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 "tainted" marker, done as a one-element table
103 .itable none 0 0 1 10pt left
107 . --- A macro for a tainted variable, adding a taint-marker
108 . --- and including the .vitem and .vindex
115 . --- A macro that generates .row, but puts &I; at the start of the first
116 . --- argument, thus indenting it. Assume a minimum of two arguments, and
117 . --- allow up to four arguments, which is as many as we'll ever need.
121 .row "&I;$1" "$2" "$3" "$4"
125 .row "&I;$1" "$2" "$3"
133 . --- Macros for option, variable, and concept index entries. For a "range"
134 . --- style of entry, use .scindex for the start and .ecindex for the end. The
135 . --- first argument of .scindex and the only argument of .ecindex must be the
136 . --- ID that ties them together.
139 &<indexterm role="concept">&
140 &<primary>&$1&</primary>&
142 &<secondary>&$2&</secondary>&
148 &<indexterm role="concept" id="$1" class="startofrange">&
149 &<primary>&$2&</primary>&
151 &<secondary>&$3&</secondary>&
157 &<indexterm role="concept" startref="$1" class="endofrange"/>&
161 &<indexterm role="option">&
162 &<primary>&$1&</primary>&
164 &<secondary>&$2&</secondary>&
170 &<indexterm role="variable">&
171 &<primary>&$1&</primary>&
173 &<secondary>&$2&</secondary>&
179 .echo "** Don't use .index; use .cindex or .oindex or .vindex"
183 . use this for a concept-index entry for a header line
185 .cindex "&'$1'& header line"
186 .cindex "header lines" $1
188 . ////////////////////////////////////////////////////////////////////////////
191 . ////////////////////////////////////////////////////////////////////////////
192 . The <bookinfo> element is removed from the XML before processing for ASCII
194 . ////////////////////////////////////////////////////////////////////////////
198 <title>Specification of the Exim Mail Transfer Agent</title>
199 <titleabbrev>The Exim MTA</titleabbrev>
203 <author><firstname>Exim</firstname><surname>Maintainers</surname></author>
204 <authorinitials>EM</authorinitials>
205 <revhistory><revision>
207 <authorinitials>EM</authorinitials>
208 </revision></revhistory>
211 </year><holder>The Exim Maintainers</holder></copyright>
216 . /////////////////////////////////////////////////////////////////////////////
217 . These implement index entries of the form "x, see y" and "x, see also y".
218 . However, the DocBook DTD doesn't allow <indexterm> entries
219 . at the top level, so we have to put the .chapter directive first.
220 . /////////////////////////////////////////////////////////////////////////////
222 .chapter "Introduction" "CHID1"
226 <indexterm role="$2">
227 <primary>$3</primary>
229 <secondary>$5</secondary>
231 <$1><emphasis>$4</emphasis></$1>
236 . NB: for the 4-arg variant the ordering is awkward
238 .seeother see "$1" "$2" "$3" "$4"
241 .seeother seealso "$1" "$2" "$3" "$4"
244 .see variable "<emphasis>$1</emphasis>, <emphasis>$2</emphasis>, etc." "numerical variables"
245 .see concept address rewriting rewriting
246 .see concept "Bounce Address Tag Validation" BATV
247 .see concept "Client SMTP Authorization" CSA
248 .see concept "CR character" "carriage return"
249 .see concept CRL "certificate revocation list"
250 .seealso concept de-tainting "tainted data"
251 .see concept delivery "bounce message" "failure report"
252 .see concept dialup "intermittently connected hosts"
253 .see concept exiscan "content scanning"
254 .see concept fallover fallback
255 .see concept filter "Sieve filter" Sieve
256 .see concept headers "header lines"
257 .see concept ident "RFC 1413"
258 .see concept "LF character" "linefeed"
259 .seealso concept maximum limit
260 .see concept monitor "Exim monitor"
261 .see concept "no_<emphasis>xxx</emphasis>" "entry for xxx"
262 .see concept NUL "binary zero"
263 .see concept "passwd file" "/etc/passwd"
264 .see concept "process id" pid
265 .see concept RBL "DNS list"
266 .see concept redirection "address redirection"
267 .see concept "return path" "envelope sender"
268 .see concept scanning "content scanning"
270 .see concept string expansion expansion
271 .see concept "top bit" "8-bit characters"
272 .see concept variables "expansion, variables"
273 .see concept "zero, binary" "binary zero"
276 . /////////////////////////////////////////////////////////////////////////////
277 . This is the real start of the first chapter. See the comment above as to why
278 . we can't have the .chapter line here.
279 . chapter "Introduction"
280 . /////////////////////////////////////////////////////////////////////////////
282 Exim is a mail transfer agent (MTA) for hosts that are running Unix or
283 Unix-like operating systems. It was designed on the assumption that it would be
284 run on hosts that are permanently connected to the Internet. However, it can be
285 used on intermittently connected hosts with suitable configuration adjustments.
287 Configuration files currently exist for the following operating systems: AIX,
288 BSD/OS (aka BSDI), Darwin (Mac OS X), DGUX, Dragonfly, FreeBSD, GNU/Hurd,
289 GNU/Linux, HI-OSF (Hitachi), HI-UX, HP-UX, IRIX, MIPS RISCOS, NetBSD, OpenBSD,
290 OpenUNIX, QNX, SCO, SCO SVR4.2 (aka UNIX-SV), Solaris (aka SunOS5), SunOS4,
291 Tru64-Unix (formerly Digital UNIX, formerly DEC-OSF1), Ultrix, and UnixWare.
292 Some of these operating systems are no longer current and cannot easily be
293 tested, so the configuration files may no longer work in practice.
295 There are also configuration files for compiling Exim in the Cygwin environment
296 that can be installed on systems running Windows. However, this document does
297 not contain any information about running Exim in the Cygwin environment.
299 The terms and conditions for the use and distribution of Exim are contained in
300 the file &_NOTICE_&. Exim is distributed under the terms of the GNU General
301 Public Licence, a copy of which may be found in the file &_LICENCE_&.
303 The use, supply, or promotion of Exim for the purpose of sending bulk,
304 unsolicited electronic mail is incompatible with the basic aims of Exim,
305 which revolve around the free provision of a service that enhances the quality
306 of personal communications. The author of Exim regards indiscriminate
307 mass-mailing as an antisocial, irresponsible abuse of the Internet.
309 Exim owes a great deal to Smail 3 and its author, Ron Karr. Without the
310 experience of running and working on the Smail 3 code, I could never have
311 contemplated starting to write a new MTA. Many of the ideas and user interfaces
312 were originally taken from Smail 3, though the actual code of Exim is entirely
313 new, and has developed far beyond the initial concept.
315 Many people, both in Cambridge and around the world, have contributed to the
316 development and the testing of Exim, and to porting it to various operating
317 systems. I am grateful to them all. The distribution now contains a file called
318 &_ACKNOWLEDGMENTS_&, in which I have started recording the names of
322 .section "Exim documentation" "SECID1"
323 . Keep this example change bar when updating the documentation!
326 .cindex "documentation"
327 This edition of the Exim specification applies to version &version() of Exim.
328 Substantive changes from the &previousversion; edition are marked in some
329 renditions of this document; this paragraph is so marked if the rendition is
330 capable of showing a change indicator.
333 This document is very much a reference manual; it is not a tutorial. The reader
334 is expected to have some familiarity with the SMTP mail transfer protocol and
335 with general Unix system administration. Although there are some discussions
336 and examples in places, the information is mostly organized in a way that makes
337 it easy to look up, rather than in a natural order for sequential reading.
338 Furthermore, this manual aims to cover every aspect of Exim in detail, including
339 a number of rarely-used, special-purpose features that are unlikely to be of
342 .cindex "books about Exim"
343 An &"easier"& discussion of Exim which provides more in-depth explanatory,
344 introductory, and tutorial material can be found in a book entitled &'The Exim
345 SMTP Mail Server'& (second edition, 2007), published by UIT Cambridge
346 (&url(https://www.uit.co.uk/exim-book/)).
348 The book also contains a chapter that gives a general introduction to SMTP and
349 Internet mail. Inevitably, however, the book is unlikely to be fully up-to-date
350 with the latest release of Exim. (Note that the earlier book about Exim,
351 published by O'Reilly, covers Exim 3, and many things have changed in Exim 4.)
353 .cindex "Debian" "information sources"
354 If you are using a Debian distribution of Exim, you will find information about
355 Debian-specific features in the file
356 &_/usr/share/doc/exim4-base/README.Debian_&.
357 The command &(man update-exim.conf)& is another source of Debian-specific
360 .cindex "&_doc/NewStuff_&"
361 .cindex "&_doc/ChangeLog_&"
363 As Exim develops, there may be features in newer versions that have not
364 yet made it into this document, which is updated only when the most significant
365 digit of the fractional part of the version number changes. Specifications of
366 new features that are not yet in this manual are placed in the file
367 &_doc/NewStuff_& in the Exim distribution.
369 Some features may be classified as &"experimental"&. These may change
370 incompatibly while they are developing, or even be withdrawn. For this reason,
371 they are not documented in this manual. Information about experimental features
372 can be found in the file &_doc/experimental.txt_&.
374 All changes to Exim (whether new features, bug fixes, or other kinds of
375 change) are noted briefly in the file called &_doc/ChangeLog_&.
377 .cindex "&_doc/spec.txt_&"
378 This specification itself is available as an ASCII file in &_doc/spec.txt_& so
379 that it can easily be searched with a text editor. Other files in the &_doc_&
383 .row &_OptionLists.txt_& "list of all options in alphabetical order"
384 .row &_dbm.discuss.txt_& "discussion about DBM libraries"
385 .row &_exim.8_& "a man page of Exim's command line options"
386 .row &_experimental.txt_& "documentation of experimental features"
387 .row &_filter.txt_& "specification of the filter language"
388 .row &_Exim3.upgrade_& "upgrade notes from release 2 to release 3"
389 .row &_Exim4.upgrade_& "upgrade notes from release 3 to release 4"
390 .row &_openssl.txt_& "installing a current OpenSSL release"
393 The main specification and the specification of the filtering language are also
394 available in other formats (HTML, PostScript, PDF, and Texinfo). Section
395 &<<SECTavail>>& below tells you how to get hold of these.
399 .section "FTP site and websites" "SECID2"
402 The primary site for Exim source distributions is the &%exim.org%& FTP site,
403 available over HTTPS, HTTP and FTP. These services, and the &%exim.org%&
404 website, are hosted at the University of Cambridge.
408 As well as Exim distribution tar files, the Exim website contains a number of
409 differently formatted versions of the documentation. A recent addition to the
410 online information is the Exim wiki (&url(https://wiki.exim.org)),
411 which contains what used to be a separate FAQ, as well as various other
412 examples, tips, and know-how that have been contributed by Exim users.
413 The wiki site should always redirect to the correct place, which is currently
414 provided by GitHub, and is open to editing by anyone with a GitHub account.
417 An Exim Bugzilla exists at &url(https://bugs.exim.org). You can use
418 this to report bugs, and also to add items to the wish list. Please search
419 first to check that you are not duplicating a previous entry.
420 Please do not ask for configuration help in the bug-tracker.
423 .section "Mailing lists" "SECID3"
424 .cindex "mailing lists" "for Exim users"
425 The following Exim mailing lists exist:
428 .row &'exim-announce@exim.org'& "Moderated, low volume announcements list"
429 .row &'exim-users@exim.org'& "General discussion list"
430 .row &'exim-dev@exim.org'& "Discussion of bugs, enhancements, etc."
431 .row &'exim-cvs@exim.org'& "Automated commit messages from the VCS"
434 You can subscribe to these lists, change your existing subscriptions, and view
435 or search the archives via the mailing lists link on the Exim home page.
436 .cindex "Debian" "mailing list for"
437 If you are using a Debian distribution of Exim, you may wish to subscribe to
438 the Debian-specific mailing list &'pkg-exim4-users@lists.alioth.debian.org'&
441 &url(https://alioth-lists.debian.net/cgi-bin/mailman/listinfo/pkg-exim4-users)
443 Please ask Debian-specific questions on that list and not on the general Exim
446 .section "Bug reports" "SECID5"
447 .cindex "bug reports"
448 .cindex "reporting bugs"
449 Reports of obvious bugs can be emailed to &'bugs@exim.org'& or reported
450 via the Bugzilla (&url(https://bugs.exim.org)). However, if you are unsure
451 whether some behaviour is a bug or not, the best thing to do is to post a
452 message to the &'exim-dev'& mailing list and have it discussed.
456 .section "Where to find the Exim distribution" "SECTavail"
458 .cindex "HTTPS download site"
459 .cindex "distribution" "FTP site"
460 .cindex "distribution" "https site"
461 The master distribution site for the Exim distribution is
463 &url(https://downloads.exim.org/)
465 The service is available over HTTPS, HTTP and FTP.
466 We encourage people to migrate to HTTPS.
468 The content served at &url(https://downloads.exim.org/) is identical to the
469 content served at &url(https://ftp.exim.org/pub/exim) and
470 &url(ftp://ftp.exim.org/pub/exim).
472 If accessing via a hostname containing &'ftp'&, then the file references that
473 follow are relative to the &_exim_& directories at these sites.
474 If accessing via the hostname &'downloads'& then the subdirectories described
475 here are top-level directories.
477 There are now quite a number of independent mirror sites around
478 the world. Those that I know about are listed in the file called &_Mirrors_&.
480 Within the top exim directory there are subdirectories called &_exim3_& (for
481 previous Exim 3 distributions), &_exim4_& (for the latest Exim 4
482 distributions), and &_Testing_& for testing versions. In the &_exim4_&
483 subdirectory, the current release can always be found in files called
487 &_exim-n.nn.tar.bz2_&
489 where &'n.nn'& is the highest such version number in the directory. The three
490 files contain identical data; the only difference is the type of compression.
491 The &_.xz_& file is usually the smallest, while the &_.gz_& file is the
492 most portable to old systems.
494 .cindex "distribution" "signing details"
495 .cindex "distribution" "public key"
496 .cindex "public key for signed distribution"
497 The distributions will be PGP signed by an individual key of the Release
498 Coordinator. This key will have a uid containing an email address in the
499 &'exim.org'& domain and will have signatures from other people, including
500 other Exim maintainers. We expect that the key will be in the "strong set" of
501 PGP keys. There should be a trust path to that key from the Exim Maintainer's
502 PGP keys, a version of which can be found in the release directory in the file
503 &_Exim-Maintainers-Keyring.asc_&. All keys used will be available in public keyserver pools,
504 such as &'pool.sks-keyservers.net'&.
506 At the time of the last update, releases were being made by Jeremy Harris and signed
507 with key &'0xBCE58C8CE41F32DF'&. Other recent keys used for signing are those
508 of Heiko Schlittermann, &'0x26101B62F69376CE'&,
509 and of Phil Pennock, &'0x4D1E900E14C1CC04'&.
511 The signatures for the tar bundles are in:
513 &_exim-n.nn.tar.xz.asc_&
514 &_exim-n.nn.tar.gz.asc_&
515 &_exim-n.nn.tar.bz2.asc_&
517 For each released version, the log of changes is made available in a
518 separate file in the directory &_ChangeLogs_& so that it is possible to
519 find out what has changed without having to download the entire distribution.
521 .cindex "documentation" "available formats"
522 The main distribution contains ASCII versions of this specification and other
523 documentation; other formats of the documents are available in separate files
524 inside the &_exim4_& directory of the FTP site:
526 &_exim-html-n.nn.tar.gz_&
527 &_exim-pdf-n.nn.tar.gz_&
528 &_exim-postscript-n.nn.tar.gz_&
529 &_exim-texinfo-n.nn.tar.gz_&
531 These tar files contain only the &_doc_& directory, not the complete
532 distribution, and are also available in &_.bz2_& and &_.xz_& forms.
535 .section "Limitations" "SECID6"
537 .cindex "limitations of Exim"
538 .cindex "bang paths" "not handled by Exim"
539 Exim is designed for use as an Internet MTA, and therefore handles addresses in
540 RFC 2822 domain format only. It cannot handle UUCP &"bang paths"&, though
541 simple two-component bang paths can be converted by a straightforward rewriting
542 configuration. This restriction does not prevent Exim from being interfaced to
543 UUCP as a transport mechanism, provided that domain addresses are used.
545 .cindex "domainless addresses"
546 .cindex "address" "without domain"
547 Exim insists that every address it handles has a domain attached. For incoming
548 local messages, domainless addresses are automatically qualified with a
549 configured domain value. Configuration options specify from which remote
550 systems unqualified addresses are acceptable. These are then qualified on
553 .cindex "transport" "external"
554 .cindex "external transports"
555 The only external transport mechanisms that are currently implemented are SMTP
556 and LMTP over a TCP/IP network (including support for IPv6). However, a pipe
557 transport is available, and there are facilities for writing messages to files
558 and pipes, optionally in &'batched SMTP'& format; these facilities can be used
559 to send messages to other transport mechanisms such as UUCP, provided they can
560 handle domain-style addresses. Batched SMTP input is also catered for.
562 Exim is not designed for storing mail for dial-in hosts. When the volumes of
563 such mail are large, it is better to get the messages &"delivered"& into files
564 (that is, off Exim's queue) and subsequently passed on to the dial-in hosts by
567 Although Exim does have basic facilities for scanning incoming messages, these
568 are not comprehensive enough to do full virus or spam scanning. Such operations
569 are best carried out using additional specialized software packages. If you
570 compile Exim with the content-scanning extension, straightforward interfaces to
571 a number of common scanners are provided.
575 .section "Runtime configuration" "SECID7"
576 Exim's runtime configuration is held in a single text file that is divided
577 into a number of sections. The entries in this file consist of keywords and
578 values, in the style of Smail 3 configuration files. A default configuration
579 file which is suitable for simple online installations is provided in the
580 distribution, and is described in chapter &<<CHAPdefconfil>>& below.
583 .section "Calling interface" "SECID8"
584 .cindex "Sendmail compatibility" "command line interface"
585 Like many MTAs, Exim has adopted the Sendmail command line interface so that it
586 can be a straight replacement for &_/usr/lib/sendmail_& or
587 &_/usr/sbin/sendmail_& when sending mail, but you do not need to know anything
588 about Sendmail in order to run Exim. For actions other than sending messages,
589 Sendmail-compatible options also exist, but those that produce output (for
590 example, &%-bp%&, which lists the messages in the queue) do so in Exim's own
591 format. There are also some additional options that are compatible with Smail
592 3, and some further options that are new to Exim. Chapter &<<CHAPcommandline>>&
593 documents all Exim's command line options. This information is automatically
594 made into the man page that forms part of the Exim distribution.
596 Control of messages in the queue can be done via certain privileged command
597 line options. There is also an optional monitor program called &'eximon'&,
598 which displays current information in an X window, and which contains a menu
599 interface to Exim's command line administration options.
603 .section "Terminology" "SECID9"
604 .cindex "terminology definitions"
605 .cindex "body of message" "definition of"
606 The &'body'& of a message is the actual data that the sender wants to transmit.
607 It is the last part of a message and is separated from the &'header'& (see
608 below) by a blank line.
610 .cindex "bounce message" "definition of"
611 When a message cannot be delivered, it is normally returned to the sender in a
612 delivery failure message or a &"non-delivery report"& (NDR). The term
613 &'bounce'& is commonly used for this action, and the error reports are often
614 called &'bounce messages'&. This is a convenient shorthand for &"delivery
615 failure error report"&. Such messages have an empty sender address in the
616 message's &'envelope'& (see below) to ensure that they cannot themselves give
617 rise to further bounce messages.
619 The term &'default'& appears frequently in this manual. It is used to qualify a
620 value which is used in the absence of any setting in the configuration. It may
621 also qualify an action which is taken unless a configuration setting specifies
624 The term &'defer'& is used when the delivery of a message to a specific
625 destination cannot immediately take place for some reason (a remote host may be
626 down, or a user's local mailbox may be full). Such deliveries are &'deferred'&
629 The word &'domain'& is sometimes used to mean all but the first component of a
630 host's name. It is &'not'& used in that sense here, where it normally refers to
631 the part of an email address following the @ sign.
633 .cindex "envelope, definition of"
634 .cindex "sender" "definition of"
635 A message in transit has an associated &'envelope'&, as well as a header and a
636 body. The envelope contains a sender address (to which bounce messages should
637 be delivered), and any number of recipient addresses. References to the
638 sender or the recipients of a message usually mean the addresses in the
639 envelope. An MTA uses these addresses for delivery, and for returning bounce
640 messages, not the addresses that appear in the header lines.
642 .cindex "message" "header, definition of"
643 .cindex "header section" "definition of"
644 The &'header'& of a message is the first part of a message's text, consisting
645 of a number of lines, each of which has a name such as &'From:'&, &'To:'&,
646 &'Subject:'&, etc. Long header lines can be split over several text lines by
647 indenting the continuations. The header is separated from the body by a blank
650 .cindex "local part" "definition of"
651 .cindex "domain" "definition of"
652 The term &'local part'&, which is taken from RFC 2822, is used to refer to the
653 part of an email address that precedes the @ sign. The part that follows the
654 @ sign is called the &'domain'& or &'mail domain'&.
656 .cindex "local delivery" "definition of"
657 .cindex "remote delivery, definition of"
658 The terms &'local delivery'& and &'remote delivery'& are used to distinguish
659 delivery to a file or a pipe on the local host from delivery by SMTP over
660 TCP/IP to another host. As far as Exim is concerned, all hosts other than the
661 host it is running on are &'remote'&.
663 .cindex "return path" "definition of"
664 &'Return path'& is another name that is used for the sender address in a
667 .cindex "queue" "definition of"
668 The term &'queue'& is used to refer to the set of messages awaiting delivery
669 because this term is in widespread use in the context of MTAs. However, in
670 Exim's case, the reality is more like a pool than a queue, because there is
671 normally no ordering of waiting messages.
673 .cindex "queue runner" "definition of"
674 The term &'queue runner'& is used to describe a process that scans the queue
675 and attempts to deliver those messages whose retry times have come. This term
676 is used by other MTAs and also relates to the command &%runq%&, but in Exim
677 the waiting messages are normally processed in an unpredictable order.
679 .cindex "spool directory" "definition of"
680 The term &'spool directory'& is used for a directory in which Exim keeps the
681 messages in its queue &-- that is, those that it is in the process of
682 delivering. This should not be confused with the directory in which local
683 mailboxes are stored, which is called a &"spool directory"& by some people. In
684 the Exim documentation, &"spool"& is always used in the first sense.
691 . ////////////////////////////////////////////////////////////////////////////
692 . ////////////////////////////////////////////////////////////////////////////
694 .chapter "Incorporated code" "CHID2"
695 .cindex "incorporated code"
696 .cindex "regular expressions" "library"
699 A number of pieces of external code are included in the Exim distribution.
702 Regular expressions are supported in the main Exim program and in the
703 Exim monitor using the freely-distributable PCRE2 library, copyright
704 © University of Cambridge. The source to PCRE2 is not longer shipped with
705 Exim, so you will need to use the version of PCRE2 shipped with your system,
706 or obtain and install the full version of the library from
707 &url(https://github.com/PhilipHazel/pcre2/releases).
709 .cindex "cdb" "acknowledgment"
710 Support for the cdb (Constant DataBase) lookup method is provided by code
711 contributed by Nigel Metheringham of (at the time he contributed it) Planet
712 Online Ltd. The implementation is completely contained within the code of Exim.
713 It does not link against an external cdb library. The code contains the
714 following statements:
717 Copyright © 1998 Nigel Metheringham, Planet Online Ltd
719 This program is free software; you can redistribute it and/or modify it under
720 the terms of the GNU General Public License as published by the Free Software
721 Foundation; either version 2 of the License, or (at your option) any later
723 This code implements Dan Bernstein's Constant DataBase (cdb) spec. Information,
724 the spec and sample code for cdb can be obtained from
725 &url(https://cr.yp.to/cdb.html). This implementation borrows
726 some code from Dan Bernstein's implementation (which has no license
727 restrictions applied to it).
730 .cindex "SPA authentication"
731 .cindex "Samba project"
732 .cindex "Microsoft Secure Password Authentication"
733 Client support for Microsoft's &'Secure Password Authentication'& is provided
734 by code contributed by Marc Prud'hommeaux. Server support was contributed by
735 Tom Kistner. This includes code taken from the Samba project, which is released
739 .cindex "&'pwcheck'& daemon"
740 .cindex "&'pwauthd'& daemon"
741 Support for calling the Cyrus &'pwcheck'& and &'saslauthd'& daemons is provided
742 by code taken from the Cyrus-SASL library and adapted by Alexander S.
743 Sabourenkov. The permission notice appears below, in accordance with the
744 conditions expressed therein.
747 Copyright © 2001 Carnegie Mellon University. All rights reserved.
749 Redistribution and use in source and binary forms, with or without
750 modification, are permitted provided that the following conditions
754 Redistributions of source code must retain the above copyright
755 notice, this list of conditions and the following disclaimer.
757 Redistributions in binary form must reproduce the above copyright
758 notice, this list of conditions and the following disclaimer in
759 the documentation and/or other materials provided with the
762 The name &"Carnegie Mellon University"& must not be used to
763 endorse or promote products derived from this software without
764 prior written permission. For permission or any other legal
765 details, please contact
767 Office of Technology Transfer
768 Carnegie Mellon University
770 Pittsburgh, PA 15213-3890
771 (412) 268-4387, fax: (412) 268-7395
772 tech-transfer@andrew.cmu.edu
775 Redistributions of any form whatsoever must retain the following
778 &"This product includes software developed by Computing Services
779 at Carnegie Mellon University (&url(https://www.cmu.edu/computing/)."&
781 CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
782 THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
783 AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
784 FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
785 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
786 AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
787 OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
792 .cindex "Exim monitor" "acknowledgment"
795 The Exim Monitor program, which is an X-Window application, includes
796 modified versions of the Athena StripChart and TextPop widgets.
797 This code is copyright by DEC and MIT, and their permission notice appears
798 below, in accordance with the conditions expressed therein.
801 Copyright 1987, 1988 by Digital Equipment Corporation, Maynard, Massachusetts,
802 and the Massachusetts Institute of Technology, Cambridge, Massachusetts.
806 Permission to use, copy, modify, and distribute this software and its
807 documentation for any purpose and without fee is hereby granted,
808 provided that the above copyright notice appear in all copies and that
809 both that copyright notice and this permission notice appear in
810 supporting documentation, and that the names of Digital or MIT not be
811 used in advertising or publicity pertaining to distribution of the
812 software without specific, written prior permission.
814 DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
815 ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
816 DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
817 ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
818 WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
819 ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
824 .cindex "opendmarc" "acknowledgment"
825 The DMARC implementation uses the OpenDMARC library which is Copyrighted by
826 The Trusted Domain Project. Portions of Exim source which use OpenDMARC
827 derived code are indicated in the respective source files. The full OpenDMARC
828 license is provided in the LICENSE.opendmarc file contained in the distributed
832 Many people have contributed code fragments, some large, some small, that were
833 not covered by any specific license requirements. It is assumed that the
834 contributors are happy to see their code incorporated into Exim under the GPL.
841 . ////////////////////////////////////////////////////////////////////////////
842 . ////////////////////////////////////////////////////////////////////////////
844 .chapter "How Exim receives and delivers mail" "CHID11" &&&
845 "Receiving and delivering mail"
848 .section "Overall philosophy" "SECID10"
849 .cindex "design philosophy"
850 Exim is designed to work efficiently on systems that are permanently connected
851 to the Internet and are handling a general mix of mail. In such circumstances,
852 most messages can be delivered immediately. Consequently, Exim does not
853 maintain independent queues of messages for specific domains or hosts, though
854 it does try to send several messages in a single SMTP connection after a host
855 has been down, and it also maintains per-host retry information.
858 .section "Policy control" "SECID11"
859 .cindex "policy control" "overview"
860 Policy controls are now an important feature of MTAs that are connected to the
861 Internet. Perhaps their most important job is to stop MTAs from being abused as
862 &"open relays"& by misguided individuals who send out vast amounts of
863 unsolicited junk and want to disguise its source. Exim provides flexible
864 facilities for specifying policy controls on incoming mail:
867 .cindex "&ACL;" "introduction"
868 Exim 4 (unlike previous versions of Exim) implements policy controls on
869 incoming mail by means of &'Access Control Lists'& (ACLs). Each list is a
870 series of statements that may either grant or deny access. ACLs can be used at
871 several places in the SMTP dialogue while receiving a message from a remote
872 host. However, the most common places are after each RCPT command, and at the
873 very end of the message. The sysadmin can specify conditions for accepting or
874 rejecting individual recipients or the entire message, respectively, at these
875 two points (see chapter &<<CHAPACL>>&). Denial of access results in an SMTP
878 An ACL is also available for locally generated, non-SMTP messages. In this
879 case, the only available actions are to accept or deny the entire message.
881 When Exim is compiled with the content-scanning extension, facilities are
882 provided in the ACL mechanism for passing the message to external virus and/or
883 spam scanning software. The result of such a scan is passed back to the ACL,
884 which can then use it to decide what to do with the message.
886 When a message has been received, either from a remote host or from the local
887 host, but before the final acknowledgment has been sent, a locally supplied C
888 function called &[local_scan()]& can be run to inspect the message and decide
889 whether to accept it or not (see chapter &<<CHAPlocalscan>>&). If the message
890 is accepted, the list of recipients can be modified by the function.
892 Using the &[local_scan()]& mechanism is another way of calling external scanner
893 software. The &%SA-Exim%& add-on package works this way. It does not require
894 Exim to be compiled with the content-scanning extension.
896 After a message has been accepted, a further checking mechanism is available in
897 the form of the &'system filter'& (see chapter &<<CHAPsystemfilter>>&). This
898 runs at the start of every delivery process.
903 .section "User filters" "SECID12"
904 .cindex "filter" "introduction"
905 .cindex "Sieve filter"
906 In a conventional Exim configuration, users are able to run private filters by
907 setting up appropriate &_.forward_& files in their home directories. See
908 chapter &<<CHAPredirect>>& (about the &(redirect)& router) for the
909 configuration needed to support this, and the separate document entitled
910 &'Exim's interfaces to mail filtering'& for user details. Two different kinds
911 of filtering are available:
914 Sieve filters are written in the standard filtering language that is defined
917 Exim filters are written in a syntax that is unique to Exim, but which is more
918 powerful than Sieve, which it pre-dates.
921 User filters are run as part of the routing process, described below.
925 .section "Message identification" "SECTmessiden"
926 .cindex "message ids" "details of format"
927 .cindex "format" "of message id"
928 .cindex "id of message"
933 Every message handled by Exim is given a &'message id'& which is sixteen
934 characters long. It is divided into three parts, separated by hyphens, for
935 example &`16VDhn-0001bo-D3`&. Each part is a sequence of letters and digits,
936 normally encoding numbers in base 62. However, in the Darwin operating
937 system (Mac OS X) and when Exim is compiled to run under Cygwin, base 36
938 (avoiding the use of lower case letters) is used instead, because the message
939 id is used to construct filenames, and the names of files in those systems are
940 not always case-sensitive.
942 .cindex "pid (process id)" "re-use of"
943 The detail of the contents of the message id have changed as Exim has evolved.
944 Earlier versions relied on the operating system not re-using a process id (pid)
945 within one second. On modern operating systems, this assumption can no longer
946 be made, so the algorithm had to be changed. To retain backward compatibility,
947 the format of the message id was retained, which is why the following rules are
951 The first six characters of the message id are the time at which the message
952 started to be received, to a granularity of one second. That is, this field
953 contains the number of seconds since the start of the epoch (the normal Unix
954 way of representing the date and time of day).
956 After the first hyphen, the next six characters are the id of the process that
957 received the message.
959 There are two different possibilities for the final two characters:
961 .oindex "&%localhost_number%&"
962 If &%localhost_number%& is not set, this value is the fractional part of the
963 time of reception, normally in units of 1/2000 of a second, but for systems
964 that must use base 36 instead of base 62 (because of case-insensitive file
965 systems), the units are 1/1000 of a second.
967 If &%localhost_number%& is set, it is multiplied by 200 (100) and added to
968 the fractional part of the time, which in this case is in units of 1/200
973 After a message has been received, Exim waits for the clock to tick at the
974 appropriate resolution before proceeding, so that if another message is
975 received by the same process, or by another process with the same (re-used)
976 pid, it is guaranteed that the time will be different. In most cases, the clock
977 will already have ticked while the message was being received.
980 .section "Receiving mail" "SECID13"
981 .cindex "receiving mail"
982 .cindex "message" "reception"
983 The only way Exim can receive mail from another host is using SMTP over
984 TCP/IP, in which case the sender and recipient addresses are transferred using
985 SMTP commands. However, from a locally running process (such as a user's MUA),
986 there are several possibilities:
989 If the process runs Exim with the &%-bm%& option, the message is read
990 non-interactively (usually via a pipe), with the recipients taken from the
991 command line, or from the body of the message if &%-t%& is also used.
993 If the process runs Exim with the &%-bS%& option, the message is also read
994 non-interactively, but in this case the recipients are listed at the start of
995 the message in a series of SMTP RCPT commands, terminated by a DATA
996 command. This is called &"batch SMTP"& format,
997 but it isn't really SMTP. The SMTP commands are just another way of passing
998 envelope addresses in a non-interactive submission.
1000 If the process runs Exim with the &%-bs%& option, the message is read
1001 interactively, using the SMTP protocol. A two-way pipe is normally used for
1002 passing data between the local process and the Exim process.
1003 This is &"real"& SMTP and is handled in the same way as SMTP over TCP/IP. For
1004 example, the ACLs for SMTP commands are used for this form of submission.
1006 A local process may also make a TCP/IP call to the host's loopback address
1007 (127.0.0.1) or any other of its IP addresses. When receiving messages, Exim
1008 does not treat the loopback address specially. It treats all such connections
1009 in the same way as connections from other hosts.
1013 .cindex "message sender, constructed by Exim"
1014 .cindex "sender" "constructed by Exim"
1015 In the three cases that do not involve TCP/IP, the sender address is
1016 constructed from the login name of the user that called Exim and a default
1017 qualification domain (which can be set by the &%qualify_domain%& configuration
1018 option). For local or batch SMTP, a sender address that is passed using the
1019 SMTP MAIL command is ignored. However, the system administrator may allow
1020 certain users (&"trusted users"&) to specify a different sender addresses
1021 unconditionally, or all users to specify certain forms of different sender
1022 address. The &%-f%& option or the SMTP MAIL command is used to specify these
1023 different addresses. See section &<<SECTtrustedadmin>>& for details of trusted
1024 users, and the &%untrusted_set_sender%& option for a way of allowing untrusted
1025 users to change sender addresses.
1027 Messages received by either of the non-interactive mechanisms are subject to
1028 checking by the non-SMTP ACL if one is defined. Messages received using SMTP
1029 (either over TCP/IP or interacting with a local process) can be checked by a
1030 number of ACLs that operate at different times during the SMTP session. Either
1031 individual recipients or the entire message can be rejected if local policy
1032 requirements are not met. The &[local_scan()]& function (see chapter
1033 &<<CHAPlocalscan>>&) is run for all incoming messages.
1035 Exim can be configured not to start a delivery process when a message is
1036 received; this can be unconditional, or depend on the number of incoming SMTP
1037 connections or the system load. In these situations, new messages wait on the
1038 queue until a queue runner process picks them up. However, in standard
1039 configurations under normal conditions, delivery is started as soon as a
1040 message is received.
1046 .section "Handling an incoming message" "SECID14"
1047 .cindex "spool directory" "files that hold a message"
1048 .cindex "file" "how a message is held"
1049 When Exim accepts a message, it writes two files in its spool directory. The
1050 first contains the envelope information, the current status of the message, and
1051 the header lines, and the second contains the body of the message. The names of
1052 the two spool files consist of the message id, followed by &`-H`& for the
1053 file containing the envelope and header, and &`-D`& for the data file.
1055 .cindex "spool directory" "&_input_& sub-directory"
1056 By default, all these message files are held in a single directory called
1057 &_input_& inside the general Exim spool directory. Some operating systems do
1058 not perform very well if the number of files in a directory gets large; to
1059 improve performance in such cases, the &%split_spool_directory%& option can be
1060 used. This causes Exim to split up the input files into 62 sub-directories
1061 whose names are single letters or digits. When this is done, the queue is
1062 processed one sub-directory at a time instead of all at once, which can improve
1063 overall performance even when there are not enough files in each directory to
1064 affect file system performance.
1066 The envelope information consists of the address of the message's sender and
1067 the addresses of the recipients. This information is entirely separate from
1068 any addresses contained in the header lines. The status of the message includes
1069 a list of recipients who have already received the message. The format of the
1070 first spool file is described in chapter &<<CHAPspool>>&.
1072 .cindex "rewriting" "addresses"
1073 Address rewriting that is specified in the rewrite section of the configuration
1074 (see chapter &<<CHAPrewrite>>&) is done once and for all on incoming addresses,
1075 both in the header lines and the envelope, at the time the message is accepted.
1076 If during the course of delivery additional addresses are generated (for
1077 example, via aliasing), these new addresses are rewritten as soon as they are
1078 generated. At the time a message is actually delivered (transported) further
1079 rewriting can take place; because this is a transport option, it can be
1080 different for different forms of delivery. It is also possible to specify the
1081 addition or removal of certain header lines at the time the message is
1082 delivered (see chapters &<<CHAProutergeneric>>& and
1083 &<<CHAPtransportgeneric>>&).
1087 .section "Life of a message" "SECID15"
1088 .cindex "message" "life of"
1089 .cindex "message" "frozen"
1090 A message remains in the spool directory until it is completely delivered to
1091 its recipients or to an error address, or until it is deleted by an
1092 administrator or by the user who originally created it. In cases when delivery
1093 cannot proceed &-- for example when a message can neither be delivered to its
1094 recipients nor returned to its sender, the message is marked &"frozen"& on the
1095 spool, and no more deliveries are attempted.
1097 .cindex "frozen messages" "thawing"
1098 .cindex "message" "thawing frozen"
1099 An administrator can &"thaw"& such messages when the problem has been
1100 corrected, and can also freeze individual messages by hand if necessary. In
1101 addition, an administrator can force a delivery error, causing a bounce message
1104 .oindex "&%timeout_frozen_after%&"
1105 .oindex "&%ignore_bounce_errors_after%&"
1106 There are options called &%ignore_bounce_errors_after%& and
1107 &%timeout_frozen_after%&, which discard frozen messages after a certain time.
1108 The first applies only to frozen bounces, the second to all frozen messages.
1110 .cindex "message" "log file for"
1111 .cindex "log" "file for each message"
1112 While Exim is working on a message, it writes information about each delivery
1113 attempt to its main log file. This includes successful, unsuccessful, and
1114 delayed deliveries for each recipient (see chapter &<<CHAPlog>>&). The log
1115 lines are also written to a separate &'message log'& file for each message.
1116 These logs are solely for the benefit of the administrator and are normally
1117 deleted along with the spool files when processing of a message is complete.
1118 The use of individual message logs can be disabled by setting
1119 &%no_message_logs%&; this might give an improvement in performance on very busy
1122 .cindex "journal file"
1123 .cindex "file" "journal"
1124 All the information Exim itself needs to set up a delivery is kept in the first
1125 spool file, along with the header lines. When a successful delivery occurs, the
1126 address is immediately written at the end of a journal file, whose name is the
1127 message id followed by &`-J`&. At the end of a delivery run, if there are some
1128 addresses left to be tried again later, the first spool file (the &`-H`& file)
1129 is updated to indicate which these are, and the journal file is then deleted.
1130 Updating the spool file is done by writing a new file and renaming it, to
1131 minimize the possibility of data loss.
1133 Should the system or Exim crash after a successful delivery but before
1134 the spool file has been updated, the journal is left lying around. The next
1135 time Exim attempts to deliver the message, it reads the journal file and
1136 updates the spool file before proceeding. This minimizes the chances of double
1137 deliveries caused by crashes.
1141 .section "Processing an address for delivery" "SECTprocaddress"
1142 .cindex "drivers" "definition of"
1143 .cindex "router" "definition of"
1144 .cindex "transport" "definition of"
1145 The main delivery processing elements of Exim are called &'routers'& and
1146 &'transports'&, and collectively these are known as &'drivers'&. Code for a
1147 number of them is provided in the source distribution, and compile-time options
1148 specify which ones are included in the binary. Runtime options specify which
1149 ones are actually used for delivering messages.
1151 .cindex "drivers" "instance definition"
1152 Each driver that is specified in the runtime configuration is an &'instance'&
1153 of that particular driver type. Multiple instances are allowed; for example,
1154 you can set up several different &(smtp)& transports, each with different
1155 option values that might specify different ports or different timeouts. Each
1156 instance has its own identifying name. In what follows we will normally use the
1157 instance name when discussing one particular instance (that is, one specific
1158 configuration of the driver), and the generic driver name when discussing
1159 the driver's features in general.
1161 A &'router'& is a driver that operates on an address, either determining how
1162 its delivery should happen, by assigning it to a specific transport, or
1163 converting the address into one or more new addresses (for example, via an
1164 alias file). A router may also explicitly choose to fail an address, causing it
1167 A &'transport'& is a driver that transmits a copy of the message from Exim's
1168 spool to some destination. There are two kinds of transport: for a &'local'&
1169 transport, the destination is a file or a pipe on the local host, whereas for a
1170 &'remote'& transport the destination is some other host. A message is passed
1171 to a specific transport as a result of successful routing. If a message has
1172 several recipients, it may be passed to a number of different transports.
1174 .cindex "preconditions" "definition of"
1175 An address is processed by passing it to each configured router instance in
1176 turn, subject to certain preconditions, until a router accepts the address or
1177 specifies that it should be bounced. We will describe this process in more
1178 detail shortly. First, as a simple example, we consider how each recipient
1179 address in a message is processed in a small configuration of three routers.
1181 To make this a more concrete example, it is described in terms of some actual
1182 routers, but remember, this is only an example. You can configure Exim's
1183 routers in many different ways, and there may be any number of routers in a
1186 The first router that is specified in a configuration is often one that handles
1187 addresses in domains that are not recognized specifically by the local host.
1188 Typically these are addresses for arbitrary domains on the Internet. A precondition
1189 is set up which looks for the special domains known to the host (for example,
1190 its own domain name), and the router is run for addresses that do &'not'&
1191 match. Typically, this is a router that looks up domains in the DNS in order to
1192 find the hosts to which this address routes. If it succeeds, the address is
1193 assigned to a suitable SMTP transport; if it does not succeed, the router is
1194 configured to fail the address.
1196 The second router is reached only when the domain is recognized as one that
1197 &"belongs"& to the local host. This router does redirection &-- also known as
1198 aliasing and forwarding. When it generates one or more new addresses from the
1199 original, each of them is routed independently from the start. Otherwise, the
1200 router may cause an address to fail, or it may simply decline to handle the
1201 address, in which case the address is passed to the next router.
1203 The final router in many configurations is one that checks to see if the
1204 address belongs to a local mailbox. The precondition may involve a check to
1205 see if the local part is the name of a login account, or it may look up the
1206 local part in a file or a database. If its preconditions are not met, or if
1207 the router declines, we have reached the end of the routers. When this happens,
1208 the address is bounced.
1212 .section "Processing an address for verification" "SECID16"
1213 .cindex "router" "for verification"
1214 .cindex "verifying address" "overview"
1215 As well as being used to decide how to deliver to an address, Exim's routers
1216 are also used for &'address verification'&. Verification can be requested as
1217 one of the checks to be performed in an ACL for incoming messages, on both
1218 sender and recipient addresses, and it can be tested using the &%-bv%& and
1219 &%-bvs%& command line options.
1221 When an address is being verified, the routers are run in &"verify mode"&. This
1222 does not affect the way the routers work, but it is a state that can be
1223 detected. By this means, a router can be skipped or made to behave differently
1224 when verifying. A common example is a configuration in which the first router
1225 sends all messages to a message-scanning program unless they have been
1226 previously scanned. Thus, the first router accepts all addresses without any
1227 checking, making it useless for verifying. Normally, the &%no_verify%& option
1228 would be set for such a router, causing it to be skipped in verify mode.
1233 .section "Running an individual router" "SECTrunindrou"
1234 .cindex "router" "running details"
1235 .cindex "preconditions" "checking"
1236 .cindex "router" "result of running"
1237 As explained in the example above, a number of preconditions are checked before
1238 running a router. If any are not met, the router is skipped, and the address is
1239 passed to the next router. When all the preconditions on a router &'are'& met,
1240 the router is run. What happens next depends on the outcome, which is one of
1244 &'accept'&: The router accepts the address, and either assigns it to a
1245 transport or generates one or more &"child"& addresses. Processing the
1246 original address ceases
1247 .oindex "&%unseen%&"
1248 unless the &%unseen%& option is set on the router. This option
1249 can be used to set up multiple deliveries with different routing (for example,
1250 for keeping archive copies of messages). When &%unseen%& is set, the address is
1251 passed to the next router. Normally, however, an &'accept'& return marks the
1254 Any child addresses generated by the router are processed independently,
1255 starting with the first router by default. It is possible to change this by
1256 setting the &%redirect_router%& option to specify which router to start at for
1257 child addresses. Unlike &%pass_router%& (see below) the router specified by
1258 &%redirect_router%& may be anywhere in the router configuration.
1260 &'pass'&: The router recognizes the address, but cannot handle it itself. It
1261 requests that the address be passed to another router. By default, the address
1262 is passed to the next router, but this can be changed by setting the
1263 &%pass_router%& option. However, (unlike &%redirect_router%&) the named router
1264 must be below the current router (to avoid loops).
1266 &'decline'&: The router declines to accept the address because it does not
1267 recognize it at all. By default, the address is passed to the next router, but
1268 this can be prevented by setting the &%no_more%& option. When &%no_more%& is
1269 set, all the remaining routers are skipped. In effect, &%no_more%& converts
1270 &'decline'& into &'fail'&.
1272 &'fail'&: The router determines that the address should fail, and queues it for
1273 the generation of a bounce message. There is no further processing of the
1274 original address unless &%unseen%& is set on the router.
1276 &'defer'&: The router cannot handle the address at the present time. (A
1277 database may be offline, or a DNS lookup may have timed out.) No further
1278 processing of the address happens in this delivery attempt. It is tried again
1279 next time the message is considered for delivery.
1281 &'error'&: There is some error in the router (for example, a syntax error in
1282 its configuration). The action is as for defer.
1285 If an address reaches the end of the routers without having been accepted by
1286 any of them, it is bounced as unrouteable. The default error message in this
1287 situation is &"unrouteable address"&, but you can set your own message by
1288 making use of the &%cannot_route_message%& option. This can be set for any
1289 router; the value from the last router that &"saw"& the address is used.
1291 Sometimes while routing you want to fail a delivery when some conditions are
1292 met but others are not, instead of passing the address on for further routing.
1293 You can do this by having a second router that explicitly fails the delivery
1294 when the relevant conditions are met. The &(redirect)& router has a &"fail"&
1295 facility for this purpose.
1298 .section "Duplicate addresses" "SECID17"
1299 .cindex "case of local parts"
1300 .cindex "address duplicate, discarding"
1301 .cindex "duplicate addresses"
1302 Once routing is complete, Exim scans the addresses that are assigned to local
1303 and remote transports and discards any duplicates that it finds. During this
1304 check, local parts are treated case-sensitively. This happens only when
1305 actually delivering a message; when testing routers with &%-bt%&, all the
1306 routed addresses are shown.
1310 .section "Router preconditions" "SECTrouprecon"
1311 .cindex "router" "preconditions, order of processing"
1312 .cindex "preconditions" "order of processing"
1313 The preconditions that are tested for each router are listed below, in the
1314 order in which they are tested. The individual configuration options are
1315 described in more detail in chapter &<<CHAProutergeneric>>&.
1318 .cindex affix "router precondition"
1319 The &%local_part_prefix%& and &%local_part_suffix%& options can specify that
1320 the local parts handled by the router may or must have certain prefixes and/or
1321 suffixes. If a mandatory affix (prefix or suffix) is not present, the router is
1322 skipped. These conditions are tested first. When an affix is present, it is
1323 removed from the local part before further processing, including the evaluation
1324 of any other conditions.
1326 Routers can be designated for use only when not verifying an address, that is,
1327 only when routing it for delivery (or testing its delivery routing). If the
1328 &%verify%& option is set false, the router is skipped when Exim is verifying an
1330 Setting the &%verify%& option actually sets two options, &%verify_sender%& and
1331 &%verify_recipient%&, which independently control the use of the router for
1332 sender and recipient verification. You can set these options directly if
1333 you want a router to be used for only one type of verification.
1334 Note that cutthrough delivery is classed as a recipient verification for this purpose.
1336 If the &%address_test%& option is set false, the router is skipped when Exim is
1337 run with the &%-bt%& option to test an address routing. This can be helpful
1338 when the first router sends all new messages to a scanner of some sort; it
1339 makes it possible to use &%-bt%& to test subsequent delivery routing without
1340 having to simulate the effect of the scanner.
1342 Routers can be designated for use only when verifying an address, as
1343 opposed to routing it for delivery. The &%verify_only%& option controls this.
1344 Again, cutthrough delivery counts as a verification.
1346 Individual routers can be explicitly skipped when running the routers to
1347 check an address given in the SMTP EXPN command (see the &%expn%& option).
1350 If the &%domains%& option is set, the domain of the address must be in the set
1351 of domains that it defines.
1352 .cindex "tainted data" "de-tainting"
1353 .cindex "de-tainting" "using router domains option"
1354 A match verifies the variable &$domain$& (which carries tainted data)
1355 and assigns an untainted value to the &$domain_data$& variable.
1356 Such an untainted value is often needed in the transport.
1357 For specifics of the matching operation and the resulting untainted value,
1358 refer to section &<<SECTdomainlist>>&.
1360 When an untainted value is wanted, use this option
1361 rather than the generic &%condition%& option.
1364 .vindex "&$local_part_prefix$&"
1365 .vindex "&$local_part_prefix_v$&"
1366 .vindex "&$local_part$&"
1367 .vindex "&$local_part_suffix$&"
1368 .vindex "&$local_part_suffix_v$&"
1369 .cindex affix "router precondition"
1370 If the &%local_parts%& option is set, the local part of the address must be in
1371 the set of local parts that it defines.
1372 A match verifies the variable &$local_part$& (which carries tainted data)
1373 and assigns an untainted value to the &$local_part_data$& variable.
1374 Such an untainted value is often needed in the transport.
1375 For specifics of the matching operation and the resulting untainted value,
1376 refer to section &<<SECTlocparlis>>&.
1378 When an untainted value is wanted, use this option
1379 rather than the generic &%condition%& option.
1381 If &%local_part_prefix%& or
1382 &%local_part_suffix%& is in use, the prefix or suffix is removed from the local
1383 part before this check. If you want to do precondition tests on local parts
1384 that include affixes, you can do so by using a &%condition%& option (see below)
1385 that uses the variables &$local_part$&, &$local_part_prefix$&,
1386 &$local_part_prefix_v$&, &$local_part_suffix$&
1387 and &$local_part_suffix_v$& as necessary.
1390 .vindex "&$local_user_uid$&"
1391 .vindex "&$local_user_gid$&"
1393 If the &%check_local_user%& option is set, the local part must be the name of
1394 an account on the local host. If this check succeeds, the uid and gid of the
1395 local user are placed in &$local_user_uid$& and &$local_user_gid$& and the
1396 user's home directory is placed in &$home$&; these values can be used in the
1397 remaining preconditions.
1400 If the &%router_home_directory%& option is set, it is expanded at this point,
1401 because it overrides the value of &$home$&. If this expansion were left till
1402 later, the value of &$home$& as set by &%check_local_user%& would be used in
1403 subsequent tests. Having two different values of &$home$& in the same router
1404 could lead to confusion.
1407 If the &%senders%& option is set, the envelope sender address must be in the
1408 set of addresses that it defines.
1411 If the &%require_files%& option is set, the existence or non-existence of
1412 specified files is tested.
1415 .cindex "customizing" "precondition"
1416 If the &%condition%& option is set, it is evaluated and tested. This option
1417 uses an expanded string to allow you to set up your own custom preconditions.
1418 Expanded strings are described in chapter &<<CHAPexpand>>&.
1420 Note that while using
1421 this option for address matching technically works,
1422 it does not set any de-tainted values.
1423 Such values are often needed, either for router-specific options or
1424 for transport options.
1425 Using the &%domains%& and &%local_parts%& options is usually the most
1426 convenient way to obtain them.
1430 Note that &%require_files%& comes near the end of the list, so you cannot use
1431 it to check for the existence of a file in which to lookup up a domain, local
1432 part, or sender. However, as these options are all expanded, you can use the
1433 &%exists%& expansion condition to make such tests within each condition. The
1434 &%require_files%& option is intended for checking files that the router may be
1435 going to use internally, or which are needed by a specific transport (for
1436 example, &_.procmailrc_&).
1440 .section "Delivery in detail" "SECID18"
1441 .cindex "delivery" "in detail"
1442 When a message is to be delivered, the sequence of events is as follows:
1445 If a system-wide filter file is specified, the message is passed to it. The
1446 filter may add recipients to the message, replace the recipients, discard the
1447 message, cause a new message to be generated, or cause the message delivery to
1448 fail. The format of the system filter file is the same as for Exim user filter
1449 files, described in the separate document entitled &'Exim's interfaces to mail
1451 .cindex "Sieve filter" "not available for system filter"
1452 (&*Note*&: Sieve cannot be used for system filter files.)
1454 Some additional features are available in system filters &-- see chapter
1455 &<<CHAPsystemfilter>>& for details. Note that a message is passed to the system
1456 filter only once per delivery attempt, however many recipients it has. However,
1457 if there are several delivery attempts because one or more addresses could not
1458 be immediately delivered, the system filter is run each time. The filter
1459 condition &%first_delivery%& can be used to detect the first run of the system
1462 Each recipient address is offered to each configured router, in turn, subject to
1463 its preconditions, until one is able to handle it. If no router can handle the
1464 address, that is, if they all decline, the address is failed. Because routers
1465 can be targeted at particular domains, several locally handled domains can be
1466 processed entirely independently of each other.
1468 .cindex "routing" "loops in"
1469 .cindex "loop" "while routing"
1470 A router that accepts an address may assign it to a local or a remote
1471 transport. However, the transport is not run at this time. Instead, the address
1472 is placed on a list for the particular transport, which will be run later.
1473 Alternatively, the router may generate one or more new addresses (typically
1474 from alias, forward, or filter files). New addresses are fed back into this
1475 process from the top, but in order to avoid loops, a router ignores any address
1476 which has an identically-named ancestor that was processed by itself.
1478 When all the routing has been done, addresses that have been successfully
1479 handled are passed to their assigned transports. When local transports are
1480 doing real local deliveries, they handle only one address at a time, but if a
1481 local transport is being used as a pseudo-remote transport (for example, to
1482 collect batched SMTP messages for transmission by some other means) multiple
1483 addresses can be handled. Remote transports can always handle more than one
1484 address at a time, but can be configured not to do so, or to restrict multiple
1485 addresses to the same domain.
1487 Each local delivery to a file or a pipe runs in a separate process under a
1488 non-privileged uid, and these deliveries are run one at a time. Remote
1489 deliveries also run in separate processes, normally under a uid that is private
1490 to Exim (&"the Exim user"&), but in this case, several remote deliveries can be
1491 run in parallel. The maximum number of simultaneous remote deliveries for any
1492 one message is set by the &%remote_max_parallel%& option.
1493 The order in which deliveries are done is not defined, except that all local
1494 deliveries happen before any remote deliveries.
1496 .cindex "queue runner"
1497 When it encounters a local delivery during a queue run, Exim checks its retry
1498 database to see if there has been a previous temporary delivery failure for the
1499 address before running the local transport. If there was a previous failure,
1500 Exim does not attempt a new delivery until the retry time for the address is
1501 reached. However, this happens only for delivery attempts that are part of a
1502 queue run. Local deliveries are always attempted when delivery immediately
1503 follows message reception, even if retry times are set for them. This makes for
1504 better behaviour if one particular message is causing problems (for example,
1505 causing quota overflow, or provoking an error in a filter file).
1507 .cindex "delivery" "retry in remote transports"
1508 Remote transports do their own retry handling, since an address may be
1509 deliverable to one of a number of hosts, each of which may have a different
1510 retry time. If there have been previous temporary failures and no host has
1511 reached its retry time, no delivery is attempted, whether in a queue run or
1512 not. See chapter &<<CHAPretry>>& for details of retry strategies.
1514 If there were any permanent errors, a bounce message is returned to an
1515 appropriate address (the sender in the common case), with details of the error
1516 for each failing address. Exim can be configured to send copies of bounce
1517 messages to other addresses.
1519 .cindex "delivery" "deferral"
1520 If one or more addresses suffered a temporary failure, the message is left on
1521 the queue, to be tried again later. Delivery of these addresses is said to be
1524 When all the recipient addresses have either been delivered or bounced,
1525 handling of the message is complete. The spool files and message log are
1526 deleted, though the message log can optionally be preserved if required.
1532 .section "Retry mechanism" "SECID19"
1533 .cindex "delivery" "retry mechanism"
1534 .cindex "retry" "description of mechanism"
1535 .cindex "queue runner"
1536 Exim's mechanism for retrying messages that fail to get delivered at the first
1537 attempt is the queue runner process. You must either run an Exim daemon that
1538 uses the &%-q%& option with a time interval to start queue runners at regular
1539 intervals or use some other means (such as &'cron'&) to start them. If you do
1540 not arrange for queue runners to be run, messages that fail temporarily at the
1541 first attempt will remain in your queue forever. A queue runner process works
1542 its way through the queue, one message at a time, trying each delivery that has
1543 passed its retry time.
1544 You can run several queue runners at once.
1546 Exim uses a set of configured rules to determine when next to retry the failing
1547 address (see chapter &<<CHAPretry>>&). These rules also specify when Exim
1548 should give up trying to deliver to the address, at which point it generates a
1549 bounce message. If no retry rules are set for a particular host, address, and
1550 error combination, no retries are attempted, and temporary errors are treated
1555 .section "Temporary delivery failure" "SECID20"
1556 .cindex "delivery" "temporary failure"
1557 There are many reasons why a message may not be immediately deliverable to a
1558 particular address. Failure to connect to a remote machine (because it, or the
1559 connection to it, is down) is one of the most common. Temporary failures may be
1560 detected during routing as well as during the transport stage of delivery.
1561 Local deliveries may be delayed if NFS files are unavailable, or if a mailbox
1562 is on a file system where the user is over quota. Exim can be configured to
1563 impose its own quotas on local mailboxes; where system quotas are set they will
1566 If a host is unreachable for a period of time, a number of messages may be
1567 waiting for it by the time it recovers, and sending them in a single SMTP
1568 connection is clearly beneficial. Whenever a delivery to a remote host is
1570 .cindex "hints database" "deferred deliveries"
1571 Exim makes a note in its hints database, and whenever a successful
1572 SMTP delivery has happened, it looks to see if any other messages are waiting
1573 for the same host. If any are found, they are sent over the same SMTP
1574 connection, subject to a configuration limit as to the maximum number in any
1579 .section "Permanent delivery failure" "SECID21"
1580 .cindex "delivery" "permanent failure"
1581 .cindex "bounce message" "when generated"
1582 When a message cannot be delivered to some or all of its intended recipients, a
1583 bounce message is generated. Temporary delivery failures turn into permanent
1584 errors when their timeout expires. All the addresses that fail in a given
1585 delivery attempt are listed in a single message. If the original message has
1586 many recipients, it is possible for some addresses to fail in one delivery
1587 attempt and others to fail subsequently, giving rise to more than one bounce
1588 message. The wording of bounce messages can be customized by the administrator.
1589 See chapter &<<CHAPemsgcust>>& for details.
1591 .cindex "&'X-Failed-Recipients:'& header line"
1592 Bounce messages contain an &'X-Failed-Recipients:'& header line that lists the
1593 failed addresses, for the benefit of programs that try to analyse such messages
1596 .cindex "bounce message" "recipient of"
1597 A bounce message is normally sent to the sender of the original message, as
1598 obtained from the message's envelope. For incoming SMTP messages, this is the
1599 address given in the MAIL command. However, when an address is expanded via a
1600 forward or alias file, an alternative address can be specified for delivery
1601 failures of the generated addresses. For a mailing list expansion (see section
1602 &<<SECTmailinglists>>&) it is common to direct bounce messages to the manager
1607 .section "Failures to deliver bounce messages" "SECID22"
1608 .cindex "bounce message" "failure to deliver"
1609 If a bounce message (either locally generated or received from a remote host)
1610 itself suffers a permanent delivery failure, the message is left in the queue,
1611 but it is frozen, awaiting the attention of an administrator. There are options
1612 that can be used to make Exim discard such failed messages, or to keep them
1613 for only a short time (see &%timeout_frozen_after%& and
1614 &%ignore_bounce_errors_after%&).
1620 . ////////////////////////////////////////////////////////////////////////////
1621 . ////////////////////////////////////////////////////////////////////////////
1623 .chapter "Building and installing Exim" "CHID3"
1624 .scindex IIDbuex "building Exim"
1626 .section "Unpacking" "SECID23"
1627 Exim is distributed as a gzipped or bzipped tar file which, when unpacked,
1628 creates a directory with the name of the current release (for example,
1629 &_exim-&version()_&) into which the following files are placed:
1632 .irow &_ACKNOWLEDGMENTS_& "contains some acknowledgments"
1633 .irow &_CHANGES_& "contains a reference to where changes are &&&
1635 .irow &_LICENCE_& "the GNU General Public Licence"
1636 .irow &_Makefile_& "top-level make file"
1637 .irow &_NOTICE_& "conditions for the use of Exim"
1638 .irow &_README_& "list of files, directories and simple build &&&
1642 Other files whose names begin with &_README_& may also be present. The
1643 following subdirectories are created:
1646 .irow &_Local_& "an empty directory for local configuration files"
1647 .irow &_OS_& "OS-specific files"
1648 .irow &_doc_& "documentation files"
1649 .irow &_exim_monitor_& "source files for the Exim monitor"
1650 .irow &_scripts_& "scripts used in the build process"
1651 .irow &_src_& "remaining source files"
1652 .irow &_util_& "independent utilities"
1655 The main utility programs are contained in the &_src_& directory and are built
1656 with the Exim binary. The &_util_& directory contains a few optional scripts
1657 that may be useful to some sites.
1660 .section "Multiple machine architectures and operating systems" "SECID24"
1661 .cindex "building Exim" "multiple OS/architectures"
1662 The building process for Exim is arranged to make it easy to build binaries for
1663 a number of different architectures and operating systems from the same set of
1664 source files. Compilation does not take place in the &_src_& directory.
1665 Instead, a &'build directory'& is created for each architecture and operating
1667 .cindex "symbolic link" "to build directory"
1668 Symbolic links to the sources are installed in this directory, which is where
1669 the actual building takes place. In most cases, Exim can discover the machine
1670 architecture and operating system for itself, but the defaults can be
1671 overridden if necessary.
1672 .cindex compiler requirements
1673 .cindex compiler version
1674 A C99-capable compiler will be required for the build.
1677 .section "PCRE2 library" "SECTpcre"
1678 .cindex "PCRE2 library"
1679 Exim no longer has an embedded regular-expression library as the vast majority of
1680 modern systems include PCRE2 as a system library, although you may need to
1681 install the PCRE2 package or the PCRE2 development package for your operating
1682 system. If your system has a normal PCRE2 installation the Exim build
1683 process will need no further configuration. If the library or the
1684 headers are in an unusual location you will need to either set the PCRE2_LIBS
1685 and INCLUDE directives appropriately,
1686 or set PCRE2_CONFIG=yes to use the installed &(pcre-config)& command.
1687 If your operating system has no
1688 PCRE2 support then you will need to obtain and build the current PCRE2
1689 from &url(https://github.com/PhilipHazel/pcre2/releases).
1690 More information on PCRE2 is available at &url(https://www.pcre.org/).
1692 .section "DBM libraries" "SECTdb"
1693 .cindex "DBM libraries" "discussion of"
1694 .cindex "hints database" "DBM files used for"
1695 Even if you do not use any DBM files in your configuration, Exim still needs a
1696 DBM library in order to operate, because it uses indexed files for its hints
1697 databases. Unfortunately, there are a number of DBM libraries in existence, and
1698 different operating systems often have different ones installed.
1700 .cindex "Solaris" "DBM library for"
1701 .cindex "IRIX, DBM library for"
1702 .cindex "BSD, DBM library for"
1703 .cindex "Linux, DBM library for"
1704 If you are using Solaris, IRIX, one of the modern BSD systems, or a modern
1705 Linux distribution, the DBM configuration should happen automatically, and you
1706 may be able to ignore this section. Otherwise, you may have to learn more than
1707 you would like about DBM libraries from what follows.
1709 .cindex "&'ndbm'& DBM library"
1710 Licensed versions of Unix normally contain a library of DBM functions operating
1711 via the &'ndbm'& interface, and this is what Exim expects by default. Free
1712 versions of Unix seem to vary in what they contain as standard. In particular,
1713 some early versions of Linux have no default DBM library, and different
1714 distributors have chosen to bundle different libraries with their packaged
1715 versions. However, the more recent releases seem to have standardized on the
1716 Berkeley DB library.
1718 Different DBM libraries have different conventions for naming the files they
1719 use. When a program opens a file called &_dbmfile_&, there are several
1723 A traditional &'ndbm'& implementation, such as that supplied as part of
1724 Solaris, operates on two files called &_dbmfile.dir_& and &_dbmfile.pag_&.
1726 .cindex "&'gdbm'& DBM library"
1727 The GNU library, &'gdbm'&, operates on a single file. If used via its &'ndbm'&
1728 compatibility interface it makes two different hard links to it with names
1729 &_dbmfile.dir_& and &_dbmfile.pag_&, but if used via its native interface, the
1730 filename is used unmodified.
1732 .cindex "Berkeley DB library"
1733 The Berkeley DB package, if called via its &'ndbm'& compatibility interface,
1734 operates on a single file called &_dbmfile.db_&, but otherwise looks to the
1735 programmer exactly the same as the traditional &'ndbm'& implementation.
1737 If the Berkeley package is used in its native mode, it operates on a single
1738 file called &_dbmfile_&; the programmer's interface is somewhat different to
1739 the traditional &'ndbm'& interface.
1741 To complicate things further, there are several very different versions of the
1742 Berkeley DB package. Version 1.85 was stable for a very long time, releases
1743 2.&'x'& and 3.&'x'& were current for a while,
1744 but the latest versions when Exim last revamped support were numbered 5.&'x'&.
1745 Maintenance of some of the earlier releases has ceased,
1746 and Exim no longer supports versions before 3.&'x'&.
1747 All versions of Berkeley DB could be obtained from
1748 &url(http://www.sleepycat.com/), which is now a redirect to their new owner's
1749 page with far newer versions listed.
1750 It is probably wise to plan to move your storage configurations away from
1751 Berkeley DB format, as today there are smaller and simpler alternatives more
1752 suited to Exim's usage model.
1754 .cindex "&'tdb'& DBM library"
1755 Yet another DBM library, called &'tdb'&, is available from
1756 &url(https://sourceforge.net/projects/tdb/files/). It has its own interface, and also
1757 operates on a single file.
1761 .cindex "DBM libraries" "configuration for building"
1762 Exim and its utilities can be compiled to use any of these interfaces. In order
1763 to use any version of the Berkeley DB package in native mode, you must set
1764 USE_DB in an appropriate configuration file (typically
1765 &_Local/Makefile_&). For example:
1769 Similarly, for gdbm you set USE_GDBM, and for tdb you set USE_TDB. An
1770 error is diagnosed if you set more than one of these.
1771 You can set USE_NDBM if needed to override an operating system default.
1773 At the lowest level, the build-time configuration sets none of these options,
1774 thereby assuming an interface of type (1). However, some operating system
1775 configuration files (for example, those for the BSD operating systems and
1776 Linux) assume type (4) by setting USE_DB as their default, and the
1777 configuration files for Cygwin set USE_GDBM. Anything you set in
1778 &_Local/Makefile_&, however, overrides these system defaults.
1780 As well as setting USE_DB, USE_GDBM, or USE_TDB, it may also be
1781 necessary to set DBMLIB, to cause inclusion of the appropriate library, as
1782 in one of these lines:
1786 DBMLIB = -lgdbm -lgdbm_compat
1788 The last of those was for a Linux having GDBM provide emulated NDBM facilities.
1789 Settings like that will work if the DBM library is installed in the standard
1790 place. Sometimes it is not, and the library's header file may also not be in
1791 the default path. You may need to set INCLUDE to specify where the header
1792 file is, and to specify the path to the library more fully in DBMLIB, as in
1795 INCLUDE=-I/usr/local/include/db-4.1
1796 DBMLIB=/usr/local/lib/db-4.1/libdb.a
1798 There is further detailed discussion about the various DBM libraries in the
1799 file &_doc/dbm.discuss.txt_& in the Exim distribution.
1803 .section "Pre-building configuration" "SECID25"
1804 .cindex "building Exim" "pre-building configuration"
1805 .cindex "configuration for building Exim"
1806 .cindex "&_Local/Makefile_&"
1807 .cindex "&_src/EDITME_&"
1808 Before building Exim, a local configuration file that specifies options
1809 independent of any operating system has to be created with the name
1810 &_Local/Makefile_&. A template for this file is supplied as the file
1811 &_src/EDITME_&, and it contains full descriptions of all the option settings
1812 therein. These descriptions are therefore not repeated here. If you are
1813 building Exim for the first time, the simplest thing to do is to copy
1814 &_src/EDITME_& to &_Local/Makefile_&, then read it and edit it appropriately.
1816 There are three settings that you must supply, because Exim will not build
1817 without them. They are the location of the runtime configuration file
1818 (CONFIGURE_FILE), the directory in which Exim binaries will be installed
1819 (BIN_DIRECTORY), and the identity of the Exim user (EXIM_USER and
1820 maybe EXIM_GROUP as well). The value of CONFIGURE_FILE can in fact be
1821 a colon-separated list of filenames; Exim uses the first of them that exists.
1823 There are a few other parameters that can be specified either at build time or
1824 at runtime, to enable the same binary to be used on a number of different
1825 machines. However, if the locations of Exim's spool directory and log file
1826 directory (if not within the spool directory) are fixed, it is recommended that
1827 you specify them in &_Local/Makefile_& instead of at runtime, so that errors
1828 detected early in Exim's execution (such as a malformed configuration file) can
1831 .cindex "content scanning" "specifying at build time"
1832 Exim's interfaces for calling virus and spam scanning software directly from
1833 access control lists are not compiled by default. If you want to include these
1834 facilities, you need to set
1836 WITH_CONTENT_SCAN=yes
1838 in your &_Local/Makefile_&. For details of the facilities themselves, see
1839 chapter &<<CHAPexiscan>>&.
1842 .cindex "&_Local/eximon.conf_&"
1843 .cindex "&_exim_monitor/EDITME_&"
1844 If you are going to build the Exim monitor, a similar configuration process is
1845 required. The file &_exim_monitor/EDITME_& must be edited appropriately for
1846 your installation and saved under the name &_Local/eximon.conf_&. If you are
1847 happy with the default settings described in &_exim_monitor/EDITME_&,
1848 &_Local/eximon.conf_& can be empty, but it must exist.
1850 This is all the configuration that is needed in straightforward cases for known
1851 operating systems. However, the building process is set up so that it is easy
1852 to override options that are set by default or by operating-system-specific
1853 configuration files, for example, to change the C compiler, which
1854 defaults to &%gcc%&. See section &<<SECToverride>>& below for details of how to
1859 .section "Support for iconv()" "SECID26"
1860 .cindex "&[iconv()]& support"
1862 The contents of header lines in messages may be encoded according to the rules
1863 described RFC 2047. This makes it possible to transmit characters that are not
1864 in the ASCII character set, and to label them as being in a particular
1865 character set. When Exim is inspecting header lines by means of the &%$h_%&
1866 mechanism, it decodes them, and translates them into a specified character set
1867 (default is set at build time). The translation is possible only if the operating system
1868 supports the &[iconv()]& function.
1870 However, some of the operating systems that supply &[iconv()]& do not support
1871 very many conversions. The GNU &%libiconv%& library (available from
1872 &url(https://www.gnu.org/software/libiconv/)) can be installed on such
1873 systems to remedy this deficiency, as well as on systems that do not supply
1874 &[iconv()]& at all. After installing &%libiconv%&, you should add
1878 to your &_Local/Makefile_& and rebuild Exim.
1882 .section "Including TLS/SSL encryption support" "SECTinctlsssl"
1883 .cindex "TLS" "including support for TLS"
1884 .cindex "encryption" "including support for"
1885 .cindex "OpenSSL" "building Exim with"
1886 .cindex "GnuTLS" "building Exim with"
1887 Exim is usually built to support encrypted SMTP connections, using the STARTTLS
1888 command as per RFC 2487. It can also support clients that expect to
1889 start a TLS session immediately on connection to a non-standard port (see the
1890 &%tls_on_connect_ports%& runtime option and the &%-tls-on-connect%& command
1893 If you want to build Exim with TLS support, you must first install either the
1894 OpenSSL or GnuTLS library. There is no cryptographic code in Exim itself for
1897 If you do not want TLS support you should set
1901 in &_Local/Makefile_&.
1903 If OpenSSL is installed, you should set
1906 TLS_LIBS=-lssl -lcrypto
1908 in &_Local/Makefile_&. You may also need to specify the locations of the
1909 OpenSSL library and include files. For example:
1912 TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto
1913 TLS_INCLUDE=-I/usr/local/openssl/include/
1915 .cindex "pkg-config" "OpenSSL"
1916 If you have &'pkg-config'& available, then instead you can just use:
1919 USE_OPENSSL_PC=openssl
1921 .cindex "USE_GNUTLS"
1922 If GnuTLS is installed, you should set
1925 TLS_LIBS=-lgnutls -ltasn1 -lgcrypt
1927 in &_Local/Makefile_&, and again you may need to specify the locations of the
1928 library and include files. For example:
1931 TLS_LIBS=-L/usr/gnu/lib -lgnutls -ltasn1 -lgcrypt
1932 TLS_INCLUDE=-I/usr/gnu/include
1934 .cindex "pkg-config" "GnuTLS"
1935 If you have &'pkg-config'& available, then instead you can just use:
1938 USE_GNUTLS_PC=gnutls
1941 You do not need to set TLS_INCLUDE if the relevant directory is already
1942 specified in INCLUDE. Details of how to configure Exim to make use of TLS are
1943 given in chapter &<<CHAPTLS>>&.
1948 .section "Use of tcpwrappers" "SECID27"
1950 .cindex "tcpwrappers, building Exim to support"
1951 .cindex "USE_TCP_WRAPPERS"
1952 .cindex "TCP_WRAPPERS_DAEMON_NAME"
1953 .cindex "tcp_wrappers_daemon_name"
1954 Exim can be linked with the &'tcpwrappers'& library in order to check incoming
1955 SMTP calls using the &'tcpwrappers'& control files. This may be a convenient
1956 alternative to Exim's own checking facilities for installations that are
1957 already making use of &'tcpwrappers'& for other purposes. To do this, you
1958 should set USE_TCP_WRAPPERS in &_Local/Makefile_&, arrange for the file
1959 &_tcpd.h_& to be available at compile time, and also ensure that the library
1960 &_libwrap.a_& is available at link time, typically by including &%-lwrap%& in
1961 EXTRALIBS_EXIM. For example, if &'tcpwrappers'& is installed in &_/usr/local_&,
1964 USE_TCP_WRAPPERS=yes
1965 CFLAGS=-O -I/usr/local/include
1966 EXTRALIBS_EXIM=-L/usr/local/lib -lwrap
1968 in &_Local/Makefile_&. The daemon name to use in the &'tcpwrappers'& control
1969 files is &"exim"&. For example, the line
1971 exim : LOCAL 192.168.1. .friendly.domain.example
1973 in your &_/etc/hosts.allow_& file allows connections from the local host, from
1974 the subnet 192.168.1.0/24, and from all hosts in &'friendly.domain.example'&.
1975 All other connections are denied. The daemon name used by &'tcpwrappers'&
1976 can be changed at build time by setting TCP_WRAPPERS_DAEMON_NAME in
1977 &_Local/Makefile_&, or by setting tcp_wrappers_daemon_name in the
1978 configure file. Consult the &'tcpwrappers'& documentation for
1982 .section "Including support for IPv6" "SECID28"
1983 .cindex "IPv6" "including support for"
1984 Exim contains code for use on systems that have IPv6 support. Setting
1985 &`HAVE_IPV6=YES`& in &_Local/Makefile_& causes the IPv6 code to be included;
1986 it may also be necessary to set IPV6_INCLUDE and IPV6_LIBS on systems
1987 where the IPv6 support is not fully integrated into the normal include and
1990 Two different types of DNS record for handling IPv6 addresses have been
1991 defined. AAAA records (analogous to A records for IPv4) are in use, and are
1992 currently seen as the mainstream. Another record type called A6 was proposed
1993 as better than AAAA because it had more flexibility. However, it was felt to be
1994 over-complex, and its status was reduced to &"experimental"&.
1996 have a compile option for including A6 record support but this has now been
2001 .section "Dynamically loaded lookup module support" "SECTdynamicmodules"
2002 .cindex "lookup modules"
2003 .cindex "dynamic modules"
2004 .cindex ".so building"
2005 On some platforms, Exim supports not compiling all lookup types directly into
2006 the main binary, instead putting some into external modules which can be loaded
2008 This permits packagers to build Exim with support for lookups with extensive
2009 library dependencies without requiring all users to install all of those
2011 Most, but not all, lookup types can be built this way.
2013 Set &`LOOKUP_MODULE_DIR`& to the directory into which the modules will be
2014 installed; Exim will only load modules from that directory, as a security
2015 measure. You will need to set &`CFLAGS_DYNAMIC`& if not already defined
2016 for your OS; see &_OS/Makefile-Linux_& for an example.
2017 Some other requirements for adjusting &`EXTRALIBS`& may also be necessary,
2018 see &_src/EDITME_& for details.
2020 Then, for each module to be loaded dynamically, define the relevant
2021 &`LOOKUP_`&<&'lookup_type'&> flags to have the value "2" instead of "yes".
2022 For example, this will build in lsearch but load sqlite and mysql support
2031 .section "The building process" "SECID29"
2032 .cindex "build directory"
2033 Once &_Local/Makefile_& (and &_Local/eximon.conf_&, if required) have been
2034 created, run &'make'& at the top level. It determines the architecture and
2035 operating system types, and creates a build directory if one does not exist.
2036 For example, on a Sun system running Solaris 8, the directory
2037 &_build-SunOS5-5.8-sparc_& is created.
2038 .cindex "symbolic link" "to source files"
2039 Symbolic links to relevant source files are installed in the build directory.
2041 If this is the first time &'make'& has been run, it calls a script that builds
2042 a make file inside the build directory, using the configuration files from the
2043 &_Local_& directory. The new make file is then passed to another instance of
2044 &'make'&. This does the real work, building a number of utility scripts, and
2045 then compiling and linking the binaries for the Exim monitor (if configured), a
2046 number of utility programs, and finally Exim itself. The command &`make
2047 makefile`& can be used to force a rebuild of the make file in the build
2048 directory, should this ever be necessary.
2050 If you have problems building Exim, check for any comments there may be in the
2051 &_README_& file concerning your operating system, and also take a look at the
2052 FAQ, where some common problems are covered.
2056 .section 'Output from &"make"&' "SECID283"
2057 The output produced by the &'make'& process for compile lines is often very
2058 unreadable, because these lines can be very long. For this reason, the normal
2059 output is suppressed by default, and instead output similar to that which
2060 appears when compiling the 2.6 Linux kernel is generated: just a short line for
2061 each module that is being compiled or linked. However, it is still possible to
2062 get the full output, by calling &'make'& like this:
2066 The value of FULLECHO defaults to &"@"&, the flag character that suppresses
2067 command reflection in &'make'&. When you ask for the full output, it is
2068 given in addition to the short output.
2072 .section "Overriding build-time options for Exim" "SECToverride"
2073 .cindex "build-time options, overriding"
2074 The main make file that is created at the beginning of the building process
2075 consists of the concatenation of a number of files which set configuration
2076 values, followed by a fixed set of &'make'& instructions. If a value is set
2077 more than once, the last setting overrides any previous ones. This provides a
2078 convenient way of overriding defaults. The files that are concatenated are, in
2081 &_OS/Makefile-Default_&
2082 &_OS/Makefile-_&<&'ostype'&>
2084 &_Local/Makefile-_&<&'ostype'&>
2085 &_Local/Makefile-_&<&'archtype'&>
2086 &_Local/Makefile-_&<&'ostype'&>-<&'archtype'&>
2087 &_OS/Makefile-Base_&
2089 .cindex "&_Local/Makefile_&"
2090 .cindex "building Exim" "operating system type"
2091 .cindex "building Exim" "architecture type"
2092 where <&'ostype'&> is the operating system type and <&'archtype'&> is the
2093 architecture type. &_Local/Makefile_& is required to exist, and the building
2094 process fails if it is absent. The other three &_Local_& files are optional,
2095 and are often not needed.
2097 The values used for <&'ostype'&> and <&'archtype'&> are obtained from scripts
2098 called &_scripts/os-type_& and &_scripts/arch-type_& respectively. If either of
2099 the environment variables EXIM_OSTYPE or EXIM_ARCHTYPE is set, their
2100 values are used, thereby providing a means of forcing particular settings.
2101 Otherwise, the scripts try to get values from the &%uname%& command. If this
2102 fails, the shell variables OSTYPE and ARCHTYPE are inspected. A number
2103 of &'ad hoc'& transformations are then applied, to produce the standard names
2104 that Exim expects. You can run these scripts directly from the shell in order
2105 to find out what values are being used on your system.
2108 &_OS/Makefile-Default_& contains comments about the variables that are set
2109 therein. Some (but not all) are mentioned below. If there is something that
2110 needs changing, review the contents of this file and the contents of the make
2111 file for your operating system (&_OS/Makefile-<ostype>_&) to see what the
2115 .cindex "building Exim" "overriding default settings"
2116 If you need to change any of the values that are set in &_OS/Makefile-Default_&
2117 or in &_OS/Makefile-<ostype>_&, or to add any new definitions, you do not
2118 need to change the original files. Instead, you should make the changes by
2119 putting the new values in an appropriate &_Local_& file. For example,
2120 .cindex "Tru64-Unix build-time settings"
2121 when building Exim in many releases of the Tru64-Unix (formerly Digital UNIX,
2122 formerly DEC-OSF1) operating system, it is necessary to specify that the C
2123 compiler is called &'cc'& rather than &'gcc'&. Also, the compiler must be
2124 called with the option &%-std1%&, to make it recognize some of the features of
2125 Standard C that Exim uses. (Most other compilers recognize Standard C by
2126 default.) To do this, you should create a file called &_Local/Makefile-OSF1_&
2127 containing the lines
2132 If you are compiling for just one operating system, it may be easier to put
2133 these lines directly into &_Local/Makefile_&.
2135 Keeping all your local configuration settings separate from the distributed
2136 files makes it easy to transfer them to new versions of Exim simply by copying
2137 the contents of the &_Local_& directory.
2140 .cindex "NIS lookup type" "including support for"
2141 .cindex "NIS+ lookup type" "including support for"
2142 .cindex "LDAP" "including support for"
2143 .cindex "lookup" "inclusion in binary"
2144 Exim contains support for doing LDAP, NIS, NIS+, and other kinds of file
2145 lookup, but not all systems have these components installed, so the default is
2146 not to include the relevant code in the binary. All the different kinds of file
2147 and database lookup that Exim supports are implemented as separate code modules
2148 which are included only if the relevant compile-time options are set. In the
2149 case of LDAP, NIS, and NIS+, the settings for &_Local/Makefile_& are:
2155 and similar settings apply to the other lookup types. They are all listed in
2156 &_src/EDITME_&. In many cases the relevant include files and interface
2157 libraries need to be installed before compiling Exim.
2158 .cindex "cdb" "including support for"
2159 However, there are some optional lookup types (such as cdb) for which
2160 the code is entirely contained within Exim, and no external include
2161 files or libraries are required. When a lookup type is not included in the
2162 binary, attempts to configure Exim to use it cause runtime configuration
2165 .cindex "pkg-config" "lookups"
2166 .cindex "pkg-config" "authenticators"
2167 Many systems now use a tool called &'pkg-config'& to encapsulate information
2168 about how to compile against a library; Exim has some initial support for
2169 being able to use pkg-config for lookups and authenticators. For any given
2170 makefile variable which starts &`LOOKUP_`& or &`AUTH_`&, you can add a new
2171 variable with the &`_PC`& suffix in the name and assign as the value the
2172 name of the package to be queried. The results of querying via the
2173 &'pkg-config'& command will be added to the appropriate Makefile variables
2174 with &`+=`& directives, so your version of &'make'& will need to support that
2175 syntax. For instance:
2178 LOOKUP_SQLITE_PC=sqlite3
2180 AUTH_GSASL_PC=libgsasl
2181 AUTH_HEIMDAL_GSSAPI=yes
2182 AUTH_HEIMDAL_GSSAPI_PC=heimdal-gssapi
2185 .cindex "Perl" "including support for"
2186 Exim can be linked with an embedded Perl interpreter, allowing Perl
2187 subroutines to be called during string expansion. To enable this facility,
2191 must be defined in &_Local/Makefile_&. Details of this facility are given in
2192 chapter &<<CHAPperl>>&.
2194 .cindex "X11 libraries, location of"
2195 The location of the X11 libraries is something that varies a lot between
2196 operating systems, and there may be different versions of X11 to cope
2197 with. Exim itself makes no use of X11, but if you are compiling the Exim
2198 monitor, the X11 libraries must be available.
2199 The following three variables are set in &_OS/Makefile-Default_&:
2202 XINCLUDE=-I$(X11)/include
2203 XLFLAGS=-L$(X11)/lib
2205 These are overridden in some of the operating-system configuration files. For
2206 example, in &_OS/Makefile-SunOS5_& there is
2209 XINCLUDE=-I$(X11)/include
2210 XLFLAGS=-L$(X11)/lib -R$(X11)/lib
2212 If you need to override the default setting for your operating system, place a
2213 definition of all three of these variables into your
2214 &_Local/Makefile-<ostype>_& file.
2217 If you need to add any extra libraries to the link steps, these can be put in a
2218 variable called EXTRALIBS, which appears in all the link commands, but by
2219 default is not defined. In contrast, EXTRALIBS_EXIM is used only on the
2220 command for linking the main Exim binary, and not for any associated utilities.
2222 .cindex "DBM libraries" "configuration for building"
2223 There is also DBMLIB, which appears in the link commands for binaries that
2224 use DBM functions (see also section &<<SECTdb>>&). Finally, there is
2225 EXTRALIBS_EXIMON, which appears only in the link step for the Exim monitor
2226 binary, and which can be used, for example, to include additional X11
2229 .cindex "configuration file" "editing"
2230 The make file copes with rebuilding Exim correctly if any of the configuration
2231 files are edited. However, if an optional configuration file is deleted, it is
2232 necessary to touch the associated non-optional file (that is,
2233 &_Local/Makefile_& or &_Local/eximon.conf_&) before rebuilding.
2236 .section "OS-specific header files" "SECID30"
2238 .cindex "building Exim" "OS-specific C header files"
2239 The &_OS_& directory contains a number of files with names of the form
2240 &_os.h-<ostype>_&. These are system-specific C header files that should not
2241 normally need to be changed. There is a list of macro settings that are
2242 recognized in the file &_OS/os.configuring_&, which should be consulted if you
2243 are porting Exim to a new operating system.
2247 .section "Overriding build-time options for the monitor" "SECID31"
2248 .cindex "building Eximon"
2249 A similar process is used for overriding things when building the Exim monitor,
2250 where the files that are involved are
2252 &_OS/eximon.conf-Default_&
2253 &_OS/eximon.conf-_&<&'ostype'&>
2254 &_Local/eximon.conf_&
2255 &_Local/eximon.conf-_&<&'ostype'&>
2256 &_Local/eximon.conf-_&<&'archtype'&>
2257 &_Local/eximon.conf-_&<&'ostype'&>-<&'archtype'&>
2259 .cindex "&_Local/eximon.conf_&"
2260 As with Exim itself, the final three files need not exist, and in this case the
2261 &_OS/eximon.conf-<ostype>_& file is also optional. The default values in
2262 &_OS/eximon.conf-Default_& can be overridden dynamically by setting environment
2263 variables of the same name, preceded by EXIMON_. For example, setting
2264 EXIMON_LOG_DEPTH in the environment overrides the value of
2265 LOG_DEPTH at runtime.
2269 .section "Installing Exim binaries and scripts" "SECID32"
2270 .cindex "installing Exim"
2271 .cindex "BIN_DIRECTORY"
2272 The command &`make install`& runs the &(exim_install)& script with no
2273 arguments. The script copies binaries and utility scripts into the directory
2274 whose name is specified by the BIN_DIRECTORY setting in &_Local/Makefile_&.
2275 .cindex "setuid" "installing Exim with"
2276 The install script copies files only if they are newer than the files they are
2277 going to replace. The Exim binary is required to be owned by root and have the
2278 &'setuid'& bit set, for normal configurations. Therefore, you must run &`make
2279 install`& as root so that it can set up the Exim binary in this way. However, in
2280 some special situations (for example, if a host is doing no local deliveries)
2281 it may be possible to run Exim without making the binary setuid root (see
2282 chapter &<<CHAPsecurity>>& for details).
2284 .cindex "CONFIGURE_FILE"
2285 Exim's runtime configuration file is named by the CONFIGURE_FILE setting
2286 in &_Local/Makefile_&. If this names a single file, and the file does not
2287 exist, the default configuration file &_src/configure.default_& is copied there
2288 by the installation script. If a runtime configuration file already exists, it
2289 is left alone. If CONFIGURE_FILE is a colon-separated list, naming several
2290 alternative files, no default is installed.
2292 .cindex "system aliases file"
2293 .cindex "&_/etc/aliases_&"
2294 One change is made to the default configuration file when it is installed: the
2295 default configuration contains a router that references a system aliases file.
2296 The path to this file is set to the value specified by
2297 SYSTEM_ALIASES_FILE in &_Local/Makefile_& (&_/etc/aliases_& by default).
2298 If the system aliases file does not exist, the installation script creates it,
2299 and outputs a comment to the user.
2301 The created file contains no aliases, but it does contain comments about the
2302 aliases a site should normally have. Mail aliases have traditionally been
2303 kept in &_/etc/aliases_&. However, some operating systems are now using
2304 &_/etc/mail/aliases_&. You should check if yours is one of these, and change
2305 Exim's configuration if necessary.
2307 The default configuration uses the local host's name as the only local domain,
2308 and is set up to do local deliveries into the shared directory &_/var/mail_&,
2309 running as the local user. System aliases and &_.forward_& files in users' home
2310 directories are supported, but no NIS or NIS+ support is configured. Domains
2311 other than the name of the local host are routed using the DNS, with delivery
2314 It is possible to install Exim for special purposes (such as building a binary
2315 distribution) in a private part of the file system. You can do this by a
2318 make DESTDIR=/some/directory/ install
2320 This has the effect of pre-pending the specified directory to all the file
2321 paths, except the name of the system aliases file that appears in the default
2322 configuration. (If a default alias file is created, its name &'is'& modified.)
2323 For backwards compatibility, ROOT is used if DESTDIR is not set,
2324 but this usage is deprecated.
2326 .cindex "installing Exim" "what is not installed"
2327 Running &'make install'& does not copy the Exim 4 conversion script
2328 &'convert4r4'&. You will probably run this only once if you are
2329 upgrading from Exim 3. None of the documentation files in the &_doc_&
2330 directory are copied, except for the info files when you have set
2331 INFO_DIRECTORY, as described in section &<<SECTinsinfdoc>>& below.
2333 For the utility programs, old versions are renamed by adding the suffix &_.O_&
2334 to their names. The Exim binary itself, however, is handled differently. It is
2335 installed under a name that includes the version number and the compile number,
2336 for example, &_exim-&version()-1_&. The script then arranges for a symbolic link
2337 called &_exim_& to point to the binary. If you are updating a previous version
2338 of Exim, the script takes care to ensure that the name &_exim_& is never absent
2339 from the directory (as seen by other processes).
2341 .cindex "installing Exim" "testing the script"
2342 If you want to see what the &'make install'& will do before running it for
2343 real, you can pass the &%-n%& option to the installation script by this
2346 make INSTALL_ARG=-n install
2348 The contents of the variable INSTALL_ARG are passed to the installation
2349 script. You do not need to be root to run this test. Alternatively, you can run
2350 the installation script directly, but this must be from within the build
2351 directory. For example, from the top-level Exim directory you could use this
2354 (cd build-SunOS5-5.5.1-sparc; ../scripts/exim_install -n)
2356 .cindex "installing Exim" "install script options"
2357 There are two other options that can be supplied to the installation script.
2360 &%-no_chown%& bypasses the call to change the owner of the installed binary
2361 to root, and the call to make it a setuid binary.
2363 &%-no_symlink%& bypasses the setting up of the symbolic link &_exim_& to the
2367 INSTALL_ARG can be used to pass these options to the script. For example:
2369 make INSTALL_ARG=-no_symlink install
2371 The installation script can also be given arguments specifying which files are
2372 to be copied. For example, to install just the Exim binary, and nothing else,
2373 without creating the symbolic link, you could use:
2375 make INSTALL_ARG='-no_symlink exim' install
2380 .section "Installing info documentation" "SECTinsinfdoc"
2381 .cindex "installing Exim" "&'info'& documentation"
2382 Not all systems use the GNU &'info'& system for documentation, and for this
2383 reason, the Texinfo source of Exim's documentation is not included in the main
2384 distribution. Instead it is available separately from the FTP site (see section
2387 If you have defined INFO_DIRECTORY in &_Local/Makefile_& and the Texinfo
2388 source of the documentation is found in the source tree, running &`make
2389 install`& automatically builds the info files and installs them.
2393 .section "Setting up the spool directory" "SECID33"
2394 .cindex "spool directory" "creating"
2395 When it starts up, Exim tries to create its spool directory if it does not
2396 exist. The Exim uid and gid are used for the owner and group of the spool
2397 directory. Sub-directories are automatically created in the spool directory as
2403 .section "Testing" "SECID34"
2404 .cindex "testing" "installation"
2405 Having installed Exim, you can check that the runtime configuration file is
2406 syntactically valid by running the following command, which assumes that the
2407 Exim binary directory is within your PATH environment variable:
2411 If there are any errors in the configuration file, Exim outputs error messages.
2412 Otherwise it outputs the version number and build date,
2413 the DBM library that is being used, and information about which drivers and
2414 other optional code modules are included in the binary.
2415 Some simple routing tests can be done by using the address testing option. For
2418 &`exim -bt`& <&'local username'&>
2420 should verify that it recognizes a local mailbox, and
2422 &`exim -bt`& <&'remote address'&>
2424 a remote one. Then try getting it to deliver mail, both locally and remotely.
2425 This can be done by passing messages directly to Exim, without going through a
2426 user agent. For example:
2428 exim -v postmaster@your.domain.example
2429 From: user@your.domain.example
2430 To: postmaster@your.domain.example
2431 Subject: Testing Exim
2433 This is a test message.
2436 The &%-v%& option causes Exim to output some verification of what it is doing.
2437 In this case you should see copies of three log lines, one for the message's
2438 arrival, one for its delivery, and one containing &"Completed"&.
2440 .cindex "delivery" "problems with"
2441 If you encounter problems, look at Exim's log files (&'mainlog'& and
2442 &'paniclog'&) to see if there is any relevant information there. Another source
2443 of information is running Exim with debugging turned on, by specifying the
2444 &%-d%& option. If a message is stuck on Exim's spool, you can force a delivery
2445 with debugging turned on by a command of the form
2447 &`exim -d -M`& <&'exim-message-id'&>
2449 You must be root or an &"admin user"& in order to do this. The &%-d%& option
2450 produces rather a lot of output, but you can cut this down to specific areas.
2451 For example, if you use &%-d-all+route%& only the debugging information
2452 relevant to routing is included. (See the &%-d%& option in chapter
2453 &<<CHAPcommandline>>& for more details.)
2455 .cindex '&"sticky"& bit'
2456 .cindex "lock files"
2457 One specific problem that has shown up on some sites is the inability to do
2458 local deliveries into a shared mailbox directory, because it does not have the
2459 &"sticky bit"& set on it. By default, Exim tries to create a lock file before
2460 writing to a mailbox file, and if it cannot create the lock file, the delivery
2461 is deferred. You can get round this either by setting the &"sticky bit"& on the
2462 directory, or by setting a specific group for local deliveries and allowing
2463 that group to create files in the directory (see the comments above the
2464 &(local_delivery)& transport in the default configuration file). Another
2465 approach is to configure Exim not to use lock files, but just to rely on
2466 &[fcntl()]& locking instead. However, you should do this only if all user
2467 agents also use &[fcntl()]& locking. For further discussion of locking issues,
2468 see chapter &<<CHAPappendfile>>&.
2470 One thing that cannot be tested on a system that is already running an MTA is
2471 the receipt of incoming SMTP mail on the standard SMTP port. However, the
2472 &%-oX%& option can be used to run an Exim daemon that listens on some other
2473 port, or &'inetd'& can be used to do this. The &%-bh%& option and the
2474 &'exim_checkaccess'& utility can be used to check out policy controls on
2477 Testing a new version on a system that is already running Exim can most easily
2478 be done by building a binary with a different CONFIGURE_FILE setting. From
2479 within the runtime configuration, all other file and directory names
2480 that Exim uses can be altered, in order to keep it entirely clear of the
2484 .section "Replacing another MTA with Exim" "SECID35"
2485 .cindex "replacing another MTA"
2486 Building and installing Exim for the first time does not of itself put it in
2487 general use. The name by which the system's MTA is called by mail user agents
2488 is either &_/usr/sbin/sendmail_&, or &_/usr/lib/sendmail_& (depending on the
2489 operating system), and it is necessary to make this name point to the &'exim'&
2490 binary in order to get the user agents to pass messages to Exim. This is
2491 normally done by renaming any existing file and making &_/usr/sbin/sendmail_&
2492 or &_/usr/lib/sendmail_&
2493 .cindex "symbolic link" "to &'exim'& binary"
2494 a symbolic link to the &'exim'& binary. It is a good idea to remove any setuid
2495 privilege and executable status from the old MTA. It is then necessary to stop
2496 and restart the mailer daemon, if one is running.
2498 .cindex "FreeBSD, MTA indirection"
2499 .cindex "&_/etc/mail/mailer.conf_&"
2500 Some operating systems have introduced alternative ways of switching MTAs. For
2501 example, if you are running FreeBSD, you need to edit the file
2502 &_/etc/mail/mailer.conf_& instead of setting up a symbolic link as just
2503 described. A typical example of the contents of this file for running Exim is
2506 sendmail /usr/exim/bin/exim
2507 send-mail /usr/exim/bin/exim
2508 mailq /usr/exim/bin/exim -bp
2509 newaliases /usr/bin/true
2511 Once you have set up the symbolic link, or edited &_/etc/mail/mailer.conf_&,
2512 your Exim installation is &"live"&. Check it by sending a message from your
2513 favourite user agent.
2515 You should consider what to tell your users about the change of MTA. Exim may
2516 have different capabilities to what was previously running, and there are
2517 various operational differences such as the text of messages produced by
2518 command line options and in bounce messages. If you allow your users to make
2519 use of Exim's filtering capabilities, you should make the document entitled
2520 &'Exim's interface to mail filtering'& available to them.
2524 .section "Running the daemon" SECTdaemonLaunch
2525 The most common command line for launching the Exim daemon looks like
2529 This starts a daemon which
2531 listens for incoming smtp connections, launching handler processes for
2534 starts a queue-runner process every five minutes, to inspect queued messages
2535 and run delivery attempts on any that have arrived at their retry time
2537 Should a queue run take longer than the time between queue-runner starts,
2538 they will run in parallel.
2539 Numbers of jobs of the various types are subject to policy controls
2540 defined in the configuration.
2543 .section "Upgrading Exim" "SECID36"
2544 .cindex "upgrading Exim"
2545 If you are already running Exim on your host, building and installing a new
2546 version automatically makes it available to MUAs, or any other programs that
2547 call the MTA directly. However, if you are running an Exim daemon, you do need
2548 .cindex restart "on HUP signal"
2549 .cindex signal "HUP, to restart"
2550 to send it a HUP signal, to make it re-execute itself, and thereby pick up the
2551 new binary. You do not need to stop processing mail in order to install a new
2552 version of Exim. The install script does not modify an existing runtime
2558 .section "Stopping the Exim daemon on Solaris" "SECID37"
2559 .cindex "Solaris" "stopping Exim on"
2560 The standard command for stopping the mailer daemon on Solaris is
2562 /etc/init.d/sendmail stop
2564 If &_/usr/lib/sendmail_& has been turned into a symbolic link, this script
2565 fails to stop Exim because it uses the command &'ps -e'& and greps the output
2566 for the text &"sendmail"&; this is not present because the actual program name
2567 (that is, &"exim"&) is given by the &'ps'& command with these options. A
2568 solution is to replace the line that finds the process id with something like
2570 pid=`cat /var/spool/exim/exim-daemon.pid`
2572 to obtain the daemon's pid directly from the file that Exim saves it in.
2574 Note, however, that stopping the daemon does not &"stop Exim"&. Messages can
2575 still be received from local processes, and if automatic delivery is configured
2576 (the normal case), deliveries will still occur.
2581 . ////////////////////////////////////////////////////////////////////////////
2582 . ////////////////////////////////////////////////////////////////////////////
2584 .chapter "The Exim command line" "CHAPcommandline"
2585 .scindex IIDclo1 "command line" "options"
2586 .scindex IIDclo2 "options" "command line"
2587 Exim's command line takes the standard Unix form of a sequence of options,
2588 each starting with a hyphen character, followed by a number of arguments. The
2589 options are compatible with the main options of Sendmail, and there are also
2590 some additional options, some of which are compatible with Smail 3. Certain
2591 combinations of options do not make sense, and provoke an error if used.
2592 The form of the arguments depends on which options are set.
2595 .section "Setting options by program name" "SECID38"
2597 If Exim is called under the name &'mailq'&, it behaves as if the option &%-bp%&
2598 were present before any other options.
2599 The &%-bp%& option requests a listing of the contents of the mail queue on the
2601 This feature is for compatibility with some systems that contain a command of
2602 that name in one of the standard libraries, symbolically linked to
2603 &_/usr/sbin/sendmail_& or &_/usr/lib/sendmail_&.
2606 If Exim is called under the name &'rsmtp'& it behaves as if the option &%-bS%&
2607 were present before any other options, for compatibility with Smail. The
2608 &%-bS%& option is used for reading in a number of messages in batched SMTP
2612 If Exim is called under the name &'rmail'& it behaves as if the &%-i%& and
2613 &%-oee%& options were present before any other options, for compatibility with
2614 Smail. The name &'rmail'& is used as an interface by some UUCP systems.
2617 .cindex "queue runner"
2618 If Exim is called under the name &'runq'& it behaves as if the option &%-q%&
2619 were present before any other options, for compatibility with Smail. The &%-q%&
2620 option causes a single queue runner process to be started.
2622 .cindex "&'newaliases'&"
2623 .cindex "alias file" "building"
2624 .cindex "Sendmail compatibility" "calling Exim as &'newaliases'&"
2625 If Exim is called under the name &'newaliases'& it behaves as if the option
2626 &%-bi%& were present before any other options, for compatibility with Sendmail.
2627 This option is used for rebuilding Sendmail's alias file. Exim does not have
2628 the concept of a single alias file, but can be configured to run a given
2629 command if called with the &%-bi%& option.
2632 .section "Trusted and admin users" "SECTtrustedadmin"
2633 Some Exim options are available only to &'trusted users'& and others are
2634 available only to &'admin users'&. In the description below, the phrases &"Exim
2635 user"& and &"Exim group"& mean the user and group defined by EXIM_USER and
2636 EXIM_GROUP in &_Local/Makefile_& or set by the &%exim_user%& and
2637 &%exim_group%& options. These do not necessarily have to use the name &"exim"&.
2640 .cindex "trusted users" "definition of"
2641 .cindex "user" "trusted definition of"
2642 The trusted users are root, the Exim user, any user listed in the
2643 &%trusted_users%& configuration option, and any user whose current group or any
2644 supplementary group is one of those listed in the &%trusted_groups%&
2645 configuration option. Note that the Exim group is not automatically trusted.
2647 .cindex '&"From"& line'
2648 .cindex "envelope from"
2649 .cindex "envelope sender"
2650 Trusted users are always permitted to use the &%-f%& option or a leading
2651 &"From&~"& line to specify the envelope sender of a message that is passed to
2652 Exim through the local interface (see the &%-bm%& and &%-f%& options below).
2653 See the &%untrusted_set_sender%& option for a way of permitting non-trusted
2654 users to set envelope senders.
2658 For a trusted user, there is never any check on the contents of the &'From:'&
2659 header line, and a &'Sender:'& line is never added. Furthermore, any existing
2660 &'Sender:'& line in incoming local (non-TCP/IP) messages is not removed.
2662 Trusted users may also specify a host name, host address, interface address,
2663 protocol name, ident value, and authentication data when submitting a message
2664 locally. Thus, they are able to insert messages into Exim's queue locally that
2665 have the characteristics of messages received from a remote host. Untrusted
2666 users may in some circumstances use &%-f%&, but can never set the other values
2667 that are available to trusted users.
2669 .cindex "user" "admin definition of"
2670 .cindex "admin user" "definition of"
2671 The admin users are root, the Exim user, and any user that is a member of the
2672 Exim group or of any group listed in the &%admin_groups%& configuration option.
2673 The current group does not have to be one of these groups.
2675 Admin users are permitted to list the queue, and to carry out certain
2676 operations on messages, for example, to force delivery failures. It is also
2677 necessary to be an admin user in order to see the full information provided by
2678 the Exim monitor, and full debugging output.
2680 By default, the use of the &%-M%&, &%-q%&, &%-R%&, and &%-S%& options to cause
2681 Exim to attempt delivery of messages on its queue is restricted to admin users.
2682 However, this restriction can be relaxed by setting the &%prod_requires_admin%&
2683 option false (that is, specifying &%no_prod_requires_admin%&).
2685 Similarly, the use of the &%-bp%& option to list all the messages in the queue
2686 is restricted to admin users unless &%queue_list_requires_admin%& is set
2691 &*Warning*&: If you configure your system so that admin users are able to
2692 edit Exim's configuration file, you are giving those users an easy way of
2693 getting root. There is further discussion of this issue at the start of chapter
2699 .section "Command line options" "SECID39"
2700 Exim's command line options are described in alphabetical order below. If none
2701 of the options that specifies a specific action (such as starting the daemon or
2702 a queue runner, or testing an address, or receiving a message in a specific
2703 format, or listing the queue) are present, and there is at least one argument
2704 on the command line, &%-bm%& (accept a local message on the standard input,
2705 with the arguments specifying the recipients) is assumed. Otherwise, Exim
2706 outputs a brief message about itself and exits.
2708 . ////////////////////////////////////////////////////////////////////////////
2709 . Insert a stylized XML comment here, to identify the start of the command line
2710 . options. This is for the benefit of the Perl script that automatically
2711 . creates a man page for the options.
2712 . ////////////////////////////////////////////////////////////////////////////
2715 <!-- === Start of command line options === -->
2722 .cindex "options" "command line; terminating"
2723 This is a pseudo-option whose only purpose is to terminate the options and
2724 therefore to cause subsequent command line items to be treated as arguments
2725 rather than options, even if they begin with hyphens.
2728 .oindex "&%--help%&"
2729 This option causes Exim to output a few sentences stating what it is.
2730 The same output is generated if the Exim binary is called with no options and
2733 .vitem &%--version%&
2734 .oindex "&%--version%&"
2735 This option is an alias for &%-bV%& and causes version information to be
2742 These options are used by Sendmail for selecting configuration files and are
2745 .vitem &%-B%&<&'type'&>
2747 .cindex "8-bit characters"
2748 .cindex "Sendmail compatibility" "8-bit characters"
2749 This is a Sendmail option for selecting 7 or 8 bit processing. Exim is 8-bit
2750 clean; it ignores this option.
2755 .cindex "SMTP" "listener"
2756 .cindex "queue runner"
2757 This option runs Exim as a daemon, awaiting incoming SMTP connections. Usually
2758 the &%-bd%& option is combined with the &%-q%&<&'time'&> option, to specify
2759 that the daemon should also initiate periodic queue runs.
2761 The &%-bd%& option can be used only by an admin user. If either of the &%-d%&
2762 (debugging) or &%-v%& (verifying) options are set, the daemon does not
2763 disconnect from the controlling terminal. When running this way, it can be
2764 stopped by pressing ctrl-C.
2766 By default, Exim listens for incoming connections to the standard SMTP port on
2767 all the host's running interfaces. However, it is possible to listen on other
2768 ports, on multiple ports, and only on specific interfaces. Chapter
2769 &<<CHAPinterfaces>>& contains a description of the options that control this.
2771 When a listening daemon
2772 .cindex "daemon" "process id (pid)"
2773 .cindex "pid (process id)" "of daemon"
2774 is started without the use of &%-oX%& (that is, without overriding the normal
2775 configuration), it writes its process id to a file called &_exim-daemon.pid_&
2776 in Exim's spool directory. This location can be overridden by setting
2777 PID_FILE_PATH in &_Local/Makefile_&. The file is written while Exim is still
2780 When &%-oX%& is used on the command line to start a listening daemon, the
2781 process id is not written to the normal pid file path. However, &%-oP%& can be
2782 used to specify a path on the command line if a pid file is required.
2786 .cindex restart "on HUP signal"
2787 .cindex signal "HUP, to restart"
2788 .cindex "daemon" "restarting"
2789 .cindex signal "to reload configuration"
2790 .cindex daemon "reload configuration"
2791 .cindex reload configuration
2792 can be used to cause the daemon to re-execute itself. This should be done
2793 whenever Exim's configuration file, or any file that is incorporated into it by
2794 means of the &%.include%& facility, is changed, and also whenever a new version
2795 of Exim is installed. It is not necessary to do this when other files that are
2796 referenced from the configuration (for example, alias files) are changed,
2797 because these are reread each time they are used.
2801 This option has the same effect as &%-bd%& except that it never disconnects
2802 from the controlling terminal, even when no debugging is specified.
2806 .cindex "testing" "string expansion"
2807 .cindex "expansion" "testing"
2808 Run Exim in expansion testing mode. Exim discards its root privilege, to
2809 prevent ordinary users from using this mode to read otherwise inaccessible
2810 files. If no arguments are given, Exim runs interactively, prompting for lines
2811 of data. Otherwise, it processes each argument in turn.
2813 If Exim was built with USE_READLINE=yes in &_Local/Makefile_&, it tries
2814 to load the &%libreadline%& library dynamically whenever the &%-be%& option is
2815 used without command line arguments. If successful, it uses the &[readline()]&
2816 function, which provides extensive line-editing facilities, for reading the
2817 test data. A line history is supported.
2819 Long expansion expressions can be split over several lines by using backslash
2820 continuations. As in Exim's runtime configuration, white space at the start of
2821 continuation lines is ignored. Each argument or data line is passed through the
2822 string expansion mechanism, and the result is output. Variable values from the
2823 configuration file (for example, &$qualify_domain$&) are available, but no
2824 message-specific values (such as &$message_exim_id$&) are set, because no message
2825 is being processed (but see &%-bem%& and &%-Mset%&).
2827 &*Note*&: If you use this mechanism to test lookups, and you change the data
2828 files or databases you are using, you must exit and restart Exim before trying
2829 the same lookup again. Otherwise, because each Exim process caches the results
2830 of lookups, you will just get the same result as before.
2832 Macro processing is done on lines before string-expansion: new macros can be
2833 defined and macros will be expanded.
2834 Because macros in the config file are often used for secrets, those are only
2835 available to admin users.
2838 The word &"set"& at the start of a line, followed by a single space,
2839 is recognised specially as defining a value for a variable.
2840 The syntax is otherwise the same as the ACL modifier &"set ="&.
2843 .vitem &%-bem%&&~<&'filename'&>
2845 .cindex "testing" "string expansion"
2846 .cindex "expansion" "testing"
2847 This option operates like &%-be%& except that it must be followed by the name
2848 of a file. For example:
2850 exim -bem /tmp/testmessage
2852 The file is read as a message (as if receiving a locally-submitted non-SMTP
2853 message) before any of the test expansions are done. Thus, message-specific
2854 variables such as &$message_size$& and &$header_from:$& are available. However,
2855 no &'Received:'& header is added to the message. If the &%-t%& option is set,
2856 recipients are read from the headers in the normal way, and are shown in the
2857 &$recipients$& variable. Note that recipients cannot be given on the command
2858 line, because further arguments are taken as strings to expand (just like
2861 .vitem &%-bF%&&~<&'filename'&>
2863 .cindex "system filter" "testing"
2864 .cindex "testing" "system filter"
2865 This option is the same as &%-bf%& except that it assumes that the filter being
2866 tested is a system filter. The additional commands that are available only in
2867 system filters are recognized.
2869 .vitem &%-bf%&&~<&'filename'&>
2871 .cindex "filter" "testing"
2872 .cindex "testing" "filter file"
2873 .cindex "forward file" "testing"
2874 .cindex "testing" "forward file"
2875 .cindex "Sieve filter" "testing"
2876 This option runs Exim in user filter testing mode; the file is the filter file
2877 to be tested, and a test message must be supplied on the standard input. If
2878 there are no message-dependent tests in the filter, an empty file can be
2881 If you want to test a system filter file, use &%-bF%& instead of &%-bf%&. You
2882 can use both &%-bF%& and &%-bf%& on the same command, in order to test a system
2883 filter and a user filter in the same run. For example:
2885 exim -bF /system/filter -bf /user/filter </test/message
2887 This is helpful when the system filter adds header lines or sets filter
2888 variables that are used by the user filter.
2890 If the test filter file does not begin with one of the special lines
2895 it is taken to be a normal &_.forward_& file, and is tested for validity under
2896 that interpretation. See sections &<<SECTitenonfilred>>& to
2897 &<<SECTspecitredli>>& for a description of the possible contents of non-filter
2900 The result of an Exim command that uses &%-bf%&, provided no errors are
2901 detected, is a list of the actions that Exim would try to take if presented
2902 with the message for real. More details of filter testing are given in the
2903 separate document entitled &'Exim's interfaces to mail filtering'&.
2905 When testing a filter file,
2906 .cindex "&""From""& line"
2907 .cindex "envelope from"
2908 .cindex "envelope sender"
2909 .oindex "&%-f%&" "for filter testing"
2910 the envelope sender can be set by the &%-f%& option,
2911 or by a &"From&~"& line at the start of the test message. Various parameters
2912 that would normally be taken from the envelope recipient address of the message
2913 can be set by means of additional command line options (see the next four
2916 .vitem &%-bfd%&&~<&'domain'&>
2918 .vindex "&$qualify_domain$&"
2919 This sets the domain of the recipient address when a filter file is being
2920 tested by means of the &%-bf%& option. The default is the value of
2923 .vitem &%-bfl%&&~<&'local&~part'&>
2925 This sets the local part of the recipient address when a filter file is being
2926 tested by means of the &%-bf%& option. The default is the username of the
2927 process that calls Exim. A local part should be specified with any prefix or
2928 suffix stripped, because that is how it appears to the filter when a message is
2929 actually being delivered.
2931 .vitem &%-bfp%&&~<&'prefix'&>
2933 .cindex affix "filter testing"
2934 This sets the prefix of the local part of the recipient address when a filter
2935 file is being tested by means of the &%-bf%& option. The default is an empty
2938 .vitem &%-bfs%&&~<&'suffix'&>
2940 .cindex affix "filter testing"
2941 This sets the suffix of the local part of the recipient address when a filter
2942 file is being tested by means of the &%-bf%& option. The default is an empty
2945 .vitem &%-bh%&&~<&'IP&~address'&>
2947 .cindex "testing" "incoming SMTP"
2948 .cindex "SMTP" "testing incoming"
2949 .cindex "testing" "relay control"
2950 .cindex "relaying" "testing configuration"
2951 .cindex "policy control" "testing"
2952 .cindex "debugging" "&%-bh%& option"
2953 This option runs a fake SMTP session as if from the given IP address, using the
2954 standard input and output. The IP address may include a port number at the end,
2955 after a full stop. For example:
2957 exim -bh 10.9.8.7.1234
2958 exim -bh fe80::a00:20ff:fe86:a061.5678
2960 When an IPv6 address is given, it is converted into canonical form. In the case
2961 of the second example above, the value of &$sender_host_address$& after
2962 conversion to the canonical form is
2963 &`fe80:0000:0000:0a00:20ff:fe86:a061.5678`&.
2965 Comments as to what is going on are written to the standard error file. These
2966 include lines beginning with &"LOG"& for anything that would have been logged.
2967 This facility is provided for testing configuration options for incoming
2968 messages, to make sure they implement the required policy. For example, you can
2969 test your relay controls using &%-bh%&.
2973 You can test features of the configuration that rely on ident (RFC 1413)
2974 information by using the &%-oMt%& option. However, Exim cannot actually perform
2975 an ident callout when testing using &%-bh%& because there is no incoming SMTP
2978 &*Warning 2*&: Address verification callouts (see section &<<SECTcallver>>&)
2979 are also skipped when testing using &%-bh%&. If you want these callouts to
2980 occur, use &%-bhc%& instead.
2982 Messages supplied during the testing session are discarded, and nothing is
2983 written to any of the real log files. There may be pauses when DNS (and other)
2984 lookups are taking place, and of course these may time out. The &%-oMi%& option
2985 can be used to specify a specific IP interface and port if this is important,
2986 and &%-oMaa%& and &%-oMai%& can be used to set parameters as if the SMTP
2987 session were authenticated.
2989 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%& whose
2990 output just states whether a given recipient address from a given host is
2991 acceptable or not. See section &<<SECTcheckaccess>>&.
2993 Features such as authentication and encryption, where the client input is not
2994 plain text, cannot easily be tested with &%-bh%&. Instead, you should use a
2995 specialized SMTP test program such as
2996 &url(https://www.jetmore.org/john/code/swaks/,swaks).
2998 .vitem &%-bhc%&&~<&'IP&~address'&>
3000 This option operates in the same way as &%-bh%&, except that address
3001 verification callouts are performed if required. This includes consulting and
3002 updating the callout cache database.
3006 .cindex "alias file" "building"
3007 .cindex "building alias file"
3008 .cindex "Sendmail compatibility" "&%-bi%& option"
3009 Sendmail interprets the &%-bi%& option as a request to rebuild its alias file.
3010 Exim does not have the concept of a single alias file, and so it cannot mimic
3011 this behaviour. However, calls to &_/usr/lib/sendmail_& with the &%-bi%& option
3012 tend to appear in various scripts such as NIS make files, so the option must be
3015 If &%-bi%& is encountered, the command specified by the &%bi_command%&
3016 configuration option is run, under the uid and gid of the caller of Exim. If
3017 the &%-oA%& option is used, its value is passed to the command as an argument.
3018 The command set by &%bi_command%& may not contain arguments. The command can
3019 use the &'exim_dbmbuild'& utility, or some other means, to rebuild alias files
3020 if this is required. If the &%bi_command%& option is not set, calling Exim with
3023 . // Keep :help first, then the rest in alphabetical order
3025 .oindex "&%-bI:help%&"
3026 .cindex "querying exim information"
3027 We shall provide various options starting &`-bI:`& for querying Exim for
3028 information. The output of many of these will be intended for machine
3029 consumption. This one is not. The &%-bI:help%& option asks Exim for a
3030 synopsis of supported options beginning &`-bI:`&. Use of any of these
3031 options shall cause Exim to exit after producing the requested output.
3034 .oindex "&%-bI:dscp%&"
3035 .cindex "DSCP" "values"
3036 This option causes Exim to emit an alphabetically sorted list of all
3037 recognised DSCP names.
3039 .vitem &%-bI:sieve%&
3040 .oindex "&%-bI:sieve%&"
3041 .cindex "Sieve filter" "capabilities"
3042 This option causes Exim to emit an alphabetically sorted list of all supported
3043 Sieve protocol extensions on stdout, one per line. This is anticipated to be
3044 useful for ManageSieve (RFC 5804) implementations, in providing that protocol's
3045 &`SIEVE`& capability response line. As the precise list may depend upon
3046 compile-time build options, which this option will adapt to, this is the only
3047 way to guarantee a correct response.
3051 .cindex "local message reception"
3052 This option runs an Exim receiving process that accepts an incoming,
3053 locally-generated message on the standard input. The recipients are given as the
3054 command arguments (except when &%-t%& is also present &-- see below). Each
3055 argument can be a comma-separated list of RFC 2822 addresses. This is the
3056 default option for selecting the overall action of an Exim call; it is assumed
3057 if no other conflicting option is present.
3059 If any addresses in the message are unqualified (have no domain), they are
3060 qualified by the values of the &%qualify_domain%& or &%qualify_recipient%&
3061 options, as appropriate. The &%-bnq%& option (see below) provides a way of
3062 suppressing this for special cases.
3064 Policy checks on the contents of local messages can be enforced by means of
3065 the non-SMTP ACL. See chapter &<<CHAPACL>>& for details.
3067 .cindex "return code" "for &%-bm%&"
3068 The return code is zero if the message is successfully accepted. Otherwise, the
3069 action is controlled by the &%-oe%&&'x'& option setting &-- see below.
3072 .cindex "message" "format"
3073 .cindex "format" "message"
3074 .cindex "&""From""& line"
3075 .cindex "UUCP" "&""From""& line"
3076 .cindex "Sendmail compatibility" "&""From""& line"
3077 of the message must be as defined in RFC 2822, except that, for
3078 compatibility with Sendmail and Smail, a line in one of the forms
3080 From sender Fri Jan 5 12:55 GMT 1997
3081 From sender Fri, 5 Jan 97 12:55:01
3083 (with the weekday optional, and possibly with additional text after the date)
3084 is permitted to appear at the start of the message. There appears to be no
3085 authoritative specification of the format of this line. Exim recognizes it by
3086 matching against the regular expression defined by the &%uucp_from_pattern%&
3087 option, which can be changed if necessary.
3089 .oindex "&%-f%&" "overriding &""From""& line"
3090 The specified sender is treated as if it were given as the argument to the
3091 &%-f%& option, but if a &%-f%& option is also present, its argument is used in
3092 preference to the address taken from the message. The caller of Exim must be a
3093 trusted user for the sender of a message to be set in this way.
3095 .vitem &%-bmalware%&&~<&'filename'&>
3096 .oindex "&%-bmalware%&"
3097 .cindex "testing", "malware"
3098 .cindex "malware scan test"
3099 This debugging option causes Exim to scan the given file or directory
3100 (depending on the used scanner interface),
3101 using the malware scanning framework. The option of &%av_scanner%& influences
3102 this option, so if &%av_scanner%&'s value is dependent upon an expansion then
3103 the expansion should have defaults which apply to this invocation. ACLs are
3104 not invoked, so if &%av_scanner%& references an ACL variable then that variable
3105 will never be populated and &%-bmalware%& will fail.
3107 Exim will have changed working directory before resolving the filename, so
3108 using fully qualified pathnames is advisable. Exim will be running as the Exim
3109 user when it tries to open the file, rather than as the invoking user.
3110 This option requires admin privileges.
3112 The &%-bmalware%& option will not be extended to be more generally useful,
3113 there are better tools for file-scanning. This option exists to help
3114 administrators verify their Exim and AV scanner configuration.
3118 .cindex "address qualification, suppressing"
3119 By default, Exim automatically qualifies unqualified addresses (those
3120 without domains) that appear in messages that are submitted locally (that
3121 is, not over TCP/IP). This qualification applies both to addresses in
3122 envelopes, and addresses in header lines. Sender addresses are qualified using
3123 &%qualify_domain%&, and recipient addresses using &%qualify_recipient%& (which
3124 defaults to the value of &%qualify_domain%&).
3126 Sometimes, qualification is not wanted. For example, if &%-bS%& (batch SMTP) is
3127 being used to re-submit messages that originally came from remote hosts after
3128 content scanning, you probably do not want to qualify unqualified addresses in
3129 header lines. (Such lines will be present only if you have not enabled a header
3130 syntax check in the appropriate ACL.)
3132 The &%-bnq%& option suppresses all qualification of unqualified addresses in
3133 messages that originate on the local host. When this is used, unqualified
3134 addresses in the envelope provoke errors (causing message rejection) and
3135 unqualified addresses in header lines are left alone.
3140 .cindex "configuration options" "extracting"
3141 .cindex "options" "configuration &-- extracting"
3142 If this option is given with no arguments, it causes the values of all Exim's
3143 main configuration options to be written to the standard output. The values
3144 of one or more specific options can be requested by giving their names as
3145 arguments, for example:
3147 exim -bP qualify_domain hold_domains
3149 .cindex "hiding configuration option values"
3150 .cindex "configuration options" "hiding value of"
3151 .cindex "options" "hiding value of"
3152 However, any option setting that is preceded by the word &"hide"& in the
3153 configuration file is not shown in full, except to an admin user. For other
3154 users, the output is as in this example:
3156 mysql_servers = <value not displayable>
3158 If &%config%& is given as an argument, the config is
3159 output, as it was parsed, any include file resolved, any comment removed.
3161 If &%config_file%& is given as an argument, the name of the runtime
3162 configuration file is output. (&%configure_file%& works too, for
3163 backward compatibility.)
3164 If a list of configuration files was supplied, the value that is output here
3165 is the name of the file that was actually used.
3167 .cindex "options" "hiding name of"
3168 If the &%-n%& flag is given, then for most modes of &%-bP%& operation the
3169 name will not be output.
3171 .cindex "daemon" "process id (pid)"
3172 .cindex "pid (process id)" "of daemon"
3173 If &%log_file_path%& or &%pid_file_path%& are given, the names of the
3174 directories where log files and daemon pid files are written are output,
3175 respectively. If these values are unset, log files are written in a
3176 sub-directory of the spool directory called &%log%&, and the pid file is
3177 written directly into the spool directory.
3179 If &%-bP%& is followed by a name preceded by &`+`&, for example,
3181 exim -bP +local_domains
3183 it searches for a matching named list of any type (domain, host, address, or
3184 local part) and outputs what it finds.
3186 .cindex "options" "router &-- extracting"
3187 .cindex "options" "transport &-- extracting"
3188 .cindex "options" "authenticator &-- extracting"
3189 If one of the words &%router%&, &%transport%&, or &%authenticator%& is given,
3190 followed by the name of an appropriate driver instance, the option settings for
3191 that driver are output. For example:
3193 exim -bP transport local_delivery
3195 The generic driver options are output first, followed by the driver's private
3196 options. A list of the names of drivers of a particular type can be obtained by
3197 using one of the words &%router_list%&, &%transport_list%&, or
3198 &%authenticator_list%&, and a complete list of all drivers with their option
3199 settings can be obtained by using &%routers%&, &%transports%&, or
3202 .cindex "environment"
3203 If &%environment%& is given as an argument, the set of environment
3204 variables is output, line by line. Using the &%-n%& flag suppresses the value of the
3207 .cindex "options" "macro &-- extracting"
3208 If invoked by an admin user, then &%macro%&, &%macro_list%& and &%macros%&
3209 are available, similarly to the drivers. Because macros are sometimes used
3210 for storing passwords, this option is restricted.
3211 The output format is one item per line.
3212 For the "-bP macro <name>" form, if no such macro is found
3213 the exit status will be nonzero.
3217 .cindex "queue" "listing messages in"
3218 .cindex "listing" "messages in the queue"
3219 This option requests a listing of the contents of the mail queue on the
3220 standard output. If the &%-bp%& option is followed by a list of message ids,
3221 just those messages are listed. By default, this option can be used only by an
3222 admin user. However, the &%queue_list_requires_admin%& option can be set false
3223 to allow any user to see the queue.
3225 Each message in the queue is displayed as in the following example:
3227 25m 2.9K 0t5C6f-0000c8-00 <alice@wonderland.fict.example>
3228 red.king@looking-glass.fict.example
3231 .cindex "message" "size in queue listing"
3232 .cindex "size" "of message"
3233 The first line contains the length of time the message has been in the queue
3234 (in this case 25 minutes), the size of the message (2.9K), the unique local
3235 identifier for the message, and the message sender, as contained in the
3236 envelope. For bounce messages, the sender address is empty, and appears as
3237 &"<>"&. If the message was submitted locally by an untrusted user who overrode
3238 the default sender address, the user's login name is shown in parentheses
3239 before the sender address.
3241 .cindex "frozen messages" "in queue listing"
3242 If the message is frozen (attempts to deliver it are suspended) then the text
3243 &"*** frozen ***"& is displayed at the end of this line.
3245 The recipients of the message (taken from the envelope, not the headers) are
3246 displayed on subsequent lines. Those addresses to which the message has already
3247 been delivered are marked with the letter D. If an original address gets
3248 expanded into several addresses via an alias or forward file, the original is
3249 displayed with a D only when deliveries for all of its child addresses are
3255 This option operates like &%-bp%&, but in addition it shows delivered addresses
3256 that were generated from the original top level address(es) in each message by
3257 alias or forwarding operations. These addresses are flagged with &"+D"& instead
3263 .cindex "queue" "count of messages on"
3264 This option counts the number of messages in the queue, and writes the total
3265 to the standard output. It is restricted to admin users, unless
3266 &%queue_list_requires_admin%& is set false.
3271 This option operates like &%-bp%&, but the output is not sorted into
3272 chronological order of message arrival. This can speed it up when there are
3273 lots of messages in the queue, and is particularly useful if the output is
3274 going to be post-processed in a way that doesn't need the sorting.
3278 This option is a combination of &%-bpr%& and &%-bpa%&.
3282 This option is a combination of &%-bpr%& and &%-bpu%&.
3287 This option operates like &%-bp%& but shows only undelivered top-level
3288 addresses for each message displayed. Addresses generated by aliasing or
3289 forwarding are not shown, unless the message was deferred after processing by a
3290 router with the &%one_time%& option set.
3295 .cindex "testing" "retry configuration"
3296 .cindex "retry" "configuration testing"
3297 This option is for testing retry rules, and it must be followed by up to three
3298 arguments. It causes Exim to look for a retry rule that matches the values
3299 and to write it to the standard output. For example:
3301 exim -brt bach.comp.mus.example
3302 Retry rule: *.comp.mus.example F,2h,15m; F,4d,30m;
3304 See chapter &<<CHAPretry>>& for a description of Exim's retry rules. The first
3305 argument, which is required, can be a complete address in the form
3306 &'local_part@domain'&, or it can be just a domain name. If the second argument
3307 contains a dot, it is interpreted as an optional second domain name; if no
3308 retry rule is found for the first argument, the second is tried. This ties in
3309 with Exim's behaviour when looking for retry rules for remote hosts &-- if no
3310 rule is found that matches the host, one that matches the mail domain is
3311 sought. Finally, an argument that is the name of a specific delivery error, as
3312 used in setting up retry rules, can be given. For example:
3314 exim -brt haydn.comp.mus.example quota_3d
3315 Retry rule: *@haydn.comp.mus.example quota_3d F,1h,15m
3320 .cindex "testing" "rewriting"
3321 .cindex "rewriting" "testing"
3322 This option is for testing address rewriting rules, and it must be followed by
3323 a single argument, consisting of either a local part without a domain, or a
3324 complete address with a fully qualified domain. Exim outputs how this address
3325 would be rewritten for each possible place it might appear. See chapter
3326 &<<CHAPrewrite>>& for further details.
3330 .cindex "SMTP" "batched incoming"
3331 .cindex "batched SMTP input"
3332 This option is used for batched SMTP input, which is an alternative interface
3333 for non-interactive local message submission. A number of messages can be
3334 submitted in a single run. However, despite its name, this is not really SMTP
3335 input. Exim reads each message's envelope from SMTP commands on the standard
3336 input, but generates no responses. If the caller is trusted, or
3337 &%untrusted_set_sender%& is set, the senders in the SMTP MAIL commands are
3338 believed; otherwise the sender is always the caller of Exim.
3340 The message itself is read from the standard input, in SMTP format (leading
3341 dots doubled), terminated by a line containing just a single dot. An error is
3342 provoked if the terminating dot is missing. A further message may then follow.
3344 As for other local message submissions, the contents of incoming batch SMTP
3345 messages can be checked using the non-SMTP ACL (see chapter &<<CHAPACL>>&).
3346 Unqualified addresses are automatically qualified using &%qualify_domain%& and
3347 &%qualify_recipient%&, as appropriate, unless the &%-bnq%& option is used.
3349 Some other SMTP commands are recognized in the input. HELO and EHLO act
3350 as RSET; VRFY, EXPN, ETRN, and HELP act as NOOP;
3351 QUIT quits, ignoring the rest of the standard input.
3353 .cindex "return code" "for &%-bS%&"
3354 If any error is encountered, reports are written to the standard output and
3355 error streams, and Exim gives up immediately. The return code is 0 if no error
3356 was detected; it is 1 if one or more messages were accepted before the error
3357 was detected; otherwise it is 2.
3359 More details of input using batched SMTP are given in section
3360 &<<SECTincomingbatchedSMTP>>&.
3364 .cindex "SMTP" "local input"
3365 .cindex "local SMTP input"
3366 This option causes Exim to accept one or more messages by reading SMTP commands
3367 on the standard input, and producing SMTP replies on the standard output. SMTP
3368 policy controls, as defined in ACLs (see chapter &<<CHAPACL>>&) are applied.
3369 Some user agents use this interface as a way of passing locally-generated
3370 messages to the MTA.
3373 .cindex "sender" "source of"
3374 this usage, if the caller of Exim is trusted, or &%untrusted_set_sender%& is
3375 set, the senders of messages are taken from the SMTP MAIL commands.
3376 Otherwise the content of these commands is ignored and the sender is set up as
3377 the calling user. Unqualified addresses are automatically qualified using
3378 &%qualify_domain%& and &%qualify_recipient%&, as appropriate, unless the
3379 &%-bnq%& option is used.
3383 &%-bs%& option is also used to run Exim from &'inetd'&, as an alternative to
3384 using a listening daemon. Exim can distinguish the two cases by checking
3385 whether the standard input is a TCP/IP socket. When Exim is called from
3386 &'inetd'&, the source of the mail is assumed to be remote, and the comments
3387 above concerning senders and qualification do not apply. In this situation,
3388 Exim behaves in exactly the same way as it does when receiving a message via
3389 the listening daemon.
3393 .cindex "testing" "addresses"
3394 .cindex "address" "testing"
3395 This option runs Exim in address testing mode, in which each argument is taken
3396 as a recipient address to be tested for deliverability. The results are
3397 written to the standard output. If a test fails, and the caller is not an admin
3398 user, no details of the failure are output, because these might contain
3399 sensitive information such as usernames and passwords for database lookups.
3401 If no arguments are given, Exim runs in an interactive manner, prompting with a
3402 right angle bracket for addresses to be tested.
3404 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3405 &[readline()]& function, because it is running as &'root'& and there are
3408 Each address is handled as if it were the recipient address of a message
3409 (compare the &%-bv%& option). It is passed to the routers and the result is
3410 written to the standard output. However, any router that has
3411 &%no_address_test%& set is bypassed. This can make &%-bt%& easier to use for
3412 genuine routing tests if your first router passes everything to a scanner
3415 .cindex "return code" "for &%-bt%&"
3416 The return code is 2 if any address failed outright; it is 1 if no address
3417 failed outright but at least one could not be resolved for some reason. Return
3418 code 0 is given only when all addresses succeed.
3420 .cindex "duplicate addresses"
3421 &*Note*&: When actually delivering a message, Exim removes duplicate recipient
3422 addresses after routing is complete, so that only one delivery takes place.
3423 This does not happen when testing with &%-bt%&; the full results of routing are
3426 &*Warning*&: &%-bt%& can only do relatively simple testing. If any of the
3427 routers in the configuration makes any tests on the sender address of a
3429 .oindex "&%-f%&" "for address testing"
3430 you can use the &%-f%& option to set an appropriate sender when running
3431 &%-bt%& tests. Without it, the sender is assumed to be the calling user at the
3432 default qualifying domain. However, if you have set up (for example) routers
3433 whose behaviour depends on the contents of an incoming message, you cannot test
3434 those conditions using &%-bt%&. The &%-N%& option provides a possible way of
3439 .cindex "version number of Exim"
3440 This option causes Exim to write the current version number, compilation
3441 number, and compilation date of the &'exim'& binary to the standard output.
3442 It also lists the DBM library that is being used, the optional modules (such as
3443 specific lookup types), the drivers that are included in the binary, and the
3444 name of the runtime configuration file that is in use.
3446 As part of its operation, &%-bV%& causes Exim to read and syntax check its
3447 configuration file. However, this is a static check only. It cannot check
3448 values that are to be expanded. For example, although a misspelt ACL verb is
3449 detected, an error in the verb's arguments is not. You cannot rely on &%-bV%&
3450 alone to discover (for example) all the typos in the configuration; some
3451 realistic testing is needed. The &%-bh%& and &%-N%& options provide more
3452 dynamic testing facilities.
3456 .cindex "verifying address" "using &%-bv%&"
3457 .cindex "address" "verification"
3458 This option runs Exim in address verification mode, in which each argument is
3459 taken as a recipient address to be verified by the routers. (This does
3460 not involve any verification callouts). During normal operation, verification
3461 happens mostly as a consequence processing a &%verify%& condition in an ACL
3462 (see chapter &<<CHAPACL>>&). If you want to test an entire ACL, possibly
3463 including callouts, see the &%-bh%& and &%-bhc%& options.
3465 If verification fails, and the caller is not an admin user, no details of the
3466 failure are output, because these might contain sensitive information such as
3467 usernames and passwords for database lookups.
3469 If no arguments are given, Exim runs in an interactive manner, prompting with a
3470 right angle bracket for addresses to be verified.
3472 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3473 &[readline()]& function, because it is running as &'exim'& and there are
3476 Verification differs from address testing (the &%-bt%& option) in that routers
3477 that have &%no_verify%& set are skipped, and if the address is accepted by a
3478 router that has &%fail_verify%& set, verification fails. The address is
3479 verified as a recipient if &%-bv%& is used; to test verification for a sender
3480 address, &%-bvs%& should be used.
3482 If the &%-v%& option is not set, the output consists of a single line for each
3483 address, stating whether it was verified or not, and giving a reason in the
3484 latter case. Without &%-v%&, generating more than one address by redirection
3485 causes verification to end successfully, without considering the generated
3486 addresses. However, if just one address is generated, processing continues,
3487 and the generated address must verify successfully for the overall verification
3490 When &%-v%& is set, more details are given of how the address has been handled,
3491 and in the case of address redirection, all the generated addresses are also
3492 considered. Verification may succeed for some and fail for others.
3495 .cindex "return code" "for &%-bv%&"
3496 return code is 2 if any address failed outright; it is 1 if no address
3497 failed outright but at least one could not be resolved for some reason. Return
3498 code 0 is given only when all addresses succeed.
3500 If any of the routers in the configuration makes any tests on the sender
3501 address of a message, you should use the &%-f%& option to set an appropriate
3502 sender when running &%-bv%& tests. Without it, the sender is assumed to be the
3503 calling user at the default qualifying domain.
3507 This option acts like &%-bv%&, but verifies the address as a sender rather
3508 than a recipient address. This affects any rewriting and qualification that
3515 .cindex "inetd" "wait mode"
3516 This option runs Exim as a daemon, awaiting incoming SMTP connections,
3517 similarly to the &%-bd%& option. All port specifications on the command-line
3518 and in the configuration file are ignored. Queue-running may not be specified.
3520 In this mode, Exim expects to be passed a socket as fd 0 (stdin) which is
3521 listening for connections. This permits the system to start up and have
3522 inetd (or equivalent) listen on the SMTP ports, starting an Exim daemon for
3523 each port only when the first connection is received.
3525 If the option is given as &%-bw%&<&'time'&> then the time is a timeout, after
3526 which the daemon will exit, which should cause inetd to listen once more.
3528 .vitem &%-C%&&~<&'filelist'&>
3530 .cindex "configuration file" "alternate"
3531 .cindex "CONFIGURE_FILE"
3532 .cindex "alternate configuration file"
3533 This option causes Exim to find the runtime configuration file from the given
3534 list instead of from the list specified by the CONFIGURE_FILE
3535 compile-time setting. Usually, the list will consist of just a single filename,
3536 but it can be a colon-separated list of names. In this case, the first
3537 file that exists is used. Failure to open an existing file stops Exim from
3538 proceeding any further along the list, and an error is generated.
3540 When this option is used by a caller other than root, and the list is different
3541 from the compiled-in list, Exim gives up its root privilege immediately, and
3542 runs with the real and effective uid and gid set to those of the caller.
3543 However, if a TRUSTED_CONFIG_LIST file is defined in &_Local/Makefile_&, that
3544 file contains a list of full pathnames, one per line, for configuration files
3545 which are trusted. Root privilege is retained for any configuration file so
3546 listed, as long as the caller is the Exim user (or the user specified in the
3547 CONFIGURE_OWNER option, if any), and as long as the configuration file is
3548 not writeable by inappropriate users or groups.
3550 Leaving TRUSTED_CONFIG_LIST unset precludes the possibility of testing a
3551 configuration using &%-C%& right through message reception and delivery,
3552 even if the caller is root. The reception works, but by that time, Exim is
3553 running as the Exim user, so when it re-executes to regain privilege for the
3554 delivery, the use of &%-C%& causes privilege to be lost. However, root can
3555 test reception and delivery using two separate commands (one to put a message
3556 in the queue, using &%-odq%&, and another to do the delivery, using &%-M%&).
3558 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
3559 prefix string with which any file named in a &%-C%& command line option
3560 must start. In addition, the filename must not contain the sequence &`/../`&.
3561 However, if the value of the &%-C%& option is identical to the value of
3562 CONFIGURE_FILE in &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as
3563 usual. There is no default setting for ALT_CONFIG_PREFIX; when it is
3564 unset, any filename can be used with &%-C%&.
3566 ALT_CONFIG_PREFIX can be used to confine alternative configuration files
3567 to a directory to which only root has access. This prevents someone who has
3568 broken into the Exim account from running a privileged Exim with an arbitrary
3571 The &%-C%& facility is useful for ensuring that configuration files are
3572 syntactically correct, but cannot be used for test deliveries, unless the
3573 caller is privileged, or unless it is an exotic configuration that does not
3574 require privilege. No check is made on the owner or group of the files
3575 specified by this option.
3578 .vitem &%-D%&<&'macro'&>=<&'value'&>
3580 .cindex "macro" "setting on command line"
3581 This option can be used to override macro definitions in the configuration file
3582 (see section &<<SECTmacrodefs>>&). However, like &%-C%&, if it is used by an
3583 unprivileged caller, it causes Exim to give up its root privilege.
3584 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
3585 completely disabled, and its use causes an immediate error exit.
3587 If WHITELIST_D_MACROS is defined in &_Local/Makefile_& then it should be a
3588 colon-separated list of macros which are considered safe and, if &%-D%& only
3589 supplies macros from this list, and the values are acceptable, then Exim will
3590 not give up root privilege if the caller is root, the Exim run-time user, or
3591 the CONFIGURE_OWNER, if set. This is a transition mechanism and is expected
3592 to be removed in the future. Acceptable values for the macros satisfy the
3593 regexp: &`^[A-Za-z0-9_/.-]*$`&
3595 The entire option (including equals sign if present) must all be within one
3596 command line item. &%-D%& can be used to set the value of a macro to the empty
3597 string, in which case the equals sign is optional. These two commands are
3603 To include spaces in a macro definition item, quotes must be used. If you use
3604 quotes, spaces are permitted around the macro name and the equals sign. For
3607 exim '-D ABC = something' ...
3609 &%-D%& may be repeated up to 10 times on a command line.
3610 Only macro names up to 22 letters long can be set.
3613 .vitem &%-d%&<&'debug&~options'&>
3615 .cindex "debugging" "list of selectors"
3616 .cindex "debugging" "&%-d%& option"
3617 This option causes debugging information to be written to the standard
3618 error stream. It is restricted to admin users because debugging output may show
3619 database queries that contain password information. Also, the details of users'
3620 filter files should be protected. If a non-admin user uses &%-d%&, Exim
3621 writes an error message to the standard error stream and exits with a non-zero
3624 When &%-d%& is used, &%-v%& is assumed. If &%-d%& is given on its own, a lot of
3625 standard debugging data is output. This can be reduced, or increased to include
3626 some more rarely needed information, by directly following &%-d%& with a string
3627 made up of names preceded by plus or minus characters. These add or remove sets
3628 of debugging data, respectively. For example, &%-d+filter%& adds filter
3629 debugging, whereas &%-d-all+filter%& selects only filter debugging. Note that
3630 no spaces are allowed in the debug setting. The available debugging categories
3632 .itable none 0 0 2 20* left 80* left
3633 .irow acl "ACL interpretation"
3634 .irow auth "authenticators"
3635 .irow deliver "general delivery logic"
3636 .irow dns "DNS lookups (see also resolver)"
3637 .irow dnsbl "DNS black list (aka RBL) code"
3638 .irow exec "arguments for &[execv()]& calls"
3639 .irow expand "detailed debugging for string expansions"
3640 .irow filter "filter handling"
3641 .irow hints_lookup "hints data lookups"
3642 .irow host_lookup "all types of name-to-IP address handling"
3643 .irow ident "ident lookup"
3644 .irow interface "lists of local interfaces"
3645 .irow lists "matching things in lists"
3646 .irow load "system load checks"
3647 .irow local_scan "can be used by &[local_scan()]& (see chapter &&&
3648 &<<CHAPlocalscan>>&)"
3649 .irow lookup "general lookup code and all lookups"
3650 .irow memory "memory handling"
3651 .irow noutf8 "modifier: avoid UTF-8 line-drawing"
3652 .irow pid "modifier: add pid to debug output lines"
3653 .irow process_info "setting info for the process log"
3654 .irow queue_run "queue runs"
3655 .irow receive "general message reception logic"
3656 .irow resolver "turn on the DNS resolver's debugging output"
3657 .irow retry "retry handling"
3658 .irow rewrite "address rewriting""
3659 .irow route "address routing"
3660 .irow timestamp "modifier: add timestamp to debug output lines"
3661 .irow tls "TLS logic"
3662 .irow transport "transports"
3663 .irow uid "changes of uid/gid and looking up uid/gid"
3664 .irow verify "address verification logic"
3665 .irow all "almost all of the above (see below), and also &%-v%&"
3667 The &`all`& option excludes &`memory`& when used as &`+all`&, but includes it
3668 for &`-all`&. The reason for this is that &`+all`& is something that people
3669 tend to use when generating debug output for Exim maintainers. If &`+memory`&
3670 is included, an awful lot of output that is very rarely of interest is
3671 generated, so it now has to be explicitly requested. However, &`-all`& does
3672 turn everything off.
3674 .cindex "resolver, debugging output"
3675 .cindex "DNS resolver, debugging output"
3676 The &`resolver`& option produces output only if the DNS resolver was compiled
3677 with DEBUG enabled. This is not the case in some operating systems. Also,
3678 unfortunately, debugging output from the DNS resolver is written to stdout
3681 The default (&%-d%& with no argument) omits &`expand`&, &`filter`&,
3682 &`interface`&, &`load`&, &`memory`&, &`pid`&, &`resolver`&, and &`timestamp`&.
3683 However, the &`pid`& selector is forced when debugging is turned on for a
3684 daemon, which then passes it on to any re-executed Exims. Exim also
3685 automatically adds the pid to debug lines when several remote deliveries are
3688 The &`timestamp`& selector causes the current time to be inserted at the start
3689 of all debug output lines. This can be useful when trying to track down delays
3692 .cindex debugging "UTF-8 in"
3693 .cindex UTF-8 "in debug output"
3694 The &`noutf8`& selector disables the use of
3695 UTF-8 line-drawing characters to group related information.
3696 When disabled. ascii-art is used instead.
3697 Using the &`+all`& option does not set this modifier,
3699 If the &%debug_print%& option is set in any driver, it produces output whenever
3700 any debugging is selected, or if &%-v%& is used.
3702 .vitem &%-dd%&<&'debug&~options'&>
3704 This option behaves exactly like &%-d%& except when used on a command that
3705 starts a daemon process. In that case, debugging is turned off for the
3706 subprocesses that the daemon creates. Thus, it is useful for monitoring the
3707 behaviour of the daemon without creating as much output as full debugging does.
3710 .oindex "&%-dropcr%&"
3711 This is an obsolete option that is now a no-op. It used to affect the way Exim
3712 handled CR and LF characters in incoming messages. What happens now is
3713 described in section &<<SECTlineendings>>&.
3717 .cindex "bounce message" "generating"
3718 This option specifies that an incoming message is a locally-generated delivery
3719 failure report. It is used internally by Exim when handling delivery failures
3720 and is not intended for external use. Its only effect is to stop Exim
3721 generating certain messages to the postmaster, as otherwise message cascades
3722 could occur in some situations. As part of the same option, a message id may
3723 follow the characters &%-E%&. If it does, the log entry for the receipt of the
3724 new message contains the id, following &"R="&, as a cross-reference.
3727 .oindex "&%-e%&&'x'&"
3728 There are a number of Sendmail options starting with &%-oe%& which seem to be
3729 called by various programs without the leading &%o%& in the option. For
3730 example, the &%vacation%& program uses &%-eq%&. Exim treats all options of the
3731 form &%-e%&&'x'& as synonymous with the corresponding &%-oe%&&'x'& options.
3733 .vitem &%-F%&&~<&'string'&>
3735 .cindex "sender" "name"
3736 .cindex "name" "of sender"
3737 This option sets the sender's full name for use when a locally-generated
3738 message is being accepted. In the absence of this option, the user's &'gecos'&
3739 entry from the password data is used. As users are generally permitted to alter
3740 their &'gecos'& entries, no security considerations are involved. White space
3741 between &%-F%& and the <&'string'&> is optional.
3743 .vitem &%-f%&&~<&'address'&>
3745 .cindex "sender" "address"
3746 .cindex "address" "sender"
3747 .cindex "trusted users"
3748 .cindex "envelope from"
3749 .cindex "envelope sender"
3750 .cindex "user" "trusted"
3751 This option sets the address of the envelope sender of a locally-generated
3752 message (also known as the return path). The option can normally be used only
3753 by a trusted user, but &%untrusted_set_sender%& can be set to allow untrusted
3756 Processes running as root or the Exim user are always trusted. Other
3757 trusted users are defined by the &%trusted_users%& or &%trusted_groups%&
3758 options. In the absence of &%-f%&, or if the caller is not trusted, the sender
3759 of a local message is set to the caller's login name at the default qualify
3762 There is one exception to the restriction on the use of &%-f%&: an empty sender
3763 can be specified by any user, trusted or not, to create a message that can
3764 never provoke a bounce. An empty sender can be specified either as an empty
3765 string, or as a pair of angle brackets with nothing between them, as in these
3766 examples of shell commands:
3768 exim -f '<>' user@domain
3769 exim -f "" user@domain
3771 In addition, the use of &%-f%& is not restricted when testing a filter file
3772 with &%-bf%& or when testing or verifying addresses using the &%-bt%& or
3775 Allowing untrusted users to change the sender address does not of itself make
3776 it possible to send anonymous mail. Exim still checks that the &'From:'& header
3777 refers to the local user, and if it does not, it adds a &'Sender:'& header,
3778 though this can be overridden by setting &%no_local_from_check%&.
3781 .cindex "&""From""& line"
3782 space between &%-f%& and the <&'address'&> is optional (that is, they can be
3783 given as two arguments or one combined argument). The sender of a
3784 locally-generated message can also be set (when permitted) by an initial
3785 &"From&~"& line in the message &-- see the description of &%-bm%& above &-- but
3786 if &%-f%& is also present, it overrides &"From&~"&.
3790 .cindex "submission fixups, suppressing (command-line)"
3791 This option is equivalent to an ACL applying:
3793 control = suppress_local_fixups
3795 for every message received. Note that Sendmail will complain about such
3796 bad formatting, where Exim silently just does not fix it up. This may change
3799 As this affects audit information, the caller must be a trusted user to use
3802 .vitem &%-h%&&~<&'number'&>
3804 .cindex "Sendmail compatibility" "&%-h%& option ignored"
3805 This option is accepted for compatibility with Sendmail, but has no effect. (In
3806 Sendmail it overrides the &"hop count"& obtained by counting &'Received:'&
3811 .cindex "Solaris" "&'mail'& command"
3812 .cindex "dot" "in incoming non-SMTP message"
3813 This option, which has the same effect as &%-oi%&, specifies that a dot on a
3814 line by itself should not terminate an incoming, non-SMTP message.
3815 Solaris 2.4 (SunOS 5.4) Sendmail has a similar &%-i%& processing option
3816 &url(https://docs.oracle.com/cd/E19457-01/801-6680-1M/801-6680-1M.pdf),
3817 p. 1M-529), and therefore a &%-oi%& command line option, which both are used
3818 by its &'mailx'& command.
3820 .vitem &%-L%&&~<&'tag'&>
3822 .cindex "syslog" "process name; set with flag"
3823 This option is equivalent to setting &%syslog_processname%& in the config
3824 file and setting &%log_file_path%& to &`syslog`&.
3825 Its use is restricted to administrators. The configuration file has to be
3826 read and parsed, to determine access rights, before this is set and takes
3827 effect, so early configuration file errors will not honour this flag.
3829 The tag should not be longer than 32 characters.
3831 .vitem &%-M%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3833 .cindex "forcing delivery"
3834 .cindex "delivery" "forcing attempt"
3835 .cindex "frozen messages" "forcing delivery"
3836 This option requests Exim to run a delivery attempt on each message in turn. If
3837 any of the messages are frozen, they are automatically thawed before the
3838 delivery attempt. The settings of &%queue_domains%&, &%queue_smtp_domains%&,
3839 and &%hold_domains%& are ignored.
3842 .cindex "hints database" "overriding retry hints"
3843 hints for any of the addresses are overridden &-- Exim tries to deliver even if
3844 the normal retry time has not yet been reached. This option requires the caller
3845 to be an admin user. However, there is an option called &%prod_requires_admin%&
3846 which can be set false to relax this restriction (and also the same requirement
3847 for the &%-q%&, &%-R%&, and &%-S%& options).
3849 The deliveries happen synchronously, that is, the original Exim process does
3850 not terminate until all the delivery attempts have finished. No output is
3851 produced unless there is a serious error. If you want to see what is happening,
3852 use the &%-v%& option as well, or inspect Exim's main log.
3854 .vitem &%-Mar%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3856 .cindex "message" "adding recipients"
3857 .cindex "recipient" "adding"
3858 This option requests Exim to add the addresses to the list of recipients of the
3859 message (&"ar"& for &"add recipients"&). The first argument must be a message
3860 id, and the remaining ones must be email addresses. However, if the message is
3861 active (in the middle of a delivery attempt), it is not altered. This option
3862 can be used only by an admin user.
3864 .vitem "&%-MC%&&~<&'transport'&>&~<&'hostname'&>&&&
3866 &~<&'sequence&~number'&>&&&
3867 &~<&'message&~id'&>"
3869 .cindex "SMTP" "passed connection"
3870 .cindex "SMTP" "multiple deliveries"
3871 .cindex "multiple SMTP deliveries"
3872 This option is not intended for use by external callers. It is used internally
3873 by Exim to invoke another instance of itself to deliver a waiting message using
3874 an existing SMTP connection, which is passed as the standard input. Details are
3875 given in chapter &<<CHAPSMTP>>&. This must be the final option, and the caller
3876 must be root or the Exim user in order to use it.
3880 This option is not intended for use by external callers. It is used internally
3881 by Exim in conjunction with the &%-MC%& option. It signifies that the
3882 connection to the remote host has been authenticated.
3886 This option is not intended for use by external callers. It is used internally
3887 by Exim in conjunction with the &%-MC%& option. It signifies that the
3888 remote host supports the ESMTP &_DSN_& extension.
3892 This option is not intended for use by external callers. It is used internally
3893 by Exim in conjunction with the &%-d%& option
3894 to pass on an information string on the purpose of the process.
3896 .vitem &%-MCG%&&~<&'queue&~name'&>
3898 This option is not intended for use by external callers. It is used internally
3899 by Exim in conjunction with the &%-MC%& option. It signifies that an
3900 alternate queue is used, named by the following argument.
3904 This option is not intended for use by external callers. It is used internally
3905 by Exim in conjunction with the &%-MC%& option. It signifies that a
3906 remote host supports the ESMTP &_CHUNKING_& extension.
3910 This option is not intended for use by external callers. It is used internally
3911 by Exim in conjunction with the &%-MC%& option. It signifies that the server to
3912 which Exim is connected advertised limits on numbers of mails, recipients or
3914 The limits are given by the following three arguments.
3918 This option is not intended for use by external callers. It is used internally
3919 by Exim in conjunction with the &%-MC%& option. It signifies that the server to
3920 which Exim is connected supports pipelining.
3924 This option is not intended for use by external callers. It is used internally
3925 by Exim in conjunction with the &%-MC%& option. It signifies that the connection
3926 t a remote server is via a SOCKS proxy, using addresses and ports given by
3927 the following four arguments.
3929 .vitem &%-MCQ%&&~<&'process&~id'&>&~<&'pipe&~fd'&>
3931 This option is not intended for use by external callers. It is used internally
3932 by Exim in conjunction with the &%-MC%& option when the original delivery was
3933 started by a queue runner. It passes on the process id of the queue runner,
3934 together with the file descriptor number of an open pipe. Closure of the pipe
3935 signals the final completion of the sequence of processes that are passing
3936 messages through the same SMTP connection.
3938 .vitem &%-MCq%&&~<&'recipient&~address'&>&~<&'size'&>
3940 This option is not intended for use by external callers. It is used internally
3941 by Exim to implement quota checking for local users.
3945 This option is not intended for use by external callers. It is used internally
3946 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3947 ESMTP SIZE option should be used on messages delivered down the existing
3952 This option is not intended for use by external callers. It is used internally
3953 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3954 host to which Exim is connected supports TLS encryption.
3956 .vitem &%-MCr%&&~<&'SNI'&> &&&
3960 These options are not intended for use by external callers. It is used internally
3961 by Exim in conjunction with the &%-MCt%& option, and passes on the fact that
3962 a TLS Server Name Indication was sent as part of the channel establishment.
3963 The argument gives the SNI string.
3964 The "r" variant indicates a DANE-verified connection.
3966 .vitem &%-MCt%&&~<&'IP&~address'&>&~<&'port'&>&~<&'cipher'&>
3968 This option is not intended for use by external callers. It is used internally
3969 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3970 connection is being proxied by a parent process for handling TLS encryption.
3971 The arguments give the local address and port being proxied, and the TLS cipher.
3973 .vitem &%-Mc%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3975 .cindex "hints database" "not overridden by &%-Mc%&"
3976 .cindex "delivery" "manually started &-- not forced"
3977 This option requests Exim to run a delivery attempt on each message, in turn,
3978 but unlike the &%-M%& option, it does check for retry hints, and respects any
3979 that are found. This option is not very useful to external callers. It is
3980 provided mainly for internal use by Exim when it needs to re-invoke itself in
3981 order to regain root privilege for a delivery (see chapter &<<CHAPsecurity>>&).
3982 However, &%-Mc%& can be useful when testing, in order to run a delivery that
3983 respects retry times and other options such as &%hold_domains%& that are
3984 overridden when &%-M%& is used. Such a delivery does not count as a queue run.
3985 If you want to run a specific delivery as if in a queue run, you should use
3986 &%-q%& with a message id argument. A distinction between queue run deliveries
3987 and other deliveries is made in one or two places.
3989 .vitem &%-Mes%&&~<&'message&~id'&>&~<&'address'&>
3991 .cindex "message" "changing sender"
3992 .cindex "sender" "changing"
3993 This option requests Exim to change the sender address in the message to the
3994 given address, which must be a fully qualified address or &"<>"& (&"es"& for
3995 &"edit sender"&). There must be exactly two arguments. The first argument must
3996 be a message id, and the second one an email address. However, if the message
3997 is active (in the middle of a delivery attempt), its status is not altered.
