malware_name$&"
34443 When a virus is found, the condition sets up an expansion variable called
34444 &$malware_name$& that contains the name of the virus. You can use it in a
34445 &%message%& modifier that specifies the error returned to the sender, and/or in
34448 Beware the interaction of Exim's &%message_size_limit%& with any size limits
34449 imposed by your anti-virus scanner.
34451 Here is a very simple scanning example:
34454 message = This message contains malware ($malware_name)
34456 The next example accepts messages when there is a problem with the scanner:
34458 deny malware = */defer_ok
34459 message = This message contains malware ($malware_name)
34461 The next example shows how to use an ACL variable to scan with both sophie and
34462 aveserver. It assumes you have set:
34464 av_scanner = $acl_m0
34466 in the main Exim configuration.
34468 deny set acl_m0 = sophie
34470 message = This message contains malware ($malware_name)
34472 deny set acl_m0 = aveserver
34474 message = This message contains malware ($malware_name)
34478 .section "Scanning with SpamAssassin and Rspamd" "SECTscanspamass"
34479 .cindex "content scanning" "for spam"
34480 .cindex "spam scanning"
34481 .cindex "SpamAssassin"
34483 The &%spam%& ACL condition calls SpamAssassin's &%spamd%& daemon to get a spam
34484 score and a report for the message.
34485 Support is also provided for Rspamd.
34487 For more information about installation and configuration of SpamAssassin or
34488 Rspamd refer to their respective websites at
34489 &url(https://spamassassin.apache.org/) and &url(https://www.rspamd.com/)
34491 SpamAssassin can be installed with CPAN by running:
34493 perl -MCPAN -e 'install Mail::SpamAssassin'
34495 SpamAssassin has its own set of configuration files. Please review its
34496 documentation to see how you can tweak it. The default installation should work
34499 .oindex "&%spamd_address%&"
34500 By default, SpamAssassin listens on 127.0.0.1, TCP port 783 and if you
34501 intend to use an instance running on the local host you do not need to set
34502 &%spamd_address%&. If you intend to use another host or port for SpamAssassin,
34503 you must set the &%spamd_address%& option in the global part of the Exim
34504 configuration as follows (example):
34506 spamd_address = 192.168.99.45 783
34508 The SpamAssassin protocol relies on a TCP half-close from the client.
34509 If your SpamAssassin client side is running a Linux system with an
34510 iptables firewall, consider setting
34511 &%net.netfilter.nf_conntrack_tcp_timeout_close_wait%& to at least the
34512 timeout, Exim uses when waiting for a response from the SpamAssassin
34513 server (currently defaulting to 120s). With a lower value the Linux
34514 connection tracking may consider your half-closed connection as dead too
34518 To use Rspamd (which by default listens on all local addresses
34520 you should add &%variant=rspamd%& after the address/port pair, for example:
34522 spamd_address = 127.0.0.1 11333 variant=rspamd
34525 As of version 2.60, &%SpamAssassin%& also supports communication over UNIX
34526 sockets. If you want to us these, supply &%spamd_address%& with an absolute
34527 filename instead of an address/port pair:
34529 spamd_address = /var/run/spamd_socket
34531 You can have multiple &%spamd%& servers to improve scalability. These can
34532 reside on other hardware reachable over the network. To specify multiple
34533 &%spamd%& servers, put multiple address/port pairs in the &%spamd_address%&
34534 option, separated with colons (the separator can be changed in the usual way &<<SECTlistsepchange>>&):
34536 spamd_address = 192.168.2.10 783 : \
34537 192.168.2.11 783 : \
34540 Up to 32 &%spamd%& servers are supported.
34541 When a server fails to respond to the connection attempt, all other
34542 servers are tried until one succeeds. If no server responds, the &%spam%&
34545 Unix and TCP socket specifications may be mixed in any order.
34546 Each element of the list is a list itself, space-separated by default
34547 and changeable in the usual way (&<<SECTlistsepchange>>&);
34548 take care to not double the separator.
34550 For TCP socket specifications a host name or IP (v4 or v6, but
34551 subject to list-separator quoting rules) address can be used,
34552 and the port can be one or a dash-separated pair.
34553 In the latter case, the range is tried in strict order.
34555 Elements after the first for Unix sockets, or second for TCP socket,
34557 The supported options are:
34559 pri=<priority> Selection priority
34560 weight=<value> Selection bias
34561 time=<start>-<end> Use only between these times of day
34562 retry=<timespec> Retry on connect fail
34563 tmo=<timespec> Connection time limit
34564 variant=rspamd Use Rspamd rather than SpamAssassin protocol
34567 The &`pri`& option specifies a priority for the server within the list,
34568 higher values being tried first.
34569 The default priority is 1.
34571 The &`weight`& option specifies a selection bias.
34572 Within a priority set
34573 servers are queried in a random fashion, weighted by this value.
34574 The default value for selection bias is 1.
34576 Time specifications for the &`time`& option are <hour>.<minute>.<second>
34577 in the local time zone; each element being one or more digits.
34578 Either the seconds or both minutes and seconds, plus the leading &`.`&
34579 characters, may be omitted and will be taken as zero.
34581 Timeout specifications for the &`retry`& and &`tmo`& options
34582 are the usual Exim time interval standard, e.g. &`20s`& or &`1m`&.
34584 The &`tmo`& option specifies an overall timeout for communication.
34585 The default value is two minutes.
34587 The &`retry`& option specifies a time after which a single retry for
34588 a failed connect is made.
34589 The default is to not retry.
34591 The &%spamd_address%& variable is expanded before use if it starts with
34592 a dollar sign. In this case, the expansion may return a string that is
34593 used as the list so that multiple spamd servers can be the result of an
34596 .vindex "&$callout_address$&"
34597 When a connection is made to the server the expansion variable &$callout_address$&
34598 is set to record the actual address used.
34600 .section "Calling SpamAssassin from an Exim ACL" "SECID206"
34601 Here is a simple example of the use of the &%spam%& condition in a DATA ACL:
34604 message = This message was classified as SPAM
34606 The right-hand side of the &%spam%& condition specifies a name. This is
34607 relevant if you have set up multiple SpamAssassin profiles. If you do not want
34608 to scan using a specific profile, but rather use the SpamAssassin system-wide
34609 default profile, you can scan for an unknown name, or simply use &"nobody"&.
34610 Rspamd does not use this setting. However, you must put something on the
34613 The name allows you to use per-domain or per-user antispam profiles in
34614 principle, but this is not straightforward in practice, because a message may
34615 have multiple recipients, not necessarily all in the same domain. Because the
34616 &%spam%& condition has to be called from a DATA-time ACL in order to be able to
34617 read the contents of the message, the variables &$local_part$& and &$domain$&
34619 Careful enforcement of single-recipient messages
34620 (e.g. by responding with defer in the recipient ACL for all recipients
34622 or the use of PRDR,
34623 .cindex "PRDR" "use for per-user SpamAssassin profiles"
34624 are needed to use this feature.
34626 The right-hand side of the &%spam%& condition is expanded before being used, so
34627 you can put lookups or conditions there. When the right-hand side evaluates to
34628 &"0"& or &"false"&, no scanning is done and the condition fails immediately.
34631 Scanning with SpamAssassin uses a lot of resources. If you scan every message,
34632 large ones may cause significant performance degradation. As most spam messages
34633 are quite small, it is recommended that you do not scan the big ones. For
34636 deny condition = ${if < {$message_size}{10K}}
34638 message = This message was classified as SPAM
34641 The &%spam%& condition returns true if the threshold specified in the user's
34642 SpamAssassin profile has been matched or exceeded. If you want to use the
34643 &%spam%& condition for its side effects (see the variables below), you can make
34644 it always return &"true"& by appending &`:true`& to the username.
34646 .cindex "spam scanning" "returned variables"
34647 When the &%spam%& condition is run, it sets up a number of expansion
34649 Except for &$spam_report$&,
34650 these variables are saved with the received message so are
34651 available for use at delivery time.
34654 .vitem &$spam_score$&
34655 The spam score of the message, for example, &"3.4"& or &"30.5"&. This is useful
34656 for inclusion in log or reject messages.
34658 .vitem &$spam_score_int$&
34659 The spam score of the message, multiplied by ten, as an integer value. For
34660 example &"34"& or &"305"&. It may appear to disagree with &$spam_score$&
34661 because &$spam_score$& is rounded and &$spam_score_int$& is truncated.
34662 The integer value is useful for numeric comparisons in conditions.
34664 .vitem &$spam_bar$&
34665 A string consisting of a number of &"+"& or &"-"& characters, representing the
34666 integer part of the spam score value. A spam score of 4.4 would have a
34667 &$spam_bar$& value of &"++++"&. This is useful for inclusion in warning
34668 headers, since MUAs can match on such strings. The maximum length of the
34669 spam bar is 50 characters.
34671 .vitem &$spam_report$&
34672 A multiline text table, containing the full SpamAssassin report for the
34673 message. Useful for inclusion in headers or reject messages.
34674 This variable is only usable in a DATA-time ACL.
34675 Beware that SpamAssassin may return non-ASCII characters, especially
34676 when running in country-specific locales, which are not legal
34677 unencoded in headers.
34679 .vitem &$spam_action$&
34680 For SpamAssassin either 'reject' or 'no action' depending on the
34681 spam score versus threshold.
34682 For Rspamd, the recommended action.
34686 The &%spam%& condition caches its results unless expansion in
34687 spamd_address was used. If you call it again with the same user name, it
34688 does not scan again, but rather returns the same values as before.
34690 The &%spam%& condition returns DEFER if there is any error while running
34691 the message through SpamAssassin or if the expansion of spamd_address
34692 failed. If you want to treat DEFER as FAIL (to pass on to the next ACL
34693 statement block), append &`/defer_ok`& to the right-hand side of the
34694 spam condition, like this:
34696 deny spam = joe/defer_ok
34697 message = This message was classified as SPAM
34699 This causes messages to be accepted even if there is a problem with &%spamd%&.
34701 Here is a longer, commented example of the use of the &%spam%&
34704 # put headers in all messages (no matter if spam or not)
34705 warn spam = nobody:true
34706 add_header = X-Spam-Score: $spam_score ($spam_bar)
34707 add_header = X-Spam-Report: $spam_report
34709 # add second subject line with *SPAM* marker when message
34710 # is over threshold
34712 add_header = Subject: *SPAM* $h_Subject:
34714 # reject spam at high scores (> 12)
34715 deny spam = nobody:true
34716 condition = ${if >{$spam_score_int}{120}{1}{0}}
34717 message = This message scored $spam_score spam points.
34722 .section "Scanning MIME parts" "SECTscanmimepart"
34723 .cindex "content scanning" "MIME parts"
34724 .cindex "MIME content scanning"
34725 .oindex "&%acl_smtp_mime%&"
34726 .oindex "&%acl_not_smtp_mime%&"
34727 The &%acl_smtp_mime%& global option specifies an ACL that is called once for
34728 each MIME part of an SMTP message, including multipart types, in the sequence
34729 of their position in the message. Similarly, the &%acl_not_smtp_mime%& option
34730 specifies an ACL that is used for the MIME parts of non-SMTP messages. These
34731 options may both refer to the same ACL if you want the same processing in both
34734 These ACLs are called (possibly many times) just before the &%acl_smtp_data%&
34735 ACL in the case of an SMTP message, or just before the &%acl_not_smtp%& ACL in
34736 the case of a non-SMTP message. However, a MIME ACL is called only if the
34737 message contains a &'Content-Type:'& header line. When a call to a MIME
34738 ACL does not yield &"accept"&, ACL processing is aborted and the appropriate
34739 result code is sent to the client. In the case of an SMTP message, the
34740 &%acl_smtp_data%& ACL is not called when this happens.
34742 You cannot use the &%malware%& or &%spam%& conditions in a MIME ACL; these can
34743 only be used in the DATA or non-SMTP ACLs. However, you can use the &%regex%&
34744 condition to match against the raw MIME part. You can also use the
34745 &%mime_regex%& condition to match against the decoded MIME part (see section
34746 &<<SECTscanregex>>&).
34748 At the start of a MIME ACL, a number of variables are set from the header
34749 information for the relevant MIME part. These are described below. The contents
34750 of the MIME part are not by default decoded into a disk file except for MIME
34751 parts whose content-type is &"message/rfc822"&. If you want to decode a MIME
34752 part into a disk file, you can use the &%decode%& condition. The general
34755 &`decode = [/`&<&'path'&>&`/]`&<&'filename'&>
34757 The right hand side is expanded before use. After expansion,
34761 &"0"& or &"false"&, in which case no decoding is done.
34763 The string &"default"&. In that case, the file is put in the temporary
34764 &"default"& directory <&'spool_directory'&>&_/scan/_&<&'message_id'&>&_/_& with
34765 a sequential filename consisting of the message id and a sequence number. The
34766 full path and name is available in &$mime_decoded_filename$& after decoding.
34768 A full path name starting with a slash. If the full name is an existing
34769 directory, it is used as a replacement for the default directory. The filename
34770 is then sequentially assigned. If the path does not exist, it is used as
34771 the full path and filename.
34773 If the string does not start with a slash, it is used as the
34774 filename, and the default path is then used.
34776 The &%decode%& condition normally succeeds. It is only false for syntax
34777 errors or unusual circumstances such as memory shortages. You can easily decode
34778 a file with its original, proposed filename using
34780 decode = $mime_filename
34782 However, you should keep in mind that &$mime_filename$& might contain
34783 anything. If you place files outside of the default path, they are not
34784 automatically unlinked.
34786 For RFC822 attachments (these are messages attached to messages, with a
34787 content-type of &"message/rfc822"&), the ACL is called again in the same manner
34788 as for the primary message, only that the &$mime_is_rfc822$& expansion
34789 variable is set (see below). Attached messages are always decoded to disk
34790 before being checked, and the files are unlinked once the check is done.
34792 The MIME ACL supports the &%regex%& and &%mime_regex%& conditions. These can be
34793 used to match regular expressions against raw and decoded MIME parts,
34794 respectively. They are described in section &<<SECTscanregex>>&.
34796 .cindex "MIME content scanning" "returned variables"
34797 The following list describes all expansion variables that are
34798 available in the MIME ACL:
34801 .vitem &$mime_anomaly_level$& &&&
34802 &$mime_anomaly_text$&
34803 .vindex &$mime_anomaly_level$&
34804 .vindex &$mime_anomaly_text$&
34805 If there are problems decoding, these variables contain information on
34806 the detected issue.
34808 .vitem &$mime_boundary$&
34809 .vindex &$mime_boundary$&
34810 If the current part is a multipart (see &$mime_is_multipart$& below), it should
34811 have a boundary string, which is stored in this variable. If the current part
34812 has no boundary parameter in the &'Content-Type:'& header, this variable
34813 contains the empty string.
34815 .vitem &$mime_charset$&
34816 .vindex &$mime_charset$&
34817 This variable contains the character set identifier, if one was found in the
34818 &'Content-Type:'& header. Examples for charset identifiers are:
34824 Please note that this value is not normalized, so you should do matches
34825 case-insensitively.
34827 .vitem &$mime_content_description$&
34828 .vindex &$mime_content_description$&
34829 This variable contains the normalized content of the &'Content-Description:'&
34830 header. It can contain a human-readable description of the parts content. Some
34831 implementations repeat the filename for attachments here, but they are usually
34832 only used for display purposes.
34834 .vitem &$mime_content_disposition$&
34835 .vindex &$mime_content_disposition$&
34836 This variable contains the normalized content of the &'Content-Disposition:'&
34837 header. You can expect strings like &"attachment"& or &"inline"& here.
34839 .vitem &$mime_content_id$&
34840 .vindex &$mime_content_id$&
34841 This variable contains the normalized content of the &'Content-ID:'& header.
34842 This is a unique ID that can be used to reference a part from another part.
34844 .vitem &$mime_content_size$&
34845 .vindex &$mime_content_size$&
34846 This variable is set only after the &%decode%& modifier (see above) has been
34847 successfully run. It contains the size of the decoded part in kilobytes. The
34848 size is always rounded up to full kilobytes, so only a completely empty part
34849 has a &$mime_content_size$& of zero.
34851 .vitem &$mime_content_transfer_encoding$&
34852 .vindex &$mime_content_transfer_encoding$&
34853 This variable contains the normalized content of the
34854 &'Content-transfer-encoding:'& header. This is a symbolic name for an encoding
34855 type. Typical values are &"base64"& and &"quoted-printable"&.
34857 .vitem &$mime_content_type$&
34858 .vindex &$mime_content_type$&
34859 If the MIME part has a &'Content-Type:'& header, this variable contains its
34860 value, lowercased, and without any options (like &"name"& or &"charset"&). Here
34861 are some examples of popular MIME types, as they may appear in this variable:
34865 application/octet-stream
34869 If the MIME part has no &'Content-Type:'& header, this variable contains the
34872 .vitem &$mime_decoded_filename$&
34873 .vindex &$mime_decoded_filename$&
34874 This variable is set only after the &%decode%& modifier (see above) has been
34875 successfully run. It contains the full path and filename of the file
34876 containing the decoded data.
34881 .vitem &$mime_filename$&
34882 .vindex &$mime_filename$&
34883 This is perhaps the most important of the MIME variables. It contains a
34884 proposed filename for an attachment, if one was found in either the
34885 &'Content-Type:'& or &'Content-Disposition:'& headers. The filename will be
34888 decoded, but no additional sanity checks are done.
34890 found, this variable contains the empty string.
34892 .vitem &$mime_is_coverletter$&
34893 .vindex &$mime_is_coverletter$&
34894 This variable attempts to differentiate the &"cover letter"& of an e-mail from
34895 attached data. It can be used to clamp down on flashy or unnecessarily encoded
34896 content in the cover letter, while not restricting attachments at all.
34898 The variable contains 1 (true) for a MIME part believed to be part of the
34899 cover letter, and 0 (false) for an attachment. At present, the algorithm is as
34903 The outermost MIME part of a message is always a cover letter.
34906 If a multipart/alternative or multipart/related MIME part is a cover letter,
34907 so are all MIME subparts within that multipart.
34910 If any other multipart is a cover letter, the first subpart is a cover letter,
34911 and the rest are attachments.
34914 All parts contained within an attachment multipart are attachments.
34917 As an example, the following will ban &"HTML mail"& (including that sent with
34918 alternative plain text), while allowing HTML files to be attached. HTML
34919 coverletter mail attached to non-HTML coverletter mail will also be allowed:
34921 deny !condition = $mime_is_rfc822
34922 condition = $mime_is_coverletter
34923 condition = ${if eq{$mime_content_type}{text/html}{1}{0}}
34924 message = HTML mail is not accepted here
34927 .vitem &$mime_is_multipart$&
34928 .vindex &$mime_is_multipart$&
34929 This variable has the value 1 (true) when the current part has the main type
34930 &"multipart"&, for example, &"multipart/alternative"& or &"multipart/mixed"&.
34931 Since multipart entities only serve as containers for other parts, you may not
34932 want to carry out specific actions on them.
34934 .vitem &$mime_is_rfc822$&
34935 .vindex &$mime_is_rfc822$&
34936 This variable has the value 1 (true) if the current part is not a part of the
34937 checked message itself, but part of an attached message. Attached message
34938 decoding is fully recursive.
34940 .vitem &$mime_part_count$&
34941 .vindex &$mime_part_count$&
34942 This variable is a counter that is raised for each processed MIME part. It
34943 starts at zero for the very first part (which is usually a multipart). The
34944 counter is per-message, so it is reset when processing RFC822 attachments (see
34945 &$mime_is_rfc822$&). The counter stays set after &%acl_smtp_mime%& is
34946 complete, so you can use it in the DATA ACL to determine the number of MIME
34947 parts of a message. For non-MIME messages, this variable contains the value -1.
34952 .section "Scanning with regular expressions" "SECTscanregex"
34953 .cindex "content scanning" "with regular expressions"
34954 .cindex "regular expressions" "content scanning with"
34955 You can specify your own custom regular expression matches on the full body of
34956 the message, or on individual MIME parts.
34958 The &%regex%& condition takes one or more regular expressions as arguments and
34959 matches them against the full message (when called in the DATA ACL) or a raw
34960 MIME part (when called in the MIME ACL). The &%regex%& condition matches
34961 linewise, with a maximum line length of 32K characters. That means you cannot
34962 have multiline matches with the &%regex%& condition.
34964 The &%mime_regex%& condition can be called only in the MIME ACL. It matches up
34965 to 32K of decoded content (the whole content at once, not linewise). If the
34966 part has not been decoded with the &%decode%& modifier earlier in the ACL, it
34967 is decoded automatically when &%mime_regex%& is executed (using default path
34968 and filename values). If the decoded data is larger than 32K, only the first
34969 32K characters are checked.
34971 The regular expressions are passed as a colon-separated list. To include a
34972 literal colon, you must double it. Since the whole right-hand side string is
34973 expanded before being used, you must also escape dollar signs and backslashes
34974 with more backslashes, or use the &`\N`& facility to disable expansion.
34975 Here is a simple example that contains two regular expressions:
34977 deny regex = [Mm]ortgage : URGENT BUSINESS PROPOSAL
34978 message = contains blacklisted regex ($regex_match_string)
34980 The conditions returns true if any one of the regular expressions matches. The
34981 &$regex_match_string$& expansion variable is then set up and contains the
34982 matching regular expression.
34983 The expansion variables &$regex1$& &$regex2$& etc
34984 are set to any substrings captured by the regular expression.
34986 &*Warning*&: With large messages, these conditions can be fairly
34994 . ////////////////////////////////////////////////////////////////////////////
34995 . ////////////////////////////////////////////////////////////////////////////
34997 .chapter "Adding a local scan function to Exim" "CHAPlocalscan" &&&
34998 "Local scan function"
34999 .scindex IIDlosca "&[local_scan()]& function" "description of"
35000 .cindex "customizing" "input scan using C function"
35001 .cindex "policy control" "by local scan function"
35002 In these days of email worms, viruses, and ever-increasing spam, some sites
35003 want to apply a lot of checking to messages before accepting them.
35005 The content scanning extension (chapter &<<CHAPexiscan>>&) has facilities for
35006 passing messages to external virus and spam scanning software. You can also do
35007 a certain amount in Exim itself through string expansions and the &%condition%&
35008 condition in the ACL that runs after the SMTP DATA command or the ACL for
35009 non-SMTP messages (see chapter &<<CHAPACL>>&), but this has its limitations.
35011 To allow for further customization to a site's own requirements, there is the
35012 possibility of linking Exim with a private message scanning function, written
35013 in C. If you want to run code that is written in something other than C, you
35014 can of course use a little C stub to call it.
35016 The local scan function is run once for every incoming message, at the point
35017 when Exim is just about to accept the message.
35018 It can therefore be used to control non-SMTP messages from local processes as
35019 well as messages arriving via SMTP.
35021 Exim applies a timeout to calls of the local scan function, and there is an
35022 option called &%local_scan_timeout%& for setting it. The default is 5 minutes.
35023 Zero means &"no timeout"&.
35024 Exim also sets up signal handlers for SIGSEGV, SIGILL, SIGFPE, and SIGBUS
35025 before calling the local scan function, so that the most common types of crash
35026 are caught. If the timeout is exceeded or one of those signals is caught, the
35027 incoming message is rejected with a temporary error if it is an SMTP message.
35028 For a non-SMTP message, the message is dropped and Exim ends with a non-zero
35029 code. The incident is logged on the main and reject logs.
35033 .section "Building Exim to use a local scan function" "SECID207"
35034 .cindex "&[local_scan()]& function" "building Exim to use"
35035 To make use of the local scan function feature, you must tell Exim where your
35036 function is before building Exim, by setting
35037 both HAVE_LOCAL_SCAN and
35038 LOCAL_SCAN_SOURCE in your
35039 &_Local/Makefile_&. A recommended place to put it is in the &_Local_&
35040 directory, so you might set
35042 HAVE_LOCAL_SCAN=yes
35043 LOCAL_SCAN_SOURCE=Local/local_scan.c
35045 for example. The function must be called &[local_scan()]&;
35046 the source file(s) for it should first #define LOCAL_SCAN
35047 and then #include "local_scan.h".
35049 Exim after it has received a message, when the success return code is about to
35050 be sent. This is after all the ACLs have been run. The return code from your
35051 function controls whether the message is actually accepted or not. There is a
35052 commented template function (that just accepts the message) in the file
35053 _src/local_scan.c_.
35055 If you want to make use of Exim's runtime configuration file to set options
35056 for your &[local_scan()]& function, you must also set
35058 LOCAL_SCAN_HAS_OPTIONS=yes
35060 in &_Local/Makefile_& (see section &<<SECTconoptloc>>& below).
35065 .section "API for local_scan()" "SECTapiforloc"
35066 .cindex "&[local_scan()]& function" "API description"
35067 .cindex &%dlfunc%& "API description"
35068 You must include this line near the start of your code:
35071 #include "local_scan.h"
35073 This header file defines a number of variables and other values, and the
35074 prototype for the function itself. Exim is coded to use unsigned char values
35075 almost exclusively, and one of the things this header defines is a shorthand
35076 for &`unsigned char`& called &`uschar`&.
35077 It also makes available the following macro definitions, to simplify casting character
35078 strings and pointers to character strings:
35080 #define CS (char *)
35081 #define CCS (const char *)
35082 #define CSS (char **)
35083 #define US (unsigned char *)
35084 #define CUS (const unsigned char *)
35085 #define USS (unsigned char **)
35087 The function prototype for &[local_scan()]& is:
35089 extern int local_scan(int fd, uschar **return_text);
35091 The arguments are as follows:
35094 &%fd%& is a file descriptor for the file that contains the body of the message
35095 (the -D file). The file is open for reading and writing, but updating it is not
35096 recommended. &*Warning*&: You must &'not'& close this file descriptor.
35098 The descriptor is positioned at character 19 of the file, which is the first
35099 character of the body itself, because the first 19 characters are the message
35100 id followed by &`-D`& and a newline. If you rewind the file, you should use the
35101 macro SPOOL_DATA_START_OFFSET to reset to the start of the data, just in
35102 case this changes in some future version.
35104 &%return_text%& is an address which you can use to return a pointer to a text
35105 string at the end of the function. The value it points to on entry is NULL.
35108 The function must return an &%int%& value which is one of the following macros:
35111 .vitem &`LOCAL_SCAN_ACCEPT`&
35112 .vindex "&$local_scan_data$&"
35113 The message is accepted. If you pass back a string of text, it is saved with
35114 the message, and made available in the variable &$local_scan_data$&. No
35115 newlines are permitted (if there are any, they are turned into spaces) and the
35116 maximum length of text is 1000 characters.
35118 .vitem &`LOCAL_SCAN_ACCEPT_FREEZE`&
35119 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
35120 queued without immediate delivery, and is frozen.
35122 .vitem &`LOCAL_SCAN_ACCEPT_QUEUE`&
35123 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
35124 queued without immediate delivery.
35126 .vitem &`LOCAL_SCAN_REJECT`&
35127 The message is rejected; the returned text is used as an error message which is
35128 passed back to the sender and which is also logged. Newlines are permitted &--
35129 they cause a multiline response for SMTP rejections, but are converted to
35130 &`\n`& in log lines. If no message is given, &"Administrative prohibition"& is
35133 .vitem &`LOCAL_SCAN_TEMPREJECT`&
35134 The message is temporarily rejected; the returned text is used as an error
35135 message as for LOCAL_SCAN_REJECT. If no message is given, &"Temporary local
35138 .vitem &`LOCAL_SCAN_REJECT_NOLOGHDR`&
35139 This behaves as LOCAL_SCAN_REJECT, except that the header of the rejected
35140 message is not written to the reject log. It has the effect of unsetting the
35141 &%rejected_header%& log selector for just this rejection. If
35142 &%rejected_header%& is already unset (see the discussion of the
35143 &%log_selection%& option in section &<<SECTlogselector>>&), this code is the
35144 same as LOCAL_SCAN_REJECT.
35146 .vitem &`LOCAL_SCAN_TEMPREJECT_NOLOGHDR`&
35147 This code is a variation of LOCAL_SCAN_TEMPREJECT in the same way that
35148 LOCAL_SCAN_REJECT_NOLOGHDR is a variation of LOCAL_SCAN_REJECT.
35151 If the message is not being received by interactive SMTP, rejections are
35152 reported by writing to &%stderr%& or by sending an email, as configured by the
35153 &%-oe%& command line options.
35157 .section "Configuration options for local_scan()" "SECTconoptloc"
35158 .cindex "&[local_scan()]& function" "configuration options"
35159 It is possible to have option settings in the main configuration file
35160 that set values in static variables in the &[local_scan()]& module. If you
35161 want to do this, you must have the line
35163 LOCAL_SCAN_HAS_OPTIONS=yes
35165 in your &_Local/Makefile_& when you build Exim. (This line is in
35166 &_OS/Makefile-Default_&, commented out). Then, in the &[local_scan()]& source
35167 file, you must define static variables to hold the option values, and a table
35170 The table must be a vector called &%local_scan_options%&, of type
35171 &`optionlist`&. Each entry is a triplet, consisting of a name, an option type,
35172 and a pointer to the variable that holds the value. The entries must appear in
35173 alphabetical order. Following &%local_scan_options%& you must also define a
35174 variable called &%local_scan_options_count%& that contains the number of
35175 entries in the table. Here is a short example, showing two kinds of option:
35177 static int my_integer_option = 42;
35178 static uschar *my_string_option = US"a default string";
35180 optionlist local_scan_options[] = {
35181 { "my_integer", opt_int, &my_integer_option },
35182 { "my_string", opt_stringptr, &my_string_option }
35185 int local_scan_options_count =
35186 sizeof(local_scan_options)/sizeof(optionlist);
35188 The values of the variables can now be changed from Exim's runtime
35189 configuration file by including a local scan section as in this example:
35193 my_string = some string of text...
35195 The available types of option data are as follows:
35198 .vitem &*opt_bool*&
35199 This specifies a boolean (true/false) option. The address should point to a
35200 variable of type &`BOOL`&, which will be set to TRUE or FALSE, which are macros
35201 that are defined as &"1"& and &"0"&, respectively. If you want to detect
35202 whether such a variable has been set at all, you can initialize it to
35203 TRUE_UNSET. (BOOL variables are integers underneath, so can hold more than two
35206 .vitem &*opt_fixed*&
35207 This specifies a fixed point number, such as is used for load averages.
35208 The address should point to a variable of type &`int`&. The value is stored
35209 multiplied by 1000, so, for example, 1.4142 is truncated and stored as 1414.
35212 This specifies an integer; the address should point to a variable of type
35213 &`int`&. The value may be specified in any of the integer formats accepted by
35216 .vitem &*opt_mkint*&
35217 This is the same as &%opt_int%&, except that when such a value is output in a
35218 &%-bP%& listing, if it is an exact number of kilobytes or megabytes, it is
35219 printed with the suffix K or M.
35221 .vitem &*opt_octint*&
35222 This also specifies an integer, but the value is always interpreted as an
35223 octal integer, whether or not it starts with the digit zero, and it is
35224 always output in octal.
35226 .vitem &*opt_stringptr*&
35227 This specifies a string value; the address must be a pointer to a
35228 variable that points to a string (for example, of type &`uschar *`&).
35230 .vitem &*opt_time*&
35231 This specifies a time interval value. The address must point to a variable of
35232 type &`int`&. The value that is placed there is a number of seconds.
35235 If the &%-bP%& command line option is followed by &`local_scan`&, Exim prints
35236 out the values of all the &[local_scan()]& options.
35240 .section "Available Exim variables" "SECID208"
35241 .cindex "&[local_scan()]& function" "available Exim variables"
35242 The header &_local_scan.h_& gives you access to a number of C variables. These
35243 are the only ones that are guaranteed to be maintained from release to release.
35244 Note, however, that you can obtain the value of any Exim expansion variable,
35245 including &$recipients$&, by calling &'expand_string()'&. The exported
35246 C variables are as follows:
35249 .vitem &*int&~body_linecount*&
35250 This variable contains the number of lines in the message's body.
35251 It is not valid if the &%spool_wireformat%& option is used.
35253 .vitem &*int&~body_zerocount*&
35254 This variable contains the number of binary zero bytes in the message's body.
35255 It is not valid if the &%spool_wireformat%& option is used.
35257 .vitem &*unsigned&~int&~debug_selector*&
35258 This variable is set to zero when no debugging is taking place. Otherwise, it
35259 is a bitmap of debugging selectors. Two bits are identified for use in
35260 &[local_scan()]&; they are defined as macros:
35263 The &`D_v`& bit is set when &%-v%& was present on the command line. This is a
35264 testing option that is not privileged &-- any caller may set it. All the
35265 other selector bits can be set only by admin users.
35268 The &`D_local_scan`& bit is provided for use by &[local_scan()]&; it is set
35269 by the &`+local_scan`& debug selector. It is not included in the default set
35273 Thus, to write to the debugging output only when &`+local_scan`& has been
35274 selected, you should use code like this:
35276 if ((debug_selector & D_local_scan) != 0)
35277 debug_printf("xxx", ...);
35279 .vitem &*uschar&~*expand_string_message*&
35280 After a failing call to &'expand_string()'& (returned value NULL), the
35281 variable &%expand_string_message%& contains the error message, zero-terminated.
35283 .vitem &*header_line&~*header_list*&
35284 A pointer to a chain of header lines. The &%header_line%& structure is
35287 .vitem &*header_line&~*header_last*&
35288 A pointer to the last of the header lines.
35290 .vitem &*const&~uschar&~*headers_charset*&
35291 The value of the &%headers_charset%& configuration option.
35293 .vitem &*BOOL&~host_checking*&
35294 This variable is TRUE during a host checking session that is initiated by the
35295 &%-bh%& command line option.
35297 .vitem &*uschar&~*interface_address*&
35298 The IP address of the interface that received the message, as a string. This
35299 is NULL for locally submitted messages.
35301 .vitem &*int&~interface_port*&
35302 The port on which this message was received. When testing with the &%-bh%&
35303 command line option, the value of this variable is -1 unless a port has been
35304 specified via the &%-oMi%& option.
35306 .vitem &*uschar&~*message_id*&
35307 This variable contains Exim's message id for the incoming message (the value of
35308 &$message_exim_id$&) as a zero-terminated string.
35310 .vitem &*uschar&~*received_protocol*&
35311 The name of the protocol by which the message was received.
35313 .vitem &*int&~recipients_count*&
35314 The number of accepted recipients.
35316 .vitem &*recipient_item&~*recipients_list*&
35317 .cindex "recipient" "adding in local scan"
35318 .cindex "recipient" "removing in local scan"
35319 The list of accepted recipients, held in a vector of length
35320 &%recipients_count%&. The &%recipient_item%& structure is discussed below. You
35321 can add additional recipients by calling &'receive_add_recipient()'& (see
35322 below). You can delete recipients by removing them from the vector and
35323 adjusting the value in &%recipients_count%&. In particular, by setting
35324 &%recipients_count%& to zero you remove all recipients. If you then return the
35325 value &`LOCAL_SCAN_ACCEPT`&, the message is accepted, but immediately
35326 blackholed. To replace the recipients, you can set &%recipients_count%& to zero
35327 and then call &'receive_add_recipient()'& as often as needed.
35329 .vitem &*uschar&~*sender_address*&
35330 The envelope sender address. For bounce messages this is the empty string.
35332 .vitem &*uschar&~*sender_host_address*&
35333 The IP address of the sending host, as a string. This is NULL for
35334 locally-submitted messages.
35336 .vitem &*uschar&~*sender_host_authenticated*&
35337 The name of the authentication mechanism that was used, or NULL if the message
35338 was not received over an authenticated SMTP connection.
35340 .vitem &*uschar&~*sender_host_name*&
35341 The name of the sending host, if known.
35343 .vitem &*int&~sender_host_port*&
35344 The port on the sending host.
35346 .vitem &*BOOL&~smtp_input*&
35347 This variable is TRUE for all SMTP input, including BSMTP.
35349 .vitem &*BOOL&~smtp_batched_input*&
35350 This variable is TRUE for BSMTP input.
35352 .vitem &*int&~store_pool*&
35353 The contents of this variable control which pool of memory is used for new
35354 requests. See section &<<SECTmemhanloc>>& for details.
35358 .section "Structure of header lines" "SECID209"
35359 The &%header_line%& structure contains the members listed below.
35360 You can add additional header lines by calling the &'header_add()'& function
35361 (see below). You can cause header lines to be ignored (deleted) by setting
35366 .vitem &*struct&~header_line&~*next*&
35367 A pointer to the next header line, or NULL for the last line.
35369 .vitem &*int&~type*&
35370 A code identifying certain headers that Exim recognizes. The codes are printing
35371 characters, and are documented in chapter &<<CHAPspool>>& of this manual.
35372 Notice in particular that any header line whose type is * is not transmitted
35373 with the message. This flagging is used for header lines that have been
35374 rewritten, or are to be removed (for example, &'Envelope-sender:'& header
35375 lines.) Effectively, * means &"deleted"&.
35377 .vitem &*int&~slen*&
35378 The number of characters in the header line, including the terminating and any
35381 .vitem &*uschar&~*text*&
35382 A pointer to the text of the header. It always ends with a newline, followed by
35383 a zero byte. Internal newlines are preserved.
35388 .section "Structure of recipient items" "SECID210"
35389 The &%recipient_item%& structure contains these members:
35392 .vitem &*uschar&~*address*&
35393 This is a pointer to the recipient address as it was received.
35395 .vitem &*int&~pno*&
35396 This is used in later Exim processing when top level addresses are created by
35397 the &%one_time%& option. It is not relevant at the time &[local_scan()]& is run
35398 and must always contain -1 at this stage.
35400 .vitem &*uschar&~*errors_to*&
35401 If this value is not NULL, bounce messages caused by failing to deliver to the
35402 recipient are sent to the address it contains. In other words, it overrides the
35403 envelope sender for this one recipient. (Compare the &%errors_to%& generic
35404 router option.) If a &[local_scan()]& function sets an &%errors_to%& field to
35405 an unqualified address, Exim qualifies it using the domain from
35406 &%qualify_recipient%&. When &[local_scan()]& is called, the &%errors_to%& field
35407 is NULL for all recipients.
35412 .section "Available Exim functions" "SECID211"
35413 .cindex "&[local_scan()]& function" "available Exim functions"
35414 The header &_local_scan.h_& gives you access to a number of Exim functions.
35415 These are the only ones that are guaranteed to be maintained from release to
35419 .vitem "&*pid_t&~child_open(uschar&~**argv,&~uschar&~**envp,&~int&~newumask,&&&
35420 &~int&~*infdptr,&~int&~*outfdptr, &~&~BOOL&~make_leader)*&"
35422 This function creates a child process that runs the command specified by
35423 &%argv%&. The environment for the process is specified by &%envp%&, which can
35424 be NULL if no environment variables are to be passed. A new umask is supplied
35425 for the process in &%newumask%&.
35427 Pipes to the standard input and output of the new process are set up
35428 and returned to the caller via the &%infdptr%& and &%outfdptr%& arguments. The
35429 standard error is cloned to the standard output. If there are any file
35430 descriptors &"in the way"& in the new process, they are closed. If the final
35431 argument is TRUE, the new process is made into a process group leader.
35433 The function returns the pid of the new process, or -1 if things go wrong.
35435 .vitem &*int&~child_close(pid_t&~pid,&~int&~timeout)*&
35436 This function waits for a child process to terminate, or for a timeout (in
35437 seconds) to expire. A timeout value of zero means wait as long as it takes. The
35438 return value is as follows:
35443 The process terminated by a normal exit and the value is the process
35449 The process was terminated by a signal and the value is the negation of the
35455 The process timed out.
35459 The was some other error in wait(); &%errno%& is still set.
35462 .vitem &*pid_t&~child_open_exim(int&~*fd)*&
35463 This function provide you with a means of submitting a new message to
35464 Exim. (Of course, you can also call &_/usr/sbin/sendmail_& yourself if you
35465 want, but this packages it all up for you.) The function creates a pipe,
35466 forks a subprocess that is running
35468 exim -t -oem -oi -f <>
35470 and returns to you (via the &`int *`& argument) a file descriptor for the pipe
35471 that is connected to the standard input. The yield of the function is the PID
35472 of the subprocess. You can then write a message to the file descriptor, with
35473 recipients in &'To:'&, &'Cc:'&, and/or &'Bcc:'& header lines.
35475 When you have finished, call &'child_close()'& to wait for the process to
35476 finish and to collect its ending status. A timeout value of zero is usually
35477 fine in this circumstance. Unless you have made a mistake with the recipient
35478 addresses, you should get a return code of zero.
35481 .vitem &*pid_t&~child_open_exim2(int&~*fd,&~uschar&~*sender,&~uschar&~&&&
35482 *sender_authentication)*&
35483 This function is a more sophisticated version of &'child_open()'&. The command
35486 &`exim -t -oem -oi -f `&&'sender'&&` -oMas `&&'sender_authentication'&
35488 The third argument may be NULL, in which case the &%-oMas%& option is omitted.
35491 .vitem &*void&~debug_printf(char&~*,&~...)*&
35492 This is Exim's debugging function, with arguments as for &'(printf()'&. The
35493 output is written to the standard error stream. If no debugging is selected,
35494 calls to &'debug_printf()'& have no effect. Normally, you should make calls
35495 conditional on the &`local_scan`& debug selector by coding like this:
35497 if ((debug_selector & D_local_scan) != 0)
35498 debug_printf("xxx", ...);
35501 .vitem &*uschar&~*expand_string(uschar&~*string)*&
35502 This is an interface to Exim's string expansion code. The return value is the
35503 expanded string, or NULL if there was an expansion failure.
35504 The C variable &%expand_string_message%& contains an error message after an
35505 expansion failure. If expansion does not change the string, the return value is
35506 the pointer to the input string. Otherwise, the return value points to a new
35507 block of memory that was obtained by a call to &'store_get()'&. See section
35508 &<<SECTmemhanloc>>& below for a discussion of memory handling.
35510 .vitem &*void&~header_add(int&~type,&~char&~*format,&~...)*&
35511 This function allows you to an add additional header line at the end of the
35512 existing ones. The first argument is the type, and should normally be a space
35513 character. The second argument is a format string and any number of
35514 substitution arguments as for &[sprintf()]&. You may include internal newlines
35515 if you want, and you must ensure that the string ends with a newline.
35517 .vitem "&*void&~header_add_at_position(BOOL&~after,&~uschar&~*name,&~&&&
35518 BOOL&~topnot,&~int&~type,&~char&~*format, &~&~...)*&"
35519 This function adds a new header line at a specified point in the header
35520 chain. The header itself is specified as for &'header_add()'&.
35522 If &%name%& is NULL, the new header is added at the end of the chain if
35523 &%after%& is true, or at the start if &%after%& is false. If &%name%& is not
35524 NULL, the header lines are searched for the first non-deleted header that
35525 matches the name. If one is found, the new header is added before it if
35526 &%after%& is false. If &%after%& is true, the new header is added after the
35527 found header and any adjacent subsequent ones with the same name (even if
35528 marked &"deleted"&). If no matching non-deleted header is found, the &%topnot%&
35529 option controls where the header is added. If it is true, addition is at the
35530 top; otherwise at the bottom. Thus, to add a header after all the &'Received:'&
35531 headers, or at the top if there are no &'Received:'& headers, you could use
35533 header_add_at_position(TRUE, US"Received", TRUE,
35534 ' ', "X-xxx: ...");
35536 Normally, there is always at least one non-deleted &'Received:'& header, but
35537 there may not be if &%received_header_text%& expands to an empty string.