3998 This option can be used only by an admin user.
4000 .vitem &%-Mf%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4002 .cindex "freezing messages"
4003 .cindex "message" "manually freezing"
4004 This option requests Exim to mark each listed message as &"frozen"&. This
4005 prevents any delivery attempts taking place until the message is &"thawed"&,
4006 either manually or as a result of the &%auto_thaw%& configuration option.
4007 However, if any of the messages are active (in the middle of a delivery
4008 attempt), their status is not altered. This option can be used only by an admin
4011 .vitem &%-Mg%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4013 .cindex "giving up on messages"
4014 .cindex "message" "abandoning delivery attempts"
4015 .cindex "delivery" "abandoning further attempts"
4016 This option requests Exim to give up trying to deliver the listed messages,
4017 including any that are frozen. However, if any of the messages are active,
4018 their status is not altered. For non-bounce messages, a delivery error message
4019 is sent to the sender, containing the text &"cancelled by administrator"&.
4020 Bounce messages are just discarded. This option can be used only by an admin
4023 .vitem &%-MG%&&~<&'queue&~name'&>&~<&'message&~id'&>&~<&'message&~id'&>&~...
4026 .cindex "named queues" "moving messages"
4027 .cindex "queue" "moving messages"
4028 This option requests that each listed message be moved from its current
4029 queue to the given named queue.
4030 The destination queue name argument is required, but can be an empty
4031 string to define the default queue.
4032 If the messages are not currently located in the default queue,
4033 a &%-qG<name>%& option will be required to define the source queue.
4035 .vitem &%-Mmad%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4037 .cindex "delivery" "cancelling all"
4038 This option requests Exim to mark all the recipient addresses in the messages
4039 as already delivered (&"mad"& for &"mark all delivered"&). However, if any
4040 message is active (in the middle of a delivery attempt), its status is not
4041 altered. This option can be used only by an admin user.
4043 .vitem &%-Mmd%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
4045 .cindex "delivery" "cancelling by address"
4046 .cindex "recipient" "removing"
4047 .cindex "removing recipients"
4048 This option requests Exim to mark the given addresses as already delivered
4049 (&"md"& for &"mark delivered"&). The first argument must be a message id, and
4050 the remaining ones must be email addresses. These are matched to recipient
4051 addresses in the message in a case-sensitive manner. If the message is active
4052 (in the middle of a delivery attempt), its status is not altered. This option
4053 can be used only by an admin user.
4055 .vitem &%-Mrm%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4057 .cindex "removing messages"
4058 .cindex "abandoning mail"
4059 .cindex "message" "manually discarding"
4060 This option requests Exim to remove the given messages from the queue. No
4061 bounce messages are sent; each message is simply forgotten. However, if any of
4062 the messages are active, their status is not altered. This option can be used
4063 only by an admin user or by the user who originally caused the message to be
4064 placed in the queue.
4069 . .cindex REQUIRETLS
4070 . This option is used to request REQUIRETLS processing on the message.
4071 . It is used internally by Exim in conjunction with -E when generating
4075 .vitem &%-Mset%&&~<&'message&~id'&>
4077 .cindex "testing" "string expansion"
4078 .cindex "expansion" "testing"
4079 This option is useful only in conjunction with &%-be%& (that is, when testing
4080 string expansions). Exim loads the given message from its spool before doing
4081 the test expansions, thus setting message-specific variables such as
4082 &$message_size$& and the header variables. The &$recipients$& variable is made
4083 available. This feature is provided to make it easier to test expansions that
4084 make use of these variables. However, this option can be used only by an admin
4085 user. See also &%-bem%&.
4087 .vitem &%-Mt%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4089 .cindex "thawing messages"
4090 .cindex "unfreezing messages"
4091 .cindex "frozen messages" "thawing"
4092 .cindex "message" "thawing frozen"
4093 This option requests Exim to &"thaw"& any of the listed messages that are
4094 &"frozen"&, so that delivery attempts can resume. However, if any of the
4095 messages are active, their status is not altered. This option can be used only
4098 .vitem &%-Mvb%&&~<&'message&~id'&>
4100 .cindex "listing" "message body"
4101 .cindex "message" "listing body of"
4102 This option causes the contents of the message body (-D) spool file to be
4103 written to the standard output. This option can be used only by an admin user.
4105 .vitem &%-Mvc%&&~<&'message&~id'&>
4107 .cindex "message" "listing in RFC 2822 format"
4108 .cindex "listing" "message in RFC 2822 format"
4109 This option causes a copy of the complete message (header lines plus body) to
4110 be written to the standard output in RFC 2822 format. This option can be used
4111 only by an admin user.
4113 .vitem &%-Mvh%&&~<&'message&~id'&>
4115 .cindex "listing" "message headers"
4116 .cindex "header lines" "listing"
4117 .cindex "message" "listing header lines"
4118 This option causes the contents of the message headers (-H) spool file to be
4119 written to the standard output. This option can be used only by an admin user.
4121 .vitem &%-Mvl%&&~<&'message&~id'&>
4123 .cindex "listing" "message log"
4124 .cindex "message" "listing message log"
4125 This option causes the contents of the message log spool file to be written to
4126 the standard output. This option can be used only by an admin user.
4130 This is a synonym for &%-om%& that is accepted by Sendmail
4131 (&url(https://docs.oracle.com/cd/E19457-01/801-6680-1M/801-6680-1M.pdf)
4132 p. 1M-258), so Exim treats it that way too.
4136 .cindex "debugging" "&%-N%& option"
4137 .cindex "debugging" "suppressing delivery"
4138 This is a debugging option that inhibits delivery of a message at the transport
4139 level. It implies &%-v%&. Exim goes through many of the motions of delivery &--
4140 it just doesn't actually transport the message, but instead behaves as if it
4141 had successfully done so. However, it does not make any updates to the retry
4142 database, and the log entries for deliveries are flagged with &"*>"& rather
4145 Because &%-N%& discards any message to which it applies, only root or the Exim
4146 user are allowed to use it with &%-bd%&, &%-q%&, &%-R%& or &%-M%&. In other
4147 words, an ordinary user can use it only when supplying an incoming message to
4148 which it will apply. Although transportation never fails when &%-N%& is set, an
4149 address may be deferred because of a configuration problem on a transport, or a
4150 routing problem. Once &%-N%& has been used for a delivery attempt, it sticks to
4151 the message, and applies to any subsequent delivery attempts that may happen
4156 This option is interpreted by Sendmail to mean &"no aliasing"&.
4157 For normal modes of operation, it is ignored by Exim.
4158 When combined with &%-bP%& it makes the output more terse (suppresses
4159 option names, environment values and config pretty printing).
4161 .vitem &%-O%&&~<&'data'&>
4163 This option is interpreted by Sendmail to mean &`set option`&. It is ignored by
4166 .vitem &%-oA%&&~<&'file&~name'&>
4168 .cindex "Sendmail compatibility" "&%-oA%& option"
4169 This option is used by Sendmail in conjunction with &%-bi%& to specify an
4170 alternative alias filename. Exim handles &%-bi%& differently; see the
4173 .vitem &%-oB%&&~<&'n'&>
4175 .cindex "SMTP" "passed connection"
4176 .cindex "SMTP" "multiple deliveries"
4177 .cindex "multiple SMTP deliveries"
4178 This is a debugging option which limits the maximum number of messages that can
4179 be delivered down one SMTP connection, overriding the value set in any &(smtp)&
4180 transport. If <&'n'&> is omitted, the limit is set to 1.
4184 .cindex "background delivery"
4185 .cindex "delivery" "in the background"
4186 This option applies to all modes in which Exim accepts incoming messages,
4187 including the listening daemon. It requests &"background"& delivery of such
4188 messages, which means that the accepting process automatically starts a
4189 delivery process for each message received, but does not wait for the delivery
4190 processes to finish.
4192 When all the messages have been received, the reception process exits,
4193 leaving the delivery processes to finish in their own time. The standard output
4194 and error streams are closed at the start of each delivery process.
4195 This is the default action if none of the &%-od%& options are present.
4197 If one of the queueing options in the configuration file
4198 (&%queue_only%& or &%queue_only_file%&, for example) is in effect, &%-odb%&
4199 overrides it if &%queue_only_override%& is set true, which is the default
4200 setting. If &%queue_only_override%& is set false, &%-odb%& has no effect.
4204 .cindex "foreground delivery"
4205 .cindex "delivery" "in the foreground"
4206 This option requests &"foreground"& (synchronous) delivery when Exim has
4207 accepted a locally-generated message. (For the daemon it is exactly the same as
4208 &%-odb%&.) A delivery process is automatically started to deliver the message,
4209 and Exim waits for it to complete before proceeding.
4211 The original Exim reception process does not finish until the delivery
4212 process for the final message has ended. The standard error stream is left open
4215 However, like &%-odb%&, this option has no effect if &%queue_only_override%& is
4216 false and one of the queueing options in the configuration file is in effect.
4218 If there is a temporary delivery error during foreground delivery, the
4219 message is left in the queue for later delivery, and the original reception
4220 process exits. See chapter &<<CHAPnonqueueing>>& for a way of setting up a
4221 restricted configuration that never queues messages.
4226 This option is synonymous with &%-odf%&. It is provided for compatibility with
4231 .cindex "non-immediate delivery"
4232 .cindex "delivery" "suppressing immediate"
4233 .cindex "queueing incoming messages"
4234 This option applies to all modes in which Exim accepts incoming messages,
4235 including the listening daemon. It specifies that the accepting process should
4236 not automatically start a delivery process for each message received. Messages
4237 are placed in the queue, and remain there until a subsequent queue runner
4238 process encounters them. There are several configuration options (such as
4239 &%queue_only%&) that can be used to queue incoming messages under certain
4240 conditions. This option overrides all of them and also &%-odqs%&. It always
4245 .cindex "SMTP" "delaying delivery"
4246 .cindex "first pass routing"
4247 This option is a hybrid between &%-odb%&/&%-odi%& and &%-odq%&.
4248 However, like &%-odb%& and &%-odi%&, this option has no effect if
4249 &%queue_only_override%& is false and one of the queueing options in the
4250 configuration file is in effect.
4252 When &%-odqs%& does operate, a delivery process is started for each incoming
4253 message, in the background by default, but in the foreground if &%-odi%& is
4254 also present. The recipient addresses are routed, and local deliveries are done
4255 in the normal way. However, if any SMTP deliveries are required, they are not
4256 done at this time, so the message remains in the queue until a subsequent queue
4257 runner process encounters it. Because routing was done, Exim knows which
4258 messages are waiting for which hosts, and so a number of messages for the same
4259 host can be sent in a single SMTP connection. The &%queue_smtp_domains%&
4260 configuration option has the same effect for specific domains. See also the
4265 .cindex "error" "reporting"
4266 If an error is detected while a non-SMTP message is being received (for
4267 example, a malformed address), the error is reported to the sender in a mail
4270 .cindex "return code" "for &%-oee%&"
4272 this error message is successfully sent, the Exim receiving process
4273 exits with a return code of zero. If not, the return code is 2 if the problem
4274 is that the original message has no recipients, or 1 for any other error.
4275 This is the default &%-oe%&&'x'& option if Exim is called as &'rmail'&.
4279 .cindex "error" "reporting"
4280 .cindex "return code" "for &%-oem%&"
4281 This is the same as &%-oee%&, except that Exim always exits with a non-zero
4282 return code, whether or not the error message was successfully sent.
4283 This is the default &%-oe%&&'x'& option, unless Exim is called as &'rmail'&.
4287 .cindex "error" "reporting"
4288 If an error is detected while a non-SMTP message is being received, the
4289 error is reported by writing a message to the standard error file (stderr).
4290 .cindex "return code" "for &%-oep%&"
4291 The return code is 1 for all errors.
4295 .cindex "error" "reporting"
4296 This option is supported for compatibility with Sendmail, but has the same
4301 .cindex "error" "reporting"
4302 This option is supported for compatibility with Sendmail, but has the same
4307 .cindex "dot" "in incoming non-SMTP message"
4308 This option, which has the same effect as &%-i%&, specifies that a dot on a
4309 line by itself should not terminate an incoming, non-SMTP message. Otherwise, a
4310 single dot does terminate, though Exim does no special processing for other
4311 lines that start with a dot. This option is set by default if Exim is called as
4312 &'rmail'&. See also &%-ti%&.
4315 .oindex "&%-oitrue%&"
4316 This option is treated as synonymous with &%-oi%&.
4318 .vitem &%-oMa%&&~<&'host&~address'&>
4320 .cindex "sender" "host address, specifying for local message"
4321 A number of options starting with &%-oM%& can be used to set values associated
4322 with remote hosts on locally-submitted messages (that is, messages not received
4323 over TCP/IP). These options can be used by any caller in conjunction with the
4324 &%-bh%&, &%-be%&, &%-bf%&, &%-bF%&, &%-bt%&, or &%-bv%& testing options. In
4325 other circumstances, they are ignored unless the caller is trusted.
4327 The &%-oMa%& option sets the sender host address. This may include a port
4328 number at the end, after a full stop (period). For example:
4330 exim -bs -oMa 10.9.8.7.1234
4332 An alternative syntax is to enclose the IP address in square brackets,
4333 followed by a colon and the port number:
4335 exim -bs -oMa [10.9.8.7]:1234
4337 The IP address is placed in the &$sender_host_address$& variable, and the
4338 port, if present, in &$sender_host_port$&. If both &%-oMa%& and &%-bh%&
4339 are present on the command line, the sender host IP address is taken from
4340 whichever one is last.
4342 .vitem &%-oMaa%&&~<&'name'&>
4344 .cindex "authentication" "name, specifying for local message"
4345 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMaa%&
4346 option sets the value of &$sender_host_authenticated$& (the authenticator
4347 name). See chapter &<<CHAPSMTPAUTH>>& for a discussion of SMTP authentication.
4348 This option can be used with &%-bh%& and &%-bs%& to set up an
4349 authenticated SMTP session without actually using the SMTP AUTH command.
4351 .vitem &%-oMai%&&~<&'string'&>
4353 .cindex "authentication" "id, specifying for local message"
4354 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMai%&
4355 option sets the value of &$authenticated_id$& (the id that was authenticated).
4356 This overrides the default value (the caller's login id, except with &%-bh%&,
4357 where there is no default) for messages from local sources. See chapter
4358 &<<CHAPSMTPAUTH>>& for a discussion of authenticated ids.
4360 .vitem &%-oMas%&&~<&'address'&>
4362 .cindex "authentication" "sender, specifying for local message"
4363 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMas%&
4364 option sets the authenticated sender value in &$authenticated_sender$&. It
4365 overrides the sender address that is created from the caller's login id for
4366 messages from local sources, except when &%-bh%& is used, when there is no
4367 default. For both &%-bh%& and &%-bs%&, an authenticated sender that is
4368 specified on a MAIL command overrides this value. See chapter
4369 &<<CHAPSMTPAUTH>>& for a discussion of authenticated senders.
4371 .vitem &%-oMi%&&~<&'interface&~address'&>
4373 .cindex "interface" "address, specifying for local message"
4374 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMi%&
4375 option sets the IP interface address value. A port number may be included,
4376 using the same syntax as for &%-oMa%&. The interface address is placed in
4377 &$received_ip_address$& and the port number, if present, in &$received_port$&.
4379 .vitem &%-oMm%&&~<&'message&~reference'&>
4381 .cindex "message reference" "message reference, specifying for local message"
4382 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMm%&
4383 option sets the message reference, e.g. message-id, and is logged during
4384 delivery. This is useful when some kind of audit trail is required to tie
4385 messages together. The format of the message reference is checked and will
4386 abort if the format is invalid. The option will only be accepted if exim is
4387 running in trusted mode, not as any regular user.
4389 The best example of a message reference is when Exim sends a bounce message.
4390 The message reference is the message-id of the original message for which Exim
4391 is sending the bounce.
4393 .vitem &%-oMr%&&~<&'protocol&~name'&>
4395 .cindex "protocol, specifying for local message"
4396 .vindex "&$received_protocol$&"
4397 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMr%&
4398 option sets the received protocol value that is stored in
4399 &$received_protocol$&. However, it does not apply (and is ignored) when &%-bh%&
4400 or &%-bs%& is used. For &%-bh%&, the protocol is forced to one of the standard
4401 SMTP protocol names (see the description of &$received_protocol$& in section
4402 &<<SECTexpvar>>&). For &%-bs%&, the protocol is always &"local-"& followed by
4403 one of those same names. For &%-bS%& (batched SMTP) however, the protocol can
4404 be set by &%-oMr%&. Repeated use of this option is not supported.
4406 .vitem &%-oMs%&&~<&'host&~name'&>
4408 .cindex "sender" "host name, specifying for local message"
4409 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMs%&
4410 option sets the sender host name in &$sender_host_name$&. When this option is
4411 present, Exim does not attempt to look up a host name from an IP address; it
4412 uses the name it is given.
4414 .vitem &%-oMt%&&~<&'ident&~string'&>
4416 .cindex "sender" "ident string, specifying for local message"
4417 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMt%&
4418 option sets the sender ident value in &$sender_ident$&. The default setting for
4419 local callers is the login id of the calling process, except when &%-bh%& is
4420 used, when there is no default.
4424 .cindex "Sendmail compatibility" "&%-om%& option ignored"
4425 In Sendmail, this option means &"me too"&, indicating that the sender of a
4426 message should receive a copy of the message if the sender appears in an alias
4427 expansion. Exim always does this, so the option does nothing.
4431 .cindex "Sendmail compatibility" "&%-oo%& option ignored"
4432 This option is ignored. In Sendmail it specifies &"old style headers"&,
4433 whatever that means.
4435 .vitem &%-oP%&&~<&'path'&>
4437 .cindex "pid (process id)" "of daemon"
4438 .cindex "daemon" "process id (pid)"
4439 This option is useful only in conjunction with &%-bd%& or &%-q%& with a time
4440 value. The option specifies the file to which the process id of the daemon is
4441 written. When &%-oX%& is used with &%-bd%&, or when &%-q%& with a time is used
4442 without &%-bd%&, this is the only way of causing Exim to write a pid file,
4443 because in those cases, the normal pid file is not used.
4447 .cindex "pid (process id)" "of daemon"
4448 .cindex "daemon" "process id (pid)"
4449 This option is not intended for general use.
4450 The daemon uses it when terminating due to a SIGTEM, possibly in
4451 combination with &%-oP%&&~<&'path'&>.
4452 It causes the pid file to be removed.
4454 .vitem &%-or%&&~<&'time'&>
4456 .cindex "timeout" "for non-SMTP input"
4457 This option sets a timeout value for incoming non-SMTP messages. If it is not
4458 set, Exim will wait forever for the standard input. The value can also be set
4459 by the &%receive_timeout%& option. The format used for specifying times is
4460 described in section &<<SECTtimeformat>>&.
4462 .vitem &%-os%&&~<&'time'&>
4464 .cindex "timeout" "for SMTP input"
4465 .cindex "SMTP" "input timeout"
4466 This option sets a timeout value for incoming SMTP messages. The timeout
4467 applies to each SMTP command and block of data. The value can also be set by
4468 the &%smtp_receive_timeout%& option; it defaults to 5 minutes. The format used
4469 for specifying times is described in section &<<SECTtimeformat>>&.
4473 This option has exactly the same effect as &%-v%&.
4475 .vitem &%-oX%&&~<&'number&~or&~string'&>
4477 .cindex "TCP/IP" "setting listening ports"
4478 .cindex "TCP/IP" "setting listening interfaces"
4479 .cindex "port" "receiving TCP/IP"
4480 This option is relevant only when the &%-bd%& (start listening daemon) option
4481 is also given. It controls which ports and interfaces the daemon uses. Details
4482 of the syntax, and how it interacts with configuration file options, are given
4483 in chapter &<<CHAPinterfaces>>&. When &%-oX%& is used to start a daemon, no pid
4484 file is written unless &%-oP%& is also present to specify a pid filename.
4488 .cindex "daemon notifier socket"
4489 This option controls the creation of an inter-process communications endpoint
4491 It is only relevant when the &%-bd%& (start listening daemon) option is also
4493 Normally the daemon creates this socket, unless a &%-oX%& and &*no*& &%-oP%&
4494 option is also present.
4495 If this option is given then the socket will not be created. This could be
4496 required if the system is running multiple daemons.
4498 The socket is currently used for
4500 fast ramp-up of queue runner processes
4502 obtaining a current queue size
4507 .cindex "Perl" "starting the interpreter"
4508 This option applies when an embedded Perl interpreter is linked with Exim (see
4509 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4510 option, forcing the starting of the interpreter to be delayed until it is
4515 .cindex "Perl" "starting the interpreter"
4516 This option applies when an embedded Perl interpreter is linked with Exim (see
4517 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4518 option, forcing the starting of the interpreter to occur as soon as Exim is
4521 .vitem &%-p%&<&'rval'&>:<&'sval'&>
4523 For compatibility with Sendmail, this option is equivalent to
4525 &`-oMr`& <&'rval'&> &`-oMs`& <&'sval'&>
4527 It sets the incoming protocol and host name (for trusted callers). The
4528 host name and its colon can be omitted when only the protocol is to be set.
4529 Note the Exim already has two private options, &%-pd%& and &%-ps%&, that refer
4530 to embedded Perl. It is therefore impossible to set a protocol value of &`d`&
4531 or &`s`& using this option (but that does not seem a real limitation).
4532 Repeated use of this option is not supported.
4536 .cindex "queue runner" "starting manually"
4537 This option is normally restricted to admin users. However, there is a
4538 configuration option called &%prod_requires_admin%& which can be set false to
4539 relax this restriction (and also the same requirement for the &%-M%&, &%-R%&,
4540 and &%-S%& options).
4542 .cindex "queue runner" "description of operation"
4543 If other commandline options do not specify an action,
4544 the &%-q%& option starts one queue runner process. This scans the queue of
4545 waiting messages, and runs a delivery process for each one in turn. It waits
4546 for each delivery process to finish before starting the next one. A delivery
4547 process may not actually do any deliveries if the retry times for the addresses
4548 have not been reached. Use &%-qf%& (see below) if you want to override this.
4551 .cindex "SMTP" "passed connection"
4552 .cindex "SMTP" "multiple deliveries"
4553 .cindex "multiple SMTP deliveries"
4554 the delivery process spawns other processes to deliver other messages down
4555 passed SMTP connections, the queue runner waits for these to finish before
4558 When all the queued messages have been considered, the original queue runner
4559 process terminates. In other words, a single pass is made over the waiting
4560 mail, one message at a time. Use &%-q%& with a time (see below) if you want
4561 this to be repeated periodically.
4563 Exim processes the waiting messages in an unpredictable order. It isn't very
4564 random, but it is likely to be different each time, which is all that matters.
4565 If one particular message screws up a remote MTA, other messages to the same
4566 MTA have a chance of getting through if they get tried first.
4568 It is possible to cause the messages to be processed in lexical message id
4569 order, which is essentially the order in which they arrived, by setting the
4570 &%queue_run_in_order%& option, but this is not recommended for normal use.
4572 .vitem &%-q%&<&'qflags'&>
4573 The &%-q%& option may be followed by one or more flag letters that change its
4574 behaviour. They are all optional, but if more than one is present, they must
4575 appear in the correct order. Each flag is described in a separate item below.
4579 .cindex "queue" "double scanning"
4580 .cindex "queue" "routing"
4581 .cindex "routing" "whole queue before delivery"
4582 .cindex "first pass routing"
4583 .cindex "queue runner" "two phase"
4584 An option starting with &%-qq%& requests a two-stage queue run. In the first
4585 stage, the queue is scanned as if the &%queue_smtp_domains%& option matched
4586 every domain. Addresses are routed, local deliveries happen, but no remote
4589 Performance will be best if the &%queue_run_in_order%& option is false.
4590 If that is so and the &%queue_fast_ramp%& option is true then
4591 in the first phase of the run,
4592 once a threshold number of messages are routed for a given host,
4593 a delivery process is forked in parallel with the rest of the scan.
4595 .cindex "hints database" "remembering routing"
4596 The hints database that remembers which messages are waiting for specific hosts
4597 is updated, as if delivery to those hosts had been deferred. After this is
4598 complete, a second, normal queue scan happens, with routing and delivery taking
4599 place as normal. Messages that are routed to the same host should mostly be
4600 delivered down a single SMTP
4601 .cindex "SMTP" "passed connection"
4602 .cindex "SMTP" "multiple deliveries"
4603 .cindex "multiple SMTP deliveries"
4604 connection because of the hints that were set up during the first queue scan.
4605 This option may be useful for hosts that are connected to the Internet
4608 .vitem &%-q[q]i...%&
4610 .cindex "queue" "initial delivery"
4611 If the &'i'& flag is present, the queue runner runs delivery processes only for
4612 those messages that haven't previously been tried. (&'i'& stands for &"initial
4613 delivery"&.) This can be helpful if you are putting messages in the queue using
4614 &%-odq%& and want a queue runner just to process the new messages.
4616 .vitem &%-q[q][i]f...%&
4618 .cindex "queue" "forcing delivery"
4619 .cindex "delivery" "forcing in queue run"
4620 If one &'f'& flag is present, a delivery attempt is forced for each non-frozen
4621 message, whereas without &'f'& only those non-frozen addresses that have passed
4622 their retry times are tried.
4624 .vitem &%-q[q][i]ff...%&
4626 .cindex "frozen messages" "forcing delivery"
4627 If &'ff'& is present, a delivery attempt is forced for every message, whether
4630 .vitem &%-q[q][i][f[f]]l%&
4632 .cindex "queue" "local deliveries only"
4633 The &'l'& (the letter &"ell"&) flag specifies that only local deliveries are to
4634 be done. If a message requires any remote deliveries, it remains in the queue
4637 .vitem &%-q[q][i][f[f]][l][G<name>[/<time>]]]%&
4640 .cindex "named queues" "deliver from"
4641 .cindex "queue" "delivering specific messages"
4642 If the &'G'& flag and a name is present, the queue runner operates on the
4643 queue with the given name rather than the default queue.
4644 The name should not contain a &'/'& character.
4645 For a periodic queue run (see below)
4646 append to the name a slash and a time value.
4648 If other commandline options specify an action, a &'-qG<name>'& option
4649 will specify a queue to operate on.
4652 exim -bp -qGquarantine
4654 exim -qGoffpeak -Rf @special.domain.example
4657 .vitem &%-q%&<&'qflags'&>&~<&'start&~id'&>&~<&'end&~id'&>
4658 When scanning the queue, Exim can be made to skip over messages whose ids are
4659 lexically less than a given value by following the &%-q%& option with a
4660 starting message id. For example:
4662 exim -q 0t5C6f-0000c8-00
4664 Messages that arrived earlier than &`0t5C6f-0000c8-00`& are not inspected. If a
4665 second message id is given, messages whose ids are lexically greater than it
4666 are also skipped. If the same id is given twice, for example,
4668 exim -q 0t5C6f-0000c8-00 0t5C6f-0000c8-00
4670 just one delivery process is started, for that message. This differs from
4671 &%-M%& in that retry data is respected, and it also differs from &%-Mc%& in
4672 that it counts as a delivery from a queue run. Note that the selection
4673 mechanism does not affect the order in which the messages are scanned. There
4674 are also other ways of selecting specific sets of messages for delivery in a
4675 queue run &-- see &%-R%& and &%-S%&.
4677 .vitem &%-q%&<&'qflags'&><&'time'&>
4678 .cindex "queue runner" "starting periodically"
4679 .cindex "periodic queue running"
4680 When a time value is present, the &%-q%& option causes Exim to run as a daemon,
4681 starting a queue runner process at intervals specified by the given time value
4682 (whose format is described in section &<<SECTtimeformat>>&). This form of the
4683 &%-q%& option is commonly combined with the &%-bd%& option, in which case a
4684 single daemon process handles both functions. A common way of starting up a
4685 combined daemon at system boot time is to use a command such as
4687 /usr/exim/bin/exim -bd -q30m
4689 Such a daemon listens for incoming SMTP calls, and also starts a queue runner
4690 process every 30 minutes.
4692 When a daemon is started by &%-q%& with a time value, but without &%-bd%&, no
4693 pid file is written unless one is explicitly requested by the &%-oP%& option.
4695 .vitem &%-qR%&<&'rsflags'&>&~<&'string'&>
4697 This option is synonymous with &%-R%&. It is provided for Sendmail
4700 .vitem &%-qS%&<&'rsflags'&>&~<&'string'&>
4702 This option is synonymous with &%-S%&.
4704 .vitem &%-R%&<&'rsflags'&>&~<&'string'&>
4706 .cindex "queue runner" "for specific recipients"
4707 .cindex "delivery" "to given domain"
4708 .cindex "domain" "delivery to"
4709 The <&'rsflags'&> may be empty, in which case the white space before the string
4710 is optional, unless the string is &'f'&, &'ff'&, &'r'&, &'rf'&, or &'rff'&,
4711 which are the possible values for <&'rsflags'&>. White space is required if
4712 <&'rsflags'&> is not empty.
4714 This option is similar to &%-q%& with no time value, that is, it causes Exim to
4715 perform a single queue run, except that, when scanning the messages on the
4716 queue, Exim processes only those that have at least one undelivered recipient
4717 address containing the given string, which is checked in a case-independent
4718 way. If the <&'rsflags'&> start with &'r'&, <&'string'&> is interpreted as a
4719 regular expression; otherwise it is a literal string.
4721 If you want to do periodic queue runs for messages with specific recipients,
4722 you can combine &%-R%& with &%-q%& and a time value. For example:
4724 exim -q25m -R @special.domain.example
4726 This example does a queue run for messages with recipients in the given domain
4727 every 25 minutes. Any additional flags that are specified with &%-q%& are
4728 applied to each queue run.
4730 Once a message is selected for delivery by this mechanism, all its addresses
4731 are processed. For the first selected message, Exim overrides any retry
4732 information and forces a delivery attempt for each undelivered address. This
4733 means that if delivery of any address in the first message is successful, any
4734 existing retry information is deleted, and so delivery attempts for that
4735 address in subsequently selected messages (which are processed without forcing)
4736 will run. However, if delivery of any address does not succeed, the retry
4737 information is updated, and in subsequently selected messages, the failing
4738 address will be skipped.
4740 .cindex "frozen messages" "forcing delivery"
4741 If the <&'rsflags'&> contain &'f'& or &'ff'&, the delivery forcing applies to
4742 all selected messages, not just the first; frozen messages are included when
4745 The &%-R%& option makes it straightforward to initiate delivery of all messages
4746 to a given domain after a host has been down for some time. When the SMTP
4747 command ETRN is accepted by its ACL (see chapter &<<CHAPACL>>&), its default
4748 effect is to run Exim with the &%-R%& option, but it can be configured to run
4749 an arbitrary command instead.
4753 This is a documented (for Sendmail) obsolete alternative name for &%-f%&.
4755 .vitem &%-S%&<&'rsflags'&>&~<&'string'&>
4757 .cindex "delivery" "from given sender"
4758 .cindex "queue runner" "for specific senders"
4759 This option acts like &%-R%& except that it checks the string against each
4760 message's sender instead of against the recipients. If &%-R%& is also set, both
4761 conditions must be met for a message to be selected. If either of the options
4762 has &'f'& or &'ff'& in its flags, the associated action is taken.
4764 .vitem &%-Tqt%&&~<&'times'&>
4766 This is an option that is exclusively for use by the Exim testing suite. It is not
4767 recognized when Exim is run normally. It allows for the setting up of explicit
4768 &"queue times"& so that various warning/retry features can be tested.
4772 .cindex "recipient" "extracting from header lines"
4776 When Exim is receiving a locally-generated, non-SMTP message on its standard
4777 input, the &%-t%& option causes the recipients of the message to be obtained
4778 from the &'To:'&, &'Cc:'&, and &'Bcc:'& header lines in the message instead of
4779 from the command arguments. The addresses are extracted before any rewriting
4780 takes place and the &'Bcc:'& header line, if present, is then removed.
4782 .cindex "Sendmail compatibility" "&%-t%& option"
4783 If the command has any arguments, they specify addresses to which the message
4784 is &'not'& to be delivered. That is, the argument addresses are removed from
4785 the recipients list obtained from the headers. This is compatible with Smail 3
4786 and in accordance with the documented behaviour of several versions of
4787 Sendmail, as described in man pages on a number of operating systems (e.g.
4788 Solaris 8, IRIX 6.5, HP-UX 11). However, some versions of Sendmail &'add'&
4789 argument addresses to those obtained from the headers, and the O'Reilly
4790 Sendmail book documents it that way. Exim can be made to add argument addresses
4791 instead of subtracting them by setting the option
4792 &%extract_addresses_remove_arguments%& false.
4794 .cindex "&%Resent-%& header lines" "with &%-t%&"
4795 If there are any &%Resent-%& header lines in the message, Exim extracts
4796 recipients from all &'Resent-To:'&, &'Resent-Cc:'&, and &'Resent-Bcc:'& header
4797 lines instead of from &'To:'&, &'Cc:'&, and &'Bcc:'&. This is for compatibility
4798 with Sendmail and other MTAs. (Prior to release 4.20, Exim gave an error if
4799 &%-t%& was used in conjunction with &%Resent-%& header lines.)
4801 RFC 2822 talks about different sets of &%Resent-%& header lines (for when a
4802 message is resent several times). The RFC also specifies that they should be
4803 added at the front of the message, and separated by &'Received:'& lines. It is
4804 not at all clear how &%-t%& should operate in the present of multiple sets,
4805 nor indeed exactly what constitutes a &"set"&.
4806 In practice, it seems that MUAs do not follow the RFC. The &%Resent-%& lines
4807 are often added at the end of the header, and if a message is resent more than
4808 once, it is common for the original set of &%Resent-%& headers to be renamed as
4809 &%X-Resent-%& when a new set is added. This removes any possible ambiguity.
4813 This option is exactly equivalent to &%-t%& &%-i%&. It is provided for
4814 compatibility with Sendmail.
4816 .vitem &%-tls-on-connect%&
4817 .oindex "&%-tls-on-connect%&"
4818 .cindex "TLS" "use without STARTTLS"
4819 .cindex "TLS" "automatic start"
4820 This option is available when Exim is compiled with TLS support. It forces all
4821 incoming SMTP connections to behave as if the incoming port is listed in the
4822 &%tls_on_connect_ports%& option. See section &<<SECTsupobssmt>>& and chapter
4823 &<<CHAPTLS>>& for further details.
4828 .cindex "Sendmail compatibility" "&%-U%& option ignored"
4829 Sendmail uses this option for &"initial message submission"&, and its
4830 documentation states that in future releases, it may complain about
4831 syntactically invalid messages rather than fixing them when this flag is not
4832 set. Exim ignores this option.
4836 This option causes Exim to write information to the standard error stream,
4837 describing what it is doing. In particular, it shows the log lines for
4838 receiving and delivering a message, and if an SMTP connection is made, the SMTP
4839 dialogue is shown. Some of the log lines shown may not actually be written to
4840 the log if the setting of &%log_selector%& discards them. Any relevant
4841 selectors are shown with each log line. If none are shown, the logging is
4846 AIX uses &%-x%& for a private purpose (&"mail from a local mail program has
4847 National Language Support extended characters in the body of the mail item"&).
4848 It sets &%-x%& when calling the MTA from its &%mail%& command. Exim ignores
4851 .vitem &%-X%&&~<&'logfile'&>
4853 This option is interpreted by Sendmail to cause debug information to be sent
4854 to the named file. It is ignored by Exim.
4856 .vitem &%-z%&&~<&'log-line'&>
4858 This option writes its argument to Exim's logfile.
4859 Use is restricted to administrators; the intent is for operational notes.
4860 Quotes should be used to maintain a multi-word item as a single argument,
4868 . ////////////////////////////////////////////////////////////////////////////
4869 . Insert a stylized DocBook comment here, to identify the end of the command
4870 . line options. This is for the benefit of the Perl script that automatically
4871 . creates a man page for the options.
4872 . ////////////////////////////////////////////////////////////////////////////
4875 <!-- === End of command line options === -->
4882 . ////////////////////////////////////////////////////////////////////////////
4883 . ////////////////////////////////////////////////////////////////////////////
4886 .chapter "The Exim runtime configuration file" "CHAPconf" &&&
4887 "The runtime configuration file"
4889 .cindex "runtime configuration"
4890 .cindex "configuration file" "general description"
4891 .cindex "CONFIGURE_FILE"
4892 .cindex "configuration file" "errors in"
4893 .cindex "error" "in configuration file"
4894 .cindex "return code" "for bad configuration"
4895 Exim uses a single runtime configuration file that is read whenever an Exim
4896 binary is executed. Note that in normal operation, this happens frequently,
4897 because Exim is designed to operate in a distributed manner, without central
4900 If a syntax error is detected while reading the configuration file, Exim
4901 writes a message on the standard error, and exits with a non-zero return code.
4902 The message is also written to the panic log. &*Note*&: Only simple syntax
4903 errors can be detected at this time. The values of any expanded options are
4904 not checked until the expansion happens, even when the expansion does not
4905 actually alter the string.
4907 The name of the configuration file is compiled into the binary for security
4908 reasons, and is specified by the CONFIGURE_FILE compilation option. In
4909 most configurations, this specifies a single file. However, it is permitted to
4910 give a colon-separated list of filenames, in which case Exim uses the first
4911 existing file in the list.
4914 .cindex "EXIM_GROUP"
4915 .cindex "CONFIGURE_OWNER"
4916 .cindex "CONFIGURE_GROUP"
4917 .cindex "configuration file" "ownership"
4918 .cindex "ownership" "configuration file"
4919 The runtime configuration file must be owned by root or by the user that is
4920 specified at compile time by the CONFIGURE_OWNER option (if set). The
4921 configuration file must not be world-writeable, or group-writeable unless its
4922 group is the root group or the one specified at compile time by the
4923 CONFIGURE_GROUP option.
4925 &*Warning*&: In a conventional configuration, where the Exim binary is setuid
4926 to root, anybody who is able to edit the runtime configuration file has an
4927 easy way to run commands as root. If you specify a user or group in the
4928 CONFIGURE_OWNER or CONFIGURE_GROUP options, then that user and/or any users
4929 who are members of that group will trivially be able to obtain root privileges.
4931 Up to Exim version 4.72, the runtime configuration file was also permitted to
4932 be writeable by the Exim user and/or group. That has been changed in Exim 4.73
4933 since it offered a simple privilege escalation for any attacker who managed to
4934 compromise the Exim user account.
4936 A default configuration file, which will work correctly in simple situations,
4937 is provided in the file &_src/configure.default_&. If CONFIGURE_FILE
4938 defines just one filename, the installation process copies the default
4939 configuration to a new file of that name if it did not previously exist. If
4940 CONFIGURE_FILE is a list, no default is automatically installed. Chapter
4941 &<<CHAPdefconfil>>& is a &"walk-through"& discussion of the default
4946 .section "Using a different configuration file" "SECID40"
4947 .cindex "configuration file" "alternate"
4948 A one-off alternate configuration can be specified by the &%-C%& command line
4949 option, which may specify a single file or a list of files. However, when
4950 &%-C%& is used, Exim gives up its root privilege, unless called by root (or
4951 unless the argument for &%-C%& is identical to the built-in value from
4952 CONFIGURE_FILE), or is listed in the TRUSTED_CONFIG_LIST file and the caller
4953 is the Exim user or the user specified in the CONFIGURE_OWNER setting. &%-C%&
4954 is useful mainly for checking the syntax of configuration files before
4955 installing them. No owner or group checks are done on a configuration file
4956 specified by &%-C%&, if root privilege has been dropped.
4958 Even the Exim user is not trusted to specify an arbitrary configuration file
4959 with the &%-C%& option to be used with root privileges, unless that file is
4960 listed in the TRUSTED_CONFIG_LIST file. This locks out the possibility of
4961 testing a configuration using &%-C%& right through message reception and
4962 delivery, even if the caller is root. The reception works, but by that time,
4963 Exim is running as the Exim user, so when it re-execs to regain privilege for
4964 the delivery, the use of &%-C%& causes privilege to be lost. However, root
4965 can test reception and delivery using two separate commands (one to put a
4966 message in the queue, using &%-odq%&, and another to do the delivery, using
4969 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
4970 prefix string with which any file named in a &%-C%& command line option must
4971 start. In addition, the filename must not contain the sequence &"&`/../`&"&.
4972 There is no default setting for ALT_CONFIG_PREFIX; when it is unset, any
4973 filename can be used with &%-C%&.
4975 One-off changes to a configuration can be specified by the &%-D%& command line
4976 option, which defines and overrides values for macros used inside the
4977 configuration file. However, like &%-C%&, the use of this option by a
4978 non-privileged user causes Exim to discard its root privilege.
4979 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
4980 completely disabled, and its use causes an immediate error exit.
4982 The WHITELIST_D_MACROS option in &_Local/Makefile_& permits the binary builder
4983 to declare certain macro names trusted, such that root privilege will not
4984 necessarily be discarded.
4985 WHITELIST_D_MACROS defines a colon-separated list of macros which are
4986 considered safe and, if &%-D%& only supplies macros from this list, and the
4987 values are acceptable, then Exim will not give up root privilege if the caller
4988 is root, the Exim run-time user, or the CONFIGURE_OWNER, if set. This is a
4989 transition mechanism and is expected to be removed in the future. Acceptable
4990 values for the macros satisfy the regexp: &`^[A-Za-z0-9_/.-]*$`&
4992 Some sites may wish to use the same Exim binary on different machines that
4993 share a file system, but to use different configuration files on each machine.
4994 If CONFIGURE_FILE_USE_NODE is defined in &_Local/Makefile_&, Exim first
4995 looks for a file whose name is the configuration filename followed by a dot
4996 and the machine's node name, as obtained from the &[uname()]& function. If this
4997 file does not exist, the standard name is tried. This processing occurs for
4998 each filename in the list given by CONFIGURE_FILE or &%-C%&.
5000 In some esoteric situations different versions of Exim may be run under
5001 different effective uids and the CONFIGURE_FILE_USE_EUID is defined to
5002 help with this. See the comments in &_src/EDITME_& for details.
5006 .section "Configuration file format" "SECTconffilfor"
5007 .cindex "configuration file" "format of"
5008 .cindex "format" "configuration file"
5009 Exim's configuration file is divided into a number of different parts. General
5010 option settings must always appear at the start of the file. The other parts
5011 are all optional, and may appear in any order. Each part other than the first
5012 is introduced by the word &"begin"& followed by at least one literal
5013 space, and the name of the part. The optional parts are:
5016 &'ACL'&: Access control lists for controlling incoming SMTP mail (see chapter
5019 .cindex "AUTH" "configuration"
5020 &'authenticators'&: Configuration settings for the authenticator drivers. These
5021 are concerned with the SMTP AUTH command (see chapter &<<CHAPSMTPAUTH>>&).
5023 &'routers'&: Configuration settings for the router drivers. Routers process
5024 addresses and determine how the message is to be delivered (see chapters
5025 &<<CHAProutergeneric>>&&--&<<CHAPredirect>>&).
5027 &'transports'&: Configuration settings for the transport drivers. Transports
5028 define mechanisms for copying messages to destinations (see chapters
5029 &<<CHAPtransportgeneric>>&&--&<<CHAPsmtptrans>>&).
5031 &'retry'&: Retry rules, for use when a message cannot be delivered immediately.
5032 If there is no retry section, or if it is empty (that is, no retry rules are
5033 defined), Exim will not retry deliveries. In this situation, temporary errors
5034 are treated the same as permanent errors. Retry rules are discussed in chapter
5037 &'rewrite'&: Global address rewriting rules, for use when a message arrives and
5038 when new addresses are generated during delivery. Rewriting is discussed in
5039 chapter &<<CHAPrewrite>>&.
5041 &'local_scan'&: Private options for the &[local_scan()]& function. If you
5042 want to use this feature, you must set
5044 LOCAL_SCAN_HAS_OPTIONS=yes
5046 in &_Local/Makefile_& before building Exim. Details of the &[local_scan()]&
5047 facility are given in chapter &<<CHAPlocalscan>>&.
5050 .cindex "configuration file" "leading white space in"
5051 .cindex "configuration file" "trailing white space in"
5052 .cindex "white space" "in configuration file"
5053 Leading and trailing white space in configuration lines is always ignored.
5055 Blank lines in the file, and lines starting with a # character (ignoring
5056 leading white space) are treated as comments and are ignored. &*Note*&: A
5057 # character other than at the beginning of a line is not treated specially,
5058 and does not introduce a comment.
5060 Any non-comment line can be continued by ending it with a backslash. Note that
5061 the general rule for white space means that trailing white space after the
5062 backslash and leading white space at the start of continuation
5063 lines is ignored. Comment lines beginning with # (but not empty lines) may
5064 appear in the middle of a sequence of continuation lines.
5066 A convenient way to create a configuration file is to start from the
5067 default, which is supplied in &_src/configure.default_&, and add, delete, or
5068 change settings as required.
5070 The ACLs, retry rules, and rewriting rules have their own syntax which is
5071 described in chapters &<<CHAPACL>>&, &<<CHAPretry>>&, and &<<CHAPrewrite>>&,
5072 respectively. The other parts of the configuration file have some syntactic
5073 items in common, and these are described below, from section &<<SECTcos>>&
5074 onwards. Before that, the inclusion, macro, and conditional facilities are
5079 .section "File inclusions in the configuration file" "SECID41"
5080 .cindex "inclusions in configuration file"
5081 .cindex "configuration file" "including other files"
5082 .cindex "&`.include`& in configuration file"
5083 .cindex "&`.include_if_exists`& in configuration file"
5084 You can include other files inside Exim's runtime configuration file by
5087 &`.include`& <&'filename'&>
5088 &`.include_if_exists`& <&'filename'&>
5090 on a line by itself. Double quotes round the filename are optional. If you use
5091 the first form, a configuration error occurs if the file does not exist; the
5092 second form does nothing for non-existent files.
5093 The first form allows a relative name. It is resolved relative to
5094 the directory of the including file. For the second form an absolute filename
5097 Includes may be nested to any depth, but remember that Exim reads its
5098 configuration file often, so it is a good idea to keep them to a minimum.
5099 If you change the contents of an included file, you must HUP the daemon,
5100 because an included file is read only when the configuration itself is read.
5102 The processing of inclusions happens early, at a physical line level, so, like
5103 comment lines, an inclusion can be used in the middle of an option setting,
5106 hosts_lookup = a.b.c \
5109 Include processing happens after macro processing (see below). Its effect is to
5110 process the lines of the included file as if they occurred inline where the
5115 .section "Macros in the configuration file" "SECTmacrodefs"
5116 .cindex "macro" "description of"
5117 .cindex "configuration file" "macros"
5118 If a line in the main part of the configuration (that is, before the first
5119 &"begin"& line) begins with an upper case letter, it is taken as a macro
5120 definition, and must be of the form
5122 <&'name'&> = <&'rest of line'&>
5124 The name must consist of letters, digits, and underscores, and need not all be
5125 in upper case, though that is recommended. The rest of the line, including any
5126 continuations, is the replacement text, and has leading and trailing white
5127 space removed. Quotes are not removed. The replacement text can never end with
5128 a backslash character, but this doesn't seem to be a serious limitation.
5130 Macros may also be defined between router, transport, authenticator, or ACL
5131 definitions. They may not, however, be defined within an individual driver or
5132 ACL, or in the &%local_scan%&, retry, or rewrite sections of the configuration.
5134 .section "Macro substitution" "SECID42"
5135 Once a macro is defined, all subsequent lines in the file (and any included
5136 files) are scanned for the macro name; if there are several macros, the line is
5137 scanned for each, in turn, in the order in which the macros are defined. The
5138 replacement text is not re-scanned for the current macro, though it is scanned
5139 for subsequently defined macros. For this reason, a macro name may not contain
5140 the name of a previously defined macro as a substring. You could, for example,
5143 &`ABCD_XYZ = `&<&'something'&>
5144 &`ABCD = `&<&'something else'&>
5146 but putting the definitions in the opposite order would provoke a configuration
5147 error. Macro expansion is applied to individual physical lines from the file,
5148 before checking for line continuation or file inclusion (see above). If a line
5149 consists solely of a macro name, and the expansion of the macro is empty, the
5150 line is ignored. A macro at the start of a line may turn the line into a
5151 comment line or a &`.include`& line.
5154 .section "Redefining macros" "SECID43"
5155 Once defined, the value of a macro can be redefined later in the configuration
5156 (or in an included file). Redefinition is specified by using &'=='& instead of
5161 MAC == updated value
5163 Redefinition does not alter the order in which the macros are applied to the
5164 subsequent lines of the configuration file. It is still the same order in which
5165 the macros were originally defined. All that changes is the macro's value.
5166 Redefinition makes it possible to accumulate values. For example:
5170 MAC == MAC and something added
5172 This can be helpful in situations where the configuration file is built
5173 from a number of other files.
5175 .section "Overriding macro values" "SECID44"
5176 The values set for macros in the configuration file can be overridden by the
5177 &%-D%& command line option, but Exim gives up its root privilege when &%-D%& is
5178 used, unless called by root or the Exim user. A definition on the command line
5179 using the &%-D%& option causes all definitions and redefinitions within the
5184 .section "Example of macro usage" "SECID45"
5185 As an example of macro usage, consider a configuration where aliases are looked
5186 up in a MySQL database. It helps to keep the file less cluttered if long
5187 strings such as SQL statements are defined separately as macros, for example:
5189 ALIAS_QUERY = select mailbox from user where \
5190 login='${quote_mysql:$local_part}';
5192 This can then be used in a &(redirect)& router setting like this:
5194 data = ${lookup mysql{ALIAS_QUERY}}
5196 In earlier versions of Exim macros were sometimes used for domain, host, or
5197 address lists. In Exim 4 these are handled better by named lists &-- see
5198 section &<<SECTnamedlists>>&.
5201 .section "Builtin macros" "SECTbuiltinmacros"
5202 Exim defines some macros depending on facilities available, which may
5203 differ due to build-time definitions and from one release to another.
5204 All of these macros start with an underscore.
5205 They can be used to conditionally include parts of a configuration
5208 The following classes of macros are defined:
5210 &` _HAVE_* `& build-time defines
5211 &` _DRIVER_ROUTER_* `& router drivers
5212 &` _DRIVER_TRANSPORT_* `& transport drivers
5213 &` _DRIVER_AUTHENTICATOR_* `& authenticator drivers
5214 &` _LOG_* `& log_selector values
5215 &` _OPT_MAIN_* `& main config options
5216 &` _OPT_ROUTERS_* `& generic router options
5217 &` _OPT_TRANSPORTS_* `& generic transport options
5218 &` _OPT_AUTHENTICATORS_* `& generic authenticator options
5219 &` _OPT_ROUTER_*_* `& private router options
5220 &` _OPT_TRANSPORT_*_* `& private transport options
5221 &` _OPT_AUTHENTICATOR_*_* `& private authenticator options
5224 Use an &"exim -bP macros"& command to get the list of macros.
5227 .section "Conditional skips in the configuration file" "SECID46"
5228 .cindex "configuration file" "conditional skips"
5229 .cindex "&`.ifdef`&"
5230 You can use the directives &`.ifdef`&, &`.ifndef`&, &`.elifdef`&,
5231 &`.elifndef`&, &`.else`&, and &`.endif`& to dynamically include or exclude
5232 portions of the configuration file. The processing happens whenever the file is
5233 read (that is, when an Exim binary starts to run).
5235 The implementation is very simple. Instances of the first four directives must
5236 be followed by text that includes the names of one or macros. The condition
5237 that is tested is whether or not any macro substitution has taken place in the
5241 message_size_limit = 50M
5243 message_size_limit = 100M
5246 sets a message size limit of 50M if the macro &`AAA`& is defined
5247 (or &`A`& or &`AA`&), and 100M
5248 otherwise. If there is more than one macro named on the line, the condition
5249 is true if any of them are defined. That is, it is an &"or"& condition. To
5250 obtain an &"and"& condition, you need to use nested &`.ifdef`&s.
5252 Although you can use a macro expansion to generate one of these directives,
5253 it is not very useful, because the condition &"there was a macro substitution
5254 in this line"& will always be true.
5256 Text following &`.else`& and &`.endif`& is ignored, and can be used as comment
5257 to clarify complicated nestings.
5261 .section "Common option syntax" "SECTcos"
5262 .cindex "common option syntax"
5263 .cindex "syntax of common options"
5264 .cindex "configuration file" "common option syntax"
5265 For the main set of options, driver options, and &[local_scan()]& options,
5266 each setting is on a line by itself, and starts with a name consisting of
5267 lower-case letters and underscores. Many options require a data value, and in
5268 these cases the name must be followed by an equals sign (with optional white
5269 space) and then the value. For example:
5271 qualify_domain = mydomain.example.com
5273 .cindex "hiding configuration option values"
5274 .cindex "configuration options" "hiding value of"
5275 .cindex "options" "hiding value of"
5276 Some option settings may contain sensitive data, for example, passwords for
5277 accessing databases. To stop non-admin users from using the &%-bP%& command
5278 line option to read these values, you can precede the option settings with the
5279 word &"hide"&. For example:
5281 hide mysql_servers = localhost/users/admin/secret-password
5283 For non-admin users, such options are displayed like this:
5285 mysql_servers = <value not displayable>
5287 If &"hide"& is used on a driver option, it hides the value of that option on
5288 all instances of the same driver.
5290 The following sections describe the syntax used for the different data types
5291 that are found in option settings.
5294 .section "Boolean options" "SECID47"
5295 .cindex "format" "boolean"
5296 .cindex "boolean configuration values"
5297 .oindex "&%no_%&&'xxx'&"
5298 .oindex "&%not_%&&'xxx'&"
5299 Options whose type is given as boolean are on/off switches. There are two
5300 different ways of specifying such options: with and without a data value. If
5301 the option name is specified on its own without data, the switch is turned on;
5302 if it is preceded by &"no_"& or &"not_"& the switch is turned off. However,
5303 boolean options may be followed by an equals sign and one of the words
5304 &"true"&, &"false"&, &"yes"&, or &"no"&, as an alternative syntax. For example,
5305 the following two settings have exactly the same effect:
5310 The following two lines also have the same (opposite) effect:
5315 You can use whichever syntax you prefer.
5320 .section "Integer values" "SECID48"
5321 .cindex "integer configuration values"
5322 .cindex "format" "integer"
5323 If an option's type is given as &"integer"&, the value can be given in decimal,
5324 hexadecimal, or octal. If it starts with a digit greater than zero, a decimal
5325 number is assumed. Otherwise, it is treated as an octal number unless it starts
5326 with the characters &"0x"&, in which case the remainder is interpreted as a
5329 If an integer value is followed by the letter K, it is multiplied by 1024; if
5330 it is followed by the letter M, it is multiplied by 1024x1024;
5331 if by the letter G, 1024x1024x1024.
5333 of integer option settings are output, values which are an exact multiple of
5334 1024 or 1024x1024 are sometimes, but not always, printed using the letters K
5335 and M. The printing style is independent of the actual input format that was
5339 .section "Octal integer values" "SECID49"
5340 .cindex "integer format"
5341 .cindex "format" "octal integer"
5342 If an option's type is given as &"octal integer"&, its value is always
5343 interpreted as an octal number, whether or not it starts with the digit zero.
5344 Such options are always output in octal.
5347 .section "Fixed point numbers" "SECID50"
5348 .cindex "fixed point configuration values"
5349 .cindex "format" "fixed point"
5350 If an option's type is given as &"fixed-point"&, its value must be a decimal
5351 integer, optionally followed by a decimal point and up to three further digits.
5355 .section "Time intervals" "SECTtimeformat"
5356 .cindex "time interval" "specifying in configuration"
5357 .cindex "format" "time interval"
5358 A time interval is specified as a sequence of numbers, each followed by one of
5359 the following letters, with no intervening white space:
5369 For example, &"3h50m"& specifies 3 hours and 50 minutes. The values of time
5370 intervals are output in the same format. Exim does not restrict the values; it
5371 is perfectly acceptable, for example, to specify &"90m"& instead of &"1h30m"&.
5375 .section "String values" "SECTstrings"
5376 .cindex "string" "format of configuration values"
5377 .cindex "format" "string"
5378 If an option's type is specified as &"string"&, the value can be specified with
5379 or without double-quotes. If it does not start with a double-quote, the value
5380 consists of the remainder of the line plus any continuation lines, starting at
5381 the first character after any leading white space, with trailing white space
5382 removed, and with no interpretation of the characters in the string. Because
5383 Exim removes comment lines (those beginning with #) at an early stage, they can
5384 appear in the middle of a multi-line string. The following two settings are
5385 therefore equivalent:
5387 trusted_users = uucp:mail
5388 trusted_users = uucp:\
5389 # This comment line is ignored
5392 .cindex "string" "quoted"
5393 .cindex "escape characters in quoted strings"
5394 If a string does start with a double-quote, it must end with a closing
5395 double-quote, and any backslash characters other than those used for line
5396 continuation are interpreted as escape characters, as follows:
5399 .irow &`\\`& "single backslash"
5400 .irow &`\n`& "newline"
5401 .irow &`\r`& "carriage return"
5403 .irow "&`\`&<&'octal digits'&>" "up to 3 octal digits specify one character"
5404 .irow "&`\x`&<&'hex digits'&>" "up to 2 hexadecimal digits specify one &&&
5408 If a backslash is followed by some other character, including a double-quote
5409 character, that character replaces the pair.
5411 Quoting is necessary only if you want to make use of the backslash escapes to
5412 insert special characters, or if you need to specify a value with leading or
5413 trailing spaces. These cases are rare, so quoting is almost never needed in
5414 current versions of Exim. In versions of Exim before 3.14, quoting was required
5415 in order to continue lines, so you may come across older configuration files
5416 and examples that apparently quote unnecessarily.
5419 .section "Expanded strings" "SECID51"
5420 .cindex "expansion" "definition of"
5421 Some strings in the configuration file are subjected to &'string expansion'&,
5422 by which means various parts of the string may be changed according to the
5423 circumstances (see chapter &<<CHAPexpand>>&). The input syntax for such strings
5424 is as just described; in particular, the handling of backslashes in quoted
5425 strings is done as part of the input process, before expansion takes place.
5426 However, backslash is also an escape character for the expander, so any
5427 backslashes that are required for that reason must be doubled if they are
5428 within a quoted configuration string.
5431 .section "User and group names" "SECID52"
5432 .cindex "user name" "format of"
5433 .cindex "format" "user name"
5434 .cindex "groups" "name format"
5435 .cindex "format" "group name"
5436 User and group names are specified as strings, using the syntax described
5437 above, but the strings are interpreted specially. A user or group name must
5438 either consist entirely of digits, or be a name that can be looked up using the
5439 &[getpwnam()]& or &[getgrnam()]& function, as appropriate.
5442 .section "List construction" "SECTlistconstruct"
5443 .cindex "list" "syntax of in configuration"
5444 .cindex "format" "list item in configuration"
5445 .cindex "string" "list, definition of"
5446 The data for some configuration options is a list of items, with colon as the
5447 default separator. Many of these options are shown with type &"string list"& in
5448 the descriptions later in this document. Others are listed as &"domain list"&,
5449 &"host list"&, &"address list"&, or &"local part list"&. Syntactically, they
5450 are all the same; however, those other than &"string list"& are subject to
5451 particular kinds of interpretation, as described in chapter
5452 &<<CHAPdomhosaddlists>>&.
5454 In all these cases, the entire list is treated as a single string as far as the
5455 input syntax is concerned. The &%trusted_users%& setting in section
5456 &<<SECTstrings>>& above is an example. If a colon is actually needed in an item
5457 in a list, it must be entered as two colons. Leading and trailing white space
5458 on each item in a list is ignored. This makes it possible to include items that
5459 start with a colon, and in particular, certain forms of IPv6 address. For
5462 local_interfaces = 127.0.0.1 : ::::1
5464 contains two IP addresses, the IPv4 address 127.0.0.1 and the IPv6 address ::1.
5466 &*Note*&: Although leading and trailing white space is ignored in individual
5467 list items, it is not ignored when parsing the list. The spaces around the first
5468 colon in the example above are necessary. If they were not there, the list would
5469 be interpreted as the two items 127.0.0.1:: and 1.
5471 .section "Changing list separators" "SECTlistsepchange"
5472 .cindex "list separator" "changing"
5473 .cindex "IPv6" "addresses in lists"
5474 Doubling colons in IPv6 addresses is an unwelcome chore, so a mechanism was
5475 introduced to allow the separator character to be changed. If a list begins
5476 with a left angle bracket, followed by any punctuation character, that
5477 character is used instead of colon as the list separator. For example, the list
5478 above can be rewritten to use a semicolon separator like this:
5480 local_interfaces = <; 127.0.0.1 ; ::1
5482 This facility applies to all lists, with the exception of the list in
5483 &%log_file_path%&. It is recommended that the use of non-colon separators be
5484 confined to circumstances where they really are needed.
5486 .cindex "list separator" "newline as"
5487 .cindex "newline" "as list separator"
5488 It is also possible to use newline and other control characters (those with
5489 code values less than 32, plus DEL) as separators in lists. Such separators
5490 must be provided literally at the time the list is processed. For options that
5491 are string-expanded, you can write the separator using a normal escape
5492 sequence. This will be processed by the expander before the string is
5493 interpreted as a list. For example, if a newline-separated list of domains is
5494 generated by a lookup, you can process it directly by a line such as this:
5496 domains = <\n ${lookup mysql{.....}}
5498 This avoids having to change the list separator in such data. You are unlikely
5499 to want to use a control character as a separator in an option that is not
5500 expanded, because the value is literal text. However, it can be done by giving
5501 the value in quotes. For example:
5503 local_interfaces = "<\n 127.0.0.1 \n ::1"
5505 Unlike printing character separators, which can be included in list items by
5506 doubling, it is not possible to include a control character as data when it is
5507 set as the separator. Two such characters in succession are interpreted as
5508 enclosing an empty list item.
5512 .section "Empty items in lists" "SECTempitelis"
5513 .cindex "list" "empty item in"
5514 An empty item at the end of a list is always ignored. In other words, trailing
5515 separator characters are ignored. Thus, the list in
5517 senders = user@domain :
5519 contains only a single item. If you want to include an empty string as one item
5520 in a list, it must not be the last item. For example, this list contains three
5521 items, the second of which is empty:
5523 senders = user1@domain : : user2@domain
5525 &*Note*&: There must be white space between the two colons, as otherwise they
5526 are interpreted as representing a single colon data character (and the list
5527 would then contain just one item). If you want to specify a list that contains
5528 just one, empty item, you can do it as in this example:
5532 In this case, the first item is empty, and the second is discarded because it
5533 is at the end of the list.
5538 .section "Format of driver configurations" "SECTfordricon"
5539 .cindex "drivers" "configuration format"
5540 There are separate parts in the configuration for defining routers, transports,
5541 and authenticators. In each part, you are defining a number of driver
5542 instances, each with its own set of options. Each driver instance is defined by
5543 a sequence of lines like this:
5545 <&'instance name'&>:
5550 In the following example, the instance name is &(localuser)&, and it is
5551 followed by three options settings:
5556 transport = local_delivery
5558 For each driver instance, you specify which Exim code module it uses &-- by the
5559 setting of the &%driver%& option &-- and (optionally) some configuration
5560 settings. For example, in the case of transports, if you want a transport to
5561 deliver with SMTP you would use the &(smtp)& driver; if you want to deliver to
5562 a local file you would use the &(appendfile)& driver. Each of the drivers is
5563 described in detail in its own separate chapter later in this manual.
5565 You can have several routers, transports, or authenticators that are based on
5566 the same underlying driver (each must have a different instance name).
5568 The order in which routers are defined is important, because addresses are
5569 passed to individual routers one by one, in order. The order in which
5570 transports are defined does not matter at all. The order in which
5571 authenticators are defined is used only when Exim, as a client, is searching
5572 them to find one that matches an authentication mechanism offered by the
5575 .cindex "generic options"
5576 .cindex "options" "generic &-- definition of"
5577 Within a driver instance definition, there are two kinds of option: &'generic'&
5578 and &'private'&. The generic options are those that apply to all drivers of the
5579 same type (that is, all routers, all transports or all authenticators). The
5580 &%driver%& option is a generic option that must appear in every definition.
5581 .cindex "private options"
5582 The private options are special for each driver, and none need appear, because
5583 they all have default values.
5585 The options may appear in any order, except that the &%driver%& option must
5586 precede any private options, since these depend on the particular driver. For
5587 this reason, it is recommended that &%driver%& always be the first option.
5589 Driver instance names, which are used for reference in log entries and
5590 elsewhere, can be any sequence of letters, digits, and underscores (starting
5591 with a letter) and must be unique among drivers of the same type. A router and
5592 a transport (for example) can each have the same name, but no two router
5593 instances can have the same name. The name of a driver instance should not be
5594 confused with the name of the underlying driver module. For example, the
5595 configuration lines:
5600 create an instance of the &(smtp)& transport driver whose name is
5601 &(remote_smtp)&. The same driver code can be used more than once, with
5602 different instance names and different option settings each time. A second
5603 instance of the &(smtp)& transport, with different options, might be defined
5609 command_timeout = 10s
5611 The names &(remote_smtp)& and &(special_smtp)& would be used to reference
5612 these transport instances from routers, and these names would appear in log
5615 Comment lines may be present in the middle of driver specifications. The full
5616 list of option settings for any particular driver instance, including all the
5617 defaulted values, can be extracted by making use of the &%-bP%& command line
5625 . ////////////////////////////////////////////////////////////////////////////
5626 . ////////////////////////////////////////////////////////////////////////////
5628 .chapter "The default configuration file" "CHAPdefconfil"
5629 .scindex IIDconfiwal "configuration file" "default &""walk through""&"
5630 .cindex "default" "configuration file &""walk through""&"
5631 The default configuration file supplied with Exim as &_src/configure.default_&
5632 is sufficient for a host with simple mail requirements. As an introduction to
5633 the way Exim is configured, this chapter &"walks through"& the default
5634 configuration, giving brief explanations of the settings. Detailed descriptions
5635 of the options are given in subsequent chapters. The default configuration file
5636 itself contains extensive comments about ways you might want to modify the
5637 initial settings. However, note that there are many options that are not
5638 mentioned at all in the default configuration.
5642 .section "Macros" "SECTdefconfmacros"
5643 All macros should be defined before any options.
5645 One macro is specified, but commented out, in the default configuration:
5647 # ROUTER_SMARTHOST=MAIL.HOSTNAME.FOR.CENTRAL.SERVER.EXAMPLE
5649 If all off-site mail is expected to be delivered to a "smarthost", then set the
5650 hostname here and uncomment the macro. This will affect which router is used
5651 later on. If this is left commented out, then Exim will perform direct-to-MX
5652 deliveries using a &(dnslookup)& router.
5654 In addition to macros defined here, Exim includes a number of built-in macros
5655 to enable configuration to be guarded by a binary built with support for a
5656 given feature. See section &<<SECTbuiltinmacros>>& for more details.
5659 .section "Main configuration settings" "SECTdefconfmain"
5660 The main (global) configuration option settings section must always come first
5661 in the file, after the macros.
5662 The first thing you'll see in the file, after some initial comments, is the line
5664 # primary_hostname =
5666 This is a commented-out setting of the &%primary_hostname%& option. Exim needs
5667 to know the official, fully qualified name of your host, and this is where you
5668 can specify it. However, in most cases you do not need to set this option. When
5669 it is unset, Exim uses the &[uname()]& system function to obtain the host name.
5671 The first three non-comment configuration lines are as follows:
5673 domainlist local_domains = @
5674 domainlist relay_to_domains =
5675 hostlist relay_from_hosts = 127.0.0.1
5677 These are not, in fact, option settings. They are definitions of two named
5678 domain lists and one named host list. Exim allows you to give names to lists of
5679 domains, hosts, and email addresses, in order to make it easier to manage the
5680 configuration file (see section &<<SECTnamedlists>>&).
5682 The first line defines a domain list called &'local_domains'&; this is used
5683 later in the configuration to identify domains that are to be delivered
5686 .cindex "@ in a domain list"
5687 There is just one item in this list, the string &"@"&. This is a special form
5688 of entry which means &"the name of the local host"&. Thus, if the local host is
5689 called &'a.host.example'&, mail to &'any.user@a.host.example'& is expected to
5690 be delivered locally. Because the local host's name is referenced indirectly,
5691 the same configuration file can be used on different hosts.
5693 The second line defines a domain list called &'relay_to_domains'&, but the
5694 list itself is empty. Later in the configuration we will come to the part that
5695 controls mail relaying through the local host; it allows relaying to any
5696 domains in this list. By default, therefore, no relaying on the basis of a mail
5697 domain is permitted.
5699 The third line defines a host list called &'relay_from_hosts'&. This list is
5700 used later in the configuration to permit relaying from any host or IP address
5701 that matches the list. The default contains just the IP address of the IPv4
5702 loopback interface, which means that processes on the local host are able to
5703 submit mail for relaying by sending it over TCP/IP to that interface. No other
5704 hosts are permitted to submit messages for relaying.
5706 Just to be sure there's no misunderstanding: at this point in the configuration
5707 we aren't actually setting up any controls. We are just defining some domains
5708 and hosts that will be used in the controls that are specified later.
5710 The next two configuration lines are genuine option settings:
5712 acl_smtp_rcpt = acl_check_rcpt
5713 acl_smtp_data = acl_check_data
5715 These options specify &'Access Control Lists'& (ACLs) that are to be used
5716 during an incoming SMTP session for every recipient of a message (every RCPT
5717 command), and after the contents of the message have been received,
5718 respectively. The names of the lists are &'acl_check_rcpt'& and
5719 &'acl_check_data'&, and we will come to their definitions below, in the ACL
5720 section of the configuration. The RCPT ACL controls which recipients are
5721 accepted for an incoming message &-- if a configuration does not provide an ACL
5722 to check recipients, no SMTP mail can be accepted. The DATA ACL allows the
5723 contents of a message to be checked.
5725 Two commented-out option settings are next:
5727 # av_scanner = clamd:/tmp/clamd
5728 # spamd_address = 127.0.0.1 783
5730 These are example settings that can be used when Exim is compiled with the
5731 content-scanning extension. The first specifies the interface to the virus
5732 scanner, and the second specifies the interface to SpamAssassin. Further
5733 details are given in chapter &<<CHAPexiscan>>&.
5735 Three more commented-out option settings follow:
5737 # tls_advertise_hosts = *
5738 # tls_certificate = /etc/ssl/exim.crt
5739 # tls_privatekey = /etc/ssl/exim.pem
5741 These are example settings that can be used when Exim is compiled with
5742 support for TLS (aka SSL) as described in section &<<SECTinctlsssl>>&. The
5743 first one specifies the list of clients that are allowed to use TLS when
5744 connecting to this server; in this case, the wildcard means all clients. The
5745 other options specify where Exim should find its TLS certificate and private
5746 key, which together prove the server's identity to any clients that connect.
5747 More details are given in chapter &<<CHAPTLS>>&.
5749 Another two commented-out option settings follow:
5751 # daemon_smtp_ports = 25 : 465 : 587
5752 # tls_on_connect_ports = 465
5754 .cindex "port" "465 and 587"
5755 .cindex "port" "for message submission"
5756 .cindex "message" "submission, ports for"
5757 .cindex "submissions protocol"
5758 .cindex "smtps protocol"
5759 .cindex "ssmtp protocol"
5760 .cindex "SMTP" "submissions protocol"
5761 .cindex "SMTP" "ssmtp protocol"
5762 .cindex "SMTP" "smtps protocol"
5763 These options provide better support for roaming users who wish to use this
5764 server for message submission. They are not much use unless you have turned on
5765 TLS (as described in the previous paragraph) and authentication (about which
5766 more in section &<<SECTdefconfauth>>&).
5767 Mail submission from mail clients (MUAs) should be separate from inbound mail
5768 to your domain (MX delivery) for various good reasons (eg, ability to impose
5769 much saner TLS protocol and ciphersuite requirements without unintended
5771 RFC 6409 (previously 4409) specifies use of port 587 for SMTP Submission,
5772 which uses STARTTLS, so this is the &"submission"& port.
5773 RFC 8314 specifies use of port 465 as the &"submissions"& protocol,
5774 which should be used in preference to 587.
5775 You should also consider deploying SRV records to help clients find
5777 Older names for &"submissions"& are &"smtps"& and &"ssmtp"&.
5779 Two more commented-out options settings follow:
5782 # qualify_recipient =
5784 The first of these specifies a domain that Exim uses when it constructs a
5785 complete email address from a local login name. This is often needed when Exim
5786 receives a message from a local process. If you do not set &%qualify_domain%&,
5787 the value of &%primary_hostname%& is used. If you set both of these options,
5788 you can have different qualification domains for sender and recipient
5789 addresses. If you set only the first one, its value is used in both cases.
5791 .cindex "domain literal" "recognizing format"
5792 The following line must be uncommented if you want Exim to recognize
5793 addresses of the form &'user@[10.11.12.13]'& that is, with a &"domain literal"&
5794 (an IP address within square brackets) instead of a named domain.
5796 # allow_domain_literals
5798 The RFCs still require this form, but many people think that in the modern
5799 Internet it makes little sense to permit mail to be sent to specific hosts by
5800 quoting their IP addresses. This ancient format has been used by people who
5801 try to abuse hosts by using them for unwanted relaying. However, some
5802 people believe there are circumstances (for example, messages addressed to
5803 &'postmaster'&) where domain literals are still useful.
5805 The next configuration line is a kind of trigger guard:
5809 It specifies that no delivery must ever be run as the root user. The normal
5810 convention is to set up &'root'& as an alias for the system administrator. This
5811 setting is a guard against slips in the configuration.
5812 The list of users specified by &%never_users%& is not, however, the complete
5813 list; the build-time configuration in &_Local/Makefile_& has an option called
5814 FIXED_NEVER_USERS specifying a list that cannot be overridden. The
5815 contents of &%never_users%& are added to this list. By default
5816 FIXED_NEVER_USERS also specifies root.
5818 When a remote host connects to Exim in order to send mail, the only information
5819 Exim has about the host's identity is its IP address. The next configuration
5824 specifies that Exim should do a reverse DNS lookup on all incoming connections,
5825 in order to get a host name. This improves the quality of the logging
5826 information, but if you feel it is too expensive, you can remove it entirely,
5827 or restrict the lookup to hosts on &"nearby"& networks.
5828 Note that it is not always possible to find a host name from an IP address,
5829 because not all DNS reverse zones are maintained, and sometimes DNS servers are
5832 The next two lines are concerned with &'ident'& callbacks, as defined by RFC
5833 1413 (hence their names):
5836 rfc1413_query_timeout = 0s
5838 These settings cause Exim to avoid ident callbacks for all incoming SMTP calls.
5839 Few hosts offer RFC1413 service these days; calls have to be
5840 terminated by a timeout and this needlessly delays the startup
5841 of an incoming SMTP connection.
5842 If you have hosts for which you trust RFC1413 and need this
5843 information, you can change this.
5845 This line enables an efficiency SMTP option. It is negotiated by clients
5846 and not expected to cause problems but can be disabled if needed.
5851 When Exim receives messages over SMTP connections, it expects all addresses to
5852 be fully qualified with a domain, as required by the SMTP definition. However,
5853 if you are running a server to which simple clients submit messages, you may
5854 find that they send unqualified addresses. The two commented-out options:
5856 # sender_unqualified_hosts =
5857 # recipient_unqualified_hosts =
5859 show how you can specify hosts that are permitted to send unqualified sender
5860 and recipient addresses, respectively.
5862 The &%log_selector%& option is used to increase the detail of logging
5865 log_selector = +smtp_protocol_error +smtp_syntax_error \
5866 +tls_certificate_verified
5869 The &%percent_hack_domains%& option is also commented out:
5871 # percent_hack_domains =
5873 It provides a list of domains for which the &"percent hack"& is to operate.
5874 This is an almost obsolete form of explicit email routing. If you do not know
5875 anything about it, you can safely ignore this topic.
5877 The next two settings in the main part of the default configuration are
5878 concerned with messages that have been &"frozen"& on Exim's queue. When a
5879 message is frozen, Exim no longer continues to try to deliver it. Freezing
5880 occurs when a bounce message encounters a permanent failure because the sender
5881 address of the original message that caused the bounce is invalid, so the
5882 bounce cannot be delivered. This is probably the most common case, but there
5883 are also other conditions that cause freezing, and frozen messages are not
5884 always bounce messages.
5886 ignore_bounce_errors_after = 2d
5887 timeout_frozen_after = 7d
5889 The first of these options specifies that failing bounce messages are to be
5890 discarded after 2 days in the queue. The second specifies that any frozen
5891 message (whether a bounce message or not) is to be timed out (and discarded)
5892 after a week. In this configuration, the first setting ensures that no failing
5893 bounce message ever lasts a week.
5895 Exim queues it's messages in a spool directory. If you expect to have
5896 large queues, you may consider using this option. It splits the spool
5897 directory into subdirectories to avoid file system degradation from
5898 many files in a single directory, resulting in better performance.
5899 Manual manipulation of queued messages becomes more complex (though fortunately
5902 # split_spool_directory = true
5905 In an ideal world everybody follows the standards. For non-ASCII
5906 messages RFC 2047 is a standard, allowing a maximum line length of 76
5907 characters. Exim adheres that standard and won't process messages which
5908 violate this standard. (Even ${rfc2047:...} expansions will fail.)
5909 In particular, the Exim maintainers have had multiple reports of
5910 problems from Russian administrators of issues until they disable this
5911 check, because of some popular, yet buggy, mail composition software.
5913 # check_rfc2047_length = false
5916 If you need to be strictly RFC compliant you may wish to disable the
5917 8BITMIME advertisement. Use this, if you exchange mails with systems
5918 that are not 8-bit clean.
5920 # accept_8bitmime = false
5923 Libraries you use may depend on specific environment settings. This
5924 imposes a security risk (e.g. PATH). There are two lists:
5925 &%keep_environment%& for the variables to import as they are, and
5926 &%add_environment%& for variables we want to set to a fixed value.
5927 Note that TZ is handled separately, by the &%timezone%& runtime
5928 option and by the TIMEZONE_DEFAULT buildtime option.
5930 # keep_environment = ^LDAP
5931 # add_environment = PATH=/usr/bin::/bin
5935 .section "ACL configuration" "SECID54"
5936 .cindex "default" "ACLs"
5937 .cindex "&ACL;" "default configuration"
5938 In the default configuration, the ACL section follows the main configuration.
5939 It starts with the line
5943 and it contains the definitions of two ACLs, called &'acl_check_rcpt'& and
5944 &'acl_check_data'&, that were referenced in the settings of &%acl_smtp_rcpt%&
5945 and &%acl_smtp_data%& above.
5947 .cindex "RCPT" "ACL for"
5948 The first ACL is used for every RCPT command in an incoming SMTP message. Each
5949 RCPT command specifies one of the message's recipients. The ACL statements
5950 are considered in order, until the recipient address is either accepted or
5951 rejected. The RCPT command is then accepted or rejected, according to the
5952 result of the ACL processing.
5956 This line, consisting of a name terminated by a colon, marks the start of the
5961 This ACL statement accepts the recipient if the sending host matches the list.
5962 But what does that strange list mean? It doesn't actually contain any host
5963 names or IP addresses. The presence of the colon puts an empty item in the
5964 list; Exim matches this only if the incoming message did not come from a remote
5965 host, because in that case, the remote hostname is empty. The colon is
5966 important. Without it, the list itself is empty, and can never match anything.
5968 What this statement is doing is to accept unconditionally all recipients in
5969 messages that are submitted by SMTP from local processes using the standard
5970 input and output (that is, not using TCP/IP). A number of MUAs operate in this
5973 deny domains = +local_domains
5974 local_parts = ^[.] : ^.*[@%!/|]
5975 message = Restricted characters in address
5977 deny domains = !+local_domains
5978 local_parts = ^[./|] : ^.*[@%!] : ^.*/\\.\\./
5979 message = Restricted characters in address
5981 These statements are concerned with local parts that contain any of the
5982 characters &"@"&, &"%"&, &"!"&, &"/"&, &"|"&, or dots in unusual places.
5983 Although these characters are entirely legal in local parts (in the case of
5984 &"@"& and leading dots, only if correctly quoted), they do not commonly occur
5985 in Internet mail addresses.
5987 The first three have in the past been associated with explicitly routed
5988 addresses (percent is still sometimes used &-- see the &%percent_hack_domains%&
5989 option). Addresses containing these characters are regularly tried by spammers
5990 in an attempt to bypass relaying restrictions, and also by open relay testing
5991 programs. Unless you really need them it is safest to reject these characters
5992 at this early stage. This configuration is heavy-handed in rejecting these
5993 characters for all messages it accepts from remote hosts. This is a deliberate
5994 policy of being as safe as possible.
5996 The first rule above is stricter, and is applied to messages that are addressed
5997 to one of the local domains handled by this host. This is implemented by the
5998 first condition, which restricts it to domains that are listed in the
5999 &'local_domains'& domain list. The &"+"& character is used to indicate a
6000 reference to a named list. In this configuration, there is just one domain in
6001 &'local_domains'&, but in general there may be many.
6003 The second condition on the first statement uses two regular expressions to
6004 block local parts that begin with a dot or contain &"@"&, &"%"&, &"!"&, &"/"&,
6005 or &"|"&. If you have local accounts that include these characters, you will
6006 have to modify this rule.
6008 Empty components (two dots in a row) are not valid in RFC 2822, but Exim
6009 allows them because they have been encountered in practice. (Consider the
6010 common convention of local parts constructed as
6011 &"&'first-initial.second-initial.family-name'&"& when applied to someone like
6012 the author of Exim, who has no second initial.) However, a local part starting
6013 with a dot or containing &"/../"& can cause trouble if it is used as part of a
6014 filename (for example, for a mailing list). This is also true for local parts
6015 that contain slashes. A pipe symbol can also be troublesome if the local part
6016 is incorporated unthinkingly into a shell command line.
6018 The second rule above applies to all other domains, and is less strict. This
6019 allows your own users to send outgoing messages to sites that use slashes
6020 and vertical bars in their local parts. It blocks local parts that begin
6021 with a dot, slash, or vertical bar, but allows these characters within the
6022 local part. However, the sequence &"/../"& is barred. The use of &"@"&, &"%"&,
6023 and &"!"& is blocked, as before. The motivation here is to prevent your users
6024 (or your users' viruses) from mounting certain kinds of attack on remote sites.
6026 accept local_parts = postmaster
6027 domains = +local_domains
6029 This statement, which has two conditions, accepts an incoming address if the
6030 local part is &'postmaster'& and the domain is one of those listed in the
6031 &'local_domains'& domain list. The &"+"& character is used to indicate a
6032 reference to a named list. In this configuration, there is just one domain in
6033 &'local_domains'&, but in general there may be many.
6035 The presence of this statement means that mail to postmaster is never blocked
6036 by any of the subsequent tests. This can be helpful while sorting out problems
6037 in cases where the subsequent tests are incorrectly denying access.
6039 require verify = sender
6041 This statement requires the sender address to be verified before any subsequent
6042 ACL statement can be used. If verification fails, the incoming recipient
6043 address is refused. Verification consists of trying to route the address, to
6044 see if a bounce message could be delivered to it. In the case of remote
6045 addresses, basic verification checks only the domain, but &'callouts'& can be
6046 used for more verification if required. Section &<<SECTaddressverification>>&
6047 discusses the details of address verification.
6049 accept hosts = +relay_from_hosts
6050 control = submission
6052 This statement accepts the address if the message is coming from one of the
6053 hosts that are defined as being allowed to relay through this host. Recipient
6054 verification is omitted here, because in many cases the clients are dumb MUAs
6055 that do not cope well with SMTP error responses. For the same reason, the
6056 second line specifies &"submission mode"& for messages that are accepted. This
6057 is described in detail in section &<<SECTsubmodnon>>&; it causes Exim to fix
6058 messages that are deficient in some way, for example, because they lack a
6059 &'Date:'& header line. If you are actually relaying out from MTAs, you should
6060 probably add recipient verification here, and disable submission mode.
6062 accept authenticated = *
6063 control = submission
6065 This statement accepts the address if the client host has authenticated itself.
6066 Submission mode is again specified, on the grounds that such messages are most
6067 likely to come from MUAs. The default configuration does not define any
6068 authenticators, though it does include some nearly complete commented-out
6069 examples described in &<<SECTdefconfauth>>&. This means that no client can in
6070 fact authenticate until you complete the authenticator definitions.
6072 require message = relay not permitted
6073 domains = +local_domains : +relay_to_domains
6075 This statement rejects the address if its domain is neither a local domain nor
6076 one of the domains for which this host is a relay.
6078 require verify = recipient
6080 This statement requires the recipient address to be verified; if verification
6081 fails, the address is rejected.
6083 # deny dnslists = black.list.example
6084 # message = rejected because $sender_host_address \
6085 # is in a black list at $dnslist_domain\n\
6088 # warn dnslists = black.list.example
6089 # add_header = X-Warning: $sender_host_address is in \
6090 # a black list at $dnslist_domain
6091 # log_message = found in $dnslist_domain
6093 These commented-out lines are examples of how you could configure Exim to check
6094 sending hosts against a DNS black list. The first statement rejects messages
6095 from blacklisted hosts, whereas the second just inserts a warning header
6098 # require verify = csa
6100 This commented-out line is an example of how you could turn on client SMTP
6101 authorization (CSA) checking. Such checks do DNS lookups for special SRV
6106 The final statement in the first ACL unconditionally accepts any recipient
6107 address that has successfully passed all the previous tests.
6111 This line marks the start of the second ACL, and names it. Most of the contents
6112 of this ACL are commented out:
6115 # message = This message contains a virus \
6118 These lines are examples of how to arrange for messages to be scanned for
6119 viruses when Exim has been compiled with the content-scanning extension, and a
6120 suitable virus scanner is installed. If the message is found to contain a
6121 virus, it is rejected with the given custom error message.
6123 # warn spam = nobody
6124 # message = X-Spam_score: $spam_score\n\
6125 # X-Spam_score_int: $spam_score_int\n\
6126 # X-Spam_bar: $spam_bar\n\
6127 # X-Spam_report: $spam_report
6129 These lines are an example of how to arrange for messages to be scanned by
6130 SpamAssassin when Exim has been compiled with the content-scanning extension,
6131 and SpamAssassin has been installed. The SpamAssassin check is run with
6132 &`nobody`& as its user parameter, and the results are added to the message as a
6133 series of extra header line. In this case, the message is not rejected,
6134 whatever the spam score.
6138 This final line in the DATA ACL accepts the message unconditionally.
6141 .section "Router configuration" "SECID55"
6142 .cindex "default" "routers"
6143 .cindex "routers" "default"
6144 The router configuration comes next in the default configuration, introduced
6149 Routers are the modules in Exim that make decisions about where to send
6150 messages. An address is passed to each router, in turn, until it is either
6151 accepted, or failed. This means that the order in which you define the routers
6152 matters. Each router is fully described in its own chapter later in this
6153 manual. Here we give only brief overviews.
6156 # driver = ipliteral
6157 # domains = !+local_domains
6158 # transport = remote_smtp
6160 .cindex "domain literal" "default router"
6161 This router is commented out because the majority of sites do not want to
6162 support domain literal addresses (those of the form &'user@[10.9.8.7]'&). If
6163 you uncomment this router, you also need to uncomment the setting of
6164 &%allow_domain_literals%& in the main part of the configuration.
6166 Which router is used next depends upon whether or not the ROUTER_SMARTHOST
6167 macro has been defined, per
6169 .ifdef ROUTER_SMARTHOST
6178 If ROUTER_SMARTHOST has been defined, either at the top of the file or on the
6179 command-line, then we route all non-local mail to that smarthost; otherwise, we'll
6180 perform DNS lookups for direct-to-MX lookup. Any mail which is to a local domain will
6181 skip these routers because of the &%domains%& option.
6185 driver = manualroute
6186 domains = ! +local_domains
6187 transport = smarthost_smtp
6188 route_data = ROUTER_SMARTHOST
6189 ignore_target_hosts = <; 0.0.0.0 ; 127.0.0.0/8 ; ::1
6192 This router only handles mail which is not to any local domains; this is
6193 specified by the line
6195 domains = ! +local_domains
6197 The &%domains%& option lists the domains to which this router applies, but the
6198 exclamation mark is a negation sign, so the router is used only for domains
6199 that are not in the domain list called &'local_domains'& (which was defined at
6200 the start of the configuration). The plus sign before &'local_domains'&
6201 indicates that it is referring to a named list. Addresses in other domains are
6202 passed on to the following routers.
6204 The name of the router driver is &(manualroute)& because we are manually
6205 specifying how mail should be routed onwards, instead of using DNS MX.
6206 While the name of this router instance is arbitrary, the &%driver%& option must
6207 be one of the driver modules that is in the Exim binary.
6209 With no pre-conditions other than &%domains%&, all mail for non-local domains
6210 will be handled by this router, and the &%no_more%& setting will ensure that no
6211 other routers will be used for messages matching the pre-conditions. See
6212 &<<SECTrouprecon>>& for more on how the pre-conditions apply. For messages which
6213 are handled by this router, we provide a hostname to deliver to in &%route_data%&
6214 and the macro supplies the value; the address is then queued for the
6215 &(smarthost_smtp)& transport.
6220 domains = ! +local_domains
6221 transport = remote_smtp
6222 ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
6225 The &%domains%& option behaves as per smarthost, above.
6227 The name of the router driver is &(dnslookup)&,
6228 and is specified by the &%driver%& option. Do not be confused by the fact that
6229 the name of this router instance is the same as the name of the driver. The
6230 instance name is arbitrary, but the name set in the &%driver%& option must be
6231 one of the driver modules that is in the Exim binary.
6233 The &(dnslookup)& router routes addresses by looking up their domains in the
6234 DNS in order to obtain a list of hosts to which the address is routed. If the
6235 router succeeds, the address is queued for the &(remote_smtp)& transport, as
6236 specified by the &%transport%& option. If the router does not find the domain
6237 in the DNS, no further routers are tried because of the &%no_more%& setting, so
6238 the address fails and is bounced.
6240 The &%ignore_target_hosts%& option specifies a list of IP addresses that are to
6241 be entirely ignored. This option is present because a number of cases have been
6242 encountered where MX records in the DNS point to host names
6243 whose IP addresses are 0.0.0.0 or are in the 127 subnet (typically 127.0.0.1).
6244 Completely ignoring these IP addresses causes Exim to fail to route the
6245 email address, so it bounces. Otherwise, Exim would log a routing problem, and
6246 continue to try to deliver the message periodically until the address timed
6253 data = ${lookup{$local_part}lsearch{/etc/aliases}}
6255 file_transport = address_file
6256 pipe_transport = address_pipe
6258 Control reaches this and subsequent routers only for addresses in the local
6259 domains. This router checks to see whether the local part is defined as an
6260 alias in the &_/etc/aliases_& file, and if so, redirects it according to the
6261 data that it looks up from that file. If no data is found for the local part,
6262 the value of the &%data%& option is empty, causing the address to be passed to
6265 &_/etc/aliases_& is a conventional name for the system aliases file that is
6266 often used. That is why it is referenced by from the default configuration
6267 file. However, you can change this by setting SYSTEM_ALIASES_FILE in
6268 &_Local/Makefile_& before building Exim.
6273 # local_part_suffix = +* : -*
6274 # local_part_suffix_optional
6275 file = $home/.forward
6280 file_transport = address_file
6281 pipe_transport = address_pipe
6282 reply_transport = address_reply
6284 This is the most complicated router in the default configuration. It is another
6285 redirection router, but this time it is looking for forwarding data set up by
6286 individual users. The &%check_local_user%& setting specifies a check that the
6287 local part of the address is the login name of a local user. If it is not, the
6288 router is skipped. The two commented options that follow &%check_local_user%&,
6291 # local_part_suffix = +* : -*
6292 # local_part_suffix_optional
6294 .vindex "&$local_part_suffix$&"
6295 show how you can specify the recognition of local part suffixes. If the first
6296 is uncommented, a suffix beginning with either a plus or a minus sign, followed
6297 by any sequence of characters, is removed from the local part and placed in the
6298 variable &$local_part_suffix$&. The second suffix option specifies that the
6299 presence of a suffix in the local part is optional. When a suffix is present,
6300 the check for a local login uses the local part with the suffix removed.
6302 When a local user account is found, the file called &_.forward_& in the user's
6303 home directory is consulted. If it does not exist, or is empty, the router
6304 declines. Otherwise, the contents of &_.forward_& are interpreted as
6305 redirection data (see chapter &<<CHAPredirect>>& for more details).
6307 .cindex "Sieve filter" "enabling in default router"
6308 Traditional &_.forward_& files contain just a list of addresses, pipes, or
6309 files. Exim supports this by default. However, if &%allow_filter%& is set (it
6310 is commented out by default), the contents of the file are interpreted as a set
6311 of Exim or Sieve filtering instructions, provided the file begins with &"#Exim
6312 filter"& or &"#Sieve filter"&, respectively. User filtering is discussed in the
6313 separate document entitled &'Exim's interfaces to mail filtering'&.
6315 The &%no_verify%& and &%no_expn%& options mean that this router is skipped when
6316 verifying addresses, or when running as a consequence of an SMTP EXPN command.
6317 There are two reasons for doing this:
6320 Whether or not a local user has a &_.forward_& file is not really relevant when
6321 checking an address for validity; it makes sense not to waste resources doing
6324 More importantly, when Exim is verifying addresses or handling an EXPN
6325 command during an SMTP session, it is running as the Exim user, not as root.
6326 The group is the Exim group, and no additional groups are set up.
6327 It may therefore not be possible for Exim to read users' &_.forward_& files at
6331 The setting of &%check_ancestor%& prevents the router from generating a new
6332 address that is the same as any previous address that was redirected. (This
6333 works round a problem concerning a bad interaction between aliasing and
6334 forwarding &-- see section &<<SECTredlocmai>>&).
6336 The final three option settings specify the transports that are to be used when
6337 forwarding generates a direct delivery to a file, or to a pipe, or sets up an
6338 auto-reply, respectively. For example, if a &_.forward_& file contains
6340 a.nother@elsewhere.example, /home/spqr/archive
6342 the delivery to &_/home/spqr/archive_& is done by running the &%address_file%&
6348 # local_part_suffix = +* : -*
6349 # local_part_suffix_optional
6350 transport = local_delivery
6352 The final router sets up delivery into local mailboxes, provided that the local
6353 part is the name of a local login, by accepting the address and assigning it to
6354 the &(local_delivery)& transport. Otherwise, we have reached the end of the
6355 routers, so the address is bounced. The commented suffix settings fulfil the
6356 same purpose as they do for the &(userforward)& router.
6359 .section "Transport configuration" "SECID56"
6360 .cindex "default" "transports"
6361 .cindex "transports" "default"
6362 Transports define mechanisms for actually delivering messages. They operate
6363 only when referenced from routers, so the order in which they are defined does
6364 not matter. The transports section of the configuration starts with
6368 Two remote transports and four local transports are defined.
6372 message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}
6377 This transport is used for delivering messages over SMTP connections.
6378 The list of remote hosts comes from the router.
6379 The &%message_size_limit%& usage is a hack to avoid sending on messages
6380 with over-long lines.
6382 The &%hosts_try_prdr%& option enables an efficiency SMTP option. It is
6383 negotiated between client and server and not expected to cause problems
6384 but can be disabled if needed. The built-in macro _HAVE_PRDR guards the
6385 use of the &%hosts_try_prdr%& configuration option.
6387 The other remote transport is used when delivering to a specific smarthost
6388 with whom there must be some kind of existing relationship, instead of the
6389 usual federated system.
6394 message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}
6398 # Comment out any of these which you have to, then file a Support
6399 # request with your smarthost provider to get things fixed:
6400 hosts_require_tls = *
6401 tls_verify_hosts = *
6402 # As long as tls_verify_hosts is enabled, this this will have no effect,
6403 # but if you have to comment it out then this will at least log whether
6404 # you succeed or not:
6405 tls_try_verify_hosts = *
6407 # The SNI name should match the name which we'll expect to verify;
6408 # many mail systems don't use SNI and this doesn't matter, but if it does,
6409 # we need to send a name which the remote site will recognize.
6410 # This _should_ be the name which the smarthost operators specified as
6411 # the hostname for sending your mail to.
6412 tls_sni = ROUTER_SMARTHOST
6414 .ifdef _HAVE_OPENSSL
6415 tls_require_ciphers = HIGH:!aNULL:@STRENGTH
6418 tls_require_ciphers = SECURE192:-VERS-SSL3.0:-VERS-TLS1.0:-VERS-TLS1.1
6425 After the same &%message_size_limit%& hack, we then specify that this Transport
6426 can handle messages to multiple domains in one run. The assumption here is
6427 that you're routing all non-local mail to the same place and that place is
6428 happy to take all messages from you as quickly as possible.
6429 All other options depend upon built-in macros; if Exim was built without TLS support
6430 then no other options are defined.
6431 If TLS is available, then we configure "stronger than default" TLS ciphersuites
6432 and versions using the &%tls_require_ciphers%& option, where the value to be
6433 used depends upon the library providing TLS.
6434 Beyond that, the options adopt the stance that you should have TLS support available
6435 from your smarthost on today's Internet, so we turn on requiring TLS for the
6436 mail to be delivered, and requiring that the certificate be valid, and match
6437 the expected hostname. The &%tls_sni%& option can be used by service providers
6438 to select an appropriate certificate to present to you and here we re-use the
6439 ROUTER_SMARTHOST macro, because that is unaffected by CNAMEs present in DNS.
6440 You want to specify the hostname which you'll expect to validate for, and that
6441 should not be subject to insecure tampering via DNS results.
6443 For the &%hosts_try_prdr%& option see the previous transport.
6445 All other options are defaulted.
6449 file = /var/mail/$local_part_data
6456 This &(appendfile)& transport is used for local delivery to user mailboxes in
6457 traditional BSD mailbox format.
6459 We prefer to avoid using &$local_part$& directly to define the mailbox filename,
6460 as it is provided by a potential bad actor.
6461 Instead we use &$local_part_data$&,
6462 the result of looking up &$local_part$& in the user database
6463 (done by using &%check_local_user%& in the the router).
6465 By default &(appendfile)& runs under the uid and gid of the
6466 local user, which requires the sticky bit to be set on the &_/var/mail_&
6467 directory. Some systems use the alternative approach of running mail deliveries
6468 under a particular group instead of using the sticky bit. The commented options
6469 show how this can be done.
6471 Exim adds three headers to the message as it delivers it: &'Delivery-date:'&,
6472 &'Envelope-to:'& and &'Return-path:'&. This action is requested by the three
6473 similarly-named options above.
6479 This transport is used for handling deliveries to pipes that are generated by
6480 redirection (aliasing or users' &_.forward_& files). The &%return_output%&
6481 option specifies that any output on stdout or stderr generated by the pipe is to
6482 be returned to the sender.
6490 This transport is used for handling deliveries to files that are generated by
6491 redirection. The name of the file is not specified in this instance of
6492 &(appendfile)&, because it comes from the &(redirect)& router.
6497 This transport is used for handling automatic replies generated by users'
6502 .section "Default retry rule" "SECID57"
6503 .cindex "retry" "default rule"
6504 .cindex "default" "retry rule"
6505 The retry section of the configuration file contains rules which affect the way
6506 Exim retries deliveries that cannot be completed at the first attempt. It is
6507 introduced by the line
6511 In the default configuration, there is just one rule, which applies to all
6514 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
6516 This causes any temporarily failing address to be retried every 15 minutes for
6517 2 hours, then at intervals starting at one hour and increasing by a factor of
6518 1.5 until 16 hours have passed, then every 6 hours up to 4 days. If an address
6519 is not delivered after 4 days of temporary failure, it is bounced. The time is
6520 measured from first failure, not from the time the message was received.
6522 If the retry section is removed from the configuration, or is empty (that is,
6523 if no retry rules are defined), Exim will not retry deliveries. This turns
6524 temporary errors into permanent errors.
6527 .section "Rewriting configuration" "SECID58"
6528 The rewriting section of the configuration, introduced by
6532 contains rules for rewriting addresses in messages as they arrive. There are no
6533 rewriting rules in the default configuration file.
6537 .section "Authenticators configuration" "SECTdefconfauth"
6538 .cindex "AUTH" "configuration"
6539 The authenticators section of the configuration, introduced by
6541 begin authenticators
6543 defines mechanisms for the use of the SMTP AUTH command. The default
6544 configuration file contains two commented-out example authenticators
6545 which support plaintext username/password authentication using the
6546 standard PLAIN mechanism and the traditional but non-standard LOGIN
6547 mechanism, with Exim acting as the server. PLAIN and LOGIN are enough
6548 to support most MUA software.
6550 The example PLAIN authenticator looks like this:
6553 # driver = plaintext
6554 # server_set_id = $auth2
6555 # server_prompts = :
6556 # server_condition = Authentication is not yet configured
6557 # server_advertise_condition = ${if def:tls_in_cipher }
6559 And the example LOGIN authenticator looks like this:
6562 # driver = plaintext
6563 # server_set_id = $auth1
6564 # server_prompts = <| Username: | Password:
6565 # server_condition = Authentication is not yet configured
6566 # server_advertise_condition = ${if def:tls_in_cipher }
6569 The &%server_set_id%& option makes Exim remember the authenticated username
6570 in &$authenticated_id$&, which can be used later in ACLs or routers. The
6571 &%server_prompts%& option configures the &(plaintext)& authenticator so
6572 that it implements the details of the specific authentication mechanism,
6573 i.e. PLAIN or LOGIN. The &%server_advertise_condition%& setting controls
6574 when Exim offers authentication to clients; in the examples, this is only
6575 when TLS or SSL has been started, so to enable the authenticators you also
6576 need to add support for TLS as described in section &<<SECTdefconfmain>>&.
6578 The &%server_condition%& setting defines how to verify that the username and
6579 password are correct. In the examples it just produces an error message.
6580 To make the authenticators work, you can use a string expansion
6581 expression like one of the examples in chapter &<<CHAPplaintext>>&.
6583 Beware that the sequence of the parameters to PLAIN and LOGIN differ; the
6584 usercode and password are in different positions.
6585 Chapter &<<CHAPplaintext>>& covers both.
6587 .ecindex IIDconfiwal
6591 . ////////////////////////////////////////////////////////////////////////////
6592 . ////////////////////////////////////////////////////////////////////////////
6594 .chapter "Regular expressions" "CHAPregexp"
6596 .cindex "regular expressions" "library"
6598 Exim supports the use of regular expressions in many of its options. It
6599 uses the PCRE2 regular expression library; this provides regular expression
6600 matching that is compatible with Perl 5. The syntax and semantics of
6601 regular expressions is discussed in
6602 online Perl manpages, in
6603 many Perl reference books, and also in
6604 Jeffrey Friedl's &'Mastering Regular Expressions'&, which is published by
6605 O'Reilly (see &url(http://www.oreilly.com/catalog/regex2/)).
6606 . --- the http: URL here redirects to another page with the ISBN in the URL
6607 . --- where trying to use https: just redirects back to http:, so sticking
6608 . --- to the old URL for now. 2018-09-07.
6610 The documentation for the syntax and semantics of the regular expressions that
6611 are supported by PCRE2 is included in the PCRE2 distribution, and no further
6612 description is included here. The PCRE2 functions are called from Exim using
6613 the default option settings (that is, with no PCRE2 options set), except that
6614 the PCRE2_CASELESS option is set when the matching is required to be
6617 In most cases, when a regular expression is required in an Exim configuration,
6618 it has to start with a circumflex, in order to distinguish it from plain text
6619 or an &"ends with"& wildcard. In this example of a configuration setting, the
6620 second item in the colon-separated list is a regular expression.
6622 domains = a.b.c : ^\\d{3} : *.y.z : ...
6624 The doubling of the backslash is required because of string expansion that
6625 precedes interpretation &-- see section &<<SECTlittext>>& for more discussion
6626 of this issue, and a way of avoiding the need for doubling backslashes. The
6627 regular expression that is eventually used in this example contains just one
6628 backslash. The circumflex is included in the regular expression, and has the
6629 normal effect of &"anchoring"& it to the start of the string that is being
6632 There are, however, two cases where a circumflex is not required for the
6633 recognition of a regular expression: these are the &%match%& condition in a
6634 string expansion, and the &%matches%& condition in an Exim filter file. In
6635 these cases, the relevant string is always treated as a regular expression; if
6636 it does not start with a circumflex, the expression is not anchored, and can
6637 match anywhere in the subject string.
6639 In all cases, if you want a regular expression to match at the end of a string,
6640 you must code the $ metacharacter to indicate this. For example:
6642 domains = ^\\d{3}\\.example
6644 matches the domain &'123.example'&, but it also matches &'123.example.com'&.
6647 domains = ^\\d{3}\\.example\$
6649 if you want &'example'& to be the top-level domain. The backslash before the
6650 $ is needed because string expansion also interprets dollar characters.
6654 . ////////////////////////////////////////////////////////////////////////////
6655 . ////////////////////////////////////////////////////////////////////////////
6657 .chapter "File and database lookups" "CHAPfdlookup"
6658 .scindex IIDfidalo1 "file" "lookups"
6659 .scindex IIDfidalo2 "database" "lookups"
6660 .cindex "lookup" "description of"
6661 Exim can be configured to look up data in files or databases as it processes
6662 messages. Two different kinds of syntax are used:
6665 A string that is to be expanded may contain explicit lookup requests. These
6666 cause parts of the string to be replaced by data that is obtained from the
6667 lookup. Lookups of this type are conditional expansion items. Different results
6668 can be defined for the cases of lookup success and failure. See chapter
6669 &<<CHAPexpand>>&, where string expansions are described in detail.
6670 The key for the lookup is &*specified*& as part of the string expansion.
6672 Lists of domains, hosts, and email addresses can contain lookup requests as a
6673 way of avoiding excessively long linear lists. In this case, the data that is
6674 returned by the lookup is often (but not always) discarded; whether the lookup
6675 succeeds or fails is what really counts. These kinds of list are described in
6676 chapter &<<CHAPdomhosaddlists>>&.
6677 The key for the lookup is &*implicit*&,
6678 given by the context in which the list is expanded.
6681 String expansions, lists, and lookups interact with each other in such a way
6682 that there is no order in which to describe any one of them that does not
6683 involve references to the others. Each of these three chapters makes more sense
6684 if you have read the other two first. If you are reading this for the first
6685 time, be aware that some of it will make a lot more sense after you have read
6686 chapters &<<CHAPdomhosaddlists>>& and &<<CHAPexpand>>&.
6688 .section "Examples of different lookup syntax" "SECID60"
6689 It is easy to confuse the two different kinds of lookup, especially as the
6690 lists that may contain the second kind are always expanded before being
6691 processed as lists. Therefore, they may also contain lookups of the first kind.
6692 Be careful to distinguish between the following two examples:
6694 domains = ${lookup{$sender_host_address}lsearch{/some/file}}
6695 domains = lsearch;/some/file
6697 The first uses a string expansion, the result of which must be a domain list.
6698 The key for an expansion-style lookup must be given explicitly.
6699 No strings have been specified for a successful or a failing lookup; the
6700 defaults in this case are the looked-up data and an empty string, respectively.
6701 The expansion takes place before the string is processed as a list, and the
6702 file that is searched could contain lines like this:
6704 192.168.3.4: domain1:domain2:...
6705 192.168.1.9: domain3:domain4:...
6707 When the lookup succeeds, the result of the expansion is a list of domains (and
6708 possibly other types of item that are allowed in domain lists).
6709 .cindex "tainted data" "de-tainting"
6710 .cindex "de-tainting" "using a lookup expansion""
6711 The result of the expansion is not tainted.
6713 In the second example, the lookup is a single item in a domain list. It causes
6714 Exim to use a lookup to see if the domain that is being processed can be found
6716 The file could contains lines like this:
6721 Any data that follows the keys is not relevant when checking that the domain
6722 matches the list item.
6724 The key for a list-style lookup is implicit, from the lookup context, if
6725 the lookup is a single-key type (see below).
6726 For query-style lookup types the key must be given explicitly.
6728 It is possible, though no doubt confusing, to use both kinds of lookup at once.
6729 Consider a file containing lines like this:
6731 192.168.5.6: lsearch;/another/file
6733 If the value of &$sender_host_address$& is 192.168.5.6, expansion of the
6734 first &%domains%& setting above generates the second setting, which therefore
6735 causes a second lookup to occur.
6737 The lookup type may optionally be followed by a comma
6738 and a comma-separated list of options.
6739 Each option is a &"name=value"& pair.
6740 Whether an option is meaningful depends on the lookup type.
6742 All lookups support the option &"cache=no_rd"&.
6743 If this is given then the cache that Exim manages for lookup results
6744 is not checked before doing the lookup.
6745 The result of the lookup is still written to the cache.
6747 The rest of this chapter describes the different lookup types that are
6748 available. Any of them can be used in any part of the configuration where a
6749 lookup is permitted.
6752 .section "Lookup types" "SECID61"
6753 .cindex "lookup" "types of"
6754 .cindex "single-key lookup" "definition of"
6755 Two different types of data lookup are implemented:
6758 The &'single-key'& type requires the specification of a file in which to look,
6759 and a single key to search for. The key must be a non-empty string for the
6760 lookup to succeed. The lookup type determines how the file is searched.
6761 .cindex "tainted data" "single-key lookups"
6762 The file string may not be tainted.
6764 .cindex "tainted data" "de-tainting"
6765 .cindex "de-tainting" "using a single-key lookup"
6766 All single-key lookups support the option &"ret=key"&.
6767 If this is given and the lookup
6768 (either underlying implementation or cached value)
6769 returns data, the result is replaced with a non-tainted
6770 version of the lookup key.
6772 .cindex "query-style lookup" "definition of"
6773 The &'query-style'& type accepts a generalized database query. No particular
6774 key value is assumed by Exim for query-style lookups. You can use whichever
6775 Exim variables you need to construct the database query.
6776 .cindex "tainted data" "quoting for lookups"
6777 If tainted data is used in the query then it should be quuted by
6778 using the &*${quote_*&<&'lookup-type'&>&*:*&<&'string'&>&*}*& expansion operator
6779 appropriate for the lookup.
6782 The code for each lookup type is in a separate source file that is included in
6783 the binary of Exim only if the corresponding compile-time option is set. The
6784 default settings in &_src/EDITME_& are:
6789 which means that only linear searching and DBM lookups are included by default.
6790 For some types of lookup (e.g. SQL databases), you need to install appropriate
6791 libraries and header files before building Exim.
6796 .section "Single-key lookup types" "SECTsinglekeylookups"
6797 .cindex "lookup" "single-key types"
6798 .cindex "single-key lookup" "list of types"
6799 The following single-key lookup types are implemented:
6802 .cindex "cdb" "description of"
6803 .cindex "lookup" "cdb"
6804 .cindex "binary zero" "in lookup key"
6805 &(cdb)&: The given file is searched as a Constant DataBase file, using the key
6806 string without a terminating binary zero. The cdb format is designed for
6807 indexed files that are read frequently and never updated, except by total
6808 re-creation. As such, it is particularly suitable for large files containing
6809 aliases or other indexed data referenced by an MTA. Information about cdb and
6810 tools for building the files can be found in several places:
6812 &url(https://cr.yp.to/cdb.html)
6813 &url(https://www.corpit.ru/mjt/tinycdb.html)
6814 &url(https://packages.debian.org/stable/utils/freecdb)
6815 &url(https://github.com/philpennock/cdbtools) (in Go)
6817 A cdb distribution is not needed in order to build Exim with cdb support,
6818 because the code for reading cdb files is included directly in Exim itself.
6819 However, no means of building or testing cdb files is provided with Exim, so
6820 you need to obtain a cdb distribution in order to do this.
6822 .cindex "DBM" "lookup type"
6823 .cindex "lookup" "dbm"
6824 .cindex "binary zero" "in lookup key"
6825 &(dbm)&: Calls to DBM library functions are used to extract data from the given
6826 DBM file by looking up the record with the given key. A terminating binary
6827 zero is included in the key that is passed to the DBM library. See section
6828 &<<SECTdb>>& for a discussion of DBM libraries.
6830 .cindex "Berkeley DB library" "file format"
6831 For all versions of Berkeley DB, Exim uses the DB_HASH style of database
6832 when building DBM files using the &%exim_dbmbuild%& utility. However, when
6833 using Berkeley DB versions 3 or 4, it opens existing databases for reading with
6834 the DB_UNKNOWN option. This enables it to handle any of the types of database
6835 that the library supports, and can be useful for accessing DBM files created by
6836 other applications. (For earlier DB versions, DB_HASH is always used.)
6838 .cindex "lookup" "dbmjz"
6839 .cindex "lookup" "dbm &-- embedded NULs"
6841 .cindex "dbmjz lookup type"
6842 &(dbmjz)&: This is the same as &(dbm)&, except that the lookup key is
6843 interpreted as an Exim list; the elements of the list are joined together with
6844 ASCII NUL characters to form the lookup key. An example usage would be to
6845 authenticate incoming SMTP calls using the passwords from Cyrus SASL's
6846 &_/etc/sasldb2_& file with the &(gsasl)& authenticator or Exim's own
6847 &(cram_md5)& authenticator.
6849 .cindex "lookup" "dbmnz"
6850 .cindex "lookup" "dbm &-- terminating zero"
6851 .cindex "binary zero" "in lookup key"
6853 .cindex "&_/etc/userdbshadow.dat_&"
6854 .cindex "dbmnz lookup type"
6855 &(dbmnz)&: This is the same as &(dbm)&, except that a terminating binary zero
6856 is not included in the key that is passed to the DBM library. You may need this
6857 if you want to look up data in files that are created by or shared with some
6858 other application that does not use terminating zeros. For example, you need to
6859 use &(dbmnz)& rather than &(dbm)& if you want to authenticate incoming SMTP
6860 calls using the passwords from Courier's &_/etc/userdbshadow.dat_& file. Exim's
6861 utility program for creating DBM files (&'exim_dbmbuild'&) includes the zeros
6862 by default, but has an option to omit them (see section &<<SECTdbmbuild>>&).
6864 .cindex "lookup" "dsearch"
6865 .cindex "dsearch lookup type"
6866 &(dsearch)&: The given file must be an
6868 directory path; this is searched for an entry
6869 whose name is the key by calling the &[lstat()]& function.
6871 contain any forward slash characters.
6872 If &[lstat()]& succeeds then so does the lookup.
6873 .cindex "tainted data" "dsearch result"
6874 The result is regarded as untainted.
6876 Options for the lookup can be given by appending them after the word "dsearch",
6877 separated by a comma. Options, if present, are a comma-separated list having
6878 each element starting with a tag name and an equals.
6880 Two options are supported, for the return value and for filtering match
6882 The "ret" option requests an alternate result value of
6883 the entire path for the entry. Example:
6885 ${lookup {passwd} dsearch,ret=full {/etc}}
6887 The default result is just the requested entry.
6888 The "filter" option requests that only directory entries of a given type
6889 are matched. The match value is one of "file", "dir" or "subdir" (the latter
6890 not matching "." or ".."). Example:
6892 ${lookup {passwd} dsearch,filter=file {/etc}}
6894 The default matching is for any entry type, including directories
6897 An example of how this
6898 lookup can be used to support virtual domains is given in section
6899 &<<SECTvirtualdomains>>&.
6901 .cindex "lookup" "iplsearch"
6902 .cindex "iplsearch lookup type"
6903 &(iplsearch)&: The given file is a text file containing keys and data. A key is
6904 terminated by a colon or white space or the end of the line. The keys in the
6905 file must be IP addresses, or IP addresses with CIDR masks. Keys that involve
6906 IPv6 addresses must be enclosed in quotes to prevent the first internal colon
6907 being interpreted as a key terminator. For example:
6909 1.2.3.4: data for 1.2.3.4
6910 192.168.0.0/16: data for 192.168.0.0/16
6911 "abcd::cdab": data for abcd::cdab
6912 "abcd:abcd::/32" data for abcd:abcd::/32
6914 The key for an &(iplsearch)& lookup must be an IP address (without a mask). The
6915 file is searched linearly, using the CIDR masks where present, until a matching
6916 key is found. The first key that matches is used; there is no attempt to find a
6917 &"best"& match. Apart from the way the keys are matched, the processing for
6918 &(iplsearch)& is the same as for &(lsearch)&.
6920 &*Warning 1*&: Unlike most other single-key lookup types, a file of data for
6921 &(iplsearch)& can &'not'& be turned into a DBM or cdb file, because those
6922 lookup types support only literal keys.
6924 &*Warning 2*&: In a host list, you must always use &(net-iplsearch)& so that
6925 the implicit key is the host's IP address rather than its name (see section
6926 &<<SECThoslispatsikey>>&).
6928 &*Warning 3*&: Do not use an IPv4-mapped IPv6 address for a key; use the
6929 IPv4, in dotted-quad form. (Exim converts IPv4-mapped IPv6 addresses to this
6930 notation before executing the lookup.)
6932 One option is supported, "ret=full", to request the return of the entire line
6933 rather than omitting the key portion.
6934 Note however that the key portion will have been de-quoted.
6938 .cindex json "lookup type"
6939 .cindex JSON expansions
6940 &(json)&: The given file is a text file with a JSON structure.
6941 An element of the structure is extracted, defined by the search key.
6942 The key is a list of subelement selectors
6943 (colon-separated by default but changeable in the usual way)
6944 which are applied in turn to select smaller and smaller portions
6945 of the JSON structure.
6946 If a selector is numeric, it must apply to a JSON array; the (zero-based)
6947 nunbered array element is selected.
6948 Otherwise it must apply to a JSON object; the named element is selected.
6949 The final resulting element can be a simple JSON type or a JSON object
6950 or array; for the latter two a string-representation of the JSON
6952 For elements of type string, the returned value is de-quoted.
6958 .cindex database lmdb
6959 &(lmdb)&: The given file is an LMDB database.
6960 LMDB is a memory-mapped key-value store,
6961 with API modeled loosely on that of BerkeleyDB.
6962 See &url(https://symas.com/products/lightning-memory-mapped-database/)
6963 for the feature set and operation modes.
6965 Exim provides read-only access via the LMDB C library.
6966 The library can be obtained from &url(https://github.com/LMDB/lmdb)
6967 or your operating system package repository.
6968 To enable LMDB support in Exim set LOOKUP_LMDB=yes in &_Local/Makefile_&.
6970 You will need to separately create the LMDB database file,
6971 possibly using the &"mdb_load"& utility.
6975 .cindex "linear search"
6976 .cindex "lookup" "lsearch"
6977 .cindex "lsearch lookup type"
6978 .cindex "case sensitivity" "in lsearch lookup"
6979 &(lsearch)&: The given file is a text file that is searched linearly for a
6980 line beginning with the search key, terminated by a colon or white space or the
6981 end of the line. The search is case-insensitive; that is, upper and lower case
6982 letters are treated as the same. The first occurrence of the key that is found
6983 in the file is used.
6985 White space between the key and the colon is permitted. The remainder of the
6986 line, with leading and trailing white space removed, is the data. This can be
6987 continued onto subsequent lines by starting them with any amount of white
6988 space, but only a single space character is included in the data at such a
6989 junction. If the data begins with a colon, the key must be terminated by a
6994 Empty lines and lines beginning with # are ignored, even if they occur in the
6995 middle of an item. This is the traditional textual format of alias files. Note
6996 that the keys in an &(lsearch)& file are literal strings. There is no
6997 wildcarding of any kind.
6999 .cindex "lookup" "lsearch &-- colons in keys"
7000 .cindex "white space" "in lsearch key"
7001 In most &(lsearch)& files, keys are not required to contain colons or #
7002 characters, or white space. However, if you need this feature, it is available.
7003 If a key begins with a doublequote character, it is terminated only by a
7004 matching quote (or end of line), and the normal escaping rules apply to its
7005 contents (see section &<<SECTstrings>>&). An optional colon is permitted after
7006 quoted keys (exactly as for unquoted keys). There is no special handling of
7007 quotes for the data part of an &(lsearch)& line.
7010 .cindex "NIS lookup type"
7011 .cindex "lookup" "NIS"
7012 .cindex "binary zero" "in lookup key"
7013 &(nis)&: The given file is the name of a NIS map, and a NIS lookup is done with
7014 the given key, without a terminating binary zero. There is a variant called
7015 &(nis0)& which does include the terminating binary zero in the key. This is
7016 reportedly needed for Sun-style alias files. Exim does not recognize NIS
7017 aliases; the full map names must be used.
7020 .cindex "wildlsearch lookup type"
7021 .cindex "lookup" "wildlsearch"
7022 .cindex "nwildlsearch lookup type"
7023 .cindex "lookup" "nwildlsearch"
7024 &(wildlsearch)& or &(nwildlsearch)&: These search a file linearly, like
7025 &(lsearch)&, but instead of being interpreted as a literal string, each key in
7026 the file may be wildcarded. The difference between these two lookup types is
7027 that for &(wildlsearch)&, each key in the file is string-expanded before being
7028 used, whereas for &(nwildlsearch)&, no expansion takes place.
7030 .cindex "case sensitivity" "in (n)wildlsearch lookup"
7031 Like &(lsearch)&, the testing is done case-insensitively. However, keys in the
7032 file that are regular expressions can be made case-sensitive by the use of
7033 &`(-i)`& within the pattern. The following forms of wildcard are recognized:
7035 . ==== As this is a nested list, any displays it contains must be indented
7036 . ==== as otherwise they are too far to the left.
7039 The string may begin with an asterisk to mean &"ends with"&. For example:
7041 *.a.b.c data for anything.a.b.c
7042 *fish data for anythingfish
7045 The string may begin with a circumflex to indicate a regular expression. For
7046 example, for &(wildlsearch)&:
7048 ^\N\d+\.a\.b\N data for <digits>.a.b
7050 Note the use of &`\N`& to disable expansion of the contents of the regular
7051 expression. If you are using &(nwildlsearch)&, where the keys are not
7052 string-expanded, the equivalent entry is:
7054 ^\d+\.a\.b data for <digits>.a.b
7056 The case-insensitive flag is set at the start of compiling the regular
7057 expression, but it can be turned off by using &`(-i)`& at an appropriate point.
7058 For example, to make the entire pattern case-sensitive:
7060 ^(?-i)\d+\.a\.b data for <digits>.a.b
7063 If the regular expression contains white space or colon characters, you must
7064 either quote it (see &(lsearch)& above), or represent these characters in other
7065 ways. For example, &`\s`& can be used for white space and &`\x3A`& for a
7066 colon. This may be easier than quoting, because if you quote, you have to
7067 escape all the backslashes inside the quotes.
7069 &*Note*&: It is not possible to capture substrings in a regular expression
7070 match for later use, because the results of all lookups are cached. If a lookup
7071 is repeated, the result is taken from the cache, and no actual pattern matching
7072 takes place. The values of all the numeric variables are unset after a
7073 &((n)wildlsearch)& match.
7076 Although I cannot see it being of much use, the general matching function that
7077 is used to implement &((n)wildlsearch)& means that the string may begin with a
7078 lookup name terminated by a semicolon, and followed by lookup data. For
7081 cdb;/some/file data for keys that match the file
7083 The data that is obtained from the nested lookup is discarded.
7086 Keys that do not match any of these patterns are interpreted literally. The
7087 continuation rules for the data are the same as for &(lsearch)&, and keys may
7088 be followed by optional colons.
7090 &*Warning*&: Unlike most other single-key lookup types, a file of data for
7091 &((n)wildlsearch)& can &'not'& be turned into a DBM or cdb file, because those
7092 lookup types support only literal keys.
7095 .cindex "spf lookup type"
7096 .cindex "lookup" "spf"
7097 &(spf)&: If Exim is built with SPF support, manual lookups can be done
7098 (as opposed to the standard ACL condition method).
7099 For details see section &<<SECSPF>>&.
7103 .section "Query-style lookup types" "SECTquerystylelookups"
7104 .cindex "lookup" "query-style types"
7105 .cindex "query-style lookup" "list of types"
7106 The supported query-style lookup types are listed below. Further details about
7107 many of them are given in later sections.
7110 .cindex "DNS" "as a lookup type"
7111 .cindex "lookup" "DNS"
7112 &(dnsdb)&: This does a DNS search for one or more records whose domain names
7113 are given in the supplied query. The resulting data is the contents of the
7114 records. See section &<<SECTdnsdb>>&.
7116 .cindex "InterBase lookup type"
7117 .cindex "lookup" "InterBase"
7118 &(ibase)&: This does a lookup in an InterBase database.
7120 .cindex "LDAP" "lookup type"
7121 .cindex "lookup" "LDAP"
7122 &(ldap)&: This does an LDAP lookup using a query in the form of a URL, and
7123 returns attributes from a single entry. There is a variant called &(ldapm)&
7124 that permits values from multiple entries to be returned. A third variant
7125 called &(ldapdn)& returns the Distinguished Name of a single entry instead of
7126 any attribute values. See section &<<SECTldap>>&.
7128 .cindex "MySQL" "lookup type"
7129 .cindex "lookup" "MySQL"
7130 &(mysql)&: The format of the query is an SQL statement that is passed to a
7131 MySQL database. See section &<<SECTsql>>&.
7133 .cindex "NIS+ lookup type"
7134 .cindex "lookup" "NIS+"
7135 &(nisplus)&: This does a NIS+ lookup using a query that can specify the name of
7136 the field to be returned. See section &<<SECTnisplus>>&.
7138 .cindex "Oracle" "lookup type"
7139 .cindex "lookup" "Oracle"
7140 &(oracle)&: The format of the query is an SQL statement that is passed to an
7141 Oracle database. See section &<<SECTsql>>&.
7143 .cindex "lookup" "passwd"
7144 .cindex "passwd lookup type"
7145 .cindex "&_/etc/passwd_&"
7146 &(passwd)& is a query-style lookup with queries that are just user names. The
7147 lookup calls &[getpwnam()]& to interrogate the system password data, and on
7148 success, the result string is the same as you would get from an &(lsearch)&
7149 lookup on a traditional &_/etc/passwd file_&, though with &`*`& for the
7150 password value. For example:
7152 *:42:42:King Rat:/home/kr:/bin/bash
7155 .cindex "PostgreSQL lookup type"
7156 .cindex "lookup" "PostgreSQL"
7157 &(pgsql)&: The format of the query is an SQL statement that is passed to a
7158 PostgreSQL database. See section &<<SECTsql>>&.
7161 .cindex "Redis lookup type"
7162 .cindex lookup Redis
7163 &(redis)&: The format of the query is either a simple get or simple set,
7164 passed to a Redis database. See section &<<SECTsql>>&.
7167 .cindex "sqlite lookup type"
7168 .cindex "lookup" "sqlite"
7169 &(sqlite)&: The format of the query is
7170 an SQL statement that is passed to an SQLite database. See section &<<SECTsqlite>>&.
7173 &(testdb)&: This is a lookup type that is used for testing Exim. It is
7174 not likely to be useful in normal operation.
7176 .cindex "whoson lookup type"
7177 .cindex "lookup" "whoson"
7178 . --- still http:-only, 2018-09-07
7179 &(whoson)&: &'Whoson'& (&url(http://whoson.sourceforge.net)) is a protocol that
7180 allows a server to check whether a particular (dynamically allocated) IP
7181 address is currently allocated to a known (trusted) user and, optionally, to
7182 obtain the identity of the said user. For SMTP servers, &'Whoson'& was popular
7183 at one time for &"POP before SMTP"& authentication, but that approach has been
7184 superseded by SMTP authentication. In Exim, &'Whoson'& can be used to implement
7185 &"POP before SMTP"& checking using ACL statements such as
7187 require condition = \
7188 ${lookup whoson {$sender_host_address}{yes}{no}}
7190 The query consists of a single IP address. The value returned is the name of
7191 the authenticated user, which is stored in the variable &$value$&. However, in
7192 this example, the data in &$value$& is not used; the result of the lookup is
7193 one of the fixed strings &"yes"& or &"no"&.
7198 .section "Temporary errors in lookups" "SECID63"
7199 .cindex "lookup" "temporary error in"
7200 Lookup functions can return temporary error codes if the lookup cannot be
7201 completed. For example, an SQL or LDAP database might be unavailable. For this
7202 reason, it is not advisable to use a lookup that might do this for critical
7203 options such as a list of local domains.
7205 When a lookup cannot be completed in a router or transport, delivery
7206 of the message (to the relevant address) is deferred, as for any other
7207 temporary error. In other circumstances Exim may assume the lookup has failed,
7208 or may give up altogether.
7212 .section "Default values in single-key lookups" "SECTdefaultvaluelookups"
7213 .cindex "wildcard lookups"
7214 .cindex "lookup" "default values"
7215 .cindex "lookup" "wildcard"
7216 .cindex "lookup" "* added to type"
7217 .cindex "default" "in single-key lookups"
7218 In this context, a &"default value"& is a value specified by the administrator
7219 that is to be used if a lookup fails.
7221 &*Note:*& This section applies only to single-key lookups. For query-style
7222 lookups, the facilities of the query language must be used. An attempt to
7223 specify a default for a query-style lookup provokes an error.
7225 If &"*"& is added to a single-key lookup type (for example, &%lsearch*%&)
7226 and the initial lookup fails, the key &"*"& is looked up in the file to
7227 provide a default value. See also the section on partial matching below.
7229 .cindex "*@ with single-key lookup"
7230 .cindex "lookup" "*@ added to type"
7231 .cindex "alias file" "per-domain default"
7232 Alternatively, if &"*@"& is added to a single-key lookup type (for example
7233 &%dbm*@%&) then, if the initial lookup fails and the key contains an @
7234 character, a second lookup is done with everything before the last @ replaced
7235 by *. This makes it possible to provide per-domain defaults in alias files
7236 that include the domains in the keys. If the second lookup fails (or doesn't
7237 take place because there is no @ in the key), &"*"& is looked up.
7238 For example, a &(redirect)& router might contain:
7240 data = ${lookup{$local_part@$domain}lsearch*@{/etc/mix-aliases}}
7242 Suppose the address that is being processed is &'jane@eyre.example'&. Exim
7243 looks up these keys, in this order:
7249 The data is taken from whichever key it finds first. &*Note*&: In an
7250 &(lsearch)& file, this does not mean the first of these keys in the file. A
7251 complete scan is done for each key, and only if it is not found at all does
7252 Exim move on to try the next key.
7256 .section "Partial matching in single-key lookups" "SECTpartiallookup"
7257 .cindex "partial matching"
7258 .cindex "wildcard lookups"
7259 .cindex "lookup" "partial matching"
7260 .cindex "lookup" "wildcard"
7261 .cindex "asterisk" "in search type"
7262 The normal operation of a single-key lookup is to search the file for an exact
7263 match with the given key. However, in a number of situations where domains are
7264 being looked up, it is useful to be able to do partial matching. In this case,
7265 information in the file that has a key starting with &"*."& is matched by any
7266 domain that ends with the components that follow the full stop. For example, if
7267 a key in a DBM file is
7269 *.dates.fict.example
7271 then when partial matching is enabled this is matched by (amongst others)
7272 &'2001.dates.fict.example'& and &'1984.dates.fict.example'&. It is also matched
7273 by &'dates.fict.example'&, if that does not appear as a separate key in the
7276 &*Note*&: Partial matching is not available for query-style lookups. It is
7277 also not available for any lookup items in address lists (see section
7278 &<<SECTaddresslist>>&).
7280 Partial matching is implemented by doing a series of separate lookups using
7281 keys constructed by modifying the original subject key. This means that it can
7282 be used with any of the single-key lookup types, provided that
7283 partial matching keys
7284 beginning with a special prefix (default &"*."&) are included in the data file.
7285 Keys in the file that do not begin with the prefix are matched only by
7286 unmodified subject keys when partial matching is in use.
7288 Partial matching is requested by adding the string &"partial-"& to the front of
7289 the name of a single-key lookup type, for example, &%partial-dbm%&. When this
7290 is done, the subject key is first looked up unmodified; if that fails, &"*."&
7291 is added at the start of the subject key, and it is looked up again. If that
7292 fails, further lookups are tried with dot-separated components removed from the
7293 start of the subject key, one-by-one, and &"*."& added on the front of what
7296 A minimum number of two non-* components are required. This can be adjusted
7297 by including a number before the hyphen in the search type. For example,
7298 &%partial3-lsearch%& specifies a minimum of three non-* components in the
7299 modified keys. Omitting the number is equivalent to &"partial2-"&. If the
7300 subject key is &'2250.dates.fict.example'& then the following keys are looked
7301 up when the minimum number of non-* components is two:
7303 2250.dates.fict.example
7304 *.2250.dates.fict.example
7305 *.dates.fict.example
7308 As soon as one key in the sequence is successfully looked up, the lookup
7311 .cindex "lookup" "partial matching &-- changing prefix"
7312 .cindex "prefix" "for partial matching"
7313 The use of &"*."& as the partial matching prefix is a default that can be
7314 changed. The motivation for this feature is to allow Exim to operate with file
7315 formats that are used by other MTAs. A different prefix can be supplied in
7316 parentheses instead of the hyphen after &"partial"&. For example:
7318 domains = partial(.)lsearch;/some/file
7320 In this example, if the domain is &'a.b.c'&, the sequence of lookups is
7321 &`a.b.c`&, &`.a.b.c`&, and &`.b.c`& (the default minimum of 2 non-wild
7322 components is unchanged). The prefix may consist of any punctuation characters
7323 other than a closing parenthesis. It may be empty, for example:
7325 domains = partial1()cdb;/some/file
7327 For this example, if the domain is &'a.b.c'&, the sequence of lookups is
7328 &`a.b.c`&, &`b.c`&, and &`c`&.
7330 If &"partial0"& is specified, what happens at the end (when the lookup with
7331 just one non-wild component has failed, and the original key is shortened right
7332 down to the null string) depends on the prefix:
7335 If the prefix has zero length, the whole lookup fails.
7337 If the prefix has length 1, a lookup for just the prefix is done. For
7338 example, the final lookup for &"partial0(.)"& is for &`.`& alone.
7340 Otherwise, if the prefix ends in a dot, the dot is removed, and the
7341 remainder is looked up. With the default prefix, therefore, the final lookup is
7342 for &"*"& on its own.
7344 Otherwise, the whole prefix is looked up.
7348 If the search type ends in &"*"& or &"*@"& (see section
7349 &<<SECTdefaultvaluelookups>>& above), the search for an ultimate default that
7350 this implies happens after all partial lookups have failed. If &"partial0"& is
7351 specified, adding &"*"& to the search type has no effect with the default
7352 prefix, because the &"*"& key is already included in the sequence of partial
7353 lookups. However, there might be a use for lookup types such as
7354 &"partial0(.)lsearch*"&.
7356 The use of &"*"& in lookup partial matching differs from its use as a wildcard
7357 in domain lists and the like. Partial matching works only in terms of
7358 dot-separated components; a key such as &`*fict.example`&
7359 in a database file is useless, because the asterisk in a partial matching
7360 subject key is always followed by a dot.
7365 .section "Lookup caching" "SECID64"
7366 .cindex "lookup" "caching"
7367 .cindex "caching" "lookup data"
7368 Exim caches all lookup results in order to avoid needless repetition of
7369 lookups. However, because (apart from the daemon) Exim operates as a collection
7370 of independent, short-lived processes, this caching applies only within a
7371 single Exim process. There is no inter-process lookup caching facility.
7373 If an option &"cache=no_rd"& is used on the lookup then
7374 the cache is only written to, cached data is not used for the operation
7375 and a real lookup is done.
7377 For single-key lookups, Exim keeps the relevant files open in case there is
7378 another lookup that needs them. In some types of configuration this can lead to
7379 many files being kept open for messages with many recipients. To avoid hitting
7380 the operating system limit on the number of simultaneously open files, Exim
7381 closes the least recently used file when it needs to open more files than its
7382 own internal limit, which can be changed via the &%lookup_open_max%& option.
7384 The single-key lookup files are closed and the lookup caches are flushed at
7385 strategic points during delivery &-- for example, after all routing is
7391 .section "Quoting lookup data" "SECID65"
7392 .cindex "lookup" "quoting"
7393 .cindex "quoting" "in lookups"
7394 When data from an incoming message is included in a query-style lookup, there
7395 is the possibility of special characters in the data messing up the syntax of
7396 the query. For example, a NIS+ query that contains
7400 will be broken if the local part happens to contain a closing square bracket.
7401 For NIS+, data can be enclosed in double quotes like this:
7403 [name="$local_part"]
7405 but this still leaves the problem of a double quote in the data. The rule for
7406 NIS+ is that double quotes must be doubled. Other lookup types have different
7407 rules, and to cope with the differing requirements, an expansion operator
7408 of the following form is provided:
7410 ${quote_<lookup-type>:<string>}
7412 For example, the safest way to write the NIS+ query is
7414 [name="${quote_nisplus:$local_part}"]
7416 See chapter &<<CHAPexpand>>& for full coverage of string expansions. The quote
7417 operator can be used for all lookup types, but has no effect for single-key
7418 lookups, since no quoting is ever needed in their key strings.
7423 .section "More about dnsdb" "SECTdnsdb"
7424 .cindex "dnsdb lookup"
7425 .cindex "lookup" "dnsdb"
7426 .cindex "DNS" "as a lookup type"
7427 The &(dnsdb)& lookup type uses the DNS as its database. A simple query consists
7428 of a record type and a domain name, separated by an equals sign. For example,
7429 an expansion string could contain:
7431 ${lookup dnsdb{mx=a.b.example}{$value}fail}
7433 If the lookup succeeds, the result is placed in &$value$&, which in this case
7434 is used on its own as the result. If the lookup does not succeed, the
7435 &`fail`& keyword causes a &'forced expansion failure'& &-- see section
7436 &<<SECTforexpfai>>& for an explanation of what this means.
7438 The supported DNS record types are A, CNAME, MX, NS, PTR, SOA, SPF, SRV, TLSA
7439 and TXT, and, when Exim is compiled with IPv6 support, AAAA.
7440 If no type is given, TXT is assumed.
7442 For any record type, if multiple records are found, the data is returned as a
7443 concatenation, with newline as the default separator. The order, of course,
7444 depends on the DNS resolver. You can specify a different separator character
7445 between multiple records by putting a right angle-bracket followed immediately
7446 by the new separator at the start of the query. For example:
7448 ${lookup dnsdb{>: a=host1.example}}
7450 It is permitted to specify a space as the separator character. Further
7451 white space is ignored.
7452 For lookup types that return multiple fields per record,
7453 an alternate field separator can be specified using a comma after the main
7454 separator character, followed immediately by the field separator.
7456 .cindex "PTR record" "in &(dnsdb)& lookup"
7457 When the type is PTR,
7458 the data can be an IP address, written as normal; inversion and the addition of
7459 &%in-addr.arpa%& or &%ip6.arpa%& happens automatically. For example:
7461 ${lookup dnsdb{ptr=192.168.4.5}{$value}fail}
7463 If the data for a PTR record is not a syntactically valid IP address, it is not
7464 altered and nothing is added.
7466 .cindex "MX record" "in &(dnsdb)& lookup"
7467 .cindex "SRV record" "in &(dnsdb)& lookup"
7468 For an MX lookup, both the preference value and the host name are returned for
7469 each record, separated by a space. For an SRV lookup, the priority, weight,
7470 port, and host name are returned for each record, separated by spaces.
7471 The field separator can be modified as above.
7473 .cindex "TXT record" "in &(dnsdb)& lookup"
7474 .cindex "SPF record" "in &(dnsdb)& lookup"
7475 For TXT records with multiple items of data, only the first item is returned,
7476 unless a field separator is specified.
7477 To concatenate items without a separator, use a semicolon instead.
7479 default behaviour is to concatenate multiple items without using a separator.
7481 ${lookup dnsdb{>\n,: txt=a.b.example}}
7482 ${lookup dnsdb{>\n; txt=a.b.example}}
7483 ${lookup dnsdb{spf=example.org}}
7485 It is permitted to specify a space as the separator character. Further
7486 white space is ignored.
7488 .cindex "SOA record" "in &(dnsdb)& lookup"
7489 For an SOA lookup, while no result is obtained the lookup is redone with
7490 successively more leading components dropped from the given domain.
7491 Only the primary-nameserver field is returned unless a field separator is
7494 ${lookup dnsdb{>:,; soa=a.b.example.com}}
7497 .section "Dnsdb lookup modifiers" "SECTdnsdb_mod"
7498 .cindex "dnsdb modifiers"
7499 .cindex "modifiers" "dnsdb"
7500 .cindex "options" "dnsdb"
7501 Modifiers for &(dnsdb)& lookups are given by optional keywords,
7502 each followed by a comma,
7503 that may appear before the record type.
7505 The &(dnsdb)& lookup fails only if all the DNS lookups fail. If there is a
7506 temporary DNS error for any of them, the behaviour is controlled by
7507 a defer-option modifier.
7508 The possible keywords are
7509 &"defer_strict"&, &"defer_never"&, and &"defer_lax"&.
7510 With &"strict"& behaviour, any temporary DNS error causes the
7511 whole lookup to defer. With &"never"& behaviour, a temporary DNS error is
7512 ignored, and the behaviour is as if the DNS lookup failed to find anything.
7513 With &"lax"& behaviour, all the queries are attempted, but a temporary DNS
7514 error causes the whole lookup to defer only if none of the other lookups
7515 succeed. The default is &"lax"&, so the following lookups are equivalent:
7517 ${lookup dnsdb{defer_lax,a=one.host.com:two.host.com}}
7518 ${lookup dnsdb{a=one.host.com:two.host.com}}
7520 Thus, in the default case, as long as at least one of the DNS lookups
7521 yields some data, the lookup succeeds.
7523 .cindex "DNSSEC" "dns lookup"
7524 Use of &(DNSSEC)& is controlled by a dnssec modifier.
7525 The possible keywords are
7526 &"dnssec_strict"&, &"dnssec_lax"&, and &"dnssec_never"&.
7527 With &"strict"& or &"lax"& DNSSEC information is requested
7529 With &"strict"& a response from the DNS resolver that
7530 is not labelled as authenticated data
7531 is treated as equivalent to a temporary DNS error.
7532 The default is &"lax"&.
7534 See also the &$lookup_dnssec_authenticated$& variable.
7536 .cindex timeout "dns lookup"
7537 .cindex "DNS" timeout
7538 Timeout for the dnsdb lookup can be controlled by a retrans modifier.
7539 The form is &"retrans_VAL"& where VAL is an Exim time specification
7541 The default value is set by the main configuration option &%dns_retrans%&.
7543 Retries for the dnsdb lookup can be controlled by a retry modifier.
7544 The form if &"retry_VAL"& where VAL is an integer.
7545 The default count is set by the main configuration option &%dns_retry%&.
7547 .cindex caching "of dns lookup"
7548 .cindex TTL "of dns lookup"
7550 Dnsdb lookup results are cached within a single process (and its children).
7551 The cache entry lifetime is limited to the smallest time-to-live (TTL)
7552 value of the set of returned DNS records.
7555 .section "Pseudo dnsdb record types" "SECID66"
7556 .cindex "MX record" "in &(dnsdb)& lookup"
7557 By default, both the preference value and the host name are returned for
7558 each MX record, separated by a space. If you want only host names, you can use
7559 the pseudo-type MXH:
7561 ${lookup dnsdb{mxh=a.b.example}}
7563 In this case, the preference values are omitted, and just the host names are
7566 .cindex "name server for enclosing domain"
7567 Another pseudo-type is ZNS (for &"zone NS"&). It performs a lookup for NS
7568 records on the given domain, but if none are found, it removes the first
7569 component of the domain name, and tries again. This process continues until NS
7570 records are found or there are no more components left (or there is a DNS
7571 error). In other words, it may return the name servers for a top-level domain,
7572 but it never returns the root name servers. If there are no NS records for the
7573 top-level domain, the lookup fails. Consider these examples:
7575 ${lookup dnsdb{zns=xxx.quercite.com}}
7576 ${lookup dnsdb{zns=xxx.edu}}
7578 Assuming that in each case there are no NS records for the full domain name,
7579 the first returns the name servers for &%quercite.com%&, and the second returns
7580 the name servers for &%edu%&.
7582 You should be careful about how you use this lookup because, unless the
7583 top-level domain does not exist, the lookup always returns some host names. The
7584 sort of use to which this might be put is for seeing if the name servers for a
7585 given domain are on a blacklist. You can probably assume that the name servers
7586 for the high-level domains such as &%com%& or &%co.uk%& are not going to be on
7589 .cindex "CSA" "in &(dnsdb)& lookup"
7590 A third pseudo-type is CSA (Client SMTP Authorization). This looks up SRV
7591 records according to the CSA rules, which are described in section
7592 &<<SECTverifyCSA>>&. Although &(dnsdb)& supports SRV lookups directly, this is
7593 not sufficient because of the extra parent domain search behaviour of CSA. The
7594 result of a successful lookup such as:
7596 ${lookup dnsdb {csa=$sender_helo_name}}
7598 has two space-separated fields: an authorization code and a target host name.
7599 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
7600 authorization required but absent, or &"?"& for unknown.
7602 .cindex "A+" "in &(dnsdb)& lookup"
7603 The pseudo-type A+ performs an AAAA
7604 and then an A lookup. All results are returned; defer processing
7605 (see below) is handled separately for each lookup. Example:
7607 ${lookup dnsdb {>; a+=$sender_helo_name}}
7611 .section "Multiple dnsdb lookups" "SECID67"
7612 In the previous sections, &(dnsdb)& lookups for a single domain are described.
7613 However, you can specify a list of domains or IP addresses in a single
7614 &(dnsdb)& lookup. The list is specified in the normal Exim way, with colon as
7615 the default separator, but with the ability to change this. For example:
7617 ${lookup dnsdb{one.domain.com:two.domain.com}}
7618 ${lookup dnsdb{a=one.host.com:two.host.com}}
7619 ${lookup dnsdb{ptr = <; 1.2.3.4 ; 4.5.6.8}}
7621 In order to retain backwards compatibility, there is one special case: if
7622 the lookup type is PTR and no change of separator is specified, Exim looks
7623 to see if the rest of the string is precisely one IPv6 address. In this
7624 case, it does not treat it as a list.
7626 The data from each lookup is concatenated, with newline separators by default,
7627 in the same way that multiple DNS records for a single item are handled. A
7628 different separator can be specified, as described above.
7633 .section "More about LDAP" "SECTldap"
7634 .cindex "LDAP" "lookup, more about"
7635 .cindex "lookup" "LDAP"
7636 .cindex "Solaris" "LDAP"
7637 The original LDAP implementation came from the University of Michigan; this has
7638 become &"Open LDAP"&, and there are now two different releases. Another
7639 implementation comes from Netscape, and Solaris 7 and subsequent releases
7640 contain inbuilt LDAP support. Unfortunately, though these are all compatible at
7641 the lookup function level, their error handling is different. For this reason
7642 it is necessary to set a compile-time variable when building Exim with LDAP, to
7643 indicate which LDAP library is in use. One of the following should appear in
7644 your &_Local/Makefile_&:
7646 LDAP_LIB_TYPE=UMICHIGAN
7647 LDAP_LIB_TYPE=OPENLDAP1
7648 LDAP_LIB_TYPE=OPENLDAP2
7649 LDAP_LIB_TYPE=NETSCAPE
7650 LDAP_LIB_TYPE=SOLARIS
7652 If LDAP_LIB_TYPE is not set, Exim assumes &`OPENLDAP1`&, which has the
7653 same interface as the University of Michigan version.
7655 There are three LDAP lookup types in Exim. These behave slightly differently in
7656 the way they handle the results of a query:
7659 &(ldap)& requires the result to contain just one entry; if there are more, it
7662 &(ldapdn)& also requires the result to contain just one entry, but it is the
7663 Distinguished Name that is returned rather than any attribute values.
7665 &(ldapm)& permits the result to contain more than one entry; the attributes
7666 from all of them are returned.
7670 For &(ldap)& and &(ldapm)&, if a query finds only entries with no attributes,
7671 Exim behaves as if the entry did not exist, and the lookup fails. The format of
7672 the data returned by a successful lookup is described in the next section.
7673 First we explain how LDAP queries are coded.
7676 .section "Format of LDAP queries" "SECTforldaque"
7677 .cindex "LDAP" "query format"
7678 An LDAP query takes the form of a URL as defined in RFC 2255. For example, in
7679 the configuration of a &(redirect)& router one might have this setting:
7681 data = ${lookup ldap \
7682 {ldap:///cn=$local_part,o=University%20of%20Cambridge,\
7683 c=UK?mailbox?base?}}
7685 .cindex "LDAP" "with TLS"
7686 The URL may begin with &`ldap`& or &`ldaps`& if your LDAP library supports
7687 secure (encrypted) LDAP connections. The second of these ensures that an
7688 encrypted TLS connection is used.
7690 With sufficiently modern LDAP libraries, Exim supports forcing TLS over regular
7691 LDAP connections, rather than the SSL-on-connect &`ldaps`&.
7692 See the &%ldap_start_tls%& option.
7694 Starting with Exim 4.83, the initialization of LDAP with TLS is more tightly
7695 controlled. Every part of the TLS configuration can be configured by settings in
7696 &_exim.conf_&. Depending on the version of the client libraries installed on
7697 your system, some of the initialization may have required setting options in
7698 &_/etc/ldap.conf_& or &_~/.ldaprc_& to get TLS working with self-signed
7699 certificates. This revealed a nuance where the current UID that exim was
7700 running as could affect which config files it read. With Exim 4.83, these
7701 methods become optional, only taking effect if not specifically set in
7705 .section "LDAP quoting" "SECID68"
7706 .cindex "LDAP" "quoting"
7707 Two levels of quoting are required in LDAP queries, the first for LDAP itself
7708 and the second because the LDAP query is represented as a URL. Furthermore,
7709 within an LDAP query, two different kinds of quoting are required. For this
7710 reason, there are two different LDAP-specific quoting operators.
7712 The &%quote_ldap%& operator is designed for use on strings that are part of
7713 filter specifications. Conceptually, it first does the following conversions on
7721 in accordance with RFC 2254. The resulting string is then quoted according
7722 to the rules for URLs, that is, all non-alphanumeric characters except
7726 are converted to their hex values, preceded by a percent sign. For example:
7728 ${quote_ldap: a(bc)*, a<yz>; }
7732 %20a%5C28bc%5C29%5C2A%2C%20a%3Cyz%3E%3B%20
7734 Removing the URL quoting, this is (with a leading and a trailing space):
7736 a\28bc\29\2A, a<yz>;
7738 The &%quote_ldap_dn%& operator is designed for use on strings that are part of
7739 base DN specifications in queries. Conceptually, it first converts the string
7740 by inserting a backslash in front of any of the following characters:
7744 It also inserts a backslash before any leading spaces or # characters, and
7745 before any trailing spaces. (These rules are in RFC 2253.) The resulting string
7746 is then quoted according to the rules for URLs. For example:
7748 ${quote_ldap_dn: a(bc)*, a<yz>; }
7752 %5C%20a(bc)*%5C%2C%20a%5C%3Cyz%5C%3E%5C%3B%5C%20
7754 Removing the URL quoting, this is (with a trailing space):
7756 \ a(bc)*\, a\<yz\>\;\
7758 There are some further comments about quoting in the section on LDAP
7759 authentication below.
7762 .section "LDAP connections" "SECID69"
7763 .cindex "LDAP" "connections"
7764 The connection to an LDAP server may either be over TCP/IP, or, when OpenLDAP
7765 is in use, via a Unix domain socket. The example given above does not specify
7766 an LDAP server. A server that is reached by TCP/IP can be specified in a query
7769 ldap://<hostname>:<port>/...
7771 If the port (and preceding colon) are omitted, the standard LDAP port (389) is
7772 used. When no server is specified in a query, a list of default servers is
7773 taken from the &%ldap_default_servers%& configuration option. This supplies a
7774 colon-separated list of servers which are tried in turn until one successfully
7775 handles a query, or there is a serious error. Successful handling either
7776 returns the requested data, or indicates that it does not exist. Serious errors
7777 are syntactical, or multiple values when only a single value is expected.
7778 Errors which cause the next server to be tried are connection failures, bind
7779 failures, and timeouts.
7781 For each server name in the list, a port number can be given. The standard way
7782 of specifying a host and port is to use a colon separator (RFC 1738). Because
7783 &%ldap_default_servers%& is a colon-separated list, such colons have to be
7784 doubled. For example
7786 ldap_default_servers = ldap1.example.com::145:ldap2.example.com
7788 If &%ldap_default_servers%& is unset, a URL with no server name is passed
7789 to the LDAP library with no server name, and the library's default (normally
7790 the local host) is used.
7792 If you are using the OpenLDAP library, you can connect to an LDAP server using
7793 a Unix domain socket instead of a TCP/IP connection. This is specified by using
7794 &`ldapi`& instead of &`ldap`& in LDAP queries. What follows here applies only
7795 to OpenLDAP. If Exim is compiled with a different LDAP library, this feature is
7798 For this type of connection, instead of a host name for the server, a pathname
7799 for the socket is required, and the port number is not relevant. The pathname
7800 can be specified either as an item in &%ldap_default_servers%&, or inline in
7801 the query. In the former case, you can have settings such as
7803 ldap_default_servers = /tmp/ldap.sock : backup.ldap.your.domain
7805 When the pathname is given in the query, you have to escape the slashes as
7806 &`%2F`& to fit in with the LDAP URL syntax. For example:
7808 ${lookup ldap {ldapi://%2Ftmp%2Fldap.sock/o=...
7810 When Exim processes an LDAP lookup and finds that the &"hostname"& is really
7811 a pathname, it uses the Unix domain socket code, even if the query actually
7812 specifies &`ldap`& or &`ldaps`&. In particular, no encryption is used for a
7813 socket connection. This behaviour means that you can use a setting of
7814 &%ldap_default_servers%& such as in the example above with traditional &`ldap`&
7815 or &`ldaps`& queries, and it will work. First, Exim tries a connection via
7816 the Unix domain socket; if that fails, it tries a TCP/IP connection to the
7819 If an explicit &`ldapi`& type is given in a query when a host name is
7820 specified, an error is diagnosed. However, if there are more items in
7821 &%ldap_default_servers%&, they are tried. In other words:
7824 Using a pathname with &`ldap`& or &`ldaps`& forces the use of the Unix domain
7827 Using &`ldapi`& with a host name causes an error.
7831 Using &`ldapi`& with no host or path in the query, and no setting of
7832 &%ldap_default_servers%&, does whatever the library does by default.
7836 .section "LDAP authentication and control information" "SECID70"
7837 .cindex "LDAP" "authentication"
7838 The LDAP URL syntax provides no way of passing authentication and other control
7839 information to the server. To make this possible, the URL in an LDAP query may
7840 be preceded by any number of <&'name'&>=<&'value'&> settings, separated by
7841 spaces. If a value contains spaces it must be enclosed in double quotes, and
7842 when double quotes are used, backslash is interpreted in the usual way inside
7843 them. The following names are recognized:
7844 .itable none 0 0 2 20* left 80* left
7845 .irow DEREFERENCE "set the dereferencing parameter"
7846 .irow NETTIME "set a timeout for a network operation"
7847 .irow USER "set the DN, for authenticating the LDAP bind"
7848 .irow PASS "set the password, likewise"
7849 .irow REFERRALS "set the referrals parameter"
7850 .irow SERVERS "set alternate server list for this query only"
7851 .irow SIZE "set the limit for the number of entries returned"
7852 .irow TIME "set the maximum waiting time for a query"
7854 The value of the DEREFERENCE parameter must be one of the words &"never"&,
7855 &"searching"&, &"finding"&, or &"always"&. The value of the REFERRALS parameter
7856 must be &"follow"& (the default) or &"nofollow"&. The latter stops the LDAP
7857 library from trying to follow referrals issued by the LDAP server.
7859 .cindex LDAP timeout
7860 .cindex timeout "LDAP lookup"
7861 The name CONNECT is an obsolete name for NETTIME, retained for
7862 backwards compatibility. This timeout (specified as a number of seconds) is
7863 enforced from the client end for operations that can be carried out over a
7864 network. Specifically, it applies to network connections and calls to the
7865 &'ldap_result()'& function. If the value is greater than zero, it is used if
7866 LDAP_OPT_NETWORK_TIMEOUT is defined in the LDAP headers (OpenLDAP), or
7867 if LDAP_X_OPT_CONNECT_TIMEOUT is defined in the LDAP headers (Netscape
7868 SDK 4.1). A value of zero forces an explicit setting of &"no timeout"& for
7869 Netscape SDK; for OpenLDAP no action is taken.
7871 The TIME parameter (also a number of seconds) is passed to the server to
7872 set a server-side limit on the time taken to complete a search.
7874 The SERVERS parameter allows you to specify an alternate list of ldap servers
7875 to use for an individual lookup. The global &%ldap_default_servers%& option provides a
7876 default list of ldap servers, and a single lookup can specify a single ldap
7877 server to use. But when you need to do a lookup with a list of servers that is
7878 different than the default list (maybe different order, maybe a completely
7879 different set of servers), the SERVERS parameter allows you to specify this
7880 alternate list (colon-separated).
7882 Here is an example of an LDAP query in an Exim lookup that uses some of these
7883 values. This is a single line, folded to fit on the page:
7886 {user="cn=manager,o=University of Cambridge,c=UK" pass=secret
7887 ldap:///o=University%20of%20Cambridge,c=UK?sn?sub?(cn=foo)}
7890 The encoding of spaces as &`%20`& is a URL thing which should not be done for
7891 any of the auxiliary data. Exim configuration settings that include lookups
7892 which contain password information should be preceded by &"hide"& to prevent
7893 non-admin users from using the &%-bP%& option to see their values.
7895 The auxiliary data items may be given in any order. The default is no
7896 connection timeout (the system timeout is used), no user or password, no limit
7897 on the number of entries returned, and no time limit on queries.
7899 When a DN is quoted in the USER= setting for LDAP authentication, Exim
7900 removes any URL quoting that it may contain before passing it LDAP. Apparently
7901 some libraries do this for themselves, but some do not. Removing the URL
7902 quoting has two advantages:
7905 It makes it possible to use the same &%quote_ldap_dn%& expansion for USER=
7906 DNs as with DNs inside actual queries.
7908 It permits spaces inside USER= DNs.
7911 For example, a setting such as
7913 USER=cn=${quote_ldap_dn:$1}
7915 should work even if &$1$& contains spaces.
7917 Expanded data for the PASS= value should be quoted using the &%quote%&
7918 expansion operator, rather than the LDAP quote operators. The only reason this
7919 field needs quoting is to ensure that it conforms to the Exim syntax, which
7920 does not allow unquoted spaces. For example:
7924 The LDAP authentication mechanism can be used to check passwords as part of
7925 SMTP authentication. See the &%ldapauth%& expansion string condition in chapter
7930 .section "Format of data returned by LDAP" "SECID71"
7931 .cindex "LDAP" "returned data formats"
7932 The &(ldapdn)& lookup type returns the Distinguished Name from a single entry
7933 as a sequence of values, for example
7935 cn=manager,o=University of Cambridge,c=UK
7937 The &(ldap)& lookup type generates an error if more than one entry matches the
7938 search filter, whereas &(ldapm)& permits this case, and inserts a newline in
7939 the result between the data from different entries. It is possible for multiple
7940 values to be returned for both &(ldap)& and &(ldapm)&, but in the former case
7941 you know that whatever values are returned all came from a single entry in the
7944 In the common case where you specify a single attribute in your LDAP query, the
7945 result is not quoted, and does not contain the attribute name. If the attribute
7946 has multiple values, they are separated by commas. Any comma that is
7947 part of an attribute's value is doubled.
7949 If you specify multiple attributes, the result contains space-separated, quoted
7950 strings, each preceded by the attribute name and an equals sign. Within the
7951 quotes, the quote character, backslash, and newline are escaped with
7952 backslashes, and commas are used to separate multiple values for the attribute.
7953 Any commas in attribute values are doubled
7954 (permitting treatment of the values as a comma-separated list).
7955 Apart from the escaping, the string within quotes takes the same form as the
7956 output when a single attribute is requested. Specifying no attributes is the
7957 same as specifying all of an entry's attributes.