35540 .vitem &*void&~header_remove(int&~occurrence,&~uschar&~*name)*&
35541 This function removes header lines. If &%occurrence%& is zero or negative, all
35542 occurrences of the header are removed. If occurrence is greater than zero, that
35543 particular instance of the header is removed. If no header(s) can be found that
35544 match the specification, the function does nothing.
35547 .vitem "&*BOOL&~header_testname(header_line&~*hdr,&~uschar&~*name,&~&&&
35548 int&~length,&~BOOL&~notdel)*&"
35549 This function tests whether the given header has the given name. It is not just
35550 a string comparison, because white space is permitted between the name and the
35551 colon. If the &%notdel%& argument is true, a false return is forced for all
35552 &"deleted"& headers; otherwise they are not treated specially. For example:
35554 if (header_testname(h, US"X-Spam", 6, TRUE)) ...
35556 .vitem &*uschar&~*lss_b64encode(uschar&~*cleartext,&~int&~length)*&
35557 .cindex "base64 encoding" "functions for &[local_scan()]& use"
35558 This function base64-encodes a string, which is passed by address and length.
35559 The text may contain bytes of any value, including zero. The result is passed
35560 back in dynamic memory that is obtained by calling &'store_get()'&. It is
35563 .vitem &*int&~lss_b64decode(uschar&~*codetext,&~uschar&~**cleartext)*&
35564 This function decodes a base64-encoded string. Its arguments are a
35565 zero-terminated base64-encoded string and the address of a variable that is set
35566 to point to the result, which is in dynamic memory. The length of the decoded
35567 string is the yield of the function. If the input is invalid base64 data, the
35568 yield is -1. A zero byte is added to the end of the output string to make it
35569 easy to interpret as a C string (assuming it contains no zeros of its own). The
35570 added zero byte is not included in the returned count.
35572 .vitem &*int&~lss_match_domain(uschar&~*domain,&~uschar&~*list)*&
35573 This function checks for a match in a domain list. Domains are always
35574 matched caselessly. The return value is one of the following:
35575 .itable none 0 0 2 15* left 85* left
35576 .irow &`OK`& "match succeeded"
35577 .irow &`FAIL`& "match failed"
35578 .irow &`DEFER`& "match deferred"
35580 DEFER is usually caused by some kind of lookup defer, such as the
35581 inability to contact a database.
35583 .vitem "&*int&~lss_match_local_part(uschar&~*localpart,&~uschar&~*list,&~&&&
35585 This function checks for a match in a local part list. The third argument
35586 controls case-sensitivity. The return values are as for
35587 &'lss_match_domain()'&.
35589 .vitem "&*int&~lss_match_address(uschar&~*address,&~uschar&~*list,&~&&&
35591 This function checks for a match in an address list. The third argument
35592 controls the case-sensitivity of the local part match. The domain is always
35593 matched caselessly. The return values are as for &'lss_match_domain()'&.
35595 .vitem "&*int&~lss_match_host(uschar&~*host_name,&~uschar&~*host_address,&~&&&
35597 This function checks for a match in a host list. The most common usage is
35600 lss_match_host(sender_host_name, sender_host_address, ...)
35602 .vindex "&$sender_host_address$&"
35603 An empty address field matches an empty item in the host list. If the host name
35604 is NULL, the name corresponding to &$sender_host_address$& is automatically
35605 looked up if a host name is required to match an item in the list. The return
35606 values are as for &'lss_match_domain()'&, but in addition, &'lss_match_host()'&
35607 returns ERROR in the case when it had to look up a host name, but the lookup
35610 .vitem "&*void&~log_write(unsigned&~int&~selector,&~int&~which,&~char&~&&&
35612 This function writes to Exim's log files. The first argument should be zero (it
35613 is concerned with &%log_selector%&). The second argument can be &`LOG_MAIN`& or
35614 &`LOG_REJECT`& or &`LOG_PANIC`& or the inclusive &"or"& of any combination of
35615 them. It specifies to which log or logs the message is written. The remaining
35616 arguments are a format and relevant insertion arguments. The string should not
35617 contain any newlines, not even at the end.
35620 .vitem &*void&~receive_add_recipient(uschar&~*address,&~int&~pno)*&
35621 This function adds an additional recipient to the message. The first argument
35622 is the recipient address. If it is unqualified (has no domain), it is qualified
35623 with the &%qualify_recipient%& domain. The second argument must always be -1.
35625 This function does not allow you to specify a private &%errors_to%& address (as
35626 described with the structure of &%recipient_item%& above), because it pre-dates
35627 the addition of that field to the structure. However, it is easy to add such a
35628 value afterwards. For example:
35630 receive_add_recipient(US"monitor@mydom.example", -1);
35631 recipients_list[recipients_count-1].errors_to =
35632 US"postmaster@mydom.example";
35635 .vitem &*BOOL&~receive_remove_recipient(uschar&~*recipient)*&
35636 This is a convenience function to remove a named recipient from the list of
35637 recipients. It returns true if a recipient was removed, and false if no
35638 matching recipient could be found. The argument must be a complete email
35645 .vitem "&*uschar&~rfc2047_decode(uschar&~*string,&~BOOL&~lencheck,&&&
35646 &~uschar&~*target,&~int&~zeroval,&~int&~*lenptr, &~&~uschar&~**error)*&"
35647 This function decodes strings that are encoded according to RFC 2047. Typically
35648 these are the contents of header lines. First, each &"encoded word"& is decoded
35649 from the Q or B encoding into a byte-string. Then, if provided with the name of
35650 a charset encoding, and if the &[iconv()]& function is available, an attempt is
35651 made to translate the result to the named character set. If this fails, the
35652 binary string is returned with an error message.
35654 The first argument is the string to be decoded. If &%lencheck%& is TRUE, the
35655 maximum MIME word length is enforced. The third argument is the target
35656 encoding, or NULL if no translation is wanted.
35658 .cindex "binary zero" "in RFC 2047 decoding"
35659 .cindex "RFC 2047" "binary zero in"
35660 If a binary zero is encountered in the decoded string, it is replaced by the
35661 contents of the &%zeroval%& argument. For use with Exim headers, the value must
35662 not be 0 because header lines are handled as zero-terminated strings.
35664 The function returns the result of processing the string, zero-terminated; if
35665 &%lenptr%& is not NULL, the length of the result is set in the variable to
35666 which it points. When &%zeroval%& is 0, &%lenptr%& should not be NULL.
35668 If an error is encountered, the function returns NULL and uses the &%error%&
35669 argument to return an error message. The variable pointed to by &%error%& is
35670 set to NULL if there is no error; it may be set non-NULL even when the function
35671 returns a non-NULL value if decoding was successful, but there was a problem
35675 .vitem &*int&~smtp_fflush(void)*&
35676 This function is used in conjunction with &'smtp_printf()'&, as described
35679 .vitem &*void&~smtp_printf(char&~*,BOOL,&~...)*&
35680 The arguments of this function are almost like &[printf()]&; it writes to the SMTP
35681 output stream. You should use this function only when there is an SMTP output
35682 stream, that is, when the incoming message is being received via interactive
35683 SMTP. This is the case when &%smtp_input%& is TRUE and &%smtp_batched_input%&
35684 is FALSE. If you want to test for an incoming message from another host (as
35685 opposed to a local process that used the &%-bs%& command line option), you can
35686 test the value of &%sender_host_address%&, which is non-NULL when a remote host
35689 If an SMTP TLS connection is established, &'smtp_printf()'& uses the TLS
35690 output function, so it can be used for all forms of SMTP connection.
35692 The second argument is used to request that the data be buffered
35693 (when TRUE) or flushed (along with any previously buffered, when FALSE).
35694 This is advisory only, but likely to save on system-calls and packets
35695 sent when a sequence of calls to the function are made.
35697 The argument was added in Exim version 4.90 - changing the API/ABI.
35698 Nobody noticed until 4.93 was imminent, at which point the
35699 ABI version number was incremented.
35701 Strings that are written by &'smtp_printf()'& from within &[local_scan()]&
35702 must start with an appropriate response code: 550 if you are going to return
35703 LOCAL_SCAN_REJECT, 451 if you are going to return
35704 LOCAL_SCAN_TEMPREJECT, and 250 otherwise. Because you are writing the
35705 initial lines of a multi-line response, the code must be followed by a hyphen
35706 to indicate that the line is not the final response line. You must also ensure
35707 that the lines you write terminate with CRLF. For example:
35709 smtp_printf("550-this is some extra info\r\n");
35710 return LOCAL_SCAN_REJECT;
35712 Note that you can also create multi-line responses by including newlines in
35713 the data returned via the &%return_text%& argument. The added value of using
35714 &'smtp_printf()'& is that, for instance, you could introduce delays between
35715 multiple output lines.
35717 The &'smtp_printf()'& function does not return any error indication, because it
35719 guarantee a flush of
35720 pending output, and therefore does not test
35721 the state of the stream. (In the main code of Exim, flushing and error
35722 detection is done when Exim is ready for the next SMTP input command.) If
35723 you want to flush the output and check for an error (for example, the
35724 dropping of a TCP/IP connection), you can call &'smtp_fflush()'&, which has no
35725 arguments. It flushes the output stream, and returns a non-zero value if there
35728 .vitem &*void&~*store_get(int,BOOL)*&
35729 This function accesses Exim's internal store (memory) manager. It gets a new
35730 chunk of memory whose size is given by the first argument.
35731 The second argument should be given as TRUE if the memory will be used for
35732 data possibly coming from an attacker (eg. the message content),
35733 FALSE if it is locally-sourced.
35734 Exim bombs out if it ever
35735 runs out of memory. See the next section for a discussion of memory handling.
35737 .vitem &*void&~*store_get_perm(int,BOOL)*&
35738 This function is like &'store_get()'&, but it always gets memory from the
35739 permanent pool. See the next section for a discussion of memory handling.
35741 .vitem &*uschar&~*string_copy(uschar&~*string)*&
35744 .vitem &*uschar&~*string_copyn(uschar&~*string,&~int&~length)*&
35747 .vitem &*uschar&~*string_sprintf(char&~*format,&~...)*&
35748 These three functions create strings using Exim's dynamic memory facilities.
35749 The first makes a copy of an entire string. The second copies up to a maximum
35750 number of characters, indicated by the second argument. The third uses a format
35751 and insertion arguments to create a new string. In each case, the result is a
35752 pointer to a new string in the current memory pool. See the next section for
35758 .section "More about Exim's memory handling" "SECTmemhanloc"
35759 .cindex "&[local_scan()]& function" "memory handling"
35760 No function is provided for freeing memory, because that is never needed.
35761 The dynamic memory that Exim uses when receiving a message is automatically
35762 recycled if another message is received by the same process (this applies only
35763 to incoming SMTP connections &-- other input methods can supply only one
35764 message at a time). After receiving the last message, a reception process
35767 Because it is recycled, the normal dynamic memory cannot be used for holding
35768 data that must be preserved over a number of incoming messages on the same SMTP
35769 connection. However, Exim in fact uses two pools of dynamic memory; the second
35770 one is not recycled, and can be used for this purpose.
35772 If you want to allocate memory that remains available for subsequent messages
35773 in the same SMTP connection, you should set
35775 store_pool = POOL_PERM
35777 before calling the function that does the allocation. There is no need to
35778 restore the value if you do not need to; however, if you do want to revert to
35779 the normal pool, you can either restore the previous value of &%store_pool%& or
35780 set it explicitly to POOL_MAIN.
35782 The pool setting applies to all functions that get dynamic memory, including
35783 &'expand_string()'&, &'store_get()'&, and the &'string_xxx()'& functions.
35784 There is also a convenience function called &'store_get_perm()'& that gets a
35785 block of memory from the permanent pool while preserving the value of
35792 . ////////////////////////////////////////////////////////////////////////////
35793 . ////////////////////////////////////////////////////////////////////////////
35795 .chapter "System-wide message filtering" "CHAPsystemfilter"
35796 .scindex IIDsysfil1 "filter" "system filter"
35797 .scindex IIDsysfil2 "filtering all mail"
35798 .scindex IIDsysfil3 "system filter"
35799 The previous chapters (on ACLs and the local scan function) describe checks
35800 that can be applied to messages before they are accepted by a host. There is
35801 also a mechanism for checking messages once they have been received, but before
35802 they are delivered. This is called the &'system filter'&.
35804 The system filter operates in a similar manner to users' filter files, but it
35805 is run just once per message (however many recipients the message has).
35806 It should not normally be used as a substitute for routing, because &%deliver%&
35807 commands in a system router provide new envelope recipient addresses.
35808 The system filter must be an Exim filter. It cannot be a Sieve filter.
35810 The system filter is run at the start of a delivery attempt, before any routing
35811 is done. If a message fails to be completely delivered at the first attempt,
35812 the system filter is run again at the start of every retry.
35813 If you want your filter to do something only once per message, you can make use
35814 of the &%first_delivery%& condition in an &%if%& command in the filter to
35815 prevent it happening on retries.
35817 .vindex "&$domain$&"
35818 .vindex "&$local_part$&"
35819 &*Warning*&: Because the system filter runs just once, variables that are
35820 specific to individual recipient addresses, such as &$local_part$& and
35821 &$domain$&, are not set, and the &"personal"& condition is not meaningful. If
35822 you want to run a centrally-specified filter for each recipient address
35823 independently, you can do so by setting up a suitable &(redirect)& router, as
35824 described in section &<<SECTperaddfil>>& below.
35827 .section "Specifying a system filter" "SECID212"
35828 .cindex "uid (user id)" "system filter"
35829 .cindex "gid (group id)" "system filter"
35830 The name of the file that contains the system filter must be specified by
35831 setting &%system_filter%&. If you want the filter to run under a uid and gid
35832 other than root, you must also set &%system_filter_user%& and
35833 &%system_filter_group%& as appropriate. For example:
35835 system_filter = /etc/mail/exim.filter
35836 system_filter_user = exim
35838 If a system filter generates any deliveries directly to files or pipes (via the
35839 &%save%& or &%pipe%& commands), transports to handle these deliveries must be
35840 specified by setting &%system_filter_file_transport%& and
35841 &%system_filter_pipe_transport%&, respectively. Similarly,
35842 &%system_filter_reply_transport%& must be set to handle any messages generated
35843 by the &%reply%& command.
35846 .section "Testing a system filter" "SECID213"
35847 You can run simple tests of a system filter in the same way as for a user
35848 filter, but you should use &%-bF%& rather than &%-bf%&, so that features that
35849 are permitted only in system filters are recognized.
35851 If you want to test the combined effect of a system filter and a user filter,
35852 you can use both &%-bF%& and &%-bf%& on the same command line.
35856 .section "Contents of a system filter" "SECID214"
35857 The language used to specify system filters is the same as for users' filter
35858 files. It is described in the separate end-user document &'Exim's interface to
35859 mail filtering'&. However, there are some additional features that are
35860 available only in system filters; these are described in subsequent sections.
35861 If they are encountered in a user's filter file or when testing with &%-bf%&,
35864 .cindex "frozen messages" "manual thaw; testing in filter"
35865 There are two special conditions which, though available in users' filter
35866 files, are designed for use in system filters. The condition &%first_delivery%&
35867 is true only for the first attempt at delivering a message, and
35868 &%manually_thawed%& is true only if the message has been frozen, and
35869 subsequently thawed by an admin user. An explicit forced delivery counts as a
35870 manual thaw, but thawing as a result of the &%auto_thaw%& setting does not.
35872 &*Warning*&: If a system filter uses the &%first_delivery%& condition to
35873 specify an &"unseen"& (non-significant) delivery, and that delivery does not
35874 succeed, it will not be tried again.
35875 If you want Exim to retry an unseen delivery until it succeeds, you should
35876 arrange to set it up every time the filter runs.
35878 When a system filter finishes running, the values of the variables &$n0$& &--
35879 &$n9$& are copied into &$sn0$& &-- &$sn9$& and are thereby made available to
35880 users' filter files. Thus a system filter can, for example, set up &"scores"&
35881 to which users' filter files can refer.
35885 .section "Additional variable for system filters" "SECID215"
35886 .vindex "&$recipients$&"
35887 The expansion variable &$recipients$&, containing a list of all the recipients
35888 of the message (separated by commas and white space), is available in system
35889 filters. It is not available in users' filters for privacy reasons.
35893 .section "Defer, freeze, and fail commands for system filters" "SECID216"
35894 .cindex "freezing messages"
35895 .cindex "message" "freezing"
35896 .cindex "message" "forced failure"
35897 .cindex "&%fail%&" "in system filter"
35898 .cindex "&%freeze%& in system filter"
35899 .cindex "&%defer%& in system filter"
35900 There are three extra commands (&%defer%&, &%freeze%& and &%fail%&) which are
35901 always available in system filters, but are not normally enabled in users'
35902 filters. (See the &%allow_defer%&, &%allow_freeze%& and &%allow_fail%& options
35903 for the &(redirect)& router.) These commands can optionally be followed by the
35904 word &%text%& and a string containing an error message, for example:
35906 fail text "this message looks like spam to me"
35908 The keyword &%text%& is optional if the next character is a double quote.
35910 The &%defer%& command defers delivery of the original recipients of the
35911 message. The &%fail%& command causes all the original recipients to be failed,
35912 and a bounce message to be created. The &%freeze%& command suspends all
35913 delivery attempts for the original recipients. In all cases, any new deliveries
35914 that are specified by the filter are attempted as normal after the filter has
35917 The &%freeze%& command is ignored if the message has been manually unfrozen and
35918 not manually frozen since. This means that automatic freezing by a system
35919 filter can be used as a way of checking out suspicious messages. If a message
35920 is found to be all right, manually unfreezing it allows it to be delivered.
35922 .cindex "log" "&%fail%& command log line"
35923 .cindex "&%fail%&" "log line; reducing"
35924 The text given with a fail command is used as part of the bounce message as
35925 well as being written to the log. If the message is quite long, this can fill
35926 up a lot of log space when such failures are common. To reduce the size of the
35927 log message, Exim interprets the text in a special way if it starts with the
35928 two characters &`<<`& and contains &`>>`& later. The text between these two
35929 strings is written to the log, and the rest of the text is used in the bounce
35930 message. For example:
35932 fail "<<filter test 1>>Your message is rejected \
35933 because it contains attachments that we are \
35934 not prepared to receive."
35937 .cindex "loop" "caused by &%fail%&"
35938 Take great care with the &%fail%& command when basing the decision to fail on
35939 the contents of the message, because the bounce message will of course include
35940 the contents of the original message and will therefore trigger the &%fail%&
35941 command again (causing a mail loop) unless steps are taken to prevent this.
35942 Testing the &%error_message%& condition is one way to prevent this. You could
35945 if $message_body contains "this is spam" and not error_message
35946 then fail text "spam is not wanted here" endif
35948 though of course that might let through unwanted bounce messages. The
35949 alternative is clever checking of the body and/or headers to detect bounces
35950 generated by the filter.
35952 The interpretation of a system filter file ceases after a
35954 &%freeze%&, or &%fail%& command is obeyed. However, any deliveries that were
35955 set up earlier in the filter file are honoured, so you can use a sequence such
35961 to send a specified message when the system filter is freezing (or deferring or
35962 failing) a message. The normal deliveries for the message do not, of course,
35967 .section "Adding and removing headers in a system filter" "SECTaddremheasys"
35968 .cindex "header lines" "adding; in system filter"
35969 .cindex "header lines" "removing; in system filter"
35970 .cindex "filter" "header lines; adding/removing"
35971 Two filter commands that are available only in system filters are:
35973 headers add <string>
35974 headers remove <string>
35976 The argument for the &%headers add%& is a string that is expanded and then
35977 added to the end of the message's headers. It is the responsibility of the
35978 filter maintainer to make sure it conforms to RFC 2822 syntax. Leading white
35979 space is ignored, and if the string is otherwise empty, or if the expansion is
35980 forced to fail, the command has no effect.
35982 You can use &"\n"& within the string, followed by white space, to specify
35983 continued header lines. More than one header may be added in one command by
35984 including &"\n"& within the string without any following white space. For
35987 headers add "X-header-1: ....\n \
35988 continuation of X-header-1 ...\n\
35991 Note that the header line continuation white space after the first newline must
35992 be placed before the backslash that continues the input string, because white
35993 space after input continuations is ignored.
35995 The argument for &%headers remove%& is a colon-separated list of header names.
35996 This command applies only to those headers that are stored with the message;
35997 those that are added at delivery time (such as &'Envelope-To:'& and
35998 &'Return-Path:'&) cannot be removed by this means. If there is more than one
35999 header with the same name, they are all removed.
36001 The &%headers%& command in a system filter makes an immediate change to the set
36002 of header lines that was received with the message (with possible additions
36003 from ACL processing). Subsequent commands in the system filter operate on the
36004 modified set, which also forms the basis for subsequent message delivery.
36005 Unless further modified during routing or transporting, this set of headers is
36006 used for all recipients of the message.
36008 During routing and transporting, the variables that refer to the contents of
36009 header lines refer only to those lines that are in this set. Thus, header lines
36010 that are added by a system filter are visible to users' filter files and to all
36011 routers and transports. This contrasts with the manipulation of header lines by
36012 routers and transports, which is not immediate, but which instead is saved up
36013 until the message is actually being written (see section
36014 &<<SECTheadersaddrem>>&).
36016 If the message is not delivered at the first attempt, header lines that were
36017 added by the system filter are stored with the message, and so are still
36018 present at the next delivery attempt. Header lines that were removed are still
36019 present, but marked &"deleted"& so that they are not transported with the
36020 message. For this reason, it is usual to make the &%headers%& command
36021 conditional on &%first_delivery%& so that the set of header lines is not
36022 modified more than once.
36024 Because header modification in a system filter acts immediately, you have to
36025 use an indirect approach if you want to modify the contents of a header line.
36028 headers add "Old-Subject: $h_subject:"
36029 headers remove "Subject"
36030 headers add "Subject: new subject (was: $h_old-subject:)"
36031 headers remove "Old-Subject"
36036 .section "Setting an errors address in a system filter" "SECID217"
36037 .cindex "envelope from"
36038 .cindex "envelope sender"
36039 In a system filter, if a &%deliver%& command is followed by
36041 errors_to <some address>
36043 in order to change the envelope sender (and hence the error reporting) for that
36044 delivery, any address may be specified. (In a user filter, only the current
36045 user's address can be set.) For example, if some mail is being monitored, you
36048 unseen deliver monitor@spying.example errors_to root@local.example
36050 to take a copy which would not be sent back to the normal error reporting
36051 address if its delivery failed.
36055 .section "Per-address filtering" "SECTperaddfil"
36056 .vindex "&$domain_data$&"
36057 .vindex "&$local_part_data$&"
36058 In contrast to the system filter, which is run just once per message for each
36059 delivery attempt, it is also possible to set up a system-wide filtering
36060 operation that runs once for each recipient address. In this case, variables
36061 such as &$local_part_data$& and &$domain_data$& can be used,
36062 and indeed, the choice of filter file could be made dependent on them.
36063 This is an example of a router which implements such a filter:
36068 domains = +local_domains
36069 file = /central/filters/$local_part_data
36074 The filter is run in a separate process under its own uid. Therefore, either
36075 &%check_local_user%& must be set (as above), in which case the filter is run as
36076 the local user, or the &%user%& option must be used to specify which user to
36077 use. If both are set, &%user%& overrides.
36079 Care should be taken to ensure that none of the commands in the filter file
36080 specify a significant delivery if the message is to go on to be delivered to
36081 its intended recipient. The router will not then claim to have dealt with the
36082 address, so it will be passed on to subsequent routers to be delivered in the
36084 .ecindex IIDsysfil1
36085 .ecindex IIDsysfil2
36086 .ecindex IIDsysfil3
36093 . ////////////////////////////////////////////////////////////////////////////
36094 . ////////////////////////////////////////////////////////////////////////////
36096 .chapter "Message processing" "CHAPmsgproc"
36097 .scindex IIDmesproc "message" "general processing"
36098 Exim performs various transformations on the sender and recipient addresses of
36099 all messages that it handles, and also on the messages' header lines. Some of
36100 these are optional and configurable, while others always take place. All of
36101 this processing, except rewriting as a result of routing, and the addition or
36102 removal of header lines while delivering, happens when a message is received,
36103 before it is placed on Exim's queue.
36105 Some of the automatic processing takes place by default only for
36106 &"locally-originated"& messages. This adjective is used to describe messages
36107 that are not received over TCP/IP, but instead are passed to an Exim process on
36108 its standard input. This includes the interactive &"local SMTP"& case that is
36109 set up by the &%-bs%& command line option.
36111 &*Note*&: Messages received over TCP/IP on the loopback interface (127.0.0.1
36112 or ::1) are not considered to be locally-originated. Exim does not treat the
36113 loopback interface specially in any way.
36115 If you want the loopback interface to be treated specially, you must ensure
36116 that there are appropriate entries in your ACLs.
36121 .section "Submission mode for non-local messages" "SECTsubmodnon"
36122 .cindex "message" "submission"
36123 .cindex "submission mode"
36124 Processing that happens automatically for locally-originated messages (unless
36125 &%suppress_local_fixups%& is set) can also be requested for messages that are
36126 received over TCP/IP. The term &"submission mode"& is used to describe this
36127 state. Submission mode is set by the modifier
36129 control = submission
36131 in a MAIL, RCPT, or pre-data ACL for an incoming message (see sections
36132 &<<SECTACLmodi>>& and &<<SECTcontrols>>&). This makes Exim treat the message as
36133 a local submission, and is normally used when the source of the message is
36134 known to be an MUA running on a client host (as opposed to an MTA). For
36135 example, to set submission mode for messages originating on the IPv4 loopback
36136 interface, you could include the following in the MAIL ACL:
36138 warn hosts = 127.0.0.1
36139 control = submission
36141 .cindex "&%sender_retain%& submission option"
36142 There are some options that can be used when setting submission mode. A slash
36143 is used to separate options. For example:
36145 control = submission/sender_retain
36147 Specifying &%sender_retain%& has the effect of setting &%local_sender_retain%&
36148 true and &%local_from_check%& false for the current incoming message. The first
36149 of these allows an existing &'Sender:'& header in the message to remain, and
36150 the second suppresses the check to ensure that &'From:'& matches the
36151 authenticated sender. With this setting, Exim still fixes up messages by adding
36152 &'Date:'& and &'Message-ID:'& header lines if they are missing, but makes no
36153 attempt to check sender authenticity in header lines.
36155 When &%sender_retain%& is not set, a submission mode setting may specify a
36156 domain to be used when generating a &'From:'& or &'Sender:'& header line. For
36159 control = submission/domain=some.domain
36161 The domain may be empty. How this value is used is described in sections
36162 &<<SECTthefrohea>>& and &<<SECTthesenhea>>&. There is also a &%name%& option
36163 that allows you to specify the user's full name for inclusion in a created
36164 &'Sender:'& or &'From:'& header line. For example:
36166 accept authenticated = *
36167 control = submission/domain=wonderland.example/\
36168 name=${lookup {$authenticated_id} \
36169 lsearch {/etc/exim/namelist}}
36171 Because the name may contain any characters, including slashes, the &%name%&
36172 option must be given last. The remainder of the string is used as the name. For
36173 the example above, if &_/etc/exim/namelist_& contains:
36175 bigegg: Humpty Dumpty
36177 then when the sender has authenticated as &'bigegg'&, the generated &'Sender:'&
36180 Sender: Humpty Dumpty <bigegg@wonderland.example>
36182 .cindex "return path" "in submission mode"
36183 By default, submission mode forces the return path to the same address as is
36184 used to create the &'Sender:'& header. However, if &%sender_retain%& is
36185 specified, the return path is also left unchanged.
36187 &*Note*&: The changes caused by submission mode take effect after the predata
36188 ACL. This means that any sender checks performed before the fix-ups use the
36189 untrusted sender address specified by the user, not the trusted sender address
36190 specified by submission mode. Although this might be slightly unexpected, it
36191 does mean that you can configure ACL checks to spot that a user is trying to
36192 spoof another's address.
36194 .section "Line endings" "SECTlineendings"
36195 .cindex "line endings"
36196 .cindex "carriage return"
36198 RFC 2821 specifies that CRLF (two characters: carriage-return, followed by
36199 linefeed) is the line ending for messages transmitted over the Internet using
36200 SMTP over TCP/IP. However, within individual operating systems, different
36201 conventions are used. For example, Unix-like systems use just LF, but others
36202 use CRLF or just CR.
36204 Exim was designed for Unix-like systems, and internally, it stores messages
36205 using the system's convention of a single LF as a line terminator. When
36206 receiving a message, all line endings are translated to this standard format.
36207 Originally, it was thought that programs that passed messages directly to an
36208 MTA within an operating system would use that system's convention. Experience
36209 has shown that this is not the case; for example, there are Unix applications
36210 that use CRLF in this circumstance. For this reason, and for compatibility with
36211 other MTAs, the way Exim handles line endings for all messages is now as
36215 LF not preceded by CR is treated as a line ending.
36217 CR is treated as a line ending; if it is immediately followed by LF, the LF
36220 The sequence &"CR, dot, CR"& does not terminate an incoming SMTP message,
36221 nor a local message in the state where a line containing only a dot is a
36224 If a bare CR is encountered within a header line, an extra space is added after
36225 the line terminator so as not to end the header line. The reasoning behind this
36226 is that bare CRs in header lines are most likely either to be mistakes, or
36227 people trying to play silly games.
36229 If the first header line received in a message ends with CRLF, a subsequent
36230 bare LF in a header line is treated in the same way as a bare CR in a header
36238 .section "Unqualified addresses" "SECID218"
36239 .cindex "unqualified addresses"
36240 .cindex "address" "qualification"
36241 By default, Exim expects every envelope address it receives from an external
36242 host to be fully qualified. Unqualified addresses cause negative responses to
36243 SMTP commands. However, because SMTP is used as a means of transporting
36244 messages from MUAs running on personal workstations, there is sometimes a
36245 requirement to accept unqualified addresses from specific hosts or IP networks.
36247 Exim has two options that separately control which hosts may send unqualified
36248 sender or recipient addresses in SMTP commands, namely
36249 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&. In both
36250 cases, if an unqualified address is accepted, it is qualified by adding the
36251 value of &%qualify_domain%& or &%qualify_recipient%&, as appropriate.
36253 .oindex "&%qualify_domain%&"
36254 .oindex "&%qualify_recipient%&"
36255 Unqualified addresses in header lines are automatically qualified for messages
36256 that are locally originated, unless the &%-bnq%& option is given on the command
36257 line. For messages received over SMTP, unqualified addresses in header lines
36258 are qualified only if unqualified addresses are permitted in SMTP commands. In
36259 other words, such qualification is also controlled by
36260 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&,
36265 .section "The UUCP From line" "SECID219"
36266 .cindex "&""From""& line"
36267 .cindex "UUCP" "&""From""& line"
36268 .cindex "sender" "address"
36269 .oindex "&%uucp_from_pattern%&"
36270 .oindex "&%uucp_from_sender%&"
36271 .cindex "envelope from"
36272 .cindex "envelope sender"
36273 .cindex "Sendmail compatibility" "&""From""& line"
36274 Messages that have come from UUCP (and some other applications) often begin
36275 with a line containing the envelope sender and a timestamp, following the word
36276 &"From"&. Examples of two common formats are:
36278 From a.oakley@berlin.mus Fri Jan 5 12:35 GMT 1996
36279 From f.butler@berlin.mus Fri, 7 Jan 97 14:00:00 GMT
36281 This line precedes the RFC 2822 header lines. For compatibility with Sendmail,
36282 Exim recognizes such lines at the start of messages that are submitted to it
36283 via the command line (that is, on the standard input). It does not recognize
36284 such lines in incoming SMTP messages, unless the sending host matches
36285 &%ignore_fromline_hosts%& or the &%-bs%& option was used for a local message
36286 and &%ignore_fromline_local%& is set. The recognition is controlled by a
36287 regular expression that is defined by the &%uucp_from_pattern%& option, whose
36288 default value matches the two common cases shown above and puts the address
36289 that follows &"From"& into &$1$&.
36291 .cindex "numerical variables (&$1$& &$2$& etc)" "in &""From ""& line handling"
36292 When the caller of Exim for a non-SMTP message that contains a &"From"& line is
36293 a trusted user, the message's sender address is constructed by expanding the
36294 contents of &%uucp_sender_address%&, whose default value is &"$1"&. This is
36295 then parsed as an RFC 2822 address. If there is no domain, the local part is
36296 qualified with &%qualify_domain%& unless it is the empty string. However, if
36297 the command line &%-f%& option is used, it overrides the &"From"& line.
36299 If the caller of Exim is not trusted, the &"From"& line is recognized, but the
36300 sender address is not changed. This is also the case for incoming SMTP messages
36301 that are permitted to contain &"From"& lines.
36303 Only one &"From"& line is recognized. If there is more than one, the second is
36304 treated as a data line that starts the body of the message, as it is not valid
36305 as a header line. This also happens if a &"From"& line is present in an
36306 incoming SMTP message from a source that is not permitted to send them.
36310 .section "Header lines"
36311 .subsection "Resent- header lines" SECID220
36313 RFC 2822 makes provision for sets of header lines starting with the string
36314 &`Resent-`& to be added to a message when it is resent by the original
36315 recipient to somebody else. These headers are &'Resent-Date:'&,
36316 &'Resent-From:'&, &'Resent-Sender:'&, &'Resent-To:'&, &'Resent-Cc:'&,
36317 &'Resent-Bcc:'& and &'Resent-Message-ID:'&. The RFC says:
36320 &'Resent fields are strictly informational. They MUST NOT be used in the normal
36321 processing of replies or other such automatic actions on messages.'&
36324 This leaves things a bit vague as far as other processing actions such as
36325 address rewriting are concerned. Exim treats &%Resent-%& header lines as
36329 A &'Resent-From:'& line that just contains the login id of the submitting user
36330 is automatically rewritten in the same way as &'From:'& (see below).
36332 If there's a rewriting rule for a particular header line, it is also applied to
36333 &%Resent-%& header lines of the same type. For example, a rule that rewrites
36334 &'From:'& also rewrites &'Resent-From:'&.
36336 For local messages, if &'Sender:'& is removed on input, &'Resent-Sender:'& is
36339 For a locally-submitted message,
36340 if there are any &%Resent-%& header lines but no &'Resent-Date:'&,
36341 &'Resent-From:'&, or &'Resent-Message-Id:'&, they are added as necessary. It is
36342 the contents of &'Resent-Message-Id:'& (rather than &'Message-Id:'&) which are
36343 included in log lines in this case.
36345 The logic for adding &'Sender:'& is duplicated for &'Resent-Sender:'& when any
36346 &%Resent-%& header lines are present.
36352 .subsection Auto-Submitted: SECID221
36353 Whenever Exim generates an autoreply, a bounce, or a delay warning message, it
36354 includes the header line:
36356 Auto-Submitted: auto-replied
36359 .subsection Bcc: SECID222
36360 .cindex "&'Bcc:'& header line"
36361 If Exim is called with the &%-t%& option, to take recipient addresses from a
36362 message's header, it removes any &'Bcc:'& header line that may exist (after
36363 extracting its addresses). If &%-t%& is not present on the command line, any
36364 existing &'Bcc:'& is not removed.
36367 .subsection Date: SECID223
36369 If a locally-generated or submission-mode message has no &'Date:'& header line,
36370 Exim adds one, using the current date and time, unless the
36371 &%suppress_local_fixups%& control has been specified.
36373 .subsection Delivery-date: SECID224
36374 .cindex "&'Delivery-date:'& header line"
36375 .oindex "&%delivery_date_remove%&"
36376 &'Delivery-date:'& header lines are not part of the standard RFC 2822 header
36377 set. Exim can be configured to add them to the final delivery of messages. (See
36378 the generic &%delivery_date_add%& transport option.) They should not be present
36379 in messages in transit. If the &%delivery_date_remove%& configuration option is
36380 set (the default), Exim removes &'Delivery-date:'& header lines from incoming
36384 .subsection Envelope-to: SECID225
36385 .chindex Envelope-to:
36386 .oindex "&%envelope_to_remove%&"
36387 &'Envelope-to:'& header lines are not part of the standard RFC 2822 header set.
36388 Exim can be configured to add them to the final delivery of messages. (See the
36389 generic &%envelope_to_add%& transport option.) They should not be present in
36390 messages in transit. If the &%envelope_to_remove%& configuration option is set
36391 (the default), Exim removes &'Envelope-to:'& header lines from incoming
36395 .subsection From: SECTthefrohea
36397 .cindex "Sendmail compatibility" "&""From""& line"
36398 .cindex "message" "submission"
36399 .cindex "submission mode"
36400 If a submission-mode message does not contain a &'From:'& header line, Exim
36401 adds one if either of the following conditions is true:
36404 The envelope sender address is not empty (that is, this is not a bounce
36405 message). The added header line copies the envelope sender address.
36407 .vindex "&$authenticated_id$&"
36408 The SMTP session is authenticated and &$authenticated_id$& is not empty.
36410 .vindex "&$qualify_domain$&"
36411 If no domain is specified by the submission control, the local part is
36412 &$authenticated_id$& and the domain is &$qualify_domain$&.
36414 If a non-empty domain is specified by the submission control, the local
36415 part is &$authenticated_id$&, and the domain is the specified domain.
36417 If an empty domain is specified by the submission control,
36418 &$authenticated_id$& is assumed to be the complete address.
36422 A non-empty envelope sender takes precedence.
36424 If a locally-generated incoming message does not contain a &'From:'& header
36425 line, and the &%suppress_local_fixups%& control is not set, Exim adds one
36426 containing the sender's address. The calling user's login name and full name
36427 are used to construct the address, as described in section &<<SECTconstr>>&.
36428 They are obtained from the password data by calling &[getpwuid()]& (but see the
36429 &%unknown_login%& configuration option). The address is qualified with
36430 &%qualify_domain%&.
36432 For compatibility with Sendmail, if an incoming, non-SMTP message has a
36433 &'From:'& header line containing just the unqualified login name of the calling
36434 user, this is replaced by an address containing the user's login name and full
36435 name as described in section &<<SECTconstr>>&.
36438 .subsection Message-ID: SECID226
36439 .chindex Message-ID:
36440 .cindex "message" "submission"
36441 .oindex "&%message_id_header_text%&"
36442 If a locally-generated or submission-mode incoming message does not contain a
36443 &'Message-ID:'& or &'Resent-Message-ID:'& header line, and the
36444 &%suppress_local_fixups%& control is not set, Exim adds a suitable header line
36445 to the message. If there are any &'Resent-:'& headers in the message, it
36446 creates &'Resent-Message-ID:'&. The id is constructed from Exim's internal
36447 message id, preceded by the letter E to ensure it starts with a letter, and
36448 followed by @ and the primary host name. Additional information can be included
36449 in this header line by setting the &%message_id_header_text%& and/or
36450 &%message_id_header_domain%& options.
36453 .subsection Received: SECID227
36455 A &'Received:'& header line is added at the start of every message. The
36456 contents are defined by the &%received_header_text%& configuration option, and
36457 Exim automatically adds a semicolon and a timestamp to the configured string.
36459 The &'Received:'& header is generated as soon as the message's header lines
36460 have been received. At this stage, the timestamp in the &'Received:'& header
36461 line is the time that the message started to be received. This is the value
36462 that is seen by the DATA ACL and by the &[local_scan()]& function.
36464 Once a message is accepted, the timestamp in the &'Received:'& header line is
36465 changed to the time of acceptance, which is (apart from a small delay while the
36466 -H spool file is written) the earliest time at which delivery could start.
36469 .subsection References: SECID228
36470 .chindex References:
36471 Messages created by the &(autoreply)& transport include a &'References:'&
36472 header line. This is constructed according to the rules that are described in
36473 section 3.64 of RFC 2822 (which states that replies should contain such a
36474 header line), and section 3.14 of RFC 3834 (which states that automatic
36475 responses are not different in this respect). However, because some mail
36476 processing software does not cope well with very long header lines, no more
36477 than 12 message IDs are copied from the &'References:'& header line in the
36478 incoming message. If there are more than 12, the first one and then the final
36479 11 are copied, before adding the message ID of the incoming message.
36483 .subsection Return-path: SECID229
36484 .chindex Return-path:
36485 .oindex "&%return_path_remove%&"
36486 &'Return-path:'& header lines are defined as something an MTA may insert when
36487 it does the final delivery of messages. (See the generic &%return_path_add%&
36488 transport option.) Therefore, they should not be present in messages in
36489 transit. If the &%return_path_remove%& configuration option is set (the
36490 default), Exim removes &'Return-path:'& header lines from incoming messages.
36494 .subsection Sender: SECTthesenhea
36495 .cindex "&'Sender:'& header line"
36496 .cindex "message" "submission"
36498 For a locally-originated message from an untrusted user, Exim may remove an
36499 existing &'Sender:'& header line, and it may add a new one. You can modify
36500 these actions by setting the &%local_sender_retain%& option true, the
36501 &%local_from_check%& option false, or by using the &%suppress_local_fixups%&
36504 When a local message is received from an untrusted user and
36505 &%local_from_check%& is true (the default), and the &%suppress_local_fixups%&
36506 control has not been set, a check is made to see if the address given in the
36507 &'From:'& header line is the correct (local) sender of the message. The address
36508 that is expected has the login name as the local part and the value of
36509 &%qualify_domain%& as the domain. Prefixes and suffixes for the local part can
36510 be permitted by setting &%local_from_prefix%& and &%local_from_suffix%&
36511 appropriately. If &'From:'& does not contain the correct sender, a &'Sender:'&
36512 line is added to the message.
36514 If you set &%local_from_check%& false, this checking does not occur. However,
36515 the removal of an existing &'Sender:'& line still happens, unless you also set
36516 &%local_sender_retain%& to be true. It is not possible to set both of these
36517 options true at the same time.
36519 .cindex "submission mode"
36520 By default, no processing of &'Sender:'& header lines is done for messages
36521 received over TCP/IP or for messages submitted by trusted users. However, when
36522 a message is received over TCP/IP in submission mode, and &%sender_retain%& is
36523 not specified on the submission control, the following processing takes place:
36525 .vindex "&$authenticated_id$&"
36526 First, any existing &'Sender:'& lines are removed. Then, if the SMTP session is
36527 authenticated, and &$authenticated_id$& is not empty, a sender address is
36528 created as follows:
36531 .vindex "&$qualify_domain$&"
36532 If no domain is specified by the submission control, the local part is
36533 &$authenticated_id$& and the domain is &$qualify_domain$&.
36535 If a non-empty domain is specified by the submission control, the local part
36536 is &$authenticated_id$&, and the domain is the specified domain.
36538 If an empty domain is specified by the submission control,
36539 &$authenticated_id$& is assumed to be the complete address.
36542 This address is compared with the address in the &'From:'& header line. If they
36543 are different, a &'Sender:'& header line containing the created address is
36544 added. Prefixes and suffixes for the local part in &'From:'& can be permitted
36545 by setting &%local_from_prefix%& and &%local_from_suffix%& appropriately.
36547 .cindex "return path" "created from &'Sender:'&"
36548 &*Note*&: Whenever a &'Sender:'& header line is created, the return path for
36549 the message (the envelope sender address) is changed to be the same address,
36550 except in the case of submission mode when &%sender_retain%& is specified.
36554 .section "Adding and removing header lines in routers and transports" &&&
36555 "SECTheadersaddrem"
36556 .cindex "header lines" "adding; in router or transport"
36557 .cindex "header lines" "removing; in router or transport"
36558 When a message is delivered, the addition and removal of header lines can be
36559 specified in a system filter, or on any of the routers and transports that
36560 process the message. Section &<<SECTaddremheasys>>& contains details about
36561 modifying headers in a system filter. Header lines can also be added in an ACL
36562 as a message is received (see section &<<SECTaddheadacl>>&).
36564 In contrast to what happens in a system filter, header modifications that are
36565 specified on routers and transports apply only to the particular recipient
36566 addresses that are being processed by those routers and transports. These
36567 changes do not actually take place until a copy of the message is being
36568 transported. Therefore, they do not affect the basic set of header lines, and
36569 they do not affect the values of the variables that refer to header lines.
36571 &*Note*&: In particular, this means that any expansions in the configuration of
36572 the transport cannot refer to the modified header lines, because such
36573 expansions all occur before the message is actually transported.
36575 For both routers and transports, the argument of a &%headers_add%&
36576 option must be in the form of one or more RFC 2822 header lines, separated by
36577 newlines (coded as &"\n"&). For example:
36579 headers_add = X-added-header: added by $primary_hostname\n\
36580 X-added-second: another added header line
36582 Exim does not check the syntax of these added header lines.
36584 Multiple &%headers_add%& options for a single router or transport can be
36585 specified; the values will append to a single list of header lines.
36586 Each header-line is separately expanded.
36588 The argument of a &%headers_remove%& option must consist of a colon-separated
36589 list of header names. This is confusing, because header names themselves are
36590 often terminated by colons. In this case, the colons are the list separators,
36591 not part of the names. For example:
36593 headers_remove = return-receipt-to:acknowledge-to
36596 Multiple &%headers_remove%& options for a single router or transport can be
36597 specified; the arguments will append to a single header-names list.
36598 Each item is separately expanded.
36599 Note that colons in complex expansions which are used to
36600 form all or part of a &%headers_remove%& list
36601 will act as list separators.
36603 When &%headers_add%& or &%headers_remove%& is specified on a router,
36604 items are expanded at routing time,
36605 and then associated with all addresses that are
36606 accepted by that router, and also with any new addresses that it generates. If
36607 an address passes through several routers as a result of aliasing or
36608 forwarding, the changes are cumulative.
36610 .oindex "&%unseen%&"
36611 However, this does not apply to multiple routers that result from the use of
36612 the &%unseen%& option. Any header modifications that were specified by the
36613 &"unseen"& router or its predecessors apply only to the &"unseen"& delivery.
36615 Addresses that end up with different &%headers_add%& or &%headers_remove%&
36616 settings cannot be delivered together in a batch, so a transport is always
36617 dealing with a set of addresses that have the same header-processing
36620 The transport starts by writing the original set of header lines that arrived
36621 with the message, possibly modified by the system filter. As it writes out
36622 these lines, it consults the list of header names that were attached to the
36623 recipient address(es) by &%headers_remove%& options in routers, and it also
36624 consults the transport's own &%headers_remove%& option. Header lines whose
36625 names are on either of these lists are not written out. If there are multiple
36626 instances of any listed header, they are all skipped.
36628 After the remaining original header lines have been written, new header
36629 lines that were specified by routers' &%headers_add%& options are written, in
36630 the order in which they were attached to the address. These are followed by any
36631 header lines specified by the transport's &%headers_add%& option.
36633 This way of handling header line modifications in routers and transports has
36634 the following consequences:
36637 The original set of header lines, possibly modified by the system filter,
36638 remains &"visible"&, in the sense that the &$header_$&&'xxx'& variables refer
36639 to it, at all times.
36641 Header lines that are added by a router's
36642 &%headers_add%& option are not accessible by means of the &$header_$&&'xxx'&
36643 expansion syntax in subsequent routers or the transport.
36645 Conversely, header lines that are specified for removal by &%headers_remove%&
36646 in a router remain visible to subsequent routers and the transport.
36648 Headers added to an address by &%headers_add%& in a router cannot be removed by
36649 a later router or by a transport.
36651 An added header can refer to the contents of an original header that is to be
36652 removed, even it has the same name as the added header. For example:
36654 headers_remove = subject
36655 headers_add = Subject: new subject (was: $h_subject:)
36659 &*Warning*&: The &%headers_add%& and &%headers_remove%& options cannot be used
36660 for a &(redirect)& router that has the &%one_time%& option set.
36666 .section "Constructed addresses" "SECTconstr"
36667 .cindex "address" "constructed"
36668 .cindex "constructed address"
36669 When Exim constructs a sender address for a locally-generated message, it uses
36672 <&'user name'&>&~&~<&'login'&&`@`&&'qualify_domain'&>
36676 Zaphod Beeblebrox <zaphod@end.univ.example>
36678 The user name is obtained from the &%-F%& command line option if set, or
36679 otherwise by looking up the calling user by &[getpwuid()]& and extracting the
36680 &"gecos"& field from the password entry. If the &"gecos"& field contains an
36681 ampersand character, this is replaced by the login name with the first letter
36682 upper cased, as is conventional in a number of operating systems. See the
36683 &%gecos_name%& option for a way to tailor the handling of the &"gecos"& field.
36684 The &%unknown_username%& option can be used to specify user names in cases when
36685 there is no password file entry.
36688 In all cases, the user name is made to conform to RFC 2822 by quoting all or
36689 parts of it if necessary. In addition, if it contains any non-printing
36690 characters, it is encoded as described in RFC 2047, which defines a way of
36691 including non-ASCII characters in header lines. The value of the
36692 &%headers_charset%& option specifies the name of the encoding that is used (the
36693 characters are assumed to be in this encoding). The setting of
36694 &%print_topbitchars%& controls whether characters with the top bit set (that
36695 is, with codes greater than 127) count as printing characters or not.
36699 .section "Case of local parts" "SECID230"
36700 .cindex "case of local parts"
36701 .cindex "local part" "case of"
36702 RFC 2822 states that the case of letters in the local parts of addresses cannot
36703 be assumed to be non-significant. Exim preserves the case of local parts of
36704 addresses, but by default it uses a lower-cased form when it is routing,
36705 because on most Unix systems, usernames are in lower case and case-insensitive
36706 routing is required. However, any particular router can be made to use the
36707 original case for local parts by setting the &%caseful_local_part%& generic
36710 .cindex "mixed-case login names"
36711 If you must have mixed-case user names on your system, the best way to proceed,
36712 assuming you want case-independent handling of incoming email, is to set up
36713 your first router to convert incoming local parts in your domains to the
36714 correct case by means of a file lookup. For example:
36718 domains = +local_domains
36719 data = ${lookup{$local_part}cdb\
36720 {/etc/usercased.cdb}{$value}fail}\
36723 For this router, the local part is forced to lower case by the default action
36724 (&%caseful_local_part%& is not set). The lower-cased local part is used to look
36725 up a new local part in the correct case. If you then set &%caseful_local_part%&
36726 on any subsequent routers which process your domains, they will operate on
36727 local parts with the correct case in a case-sensitive manner.
36731 .section "Dots in local parts" "SECID231"
36732 .cindex "dot" "in local part"
36733 .cindex "local part" "dots in"
36734 RFC 2822 forbids empty components in local parts. That is, an unquoted local
36735 part may not begin or end with a dot, nor have two consecutive dots in the
36736 middle. However, it seems that many MTAs do not enforce this, so Exim permits
36737 empty components for compatibility.
36741 .section "Rewriting addresses" "SECID232"
36742 .cindex "rewriting" "addresses"
36743 Rewriting of sender and recipient addresses, and addresses in headers, can
36744 happen automatically, or as the result of configuration options, as described
36745 in chapter &<<CHAPrewrite>>&. The headers that may be affected by this are
36746 &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-To:'&, &'Sender:'&, and &'To:'&.
36748 Automatic rewriting includes qualification, as mentioned above. The other case
36749 in which it can happen is when an incomplete non-local domain is given. The
36750 routing process may cause this to be expanded into the full domain name. For
36751 example, a header such as
36755 might get rewritten as
36757 To: hare@teaparty.wonderland.fict.example
36759 Rewriting as a result of routing is the one kind of message processing that
36760 does not happen at input time, as it cannot be done until the address has
36763 Strictly, one should not do &'any'& deliveries of a message until all its
36764 addresses have been routed, in case any of the headers get changed as a
36765 result of routing. However, doing this in practice would hold up many
36766 deliveries for unreasonable amounts of time, just because one address could not
36767 immediately be routed. Exim therefore does not delay other deliveries when
36768 routing of one or more addresses is deferred.
36769 .ecindex IIDmesproc
36773 . ////////////////////////////////////////////////////////////////////////////
36774 . ////////////////////////////////////////////////////////////////////////////
36776 .chapter "SMTP processing" "CHAPSMTP"
36777 .scindex IIDsmtpproc1 "SMTP" "processing details"
36778 .scindex IIDsmtpproc2 "LMTP" "processing details"
36779 Exim supports a number of different ways of using the SMTP protocol, and its
36780 LMTP variant, which is an interactive protocol for transferring messages into a
36781 closed mail store application. This chapter contains details of how SMTP is
36782 processed. For incoming mail, the following are available:
36785 SMTP over TCP/IP (Exim daemon or &'inetd'&);
36787 SMTP over the standard input and output (the &%-bs%& option);
36789 Batched SMTP on the standard input (the &%-bS%& option).
36792 For mail delivery, the following are available:
36795 SMTP over TCP/IP (the &(smtp)& transport);
36797 LMTP over TCP/IP (the &(smtp)& transport with the &%protocol%& option set to
36800 LMTP over a pipe to a process running in the local host (the &(lmtp)&
36803 Batched SMTP to a file or pipe (the &(appendfile)& and &(pipe)& transports with
36804 the &%use_bsmtp%& option set).
36807 &'Batched SMTP'& is the name for a process in which batches of messages are
36808 stored in or read from files (or pipes), in a format in which SMTP commands are
36809 used to contain the envelope information.
36813 .section "Outgoing SMTP and LMTP over TCP/IP" "SECToutSMTPTCP"
36814 .cindex "SMTP" "outgoing over TCP/IP"
36815 .cindex "outgoing SMTP over TCP/IP"
36816 .cindex "LMTP" "over TCP/IP"
36817 .cindex "outgoing LMTP over TCP/IP"
36820 .cindex "SIZE" "option on MAIL command"
36821 Outgoing SMTP and LMTP over TCP/IP is implemented by the &(smtp)& transport.
36822 The &%protocol%& option selects which protocol is to be used, but the actual
36823 processing is the same in both cases.
36825 .cindex "ESMTP extensions" SIZE
36826 If, in response to its EHLO command, Exim is told that the SIZE
36827 extension is supported, it adds SIZE=<&'n'&> to each subsequent MAIL
36828 command. The value of <&'n'&> is the message size plus the value of the
36829 &%size_addition%& option (default 1024) to allow for additions to the message
36830 such as per-transport header lines, or changes made in a
36831 .cindex "transport" "filter"
36832 .cindex "filter" "transport filter"
36833 transport filter. If &%size_addition%& is set negative, the use of SIZE is
36836 If the remote server advertises support for PIPELINING, Exim uses the
36837 pipelining extension to SMTP (RFC 2197) to reduce the number of TCP/IP packets
36838 required for the transaction.
36840 If the remote server advertises support for the STARTTLS command, and Exim
36841 was built to support TLS encryption, it tries to start a TLS session unless the
36842 server matches &%hosts_avoid_tls%&. See chapter &<<CHAPTLS>>& for more details.
36843 Either a match in that or &%hosts_verify_avoid_tls%& apply when the transport
36844 is called for verification.
36846 If the remote server advertises support for the AUTH command, Exim scans
36847 the authenticators configuration for any suitable client settings, as described
36848 in chapter &<<CHAPSMTPAUTH>>&.
36850 .cindex "carriage return"
36852 Responses from the remote host are supposed to be terminated by CR followed by
36853 LF. However, there are known to be hosts that do not send CR characters, so in
36854 order to be able to interwork with such hosts, Exim treats LF on its own as a
36857 If a message contains a number of different addresses, all those with the same
36858 characteristics (for example, the same envelope sender) that resolve to the
36859 same set of hosts, in the same order, are sent in a single SMTP transaction,
36860 even if they are for different domains, unless there are more than the setting
36861 of the &%max_rcpt%&s option in the &(smtp)& transport allows, in which case
36862 they are split into groups containing no more than &%max_rcpt%&s addresses
36863 each. If &%remote_max_parallel%& is greater than one, such groups may be sent
36864 in parallel sessions. The order of hosts with identical MX values is not
36865 significant when checking whether addresses can be batched in this way.
36867 When the &(smtp)& transport suffers a temporary failure that is not
36868 message-related, Exim updates its transport-specific database, which contains
36869 records indexed by host name that remember which messages are waiting for each
36870 particular host. It also updates the retry database with new retry times.
36872 .cindex "hints database" "retry keys"
36873 Exim's retry hints are based on host name plus IP address, so if one address of
36874 a multi-homed host is broken, it will soon be skipped most of the time.
36875 See the next section for more detail about error handling.
36877 .cindex "SMTP" "passed connection"
36878 .cindex "SMTP" "batching over TCP/IP"
36879 When a message is successfully delivered over a TCP/IP SMTP connection, Exim
36880 looks in the hints database for the transport to see if there are any queued
36881 messages waiting for the host to which it is connected. If it finds one, it
36882 creates a new Exim process using the &%-MC%& option (which can only be used by
36883 a process running as root or the Exim user) and passes the TCP/IP socket to it
36884 so that it can deliver another message using the same socket. The new process
36885 does only those deliveries that are routed to the connected host, and may in
36886 turn pass the socket on to a third process, and so on.
36888 The &%connection_max_messages%& option of the &(smtp)& transport can be used to
36889 limit the number of messages sent down a single TCP/IP connection.
36891 .cindex "asterisk" "after IP address"
36892 The second and subsequent messages delivered down an existing connection are
36893 identified in the main log by the addition of an asterisk after the closing
36894 square bracket of the IP address.
36899 .subsection "Errors in outgoing SMTP" SECToutSMTPerr
36900 .cindex "error" "in outgoing SMTP"
36901 .cindex "SMTP" "errors in outgoing"
36902 .cindex "host" "error"
36903 Three different kinds of error are recognized for outgoing SMTP: host errors,
36904 message errors, and recipient errors.
36907 .vitem "&*Host errors*&"
36908 A host error is not associated with a particular message or with a
36909 particular recipient of a message. The host errors are:
36912 Connection refused or timed out,
36914 Any error response code on connection,
36916 Any error response code to EHLO or HELO,
36918 Loss of connection at any time, except after &"."&,
36920 I/O errors at any time,
36922 Timeouts during the session, other than in response to MAIL, RCPT or
36923 the &"."& at the end of the data.
36926 For a host error, a permanent error response on connection, or in response to
36927 EHLO, causes all addresses routed to the host to be failed. Any other host
36928 error causes all addresses to be deferred, and retry data to be created for the
36929 host. It is not tried again, for any message, until its retry time arrives. If
36930 the current set of addresses are not all delivered in this run (to some
36931 alternative host), the message is added to the list of those waiting for this
36932 host, so if it is still undelivered when a subsequent successful delivery is
36933 made to the host, it will be sent down the same SMTP connection.
36935 .vitem "&*Message errors*&"
36936 .cindex "message" "error"
36937 A message error is associated with a particular message when sent to a
36938 particular host, but not with a particular recipient of the message. The
36939 message errors are:
36942 Any error response code to MAIL, DATA, or the &"."& that terminates
36945 Timeout after MAIL,
36947 Timeout or loss of connection after the &"."& that terminates the data. A
36948 timeout after the DATA command itself is treated as a host error, as is loss of
36949 connection at any other time.
36952 For a message error, a permanent error response (5&'xx'&) causes all addresses
36953 to be failed, and a delivery error report to be returned to the sender. A
36954 temporary error response (4&'xx'&), or one of the timeouts, causes all
36955 addresses to be deferred. Retry data is not created for the host, but instead,
36956 a retry record for the combination of host plus message id is created. The
36957 message is not added to the list of those waiting for this host. This ensures
36958 that the failing message will not be sent to this host again until the retry
36959 time arrives. However, other messages that are routed to the host are not
36960 affected, so if it is some property of the message that is causing the error,
36961 it will not stop the delivery of other mail.
36963 If the remote host specified support for the SIZE parameter in its response
36964 to EHLO, Exim adds SIZE=&'nnn'& to the MAIL command, so an
36965 over-large message will cause a message error because the error arrives as a
36968 .vitem "&*Recipient errors*&"
36969 .cindex "recipient" "error"
36970 A recipient error is associated with a particular recipient of a message. The
36971 recipient errors are:
36974 Any error response to RCPT,
36976 Timeout after RCPT.
36979 For a recipient error, a permanent error response (5&'xx'&) causes the
36980 recipient address to be failed, and a bounce message to be returned to the
36981 sender. A temporary error response (4&'xx'&) or a timeout causes the failing
36982 address to be deferred, and routing retry data to be created for it. This is
36983 used to delay processing of the address in subsequent queue runs, until its
36984 routing retry time arrives. This applies to all messages, but because it
36985 operates only in queue runs, one attempt will be made to deliver a new message
36986 to the failing address before the delay starts to operate. This ensures that,
36987 if the failure is really related to the message rather than the recipient
36988 (&"message too big for this recipient"& is a possible example), other messages
36989 have a chance of getting delivered. If a delivery to the address does succeed,
36990 the retry information gets cleared, so all stuck messages get tried again, and
36991 the retry clock is reset.
36993 The message is not added to the list of those waiting for this host. Use of the
36994 host for other messages is unaffected, and except in the case of a timeout,
36995 other recipients are processed independently, and may be successfully delivered
36996 in the current SMTP session. After a timeout it is of course impossible to
36997 proceed with the session, so all addresses get deferred. However, those other
36998 than the one that failed do not suffer any subsequent retry delays. Therefore,
36999 if one recipient is causing trouble, the others have a chance of getting
37000 through when a subsequent delivery attempt occurs before the failing
37001 recipient's retry time.
37004 In all cases, if there are other hosts (or IP addresses) available for the
37005 current set of addresses (for example, from multiple MX records), they are
37006 tried in this run for any undelivered addresses, subject of course to their
37007 own retry data. In other words, recipient error retry data does not take effect
37008 until the next delivery attempt.
37010 Some hosts have been observed to give temporary error responses to every
37011 MAIL command at certain times (&"insufficient space"& has been seen). It
37012 would be nice if such circumstances could be recognized, and defer data for the
37013 host itself created, but this is not possible within the current Exim design.
37014 What actually happens is that retry data for every (host, message) combination
37017 The reason that timeouts after MAIL and RCPT are treated specially is that
37018 these can sometimes arise as a result of the remote host's verification
37019 procedures. Exim makes this assumption, and treats them as if a temporary error
37020 response had been received. A timeout after &"."& is treated specially because
37021 it is known that some broken implementations fail to recognize the end of the
37022 message if the last character of the last line is a binary zero. Thus, it is
37023 helpful to treat this case as a message error.
37025 Timeouts at other times are treated as host errors, assuming a problem with the
37026 host, or the connection to it. If a timeout after MAIL, RCPT,
37027 or &"."& is really a connection problem, the assumption is that at the next try
37028 the timeout is likely to occur at some other point in the dialogue, causing it
37029 then to be treated as a host error.
37031 There is experimental evidence that some MTAs drop the connection after the
37032 terminating &"."& if they do not like the contents of the message for some
37033 reason, in contravention of the RFC, which indicates that a 5&'xx'& response
37034 should be given. That is why Exim treats this case as a message rather than a
37035 host error, in order not to delay other messages to the same host.
37040 .section "Incoming SMTP messages over TCP/IP" "SECID233"
37041 .cindex "SMTP" "incoming over TCP/IP"
37042 .cindex "incoming SMTP over TCP/IP"
37045 Incoming SMTP messages can be accepted in one of two ways: by running a
37046 listening daemon, or by using &'inetd'&. In the latter case, the entry in
37047 &_/etc/inetd.conf_& should be like this:
37049 smtp stream tcp nowait exim /opt/exim/bin/exim in.exim -bs
37051 Exim distinguishes between this case and the case of a locally running user
37052 agent using the &%-bs%& option by checking whether or not the standard input is
37053 a socket. When it is, either the port must be privileged (less than 1024), or
37054 the caller must be root or the Exim user. If any other user passes a socket
37055 with an unprivileged port number, Exim prints a message on the standard error
37056 stream and exits with an error code.
37058 By default, Exim does not make a log entry when a remote host connects or
37059 disconnects (either via the daemon or &'inetd'&), unless the disconnection is
37060 unexpected. It can be made to write such log entries by setting the
37061 &%smtp_connection%& log selector.
37063 .cindex "carriage return"
37065 Commands from the remote host are supposed to be terminated by CR followed by
37066 LF. However, there are known to be hosts that do not send CR characters. In
37067 order to be able to interwork with such hosts, Exim treats LF on its own as a
37069 Furthermore, because common code is used for receiving messages from all
37070 sources, a CR on its own is also interpreted as a line terminator. However, the
37071 sequence &"CR, dot, CR"& does not terminate incoming SMTP data.
37073 .cindex "EHLO" "invalid data"
37074 .cindex "HELO" "invalid data"
37075 One area that sometimes gives rise to problems concerns the EHLO or
37076 HELO commands. Some clients send syntactically invalid versions of these
37077 commands, which Exim rejects by default. (This is nothing to do with verifying
37078 the data that is sent, so &%helo_verify_hosts%& is not relevant.) You can tell
37079 Exim not to apply a syntax check by setting &%helo_accept_junk_hosts%& to
37080 match the broken hosts that send invalid commands.
37082 .cindex "SIZE option on MAIL command"
37083 .cindex "MAIL" "SIZE option"
37084 The amount of disk space available is checked whenever SIZE is received on
37085 a MAIL command, independently of whether &%message_size_limit%& or
37086 &%check_spool_space%& is configured, unless &%smtp_check_spool_space%& is set
37087 false. A temporary error is given if there is not enough space. If
37088 &%check_spool_space%& is set, the check is for that amount of space plus the
37089 value given with SIZE, that is, it checks that the addition of the incoming
37090 message will not reduce the space below the threshold.
37092 When a message is successfully received, Exim includes the local message id in
37093 its response to the final &"."& that terminates the data. If the remote host
37094 logs this text it can help with tracing what has happened to a message.
37096 The Exim daemon can limit the number of simultaneous incoming connections it is
37097 prepared to handle (see the &%smtp_accept_max%& option). It can also limit the
37098 number of simultaneous incoming connections from a single remote host (see the
37099 &%smtp_accept_max_per_host%& option). Additional connection attempts are
37100 rejected using the SMTP temporary error code 421.
37102 The Exim daemon does not rely on the SIGCHLD signal to detect when a
37103 subprocess has finished, as this can get lost at busy times. Instead, it looks
37104 for completed subprocesses every time it wakes up. Provided there are other
37105 things happening (new incoming calls, starts of queue runs), completed
37106 processes will be noticed and tidied away. On very quiet systems you may
37107 sometimes see a &"defunct"& Exim process hanging about. This is not a problem;
37108 it will be noticed when the daemon next wakes up.
37110 When running as a daemon, Exim can reserve some SMTP slots for specific hosts,
37111 and can also be set up to reject SMTP calls from non-reserved hosts at times of
37112 high system load &-- for details see the &%smtp_accept_reserve%&,
37113 &%smtp_load_reserve%&, and &%smtp_reserve_hosts%& options. The load check
37114 applies in both the daemon and &'inetd'& cases.
37116 Exim normally starts a delivery process for each message received, though this
37117 can be varied by means of the &%-odq%& command line option and the
37118 &%queue_only%&, &%queue_only_file%&, and &%queue_only_load%& options. The
37119 number of simultaneously running delivery processes started in this way from
37120 SMTP input can be limited by the &%smtp_accept_queue%& and
37121 &%smtp_accept_queue_per_connection%& options. When either limit is reached,
37122 subsequently received messages are just put on the input queue without starting
37123 a delivery process.
37125 The controls that involve counts of incoming SMTP calls (&%smtp_accept_max%&,
37126 &%smtp_accept_queue%&, &%smtp_accept_reserve%&) are not available when Exim is
37127 started up from the &'inetd'& daemon, because in that case each connection is
37128 handled by an entirely independent Exim process. Control by load average is,
37129 however, available with &'inetd'&.
37131 Exim can be configured to verify addresses in incoming SMTP commands as they
37132 are received. See chapter &<<CHAPACL>>& for details. It can also be configured
37133 to rewrite addresses at this time &-- before any syntax checking is done. See
37134 section &<<SSECTrewriteS>>&.
37136 Exim can also be configured to limit the rate at which a client host submits
37137 MAIL and RCPT commands in a single SMTP session. See the
37138 &%smtp_ratelimit_hosts%& option.
37142 .subsection "Unrecognized SMTP commands" SECID234
37143 .cindex "SMTP" "unrecognized commands"
37144 If Exim receives more than &%smtp_max_unknown_commands%& unrecognized SMTP
37145 commands during a single SMTP connection, it drops the connection after sending
37146 the error response to the last command. The default value for
37147 &%smtp_max_unknown_commands%& is 3. This is a defence against some kinds of
37148 abuse that subvert web servers into making connections to SMTP ports; in these
37149 circumstances, a number of non-SMTP lines are sent first.
37152 .subsection "Syntax and protocol errors in SMTP commands" SECID235
37153 .cindex "SMTP" "syntax errors"
37154 .cindex "SMTP" "protocol errors"
37155 A syntax error is detected if an SMTP command is recognized, but there is
37156 something syntactically wrong with its data, for example, a malformed email
37157 address in a RCPT command. Protocol errors include invalid command
37158 sequencing such as RCPT before MAIL. If Exim receives more than
37159 &%smtp_max_synprot_errors%& such commands during a single SMTP connection, it
37160 drops the connection after sending the error response to the last command. The
37161 default value for &%smtp_max_synprot_errors%& is 3. This is a defence against
37162 broken clients that loop sending bad commands (yes, it has been seen).
37166 .subsection "Use of non-mail SMTP commands" SECID236
37167 .cindex "SMTP" "non-mail commands"
37168 The &"non-mail"& SMTP commands are those other than MAIL, RCPT, and
37169 DATA. Exim counts such commands, and drops the connection if there are too
37170 many of them in a single SMTP session. This action catches some
37171 denial-of-service attempts and things like repeated failing AUTHs, or a mad
37172 client looping sending EHLO. The global option &%smtp_accept_max_nonmail%&
37173 defines what &"too many"& means. Its default value is 10.
37175 When a new message is expected, one occurrence of RSET is not counted. This
37176 allows a client to send one RSET between messages (this is not necessary,
37177 but some clients do it). Exim also allows one uncounted occurrence of HELO
37178 or EHLO, and one occurrence of STARTTLS between messages. After
37179 starting up a TLS session, another EHLO is expected, and so it too is not
37182 The first occurrence of AUTH in a connection, or immediately following
37183 STARTTLS is also not counted. Otherwise, all commands other than MAIL,
37184 RCPT, DATA, and QUIT are counted.
37186 You can control which hosts are subject to the limit set by
37187 &%smtp_accept_max_nonmail%& by setting
37188 &%smtp_accept_max_nonmail_hosts%&. The default value is &`*`&, which makes
37189 the limit apply to all hosts. This option means that you can exclude any
37190 specific badly-behaved hosts that you have to live with.
37195 .subsection "The VRFY and EXPN commands" SECID237
37196 When Exim receives a VRFY or EXPN command on a TCP/IP connection, it
37197 runs the ACL specified by &%acl_smtp_vrfy%& or &%acl_smtp_expn%& (as
37198 appropriate) in order to decide whether the command should be accepted or not.
37200 .cindex "VRFY" "processing"
37201 When no ACL is defined for VRFY, or if it rejects without
37202 setting an explicit response code, the command is accepted
37203 (with a 252 SMTP response code)
37204 in order to support awkward clients that do a VRFY before every RCPT.
37205 When VRFY is accepted, it runs exactly the same code as when Exim is
37206 called with the &%-bv%& option, and returns 250/451/550
37207 SMTP response codes.
37209 .cindex "EXPN" "processing"
37210 If no ACL for EXPN is defined, the command is rejected.
37211 When EXPN is accepted, a single-level expansion of the address is done.
37212 EXPN is treated as an &"address test"& (similar to the &%-bt%& option) rather
37213 than a verification (the &%-bv%& option). If an unqualified local part is given
37214 as the argument to EXPN, it is qualified with &%qualify_domain%&. Rejections
37215 of VRFY and EXPN commands are logged on the main and reject logs, and
37216 VRFY verification failures are logged in the main log for consistency with
37221 .subsection "The ETRN command" SECTETRN
37222 .cindex "ETRN" "processing"
37223 .cindex "ESMTP extensions" ETRN
37224 RFC 1985 describes an ESMTP command called ETRN that is designed to
37225 overcome the security problems of the TURN command (which has fallen into
37226 disuse). When Exim receives an ETRN command on a TCP/IP connection, it runs
37227 the ACL specified by &%acl_smtp_etrn%& in order to decide whether the command
37228 should be accepted or not. If no ACL is defined, the command is rejected.
37230 The ETRN command is concerned with &"releasing"& messages that are awaiting
37231 delivery to certain hosts. As Exim does not organize its message queue by host,
37232 the only form of ETRN that is supported by default is the one where the
37233 text starts with the &"#"& prefix, in which case the remainder of the text is
37234 specific to the SMTP server. A valid ETRN command causes a run of Exim with
37235 the &%-R%& option to happen, with the remainder of the ETRN text as its
37236 argument. For example,
37244 which causes a delivery attempt on all messages with undelivered addresses
37245 containing the text &"brigadoon"&. When &%smtp_etrn_serialize%& is set (the
37246 default), Exim prevents the simultaneous execution of more than one queue run
37247 for the same argument string as a result of an ETRN command. This stops
37248 a misbehaving client from starting more than one queue runner at once.
37250 .cindex "hints database" "ETRN serialization"
37251 Exim implements the serialization by means of a hints database in which a
37252 record is written whenever a process is started by ETRN, and deleted when
37253 the process completes. However, Exim does not keep the SMTP session waiting for
37254 the ETRN process to complete. Once ETRN is accepted, the client is sent
37255 a &"success"& return code. Obviously there is scope for hints records to get
37256 left lying around if there is a system or program crash. To guard against this,
37257 Exim ignores any records that are more than six hours old.
37259 .oindex "&%smtp_etrn_command%&"
37260 For more control over what ETRN does, the &%smtp_etrn_command%& option can
37261 used. This specifies a command that is run whenever ETRN is received,
37262 whatever the form of its argument. For
37265 smtp_etrn_command = /etc/etrn_command $domain \
37266 $sender_host_address
37268 .vindex "&$domain$&"
37269 The string is split up into arguments which are independently expanded. The
37270 expansion variable &$domain$& is set to the argument of the ETRN command,
37271 and no syntax checking is done on the contents of this argument. Exim does not
37272 wait for the command to complete, so its status code is not checked. Exim runs
37273 under its own uid and gid when receiving incoming SMTP, so it is not possible
37274 for it to change them before running the command.
37278 .section "Incoming local SMTP" "SECID238"
37279 .cindex "SMTP" "local incoming"
37280 Some user agents use SMTP to pass messages to their local MTA using the
37281 standard input and output, as opposed to passing the envelope on the command
37282 line and writing the message to the standard input. This is supported by the
37283 &%-bs%& option. This form of SMTP is handled in the same way as incoming
37284 messages over TCP/IP (including the use of ACLs), except that the envelope
37285 sender given in a MAIL command is ignored unless the caller is trusted. In
37286 an ACL you can detect this form of SMTP input by testing for an empty host
37287 identification. It is common to have this as the first line in the ACL that
37288 runs for RCPT commands:
37292 This accepts SMTP messages from local processes without doing any other tests.
37296 .section "Outgoing batched SMTP" "SECTbatchSMTP"
37297 .cindex "SMTP" "batched outgoing"
37298 .cindex "batched SMTP output"
37299 Both the &(appendfile)& and &(pipe)& transports can be used for handling
37300 batched SMTP. Each has an option called &%use_bsmtp%& which causes messages to
37301 be output in BSMTP format. No SMTP responses are possible for this form of
37302 delivery. All it is doing is using SMTP commands as a way of transmitting the
37303 envelope along with the message.
37305 The message is written to the file or pipe preceded by the SMTP commands
37306 MAIL and RCPT, and followed by a line containing a single dot. Lines in
37307 the message that start with a dot have an extra dot added. The SMTP command
37308 HELO is not normally used. If it is required, the &%message_prefix%& option
37309 can be used to specify it.
37311 Because &(appendfile)& and &(pipe)& are both local transports, they accept only
37312 one recipient address at a time by default. However, you can arrange for them
37313 to handle several addresses at once by setting the &%batch_max%& option. When
37314 this is done for BSMTP, messages may contain multiple RCPT commands. See
37315 chapter &<<CHAPbatching>>& for more details.
37318 When one or more addresses are routed to a BSMTP transport by a router that
37319 sets up a host list, the name of the first host on the list is available to the
37320 transport in the variable &$host$&. Here is an example of such a transport and
37325 driver = manualroute
37326 transport = smtp_appendfile
37327 route_list = domain.example batch.host.example
37331 driver = appendfile
37332 directory = /var/bsmtp/$host
37337 This causes messages addressed to &'domain.example'& to be written in BSMTP
37338 format to &_/var/bsmtp/batch.host.example_&, with only a single copy of each
37339 message (unless there are more than 1000 recipients).
37343 .section "Incoming batched SMTP" "SECTincomingbatchedSMTP"
37344 .cindex "SMTP" "batched incoming"
37345 .cindex "batched SMTP input"
37346 The &%-bS%& command line option causes Exim to accept one or more messages by
37347 reading SMTP on the standard input, but to generate no responses. If the caller
37348 is trusted, the senders in the MAIL commands are believed; otherwise the
37349 sender is always the caller of Exim. Unqualified senders and receivers are not
37350 rejected (there seems little point) but instead just get qualified. HELO
37351 and EHLO act as RSET; VRFY, EXPN, ETRN and HELP, act
37352 as NOOP; QUIT quits.
37354 Minimal policy checking is done for BSMTP input. Only the non-SMTP
37355 ACL is run in the same way as for non-SMTP local input.
37357 If an error is detected while reading a message, including a missing &"."& at
37358 the end, Exim gives up immediately. It writes details of the error to the
37359 standard output in a stylized way that the calling program should be able to
37360 make some use of automatically, for example:
37362 554 Unexpected end of file
37363 Transaction started in line 10
37364 Error detected in line 14
37366 It writes a more verbose version, for human consumption, to the standard error
37369 An error was detected while processing a file of BSMTP input.
37370 The error message was:
37372 501 '>' missing at end of address
37374 The SMTP transaction started in line 10.
37375 The error was detected in line 12.
37376 The SMTP command at fault was:
37378 rcpt to:<malformed@in.com.plete
37380 1 previous message was successfully processed.
37381 The rest of the batch was abandoned.
37383 The return code from Exim is zero only if there were no errors. It is 1 if some
37384 messages were accepted before an error was detected, and 2 if no messages were
37386 .ecindex IIDsmtpproc1
37387 .ecindex IIDsmtpproc2
37391 . ////////////////////////////////////////////////////////////////////////////
37392 . ////////////////////////////////////////////////////////////////////////////
37394 .chapter "Customizing bounce and warning messages" "CHAPemsgcust" &&&
37395 "Customizing messages"
37396 When a message fails to be delivered, or remains in the queue for more than a
37397 configured amount of time, Exim sends a message to the original sender, or
37398 to an alternative configured address. The text of these messages is built into
37399 the code of Exim, but it is possible to change it, either by adding a single
37400 string, or by replacing each of the paragraphs by text supplied in a file.
37402 The &'From:'& and &'To:'& header lines are automatically generated; you can
37403 cause a &'Reply-To:'& line to be added by setting the &%errors_reply_to%&
37404 option. Exim also adds the line
37406 Auto-Submitted: auto-generated
37408 to all warning and bounce messages,
37411 .section "Customizing bounce messages" "SECID239"
37412 .cindex "customizing" "bounce message"
37413 .cindex "bounce message" "customizing"
37414 If &%bounce_message_text%& is set, its contents are included in the default
37415 message immediately after &"This message was created automatically by mail
37416 delivery software."& The string is not expanded. It is not used if
37417 &%bounce_message_file%& is set.
37419 When &%bounce_message_file%& is set, it must point to a template file for
37420 constructing error messages. The file consists of a series of text items,
37421 separated by lines consisting of exactly four asterisks. If the file cannot be
37422 opened, default text is used and a message is written to the main and panic
37423 logs. If any text item in the file is empty, default text is used for that
37426 .vindex "&$bounce_recipient$&"
37427 .vindex "&$bounce_return_size_limit$&"
37428 Each item of text that is read from the file is expanded, and there are two
37429 expansion variables which can be of use here: &$bounce_recipient$& is set to
37430 the recipient of an error message while it is being created, and
37431 &$bounce_return_size_limit$& contains the value of the &%return_size_limit%&
37432 option, rounded to a whole number.
37434 The items must appear in the file in the following order:
37437 The first item is included in the headers, and should include at least a
37438 &'Subject:'& header. Exim does not check the syntax of these headers.
37440 The second item forms the start of the error message. After it, Exim lists the
37441 failing addresses with their error messages.
37443 The third item is used to introduce any text from pipe transports that is to be
37444 returned to the sender. It is omitted if there is no such text.
37446 The fourth, fifth and sixth items will be ignored and may be empty.
37447 The fields exist for back-compatibility
37450 The default state (&%bounce_message_file%& unset) is equivalent to the
37451 following file, in which the sixth item is empty. The &'Subject:'& and some
37452 other lines have been split in order to fit them on the page:
37454 Subject: Mail delivery failed
37455 ${if eq{$sender_address}{$bounce_recipient}
37456 {: returning message to sender}}
37458 This message was created automatically by mail delivery software.
37460 A message ${if eq{$sender_address}{$bounce_recipient}
37461 {that you sent }{sent by
37465 }}could not be delivered to all of its recipients.
37466 This is a permanent error. The following address(es) failed:
37468 The following text was generated during the delivery attempt(s):
37470 ------ This is a copy of the message, including all the headers.
37473 ------ The body of the message is $message_size characters long;
37475 ------ $bounce_return_size_limit or so are included here.
37478 .section "Customizing warning messages" "SECTcustwarn"
37479 .cindex "customizing" "warning message"
37480 .cindex "warning of delay" "customizing the message"
37481 The option &%warn_message_file%& can be pointed at a template file for use when
37482 warnings about message delays are created. In this case there are only three
37486 The first item is included in the headers, and should include at least a
37487 &'Subject:'& header. Exim does not check the syntax of these headers.
37489 The second item forms the start of the warning message. After it, Exim lists
37490 the delayed addresses.
37492 The third item then ends the message.
37495 The default state is equivalent to the following file, except that some lines
37496 have been split here, in order to fit them on the page:
37498 Subject: Warning: message $message_exim_id delayed
37499 $warn_message_delay
37501 This message was created automatically by mail delivery software.
37503 A message ${if eq{$sender_address}{$warn_message_recipients}
37504 {that you sent }{sent by
37508 }}has not been delivered to all of its recipients after
37509 more than $warn_message_delay in the queue on $primary_hostname.
37511 The message identifier is: $message_exim_id
37512 The subject of the message is: $h_subject
37513 The date of the message is: $h_date
37515 The following address(es) have not yet been delivered:
37517 No action is required on your part. Delivery attempts will
37518 continue for some time, and this warning may be repeated at
37519 intervals if the message remains undelivered. Eventually the
37520 mail delivery software will give up, and when that happens,
37521 the message will be returned to you.
37523 .vindex "&$warn_message_delay$&"
37524 .vindex "&$warn_message_recipients$&"
37525 However, in the default state the subject and date lines are omitted if no
37526 appropriate headers exist. During the expansion of this file,
37527 &$warn_message_delay$& is set to the delay time in one of the forms &"<&'n'&>
37528 minutes"& or &"<&'n'&> hours"&, and &$warn_message_recipients$& contains a list
37529 of recipients for the warning message. There may be more than one if there are
37530 multiple addresses with different &%errors_to%& settings on the routers that
37536 . ////////////////////////////////////////////////////////////////////////////
37537 . ////////////////////////////////////////////////////////////////////////////
37539 .chapter "Some common configuration settings" "CHAPcomconreq"
37540 This chapter discusses some configuration settings that seem to be fairly
37541 common. More examples and discussion can be found in the Exim book.
37545 .section "Sending mail to a smart host" "SECID240"
37546 .cindex "smart host" "example router"
37547 If you want to send all mail for non-local domains to a &"smart host"&, you
37548 should replace the default &(dnslookup)& router with a router which does the
37549 routing explicitly:
37551 send_to_smart_host:
37552 driver = manualroute
37553 route_list = !+local_domains smart.host.name
37554 transport = remote_smtp
37556 You can use the smart host's IP address instead of the name if you wish.
37557 If you are using Exim only to submit messages to a smart host, and not for
37558 receiving incoming messages, you can arrange for it to do the submission
37559 synchronously by setting the &%mua_wrapper%& option (see chapter
37560 &<<CHAPnonqueueing>>&).
37565 .section "Using Exim to handle mailing lists" "SECTmailinglists"
37566 .cindex "mailing lists"
37567 Exim can be used to run simple mailing lists, but for large and/or complicated
37568 requirements, the use of additional specialized mailing list software such as
37569 Majordomo or Mailman is recommended.
37571 The &(redirect)& router can be used to handle mailing lists where each list
37572 is maintained in a separate file, which can therefore be managed by an
37573 independent manager. The &%domains%& router option can be used to run these
37574 lists in a separate domain from normal mail. For example:
37578 domains = lists.example
37579 file = ${lookup {$local_part} dsearch,ret=full {/usr/lists}}
37582 errors_to = ${quote_local_part:$local_part-request}@lists.example
37585 This router is skipped for domains other than &'lists.example'&. For addresses
37586 in that domain, it looks for a file that matches the local part. If there is no
37587 such file, the router declines, but because &%no_more%& is set, no subsequent
37588 routers are tried, and so the whole delivery fails.
37590 The &%forbid_pipe%& and &%forbid_file%& options prevent a local part from being
37591 expanded into a filename or a pipe delivery, which is usually inappropriate in
37594 .oindex "&%errors_to%&"
37595 The &%errors_to%& option specifies that any delivery errors caused by addresses
37596 taken from a mailing list are to be sent to the given address rather than the
37597 original sender of the message. However, before acting on this, Exim verifies
37598 the error address, and ignores it if verification fails.
37600 For example, using the configuration above, mail sent to
37601 &'dicts@lists.example'& is passed on to those addresses contained in
37602 &_/usr/lists/dicts_&, with error reports directed to
37603 &'dicts-request@lists.example'&, provided that this address can be verified.