7959 Here are some examples of the output format. The first line of each pair is an
7960 LDAP query, and the second is the data that is returned. The attribute called
7961 &%attr1%& has two values, one of them with an embedded comma, whereas
7962 &%attr2%& has only one value. Both attributes are derived from &%attr%&
7963 (they have SUP &%attr%& in their schema definitions).
7966 ldap:///o=base?attr1?sub?(uid=fred)
7969 ldap:///o=base?attr2?sub?(uid=fred)
7972 ldap:///o=base?attr?sub?(uid=fred)
7973 value1.1,value1,,2,value two
7975 ldap:///o=base?attr1,attr2?sub?(uid=fred)
7976 attr1="value1.1,value1,,2" attr2="value two"
7978 ldap:///o=base??sub?(uid=fred)
7979 objectClass="top" attr1="value1.1,value1,,2" attr2="value two"
7982 make use of Exim's &%-be%& option to run expansion tests and thereby check the
7983 results of LDAP lookups.
7984 The &%extract%& operator in string expansions can be used to pick out
7985 individual fields from data that consists of &'key'&=&'value'& pairs.
7986 The &%listextract%& operator should be used to pick out individual values
7987 of attributes, even when only a single value is expected.
7988 The doubling of embedded commas allows you to use the returned data as a
7989 comma separated list (using the "<," syntax for changing the input list separator).
7994 .section "More about NIS+" "SECTnisplus"
7995 .cindex "NIS+ lookup type"
7996 .cindex "lookup" "NIS+"
7997 NIS+ queries consist of a NIS+ &'indexed name'& followed by an optional colon
7998 and field name. If this is given, the result of a successful query is the
7999 contents of the named field; otherwise the result consists of a concatenation
8000 of &'field-name=field-value'& pairs, separated by spaces. Empty values and
8001 values containing spaces are quoted. For example, the query
8003 [name=mg1456],passwd.org_dir
8005 might return the string
8007 name=mg1456 passwd="" uid=999 gid=999 gcos="Martin Guerre"
8008 home=/home/mg1456 shell=/bin/bash shadow=""
8010 (split over two lines here to fit on the page), whereas
8012 [name=mg1456],passwd.org_dir:gcos
8018 with no quotes. A NIS+ lookup fails if NIS+ returns more than one table entry
8019 for the given indexed key. The effect of the &%quote_nisplus%& expansion
8020 operator is to double any quote characters within the text.
8024 .section "SQL lookups" "SECTsql"
8025 .cindex "SQL lookup types"
8026 .cindex "MySQL" "lookup type"
8027 .cindex "PostgreSQL lookup type"
8028 .cindex "lookup" "MySQL"
8029 .cindex "lookup" "PostgreSQL"
8030 .cindex "Oracle" "lookup type"
8031 .cindex "lookup" "Oracle"
8032 .cindex "InterBase lookup type"
8033 .cindex "lookup" "InterBase"
8034 .cindex "Redis lookup type"
8035 .cindex lookup Redis
8036 Exim can support lookups in InterBase, MySQL, Oracle, PostgreSQL, Redis,
8038 databases. Queries for these databases contain SQL statements, so an example
8041 ${lookup mysql{select mailbox from users where id='userx'}\
8044 If the result of the query contains more than one field, the data for each
8045 field in the row is returned, preceded by its name, so the result of
8047 ${lookup pgsql{select home,name from users where id='userx'}\
8052 home=/home/userx name="Mister X"
8054 Empty values and values containing spaces are double quoted, with embedded
8055 quotes escaped by a backslash. If the result of the query contains just one
8056 field, the value is passed back verbatim, without a field name, for example:
8060 If the result of the query yields more than one row, it is all concatenated,
8061 with a newline between the data for each row.
8064 .section "More about MySQL, PostgreSQL, Oracle, InterBase, and Redis" "SECID72"
8065 .cindex "MySQL" "lookup type"
8066 .cindex "PostgreSQL lookup type"
8067 .cindex "lookup" "MySQL"
8068 .cindex "lookup" "PostgreSQL"
8069 .cindex "Oracle" "lookup type"
8070 .cindex "lookup" "Oracle"
8071 .cindex "InterBase lookup type"
8072 .cindex "lookup" "InterBase"
8073 .cindex "Redis lookup type"
8074 .cindex lookup Redis
8075 If any MySQL, PostgreSQL, Oracle, InterBase or Redis lookups are used, the
8076 &%mysql_servers%&, &%pgsql_servers%&, &%oracle_servers%&, &%ibase_servers%&,
8077 or &%redis_servers%&
8078 option (as appropriate) must be set to a colon-separated list of server
8080 .oindex &%mysql_servers%&
8081 .oindex &%pgsql_servers%&
8082 .oindex &%oracle_servers%&
8083 .oindex &%ibase_servers%&
8084 .oindex &%redis_servers%&
8085 (For MySQL and PostgreSQL, the global option need not be set if all
8086 queries contain their own server information &-- see section
8087 &<<SECTspeserque>>&.)
8089 each item in the list is a slash-separated list of four
8090 items: host name, database name, user name, and password. In the case of
8091 Oracle, the host name field is used for the &"service name"&, and the database
8092 name field is not used and should be empty. For example:
8094 hide oracle_servers = oracle.plc.example//userx/abcdwxyz
8096 Because password data is sensitive, you should always precede the setting with
8097 &"hide"&, to prevent non-admin users from obtaining the setting via the &%-bP%&
8098 option. Here is an example where two MySQL servers are listed:
8100 hide mysql_servers = localhost/users/root/secret:\
8101 otherhost/users/root/othersecret
8103 For MySQL and PostgreSQL, a host may be specified as <&'name'&>:<&'port'&> but
8104 because this is a colon-separated list, the colon has to be doubled. For each
8105 query, these parameter groups are tried in order until a connection is made and
8106 a query is successfully processed. The result of a query may be that no data is
8107 found, but that is still a successful query. In other words, the list of
8108 servers provides a backup facility, not a list of different places to look.
8110 For Redis the global option need not be specified if all queries contain their
8111 own server information &-- see section &<<SECTspeserque>>&.
8112 If specified, the option must be set to a colon-separated list of server
8114 Each item in the list is a slash-separated list of three items:
8115 host, database number, and password.
8117 The host is required and may be either an IPv4 address and optional
8118 port number (separated by a colon, which needs doubling due to the
8119 higher-level list), or a Unix socket pathname enclosed in parentheses
8121 The database number is optional; if present that number is selected in the backend
8123 The password is optional; if present it is used to authenticate to the backend
8126 The &%quote_mysql%&, &%quote_pgsql%&, and &%quote_oracle%& expansion operators
8127 convert newline, tab, carriage return, and backspace to \n, \t, \r, and \b
8128 respectively, and the characters single-quote, double-quote, and backslash
8129 itself are escaped with backslashes.
8131 The &%quote_redis%& expansion operator
8132 escapes whitespace and backslash characters with a backslash.
8134 .section "Specifying the server in the query" "SECTspeserque"
8135 For MySQL, PostgreSQL and Redis lookups (but not currently for Oracle and InterBase),
8136 it is possible to specify a list of servers with an individual query. This is
8137 done by appending a comma-separated option to the query type:
8139 &`,servers=`&&'server1:server2:server3:...'&
8141 Each item in the list may take one of two forms:
8143 If it contains no slashes it is assumed to be just a host name. The appropriate
8144 global option (&%mysql_servers%& or &%pgsql_servers%&) is searched for a host
8145 of the same name, and the remaining parameters (database, user, password) are
8148 If it contains any slashes, it is taken as a complete parameter set.
8150 The list of servers is used in exactly the same way as the global list.
8151 Once a connection to a server has happened and a query has been
8152 successfully executed, processing of the lookup ceases.
8154 This feature is intended for use in master/slave situations where updates
8155 are occurring and you want to update the master rather than a slave. If the
8156 master is in the list as a backup for reading, you might have a global setting
8159 mysql_servers = slave1/db/name/pw:\
8163 In an updating lookup, you could then write:
8165 ${lookup mysql,servers=master {UPDATE ...} }
8167 That query would then be sent only to the master server. If, on the other hand,
8168 the master is not to be used for reading, and so is not present in the global
8169 option, you can still update it by a query of this form:
8171 ${lookup pgsql,servers=master/db/name/pw {UPDATE ...} }
8174 An older syntax places the servers specification before the query,
8175 semicolon separated:
8177 ${lookup mysql{servers=master; UPDATE ...} }
8179 The new version avoids potential issues with tainted
8180 arguments in the query, for explicit expansion.
8181 &*Note*&: server specifications in list-style lookups are still problematic.
8184 .section "Special MySQL features" "SECID73"
8185 For MySQL, an empty host name or the use of &"localhost"& in &%mysql_servers%&
8186 causes a connection to the server on the local host by means of a Unix domain
8187 socket. An alternate socket can be specified in parentheses.
8188 An option group name for MySQL option files can be specified in square brackets;
8189 the default value is &"exim"&.
8190 The full syntax of each item in &%mysql_servers%& is:
8192 <&'hostname'&>::<&'port'&>(<&'socket name'&>)[<&'option group'&>]/&&&
8193 <&'database'&>/<&'user'&>/<&'password'&>
8195 Any of the four sub-parts of the first field can be omitted. For normal use on
8196 the local host it can be left blank or set to just &"localhost"&.
8198 No database need be supplied &-- but if it is absent here, it must be given in
8201 If a MySQL query is issued that does not request any data (an insert, update,
8202 or delete command), the result of the lookup is the number of rows affected.
8204 &*Warning*&: This can be misleading. If an update does not actually change
8205 anything (for example, setting a field to the value it already has), the result
8206 is zero because no rows are affected.
8209 .section "Special PostgreSQL features" "SECID74"
8210 PostgreSQL lookups can also use Unix domain socket connections to the database.
8211 This is usually faster and costs less CPU time than a TCP/IP connection.
8212 However it can be used only if the mail server runs on the same machine as the
8213 database server. A configuration line for PostgreSQL via Unix domain sockets
8216 hide pgsql_servers = (/tmp/.s.PGSQL.5432)/db/user/password : ...
8218 In other words, instead of supplying a host name, a path to the socket is
8219 given. The path name is enclosed in parentheses so that its slashes aren't
8220 visually confused with the delimiters for the other server parameters.
8222 If a PostgreSQL query is issued that does not request any data (an insert,
8223 update, or delete command), the result of the lookup is the number of rows
8226 .section "More about SQLite" "SECTsqlite"
8227 .cindex "lookup" "SQLite"
8228 .cindex "sqlite lookup type"
8229 SQLite is different to the other SQL lookups because a filename is required in
8230 addition to the SQL query. An SQLite database is a single file, and there is no
8231 daemon as in the other SQL databases.
8233 .oindex &%sqlite_dbfile%&
8234 There are two ways of
8235 specifying the file.
8236 The first is is by using the &%sqlite_dbfile%& main option.
8237 The second, which allows separate files for each query,
8238 is to use an option appended, comma-separated, to the &"sqlite"&
8239 lookup type word. The option is the word &"file"&, then an equals,
8241 The filename in this case cannot contain whitespace or open-brace charachters.
8243 A deprecated method is available, prefixing the query with the filename
8244 separated by white space.
8246 .cindex "tainted data" "sqlite file"
8247 the query cannot use any tainted values, as that taints
8248 the entire query including the filename - resulting in a refusal to open
8251 In all the above cases the filename must be an absolute path.
8253 Here is a lookup expansion example:
8255 sqlite_dbfile = /some/thing/sqlitedb
8257 ${lookup sqlite {select name from aliases where id='userx';}}
8259 In a list, the syntax is similar. For example:
8261 domainlist relay_to_domains = sqlite;\
8262 select * from relays where ip='$sender_host_address';
8264 The only character affected by the &%quote_sqlite%& operator is a single
8265 quote, which it doubles.
8267 .cindex timeout SQLite
8268 .cindex sqlite "lookup timeout"
8269 The SQLite library handles multiple simultaneous accesses to the database
8270 internally. Multiple readers are permitted, but only one process can
8271 update at once. Attempts to access the database while it is being updated
8272 are rejected after a timeout period, during which the SQLite library
8273 waits for the lock to be released. In Exim, the default timeout is set
8274 to 5 seconds, but it can be changed by means of the &%sqlite_lock_timeout%&
8277 .section "More about Redis" "SECTredis"
8278 .cindex "lookup" "Redis"
8279 .cindex "redis lookup type"
8280 Redis is a non-SQL database. Commands are simple get and set.
8283 ${lookup redis{set keyname ${quote_redis:objvalue plus}}}
8284 ${lookup redis{get keyname}}
8287 As of release 4.91, "lightweight" support for Redis Cluster is available.
8288 Requires &%redis_servers%& list to contain all the servers in the cluster, all
8289 of which must be reachable from the running exim instance. If the cluster has
8290 master/slave replication, the list must contain all the master and slave
8293 When the Redis Cluster returns a "MOVED" response to a query, Exim does not
8294 immediately follow the redirection but treats the response as a DEFER, moving on
8295 to the next server in the &%redis_servers%& list until the correct server is
8302 . ////////////////////////////////////////////////////////////////////////////
8303 . ////////////////////////////////////////////////////////////////////////////
8305 .chapter "Domain, host, address, and local part lists" &&&
8306 "CHAPdomhosaddlists" &&&
8307 "Domain, host, and address lists"
8308 .scindex IIDdohoadli "lists of domains; hosts; etc."
8309 A number of Exim configuration options contain lists of domains, hosts,
8310 email addresses, or local parts. For example, the &%hold_domains%& option
8311 contains a list of domains whose delivery is currently suspended. These lists
8312 are also used as data in ACL statements (see chapter &<<CHAPACL>>&), and as
8313 arguments to expansion conditions such as &%match_domain%&.
8315 Each item in one of these lists is a pattern to be matched against a domain,
8316 host, email address, or local part, respectively. In the sections below, the
8317 different types of pattern for each case are described, but first we cover some
8318 general facilities that apply to all four kinds of list.
8320 Note that other parts of Exim use a &'string list'& which does not
8321 support all the complexity available in
8322 domain, host, address and local part lists.
8326 .section "Expansion of lists" "SECTlistexpand"
8327 .cindex "expansion" "of lists"
8328 Each list is expanded as a single string before it is used.
8330 &'Exception: the router headers_remove option, where list-item
8331 splitting is done before string-expansion.'&
8334 expansion must be a list, possibly containing empty items, which is split up
8335 into separate items for matching. By default, colon is the separator character,
8336 but this can be varied if necessary. See sections &<<SECTlistconstruct>>& and
8337 &<<SECTempitelis>>& for details of the list syntax; the second of these
8338 discusses the way to specify empty list items.
8341 If the string expansion is forced to fail, Exim behaves as if the item it is
8342 testing (domain, host, address, or local part) is not in the list. Other
8343 expansion failures cause temporary errors.
8345 If an item in a list is a regular expression, backslashes, dollars and possibly
8346 other special characters in the expression must be protected against
8347 misinterpretation by the string expander. The easiest way to do this is to use
8348 the &`\N`& expansion feature to indicate that the contents of the regular
8349 expression should not be expanded. For example, in an ACL you might have:
8351 deny senders = \N^\d{8}\w@.*\.baddomain\.example$\N : \
8352 ${lookup{$domain}lsearch{/badsenders/bydomain}}
8354 The first item is a regular expression that is protected from expansion by
8355 &`\N`&, whereas the second uses the expansion to obtain a list of unwanted
8356 senders based on the receiving domain.
8361 .section "Negated items in lists" "SECID76"
8362 .cindex "list" "negation"
8363 .cindex "negation" "in lists"
8364 Items in a list may be positive or negative. Negative items are indicated by a
8365 leading exclamation mark, which may be followed by optional white space. A list
8366 defines a set of items (domains, etc). When Exim processes one of these lists,
8367 it is trying to find out whether a domain, host, address, or local part
8368 (respectively) is in the set that is defined by the list. It works like this:
8370 The list is scanned from left to right. If a positive item is matched, the
8371 subject that is being checked is in the set; if a negative item is matched, the
8372 subject is not in the set. If the end of the list is reached without the
8373 subject having matched any of the patterns, it is in the set if the last item
8374 was a negative one, but not if it was a positive one. For example, the list in
8376 domainlist relay_to_domains = !a.b.c : *.b.c
8378 matches any domain ending in &'.b.c'& except for &'a.b.c'&. Domains that match
8379 neither &'a.b.c'& nor &'*.b.c'& do not match, because the last item in the
8380 list is positive. However, if the setting were
8382 domainlist relay_to_domains = !a.b.c
8384 then all domains other than &'a.b.c'& would match because the last item in the
8385 list is negative. In other words, a list that ends with a negative item behaves
8386 as if it had an extra item &`:*`& on the end.
8388 Another way of thinking about positive and negative items in lists is to read
8389 the connector as &"or"& after a positive item and as &"and"& after a negative
8394 .section "File names in lists" "SECTfilnamlis"
8395 .cindex "list" "filename in"
8396 If an item in a domain, host, address, or local part list is an absolute
8397 filename (beginning with a slash character), each line of the file is read and
8398 processed as if it were an independent item in the list, except that further
8399 filenames are not allowed,
8400 and no expansion of the data from the file takes place.
8401 Empty lines in the file are ignored, and the file may also contain comment
8405 For domain and host lists, if a # character appears anywhere in a line of the
8406 file, it and all following characters are ignored.
8408 Because local parts may legitimately contain # characters, a comment in an
8409 address list or local part list file is recognized only if # is preceded by
8410 white space or the start of the line. For example:
8412 not#comment@x.y.z # but this is a comment
8416 Putting a filename in a list has the same effect as inserting each line of the
8417 file as an item in the list (blank lines and comments excepted). However, there
8418 is one important difference: the file is read each time the list is processed,
8419 so if its contents vary over time, Exim's behaviour changes.
8421 If a filename is preceded by an exclamation mark, the sense of any match
8422 within the file is inverted. For example, if
8424 hold_domains = !/etc/nohold-domains
8426 and the file contains the lines
8431 then &'a.b.c'& is in the set of domains defined by &%hold_domains%&, whereas
8432 any domain matching &`*.b.c`& is not.
8436 .section "An lsearch file is not an out-of-line list" "SECID77"
8437 As will be described in the sections that follow, lookups can be used in lists
8438 to provide indexed methods of checking list membership. There has been some
8439 confusion about the way &(lsearch)& lookups work in lists. Because
8440 an &(lsearch)& file contains plain text and is scanned sequentially, it is
8441 sometimes thought that it is allowed to contain wild cards and other kinds of
8442 non-constant pattern. This is not the case. The keys in an &(lsearch)& file are
8443 always fixed strings, just as for any other single-key lookup type.
8445 If you want to use a file to contain wild-card patterns that form part of a
8446 list, just give the filename on its own, without a search type, as described
8447 in the previous section. You could also use the &(wildlsearch)& or
8448 &(nwildlsearch)&, but there is no advantage in doing this.
8453 .section "Results of list checking" SECTlistresults
8454 The primary result of doing a list check is a truth value.
8455 In some contexts additional information is stored
8456 about the list element that matched:
8459 A &%hosts%& ACL condition
8460 will store a result in the &$host_data$& variable.
8462 A &%local_parts%& router option or &%local_parts%& ACL condition
8463 will store a result in the &$local_part_data$& variable.
8465 A &%domains%& router option or &%domains%& ACL condition
8466 will store a result in the &$domain_data$& variable.
8468 A &%senders%& router option or &%senders%& ACL condition
8469 will store a result in the &$sender_data$& variable.
8471 A &%recipients%& ACL condition
8472 will store a result in the &$recipient_data$& variable.
8475 The detail of the additional information depends on the
8476 type of match and is given below as the &*value*& information.
8481 .section "Named lists" "SECTnamedlists"
8482 .cindex "named lists"
8483 .cindex "list" "named"
8484 A list of domains, hosts, email addresses, or local parts can be given a name
8485 which is then used to refer to the list elsewhere in the configuration. This is
8486 particularly convenient if the same list is required in several different
8487 places. It also allows lists to be given meaningful names, which can improve
8488 the readability of the configuration. For example, it is conventional to define
8489 a domain list called &'local_domains'& for all the domains that are handled
8490 locally on a host, using a configuration line such as
8492 domainlist local_domains = localhost:my.dom.example
8494 Named lists are referenced by giving their name preceded by a plus sign, so,
8495 for example, a router that is intended to handle local domains would be
8496 configured with the line
8498 domains = +local_domains
8500 The first router in a configuration is often one that handles all domains
8501 except the local ones, using a configuration with a negated item like this:
8505 domains = ! +local_domains
8506 transport = remote_smtp
8509 The four kinds of named list are created by configuration lines starting with
8510 the words &%domainlist%&, &%hostlist%&, &%addresslist%&, or &%localpartlist%&,
8511 respectively. Then there follows the name that you are defining, followed by an
8512 equals sign and the list itself. For example:
8514 hostlist relay_from_hosts = 192.168.23.0/24 : my.friend.example
8515 addresslist bad_senders = cdb;/etc/badsenders
8517 A named list may refer to other named lists:
8519 domainlist dom1 = first.example : second.example
8520 domainlist dom2 = +dom1 : third.example
8521 domainlist dom3 = fourth.example : +dom2 : fifth.example
8523 &*Warning*&: If the last item in a referenced list is a negative one, the
8524 effect may not be what you intended, because the negation does not propagate
8525 out to the higher level. For example, consider:
8527 domainlist dom1 = !a.b
8528 domainlist dom2 = +dom1 : *.b
8530 The second list specifies &"either in the &%dom1%& list or &'*.b'&"&. The first
8531 list specifies just &"not &'a.b'&"&, so the domain &'x.y'& matches it. That
8532 means it matches the second list as well. The effect is not the same as
8534 domainlist dom2 = !a.b : *.b
8536 where &'x.y'& does not match. It's best to avoid negation altogether in
8537 referenced lists if you can.
8539 .cindex "hiding named list values"
8540 .cindex "named lists" "hiding value of"
8541 Some named list definitions may contain sensitive data, for example, passwords for
8542 accessing databases. To stop non-admin users from using the &%-bP%& command
8543 line option to read these values, you can precede the definition with the
8544 word &"hide"&. For example:
8546 hide domainlist filter_for_domains = ldap;PASS=secret ldap::/// ...
8550 Named lists may have a performance advantage. When Exim is routing an
8551 address or checking an incoming message, it caches the result of tests on named
8552 lists. So, if you have a setting such as
8554 domains = +local_domains
8556 on several of your routers
8557 or in several ACL statements,
8558 the actual test is done only for the first one. However, the caching works only
8559 if there are no expansions within the list itself or any sublists that it
8560 references. In other words, caching happens only for lists that are known to be
8561 the same each time they are referenced.
8563 By default, there may be up to 16 named lists of each type. This limit can be
8564 extended by changing a compile-time variable. The use of domain and host lists
8565 is recommended for concepts such as local domains, relay domains, and relay
8566 hosts. The default configuration is set up like this.
8570 .section "Named lists compared with macros" "SECID78"
8571 .cindex "list" "named compared with macro"
8572 .cindex "macro" "compared with named list"
8573 At first sight, named lists might seem to be no different from macros in the
8574 configuration file. However, macros are just textual substitutions. If you
8577 ALIST = host1 : host2
8578 auth_advertise_hosts = !ALIST
8580 it probably won't do what you want, because that is exactly the same as
8582 auth_advertise_hosts = !host1 : host2
8584 Notice that the second host name is not negated. However, if you use a host
8587 hostlist alist = host1 : host2
8588 auth_advertise_hosts = ! +alist
8590 the negation applies to the whole list, and so that is equivalent to
8592 auth_advertise_hosts = !host1 : !host2
8596 .section "Named list caching" "SECID79"
8597 .cindex "list" "caching of named"
8598 .cindex "caching" "named lists"
8599 While processing a message, Exim caches the result of checking a named list if
8600 it is sure that the list is the same each time. In practice, this means that
8601 the cache operates only if the list contains no $ characters, which guarantees
8602 that it will not change when it is expanded. Sometimes, however, you may have
8603 an expanded list that you know will be the same each time within a given
8604 message. For example:
8606 domainlist special_domains = \
8607 ${lookup{$sender_host_address}cdb{/some/file}}
8609 This provides a list of domains that depends only on the sending host's IP
8610 address. If this domain list is referenced a number of times (for example,
8611 in several ACL lines, or in several routers) the result of the check is not
8612 cached by default, because Exim does not know that it is going to be the
8613 same list each time.
8615 By appending &`_cache`& to &`domainlist`& you can tell Exim to go ahead and
8616 cache the result anyway. For example:
8618 domainlist_cache special_domains = ${lookup{...
8620 If you do this, you should be absolutely sure that caching is going to do
8621 the right thing in all cases. When in doubt, leave it out.
8625 .section "Domain lists" "SECTdomainlist"
8626 .cindex "domain list" "patterns for"
8627 .cindex "list" "domain list"
8628 Domain lists contain patterns that are to be matched against a mail domain.
8629 The following types of item may appear in domain lists:
8632 .cindex "primary host name"
8633 .cindex "host name" "matched in domain list"
8634 .oindex "&%primary_hostname%&"
8635 .cindex "domain list" "matching primary host name"
8636 .cindex "@ in a domain list"
8637 If a pattern consists of a single @ character, it matches the local host name,
8638 as set by the &%primary_hostname%& option (or defaulted). This makes it
8639 possible to use the same configuration file on several different hosts that
8640 differ only in their names.
8642 The value for a match will be the primary host name.
8646 .cindex "@[] in a domain list"
8647 .cindex "domain list" "matching local IP interfaces"
8648 .cindex "domain literal"
8649 If a pattern consists of the string &`@[]`& it matches an IP address enclosed
8650 in square brackets (as in an email address that contains a domain literal), but
8651 only if that IP address is recognized as local for email routing purposes. The
8652 &%local_interfaces%& and &%extra_local_interfaces%& options can be used to
8653 control which of a host's several IP addresses are treated as local.
8654 In today's Internet, the use of domain literals is controversial;
8655 see the &%allow_domain_literals%& main option.
8657 The value for a match will be the string &`@[]`&.
8662 .cindex "@mx_primary"
8663 .cindex "@mx_secondary"
8664 .cindex "domain list" "matching MX pointers to local host"
8665 If a pattern consists of the string &`@mx_any`& it matches any domain that
8666 has an MX record pointing to the local host or to any host that is listed in
8667 .oindex "&%hosts_treat_as_local%&"
8668 &%hosts_treat_as_local%&. The items &`@mx_primary`& and &`@mx_secondary`&
8669 are similar, except that the first matches only when a primary MX target is the
8670 local host, and the second only when no primary MX target is the local host,
8671 but a secondary MX target is. &"Primary"& means an MX record with the lowest
8672 preference value &-- there may of course be more than one of them.
8674 The MX lookup that takes place when matching a pattern of this type is
8675 performed with the resolver options for widening names turned off. Thus, for
8676 example, a single-component domain will &'not'& be expanded by adding the
8677 resolver's default domain. See the &%qualify_single%& and &%search_parents%&
8678 options of the &(dnslookup)& router for a discussion of domain widening.
8680 Sometimes you may want to ignore certain IP addresses when using one of these
8681 patterns. You can specify this by following the pattern with &`/ignore=`&<&'ip
8682 list'&>, where <&'ip list'&> is a list of IP addresses. These addresses are
8683 ignored when processing the pattern (compare the &%ignore_target_hosts%& option
8684 on a router). For example:
8686 domains = @mx_any/ignore=127.0.0.1
8688 This example matches any domain that has an MX record pointing to one of
8689 the local host's IP addresses other than 127.0.0.1.
8691 The list of IP addresses is in fact processed by the same code that processes
8692 host lists, so it may contain CIDR-coded network specifications and it may also
8693 contain negative items.
8695 Because the list of IP addresses is a sublist within a domain list, you have to
8696 be careful about delimiters if there is more than one address. Like any other
8697 list, the default delimiter can be changed. Thus, you might have:
8699 domains = @mx_any/ignore=<;127.0.0.1;0.0.0.0 : \
8700 an.other.domain : ...
8702 so that the sublist uses semicolons for delimiters. When IPv6 addresses are
8703 involved, it is easiest to change the delimiter for the main list as well:
8705 domains = <? @mx_any/ignore=<;127.0.0.1;::1 ? \
8706 an.other.domain ? ...
8708 The value for a match will be the list element string (starting &`@mx_`&).
8712 .cindex "asterisk" "in domain list"
8713 .cindex "domain list" "asterisk in"
8714 .cindex "domain list" "matching &""ends with""&"
8715 If a pattern starts with an asterisk, the remaining characters of the pattern
8716 are compared with the terminating characters of the domain. The use of &"*"& in
8717 domain lists differs from its use in partial matching lookups. In a domain
8718 list, the character following the asterisk need not be a dot, whereas partial
8719 matching works only in terms of dot-separated components. For example, a domain
8720 list item such as &`*key.ex`& matches &'donkey.ex'& as well as
8723 The value for a match will be the list element string (starting with the asterisk).
8724 Additionally, &$0$& will be set to the matched string
8725 and &$1$& to the variable portion which the asterisk matched.
8728 .cindex "regular expressions" "in domain list"
8729 .cindex "domain list" "matching regular expression"
8730 If a pattern starts with a circumflex character, it is treated as a regular
8731 expression, and matched against the domain using a regular expression matching
8732 function. The circumflex is treated as part of the regular expression.
8733 Email domains are case-independent, so this regular expression match is by
8734 default case-independent, but you can make it case-dependent by starting it
8735 with &`(?-i)`&. References to descriptions of the syntax of regular expressions
8736 are given in chapter &<<CHAPregexp>>&.
8738 &*Warning*&: Because domain lists are expanded before being processed, you
8739 must escape any backslash and dollar characters in the regular expression, or
8740 use the special &`\N`& sequence (see chapter &<<CHAPexpand>>&) to specify that
8741 it is not to be expanded (unless you really do want to build a regular
8742 expression by expansion, of course).
8744 The value for a match will be the list element string (starting with the circumflex).
8745 Additionally, &$0$& will be set to the string matching the regular expression,
8746 and &$1$& (onwards) to any submatches identified by parentheses.
8751 .cindex "lookup" "in domain list"
8752 .cindex "domain list" "matching by lookup"
8753 If a pattern starts with the name of a single-key lookup type followed by a
8754 semicolon (for example, &"dbm;"& or &"lsearch;"&), the remainder of the pattern
8755 must be a filename in a suitable format for the lookup type. For example, for
8756 &"cdb;"& it must be an absolute path:
8758 domains = cdb;/etc/mail/local_domains.cdb
8760 The appropriate type of lookup is done on the file using the domain name as the
8761 key. In most cases, the value resulting from the lookup is not used; Exim is interested
8762 only in whether or not the key is present in the file. However, when a lookup
8763 is used for the &%domains%& option on a router
8764 or a &%domains%& condition in an ACL statement, the value is preserved in the
8765 &$domain_data$& variable and can be referred to in other router options or
8766 other statements in the same ACL.
8767 .cindex "tainted data" "de-tainting"
8768 .cindex "de-tainting" "using ACL domains condition"
8769 The value will be untainted.
8771 &*Note*&: If the data result of the lookup (as opposed to the key)
8772 is empty, then this empty value is stored in &$domain_data$&.
8773 The option to return the key for the lookup, as the value,
8774 may be what is wanted.
8778 Any of the single-key lookup type names may be preceded by
8779 &`partial`&<&'n'&>&`-`&, where the <&'n'&> is optional, for example,
8781 domains = partial-dbm;/partial/domains
8783 This causes partial matching logic to be invoked; a description of how this
8784 works is given in section &<<SECTpartiallookup>>&.
8787 .cindex "asterisk" "in lookup type"
8788 Any of the single-key lookup types may be followed by an asterisk. This causes
8789 a default lookup for a key consisting of a single asterisk to be done if the
8790 original lookup fails. This is not a useful feature when using a domain list to
8791 select particular domains (because any domain would match), but it might have
8792 value if the result of the lookup is being used via the &$domain_data$&
8796 If the pattern starts with the name of a query-style lookup type followed by a
8797 semicolon (for example, &"nisplus;"& or &"ldap;"&), the remainder of the
8798 pattern must be an appropriate query for the lookup type, as described in
8799 chapter &<<CHAPfdlookup>>&. For example:
8801 hold_domains = mysql;select domain from holdlist \
8802 where domain = '${quote_mysql:$domain}';
8804 In most cases, the value resulting from the lookup is not used (so for an SQL query, for
8805 example, it doesn't matter what field you select). Exim is interested only in
8806 whether or not the query succeeds. However, when a lookup is used for the
8807 &%domains%& option on a router, the value is preserved in the &$domain_data$&
8808 variable and can be referred to in other options.
8809 .cindex "tainted data" "de-tainting"
8810 .cindex "de-tainting" "using router domains option"
8811 The value will be untainted.
8814 If the pattern starts with the name of a lookup type
8815 of either kind (single-key or query-style) it may be
8816 followed by a comma and options,
8817 The options are lookup-type specific and consist of a comma-separated list.
8818 Each item starts with a tag and and equals "=" sign.
8821 .cindex "domain list" "matching literal domain name"
8822 If none of the above cases apply, a caseless textual comparison is made
8823 between the pattern and the domain.
8825 The value for a match will be the list element string.
8826 .cindex "tainted data" "de-tainting"
8827 Note that this is commonly untainted
8828 (depending on the way the list was created).
8829 Specifically, explicit text in the configuration file in not tainted.
8830 This is a useful way of obtaining an untainted equivalent to
8831 the domain, for later operations.
8833 However if the list (including one-element lists)
8834 is created by expanding a variable containing tainted data,
8835 it is tainted and so will the match value be.
8839 Here is an example that uses several different kinds of pattern:
8841 domainlist funny_domains = \
8844 *.foundation.fict.example : \
8845 \N^[1-2]\d{3}\.fict\.example$\N : \
8846 partial-dbm;/opt/data/penguin/book : \
8847 nis;domains.byname : \
8848 nisplus;[name=$domain,status=local],domains.org_dir
8850 There are obvious processing trade-offs among the various matching modes. Using
8851 an asterisk is faster than a regular expression, and listing a few names
8852 explicitly probably is too. The use of a file or database lookup is expensive,
8853 but may be the only option if hundreds of names are required. Because the
8854 patterns are tested in order, it makes sense to put the most commonly matched
8859 .section "Host lists" "SECThostlist"
8860 .cindex "host list" "patterns in"
8861 .cindex "list" "host list"
8862 Host lists are used to control what remote hosts are allowed to do. For
8863 example, some hosts may be allowed to use the local host as a relay, and some
8864 may be permitted to use the SMTP ETRN command. Hosts can be identified in
8865 two different ways, by name or by IP address. In a host list, some types of
8866 pattern are matched to a host name, and some are matched to an IP address.
8867 You need to be particularly careful with this when single-key lookups are
8868 involved, to ensure that the right value is being used as the key.
8871 .section "Special host list patterns" "SECID80"
8872 .cindex "empty item in hosts list"
8873 .cindex "host list" "empty string in"
8874 If a host list item is the empty string, it matches only when no remote host is
8875 involved. This is the case when a message is being received from a local
8876 process using SMTP on the standard input, that is, when a TCP/IP connection is
8879 .cindex "asterisk" "in host list"
8880 The special pattern &"*"& in a host list matches any host or no host. Neither
8881 the IP address nor the name is actually inspected.
8885 .section "Host list patterns that match by IP address" "SECThoslispatip"
8886 .cindex "host list" "matching IP addresses"
8887 If an IPv4 host calls an IPv6 host and the call is accepted on an IPv6 socket,
8888 the incoming address actually appears in the IPv6 host as
8889 &`::ffff:`&<&'v4address'&>. When such an address is tested against a host
8890 list, it is converted into a traditional IPv4 address first. (Not all operating
8891 systems accept IPv4 calls on IPv6 sockets, as there have been some security
8894 The following types of pattern in a host list check the remote host by
8895 inspecting its IP address:
8898 If the pattern is a plain domain name (not a regular expression, not starting
8899 with *, not a lookup of any kind), Exim calls the operating system function
8900 to find the associated IP address(es). Exim uses the newer
8901 &[getipnodebyname()]& function when available, otherwise &[gethostbyname()]&.
8902 This typically causes a forward DNS lookup of the name. The result is compared
8903 with the IP address of the subject host.
8905 If there is a temporary problem (such as a DNS timeout) with the host name
8906 lookup, a temporary error occurs. For example, if the list is being used in an
8907 ACL condition, the ACL gives a &"defer"& response, usually leading to a
8908 temporary SMTP error code. If no IP address can be found for the host name,
8909 what happens is described in section &<<SECTbehipnot>>& below.
8912 .cindex "@ in a host list"
8913 If the pattern is &"@"&, the primary host name is substituted and used as a
8914 domain name, as just described.
8917 If the pattern is an IP address, it is matched against the IP address of the
8918 subject host. IPv4 addresses are given in the normal &"dotted-quad"& notation.
8919 IPv6 addresses can be given in colon-separated format, but the colons have to
8920 be doubled so as not to be taken as item separators when the default list
8921 separator is used. IPv6 addresses are recognized even when Exim is compiled
8922 without IPv6 support. This means that if they appear in a host list on an
8923 IPv4-only host, Exim will not treat them as host names. They are just addresses
8924 that can never match a client host.
8927 .cindex "@[] in a host list"
8928 If the pattern is &"@[]"&, it matches the IP address of any IP interface on
8929 the local host. For example, if the local host is an IPv4 host with one
8930 interface address 10.45.23.56, these two ACL statements have the same effect:
8932 accept hosts = 127.0.0.1 : 10.45.23.56
8936 .cindex "CIDR notation"
8937 If the pattern is an IP address followed by a slash and a mask length, for
8942 , it is matched against the IP address of the subject
8943 host under the given mask. This allows an entire network of hosts to be
8944 included (or excluded) by a single item. The mask uses CIDR notation; it
8945 specifies the number of address bits that must match, starting from the most
8946 significant end of the address.
8948 &*Note*&: The mask is &'not'& a count of addresses, nor is it the high number
8949 of a range of addresses. It is the number of bits in the network portion of the
8950 address. The above example specifies a 24-bit netmask, so it matches all 256
8951 addresses in the 10.11.42.0 network. An item such as
8955 matches just two addresses, 192.168.23.236 and 192.168.23.237. A mask value of
8956 32 for an IPv4 address is the same as no mask at all; just a single address
8959 Here is another example which shows an IPv4 and an IPv6 network:
8961 recipient_unqualified_hosts = 192.168.0.0/16: \
8962 3ffe::ffff::836f::::/48
8964 The doubling of list separator characters applies only when these items
8965 appear inline in a host list. It is not required when indirecting via a file.
8968 recipient_unqualified_hosts = /opt/exim/unqualnets
8970 could make use of a file containing
8975 to have exactly the same effect as the previous example. When listing IPv6
8976 addresses inline, it is usually more convenient to use the facility for
8977 changing separator characters. This list contains the same two networks:
8979 recipient_unqualified_hosts = <; 172.16.0.0/12; \
8982 The separator is changed to semicolon by the leading &"<;"& at the start of the
8988 .section "Host list patterns for single-key lookups by host address" &&&
8989 "SECThoslispatsikey"
8990 .cindex "host list" "lookup of IP address"
8991 When a host is to be identified by a single-key lookup of its complete IP
8992 address, the pattern takes this form:
8994 &`net-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
8998 hosts_lookup = net-cdb;/hosts-by-ip.db
9000 The text form of the IP address of the subject host is used as the lookup key.
9001 IPv6 addresses are converted to an unabbreviated form, using lower case
9002 letters, with dots as separators because colon is the key terminator in
9003 &(lsearch)& files. [Colons can in fact be used in keys in &(lsearch)& files by
9004 quoting the keys, but this is a facility that was added later.] The data
9005 returned by the lookup is not used.
9007 .cindex "IP address" "masking"
9008 .cindex "host list" "masked IP address"
9009 Single-key lookups can also be performed using masked IP addresses, using
9010 patterns of this form:
9012 &`net<`&&'number'&&`>-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
9016 net24-dbm;/networks.db
9018 The IP address of the subject host is masked using <&'number'&> as the mask
9019 length. A textual string is constructed from the masked value, followed by the
9020 mask, and this is used as the lookup key. For example, if the host's IP address
9021 is 192.168.34.6, the key that is looked up for the above example is
9022 &"192.168.34.0/24"&.
9024 When an IPv6 address is converted to a string, dots are normally used instead
9025 of colons, so that keys in &(lsearch)& files need not contain colons (which
9026 terminate &(lsearch)& keys). This was implemented some time before the ability
9027 to quote keys was made available in &(lsearch)& files. However, the more
9028 recently implemented &(iplsearch)& files do require colons in IPv6 keys
9029 (notated using the quoting facility) so as to distinguish them from IPv4 keys.
9030 For this reason, when the lookup type is &(iplsearch)&, IPv6 addresses are
9031 converted using colons and not dots.
9032 In all cases except IPv4-mapped IPv6, full, unabbreviated IPv6
9033 addresses are always used.
9034 The latter are converted to IPv4 addresses, in dotted-quad form.
9036 Ideally, it would be nice to tidy up this anomalous situation by changing to
9037 colons in all cases, given that quoting is now available for &(lsearch)&.
9038 However, this would be an incompatible change that might break some existing
9041 &*Warning*&: Specifying &%net32-%& (for an IPv4 address) or &%net128-%& (for an
9042 IPv6 address) is not the same as specifying just &%net-%& without a number. In
9043 the former case the key strings include the mask value, whereas in the latter
9044 case the IP address is used on its own.
9048 .section "Host list patterns that match by host name" "SECThoslispatnam"
9049 .cindex "host" "lookup failures"
9050 .cindex "unknown host name"
9051 .cindex "host list" "matching host name"
9052 There are several types of pattern that require Exim to know the name of the
9053 remote host. These are either wildcard patterns or lookups by name. (If a
9054 complete hostname is given without any wildcarding, it is used to find an IP
9055 address to match against, as described in section &<<SECThoslispatip>>&
9058 If the remote host name is not already known when Exim encounters one of these
9059 patterns, it has to be found from the IP address.
9060 Although many sites on the Internet are conscientious about maintaining reverse
9061 DNS data for their hosts, there are also many that do not do this.
9062 Consequently, a name cannot always be found, and this may lead to unwanted
9063 effects. Take care when configuring host lists with wildcarded name patterns.
9064 Consider what will happen if a name cannot be found.
9066 Because of the problems of determining host names from IP addresses, matching
9067 against host names is not as common as matching against IP addresses.
9069 By default, in order to find a host name, Exim first does a reverse DNS lookup;
9070 if no name is found in the DNS, the system function (&[gethostbyaddr()]& or
9071 &[getipnodebyaddr()]& if available) is tried. The order in which these lookups
9072 are done can be changed by setting the &%host_lookup_order%& option. For
9073 security, once Exim has found one or more names, it looks up the IP addresses
9074 for these names and compares them with the IP address that it started with.
9075 Only those names whose IP addresses match are accepted. Any other names are
9076 discarded. If no names are left, Exim behaves as if the host name cannot be
9077 found. In the most common case there is only one name and one IP address.
9079 There are some options that control what happens if a host name cannot be
9080 found. These are described in section &<<SECTbehipnot>>& below.
9082 .cindex "host" "alias for"
9083 .cindex "alias for host"
9084 As a result of aliasing, hosts may have more than one name. When processing any
9085 of the following types of pattern, all the host's names are checked:
9088 .cindex "asterisk" "in host list"
9089 If a pattern starts with &"*"& the remainder of the item must match the end of
9090 the host name. For example, &`*.b.c`& matches all hosts whose names end in
9091 &'.b.c'&. This special simple form is provided because this is a very common
9092 requirement. Other kinds of wildcarding require the use of a regular
9095 .cindex "regular expressions" "in host list"
9096 .cindex "host list" "regular expression in"
9097 If the item starts with &"^"& it is taken to be a regular expression which is
9098 matched against the host name. Host names are case-independent, so this regular
9099 expression match is by default case-independent, but you can make it
9100 case-dependent by starting it with &`(?-i)`&. References to descriptions of the
9101 syntax of regular expressions are given in chapter &<<CHAPregexp>>&. For
9106 is a regular expression that matches either of the two hosts &'a.c.d'& or
9107 &'b.c.d'&. When a regular expression is used in a host list, you must take care
9108 that backslash and dollar characters are not misinterpreted as part of the
9109 string expansion. The simplest way to do this is to use &`\N`& to mark that
9110 part of the string as non-expandable. For example:
9112 sender_unqualified_hosts = \N^(a|b)\.c\.d$\N : ....
9114 &*Warning*&: If you want to match a complete host name, you must include the
9115 &`$`& terminating metacharacter in the regular expression, as in the above
9116 example. Without it, a match at the start of the host name is all that is
9123 .section "Behaviour when an IP address or name cannot be found" "SECTbehipnot"
9124 .cindex "host" "lookup failures, permanent"
9125 While processing a host list, Exim may need to look up an IP address from a
9126 name (see section &<<SECThoslispatip>>&), or it may need to look up a host name
9127 from an IP address (see section &<<SECThoslispatnam>>&). In either case, the
9128 behaviour when it fails to find the information it is seeking is the same.
9130 &*Note*&: This section applies to permanent lookup failures. It does &'not'&
9131 apply to temporary DNS errors, whose handling is described in the next section.
9133 .cindex "&`+include_unknown`&"
9134 .cindex "&`+ignore_unknown`&"
9135 Exim parses a host list from left to right. If it encounters a permanent
9136 lookup failure in any item in the host list before it has found a match,
9137 Exim treats it as a failure and the default behavior is as if the host
9138 does not match the list. This may not always be what you want to happen.
9139 To change Exim's behaviour, the special items &`+include_unknown`& or
9140 &`+ignore_unknown`& may appear in the list (at top level &-- they are
9141 not recognized in an indirected file).
9144 If any item that follows &`+include_unknown`& requires information that
9145 cannot found, Exim behaves as if the host does match the list. For example,
9147 host_reject_connection = +include_unknown:*.enemy.ex
9149 rejects connections from any host whose name matches &`*.enemy.ex`&, and also
9150 any hosts whose name it cannot find.
9153 If any item that follows &`+ignore_unknown`& requires information that cannot
9154 be found, Exim ignores that item and proceeds to the rest of the list. For
9157 accept hosts = +ignore_unknown : friend.example : \
9160 accepts from any host whose name is &'friend.example'& and from 192.168.4.5,
9161 whether or not its host name can be found. Without &`+ignore_unknown`&, if no
9162 name can be found for 192.168.4.5, it is rejected.
9165 Both &`+include_unknown`& and &`+ignore_unknown`& may appear in the same
9166 list. The effect of each one lasts until the next, or until the end of the
9169 .section "Mixing wildcarded host names and addresses in host lists" &&&
9171 .cindex "host list" "mixing names and addresses in"
9173 This section explains the host/ip processing logic with the same concepts
9174 as the previous section, but specifically addresses what happens when a
9175 wildcarded hostname is one of the items in the hostlist.
9178 If you have name lookups or wildcarded host names and
9179 IP addresses in the same host list, you should normally put the IP
9180 addresses first. For example, in an ACL you could have:
9182 accept hosts = 10.9.8.7 : *.friend.example
9184 The reason you normally would order it this way lies in the
9185 left-to-right way that Exim processes lists. It can test IP addresses
9186 without doing any DNS lookups, but when it reaches an item that requires
9187 a host name, it fails if it cannot find a host name to compare with the
9188 pattern. If the above list is given in the opposite order, the
9189 &%accept%& statement fails for a host whose name cannot be found, even
9190 if its IP address is 10.9.8.7.
9193 If you really do want to do the name check first, and still recognize the IP
9194 address, you can rewrite the ACL like this:
9196 accept hosts = *.friend.example
9197 accept hosts = 10.9.8.7
9199 If the first &%accept%& fails, Exim goes on to try the second one. See chapter
9200 &<<CHAPACL>>& for details of ACLs. Alternatively, you can use
9201 &`+ignore_unknown`&, which was discussed in depth in the first example in
9206 .section "Temporary DNS errors when looking up host information" &&&
9208 .cindex "host" "lookup failures, temporary"
9209 .cindex "&`+include_defer`&"
9210 .cindex "&`+ignore_defer`&"
9211 A temporary DNS lookup failure normally causes a defer action (except when
9212 &%dns_again_means_nonexist%& converts it into a permanent error). However,
9213 host lists can include &`+ignore_defer`& and &`+include_defer`&, analogous to
9214 &`+ignore_unknown`& and &`+include_unknown`&, as described in the previous
9215 section. These options should be used with care, probably only in non-critical
9216 host lists such as whitelists.
9220 .section "Host list patterns for single-key lookups by host name" &&&
9221 "SECThoslispatnamsk"
9222 .cindex "unknown host name"
9223 .cindex "host list" "matching host name"
9224 If a pattern is of the form
9226 <&'single-key-search-type'&>;<&'search-data'&>
9230 dbm;/host/accept/list
9232 a single-key lookup is performed, using the host name as its key. If the
9233 lookup succeeds, the host matches the item. The actual data that is looked up
9236 &*Reminder*&: With this kind of pattern, you must have host &'names'& as
9237 keys in the file, not IP addresses. If you want to do lookups based on IP
9238 addresses, you must precede the search type with &"net-"& (see section
9239 &<<SECThoslispatsikey>>&). There is, however, no reason why you could not use
9240 two items in the same list, one doing an address lookup and one doing a name
9241 lookup, both using the same file.
9245 .section "Host list patterns for query-style lookups" "SECID81"
9246 If a pattern is of the form
9248 <&'query-style-search-type'&>;<&'query'&>
9250 the query is obeyed, and if it succeeds, the host matches the item. The actual
9251 data that is looked up is not used. The variables &$sender_host_address$& and
9252 &$sender_host_name$& can be used in the query. For example:
9254 hosts_lookup = pgsql;\
9255 select ip from hostlist where ip='$sender_host_address'
9257 The value of &$sender_host_address$& for an IPv6 address contains colons. You
9258 can use the &%sg%& expansion item to change this if you need to. If you want to
9259 use masked IP addresses in database queries, you can use the &%mask%& expansion
9262 If the query contains a reference to &$sender_host_name$&, Exim automatically
9263 looks up the host name if it has not already done so. (See section
9264 &<<SECThoslispatnam>>& for comments on finding host names.)
9266 Historical note: prior to release 4.30, Exim would always attempt to find a
9267 host name before running the query, unless the search type was preceded by
9268 &`net-`&. This is no longer the case. For backwards compatibility, &`net-`& is
9269 still recognized for query-style lookups, but its presence or absence has no
9270 effect. (Of course, for single-key lookups, &`net-`& &'is'& important.
9271 See section &<<SECThoslispatsikey>>&.)
9277 .section "Address lists" "SECTaddresslist"
9278 .cindex "list" "address list"
9279 .cindex "address list" "empty item"
9280 .cindex "address list" "patterns"
9281 Address lists contain patterns that are matched against mail addresses. There
9282 is one special case to be considered: the sender address of a bounce message is
9283 always empty. You can test for this by providing an empty item in an address
9284 list. For example, you can set up a router to process bounce messages by
9285 using this option setting:
9289 The presence of the colon creates an empty item. If you do not provide any
9290 data, the list is empty and matches nothing. The empty sender can also be
9291 detected by a regular expression that matches an empty string,
9292 and by a query-style lookup that succeeds when &$sender_address$& is empty.
9294 Non-empty items in an address list can be straightforward email addresses. For
9297 senders = jbc@askone.example : hs@anacreon.example
9299 A certain amount of wildcarding is permitted. If a pattern contains an @
9300 character, but is not a regular expression and does not begin with a
9301 semicolon-terminated lookup type (described below), the local part of the
9302 subject address is compared with the local part of the pattern, which may start
9303 with an asterisk. If the local parts match, the domain is checked in exactly
9304 the same way as for a pattern in a domain list. For example, the domain can be
9305 wildcarded, refer to a named list, or be a lookup:
9307 deny senders = *@*.spamming.site:\
9308 *@+hostile_domains:\
9309 bozo@partial-lsearch;/list/of/dodgy/sites:\
9310 *@dbm;/bad/domains.db
9312 .cindex "local part" "starting with !"
9313 .cindex "address list" "local part starting with !"
9314 If a local part that begins with an exclamation mark is required, it has to be
9315 specified using a regular expression, because otherwise the exclamation mark is
9316 treated as a sign of negation, as is standard in lists.
9318 If a non-empty pattern that is not a regular expression or a lookup does not
9319 contain an @ character, it is matched against the domain part of the subject
9320 address. The only two formats that are recognized this way are a literal
9321 domain, or a domain pattern that starts with *. In both these cases, the effect
9322 is the same as if &`*@`& preceded the pattern. For example:
9324 deny senders = enemy.domain : *.enemy.domain
9327 The following kinds of more complicated address list pattern can match any
9328 address, including the empty address that is characteristic of bounce message
9332 .cindex "regular expressions" "in address list"
9333 .cindex "address list" "regular expression in"
9334 If (after expansion) a pattern starts with &"^"&, a regular expression match is
9335 done against the complete address, with the pattern as the regular expression.
9336 You must take care that backslash and dollar characters are not misinterpreted
9337 as part of the string expansion. The simplest way to do this is to use &`\N`&
9338 to mark that part of the string as non-expandable. For example:
9340 deny senders = \N^.*this.*@example\.com$\N : \
9341 \N^\d{8}.+@spamhaus.example$\N : ...
9343 The &`\N`& sequences are removed by the expansion, so these items do indeed
9344 start with &"^"& by the time they are being interpreted as address patterns.
9347 .cindex "address list" "lookup for complete address"
9348 Complete addresses can be looked up by using a pattern that starts with a
9349 lookup type terminated by a semicolon, followed by the data for the lookup. For
9352 deny senders = cdb;/etc/blocked.senders : \
9353 mysql;select address from blocked where \
9354 address='${quote_mysql:$sender_address}'
9356 Both query-style and single-key lookup types can be used. For a single-key
9357 lookup type, Exim uses the complete address as the key. However, empty keys are
9358 not supported for single-key lookups, so a match against the empty address
9359 always fails. This restriction does not apply to query-style lookups.
9361 Partial matching for single-key lookups (section &<<SECTpartiallookup>>&)
9362 cannot be used, and is ignored if specified, with an entry being written to the
9364 .cindex "*@ with single-key lookup"
9365 However, you can configure lookup defaults, as described in section
9366 &<<SECTdefaultvaluelookups>>&, but this is useful only for the &"*@"& type of
9367 default. For example, with this lookup:
9369 accept senders = lsearch*@;/some/file
9371 the file could contains lines like this:
9373 user1@domain1.example
9376 and for the sender address &'nimrod@jaeger.example'&, the sequence of keys
9379 nimrod@jaeger.example
9383 &*Warning 1*&: Do not include a line keyed by &"*"& in the file, because that
9384 would mean that every address matches, thus rendering the test useless.
9386 &*Warning 2*&: Do not confuse these two kinds of item:
9388 deny recipients = dbm*@;/some/file
9389 deny recipients = *@dbm;/some/file
9391 The first does a whole address lookup, with defaulting, as just described,
9392 because it starts with a lookup type. The second matches the local part and
9393 domain independently, as described in a bullet point below.
9397 The following kinds of address list pattern can match only non-empty addresses.
9398 If the subject address is empty, a match against any of these pattern types
9403 .cindex "@@ with single-key lookup"
9404 .cindex "address list" "@@ lookup type"
9405 .cindex "address list" "split local part and domain"
9406 If a pattern starts with &"@@"& followed by a single-key lookup item
9407 (for example, &`@@lsearch;/some/file`&), the address that is being checked is
9408 split into a local part and a domain. The domain is looked up in the file. If
9409 it is not found, there is no match. If it is found, the data that is looked up
9410 from the file is treated as a colon-separated list of local part patterns, each
9411 of which is matched against the subject local part in turn.
9413 .cindex "asterisk" "in address list"
9414 The lookup may be a partial one, and/or one involving a search for a default
9415 keyed by &"*"& (see section &<<SECTdefaultvaluelookups>>&). The local part
9416 patterns that are looked up can be regular expressions or begin with &"*"&, or
9417 even be further lookups. They may also be independently negated. For example,
9420 deny senders = @@dbm;/etc/reject-by-domain
9422 the data from which the DBM file is built could contain lines like
9424 baddomain.com: !postmaster : *
9426 to reject all senders except &%postmaster%& from that domain.
9428 .cindex "local part" "starting with !"
9429 If a local part that actually begins with an exclamation mark is required, it
9430 has to be specified using a regular expression. In &(lsearch)& files, an entry
9431 may be split over several lines by indenting the second and subsequent lines,
9432 but the separating colon must still be included at line breaks. White space
9433 surrounding the colons is ignored. For example:
9435 aol.com: spammer1 : spammer2 : ^[0-9]+$ :
9438 As in all colon-separated lists in Exim, a colon can be included in an item by
9441 If the last item in the list starts with a right angle-bracket, the remainder
9442 of the item is taken as a new key to look up in order to obtain a continuation
9443 list of local parts. The new key can be any sequence of characters. Thus one
9444 might have entries like
9446 aol.com: spammer1 : spammer 2 : >*
9447 xyz.com: spammer3 : >*
9450 in a file that was searched with &%@@dbm*%&, to specify a match for 8-digit
9451 local parts for all domains, in addition to the specific local parts listed for
9452 each domain. Of course, using this feature costs another lookup each time a
9453 chain is followed, but the effort needed to maintain the data is reduced.
9455 .cindex "loop" "in lookups"
9456 It is possible to construct loops using this facility, and in order to catch
9457 them, the chains may be no more than fifty items long.
9460 The @@<&'lookup'&> style of item can also be used with a query-style
9461 lookup, but in this case, the chaining facility is not available. The lookup
9462 can only return a single list of local parts.
9465 &*Warning*&: There is an important difference between the address list items
9466 in these two examples:
9469 senders = *@+my_list
9471 In the first one, &`my_list`& is a named address list, whereas in the second
9472 example it is a named domain list.
9477 .section "Case of letters in address lists" "SECTcasletadd"
9478 .cindex "case of local parts"
9479 .cindex "address list" "case forcing"
9480 .cindex "case forcing in address lists"
9481 Domains in email addresses are always handled caselessly, but for local parts
9482 case may be significant on some systems (see &%caseful_local_part%& for how
9483 Exim deals with this when routing addresses). However, RFC 2505 (&'Anti-Spam
9484 Recommendations for SMTP MTAs'&) suggests that matching of addresses to
9485 blocking lists should be done in a case-independent manner. Since most address
9486 lists in Exim are used for this kind of control, Exim attempts to do this by
9489 The domain portion of an address is always lowercased before matching it to an
9490 address list. The local part is lowercased by default, and any string
9491 comparisons that take place are done caselessly. This means that the data in
9492 the address list itself, in files included as plain filenames, and in any file
9493 that is looked up using the &"@@"& mechanism, can be in any case. However, the
9494 keys in files that are looked up by a search type other than &(lsearch)& (which
9495 works caselessly) must be in lower case, because these lookups are not
9498 .cindex "&`+caseful`&"
9499 To allow for the possibility of caseful address list matching, if an item in
9500 an address list is the string &"+caseful"&, the original case of the local
9501 part is restored for any comparisons that follow, and string comparisons are no
9502 longer case-independent. This does not affect the domain, which remains in
9503 lower case. However, although independent matches on the domain alone are still
9504 performed caselessly, regular expressions that match against an entire address
9505 become case-sensitive after &"+caseful"& has been seen.
9509 .section "Local part lists" "SECTlocparlis"
9510 .cindex "list" "local part list"
9511 .cindex "local part" "list"
9512 These behave in the same way as domain and host lists, with the following
9515 Case-sensitivity in local part lists is handled in the same way as for address
9516 lists, as just described. The &"+caseful"& item can be used if required. In a
9517 setting of the &%local_parts%& option in a router with &%caseful_local_part%&
9518 set false, the subject is lowercased and the matching is initially
9519 case-insensitive. In this case, &"+caseful"& will restore case-sensitive
9520 matching in the local part list, but not elsewhere in the router. If
9521 &%caseful_local_part%& is set true in a router, matching in the &%local_parts%&
9522 option is case-sensitive from the start.
9524 If a local part list is indirected to a file (see section &<<SECTfilnamlis>>&),
9525 comments are handled in the same way as address lists &-- they are recognized
9526 only if the # is preceded by white space or the start of the line.
9527 Otherwise, local part lists are matched in the same way as domain lists, except
9528 that the special items that refer to the local host (&`@`&, &`@[]`&,
9529 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`&) are not recognized.
9530 Refer to section &<<SECTdomainlist>>& for details of the other available item
9532 .ecindex IIDdohoadli
9537 . ////////////////////////////////////////////////////////////////////////////
9538 . ////////////////////////////////////////////////////////////////////////////
9540 .chapter "String expansions" "CHAPexpand"
9541 .scindex IIDstrexp "expansion" "of strings"
9542 Many strings in Exim's runtime configuration are expanded before use. Some of
9543 them are expanded every time they are used; others are expanded only once.
9545 When a string is being expanded it is copied verbatim from left to right except
9546 .cindex expansion "string concatenation"
9547 when a dollar or backslash character is encountered. A dollar specifies the
9548 start of a portion of the string that is interpreted and replaced as described
9549 below in section &<<SECTexpansionitems>>& onwards. Backslash is used as an
9550 escape character, as described in the following section.
9552 Whether a string is expanded depends upon the context. Usually this is solely
9553 dependent upon the option for which a value is sought; in this documentation,
9554 options for which string expansion is performed are marked with † after
9555 the data type. ACL rules always expand strings. A couple of expansion
9556 conditions do not expand some of the brace-delimited branches, for security
9558 .cindex "tainted data" expansion
9559 .cindex "tainted data" definition
9560 .cindex expansion "tainted data"
9561 and expansion of data deriving from the sender (&"tainted data"&)
9562 is not permitted (including acessing a file using a tainted name).
9564 Common ways of obtaining untainted equivalents of variables with
9566 .cindex "tainted data" "de-tainting"
9567 come down to using the tainted value as a lookup key in a trusted database.
9568 This database could be the filesystem structure,
9569 or the password file,
9570 or accessed via a DBMS.
9571 Specific methods are indexed under &"de-tainting"&.
9575 .section "Literal text in expanded strings" "SECTlittext"
9576 .cindex "expansion" "including literal text"
9577 An uninterpreted dollar can be included in an expanded string by putting a
9578 backslash in front of it. A backslash can be used to prevent any special
9579 character being treated specially in an expansion, including backslash itself.
9580 If the string appears in quotes in the configuration file, two backslashes are
9581 required because the quotes themselves cause interpretation of backslashes when
9582 the string is read in (see section &<<SECTstrings>>&).
9584 .cindex "expansion" "non-expandable substrings"
9585 A portion of the string can specified as non-expandable by placing it between
9586 two occurrences of &`\N`&. This is particularly useful for protecting regular
9587 expressions, which often contain backslashes and dollar signs. For example:
9589 deny senders = \N^\d{8}[a-z]@some\.site\.example$\N
9591 On encountering the first &`\N`&, the expander copies subsequent characters
9592 without interpretation until it reaches the next &`\N`& or the end of the
9597 .section "Character escape sequences in expanded strings" "SECID82"
9598 .cindex "expansion" "escape sequences"
9599 A backslash followed by one of the letters &"n"&, &"r"&, or &"t"& in an
9600 expanded string is recognized as an escape sequence for the character newline,
9601 carriage return, or tab, respectively. A backslash followed by up to three
9602 octal digits is recognized as an octal encoding for a single character, and a
9603 backslash followed by &"x"& and up to two hexadecimal digits is a hexadecimal
9606 These escape sequences are also recognized in quoted strings when they are read
9607 in. Their interpretation in expansions as well is useful for unquoted strings,
9608 and for other cases such as looked-up strings that are then expanded.
9611 .section "Testing string expansions" "SECID83"
9612 .cindex "expansion" "testing"
9613 .cindex "testing" "string expansion"
9615 Many expansions can be tested by calling Exim with the &%-be%& option. This
9616 takes the command arguments, or lines from the standard input if there are no
9617 arguments, runs them through the string expansion code, and writes the results
9618 to the standard output. Variables based on configuration values are set up, but
9619 since no message is being processed, variables such as &$local_part$& have no
9620 value. Nevertheless the &%-be%& option can be useful for checking out file and
9621 database lookups, and the use of expansion operators such as &%sg%&, &%substr%&
9624 Exim gives up its root privilege when it is called with the &%-be%& option, and
9625 instead runs under the uid and gid it was called with, to prevent users from
9626 using &%-be%& for reading files to which they do not have access.
9629 If you want to test expansions that include variables whose values are taken
9630 from a message, there are two other options that can be used. The &%-bem%&
9631 option is like &%-be%& except that it is followed by a filename. The file is
9632 read as a message before doing the test expansions. For example:
9634 exim -bem /tmp/test.message '$h_subject:'
9636 The &%-Mset%& option is used in conjunction with &%-be%& and is followed by an
9637 Exim message identifier. For example:
9639 exim -be -Mset 1GrA8W-0004WS-LQ '$recipients'
9641 This loads the message from Exim's spool before doing the test expansions, and
9642 is therefore restricted to admin users.
9645 .section "Forced expansion failure" "SECTforexpfai"
9646 .cindex "expansion" "forced failure"
9647 A number of expansions that are described in the following section have
9648 alternative &"true"& and &"false"& substrings, enclosed in brace characters
9649 (which are sometimes called &"curly brackets"&). Which of the two strings is
9650 used depends on some condition that is evaluated as part of the expansion. If,
9651 instead of a &"false"& substring, the word &"fail"& is used (not in braces),
9652 the entire string expansion fails in a way that can be detected by the code
9653 that requested the expansion. This is called &"forced expansion failure"&, and
9654 its consequences depend on the circumstances. In some cases it is no different
9655 from any other expansion failure, but in others a different action may be
9656 taken. Such variations are mentioned in the documentation of the option that is
9662 .section "Expansion items" "SECTexpansionitems"
9663 The following items are recognized in expanded strings. White space may be used
9664 between sub-items that are keywords or substrings enclosed in braces inside an
9665 outer set of braces, to improve readability. &*Warning*&: Within braces,
9666 white space is significant.
9669 .vitem &*$*&<&'variable&~name'&>&~or&~&*${*&<&'variable&~name'&>&*}*&
9670 .cindex "expansion" "variables"
9671 Substitute the contents of the named variable, for example:
9676 The second form can be used to separate the name from subsequent alphanumeric
9677 characters. This form (using braces) is available only for variables; it does
9678 &'not'& apply to message headers. The names of the variables are given in
9679 section &<<SECTexpvar>>& below. If the name of a non-existent variable is
9680 given, the expansion fails.
9682 .vitem &*${*&<&'op'&>&*:*&<&'string'&>&*}*&
9683 .cindex "expansion" "operators"
9684 The string is first itself expanded, and then the operation specified by
9685 <&'op'&> is applied to it. For example:
9689 The string starts with the first character after the colon, which may be
9690 leading white space. A list of operators is given in section &<<SECTexpop>>&
9691 below. The operator notation is used for simple expansion items that have just
9692 one argument, because it reduces the number of braces and therefore makes the
9693 string easier to understand.
9695 .vitem &*$bheader_*&<&'header&~name'&>&*:*&&~or&~&*$bh_*&<&'header&~name'&>&*:*&
9696 This item inserts &"basic"& header lines. It is described with the &%header%&
9697 expansion item below.
9700 .vitem "&*${acl{*&<&'name'&>&*}{*&<&'arg'&>&*}...}*&"
9701 .cindex "expansion" "calling an acl"
9702 .cindex "&%acl%&" "call from expansion"
9703 The name and zero to nine argument strings are first expanded separately. The expanded
9704 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
9705 Any unused are made empty. The variable &$acl_narg$& is set to the number of
9706 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
9707 and may use the variables; if another acl expansion is used the values
9708 are restored after it returns. If the ACL sets
9709 a value using a "message =" modifier and returns accept or deny, the value becomes
9710 the result of the expansion.
9711 If no message is set and the ACL returns accept or deny
9712 the expansion result is an empty string.
9713 If the ACL returns defer the result is a forced-fail. Otherwise the expansion fails.
9716 .vitem "&*${authresults{*&<&'authserv-id'&>&*}}*&"
9717 .cindex authentication "results header"
9718 .chindex Authentication-Results:
9719 .cindex authentication "expansion item"
9720 This item returns a string suitable for insertion as an
9721 &'Authentication-Results:'&
9723 The given <&'authserv-id'&> is included in the result; typically this
9724 will be a domain name identifying the system performing the authentications.
9725 Methods that might be present in the result include:
9734 Example use (as an ACL modifier):
9736 add_header = :at_start:${authresults {$primary_hostname}}
9738 This is safe even if no authentication results are available.
9741 .vitem "&*${certextract{*&<&'field'&>&*}{*&<&'certificate'&>&*}&&&
9742 {*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9743 .cindex "expansion" "extracting certificate fields"
9744 .cindex "&%certextract%&" "certificate fields"
9745 .cindex "certificate" "extracting fields"
9746 The <&'certificate'&> must be a variable of type certificate.
9747 The field name is expanded and used to retrieve the relevant field from
9748 the certificate. Supported fields are:
9752 &`subject `& RFC4514 DN
9753 &`issuer `& RFC4514 DN
9758 &`subj_altname `& tagged list
9762 If the field is found,
9763 <&'string2'&> is expanded, and replaces the whole item;
9764 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
9765 variable &$value$& contains the value that has been extracted. Afterwards, it
9766 is restored to any previous value it might have had.
9768 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
9769 key is not found. If {<&'string2'&>} is also omitted, the value that was
9772 Some field names take optional modifiers, appended and separated by commas.
9774 The field selectors marked as "RFC4514" above
9775 output a Distinguished Name string which is
9777 parseable by Exim as a comma-separated tagged list
9778 (the exceptions being elements containing commas).
9779 RDN elements of a single type may be selected by
9780 a modifier of the type label; if so the expansion
9781 result is a list (newline-separated by default).
9782 The separator may be changed by another modifier of
9783 a right angle-bracket followed immediately by the new separator.
9784 Recognised RDN type labels include "CN", "O", "OU" and "DC".
9786 The field selectors marked as "time" above
9787 take an optional modifier of "int"
9788 for which the result is the number of seconds since epoch.
9789 Otherwise the result is a human-readable string
9790 in the timezone selected by the main "timezone" option.
9792 The field selectors marked as "list" above return a list,
9793 newline-separated by default,
9794 (embedded separator characters in elements are doubled).
9795 The separator may be changed by a modifier of
9796 a right angle-bracket followed immediately by the new separator.
9798 The field selectors marked as "tagged" above
9799 prefix each list element with a type string and an equals sign.
9800 Elements of only one type may be selected by a modifier
9801 which is one of "dns", "uri" or "mail";
9802 if so the element tags are omitted.
9804 If not otherwise noted field values are presented in human-readable form.
9806 .vitem "&*${dlfunc{*&<&'file'&>&*}{*&<&'function'&>&*}{*&<&'arg'&>&*}&&&
9807 {*&<&'arg'&>&*}...}*&"
9809 This expansion dynamically loads and then calls a locally-written C function.
9810 This functionality is available only if Exim is compiled with
9814 set in &_Local/Makefile_&. Once loaded, Exim remembers the dynamically loaded
9815 object so that it doesn't reload the same object file in the same Exim process
9816 (but of course Exim does start new processes frequently).
9818 There may be from zero to eight arguments to the function.
9821 a local function that is to be called in this way,
9822 first &_DLFUNC_IMPL_& should be defined,
9823 and second &_local_scan.h_& should be included.
9824 The Exim variables and functions that are defined by that API
9825 are also available for dynamically loaded functions. The function itself
9826 must have the following type:
9828 int dlfunction(uschar **yield, int argc, uschar *argv[])
9830 Where &`uschar`& is a typedef for &`unsigned char`& in &_local_scan.h_&. The
9831 function should return one of the following values:
9833 &`OK`&: Success. The string that is placed in the variable &'yield'& is put
9834 into the expanded string that is being built.
9836 &`FAIL`&: A non-forced expansion failure occurs, with the error message taken
9837 from &'yield'&, if it is set.
9839 &`FAIL_FORCED`&: A forced expansion failure occurs, with the error message
9840 taken from &'yield'& if it is set.
9842 &`ERROR`&: Same as &`FAIL`&, except that a panic log entry is written.
9844 When compiling a function that is to be used in this way with gcc,
9845 you need to add &%-shared%& to the gcc command. Also, in the Exim build-time
9846 configuration, you must add &%-export-dynamic%& to EXTRALIBS.
9849 .vitem "&*${env{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&"
9850 .cindex "expansion" "extracting value from environment"
9851 .cindex "environment" "values from"
9852 The key is first expanded separately, and leading and trailing white space
9854 This is then searched for as a name in the environment.
9855 If a variable is found then its value is placed in &$value$&
9856 and <&'string1'&> is expanded, otherwise <&'string2'&> is expanded.
9858 Instead of {<&'string2'&>} the word &"fail"& (not in curly brackets) can
9859 appear, for example:
9861 ${env{USER}{$value} fail }
9863 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9864 {<&'string1'&>} must be present for &"fail"& to be recognized.
9866 If {<&'string2'&>} is omitted an empty string is substituted on
9868 If {<&'string1'&>} is omitted the search result is substituted on
9871 The environment is adjusted by the &%keep_environment%& and
9872 &%add_environment%& main section options.
9875 .vitem "&*${extract{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9876 {*&<&'string3'&>&*}}*&"
9877 .cindex "expansion" "extracting substrings by key"
9878 .cindex "&%extract%&" "substrings by key"
9879 The key and <&'string1'&> are first expanded separately. Leading and trailing
9880 white space is removed from the key (but not from any of the strings). The key
9881 must not be empty and must not consist entirely of digits.
9882 The expanded <&'string1'&> must be of the form:
9884 <&'key1'&> = <&'value1'&> <&'key2'&> = <&'value2'&> ...
9887 where the equals signs and spaces (but not both) are optional. If any of the
9888 values contain white space, they must be enclosed in double quotes, and any
9889 values that are enclosed in double quotes are subject to escape processing as
9890 described in section &<<SECTstrings>>&. The expanded <&'string1'&> is searched
9891 for the value that corresponds to the key. The search is case-insensitive. If
9892 the key is found, <&'string2'&> is expanded, and replaces the whole item;
9893 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
9894 variable &$value$& contains the value that has been extracted. Afterwards, it
9895 is restored to any previous value it might have had.
9897 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
9898 key is not found. If {<&'string2'&>} is also omitted, the value that was
9899 extracted is used. Thus, for example, these two expansions are identical, and
9902 ${extract{gid}{uid=1984 gid=2001}}
9903 ${extract{gid}{uid=1984 gid=2001}{$value}}
9905 Instead of {<&'string3'&>} the word &"fail"& (not in curly brackets) can
9906 appear, for example:
9908 ${extract{Z}{A=... B=...}{$value} fail }
9910 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9911 {<&'string2'&>} must be present for &"fail"& to be recognized.
9913 .vitem "&*${extract json{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9914 {*&<&'string3'&>&*}}*&" &&&
9915 "&*${extract jsons{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9916 {*&<&'string3'&>&*}}*&"
9917 .cindex "expansion" "extracting from JSON object"
9918 .cindex JSON expansions
9919 The key and <&'string1'&> are first expanded separately. Leading and trailing
9920 white space is removed from the key (but not from any of the strings). The key
9921 must not be empty and must not consist entirely of digits.
9922 The expanded <&'string1'&> must be of the form:
9924 { <&'"key1"'&> : <&'value1'&> , <&'"key2"'&> , <&'value2'&> ... }
9927 The braces, commas and colons, and the quoting of the member name are required;
9928 the spaces are optional.
9929 Matching of the key against the member names is done case-sensitively.
9930 For the &"json"& variant,
9931 if a returned value is a JSON string, it retains its leading and
9933 For the &"jsons"& variant, which is intended for use with JSON strings, the
9934 leading and trailing quotes are removed from the returned value.
9935 . XXX should be a UTF-8 compare
9937 The results of matching are handled as above.
9940 .vitem "&*${extract{*&<&'number'&>&*}{*&<&'separators'&>&*}&&&
9941 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9942 .cindex "expansion" "extracting substrings by number"
9943 .cindex "&%extract%&" "substrings by number"
9944 The <&'number'&> argument must consist entirely of decimal digits,
9945 apart from leading and trailing white space, which is ignored.
9946 This is what distinguishes this form of &%extract%& from the previous kind. It
9947 behaves in the same way, except that, instead of extracting a named field, it
9948 extracts from <&'string1'&> the field whose number is given as the first
9949 argument. You can use &$value$& in <&'string2'&> or &`fail`& instead of
9950 <&'string3'&> as before.
9952 The fields in the string are separated by any one of the characters in the
9953 separator string. These may include space or tab characters.
9954 The first field is numbered one. If the number is negative, the fields are
9955 counted from the end of the string, with the rightmost one numbered -1. If the
9956 number given is zero, the entire string is returned. If the modulus of the
9957 number is greater than the number of fields in the string, the result is the
9958 expansion of <&'string3'&>, or the empty string if <&'string3'&> is not
9959 provided. For example:
9961 ${extract{2}{:}{x:42:99:& Mailer::/bin/bash}}
9965 ${extract{-4}{:}{x:42:99:& Mailer::/bin/bash}}
9967 yields &"99"&. Two successive separators mean that the field between them is
9968 empty (for example, the fifth field above).
9971 .vitem "&*${extract json {*&<&'number'&>&*}}&&&
9972 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&" &&&
9973 "&*${extract jsons{*&<&'number'&>&*}}&&&
9974 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9975 .cindex "expansion" "extracting from JSON array"
9976 .cindex JSON expansions
9977 The <&'number'&> argument must consist entirely of decimal digits,
9978 apart from leading and trailing white space, which is ignored.
9980 Field selection and result handling is as above;
9981 there is no choice of field separator.
9982 For the &"json"& variant,
9983 if a returned value is a JSON string, it retains its leading and
9985 For the &"jsons"& variant, which is intended for use with JSON strings, the
9986 leading and trailing quotes are removed from the returned value.
9989 .vitem &*${filter{*&<&'string'&>&*}{*&<&'condition'&>&*}}*&
9990 .cindex "list" "selecting by condition"
9991 .cindex "expansion" "selecting from list by condition"
9993 After expansion, <&'string'&> is interpreted as a list, colon-separated by
9994 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
9996 in this list, its value is place in &$item$&, and then the condition is
9997 evaluated. If the condition is true, &$item$& is added to the output as an
9998 item in a new list; if the condition is false, the item is discarded. The
9999 separator used for the output list is the same as the one used for the
10000 input, but a separator setting is not included in the output. For example:
10002 ${filter{a:b:c}{!eq{$item}{b}}}
10004 yields &`a:c`&. At the end of the expansion, the value of &$item$& is restored
10005 to what it was before. See also the &%map%& and &%reduce%& expansion items.
10008 .vitem &*${hash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10009 .cindex "hash function" "textual"
10010 .cindex "expansion" "textual hash"
10011 This is a textual hashing function, and was the first to be implemented in
10012 early versions of Exim. In current releases, there are other hashing functions
10013 (numeric, MD5, and SHA-1), which are described below.
10015 The first two strings, after expansion, must be numbers. Call them <&'m'&> and
10016 <&'n'&>. If you are using fixed values for these numbers, that is, if
10017 <&'string1'&> and <&'string2'&> do not change when they are expanded, you can
10018 use the simpler operator notation that avoids some of the braces:
10020 ${hash_<n>_<m>:<string>}
10022 The second number is optional (in both notations). If <&'n'&> is greater than
10023 or equal to the length of the string, the expansion item returns the string.
10024 Otherwise it computes a new string of length <&'n'&> by applying a hashing
10025 function to the string. The new string consists of characters taken from the
10026 first <&'m'&> characters of the string
10028 abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQWRSTUVWXYZ0123456789
10030 If <&'m'&> is not present the value 26 is used, so that only lower case
10031 letters appear. For example:
10033 &`$hash{3}{monty}} `& yields &`jmg`&
10034 &`$hash{5}{monty}} `& yields &`monty`&
10035 &`$hash{4}{62}{monty python}}`& yields &`fbWx`&
10038 .vitem "&*$header_*&<&'header&~name'&>&*:*&&~or&~&&&
10039 &*$h_*&<&'header&~name'&>&*:*&" &&&
10040 "&*$bheader_*&<&'header&~name'&>&*:*&&~or&~&&&
10041 &*$bh_*&<&'header&~name'&>&*:*&" &&&
10042 "&*$lheader_*&<&'header&~name'&>&*:*&&~or&~&&&
10043 &*$lh_*&<&'header&~name'&>&*:*&" &&&
10044 "&*$rheader_*&<&'header&~name'&>&*:*&&~or&~&&&
10045 &*$rh_*&<&'header&~name'&>&*:*&"
10046 .cindex "expansion" "header insertion"
10047 .vindex "&$header_$&"
10048 .vindex "&$bheader_$&"
10049 .vindex "&$lheader_$&"
10050 .vindex "&$rheader_$&"
10051 .cindex "header lines" "in expansion strings"
10052 .cindex "header lines" "character sets"
10053 .cindex "header lines" "decoding"
10054 Substitute the contents of the named message header line, for example
10058 The newline that terminates a header line is not included in the expansion, but
10059 internal newlines (caused by splitting the header line over several physical
10060 lines) may be present.
10062 The difference between the four pairs of expansions is in the way
10063 the data in the header line is interpreted.
10066 .cindex "white space" "in header lines"
10067 &%rheader%& gives the original &"raw"& content of the header line, with no
10068 processing at all, and without the removal of leading and trailing white space.
10071 .cindex "list" "of header lines"
10072 &%lheader%& gives a colon-separated list, one element per header when there
10073 are multiple headers with a given name.
10074 Any embedded colon characters within an element are doubled, so normal Exim
10075 list-processing facilities can be used.
10076 The terminating newline of each element is removed; in other respects
10077 the content is &"raw"&.
10080 .cindex "base64 encoding" "in header lines"
10081 &%bheader%& removes leading and trailing white space, and then decodes base64
10082 or quoted-printable MIME &"words"& within the header text, but does no
10083 character set translation. If decoding of what looks superficially like a MIME
10084 &"word"& fails, the raw string is returned. If decoding
10085 .cindex "binary zero" "in header line"
10086 produces a binary zero character, it is replaced by a question mark &-- this is
10087 what Exim does for binary zeros that are actually received in header lines.
10090 &%header%& tries to translate the string as decoded by &%bheader%& to a
10091 standard character set. This is an attempt to produce the same string as would
10092 be displayed on a user's MUA. If translation fails, the &%bheader%& string is
10093 returned. Translation is attempted only on operating systems that support the
10094 &[iconv()]& function. This is indicated by the compile-time macro HAVE_ICONV in
10095 a system Makefile or in &_Local/Makefile_&.
10098 In a filter file, the target character set for &%header%& can be specified by a
10099 command of the following form:
10101 headers charset "UTF-8"
10103 This command affects all references to &$h_$& (or &$header_$&) expansions in
10104 subsequently obeyed filter commands. In the absence of this command, the target
10105 character set in a filter is taken from the setting of the &%headers_charset%&
10106 option in the runtime configuration. The value of this option defaults to the
10107 value of HEADERS_CHARSET in &_Local/Makefile_&. The ultimate default is
10110 Header names follow the syntax of RFC 2822, which states that they may contain
10111 any printing characters except space and colon. Consequently, curly brackets
10112 &'do not'& terminate header names, and should not be used to enclose them as
10113 if they were variables. Attempting to do so causes a syntax error.
10115 Only header lines that are common to all copies of a message are visible to
10116 this mechanism. These are the original header lines that are received with the
10117 message, and any that are added by an ACL statement or by a system
10118 filter. Header lines that are added to a particular copy of a message by a
10119 router or transport are not accessible.
10121 For incoming SMTP messages, no header lines are visible in
10122 ACLs that are obeyed before the data phase completes,
10123 because the header structure is not set up until the message is received.
10124 They are visible in DKIM, PRDR and DATA ACLs.
10125 Header lines that are added in a RCPT ACL (for example)
10126 are saved until the message's incoming header lines are available, at which
10127 point they are added.
10128 When any of the above ACLs are
10129 running, however, header lines added by earlier ACLs are visible.
10131 Upper case and lower case letters are synonymous in header names. If the
10132 following character is white space, the terminating colon may be omitted, but
10133 this is not recommended, because you may then forget it when it is needed. When
10134 white space terminates the header name, this white space is included in the
10135 expanded string. If the message does not contain the given header, the
10136 expansion item is replaced by an empty string. (See the &%def%& condition in
10137 section &<<SECTexpcond>>& for a means of testing for the existence of a
10140 If there is more than one header with the same name, they are all concatenated
10141 to form the substitution string, up to a maximum length of 64K. Unless
10142 &%rheader%& is being used, leading and trailing white space is removed from
10143 each header before concatenation, and a completely empty header is ignored. A
10144 newline character is then inserted between non-empty headers, but there is no
10145 newline at the very end. For the &%header%& and &%bheader%& expansion, for
10146 those headers that contain lists of addresses, a comma is also inserted at the
10147 junctions between headers. This does not happen for the &%rheader%& expansion.
10149 .cindex "tainted data" "message headers"
10150 When the headers are from an incoming message,
10151 the result of expanding any of these variables is tainted.
10154 .vitem &*${hmac{*&<&'hashname'&>&*}{*&<&'secret'&>&*}{*&<&'string'&>&*}}*&
10155 .cindex "expansion" "hmac hashing"
10157 This function uses cryptographic hashing (either MD5 or SHA-1) to convert a
10158 shared secret and some text into a message authentication code, as specified in
10159 RFC 2104. This differs from &`${md5:secret_text...}`& or
10160 &`${sha1:secret_text...}`& in that the hmac step adds a signature to the
10161 cryptographic hash, allowing for authentication that is not possible with MD5
10162 or SHA-1 alone. The hash name must expand to either &`md5`& or &`sha1`& at
10163 present. For example:
10165 ${hmac{md5}{somesecret}{$primary_hostname $tod_log}}
10167 For the hostname &'mail.example.com'& and time 2002-10-17 11:30:59, this
10170 dd97e3ba5d1a61b5006108f8c8252953
10172 As an example of how this might be used, you might put in the main part of
10173 an Exim configuration:
10175 SPAMSCAN_SECRET=cohgheeLei2thahw
10177 In a router or a transport you could then have:
10180 X-Spam-Scanned: ${primary_hostname} ${message_exim_id} \
10181 ${hmac{md5}{SPAMSCAN_SECRET}\
10182 {${primary_hostname},${message_exim_id},$h_message-id:}}
10184 Then given a message, you can check where it was scanned by looking at the
10185 &'X-Spam-Scanned:'& header line. If you know the secret, you can check that
10186 this header line is authentic by recomputing the authentication code from the
10187 host name, message ID and the &'Message-id:'& header line. This can be done
10188 using Exim's &%-be%& option, or by other means, for example, by using the
10189 &'hmac_md5_hex()'& function in Perl.
10192 .vitem &*${if&~*&<&'condition'&>&*&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
10193 .cindex "expansion" "conditional"
10194 .cindex "&%if%&, expansion item"
10195 If <&'condition'&> is true, <&'string1'&> is expanded and replaces the whole
10196 item; otherwise <&'string2'&> is used. The available conditions are described
10197 in section &<<SECTexpcond>>& below. For example:
10199 ${if eq {$local_part}{postmaster} {yes}{no} }
10201 The second string need not be present; if it is not and the condition is not
10202 true, the item is replaced with nothing. Alternatively, the word &"fail"& may
10203 be present instead of the second string (without any curly brackets). In this
10204 case, the expansion is forced to fail if the condition is not true (see section
10205 &<<SECTforexpfai>>&).
10207 If both strings are omitted, the result is the string &`true`& if the condition
10208 is true, and the empty string if the condition is false. This makes it less
10209 cumbersome to write custom ACL and router conditions. For example, instead of
10211 condition = ${if >{$acl_m4}{3}{true}{false}}
10215 condition = ${if >{$acl_m4}{3}}
10220 .vitem &*${imapfolder{*&<&'foldername'&>&*}}*&
10221 .cindex expansion "imap folder"
10222 .cindex "&%imapfolder%& expansion item"
10223 This item converts a (possibly multilevel, or with non-ASCII characters)
10224 folder specification to a Maildir name for filesystem use.
10225 For information on internationalisation support see &<<SECTi18nMDA>>&.
10229 .vitem &*${length{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
10230 .cindex "expansion" "string truncation"
10231 .cindex "&%length%& expansion item"
10232 The &%length%& item is used to extract the initial portion of a string. Both
10233 strings are expanded, and the first one must yield a number, <&'n'&>, say. If
10234 you are using a fixed value for the number, that is, if <&'string1'&> does not
10235 change when expanded, you can use the simpler operator notation that avoids
10236 some of the braces:
10238 ${length_<n>:<string>}
10240 The result of this item is either the first <&'n'&> bytes or the whole
10241 of <&'string2'&>, whichever is the shorter. Do not confuse &%length%& with
10242 &%strlen%&, which gives the length of a string.
10243 All measurement is done in bytes and is not UTF-8 aware.
10246 .vitem "&*${listextract{*&<&'number'&>&*}&&&
10247 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
10248 .cindex "expansion" "extracting list elements by number"
10249 .cindex "&%listextract%&" "extract list elements by number"
10250 .cindex "list" "extracting elements by number"
10251 The <&'number'&> argument must consist entirely of decimal digits,
10252 apart from an optional leading minus,
10253 and leading and trailing white space (which is ignored).
10255 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
10256 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10258 The first field of the list is numbered one.
10259 If the number is negative, the fields are
10260 counted from the end of the list, with the rightmost one numbered -1.
10261 The numbered element of the list is extracted and placed in &$value$&,
10262 then <&'string2'&> is expanded as the result.
10264 If the modulus of the
10265 number is zero or greater than the number of fields in the string,
10266 the result is the expansion of <&'string3'&>.
10270 ${listextract{2}{x:42:99}}
10274 ${listextract{-3}{<, x,42,99,& Mailer,,/bin/bash}{result: $value}}
10276 yields &"result: 42"&.
10278 If {<&'string3'&>} is omitted, an empty string is used for string3.
10279 If {<&'string2'&>} is also omitted, the value that was
10281 You can use &`fail`& instead of {<&'string3'&>} as in a string extract.
10284 .vitem &*${listquote{*&<&'separator'&>&*}{*&<&'string'&>&*}}*&
10285 .cindex quoting "for list"
10286 .cindex list quoting
10287 This item doubles any occurrence of the separator character
10288 in the given string.
10289 An empty string is replaced with a single space.
10290 This converts the string into a safe form for use as a list element,
10291 in a list using the given separator.
10294 .vitem "&*${lookup&~{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&&
10295 {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&" &&&
10296 "&*${lookup&~*&<&'search&~type'&>&*&~{*&<&'query'&>&*}&~&&&
10297 {*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
10298 .cindex "expansion" "lookup in"
10299 .cindex "file" "lookups"
10300 .cindex "lookup" "in expanded string"
10301 The two forms of lookup item specify data lookups in files and databases, as
10302 discussed in chapter &<<CHAPfdlookup>>&. The first form is used for single-key
10303 lookups, and the second is used for query-style lookups. The <&'key'&>,
10304 <&'file'&>, and <&'query'&> strings are expanded before use.
10306 If there is any white space in a lookup item which is part of a filter command,
10307 a retry or rewrite rule, a routing rule for the &(manualroute)& router, or any
10308 other place where white space is significant, the lookup item must be enclosed
10309 in double quotes. The use of data lookups in users' filter files may be locked
10310 out by the system administrator.
10312 .vindex "&$value$&"
10313 If the lookup succeeds, <&'string1'&> is expanded and replaces the entire item.
10314 During its expansion, the variable &$value$& contains the data returned by the
10315 lookup. Afterwards it reverts to the value it had previously (at the outer
10316 level it is empty). If the lookup fails, <&'string2'&> is expanded and replaces
10317 the entire item. If {<&'string2'&>} is omitted, the replacement is the empty
10318 string on failure. If <&'string2'&> is provided, it can itself be a nested
10319 lookup, thus providing a mechanism for looking up a default value when the
10320 original lookup fails.
10322 If a nested lookup is used as part of <&'string1'&>, &$value$& contains the
10323 data for the outer lookup while the parameters of the second lookup are
10324 expanded, and also while <&'string2'&> of the second lookup is expanded, should
10325 the second lookup fail. Instead of {<&'string2'&>} the word &"fail"& can
10326 appear, and in this case, if the lookup fails, the entire expansion is forced
10327 to fail (see section &<<SECTforexpfai>>&). If both {<&'string1'&>} and
10328 {<&'string2'&>} are omitted, the result is the looked up value in the case of a
10329 successful lookup, and nothing in the case of failure.
10331 For single-key lookups, the string &"partial"& is permitted to precede the
10332 search type in order to do partial matching, and * or *@ may follow a search
10333 type to request default lookups if the key does not match (see sections
10334 &<<SECTdefaultvaluelookups>>& and &<<SECTpartiallookup>>& for details).
10336 .cindex "numerical variables (&$1$& &$2$& etc)" "in lookup expansion"
10337 If a partial search is used, the variables &$1$& and &$2$& contain the wild
10338 and non-wild parts of the key during the expansion of the replacement text.
10339 They return to their previous values at the end of the lookup item.
10341 This example looks up the postmaster alias in the conventional alias file:
10343 ${lookup {postmaster} lsearch {/etc/aliases} {$value}}
10345 This example uses NIS+ to look up the full name of the user corresponding to
10346 the local part of an address, forcing the expansion to fail if it is not found:
10348 ${lookup nisplus {[name=$local_part],passwd.org_dir:gcos} \
10353 .vitem &*${map{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
10354 .cindex "expansion" "list creation"
10356 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
10357 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10359 in this list, its value is place in &$item$&, and then <&'string2'&> is
10360 expanded and added to the output as an item in a new list. The separator used
10361 for the output list is the same as the one used for the input, but a separator
10362 setting is not included in the output. For example:
10364 ${map{a:b:c}{[$item]}} ${map{<- x-y-z}{($item)}}
10366 expands to &`[a]:[b]:[c] (x)-(y)-(z)`&. At the end of the expansion, the
10367 value of &$item$& is restored to what it was before. See also the &%filter%&
10368 and &%reduce%& expansion items.
10370 .vitem &*${nhash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10371 .cindex "expansion" "numeric hash"
10372 .cindex "hash function" "numeric"
10373 The three strings are expanded; the first two must yield numbers. Call them
10374 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
10375 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
10376 can use the simpler operator notation that avoids some of the braces:
10378 ${nhash_<n>_<m>:<string>}
10380 The second number is optional (in both notations). If there is only one number,
10381 the result is a number in the range 0&--<&'n'&>-1. Otherwise, the string is
10382 processed by a div/mod hash function that returns two numbers, separated by a
10383 slash, in the ranges 0 to <&'n'&>-1 and 0 to <&'m'&>-1, respectively. For
10386 ${nhash{8}{64}{supercalifragilisticexpialidocious}}
10388 returns the string &"6/33"&.
10392 .vitem &*${perl{*&<&'subroutine'&>&*}{*&<&'arg'&>&*}{*&<&'arg'&>&*}...}*&
10393 .cindex "Perl" "use in expanded string"
10394 .cindex "expansion" "calling Perl from"
10395 This item is available only if Exim has been built to include an embedded Perl
10396 interpreter. The subroutine name and the arguments are first separately
10397 expanded, and then the Perl subroutine is called with those arguments. No
10398 additional arguments need be given; the maximum number permitted, including the
10399 name of the subroutine, is nine.
10401 The return value of the subroutine is inserted into the expanded string, unless
10402 the return value is &%undef%&. In that case, the entire expansion is
10403 forced to fail, in the same way as an explicit &"fail"& on a lookup item
10404 does (see section &<<SECTforexpfai>>&). Whatever you return is evaluated
10405 in a scalar context, thus the return value is a scalar. For example, if you
10406 return a Perl vector, the return value is the size of the vector,
10409 If the subroutine exits by calling Perl's &%die%& function, the expansion fails
10410 with the error message that was passed to &%die%&. More details of the embedded
10411 Perl facility are given in chapter &<<CHAPperl>>&.
10413 The &(redirect)& router has an option called &%forbid_filter_perl%& which locks
10414 out the use of this expansion item in filter files.
10417 .vitem &*${prvs{*&<&'address'&>&*}{*&<&'secret'&>&*}{*&<&'keynumber'&>&*}}*&
10418 .cindex "&%prvs%& expansion item"
10419 The first argument is a complete email address and the second is secret
10420 keystring. The third argument, specifying a key number, is optional. If absent,
10421 it defaults to 0. The result of the expansion is a prvs-signed email address,
10422 to be typically used with the &%return_path%& option on an &(smtp)& transport
10423 as part of a bounce address tag validation (BATV) scheme. For more discussion
10424 and an example, see section &<<SECTverifyPRVS>>&.
10426 .vitem "&*${prvscheck{*&<&'address'&>&*}{*&<&'secret'&>&*}&&&
10427 {*&<&'string'&>&*}}*&"
10428 .cindex "&%prvscheck%& expansion item"
10429 This expansion item is the complement of the &%prvs%& item. It is used for
10430 checking prvs-signed addresses. If the expansion of the first argument does not
10431 yield a syntactically valid prvs-signed address, the whole item expands to the
10432 empty string. When the first argument does expand to a syntactically valid
10433 prvs-signed address, the second argument is expanded, with the prvs-decoded
10434 version of the address and the key number extracted from the address in the
10435 variables &$prvscheck_address$& and &$prvscheck_keynum$&, respectively.
10437 These two variables can be used in the expansion of the second argument to
10438 retrieve the secret. The validity of the prvs-signed address is then checked
10439 against the secret. The result is stored in the variable &$prvscheck_result$&,
10440 which is empty for failure or &"1"& for success.
10442 The third argument is optional; if it is missing, it defaults to an empty
10443 string. This argument is now expanded. If the result is an empty string, the
10444 result of the expansion is the decoded version of the address. This is the case
10445 whether or not the signature was valid. Otherwise, the result of the expansion
10446 is the expansion of the third argument.
10448 All three variables can be used in the expansion of the third argument.
10449 However, once the expansion is complete, only &$prvscheck_result$& remains set.
10450 For more discussion and an example, see section &<<SECTverifyPRVS>>&.
10452 .vitem &*${readfile{*&<&'file&~name'&>&*}{*&<&'eol&~string'&>&*}}*&
10453 .cindex "expansion" "inserting an entire file"
10454 .cindex "file" "inserting into expansion"
10455 .cindex "&%readfile%& expansion item"
10456 The filename and end-of-line (eol) string are first expanded separately. The file is
10457 then read, and its contents replace the entire item. All newline characters in
10458 the file are replaced by the end-of-line string if it is present. Otherwise,
10459 newlines are left in the string.
10460 String expansion is not applied to the contents of the file. If you want this,
10461 you must wrap the item in an &%expand%& operator. If the file cannot be read,
10462 the string expansion fails.
10464 The &(redirect)& router has an option called &%forbid_filter_readfile%& which
10465 locks out the use of this expansion item in filter files.
10469 .vitem "&*${readsocket{*&<&'name'&>&*}{*&<&'request'&>&*}&&&
10470 {*&<&'options'&>&*}{*&<&'eol&~string'&>&*}{*&<&'fail&~string'&>&*}}*&"
10471 .cindex "expansion" "inserting from a socket"
10472 .cindex "socket, use of in expansion"
10473 .cindex "&%readsocket%& expansion item"
10474 This item inserts data from a Unix domain or TCP socket into the expanded
10475 string. The minimal way of using it uses just two arguments, as in these
10478 ${readsocket{/socket/name}{request string}}
10479 ${readsocket{inet:some.host:1234}{request string}}
10481 For a Unix domain socket, the first substring must be the path to the socket.
10482 For an Internet socket, the first substring must contain &`inet:`& followed by
10483 a host name or IP address, followed by a colon and a port, which can be a
10484 number or the name of a TCP port in &_/etc/services_&. An IP address may
10485 optionally be enclosed in square brackets. This is best for IPv6 addresses. For
10488 ${readsocket{inet:[::1]:1234}{request string}}
10490 Only a single host name may be given, but if looking it up yields more than
10491 one IP address, they are each tried in turn until a connection is made. For
10492 both kinds of socket, Exim makes a connection, writes the request string
10493 (unless it is an empty string; no terminating NUL is ever sent)
10494 and reads from the socket until an end-of-file
10495 is read. A timeout of 5 seconds is applied. Additional, optional arguments
10496 extend what can be done. Firstly, you can vary the timeout. For example:
10498 ${readsocket{/socket/name}{request string}{3s}}
10501 The third argument is a list of options, of which the first element is the timeout
10502 and must be present if any options are given.
10503 Further elements are options of form &'name=value'&.
10506 ${readsocket{/socket/name}{request string}{3s:shutdown=no}}
10509 The following option names are recognised:
10512 Defines if the result data can be cached for use by a later identical
10513 request in the same process.
10514 Values are &"yes"& or &"no"& (the default).
10515 If not, all cached results for this connection specification
10516 will be invalidated.
10520 Defines whether or not a write-shutdown is done on the connection after
10521 sending the request. Values are &"yes"& (the default) or &"no"&
10522 (preferred, eg. by some webservers).
10526 Controls the use of TLS on the connection.
10527 Values are &"yes"& or &"no"& (the default).
10528 If it is enabled, a shutdown as described above is never done.
10532 A fourth argument allows you to change any newlines that are in the data
10533 that is read, in the same way as for &%readfile%& (see above). This example
10534 turns them into spaces:
10536 ${readsocket{inet:127.0.0.1:3294}{request string}{3s}{ }}
10538 As with all expansions, the substrings are expanded before the processing
10539 happens. Errors in these sub-expansions cause the expansion to fail. In
10540 addition, the following errors can occur:
10543 Failure to create a socket file descriptor;
10545 Failure to connect the socket;
10547 Failure to write the request string;
10549 Timeout on reading from the socket.
10552 By default, any of these errors causes the expansion to fail. However, if
10553 you supply a fifth substring, it is expanded and used when any of the above
10554 errors occurs. For example:
10556 ${readsocket{/socket/name}{request string}{3s}{\n}\
10559 You can test for the existence of a Unix domain socket by wrapping this
10560 expansion in &`${if exists`&, but there is a race condition between that test
10561 and the actual opening of the socket, so it is safer to use the fifth argument
10562 if you want to be absolutely sure of avoiding an expansion error for a
10563 non-existent Unix domain socket, or a failure to connect to an Internet socket.
10565 The &(redirect)& router has an option called &%forbid_filter_readsocket%& which
10566 locks out the use of this expansion item in filter files.
10569 .vitem &*${reduce{*&<&'string1'&>}{<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10570 .cindex "expansion" "reducing a list to a scalar"
10571 .cindex "list" "reducing to a scalar"
10572 .vindex "&$value$&"
10574 This operation reduces a list to a single, scalar string. After expansion,
10575 <&'string1'&> is interpreted as a list, colon-separated by default, but the
10576 separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10577 Then <&'string2'&> is expanded and
10578 assigned to the &$value$& variable. After this, each item in the <&'string1'&>
10579 list is assigned to &$item$&, in turn, and <&'string3'&> is expanded for each of
10580 them. The result of that expansion is assigned to &$value$& before the next
10581 iteration. When the end of the list is reached, the final value of &$value$& is
10582 added to the expansion output. The &%reduce%& expansion item can be used in a
10583 number of ways. For example, to add up a list of numbers:
10585 ${reduce {<, 1,2,3}{0}{${eval:$value+$item}}}
10587 The result of that expansion would be &`6`&. The maximum of a list of numbers
10590 ${reduce {3:0:9:4:6}{0}{${if >{$item}{$value}{$item}{$value}}}}
10592 At the end of a &*reduce*& expansion, the values of &$item$& and &$value$& are
10593 restored to what they were before. See also the &%filter%& and &%map%&
10596 .vitem &*$rheader_*&<&'header&~name'&>&*:*&&~or&~&*$rh_*&<&'header&~name'&>&*:*&
10597 This item inserts &"raw"& header lines. It is described with the &%header%&
10598 expansion item in section &<<SECTexpansionitems>>& above.
10600 .vitem "&*${run <&'options'&> {*&<&'command&~arg&~list'&>&*}{*&<&'string1'&>&*}&&&
10601 {*&<&'string2'&>&*}}*&"
10602 .cindex "expansion" "running a command"
10603 .cindex "&%run%& expansion item"
10604 This item runs an external command, as a subprocess.
10605 One option is supported after the word &'run'&, comma-separated.
10607 If the option &'preexpand'& is not used,
10608 the command string is split into individual arguments by spaces
10609 and then each argument is expanded.
10610 Then the command is run
10611 in a separate process, but under the same uid and gid. As in other command
10612 executions from Exim, a shell is not used by default. If the command requires
10613 a shell, you must explicitly code it.
10614 The command name may not be tainted, but the remaining arguments can be.
10616 &*Note*&: if tainted arguments are used, they are supplied by a
10617 potential attacker;
10618 a careful assessment for security vulnerabilities should be done.
10620 If the option &'preexpand'& is used,
10621 the command and its arguments are first expanded as one string. The result is
10622 split apart into individual arguments by spaces, and then the command is run
10624 Since the arguments are split by spaces, when there is a variable expansion
10625 which has an empty result, it will cause the situation that the argument will
10626 simply be omitted when the program is actually executed by Exim. If the
10627 script/program requires a specific number of arguments and the expanded
10628 variable could possibly result in this empty expansion, the variable must be
10629 quoted. This is more difficult if the expanded variable itself could result
10630 in a string containing quotes, because it would interfere with the quotes
10631 around the command arguments. A possible guard against this is to wrap the
10632 variable in the &%sg%& operator to change any quote marks to some other
10634 Neither the command nor any argument may be tainted.
10636 The standard input for the command exists, but is empty. The standard output
10637 and standard error are set to the same file descriptor.
10638 .cindex "return code" "from &%run%& expansion"
10639 .vindex "&$value$&"
10640 If the command succeeds (gives a zero return code) <&'string1'&> is expanded
10641 and replaces the entire item; during this expansion, the standard output/error
10642 from the command is in the variable &$value$&. If the command fails,
10643 <&'string2'&>, if present, is expanded and used. Once again, during the
10644 expansion, the standard output/error from the command is in the variable
10647 If <&'string2'&> is absent, the result is empty. Alternatively, <&'string2'&>
10648 can be the word &"fail"& (not in braces) to force expansion failure if the
10649 command does not succeed. If both strings are omitted, the result is contents
10650 of the standard output/error on success, and nothing on failure.
10652 .vindex "&$run_in_acl$&"
10653 The standard output/error of the command is put in the variable &$value$&.
10654 In this ACL example, the output of a command is logged for the admin to
10657 warn condition = ${run{/usr/bin/id}{yes}{no}}
10658 log_message = Output of id: $value
10660 If the command requires shell idioms, such as the > redirect operator, the
10661 shell must be invoked directly, such as with:
10663 ${run{/bin/bash -c "/usr/bin/id >/tmp/id"}{yes}{yes}}
10666 .vindex "&$runrc$&"
10667 The return code from the command is put in the variable &$runrc$&, and this
10668 remains set afterwards, so in a filter file you can do things like this:
10670 if "${run{x y z}{}}$runrc" is 1 then ...
10671 elif $runrc is 2 then ...
10675 If execution of the command fails (for example, the command does not exist),
10676 the return code is 127 &-- the same code that shells use for non-existent
10679 &*Warning*&: In a router or transport, you cannot assume the order in which
10680 option values are expanded, except for those preconditions whose order of
10681 testing is documented. Therefore, you cannot reliably expect to set &$runrc$&
10682 by the expansion of one option, and use it in another.
10684 The &(redirect)& router has an option called &%forbid_filter_run%& which locks
10685 out the use of this expansion item in filter files.
10688 .vitem &*${sg{*&<&'subject'&>&*}{*&<&'regex'&>&*}{*&<&'replacement'&>&*}}*&
10689 .cindex "expansion" "string substitution"
10690 .cindex "&%sg%& expansion item"
10691 This item works like Perl's substitution operator (s) with the global (/g)
10692 option; hence its name. However, unlike the Perl equivalent, Exim does not
10693 modify the subject string; instead it returns the modified string for insertion
10694 into the overall expansion. The item takes three arguments: the subject string,
10695 a regular expression, and a substitution string. For example:
10697 ${sg{abcdefabcdef}{abc}{xyz}}
10699 yields &"xyzdefxyzdef"&. Because all three arguments are expanded before use,
10700 if any $, } or \ characters are required in the regular expression or in the
10701 substitution string, they have to be escaped. For example:
10703 ${sg{abcdef}{^(...)(...)\$}{\$2\$1}}
10705 yields &"defabc"&, and
10707 ${sg{1=A 4=D 3=C}{\N(\d+)=\N}{K\$1=}}
10709 yields &"K1=A K4=D K3=C"&. Note the use of &`\N`& to protect the contents of
10710 the regular expression from string expansion.
10712 The regular expression is compiled in 8-bit mode, working against bytes
10713 rather than any Unicode-aware character handling.
10716 .vitem &*${sort{*&<&'string'&>&*}{*&<&'comparator'&>&*}{*&<&'extractor'&>&*}}*&
10717 .cindex sorting "a list"
10718 .cindex list sorting
10719 .cindex expansion "list sorting"
10720 After expansion, <&'string'&> is interpreted as a list, colon-separated by
10721 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10722 The <&'comparator'&> argument is interpreted as the operator
10723 of a two-argument expansion condition.
10724 The numeric operators plus ge, gt, le, lt (and ~i variants) are supported.
10725 The comparison should return true when applied to two values
10726 if the first value should sort before the second value.
10727 The <&'extractor'&> expansion is applied repeatedly to elements of the list,
10728 the element being placed in &$item$&,
10729 to give values for comparison.
10731 The item result is a sorted list,
10732 with the original list separator,
10733 of the list elements (in full) of the original.
10737 ${sort{3:2:1:4}{<}{$item}}
10739 sorts a list of numbers, and
10741 ${sort {${lookup dnsdb{>:,,mx=example.com}}} {<} {${listextract{1}{<,$item}}}}
10743 will sort an MX lookup into priority order.
10747 .vitem &*${srs_encode&~{*&<&'secret'&>&*}{*&<&'return&~path'&>&*}{*&<&'original&~domain'&>&*}}*&
10748 SRS encoding. See SECT &<<SECTSRS>>& for details.
10752 .vitem &*${substr{*&<&'start'&>&*}{*&<&'len'&>&*}{*&<&'subject'&>&*}}*&
10753 .cindex "&%substr%& expansion item"
10754 .cindex "substring extraction"
10755 .cindex "expansion" "substring extraction"
10756 The three strings are expanded; the first two must yield numbers. Call them
10757 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
10758 if <&'start'&> and <&'len'&> do not change when they are expanded, you
10759 can use the simpler operator notation that avoids some of the braces:
10761 ${substr_<n>_<m>:<subject>}
10763 The second number is optional (in both notations).
10764 If it is absent in the simpler format, the preceding underscore must also be
10767 The &%substr%& item can be used to extract more general substrings than
10768 &%length%&. The first number, <&'n'&>, is a starting offset, and <&'m'&> is the
10769 length required. For example
10771 ${substr{3}{2}{$local_part}}
10773 If the starting offset is greater than the string length the result is the
10774 null string; if the length plus starting offset is greater than the string
10775 length, the result is the right-hand part of the string, starting from the
10776 given offset. The first byte (character) in the string has offset zero.
10778 The &%substr%& expansion item can take negative offset values to count
10779 from the right-hand end of its operand. The last byte (character) is offset -1,
10780 the second-last is offset -2, and so on. Thus, for example,
10782 ${substr{-5}{2}{1234567}}
10784 yields &"34"&. If the absolute value of a negative offset is greater than the
10785 length of the string, the substring starts at the beginning of the string, and
10786 the length is reduced by the amount of overshoot. Thus, for example,
10788 ${substr{-5}{2}{12}}
10790 yields an empty string, but
10792 ${substr{-3}{2}{12}}
10796 When the second number is omitted from &%substr%&, the remainder of the string
10797 is taken if the offset is positive. If it is negative, all bytes (characters) in the
10798 string preceding the offset point are taken. For example, an offset of -1 and
10799 no length, as in these semantically identical examples:
10802 ${substr{-1}{abcde}}
10804 yields all but the last character of the string, that is, &"abcd"&.
10806 All measurement is done in bytes and is not UTF-8 aware.
10810 .vitem "&*${tr{*&<&'subject'&>&*}{*&<&'characters'&>&*}&&&
10811 {*&<&'replacements'&>&*}}*&"
10812 .cindex "expansion" "character translation"
10813 .cindex "&%tr%& expansion item"
10814 This item does single-character (in bytes) translation on its subject string. The second
10815 argument is a list of characters to be translated in the subject string. Each
10816 matching character is replaced by the corresponding character from the
10817 replacement list. For example
10819 ${tr{abcdea}{ac}{13}}
10821 yields &`1b3de1`&. If there are duplicates in the second character string, the
10822 last occurrence is used. If the third string is shorter than the second, its
10823 last character is replicated. However, if it is empty, no translation takes
10826 All character handling is done in bytes and is not UTF-8 aware.
10832 .section "Expansion operators" "SECTexpop"
10833 .cindex "expansion" "operators"
10834 For expansion items that perform transformations on a single argument string,
10835 the &"operator"& notation is used because it is simpler and uses fewer braces.
10836 The substring is first expanded before the operation is applied to it. The
10837 following operations can be performed:
10840 .vitem &*${address:*&<&'string'&>&*}*&
10841 .cindex "expansion" "RFC 2822 address handling"
10842 .cindex "&%address%& expansion item"
10843 The string is interpreted as an RFC 2822 address, as it might appear in a
10844 header line, and the effective address is extracted from it. If the string does
10845 not parse successfully, the result is empty.
10847 The parsing correctly handles SMTPUTF8 Unicode in the string.
10850 .vitem &*${addresses:*&<&'string'&>&*}*&
10851 .cindex "expansion" "RFC 2822 address handling"
10852 .cindex "&%addresses%& expansion item"
10853 The string (after expansion) is interpreted as a list of addresses in RFC
10854 2822 format, such as can be found in a &'To:'& or &'Cc:'& header line. The
10855 operative address (&'local-part@domain'&) is extracted from each item, and the
10856 result of the expansion is a colon-separated list, with appropriate
10857 doubling of colons should any happen to be present in the email addresses.
10858 Syntactically invalid RFC2822 address items are omitted from the output.
10860 It is possible to specify a character other than colon for the output
10861 separator by starting the string with > followed by the new separator
10862 character. For example:
10864 ${addresses:>& Chief <ceo@up.stairs>, sec@base.ment (dogsbody)}
10866 expands to &`ceo@up.stairs&&sec@base.ment`&. The string is expanded
10867 first, so if the expanded string starts with >, it may change the output
10868 separator unintentionally. This can be avoided by setting the output
10869 separator explicitly:
10871 ${addresses:>:$h_from:}
10874 Compare the &%address%& (singular)
10875 expansion item, which extracts the working address from a single RFC2822
10876 address. See the &%filter%&, &%map%&, and &%reduce%& items for ways of
10879 To clarify "list of addresses in RFC 2822 format" mentioned above, Exim follows
10880 a strict interpretation of header line formatting. Exim parses the bare,
10881 unquoted portion of an email address and if it finds a comma, treats it as an
10882 email address separator. For the example header line:
10884 From: =?iso-8859-2?Q?Last=2C_First?= <user@example.com>
10886 The first example below demonstrates that Q-encoded email addresses are parsed
10887 properly if it is given the raw header (in this example, &`$rheader_from:`&).
10888 It does not see the comma because it's still encoded as "=2C". The second
10889 example below is passed the contents of &`$header_from:`&, meaning it gets
10890 de-mimed. Exim sees the decoded "," so it treats it as &*two*& email addresses.
10891 The third example shows that the presence of a comma is skipped when it is
10892 quoted. The fourth example shows SMTPUTF8 handling.
10894 # exim -be '${addresses:From: \
10895 =?iso-8859-2?Q?Last=2C_First?= <user@example.com>}'
10897 # exim -be '${addresses:From: Last, First <user@example.com>}'
10898 Last:user@example.com
10899 # exim -be '${addresses:From: "Last, First" <user@example.com>}'
10901 # exim -be '${addresses:フィル <フィリップ@example.jp>}'
10905 .vitem &*${base32:*&<&'digits'&>&*}*&
10906 .cindex "&%base32%& expansion item"
10907 .cindex "expansion" "conversion to base 32"
10908 The string must consist entirely of decimal digits. The number is converted to
10909 base 32 and output as a (empty, for zero) string of characters.
10910 Only lowercase letters are used.
10912 .vitem &*${base32d:*&<&'base-32&~digits'&>&*}*&
10913 .cindex "&%base32d%& expansion item"
10914 .cindex "expansion" "conversion to base 32"
10915 The string must consist entirely of base-32 digits.
10916 The number is converted to decimal and output as a string.
10918 .vitem &*${base62:*&<&'digits'&>&*}*&
10919 .cindex "&%base62%& expansion item"
10920 .cindex "expansion" "conversion to base 62"
10921 The string must consist entirely of decimal digits. The number is converted to
10922 base 62 and output as a string of six characters, including leading zeros. In
10923 the few operating environments where Exim uses base 36 instead of base 62 for
10924 its message identifiers (because those systems do not have case-sensitive
10925 filenames), base 36 is used by this operator, despite its name. &*Note*&: Just
10926 to be absolutely clear: this is &'not'& base64 encoding.
10928 .vitem &*${base62d:*&<&'base-62&~digits'&>&*}*&
10929 .cindex "&%base62d%& expansion item"
10930 .cindex "expansion" "conversion to base 62"
10931 The string must consist entirely of base-62 digits, or, in operating
10932 environments where Exim uses base 36 instead of base 62 for its message
10933 identifiers, base-36 digits. The number is converted to decimal and output as a
10936 .vitem &*${base64:*&<&'string'&>&*}*&
10937 .cindex "expansion" "base64 encoding"
10938 .cindex "base64 encoding" "in string expansion"
10939 .cindex "&%base64%& expansion item"
10940 .cindex certificate "base64 of DER"
10941 This operator converts a string into one that is base64 encoded.
10943 If the string is a single variable of type certificate,
10944 returns the base64 encoding of the DER form of the certificate.
10947 .vitem &*${base64d:*&<&'string'&>&*}*&
10948 .cindex "expansion" "base64 decoding"
10949 .cindex "base64 decoding" "in string expansion"
10950 .cindex "&%base64d%& expansion item"
10951 This operator converts a base64-encoded string into the un-coded form.
10954 .vitem &*${domain:*&<&'string'&>&*}*&
10955 .cindex "domain" "extraction"
10956 .cindex "expansion" "domain extraction"
10957 The string is interpreted as an RFC 2822 address and the domain is extracted
10958 from it. If the string does not parse successfully, the result is empty.
10961 .vitem &*${escape:*&<&'string'&>&*}*&
10962 .cindex "expansion" "escaping non-printing characters"
10963 .cindex "&%escape%& expansion item"
10964 If the string contains any non-printing characters, they are converted to
10965 escape sequences starting with a backslash. Whether characters with the most
10966 significant bit set (so-called &"8-bit characters"&) count as printing or not
10967 is controlled by the &%print_topbitchars%& option.
10969 .vitem &*${escape8bit:*&<&'string'&>&*}*&
10970 .cindex "expansion" "escaping 8-bit characters"
10971 .cindex "&%escape8bit%& expansion item"
10972 If the string contains any characters with the most significant bit set,
10973 they are converted to escape sequences starting with a backslash.
10974 Backslashes and DEL characters are also converted.
10977 .vitem &*${eval:*&<&'string'&>&*}*&&~and&~&*${eval10:*&<&'string'&>&*}*&
10978 .cindex "expansion" "expression evaluation"
10979 .cindex "expansion" "arithmetic expression"
10980 .cindex "&%eval%& expansion item"
10981 These items supports simple arithmetic and bitwise logical operations in
10982 expansion strings. The string (after expansion) must be a conventional
10983 arithmetic expression, but it is limited to basic arithmetic operators, bitwise
10984 logical operators, and parentheses. All operations are carried out using
10985 integer arithmetic. The operator priorities are as follows (the same as in the
10986 C programming language):
10988 .irow &'highest:'& "not (~), negate (-)"
10989 .irow "" "multiply (*), divide (/), remainder (%)"
10990 .irow "" "plus (+), minus (-)"
10991 .irow "" "shift-left (<<), shift-right (>>)"
10992 .irow "" "and (&&)"
10994 .irow &'lowest:'& "or (|)"
10996 Binary operators with the same priority are evaluated from left to right. White
10997 space is permitted before or after operators.
10999 For &%eval%&, numbers may be decimal, octal (starting with &"0"&) or
11000 hexadecimal (starting with &"0x"&). For &%eval10%&, all numbers are taken as
11001 decimal, even if they start with a leading zero; hexadecimal numbers are not
11002 permitted. This can be useful when processing numbers extracted from dates or
11003 times, which often do have leading zeros.
11005 A number may be followed by &"K"&, &"M"& or &"G"& to multiply it by 1024, 1024*1024
11007 respectively. Negative numbers are supported. The result of the computation is
11008 a decimal representation of the answer (without &"K"&, &"M"& or &"G"&). For example:
11011 &`${eval:1+1} `& yields 2
11012 &`${eval:1+2*3} `& yields 7
11013 &`${eval:(1+2)*3} `& yields 9
11014 &`${eval:2+42%5} `& yields 4
11015 &`${eval:0xc&5} `& yields 4
11016 &`${eval:0xc|5} `& yields 13
11017 &`${eval:0xc^5} `& yields 9
11018 &`${eval:0xc>>1} `& yields 6
11019 &`${eval:0xc<<1} `& yields 24
11020 &`${eval:~255&0x1234} `& yields 4608
11021 &`${eval:-(~255&0x1234)} `& yields -4608
11024 As a more realistic example, in an ACL you might have
11028 {>{$rcpt_count}{10}} \
11031 {$recipients_count} \
11032 {${eval:$rcpt_count/2}} \
11035 message = Too many bad recipients
11037 The condition is true if there have been more than 10 RCPT commands and
11038 fewer than half of them have resulted in a valid recipient.
11041 .vitem &*${expand:*&<&'string'&>&*}*&
11042 .cindex "expansion" "re-expansion of substring"
11043 The &%expand%& operator causes a string to be expanded for a second time. For
11046 ${expand:${lookup{$domain}dbm{/some/file}{$value}}}
11048 first looks up a string in a file while expanding the operand for &%expand%&,
11049 and then re-expands what it has found.
11052 .vitem &*${from_utf8:*&<&'string'&>&*}*&
11054 .cindex "UTF-8" "conversion from"
11055 .cindex "expansion" "UTF-8 conversion"
11056 .cindex "&%from_utf8%& expansion item"
11057 The world is slowly moving towards Unicode, although there are no standards for
11058 email yet. However, other applications (including some databases) are starting
11059 to store data in Unicode, using UTF-8 encoding. This operator converts from a
11060 UTF-8 string to an ISO-8859-1 string. UTF-8 code values greater than 255 are
11061 converted to underscores. The input must be a valid UTF-8 string. If it is not,
11062 the result is an undefined sequence of bytes.
11064 Unicode code points with values less than 256 are compatible with ASCII and
11065 ISO-8859-1 (also known as Latin-1).
11066 For example, character 169 is the copyright symbol in both cases, though the
11067 way it is encoded is different. In UTF-8, more than one byte is needed for
11068 characters with code values greater than 127, whereas ISO-8859-1 is a
11069 single-byte encoding (but thereby limited to 256 characters). This makes
11070 translation from UTF-8 to ISO-8859-1 straightforward.
11073 .vitem &*${hash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
11074 .cindex "hash function" "textual"
11075 .cindex "expansion" "textual hash"
11076 The &%hash%& operator is a simpler interface to the hashing function that can
11077 be used when the two parameters are fixed numbers (as opposed to strings that
11078 change when expanded). The effect is the same as
11080 ${hash{<n>}{<m>}{<string>}}
11082 See the description of the general &%hash%& item above for details. The
11083 abbreviation &%h%& can be used when &%hash%& is used as an operator.
11087 .vitem &*${hex2b64:*&<&'hexstring'&>&*}*&
11088 .cindex "base64 encoding" "conversion from hex"
11089 .cindex "expansion" "hex to base64"
11090 .cindex "&%hex2b64%& expansion item"
11091 This operator converts a hex string into one that is base64 encoded. This can
11092 be useful for processing the output of the various hashing functions.
11096 .vitem &*${hexquote:*&<&'string'&>&*}*&
11097 .cindex "quoting" "hex-encoded unprintable characters"
11098 .cindex "&%hexquote%& expansion item"
11099 This operator converts non-printable characters in a string into a hex
11100 escape form. Byte values between 33 (!) and 126 (~) inclusive are left
11101 as is, and other byte values are converted to &`\xNN`&, for example, a
11102 byte value 127 is converted to &`\x7f`&.
11105 .vitem &*${ipv6denorm:*&<&'string'&>&*}*&
11106 .cindex "&%ipv6denorm%& expansion item"
11107 .cindex "IP address" normalisation
11108 This expands an IPv6 address to a full eight-element colon-separated set
11109 of hex digits including leading zeroes.
11110 A trailing ipv4-style dotted-decimal set is converted to hex.
11111 Pure IPv4 addresses are converted to IPv4-mapped IPv6.
11113 .vitem &*${ipv6norm:*&<&'string'&>&*}*&
11114 .cindex "&%ipv6norm%& expansion item"
11115 .cindex "IP address" normalisation
11116 .cindex "IP address" "canonical form"
11117 This converts an IPv6 address to canonical form.
11118 Leading zeroes of groups are omitted, and the longest
11119 set of zero-valued groups is replaced with a double colon.
11120 A trailing ipv4-style dotted-decimal set is converted to hex.
11121 Pure IPv4 addresses are converted to IPv4-mapped IPv6.
11124 .vitem &*${lc:*&<&'string'&>&*}*&
11125 .cindex "case forcing in strings"
11126 .cindex "string" "case forcing"
11127 .cindex "lower casing"
11128 .cindex "expansion" "case forcing"
11129 .cindex "&%lc%& expansion item"
11130 This forces the letters in the string into lower-case, for example:
11134 Case is defined per the system C locale.
11136 .vitem &*${length_*&<&'number'&>&*:*&<&'string'&>&*}*&
11137 .cindex "expansion" "string truncation"
11138 .cindex "&%length%& expansion item"
11139 The &%length%& operator is a simpler interface to the &%length%& function that
11140 can be used when the parameter is a fixed number (as opposed to a string that
11141 changes when expanded). The effect is the same as
11143 ${length{<number>}{<string>}}
11145 See the description of the general &%length%& item above for details. Note that
11146 &%length%& is not the same as &%strlen%&. The abbreviation &%l%& can be used
11147 when &%length%& is used as an operator.
11148 All measurement is done in bytes and is not UTF-8 aware.
11151 .vitem &*${listcount:*&<&'string'&>&*}*&
11152 .cindex "expansion" "list item count"
11153 .cindex "list" "item count"
11154 .cindex "list" "count of items"
11155 .cindex "&%listcount%& expansion item"
11156 The string is interpreted as a list and the number of items is returned.
11159 .vitem &*${listnamed:*&<&'name'&>&*}*&&~and&~&*${listnamed_*&<&'type'&>&*:*&<&'name'&>&*}*&
11160 .cindex "expansion" "named list"
11161 .cindex "&%listnamed%& expansion item"
11162 The name is interpreted as a named list and the content of the list is returned,
11163 expanding any referenced lists, re-quoting as needed for colon-separation.
11164 If the optional type is given it must be one of "a", "d", "h" or "l"
11165 and selects address-, domain-, host- or localpart- lists to search among respectively.
11166 Otherwise all types are searched in an undefined order and the first
11167 matching list is returned.
11168 &*Note*&: Neither string-expansion of lists referenced by named-list syntax elements,
11169 nor expansion of lookup elements, is done by the &%listnamed%& operator.
11172 .vitem &*${local_part:*&<&'string'&>&*}*&
11173 .cindex "expansion" "local part extraction"
11174 .cindex "&%local_part%& expansion item"
11175 The string is interpreted as an RFC 2822 address and the local part is
11176 extracted from it. If the string does not parse successfully, the result is
11178 The parsing correctly handles SMTPUTF8 Unicode in the string.
11181 .vitem &*${mask:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*& &&&
11182 &*${mask_n:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*&
11183 .cindex "masked IP address"
11184 .cindex "IP address" "masking"
11185 .cindex "CIDR notation"
11186 .cindex "expansion" "IP address masking"
11187 .cindex "&%mask%& expansion item"
11188 If the form of the string to be operated on is not an IP address followed by a
11189 slash and an integer (that is, a network address in CIDR notation), the
11190 expansion fails. Otherwise, this operator converts the IP address to binary,
11191 masks off the least significant bits according to the bit count, and converts
11192 the result back to text, with mask appended. For example,
11194 ${mask:10.111.131.206/28}
11196 returns the string &"10.111.131.192/28"&.
11198 Since this operation is expected to
11199 be mostly used for looking up masked addresses in files, the
11202 address uses dots to separate components instead of colons, because colon
11203 terminates a key string in lsearch files. So, for example,
11205 ${mask:3ffe:ffff:836f:0a00:000a:0800:200a:c031/99}
11209 3ffe.ffff.836f.0a00.000a.0800.2000.0000/99
11211 If the optional form &*mask_n*& is used, IPv6 address result are instead
11212 returned in normailsed form, using colons and with zero-compression.
11213 Letters in IPv6 addresses are always output in lower case.
11216 .vitem &*${md5:*&<&'string'&>&*}*&
11218 .cindex "expansion" "MD5 hash"
11219 .cindex certificate fingerprint
11220 .cindex "&%md5%& expansion item"
11221 The &%md5%& operator computes the MD5 hash value of the string, and returns it
11222 as a 32-digit hexadecimal number, in which any letters are in lower case.
11224 If the string is a single variable of type certificate,
11225 returns the MD5 hash fingerprint of the certificate.
11228 .vitem &*${nhash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
11229 .cindex "expansion" "numeric hash"
11230 .cindex "hash function" "numeric"
11231 The &%nhash%& operator is a simpler interface to the numeric hashing function
11232 that can be used when the two parameters are fixed numbers (as opposed to
11233 strings that change when expanded). The effect is the same as
11235 ${nhash{<n>}{<m>}{<string>}}
11237 See the description of the general &%nhash%& item above for details.
11240 .vitem &*${quote:*&<&'string'&>&*}*&
11241 .cindex "quoting" "in string expansions"
11242 .cindex "expansion" "quoting"
11243 .cindex "&%quote%& expansion item"
11244 The &%quote%& operator puts its argument into double quotes if it
11245 is an empty string or
11246 contains anything other than letters, digits, underscores, dots, and hyphens.
11247 Any occurrences of double quotes and backslashes are escaped with a backslash.
11248 Newlines and carriage returns are converted to &`\n`& and &`\r`&,
11249 respectively For example,
11257 The place where this is useful is when the argument is a substitution from a
11258 variable or a message header.
11260 .vitem &*${quote_local_part:*&<&'string'&>&*}*&
11261 .cindex "&%quote_local_part%& expansion item"
11262 This operator is like &%quote%&, except that it quotes the string only if
11263 required to do so by the rules of RFC 2822 for quoting local parts. For
11264 example, a plus sign would not cause quoting (but it would for &%quote%&).
11265 If you are creating a new email address from the contents of &$local_part$&
11266 (or any other unknown data), you should always use this operator.
11268 This quoting determination is not SMTPUTF8-aware, thus quoting non-ASCII data
11269 will likely use the quoting form.
11270 Thus &'${quote_local_part:フィル}'& will always become &'"フィル"'&.
11273 .vitem &*${quote_*&<&'lookup-type'&>&*:*&<&'string'&>&*}*&
11274 .cindex "quoting" "lookup-specific"
11275 This operator applies lookup-specific quoting rules to the string. Each
11276 query-style lookup type has its own quoting rules which are described with
11277 the lookups in chapter &<<CHAPfdlookup>>&. For example,
11279 ${quote_ldap:two * two}
11285 For single-key lookup types, no quoting is ever necessary and this operator
11286 yields an unchanged string.
11289 .vitem &*${randint:*&<&'n'&>&*}*&
11290 .cindex "random number"
11291 This operator returns a somewhat random number which is less than the
11292 supplied number and is at least 0. The quality of this randomness depends
11293 on how Exim was built; the values are not suitable for keying material.
11294 If Exim is linked against OpenSSL then RAND_pseudo_bytes() is used.
11295 If Exim is linked against GnuTLS then gnutls_rnd(GNUTLS_RND_NONCE) is used,
11296 for versions of GnuTLS with that function.
11297 Otherwise, the implementation may be arc4random(), random() seeded by
11298 srandomdev() or srandom(), or a custom implementation even weaker than
11302 .vitem &*${reverse_ip:*&<&'ipaddr'&>&*}*&
11303 .cindex "expansion" "IP address"
11304 This operator reverses an IP address; for IPv4 addresses, the result is in
11305 dotted-quad decimal form, while for IPv6 addresses the result is in
11306 dotted-nibble hexadecimal form. In both cases, this is the "natural" form
11307 for DNS. For example,
11309 ${reverse_ip:192.0.2.4}
11310 ${reverse_ip:2001:0db8:c42:9:1:abcd:192.0.2.127}
11315 f.7.2.0.0.0.0.c.d.c.b.a.1.0.0.0.9.0.0.0.2.4.c.0.8.b.d.0.1.0.0.2
11319 .vitem &*${rfc2047:*&<&'string'&>&*}*&
11320 .cindex "expansion" "RFC 2047"
11321 .cindex "RFC 2047" "expansion operator"
11322 .cindex "&%rfc2047%& expansion item"
11323 This operator encodes text according to the rules of RFC 2047. This is an
11324 encoding that is used in header lines to encode non-ASCII characters. It is
11325 assumed that the input string is in the encoding specified by the
11326 &%headers_charset%& option, which gets its default at build time. If the string
11327 contains only characters in the range 33&--126, and no instances of the
11330 ? = ( ) < > @ , ; : \ " . [ ] _
11332 it is not modified. Otherwise, the result is the RFC 2047 encoding of the
11333 string, using as many &"encoded words"& as necessary to encode all the
11337 .vitem &*${rfc2047d:*&<&'string'&>&*}*&
11338 .cindex "expansion" "RFC 2047"
11339 .cindex "RFC 2047" "decoding"
11340 .cindex "&%rfc2047d%& expansion item"
11341 This operator decodes strings that are encoded as per RFC 2047. Binary zero
11342 bytes are replaced by question marks. Characters are converted into the
11343 character set defined by &%headers_charset%&. Overlong RFC 2047 &"words"& are
11344 not recognized unless &%check_rfc2047_length%& is set false.
11346 &*Note*&: If you use &%$header%&_&'xxx'&&*:*& (or &%$h%&_&'xxx'&&*:*&) to
11347 access a header line, RFC 2047 decoding is done automatically. You do not need
11348 to use this operator as well.
11352 .vitem &*${rxquote:*&<&'string'&>&*}*&
11353 .cindex "quoting" "in regular expressions"
11354 .cindex "regular expressions" "quoting"
11355 .cindex "&%rxquote%& expansion item"
11356 The &%rxquote%& operator inserts a backslash before any non-alphanumeric
11357 characters in its argument. This is useful when substituting the values of
11358 variables or headers inside regular expressions.
11361 .vitem &*${sha1:*&<&'string'&>&*}*&
11362 .cindex "SHA-1 hash"
11363 .cindex "expansion" "SHA-1 hashing"
11364 .cindex certificate fingerprint
11365 .cindex "&%sha1%& expansion item"
11366 The &%sha1%& operator computes the SHA-1 hash value of the string, and returns
11367 it as a 40-digit hexadecimal number, in which any letters are in upper case.
11369 If the string is a single variable of type certificate,
11370 returns the SHA-1 hash fingerprint of the certificate.
11373 .vitem &*${sha256:*&<&'string'&>&*}*& &&&
11374 &*${sha2:*&<&'string'&>&*}*& &&&
11375 &*${sha2_<n>:*&<&'string'&>&*}*&
11376 .cindex "SHA-256 hash"
11377 .cindex "SHA-2 hash"
11378 .cindex certificate fingerprint
11379 .cindex "expansion" "SHA-256 hashing"
11380 .cindex "&%sha256%& expansion item"
11381 .cindex "&%sha2%& expansion item"
11382 The &%sha256%& operator computes the SHA-256 hash value of the string
11384 it as a 64-digit hexadecimal number, in which any letters are in upper case.
11386 If the string is a single variable of type certificate,
11387 returns the SHA-256 hash fingerprint of the certificate.
11389 The operator can also be spelled &%sha2%& and does the same as &%sha256%&
11390 (except for certificates, which are not supported).
11391 Finally, if an underbar
11392 and a number is appended it specifies the output length, selecting a
11393 member of the SHA-2 family of hash functions.
11394 Values of 256, 384 and 512 are accepted, with 256 being the default.
11397 .vitem &*${sha3:*&<&'string'&>&*}*& &&&
11398 &*${sha3_<n>:*&<&'string'&>&*}*&
11399 .cindex "SHA3 hash"
11400 .cindex "expansion" "SHA3 hashing"
11401 .cindex "&%sha3%& expansion item"
11402 The &%sha3%& operator computes the SHA3-256 hash value of the string
11404 it as a 64-digit hexadecimal number, in which any letters are in upper case.
11406 If a number is appended, separated by an underbar, it specifies
11407 the output length. Values of 224, 256, 384 and 512 are accepted;
11408 with 256 being the default.
11410 The &%sha3%& expansion item is only supported if Exim has been
11411 compiled with GnuTLS 3.5.0 or later,
11412 or OpenSSL 1.1.1 or later.
11413 The macro "_CRYPTO_HASH_SHA3" will be defined if it is supported.
11416 .vitem &*${stat:*&<&'string'&>&*}*&
11417 .cindex "expansion" "statting a file"
11418 .cindex "file" "extracting characteristics"
11419 .cindex "&%stat%& expansion item"
11420 The string, after expansion, must be a file path. A call to the &[stat()]&
11421 function is made for this path. If &[stat()]& fails, an error occurs and the
11422 expansion fails. If it succeeds, the data from the stat replaces the item, as a
11423 series of <&'name'&>=<&'value'&> pairs, where the values are all numerical,
11424 except for the value of &"smode"&. The names are: &"mode"& (giving the mode as
11425 a 4-digit octal number), &"smode"& (giving the mode in symbolic format as a
11426 10-character string, as for the &'ls'& command), &"inode"&, &"device"&,
11427 &"links"&, &"uid"&, &"gid"&, &"size"&, &"atime"&, &"mtime"&, and &"ctime"&. You
11428 can extract individual fields using the &%extract%& expansion item.
11430 The use of the &%stat%& expansion in users' filter files can be locked out by
11431 the system administrator. &*Warning*&: The file size may be incorrect on 32-bit
11432 systems for files larger than 2GB.
11434 .vitem &*${str2b64:*&<&'string'&>&*}*&
11435 .cindex "&%str2b64%& expansion item"
11436 Now deprecated, a synonym for the &%base64%& expansion operator.
11440 .vitem &*${strlen:*&<&'string'&>&*}*&
11441 .cindex "expansion" "string length"
11442 .cindex "string" "length in expansion"
11443 .cindex "&%strlen%& expansion item"
11444 The item is replaced by the length of the expanded string, expressed as a
11445 decimal number. &*Note*&: Do not confuse &%strlen%& with &%length%&.
11446 All measurement is done in bytes and is not UTF-8 aware.
11449 .vitem &*${substr_*&<&'start'&>&*_*&<&'length'&>&*:*&<&'string'&>&*}*&
11450 .cindex "&%substr%& expansion item"
11451 .cindex "substring extraction"
11452 .cindex "expansion" "substring expansion"
11453 The &%substr%& operator is a simpler interface to the &%substr%& function that
11454 can be used when the two parameters are fixed numbers (as opposed to strings
11455 that change when expanded). The effect is the same as
11457 ${substr{<start>}{<length>}{<string>}}
11459 See the description of the general &%substr%& item above for details. The
11460 abbreviation &%s%& can be used when &%substr%& is used as an operator.
11461 All measurement is done in bytes and is not UTF-8 aware.
11463 .vitem &*${time_eval:*&<&'string'&>&*}*&
11464 .cindex "&%time_eval%& expansion item"
11465 .cindex "time interval" "decoding"
11466 This item converts an Exim time interval such as &`2d4h5m`& into a number of
11469 .vitem &*${time_interval:*&<&'string'&>&*}*&
11470 .cindex "&%time_interval%& expansion item"
11471 .cindex "time interval" "formatting"
11472 The argument (after sub-expansion) must be a sequence of decimal digits that
11473 represents an interval of time as a number of seconds. It is converted into a
11474 number of larger units and output in Exim's normal time format, for example,
11477 .vitem &*${uc:*&<&'string'&>&*}*&
11478 .cindex "case forcing in strings"
11479 .cindex "string" "case forcing"
11480 .cindex "upper casing"
11481 .cindex "expansion" "case forcing"
11482 .cindex "&%uc%& expansion item"
11483 This forces the letters in the string into upper-case.
11484 Case is defined per the system C locale.
11486 .vitem &*${utf8clean:*&<&'string'&>&*}*&
11487 .cindex "correction of invalid utf-8 sequences in strings"
11488 .cindex "utf-8" "utf-8 sequences"
11489 .cindex "incorrect utf-8"
11490 .cindex "expansion" "utf-8 forcing"
11491 .cindex "&%utf8clean%& expansion item"
11492 This replaces any invalid utf-8 sequence in the string by the character &`?`&.
11493 In versions of Exim before 4.92, this did not correctly do so for a truncated
11494 final codepoint's encoding, and the character would be silently dropped.
11495 If you must handle detection of this scenario across both sets of Exim behavior,
11496 the complexity will depend upon the task.
11497 For instance, to detect if the first character is multibyte and a 1-byte
11498 extraction can be successfully used as a path component (as is common for
11499 dividing up delivery folders), you might use:
11501 condition = ${if inlist{${utf8clean:${length_1:$local_part}}}{:?}{yes}{no}}
11503 (which will false-positive if the first character of the local part is a
11504 literal question mark).
11506 .vitem "&*${utf8_domain_to_alabel:*&<&'string'&>&*}*&" &&&
11507 "&*${utf8_domain_from_alabel:*&<&'string'&>&*}*&" &&&
11508 "&*${utf8_localpart_to_alabel:*&<&'string'&>&*}*&" &&&
11509 "&*${utf8_localpart_from_alabel:*&<&'string'&>&*}*&"
11510 .cindex expansion UTF-8
11511 .cindex UTF-8 expansion
11513 .cindex internationalisation
11514 .cindex "&%utf8_domain_to_alabel%& expansion item"
11515 .cindex "&%utf8_domain_from_alabel%& expansion item"
11516 .cindex "&%utf8_localpart_to_alabel%& expansion item"
11517 .cindex "&%utf8_localpart_from_alabel%& expansion item"
11518 These convert EAI mail name components between UTF-8 and a-label forms.
11519 For information on internationalisation support see &<<SECTi18nMTA>>&.
11527 .section "Expansion conditions" "SECTexpcond"
11528 .scindex IIDexpcond "expansion" "conditions"
11529 The following conditions are available for testing by the &%${if%& construct
11530 while expanding strings:
11533 .vitem &*!*&<&'condition'&>
11534 .cindex "expansion" "negating a condition"
11535 .cindex "negation" "in expansion condition"
11536 Preceding any condition with an exclamation mark negates the result of the
11539 .vitem <&'symbolic&~operator'&>&~&*{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11540 .cindex "numeric comparison"
11541 .cindex "expansion" "numeric comparison"
11542 There are a number of symbolic operators for doing numeric comparisons. They
11544 .itable none 0 0 2 10* left 90* left
11546 .irow "== " "equal"
11547 .irow "> " "greater"
11548 .irow ">= " "greater or equal"
11550 .irow "<= " "less or equal"
11554 ${if >{$message_size}{10M} ...
11556 Note that the general negation operator provides for inequality testing. The
11557 two strings must take the form of optionally signed decimal integers,
11558 optionally followed by one of the letters &"K"&, &"M"& or &"G"& (in either upper or
11559 lower case), signifying multiplication by 1024, 1024*1024 or 1024*1024*1024, respectively.
11560 As a special case, the numerical value of an empty string is taken as
11563 In all cases, a relative comparator OP is testing if <&'string1'&> OP
11564 <&'string2'&>; the above example is checking if &$message_size$& is larger than
11565 10M, not if 10M is larger than &$message_size$&.
11568 .vitem &*acl&~{{*&<&'name'&>&*}{*&<&'arg1'&>&*}&&&
11569 {*&<&'arg2'&>&*}...}*&
11570 .cindex "expansion" "calling an acl"
11571 .cindex "&%acl%&" "expansion condition"
11572 The name and zero to nine argument strings are first expanded separately. The expanded
11573 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
11574 Any unused are made empty. The variable &$acl_narg$& is set to the number of
11575 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
11576 and may use the variables; if another acl expansion is used the values
11577 are restored after it returns. If the ACL sets
11578 a value using a "message =" modifier the variable $value becomes
11579 the result of the expansion, otherwise it is empty.
11580 If the ACL returns accept the condition is true; if deny, false.
11581 If the ACL returns defer the result is a forced-fail.
11583 .vitem &*bool&~{*&<&'string'&>&*}*&
11584 .cindex "expansion" "boolean parsing"
11585 .cindex "&%bool%& expansion condition"
11586 This condition turns a string holding a true or false representation into
11587 a boolean state. It parses &"true"&, &"false"&, &"yes"& and &"no"&
11588 (case-insensitively); also integer numbers map to true if non-zero,
11590 An empty string is treated as false.
11591 Leading and trailing whitespace is ignored;
11592 thus a string consisting only of whitespace is false.
11593 All other string values will result in expansion failure.
11595 When combined with ACL variables, this expansion condition will let you
11596 make decisions in one place and act on those decisions in another place.
11599 ${if bool{$acl_m_privileged_sender} ...
11603 .vitem &*bool_lax&~{*&<&'string'&>&*}*&
11604 .cindex "expansion" "boolean parsing"
11605 .cindex "&%bool_lax%& expansion condition"
11606 Like &%bool%&, this condition turns a string into a boolean state. But
11607 where &%bool%& accepts a strict set of strings, &%bool_lax%& uses the same
11608 loose definition that the Router &%condition%& option uses. The empty string
11609 and the values &"false"&, &"no"& and &"0"& map to false, all others map to
11610 true. Leading and trailing whitespace is ignored.
11612 Note that where &"bool{00}"& is false, &"bool_lax{00}"& is true.
11614 .vitem &*crypteq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11615 .cindex "expansion" "encrypted comparison"
11616 .cindex "encrypted strings, comparing"
11617 .cindex "&%crypteq%& expansion condition"
11618 This condition is included in the Exim binary if it is built to support any
11619 authentication mechanisms (see chapter &<<CHAPSMTPAUTH>>&). Otherwise, it is
11620 necessary to define SUPPORT_CRYPTEQ in &_Local/Makefile_& to get &%crypteq%&
11621 included in the binary.
11623 The &%crypteq%& condition has two arguments. The first is encrypted and
11624 compared against the second, which is already encrypted. The second string may
11625 be in the LDAP form for storing encrypted strings, which starts with the
11626 encryption type in curly brackets, followed by the data. If the second string
11627 does not begin with &"{"& it is assumed to be encrypted with &[crypt()]& or
11628 &[crypt16()]& (see below), since such strings cannot begin with &"{"&.
11629 Typically this will be a field from a password file. An example of an encrypted
11630 string in LDAP form is:
11632 {md5}CY9rzUYh03PK3k6DJie09g==
11634 If such a string appears directly in an expansion, the curly brackets have to
11635 be quoted, because they are part of the expansion syntax. For example:
11637 ${if crypteq {test}{\{md5\}CY9rzUYh03PK3k6DJie09g==}{yes}{no}}
11639 The following encryption types (whose names are matched case-independently) are
11644 .cindex "base64 encoding" "in encrypted password"
11645 &%{md5}%& computes the MD5 digest of the first string, and expresses this as
11646 printable characters to compare with the remainder of the second string. If the
11647 length of the comparison string is 24, Exim assumes that it is base64 encoded
11648 (as in the above example). If the length is 32, Exim assumes that it is a
11649 hexadecimal encoding of the MD5 digest. If the length not 24 or 32, the
11653 .cindex "SHA-1 hash"
11654 &%{sha1}%& computes the SHA-1 digest of the first string, and expresses this as
11655 printable characters to compare with the remainder of the second string. If the
11656 length of the comparison string is 28, Exim assumes that it is base64 encoded.
11657 If the length is 40, Exim assumes that it is a hexadecimal encoding of the
11658 SHA-1 digest. If the length is not 28 or 40, the comparison fails.
11661 .cindex "&[crypt()]&"
11662 &%{crypt}%& calls the &[crypt()]& function, which traditionally used to use
11663 only the first eight characters of the password. However, in modern operating
11664 systems this is no longer true, and in many cases the entire password is used,
11665 whatever its length.
11668 .cindex "&[crypt16()]&"
11669 &%{crypt16}%& calls the &[crypt16()]& function, which was originally created to
11670 use up to 16 characters of the password in some operating systems. Again, in
11671 modern operating systems, more characters may be used.
11673 Exim has its own version of &[crypt16()]&, which is just a double call to
11674 &[crypt()]&. For operating systems that have their own version, setting
11675 HAVE_CRYPT16 in &_Local/Makefile_& when building Exim causes it to use the
11676 operating system version instead of its own. This option is set by default in
11677 the OS-dependent &_Makefile_& for those operating systems that are known to
11678 support &[crypt16()]&.
11680 Some years after Exim's &[crypt16()]& was implemented, a user discovered that
11681 it was not using the same algorithm as some operating systems' versions. It
11682 turns out that as well as &[crypt16()]& there is a function called
11683 &[bigcrypt()]& in some operating systems. This may or may not use the same
11684 algorithm, and both of them may be different to Exim's built-in &[crypt16()]&.
11686 However, since there is now a move away from the traditional &[crypt()]&
11687 functions towards using SHA1 and other algorithms, tidying up this area of
11688 Exim is seen as very low priority.
11690 If you do not put a encryption type (in curly brackets) in a &%crypteq%&
11691 comparison, the default is usually either &`{crypt}`& or &`{crypt16}`&, as
11692 determined by the setting of DEFAULT_CRYPT in &_Local/Makefile_&. The default
11693 default is &`{crypt}`&. Whatever the default, you can always use either
11694 function by specifying it explicitly in curly brackets.
11696 .vitem &*def:*&<&'variable&~name'&>
11697 .cindex "expansion" "checking for empty variable"
11698 .cindex "&%def%& expansion condition"
11699 The &%def%& condition must be followed by the name of one of the expansion
11700 variables defined in section &<<SECTexpvar>>&. The condition is true if the
11701 variable does not contain the empty string. For example:
11703 ${if def:sender_ident {from $sender_ident}}
11705 Note that the variable name is given without a leading &%$%& character. If the
11706 variable does not exist, the expansion fails.
11708 .vitem "&*def:header_*&<&'header&~name'&>&*:*&&~&~or&~&&&
11709 &~&*def:h_*&<&'header&~name'&>&*:*&"
11710 .cindex "expansion" "checking header line existence"
11711 This condition is true if a message is being processed and the named header
11712 exists in the message. For example,
11714 ${if def:header_reply-to:{$h_reply-to:}{$h_from:}}
11716 &*Note*&: No &%$%& appears before &%header_%& or &%h_%& in the condition, and
11717 the header name must be terminated by a colon if white space does not follow.
11719 .vitem &*eq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11720 &*eqi&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11721 .cindex "string" "comparison"
11722 .cindex "expansion" "string comparison"
11723 .cindex "&%eq%& expansion condition"
11724 .cindex "&%eqi%& expansion condition"
11725 The two substrings are first expanded. The condition is true if the two
11726 resulting strings are identical. For &%eq%& the comparison includes the case of
11727 letters, whereas for &%eqi%& the comparison is case-independent, where
11728 case is defined per the system C locale.
11730 .vitem &*exists&~{*&<&'file&~name'&>&*}*&
11731 .cindex "expansion" "file existence test"
11732 .cindex "file" "existence test"
11733 .cindex "&%exists%&, expansion condition"
11734 The substring is first expanded and then interpreted as an absolute path. The
11735 condition is true if the named file (or directory) exists. The existence test
11736 is done by calling the &[stat()]& function. The use of the &%exists%& test in
11737 users' filter files may be locked out by the system administrator.
11739 &*Note:*& Testing a path using this condition is not a sufficient way of
11741 Consider using a dsearch lookup.
11743 .vitem &*first_delivery*&
11744 .cindex "delivery" "first"
11745 .cindex "first delivery"
11746 .cindex "expansion" "first delivery test"
11747 .cindex "&%first_delivery%& expansion condition"
11748 This condition, which has no data, is true during a message's first delivery
11749 attempt. It is false during any subsequent delivery attempts.
11752 .vitem "&*forall{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&" &&&
11753 "&*forany{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&"
11754 .cindex "list" "iterative conditions"
11755 .cindex "expansion" "&*forall*& condition"
11756 .cindex "expansion" "&*forany*& condition"
11758 These conditions iterate over a list. The first argument is expanded to form
11759 the list. By default, the list separator is a colon, but it can be changed by
11760 the normal method (&<<SECTlistsepchange>>&).
11761 The second argument is interpreted as a condition that is to
11762 be applied to each item in the list in turn. During the interpretation of the
11763 condition, the current list item is placed in a variable called &$item$&.
11765 For &*forany*&, interpretation stops if the condition is true for any item, and
11766 the result of the whole condition is true. If the condition is false for all
11767 items in the list, the overall condition is false.
11769 For &*forall*&, interpretation stops if the condition is false for any item,
11770 and the result of the whole condition is false. If the condition is true for
11771 all items in the list, the overall condition is true.
11773 Note that negation of &*forany*& means that the condition must be false for all
11774 items for the overall condition to succeed, and negation of &*forall*& means
11775 that the condition must be false for at least one item. In this example, the
11776 list separator is changed to a comma:
11778 ${if forany{<, $recipients}{match{$item}{^user3@}}{yes}{no}}
11780 The value of &$item$& is saved and restored while &%forany%& or &%forall%& is
11781 being processed, to enable these expansion items to be nested.
11783 To scan a named list, expand it with the &*listnamed*& operator.
11785 .vitem "&*forall_json{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
11786 "&*forany_json{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
11787 "&*forall_jsons{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
11788 "&*forany_jsons{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&"
11789 .cindex JSON "iterative conditions"
11790 .cindex JSON expansions
11791 .cindex expansion "&*forall_json*& condition"
11792 .cindex expansion "&*forany_json*& condition"
11793 .cindex expansion "&*forall_jsons*& condition"
11794 .cindex expansion "&*forany_jsons*& condition"
11795 As for the above, except that the first argument must, after expansion,
11797 The array separator is not changeable.
11798 For the &"jsons"& variants the elements are expected to be JSON strings
11799 and have their quotes removed before the evaluation of the condition.
11803 .vitem &*ge&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11804 &*gei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11805 .cindex "string" "comparison"
11806 .cindex "expansion" "string comparison"
11807 .cindex "&%ge%& expansion condition"
11808 .cindex "&%gei%& expansion condition"
11809 The two substrings are first expanded. The condition is true if the first
11810 string is lexically greater than or equal to the second string. For &%ge%& the
11811 comparison includes the case of letters, whereas for &%gei%& the comparison is
11813 Case and collation order are defined per the system C locale.
11815 .vitem &*gt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11816 &*gti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11817 .cindex "string" "comparison"
11818 .cindex "expansion" "string comparison"
11819 .cindex "&%gt%& expansion condition"
11820 .cindex "&%gti%& expansion condition"
11821 The two substrings are first expanded. The condition is true if the first
11822 string is lexically greater than the second string. For &%gt%& the comparison
11823 includes the case of letters, whereas for &%gti%& the comparison is
11825 Case and collation order are defined per the system C locale.
11828 .vitem &*inbound_srs&~{*&<&'local&~part'&>&*}{*&<&'secret'&>&*}*&
11829 SRS decode. See SECT &<<SECTSRS>>& for details.
11832 .vitem &*inlist&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11833 &*inlisti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11834 .cindex "string" "comparison"
11835 .cindex "list" "iterative conditions"
11836 Both strings are expanded; the second string is treated as a list of simple
11837 strings; if the first string is a member of the second, then the condition
11839 For the case-independent &%inlisti%& condition, case is defined per the system C locale.
11841 These are simpler to use versions of the more powerful &*forany*& condition.
11842 Examples, and the &*forany*& equivalents:
11844 ${if inlist{needle}{foo:needle:bar}}
11845 ${if forany{foo:needle:bar}{eq{$item}{needle}}}
11846 ${if inlisti{Needle}{fOo:NeeDLE:bAr}}
11847 ${if forany{fOo:NeeDLE:bAr}{eqi{$item}{Needle}}}
11850 The variable &$value$& will be set for a successful match and can be
11851 used in the success clause of an &%if%& expansion item using the condition.
11852 .cindex "tainted data" "de-tainting"
11853 .cindex "de-tainting" "using an inlist expansion condition"
11854 It will have the same taint status as the list; expansions such as
11856 ${if inlist {$h_mycode:} {0 : 1 : 42} {$value}}
11858 can be used for de-tainting.
11859 Any previous &$value$& is restored after the if.
11862 .vitem &*isip&~{*&<&'string'&>&*}*& &&&
11863 &*isip4&~{*&<&'string'&>&*}*& &&&
11864 &*isip6&~{*&<&'string'&>&*}*&
11865 .cindex "IP address" "testing string format"
11866 .cindex "string" "testing for IP address"
11867 .cindex "&%isip%& expansion condition"
11868 .cindex "&%isip4%& expansion condition"
11869 .cindex "&%isip6%& expansion condition"
11870 The substring is first expanded, and then tested to see if it has the form of
11871 an IP address. Both IPv4 and IPv6 addresses are valid for &%isip%&, whereas
11872 &%isip4%& and &%isip6%& test specifically for IPv4 or IPv6 addresses.
11874 For an IPv4 address, the test is for four dot-separated components, each of
11875 which consists of from one to three digits. For an IPv6 address, up to eight
11876 colon-separated components are permitted, each containing from one to four
11877 hexadecimal digits. There may be fewer than eight components if an empty
11878 component (adjacent colons) is present. Only one empty component is permitted.
11880 &*Note*&: The checks used to be just on the form of the address; actual numerical
11881 values were not considered. Thus, for example, 999.999.999.999 passed the IPv4
11883 This is no longer the case.
11885 The main use of these tests is to distinguish between IP addresses and
11886 host names, or between IPv4 and IPv6 addresses. For example, you could use
11888 ${if isip4{$sender_host_address}...
11890 to test which IP version an incoming SMTP connection is using.