37604 There could be a file called &_/usr/lists/dicts-request_& containing
37605 the address(es) of this particular list's manager(s), but other approaches,
37606 such as setting up an earlier router (possibly using the &%local_part_prefix%&
37607 or &%local_part_suffix%& options) to handle addresses of the form
37608 &%owner-%&&'xxx'& or &%xxx-%&&'request'&, are also possible.
37612 .section "Syntax errors in mailing lists" "SECID241"
37613 .cindex "mailing lists" "syntax errors in"
37614 If an entry in redirection data contains a syntax error, Exim normally defers
37615 delivery of the original address. That means that a syntax error in a mailing
37616 list holds up all deliveries to the list. This may not be appropriate when a
37617 list is being maintained automatically from data supplied by users, and the
37618 addresses are not rigorously checked.
37620 If the &%skip_syntax_errors%& option is set, the &(redirect)& router just skips
37621 entries that fail to parse, noting the incident in the log. If in addition
37622 &%syntax_errors_to%& is set to a verifiable address, a message is sent to it
37623 whenever a broken address is skipped. It is usually appropriate to set
37624 &%syntax_errors_to%& to the same address as &%errors_to%&.
37628 .section "Re-expansion of mailing lists" "SECID242"
37629 .cindex "mailing lists" "re-expansion of"
37630 Exim remembers every individual address to which a message has been delivered,
37631 in order to avoid duplication, but it normally stores only the original
37632 recipient addresses with a message. If all the deliveries to a mailing list
37633 cannot be done at the first attempt, the mailing list is re-expanded when the
37634 delivery is next tried. This means that alterations to the list are taken into
37635 account at each delivery attempt, so addresses that have been added to
37636 the list since the message arrived will therefore receive a copy of the
37637 message, even though it pre-dates their subscription.
37639 If this behaviour is felt to be undesirable, the &%one_time%& option can be set
37640 on the &(redirect)& router. If this is done, any addresses generated by the
37641 router that fail to deliver at the first attempt are added to the message as
37642 &"top level"& addresses, and the parent address that generated them is marked
37643 &"delivered"&. Thus, expansion of the mailing list does not happen again at the
37644 subsequent delivery attempts. The disadvantage of this is that if any of the
37645 failing addresses are incorrect, correcting them in the file has no effect on
37646 pre-existing messages.
37648 The original top-level address is remembered with each of the generated
37649 addresses, and is output in any log messages. However, any intermediate parent
37650 addresses are not recorded. This makes a difference to the log only if the
37651 &%all_parents%& selector is set, but for mailing lists there is normally only
37652 one level of expansion anyway.
37656 .section "Closed mailing lists" "SECID243"
37657 .cindex "mailing lists" "closed"
37658 The examples so far have assumed open mailing lists, to which anybody may
37659 send mail. It is also possible to set up closed lists, where mail is accepted
37660 from specified senders only. This is done by making use of the generic
37661 &%senders%& option to restrict the router that handles the list.
37663 The following example uses the same file as a list of recipients and as a list
37664 of permitted senders. It requires three routers:
37668 domains = lists.example
37669 local_part_suffix = -request
37670 local_parts = ${lookup {$local_part} dsearch,filter=file {/usr/lists}}
37671 file = /usr/lists/${local_part_data}-request
37676 domains = lists.example
37677 local_parts = ${lookup {$local_part} dsearch,filter=file,ret=full {/usr/lists}}
37678 senders = ${if exists {$local_part_data} {lsearch;$local_part_data}{*}}
37679 file = ${lookup {$local_part} dsearch,ret=full {/usr/lists}}
37682 errors_to = ${quote_local_part:$local_part-request}@lists.example
37687 domains = lists.example
37689 data = :fail: $local_part@lists.example is a closed mailing list
37691 All three routers have the same &%domains%& setting, so for any other domains,
37692 they are all skipped. The first router runs only if the local part ends in
37693 &%-request%&. It handles messages to the list manager(s) by means of an open
37696 The second router runs only if the &%senders%& precondition is satisfied. It
37697 checks for the existence of a list that corresponds to the local part, and then
37698 checks that the sender is on the list by means of a linear search. It is
37699 necessary to check for the existence of the file before trying to search it,
37700 because otherwise Exim thinks there is a configuration error. If the file does
37701 not exist, the expansion of &%senders%& is *, which matches all senders. This
37702 means that the router runs, but because there is no list, declines, and
37703 &%no_more%& ensures that no further routers are run. The address fails with an
37704 &"unrouteable address"& error.
37706 The third router runs only if the second router is skipped, which happens when
37707 a mailing list exists, but the sender is not on it. This router forcibly fails
37708 the address, giving a suitable error message.
37713 .section "Variable Envelope Return Paths (VERP)" "SECTverp"
37715 .cindex "Variable Envelope Return Paths"
37716 .cindex "envelope from"
37717 .cindex "envelope sender"
37718 Variable Envelope Return Paths &-- see &url(https://cr.yp.to/proto/verp.txt) &--
37719 are a way of helping mailing list administrators discover which subscription
37720 address is the cause of a particular delivery failure. The idea is to encode
37721 the original recipient address in the outgoing envelope sender address, so that
37722 if the message is forwarded by another host and then subsequently bounces, the
37723 original recipient can be extracted from the recipient address of the bounce.
37725 .oindex &%errors_to%&
37726 .oindex &%return_path%&
37727 Envelope sender addresses can be modified by Exim using two different
37728 facilities: the &%errors_to%& option on a router (as shown in previous mailing
37729 list examples), or the &%return_path%& option on a transport. The second of
37730 these is effective only if the message is successfully delivered to another
37731 host; it is not used for errors detected on the local host (see the description
37732 of &%return_path%& in chapter &<<CHAPtransportgeneric>>&). Here is an example
37733 of the use of &%return_path%& to implement VERP on an &(smtp)& transport:
37739 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
37740 {${quote_local_part:$1-request+$local_part=$domain}@your.dom.example}fail}
37742 This has the effect of rewriting the return path (envelope sender) on outgoing
37743 SMTP messages, if the local part of the original return path ends in
37744 &"-request"&, and the domain is &'your.dom.example'&. The rewriting inserts the
37745 local part and domain of the recipient into the return path. Suppose, for
37746 example, that a message whose return path has been set to
37747 &'somelist-request@your.dom.example'& is sent to
37748 &'subscriber@other.dom.example'&. In the transport, the return path is
37751 somelist-request+subscriber=other.dom.example@your.dom.example
37753 .vindex "&$local_part$&"
37754 For this to work, you must tell Exim to send multiple copies of messages that
37755 have more than one recipient, so that each copy has just one recipient. This is
37756 achieved by setting &%max_rcpt%& to 1. Without this, a single copy of a message
37757 might be sent to several different recipients in the same domain, in which case
37758 &$local_part$& is not available in the transport, because it is not unique.
37760 Unless your host is doing nothing but mailing list deliveries, you should
37761 probably use a separate transport for the VERP deliveries, so as not to use
37762 extra resources in making one-per-recipient copies for other deliveries. This
37763 can easily be done by expanding the &%transport%& option in the router:
37767 domains = ! +local_domains
37769 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
37770 {verp_smtp}{remote_smtp}}
37773 If you want to change the return path using &%errors_to%& in a router instead
37774 of using &%return_path%& in the transport, you need to set &%errors_to%& on all
37775 routers that handle mailing list addresses. This will ensure that all delivery
37776 errors, including those detected on the local host, are sent to the VERP
37779 On a host that does no local deliveries and has no manual routing, only the
37780 &(dnslookup)& router needs to be changed. A special transport is not needed for
37781 SMTP deliveries. Every mailing list recipient has its own return path value,
37782 and so Exim must hand them to the transport one at a time. Here is an example
37783 of a &(dnslookup)& router that implements VERP:
37787 domains = ! +local_domains
37788 transport = remote_smtp
37790 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}}
37791 {${quote_local_part:$1-request+$local_part=$domain}@your.dom.example}fail}
37794 Before you start sending out messages with VERPed return paths, you must also
37795 configure Exim to accept the bounce messages that come back to those paths.
37796 Typically this is done by setting a &%local_part_suffix%& option for a
37797 router, and using this to route the messages to wherever you want to handle
37800 The overhead incurred in using VERP depends very much on the size of the
37801 message, the number of recipient addresses that resolve to the same remote
37802 host, and the speed of the connection over which the message is being sent. If
37803 a lot of addresses resolve to the same host and the connection is slow, sending
37804 a separate copy of the message for each address may take substantially longer
37805 than sending a single copy with many recipients (for which VERP cannot be
37813 .section "Virtual domains" "SECTvirtualdomains"
37814 .cindex "virtual domains"
37815 .cindex "domain" "virtual"
37816 The phrase &'virtual domain'& is unfortunately used with two rather different
37820 A domain for which there are no real mailboxes; all valid local parts are
37821 aliases for other email addresses. Common examples are organizational
37822 top-level domains and &"vanity"& domains.
37824 One of a number of independent domains that are all handled by the same host,
37825 with mailboxes on that host, but where the mailbox owners do not necessarily
37826 have login accounts on that host.
37829 The first usage is probably more common, and does seem more &"virtual"& than
37830 the second. This kind of domain can be handled in Exim with a straightforward
37831 aliasing router. One approach is to create a separate alias file for each
37832 virtual domain. Exim can test for the existence of the alias file to determine
37833 whether the domain exists. The &(dsearch)& lookup type is useful here, leading
37834 to a router of this form:
37838 domains = dsearch;/etc/mail/virtual
37839 data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain_data}}
37842 The &%domains%& option specifies that the router is to be skipped, unless there
37843 is a file in the &_/etc/mail/virtual_& directory whose name is the same as the
37844 domain that is being processed.
37845 The &(dsearch)& lookup used results in an untainted version of &$domain$&
37846 being placed into the &$domain_data$& variable.
37848 When the router runs, it looks up the local
37849 part in the file to find a new address (or list of addresses). The &%no_more%&
37850 setting ensures that if the lookup fails (leading to &%data%& being an empty
37851 string), Exim gives up on the address without trying any subsequent routers.
37853 This one router can handle all the virtual domains because the alias filenames
37854 follow a fixed pattern. Permissions can be arranged so that appropriate people
37855 can edit the different alias files. A successful aliasing operation results in
37856 a new envelope recipient address, which is then routed from scratch.
37858 The other kind of &"virtual"& domain can also be handled in a straightforward
37859 way. One approach is to create a file for each domain containing a list of
37860 valid local parts, and use it in a router like this:
37864 domains = dsearch;/etc/mail/domains
37865 local_parts = lsearch;/etc/mail/domains/$domain
37866 transport = my_mailboxes
37868 The address is accepted if there is a file for the domain, and the local part
37869 can be found in the file. The &%domains%& option is used to check for the
37870 file's existence because &%domains%& is tested before the &%local_parts%&
37871 option (see section &<<SECTrouprecon>>&). You cannot use &%require_files%&,
37872 because that option is tested after &%local_parts%&. The transport is as
37876 driver = appendfile
37877 file = /var/mail/$domain_data/$local_part_data
37880 This uses a directory of mailboxes for each domain. The &%user%& setting is
37881 required, to specify which uid is to be used for writing to the mailboxes.
37883 The configuration shown here is just one example of how you might support this
37884 requirement. There are many other ways this kind of configuration can be set
37885 up, for example, by using a database instead of separate files to hold all the
37886 information about the domains.
37890 .section "Multiple user mailboxes" "SECTmulbox"
37891 .cindex "multiple mailboxes"
37892 .cindex "mailbox" "multiple"
37893 .cindex "local part" "prefix"
37894 .cindex "local part" "suffix"
37895 Heavy email users often want to operate with multiple mailboxes, into which
37896 incoming mail is automatically sorted. A popular way of handling this is to
37897 allow users to use multiple sender addresses, so that replies can easily be
37898 identified. Users are permitted to add prefixes or suffixes to their local
37899 parts for this purpose. The wildcard facility of the generic router options
37900 &%local_part_prefix%& and &%local_part_suffix%& can be used for this. For
37901 example, consider this router:
37906 file = $home/.forward
37907 local_part_suffix = -*
37908 local_part_suffix_optional
37911 .vindex "&$local_part_suffix$&"
37912 It runs a user's &_.forward_& file for all local parts of the form
37913 &'username-*'&. Within the filter file the user can distinguish different
37914 cases by testing the variable &$local_part_suffix$&. For example:
37916 if $local_part_suffix contains -special then
37917 save /home/$local_part_data/Mail/special
37920 If the filter file does not exist, or does not deal with such addresses, they
37921 fall through to subsequent routers, and, assuming no subsequent use of the
37922 &%local_part_suffix%& option is made, they presumably fail. Thus, users have
37923 control over which suffixes are valid.
37925 Alternatively, a suffix can be used to trigger the use of a different
37926 &_.forward_& file &-- which is the way a similar facility is implemented in
37932 local_part_suffix = -*
37933 local_part_suffix_optional
37934 file = ${lookup {.forward$local_part_suffix} dsearch,ret=full {$home} {$value}fail}
37937 If there is no suffix, &_.forward_& is used; if the suffix is &'-special'&, for
37938 example, &_.forward-special_& is used. Once again, if the appropriate file
37939 does not exist, or does not deal with the address, it is passed on to
37940 subsequent routers, which could, if required, look for an unqualified
37941 &_.forward_& file to use as a default.
37945 .section "Simplified vacation processing" "SECID244"
37946 .cindex "vacation processing"
37947 The traditional way of running the &'vacation'& program is for a user to set up
37948 a pipe command in a &_.forward_& file
37949 (see section &<<SECTspecitredli>>& for syntax details).
37950 This is prone to error by inexperienced users. There are two features of Exim
37951 that can be used to make this process simpler for users:
37954 A local part prefix such as &"vacation-"& can be specified on a router which
37955 can cause the message to be delivered directly to the &'vacation'& program, or
37956 alternatively can use Exim's &(autoreply)& transport. The contents of a user's
37957 &_.forward_& file are then much simpler. For example:
37959 spqr, vacation-spqr
37962 The &%require_files%& generic router option can be used to trigger a
37963 vacation delivery by checking for the existence of a certain file in the
37964 user's home directory. The &%unseen%& generic option should also be used, to
37965 ensure that the original delivery also proceeds. In this case, all the user has
37966 to do is to create a file called, say, &_.vacation_&, containing a vacation
37970 Another advantage of both these methods is that they both work even when the
37971 use of arbitrary pipes by users is locked out.
37975 .section "Taking copies of mail" "SECID245"
37976 .cindex "message" "copying every"
37977 Some installations have policies that require archive copies of all messages to
37978 be made. A single copy of each message can easily be taken by an appropriate
37979 command in a system filter, which could, for example, use a different file for
37980 each day's messages.
37982 There is also a shadow transport mechanism that can be used to take copies of
37983 messages that are successfully delivered by local transports, one copy per
37984 delivery. This could be used, &'inter alia'&, to implement automatic
37985 notification of delivery by sites that insist on doing such things.
37989 .section "Intermittently connected hosts" "SECID246"
37990 .cindex "intermittently connected hosts"
37991 It has become quite common (because it is cheaper) for hosts to connect to the
37992 Internet periodically rather than remain connected all the time. The normal
37993 arrangement is that mail for such hosts accumulates on a system that is
37994 permanently connected.
37996 Exim was designed for use on permanently connected hosts, and so it is not
37997 particularly well-suited to use in an intermittently connected environment.
37998 Nevertheless there are some features that can be used.
38001 .section "Exim on the upstream server host" "SECID247"
38002 It is tempting to arrange for incoming mail for the intermittently connected
38003 host to remain in Exim's queue until the client connects. However, this
38004 approach does not scale very well. Two different kinds of waiting message are
38005 being mixed up in the same queue &-- those that cannot be delivered because of
38006 some temporary problem, and those that are waiting for their destination host
38007 to connect. This makes it hard to manage the queue, as well as wasting
38008 resources, because each queue runner scans the entire queue.
38010 A better approach is to separate off those messages that are waiting for an
38011 intermittently connected host. This can be done by delivering these messages
38012 into local files in batch SMTP, &"mailstore"&, or other envelope-preserving
38013 format, from where they are transmitted by other software when their
38014 destination connects. This makes it easy to collect all the mail for one host
38015 in a single directory, and to apply local timeout rules on a per-message basis
38018 On a very small scale, leaving the mail on Exim's queue can be made to work. If
38019 you are doing this, you should configure Exim with a long retry period for the
38020 intermittent host. For example:
38022 cheshire.wonderland.fict.example * F,5d,24h
38024 This stops a lot of failed delivery attempts from occurring, but Exim remembers
38025 which messages it has queued up for that host. Once the intermittent host comes
38026 online, forcing delivery of one message (either by using the &%-M%& or &%-R%&
38027 options, or by using the ETRN SMTP command (see section &<<SECTETRN>>&)
38028 causes all the queued up messages to be delivered, often down a single SMTP
38029 connection. While the host remains connected, any new messages get delivered
38032 If the connecting hosts do not have fixed IP addresses, that is, if a host is
38033 issued with a different IP address each time it connects, Exim's retry
38034 mechanisms on the holding host get confused, because the IP address is normally
38035 used as part of the key string for holding retry information. This can be
38036 avoided by unsetting &%retry_include_ip_address%& on the &(smtp)& transport.
38037 Since this has disadvantages for permanently connected hosts, it is best to
38038 arrange a separate transport for the intermittently connected ones.
38042 .section "Exim on the intermittently connected client host" "SECID248"
38043 The value of &%smtp_accept_queue_per_connection%& should probably be
38044 increased, or even set to zero (that is, disabled) on the intermittently
38045 connected host, so that all incoming messages down a single connection get
38046 delivered immediately.
38048 .cindex "SMTP" "passed connection"
38049 .cindex "SMTP" "multiple deliveries"
38050 .cindex "multiple SMTP deliveries"
38051 .cindex "first pass routing"
38052 Mail waiting to be sent from an intermittently connected host will probably
38053 not have been routed, because without a connection DNS lookups are not
38054 possible. This means that if a normal queue run is done at connection time,
38055 each message is likely to be sent in a separate SMTP session. This can be
38056 avoided by starting the queue run with a command line option beginning with
38057 &%-qq%& instead of &%-q%&. In this case, the queue is scanned twice. In the
38058 first pass, routing is done but no deliveries take place. The second pass is a
38059 normal queue run; since all the messages have been previously routed, those
38060 destined for the same host are likely to get sent as multiple deliveries in a
38061 single SMTP connection.
38065 . ////////////////////////////////////////////////////////////////////////////
38066 . ////////////////////////////////////////////////////////////////////////////
38068 .chapter "Using Exim as a non-queueing client" "CHAPnonqueueing" &&&
38069 "Exim as a non-queueing client"
38070 .cindex "client, non-queueing"
38071 .cindex "smart host" "suppressing queueing"
38072 On a personal computer, it is a common requirement for all
38073 email to be sent to a &"smart host"&. There are plenty of MUAs that can be
38074 configured to operate that way, for all the popular operating systems.
38075 However, there are some MUAs for Unix-like systems that cannot be so
38076 configured: they submit messages using the command line interface of
38077 &_/usr/sbin/sendmail_&. Furthermore, utility programs such as &'cron'& submit
38080 If the personal computer runs continuously, there is no problem, because it can
38081 run a conventional MTA that handles delivery to the smart host, and deal with
38082 any delays via its queueing mechanism. However, if the computer does not run
38083 continuously or runs different operating systems at different times, queueing
38084 email is not desirable.
38086 There is therefore a requirement for something that can provide the
38087 &_/usr/sbin/sendmail_& interface but deliver messages to a smart host without
38088 any queueing or retrying facilities. Furthermore, the delivery to the smart
38089 host should be synchronous, so that if it fails, the sending MUA is immediately
38090 informed. In other words, we want something that extends an MUA that submits
38091 to a local MTA via the command line so that it behaves like one that submits
38092 to a remote smart host using TCP/SMTP.
38094 There are a number of applications (for example, there is one called &'ssmtp'&)
38095 that do this job. However, people have found them to be lacking in various
38096 ways. For instance, you might want to allow aliasing and forwarding to be done
38097 before sending a message to the smart host.
38099 Exim already had the necessary infrastructure for doing this job. Just a few
38100 tweaks were needed to make it behave as required, though it is somewhat of an
38101 overkill to use a fully-featured MTA for this purpose.
38103 .oindex "&%mua_wrapper%&"
38104 There is a Boolean global option called &%mua_wrapper%&, defaulting false.
38105 Setting &%mua_wrapper%& true causes Exim to run in a special mode where it
38106 assumes that it is being used to &"wrap"& a command-line MUA in the manner
38107 just described. As well as setting &%mua_wrapper%&, you also need to provide a
38108 compatible router and transport configuration. Typically there will be just one
38109 router and one transport, sending everything to a smart host.
38111 When run in MUA wrapping mode, the behaviour of Exim changes in the
38115 A daemon cannot be run, nor will Exim accept incoming messages from &'inetd'&.
38116 In other words, the only way to submit messages is via the command line.
38118 Each message is synchronously delivered as soon as it is received (&%-odi%& is
38119 assumed). All queueing options (&%queue_only%&, &%queue_smtp_domains%&,
38120 &%control%& in an ACL, etc.) are quietly ignored. The Exim reception process
38121 does not finish until the delivery attempt is complete. If the delivery is
38122 successful, a zero return code is given.
38124 Address redirection is permitted, but the final routing for all addresses must
38125 be to the same remote transport, and to the same list of hosts. Furthermore,
38126 the return address (envelope sender) must be the same for all recipients, as
38127 must any added or deleted header lines. In other words, it must be possible to
38128 deliver the message in a single SMTP transaction, however many recipients there
38131 If these conditions are not met, or if routing any address results in a
38132 failure or defer status, or if Exim is unable to deliver all the recipients
38133 successfully to one of the smart hosts, delivery of the entire message fails.
38135 Because no queueing is allowed, all failures are treated as permanent; there
38136 is no distinction between 4&'xx'& and 5&'xx'& SMTP response codes from the
38137 smart host. Furthermore, because only a single yes/no response can be given to
38138 the caller, it is not possible to deliver to some recipients and not others. If
38139 there is an error (temporary or permanent) for any recipient, all are failed.
38141 If more than one smart host is listed, Exim will try another host after a
38142 connection failure or a timeout, in the normal way. However, if this kind of
38143 failure happens for all the hosts, the delivery fails.
38145 When delivery fails, an error message is written to the standard error stream
38146 (as well as to Exim's log), and Exim exits to the caller with a return code
38147 value 1. The message is expunged from Exim's spool files. No bounce messages
38148 are ever generated.
38150 No retry data is maintained, and any retry rules are ignored.
38152 A number of Exim options are overridden: &%deliver_drop_privilege%& is forced
38153 true, &%max_rcpt%& in the &(smtp)& transport is forced to &"unlimited"&,
38154 &%remote_max_parallel%& is forced to one, and fallback hosts are ignored.
38157 The overall effect is that Exim makes a single synchronous attempt to deliver
38158 the message, failing if there is any kind of problem. Because no local
38159 deliveries are done and no daemon can be run, Exim does not need root
38160 privilege. It should be possible to run it setuid to &'exim'& instead of setuid
38161 to &'root'&. See section &<<SECTrunexiwitpri>>& for a general discussion about
38162 the advantages and disadvantages of running without root privilege.
38167 . ////////////////////////////////////////////////////////////////////////////
38168 . ////////////////////////////////////////////////////////////////////////////
38170 .chapter "Log files" "CHAPlog"
38171 .scindex IIDloggen "log" "general description"
38172 .cindex "log" "types of"
38173 Exim writes three different logs, referred to as the main log, the reject log,
38178 The main log records the arrival of each message and each delivery in a single
38179 line in each case. The format is as compact as possible, in an attempt to keep
38180 down the size of log files. Two-character flag sequences make it easy to pick
38181 out these lines. A number of other events are recorded in the main log. Some of
38182 them are optional, in which case the &%log_selector%& option controls whether
38183 they are included or not. A Perl script called &'eximstats'&, which does simple
38184 analysis of main log files, is provided in the Exim distribution (see section
38185 &<<SECTmailstat>>&).
38187 .cindex "reject log"
38188 The reject log records information from messages that are rejected as a result
38189 of a configuration option (that is, for policy reasons).
38190 The first line of each rejection is a copy of the line that is also written to
38191 the main log. Then, if the message's header has been read at the time the log
38192 is written, its contents are written to this log. Only the original header
38193 lines are available; header lines added by ACLs are not logged. You can use the
38194 reject log to check that your policy controls are working correctly; on a busy
38195 host this may be easier than scanning the main log for rejection messages. You
38196 can suppress the writing of the reject log by setting &%write_rejectlog%&
38199 .cindex "panic log"
38200 .cindex "system log"
38201 When certain serious errors occur, Exim writes entries to its panic log. If the
38202 error is sufficiently disastrous, Exim bombs out afterwards. Panic log entries
38203 are usually written to the main log as well, but can get lost amid the mass of
38204 other entries. The panic log should be empty under normal circumstances. It is
38205 therefore a good idea to check it (or to have a &'cron'& script check it)
38206 regularly, in order to become aware of any problems. When Exim cannot open its
38207 panic log, it tries as a last resort to write to the system log (syslog). This
38208 is opened with LOG_PID+LOG_CONS and the facility code of LOG_MAIL. The
38209 message itself is written at priority LOG_CRIT.
38212 Every log line starts with a timestamp, in the format shown in the following
38213 example. Note that many of the examples shown in this chapter are line-wrapped.
38214 In the log file, this would be all on one line:
38216 2001-09-16 16:09:47 SMTP connection from [127.0.0.1] closed
38219 By default, the timestamps are in the local timezone. There are two
38220 ways of changing this:
38223 You can set the &%timezone%& option to a different time zone; in particular, if
38228 the timestamps will be in UTC (aka GMT).
38230 If you set &%log_timezone%& true, the time zone is added to the timestamp, for
38233 2003-04-25 11:17:07 +0100 Start queue run: pid=12762
38237 .cindex "log" "process ids in"
38238 .cindex "pid (process id)" "in log lines"
38239 Exim does not include its process id in log lines by default, but you can
38240 request that it does so by specifying the &`pid`& log selector (see section
38241 &<<SECTlogselector>>&). When this is set, the process id is output, in square
38242 brackets, immediately after the time and date.
38247 .section "Where the logs are written" "SECTwhelogwri"
38248 .cindex "log" "destination"
38249 .cindex "log" "to file"
38250 .cindex "log" "to syslog"
38252 The logs may be written to local files, or to syslog, or both. However, it
38253 should be noted that many syslog implementations use UDP as a transport, and
38254 are therefore unreliable in the sense that messages are not guaranteed to
38255 arrive at the loghost, nor is the ordering of messages necessarily maintained.
38256 It has also been reported that on large log files (tens of megabytes) you may
38257 need to tweak syslog to prevent it syncing the file with each write &-- on
38258 Linux this has been seen to make syslog take 90% plus of CPU time.
38260 The destination for Exim's logs is configured by setting LOG_FILE_PATH in
38261 &_Local/Makefile_& or by setting &%log_file_path%& in the runtime
38262 configuration. This latter string is expanded, so it can contain, for example,
38263 references to the host name:
38265 log_file_path = /var/log/$primary_hostname/exim_%slog
38267 It is generally advisable, however, to set the string in &_Local/Makefile_&
38268 rather than at runtime, because then the setting is available right from the
38269 start of Exim's execution. Otherwise, if there's something it wants to log
38270 before it has read the configuration file (for example, an error in the
38271 configuration file) it will not use the path you want, and may not be able to
38274 The value of LOG_FILE_PATH or &%log_file_path%& is a colon-separated
38275 list, currently limited to at most two items. This is one option where the
38276 facility for changing a list separator may not be used. The list must always be
38277 colon-separated. If an item in the list is &"syslog"& then syslog is used;
38278 otherwise the item must either be an absolute path, containing &`%s`& at the
38279 point where &"main"&, &"reject"&, or &"panic"& is to be inserted, or be empty,
38280 implying the use of a default path.
38282 When Exim encounters an empty item in the list, it searches the list defined by
38283 LOG_FILE_PATH, and uses the first item it finds that is neither empty nor
38284 &"syslog"&. This means that an empty item in &%log_file_path%& can be used to
38285 mean &"use the path specified at build time"&. If no such item exists, log
38286 files are written in the &_log_& subdirectory of the spool directory. This is
38287 equivalent to the configuration file setting:
38289 log_file_path = $spool_directory/log/%slog
38291 If you do not specify anything at build time or runtime,
38292 or if you unset the option at runtime (i.e. &`log_file_path = `&),
38293 that is where the logs are written.
38295 A log file path may also contain &`%D`& or &`%M`& if datestamped log filenames
38296 are in use &-- see section &<<SECTdatlogfil>>& below.
38298 Here are some examples of possible Makefile settings:
38300 &`LOG_FILE_PATH=syslog `& syslog only
38301 &`LOG_FILE_PATH=:syslog `& syslog and default path
38302 &`LOG_FILE_PATH=syslog : /usr/log/exim_%s `& syslog and specified path
38303 &`LOG_FILE_PATH=/usr/log/exim_%s `& specified path only
38305 If there are more than two paths in the list, the first is used and a panic
38310 .section "Logging to local files that are periodically &""cycled""&" "SECID285"
38311 .cindex "log" "cycling local files"
38312 .cindex "cycling logs"
38313 .cindex "&'exicyclog'&"
38314 .cindex "log" "local files; writing to"
38315 Some operating systems provide centralized and standardized methods for cycling
38316 log files. For those that do not, a utility script called &'exicyclog'& is
38317 provided (see section &<<SECTcyclogfil>>&). This renames and compresses the
38318 main and reject logs each time it is called. The maximum number of old logs to
38319 keep can be set. It is suggested this script is run as a daily &'cron'& job.
38321 An Exim delivery process opens the main log when it first needs to write to it,
38322 and it keeps the file open in case subsequent entries are required &-- for
38323 example, if a number of different deliveries are being done for the same
38324 message. However, remote SMTP deliveries can take a long time, and this means
38325 that the file may be kept open long after it is renamed if &'exicyclog'& or
38326 something similar is being used to rename log files on a regular basis. To
38327 ensure that a switch of log files is noticed as soon as possible, Exim calls
38328 &[stat()]& on the main log's name before reusing an open file, and if the file
38329 does not exist, or its inode has changed, the old file is closed and Exim
38330 tries to open the main log from scratch. Thus, an old log file may remain open
38331 for quite some time, but no Exim processes should write to it once it has been
38336 .section "Datestamped log files" "SECTdatlogfil"
38337 .cindex "log" "datestamped files"
38338 Instead of cycling the main and reject log files by renaming them
38339 periodically, some sites like to use files whose names contain a datestamp,
38340 for example, &_mainlog-20031225_&. The datestamp is in the form &_yyyymmdd_& or
38341 &_yyyymm_&. Exim has support for this way of working. It is enabled by setting
38342 the &%log_file_path%& option to a path that includes &`%D`& or &`%M`& at the
38343 point where the datestamp is required. For example:
38345 log_file_path = /var/spool/exim/log/%slog-%D
38346 log_file_path = /var/log/exim-%s-%D.log
38347 log_file_path = /var/spool/exim/log/%D-%slog
38348 log_file_path = /var/log/exim/%s.%M
38350 As before, &`%s`& is replaced by &"main"& or &"reject"&; the following are
38351 examples of names generated by the above examples:
38353 /var/spool/exim/log/mainlog-20021225
38354 /var/log/exim-reject-20021225.log
38355 /var/spool/exim/log/20021225-mainlog
38356 /var/log/exim/main.200212
38358 When this form of log file is specified, Exim automatically switches to new
38359 files at midnight. It does not make any attempt to compress old logs; you
38360 will need to write your own script if you require this. You should not
38361 run &'exicyclog'& with this form of logging.
38363 The location of the panic log is also determined by &%log_file_path%&, but it
38364 is not datestamped, because rotation of the panic log does not make sense.
38365 When generating the name of the panic log, &`%D`& or &`%M`& are removed from
38366 the string. In addition, if it immediately follows a slash, a following
38367 non-alphanumeric character is removed; otherwise a preceding non-alphanumeric
38368 character is removed. Thus, the four examples above would give these panic
38371 /var/spool/exim/log/paniclog
38372 /var/log/exim-panic.log
38373 /var/spool/exim/log/paniclog
38374 /var/log/exim/panic
38378 .section "Logging to syslog" "SECID249"
38379 .cindex "log" "syslog; writing to"
38380 The use of syslog does not change what Exim logs or the format of its messages,
38381 except in one respect. If &%syslog_timestamp%& is set false, the timestamps on
38382 Exim's log lines are omitted when these lines are sent to syslog. Apart from
38383 that, the same strings are written to syslog as to log files. The syslog
38384 &"facility"& is set to LOG_MAIL, and the program name to &"exim"&
38385 by default, but you can change these by setting the &%syslog_facility%& and
38386 &%syslog_processname%& options, respectively. If Exim was compiled with
38387 SYSLOG_LOG_PID set in &_Local/Makefile_& (this is the default in
38388 &_src/EDITME_&), then, on systems that permit it (all except ULTRIX), the
38389 LOG_PID flag is set so that the &[syslog()]& call adds the pid as well as
38390 the time and host name to each line.
38391 The three log streams are mapped onto syslog priorities as follows:
38394 &'mainlog'& is mapped to LOG_INFO
38396 &'rejectlog'& is mapped to LOG_NOTICE
38398 &'paniclog'& is mapped to LOG_ALERT
38401 Many log lines are written to both &'mainlog'& and &'rejectlog'&, and some are
38402 written to both &'mainlog'& and &'paniclog'&, so there will be duplicates if
38403 these are routed by syslog to the same place. You can suppress this duplication
38404 by setting &%syslog_duplication%& false.
38406 Exim's log lines can sometimes be very long, and some of its &'rejectlog'&
38407 entries contain multiple lines when headers are included. To cope with both
38408 these cases, entries written to syslog are split into separate &[syslog()]&
38409 calls at each internal newline, and also after a maximum of
38410 870 data characters. (This allows for a total syslog line length of 1024, when
38411 additions such as timestamps are added.) If you are running a syslog
38412 replacement that can handle lines longer than the 1024 characters allowed by
38413 RFC 3164, you should set
38415 SYSLOG_LONG_LINES=yes
38417 in &_Local/Makefile_& before building Exim. That stops Exim from splitting long
38418 lines, but it still splits at internal newlines in &'reject'& log entries.
38420 To make it easy to re-assemble split lines later, each component of a split
38421 entry starts with a string of the form [<&'n'&>/<&'m'&>] or [<&'n'&>\<&'m'&>]
38422 where <&'n'&> is the component number and <&'m'&> is the total number of
38423 components in the entry. The / delimiter is used when the line was split
38424 because it was too long; if it was split because of an internal newline, the \
38425 delimiter is used. For example, supposing the length limit to be 50 instead of
38426 870, the following would be the result of a typical rejection message to
38427 &'mainlog'& (LOG_INFO), each line in addition being preceded by the time, host
38428 name, and pid as added by syslog:
38430 [1/5] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected from
38431 [2/5] [127.0.0.1] (ph10): syntax error in 'From' header
38432 [3/5] when scanning for sender: missing or malformed lo
38433 [4/5] cal part in "<>" (envelope sender is <ph10@cam.exa
38436 The same error might cause the following lines to be written to &"rejectlog"&
38439 [1/18] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected fro
38440 [2/18] m [127.0.0.1] (ph10): syntax error in 'From' head
38441 [3/18] er when scanning for sender: missing or malformed
38442 [4/18] local part in "<>" (envelope sender is <ph10@cam
38444 [6\18] Recipients: ph10@some.domain.cam.example
38445 [7\18] P Received: from [127.0.0.1] (ident=ph10)
38446 [8\18] by xxxxx.cam.example with smtp (Exim 4.00)
38447 [9\18] id 16RdAL-0006pc-00
38448 [10/18] for ph10@cam.example; Mon, 16 Sep 2002 16:
38449 [11\18] 09:43 +0100
38451 [13\18] Subject: this is a test header
38452 [18\18] X-something: this is another header
38453 [15/18] I Message-Id: <E16RdAL-0006pc-00@xxxxx.cam.examp
38456 [18/18] Date: Mon, 16 Sep 2002 16:09:43 +0100
38458 Log lines that are neither too long nor contain newlines are written to syslog
38459 without modification.
38461 If only syslog is being used, the Exim monitor is unable to provide a log tail
38462 display, unless syslog is routing &'mainlog'& to a file on the local host and
38463 the environment variable EXIMON_LOG_FILE_PATH is set to tell the monitor
38468 .section "Log line flags" "SECID250"
38469 One line is written to the main log for each message received, and for each
38470 successful, unsuccessful, and delayed delivery. These lines can readily be
38471 picked out by the distinctive two-character flags that immediately follow the
38472 timestamp. The flags are:
38473 .itable none 0 0 2 10* left 90* left
38474 .irow &%<=%& "message arrival"
38475 .irow &%(=%& "message fakereject"
38476 .irow &%=>%& "normal message delivery"
38477 .irow &%->%& "additional address in same delivery"
38478 .irow &%>>%& "cutthrough message delivery"
38479 .irow &%*>%& "delivery suppressed by &%-N%&"
38480 .irow &%**%& "delivery failed; address bounced"
38481 .irow &%==%& "delivery deferred; temporary problem"
38485 .section "Logging message reception" "SECID251"
38486 .cindex "log" "reception line"
38487 The format of the single-line entry in the main log that is written for every
38488 message received is shown in the basic example below, which is split over
38489 several lines in order to fit it on the page:
38491 2002-10-31 08:57:53 16ZCW1-0005MB-00 <= kryten@dwarf.fict.example
38492 H=mailer.fict.example [192.168.123.123] U=exim
38493 P=smtp S=5678 id=<incoming message id>
38495 The address immediately following &"<="& is the envelope sender address. A
38496 bounce message is shown with the sender address &"<>"&, and if it is locally
38497 generated, this is followed by an item of the form
38501 which is a reference to the message that caused the bounce to be sent.
38505 For messages from other hosts, the H and U fields identify the remote host and
38506 record the RFC 1413 identity of the user that sent the message, if one was
38507 received. The number given in square brackets is the IP address of the sending
38508 host. If there is a single, unparenthesized host name in the H field, as
38509 above, it has been verified to correspond to the IP address (see the
38510 &%host_lookup%& option). If the name is in parentheses, it was the name quoted
38511 by the remote host in the SMTP HELO or EHLO command, and has not been
38512 verified. If verification yields a different name to that given for HELO or
38513 EHLO, the verified name appears first, followed by the HELO or EHLO
38514 name in parentheses.
38516 Misconfigured hosts (and mail forgers) sometimes put an IP address, with or
38517 without brackets, in the HELO or EHLO command, leading to entries in
38518 the log containing text like these examples:
38520 H=(10.21.32.43) [192.168.8.34]
38521 H=([10.21.32.43]) [192.168.8.34]
38523 This can be confusing. Only the final address in square brackets can be relied
38526 For locally generated messages (that is, messages not received over TCP/IP),
38527 the H field is omitted, and the U field contains the login name of the caller
38530 .cindex "authentication" "logging"
38531 .cindex "AUTH" "logging"
38532 For all messages, the P field specifies the protocol used to receive the
38533 message. This is the value that is stored in &$received_protocol$&. In the case
38534 of incoming SMTP messages, the value indicates whether or not any SMTP
38535 extensions (ESMTP), encryption, or authentication were used. If the SMTP
38536 session was encrypted, there is an additional X field that records the cipher
38537 suite that was used.
38539 .cindex log protocol
38540 The protocol is set to &"esmtpsa"& or &"esmtpa"& for messages received from
38541 hosts that have authenticated themselves using the SMTP AUTH command. The first
38542 value is used when the SMTP connection was encrypted (&"secure"&). In this case
38543 there is an additional item A= followed by the name of the authenticator that
38544 was used. If an authenticated identification was set up by the authenticator's
38545 &%server_set_id%& option, this is logged too, separated by a colon from the
38546 authenticator name.
38548 .cindex "size" "of message"
38549 The id field records the existing message id, if present. The size of the
38550 received message is given by the S field. When the message is delivered,
38551 headers may be removed or added, so that the size of delivered copies of the
38552 message may not correspond with this value (and indeed may be different to each
38555 The &%log_selector%& option can be used to request the logging of additional
38556 data when a message is received. See section &<<SECTlogselector>>& below.
38560 .section "Logging deliveries" "SECID252"
38561 .cindex "log" "delivery line"
38562 The format of the single-line entry in the main log that is written for every
38563 delivery is shown in one of the examples below, for local and remote
38564 deliveries, respectively. Each example has been split into multiple lines in order
38565 to fit it on the page:
38567 2002-10-31 08:59:13 16ZCW1-0005MB-00 => marv
38568 <marv@hitch.fict.example> R=localuser T=local_delivery
38569 2002-10-31 09:00:10 16ZCW1-0005MB-00 =>
38570 monk@holistic.fict.example R=dnslookup T=remote_smtp
38571 H=holistic.fict.example [192.168.234.234]
38573 For ordinary local deliveries, the original address is given in angle brackets
38574 after the final delivery address, which might be a pipe or a file. If
38575 intermediate address(es) exist between the original and the final address, the
38576 last of these is given in parentheses after the final address. The R and T
38577 fields record the router and transport that were used to process the address.
38579 If SMTP AUTH was used for the delivery there is an additional item A=
38580 followed by the name of the authenticator that was used.
38581 If an authenticated identification was set up by the authenticator's &%client_set_id%&
38582 option, this is logged too, as a second colon-separated list item.
38583 Optionally (see the &%smtp_mailauth%& &%log_selector%&) there may be a third list item.
38585 If a shadow transport was run after a successful local delivery, the log line
38586 for the successful delivery has an item added on the end, of the form
38588 &`ST=<`&&'shadow transport name'&&`>`&
38590 If the shadow transport did not succeed, the error message is put in
38591 parentheses afterwards.
38593 .cindex "asterisk" "after IP address"
38594 When more than one address is included in a single delivery (for example, two
38595 SMTP RCPT commands in one transaction) the second and subsequent addresses are
38596 flagged with &`->`& instead of &`=>`&. When two or more messages are delivered
38597 down a single SMTP connection, an asterisk follows the
38598 remote IP address (and port if enabled)
38599 in the log lines for the second and subsequent messages.
38600 When two or more messages are delivered down a single TLS connection, the
38601 DNS and some TLS-related information logged for the first message delivered
38602 will not be present in the log lines for the second and subsequent messages.
38603 TLS cipher information is still available.
38605 .cindex "delivery" "cutthrough; logging"
38606 .cindex "cutthrough" "logging"
38607 When delivery is done in cutthrough mode it is flagged with &`>>`& and the log
38608 line precedes the reception line, since cutthrough waits for a possible
38609 rejection from the destination in case it can reject the sourced item.
38611 The generation of a reply message by a filter file gets logged as a
38612 &"delivery"& to the addressee, preceded by &">"&.
38614 The &%log_selector%& option can be used to request the logging of additional
38615 data when a message is delivered. See section &<<SECTlogselector>>& below.