11892 .vitem &*ldapauth&~{*&<&'ldap&~query'&>&*}*&
11893 .cindex "LDAP" "use for authentication"
11894 .cindex "expansion" "LDAP authentication test"
11895 .cindex "&%ldapauth%& expansion condition"
11896 This condition supports user authentication using LDAP. See section
11897 &<<SECTldap>>& for details of how to use LDAP in lookups and the syntax of
11898 queries. For this use, the query must contain a user name and password. The
11899 query itself is not used, and can be empty. The condition is true if the
11900 password is not empty, and the user name and password are accepted by the LDAP
11901 server. An empty password is rejected without calling LDAP because LDAP binds
11902 with an empty password are considered anonymous regardless of the username, and
11903 will succeed in most configurations. See chapter &<<CHAPSMTPAUTH>>& for details
11904 of SMTP authentication, and chapter &<<CHAPplaintext>>& for an example of how
11908 .vitem &*le&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11909 &*lei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11910 .cindex "string" "comparison"
11911 .cindex "expansion" "string comparison"
11912 .cindex "&%le%& expansion condition"
11913 .cindex "&%lei%& expansion condition"
11914 The two substrings are first expanded. The condition is true if the first
11915 string is lexically less than or equal to the second string. For &%le%& the
11916 comparison includes the case of letters, whereas for &%lei%& the comparison is
11918 Case and collation order are defined per the system C locale.
11920 .vitem &*lt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11921 &*lti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11922 .cindex "string" "comparison"
11923 .cindex "expansion" "string comparison"
11924 .cindex "&%lt%& expansion condition"
11925 .cindex "&%lti%& expansion condition"
11926 The two substrings are first expanded. The condition is true if the first
11927 string is lexically less than the second string. For &%lt%& the comparison
11928 includes the case of letters, whereas for &%lti%& the comparison is
11930 Case and collation order are defined per the system C locale.
11933 .vitem &*match&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11934 .cindex "expansion" "regular expression comparison"
11935 .cindex "regular expressions" "match in expanded string"
11936 .cindex "&%match%& expansion condition"
11937 The two substrings are first expanded. The second is then treated as a regular
11938 expression and applied to the first. Because of the pre-expansion, if the
11939 regular expression contains dollar, or backslash characters, they must be
11940 escaped. Care must also be taken if the regular expression contains braces
11941 (curly brackets). A closing brace must be escaped so that it is not taken as a
11942 premature termination of <&'string2'&>. The easiest approach is to use the
11943 &`\N`& feature to disable expansion of the regular expression.
11946 ${if match {$local_part}{\N^\d{3}\N} ...
11948 If the whole expansion string is in double quotes, further escaping of
11949 backslashes is also required.
11951 The condition is true if the regular expression match succeeds.
11952 The regular expression is not required to begin with a circumflex
11953 metacharacter, but if there is no circumflex, the expression is not anchored,
11954 and it may match anywhere in the subject, not just at the start. If you want
11955 the pattern to match at the end of the subject, you must include the &`$`&
11956 metacharacter at an appropriate point.
11957 All character handling is done in bytes and is not UTF-8 aware,
11958 but we might change this in a future Exim release.
11960 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%if%& expansion"
11961 At the start of an &%if%& expansion the values of the numeric variable
11962 substitutions &$1$& etc. are remembered. Obeying a &%match%& condition that
11963 succeeds causes them to be reset to the substrings of that condition and they
11964 will have these values during the expansion of the success string. At the end
11965 of the &%if%& expansion, the previous values are restored. After testing a
11966 combination of conditions using &%or%&, the subsequent values of the numeric
11967 variables are those of the condition that succeeded.
11969 .vitem &*match_address&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11970 .cindex "&%match_address%& expansion condition"
11971 See &*match_local_part*&.
11973 .vitem &*match_domain&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11974 .cindex "&%match_domain%& expansion condition"
11975 See &*match_local_part*&.
11977 .vitem &*match_ip&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11978 .cindex "&%match_ip%& expansion condition"
11979 This condition matches an IP address to a list of IP address patterns. It must
11980 be followed by two argument strings. The first (after expansion) must be an IP
11981 address or an empty string. The second (not expanded) is a restricted host
11982 list that can match only an IP address, not a host name. For example:
11984 ${if match_ip{$sender_host_address}{1.2.3.4:5.6.7.8}{...}{...}}
11986 The specific types of host list item that are permitted in the list are:
11989 An IP address, optionally with a CIDR mask.
11991 A single asterisk, which matches any IP address.
11993 An empty item, which matches only if the IP address is empty. This could be
11994 useful for testing for a locally submitted message or one from specific hosts
11995 in a single test such as
11996 . ==== As this is a nested list, any displays it contains must be indented
11997 . ==== as otherwise they are too far to the left. This comment applies to
11998 . ==== the use of xmlto plus fop. There's no problem when formatting with
11999 . ==== sdop, with or without the extra indent.
12001 ${if match_ip{$sender_host_address}{:4.3.2.1:...}{...}{...}}
12003 where the first item in the list is the empty string.
12005 The item @[] matches any of the local host's interface addresses.
12007 Single-key lookups are assumed to be like &"net-"& style lookups in host lists,
12008 even if &`net-`& is not specified. There is never any attempt to turn the IP
12009 address into a host name. The most common type of linear search for
12010 &*match_ip*& is likely to be &*iplsearch*&, in which the file can contain CIDR
12011 masks. For example:
12013 ${if match_ip{$sender_host_address}{iplsearch;/some/file}...
12015 It is of course possible to use other kinds of lookup, and in such a case, you
12016 do need to specify the &`net-`& prefix if you want to specify a specific
12017 address mask, for example:
12019 ${if match_ip{$sender_host_address}{net24-dbm;/some/file}...
12021 However, unless you are combining a &%match_ip%& condition with others, it is
12022 just as easy to use the fact that a lookup is itself a condition, and write:
12024 ${lookup{${mask:$sender_host_address/24}}dbm{/a/file}...
12028 Note that <&'string2'&> is not itself subject to string expansion, unless
12029 Exim was built with the EXPAND_LISTMATCH_RHS option.
12031 Consult section &<<SECThoslispatip>>& for further details of these patterns.
12033 .vitem &*match_local_part&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
12034 .cindex "domain list" "in expansion condition"
12035 .cindex "address list" "in expansion condition"
12036 .cindex "local part" "list, in expansion condition"
12037 .cindex "&%match_local_part%& expansion condition"
12038 This condition, together with &%match_address%& and &%match_domain%&, make it
12039 possible to test domain, address, and local part lists within expansions. Each
12040 condition requires two arguments: an item and a list to match. A trivial
12043 ${if match_domain{a.b.c}{x.y.z:a.b.c:p.q.r}{yes}{no}}
12045 In each case, the second argument may contain any of the allowable items for a
12046 list of the appropriate type. Also, because the second argument
12047 is a standard form of list, it is possible to refer to a named list.
12048 Thus, you can use conditions like this:
12050 ${if match_domain{$domain}{+local_domains}{...
12052 .cindex "&`+caseful`&"
12053 For address lists, the matching starts off caselessly, but the &`+caseful`&
12054 item can be used, as in all address lists, to cause subsequent items to
12055 have their local parts matched casefully. Domains are always matched
12058 The variable &$value$& will be set for a successful match and can be
12059 used in the success clause of an &%if%& expansion item using the condition.
12060 .cindex "tainted data" "de-tainting"
12061 .cindex "de-tainting" "using a match_local_part expansion condition"
12062 It will have the same taint status as the list; expansions such as
12064 ${if match_local_part {$local_part} {alice : bill : charlotte : dave} {$value}}
12066 can be used for de-tainting.
12067 Any previous &$value$& is restored after the if.
12069 Note that <&'string2'&> is not itself subject to string expansion, unless
12070 Exim was built with the EXPAND_LISTMATCH_RHS option.
12072 &*Note*&: Host lists are &'not'& supported in this way. This is because
12073 hosts have two identities: a name and an IP address, and it is not clear
12074 how to specify cleanly how such a test would work. However, IP addresses can be
12075 matched using &%match_ip%&.
12077 .vitem &*pam&~{*&<&'string1'&>&*:*&<&'string2'&>&*:...}*&
12078 .cindex "PAM authentication"
12079 .cindex "AUTH" "with PAM"
12080 .cindex "Solaris" "PAM support"
12081 .cindex "expansion" "PAM authentication test"
12082 .cindex "&%pam%& expansion condition"
12083 &'Pluggable Authentication Modules'&
12084 (&url(https://mirrors.edge.kernel.org/pub/linux/libs/pam/)) are a facility that is
12085 available in Solaris
12086 and in some GNU/Linux distributions.
12087 The Exim support, which is intended for use in conjunction with
12088 the SMTP AUTH command, is available only if Exim is compiled with
12092 in &_Local/Makefile_&. You probably need to add &%-lpam%& to EXTRALIBS, and
12093 in some releases of GNU/Linux &%-ldl%& is also needed.
12095 The argument string is first expanded, and the result must be a
12096 colon-separated list of strings. Leading and trailing white space is ignored.
12097 The PAM module is initialized with the service name &"exim"& and the user name
12098 taken from the first item in the colon-separated data string (<&'string1'&>).
12099 The remaining items in the data string are passed over in response to requests
12100 from the authentication function. In the simple case there will only be one
12101 request, for a password, so the data consists of just two strings.
12103 There can be problems if any of the strings are permitted to contain colon
12104 characters. In the usual way, these have to be doubled to avoid being taken as
12106 The &%listquote%& expansion item can be used for this.
12107 For example, the configuration
12108 of a LOGIN authenticator might contain this setting:
12110 server_condition = ${if pam{$auth1:${listquote{:}{$auth2}}}}
12112 In some operating systems, PAM authentication can be done only from a process
12113 running as root. Since Exim is running as the Exim user when receiving
12114 messages, this means that PAM cannot be used directly in those systems.
12115 . --- 2018-09-07: the pam_exim modified variant has gone, removed claims re using Exim via that
12118 .vitem &*pwcheck&~{*&<&'string1'&>&*:*&<&'string2'&>&*}*&
12119 .cindex "&'pwcheck'& daemon"
12121 .cindex "expansion" "&'pwcheck'& authentication test"
12122 .cindex "&%pwcheck%& expansion condition"
12123 This condition supports user authentication using the Cyrus &'pwcheck'& daemon.
12124 This is one way of making it possible for passwords to be checked by a process
12125 that is not running as root. &*Note*&: The use of &'pwcheck'& is now
12126 deprecated. Its replacement is &'saslauthd'& (see below).
12128 The pwcheck support is not included in Exim by default. You need to specify
12129 the location of the pwcheck daemon's socket in &_Local/Makefile_& before
12130 building Exim. For example:
12132 CYRUS_PWCHECK_SOCKET=/var/pwcheck/pwcheck
12134 You do not need to install the full Cyrus software suite in order to use
12135 the pwcheck daemon. You can compile and install just the daemon alone
12136 from the Cyrus SASL library. Ensure that &'exim'& is the only user that has
12137 access to the &_/var/pwcheck_& directory.
12139 The &%pwcheck%& condition takes one argument, which must be the user name and
12140 password, separated by a colon. For example, in a LOGIN authenticator
12141 configuration, you might have this:
12143 server_condition = ${if pwcheck{$auth1:$auth2}}
12145 Again, for a PLAIN authenticator configuration, this would be:
12147 server_condition = ${if pwcheck{$auth2:$auth3}}
12149 .vitem &*queue_running*&
12150 .cindex "queue runner" "detecting when delivering from"
12151 .cindex "expansion" "queue runner test"
12152 .cindex "&%queue_running%& expansion condition"
12153 This condition, which has no data, is true during delivery attempts that are
12154 initiated by queue runner processes, and false otherwise.
12157 .vitem &*radius&~{*&<&'authentication&~string'&>&*}*&
12159 .cindex "expansion" "Radius authentication"
12160 .cindex "&%radius%& expansion condition"
12161 Radius authentication (RFC 2865) is supported in a similar way to PAM. You must
12162 set RADIUS_CONFIG_FILE in &_Local/Makefile_& to specify the location of
12163 the Radius client configuration file in order to build Exim with Radius
12166 With just that one setting, Exim expects to be linked with the &%radiusclient%&
12167 library, using the original API. If you are using release 0.4.0 or later of
12168 this library, you need to set
12170 RADIUS_LIB_TYPE=RADIUSCLIENTNEW
12172 in &_Local/Makefile_& when building Exim. You can also link Exim with the
12173 &%libradius%& library that comes with FreeBSD. To do this, set
12175 RADIUS_LIB_TYPE=RADLIB
12177 in &_Local/Makefile_&, in addition to setting RADIUS_CONFIGURE_FILE.
12178 You may also have to supply a suitable setting in EXTRALIBS so that the
12179 Radius library can be found when Exim is linked.
12181 The string specified by RADIUS_CONFIG_FILE is expanded and passed to the
12182 Radius client library, which calls the Radius server. The condition is true if
12183 the authentication is successful. For example:
12185 server_condition = ${if radius{<arguments>}}
12189 .vitem "&*saslauthd&~{{*&<&'user'&>&*}{*&<&'password'&>&*}&&&
12190 {*&<&'service'&>&*}{*&<&'realm'&>&*}}*&"
12191 .cindex "&'saslauthd'& daemon"
12193 .cindex "expansion" "&'saslauthd'& authentication test"
12194 .cindex "&%saslauthd%& expansion condition"
12195 This condition supports user authentication using the Cyrus &'saslauthd'&
12196 daemon. This replaces the older &'pwcheck'& daemon, which is now deprecated.
12197 Using this daemon is one way of making it possible for passwords to be checked
12198 by a process that is not running as root.
12200 The saslauthd support is not included in Exim by default. You need to specify
12201 the location of the saslauthd daemon's socket in &_Local/Makefile_& before
12202 building Exim. For example:
12204 CYRUS_SASLAUTHD_SOCKET=/var/state/saslauthd/mux
12206 You do not need to install the full Cyrus software suite in order to use
12207 the saslauthd daemon. You can compile and install just the daemon alone
12208 from the Cyrus SASL library.
12210 Up to four arguments can be supplied to the &%saslauthd%& condition, but only
12211 two are mandatory. For example:
12213 server_condition = ${if saslauthd{{$auth1}{$auth2}}}
12215 The service and the realm are optional (which is why the arguments are enclosed
12216 in their own set of braces). For details of the meaning of the service and
12217 realm, and how to run the daemon, consult the Cyrus documentation.
12222 .section "Combining expansion conditions" "SECID84"
12223 .cindex "expansion" "combining conditions"
12224 Several conditions can be tested at once by combining them using the &%and%&
12225 and &%or%& combination conditions. Note that &%and%& and &%or%& are complete
12226 conditions on their own, and precede their lists of sub-conditions. Each
12227 sub-condition must be enclosed in braces within the overall braces that contain
12228 the list. No repetition of &%if%& is used.
12232 .vitem &*or&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
12233 .cindex "&""or""& expansion condition"
12234 .cindex "expansion" "&""or""& of conditions"
12235 The sub-conditions are evaluated from left to right. The condition is true if
12236 any one of the sub-conditions is true.
12239 ${if or {{eq{$local_part}{spqr}}{eq{$domain}{testing.com}}}...
12241 When a true sub-condition is found, the following ones are parsed but not
12242 evaluated. If there are several &"match"& sub-conditions the values of the
12243 numeric variables afterwards are taken from the first one that succeeds.
12245 .vitem &*and&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
12246 .cindex "&""and""& expansion condition"
12247 .cindex "expansion" "&""and""& of conditions"
12248 The sub-conditions are evaluated from left to right. The condition is true if
12249 all of the sub-conditions are true. If there are several &"match"&
12250 sub-conditions, the values of the numeric variables afterwards are taken from
12251 the last one. When a false sub-condition is found, the following ones are
12252 parsed but not evaluated.
12254 .ecindex IIDexpcond
12259 .section "Expansion variables" "SECTexpvar"
12260 .cindex "expansion" "variables, list of"
12261 This section contains an alphabetical list of all the expansion variables. Some
12262 of them are available only when Exim is compiled with specific options such as
12263 support for TLS or the content scanning extension.
12264 .cindex "tainted data"
12265 Variables marked as &'tainted'& are likely to carry data supplied by
12266 a potential attacker.
12267 Variables without such marking may also, depending on how their
12268 values are created.
12269 Such variables should not be further expanded,
12271 or used as command-line arguments for external commands.
12274 .vitem "&$0$&, &$1$&, etc"
12275 .cindex "numerical variables (&$1$& &$2$& etc)"
12276 When a &%match%& expansion condition succeeds, these variables contain the
12277 captured substrings identified by the regular expression during subsequent
12278 processing of the success string of the containing &%if%& expansion item.
12279 In the expansion condition case
12280 they do not retain their values afterwards; in fact, their previous
12281 values are restored at the end of processing an &%if%& item. The numerical
12282 variables may also be set externally by some other matching process which
12283 precedes the expansion of the string. For example, the commands available in
12284 Exim filter files include an &%if%& command with its own regular expression
12285 matching condition.
12286 If the subject string was tainted then any captured substring will also be.
12288 .vitem "&$acl_arg1$&, &$acl_arg2$&, etc"
12289 Within an acl condition, expansion condition or expansion item
12290 any arguments are copied to these variables,
12291 any unused variables being made empty.
12293 .vitem "&$acl_c...$&"
12294 Values can be placed in these variables by the &%set%& modifier in an ACL. They
12295 can be given any name that starts with &$acl_c$& and is at least six characters
12296 long, but the sixth character must be either a digit or an underscore. For
12297 example: &$acl_c5$&, &$acl_c_mycount$&. The values of the &$acl_c...$&
12298 variables persist throughout the lifetime of an SMTP connection. They can be
12299 used to pass information between ACLs and between different invocations of the
12300 same ACL. When a message is received, the values of these variables are saved
12301 with the message, and can be accessed by filters, routers, and transports
12302 during subsequent delivery.
12304 .vitem "&$acl_m...$&"
12305 These variables are like the &$acl_c...$& variables, except that their values
12306 are reset after a message has been received. Thus, if several messages are
12307 received in one SMTP connection, &$acl_m...$& values are not passed on from one
12308 message to the next, as &$acl_c...$& values are. The &$acl_m...$& variables are
12309 also reset by MAIL, RSET, EHLO, HELO, and after starting a TLS session. When a
12310 message is received, the values of these variables are saved with the message,
12311 and can be accessed by filters, routers, and transports during subsequent
12314 .vitem &$acl_narg$&
12315 Within an acl condition, expansion condition or expansion item
12316 this variable has the number of arguments.
12318 .vitem &$acl_verify_message$&
12319 .vindex "&$acl_verify_message$&"
12320 After an address verification has failed, this variable contains the failure
12321 message. It retains its value for use in subsequent modifiers of the verb.
12322 The message can be preserved by coding like this:
12324 warn !verify = sender
12325 set acl_m0 = $acl_verify_message
12327 You can use &$acl_verify_message$& during the expansion of the &%message%& or
12328 &%log_message%& modifiers, to include information about the verification
12330 &*Note*&: The variable is cleared at the end of processing the ACL verb.
12332 .vitem &$address_data$&
12333 .vindex "&$address_data$&"
12334 This variable is set by means of the &%address_data%& option in routers. The
12335 value then remains with the address while it is processed by subsequent routers
12336 and eventually a transport. If the transport is handling multiple addresses,
12337 the value from the first address is used. See chapter &<<CHAProutergeneric>>&
12338 for more details. &*Note*&: The contents of &$address_data$& are visible in
12341 If &$address_data$& is set when the routers are called from an ACL to verify
12342 a recipient address, the final value is still in the variable for subsequent
12343 conditions and modifiers of the ACL statement. If routing the address caused it
12344 to be redirected to just one address, the child address is also routed as part
12345 of the verification, and in this case the final value of &$address_data$& is
12346 from the child's routing.
12348 If &$address_data$& is set when the routers are called from an ACL to verify a
12349 sender address, the final value is also preserved, but this time in
12350 &$sender_address_data$&, to distinguish it from data from a recipient
12353 In both cases (recipient and sender verification), the value does not persist
12354 after the end of the current ACL statement. If you want to preserve
12355 these values for longer, you can save them in ACL variables.
12357 .vitem &$address_file$&
12358 .vindex "&$address_file$&"
12359 When, as a result of aliasing, forwarding, or filtering, a message is directed
12360 to a specific file, this variable holds the name of the file when the transport
12361 is running. At other times, the variable is empty. For example, using the
12362 default configuration, if user &%r2d2%& has a &_.forward_& file containing
12364 /home/r2d2/savemail
12366 then when the &(address_file)& transport is running, &$address_file$&
12367 contains the text string &`/home/r2d2/savemail`&.
12368 .cindex "Sieve filter" "value of &$address_file$&"
12369 For Sieve filters, the value may be &"inbox"& or a relative folder name. It is
12370 then up to the transport configuration to generate an appropriate absolute path
12371 to the relevant file.
12373 .vitem &$address_pipe$&
12374 .vindex "&$address_pipe$&"
12375 When, as a result of aliasing or forwarding, a message is directed to a pipe,
12376 this variable holds the pipe command when the transport is running.
12378 .vitem "&$auth1$& &-- &$auth4$&"
12379 .vindex "&$auth1$&, &$auth2$&, etc"
12380 These variables are used in SMTP authenticators (see chapters
12381 &<<CHAPplaintext>>&&--&<<CHAPtlsauth>>&). Elsewhere, they are empty.
12383 .vitem &$authenticated_id$&
12384 .cindex "authentication" "id"
12385 .vindex "&$authenticated_id$&"
12386 When a server successfully authenticates a client it may be configured to
12387 preserve some of the authentication information in the variable
12388 &$authenticated_id$& (see chapter &<<CHAPSMTPAUTH>>&). For example, a
12389 user/password authenticator configuration might preserve the user name for use
12390 in the routers. Note that this is not the same information that is saved in
12391 &$sender_host_authenticated$&.
12393 When a message is submitted locally (that is, not over a TCP connection)
12394 the value of &$authenticated_id$& is normally the login name of the calling
12395 process. However, a trusted user can override this by means of the &%-oMai%&
12396 command line option.
12397 This second case also sets up information used by the
12398 &$authresults$& expansion item.
12400 .vitem &$authenticated_fail_id$&
12401 .cindex "authentication" "fail" "id"
12402 .vindex "&$authenticated_fail_id$&"
12403 When an authentication attempt fails, the variable &$authenticated_fail_id$&
12404 will contain the failed authentication id. If more than one authentication
12405 id is attempted, it will contain only the last one. The variable is
12406 available for processing in the ACL's, generally the quit or notquit ACL.
12407 A message to a local recipient could still be accepted without requiring
12408 authentication, which means this variable could also be visible in all of
12412 .tvar &$authenticated_sender$&
12413 .cindex "sender" "authenticated"
12414 .cindex "authentication" "sender"
12415 .cindex "AUTH" "on MAIL command"
12416 When acting as a server, Exim takes note of the AUTH= parameter on an incoming
12417 SMTP MAIL command if it believes the sender is sufficiently trusted, as
12418 described in section &<<SECTauthparamail>>&. Unless the data is the string
12419 &"<>"&, it is set as the authenticated sender of the message, and the value is
12420 available during delivery in the &$authenticated_sender$& variable. If the
12421 sender is not trusted, Exim accepts the syntax of AUTH=, but ignores the data.
12423 .vindex "&$qualify_domain$&"
12424 When a message is submitted locally (that is, not over a TCP connection), the
12425 value of &$authenticated_sender$& is an address constructed from the login
12426 name of the calling process and &$qualify_domain$&, except that a trusted user
12427 can override this by means of the &%-oMas%& command line option.
12430 .vitem &$authentication_failed$&
12431 .cindex "authentication" "failure"
12432 .vindex "&$authentication_failed$&"
12433 This variable is set to &"1"& in an Exim server if a client issues an AUTH
12434 command that does not succeed. Otherwise it is set to &"0"&. This makes it
12435 possible to distinguish between &"did not try to authenticate"&
12436 (&$sender_host_authenticated$& is empty and &$authentication_failed$& is set to
12437 &"0"&) and &"tried to authenticate but failed"& (&$sender_host_authenticated$&
12438 is empty and &$authentication_failed$& is set to &"1"&).
12439 Failure includes cancellation of a authentication attempt,
12440 and any negative response to an AUTH command,
12441 (including, for example, an attempt to use an undefined mechanism).
12443 .vitem &$av_failed$&
12444 .cindex "content scanning" "AV scanner failure"
12445 This variable is available when Exim is compiled with the content-scanning
12446 extension. It is set to &"0"& by default, but will be set to &"1"& if any
12447 problem occurs with the virus scanner (specified by &%av_scanner%&) during
12448 the ACL malware condition.
12450 .vitem &$body_linecount$&
12451 .cindex "message body" "line count"
12452 .cindex "body of message" "line count"
12453 .vindex "&$body_linecount$&"
12454 When a message is being received or delivered, this variable contains the
12455 number of lines in the message's body. See also &$message_linecount$&.
12457 .vitem &$body_zerocount$&
12458 .cindex "message body" "binary zero count"
12459 .cindex "body of message" "binary zero count"
12460 .cindex "binary zero" "in message body"
12461 .vindex "&$body_zerocount$&"
12462 When a message is being received or delivered, this variable contains the
12463 number of binary zero bytes (ASCII NULs) in the message's body.
12465 .vitem &$bounce_recipient$&
12466 .vindex "&$bounce_recipient$&"
12467 This is set to the recipient address of a bounce message while Exim is creating
12468 it. It is useful if a customized bounce message text file is in use (see
12469 chapter &<<CHAPemsgcust>>&).
12471 .vitem &$bounce_return_size_limit$&
12472 .vindex "&$bounce_return_size_limit$&"
12473 This contains the value set in the &%bounce_return_size_limit%& option, rounded
12474 up to a multiple of 1000. It is useful when a customized error message text
12475 file is in use (see chapter &<<CHAPemsgcust>>&).
12477 .vitem &$caller_gid$&
12478 .cindex "gid (group id)" "caller"
12479 .vindex "&$caller_gid$&"
12480 The real group id under which the process that called Exim was running. This is
12481 not the same as the group id of the originator of a message (see
12482 &$originator_gid$&). If Exim re-execs itself, this variable in the new
12483 incarnation normally contains the Exim gid.
12485 .vitem &$caller_uid$&
12486 .cindex "uid (user id)" "caller"
12487 .vindex "&$caller_uid$&"
12488 The real user id under which the process that called Exim was running. This is
12489 not the same as the user id of the originator of a message (see
12490 &$originator_uid$&). If Exim re-execs itself, this variable in the new
12491 incarnation normally contains the Exim uid.
12493 .vitem &$callout_address$&
12494 .vindex "&$callout_address$&"
12495 After a callout for verification, spamd or malware daemon service, the
12496 address that was connected to.
12498 .vitem &$compile_number$&
12499 .vindex "&$compile_number$&"
12500 The building process for Exim keeps a count of the number
12501 of times it has been compiled. This serves to distinguish different
12502 compilations of the same version of Exim.
12504 .vitem &$config_dir$&
12505 .vindex "&$config_dir$&"
12506 The directory name of the main configuration file. That is, the content of
12507 &$config_file$& with the last component stripped. The value does not
12508 contain the trailing slash. If &$config_file$& does not contain a slash,
12509 &$config_dir$& is ".".
12511 .vitem &$config_file$&
12512 .vindex "&$config_file$&"
12513 The name of the main configuration file Exim is using.
12515 .vitem &$dkim_verify_status$&
12516 Results of DKIM verification.
12517 For details see section &<<SECDKIMVFY>>&.
12519 .vitem &$dkim_cur_signer$& &&&
12520 &$dkim_verify_reason$& &&&
12521 &$dkim_domain$& &&&
12522 &$dkim_identity$& &&&
12523 &$dkim_selector$& &&&
12525 &$dkim_canon_body$& &&&
12526 &$dkim_canon_headers$& &&&
12527 &$dkim_copiedheaders$& &&&
12528 &$dkim_bodylength$& &&&
12529 &$dkim_created$& &&&
12530 &$dkim_expires$& &&&
12531 &$dkim_headernames$& &&&
12532 &$dkim_key_testing$& &&&
12533 &$dkim_key_nosubdomains$& &&&
12534 &$dkim_key_srvtype$& &&&
12535 &$dkim_key_granularity$& &&&
12536 &$dkim_key_notes$& &&&
12537 &$dkim_key_length$&
12538 These variables are only available within the DKIM ACL.
12539 For details see section &<<SECDKIMVFY>>&.
12541 .vitem &$dkim_signers$&
12542 .vindex &$dkim_signers$&
12543 When a message has been received this variable contains
12544 a colon-separated list of signer domains and identities for the message.
12545 For details see section &<<SECDKIMVFY>>&.
12547 .vitem &$dmarc_domain_policy$& &&&
12548 &$dmarc_status$& &&&
12549 &$dmarc_status_text$& &&&
12550 &$dmarc_used_domains$&
12551 Results of DMARC verification.
12552 For details see section &<<SECDMARC>>&.
12554 .vitem &$dnslist_domain$& &&&
12555 &$dnslist_matched$& &&&
12556 &$dnslist_text$& &&&
12558 .vindex "&$dnslist_domain$&"
12559 .vindex "&$dnslist_matched$&"
12560 .vindex "&$dnslist_text$&"
12561 .vindex "&$dnslist_value$&"
12562 .cindex "black list (DNS)"
12563 When a DNS (black) list lookup succeeds, these variables are set to contain
12564 the following data from the lookup: the list's domain name, the key that was
12565 looked up, the contents of any associated TXT record, and the value from the
12566 main A record. See section &<<SECID204>>& for more details.
12569 When an address is being routed, or delivered on its own, this variable
12570 contains the domain. Uppercase letters in the domain are converted into lower
12571 case for &$domain$&.
12573 Global address rewriting happens when a message is received, so the value of
12574 &$domain$& during routing and delivery is the value after rewriting. &$domain$&
12575 is set during user filtering, but not during system filtering, because a
12576 message may have many recipients and the system filter is called just once.
12578 When more than one address is being delivered at once (for example, several
12579 RCPT commands in one SMTP delivery), &$domain$& is set only if they all
12580 have the same domain. Transports can be restricted to handling only one domain
12581 at a time if the value of &$domain$& is required at transport time &-- this is
12582 the default for local transports. For further details of the environment in
12583 which local transports are run, see chapter &<<CHAPenvironment>>&.
12585 .oindex "&%delay_warning_condition%&"
12586 At the end of a delivery, if all deferred addresses have the same domain, it is
12587 set in &$domain$& during the expansion of &%delay_warning_condition%&.
12589 The &$domain$& variable is also used in some other circumstances:
12592 When an ACL is running for a RCPT command, &$domain$& contains the domain of
12593 the recipient address. The domain of the &'sender'& address is in
12594 &$sender_address_domain$& at both MAIL time and at RCPT time. &$domain$& is not
12595 normally set during the running of the MAIL ACL. However, if the sender address
12596 is verified with a callout during the MAIL ACL, the sender domain is placed in
12597 &$domain$& during the expansions of &%hosts%&, &%interface%&, and &%port%& in
12598 the &(smtp)& transport.
12601 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
12602 &$domain$& contains the domain portion of the address that is being rewritten;
12603 it can be used in the expansion of the replacement address, for example, to
12604 rewrite domains by file lookup.
12607 With one important exception, whenever a domain list is being scanned,
12608 &$domain$& contains the subject domain. &*Exception*&: When a domain list in
12609 a &%sender_domains%& condition in an ACL is being processed, the subject domain
12610 is in &$sender_address_domain$& and not in &$domain$&. It works this way so
12611 that, in a RCPT ACL, the sender domain list can be dependent on the
12612 recipient domain (which is what is in &$domain$& at this time).
12615 .cindex "ETRN" "value of &$domain$&"
12616 .oindex "&%smtp_etrn_command%&"
12617 When the &%smtp_etrn_command%& option is being expanded, &$domain$& contains
12618 the complete argument of the ETRN command (see section &<<SECTETRN>>&).
12621 .cindex "tainted data"
12622 If the origin of the data is an incoming message,
12623 the result of expanding this variable is tainted and may not
12624 be further expanded or used as a filename.
12625 When an untainted version is needed, one should be obtained from
12626 looking up the value in a local (therefore trusted) database.
12627 Often &$domain_data$& is usable in this role.
12630 .vitem &$domain_data$&
12631 .vindex "&$domain_data$&"
12632 When the &%domains%& condition on a router
12635 against a list, the match value is copied to &$domain_data$&.
12636 This is an enhancement over previous versions of Exim, when it only
12637 applied to the data read by a lookup.
12638 For details on match values see section &<<SECTlistresults>>& et. al.
12640 If the router routes the
12641 address to a transport, the value is available in that transport. If the
12642 transport is handling multiple addresses, the value from the first address is
12645 &$domain_data$& set in an ACL is available during
12646 the rest of the ACL statement.
12648 .vitem &$exim_gid$&
12649 .vindex "&$exim_gid$&"
12650 This variable contains the numerical value of the Exim group id.
12652 .vitem &$exim_path$&
12653 .vindex "&$exim_path$&"
12654 This variable contains the path to the Exim binary.
12656 .vitem &$exim_uid$&
12657 .vindex "&$exim_uid$&"
12658 This variable contains the numerical value of the Exim user id.
12660 .vitem &$exim_version$&
12661 .vindex "&$exim_version$&"
12662 This variable contains the version string of the Exim build.
12663 The first character is a major version number, currently 4.
12664 Then after a dot, the next group of digits is a minor version number.
12665 There may be other characters following the minor version.
12666 This value may be overridden by the &%exim_version%& main config option.
12668 .vitem &$header_$&<&'name'&>
12670 This is not strictly an expansion variable. It is expansion syntax for
12671 inserting the message header line with the given name. Note that the name must
12672 be terminated by colon or white space, because it may contain a wide variety of
12673 characters. Note also that braces must &'not'& be used.
12674 See the full description in section &<<SECTexpansionitems>>& above.
12676 .vitem &$headers_added$&
12677 .vindex "&$headers_added$&"
12678 Within an ACL this variable contains the headers added so far by
12679 the ACL modifier add_header (section &<<SECTaddheadacl>>&).
12680 The headers are a newline-separated list.
12684 When the &%check_local_user%& option is set for a router, the user's home
12685 directory is placed in &$home$& when the check succeeds. In particular, this
12686 means it is set during the running of users' filter files. A router may also
12687 explicitly set a home directory for use by a transport; this can be overridden
12688 by a setting on the transport itself.
12690 When running a filter test via the &%-bf%& option, &$home$& is set to the value
12691 of the environment variable HOME, which is subject to the
12692 &%keep_environment%& and &%add_environment%& main config options.
12696 If a router assigns an address to a transport (any transport), and passes a
12697 list of hosts with the address, the value of &$host$& when the transport starts
12698 to run is the name of the first host on the list. Note that this applies both
12699 to local and remote transports.
12701 .cindex "transport" "filter"
12702 .cindex "filter" "transport filter"
12703 For the &(smtp)& transport, if there is more than one host, the value of
12704 &$host$& changes as the transport works its way through the list. In
12705 particular, when the &(smtp)& transport is expanding its options for encryption
12706 using TLS, or for specifying a transport filter (see chapter
12707 &<<CHAPtransportgeneric>>&), &$host$& contains the name of the host to which it
12710 When used in the client part of an authenticator configuration (see chapter
12711 &<<CHAPSMTPAUTH>>&), &$host$& contains the name of the server to which the
12712 client is connected.
12715 .vitem &$host_address$&
12716 .vindex "&$host_address$&"
12717 This variable is set to the remote host's IP address whenever &$host$& is set
12718 for a remote connection. It is also set to the IP address that is being checked
12719 when the &%ignore_target_hosts%& option is being processed.
12721 .vitem &$host_data$&
12722 .vindex "&$host_data$&"
12723 If a &%hosts%& condition in an ACL is satisfied by means of a lookup, the
12724 result of the lookup is made available in the &$host_data$& variable. This
12725 allows you, for example, to do things like this:
12727 deny hosts = net-lsearch;/some/file
12728 message = $host_data
12731 .vitem &$host_lookup_deferred$&
12732 .cindex "host name" "lookup, failure of"
12733 .vindex "&$host_lookup_deferred$&"
12734 This variable normally contains &"0"&, as does &$host_lookup_failed$&. When a
12735 message comes from a remote host and there is an attempt to look up the host's
12736 name from its IP address, and the attempt is not successful, one of these
12737 variables is set to &"1"&.
12740 If the lookup receives a definite negative response (for example, a DNS lookup
12741 succeeded, but no records were found), &$host_lookup_failed$& is set to &"1"&.
12744 If there is any kind of problem during the lookup, such that Exim cannot
12745 tell whether or not the host name is defined (for example, a timeout for a DNS
12746 lookup), &$host_lookup_deferred$& is set to &"1"&.
12749 Looking up a host's name from its IP address consists of more than just a
12750 single reverse lookup. Exim checks that a forward lookup of at least one of the
12751 names it receives from a reverse lookup yields the original IP address. If this
12752 is not the case, Exim does not accept the looked up name(s), and
12753 &$host_lookup_failed$& is set to &"1"&. Thus, being able to find a name from an
12754 IP address (for example, the existence of a PTR record in the DNS) is not
12755 sufficient on its own for the success of a host name lookup. If the reverse
12756 lookup succeeds, but there is a lookup problem such as a timeout when checking
12757 the result, the name is not accepted, and &$host_lookup_deferred$& is set to
12758 &"1"&. See also &$sender_host_name$&.
12760 .cindex authentication "expansion item"
12761 Performing these checks sets up information used by the
12762 &%authresults%& expansion item.
12765 .vitem &$host_lookup_failed$&
12766 .vindex "&$host_lookup_failed$&"
12767 See &$host_lookup_deferred$&.
12769 .vitem &$host_port$&
12770 .vindex "&$host_port$&"
12771 This variable is set to the remote host's TCP port whenever &$host$& is set
12772 for an outbound connection.
12774 .vitem &$initial_cwd$&
12775 .vindex "&$initial_cwd$&
12776 This variable contains the full path name of the initial working
12777 directory of the current Exim process. This may differ from the current
12778 working directory, as Exim changes this to "/" during early startup, and
12779 to &$spool_directory$& later.
12782 .vindex "&$inode$&"
12783 The only time this variable is set is while expanding the &%directory_file%&
12784 option in the &(appendfile)& transport. The variable contains the inode number
12785 of the temporary file which is about to be renamed. It can be used to construct
12786 a unique name for the file.
12788 .vitem &$interface_address$& &&&
12790 .vindex "&$interface_address$&"
12791 .vindex "&$interface_port$&"
12792 These are obsolete names for &$received_ip_address$& and &$received_port$&.
12796 This variable is used during the expansion of &*forall*& and &*forany*&
12797 conditions (see section &<<SECTexpcond>>&), and &*filter*&, &*map*&, and
12798 &*reduce*& items (see section &<<SECTexpcond>>&). In other circumstances, it is
12802 .vindex "&$ldap_dn$&"
12803 This variable, which is available only when Exim is compiled with LDAP support,
12804 contains the DN from the last entry in the most recently successful LDAP
12807 .vitem &$load_average$&
12808 .vindex "&$load_average$&"
12809 This variable contains the system load average, multiplied by 1000 so that it
12810 is an integer. For example, if the load average is 0.21, the value of the
12811 variable is 210. The value is recomputed every time the variable is referenced.
12813 .tvar &$local_part$&
12814 When an address is being routed, or delivered on its own, this
12815 variable contains the local part. When a number of addresses are being
12816 delivered together (for example, multiple RCPT commands in an SMTP
12817 session), &$local_part$& is not set.
12819 Global address rewriting happens when a message is received, so the value of
12820 &$local_part$& during routing and delivery is the value after rewriting.
12821 &$local_part$& is set during user filtering, but not during system filtering,
12822 because a message may have many recipients and the system filter is called just
12825 .cindex "tainted data"
12826 If the origin of the data is an incoming message,
12827 the result of expanding this variable is tainted and
12828 may not be further expanded or used as a filename.
12830 &*Warning*&: the content of this variable is usually provided by a potential
12832 Consider carefully the implications of using it unvalidated as a name
12834 This presents issues for users' &_.forward_& and filter files.
12835 For traditional full user accounts, use &%check_local_users%& and the
12836 &$local_part_data$& variable rather than this one.
12837 For virtual users, store a suitable pathname component in the database
12838 which is used for account name validation, and use that retrieved value
12839 rather than this variable.
12840 Often &$local_part_data$& is usable in this role.
12841 If needed, use a router &%address_data%& or &%set%& option for
12842 the retrieved data.
12844 When a message is being delivered to a file, pipe, or autoreply transport as a
12845 result of aliasing or forwarding, &$local_part$& is set to the local part of
12846 the parent address, not to the filename or command (see &$address_file$& and
12849 When an ACL is running for a RCPT command, &$local_part$& contains the
12850 local part of the recipient address.
12852 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
12853 &$local_part$& contains the local part of the address that is being rewritten;
12854 it can be used in the expansion of the replacement address, for example.
12856 In all cases, all quoting is removed from the local part. For example, for both
12859 "abc:xyz"@test.example
12860 abc\:xyz@test.example
12862 the value of &$local_part$& is
12866 If you use &$local_part$& to create another address, you should always wrap it
12867 inside a quoting operator. For example, in a &(redirect)& router you could
12870 data = ${quote_local_part:$local_part}@new.domain.example
12872 &*Note*&: The value of &$local_part$& is normally lower cased. If you want
12873 to process local parts in a case-dependent manner in a router, you can set the
12874 &%caseful_local_part%& option (see chapter &<<CHAProutergeneric>>&).
12876 .vitem &$local_part_data$&
12877 .vindex "&$local_part_data$&"
12878 When the &%local_parts%& condition on a router or ACL
12879 matches a local part list
12880 the match value is copied to &$local_part_data$&.
12881 This is an enhancement over previous versions of Exim, when it only
12882 applied to the data read by a lookup.
12883 For details on match values see section &<<SECTlistresults>>& et. al.
12885 The &%check_local_user%& router option also sets this variable.
12887 .vindex &$local_part_prefix$& &&&
12888 &$local_part_prefix_v$& &&&
12889 &$local_part_suffix$& &&&
12890 &$local_part_suffix_v$&
12891 .cindex affix variables
12892 If a local part prefix or suffix has been recognized, it is not included in the
12893 value of &$local_part$& during routing and subsequent delivery. The values of
12894 any prefix or suffix are in &$local_part_prefix$& and
12895 &$local_part_suffix$&, respectively.
12896 .cindex "tainted data"
12897 If the specification did not include a wildcard then
12898 the affix variable value is not tainted.
12900 If the affix specification included a wildcard then the portion of
12901 the affix matched by the wildcard is in
12902 &$local_part_prefix_v$& or &$local_part_suffix_v$& as appropriate,
12903 and both the whole and varying values are tainted.
12905 .vitem &$local_scan_data$&
12906 .vindex "&$local_scan_data$&"
12907 This variable contains the text returned by the &[local_scan()]& function when
12908 a message is received. See chapter &<<CHAPlocalscan>>& for more details.
12910 .vitem &$local_user_gid$&
12911 .vindex "&$local_user_gid$&"
12912 See &$local_user_uid$&.
12914 .vitem &$local_user_uid$&
12915 .vindex "&$local_user_uid$&"
12916 This variable and &$local_user_gid$& are set to the uid and gid after the
12917 &%check_local_user%& router precondition succeeds. This means that their values
12918 are available for the remaining preconditions (&%senders%&, &%require_files%&,
12919 and &%condition%&), for the &%address_data%& expansion, and for any
12920 router-specific expansions. At all other times, the values in these variables
12921 are &`(uid_t)(-1)`& and &`(gid_t)(-1)`&, respectively.
12923 .vitem &$localhost_number$&
12924 .vindex "&$localhost_number$&"
12925 This contains the expanded value of the
12926 &%localhost_number%& option. The expansion happens after the main options have
12929 .vitem &$log_inodes$&
12930 .vindex "&$log_inodes$&"
12931 The number of free inodes in the disk partition where Exim's
12932 log files are being written. The value is recalculated whenever the variable is
12933 referenced. If the relevant file system does not have the concept of inodes,
12934 the value of is -1. See also the &%check_log_inodes%& option.
12936 .vitem &$log_space$&
12937 .vindex "&$log_space$&"
12938 The amount of free space (as a number of kilobytes) in the disk
12939 partition where Exim's log files are being written. The value is recalculated
12940 whenever the variable is referenced. If the operating system does not have the
12941 ability to find the amount of free space (only true for experimental systems),
12942 the space value is -1. See also the &%check_log_space%& option.
12945 .vitem &$lookup_dnssec_authenticated$&
12946 .vindex "&$lookup_dnssec_authenticated$&"
12947 This variable is set after a DNS lookup done by
12948 a dnsdb lookup expansion, dnslookup router or smtp transport.
12949 .cindex "DNS" "DNSSEC"
12950 It will be empty if &(DNSSEC)& was not requested,
12951 &"no"& if the result was not labelled as authenticated data
12952 and &"yes"& if it was.
12953 Results that are labelled as authoritative answer that match
12954 the &%dns_trust_aa%& configuration variable count also
12955 as authenticated data.
12957 .vitem &$mailstore_basename$&
12958 .vindex "&$mailstore_basename$&"
12959 This variable is set only when doing deliveries in &"mailstore"& format in the
12960 &(appendfile)& transport. During the expansion of the &%mailstore_prefix%&,
12961 &%mailstore_suffix%&, &%message_prefix%&, and &%message_suffix%& options, it
12962 contains the basename of the files that are being written, that is, the name
12963 without the &".tmp"&, &".env"&, or &".msg"& suffix. At all other times, this
12966 .vitem &$malware_name$&
12967 .vindex "&$malware_name$&"
12968 This variable is available when Exim is compiled with the
12969 content-scanning extension. It is set to the name of the virus that was found
12970 when the ACL &%malware%& condition is true (see section &<<SECTscanvirus>>&).
12972 .vitem &$max_received_linelength$&
12973 .vindex "&$max_received_linelength$&"
12974 .cindex "maximum" "line length"
12975 .cindex "line length" "maximum"
12976 This variable contains the number of bytes in the longest line that was
12977 received as part of the message, not counting the line termination
12979 It is not valid if the &%spool_wireformat%& option is used.
12981 .vitem &$message_age$&
12982 .cindex "message" "age of"
12983 .vindex "&$message_age$&"
12984 This variable is set at the start of a delivery attempt to contain the number
12985 of seconds since the message was received. It does not change during a single
12988 .tvar &$message_body$&
12989 .cindex "body of message" "expansion variable"
12990 .cindex "message body" "in expansion"
12991 .cindex "binary zero" "in message body"
12992 .oindex "&%message_body_visible%&"
12993 This variable contains the initial portion of a message's body while it is
12994 being delivered, and is intended mainly for use in filter files. The maximum
12995 number of characters of the body that are put into the variable is set by the
12996 &%message_body_visible%& configuration option; the default is 500.
12998 .oindex "&%message_body_newlines%&"
12999 By default, newlines are converted into spaces in &$message_body$&, to make it
13000 easier to search for phrases that might be split over a line break. However,
13001 this can be disabled by setting &%message_body_newlines%& to be true. Binary
13002 zeros are always converted into spaces.
13004 .tvar &$message_body_end$&
13005 .cindex "body of message" "expansion variable"
13006 .cindex "message body" "in expansion"
13007 This variable contains the final portion of a message's
13008 body while it is being delivered. The format and maximum size are as for
13011 .vitem &$message_body_size$&
13012 .cindex "body of message" "size"
13013 .cindex "message body" "size"
13014 .vindex "&$message_body_size$&"
13015 When a message is being delivered, this variable contains the size of the body
13016 in bytes. The count starts from the character after the blank line that
13017 separates the body from the header. Newlines are included in the count. See
13018 also &$message_size$&, &$body_linecount$&, and &$body_zerocount$&.
13020 If the spool file is wireformat
13021 (see the &%spool_wireformat%& main option)
13022 the CRLF line-terminators are included in the count.
13024 .vitem &$message_exim_id$&
13025 .vindex "&$message_exim_id$&"
13026 When a message is being received or delivered, this variable contains the
13027 unique message id that is generated and used by Exim to identify the message.
13028 An id is not created for a message until after its header has been successfully
13029 received. &*Note*&: This is &'not'& the contents of the &'Message-ID:'& header
13030 line; it is the local id that Exim assigns to the message, for example:
13031 &`1BXTIK-0001yO-VA`&.
13033 .tvar &$message_headers$&
13034 This variable contains a concatenation of all the header lines when a message
13035 is being processed, except for lines added by routers or transports. The header
13036 lines are separated by newline characters. Their contents are decoded in the
13037 same way as a header line that is inserted by &%bheader%&.
13039 .tvar &$message_headers_raw$&
13040 This variable is like &$message_headers$& except that no processing of the
13041 contents of header lines is done.
13043 .vitem &$message_id$&
13044 This is an old name for &$message_exim_id$&. It is now deprecated.
13046 .vitem &$message_linecount$&
13047 .vindex "&$message_linecount$&"
13048 This variable contains the total number of lines in the header and body of the
13049 message. Compare &$body_linecount$&, which is the count for the body only.
13050 During the DATA and content-scanning ACLs, &$message_linecount$& contains the
13051 number of lines received. Before delivery happens (that is, before filters,
13052 routers, and transports run) the count is increased to include the
13053 &'Received:'& header line that Exim standardly adds, and also any other header
13054 lines that are added by ACLs. The blank line that separates the message header
13055 from the body is not counted.
13057 As with the special case of &$message_size$&, during the expansion of the
13058 appendfile transport's maildir_tag option in maildir format, the value of
13059 &$message_linecount$& is the precise size of the number of newlines in the
13060 file that has been written (minus one for the blank line between the
13061 header and the body).
13063 Here is an example of the use of this variable in a DATA ACL:
13066 ${if <{250}{${eval:$message_linecount - $body_linecount}}}
13067 message = Too many lines in message header
13069 In the MAIL and RCPT ACLs, the value is zero because at that stage the
13070 message has not yet been received.
13072 This variable is not valid if the &%spool_wireformat%& option is used.
13074 .vitem &$message_size$&
13075 .cindex "size" "of message"
13076 .cindex "message" "size"
13077 .vindex "&$message_size$&"
13078 When a message is being processed, this variable contains its size in bytes. In
13079 most cases, the size includes those headers that were received with the
13080 message, but not those (such as &'Envelope-to:'&) that are added to individual
13081 deliveries as they are written. However, there is one special case: during the
13082 expansion of the &%maildir_tag%& option in the &(appendfile)& transport while
13083 doing a delivery in maildir format, the value of &$message_size$& is the
13084 precise size of the file that has been written. See also
13085 &$message_body_size$&, &$body_linecount$&, and &$body_zerocount$&.
13087 .cindex "RCPT" "value of &$message_size$&"
13088 While running a per message ACL (mail/rcpt/predata), &$message_size$&
13089 contains the size supplied on the MAIL command, or -1 if no size was given. The
13090 value may not, of course, be truthful.
13092 .vitem &$mime_anomaly_level$& &&&
13093 &$mime_anomaly_text$& &&&
13094 &$mime_boundary$& &&&
13095 &$mime_charset$& &&&
13096 &$mime_content_description$& &&&
13097 &$mime_content_disposition$& &&&
13098 &$mime_content_id$& &&&
13099 &$mime_content_size$& &&&
13100 &$mime_content_transfer_encoding$& &&&
13101 &$mime_content_type$& &&&
13102 &$mime_decoded_filename$& &&&
13103 &$mime_filename$& &&&
13104 &$mime_is_coverletter$& &&&
13105 &$mime_is_multipart$& &&&
13106 &$mime_is_rfc822$& &&&
13107 &$mime_part_count$&
13108 A number of variables whose names start with &$mime$& are
13109 available when Exim is compiled with the content-scanning extension. For
13110 details, see section &<<SECTscanmimepart>>&.
13112 .vitem "&$n0$& &-- &$n9$&"
13113 These variables are counters that can be incremented by means
13114 of the &%add%& command in filter files.
13116 .tvar &$original_domain$&
13117 .vindex "&$domain$&"
13118 When a top-level address is being processed for delivery, this contains the
13119 same value as &$domain$&. However, if a &"child"& address (for example,
13120 generated by an alias, forward, or filter file) is being processed, this
13121 variable contains the domain of the original address (lower cased). This
13122 differs from &$parent_domain$& only when there is more than one level of
13123 aliasing or forwarding. When more than one address is being delivered in a
13124 single transport run, &$original_domain$& is not set.
13126 If a new address is created by means of a &%deliver%& command in a system
13127 filter, it is set up with an artificial &"parent"& address. This has the local
13128 part &'system-filter'& and the default qualify domain.
13130 .tvar &$original_local_part$&
13131 .vindex "&$local_part$&"
13132 When a top-level address is being processed for delivery, this contains the
13133 same value as &$local_part$&, unless a prefix or suffix was removed from the
13134 local part, because &$original_local_part$& always contains the full local
13135 part. When a &"child"& address (for example, generated by an alias, forward, or
13136 filter file) is being processed, this variable contains the full local part of
13137 the original address.
13139 If the router that did the redirection processed the local part
13140 case-insensitively, the value in &$original_local_part$& is in lower case.
13141 This variable differs from &$parent_local_part$& only when there is more than
13142 one level of aliasing or forwarding. When more than one address is being
13143 delivered in a single transport run, &$original_local_part$& is not set.
13145 If a new address is created by means of a &%deliver%& command in a system
13146 filter, it is set up with an artificial &"parent"& address. This has the local
13147 part &'system-filter'& and the default qualify domain.
13149 .vitem &$originator_gid$&
13150 .cindex "gid (group id)" "of originating user"
13151 .cindex "sender" "gid"
13152 .vindex "&$caller_gid$&"
13153 .vindex "&$originator_gid$&"
13154 This variable contains the value of &$caller_gid$& that was set when the
13155 message was received. For messages received via the command line, this is the
13156 gid of the sending user. For messages received by SMTP over TCP/IP, this is
13157 normally the gid of the Exim user.
13159 .vitem &$originator_uid$&
13160 .cindex "uid (user id)" "of originating user"
13161 .cindex "sender" "uid"
13162 .vindex "&$caller_uid$&"
13163 .vindex "&$originator_uid$&"
13164 The value of &$caller_uid$& that was set when the message was received. For
13165 messages received via the command line, this is the uid of the sending user.
13166 For messages received by SMTP over TCP/IP, this is normally the uid of the Exim
13169 .tvar &$parent_domain$&
13170 This variable is similar to &$original_domain$& (see
13171 above), except that it refers to the immediately preceding parent address.
13173 .tvar &$parent_local_part$&
13174 This variable is similar to &$original_local_part$&
13175 (see above), except that it refers to the immediately preceding parent address.
13178 .cindex "pid (process id)" "of current process"
13180 This variable contains the current process id.
13182 .vitem &$pipe_addresses$&
13183 .cindex "filter" "transport filter"
13184 .cindex "transport" "filter"
13185 .vindex "&$pipe_addresses$&"
13186 This is not an expansion variable, but is mentioned here because the string
13187 &`$pipe_addresses`& is handled specially in the command specification for the
13188 &(pipe)& transport (chapter &<<CHAPpipetransport>>&) and in transport filters
13189 (described under &%transport_filter%& in chapter &<<CHAPtransportgeneric>>&).
13190 It cannot be used in general expansion strings, and provokes an &"unknown
13191 variable"& error if encountered.
13192 &*Note*&: This value permits data supplied by a potential attacker to
13193 be used in the command for a &(pipe)& transport.
13194 Such configurations should be carefully assessed for security vulnerbilities.
13196 .vitem &$primary_hostname$&
13197 .vindex "&$primary_hostname$&"
13198 This variable contains the value set by &%primary_hostname%& in the
13199 configuration file, or read by the &[uname()]& function. If &[uname()]& returns
13200 a single-component name, Exim calls &[gethostbyname()]& (or
13201 &[getipnodebyname()]& where available) in an attempt to acquire a fully
13202 qualified host name. See also &$smtp_active_hostname$&.
13205 .vitem &$proxy_external_address$& &&&
13206 &$proxy_external_port$& &&&
13207 &$proxy_local_address$& &&&
13208 &$proxy_local_port$& &&&
13210 These variables are only available when built with Proxy Protocol
13212 For details see chapter &<<SECTproxyInbound>>&.
13214 .vitem &$prdr_requested$&
13215 .cindex "PRDR" "variable for"
13216 This variable is set to &"yes"& if PRDR was requested by the client for the
13217 current message, otherwise &"no"&.
13219 .vitem &$prvscheck_address$& &&&
13220 &$prvscheck_keynum$& &&&
13221 &$prvscheck_result$&
13222 These variables are used in conjunction with the &%prvscheck%& expansion item,
13223 which is described in sections &<<SECTexpansionitems>>& and
13224 &<<SECTverifyPRVS>>&.
13226 .vitem &$qualify_domain$&
13227 .vindex "&$qualify_domain$&"
13228 The value set for the &%qualify_domain%& option in the configuration file.
13230 .vitem &$qualify_recipient$&
13231 .vindex "&$qualify_recipient$&"
13232 The value set for the &%qualify_recipient%& option in the configuration file,
13233 or if not set, the value of &$qualify_domain$&.
13235 .vitem &$queue_name$&
13236 .vindex &$queue_name$&
13237 .cindex "named queues" variable
13238 .cindex queues named
13239 The name of the spool queue in use; empty for the default queue.
13241 .vitem &$queue_size$&
13242 .vindex "&$queue_size$&"
13243 .cindex "queue" "size of"
13244 .cindex "spool" "number of messages"
13245 This variable contains the number of messages queued.
13246 It is evaluated on demand, but no more often than once every minute.
13247 If there is no daemon notifier socket open, the value will be
13252 .cindex router variables
13253 Values can be placed in these variables by the &%set%& option of a router.
13254 They can be given any name that starts with &$r_$&.
13255 The values persist for the address being handled through subsequent routers
13256 and the eventual transport.
13258 .vitem &$rcpt_count$&
13259 .vindex "&$rcpt_count$&"
13260 When a message is being received by SMTP, this variable contains the number of
13261 RCPT commands received for the current message. If this variable is used in a
13262 RCPT ACL, its value includes the current command.
13264 .vitem &$rcpt_defer_count$&
13265 .vindex "&$rcpt_defer_count$&"
13266 .cindex "4&'xx'& responses" "count of"
13267 When a message is being received by SMTP, this variable contains the number of
13268 RCPT commands in the current message that have previously been rejected with a
13269 temporary (4&'xx'&) response.
13271 .vitem &$rcpt_fail_count$&
13272 .vindex "&$rcpt_fail_count$&"
13273 When a message is being received by SMTP, this variable contains the number of
13274 RCPT commands in the current message that have previously been rejected with a
13275 permanent (5&'xx'&) response.
13277 .vitem &$received_count$&
13278 .vindex "&$received_count$&"
13279 This variable contains the number of &'Received:'& header lines in the message,
13280 including the one added by Exim (so its value is always greater than zero). It
13281 is available in the DATA ACL, the non-SMTP ACL, and while routing and
13284 .tvar &$received_for$&
13285 If there is only a single recipient address in an incoming message, this
13286 variable contains that address when the &'Received:'& header line is being
13287 built. The value is copied after recipient rewriting has happened, but before
13288 the &[local_scan()]& function is run.
13290 .vitem &$received_ip_address$& &&&
13292 .vindex "&$received_ip_address$&"
13293 .vindex "&$received_port$&"
13294 As soon as an Exim server starts processing an incoming TCP/IP connection, these
13295 variables are set to the address and port on the local IP interface.
13296 (The remote IP address and port are in
13297 &$sender_host_address$& and &$sender_host_port$&.) When testing with &%-bh%&,
13298 the port value is -1 unless it has been set using the &%-oMi%& command line
13301 As well as being useful in ACLs (including the &"connect"& ACL), these variable
13302 could be used, for example, to make the filename for a TLS certificate depend
13303 on which interface and/or port is being used for the incoming connection. The
13304 values of &$received_ip_address$& and &$received_port$& are saved with any
13305 messages that are received, thus making these variables available at delivery
13307 For outbound connections see &$sending_ip_address$&.
13309 .vitem &$received_protocol$&
13310 .vindex "&$received_protocol$&"
13311 When a message is being processed, this variable contains the name of the
13312 protocol by which it was received. Most of the names used by Exim are defined
13313 by RFCs 821, 2821, and 3848. They start with &"smtp"& (the client used HELO) or
13314 &"esmtp"& (the client used EHLO). This can be followed by &"s"& for secure
13315 (encrypted) and/or &"a"& for authenticated. Thus, for example, if the protocol
13316 is set to &"esmtpsa"&, the message was received over an encrypted SMTP
13317 connection and the client was successfully authenticated.
13319 Exim uses the protocol name &"smtps"& for the case when encryption is
13320 automatically set up on connection without the use of STARTTLS (see
13321 &%tls_on_connect_ports%&), and the client uses HELO to initiate the
13322 encrypted SMTP session. The name &"smtps"& is also used for the rare situation
13323 where the client initially uses EHLO, sets up an encrypted connection using
13324 STARTTLS, and then uses HELO afterwards.
13326 The &%-oMr%& option provides a way of specifying a custom protocol name for
13327 messages that are injected locally by trusted callers. This is commonly used to
13328 identify messages that are being re-injected after some kind of scanning.
13330 .vitem &$received_time$&
13331 .vindex "&$received_time$&"
13332 This variable contains the date and time when the current message was received,
13333 as a number of seconds since the start of the Unix epoch.
13335 .vitem &$recipient_data$&
13336 .vindex "&$recipient_data$&"
13337 This variable is set after an indexing lookup success in an ACL &%recipients%&
13338 condition. It contains the data from the lookup, and the value remains set
13339 until the next &%recipients%& test. Thus, you can do things like this:
13341 &`require recipients = cdb*@;/some/file`&
13342 &`deny `&&'some further test involving'& &`$recipient_data`&
13344 &*Warning*&: This variable is set only when a lookup is used as an indexing
13345 method in the address list, using the semicolon syntax as in the example above.
13346 The variable is not set for a lookup that is used as part of the string
13347 expansion that all such lists undergo before being interpreted.
13349 .vitem &$recipient_verify_failure$&
13350 .vindex "&$recipient_verify_failure$&"
13351 In an ACL, when a recipient verification fails, this variable contains
13352 information about the failure. It is set to one of the following words:
13355 &"qualify"&: The address was unqualified (no domain), and the message
13356 was neither local nor came from an exempted host.
13359 &"route"&: Routing failed.
13362 &"mail"&: Routing succeeded, and a callout was attempted; rejection occurred at
13363 or before the MAIL command (that is, on initial connection, HELO, or
13367 &"recipient"&: The RCPT command in a callout was rejected.
13370 &"postmaster"&: The postmaster check in a callout was rejected.
13373 The main use of this variable is expected to be to distinguish between
13374 rejections of MAIL and rejections of RCPT.
13376 .tvar &$recipients$&
13377 This variable contains a list of envelope recipients for a message. A comma and
13378 a space separate the addresses in the replacement text. However, the variable
13379 is not generally available, to prevent exposure of Bcc recipients in
13380 unprivileged users' filter files. You can use &$recipients$& only in these
13384 In a system filter file.
13386 In the ACLs associated with the DATA command and with non-SMTP messages, that
13387 is, the ACLs defined by &%acl_smtp_predata%&, &%acl_smtp_data%&,
13388 &%acl_smtp_mime%&, &%acl_not_smtp_start%&, &%acl_not_smtp%&, and
13389 &%acl_not_smtp_mime%&.
13391 From within a &[local_scan()]& function.
13395 .vitem &$recipients_count$&
13396 .vindex "&$recipients_count$&"
13397 When a message is being processed, this variable contains the number of
13398 envelope recipients that came with the message. Duplicates are not excluded
13399 from the count. While a message is being received over SMTP, the number
13400 increases for each accepted recipient. It can be referenced in an ACL.
13403 .vitem &$regex_match_string$&
13404 .vindex "&$regex_match_string$&"
13405 This variable is set to contain the matching regular expression after a
13406 &%regex%& ACL condition has matched (see section &<<SECTscanregex>>&).
13408 .vitem "&$regex1$&, &$regex2$&, etc"
13409 .cindex "regex submatch variables (&$1regex$& &$2regex$& etc)"
13410 When a &%regex%& or &%mime_regex%& ACL condition succeeds,
13411 these variables contain the
13412 captured substrings identified by the regular expression.
13413 If the subject string was tainted then so will any captured substring.
13416 .tvar &$reply_address$&
13417 When a message is being processed, this variable contains the contents of the
13418 &'Reply-To:'& header line if one exists and it is not empty, or otherwise the
13419 contents of the &'From:'& header line. Apart from the removal of leading
13420 white space, the value is not processed in any way. In particular, no RFC 2047
13421 decoding or character code translation takes place.
13423 .vitem &$return_path$&
13424 .vindex "&$return_path$&"
13425 When a message is being delivered, this variable contains the return path &--
13426 the sender field that will be sent as part of the envelope. It is not enclosed
13427 in <> characters. At the start of routing an address, &$return_path$& has the
13428 same value as &$sender_address$&, but if, for example, an incoming message to a
13429 mailing list has been expanded by a router which specifies a different address
13430 for bounce messages, &$return_path$& subsequently contains the new bounce
13431 address, whereas &$sender_address$& always contains the original sender address
13432 that was received with the message. In other words, &$sender_address$& contains
13433 the incoming envelope sender, and &$return_path$& contains the outgoing
13436 .vitem &$return_size_limit$&
13437 .vindex "&$return_size_limit$&"
13438 This is an obsolete name for &$bounce_return_size_limit$&.
13440 .vitem &$router_name$&
13441 .cindex "router" "name"
13442 .cindex "name" "of router"
13443 .vindex "&$router_name$&"
13444 During the running of a router this variable contains its name.
13447 .cindex "return code" "from &%run%& expansion"
13448 .vindex "&$runrc$&"
13449 This variable contains the return code from a command that is run by the
13450 &%${run...}%& expansion item. &*Warning*&: In a router or transport, you cannot
13451 assume the order in which option values are expanded, except for those
13452 preconditions whose order of testing is documented. Therefore, you cannot
13453 reliably expect to set &$runrc$& by the expansion of one option, and use it in
13456 .vitem &$self_hostname$&
13457 .oindex "&%self%&" "value of host name"
13458 .vindex "&$self_hostname$&"
13459 When an address is routed to a supposedly remote host that turns out to be the
13460 local host, what happens is controlled by the &%self%& generic router option.
13461 One of its values causes the address to be passed to another router. When this
13462 happens, &$self_hostname$& is set to the name of the local host that the
13463 original router encountered. In other circumstances its contents are null.
13465 .tvar &$sender_address$&
13466 When a message is being processed, this variable contains the sender's address
13467 that was received in the message's envelope. The case of letters in the address
13468 is retained, in both the local part and the domain. For bounce messages, the
13469 value of this variable is the empty string. See also &$return_path$&.
13471 .vitem &$sender_address_data$&
13472 .vindex "&$address_data$&"
13473 .vindex "&$sender_address_data$&"
13474 If &$address_data$& is set when the routers are called from an ACL to verify a
13475 sender address, the final value is preserved in &$sender_address_data$&, to
13476 distinguish it from data from a recipient address. The value does not persist
13477 after the end of the current ACL statement. If you want to preserve it for
13478 longer, you can save it in an ACL variable.
13480 .tvar &$sender_address_domain$&
13481 The domain portion of &$sender_address$&.
13483 .tvar &$sender_address_local_part$&
13484 The local part portion of &$sender_address$&.
13486 .vitem &$sender_data$&
13487 .vindex "&$sender_data$&"
13488 This variable is set after a lookup success in an ACL &%senders%& condition or
13489 in a router &%senders%& option. It contains the data from the lookup, and the
13490 value remains set until the next &%senders%& test. Thus, you can do things like
13493 &`require senders = cdb*@;/some/file`&
13494 &`deny `&&'some further test involving'& &`$sender_data`&
13496 &*Warning*&: This variable is set only when a lookup is used as an indexing
13497 method in the address list, using the semicolon syntax as in the example above.
13498 The variable is not set for a lookup that is used as part of the string
13499 expansion that all such lists undergo before being interpreted.
13501 .vitem &$sender_fullhost$&
13502 .vindex "&$sender_fullhost$&"
13503 When a message is received from a remote host, this variable contains the host
13504 name and IP address in a single string. It ends with the IP address in square
13505 brackets, followed by a colon and a port number if the logging of ports is
13506 enabled. The format of the rest of the string depends on whether the host
13507 issued a HELO or EHLO SMTP command, and whether the host name was verified by
13508 looking up its IP address. (Looking up the IP address can be forced by the
13509 &%host_lookup%& option, independent of verification.) A plain host name at the
13510 start of the string is a verified host name; if this is not present,
13511 verification either failed or was not requested. A host name in parentheses is
13512 the argument of a HELO or EHLO command. This is omitted if it is identical to
13513 the verified host name or to the host's IP address in square brackets.
13515 .vitem &$sender_helo_dnssec$&
13516 .vindex "&$sender_helo_dnssec$&"
13517 This boolean variable is true if a successful HELO verification was
13518 .cindex "DNS" "DNSSEC"
13519 done using DNS information the resolver library stated was authenticated data.
13521 .tvar &$sender_helo_name$&
13522 When a message is received from a remote host that has issued a HELO or EHLO
13523 command, the argument of that command is placed in this variable. It is also
13524 set if HELO or EHLO is used when a message is received using SMTP locally via
13525 the &%-bs%& or &%-bS%& options.
13527 .vitem &$sender_host_address$&
13528 .vindex "&$sender_host_address$&"
13529 When a message is received from a remote host using SMTP,
13530 this variable contains that
13531 host's IP address. For locally non-SMTP submitted messages, it is empty.
13533 .vitem &$sender_host_authenticated$&
13534 .vindex "&$sender_host_authenticated$&"
13535 This variable contains the name (not the public name) of the authenticator
13536 driver that successfully authenticated the client from which the message was
13537 received. It is empty if there was no successful authentication. See also
13538 &$authenticated_id$&.
13540 .vitem &$sender_host_dnssec$&
13541 .vindex "&$sender_host_dnssec$&"
13542 If an attempt to populate &$sender_host_name$& has been made
13543 (by reference, &%hosts_lookup%& or
13544 otherwise) then this boolean will have been set true if, and only if, the
13545 resolver library states that both
13546 the reverse and forward DNS were authenticated data. At all
13547 other times, this variable is false.
13549 .cindex "DNS" "DNSSEC"
13550 It is likely that you will need to coerce DNSSEC support on in the resolver
13551 library, by setting:
13556 In addition, on Linux with glibc 2.31 or newer the resolver library will
13557 default to stripping out a successful validation status.
13558 This will break a previously working Exim installation.
13559 Provided that you do trust the resolver (ie, is on localhost) you can tell
13560 glibc to pass through any successful validation with a new option in
13561 &_/etc/resolv.conf_&:
13566 Exim does not perform DNSSEC validation itself, instead leaving that to a
13567 validating resolver (e.g. unbound, or bind with suitable configuration).
13569 If you have changed &%host_lookup_order%& so that &`bydns`& is not the first
13570 mechanism in the list, then this variable will be false.
13572 This requires that your system resolver library support EDNS0 (and that
13573 DNSSEC flags exist in the system headers). If the resolver silently drops
13574 all EDNS0 options, then this will have no effect. OpenBSD's asr resolver
13575 is known to currently ignore EDNS0, documented in CAVEATS of asr_run(3).
13578 .tvar &$sender_host_name$&
13579 When a message is received from a remote host, this variable contains the
13580 host's name as obtained by looking up its IP address. For messages received by
13581 other means, this variable is empty.
13583 .vindex "&$host_lookup_failed$&"
13584 If the host name has not previously been looked up, a reference to
13585 &$sender_host_name$& triggers a lookup (for messages from remote hosts).
13586 A looked up name is accepted only if it leads back to the original IP address
13587 via a forward lookup. If either the reverse or the forward lookup fails to find
13588 any data, or if the forward lookup does not yield the original IP address,
13589 &$sender_host_name$& remains empty, and &$host_lookup_failed$& is set to &"1"&.
13591 .vindex "&$host_lookup_deferred$&"
13592 However, if either of the lookups cannot be completed (for example, there is a
13593 DNS timeout), &$host_lookup_deferred$& is set to &"1"&, and
13594 &$host_lookup_failed$& remains set to &"0"&.
13596 Once &$host_lookup_failed$& is set to &"1"&, Exim does not try to look up the
13597 host name again if there is a subsequent reference to &$sender_host_name$&
13598 in the same Exim process, but it does try again if &$host_lookup_deferred$&
13601 Exim does not automatically look up every calling host's name. If you want
13602 maximum efficiency, you should arrange your configuration so that it avoids
13603 these lookups altogether. The lookup happens only if one or more of the
13604 following are true:
13607 A string containing &$sender_host_name$& is expanded.
13609 The calling host matches the list in &%host_lookup%&. In the default
13610 configuration, this option is set to *, so it must be changed if lookups are
13611 to be avoided. (In the code, the default for &%host_lookup%& is unset.)
13613 Exim needs the host name in order to test an item in a host list. The items
13614 that require this are described in sections &<<SECThoslispatnam>>& and
13615 &<<SECThoslispatnamsk>>&.
13617 The calling host matches &%helo_try_verify_hosts%& or &%helo_verify_hosts%&.
13618 In this case, the host name is required to compare with the name quoted in any
13619 EHLO or HELO commands that the client issues.
13621 The remote host issues a EHLO or HELO command that quotes one of the
13622 domains in &%helo_lookup_domains%&. The default value of this option is
13623 . ==== As this is a nested list, any displays it contains must be indented
13624 . ==== as otherwise they are too far to the left.
13626 helo_lookup_domains = @ : @[]
13628 which causes a lookup if a remote host (incorrectly) gives the server's name or
13629 IP address in an EHLO or HELO command.
13633 .vitem &$sender_host_port$&
13634 .vindex "&$sender_host_port$&"
13635 When a message is received from a remote host, this variable contains the port
13636 number that was used on the remote host.
13638 .vitem &$sender_ident$&
13639 .vindex "&$sender_ident$&"
13640 When a message is received from a remote host, this variable contains the
13641 identification received in response to an RFC 1413 request. When a message has
13642 been received locally, this variable contains the login name of the user that
13645 .vitem &$sender_rate_$&&'xxx'&
13646 A number of variables whose names begin &$sender_rate_$& are set as part of the
13647 &%ratelimit%& ACL condition. Details are given in section
13648 &<<SECTratelimiting>>&.
13650 .vitem &$sender_rcvhost$&
13651 .cindex "DNS" "reverse lookup"
13652 .cindex "reverse DNS lookup"
13653 .vindex "&$sender_rcvhost$&"
13654 This is provided specifically for use in &'Received:'& headers. It starts with
13655 either the verified host name (as obtained from a reverse DNS lookup) or, if
13656 there is no verified host name, the IP address in square brackets. After that
13657 there may be text in parentheses. When the first item is a verified host name,
13658 the first thing in the parentheses is the IP address in square brackets,
13659 followed by a colon and a port number if port logging is enabled. When the
13660 first item is an IP address, the port is recorded as &"port=&'xxxx'&"& inside
13663 There may also be items of the form &"helo=&'xxxx'&"& if HELO or EHLO
13664 was used and its argument was not identical to the real host name or IP
13665 address, and &"ident=&'xxxx'&"& if an RFC 1413 ident string is available. If
13666 all three items are present in the parentheses, a newline and tab are inserted
13667 into the string, to improve the formatting of the &'Received:'& header.
13669 .vitem &$sender_verify_failure$&
13670 .vindex "&$sender_verify_failure$&"
13671 In an ACL, when a sender verification fails, this variable contains information
13672 about the failure. The details are the same as for
13673 &$recipient_verify_failure$&.
13675 .vitem &$sending_ip_address$&
13676 .vindex "&$sending_ip_address$&"
13677 This variable is set whenever an outgoing SMTP connection to another host has
13678 been set up. It contains the IP address of the local interface that is being
13679 used. This is useful if a host that has more than one IP address wants to take
13680 on different personalities depending on which one is being used. For incoming
13681 connections, see &$received_ip_address$&.
13683 .vitem &$sending_port$&
13684 .vindex "&$sending_port$&"
13685 This variable is set whenever an outgoing SMTP connection to another host has
13686 been set up. It contains the local port that is being used. For incoming
13687 connections, see &$received_port$&.
13689 .vitem &$smtp_active_hostname$&
13690 .vindex "&$smtp_active_hostname$&"
13691 During an incoming SMTP session, this variable contains the value of the active
13692 host name, as specified by the &%smtp_active_hostname%& option. The value of
13693 &$smtp_active_hostname$& is saved with any message that is received, so its
13694 value can be consulted during routing and delivery.
13696 .tvar &$smtp_command$&
13697 During the processing of an incoming SMTP command, this variable contains the
13698 entire command. This makes it possible to distinguish between HELO and EHLO in
13699 the HELO ACL, and also to distinguish between commands such as these:
13704 For a MAIL command, extra parameters such as SIZE can be inspected. For a RCPT
13705 command, the address in &$smtp_command$& is the original address before any
13706 rewriting, whereas the values in &$local_part$& and &$domain$& are taken from
13707 the address after SMTP-time rewriting.
13709 .tvar &$smtp_command_argument$&
13710 .cindex "SMTP" "command, argument for"
13711 While an ACL is running to check an SMTP command, this variable contains the
13712 argument, that is, the text that follows the command name, with leading white
13713 space removed. Following the introduction of &$smtp_command$&, this variable is
13714 somewhat redundant, but is retained for backwards compatibility.
13716 .vitem &$smtp_command_history$&
13717 .cindex SMTP "command history"
13718 .vindex "&$smtp_command_history$&"
13719 A comma-separated list (with no whitespace) of the most-recent SMTP commands
13720 received, in time-order left to right. Only a limited number of commands
13723 .vitem &$smtp_count_at_connection_start$&
13724 .vindex "&$smtp_count_at_connection_start$&"
13725 This variable is set greater than zero only in processes spawned by the Exim
13726 daemon for handling incoming SMTP connections. The name is deliberately long,
13727 in order to emphasize what the contents are. When the daemon accepts a new
13728 connection, it increments this variable. A copy of the variable is passed to
13729 the child process that handles the connection, but its value is fixed, and
13730 never changes. It is only an approximation of how many incoming connections
13731 there actually are, because many other connections may come and go while a
13732 single connection is being processed. When a child process terminates, the
13733 daemon decrements its copy of the variable.
13735 .vitem "&$sn0$& &-- &$sn9$&"
13736 These variables are copies of the values of the &$n0$& &-- &$n9$& accumulators
13737 that were current at the end of the system filter file. This allows a system
13738 filter file to set values that can be tested in users' filter files. For
13739 example, a system filter could set a value indicating how likely it is that a
13740 message is junk mail.
13742 .vitem &$spam_score$& &&&
13743 &$spam_score_int$& &&&
13745 &$spam_report$& &&&
13747 A number of variables whose names start with &$spam$& are available when Exim
13748 is compiled with the content-scanning extension. For details, see section
13749 &<<SECTscanspamass>>&.
13751 .vitem &$spf_header_comment$& &&&
13752 &$spf_received$& &&&
13754 &$spf_result_guessed$& &&&
13755 &$spf_smtp_comment$&
13756 These variables are only available if Exim is built with SPF support.
13757 For details see section &<<SECSPF>>&.
13759 .vitem &$spool_directory$&
13760 .vindex "&$spool_directory$&"
13761 The name of Exim's spool directory.
13763 .vitem &$spool_inodes$&
13764 .vindex "&$spool_inodes$&"
13765 The number of free inodes in the disk partition where Exim's spool files are
13766 being written. The value is recalculated whenever the variable is referenced.
13767 If the relevant file system does not have the concept of inodes, the value of
13768 is -1. See also the &%check_spool_inodes%& option.
13770 .vitem &$spool_space$&
13771 .vindex "&$spool_space$&"
13772 The amount of free space (as a number of kilobytes) in the disk partition where
13773 Exim's spool files are being written. The value is recalculated whenever the
13774 variable is referenced. If the operating system does not have the ability to
13775 find the amount of free space (only true for experimental systems), the space
13776 value is -1. For example, to check in an ACL that there is at least 50
13777 megabytes free on the spool, you could write:
13779 condition = ${if > {$spool_space}{50000}}
13781 See also the &%check_spool_space%& option.
13784 .vitem &$thisaddress$&
13785 .vindex "&$thisaddress$&"
13786 This variable is set only during the processing of the &%foranyaddress%&
13787 command in a filter file. Its use is explained in the description of that
13788 command, which can be found in the separate document entitled &'Exim's
13789 interfaces to mail filtering'&.
13791 .vitem &$tls_in_bits$&
13792 .vindex "&$tls_in_bits$&"
13793 Contains an approximation of the TLS cipher's bit-strength
13794 on the inbound connection; the meaning of
13795 this depends upon the TLS implementation used.
13796 If TLS has not been negotiated, the value will be 0.
13797 The value of this is automatically fed into the Cyrus SASL authenticator
13798 when acting as a server, to specify the "external SSF" (a SASL term).
13800 The deprecated &$tls_bits$& variable refers to the inbound side
13801 except when used in the context of an outbound SMTP delivery, when it refers to
13804 .vitem &$tls_out_bits$&
13805 .vindex "&$tls_out_bits$&"
13806 Contains an approximation of the TLS cipher's bit-strength
13807 on an outbound SMTP connection; the meaning of
13808 this depends upon the TLS implementation used.
13809 If TLS has not been negotiated, the value will be 0.
13811 .vitem &$tls_in_ourcert$&
13812 .vindex "&$tls_in_ourcert$&"
13813 .cindex certificate variables
13814 This variable refers to the certificate presented to the peer of an
13815 inbound connection when the message was received.
13816 It is only useful as the argument of a
13817 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13818 or a &%def%& condition.
13820 &*Note*&: Under versions of OpenSSL preceding 1.1.1,
13821 when a list of more than one
13822 file is used for &%tls_certificate%&, this variable is not reliable.
13823 The macro "_TLS_BAD_MULTICERT_IN_OURCERT" will be defined for those versions.
13825 .vitem &$tls_in_peercert$&
13826 .vindex "&$tls_in_peercert$&"
13827 This variable refers to the certificate presented by the peer of an
13828 inbound connection when the message was received.
13829 It is only useful as the argument of a
13830 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13831 or a &%def%& condition.
13832 If certificate verification fails it may refer to a failing chain element
13833 which is not the leaf.
13835 .vitem &$tls_out_ourcert$&
13836 .vindex "&$tls_out_ourcert$&"
13837 This variable refers to the certificate presented to the peer of an
13838 outbound connection. It is only useful as the argument of a
13839 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13840 or a &%def%& condition.
13842 .vitem &$tls_out_peercert$&
13843 .vindex "&$tls_out_peercert$&"
13844 This variable refers to the certificate presented by the peer of an
13845 outbound connection. It is only useful as the argument of a
13846 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13847 or a &%def%& condition.
13848 If certificate verification fails it may refer to a failing chain element
13849 which is not the leaf.
13851 .vitem &$tls_in_certificate_verified$&
13852 .vindex "&$tls_in_certificate_verified$&"
13853 This variable is set to &"1"& if a TLS certificate was verified when the
13854 message was received, and &"0"& otherwise.
13856 The deprecated &$tls_certificate_verified$& variable refers to the inbound side
13857 except when used in the context of an outbound SMTP delivery, when it refers to
13860 .vitem &$tls_out_certificate_verified$&
13861 .vindex "&$tls_out_certificate_verified$&"
13862 This variable is set to &"1"& if a TLS certificate was verified when an
13863 outbound SMTP connection was made,
13864 and &"0"& otherwise.
13866 .vitem &$tls_in_cipher$&
13867 .vindex "&$tls_in_cipher$&"
13868 .vindex "&$tls_cipher$&"
13869 When a message is received from a remote host over an encrypted SMTP
13870 connection, this variable is set to the cipher suite that was negotiated, for
13871 example DES-CBC3-SHA. In other circumstances, in particular, for message
13872 received over unencrypted connections, the variable is empty. Testing
13873 &$tls_in_cipher$& for emptiness is one way of distinguishing between encrypted and
13874 non-encrypted connections during ACL processing.
13876 The deprecated &$tls_cipher$& variable is the same as &$tls_in_cipher$& during message reception,
13877 but in the context of an outward SMTP delivery taking place via the &(smtp)& transport
13878 becomes the same as &$tls_out_cipher$&.
13880 .vitem &$tls_in_cipher_std$&
13881 .vindex "&$tls_in_cipher_std$&"
13882 As above, but returning the RFC standard name for the cipher suite.
13884 .vitem &$tls_out_cipher$&
13885 .vindex "&$tls_out_cipher$&"
13887 cleared before any outgoing SMTP connection is made,
13888 and then set to the outgoing cipher suite if one is negotiated. See chapter
13889 &<<CHAPTLS>>& for details of TLS support and chapter &<<CHAPsmtptrans>>& for
13890 details of the &(smtp)& transport.
13892 .vitem &$tls_out_cipher_std$&
13893 .vindex "&$tls_out_cipher_std$&"
13894 As above, but returning the RFC standard name for the cipher suite.
13896 .vitem &$tls_out_dane$&
13897 .vindex &$tls_out_dane$&
13898 DANE active status. See section &<<SECDANE>>&.
13900 .vitem &$tls_in_ocsp$&
13901 .vindex "&$tls_in_ocsp$&"
13902 When a message is received from a remote client connection
13903 the result of any OCSP request from the client is encoded in this variable:
13905 0 OCSP proof was not requested (default value)
13906 1 No response to request
13907 2 Response not verified
13908 3 Verification failed
13909 4 Verification succeeded
13912 .vitem &$tls_out_ocsp$&
13913 .vindex "&$tls_out_ocsp$&"
13914 When a message is sent to a remote host connection
13915 the result of any OCSP request made is encoded in this variable.
13916 See &$tls_in_ocsp$& for values.
13918 .vitem &$tls_in_peerdn$&
13919 .vindex "&$tls_in_peerdn$&"
13920 .vindex "&$tls_peerdn$&"
13921 .cindex certificate "extracting fields"
13922 When a message is received from a remote host over an encrypted SMTP
13923 connection, and Exim is configured to request a certificate from the client,
13924 the value of the Distinguished Name of the certificate is made available in the
13925 &$tls_in_peerdn$& during subsequent processing.
13926 If certificate verification fails it may refer to a failing chain element
13927 which is not the leaf.
13929 The deprecated &$tls_peerdn$& variable refers to the inbound side
13930 except when used in the context of an outbound SMTP delivery, when it refers to
13933 .vitem &$tls_out_peerdn$&
13934 .vindex "&$tls_out_peerdn$&"
13935 When a message is being delivered to a remote host over an encrypted SMTP
13936 connection, and Exim is configured to request a certificate from the server,
13937 the value of the Distinguished Name of the certificate is made available in the
13938 &$tls_out_peerdn$& during subsequent processing.
13939 If certificate verification fails it may refer to a failing chain element
13940 which is not the leaf.
13943 .vitem &$tls_in_resumption$& &&&
13944 &$tls_out_resumption$&
13945 .vindex &$tls_in_resumption$&
13946 .vindex &$tls_out_resumption$&
13947 .cindex TLS resumption
13948 Observability for TLS session resumption. See &<<SECTresumption>>& for details.
13951 .tvar &$tls_in_sni$&
13952 .vindex "&$tls_sni$&"
13953 .cindex "TLS" "Server Name Indication"
13955 .cindex SNI "observability on server"
13956 When a TLS session is being established, if the client sends the Server
13957 Name Indication extension, the value will be placed in this variable.
13958 If the variable appears in &%tls_certificate%& then this option and
13959 some others, described in &<<SECTtlssni>>&,
13960 will be re-expanded early in the TLS session, to permit
13961 a different certificate to be presented (and optionally a different key to be
13962 used) to the client, based upon the value of the SNI extension.
13964 The deprecated &$tls_sni$& variable refers to the inbound side
13965 except when used in the context of an outbound SMTP delivery, when it refers to
13968 .vitem &$tls_out_sni$&
13969 .vindex "&$tls_out_sni$&"
13970 .cindex "TLS" "Server Name Indication"
13972 .cindex SNI "observability in client"
13974 SMTP deliveries, this variable reflects the value of the &%tls_sni%& option on
13977 .vitem &$tls_out_tlsa_usage$&
13978 .vindex &$tls_out_tlsa_usage$&
13979 Bitfield of TLSA record types found. See section &<<SECDANE>>&.
13981 .vitem &$tls_in_ver$&
13982 .vindex "&$tls_in_ver$&"
13983 When a message is received from a remote host over an encrypted SMTP connection
13984 this variable is set to the protocol version, eg &'TLS1.2'&.
13986 .vitem &$tls_out_ver$&
13987 .vindex "&$tls_out_ver$&"
13988 When a message is being delivered to a remote host over an encrypted SMTP connection
13989 this variable is set to the protocol version.
13992 .vitem &$tod_bsdinbox$&
13993 .vindex "&$tod_bsdinbox$&"
13994 The time of day and the date, in the format required for BSD-style mailbox
13995 files, for example: Thu Oct 17 17:14:09 1995.
13997 .vitem &$tod_epoch$&
13998 .vindex "&$tod_epoch$&"
13999 The time and date as a number of seconds since the start of the Unix epoch.
14001 .vitem &$tod_epoch_l$&
14002 .vindex "&$tod_epoch_l$&"
14003 The time and date as a number of microseconds since the start of the Unix epoch.
14005 .vitem &$tod_full$&
14006 .vindex "&$tod_full$&"
14007 A full version of the time and date, for example: Wed, 16 Oct 1995 09:51:40
14008 +0100. The timezone is always given as a numerical offset from UTC, with
14009 positive values used for timezones that are ahead (east) of UTC, and negative
14010 values for those that are behind (west).
14013 .vindex "&$tod_log$&"
14014 The time and date in the format used for writing Exim's log files, for example:
14015 1995-10-12 15:32:29, but without a timezone.
14017 .vitem &$tod_logfile$&
14018 .vindex "&$tod_logfile$&"
14019 This variable contains the date in the format yyyymmdd. This is the format that
14020 is used for datestamping log files when &%log_file_path%& contains the &`%D`&
14023 .vitem &$tod_zone$&
14024 .vindex "&$tod_zone$&"
14025 This variable contains the numerical value of the local timezone, for example:
14028 .vitem &$tod_zulu$&
14029 .vindex "&$tod_zulu$&"
14030 This variable contains the UTC date and time in &"Zulu"& format, as specified
14031 by ISO 8601, for example: 20030221154023Z.
14033 .vitem &$transport_name$&
14034 .cindex "transport" "name"
14035 .cindex "name" "of transport"
14036 .vindex "&$transport_name$&"
14037 During the running of a transport, this variable contains its name.
14040 .vindex "&$value$&"
14041 This variable contains the result of an expansion lookup, extraction operation,
14042 or external command, as described above. It is also used during a
14043 &*reduce*& expansion.
14045 .vitem &$verify_mode$&
14046 .vindex "&$verify_mode$&"
14047 While a router or transport is being run in verify mode or for cutthrough delivery,
14048 contains "S" for sender-verification or "R" for recipient-verification.
14051 .vitem &$version_number$&
14052 .vindex "&$version_number$&"
14053 The version number of Exim. Same as &$exim_version$&, may be overridden
14054 by the &%exim_version%& main config option.
14056 .vitem &$warn_message_delay$&
14057 .vindex "&$warn_message_delay$&"
14058 This variable is set only during the creation of a message warning about a
14059 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
14061 .vitem &$warn_message_recipients$&
14062 .vindex "&$warn_message_recipients$&"
14063 This variable is set only during the creation of a message warning about a
14064 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
14070 . ////////////////////////////////////////////////////////////////////////////
14071 . ////////////////////////////////////////////////////////////////////////////
14073 .chapter "Embedded Perl" "CHAPperl"
14074 .scindex IIDperl "Perl" "calling from Exim"
14075 Exim can be built to include an embedded Perl interpreter. When this is done,
14076 Perl subroutines can be called as part of the string expansion process. To make
14077 use of the Perl support, you need version 5.004 or later of Perl installed on
14078 your system. To include the embedded interpreter in the Exim binary, include
14083 in your &_Local/Makefile_& and then build Exim in the normal way.
14086 .section "Setting up so Perl can be used" "SECID85"
14087 .oindex "&%perl_startup%&"
14088 Access to Perl subroutines is via a global configuration option called
14089 &%perl_startup%& and an expansion string operator &%${perl ...}%&. If there is
14090 no &%perl_startup%& option in the Exim configuration file then no Perl
14091 interpreter is started and there is almost no overhead for Exim (since none of
14092 the Perl library will be paged in unless used). If there is a &%perl_startup%&
14093 option then the associated value is taken to be Perl code which is executed in
14094 a newly created Perl interpreter.
14096 The value of &%perl_startup%& is not expanded in the Exim sense, so you do not
14097 need backslashes before any characters to escape special meanings. The option
14098 should usually be something like
14100 perl_startup = do '/etc/exim.pl'
14102 where &_/etc/exim.pl_& is Perl code which defines any subroutines you want to
14103 use from Exim. Exim can be configured either to start up a Perl interpreter as
14104 soon as it is entered, or to wait until the first time it is needed. Starting
14105 the interpreter at the beginning ensures that it is done while Exim still has
14106 its setuid privilege, but can impose an unnecessary overhead if Perl is not in
14107 fact used in a particular run. Also, note that this does not mean that Exim is
14108 necessarily running as root when Perl is called at a later time. By default,
14109 the interpreter is started only when it is needed, but this can be changed in
14113 .oindex "&%perl_at_start%&"
14114 Setting &%perl_at_start%& (a boolean option) in the configuration requests
14115 a startup when Exim is entered.
14117 The command line option &%-ps%& also requests a startup when Exim is entered,
14118 overriding the setting of &%perl_at_start%&.
14121 There is also a command line option &%-pd%& (for delay) which suppresses the
14122 initial startup, even if &%perl_at_start%& is set.
14125 .oindex "&%perl_taintmode%&"
14126 .cindex "Perl" "taintmode"
14127 To provide more security executing Perl code via the embedded Perl
14128 interpreter, the &%perl_taintmode%& option can be set. This enables the
14129 taint mode of the Perl interpreter. You are encouraged to set this
14130 option to a true value. To avoid breaking existing installations, it
14133 &*Note*&: This is entirely separate from Exim's tainted-data tracking.
14136 .section "Calling Perl subroutines" "SECID86"
14137 When the configuration file includes a &%perl_startup%& option you can make use
14138 of the string expansion item to call the Perl subroutines that are defined
14139 by the &%perl_startup%& code. The operator is used in any of the following
14143 ${perl{foo}{argument}}
14144 ${perl{foo}{argument1}{argument2} ... }
14146 which calls the subroutine &%foo%& with the given arguments. A maximum of eight
14147 arguments may be passed. Passing more than this results in an expansion failure
14148 with an error message of the form
14150 Too many arguments passed to Perl subroutine "foo" (max is 8)
14152 The return value of the Perl subroutine is evaluated in a scalar context before
14153 it is passed back to Exim to be inserted into the expanded string. If the
14154 return value is &'undef'&, the expansion is forced to fail in the same way as
14155 an explicit &"fail"& on an &%if%& or &%lookup%& item. If the subroutine aborts
14156 by obeying Perl's &%die%& function, the expansion fails with the error message
14157 that was passed to &%die%&.
14160 .section "Calling Exim functions from Perl" "SECID87"
14161 Within any Perl code called from Exim, the function &'Exim::expand_string()'&
14162 is available to call back into Exim's string expansion function. For example,
14165 my $lp = Exim::expand_string('$local_part');
14167 makes the current Exim &$local_part$& available in the Perl variable &$lp$&.
14168 Note those are single quotes and not double quotes to protect against
14169 &$local_part$& being interpolated as a Perl variable.
14171 If the string expansion is forced to fail by a &"fail"& item, the result of
14172 &'Exim::expand_string()'& is &%undef%&. If there is a syntax error in the
14173 expansion string, the Perl call from the original expansion string fails with
14174 an appropriate error message, in the same way as if &%die%& were used.
14176 .cindex "debugging" "from embedded Perl"
14177 .cindex "log" "writing from embedded Perl"
14178 Two other Exim functions are available for use from within Perl code.
14179 &'Exim::debug_write()'& writes a string to the standard error stream if Exim's
14180 debugging is enabled. If you want a newline at the end, you must supply it.
14181 &'Exim::log_write()'& writes a string to Exim's main log, adding a leading
14182 timestamp. In this case, you should not supply a terminating newline.
14185 .section "Use of standard output and error by Perl" "SECID88"
14186 .cindex "Perl" "standard output and error"
14187 You should not write to the standard error or output streams from within your
14188 Perl code, as it is not defined how these are set up. In versions of Exim
14189 before 4.50, it is possible for the standard output or error to refer to the
14190 SMTP connection during message reception via the daemon. Writing to this stream
14191 is certain to cause chaos. From Exim 4.50 onwards, the standard output and
14192 error streams are connected to &_/dev/null_& in the daemon. The chaos is
14193 avoided, but the output is lost.
14195 .cindex "Perl" "use of &%warn%&"
14196 The Perl &%warn%& statement writes to the standard error stream by default.
14197 Calls to &%warn%& may be embedded in Perl modules that you use, but over which
14198 you have no control. When Exim starts up the Perl interpreter, it arranges for
14199 output from the &%warn%& statement to be written to the Exim main log. You can
14200 change this by including appropriate Perl magic somewhere in your Perl code.
14201 For example, to discard &%warn%& output completely, you need this:
14203 $SIG{__WARN__} = sub { };
14205 Whenever a &%warn%& is obeyed, the anonymous subroutine is called. In this
14206 example, the code for the subroutine is empty, so it does nothing, but you can
14207 include any Perl code that you like. The text of the &%warn%& message is passed
14208 as the first subroutine argument.
14212 . ////////////////////////////////////////////////////////////////////////////
14213 . ////////////////////////////////////////////////////////////////////////////
14215 .chapter "Starting the daemon and the use of network interfaces" &&&
14216 "CHAPinterfaces" &&&
14217 "Starting the daemon"
14218 .cindex "daemon" "starting"
14219 .cindex "interface" "listening"
14220 .cindex "network interface"
14221 .cindex "interface" "network"
14222 .cindex "IP address" "for listening"
14223 .cindex "daemon" "listening IP addresses"
14224 .cindex "TCP/IP" "setting listening interfaces"
14225 .cindex "TCP/IP" "setting listening ports"
14226 A host that is connected to a TCP/IP network may have one or more physical
14227 hardware network interfaces. Each of these interfaces may be configured as one
14228 or more &"logical"& interfaces, which are the entities that a program actually
14229 works with. Each of these logical interfaces is associated with an IP address.
14230 In addition, TCP/IP software supports &"loopback"& interfaces (127.0.0.1 in
14231 IPv4 and ::1 in IPv6), which do not use any physical hardware. Exim requires
14232 knowledge about the host's interfaces for use in three different circumstances:
14235 When a listening daemon is started, Exim needs to know which interfaces
14236 and ports to listen on.
14238 When Exim is routing an address, it needs to know which IP addresses
14239 are associated with local interfaces. This is required for the correct
14240 processing of MX lists by removing the local host and others with the
14241 same or higher priority values. Also, Exim needs to detect cases
14242 when an address is routed to an IP address that in fact belongs to the
14243 local host. Unless the &%self%& router option or the &%allow_localhost%&
14244 option of the smtp transport is set (as appropriate), this is treated
14245 as an error situation.
14247 When Exim connects to a remote host, it may need to know which interface to use
14248 for the outgoing connection.
14252 Exim's default behaviour is likely to be appropriate in the vast majority
14253 of cases. If your host has only one interface, and you want all its IP
14254 addresses to be treated in the same way, and you are using only the
14255 standard SMTP port, you should not need to take any special action. The
14256 rest of this chapter does not apply to you.
14258 In a more complicated situation you may want to listen only on certain
14259 interfaces, or on different ports, and for this reason there are a number of
14260 options that can be used to influence Exim's behaviour. The rest of this
14261 chapter describes how they operate.
14263 When a message is received over TCP/IP, the interface and port that were
14264 actually used are set in &$received_ip_address$& and &$received_port$&.
14268 .section "Starting a listening daemon" "SECID89"
14269 When a listening daemon is started (by means of the &%-bd%& command line
14270 option), the interfaces and ports on which it listens are controlled by the
14274 &%daemon_smtp_ports%& contains a list of default ports
14276 (For backward compatibility, this option can also be specified in the singular.)
14278 &%local_interfaces%& contains list of interface IP addresses on which to
14279 listen. Each item may optionally also specify a port.
14282 The default list separator in both cases is a colon, but this can be changed as
14283 described in section &<<SECTlistsepchange>>&. When IPv6 addresses are involved,
14284 it is usually best to change the separator to avoid having to double all the
14285 colons. For example:
14287 local_interfaces = <; 127.0.0.1 ; \
14290 3ffe:ffff:836f::fe86:a061
14292 There are two different formats for specifying a port along with an IP address
14293 in &%local_interfaces%&:
14296 The port is added onto the address with a dot separator. For example, to listen
14297 on port 1234 on two different IP addresses:
14299 local_interfaces = <; 192.168.23.65.1234 ; \
14300 3ffe:ffff:836f::fe86:a061.1234
14303 The IP address is enclosed in square brackets, and the port is added
14304 with a colon separator, for example:
14306 local_interfaces = <; [192.168.23.65]:1234 ; \
14307 [3ffe:ffff:836f::fe86:a061]:1234
14311 When a port is not specified, the value of &%daemon_smtp_ports%& is used. The
14312 default setting contains just one port:
14314 daemon_smtp_ports = smtp
14316 If more than one port is listed, each interface that does not have its own port
14317 specified listens on all of them. Ports that are listed in
14318 &%daemon_smtp_ports%& can be identified either by name (defined in
14319 &_/etc/services_&) or by number. However, when ports are given with individual
14320 IP addresses in &%local_interfaces%&, only numbers (not names) can be used.
14324 .section "Special IP listening addresses" "SECID90"
14325 The addresses 0.0.0.0 and ::0 are treated specially. They are interpreted
14326 as &"all IPv4 interfaces"& and &"all IPv6 interfaces"&, respectively. In each
14327 case, Exim tells the TCP/IP stack to &"listen on all IPv&'x'& interfaces"&
14328 instead of setting up separate listening sockets for each interface. The
14329 default value of &%local_interfaces%& is
14331 local_interfaces = 0.0.0.0
14333 when Exim is built without IPv6 support; otherwise it is:
14335 local_interfaces = <; ::0 ; 0.0.0.0
14337 Thus, by default, Exim listens on all available interfaces, on the SMTP port.
14341 .section "Overriding local_interfaces and daemon_smtp_ports" "SECID91"
14342 The &%-oX%& command line option can be used to override the values of
14343 &%daemon_smtp_ports%& and/or &%local_interfaces%& for a particular daemon
14344 instance. Another way of doing this would be to use macros and the &%-D%&
14345 option. However, &%-oX%& can be used by any admin user, whereas modification of
14346 the runtime configuration by &%-D%& is allowed only when the caller is root or
14349 The value of &%-oX%& is a list of items. The default colon separator can be
14350 changed in the usual way (&<<SECTlistsepchange>>&) if required.
14351 If there are any items that do not
14352 contain dots or colons (that is, are not IP addresses), the value of
14353 &%daemon_smtp_ports%& is replaced by the list of those items. If there are any
14354 items that do contain dots or colons, the value of &%local_interfaces%& is
14355 replaced by those items. Thus, for example,
14359 overrides &%daemon_smtp_ports%&, but leaves &%local_interfaces%& unchanged,
14362 -oX 192.168.34.5.1125
14364 overrides &%local_interfaces%&, leaving &%daemon_smtp_ports%& unchanged.
14365 (However, since &%local_interfaces%& now contains no items without ports, the
14366 value of &%daemon_smtp_ports%& is no longer relevant in this example.)
14370 .section "Support for the submissions (aka SSMTP or SMTPS) protocol" "SECTsupobssmt"
14371 .cindex "submissions protocol"
14372 .cindex "ssmtp protocol"
14373 .cindex "smtps protocol"
14374 .cindex "SMTP" "ssmtp protocol"
14375 .cindex "SMTP" "smtps protocol"
14376 Exim supports the use of TLS-on-connect, used by mail clients in the
14377 &"submissions"& protocol, historically also known as SMTPS or SSMTP.
14378 For some years, IETF Standards Track documents only blessed the
14379 STARTTLS-based Submission service (port 587) while common practice was to support
14380 the same feature set on port 465, but using TLS-on-connect.
14381 If your installation needs to provide service to mail clients
14382 (Mail User Agents, MUAs) then you should provide service on both the 587 and
14385 If the &%tls_on_connect_ports%& option is set to a list of port numbers or
14386 service names, connections to those ports must first establish TLS, before
14387 proceeding to the application layer use of the SMTP protocol.
14389 The common use of this option is expected to be
14391 tls_on_connect_ports = 465
14394 There is also a command line option &%-tls-on-connect%&, which forces all ports
14395 to behave in this way when a daemon is started.
14397 &*Warning*&: Setting &%tls_on_connect_ports%& does not of itself cause the
14398 daemon to listen on those ports. You must still specify them in
14399 &%daemon_smtp_ports%&, &%local_interfaces%&, or the &%-oX%& option. (This is
14400 because &%tls_on_connect_ports%& applies to &%inetd%& connections as well as to
14401 connections via the daemon.)
14406 .section "IPv6 address scopes" "SECID92"
14407 .cindex "IPv6" "address scopes"
14408 IPv6 addresses have &"scopes"&, and a host with multiple hardware interfaces
14409 can, in principle, have the same link-local IPv6 address on different
14410 interfaces. Thus, additional information is needed, over and above the IP
14411 address, to distinguish individual interfaces. A convention of using a
14412 percent sign followed by something (often the interface name) has been
14413 adopted in some cases, leading to addresses like this:
14415 fe80::202:b3ff:fe03:45c1%eth0
14417 To accommodate this usage, a percent sign followed by an arbitrary string is
14418 allowed at the end of an IPv6 address. By default, Exim calls &[getaddrinfo()]&
14419 to convert a textual IPv6 address for actual use. This function recognizes the
14420 percent convention in operating systems that support it, and it processes the
14421 address appropriately. Unfortunately, some older libraries have problems with
14422 &[getaddrinfo()]&. If
14424 IPV6_USE_INET_PTON=yes
14426 is set in &_Local/Makefile_& (or an OS-dependent Makefile) when Exim is built,
14427 Exim uses &'inet_pton()'& to convert a textual IPv6 address for actual use,
14428 instead of &[getaddrinfo()]&. (Before version 4.14, it always used this
14429 function.) Of course, this means that the additional functionality of
14430 &[getaddrinfo()]& &-- recognizing scoped addresses &-- is lost.
14432 .section "Disabling IPv6" "SECID93"
14433 .cindex "IPv6" "disabling"
14434 Sometimes it happens that an Exim binary that was compiled with IPv6 support is
14435 run on a host whose kernel does not support IPv6. The binary will fall back to
14436 using IPv4, but it may waste resources looking up AAAA records, and trying to
14437 connect to IPv6 addresses, causing delays to mail delivery. If you set the
14438 .oindex "&%disable_ipv6%&"
14439 &%disable_ipv6%& option true, even if the Exim binary has IPv6 support, no IPv6
14440 activities take place. AAAA records are never looked up, and any IPv6 addresses
14441 that are listed in &%local_interfaces%&, data for the &(manualroute)& router,
14442 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
14443 to handle IPv6 literal addresses.
14445 On the other hand, when IPv6 is in use, there may be times when you want to
14446 disable it for certain hosts or domains. You can use the &%dns_ipv4_lookup%&
14447 option to globally suppress the lookup of AAAA records for specified domains,
14448 and you can use the &%ignore_target_hosts%& generic router option to ignore
14449 IPv6 addresses in an individual router.
14453 .section "Examples of starting a listening daemon" "SECID94"
14454 The default case in an IPv6 environment is
14456 daemon_smtp_ports = smtp
14457 local_interfaces = <; ::0 ; 0.0.0.0
14459 This specifies listening on the smtp port on all IPv6 and IPv4 interfaces.
14460 Either one or two sockets may be used, depending on the characteristics of
14461 the TCP/IP stack. (This is complicated and messy; for more information,
14462 read the comments in the &_daemon.c_& source file.)
14464 To specify listening on ports 25 and 26 on all interfaces:
14466 daemon_smtp_ports = 25 : 26
14468 (leaving &%local_interfaces%& at the default setting) or, more explicitly:
14470 local_interfaces = <; ::0.25 ; ::0.26 \
14471 0.0.0.0.25 ; 0.0.0.0.26
14473 To listen on the default port on all IPv4 interfaces, and on port 26 on the
14474 IPv4 loopback address only:
14476 local_interfaces = 0.0.0.0 : 127.0.0.1.26
14478 To specify listening on the default port on specific interfaces only:
14480 local_interfaces = 10.0.0.67 : 192.168.34.67
14482 &*Warning*&: Such a setting excludes listening on the loopback interfaces.
14486 .section "Recognizing the local host" "SECTreclocipadd"
14487 The &%local_interfaces%& option is also used when Exim needs to determine
14488 whether or not an IP address refers to the local host. That is, the IP
14489 addresses of all the interfaces on which a daemon is listening are always
14492 For this usage, port numbers in &%local_interfaces%& are ignored. If either of
14493 the items 0.0.0.0 or ::0 are encountered, Exim gets a complete list of
14494 available interfaces from the operating system, and extracts the relevant
14495 (that is, IPv4 or IPv6) addresses to use for checking.
14497 Some systems set up large numbers of virtual interfaces in order to provide
14498 many virtual web servers. In this situation, you may want to listen for
14499 email on only a few of the available interfaces, but nevertheless treat all
14500 interfaces as local when routing. You can do this by setting
14501 &%extra_local_interfaces%& to a list of IP addresses, possibly including the
14502 &"all"& wildcard values. These addresses are recognized as local, but are not
14503 used for listening. Consider this example:
14505 local_interfaces = <; 127.0.0.1 ; ::1 ; \
14507 3ffe:2101:12:1:a00:20ff:fe86:a061
14509 extra_local_interfaces = <; ::0 ; 0.0.0.0
14511 The daemon listens on the loopback interfaces and just one IPv4 and one IPv6
14512 address, but all available interface addresses are treated as local when
14515 In some environments the local host name may be in an MX list, but with an IP
14516 address that is not assigned to any local interface. In other cases it may be
14517 desirable to treat other host names as if they referred to the local host. Both
14518 these cases can be handled by setting the &%hosts_treat_as_local%& option.
14519 This contains host names rather than IP addresses. When a host is referenced
14520 during routing, either via an MX record or directly, it is treated as the local
14521 host if its name matches &%hosts_treat_as_local%&, or if any of its IP
14522 addresses match &%local_interfaces%& or &%extra_local_interfaces%&.
14526 .section "Delivering to a remote host" "SECID95"
14527 Delivery to a remote host is handled by the smtp transport. By default, it
14528 allows the system's TCP/IP functions to choose which interface to use (if
14529 there is more than one) when connecting to a remote host. However, the
14530 &%interface%& option can be set to specify which interface is used. See the
14531 description of the smtp transport in chapter &<<CHAPsmtptrans>>& for more
14537 . ////////////////////////////////////////////////////////////////////////////
14538 . ////////////////////////////////////////////////////////////////////////////
14540 .chapter "Main configuration" "CHAPmainconfig"
14541 .scindex IIDconfima "configuration file" "main section"
14542 .scindex IIDmaiconf "main configuration"
14543 The first part of the runtime configuration file contains three types of item:
14546 Macro definitions: These lines start with an upper case letter. See section
14547 &<<SECTmacrodefs>>& for details of macro processing.
14549 Named list definitions: These lines start with one of the words &"domainlist"&,
14550 &"hostlist"&, &"addresslist"&, or &"localpartlist"&. Their use is described in
14551 section &<<SECTnamedlists>>&.
14553 Main configuration settings: Each setting occupies one line of the file
14554 (with possible continuations). If any setting is preceded by the word
14555 &"hide"&, the &%-bP%& command line option displays its value to admin users
14556 only. See section &<<SECTcos>>& for a description of the syntax of these option
14560 This chapter specifies all the main configuration options, along with their
14561 types and default values. For ease of finding a particular option, they appear
14562 in alphabetical order in section &<<SECTalomo>>& below. However, because there
14563 are now so many options, they are first listed briefly in functional groups, as
14564 an aid to finding the name of the option you are looking for. Some options are
14565 listed in more than one group.
14567 .section "Miscellaneous" "SECID96"
14569 .row &%add_environment%& "environment variables"
14570 .row &%bi_command%& "to run for &%-bi%& command line option"
14571 .row &%debug_store%& "do extra internal checks"
14572 .row &%disable_ipv6%& "do no IPv6 processing"
14573 .row &%keep_environment%& "environment variables"
14574 .row &%keep_malformed%& "for broken files &-- should not happen"
14575 .row &%localhost_number%& "for unique message ids in clusters"
14576 .row &%message_body_newlines%& "retain newlines in &$message_body$&"
14577 .row &%message_body_visible%& "how much to show in &$message_body$&"
14578 .row &%mua_wrapper%& "run in &""MUA wrapper""& mode"
14579 .row &%print_topbitchars%& "top-bit characters are printing"
14580 .row &%spool_wireformat%& "use wire-format spool data files when possible"
14581 .row &%timezone%& "force time zone"
14585 .section "Exim parameters" "SECID97"
14587 .row &%exim_group%& "override compiled-in value"
14588 .row &%exim_path%& "override compiled-in value"
14589 .row &%exim_user%& "override compiled-in value"
14590 .row &%primary_hostname%& "default from &[uname()]&"
14591 .row &%split_spool_directory%& "use multiple directories"
14592 .row &%spool_directory%& "override compiled-in value"
14597 .section "Privilege controls" "SECID98"
14599 .row &%admin_groups%& "groups that are Exim admin users"
14600 .row &%commandline_checks_require_admin%& "require admin for various checks"
14601 .row &%deliver_drop_privilege%& "drop root for delivery processes"
14602 .row &%local_from_check%& "insert &'Sender:'& if necessary"
14603 .row &%local_from_prefix%& "for testing &'From:'& for local sender"
14604 .row &%local_from_suffix%& "for testing &'From:'& for local sender"
14605 .row &%local_sender_retain%& "keep &'Sender:'& from untrusted user"
14606 .row &%never_users%& "do not run deliveries as these"
14607 .row &%prod_requires_admin%& "forced delivery requires admin user"
14608 .row &%queue_list_requires_admin%& "queue listing requires admin user"
14609 .row &%trusted_groups%& "groups that are trusted"
14610 .row &%trusted_users%& "users that are trusted"
14615 .section "Logging" "SECID99"
14617 .row &%event_action%& "custom logging"
14618 .row &%hosts_connection_nolog%& "exemption from connect logging"
14619 .row &%log_file_path%& "override compiled-in value"
14620 .row &%log_selector%& "set/unset optional logging"
14621 .row &%log_timezone%& "add timezone to log lines"
14622 .row &%message_logs%& "create per-message logs"
14623 .row &%preserve_message_logs%& "after message completion"
14624 .row &%panic_coredump%& "request coredump on fatal errors"
14625 .row &%process_log_path%& "for SIGUSR1 and &'exiwhat'&"
14626 .row &%slow_lookup_log%& "control logging of slow DNS lookups"
14627 .row &%syslog_duplication%& "controls duplicate log lines on syslog"
14628 .row &%syslog_facility%& "set syslog &""facility""& field"
14629 .row &%syslog_pid%& "pid in syslog lines"
14630 .row &%syslog_processname%& "set syslog &""ident""& field"
14631 .row &%syslog_timestamp%& "timestamp syslog lines"
14632 .row &%write_rejectlog%& "control use of message log"
14637 .section "Frozen messages" "SECID100"
14639 .row &%auto_thaw%& "sets time for retrying frozen messages"
14640 .row &%freeze_tell%& "send message when freezing"
14641 .row &%move_frozen_messages%& "to another directory"
14642 .row &%timeout_frozen_after%& "keep frozen messages only so long"
14647 .section "Data lookups" "SECID101"
14649 .row &%ibase_servers%& "InterBase servers"
14650 .row &%ldap_ca_cert_dir%& "dir of CA certs to verify LDAP server's"
14651 .row &%ldap_ca_cert_file%& "file of CA certs to verify LDAP server's"
14652 .row &%ldap_cert_file%& "client cert file for LDAP"
14653 .row &%ldap_cert_key%& "client key file for LDAP"
14654 .row &%ldap_cipher_suite%& "TLS negotiation preference control"
14655 .row &%ldap_default_servers%& "used if no server in query"
14656 .row &%ldap_require_cert%& "action to take without LDAP server cert"
14657 .row &%ldap_start_tls%& "require TLS within LDAP"
14658 .row &%ldap_version%& "set protocol version"
14659 .row &%lookup_open_max%& "lookup files held open"
14660 .row &%mysql_servers%& "default MySQL servers"
14661 .row &%oracle_servers%& "Oracle servers"
14662 .row &%pgsql_servers%& "default PostgreSQL servers"
14663 .row &%sqlite_lock_timeout%& "as it says"
14668 .section "Message ids" "SECID102"
14670 .row &%message_id_header_domain%& "used to build &'Message-ID:'& header"
14671 .row &%message_id_header_text%& "ditto"
14676 .section "Embedded Perl Startup" "SECID103"
14678 .row &%perl_at_start%& "always start the interpreter"
14679 .row &%perl_startup%& "code to obey when starting Perl"
14680 .row &%perl_taintmode%& "enable taint mode in Perl"
14685 .section "Daemon" "SECID104"
14687 .row &%daemon_smtp_ports%& "default ports"
14688 .row &%daemon_startup_retries%& "number of times to retry"
14689 .row &%daemon_startup_sleep%& "time to sleep between tries"
14690 .row &%extra_local_interfaces%& "not necessarily listened on"
14691 .row &%local_interfaces%& "on which to listen, with optional ports"
14692 .row &%notifier_socket%& "override compiled-in value"
14693 .row &%pid_file_path%& "override compiled-in value"
14694 .row &%queue_run_max%& "maximum simultaneous queue runners"
14695 .row &%smtp_backlog_monitor%& "level to log listen backlog"
14700 .section "Resource control" "SECID105"
14702 .row &%check_log_inodes%& "before accepting a message"
14703 .row &%check_log_space%& "before accepting a message"
14704 .row &%check_spool_inodes%& "before accepting a message"
14705 .row &%check_spool_space%& "before accepting a message"
14706 .row &%deliver_queue_load_max%& "no queue deliveries if load high"
14707 .row &%queue_only_load%& "queue incoming if load high"
14708 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
14709 .row &%queue_run_max%& "maximum simultaneous queue runners"
14710 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
14711 .row &%smtp_accept_max%& "simultaneous incoming connections"
14712 .row &%smtp_accept_max_nonmail%& "non-mail commands"
14713 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
14714 .row &%smtp_accept_max_per_connection%& "messages per connection"
14715 .row &%smtp_accept_max_per_host%& "connections from one host"
14716 .row &%smtp_accept_queue%& "queue mail if more connections"
14717 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
14719 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
14720 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
14721 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
14722 .row &%smtp_load_reserve%& "SMTP from reserved hosts if load high"
14723 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
14728 .section "Policy controls" "SECID106"
14730 .row &%acl_not_smtp%& "ACL for non-SMTP messages"
14731 .row &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
14732 .row &%acl_not_smtp_start%& "ACL for start of non-SMTP message"
14733 .row &%acl_smtp_auth%& "ACL for AUTH"
14734 .row &%acl_smtp_connect%& "ACL for connection"
14735 .row &%acl_smtp_data%& "ACL for DATA"
14736 .row &%acl_smtp_data_prdr%& "ACL for DATA, per-recipient"
14737 .row &%acl_smtp_dkim%& "ACL for DKIM verification"
14738 .row &%acl_smtp_etrn%& "ACL for ETRN"
14739 .row &%acl_smtp_expn%& "ACL for EXPN"
14740 .row &%acl_smtp_helo%& "ACL for EHLO or HELO"
14741 .row &%acl_smtp_mail%& "ACL for MAIL"
14742 .row &%acl_smtp_mailauth%& "ACL for AUTH on MAIL command"
14743 .row &%acl_smtp_mime%& "ACL for MIME parts"
14744 .row &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
14745 .row &%acl_smtp_predata%& "ACL for start of data"
14746 .row &%acl_smtp_quit%& "ACL for QUIT"
14747 .row &%acl_smtp_rcpt%& "ACL for RCPT"
14748 .row &%acl_smtp_starttls%& "ACL for STARTTLS"
14749 .row &%acl_smtp_vrfy%& "ACL for VRFY"
14750 .row &%av_scanner%& "specify virus scanner"
14751 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
14753 .row &%dns_cname_loops%& "follow CNAMEs returned by resolver"
14754 .row &%dns_csa_search_limit%& "control CSA parent search depth"
14755 .row &%dns_csa_use_reverse%& "en/disable CSA IP reverse search"
14756 .row &%header_maxsize%& "total size of message header"
14757 .row &%header_line_maxsize%& "individual header line limit"
14758 .row &%helo_accept_junk_hosts%& "allow syntactic junk from these hosts"
14759 .row &%helo_allow_chars%& "allow illegal chars in HELO names"
14760 .row &%helo_lookup_domains%& "lookup hostname for these HELO names"
14761 .row &%helo_try_verify_hosts%& "HELO soft-checked for these hosts"
14762 .row &%helo_verify_hosts%& "HELO hard-checked for these hosts"
14763 .row &%host_lookup%& "host name looked up for these hosts"
14764 .row &%host_lookup_order%& "order of DNS and local name lookups"
14765 .row &%hosts_proxy%& "use proxy protocol for these hosts"
14766 .row &%host_reject_connection%& "reject connection from these hosts"
14767 .row &%hosts_treat_as_local%& "useful in some cluster configurations"
14768 .row &%local_scan_timeout%& "timeout for &[local_scan()]&"
14769 .row &%message_size_limit%& "for all messages"
14770 .row &%percent_hack_domains%& "recognize %-hack for these domains"
14771 .row &%proxy_protocol_timeout%& "timeout for proxy protocol negotiation"
14772 .row &%spamd_address%& "set interface to SpamAssassin"
14773 .row &%strict_acl_vars%& "object to unset ACL variables"
14774 .row &%spf_smtp_comment_template%& "template for &$spf_smtp_comment$&"
14779 .section "Callout cache" "SECID107"
14781 .row &%callout_domain_negative_expire%& "timeout for negative domain cache &&&
14783 .row &%callout_domain_positive_expire%& "timeout for positive domain cache &&&
14785 .row &%callout_negative_expire%& "timeout for negative address cache item"
14786 .row &%callout_positive_expire%& "timeout for positive address cache item"
14787 .row &%callout_random_local_part%& "string to use for &""random""& testing"
14792 .section "TLS" "SECID108"
14794 .row &%gnutls_compat_mode%& "use GnuTLS compatibility mode"
14795 .row &%gnutls_allow_auto_pkcs11%& "allow GnuTLS to autoload PKCS11 modules"
14796 .row &%hosts_require_alpn%& "mandatory ALPN"
14797 .row &%hosts_require_helo%& "mandatory HELO/EHLO"
14798 .row &%openssl_options%& "adjust OpenSSL compatibility options"
14799 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
14800 .row &%tls_alpn%& "acceptable protocol names"
14801 .row &%tls_certificate%& "location of server certificate"
14802 .row &%tls_crl%& "certificate revocation list"
14803 .row &%tls_dh_max_bits%& "clamp D-H bit count suggestion"
14804 .row &%tls_dhparam%& "DH parameters for server"
14805 .row &%tls_eccurve%& "EC curve selection for server"
14806 .row &%tls_ocsp_file%& "location of server certificate status proof"
14807 .row &%tls_on_connect_ports%& "specify SSMTP (SMTPS) ports"
14808 .row &%tls_privatekey%& "location of server private key"
14809 .row &%tls_remember_esmtp%& "don't reset after starting TLS"
14810 .row &%tls_require_ciphers%& "specify acceptable ciphers"
14811 .row &%tls_try_verify_hosts%& "try to verify client certificate"
14812 .row &%tls_verify_certificates%& "expected client certificates"
14813 .row &%tls_verify_hosts%& "insist on client certificate verify"
14818 .section "Local user handling" "SECID109"
14820 .row &%finduser_retries%& "useful in NIS environments"
14821 .row &%gecos_name%& "used when creating &'Sender:'&"
14822 .row &%gecos_pattern%& "ditto"
14823 .row &%max_username_length%& "for systems that truncate"
14824 .row &%unknown_login%& "used when no login name found"
14825 .row &%unknown_username%& "ditto"
14826 .row &%uucp_from_pattern%& "for recognizing &""From ""& lines"
14827 .row &%uucp_from_sender%& "ditto"
14832 .section "All incoming messages (SMTP and non-SMTP)" "SECID110"
14834 .row &%header_maxsize%& "total size of message header"
14835 .row &%header_line_maxsize%& "individual header line limit"
14836 .row &%message_size_limit%& "applies to all messages"
14837 .row &%percent_hack_domains%& "recognize %-hack for these domains"
14838 .row &%received_header_text%& "expanded to make &'Received:'&"
14839 .row &%received_headers_max%& "for mail loop detection"
14840 .row &%recipients_max%& "limit per message"
14841 .row &%recipients_max_reject%& "permanently reject excess recipients"
14847 .section "Non-SMTP incoming messages" "SECID111"
14849 .row &%receive_timeout%& "for non-SMTP messages"
14856 .section "Incoming SMTP messages" "SECID112"
14857 See also the &'Policy controls'& section above.
14860 .row &%dkim_verify_hashes%& "DKIM hash methods accepted for signatures"
14861 .row &%dkim_verify_keytypes%& "DKIM key types accepted for signatures"
14862 .row &%dkim_verify_min_keysizes%& "DKIM key sizes accepted for signatures"
14863 .row &%dkim_verify_signers%& "DKIM domains for which DKIM ACL is run"
14864 .row &%dmarc_forensic_sender%& "DMARC sender for report messages"
14865 .row &%dmarc_history_file%& "DMARC results log"
14866 .row &%dmarc_tld_file%& "DMARC toplevel domains file"
14867 .row &%host_lookup%& "host name looked up for these hosts"
14868 .row &%host_lookup_order%& "order of DNS and local name lookups"
14869 .row &%recipient_unqualified_hosts%& "may send unqualified recipients"
14870 .row &%rfc1413_hosts%& "make ident calls to these hosts"
14871 .row &%rfc1413_query_timeout%& "zero disables ident calls"
14872 .row &%sender_unqualified_hosts%& "may send unqualified senders"
14873 .row &%smtp_accept_keepalive%& "some TCP/IP magic"
14874 .row &%smtp_accept_max%& "simultaneous incoming connections"
14875 .row &%smtp_accept_max_nonmail%& "non-mail commands"
14876 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
14877 .row &%smtp_accept_max_per_connection%& "messages per connection"
14878 .row &%smtp_accept_max_per_host%& "connections from one host"
14879 .row &%smtp_accept_queue%& "queue mail if more connections"
14880 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
14882 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
14883 .row &%smtp_active_hostname%& "host name to use in messages"
14884 .row &%smtp_banner%& "text for welcome banner"
14885 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
14886 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
14887 .row &%smtp_enforce_sync%& "of SMTP command/responses"
14888 .row &%smtp_etrn_command%& "what to run for ETRN"
14889 .row &%smtp_etrn_serialize%& "only one at once"
14890 .row &%smtp_load_reserve%& "only reserve hosts if this load"
14891 .row &%smtp_max_unknown_commands%& "before dropping connection"
14892 .row &%smtp_ratelimit_hosts%& "apply ratelimiting to these hosts"
14893 .row &%smtp_ratelimit_mail%& "ratelimit for MAIL commands"
14894 .row &%smtp_ratelimit_rcpt%& "ratelimit for RCPT commands"
14895 .row &%smtp_receive_timeout%& "per command or data line"
14896 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
14897 .row &%smtp_return_error_details%& "give detail on rejections"
14902 .section "SMTP extensions" "SECID113"
14904 .row &%accept_8bitmime%& "advertise 8BITMIME"
14905 .row &%auth_advertise_hosts%& "advertise AUTH to these hosts"
14906 .row &%chunking_advertise_hosts%& "advertise CHUNKING to these hosts"
14907 .row &%dsn_advertise_hosts%& "advertise DSN extensions to these hosts"
14908 .row &%ignore_fromline_hosts%& "allow &""From ""& from these hosts"
14909 .row &%ignore_fromline_local%& "allow &""From ""& from local SMTP"
14910 .row &%pipelining_advertise_hosts%& "advertise pipelining to these hosts"
14911 .row &%pipelining_connect_advertise_hosts%& "advertise pipelining to these hosts"
14912 .row &%prdr_enable%& "advertise PRDR to all hosts"
14913 .row &%smtputf8_advertise_hosts%& "advertise SMTPUTF8 to these hosts"
14914 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
14919 .section "Processing messages" "SECID114"
14921 .row &%allow_domain_literals%& "recognize domain literal syntax"
14922 .row &%allow_mx_to_ip%& "allow MX to point to IP address"
14923 .row &%allow_utf8_domains%& "in addresses"
14924 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
14926 .row &%delivery_date_remove%& "from incoming messages"
14927 .row &%envelope_to_remove%& "from incoming messages"
14928 .row &%extract_addresses_remove_arguments%& "affects &%-t%& processing"
14929 .row &%headers_charset%& "default for translations"
14930 .row &%qualify_domain%& "default for senders"
14931 .row &%qualify_recipient%& "default for recipients"
14932 .row &%return_path_remove%& "from incoming messages"
14933 .row &%strip_excess_angle_brackets%& "in addresses"
14934 .row &%strip_trailing_dot%& "at end of addresses"
14935 .row &%untrusted_set_sender%& "untrusted can set envelope sender"
14940 .section "System filter" "SECID115"
14942 .row &%system_filter%& "locate system filter"
14943 .row &%system_filter_directory_transport%& "transport for delivery to a &&&
14945 .row &%system_filter_file_transport%& "transport for delivery to a file"
14946 .row &%system_filter_group%& "group for filter running"
14947 .row &%system_filter_pipe_transport%& "transport for delivery to a pipe"
14948 .row &%system_filter_reply_transport%& "transport for autoreply delivery"
14949 .row &%system_filter_user%& "user for filter running"
14954 .section "Routing and delivery" "SECID116"
14956 .row &%disable_ipv6%& "do no IPv6 processing"
14957 .row &%dns_again_means_nonexist%& "for broken domains"
14958 .row &%dns_check_names_pattern%& "pre-DNS syntax check"
14959 .row &%dns_dnssec_ok%& "parameter for resolver"
14960 .row &%dns_ipv4_lookup%& "only v4 lookup for these domains"
14961 .row &%dns_retrans%& "parameter for resolver"
14962 .row &%dns_retry%& "parameter for resolver"
14963 .row &%dns_trust_aa%& "DNS zones trusted as authentic"
14964 .row &%dns_use_edns0%& "parameter for resolver"
14965 .row &%hold_domains%& "hold delivery for these domains"
14966 .row &%local_interfaces%& "for routing checks"
14967 .row &%queue_domains%& "no immediate delivery for these"
14968 .row &%queue_fast_ramp%& "parallel delivery with 2-phase queue run"
14969 .row &%queue_only%& "no immediate delivery at all"
14970 .row &%queue_only_file%& "no immediate delivery if file exists"
14971 .row &%queue_only_load%& "no immediate delivery if load is high"
14972 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
14973 .row &%queue_only_override%& "allow command line to override"
14974 .row &%queue_run_in_order%& "order of arrival"
14975 .row &%queue_run_max%& "of simultaneous queue runners"
14976 .row &%queue_smtp_domains%& "no immediate SMTP delivery for these"
14977 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
14978 .row &%remote_sort_domains%& "order of remote deliveries"
14979 .row &%retry_data_expire%& "timeout for retry data"
14980 .row &%retry_interval_max%& "safety net for retry rules"
14985 .section "Bounce and warning messages" "SECID117"
14987 .row &%bounce_message_file%& "content of bounce"
14988 .row &%bounce_message_text%& "content of bounce"
14989 .row &%bounce_return_body%& "include body if returning message"
14990 .row &%bounce_return_linesize_limit%& "limit on returned message line length"
14991 .row &%bounce_return_message%& "include original message in bounce"
14992 .row &%bounce_return_size_limit%& "limit on returned message"
14993 .row &%bounce_sender_authentication%& "send authenticated sender with bounce"
14994 .row &%dsn_from%& "set &'From:'& contents in bounces"
14995 .row &%errors_copy%& "copy bounce messages"
14996 .row &%errors_reply_to%& "&'Reply-to:'& in bounces"
14997 .row &%delay_warning%& "time schedule"
14998 .row &%delay_warning_condition%& "condition for warning messages"
14999 .row &%ignore_bounce_errors_after%& "discard undeliverable bounces"
15000 .row &%smtp_return_error_details%& "give detail on rejections"
15001 .row &%warn_message_file%& "content of warning message"
15006 .section "Alphabetical list of main options" "SECTalomo"
15007 Those options that undergo string expansion before use are marked with
15010 .option accept_8bitmime main boolean true
15012 .cindex "8-bit characters"
15013 .cindex "log" "selectors"
15014 .cindex "log" "8BITMIME"
15015 .cindex "ESMTP extensions" 8BITMIME
15016 This option causes Exim to send 8BITMIME in its response to an SMTP
15017 EHLO command, and to accept the BODY= parameter on MAIL commands.
15018 However, though Exim is 8-bit clean, it is not a protocol converter, and it
15019 takes no steps to do anything special with messages received by this route.
15021 Historically Exim kept this option off by default, but the maintainers
15022 feel that in today's Internet, this causes more problems than it solves.
15023 It now defaults to true.
15024 A more detailed analysis of the issues is provided by Dan Bernstein:
15026 &url(https://cr.yp.to/smtp/8bitmime.html)
15029 To log received 8BITMIME status use
15031 log_selector = +8bitmime
15034 .option acl_not_smtp main string&!! unset
15035 .cindex "&ACL;" "for non-SMTP messages"
15036 .cindex "non-SMTP messages" "ACLs for"
15037 This option defines the ACL that is run when a non-SMTP message has been
15038 read and is on the point of being accepted. See chapter &<<CHAPACL>>& for
15041 .option acl_not_smtp_mime main string&!! unset
15042 This option defines the ACL that is run for individual MIME parts of non-SMTP
15043 messages. It operates in exactly the same way as &%acl_smtp_mime%& operates for
15046 .option acl_not_smtp_start main string&!! unset
15047 .cindex "&ACL;" "at start of non-SMTP message"
15048 .cindex "non-SMTP messages" "ACLs for"
15049 This option defines the ACL that is run before Exim starts reading a
15050 non-SMTP message. See chapter &<<CHAPACL>>& for further details.
15052 .option acl_smtp_auth main string&!! unset
15053 .cindex "&ACL;" "setting up for SMTP commands"
15054 .cindex "AUTH" "ACL for"
15055 This option defines the ACL that is run when an SMTP AUTH command is
15056 received. See chapter &<<CHAPACL>>& for further details.
15058 .option acl_smtp_connect main string&!! unset
15059 .cindex "&ACL;" "on SMTP connection"
15060 This option defines the ACL that is run when an SMTP connection is received.
15061 See chapter &<<CHAPACL>>& for further details.
15063 .option acl_smtp_data main string&!! unset
15064 .cindex "DATA" "ACL for"
15065 This option defines the ACL that is run after an SMTP DATA command has been
15066 processed and the message itself has been received, but before the final
15067 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
15069 .option acl_smtp_data_prdr main string&!! accept
15070 .cindex "PRDR" "ACL for"
15071 .cindex "DATA" "PRDR ACL for"
15072 .cindex "&ACL;" "PRDR-related"
15073 .cindex "&ACL;" "per-user data processing"
15074 This option defines the ACL that,
15075 if the PRDR feature has been negotiated,
15076 is run for each recipient after an SMTP DATA command has been
15077 processed and the message itself has been received, but before the
15078 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
15080 .option acl_smtp_dkim main string&!! unset
15081 .cindex DKIM "ACL for"
15082 This option defines the ACL that is run for each DKIM signature
15083 (by default, or as specified in the dkim_verify_signers option)
15084 of a received message.
15085 See section &<<SECDKIMVFY>>& for further details.
15087 .option acl_smtp_etrn main string&!! unset
15088 .cindex "ETRN" "ACL for"
15089 This option defines the ACL that is run when an SMTP ETRN command is
15090 received. See chapter &<<CHAPACL>>& for further details.
15092 .option acl_smtp_expn main string&!! unset
15093 .cindex "EXPN" "ACL for"
15094 This option defines the ACL that is run when an SMTP EXPN command is
15095 received. See chapter &<<CHAPACL>>& for further details.
15097 .option acl_smtp_helo main string&!! unset
15098 .cindex "EHLO" "ACL for"
15099 .cindex "HELO" "ACL for"
15100 This option defines the ACL that is run when an SMTP EHLO or HELO
15101 command is received. See chapter &<<CHAPACL>>& for further details.
15104 .option acl_smtp_mail main string&!! unset
15105 .cindex "MAIL" "ACL for"
15106 This option defines the ACL that is run when an SMTP MAIL command is
15107 received. See chapter &<<CHAPACL>>& for further details.
15109 .option acl_smtp_mailauth main string&!! unset
15110 .cindex "AUTH" "on MAIL command"
15111 This option defines the ACL that is run when there is an AUTH parameter on
15112 a MAIL command. See chapter &<<CHAPACL>>& for details of ACLs, and chapter
15113 &<<CHAPSMTPAUTH>>& for details of authentication.
15115 .option acl_smtp_mime main string&!! unset
15116 .cindex "MIME content scanning" "ACL for"
15117 This option is available when Exim is built with the content-scanning
15118 extension. It defines the ACL that is run for each MIME part in a message. See
15119 section &<<SECTscanmimepart>>& for details.
15121 .option acl_smtp_notquit main string&!! unset
15122 .cindex "not-QUIT, ACL for"
15123 This option defines the ACL that is run when an SMTP session
15124 ends without a QUIT command being received.
15125 See chapter &<<CHAPACL>>& for further details.
15127 .option acl_smtp_predata main string&!! unset
15128 This option defines the ACL that is run when an SMTP DATA command is
15129 received, before the message itself is received. See chapter &<<CHAPACL>>& for
15132 .option acl_smtp_quit main string&!! unset
15133 .cindex "QUIT, ACL for"
15134 This option defines the ACL that is run when an SMTP QUIT command is
15135 received. See chapter &<<CHAPACL>>& for further details.
15137 .option acl_smtp_rcpt main string&!! unset
15138 .cindex "RCPT" "ACL for"
15139 This option defines the ACL that is run when an SMTP RCPT command is
15140 received. See chapter &<<CHAPACL>>& for further details.
15142 .option acl_smtp_starttls main string&!! unset
15143 .cindex "STARTTLS, ACL for"
15144 This option defines the ACL that is run when an SMTP STARTTLS command is
15145 received. See chapter &<<CHAPACL>>& for further details.
15147 .option acl_smtp_vrfy main string&!! unset
15148 .cindex "VRFY" "ACL for"
15149 This option defines the ACL that is run when an SMTP VRFY command is
15150 received. See chapter &<<CHAPACL>>& for further details.
15152 .option add_environment main "string list" empty
15153 .cindex "environment" "set values"
15154 This option adds individual environment variables that the
15155 currently linked libraries and programs in child processes may use.
15156 Each list element should be of the form &"name=value"&.
15158 See &<<SECTpipeenv>>& for the environment of &(pipe)& transports.
15160 .option admin_groups main "string list&!!" unset
15161 .cindex "admin user"
15162 This option is expanded just once, at the start of Exim's processing. If the
15163 current group or any of the supplementary groups of an Exim caller is in this
15164 colon-separated list, the caller has admin privileges. If all your system
15165 programmers are in a specific group, for example, you can give them all Exim
15166 admin privileges by putting that group in &%admin_groups%&. However, this does
15167 not permit them to read Exim's spool files (whose group owner is the Exim gid).
15168 To permit this, you have to add individuals to the Exim group.
15170 .option allow_domain_literals main boolean false
15171 .cindex "domain literal"
15172 If this option is set, the RFC 2822 domain literal format is permitted in
15173 email addresses. The option is not set by default, because the domain literal
15174 format is not normally required these days, and few people know about it. It
15175 has, however, been exploited by mail abusers.
15177 Unfortunately, it seems that some DNS black list maintainers are using this
15178 format to report black listing to postmasters. If you want to accept messages
15179 addressed to your hosts by IP address, you need to set
15180 &%allow_domain_literals%& true, and also to add &`@[]`& to the list of local
15181 domains (defined in the named domain list &%local_domains%& in the default
15182 configuration). This &"magic string"& matches the domain literal form of all
15183 the local host's IP addresses.
15185 .option allow_mx_to_ip main boolean false
15186 .cindex "MX record" "pointing to IP address"
15187 It appears that more and more DNS zone administrators are breaking the rules
15188 and putting domain names that look like IP addresses on the right hand side of
15189 MX records. Exim follows the rules and rejects this, giving an error message
15190 that explains the misconfiguration. However, some other MTAs support this
15191 practice, so to avoid &"Why can't Exim do this?"& complaints,
15192 &%allow_mx_to_ip%& exists, in order to enable this heinous activity. It is not
15193 recommended, except when you have no other choice.
15195 .option allow_utf8_domains main boolean false
15196 .cindex "domain" "UTF-8 characters in"
15197 .cindex "UTF-8" "in domain name"
15198 Lots of discussion is going on about internationalized domain names. One
15199 camp is strongly in favour of just using UTF-8 characters, and it seems
15200 that at least two other MTAs permit this.
15201 This option allows Exim users to experiment if they wish.
15203 If it is set true, Exim's domain parsing function allows valid
15204 UTF-8 multicharacters to appear in domain name components, in addition to
15205 letters, digits, and hyphens.
15207 If Exim is built with internationalization support
15208 and the SMTPUTF8 ESMTP option is in use (see chapter &<<CHAPi18n>>&)
15209 this option can be left as default.
15211 if you want to look up such domain names in the DNS, you must also
15212 adjust the value of &%dns_check_names_pattern%& to match the extended form. A
15213 suitable setting is:
15215 dns_check_names_pattern = (?i)^(?>(?(1)\.|())[a-z0-9\xc0-\xff]\
15216 (?>[-a-z0-9\x80-\xff]*[a-z0-9\x80-\xbf])?)+$
15218 Alternatively, you can just disable this feature by setting
15220 dns_check_names_pattern =
15222 That is, set the option to an empty string so that no check is done.
15225 .option auth_advertise_hosts main "host list&!!" *
15226 .cindex "authentication" "advertising"
15227 .cindex "AUTH" "advertising"
15228 .cindex "ESMTP extensions" AUTH
15229 If any server authentication mechanisms are configured, Exim advertises them in
15230 response to an EHLO command only if the calling host matches this list.
15231 Otherwise, Exim does not advertise AUTH.
15232 Exim does not accept AUTH commands from clients to which it has not
15233 advertised the availability of AUTH. The advertising of individual
15234 authentication mechanisms can be controlled by the use of the
15235 &%server_advertise_condition%& generic authenticator option on the individual
15236 authenticators. See chapter &<<CHAPSMTPAUTH>>& for further details.
15238 Certain mail clients (for example, Netscape) require the user to provide a name
15239 and password for authentication if AUTH is advertised, even though it may
15240 not be needed (the host may accept messages from hosts on its local LAN without
15241 authentication, for example). The &%auth_advertise_hosts%& option can be used
15242 to make these clients more friendly by excluding them from the set of hosts to
15243 which Exim advertises AUTH.
15245 .cindex "AUTH" "advertising when encrypted"
15246 If you want to advertise the availability of AUTH only when the connection
15247 is encrypted using TLS, you can make use of the fact that the value of this
15248 option is expanded, with a setting like this:
15250 auth_advertise_hosts = ${if eq{$tls_in_cipher}{}{}{*}}
15252 .vindex "&$tls_in_cipher$&"
15253 If &$tls_in_cipher$& is empty, the session is not encrypted, and the result of
15254 the expansion is empty, thus matching no hosts. Otherwise, the result of the
15255 expansion is *, which matches all hosts.
15258 .option auto_thaw main time 0s
15259 .cindex "thawing messages"
15260 .cindex "unfreezing messages"
15261 If this option is set to a time greater than zero, a queue runner will try a
15262 new delivery attempt on any frozen message, other than a bounce message, if
15263 this much time has passed since it was frozen. This may result in the message
15264 being re-frozen if nothing has changed since the last attempt. It is a way of
15265 saying &"keep on trying, even though there are big problems"&.
15267 &*Note*&: This is an old option, which predates &%timeout_frozen_after%& and
15268 &%ignore_bounce_errors_after%&. It is retained for compatibility, but it is not
15269 thought to be very useful any more, and its use should probably be avoided.
15272 .option av_scanner main string "see below"
15273 This option is available if Exim is built with the content-scanning extension.
15274 It specifies which anti-virus scanner to use. The default value is:
15276 sophie:/var/run/sophie
15278 If the value of &%av_scanner%& starts with a dollar character, it is expanded
15279 before use. See section &<<SECTscanvirus>>& for further details.
15282 .option bi_command main string unset
15284 This option supplies the name of a command that is run when Exim is called with
15285 the &%-bi%& option (see chapter &<<CHAPcommandline>>&). The string value is
15286 just the command name, it is not a complete command line. If an argument is
15287 required, it must come from the &%-oA%& command line option.
15290 .option bounce_message_file main string&!! unset
15291 .cindex "bounce message" "customizing"
15292 .cindex "customizing" "bounce message"
15293 This option defines a template file containing paragraphs of text to be used
15294 for constructing bounce messages. Details of the file's contents are given in
15295 chapter &<<CHAPemsgcust>>&.
15296 .cindex bounce_message_file "tainted data"
15297 The option is expanded to give the file path, which must be
15298 absolute and untainted.
15299 See also &%warn_message_file%&.
15302 .option bounce_message_text main string unset
15303 When this option is set, its contents are included in the default bounce
15304 message immediately after &"This message was created automatically by mail
15305 delivery software."& It is not used if &%bounce_message_file%& is set.
15307 .option bounce_return_body main boolean true
15308 .cindex "bounce message" "including body"
15309 This option controls whether the body of an incoming message is included in a
15310 bounce message when &%bounce_return_message%& is true. The default setting
15311 causes the entire message, both header and body, to be returned (subject to the
15312 value of &%bounce_return_size_limit%&). If this option is false, only the
15313 message header is included. In the case of a non-SMTP message containing an
15314 error that is detected during reception, only those header lines preceding the
15315 point at which the error was detected are returned.
15316 .cindex "bounce message" "including original"
15318 .option bounce_return_linesize_limit main integer 998
15319 .cindex "size" "of bounce lines, limit"
15320 .cindex "bounce message" "line length limit"
15321 .cindex "limit" "bounce message line length"
15322 This option sets a limit in bytes on the line length of messages
15323 that are returned to senders due to delivery problems,
15324 when &%bounce_return_message%& is true.
15325 The default value corresponds to RFC limits.
15326 If the message being returned has lines longer than this value it is
15327 treated as if the &%bounce_return_size_limit%& (below) restriction was exceeded.
15329 The option also applies to bounces returned when an error is detected
15330 during reception of a message.
15331 In this case lines from the original are truncated.
15333 The option does not apply to messages generated by an &(autoreply)& transport.
15336 .option bounce_return_message main boolean true
15337 If this option is set false, none of the original message is included in
15338 bounce messages generated by Exim. See also &%bounce_return_size_limit%& and
15339 &%bounce_return_body%&.
15342 .option bounce_return_size_limit main integer 100K
15343 .cindex "size" "of bounce, limit"
15344 .cindex "bounce message" "size limit"
15345 .cindex "limit" "bounce message size"
15346 This option sets a limit in bytes on the size of messages that are returned to
15347 senders as part of bounce messages when &%bounce_return_message%& is true. The
15348 limit should be less than the value of the global &%message_size_limit%& and of
15349 any &%message_size_limit%& settings on transports, to allow for the bounce text
15350 that Exim generates. If this option is set to zero there is no limit.
15352 When the body of any message that is to be included in a bounce message is
15353 greater than the limit, it is truncated, and a comment pointing this out is
15354 added at the top. The actual cutoff may be greater than the value given, owing
15355 to the use of buffering for transferring the message in chunks (typically 8K in
15356 size). The idea is to save bandwidth on those undeliverable 15-megabyte
15359 .option bounce_sender_authentication main string unset
15360 .cindex "bounce message" "sender authentication"
15361 .cindex "authentication" "bounce message"
15362 .cindex "AUTH" "on bounce message"
15363 This option provides an authenticated sender address that is sent with any
15364 bounce messages generated by Exim that are sent over an authenticated SMTP
15365 connection. A typical setting might be:
15367 bounce_sender_authentication = mailer-daemon@my.domain.example
15369 which would cause bounce messages to be sent using the SMTP command:
15371 MAIL FROM:<> AUTH=mailer-daemon@my.domain.example
15373 The value of &%bounce_sender_authentication%& must always be a complete email
15376 .option callout_domain_negative_expire main time 3h
15377 .cindex "caching" "callout timeouts"
15378 .cindex "callout" "caching timeouts"
15379 This option specifies the expiry time for negative callout cache data for a
15380 domain. See section &<<SECTcallver>>& for details of callout verification, and
15381 section &<<SECTcallvercache>>& for details of the caching.
15384 .option callout_domain_positive_expire main time 7d
15385 This option specifies the expiry time for positive callout cache data for a
15386 domain. See section &<<SECTcallver>>& for details of callout verification, and
15387 section &<<SECTcallvercache>>& for details of the caching.
15390 .option callout_negative_expire main time 2h
15391 This option specifies the expiry time for negative callout cache data for an
15392 address. See section &<<SECTcallver>>& for details of callout verification, and
15393 section &<<SECTcallvercache>>& for details of the caching.
15396 .option callout_positive_expire main time 24h
15397 This option specifies the expiry time for positive callout cache data for an
15398 address. See section &<<SECTcallver>>& for details of callout verification, and
15399 section &<<SECTcallvercache>>& for details of the caching.
15402 .option callout_random_local_part main string&!! "see below"
15403 This option defines the &"random"& local part that can be used as part of
15404 callout verification. The default value is
15406 $primary_hostname-$tod_epoch-testing
15408 See section &<<CALLaddparcall>>& for details of how this value is used.
15411 .option check_log_inodes main integer 100
15412 See &%check_spool_space%& below.
15415 .option check_log_space main integer 10M
15416 See &%check_spool_space%& below.
15418 .oindex "&%check_rfc2047_length%&"
15419 .cindex "RFC 2047" "disabling length check"
15420 .option check_rfc2047_length main boolean true
15421 RFC 2047 defines a way of encoding non-ASCII characters in headers using a
15422 system of &"encoded words"&. The RFC specifies a maximum length for an encoded
15423 word; strings to be encoded that exceed this length are supposed to use
15424 multiple encoded words. By default, Exim does not recognize encoded words that
15425 exceed the maximum length. However, it seems that some software, in violation
15426 of the RFC, generates overlong encoded words. If &%check_rfc2047_length%& is
15427 set false, Exim recognizes encoded words of any length.
15430 .option check_spool_inodes main integer 100
15431 See &%check_spool_space%& below.
15434 .option check_spool_space main integer 10M
15435 .cindex "checking disk space"
15436 .cindex "disk space, checking"
15437 .cindex "spool directory" "checking space"
15438 The four &%check_...%& options allow for checking of disk resources before a
15439 message is accepted.
15441 .vindex "&$log_inodes$&"
15442 .vindex "&$log_space$&"
15443 .vindex "&$spool_inodes$&"
15444 .vindex "&$spool_space$&"
15445 When any of these options are nonzero, they apply to all incoming messages. If you
15446 want to apply different checks to different kinds of message, you can do so by
15447 testing the variables &$log_inodes$&, &$log_space$&, &$spool_inodes$&, and
15448 &$spool_space$& in an ACL with appropriate additional conditions.
15451 &%check_spool_space%& and &%check_spool_inodes%& check the spool partition if
15452 either value is greater than zero, for example:
15454 check_spool_space = 100M
15455 check_spool_inodes = 100
15457 The spool partition is the one that contains the directory defined by
15458 SPOOL_DIRECTORY in &_Local/Makefile_&. It is used for holding messages in
15461 &%check_log_space%& and &%check_log_inodes%& check the partition in which log
15462 files are written if either is greater than zero. These should be set only if
15463 &%log_file_path%& and &%spool_directory%& refer to different partitions.
15465 If there is less space or fewer inodes than requested, Exim refuses to accept
15466 incoming mail. In the case of SMTP input this is done by giving a 452 temporary
15467 error response to the MAIL command. If ESMTP is in use and there was a
15468 SIZE parameter on the MAIL command, its value is added to the
15469 &%check_spool_space%& value, and the check is performed even if
15470 &%check_spool_space%& is zero, unless &%no_smtp_check_spool_space%& is set.
15472 The values for &%check_spool_space%& and &%check_log_space%& are held as a
15473 number of kilobytes (though specified in bytes).
15474 If a non-multiple of 1024 is specified, it is rounded up.
15476 For non-SMTP input and for batched SMTP input, the test is done at start-up; on
15477 failure a message is written to stderr and Exim exits with a non-zero code, as
15478 it obviously cannot send an error message of any kind.
15480 There is a slight performance penalty for these checks.
15481 Versions of Exim preceding 4.88 had these disabled by default;
15482 high-rate installations confident they will never run out of resources
15483 may wish to deliberately disable them.
15485 .option chunking_advertise_hosts main "host list&!!" *
15486 .cindex CHUNKING advertisement
15487 .cindex "RFC 3030" "CHUNKING"
15488 .cindex "ESMTP extensions" CHUNKING
15489 The CHUNKING extension (RFC3030) will be advertised in the EHLO message to
15491 Hosts may use the BDAT command as an alternate to DATA.
15493 .option commandline_checks_require_admin main boolean &`false`&
15494 .cindex "restricting access to features"
15495 This option restricts various basic checking features to require an
15496 administrative user.
15497 This affects most of the &%-b*%& options, such as &%-be%&.
15499 .option debug_store main boolean &`false`&
15500 .cindex debugging "memory corruption"
15501 .cindex memory debugging
15502 This option, when true, enables extra checking in Exim's internal memory
15503 management. For use when a memory corruption issue is being investigated,
15504 it should normally be left as default.
15506 .option daemon_smtp_ports main string &`smtp`&
15507 .cindex "port" "for daemon"
15508 .cindex "TCP/IP" "setting listening ports"
15509 This option specifies one or more default SMTP ports on which the Exim daemon
15510 listens. See chapter &<<CHAPinterfaces>>& for details of how it is used. For
15511 backward compatibility, &%daemon_smtp_port%& (singular) is a synonym.
15513 .option daemon_startup_retries main integer 9
15514 .cindex "daemon startup, retrying"
15515 This option, along with &%daemon_startup_sleep%&, controls the retrying done by
15516 the daemon at startup when it cannot immediately bind a listening socket
15517 (typically because the socket is already in use): &%daemon_startup_retries%&
15518 defines the number of retries after the first failure, and
15519 &%daemon_startup_sleep%& defines the length of time to wait between retries.
15521 .option daemon_startup_sleep main time 30s
15522 See &%daemon_startup_retries%&.
15524 .option delay_warning main "time list" 24h
15525 .cindex "warning of delay"
15526 .cindex "delay warning, specifying"
15527 .cindex "queue" "delay warning"
15528 When a message is delayed, Exim sends a warning message to the sender at
15529 intervals specified by this option. The data is a colon-separated list of times
15530 after which to send warning messages. If the value of the option is an empty
15531 string or a zero time, no warnings are sent. Up to 10 times may be given. If a
15532 message has been in the queue for longer than the last time, the last interval
15533 between the times is used to compute subsequent warning times. For example,
15536 delay_warning = 4h:8h:24h
15538 the first message is sent after 4 hours, the second after 8 hours, and
15539 the third one after 24 hours. After that, messages are sent every 16 hours,
15540 because that is the interval between the last two times on the list. If you set
15541 just one time, it specifies the repeat interval. For example, with:
15545 messages are repeated every six hours. To stop warnings after a given time, set
15546 a very large time at the end of the list. For example:
15548 delay_warning = 2h:12h:99d
15550 Note that the option is only evaluated at the time a delivery attempt fails,
15551 which depends on retry and queue-runner configuration.
15552 Typically retries will be configured more frequently than warning messages.
15554 .option delay_warning_condition main string&!! "see below"
15555 .vindex "&$domain$&"
15556 The string is expanded at the time a warning message might be sent. If all the
15557 deferred addresses have the same domain, it is set in &$domain$& during the
15558 expansion. Otherwise &$domain$& is empty. If the result of the expansion is a
15559 forced failure, an empty string, or a string matching any of &"0"&, &"no"& or
15560 &"false"& (the comparison being done caselessly) then the warning message is
15561 not sent. The default is:
15563 delay_warning_condition = ${if or {\
15564 { !eq{$h_list-id:$h_list-post:$h_list-subscribe:}{} }\
15565 { match{$h_precedence:}{(?i)bulk|list|junk} }\
15566 { match{$h_auto-submitted:}{(?i)auto-generated|auto-replied} }\
15569 This suppresses the sending of warnings for messages that contain &'List-ID:'&,
15570 &'List-Post:'&, or &'List-Subscribe:'& headers, or have &"bulk"&, &"list"& or
15571 &"junk"& in a &'Precedence:'& header, or have &"auto-generated"& or
15572 &"auto-replied"& in an &'Auto-Submitted:'& header.
15574 .option deliver_drop_privilege main boolean false
15575 .cindex "unprivileged delivery"
15576 .cindex "delivery" "unprivileged"
15577 If this option is set true, Exim drops its root privilege at the start of a
15578 delivery process, and runs as the Exim user throughout. This severely restricts
15579 the kinds of local delivery that are possible, but is viable in certain types
15580 of configuration. There is a discussion about the use of root privilege in
15581 chapter &<<CHAPsecurity>>&.
15583 .option deliver_queue_load_max main fixed-point unset
15584 .cindex "load average"
15585 .cindex "queue runner" "abandoning"
15586 When this option is set, a queue run is abandoned if the system load average
15587 becomes greater than the value of the option. The option has no effect on
15588 ancient operating systems on which Exim cannot determine the load average.
15589 See also &%queue_only_load%& and &%smtp_load_reserve%&.
15592 .option delivery_date_remove main boolean true
15593 .cindex "&'Delivery-date:'& header line"
15594 Exim's transports have an option for adding a &'Delivery-date:'& header to a
15595 message when it is delivered, in exactly the same way as &'Return-path:'& is
15596 handled. &'Delivery-date:'& records the actual time of delivery. Such headers
15597 should not be present in incoming messages, and this option causes them to be
15598 removed at the time the message is received, to avoid any problems that might
15599 occur when a delivered message is subsequently sent on to some other recipient.
15601 .option disable_fsync main boolean false
15602 .cindex "&[fsync()]&, disabling"
15603 This option is available only if Exim was built with the compile-time option
15604 ENABLE_DISABLE_FSYNC. When this is not set, a reference to &%disable_fsync%& in
15605 a runtime configuration generates an &"unknown option"& error. You should not
15606 build Exim with ENABLE_DISABLE_FSYNC or set &%disable_fsync%& unless you
15607 really, really, really understand what you are doing. &'No pre-compiled
15608 distributions of Exim should ever make this option available.'&
15610 When &%disable_fsync%& is set true, Exim no longer calls &[fsync()]& to force
15611 updated files' data to be written to disc before continuing. Unexpected events
15612 such as crashes and power outages may cause data to be lost or scrambled.
15613 Here be Dragons. &*Beware.*&
15616 .option disable_ipv6 main boolean false
15617 .cindex "IPv6" "disabling"
15618 If this option is set true, even if the Exim binary has IPv6 support, no IPv6
15619 activities take place. AAAA records are never looked up, and any IPv6 addresses
15620 that are listed in &%local_interfaces%&, data for the &%manualroute%& router,
15621 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
15622 to handle IPv6 literal addresses.
15625 .option dkim_verify_hashes main "string list" "sha256 : sha512"
15626 .cindex DKIM "selecting signature algorithms"
15627 This option gives a list of hash types which are acceptable in signatures,
15628 and an order of processing.
15629 Signatures with algorithms not in the list will be ignored.
15631 Acceptable values include:
15638 Note that the acceptance of sha1 violates RFC 8301.
15640 .option dkim_verify_keytypes main "string list" "ed25519 : rsa"
15641 This option gives a list of key types which are acceptable in signatures,
15642 and an order of processing.