38618 .section "Discarded deliveries" "SECID253"
38619 .cindex "discarded messages"
38620 .cindex "message" "discarded"
38621 .cindex "delivery" "discarded; logging"
38622 When a message is discarded as a result of the command &"seen finish"& being
38623 obeyed in a filter file which generates no deliveries, a log entry of the form
38625 2002-12-10 00:50:49 16auJc-0001UB-00 => discarded
38626 <low.club@bridge.example> R=userforward
38628 is written, to record why no deliveries are logged. When a message is discarded
38629 because it is aliased to &":blackhole:"& the log line is like this:
38631 1999-03-02 09:44:33 10HmaX-0005vi-00 => :blackhole:
38632 <hole@nowhere.example> R=blackhole_router
38636 .section "Deferred deliveries" "SECID254"
38637 When a delivery is deferred, a line of the following form is logged:
38639 2002-12-19 16:20:23 16aiQz-0002Q5-00 == marvin@endrest.example
38640 R=dnslookup T=smtp defer (146): Connection refused
38642 In the case of remote deliveries, the error is the one that was given for the
38643 last IP address that was tried. Details of individual SMTP failures are also
38644 written to the log, so the above line would be preceded by something like
38646 2002-12-19 16:20:23 16aiQz-0002Q5-00 Failed to connect to
38647 mail1.endrest.example [192.168.239.239]: Connection refused
38649 When a deferred address is skipped because its retry time has not been reached,
38650 a message is written to the log, but this can be suppressed by setting an
38651 appropriate value in &%log_selector%&.
38655 .section "Delivery failures" "SECID255"
38656 .cindex "delivery" "failure; logging"
38657 If a delivery fails because an address cannot be routed, a line of the
38658 following form is logged:
38660 1995-12-19 16:20:23 0tRiQz-0002Q5-00 ** jim@trek99.example
38661 <jim@trek99.example>: unknown mail domain
38663 If a delivery fails at transport time, the router and transport are shown, and
38664 the response from the remote host is included, as in this example:
38666 2002-07-11 07:14:17 17SXDU-000189-00 ** ace400@pb.example
38667 R=dnslookup T=remote_smtp: SMTP error from remote mailer
38668 after pipelined RCPT TO:<ace400@pb.example>: host
38669 pbmail3.py.example [192.168.63.111]: 553 5.3.0
38670 <ace400@pb.example>...Addressee unknown
38672 The word &"pipelined"& indicates that the SMTP PIPELINING extension was being
38673 used. See &%hosts_avoid_esmtp%& in the &(smtp)& transport for a way of
38674 disabling PIPELINING. The log lines for all forms of delivery failure are
38675 flagged with &`**`&.
38679 .section "Fake deliveries" "SECID256"
38680 .cindex "delivery" "fake; logging"
38681 If a delivery does not actually take place because the &%-N%& option has been
38682 used to suppress it, a normal delivery line is written to the log, except that
38683 &"=>"& is replaced by &"*>"&.
38687 .section "Completion" "SECID257"
38690 2002-10-31 09:00:11 16ZCW1-0005MB-00 Completed
38692 is written to the main log when a message is about to be removed from the spool
38693 at the end of its processing.
38698 .section "Summary of Fields in Log Lines" "SECID258"
38699 .cindex "log" "summary of fields"
38700 A summary of the field identifiers that are used in log lines is shown in
38701 the following table:
38703 &`A `& authenticator name (and optional id and sender)
38704 &`C `& SMTP confirmation on delivery
38705 &` `& command list for &"no mail in SMTP session"&
38706 &`CV `& certificate verification status
38707 &`D `& duration of &"no mail in SMTP session"&
38708 &`DKIM`& domain verified in incoming message
38709 &`DN `& distinguished name from peer certificate
38710 &`DS `& DNSSEC secured lookups
38711 &`DT `& on &`=>`&, &'=='& and &'**'& lines: time taken for, or to attempt, a delivery
38712 &`F `& sender address (on delivery lines)
38713 &`H `& host name and IP address
38714 &`I `& local interface used
38715 &`id `& message id (from header) for incoming message
38716 &`K `& CHUNKING extension used
38717 &`L `& on &`<=`& and &`=>`& lines: PIPELINING extension used
38718 &`M8S `& 8BITMIME status for incoming message
38719 &`P `& on &`<=`& lines: protocol used
38720 &` `& on &`=>`& and &`**`& lines: return path
38721 &`PRDR`& PRDR extension used
38722 &`PRX `& on &`<=`& and &`=>`& lines: proxy address
38723 &`Q `& alternate queue name
38724 &`QT `& on &`=>`& lines: time spent on queue so far
38725 &` `& on &"Completed"& lines: time spent on queue
38726 &`R `& on &`<=`& lines: reference for local bounce
38727 &` `& on &`=>`& &`>>`& &`**`& and &`==`& lines: router name
38728 &`RT `& on &`<=`& lines: time taken for reception
38729 &`S `& size of message in bytes
38730 &`SNI `& server name indication from TLS client hello
38731 &`ST `& shadow transport name
38732 &`T `& on &`<=`& lines: message subject (topic)
38733 &`TFO `& connection took advantage of TCP Fast Open
38734 &` `& on &`=>`& &`**`& and &`==`& lines: transport name
38735 &`U `& local user or RFC 1413 identity
38736 &`X `& TLS cipher suite
38740 .section "Other log entries" "SECID259"
38741 Various other types of log entry are written from time to time. Most should be
38742 self-explanatory. Among the more common are:
38745 .cindex "retry" "time not reached"
38746 &'retry time not reached'&&~&~An address previously suffered a temporary error
38747 during routing or local delivery, and the time to retry has not yet arrived.
38748 This message is not written to an individual message log file unless it happens
38749 during the first delivery attempt.
38751 &'retry time not reached for any host'&&~&~An address previously suffered
38752 temporary errors during remote delivery, and the retry time has not yet arrived
38753 for any of the hosts to which it is routed.
38755 .cindex "spool directory" "file locked"
38756 &'spool file locked'&&~&~An attempt to deliver a message cannot proceed because
38757 some other Exim process is already working on the message. This can be quite
38758 common if queue running processes are started at frequent intervals. The
38759 &'exiwhat'& utility script can be used to find out what Exim processes are
38762 .cindex "error" "ignored"
38763 &'error ignored'&&~&~There are several circumstances that give rise to this
38766 Exim failed to deliver a bounce message whose age was greater than
38767 &%ignore_bounce_errors_after%&. The bounce was discarded.
38769 A filter file set up a delivery using the &"noerror"& option, and the delivery
38770 failed. The delivery was discarded.
38772 A delivery set up by a router configured with
38773 . ==== As this is a nested list, any displays it contains must be indented
38774 . ==== as otherwise they are too far to the left.
38778 failed. The delivery was discarded.
38781 .cindex DKIM "log line"
38782 &'DKIM: d='&&~&~Verbose results of a DKIM verification attempt, if enabled for
38783 logging and the message has a DKIM signature header.
38790 .section "Reducing or increasing what is logged" "SECTlogselector"
38791 .cindex "log" "selectors"
38792 By setting the &%log_selector%& global option, you can disable some of Exim's
38793 default logging, or you can request additional logging. The value of
38794 &%log_selector%& is made up of names preceded by plus or minus characters. For
38797 log_selector = +arguments -retry_defer
38799 The list of optional log items is in the following table, with the default
38800 selection marked by asterisks:
38801 .itable none 0 0 3 2.8in left 10pt center 3in left
38802 .irow &`8bitmime`& "received 8BITMIME status"
38803 .irow &`acl_warn_skipped`& * "skipped &%warn%& statement in ACL"
38804 .irow &`address_rewrite`& "address rewriting"
38805 .irow &`all_parents`& "all parents in => lines"
38806 .irow &`arguments`& "command line arguments"
38807 .irow &`connection_reject`& * "connection rejections"
38808 .irow &`delay_delivery`& * "immediate delivery delayed"
38809 .irow &`deliver_time`& "time taken to attempt delivery"
38810 .irow &`delivery_size`& "add &`S=`&&'nnn'& to => lines"
38811 .irow &`dkim`& * "DKIM verified domain on <= lines"
38812 .irow &`dkim_verbose`& "separate full DKIM verification result line, per signature"
38813 .irow &`dnslist_defer`& * "defers of DNS list (aka RBL) lookups"
38814 .irow &`dnssec`& "DNSSEC secured lookups"
38815 .irow &`etrn`& * "ETRN commands"
38816 .irow &`host_lookup_failed`& * "as it says"
38817 .irow &`ident_timeout`& "timeout for ident connection"
38818 .irow &`incoming_interface`& "local interface on <= and => lines"
38819 .irow &`incoming_port`& "remote port on <= lines"
38820 .irow &`lost_incoming_connection`& * "as it says (includes timeouts)"
38821 .irow &`millisec`& "millisecond timestamps and RT,QT,DT,D times"
38822 .irow &`msg_id`& * "on <= lines, Message-ID: header value"
38823 .irow &`msg_id_created`& "on <= lines, Message-ID: header value when one had to be added"
38824 .irow &`outgoing_interface`& "local interface on => lines"
38825 .irow &`outgoing_port`& "add remote port to => lines"
38826 .irow &`queue_run`& * "start and end queue runs"
38827 .irow &`queue_time`& "time on queue for one recipient"
38828 .irow &`queue_time_exclusive`& "exclude recieve time from QT times"
38829 .irow &`queue_time_overall`& "time on queue for whole message"
38830 .irow &`pid`& "Exim process id"
38831 .irow &`pipelining`& "PIPELINING use, on <= and => lines"
38832 .irow &`proxy`& "proxy address on <= and => lines"
38833 .irow &`receive_time`& "time taken to receive message"
38834 .irow &`received_recipients`& "recipients on <= lines"
38835 .irow &`received_sender`& "sender on <= lines"
38836 .irow &`rejected_header`& * "header contents on reject log"
38837 .irow &`retry_defer`& * "&<quote>&retry time not reached&</quote>&"
38838 .irow &`return_path_on_delivery`& "put return path on => and ** lines"
38839 .irow &`sender_on_delivery`& "add sender to => lines"
38840 .irow &`sender_verify_fail`& * "sender verification failures"
38841 .irow &`size_reject`& * "rejection because too big"
38842 .irow &`skip_delivery`& * "delivery skipped in a queue run"
38843 .irow &`smtp_confirmation`& * "SMTP confirmation on => lines"
38844 .irow &`smtp_connection`& "incoming SMTP connections"
38845 .irow &`smtp_incomplete_transaction`& "incomplete SMTP transactions"
38846 .irow &`smtp_mailauth`& "AUTH argument to MAIL commands"
38847 .irow &`smtp_no_mail`& "session with no MAIL commands"
38848 .irow &`smtp_protocol_error`& "SMTP protocol errors"
38849 .irow &`smtp_syntax_error`& "SMTP syntax errors"
38850 .irow &`subject`& "contents of &'Subject:'& on <= lines"
38851 .irow &`tls_certificate_verified`& * "certificate verification status"
38852 .irow &`tls_cipher`& * "TLS cipher suite on <= and => lines"
38853 .irow &`tls_peerdn`& "TLS peer DN on <= and => lines"
38854 .irow &`tls_resumption`& "append * to cipher field"
38855 .irow &`tls_sni`& "TLS SNI on <= lines"
38856 .irow &`unknown_in_list`& "DNS lookup failed in list match"
38857 .irow &`all`& "&*all of the above*&"
38859 See also the &%slow_lookup_log%& main configuration option,
38860 section &<<SECID99>>&
38862 More details on each of these items follows:
38866 .cindex "log" "8BITMIME"
38867 &%8bitmime%&: This causes Exim to log any 8BITMIME status of received messages,
38868 which may help in tracking down interoperability issues with ancient MTAs
38869 that are not 8bit clean. This is added to the &"<="& line, tagged with
38870 &`M8S=`& and a value of &`0`&, &`7`& or &`8`&, corresponding to "not given",
38871 &`7BIT`& and &`8BITMIME`& respectively.
38873 .cindex "&%warn%& ACL verb" "log when skipping"
38874 &%acl_warn_skipped%&: When an ACL &%warn%& statement is skipped because one of
38875 its conditions cannot be evaluated, a log line to this effect is written if
38876 this log selector is set.
38878 .cindex "log" "rewriting"
38879 .cindex "rewriting" "logging"
38880 &%address_rewrite%&: This applies both to global rewrites and per-transport
38881 rewrites, but not to rewrites in filters run as an unprivileged user (because
38882 such users cannot access the log).
38884 .cindex "log" "full parentage"
38885 &%all_parents%&: Normally only the original and final addresses are logged on
38886 delivery lines; with this selector, intermediate parents are given in
38887 parentheses between them.
38889 .cindex "log" "Exim arguments"
38890 .cindex "Exim arguments, logging"
38891 &%arguments%&: This causes Exim to write the arguments with which it was called
38892 to the main log, preceded by the current working directory. This is a debugging
38893 feature, added to make it easier to find out how certain MUAs call
38894 &_/usr/sbin/sendmail_&. The logging does not happen if Exim has given up root
38895 privilege because it was called with the &%-C%& or &%-D%& options. Arguments
38896 that are empty or that contain white space are quoted. Non-printing characters
38897 are shown as escape sequences. This facility cannot log unrecognized arguments,
38898 because the arguments are checked before the configuration file is read. The
38899 only way to log such cases is to interpose a script such as &_util/logargs.sh_&
38900 between the caller and Exim.
38902 .cindex "log" "connection rejections"
38903 &%connection_reject%&: A log entry is written whenever an incoming SMTP
38904 connection is rejected, for whatever reason.
38906 .cindex "log" "delayed delivery"
38907 .cindex "delayed delivery, logging"
38908 &%delay_delivery%&: A log entry is written whenever a delivery process is not
38909 started for an incoming message because the load is too high or too many
38910 messages were received on one connection. Logging does not occur if no delivery
38911 process is started because &%queue_only%& is set or &%-odq%& was used.
38913 .cindex "log" "delivery duration"
38914 &%deliver_time%&: For each delivery, the amount of real time it has taken to
38915 perform the actual delivery is logged as DT=<&'time'&>, for example, &`DT=1s`&.
38916 If millisecond logging is enabled, short times will be shown with greater
38917 precision, eg. &`DT=0.304s`&.
38919 .cindex "log" "message size on delivery"
38920 .cindex "size" "of message"
38921 &%delivery_size%&: For each delivery, the size of message delivered is added to
38922 the &"=>"& line, tagged with S=.
38924 .cindex log "DKIM verification"
38925 .cindex DKIM "verification logging"
38926 &%dkim%&: For message acceptance log lines, when an DKIM signature in the header
38927 verifies successfully a tag of DKIM is added, with one of the verified domains.
38929 .cindex log "DKIM verification"
38930 .cindex DKIM "verification logging"
38931 &%dkim_verbose%&: A log entry is written for each attempted DKIM verification.
38933 .cindex "log" "dnslist defer"
38934 .cindex "DNS list" "logging defer"
38935 .cindex "black list (DNS)"
38936 &%dnslist_defer%&: A log entry is written if an attempt to look up a host in a
38937 DNS black list suffers a temporary error.
38940 .cindex dnssec logging
38941 &%dnssec%&: For message acceptance and (attempted) delivery log lines, when
38942 dns lookups gave secure results a tag of DS is added.
38943 For acceptance this covers the reverse and forward lookups for host name verification.
38944 It does not cover helo-name verification.
38945 For delivery this covers the SRV, MX, A and/or AAAA lookups.
38947 .cindex "log" "ETRN commands"
38948 .cindex "ETRN" "logging"
38949 &%etrn%&: Every valid ETRN command that is received is logged, before the ACL
38950 is run to determine whether or not it is actually accepted. An invalid ETRN
38951 command, or one received within a message transaction is not logged by this
38952 selector (see &%smtp_syntax_error%& and &%smtp_protocol_error%&).
38954 .cindex "log" "host lookup failure"
38955 &%host_lookup_failed%&: When a lookup of a host's IP addresses fails to find
38956 any addresses, or when a lookup of an IP address fails to find a host name, a
38957 log line is written. This logging does not apply to direct DNS lookups when
38958 routing email addresses, but it does apply to &"byname"& lookups.
38960 .cindex "log" "ident timeout"
38961 .cindex "RFC 1413" "logging timeout"
38962 &%ident_timeout%&: A log line is written whenever an attempt to connect to a
38963 client's ident port times out.
38965 .cindex "log" "incoming interface"
38966 .cindex "log" "outgoing interface"
38967 .cindex "log" "local interface"
38968 .cindex "log" "local address and port"
38969 .cindex "TCP/IP" "logging local address and port"
38970 .cindex "interface" "logging"
38971 &%incoming_interface%&: The interface on which a message was received is added
38972 to the &"<="& line as an IP address in square brackets, tagged by I= and
38973 followed by a colon and the port number. The local interface and port are also
38974 added to other SMTP log lines, for example, &"SMTP connection from"&, to
38975 rejection lines, and (despite the name) to outgoing
38976 &"=>"&, &"->"&, &"=="& and &"**"& lines.
38977 The latter can be disabled by turning off the &%outgoing_interface%& option.
38979 .cindex log "incoming proxy address"
38980 .cindex proxy "logging proxy address"
38981 .cindex "TCP/IP" "logging proxy address"
38982 &%proxy%&: The internal (closest to the system running Exim) IP address
38983 of the proxy, tagged by PRX=, on the &"<="& line for a message accepted
38984 on a proxied connection
38985 or the &"=>"& line for a message delivered on a proxied connection.
38986 See &<<SECTproxyInbound>>& for more information.
38988 .cindex "log" "incoming remote port"
38989 .cindex "port" "logging remote"
38990 .cindex "TCP/IP" "logging incoming remote port"
38991 .vindex "&$sender_fullhost$&"
38992 .vindex "&$sender_rcvhost$&"
38993 &%incoming_port%&: The remote port number from which a message was received is
38994 added to log entries and &'Received:'& header lines, following the IP address
38995 in square brackets, and separated from it by a colon. This is implemented by
38996 changing the value that is put in the &$sender_fullhost$& and
38997 &$sender_rcvhost$& variables. Recording the remote port number has become more
38998 important with the widening use of NAT (see RFC 2505).
39000 .cindex "log" "dropped connection"
39001 &%lost_incoming_connection%&: A log line is written when an incoming SMTP
39002 connection is unexpectedly dropped.
39004 .cindex "log" "millisecond timestamps"
39005 .cindex millisecond logging
39006 .cindex timestamps "millisecond, in logs"
39007 &%millisec%&: Timestamps have a period and three decimal places of finer granularity
39008 appended to the seconds value.
39010 .cindex "log" "message id"
39011 &%msg_id%&: The value of the Message-ID: header.
39013 &%msg_id_created%&: The value of the Message-ID: header, when one had to be created.
39014 This will be either because the message is a bounce, or was submitted locally
39015 (submission mode) without one.
39016 The field identifier will have an asterix appended: &"id*="&.
39018 .cindex "log" "outgoing interface"
39019 .cindex "log" "local interface"
39020 .cindex "log" "local address and port"
39021 .cindex "TCP/IP" "logging local address and port"
39022 .cindex "interface" "logging"
39023 &%outgoing_interface%&: If &%incoming_interface%& is turned on, then the
39024 interface on which a message was sent is added to delivery lines as an I= tag
39025 followed by IP address in square brackets. You can disable this by turning
39026 off the &%outgoing_interface%& option.
39028 .cindex "log" "outgoing remote port"
39029 .cindex "port" "logging outgoing remote"
39030 .cindex "TCP/IP" "logging outgoing remote port"
39031 &%outgoing_port%&: The remote port number is added to delivery log lines (those
39032 containing => tags) following the IP address.
39033 The local port is also added if &%incoming_interface%& and
39034 &%outgoing_interface%& are both enabled.
39035 This option is not included in the default setting, because for most ordinary
39036 configurations, the remote port number is always 25 (the SMTP port), and the
39037 local port is a random ephemeral port.
39039 .cindex "log" "process ids in"
39040 .cindex "pid (process id)" "in log lines"
39041 &%pid%&: The current process id is added to every log line, in square brackets,
39042 immediately after the time and date.
39044 .cindex log pipelining
39045 .cindex pipelining "logging outgoing"
39046 &%pipelining%&: A field is added to delivery and accept
39047 log lines when the ESMTP PIPELINING extension was used.
39048 The field is a single "L".
39050 On accept lines, where PIPELINING was offered but not used by the client,
39051 the field has a minus appended.
39053 .cindex "pipelining" "early connection"
39054 If Exim is built without the DISABLE_PIPE_CONNECT build option
39055 accept "L" fields have a period appended if the feature was
39056 offered but not used, or an asterisk appended if used.
39057 Delivery "L" fields have an asterisk appended if used.
39060 .cindex "log" "queue run"
39061 .cindex "queue runner" "logging"
39062 &%queue_run%&: The start and end of every queue run are logged.
39064 .cindex "log" "queue time"
39065 &%queue_time%&: The amount of time the message has been in the queue on the
39066 local host is logged as QT=<&'time'&> on delivery (&`=>`&) lines, for example,
39068 If millisecond logging is enabled, short times will be shown with greater
39069 precision, eg. &`QT=1.578s`&.
39071 &%queue_time_overall%&: The amount of time the message has been in the queue on
39072 the local host is logged as QT=<&'time'&> on &"Completed"& lines, for
39073 example, &`QT=3m45s`&.
39075 .cindex "log" "receive duration"
39076 &%receive_time%&: For each message, the amount of real time it has taken to
39077 perform the reception is logged as RT=<&'time'&>, for example, &`RT=1s`&.
39078 If millisecond logging is enabled, short times will be shown with greater
39079 precision, eg. &`RT=0.204s`&.
39081 .cindex "log" "recipients"
39082 &%received_recipients%&: The recipients of a message are listed in the main log
39083 as soon as the message is received. The list appears at the end of the log line
39084 that is written when a message is received, preceded by the word &"for"&. The
39085 addresses are listed after they have been qualified, but before any rewriting
39087 Recipients that were discarded by an ACL for MAIL or RCPT do not appear
39090 .cindex "log" "sender reception"
39091 &%received_sender%&: The unrewritten original sender of a message is added to
39092 the end of the log line that records the message's arrival, after the word
39093 &"from"& (before the recipients if &%received_recipients%& is also set).
39095 .cindex "log" "header lines for rejection"
39096 &%rejected_header%&: If a message's header has been received at the time a
39097 rejection is written to the reject log, the complete header is added to the
39098 log. Header logging can be turned off individually for messages that are
39099 rejected by the &[local_scan()]& function (see section &<<SECTapiforloc>>&).
39101 .cindex "log" "retry defer"
39102 &%retry_defer%&: A log line is written if a delivery is deferred because a
39103 retry time has not yet been reached. However, this &"retry time not reached"&
39104 message is always omitted from individual message logs after the first delivery
39107 .cindex "log" "return path"
39108 &%return_path_on_delivery%&: The return path that is being transmitted with
39109 the message is included in delivery and bounce lines, using the tag P=.
39110 This is omitted if no delivery actually happens, for example, if routing fails,
39111 or if delivery is to &_/dev/null_& or to &`:blackhole:`&.
39113 .cindex "log" "sender on delivery"
39114 &%sender_on_delivery%&: The message's sender address is added to every delivery
39115 and bounce line, tagged by F= (for &"from"&).
39116 This is the original sender that was received with the message; it is not
39117 necessarily the same as the outgoing return path.
39119 .cindex "log" "sender verify failure"
39120 &%sender_verify_fail%&: If this selector is unset, the separate log line that
39121 gives details of a sender verification failure is not written. Log lines for
39122 the rejection of SMTP commands contain just &"sender verify failed"&, so some
39125 .cindex "log" "size rejection"
39126 &%size_reject%&: A log line is written whenever a message is rejected because
39129 .cindex "log" "frozen messages; skipped"
39130 .cindex "frozen messages" "logging skipping"
39131 &%skip_delivery%&: A log line is written whenever a message is skipped during a
39132 queue run because it another process is already delivering it or because
39134 .cindex "&""spool file is locked""&"
39135 .cindex "&""message is frozen""&"
39136 The message that is written is either &"spool file is locked"& or
39137 &"message is frozen"&.
39139 .cindex "log" "smtp confirmation"
39140 .cindex "SMTP" "logging confirmation"
39141 .cindex "LMTP" "logging confirmation"
39142 &%smtp_confirmation%&: The response to the final &"."& in the SMTP or LMTP dialogue for
39143 outgoing messages is added to delivery log lines in the form &`C=`&<&'text'&>.
39144 A number of MTAs (including Exim) return an identifying string in this
39147 .cindex "log" "SMTP connections"
39148 .cindex "SMTP" "logging connections"
39149 &%smtp_connection%&: A log line is written whenever an incoming SMTP connection is
39150 established or closed, unless the connection is from a host that matches
39151 &%hosts_connection_nolog%&. (In contrast, &%lost_incoming_connection%& applies
39152 only when the closure is unexpected.) This applies to connections from local
39153 processes that use &%-bs%& as well as to TCP/IP connections. If a connection is
39154 dropped in the middle of a message, a log line is always written, whether or
39155 not this selector is set, but otherwise nothing is written at the start and end
39156 of connections unless this selector is enabled.
39158 For TCP/IP connections to an Exim daemon, the current number of connections is
39159 included in the log message for each new connection, but note that the count is
39160 reset if the daemon is restarted.
39161 Also, because connections are closed (and the closure is logged) in
39162 subprocesses, the count may not include connections that have been closed but
39163 whose termination the daemon has not yet noticed. Thus, while it is possible to
39164 match up the opening and closing of connections in the log, the value of the
39165 logged counts may not be entirely accurate.
39167 .cindex "log" "SMTP transaction; incomplete"
39168 .cindex "SMTP" "logging incomplete transactions"
39169 &%smtp_incomplete_transaction%&: When a mail transaction is aborted by
39170 RSET, QUIT, loss of connection, or otherwise, the incident is logged,
39171 and the message sender plus any accepted recipients are included in the log
39172 line. This can provide evidence of dictionary attacks.
39174 .cindex "log" "non-MAIL SMTP sessions"
39175 .cindex "MAIL" "logging session without"
39176 &%smtp_no_mail%&: A line is written to the main log whenever an accepted SMTP
39177 connection terminates without having issued a MAIL command. This includes both
39178 the case when the connection is dropped, and the case when QUIT is used. It
39179 does not include cases where the connection is rejected right at the start (by
39180 an ACL, or because there are too many connections, or whatever). These cases
39181 already have their own log lines.
39183 The log line that is written contains the identity of the client in the usual
39184 way, followed by D= and a time, which records the duration of the connection.
39185 If the connection was authenticated, this fact is logged exactly as it is for
39186 an incoming message, with an A= item. If the connection was encrypted, CV=,
39187 DN=, and X= items may appear as they do for an incoming message, controlled by
39188 the same logging options.
39190 Finally, if any SMTP commands were issued during the connection, a C= item
39191 is added to the line, listing the commands that were used. For example,
39195 shows that the client issued QUIT straight after EHLO. If there were fewer
39196 than 20 commands, they are all listed. If there were more than 20 commands,
39197 the last 20 are listed, preceded by &"..."&. However, with the default
39198 setting of 10 for &%smtp_accept_max_nonmail%&, the connection will in any case
39199 have been aborted before 20 non-mail commands are processed.
39201 &%smtp_mailauth%&: A third subfield with the authenticated sender,
39202 colon-separated, is appended to the A= item for a message arrival or delivery
39203 log line, if an AUTH argument to the SMTP MAIL command (see &<<SECTauthparamail>>&)
39204 was accepted or used.
39206 .cindex "log" "SMTP protocol error"
39207 .cindex "SMTP" "logging protocol error"
39208 &%smtp_protocol_error%&: A log line is written for every SMTP protocol error
39209 encountered. Exim does not have perfect detection of all protocol errors
39210 because of transmission delays and the use of pipelining. If PIPELINING has
39211 been advertised to a client, an Exim server assumes that the client will use
39212 it, and therefore it does not count &"expected"& errors (for example, RCPT
39213 received after rejecting MAIL) as protocol errors.
39215 .cindex "SMTP" "logging syntax errors"
39216 .cindex "SMTP" "syntax errors; logging"
39217 .cindex "SMTP" "unknown command; logging"
39218 .cindex "log" "unknown SMTP command"
39219 .cindex "log" "SMTP syntax error"
39220 &%smtp_syntax_error%&: A log line is written for every SMTP syntax error
39221 encountered. An unrecognized command is treated as a syntax error. For an
39222 external connection, the host identity is given; for an internal connection
39223 using &%-bs%& the sender identification (normally the calling user) is given.
39225 .cindex "log" "subject"
39226 .cindex "subject, logging"
39227 &%subject%&: The subject of the message is added to the arrival log line,
39228 preceded by &"T="& (T for &"topic"&, since S is already used for &"size"&).
39229 Any MIME &"words"& in the subject are decoded. The &%print_topbitchars%& option
39230 specifies whether characters with values greater than 127 should be logged
39231 unchanged, or whether they should be rendered as escape sequences.
39233 .cindex "log" "certificate verification"
39235 .cindex DANE logging
39236 &%tls_certificate_verified%&: An extra item is added to <= and => log lines
39237 when TLS is in use. The item is &`CV=yes`& if the peer's certificate was
39239 using a CA trust anchor,
39240 &`CV=dane`& if using a DNS trust anchor,
39241 and &`CV=no`& if not.
39243 .cindex "log" "TLS cipher"
39244 .cindex "TLS" "logging cipher"
39245 &%tls_cipher%&: When a message is sent or received over an encrypted
39246 connection, the cipher suite used is added to the log line, preceded by X=.
39248 .cindex "log" "TLS peer DN"
39249 .cindex "TLS" "logging peer DN"
39250 &%tls_peerdn%&: When a message is sent or received over an encrypted
39251 connection, and a certificate is supplied by the remote host, the peer DN is
39252 added to the log line, preceded by DN=.
39254 .cindex "log" "TLS resumption"
39255 .cindex "TLS" "logging session resumption"
39256 &%tls_resumption%&: When a message is sent or received over an encrypted
39257 connection and the TLS session resumed one used on a previous TCP connection,
39258 an asterisk is appended to the X= cipher field in the log line.
39260 .cindex "log" "TLS SNI"
39261 .cindex "TLS" "logging SNI"
39262 .cindex SNI logging
39263 &%tls_sni%&: When a message is received over an encrypted connection, and
39264 the remote host provided the Server Name Indication extension, the SNI is
39265 added to the log line, preceded by SNI=.
39267 .cindex "log" "DNS failure in list"
39268 &%unknown_in_list%&: This setting causes a log entry to be written when the
39269 result of a list match is failure because a DNS lookup failed.
39273 .section "Message log" "SECID260"
39274 .cindex "message" "log file for"
39275 .cindex "log" "message log; description of"
39276 .cindex "&_msglog_& directory"
39277 .oindex "&%preserve_message_logs%&"
39278 In addition to the general log files, Exim writes a log file for each message
39279 that it handles. The names of these per-message logs are the message ids, and
39280 they are kept in the &_msglog_& sub-directory of the spool directory. Each
39281 message log contains copies of the log lines that apply to the message. This
39282 makes it easier to inspect the status of an individual message without having
39283 to search the main log. A message log is deleted when processing of the message
39284 is complete, unless &%preserve_message_logs%& is set, but this should be used
39285 only with great care because they can fill up your disk very quickly.
39287 On a heavily loaded system, it may be desirable to disable the use of
39288 per-message logs, in order to reduce disk I/O. This can be done by setting the
39289 &%message_logs%& option false.
39295 . ////////////////////////////////////////////////////////////////////////////
39296 . ////////////////////////////////////////////////////////////////////////////
39298 .chapter "Exim utilities" "CHAPutils"
39299 .scindex IIDutils "utilities"
39300 A number of utility scripts and programs are supplied with Exim and are
39301 described in this chapter. There is also the Exim Monitor, which is covered in
39302 the next chapter. The utilities described here are:
39304 .itable none 0 0 3 7* left 15* left 40* left
39305 .irow &<<SECTfinoutwha>>& &'exiwhat'& &&&
39306 "list what Exim processes are doing"
39307 .irow &<<SECTgreptheque>>& &'exiqgrep'& "grep the queue"
39308 .irow &<<SECTsumtheque>>& &'exiqsumm'& "summarize the queue"
39309 .irow &<<SECTextspeinf>>& &'exigrep'& "search the main log"
39310 .irow &<<SECTexipick>>& &'exipick'& "select messages on &&&
39312 .irow &<<SECTcyclogfil>>& &'exicyclog'& "cycle (rotate) log files"
39313 .irow &<<SECTmailstat>>& &'eximstats'& &&&
39314 "extract statistics from the log"
39315 .irow &<<SECTcheckaccess>>& &'exim_checkaccess'& &&&
39316 "check address acceptance from given IP"
39317 .irow &<<SECTdbmbuild>>& &'exim_dbmbuild'& "build a DBM file"
39318 .irow &<<SECTfinindret>>& &'exinext'& "extract retry information"
39319 .irow &<<SECTdumpdb>>& &'exim_dumpdb'& "dump a hints database"
39320 .irow &<<SECTtidydb>>& &'exim_tidydb'& "clean up a hints database"
39321 .irow &<<SECTfixdb>>& &'exim_fixdb'& "patch a hints database"
39322 .irow &<<SECTmailboxmaint>>& &'exim_lock'& "lock a mailbox file"
39325 Another utility that might be of use to sites with many MTAs is Tom Kistner's
39326 &'exilog'&. It provides log visualizations across multiple Exim servers. See
39327 &url(https://duncanthrax.net/exilog/) for details.
39332 .section "Finding out what Exim processes are doing (exiwhat)" "SECTfinoutwha"
39333 .cindex "&'exiwhat'&"
39334 .cindex "process, querying"
39336 On operating systems that can restart a system call after receiving a signal
39337 (most modern OS), an Exim process responds to the SIGUSR1 signal by writing
39338 a line describing what it is doing to the file &_exim-process.info_& in the
39339 Exim spool directory. The &'exiwhat'& script sends the signal to all Exim
39340 processes it can find, having first emptied the file. It then waits for one
39341 second to allow the Exim processes to react before displaying the results. In
39342 order to run &'exiwhat'& successfully you have to have sufficient privilege to
39343 send the signal to the Exim processes, so it is normally run as root.
39345 &*Warning*&: This is not an efficient process. It is intended for occasional
39346 use by system administrators. It is not sensible, for example, to set up a
39347 script that sends SIGUSR1 signals to Exim processes at short intervals.
39350 Unfortunately, the &'ps'& command that &'exiwhat'& uses to find Exim processes
39351 varies in different operating systems. Not only are different options used,
39352 but the format of the output is different. For this reason, there are some
39353 system configuration options that configure exactly how &'exiwhat'& works. If
39354 it doesn't seem to be working for you, check the following compile-time
39356 .itable none 0 0 2 30* left 70* left
39357 .irow &`EXIWHAT_PS_CMD`& "the command for running &'ps'&"
39358 .irow &`EXIWHAT_PS_ARG`& "the argument for &'ps'&"
39359 .irow &`EXIWHAT_EGREP_ARG`& "the argument for &'egrep'& to select from &'ps'& output"
39360 .irow &`EXIWHAT_KILL_ARG`& "the argument for the &'kill'& command"
39362 An example of typical output from &'exiwhat'& is
39364 164 daemon: -q1h, listening on port 25
39365 10483 running queue: waiting for 0tAycK-0002ij-00 (10492)
39366 10492 delivering 0tAycK-0002ij-00 to mail.ref.example
39367 [10.19.42.42] (editor@ref.example)
39368 10592 handling incoming call from [192.168.243.242]
39369 10628 accepting a local non-SMTP message
39371 The first number in the output line is the process number. The third line has
39372 been split here, in order to fit it on the page.
39376 .section "Selective queue listing (exiqgrep)" "SECTgreptheque"
39377 .cindex "&'exiqgrep'&"
39378 .cindex "queue" "grepping"
39379 This utility is a Perl script contributed by Matt Hubbard. It runs
39383 or (in case &*-a*& switch is specified)
39387 to obtain a queue listing, and then greps the output to select messages
39388 that match given criteria. The following selection options are available:
39391 .vitem &*-f*&&~<&'regex'&>
39392 Match the sender address using a case-insensitive search. The field that is
39393 tested is enclosed in angle brackets, so you can test for bounce messages with
39397 .vitem &*-r*&&~<&'regex'&>
39398 Match a recipient address using a case-insensitive search. The field that is
39399 tested is not enclosed in angle brackets.
39401 .vitem &*-s*&&~<&'regex'&>
39402 Match against the size field.
39404 .vitem &*-y*&&~<&'seconds'&>
39405 Match messages that are younger than the given time.
39407 .vitem &*-o*&&~<&'seconds'&>
39408 Match messages that are older than the given time.
39411 Match only frozen messages.
39414 Match only non-frozen messages.
39416 .vitem &*-G*&&~<&'queuename'&>
39417 Match only messages in the given queue. Without this, the default queue is searched.
39420 The following options control the format of the output:
39424 Display only the count of matching messages.
39427 Long format &-- display the full message information as output by Exim. This is
39431 Display message ids only.
39434 Brief format &-- one line per message.
39437 Display messages in reverse order.
39440 Include delivered recipients in queue listing.
39443 The following options give alternates for configuration:
39446 .vitem &*-C*&&~<&'config&~file'&>
39447 is used to specify an alternate &_exim.conf_& which might
39448 contain alternate exim configuration the queue management might be using.
39450 .vitem &*-E*&&~<&'path'&>
39451 can be used to specify a path for the exim binary,
39452 overriding the built-in one.
39455 There is one more option, &%-h%&, which outputs a list of options.
39456 At least one selection option, or either the &*-c*& or &*-h*& option, must be given.
39460 .section "Summarizing the queue (exiqsumm)" "SECTsumtheque"
39461 .cindex "&'exiqsumm'&"
39462 .cindex "queue" "summary"
39463 The &'exiqsumm'& utility is a Perl script which reads the output of &`exim
39464 -bp`& and produces a summary of the messages in the queue. Thus, you use it by
39465 running a command such as
39467 exim -bp | exiqsumm
39469 The output consists of one line for each domain that has messages waiting for
39470 it, as in the following example:
39472 3 2322 74m 66m msn.com.example
39474 Each line lists the number of pending deliveries for a domain, their total
39475 volume, and the length of time that the oldest and the newest messages have
39476 been waiting. Note that the number of pending deliveries is greater than the
39477 number of messages when messages have more than one recipient.
39479 A summary line is output at the end. By default the output is sorted on the
39480 domain name, but &'exiqsumm'& has the options &%-a%& and &%-c%&, which cause
39481 the output to be sorted by oldest message and by count of messages,
39482 respectively. There are also three options that split the messages for each
39483 domain into two or more subcounts: &%-b%& separates bounce messages, &%-f%&
39484 separates frozen messages, and &%-s%& separates messages according to their
39487 The output of &'exim -bp'& contains the original addresses in the message, so
39488 this also applies to the output from &'exiqsumm'&. No domains from addresses
39489 generated by aliasing or forwarding are included (unless the &%one_time%&
39490 option of the &(redirect)& router has been used to convert them into &"top
39491 level"& addresses).
39496 .section "Extracting specific information from the log (exigrep)" &&&
39498 .cindex "&'exigrep'&"
39499 .cindex "log" "extracts; grepping for"
39500 The &'exigrep'& utility is a Perl script that searches one or more main log
39501 files for entries that match a given pattern. When it finds a match, it
39502 extracts all the log entries for the relevant message, not just those that
39503 match the pattern. Thus, &'exigrep'& can extract complete log entries for a
39504 given message, or all mail for a given user, or for a given host, for example.
39505 The input files can be in Exim log format or syslog format.
39506 If a matching log line is not associated with a specific message, it is
39507 included in &'exigrep'&'s output without any additional lines. The usage is:
39509 &`exigrep [-t<`&&'n'&&`>] [-I] [-l] [-M] [-v] <`&&'pattern'&&`> [<`&&'log file'&&`>] ...`&
39511 If no log filenames are given on the command line, the standard input is read.
39513 The &%-t%& argument specifies a number of seconds. It adds an additional
39514 condition for message selection. Messages that are complete are shown only if
39515 they spent more than <&'n'&> seconds in the queue.
39517 By default, &'exigrep'& does case-insensitive matching. The &%-I%& option
39518 makes it case-sensitive. This may give a performance improvement when searching
39519 large log files. Without &%-I%&, the Perl pattern matches use Perl's &`/i`&
39520 option; with &%-I%& they do not. In both cases it is possible to change the
39521 case sensitivity within the pattern by using &`(?i)`& or &`(?-i)`&.
39523 The &%-l%& option means &"literal"&, that is, treat all characters in the
39524 pattern as standing for themselves. Otherwise the pattern must be a Perl
39525 regular expression.
39527 The &%-v%& option inverts the matching condition. That is, a line is selected
39528 if it does &'not'& match the pattern.
39530 The &%-M%& options means &"related messages"&. &'exigrep'& will show messages
39531 that are generated as a result/response to a message that &'exigrep'& matched
39535 user_a sends a message to user_b, which generates a bounce back to user_b. If
39536 &'exigrep'& is used to search for &"user_a"&, only the first message will be
39537 displayed. But if &'exigrep'& is used to search for &"user_b"&, the first and
39538 the second (bounce) message will be displayed. Using &%-M%& with &'exigrep'&
39539 when searching for &"user_a"& will show both messages since the bounce is
39540 &"related"& to or a &"result"& of the first message that was found by the
39543 If the location of a &'zcat'& command is known from the definition of
39544 ZCAT_COMMAND in &_Local/Makefile_&, &'exigrep'& automatically passes any file
39545 whose name ends in COMPRESS_SUFFIX through &'zcat'& as it searches it.
39546 If the ZCAT_COMMAND is not executable, &'exigrep'& tries to use
39547 autodetection of some well known compression extensions.
39550 .section "Selecting messages by various criteria (exipick)" "SECTexipick"
39551 .cindex "&'exipick'&"
39552 John Jetmore's &'exipick'& utility is included in the Exim distribution. It
39553 lists messages from the queue according to a variety of criteria. For details
39554 of &'exipick'&'s facilities, run &'exipick'& with
39555 the &%--help%& option.
39558 .section "Cycling log files (exicyclog)" "SECTcyclogfil"
39559 .cindex "log" "cycling local files"
39560 .cindex "cycling logs"
39561 .cindex "&'exicyclog'&"
39562 The &'exicyclog'& script can be used to cycle (rotate) &'mainlog'& and
39563 &'rejectlog'& files. This is not necessary if only syslog is being used, or if
39564 you are using log files with datestamps in their names (see section
39565 &<<SECTdatlogfil>>&). Some operating systems have their own standard mechanisms
39566 for log cycling, and these can be used instead of &'exicyclog'& if preferred.
39567 There are two command line options for &'exicyclog'&:
39569 &%-k%& <&'count'&> specifies the number of log files to keep, overriding the
39570 default that is set when Exim is built. The default default is 10.
39572 &%-l%& <&'path'&> specifies the log file path, in the same format as Exim's
39573 &%log_file_path%& option (for example, &`/var/log/exim_%slog`&), again
39574 overriding the script's default, which is to find the setting from Exim's
39578 Each time &'exicyclog'& is run the filenames get &"shuffled down"& by one. If
39579 the main log filename is &_mainlog_& (the default) then when &'exicyclog'& is
39580 run &_mainlog_& becomes &_mainlog.01_&, the previous &_mainlog.01_& becomes
39581 &_mainlog.02_& and so on, up to the limit that is set in the script or by the
39582 &%-k%& option. Log files whose numbers exceed the limit are discarded. Reject
39583 logs are handled similarly.