15643 Signatures with algorithms not in the list will be ignored.
15646 .option dkim_verify_min_keysizes main "string list" "rsa=1024 ed25519=250"
15647 This option gives a list of key sizes which are acceptable in signatures.
15648 The list is keyed by the algorithm type for the key; the values are in bits.
15649 Signatures with keys smaller than given by this option will fail verification.
15651 The default enforces the RFC 8301 minimum key size for RSA signatures.
15653 .option dkim_verify_minimal main boolean false
15654 If set to true, verification of signatures will terminate after the
15657 .option dkim_verify_signers main "domain list&!!" $dkim_signers
15658 .cindex DKIM "controlling calls to the ACL"
15659 This option gives a list of DKIM domains for which the DKIM ACL is run.
15660 It is expanded after the message is received; by default it runs
15661 the ACL once for each signature in the message.
15662 See section &<<SECDKIMVFY>>&.
15665 .option dmarc_forensic_sender main string&!! unset
15666 .option dmarc_history_file main string unset
15667 .option dmarc_tld_file main string unset
15668 .cindex DMARC "main section options"
15669 These options control DMARC processing.
15670 See section &<<SECDMARC>>& for details.
15673 .option dns_again_means_nonexist main "domain list&!!" unset
15674 .cindex "DNS" "&""try again""& response; overriding"
15675 DNS lookups give a &"try again"& response for the DNS errors
15676 &"non-authoritative host not found"& and &"SERVERFAIL"&. This can cause Exim to
15677 keep trying to deliver a message, or to give repeated temporary errors to
15678 incoming mail. Sometimes the effect is caused by a badly set up name server and
15679 may persist for a long time. If a domain which exhibits this problem matches
15680 anything in &%dns_again_means_nonexist%&, it is treated as if it did not exist.
15681 This option should be used with care. You can make it apply to reverse lookups
15682 by a setting such as this:
15684 dns_again_means_nonexist = *.in-addr.arpa
15686 This option applies to all DNS lookups that Exim does. It also applies when the
15687 &[gethostbyname()]& or &[getipnodebyname()]& functions give temporary errors,
15688 since these are most likely to be caused by DNS lookup problems. The
15689 &(dnslookup)& router has some options of its own for controlling what happens
15690 when lookups for MX or SRV records give temporary errors. These more specific
15691 options are applied after this global option.
15693 .option dns_check_names_pattern main string "see below"
15694 .cindex "DNS" "pre-check of name syntax"
15695 When this option is set to a non-empty string, it causes Exim to check domain
15696 names for characters that are not allowed in host names before handing them to
15697 the DNS resolver, because some resolvers give temporary errors for names that
15698 contain unusual characters. If a domain name contains any unwanted characters,
15699 a &"not found"& result is forced, and the resolver is not called. The check is
15700 done by matching the domain name against a regular expression, which is the
15701 value of this option. The default pattern is
15703 dns_check_names_pattern = \
15704 (?i)^(?>(?(1)\.|())[^\W_](?>[a-z0-9/-]*[^\W_])?)+$
15706 which permits only letters, digits, slashes, and hyphens in components, but
15707 they must start and end with a letter or digit. Slashes are not, in fact,
15708 permitted in host names, but they are found in certain NS records (which can be
15709 accessed in Exim by using a &%dnsdb%& lookup). If you set
15710 &%allow_utf8_domains%&, you must modify this pattern, or set the option to an
15713 .option dns_csa_search_limit main integer 5
15714 This option controls the depth of parental searching for CSA SRV records in the
15715 DNS, as described in more detail in section &<<SECTverifyCSA>>&.
15717 .option dns_csa_use_reverse main boolean true
15718 This option controls whether or not an IP address, given as a CSA domain, is
15719 reversed and looked up in the reverse DNS, as described in more detail in
15720 section &<<SECTverifyCSA>>&.
15722 .option dns_cname_loops main integer 1
15723 .cindex DNS "CNAME following"
15724 This option controls the following of CNAME chains, needed if the resolver does
15725 not do it internally.
15726 As of 2018 most should, and the default can be left.
15727 If you have an ancient one, a value of 10 is likely needed.
15729 The default value of one CNAME-follow is needed
15730 thanks to the observed return for an MX request,
15731 given no MX presence but a CNAME to an A, of the CNAME.
15734 .option dns_dnssec_ok main integer -1
15735 .cindex "DNS" "resolver options"
15736 .cindex "DNS" "DNSSEC"
15737 If this option is set to a non-negative number then Exim will initialise the
15738 DNS resolver library to either use or not use DNSSEC, overriding the system
15739 default. A value of 0 coerces DNSSEC off, a value of 1 coerces DNSSEC on.
15741 If the resolver library does not support DNSSEC then this option has no effect.
15743 On Linux with glibc 2.31 or newer this is insufficient, the resolver library
15744 will default to stripping out a successful validation status.
15745 This will break a previously working Exim installation.
15746 Provided that you do trust the resolver (ie, is on localhost) you can tell
15747 glibc to pass through any successful validation with a new option in
15748 &_/etc/resolv.conf_&:
15754 .option dns_ipv4_lookup main "domain list&!!" unset
15755 .cindex "IPv6" "DNS lookup for AAAA records"
15756 .cindex "DNS" "IPv6 lookup for AAAA records"
15757 .cindex DNS "IPv6 disabling"
15758 When Exim is compiled with IPv6 support and &%disable_ipv6%& is not set, it
15759 looks for IPv6 address records (AAAA records) as well as IPv4 address records
15760 (A records) when trying to find IP addresses for hosts, unless the host's
15761 domain matches this list.
15763 This is a fudge to help with name servers that give big delays or otherwise do
15764 not work for the AAAA record type. In due course, when the world's name
15765 servers have all been upgraded, there should be no need for this option.
15766 Note that all lookups, including those done for verification, are affected;
15767 this will result in verify failure for IPv6 connections or ones using names
15768 only valid for IPv6 addresses.
15771 .option dns_retrans main time 0s
15772 .cindex "DNS" "resolver options"
15773 .cindex timeout "dns lookup"
15774 .cindex "DNS" timeout
15775 The options &%dns_retrans%& and &%dns_retry%& can be used to set the
15776 retransmission and retry parameters for DNS lookups. Values of zero (the
15777 defaults) leave the system default settings unchanged. The first value is the
15778 time between retries, and the second is the number of retries. It isn't
15779 totally clear exactly how these settings affect the total time a DNS lookup may
15780 take. I haven't found any documentation about timeouts on DNS lookups; these
15781 parameter values are available in the external resolver interface structure,
15782 but nowhere does it seem to describe how they are used or what you might want
15784 See also the &%slow_lookup_log%& option.
15787 .option dns_retry main integer 0
15788 See &%dns_retrans%& above.
15791 .option dns_trust_aa main "domain list&!!" unset
15792 .cindex "DNS" "resolver options"
15793 .cindex "DNS" "DNSSEC"
15794 If this option is set then lookup results marked with the AA bit
15795 (Authoritative Answer) are trusted the same way as if they were
15796 DNSSEC-verified. The authority section's name of the answer must
15797 match with this expanded domain list.
15799 Use this option only if you talk directly to a resolver that is
15800 authoritative for some zones and does not set the AD (Authentic Data)
15801 bit in the answer. Some DNS servers may have an configuration option to
15802 mark the answers from their own zones as verified (they set the AD bit).
15803 Others do not have this option. It is considered as poor practice using
15804 a resolver that is an authoritative server for some zones.
15806 Use this option only if you really have to (e.g. if you want
15807 to use DANE for remote delivery to a server that is listed in the DNS
15808 zones that your resolver is authoritative for).
15810 If the DNS answer packet has the AA bit set and contains resource record
15811 in the answer section, the name of the first NS record appearing in the
15812 authority section is compared against the list. If the answer packet is
15813 authoritative but the answer section is empty, the name of the first SOA
15814 record in the authoritative section is used instead.
15816 .cindex "DNS" "resolver options"
15817 .option dns_use_edns0 main integer -1
15818 .cindex "DNS" "resolver options"
15819 .cindex "DNS" "EDNS0"
15820 .cindex "DNS" "OpenBSD
15821 If this option is set to a non-negative number then Exim will initialise the
15822 DNS resolver library to either use or not use EDNS0 extensions, overriding
15823 the system default. A value of 0 coerces EDNS0 off, a value of 1 coerces EDNS0
15826 If the resolver library does not support EDNS0 then this option has no effect.
15828 OpenBSD's asr resolver routines are known to ignore the EDNS0 option; this
15829 means that DNSSEC will not work with Exim on that platform either, unless Exim
15830 is linked against an alternative DNS client library.
15833 .option drop_cr main boolean false
15834 This is an obsolete option that is now a no-op. It used to affect the way Exim
15835 handled CR and LF characters in incoming messages. What happens now is
15836 described in section &<<SECTlineendings>>&.
15838 .option dsn_advertise_hosts main "host list&!!" unset
15839 .cindex "bounce messages" "success"
15840 .cindex "DSN" "success"
15841 .cindex "Delivery Status Notification" "success"
15842 .cindex "ESMTP extensions" DSN
15843 DSN extensions (RFC3461) will be advertised in the EHLO message to,
15844 and accepted from, these hosts.
15845 Hosts may use the NOTIFY and ORCPT options on RCPT TO commands,
15846 and RET and ENVID options on MAIL FROM commands.
15847 A NOTIFY=SUCCESS option requests success-DSN messages.
15848 A NOTIFY= option with no argument requests that no delay or failure DSNs
15850 &*Note*&: Supplying success-DSN messages has been criticised
15851 on privacy grounds; it can leak details of internal forwarding.
15853 .option dsn_from main "string&!!" "see below"
15854 .cindex "&'From:'& header line" "in bounces"
15855 .cindex "bounce messages" "&'From:'& line, specifying"
15856 This option can be used to vary the contents of &'From:'& header lines in
15857 bounces and other automatically generated messages (&"Delivery Status
15858 Notifications"& &-- hence the name of the option). The default setting is:
15860 dsn_from = Mail Delivery System <Mailer-Daemon@$qualify_domain>
15862 The value is expanded every time it is needed. If the expansion fails, a
15863 panic is logged, and the default value is used.
15865 .option envelope_to_remove main boolean true
15866 .cindex "&'Envelope-to:'& header line"
15867 Exim's transports have an option for adding an &'Envelope-to:'& header to a
15868 message when it is delivered, in exactly the same way as &'Return-path:'& is
15869 handled. &'Envelope-to:'& records the original recipient address from the
15870 message's envelope that caused the delivery to happen. Such headers should not
15871 be present in incoming messages, and this option causes them to be removed at
15872 the time the message is received, to avoid any problems that might occur when a
15873 delivered message is subsequently sent on to some other recipient.
15876 .option errors_copy main "string list&!!" unset
15877 .cindex "bounce message" "copy to other address"
15878 .cindex "copy of bounce message"
15879 Setting this option causes Exim to send bcc copies of bounce messages that it
15880 generates to other addresses. &*Note*&: This does not apply to bounce messages
15881 coming from elsewhere. The value of the option is a colon-separated list of
15882 items. Each item consists of a pattern, terminated by white space, followed by
15883 a comma-separated list of email addresses. If a pattern contains spaces, it
15884 must be enclosed in double quotes.
15886 Each pattern is processed in the same way as a single item in an address list
15887 (see section &<<SECTaddresslist>>&). When a pattern matches the recipient of
15888 the bounce message, the message is copied to the addresses on the list. The
15889 items are scanned in order, and once a matching one is found, no further items
15890 are examined. For example:
15892 errors_copy = spqr@mydomain postmaster@mydomain.example :\
15893 rqps@mydomain hostmaster@mydomain.example,\
15894 postmaster@mydomain.example
15896 .vindex "&$domain$&"
15897 .vindex "&$local_part$&"
15898 The address list is expanded before use. The expansion variables &$local_part$&
15899 and &$domain$& are set from the original recipient of the error message, and if
15900 there was any wildcard matching in the pattern, the expansion
15901 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%errors_copy%&"
15902 variables &$0$&, &$1$&, etc. are set in the normal way.
15905 .option errors_reply_to main string unset
15906 .cindex "bounce message" "&'Reply-to:'& in"
15907 By default, Exim's bounce and delivery warning messages contain the header line
15909 &`From: Mail Delivery System <Mailer-Daemon@`&&'qualify-domain'&&`>`&
15911 .oindex &%quota_warn_message%&
15912 where &'qualify-domain'& is the value of the &%qualify_domain%& option.
15913 A warning message that is generated by the &%quota_warn_message%& option in an
15914 &(appendfile)& transport may contain its own &'From:'& header line that
15915 overrides the default.
15917 Experience shows that people reply to bounce messages. If the
15918 &%errors_reply_to%& option is set, a &'Reply-To:'& header is added to bounce
15919 and warning messages. For example:
15921 errors_reply_to = postmaster@my.domain.example
15923 The value of the option is not expanded. It must specify a valid RFC 2822
15924 address. However, if a warning message that is generated by the
15925 &%quota_warn_message%& option in an &(appendfile)& transport contain its
15926 own &'Reply-To:'& header line, the value of the &%errors_reply_to%& option is
15930 .option event_action main string&!! unset
15932 This option declares a string to be expanded for Exim's events mechanism.
15933 For details see chapter &<<CHAPevents>>&.
15936 .option exim_group main string "compile-time configured"
15937 .cindex "gid (group id)" "Exim's own"
15938 .cindex "Exim group"
15939 This option changes the gid under which Exim runs when it gives up root
15940 privilege. The default value is compiled into the binary. The value of this
15941 option is used only when &%exim_user%& is also set. Unless it consists entirely
15942 of digits, the string is looked up using &[getgrnam()]&, and failure causes a
15943 configuration error. See chapter &<<CHAPsecurity>>& for a discussion of
15947 .option exim_path main string "see below"
15948 .cindex "Exim binary, path name"
15949 This option specifies the path name of the Exim binary, which is used when Exim
15950 needs to re-exec itself. The default is set up to point to the file &'exim'& in
15951 the directory configured at compile time by the BIN_DIRECTORY setting. It
15952 is necessary to change &%exim_path%& if, exceptionally, Exim is run from some
15954 &*Warning*&: Do not use a macro to define the value of this option, because
15955 you will break those Exim utilities that scan the configuration file to find
15956 where the binary is. (They then use the &%-bP%& option to extract option
15957 settings such as the value of &%spool_directory%&.)
15960 .option exim_user main string "compile-time configured"
15961 .cindex "uid (user id)" "Exim's own"
15962 .cindex "Exim user"
15963 This option changes the uid under which Exim runs when it gives up root
15964 privilege. The default value is compiled into the binary. Ownership of the run
15965 time configuration file and the use of the &%-C%& and &%-D%& command line
15966 options is checked against the values in the binary, not what is set here.
15968 Unless it consists entirely of digits, the string is looked up using
15969 &[getpwnam()]&, and failure causes a configuration error. If &%exim_group%& is
15970 not also supplied, the gid is taken from the result of &[getpwnam()]& if it is
15971 used. See chapter &<<CHAPsecurity>>& for a discussion of security issues.
15974 .option exim_version main string "current version"
15975 .cindex "Exim version"
15976 .cindex customizing "version number"
15977 .cindex "version number of Exim" override
15978 This option overrides the &$version_number$&/&$exim_version$& that Exim reports in
15979 various places. Use with care; this may fool stupid security scanners.
15982 .option extra_local_interfaces main "string list" unset
15983 This option defines network interfaces that are to be considered local when
15984 routing, but which are not used for listening by the daemon. See section
15985 &<<SECTreclocipadd>>& for details.
15988 . Allow this long option name to split; give it unsplit as a fifth argument
15989 . for the automatic .oindex that is generated by .option.
15991 .option "extract_addresses_remove_arguments" main boolean true &&&
15992 extract_addresses_remove_arguments
15994 .cindex "command line" "addresses with &%-t%&"
15995 .cindex "Sendmail compatibility" "&%-t%& option"
15996 According to some Sendmail documentation (Sun, IRIX, HP-UX), if any addresses
15997 are present on the command line when the &%-t%& option is used to build an
15998 envelope from a message's &'To:'&, &'Cc:'& and &'Bcc:'& headers, the command
15999 line addresses are removed from the recipients list. This is also how Smail
16000 behaves. However, other Sendmail documentation (the O'Reilly book) states that
16001 command line addresses are added to those obtained from the header lines. When
16002 &%extract_addresses_remove_arguments%& is true (the default), Exim subtracts
16003 argument headers. If it is set false, Exim adds rather than removes argument
16007 .option finduser_retries main integer 0
16008 .cindex "NIS, retrying user lookups"
16009 On systems running NIS or other schemes in which user and group information is
16010 distributed from a remote system, there can be times when &[getpwnam()]& and
16011 related functions fail, even when given valid data, because things time out.
16012 Unfortunately these failures cannot be distinguished from genuine &"not found"&
16013 errors. If &%finduser_retries%& is set greater than zero, Exim will try that
16014 many extra times to find a user or a group, waiting for one second between
16017 .cindex "&_/etc/passwd_&" "multiple reading of"
16018 You should not set this option greater than zero if your user information is in
16019 a traditional &_/etc/passwd_& file, because it will cause Exim needlessly to
16020 search the file multiple times for non-existent users, and also cause delay.
16024 .option freeze_tell main "string list, comma separated" unset
16025 .cindex "freezing messages" "sending a message when freezing"
16026 On encountering certain errors, or when configured to do so in a system filter,
16027 ACL, or special router, Exim freezes a message. This means that no further
16028 delivery attempts take place until an administrator thaws the message, or the
16029 &%auto_thaw%&, &%ignore_bounce_errors_after%&, or &%timeout_frozen_after%&
16030 feature cause it to be processed. If &%freeze_tell%& is set, Exim generates a
16031 warning message whenever it freezes something, unless the message it is
16032 freezing is a locally-generated bounce message. (Without this exception there
16033 is the possibility of looping.) The warning message is sent to the addresses
16034 supplied as the comma-separated value of this option. If several of the
16035 message's addresses cause freezing, only a single message is sent. If the
16036 freezing was automatic, the reason(s) for freezing can be found in the message
16037 log. If you configure freezing in a filter or ACL, you must arrange for any
16038 logging that you require.
16041 .option gecos_name main string&!! unset
16043 .cindex "&""gecos""& field, parsing"
16044 Some operating systems, notably HP-UX, use the &"gecos"& field in the system
16045 password file to hold other information in addition to users' real names. Exim
16046 looks up this field for use when it is creating &'Sender:'& or &'From:'&
16047 headers. If either &%gecos_pattern%& or &%gecos_name%& are unset, the contents
16048 of the field are used unchanged, except that, if an ampersand is encountered,
16049 it is replaced by the user's login name with the first character forced to
16050 upper case, since this is a convention that is observed on many systems.
16052 When these options are set, &%gecos_pattern%& is treated as a regular
16053 expression that is to be applied to the field (again with && replaced by the
16054 login name), and if it matches, &%gecos_name%& is expanded and used as the
16057 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%gecos_name%&"
16058 Numeric variables such as &$1$&, &$2$&, etc. can be used in the expansion to
16059 pick up sub-fields that were matched by the pattern. In HP-UX, where the user's
16060 name terminates at the first comma, the following can be used:
16062 gecos_pattern = ([^,]*)
16066 .option gecos_pattern main string unset
16067 See &%gecos_name%& above.
16070 .option gnutls_compat_mode main boolean unset
16071 This option controls whether GnuTLS is used in compatibility mode in an Exim
16072 server. This reduces security slightly, but improves interworking with older
16073 implementations of TLS.
16076 .option gnutls_allow_auto_pkcs11 main boolean unset
16077 This option will let GnuTLS (2.12.0 or later) autoload PKCS11 modules with
16078 the p11-kit configuration files in &_/etc/pkcs11/modules/_&.
16081 &url(https://www.gnutls.org/manual/gnutls.html#Smart-cards-and-HSMs)
16086 .option headers_charset main string "see below"
16087 This option sets a default character set for translating from encoded MIME
16088 &"words"& in header lines, when referenced by an &$h_xxx$& expansion item. The
16089 default is the value of HEADERS_CHARSET in &_Local/Makefile_&. The
16090 ultimate default is ISO-8859-1. For more details see the description of header
16091 insertions in section &<<SECTexpansionitems>>&.
16095 .option header_maxsize main integer "see below"
16096 .cindex "header section" "maximum size of"
16097 .cindex "limit" "size of message header section"
16098 This option controls the overall maximum size of a message's header
16099 section. The default is the value of HEADER_MAXSIZE in
16100 &_Local/Makefile_&; the default for that is 1M. Messages with larger header
16101 sections are rejected.
16104 .option header_line_maxsize main integer 0
16105 .cindex "header lines" "maximum size of"
16106 .cindex "limit" "size of one header line"
16107 This option limits the length of any individual header line in a message, after
16108 all the continuations have been joined together. Messages with individual
16109 header lines that are longer than the limit are rejected. The default value of
16110 zero means &"no limit"&.
16115 .option helo_accept_junk_hosts main "host list&!!" unset
16116 .cindex "HELO" "accepting junk data"
16117 .cindex "EHLO" "accepting junk data"
16118 Exim checks the syntax of HELO and EHLO commands for incoming SMTP
16119 mail, and gives an error response for invalid data. Unfortunately, there are
16120 some SMTP clients that send syntactic junk. They can be accommodated by setting
16121 this option. Note that this is a syntax check only. See &%helo_verify_hosts%&
16122 if you want to do semantic checking.
16123 See also &%helo_allow_chars%& for a way of extending the permitted character
16127 .option helo_allow_chars main string unset
16128 .cindex "HELO" "underscores in"
16129 .cindex "EHLO" "underscores in"
16130 .cindex "underscore in EHLO/HELO"
16131 This option can be set to a string of rogue characters that are permitted in
16132 all EHLO and HELO names in addition to the standard letters, digits,
16133 hyphens, and dots. If you really must allow underscores, you can set
16135 helo_allow_chars = _
16137 Note that the value is one string, not a list.
16140 .option helo_lookup_domains main "domain list&!!" &`@:@[]`&
16141 .cindex "HELO" "forcing reverse lookup"
16142 .cindex "EHLO" "forcing reverse lookup"
16143 If the domain given by a client in a HELO or EHLO command matches this
16144 list, a reverse lookup is done in order to establish the host's true name. The
16145 default forces a lookup if the client host gives the server's name or any of
16146 its IP addresses (in brackets), something that broken clients have been seen to
16150 .option helo_try_verify_hosts main "host list&!!" unset
16151 .cindex "HELO verifying" "optional"
16152 .cindex "EHLO" "verifying, optional"
16153 By default, Exim just checks the syntax of HELO and EHLO commands (see
16154 &%helo_accept_junk_hosts%& and &%helo_allow_chars%&). However, some sites like
16155 to do more extensive checking of the data supplied by these commands. The ACL
16156 condition &`verify = helo`& is provided to make this possible.
16157 Formerly, it was necessary also to set this option (&%helo_try_verify_hosts%&)
16158 to force the check to occur. From release 4.53 onwards, this is no longer
16159 necessary. If the check has not been done before &`verify = helo`& is
16160 encountered, it is done at that time. Consequently, this option is obsolete.
16161 Its specification is retained here for backwards compatibility.
16163 When an EHLO or HELO command is received, if the calling host matches
16164 &%helo_try_verify_hosts%&, Exim checks that the host name given in the HELO or
16165 EHLO command either:
16168 is an IP literal matching the calling address of the host, or
16170 .cindex "DNS" "reverse lookup"
16171 .cindex "reverse DNS lookup"
16172 matches the host name that Exim obtains by doing a reverse lookup of the
16173 calling host address, or
16175 when looked up in DNS yields the calling host address.
16178 However, the EHLO or HELO command is not rejected if any of the checks
16179 fail. Processing continues, but the result of the check is remembered, and can
16180 be detected later in an ACL by the &`verify = helo`& condition.
16182 If DNS was used for successful verification, the variable
16183 .cindex "DNS" "DNSSEC"
16184 &$helo_verify_dnssec$& records the DNSSEC status of the lookups.
16186 .option helo_verify_hosts main "host list&!!" unset
16187 .cindex "HELO verifying" "mandatory"
16188 .cindex "EHLO" "verifying, mandatory"
16189 Like &%helo_try_verify_hosts%&, this option is obsolete, and retained only for
16190 backwards compatibility. For hosts that match this option, Exim checks the host
16191 name given in the HELO or EHLO in the same way as for
16192 &%helo_try_verify_hosts%&. If the check fails, the HELO or EHLO command is
16193 rejected with a 550 error, and entries are written to the main and reject logs.
16194 If a MAIL command is received before EHLO or HELO, it is rejected with a 503
16197 .option hold_domains main "domain list&!!" unset
16198 .cindex "domain" "delaying delivery"
16199 .cindex "delivery" "delaying certain domains"
16200 This option allows mail for particular domains to be held in the queue
16201 manually. The option is overridden if a message delivery is forced with the
16202 &%-M%&, &%-qf%&, &%-Rf%& or &%-Sf%& options, and also while testing or
16203 verifying addresses using &%-bt%& or &%-bv%&. Otherwise, if a domain matches an
16204 item in &%hold_domains%&, no routing or delivery for that address is done, and
16205 it is deferred every time the message is looked at.
16207 This option is intended as a temporary operational measure for delaying the
16208 delivery of mail while some problem is being sorted out, or some new
16209 configuration tested. If you just want to delay the processing of some
16210 domains until a queue run occurs, you should use &%queue_domains%& or
16211 &%queue_smtp_domains%&, not &%hold_domains%&.
16213 A setting of &%hold_domains%& does not override Exim's code for removing
16214 messages from the queue if they have been there longer than the longest retry
16215 time in any retry rule. If you want to hold messages for longer than the normal
16216 retry times, insert a dummy retry rule with a long retry time.
16219 .option host_lookup main "host list&!!" unset
16220 .cindex "host name" "lookup, forcing"
16221 Exim does not look up the name of a calling host from its IP address unless it
16222 is required to compare against some host list, or the host matches
16223 &%helo_try_verify_hosts%& or &%helo_verify_hosts%&, or the host matches this
16224 option (which normally contains IP addresses rather than host names). The
16225 default configuration file contains
16229 which causes a lookup to happen for all hosts. If the expense of these lookups
16230 is felt to be too great, the setting can be changed or removed.
16232 After a successful reverse lookup, Exim does a forward lookup on the name it
16233 has obtained, to verify that it yields the IP address that it started with. If
16234 this check fails, Exim behaves as if the name lookup failed.
16236 .vindex "&$host_lookup_failed$&"
16237 .vindex "&$sender_host_name$&"
16238 After any kind of failure, the host name (in &$sender_host_name$&) remains
16239 unset, and &$host_lookup_failed$& is set to the string &"1"&. See also
16240 &%dns_again_means_nonexist%&, &%helo_lookup_domains%&, and
16241 &`verify = reverse_host_lookup`& in ACLs.
16244 .option host_lookup_order main "string list" &`bydns:byaddr`&
16245 This option specifies the order of different lookup methods when Exim is trying
16246 to find a host name from an IP address. The default is to do a DNS lookup
16247 first, and then to try a local lookup (using &[gethostbyaddr()]& or equivalent)
16248 if that fails. You can change the order of these lookups, or omit one entirely,
16251 &*Warning*&: The &"byaddr"& method does not always yield aliases when there are
16252 multiple PTR records in the DNS and the IP address is not listed in
16253 &_/etc/hosts_&. Different operating systems give different results in this
16254 case. That is why the default tries a DNS lookup first.
16258 .option host_reject_connection main "host list&!!" unset
16259 .cindex "host" "rejecting connections from"
16260 If this option is set, incoming SMTP calls from the hosts listed are rejected
16261 as soon as the connection is made.
16262 This option is obsolete, and retained only for backward compatibility, because
16263 nowadays the ACL specified by &%acl_smtp_connect%& can also reject incoming
16264 connections immediately.
16266 The ability to give an immediate rejection (either by this option or using an
16267 ACL) is provided for use in unusual cases. Many hosts will just try again,
16268 sometimes without much delay. Normally, it is better to use an ACL to reject
16269 incoming messages at a later stage, such as after RCPT commands. See
16270 chapter &<<CHAPACL>>&.
16273 .option hosts_connection_nolog main "host list&!!" unset
16274 .cindex "host" "not logging connections from"
16275 This option defines a list of hosts for which connection logging does not
16276 happen, even though the &%smtp_connection%& log selector is set. For example,
16277 you might want not to log SMTP connections from local processes, or from
16278 127.0.0.1, or from your local LAN. This option is consulted in the main loop of
16279 the daemon; you should therefore strive to restrict its value to a short inline
16280 list of IP addresses and networks. To disable logging SMTP connections from
16281 local processes, you must create a host list with an empty item. For example:
16283 hosts_connection_nolog = :
16286 The hosts affected by this option also do not log "no MAIL in SMTP connection"
16287 lines, as may commonly be produced by a monitoring system.
16291 .option hosts_require_alpn main "host list&!!" unset
16292 .cindex ALPN "require negotiation in server"
16294 .cindex TLS "Application Layer Protocol Names"
16295 If the TLS library supports ALPN
16296 then a successful negotiation of ALPN will be required for any client
16297 matching the list, for TLS to be used.
16298 See also the &%tls_alpn%& option.
16300 &*Note*&: prevention of fallback to in-clear connection is not
16301 managed by this option, and should be done separately.
16304 .option hosts_require_helo main "host list&!!" *
16305 .cindex "HELO/EHLO" requiring
16306 Exim will require an accepted HELO or EHLO command from a host matching
16307 this list, before accepting a MAIL command.
16310 .option hosts_proxy main "host list&!!" unset
16311 .cindex proxy "proxy protocol"
16312 This option enables use of Proxy Protocol proxies for incoming
16313 connections. For details see section &<<SECTproxyInbound>>&.
16316 .option hosts_treat_as_local main "domain list&!!" unset
16317 .cindex "local host" "domains treated as"
16318 .cindex "host" "treated as local"
16319 If this option is set, any host names that match the domain list are treated as
16320 if they were the local host when Exim is scanning host lists obtained from MX
16322 or other sources. Note that the value of this option is a domain list, not a
16323 host list, because it is always used to check host names, not IP addresses.
16325 This option also applies when Exim is matching the special items
16326 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`& in a domain list (see
16327 section &<<SECTdomainlist>>&), and when checking the &%hosts%& option in the
16328 &(smtp)& transport for the local host (see the &%allow_localhost%& option in
16329 that transport). See also &%local_interfaces%&, &%extra_local_interfaces%&, and
16330 chapter &<<CHAPinterfaces>>&, which contains a discussion about local network
16331 interfaces and recognizing the local host.
16334 .option ibase_servers main "string list" unset
16335 .cindex "InterBase" "server list"
16336 This option provides a list of InterBase servers and associated connection data,
16337 to be used in conjunction with &(ibase)& lookups (see section &<<SECID72>>&).
16338 The option is available only if Exim has been built with InterBase support.
16342 .option ignore_bounce_errors_after main time 10w
16343 .cindex "bounce message" "discarding"
16344 .cindex "discarding bounce message"
16345 This option affects the processing of bounce messages that cannot be delivered,
16346 that is, those that suffer a permanent delivery failure. (Bounce messages that
16347 suffer temporary delivery failures are of course retried in the usual way.)
16349 After a permanent delivery failure, bounce messages are frozen,
16350 because there is no sender to whom they can be returned. When a frozen bounce
16351 message has been in the queue for more than the given time, it is unfrozen at
16352 the next queue run, and a further delivery is attempted. If delivery fails
16353 again, the bounce message is discarded. This makes it possible to keep failed
16354 bounce messages around for a shorter time than the normal maximum retry time
16355 for frozen messages. For example,
16357 ignore_bounce_errors_after = 12h
16359 retries failed bounce message deliveries after 12 hours, discarding any further
16360 failures. If the value of this option is set to a zero time period, bounce
16361 failures are discarded immediately. Setting a very long time (as in the default
16362 value) has the effect of disabling this option. For ways of automatically
16363 dealing with other kinds of frozen message, see &%auto_thaw%& and
16364 &%timeout_frozen_after%&.
16367 .option ignore_fromline_hosts main "host list&!!" unset
16368 .cindex "&""From""& line"
16369 .cindex "UUCP" "&""From""& line"
16370 Some broken SMTP clients insist on sending a UUCP-like &"From&~"& line before
16371 the headers of a message. By default this is treated as the start of the
16372 message's body, which means that any following headers are not recognized as
16373 such. Exim can be made to ignore it by setting &%ignore_fromline_hosts%& to
16374 match those hosts that insist on sending it. If the sender is actually a local
16375 process rather than a remote host, and is using &%-bs%& to inject the messages,
16376 &%ignore_fromline_local%& must be set to achieve this effect.
16379 .option ignore_fromline_local main boolean false
16380 See &%ignore_fromline_hosts%& above.
16382 .option keep_environment main "string list" unset
16383 .cindex "environment" "values from"
16384 This option contains a string list of environment variables to keep.
16385 You have to trust these variables or you have to be sure that
16386 these variables do not impose any security risk. Keep in mind that
16387 during the startup phase Exim is running with an effective UID 0 in most
16388 installations. As the default value is an empty list, the default
16389 environment for using libraries, running embedded Perl code, or running
16390 external binaries is empty, and does not not even contain PATH or HOME.
16392 Actually the list is interpreted as a list of patterns
16393 (&<<SECTlistexpand>>&), except that it is not expanded first.
16395 WARNING: Macro substitution is still done first, so having a macro
16396 FOO and having FOO_HOME in your &%keep_environment%& option may have
16397 unexpected results. You may work around this using a regular expression
16398 that does not match the macro name: ^[F]OO_HOME$.
16400 Current versions of Exim issue a warning during startup if you do not mention
16401 &%keep_environment%& in your runtime configuration file and if your
16402 current environment is not empty. Future versions may not issue that warning
16405 See the &%add_environment%& main config option for a way to set
16406 environment variables to a fixed value. The environment for &(pipe)&
16407 transports is handled separately, see section &<<SECTpipeenv>>& for
16411 .option keep_malformed main time 4d
16412 This option specifies the length of time to keep messages whose spool files
16413 have been corrupted in some way. This should, of course, never happen. At the
16414 next attempt to deliver such a message, it gets removed. The incident is
16418 .option ldap_ca_cert_dir main string unset
16419 .cindex "LDAP", "TLS CA certificate directory"
16420 .cindex certificate "directory for LDAP"
16421 This option indicates which directory contains CA certificates for verifying
16422 a TLS certificate presented by an LDAP server.
16423 While Exim does not provide a default value, your SSL library may.
16424 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
16425 and constrained to be a directory.
16428 .option ldap_ca_cert_file main string unset
16429 .cindex "LDAP", "TLS CA certificate file"
16430 .cindex certificate "file for LDAP"
16431 This option indicates which file contains CA certificates for verifying
16432 a TLS certificate presented by an LDAP server.
16433 While Exim does not provide a default value, your SSL library may.
16434 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
16435 and constrained to be a file.
16438 .option ldap_cert_file main string unset
16439 .cindex "LDAP" "TLS client certificate file"
16440 .cindex certificate "file for LDAP"
16441 This option indicates which file contains an TLS client certificate which
16442 Exim should present to the LDAP server during TLS negotiation.
16443 Should be used together with &%ldap_cert_key%&.
16446 .option ldap_cert_key main string unset
16447 .cindex "LDAP" "TLS client key file"
16448 .cindex certificate "key for LDAP"
16449 This option indicates which file contains the secret/private key to use
16450 to prove identity to the LDAP server during TLS negotiation.
16451 Should be used together with &%ldap_cert_file%&, which contains the
16452 identity to be proven.
16455 .option ldap_cipher_suite main string unset
16456 .cindex "LDAP" "TLS cipher suite"
16457 This controls the TLS cipher-suite negotiation during TLS negotiation with
16458 the LDAP server. See &<<SECTreqciphssl>>& for more details of the format of
16459 cipher-suite options with OpenSSL (as used by LDAP client libraries).
16462 .option ldap_default_servers main "string list" unset
16463 .cindex "LDAP" "default servers"
16464 This option provides a list of LDAP servers which are tried in turn when an
16465 LDAP query does not contain a server. See section &<<SECTforldaque>>& for
16466 details of LDAP queries. This option is available only when Exim has been built
16470 .option ldap_require_cert main string unset.
16471 .cindex "LDAP" "policy for LDAP server TLS cert presentation"
16472 This should be one of the values "hard", "demand", "allow", "try" or "never".
16473 A value other than one of these is interpreted as "never".
16474 See the entry "TLS_REQCERT" in your system man page for ldap.conf(5).
16475 Although Exim does not set a default, the LDAP library probably defaults
16479 .option ldap_start_tls main boolean false
16480 .cindex "LDAP" "whether or not to negotiate TLS"
16481 If set, Exim will attempt to negotiate TLS with the LDAP server when
16482 connecting on a regular LDAP port. This is the LDAP equivalent of SMTP's
16483 "STARTTLS". This is distinct from using "ldaps", which is the LDAP form
16485 In the event of failure to negotiate TLS, the action taken is controlled
16486 by &%ldap_require_cert%&.
16487 This option is ignored for &`ldapi`& connections.
16490 .option ldap_version main integer unset
16491 .cindex "LDAP" "protocol version, forcing"
16492 This option can be used to force Exim to set a specific protocol version for
16493 LDAP. If it option is unset, it is shown by the &%-bP%& command line option as
16494 -1. When this is the case, the default is 3 if LDAP_VERSION3 is defined in
16495 the LDAP headers; otherwise it is 2. This option is available only when Exim
16496 has been built with LDAP support.
16500 .option local_from_check main boolean true
16501 .cindex "&'Sender:'& header line" "disabling addition of"
16502 .cindex "&'From:'& header line" "disabling checking of"
16503 When a message is submitted locally (that is, not over a TCP/IP connection) by
16504 an untrusted user, Exim removes any existing &'Sender:'& header line, and
16505 checks that the &'From:'& header line matches the login of the calling user and
16506 the domain specified by &%qualify_domain%&.
16508 &*Note*&: An unqualified address (no domain) in the &'From:'& header in a
16509 locally submitted message is automatically qualified by Exim, unless the
16510 &%-bnq%& command line option is used.
16512 You can use &%local_from_prefix%& and &%local_from_suffix%& to permit affixes
16513 on the local part. If the &'From:'& header line does not match, Exim adds a
16514 &'Sender:'& header with an address constructed from the calling user's login
16515 and the default qualify domain.
16517 If &%local_from_check%& is set false, the &'From:'& header check is disabled,
16518 and no &'Sender:'& header is ever added. If, in addition, you want to retain
16519 &'Sender:'& header lines supplied by untrusted users, you must also set
16520 &%local_sender_retain%& to be true.
16522 .cindex "envelope from"
16523 .cindex "envelope sender"
16524 These options affect only the header lines in the message. The envelope sender
16525 is still forced to be the login id at the qualify domain unless
16526 &%untrusted_set_sender%& permits the user to supply an envelope sender.
16528 For messages received over TCP/IP, an ACL can specify &"submission mode"& to
16529 request similar header line checking. See section &<<SECTthesenhea>>&, which
16530 has more details about &'Sender:'& processing.
16535 .option local_from_prefix main string unset
16536 When Exim checks the &'From:'& header line of locally submitted messages for
16537 matching the login id (see &%local_from_check%& above), it can be configured to
16538 ignore certain prefixes and suffixes in the local part of the address. This is
16539 done by setting &%local_from_prefix%& and/or &%local_from_suffix%& to
16540 appropriate lists, in the same form as the &%local_part_prefix%& and
16541 &%local_part_suffix%& router options (see chapter &<<CHAProutergeneric>>&). For
16544 local_from_prefix = *-
16546 is set, a &'From:'& line containing
16548 From: anything-user@your.domain.example
16550 will not cause a &'Sender:'& header to be added if &'user@your.domain.example'&
16551 matches the actual sender address that is constructed from the login name and
16555 .option local_from_suffix main string unset
16556 See &%local_from_prefix%& above.
16559 .option local_interfaces main "string list" "see below"
16560 This option controls which network interfaces are used by the daemon for
16561 listening; they are also used to identify the local host when routing. Chapter
16562 &<<CHAPinterfaces>>& contains a full description of this option and the related
16563 options &%daemon_smtp_ports%&, &%extra_local_interfaces%&,
16564 &%hosts_treat_as_local%&, and &%tls_on_connect_ports%&. The default value for
16565 &%local_interfaces%& is
16567 local_interfaces = 0.0.0.0
16569 when Exim is built without IPv6 support; otherwise it is
16571 local_interfaces = <; ::0 ; 0.0.0.0
16574 .option local_scan_timeout main time 5m
16575 .cindex "timeout" "for &[local_scan()]& function"
16576 .cindex "&[local_scan()]& function" "timeout"
16577 This timeout applies to the &[local_scan()]& function (see chapter
16578 &<<CHAPlocalscan>>&). Zero means &"no timeout"&. If the timeout is exceeded,
16579 the incoming message is rejected with a temporary error if it is an SMTP
16580 message. For a non-SMTP message, the message is dropped and Exim ends with a
16581 non-zero code. The incident is logged on the main and reject logs.
16585 .option local_sender_retain main boolean false
16586 .cindex "&'Sender:'& header line" "retaining from local submission"
16587 When a message is submitted locally (that is, not over a TCP/IP connection) by
16588 an untrusted user, Exim removes any existing &'Sender:'& header line. If you
16589 do not want this to happen, you must set &%local_sender_retain%&, and you must
16590 also set &%local_from_check%& to be false (Exim will complain if you do not).
16591 See also the ACL modifier &`control = suppress_local_fixups`&. Section
16592 &<<SECTthesenhea>>& has more details about &'Sender:'& processing.
16597 .option localhost_number main string&!! unset
16598 .cindex "host" "locally unique number for"
16599 .cindex "message ids" "with multiple hosts"
16600 .vindex "&$localhost_number$&"
16601 Exim's message ids are normally unique only within the local host. If
16602 uniqueness among a set of hosts is required, each host must set a different
16603 value for the &%localhost_number%& option. The string is expanded immediately
16604 after reading the configuration file (so that a number can be computed from the
16605 host name, for example) and the result of the expansion must be a number in the
16606 range 0&--16 (or 0&--10 on operating systems with case-insensitive file
16607 systems). This is available in subsequent string expansions via the variable
16608 &$localhost_number$&. When &%localhost_number is set%&, the final two
16609 characters of the message id, instead of just being a fractional part of the
16610 time, are computed from the time and the local host number as described in
16611 section &<<SECTmessiden>>&.
16615 .option log_file_path main "string list&!!" "set at compile time"
16616 .cindex "log" "file path for"
16617 This option sets the path which is used to determine the names of Exim's log
16618 files, or indicates that logging is to be to syslog, or both. It is expanded
16619 when Exim is entered, so it can, for example, contain a reference to the host
16620 name. If no specific path is set for the log files at compile or runtime,
16621 or if the option is unset at runtime (i.e. &`log_file_path = `&)
16622 they are written in a sub-directory called &_log_& in Exim's spool directory.
16623 A path must start with a slash.
16624 To send to syslog, use the word &"syslog"&.
16625 Chapter &<<CHAPlog>>& contains further details about Exim's logging, and
16626 section &<<SECTwhelogwri>>& describes how the contents of &%log_file_path%& are
16627 used. If this string is fixed at your installation (contains no expansion
16628 variables) it is recommended that you do not set this option in the
16629 configuration file, but instead supply the path using LOG_FILE_PATH in
16630 &_Local/Makefile_& so that it is available to Exim for logging errors detected
16631 early on &-- in particular, failure to read the configuration file.
16634 .option log_selector main string unset
16635 .cindex "log" "selectors"
16636 This option can be used to reduce or increase the number of things that Exim
16637 writes to its log files. Its argument is made up of names preceded by plus or
16638 minus characters. For example:
16640 log_selector = +arguments -retry_defer
16642 A list of possible names and what they control is given in the chapter on
16643 logging, in section &<<SECTlogselector>>&.
16646 .option log_timezone main boolean false
16647 .cindex "log" "timezone for entries"
16648 .vindex "&$tod_log$&"
16649 .vindex "&$tod_zone$&"
16650 By default, the timestamps on log lines are in local time without the
16651 timezone. This means that if your timezone changes twice a year, the timestamps
16652 in log lines are ambiguous for an hour when the clocks go back. One way of
16653 avoiding this problem is to set the timezone to UTC. An alternative is to set
16654 &%log_timezone%& true. This turns on the addition of the timezone offset to
16655 timestamps in log lines. Turning on this option can add quite a lot to the size
16656 of log files because each line is extended by 6 characters. Note that the
16657 &$tod_log$& variable contains the log timestamp without the zone, but there is
16658 another variable called &$tod_zone$& that contains just the timezone offset.
16661 .option lookup_open_max main integer 25
16662 .cindex "too many open files"
16663 .cindex "open files, too many"
16664 .cindex "file" "too many open"
16665 .cindex "lookup" "maximum open files"
16666 .cindex "limit" "open files for lookups"
16667 This option limits the number of simultaneously open files for single-key
16668 lookups that use regular files (that is, &(lsearch)&, &(dbm)&, and &(cdb)&).
16669 Exim normally keeps these files open during routing, because often the same
16670 file is required several times. If the limit is reached, Exim closes the least
16671 recently used file. Note that if you are using the &'ndbm'& library, it
16672 actually opens two files for each logical DBM database, though it still counts
16673 as one for the purposes of &%lookup_open_max%&. If you are getting &"too many
16674 open files"& errors with NDBM, you need to reduce the value of
16675 &%lookup_open_max%&.
16678 .option max_username_length main integer 0
16679 .cindex "length of login name"
16680 .cindex "user name" "maximum length"
16681 .cindex "limit" "user name length"
16682 Some operating systems are broken in that they truncate long arguments to
16683 &[getpwnam()]& to eight characters, instead of returning &"no such user"&. If
16684 this option is set greater than zero, any attempt to call &[getpwnam()]& with
16685 an argument that is longer behaves as if &[getpwnam()]& failed.
16688 .option message_body_newlines main bool false
16689 .cindex "message body" "newlines in variables"
16690 .cindex "newline" "in message body variables"
16691 .vindex "&$message_body$&"
16692 .vindex "&$message_body_end$&"
16693 By default, newlines in the message body are replaced by spaces when setting
16694 the &$message_body$& and &$message_body_end$& expansion variables. If this
16695 option is set true, this no longer happens.
16698 .option message_body_visible main integer 500
16699 .cindex "body of message" "visible size"
16700 .cindex "message body" "visible size"
16701 .vindex "&$message_body$&"
16702 .vindex "&$message_body_end$&"
16703 This option specifies how much of a message's body is to be included in the
16704 &$message_body$& and &$message_body_end$& expansion variables.
16707 .option message_id_header_domain main string&!! unset
16708 .cindex "&'Message-ID:'& header line"
16709 If this option is set, the string is expanded and used as the right hand side
16710 (domain) of the &'Message-ID:'& header that Exim creates if a
16711 locally-originated incoming message does not have one. &"Locally-originated"&
16712 means &"not received over TCP/IP."&
16713 Otherwise, the primary host name is used.
16714 Only letters, digits, dot and hyphen are accepted; any other characters are
16715 replaced by hyphens. If the expansion is forced to fail, or if the result is an
16716 empty string, the option is ignored.
16719 .option message_id_header_text main string&!! unset
16720 If this variable is set, the string is expanded and used to augment the text of
16721 the &'Message-id:'& header that Exim creates if a locally-originated incoming
16722 message does not have one. The text of this header is required by RFC 2822 to
16723 take the form of an address. By default, Exim uses its internal message id as
16724 the local part, and the primary host name as the domain. If this option is set,
16725 it is expanded, and provided the expansion is not forced to fail, and does not
16726 yield an empty string, the result is inserted into the header immediately
16727 before the @, separated from the internal message id by a dot. Any characters
16728 that are illegal in an address are automatically converted into hyphens. This
16729 means that variables such as &$tod_log$& can be used, because the spaces and
16730 colons will become hyphens.
16733 .option message_logs main boolean true
16734 .cindex "message logs" "disabling"
16735 .cindex "log" "message log; disabling"
16736 If this option is turned off, per-message log files are not created in the
16737 &_msglog_& spool sub-directory. This reduces the amount of disk I/O required by
16738 Exim, by reducing the number of files involved in handling a message from a
16739 minimum of four (header spool file, body spool file, delivery journal, and
16740 per-message log) to three. The other major I/O activity is Exim's main log,
16741 which is not affected by this option.
16744 .option message_size_limit main string&!! 50M
16745 .cindex "message" "size limit"
16746 .cindex "limit" "message size"
16747 .cindex "size" "of message, limit"
16748 This option limits the maximum size of message that Exim will process. The
16749 value is expanded for each incoming connection so, for example, it can be made
16750 to depend on the IP address of the remote host for messages arriving via
16751 TCP/IP. After expansion, the value must be a sequence of decimal digits,
16752 optionally followed by K or M.
16754 .cindex "SIZE" "ESMTP extension, advertising"
16755 .cindex "ESMTP extensions" SIZE
16756 If nonzero the value will be advertised as a parameter to the ESMTP SIZE
16757 service extension keyword.
16759 &*Note*&: This limit cannot be made to depend on a message's sender or any
16760 other properties of an individual message, because it has to be advertised in
16761 the server's response to EHLO. String expansion failure causes a temporary
16762 error. A value of zero means no limit, but its use is not recommended. See also
16763 &%bounce_return_size_limit%&.
16765 Incoming SMTP messages are failed with a 552 error if the limit is
16766 exceeded; locally-generated messages either get a stderr message or a delivery
16767 failure message to the sender, depending on the &%-oe%& setting. Rejection of
16768 an oversized message is logged in both the main and the reject logs. See also
16769 the generic transport option &%message_size_limit%&, which limits the size of
16770 message that an individual transport can process.
16772 If you use a virus-scanner and set this option to to a value larger than the
16773 maximum size that your virus-scanner is configured to support, you may get
16774 failures triggered by large mails. The right size to configure for the
16775 virus-scanner depends upon what data is passed and the options in use but it's
16776 probably safest to just set it to a little larger than this value. E.g., with a
16777 default Exim message size of 50M and a default ClamAV StreamMaxLength of 10M,
16778 some problems may result.
16780 A value of 0 will disable size limit checking; Exim will still advertise the
16781 SIZE extension in an EHLO response, but without a limit, so as to permit
16782 SMTP clients to still indicate the message size along with the MAIL verb.
16785 .option move_frozen_messages main boolean false
16786 .cindex "frozen messages" "moving"
16787 This option, which is available only if Exim has been built with the setting
16789 SUPPORT_MOVE_FROZEN_MESSAGES=yes
16791 in &_Local/Makefile_&, causes frozen messages and their message logs to be
16792 moved from the &_input_& and &_msglog_& directories on the spool to &_Finput_&
16793 and &_Fmsglog_&, respectively. There is currently no support in Exim or the
16794 standard utilities for handling such moved messages, and they do not show up in
16795 lists generated by &%-bp%& or by the Exim monitor.
16798 .option mua_wrapper main boolean false
16799 Setting this option true causes Exim to run in a very restrictive mode in which
16800 it passes messages synchronously to a smart host. Chapter &<<CHAPnonqueueing>>&
16801 contains a full description of this facility.
16805 .option mysql_servers main "string list" unset
16806 .cindex "MySQL" "server list"
16807 This option provides a list of MySQL servers and associated connection data, to
16808 be used in conjunction with &(mysql)& lookups (see section &<<SECID72>>&). The
16809 option is available only if Exim has been built with MySQL support.
16812 .option never_users main "string list&!!" unset
16813 This option is expanded just once, at the start of Exim's processing. Local
16814 message deliveries are normally run in processes that are setuid to the
16815 recipient, and remote deliveries are normally run under Exim's own uid and gid.
16816 It is usually desirable to prevent any deliveries from running as root, as a
16819 When Exim is built, an option called FIXED_NEVER_USERS can be set to a
16820 list of users that must not be used for local deliveries. This list is fixed in
16821 the binary and cannot be overridden by the configuration file. By default, it
16822 contains just the single user name &"root"&. The &%never_users%& runtime option
16823 can be used to add more users to the fixed list.
16825 If a message is to be delivered as one of the users on the fixed list or the
16826 &%never_users%& list, an error occurs, and delivery is deferred. A common
16829 never_users = root:daemon:bin
16831 Including root is redundant if it is also on the fixed list, but it does no
16832 harm. This option overrides the &%pipe_as_creator%& option of the &(pipe)&
16836 .option notifier_socket main string "$spool_directory/exim_daemon_notify"
16837 This option gives the name for a unix-domain socket on which the daemon
16838 listens for work and information-requests.
16839 Only installations running multiple daemons sharing a spool directory
16840 should need to modify the default.
16842 The option is expanded before use.
16843 If the platform supports Linux-style abstract socket names, the result
16844 is used with a nul byte prefixed.
16846 it should be a full path name and use a directory accessible
16849 If this option is set as empty,
16850 or the command line &%-oY%& option is used, or
16851 the command line uses a &%-oX%& option and does not use &%-oP%&,
16852 then a notifier socket is not created.
16855 .option openssl_options main "string list" "+no_sslv2 +no_sslv3 +single_dh_use +no_ticket +no_renegotiation"
16856 .cindex "OpenSSL "compatibility options"
16857 This option allows an administrator to adjust the SSL options applied
16858 by OpenSSL to connections. It is given as a space-separated list of items,
16859 each one to be +added or -subtracted from the current value.
16861 This option is only available if Exim is built against OpenSSL. The values
16862 available for this option vary according to the age of your OpenSSL install.
16863 The &"all"& value controls a subset of flags which are available, typically
16864 the bug workaround options. The &'SSL_CTX_set_options'& man page will
16865 list the values known on your system and Exim should support all the
16866 &"bug workaround"& options and many of the &"modifying"& options. The Exim
16867 names lose the leading &"SSL_OP_"& and are lower-cased.
16869 Note that adjusting the options can have severe impact upon the security of
16870 SSL as used by Exim. It is possible to disable safety checks and shoot
16871 yourself in the foot in various unpleasant ways. This option should not be
16872 adjusted lightly. An unrecognised item will be detected at startup, by
16873 invoking Exim with the &%-bV%& flag.
16875 The option affects Exim operating both as a server and as a client.
16877 Historical note: prior to release 4.80, Exim defaulted this value to
16878 "+dont_insert_empty_fragments", which may still be needed for compatibility
16879 with some clients, but which lowers security by increasing exposure to
16880 some now infamous attacks.
16884 # Make both old MS and old Eudora happy:
16885 openssl_options = -all +microsoft_big_sslv3_buffer \
16886 +dont_insert_empty_fragments
16888 # Disable older protocol versions:
16889 openssl_options = +no_sslv2 +no_sslv3
16892 Possible options may include:
16896 &`allow_unsafe_legacy_renegotiation`&
16898 &`cipher_server_preference`&
16900 &`dont_insert_empty_fragments`&
16904 &`legacy_server_connect`&
16906 &`microsoft_big_sslv3_buffer`&
16908 &`microsoft_sess_id_bug`&
16910 &`msie_sslv2_rsa_padding`&
16912 &`netscape_challenge_bug`&
16914 &`netscape_reuse_cipher_change_bug`&
16918 &`no_session_resumption_on_renegotiation`&
16932 &`safari_ecdhe_ecdsa_bug`&
16936 &`single_ecdh_use`&
16938 &`ssleay_080_client_dh_bug`&
16940 &`sslref2_reuse_cert_type_bug`&
16942 &`tls_block_padding_bug`&
16946 &`tls_rollback_bug`&
16949 As an aside, the &`safari_ecdhe_ecdsa_bug`& item is a misnomer and affects
16950 all clients connecting using the MacOS SecureTransport TLS facility prior
16951 to MacOS 10.8.4, including email clients. If you see old MacOS clients failing
16952 to negotiate TLS then this option value might help, provided that your OpenSSL
16953 release is new enough to contain this work-around. This may be a situation
16954 where you have to upgrade OpenSSL to get buggy clients working.
16957 .option oracle_servers main "string list" unset
16958 .cindex "Oracle" "server list"
16959 This option provides a list of Oracle servers and associated connection data,
16960 to be used in conjunction with &(oracle)& lookups (see section &<<SECID72>>&).
16961 The option is available only if Exim has been built with Oracle support.
16965 .option panic_coredump main boolean false
16966 This option is rarely needed but can help for some debugging investigations.
16967 If set, when an internal error is detected by Exim which is sufficient
16968 to terminate the process
16969 (all such are logged in the paniclog)
16970 then a coredump is requested.
16972 Note that most systems require additional administrative configuration
16973 to permit write a core file for a setuid program, which is Exim's
16974 common installed configuration.
16977 .option percent_hack_domains main "domain list&!!" unset
16978 .cindex "&""percent hack""&"
16979 .cindex "source routing" "in email address"
16980 .cindex "address" "source-routed"
16981 The &"percent hack"& is the convention whereby a local part containing a
16982 percent sign is re-interpreted as a new email address, with the percent
16983 replaced by @. This is sometimes called &"source routing"&, though that term is
16984 also applied to RFC 2822 addresses that begin with an @ character. If this
16985 option is set, Exim implements the percent facility for those domains listed,
16986 but no others. This happens before an incoming SMTP address is tested against
16989 &*Warning*&: The &"percent hack"& has often been abused by people who are
16990 trying to get round relaying restrictions. For this reason, it is best avoided
16991 if at all possible. Unfortunately, a number of less security-conscious MTAs
16992 implement it unconditionally. If you are running Exim on a gateway host, and
16993 routing mail through to internal MTAs without processing the local parts, it is
16994 a good idea to reject recipient addresses with percent characters in their
16995 local parts. Exim's default configuration does this.
16998 .option perl_at_start main boolean false
17000 This option is available only when Exim is built with an embedded Perl
17001 interpreter. See chapter &<<CHAPperl>>& for details of its use.
17004 .option perl_startup main string unset
17006 This option is available only when Exim is built with an embedded Perl
17007 interpreter. See chapter &<<CHAPperl>>& for details of its use.
17009 .option perl_taintmode main boolean false
17011 This option enables the taint mode of the embedded Perl interpreter.
17014 .option pgsql_servers main "string list" unset
17015 .cindex "PostgreSQL lookup type" "server list"
17016 This option provides a list of PostgreSQL servers and associated connection
17017 data, to be used in conjunction with &(pgsql)& lookups (see section
17018 &<<SECID72>>&). The option is available only if Exim has been built with
17019 PostgreSQL support.
17022 .option pid_file_path main string&!! "set at compile time"
17023 .cindex "daemon" "pid file path"
17024 .cindex "pid file, path for"
17025 This option sets the name of the file to which the Exim daemon writes its
17026 process id. The string is expanded, so it can contain, for example, references
17029 pid_file_path = /var/log/$primary_hostname/exim.pid
17031 If no path is set, the pid is written to the file &_exim-daemon.pid_& in Exim's
17033 The value set by the option can be overridden by the &%-oP%& command line
17034 option. A pid file is not written if a &"non-standard"& daemon is run by means
17035 of the &%-oX%& option, unless a path is explicitly supplied by &%-oP%&.
17038 .option pipelining_advertise_hosts main "host list&!!" *
17039 .cindex "PIPELINING" "suppressing advertising"
17040 .cindex "ESMTP extensions" PIPELINING
17041 This option can be used to suppress the advertisement of the SMTP
17042 PIPELINING extension to specific hosts. See also the &*no_pipelining*&
17043 control in section &<<SECTcontrols>>&. When PIPELINING is not advertised and
17044 &%smtp_enforce_sync%& is true, an Exim server enforces strict synchronization
17045 for each SMTP command and response. When PIPELINING is advertised, Exim assumes
17046 that clients will use it; &"out of order"& commands that are &"expected"& do
17047 not count as protocol errors (see &%smtp_max_synprot_errors%&).
17049 .option pipelining_connect_advertise_hosts main "host list&!!" *
17050 .cindex "pipelining" "early connection"
17051 .cindex "pipelining" PIPECONNECT
17052 .cindex "ESMTP extensions" PIPECONNECT
17053 If Exim is built without the DISABLE_PIPE_CONNECT build option
17054 this option controls which hosts the facility is advertised to
17055 and from which pipeline early-connection (before MAIL) SMTP
17056 commands are acceptable.
17057 When used, the pipelining saves on roundtrip times.
17059 See also the &%hosts_pipe_connect%& smtp transport option.
17061 The SMTP service extension keyword advertised is &"PIPECONNECT"&;
17062 it permits the client to pipeline
17063 TCP connection and hello command (inclear phase),
17064 or TLS-establishment and hello command (encrypted phase),
17065 on later connections to the same host.
17068 .option prdr_enable main boolean false
17069 .cindex "PRDR" "enabling on server"
17070 .cindex "ESMTP extensions" PRDR
17071 This option can be used to enable the Per-Recipient Data Response extension
17072 to SMTP, defined by Eric Hall.
17073 If the option is set, PRDR is advertised by Exim when operating as a server.
17074 If the client requests PRDR, and more than one recipient, for a message
17075 an additional ACL is called for each recipient after the message content
17076 is received. See section &<<SECTPRDRACL>>&.
17078 .option preserve_message_logs main boolean false
17079 .cindex "message logs" "preserving"
17080 If this option is set, message log files are not deleted when messages are
17081 completed. Instead, they are moved to a sub-directory of the spool directory
17082 called &_msglog.OLD_&, where they remain available for statistical or debugging
17083 purposes. This is a dangerous option to set on systems with any appreciable
17084 volume of mail. Use with care!
17087 .option primary_hostname main string "see below"
17088 .cindex "name" "of local host"
17089 .cindex "host" "name of local"
17090 .cindex "local host" "name of"
17091 .vindex "&$primary_hostname$&"
17092 This specifies the name of the current host. It is used in the default EHLO or
17093 HELO command for outgoing SMTP messages (changeable via the &%helo_data%&
17094 option in the &(smtp)& transport), and as the default for &%qualify_domain%&.
17095 The value is also used by default in some SMTP response messages from an Exim
17096 server. This can be changed dynamically by setting &%smtp_active_hostname%&.
17098 If &%primary_hostname%& is not set, Exim calls &[uname()]& to find the host
17099 name. If this fails, Exim panics and dies. If the name returned by &[uname()]&
17100 contains only one component, Exim passes it to &[gethostbyname()]& (or
17101 &[getipnodebyname()]& when available) in order to obtain the fully qualified
17102 version. The variable &$primary_hostname$& contains the host name, whether set
17103 explicitly by this option, or defaulted.
17106 .option print_topbitchars main boolean false
17107 .cindex "printing characters"
17108 .cindex "8-bit characters"
17109 By default, Exim considers only those characters whose codes lie in the range
17110 32&--126 to be printing characters. In a number of circumstances (for example,
17111 when writing log entries) non-printing characters are converted into escape
17112 sequences, primarily to avoid messing up the layout. If &%print_topbitchars%&
17113 is set, code values of 128 and above are also considered to be printing
17116 This option also affects the header syntax checks performed by the
17117 &(autoreply)& transport, and whether Exim uses RFC 2047 encoding of
17118 the user's full name when constructing From: and Sender: addresses (as
17119 described in section &<<SECTconstr>>&). Setting this option can cause
17120 Exim to generate eight bit message headers that do not conform to the
17124 .option process_log_path main string unset
17125 .cindex "process log path"
17126 .cindex "log" "process log"
17127 .cindex "&'exiwhat'&"
17128 This option sets the name of the file to which an Exim process writes its
17129 &"process log"& when sent a USR1 signal. This is used by the &'exiwhat'&
17130 utility script. If this option is unset, the file called &_exim-process.info_&
17131 in Exim's spool directory is used. The ability to specify the name explicitly
17132 can be useful in environments where two different Exims are running, using
17133 different spool directories.
17136 .option prod_requires_admin main boolean true
17137 .cindex "restricting access to features"
17141 The &%-M%&, &%-R%&, and &%-q%& command-line options require the caller to be an
17142 admin user unless &%prod_requires_admin%& is set false. See also
17143 &%queue_list_requires_admin%& and &%commandline_checks_require_admin%&.
17146 .option proxy_protocol_timeout main time 3s
17147 .cindex proxy "proxy protocol"
17148 This option sets the timeout for proxy protocol negotiation.
17149 For details see section &<<SECTproxyInbound>>&.
17152 .option qualify_domain main string "see below"
17153 .cindex "domain" "for qualifying addresses"
17154 .cindex "address" "qualification"
17155 This option specifies the domain name that is added to any envelope sender
17156 addresses that do not have a domain qualification. It also applies to
17157 recipient addresses if &%qualify_recipient%& is not set. Unqualified addresses
17158 are accepted by default only for locally-generated messages. Qualification is
17159 also applied to addresses in header lines such as &'From:'& and &'To:'& for
17160 locally-generated messages, unless the &%-bnq%& command line option is used.
17162 Messages from external sources must always contain fully qualified addresses,
17163 unless the sending host matches &%sender_unqualified_hosts%& or
17164 &%recipient_unqualified_hosts%& (as appropriate), in which case incoming
17165 addresses are qualified with &%qualify_domain%& or &%qualify_recipient%& as
17166 necessary. Internally, Exim always works with fully qualified envelope
17167 addresses. If &%qualify_domain%& is not set, it defaults to the
17168 &%primary_hostname%& value.
17171 .option qualify_recipient main string "see below"
17172 This option allows you to specify a different domain for qualifying recipient
17173 addresses to the one that is used for senders. See &%qualify_domain%& above.
17177 .option queue_domains main "domain list&!!" unset
17178 .cindex "domain" "specifying non-immediate delivery"
17179 .cindex "queueing incoming messages"
17180 .cindex "message" "queueing certain domains"
17181 This option lists domains for which immediate delivery is not required.
17182 A delivery process is started whenever a message is received, but only those
17183 domains that do not match are processed. All other deliveries wait until the
17184 next queue run. See also &%hold_domains%& and &%queue_smtp_domains%&.
17187 .option queue_fast_ramp main boolean true
17188 .cindex "queue runner" "two phase"
17189 .cindex "queue" "double scanning"
17190 If set to true, two-phase queue runs, initiated using &%-qq%& on the
17191 command line, may start parallel delivery processes during their first
17192 phase. This will be done when a threshold number of messages have been
17193 routed for a single host.
17196 .option queue_list_requires_admin main boolean true
17197 .cindex "restricting access to features"
17199 The &%-bp%& command-line option, which lists the messages that are on the
17200 queue, requires the caller to be an admin user unless
17201 &%queue_list_requires_admin%& is set false.
17202 See also &%prod_requires_admin%& and &%commandline_checks_require_admin%&.
17205 .option queue_only main boolean false
17206 .cindex "queueing incoming messages"
17207 .cindex "message" "queueing unconditionally"
17208 If &%queue_only%& is set, a delivery process is not automatically started
17209 whenever a message is received. Instead, the message waits in the queue for the
17210 next queue run. Even if &%queue_only%& is false, incoming messages may not get
17211 delivered immediately when certain conditions (such as heavy load) occur.
17213 The &%-odq%& command line has the same effect as &%queue_only%&. The &%-odb%&
17214 and &%-odi%& command line options override &%queue_only%& unless
17215 &%queue_only_override%& is set false. See also &%queue_only_file%&,
17216 &%queue_only_load%&, and &%smtp_accept_queue%&.
17219 .option queue_only_file main string unset
17220 .cindex "queueing incoming messages"
17221 .cindex "message" "queueing by file existence"
17222 This option can be set to a colon-separated list of absolute path names, each
17223 one optionally preceded by &"smtp"&. When Exim is receiving a message,
17224 it tests for the existence of each listed path using a call to &[stat()]&. For
17225 each path that exists, the corresponding queueing option is set.
17226 For paths with no prefix, &%queue_only%& is set; for paths prefixed by
17227 &"smtp"&, &%queue_smtp_domains%& is set to match all domains. So, for example,
17229 queue_only_file = smtp/some/file
17231 causes Exim to behave as if &%queue_smtp_domains%& were set to &"*"& whenever
17232 &_/some/file_& exists.
17235 .option queue_only_load main fixed-point unset
17236 .cindex "load average"
17237 .cindex "queueing incoming messages"
17238 .cindex "message" "queueing by load"
17239 If the system load average is higher than this value, incoming messages from
17240 all sources are queued, and no automatic deliveries are started. If this
17241 happens during local or remote SMTP input, all subsequent messages received on
17242 the same SMTP connection are queued by default, whatever happens to the load in
17243 the meantime, but this can be changed by setting &%queue_only_load_latch%&
17246 Deliveries will subsequently be performed by queue runner processes. This
17247 option has no effect on ancient operating systems on which Exim cannot
17248 determine the load average. See also &%deliver_queue_load_max%& and
17249 &%smtp_load_reserve%&.
17252 .option queue_only_load_latch main boolean true
17253 .cindex "load average" "re-evaluating per message"
17254 When this option is true (the default), once one message has been queued
17255 because the load average is higher than the value set by &%queue_only_load%&,
17256 all subsequent messages received on the same SMTP connection are also queued.
17257 This is a deliberate choice; even though the load average may fall below the
17258 threshold, it doesn't seem right to deliver later messages on the same
17259 connection when not delivering earlier ones. However, there are special
17260 circumstances such as very long-lived connections from scanning appliances
17261 where this is not the best strategy. In such cases, &%queue_only_load_latch%&
17262 should be set false. This causes the value of the load average to be
17263 re-evaluated for each message.
17266 .option queue_only_override main boolean true
17267 .cindex "queueing incoming messages"
17268 When this option is true, the &%-od%&&'x'& command line options override the
17269 setting of &%queue_only%& or &%queue_only_file%& in the configuration file. If
17270 &%queue_only_override%& is set false, the &%-od%&&'x'& options cannot be used
17271 to override; they are accepted, but ignored.
17274 .option queue_run_in_order main boolean false
17275 .cindex "queue runner" "processing messages in order"
17276 If this option is set, queue runs happen in order of message arrival instead of
17277 in an arbitrary order. For this to happen, a complete list of the entire queue
17278 must be set up before the deliveries start. When the queue is all held in a
17279 single directory (the default), a single list is created for both the ordered
17280 and the non-ordered cases. However, if &%split_spool_directory%& is set, a
17281 single list is not created when &%queue_run_in_order%& is false. In this case,
17282 the sub-directories are processed one at a time (in a random order), and this
17283 avoids setting up one huge list for the whole queue. Thus, setting
17284 &%queue_run_in_order%& with &%split_spool_directory%& may degrade performance
17285 when the queue is large, because of the extra work in setting up the single,
17286 large list. In most situations, &%queue_run_in_order%& should not be set.
17290 .option queue_run_max main integer&!! 5
17291 .cindex "queue runner" "maximum number of"
17292 This controls the maximum number of queue runner processes that an Exim daemon
17293 can run simultaneously. This does not mean that it starts them all at once,
17294 but rather that if the maximum number are still running when the time comes to
17295 start another one, it refrains from starting another one. This can happen with
17296 very large queues and/or very sluggish deliveries. This option does not,
17297 however, interlock with other processes, so additional queue runners can be
17298 started by other means, or by killing and restarting the daemon.
17300 Setting this option to zero does not suppress queue runs; rather, it disables
17301 the limit, allowing any number of simultaneous queue runner processes to be
17302 run. If you do not want queue runs to occur, omit the &%-q%&&'xx'& setting on
17303 the daemon's command line.
17305 .cindex queues named
17306 .cindex "named queues" "resource limit"
17307 To set limits for different named queues use
17308 an expansion depending on the &$queue_name$& variable.
17310 .option queue_smtp_domains main "domain list&!!" unset
17311 .cindex "queueing incoming messages"
17312 .cindex "message" "queueing remote deliveries"
17313 .cindex "first pass routing"
17314 When this option is set, a delivery process is started whenever a message is
17315 received, routing is performed, and local deliveries take place.
17316 However, if any SMTP deliveries are required for domains that match
17317 &%queue_smtp_domains%&, they are not immediately delivered, but instead the
17318 message waits in the queue for the next queue run. Since routing of the message
17319 has taken place, Exim knows to which remote hosts it must be delivered, and so
17320 when the queue run happens, multiple messages for the same host are delivered
17321 over a single SMTP connection. The &%-odqs%& command line option causes all
17322 SMTP deliveries to be queued in this way, and is equivalent to setting
17323 &%queue_smtp_domains%& to &"*"&. See also &%hold_domains%& and
17327 .option receive_timeout main time 0s
17328 .cindex "timeout" "for non-SMTP input"
17329 This option sets the timeout for accepting a non-SMTP message, that is, the
17330 maximum time that Exim waits when reading a message on the standard input. If
17331 the value is zero, it will wait forever. This setting is overridden by the
17332 &%-or%& command line option. The timeout for incoming SMTP messages is
17333 controlled by &%smtp_receive_timeout%&.
17335 .option received_header_text main string&!! "see below"
17336 .cindex "customizing" "&'Received:'& header"
17337 .cindex "&'Received:'& header line" "customizing"
17338 This string defines the contents of the &'Received:'& message header that is
17339 added to each message, except for the timestamp, which is automatically added
17340 on at the end (preceded by a semicolon). The string is expanded each time it is
17341 used. If the expansion yields an empty string, no &'Received:'& header line is
17342 added to the message. Otherwise, the string should start with the text
17343 &"Received:"& and conform to the RFC 2822 specification for &'Received:'&
17345 The default setting is:
17348 received_header_text = Received: \
17349 ${if def:sender_rcvhost {from $sender_rcvhost\n\t}\
17350 {${if def:sender_ident \
17351 {from ${quote_local_part:$sender_ident} }}\
17352 ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\
17353 by $primary_hostname \
17354 ${if def:received_protocol {with $received_protocol }}\
17355 ${if def:tls_in_ver { ($tls_in_ver)}}\
17356 ${if def:tls_in_cipher_std { tls $tls_in_cipher_std\n\t}}\
17357 (Exim $version_number)\n\t\
17358 ${if def:sender_address \
17359 {(envelope-from <$sender_address>)\n\t}}\
17360 id $message_exim_id\
17361 ${if def:received_for {\n\tfor $received_for}}
17364 The references to the TLS version and cipher are
17365 omitted when Exim is built without TLS
17366 support. The use of conditional expansions ensures that this works for both
17367 locally generated messages and messages received from remote hosts, giving
17368 header lines such as the following:
17370 Received: from scrooge.carol.example ([192.168.12.25] ident=root)
17371 by marley.carol.example with esmtp (Exim 4.00)
17372 (envelope-from <bob@carol.example>)
17373 id 16IOWa-00019l-00
17374 for chas@dickens.example; Tue, 25 Dec 2001 14:43:44 +0000
17375 Received: by scrooge.carol.example with local (Exim 4.00)
17376 id 16IOWW-000083-00; Tue, 25 Dec 2001 14:43:41 +0000
17378 Until the body of the message has been received, the timestamp is the time when
17379 the message started to be received. Once the body has arrived, and all policy
17380 checks have taken place, the timestamp is updated to the time at which the
17381 message was accepted.
17384 .option received_headers_max main integer 30
17385 .cindex "loop" "prevention"
17386 .cindex "mail loop prevention"
17387 .cindex "&'Received:'& header line" "counting"
17388 When a message is to be delivered, the number of &'Received:'& headers is
17389 counted, and if it is greater than this parameter, a mail loop is assumed to
17390 have occurred, the delivery is abandoned, and an error message is generated.
17391 This applies to both local and remote deliveries.
17394 .option recipient_unqualified_hosts main "host list&!!" unset
17395 .cindex "unqualified addresses"
17396 .cindex "host" "unqualified addresses from"
17397 This option lists those hosts from which Exim is prepared to accept unqualified
17398 recipient addresses in message envelopes. The addresses are made fully
17399 qualified by the addition of the &%qualify_recipient%& value. This option also
17400 affects message header lines. Exim does not reject unqualified recipient
17401 addresses in headers, but it qualifies them only if the message came from a
17402 host that matches &%recipient_unqualified_hosts%&,
17403 or if the message was submitted locally (not using TCP/IP), and the &%-bnq%&
17404 option was not set.
17407 .option recipients_max main integer 50000
17408 .cindex "limit" "number of recipients"
17409 .cindex "recipient" "maximum number"
17410 If this option is set greater than zero, it specifies the maximum number of
17411 original recipients for any message. Additional recipients that are generated
17412 by aliasing or forwarding do not count. SMTP messages get a 452 response for
17413 all recipients over the limit; earlier recipients are delivered as normal.
17414 Non-SMTP messages with too many recipients are failed, and no deliveries are
17417 .cindex "RCPT" "maximum number of incoming"
17418 &*Note*&: The RFCs specify that an SMTP server should accept at least 100
17419 RCPT commands in a single message.
17422 .option recipients_max_reject main boolean false
17423 If this option is set true, Exim rejects SMTP messages containing too many
17424 recipients by giving 552 errors to the surplus RCPT commands, and a 554
17425 error to the eventual DATA command. Otherwise (the default) it gives a 452
17426 error to the surplus RCPT commands and accepts the message on behalf of the
17427 initial set of recipients. The remote server should then re-send the message
17428 for the remaining recipients at a later time.
17431 .option remote_max_parallel main integer 4
17432 .cindex "delivery" "parallelism for remote"
17433 This option controls parallel delivery of one message to a number of remote
17434 hosts. If the value is less than 2, parallel delivery is disabled, and Exim
17435 does all the remote deliveries for a message one by one. Otherwise, if a single
17436 message has to be delivered to more than one remote host, or if several copies
17437 have to be sent to the same remote host, up to &%remote_max_parallel%&
17438 deliveries are done simultaneously. If more than &%remote_max_parallel%&
17439 deliveries are required, the maximum number of processes are started, and as
17440 each one finishes, another is begun. The order of starting processes is the
17441 same as if sequential delivery were being done, and can be controlled by the
17442 &%remote_sort_domains%& option. If parallel delivery takes place while running
17443 with debugging turned on, the debugging output from each delivery process is
17444 tagged with its process id.
17446 This option controls only the maximum number of parallel deliveries for one
17447 message in one Exim delivery process. Because Exim has no central queue
17448 manager, there is no way of controlling the total number of simultaneous
17449 deliveries if the configuration allows a delivery attempt as soon as a message
17452 See also the &%max_parallel%& generic transport option,
17453 and the &%serialize_hosts%& smtp transport option.
17455 .cindex "number of deliveries"
17456 .cindex "delivery" "maximum number of"
17457 If you want to control the total number of deliveries on the system, you
17458 need to set the &%queue_only%& option. This ensures that all incoming messages
17459 are added to the queue without starting a delivery process. Then set up an Exim
17460 daemon to start queue runner processes at appropriate intervals (probably
17461 fairly often, for example, every minute), and limit the total number of queue
17462 runners by setting the &%queue_run_max%& parameter. Because each queue runner
17463 delivers only one message at a time, the maximum number of deliveries that can
17464 then take place at once is &%queue_run_max%& multiplied by
17465 &%remote_max_parallel%&.
17467 If it is purely remote deliveries you want to control, use
17468 &%queue_smtp_domains%& instead of &%queue_only%&. This has the added benefit of
17469 doing the SMTP routing before queueing, so that several messages for the same
17470 host will eventually get delivered down the same connection.
17473 .option remote_sort_domains main "domain list&!!" unset
17474 .cindex "sorting remote deliveries"
17475 .cindex "delivery" "sorting remote"
17476 When there are a number of remote deliveries for a message, they are sorted by
17477 domain into the order given by this list. For example,
17479 remote_sort_domains = *.cam.ac.uk:*.uk
17481 would attempt to deliver to all addresses in the &'cam.ac.uk'& domain first,
17482 then to those in the &%uk%& domain, then to any others.
17485 .option retry_data_expire main time 7d
17486 .cindex "hints database" "data expiry"
17487 This option sets a &"use before"& time on retry information in Exim's hints
17488 database. Any older retry data is ignored. This means that, for example, once a
17489 host has not been tried for 7 days, Exim behaves as if it has no knowledge of
17493 .option retry_interval_max main time 24h
17494 .cindex "retry" "limit on interval"
17495 .cindex "limit" "on retry interval"
17496 Chapter &<<CHAPretry>>& describes Exim's mechanisms for controlling the
17497 intervals between delivery attempts for messages that cannot be delivered
17498 straight away. This option sets an overall limit to the length of time between
17499 retries. It cannot be set greater than 24 hours; any attempt to do so forces
17503 .option return_path_remove main boolean true
17504 .cindex "&'Return-path:'& header line" "removing"
17505 RFC 2821, section 4.4, states that an SMTP server must insert a
17506 &'Return-path:'& header line into a message when it makes a &"final delivery"&.
17507 The &'Return-path:'& header preserves the sender address as received in the
17508 MAIL command. This description implies that this header should not be present
17509 in an incoming message. If &%return_path_remove%& is true, any existing
17510 &'Return-path:'& headers are removed from messages at the time they are
17511 received. Exim's transports have options for adding &'Return-path:'& headers at
17512 the time of delivery. They are normally used only for final local deliveries.
17515 .option return_size_limit main integer 100K
17516 This option is an obsolete synonym for &%bounce_return_size_limit%&.
17519 .option rfc1413_hosts main "host list&!!" @[]
17521 .cindex "host" "for RFC 1413 calls"
17522 RFC 1413 identification calls are made to any client host which matches
17523 an item in the list.
17524 The default value specifies just this host, being any local interface
17527 .option rfc1413_query_timeout main time 0s
17528 .cindex "RFC 1413" "query timeout"
17529 .cindex "timeout" "for RFC 1413 call"
17530 This sets the timeout on RFC 1413 identification calls. If it is set to zero,
17531 no RFC 1413 calls are ever made.
17534 .option sender_unqualified_hosts main "host list&!!" unset
17535 .cindex "unqualified addresses"
17536 .cindex "host" "unqualified addresses from"
17537 This option lists those hosts from which Exim is prepared to accept unqualified
17538 sender addresses. The addresses are made fully qualified by the addition of
17539 &%qualify_domain%&. This option also affects message header lines. Exim does
17540 not reject unqualified addresses in headers that contain sender addresses, but
17541 it qualifies them only if the message came from a host that matches
17542 &%sender_unqualified_hosts%&, or if the message was submitted locally (not
17543 using TCP/IP), and the &%-bnq%& option was not set.
17546 .option slow_lookup_log main integer 0
17547 .cindex "logging" "slow lookups"
17548 .cindex "dns" "logging slow lookups"
17549 This option controls logging of slow lookups.
17550 If the value is nonzero it is taken as a number of milliseconds
17551 and lookups taking longer than this are logged.
17552 Currently this applies only to DNS lookups.
17556 .option smtp_accept_keepalive main boolean true
17557 .cindex "keepalive" "on incoming connection"
17558 This option controls the setting of the SO_KEEPALIVE option on incoming
17559 TCP/IP socket connections. When set, it causes the kernel to probe idle
17560 connections periodically, by sending packets with &"old"& sequence numbers. The
17561 other end of the connection should send an acknowledgment if the connection is
17562 still okay or a reset if the connection has been aborted. The reason for doing
17563 this is that it has the beneficial effect of freeing up certain types of
17564 connection that can get stuck when the remote host is disconnected without
17565 tidying up the TCP/IP call properly. The keepalive mechanism takes several
17566 hours to detect unreachable hosts.
17570 .option smtp_accept_max main integer 20
17571 .cindex "limit" "incoming SMTP connections"
17572 .cindex "SMTP" "incoming connection count"
17574 This option specifies the maximum number of simultaneous incoming SMTP calls
17575 that Exim will accept. It applies only to the listening daemon; there is no
17576 control (in Exim) when incoming SMTP is being handled by &'inetd'&. If the
17577 value is set to zero, no limit is applied. However, it is required to be
17578 non-zero if either &%smtp_accept_max_per_host%& or &%smtp_accept_queue%& is
17579 set. See also &%smtp_accept_reserve%& and &%smtp_load_reserve%&.
17581 A new SMTP connection is immediately rejected if the &%smtp_accept_max%& limit
17582 has been reached. If not, Exim first checks &%smtp_accept_max_per_host%&. If
17583 that limit has not been reached for the client host, &%smtp_accept_reserve%&
17584 and &%smtp_load_reserve%& are then checked before accepting the connection.
17587 .option smtp_accept_max_nonmail main integer 10
17588 .cindex "limit" "non-mail SMTP commands"
17589 .cindex "SMTP" "limiting non-mail commands"
17590 Exim counts the number of &"non-mail"& commands in an SMTP session, and drops
17591 the connection if there are too many. This option defines &"too many"&. The
17592 check catches some denial-of-service attacks, repeated failing AUTHs, or a mad
17593 client looping sending EHLO, for example. The check is applied only if the
17594 client host matches &%smtp_accept_max_nonmail_hosts%&.
17596 When a new message is expected, one occurrence of RSET is not counted. This
17597 allows a client to send one RSET between messages (this is not necessary,
17598 but some clients do it). Exim also allows one uncounted occurrence of HELO
17599 or EHLO, and one occurrence of STARTTLS between messages. After
17600 starting up a TLS session, another EHLO is expected, and so it too is not
17601 counted. The first occurrence of AUTH in a connection, or immediately
17602 following STARTTLS is not counted. Otherwise, all commands other than
17603 MAIL, RCPT, DATA, and QUIT are counted.
17606 .option smtp_accept_max_nonmail_hosts main "host list&!!" *
17607 You can control which hosts are subject to the &%smtp_accept_max_nonmail%&
17608 check by setting this option. The default value makes it apply to all hosts. By
17609 changing the value, you can exclude any badly-behaved hosts that you have to
17613 . Allow this long option name to split; give it unsplit as a fifth argument
17614 . for the automatic .oindex that is generated by .option.
17615 . We insert " &~&~" which is both pretty nasty visually and results in
17616 . non-searchable text. HowItWorks.txt mentions an option for inserting
17617 . zero-width-space, which would be nicer visually and results in (at least)
17618 . html that Firefox will split on when it's forced to reflow (rather than
17619 . inserting a horizontal scrollbar). However, the text is still not
17620 . searchable. NM changed this occurrence for bug 1197 to no longer allow
17621 . the option name to split.
17623 .option "smtp_accept_max_per_connection" main integer&!! 1000 &&&
17624 smtp_accept_max_per_connection
17625 .cindex "SMTP" "limiting incoming message count"
17626 .cindex "limit" "messages per SMTP connection"
17627 The value of this option limits the number of MAIL commands that Exim is
17628 prepared to accept over a single SMTP connection, whether or not each command
17629 results in the transfer of a message. After the limit is reached, a 421
17630 response is given to subsequent MAIL commands. This limit is a safety
17631 precaution against a client that goes mad (incidents of this type have been
17633 The option is expanded after the HELO or EHLO is received
17634 and may depend on values available at that time.
17635 An empty or zero value after expansion removes the limit.
17638 .option smtp_accept_max_per_host main string&!! unset
17639 .cindex "limit" "SMTP connections from one host"
17640 .cindex "host" "limiting SMTP connections from"
17641 This option restricts the number of simultaneous IP connections from a single
17642 host (strictly, from a single IP address) to the Exim daemon. The option is
17643 expanded, to enable different limits to be applied to different hosts by
17644 reference to &$sender_host_address$&. Once the limit is reached, additional
17645 connection attempts from the same host are rejected with error code 421. This
17646 is entirely independent of &%smtp_accept_reserve%&. The option's default value
17647 of zero imposes no limit. If this option is set greater than zero, it is
17648 required that &%smtp_accept_max%& be non-zero.
17650 &*Warning*&: When setting this option you should not use any expansion
17651 constructions that take an appreciable amount of time. The expansion and test
17652 happen in the main daemon loop, in order to reject additional connections
17653 without forking additional processes (otherwise a denial-of-service attack
17654 could cause a vast number or processes to be created). While the daemon is
17655 doing this processing, it cannot accept any other incoming connections.
17659 .option smtp_accept_queue main integer 0
17660 .cindex "SMTP" "incoming connection count"
17661 .cindex "queueing incoming messages"
17662 .cindex "message" "queueing by SMTP connection count"
17663 If the number of simultaneous incoming SMTP connections being handled via the
17664 listening daemon exceeds this value, messages received by SMTP are just placed
17665 in the queue; no delivery processes are started automatically. The count is
17666 fixed at the start of an SMTP connection. It cannot be updated in the
17667 subprocess that receives messages, and so the queueing or not queueing applies
17668 to all messages received in the same connection.
17670 A value of zero implies no limit, and clearly any non-zero value is useful only
17671 if it is less than the &%smtp_accept_max%& value (unless that is zero). See
17672 also &%queue_only%&, &%queue_only_load%&, &%queue_smtp_domains%&, and the
17673 various &%-od%&&'x'& command line options.
17676 . See the comment on smtp_accept_max_per_connection
17678 .option "smtp_accept_queue_per_connection" main integer 10 &&&
17679 smtp_accept_queue_per_connection
17680 .cindex "queueing incoming messages"
17681 .cindex "message" "queueing by message count"
17682 This option limits the number of delivery processes that Exim starts
17683 automatically when receiving messages via SMTP, whether via the daemon or by
17684 the use of &%-bs%& or &%-bS%&. If the value of the option is greater than zero,
17685 and the number of messages received in a single SMTP session exceeds this
17686 number, subsequent messages are placed in the queue, but no delivery processes
17687 are started. This helps to limit the number of Exim processes when a server
17688 restarts after downtime and there is a lot of mail waiting for it on other
17689 systems. On large systems, the default should probably be increased, and on
17690 dial-in client systems it should probably be set to zero (that is, disabled).
17693 .option smtp_accept_reserve main integer 0
17694 .cindex "SMTP" "incoming call count"
17695 .cindex "host" "reserved"
17696 When &%smtp_accept_max%& is set greater than zero, this option specifies a
17697 number of SMTP connections that are reserved for connections from the hosts
17698 that are specified in &%smtp_reserve_hosts%&. The value set in
17699 &%smtp_accept_max%& includes this reserve pool. The specified hosts are not
17700 restricted to this number of connections; the option specifies a minimum number
17701 of connection slots for them, not a maximum. It is a guarantee that this group
17702 of hosts can always get at least &%smtp_accept_reserve%& connections. However,
17703 the limit specified by &%smtp_accept_max_per_host%& is still applied to each
17706 For example, if &%smtp_accept_max%& is set to 50 and &%smtp_accept_reserve%& is
17707 set to 5, once there are 45 active connections (from any hosts), new
17708 connections are accepted only from hosts listed in &%smtp_reserve_hosts%&,
17709 provided the other criteria for acceptance are met.
17712 .option smtp_active_hostname main string&!! unset
17713 .cindex "host" "name in SMTP responses"
17714 .cindex "SMTP" "host name in responses"
17715 .vindex "&$primary_hostname$&"
17716 This option is provided for multi-homed servers that want to masquerade as
17717 several different hosts. At the start of an incoming SMTP connection, its value
17718 is expanded and used instead of the value of &$primary_hostname$& in SMTP
17719 responses. For example, it is used as domain name in the response to an
17720 incoming HELO or EHLO command.
17722 .vindex "&$smtp_active_hostname$&"
17723 The active hostname is placed in the &$smtp_active_hostname$& variable, which
17724 is saved with any messages that are received. It is therefore available for use
17725 in routers and transports when the message is later delivered.
17727 If this option is unset, or if its expansion is forced to fail, or if the
17728 expansion results in an empty string, the value of &$primary_hostname$& is
17729 used. Other expansion failures cause a message to be written to the main and
17730 panic logs, and the SMTP command receives a temporary error. Typically, the
17731 value of &%smtp_active_hostname%& depends on the incoming interface address.
17734 smtp_active_hostname = ${if eq{$received_ip_address}{10.0.0.1}\
17735 {cox.mydomain}{box.mydomain}}
17738 Although &$smtp_active_hostname$& is primarily concerned with incoming
17739 messages, it is also used as the default for HELO commands in callout
17740 verification if there is no remote transport from which to obtain a
17741 &%helo_data%& value.
17743 .option smtp_backlog_monitor main integer 0
17744 .cindex "connection backlog" monitoring
17745 If this option is set to greater than zero, and the backlog of available
17746 TCP connections on a socket listening for SMTP is larger than it, a line
17747 is logged giving the value and the socket address and port.
17748 The value is retrived jsut before an accept call.
17749 This facility is only available on Linux.
17751 .option smtp_banner main string&!! "see below"
17752 .cindex "SMTP" "welcome banner"
17753 .cindex "banner for SMTP"
17754 .cindex "welcome banner for SMTP"
17755 .cindex "customizing" "SMTP banner"
17756 This string, which is expanded every time it is used, is output as the initial
17757 positive response to an SMTP connection. The default setting is:
17759 smtp_banner = $smtp_active_hostname ESMTP Exim \
17760 $version_number $tod_full
17762 Failure to expand the string causes a panic error. If you want to create a
17763 multiline response to the initial SMTP connection, use &"\n"& in the string at
17764 appropriate points, but not at the end. Note that the 220 code is not included
17765 in this string. Exim adds it automatically (several times in the case of a
17766 multiline response).
17769 .option smtp_check_spool_space main boolean true
17770 .cindex "checking disk space"
17771 .cindex "disk space, checking"
17772 .cindex "spool directory" "checking space"
17773 When this option is set, if an incoming SMTP session encounters the SIZE
17774 option on a MAIL command, it checks that there is enough space in the
17775 spool directory's partition to accept a message of that size, while still
17776 leaving free the amount specified by &%check_spool_space%& (even if that value
17777 is zero). If there isn't enough space, a temporary error code is returned.
17780 .option smtp_connect_backlog main integer 20
17781 .cindex "connection backlog" "set maximum"
17782 .cindex "SMTP" "connection backlog"
17783 .cindex "backlog of connections"
17784 This option specifies a maximum number of waiting SMTP connections. Exim passes
17785 this value to the TCP/IP system when it sets up its listener. Once this number
17786 of connections are waiting for the daemon's attention, subsequent connection
17787 attempts are refused at the TCP/IP level. At least, that is what the manuals
17788 say; in some circumstances such connection attempts have been observed to time
17789 out instead. For large systems it is probably a good idea to increase the
17790 value (to 50, say). It also gives some protection against denial-of-service
17791 attacks by SYN flooding.
17794 .option smtp_enforce_sync main boolean true
17795 .cindex "SMTP" "synchronization checking"
17796 .cindex "synchronization checking in SMTP"
17797 The SMTP protocol specification requires the client to wait for a response from
17798 the server at certain points in the dialogue. Without PIPELINING these
17799 synchronization points are after every command; with PIPELINING they are
17800 fewer, but they still exist.
17802 Some spamming sites send out a complete set of SMTP commands without waiting
17803 for any response. Exim protects against this by rejecting a message if the
17804 client has sent further input when it should not have. The error response &"554
17805 SMTP synchronization error"& is sent, and the connection is dropped. Testing
17806 for this error cannot be perfect because of transmission delays (unexpected
17807 input may be on its way but not yet received when Exim checks). However, it
17808 does detect many instances.
17810 The check can be globally disabled by setting &%smtp_enforce_sync%& false.
17811 If you want to disable the check selectively (for example, only for certain
17812 hosts), you can do so by an appropriate use of a &%control%& modifier in an ACL
17813 (see section &<<SECTcontrols>>&). See also &%pipelining_advertise_hosts%&.
17817 .option smtp_etrn_command main string&!! unset
17818 .cindex "ETRN" "command to be run"
17819 .cindex "ESMTP extensions" ETRN
17820 .vindex "&$domain$&"
17821 If this option is set, the given command is run whenever an SMTP ETRN
17822 command is received from a host that is permitted to issue such commands (see
17823 chapter &<<CHAPACL>>&). The string is split up into separate arguments which
17824 are independently expanded. The expansion variable &$domain$& is set to the
17825 argument of the ETRN command, and no syntax checking is done on it. For
17828 smtp_etrn_command = /etc/etrn_command $domain \
17829 $sender_host_address
17831 If the option is not set, the argument for the ETRN command must
17832 be a &'#'& followed by an address string.
17833 In this case an &'exim -R <string>'& command is used;
17834 if the ETRN ACL has set up a named-queue then &'-MCG <queue>'& is appended.
17836 A new process is created to run the command, but Exim does not wait for it to
17837 complete. Consequently, its status cannot be checked. If the command cannot be
17838 run, a line is written to the panic log, but the ETRN caller still receives
17839 a 250 success response. Exim is normally running under its own uid when
17840 receiving SMTP, so it is not possible for it to change the uid before running
17844 .option smtp_etrn_serialize main boolean true
17845 .cindex "ETRN" "serializing"
17846 When this option is set, it prevents the simultaneous execution of more than
17847 one identical command as a result of ETRN in an SMTP connection. See
17848 section &<<SECTETRN>>& for details.
17851 .option smtp_load_reserve main fixed-point unset
17852 .cindex "load average"
17853 If the system load average ever gets higher than this, incoming SMTP calls are
17854 accepted only from those hosts that match an entry in &%smtp_reserve_hosts%&.
17855 If &%smtp_reserve_hosts%& is not set, no incoming SMTP calls are accepted when
17856 the load is over the limit. The option has no effect on ancient operating
17857 systems on which Exim cannot determine the load average. See also
17858 &%deliver_queue_load_max%& and &%queue_only_load%&.
17862 .option smtp_max_synprot_errors main integer 3
17863 .cindex "SMTP" "limiting syntax and protocol errors"
17864 .cindex "limit" "SMTP syntax and protocol errors"
17865 Exim rejects SMTP commands that contain syntax or protocol errors. In
17866 particular, a syntactically invalid email address, as in this command:
17868 RCPT TO:<abc xyz@a.b.c>
17870 causes immediate rejection of the command, before any other tests are done.
17871 (The ACL cannot be run if there is no valid address to set up for it.) An
17872 example of a protocol error is receiving RCPT before MAIL. If there are
17873 too many syntax or protocol errors in one SMTP session, the connection is
17874 dropped. The limit is set by this option.
17876 .cindex "PIPELINING" "expected errors"
17877 When the PIPELINING extension to SMTP is in use, some protocol errors are
17878 &"expected"&, for instance, a RCPT command after a rejected MAIL command.
17879 Exim assumes that PIPELINING will be used if it advertises it (see
17880 &%pipelining_advertise_hosts%&), and in this situation, &"expected"& errors do
17881 not count towards the limit.
17885 .option smtp_max_unknown_commands main integer 3
17886 .cindex "SMTP" "limiting unknown commands"
17887 .cindex "limit" "unknown SMTP commands"
17888 If there are too many unrecognized commands in an incoming SMTP session, an
17889 Exim server drops the connection. This is a defence against some kinds of abuse
17892 into making connections to SMTP ports; in these circumstances, a number of
17893 non-SMTP command lines are sent first.
17897 .option smtp_ratelimit_hosts main "host list&!!" unset
17898 .cindex "SMTP" "rate limiting"
17899 .cindex "limit" "rate of message arrival"
17900 .cindex "RCPT" "rate limiting"
17901 Some sites find it helpful to be able to limit the rate at which certain hosts
17902 can send them messages, and the rate at which an individual message can specify
17905 Exim has two rate-limiting facilities. This section describes the older
17906 facility, which can limit rates within a single connection. The newer
17907 &%ratelimit%& ACL condition can limit rates across all connections. See section
17908 &<<SECTratelimiting>>& for details of the newer facility.
17910 When a host matches &%smtp_ratelimit_hosts%&, the values of
17911 &%smtp_ratelimit_mail%& and &%smtp_ratelimit_rcpt%& are used to control the
17912 rate of acceptance of MAIL and RCPT commands in a single SMTP session,
17913 respectively. Each option, if set, must contain a set of four comma-separated
17917 A threshold, before which there is no rate limiting.
17919 An initial time delay. Unlike other times in Exim, numbers with decimal
17920 fractional parts are allowed here.
17922 A factor by which to increase the delay each time.
17924 A maximum value for the delay. This should normally be less than 5 minutes,
17925 because after that time, the client is liable to timeout the SMTP command.
17928 For example, these settings have been used successfully at the site which
17929 first suggested this feature, for controlling mail from their customers:
17931 smtp_ratelimit_mail = 2,0.5s,1.05,4m
17932 smtp_ratelimit_rcpt = 4,0.25s,1.015,4m
17934 The first setting specifies delays that are applied to MAIL commands after
17935 two have been received over a single connection. The initial delay is 0.5
17936 seconds, increasing by a factor of 1.05 each time. The second setting applies
17937 delays to RCPT commands when more than four occur in a single message.
17940 .option smtp_ratelimit_mail main string unset
17941 See &%smtp_ratelimit_hosts%& above.
17944 .option smtp_ratelimit_rcpt main string unset
17945 See &%smtp_ratelimit_hosts%& above.
17948 .option smtp_receive_timeout main time&!! 5m
17949 .cindex "timeout" "for SMTP input"
17950 .cindex "SMTP" "input timeout"
17951 This sets a timeout value for SMTP reception. It applies to all forms of SMTP
17952 input, including batch SMTP. If a line of input (either an SMTP command or a
17953 data line) is not received within this time, the SMTP connection is dropped and
17954 the message is abandoned.
17955 A line is written to the log containing one of the following messages:
17957 SMTP command timeout on connection from...
17958 SMTP data timeout on connection from...
17960 The former means that Exim was expecting to read an SMTP command; the latter
17961 means that it was in the DATA phase, reading the contents of a message.
17963 If the first character of the option is a &"$"& the option is
17964 expanded before use and may depend on
17965 &$sender_host_name$&, &$sender_host_address$& and &$sender_host_port$&.
17969 The value set by this option can be overridden by the
17970 &%-os%& command-line option. A setting of zero time disables the timeout, but
17971 this should never be used for SMTP over TCP/IP. (It can be useful in some cases
17972 of local input using &%-bs%& or &%-bS%&.) For non-SMTP input, the reception
17973 timeout is controlled by &%receive_timeout%& and &%-or%&.
17976 .option smtp_reserve_hosts main "host list&!!" unset
17977 This option defines hosts for which SMTP connections are reserved; see
17978 &%smtp_accept_reserve%& and &%smtp_load_reserve%& above.
17981 .option smtp_return_error_details main boolean false
17982 .cindex "SMTP" "details policy failures"
17983 .cindex "policy control" "rejection, returning details"
17984 In the default state, Exim uses bland messages such as
17985 &"Administrative prohibition"& when it rejects SMTP commands for policy
17986 reasons. Many sysadmins like this because it gives away little information
17987 to spammers. However, some other sysadmins who are applying strict checking
17988 policies want to give out much fuller information about failures. Setting
17989 &%smtp_return_error_details%& true causes Exim to be more forthcoming. For
17990 example, instead of &"Administrative prohibition"&, it might give:
17992 550-Rejected after DATA: '>' missing at end of address:
17993 550 failing address in "From" header is: <user@dom.ain
17997 .option smtputf8_advertise_hosts main "host list&!!" *
17998 .cindex "SMTPUTF8" "ESMTP extension, advertising"
17999 .cindex "ESMTP extensions" SMTPUTF8
18000 When Exim is built with support for internationalised mail names,
18001 the availability thereof is advertised in
18002 response to EHLO only to those client hosts that match this option. See
18003 chapter &<<CHAPi18n>>& for details of Exim's support for internationalisation.
18006 .option spamd_address main string "127.0.0.1 783"
18007 This option is available when Exim is compiled with the content-scanning
18008 extension. It specifies how Exim connects to SpamAssassin's &%spamd%& daemon.
18009 See section &<<SECTscanspamass>>& for more details.
18013 .option spf_guess main string "v=spf1 a/24 mx/24 ptr ?all"
18014 This option is available when Exim is compiled with SPF support.
18015 See section &<<SECSPF>>& for more details.
18017 .option spf_smtp_comment_template main string&!! "Please%_see%_http://www.open-spf.org/Why"
18018 This option is available when Exim is compiled with SPF support. It
18019 allows the customisation of the SMTP comment that the SPF library
18020 generates. You are strongly encouraged to link to your own explanative
18021 site. The template must not contain spaces. If you need spaces in the
18022 output, use the proper placeholder. If libspf2 can not parse the
18023 template, it uses a built-in default broken link. The following placeholders
18024 (along with Exim variables (but see below)) are allowed in the template:
18028 &*%{L}*&: Envelope sender's local part.
18030 &*%{S}*&: Envelope sender.
18032 &*%{O}*&: Envelope sender's domain.
18034 &*%{D}*&: Current(?) domain.
18036 &*%{I}*&: SMTP client Ip.
18038 &*%{C}*&: SMTP client pretty IP.
18040 &*%{T}*&: Epoch time (UTC).
18042 &*%{P}*&: SMTP client domain name.
18044 &*%{V}*&: IP version.
18046 &*%{H}*&: EHLO/HELO domain.
18048 &*%{R}*&: Receiving domain.
18050 The capitalized placeholders do proper URL encoding, if you use them
18051 lowercased, no encoding takes place. This list was compiled from the
18054 A note on using Exim variables: As
18055 currently the SPF library is initialized before the SMTP EHLO phase,
18056 the variables useful for expansion are quite limited.
18059 .option split_spool_directory main boolean false
18060 .cindex "multiple spool directories"
18061 .cindex "spool directory" "split"
18062 .cindex "directories, multiple"
18063 If this option is set, it causes Exim to split its input directory into 62
18064 subdirectories, each with a single alphanumeric character as its name. The
18065 sixth character of the message id is used to allocate messages to
18066 subdirectories; this is the least significant base-62 digit of the time of
18067 arrival of the message.
18069 Splitting up the spool in this way may provide better performance on systems
18070 where there are long mail queues, by reducing the number of files in any one
18071 directory. The msglog directory is also split up in a similar way to the input
18072 directory; however, if &%preserve_message_logs%& is set, all old msglog files
18073 are still placed in the single directory &_msglog.OLD_&.
18075 It is not necessary to take any special action for existing messages when
18076 changing &%split_spool_directory%&. Exim notices messages that are in the
18077 &"wrong"& place, and continues to process them. If the option is turned off
18078 after a period of being on, the subdirectories will eventually empty and be
18079 automatically deleted.
18081 When &%split_spool_directory%& is set, the behaviour of queue runner processes
18082 changes. Instead of creating a list of all messages in the queue, and then
18083 trying to deliver each one, in turn, it constructs a list of those in one
18084 sub-directory and tries to deliver them, before moving on to the next
18085 sub-directory. The sub-directories are processed in a random order. This
18086 spreads out the scanning of the input directories, and uses less memory. It is
18087 particularly beneficial when there are lots of messages in the queue. However,
18088 if &%queue_run_in_order%& is set, none of this new processing happens. The
18089 entire queue has to be scanned and sorted before any deliveries can start.
18092 .option spool_directory main string&!! "set at compile time"
18093 .cindex "spool directory" "path to"
18094 This defines the directory in which Exim keeps its spool, that is, the messages
18095 it is waiting to deliver. The default value is taken from the compile-time
18096 configuration setting, if there is one. If not, this option must be set. The
18097 string is expanded, so it can contain, for example, a reference to
18098 &$primary_hostname$&.
18100 If the spool directory name is fixed on your installation, it is recommended
18101 that you set it at build time rather than from this option, particularly if the
18102 log files are being written to the spool directory (see &%log_file_path%&).
18103 Otherwise log files cannot be used for errors that are detected early on, such
18104 as failures in the configuration file.
18106 By using this option to override the compiled-in path, it is possible to run
18107 tests of Exim without using the standard spool.
18109 .option spool_wireformat main boolean false
18110 .cindex "spool directory" "file formats"
18111 If this option is set, Exim may for some messages use an alternative format
18112 for data-files in the spool which matches the wire format.
18113 Doing this permits more efficient message reception and transmission.
18114 Currently it is only done for messages received using the ESMTP CHUNKING
18117 The following variables will not have useful values:
18119 $max_received_linelength
18124 Users of the local_scan() API (see &<<CHAPlocalscan>>&),
18125 and any external programs which are passed a reference to a message data file
18126 (except via the &"regex"&, &"malware"& or &"spam"&) ACL conditions)
18127 will need to be aware of the different formats potentially available.
18129 Using any of the ACL conditions noted will negate the reception benefit
18130 (as a Unix-mbox-format file is constructed for them).
18131 The transmission benefit is maintained.
18133 .option sqlite_lock_timeout main time 5s
18134 .cindex "sqlite lookup type" "lock timeout"
18135 This option controls the timeout that the &(sqlite)& lookup uses when trying to
18136 access an SQLite database. See section &<<SECTsqlite>>& for more details.
18138 .option strict_acl_vars main boolean false
18139 .cindex "&ACL;" "variables, handling unset"
18140 This option controls what happens if a syntactically valid but undefined ACL
18141 variable is referenced. If it is false (the default), an empty string
18142 is substituted; if it is true, an error is generated. See section
18143 &<<SECTaclvariables>>& for details of ACL variables.
18145 .option strip_excess_angle_brackets main boolean false
18146 .cindex "angle brackets, excess"
18147 If this option is set, redundant pairs of angle brackets round &"route-addr"&
18148 items in addresses are stripped. For example, &'<<xxx@a.b.c.d>>'& is
18149 treated as &'<xxx@a.b.c.d>'&. If this is in the envelope and the message is
18150 passed on to another MTA, the excess angle brackets are not passed on. If this
18151 option is not set, multiple pairs of angle brackets cause a syntax error.
18154 .option strip_trailing_dot main boolean false
18155 .cindex "trailing dot on domain"
18156 .cindex "dot" "trailing on domain"
18157 If this option is set, a trailing dot at the end of a domain in an address is
18158 ignored. If this is in the envelope and the message is passed on to another
18159 MTA, the dot is not passed on. If this option is not set, a dot at the end of a
18160 domain causes a syntax error.
18161 However, addresses in header lines are checked only when an ACL requests header
18165 .option syslog_duplication main boolean true
18166 .cindex "syslog" "duplicate log lines; suppressing"
18167 When Exim is logging to syslog, it writes the log lines for its three
18168 separate logs at different syslog priorities so that they can in principle
18169 be separated on the logging hosts. Some installations do not require this
18170 separation, and in those cases, the duplication of certain log lines is a
18171 nuisance. If &%syslog_duplication%& is set false, only one copy of any
18172 particular log line is written to syslog. For lines that normally go to
18173 both the main log and the reject log, the reject log version (possibly
18174 containing message header lines) is written, at LOG_NOTICE priority.
18175 Lines that normally go to both the main and the panic log are written at
18176 the LOG_ALERT priority.
18179 .option syslog_facility main string unset
18180 .cindex "syslog" "facility; setting"
18181 This option sets the syslog &"facility"& name, used when Exim is logging to
18182 syslog. The value must be one of the strings &"mail"&, &"user"&, &"news"&,
18183 &"uucp"&, &"daemon"&, or &"local&'x'&"& where &'x'& is a digit between 0 and 7.
18184 If this option is unset, &"mail"& is used. See chapter &<<CHAPlog>>& for
18185 details of Exim's logging.
18188 .option syslog_pid main boolean true
18189 .cindex "syslog" "pid"
18190 If &%syslog_pid%& is set false, the PID on Exim's log lines are
18191 omitted when these lines are sent to syslog. (Syslog normally prefixes
18192 the log lines with the PID of the logging process automatically.) You need
18193 to enable the &`+pid`& log selector item, if you want Exim to write it's PID
18194 into the logs.) See chapter &<<CHAPlog>>& for details of Exim's logging.
18198 .option syslog_processname main string &`exim`&
18199 .cindex "syslog" "process name; setting"
18200 This option sets the syslog &"ident"& name, used when Exim is logging to
18201 syslog. The value must be no longer than 32 characters. See chapter
18202 &<<CHAPlog>>& for details of Exim's logging.
18206 .option syslog_timestamp main boolean true
18207 .cindex "syslog" "timestamps"
18208 .cindex timestamps syslog
18209 If &%syslog_timestamp%& is set false, the timestamps on Exim's log lines are
18210 omitted when these lines are sent to syslog. See chapter &<<CHAPlog>>& for
18211 details of Exim's logging.
18214 .option system_filter main string&!! unset
18215 .cindex "filter" "system filter"
18216 .cindex "system filter" "specifying"
18217 .cindex "Sieve filter" "not available for system filter"
18218 This option specifies an Exim filter file that is applied to all messages at
18219 the start of each delivery attempt, before any routing is done. System filters
18220 must be Exim filters; they cannot be Sieve filters. If the system filter
18221 generates any deliveries to files or pipes, or any new mail messages, the
18222 appropriate &%system_filter_..._transport%& option(s) must be set, to define
18223 which transports are to be used. Details of this facility are given in chapter
18224 &<<CHAPsystemfilter>>&.
18225 A forced expansion failure results in no filter operation.
18228 .option system_filter_directory_transport main string&!! unset
18229 .vindex "&$address_file$&"
18230 This sets the name of the transport driver that is to be used when the
18231 &%save%& command in a system message filter specifies a path ending in &"/"&,
18232 implying delivery of each message into a separate file in some directory.
18233 During the delivery, the variable &$address_file$& contains the path name.
18236 .option system_filter_file_transport main string&!! unset
18237 .cindex "file" "transport for system filter"
18238 This sets the name of the transport driver that is to be used when the &%save%&
18239 command in a system message filter specifies a path not ending in &"/"&. During
18240 the delivery, the variable &$address_file$& contains the path name.
18242 .option system_filter_group main string unset
18243 .cindex "gid (group id)" "system filter"
18244 This option is used only when &%system_filter_user%& is also set. It sets the
18245 gid under which the system filter is run, overriding any gid that is associated
18246 with the user. The value may be numerical or symbolic.
18248 .option system_filter_pipe_transport main string&!! unset
18249 .cindex "&(pipe)& transport" "for system filter"
18250 .vindex "&$address_pipe$&"
18251 This specifies the transport driver that is to be used when a &%pipe%& command
18252 is used in a system filter. During the delivery, the variable &$address_pipe$&
18253 contains the pipe command.
18256 .option system_filter_reply_transport main string&!! unset
18257 .cindex "&(autoreply)& transport" "for system filter"
18258 This specifies the transport driver that is to be used when a &%mail%& command
18259 is used in a system filter.
18262 .option system_filter_user main string unset
18263 .cindex "uid (user id)" "system filter"
18264 If this option is set to root, the system filter is run in the main Exim
18265 delivery process, as root. Otherwise, the system filter runs in a separate
18266 process, as the given user, defaulting to the Exim run-time user.
18267 Unless the string consists entirely of digits, it
18268 is looked up in the password data. Failure to find the named user causes a
18269 configuration error. The gid is either taken from the password data, or
18270 specified by &%system_filter_group%&. When the uid is specified numerically,
18271 &%system_filter_group%& is required to be set.
18273 If the system filter generates any pipe, file, or reply deliveries, the uid
18274 under which the filter is run is used when transporting them, unless a
18275 transport option overrides.
18278 .option tcp_nodelay main boolean true
18279 .cindex "daemon" "TCP_NODELAY on sockets"
18280 .cindex "Nagle algorithm"
18281 .cindex "TCP_NODELAY on listening sockets"
18282 If this option is set false, it stops the Exim daemon setting the
18283 TCP_NODELAY option on its listening sockets. Setting TCP_NODELAY
18284 turns off the &"Nagle algorithm"&, which is a way of improving network
18285 performance in interactive (character-by-character) situations. Turning it off
18286 should improve Exim's performance a bit, so that is what happens by default.
18287 However, it appears that some broken clients cannot cope, and time out. Hence
18288 this option. It affects only those sockets that are set up for listening by the
18289 daemon. Sockets created by the smtp transport for delivering mail always set
18293 .option timeout_frozen_after main time 0s
18294 .cindex "frozen messages" "timing out"
18295 .cindex "timeout" "frozen messages"
18296 If &%timeout_frozen_after%& is set to a time greater than zero, a frozen
18297 message of any kind that has been in the queue for longer than the given time
18298 is automatically cancelled at the next queue run. If the frozen message is a
18299 bounce message, it is just discarded; otherwise, a bounce is sent to the
18300 sender, in a similar manner to cancellation by the &%-Mg%& command line option.
18301 If you want to timeout frozen bounce messages earlier than other kinds of
18302 frozen message, see &%ignore_bounce_errors_after%&.
18304 &*Note:*& the default value of zero means no timeouts; with this setting,
18305 frozen messages remain in the queue forever (except for any frozen bounce
18306 messages that are released by &%ignore_bounce_errors_after%&).
18309 .option timezone main string unset
18310 .cindex "timezone, setting"
18311 .cindex "environment" "values from"
18312 The value of &%timezone%& is used to set the environment variable TZ while
18313 running Exim (if it is different on entry). This ensures that all timestamps
18314 created by Exim are in the required timezone. If you want all your timestamps
18315 to be in UTC (aka GMT) you should set
18319 The default value is taken from TIMEZONE_DEFAULT in &_Local/Makefile_&,
18320 or, if that is not set, from the value of the TZ environment variable when Exim
18321 is built. If &%timezone%& is set to the empty string, either at build or run
18322 time, any existing TZ variable is removed from the environment when Exim
18323 runs. This is appropriate behaviour for obtaining wall-clock time on some, but
18324 unfortunately not all, operating systems.
18327 .option tls_advertise_hosts main "host list&!!" *
18328 .cindex "TLS" "advertising"
18329 .cindex "encryption" "on SMTP connection"
18330 .cindex "SMTP" "encrypted connection"
18331 .cindex "ESMTP extensions" STARTTLS
18332 When Exim is built with support for TLS encrypted connections, the availability
18333 of the STARTTLS command to set up an encrypted session is advertised in
18334 response to EHLO only to those client hosts that match this option. See
18335 chapter &<<CHAPTLS>>& for details of Exim's support for TLS.
18336 Note that the default value requires that a certificate be supplied
18337 using the &%tls_certificate%& option. If TLS support for incoming connections
18338 is not required the &%tls_advertise_hosts%& option should be set empty.
18341 .option tls_alpn main "string list&!!" "smtp : esmtp"
18342 .cindex TLS "Application Layer Protocol Names"
18344 .cindex ALPN "set acceptable names for server"
18345 If this option is set,
18346 the TLS library supports ALPN,
18347 and the client offers either more than
18348 ALPN name or a name which does not match the list,
18349 the TLS connection is declined.
18352 .option tls_certificate main "string list&!!" unset
18353 .cindex "TLS" "server certificate; location of"
18354 .cindex "certificate" "server, location of"
18355 The value of this option is expanded, and must then be a list of absolute paths to
18356 files which contain the server's certificates (in PEM format).
18357 Commonly only one file is needed.
18358 The server's private key is also
18359 assumed to be in this file if &%tls_privatekey%& is unset. See chapter
18360 &<<CHAPTLS>>& for further details.
18362 &*Note*&: The certificates defined by this option are used only when Exim is
18363 receiving incoming messages as a server. If you want to supply certificates for
18364 use when sending messages as a client, you must set the &%tls_certificate%&
18365 option in the relevant &(smtp)& transport.
18367 &*Note*&: If you use filenames based on IP addresses, change the list
18368 separator in the usual way (&<<SECTlistsepchange>>&) to avoid confusion under IPv6.
18370 &*Note*&: Under versions of OpenSSL preceding 1.1.1,
18371 when a list of more than one
18372 file is used, the &$tls_in_ourcert$& variable is unreliable.
18373 The macro "_TLS_BAD_MULTICERT_IN_OURCERT" will be defined for those versions.
18375 .cindex SNI "selecting server certificate based on"
18376 If the option contains &$tls_out_sni$& and Exim is built against OpenSSL, then
18377 if the OpenSSL build supports TLS extensions and the TLS client sends the
18378 Server Name Indication extension, then this option and others documented in
18379 &<<SECTtlssni>>& will be re-expanded.
18381 If this option is unset or empty a self-signed certificate will be
18383 Under Linux this is generated at daemon startup; on other platforms it will be
18384 generated fresh for every connection.
18386 .option tls_crl main string&!! unset
18387 .cindex "TLS" "server certificate revocation list"
18388 .cindex "certificate" "revocation list for server"
18389 This option specifies a certificate revocation list. The expanded value must
18390 be the name of a file that contains CRLs in PEM format.
18392 Under OpenSSL the option can specify a directory with CRL files.
18394 &*Note:*& Under OpenSSL the option must, if given, supply a CRL
18395 for each signing element of the certificate chain (i.e. all but the leaf).
18396 For the file variant this can be multiple PEM blocks in the one file.
18398 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
18401 .option tls_dh_max_bits main integer 2236
18402 .cindex "TLS" "D-H bit count"
18403 The number of bits used for Diffie-Hellman key-exchange may be suggested by
18404 the chosen TLS library. That value might prove to be too high for
18405 interoperability. This option provides a maximum clamp on the value
18406 suggested, trading off security for interoperability.
18408 The value must be at least 1024.
18410 The value 2236 was chosen because, at time of adding the option, it was the
18411 hard-coded maximum value supported by the NSS cryptographic library, as used
18412 by Thunderbird, while GnuTLS was suggesting 2432 bits as normal.
18414 If you prefer more security and are willing to break some clients, raise this
18417 Note that the value passed to GnuTLS for *generating* a new prime may be a
18418 little less than this figure, because GnuTLS is inexact and may produce a
18419 larger prime than requested.
18422 .option tls_dhparam main string&!! unset
18423 .cindex "TLS" "D-H parameters for server"
18424 The value of this option is expanded and indicates the source of DH parameters
18425 to be used by Exim.
18427 &*Note: The Exim Maintainers strongly recommend using a filename with site-generated
18428 local DH parameters*&, which has been supported across all versions of Exim. The
18429 other specific constants available are a fallback so that even when
18430 "unconfigured", Exim can offer Perfect Forward Secrecy in older ciphersuites in TLS.
18432 If &%tls_dhparam%& is a filename starting with a &`/`&,
18433 then it names a file from which DH
18434 parameters should be loaded. If the file exists, it should hold a PEM-encoded
18435 PKCS#3 representation of the DH prime. If the file does not exist, for
18436 OpenSSL it is an error. For GnuTLS, Exim will attempt to create the file and
18437 fill it with a generated DH prime. For OpenSSL, if the DH bit-count from
18438 loading the file is greater than &%tls_dh_max_bits%& then it will be ignored,
18439 and treated as though the &%tls_dhparam%& were set to "none".
18441 If this option expands to the string "none", then no DH parameters will be
18444 If this option expands to the string "historic" and Exim is using GnuTLS, then
18445 Exim will attempt to load a file from inside the spool directory. If the file
18446 does not exist, Exim will attempt to create it.
18447 See section &<<SECTgnutlsparam>>& for further details.
18449 If Exim is using OpenSSL and this option is empty or unset, then Exim will load
18450 a default DH prime; the default is Exim-specific but lacks verifiable provenance.
18452 In older versions of Exim the default was the 2048 bit prime described in section
18453 2.2 of RFC 5114, "2048-bit MODP Group with 224-bit Prime Order Subgroup", which
18454 in IKE is assigned number 23.
18456 Otherwise, the option must expand to the name used by Exim for any of a number
18457 of DH primes specified in RFC 2409, RFC 3526, RFC 5114, RFC 7919, or from other
18458 sources. As names, Exim uses a standard specified name, else "ike" followed by
18459 the number used by IKE, or "default" which corresponds to
18460 &`exim.dev.20160529.3`&.
18462 The available standard primes are:
18463 &`ffdhe2048`&, &`ffdhe3072`&, &`ffdhe4096`&, &`ffdhe6144`&, &`ffdhe8192`&,
18464 &`ike1`&, &`ike2`&, &`ike5`&,
18465 &`ike14`&, &`ike15`&, &`ike16`&, &`ike17`&, &`ike18`&,
18466 &`ike22`&, &`ike23`& and &`ike24`&.
18468 The available additional primes are:
18469 &`exim.dev.20160529.1`&, &`exim.dev.20160529.2`& and &`exim.dev.20160529.3`&.
18471 Some of these will be too small to be accepted by clients.
18472 Some may be too large to be accepted by clients.
18473 The open cryptographic community has suspicions about the integrity of some
18474 of the later IKE values, which led into RFC7919 providing new fixed constants
18475 (the "ffdhe" identifiers).
18477 At this point, all of the "ike" values should be considered obsolete;
18478 they are still in Exim to avoid breaking unusual configurations, but are
18479 candidates for removal the next time we have backwards-incompatible changes.
18480 Two of them in particular (&`ike1`& and &`ike22`&) are called out by RFC 8247
18481 as MUST NOT use for IPSEC, and two more (&`ike23`& and &`ike24`&) as
18483 Because of this, Exim regards them as deprecated; if either of the first pair
18484 are used, warnings will be logged in the paniclog, and if any are used then
18485 warnings will be logged in the mainlog.
18486 All four will be removed in a future Exim release.
18488 The TLS protocol does not negotiate an acceptable size for this; clients tend
18489 to hard-drop connections if what is offered by the server is unacceptable,
18490 whether too large or too small, and there's no provision for the client to
18491 tell the server what these constraints are. Thus, as a server operator, you
18492 need to make an educated guess as to what is most likely to work for your
18495 Some known size constraints suggest that a bit-size in the range 2048 to 2236
18496 is most likely to maximise interoperability. The upper bound comes from
18497 applications using the Mozilla Network Security Services (NSS) library, which
18498 used to set its &`DH_MAX_P_BITS`& upper-bound to 2236. This affects many
18499 mail user agents (MUAs). The lower bound comes from Debian installs of Exim4
18500 prior to the 4.80 release, as Debian used to patch Exim to raise the minimum
18501 acceptable bound from 1024 to 2048.
18504 .option tls_eccurve main string&!! &`auto`&
18505 .cindex TLS "EC cryptography"
18506 This option selects a EC curve for use by Exim when used with OpenSSL.
18507 It has no effect when Exim is used with GnuTLS.
18509 After expansion it must contain a valid EC curve parameter, such as
18510 &`prime256v1`&, &`secp384r1`&, or &`P-512`&. Consult your OpenSSL manual
18511 for valid selections.
18513 For OpenSSL versions before (and not including) 1.0.2, the string
18514 &`auto`& selects &`prime256v1`&. For more recent OpenSSL versions
18515 &`auto`& tells the library to choose.
18517 If the option expands to an empty string, no EC curves will be enabled.
18520 .option tls_ocsp_file main string&!! unset
18521 .cindex TLS "certificate status"
18522 .cindex TLS "OCSP proof file"
18524 must if set expand to the absolute path to a file which contains a current
18525 status proof for the server's certificate, as obtained from the
18526 Certificate Authority.
18528 Usable for GnuTLS 3.4.4 or 3.3.17 or OpenSSL 1.1.0 (or later).
18529 The macro "_HAVE_TLS_OCSP" will be defined for those versions.
18531 For OpenSSL 1.1.0 or later, and
18532 for GnuTLS 3.5.6 or later the expanded value of this option can be a list
18533 of files, to match a list given for the &%tls_certificate%& option.
18534 The ordering of the two lists must match.
18535 The macro "_HAVE_TLS_OCSP_LIST" will be defined for those versions.
18537 The file(s) should be in DER format,
18538 except for GnuTLS 3.6.3 or later
18540 when an optional filetype prefix can be used.
18541 The prefix must be one of "DER" or "PEM", followed by
18542 a single space. If one is used it sets the format for subsequent
18543 files in the list; the initial format is DER.
18544 If multiple proofs are wanted, for multiple chain elements
18545 (this only works under TLS1.3)
18546 they must be coded as a combined OCSP response.
18548 Although GnuTLS will accept PEM files with multiple separate
18549 PEM blobs (ie. separate OCSP responses), it sends them in the
18550 TLS Certificate record interleaved with the certificates of the chain;
18551 although a GnuTLS client is happy with that, an OpenSSL client is not.
18553 .option tls_on_connect_ports main "string list" unset
18556 This option specifies a list of incoming SSMTP (aka SMTPS) ports that should
18557 operate the SSMTP (SMTPS) protocol, where a TLS session is immediately
18558 set up without waiting for the client to issue a STARTTLS command. For
18559 further details, see section &<<SECTsupobssmt>>&.
18563 .option tls_privatekey main "string list&!!" unset
18564 .cindex "TLS" "server private key; location of"
18565 The value of this option is expanded, and must then be a list of absolute paths to
18566 files which contains the server's private keys.
18567 If this option is unset, or if
18568 the expansion is forced to fail, or the result is an empty string, the private
18569 key is assumed to be in the same file as the server's certificates. See chapter
18570 &<<CHAPTLS>>& for further details.
18572 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
18575 .option tls_remember_esmtp main boolean false
18576 .cindex "TLS" "esmtp state; remembering"
18577 .cindex "TLS" "broken clients"
18578 If this option is set true, Exim violates the RFCs by remembering that it is in
18579 &"esmtp"& state after successfully negotiating a TLS session. This provides
18580 support for broken clients that fail to send a new EHLO after starting a
18584 .option tls_require_ciphers main string&!! unset
18585 .cindex "TLS" "requiring specific ciphers"
18586 .cindex "cipher" "requiring specific"
18587 This option controls which ciphers can be used for incoming TLS connections.
18588 The &(smtp)& transport has an option of the same name for controlling outgoing
18589 connections. This option is expanded for each connection, so can be varied for
18590 different clients if required. The value of this option must be a list of
18591 permitted cipher suites. The OpenSSL and GnuTLS libraries handle cipher control
18592 in somewhat different ways. If GnuTLS is being used, the client controls the
18593 preference order of the available ciphers. Details are given in sections
18594 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
18597 .option tls_resumption_hosts main "host list&!!" unset
18598 .cindex TLS resumption
18599 This option controls which connections to offer the TLS resumption feature.
18600 See &<<SECTresumption>>& for details.
18603 .option tls_try_verify_hosts main "host list&!!" unset
18604 .cindex "TLS" "client certificate verification"
18605 .cindex "certificate" "verification of client"
18606 See &%tls_verify_hosts%& below.
18609 .option tls_verify_certificates main string&!! system
18610 .cindex "TLS" "client certificate verification"
18611 .cindex "certificate" "verification of client"
18612 The value of this option is expanded, and must then be either the
18614 or the absolute path to
18615 a file or directory containing permitted certificates for clients that
18616 match &%tls_verify_hosts%& or &%tls_try_verify_hosts%&.
18618 The "system" value for the option will use a
18619 system default location compiled into the SSL library.
18620 This is not available for GnuTLS versions preceding 3.0.20,
18621 and will be taken as empty; an explicit location
18624 The use of a directory for the option value is not available for GnuTLS versions
18625 preceding 3.3.6 and a single file must be used.
18627 With OpenSSL the certificates specified
18629 either by file or directory
18630 are added to those given by the system default location.
18632 These certificates should be for the certificate authorities trusted, rather
18633 than the public cert of individual clients. With both OpenSSL and GnuTLS, if
18634 the value is a file then the certificates are sent by Exim as a server to
18635 connecting clients, defining the list of accepted certificate authorities.
18636 Thus the values defined should be considered public data. To avoid this,
18637 use the explicit directory version. (If your peer is Exim up to 4.85,
18638 using GnuTLS, you may need to send the CAs (thus using the file
18639 variant). Otherwise the peer doesn't send its certificate.)
18641 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
18643 A forced expansion failure or setting to an empty string is equivalent to
18647 .option tls_verify_hosts main "host list&!!" unset
18648 .cindex "TLS" "client certificate verification"
18649 .cindex "certificate" "verification of client"
18650 This option, along with &%tls_try_verify_hosts%&, controls the checking of
18651 certificates from clients. The expected certificates are defined by
18652 &%tls_verify_certificates%&, which must be set. A configuration error occurs if
18653 either &%tls_verify_hosts%& or &%tls_try_verify_hosts%& is set and
18654 &%tls_verify_certificates%& is not set.
18656 Any client that matches &%tls_verify_hosts%& is constrained by
18657 &%tls_verify_certificates%&. When the client initiates a TLS session, it must
18658 present one of the listed certificates. If it does not, the connection is
18660 &*Warning*&: Including a host in &%tls_verify_hosts%& does not require
18661 the host to use TLS. It can still send SMTP commands through unencrypted
18662 connections. Forcing a client to use TLS has to be done separately using an
18663 ACL to reject inappropriate commands when the connection is not encrypted.
18665 A weaker form of checking is provided by &%tls_try_verify_hosts%&. If a client
18666 matches this option (but not &%tls_verify_hosts%&), Exim requests a
18667 certificate and checks it against &%tls_verify_certificates%&, but does not
18668 abort the connection if there is no certificate or if it does not match. This
18669 state can be detected in an ACL, which makes it possible to implement policies
18670 such as &"accept for relay only if a verified certificate has been received,
18671 but accept for local delivery if encrypted, even without a verified
18674 Client hosts that match neither of these lists are not asked to present
18678 .option trusted_groups main "string list&!!" unset
18679 .cindex "trusted groups"
18680 .cindex "groups" "trusted"
18681 This option is expanded just once, at the start of Exim's processing. If this
18682 option is set, any process that is running in one of the listed groups, or
18683 which has one of them as a supplementary group, is trusted. The groups can be
18684 specified numerically or by name. See section &<<SECTtrustedadmin>>& for
18685 details of what trusted callers are permitted to do. If neither
18686 &%trusted_groups%& nor &%trusted_users%& is set, only root and the Exim user
18689 .option trusted_users main "string list&!!" unset
18690 .cindex "trusted users"
18691 .cindex "user" "trusted"
18692 This option is expanded just once, at the start of Exim's processing. If this
18693 option is set, any process that is running as one of the listed users is
18694 trusted. The users can be specified numerically or by name. See section
18695 &<<SECTtrustedadmin>>& for details of what trusted callers are permitted to do.
18696 If neither &%trusted_groups%& nor &%trusted_users%& is set, only root and the
18697 Exim user are trusted.
18699 .option unknown_login main string&!! unset
18700 .cindex "uid (user id)" "unknown caller"
18701 .vindex "&$caller_uid$&"
18702 This is a specialized feature for use in unusual configurations. By default, if
18703 the uid of the caller of Exim cannot be looked up using &[getpwuid()]&, Exim
18704 gives up. The &%unknown_login%& option can be used to set a login name to be
18705 used in this circumstance. It is expanded, so values like &%user$caller_uid%&
18706 can be set. When &%unknown_login%& is used, the value of &%unknown_username%&
18707 is used for the user's real name (gecos field), unless this has been set by the
18710 .option unknown_username main string unset
18711 See &%unknown_login%&.
18713 .option untrusted_set_sender main "address list&!!" unset
18714 .cindex "trusted users"
18715 .cindex "sender" "setting by untrusted user"
18716 .cindex "untrusted user setting sender"
18717 .cindex "user" "untrusted setting sender"
18718 .cindex "envelope from"
18719 .cindex "envelope sender"
18720 When an untrusted user submits a message to Exim using the standard input, Exim
18721 normally creates an envelope sender address from the user's login and the
18722 default qualification domain. Data from the &%-f%& option (for setting envelope
18723 senders on non-SMTP messages) or the SMTP MAIL command (if &%-bs%& or &%-bS%&
18724 is used) is ignored.
18726 However, untrusted users are permitted to set an empty envelope sender address,
18727 to declare that a message should never generate any bounces. For example:
18729 exim -f '<>' user@domain.example
18731 .vindex "&$sender_ident$&"
18732 The &%untrusted_set_sender%& option allows you to permit untrusted users to set
18733 other envelope sender addresses in a controlled way. When it is set, untrusted
18734 users are allowed to set envelope sender addresses that match any of the
18735 patterns in the list. Like all address lists, the string is expanded. The
18736 identity of the user is in &$sender_ident$&, so you can, for example, restrict
18737 users to setting senders that start with their login ids
18738 followed by a hyphen
18739 by a setting like this:
18741 untrusted_set_sender = ^$sender_ident-
18743 If you want to allow untrusted users to set envelope sender addresses without
18744 restriction, you can use
18746 untrusted_set_sender = *
18748 The &%untrusted_set_sender%& option applies to all forms of local input, but
18749 only to the setting of the envelope sender. It does not permit untrusted users
18750 to use the other options which trusted user can use to override message
18751 parameters. Furthermore, it does not stop Exim from removing an existing
18752 &'Sender:'& header in the message, or from adding a &'Sender:'& header if
18753 necessary. See &%local_sender_retain%& and &%local_from_check%& for ways of
18754 overriding these actions. The handling of the &'Sender:'& header is also
18755 described in section &<<SECTthesenhea>>&.
18757 The log line for a message's arrival shows the envelope sender following
18758 &"<="&. For local messages, the user's login always follows, after &"U="&. In
18759 &%-bp%& displays, and in the Exim monitor, if an untrusted user sets an
18760 envelope sender address, the user's login is shown in parentheses after the
18764 .option uucp_from_pattern main string "see below"
18765 .cindex "&""From""& line"
18766 .cindex "UUCP" "&""From""& line"
18767 Some applications that pass messages to an MTA via a command line interface use
18768 an initial line starting with &"From&~"& to pass the envelope sender. In
18769 particular, this is used by UUCP software. Exim recognizes such a line by means
18770 of a regular expression that is set in &%uucp_from_pattern%&. When the pattern
18771 matches, the sender address is constructed by expanding the contents of
18772 &%uucp_from_sender%&, provided that the caller of Exim is a trusted user. The
18773 default pattern recognizes lines in the following two forms:
18775 From ph10 Fri Jan 5 12:35 GMT 1996
18776 From ph10 Fri, 7 Jan 97 14:00:00 GMT
18778 The pattern can be seen by running
18780 exim -bP uucp_from_pattern
18782 It checks only up to the hours and minutes, and allows for a 2-digit or 4-digit
18783 year in the second case. The first word after &"From&~"& is matched in the
18784 regular expression by a parenthesized subpattern. The default value for
18785 &%uucp_from_sender%& is &"$1"&, which therefore just uses this first word
18786 (&"ph10"& in the example above) as the message's sender. See also
18787 &%ignore_fromline_hosts%&.
18790 .option uucp_from_sender main string&!! &`$1`&
18791 See &%uucp_from_pattern%& above.
18794 .option warn_message_file main string&!! unset
18795 .cindex "warning of delay" "customizing the message"
18796 .cindex "customizing" "warning message"
18797 This option defines a template file containing paragraphs of text to be used
18798 for constructing the warning message which is sent by Exim when a message has
18799 been in the queue for a specified amount of time, as specified by
18800 &%delay_warning%&. Details of the file's contents are given in chapter
18801 &<<CHAPemsgcust>>&.
18802 .cindex warn_message_file "tainted data"
18803 The option is expanded to give the file path, which must be
18804 absolute and untainted.
18805 See also &%bounce_message_file%&.
18808 .option write_rejectlog main boolean true
18809 .cindex "reject log" "disabling"
18810 If this option is set false, Exim no longer writes anything to the reject log.
18811 See chapter &<<CHAPlog>>& for details of what Exim writes to its logs.
18812 .ecindex IIDconfima
18813 .ecindex IIDmaiconf
18818 . ////////////////////////////////////////////////////////////////////////////
18819 . ////////////////////////////////////////////////////////////////////////////
18821 .chapter "Generic options for routers" "CHAProutergeneric"
18822 .scindex IIDgenoprou1 "options" "generic; for routers"
18823 .scindex IIDgenoprou2 "generic options" "router"
18824 This chapter describes the generic options that apply to all routers.
18825 Those that are preconditions are marked with ‡ in the &"use"& field.
18827 For a general description of how a router operates, see sections
18828 &<<SECTrunindrou>>& and &<<SECTrouprecon>>&. The latter specifies the order in
18829 which the preconditions are tested. The order of expansion of the options that
18830 provide data for a transport is: &%errors_to%&, &%headers_add%&,
18831 &%headers_remove%&, &%transport%&.
18833 The name of a router is limited to be &drivernamemax; ASCII characters long;
18834 prior to Exim 4.95 names would be silently truncated at this length, but now
18838 .option address_data routers string&!! unset
18839 .cindex "router" "data attached to address"
18840 The string is expanded just before the router is run, that is, after all the
18841 precondition tests have succeeded. If the expansion is forced to fail, the
18842 router declines, the value of &%address_data%& remains unchanged, and the
18843 &%more%& option controls what happens next. Other expansion failures cause
18844 delivery of the address to be deferred.
18846 .vindex "&$address_data$&"
18847 When the expansion succeeds, the value is retained with the address, and can be
18848 accessed using the variable &$address_data$& in the current router, subsequent
18849 routers, and the eventual transport.
18851 &*Warning*&: If the current or any subsequent router is a &(redirect)& router
18852 that runs a user's filter file, the contents of &$address_data$& are accessible
18853 in the filter. This is not normally a problem, because such data is usually
18854 either not confidential or it &"belongs"& to the current user, but if you do
18855 put confidential data into &$address_data$& you need to remember this point.
18857 Even if the router declines or passes, the value of &$address_data$& remains
18858 with the address, though it can be changed by another &%address_data%& setting
18859 on a subsequent router. If a router generates child addresses, the value of
18860 &$address_data$& propagates to them. This also applies to the special kind of
18861 &"child"& that is generated by a router with the &%unseen%& option.
18863 The idea of &%address_data%& is that you can use it to look up a lot of data
18864 for the address once, and then pick out parts of the data later. For example,
18865 you could use a single LDAP lookup to return a string of the form
18867 uid=1234 gid=5678 mailbox=/mail/xyz forward=/home/xyz/.forward
18869 In the transport you could pick out the mailbox by a setting such as
18871 file = ${extract{mailbox}{$address_data}}
18873 This makes the configuration file less messy, and also reduces the number of
18874 lookups (though Exim does cache lookups).
18876 See also the &%set%& option below.
18878 .vindex "&$sender_address_data$&"
18879 .vindex "&$address_data$&"
18880 The &%address_data%& facility is also useful as a means of passing information
18881 from one router to another, and from a router to a transport. In addition, if
18882 &$address_data$& is set by a router when verifying a recipient address from an
18883 ACL, it remains available for use in the rest of the ACL statement. After
18884 verifying a sender, the value is transferred to &$sender_address_data$&.
18888 .option address_test routers&!? boolean true
18890 .cindex "router" "skipping when address testing"
18891 If this option is set false, the router is skipped when routing is being tested
18892 by means of the &%-bt%& command line option. This can be a convenience when
18893 your first router sends messages to an external scanner, because it saves you
18894 having to set the &"already scanned"& indicator when testing real address
18899 .option cannot_route_message routers string&!! unset
18900 .cindex "router" "customizing &""cannot route""& message"
18901 .cindex "customizing" "&""cannot route""& message"
18902 This option specifies a text message that is used when an address cannot be
18903 routed because Exim has run out of routers. The default message is
18904 &"Unrouteable address"&. This option is useful only on routers that have
18905 &%more%& set false, or on the very last router in a configuration, because the
18906 value that is used is taken from the last router that is considered. This
18907 includes a router that is skipped because its preconditions are not met, as
18908 well as a router that declines. For example, using the default configuration,
18911 cannot_route_message = Remote domain not found in DNS
18913 on the first router, which is a &(dnslookup)& router with &%more%& set false,
18916 cannot_route_message = Unknown local user
18918 on the final router that checks for local users. If string expansion fails for
18919 this option, the default message is used. Unless the expansion failure was
18920 explicitly forced, a message about the failure is written to the main and panic
18921 logs, in addition to the normal message about the routing failure.
18924 .option caseful_local_part routers boolean false
18925 .cindex "case of local parts"
18926 .cindex "router" "case of local parts"
18927 By default, routers handle the local parts of addresses in a case-insensitive
18928 manner, though the actual case is preserved for transmission with the message.
18929 If you want the case of letters to be significant in a router, you must set
18930 this option true. For individual router options that contain address or local
18931 part lists (for example, &%local_parts%&), case-sensitive matching can be
18932 turned on by &"+caseful"& as a list item. See section &<<SECTcasletadd>>& for
18935 .vindex "&$local_part$&"
18936 .vindex "&$original_local_part$&"
18937 .vindex "&$parent_local_part$&"
18938 The value of the &$local_part$& variable is forced to lower case while a
18939 router is running unless &%caseful_local_part%& is set. When a router assigns
18940 an address to a transport, the value of &$local_part$& when the transport runs
18941 is the same as it was in the router. Similarly, when a router generates child
18942 addresses by aliasing or forwarding, the values of &$original_local_part$&
18943 and &$parent_local_part$& are those that were used by the redirecting router.
18945 This option applies to the processing of an address by a router. When a
18946 recipient address is being processed in an ACL, there is a separate &%control%&
18947 modifier that can be used to specify case-sensitive processing within the ACL
18948 (see section &<<SECTcontrols>>&).
18952 .option check_local_user routers&!? boolean false
18953 .cindex "local user, checking in router"
18954 .cindex "router" "checking for local user"
18955 .cindex "&_/etc/passwd_&"
18957 When this option is true, Exim checks that the local part of the recipient
18958 address (with affixes removed if relevant) is the name of an account on the
18959 local system. The check is done by calling the &[getpwnam()]& function rather
18960 than trying to read &_/etc/passwd_& directly. This means that other methods of
18961 holding password data (such as NIS) are supported. If the local part is a local
18963 .cindex "tainted data" "de-tainting"
18964 .cindex "de-tainting" "using router check_local_user option"
18965 &$local_part_data$& is set to an untainted version of the local part and
18966 &$home$& is set from the password data. The latter can be tested in other
18967 preconditions that are evaluated after this one (the order of evaluation is
18968 given in section &<<SECTrouprecon>>&). However, the value of &$home$& can be
18969 overridden by &%router_home_directory%&. If the local part is not a local user,
18970 the router is skipped.
18972 If you want to check that the local part is either the name of a local user
18973 or matches something else, you cannot combine &%check_local_user%& with a
18974 setting of &%local_parts%&, because that specifies the logical &'and'& of the
18975 two conditions. However, you can use a &(passwd)& lookup in a &%local_parts%&
18976 setting to achieve this. For example:
18978 local_parts = passwd;$local_part : lsearch;/etc/other/users
18980 Note, however, that the side effects of &%check_local_user%& (such as setting
18981 up a home directory) do not occur when a &(passwd)& lookup is used in a
18982 &%local_parts%& (or any other) precondition.
18986 .option condition routers&!? string&!! unset
18987 .cindex "router" "customized precondition"
18988 This option specifies a general precondition test that has to succeed for the
18989 router to be called. The &%condition%& option is the last precondition to be
18990 evaluated (see section &<<SECTrouprecon>>&). The string is expanded, and if the
18991 result is a forced failure, or an empty string, or one of the strings &"0"& or
18992 &"no"& or &"false"& (checked without regard to the case of the letters), the
18993 router is skipped, and the address is offered to the next one.
18995 If the result is any other value, the router is run (as this is the last
18996 precondition to be evaluated, all the other preconditions must be true).
18998 This option is unusual in that multiple &%condition%& options may be present.
18999 All &%condition%& options must succeed.
19001 The &%condition%& option provides a means of applying custom conditions to the
19002 running of routers. Note that in the case of a simple conditional expansion,
19003 the default expansion values are exactly what is wanted. For example:
19005 condition = ${if >{$message_age}{600}}
19007 Because of the default behaviour of the string expansion, this is equivalent to
19009 condition = ${if >{$message_age}{600}{true}{}}
19012 A multiple condition example, which succeeds:
19014 condition = ${if >{$message_age}{600}}
19015 condition = ${if !eq{${lc:$local_part}}{postmaster}}
19019 If the expansion fails (other than forced failure) delivery is deferred. Some
19020 of the other precondition options are common special cases that could in fact
19021 be specified using &%condition%&.
19023 Historical note: We have &%condition%& on ACLs and on Routers. Routers
19024 are far older, and use one set of semantics. ACLs are newer and when
19025 they were created, the ACL &%condition%& process was given far stricter
19026 parse semantics. The &%bool{}%& expansion condition uses the same rules as
19027 ACLs. The &%bool_lax{}%& expansion condition uses the same rules as
19028 Routers. More pointedly, the &%bool_lax{}%& was written to match the existing
19029 Router rules processing behavior.
19031 This is best illustrated in an example:
19033 # If used in an ACL condition will fail with a syntax error, but
19034 # in a router condition any extra characters are treated as a string
19036 $ exim -be '${if eq {${lc:GOOGLE.com}} {google.com}} {yes} {no}}'
19039 $ exim -be '${if eq {${lc:WHOIS.com}} {google.com}} {yes} {no}}'
19042 In each example above, the &%if%& statement actually ends after
19043 &"{google.com}}"&. Since no true or false braces were defined, the
19044 default &%if%& behavior is to return a boolean true or a null answer
19045 (which evaluates to false). The rest of the line is then treated as a
19046 string. So the first example resulted in the boolean answer &"true"&
19047 with the string &" {yes} {no}}"& appended to it. The second example
19048 resulted in the null output (indicating false) with the string
19049 &" {yes} {no}}"& appended to it.
19051 In fact you can put excess forward braces in too. In the router
19052 &%condition%&, Exim's parser only looks for &"{"& symbols when they
19053 mean something, like after a &"$"& or when required as part of a
19054 conditional. But otherwise &"{"& and &"}"& are treated as ordinary
19057 Thus, in a Router, the above expansion strings will both always evaluate
19058 true, as the result of expansion is a non-empty string which doesn't
19059 match an explicit false value. This can be tricky to debug. By
19060 contrast, in an ACL either of those strings will always result in an
19061 expansion error because the result doesn't look sufficiently boolean.
19064 .option debug_print routers string&!! unset
19065 .cindex "testing" "variables in drivers"
19066 If this option is set and debugging is enabled (see the &%-d%& command line
19067 option) or in address-testing mode (see the &%-bt%& command line option),
19068 the string is expanded and included in the debugging output.
19069 If expansion of the string fails, the error message is written to the debugging
19070 output, and Exim carries on processing.
19071 This option is provided to help with checking out the values of variables and
19072 so on when debugging router configurations. For example, if a &%condition%&
19073 option appears not to be working, &%debug_print%& can be used to output the
19074 variables it references. The output happens after checks for &%domains%&,
19075 &%local_parts%&, and &%check_local_user%& but before any other preconditions
19076 are tested. A newline is added to the text if it does not end with one.
19077 The variable &$router_name$& contains the name of the router.
19081 .option disable_logging routers boolean false
19082 If this option is set true, nothing is logged for any routing errors
19083 or for any deliveries caused by this router. You should not set this option
19084 unless you really, really know what you are doing. See also the generic
19085 transport option of the same name.
19087 .option dnssec_request_domains routers "domain list&!!" *
19088 .cindex "MX record" "security"
19089 .cindex "DNSSEC" "MX lookup"
19090 .cindex "security" "MX lookup"
19091 .cindex "DNS" "DNSSEC"
19092 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
19093 the DNSSEC request bit set.
19094 This applies to all of the SRV, MX, AAAA, A lookup sequence.
19096 .option dnssec_require_domains routers "domain list&!!" unset
19097 .cindex "MX record" "security"
19098 .cindex "DNSSEC" "MX lookup"
19099 .cindex "security" "MX lookup"
19100 .cindex "DNS" "DNSSEC"
19101 DNS lookups for domains matching &%dnssec_require_domains%& will be done with
19102 the DNSSEC request bit set. Any returns not having the Authenticated Data bit
19103 (AD bit) set will be ignored and logged as a host-lookup failure.
19104 This applies to all of the SRV, MX, AAAA, A lookup sequence.
19107 .option domains routers&!? "domain list&!!" unset
19108 .cindex "router" "restricting to specific domains"
19109 .vindex "&$domain_data$&"
19110 If this option is set, the router is skipped unless the current domain matches
19111 the list. If the match is achieved by means of a file lookup, the data that the
19112 lookup returned for the domain is placed in &$domain_data$& for use in string
19113 expansions of the driver's private options and in the transport.
19114 See section &<<SECTrouprecon>>& for
19115 a list of the order in which preconditions are evaluated.
19119 .option driver routers string unset
19120 This option must always be set. It specifies which of the available routers is
19124 .option dsn_lasthop routers boolean false
19125 .cindex "DSN" "success"
19126 .cindex "Delivery Status Notification" "success"
19127 If this option is set true, and extended DSN (RFC3461) processing is in effect,
19128 Exim will not pass on DSN requests to downstream DSN-aware hosts but will
19129 instead send a success DSN as if the next hop does not support DSN.
19130 Not effective on redirect routers.
19134 .option errors_to routers string&!! unset
19135 .cindex "envelope from"
19136 .cindex "envelope sender"
19137 .cindex "router" "changing address for errors"
19138 If a router successfully handles an address, it may assign the address to a
19139 transport for delivery or it may generate child addresses. In both cases, if
19140 there is a delivery problem during later processing, the resulting bounce
19141 message is sent to the address that results from expanding this string,
19142 provided that the address verifies successfully. The &%errors_to%& option is
19143 expanded before &%headers_add%&, &%headers_remove%&, and &%transport%&.
19145 The &%errors_to%& setting associated with an address can be overridden if it
19146 subsequently passes through other routers that have their own &%errors_to%&
19147 settings, or if the message is delivered by a transport with a &%return_path%&
19150 If &%errors_to%& is unset, or the expansion is forced to fail, or the result of
19151 the expansion fails to verify, the errors address associated with the incoming
19152 address is used. At top level, this is the envelope sender. A non-forced
19153 expansion failure causes delivery to be deferred.
19155 If an address for which &%errors_to%& has been set ends up being delivered over
19156 SMTP, the envelope sender for that delivery is the &%errors_to%& value, so that
19157 any bounces that are generated by other MTAs on the delivery route are also
19158 sent there. You can set &%errors_to%& to the empty string by either of these
19164 An expansion item that yields an empty string has the same effect. If you do
19165 this, a locally detected delivery error for addresses processed by this router
19166 no longer gives rise to a bounce message; the error is discarded. If the
19167 address is delivered to a remote host, the return path is set to &`<>`&, unless
19168 overridden by the &%return_path%& option on the transport.
19170 .vindex "&$address_data$&"
19171 If for some reason you want to discard local errors, but use a non-empty
19172 MAIL command for remote delivery, you can preserve the original return
19173 path in &$address_data$& in the router, and reinstate it in the transport by
19174 setting &%return_path%&.
19176 The most common use of &%errors_to%& is to direct mailing list bounces to the
19177 manager of the list, as described in section &<<SECTmailinglists>>&, or to
19178 implement VERP (Variable Envelope Return Paths) (see section &<<SECTverp>>&).
19182 .option expn routers&!? boolean true
19183 .cindex "address" "testing"
19184 .cindex "testing" "addresses"
19185 .cindex "EXPN" "router skipping"
19186 .cindex "router" "skipping for EXPN"
19187 If this option is turned off, the router is skipped when testing an address
19188 as a result of processing an SMTP EXPN command. You might, for example,
19189 want to turn it off on a router for users' &_.forward_& files, while leaving it
19190 on for the system alias file.
19191 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19194 The use of the SMTP EXPN command is controlled by an ACL (see chapter
19195 &<<CHAPACL>>&). When Exim is running an EXPN command, it is similar to testing
19196 an address with &%-bt%&. Compare VRFY, whose counterpart is &%-bv%&.
19200 .option fail_verify routers boolean false
19201 .cindex "router" "forcing verification failure"
19202 Setting this option has the effect of setting both &%fail_verify_sender%& and
19203 &%fail_verify_recipient%& to the same value.
19207 .option fail_verify_recipient routers boolean false
19208 If this option is true and an address is accepted by this router when
19209 verifying a recipient, verification fails.
19213 .option fail_verify_sender routers boolean false
19214 If this option is true and an address is accepted by this router when
19215 verifying a sender, verification fails.
19219 .option fallback_hosts routers "string list" unset
19220 .cindex "router" "fallback hosts"
19221 .cindex "fallback" "hosts specified on router"
19222 String expansion is not applied to this option. The argument must be a
19223 colon-separated list of host names or IP addresses. The list separator can be
19224 changed (see section &<<SECTlistsepchange>>&), and a port can be specified with
19225 each name or address. In fact, the format of each item is exactly the same as
19226 defined for the list of hosts in a &(manualroute)& router (see section
19227 &<<SECTformatonehostitem>>&).
19229 If a router queues an address for a remote transport, this host list is
19230 associated with the address, and used instead of the transport's fallback host
19231 list. If &%hosts_randomize%& is set on the transport, the order of the list is
19232 randomized for each use. See the &%fallback_hosts%& option of the &(smtp)&
19233 transport for further details.
19236 .option group routers string&!! "see below"
19237 .cindex "gid (group id)" "local delivery"
19238 .cindex "local transports" "uid and gid"
19239 .cindex "transport" "local"
19240 .cindex "router" "setting group"
19241 When a router queues an address for a transport, and the transport does not
19242 specify a group, the group given here is used when running the delivery
19244 The group may be specified numerically or by name. If expansion fails, the
19245 error is logged and delivery is deferred.
19246 The default is unset, unless &%check_local_user%& is set, when the default
19247 is taken from the password information. See also &%initgroups%& and &%user%&
19248 and the discussion in chapter &<<CHAPenvironment>>&.
19252 .option headers_add routers list&!! unset
19253 .cindex "header lines" "adding"
19254 .cindex "router" "adding header lines"
19255 This option specifies a list of text headers,
19256 newline-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
19257 that is associated with any addresses that are accepted by the router.
19258 Each item is separately expanded, at routing time. However, this
19259 option has no effect when an address is just being verified. The way in which
19260 the text is used to add header lines at transport time is described in section
19261 &<<SECTheadersaddrem>>&. New header lines are not actually added until the
19262 message is in the process of being transported. This means that references to
19263 header lines in string expansions in the transport's configuration do not
19264 &"see"& the added header lines.
19266 The &%headers_add%& option is expanded after &%errors_to%&, but before
19267 &%headers_remove%& and &%transport%&. If an item is empty, or if
19268 an item expansion is forced to fail, the item has no effect. Other expansion
19269 failures are treated as configuration errors.
19271 Unlike most options, &%headers_add%& can be specified multiple times
19272 for a router; all listed headers are added.
19274 &*Warning 1*&: The &%headers_add%& option cannot be used for a &(redirect)&
19275 router that has the &%one_time%& option set.
19277 .cindex "duplicate addresses"
19278 .oindex "&%unseen%&"
19279 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
19280 additions are deleted when the address is passed on to subsequent routers.
19281 For a &%redirect%& router, if a generated address is the same as the incoming
19282 address, this can lead to duplicate addresses with different header
19283 modifications. Exim does not do duplicate deliveries (except, in certain
19284 circumstances, to pipes -- see section &<<SECTdupaddr>>&), but it is undefined
19285 which of the duplicates is discarded, so this ambiguous situation should be
19286 avoided. The &%repeat_use%& option of the &%redirect%& router may be of help.
19290 .option headers_remove routers list&!! unset
19291 .cindex "header lines" "removing"
19292 .cindex "router" "removing header lines"
19293 This option specifies a list of text headers,
19294 colon-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
19295 that is associated with any addresses that are accepted by the router.
19296 However, the option has no effect when an address is just being verified.
19297 Each list item is separately expanded, at transport time.
19298 If an item ends in *, it will match any header with the given prefix.
19300 the text is used to remove header lines at transport time is described in
19301 section &<<SECTheadersaddrem>>&. Header lines are not actually removed until
19302 the message is in the process of being transported. This means that references
19303 to header lines in string expansions in the transport's configuration still
19304 &"see"& the original header lines.
19306 The &%headers_remove%& option is handled after &%errors_to%& and
19307 &%headers_add%&, but before &%transport%&. If an item expansion is forced to fail,
19308 the item has no effect. Other expansion failures are treated as configuration
19311 Unlike most options, &%headers_remove%& can be specified multiple times
19312 for a router; all listed headers are removed.
19314 &*Warning 1*&: The &%headers_remove%& option cannot be used for a &(redirect)&
19315 router that has the &%one_time%& option set.
19317 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
19318 removal requests are deleted when the address is passed on to subsequent
19319 routers, and this can lead to problems with duplicates -- see the similar
19320 warning for &%headers_add%& above.
19322 &*Warning 3*&: Because of the separate expansion of the list items,
19323 items that contain a list separator must have it doubled.
19324 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
19328 .option ignore_target_hosts routers "host list&!!" unset
19329 .cindex "IP address" "discarding"
19330 .cindex "router" "discarding IP addresses"
19331 Although this option is a host list, it should normally contain IP address
19332 entries rather than names. If any host that is looked up by the router has an
19333 IP address that matches an item in this list, Exim behaves as if that IP
19334 address did not exist. This option allows you to cope with rogue DNS entries
19337 remote.domain.example. A 127.0.0.1
19341 ignore_target_hosts = 127.0.0.1
19343 on the relevant router. If all the hosts found by a &(dnslookup)& router are
19344 discarded in this way, the router declines. In a conventional configuration, an
19345 attempt to mail to such a domain would normally provoke the &"unrouteable
19346 domain"& error, and an attempt to verify an address in the domain would fail.
19347 Similarly, if &%ignore_target_hosts%& is set on an &(ipliteral)& router, the
19348 router declines if presented with one of the listed addresses.
19350 You can use this option to disable the use of IPv4 or IPv6 for mail delivery by
19351 means of the first or the second of the following settings, respectively:
19353 ignore_target_hosts = 0.0.0.0/0
19354 ignore_target_hosts = <; 0::0/0
19356 The pattern in the first line matches all IPv4 addresses, whereas the pattern
19357 in the second line matches all IPv6 addresses.
19359 This option may also be useful for ignoring link-local and site-local IPv6
19360 addresses. Because, like all host lists, the value of &%ignore_target_hosts%&
19361 is expanded before use as a list, it is possible to make it dependent on the
19362 domain that is being routed.
19364 .vindex "&$host_address$&"
19365 During its expansion, &$host_address$& is set to the IP address that is being
19368 .option initgroups routers boolean false
19369 .cindex "additional groups"
19370 .cindex "groups" "additional"
19371 .cindex "local transports" "uid and gid"
19372 .cindex "transport" "local"
19373 If the router queues an address for a transport, and this option is true, and
19374 the uid supplied by the router is not overridden by the transport, the
19375 &[initgroups()]& function is called when running the transport to ensure that
19376 any additional groups associated with the uid are set up. See also &%group%&
19377 and &%user%& and the discussion in chapter &<<CHAPenvironment>>&.
19381 .option local_part_prefix routers&!? "string list" unset
19382 .cindex affix "router precondition"
19383 .cindex "router" "prefix for local part"
19384 .cindex "prefix" "for local part, used in router"
19385 If this option is set, the router is skipped unless the local part starts with
19386 one of the given strings, or &%local_part_prefix_optional%& is true. See
19387 section &<<SECTrouprecon>>& for a list of the order in which preconditions are
19390 The list is scanned from left to right, and the first prefix that matches is
19391 used. A limited form of wildcard is available; if the prefix begins with an
19392 asterisk, it matches the longest possible sequence of arbitrary characters at
19393 the start of the local part. An asterisk should therefore always be followed by
19394 some character that does not occur in normal local parts.
19395 .cindex "multiple mailboxes"
19396 .cindex "mailbox" "multiple"
19397 Wildcarding can be used to set up multiple user mailboxes, as described in
19398 section &<<SECTmulbox>>&.
19400 .vindex "&$local_part$&"
19401 .vindex "&$local_part_prefix$&"
19402 During the testing of the &%local_parts%& option, and while the router is
19403 running, the prefix is removed from the local part, and is available in the
19404 expansion variable &$local_part_prefix$&. When a message is being delivered, if
19405 the router accepts the address, this remains true during subsequent delivery by
19406 a transport. In particular, the local part that is transmitted in the RCPT
19407 command for LMTP, SMTP, and BSMTP deliveries has the prefix removed by default.
19408 This behaviour can be overridden by setting &%rcpt_include_affixes%& true on
19409 the relevant transport.
19411 .vindex &$local_part_prefix_v$&
19412 If wildcarding (above) was used then the part of the prefix matching the
19413 wildcard is available in &$local_part_prefix_v$&.
19415 When an address is being verified, &%local_part_prefix%& affects only the
19416 behaviour of the router. If the callout feature of verification is in use, this
19417 means that the full address, including the prefix, will be used during the
19420 The prefix facility is commonly used to handle local parts of the form
19421 &%owner-something%&. Another common use is to support local parts of the form
19422 &%real-username%& to bypass a user's &_.forward_& file &-- helpful when trying
19423 to tell a user their forwarding is broken &-- by placing a router like this one
19424 immediately before the router that handles &_.forward_& files:
19428 local_part_prefix = real-
19430 transport = local_delivery
19432 For security, it would probably be a good idea to restrict the use of this
19433 router to locally-generated messages, using a condition such as this:
19435 condition = ${if match {$sender_host_address}\
19436 {\N^(|127\.0\.0\.1)$\N}}
19439 If both &%local_part_prefix%& and &%local_part_suffix%& are set for a router,
19440 both conditions must be met if not optional. Care must be taken if wildcards
19441 are used in both a prefix and a suffix on the same router. Different
19442 separator characters must be used to avoid ambiguity.
19445 .option local_part_prefix_optional routers boolean false
19446 See &%local_part_prefix%& above.
19450 .option local_part_suffix routers&!? "string list" unset
19451 .cindex "router" "suffix for local part"
19452 .cindex "suffix for local part" "used in router"
19453 This option operates in the same way as &%local_part_prefix%&, except that the
19454 local part must end (rather than start) with the given string, the
19455 &%local_part_suffix_optional%& option determines whether the suffix is
19456 mandatory, and the wildcard * character, if present, must be the last
19457 character of the suffix. This option facility is commonly used to handle local
19458 parts of the form &%something-request%& and multiple user mailboxes of the form
19462 .option local_part_suffix_optional routers boolean false
19463 See &%local_part_suffix%& above.
19467 .option local_parts routers&!? "local part list&!!" unset
19468 .cindex "router" "restricting to specific local parts"
19469 .cindex "local part" "checking in router"
19470 The router is run only if the local part of the address matches the list.
19471 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19473 section &<<SECTlocparlis>>& for a discussion of local part lists. Because the
19474 string is expanded, it is possible to make it depend on the domain, for
19477 local_parts = dbm;/usr/local/specials/$domain_data
19479 .vindex "&$local_part_data$&"
19480 If the match is achieved by a lookup, the data that the lookup returned
19481 for the local part is placed in the variable &$local_part_data$& for use in
19482 expansions of the router's private options or in the transport.
19483 You might use this option, for
19484 example, if you have a large number of local virtual domains, and you want to
19485 send all postmaster mail to the same place without having to set up an alias in
19486 each virtual domain:
19490 local_parts = postmaster
19491 data = postmaster@real.domain.example
19495 .option log_as_local routers boolean "see below"
19496 .cindex "log" "delivery line"
19497 .cindex "delivery" "log line format"
19498 Exim has two logging styles for delivery, the idea being to make local
19499 deliveries stand out more visibly from remote ones. In the &"local"& style, the
19500 recipient address is given just as the local part, without a domain. The use of
19501 this style is controlled by this option. It defaults to true for the &(accept)&
19502 router, and false for all the others. This option applies only when a
19503 router assigns an address to a transport. It has no effect on routers that
19504 redirect addresses.
19508 .option more routers boolean&!! true
19509 The result of string expansion for this option must be a valid boolean value,
19510 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
19511 result causes an error, and delivery is deferred. If the expansion is forced to
19512 fail, the default value for the option (true) is used. Other failures cause
19513 delivery to be deferred.
19515 If this option is set false, and the router declines to handle the address, no
19516 further routers are tried, routing fails, and the address is bounced.
19518 However, if the router explicitly passes an address to the following router by
19519 means of the setting
19523 or otherwise, the setting of &%more%& is ignored. Also, the setting of &%more%&
19524 does not affect the behaviour if one of the precondition tests fails. In that
19525 case, the address is always passed to the next router.
19527 Note that &%address_data%& is not considered to be a precondition. If its
19528 expansion is forced to fail, the router declines, and the value of &%more%&
19529 controls what happens next.
19532 .option pass_on_timeout routers boolean false
19533 .cindex "timeout" "of router"
19534 .cindex "router" "timeout"
19535 If a router times out during a host lookup, it normally causes deferral of the
19536 address. If &%pass_on_timeout%& is set, the address is passed on to the next
19537 router, overriding &%no_more%&. This may be helpful for systems that are
19538 intermittently connected to the Internet, or those that want to pass to a smart
19539 host any messages that cannot immediately be delivered.
19541 There are occasional other temporary errors that can occur while doing DNS
19542 lookups. They are treated in the same way as a timeout, and this option
19543 applies to all of them.
19547 .option pass_router routers string unset
19548 .cindex "router" "go to after &""pass""&"
19549 Routers that recognize the generic &%self%& option (&(dnslookup)&,
19550 &(ipliteral)&, and &(manualroute)&) are able to return &"pass"&, forcing
19551 routing to continue, and overriding a false setting of &%more%&. When one of
19552 these routers returns &"pass"&, the address is normally handed on to the next
19553 router in sequence. This can be changed by setting &%pass_router%& to the name
19554 of another router. However (unlike &%redirect_router%&) the named router must
19555 be below the current router, to avoid loops. Note that this option applies only
19556 to the special case of &"pass"&. It does not apply when a router returns
19557 &"decline"& because it cannot handle an address.
19561 .option redirect_router routers string unset
19562 .cindex "router" "start at after redirection"
19563 Sometimes an administrator knows that it is pointless to reprocess addresses
19564 generated from alias or forward files with the same router again. For
19565 example, if an alias file translates real names into login ids there is no
19566 point searching the alias file a second time, especially if it is a large file.
19568 The &%redirect_router%& option can be set to the name of any router instance.
19569 It causes the routing of any generated addresses to start at the named router
19570 instead of at the first router. This option has no effect if the router in
19571 which it is set does not generate new addresses.
19575 .option require_files routers&!? "string list&!!" unset
19576 .cindex "file" "requiring for router"
19577 .cindex "router" "requiring file existence"
19578 This option provides a general mechanism for predicating the running of a
19579 router on the existence or non-existence of certain files or directories.
19580 Before running a router, as one of its precondition tests, Exim works its way
19581 through the &%require_files%& list, expanding each item separately.
19583 Because the list is split before expansion, any colons in expansion items must
19584 be doubled, or the facility for using a different list separator must be used
19585 (&<<SECTlistsepchange>>&).
19586 If any expansion is forced to fail, the item is ignored. Other expansion
19587 failures cause routing of the address to be deferred.
19589 If any expanded string is empty, it is ignored. Otherwise, except as described
19590 below, each string must be a fully qualified file path, optionally preceded by
19591 &"!"&. The paths are passed to the &[stat()]& function to test for the
19592 existence of the files or directories. The router is skipped if any paths not
19593 preceded by &"!"& do not exist, or if any paths preceded by &"!"& do exist.
19596 If &[stat()]& cannot determine whether a file exists or not, delivery of
19597 the message is deferred. This can happen when NFS-mounted filesystems are
19600 This option is checked after the &%domains%&, &%local_parts%&, and &%senders%&
19601 options, so you cannot use it to check for the existence of a file in which to
19602 look up a domain, local part, or sender. (See section &<<SECTrouprecon>>& for a
19603 full list of the order in which preconditions are evaluated.) However, as
19604 these options are all expanded, you can use the &%exists%& expansion condition
19605 to make such tests. The &%require_files%& option is intended for checking files
19606 that the router may be going to use internally, or which are needed by a
19607 transport (e.g., &_.procmailrc_&).
19609 During delivery, the &[stat()]& function is run as root, but there is a
19610 facility for some checking of the accessibility of a file by another user.
19611 This is not a proper permissions check, but just a &"rough"& check that
19612 operates as follows:
19614 If an item in a &%require_files%& list does not contain any forward slash
19615 characters, it is taken to be the user (and optional group, separated by a
19616 comma) to be checked for subsequent files in the list. If no group is specified
19617 but the user is specified symbolically, the gid associated with the uid is
19620 require_files = mail:/some/file
19621 require_files = $local_part_data:$home/.procmailrc
19623 If a user or group name in a &%require_files%& list does not exist, the
19624 &%require_files%& condition fails.
19626 Exim performs the check by scanning along the components of the file path, and
19627 checking the access for the given uid and gid. It checks for &"x"& access on
19628 directories, and &"r"& access on the final file. Note that this means that file
19629 access control lists, if the operating system has them, are ignored.
19631 &*Warning 1*&: When the router is being run to verify addresses for an
19632 incoming SMTP message, Exim is not running as root, but under its own uid. This
19633 may affect the result of a &%require_files%& check. In particular, &[stat()]&
19634 may yield the error EACCES (&"Permission denied"&). This means that the Exim
19635 user is not permitted to read one of the directories on the file's path.
19637 &*Warning 2*&: Even when Exim is running as root while delivering a message,
19638 &[stat()]& can yield EACCES for a file in an NFS directory that is mounted
19639 without root access. In this case, if a check for access by a particular user
19640 is requested, Exim creates a subprocess that runs as that user, and tries the
19641 check again in that process.
19643 The default action for handling an unresolved EACCES is to consider it to
19644 be caused by a configuration error, and routing is deferred because the
19645 existence or non-existence of the file cannot be determined. However, in some
19646 circumstances it may be desirable to treat this condition as if the file did
19647 not exist. If the filename (or the exclamation mark that precedes the filename
19648 for non-existence) is preceded by a plus sign, the EACCES error is treated
19649 as if the file did not exist. For example:
19651 require_files = +/some/file
19653 If the router is not an essential part of verification (for example, it
19654 handles users' &_.forward_& files), another solution is to set the &%verify%&
19655 option false so that the router is skipped when verifying.
19659 .option retry_use_local_part routers boolean "see below"
19660 .cindex "hints database" "retry keys"
19661 .cindex "local part" "in retry keys"
19662 When a delivery suffers a temporary routing failure, a retry record is created
19663 in Exim's hints database. For addresses whose routing depends only on the
19664 domain, the key for the retry record should not involve the local part, but for
19665 other addresses, both the domain and the local part should be included.
19666 Usually, remote routing is of the former kind, and local routing is of the
19669 This option controls whether the local part is used to form the key for retry
19670 hints for addresses that suffer temporary errors while being handled by this
19671 router. The default value is true for any router that has any of
19672 &%check_local_user%&,
19675 &%local_part_prefix%&,
19676 &%local_part_suffix%&,
19679 set, and false otherwise. Note that this option does not apply to hints keys
19680 for transport delays; they are controlled by a generic transport option of the
19683 Failing to set this option when it is needed
19684 (because a remote router handles only some of the local-parts for a domain)
19685 can result in incorrect error messages being generated.
19687 The setting of &%retry_use_local_part%& applies only to the router on which it
19688 appears. If the router generates child addresses, they are routed
19689 independently; this setting does not become attached to them.
19693 .option router_home_directory routers string&!! unset
19694 .cindex "router" "home directory for"
19695 .cindex "home directory" "for router"
19697 This option sets a home directory for use while the router is running. (Compare
19698 &%transport_home_directory%&, which sets a home directory for later
19699 transporting.) In particular, if used on a &(redirect)& router, this option
19700 sets a value for &$home$& while a filter is running. The value is expanded;
19701 forced expansion failure causes the option to be ignored &-- other failures
19702 cause the router to defer.
19704 Expansion of &%router_home_directory%& happens immediately after the
19705 &%check_local_user%& test (if configured), before any further expansions take
19707 (See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19709 While the router is running, &%router_home_directory%& overrides the value of
19710 &$home$& that came from &%check_local_user%&.
19712 When a router accepts an address and assigns it to a local transport (including
19713 the cases when a &(redirect)& router generates a pipe, file, or autoreply
19714 delivery), the home directory setting for the transport is taken from the first
19715 of these values that is set:
19718 The &%home_directory%& option on the transport;
19720 The &%transport_home_directory%& option on the router;
19722 The password data if &%check_local_user%& is set on the router;
19724 The &%router_home_directory%& option on the router.
19727 In other words, &%router_home_directory%& overrides the password data for the
19728 router, but not for the transport.
19732 .option self routers string freeze
19733 .cindex "MX record" "pointing to local host"
19734 .cindex "local host" "MX pointing to"
19735 This option applies to those routers that use a recipient address to find a
19736 list of remote hosts. Currently, these are the &(dnslookup)&, &(ipliteral)&,
19737 and &(manualroute)& routers.
19738 Certain configurations of the &(queryprogram)& router can also specify a list
19740 Usually such routers are configured to send the message to a remote host via an
19741 &(smtp)& transport. The &%self%& option specifies what happens when the first
19742 host on the list turns out to be the local host.
19743 The way in which Exim checks for the local host is described in section
19744 &<<SECTreclocipadd>>&.
19746 Normally this situation indicates either an error in Exim's configuration (for
19747 example, the router should be configured not to process this domain), or an
19748 error in the DNS (for example, the MX should not point to this host). For this
19749 reason, the default action is to log the incident, defer the address, and
19750 freeze the message. The following alternatives are provided for use in special
19755 Delivery of the message is tried again later, but the message is not frozen.
19757 .vitem "&%reroute%&: <&'domain'&>"
19758 The domain is changed to the given domain, and the address is passed back to
19759 be reprocessed by the routers. No rewriting of headers takes place. This
19760 behaviour is essentially a redirection.
19762 .vitem "&%reroute: rewrite:%& <&'domain'&>"
19763 The domain is changed to the given domain, and the address is passed back to be
19764 reprocessed by the routers. Any headers that contain the original domain are
19769 .vindex "&$self_hostname$&"
19770 The router passes the address to the next router, or to the router named in the
19771 &%pass_router%& option if it is set. This overrides &%no_more%&. During
19772 subsequent routing and delivery, the variable &$self_hostname$& contains the
19773 name of the local host that the router encountered. This can be used to
19774 distinguish between different cases for hosts with multiple names. The
19780 ensures that only those addresses that routed to the local host are passed on.
19781 Without &%no_more%&, addresses that were declined for other reasons would also
19782 be passed to the next router.
19785 Delivery fails and an error report is generated.
19788 .cindex "local host" "sending to"
19789 The anomaly is ignored and the address is queued for the transport. This
19790 setting should be used with extreme caution. For an &(smtp)& transport, it
19791 makes sense only in cases where the program that is listening on the SMTP port
19792 is not this version of Exim. That is, it must be some other MTA, or Exim with a
19793 different configuration file that handles the domain in another way.
19798 .option senders routers&!? "address list&!!" unset
19799 .cindex "router" "checking senders"
19800 If this option is set, the router is skipped unless the message's sender
19801 address matches something on the list.
19802 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19805 There are issues concerning verification when the running of routers is
19806 dependent on the sender. When Exim is verifying the address in an &%errors_to%&
19807 setting, it sets the sender to the null string. When using the &%-bt%& option
19808 to check a configuration file, it is necessary also to use the &%-f%& option to
19809 set an appropriate sender. For incoming mail, the sender is unset when
19810 verifying the sender, but is available when verifying any recipients. If the
19811 SMTP VRFY command is enabled, it must be used after MAIL if the sender address
19815 .option set routers "string list" unset
19816 .cindex router variables
19817 This option may be used multiple times on a router;
19818 because of this the list aspect is mostly irrelevant.
19819 The list separator is a semicolon but can be changed in the
19822 Each list-element given must be of the form &"name = value"&
19823 and the names used must start with the string &"r_"&.
19824 Values containing a list-separator should have them doubled.
19825 When a router runs, the strings are evaluated in order,
19826 to create variables which are added to the set associated with
19828 This is done immediately after all the preconditions, before the
19829 evaluation of the &%address_data%& option.
19830 The variable is set with the expansion of the value.
19831 The variables can be used by the router options
19832 (not including any preconditions)
19833 and by the transport.
19834 Later definitions of a given named variable will override former ones.
19835 Variable use is via the usual &$r_...$& syntax.
19837 This is similar to the &%address_data%& option, except that
19838 many independent variables can be used, with choice of naming.
19841 .option translate_ip_address routers string&!! unset
19842 .cindex "IP address" "translating"
19843 .cindex "packet radio"
19844 .cindex "router" "IP address translation"
19845 There exist some rare networking situations (for example, packet radio) where
19846 it is helpful to be able to translate IP addresses generated by normal routing
19847 mechanisms into other IP addresses, thus performing a kind of manual IP
19848 routing. This should be done only if the normal IP routing of the TCP/IP stack
19849 is inadequate or broken. Because this is an extremely uncommon requirement, the
19850 code to support this option is not included in the Exim binary unless
19851 SUPPORT_TRANSLATE_IP_ADDRESS=yes is set in &_Local/Makefile_&.
19853 .vindex "&$host_address$&"
19854 The &%translate_ip_address%& string is expanded for every IP address generated
19855 by the router, with the generated address set in &$host_address$&. If the
19856 expansion is forced to fail, no action is taken.
19857 For any other expansion error, delivery of the message is deferred.
19858 If the result of the expansion is an IP address, that replaces the original
19859 address; otherwise the result is assumed to be a host name &-- this is looked
19860 up using &[gethostbyname()]& (or &[getipnodebyname()]& when available) to
19861 produce one or more replacement IP addresses. For example, to subvert all IP
19862 addresses in some specific networks, this could be added to a router:
19864 translate_ip_address = \
19865 ${lookup{${mask:$host_address/26}}lsearch{/some/file}\
19868 The file would contain lines like
19870 10.2.3.128/26 some.host
19871 10.8.4.34/26 10.44.8.15
19873 You should not make use of this facility unless you really understand what you
19878 .option transport routers string&!! unset
19879 This option specifies the transport to be used when a router accepts an address
19880 and sets it up for delivery. A transport is never needed if a router is used
19881 only for verification. The value of the option is expanded at routing time,
19882 after the expansion of &%errors_to%&, &%headers_add%&, and &%headers_remove%&,
19883 and result must be the name of one of the configured transports. If it is not,
19884 delivery is deferred.
19886 The &%transport%& option is not used by the &(redirect)& router, but it does
19887 have some private options that set up transports for pipe and file deliveries
19888 (see chapter &<<CHAPredirect>>&).
19892 .option transport_current_directory routers string&!! unset
19893 .cindex "current directory for local transport"
19894 This option associates a current directory with any address that is routed
19895 to a local transport. This can happen either because a transport is
19896 explicitly configured for the router, or because it generates a delivery to a
19897 file or a pipe. During the delivery process (that is, at transport time), this
19898 option string is expanded and is set as the current directory, unless
19899 overridden by a setting on the transport.
19900 If the expansion fails for any reason, including forced failure, an error is
19901 logged, and delivery is deferred.
19902 See chapter &<<CHAPenvironment>>& for details of the local delivery
19908 .option transport_home_directory routers string&!! "see below"
19909 .cindex "home directory" "for local transport"
19910 This option associates a home directory with any address that is routed to a
19911 local transport. This can happen either because a transport is explicitly
19912 configured for the router, or because it generates a delivery to a file or a
19913 pipe. During the delivery process (that is, at transport time), the option
19914 string is expanded and is set as the home directory, unless overridden by a
19915 setting of &%home_directory%& on the transport.
19916 If the expansion fails for any reason, including forced failure, an error is
19917 logged, and delivery is deferred.
19919 If the transport does not specify a home directory, and
19920 &%transport_home_directory%& is not set for the router, the home directory for
19921 the transport is taken from the password data if &%check_local_user%& is set for
19922 the router. Otherwise it is taken from &%router_home_directory%& if that option
19923 is set; if not, no home directory is set for the transport.
19925 See chapter &<<CHAPenvironment>>& for further details of the local delivery
19931 .option unseen routers boolean&!! false
19932 .cindex "router" "carrying on after success"
19933 The result of string expansion for this option must be a valid boolean value,
19934 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
19935 result causes an error, and delivery is deferred. If the expansion is forced to
19936 fail, the default value for the option (false) is used. Other failures cause
19937 delivery to be deferred.
19939 When this option is set true, routing does not cease if the router accepts the
19940 address. Instead, a copy of the incoming address is passed to the next router,
19941 overriding a false setting of &%more%&. There is little point in setting
19942 &%more%& false if &%unseen%& is always true, but it may be useful in cases when
19943 the value of &%unseen%& contains expansion items (and therefore, presumably, is
19944 sometimes true and sometimes false).
19946 .cindex "copy of message (&%unseen%& option)"
19947 Setting the &%unseen%& option has a similar effect to the &%unseen%& command
19948 qualifier in filter files. It can be used to cause copies of messages to be
19949 delivered to some other destination, while also carrying out a normal delivery.
19950 In effect, the current address is made into a &"parent"& that has two children
19951 &-- one that is delivered as specified by this router, and a clone that goes on
19952 to be routed further. For this reason, &%unseen%& may not be combined with the
19953 &%one_time%& option in a &(redirect)& router.
19955 &*Warning*&: Header lines added to the address (or specified for removal) by
19956 this router or by previous routers affect the &"unseen"& copy of the message
19957 only. The clone that continues to be processed by further routers starts with
19958 no added headers and none specified for removal. For a &%redirect%& router, if
19959 a generated address is the same as the incoming address, this can lead to
19960 duplicate addresses with different header modifications. Exim does not do
19961 duplicate deliveries (except, in certain circumstances, to pipes -- see section
19962 &<<SECTdupaddr>>&), but it is undefined which of the duplicates is discarded,
19963 so this ambiguous situation should be avoided. The &%repeat_use%& option of the
19964 &%redirect%& router may be of help.
19966 Unlike the handling of header modifications, any data that was set by the
19967 &%address_data%& option in the current or previous routers &'is'& passed on to
19968 subsequent routers.
19971 .option user routers string&!! "see below"
19972 .cindex "uid (user id)" "local delivery"
19973 .cindex "local transports" "uid and gid"
19974 .cindex "transport" "local"
19975 .cindex "router" "user for filter processing"
19976 .cindex "filter" "user for processing"
19977 When a router queues an address for a transport, and the transport does not
19978 specify a user, the user given here is used when running the delivery process.
19979 The user may be specified numerically or by name. If expansion fails, the
19980 error is logged and delivery is deferred.
19981 This user is also used by the &(redirect)& router when running a filter file.
19982 The default is unset, except when &%check_local_user%& is set. In this case,
19983 the default is taken from the password information. If the user is specified as
19984 a name, and &%group%& is not set, the group associated with the user is used.
19985 See also &%initgroups%& and &%group%& and the discussion in chapter
19986 &<<CHAPenvironment>>&.
19990 .option verify routers&!? boolean true
19991 Setting this option has the effect of setting &%verify_sender%& and
19992 &%verify_recipient%& to the same value.
19995 .option verify_only routers&!? boolean false
19996 .cindex "EXPN" "with &%verify_only%&"
19998 .cindex "router" "used only when verifying"
19999 If this option is set, the router is used only when verifying an address,
20000 delivering in cutthrough mode or
20001 testing with the &%-bv%& option, not when actually doing a delivery, testing
20002 with the &%-bt%& option, or running the SMTP EXPN command. It can be further
20003 restricted to verifying only senders or recipients by means of
20004 &%verify_sender%& and &%verify_recipient%&.
20006 &*Warning*&: When the router is being run to verify addresses for an incoming
20007 SMTP message, Exim is not running as root, but under its own uid. If the router
20008 accesses any files, you need to make sure that they are accessible to the Exim
20012 .option verify_recipient routers&!? boolean true
20013 If this option is false, the router is skipped when verifying recipient
20015 delivering in cutthrough mode
20016 or testing recipient verification using &%-bv%&.
20017 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
20019 See also the &$verify_mode$& variable.
20022 .option verify_sender routers&!? boolean true
20023 If this option is false, the router is skipped when verifying sender addresses
20024 or testing sender verification using &%-bvs%&.
20025 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
20027 See also the &$verify_mode$& variable.
20028 .ecindex IIDgenoprou1
20029 .ecindex IIDgenoprou2
20036 . ////////////////////////////////////////////////////////////////////////////
20037 . ////////////////////////////////////////////////////////////////////////////
20039 .chapter "The accept router" "CHID4"
20040 .cindex "&(accept)& router"
20041 .cindex "routers" "&(accept)&"
20042 The &(accept)& router has no private options of its own. Unless it is being
20043 used purely for verification (see &%verify_only%&) a transport is required to
20044 be defined by the generic &%transport%& option. If the preconditions that are
20045 specified by generic options are met, the router accepts the address and queues
20046 it for the given transport. The most common use of this router is for setting
20047 up deliveries to local mailboxes. For example:
20051 domains = mydomain.example
20053 transport = local_delivery
20055 The &%domains%& condition in this example checks the domain of the address, and
20056 &%check_local_user%& checks that the local part is the login of a local user.
20057 When both preconditions are met, the &(accept)& router runs, and queues the
20058 address for the &(local_delivery)& transport.
20065 . ////////////////////////////////////////////////////////////////////////////
20066 . ////////////////////////////////////////////////////////////////////////////
20068 .chapter "The dnslookup router" "CHAPdnslookup"
20069 .scindex IIDdnsrou1 "&(dnslookup)& router"
20070 .scindex IIDdnsrou2 "routers" "&(dnslookup)&"
20071 The &(dnslookup)& router looks up the hosts that handle mail for the
20072 recipient's domain in the DNS. A transport must always be set for this router,
20073 unless &%verify_only%& is set.
20075 If SRV support is configured (see &%check_srv%& below), Exim first searches for
20076 SRV records. If none are found, or if SRV support is not configured,
20077 MX records are looked up. If no MX records exist, address records are sought.
20078 However, &%mx_domains%& can be set to disable the direct use of address
20081 MX records of equal priority are sorted by Exim into a random order. Exim then
20082 looks for address records for the host names obtained from MX or SRV records.
20083 When a host has more than one IP address, they are sorted into a random order,
20084 except that IPv6 addresses are sorted before IPv4 addresses. If all the
20085 IP addresses found are discarded by a setting of the &%ignore_target_hosts%&
20086 generic option, the router declines.
20088 Unless they have the highest priority (lowest MX value), MX records that point
20089 to the local host, or to any host name that matches &%hosts_treat_as_local%&,
20090 are discarded, together with any other MX records of equal or lower priority.
20092 .cindex "MX record" "pointing to local host"
20093 .cindex "local host" "MX pointing to"
20094 .oindex "&%self%&" "in &(dnslookup)& router"
20095 If the host pointed to by the highest priority MX record, or looked up as an
20096 address record, is the local host, or matches &%hosts_treat_as_local%&, what
20097 happens is controlled by the generic &%self%& option.
20100 .section "Problems with DNS lookups" "SECTprowitdnsloo"
20101 There have been problems with DNS servers when SRV records are looked up.
20102 Some misbehaving servers return a DNS error or timeout when a non-existent
20103 SRV record is sought. Similar problems have in the past been reported for
20104 MX records. The global &%dns_again_means_nonexist%& option can help with this
20105 problem, but it is heavy-handed because it is a global option.
20107 For this reason, there are two options, &%srv_fail_domains%& and
20108 &%mx_fail_domains%&, that control what happens when a DNS lookup in a
20109 &(dnslookup)& router results in a DNS failure or a &"try again"& response. If
20110 an attempt to look up an SRV or MX record causes one of these results, and the
20111 domain matches the relevant list, Exim behaves as if the DNS had responded &"no
20112 such record"&. In the case of an SRV lookup, this means that the router
20113 proceeds to look for MX records; in the case of an MX lookup, it proceeds to
20114 look for A or AAAA records, unless the domain matches &%mx_domains%&, in which
20115 case routing fails.
20118 .section "Declining addresses by dnslookup" "SECTdnslookupdecline"
20119 .cindex "&(dnslookup)& router" "declines"
20120 There are a few cases where a &(dnslookup)& router will decline to accept
20121 an address; if such a router is expected to handle "all remaining non-local
20122 domains", then it is important to set &%no_more%&.
20124 The router will defer rather than decline if the domain
20125 is found in the &%fail_defer_domains%& router option.
20127 Reasons for a &(dnslookup)& router to decline currently include:
20129 The domain does not exist in DNS
20131 The domain exists but the MX record's host part is just "."; this is a common
20132 convention (borrowed from SRV) used to indicate that there is no such service
20133 for this domain and to not fall back to trying A/AAAA records.
20135 Ditto, but for SRV records, when &%check_srv%& is set on this router.
20137 MX record points to a non-existent host.
20139 MX record points to an IP address and the main section option
20140 &%allow_mx_to_ip%& is not set.
20142 MX records exist and point to valid hosts, but all hosts resolve only to
20143 addresses blocked by the &%ignore_target_hosts%& generic option on this router.
20145 The domain is not syntactically valid (see also &%allow_utf8_domains%& and
20146 &%dns_check_names_pattern%& for handling one variant of this)
20148 &%check_secondary_mx%& is set on this router but the local host can
20149 not be found in the MX records (see below)
20155 .section "Private options for dnslookup" "SECID118"
20156 .cindex "options" "&(dnslookup)& router"
20157 The private options for the &(dnslookup)& router are as follows:
20159 .option check_secondary_mx dnslookup boolean false
20160 .cindex "MX record" "checking for secondary"
20161 If this option is set, the router declines unless the local host is found in
20162 (and removed from) the list of hosts obtained by MX lookup. This can be used to
20163 process domains for which the local host is a secondary mail exchanger
20164 differently to other domains. The way in which Exim decides whether a host is
20165 the local host is described in section &<<SECTreclocipadd>>&.
20168 .option check_srv dnslookup string&!! unset
20169 .cindex "SRV record" "enabling use of"
20170 The &(dnslookup)& router supports the use of SRV records (see RFC 2782) in
20171 addition to MX and address records. The support is disabled by default. To
20172 enable SRV support, set the &%check_srv%& option to the name of the service
20173 required. For example,
20177 looks for SRV records that refer to the normal smtp service. The option is
20178 expanded, so the service name can vary from message to message or address
20179 to address. This might be helpful if SRV records are being used for a
20180 submission service. If the expansion is forced to fail, the &%check_srv%&
20181 option is ignored, and the router proceeds to look for MX records in the
20184 When the expansion succeeds, the router searches first for SRV records for
20185 the given service (it assumes TCP protocol). A single SRV record with a
20186 host name that consists of just a single dot indicates &"no such service for
20187 this domain"&; if this is encountered, the router declines. If other kinds of
20188 SRV record are found, they are used to construct a host list for delivery
20189 according to the rules of RFC 2782. MX records are not sought in this case.
20191 When no SRV records are found, MX records (and address records) are sought in
20192 the traditional way. In other words, SRV records take precedence over MX
20193 records, just as MX records take precedence over address records. Note that
20194 this behaviour is not sanctioned by RFC 2782, though a previous draft RFC
20195 defined it. It is apparently believed that MX records are sufficient for email
20196 and that SRV records should not be used for this purpose. However, SRV records
20197 have an additional &"weight"& feature which some people might find useful when
20198 trying to split an SMTP load between hosts of different power.
20200 See section &<<SECTprowitdnsloo>>& above for a discussion of Exim's behaviour
20201 when there is a DNS lookup error.
20206 .option fail_defer_domains dnslookup "domain list&!!" unset
20207 .cindex "MX record" "not found"
20208 DNS lookups for domains matching &%fail_defer_domains%&
20209 which find no matching record will cause the router to defer
20210 rather than the default behaviour of decline.
20211 This maybe be useful for queueing messages for a newly created
20212 domain while the DNS configuration is not ready.
20213 However, it will result in any message with mistyped domains
20217 .option ipv4_only "string&!!" unset
20218 .cindex IPv6 disabling
20219 .cindex DNS "IPv6 disabling"
20220 The string is expanded, and if the result is anything but a forced failure,
20221 or an empty string, or one of the strings “0” or “no” or “false”
20222 (checked without regard to the case of the letters),
20223 only A records are used.
20225 .option ipv4_prefer "string&!!" unset
20226 .cindex IPv4 preference
20227 .cindex DNS "IPv4 preference"
20228 The string is expanded, and if the result is anything but a forced failure,
20229 or an empty string, or one of the strings “0” or “no” or “false”
20230 (checked without regard to the case of the letters),
20231 A records are sorted before AAAA records (inverting the default).
20233 .option mx_domains dnslookup "domain list&!!" unset
20234 .cindex "MX record" "required to exist"
20235 .cindex "SRV record" "required to exist"
20236 A domain that matches &%mx_domains%& is required to have either an MX or an SRV
20237 record in order to be recognized. (The name of this option could be improved.)
20238 For example, if all the mail hosts in &'fict.example'& are known to have MX
20239 records, except for those in &'discworld.fict.example'&, you could use this
20242 mx_domains = ! *.discworld.fict.example : *.fict.example
20244 This specifies that messages addressed to a domain that matches the list but
20245 has no MX record should be bounced immediately instead of being routed using
20246 the address record.
20249 .option mx_fail_domains dnslookup "domain list&!!" unset
20250 If the DNS lookup for MX records for one of the domains in this list causes a
20251 DNS lookup error, Exim behaves as if no MX records were found. See section
20252 &<<SECTprowitdnsloo>>& for more discussion.
20257 .option qualify_single dnslookup boolean true
20258 .cindex "DNS" "resolver options"
20259 .cindex "DNS" "qualifying single-component names"
20260 When this option is true, the resolver option RES_DEFNAMES is set for DNS
20261 lookups. Typically, but not standardly, this causes the resolver to qualify
20262 single-component names with the default domain. For example, on a machine
20263 called &'dictionary.ref.example'&, the domain &'thesaurus'& would be changed to
20264 &'thesaurus.ref.example'& inside the resolver. For details of what your
20265 resolver actually does, consult your man pages for &'resolver'& and
20270 .option rewrite_headers dnslookup boolean true
20271 .cindex "rewriting" "header lines"
20272 .cindex "header lines" "rewriting"
20273 If the domain name in the address that is being processed is not fully
20274 qualified, it may be expanded to its full form by a DNS lookup. For example, if
20275 an address is specified as &'dormouse@teaparty'&, the domain might be
20276 expanded to &'teaparty.wonderland.fict.example'&. Domain expansion can also
20277 occur as a result of setting the &%widen_domains%& option. If
20278 &%rewrite_headers%& is true, all occurrences of the abbreviated domain name in
20279 any &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-to:'&, &'Sender:'&, and &'To:'&
20280 header lines of the message are rewritten with the full domain name.
20282 This option should be turned off only when it is known that no message is
20283 ever going to be sent outside an environment where the abbreviation makes
20286 When an MX record is looked up in the DNS and matches a wildcard record, name
20287 servers normally return a record containing the name that has been looked up,
20288 making it impossible to detect whether a wildcard was present or not. However,
20289 some name servers have recently been seen to return the wildcard entry. If the
20290 name returned by a DNS lookup begins with an asterisk, it is not used for
20294 .option same_domain_copy_routing dnslookup boolean false
20295 .cindex "address" "copying routing"
20296 Addresses with the same domain are normally routed by the &(dnslookup)& router
20297 to the same list of hosts. However, this cannot be presumed, because the router
20298 options and preconditions may refer to the local part of the address. By
20299 default, therefore, Exim routes each address in a message independently. DNS
20300 servers run caches, so repeated DNS lookups are not normally expensive, and in
20301 any case, personal messages rarely have more than a few recipients.
20303 If you are running mailing lists with large numbers of subscribers at the same
20304 domain, and you are using a &(dnslookup)& router which is independent of the
20305 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
20306 lookups for identical domains in one message. In this case, when &(dnslookup)&
20307 routes an address to a remote transport, any other unrouted addresses in the
20308 message that have the same domain are automatically given the same routing
20309 without processing them independently,
20310 provided the following conditions are met:
20313 No router that processed the address specified &%headers_add%& or
20314 &%headers_remove%&.
20316 The router did not change the address in any way, for example, by &"widening"&
20323 .option search_parents dnslookup boolean false
20324 .cindex "DNS" "resolver options"
20325 When this option is true, the resolver option RES_DNSRCH is set for DNS
20326 lookups. This is different from the &%qualify_single%& option in that it
20327 applies to domains containing dots. Typically, but not standardly, it causes
20328 the resolver to search for the name in the current domain and in parent
20329 domains. For example, on a machine in the &'fict.example'& domain, if looking
20330 up &'teaparty.wonderland'& failed, the resolver would try
20331 &'teaparty.wonderland.fict.example'&. For details of what your resolver
20332 actually does, consult your man pages for &'resolver'& and &'resolv.conf'&.
20334 Setting this option true can cause problems in domains that have a wildcard MX
20335 record, because any domain that does not have its own MX record matches the
20340 .option srv_fail_domains dnslookup "domain list&!!" unset
20341 If the DNS lookup for SRV records for one of the domains in this list causes a
20342 DNS lookup error, Exim behaves as if no SRV records were found. See section
20343 &<<SECTprowitdnsloo>>& for more discussion.
20348 .option widen_domains dnslookup "string list" unset
20349 .cindex "domain" "partial; widening"
20350 If a DNS lookup fails and this option is set, each of its strings in turn is
20351 added onto the end of the domain, and the lookup is tried again. For example,
20354 widen_domains = fict.example:ref.example
20356 is set and a lookup of &'klingon.dictionary'& fails,
20357 &'klingon.dictionary.fict.example'& is looked up, and if this fails,
20358 &'klingon.dictionary.ref.example'& is tried. Note that the &%qualify_single%&
20359 and &%search_parents%& options can cause some widening to be undertaken inside
20360 the DNS resolver. &%widen_domains%& is not applied to sender addresses
20361 when verifying, unless &%rewrite_headers%& is false (not the default).
20364 .section "Effect of qualify_single and search_parents" "SECID119"
20365 When a domain from an envelope recipient is changed by the resolver as a result
20366 of the &%qualify_single%& or &%search_parents%& options, Exim rewrites the
20367 corresponding address in the message's header lines unless &%rewrite_headers%&
20368 is set false. Exim then re-routes the address, using the full domain.
20370 These two options affect only the DNS lookup that takes place inside the router
20371 for the domain of the address that is being routed. They do not affect lookups
20372 such as that implied by
20376 that may happen while processing a router precondition before the router is
20377 entered. No widening ever takes place for these lookups.
20378 .ecindex IIDdnsrou1
20379 .ecindex IIDdnsrou2
20389 . ////////////////////////////////////////////////////////////////////////////
20390 . ////////////////////////////////////////////////////////////////////////////
20392 .chapter "The ipliteral router" "CHID5"
20393 .cindex "&(ipliteral)& router"
20394 .cindex "domain literal" "routing"
20395 .cindex "routers" "&(ipliteral)&"
20396 This router has no private options. Unless it is being used purely for
20397 verification (see &%verify_only%&) a transport is required to be defined by the
20398 generic &%transport%& option. The router accepts the address if its domain part
20399 takes the form of an RFC 2822 domain literal. For example, the &(ipliteral)&
20400 router handles the address
20404 by setting up delivery to the host with that IP address. IPv4 domain literals
20405 consist of an IPv4 address enclosed in square brackets. IPv6 domain literals
20406 are similar, but the address is preceded by &`ipv6:`&. For example:
20408 postmaster@[ipv6:fe80::a00:20ff:fe86:a061.5678]
20410 Exim allows &`ipv4:`& before IPv4 addresses, for consistency, and on the
20411 grounds that sooner or later somebody will try it.
20413 .oindex "&%self%&" "in &(ipliteral)& router"
20414 If the IP address matches something in &%ignore_target_hosts%&, the router
20415 declines. If an IP literal turns out to refer to the local host, the generic
20416 &%self%& option determines what happens.
20418 The RFCs require support for domain literals; however, their use is
20419 controversial in today's Internet. If you want to use this router, you must
20420 also set the main configuration option &%allow_domain_literals%&. Otherwise,
20421 Exim will not recognize the domain literal syntax in addresses.
20425 . ////////////////////////////////////////////////////////////////////////////
20426 . ////////////////////////////////////////////////////////////////////////////
20428 .chapter "The iplookup router" "CHID6"
20429 .cindex "&(iplookup)& router"
20430 .cindex "routers" "&(iplookup)&"
20431 The &(iplookup)& router was written to fulfil a specific requirement in
20432 Cambridge University (which in fact no longer exists). For this reason, it is
20433 not included in the binary of Exim by default. If you want to include it, you
20436 ROUTER_IPLOOKUP=yes
20438 in your &_Local/Makefile_& configuration file.
20440 The &(iplookup)& router routes an address by sending it over a TCP or UDP
20441 connection to one or more specific hosts. The host can then return the same or
20442 a different address &-- in effect rewriting the recipient address in the
20443 message's envelope. The new address is then passed on to subsequent routers. If
20444 this process fails, the address can be passed on to other routers, or delivery
20445 can be deferred. Since &(iplookup)& is just a rewriting router, a transport
20446 must not be specified for it.
20448 .cindex "options" "&(iplookup)& router"
20449 .option hosts iplookup string unset
20450 This option must be supplied. Its value is a colon-separated list of host
20451 names. The hosts are looked up using &[gethostbyname()]&
20452 (or &[getipnodebyname()]& when available)
20453 and are tried in order until one responds to the query. If none respond, what
20454 happens is controlled by &%optional%&.
20457 .option optional iplookup boolean false
20458 If &%optional%& is true, if no response is obtained from any host, the address
20459 is passed to the next router, overriding &%no_more%&. If &%optional%& is false,
20460 delivery to the address is deferred.
20463 .option port iplookup integer 0
20464 .cindex "port" "&(iplookup)& router"
20465 This option must be supplied. It specifies the port number for the TCP or UDP
20469 .option protocol iplookup string udp
20470 This option can be set to &"udp"& or &"tcp"& to specify which of the two
20471 protocols is to be used.
20474 .option query iplookup string&!! "see below"
20475 This defines the content of the query that is sent to the remote hosts. The
20478 $local_part@$domain $local_part@$domain
20480 The repetition serves as a way of checking that a response is to the correct
20481 query in the default case (see &%response_pattern%& below).
20484 .option reroute iplookup string&!! unset
20485 If this option is not set, the rerouted address is precisely the byte string
20486 returned by the remote host, up to the first white space, if any. If set, the
20487 string is expanded to form the rerouted address. It can include parts matched
20488 in the response by &%response_pattern%& by means of numeric variables such as
20489 &$1$&, &$2$&, etc. The variable &$0$& refers to the entire input string,
20490 whether or not a pattern is in use. In all cases, the rerouted address must end
20491 up in the form &'local_part@domain'&.
20494 .option response_pattern iplookup string unset
20495 This option can be set to a regular expression that is applied to the string
20496 returned from the remote host. If the pattern does not match the response, the
20497 router declines. If &%response_pattern%& is not set, no checking of the
20498 response is done, unless the query was defaulted, in which case there is a
20499 check that the text returned after the first white space is the original
20500 address. This checks that the answer that has been received is in response to
20501 the correct question. For example, if the response is just a new domain, the
20502 following could be used:
20504 response_pattern = ^([^@]+)$
20505 reroute = $local_part@$1
20508 .option timeout iplookup time 5s
20509 This specifies the amount of time to wait for a response from the remote
20510 machine. The same timeout is used for the &[connect()]& function for a TCP
20511 call. It does not apply to UDP.
20516 . ////////////////////////////////////////////////////////////////////////////
20517 . ////////////////////////////////////////////////////////////////////////////
20519 .chapter "The manualroute router" "CHID7"
20520 .scindex IIDmanrou1 "&(manualroute)& router"
20521 .scindex IIDmanrou2 "routers" "&(manualroute)&"
20522 .cindex "domain" "manually routing"
20523 The &(manualroute)& router is so-called because it provides a way of manually
20524 routing an address according to its domain. It is mainly used when you want to
20525 route addresses to remote hosts according to your own rules, bypassing the
20526 normal DNS routing that looks up MX records. However, &(manualroute)& can also
20527 route to local transports, a facility that may be useful if you want to save
20528 messages for dial-in hosts in local files.
20530 The &(manualroute)& router compares a list of domain patterns with the domain
20531 it is trying to route. If there is no match, the router declines. Each pattern
20532 has associated with it a list of hosts and some other optional data, which may
20533 include a transport. The combination of a pattern and its data is called a
20534 &"routing rule"&. For patterns that do not have an associated transport, the
20535 generic &%transport%& option must specify a transport, unless the router is
20536 being used purely for verification (see &%verify_only%&).
20539 In the case of verification, matching the domain pattern is sufficient for the
20540 router to accept the address. When actually routing an address for delivery,
20541 an address that matches a domain pattern is queued for the associated
20542 transport. If the transport is not a local one, a host list must be associated
20543 with the pattern; IP addresses are looked up for the hosts, and these are
20544 passed to the transport along with the mail address. For local transports, a
20545 host list is optional. If it is present, it is passed in &$host$& as a single
20548 The list of routing rules can be provided as an inline string in
20549 &%route_list%&, or the data can be obtained by looking up the domain in a file
20550 or database by setting &%route_data%&. Only one of these settings may appear in
20551 any one instance of &(manualroute)&. The format of routing rules is described
20552 below, following the list of private options.
20555 .section "Private options for manualroute" "SECTprioptman"
20557 .cindex "options" "&(manualroute)& router"
20558 The private options for the &(manualroute)& router are as follows:
20560 .option host_all_ignored manualroute string defer
20561 See &%host_find_failed%&.
20563 .option host_find_failed manualroute string freeze
20564 This option controls what happens when &(manualroute)& tries to find an IP
20565 address for a host, and the host does not exist. The option can be set to one
20566 of the following values:
20575 The default (&"freeze"&) assumes that this state is a serious configuration
20576 error. The difference between &"pass"& and &"decline"& is that the former
20577 forces the address to be passed to the next router (or the router defined by
20580 overriding &%no_more%&, whereas the latter passes the address to the next
20581 router only if &%more%& is true.
20583 The value &"ignore"& causes Exim to completely ignore a host whose IP address
20584 cannot be found. If all the hosts in the list are ignored, the behaviour is
20585 controlled by the &%host_all_ignored%& option. This takes the same values
20586 as &%host_find_failed%&, except that it cannot be set to &"ignore"&.
20588 The &%host_find_failed%& option applies only to a definite &"does not exist"&
20589 state; if a host lookup gets a temporary error, delivery is deferred unless the
20590 generic &%pass_on_timeout%& option is set.
20593 .option hosts_randomize manualroute boolean false
20594 .cindex "randomized host list"
20595 .cindex "host" "list of; randomized"
20596 If this option is set, the order of the items in a host list in a routing rule
20597 is randomized each time the list is used, unless an option in the routing rule
20598 overrides (see below). Randomizing the order of a host list can be used to do
20599 crude load sharing. However, if more than one mail address is routed by the
20600 same router to the same host list, the host lists are considered to be the same
20601 (even though they may be randomized into different orders) for the purpose of
20602 deciding whether to batch the deliveries into a single SMTP transaction.
20604 When &%hosts_randomize%& is true, a host list may be split
20605 into groups whose order is separately randomized. This makes it possible to
20606 set up MX-like behaviour. The boundaries between groups are indicated by an
20607 item that is just &`+`& in the host list. For example:
20609 route_list = * host1:host2:host3:+:host4:host5
20611 The order of the first three hosts and the order of the last two hosts is
20612 randomized for each use, but the first three always end up before the last two.
20613 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored. If a
20614 randomized host list is passed to an &(smtp)& transport that also has
20615 &%hosts_randomize set%&, the list is not re-randomized.
20618 .option route_data manualroute string&!! unset
20619 If this option is set, it must expand to yield the data part of a routing rule.
20620 Typically, the expansion string includes a lookup based on the domain. For
20623 route_data = ${lookup{$domain}dbm{/etc/routes}}
20625 If the expansion is forced to fail, or the result is an empty string, the
20626 router declines. Other kinds of expansion failure cause delivery to be
20630 .option route_list manualroute "string list" unset
20631 This string is a list of routing rules, in the form defined below. Note that,
20632 unlike most string lists, the items are separated by semicolons. This is so
20633 that they may contain colon-separated host lists.
20636 .option same_domain_copy_routing manualroute boolean false
20637 .cindex "address" "copying routing"
20638 Addresses with the same domain are normally routed by the &(manualroute)&
20639 router to the same list of hosts. However, this cannot be presumed, because the
20640 router options and preconditions may refer to the local part of the address. By
20641 default, therefore, Exim routes each address in a message independently. DNS
20642 servers run caches, so repeated DNS lookups are not normally expensive, and in
20643 any case, personal messages rarely have more than a few recipients.
20645 If you are running mailing lists with large numbers of subscribers at the same
20646 domain, and you are using a &(manualroute)& router which is independent of the
20647 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
20648 lookups for identical domains in one message. In this case, when
20649 &(manualroute)& routes an address to a remote transport, any other unrouted
20650 addresses in the message that have the same domain are automatically given the
20651 same routing without processing them independently. However, this is only done
20652 if &%headers_add%& and &%headers_remove%& are unset.
20657 .section "Routing rules in route_list" "SECID120"
20658 The value of &%route_list%& is a string consisting of a sequence of routing
20659 rules, separated by semicolons. If a semicolon is needed in a rule, it can be
20660 entered as two semicolons. Alternatively, the list separator can be changed as
20661 described (for colon-separated lists) in section &<<SECTlistconstruct>>&.
20662 Empty rules are ignored. The format of each rule is
20664 <&'domain pattern'&> <&'list of hosts'&> <&'options'&>
20666 The following example contains two rules, each with a simple domain pattern and
20670 dict.ref.example mail-1.ref.example:mail-2.ref.example ; \
20671 thes.ref.example mail-3.ref.example:mail-4.ref.example
20673 The three parts of a rule are separated by white space. The pattern and the
20674 list of hosts can be enclosed in quotes if necessary, and if they are, the
20675 usual quoting rules apply. Each rule in a &%route_list%& must start with a
20676 single domain pattern, which is the only mandatory item in the rule. The
20677 pattern is in the same format as one item in a domain list (see section
20678 &<<SECTdomainlist>>&),
20679 except that it may not be the name of an interpolated file.
20680 That is, it may be wildcarded, or a regular expression, or a file or database
20681 lookup (with semicolons doubled, because of the use of semicolon as a separator
20682 in a &%route_list%&).
20684 The rules in &%route_list%& are searched in order until one of the patterns
20685 matches the domain that is being routed. The list of hosts and then options are
20686 then used as described below. If there is no match, the router declines. When
20687 &%route_list%& is set, &%route_data%& must not be set.
20691 .section "Routing rules in route_data" "SECID121"
20692 The use of &%route_list%& is convenient when there are only a small number of
20693 routing rules. For larger numbers, it is easier to use a file or database to
20694 hold the routing information, and use the &%route_data%& option instead.
20695 The value of &%route_data%& is a list of hosts, followed by (optional) options.
20696 Most commonly, &%route_data%& is set as a string that contains an
20697 expansion lookup. For example, suppose we place two routing rules in a file
20700 dict.ref.example: mail-1.ref.example:mail-2.ref.example
20701 thes.ref.example: mail-3.ref.example:mail-4.ref.example
20703 This data can be accessed by setting
20705 route_data = ${lookup{$domain}lsearch{/the/file/name}}
20707 Failure of the lookup results in an empty string, causing the router to
20708 decline. However, you do not have to use a lookup in &%route_data%&. The only
20709 requirement is that the result of expanding the string is a list of hosts,
20710 possibly followed by options, separated by white space. The list of hosts must
20711 be enclosed in quotes if it contains white space.
20716 .section "Format of the list of hosts" "SECID122"
20717 A list of hosts, whether obtained via &%route_data%& or &%route_list%&, is
20718 always separately expanded before use. If the expansion fails, the router
20719 declines. The result of the expansion must be a colon-separated list of names
20720 and/or IP addresses, optionally also including ports.
20721 If the list is written with spaces, it must be protected with quotes.
20722 The format of each item
20723 in the list is described in the next section. The list separator can be changed
20724 as described in section &<<SECTlistsepchange>>&.
20726 If the list of hosts was obtained from a &%route_list%& item, the following
20727 variables are set during its expansion:
20730 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(manualroute)& router"
20731 If the domain was matched against a regular expression, the numeric variables
20732 &$1$&, &$2$&, etc. may be set. For example:
20734 route_list = ^domain(\d+) host-$1.text.example
20737 &$0$& is always set to the entire domain.
20739 &$1$& is also set when partial matching is done in a file lookup.
20742 .vindex "&$value$&"
20743 If the pattern that matched the domain was a lookup item, the data that was
20744 looked up is available in the expansion variable &$value$&. For example:
20746 route_list = lsearch;;/some/file.routes $value
20750 Note the doubling of the semicolon in the pattern that is necessary because
20751 semicolon is the default route list separator.
20755 .section "Format of one host item" "SECTformatonehostitem"
20756 Each item in the list of hosts can be either a host name or an IP address,
20757 optionally with an attached port number, or it can be a single "+"
20758 (see &%hosts_randomize%&).
20759 When no port is given, an IP address
20760 is not enclosed in brackets. When a port is specified, it overrides the port
20761 specification on the transport. The port is separated from the name or address
20762 by a colon. This leads to some complications:
20765 Because colon is the default separator for the list of hosts, either
20766 the colon that specifies a port must be doubled, or the list separator must
20767 be changed. The following two examples have the same effect:
20769 route_list = * "host1.tld::1225 : host2.tld::1226"
20770 route_list = * "<+ host1.tld:1225 + host2.tld:1226"
20773 When IPv6 addresses are involved, it gets worse, because they contain
20774 colons of their own. To make this case easier, it is permitted to
20775 enclose an IP address (either v4 or v6) in square brackets if a port
20776 number follows. For example:
20778 route_list = * "</ [10.1.1.1]:1225 / [::1]:1226"
20782 .section "How the list of hosts is used" "SECThostshowused"
20783 When an address is routed to an &(smtp)& transport by &(manualroute)&, each of
20784 the hosts is tried, in the order specified, when carrying out the SMTP
20785 delivery. However, the order can be changed by setting the &%hosts_randomize%&
20786 option, either on the router (see section &<<SECTprioptman>>& above), or on the
20789 Hosts may be listed by name or by IP address. An unadorned name in the list of
20790 hosts is interpreted as a host name. A name that is followed by &`/MX`& is
20791 interpreted as an indirection to a sublist of hosts obtained by looking up MX
20792 records in the DNS. For example:
20794 route_list = * x.y.z:p.q.r/MX:e.f.g
20796 If this feature is used with a port specifier, the port must come last. For
20799 route_list = * dom1.tld/mx::1225
20801 If the &%hosts_randomize%& option is set, the order of the items in the list is
20802 randomized before any lookups are done. Exim then scans the list; for any name
20803 that is not followed by &`/MX`& it looks up an IP address. If this turns out to
20804 be an interface on the local host and the item is not the first in the list,
20805 Exim discards it and any subsequent items. If it is the first item, what
20806 happens is controlled by the
20807 .oindex "&%self%&" "in &(manualroute)& router"
20808 &%self%& option of the router.
20810 A name on the list that is followed by &`/MX`& is replaced with the list of
20811 hosts obtained by looking up MX records for the name. This is always a DNS
20812 lookup; the &%bydns%& and &%byname%& options (see section &<<SECThowoptused>>&
20813 below) are not relevant here. The order of these hosts is determined by the
20814 preference values in the MX records, according to the usual rules. Because
20815 randomizing happens before the MX lookup, it does not affect the order that is
20816 defined by MX preferences.
20818 If the local host is present in the sublist obtained from MX records, but is
20819 not the most preferred host in that list, it and any equally or less
20820 preferred hosts are removed before the sublist is inserted into the main list.
20822 If the local host is the most preferred host in the MX list, what happens
20823 depends on where in the original list of hosts the &`/MX`& item appears. If it
20824 is not the first item (that is, there are previous hosts in the main list),
20825 Exim discards this name and any subsequent items in the main list.
20827 If the MX item is first in the list of hosts, and the local host is the
20828 most preferred host, what happens is controlled by the &%self%& option of the
20831 DNS failures when lookup up the MX records are treated in the same way as DNS
20832 failures when looking up IP addresses: &%pass_on_timeout%& and
20833 &%host_find_failed%& are used when relevant.
20835 The generic &%ignore_target_hosts%& option applies to all hosts in the list,
20836 whether obtained from an MX lookup or not.
20840 .section "How the options are used" "SECThowoptused"
20841 The options are a sequence of words, space-separated.
20842 One of the words can be the name of a transport; this overrides the
20843 &%transport%& option on the router for this particular routing rule only. The
20844 other words (if present) control randomization of the list of hosts on a
20845 per-rule basis, and how the IP addresses of the hosts are to be found when
20846 routing to a remote transport. These options are as follows:
20849 &%randomize%&: randomize the order of the hosts in this list, overriding the
20850 setting of &%hosts_randomize%& for this routing rule only.
20852 &%no_randomize%&: do not randomize the order of the hosts in this list,
20853 overriding the setting of &%hosts_randomize%& for this routing rule only.
20855 &%byname%&: use &[getipnodebyname()]& (&[gethostbyname()]& on older systems) to
20856 find IP addresses. This function may ultimately cause a DNS lookup, but it may
20857 also look in &_/etc/hosts_& or other sources of information.
20859 &%bydns%&: look up address records for the hosts directly in the DNS; fail if
20860 no address records are found. If there is a temporary DNS error (such as a
20861 timeout), delivery is deferred.
20863 &%ipv4_only%&: in direct DNS lookups, look up only A records.
20865 &%ipv4_prefer%&: in direct DNS lookups, sort A records before AAAA records.
20870 route_list = domain1 host1:host2:host3 randomize bydns;\
20871 domain2 host4:host5
20873 If neither &%byname%& nor &%bydns%& is given, Exim behaves as follows: First, a
20874 DNS lookup is done. If this yields anything other than HOST_NOT_FOUND, that
20875 result is used. Otherwise, Exim goes on to try a call to &[getipnodebyname()]&
20876 or &[gethostbyname()]&, and the result of the lookup is the result of that
20879 &*Warning*&: It has been discovered that on some systems, if a DNS lookup
20880 called via &[getipnodebyname()]& times out, HOST_NOT_FOUND is returned
20881 instead of TRY_AGAIN. That is why the default action is to try a DNS
20882 lookup first. Only if that gives a definite &"no such host"& is the local
20885 &*Compatibility*&: From Exim 4.85 until fixed for 4.90, there was an
20886 inadvertent constraint that a transport name as an option had to be the last
20891 If no IP address for a host can be found, what happens is controlled by the
20892 &%host_find_failed%& option.
20895 When an address is routed to a local transport, IP addresses are not looked up.
20896 The host list is passed to the transport in the &$host$& variable.
20900 .section "Manualroute examples" "SECID123"
20901 In some of the examples that follow, the presence of the &%remote_smtp%&
20902 transport, as defined in the default configuration file, is assumed:
20905 .cindex "smart host" "example router"
20906 The &(manualroute)& router can be used to forward all external mail to a
20907 &'smart host'&. If you have set up, in the main part of the configuration, a
20908 named domain list that contains your local domains, for example:
20910 domainlist local_domains = my.domain.example
20912 You can arrange for all other domains to be routed to a smart host by making
20913 your first router something like this:
20916 driver = manualroute
20917 domains = !+local_domains
20918 transport = remote_smtp
20919 route_list = * smarthost.ref.example
20921 This causes all non-local addresses to be sent to the single host
20922 &'smarthost.ref.example'&. If a colon-separated list of smart hosts is given,
20923 they are tried in order
20924 (but you can use &%hosts_randomize%& to vary the order each time).
20925 Another way of configuring the same thing is this:
20928 driver = manualroute
20929 transport = remote_smtp
20930 route_list = !+local_domains smarthost.ref.example
20932 There is no difference in behaviour between these two routers as they stand.
20933 However, they behave differently if &%no_more%& is added to them. In the first
20934 example, the router is skipped if the domain does not match the &%domains%&
20935 precondition; the following router is always tried. If the router runs, it
20936 always matches the domain and so can never decline. Therefore, &%no_more%&
20937 would have no effect. In the second case, the router is never skipped; it
20938 always runs. However, if it doesn't match the domain, it declines. In this case
20939 &%no_more%& would prevent subsequent routers from running.
20942 .cindex "mail hub example"
20943 A &'mail hub'& is a host which receives mail for a number of domains via MX
20944 records in the DNS and delivers it via its own private routing mechanism. Often
20945 the final destinations are behind a firewall, with the mail hub being the one
20946 machine that can connect to machines both inside and outside the firewall. The
20947 &(manualroute)& router is usually used on a mail hub to route incoming messages
20948 to the correct hosts. For a small number of domains, the routing can be inline,
20949 using the &%route_list%& option, but for a larger number a file or database
20950 lookup is easier to manage.
20952 If the domain names are in fact the names of the machines to which the mail is
20953 to be sent by the mail hub, the configuration can be quite simple. For
20957 driver = manualroute
20958 transport = remote_smtp
20959 route_list = *.rhodes.tvs.example $domain
20961 This configuration routes domains that match &`*.rhodes.tvs.example`& to hosts
20962 whose names are the same as the mail domains. A similar approach can be taken
20963 if the host name can be obtained from the domain name by a string manipulation
20964 that the expansion facilities can handle. Otherwise, a lookup based on the
20965 domain can be used to find the host:
20968 driver = manualroute
20969 transport = remote_smtp
20970 route_data = ${lookup {$domain} cdb {/internal/host/routes}}
20972 The result of the lookup must be the name or IP address of the host (or
20973 hosts) to which the address is to be routed. If the lookup fails, the route
20974 data is empty, causing the router to decline. The address then passes to the
20978 .cindex "batched SMTP output example"
20979 .cindex "SMTP" "batched outgoing; example"
20980 You can use &(manualroute)& to deliver messages to pipes or files in batched
20981 SMTP format for onward transportation by some other means. This is one way of
20982 storing mail for a dial-up host when it is not connected. The route list entry
20983 can be as simple as a single domain name in a configuration like this:
20986 driver = manualroute
20987 transport = batchsmtp_appendfile
20988 route_list = saved.domain.example
20990 though often a pattern is used to pick up more than one domain. If there are
20991 several domains or groups of domains with different transport requirements,
20992 different transports can be listed in the routing information:
20995 driver = manualroute
20997 *.saved.domain1.example $domain batch_appendfile; \
20998 *.saved.domain2.example \
20999 ${lookup{$domain}dbm{/domain2/hosts}{$value}fail} \
21002 .vindex "&$domain$&"
21004 The first of these just passes the domain in the &$host$& variable, which
21005 doesn't achieve much (since it is also in &$domain$&), but the second does a
21006 file lookup to find a value to pass, causing the router to decline to handle
21007 the address if the lookup fails.
21010 .cindex "UUCP" "example of router for"
21011 Routing mail directly to UUCP software is a specific case of the use of
21012 &(manualroute)& in a gateway to another mail environment. This is an example of
21013 one way it can be done:
21019 command = /usr/local/bin/uux -r - \
21020 ${substr_-5:$host}!rmail ${local_part}
21021 return_fail_output = true
21026 driver = manualroute
21028 ${lookup{$domain}lsearch{/usr/local/exim/uucphosts}}
21030 The file &_/usr/local/exim/uucphosts_& contains entries like
21032 darksite.ethereal.example: darksite.UUCP
21034 It can be set up more simply without adding and removing &".UUCP"& but this way
21035 makes clear the distinction between the domain name
21036 &'darksite.ethereal.example'& and the UUCP host name &'darksite'&.
21038 .ecindex IIDmanrou1
21039 .ecindex IIDmanrou2
21048 . ////////////////////////////////////////////////////////////////////////////
21049 . ////////////////////////////////////////////////////////////////////////////
21051 .chapter "The queryprogram router" "CHAPdriverlast"
21052 .scindex IIDquerou1 "&(queryprogram)& router"
21053 .scindex IIDquerou2 "routers" "&(queryprogram)&"
21054 .cindex "routing" "by external program"
21055 The &(queryprogram)& router routes an address by running an external command
21056 and acting on its output. This is an expensive way to route, and is intended
21057 mainly for use in lightly-loaded systems, or for performing experiments.
21058 However, if it is possible to use the precondition options (&%domains%&,
21059 &%local_parts%&, etc) to skip this router for most addresses, it could sensibly
21060 be used in special cases, even on a busy host. There are the following private
21062 .cindex "options" "&(queryprogram)& router"
21064 .option command queryprogram string&!! unset
21065 This option must be set. It specifies the command that is to be run. The
21066 command is split up into a command name and arguments, and then each is
21067 expanded separately (exactly as for a &(pipe)& transport, described in chapter
21068 &<<CHAPpipetransport>>&).
21071 .option command_group queryprogram string unset
21072 .cindex "gid (group id)" "in &(queryprogram)& router"
21073 This option specifies a gid to be set when running the command while routing an
21074 address for deliver. It must be set if &%command_user%& specifies a numerical
21075 uid. If it begins with a digit, it is interpreted as the numerical value of the
21076 gid. Otherwise it is looked up using &[getgrnam()]&.
21079 .option command_user queryprogram string unset
21080 .cindex "uid (user id)" "for &(queryprogram)&"
21081 This option must be set. It specifies the uid which is set when running the
21082 command while routing an address for delivery. If the value begins with a digit,
21083 it is interpreted as the numerical value of the uid. Otherwise, it is looked up
21084 using &[getpwnam()]& to obtain a value for the uid and, if &%command_group%& is
21085 not set, a value for the gid also.
21087 &*Warning:*& Changing uid and gid is possible only when Exim is running as
21088 root, which it does during a normal delivery in a conventional configuration.
21089 However, when an address is being verified during message reception, Exim is
21090 usually running as the Exim user, not as root. If the &(queryprogram)& router
21091 is called from a non-root process, Exim cannot change uid or gid before running
21092 the command. In this circumstance the command runs under the current uid and
21096 .option current_directory queryprogram string /
21097 This option specifies an absolute path which is made the current directory
21098 before running the command.
21101 .option timeout queryprogram time 1h
21102 If the command does not complete within the timeout period, its process group
21103 is killed and the message is frozen. A value of zero time specifies no
21107 The standard output of the command is connected to a pipe, which is read when
21108 the command terminates. It should consist of a single line of output,
21109 containing up to five fields, separated by white space. The maximum length of
21110 the line is 1023 characters. Longer lines are silently truncated. The first
21111 field is one of the following words (case-insensitive):
21114 &'Accept'&: routing succeeded; the remaining fields specify what to do (see
21117 &'Decline'&: the router declines; pass the address to the next router, unless
21118 &%no_more%& is set.
21120 &'Fail'&: routing failed; do not pass the address to any more routers. Any
21121 subsequent text on the line is an error message. If the router is run as part
21122 of address verification during an incoming SMTP message, the message is
21123 included in the SMTP response.
21125 &'Defer'&: routing could not be completed at this time; try again later. Any
21126 subsequent text on the line is an error message which is logged. It is not
21127 included in any SMTP response.
21129 &'Freeze'&: the same as &'defer'&, except that the message is frozen.
21131 &'Pass'&: pass the address to the next router (or the router specified by
21132 &%pass_router%&), overriding &%no_more%&.
21134 &'Redirect'&: the message is redirected. The remainder of the line is a list of
21135 new addresses, which are routed independently, starting with the first router,
21136 or the router specified by &%redirect_router%&, if set.
21139 When the first word is &'accept'&, the remainder of the line consists of a
21140 number of keyed data values, as follows (split into two lines here, to fit on
21143 ACCEPT TRANSPORT=<transport> HOSTS=<list of hosts>
21144 LOOKUP=byname|bydns DATA=<text>
21146 The data items can be given in any order, and all are optional. If no transport
21147 is included, the transport specified by the generic &%transport%& option is
21148 used. The list of hosts and the lookup type are needed only if the transport is
21149 an &(smtp)& transport that does not itself supply a list of hosts.
21151 The format of the list of hosts is the same as for the &(manualroute)& router.
21152 As well as host names and IP addresses with optional port numbers, as described
21153 in section &<<SECTformatonehostitem>>&, it may contain names followed by
21154 &`/MX`& to specify sublists of hosts that are obtained by looking up MX records
21155 (see section &<<SECThostshowused>>&).
21157 If the lookup type is not specified, Exim behaves as follows when trying to
21158 find an IP address for each host: First, a DNS lookup is done. If this yields
21159 anything other than HOST_NOT_FOUND, that result is used. Otherwise, Exim
21160 goes on to try a call to &[getipnodebyname()]& or &[gethostbyname()]&, and the
21161 result of the lookup is the result of that call.
21163 .vindex "&$address_data$&"
21164 If the DATA field is set, its value is placed in the &$address_data$&
21165 variable. For example, this return line
21167 accept hosts=x1.y.example:x2.y.example data="rule1"
21169 routes the address to the default transport, passing a list of two hosts. When
21170 the transport runs, the string &"rule1"& is in &$address_data$&.
21171 .ecindex IIDquerou1
21172 .ecindex IIDquerou2
21177 . ////////////////////////////////////////////////////////////////////////////
21178 . ////////////////////////////////////////////////////////////////////////////
21180 .chapter "The redirect router" "CHAPredirect"
21181 .scindex IIDredrou1 "&(redirect)& router"
21182 .scindex IIDredrou2 "routers" "&(redirect)&"
21183 .cindex "alias file" "in a &(redirect)& router"
21184 .cindex "address redirection" "&(redirect)& router"
21185 The &(redirect)& router handles several kinds of address redirection. Its most
21186 common uses are for resolving local part aliases from a central alias file
21187 (usually called &_/etc/aliases_&) and for handling users' personal &_.forward_&
21188 files, but it has many other potential uses. The incoming address can be
21189 redirected in several different ways:
21192 It can be replaced by one or more new addresses which are themselves routed
21195 It can be routed to be delivered to a given file or directory.
21197 It can be routed to be delivered to a specified pipe command.
21199 It can cause an automatic reply to be generated.
21201 It can be forced to fail, optionally with a custom error message.
21203 It can be temporarily deferred, optionally with a custom message.
21205 It can be discarded.
21208 The generic &%transport%& option must not be set for &(redirect)& routers.
21209 However, there are some private options which define transports for delivery to
21210 files and pipes, and for generating autoreplies. See the &%file_transport%&,
21211 &%pipe_transport%& and &%reply_transport%& descriptions below.
21213 If success DSNs have been requested
21214 .cindex "DSN" "success"
21215 .cindex "Delivery Status Notification" "success"
21216 redirection triggers one and the DSN options are not passed any further.
21220 .section "Redirection data" "SECID124"
21221 The router operates by interpreting a text string which it obtains either by
21222 expanding the contents of the &%data%& option, or by reading the entire
21223 contents of a file whose name is given in the &%file%& option. These two
21224 options are mutually exclusive. The first is commonly used for handling system
21225 aliases, in a configuration like this:
21229 data = ${lookup{$local_part}lsearch{/etc/aliases}}
21231 If the lookup fails, the expanded string in this example is empty. When the
21232 expansion of &%data%& results in an empty string, the router declines. A forced
21233 expansion failure also causes the router to decline; other expansion failures
21234 cause delivery to be deferred.
21236 A configuration using &%file%& is commonly used for handling users'
21237 &_.forward_& files, like this:
21242 file = $home/.forward
21245 If the file does not exist, or causes no action to be taken (for example, it is
21246 empty or consists only of comments), the router declines. &*Warning*&: This
21247 is not the case when the file contains syntactically valid items that happen to
21248 yield empty addresses, for example, items containing only RFC 2822 address
21251 .cindex "tainted data" "in filenames"
21252 .cindex redirect "tainted data"
21253 Tainted data may not be used for a filename.
21255 &*Warning*&: It is unwise to use &$local_part$& or &$domain$&
21256 directly for redirection,
21257 as they are provided by a potential attacker.
21258 In the examples above, &$local_part$& is used for looking up data held locally
21259 on the system, and not used directly (the second example derives &$home$& via
21260 the passsword file or database, using &$local_part$&).
21264 .section "Forward files and address verification" "SECID125"
21265 .cindex "address redirection" "while verifying"
21266 It is usual to set &%no_verify%& on &(redirect)& routers which handle users'
21267 &_.forward_& files, as in the example above. There are two reasons for this:
21270 When Exim is receiving an incoming SMTP message from a remote host, it is
21271 running under the Exim uid, not as root. Exim is unable to change uid to read
21272 the file as the user, and it may not be able to read it as the Exim user. So in
21273 practice the router may not be able to operate.
21275 However, even when the router can operate, the existence of a &_.forward_& file
21276 is unimportant when verifying an address. What should be checked is whether the
21277 local part is a valid user name or not. Cutting out the redirection processing
21278 saves some resources.
21286 .section "Interpreting redirection data" "SECID126"
21287 .cindex "Sieve filter" "specifying in redirection data"
21288 .cindex "filter" "specifying in redirection data"
21289 The contents of the data string, whether obtained from &%data%& or &%file%&,
21290 can be interpreted in two different ways:
21293 If the &%allow_filter%& option is set true, and the data begins with the text
21294 &"#Exim filter"& or &"#Sieve filter"&, it is interpreted as a list of
21295 &'filtering'& instructions in the form of an Exim or Sieve filter file,
21296 respectively. Details of the syntax and semantics of filter files are described
21297 in a separate document entitled &'Exim's interfaces to mail filtering'&; this
21298 document is intended for use by end users.
21300 Otherwise, the data must be a comma-separated list of redirection items, as
21301 described in the next section.
21304 When a message is redirected to a file (a &"mail folder"&), the filename given
21305 in a non-filter redirection list must always be an absolute path. A filter may
21306 generate a relative path &-- how this is handled depends on the transport's
21307 configuration. See section &<<SECTfildiropt>>& for a discussion of this issue
21308 for the &(appendfile)& transport.
21312 .section "Items in a non-filter redirection list" "SECTitenonfilred"
21313 .cindex "address redirection" "non-filter list items"
21314 When the redirection data is not an Exim or Sieve filter, for example, if it
21315 comes from a conventional alias or forward file, it consists of a list of
21316 addresses, filenames, pipe commands, or certain special items (see section
21317 &<<SECTspecitredli>>& below). The special items can be individually enabled or
21318 disabled by means of options whose names begin with &%allow_%& or &%forbid_%&,
21319 depending on their default values. The items in the list are separated by
21320 commas or newlines.
21321 If a comma is required in an item, the entire item must be enclosed in double
21324 Lines starting with a # character are comments, and are ignored, and # may
21325 also appear following a comma, in which case everything between the # and the
21326 next newline character is ignored.
21328 If an item is entirely enclosed in double quotes, these are removed. Otherwise
21329 double quotes are retained because some forms of mail address require their use
21330 (but never to enclose the entire address). In the following description,
21331 &"item"& refers to what remains after any surrounding double quotes have been
21334 .vindex "&$local_part$&"
21335 &*Warning*&: If you use an Exim expansion to construct a redirection address,
21336 and the expansion contains a reference to &$local_part$&, you should make use
21337 of the &%quote_local_part%& expansion operator, in case the local part contains
21338 special characters. For example, to redirect all mail for the domain
21339 &'obsolete.example'&, retaining the existing local part, you could use this
21342 data = ${quote_local_part:$local_part}@newdomain.example
21346 .section "Redirecting to a local mailbox" "SECTredlocmai"
21347 .cindex "routing" "loops in"
21348 .cindex "loop" "while routing, avoidance of"
21349 .cindex "address redirection" "to local mailbox"
21350 A redirection item may safely be the same as the address currently under
21351 consideration. This does not cause a routing loop, because a router is
21352 automatically skipped if any ancestor of the address that is being processed
21353 is the same as the current address and was processed by the current router.
21354 Such an address is therefore passed to the following routers, so it is handled
21355 as if there were no redirection. When making this loop-avoidance test, the
21356 complete local part, including any prefix or suffix, is used.
21358 .cindex "address redirection" "local part without domain"
21359 Specifying the same local part without a domain is a common usage in personal
21360 filter files when the user wants to have messages delivered to the local
21361 mailbox and also forwarded elsewhere. For example, the user whose login is
21362 &'cleo'& might have a &_.forward_& file containing this:
21364 cleo, cleopatra@egypt.example
21366 .cindex "backslash in alias file"
21367 .cindex "alias file" "backslash in"
21368 For compatibility with other MTAs, such unqualified local parts may be
21369 preceded by &"\"&, but this is not a requirement for loop prevention. However,
21370 it does make a difference if more than one domain is being handled
21373 If an item begins with &"\"& and the rest of the item parses as a valid RFC
21374 2822 address that does not include a domain, the item is qualified using the
21375 domain of the incoming address. In the absence of a leading &"\"&, unqualified
21376 addresses are qualified using the value in &%qualify_recipient%&, but you can
21377 force the incoming domain to be used by setting &%qualify_preserve_domain%&.
21379 Care must be taken if there are alias names for local users.
21380 Consider an MTA handling a single local domain where the system alias file
21385 Now suppose that Sam (whose login id is &'spqr'&) wants to save copies of
21386 messages in the local mailbox, and also forward copies elsewhere. He creates
21389 Sam.Reman, spqr@reme.elsewhere.example
21391 With these settings, an incoming message addressed to &'Sam.Reman'& fails. The
21392 &(redirect)& router for system aliases does not process &'Sam.Reman'& the
21393 second time round, because it has previously routed it,
21394 and the following routers presumably cannot handle the alias. The forward file
21395 should really contain
21397 spqr, spqr@reme.elsewhere.example
21399 but because this is such a common error, the &%check_ancestor%& option (see
21400 below) exists to provide a way to get round it. This is normally set on a
21401 &(redirect)& router that is handling users' &_.forward_& files.
21405 .section "Special items in redirection lists" "SECTspecitredli"
21406 In addition to addresses, the following types of item may appear in redirection
21407 lists (that is, in non-filter redirection data):
21410 .cindex "pipe" "in redirection list"
21411 .cindex "address redirection" "to pipe"
21412 An item is treated as a pipe command if it begins with &"|"& and does not parse
21413 as a valid RFC 2822 address that includes a domain. A transport for running the
21414 command must be specified by the &%pipe_transport%& option.
21415 Normally, either the router or the transport specifies a user and a group under
21416 which to run the delivery. The default is to use the Exim user and group.
21418 Single or double quotes can be used for enclosing the individual arguments of
21419 the pipe command; no interpretation of escapes is done for single quotes. If
21420 the command contains a comma character, it is necessary to put the whole item
21421 in double quotes, for example:
21423 "|/some/command ready,steady,go"
21425 since items in redirection lists are terminated by commas. Do not, however,
21426 quote just the command. An item such as
21428 |"/some/command ready,steady,go"
21430 is interpreted as a pipe with a rather strange command name, and no arguments.
21432 Note that the above example assumes that the text comes from a lookup source
21433 of some sort, so that the quotes are part of the data. If composing a
21434 redirect router with a &%data%& option directly specifying this command, the
21435 quotes will be used by the configuration parser to define the extent of one
21436 string, but will not be passed down into the redirect router itself. There
21437 are two main approaches to get around this: escape quotes to be part of the
21438 data itself, or avoid using this mechanism and instead create a custom
21439 transport with the &%command%& option set and reference that transport from
21440 an &%accept%& router.
21443 .cindex "file" "in redirection list"
21444 .cindex "address redirection" "to file"
21445 An item is interpreted as a path name if it begins with &"/"& and does not
21446 parse as a valid RFC 2822 address that includes a domain. For example,
21448 /home/world/minbari
21450 is treated as a filename, but
21452 /s=molari/o=babylon/@x400gate.way
21454 is treated as an address. For a filename, a transport must be specified using
21455 the &%file_transport%& option. However, if the generated path name ends with a
21456 forward slash character, it is interpreted as a directory name rather than a
21457 filename, and &%directory_transport%& is used instead.
21459 Normally, either the router or the transport specifies a user and a group under
21460 which to run the delivery. The default is to use the Exim user and group.
21462 .cindex "&_/dev/null_&"
21463 However, if a redirection item is the path &_/dev/null_&, delivery to it is
21464 bypassed at a high level, and the log entry shows &"**bypassed**"&
21465 instead of a transport name. In this case the user and group are not used.
21468 .cindex "included address list"
21469 .cindex "address redirection" "included external list"
21470 If an item is of the form
21472 :include:<path name>
21474 a list of further items is taken from the given file and included at that
21475 point. &*Note*&: Such a file can not be a filter file; it is just an
21476 out-of-line addition to the list. The items in the included list are separated
21477 by commas or newlines and are not subject to expansion. If this is the first
21478 item in an alias list in an &(lsearch)& file, a colon must be used to terminate
21479 the alias name. This example is incorrect:
21481 list1 :include:/opt/lists/list1
21483 It must be given as
21485 list1: :include:/opt/lists/list1
21487 .cindex "tainted data" "in filenames"
21488 .cindex redirect "tainted data"
21489 Tainted data may not be used for a filename.
21491 .cindex "address redirection" "to black hole"
21492 .cindex "delivery" "discard"
21493 .cindex "delivery" "blackhole"
21494 .cindex "black hole"
21495 .cindex "abandoning mail"
21496 Sometimes you want to throw away mail to a particular local part. Making the
21497 &%data%& option expand to an empty string does not work, because that causes
21498 the router to decline. Instead, the alias item
21502 can be used. It does what its name implies. No delivery is
21503 done, and no error message is generated. This has the same effect as specifying
21504 &_/dev/null_& as a destination, but it can be independently disabled.
21506 &*Warning*&: If &':blackhole:'& appears anywhere in a redirection list, no
21507 delivery is done for the original local part, even if other redirection items
21508 are present. If you are generating a multi-item list (for example, by reading a
21509 database) and need the ability to provide a no-op item, you must use
21513 .cindex "delivery" "forcing failure"
21514 .cindex "delivery" "forcing deferral"
21515 .cindex "failing delivery" "forcing"
21516 .cindex "deferred delivery, forcing"
21517 .cindex "customizing" "failure message"
21518 An attempt to deliver a particular address can be deferred or forced to fail by
21519 redirection items of the form
21524 respectively. When a redirection list contains such an item, it applies
21525 to the entire redirection; any other items in the list are ignored. Any
21526 text following &':fail:'& or &':defer:'& is placed in the error text
21527 associated with the failure. For example, an alias file might contain:
21529 X.Employee: :fail: Gone away, no forwarding address
21531 In the case of an address that is being verified from an ACL or as the subject
21533 .cindex "VRFY" "error text, display of"
21534 VRFY command, the text is included in the SMTP error response by
21536 .cindex "EXPN" "error text, display of"
21537 The text is not included in the response to an EXPN command. In non-SMTP cases
21538 the text is included in the error message that Exim generates.
21540 .cindex "SMTP" "error codes"
21541 By default for verify, Exim sends a 451 SMTP code for a &':defer:'&, and 550 for
21542 &':fail:'&. However, if the message starts with three digits followed by a
21543 space, optionally followed by an extended code of the form &'n.n.n'&, also
21544 followed by a space, and the very first digit is the same as the default error
21545 code, the code from the message is used instead. If the very first digit is
21546 incorrect, a panic error is logged, and the default code is used. You can
21547 suppress the use of the supplied code in a redirect router by setting the
21548 &%forbid_smtp_code%& option true. In this case, any SMTP code is quietly
21551 .vindex "&$acl_verify_message$&"
21552 In an ACL, an explicitly provided message overrides the default, but the
21553 default message is available in the variable &$acl_verify_message$& and can
21554 therefore be included in a custom message if this is desired.
21556 Normally the error text is the rest of the redirection list &-- a comma does
21557 not terminate it &-- but a newline does act as a terminator. Newlines are not
21558 normally present in alias expansions. In &(lsearch)& lookups they are removed
21559 as part of the continuation process, but they may exist in other kinds of
21560 lookup and in &':include:'& files.
21562 During routing for message delivery (as opposed to verification), a redirection
21563 containing &':fail:'& causes an immediate failure of the incoming address,
21564 whereas &':defer:'& causes the message to remain in the queue so that a
21565 subsequent delivery attempt can happen at a later time. If an address is
21566 deferred for too long, it will ultimately fail, because the normal retry
21570 .cindex "alias file" "exception to default"
21571 Sometimes it is useful to use a single-key search type with a default (see
21572 chapter &<<CHAPfdlookup>>&) to look up aliases. However, there may be a need
21573 for exceptions to the default. These can be handled by aliasing them to
21574 &':unknown:'&. This differs from &':fail:'& in that it causes the &(redirect)&
21575 router to decline, whereas &':fail:'& forces routing to fail. A lookup which
21576 results in an empty redirection list has the same effect.
21580 .section "Duplicate addresses" "SECTdupaddr"
21581 .cindex "duplicate addresses"
21582 .cindex "address duplicate, discarding"
21583 .cindex "pipe" "duplicated"
21584 Exim removes duplicate addresses from the list to which it is delivering, so as
21585 to deliver just one copy to each address. This does not apply to deliveries
21586 routed to pipes by different immediate parent addresses, but an indirect
21587 aliasing scheme of the type
21589 pipe: |/some/command $local_part
21593 does not work with a message that is addressed to both local parts, because
21594 when the second is aliased to the intermediate local part &"pipe"& it gets
21595 discarded as being the same as a previously handled address. However, a scheme
21598 localpart1: |/some/command $local_part
21599 localpart2: |/some/command $local_part
21601 does result in two different pipe deliveries, because the immediate parents of
21602 the pipes are distinct.
21606 .section "Repeated redirection expansion" "SECID128"
21607 .cindex "repeated redirection expansion"
21608 .cindex "address redirection" "repeated for each delivery attempt"
21609 When a message cannot be delivered to all of its recipients immediately,
21610 leading to two or more delivery attempts, redirection expansion is carried out
21611 afresh each time for those addresses whose children were not all previously
21612 delivered. If redirection is being used as a mailing list, this can lead to new
21613 members of the list receiving copies of old messages. The &%one_time%& option
21614 can be used to avoid this.
21617 .section "Errors in redirection lists" "SECID129"
21618 .cindex "address redirection" "errors"
21619 If &%skip_syntax_errors%& is set, a malformed address that causes a parsing
21620 error is skipped, and an entry is written to the main log. This may be useful
21621 for mailing lists that are automatically managed. Otherwise, if an error is
21622 detected while generating the list of new addresses, the original address is
21623 deferred. See also &%syntax_errors_to%&.
21627 .section "Private options for the redirect router" "SECID130"
21629 .cindex "options" "&(redirect)& router"
21630 The private options for the &(redirect)& router are as follows:
21633 .option allow_defer redirect boolean false
21634 Setting this option allows the use of &':defer:'& in non-filter redirection
21635 data, or the &%defer%& command in an Exim filter file.
21638 .option allow_fail redirect boolean false
21639 .cindex "failing delivery" "from filter"
21640 If this option is true, the &':fail:'& item can be used in a redirection list,
21641 and the &%fail%& command may be used in an Exim filter file.
21644 .option allow_filter redirect boolean false
21645 .cindex "filter" "enabling use of"
21646 .cindex "Sieve filter" "enabling use of"
21647 Setting this option allows Exim to interpret redirection data that starts with
21648 &"#Exim filter"& or &"#Sieve filter"& as a set of filtering instructions. There
21649 are some features of Exim filter files that some administrators may wish to
21650 lock out; see the &%forbid_filter_%&&'xxx'& options below.
21652 It is also possible to lock out Exim filters or Sieve filters while allowing
21653 the other type; see &%forbid_exim_filter%& and &%forbid_sieve_filter%&.
21656 The filter is run using the uid and gid set by the generic &%user%& and
21657 &%group%& options. These take their defaults from the password data if
21658 &%check_local_user%& is set, so in the normal case of users' personal filter
21659 files, the filter is run as the relevant user. When &%allow_filter%& is set
21660 true, Exim insists that either &%check_local_user%& or &%user%& is set.
21664 .option allow_freeze redirect boolean false
21665 .cindex "freezing messages" "allowing in filter"
21666 Setting this option allows the use of the &%freeze%& command in an Exim filter.
21667 This command is more normally encountered in system filters, and is disabled by
21668 default for redirection filters because it isn't something you usually want to
21669 let ordinary users do.
21673 .option check_ancestor redirect boolean false
21674 This option is concerned with handling generated addresses that are the same
21675 as some address in the list of redirection ancestors of the current address.
21676 Although it is turned off by default in the code, it is set in the default
21677 configuration file for handling users' &_.forward_& files. It is recommended
21678 for this use of the &(redirect)& router.
21680 When &%check_ancestor%& is set, if a generated address (including the domain)
21681 is the same as any ancestor of the current address, it is replaced by a copy of
21682 the current address. This helps in the case where local part A is aliased to B,
21683 and B has a &_.forward_& file pointing back to A. For example, within a single
21684 domain, the local part &"Joe.Bloggs"& is aliased to &"jb"& and
21685 &_&~jb/.forward_& contains:
21687 \Joe.Bloggs, <other item(s)>
21689 Without the &%check_ancestor%& setting, either local part (&"jb"& or
21690 &"joe.bloggs"&) gets processed once by each router and so ends up as it was
21691 originally. If &"jb"& is the real mailbox name, mail to &"jb"& gets delivered
21692 (having been turned into &"joe.bloggs"& by the &_.forward_& file and back to
21693 &"jb"& by the alias), but mail to &"joe.bloggs"& fails. Setting
21694 &%check_ancestor%& on the &(redirect)& router that handles the &_.forward_&
21695 file prevents it from turning &"jb"& back into &"joe.bloggs"& when that was the
21696 original address. See also the &%repeat_use%& option below.
21699 .option check_group redirect boolean "see below"
21700 When the &%file%& option is used, the group owner of the file is checked only
21701 when this option is set. The permitted groups are those listed in the
21702 &%owngroups%& option, together with the user's default group if
21703 &%check_local_user%& is set. If the file has the wrong group, routing is
21704 deferred. The default setting for this option is true if &%check_local_user%&
21705 is set and the &%modemask%& option permits the group write bit, or if the
21706 &%owngroups%& option is set. Otherwise it is false, and no group check occurs.
21710 .option check_owner redirect boolean "see below"
21711 When the &%file%& option is used, the owner of the file is checked only when
21712 this option is set. If &%check_local_user%& is set, the local user is
21713 permitted; otherwise the owner must be one of those listed in the &%owners%&
21714 option. The default value for this option is true if &%check_local_user%& or
21715 &%owners%& is set. Otherwise the default is false, and no owner check occurs.
21718 .option data redirect string&!! unset
21719 This option is mutually exclusive with &%file%&. One or other of them must be
21720 set, but not both. The contents of &%data%& are expanded, and then used as the
21721 list of forwarding items, or as a set of filtering instructions. If the
21722 expansion is forced to fail, or the result is an empty string or a string that
21723 has no effect (consists entirely of comments), the router declines.
21725 When filtering instructions are used, the string must begin with &"#Exim
21726 filter"&, and all comments in the string, including this initial one, must be
21727 terminated with newline characters. For example:
21729 data = #Exim filter\n\
21730 if $h_to: contains Exim then save $home/mail/exim endif
21732 If you are reading the data from a database where newlines cannot be included,
21733 you can use the &${sg}$& expansion item to turn the escape string of your
21734 choice into a newline.
21737 .option directory_transport redirect string&!! unset
21738 A &(redirect)& router sets up a direct delivery to a directory when a path name
21739 ending with a slash is specified as a new &"address"&. The transport used is
21740 specified by this option, which, after expansion, must be the name of a
21741 configured transport. This should normally be an &(appendfile)& transport.
21744 .option file redirect string&!! unset
21745 This option specifies the name of a file that contains the redirection data. It
21746 is mutually exclusive with the &%data%& option. The string is expanded before
21747 use; if the expansion is forced to fail, the router declines. Other expansion
21748 failures cause delivery to be deferred. The result of a successful expansion
21749 must be an absolute path. The entire file is read and used as the redirection
21750 data. If the data is an empty string or a string that has no effect (consists
21751 entirely of comments), the router declines.
21753 .cindex "NFS" "checking for file existence"
21754 If the attempt to open the file fails with a &"does not exist"& error, Exim
21755 runs a check on the containing directory,
21756 unless &%ignore_enotdir%& is true (see below).
21757 If the directory does not appear to exist, delivery is deferred. This can
21758 happen when users' &_.forward_& files are in NFS-mounted directories, and there
21759 is a mount problem. If the containing directory does exist, but the file does
21760 not, the router declines.
21763 .option file_transport redirect string&!! unset
21764 .vindex "&$address_file$&"
21765 A &(redirect)& router sets up a direct delivery to a file when a path name not
21766 ending in a slash is specified as a new &"address"&. The transport used is
21767 specified by this option, which, after expansion, must be the name of a
21768 configured transport. This should normally be an &(appendfile)& transport. When
21769 it is running, the filename is in &$address_file$&.
21772 .option filter_prepend_home redirect boolean true
21773 When this option is true, if a &(save)& command in an Exim filter specifies a
21774 relative path, and &$home$& is defined, it is automatically prepended to the
21775 relative path. If this option is set false, this action does not happen. The
21776 relative path is then passed to the transport unmodified.
21779 .option forbid_blackhole redirect boolean false
21780 .cindex "restricting access to features"
21781 .cindex "filter" "locking out certain features"
21782 If this option is true, the &':blackhole:'& item may not appear in a
21786 .option forbid_exim_filter redirect boolean false
21787 .cindex "restricting access to features"
21788 .cindex "filter" "locking out certain features"
21789 If this option is set true, only Sieve filters are permitted when
21790 &%allow_filter%& is true.
21795 .option forbid_file redirect boolean false
21796 .cindex "restricting access to features"
21797 .cindex "delivery" "to file; forbidding"
21798 .cindex "filter" "locking out certain features"
21799 .cindex "Sieve filter" "forbidding delivery to a file"
21800 .cindex "Sieve filter" "&""keep""& facility; disabling"
21801 If this option is true, this router may not generate a new address that
21802 specifies delivery to a local file or directory, either from a filter or from a
21803 conventional forward file. This option is forced to be true if &%one_time%& is
21804 set. It applies to Sieve filters as well as to Exim filters, but if true, it
21805 locks out the Sieve's &"keep"& facility.
21808 .option forbid_filter_dlfunc redirect boolean false
21809 .cindex "restricting access to features"
21810 .cindex "filter" "locking out certain features"
21811 If this option is true, string expansions in Exim filters are not allowed to
21812 make use of the &%dlfunc%& expansion facility to run dynamically loaded
21815 .option forbid_filter_existstest redirect boolean false
21816 .cindex "restricting access to features"
21817 .cindex "filter" "locking out certain features"
21818 .cindex "expansion" "statting a file"
21819 If this option is true, string expansions in Exim filters are not allowed to
21820 make use of the &%exists%& condition or the &%stat%& expansion item.
21822 .option forbid_filter_logwrite redirect boolean false
21823 .cindex "restricting access to features"
21824 .cindex "filter" "locking out certain features"
21825 If this option is true, use of the logging facility in Exim filters is not
21826 permitted. Logging is in any case available only if the filter is being run
21827 under some unprivileged uid (which is normally the case for ordinary users'
21828 &_.forward_& files).
21831 .option forbid_filter_lookup redirect boolean false
21832 .cindex "restricting access to features"
21833 .cindex "filter" "locking out certain features"
21834 If this option is true, string expansions in Exim filter files are not allowed
21835 to make use of &%lookup%& items.
21838 .option forbid_filter_perl redirect boolean false
21839 .cindex "restricting access to features"
21840 .cindex "filter" "locking out certain features"
21841 This option has an effect only if Exim is built with embedded Perl support. If
21842 it is true, string expansions in Exim filter files are not allowed to make use
21843 of the embedded Perl support.
21846 .option forbid_filter_readfile redirect boolean false
21847 .cindex "restricting access to features"
21848 .cindex "filter" "locking out certain features"
21849 If this option is true, string expansions in Exim filter files are not allowed
21850 to make use of &%readfile%& items.
21853 .option forbid_filter_readsocket redirect boolean false
21854 .cindex "restricting access to features"
21855 .cindex "filter" "locking out certain features"
21856 If this option is true, string expansions in Exim filter files are not allowed
21857 to make use of &%readsocket%& items.
21860 .option forbid_filter_reply redirect boolean false
21861 .cindex "restricting access to features"
21862 .cindex "filter" "locking out certain features"
21863 If this option is true, this router may not generate an automatic reply
21864 message. Automatic replies can be generated only from Exim or Sieve filter
21865 files, not from traditional forward files. This option is forced to be true if
21866 &%one_time%& is set.
21869 .option forbid_filter_run redirect boolean false
21870 .cindex "restricting access to features"
21871 .cindex "filter" "locking out certain features"
21872 If this option is true, string expansions in Exim filter files are not allowed
21873 to make use of &%run%& items.
21876 .option forbid_include redirect boolean false
21877 .cindex "restricting access to features"
21878 .cindex "filter" "locking out certain features"
21879 If this option is true, items of the form
21881 :include:<path name>
21883 are not permitted in non-filter redirection lists.
21886 .option forbid_pipe redirect boolean false
21887 .cindex "restricting access to features"
21888 .cindex "filter" "locking out certain features"
21889 .cindex "delivery" "to pipe; forbidding"
21890 If this option is true, this router may not generate a new address which
21891 specifies delivery to a pipe, either from an Exim filter or from a conventional
21892 forward file. This option is forced to be true if &%one_time%& is set.
21895 .option forbid_sieve_filter redirect boolean false
21896 .cindex "restricting access to features"
21897 .cindex "filter" "locking out certain features"
21898 If this option is set true, only Exim filters are permitted when
21899 &%allow_filter%& is true.
21902 .cindex "SMTP" "error codes"
21903 .option forbid_smtp_code redirect boolean false
21904 If this option is set true, any SMTP error codes that are present at the start
21905 of messages specified for &`:defer:`& or &`:fail:`& are quietly ignored, and
21906 the default codes (451 and 550, respectively) are always used.
21911 .option hide_child_in_errmsg redirect boolean false
21912 .cindex "bounce message" "redirection details; suppressing"
21913 If this option is true, it prevents Exim from quoting a child address if it
21914 generates a bounce or delay message for it. Instead it says &"an address
21915 generated from <&'the top level address'&>"&. Of course, this applies only to
21916 bounces generated locally. If a message is forwarded to another host, &'its'&
21917 bounce may well quote the generated address.
21920 .option ignore_eacces redirect boolean false
21922 If this option is set and an attempt to open a redirection file yields the
21923 EACCES error (permission denied), the &(redirect)& router behaves as if the
21924 file did not exist.
21927 .option ignore_enotdir redirect boolean false
21929 If this option is set and an attempt to open a redirection file yields the
21930 ENOTDIR error (something on the path is not a directory), the &(redirect)&
21931 router behaves as if the file did not exist.
21933 Setting &%ignore_enotdir%& has another effect as well: When a &(redirect)&
21934 router that has the &%file%& option set discovers that the file does not exist
21935 (the ENOENT error), it tries to &[stat()]& the parent directory, as a check
21936 against unmounted NFS directories. If the parent can not be statted, delivery
21937 is deferred. However, it seems wrong to do this check when &%ignore_enotdir%&
21938 is set, because that option tells Exim to ignore &"something on the path is not
21939 a directory"& (the ENOTDIR error). This is a confusing area, because it seems
21940 that some operating systems give ENOENT where others give ENOTDIR.
21944 .option include_directory redirect string unset
21945 If this option is set, the path names of any &':include:'& items in a
21946 redirection list must start with this directory.
21949 .option modemask redirect "octal integer" 022
21950 This specifies mode bits which must not be set for a file specified by the
21951 &%file%& option. If any of the forbidden bits are set, delivery is deferred.
21954 .option one_time redirect boolean false
21955 .cindex "one-time aliasing/forwarding expansion"
21956 .cindex "alias file" "one-time expansion"
21957 .cindex "forward file" "one-time expansion"
21958 .cindex "mailing lists" "one-time expansion"
21959 .cindex "address redirection" "one-time expansion"
21960 Sometimes the fact that Exim re-evaluates aliases and reprocesses redirection
21961 files each time it tries to deliver a message causes a problem when one or more
21962 of the generated addresses fails be delivered at the first attempt. The problem
21963 is not one of duplicate delivery &-- Exim is clever enough to handle that &--
21964 but of what happens when the redirection list changes during the time that the
21965 message is on Exim's queue. This is particularly true in the case of mailing
21966 lists, where new subscribers might receive copies of messages that were posted
21967 before they subscribed.
21969 If &%one_time%& is set and any addresses generated by the router fail to
21970 deliver at the first attempt, the failing addresses are added to the message as
21971 &"top level"& addresses, and the parent address that generated them is marked
21972 &"delivered"&. Thus, redirection does not happen again at the next delivery
21975 &*Warning 1*&: Any header line addition or removal that is specified by this
21976 router would be lost if delivery did not succeed at the first attempt. For this
21977 reason, the &%headers_add%& and &%headers_remove%& generic options are not
21978 permitted when &%one_time%& is set.
21980 &*Warning 2*&: To ensure that the router generates only addresses (as opposed
21981 to pipe or file deliveries or auto-replies) &%forbid_file%&, &%forbid_pipe%&,
21982 and &%forbid_filter_reply%& are forced to be true when &%one_time%& is set.
21984 &*Warning 3*&: The &%unseen%& generic router option may not be set with
21987 The original top-level address is remembered with each of the generated
21988 addresses, and is output in any log messages. However, any intermediate parent
21989 addresses are not recorded. This makes a difference to the log only if
21990 &%all_parents%& log selector is set. It is expected that &%one_time%& will
21991 typically be used for mailing lists, where there is normally just one level of
21995 .option owners redirect "string list" unset
21996 .cindex "ownership" "alias file"
21997 .cindex "ownership" "forward file"
21998 .cindex "alias file" "ownership"
21999 .cindex "forward file" "ownership"
22000 This specifies a list of permitted owners for the file specified by &%file%&.
22001 This list is in addition to the local user when &%check_local_user%& is set.
22002 See &%check_owner%& above.
22005 .option owngroups redirect "string list" unset
22006 This specifies a list of permitted groups for the file specified by &%file%&.
22007 The list is in addition to the local user's primary group when
22008 &%check_local_user%& is set. See &%check_group%& above.
22011 .option pipe_transport redirect string&!! unset
22012 .vindex "&$address_pipe$&"
22013 A &(redirect)& router sets up a direct delivery to a pipe when a string
22014 starting with a vertical bar character is specified as a new &"address"&. The
22015 transport used is specified by this option, which, after expansion, must be the
22016 name of a configured transport. This should normally be a &(pipe)& transport.
22017 When the transport is run, the pipe command is in &$address_pipe$&.
22020 .option qualify_domain redirect string&!! unset
22021 .vindex "&$qualify_recipient$&"
22022 If this option is set, and an unqualified address (one without a domain) is
22023 generated, and that address would normally be qualified by the global setting
22024 in &%qualify_recipient%&, it is instead qualified with the domain specified by
22025 expanding this string. If the expansion fails, the router declines. If you want
22026 to revert to the default, you can have the expansion generate
22027 &$qualify_recipient$&.
22029 This option applies to all unqualified addresses generated by Exim filters,
22030 but for traditional &_.forward_& files, it applies only to addresses that are
22031 not preceded by a backslash. Sieve filters cannot generate unqualified
22034 .option qualify_preserve_domain redirect boolean false
22035 .cindex "domain" "in redirection; preserving"
22036 .cindex "preserving domain in redirection"
22037 .cindex "address redirection" "domain; preserving"
22038 If this option is set, the router's local &%qualify_domain%& option must not be
22039 set (a configuration error occurs if it is). If an unqualified address (one
22040 without a domain) is generated, it is qualified with the domain of the parent
22041 address (the immediately preceding ancestor) instead of the global
22042 &%qualify_recipient%& value. In the case of a traditional &_.forward_& file,
22043 this applies whether or not the address is preceded by a backslash.
22046 .option repeat_use redirect boolean true
22047 If this option is set false, the router is skipped for a child address that has
22048 any ancestor that was routed by this router. This test happens before any of
22049 the other preconditions are tested. Exim's default anti-looping rules skip
22050 only when the ancestor is the same as the current address. See also
22051 &%check_ancestor%& above and the generic &%redirect_router%& option.
22054 .option reply_transport redirect string&!! unset
22055 A &(redirect)& router sets up an automatic reply when a &%mail%& or
22056 &%vacation%& command is used in a filter file. The transport used is specified
22057 by this option, which, after expansion, must be the name of a configured
22058 transport. This should normally be an &(autoreply)& transport. Other transports
22059 are unlikely to do anything sensible or useful.
22062 .option rewrite redirect boolean true
22063 .cindex "address redirection" "disabling rewriting"
22064 If this option is set false, addresses generated by the router are not
22065 subject to address rewriting. Otherwise, they are treated like new addresses
22066 and are rewritten according to the global rewriting rules.
22069 .option sieve_subaddress redirect string&!! unset
22070 The value of this option is passed to a Sieve filter to specify the
22071 :subaddress part of an address.
22073 .option sieve_useraddress redirect string&!! unset
22074 The value of this option is passed to a Sieve filter to specify the :user part
22075 of an address. However, if it is unset, the entire original local part
22076 (including any prefix or suffix) is used for :user.
22079 .option sieve_vacation_directory redirect string&!! unset
22080 .cindex "Sieve filter" "vacation directory"
22081 To enable the &"vacation"& extension for Sieve filters, you must set
22082 &%sieve_vacation_directory%& to the directory where vacation databases are held
22083 (do not put anything else in that directory), and ensure that the
22084 &%reply_transport%& option refers to an &(autoreply)& transport. Each user
22085 needs their own directory; Exim will create it if necessary.
22089 .option skip_syntax_errors redirect boolean false
22090 .cindex "forward file" "broken"
22091 .cindex "address redirection" "broken files"
22092 .cindex "alias file" "broken"
22093 .cindex "broken alias or forward files"
22094 .cindex "ignoring faulty addresses"
22095 .cindex "skipping faulty addresses"
22096 .cindex "error" "skipping bad syntax"
22097 If &%skip_syntax_errors%& is set, syntactically malformed addresses in
22098 non-filter redirection data are skipped, and each failing address is logged. If
22099 &%syntax_errors_to%& is set, a message is sent to the address it defines,
22100 giving details of the failures. If &%syntax_errors_text%& is set, its contents
22101 are expanded and placed at the head of the error message generated by
22102 &%syntax_errors_to%&. Usually it is appropriate to set &%syntax_errors_to%& to
22103 be the same address as the generic &%errors_to%& option. The
22104 &%skip_syntax_errors%& option is often used when handling mailing lists.
22106 If all the addresses in a redirection list are skipped because of syntax
22107 errors, the router declines to handle the original address, and it is passed to
22108 the following routers.
22110 If &%skip_syntax_errors%& is set when an Exim filter is interpreted, any syntax
22111 error in the filter causes filtering to be abandoned without any action being
22112 taken. The incident is logged, and the router declines to handle the address,
22113 so it is passed to the following routers.
22115 .cindex "Sieve filter" "syntax errors in"
22116 Syntax errors in a Sieve filter file cause the &"keep"& action to occur. This
22117 action is specified by RFC 3028. The values of &%skip_syntax_errors%&,
22118 &%syntax_errors_to%&, and &%syntax_errors_text%& are not used.
22120 &%skip_syntax_errors%& can be used to specify that errors in users' forward
22121 lists or filter files should not prevent delivery. The &%syntax_errors_to%&
22122 option, used with an address that does not get redirected, can be used to
22123 notify users of these errors, by means of a router like this:
22129 file = $home/.forward
22130 file_transport = address_file
22131 pipe_transport = address_pipe
22132 reply_transport = address_reply
22135 syntax_errors_to = real-$local_part@$domain
22136 syntax_errors_text = \
22137 This is an automatically generated message. An error has\n\
22138 been found in your .forward file. Details of the error are\n\
22139 reported below. While this error persists, you will receive\n\
22140 a copy of this message for every message that is addressed\n\
22141 to you. If your .forward file is a filter file, or if it is\n\
22142 a non-filter file containing no valid forwarding addresses,\n\
22143 a copy of each incoming message will be put in your normal\n\
22144 mailbox. If a non-filter file contains at least one valid\n\
22145 forwarding address, forwarding to the valid addresses will\n\
22146 happen, and those will be the only deliveries that occur.
22148 You also need a router to ensure that local addresses that are prefixed by
22149 &`real-`& are recognized, but not forwarded or filtered. For example, you could
22150 put this immediately before the &(userforward)& router:
22155 local_part_prefix = real-
22156 transport = local_delivery
22158 For security, it would probably be a good idea to restrict the use of this
22159 router to locally-generated messages, using a condition such as this:
22161 condition = ${if match {$sender_host_address}\
22162 {\N^(|127\.0\.0\.1)$\N}}
22166 .option syntax_errors_text redirect string&!! unset
22167 See &%skip_syntax_errors%& above.
22170 .option syntax_errors_to redirect string unset
22171 See &%skip_syntax_errors%& above.
22172 .ecindex IIDredrou1
22173 .ecindex IIDredrou2
22180 . ////////////////////////////////////////////////////////////////////////////
22181 . ////////////////////////////////////////////////////////////////////////////
22183 .chapter "Environment for running local transports" "CHAPenvironment" &&&
22184 "Environment for local transports"
22185 .scindex IIDenvlotra1 "local transports" "environment for"
22186 .scindex IIDenvlotra2 "environment" "local transports"
22187 .scindex IIDenvlotra3 "transport" "local; environment for"
22188 Local transports handle deliveries to files and pipes. (The &(autoreply)&
22189 transport can be thought of as similar to a pipe.) Exim always runs transports
22190 in subprocesses, under specified uids and gids. Typical deliveries to local
22191 mailboxes run under the uid and gid of the local user.
22193 Exim also sets a specific current directory while running the transport; for
22194 some transports a home directory setting is also relevant. The &(pipe)&
22195 transport is the only one that sets up environment variables; see section
22196 &<<SECTpipeenv>>& for details.
22198 The values used for the uid, gid, and the directories may come from several
22199 different places. In many cases, the router that handles the address associates
22200 settings with that address as a result of its &%check_local_user%&, &%group%&,
22201 or &%user%& options. However, values may also be given in the transport's own
22202 configuration, and these override anything that comes from the router.
22206 .section "Concurrent deliveries" "SECID131"
22207 .cindex "concurrent deliveries"
22208 .cindex "simultaneous deliveries"
22209 If two different messages for the same local recipient arrive more or less
22210 simultaneously, the two delivery processes are likely to run concurrently. When
22211 the &(appendfile)& transport is used to write to a file, Exim applies locking
22212 rules to stop concurrent processes from writing to the same file at the same
22215 However, when you use a &(pipe)& transport, it is up to you to arrange any
22216 locking that is needed. Here is a silly example:
22220 command = /bin/sh -c 'cat >>/some/file'
22222 This is supposed to write the message at the end of the file. However, if two
22223 messages arrive at the same time, the file will be scrambled. You can use the
22224 &%exim_lock%& utility program (see section &<<SECTmailboxmaint>>&) to lock a
22225 file using the same algorithm that Exim itself uses.
22230 .section "Uids and gids" "SECTenvuidgid"
22231 .cindex "local transports" "uid and gid"
22232 .cindex "transport" "local; uid and gid"
22233 All transports have the options &%group%& and &%user%&. If &%group%& is set, it
22234 overrides any group that the router set in the address, even if &%user%& is not
22235 set for the transport. This makes it possible, for example, to run local mail
22236 delivery under the uid of the recipient (set by the router), but in a special
22237 group (set by the transport). For example:
22240 # User/group are set by check_local_user in this router
22244 transport = group_delivery
22247 # This transport overrides the group
22249 driver = appendfile
22250 file = /var/spool/mail/$local_part_data
22253 If &%user%& is set for a transport, its value overrides what is set in the
22254 address by the router. If &%user%& is non-numeric and &%group%& is not set, the
22255 gid associated with the user is used. If &%user%& is numeric, &%group%& must be
22258 .oindex "&%initgroups%&"
22259 When the uid is taken from the transport's configuration, the &[initgroups()]&
22260 function is called for the groups associated with that uid if the
22261 &%initgroups%& option is set for the transport. When the uid is not specified
22262 by the transport, but is associated with the address by a router, the option
22263 for calling &[initgroups()]& is taken from the router configuration.
22265 .cindex "&(pipe)& transport" "uid for"
22266 The &(pipe)& transport contains the special option &%pipe_as_creator%&. If this
22267 is set and &%user%& is not set, the uid of the process that called Exim to
22268 receive the message is used, and if &%group%& is not set, the corresponding
22269 original gid is also used.
22271 This is the detailed preference order for obtaining a gid; the first of the
22272 following that is set is used:
22275 A &%group%& setting of the transport;
22277 A &%group%& setting of the router;
22279 A gid associated with a user setting of the router, either as a result of
22280 &%check_local_user%& or an explicit non-numeric &%user%& setting;
22282 The group associated with a non-numeric &%user%& setting of the transport;
22284 In a &(pipe)& transport, the creator's gid if &%deliver_as_creator%& is set and
22285 the uid is the creator's uid;
22287 The Exim gid if the Exim uid is being used as a default.
22290 If, for example, the user is specified numerically on the router and there are
22291 no group settings, no gid is available. In this situation, an error occurs.
22292 This is different for the uid, for which there always is an ultimate default.
22293 The first of the following that is set is used:
22296 A &%user%& setting of the transport;
22298 In a &(pipe)& transport, the creator's uid if &%deliver_as_creator%& is set;
22300 A &%user%& setting of the router;
22302 A &%check_local_user%& setting of the router;
22307 Of course, an error will still occur if the uid that is chosen is on the
22308 &%never_users%& list.
22314 .section "Current and home directories" "SECID132"
22315 .cindex "current directory for local transport"
22316 .cindex "home directory" "for local transport"
22317 .cindex "transport" "local; home directory for"
22318 .cindex "transport" "local; current directory for"
22319 Routers may set current and home directories for local transports by means of
22320 the &%transport_current_directory%& and &%transport_home_directory%& options.
22321 However, if the transport's &%current_directory%& or &%home_directory%& options
22322 are set, they override the router's values. In detail, the home directory
22323 for a local transport is taken from the first of these values that is set:
22326 The &%home_directory%& option on the transport;
22328 The &%transport_home_directory%& option on the router;
22330 The password data if &%check_local_user%& is set on the router;
22332 The &%router_home_directory%& option on the router.
22335 The current directory is taken from the first of these values that is set:
22338 The &%current_directory%& option on the transport;
22340 The &%transport_current_directory%& option on the router.
22344 If neither the router nor the transport sets a current directory, Exim uses the
22345 value of the home directory, if it is set. Otherwise it sets the current
22346 directory to &_/_& before running a local transport.
22350 .section "Expansion variables derived from the address" "SECID133"
22351 .vindex "&$domain$&"
22352 .vindex "&$local_part$&"
22353 .vindex "&$original_domain$&"
22354 Normally a local delivery is handling a single address, and in that case the
22355 variables such as &$domain$& and &$local_part$& are set during local
22356 deliveries. However, in some circumstances more than one address may be handled
22357 at once (for example, while writing batch SMTP for onward transmission by some
22358 other means). In this case, the variables associated with the local part are
22359 never set, &$domain$& is set only if all the addresses have the same domain,
22360 and &$original_domain$& is never set.
22361 .ecindex IIDenvlotra1
22362 .ecindex IIDenvlotra2
22363 .ecindex IIDenvlotra3
22371 . ////////////////////////////////////////////////////////////////////////////
22372 . ////////////////////////////////////////////////////////////////////////////
22374 .chapter "Generic options for transports" "CHAPtransportgeneric"
22375 .scindex IIDgenoptra1 "generic options" "transport"
22376 .scindex IIDgenoptra2 "options" "generic; for transports"
22377 .scindex IIDgenoptra3 "transport" "generic options for"
22378 The name of a transport is limited to be &drivernamemax; ASCII characters long;
22379 prior to Exim 4.95 names would be silently truncated at this length, but now
22382 The following generic options apply to all transports:
22385 .option body_only transports boolean false
22386 .cindex "transport" "body only"
22387 .cindex "message" "transporting body only"
22388 .cindex "body of message" "transporting"
22389 If this option is set, the message's headers are not transported. It is
22390 mutually exclusive with &%headers_only%&. If it is used with the &(appendfile)&
22391 or &(pipe)& transports, the settings of &%message_prefix%& and
22392 &%message_suffix%& should be checked, because this option does not
22393 automatically suppress them.
22396 .option current_directory transports string&!! unset
22397 .cindex "transport" "current directory for"
22398 This specifies the current directory that is to be set while running the
22399 transport, overriding any value that may have been set by the router.
22400 If the expansion fails for any reason, including forced failure, an error is
22401 logged, and delivery is deferred.
22404 .option disable_logging transports boolean false
22405 If this option is set true, nothing is logged for any
22406 deliveries by the transport or for any
22407 transport errors. You should not set this option unless you really, really know
22408 what you are doing.
22411 .option debug_print transports string&!! unset
22412 .cindex "testing" "variables in drivers"
22413 If this option is set and debugging is enabled (see the &%-d%& command line
22414 option), the string is expanded and included in the debugging output when the
22416 If expansion of the string fails, the error message is written to the debugging
22417 output, and Exim carries on processing.
22418 This facility is provided to help with checking out the values of variables and
22419 so on when debugging driver configurations. For example, if a &%headers_add%&
22420 option is not working properly, &%debug_print%& could be used to output the
22421 variables it references. A newline is added to the text if it does not end with
22423 The variables &$transport_name$& and &$router_name$& contain the name of the
22424 transport and the router that called it.
22426 .option delivery_date_add transports boolean false
22427 .cindex "&'Delivery-date:'& header line"
22428 If this option is true, a &'Delivery-date:'& header is added to the message.
22429 This gives the actual time the delivery was made. As this is not a standard
22430 header, Exim has a configuration option (&%delivery_date_remove%&) which
22431 requests its removal from incoming messages, so that delivered messages can
22432 safely be resent to other recipients.
22435 .option driver transports string unset
22436 This specifies which of the available transport drivers is to be used.
22437 There is no default, and this option must be set for every transport.
22440 .option envelope_to_add transports boolean false
22441 .cindex "&'Envelope-to:'& header line"
22442 If this option is true, an &'Envelope-to:'& header is added to the message.
22443 This gives the original address(es) in the incoming envelope that caused this
22444 delivery to happen. More than one address may be present if the transport is
22445 configured to handle several addresses at once, or if more than one original
22446 address was redirected to the same final address. As this is not a standard
22447 header, Exim has a configuration option (&%envelope_to_remove%&) which requests
22448 its removal from incoming messages, so that delivered messages can safely be
22449 resent to other recipients.
22451 &*Note:*& If used on a transport handling multiple recipients
22452 (the smtp transport unless &%rcpt_max%& is 1, the appendfile, pipe or lmtp
22453 transport if &%batch_max%& is greater than 1)
22454 then information about Bcc recipients will be leaked.
22455 Doing so is generally not advised.
22458 .option event_action transports string&!! unset
22460 This option declares a string to be expanded for Exim's events mechanism.
22461 For details see chapter &<<CHAPevents>>&.
22464 .option group transports string&!! "Exim group"
22465 .cindex "transport" "group; specifying"
22466 This option specifies a gid for running the transport process, overriding any
22467 value that the router supplies, and also overriding any value associated with
22468 &%user%& (see below).
22471 .option headers_add transports list&!! unset
22472 .cindex "header lines" "adding in transport"
22473 .cindex "transport" "header lines; adding"
22474 This option specifies a list of text headers,
22475 newline-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
22476 which are (separately) expanded and added to the header
22477 portion of a message as it is transported, as described in section
22478 &<<SECTheadersaddrem>>&. Additional header lines can also be specified by
22479 routers. If the result of the expansion is an empty string, or if the expansion
22480 is forced to fail, no action is taken. Other expansion failures are treated as
22481 errors and cause the delivery to be deferred.
22483 Unlike most options, &%headers_add%& can be specified multiple times
22484 for a transport; all listed headers are added.
22487 .option headers_only transports boolean false
22488 .cindex "transport" "header lines only"
22489 .cindex "message" "transporting headers only"
22490 .cindex "header lines" "transporting"
22491 If this option is set, the message's body is not transported. It is mutually
22492 exclusive with &%body_only%&. If it is used with the &(appendfile)& or &(pipe)&
22493 transports, the settings of &%message_prefix%& and &%message_suffix%& should be
22494 checked, since this option does not automatically suppress them.
22497 .option headers_remove transports list&!! unset
22498 .cindex "header lines" "removing"
22499 .cindex "transport" "header lines; removing"
22500 This option specifies a list of text headers,
22501 colon-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
22502 to be removed from the message.
22503 However, the option has no effect when an address is just being verified.
22504 Each list item is separately expanded.
22505 If the result of the expansion is an empty string, or if the expansion
22506 is forced to fail, no action is taken. Other expansion failures are treated as
22507 errors and cause the delivery to be deferred.
22508 If an item ends in *, it will match any header with the given prefix.
22510 Matching headers are omitted from the message as it is transported, as described
22511 in section &<<SECTheadersaddrem>>&. Header removal can also be specified by
22514 Unlike most options, &%headers_remove%& can be specified multiple times
22515 for a transport; all listed headers are removed.
22517 &*Warning*&: Because of the separate expansion of the list items,
22518 items that contain a list separator must have it doubled.
22519 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
22523 .option headers_rewrite transports string unset
22524 .cindex "transport" "header lines; rewriting"
22525 .cindex "rewriting" "at transport time"
22526 This option allows addresses in header lines to be rewritten at transport time,
22527 that is, as the message is being copied to its destination. The contents of the
22528 option are a colon-separated list of rewriting rules. Each rule is in exactly
22529 the same form as one of the general rewriting rules that are applied when a
22530 message is received. These are described in chapter &<<CHAPrewrite>>&. For
22533 headers_rewrite = a@b c@d f : \
22536 changes &'a@b'& into &'c@d'& in &'From:'& header lines, and &'x@y'& into
22537 &'w@z'& in all address-bearing header lines. The rules are applied to the
22538 header lines just before they are written out at transport time, so they affect
22539 only those copies of the message that pass through the transport. However, only
22540 the message's original header lines, and any that were added by a system
22541 filter, are rewritten. If a router or transport adds header lines, they are not
22542 affected by this option. These rewriting rules are &'not'& applied to the
22543 envelope. You can change the return path using &%return_path%&, but you cannot
22544 change envelope recipients at this time.
22547 .option home_directory transports string&!! unset
22548 .cindex "transport" "home directory for"
22550 This option specifies a home directory setting for a local transport,
22551 overriding any value that may be set by the router. The home directory is
22552 placed in &$home$& while expanding the transport's private options. It is also
22553 used as the current directory if no current directory is set by the
22554 &%current_directory%& option on the transport or the
22555 &%transport_current_directory%& option on the router. If the expansion fails
22556 for any reason, including forced failure, an error is logged, and delivery is
22560 .option initgroups transports boolean false
22561 .cindex "additional groups"
22562 .cindex "groups" "additional"
22563 .cindex "transport" "group; additional"
22564 If this option is true and the uid for the delivery process is provided by the
22565 transport, the &[initgroups()]& function is called when running the transport
22566 to ensure that any additional groups associated with the uid are set up.
22569 .option max_parallel transports integer&!! unset
22570 .cindex limit "transport parallelism"
22571 .cindex transport "parallel processes"
22572 .cindex transport "concurrency limit"
22573 .cindex "delivery" "parallelism for transport"
22574 If this option is set and expands to an integer greater than zero
22575 it limits the number of concurrent runs of the transport.
22576 The control does not apply to shadow transports.
22578 .cindex "hints database" "transport concurrency control"
22579 Exim implements this control by means of a hints database in which a record is
22580 incremented whenever a transport process is being created. The record
22581 is decremented and possibly removed when the process terminates.
22582 Obviously there is scope for
22583 records to get left lying around if there is a system or program crash. To
22584 guard against this, Exim ignores any records that are more than six hours old.
22586 If you use this option, you should also arrange to delete the
22587 relevant hints database whenever your system reboots. The names of the files
22588 start with &_misc_& and they are kept in the &_spool/db_& directory. There
22589 may be one or two files, depending on the type of DBM in use. The same files
22590 are used for ETRN and smtp transport serialization.
22593 .option message_size_limit transports string&!! 0
22594 .cindex "limit" "message size per transport"
22595 .cindex "size" "of message, limit"
22596 .cindex "transport" "message size; limiting"
22597 This option controls the size of messages passed through the transport. It is
22598 expanded before use; the result of the expansion must be a sequence of decimal
22599 digits, optionally followed by K or M. If the expansion fails for any reason,
22600 including forced failure, or if the result is not of the required form,
22601 delivery is deferred. If the value is greater than zero and the size of a
22602 message exceeds this limit, the address is failed. If there is any chance that
22603 the resulting bounce message could be routed to the same transport, you should
22604 ensure that &%return_size_limit%& is less than the transport's
22605 &%message_size_limit%&, as otherwise the bounce message will fail to get
22610 .option rcpt_include_affixes transports boolean false
22611 .cindex "prefix" "for local part, including in envelope"
22612 .cindex "suffix for local part" "including in envelope"
22613 .cindex "local part" "prefix"
22614 .cindex "local part" "suffix"
22615 When this option is false (the default), and an address that has had any
22616 affixes (prefixes or suffixes) removed from the local part is delivered by any
22617 form of SMTP or LMTP, the affixes are not included. For example, if a router
22620 local_part_prefix = *-
22622 routes the address &'abc-xyz@some.domain'& to an SMTP transport, the envelope
22625 RCPT TO:<xyz@some.domain>
22627 This is also the case when an ACL-time callout is being used to verify a
22628 recipient address. However, if &%rcpt_include_affixes%& is set true, the
22629 whole local part is included in the RCPT command. This option applies to BSMTP
22630 deliveries by the &(appendfile)& and &(pipe)& transports as well as to the
22631 &(lmtp)& and &(smtp)& transports.
22634 .option retry_use_local_part transports boolean "see below"
22635 .cindex "hints database" "retry keys"
22636 When a delivery suffers a temporary failure, a retry record is created
22637 in Exim's hints database. For remote deliveries, the key for the retry record
22638 is based on the name and/or IP address of the failing remote host. For local
22639 deliveries, the key is normally the entire address, including both the local
22640 part and the domain. This is suitable for most common cases of local delivery
22641 temporary failure &-- for example, exceeding a mailbox quota should delay only
22642 deliveries to that mailbox, not to the whole domain.
22644 However, in some special cases you may want to treat a temporary local delivery
22645 as a failure associated with the domain, and not with a particular local part.
22646 (For example, if you are storing all mail for some domain in files.) You can do
22647 this by setting &%retry_use_local_part%& false.
22649 For all the local transports, its default value is true. For remote transports,
22650 the default value is false for tidiness, but changing the value has no effect
22651 on a remote transport in the current implementation.
22654 .option return_path transports string&!! unset
22655 .cindex "envelope sender"
22656 .cindex "envelope from"
22657 .cindex "transport" "return path; changing"
22658 .cindex "return path" "changing in transport"
22659 If this option is set, the string is expanded at transport time and replaces
22660 the existing return path (envelope sender) value in the copy of the message
22661 that is being delivered. An empty return path is permitted. This feature is
22662 designed for remote deliveries, where the value of this option is used in the
22663 SMTP MAIL command. If you set &%return_path%& for a local transport, the
22664 only effect is to change the address that is placed in the &'Return-path:'&
22665 header line, if one is added to the message (see the next option).
22667 &*Note:*& A changed return path is not logged unless you add
22668 &%return_path_on_delivery%& to the log selector.
22670 .vindex "&$return_path$&"
22671 The expansion can refer to the existing value via &$return_path$&. This is
22672 either the message's envelope sender, or an address set by the
22673 &%errors_to%& option on a router. If the expansion is forced to fail, no
22674 replacement occurs; if it fails for another reason, delivery is deferred. This
22675 option can be used to support VERP (Variable Envelope Return Paths) &-- see
22676 section &<<SECTverp>>&.
22678 &*Note*&: If a delivery error is detected locally, including the case when a
22679 remote server rejects a message at SMTP time, the bounce message is not sent to
22680 the value of this option. It is sent to the previously set errors address.
22681 This defaults to the incoming sender address, but can be changed by setting
22682 &%errors_to%& in a router.
22686 .option return_path_add transports boolean false
22687 .chindex Return-path:
22688 If this option is true, a &'Return-path:'& header is added to the message.
22689 Although the return path is normally available in the prefix line of BSD
22690 mailboxes, this is commonly not displayed by MUAs, and so the user does not
22691 have easy access to it.
22693 RFC 2821 states that the &'Return-path:'& header is added to a message &"when
22694 the delivery SMTP server makes the final delivery"&. This implies that this
22695 header should not be present in incoming messages. Exim has a configuration
22696 option, &%return_path_remove%&, which requests removal of this header from
22697 incoming messages, so that delivered messages can safely be resent to other
22701 .option shadow_condition transports string&!! unset
22702 See &%shadow_transport%& below.
22705 .option shadow_transport transports string unset
22706 .cindex "shadow transport"
22707 .cindex "transport" "shadow"
22708 A local transport may set the &%shadow_transport%& option to the name of
22709 another local transport. Shadow remote transports are not supported.
22711 Whenever a delivery to the main transport succeeds, and either
22712 &%shadow_condition%& is unset, or its expansion does not result in the empty
22713 string or one of the strings &"0"& or &"no"& or &"false"&, the message is also
22714 passed to the shadow transport, with the same delivery address or addresses. If
22715 expansion fails, no action is taken except that non-forced expansion failures
22716 cause a log line to be written.
22718 The result of the shadow transport is discarded and does not affect the
22719 subsequent processing of the message. Only a single level of shadowing is
22720 provided; the &%shadow_transport%& option is ignored on any transport when it
22721 is running as a shadow. Options concerned with output from pipes are also
22722 ignored. The log line for the successful delivery has an item added on the end,
22725 ST=<shadow transport name>
22727 If the shadow transport did not succeed, the error message is put in
22728 parentheses afterwards. Shadow transports can be used for a number of different
22729 purposes, including keeping more detailed log information than Exim normally
22730 provides, and implementing automatic acknowledgment policies based on message
22731 headers that some sites insist on.
22734 .option transport_filter transports string&!! unset
22735 .cindex "transport" "filter"
22736 .cindex "filter" "transport filter"
22737 This option sets up a filtering (in the Unix shell sense) process for messages
22738 at transport time. It should not be confused with mail filtering as set up by
22739 individual users or via a system filter.
22740 If unset, or expanding to an empty string, no filtering is done.
22742 When the message is about to be written out, the command specified by
22743 &%transport_filter%& is started up in a separate, parallel process, and
22744 the entire message, including the header lines, is passed to it on its standard
22745 input (this in fact is done from a third process, to avoid deadlock). The
22746 command must be specified as an absolute path.
22748 The lines of the message that are written to the transport filter are
22749 terminated by newline (&"\n"&). The message is passed to the filter before any
22750 SMTP-specific processing, such as turning &"\n"& into &"\r\n"& and escaping
22751 lines beginning with a dot, and also before any processing implied by the
22752 settings of &%check_string%& and &%escape_string%& in the &(appendfile)& or
22753 &(pipe)& transports.
22755 The standard error for the filter process is set to the same destination as its
22756 standard output; this is read and written to the message's ultimate
22757 destination. The process that writes the message to the filter, the
22758 filter itself, and the original process that reads the result and delivers it
22759 are all run in parallel, like a shell pipeline.
22761 The filter can perform any transformations it likes, but of course should take
22762 care not to break RFC 2822 syntax. Exim does not check the result, except to
22763 test for a final newline when SMTP is in use. All messages transmitted over
22764 SMTP must end with a newline, so Exim supplies one if it is missing.
22766 .cindex "content scanning" "per user"
22767 A transport filter can be used to provide content-scanning on a per-user basis
22768 at delivery time if the only required effect of the scan is to modify the
22769 message. For example, a content scan could insert a new header line containing
22770 a spam score. This could be interpreted by a filter in the user's MUA. It is
22771 not possible to discard a message at this stage.
22773 .cindex "SIZE" "ESMTP extension"
22774 A problem might arise if the filter increases the size of a message that is
22775 being sent down an SMTP connection. If the receiving SMTP server has indicated
22776 support for the SIZE parameter, Exim will have sent the size of the message
22777 at the start of the SMTP session. If what is actually sent is substantially
22778 more, the server might reject the message. This can be worked round by setting
22779 the &%size_addition%& option on the &(smtp)& transport, either to allow for
22780 additions to the message, or to disable the use of SIZE altogether.
22782 .vindex "&$pipe_addresses$&"
22783 The value of the &%transport_filter%& option is the command string for starting
22784 the filter, which is run directly from Exim, not under a shell. The string is
22785 parsed by Exim in the same way as a command string for the &(pipe)& transport:
22786 Exim breaks it up into arguments and then expands each argument separately (see
22787 section &<<SECThowcommandrun>>&). Any kind of expansion failure causes delivery
22788 to be deferred. The special argument &$pipe_addresses$& is replaced by a number
22789 of arguments, one for each address that applies to this delivery. (This isn't
22790 an ideal name for this feature here, but as it was already implemented for the
22791 &(pipe)& transport, it seemed sensible not to change it.)
22794 .vindex "&$host_address$&"
22795 The expansion variables &$host$& and &$host_address$& are available when the
22796 transport is a remote one. They contain the name and IP address of the host to
22797 which the message is being sent. For example:
22798 . used to have $sender_address in this cmdline, but it's tainted
22800 transport_filter = /some/directory/transport-filter.pl \
22801 $host $host_address $pipe_addresses
22804 Two problems arise if you want to use more complicated expansion items to
22805 generate transport filter commands, both of which due to the fact that the
22806 command is split up &'before'& expansion.
22808 If an expansion item contains white space, you must quote it, so that it is all
22809 part of the same command item. If the entire option setting is one such
22810 expansion item, you have to take care what kind of quoting you use. For
22813 transport_filter = '/bin/cmd${if eq{$host}{a.b.c}{1}{2}}'
22815 This runs the command &(/bin/cmd1)& if the host name is &'a.b.c'&, and
22816 &(/bin/cmd2)& otherwise. If double quotes had been used, they would have been
22817 stripped by Exim when it read the option's value. When the value is used, if
22818 the single quotes were missing, the line would be split into two items,
22819 &`/bin/cmd${if`& and &`eq{$host}{a.b.c}{1}{2}`&, and an error would occur when
22820 Exim tried to expand the first one.
22822 Except for the special case of &$pipe_addresses$& that is mentioned above, an
22823 expansion cannot generate multiple arguments, or a command name followed by
22824 arguments. Consider this example:
22826 transport_filter = ${lookup{$host}lsearch{/a/file}\
22827 {$value}{/bin/cat}}
22829 The result of the lookup is interpreted as the name of the command, even
22830 if it contains white space. The simplest way round this is to use a shell:
22832 transport_filter = /bin/sh -c ${lookup{$host}lsearch{/a/file}\
22833 {$value}{/bin/cat}}
22837 The filter process is run under the same uid and gid as the normal delivery.
22838 For remote deliveries this is the Exim uid/gid by default. The command should
22839 normally yield a zero return code. Transport filters are not supposed to fail.
22840 A non-zero code is taken to mean that the transport filter encountered some
22841 serious problem. Delivery of the message is deferred; the message remains on
22842 the queue and is tried again later. It is not possible to cause a message to be
22843 bounced from a transport filter.
22845 If a transport filter is set on an autoreply transport, the original message is
22846 passed through the filter as it is being copied into the newly generated
22847 message, which happens if the &%return_message%& option is set.
22850 .option transport_filter_timeout transports time 5m
22851 .cindex "transport" "filter, timeout"
22852 When Exim is reading the output of a transport filter, it applies a timeout
22853 that can be set by this option. Exceeding the timeout is normally treated as a
22854 temporary delivery failure. However, if a transport filter is used with a
22855 &(pipe)& transport, a timeout in the transport filter is treated in the same
22856 way as a timeout in the pipe command itself. By default, a timeout is a hard
22857 error, but if the &(pipe)& transport's &%timeout_defer%& option is set true, it
22858 becomes a temporary error.
22861 .option user transports string&!! "Exim user"
22862 .cindex "uid (user id)" "local delivery"
22863 .cindex "transport" "user, specifying"
22864 This option specifies the user under whose uid the delivery process is to be
22865 run, overriding any uid that may have been set by the router. If the user is
22866 given as a name, the uid is looked up from the password data, and the
22867 associated group is taken as the value of the gid to be used if the &%group%&
22870 For deliveries that use local transports, a user and group are normally
22871 specified explicitly or implicitly (for example, as a result of
22872 &%check_local_user%&) by the router or transport.
22874 .cindex "hints database" "access by remote transport"
22875 For remote transports, you should leave this option unset unless you really are
22876 sure you know what you are doing. When a remote transport is running, it needs
22877 to be able to access Exim's hints databases, because each host may have its own
22879 .ecindex IIDgenoptra1
22880 .ecindex IIDgenoptra2
22881 .ecindex IIDgenoptra3
22888 . ////////////////////////////////////////////////////////////////////////////
22889 . ////////////////////////////////////////////////////////////////////////////
22891 .chapter "Address batching in local transports" "CHAPbatching" &&&
22893 .cindex "transport" "local; address batching in"
22894 The only remote transport (&(smtp)&) is normally configured to handle more than
22895 one address at a time, so that when several addresses are routed to the same
22896 remote host, just one copy of the message is sent. Local transports, however,
22897 normally handle one address at a time. That is, a separate instance of the
22898 transport is run for each address that is routed to the transport. A separate
22899 copy of the message is delivered each time.
22901 .cindex "batched local delivery"
22902 .oindex "&%batch_max%&"
22903 .oindex "&%batch_id%&"
22904 In special cases, it may be desirable to handle several addresses at once in a
22905 local transport, for example:
22908 In an &(appendfile)& transport, when storing messages in files for later
22909 delivery by some other means, a single copy of the message with multiple
22910 recipients saves space.
22912 In an &(lmtp)& transport, when delivering over &"local SMTP"& to some process,
22913 a single copy saves time, and is the normal way LMTP is expected to work.
22915 In a &(pipe)& transport, when passing the message
22916 to a scanner program or
22917 to some other delivery mechanism such as UUCP, multiple recipients may be
22921 These three local transports all have the same options for controlling multiple
22922 (&"batched"&) deliveries, namely &%batch_max%& and &%batch_id%&. To save
22923 repeating the information for each transport, these options are described here.
22925 The &%batch_max%& option specifies the maximum number of addresses that can be
22926 delivered together in a single run of the transport. Its default value is one
22927 (no batching). When more than one address is routed to a transport that has a
22928 &%batch_max%& value greater than one, the addresses are delivered in a batch
22929 (that is, in a single run of the transport with multiple recipients), subject
22930 to certain conditions:
22933 .vindex "&$local_part$&"
22934 If any of the transport's options contain a reference to &$local_part$&, no
22935 batching is possible.
22937 .vindex "&$domain$&"
22938 If any of the transport's options contain a reference to &$domain$&, only
22939 addresses with the same domain are batched.
22941 .cindex "customizing" "batching condition"
22942 If &%batch_id%& is set, it is expanded for each address, and only those
22943 addresses with the same expanded value are batched. This allows you to specify
22944 customized batching conditions. Failure of the expansion for any reason,
22945 including forced failure, disables batching, but it does not stop the delivery
22948 Batched addresses must also have the same errors address (where to send
22949 delivery errors), the same header additions and removals, the same user and
22950 group for the transport, and if a host list is present, the first host must
22954 In the case of the &(appendfile)& and &(pipe)& transports, batching applies
22955 both when the file or pipe command is specified in the transport, and when it
22956 is specified by a &(redirect)& router, but all the batched addresses must of
22957 course be routed to the same file or pipe command. These two transports have an
22958 option called &%use_bsmtp%&, which causes them to deliver the message in
22959 &"batched SMTP"& format, with the envelope represented as SMTP commands. The
22960 &%check_string%& and &%escape_string%& options are forced to the values
22963 escape_string = ".."
22965 when batched SMTP is in use. A full description of the batch SMTP mechanism is
22966 given in section &<<SECTbatchSMTP>>&. The &(lmtp)& transport does not have a
22967 &%use_bsmtp%& option, because it always delivers using the SMTP protocol.
22969 .cindex "&'Envelope-to:'& header line"
22970 If the generic &%envelope_to_add%& option is set for a batching transport, the
22971 &'Envelope-to:'& header that is added to the message contains all the addresses
22972 that are being processed together. If you are using a batching &(appendfile)&
22973 transport without &%use_bsmtp%&, the only way to preserve the recipient
22974 addresses is to set the &%envelope_to_add%& option.
22976 .cindex "&(pipe)& transport" "with multiple addresses"
22977 .vindex "&$pipe_addresses$&"
22978 If you are using a &(pipe)& transport without BSMTP, and setting the
22979 transport's &%command%& option, you can include &$pipe_addresses$& as part of
22980 the command. This is not a true variable; it is a bit of magic that causes each
22981 of the recipient addresses to be inserted into the command as a separate
22982 argument. This provides a way of accessing all the addresses that are being
22983 delivered in the batch. &*Note:*& This is not possible for pipe commands that
22984 are specified by a &(redirect)& router.
22989 . ////////////////////////////////////////////////////////////////////////////
22990 . ////////////////////////////////////////////////////////////////////////////
22992 .chapter "The appendfile transport" "CHAPappendfile"
22993 .scindex IIDapptra1 "&(appendfile)& transport"
22994 .scindex IIDapptra2 "transports" "&(appendfile)&"
22995 .cindex "directory creation"
22996 .cindex "creating directories"
22997 The &(appendfile)& transport delivers a message by appending it to an existing
22998 file, or by creating an entirely new file in a specified directory. Single
22999 files to which messages are appended can be in the traditional Unix mailbox
23000 format, or optionally in the MBX format supported by the Pine MUA and
23001 University of Washington IMAP daemon, &'inter alia'&. When each message is
23002 being delivered as a separate file, &"maildir"& format can optionally be used
23003 to give added protection against failures that happen part-way through the
23004 delivery. A third form of separate-file delivery known as &"mailstore"& is also
23005 supported. For all file formats, Exim attempts to create as many levels of
23006 directory as necessary, provided that &%create_directory%& is set.
23008 The code for the optional formats is not included in the Exim binary by
23009 default. It is necessary to set SUPPORT_MBX, SUPPORT_MAILDIR and/or
23010 SUPPORT_MAILSTORE in &_Local/Makefile_& to have the appropriate code
23013 .cindex "quota" "system"
23014 Exim recognizes system quota errors, and generates an appropriate message. Exim
23015 also supports its own quota control within the transport, for use when the
23016 system facility is unavailable or cannot be used for some reason.
23018 If there is an error while appending to a file (for example, quota exceeded or
23019 partition filled), Exim attempts to reset the file's length and last
23020 modification time back to what they were before. If there is an error while
23021 creating an entirely new file, the new file is removed.
23023 Before appending to a file, a number of security checks are made, and the
23024 file is locked. A detailed description is given below, after the list of
23027 The &(appendfile)& transport is most commonly used for local deliveries to
23028 users' mailboxes. However, it can also be used as a pseudo-remote transport for
23029 putting messages into files for remote delivery by some means other than Exim.
23030 &"Batch SMTP"& format is often used in this case (see the &%use_bsmtp%&
23035 .section "The file and directory options" "SECTfildiropt"
23036 The &%file%& option specifies a single file, to which the message is appended;
23037 the &%directory%& option specifies a directory, in which a new file containing
23038 the message is created. Only one of these two options can be set, and for
23039 normal deliveries to mailboxes, one of them &'must'& be set.
23041 .vindex "&$address_file$&"
23042 .vindex "&$local_part$&"
23043 However, &(appendfile)& is also used for delivering messages to files or
23044 directories whose names (or parts of names) are obtained from alias,
23045 forwarding, or filtering operations (for example, a &%save%& command in a
23046 user's Exim filter). When such a transport is running, &$local_part$& contains
23047 the local part that was aliased or forwarded, and &$address_file$& contains the
23048 name (or partial name) of the file or directory generated by the redirection
23049 operation. There are two cases:
23052 If neither &%file%& nor &%directory%& is set, the redirection operation
23053 must specify an absolute path (one that begins with &`/`&). This is the most
23054 common case when users with local accounts use filtering to sort mail into
23055 different folders. See for example, the &(address_file)& transport in the
23056 default configuration. If the path ends with a slash, it is assumed to be the
23057 name of a directory. A delivery to a directory can also be forced by setting
23058 &%maildir_format%& or &%mailstore_format%&.
23060 If &%file%& or &%directory%& is set for a delivery from a redirection, it is
23061 used to determine the file or directory name for the delivery. Normally, the
23062 contents of &$address_file$& are used in some way in the string expansion.
23064 If the &%create_file%& option is set to a path which
23065 matches (see the option definition below for details)
23066 a file or directory name
23067 for the delivery, that name becomes de-tainted.
23069 .cindex "tainted data" "in filenames"
23070 .cindex appendfile "tainted data"
23071 Tainted data may not be used for a file or directory name.
23072 This means that, for instance, &$local_part$& cannot be used directly
23073 as a component of a path. It can however be used as the key for a lookup
23074 which returns a path (or component).
23077 .cindex "Sieve filter" "configuring &(appendfile)&"
23078 .cindex "Sieve filter" "relative mailbox path handling"
23079 As an example of the second case, consider an environment where users do not
23080 have home directories. They may be permitted to use Exim filter commands of the
23085 or Sieve filter commands of the form:
23087 require "fileinto";
23088 fileinto "folder23";
23090 In this situation, the expansion of &%file%& or &%directory%& in the transport
23091 must transform the relative path into an appropriate absolute filename. In the
23092 case of Sieve filters, the name &'inbox'& must be handled. It is the name that
23093 is used as a result of a &"keep"& action in the filter. This example shows one
23094 way of handling this requirement:
23096 file = ${if eq{$address_file}{inbox} \
23097 {/var/mail/$local_part_data} \
23098 {${if eq{${substr_0_1:$address_file}}{/} \
23100 {$home/mail/$address_file} \
23104 With this setting of &%file%&, &'inbox'& refers to the standard mailbox
23105 location, absolute paths are used without change, and other folders are in the
23106 &_mail_& directory within the home directory.
23108 &*Note 1*&: While processing an Exim filter, a relative path such as
23109 &_folder23_& is turned into an absolute path if a home directory is known to
23110 the router. In particular, this is the case if &%check_local_user%& is set. If
23111 you want to prevent this happening at routing time, you can set
23112 &%router_home_directory%& empty. This forces the router to pass the relative
23113 path to the transport.
23115 &*Note 2*&: An absolute path in &$address_file$& is not treated specially;
23116 the &%file%& or &%directory%& option is still used if it is set.
23121 .section "Private options for appendfile" "SECID134"
23122 .cindex "options" "&(appendfile)& transport"
23126 .option allow_fifo appendfile boolean false
23127 .cindex "fifo (named pipe)"
23128 .cindex "named pipe (fifo)"
23129 .cindex "pipe" "named (fifo)"
23130 Setting this option permits delivery to named pipes (FIFOs) as well as to
23131 regular files. If no process is reading the named pipe at delivery time, the
23132 delivery is deferred.
23135 .option allow_symlink appendfile boolean false
23136 .cindex "symbolic link" "to mailbox"
23137 .cindex "mailbox" "symbolic link"
23138 By default, &(appendfile)& will not deliver if the path name for the file is
23139 that of a symbolic link. Setting this option relaxes that constraint, but there
23140 are security issues involved in the use of symbolic links. Be sure you know
23141 what you are doing if you set this. Details of exactly what this option affects
23142 are included in the discussion which follows this list of options.
23145 .option batch_id appendfile string&!! unset
23146 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
23147 However, batching is automatically disabled for &(appendfile)& deliveries that
23148 happen as a result of forwarding or aliasing or other redirection directly to a
23152 .option batch_max appendfile integer 1
23153 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
23156 .option check_group appendfile boolean false
23157 When this option is set, the group owner of the file defined by the &%file%&
23158 option is checked to see that it is the same as the group under which the
23159 delivery process is running. The default setting is false because the default
23160 file mode is 0600, which means that the group is irrelevant.
23163 .option check_owner appendfile boolean true
23164 When this option is set, the owner of the file defined by the &%file%& option
23165 is checked to ensure that it is the same as the user under which the delivery
23166 process is running.
23169 .option check_string appendfile string "see below"
23170 .cindex "&""From""& line"
23171 As &(appendfile)& writes the message, the start of each line is tested for
23172 matching &%check_string%&, and if it does, the initial matching characters are
23173 replaced by the contents of &%escape_string%&. The value of &%check_string%& is
23174 a literal string, not a regular expression, and the case of any letters it
23175 contains is significant.
23177 If &%use_bsmtp%& is set the values of &%check_string%& and &%escape_string%&
23178 are forced to &"."& and &".."& respectively, and any settings in the
23179 configuration are ignored. Otherwise, they default to &"From&~"& and
23180 &">From&~"& when the &%file%& option is set, and unset when any of the
23181 &%directory%&, &%maildir%&, or &%mailstore%& options are set.
23183 The default settings, along with &%message_prefix%& and &%message_suffix%&, are
23184 suitable for traditional &"BSD"& mailboxes, where a line beginning with
23185 &"From&~"& indicates the start of a new message. All four options need changing
23186 if another format is used. For example, to deliver to mailboxes in MMDF format:
23187 .cindex "MMDF format mailbox"
23188 .cindex "mailbox" "MMDF format"
23190 check_string = "\1\1\1\1\n"
23191 escape_string = "\1\1\1\1 \n"
23192 message_prefix = "\1\1\1\1\n"
23193 message_suffix = "\1\1\1\1\n"
23195 .option create_directory appendfile boolean true
23196 .cindex "directory creation"
23197 When this option is true, Exim attempts to create any missing superior
23198 directories for the file that it is about to write. A created directory's mode
23199 is given by the &%directory_mode%& option.
23201 The group ownership of a newly created directory is highly dependent on the
23202 operating system (and possibly the file system) that is being used. For
23203 example, in Solaris, if the parent directory has the setgid bit set, its group
23204 is propagated to the child; if not, the currently set group is used. However,
23205 in FreeBSD, the parent's group is always used.
23209 .option create_file appendfile string anywhere
23210 This option constrains the location of files and directories that are created
23211 by this transport. It applies to files defined by the &%file%& option and
23212 directories defined by the &%directory%& option. In the case of maildir
23213 delivery, it applies to the top level directory, not the maildir directories
23216 The option must be set to one of the words &"anywhere"&, &"inhome"&, or
23217 &"belowhome"&, or to an absolute path.
23219 In the second and third cases, a home directory must have been
23220 set for the transport, and the file or directory being created must
23222 The "belowhome" checking additionally checks for attempts to use "../"
23223 to evade the testing.
23224 This option is not useful when an explicit filename is
23225 given for normal mailbox deliveries. It is intended for the case when filenames
23226 are generated from users' &_.forward_& files. These are usually handled
23227 by an &(appendfile)& transport called &%address_file%&. See also
23228 &%file_must_exist%&.
23230 In the fourth case,
23231 the value given for this option must be an absolute path for an
23232 existing directory.
23233 The value is used for checking instead of a home directory;
23234 checking is done in "belowhome" mode.
23236 .cindex "tainted data" "de-tainting"
23237 .cindex "de-tainting" "using appendfile create_file option"
23238 If "belowhome" checking is used, the file or directory path
23239 becomes de-tainted.
23242 .option directory appendfile string&!! unset
23243 This option is mutually exclusive with the &%file%& option, but one of &%file%&
23244 or &%directory%& must be set, unless the delivery is the direct result of a
23245 redirection (see section &<<SECTfildiropt>>&).
23247 When &%directory%& is set, the string is expanded, and the message is delivered
23248 into a new file or files in or below the given directory, instead of being
23249 appended to a single mailbox file. A number of different formats are provided
23250 (see &%maildir_format%& and &%mailstore_format%&), and see section
23251 &<<SECTopdir>>& for further details of this form of delivery.
23253 The result of expansion must not be tainted, unless the &%create_file%& option
23257 .option directory_file appendfile string&!! "see below"
23259 .vindex "&$inode$&"
23260 When &%directory%& is set, but neither &%maildir_format%& nor
23261 &%mailstore_format%& is set, &(appendfile)& delivers each message into a file
23262 whose name is obtained by expanding this string. The default value is:
23264 q${base62:$tod_epoch}-$inode
23266 This generates a unique name from the current time, in base 62 form, and the
23267 inode of the file. The variable &$inode$& is available only when expanding this
23271 .option directory_mode appendfile "octal integer" 0700
23272 If &(appendfile)& creates any directories as a result of the
23273 &%create_directory%& option, their mode is specified by this option.
23276 .option escape_string appendfile string "see description"
23277 See &%check_string%& above.
23280 .option file appendfile string&!! unset
23281 This option is mutually exclusive with the &%directory%& option, but one of
23282 &%file%& or &%directory%& must be set, unless the delivery is the direct result
23283 of a redirection (see section &<<SECTfildiropt>>&). The &%file%& option
23284 specifies a single file, to which the message is appended. One or more of
23285 &%use_fcntl_lock%&, &%use_flock_lock%&, or &%use_lockfile%& must be set with
23288 The result of expansion must not be tainted, unless the &%create_file%& option
23291 .cindex "NFS" "lock file"
23292 .cindex "locking files"
23293 .cindex "lock files"
23294 If you are using more than one host to deliver over NFS into the same
23295 mailboxes, you should always use lock files.
23297 The string value is expanded for each delivery, and must yield an absolute
23298 path. The most common settings of this option are variations on one of these
23301 file = /var/spool/mail/$local_part_data
23302 file = /home/$local_part_data/inbox
23305 .cindex "&""sticky""& bit"
23306 In the first example, all deliveries are done into the same directory. If Exim
23307 is configured to use lock files (see &%use_lockfile%& below) it must be able to
23308 create a file in the directory, so the &"sticky"& bit must be turned on for
23309 deliveries to be possible, or alternatively the &%group%& option can be used to
23310 run the delivery under a group id which has write access to the directory.
23314 .option file_format appendfile string unset
23315 .cindex "file" "mailbox; checking existing format"
23316 This option requests the transport to check the format of an existing file
23317 before adding to it. The check consists of matching a specific string at the
23318 start of the file. The value of the option consists of an even number of
23319 colon-separated strings. The first of each pair is the test string, and the
23320 second is the name of a transport. If the transport associated with a matched
23321 string is not the current transport, control is passed over to the other
23322 transport. For example, suppose the standard &(local_delivery)& transport has
23325 file_format = "From : local_delivery :\
23326 \1\1\1\1\n : local_mmdf_delivery"
23328 Mailboxes that begin with &"From"& are still handled by this transport, but if
23329 a mailbox begins with four binary ones followed by a newline, control is passed
23330 to a transport called &%local_mmdf_delivery%&, which presumably is configured
23331 to do the delivery in MMDF format. If a mailbox does not exist or is empty, it
23332 is assumed to match the current transport. If the start of a mailbox doesn't
23333 match any string, or if the transport named for a given string is not defined,
23334 delivery is deferred.
23337 .option file_must_exist appendfile boolean false
23338 If this option is true, the file specified by the &%file%& option must exist.
23339 A temporary error occurs if it does not, causing delivery to be deferred.
23340 If this option is false, the file is created if it does not exist.
23343 .option lock_fcntl_timeout appendfile time 0s
23344 .cindex "timeout" "mailbox locking"
23345 .cindex "mailbox" "locking, blocking and non-blocking"
23346 .cindex "locking files"
23347 By default, the &(appendfile)& transport uses non-blocking calls to &[fcntl()]&
23348 when locking an open mailbox file. If the call fails, the delivery process
23349 sleeps for &%lock_interval%& and tries again, up to &%lock_retries%& times.
23350 Non-blocking calls are used so that the file is not kept open during the wait
23351 for the lock; the reason for this is to make it as safe as possible for
23352 deliveries over NFS in the case when processes might be accessing an NFS
23353 mailbox without using a lock file. This should not be done, but
23354 misunderstandings and hence misconfigurations are not unknown.
23356 On a busy system, however, the performance of a non-blocking lock approach is
23357 not as good as using a blocking lock with a timeout. In this case, the waiting
23358 is done inside the system call, and Exim's delivery process acquires the lock
23359 and can proceed as soon as the previous lock holder releases it.
23361 If &%lock_fcntl_timeout%& is set to a non-zero time, blocking locks, with that
23362 timeout, are used. There may still be some retrying: the maximum number of
23365 (lock_retries * lock_interval) / lock_fcntl_timeout
23367 rounded up to the next whole number. In other words, the total time during
23368 which &(appendfile)& is trying to get a lock is roughly the same, unless
23369 &%lock_fcntl_timeout%& is set very large.
23371 You should consider setting this option if you are getting a lot of delayed
23372 local deliveries because of errors of the form
23374 failed to lock mailbox /some/file (fcntl)
23377 .option lock_flock_timeout appendfile time 0s
23378 This timeout applies to file locking when using &[flock()]& (see
23379 &%use_flock%&); the timeout operates in a similar manner to
23380 &%lock_fcntl_timeout%&.