39585 If the limit is greater than 99, the script uses 3-digit numbers such as
39586 &_mainlog.001_&, &_mainlog.002_&, etc. If you change from a number less than 99
39587 to one that is greater, or &'vice versa'&, you will have to fix the names of
39588 any existing log files.
39590 If no &_mainlog_& file exists, the script does nothing. Files that &"drop off"&
39591 the end are deleted. All files with numbers greater than 01 are compressed,
39592 using a compression command which is configured by the COMPRESS_COMMAND
39593 setting in &_Local/Makefile_&. It is usual to run &'exicyclog'& daily from a
39594 root &%crontab%& entry of the form
39596 1 0 * * * su exim -c /usr/exim/bin/exicyclog
39598 assuming you have used the name &"exim"& for the Exim user. You can run
39599 &'exicyclog'& as root if you wish, but there is no need.
39603 .section "Mail statistics (eximstats)" "SECTmailstat"
39604 .cindex "statistics"
39605 .cindex "&'eximstats'&"
39606 A Perl script called &'eximstats'& is provided for extracting statistical
39607 information from log files. The output is either plain text, or HTML.
39608 . --- 2018-09-07: LogReport's Lire appears to be dead; website is a Yahoo Japan
39609 . --- 404 error and everything else points to that.
39611 The &'eximstats'& script has been hacked about quite a bit over time. The
39612 latest version is the result of some extensive revision by Steve Campbell. A
39613 lot of information is given by default, but there are options for suppressing
39614 various parts of it. Following any options, the arguments to the script are a
39615 list of files, which should be main log files. For example:
39617 eximstats -nr /var/spool/exim/log/mainlog.01
39619 By default, &'eximstats'& extracts information about the number and volume of
39620 messages received from or delivered to various hosts. The information is sorted
39621 both by message count and by volume, and the top fifty hosts in each category
39622 are listed on the standard output. Similar information, based on email
39623 addresses or domains instead of hosts can be requested by means of various
39624 options. For messages delivered and received locally, similar statistics are
39625 also produced per user.
39627 The output also includes total counts and statistics about delivery errors, and
39628 histograms showing the number of messages received and deliveries made in each
39629 hour of the day. A delivery with more than one address in its envelope (for
39630 example, an SMTP transaction with more than one RCPT command) is counted
39631 as a single delivery by &'eximstats'&.
39633 Though normally more deliveries than receipts are reported (as messages may
39634 have multiple recipients), it is possible for &'eximstats'& to report more
39635 messages received than delivered, even though the queue is empty at the start
39636 and end of the period in question. If an incoming message contains no valid
39637 recipients, no deliveries are recorded for it. A bounce message is handled as
39638 an entirely separate message.
39640 &'eximstats'& always outputs a grand total summary giving the volume and number
39641 of messages received and deliveries made, and the number of hosts involved in
39642 each case. It also outputs the number of messages that were delayed (that is,
39643 not completely delivered at the first attempt), and the number that had at
39644 least one address that failed.
39646 The remainder of the output is in sections that can be independently disabled
39647 or modified by various options. It consists of a summary of deliveries by
39648 transport, histograms of messages received and delivered per time interval
39649 (default per hour), information about the time messages spent in the queue,
39650 a list of relayed messages, lists of the top fifty sending hosts, local
39651 senders, destination hosts, and destination local users by count and by volume,
39652 and a list of delivery errors that occurred.
39654 The relay information lists messages that were actually relayed, that is, they
39655 came from a remote host and were directly delivered to some other remote host,
39656 without being processed (for example, for aliasing or forwarding) locally.
39658 There are quite a few options for &'eximstats'& to control exactly what it
39659 outputs. These are documented in the Perl script itself, and can be extracted
39660 by running the command &(perldoc)& on the script. For example:
39662 perldoc /usr/exim/bin/eximstats
39665 .section "Checking access policy (exim_checkaccess)" "SECTcheckaccess"
39666 .cindex "&'exim_checkaccess'&"
39667 .cindex "policy control" "checking access"
39668 .cindex "checking access"
39669 The &%-bh%& command line argument allows you to run a fake SMTP session with
39670 debugging output, in order to check what Exim is doing when it is applying
39671 policy controls to incoming SMTP mail. However, not everybody is sufficiently
39672 familiar with the SMTP protocol to be able to make full use of &%-bh%&, and
39673 sometimes you just want to answer the question &"Does this address have
39674 access?"& without bothering with any further details.
39676 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%&. It takes
39677 two arguments, an IP address and an email address:
39679 exim_checkaccess 10.9.8.7 A.User@a.domain.example
39681 The utility runs a call to Exim with the &%-bh%& option, to test whether the
39682 given email address would be accepted in a RCPT command in a TCP/IP
39683 connection from the host with the given IP address. The output of the utility
39684 is either the word &"accepted"&, or the SMTP error response, for example:
39687 550 Relay not permitted
39689 When running this test, the utility uses &`<>`& as the envelope sender address
39690 for the MAIL command, but you can change this by providing additional
39691 options. These are passed directly to the Exim command. For example, to specify
39692 that the test is to be run with the sender address &'himself@there.example'&
39695 exim_checkaccess 10.9.8.7 A.User@a.domain.example \
39696 -f himself@there.example
39698 Note that these additional Exim command line items must be given after the two
39699 mandatory arguments.
39701 Because the &%exim_checkaccess%& uses &%-bh%&, it does not perform callouts
39702 while running its checks. You can run checks that include callouts by using
39703 &%-bhc%&, but this is not yet available in a &"packaged"& form.
39707 .section "Making DBM files (exim_dbmbuild)" "SECTdbmbuild"
39708 .cindex "DBM" "building dbm files"
39709 .cindex "building DBM files"
39710 .cindex "&'exim_dbmbuild'&"
39711 .cindex "lower casing"
39712 .cindex "binary zero" "in lookup key"
39713 The &'exim_dbmbuild'& program reads an input file containing keys and data in
39714 the format used by the &(lsearch)& lookup (see section
39715 &<<SECTsinglekeylookups>>&). It writes a DBM file using the lower-cased alias
39716 names as keys and the remainder of the information as data. The lower-casing
39717 can be prevented by calling the program with the &%-nolc%& option.
39719 A terminating zero is included as part of the key string. This is expected by
39720 the &(dbm)& lookup type. However, if the option &%-nozero%& is given,
39721 &'exim_dbmbuild'& creates files without terminating zeroes in either the key
39722 strings or the data strings. The &(dbmnz)& lookup type can be used with such
39725 The program requires two arguments: the name of the input file (which can be a
39726 single hyphen to indicate the standard input), and the name of the output file.
39727 It creates the output under a temporary name, and then renames it if all went
39731 If the native DB interface is in use (USE_DB is set in a compile-time
39732 configuration file &-- this is common in free versions of Unix) the two
39733 filenames must be different, because in this mode the Berkeley DB functions
39734 create a single output file using exactly the name given. For example,
39736 exim_dbmbuild /etc/aliases /etc/aliases.db
39738 reads the system alias file and creates a DBM version of it in
39739 &_/etc/aliases.db_&.
39741 In systems that use the &'ndbm'& routines (mostly proprietary versions of
39742 Unix), two files are used, with the suffixes &_.dir_& and &_.pag_&. In this
39743 environment, the suffixes are added to the second argument of
39744 &'exim_dbmbuild'&, so it can be the same as the first. This is also the case
39745 when the Berkeley functions are used in compatibility mode (though this is not
39746 recommended), because in that case it adds a &_.db_& suffix to the filename.
39748 If a duplicate key is encountered, the program outputs a warning, and when it
39749 finishes, its return code is 1 rather than zero, unless the &%-noduperr%&
39750 option is used. By default, only the first of a set of duplicates is used &--
39751 this makes it compatible with &(lsearch)& lookups. There is an option
39752 &%-lastdup%& which causes it to use the data for the last duplicate instead.
39753 There is also an option &%-nowarn%&, which stops it listing duplicate keys to
39754 &%stderr%&. For other errors, where it doesn't actually make a new file, the
39760 .section "Finding individual retry times (exinext)" "SECTfinindret"
39761 .cindex "retry" "times"
39762 .cindex "&'exinext'&"
39763 A utility called &'exinext'& (mostly a Perl script) provides the ability to
39764 fish specific information out of the retry database. Given a mail domain (or a
39765 complete address), it looks up the hosts for that domain, and outputs any retry
39766 information for the hosts or for the domain. At present, the retry information
39767 is obtained by running &'exim_dumpdb'& (see below) and post-processing the
39768 output. For example:
39770 $ exinext piglet@milne.fict.example
39771 kanga.milne.example:192.168.8.1 error 146: Connection refused
39772 first failed: 21-Feb-1996 14:57:34
39773 last tried: 21-Feb-1996 14:57:34
39774 next try at: 21-Feb-1996 15:02:34
39775 roo.milne.example:192.168.8.3 error 146: Connection refused
39776 first failed: 20-Jan-1996 13:12:08
39777 last tried: 21-Feb-1996 11:42:03
39778 next try at: 21-Feb-1996 19:42:03
39779 past final cutoff time
39781 You can also give &'exinext'& a local part, without a domain, and it
39782 will give any retry information for that local part in your default domain.
39783 A message id can be used to obtain retry information pertaining to a specific
39784 message. This exists only when an attempt to deliver a message to a remote host
39785 suffers a message-specific error (see section &<<SECToutSMTPerr>>&).
39786 &'exinext'& is not particularly efficient, but then it is not expected to be
39789 The &'exinext'& utility calls Exim to find out information such as the location
39790 of the spool directory. The utility has &%-C%& and &%-D%& options, which are
39791 passed on to the &'exim'& commands. The first specifies an alternate Exim
39792 configuration file, and the second sets macros for use within the configuration
39793 file. These features are mainly to help in testing, but might also be useful in
39794 environments where more than one configuration file is in use.
39798 .section "Hints database maintenance" "SECThindatmai"
39799 .cindex "hints database" "maintenance"
39800 .cindex "maintaining Exim's hints database"
39801 Three utility programs are provided for maintaining the DBM files that Exim
39802 uses to contain its delivery hint information. Each program requires two
39803 arguments. The first specifies the name of Exim's spool directory, and the
39804 second is the name of the database it is to operate on. These are as follows:
39807 &'retry'&: the database of retry information
39809 &'wait-'&<&'transport name'&>: databases of information about messages waiting
39812 &'callout'&: the callout cache
39814 &'ratelimit'&: the data for implementing the ratelimit ACL condition
39816 &'tls'&: TLS session resumption data
39818 &'misc'&: other hints data
39821 The &'misc'& database is used for
39824 Serializing ETRN runs (when &%smtp_etrn_serialize%& is set)
39826 Serializing delivery to a specific host (when &%serialize_hosts%& is set in an
39827 &(smtp)& transport)
39829 Limiting the concurrency of specific transports (when &%max_parallel%& is set
39835 .section "exim_dumpdb" "SECTdumpdb"
39836 .cindex "&'exim_dumpdb'&"
39837 The entire contents of a database are written to the standard output by the
39838 &'exim_dumpdb'& program,
39839 taking as arguments the spool and database names.
39840 An option &'-z'& may be given to request times in UTC;
39841 otherwise times are in the local timezone.
39842 An option &'-k'& may be given to dump only the record keys.
39843 For example, to dump the retry database:
39845 exim_dumpdb /var/spool/exim retry
39847 For the retry database
39848 two lines of output are produced for each entry:
39850 T:mail.ref.example:192.168.242.242 146 77 Connection refused
39851 31-Oct-1995 12:00:12 02-Nov-1995 12:21:39 02-Nov-1995 20:21:39 *
39853 The first item on the first line is the key of the record. It starts with one
39854 of the letters R, or T, depending on whether it refers to a routing or
39855 transport retry. For a local delivery, the next part is the local address; for
39856 a remote delivery it is the name of the remote host, followed by its failing IP
39857 address (unless &%retry_include_ip_address%& is set false on the &(smtp)&
39858 transport). If the remote port is not the standard one (port 25), it is added
39859 to the IP address. Then there follows an error code, an additional error code,
39860 and a textual description of the error.
39862 The three times on the second line are the time of first failure, the time of
39863 the last delivery attempt, and the computed time for the next attempt. The line
39864 ends with an asterisk if the cutoff time for the last retry rule has been
39867 Each output line from &'exim_dumpdb'& for the &'wait-xxx'& databases
39868 consists of a host name followed by a list of ids for messages that are or were
39869 waiting to be delivered to that host. If there are a very large number for any
39870 one host, continuation records, with a sequence number added to the host name,
39871 may be seen. The data in these records is often out of date, because a message
39872 may be routed to several alternative hosts, and Exim makes no effort to keep
39877 .section "exim_tidydb" "SECTtidydb"
39878 .cindex "&'exim_tidydb'&"
39879 The &'exim_tidydb'& utility program is used to tidy up the contents of a hints
39880 database. If run with no options, it removes all records that are more than 30
39881 days old. The age is calculated from the date and time that the record was last
39882 updated. Note that, in the case of the retry database, it is &'not'& the time
39883 since the first delivery failure. Information about a host that has been down
39884 for more than 30 days will remain in the database, provided that the record is
39885 updated sufficiently often.
39887 The cutoff date can be altered by means of the &%-t%& option, which must be
39888 followed by a time. For example, to remove all records older than a week from
39889 the retry database:
39891 exim_tidydb -t 7d /var/spool/exim retry
39893 Both the &'wait-xxx'& and &'retry'& databases contain items that involve
39894 message ids. In the former these appear as data in records keyed by host &--
39895 they were messages that were waiting for that host &-- and in the latter they
39896 are the keys for retry information for messages that have suffered certain
39897 types of error. When &'exim_tidydb'& is run, a check is made to ensure that
39898 message ids in database records are those of messages that are still on the
39899 queue. Message ids for messages that no longer exist are removed from
39900 &'wait-xxx'& records, and if this leaves any records empty, they are deleted.
39901 For the &'retry'& database, records whose keys are non-existent message ids are
39902 removed. The &'exim_tidydb'& utility outputs comments on the standard output
39903 whenever it removes information from the database.
39905 Certain records are automatically removed by Exim when they are no longer
39906 needed, but others are not. For example, if all the MX hosts for a domain are
39907 down, a retry record is created for each one. If the primary MX host comes back
39908 first, its record is removed when Exim successfully delivers to it, but the
39909 records for the others remain because Exim has not tried to use those hosts.
39911 It is important, therefore, to run &'exim_tidydb'& periodically on all the
39912 hints databases. You should do this at a quiet time of day, because it requires
39913 a database to be locked (and therefore inaccessible to Exim) while it does its
39914 work. Removing records from a DBM file does not normally make the file smaller,
39915 but all the common DBM libraries are able to re-use the space that is released.
39916 After an initial phase of increasing in size, the databases normally reach a
39917 point at which they no longer get any bigger, as long as they are regularly
39920 &*Warning*&: If you never run &'exim_tidydb'&, the space used by the hints
39921 databases is likely to keep on increasing.
39926 .section "exim_fixdb" "SECTfixdb"
39927 .cindex "&'exim_fixdb'&"
39928 The &'exim_fixdb'& program is a utility for interactively modifying databases.
39929 Its main use is for testing Exim, but it might also be occasionally useful for
39930 getting round problems in a live system. Its interface
39931 is somewhat crude. On entry, it prompts for input with a right angle-bracket. A
39932 key of a database record can then be entered, and the data for that record is
39935 If &"d"& is typed at the next prompt, the entire record is deleted. For all
39936 except the &'retry'& database, that is the only operation that can be carried
39937 out. For the &'retry'& database, each field is output preceded by a number, and
39938 data for individual fields can be changed by typing the field number followed
39939 by new data, for example:
39943 resets the time of the next delivery attempt. Time values are given as a
39944 sequence of digit pairs for year, month, day, hour, and minute. Colons can be
39945 used as optional separators.
39947 Both displayed and input times are in the local timezone by default.
39948 If an option &'-z'& is used on the command line, displayed times
39954 .section "Mailbox maintenance (exim_lock)" "SECTmailboxmaint"
39955 .cindex "mailbox" "maintenance"
39956 .cindex "&'exim_lock'&"
39957 .cindex "locking mailboxes"
39958 The &'exim_lock'& utility locks a mailbox file using the same algorithm as
39959 Exim. For a discussion of locking issues, see section &<<SECTopappend>>&.
39960 &'Exim_lock'& can be used to prevent any modification of a mailbox by Exim or
39961 a user agent while investigating a problem. The utility requires the name of
39962 the file as its first argument. If the locking is successful, the second
39963 argument is run as a command (using C's &[system()]& function); if there is no
39964 second argument, the value of the SHELL environment variable is used; if this
39965 is unset or empty, &_/bin/sh_& is run. When the command finishes, the mailbox
39966 is unlocked and the utility ends. The following options are available:
39970 Use &[fcntl()]& locking on the open mailbox.
39973 Use &[flock()]& locking on the open mailbox, provided the operating system
39976 .vitem &%-interval%&
39977 This must be followed by a number, which is a number of seconds; it sets the
39978 interval to sleep between retries (default 3).
39980 .vitem &%-lockfile%&
39981 Create a lock file before opening the mailbox.
39984 Lock the mailbox using MBX rules.
39987 Suppress verification output.
39989 .vitem &%-retries%&
39990 This must be followed by a number; it sets the number of times to try to get
39991 the lock (default 10).
39993 .vitem &%-restore_time%&
39994 This option causes &%exim_lock%& to restore the modified and read times to the
39995 locked file before exiting. This allows you to access a locked mailbox (for
39996 example, to take a backup copy) without disturbing the times that the user
39999 .vitem &%-timeout%&
40000 This must be followed by a number, which is a number of seconds; it sets a
40001 timeout to be used with a blocking &[fcntl()]& lock. If it is not set (the
40002 default), a non-blocking call is used.
40005 Generate verbose output.
40008 If none of &%-fcntl%&, &%-flock%&, &%-lockfile%& or &%-mbx%& are given, the
40009 default is to create a lock file and also to use &[fcntl()]& locking on the
40010 mailbox, which is the same as Exim's default. The use of &%-flock%& or
40011 &%-fcntl%& requires that the file be writeable; the use of &%-lockfile%&
40012 requires that the directory containing the file be writeable. Locking by lock
40013 file does not last forever; Exim assumes that a lock file is expired if it is
40014 more than 30 minutes old.
40016 The &%-mbx%& option can be used with either or both of &%-fcntl%& or
40017 &%-flock%&. It assumes &%-fcntl%& by default. MBX locking causes a shared lock
40018 to be taken out on the open mailbox, and an exclusive lock on the file
40019 &_/tmp/.n.m_& where &'n'& and &'m'& are the device number and inode
40020 number of the mailbox file. When the locking is released, if an exclusive lock
40021 can be obtained for the mailbox, the file in &_/tmp_& is deleted.
40023 The default output contains verification of the locking that takes place. The
40024 &%-v%& option causes some additional information to be given. The &%-q%& option
40025 suppresses all output except error messages.
40029 exim_lock /var/spool/mail/spqr
40031 runs an interactive shell while the file is locked, whereas
40033 &`exim_lock -q /var/spool/mail/spqr <<End`&
40034 <&'some commands'&>
40037 runs a specific non-interactive sequence of commands while the file is locked,
40038 suppressing all verification output. A single command can be run by a command
40041 exim_lock -q /var/spool/mail/spqr \
40042 "cp /var/spool/mail/spqr /some/where"
40044 Note that if a command is supplied, it must be entirely contained within the
40045 second argument &-- hence the quotes.
40049 . ////////////////////////////////////////////////////////////////////////////
40050 . ////////////////////////////////////////////////////////////////////////////
40052 .chapter "The Exim monitor" "CHAPeximon"
40053 .scindex IIDeximon "Exim monitor" "description"
40054 .cindex "X-windows"
40055 .cindex "&'eximon'&"
40056 .cindex "Local/eximon.conf"
40057 .cindex "&_exim_monitor/EDITME_&"
40058 The Exim monitor is an application which displays in an X window information
40059 about the state of Exim's queue and what Exim is doing. An admin user can
40060 perform certain operations on messages from this GUI interface; however all
40061 such facilities are also available from the command line, and indeed, the
40062 monitor itself makes use of the command line to perform any actions requested.
40066 .section "Running the monitor" "SECID264"
40067 The monitor is started by running the script called &'eximon'&. This is a shell
40068 script that sets up a number of environment variables, and then runs the
40069 binary called &_eximon.bin_&. The default appearance of the monitor window can
40070 be changed by editing the &_Local/eximon.conf_& file created by editing
40071 &_exim_monitor/EDITME_&. Comments in that file describe what the various
40072 parameters are for.
40074 The parameters that get built into the &'eximon'& script can be overridden for
40075 a particular invocation by setting up environment variables of the same names,
40076 preceded by &`EXIMON_`&. For example, a shell command such as
40078 EXIMON_LOG_DEPTH=400 eximon
40080 (in a Bourne-compatible shell) runs &'eximon'& with an overriding setting of
40081 the LOG_DEPTH parameter. If EXIMON_LOG_FILE_PATH is set in the environment, it
40082 overrides the Exim log file configuration. This makes it possible to have
40083 &'eximon'& tailing log data that is written to syslog, provided that MAIL.INFO
40084 syslog messages are routed to a file on the local host.
40086 X resources can be used to change the appearance of the window in the normal
40087 way. For example, a resource setting of the form
40089 Eximon*background: gray94
40091 changes the colour of the background to light grey rather than white. The
40092 stripcharts are drawn with both the data lines and the reference lines in
40093 black. This means that the reference lines are not visible when on top of the
40094 data. However, their colour can be changed by setting a resource called
40095 &"highlight"& (an odd name, but that's what the Athena stripchart widget uses).
40096 For example, if your X server is running Unix, you could set up lighter
40097 reference lines in the stripcharts by obeying
40100 Eximon*highlight: gray
40103 .cindex "admin user"
40104 In order to see the contents of messages in the queue, and to operate on them,
40105 &'eximon'& must either be run as root or by an admin user.
40107 The command-line parameters of &'eximon'& are passed to &_eximon.bin_& and may
40108 contain X11 resource parameters interpreted by the X11 library. In addition,
40109 if the first parameter starts with the string "gdb" then it is removed and the
40110 binary is invoked under gdb (the parameter is used as the gdb command-name, so
40111 versioned variants of gdb can be invoked).
40113 The monitor's window is divided into three parts. The first contains one or
40114 more stripcharts and two action buttons, the second contains a &"tail"& of the
40115 main log file, and the third is a display of the queue of messages awaiting
40116 delivery, with two more action buttons. The following sections describe these
40117 different parts of the display.
40122 .section "The stripcharts" "SECID265"
40123 .cindex "stripchart"
40124 The first stripchart is always a count of messages in the queue. Its name can
40125 be configured by setting QUEUE_STRIPCHART_NAME in the
40126 &_Local/eximon.conf_& file. The remaining stripcharts are defined in the
40127 configuration script by regular expression matches on log file entries, making
40128 it possible to display, for example, counts of messages delivered to certain
40129 hosts or using certain transports. The supplied defaults display counts of
40130 received and delivered messages, and of local and SMTP deliveries. The default
40131 period between stripchart updates is one minute; this can be adjusted by a
40132 parameter in the &_Local/eximon.conf_& file.
40134 The stripchart displays rescale themselves automatically as the value they are
40135 displaying changes. There are always 10 horizontal lines in each chart; the
40136 title string indicates the value of each division when it is greater than one.
40137 For example, &"x2"& means that each division represents a value of 2.
40139 It is also possible to have a stripchart which shows the percentage fullness of
40140 a particular disk partition, which is useful when local deliveries are confined
40141 to a single partition.
40143 .cindex "&%statvfs%& function"
40144 This relies on the availability of the &[statvfs()]& function or equivalent in
40145 the operating system. Most, but not all versions of Unix that support Exim have
40146 this. For this particular stripchart, the top of the chart always represents
40147 100%, and the scale is given as &"x10%"&. This chart is configured by setting
40148 SIZE_STRIPCHART and (optionally) SIZE_STRIPCHART_NAME in the
40149 &_Local/eximon.conf_& file.
40154 .section "Main action buttons" "SECID266"
40155 .cindex "size" "of monitor window"
40156 .cindex "Exim monitor" "window size"
40157 .cindex "window size"
40158 Below the stripcharts there is an action button for quitting the monitor. Next
40159 to this is another button marked &"Size"&. They are placed here so that
40160 shrinking the window to its default minimum size leaves just the queue count
40161 stripchart and these two buttons visible. Pressing the &"Size"& button causes
40162 the window to expand to its maximum size, unless it is already at the maximum,
40163 in which case it is reduced to its minimum.
40165 When expanding to the maximum, if the window cannot be fully seen where it
40166 currently is, it is moved back to where it was the last time it was at full
40167 size. When it is expanding from its minimum size, the old position is
40168 remembered, and next time it is reduced to the minimum it is moved back there.
40170 The idea is that you can keep a reduced window just showing one or two
40171 stripcharts at a convenient place on your screen, easily expand it to show
40172 the full window when required, and just as easily put it back to what it was.
40173 The idea is copied from what the &'twm'& window manager does for its
40174 &'f.fullzoom'& action. The minimum size of the window can be changed by setting
40175 the MIN_HEIGHT and MIN_WIDTH values in &_Local/eximon.conf_&.
40177 Normally, the monitor starts up with the window at its full size, but it can be
40178 built so that it starts up with the window at its smallest size, by setting
40179 START_SMALL=yes in &_Local/eximon.conf_&.
40183 .section "The log display" "SECID267"
40184 .cindex "log" "tail of; in monitor"
40185 The second section of the window is an area in which a display of the tail of
40186 the main log is maintained.
40187 To save space on the screen, the timestamp on each log line is shortened by
40188 removing the date and, if &%log_timezone%& is set, the timezone.
40189 The log tail is not available when the only destination for logging data is
40190 syslog, unless the syslog lines are routed to a local file whose name is passed
40191 to &'eximon'& via the EXIMON_LOG_FILE_PATH environment variable.
40193 The log sub-window has a scroll bar at its lefthand side which can be used to
40194 move back to look at earlier text, and the up and down arrow keys also have a
40195 scrolling effect. The amount of log that is kept depends on the setting of
40196 LOG_BUFFER in &_Local/eximon.conf_&, which specifies the amount of memory
40197 to use. When this is full, the earlier 50% of data is discarded &-- this is
40198 much more efficient than throwing it away line by line. The sub-window also has
40199 a horizontal scroll bar for accessing the ends of long log lines. This is the
40200 only means of horizontal scrolling; the right and left arrow keys are not
40201 available. Text can be cut from this part of the window using the mouse in the
40202 normal way. The size of this subwindow is controlled by parameters in the
40203 configuration file &_Local/eximon.conf_&.
40205 Searches of the text in the log window can be carried out by means of the ^R
40206 and ^S keystrokes, which default to a reverse and a forward search,
40207 respectively. The search covers only the text that is displayed in the window.
40208 It cannot go further back up the log.
40210 The point from which the search starts is indicated by a caret marker. This is
40211 normally at the end of the text in the window, but can be positioned explicitly
40212 by pointing and clicking with the left mouse button, and is moved automatically
40213 by a successful search. If new text arrives in the window when it is scrolled
40214 back, the caret remains where it is, but if the window is not scrolled back,
40215 the caret is moved to the end of the new text.
40217 Pressing ^R or ^S pops up a window into which the search text can be typed.
40218 There are buttons for selecting forward or reverse searching, for carrying out
40219 the search, and for cancelling. If the &"Search"& button is pressed, the search
40220 happens and the window remains so that further searches can be done. If the
40221 &"Return"& key is pressed, a single search is done and the window is closed. If
40222 ^C is typed the search is cancelled.
40224 The searching facility is implemented using the facilities of the Athena text
40225 widget. By default this pops up a window containing both &"search"& and
40226 &"replace"& options. In order to suppress the unwanted &"replace"& portion for
40227 eximon, a modified version of the &%TextPop%& widget is distributed with Exim.
40228 However, the linkers in BSDI and HP-UX seem unable to handle an externally
40229 provided version of &%TextPop%& when the remaining parts of the text widget
40230 come from the standard libraries. The compile-time option EXIMON_TEXTPOP can be
40231 unset to cut out the modified &%TextPop%&, making it possible to build Eximon
40232 on these systems, at the expense of having unwanted items in the search popup
40237 .section "The queue display" "SECID268"
40238 .cindex "queue" "display in monitor"
40239 The bottom section of the monitor window contains a list of all messages that
40240 are in the queue, which includes those currently being received or delivered,
40241 as well as those awaiting delivery. The size of this subwindow is controlled by
40242 parameters in the configuration file &_Local/eximon.conf_&, and the frequency
40243 at which it is updated is controlled by another parameter in the same file &--
40244 the default is 5 minutes, since queue scans can be quite expensive. However,
40245 there is an &"Update"& action button just above the display which can be used
40246 to force an update of the queue display at any time.
40248 When a host is down for some time, a lot of pending mail can build up for it,
40249 and this can make it hard to deal with other messages in the queue. To help
40250 with this situation there is a button next to &"Update"& called &"Hide"&. If
40251 pressed, a dialogue box called &"Hide addresses ending with"& is put up. If you
40252 type anything in here and press &"Return"&, the text is added to a chain of
40253 such texts, and if every undelivered address in a message matches at least one
40254 of the texts, the message is not displayed.
40256 If there is an address that does not match any of the texts, all the addresses
40257 are displayed as normal. The matching happens on the ends of addresses so, for
40258 example, &'cam.ac.uk'& specifies all addresses in Cambridge, while
40259 &'xxx@foo.com.example'& specifies just one specific address. When any hiding
40260 has been set up, a button called &"Unhide"& is displayed. If pressed, it
40261 cancels all hiding. Also, to ensure that hidden messages do not get forgotten,
40262 a hide request is automatically cancelled after one hour.
40264 While the dialogue box is displayed, you can't press any buttons or do anything
40265 else to the monitor window. For this reason, if you want to cut text from the
40266 queue display to use in the dialogue box, you have to do the cutting before
40267 pressing the &"Hide"& button.
40269 The queue display contains, for each unhidden queued message, the length of
40270 time it has been in the queue, the size of the message, the message id, the
40271 message sender, and the first undelivered recipient, all on one line. If it is
40272 a bounce message, the sender is shown as &"<>"&. If there is more than one
40273 recipient to which the message has not yet been delivered, subsequent ones are
40274 listed on additional lines, up to a maximum configured number, following which
40275 an ellipsis is displayed. Recipients that have already received the message are
40278 .cindex "frozen messages" "display"
40279 If a message is frozen, an asterisk is displayed at the left-hand side.
40281 The queue display has a vertical scroll bar, and can also be scrolled by means
40282 of the arrow keys. Text can be cut from it using the mouse in the normal way.
40283 The text searching facilities, as described above for the log window, are also
40284 available, but the caret is always moved to the end of the text when the queue
40285 display is updated.
40289 .section "The queue menu" "SECID269"
40290 .cindex "queue" "menu in monitor"
40291 If the &%shift%& key is held down and the left button is clicked when the mouse
40292 pointer is over the text for any message, an action menu pops up, and the first
40293 line of the queue display for the message is highlighted. This does not affect
40296 If you want to use some other event for popping up the menu, you can set the
40297 MENU_EVENT parameter in &_Local/eximon.conf_& to change the default, or
40298 set EXIMON_MENU_EVENT in the environment before starting the monitor. The
40299 value set in this parameter is a standard X event description. For example, to
40300 run eximon using &%ctrl%& rather than &%shift%& you could use
40302 EXIMON_MENU_EVENT='Ctrl<Btn1Down>' eximon
40304 The title of the menu is the message id, and it contains entries which act as
40308 &'message log'&: The contents of the message log for the message are displayed
40309 in a new text window.
40311 &'headers'&: Information from the spool file that contains the envelope
40312 information and headers is displayed in a new text window. See chapter
40313 &<<CHAPspool>>& for a description of the format of spool files.
40315 &'body'&: The contents of the spool file containing the body of the message are
40316 displayed in a new text window. There is a default limit of 20,000 bytes to the
40317 amount of data displayed. This can be changed by setting the BODY_MAX
40318 option at compile time, or the EXIMON_BODY_MAX option at runtime.
40320 &'deliver message'&: A call to Exim is made using the &%-M%& option to request
40321 delivery of the message. This causes an automatic thaw if the message is
40322 frozen. The &%-v%& option is also set, and the output from Exim is displayed in
40323 a new text window. The delivery is run in a separate process, to avoid holding
40324 up the monitor while the delivery proceeds.
40326 &'freeze message'&: A call to Exim is made using the &%-Mf%& option to request
40327 that the message be frozen.
40329 .cindex "thawing messages"
40330 .cindex "unfreezing messages"
40331 .cindex "frozen messages" "thawing"
40332 &'thaw message'&: A call to Exim is made using the &%-Mt%& option to request
40333 that the message be thawed.
40335 .cindex "delivery" "forcing failure"
40336 &'give up on msg'&: A call to Exim is made using the &%-Mg%& option to request
40337 that Exim gives up trying to deliver the message. A bounce message is generated
40338 for any remaining undelivered addresses.
40340 &'remove message'&: A call to Exim is made using the &%-Mrm%& option to request
40341 that the message be deleted from the system without generating a bounce
40344 &'add recipient'&: A dialog box is displayed into which a recipient address can
40345 be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
40346 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
40347 Otherwise it must be entered as a fully qualified address. Pressing RETURN
40348 causes a call to Exim to be made using the &%-Mar%& option to request that an
40349 additional recipient be added to the message, unless the entry box is empty, in
40350 which case no action is taken.
40352 &'mark delivered'&: A dialog box is displayed into which a recipient address
40353 can be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
40354 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
40355 Otherwise it must be entered as a fully qualified address. Pressing RETURN
40356 causes a call to Exim to be made using the &%-Mmd%& option to mark the given
40357 recipient address as already delivered, unless the entry box is empty, in which
40358 case no action is taken.
40360 &'mark all delivered'&: A call to Exim is made using the &%-Mmad%& option to
40361 mark all recipient addresses as already delivered.
40363 &'edit sender'&: A dialog box is displayed initialized with the current
40364 sender's address. Pressing RETURN causes a call to Exim to be made using the
40365 &%-Mes%& option to replace the sender address, unless the entry box is empty,
40366 in which case no action is taken. If you want to set an empty sender (as in
40367 bounce messages), you must specify it as &"<>"&. Otherwise, if the address is
40368 not qualified and the QUALIFY_DOMAIN parameter is set in &_Local/eximon.conf_&,
40369 the address is qualified with that domain.
40372 When a delivery is forced, a window showing the &%-v%& output is displayed. In
40373 other cases when a call to Exim is made, if there is any output from Exim (in
40374 particular, if the command fails) a window containing the command and the
40375 output is displayed. Otherwise, the results of the action are normally apparent
40376 from the log and queue displays. However, if you set ACTION_OUTPUT=yes in
40377 &_Local/eximon.conf_&, a window showing the Exim command is always opened, even
40378 if no output is generated.
40380 The queue display is automatically updated for actions such as freezing and
40381 thawing, unless ACTION_QUEUE_UPDATE=no has been set in
40382 &_Local/eximon.conf_&. In this case the &"Update"& button has to be used to
40383 force an update of the display after one of these actions.
40385 In any text window that is displayed as result of a menu action, the normal
40386 cut-and-paste facility is available, and searching can be carried out using ^R
40387 and ^S, as described above for the log tail window.
40394 . ////////////////////////////////////////////////////////////////////////////
40395 . ////////////////////////////////////////////////////////////////////////////
40397 .chapter "Security considerations" "CHAPsecurity"
40398 .scindex IIDsecurcon "security" "discussion of"
40399 This chapter discusses a number of issues concerned with security, some of
40400 which are also covered in other parts of this manual.
40402 For reasons that this author does not understand, some people have promoted
40403 Exim as a &"particularly secure"& mailer. Perhaps it is because of the
40404 existence of this chapter in the documentation. However, the intent of the
40405 chapter is simply to describe the way Exim works in relation to certain
40406 security concerns, not to make any specific claims about the effectiveness of
40407 its security as compared with other MTAs.
40409 What follows is a description of the way Exim is supposed to be. Best efforts
40410 have been made to try to ensure that the code agrees with the theory, but an
40411 absence of bugs can never be guaranteed. Any that are reported will get fixed
40412 as soon as possible.
40415 .section "Building a more &""hardened""& Exim" "SECID286"
40416 .cindex "security" "build-time features"
40417 There are a number of build-time options that can be set in &_Local/Makefile_&
40418 to create Exim binaries that are &"harder"& to attack, in particular by a rogue
40419 Exim administrator who does not have the root password, or by someone who has
40420 penetrated the Exim (but not the root) account. These options are as follows:
40423 ALT_CONFIG_PREFIX can be set to a string that is required to match the
40424 start of any filenames used with the &%-C%& option. When it is set, these
40425 filenames are also not allowed to contain the sequence &"/../"&. (However, if
40426 the value of the &%-C%& option is identical to the value of CONFIGURE_FILE in
40427 &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as usual.) There is no
40428 default setting for &%ALT_CONFIG_PREFIX%&.
40430 If the permitted configuration files are confined to a directory to
40431 which only root has access, this guards against someone who has broken
40432 into the Exim account from running a privileged Exim with an arbitrary
40433 configuration file, and using it to break into other accounts.
40436 If a non-trusted configuration file (i.e. not the default configuration file
40437 or one which is trusted by virtue of being listed in the TRUSTED_CONFIG_LIST
40438 file) is specified with &%-C%&, or if macros are given with &%-D%& (but see
40439 the next item), then root privilege is retained only if the caller of Exim is
40440 root. This locks out the possibility of testing a configuration using &%-C%&
40441 right through message reception and delivery, even if the caller is root. The
40442 reception works, but by that time, Exim is running as the Exim user, so when
40443 it re-execs to regain privilege for the delivery, the use of &%-C%& causes
40444 privilege to be lost. However, root can test reception and delivery using two
40448 The WHITELIST_D_MACROS build option declares some macros to be safe to override
40449 with &%-D%& if the real uid is one of root, the Exim run-time user or the
40450 CONFIGURE_OWNER, if defined. The potential impact of this option is limited by
40451 requiring the run-time value supplied to &%-D%& to match a regex that errs on
40452 the restrictive side. Requiring build-time selection of safe macros is onerous
40453 but this option is intended solely as a transition mechanism to permit
40454 previously-working configurations to continue to work after release 4.73.
40456 If DISABLE_D_OPTION is defined, the use of the &%-D%& command line option
40459 FIXED_NEVER_USERS can be set to a colon-separated list of users that are
40460 never to be used for any deliveries. This is like the &%never_users%& runtime
40461 option, but it cannot be overridden; the runtime option adds additional users
40462 to the list. The default setting is &"root"&; this prevents a non-root user who
40463 is permitted to modify the runtime file from using Exim as a way to get root.
40468 .section "Root privilege" "SECID270"
40470 .cindex "root privilege"
40471 The Exim binary is normally setuid to root, which means that it gains root
40472 privilege (runs as root) when it starts execution. In some special cases (for
40473 example, when the daemon is not in use and there are no local deliveries), it
40474 may be possible to run Exim setuid to some user other than root. This is
40475 discussed in the next section. However, in most installations, root privilege
40476 is required for two things:
40479 To set up a socket connected to the standard SMTP port (25) when initialising
40480 the listening daemon. If Exim is run from &'inetd'&, this privileged action is
40483 To be able to change uid and gid in order to read users' &_.forward_& files and
40484 perform local deliveries as the receiving user or as specified in the
40488 It is not necessary to be root to do any of the other things Exim does, such as
40489 receiving messages and delivering them externally over SMTP, and it is
40490 obviously more secure if Exim does not run as root except when necessary.
40491 For this reason, a user and group for Exim to use must be defined in
40492 &_Local/Makefile_&. These are known as &"the Exim user"& and &"the Exim
40493 group"&. Their values can be changed by the runtime configuration, though this
40494 is not recommended. Often a user called &'exim'& is used, but some sites use
40495 &'mail'& or another user name altogether.
40497 Exim uses &[setuid()]& whenever it gives up root privilege. This is a permanent
40498 abdication; the process cannot regain root afterwards. Prior to release 4.00,
40499 &[seteuid()]& was used in some circumstances, but this is no longer the case.
40501 After a new Exim process has interpreted its command line options, it changes
40502 uid and gid in the following cases:
40507 If the &%-C%& option is used to specify an alternate configuration file, or if
40508 the &%-D%& option is used to define macro values for the configuration, and the
40509 calling process is not running as root, the uid and gid are changed to those of
40510 the calling process.
40511 However, if DISABLE_D_OPTION is defined in &_Local/Makefile_&, the &%-D%&
40512 option may not be used at all.
40513 If WHITELIST_D_MACROS is defined in &_Local/Makefile_&, then some macro values
40514 can be supplied if the calling process is running as root, the Exim run-time
40515 user or CONFIGURE_OWNER, if defined.
40520 If the expansion test option (&%-be%&) or one of the filter testing options
40521 (&%-bf%& or &%-bF%&) are used, the uid and gid are changed to those of the
40524 If the process is not a daemon process or a queue runner process or a delivery
40525 process or a process for testing address routing (started with &%-bt%&), the
40526 uid and gid are changed to the Exim user and group. This means that Exim always
40527 runs under its own uid and gid when receiving messages. This also applies when
40528 testing address verification
40531 (the &%-bv%& option) and testing incoming message policy controls (the &%-bh%&
40534 For a daemon, queue runner, delivery, or address testing process, the uid
40535 remains as root at this stage, but the gid is changed to the Exim group.
40538 The processes that initially retain root privilege behave as follows:
40541 A daemon process changes the gid to the Exim group and the uid to the Exim
40542 user after setting up one or more listening sockets. The &[initgroups()]&
40543 function is called, so that if the Exim user is in any additional groups, they
40544 will be used during message reception.
40546 A queue runner process retains root privilege throughout its execution. Its
40547 job is to fork a controlled sequence of delivery processes.
40549 A delivery process retains root privilege throughout most of its execution,
40550 but any actual deliveries (that is, the transports themselves) are run in
40551 subprocesses which always change to a non-root uid and gid. For local
40552 deliveries this is typically the uid and gid of the owner of the mailbox; for
40553 remote deliveries, the Exim uid and gid are used. Once all the delivery
40554 subprocesses have been run, a delivery process changes to the Exim uid and gid
40555 while doing post-delivery tidying up such as updating the retry database and
40556 generating bounce and warning messages.
40558 While the recipient addresses in a message are being routed, the delivery
40559 process runs as root. However, if a user's filter file has to be processed,
40560 this is done in a subprocess that runs under the individual user's uid and
40561 gid. A system filter is run as root unless &%system_filter_user%& is set.
40563 A process that is testing addresses (the &%-bt%& option) runs as root so that
40564 the routing is done in the same environment as a message delivery.