23383 .option lock_interval appendfile time 3s
23384 This specifies the time to wait between attempts to lock the file. See below
23385 for details of locking.
23388 .option lock_retries appendfile integer 10
23389 This specifies the maximum number of attempts to lock the file. A value of zero
23390 is treated as 1. See below for details of locking.
23393 .option lockfile_mode appendfile "octal integer" 0600
23394 This specifies the mode of the created lock file, when a lock file is being
23395 used (see &%use_lockfile%& and &%use_mbx_lock%&).
23398 .option lockfile_timeout appendfile time 30m
23399 .cindex "timeout" "mailbox locking"
23400 When a lock file is being used (see &%use_lockfile%&), if a lock file already
23401 exists and is older than this value, it is assumed to have been left behind by
23402 accident, and Exim attempts to remove it.
23405 .option mailbox_filecount appendfile string&!! unset
23406 .cindex "mailbox" "specifying size of"
23407 .cindex "size" "of mailbox"
23408 If this option is set, it is expanded, and the result is taken as the current
23409 number of files in the mailbox. It must be a decimal number, optionally
23410 followed by K or M. This provides a way of obtaining this information from an
23411 external source that maintains the data.
23414 .option mailbox_size appendfile string&!! unset
23415 .cindex "mailbox" "specifying size of"
23416 .cindex "size" "of mailbox"
23417 If this option is set, it is expanded, and the result is taken as the current
23418 size the mailbox. It must be a decimal number, optionally followed by K or M.
23419 This provides a way of obtaining this information from an external source that
23420 maintains the data. This is likely to be helpful for maildir deliveries where
23421 it is computationally expensive to compute the size of a mailbox.
23425 .option maildir_format appendfile boolean false
23426 .cindex "maildir format" "specifying"
23427 If this option is set with the &%directory%& option, the delivery is into a new
23428 file, in the &"maildir"& format that is used by other mail software. When the
23429 transport is activated directly from a &(redirect)& router (for example, the
23430 &(address_file)& transport in the default configuration), setting
23431 &%maildir_format%& causes the path received from the router to be treated as a
23432 directory, whether or not it ends with &`/`&. This option is available only if
23433 SUPPORT_MAILDIR is present in &_Local/Makefile_&. See section
23434 &<<SECTmaildirdelivery>>& below for further details.
23437 .option maildir_quota_directory_regex appendfile string "See below"
23438 .cindex "maildir format" "quota; directories included in"
23439 .cindex "quota" "maildir; directories included in"
23440 This option is relevant only when &%maildir_use_size_file%& is set. It defines
23441 a regular expression for specifying directories, relative to the quota
23442 directory (see &%quota_directory%&), that should be included in the quota
23443 calculation. The default value is:
23445 maildir_quota_directory_regex = ^(?:cur|new|\..*)$
23447 This includes the &_cur_& and &_new_& directories, and any maildir++ folders
23448 (directories whose names begin with a dot). If you want to exclude the
23450 folder from the count (as some sites do), you need to change this setting to
23452 maildir_quota_directory_regex = ^(?:cur|new|\.(?!Trash).*)$
23454 This uses a negative lookahead in the regular expression to exclude the
23455 directory whose name is &_.Trash_&. When a directory is excluded from quota
23456 calculations, quota processing is bypassed for any messages that are delivered
23457 directly into that directory.
23460 .option maildir_retries appendfile integer 10
23461 This option specifies the number of times to retry when writing a file in
23462 &"maildir"& format. See section &<<SECTmaildirdelivery>>& below.
23465 .option maildir_tag appendfile string&!! unset
23466 This option applies only to deliveries in maildir format, and is described in
23467 section &<<SECTmaildirdelivery>>& below.
23470 .option maildir_use_size_file appendfile&!! boolean false
23471 .cindex "maildir format" "&_maildirsize_& file"
23472 The result of string expansion for this option must be a valid boolean value.
23473 If it is true, it enables support for &_maildirsize_& files. Exim
23474 creates a &_maildirsize_& file in a maildir if one does not exist, taking the
23475 quota from the &%quota%& option of the transport. If &%quota%& is unset, the
23476 value is zero. See &%maildir_quota_directory_regex%& above and section
23477 &<<SECTmaildirdelivery>>& below for further details.
23479 .option maildirfolder_create_regex appendfile string unset
23480 .cindex "maildir format" "&_maildirfolder_& file"
23481 .cindex "&_maildirfolder_&, creating"
23482 The value of this option is a regular expression. If it is unset, it has no
23483 effect. Otherwise, before a maildir delivery takes place, the pattern is
23484 matched against the name of the maildir directory, that is, the directory
23485 containing the &_new_& and &_tmp_& subdirectories that will be used for the
23486 delivery. If there is a match, Exim checks for the existence of a file called
23487 &_maildirfolder_& in the directory, and creates it if it does not exist.
23488 See section &<<SECTmaildirdelivery>>& for more details.
23491 .option mailstore_format appendfile boolean false
23492 .cindex "mailstore format" "specifying"
23493 If this option is set with the &%directory%& option, the delivery is into two
23494 new files in &"mailstore"& format. The option is available only if
23495 SUPPORT_MAILSTORE is present in &_Local/Makefile_&. See section &<<SECTopdir>>&
23496 below for further details.
23499 .option mailstore_prefix appendfile string&!! unset
23500 This option applies only to deliveries in mailstore format, and is described in
23501 section &<<SECTopdir>>& below.
23504 .option mailstore_suffix appendfile string&!! unset
23505 This option applies only to deliveries in mailstore format, and is described in
23506 section &<<SECTopdir>>& below.
23509 .option mbx_format appendfile boolean false
23510 .cindex "locking files"
23511 .cindex "file" "locking"
23512 .cindex "file" "MBX format"
23513 .cindex "MBX format, specifying"
23514 This option is available only if Exim has been compiled with SUPPORT_MBX
23515 set in &_Local/Makefile_&. If &%mbx_format%& is set with the &%file%& option,
23516 the message is appended to the mailbox file in MBX format instead of
23517 traditional Unix format. This format is supported by Pine4 and its associated
23518 IMAP and POP daemons, by means of the &'c-client'& library that they all use.
23520 &*Note*&: The &%message_prefix%& and &%message_suffix%& options are not
23521 automatically changed by the use of &%mbx_format%&. They should normally be set
23522 empty when using MBX format, so this option almost always appears in this
23529 If none of the locking options are mentioned in the configuration,
23530 &%use_mbx_lock%& is assumed and the other locking options default to false. It
23531 is possible to specify the other kinds of locking with &%mbx_format%&, but
23532 &%use_fcntl_lock%& and &%use_mbx_lock%& are mutually exclusive. MBX locking
23533 interworks with &'c-client'&, providing for shared access to the mailbox. It
23534 should not be used if any program that does not use this form of locking is
23535 going to access the mailbox, nor should it be used if the mailbox file is NFS
23536 mounted, because it works only when the mailbox is accessed from a single host.
23538 If you set &%use_fcntl_lock%& with an MBX-format mailbox, you cannot use
23539 the standard version of &'c-client'&, because as long as it has a mailbox open
23540 (this means for the whole of a Pine or IMAP session), Exim will not be able to
23541 append messages to it.
23544 .option message_prefix appendfile string&!! "see below"
23545 .cindex "&""From""& line"
23546 The string specified here is expanded and output at the start of every message.
23547 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
23548 in which case it is:
23550 message_prefix = "From ${if def:return_path{$return_path}\
23551 {MAILER-DAEMON}} $tod_bsdinbox\n"
23553 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
23554 &`\n`& to &`\r\n`& in &%message_prefix%&.
23556 .option message_suffix appendfile string&!! "see below"
23557 The string specified here is expanded and output at the end of every message.
23558 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
23559 in which case it is a single newline character. The suffix can be suppressed by
23564 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
23565 &`\n`& to &`\r\n`& in &%message_suffix%&.
23567 .option mode appendfile "octal integer" 0600
23568 If the output file is created, it is given this mode. If it already exists and
23569 has wider permissions, they are reduced to this mode. If it has narrower
23570 permissions, an error occurs unless &%mode_fail_narrower%& is false. However,
23571 if the delivery is the result of a &%save%& command in a filter file specifying
23572 a particular mode, the mode of the output file is always forced to take that
23573 value, and this option is ignored.
23576 .option mode_fail_narrower appendfile boolean true
23577 This option applies in the case when an existing mailbox file has a narrower
23578 mode than that specified by the &%mode%& option. If &%mode_fail_narrower%& is
23579 true, the delivery is deferred (&"mailbox has the wrong mode"&); otherwise Exim
23580 continues with the delivery attempt, using the existing mode of the file.
23583 .option notify_comsat appendfile boolean false
23584 If this option is true, the &'comsat'& daemon is notified after every
23585 successful delivery to a user mailbox. This is the daemon that notifies logged
23586 on users about incoming mail.
23589 .option quota appendfile string&!! unset
23590 .cindex "quota" "imposed by Exim"
23591 This option imposes a limit on the size of the file to which Exim is appending,
23592 or to the total space used in the directory tree when the &%directory%& option
23593 is set. In the latter case, computation of the space used is expensive, because
23594 all the files in the directory (and any sub-directories) have to be
23595 individually inspected and their sizes summed. (See &%quota_size_regex%& and
23596 &%maildir_use_size_file%& for ways to avoid this in environments where users
23597 have no shell access to their mailboxes).
23599 As there is no interlock against two simultaneous deliveries into a
23600 multi-file mailbox, it is possible for the quota to be overrun in this case.
23601 For single-file mailboxes, of course, an interlock is a necessity.
23603 A file's size is taken as its &'used'& value. Because of blocking effects, this
23604 may be a lot less than the actual amount of disk space allocated to the file.
23605 If the sizes of a number of files are being added up, the rounding effect can
23606 become quite noticeable, especially on systems that have large block sizes.
23607 Nevertheless, it seems best to stick to the &'used'& figure, because this is
23608 the obvious value which users understand most easily.
23610 The value of the option is expanded, and must then be a numerical value
23611 (decimal point allowed), optionally followed by one of the letters K, M, or G,
23612 for kilobytes, megabytes, or gigabytes, optionally followed by a slash
23613 and further option modifiers. If Exim is running on a system with
23614 large file support (Linux and FreeBSD have this), mailboxes larger than 2G can
23617 The option modifier &%no_check%& can be used to force delivery even if the over
23618 quota condition is met. The quota gets updated as usual.
23620 &*Note*&: A value of zero is interpreted as &"no quota"&.
23622 The expansion happens while Exim is running as root, before it changes uid for
23623 the delivery. This means that files that are inaccessible to the end user can
23624 be used to hold quota values that are looked up in the expansion. When delivery
23625 fails because this quota is exceeded, the handling of the error is as for
23626 system quota failures.
23628 By default, Exim's quota checking mimics system quotas, and restricts the
23629 mailbox to the specified maximum size, though the value is not accurate to the
23630 last byte, owing to separator lines and additional headers that may get added
23631 during message delivery. When a mailbox is nearly full, large messages may get
23632 refused even though small ones are accepted, because the size of the current
23633 message is added to the quota when the check is made. This behaviour can be
23634 changed by setting &%quota_is_inclusive%& false. When this is done, the check
23635 for exceeding the quota does not include the current message. Thus, deliveries
23636 continue until the quota has been exceeded; thereafter, no further messages are
23637 delivered. See also &%quota_warn_threshold%&.
23640 .option quota_directory appendfile string&!! unset
23641 This option defines the directory to check for quota purposes when delivering
23642 into individual files. The default is the delivery directory, or, if a file
23643 called &_maildirfolder_& exists in a maildir directory, the parent of the
23644 delivery directory.
23647 .option quota_filecount appendfile string&!! 0
23648 This option applies when the &%directory%& option is set. It limits the total
23649 number of files in the directory (compare the inode limit in system quotas). It
23650 can only be used if &%quota%& is also set. The value is expanded; an expansion
23651 failure causes delivery to be deferred. A value of zero is interpreted as
23654 The option modifier &%no_check%& can be used to force delivery even if the over
23655 quota condition is met. The quota gets updated as usual.
23657 .option quota_is_inclusive appendfile boolean true
23658 See &%quota%& above.
23661 .option quota_size_regex appendfile string unset
23662 This option applies when one of the delivery modes that writes a separate file
23663 for each message is being used. When Exim wants to find the size of one of
23664 these files in order to test the quota, it first checks &%quota_size_regex%&.
23665 If this is set to a regular expression that matches the filename, and it
23666 captures one string, that string is interpreted as a representation of the
23667 file's size. The value of &%quota_size_regex%& is not expanded.
23669 This feature is useful only when users have no shell access to their mailboxes
23670 &-- otherwise they could defeat the quota simply by renaming the files. This
23671 facility can be used with maildir deliveries, by setting &%maildir_tag%& to add
23672 the file length to the filename. For example:
23674 maildir_tag = ,S=$message_size
23675 quota_size_regex = ,S=(\d+)
23677 An alternative to &$message_size$& is &$message_linecount$&, which contains the
23678 number of lines in the message.
23680 The regular expression should not assume that the length is at the end of the
23681 filename (even though &%maildir_tag%& puts it there) because maildir MUAs
23682 sometimes add other information onto the ends of message filenames.
23684 Section &<<SECID136>>& contains further information.
23686 This option should not be used when other message-handling software
23687 may duplicate messages by making hardlinks to the files. When that is done Exim
23688 will count the message size once for each filename, in contrast with the actual
23689 disk usage. When the option is not set, calculating total usage requires
23690 a system-call per file to get the size; the number of links is then available also
23691 as is used to adjust the effective size.
23694 .option quota_warn_message appendfile string&!! "see below"
23695 See below for the use of this option. If it is not set when
23696 &%quota_warn_threshold%& is set, it defaults to
23698 quota_warn_message = "\
23699 To: $local_part@$domain\n\
23700 Subject: Your mailbox\n\n\
23701 This message is automatically created \
23702 by mail delivery software.\n\n\
23703 The size of your mailbox has exceeded \
23704 a warning threshold that is\n\
23705 set by the system administrator.\n"
23709 .option quota_warn_threshold appendfile string&!! 0
23710 .cindex "quota" "warning threshold"
23711 .cindex "mailbox" "size warning"
23712 .cindex "size" "of mailbox"
23713 This option is expanded in the same way as &%quota%& (see above). If the
23714 resulting value is greater than zero, and delivery of the message causes the
23715 size of the file or total space in the directory tree to cross the given
23716 threshold, a warning message is sent. If &%quota%& is also set, the threshold
23717 may be specified as a percentage of it by following the value with a percent
23721 quota_warn_threshold = 75%
23723 If &%quota%& is not set, a setting of &%quota_warn_threshold%& that ends with a
23724 percent sign is ignored.
23726 The warning message itself is specified by the &%quota_warn_message%& option,
23727 and it must start with a &'To:'& header line containing the recipient(s) of the
23728 warning message. These do not necessarily have to include the recipient(s) of
23729 the original message. A &'Subject:'& line should also normally be supplied. You
23730 can include any other header lines that you want. If you do not include a
23731 &'From:'& line, the default is:
23733 From: Mail Delivery System <mailer-daemon@$qualify_domain_sender>
23735 .oindex &%errors_reply_to%&
23736 If you supply a &'Reply-To:'& line, it overrides the global &%errors_reply_to%&
23739 The &%quota%& option does not have to be set in order to use this option; they
23740 are independent of one another except when the threshold is specified as a
23744 .option use_bsmtp appendfile boolean false
23745 .cindex "envelope from"
23746 .cindex "envelope sender"
23747 If this option is set true, &(appendfile)& writes messages in &"batch SMTP"&
23748 format, with the envelope sender and recipient(s) included as SMTP commands. If
23749 you want to include a leading HELO command with such messages, you can do
23750 so by setting the &%message_prefix%& option. See section &<<SECTbatchSMTP>>&
23751 for details of batch SMTP.
23754 .option use_crlf appendfile boolean false
23755 .cindex "carriage return"
23757 This option causes lines to be terminated with the two-character CRLF sequence
23758 (carriage return, linefeed) instead of just a linefeed character. In the case
23759 of batched SMTP, the byte sequence written to the file is then an exact image
23760 of what would be sent down a real SMTP connection.
23762 &*Note:*& The contents of the &%message_prefix%& and &%message_suffix%& options
23763 (which are used to supply the traditional &"From&~"& and blank line separators
23764 in Berkeley-style mailboxes) are written verbatim, so must contain their own
23765 carriage return characters if these are needed. In cases where these options
23766 have non-empty defaults, the values end with a single linefeed, so they must be
23767 changed to end with &`\r\n`& if &%use_crlf%& is set.
23770 .option use_fcntl_lock appendfile boolean "see below"
23771 This option controls the use of the &[fcntl()]& function to lock a file for
23772 exclusive use when a message is being appended. It is set by default unless
23773 &%use_flock_lock%& is set. Otherwise, it should be turned off only if you know
23774 that all your MUAs use lock file locking. When both &%use_fcntl_lock%& and
23775 &%use_flock_lock%& are unset, &%use_lockfile%& must be set.
23778 .option use_flock_lock appendfile boolean false
23779 This option is provided to support the use of &[flock()]& for file locking, for
23780 the few situations where it is needed. Most modern operating systems support
23781 &[fcntl()]& and &[lockf()]& locking, and these two functions interwork with
23782 each other. Exim uses &[fcntl()]& locking by default.
23784 This option is required only if you are using an operating system where
23785 &[flock()]& is used by programs that access mailboxes (typically MUAs), and
23786 where &[flock()]& does not correctly interwork with &[fcntl()]&. You can use
23787 both &[fcntl()]& and &[flock()]& locking simultaneously if you want.
23789 .cindex "Solaris" "&[flock()]& support"
23790 Not all operating systems provide &[flock()]&. Some versions of Solaris do not
23791 have it (and some, I think, provide a not quite right version built on top of
23792 &[lockf()]&). If the OS does not have &[flock()]&, Exim will be built without
23793 the ability to use it, and any attempt to do so will cause a configuration
23796 &*Warning*&: &[flock()]& locks do not work on NFS files (unless &[flock()]&
23797 is just being mapped onto &[fcntl()]& by the OS).
23800 .option use_lockfile appendfile boolean "see below"
23801 If this option is turned off, Exim does not attempt to create a lock file when
23802 appending to a mailbox file. In this situation, the only locking is by
23803 &[fcntl()]&. You should only turn &%use_lockfile%& off if you are absolutely
23804 sure that every MUA that is ever going to look at your users' mailboxes uses
23805 &[fcntl()]& rather than a lock file, and even then only when you are not
23806 delivering over NFS from more than one host.
23808 .cindex "NFS" "lock file"
23809 In order to append to an NFS file safely from more than one host, it is
23810 necessary to take out a lock &'before'& opening the file, and the lock file
23811 achieves this. Otherwise, even with &[fcntl()]& locking, there is a risk of
23814 The &%use_lockfile%& option is set by default unless &%use_mbx_lock%& is set.
23815 It is not possible to turn both &%use_lockfile%& and &%use_fcntl_lock%& off,
23816 except when &%mbx_format%& is set.
23819 .option use_mbx_lock appendfile boolean "see below"
23820 This option is available only if Exim has been compiled with SUPPORT_MBX
23821 set in &_Local/Makefile_&. Setting the option specifies that special MBX
23822 locking rules be used. It is set by default if &%mbx_format%& is set and none
23823 of the locking options are mentioned in the configuration. The locking rules
23824 are the same as are used by the &'c-client'& library that underlies Pine and
23825 the IMAP4 and POP daemons that come with it (see the discussion below). The
23826 rules allow for shared access to the mailbox. However, this kind of locking
23827 does not work when the mailbox is NFS mounted.
23829 You can set &%use_mbx_lock%& with either (or both) of &%use_fcntl_lock%& and
23830 &%use_flock_lock%& to control what kind of locking is used in implementing the
23831 MBX locking rules. The default is to use &[fcntl()]& if &%use_mbx_lock%& is set
23832 without &%use_fcntl_lock%& or &%use_flock_lock%&.
23837 .section "Operational details for appending" "SECTopappend"
23838 .cindex "appending to a file"
23839 .cindex "file" "appending"
23840 Before appending to a file, the following preparations are made:
23843 If the name of the file is &_/dev/null_&, no action is taken, and a success
23847 .cindex "directory creation"
23848 If any directories on the file's path are missing, Exim creates them if the
23849 &%create_directory%& option is set. A created directory's mode is given by the
23850 &%directory_mode%& option.
23853 If &%file_format%& is set, the format of an existing file is checked. If this
23854 indicates that a different transport should be used, control is passed to that
23858 .cindex "file" "locking"
23859 .cindex "locking files"
23860 .cindex "NFS" "lock file"
23861 If &%use_lockfile%& is set, a lock file is built in a way that will work
23862 reliably over NFS, as follows:
23865 Create a &"hitching post"& file whose name is that of the lock file with the
23866 current time, primary host name, and process id added, by opening for writing
23867 as a new file. If this fails with an access error, delivery is deferred.
23869 Close the hitching post file, and hard link it to the lock filename.
23871 If the call to &[link()]& succeeds, creation of the lock file has succeeded.
23872 Unlink the hitching post name.
23874 Otherwise, use &[stat()]& to get information about the hitching post file, and
23875 then unlink hitching post name. If the number of links is exactly two, creation
23876 of the lock file succeeded but something (for example, an NFS server crash and
23877 restart) caused this fact not to be communicated to the &[link()]& call.
23879 If creation of the lock file failed, wait for &%lock_interval%& and try again,
23880 up to &%lock_retries%& times. However, since any program that writes to a
23881 mailbox should complete its task very quickly, it is reasonable to time out old
23882 lock files that are normally the result of user agent and system crashes. If an
23883 existing lock file is older than &%lockfile_timeout%& Exim attempts to unlink
23884 it before trying again.
23888 A call is made to &[lstat()]& to discover whether the main file exists, and if
23889 so, what its characteristics are. If &[lstat()]& fails for any reason other
23890 than non-existence, delivery is deferred.
23893 .cindex "symbolic link" "to mailbox"
23894 .cindex "mailbox" "symbolic link"
23895 If the file does exist and is a symbolic link, delivery is deferred, unless the
23896 &%allow_symlink%& option is set, in which case the ownership of the link is
23897 checked, and then &[stat()]& is called to find out about the real file, which
23898 is then subjected to the checks below. The check on the top-level link
23899 ownership prevents one user creating a link for another's mailbox in a sticky
23900 directory, though allowing symbolic links in this case is definitely not a good
23901 idea. If there is a chain of symbolic links, the intermediate ones are not
23905 If the file already exists but is not a regular file, or if the file's owner
23906 and group (if the group is being checked &-- see &%check_group%& above) are
23907 different from the user and group under which the delivery is running,
23908 delivery is deferred.
23911 If the file's permissions are more generous than specified, they are reduced.
23912 If they are insufficient, delivery is deferred, unless &%mode_fail_narrower%&
23913 is set false, in which case the delivery is tried using the existing
23917 The file's inode number is saved, and the file is then opened for appending.
23918 If this fails because the file has vanished, &(appendfile)& behaves as if it
23919 hadn't existed (see below). For any other failures, delivery is deferred.
23922 If the file is opened successfully, check that the inode number hasn't
23923 changed, that it is still a regular file, and that the owner and permissions
23924 have not changed. If anything is wrong, defer delivery and freeze the message.
23927 If the file did not exist originally, defer delivery if the &%file_must_exist%&
23928 option is set. Otherwise, check that the file is being created in a permitted
23929 directory if the &%create_file%& option is set (deferring on failure), and then
23930 open for writing as a new file, with the O_EXCL and O_CREAT options,
23931 except when dealing with a symbolic link (the &%allow_symlink%& option must be
23932 set). In this case, which can happen if the link points to a non-existent file,
23933 the file is opened for writing using O_CREAT but not O_EXCL, because
23934 that prevents link following.
23937 .cindex "loop" "while file testing"
23938 If opening fails because the file exists, obey the tests given above for
23939 existing files. However, to avoid looping in a situation where the file is
23940 being continuously created and destroyed, the exists/not-exists loop is broken
23941 after 10 repetitions, and the message is then frozen.
23944 If opening fails with any other error, defer delivery.
23947 .cindex "file" "locking"
23948 .cindex "locking files"
23949 Once the file is open, unless both &%use_fcntl_lock%& and &%use_flock_lock%&
23950 are false, it is locked using &[fcntl()]& or &[flock()]& or both. If
23951 &%use_mbx_lock%& is false, an exclusive lock is requested in each case.
23952 However, if &%use_mbx_lock%& is true, Exim takes out a shared lock on the open
23953 file, and an exclusive lock on the file whose name is
23955 /tmp/.<device-number>.<inode-number>
23957 using the device and inode numbers of the open mailbox file, in accordance with
23958 the MBX locking rules. This file is created with a mode that is specified by
23959 the &%lockfile_mode%& option.
23961 If Exim fails to lock the file, there are two possible courses of action,
23962 depending on the value of the locking timeout. This is obtained from
23963 &%lock_fcntl_timeout%& or &%lock_flock_timeout%&, as appropriate.
23965 If the timeout value is zero, the file is closed, Exim waits for
23966 &%lock_interval%&, and then goes back and re-opens the file as above and tries
23967 to lock it again. This happens up to &%lock_retries%& times, after which the
23968 delivery is deferred.
23970 If the timeout has a value greater than zero, blocking calls to &[fcntl()]& or
23971 &[flock()]& are used (with the given timeout), so there has already been some
23972 waiting involved by the time locking fails. Nevertheless, Exim does not give up
23973 immediately. It retries up to
23975 (lock_retries * lock_interval) / <timeout>
23977 times (rounded up).
23980 At the end of delivery, Exim closes the file (which releases the &[fcntl()]&
23981 and/or &[flock()]& locks) and then deletes the lock file if one was created.
23984 .section "Operational details for delivery to a new file" "SECTopdir"
23985 .cindex "delivery" "to single file"
23986 .cindex "&""From""& line"
23987 When the &%directory%& option is set instead of &%file%&, each message is
23988 delivered into a newly-created file or set of files. When &(appendfile)& is
23989 activated directly from a &(redirect)& router, neither &%file%& nor
23990 &%directory%& is normally set, because the path for delivery is supplied by the
23991 router. (See for example, the &(address_file)& transport in the default
23992 configuration.) In this case, delivery is to a new file if either the path name
23993 ends in &`/`&, or the &%maildir_format%& or &%mailstore_format%& option is set.
23995 No locking is required while writing the message to a new file, so the various
23996 locking options of the transport are ignored. The &"From"& line that by default
23997 separates messages in a single file is not normally needed, nor is the escaping
23998 of message lines that start with &"From"&, and there is no need to ensure a
23999 newline at the end of each message. Consequently, the default values for
24000 &%check_string%&, &%message_prefix%&, and &%message_suffix%& are all unset when
24001 any of &%directory%&, &%maildir_format%&, or &%mailstore_format%& is set.
24003 If Exim is required to check a &%quota%& setting, it adds up the sizes of all
24004 the files in the delivery directory by default. However, you can specify a
24005 different directory by setting &%quota_directory%&. Also, for maildir
24006 deliveries (see below) the &_maildirfolder_& convention is honoured.
24009 .cindex "maildir format"
24010 .cindex "mailstore format"
24011 There are three different ways in which delivery to individual files can be
24012 done, controlled by the settings of the &%maildir_format%& and
24013 &%mailstore_format%& options. Note that code to support maildir or mailstore
24014 formats is not included in the binary unless SUPPORT_MAILDIR or
24015 SUPPORT_MAILSTORE, respectively, is set in &_Local/Makefile_&.
24017 .cindex "directory creation"
24018 In all three cases an attempt is made to create the directory and any necessary
24019 sub-directories if they do not exist, provided that the &%create_directory%&
24020 option is set (the default). The location of a created directory can be
24021 constrained by setting &%create_file%&. A created directory's mode is given by
24022 the &%directory_mode%& option. If creation fails, or if the
24023 &%create_directory%& option is not set when creation is required, delivery is
24028 .section "Maildir delivery" "SECTmaildirdelivery"
24029 .cindex "maildir format" "description of"
24030 If the &%maildir_format%& option is true, Exim delivers each message by writing
24031 it to a file whose name is &_tmp/<stime>.H<mtime>P<pid>.<host>_& in the
24032 directory that is defined by the &%directory%& option (the &"delivery
24033 directory"&). If the delivery is successful, the file is renamed into the
24034 &_new_& subdirectory.
24036 In the filename, <&'stime'&> is the current time of day in seconds, and
24037 <&'mtime'&> is the microsecond fraction of the time. After a maildir delivery,
24038 Exim checks that the time-of-day clock has moved on by at least one microsecond
24039 before terminating the delivery process. This guarantees uniqueness for the
24040 filename. However, as a precaution, Exim calls &[stat()]& for the file before
24041 opening it. If any response other than ENOENT (does not exist) is given,
24042 Exim waits 2 seconds and tries again, up to &%maildir_retries%& times.
24044 Before Exim carries out a maildir delivery, it ensures that subdirectories
24045 called &_new_&, &_cur_&, and &_tmp_& exist in the delivery directory. If they
24046 do not exist, Exim tries to create them and any superior directories in their
24047 path, subject to the &%create_directory%& and &%create_file%& options. If the
24048 &%maildirfolder_create_regex%& option is set, and the regular expression it
24049 contains matches the delivery directory, Exim also ensures that a file called
24050 &_maildirfolder_& exists in the delivery directory. If a missing directory or
24051 &_maildirfolder_& file cannot be created, delivery is deferred.
24053 These features make it possible to use Exim to create all the necessary files
24054 and directories in a maildir mailbox, including subdirectories for maildir++
24055 folders. Consider this example:
24057 maildir_format = true
24058 directory = /var/mail/$local_part_data\
24059 ${if eq{$local_part_suffix}{}{}\
24060 {/.${substr_1:$local_part_suffix}}}
24061 maildirfolder_create_regex = /\.[^/]+$
24063 If &$local_part_suffix$& is empty (there was no suffix for the local part),
24064 delivery is into a toplevel maildir with a name like &_/var/mail/pimbo_& (for
24065 the user called &'pimbo'&). The pattern in &%maildirfolder_create_regex%& does
24066 not match this name, so Exim will not look for or create the file
24067 &_/var/mail/pimbo/maildirfolder_&, though it will create
24068 &_/var/mail/pimbo/{cur,new,tmp}_& if necessary.
24070 However, if &$local_part_suffix$& contains &`-eximusers`& (for example),
24071 delivery is into the maildir++ folder &_/var/mail/pimbo/.eximusers_&, which
24072 does match &%maildirfolder_create_regex%&. In this case, Exim will create
24073 &_/var/mail/pimbo/.eximusers/maildirfolder_& as well as the three maildir
24074 directories &_/var/mail/pimbo/.eximusers/{cur,new,tmp}_&.
24076 &*Warning:*& Take care when setting &%maildirfolder_create_regex%& that it does
24077 not inadvertently match the toplevel maildir directory, because a
24078 &_maildirfolder_& file at top level would completely break quota calculations.
24080 .cindex "quota" "in maildir delivery"
24081 .cindex "maildir++"
24082 If Exim is required to check a &%quota%& setting before a maildir delivery, and
24083 &%quota_directory%& is not set, it looks for a file called &_maildirfolder_& in
24084 the maildir directory (alongside &_new_&, &_cur_&, &_tmp_&). If this exists,
24085 Exim assumes the directory is a maildir++ folder directory, which is one level
24086 down from the user's top level mailbox directory. This causes it to start at
24087 the parent directory instead of the current directory when calculating the
24088 amount of space used.
24090 One problem with delivering into a multi-file mailbox is that it is
24091 computationally expensive to compute the size of the mailbox for quota
24092 checking. Various approaches have been taken to reduce the amount of work
24093 needed. The next two sections describe two of them. A third alternative is to
24094 use some external process for maintaining the size data, and use the expansion
24095 of the &%mailbox_size%& option as a way of importing it into Exim.
24100 .section "Using tags to record message sizes" "SECID135"
24101 If &%maildir_tag%& is set, the string is expanded for each delivery.
24102 When the maildir file is renamed into the &_new_& sub-directory, the
24103 tag is added to its name. However, if adding the tag takes the length of the
24104 name to the point where the test &[stat()]& call fails with ENAMETOOLONG,
24105 the tag is dropped and the maildir file is created with no tag.
24108 .vindex "&$message_size$&"
24109 Tags can be used to encode the size of files in their names; see
24110 &%quota_size_regex%& above for an example. The expansion of &%maildir_tag%&
24111 happens after the message has been written. The value of the &$message_size$&
24112 variable is set to the number of bytes actually written. If the expansion is
24113 forced to fail, the tag is ignored, but a non-forced failure causes delivery to
24114 be deferred. The expanded tag may contain any printing characters except &"/"&.
24115 Non-printing characters in the string are ignored; if the resulting string is
24116 empty, it is ignored. If it starts with an alphanumeric character, a leading
24117 colon is inserted; this default has not proven to be the path that popular
24118 maildir implementations have chosen (but changing it in Exim would break
24119 backwards compatibility).
24121 For one common implementation, you might set:
24123 maildir_tag = ,S=${message_size}
24125 but you should check the documentation of the other software to be sure.
24127 It is advisable to also set &%quota_size_regex%& when setting &%maildir_tag%&
24128 as this allows Exim to extract the size from your tag, instead of having to
24129 &[stat()]& each message file.
24132 .section "Using a maildirsize file" "SECID136"
24133 .cindex "quota" "in maildir delivery"
24134 .cindex "maildir format" "&_maildirsize_& file"
24135 If &%maildir_use_size_file%& is true, Exim implements the maildir++ rules for
24136 storing quota and message size information in a file called &_maildirsize_&
24137 within the toplevel maildir directory. If this file does not exist, Exim
24138 creates it, setting the quota from the &%quota%& option of the transport. If
24139 the maildir directory itself does not exist, it is created before any attempt
24140 to write a &_maildirsize_& file.
24142 The &_maildirsize_& file is used to hold information about the sizes of
24143 messages in the maildir, thus speeding up quota calculations. The quota value
24144 in the file is just a cache; if the quota is changed in the transport, the new
24145 value overrides the cached value when the next message is delivered. The cache
24146 is maintained for the benefit of other programs that access the maildir and
24147 need to know the quota.
24149 If the &%quota%& option in the transport is unset or zero, the &_maildirsize_&
24150 file is maintained (with a zero quota setting), but no quota is imposed.
24152 A regular expression is available for controlling which directories in the
24153 maildir participate in quota calculations when a &_maildirsizefile_& is in use.
24154 See the description of the &%maildir_quota_directory_regex%& option above for
24158 .section "Mailstore delivery" "SECID137"
24159 .cindex "mailstore format" "description of"
24160 If the &%mailstore_format%& option is true, each message is written as two
24161 files in the given directory. A unique base name is constructed from the
24162 message id and the current delivery process, and the files that are written use
24163 this base name plus the suffixes &_.env_& and &_.msg_&. The &_.env_& file
24164 contains the message's envelope, and the &_.msg_& file contains the message
24165 itself. The base name is placed in the variable &$mailstore_basename$&.
24167 During delivery, the envelope is first written to a file with the suffix
24168 &_.tmp_&. The &_.msg_& file is then written, and when it is complete, the
24169 &_.tmp_& file is renamed as the &_.env_& file. Programs that access messages in
24170 mailstore format should wait for the presence of both a &_.msg_& and a &_.env_&
24171 file before accessing either of them. An alternative approach is to wait for
24172 the absence of a &_.tmp_& file.
24174 The envelope file starts with any text defined by the &%mailstore_prefix%&
24175 option, expanded and terminated by a newline if there isn't one. Then follows
24176 the sender address on one line, then all the recipient addresses, one per line.
24177 There can be more than one recipient only if the &%batch_max%& option is set
24178 greater than one. Finally, &%mailstore_suffix%& is expanded and the result
24179 appended to the file, followed by a newline if it does not end with one.
24181 If expansion of &%mailstore_prefix%& or &%mailstore_suffix%& ends with a forced
24182 failure, it is ignored. Other expansion errors are treated as serious
24183 configuration errors, and delivery is deferred. The variable
24184 &$mailstore_basename$& is available for use during these expansions.
24187 .section "Non-special new file delivery" "SECID138"
24188 If neither &%maildir_format%& nor &%mailstore_format%& is set, a single new
24189 file is created directly in the named directory. For example, when delivering
24190 messages into files in batched SMTP format for later delivery to some host (see
24191 section &<<SECTbatchSMTP>>&), a setting such as
24193 directory = /var/bsmtp/$host
24195 might be used. A message is written to a file with a temporary name, which is
24196 then renamed when the delivery is complete. The final name is obtained by
24197 expanding the contents of the &%directory_file%& option.
24198 .ecindex IIDapptra1
24199 .ecindex IIDapptra2
24206 . ////////////////////////////////////////////////////////////////////////////
24207 . ////////////////////////////////////////////////////////////////////////////
24209 .chapter "The autoreply transport" "CHID8"
24210 .scindex IIDauttra1 "transports" "&(autoreply)&"
24211 .scindex IIDauttra2 "&(autoreply)& transport"
24212 The &(autoreply)& transport is not a true transport in that it does not cause
24213 the message to be transmitted. Instead, it generates a new mail message as an
24214 automatic reply to the incoming message. &'References:'& and
24215 &'Auto-Submitted:'& header lines are included. These are constructed according
24216 to the rules in RFCs 2822 and 3834, respectively.
24218 If the router that passes the message to this transport does not have the
24219 &%unseen%& option set, the original message (for the current recipient) is not
24220 delivered anywhere. However, when the &%unseen%& option is set on the router
24221 that passes the message to this transport, routing of the address continues, so
24222 another router can set up a normal message delivery.
24225 The &(autoreply)& transport is usually run as the result of mail filtering, a
24226 &"vacation"& message being the standard example. However, it can also be run
24227 directly from a router like any other transport. To reduce the possibility of
24228 message cascades, messages created by the &(autoreply)& transport always have
24229 empty envelope sender addresses, like bounce messages.
24231 The parameters of the message to be sent can be specified in the configuration
24232 by options described below. However, these are used only when the address
24233 passed to the transport does not contain its own reply information. When the
24234 transport is run as a consequence of a
24236 or &%vacation%& command in a filter file, the parameters of the message are
24237 supplied by the filter, and passed with the address. The transport's options
24238 that define the message are then ignored (so they are not usually set in this
24239 case). The message is specified entirely by the filter or by the transport; it
24240 is never built from a mixture of options. However, the &%file_optional%&,
24241 &%mode%&, and &%return_message%& options apply in all cases.
24243 &(Autoreply)& is implemented as a local transport. When used as a result of a
24244 command in a user's filter file, &(autoreply)& normally runs under the uid and
24245 gid of the user, and with appropriate current and home directories (see chapter
24246 &<<CHAPenvironment>>&).
24248 There is a subtle difference between routing a message to a &(pipe)& transport
24249 that generates some text to be returned to the sender, and routing it to an
24250 &(autoreply)& transport. This difference is noticeable only if more than one
24251 address from the same message is so handled. In the case of a pipe, the
24252 separate outputs from the different addresses are gathered up and returned to
24253 the sender in a single message, whereas if &(autoreply)& is used, a separate
24254 message is generated for each address that is passed to it.
24256 Non-printing characters are not permitted in the header lines generated for the
24257 message that &(autoreply)& creates, with the exception of newlines that are
24258 immediately followed by white space. If any non-printing characters are found,
24259 the transport defers.
24260 Whether characters with the top bit set count as printing characters or not is
24261 controlled by the &%print_topbitchars%& global option.
24263 If any of the generic options for manipulating headers (for example,
24264 &%headers_add%&) are set on an &(autoreply)& transport, they apply to the copy
24265 of the original message that is included in the generated message when
24266 &%return_message%& is set. They do not apply to the generated message itself.
24268 .vindex "&$sender_address$&"
24269 If the &(autoreply)& transport receives return code 2 from Exim when it submits
24270 the message, indicating that there were no recipients, it does not treat this
24271 as an error. This means that autoreplies sent to &$sender_address$& when this
24272 is empty (because the incoming message is a bounce message) do not cause
24273 problems. They are just discarded.
24277 .section "Private options for autoreply" "SECID139"
24278 .cindex "options" "&(autoreply)& transport"
24280 .option bcc autoreply string&!! unset
24281 This specifies the addresses that are to receive &"blind carbon copies"& of the
24282 message when the message is specified by the transport.
24285 .option cc autoreply string&!! unset
24286 This specifies recipients of the message and the contents of the &'Cc:'& header
24287 when the message is specified by the transport.
24290 .option file autoreply string&!! unset
24291 The contents of the file are sent as the body of the message when the message
24292 is specified by the transport. If both &%file%& and &%text%& are set, the text
24293 string comes first.
24296 .option file_expand autoreply boolean false
24297 If this is set, the contents of the file named by the &%file%& option are
24298 subjected to string expansion as they are added to the message.
24301 .option file_optional autoreply boolean false
24302 If this option is true, no error is generated if the file named by the &%file%&
24303 option or passed with the address does not exist or cannot be read.
24306 .option from autoreply string&!! unset
24307 This specifies the contents of the &'From:'& header when the message is
24308 specified by the transport.
24311 .option headers autoreply string&!! unset
24312 This specifies additional RFC 2822 headers that are to be added to the message
24313 when the message is specified by the transport. Several can be given by using
24314 &"\n"& to separate them. There is no check on the format.
24317 .option log autoreply string&!! unset
24318 This option names a file in which a record of every message sent is logged when
24319 the message is specified by the transport.
24322 .option mode autoreply "octal integer" 0600
24323 If either the log file or the &"once"& file has to be created, this mode is
24327 .option never_mail autoreply "address list&!!" unset
24328 If any run of the transport creates a message with a recipient that matches any
24329 item in the list, that recipient is quietly discarded. If all recipients are
24330 discarded, no message is created. This applies both when the recipients are
24331 generated by a filter and when they are specified in the transport.
24335 .option once autoreply string&!! unset
24336 This option names a file or DBM database in which a record of each &'To:'&
24337 recipient is kept when the message is specified by the transport. &*Note*&:
24338 This does not apply to &'Cc:'& or &'Bcc:'& recipients.
24340 If &%once%& is unset, or is set to an empty string, the message is always sent.
24341 By default, if &%once%& is set to a non-empty filename, the message
24342 is not sent if a potential recipient is already listed in the database.
24343 However, if the &%once_repeat%& option specifies a time greater than zero, the
24344 message is sent if that much time has elapsed since a message was last sent to
24345 this recipient. A setting of zero time for &%once_repeat%& (the default)
24346 prevents a message from being sent a second time &-- in this case, zero means
24349 If &%once_file_size%& is zero, a DBM database is used to remember recipients,
24350 and it is allowed to grow as large as necessary. If &%once_file_size%& is set
24351 greater than zero, it changes the way Exim implements the &%once%& option.
24352 Instead of using a DBM file to record every recipient it sends to, it uses a
24353 regular file, whose size will never get larger than the given value.
24355 In the file, Exim keeps a linear list of recipient addresses and the times at
24356 which they were sent messages. If the file is full when a new address needs to
24357 be added, the oldest address is dropped. If &%once_repeat%& is not set, this
24358 means that a given recipient may receive multiple messages, but at
24359 unpredictable intervals that depend on the rate of turnover of addresses in the
24360 file. If &%once_repeat%& is set, it specifies a maximum time between repeats.
24363 .option once_file_size autoreply integer 0
24364 See &%once%& above.
24367 .option once_repeat autoreply time&!! 0s
24368 See &%once%& above.
24369 After expansion, the value of this option must be a valid time value.
24372 .option reply_to autoreply string&!! unset
24373 This specifies the contents of the &'Reply-To:'& header when the message is
24374 specified by the transport.
24377 .option return_message autoreply boolean false
24378 If this is set, a copy of the original message is returned with the new
24379 message, subject to the maximum size set in the &%return_size_limit%& global
24380 configuration option.
24383 .option subject autoreply string&!! unset
24384 This specifies the contents of the &'Subject:'& header when the message is
24385 specified by the transport. It is tempting to quote the original subject in
24386 automatic responses. For example:
24388 subject = Re: $h_subject:
24390 There is a danger in doing this, however. It may allow a third party to
24391 subscribe your users to an opt-in mailing list, provided that the list accepts
24392 bounce messages as subscription confirmations. Well-managed lists require a
24393 non-bounce message to confirm a subscription, so the danger is relatively
24398 .option text autoreply string&!! unset
24399 This specifies a single string to be used as the body of the message when the
24400 message is specified by the transport. If both &%text%& and &%file%& are set,
24401 the text comes first.
24404 .option to autoreply string&!! unset
24405 This specifies recipients of the message and the contents of the &'To:'& header
24406 when the message is specified by the transport.
24407 .ecindex IIDauttra1
24408 .ecindex IIDauttra2
24413 . ////////////////////////////////////////////////////////////////////////////
24414 . ////////////////////////////////////////////////////////////////////////////
24416 .chapter "The lmtp transport" "CHAPLMTP"
24417 .cindex "transports" "&(lmtp)&"
24418 .cindex "&(lmtp)& transport"
24419 .cindex "LMTP" "over a pipe"
24420 .cindex "LMTP" "over a socket"
24421 The &(lmtp)& transport runs the LMTP protocol (RFC 2033) over a pipe to a
24423 or by interacting with a Unix domain socket.
24424 This transport is something of a cross between the &(pipe)& and &(smtp)&
24425 transports. Exim also has support for using LMTP over TCP/IP; this is
24426 implemented as an option for the &(smtp)& transport. Because LMTP is expected
24427 to be of minority interest, the default build-time configure in &_src/EDITME_&
24428 has it commented out. You need to ensure that
24432 .cindex "options" "&(lmtp)& transport"
24433 is present in your &_Local/Makefile_& in order to have the &(lmtp)& transport
24434 included in the Exim binary. The private options of the &(lmtp)& transport are
24437 .option batch_id lmtp string&!! unset
24438 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
24441 .option batch_max lmtp integer 1
24442 This limits the number of addresses that can be handled in a single delivery.
24443 Most LMTP servers can handle several addresses at once, so it is normally a
24444 good idea to increase this value. See the description of local delivery
24445 batching in chapter &<<CHAPbatching>>&.
24448 .option command lmtp string&!! unset
24449 This option must be set if &%socket%& is not set. The string is a command which
24450 is run in a separate process. It is split up into a command name and list of
24451 arguments, each of which is separately expanded (so expansion cannot change the
24452 number of arguments). The command is run directly, not via a shell. The message
24453 is passed to the new process using the standard input and output to operate the
24456 .option ignore_quota lmtp boolean false
24457 .cindex "LMTP" "ignoring quota errors"
24458 If this option is set true, the string &`IGNOREQUOTA`& is added to RCPT
24459 commands, provided that the LMTP server has advertised support for IGNOREQUOTA
24460 in its response to the LHLO command.
24462 .option socket lmtp string&!! unset
24463 This option must be set if &%command%& is not set. The result of expansion must
24464 be the name of a Unix domain socket. The transport connects to the socket and
24465 delivers the message to it using the LMTP protocol.
24468 .option timeout lmtp time 5m
24469 The transport is aborted if the created process or Unix domain socket does not
24470 respond to LMTP commands or message input within this timeout. Delivery
24471 is deferred, and will be tried again later. Here is an example of a typical
24476 command = /some/local/lmtp/delivery/program
24480 This delivers up to 20 addresses at a time, in a mixture of domains if
24481 necessary, running as the user &'exim'&.
24485 . ////////////////////////////////////////////////////////////////////////////
24486 . ////////////////////////////////////////////////////////////////////////////
24488 .chapter "The pipe transport" "CHAPpipetransport"
24489 .scindex IIDpiptra1 "transports" "&(pipe)&"
24490 .scindex IIDpiptra2 "&(pipe)& transport"
24491 The &(pipe)& transport is used to deliver messages via a pipe to a command
24492 running in another process. One example is the use of &(pipe)& as a
24493 pseudo-remote transport for passing messages to some other delivery mechanism
24494 (such as UUCP). Another is the use by individual users to automatically process
24495 their incoming messages. The &(pipe)& transport can be used in one of the
24499 .vindex "&$local_part$&"
24500 A router routes one address to a transport in the normal way, and the
24501 transport is configured as a &(pipe)& transport. In this case, &$local_part$&
24502 contains the local part of the address (as usual), and the command that is run
24503 is specified by the &%command%& option on the transport.
24505 .vindex "&$pipe_addresses$&"
24506 If the &%batch_max%& option is set greater than 1 (the default is 1), the
24507 transport can handle more than one address in a single run. In this case, when
24508 more than one address is routed to the transport, &$local_part$& is not set
24509 (because it is not unique). However, the pseudo-variable &$pipe_addresses$&
24510 (described in section &<<SECThowcommandrun>>& below) contains all the addresses
24511 that are routed to the transport.
24513 .vindex "&$address_pipe$&"
24514 A router redirects an address directly to a pipe command (for example, from an
24515 alias or forward file). In this case, &$address_pipe$& contains the text of the
24516 pipe command, and the &%command%& option on the transport is ignored unless
24517 &%force_command%& is set. If only one address is being transported
24518 (&%batch_max%& is not greater than one, or only one address was redirected to
24519 this pipe command), &$local_part$& contains the local part that was redirected.
24523 The &(pipe)& transport is a non-interactive delivery method. Exim can also
24524 deliver messages over pipes using the LMTP interactive protocol. This is
24525 implemented by the &(lmtp)& transport.
24527 In the case when &(pipe)& is run as a consequence of an entry in a local user's
24528 &_.forward_& file, the command runs under the uid and gid of that user. In
24529 other cases, the uid and gid have to be specified explicitly, either on the
24530 transport or on the router that handles the address. Current and &"home"&
24531 directories are also controllable. See chapter &<<CHAPenvironment>>& for
24532 details of the local delivery environment and chapter &<<CHAPbatching>>&
24533 for a discussion of local delivery batching.
24535 .cindex "tainted data" "in pipe command"
24536 .cindex pipe "tainted data"
24537 Tainted data may not be used for the command name.
24540 .section "Concurrent delivery" "SECID140"
24541 If two messages arrive at almost the same time, and both are routed to a pipe
24542 delivery, the two pipe transports may be run concurrently. You must ensure that
24543 any pipe commands you set up are robust against this happening. If the commands
24544 write to a file, the &%exim_lock%& utility might be of use.
24545 Alternatively the &%max_parallel%& option could be used with a value
24546 of "1" to enforce serialization.
24551 .section "Returned status and data" "SECID141"
24552 .cindex "&(pipe)& transport" "returned data"
24553 If the command exits with a non-zero return code, the delivery is deemed to
24554 have failed, unless either the &%ignore_status%& option is set (in which case
24555 the return code is treated as zero), or the return code is one of those listed
24556 in the &%temp_errors%& option, which are interpreted as meaning &"try again
24557 later"&. In this case, delivery is deferred. Details of a permanent failure are
24558 logged, but are not included in the bounce message, which merely contains
24559 &"local delivery failed"&.
24561 If the command exits on a signal and the &%freeze_signal%& option is set then
24562 the message will be frozen in the queue. If that option is not set, a bounce
24563 will be sent as normal.
24565 If the return code is greater than 128 and the command being run is a shell
24566 script, it normally means that the script was terminated by a signal whose
24567 value is the return code minus 128. The &%freeze_signal%& option does not
24568 apply in this case.
24570 If Exim is unable to run the command (that is, if &[execve()]& fails), the
24571 return code is set to 127. This is the value that a shell returns if it is
24572 asked to run a non-existent command. The wording for the log line suggests that
24573 a non-existent command may be the problem.
24575 The &%return_output%& option can affect the result of a pipe delivery. If it is
24576 set and the command produces any output on its standard output or standard
24577 error streams, the command is considered to have failed, even if it gave a zero
24578 return code or if &%ignore_status%& is set. The output from the command is
24579 included as part of the bounce message. The &%return_fail_output%& option is
24580 similar, except that output is returned only when the command exits with a
24581 failure return code, that is, a value other than zero or a code that matches
24586 .section "How the command is run" "SECThowcommandrun"
24587 .cindex "&(pipe)& transport" "path for command"
24588 The command line is (by default) broken down into a command name and arguments
24589 by the &(pipe)& transport itself. The &%allow_commands%& and
24590 &%restrict_to_path%& options can be used to restrict the commands that may be
24593 .cindex "quoting" "in pipe command"
24594 Unquoted arguments are delimited by white space. If an argument appears in
24595 double quotes, backslash is interpreted as an escape character in the usual
24596 way. If an argument appears in single quotes, no escaping is done.
24598 String expansion is applied to the command line except when it comes from a
24599 traditional &_.forward_& file (commands from a filter file are expanded). The
24600 expansion is applied to each argument in turn rather than to the whole line.
24601 For this reason, any string expansion item that contains white space must be
24602 quoted so as to be contained within a single argument. A setting such as
24604 command = /some/path ${if eq{$local_part}{postmaster}{xx}{yy}}
24606 will not work, because the expansion item gets split between several
24607 arguments. You have to write
24609 command = /some/path "${if eq{$local_part}{postmaster}{xx}{yy}}"
24611 to ensure that it is all in one argument. The expansion is done in this way,
24612 argument by argument, so that the number of arguments cannot be changed as a
24613 result of expansion, and quotes or backslashes in inserted variables do not
24614 interact with external quoting. However, this leads to problems if you want to
24615 generate multiple arguments (or the command name plus arguments) from a single
24616 expansion. In this situation, the simplest solution is to use a shell. For
24619 command = /bin/sh -c ${lookup{$local_part}lsearch{/some/file}}
24622 .cindex "transport" "filter"
24623 .cindex "filter" "transport filter"
24624 .vindex "&$pipe_addresses$&"
24625 Special handling takes place when an argument consists of precisely the text
24626 &`$pipe_addresses`& (no quotes).
24627 This is not a general expansion variable; the only
24628 place this string is recognized is when it appears as an argument for a pipe or
24629 transport filter command. It causes each address that is being handled to be
24630 inserted in the argument list at that point &'as a separate argument'&. This
24631 avoids any problems with spaces or shell metacharacters, and is of use when a
24632 &(pipe)& transport is handling groups of addresses in a batch.
24634 If &%force_command%& is enabled on the transport, special handling takes place
24635 for an argument that consists of precisely the text &`$address_pipe`&. It
24636 is handled similarly to &$pipe_addresses$& above. It is expanded and each
24637 argument is inserted in the argument list at that point
24638 &'as a separate argument'&. The &`$address_pipe`& item does not need to be
24639 the only item in the argument; in fact, if it were then &%force_command%&
24640 should behave as a no-op. Rather, it should be used to adjust the command
24641 run while preserving the argument vector separation.
24643 After splitting up into arguments and expansion, the resulting command is run
24644 in a subprocess directly from the transport, &'not'& under a shell. The
24645 message that is being delivered is supplied on the standard input, and the
24646 standard output and standard error are both connected to a single pipe that is
24647 read by Exim. The &%max_output%& option controls how much output the command
24648 may produce, and the &%return_output%& and &%return_fail_output%& options
24649 control what is done with it.
24651 Not running the command under a shell (by default) lessens the security risks
24652 in cases when a command from a user's filter file is built out of data that was
24653 taken from an incoming message. If a shell is required, it can of course be
24654 explicitly specified as the command to be run. However, there are circumstances
24655 where existing commands (for example, in &_.forward_& files) expect to be run
24656 under a shell and cannot easily be modified. To allow for these cases, there is
24657 an option called &%use_shell%&, which changes the way the &(pipe)& transport
24658 works. Instead of breaking up the command line as just described, it expands it
24659 as a single string and passes the result to &_/bin/sh_&. The
24660 &%restrict_to_path%& option and the &$pipe_addresses$& facility cannot be used
24661 with &%use_shell%&, and the whole mechanism is inherently less secure.
24665 .section "Environment variables" "SECTpipeenv"
24666 .cindex "&(pipe)& transport" "environment for command"
24667 .cindex "environment" "&(pipe)& transport"
24668 The environment variables listed below are set up when the command is invoked.
24669 This list is a compromise for maximum compatibility with other MTAs. Note that
24670 the &%environment%& option can be used to add additional variables to this
24671 environment. The environment for the &(pipe)& transport is not subject
24672 to the &%add_environment%& and &%keep_environment%& main config options.
24673 &*Note*&: Using enviroment variables loses track of tainted data.
24674 Writers of &(pipe)& transport commands should be wary of data supplied
24675 by potential attackers.
24677 &`DOMAIN `& the domain of the address
24678 &`HOME `& the home directory, if set
24679 &`HOST `& the host name when called from a router (see below)
24680 &`LOCAL_PART `& see below
24681 &`LOCAL_PART_PREFIX `& see below
24682 &`LOCAL_PART_SUFFIX `& see below
24683 &`LOGNAME `& see below
24684 &`MESSAGE_ID `& Exim's local ID for the message
24685 &`PATH `& as specified by the &%path%& option below
24686 &`QUALIFY_DOMAIN `& the sender qualification domain
24687 &`RECIPIENT `& the complete recipient address
24688 &`SENDER `& the sender of the message (empty if a bounce)
24689 &`SHELL `& &`/bin/sh`&
24690 &`TZ `& the value of the &%timezone%& option, if set
24691 &`USER `& see below
24693 When a &(pipe)& transport is called directly from (for example) an &(accept)&
24694 router, LOCAL_PART is set to the local part of the address. When it is
24695 called as a result of a forward or alias expansion, LOCAL_PART is set to
24696 the local part of the address that was expanded. In both cases, any affixes are
24697 removed from the local part, and made available in LOCAL_PART_PREFIX and
24698 LOCAL_PART_SUFFIX, respectively. LOGNAME and USER are set to the
24699 same value as LOCAL_PART for compatibility with other MTAs.
24702 HOST is set only when a &(pipe)& transport is called from a router that
24703 associates hosts with an address, typically when using &(pipe)& as a
24704 pseudo-remote transport. HOST is set to the first host name specified by
24708 If the transport's generic &%home_directory%& option is set, its value is used
24709 for the HOME environment variable. Otherwise, a home directory may be set
24710 by the router's &%transport_home_directory%& option, which defaults to the
24711 user's home directory if &%check_local_user%& is set.
24714 .section "Private options for pipe" "SECID142"
24715 .cindex "options" "&(pipe)& transport"
24719 .option allow_commands pipe "string list&!!" unset
24720 .cindex "&(pipe)& transport" "permitted commands"
24721 The string is expanded, and is then interpreted as a colon-separated list of
24722 permitted commands. If &%restrict_to_path%& is not set, the only commands
24723 permitted are those in the &%allow_commands%& list. They need not be absolute
24724 paths; the &%path%& option is still used for relative paths. If
24725 &%restrict_to_path%& is set with &%allow_commands%&, the command must either be
24726 in the &%allow_commands%& list, or a name without any slashes that is found on
24727 the path. In other words, if neither &%allow_commands%& nor
24728 &%restrict_to_path%& is set, there is no restriction on the command, but
24729 otherwise only commands that are permitted by one or the other are allowed. For
24732 allow_commands = /usr/bin/vacation
24734 and &%restrict_to_path%& is not set, the only permitted command is
24735 &_/usr/bin/vacation_&. The &%allow_commands%& option may not be set if
24736 &%use_shell%& is set.
24739 .option batch_id pipe string&!! unset
24740 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
24743 .option batch_max pipe integer 1
24744 This limits the number of addresses that can be handled in a single delivery.
24745 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
24748 .option check_string pipe string unset
24749 As &(pipe)& writes the message, the start of each line is tested for matching
24750 &%check_string%&, and if it does, the initial matching characters are replaced
24751 by the contents of &%escape_string%&, provided both are set. The value of
24752 &%check_string%& is a literal string, not a regular expression, and the case of
24753 any letters it contains is significant. When &%use_bsmtp%& is set, the contents
24754 of &%check_string%& and &%escape_string%& are forced to values that implement
24755 the SMTP escaping protocol. Any settings made in the configuration file are
24759 .option command pipe string&!! unset
24760 This option need not be set when &(pipe)& is being used to deliver to pipes
24761 obtained directly from address redirections. In other cases, the option must be
24762 set, to provide a command to be run. It need not yield an absolute path (see
24763 the &%path%& option below). The command is split up into separate arguments by
24764 Exim, and each argument is separately expanded, as described in section
24765 &<<SECThowcommandrun>>& above.
24767 .cindex "tainted data"
24768 No part of the resulting command may be tainted.
24771 .option environment pipe string&!! unset
24772 .cindex "&(pipe)& transport" "environment for command"
24773 .cindex "environment" "&(pipe)& transport"
24774 This option is used to add additional variables to the environment in which the
24775 command runs (see section &<<SECTpipeenv>>& for the default list). Its value is
24776 a string which is expanded, and then interpreted as a colon-separated list of
24777 environment settings of the form <&'name'&>=<&'value'&>.
24780 .option escape_string pipe string unset
24781 See &%check_string%& above.
24784 .option freeze_exec_fail pipe boolean false
24785 .cindex "exec failure"
24786 .cindex "failure of exec"
24787 .cindex "&(pipe)& transport" "failure of exec"
24788 Failure to exec the command in a pipe transport is by default treated like
24789 any other failure while running the command. However, if &%freeze_exec_fail%&
24790 is set, failure to exec is treated specially, and causes the message to be
24791 frozen, whatever the setting of &%ignore_status%&.
24794 .option freeze_signal pipe boolean false
24795 .cindex "signal exit"
24796 .cindex "&(pipe)& transport", "signal exit"
24797 Normally if the process run by a command in a pipe transport exits on a signal,
24798 a bounce message is sent. If &%freeze_signal%& is set, the message will be
24799 frozen in Exim's queue instead.
24802 .option force_command pipe boolean false
24803 .cindex "force command"
24804 .cindex "&(pipe)& transport", "force command"
24805 Normally when a router redirects an address directly to a pipe command
24806 the &%command%& option on the transport is ignored. If &%force_command%&
24807 is set, the &%command%& option will used. This is especially
24808 useful for forcing a wrapper or additional argument to be added to the
24809 command. For example:
24811 command = /usr/bin/remote_exec myhost -- $address_pipe
24815 Note that &$address_pipe$& is handled specially in &%command%& when
24816 &%force_command%& is set, expanding out to the original argument vector as
24817 separate items, similarly to a Unix shell &`"$@"`& construct.
24820 .option ignore_status pipe boolean false
24821 If this option is true, the status returned by the subprocess that is set up to
24822 run the command is ignored, and Exim behaves as if zero had been returned.
24823 Otherwise, a non-zero status or termination by signal causes an error return
24824 from the transport unless the status value is one of those listed in
24825 &%temp_errors%&; these cause the delivery to be deferred and tried again later.
24827 &*Note*&: This option does not apply to timeouts, which do not return a status.
24828 See the &%timeout_defer%& option for how timeouts are handled.
24831 .option log_defer_output pipe boolean false
24832 .cindex "&(pipe)& transport" "logging output"
24833 If this option is set, and the status returned by the command is
24834 one of the codes listed in &%temp_errors%& (that is, delivery was deferred),
24835 and any output was produced on stdout or stderr, the first line of it is
24836 written to the main log.
24839 .option log_fail_output pipe boolean false
24840 If this option is set, and the command returns any output on stdout or
24841 stderr, and also ends with a return code that is neither zero nor one of
24842 the return codes listed in &%temp_errors%& (that is, the delivery
24843 failed), the first line of output is written to the main log. This
24844 option and &%log_output%& are mutually exclusive. Only one of them may
24848 .option log_output pipe boolean false
24849 If this option is set and the command returns any output on stdout or
24850 stderr, the first line of output is written to the main log, whatever
24851 the return code. This option and &%log_fail_output%& are mutually
24852 exclusive. Only one of them may be set.
24855 .option max_output pipe integer 20K
24856 This specifies the maximum amount of output that the command may produce on its
24857 standard output and standard error file combined. If the limit is exceeded, the
24858 process running the command is killed. This is intended as a safety measure to
24859 catch runaway processes. The limit is applied independently of the settings of
24860 the options that control what is done with such output (for example,
24861 &%return_output%&). Because of buffering effects, the amount of output may
24862 exceed the limit by a small amount before Exim notices.
24865 .option message_prefix pipe string&!! "see below"
24866 The string specified here is expanded and output at the start of every message.
24867 The default is unset if &%use_bsmtp%& is set. Otherwise it is
24870 From ${if def:return_path{$return_path}{MAILER-DAEMON}}\
24874 .cindex "&%tmail%&"
24875 .cindex "&""From""& line"
24876 This is required by the commonly used &_/usr/bin/vacation_& program.
24877 However, it must &'not'& be present if delivery is to the Cyrus IMAP server,
24878 or to the &%tmail%& local delivery agent. The prefix can be suppressed by
24883 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
24884 &`\n`& to &`\r\n`& in &%message_prefix%&.
24887 .option message_suffix pipe string&!! "see below"
24888 The string specified here is expanded and output at the end of every message.
24889 The default is unset if &%use_bsmtp%& is set. Otherwise it is a single newline.
24890 The suffix can be suppressed by setting
24894 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
24895 &`\n`& to &`\r\n`& in &%message_suffix%&.
24898 .option path pipe string&!! "/bin:/usr/bin"
24899 This option is expanded and
24900 specifies the string that is set up in the PATH environment
24901 variable of the subprocess.
24902 If the &%command%& option does not yield an absolute path name, the command is
24903 sought in the PATH directories, in the usual way. &*Warning*&: This does not
24904 apply to a command specified as a transport filter.
24907 .option permit_coredump pipe boolean false
24908 Normally Exim inhibits core-dumps during delivery. If you have a need to get
24909 a core-dump of a pipe command, enable this command. This enables core-dumps
24910 during delivery and affects both the Exim binary and the pipe command run.
24911 It is recommended that this option remain off unless and until you have a need
24912 for it and that this only be enabled when needed, as the risk of excessive
24913 resource consumption can be quite high. Note also that Exim is typically
24914 installed as a setuid binary and most operating systems will inhibit coredumps
24915 of these by default, so further OS-specific action may be required.
24918 .option pipe_as_creator pipe boolean false
24919 .cindex "uid (user id)" "local delivery"
24920 If the generic &%user%& option is not set and this option is true, the delivery
24921 process is run under the uid that was in force when Exim was originally called
24922 to accept the message. If the group id is not otherwise set (via the generic
24923 &%group%& option), the gid that was in force when Exim was originally called to
24924 accept the message is used.
24927 .option restrict_to_path pipe boolean false
24928 When this option is set, any command name not listed in &%allow_commands%& must
24929 contain no slashes. The command is searched for only in the directories listed
24930 in the &%path%& option. This option is intended for use in the case when a pipe
24931 command has been generated from a user's &_.forward_& file. This is usually
24932 handled by a &(pipe)& transport called &%address_pipe%&.
24935 .option return_fail_output pipe boolean false
24936 If this option is true, and the command produced any output and ended with a
24937 return code other than zero or one of the codes listed in &%temp_errors%& (that
24938 is, the delivery failed), the output is returned in the bounce message.
24939 However, if the message has a null sender (that is, it is itself a bounce
24940 message), output from the command is discarded. This option and
24941 &%return_output%& are mutually exclusive. Only one of them may be set.
24945 .option return_output pipe boolean false
24946 If this option is true, and the command produced any output, the delivery is
24947 deemed to have failed whatever the return code from the command, and the output
24948 is returned in the bounce message. Otherwise, the output is just discarded.
24949 However, if the message has a null sender (that is, it is a bounce message),
24950 output from the command is always discarded, whatever the setting of this
24951 option. This option and &%return_fail_output%& are mutually exclusive. Only one
24952 of them may be set.
24956 .option temp_errors pipe "string list" "see below"
24957 .cindex "&(pipe)& transport" "temporary failure"
24958 This option contains either a colon-separated list of numbers, or a single
24959 asterisk. If &%ignore_status%& is false
24960 and &%return_output%& is not set,
24961 and the command exits with a non-zero return code, the failure is treated as
24962 temporary and the delivery is deferred if the return code matches one of the
24963 numbers, or if the setting is a single asterisk. Otherwise, non-zero return
24964 codes are treated as permanent errors. The default setting contains the codes
24965 defined by EX_TEMPFAIL and EX_CANTCREAT in &_sysexits.h_&. If Exim is
24966 compiled on a system that does not define these macros, it assumes values of 75
24967 and 73, respectively.
24970 .option timeout pipe time 1h
24971 If the command fails to complete within this time, it is killed. This normally
24972 causes the delivery to fail (but see &%timeout_defer%&). A zero time interval
24973 specifies no timeout. In order to ensure that any subprocesses created by the
24974 command are also killed, Exim makes the initial process a process group leader,
24975 and kills the whole process group on a timeout. However, this can be defeated
24976 if one of the processes starts a new process group.
24978 .option timeout_defer pipe boolean false
24979 A timeout in a &(pipe)& transport, either in the command that the transport
24980 runs, or in a transport filter that is associated with it, is by default
24981 treated as a hard error, and the delivery fails. However, if &%timeout_defer%&
24982 is set true, both kinds of timeout become temporary errors, causing the
24983 delivery to be deferred.
24985 .option umask pipe "octal integer" 022
24986 This specifies the umask setting for the subprocess that runs the command.
24989 .option use_bsmtp pipe boolean false
24990 .cindex "envelope sender"
24991 If this option is set true, the &(pipe)& transport writes messages in &"batch
24992 SMTP"& format, with the envelope sender and recipient(s) included as SMTP
24993 commands. If you want to include a leading HELO command with such messages,
24994 you can do so by setting the &%message_prefix%& option. See section
24995 &<<SECTbatchSMTP>>& for details of batch SMTP.
24997 .option use_classresources pipe boolean false
24998 .cindex "class resources (BSD)"
24999 This option is available only when Exim is running on FreeBSD, NetBSD, or
25000 BSD/OS. If it is set true, the &[setclassresources()]& function is used to set
25001 resource limits when a &(pipe)& transport is run to perform a delivery. The
25002 limits for the uid under which the pipe is to run are obtained from the login
25006 .option use_crlf pipe boolean false
25007 .cindex "carriage return"
25009 This option causes lines to be terminated with the two-character CRLF sequence
25010 (carriage return, linefeed) instead of just a linefeed character. In the case
25011 of batched SMTP, the byte sequence written to the pipe is then an exact image
25012 of what would be sent down a real SMTP connection.
25014 The contents of the &%message_prefix%& and &%message_suffix%& options are
25015 written verbatim, so must contain their own carriage return characters if these
25016 are needed. When &%use_bsmtp%& is not set, the default values for both
25017 &%message_prefix%& and &%message_suffix%& end with a single linefeed, so their
25018 values must be changed to end with &`\r\n`& if &%use_crlf%& is set.
25021 .option use_shell pipe boolean false
25022 .vindex "&$pipe_addresses$&"
25023 If this option is set, it causes the command to be passed to &_/bin/sh_&
25024 instead of being run directly from the transport, as described in section
25025 &<<SECThowcommandrun>>&. This is less secure, but is needed in some situations
25026 where the command is expected to be run under a shell and cannot easily be
25027 modified. The &%allow_commands%& and &%restrict_to_path%& options, and the
25028 &`$pipe_addresses`& facility are incompatible with &%use_shell%&. The
25029 command is expanded as a single string, and handed to &_/bin/sh_& as data for
25034 .section "Using an external local delivery agent" "SECID143"
25035 .cindex "local delivery" "using an external agent"
25036 .cindex "&'procmail'&"
25037 .cindex "external local delivery"
25038 .cindex "delivery" "&'procmail'&"
25039 .cindex "delivery" "by external agent"
25040 The &(pipe)& transport can be used to pass all messages that require local
25041 delivery to a separate local delivery agent such as &%procmail%&. When doing
25042 this, care must be taken to ensure that the pipe is run under an appropriate
25043 uid and gid. In some configurations one wants this to be a uid that is trusted
25044 by the delivery agent to supply the correct sender of the message. It may be
25045 necessary to recompile or reconfigure the delivery agent so that it trusts an
25046 appropriate user. The following is an example transport and router
25047 configuration for &%procmail%&:
25052 command = /usr/local/bin/procmail -d $local_part_data
25056 check_string = "From "
25057 escape_string = ">From "
25059 user = $local_part_data
25066 transport = procmail_pipe
25068 In this example, the pipe is run as the local user, but with the group set to
25069 &'mail'&. An alternative is to run the pipe as a specific user such as &'mail'&
25070 or &'exim'&, but in this case you must arrange for &%procmail%& to trust that
25071 user to supply a correct sender address. If you do not specify either a
25072 &%group%& or a &%user%& option, the pipe command is run as the local user. The
25073 home directory is the user's home directory by default.
25075 &*Note*&: The command that the pipe transport runs does &'not'& begin with
25079 as shown in some &%procmail%& documentation, because Exim does not by default
25080 use a shell to run pipe commands.
25083 The next example shows a transport and a router for a system where local
25084 deliveries are handled by the Cyrus IMAP server.
25085 . Used to have R: local_part_suffix = .* + T: -m $local_part_suffix_v
25086 . but that suffix is tainted so cannot be used in a command arg
25087 . Really, you'd want to use a lookup for acceptable suffixes to do real detainting
25090 local_delivery_cyrus:
25092 command = /usr/cyrus/bin/deliver \
25093 -- $local_part_data
25105 transport = local_delivery_cyrus
25107 Note the unsetting of &%message_prefix%& and &%message_suffix%&, and the use of
25108 &%return_output%& to cause any text written by Cyrus to be returned to the
25110 .ecindex IIDpiptra1
25111 .ecindex IIDpiptra2
25114 . ////////////////////////////////////////////////////////////////////////////
25115 . ////////////////////////////////////////////////////////////////////////////
25117 .chapter "The smtp transport" "CHAPsmtptrans"
25118 .scindex IIDsmttra1 "transports" "&(smtp)&"
25119 .scindex IIDsmttra2 "&(smtp)& transport"
25120 The &(smtp)& transport delivers messages over TCP/IP connections using the SMTP
25121 or LMTP protocol. The list of hosts to try can either be taken from the address
25122 that is being processed (having been set up by the router), or specified
25123 explicitly for the transport. Timeout and retry processing (see chapter
25124 &<<CHAPretry>>&) is applied to each IP address independently.
25127 .section "Multiple messages on a single connection" "SECID144"
25128 The sending of multiple messages over a single TCP/IP connection can arise in
25132 If a message contains more than &%max_rcpt%& (see below) addresses that are
25133 routed to the same host, more than one copy of the message has to be sent to
25134 that host. In this situation, multiple copies may be sent in a single run of
25135 the &(smtp)& transport over a single TCP/IP connection. (What Exim actually
25136 does when it has too many addresses to send in one message also depends on the
25137 value of the global &%remote_max_parallel%& option. Details are given in
25138 section &<<SECToutSMTPTCP>>&.)
25140 .cindex "hints database" "remembering routing"
25141 When a message has been successfully delivered over a TCP/IP connection, Exim
25142 looks in its hints database to see if there are any other messages awaiting a
25143 connection to the same host. If there are, a new delivery process is started
25144 for one of them, and the current TCP/IP connection is passed on to it. The new
25145 process may in turn send multiple copies and possibly create yet another
25150 For each copy sent over the same TCP/IP connection, a sequence counter is
25151 incremented, and if it ever gets to the value of &%connection_max_messages%&,
25152 no further messages are sent over that connection.
25156 .section "Use of the $host and $host_address variables" "SECID145"
25158 .vindex "&$host_address$&"
25159 At the start of a run of the &(smtp)& transport, the values of &$host$& and
25160 &$host_address$& are the name and IP address of the first host on the host list
25161 passed by the router. However, when the transport is about to connect to a
25162 specific host, and while it is connected to that host, &$host$& and
25163 &$host_address$& are set to the values for that host. These are the values
25164 that are in force when the &%helo_data%&, &%hosts_try_auth%&, &%interface%&,
25165 &%serialize_hosts%&, and the various TLS options are expanded.
25168 .section "Use of $tls_cipher and $tls_peerdn" "usecippeer"
25169 .vindex &$tls_bits$&
25170 .vindex &$tls_cipher$&
25171 .vindex &$tls_peerdn$&
25172 .vindex &$tls_sni$&
25173 At the start of a run of the &(smtp)& transport, the values of &$tls_bits$&,
25174 &$tls_cipher$&, &$tls_peerdn$& and &$tls_sni$&
25175 are the values that were set when the message was received.
25176 These are the values that are used for options that are expanded before any
25177 SMTP connections are made. Just before each connection is made, these four
25178 variables are emptied. If TLS is subsequently started, they are set to the
25179 appropriate values for the outgoing connection, and these are the values that
25180 are in force when any authenticators are run and when the
25181 &%authenticated_sender%& option is expanded.
25183 These variables are deprecated in favour of &$tls_in_cipher$& et. al.
25184 and will be removed in a future release.
25187 .section "Private options for smtp" "SECID146"
25188 .cindex "options" "&(smtp)& transport"
25189 The private options of the &(smtp)& transport are as follows:
25192 .option address_retry_include_sender smtp boolean true
25193 .cindex "4&'xx'& responses" "retrying after"
25194 When an address is delayed because of a 4&'xx'& response to a RCPT command, it
25195 is the combination of sender and recipient that is delayed in subsequent queue
25196 runs until the retry time is reached. You can delay the recipient without
25197 reference to the sender (which is what earlier versions of Exim did), by
25198 setting &%address_retry_include_sender%& false. However, this can lead to
25199 problems with servers that regularly issue 4&'xx'& responses to RCPT commands.
25201 .option allow_localhost smtp boolean false
25202 .cindex "local host" "sending to"
25203 .cindex "fallback" "hosts specified on transport"
25204 When a host specified in &%hosts%& or &%fallback_hosts%& (see below) turns out
25205 to be the local host, or is listed in &%hosts_treat_as_local%&, delivery is
25206 deferred by default. However, if &%allow_localhost%& is set, Exim goes on to do
25207 the delivery anyway. This should be used only in special cases when the
25208 configuration ensures that no looping will result (for example, a differently
25209 configured Exim is listening on the port to which the message is sent).
25212 .option authenticated_sender smtp string&!! unset
25214 When Exim has authenticated as a client, or if &%authenticated_sender_force%&
25215 is true, this option sets a value for the AUTH= item on outgoing MAIL commands,
25216 overriding any existing authenticated sender value. If the string expansion is
25217 forced to fail, the option is ignored. Other expansion failures cause delivery
25218 to be deferred. If the result of expansion is an empty string, that is also
25221 The expansion happens after the outgoing connection has been made and TLS
25222 started, if required. This means that the &$host$&, &$host_address$&,
25223 &$tls_out_cipher$&, and &$tls_out_peerdn$& variables are set according to the
25224 particular connection.
25226 If the SMTP session is not authenticated, the expansion of
25227 &%authenticated_sender%& still happens (and can cause the delivery to be
25228 deferred if it fails), but no AUTH= item is added to MAIL commands
25229 unless &%authenticated_sender_force%& is true.
25231 This option allows you to use the &(smtp)& transport in LMTP mode to
25232 deliver mail to Cyrus IMAP and provide the proper local part as the
25233 &"authenticated sender"&, via a setting such as:
25235 authenticated_sender = $local_part
25237 This removes the need for IMAP subfolders to be assigned special ACLs to
25238 allow direct delivery to those subfolders.
25240 Because of expected uses such as that just described for Cyrus (when no
25241 domain is involved), there is no checking on the syntax of the provided
25245 .option authenticated_sender_force smtp boolean false
25246 If this option is set true, the &%authenticated_sender%& option's value
25247 is used for the AUTH= item on outgoing MAIL commands, even if Exim has not
25248 authenticated as a client.
25251 .option command_timeout smtp time 5m
25252 .cindex timeout "smtp transport command"
25253 This sets a timeout for receiving a response to an SMTP command that has been
25254 sent out. It is also used when waiting for the initial banner line from the
25255 remote host. Its value must not be zero.
25258 .option connect_timeout smtp time 5m
25259 .cindex timeout "smtp transport connect"
25260 This sets a timeout for the &[connect()]& function, which sets up a TCP/IP call
25261 to a remote host. A setting of zero allows the system timeout (typically
25262 several minutes) to act. To have any effect, the value of this option must be
25263 less than the system timeout. However, it has been observed that on some
25264 systems there is no system timeout, which is why the default value for this
25265 option is 5 minutes, a value recommended by RFC 1123.
25268 .option connection_max_messages smtp integer 500
25269 .cindex "SMTP" "passed connection"
25270 .cindex "SMTP" "multiple deliveries"
25271 .cindex "multiple SMTP deliveries"
25272 This controls the maximum number of separate message deliveries that are sent
25273 over a single TCP/IP connection. If the value is zero, there is no limit.
25274 For testing purposes, this value can be overridden by the &%-oB%& command line
25278 .option dane_require_tls_ciphers smtp string&!! unset
25279 .cindex "TLS" "requiring specific ciphers for DANE"
25280 .cindex "cipher" "requiring specific"
25281 .cindex DANE "TLS ciphers"
25282 This option may be used to override &%tls_require_ciphers%& for connections
25283 where DANE has been determined to be in effect.
25284 If not set, then &%tls_require_ciphers%& will be used.
25285 Normal SMTP delivery is not able to make strong demands of TLS cipher
25286 configuration, because delivery will fall back to plaintext. Once DANE has
25287 been determined to be in effect, there is no plaintext fallback and making the
25288 TLS cipherlist configuration stronger will increase security, rather than
25289 counter-intuitively decreasing it.
25290 If the option expands to be empty or is forced to fail, then it will
25291 be treated as unset and &%tls_require_ciphers%& will be used instead.
25294 .option data_timeout smtp time 5m
25295 .cindex timeout "for transmitted SMTP data blocks"
25296 This sets a timeout for the transmission of each block in the data portion of
25297 the message. As a result, the overall timeout for a message depends on the size
25298 of the message. Its value must not be zero. See also &%final_timeout%&.
25301 .option dkim_canon smtp string&!! unset
25302 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25303 .option dkim_domain smtp "string list&!!" unset
25304 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25305 .option dkim_hash smtp string&!! sha256
25306 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25307 .option dkim_identity smtp string&!! unset
25308 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25309 .option dkim_private_key smtp string&!! unset
25310 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25311 .option dkim_selector smtp string&!! unset
25312 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25313 .option dkim_strict smtp string&!! unset
25314 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25315 .option dkim_sign_headers smtp string&!! "per RFC"
25316 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25317 .option dkim_timestamps smtp string&!! unset
25318 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25321 .option delay_after_cutoff smtp boolean true
25322 .cindex "final cutoff" "retries, controlling"
25323 .cindex retry "final cutoff"
25324 This option controls what happens when all remote IP addresses for a given
25325 domain have been inaccessible for so long that they have passed their retry
25328 In the default state, if the next retry time has not been reached for any of
25329 them, the address is bounced without trying any deliveries. In other words,
25330 Exim delays retrying an IP address after the final cutoff time until a new
25331 retry time is reached, and can therefore bounce an address without ever trying
25332 a delivery, when machines have been down for a long time. Some people are
25333 unhappy at this prospect, so...
25335 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
25336 addresses are past their final cutoff time, Exim tries to deliver to those
25337 IP addresses that have not been tried since the message arrived. If there are
25338 none, of if they all fail, the address is bounced. In other words, it does not
25339 delay when a new message arrives, but immediately tries those expired IP
25340 addresses that haven't been tried since the message arrived. If there is a
25341 continuous stream of messages for the dead hosts, unsetting
25342 &%delay_after_cutoff%& means that there will be many more attempts to deliver
25346 .option dns_qualify_single smtp boolean true
25347 If the &%hosts%& or &%fallback_hosts%& option is being used,
25348 and the &%gethostbyname%& option is false,
25349 the RES_DEFNAMES resolver option is set. See the &%qualify_single%& option
25350 in chapter &<<CHAPdnslookup>>& for more details.
25353 .option dns_search_parents smtp boolean false
25354 If the &%hosts%& or &%fallback_hosts%& option is being used, and the
25355 &%gethostbyname%& option is false, the RES_DNSRCH resolver option is set.
25356 See the &%search_parents%& option in chapter &<<CHAPdnslookup>>& for more
25360 .option dnssec_request_domains smtp "domain list&!!" *
25361 .cindex "MX record" "security"
25362 .cindex "DNSSEC" "MX lookup"
25363 .cindex "security" "MX lookup"
25364 .cindex "DNS" "DNSSEC"
25365 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
25366 the DNSSEC request bit set. Setting this transport option is only useful if the
25367 transport overrides or sets the host names. See the &%dnssec_request_domains%&
25372 .option dnssec_require_domains smtp "domain list&!!" unset
25373 .cindex "MX record" "security"
25374 .cindex "DNSSEC" "MX lookup"
25375 .cindex "security" "MX lookup"
25376 .cindex "DNS" "DNSSEC"
25377 DNS lookups for domains matching &%dnssec_require_domains%& will be done with
25378 the DNSSEC request bit set. Setting this transport option is only
25379 useful if the transport overrides or sets the host names. See the
25380 &%dnssec_require_domains%& router option.
25384 .option dscp smtp string&!! unset
25385 .cindex "DCSP" "outbound"
25386 This option causes the DSCP value associated with a socket to be set to one
25387 of a number of fixed strings or to numeric value.
25388 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
25389 Common values include &`throughput`&, &`mincost`&, and on newer systems
25390 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
25392 The outbound packets from Exim will be marked with this value in the header
25393 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
25394 that these values will have any effect, not be stripped by networking
25395 equipment, or do much of anything without cooperation with your Network
25396 Engineer and those of all network operators between the source and destination.
25399 .option fallback_hosts smtp "string list" unset
25400 .cindex "fallback" "hosts specified on transport"
25401 String expansion is not applied to this option. The argument must be a
25402 colon-separated list of host names or IP addresses, optionally also including
25403 port numbers, though the separator can be changed, as described in section
25404 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
25405 item in a &%route_list%& setting for the &(manualroute)& router, as described
25406 in section &<<SECTformatonehostitem>>&.
25408 Fallback hosts can also be specified on routers, which associate them with the
25409 addresses they process. As for the &%hosts%& option without &%hosts_override%&,
25410 &%fallback_hosts%& specified on the transport is used only if the address does
25411 not have its own associated fallback host list. Unlike &%hosts%&, a setting of
25412 &%fallback_hosts%& on an address is not overridden by &%hosts_override%&.
25413 However, &%hosts_randomize%& does apply to fallback host lists.
25415 If Exim is unable to deliver to any of the hosts for a particular address, and
25416 the errors are not permanent rejections, the address is put on a separate
25417 transport queue with its host list replaced by the fallback hosts, unless the
25418 address was routed via MX records and the current host was in the original MX
25419 list. In that situation, the fallback host list is not used.
25421 Once normal deliveries are complete, the fallback queue is delivered by
25422 re-running the same transports with the new host lists. If several failing
25423 addresses have the same fallback hosts (and &%max_rcpt%& permits it), a single
25424 copy of the message is sent.
25426 The resolution of the host names on the fallback list is controlled by the
25427 &%gethostbyname%& option, as for the &%hosts%& option. Fallback hosts apply
25428 both to cases when the host list comes with the address and when it is taken
25429 from &%hosts%&. This option provides a &"use a smart host only if delivery
25433 .option final_timeout smtp time 10m
25434 .cindex timeout "for transmitted SMTP data accept"
25435 This is the timeout that applies while waiting for the response to the final
25436 line containing just &"."& that terminates a message. Its value must not be
25439 .option gethostbyname smtp boolean false
25440 If this option is true when the &%hosts%& and/or &%fallback_hosts%& options are
25441 being used, names are looked up using &[gethostbyname()]&
25442 (or &[getipnodebyname()]& when available)
25443 instead of using the DNS. Of course, that function may in fact use the DNS, but
25444 it may also consult other sources of information such as &_/etc/hosts_&.
25446 .option gnutls_compat_mode smtp boolean unset
25447 This option controls whether GnuTLS is used in compatibility mode in an Exim
25448 server. This reduces security slightly, but improves interworking with older
25449 implementations of TLS.
25451 .option helo_data smtp string&!! "see below"
25452 .cindex "HELO" "argument, setting"
25453 .cindex "EHLO" "argument, setting"
25454 .cindex "LHLO argument setting"
25455 The value of this option is expanded after a connection to a another host has
25456 been set up. The result is used as the argument for the EHLO, HELO, or LHLO
25457 command that starts the outgoing SMTP or LMTP session. The default value of the
25462 During the expansion, the variables &$host$& and &$host_address$& are set to
25463 the identity of the remote host, and the variables &$sending_ip_address$& and
25464 &$sending_port$& are set to the local IP address and port number that are being
25465 used. These variables can be used to generate different values for different
25466 servers or different local IP addresses. For example, if you want the string
25467 that is used for &%helo_data%& to be obtained by a DNS lookup of the outgoing
25468 interface address, you could use this:
25470 helo_data = ${lookup dnsdb{ptr=$sending_ip_address} \
25471 {${listextract{1}{<\n $value}}} \
25472 {$primary_hostname}}
25474 The use of &%helo_data%& applies both to sending messages and when doing
25477 .option host_name_extract smtp "string list&!!" "see below"
25478 .cindex "load balancer" "hosts behind"
25479 .cindex TLS resumption
25480 Some mail-accepting sites
25481 (notably Microsoft)
25482 operate many servers behind a network load-balancer. When this is done,
25483 with separated TLS session caches, TLS session resuption becomes problematic.
25484 It will only succeed when the same server happens to be selected by the
25485 load-balancer, matching the session stored in the client's cache.
25487 Exim can pull out a server name, if there is one, from the response to the
25488 client's SMTP EHLO command.
25489 The default value of this option:
25491 ${if and { {match {$host} {.outlook.com\$}} \
25492 {match {$item} {\N^250-([\w.]+)\s\N}} \
25495 suffices for one known case.
25496 During the expansion of this option the &$item$& variable will have the
25497 server's EHLO response.
25498 The result of the option expansion is included in the key used to store and
25499 retrieve the TLS session, for session resumption.
25501 Operators of high-load sites may wish to evaluate their logs for indications
25502 of other destination sites operating load-balancers, and develop a suitable
25503 expression for this option.
25504 The smtp:ehlo event and the &$tls_out_resumption$& variable
25505 will be useful for such work.
25507 .option hosts smtp "string list&!!" unset
25508 Hosts are associated with an address by a router such as &(dnslookup)&, which
25509 finds the hosts by looking up the address domain in the DNS, or by
25510 &(manualroute)&, which has lists of hosts in its configuration. However,
25511 email addresses can be passed to the &(smtp)& transport by any router, and not
25512 all of them can provide an associated list of hosts.
25514 The &%hosts%& option specifies a list of hosts to be used if the address being
25515 processed does not have any hosts associated with it. The hosts specified by
25516 &%hosts%& are also used, whether or not the address has its own hosts, if
25517 &%hosts_override%& is set.
25519 The string is first expanded, before being interpreted as a colon-separated
25520 list of host names or IP addresses, possibly including port numbers. The
25521 separator may be changed to something other than colon, as described in section
25522 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
25523 item in a &%route_list%& setting for the &(manualroute)& router, as described
25524 in section &<<SECTformatonehostitem>>&. However, note that the &`/MX`& facility
25525 of the &(manualroute)& router is not available here.
25527 If the expansion fails, delivery is deferred. Unless the failure was caused by
25528 the inability to complete a lookup, the error is logged to the panic log as
25529 well as the main log. Host names are looked up either by searching directly for
25530 address records in the DNS or by calling &[gethostbyname()]& (or
25531 &[getipnodebyname()]& when available), depending on the setting of the
25532 &%gethostbyname%& option. When Exim is compiled with IPv6 support, if a host
25533 that is looked up in the DNS has both IPv4 and IPv6 addresses, both types of
25536 During delivery, the hosts are tried in order, subject to their retry status,
25537 unless &%hosts_randomize%& is set.
25540 .option hosts_avoid_esmtp smtp "host list&!!" unset
25541 .cindex "ESMTP, avoiding use of"
25542 .cindex "HELO" "forcing use of"
25543 .cindex "EHLO" "avoiding use of"
25544 .cindex "PIPELINING" "avoiding the use of"
25545 This option is for use with broken hosts that announce ESMTP facilities (for
25546 example, PIPELINING) and then fail to implement them properly. When a host
25547 matches &%hosts_avoid_esmtp%&, Exim sends HELO rather than EHLO at the
25548 start of the SMTP session. This means that it cannot use any of the ESMTP
25549 facilities such as AUTH, PIPELINING, SIZE, and STARTTLS.
25552 .option hosts_avoid_pipelining smtp "host list&!!" unset
25553 .cindex "PIPELINING" "avoiding the use of"
25554 .cindex "ESMTP extensions" PIPELINING
25555 Exim will not use the ESMTP PIPELINING extension when delivering to any host
25556 that matches this list, even if the server host advertises PIPELINING support.
25558 .option hosts_pipe_connect smtp "host list&!!" unset
25559 .cindex "pipelining" "early connection"
25560 .cindex "pipelining" PIPECONNECT
25561 If Exim is built with the SUPPORT_PIPE_CONNECT build option
25562 this option controls which to hosts the facility watched for
25563 and recorded, and used for subsequent connections.
25565 The retry hints database is used for the record,
25566 and records are subject to the &%retry_data_expire%& option.
25567 When used, the pipelining saves on roundtrip times.
25568 It also turns SMTP into a client-first protocol
25569 so combines well with TCP Fast Open.
25571 See also the &%pipelining_connect_advertise_hosts%& main option.
25574 When the facility is used, if the transport &%interface%& option is unset
25575 the &%helo_data%& option
25576 will be expanded before the &$sending_ip_address$& variable
25578 A check is made for the use of that variable, without the
25579 presence of a &"def:"& test on it, but suitably complex coding
25580 can avoid the check and produce unexpected results.
25581 You have been warned.
25584 .option hosts_avoid_tls smtp "host list&!!" unset
25585 .cindex "TLS" "avoiding for certain hosts"
25586 Exim will not try to start a TLS session when delivering to any host that
25587 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
25589 .option hosts_verify_avoid_tls smtp "host list&!!" unset
25590 .cindex "TLS" "avoiding for certain hosts"
25591 Exim will not try to start a TLS session for a verify callout,
25592 or when delivering in cutthrough mode,
25593 to any host that matches this list.
25596 .option hosts_max_try smtp integer 5
25597 .cindex "host" "maximum number to try"
25598 .cindex "limit" "number of hosts tried"
25599 .cindex "limit" "number of MX tried"
25600 .cindex "MX record" "maximum tried"
25601 This option limits the number of IP addresses that are tried for any one
25602 delivery in cases where there are temporary delivery errors. Section
25603 &<<SECTvalhosmax>>& describes in detail how the value of this option is used.
25606 .option hosts_max_try_hardlimit smtp integer 50
25607 This is an additional check on the maximum number of IP addresses that Exim
25608 tries for any one delivery. Section &<<SECTvalhosmax>>& describes its use and
25613 .option hosts_nopass_tls smtp "host list&!!" unset
25614 .cindex "TLS" "passing connection"
25615 .cindex "multiple SMTP deliveries"
25616 .cindex "TLS" "multiple message deliveries"
25617 For any host that matches this list, a connection on which a TLS session has
25618 been started will not be passed to a new delivery process for sending another
25619 message on the same connection. See section &<<SECTmulmessam>>& for an
25620 explanation of when this might be needed.
25622 .option hosts_noproxy_tls smtp "host list&!!" unset
25623 .cindex "TLS" "passing connection"
25624 .cindex "multiple SMTP deliveries"
25625 .cindex "TLS" "multiple message deliveries"
25626 For any host that matches this list, a TLS session which has
25627 been started will not be passed to a new delivery process for sending another
25628 message on the same session.
25630 The traditional implementation closes down TLS and re-starts it in the new
25631 process, on the same open TCP connection, for each successive message
25632 sent. If permitted by this option a pipe to to the new process is set up
25633 instead, and the original process maintains the TLS connection and proxies
25634 the SMTP connection from and to the new process and any subsequents.
25635 The new process has no access to TLS information, so cannot include it in
25640 .option hosts_override smtp boolean false
25641 If this option is set and the &%hosts%& option is also set, any hosts that are
25642 attached to the address are ignored, and instead the hosts specified by the
25643 &%hosts%& option are always used. This option does not apply to
25644 &%fallback_hosts%&.
25647 .option hosts_randomize smtp boolean false
25648 .cindex "randomized host list"
25649 .cindex "host" "list of; randomized"
25650 .cindex "fallback" "randomized hosts"
25651 If this option is set, and either the list of hosts is taken from the
25652 &%hosts%& or the &%fallback_hosts%& option, or the hosts supplied by the router
25653 were not obtained from MX records (this includes fallback hosts from the
25654 router), and were not randomized by the router, the order of trying the hosts
25655 is randomized each time the transport runs. Randomizing the order of a host
25656 list can be used to do crude load sharing.
25658 When &%hosts_randomize%& is true, a host list may be split into groups whose
25659 order is separately randomized. This makes it possible to set up MX-like
25660 behaviour. The boundaries between groups are indicated by an item that is just
25661 &`+`& in the host list. For example:
25663 hosts = host1:host2:host3:+:host4:host5
25665 The order of the first three hosts and the order of the last two hosts is
25666 randomized for each use, but the first three always end up before the last two.
25667 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored.
25669 .option hosts_require_auth smtp "host list&!!" unset
25670 .cindex "authentication" "required by client"
25671 This option provides a list of servers for which authentication must succeed
25672 before Exim will try to transfer a message. If authentication fails for
25673 servers which are not in this list, Exim tries to send unauthenticated. If
25674 authentication fails for one of these servers, delivery is deferred. This
25675 temporary error is detectable in the retry rules, so it can be turned into a
25676 hard failure if required. See also &%hosts_try_auth%&, and chapter
25677 &<<CHAPSMTPAUTH>>& for details of authentication.
25680 .option hosts_request_ocsp smtp "host list&!!" *
25681 .cindex "TLS" "requiring for certain servers"
25682 Exim will request a Certificate Status on a
25683 TLS session for any host that matches this list.
25684 &%tls_verify_certificates%& should also be set for the transport.
25686 .option hosts_require_alpn smtp "host list&!!" unset
25687 .cindex ALPN "require negotiation in client"
25689 .cindex TLS "Application Layer Protocol Names"
25690 If the TLS library supports ALPN
25691 then a successful negotiation of ALPN will be required for any host
25692 matching the list, for TLS to be used.
25693 See also the &%tls_alpn%& option.
25695 &*Note*&: prevention of fallback to in-clear connection is not
25696 managed by this option; see &%hosts_require_tls%&.
25698 .option hosts_require_dane smtp "host list&!!" unset
25699 .cindex DANE "transport options"
25700 .cindex DANE "requiring for certain servers"
25701 If built with DANE support, Exim will require that a DNSSEC-validated
25702 TLSA record is present for any host matching the list,
25703 and that a DANE-verified TLS connection is made.
25704 There will be no fallback to in-clear communication.
25705 See the &%dnssec_request_domains%& router and transport options.
25706 See section &<<SECDANE>>&.
25708 .option hosts_require_ocsp smtp "host list&!!" unset
25709 .cindex "TLS" "requiring for certain servers"
25710 Exim will request, and check for a valid Certificate Status being given, on a
25711 TLS session for any host that matches this list.
25712 &%tls_verify_certificates%& should also be set for the transport.
25714 .option hosts_require_tls smtp "host list&!!" unset
25715 .cindex "TLS" "requiring for certain servers"
25716 Exim will insist on using a TLS session when delivering to any host that
25717 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
25718 &*Note*&: This option affects outgoing mail only. To insist on TLS for
25719 incoming messages, use an appropriate ACL.
25721 .option hosts_try_auth smtp "host list&!!" unset
25722 .cindex "authentication" "optional in client"
25723 This option provides a list of servers to which, provided they announce
25724 authentication support, Exim will attempt to authenticate as a client when it
25725 connects. If authentication fails
25726 and &%hosts_require_auth%& permits,
25727 Exim will try to transfer the message unauthenticated.
25728 See also chapter &<<CHAPSMTPAUTH>>& for details of authentication.
25730 .option hosts_try_chunking smtp "host list&!!" *
25731 .cindex CHUNKING "enabling, in client"
25732 .cindex BDAT "SMTP command"
25733 .cindex "RFC 3030" "CHUNKING"
25734 This option provides a list of servers to which, provided they announce
25735 CHUNKING support, Exim will attempt to use BDAT commands rather than DATA.
25736 Unless DKIM signing is being done,
25737 BDAT will not be used in conjunction with a transport filter.
25739 .option hosts_try_dane smtp "host list&!!" *
25740 .cindex DANE "transport options"
25741 .cindex DANE "attempting for certain servers"
25742 If built with DANE support, Exim will look up a
25743 TLSA record for any host matching the list,
25744 If one is found and that lookup was DNSSEC-validated,
25745 then Exim requires that a DANE-verified TLS connection is made for that host;
25746 there will be no fallback to in-clear communication.
25747 See the &%dnssec_request_domains%& router and transport options.
25748 See section &<<SECDANE>>&.
25750 .option hosts_try_fastopen smtp "host list&!!" *
25751 .cindex "fast open, TCP" "enabling, in client"
25752 .cindex "TCP Fast Open" "enabling, in client"
25753 .cindex "RFC 7413" "TCP Fast Open"
25754 This option provides a list of servers to which, provided
25755 the facility is supported by this system, Exim will attempt to
25756 perform a TCP Fast Open.
25757 No data is sent on the SYN segment but, if the remote server also
25758 supports the facility, it can send its SMTP banner immediately after
25759 the SYN,ACK segment. This can save up to one round-trip time.
25761 The facility is only active for previously-contacted servers,
25762 as the initiator must present a cookie in the SYN segment.
25764 On (at least some) current Linux distributions the facility must be enabled
25765 in the kernel by the sysadmin before the support is usable.
25766 There is no option for control of the server side; if the system supports
25767 it it is always enabled. Note that lengthy operations in the connect ACL,
25768 such as DNSBL lookups, will still delay the emission of the SMTP banner.
25770 .option hosts_try_prdr smtp "host list&!!" *
25771 .cindex "PRDR" "enabling, optional in client"
25772 .cindex "ESMTP extensions" PRDR
25773 This option provides a list of servers to which, provided they announce
25774 PRDR support, Exim will attempt to negotiate PRDR
25775 for multi-recipient messages.
25776 The option can usually be left as default.
25778 .option interface smtp "string list&!!" unset
25779 .cindex "bind IP address"
25780 .cindex "IP address" "binding"
25782 .vindex "&$host_address$&"
25783 This option specifies which interface to bind to when making an outgoing SMTP
25784 call. The value is an IP address, not an interface name such as
25785 &`eth0`&. Do not confuse this with the interface address that was used when a
25786 message was received, which is in &$received_ip_address$&, formerly known as
25787 &$interface_address$&. The name was changed to minimize confusion with the
25788 outgoing interface address. There is no variable that contains an outgoing
25789 interface address because, unless it is set by this option, its value is
25792 During the expansion of the &%interface%& option the variables &$host$& and
25793 &$host_address$& refer to the host to which a connection is about to be made
25794 during the expansion of the string. Forced expansion failure, or an empty
25795 string result causes the option to be ignored. Otherwise, after expansion, the
25796 string must be a list of IP addresses, colon-separated by default, but the
25797 separator can be changed in the usual way (&<<SECTlistsepchange>>&).
25800 interface = <; 192.168.123.123 ; 3ffe:ffff:836f::fe86:a061
25802 The first interface of the correct type (IPv4 or IPv6) is used for the outgoing
25803 connection. If none of them are the correct type, the option is ignored. If
25804 &%interface%& is not set, or is ignored, the system's IP functions choose which
25805 interface to use if the host has more than one.
25808 .option keepalive smtp boolean true
25809 .cindex "keepalive" "on outgoing connection"
25810 This option controls the setting of SO_KEEPALIVE on outgoing TCP/IP socket
25811 connections. When set, it causes the kernel to probe idle connections
25812 periodically, by sending packets with &"old"& sequence numbers. The other end
25813 of the connection should send a acknowledgment if the connection is still okay
25814 or a reset if the connection has been aborted. The reason for doing this is
25815 that it has the beneficial effect of freeing up certain types of connection
25816 that can get stuck when the remote host is disconnected without tidying up the
25817 TCP/IP call properly. The keepalive mechanism takes several hours to detect
25821 .option lmtp_ignore_quota smtp boolean false
25822 .cindex "LMTP" "ignoring quota errors"
25823 If this option is set true when the &%protocol%& option is set to &"lmtp"&, the
25824 string &`IGNOREQUOTA`& is added to RCPT commands, provided that the LMTP server
25825 has advertised support for IGNOREQUOTA in its response to the LHLO command.
25827 .option max_rcpt smtp integer 100
25828 .cindex "RCPT" "maximum number of outgoing"
25829 This option limits the number of RCPT commands that are sent in a single
25830 SMTP message transaction. Each set of addresses is treated independently, and
25831 so can cause parallel connections to the same host if &%remote_max_parallel%&
25832 permits this. A value setting of zero disables the limit.
25835 .option message_linelength_limit smtp integer 998
25836 .cindex "line length" limit
25837 This option sets the maximum line length, in bytes, that the transport
25838 will send. Any messages with lines exceeding the given value
25839 will fail and a failure-DSN ("bounce") message will if possible be returned
25841 The default value is that defined by the SMTP standards.
25843 It is generally wise to also check in the data ACL so that messages
25844 received via SMTP can be refused without producing a bounce.
25847 .option multi_domain smtp boolean&!! true
25848 .vindex "&$domain$&"
25849 When this option is set, the &(smtp)& transport can handle a number of
25850 addresses containing a mixture of different domains provided they all resolve
25851 to the same list of hosts. Turning the option off restricts the transport to
25852 handling only one domain at a time. This is useful if you want to use
25853 &$domain$& in an expansion for the transport, because it is set only when there
25854 is a single domain involved in a remote delivery.
25856 It is expanded per-address and can depend on any of
25857 &$address_data$&, &$domain_data$&, &$local_part_data$&,
25858 &$host$&, &$host_address$& and &$host_port$&.
25860 If the connection is DANE-enabled then this option is ignored;
25861 only messages having the domain used for the DANE TLSA lookup are
25862 sent on the connection.
25864 .option port smtp string&!! "see below"
25865 .cindex "port" "sending TCP/IP"
25866 .cindex "TCP/IP" "setting outgoing port"
25867 This option specifies the TCP/IP port on the server to which Exim connects.
25868 &*Note:*& Do not confuse this with the port that was used when a message was
25869 received, which is in &$received_port$&, formerly known as &$interface_port$&.
25870 The name was changed to minimize confusion with the outgoing port. There is no
25871 variable that contains an outgoing port.
25873 If the value of this option begins with a digit it is taken as a port number;
25874 otherwise it is looked up using &[getservbyname()]&. The default value is
25876 but if &%protocol%& is set to &"lmtp"& the default is &"lmtp"&
25877 and if &%protocol%& is set to &"smtps"& the default is &"smtps"&.
25878 If the expansion fails, or if a port number cannot be found, delivery
25881 Note that at least one Linux distribution has been seen failing
25882 to put &"smtps"& in its &"/etc/services"& file, resulting is such deferrals.
25886 .option protocol smtp string smtp
25887 .cindex "LMTP" "over TCP/IP"
25888 .cindex "ssmtp protocol" "outbound"
25889 .cindex "TLS" "SSL-on-connect outbound"
25891 If this option is set to &"lmtp"& instead of &"smtp"&, the default value for
25892 the &%port%& option changes to &"lmtp"&, and the transport operates the LMTP
25893 protocol (RFC 2033) instead of SMTP. This protocol is sometimes used for local
25894 deliveries into closed message stores. Exim also has support for running LMTP
25895 over a pipe to a local process &-- see chapter &<<CHAPLMTP>>&.
25897 If this option is set to &"smtps"&, the default value for the &%port%& option
25898 changes to &"smtps"&, and the transport initiates TLS immediately after
25899 connecting, as an outbound SSL-on-connect, instead of using STARTTLS to upgrade.
25900 The Internet standards bodies used to strongly discourage use of this mode,
25901 but as of RFC 8314 it is preferred over STARTTLS for message submission
25902 (as distinct from MTA-MTA communication).
25905 .option retry_include_ip_address smtp boolean&!! true
25906 Exim normally includes both the host name and the IP address in the key it
25907 constructs for indexing retry data after a temporary delivery failure. This
25908 means that when one of several IP addresses for a host is failing, it gets
25909 tried periodically (controlled by the retry rules), but use of the other IP
25910 addresses is not affected.
25912 However, in some dialup environments hosts are assigned a different IP address
25913 each time they connect. In this situation the use of the IP address as part of
25914 the retry key leads to undesirable behaviour. Setting this option false causes
25915 Exim to use only the host name.
25916 Since it is expanded it can be made to depend on the host or domain.
25919 .option serialize_hosts smtp "host list&!!" unset
25920 .cindex "serializing connections"
25921 .cindex "host" "serializing connections"
25922 Because Exim operates in a distributed manner, if several messages for the same
25923 host arrive at around the same time, more than one simultaneous connection to
25924 the remote host can occur. This is not usually a problem except when there is a
25925 slow link between the hosts. In that situation it may be helpful to restrict
25926 Exim to one connection at a time. This can be done by setting
25927 &%serialize_hosts%& to match the relevant hosts.
25929 .cindex "hints database" "serializing deliveries to a host"
25930 Exim implements serialization by means of a hints database in which a record is
25931 written whenever a process connects to one of the restricted hosts. The record
25932 is deleted when the connection is completed. Obviously there is scope for
25933 records to get left lying around if there is a system or program crash. To
25934 guard against this, Exim ignores any records that are more than six hours old.
25936 If you set up this kind of serialization, you should also arrange to delete the
25937 relevant hints database whenever your system reboots. The names of the files
25938 start with &_misc_& and they are kept in the &_spool/db_& directory. There
25939 may be one or two files, depending on the type of DBM in use. The same files
25940 are used for ETRN serialization.
25942 See also the &%max_parallel%& generic transport option.
25945 .option size_addition smtp integer 1024
25946 .cindex "SIZE" "ESMTP extension"
25947 .cindex "message" "size issue for transport filter"
25948 .cindex "size" "of message"
25949 .cindex "transport" "filter"
25950 .cindex "filter" "transport filter"
25951 If a remote SMTP server indicates that it supports the SIZE option of the
25952 MAIL command, Exim uses this to pass over the message size at the start of
25953 an SMTP transaction. It adds the value of &%size_addition%& to the value it
25954 sends, to allow for headers and other text that may be added during delivery by
25955 configuration options or in a transport filter. It may be necessary to increase
25956 this if a lot of text is added to messages.
25958 Alternatively, if the value of &%size_addition%& is set negative, it disables
25959 the use of the SIZE option altogether.
25962 .option socks_proxy smtp string&!! unset
25963 .cindex proxy SOCKS
25964 This option enables use of SOCKS proxies for connections made by the
25965 transport. For details see section &<<SECTproxySOCKS>>&.
25968 .option tls_alpn smtp string&!! unset
25969 .cindex TLS "Application Layer Protocol Names"
25971 .cindex ALPN "set name in client"
25972 If this option is set
25973 and the TLS library supports ALPN,
25974 the value given is used.
25976 As of writing no value has been standardised for email use.
25977 The authors suggest using &"smtp"&.
25981 .option tls_certificate smtp string&!! unset
25982 .cindex "TLS" "client certificate, location of"
25983 .cindex "certificate" "client, location of"
25985 .vindex "&$host_address$&"
25986 The value of this option must be the absolute path to a file which contains the
25987 client's certificate, for possible use when sending a message over an encrypted
25988 connection. The values of &$host$& and &$host_address$& are set to the name and
25989 address of the server during the expansion. See chapter &<<CHAPTLS>>& for
25992 &*Note*&: This option must be set if you want Exim to be able to use a TLS
25993 certificate when sending messages as a client. The global option of the same
25994 name specifies the certificate for Exim as a server; it is not automatically
25995 assumed that the same certificate should be used when Exim is operating as a
25999 .option tls_crl smtp string&!! unset
26000 .cindex "TLS" "client certificate revocation list"
26001 .cindex "certificate" "revocation list for client"
26002 This option specifies a certificate revocation list. The expanded value must
26003 be the name of a file that contains a CRL in PEM format.
26006 .option tls_dh_min_bits smtp integer 1024
26007 .cindex "TLS" "Diffie-Hellman minimum acceptable size"
26008 When establishing a TLS session, if a ciphersuite which uses Diffie-Hellman
26009 key agreement is negotiated, the server will provide a large prime number
26010 for use. This option establishes the minimum acceptable size of that number.
26011 If the parameter offered by the server is too small, then the TLS handshake
26014 Only supported when using GnuTLS.
26017 .option tls_privatekey smtp string&!! unset
26018 .cindex "TLS" "client private key, location of"
26020 .vindex "&$host_address$&"
26021 The value of this option must be the absolute path to a file which contains the
26022 client's private key. This is used when sending a message over an encrypted
26023 connection using a client certificate. The values of &$host$& and
26024 &$host_address$& are set to the name and address of the server during the
26025 expansion. If this option is unset, or the expansion is forced to fail, or the
26026 result is an empty string, the private key is assumed to be in the same file as
26027 the certificate. See chapter &<<CHAPTLS>>& for details of TLS.
26030 .option tls_require_ciphers smtp string&!! unset
26031 .cindex "TLS" "requiring specific ciphers"
26032 .cindex "cipher" "requiring specific"
26034 .vindex "&$host_address$&"
26035 The value of this option must be a list of permitted cipher suites, for use
26036 when setting up an outgoing encrypted connection. (There is a global option of
26037 the same name for controlling incoming connections.) The values of &$host$& and
26038 &$host_address$& are set to the name and address of the server during the
26039 expansion. See chapter &<<CHAPTLS>>& for details of TLS; note that this option
26040 is used in different ways by OpenSSL and GnuTLS (see sections
26041 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&). For GnuTLS, the order of the
26042 ciphers is a preference order.
26045 .option tls_resumption_hosts smtp "host list&!!" unset
26046 .cindex TLS resumption
26047 This option controls which connections to use the TLS resumption feature.
26048 See &<<SECTresumption>>& for details.
26052 .option tls_sni smtp string&!! unset
26053 .cindex "TLS" "Server Name Indication"
26055 .cindex SNI "setting in client"
26056 .vindex "&$tls_sni$&"
26057 If this option is set
26058 and the connection is not DANE-validated
26059 then it sets the $tls_out_sni variable and causes any
26060 TLS session to pass this value as the Server Name Indication extension to
26061 the remote side, which can be used by the remote side to select an appropriate
26062 certificate and private key for the session.
26064 See &<<SECTtlssni>>& for more information.
26066 Note that for OpenSSL, this feature requires a build of OpenSSL that supports
26072 .option tls_tempfail_tryclear smtp boolean true
26073 .cindex "4&'xx'& responses" "to STARTTLS"
26074 When the server host is not in &%hosts_require_tls%&, and there is a problem in
26075 setting up a TLS session, this option determines whether or not Exim should try
26076 to deliver the message unencrypted. If it is set false, delivery to the
26077 current host is deferred; if there are other hosts, they are tried. If this
26078 option is set true, Exim attempts to deliver unencrypted after a 4&'xx'&
26079 response to STARTTLS. Also, if STARTTLS is accepted, but the subsequent
26080 TLS negotiation fails, Exim closes the current connection (because it is in an
26081 unknown state), opens a new one to the same host, and then tries the delivery
26085 .option tls_try_verify_hosts smtp "host list&!!" *
26086 .cindex "TLS" "server certificate verification"
26087 .cindex "certificate" "verification of server"
26088 This option gives a list of hosts for which, on encrypted connections,
26089 certificate verification will be tried but need not succeed.
26090 The &%tls_verify_certificates%& option must also be set.
26091 Note that unless the host is in this list
26092 TLS connections will be denied to hosts using self-signed certificates
26093 when &%tls_verify_certificates%& is matched.
26094 The &$tls_out_certificate_verified$& variable is set when
26095 certificate verification succeeds.
26098 .option tls_verify_cert_hostnames smtp "host list&!!" *
26099 .cindex "TLS" "server certificate hostname verification"
26100 .cindex "certificate" "verification of server"
26101 This option give a list of hosts for which,
26102 while verifying the server certificate,
26103 checks will be included on the host name
26104 (note that this will generally be the result of a DNS MX lookup)
26105 versus Subject and Subject-Alternate-Name fields. Wildcard names are permitted
26106 limited to being the initial component of a 3-or-more component FQDN.
26108 There is no equivalent checking on client certificates.
26111 .option tls_verify_certificates smtp string&!! system
26112 .cindex "TLS" "server certificate verification"
26113 .cindex "certificate" "verification of server"
26115 .vindex "&$host_address$&"
26116 The value of this option must be either the
26118 or the absolute path to
26119 a file or directory containing permitted certificates for servers,
26120 for use when setting up an encrypted connection.
26122 The "system" value for the option will use a location compiled into the SSL library.
26123 This is not available for GnuTLS versions preceding 3.0.20; a value of "system"
26124 is taken as empty and an explicit location
26127 The use of a directory for the option value is not available for GnuTLS versions
26128 preceding 3.3.6 and a single file must be used.
26130 With OpenSSL the certificates specified
26132 either by file or directory
26133 are added to those given by the system default location.
26135 The values of &$host$& and
26136 &$host_address$& are set to the name and address of the server during the
26137 expansion of this option. See chapter &<<CHAPTLS>>& for details of TLS.
26139 For back-compatibility,
26140 if neither tls_verify_hosts nor tls_try_verify_hosts are set
26141 (a single-colon empty list counts as being set)
26142 and certificate verification fails the TLS connection is closed.
26145 .option tls_verify_hosts smtp "host list&!!" unset
26146 .cindex "TLS" "server certificate verification"
26147 .cindex "certificate" "verification of server"
26148 This option gives a list of hosts for which, on encrypted connections,
26149 certificate verification must succeed.
26150 The &%tls_verify_certificates%& option must also be set.
26151 If both this option and &%tls_try_verify_hosts%& are unset
26152 operation is as if this option selected all hosts.
26153 &*Warning*&: Including a host in &%tls_verify_hosts%& does not require
26154 that connections use TLS.
26155 Fallback to in-clear communication will be done unless restricted by
26156 the &%hosts_require_tls%& option.
26158 .option utf8_downconvert smtp integer&!! -1
26159 .cindex utf8 "address downconversion"
26160 .cindex i18n "utf8 address downconversion"
26161 If built with internationalization support,
26162 this option controls conversion of UTF-8 in message envelope addresses
26164 If, after expansion, the value is 1, 0, or -1 then this value overrides
26165 any value previously set for the message. Otherwise, any previously
26166 set value is used. To permit use of a previous value,
26167 set this option to an empty string.
26168 For details on the values see section &<<SECTi18nMTA>>&.
26173 .section "How the limits for the number of hosts to try are used" &&&
26175 .cindex "host" "maximum number to try"
26176 .cindex "limit" "hosts; maximum number tried"
26177 There are two options that are concerned with the number of hosts that are
26178 tried when an SMTP delivery takes place. They are &%hosts_max_try%& and
26179 &%hosts_max_try_hardlimit%&.
26182 The &%hosts_max_try%& option limits the number of hosts that are tried
26183 for a single delivery. However, despite the term &"host"& in its name, the
26184 option actually applies to each IP address independently. In other words, a
26185 multihomed host is treated as several independent hosts, just as it is for
26188 Many of the larger ISPs have multiple MX records which often point to
26189 multihomed hosts. As a result, a list of a dozen or more IP addresses may be
26190 created as a result of routing one of these domains.
26192 Trying every single IP address on such a long list does not seem sensible; if
26193 several at the top of the list fail, it is reasonable to assume there is some
26194 problem that is likely to affect all of them. Roughly speaking, the value of
26195 &%hosts_max_try%& is the maximum number that are tried before deferring the
26196 delivery. However, the logic cannot be quite that simple.
26198 Firstly, IP addresses that are skipped because their retry times have not
26199 arrived do not count, and in addition, addresses that are past their retry
26200 limits are also not counted, even when they are tried. This means that when
26201 some IP addresses are past their retry limits, more than the value of
26202 &%hosts_max_retry%& may be tried. The reason for this behaviour is to ensure
26203 that all IP addresses are considered before timing out an email address (but
26204 see below for an exception).
26206 Secondly, when the &%hosts_max_try%& limit is reached, Exim looks down the host
26207 list to see if there is a subsequent host with a different (higher valued) MX.
26208 If there is, that host is considered next, and the current IP address is used
26209 but not counted. This behaviour helps in the case of a domain with a retry rule
26210 that hardly ever delays any hosts, as is now explained:
26212 Consider the case of a long list of hosts with one MX value, and a few with a
26213 higher MX value. If &%hosts_max_try%& is small (the default is 5) only a few
26214 hosts at the top of the list are tried at first. With the default retry rule,
26215 which specifies increasing retry times, the higher MX hosts are eventually
26216 tried when those at the top of the list are skipped because they have not
26217 reached their retry times.
26219 However, it is common practice to put a fixed short retry time on domains for
26220 large ISPs, on the grounds that their servers are rarely down for very long.
26221 Unfortunately, these are exactly the domains that tend to resolve to long lists
26222 of hosts. The short retry time means that the lowest MX hosts are tried every
26223 time. The attempts may be in a different order because of random sorting, but
26224 without the special MX check, the higher MX hosts would never be tried until
26225 all the lower MX hosts had timed out (which might be several days), because
26226 there are always some lower MX hosts that have reached their retry times. With
26227 the special check, Exim considers at least one IP address from each MX value at
26228 every delivery attempt, even if the &%hosts_max_try%& limit has already been
26231 The above logic means that &%hosts_max_try%& is not a hard limit, and in
26232 particular, Exim normally eventually tries all the IP addresses before timing
26233 out an email address. When &%hosts_max_try%& was implemented, this seemed a
26234 reasonable thing to do. Recently, however, some lunatic DNS configurations have
26235 been set up with hundreds of IP addresses for some domains. It can
26236 take a very long time indeed for an address to time out in these cases.
26238 The &%hosts_max_try_hardlimit%& option was added to help with this problem.
26239 Exim never tries more than this number of IP addresses; if it hits this limit
26240 and they are all timed out, the email address is bounced, even though not all
26241 possible IP addresses have been tried.
26242 .ecindex IIDsmttra1
26243 .ecindex IIDsmttra2
26249 . ////////////////////////////////////////////////////////////////////////////
26250 . ////////////////////////////////////////////////////////////////////////////
26252 .chapter "Address rewriting" "CHAPrewrite"
26253 .scindex IIDaddrew "rewriting" "addresses"
26254 There are some circumstances in which Exim automatically rewrites domains in
26255 addresses. The two most common are when an address is given without a domain
26256 (referred to as an &"unqualified address"&) or when an address contains an
26257 abbreviated domain that is expanded by DNS lookup.
26259 Unqualified envelope addresses are accepted only for locally submitted
26260 messages, or for messages that are received from hosts matching
26261 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
26262 appropriate. Unqualified addresses in header lines are qualified if they are in
26263 locally submitted messages, or messages from hosts that are permitted to send
26264 unqualified envelope addresses. Otherwise, unqualified addresses in header
26265 lines are neither qualified nor rewritten.
26267 One situation in which Exim does &'not'& automatically rewrite a domain is
26268 when it is the name of a CNAME record in the DNS. The older RFCs suggest that
26269 such a domain should be rewritten using the &"canonical"& name, and some MTAs
26270 do this. The new RFCs do not contain this suggestion.
26273 .section "Explicitly configured address rewriting" "SECID147"
26274 This chapter describes the rewriting rules that can be used in the
26275 main rewrite section of the configuration file, and also in the generic
26276 &%headers_rewrite%& option that can be set on any transport.
26278 Some people believe that configured address rewriting is a Mortal Sin.
26279 Others believe that life is not possible without it. Exim provides the
26280 facility; you do not have to use it.
26282 The main rewriting rules that appear in the &"rewrite"& section of the
26283 configuration file are applied to addresses in incoming messages, both envelope
26284 addresses and addresses in header lines. Each rule specifies the types of
26285 address to which it applies.
26287 Whether or not addresses in header lines are rewritten depends on the origin of
26288 the headers and the type of rewriting. Global rewriting, that is, rewriting
26289 rules from the rewrite section of the configuration file, is applied only to
26290 those headers that were received with the message. Header lines that are added
26291 by ACLs or by a system filter or by individual routers or transports (which
26292 are specific to individual recipient addresses) are not rewritten by the global
26295 Rewriting at transport time, by means of the &%headers_rewrite%& option,
26296 applies all headers except those added by routers and transports. That is, as
26297 well as the headers that were received with the message, it also applies to
26298 headers that were added by an ACL or a system filter.
26301 In general, rewriting addresses from your own system or domain has some
26302 legitimacy. Rewriting other addresses should be done only with great care and
26303 in special circumstances. The author of Exim believes that rewriting should be
26304 used sparingly, and mainly for &"regularizing"& addresses in your own domains.
26305 Although it can sometimes be used as a routing tool, this is very strongly
26308 There are two commonly encountered circumstances where rewriting is used, as
26309 illustrated by these examples:
26312 The company whose domain is &'hitch.fict.example'& has a number of hosts that
26313 exchange mail with each other behind a firewall, but there is only a single
26314 gateway to the outer world. The gateway rewrites &'*.hitch.fict.example'& as
26315 &'hitch.fict.example'& when sending mail off-site.
26317 A host rewrites the local parts of its own users so that, for example,
26318 &'fp42@hitch.fict.example'& becomes &'Ford.Prefect@hitch.fict.example'&.
26323 .section "When does rewriting happen?" "SECID148"
26324 .cindex "rewriting" "timing of"
26325 .cindex "&ACL;" "rewriting addresses in"
26326 Configured address rewriting can take place at several different stages of a
26327 message's processing.
26329 .vindex "&$sender_address$&"
26330 At the start of an ACL for MAIL, the sender address may have been rewritten
26331 by a special SMTP-time rewrite rule (see section &<<SECTrewriteS>>&), but no
26332 ordinary rewrite rules have yet been applied. If, however, the sender address
26333 is verified in the ACL, it is rewritten before verification, and remains
26334 rewritten thereafter. The subsequent value of &$sender_address$& is the
26335 rewritten address. This also applies if sender verification happens in a
26336 RCPT ACL. Otherwise, when the sender address is not verified, it is
26337 rewritten as soon as a message's header lines have been received.
26339 .vindex "&$domain$&"
26340 .vindex "&$local_part$&"
26341 Similarly, at the start of an ACL for RCPT, the current recipient's address
26342 may have been rewritten by a special SMTP-time rewrite rule, but no ordinary
26343 rewrite rules have yet been applied to it. However, the behaviour is different
26344 from the sender address when a recipient is verified. The address is rewritten
26345 for the verification, but the rewriting is not remembered at this stage. The
26346 value of &$local_part$& and &$domain$& after verification are always the same
26347 as they were before (that is, they contain the unrewritten &-- except for
26348 SMTP-time rewriting &-- address).
26350 As soon as a message's header lines have been received, all the envelope
26351 recipient addresses are permanently rewritten, and rewriting is also applied to
26352 the addresses in the header lines (if configured). This happens before adding
26353 any header lines that were specified in MAIL or RCPT ACLs, and
26354 .cindex "&[local_scan()]& function" "address rewriting; timing of"
26355 before the DATA ACL and &[local_scan()]& functions are run.
26357 When an address is being routed, either for delivery or for verification,
26358 rewriting is applied immediately to child addresses that are generated by
26359 redirection, unless &%no_rewrite%& is set on the router.
26361 .cindex "envelope from"
26362 .cindex "envelope sender" "rewriting at transport time"
26363 .cindex "rewriting" "at transport time"
26364 .cindex "header lines" "rewriting at transport time"
26365 At transport time, additional rewriting of addresses in header lines can be
26366 specified by setting the generic &%headers_rewrite%& option on a transport.
26367 This option contains rules that are identical in form to those in the rewrite
26368 section of the configuration file. They are applied to the original message
26369 header lines and any that were added by ACLs or a system filter. They are not
26370 applied to header lines that are added by routers or the transport.
26372 The outgoing envelope sender can be rewritten by means of the &%return_path%&
26373 transport option. However, it is not possible to rewrite envelope recipients at
26379 .section "Testing the rewriting rules that apply on input" "SECID149"
26380 .cindex "rewriting" "testing"
26381 .cindex "testing" "rewriting"
26382 Exim's input rewriting configuration appears in a part of the runtime
26383 configuration file headed by &"begin rewrite"&. It can be tested by the
26384 &%-brw%& command line option. This takes an address (which can be a full RFC
26385 2822 address) as its argument. The output is a list of how the address would be
26386 transformed by the rewriting rules for each of the different places it might
26387 appear in an incoming message, that is, for each different header and for the
26388 envelope sender and recipient fields. For example,
26390 exim -brw ph10@exim.workshop.example
26392 might produce the output
26394 sender: Philip.Hazel@exim.workshop.example
26395 from: Philip.Hazel@exim.workshop.example
26396 to: ph10@exim.workshop.example
26397 cc: ph10@exim.workshop.example
26398 bcc: ph10@exim.workshop.example
26399 reply-to: Philip.Hazel@exim.workshop.example
26400 env-from: Philip.Hazel@exim.workshop.example
26401 env-to: ph10@exim.workshop.example
26403 which shows that rewriting has been set up for that address when used in any of
26404 the source fields, but not when it appears as a recipient address. At the
26405 present time, there is no equivalent way of testing rewriting rules that are
26406 set for a particular transport.
26409 .section "Rewriting rules" "SECID150"
26410 .cindex "rewriting" "rules"
26411 The rewrite section of the configuration file consists of lines of rewriting
26414 <&'source pattern'&> <&'replacement'&> <&'flags'&>
26416 Rewriting rules that are specified for the &%headers_rewrite%& generic
26417 transport option are given as a colon-separated list. Each item in the list
26418 takes the same form as a line in the main rewriting configuration (except that
26419 any colons must be doubled, of course).
26421 The formats of source patterns and replacement strings are described below.
26422 Each is terminated by white space, unless enclosed in double quotes, in which
26423 case normal quoting conventions apply inside the quotes. The flags are single
26424 characters which may appear in any order. Spaces and tabs between them are
26427 For each address that could potentially be rewritten, the rules are scanned in
26428 order, and replacements for the address from earlier rules can themselves be
26429 replaced by later rules (but see the &"q"& and &"R"& flags).
26431 The order in which addresses are rewritten is undefined, may change between
26432 releases, and must not be relied on, with one exception: when a message is
26433 received, the envelope sender is always rewritten first, before any header
26434 lines are rewritten. For example, the replacement string for a rewrite of an
26435 address in &'To:'& must not assume that the message's address in &'From:'& has
26436 (or has not) already been rewritten. However, a rewrite of &'From:'& may assume
26437 that the envelope sender has already been rewritten.
26439 .vindex "&$domain$&"
26440 .vindex "&$local_part$&"
26441 The variables &$local_part$& and &$domain$& can be used in the replacement
26442 string to refer to the address that is being rewritten. Note that lookup-driven
26443 rewriting can be done by a rule of the form
26447 where the lookup key uses &$1$& and &$2$& or &$local_part$& and &$domain$& to
26448 refer to the address that is being rewritten.
26451 .section "Rewriting patterns" "SECID151"
26452 .cindex "rewriting" "patterns"
26453 .cindex "address list" "in a rewriting pattern"
26454 The source pattern in a rewriting rule is any item which may appear in an
26455 address list (see section &<<SECTaddresslist>>&). It is in fact processed as a
26456 single-item address list, which means that it is expanded before being tested
26457 against the address. As always, if you use a regular expression as a pattern,
26458 you must take care to escape dollar and backslash characters, or use the &`\N`&
26459 facility to suppress string expansion within the regular expression.
26461 Domains in patterns should be given in lower case. Local parts in patterns are
26462 case-sensitive. If you want to do case-insensitive matching of local parts, you
26463 can use a regular expression that starts with &`^(?i)`&.
26465 .cindex "numerical variables (&$1$& &$2$& etc)" "in rewriting rules"
26466 After matching, the numerical variables &$1$&, &$2$&, etc. may be set,
26467 depending on the type of match which occurred. These can be used in the
26468 replacement string to insert portions of the incoming address. &$0$& always
26469 refers to the complete incoming address. When a regular expression is used, the
26470 numerical variables are set from its capturing subexpressions. For other types
26471 of pattern they are set as follows:
26474 If a local part or domain starts with an asterisk, the numerical variables
26475 refer to the character strings matched by asterisks, with &$1$& associated with
26476 the first asterisk, and &$2$& with the second, if present. For example, if the
26479 *queen@*.fict.example
26481 is matched against the address &'hearts-queen@wonderland.fict.example'& then
26483 $0 = hearts-queen@wonderland.fict.example
26487 Note that if the local part does not start with an asterisk, but the domain
26488 does, it is &$1$& that contains the wild part of the domain.
26491 If the domain part of the pattern is a partial lookup, the wild and fixed parts
26492 of the domain are placed in the next available numerical variables. Suppose,
26493 for example, that the address &'foo@bar.baz.example'& is processed by a
26494 rewriting rule of the form
26496 &`*@partial-dbm;/some/dbm/file`& <&'replacement string'&>
26498 and the key in the file that matches the domain is &`*.baz.example`&. Then
26504 If the address &'foo@baz.example'& is looked up, this matches the same
26505 wildcard file entry, and in this case &$2$& is set to the empty string, but
26506 &$3$& is still set to &'baz.example'&. If a non-wild key is matched in a
26507 partial lookup, &$2$& is again set to the empty string and &$3$& is set to the
26508 whole domain. For non-partial domain lookups, no numerical variables are set.
26512 .section "Rewriting replacements" "SECID152"
26513 .cindex "rewriting" "replacements"
26514 If the replacement string for a rule is a single asterisk, addresses that
26515 match the pattern and the flags are &'not'& rewritten, and no subsequent
26516 rewriting rules are scanned. For example,
26518 hatta@lookingglass.fict.example * f
26520 specifies that &'hatta@lookingglass.fict.example'& is never to be rewritten in
26523 .vindex "&$domain$&"
26524 .vindex "&$local_part$&"
26525 If the replacement string is not a single asterisk, it is expanded, and must
26526 yield a fully qualified address. Within the expansion, the variables
26527 &$local_part$& and &$domain$& refer to the address that is being rewritten.
26528 Any letters they contain retain their original case &-- they are not lower
26529 cased. The numerical variables are set up according to the type of pattern that
26530 matched the address, as described above. If the expansion is forced to fail by
26531 the presence of &"fail"& in a conditional or lookup item, rewriting by the
26532 current rule is abandoned, but subsequent rules may take effect. Any other
26533 expansion failure causes the entire rewriting operation to be abandoned, and an
26534 entry written to the panic log.
26538 .section "Rewriting flags" "SECID153"
26539 There are three different kinds of flag that may appear on rewriting rules:
26542 Flags that specify which headers and envelope addresses to rewrite: E, F, T, b,
26545 A flag that specifies rewriting at SMTP time: S.
26547 Flags that control the rewriting process: Q, q, R, w.
26550 For rules that are part of the &%headers_rewrite%& generic transport option,
26551 E, F, T, and S are not permitted.
26555 .section "Flags specifying which headers and envelope addresses to rewrite" &&&
26557 .cindex "rewriting" "flags"
26558 If none of the following flag letters, nor the &"S"& flag (see section
26559 &<<SECTrewriteS>>&) are present, a main rewriting rule applies to all headers
26560 and to both the sender and recipient fields of the envelope, whereas a
26561 transport-time rewriting rule just applies to all headers. Otherwise, the
26562 rewriting rule is skipped unless the relevant addresses are being processed.
26564 &`E`& rewrite all envelope fields
26565 &`F`& rewrite the envelope From field
26566 &`T`& rewrite the envelope To field
26567 &`b`& rewrite the &'Bcc:'& header
26568 &`c`& rewrite the &'Cc:'& header
26569 &`f`& rewrite the &'From:'& header
26570 &`h`& rewrite all headers
26571 &`r`& rewrite the &'Reply-To:'& header
26572 &`s`& rewrite the &'Sender:'& header
26573 &`t`& rewrite the &'To:'& header
26575 "All headers" means all of the headers listed above that can be selected
26576 individually, plus their &'Resent-'& versions. It does not include
26577 other headers such as &'Subject:'& etc.
26579 You should be particularly careful about rewriting &'Sender:'& headers, and
26580 restrict this to special known cases in your own domains.
26583 .section "The SMTP-time rewriting flag" "SECTrewriteS"
26584 .cindex "SMTP" "rewriting malformed addresses"
26585 .cindex "RCPT" "rewriting argument of"
26586 .cindex "MAIL" "rewriting argument of"
26587 The rewrite flag &"S"& specifies a rewrite of incoming envelope addresses at
26588 SMTP time, as soon as an address is received in a MAIL or RCPT command, and
26589 before any other processing; even before syntax checking. The pattern is
26590 required to be a regular expression, and it is matched against the whole of the
26591 data for the command, including any surrounding angle brackets.
26593 .vindex "&$domain$&"
26594 .vindex "&$local_part$&"
26595 This form of rewrite rule allows for the handling of addresses that are not
26596 compliant with RFCs 2821 and 2822 (for example, &"bang paths"& in batched SMTP
26597 input). Because the input is not required to be a syntactically valid address,
26598 the variables &$local_part$& and &$domain$& are not available during the
26599 expansion of the replacement string. The result of rewriting replaces the
26600 original address in the MAIL or RCPT command.
26603 .section "Flags controlling the rewriting process" "SECID155"
26604 There are four flags which control the way the rewriting process works. These
26605 take effect only when a rule is invoked, that is, when the address is of the
26606 correct type (matches the flags) and matches the pattern:
26609 If the &"Q"& flag is set on a rule, the rewritten address is permitted to be an
26610 unqualified local part. It is qualified with &%qualify_recipient%&. In the
26611 absence of &"Q"& the rewritten address must always include a domain.
26613 If the &"q"& flag is set on a rule, no further rewriting rules are considered,
26614 even if no rewriting actually takes place because of a &"fail"& in the
26615 expansion. The &"q"& flag is not effective if the address is of the wrong type
26616 (does not match the flags) or does not match the pattern.
26618 The &"R"& flag causes a successful rewriting rule to be re-applied to the new
26619 address, up to ten times. It can be combined with the &"q"& flag, to stop
26620 rewriting once it fails to match (after at least one successful rewrite).
26622 .cindex "rewriting" "whole addresses"
26623 When an address in a header is rewritten, the rewriting normally applies only
26624 to the working part of the address, with any comments and RFC 2822 &"phrase"&
26625 left unchanged. For example, rewriting might change
26627 From: Ford Prefect <fp42@restaurant.hitch.fict.example>
26631 From: Ford Prefect <prefectf@hitch.fict.example>
26634 Sometimes there is a need to replace the whole address item, and this can be
26635 done by adding the flag letter &"w"& to a rule. If this is set on a rule that
26636 causes an address in a header line to be rewritten, the entire address is
26637 replaced, not just the working part. The replacement must be a complete RFC
26638 2822 address, including the angle brackets if necessary. If text outside angle
26639 brackets contains a character whose value is greater than 126 or less than 32
26640 (except for tab), the text is encoded according to RFC 2047. The character set
26641 is taken from &%headers_charset%&, which gets its default at build time.
26643 When the &"w"& flag is set on a rule that causes an envelope address to be
26644 rewritten, all but the working part of the replacement address is discarded.
26648 .section "Rewriting examples" "SECID156"
26649 Here is an example of the two common rewriting paradigms:
26651 *@*.hitch.fict.example $1@hitch.fict.example
26652 *@hitch.fict.example ${lookup{$1}dbm{/etc/realnames}\
26653 {$value}fail}@hitch.fict.example bctfrF
26655 Note the use of &"fail"& in the lookup expansion in the second rule, forcing
26656 the string expansion to fail if the lookup does not succeed. In this context it
26657 has the effect of leaving the original address unchanged, but Exim goes on to
26658 consider subsequent rewriting rules, if any, because the &"q"& flag is not
26659 present in that rule. An alternative to &"fail"& would be to supply &$1$&
26660 explicitly, which would cause the rewritten address to be the same as before,
26661 at the cost of a small bit of processing. Not supplying either of these is an
26662 error, since the rewritten address would then contain no local part.
26664 The first example above replaces the domain with a superior, more general
26665 domain. This may not be desirable for certain local parts. If the rule
26667 root@*.hitch.fict.example *
26669 were inserted before the first rule, rewriting would be suppressed for the
26670 local part &'root'& at any domain ending in &'hitch.fict.example'&.
26672 Rewriting can be made conditional on a number of tests, by making use of
26673 &${if$& in the expansion item. For example, to apply a rewriting rule only to
26674 messages that originate outside the local host:
26676 *@*.hitch.fict.example "${if !eq {$sender_host_address}{}\
26677 {$1@hitch.fict.example}fail}"
26679 The replacement string is quoted in this example because it contains white
26682 .cindex "rewriting" "bang paths"
26683 .cindex "bang paths" "rewriting"
26684 Exim does not handle addresses in the form of &"bang paths"&. If it sees such
26685 an address it treats it as an unqualified local part which it qualifies with
26686 the local qualification domain (if the source of the message is local or if the
26687 remote host is permitted to send unqualified addresses). Rewriting can
26688 sometimes be used to handle simple bang paths with a fixed number of
26689 components. For example, the rule
26691 \N^([^!]+)!(.*)@your.domain.example$\N $2@$1
26693 rewrites a two-component bang path &'host.name!user'& as the domain address
26694 &'user@host.name'&. However, there is a security implication in using this as
26695 a global rewriting rule for envelope addresses. It can provide a backdoor
26696 method for using your system as a relay, because the incoming addresses appear
26697 to be local. If the bang path addresses are received via SMTP, it is safer to
26698 use the &"S"& flag to rewrite them as they are received, so that relay checking
26699 can be done on the rewritten addresses.
26706 . ////////////////////////////////////////////////////////////////////////////
26707 . ////////////////////////////////////////////////////////////////////////////
26709 .chapter "Retry configuration" "CHAPretry"
26710 .scindex IIDretconf1 "retry" "configuration, description of"
26711 .scindex IIDregconf2 "configuration file" "retry section"
26712 The &"retry"& section of the runtime configuration file contains a list of
26713 retry rules that control how often Exim tries to deliver messages that cannot
26714 be delivered at the first attempt. If there are no retry rules (the section is
26715 empty or not present), there are no retries. In this situation, temporary
26716 errors are treated as permanent. The default configuration contains a single,
26717 general-purpose retry rule (see section &<<SECID57>>&). The &%-brt%& command
26718 line option can be used to test which retry rule will be used for a given
26719 address, domain and error.
26721 The most common cause of retries is temporary failure to deliver to a remote
26722 host because the host is down, or inaccessible because of a network problem.
26723 Exim's retry processing in this case is applied on a per-host (strictly, per IP
26724 address) basis, not on a per-message basis. Thus, if one message has recently
26725 been delayed, delivery of a new message to the same host is not immediately
26726 tried, but waits for the host's retry time to arrive. If the &%retry_defer%&
26727 log selector is set, the message
26728 .cindex "retry" "time not reached"
26729 &"retry time not reached"& is written to the main log whenever a delivery is
26730 skipped for this reason. Section &<<SECToutSMTPerr>>& contains more details of
26731 the handling of errors during remote deliveries.
26733 Retry processing applies to routing as well as to delivering, except as covered
26734 in the next paragraph. The retry rules do not distinguish between these
26735 actions. It is not possible, for example, to specify different behaviour for
26736 failures to route the domain &'snark.fict.example'& and failures to deliver to
26737 the host &'snark.fict.example'&. I didn't think anyone would ever need this
26738 added complication, so did not implement it. However, although they share the
26739 same retry rule, the actual retry times for routing and transporting a given
26740 domain are maintained independently.
26742 When a delivery is not part of a queue run (typically an immediate delivery on
26743 receipt of a message), the routers are always run, and local deliveries are
26744 always attempted, even if retry times are set for them. This makes for better
26745 behaviour if one particular message is causing problems (for example, causing
26746 quota overflow, or provoking an error in a filter file). If such a delivery
26747 suffers a temporary failure, the retry data is updated as normal, and
26748 subsequent delivery attempts from queue runs occur only when the retry time for
26749 the local address is reached.
26751 .section "Changing retry rules" "SECID157"
26752 If you change the retry rules in your configuration, you should consider
26753 whether or not to delete the retry data that is stored in Exim's spool area in
26754 files with names like &_db/retry_&. Deleting any of Exim's hints files is
26755 always safe; that is why they are called &"hints"&.
26757 The hints retry data contains suggested retry times based on the previous
26758 rules. In the case of a long-running problem with a remote host, it might
26759 record the fact that the host has timed out. If your new rules increase the
26760 timeout time for such a host, you should definitely remove the old retry data
26761 and let Exim recreate it, based on the new rules. Otherwise Exim might bounce
26762 messages that it should now be retaining.
26766 .section "Format of retry rules" "SECID158"
26767 .cindex "retry" "rules"
26768 Each retry rule occupies one line and consists of three or four parts,
26769 separated by white space: a pattern, an error name, an optional list of sender
26770 addresses, and a list of retry parameters. The pattern and sender lists must be
26771 enclosed in double quotes if they contain white space. The rules are searched
26772 in order until one is found where the pattern, error name, and sender list (if
26773 present) match the failing host or address, the error that occurred, and the
26774 message's sender, respectively.
26777 The pattern is any single item that may appear in an address list (see section
26778 &<<SECTaddresslist>>&). It is in fact processed as a one-item address list,
26779 which means that it is expanded before being tested against the address that
26780 has been delayed. A negated address list item is permitted. Address
26781 list processing treats a plain domain name as if it were preceded by &"*@"&,
26782 which makes it possible for many retry rules to start with just a domain. For
26785 lookingglass.fict.example * F,24h,30m;
26787 provides a rule for any address in the &'lookingglass.fict.example'& domain,
26790 alice@lookingglass.fict.example * F,24h,30m;
26792 applies only to temporary failures involving the local part &%alice%&.
26793 In practice, almost all rules start with a domain name pattern without a local
26796 .cindex "regular expressions" "in retry rules"
26797 &*Warning*&: If you use a regular expression in a retry rule pattern, it
26798 must match a complete address, not just a domain, because that is how regular
26799 expressions work in address lists.
26801 &`^\Nxyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Wrong%&
26802 &`^\N[^@]+@xyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Right%&
26806 .section "Choosing which retry rule to use for address errors" "SECID159"
26807 When Exim is looking for a retry rule after a routing attempt has failed (for
26808 example, after a DNS timeout), each line in the retry configuration is tested
26809 against the complete address only if &%retry_use_local_part%& is set for the
26810 router. Otherwise, only the domain is used, except when matching against a
26811 regular expression, when the local part of the address is replaced with &"*"&.
26812 A domain on its own can match a domain pattern, or a pattern that starts with
26813 &"*@"&. By default, &%retry_use_local_part%& is true for routers where
26814 &%check_local_user%& is true, and false for other routers.
26816 Similarly, when Exim is looking for a retry rule after a local delivery has
26817 failed (for example, after a mailbox full error), each line in the retry
26818 configuration is tested against the complete address only if
26819 &%retry_use_local_part%& is set for the transport (it defaults true for all
26822 .cindex "4&'xx'& responses" "retry rules for"
26823 However, when Exim is looking for a retry rule after a remote delivery attempt
26824 suffers an address error (a 4&'xx'& SMTP response for a recipient address), the
26825 whole address is always used as the key when searching the retry rules. The
26826 rule that is found is used to create a retry time for the combination of the
26827 failing address and the message's sender. It is the combination of sender and
26828 recipient that is delayed in subsequent queue runs until its retry time is
26829 reached. You can delay the recipient without regard to the sender by setting
26830 &%address_retry_include_sender%& false in the &(smtp)& transport but this can
26831 lead to problems with servers that regularly issue 4&'xx'& responses to RCPT
26836 .section "Choosing which retry rule to use for host and message errors" &&&
26838 For a temporary error that is not related to an individual address (for
26839 example, a connection timeout), each line in the retry configuration is checked
26840 twice. First, the name of the remote host is used as a domain name (preceded by
26841 &"*@"& when matching a regular expression). If this does not match the line,
26842 the domain from the email address is tried in a similar fashion. For example,
26843 suppose the MX records for &'a.b.c.example'& are
26845 a.b.c.example MX 5 x.y.z.example
26849 and the retry rules are
26851 p.q.r.example * F,24h,30m;
26852 a.b.c.example * F,4d,45m;
26854 and a delivery to the host &'x.y.z.example'& suffers a connection failure. The
26855 first rule matches neither the host nor the domain, so Exim looks at the second
26856 rule. This does not match the host, but it does match the domain, so it is used
26857 to calculate the retry time for the host &'x.y.z.example'&. Meanwhile, Exim
26858 tries to deliver to &'p.q.r.example'&. If this also suffers a host error, the
26859 first retry rule is used, because it matches the host.
26861 In other words, temporary failures to deliver to host &'p.q.r.example'& use the
26862 first rule to determine retry times, but for all the other hosts for the domain
26863 &'a.b.c.example'&, the second rule is used. The second rule is also used if
26864 routing to &'a.b.c.example'& suffers a temporary failure.
26866 &*Note*&: The host name is used when matching the patterns, not its IP address.
26867 However, if a message is routed directly to an IP address without the use of a
26868 host name, for example, if a &(manualroute)& router contains a setting such as:
26870 route_list = *.a.example 192.168.34.23
26872 then the &"host name"& that is used when searching for a retry rule is the
26873 textual form of the IP address.
26875 .section "Retry rules for specific errors" "SECID161"
26876 .cindex "retry" "specific errors; specifying"
26877 The second field in a retry rule is the name of a particular error, or an
26878 asterisk, which matches any error. The errors that can be tested for are:
26881 .vitem &%auth_failed%&
26882 Authentication failed when trying to send to a host in the
26883 &%hosts_require_auth%& list in an &(smtp)& transport.
26885 .vitem &%data_4xx%&
26886 A 4&'xx'& error was received for an outgoing DATA command, either immediately
26887 after the command, or after sending the message's data.
26889 .vitem &%mail_4xx%&
26890 A 4&'xx'& error was received for an outgoing MAIL command.
26892 .vitem &%rcpt_4xx%&
26893 A 4&'xx'& error was received for an outgoing RCPT command.
26896 For the three 4&'xx'& errors, either the first or both of the x's can be given
26897 as specific digits, for example: &`mail_45x`& or &`rcpt_436`&. For example, to
26898 recognize 452 errors given to RCPT commands for addresses in a certain domain,
26899 and have retries every ten minutes with a one-hour timeout, you could set up a
26900 retry rule of this form:
26902 the.domain.name rcpt_452 F,1h,10m
26904 These errors apply to both outgoing SMTP (the &(smtp)& transport) and outgoing
26905 LMTP (either the &(lmtp)& transport, or the &(smtp)& transport in LMTP mode).
26908 .vitem &%lost_connection%&
26909 A server unexpectedly closed the SMTP connection. There may, of course,
26910 legitimate reasons for this (host died, network died), but if it repeats a lot
26911 for the same host, it indicates something odd.
26914 A DNS lookup for a host failed.
26915 Note that a &%dnslookup%& router will need to have matched
26916 its &%fail_defer_domains%& option for this retry type to be usable.
26917 Also note that a &%manualroute%& router will probably need
26918 its &%host_find_failed%& option set to &%defer%&.
26920 .vitem &%refused_MX%&
26921 A connection to a host obtained from an MX record was refused.
26923 .vitem &%refused_A%&
26924 A connection to a host not obtained from an MX record was refused.
26927 A connection was refused.
26929 .vitem &%timeout_connect_MX%&
26930 A connection attempt to a host obtained from an MX record timed out.
26932 .vitem &%timeout_connect_A%&
26933 A connection attempt to a host not obtained from an MX record timed out.
26935 .vitem &%timeout_connect%&
26936 A connection attempt timed out.
26938 .vitem &%timeout_MX%&
26939 There was a timeout while connecting or during an SMTP session with a host
26940 obtained from an MX record.
26942 .vitem &%timeout_A%&
26943 There was a timeout while connecting or during an SMTP session with a host not
26944 obtained from an MX record.
26947 There was a timeout while connecting or during an SMTP session.
26949 .vitem &%tls_required%&
26950 The server was required to use TLS (it matched &%hosts_require_tls%& in the
26951 &(smtp)& transport), but either did not offer TLS, or it responded with 4&'xx'&
26952 to STARTTLS, or there was a problem setting up the TLS connection.
26955 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
26958 .vitem &%quota_%&<&'time'&>
26959 .cindex "quota" "error testing in retry rule"
26960 .cindex "retry" "quota error testing"
26961 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
26962 transport, and the mailbox has not been accessed for <&'time'&>. For example,
26963 &'quota_4d'& applies to a quota error when the mailbox has not been accessed
26967 .cindex "mailbox" "time of last read"
26968 The idea of &%quota_%&<&'time'&> is to make it possible to have shorter
26969 timeouts when the mailbox is full and is not being read by its owner. Ideally,
26970 it should be based on the last time that the user accessed the mailbox.
26971 However, it is not always possible to determine this. Exim uses the following
26975 If the mailbox is a single file, the time of last access (the &"atime"&) is
26976 used. As no new messages are being delivered (because the mailbox is over
26977 quota), Exim does not access the file, so this is the time of last user access.
26979 .cindex "maildir format" "time of last read"
26980 For a maildir delivery, the time of last modification of the &_new_&
26981 subdirectory is used. As the mailbox is over quota, no new files are created in
26982 the &_new_& subdirectory, because no new messages are being delivered. Any
26983 change to the &_new_& subdirectory is therefore assumed to be the result of an
26984 MUA moving a new message to the &_cur_& directory when it is first read. The
26985 time that is used is therefore the last time that the user read a new message.
26987 For other kinds of multi-file mailbox, the time of last access cannot be
26988 obtained, so a retry rule that uses this type of error field is never matched.
26991 The quota errors apply both to system-enforced quotas and to Exim's own quota
26992 mechanism in the &(appendfile)& transport. The &'quota'& error also applies
26993 when a local delivery is deferred because a partition is full (the ENOSPC
26998 .section "Retry rules for specified senders" "SECID162"
26999 .cindex "retry" "rules; sender-specific"
27000 You can specify retry rules that apply only when the failing message has a
27001 specific sender. In particular, this can be used to define retry rules that
27002 apply only to bounce messages. The third item in a retry rule can be of this
27005 &`senders=`&<&'address list'&>
27007 The retry timings themselves are then the fourth item. For example:
27009 * rcpt_4xx senders=: F,1h,30m
27011 matches recipient 4&'xx'& errors for bounce messages sent to any address at any
27012 host. If the address list contains white space, it must be enclosed in quotes.
27015 a.domain rcpt_452 senders="xb.dom : yc.dom" G,8h,10m,1.5
27017 &*Warning*&: This facility can be unhelpful if it is used for host errors
27018 (which do not depend on the recipient). The reason is that the sender is used
27019 only to match the retry rule. Once the rule has been found for a host error,
27020 its contents are used to set a retry time for the host, and this will apply to
27021 all messages, not just those with specific senders.
27023 When testing retry rules using &%-brt%&, you can supply a sender using the
27024 &%-f%& command line option, like this:
27026 exim -f "" -brt user@dom.ain
27028 If you do not set &%-f%& with &%-brt%&, a retry rule that contains a senders
27029 list is never matched.
27035 .section "Retry parameters" "SECID163"
27036 .cindex "retry" "parameters in rules"
27037 The third (or fourth, if a senders list is present) field in a retry rule is a
27038 sequence of retry parameter sets, separated by semicolons. Each set consists of
27040 <&'letter'&>,<&'cutoff time'&>,<&'arguments'&>
27042 The letter identifies the algorithm for computing a new retry time; the cutoff
27043 time is the time beyond which this algorithm no longer applies, and the
27044 arguments vary the algorithm's action. The cutoff time is measured from the
27045 time that the first failure for the domain (combined with the local part if
27046 relevant) was detected, not from the time the message was received.
27048 .cindex "retry" "algorithms"
27049 .cindex "retry" "fixed intervals"
27050 .cindex "retry" "increasing intervals"
27051 .cindex "retry" "random intervals"
27052 The available algorithms are:
27055 &'F'&: retry at fixed intervals. There is a single time parameter specifying
27058 &'G'&: retry at geometrically increasing intervals. The first argument
27059 specifies a starting value for the interval, and the second a multiplier, which
27060 is used to increase the size of the interval at each retry.
27062 &'H'&: retry at randomized intervals. The arguments are as for &'G'&. For each
27063 retry, the previous interval is multiplied by the factor in order to get a
27064 maximum for the next interval. The minimum interval is the first argument of
27065 the parameter, and an actual interval is chosen randomly between them. Such a
27066 rule has been found to be helpful in cluster configurations when all the
27067 members of the cluster restart at once, and may therefore synchronize their
27068 queue processing times.
27071 When computing the next retry time, the algorithm definitions are scanned in
27072 order until one whose cutoff time has not yet passed is reached. This is then
27073 used to compute a new retry time that is later than the current time. In the
27074 case of fixed interval retries, this simply means adding the interval to the
27075 current time. For geometrically increasing intervals, retry intervals are
27076 computed from the rule's parameters until one that is greater than the previous
27077 interval is found. The main configuration variable
27078 .cindex "limit" "retry interval"
27079 .cindex "retry" "interval, maximum"
27080 .oindex "&%retry_interval_max%&"
27081 &%retry_interval_max%& limits the maximum interval between retries. It
27082 cannot be set greater than &`24h`&, which is its default value.
27084 A single remote domain may have a number of hosts associated with it, and each
27085 host may have more than one IP address. Retry algorithms are selected on the
27086 basis of the domain name, but are applied to each IP address independently. If,
27087 for example, a host has two IP addresses and one is unusable, Exim will
27088 generate retry times for it and will not try to use it until its next retry
27089 time comes. Thus the good IP address is likely to be tried first most of the
27092 .cindex "hints database" "use for retrying"
27093 Retry times are hints rather than promises. Exim does not make any attempt to
27094 run deliveries exactly at the computed times. Instead, a queue runner process
27095 starts delivery processes for delayed messages periodically, and these attempt
27096 new deliveries only for those addresses that have passed their next retry time.
27097 If a new message arrives for a deferred address, an immediate delivery attempt
27098 occurs only if the address has passed its retry time. In the absence of new
27099 messages, the minimum time between retries is the interval between queue runner
27100 processes. There is not much point in setting retry times of five minutes if
27101 your queue runners happen only once an hour, unless there are a significant
27102 number of incoming messages (which might be the case on a system that is
27103 sending everything to a smart host, for example).
27105 The data in the retry hints database can be inspected by using the
27106 &'exim_dumpdb'& or &'exim_fixdb'& utility programs (see chapter
27107 &<<CHAPutils>>&). The latter utility can also be used to change the data. The
27108 &'exinext'& utility script can be used to find out what the next retry times
27109 are for the hosts associated with a particular mail domain, and also for local
27110 deliveries that have been deferred.
27113 .section "Retry rule examples" "SECID164"
27114 Here are some example retry rules:
27116 alice@wonderland.fict.example quota_5d F,7d,3h
27117 wonderland.fict.example quota_5d
27118 wonderland.fict.example * F,1h,15m; G,2d,1h,2;
27119 lookingglass.fict.example * F,24h,30m;
27120 * refused_A F,2h,20m;
27121 * * F,2h,15m; G,16h,1h,1.5; F,5d,8h
27123 The first rule sets up special handling for mail to
27124 &'alice@wonderland.fict.example'& when there is an over-quota error and the
27125 mailbox has not been read for at least 5 days. Retries continue every three
27126 hours for 7 days. The second rule handles over-quota errors for all other local
27127 parts at &'wonderland.fict.example'&; the absence of a local part has the same
27128 effect as supplying &"*@"&. As no retry algorithms are supplied, messages that
27129 fail are bounced immediately if the mailbox has not been read for at least 5
27132 The third rule handles all other errors at &'wonderland.fict.example'&; retries
27133 happen every 15 minutes for an hour, then with geometrically increasing
27134 intervals until two days have passed since a delivery first failed. After the
27135 first hour there is a delay of one hour, then two hours, then four hours, and
27136 so on (this is a rather extreme example).