40570 .section "Running Exim without privilege" "SECTrunexiwitpri"
40571 .cindex "privilege, running without"
40572 .cindex "unprivileged running"
40573 .cindex "root privilege" "running without"
40574 Some installations like to run Exim in an unprivileged state for more of its
40575 operation, for added security. Support for this mode of operation is provided
40576 by the global option &%deliver_drop_privilege%&. When this is set, the uid and
40577 gid are changed to the Exim user and group at the start of a delivery process
40578 (and also queue runner and address testing processes). This means that address
40579 routing is no longer run as root, and the deliveries themselves cannot change
40583 .cindex "daemon" "restarting"
40584 Leaving the binary setuid to root, but setting &%deliver_drop_privilege%& means
40585 that the daemon can still be started in the usual way, and it can respond
40586 correctly to SIGHUP because the re-invocation regains root privilege.
40588 An alternative approach is to make Exim setuid to the Exim user and also setgid
40589 to the Exim group. If you do this, the daemon must be started from a root
40590 process. (Calling Exim from a root process makes it behave in the way it does
40591 when it is setuid root.) However, the daemon cannot restart itself after a
40592 SIGHUP signal because it cannot regain privilege.
40594 It is still useful to set &%deliver_drop_privilege%& in this case, because it
40595 stops Exim from trying to re-invoke itself to do a delivery after a message has
40596 been received. Such a re-invocation is a waste of resources because it has no
40599 If restarting the daemon is not an issue (for example, if &%mua_wrapper%& is
40600 set, or &'inetd'& is being used instead of a daemon), having the binary setuid
40601 to the Exim user seems a clean approach, but there is one complication:
40603 In this style of operation, Exim is running with the real uid and gid set to
40604 those of the calling process, and the effective uid/gid set to Exim's values.
40605 Ideally, any association with the calling process' uid/gid should be dropped,
40606 that is, the real uid/gid should be reset to the effective values so as to
40607 discard any privileges that the caller may have. While some operating systems
40608 have a function that permits this action for a non-root effective uid, quite a
40609 number of them do not. Because of this lack of standardization, Exim does not
40610 address this problem at this time.
40612 For this reason, the recommended approach for &"mostly unprivileged"& running
40613 is to keep the Exim binary setuid to root, and to set
40614 &%deliver_drop_privilege%&. This also has the advantage of allowing a daemon to
40615 be used in the most straightforward way.
40617 If you configure Exim not to run delivery processes as root, there are a
40618 number of restrictions on what you can do:
40621 You can deliver only as the Exim user/group. You should explicitly use the
40622 &%user%& and &%group%& options to override routers or local transports that
40623 normally deliver as the recipient. This makes sure that configurations that
40624 work in this mode function the same way in normal mode. Any implicit or
40625 explicit specification of another user causes an error.
40627 Use of &_.forward_& files is severely restricted, such that it is usually
40628 not worthwhile to include them in the configuration.
40630 Users who wish to use &_.forward_& would have to make their home directory and
40631 the file itself accessible to the Exim user. Pipe and append-to-file entries,
40632 and their equivalents in Exim filters, cannot be used. While they could be
40633 enabled in the Exim user's name, that would be insecure and not very useful.
40635 Unless the local user mailboxes are all owned by the Exim user (possible in
40636 some POP3 or IMAP-only environments):
40639 They must be owned by the Exim group and be writeable by that group. This
40640 implies you must set &%mode%& in the appendfile configuration, as well as the
40641 mode of the mailbox files themselves.
40643 You must set &%no_check_owner%&, since most or all of the files will not be
40644 owned by the Exim user.
40646 You must set &%file_must_exist%&, because Exim cannot set the owner correctly
40647 on a newly created mailbox when unprivileged. This also implies that new
40648 mailboxes need to be created manually.
40653 These restrictions severely restrict what can be done in local deliveries.
40654 However, there are no restrictions on remote deliveries. If you are running a
40655 gateway host that does no local deliveries, setting &%deliver_drop_privilege%&
40656 gives more security at essentially no cost.
40658 If you are using the &%mua_wrapper%& facility (see chapter
40659 &<<CHAPnonqueueing>>&), &%deliver_drop_privilege%& is forced to be true.
40664 .section "Delivering to local files" "SECID271"
40665 Full details of the checks applied by &(appendfile)& before it writes to a file
40666 are given in chapter &<<CHAPappendfile>>&.
40670 .section "Running local commands" "SECTsecconslocalcmds"
40671 .cindex "security" "local commands"
40672 .cindex "security" "command injection attacks"
40673 There are a number of ways in which an administrator can configure Exim to run
40674 commands based upon received, untrustworthy, data. Further, in some
40675 configurations a user who can control a &_.forward_& file can also arrange to
40676 run commands. Configuration to check includes, but is not limited to:
40679 Use of &%use_shell%& in the pipe transport: various forms of shell command
40680 injection may be possible with this option present. It is dangerous and should
40681 be used only with considerable caution. Consider constraints which whitelist
40682 allowed characters in a variable which is to be used in a pipe transport that
40683 has &%use_shell%& enabled.
40685 A number of options such as &%forbid_filter_run%&, &%forbid_filter_perl%&,
40686 &%forbid_filter_dlfunc%& and so forth which restrict facilities available to
40687 &_.forward_& files in a redirect router. If Exim is running on a central mail
40688 hub to which ordinary users do not have shell access, but home directories are
40689 NFS mounted (for instance) then administrators should review the list of these
40690 forbid options available, and should bear in mind that the options that may
40691 need forbidding can change as new features are added between releases.
40693 The &%${run...}%& expansion item does not use a shell by default, but
40694 administrators can configure use of &_/bin/sh_& as part of the command.
40695 Such invocations should be viewed with prejudicial suspicion.
40697 Administrators who use embedded Perl are advised to explore how Perl's
40698 taint checking might apply to their usage.
40700 Use of &%${expand...}%& is somewhat analogous to shell's eval builtin and
40701 administrators are well advised to view its use with suspicion, in case (for
40702 instance) it allows a local-part to contain embedded Exim directives.
40704 Use of &%${match_local_part...}%& and friends becomes more dangerous if
40705 Exim was built with EXPAND_LISTMATCH_RHS defined: the second string in
40706 each can reference arbitrary lists and files, rather than just being a list
40708 The EXPAND_LISTMATCH_RHS option was added and set false by default because of
40709 real-world security vulnerabilities caused by its use with untrustworthy data
40710 injected in, for SQL injection attacks.
40711 Consider the use of the &%inlisti%& expansion condition instead.
40717 .section "Trust in configuration data" "SECTsecconfdata"
40718 .cindex "security" "data sources"
40719 .cindex "security" "regular expressions"
40720 .cindex "regular expressions" "security"
40721 .cindex "PCRE2" "security"
40722 If configuration data for Exim can come from untrustworthy sources, there
40723 are some issues to be aware of:
40726 Use of &%${expand...}%& may provide a path for shell injection attacks.
40728 Letting untrusted data provide a regular expression is unwise.
40730 Using &%${match...}%& to apply a fixed regular expression against untrusted
40731 data may result in pathological behaviour within PCRE2. Be aware of what
40732 "backtracking" means and consider options for being more strict with a regular
40733 expression. Avenues to explore include limiting what can match (avoiding &`.`&
40734 when &`[a-z0-9]`& or other character class will do), use of atomic grouping and
40735 possessive quantifiers or just not using regular expressions against untrusted
40738 It can be important to correctly use &%${quote:...}%&,
40739 &%${quote_local_part:...}%& and &%${quote_%&<&'lookup-type'&>&%:...}%& expansion
40740 items to ensure that data is correctly constructed.
40742 Some lookups might return multiple results, even though normal usage is only
40743 expected to yield one result.
40749 .section "IPv4 source routing" "SECID272"
40750 .cindex "source routing" "in IP packets"
40751 .cindex "IP source routing"
40752 Many operating systems suppress IP source-routed packets in the kernel, but
40753 some cannot be made to do this, so Exim does its own check. It logs incoming
40754 IPv4 source-routed TCP calls, and then drops them. Things are all different in
40755 IPv6. No special checking is currently done.
40759 .section "The VRFY, EXPN, and ETRN commands in SMTP" "SECID273"
40760 Support for these SMTP commands is disabled by default. If required, they can
40761 be enabled by defining suitable ACLs.
40766 .section "Privileged users" "SECID274"
40767 .cindex "trusted users"
40768 .cindex "admin user"
40769 .cindex "privileged user"
40770 .cindex "user" "trusted"
40771 .cindex "user" "admin"
40772 Exim recognizes two sets of users with special privileges. Trusted users are
40773 able to submit new messages to Exim locally, but supply their own sender
40774 addresses and information about a sending host. For other users submitting
40775 local messages, Exim sets up the sender address from the uid, and doesn't
40776 permit a remote host to be specified.
40779 However, an untrusted user is permitted to use the &%-f%& command line option
40780 in the special form &%-f <>%& to indicate that a delivery failure for the
40781 message should not cause an error report. This affects the message's envelope,
40782 but it does not affect the &'Sender:'& header. Untrusted users may also be
40783 permitted to use specific forms of address with the &%-f%& option by setting
40784 the &%untrusted_set_sender%& option.
40786 Trusted users are used to run processes that receive mail messages from some
40787 other mail domain and pass them on to Exim for delivery either locally, or over
40788 the Internet. Exim trusts a caller that is running as root, as the Exim user,
40789 as any user listed in the &%trusted_users%& configuration option, or under any
40790 group listed in the &%trusted_groups%& option.
40792 Admin users are permitted to do things to the messages on Exim's queue. They
40793 can freeze or thaw messages, cause them to be returned to their senders, remove
40794 them entirely, or modify them in various ways. In addition, admin users can run
40795 the Exim monitor and see all the information it is capable of providing, which
40796 includes the contents of files on the spool.
40800 By default, the use of the &%-M%& and &%-q%& options to cause Exim to attempt
40801 delivery of messages on its queue is restricted to admin users. This
40802 restriction can be relaxed by setting the &%no_prod_requires_admin%& option.
40803 Similarly, the use of &%-bp%& (and its variants) to list the contents of the
40804 queue is also restricted to admin users. This restriction can be relaxed by
40805 setting &%no_queue_list_requires_admin%&.
40807 Exim recognizes an admin user if the calling process is running as root or as
40808 the Exim user or if any of the groups associated with the calling process is
40809 the Exim group. It is not necessary actually to be running under the Exim
40810 group. However, if admin users who are not root or the Exim user are to access
40811 the contents of files on the spool via the Exim monitor (which runs
40812 unprivileged), Exim must be built to allow group read access to its spool
40815 By default, regular users are trusted to perform basic testing and
40816 introspection commands, as themselves. This setting can be tightened by
40817 setting the &%commandline_checks_require_admin%& option.
40818 This affects most of the checking options,
40819 such as &%-be%& and anything else &%-b*%&.
40822 .section "Spool files" "SECID275"
40823 .cindex "spool directory" "files"
40824 Exim's spool directory and everything it contains is owned by the Exim user and
40825 set to the Exim group. The mode for spool files is defined in the
40826 &_Local/Makefile_& configuration file, and defaults to 0640. This means that
40827 any user who is a member of the Exim group can access these files.
40831 .section "Use of argv[0]" "SECID276"
40832 Exim examines the last component of &%argv[0]%&, and if it matches one of a set
40833 of specific strings, Exim assumes certain options. For example, calling Exim
40834 with the last component of &%argv[0]%& set to &"rsmtp"& is exactly equivalent
40835 to calling it with the option &%-bS%&. There are no security implications in
40840 .section "Use of %f formatting" "SECID277"
40841 The only use made of &"%f"& by Exim is in formatting load average values. These
40842 are actually stored in integer variables as 1000 times the load average.
40843 Consequently, their range is limited and so therefore is the length of the
40848 .section "Embedded Exim path" "SECID278"
40849 Exim uses its own path name, which is embedded in the code, only when it needs
40850 to re-exec in order to regain root privilege. Therefore, it is not root when it
40851 does so. If some bug allowed the path to get overwritten, it would lead to an
40852 arbitrary program's being run as exim, not as root.
40856 .section "Dynamic module directory" "SECTdynmoddir"
40857 Any dynamically loadable modules must be installed into the directory
40858 defined in &`LOOKUP_MODULE_DIR`& in &_Local/Makefile_& for Exim to permit
40862 .section "Use of sprintf()" "SECID279"
40863 .cindex "&[sprintf()]&"
40864 A large number of occurrences of &"sprintf"& in the code are actually calls to
40865 &'string_sprintf()'&, a function that returns the result in malloc'd store.
40866 The intermediate formatting is done into a large fixed buffer by a function
40867 that runs through the format string itself, and checks the length of each
40868 conversion before performing it, thus preventing buffer overruns.
40870 The remaining uses of &[sprintf()]& happen in controlled circumstances where
40871 the output buffer is known to be sufficiently long to contain the converted
40876 .section "Use of debug_printf() and log_write()" "SECID280"
40877 Arbitrary strings are passed to both these functions, but they do their
40878 formatting by calling the function &'string_vformat()'&, which runs through
40879 the format string itself, and checks the length of each conversion.
40883 .section "Use of strcat() and strcpy()" "SECID281"
40884 These are used only in cases where the output buffer is known to be large
40885 enough to hold the result.
40886 .ecindex IIDsecurcon
40891 . ////////////////////////////////////////////////////////////////////////////
40892 . ////////////////////////////////////////////////////////////////////////////
40894 .chapter "Format of spool files" "CHAPspool"
40895 .scindex IIDforspo1 "format" "spool files"
40896 .scindex IIDforspo2 "spool directory" "format of files"
40897 .scindex IIDforspo3 "spool files" "format of"
40898 .cindex "spool files" "editing"
40899 A message on Exim's queue consists of two files, whose names are the message id
40900 followed by -D and -H, respectively. The data portion of the message is kept in
40901 the -D file on its own. The message's envelope, status, and headers are all
40902 kept in the -H file, whose format is described in this chapter. Each of these
40903 two files contains the final component of its own name as its first line. This
40904 is insurance against disk crashes where the directory is lost but the files
40905 themselves are recoverable.
40907 The file formats may be changed, or new formats added, at any release.
40908 Spool files are not intended as an interface to other programs
40909 and should not be used as such.
40911 Some people are tempted into editing -D files in order to modify messages. You
40912 need to be extremely careful if you do this; it is not recommended and you are
40913 on your own if you do it. Here are some of the pitfalls:
40916 You must ensure that Exim does not try to deliver the message while you are
40917 fiddling with it. The safest way is to take out a write lock on the -D file,
40918 which is what Exim itself does, using &[fcntl()]&. If you update the file in
40919 place, the lock will be retained. If you write a new file and rename it, the
40920 lock will be lost at the instant of rename.
40922 .vindex "&$body_linecount$&"
40923 If you change the number of lines in the file, the value of
40924 &$body_linecount$&, which is stored in the -H file, will be incorrect and can
40925 cause incomplete transmission of messages or undeliverable messages.
40927 If the message is in MIME format, you must take care not to break it.
40929 If the message is cryptographically signed, any change will invalidate the
40932 All in all, modifying -D files is fraught with danger.
40934 Files whose names end with -J may also be seen in the &_input_& directory (or
40935 its subdirectories when &%split_spool_directory%& is set). These are journal
40936 files, used to record addresses to which the message has been delivered during
40937 the course of a delivery attempt. If there are still undelivered recipients at
40938 the end, the -H file is updated, and the -J file is deleted. If, however, there
40939 is some kind of crash (for example, a power outage) before this happens, the -J
40940 file remains in existence. When Exim next processes the message, it notices the
40941 -J file and uses it to update the -H file before starting the next delivery
40944 Files whose names end with -K or .eml may also be seen in the spool.
40945 These are temporaries used for DKIM or malware processing, when that is used.
40946 They should be tidied up by normal operations; any old ones are probably
40947 relics of crashes and can be removed.
40949 .section "Format of the -H file" "SECID282"
40950 .cindex "uid (user id)" "in spool file"
40951 .cindex "gid (group id)" "in spool file"
40952 The second line of the -H file contains the login name for the uid of the
40953 process that called Exim to read the message, followed by the numerical uid and
40954 gid. For a locally generated message, this is normally the user who sent the
40955 message. For a message received over TCP/IP via the daemon, it is
40956 normally the Exim user.
40958 The third line of the file contains the address of the message's sender as
40959 transmitted in the envelope, contained in angle brackets. The sender address is
40960 empty for bounce messages. For incoming SMTP mail, the sender address is given
40961 in the MAIL command. For locally generated mail, the sender address is
40962 created by Exim from the login name of the current user and the configured
40963 &%qualify_domain%&. However, this can be overridden by the &%-f%& option or a
40964 leading &"From&~"& line if the caller is trusted, or if the supplied address is
40965 &"<>"& or an address that matches &%untrusted_set_senders%&.
40967 The fourth line contains two numbers. The first is the time that the message
40968 was received, in the conventional Unix form &-- the number of seconds since the
40969 start of the epoch. The second number is a count of the number of messages
40970 warning of delayed delivery that have been sent to the sender.
40972 There follow a number of lines starting with a hyphen.
40973 These contain variables, can appear in any
40974 order, and are omitted when not relevant.
40976 If there is a second hyphen after the first,
40977 the corresponding data is tainted.
40978 If there is a value in parentheses, the data is quoted for a lookup.
40980 The following word specifies a variable,
40981 and the remainder of the item depends on the variable.
40984 .vitem "&%-acl%&&~<&'number'&>&~<&'length'&>"
40985 This item is obsolete, and is not generated from Exim release 4.61 onwards;
40986 &%-aclc%& and &%-aclm%& are used instead. However, &%-acl%& is still
40987 recognized, to provide backward compatibility. In the old format, a line of
40988 this form is present for every ACL variable that is not empty. The number
40989 identifies the variable; the &%acl_c%&&*x*& variables are numbered 0&--9 and
40990 the &%acl_m%&&*x*& variables are numbered 10&--19. The length is the length of
40991 the data string for the variable. The string itself starts at the beginning of
40992 the next line, and is followed by a newline character. It may contain internal
40995 .vitem "&%-aclc%&&~<&'rest-of-name'&>&~<&'length'&>"
40996 A line of this form is present for every ACL connection variable that is
40997 defined. Note that there is a space between &%-aclc%& and the rest of the name.
40998 The length is the length of the data string for the variable. The string itself
40999 starts at the beginning of the next line, and is followed by a newline
41000 character. It may contain internal newlines.
41002 .vitem "&%-aclm%&&~<&'rest-of-name'&>&~<&'length'&>"
41003 A line of this form is present for every ACL message variable that is defined.
41004 Note that there is a space between &%-aclm%& and the rest of the name. The
41005 length is the length of the data string for the variable. The string itself
41006 starts at the beginning of the next line, and is followed by a newline
41007 character. It may contain internal newlines.
41009 .vitem "&%-active_hostname%&&~<&'hostname'&>"
41010 This is present if, when the message was received over SMTP, the value of
41011 &$smtp_active_hostname$& was different to the value of &$primary_hostname$&.
41013 .vitem &%-allow_unqualified_recipient%&
41014 This is present if unqualified recipient addresses are permitted in header
41015 lines (to stop such addresses from being qualified if rewriting occurs at
41016 transport time). Local messages that were input using &%-bnq%& and remote
41017 messages from hosts that match &%recipient_unqualified_hosts%& set this flag.
41019 .vitem &%-allow_unqualified_sender%&
41020 This is present if unqualified sender addresses are permitted in header lines
41021 (to stop such addresses from being qualified if rewriting occurs at transport
41022 time). Local messages that were input using &%-bnq%& and remote messages from
41023 hosts that match &%sender_unqualified_hosts%& set this flag.
41025 .vitem "&%-auth_id%&&~<&'text'&>"
41026 The id information for a message received on an authenticated SMTP connection
41027 &-- the value of the &$authenticated_id$& variable.
41029 .vitem "&%-auth_sender%&&~<&'address'&>"
41030 The address of an authenticated sender &-- the value of the
41031 &$authenticated_sender$& variable.
41033 .vitem "&%-body_linecount%&&~<&'number'&>"
41034 This records the number of lines in the body of the message, and is
41035 present unless &%-spool_file_wireformat%& is.
41037 .vitem "&%-body_zerocount%&&~<&'number'&>"
41038 This records the number of binary zero bytes in the body of the message, and is
41039 present if the number is greater than zero.
41041 .vitem &%-deliver_firsttime%&
41042 This is written when a new message is first added to the spool. When the spool
41043 file is updated after a deferral, it is omitted.
41045 .vitem "&%-frozen%&&~<&'time'&>"
41046 .cindex "frozen messages" "spool data"
41047 The message is frozen, and the freezing happened at <&'time'&>.
41049 .vitem "&%-helo_name%&&~<&'text'&>"
41050 This records the host name as specified by a remote host in a HELO or EHLO
41053 .vitem "&%-host_address%&&~<&'address'&>.<&'port'&>"
41054 This records the IP address of the host from which the message was received and
41055 the remote port number that was used. It is omitted for locally generated
41058 .vitem "&%-host_auth%&&~<&'text'&>"
41059 If the message was received on an authenticated SMTP connection, this records
41060 the name of the authenticator &-- the value of the
41061 &$sender_host_authenticated$& variable.
41063 .vitem &%-host_lookup_failed%&
41064 This is present if an attempt to look up the sending host's name from its IP
41065 address failed. It corresponds to the &$host_lookup_failed$& variable.
41067 .vitem "&%-host_name%&&~<&'text'&>"
41068 .cindex "reverse DNS lookup"
41069 .cindex "DNS" "reverse lookup"
41070 This records the name of the remote host from which the message was received,
41071 if the host name was looked up from the IP address when the message was being
41072 received. It is not present if no reverse lookup was done.
41074 .vitem "&%-ident%&&~<&'text'&>"
41075 For locally submitted messages, this records the login of the originating user,
41076 unless it was a trusted user and the &%-oMt%& option was used to specify an
41077 ident value. For messages received over TCP/IP, this records the ident string
41078 supplied by the remote host, if any.
41080 .vitem "&%-interface_address%&&~<&'address'&>.<&'port'&>"
41081 This records the IP address of the local interface and the port number through
41082 which a message was received from a remote host. It is omitted for locally
41083 generated messages.
41086 The message is from a local sender.
41088 .vitem &%-localerror%&
41089 The message is a locally-generated bounce message.
41091 .vitem "&%-local_scan%&&~<&'string'&>"
41092 This records the data string that was returned by the &[local_scan()]& function
41093 when the message was received &-- the value of the &$local_scan_data$&
41094 variable. It is omitted if no data was returned.
41096 .vitem &%-manual_thaw%&
41097 The message was frozen but has been thawed manually, that is, by an explicit
41098 Exim command rather than via the auto-thaw process.
41101 A testing delivery process was started using the &%-N%& option to suppress any
41102 actual deliveries, but delivery was deferred. At any further delivery attempts,
41105 .vitem &%-received_protocol%&
41106 This records the value of the &$received_protocol$& variable, which contains
41107 the name of the protocol by which the message was received.
41109 .vitem &%-sender_set_untrusted%&
41110 The envelope sender of this message was set by an untrusted local caller (used
41111 to ensure that the caller is displayed in queue listings).
41113 .vitem "&%-spam_score_int%&&~<&'number'&>"
41114 If a message was scanned by SpamAssassin, this is present. It records the value
41115 of &$spam_score_int$&.
41117 .vitem &%-spool_file_wireformat%&
41118 The -D file for this message is in wire-format (for ESMTP CHUNKING)
41119 rather than Unix-format.
41120 The line-ending is CRLF rather than newline.
41121 There is still, however, no leading-dot-stuffing.
41123 .vitem &%-tls_certificate_verified%&
41124 A TLS certificate was received from the client that sent this message, and the
41125 certificate was verified by the server.
41127 .vitem "&%-tls_cipher%&&~<&'cipher name'&>"
41128 When the message was received over an encrypted connection, this records the
41129 name of the cipher suite that was used.
41131 .vitem "&%-tls_peerdn%&&~<&'peer DN'&>"
41132 When the message was received over an encrypted connection, and a certificate
41133 was received from the client, this records the Distinguished Name from that
41137 Following the options there is a list of those addresses to which the message
41138 is not to be delivered. This set of addresses is initialized from the command
41139 line when the &%-t%& option is used and &%extract_addresses_remove_arguments%&
41140 is set; otherwise it starts out empty. Whenever a successful delivery is made,
41141 the address is added to this set. The addresses are kept internally as a
41142 balanced binary tree, and it is a representation of that tree which is written
41143 to the spool file. If an address is expanded via an alias or forward file, the
41144 original address is added to the tree when deliveries to all its child
41145 addresses are complete.
41147 If the tree is empty, there is a single line in the spool file containing just
41148 the text &"XX"&. Otherwise, each line consists of two letters, which are either
41149 Y or N, followed by an address. The address is the value for the node of the
41150 tree, and the letters indicate whether the node has a left branch and/or a
41151 right branch attached to it, respectively. If branches exist, they immediately
41152 follow. Here is an example of a three-node tree:
41154 YY darcy@austen.fict.example
41155 NN alice@wonderland.fict.example
41156 NN editor@thesaurus.ref.example
41158 After the non-recipients tree, there is a list of the message's recipients.
41159 This is a simple list, preceded by a count. It includes all the original
41160 recipients of the message, including those to whom the message has already been
41161 delivered. In the simplest case, the list contains one address per line. For
41165 editor@thesaurus.ref.example
41166 darcy@austen.fict.example
41168 alice@wonderland.fict.example
41170 However, when a child address has been added to the top-level addresses as a
41171 result of the use of the &%one_time%& option on a &(redirect)& router, each
41172 line is of the following form:
41174 <&'top-level address'&> <&'errors_to address'&> &&&
41175 <&'length'&>,<&'parent number'&>#<&'flag bits'&>
41177 The 01 flag bit indicates the presence of the three other fields that follow
41178 the top-level address. Other bits may be used in future to support additional
41179 fields. The <&'parent number'&> is the offset in the recipients list of the
41180 original parent of the &"one time"& address. The first two fields are the
41181 envelope sender that is associated with this address and its length. If the
41182 length is zero, there is no special envelope sender (there are then two space
41183 characters in the line). A non-empty field can arise from a &(redirect)& router
41184 that has an &%errors_to%& setting.
41187 A blank line separates the envelope and status information from the headers
41188 which follow. A header may occupy several lines of the file, and to save effort
41189 when reading it in, each header is preceded by a number and an identifying
41190 character. The number is the number of characters in the header, including any
41191 embedded newlines and the terminating newline. The character is one of the
41195 .row <&'blank'&> "header in which Exim has no special interest"
41196 .row &`B`& "&'Bcc:'& header"
41197 .row &`C`& "&'Cc:'& header"
41198 .row &`F`& "&'From:'& header"
41199 .row &`I`& "&'Message-id:'& header"
41200 .row &`P`& "&'Received:'& header &-- P for &""postmark""&"
41201 .row &`R`& "&'Reply-To:'& header"
41202 .row &`S`& "&'Sender:'& header"
41203 .row &`T`& "&'To:'& header"
41204 .row &`*`& "replaced or deleted header"
41207 Deleted or replaced (rewritten) headers remain in the spool file for debugging
41208 purposes. They are not transmitted when the message is delivered. Here is a
41209 typical set of headers:
41211 111P Received: by hobbit.fict.example with local (Exim 4.00)
41212 id 14y9EI-00026G-00; Fri, 11 May 2001 10:28:59 +0100
41213 049 Message-Id: <E14y9EI-00026G-00@hobbit.fict.example>
41214 038* X-rewrote-sender: bb@hobbit.fict.example
41215 042* From: Bilbo Baggins <bb@hobbit.fict.example>
41216 049F From: Bilbo Baggins <B.Baggins@hobbit.fict.example>
41217 099* To: alice@wonderland.fict.example, rdo@foundation,
41218 darcy@austen.fict.example, editor@thesaurus.ref.example
41219 104T To: alice@wonderland.fict.example, rdo@foundation.example,
41220 darcy@austen.fict.example, editor@thesaurus.ref.example
41221 038 Date: Fri, 11 May 2001 10:28:59 +0100
41223 The asterisked headers indicate that the envelope sender, &'From:'& header, and
41224 &'To:'& header have been rewritten, the last one because routing expanded the
41225 unqualified domain &'foundation'&.
41226 .ecindex IIDforspo1
41227 .ecindex IIDforspo2
41228 .ecindex IIDforspo3
41230 .section "Format of the -D file" "SECID282a"
41231 The data file is traditionally in Unix-standard format: lines are ended with
41232 an ASCII newline character.
41233 However, when the &%spool_wireformat%& main option is used some -D files
41234 can have an alternate format.
41235 This is flagged by a &%-spool_file_wireformat%& line in the corresponding -H file.
41236 The -D file lines (not including the first name-component line) are
41237 suitable for direct copying to the wire when transmitting using the
41238 ESMTP CHUNKING option, meaning lower processing overhead.
41239 Lines are terminated with an ASCII CRLF pair.
41240 There is no dot-stuffing (and no dot-termination).
41242 . ////////////////////////////////////////////////////////////////////////////
41243 . ////////////////////////////////////////////////////////////////////////////
41245 .chapter "DKIM, SPF, SRS and DMARC" "CHAPdkim" &&&
41246 "DKIM, SPF, SRS and DMARC Support"
41248 .section "DKIM (DomainKeys Identified Mail)" SECDKIM
41251 DKIM is a mechanism by which messages sent by some entity can be provably
41252 linked to a domain which that entity controls. It permits reputation to
41253 be tracked on a per-domain basis, rather than merely upon source IP address.
41254 DKIM is documented in RFC 6376.
41256 As DKIM relies on the message being unchanged in transit, messages handled
41257 by a mailing-list (which traditionally adds to the message) will not match
41258 any original DKIM signature.
41260 DKIM support is compiled into Exim by default if TLS support is present.
41261 It can be disabled by setting DISABLE_DKIM=yes in &_Local/Makefile_&.
41263 Exim's DKIM implementation allows for
41265 Signing outgoing messages: This function is implemented in the SMTP transport.
41266 It can co-exist with all other Exim features
41267 (including transport filters)
41268 except cutthrough delivery.
41270 Verifying signatures in incoming messages: This is implemented by an additional
41271 ACL (acl_smtp_dkim), which can be called several times per message, with
41272 different signature contexts.
41275 In typical Exim style, the verification implementation does not include any
41276 default "policy". Instead it enables you to build your own policy using
41277 Exim's standard controls.
41279 Please note that verification of DKIM signatures in incoming mail is turned
41280 on by default for logging (in the <= line) purposes.
41282 Additional log detail can be enabled using the &%dkim_verbose%& log_selector.
41283 When set, for each signature in incoming email,
41284 exim will log a line displaying the most important signature details, and the
41285 signature status. Here is an example (with line-breaks added for clarity):
41287 2009-09-09 10:22:28 1MlIRf-0003LU-U3 DKIM:
41288 d=facebookmail.com s=q1-2009b
41289 c=relaxed/relaxed a=rsa-sha1
41290 i=@facebookmail.com t=1252484542 [verification succeeded]
41293 You might want to turn off DKIM verification processing entirely for internal
41294 or relay mail sources. To do that, set the &%dkim_disable_verify%& ACL
41295 control modifier. This should typically be done in the RCPT ACL, at points
41296 where you accept mail from relay sources (internal hosts or authenticated
41300 .subsection "Signing outgoing messages" SECDKIMSIGN
41301 .cindex DKIM signing
41303 For signing to be usable you must have published a DKIM record in DNS.
41304 Note that RFC 8301 (which does not cover EC keys) says:
41306 rsa-sha1 MUST NOT be used for signing or verifying.
41308 Signers MUST use RSA keys of at least 1024 bits for all keys.
41309 Signers SHOULD use RSA keys of at least 2048 bits.
41312 Note also that the key content (the 'p=' field)
41313 in the DNS record is different between RSA and EC keys;
41314 for the former it is the base64 of the ASN.1 for the RSA public key
41315 (equivalent to the private-key .pem with the header/trailer stripped)
41316 but for EC keys it is the base64 of the pure key; no ASN.1 wrapping.
41318 Signing is enabled by setting private options on the SMTP transport.
41319 These options take (expandable) strings as arguments.
41321 .option dkim_domain smtp "string list&!!" unset
41322 The domain(s) you want to sign with.
41323 After expansion, this can be a list.
41324 Each element in turn,
41326 .vindex "&$dkim_domain$&"
41327 is put into the &%$dkim_domain%& expansion variable
41328 while expanding the remaining signing options.
41329 If it is empty after expansion, DKIM signing is not done,
41330 and no error will result even if &%dkim_strict%& is set.
41332 .option dkim_selector smtp "string list&!!" unset
41333 This sets the key selector string.
41334 After expansion, which can use &$dkim_domain$&, this can be a list.
41335 Each element in turn is put in the expansion
41336 .vindex "&$dkim_selector$&"
41337 variable &%$dkim_selector%& which may be used in the &%dkim_private_key%&
41338 option along with &%$dkim_domain%&.
41339 If the option is empty after expansion, DKIM signing is not done for this domain,
41340 and no error will result even if &%dkim_strict%& is set.
41342 To do, for example, dual-signing with RSA and EC keys
41343 this could be be used:
41345 dkim_selector = ec_sel : rsa_sel
41346 dkim_private_key = KEYS_DIR/$dkim_selector
41349 .option dkim_private_key smtp string&!! unset
41350 This sets the private key to use.
41351 You can use the &%$dkim_domain%& and
41352 &%$dkim_selector%& expansion variables to determine the private key to use.
41353 The result can either
41355 be a valid RSA private key in ASCII armor (.pem file), including line breaks
41357 with GnuTLS 3.6.0 or OpenSSL 1.1.1 or later,
41358 be a valid Ed25519 private key (same format as above)
41360 start with a slash, in which case it is treated as a file that contains
41363 be "0", "false" or the empty string, in which case the message will not
41364 be signed. This case will not result in an error, even if &%dkim_strict%&
41368 To generate keys under OpenSSL:
41370 openssl genrsa -out dkim_rsa.private 2048
41371 openssl rsa -in dkim_rsa.private -out /dev/stdout -pubout -outform PEM
41373 The result file from the first command should be retained, and
41374 this option set to use it.
41375 Take the base-64 lines from the output of the second command, concatenated,
41376 for the DNS TXT record.
41377 See section 3.6 of RFC6376 for the record specification.
41381 certtool --generate-privkey --rsa --bits=2048 --password='' -8 --outfile=dkim_rsa.private
41382 certtool --load-privkey=dkim_rsa.private --pubkey-info
41385 Note that RFC 8301 says:
41387 Signers MUST use RSA keys of at least 1024 bits for all keys.
41388 Signers SHOULD use RSA keys of at least 2048 bits.
41391 EC keys for DKIM are defined by RFC 8463.
41392 They are considerably smaller than RSA keys for equivalent protection.
41393 As they are a recent development, users should consider dual-signing
41394 (by setting a list of selectors, and an expansion for this option)
41395 for some transition period.
41396 The "_CRYPTO_SIGN_ED25519" macro will be defined if support is present
41399 OpenSSL 1.1.1 and GnuTLS 3.6.0 can create Ed25519 private keys:
41401 openssl genpkey -algorithm ed25519 -out dkim_ed25519.private
41402 certtool --generate-privkey --key-type=ed25519 --outfile=dkim_ed25519.private
41405 To produce the required public key value for a DNS record:
41407 openssl pkey -outform DER -pubout -in dkim_ed25519.private | tail -c +13 | base64
41408 certtool --load_privkey=dkim_ed25519.private --pubkey_info --outder | tail -c +13 | base64
41411 Exim also supports an alternate format
41412 of Ed25519 keys in DNS which was a candidate during development
41413 of the standard, but not adopted.
41414 A future release will probably drop that support.
41416 .option dkim_hash smtp string&!! sha256
41417 Can be set to any one of the supported hash methods, which are:
41419 &`sha1`& &-- should not be used, is old and insecure
41421 &`sha256`& &-- the default
41423 &`sha512`& &-- possibly more secure but less well supported
41426 Note that RFC 8301 says:
41428 rsa-sha1 MUST NOT be used for signing or verifying.
41431 .option dkim_identity smtp string&!! unset
41432 If set after expansion, the value is used to set an "i=" tag in
41433 the signing header. The DKIM standards restrict the permissible
41434 syntax of this optional tag to a mail address, with possibly-empty
41435 local part, an @, and a domain identical to or subdomain of the "d="
41436 tag value. Note that Exim does not check the value.
41438 .option dkim_canon smtp string&!! unset
41439 This option sets the canonicalization method used when signing a message.
41440 The DKIM RFC currently supports two methods: "simple" and "relaxed".
41441 The option defaults to "relaxed" when unset. Note: the current implementation
41442 only supports signing with the same canonicalization method for both headers and body.
41444 .option dkim_strict smtp string&!! unset
41445 This option defines how Exim behaves when signing a message that
41446 should be signed fails for some reason. When the expansion evaluates to
41447 either &"1"& or &"true"&, Exim will defer. Otherwise Exim will send the message
41448 unsigned. You can use the &%$dkim_domain%& and &%$dkim_selector%& expansion
41451 .option dkim_sign_headers smtp string&!! "see below"
41452 If set, this option must expand to a colon-separated
41453 list of header names.
41454 Headers with these names, or the absence or such a header, will be included
41455 in the message signature.
41456 When unspecified, the header names listed in RFC4871 will be used,
41457 whether or not each header is present in the message.
41458 The default list is available for the expansion in the macro
41459 &"_DKIM_SIGN_HEADERS"&
41460 and an oversigning variant is in &"_DKIM_OVERSIGN_HEADERS"&.
41462 If a name is repeated, multiple headers by that name (or the absence thereof)
41463 will be signed. The textually later headers in the headers part of the
41464 message are signed first, if there are multiples.
41466 A name can be prefixed with either an &"="& or a &"+"& character.
41467 If an &"="& prefix is used, all headers that are present with this name
41469 If a &"+"& prefix if used, all headers that are present with this name
41470 will be signed, and one signature added for a missing header with the
41471 name will be appended.
41473 .option dkim_timestamps smtp integer&!! unset
41474 This option controls the inclusion of timestamp information in the signature.
41475 If not set, no such information will be included.
41476 Otherwise, must be an unsigned number giving an offset in seconds from the current time
41478 (eg. 1209600 for two weeks);
41479 both creation (t=) and expiry (x=) tags will be included.
41481 RFC 6376 lists these tags as RECOMMENDED.
41484 .subsection "Verifying DKIM signatures in incoming mail" SECDKIMVFY
41485 .cindex DKIM verification
41487 Verification of DKIM signatures in SMTP incoming email is done for all
41488 messages for which an ACL control &%dkim_disable_verify%& has not been set.
41489 .cindex DKIM "selecting signature algorithms"
41490 Individual classes of signature algorithm can be ignored by changing
41491 the main options &%dkim_verify_hashes%& or &%dkim_verify_keytypes%&.
41492 The &%dkim_verify_minimal%& option can be set to cease verification
41493 processing for a message once the first passing signature is found.
41495 .cindex authentication "expansion item"
41496 Performing verification sets up information used by the
41497 &%authresults%& expansion item.
41499 For most purposes the default option settings suffice and the remainder
41500 of this section can be ignored.
41502 The results of verification are made available to the
41503 &%acl_smtp_dkim%& ACL, which can examine and modify them.
41504 A missing ACL definition defaults to accept.
41505 By default, the ACL is called once for each
41506 syntactically(!) correct signature in the incoming message.
41507 If any ACL call does not accept, the message is not accepted.
41508 If a cutthrough delivery was in progress for the message, that is
41509 summarily dropped (having wasted the transmission effort).
41511 To evaluate the verification result in the ACL
41512 a large number of expansion variables
41513 containing the signature status and its details are set up during the
41514 runtime of the ACL.
41516 Calling the ACL only for existing signatures is not sufficient to build
41517 more advanced policies. For that reason, the main option
41518 &%dkim_verify_signers%&, and an expansion variable
41519 &%$dkim_signers%& exist.
41521 The main option &%dkim_verify_signers%& can be set to a colon-separated
41522 list of DKIM domains or identities for which the ACL &%acl_smtp_dkim%& is
41523 called. It is expanded when the message has been received. At this point,
41524 the expansion variable &%$dkim_signers%& already contains a colon-separated
41525 list of signer domains and identities for the message. When
41526 &%dkim_verify_signers%& is not specified in the main configuration,
41529 dkim_verify_signers = $dkim_signers
41531 This leads to the default behaviour of calling &%acl_smtp_dkim%& for each
41532 DKIM signature in the message. Current DKIM verifiers may want to explicitly
41533 call the ACL for known domains or identities. This would be achieved as follows:
41535 dkim_verify_signers = paypal.com:ebay.com:$dkim_signers
41537 This would result in &%acl_smtp_dkim%& always being called for "paypal.com"
41538 and "ebay.com", plus all domains and identities that have signatures in the message.
41539 You can also be more creative in constructing your policy. For example:
41541 dkim_verify_signers = $sender_address_domain:$dkim_signers
41544 If a domain or identity is listed several times in the (expanded) value of
41545 &%dkim_verify_signers%&, the ACL is only called once for that domain or identity.
41547 Note that if the option is set using untrustworthy data
41548 (such as the From: header)
41549 care should be taken to force lowercase for domains
41550 and for the domain part if identities.
41551 The default setting can be regarded as trustworthy in this respect.
41553 If multiple signatures match a domain (or identity), the ACL is called once
41554 for each matching signature.
41557 Inside the DKIM ACL, the following expansion variables are
41558 available (from most to least important):
41562 .vitem &%$dkim_cur_signer%&
41563 The signer that is being evaluated in this ACL run. This can be a domain or
41564 an identity. This is one of the list items from the expanded main option
41565 &%dkim_verify_signers%& (see above).
41567 .vitem &%$dkim_verify_status%&
41568 Within the DKIM ACL,
41569 a string describing the general status of the signature. One of
41571 &%none%&: There is no signature in the message for the current domain or
41572 identity (as reflected by &%$dkim_cur_signer%&).
41574 &%invalid%&: The signature could not be verified due to a processing error.
41575 More detail is available in &%$dkim_verify_reason%&.
41577 &%fail%&: Verification of the signature failed. More detail is
41578 available in &%$dkim_verify_reason%&.
41580 &%pass%&: The signature passed verification. It is valid.
41583 This variable can be overwritten using an ACL 'set' modifier.
41584 This might, for instance, be done to enforce a policy restriction on
41585 hash-method or key-size:
41587 warn condition = ${if eq {$dkim_verify_status}{pass}}
41588 condition = ${if eq {${length_3:$dkim_algo}}{rsa}}
41589 condition = ${if or {{eq {$dkim_algo}{rsa-sha1}} \
41590 {< {$dkim_key_length}{1024}}}}
41591 logwrite = NOTE: forcing DKIM verify fail (was pass)
41592 set dkim_verify_status = fail
41593 set dkim_verify_reason = hash too weak or key too short
41596 So long as a DKIM ACL is defined (it need do no more than accept),
41597 after all the DKIM ACL runs have completed, the value becomes a
41598 colon-separated list of the values after each run.
41599 This is maintained for the mime, prdr and data ACLs.
41601 .vitem &%$dkim_verify_reason%&
41602 A string giving a little bit more detail when &%$dkim_verify_status%& is either
41603 "fail" or "invalid". One of
41605 &%pubkey_unavailable%& (when &%$dkim_verify_status%&="invalid"): The public
41606 key for the domain could not be retrieved. This may be a temporary problem.
41608 &%pubkey_syntax%& (when &%$dkim_verify_status%&="invalid"): The public key
41609 record for the domain is syntactically invalid.
41611 &%bodyhash_mismatch%& (when &%$dkim_verify_status%&="fail"): The calculated
41612 body hash does not match the one specified in the signature header. This
41613 means that the message body was modified in transit.
41615 &%signature_incorrect%& (when &%$dkim_verify_status%&="fail"): The signature
41616 could not be verified. This may mean that headers were modified,
41617 re-written or otherwise changed in a way which is incompatible with
41618 DKIM verification. It may of course also mean that the signature is forged.
41621 This variable can be overwritten, with any value, using an ACL 'set' modifier.
41623 .vitem &%$dkim_domain%&
41624 The signing domain. IMPORTANT: This variable is only populated if there is
41625 an actual signature in the message for the current domain or identity (as
41626 reflected by &%$dkim_cur_signer%&).
41628 .vitem &%$dkim_identity%&
41629 The signing identity, if present. IMPORTANT: This variable is only populated
41630 if there is an actual signature in the message for the current domain or
41631 identity (as reflected by &%$dkim_cur_signer%&).
41633 .vitem &%$dkim_selector%&
41634 The key record selector string.
41636 .vitem &%$dkim_algo%&
41637 The algorithm used. One of 'rsa-sha1' or 'rsa-sha256'.
41638 If running under GnuTLS 3.6.0 or OpenSSL 1.1.1 or later,
41639 may also be 'ed25519-sha256'.
41640 The "_CRYPTO_SIGN_ED25519" macro will be defined if support is present
41643 Note that RFC 8301 says:
41645 rsa-sha1 MUST NOT be used for signing or verifying.
41647 DKIM signatures identified as having been signed with historic
41648 algorithms (currently, rsa-sha1) have permanently failed evaluation
41651 To enforce this you must either have a DKIM ACL which checks this variable
41652 and overwrites the &$dkim_verify_status$& variable as discussed above,
41653 or have set the main option &%dkim_verify_hashes%& to exclude
41654 processing of such signatures.
41656 .vitem &%$dkim_canon_body%&
41657 The body canonicalization method. One of 'relaxed' or 'simple'.
41659 .vitem &%$dkim_canon_headers%&
41660 The header canonicalization method. One of 'relaxed' or 'simple'.
41662 .vitem &%$dkim_copiedheaders%&
41663 A transcript of headers and their values which are included in the signature
41664 (copied from the 'z=' tag of the signature).
41665 Note that RFC6376 requires that verification fail if the From: header is
41666 not included in the signature. Exim does not enforce this; sites wishing
41667 strict enforcement should code the check explicitly.
41669 .vitem &%$dkim_bodylength%&
41670 The number of signed body bytes. If zero ("0"), the body is unsigned. If no
41671 limit was set by the signer, "9999999999999" is returned. This makes sure
41672 that this variable always expands to an integer value.
41673 &*Note:*& The presence of the signature tag specifying a signing body length
41674 is one possible route to spoofing of valid DKIM signatures.
41675 A paranoid implementation might wish to regard signature where this variable
41676 shows less than the "no limit" return as being invalid.
41678 .vitem &%$dkim_created%&
41679 UNIX timestamp reflecting the date and time when the signature was created.
41680 When this was not specified by the signer, "0" is returned.
41682 .vitem &%$dkim_expires%&
41683 UNIX timestamp reflecting the date and time when the signer wants the
41684 signature to be treated as "expired". When this was not specified by the
41685 signer, "9999999999999" is returned. This makes it possible to do useful
41686 integer size comparisons against this value.
41687 Note that Exim does not check this value.
41689 .vitem &%$dkim_headernames%&
41690 A colon-separated list of names of headers included in the signature.
41692 .vitem &%$dkim_key_testing%&
41693 "1" if the key record has the "testing" flag set, "0" if not.
41695 .vitem &%$dkim_key_nosubdomains%&
41696 "1" if the key record forbids subdomaining, "0" otherwise.
41698 .vitem &%$dkim_key_srvtype%&
41699 Service type (tag s=) from the key record. Defaults to "*" if not specified
41702 .vitem &%$dkim_key_granularity%&
41703 Key granularity (tag g=) from the key record. Defaults to "*" if not specified
41706 .vitem &%$dkim_key_notes%&
41707 Notes from the key record (tag n=).
41709 .vitem &%$dkim_key_length%&
41710 Number of bits in the key.
41711 Valid only once the key is loaded, which is at the time the header signature
41712 is verified, which is after the body hash is.
41714 Note that RFC 8301 says:
41716 Verifiers MUST NOT consider signatures using RSA keys of
41717 less than 1024 bits as valid signatures.
41720 This is enforced by the default setting for the &%dkim_verify_min_keysizes%&
41725 In addition, two ACL conditions are provided:
41728 .vitem &%dkim_signers%&
41729 ACL condition that checks a colon-separated list of domains or identities
41730 for a match against the domain or identity that the ACL is currently verifying
41731 (reflected by &%$dkim_cur_signer%&). This is typically used to restrict an ACL
41732 verb to a group of domains or identities. For example:
41735 # Warn when Mail purportedly from GMail has no gmail signature
41736 warn sender_domains = gmail.com
41737 dkim_signers = gmail.com
41739 log_message = GMail sender without gmail.com DKIM signature
41742 Note that the above does not check for a total lack of DKIM signing;
41743 for that check for empty &$h_DKIM-Signature:$& in the data ACL.
41745 .vitem &%dkim_status%&
41746 ACL condition that checks a colon-separated list of possible DKIM verification
41747 results against the actual result of verification. This is typically used
41748 to restrict an ACL verb to a list of verification outcomes, for example:
41751 deny sender_domains = paypal.com:paypal.de
41752 dkim_signers = paypal.com:paypal.de
41753 dkim_status = none:invalid:fail
41754 message = Mail from Paypal with invalid/missing signature
41757 The possible status keywords are: 'none','invalid','fail' and 'pass'. Please
41758 see the documentation of the &%$dkim_verify_status%& expansion variable above
41759 for more information of what they mean.
41765 .section "SPF (Sender Policy Framework)" SECSPF
41766 .cindex SPF verification
41768 SPF is a mechanism whereby a domain may assert which IP addresses may transmit
41769 messages with its domain in the envelope from, documented by RFC 7208.
41770 For more information on SPF see &url(http://www.open-spf.org), a static copy of
41771 the &url(http://openspf.org).
41772 . --- 2019-10-28: still not https, open-spf.org is told to be a
41773 . --- web-archive copy of the now dead openspf.org site
41774 . --- See https://www.mail-archive.com/mailop@mailop.org/msg08019.html for a
41777 Messages sent by a system not authorised will fail checking of such assertions.
41778 This includes retransmissions done by traditional forwarders.
41780 SPF verification support is built into Exim if SUPPORT_SPF=yes is set in
41781 &_Local/Makefile_&. The support uses the &_libspf2_& library
41782 &url(https://www.libspf2.org/).
41783 There is no Exim involvement in the transmission of messages;
41784 publishing certain DNS records is all that is required.
41786 For verification, an ACL condition and an expansion lookup are provided.
41787 .cindex authentication "expansion item"
41788 Performing verification sets up information used by the
41789 &%authresults%& expansion item.
41792 .cindex SPF "ACL condition"
41793 .cindex ACL "spf condition"
41794 The ACL condition "spf" can be used at or after the MAIL ACL.
41795 It takes as an argument a list of strings giving the outcome of the SPF check,
41796 and will succeed for any matching outcome.
41800 The SPF check passed, the sending host is positively verified by SPF.
41803 The SPF check failed, the sending host is NOT allowed to send mail for the
41804 domain in the envelope-from address.
41806 .vitem &%softfail%&
41807 The SPF check failed, but the queried domain can't absolutely confirm that this
41811 The queried domain does not publish SPF records.
41814 The SPF check returned a "neutral" state. This means the queried domain has
41815 published a SPF record, but wants to allow outside servers to send mail under
41816 its domain as well. This should be treated like "none".
41818 .vitem &%permerror%&
41819 This indicates a syntax error in the SPF record of the queried domain.
41820 You may deny messages when this occurs.
41822 .vitem &%temperror%&
41823 This indicates a temporary error during all processing, including Exim's
41824 SPF processing. You may defer messages when this occurs.
41827 There was an error during processing of the SPF lookup
41830 You can prefix each string with an exclamation mark to invert
41831 its meaning, for example "!fail" will match all results but
41832 "fail". The string list is evaluated left-to-right, in a
41833 short-circuit fashion.
41838 message = $sender_host_address is not allowed to send mail from \
41839 ${if def:sender_address_domain \
41840 {$sender_address_domain}{$sender_helo_name}}. \
41841 Please see http://www.open-spf.org/Why;\
41842 identity=${if def:sender_address_domain \
41843 {$sender_address}{$sender_helo_name}};\
41844 ip=$sender_host_address
41847 Note: The above mentioned URL may not be as helpful as expected. You are
41848 encouraged to replace the link with a link to a site with more
41851 When the spf condition has run, it sets up several expansion
41854 .cindex SPF "verification variables"
41856 .vitem &$spf_header_comment$&
41857 .vindex &$spf_header_comment$&
41858 This contains a human-readable string describing the outcome
41859 of the SPF check. You can add it to a custom header or use
41860 it for logging purposes.
41862 .vitem &$spf_received$&
41863 .vindex &$spf_received$&
41864 This contains a complete Received-SPF: header (name and
41865 content) that can be added to the message. Please note that
41866 according to the SPF draft, this header must be added at the
41867 top of the header list, i.e. with
41869 add_header = :at_start:$spf_received
41871 See section &<<SECTaddheadacl>>& for further details.
41873 Note: in case of "Best-guess" (see below), the convention is
41874 to put this string in a header called X-SPF-Guess: instead.
41876 .vitem &$spf_result$&
41877 .vindex &$spf_result$&
41878 This contains the outcome of the SPF check in string form,
41879 currently one of pass, fail, softfail, none, neutral, permerror,
41880 temperror, or &"(invalid)"&.
41882 .vitem &$spf_result_guessed$&
41883 .vindex &$spf_result_guessed$&
41884 This boolean is true only if a best-guess operation was used
41885 and required in order to obtain a result.
41887 .vitem &$spf_smtp_comment$&
41888 .vindex &$spf_smtp_comment$&
41889 .vindex &%spf_smtp_comment_template%&
41890 This contains a string that can be used in a SMTP response
41891 to the calling party. Useful for "fail".
41892 The string is generated by the SPF library from the template configured in the main config
41893 option &%spf_smtp_comment_template%&.
41897 .cindex SPF "ACL condition"
41898 .cindex ACL "spf_guess condition"
41899 .cindex SPF "best guess"
41900 In addition to SPF, you can also perform checks for so-called
41901 "Best-guess". Strictly speaking, "Best-guess" is not standard
41902 SPF, but it is supported by the same framework that enables SPF
41904 Refer to &url(http://www.open-spf.org/FAQ/Best_guess_record)
41905 for a description of what it means.
41906 . --- 2019-10-28: still not https:
41908 To access this feature, simply use the spf_guess condition in place
41909 of the spf one. For example:
41912 deny spf_guess = fail
41913 message = $sender_host_address doesn't look trustworthy to me
41916 In case you decide to reject messages based on this check, you
41917 should note that although it uses the same framework, "Best-guess"
41918 is not SPF, and therefore you should not mention SPF at all in your
41921 When the spf_guess condition has run, it sets up the same expansion
41922 variables as when spf condition is run, described above.
41924 Additionally, since Best-guess is not standardized, you may redefine
41925 what "Best-guess" means to you by redefining the main configuration
41926 &%spf_guess%& option.
41927 For example, the following:
41930 spf_guess = v=spf1 a/16 mx/16 ptr ?all
41933 would relax host matching rules to a broader network range.
41936 .cindex SPF "lookup expansion"
41938 A lookup expansion is also available. It takes an email
41939 address as the key and an IP address
41944 ${lookup {username@domain} spf {ip.ip.ip.ip}}
41947 The lookup will return the same result strings as can appear in
41948 &$spf_result$& (pass,fail,softfail,neutral,none,err_perm,err_temp).
41954 .subsection "SRS (Sender Rewriting Scheme)" SECTSRS
41955 .cindex SRS "sender rewriting scheme"
41957 SRS can be used to modify sender addresses when forwarding so that
41958 SPF verification does not object to them.
41959 It operates by encoding the original envelope sender in a new
41960 sender local part and using a domain run by the forwarding site
41961 as the new domain for the sender. Any DSN message should be returned
41962 to this new sender at the forwarding site, which can extract the
41963 original sender from the coded local part and forward the DSN to
41966 This is a way of avoiding the breakage that SPF does to forwarding.
41967 The constructed local-part will be longer than the original,
41968 leading to possible problems with very long addresses.
41969 The changing of the sender address also hinders the tracing of mail
41972 Exim can be built to include native SRS support. To do this
41973 SUPPORT_SRS=yes must be defined in &_Local/Makefile_&.
41974 If this has been done, the macros _HAVE_SRS and _HAVE_NATIVE_SRS
41976 The support is limited to SRS0-encoding; SRS1 is not supported.
41978 .cindex SRS excoding
41979 To encode an address use this expansion item:
41981 .vitem &*${srs_encode&~{*&<&'secret'&>&*}{*&<&'return&~path'&>&*}{*&<&'original&~domain'&>&*}}*&
41982 .cindex "&%srs_encode%& expansion item"
41983 .cindex SRS "expansion item"
41984 The first argument should be a secret known and used by all systems
41985 handling the recipient domain for the original message.
41986 There is no need to periodically change this key; a timestamp is also
41988 The second argument should be given as the envelope sender address before this
41989 encoding operation.
41990 If this value is empty the the expansion result will be empty.
41991 The third argument should be the recipient domain of the message when
41992 it arrived at this system.
41995 .cindex SRS decoding
41996 To decode an address use this expansion condition:
41998 .vitem &*inbound_srs&~{*&<&'local&~part'&>&*}{*&<&'secret'&>&*}*&
41999 The first argument should be the recipient local prt as is was received.
42000 The second argument is the site secret.
42002 If the messages is not for an SRS-encoded recipient the condition will
42003 return false. If it is, the condition will return true and the variable
42004 &$srs_recipient$& will be set to the decoded (original) value.
42010 SRS_SECRET = <pick something unique for your site for this. Use on all MXs.>
42016 # if outbound, and forwarding has been done, use an alternate transport
42017 domains = ! +my_domains
42018 transport = ${if eq {$local_part@$domain} \
42019 {$original_local_part@$original_domain} \
42020 {remote_smtp} {remote_forwarded_smtp}}
42025 domains = +my_domains
42026 # detect inbound bounces which are SRS'd, and decode them
42027 condition = ${if inbound_srs {$local_part} {SRS_SECRET}}
42028 data = $srs_recipient
42030 inbound_srs_failure:
42033 domains = +my_domains
42034 # detect inbound bounces which look SRS'd but are invalid
42035 condition = ${if inbound_srs {$local_part} {}}
42037 data = :fail: Invalid SRS recipient address
42039 #... further routers here
42042 # transport; should look like the non-forward outbound
42043 # one, plus the max_rcpt and return_path options
42044 remote_forwarded_smtp:
42046 # modify the envelope from, for mails that we forward
42048 return_path = ${srs_encode {SRS_SECRET} {$return_path} {$original_domain}}
42055 .section DMARC SECDMARC
42056 .cindex DMARC verification
42058 DMARC combines feedback from SPF, DKIM, and header From: in order
42059 to attempt to provide better indicators of the authenticity of an
42060 email. This document does not explain the fundamentals; you
42061 should read and understand how it works by visiting the website at
42062 &url(http://www.dmarc.org/).
42064 If Exim is built with DMARC support,
42065 the libopendmarc library is used.
42067 For building Exim yourself, obtain the library from
42068 &url(http://sourceforge.net/projects/opendmarc/)
42069 to obtain a copy, or find it in your favorite package
42070 repository. You will need to attend to the local/Makefile feature
42071 SUPPORT_DMARC and the associated LDFLAGS addition.
42072 This description assumes
42073 that headers will be in /usr/local/include, and that the libraries
42074 are in /usr/local/lib.
42076 .subsection Configuration SSECDMARCCONFIG
42077 .cindex DMARC configuration
42079 There are three main-configuration options:
42080 .cindex DMARC "configuration options"
42082 The &%dmarc_tld_file%& option
42083 .oindex &%dmarc_tld_file%&
42084 defines the location of a text file of valid
42085 top level domains the opendmarc library uses
42086 during domain parsing. Maintained by Mozilla,
42087 the most current version can be downloaded
42088 from a link at &url(https://publicsuffix.org/list/public_suffix_list.dat).
42089 See also the util/renew-opendmarc-tlds.sh script.
42090 The default for the option is unset.
42091 If not set, DMARC processing is disabled.
42094 The &%dmarc_history_file%& option, if set
42095 .oindex &%dmarc_history_file%&
42096 defines the location of a file to log results
42097 of dmarc verification on inbound emails. The
42098 contents are importable by the opendmarc tools
42099 which will manage the data, send out DMARC
42100 reports, and expire the data. Make sure the
42101 directory of this file is writable by the user
42103 The default is unset.
42105 The &%dmarc_forensic_sender%& option
42106 .oindex &%dmarc_forensic_sender%&
42107 defines an alternate email address to use when sending a
42108 forensic report detailing alignment failures
42109 if a sender domain's dmarc record specifies it
42110 and you have configured Exim to send them.
42111 If set, this is expanded and used for the
42112 From: header line; the address is extracted
42113 from it and used for the envelope from.
42114 If not set (the default), the From: header is expanded from
42115 the dsn_from option, and <> is used for the
42118 .subsection Controls SSECDMARCCONTROLS
42119 .cindex DMARC controls
42121 By default, the DMARC processing will run for any remote,
42122 non-authenticated user. It makes sense to only verify DMARC
42123 status of messages coming from remote, untrusted sources. You can
42124 use standard conditions such as hosts, senders, etc, to decide that
42125 DMARC verification should *not* be performed for them and disable
42126 DMARC with an ACL control modifier:
42128 control = dmarc_disable_verify
42130 A DMARC record can also specify a "forensic address", which gives
42131 exim an email address to submit reports about failed alignment.
42132 Exim does not do this by default because in certain conditions it
42133 results in unintended information leakage (what lists a user might
42134 be subscribed to, etc). You must configure exim to submit forensic
42135 reports to the owner of the domain. If the DMARC record contains a
42136 forensic address and you specify the control statement below, then
42137 exim will send these forensic emails. It is also advised that you
42138 configure a &%dmarc_forensic_sender%& because the default sender address
42139 construction might be inadequate.
42141 control = dmarc_enable_forensic
42143 (AGAIN: You can choose not to send these forensic reports by simply
42144 not putting the dmarc_enable_forensic control line at any point in
42145 your exim config. If you don't tell exim to send them, it will not
42148 There are no options to either control. Both must appear before
42151 .subsection ACL SSECDMARCACL
42152 .cindex DMARC "ACL condition"
42154 DMARC checks cam be run on incoming SMTP messages by using the
42155 &"dmarc_status"& ACL condition in the DATA ACL. You are required to
42156 call the &"spf"& condition first in the ACLs, then the &"dmarc_status"&
42157 condition. Putting this condition in the ACLs is required in order
42158 for a DMARC check to actually occur. All of the variables are set
42159 up before the DATA ACL, but there is no actual DMARC check that
42160 occurs until a &"dmarc_status"& condition is encountered in the ACLs.
42162 The &"dmarc_status"& condition takes a list of strings on its
42163 right-hand side. These strings describe recommended action based
42164 on the DMARC check. To understand what the policy recommendations
42165 mean, refer to the DMARC website above. Valid strings are:
42166 .itable none 0 0 2 20* left 80* left
42167 .irow &'accept'& "The DMARC check passed and the library recommends accepting the email"
42168 .irow &'reject'& "The DMARC check failed and the library recommends rejecting the email"
42169 .irow &'quarantine'& "The DMARC check failed and the library recommends keeping it for further inspection"
42170 .irow &'none'& "The DMARC check passed and the library recommends no specific action, neutral"
42171 .irow &'norecord'& "No policy section in the DMARC record for this RFC5322.From field"
42172 .irow &'nofrom'& "Unable to determine the domain of the sender"
42173 .irow &'temperror'& "Library error or dns error"
42174 .irow &'off'& "The DMARC check was disabled for this email"
42176 You can prefix each string with an exclamation mark to invert its
42177 meaning, for example "!accept" will match all results but
42178 "accept". The string list is evaluated left-to-right in a
42179 short-circuit fashion. When a string matches the outcome of the
42180 DMARC check, the condition succeeds. If none of the listed
42181 strings matches the outcome of the DMARC check, the condition
42184 Of course, you can also use any other lookup method that Exim
42185 supports, including LDAP, Postgres, MySQL, etc, as long as the
42186 result is a list of colon-separated strings.
42188 Performing the check sets up information used by the
42189 &%authresults%& expansion item.
42191 Several expansion variables are set before the DATA ACL is
42192 processed, and you can use them in this ACL. The following
42193 expansion variables are available:
42196 .vitem &$dmarc_status$&
42197 .vindex &$dmarc_status$&
42198 .cindex DMARC result
42199 A one word status indicating what the DMARC library
42200 thinks of the email. It is a combination of the results of
42201 DMARC record lookup and the SPF/DKIM/DMARC processing results
42202 (if a DMARC record was found). The actual policy declared
42203 in the DMARC record is in a separate expansion variable.
42205 .vitem &$dmarc_status_text$&
42206 .vindex &$dmarc_status_text$&
42207 Slightly longer, human readable status.
42209 .vitem &$dmarc_used_domain$&
42210 .vindex &$dmarc_used_domain$&
42211 The domain which DMARC used to look up the DMARC policy record.
42213 .vitem &$dmarc_domain_policy$&
42214 .vindex &$dmarc_domain_policy$&
42215 The policy declared in the DMARC record. Valid values
42216 are "none", "reject" and "quarantine". It is blank when there
42217 is any error, including no DMARC record.
42220 .subsection Logging SSECDMARCLOGGING
42221 .cindex DMARC logging
42223 By default, Exim's DMARC configuration is intended to be
42224 non-intrusive and conservative. To facilitate this, Exim will not
42225 create any type of logging files without explicit configuration by
42226 you, the admin. Nor will Exim send out any emails/reports about
42227 DMARC issues without explicit configuration by you, the admin (other
42228 than typical bounce messages that may come about due to ACL
42229 processing or failure delivery issues).
42231 In order to log statistics suitable to be imported by the opendmarc
42232 tools, you need to:
42234 Configure the global option &%dmarc_history_file%&
42236 Configure cron jobs to call the appropriate opendmarc history
42237 import scripts and truncating the dmarc_history_file
42240 In order to send forensic reports, you need to:
42242 Configure the global option &%dmarc_forensic_sender%&
42244 Configure, somewhere before the DATA ACL, the control option to
42245 enable sending DMARC forensic reports
42248 .subsection Example SSECDMARCEXAMPLE
42249 .cindex DMARC example
42254 warn domains = +local_domains
42255 hosts = +local_hosts
42256 control = dmarc_disable_verify
42258 warn !domains = +screwed_up_dmarc_records
42259 control = dmarc_enable_forensic
42261 warn condition = (lookup if destined to mailing list)
42262 set acl_m_mailing_list = 1
42265 warn dmarc_status = accept : none : off
42267 log_message = DMARC DEBUG: $dmarc_status $dmarc_used_domain
42269 warn dmarc_status = !accept
42271 log_message = DMARC DEBUG: '$dmarc_status' for $dmarc_used_domain
42273 warn dmarc_status = quarantine
42275 set $acl_m_quarantine = 1
42276 # Do something in a transport with this flag variable
42278 deny condition = ${if eq{$dmarc_domain_policy}{reject}}
42279 condition = ${if eq{$acl_m_mailing_list}{1}}
42280 message = Messages from $dmarc_used_domain break mailing lists
42282 deny dmarc_status = reject
42284 message = Message from $dmarc_used_domain failed sender's DMARC policy, REJECT
42286 warn add_header = :at_start:${authresults {$primary_hostname}}
42293 . ////////////////////////////////////////////////////////////////////////////
42294 . ////////////////////////////////////////////////////////////////////////////
42296 .chapter "Proxies" "CHAPproxies" &&&
42298 .cindex "proxy support"
42299 .cindex "proxy" "access via"
42301 A proxy is an intermediate system through which communication is passed.
42302 Proxies may provide a security, availability or load-distribution function.
42305 .section "Inbound proxies" SECTproxyInbound
42306 .cindex proxy inbound
42307 .cindex proxy "server side"
42308 .cindex proxy "Proxy protocol"
42309 .cindex "Proxy protocol" proxy
42311 Exim has support for receiving inbound SMTP connections via a proxy
42312 that uses &"Proxy Protocol"& to speak to it.
42313 To include this support, include &"SUPPORT_PROXY=yes"&
42316 It was built on the HAProxy specification, found at
42317 &url(https://www.haproxy.org/download/1.8/doc/proxy-protocol.txt).
42319 The purpose of this facility is so that an application load balancer,
42320 such as HAProxy, can sit in front of several Exim servers
42321 to distribute load.
42322 Exim uses the local protocol communication with the proxy to obtain
42323 the remote SMTP system IP address and port information.
42324 There is no logging if a host passes or
42325 fails Proxy Protocol negotiation, but it can easily be determined and
42326 recorded in an ACL (example is below).
42328 Use of a proxy is enabled by setting the &%hosts_proxy%&
42329 main configuration option to a hostlist; connections from these
42330 hosts will use Proxy Protocol.
42331 Exim supports both version 1 and version 2 of the Proxy Protocol and
42332 automatically determines which version is in use.
42334 The Proxy Protocol header is the first data received on a TCP connection
42335 and is inserted before any TLS-on-connect handshake from the client; Exim
42336 negotiates TLS between Exim-as-server and the remote client, not between
42337 Exim and the proxy server. The Proxy Protocol header must be received
42338 within &%proxy_protocol_timeout%&, which defaults to 3s.
42340 The following expansion variables are usable
42341 (&"internal"& and &"external"& here refer to the interfaces
42343 .itable none 0 0 2 30* left 70* left
42344 .irow $proxy_external_address "IP of host being proxied or IP of remote interface of proxy"
42345 .irow $proxy_external_port "Port of host being proxied or Port on remote interface of proxy"
42346 .irow $proxy_local_address "IP of proxy server inbound or IP of local interface of proxy"
42347 .irow $proxy_local_port "Port of proxy server inbound or Port on local interface of proxy"
42348 .irow $proxy_session "boolean: SMTP connection via proxy"
42350 If &$proxy_session$& is set but &$proxy_external_address$& is empty
42351 there was a protocol error.
42352 The variables &$sender_host_address$& and &$sender_host_port$&
42353 will have values for the actual client system, not the proxy.
42355 Since the real connections are all coming from the proxy, and the
42356 per host connection tracking is done before Proxy Protocol is
42357 evaluated, &%smtp_accept_max_per_host%& must be set high enough to
42358 handle all of the parallel volume you expect per inbound proxy.
42359 With the option set so high, you lose the ability
42360 to protect your server from many connections from one IP.
42361 In order to prevent your server from overload, you
42362 need to add a per connection ratelimit to your connect ACL.
42363 A possible solution is:
42365 # Set max number of connections per host
42367 # Or do some kind of IP lookup in a flat file or database
42368 # LIMIT = ${lookup{$sender_host_address}iplsearch{/etc/exim/proxy_limits}}
42370 defer ratelimit = LIMIT / 5s / per_conn / strict
42371 message = Too many connections from this IP right now
42376 .section "Outbound proxies" SECTproxySOCKS
42377 .cindex proxy outbound
42378 .cindex proxy "client side"
42379 .cindex proxy SOCKS
42380 .cindex SOCKS proxy
42381 Exim has support for sending outbound SMTP via a proxy
42382 using a protocol called SOCKS5 (defined by RFC1928).
42383 The support can be optionally included by defining SUPPORT_SOCKS=yes in
42386 Use of a proxy is enabled by setting the &%socks_proxy%& option
42387 on an smtp transport.
42388 The option value is expanded and should then be a list
42389 (colon-separated by default) of proxy specifiers.
42390 Each proxy specifier is a list
42391 (space-separated by default) where the initial element
42392 is an IP address and any subsequent elements are options.
42394 Options are a string <name>=<value>.
42395 The list of options is in the following table:
42396 .itable none 0 0 2 10* left 90* left
42397 .irow &'auth'& "authentication method"
42398 .irow &'name'& "authentication username"
42399 .irow &'pass'& "authentication password"
42400 .irow &'port'& "tcp port"
42401 .irow &'tmo'& "connection timeout"
42402 .irow &'pri'& "priority"
42403 .irow &'weight'& "selection bias"
42406 More details on each of these options follows:
42409 .cindex authentication "to proxy"
42410 .cindex proxy authentication
42411 &%auth%&: Either &"none"& (default) or &"name"&.
42412 Using &"name"& selects username/password authentication per RFC 1929
42413 for access to the proxy.
42414 Default is &"none"&.
42416 &%name%&: sets the username for the &"name"& authentication method.
42419 &%pass%&: sets the password for the &"name"& authentication method.
42422 &%port%&: the TCP port number to use for the connection to the proxy.
42425 &%tmo%&: sets a connection timeout in seconds for this proxy.
42428 &%pri%&: specifies a priority for the proxy within the list,
42429 higher values being tried first.
42430 The default priority is 1.
42432 &%weight%&: specifies a selection bias.
42433 Within a priority set servers are queried in a random fashion,
42434 weighted by this value.
42435 The default value for selection bias is 1.
42438 Proxies from the list are tried according to their priority
42439 and weight settings until one responds. The timeout for the
42440 overall connection applies to the set of proxied attempts.
42442 .section Logging SECTproxyLog
42443 To log the (local) IP of a proxy in the incoming or delivery logline,
42444 add &"+proxy"& to the &%log_selector%& option.
42445 This will add a component tagged with &"PRX="& to the line.
42447 . ////////////////////////////////////////////////////////////////////////////
42448 . ////////////////////////////////////////////////////////////////////////////
42450 .chapter "Internationalisation" "CHAPi18n" &&&
42451 "Internationalisation""
42452 .cindex internationalisation "email address"
42455 .cindex utf8 "mail name handling"
42457 Exim has support for Internationalised mail names.
42458 To include this it must be built with SUPPORT_I18N and the libidn library.
42459 Standards supported are RFCs 2060, 5890, 6530 and 6533.
42461 If Exim is built with SUPPORT_I18N_2008 (in addition to SUPPORT_I18N, not
42462 instead of it) then IDNA2008 is supported; this adds an extra library
42463 requirement, upon libidn2.
42465 .section "MTA operations" SECTi18nMTA
42466 .cindex SMTPUTF8 "ESMTP option"
42467 .cindex "ESMTP extensions" SMTPUTF8
42468 The main configuration option &%smtputf8_advertise_hosts%& specifies
42469 a host list. If this matches the sending host and
42470 accept_8bitmime is true (the default) then the ESMTP option
42471 SMTPUTF8 will be advertised.
42473 If the sender specifies the SMTPUTF8 option on a MAIL command
42474 international handling for the message is enabled and
42475 the expansion variable &$message_smtputf8$& will have value TRUE.
42477 The option &%allow_utf8_domains%& is set to true for this
42478 message. All DNS lookups are converted to a-label form
42479 whatever the setting of &%allow_utf8_domains%&
42480 when Exim is built with SUPPORT_I18N.
42482 Both localparts and domain are maintained as the original
42483 UTF-8 form internally; any comparison or regular-expression use will
42484 require appropriate care. Filenames created, eg. by
42485 the appendfile transport, will have UTF-8 names.
42487 HELO names sent by the smtp transport will have any UTF-8
42488 components expanded to a-label form,
42489 and any certificate name checks will be done using the a-label
42492 .cindex log protocol
42493 .cindex SMTPUTF8 logging
42494 .cindex i18n logging
42495 Log lines and Received-by: header lines will acquire a "utf8"
42496 prefix on the protocol element, eg. utf8esmtp.
42498 The following expansion operators can be used:
42500 ${utf8_domain_to_alabel:str}
42501 ${utf8_domain_from_alabel:str}
42502 ${utf8_localpart_to_alabel:str}
42503 ${utf8_localpart_from_alabel:str}
42506 .cindex utf8 "address downconversion"
42507 .cindex i18n "utf8 address downconversion"
42509 may use the following modifier:
42511 control = utf8_downconvert
42512 control = utf8_downconvert/<value>
42514 This sets a flag requiring that envelope addresses are converted to
42515 a-label form before smtp delivery.
42516 This is usually for use in a Message Submission Agent context,
42517 but could be used for any message.
42519 If a value is appended it may be:
42520 .itable none 0 0 2 5* right 95* left
42521 .irow &`1`& "mandatory downconversion"
42522 .irow &`0`& "no downconversion"
42523 .irow &`-1`& "if SMTPUTF8 not supported by destination host"
42525 If no value is given, 1 is used.
42527 If mua_wrapper is set, the utf8_downconvert control
42528 is initially set to -1.
42530 The smtp transport has an option &%utf8_downconvert%&.
42531 If set it must expand to one of the three values described above,
42532 or an empty string.
42533 If non-empty it overrides value previously set
42534 (due to mua_wrapper or by an ACL control).
42537 There is no explicit support for VRFY and EXPN.
42538 Configurations supporting these should inspect
42539 &$smtp_command_argument$& for an SMTPUTF8 argument.
42541 There is no support for LMTP on Unix sockets.
42542 Using the "lmtp" protocol option on an smtp transport,
42543 for LMTP over TCP, should work as expected.
42545 There is no support for DSN unitext handling,
42546 and no provision for converting logging from or to UTF-8.
42550 .section "MDA operations" SECTi18nMDA
42551 To aid in constructing names suitable for IMAP folders
42552 the following expansion operator can be used:
42554 ${imapfolder {<string>} {<sep>} {<specials>}}
42557 The string is converted from the charset specified by
42558 the "headers charset" command (in a filter file)
42559 or &%headers_charset%& main configuration option (otherwise),
42561 modified UTF-7 encoding specified by RFC 2060,
42562 with the following exception: All occurrences of <sep>
42563 (which has to be a single character)
42564 are replaced with periods ("."), and all periods and slashes that are not
42565 <sep> and are not in the <specials> string are BASE64 encoded.
42567 The third argument can be omitted, defaulting to an empty string.
42568 The second argument can be omitted, defaulting to "/".
42570 This is the encoding used by Courier for Maildir names on disk, and followed
42571 by many other IMAP servers.
42575 &`${imapfolder {Foo/Bar}} `& yields &`Foo.Bar`&
42576 &`${imapfolder {Foo/Bar}{.}{/}} `& yields &`Foo&&AC8-Bar`&
42577 &`${imapfolder {Räksmörgås}} `& yields &`R&&AOQ-ksm&&APY-rg&&AOU-s`&
42580 Note that the source charset setting is vital, and also that characters
42581 must be representable in UTF-16.
42584 . ////////////////////////////////////////////////////////////////////////////
42585 . ////////////////////////////////////////////////////////////////////////////
42587 .chapter "Events" "CHAPevents" &&&
42591 The events mechanism in Exim can be used to intercept processing at a number
42592 of points. It was originally invented to give a way to do customised logging
42593 actions (for example, to a database) but can also be used to modify some
42594 processing actions.
42596 Most installations will never need to use Events.
42597 The support can be left out of a build by defining DISABLE_EVENT=yes
42598 in &_Local/Makefile_&.
42600 There are two major classes of events: main and transport.
42601 The main configuration option &%event_action%& controls reception events;
42602 a transport option &%event_action%& controls delivery events.
42604 Both options are a string which is expanded when the event fires.
42605 An example might look like:
42606 .cindex logging custom
42608 event_action = ${if eq {msg:delivery}{$event_name} \
42609 {${lookup pgsql {SELECT * FROM record_Delivery( \
42610 '${quote_pgsql:$sender_address_domain}',\
42611 '${quote_pgsql:${lc:$sender_address_local_part}}', \
42612 '${quote_pgsql:$domain}', \
42613 '${quote_pgsql:${lc:$local_part}}', \
42614 '${quote_pgsql:$host_address}', \
42615 '${quote_pgsql:${lc:$host}}', \
42616 '${quote_pgsql:$message_exim_id}')}} \
42620 Events have names which correspond to the point in process at which they fire.
42621 The name is placed in the variable &$event_name$& and the event action
42622 expansion must check this, as it will be called for every possible event type.
42624 The current list of events is:
42625 .itable all 0 0 4 25* left 10* center 15* center 50* left
42626 .row auth:fail after both "per driver per authentication attempt"
42627 .row dane:fail after transport "per connection"
42628 .row msg:complete after main "per message"
42629 .row msg:defer after transport "per message per delivery try"
42630 .row msg:delivery after transport "per recipient"
42631 .row msg:rcpt:host:defer after transport "per recipient per host"
42632 .row msg:rcpt:defer after transport "per recipient"
42633 .row msg:host:defer after transport "per host per delivery try; host errors"
42634 .row msg:fail:delivery after transport "per recipient"
42635 .row msg:fail:internal after main "per recipient"
42636 .row tcp:connect before transport "per connection"
42637 .row tcp:close after transport "per connection"
42638 .row tls:cert before both "per certificate in verification chain"
42639 .row tls:fail:connect after main "per connection"
42640 .row smtp:connect after transport "per connection"
42641 .row smtp:ehlo after transport "per connection"
42643 New event types may be added in future.
42645 The event name is a colon-separated list, defining the type of
42646 event in a tree of possibilities. It may be used as a list
42647 or just matched on as a whole. There will be no spaces in the name.
42649 The second column in the table above describes whether the event fires
42650 before or after the action is associates with. Those which fire before
42651 can be used to affect that action (more on this below).
42653 The third column in the table above says what section of the configuration
42654 should define the event action.
42656 An additional variable, &$event_data$&, is filled with information varying
42657 with the event type:
42658 .itable all 0 0 2 20* left 80* left
42659 .row auth:fail "smtp response"
42660 .row dane:fail "failure reason"
42661 .row msg:defer "error string"
42662 .row msg:delivery "smtp confirmation message"
42663 .row msg:fail:internal "failure reason"
42664 .row msg:fail:delivery "smtp error message"
42665 .row msg:host:defer "error string"
42666 .row msg:rcpt:host:defer "error string"
42667 .row msg:rcpt:defer "error string"
42668 .row tls:cert "verification chain depth"
42669 .row tls:fail:connect "error string"
42670 .row smtp:connect "smtp banner"
42671 .row smtp:ehlo "smtp ehlo response"
42674 The :defer events populate one extra variable: &$event_defer_errno$&.
42676 For complex operations an ACL expansion can be used in &%event_action%&,
42677 however due to the multiple contexts that Exim operates in during
42678 the course of its processing:
42680 variables set in transport events will not be visible outside that
42683 acl_m variables in a server context are lost on a new connection,
42684 and after smtp helo/ehlo/mail/starttls/rset commands
42686 Using an ACL expansion with the logwrite modifier can be
42687 a useful way of writing to the main log.
42689 The expansion of the event_action option should normally
42690 return an empty string. Should it return anything else the
42691 following will be forced:
42692 .itable all 0 0 2 20* left 80* left
42693 .row auth:fail "log information to write"
42694 .row tcp:connect "do not connect"
42695 .row tls:cert "refuse verification"
42696 .row smtp:connect "close connection"
42698 All other message types ignore the result string, and
42699 no other use is made of it.
42701 For a tcp:connect event, if the connection is being made to a proxy
42702 then the address and port variables will be that of the proxy and not
42705 For tls:cert events, if GnuTLS is in use this will trigger only per
42706 chain element received on the connection.
42707 For OpenSSL it will trigger for every chain element including those
42710 . ////////////////////////////////////////////////////////////////////////////
42711 . ////////////////////////////////////////////////////////////////////////////
42713 .chapter "Adding new drivers or lookup types" "CHID13" &&&
42714 "Adding drivers or lookups"
42715 .cindex "adding drivers"
42716 .cindex "new drivers, adding"
42717 .cindex "drivers" "adding new"
42718 The following actions have to be taken in order to add a new router, transport,
42719 authenticator, or lookup type to Exim:
42722 Choose a name for the driver or lookup type that does not conflict with any
42723 existing name; I will use &"newdriver"& in what follows.
42725 Add to &_src/EDITME_& the line:
42727 <&'type'&>&`_NEWDRIVER=yes`&
42729 where <&'type'&> is ROUTER, TRANSPORT, AUTH, or LOOKUP. If the
42730 code is not to be included in the binary by default, comment this line out. You
42731 should also add any relevant comments about the driver or lookup type.
42733 Add to &_src/config.h.defaults_& the line:
42735 #define <type>_NEWDRIVER
42738 Edit &_src/drtables.c_&, adding conditional code to pull in the private header
42739 and create a table entry as is done for all the other drivers and lookup types.
42741 Edit &_scripts/lookups-Makefile_& if this is a new lookup; there is a for-loop
42742 near the bottom, ranging the &`name_mod`& variable over a list of all lookups.
42743 Add your &`NEWDRIVER`& to that list.
42744 As long as the dynamic module would be named &_newdriver.so_&, you can use the
42745 simple form that most lookups have.
42747 Edit &_Makefile_& in the appropriate sub-directory (&_src/routers_&,
42748 &_src/transports_&, &_src/auths_&, or &_src/lookups_&); add a line for the new
42749 driver or lookup type and add it to the definition of OBJ.
42751 Edit &_OS/Makefile-Base_& adding a &_.o_& file for the predefined-macros, to the
42752 definition of OBJ_MACRO. Add a set of line to do the compile also.
42754 Create &_newdriver.h_& and &_newdriver.c_& in the appropriate sub-directory of
42757 Edit &_scripts/MakeLinks_& and add commands to link the &_.h_& and &_.c_& files
42758 as for other drivers and lookups.
42761 Then all you need to do is write the code! A good way to start is to make a
42762 proforma by copying an existing module of the same type, globally changing all
42763 occurrences of the name, and cutting out most of the code. Note that any
42764 options you create must be listed in alphabetical order, because the tables are
42765 searched using a binary chop procedure.
42767 There is a &_README_& file in each of the sub-directories of &_src_& describing
42768 the interface that is expected.
42773 . ////////////////////////////////////////////////////////////////////////////
42774 . ////////////////////////////////////////////////////////////////////////////
42776 . /////////////////////////////////////////////////////////////////////////////
42777 . These lines are processing instructions for the Simple DocBook Processor that
42778 . Philip Hazel has developed as a less cumbersome way of making PostScript and
42779 . PDFs than using xmlto and fop. They will be ignored by all other XML
42781 . /////////////////////////////////////////////////////////////////////////////
42786 foot_right_recto="&chaptertitle;"
42787 foot_right_verso="&chaptertitle;"
42791 .makeindex "Options index" "option"
42792 .makeindex "Variables index" "variable"
42793 .makeindex "Concept index" "concept"
42796 . /////////////////////////////////////////////////////////////////////////////
42797 . /////////////////////////////////////////////////////////////////////////////