27138 The fourth rule controls retries for the domain &'lookingglass.fict.example'&.
27139 They happen every 30 minutes for 24 hours only. The remaining two rules handle
27140 all other domains, with special action for connection refusal from hosts that
27141 were not obtained from an MX record.
27143 The final rule in a retry configuration should always have asterisks in the
27144 first two fields so as to provide a general catch-all for any addresses that do
27145 not have their own special handling. This example tries every 15 minutes for 2
27146 hours, then with intervals starting at one hour and increasing by a factor of
27147 1.5 up to 16 hours, then every 8 hours up to 5 days.
27151 .section "Timeout of retry data" "SECID165"
27152 .cindex "timeout" "of retry data"
27153 .oindex "&%retry_data_expire%&"
27154 .cindex "hints database" "data expiry"
27155 .cindex "retry" "timeout of data"
27156 Exim timestamps the data that it writes to its retry hints database. When it
27157 consults the data during a delivery it ignores any that is older than the value
27158 set in &%retry_data_expire%& (default 7 days). If, for example, a host hasn't
27159 been tried for 7 days, Exim will try to deliver to it immediately a message
27160 arrives, and if that fails, it will calculate a retry time as if it were
27161 failing for the first time.
27163 This improves the behaviour for messages routed to rarely-used hosts such as MX
27164 backups. If such a host was down at one time, and happens to be down again when
27165 Exim tries a month later, using the old retry data would imply that it had been
27166 down all the time, which is not a justified assumption.
27168 If a host really is permanently dead, this behaviour causes a burst of retries
27169 every now and again, but only if messages routed to it are rare. If there is a
27170 message at least once every 7 days the retry data never expires.
27175 .section "Long-term failures" "SECID166"
27176 .cindex "delivery failure, long-term"
27177 .cindex "retry" "after long-term failure"
27178 Special processing happens when an email address has been failing for so long
27179 that the cutoff time for the last algorithm is reached. For example, using the
27180 default retry rule:
27182 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
27184 the cutoff time is four days. Reaching the retry cutoff is independent of how
27185 long any specific message has been failing; it is the length of continuous
27186 failure for the recipient address that counts.
27188 When the cutoff time is reached for a local delivery, or for all the IP
27189 addresses associated with a remote delivery, a subsequent delivery failure
27190 causes Exim to give up on the address, and a bounce message is generated.
27191 In order to cater for new messages that use the failing address, a next retry
27192 time is still computed from the final algorithm, and is used as follows:
27194 For local deliveries, one delivery attempt is always made for any subsequent
27195 messages. If this delivery fails, the address fails immediately. The
27196 post-cutoff retry time is not used.
27198 .cindex "final cutoff" "retries, controlling"
27199 .cindex retry "final cutoff"
27200 If the delivery is remote, there are two possibilities, controlled by the
27201 .oindex "&%delay_after_cutoff%&"
27202 &%delay_after_cutoff%& option of the &(smtp)& transport. The option is true by
27203 default. Until the post-cutoff retry time for one of the IP addresses,
27204 as set by the &%retry_data_expire%& option, is
27205 reached, the failing email address is bounced immediately, without a delivery
27206 attempt taking place. After that time, one new delivery attempt is made to
27207 those IP addresses that are past their retry times, and if that still fails,
27208 the address is bounced and new retry times are computed.
27210 In other words, when all the hosts for a given email address have been failing
27211 for a long time, Exim bounces rather then defers until one of the hosts' retry
27212 times is reached. Then it tries once, and bounces if that attempt fails. This
27213 behaviour ensures that few resources are wasted in repeatedly trying to deliver
27214 to a broken destination, but if the host does recover, Exim will eventually
27217 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
27218 addresses are past their final cutoff time, Exim tries to deliver to those IP
27219 addresses that have not been tried since the message arrived. If there are
27220 no suitable IP addresses, or if they all fail, the address is bounced. In other
27221 words, it does not delay when a new message arrives, but tries the expired
27222 addresses immediately, unless they have been tried since the message arrived.
27223 If there is a continuous stream of messages for the failing domains, setting
27224 &%delay_after_cutoff%& false means that there will be many more attempts to
27225 deliver to permanently failing IP addresses than when &%delay_after_cutoff%& is
27228 .section "Deliveries that work intermittently" "SECID167"
27229 .cindex "retry" "intermittently working deliveries"
27230 Some additional logic is needed to cope with cases where a host is
27231 intermittently available, or when a message has some attribute that prevents
27232 its delivery when others to the same address get through. In this situation,
27233 because some messages are successfully delivered, the &"retry clock"& for the
27234 host or address keeps getting reset by the successful deliveries, and so
27235 failing messages remain in the queue for ever because the cutoff time is never
27238 Two exceptional actions are applied to prevent this happening. The first
27239 applies to errors that are related to a message rather than a remote host.
27240 Section &<<SECToutSMTPerr>>& has a discussion of the different kinds of error;
27241 examples of message-related errors are 4&'xx'& responses to MAIL or DATA
27242 commands, and quota failures. For this type of error, if a message's arrival
27243 time is earlier than the &"first failed"& time for the error, the earlier time
27244 is used when scanning the retry rules to decide when to try next and when to
27245 time out the address.
27247 The exceptional second action applies in all cases. If a message has been on
27248 the queue for longer than the cutoff time of any applicable retry rule for a
27249 given address, a delivery is attempted for that address, even if it is not yet
27250 time, and if this delivery fails, the address is timed out. A new retry time is
27251 not computed in this case, so that other messages for the same address are
27252 considered immediately.
27253 .ecindex IIDretconf1
27254 .ecindex IIDregconf2
27261 . ////////////////////////////////////////////////////////////////////////////
27262 . ////////////////////////////////////////////////////////////////////////////
27264 .chapter "SMTP authentication" "CHAPSMTPAUTH"
27265 .scindex IIDauthconf1 "SMTP" "authentication configuration"
27266 .scindex IIDauthconf2 "authentication"
27267 The &"authenticators"& section of Exim's runtime configuration is concerned
27268 with SMTP authentication. This facility is an extension to the SMTP protocol,
27269 described in RFC 2554, which allows a client SMTP host to authenticate itself
27270 to a server. This is a common way for a server to recognize clients that are
27271 permitted to use it as a relay. SMTP authentication is not of relevance to the
27272 transfer of mail between servers that have no managerial connection with each
27275 The name of an authenticator is limited to be &drivernamemax; ASCII characters long;
27276 prior to Exim 4.95 names would be silently truncated at this length, but now
27279 .cindex "AUTH" "description of"
27280 .cindex "ESMTP extensions" AUTH
27281 Very briefly, the way SMTP authentication works is as follows:
27284 The server advertises a number of authentication &'mechanisms'& in response to
27285 the client's EHLO command.
27287 The client issues an AUTH command, naming a specific mechanism. The command
27288 may, optionally, contain some authentication data.
27290 The server may issue one or more &'challenges'&, to which the client must send
27291 appropriate responses. In simple authentication mechanisms, the challenges are
27292 just prompts for user names and passwords. The server does not have to issue
27293 any challenges &-- in some mechanisms the relevant data may all be transmitted
27294 with the AUTH command.
27296 The server either accepts or denies authentication.
27298 If authentication succeeds, the client may optionally make use of the AUTH
27299 option on the MAIL command to pass an authenticated sender in subsequent
27300 mail transactions. Authentication lasts for the remainder of the SMTP
27303 If authentication fails, the client may give up, or it may try a different
27304 authentication mechanism, or it may try transferring mail over the
27305 unauthenticated connection.
27308 If you are setting up a client, and want to know which authentication
27309 mechanisms the server supports, you can use Telnet to connect to port 25 (the
27310 SMTP port) on the server, and issue an EHLO command. The response to this
27311 includes the list of supported mechanisms. For example:
27313 &`$ `&&*&`telnet server.example 25`&*&
27314 &`Trying 192.168.34.25...`&
27315 &`Connected to server.example.`&
27316 &`Escape character is '^]'.`&
27317 &`220 server.example ESMTP Exim 4.20 ...`&
27318 &*&`ehlo client.example`&*&
27319 &`250-server.example Hello client.example [10.8.4.5]`&
27320 &`250-SIZE 52428800`&
27325 The second-last line of this example output shows that the server supports
27326 authentication using the PLAIN mechanism. In Exim, the different authentication
27327 mechanisms are configured by specifying &'authenticator'& drivers. Like the
27328 routers and transports, which authenticators are included in the binary is
27329 controlled by build-time definitions. The following are currently available,
27330 included by setting
27333 AUTH_CYRUS_SASL=yes
27337 AUTH_HEIMDAL_GSSAPI=yes
27342 in &_Local/Makefile_&, respectively. The first of these supports the CRAM-MD5
27343 authentication mechanism (RFC 2195), and the second provides an interface to
27344 the Cyrus SASL authentication library.
27345 The third is an interface to Dovecot's authentication system, delegating the
27346 work via a socket interface.
27347 The fourth provides for negotiation of authentication done via non-SMTP means,
27348 as defined by RFC 4422 Appendix A.
27349 The fifth provides an interface to the GNU SASL authentication library, which
27350 provides mechanisms but typically not data sources.
27351 The sixth provides direct access to Heimdal GSSAPI, geared for Kerberos, but
27352 supporting setting a server keytab.
27353 The seventh can be configured to support
27354 the PLAIN authentication mechanism (RFC 2595) or the LOGIN mechanism, which is
27355 not formally documented, but used by several MUAs.
27356 The eighth authenticator
27357 supports Microsoft's &'Secure Password Authentication'& mechanism.
27358 The last is an Exim authenticator but not an SMTP one;
27359 instead it can use information from a TLS negotiation.
27361 The authenticators are configured using the same syntax as other drivers (see
27362 section &<<SECTfordricon>>&). If no authenticators are required, no
27363 authentication section need be present in the configuration file. Each
27364 authenticator can in principle have both server and client functions. When Exim
27365 is receiving SMTP mail, it is acting as a server; when it is sending out
27366 messages over SMTP, it is acting as a client. Authenticator configuration
27367 options are provided for use in both these circumstances.
27369 To make it clear which options apply to which situation, the prefixes
27370 &%server_%& and &%client_%& are used on option names that are specific to
27371 either the server or the client function, respectively. Server and client
27372 functions are disabled if none of their options are set. If an authenticator is
27373 to be used for both server and client functions, a single definition, using
27374 both sets of options, is required. For example:
27378 public_name = CRAM-MD5
27379 server_secret = ${if eq{$auth1}{ph10}{secret1}fail}
27381 client_secret = secret2
27383 The &%server_%& option is used when Exim is acting as a server, and the
27384 &%client_%& options when it is acting as a client.
27386 Descriptions of the individual authenticators are given in subsequent chapters.
27387 The remainder of this chapter covers the generic options for the
27388 authenticators, followed by general discussion of the way authentication works
27391 &*Beware:*& the meaning of &$auth1$&, &$auth2$&, ... varies on a per-driver and
27392 per-mechanism basis. Please read carefully to determine which variables hold
27393 account labels such as usercodes and which hold passwords or other
27394 authenticating data.
27396 Note that some mechanisms support two different identifiers for accounts: the
27397 &'authentication id'& and the &'authorization id'&. The contractions &'authn'&
27398 and &'authz'& are commonly encountered. The American spelling is standard here.
27399 Conceptually, authentication data such as passwords are tied to the identifier
27400 used to authenticate; servers may have rules to permit one user to act as a
27401 second user, so that after login the session is treated as though that second
27402 user had logged in. That second user is the &'authorization id'&. A robust
27403 configuration might confirm that the &'authz'& field is empty or matches the
27404 &'authn'& field. Often this is just ignored. The &'authn'& can be considered
27405 as verified data, the &'authz'& as an unverified request which the server might
27408 A &'realm'& is a text string, typically a domain name, presented by a server
27409 to a client to help it select an account and credentials to use. In some
27410 mechanisms, the client and server provably agree on the realm, but clients
27411 typically can not treat the realm as secure data to be blindly trusted.
27415 .section "Generic options for authenticators" "SECID168"
27416 .cindex "authentication" "generic options"
27417 .cindex "options" "generic; for authenticators"
27419 .option client_condition authenticators string&!! unset
27420 When Exim is authenticating as a client, it skips any authenticator whose
27421 &%client_condition%& expansion yields &"0"&, &"no"&, or &"false"&. This can be
27422 used, for example, to skip plain text authenticators when the connection is not
27423 encrypted by a setting such as:
27425 client_condition = ${if !eq{$tls_out_cipher}{}}
27429 .option client_set_id authenticators string&!! unset
27430 When client authentication succeeds, this condition is expanded; the
27431 result is used in the log lines for outbound messages.
27432 Typically it will be the user name used for authentication.
27435 .option driver authenticators string unset
27436 This option must always be set. It specifies which of the available
27437 authenticators is to be used.
27440 .option public_name authenticators string unset
27441 This option specifies the name of the authentication mechanism that the driver
27442 implements, and by which it is known to the outside world. These names should
27443 contain only upper case letters, digits, underscores, and hyphens (RFC 2222),
27444 but Exim in fact matches them caselessly. If &%public_name%& is not set, it
27445 defaults to the driver's instance name.
27448 .option server_advertise_condition authenticators string&!! unset
27449 When a server is about to advertise an authentication mechanism, the condition
27450 is expanded. If it yields the empty string, &"0"&, &"no"&, or &"false"&, the
27451 mechanism is not advertised.
27452 If the expansion fails, the mechanism is not advertised. If the failure was not
27453 forced, and was not caused by a lookup defer, the incident is logged.
27454 See section &<<SECTauthexiser>>& below for further discussion.
27457 .option server_condition authenticators string&!! unset
27458 This option must be set for a &%plaintext%& server authenticator, where it
27459 is used directly to control authentication. See section &<<SECTplainserver>>&
27462 For the &(gsasl)& authenticator, this option is required for various
27463 mechanisms; see chapter &<<CHAPgsasl>>& for details.
27465 For the other authenticators, &%server_condition%& can be used as an additional
27466 authentication or authorization mechanism that is applied after the other
27467 authenticator conditions succeed. If it is set, it is expanded when the
27468 authenticator would otherwise return a success code. If the expansion is forced
27469 to fail, authentication fails. Any other expansion failure causes a temporary
27470 error code to be returned. If the result of a successful expansion is an empty
27471 string, &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
27472 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds. For any
27473 other result, a temporary error code is returned, with the expanded string as
27477 .option server_debug_print authenticators string&!! unset
27478 If this option is set and authentication debugging is enabled (see the &%-d%&
27479 command line option), the string is expanded and included in the debugging
27480 output when the authenticator is run as a server. This can help with checking
27481 out the values of variables.
27482 If expansion of the string fails, the error message is written to the debugging
27483 output, and Exim carries on processing.
27486 .option server_set_id authenticators string&!! unset
27487 .vindex "&$authenticated_id$&"
27488 .vindex "&$authenticated_fail_id$&"
27489 When an Exim server successfully authenticates a client, this string is
27490 expanded using data from the authentication, and preserved for any incoming
27491 messages in the variable &$authenticated_id$&. It is also included in the log
27492 lines for incoming messages. For example, a user/password authenticator
27493 configuration might preserve the user name that was used to authenticate, and
27494 refer to it subsequently during delivery of the message.
27495 On a failing authentication the expansion result is instead saved in
27496 the &$authenticated_fail_id$& variable.
27497 If expansion fails, the option is ignored.
27500 .option server_mail_auth_condition authenticators string&!! unset
27501 This option allows a server to discard authenticated sender addresses supplied
27502 as part of MAIL commands in SMTP connections that are authenticated by the
27503 driver on which &%server_mail_auth_condition%& is set. The option is not used
27504 as part of the authentication process; instead its (unexpanded) value is
27505 remembered for later use.
27506 How it is used is described in the following section.
27512 .section "The AUTH parameter on MAIL commands" "SECTauthparamail"
27513 .cindex "authentication" "sender; authenticated"
27514 .cindex "AUTH" "on MAIL command"
27515 When a client supplied an AUTH= item on a MAIL command, Exim applies
27516 the following checks before accepting it as the authenticated sender of the
27520 If the connection is not using extended SMTP (that is, HELO was used rather
27521 than EHLO), the use of AUTH= is a syntax error.
27523 If the value of the AUTH= parameter is &"<>"&, it is ignored.
27525 .vindex "&$authenticated_sender$&"
27526 If &%acl_smtp_mailauth%& is defined, the ACL it specifies is run. While it is
27527 running, the value of &$authenticated_sender$& is set to the value obtained
27528 from the AUTH= parameter. If the ACL does not yield &"accept"&, the value of
27529 &$authenticated_sender$& is deleted. The &%acl_smtp_mailauth%& ACL may not
27530 return &"drop"& or &"discard"&. If it defers, a temporary error code (451) is
27531 given for the MAIL command.
27533 If &%acl_smtp_mailauth%& is not defined, the value of the AUTH= parameter
27534 is accepted and placed in &$authenticated_sender$& only if the client has
27537 If the AUTH= value was accepted by either of the two previous rules, and
27538 the client has authenticated, and the authenticator has a setting for the
27539 &%server_mail_auth_condition%&, the condition is checked at this point. The
27540 valued that was saved from the authenticator is expanded. If the expansion
27541 fails, or yields an empty string, &"0"&, &"no"&, or &"false"&, the value of
27542 &$authenticated_sender$& is deleted. If the expansion yields any other value,
27543 the value of &$authenticated_sender$& is retained and passed on with the
27548 When &$authenticated_sender$& is set for a message, it is passed on to other
27549 hosts to which Exim authenticates as a client. Do not confuse this value with
27550 &$authenticated_id$&, which is a string obtained from the authentication
27551 process, and which is not usually a complete email address.
27553 .vindex "&$sender_address$&"
27554 Whenever an AUTH= value is ignored, the incident is logged. The ACL for
27555 MAIL, if defined, is run after AUTH= is accepted or ignored. It can
27556 therefore make use of &$authenticated_sender$&. The converse is not true: the
27557 value of &$sender_address$& is not yet set up when the &%acl_smtp_mailauth%&
27562 .section "Authentication on an Exim server" "SECTauthexiser"
27563 .cindex "authentication" "on an Exim server"
27564 When Exim receives an EHLO command, it advertises the public names of those
27565 authenticators that are configured as servers, subject to the following
27569 The client host must match &%auth_advertise_hosts%& (default *).
27571 If the &%server_advertise_condition%& option is set, its expansion must not
27572 yield the empty string, &"0"&, &"no"&, or &"false"&.
27575 The order in which the authenticators are defined controls the order in which
27576 the mechanisms are advertised.
27578 Some mail clients (for example, some versions of Netscape) require the user to
27579 provide a name and password for authentication whenever AUTH is advertised,
27580 even though authentication may not in fact be needed (for example, Exim may be
27581 set up to allow unconditional relaying from the client by an IP address check).
27582 You can make such clients more friendly by not advertising AUTH to them.
27583 For example, if clients on the 10.9.8.0/24 network are permitted (by the ACL
27584 that runs for RCPT) to relay without authentication, you should set
27586 auth_advertise_hosts = ! 10.9.8.0/24
27588 so that no authentication mechanisms are advertised to them.
27590 The &%server_advertise_condition%& controls the advertisement of individual
27591 authentication mechanisms. For example, it can be used to restrict the
27592 advertisement of a particular mechanism to encrypted connections, by a setting
27595 server_advertise_condition = ${if eq{$tls_in_cipher}{}{no}{yes}}
27597 .vindex "&$tls_in_cipher$&"
27598 If the session is encrypted, &$tls_in_cipher$& is not empty, and so the expansion
27599 yields &"yes"&, which allows the advertisement to happen.
27601 When an Exim server receives an AUTH command from a client, it rejects it
27602 immediately if AUTH was not advertised in response to an earlier EHLO
27603 command. This is the case if
27606 The client host does not match &%auth_advertise_hosts%&; or
27608 No authenticators are configured with server options; or
27610 Expansion of &%server_advertise_condition%& blocked the advertising of all the
27611 server authenticators.
27615 Otherwise, Exim runs the ACL specified by &%acl_smtp_auth%& in order
27616 to decide whether to accept the command. If &%acl_smtp_auth%& is not set,
27617 AUTH is accepted from any client host.
27619 If AUTH is not rejected by the ACL, Exim searches its configuration for a
27620 server authentication mechanism that was advertised in response to EHLO and
27621 that matches the one named in the AUTH command. If it finds one, it runs
27622 the appropriate authentication protocol, and authentication either succeeds or
27623 fails. If there is no matching advertised mechanism, the AUTH command is
27624 rejected with a 504 error.
27626 .vindex "&$received_protocol$&"
27627 .vindex "&$sender_host_authenticated$&"
27628 When a message is received from an authenticated host, the value of
27629 &$received_protocol$& is set to &"esmtpa"& or &"esmtpsa"& instead of &"esmtp"&
27630 or &"esmtps"&, and &$sender_host_authenticated$& contains the name (not the
27631 public name) of the authenticator driver that successfully authenticated the
27632 client from which the message was received. This variable is empty if there was
27633 no successful authentication.
27635 .cindex authentication "expansion item"
27636 Successful authentication sets up information used by the
27637 &%authresults%& expansion item.
27642 .section "Testing server authentication" "SECID169"
27643 .cindex "authentication" "testing a server"
27644 .cindex "AUTH" "testing a server"
27645 .cindex "base64 encoding" "creating authentication test data"
27646 Exim's &%-bh%& option can be useful for testing server authentication
27647 configurations. The data for the AUTH command has to be sent using base64
27648 encoding. A quick way to produce such data for testing is the following Perl
27652 printf ("%s", encode_base64(eval "\"$ARGV[0]\""));
27654 .cindex "binary zero" "in authentication data"
27655 This interprets its argument as a Perl string, and then encodes it. The
27656 interpretation as a Perl string allows binary zeros, which are required for
27657 some kinds of authentication, to be included in the data. For example, a
27658 command line to run this script on such data might be
27660 encode '\0user\0password'
27662 Note the use of single quotes to prevent the shell interpreting the
27663 backslashes, so that they can be interpreted by Perl to specify characters
27664 whose code value is zero.
27666 &*Warning 1*&: If either of the user or password strings starts with an octal
27667 digit, you must use three zeros instead of one after the leading backslash. If
27668 you do not, the octal digit that starts your string will be incorrectly
27669 interpreted as part of the code for the first character.
27671 &*Warning 2*&: If there are characters in the strings that Perl interprets
27672 specially, you must use a Perl escape to prevent them being misinterpreted. For
27673 example, a command such as
27675 encode '\0user@domain.com\0pas$$word'
27677 gives an incorrect answer because of the unescaped &"@"& and &"$"& characters.
27679 If you have the &%mimencode%& command installed, another way to produce
27680 base64-encoded strings is to run the command
27682 echo -e -n `\0user\0password' | mimencode
27684 The &%-e%& option of &%echo%& enables the interpretation of backslash escapes
27685 in the argument, and the &%-n%& option specifies no newline at the end of its
27686 output. However, not all versions of &%echo%& recognize these options, so you
27687 should check your version before relying on this suggestion.
27691 .section "Authentication by an Exim client" "SECID170"
27692 .cindex "authentication" "on an Exim client"
27693 The &(smtp)& transport has two options called &%hosts_require_auth%& and
27694 &%hosts_try_auth%&. When the &(smtp)& transport connects to a server that
27695 announces support for authentication, and the host matches an entry in either
27696 of these options, Exim (as a client) tries to authenticate as follows:
27699 For each authenticator that is configured as a client, in the order in which
27700 they are defined in the configuration, it searches the authentication
27701 mechanisms announced by the server for one whose name matches the public name
27702 of the authenticator.
27705 .vindex "&$host_address$&"
27706 When it finds one that matches, it runs the authenticator's client code. The
27707 variables &$host$& and &$host_address$& are available for any string expansions
27708 that the client might do. They are set to the server's name and IP address. If
27709 any expansion is forced to fail, the authentication attempt is abandoned, and
27710 Exim moves on to the next authenticator. Otherwise an expansion failure causes
27711 delivery to be deferred.
27713 If the result of the authentication attempt is a temporary error or a timeout,
27714 Exim abandons trying to send the message to the host for the moment. It will
27715 try again later. If there are any backup hosts available, they are tried in the
27718 If the response to authentication is a permanent error (5&'xx'& code), Exim
27719 carries on searching the list of authenticators and tries another one if
27720 possible. If all authentication attempts give permanent errors, or if there are
27721 no attempts because no mechanisms match (or option expansions force failure),
27722 what happens depends on whether the host matches &%hosts_require_auth%& or
27723 &%hosts_try_auth%&. In the first case, a temporary error is generated, and
27724 delivery is deferred. The error can be detected in the retry rules, and thereby
27725 turned into a permanent error if you wish. In the second case, Exim tries to
27726 deliver the message unauthenticated.
27729 Note that the hostlist test for whether to do authentication can be
27730 confused if name-IP lookups change between the time the peer is decided
27731 upon and the time that the transport runs. For example, with a manualroute
27732 router given a host name, and with DNS "round-robin" used by that name: if
27733 the local resolver cache times out between the router and the transport
27734 running, the transport may get an IP for the name for its authentication
27735 check which does not match the connection peer IP.
27736 No authentication will then be done, despite the names being identical.
27738 For such cases use a separate transport which always authenticates.
27740 .cindex "AUTH" "on MAIL command"
27741 When Exim has authenticated itself to a remote server, it adds the AUTH
27742 parameter to the MAIL commands it sends, if it has an authenticated sender for
27743 the message. If the message came from a remote host, the authenticated sender
27744 is the one that was receiving on an incoming MAIL command, provided that the
27745 incoming connection was authenticated and the &%server_mail_auth%& condition
27746 allowed the authenticated sender to be retained. If a local process calls Exim
27747 to send a message, the sender address that is built from the login name and
27748 &%qualify_domain%& is treated as authenticated. However, if the
27749 &%authenticated_sender%& option is set on the &(smtp)& transport, it overrides
27750 the authenticated sender that was received with the message.
27751 .ecindex IIDauthconf1
27752 .ecindex IIDauthconf2
27759 . ////////////////////////////////////////////////////////////////////////////
27760 . ////////////////////////////////////////////////////////////////////////////
27762 .chapter "The plaintext authenticator" "CHAPplaintext"
27763 .scindex IIDplaiauth1 "&(plaintext)& authenticator"
27764 .scindex IIDplaiauth2 "authenticators" "&(plaintext)&"
27765 The &(plaintext)& authenticator can be configured to support the PLAIN and
27766 LOGIN authentication mechanisms, both of which transfer authentication data as
27767 plain (unencrypted) text (though base64 encoded). The use of plain text is a
27768 security risk; you are strongly advised to insist on the use of SMTP encryption
27769 (see chapter &<<CHAPTLS>>&) if you use the PLAIN or LOGIN mechanisms. If you do
27770 use unencrypted plain text, you should not use the same passwords for SMTP
27771 connections as you do for login accounts.
27773 .section "Avoiding cleartext use" "SECTplain_TLS"
27774 The following generic option settings will disable &(plaintext)& authenticators when
27775 TLS is not being used:
27777 server_advertise_condition = ${if def:tls_in_cipher }
27778 client_condition = ${if def:tls_out_cipher}
27781 &*Note*&: a plaintext SMTP AUTH done inside TLS is not vulnerable to casual snooping,
27782 but is still vulnerable to a Man In The Middle attack unless certificates
27783 (including their names) have been properly verified.
27785 .section "Plaintext server options" "SECID171"
27786 .cindex "options" "&(plaintext)& authenticator (server)"
27787 When configured as a server, &(plaintext)& uses the following options:
27789 .option server_condition authenticators string&!! unset
27790 This is actually a global authentication option, but it must be set in order to
27791 configure the &(plaintext)& driver as a server. Its use is described below.
27793 .option server_prompts plaintext "string list&!!" unset
27794 The contents of this option, after expansion, must be a colon-separated list of
27795 prompt strings. If expansion fails, a temporary authentication rejection is
27798 .section "Using plaintext in a server" "SECTplainserver"
27799 .cindex "AUTH" "in &(plaintext)& authenticator"
27800 .cindex "binary zero" "in &(plaintext)& authenticator"
27801 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
27802 "in &(plaintext)& authenticator"
27803 .vindex "&$auth1$&, &$auth2$&, etc"
27804 .cindex "base64 encoding" "in &(plaintext)& authenticator"
27806 When running as a server, &(plaintext)& performs the authentication test by
27807 expanding a string. The data sent by the client with the AUTH command, or in
27808 response to subsequent prompts, is base64 encoded, and so may contain any byte
27809 values when decoded. If any data is supplied with the command, it is treated as
27810 a list of strings, separated by NULs (binary zeros), the first three of which
27811 are placed in the expansion variables &$auth1$&, &$auth2$&, and &$auth3$&
27812 (neither LOGIN nor PLAIN uses more than three strings).
27814 For compatibility with previous releases of Exim, the values are also placed in
27815 the expansion variables &$1$&, &$2$&, and &$3$&. However, the use of these
27816 variables for this purpose is now deprecated, as it can lead to confusion in
27817 string expansions that also use them for other things.
27819 If there are more strings in &%server_prompts%& than the number of strings
27820 supplied with the AUTH command, the remaining prompts are used to obtain more
27821 data. Each response from the client may be a list of NUL-separated strings.
27823 .vindex "&$authenticated_id$&"
27824 Once a sufficient number of data strings have been received,
27825 &%server_condition%& is expanded. If the expansion is forced to fail,
27826 authentication fails. Any other expansion failure causes a temporary error code
27827 to be returned. If the result of a successful expansion is an empty string,
27828 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
27829 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
27830 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
27831 For any other result, a temporary error code is returned, with the expanded
27832 string as the error text.
27834 &*Warning*&: If you use a lookup in the expansion to find the user's
27835 password, be sure to make the authentication fail if the user is unknown.
27836 There are good and bad examples at the end of the next section.
27840 .section "The PLAIN authentication mechanism" "SECID172"
27841 .cindex "PLAIN authentication mechanism"
27842 .cindex authentication PLAIN
27843 .cindex "binary zero" "in &(plaintext)& authenticator"
27844 The PLAIN authentication mechanism (RFC 2595) specifies that three strings be
27845 sent as one item of data (that is, one combined string containing two NUL
27846 separators). The data is sent either as part of the AUTH command, or
27847 subsequently in response to an empty prompt from the server.
27849 The second and third strings are a user name and a corresponding password.
27850 Using a single fixed user name and password as an example, this could be
27851 configured as follows:
27855 public_name = PLAIN
27857 server_condition = \
27858 ${if and {{eq{$auth2}{username}}{eq{$auth3}{mysecret}}}}
27859 server_set_id = $auth2
27861 Note that the default result strings from &%if%& (&"true"& or an empty string)
27862 are exactly what we want here, so they need not be specified. Obviously, if the
27863 password contains expansion-significant characters such as dollar, backslash,
27864 or closing brace, they have to be escaped.
27866 The &%server_prompts%& setting specifies a single, empty prompt (empty items at
27867 the end of a string list are ignored). If all the data comes as part of the
27868 AUTH command, as is commonly the case, the prompt is not used. This
27869 authenticator is advertised in the response to EHLO as
27873 and a client host can authenticate itself by sending the command
27875 AUTH PLAIN AHVzZXJuYW1lAG15c2VjcmV0
27877 As this contains three strings (more than the number of prompts), no further
27878 data is required from the client. Alternatively, the client may just send
27882 to initiate authentication, in which case the server replies with an empty
27883 prompt. The client must respond with the combined data string.
27885 The data string is base64 encoded, as required by the RFC. This example,
27886 when decoded, is <&'NUL'&>&`username`&<&'NUL'&>&`mysecret`&, where <&'NUL'&>
27887 represents a zero byte. This is split up into three strings, the first of which
27888 is empty. The &%server_condition%& option in the authenticator checks that the
27889 second two are &`username`& and &`mysecret`& respectively.
27891 Having just one fixed user name and password, as in this example, is not very
27892 realistic, though for a small organization with only a handful of
27893 authenticating clients it could make sense.
27895 A more sophisticated instance of this authenticator could use the user name in
27896 &$auth2$& to look up a password in a file or database, and maybe do an encrypted
27897 comparison (see &%crypteq%& in chapter &<<CHAPexpand>>&). Here is a example of
27898 this approach, where the passwords are looked up in a DBM file. &*Warning*&:
27899 This is an incorrect example:
27901 server_condition = \
27902 ${if eq{$auth3}{${lookup{$auth2}dbm{/etc/authpwd}}}}
27904 The expansion uses the user name (&$auth2$&) as the key to look up a password,
27905 which it then compares to the supplied password (&$auth3$&). Why is this example
27906 incorrect? It works fine for existing users, but consider what happens if a
27907 non-existent user name is given. The lookup fails, but as no success/failure
27908 strings are given for the lookup, it yields an empty string. Thus, to defeat
27909 the authentication, all a client has to do is to supply a non-existent user
27910 name and an empty password. The correct way of writing this test is:
27912 server_condition = ${lookup{$auth2}dbm{/etc/authpwd}\
27913 {${if eq{$value}{$auth3}}} {false}}
27915 In this case, if the lookup succeeds, the result is checked; if the lookup
27916 fails, &"false"& is returned and authentication fails. If &%crypteq%& is being
27917 used instead of &%eq%&, the first example is in fact safe, because &%crypteq%&
27918 always fails if its second argument is empty. However, the second way of
27919 writing the test makes the logic clearer.
27922 .section "The LOGIN authentication mechanism" "SECID173"
27923 .cindex "LOGIN authentication mechanism"
27924 .cindex authentication LOGIN
27925 The LOGIN authentication mechanism is not documented in any RFC, but is in use
27926 in a number of programs. No data is sent with the AUTH command. Instead, a
27927 user name and password are supplied separately, in response to prompts. The
27928 plaintext authenticator can be configured to support this as in this example:
27932 public_name = LOGIN
27933 server_prompts = User Name : Password
27934 server_condition = \
27935 ${if and {{eq{$auth1}{username}}{eq{$auth2}{mysecret}}}}
27936 server_set_id = $auth1
27938 Because of the way plaintext operates, this authenticator accepts data supplied
27939 with the AUTH command (in contravention of the specification of LOGIN), but
27940 if the client does not supply it (as is the case for LOGIN clients), the prompt
27941 strings are used to obtain two data items.
27943 Some clients are very particular about the precise text of the prompts. For
27944 example, Outlook Express is reported to recognize only &"Username:"& and
27945 &"Password:"&. Here is an example of a LOGIN authenticator that uses those
27946 strings. It uses the &%ldapauth%& expansion condition to check the user
27947 name and password by binding to an LDAP server:
27951 public_name = LOGIN
27952 server_prompts = Username:: : Password::
27953 server_condition = ${if and{{ \
27956 user="uid=${quote_ldap_dn:$auth1},ou=people,o=example.org" \
27957 pass=${quote:$auth2} \
27958 ldap://ldap.example.org/} }} }
27959 server_set_id = uid=$auth1,ou=people,o=example.org
27961 We have to check that the username is not empty before using it, because LDAP
27962 does not permit empty DN components. We must also use the &%quote_ldap_dn%&
27963 operator to correctly quote the DN for authentication. However, the basic
27964 &%quote%& operator, rather than any of the LDAP quoting operators, is the
27965 correct one to use for the password, because quoting is needed only to make
27966 the password conform to the Exim syntax. At the LDAP level, the password is an
27967 uninterpreted string.
27970 .section "Support for different kinds of authentication" "SECID174"
27971 A number of string expansion features are provided for the purpose of
27972 interfacing to different ways of user authentication. These include checking
27973 traditionally encrypted passwords from &_/etc/passwd_& (or equivalent), PAM,
27974 Radius, &%ldapauth%&, &'pwcheck'&, and &'saslauthd'&. For details see section
27980 .section "Using plaintext in a client" "SECID175"
27981 .cindex "options" "&(plaintext)& authenticator (client)"
27982 The &(plaintext)& authenticator has two client options:
27984 .option client_ignore_invalid_base64 plaintext boolean false
27985 If the client receives a server prompt that is not a valid base64 string,
27986 authentication is abandoned by default. However, if this option is set true,
27987 the error in the challenge is ignored and the client sends the response as
27990 .option client_send plaintext string&!! unset
27991 The string is a colon-separated list of authentication data strings. Each
27992 string is independently expanded before being sent to the server. The first
27993 string is sent with the AUTH command; any more strings are sent in response
27994 to prompts from the server. Before each string is expanded, the value of the
27995 most recent prompt is placed in the next &$auth$&<&'n'&> variable, starting
27996 with &$auth1$& for the first prompt. Up to three prompts are stored in this
27997 way. Thus, the prompt that is received in response to sending the first string
27998 (with the AUTH command) can be used in the expansion of the second string, and
27999 so on. If an invalid base64 string is received when
28000 &%client_ignore_invalid_base64%& is set, an empty string is put in the
28001 &$auth$&<&'n'&> variable.
28003 &*Note*&: You cannot use expansion to create multiple strings, because
28004 splitting takes priority and happens first.
28006 Because the PLAIN authentication mechanism requires NUL (binary zero) bytes in
28007 the data, further processing is applied to each string before it is sent. If
28008 there are any single circumflex characters in the string, they are converted to
28009 NULs. Should an actual circumflex be required as data, it must be doubled in
28012 This is an example of a client configuration that implements the PLAIN
28013 authentication mechanism with a fixed user name and password:
28017 public_name = PLAIN
28018 client_send = ^username^mysecret
28020 The lack of colons means that the entire text is sent with the AUTH
28021 command, with the circumflex characters converted to NULs.
28022 Note that due to the ambiguity of parsing three consectutive circumflex characters
28023 there is no way to provide a password having a leading circumflex.
28027 that uses the LOGIN mechanism is:
28031 public_name = LOGIN
28032 client_send = : username : mysecret
28034 The initial colon means that the first string is empty, so no data is sent with
28035 the AUTH command itself. The remaining strings are sent in response to
28037 .ecindex IIDplaiauth1
28038 .ecindex IIDplaiauth2
28043 . ////////////////////////////////////////////////////////////////////////////
28044 . ////////////////////////////////////////////////////////////////////////////
28046 .chapter "The cram_md5 authenticator" "CHID9"
28047 .scindex IIDcramauth1 "&(cram_md5)& authenticator"
28048 .scindex IIDcramauth2 "authenticators" "&(cram_md5)&"
28049 .cindex "CRAM-MD5 authentication mechanism"
28050 .cindex authentication CRAM-MD5
28051 The CRAM-MD5 authentication mechanism is described in RFC 2195. The server
28052 sends a challenge string to the client, and the response consists of a user
28053 name and the CRAM-MD5 digest of the challenge string combined with a secret
28054 string (password) which is known to both server and client. Thus, the secret
28055 is not sent over the network as plain text, which makes this authenticator more
28056 secure than &(plaintext)&. However, the downside is that the secret has to be
28057 available in plain text at either end.
28060 .section "Using cram_md5 as a server" "SECID176"
28061 .cindex "options" "&(cram_md5)& authenticator (server)"
28062 This authenticator has one server option, which must be set to configure the
28063 authenticator as a server:
28065 .option server_secret cram_md5 string&!! unset
28066 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(cram_md5)& authenticator"
28067 When the server receives the client's response, the user name is placed in
28068 the expansion variable &$auth1$&, and &%server_secret%& is expanded to
28069 obtain the password for that user. The server then computes the CRAM-MD5 digest
28070 that the client should have sent, and checks that it received the correct
28071 string. If the expansion of &%server_secret%& is forced to fail, authentication
28072 fails. If the expansion fails for some other reason, a temporary error code is
28073 returned to the client.
28075 For compatibility with previous releases of Exim, the user name is also placed
28076 in &$1$&. However, the use of this variables for this purpose is now
28077 deprecated, as it can lead to confusion in string expansions that also use
28078 numeric variables for other things.
28080 For example, the following authenticator checks that the user name given by the
28081 client is &"ph10"&, and if so, uses &"secret"& as the password. For any other
28082 user name, authentication fails.
28086 public_name = CRAM-MD5
28087 server_secret = ${if eq{$auth1}{ph10}{secret}fail}
28088 server_set_id = $auth1
28090 .vindex "&$authenticated_id$&"
28091 If authentication succeeds, the setting of &%server_set_id%& preserves the user
28092 name in &$authenticated_id$&. A more typical configuration might look up the
28093 secret string in a file, using the user name as the key. For example:
28097 public_name = CRAM-MD5
28098 server_secret = ${lookup{$auth1}lsearch{/etc/authpwd}\
28100 server_set_id = $auth1
28102 Note that this expansion explicitly forces failure if the lookup fails
28103 because &$auth1$& contains an unknown user name.
28105 As another example, if you wish to re-use a Cyrus SASL sasldb2 file without
28106 using the relevant libraries, you need to know the realm to specify in the
28107 lookup and then ask for the &"userPassword"& attribute for that user in that
28112 public_name = CRAM-MD5
28113 server_secret = ${lookup{$auth1:mail.example.org:userPassword}\
28114 dbmjz{/etc/sasldb2}{$value}fail}
28115 server_set_id = $auth1
28118 .section "Using cram_md5 as a client" "SECID177"
28119 .cindex "options" "&(cram_md5)& authenticator (client)"
28120 When used as a client, the &(cram_md5)& authenticator has two options:
28124 .option client_name cram_md5 string&!! "the primary host name"
28125 This string is expanded, and the result used as the user name data when
28126 computing the response to the server's challenge.
28129 .option client_secret cram_md5 string&!! unset
28130 This option must be set for the authenticator to work as a client. Its value is
28131 expanded and the result used as the secret string when computing the response.
28135 .vindex "&$host_address$&"
28136 Different user names and secrets can be used for different servers by referring
28137 to &$host$& or &$host_address$& in the options. Forced failure of either
28138 expansion string is treated as an indication that this authenticator is not
28139 prepared to handle this case. Exim moves on to the next configured client
28140 authenticator. Any other expansion failure causes Exim to give up trying to
28141 send the message to the current server.
28143 A simple example configuration of a &(cram_md5)& authenticator, using fixed
28148 public_name = CRAM-MD5
28150 client_secret = secret
28152 .ecindex IIDcramauth1
28153 .ecindex IIDcramauth2
28157 . ////////////////////////////////////////////////////////////////////////////
28158 . ////////////////////////////////////////////////////////////////////////////
28160 .chapter "The cyrus_sasl authenticator" "CHID10"
28161 .scindex IIDcyrauth1 "&(cyrus_sasl)& authenticator"
28162 .scindex IIDcyrauth2 "authenticators" "&(cyrus_sasl)&"
28163 .cindex "Cyrus" "SASL library"
28165 The code for this authenticator was provided by Matthew Byng-Maddick while
28166 at A L Digital Ltd.
28168 The &(cyrus_sasl)& authenticator provides server support for the Cyrus SASL
28169 library implementation of the RFC 2222 (&"Simple Authentication and Security
28170 Layer"&). This library supports a number of authentication mechanisms,
28171 including PLAIN and LOGIN, but also several others that Exim does not support
28172 directly. In particular, there is support for Kerberos authentication.
28174 The &(cyrus_sasl)& authenticator provides a gatewaying mechanism directly to
28175 the Cyrus interface, so if your Cyrus library can do, for example, CRAM-MD5,
28176 then so can the &(cyrus_sasl)& authenticator. By default it uses the public
28177 name of the driver to determine which mechanism to support.
28179 Where access to some kind of secret file is required, for example, in GSSAPI
28180 or CRAM-MD5, it is worth noting that the authenticator runs as the Exim
28181 user, and that the Cyrus SASL library has no way of escalating privileges
28182 by default. You may also find you need to set environment variables,
28183 depending on the driver you are using.
28185 The application name provided by Exim is &"exim"&, so various SASL options may
28186 be set in &_exim.conf_& in your SASL directory. If you are using GSSAPI for
28187 Kerberos, note that because of limitations in the GSSAPI interface,
28188 changing the server keytab might need to be communicated down to the Kerberos
28189 layer independently. The mechanism for doing so is dependent upon the Kerberos
28192 For example, for older releases of Heimdal, the environment variable KRB5_KTNAME
28193 may be set to point to an alternative keytab file. Exim will pass this
28194 variable through from its own inherited environment when started as root or the
28195 Exim user. The keytab file needs to be readable by the Exim user.
28196 With newer releases of Heimdal, a setuid Exim may cause Heimdal to discard the
28197 environment variable. In practice, for those releases, the Cyrus authenticator
28198 is not a suitable interface for GSSAPI (Kerberos) support. Instead, consider
28199 the &(heimdal_gssapi)& authenticator, described in chapter &<<CHAPheimdalgss>>&
28202 .section "Using cyrus_sasl as a server" "SECID178"
28203 The &(cyrus_sasl)& authenticator has four private options. It puts the username
28204 (on a successful authentication) into &$auth1$&. For compatibility with
28205 previous releases of Exim, the username is also placed in &$1$&. However, the
28206 use of this variable for this purpose is now deprecated, as it can lead to
28207 confusion in string expansions that also use numeric variables for other
28211 .option server_hostname cyrus_sasl string&!! "see below"
28212 This option selects the hostname that is used when communicating with the
28213 library. The default value is &`$primary_hostname`&. It is up to the underlying
28214 SASL plug-in what it does with this data.
28217 .option server_mech cyrus_sasl string "see below"
28218 This option selects the authentication mechanism this driver should use. The
28219 default is the value of the generic &%public_name%& option. This option allows
28220 you to use a different underlying mechanism from the advertised name. For
28224 driver = cyrus_sasl
28225 public_name = X-ANYTHING
28226 server_mech = CRAM-MD5
28227 server_set_id = $auth1
28230 .option server_realm cyrus_sasl string&!! unset
28231 This specifies the SASL realm that the server claims to be in.
28234 .option server_service cyrus_sasl string &`smtp`&
28235 This is the SASL service that the server claims to implement.
28238 For straightforward cases, you do not need to set any of the authenticator's
28239 private options. All you need to do is to specify an appropriate mechanism as
28240 the public name. Thus, if you have a SASL library that supports CRAM-MD5 and
28241 PLAIN, you could have two authenticators as follows:
28244 driver = cyrus_sasl
28245 public_name = CRAM-MD5
28246 server_set_id = $auth1
28249 driver = cyrus_sasl
28250 public_name = PLAIN
28251 server_set_id = $auth2
28253 Cyrus SASL does implement the LOGIN authentication method, even though it is
28254 not a standard method. It is disabled by default in the source distribution,
28255 but it is present in many binary distributions.
28256 .ecindex IIDcyrauth1
28257 .ecindex IIDcyrauth2
28262 . ////////////////////////////////////////////////////////////////////////////
28263 . ////////////////////////////////////////////////////////////////////////////
28264 .chapter "The dovecot authenticator" "CHAPdovecot"
28265 .scindex IIDdcotauth1 "&(dovecot)& authenticator"
28266 .scindex IIDdcotauth2 "authenticators" "&(dovecot)&"
28267 This authenticator is an interface to the authentication facility of the
28268 Dovecot 2 POP/IMAP server, which can support a number of authentication methods.
28269 Note that Dovecot must be configured to use auth-client not auth-userdb.
28270 If you are using Dovecot to authenticate POP/IMAP clients, it might be helpful
28271 to use the same mechanisms for SMTP authentication. This is a server
28272 authenticator only. There is only one option:
28274 .option server_socket dovecot string unset
28276 This option must specify the UNIX socket that is the interface to Dovecot
28277 authentication. The &%public_name%& option must specify an authentication
28278 mechanism that Dovecot is configured to support. You can have several
28279 authenticators for different mechanisms. For example:
28283 public_name = PLAIN
28284 server_socket = /var/run/dovecot/auth-client
28285 server_set_id = $auth1
28290 server_socket = /var/run/dovecot/auth-client
28291 server_set_id = $auth1
28293 If the SMTP connection is encrypted, or if &$sender_host_address$& is equal to
28294 &$received_ip_address$& (that is, the connection is local), the &"secured"&
28295 option is passed in the Dovecot authentication command. If, for a TLS
28296 connection, a client certificate has been verified, the &"valid-client-cert"&
28297 option is passed. When authentication succeeds, the identity of the user
28298 who authenticated is placed in &$auth1$&.
28300 The Dovecot configuration to match the above will look
28303 conf.d/10-master.conf :-
28308 unix_listener auth-client {
28315 conf.d/10-auth.conf :-
28317 auth_mechanisms = plain login ntlm
28320 .ecindex IIDdcotauth1
28321 .ecindex IIDdcotauth2
28324 . ////////////////////////////////////////////////////////////////////////////
28325 . ////////////////////////////////////////////////////////////////////////////
28326 .chapter "The gsasl authenticator" "CHAPgsasl"
28327 .scindex IIDgsaslauth1 "&(gsasl)& authenticator"
28328 .scindex IIDgsaslauth2 "authenticators" "&(gsasl)&"
28329 .cindex "authentication" "GNU SASL"
28330 .cindex "authentication" "SASL"
28331 .cindex "authentication" "EXTERNAL"
28332 .cindex "authentication" "ANONYMOUS"
28333 .cindex "authentication" "PLAIN"
28334 .cindex "authentication" "LOGIN"
28335 .cindex "authentication" "DIGEST-MD5"
28336 .cindex "authentication" "CRAM-MD5"
28337 .cindex "authentication" "SCRAM family"
28338 The &(gsasl)& authenticator provides integration for the GNU SASL
28339 library and the mechanisms it provides. This is new as of the 4.80 release
28340 and there are a few areas where the library does not let Exim smoothly
28341 scale to handle future authentication mechanisms, so no guarantee can be
28342 made that any particular new authentication mechanism will be supported
28343 without code changes in Exim.
28345 The library is expected to add support in an upcoming
28346 realease for the SCRAM-SHA-256 method.
28347 The macro _HAVE_AUTH_GSASL_SCRAM_SHA_256 will be defined
28350 To see the list of mechanisms supported by the library run Exim with "auth" debug
28351 enabled and look for a line containing "GNU SASL supports".
28352 Note however that some may not have been tested from Exim.
28355 .option client_authz gsasl string&!! unset
28356 This option can be used to supply an &'authorization id'&
28357 which is different to the &'authentication_id'& provided
28358 by &%client_username%& option.
28359 If unset or (after expansion) empty it is not used,
28360 which is the common case.
28362 .option client_channelbinding gsasl boolean false
28363 See &%server_channelbinding%& below.
28365 .option client_password gsasl string&!! unset
28366 This option is exapanded before use, and should result in
28367 the password to be used, in clear.
28369 .option client_username gsasl string&!! unset
28370 This option is exapanded before use, and should result in
28371 the account name to be used.
28374 .option client_spassword gsasl string&!! unset
28375 This option is only supported for library versions 1.9.1 and greater.
28376 The macro _HAVE_AUTH_GSASL_SCRAM_S_KEY will be defined when this is so.
28378 If a SCRAM mechanism is being used and this option is set
28379 and correctly sized
28380 it is used in preference to &%client_password%&.
28381 The value after expansion should be
28382 a 40 (for SHA-1) or 64 (for SHA-256) character string
28383 with the PBKDF2-prepared password, hex-encoded.
28385 Note that this value will depend on the salt and iteration-count
28386 supplied by the server.
28387 The option is expanded before use.
28388 During the expansion &$auth1$& is set with the client username,
28389 &$auth2$& with the iteration count, and
28390 &$auth3$& with the salt.
28392 The intent of this option
28393 is to support clients that can cache thes salted password
28394 to save on recalculation costs.
28395 The cache lookup should return an unusable value
28396 (eg. an empty string)
28397 if the salt or iteration count has changed
28399 If the authentication succeeds then the above variables are set,
28400 .vindex "&$auth4$&"
28401 plus the calculated salted password value value in &$auth4$&,
28402 during the expansion of the &%client_set_id%& option.
28403 A side-effect of this expansion can be used to prime the cache.
28406 .option server_channelbinding gsasl boolean false
28407 Some authentication mechanisms are able to use external context at both ends
28408 of the session to bind the authentication to that context, and fail the
28409 authentication process if that context differs. Specifically, some TLS
28410 ciphersuites can provide identifying information about the cryptographic
28413 This should have meant that certificate identity and verification becomes a
28414 non-issue, as a man-in-the-middle attack will cause the correct client and
28415 server to see different identifiers and authentication will fail.
28418 only usable by mechanisms which support "channel binding"; at time of
28419 writing, that's the SCRAM family.
28420 When using this feature the "-PLUS" variants of the method names need to be used.
28422 This defaults off to ensure smooth upgrade across Exim releases, in case
28423 this option causes some clients to start failing. Some future release
28424 of Exim might have switched the default to be true.
28426 . However, Channel Binding in TLS has proven to be vulnerable in current versions.
28427 . Do not plan to rely upon this feature for security, ever, without consulting
28428 . with a subject matter expert (a cryptographic engineer).
28430 This option was deprecated in previous releases due to doubts over
28431 the "Triple Handshake" vulnerability.
28432 Exim takes suitable precausions (requiring Extended Master Secret if TLS
28433 Session Resumption was used) for safety.
28436 .option server_hostname gsasl string&!! "see below"
28437 This option selects the hostname that is used when communicating with the
28438 library. The default value is &`$primary_hostname`&.
28439 Some mechanisms will use this data.
28442 .option server_mech gsasl string "see below"
28443 This option selects the authentication mechanism this driver should use. The
28444 default is the value of the generic &%public_name%& option. This option allows
28445 you to use a different underlying mechanism from the advertised name. For
28450 public_name = X-ANYTHING
28451 server_mech = CRAM-MD5
28452 server_set_id = $auth1
28456 .option server_password gsasl string&!! unset
28457 Various mechanisms need access to the cleartext password on the server, so
28458 that proof-of-possession can be demonstrated on the wire, without sending
28459 the password itself.
28461 The data available for lookup varies per mechanism.
28462 In all cases, &$auth1$& is set to the &'authentication id'&.
28463 The &$auth2$& variable will always be the &'authorization id'& (&'authz'&)
28464 if available, else the empty string.
28465 The &$auth3$& variable will always be the &'realm'& if available,
28466 else the empty string.
28468 A forced failure will cause authentication to defer.
28470 If using this option, it may make sense to set the &%server_condition%&
28471 option to be simply "true".
28474 .option server_realm gsasl string&!! unset
28475 This specifies the SASL realm that the server claims to be in.
28476 Some mechanisms will use this data.
28479 .option server_scram_iter gsasl string&!! 4096
28480 This option provides data for the SCRAM family of mechanisms.
28481 The &$auth1$&, &$auth2$& and &$auth3$& variables are available
28482 when this option is expanded.
28484 The result of expansion should be a decimal number,
28485 and represents both a lower-bound on the security, and
28486 a compute cost factor imposed on the client
28487 (if it does not cache results, or the server changes
28488 either the iteration count or the salt).
28489 A minimum value of 4096 is required by the standards
28490 for all current SCRAM mechanism variants.
28492 .option server_scram_salt gsasl string&!! unset
28493 This option provides data for the SCRAM family of mechanisms.
28494 The &$auth1$&, &$auth2$& and &$auth3$& variables are available
28495 when this option is expanded.
28496 The value should be a base64-encoded string,
28497 of random data typically 4-to-16 bytes long.
28498 If unset or empty after expansion the library will provides a value for the
28499 protocol conversation.
28502 .option server_key gsasl string&!! unset
28503 .option server_skey gsasl string&!! unset
28504 These options can be used for the SCRAM family of mechanisms
28505 to provide stored information related to a password,
28506 the storage of which is preferable to plaintext.
28508 &%server_key%& is the value defined in the SCRAM standards as ServerKey;
28509 &%server_skey%& is StoredKey.
28511 They are only available for version 1.9.0 (or later) of the gsasl library.
28512 When this is so, the macros
28513 _OPT_AUTHENTICATOR_GSASL_SERVER_KEY
28514 and _HAVE_AUTH_GSASL_SCRAM_S_KEY
28517 The &$authN$& variables are available when these options are expanded.
28519 If set, the results of expansion should for each
28520 should be a 28 (for SHA-1) or 44 (for SHA-256) character string
28521 of base64-coded data, and will be used in preference to the
28522 &%server_password%& option.
28523 If unset or not of the right length, &%server_password%& will be used.
28525 The libgsasl library release includes a utility &'gsasl'& which can be used
28526 to generate these values.
28529 .option server_service gsasl string &`smtp`&
28530 This is the SASL service that the server claims to implement.
28531 Some mechanisms will use this data.
28534 .section "&(gsasl)& auth variables" "SECTgsaslauthvar"
28535 .vindex "&$auth1$&, &$auth2$&, etc"
28536 These may be set when evaluating specific options, as detailed above.
28537 They will also be set when evaluating &%server_condition%&.
28539 Unless otherwise stated below, the &(gsasl)& integration will use the following
28540 meanings for these variables:
28543 .vindex "&$auth1$&"
28544 &$auth1$&: the &'authentication id'&
28546 .vindex "&$auth2$&"
28547 &$auth2$&: the &'authorization id'&
28549 .vindex "&$auth3$&"
28550 &$auth3$&: the &'realm'&
28553 On a per-mechanism basis:
28556 .cindex "authentication" "EXTERNAL"
28557 EXTERNAL: only &$auth1$& is set, to the possibly empty &'authorization id'&;
28558 the &%server_condition%& option must be present.
28560 .cindex "authentication" "ANONYMOUS"
28561 ANONYMOUS: only &$auth1$& is set, to the possibly empty &'anonymous token'&;
28562 the &%server_condition%& option must be present.
28564 .cindex "authentication" "GSSAPI"
28565 GSSAPI: &$auth1$& will be set to the &'GSSAPI Display Name'&;
28566 &$auth2$& will be set to the &'authorization id'&,
28567 the &%server_condition%& option must be present.
28570 An &'anonymous token'& is something passed along as an unauthenticated
28571 identifier; this is analogous to FTP anonymous authentication passing an
28572 email address, or software-identifier@, as the "password".
28575 An example showing the password having the realm specified in the callback
28576 and demonstrating a Cyrus SASL to GSASL migration approach is:
28578 gsasl_cyrusless_crammd5:
28580 public_name = CRAM-MD5
28581 server_realm = imap.example.org
28582 server_password = ${lookup{$auth1:$auth3:userPassword}\
28583 dbmjz{/etc/sasldb2}{$value}fail}
28584 server_set_id = ${quote:$auth1}
28585 server_condition = yes
28589 . ////////////////////////////////////////////////////////////////////////////
28590 . ////////////////////////////////////////////////////////////////////////////
28592 .chapter "The heimdal_gssapi authenticator" "CHAPheimdalgss"
28593 .scindex IIDheimdalgssauth1 "&(heimdal_gssapi)& authenticator"
28594 .scindex IIDheimdalgssauth2 "authenticators" "&(heimdal_gssapi)&"
28595 .cindex "authentication" "GSSAPI"
28596 .cindex "authentication" "Kerberos"
28597 The &(heimdal_gssapi)& authenticator provides server integration for the
28598 Heimdal GSSAPI/Kerberos library, permitting Exim to set a keytab pathname
28601 .option server_hostname heimdal_gssapi string&!! "see below"
28602 This option selects the hostname that is used, with &%server_service%&,
28603 for constructing the GSS server name, as a &'GSS_C_NT_HOSTBASED_SERVICE'&
28604 identifier. The default value is &`$primary_hostname`&.
28606 .option server_keytab heimdal_gssapi string&!! unset
28607 If set, then Heimdal will not use the system default keytab (typically
28608 &_/etc/krb5.keytab_&) but instead the pathname given in this option.
28609 The value should be a pathname, with no &"file:"& prefix.
28611 .option server_service heimdal_gssapi string&!! "smtp"
28612 This option specifies the service identifier used, in conjunction with
28613 &%server_hostname%&, for building the identifier for finding credentials
28617 .section "&(heimdal_gssapi)& auth variables" "SECTheimdalgssauthvar"
28618 Beware that these variables will typically include a realm, thus will appear
28619 to be roughly like an email address already. The &'authzid'& in &$auth2$& is
28620 not verified, so a malicious client can set it to anything.
28622 The &$auth1$& field should be safely trustable as a value from the Key
28623 Distribution Center. Note that these are not quite email addresses.
28624 Each identifier is for a role, and so the left-hand-side may include a
28625 role suffix. For instance, &"joe/admin@EXAMPLE.ORG"&.
28627 .vindex "&$auth1$&, &$auth2$&, etc"
28629 .vindex "&$auth1$&"
28630 &$auth1$&: the &'authentication id'&, set to the GSS Display Name.
28632 .vindex "&$auth2$&"
28633 &$auth2$&: the &'authorization id'&, sent within SASL encapsulation after
28634 authentication. If that was empty, this will also be set to the
28639 . ////////////////////////////////////////////////////////////////////////////
28640 . ////////////////////////////////////////////////////////////////////////////
28642 .chapter "The spa authenticator" "CHAPspa"
28643 .scindex IIDspaauth1 "&(spa)& authenticator"
28644 .scindex IIDspaauth2 "authenticators" "&(spa)&"
28645 .cindex "authentication" "Microsoft Secure Password"
28646 .cindex "authentication" "NTLM"
28647 .cindex "Microsoft Secure Password Authentication"
28648 .cindex "NTLM authentication"
28649 The &(spa)& authenticator provides client support for Microsoft's &'Secure
28650 Password Authentication'& mechanism,
28651 which is also sometimes known as NTLM (NT LanMan). The code for client side of
28652 this authenticator was contributed by Marc Prud'hommeaux, and much of it is
28653 taken from the Samba project (&url(https://www.samba.org/)). The code for the
28654 server side was subsequently contributed by Tom Kistner. The mechanism works as
28658 After the AUTH command has been accepted, the client sends an SPA
28659 authentication request based on the user name and optional domain.
28661 The server sends back a challenge.
28663 The client builds a challenge response which makes use of the user's password
28664 and sends it to the server, which then accepts or rejects it.
28667 Encryption is used to protect the password in transit.
28671 .section "Using spa as a server" "SECID179"
28672 .cindex "options" "&(spa)& authenticator (server)"
28673 The &(spa)& authenticator has just one server option:
28675 .option server_password spa string&!! unset
28676 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(spa)& authenticator"
28677 This option is expanded, and the result must be the cleartext password for the
28678 authenticating user, whose name is at this point in &$auth1$&. For
28679 compatibility with previous releases of Exim, the user name is also placed in
28680 &$1$&. However, the use of this variable for this purpose is now deprecated, as
28681 it can lead to confusion in string expansions that also use numeric variables
28682 for other things. For example:
28687 server_password = \
28688 ${lookup{$auth1}lsearch{/etc/exim/spa_clearpass}{$value}fail}
28690 If the expansion is forced to fail, authentication fails. Any other expansion
28691 failure causes a temporary error code to be returned.
28697 .section "Using spa as a client" "SECID180"
28698 .cindex "options" "&(spa)& authenticator (client)"
28699 The &(spa)& authenticator has the following client options:
28703 .option client_domain spa string&!! unset
28704 This option specifies an optional domain for the authentication.
28707 .option client_password spa string&!! unset
28708 This option specifies the user's password, and must be set.
28711 .option client_username spa string&!! unset
28712 This option specifies the user name, and must be set. Here is an example of a
28713 configuration of this authenticator for use with the mail servers at
28719 client_username = msn/msn_username
28720 client_password = msn_plaintext_password
28721 client_domain = DOMAIN_OR_UNSET
28723 .ecindex IIDspaauth1
28724 .ecindex IIDspaauth2
28730 . ////////////////////////////////////////////////////////////////////////////
28731 . ////////////////////////////////////////////////////////////////////////////
28733 .chapter "The external authenticator" "CHAPexternauth"
28734 .scindex IIDexternauth1 "&(external)& authenticator"
28735 .scindex IIDexternauth2 "authenticators" "&(external)&"
28736 .cindex "authentication" "Client Certificate"
28737 .cindex "authentication" "X509"
28738 .cindex "Certificate-based authentication"
28739 The &(external)& authenticator provides support for
28740 authentication based on non-SMTP information.
28741 The specification is in RFC 4422 Appendix A
28742 (&url(https://tools.ietf.org/html/rfc4422)).
28743 It is only a transport and negotiation mechanism;
28744 the process of authentication is entirely controlled
28745 by the server configuration.
28747 The client presents an identity in-clear.
28748 It is probably wise for a server to only advertise,
28749 and for clients to only attempt,
28750 this authentication method on a secure (eg. under TLS) connection.
28752 One possible use, compatible with the
28753 K-9 Mail Android client (&url(https://k9mail.github.io/)),
28754 is for using X509 client certificates.
28756 It thus overlaps in function with the TLS authenticator
28757 (see &<<CHAPtlsauth>>&)
28758 but is a full SMTP SASL authenticator
28759 rather than being implicit for TLS-connection carried
28760 client certificates only.
28762 The examples and discussion in this chapter assume that
28763 client-certificate authentication is being done.
28765 The client must present a certificate,
28766 for which it must have been requested via the
28767 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& main options
28768 (see &<<CHAPTLS>>&).
28769 For authentication to be effective the certificate should be
28770 verifiable against a trust-anchor certificate known to the server.
28772 .section "External options" "SECTexternsoptions"
28773 .cindex "options" "&(external)& authenticator (server)"
28774 The &(external)& authenticator has two server options:
28776 .option server_param2 external string&!! unset
28777 .option server_param3 external string&!! unset
28778 .cindex "variables (&$auth1$& &$auth2$& etc)" "in &(external)& authenticator"
28779 These options are expanded before the &%server_condition%& option
28780 and the result are placed in &$auth2$& and &$auth3$& resectively.
28781 If the expansion is forced to fail, authentication fails. Any other expansion
28782 failure causes a temporary error code to be returned.
28784 They can be used to clarify the coding of a complex &%server_condition%&.
28786 .section "Using external in a server" "SECTexternserver"
28787 .cindex "AUTH" "in &(external)& authenticator"
28788 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
28789 "in &(external)& authenticator"
28790 .vindex "&$auth1$&, &$auth2$&, etc"
28791 .cindex "base64 encoding" "in &(external)& authenticator"
28793 When running as a server, &(external)& performs the authentication test by
28794 expanding a string. The data sent by the client with the AUTH command, or in
28795 response to subsequent prompts, is base64 encoded, and so may contain any byte
28796 values when decoded. The decoded value is treated as
28797 an identity for authentication and
28798 placed in the expansion variable &$auth1$&.
28800 For compatibility with previous releases of Exim, the value is also placed in
28801 the expansion variable &$1$&. However, the use of this
28802 variable for this purpose is now deprecated, as it can lead to confusion in
28803 string expansions that also use them for other things.
28805 .vindex "&$authenticated_id$&"
28806 Once an identity has been received,
28807 &%server_condition%& is expanded. If the expansion is forced to fail,
28808 authentication fails. Any other expansion failure causes a temporary error code
28809 to be returned. If the result of a successful expansion is an empty string,
28810 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
28811 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
28812 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
28813 For any other result, a temporary error code is returned, with the expanded
28814 string as the error text.
28818 ext_ccert_san_mail:
28820 public_name = EXTERNAL
28822 server_advertise_condition = $tls_in_certificate_verified
28823 server_param2 = ${certextract {subj_altname,mail,>:} \
28824 {$tls_in_peercert}}
28825 server_condition = ${if forany {$auth2} \
28826 {eq {$item}{$auth1}}}
28827 server_set_id = $auth1
28829 This accepts a client certificate that is verifiable against any
28830 of your configured trust-anchors
28831 (which usually means the full set of public CAs)
28832 and which has a mail-SAN matching the claimed identity sent by the client.
28834 &*Note*&: up to TLS1.2, the client cert is on the wire in-clear, including the SAN.
28835 The account name is therefore guessable by an opponent.
28836 TLS 1.3 protects both server and client certificates, and is not vulnerable
28840 .section "Using external in a client" "SECTexternclient"
28841 .cindex "options" "&(external)& authenticator (client)"
28842 The &(external)& authenticator has one client option:
28844 .option client_send external string&!! unset
28845 This option is expanded and sent with the AUTH command as the
28846 identity being asserted.
28852 public_name = EXTERNAL
28854 client_condition = ${if !eq{$tls_out_cipher}{}}
28855 client_send = myaccount@smarthost.example.net
28859 .ecindex IIDexternauth1
28860 .ecindex IIDexternauth2
28866 . ////////////////////////////////////////////////////////////////////////////
28867 . ////////////////////////////////////////////////////////////////////////////
28869 .chapter "The tls authenticator" "CHAPtlsauth"
28870 .scindex IIDtlsauth1 "&(tls)& authenticator"
28871 .scindex IIDtlsauth2 "authenticators" "&(tls)&"
28872 .cindex "authentication" "Client Certificate"
28873 .cindex "authentication" "X509"
28874 .cindex "Certificate-based authentication"
28875 The &(tls)& authenticator provides server support for
28876 authentication based on client certificates.
28878 It is not an SMTP authentication mechanism and is not
28879 advertised by the server as part of the SMTP EHLO response.
28880 It is an Exim authenticator in the sense that it affects
28881 the protocol element of the log line, can be tested for
28882 by the &%authenticated%& ACL condition, and can set
28883 the &$authenticated_id$& variable.
28885 The client must present a verifiable certificate,
28886 for which it must have been requested via the
28887 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& main options
28888 (see &<<CHAPTLS>>&).
28890 If an authenticator of this type is configured it is
28891 run before any SMTP-level communication is done,
28892 and can authenticate the connection.
28893 If it does, SMTP authentication is not offered.
28895 A maximum of one authenticator of this type may be present.
28898 .cindex "options" "&(tls)& authenticator (server)"
28899 The &(tls)& authenticator has three server options:
28901 .option server_param1 tls string&!! unset
28902 .cindex "variables (&$auth1$& &$auth2$& etc)" "in &(tls)& authenticator"
28903 This option is expanded after the TLS negotiation and
28904 the result is placed in &$auth1$&.
28905 If the expansion is forced to fail, authentication fails. Any other expansion
28906 failure causes a temporary error code to be returned.
28908 .option server_param2 tls string&!! unset
28909 .option server_param3 tls string&!! unset
28910 As above, for &$auth2$& and &$auth3$&.
28912 &%server_param1%& may also be spelled &%server_param%&.
28919 server_param1 = ${certextract {subj_altname,mail,>:} \
28920 {$tls_in_peercert}}
28921 server_condition = ${if and { {eq{$tls_in_certificate_verified}{1}} \
28924 {${lookup ldap{ldap:///\
28925 mailname=${quote_ldap_dn:${lc:$item}},\
28926 ou=users,LDAP_DC?mailid} {$value}{0} \
28928 server_set_id = ${if = {1}{${listcount:$auth1}} {$auth1}{}}
28930 This accepts a client certificate that is verifiable against any
28931 of your configured trust-anchors
28932 (which usually means the full set of public CAs)
28933 and which has a SAN with a good account name.
28935 Note that, up to TLS1.2, the client cert is on the wire in-clear, including the SAN,
28936 The account name is therefore guessable by an opponent.
28937 TLS 1.3 protects both server and client certificates, and is not vulnerable
28939 Likewise, a traditional plaintext SMTP AUTH done inside TLS is not.
28941 . An alternative might use
28943 . server_param1 = ${sha256:$tls_in_peercert}
28945 . to require one of a set of specific certs that define a given account
28946 . (the verification is still required, but mostly irrelevant).
28947 . This would help for per-device use.
28949 . However, for the future we really need support for checking a
28950 . user cert in LDAP - which probably wants a base-64 DER.
28952 .ecindex IIDtlsauth1
28953 .ecindex IIDtlsauth2
28956 Note that because authentication is traditionally an SMTP operation,
28957 the &%authenticated%& ACL condition cannot be used in
28958 a connect- or helo-ACL.
28962 . ////////////////////////////////////////////////////////////////////////////
28963 . ////////////////////////////////////////////////////////////////////////////
28965 .chapter "Encrypted SMTP connections using TLS/SSL" "CHAPTLS" &&&
28966 "Encrypted SMTP connections"
28967 .scindex IIDencsmtp1 "encryption" "on SMTP connection"
28968 .scindex IIDencsmtp2 "SMTP" "encryption"
28969 .cindex "TLS" "on SMTP connection"
28972 Support for TLS (Transport Layer Security), formerly known as SSL (Secure
28973 Sockets Layer), is implemented by making use of the OpenSSL library or the
28974 GnuTLS library (Exim requires GnuTLS release 1.0 or later). There is no
28975 cryptographic code in the Exim distribution itself for implementing TLS. In
28976 order to use this feature you must install OpenSSL or GnuTLS, and then build a
28977 version of Exim that includes TLS support (see section &<<SECTinctlsssl>>&).
28978 You also need to understand the basic concepts of encryption at a managerial
28979 level, and in particular, the way that public keys, private keys, and
28980 certificates are used.
28982 RFC 3207 defines how SMTP connections can make use of encryption. Once a
28983 connection is established, the client issues a STARTTLS command. If the
28984 server accepts this, the client and the server negotiate an encryption
28985 mechanism. If the negotiation succeeds, the data that subsequently passes
28986 between them is encrypted.
28988 Exim's ACLs can detect whether the current SMTP session is encrypted or not,
28989 and if so, what cipher suite is in use, whether the client supplied a
28990 certificate, and whether or not that certificate was verified. This makes it
28991 possible for an Exim server to deny or accept certain commands based on the
28994 &*Warning*&: Certain types of firewall and certain anti-virus products can
28995 disrupt TLS connections. You need to turn off SMTP scanning for these products
28996 in order to get TLS to work.
29000 .section "Support for the &""submissions""& (aka &""ssmtp""& and &""smtps""&) protocol" &&&
29002 .cindex "submissions protocol"
29003 .cindex "ssmtp protocol"
29004 .cindex "smtps protocol"
29005 .cindex "SMTP" "submissions protocol"
29006 .cindex "SMTP" "ssmtp protocol"
29007 .cindex "SMTP" "smtps protocol"
29008 The history of port numbers for TLS in SMTP is a little messy and has been
29009 contentious. As of RFC 8314, the common practice of using the historically
29010 allocated port 465 for "email submission but with TLS immediately upon connect
29011 instead of using STARTTLS" is officially blessed by the IETF, and recommended
29012 by them in preference to STARTTLS.
29014 The name originally assigned to the port was &"ssmtp"& or &"smtps"&, but as
29015 clarity emerged over the dual roles of SMTP, for MX delivery and Email
29016 Submission, nomenclature has shifted. The modern name is now &"submissions"&.
29018 This approach was, for a while, officially abandoned when encrypted SMTP was
29019 standardized, but many clients kept using it, even as the TCP port number was
29020 reassigned for other use.
29021 Thus you may encounter guidance claiming that you shouldn't enable use of
29023 In practice, a number of mail-clients have only ever supported submissions,
29024 not submission with STARTTLS upgrade.
29025 Ideally, offer both submission (587) and submissions (465) service.
29027 Exim supports TLS-on-connect by means of the &%tls_on_connect_ports%&
29028 global option. Its value must be a list of port numbers;
29029 the most common use is expected to be:
29031 tls_on_connect_ports = 465
29033 The port numbers specified by this option apply to all SMTP connections, both
29034 via the daemon and via &'inetd'&. You still need to specify all the ports that
29035 the daemon uses (by setting &%daemon_smtp_ports%& or &%local_interfaces%& or
29036 the &%-oX%& command line option) because &%tls_on_connect_ports%& does not add
29037 an extra port &-- rather, it specifies different behaviour on a port that is
29040 There is also a &%-tls-on-connect%& command line option. This overrides
29041 &%tls_on_connect_ports%&; it forces the TLS-only behaviour for all ports.
29048 .section "OpenSSL vs GnuTLS" "SECTopenvsgnu"
29049 .cindex "TLS" "OpenSSL &'vs'& GnuTLS"
29050 TLS is supported in Exim using either the OpenSSL or GnuTLS library.
29051 To build Exim to use OpenSSL you need to set
29057 To build Exim to use GnuTLS, you need to set
29063 You must also set TLS_LIBS and TLS_INCLUDE appropriately, so that the
29064 include files and libraries for GnuTLS can be found.
29066 There are some differences in usage when using GnuTLS instead of OpenSSL:
29069 The &%tls_verify_certificates%& option
29070 cannot be the path of a directory
29071 for GnuTLS versions before 3.3.6
29072 (for later versions, or OpenSSL, it can be either).
29074 The default value for &%tls_dhparam%& differs for historical reasons.
29076 .vindex "&$tls_in_peerdn$&"
29077 .vindex "&$tls_out_peerdn$&"
29078 Distinguished Name (DN) strings reported by the OpenSSL library use a slash for
29079 separating fields; GnuTLS uses commas, in accordance with RFC 2253. This
29080 affects the value of the &$tls_in_peerdn$& and &$tls_out_peerdn$& variables.
29082 OpenSSL identifies cipher suites using hyphens as separators, for example:
29083 DES-CBC3-SHA. GnuTLS historically used underscores, for example:
29084 RSA_ARCFOUR_SHA. What is more, OpenSSL complains if underscores are present
29085 in a cipher list. To make life simpler, Exim changes underscores to hyphens
29086 for OpenSSL and passes the string unchanged to GnuTLS (expecting the library
29087 to handle its own older variants) when processing lists of cipher suites in the
29088 &%tls_require_ciphers%& options (the global option and the &(smtp)& transport
29091 The &%tls_require_ciphers%& options operate differently, as described in the
29092 sections &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
29094 The &%tls_dh_min_bits%& SMTP transport option is only honoured by GnuTLS.
29095 When using OpenSSL, this option is ignored.
29096 (If an API is found to let OpenSSL be configured in this way,
29097 let the Exim Maintainers know and we'll likely use it).
29099 With GnuTLS, if an explicit list is used for the &%tls_privatekey%& main option
29100 main option, it must be ordered to match the &%tls_certificate%& list.
29102 Some other recently added features may only be available in one or the other.
29103 This should be documented with the feature. If the documentation does not
29104 explicitly state that the feature is infeasible in the other TLS
29105 implementation, then patches are welcome.
29107 The output from "exim -bV" will show which (if any) support was included
29109 Also, the macro "_HAVE_OPENSSL" or "_HAVE_GNUTLS" will be defined.
29113 .section "GnuTLS parameter computation" "SECTgnutlsparam"
29114 This section only applies if &%tls_dhparam%& is set to &`historic`& or to
29115 an explicit path; if the latter, then the text about generation still applies,
29116 but not the chosen filename.
29117 By default, as of Exim 4.80 a hard-coded D-H prime is used.
29118 See the documentation of &%tls_dhparam%& for more information.
29120 GnuTLS uses D-H parameters that may take a substantial amount of time
29121 to compute. It is unreasonable to re-compute them for every TLS session.
29122 Therefore, Exim keeps this data in a file in its spool directory, called
29123 &_gnutls-params-NNNN_& for some value of NNNN, corresponding to the number
29125 The file is owned by the Exim user and is readable only by
29126 its owner. Every Exim process that start up GnuTLS reads the D-H
29127 parameters from this file. If the file does not exist, the first Exim process
29128 that needs it computes the data and writes it to a temporary file which is
29129 renamed once it is complete. It does not matter if several Exim processes do
29130 this simultaneously (apart from wasting a few resources). Once a file is in
29131 place, new Exim processes immediately start using it.
29133 For maximum security, the parameters that are stored in this file should be
29134 recalculated periodically, the frequency depending on your paranoia level.
29135 If you are avoiding using the fixed D-H primes published in RFCs, then you
29136 are concerned about some advanced attacks and will wish to do this; if you do
29137 not regenerate then you might as well stick to the standard primes.
29139 Arranging this is easy in principle; just delete the file when you want new
29140 values to be computed. However, there may be a problem. The calculation of new
29141 parameters needs random numbers, and these are obtained from &_/dev/random_&.
29142 If the system is not very active, &_/dev/random_& may delay returning data
29143 until enough randomness (entropy) is available. This may cause Exim to hang for
29144 a substantial amount of time, causing timeouts on incoming connections.
29146 The solution is to generate the parameters externally to Exim. They are stored
29147 in &_gnutls-params-N_& in PEM format, which means that they can be
29148 generated externally using the &(certtool)& command that is part of GnuTLS.
29150 To replace the parameters with new ones, instead of deleting the file
29151 and letting Exim re-create it, you can generate new parameters using
29152 &(certtool)& and, when this has been done, replace Exim's cache file by
29153 renaming. The relevant commands are something like this:
29156 [ look for file; assume gnutls-params-2236 is the most recent ]
29159 # chown exim:exim new-params
29160 # chmod 0600 new-params
29161 # certtool --generate-dh-params --bits 2236 >>new-params
29162 # openssl dhparam -noout -text -in new-params | head
29163 [ check the first line, make sure it's not more than 2236;
29164 if it is, then go back to the start ("rm") and repeat
29165 until the size generated is at most the size requested ]
29166 # chmod 0400 new-params
29167 # mv new-params gnutls-params-2236
29169 If Exim never has to generate the parameters itself, the possibility of
29170 stalling is removed.
29172 The filename changed in Exim 4.80, to gain the -bits suffix. The value which
29173 Exim will choose depends upon the version of GnuTLS in use. For older GnuTLS,
29174 the value remains hard-coded in Exim as 1024. As of GnuTLS 2.12.x, there is
29175 a way for Exim to ask for the "normal" number of bits for D-H public-key usage,
29176 and Exim does so. This attempt to remove Exim from TLS policy decisions
29177 failed, as GnuTLS 2.12 returns a value higher than the current hard-coded limit
29178 of the NSS library. Thus Exim gains the &%tls_dh_max_bits%& global option,
29179 which applies to all D-H usage, client or server. If the value returned by
29180 GnuTLS is greater than &%tls_dh_max_bits%& then the value will be clamped down
29181 to &%tls_dh_max_bits%&. The default value has been set at the current NSS
29182 limit, which is still much higher than Exim historically used.
29184 The filename and bits used will change as the GnuTLS maintainers change the
29185 value for their parameter &`GNUTLS_SEC_PARAM_NORMAL`&, as clamped by
29186 &%tls_dh_max_bits%&. At the time of writing (mid 2012), GnuTLS 2.12 recommends
29187 2432 bits, while NSS is limited to 2236 bits.
29189 In fact, the requested value will be *lower* than &%tls_dh_max_bits%&, to
29190 increase the chance of the generated prime actually being within acceptable
29191 bounds, as GnuTLS has been observed to overshoot. Note the check step in the
29192 procedure above. There is no sane procedure available to Exim to double-check
29193 the size of the generated prime, so it might still be too large.
29196 .section "Requiring specific ciphers in OpenSSL" "SECTreqciphssl"
29197 .cindex "TLS" "requiring specific ciphers (OpenSSL)"
29198 .oindex "&%tls_require_ciphers%&" "OpenSSL"
29199 There is a function in the OpenSSL library that can be passed a list of cipher
29200 suites before the cipher negotiation takes place. This specifies which ciphers
29201 are acceptable for TLS versions prior to 1.3.
29202 The list is colon separated and may contain names like
29203 DES-CBC3-SHA. Exim passes the expanded value of &%tls_require_ciphers%&
29204 directly to this function call.
29205 Many systems will install the OpenSSL manual-pages, so you may have
29206 &'ciphers(1)'& available to you.
29207 The following quotation from the OpenSSL
29208 documentation specifies what forms of item are allowed in the cipher string:
29211 It can consist of a single cipher suite such as RC4-SHA.
29213 It can represent a list of cipher suites containing a certain algorithm,
29214 or cipher suites of a certain type. For example SHA1 represents all
29215 ciphers suites using the digest algorithm SHA1 and SSLv3 represents all
29218 Lists of cipher suites can be combined in a single cipher string using
29219 the + character. This is used as a logical and operation. For example
29220 SHA1+DES represents all cipher suites containing the SHA1 and the DES
29224 Each cipher string can be optionally preceded by one of the characters &`!`&,
29227 If &`!`& is used, the ciphers are permanently deleted from the list. The
29228 ciphers deleted can never reappear in the list even if they are explicitly
29231 If &`-`& is used, the ciphers are deleted from the list, but some or all
29232 of the ciphers can be added again by later options.
29234 If &`+`& is used, the ciphers are moved to the end of the list. This
29235 option does not add any new ciphers; it just moves matching existing ones.
29238 If none of these characters is present, the string is interpreted as
29239 a list of ciphers to be appended to the current preference list. If the list
29240 includes any ciphers already present they will be ignored: that is, they will
29241 not be moved to the end of the list.
29244 The OpenSSL &'ciphers(1)'& command may be used to test the results of a given
29247 # note single-quotes to get ! past any shell history expansion
29248 $ openssl ciphers 'HIGH:!MD5:!SHA1'
29251 This example will let the library defaults be permitted on the MX port, where
29252 there's probably no identity verification anyway, but ups the ante on the
29253 submission ports where the administrator might have some influence on the
29254 choice of clients used:
29256 # OpenSSL variant; see man ciphers(1)
29257 tls_require_ciphers = ${if =={$received_port}{25}\
29262 This example will prefer ECDSA-authenticated ciphers over RSA ones:
29264 tls_require_ciphers = ECDSA:RSA:!COMPLEMENTOFDEFAULT
29267 For TLS version 1.3 the control available is less fine-grained
29268 and Exim does not provide access to it at present.
29269 The value of the &%tls_require_ciphers%& option is ignored when
29270 TLS version 1.3 is negotiated.
29272 As of writing the library default cipher suite list for TLSv1.3 is
29274 TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256
29278 .section "Requiring specific ciphers or other parameters in GnuTLS" &&&
29280 .cindex "GnuTLS" "specifying parameters for"
29281 .cindex "TLS" "specifying ciphers (GnuTLS)"
29282 .cindex "TLS" "specifying key exchange methods (GnuTLS)"
29283 .cindex "TLS" "specifying MAC algorithms (GnuTLS)"
29284 .cindex "TLS" "specifying protocols (GnuTLS)"
29285 .cindex "TLS" "specifying priority string (GnuTLS)"
29286 .oindex "&%tls_require_ciphers%&" "GnuTLS"
29287 The GnuTLS library allows the caller to provide a "priority string", documented
29288 as part of the &[gnutls_priority_init]& function. This is very similar to the
29289 ciphersuite specification in OpenSSL.
29291 The &%tls_require_ciphers%& option is treated as the GnuTLS priority string
29292 and controls both protocols and ciphers.
29294 The &%tls_require_ciphers%& option is available both as an global option,
29295 controlling how Exim behaves as a server, and also as an option of the
29296 &(smtp)& transport, controlling how Exim behaves as a client. In both cases
29297 the value is string expanded. The resulting string is not an Exim list and
29298 the string is given to the GnuTLS library, so that Exim does not need to be
29299 aware of future feature enhancements of GnuTLS.
29301 Documentation of the strings accepted may be found in the GnuTLS manual, under
29302 "Priority strings". This is online as
29303 &url(https://www.gnutls.org/manual/html_node/Priority-Strings.html),
29304 but beware that this relates to GnuTLS 3, which may be newer than the version
29305 installed on your system. If you are using GnuTLS 3,
29306 then the example code
29307 &url(https://www.gnutls.org/manual/gnutls.html#Listing-the-ciphersuites-in-a-priority-string)
29308 on that site can be used to test a given string.
29312 # Disable older versions of protocols
29313 tls_require_ciphers = NORMAL:%LATEST_RECORD_VERSION:-VERS-SSL3.0
29316 Prior to Exim 4.80, an older API of GnuTLS was used, and Exim supported three
29317 additional options, "&%gnutls_require_kx%&", "&%gnutls_require_mac%&" and
29318 "&%gnutls_require_protocols%&". &%tls_require_ciphers%& was an Exim list.
29320 This example will let the library defaults be permitted on the MX port, where
29321 there's probably no identity verification anyway, and lowers security further
29322 by increasing compatibility; but this ups the ante on the submission ports
29323 where the administrator might have some influence on the choice of clients
29327 tls_require_ciphers = ${if =={$received_port}{25}\
29333 .section "Configuring an Exim server to use TLS" "SECID182"
29334 .cindex "TLS" "configuring an Exim server"
29335 .cindex "ESMTP extensions" STARTTLS
29336 When Exim has been built with TLS support, it advertises the availability of
29337 the STARTTLS command to client hosts that match &%tls_advertise_hosts%&,
29338 but not to any others. The default value of this option is *, which means
29339 that STARTTLS is always advertised. Set it to blank to never advertise;
29340 this is reasonable for systems that want to use TLS only as a client.
29342 If STARTTLS is to be used you
29343 need to set some other options in order to make TLS available.
29345 If a client issues a STARTTLS command and there is some configuration
29346 problem in the server, the command is rejected with a 454 error. If the client
29347 persists in trying to issue SMTP commands, all except QUIT are rejected
29350 554 Security failure
29352 If a STARTTLS command is issued within an existing TLS session, it is
29353 rejected with a 554 error code.
29355 To enable TLS operations on a server, the &%tls_advertise_hosts%& option
29356 must be set to match some hosts. The default is * which matches all hosts.
29358 If this is all you do, TLS encryption will be enabled but not authentication -
29359 meaning that the peer has no assurance it is actually you he is talking to.
29360 You gain protection from a passive sniffer listening on the wire but not
29361 from someone able to intercept the communication.
29363 Further protection requires some further configuration at the server end.
29365 To make TLS work you need to set, in the server,
29367 tls_certificate = /some/file/name
29368 tls_privatekey = /some/file/name
29370 These options are, in fact, expanded strings, so you can make them depend on
29371 the identity of the client that is connected if you wish. The first file
29372 contains the server's X509 certificate, and the second contains the private key
29373 that goes with it. These files need to be
29374 PEM format and readable by the Exim user, and must
29375 always be given as full path names.
29376 The key must not be password-protected.
29377 They can be the same file if both the
29378 certificate and the key are contained within it. If &%tls_privatekey%& is not
29379 set, or if its expansion is forced to fail or results in an empty string, this
29380 is assumed to be the case. The certificate file may also contain intermediate
29381 certificates that need to be sent to the client to enable it to authenticate
29382 the server's certificate.
29384 For dual-stack (eg. RSA and ECDSA) configurations, these options can be
29385 colon-separated lists of file paths. Ciphers using given authentication
29386 algorithms require the presence of a suitable certificate to supply the
29387 public-key. The server selects among the certificates to present to the
29388 client depending on the selected cipher, hence the priority ordering for
29389 ciphers will affect which certificate is used.
29391 If you do not understand about certificates and keys, please try to find a
29392 source of this background information, which is not Exim-specific. (There are a
29393 few comments below in section &<<SECTcerandall>>&.)
29395 &*Note*&: These options do not apply when Exim is operating as a client &--
29396 they apply only in the case of a server. If you need to use a certificate in an
29397 Exim client, you must set the options of the same names in an &(smtp)&
29400 With just these options, an Exim server will be able to use TLS. It does not
29401 require the client to have a certificate (but see below for how to insist on
29402 this). There is one other option that may be needed in other situations. If
29404 tls_dhparam = /some/file/name
29406 is set, the SSL library is initialized for the use of Diffie-Hellman ciphers
29407 with the parameters contained in the file.
29408 Set this to &`none`& to disable use of DH entirely, by making no prime
29413 This may also be set to a string identifying a standard prime to be used for
29414 DH; if it is set to &`default`& or, for OpenSSL, is unset, then the prime
29415 used is &`ike23`&. There are a few standard primes available, see the
29416 documentation for &%tls_dhparam%& for the complete list.
29422 for a way of generating file data.
29424 The strings supplied for these three options are expanded every time a client
29425 host connects. It is therefore possible to use different certificates and keys
29426 for different hosts, if you so wish, by making use of the client's IP address
29427 in &$sender_host_address$& to control the expansion. If a string expansion is
29428 forced to fail, Exim behaves as if the option is not set.
29430 .cindex "cipher" "logging"
29431 .cindex "log" "TLS cipher"
29432 .vindex "&$tls_in_cipher$&"
29433 The variable &$tls_in_cipher$& is set to the cipher suite that was negotiated for
29434 an incoming TLS connection. It is included in the &'Received:'& header of an
29435 incoming message (by default &-- you can, of course, change this), and it is
29436 also included in the log line that records a message's arrival, keyed by
29437 &"X="&, unless the &%tls_cipher%& log selector is turned off. The &%encrypted%&
29438 condition can be used to test for specific cipher suites in ACLs.
29440 Once TLS has been established, the ACLs that run for subsequent SMTP commands
29441 can check the name of the cipher suite and vary their actions accordingly. The
29442 cipher suite names vary, depending on which TLS library is being used. For
29443 example, OpenSSL uses the name DES-CBC3-SHA for the cipher suite which in other
29444 contexts is known as TLS_RSA_WITH_3DES_EDE_CBC_SHA. Check the OpenSSL or GnuTLS
29445 documentation for more details.
29447 For outgoing SMTP deliveries, &$tls_out_cipher$& is used and logged
29448 (again depending on the &%tls_cipher%& log selector).
29451 .section "Requesting and verifying client certificates" "SECID183"
29452 .cindex "certificate" "verification of client"
29453 .cindex "TLS" "client certificate verification"
29454 If you want an Exim server to request a certificate when negotiating a TLS
29455 session with a client, you must set either &%tls_verify_hosts%& or
29456 &%tls_try_verify_hosts%&. You can, of course, set either of them to * to
29457 apply to all TLS connections. For any host that matches one of these options,
29458 Exim requests a certificate as part of the setup of the TLS session. The
29459 contents of the certificate are verified by comparing it with a list of
29460 expected trust-anchors or certificates.
29461 These may be the system default set (depending on library version),
29462 an explicit file or,
29463 depending on library version, a directory, identified by
29464 &%tls_verify_certificates%&.
29466 A file can contain multiple certificates, concatenated end to end. If a
29469 each certificate must be in a separate file, with a name (or a symbolic link)
29470 of the form <&'hash'&>.0, where <&'hash'&> is a hash value constructed from the
29471 certificate. You can compute the relevant hash by running the command
29473 openssl x509 -hash -noout -in /cert/file
29475 where &_/cert/file_& contains a single certificate.
29477 There is no checking of names of the client against the certificate
29478 Subject Name or Subject Alternate Names.
29480 The difference between &%tls_verify_hosts%& and &%tls_try_verify_hosts%& is
29481 what happens if the client does not supply a certificate, or if the certificate
29482 does not match any of the certificates in the collection named by
29483 &%tls_verify_certificates%&. If the client matches &%tls_verify_hosts%&, the
29484 attempt to set up a TLS session is aborted, and the incoming connection is
29485 dropped. If the client matches &%tls_try_verify_hosts%&, the (encrypted) SMTP
29486 session continues. ACLs that run for subsequent SMTP commands can detect the
29487 fact that no certificate was verified, and vary their actions accordingly. For
29488 example, you can insist on a certificate before accepting a message for
29489 relaying, but not when the message is destined for local delivery.
29491 .vindex "&$tls_in_peerdn$&"
29492 When a client supplies a certificate (whether it verifies or not), the value of
29493 the Distinguished Name of the certificate is made available in the variable
29494 &$tls_in_peerdn$& during subsequent processing of the message.
29496 .cindex "log" "distinguished name"
29497 Because it is often a long text string, it is not included in the log line or
29498 &'Received:'& header by default. You can arrange for it to be logged, keyed by
29499 &"DN="&, by setting the &%tls_peerdn%& log selector, and you can use
29500 &%received_header_text%& to change the &'Received:'& header. When no
29501 certificate is supplied, &$tls_in_peerdn$& is empty.
29504 .section "Revoked certificates" "SECID184"
29505 .cindex "TLS" "revoked certificates"
29506 .cindex "revocation list"
29507 .cindex "certificate" "revocation list"
29508 .cindex "OCSP" "stapling"
29509 Certificate issuing authorities issue Certificate Revocation Lists (CRLs) when
29510 certificates are revoked. If you have such a list, you can pass it to an Exim
29511 server using the global option called &%tls_crl%& and to an Exim client using
29512 an identically named option for the &(smtp)& transport. In each case, the value
29513 of the option is expanded and must then be the name of a file that contains a
29515 The downside is that clients have to periodically re-download a potentially huge
29516 file from every certificate authority they know of.
29518 The way with most moving parts at query time is Online Certificate
29519 Status Protocol (OCSP), where the client verifies the certificate
29520 against an OCSP server run by the CA. This lets the CA track all
29521 usage of the certs. It requires running software with access to the
29522 private key of the CA, to sign the responses to the OCSP queries. OCSP
29523 is based on HTTP and can be proxied accordingly.
29525 The only widespread OCSP server implementation (known to this writer)
29526 comes as part of OpenSSL and aborts on an invalid request, such as
29527 connecting to the port and then disconnecting. This requires
29528 re-entering the passphrase each time some random client does this.
29530 The third way is OCSP Stapling; in this, the server using a certificate
29531 issued by the CA periodically requests an OCSP proof of validity from
29532 the OCSP server, then serves it up inline as part of the TLS
29533 negotiation. This approach adds no extra round trips, does not let the
29534 CA track users, scales well with number of certs issued by the CA and is
29535 resilient to temporary OCSP server failures, as long as the server
29536 starts retrying to fetch an OCSP proof some time before its current
29537 proof expires. The downside is that it requires server support.
29539 Unless Exim is built with the support disabled,
29540 or with GnuTLS earlier than version 3.3.16 / 3.4.8
29541 support for OCSP stapling is included.
29543 There is a global option called &%tls_ocsp_file%&.
29544 The file specified therein is expected to be in DER format, and contain
29545 an OCSP proof. Exim will serve it as part of the TLS handshake. This
29546 option will be re-expanded for SNI, if the &%tls_certificate%& option
29547 contains &`tls_in_sni`&, as per other TLS options.
29549 Exim does not at this time implement any support for fetching a new OCSP
29550 proof. The burden is on the administrator to handle this, outside of
29551 Exim. The file specified should be replaced atomically, so that the
29552 contents are always valid. Exim will expand the &%tls_ocsp_file%& option
29553 on each connection, so a new file will be handled transparently on the
29556 When built with OpenSSL Exim will check for a valid next update timestamp
29557 in the OCSP proof; if not present, or if the proof has expired, it will be
29560 For the client to be able to verify the stapled OCSP the server must
29561 also supply, in its stapled information, any intermediate
29562 certificates for the chain leading to the OCSP proof from the signer
29563 of the server certificate. There may be zero or one such. These
29564 intermediate certificates should be added to the server OCSP stapling
29565 file named by &%tls_ocsp_file%&.
29567 Note that the proof only covers the terminal server certificate,
29568 not any of the chain from CA to it.
29570 There is no current way to staple a proof for a client certificate.
29573 A helper script "ocsp_fetch.pl" for fetching a proof from a CA
29574 OCSP server is supplied. The server URL may be included in the
29575 server certificate, if the CA is helpful.
29577 One failure mode seen was the OCSP Signer cert expiring before the end
29578 of validity of the OCSP proof. The checking done by Exim/OpenSSL
29579 noted this as invalid overall, but the re-fetch script did not.
29583 .section "Caching of static server configuration items" "SECTserverTLScache"
29584 .cindex certificate caching
29585 .cindex privatekey caching
29586 .cindex crl caching
29587 .cindex ocsp caching
29588 .cindex ciphers caching
29589 .cindex "CA bundle" caching
29590 .cindex "certificate authorities" caching
29591 .cindex tls_certificate caching
29592 .cindex tls_privatekey caching
29593 .cindex tls_crl caching
29594 .cindex tls_ocsp_file caching
29595 .cindex tls_require_ciphers caching
29596 .cindex tls_verify_certificate caching
29597 .cindex caching certificate
29598 .cindex caching privatekey
29599 .cindex caching crl
29600 .cindex caching ocsp
29601 .cindex caching ciphers
29602 .cindex caching "certificate authorities
29603 If any of the main configuration options &%tls_certificate%&, &%tls_privatekey%&,
29604 &%tls_crl%& and &%tls_ocsp_file%& have values with no
29605 expandable elements,
29606 then the associated information is loaded at daemon startup.
29607 It is made available
29608 to child processes forked for handling received SMTP connections.
29610 This caching is currently only supported under Linux and FreeBSD.
29612 If caching is not possible, for example if an item has to be dependent
29613 on the peer host so contains a &$sender_host_name$& expansion, the load
29614 of the associated information is done at the startup of the TLS connection.
29616 The cache is invalidated and reloaded after any changes to the directories
29617 containing files specified by these options.
29619 The information specified by the main option &%tls_verify_certificates%&
29620 is similarly cached so long as it specifies files explicitly
29621 or (under GnuTLS) is the string &"system,cache"&.
29622 The latter case is not automatically invalidated;
29623 it is the operator's responsibility to arrange for a daemon restart
29624 any time the system certificate authority bundle is updated.
29625 A HUP signal is sufficient for this.
29626 The value &"system"& results in no caching under GnuTLS.
29628 The macro _HAVE_TLS_CA_CACHE will be defined if the suffix for "system"
29629 is acceptable in configurations for the Exim executavble.
29631 Caching of the system Certificate Authorities bundle can
29632 save siginificant time and processing on every TLS connection
29638 .section "Configuring an Exim client to use TLS" "SECTclientTLS"
29639 .cindex "cipher" "logging"
29640 .cindex "log" "TLS cipher"
29641 .cindex "log" "distinguished name"
29642 .cindex "TLS" "configuring an Exim client"
29643 The &%tls_cipher%& and &%tls_peerdn%& log selectors apply to outgoing SMTP
29644 deliveries as well as to incoming, the latter one causing logging of the
29645 server certificate's DN. The remaining client configuration for TLS is all
29646 within the &(smtp)& transport.
29648 .cindex "ESMTP extensions" STARTTLS
29649 It is not necessary to set any options to have TLS work in the &(smtp)&
29650 transport. If Exim is built with TLS support, and TLS is advertised by a
29651 server, the &(smtp)& transport always tries to start a TLS session. However,
29652 this can be prevented by setting &%hosts_avoid_tls%& (an option of the
29653 transport) to a list of server hosts for which TLS should not be used.
29655 If you do not want Exim to attempt to send messages unencrypted when an attempt
29656 to set up an encrypted connection fails in any way, you can set
29657 &%hosts_require_tls%& to a list of hosts for which encryption is mandatory. For
29658 those hosts, delivery is always deferred if an encrypted connection cannot be
29659 set up. If there are any other hosts for the address, they are tried in the
29662 When the server host is not in &%hosts_require_tls%&, Exim may try to deliver
29663 the message unencrypted. It always does this if the response to STARTTLS is
29664 a 5&'xx'& code. For a temporary error code, or for a failure to negotiate a TLS
29665 session after a success response code, what happens is controlled by the
29666 &%tls_tempfail_tryclear%& option of the &(smtp)& transport. If it is false,
29667 delivery to this host is deferred, and other hosts (if available) are tried. If
29668 it is true, Exim attempts to deliver unencrypted after a 4&'xx'& response to
29669 STARTTLS, and if STARTTLS is accepted, but the subsequent TLS
29670 negotiation fails, Exim closes the current connection (because it is in an
29671 unknown state), opens a new one to the same host, and then tries the delivery
29674 The &%tls_certificate%& and &%tls_privatekey%& options of the &(smtp)&
29675 transport provide the client with a certificate, which is passed to the server
29677 This is an optional thing for TLS connections, although either end
29679 If the server is Exim, it will request a certificate only if
29680 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client.
29682 &*Note*&: Do not use a certificate which has the OCSP-must-staple extension,
29683 for client use (they are usable for server use).
29684 As the TLS protocol has no means for the client to staple before TLS 1.3 it will result
29685 in failed connections.
29687 If the &%tls_verify_certificates%& option is set on the &(smtp)& transport, it
29688 specifies a collection of expected server certificates.
29690 the system default set (depending on library version),
29692 or (depending on library version) a directory.
29693 The client verifies the server's certificate
29694 against this collection, taking into account any revoked certificates that are
29695 in the list defined by &%tls_crl%&.
29696 Failure to verify fails the TLS connection unless either of the
29697 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& options are set.
29699 The &%tls_verify_hosts%& and &%tls_try_verify_hosts%& options restrict
29700 certificate verification to the listed servers. Verification either must
29701 or need not succeed respectively.
29703 The &%tls_verify_cert_hostnames%& option lists hosts for which additional
29704 name checks are made on the server certificate.
29705 The match against this list is, as per other Exim usage, the
29706 IP for the host. That is most closely associated with the
29707 name on the DNS A (or AAAA) record for the host.
29708 However, the name that needs to be in the certificate
29709 is the one at the head of any CNAME chain leading to the A record.
29710 The option defaults to always checking.
29712 The &(smtp)& transport has two OCSP-related options:
29713 &%hosts_require_ocsp%&; a host-list for which a Certificate Status
29714 is requested and required for the connection to proceed. The default
29716 &%hosts_request_ocsp%&; a host-list for which (additionally)
29717 a Certificate Status is requested (but not necessarily verified). The default
29718 value is "*" meaning that requests are made unless configured
29721 The host(s) should also be in &%hosts_require_tls%&, and
29722 &%tls_verify_certificates%& configured for the transport,
29723 for OCSP to be relevant.
29726 &%tls_require_ciphers%& is set on the &(smtp)& transport, it must contain a
29727 list of permitted cipher suites. If either of these checks fails, delivery to
29728 the current host is abandoned, and the &(smtp)& transport tries to deliver to
29729 alternative hosts, if any.
29732 These options must be set in the &(smtp)& transport for Exim to use TLS when it
29733 is operating as a client. Exim does not assume that a server certificate (set
29734 by the global options of the same name) should also be used when operating as a
29738 .vindex "&$host_address$&"
29739 All the TLS options in the &(smtp)& transport are expanded before use, with
29740 &$host$& and &$host_address$& containing the name and address of the server to
29741 which the client is connected. Forced failure of an expansion causes Exim to
29742 behave as if the relevant option were unset.
29744 .vindex &$tls_out_bits$&
29745 .vindex &$tls_out_cipher$&
29746 .vindex &$tls_out_peerdn$&
29747 .vindex &$tls_out_sni$&
29748 Before an SMTP connection is established, the
29749 &$tls_out_bits$&, &$tls_out_cipher$&, &$tls_out_peerdn$& and &$tls_out_sni$&
29750 variables are emptied. (Until the first connection, they contain the values
29751 that were set when the message was received.) If STARTTLS is subsequently
29752 successfully obeyed, these variables are set to the relevant values for the
29753 outgoing connection.
29757 .section "Caching of static client configuration items" "SECTclientTLScache"
29758 .cindex certificate caching
29759 .cindex privatekey caching
29760 .cindex crl caching
29761 .cindex ciphers caching
29762 .cindex "CA bundle" caching
29763 .cindex "certificate authorities" caching
29764 .cindex tls_certificate caching
29765 .cindex tls_privatekey caching
29766 .cindex tls_crl caching
29767 .cindex tls_require_ciphers caching
29768 .cindex tls_verify_certificate caching
29769 .cindex caching certificate
29770 .cindex caching privatekey
29771 .cindex caching crl
29772 .cindex caching ciphers
29773 .cindex caching "certificate authorities
29774 If any of the transport configuration options &%tls_certificate%&, &%tls_privatekey%&
29775 and &%tls_crl%& have values with no
29776 expandable elements,
29777 then the associated information is loaded per smtp transport
29778 at daemon startup, at the start of a queue run, or on a
29779 command-line specified message delivery.
29780 It is made available
29781 to child processes forked for handling making SMTP connections.
29783 This caching is currently only supported under Linux.
29785 If caching is not possible, the load
29786 of the associated information is done at the startup of the TLS connection.
29788 The cache is invalidated in the daemon
29789 and reloaded after any changes to the directories
29790 containing files specified by these options.
29792 The information specified by the main option &%tls_verify_certificates%&
29793 is similarly cached so long as it specifies files explicitly
29794 or (under GnuTLS) is the string &"system,cache"&.
29795 The latter case is not automatically invaludated;
29796 it is the operator's responsibility to arrange for a daemon restart
29797 any time the system certificate authority bundle is updated.
29798 A HUP signal is sufficient for this.
29799 The value &"system"& results in no caching under GnuTLS.
29801 The macro _HAVE_TLS_CA_CACHE will be defined if the suffix for "system"
29802 is acceptable in configurations for the Exim executavble.
29804 Caching of the system Certificate Authorities bundle can
29805 save siginificant time and processing on every TLS connection
29811 .section "Use of TLS Server Name Indication" "SECTtlssni"
29812 .cindex "TLS" "Server Name Indication"
29815 .vindex "&$tls_in_sni$&"
29816 .oindex "&%tls_in_sni%&"
29817 With TLS1.0 or above, there is an extension mechanism by which extra
29818 information can be included at various points in the protocol. One of these
29819 extensions, documented in RFC 6066 (and before that RFC 4366) is
29820 &"Server Name Indication"&, commonly &"SNI"&. This extension is sent by the
29821 client in the initial handshake, so that the server can examine the servername
29822 within and possibly choose to use different certificates and keys (and more)
29825 This is analogous to HTTP's &"Host:"& header, and is the main mechanism by
29826 which HTTPS-enabled web-sites can be virtual-hosted, many sites to one IP
29829 With SMTP to MX, there are the same problems here as in choosing the identity
29830 against which to validate a certificate: you can't rely on insecure DNS to
29831 provide the identity which you then cryptographically verify. So this will
29832 be of limited use in that environment.
29834 With SMTP to Submission, there is a well-defined hostname which clients are
29835 connecting to and can validate certificates against. Thus clients &*can*&
29836 choose to include this information in the TLS negotiation. If this becomes
29837 wide-spread, then hosters can choose to present different certificates to
29838 different clients. Or even negotiate different cipher suites.
29840 The &%tls_sni%& option on an SMTP transport is an expanded string; the result,
29841 if not empty, will be sent on a TLS session as part of the handshake. There's
29842 nothing more to it. Choosing a sensible value not derived insecurely is the
29843 only point of caution. The &$tls_out_sni$& variable will be set to this string
29844 for the lifetime of the client connection (including during authentication).
29846 If DANE validated the connection attempt then the value of the &%tls_sni%& option
29847 is forced to the name of the destination host, after any MX- or CNAME-following.
29849 Except during SMTP client sessions, if &$tls_in_sni$& is set then it is a string
29850 received from a client.
29851 It can be logged with the &%log_selector%& item &`+tls_sni`&.
29853 If the string &`tls_in_sni`& appears in the main section's &%tls_certificate%&
29854 option (prior to expansion) then the following options will be re-expanded
29855 during TLS session handshake, to permit alternative values to be chosen:
29858 &%tls_certificate%&
29864 &%tls_verify_certificates%&
29869 Great care should be taken to deal with matters of case, various injection
29870 attacks in the string (&`../`& or SQL), and ensuring that a valid filename
29871 can always be referenced; it is important to remember that &$tls_in_sni$& is
29872 arbitrary unverified data provided prior to authentication.
29873 Further, the initial certificate is loaded before SNI has arrived, so
29874 an expansion for &%tls_certificate%& must have a default which is used
29875 when &$tls_in_sni$& is empty.
29877 The Exim developers are proceeding cautiously and so far no other TLS options
29880 When Exim is built against OpenSSL, OpenSSL must have been built with support
29881 for TLS Extensions. This holds true for OpenSSL 1.0.0+ and 0.9.8+ with
29882 enable-tlsext in EXTRACONFIGURE. If you invoke &(openssl s_client -h)& and
29883 see &`-servername`& in the output, then OpenSSL has support.
29885 When Exim is built against GnuTLS, SNI support is available as of GnuTLS
29886 0.5.10. (Its presence predates the current API which Exim uses, so if Exim
29887 built, then you have SNI support).
29890 .cindex ALPN "general information"
29891 .cindex TLS "Application Layer Protocol Names"
29892 There is a TLS feature related to SNI
29893 called Application Layer Protocol Name (ALPN).
29894 This is intended to declare, or select, what protocol layer will be using a TLS
29896 The client for the connection proposes a set of protocol names, and
29897 the server responds with a selected one.
29898 It is not, as of 2021, commonly used for SMTP connections.
29899 However, to guard against misirected or malicious use of web clients
29900 (which often do use ALPN) against MTA ports, Exim by default check that
29901 there is no incompatible ALPN specified by a client for a TLS connection.
29902 If there is, the connection is rejected.
29904 As a client Exim does not supply ALPN by default.
29905 The behaviour of both client and server can be configured using the options
29906 &%tls_alpn%& and &%hosts_require_alpn%&.
29907 There are no variables providing observability.
29908 Some feature-specific logging may appear on denied connections, but this
29909 depends on the behavious of the peer
29910 (not all peers can send a feature-specific TLS Alert).
29912 This feature is available when Exim is built with
29913 OpenSSL 1.1.0 or later or GnuTLS 3.2.0 or later;
29914 the macro _HAVE_TLS_ALPN will be defined when this is so.
29918 .section "Multiple messages on the same encrypted TCP/IP connection" &&&
29920 .cindex "multiple SMTP deliveries with TLS"
29921 .cindex "TLS" "multiple message deliveries"
29922 Exim sends multiple messages down the same TCP/IP connection by starting up
29923 an entirely new delivery process for each message, passing the socket from
29924 one process to the next. This implementation does not fit well with the use
29925 of TLS, because there is quite a lot of state information associated with a TLS
29926 connection, not just a socket identification. Passing all the state information
29927 to a new process is not feasible. Consequently, for sending using TLS Exim
29928 starts an additional proxy process for handling the encryption, piping the
29929 unencrypted data stream from and to the delivery processes.
29931 An older mode of operation can be enabled on a per-host basis by the
29932 &%hosts_noproxy_tls%& option on the &(smtp)& transport. If the host matches
29933 this list the proxy process described above is not used; instead Exim
29934 shuts down an existing TLS session being run by the delivery process
29935 before passing the socket to a new process. The new process may then
29936 try to start a new TLS session, and if successful, may try to re-authenticate
29937 if AUTH is in use, before sending the next message.
29939 The RFC is not clear as to whether or not an SMTP session continues in clear
29940 after TLS has been shut down, or whether TLS may be restarted again later, as
29941 just described. However, if the server is Exim, this shutdown and
29942 reinitialization works. It is not known which (if any) other servers operate
29943 successfully if the client closes a TLS session and continues with unencrypted
29944 SMTP, but there are certainly some that do not work. For such servers, Exim
29945 should not pass the socket to another process, because the failure of the
29946 subsequent attempt to use it would cause Exim to record a temporary host error,
29947 and delay other deliveries to that host.
29949 To test for this case, Exim sends an EHLO command to the server after
29950 closing down the TLS session. If this fails in any way, the connection is
29951 closed instead of being passed to a new delivery process, but no retry
29952 information is recorded.
29954 There is also a manual override; you can set &%hosts_nopass_tls%& on the
29955 &(smtp)& transport to match those hosts for which Exim should not pass
29956 connections to new processes if TLS has been used.
29961 .section "Certificates and all that" "SECTcerandall"
29962 .cindex "certificate" "references to discussion"
29963 In order to understand fully how TLS works, you need to know about
29964 certificates, certificate signing, and certificate authorities.
29965 This is a large topic and an introductory guide is unsuitable for the Exim
29966 reference manual, so instead we provide pointers to existing documentation.
29968 The Apache web-server was for a long time the canonical guide, so their
29969 documentation is a good place to start; their SSL module's Introduction
29970 document is currently at
29972 &url(https://httpd.apache.org/docs/current/ssl/ssl_intro.html)
29974 and their FAQ is at
29976 &url(https://httpd.apache.org/docs/current/ssl/ssl_faq.html)
29979 Eric Rescorla's book, &'SSL and TLS'&, published by Addison-Wesley (ISBN
29980 0-201-61598-3) in 2001, contains both introductory and more in-depth
29982 More recently Ivan Ristić's book &'Bulletproof SSL and TLS'&,
29983 published by Feisty Duck (ISBN 978-1907117046) in 2013 is good.
29984 Ivan is the author of the popular TLS testing tools at
29985 &url(https://www.ssllabs.com/).
29988 .section "Certificate chains" "SECID186"
29989 A file named by &%tls_certificate%& may contain more than one
29990 certificate. This is useful in the case where the certificate that is being
29991 sent is validated by an intermediate certificate which the other end does
29992 not have. Multiple certificates must be in the correct order in the file.
29993 First the host's certificate itself, then the first intermediate
29994 certificate to validate the issuer of the host certificate, then the next
29995 intermediate certificate to validate the issuer of the first intermediate
29996 certificate, and so on, until finally (optionally) the root certificate.
29997 The root certificate must already be trusted by the recipient for
29998 validation to succeed, of course, but if it's not preinstalled, sending the
29999 root certificate along with the rest makes it available for the user to
30000 install if the receiving end is a client MUA that can interact with a user.
30002 Note that certificates using MD5 are unlikely to work on today's Internet;
30003 even if your libraries allow loading them for use in Exim when acting as a
30004 server, increasingly clients will not accept such certificates. The error
30005 diagnostics in such a case can be frustratingly vague.
30009 .section "Self-signed certificates" "SECID187"
30010 .cindex "certificate" "self-signed"
30011 You can create a self-signed certificate using the &'req'& command provided
30012 with OpenSSL, like this:
30013 . ==== Do not shorten the duration here without reading and considering
30014 . ==== the text below. Please leave it at 9999 days.
30016 openssl req -x509 -newkey rsa:1024 -keyout file1 -out file2 \
30019 &_file1_& and &_file2_& can be the same file; the key and the certificate are
30020 delimited and so can be identified independently. The &%-days%& option
30021 specifies a period for which the certificate is valid. The &%-nodes%& option is
30022 important: if you do not set it, the key is encrypted with a passphrase
30023 that you are prompted for, and any use that is made of the key causes more
30024 prompting for the passphrase. This is not helpful if you are going to use
30025 this certificate and key in an MTA, where prompting is not possible.
30027 . ==== I expect to still be working 26 years from now. The less technical
30028 . ==== debt I create, in terms of storing up trouble for my later years, the
30029 . ==== happier I will be then. We really have reached the point where we
30030 . ==== should start, at the very least, provoking thought and making folks
30031 . ==== pause before proceeding, instead of leaving all the fixes until two
30032 . ==== years before 2^31 seconds after the 1970 Unix epoch.
30034 NB: we are now past the point where 9999 days takes us past the 32-bit Unix
30035 epoch. If your system uses unsigned time_t (most do) and is 32-bit, then
30036 the above command might produce a date in the past. Think carefully about
30037 the lifetime of the systems you're deploying, and either reduce the duration
30038 of the certificate or reconsider your platform deployment. (At time of
30039 writing, reducing the duration is the most likely choice, but the inexorable
30040 progression of time takes us steadily towards an era where this will not
30041 be a sensible resolution).
30043 A self-signed certificate made in this way is sufficient for testing, and
30044 may be adequate for all your requirements if you are mainly interested in
30045 encrypting transfers, and not in secure identification.
30047 However, many clients require that the certificate presented by the server be a
30048 user (also called &"leaf"& or &"site"&) certificate, and not a self-signed
30049 certificate. In this situation, the self-signed certificate described above
30050 must be installed on the client host as a trusted root &'certification
30051 authority'& (CA), and the certificate used by Exim must be a user certificate
30052 signed with that self-signed certificate.
30054 For information on creating self-signed CA certificates and using them to sign
30055 user certificates, see the &'General implementation overview'& chapter of the
30056 Open-source PKI book, available online at
30057 &url(https://sourceforge.net/projects/ospkibook/).
30058 .ecindex IIDencsmtp1
30059 .ecindex IIDencsmtp2
30062 .section "TLS Resumption" "SECTresumption"
30063 .cindex TLS resumption
30064 TLS Session Resumption for TLS 1.2 and TLS 1.3 connections can be used (defined
30065 in RFC 5077 for 1.2). The support for this requires GnuTLS 3.6.3 or OpenSSL 1.1.1
30068 Session resumption (this is the "stateless" variant) involves the server sending
30069 a "session ticket" to the client on one connection, which can be stored by the
30070 client and used for a later session. The ticket contains sufficient state for
30071 the server to reconstruct the TLS session, avoiding some expensive crypto
30072 calculation and (on TLS1.2) one full packet roundtrip time.
30075 Operational cost/benefit:
30077 The extra data being transmitted costs a minor amount, and the client has
30078 extra costs in storing and retrieving the data.
30080 In the Exim/Gnutls implementation the extra cost on an initial connection
30081 which is TLS1.2 over a loopback path is about 6ms on 2017-laptop class hardware.
30082 The saved cost on a subsequent connection is about 4ms; three or more
30083 connections become a net win. On longer network paths, two or more
30084 connections will have an average lower startup time thanks to the one
30085 saved packet roundtrip. TLS1.3 will save the crypto cpu costs but not any
30088 .cindex "hints database" tls
30089 Since a new hints DB is used on the TLS client,
30090 the hints DB maintenance should be updated to additionally handle "tls".
30095 The session ticket is encrypted, but is obviously an additional security
30096 vulnarability surface. An attacker able to decrypt it would have access
30097 all connections using the resumed session.
30098 The session ticket encryption key is not committed to storage by the server
30099 and is rotated regularly (OpenSSL: 1hr, and one previous key is used for
30100 overlap; GnuTLS 6hr but does not specify any overlap).
30101 Tickets have limited lifetime (2hr, and new ones issued after 1hr under
30102 OpenSSL. GnuTLS 2hr, appears to not do overlap).
30104 There is a question-mark over the security of the Diffie-Helman parameters
30105 used for session negotiation.
30110 The &%log_selector%& "tls_resumption" appends an asterisk to the tls_cipher "X="
30113 The variables &$tls_in_resumption$& and &$tls_out_resumption$&
30114 have bits 0-4 indicating respectively
30115 support built, client requested ticket, client offered session,
30116 server issued ticket, resume used. A suitable decode list is provided
30117 in the builtin macro _RESUME_DECODE for in &%listextract%& expansions.
30122 The &%tls_resumption_hosts%& main option specifies a hostlist for which
30123 exim, operating as a server, will offer resumption to clients.
30124 Current best practice is to not offer the feature to MUA connection.
30125 Commonly this can be done like this:
30127 tls_resumption_hosts = ${if inlist {$received_port}{587:465} {:}{*}}
30129 If the peer host matches the list after expansion then resumption
30130 is offered and/or accepted.
30132 The &%tls_resumption_hosts%& smtp transport option performs the
30133 equivalent function for operation as a client.
30134 If the peer host matches the list after expansion then resumption
30135 is attempted (if a stored session is available) or the information
30136 stored (if supplied by the peer).
30142 In a resumed session:
30144 The variables &$tls_{in,out}_cipher$& will have values different
30145 to the original (under GnuTLS).
30147 The variables &$tls_{in,out}_ocsp$& will be "not requested" or "no response",
30148 and the &%hosts_require_ocsp%& smtp trasnport option will fail.
30149 . XXX need to do something with that hosts_require_ocsp
30155 .section DANE "SECDANE"
30157 DNS-based Authentication of Named Entities, as applied to SMTP over TLS, provides assurance to a client that
30158 it is actually talking to the server it wants to rather than some attacker operating a Man In The Middle (MITM)
30159 operation. The latter can terminate the TLS connection you make, and make another one to the server (so both
30160 you and the server still think you have an encrypted connection) and, if one of the "well known" set of
30161 Certificate Authorities has been suborned - something which *has* been seen already (2014), a verifiable
30162 certificate (if you're using normal root CAs, eg. the Mozilla set, as your trust anchors).
30164 What DANE does is replace the CAs with the DNS as the trust anchor. The assurance is limited to a) the possibility
30165 that the DNS has been suborned, b) mistakes made by the admins of the target server. The attack surface presented
30166 by (a) is thought to be smaller than that of the set of root CAs.
30168 It also allows the server to declare (implicitly) that connections to it should use TLS. An MITM could simply
30169 fail to pass on a server's STARTTLS.
30171 DANE scales better than having to maintain (and communicate via side-channel) copies of server certificates
30172 for every possible target server. It also scales (slightly) better than having to maintain on an SMTP
30173 client a copy of the standard CAs bundle. It also means not having to pay a CA for certificates.
30175 DANE requires a server operator to do three things: 1) run DNSSEC. This provides assurance to clients
30176 that DNS lookups they do for the server have not been tampered with. The domain MX record applying
30177 to this server, its A record, its TLSA record and any associated CNAME records must all be covered by
30179 2) add TLSA DNS records. These say what the server certificate for a TLS connection should be.
30180 3) offer a server certificate, or certificate chain, in TLS connections which is is anchored by one of the TLSA records.
30182 There are no changes to Exim specific to server-side operation of DANE.
30183 Support for client-side operation of DANE can be included at compile time by defining SUPPORT_DANE=yes
30184 in &_Local/Makefile_&.
30185 If it has been included, the macro "_HAVE_DANE" will be defined.
30187 A TLSA record consist of 4 fields, the "Certificate Usage", the
30188 "Selector", the "Matching type", and the "Certificate Association Data".
30189 For a detailed description of the TLSA record see
30190 &url(https://tools.ietf.org/html/rfc7671#page-5,RFC 7671).
30192 The TLSA record for the server may have "Certificate Usage" (1st) field of DANE-TA(2) or DANE-EE(3).
30193 These are the "Trust Anchor" and "End Entity" variants.
30194 The latter specifies the End Entity directly, i.e. the certificate involved is that of the server
30195 (and if only DANE-EE is used then it should be the sole one transmitted during the TLS handshake);
30196 this is appropriate for a single system, using a self-signed certificate.
30197 DANE-TA usage is effectively declaring a specific CA to be used; this might be a private CA or a public,
30199 A private CA at simplest is just a self-signed certificate (with certain
30200 attributes) which is used to sign server certificates, but running one securely
30201 does require careful arrangement.
30202 With DANE-TA, as implemented in Exim and commonly in other MTAs,
30203 the server TLS handshake must transmit the entire certificate chain from CA to server-certificate.
30204 DANE-TA is commonly used for several services and/or servers, each having a TLSA query-domain CNAME record,
30205 all of which point to a single TLSA record.
30206 DANE-TA and DANE-EE can both be used together.
30208 Our recommendation is to use DANE with a certificate from a public CA,
30209 because this enables a variety of strategies for remote clients to verify
30211 You can then publish information both via DANE and another technology,
30212 "MTA-STS", described below.
30214 When you use DANE-TA to publish trust anchor information, you ask entities
30215 outside your administrative control to trust the Certificate Authority for
30216 connections to you.
30217 If using a private CA then you should expect others to still apply the
30218 technical criteria they'd use for a public CA to your certificates.
30219 In particular, you should probably try to follow current best practices for CA
30220 operation around hash algorithms and key sizes.
30221 Do not expect other organizations to lower their security expectations just
30222 because a particular profile might be reasonable for your own internal use.
30224 When this text was last updated, this in practice means to avoid use of SHA-1
30225 and MD5; if using RSA to use key sizes of at least 2048 bits (and no larger
30226 than 4096, for interoperability); to use keyUsage fields correctly; to use
30227 random serial numbers.
30228 The list of requirements is subject to change as best practices evolve.
30229 If you're not already using a private CA, or it doesn't meet these
30230 requirements, then we encourage you to avoid all these issues and use a public
30231 CA such as &url(https://letsencrypt.org/,Let's Encrypt) instead.
30233 The TLSA record should have a "Selector" (2nd) field of SPKI(1) and
30234 a "Matching Type" (3rd) field of SHA2-512(2).
30236 For the "Certificate Authority Data" (4th) field, commands like
30239 openssl x509 -pubkey -noout <certificate.pem \
30240 | openssl rsa -outform der -pubin 2>/dev/null \
30245 are workable to create a hash of the certificate's public key.
30247 An example TLSA record for DANE-EE(3), SPKI(1), and SHA-512 (2) looks like
30250 _25._tcp.mail.example.com. TLSA 3 1 2 8BA8A336E...
30253 At the time of writing, &url(https://www.huque.com/bin/gen_tlsa)
30254 is useful for quickly generating TLSA records.
30257 For use with the DANE-TA model, server certificates must have a correct name (SubjectName or SubjectAltName).
30259 The Certificate issued by the CA published in the DANE-TA model should be
30260 issued using a strong hash algorithm.
30261 Exim, and importantly various other MTAs sending to you, will not
30262 re-enable hash algorithms which have been disabled by default in TLS
30264 This means no MD5 and no SHA-1. SHA2-256 is the minimum for reliable
30265 interoperability (and probably the maximum too, in 2018).
30267 The use of OCSP-stapling should be considered, allowing for fast revocation of certificates (which would otherwise
30268 be limited by the DNS TTL on the TLSA records). However, this is likely to only be usable with DANE-TA. NOTE: the
30269 default of requesting OCSP for all hosts is modified iff DANE is in use, to:
30272 hosts_request_ocsp = ${if or { {= {0}{$tls_out_tlsa_usage}} \
30273 {= {4}{$tls_out_tlsa_usage}} } \
30277 The (new) variable &$tls_out_tlsa_usage$& is a bitfield with numbered bits set for TLSA record usage codes.
30278 The zero above means DANE was not in use, the four means that only DANE-TA usage TLSA records were
30279 found. If the definition of &%hosts_request_ocsp%& includes the
30280 string "tls_out_tlsa_usage", they are re-expanded in time to
30281 control the OCSP request.
30283 This modification of hosts_request_ocsp is only done if it has the default value of "*". Admins who change it, and
30284 those who use &%hosts_require_ocsp%&, should consider the interaction with DANE in their OCSP settings.
30287 For client-side DANE there are three new smtp transport options, &%hosts_try_dane%&, &%hosts_require_dane%&
30288 and &%dane_require_tls_ciphers%&.
30289 The &"require"& variant will result in failure if the target host is not
30290 DNSSEC-secured. To get DNSSEC-secured hostname resolution, use
30291 the &%dnssec_request_domains%& router or transport option.
30293 DANE will only be usable if the target host has DNSSEC-secured MX, A and TLSA records.
30295 A TLSA lookup will be done if either of the above options match and the host-lookup succeeded using DNSSEC.
30296 If a TLSA lookup is done and succeeds, a DANE-verified TLS connection
30297 will be required for the host. If it does not, the host will not
30298 be used; there is no fallback to non-DANE or non-TLS.
30300 If DANE is requested and usable, then the TLS cipher list configuration
30301 prefers to use the option &%dane_require_tls_ciphers%& and falls
30302 back to &%tls_require_ciphers%& only if that is unset.
30303 This lets you configure "decent crypto" for DANE and "better than nothing
30304 crypto" as the default. Note though that while GnuTLS lets the string control
30305 which versions of TLS/SSL will be negotiated, OpenSSL does not and you're
30306 limited to ciphersuite constraints.
30308 If DANE is requested and useable (see above) the following transport options are ignored:
30312 tls_try_verify_hosts
30313 tls_verify_certificates
30315 tls_verify_cert_hostnames
30319 If DANE is not usable, whether requested or not, and CA-anchored
30320 verification evaluation is wanted, the above variables should be set appropriately.
30322 The router and transport option &%dnssec_request_domains%& must not be
30323 set to &"never"&, and &%dnssec_require_domains%& is ignored.
30325 If verification was successful using DANE then the "CV" item in the delivery log line will show as "CV=dane".
30327 There is a new variable &$tls_out_dane$& which will have "yes" if
30328 verification succeeded using DANE and "no" otherwise (only useful
30329 in combination with events; see &<<CHAPevents>>&),
30330 and a new variable &$tls_out_tlsa_usage$& (detailed above).
30332 .cindex DANE reporting
30333 An event (see &<<CHAPevents>>&) of type "dane:fail" will be raised on failures
30334 to achieve DANE-verified connection, if one was either requested and offered, or
30335 required. This is intended to support TLS-reporting as defined in
30336 &url(https://tools.ietf.org/html/draft-ietf-uta-smtp-tlsrpt-17).
30337 The &$event_data$& will be one of the Result Types defined in
30338 Section 4.3 of that document.
30340 Under GnuTLS, DANE is only supported from version 3.0.0 onwards.
30342 DANE is specified in published RFCs and decouples certificate authority trust
30343 selection from a "race to the bottom" of "you must trust everything for mail
30344 to get through". There is an alternative technology called MTA-STS, which
30345 instead publishes MX trust anchor information on an HTTPS website. At the
30346 time this text was last updated, MTA-STS was still a draft, not yet an RFC.
30347 Exim has no support for MTA-STS as a client, but Exim mail server operators
30348 can choose to publish information describing their TLS configuration using
30349 MTA-STS to let those clients who do use that protocol derive trust
30352 The MTA-STS design requires a certificate from a public Certificate Authority
30353 which is recognized by clients sending to you.
30354 That selection of which CAs are trusted by others is outside your control.
30356 The most interoperable course of action is probably to use
30357 &url(https://letsencrypt.org/,Let's Encrypt), with automated certificate
30358 renewal; to publish the anchor information in DNSSEC-secured DNS via TLSA
30359 records for DANE clients (such as Exim and Postfix) and to publish anchor
30360 information for MTA-STS as well. This is what is done for the &'exim.org'&
30361 domain itself (with caveats around occasionally broken MTA-STS because of
30362 incompatible specification changes prior to reaching RFC status).
30366 . ////////////////////////////////////////////////////////////////////////////
30367 . ////////////////////////////////////////////////////////////////////////////
30369 .chapter "Access control lists" "CHAPACL"
30370 .scindex IIDacl "&ACL;" "description"
30371 .cindex "control of incoming mail"
30372 .cindex "message" "controlling incoming"
30373 .cindex "policy control" "access control lists"
30374 Access Control Lists (ACLs) are defined in a separate section of the runtime
30375 configuration file, headed by &"begin acl"&. Each ACL definition starts with a
30376 name, terminated by a colon. Here is a complete ACL section that contains just
30377 one very small ACL:
30381 accept hosts = one.host.only
30383 You can have as many lists as you like in the ACL section, and the order in
30384 which they appear does not matter. The lists are self-terminating.
30386 The majority of ACLs are used to control Exim's behaviour when it receives
30387 certain SMTP commands. This applies both to incoming TCP/IP connections, and
30388 when a local process submits a message using SMTP by specifying the &%-bs%&
30389 option. The most common use is for controlling which recipients are accepted
30390 in incoming messages. In addition, you can define an ACL that is used to check
30391 local non-SMTP messages. The default configuration file contains an example of
30392 a realistic ACL for checking RCPT commands. This is discussed in chapter
30393 &<<CHAPdefconfil>>&.
30396 .section "Testing ACLs" "SECID188"
30397 The &%-bh%& command line option provides a way of testing your ACL
30398 configuration locally by running a fake SMTP session with which you interact.
30401 .section "Specifying when ACLs are used" "SECID189"
30402 .cindex "&ACL;" "options for specifying"
30403 In order to cause an ACL to be used, you have to name it in one of the relevant
30404 options in the main part of the configuration. These options are:
30405 .cindex "AUTH" "ACL for"
30406 .cindex "DATA" "ACLs for"
30407 .cindex "ETRN" "ACL for"
30408 .cindex "EXPN" "ACL for"
30409 .cindex "HELO" "ACL for"
30410 .cindex "EHLO" "ACL for"
30411 .cindex "DKIM" "ACL for"
30412 .cindex "MAIL" "ACL for"
30413 .cindex "QUIT, ACL for"
30414 .cindex "RCPT" "ACL for"
30415 .cindex "STARTTLS, ACL for"
30416 .cindex "VRFY" "ACL for"
30417 .cindex "SMTP" "connection, ACL for"
30418 .cindex "non-SMTP messages" "ACLs for"
30419 .cindex "MIME content scanning" "ACL for"
30420 .cindex "PRDR" "ACL for"
30423 .irow &%acl_not_smtp%& "ACL for non-SMTP messages"
30424 .irow &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
30425 .irow &%acl_not_smtp_start%& "ACL at start of non-SMTP message"
30426 .irow &%acl_smtp_auth%& "ACL for AUTH"
30427 .irow &%acl_smtp_connect%& "ACL for start of SMTP connection"
30428 .irow &%acl_smtp_data%& "ACL after DATA is complete"
30429 .irow &%acl_smtp_data_prdr%& "ACL for each recipient, after DATA is complete"
30430 .irow &%acl_smtp_dkim%& "ACL for each DKIM signer"
30431 .irow &%acl_smtp_etrn%& "ACL for ETRN"
30432 .irow &%acl_smtp_expn%& "ACL for EXPN"
30433 .irow &%acl_smtp_helo%& "ACL for HELO or EHLO"
30434 .irow &%acl_smtp_mail%& "ACL for MAIL"
30435 .irow &%acl_smtp_mailauth%& "ACL for the AUTH parameter of MAIL"
30436 .irow &%acl_smtp_mime%& "ACL for content-scanning MIME parts"
30437 .irow &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
30438 .irow &%acl_smtp_predata%& "ACL at start of DATA command"
30439 .irow &%acl_smtp_quit%& "ACL for QUIT"
30440 .irow &%acl_smtp_rcpt%& "ACL for RCPT"
30441 .irow &%acl_smtp_starttls%& "ACL for STARTTLS"
30442 .irow &%acl_smtp_vrfy%& "ACL for VRFY"
30445 For example, if you set
30447 acl_smtp_rcpt = small_acl
30449 the little ACL defined above is used whenever Exim receives a RCPT command
30450 in an SMTP dialogue. The majority of policy tests on incoming messages can be
30451 done when RCPT commands arrive. A rejection of RCPT should cause the
30452 sending MTA to give up on the recipient address contained in the RCPT
30453 command, whereas rejection at other times may cause the client MTA to keep on
30454 trying to deliver the message. It is therefore recommended that you do as much
30455 testing as possible at RCPT time.
30458 .section "The non-SMTP ACLs" "SECID190"
30459 .cindex "non-SMTP messages" "ACLs for"
30460 The non-SMTP ACLs apply to all non-interactive incoming messages, that is, they
30461 apply to batched SMTP as well as to non-SMTP messages. (Batched SMTP is not
30462 really SMTP.) Many of the ACL conditions (for example, host tests, and tests on
30463 the state of the SMTP connection such as encryption and authentication) are not
30464 relevant and are forbidden in these ACLs. However, the sender and recipients
30465 are known, so the &%senders%& and &%sender_domains%& conditions and the
30466 &$sender_address$& and &$recipients$& variables can be used. Variables such as
30467 &$authenticated_sender$& are also available. You can specify added header lines
30468 in any of these ACLs.
30470 The &%acl_not_smtp_start%& ACL is run right at the start of receiving a
30471 non-SMTP message, before any of the message has been read. (This is the
30472 analogue of the &%acl_smtp_predata%& ACL for SMTP input.) In the case of
30473 batched SMTP input, it runs after the DATA command has been reached. The
30474 result of this ACL is ignored; it cannot be used to reject a message. If you
30475 really need to, you could set a value in an ACL variable here and reject based
30476 on that in the &%acl_not_smtp%& ACL. However, this ACL can be used to set
30477 controls, and in particular, it can be used to set
30479 control = suppress_local_fixups
30481 This cannot be used in the other non-SMTP ACLs because by the time they are
30482 run, it is too late.
30484 The &%acl_not_smtp_mime%& ACL is available only when Exim is compiled with the
30485 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
30487 The &%acl_not_smtp%& ACL is run just before the &[local_scan()]& function. Any
30488 kind of rejection is treated as permanent, because there is no way of sending a
30489 temporary error for these kinds of message.
30492 .section "The SMTP connect ACL" "SECID191"
30493 .cindex "SMTP" "connection, ACL for"
30494 .oindex &%smtp_banner%&
30495 The ACL test specified by &%acl_smtp_connect%& happens at the start of an SMTP
30496 session, after the test specified by &%host_reject_connection%& (which is now
30497 an anomaly) and any TCP Wrappers testing (if configured). If the connection is
30498 accepted by an &%accept%& verb that has a &%message%& modifier, the contents of
30499 the message override the banner message that is otherwise specified by the
30500 &%smtp_banner%& option.
30502 For tls-on-connect connections, the ACL is run after the TLS connection
30503 is accepted (however, &%host_reject_connection%& is tested before).
30506 .section "The EHLO/HELO ACL" "SECID192"
30507 .cindex "EHLO" "ACL for"
30508 .cindex "HELO" "ACL for"
30509 The ACL test specified by &%acl_smtp_helo%& happens when the client issues an
30510 EHLO or HELO command, after the tests specified by &%helo_accept_junk_hosts%&,
30511 &%helo_allow_chars%&, &%helo_verify_hosts%&, and &%helo_try_verify_hosts%&.
30512 Note that a client may issue more than one EHLO or HELO command in an SMTP
30513 session, and indeed is required to issue a new EHLO or HELO after successfully
30514 setting up encryption following a STARTTLS command.
30516 Note also that a deny neither forces the client to go away nor means that
30517 mail will be refused on the connection. Consider checking for
30518 &$sender_helo_name$& being defined in a MAIL or RCPT ACL to do that.
30520 If the command is accepted by an &%accept%& verb that has a &%message%&
30521 modifier, the message may not contain more than one line (it will be truncated
30522 at the first newline and a panic logged if it does). Such a message cannot
30523 affect the EHLO options that are listed on the second and subsequent lines of
30527 .section "The DATA ACLs" "SECID193"
30528 .cindex "DATA" "ACLs for"
30529 Two ACLs are associated with the DATA command, because it is two-stage
30530 command, with two responses being sent to the client.
30531 When the DATA command is received, the ACL defined by &%acl_smtp_predata%&
30532 is obeyed. This gives you control after all the RCPT commands, but before
30533 the message itself is received. It offers the opportunity to give a negative
30534 response to the DATA command before the data is transmitted. Header lines
30535 added by MAIL or RCPT ACLs are not visible at this time, but any that
30536 are defined here are visible when the &%acl_smtp_data%& ACL is run.
30538 You cannot test the contents of the message, for example, to verify addresses
30539 in the headers, at RCPT time or when the DATA command is received. Such
30540 tests have to appear in the ACL that is run after the message itself has been
30541 received, before the final response to the DATA command is sent. This is
30542 the ACL specified by &%acl_smtp_data%&, which is the second ACL that is
30543 associated with the DATA command.
30545 .cindex CHUNKING "BDAT command"
30546 .cindex BDAT "SMTP command"
30547 .cindex "RFC 3030" CHUNKING
30548 If CHUNKING was advertised and a BDAT command sequence is received,
30549 the &%acl_smtp_predata%& ACL is not run.
30550 . XXX why not? It should be possible, for the first BDAT.
30551 The &%acl_smtp_data%& is run after the last BDAT command and all of
30552 the data specified is received.
30554 For both of these ACLs, it is not possible to reject individual recipients. An
30555 error response rejects the entire message. Unfortunately, it is known that some
30556 MTAs do not treat hard (5&'xx'&) responses to the DATA command (either
30557 before or after the data) correctly &-- they keep the message on their queues
30558 and try again later, but that is their problem, though it does waste some of
30561 The &%acl_smtp_data%& ACL is run after
30562 the &%acl_smtp_data_prdr%&,
30563 the &%acl_smtp_dkim%&
30564 and the &%acl_smtp_mime%& ACLs.
30566 .section "The SMTP DKIM ACL" "SECTDKIMACL"
30567 The &%acl_smtp_dkim%& ACL is available only when Exim is compiled with DKIM support
30568 enabled (which is the default).
30570 The ACL test specified by &%acl_smtp_dkim%& happens after a message has been
30571 received, and is executed for each DKIM signature found in a message. If not
30572 otherwise specified, the default action is to accept.
30574 This ACL is evaluated before &%acl_smtp_mime%& and &%acl_smtp_data%&.
30576 For details on the operation of DKIM, see section &<<SECDKIM>>&.
30579 .section "The SMTP MIME ACL" "SECID194"
30580 The &%acl_smtp_mime%& option is available only when Exim is compiled with the
30581 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
30583 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
30586 .section "The SMTP PRDR ACL" "SECTPRDRACL"
30587 .cindex "PRDR" "ACL for"
30588 .oindex "&%prdr_enable%&"
30589 The &%acl_smtp_data_prdr%& ACL is available only when Exim is compiled
30590 with PRDR support enabled (which is the default).
30591 It becomes active only when the PRDR feature is negotiated between
30592 client and server for a message, and more than one recipient
30595 The ACL test specified by &%acl_smtp_data_prdr%& happens after a message
30596 has been received, and is executed once for each recipient of the message
30597 with &$local_part$& and &$domain$& valid.
30598 The test may accept, defer or deny for individual recipients.
30599 The &%acl_smtp_data%& will still be called after this ACL and
30600 can reject the message overall, even if this ACL has accepted it
30601 for some or all recipients.
30603 PRDR may be used to support per-user content filtering. Without it
30604 one must defer any recipient after the first that has a different
30605 content-filter configuration. With PRDR, the RCPT-time check
30606 .cindex "PRDR" "variable for"
30607 for this can be disabled when the variable &$prdr_requested$&
30609 Any required difference in behaviour of the main DATA-time
30610 ACL should however depend on the PRDR-time ACL having run, as Exim
30611 will avoid doing so in some situations (e.g. single-recipient mails).
30613 See also the &%prdr_enable%& global option
30614 and the &%hosts_try_prdr%& smtp transport option.
30616 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
30617 If the ACL is not defined, processing completes as if
30618 the feature was not requested by the client.
30620 .section "The QUIT ACL" "SECTQUITACL"
30621 .cindex "QUIT, ACL for"
30622 The ACL for the SMTP QUIT command is anomalous, in that the outcome of the ACL
30623 does not affect the response code to QUIT, which is always 221. Thus, the ACL
30624 does not in fact control any access.
30625 For this reason, it may only accept
30626 or warn as its final result.
30628 This ACL can be used for tasks such as custom logging at the end of an SMTP
30629 session. For example, you can use ACL variables in other ACLs to count
30630 messages, recipients, etc., and log the totals at QUIT time using one or
30631 more &%logwrite%& modifiers on a &%warn%& verb.
30633 &*Warning*&: Only the &$acl_c$&&'x'& variables can be used for this, because
30634 the &$acl_m$&&'x'& variables are reset at the end of each incoming message.
30636 You do not need to have a final &%accept%&, but if you do, you can use a
30637 &%message%& modifier to specify custom text that is sent as part of the 221
30640 This ACL is run only for a &"normal"& QUIT. For certain kinds of disastrous
30641 failure (for example, failure to open a log file, or when Exim is bombing out
30642 because it has detected an unrecoverable error), all SMTP commands from the
30643 client are given temporary error responses until QUIT is received or the
30644 connection is closed. In these special cases, the QUIT ACL does not run.
30647 .section "The not-QUIT ACL" "SECTNOTQUITACL"
30648 .vindex &$acl_smtp_notquit$&
30649 The not-QUIT ACL, specified by &%acl_smtp_notquit%&, is run in most cases when
30650 an SMTP session ends without sending QUIT. However, when Exim itself is in bad
30651 trouble, such as being unable to write to its log files, this ACL is not run,
30652 because it might try to do things (such as write to log files) that make the
30653 situation even worse.
30655 Like the QUIT ACL, this ACL is provided to make it possible to do customized
30656 logging or to gather statistics, and its outcome is ignored. The &%delay%&
30657 modifier is forbidden in this ACL, and the only permitted verbs are &%accept%&
30660 .vindex &$smtp_notquit_reason$&
30661 When the not-QUIT ACL is running, the variable &$smtp_notquit_reason$& is set
30662 to a string that indicates the reason for the termination of the SMTP
30663 connection. The possible values are:
30665 .irow &`acl-drop`& "Another ACL issued a &%drop%& command"
30666 .irow &`bad-commands`& "Too many unknown or non-mail commands"
30667 .irow &`command-timeout`& "Timeout while reading SMTP commands"
30668 .irow &`connection-lost`& "The SMTP connection has been lost"
30669 .irow &`data-timeout`& "Timeout while reading message data"
30670 .irow &`local-scan-error`& "The &[local_scan()]& function crashed"
30671 .irow &`local-scan-timeout`& "The &[local_scan()]& function timed out"
30672 .irow &`signal-exit`& "SIGTERM or SIGINT"
30673 .irow &`synchronization-error`& "SMTP synchronization error"
30674 .irow &`tls-failed`& "TLS failed to start"
30676 In most cases when an SMTP connection is closed without having received QUIT,
30677 Exim sends an SMTP response message before actually closing the connection.
30678 With the exception of the &`acl-drop`& case, the default message can be
30679 overridden by the &%message%& modifier in the not-QUIT ACL. In the case of a
30680 &%drop%& verb in another ACL, it is the message from the other ACL that is
30684 .section "Finding an ACL to use" "SECID195"
30685 .cindex "&ACL;" "finding which to use"
30686 The value of an &%acl_smtp_%&&'xxx'& option is expanded before use, so
30687 you can use different ACLs in different circumstances. For example,
30689 acl_smtp_rcpt = ${if ={25}{$interface_port} \
30690 {acl_check_rcpt} {acl_check_rcpt_submit} }
30692 In the default configuration file there are some example settings for
30693 providing an RFC 4409 message &"submission"& service on port 587 and
30694 an RFC 8314 &"submissions"& service on port 465. You can use a string
30695 expansion like this to choose an ACL for MUAs on these ports which is
30696 more appropriate for this purpose than the default ACL on port 25.
30698 The expanded string does not have to be the name of an ACL in the
30699 configuration file; there are other possibilities. Having expanded the
30700 string, Exim searches for an ACL as follows:
30703 If the string begins with a slash, Exim uses it as a filename, and reads its
30704 contents as an ACL. The lines are processed in the same way as lines in the
30705 Exim configuration file. In particular, continuation lines are supported, blank
30706 lines are ignored, as are lines whose first non-whitespace character is &"#"&.
30707 If the file does not exist or cannot be read, an error occurs (typically
30708 causing a temporary failure of whatever caused the ACL to be run). For example:
30710 acl_smtp_data = /etc/acls/\
30711 ${lookup{$sender_host_address}lsearch\
30712 {/etc/acllist}{$value}{default}}
30714 This looks up an ACL file to use on the basis of the host's IP address, falling
30715 back to a default if the lookup fails. If an ACL is successfully read from a
30716 file, it is retained in memory for the duration of the Exim process, so that it
30717 can be re-used without having to re-read the file.
30719 If the string does not start with a slash, and does not contain any spaces,
30720 Exim searches the ACL section of the configuration for an ACL whose name
30721 matches the string.
30723 If no named ACL is found, or if the string contains spaces, Exim parses
30724 the string as an inline ACL. This can save typing in cases where you just
30725 want to have something like
30727 acl_smtp_vrfy = accept
30729 in order to allow free use of the VRFY command. Such a string may contain
30730 newlines; it is processed in the same way as an ACL that is read from a file.
30736 .section "ACL return codes" "SECID196"
30737 .cindex "&ACL;" "return codes"
30738 Except for the QUIT ACL, which does not affect the SMTP return code (see
30739 section &<<SECTQUITACL>>& above), the result of running an ACL is either
30740 &"accept"& or &"deny"&, or, if some test cannot be completed (for example, if a
30741 database is down), &"defer"&. These results cause 2&'xx'&, 5&'xx'&, and 4&'xx'&
30742 return codes, respectively, to be used in the SMTP dialogue. A fourth return,
30743 &"error"&, occurs when there is an error such as invalid syntax in the ACL.
30744 This also causes a 4&'xx'& return code.
30746 For the non-SMTP ACL, &"defer"& and &"error"& are treated in the same way as
30747 &"deny"&, because there is no mechanism for passing temporary errors to the
30748 submitters of non-SMTP messages.
30751 ACLs that are relevant to message reception may also return &"discard"&. This
30752 has the effect of &"accept"&, but causes either the entire message or an
30753 individual recipient address to be discarded. In other words, it is a
30754 blackholing facility. Use it with care.
30756 If the ACL for MAIL returns &"discard"&, all recipients are discarded, and no
30757 ACL is run for subsequent RCPT commands. The effect of &"discard"& in a
30758 RCPT ACL is to discard just the one recipient address. If there are no
30759 recipients left when the message's data is received, the DATA ACL is not
30760 run. A &"discard"& return from the DATA or the non-SMTP ACL discards all the
30761 remaining recipients. The &"discard"& return is not permitted for the
30762 &%acl_smtp_predata%& ACL.
30764 If the ACL for VRFY returns &"accept"&, a recipient verify (without callout)
30765 is done on the address and the result determines the SMTP response.
30768 .cindex "&[local_scan()]& function" "when all recipients discarded"
30769 The &[local_scan()]& function is always run, even if there are no remaining
30770 recipients; it may create new recipients.
30774 .section "Unset ACL options" "SECID197"
30775 .cindex "&ACL;" "unset options"
30776 The default actions when any of the &%acl_%&&'xxx'& options are unset are not
30777 all the same. &*Note*&: These defaults apply only when the relevant ACL is
30778 not defined at all. For any defined ACL, the default action when control
30779 reaches the end of the ACL statements is &"deny"&.
30781 For &%acl_smtp_quit%& and &%acl_not_smtp_start%& there is no default because
30782 these two are ACLs that are used only for their side effects. They cannot be
30783 used to accept or reject anything.
30785 For &%acl_not_smtp%&, &%acl_smtp_auth%&, &%acl_smtp_connect%&,
30786 &%acl_smtp_data%&, &%acl_smtp_helo%&, &%acl_smtp_mail%&, &%acl_smtp_mailauth%&,
30787 &%acl_smtp_mime%&, &%acl_smtp_predata%&, and &%acl_smtp_starttls%&, the action
30788 when the ACL is not defined is &"accept"&.
30790 For the others (&%acl_smtp_etrn%&, &%acl_smtp_expn%&, &%acl_smtp_rcpt%&, and
30791 &%acl_smtp_vrfy%&), the action when the ACL is not defined is &"deny"&.
30792 This means that &%acl_smtp_rcpt%& must be defined in order to receive any
30793 messages over an SMTP connection. For an example, see the ACL in the default
30794 configuration file.
30799 .section "Data for message ACLs" "SECID198"
30800 .cindex "&ACL;" "data for message ACL"
30802 .vindex &$local_part$&
30803 .vindex &$sender_address$&
30804 .vindex &$sender_host_address$&
30805 .vindex &$smtp_command$&
30806 When a MAIL or RCPT ACL, or either of the DATA ACLs, is running, the variables
30807 that contain information about the host and the message's sender (for example,
30808 &$sender_host_address$& and &$sender_address$&) are set, and can be used in ACL
30809 statements. In the case of RCPT (but not MAIL or DATA), &$domain$& and
30810 &$local_part$& are set from the argument address. The entire SMTP command
30811 is available in &$smtp_command$&.
30813 When an ACL for the AUTH parameter of MAIL is running, the variables that
30814 contain information about the host are set, but &$sender_address$& is not yet
30815 set. Section &<<SECTauthparamail>>& contains a discussion of this parameter and
30818 .vindex "&$message_size$&"
30819 The &$message_size$& variable is set to the value of the SIZE parameter on
30820 the MAIL command at MAIL, RCPT and pre-data time, or to -1 if
30821 that parameter is not given. The value is updated to the true message size by
30822 the time the final DATA ACL is run (after the message data has been
30825 .vindex "&$rcpt_count$&"
30826 .vindex "&$recipients_count$&"
30827 The &$rcpt_count$& variable increases by one for each RCPT command received.
30828 The &$recipients_count$& variable increases by one each time a RCPT command is
30829 accepted, so while an ACL for RCPT is being processed, it contains the number
30830 of previously accepted recipients. At DATA time (for both the DATA ACLs),
30831 &$rcpt_count$& contains the total number of RCPT commands, and
30832 &$recipients_count$& contains the total number of accepted recipients.
30838 .section "Data for non-message ACLs" "SECTdatfornon"
30839 .cindex "&ACL;" "data for non-message ACL"
30840 .vindex &$smtp_command_argument$&
30841 .vindex &$smtp_command$&
30842 When an ACL is being run for AUTH, EHLO, ETRN, EXPN, HELO, STARTTLS, or VRFY,
30843 the remainder of the SMTP command line is placed in &$smtp_command_argument$&,
30844 and the entire SMTP command is available in &$smtp_command$&.
30845 These variables can be tested using a &%condition%& condition. For example,
30846 here is an ACL for use with AUTH, which insists that either the session is
30847 encrypted, or the CRAM-MD5 authentication method is used. In other words, it
30848 does not permit authentication methods that use cleartext passwords on
30849 unencrypted connections.
30852 accept encrypted = *
30853 accept condition = ${if eq{${uc:$smtp_command_argument}}\
30855 deny message = TLS encryption or CRAM-MD5 required
30857 (Another way of applying this restriction is to arrange for the authenticators
30858 that use cleartext passwords not to be advertised when the connection is not
30859 encrypted. You can use the generic &%server_advertise_condition%& authenticator
30860 option to do this.)
30864 .section "Format of an ACL" "SECID199"
30865 .cindex "&ACL;" "format of"
30866 .cindex "&ACL;" "verbs, definition of"
30867 An individual ACL consists of a number of statements. Each statement starts
30868 with a verb, optionally followed by a number of conditions and &"modifiers"&.
30869 Modifiers can change the way the verb operates, define error and log messages,
30870 set variables, insert delays, and vary the processing of accepted messages.
30872 If all the conditions are met, the verb is obeyed. The same condition may be
30873 used (with different arguments) more than once in the same statement. This
30874 provides a means of specifying an &"and"& conjunction between conditions. For
30877 deny dnslists = list1.example
30878 dnslists = list2.example
30880 If there are no conditions, the verb is always obeyed. Exim stops evaluating
30881 the conditions and modifiers when it reaches a condition that fails. What
30882 happens then depends on the verb (and in one case, on a special modifier). Not
30883 all the conditions make sense at every testing point. For example, you cannot
30884 test a sender address in the ACL that is run for a VRFY command.
30887 .section "ACL verbs" "SECID200"
30888 The ACL verbs are as follows:
30891 .cindex "&%accept%& ACL verb"
30892 &%accept%&: If all the conditions are met, the ACL returns &"accept"&. If any
30893 of the conditions are not met, what happens depends on whether &%endpass%&
30894 appears among the conditions (for syntax see below). If the failing condition
30895 is before &%endpass%&, control is passed to the next ACL statement; if it is
30896 after &%endpass%&, the ACL returns &"deny"&. Consider this statement, used to
30897 check a RCPT command:
30899 accept domains = +local_domains
30903 If the recipient domain does not match the &%domains%& condition, control
30904 passes to the next statement. If it does match, the recipient is verified, and
30905 the command is accepted if verification succeeds. However, if verification
30906 fails, the ACL yields &"deny"&, because the failing condition is after
30909 The &%endpass%& feature has turned out to be confusing to many people, so its
30910 use is not recommended nowadays. It is always possible to rewrite an ACL so
30911 that &%endpass%& is not needed, and it is no longer used in the default
30914 .cindex "&%message%& ACL modifier" "with &%accept%&"
30915 If a &%message%& modifier appears on an &%accept%& statement, its action
30916 depends on whether or not &%endpass%& is present. In the absence of &%endpass%&
30917 (when an &%accept%& verb either accepts or passes control to the next
30918 statement), &%message%& can be used to vary the message that is sent when an
30919 SMTP command is accepted. For example, in a RCPT ACL you could have:
30921 &`accept `&<&'some conditions'&>
30922 &` message = OK, I will allow you through today`&
30924 You can specify an SMTP response code, optionally followed by an &"extended
30925 response code"& at the start of the message, but the first digit must be the
30926 same as would be sent by default, which is 2 for an &%accept%& verb.
30928 If &%endpass%& is present in an &%accept%& statement, &%message%& specifies
30929 an error message that is used when access is denied. This behaviour is retained
30930 for backward compatibility, but current &"best practice"& is to avoid the use
30935 .cindex "&%defer%& ACL verb"
30936 &%defer%&: If all the conditions are true, the ACL returns &"defer"& which, in
30937 an SMTP session, causes a 4&'xx'& response to be given. For a non-SMTP ACL,
30938 &%defer%& is the same as &%deny%&, because there is no way of sending a
30939 temporary error. For a RCPT command, &%defer%& is much the same as using a
30940 &(redirect)& router and &`:defer:`& while verifying, but the &%defer%& verb can
30941 be used in any ACL, and even for a recipient it might be a simpler approach.
30945 .cindex "&%deny%& ACL verb"
30946 &%deny%&: If all the conditions are met, the ACL returns &"deny"&. If any of
30947 the conditions are not met, control is passed to the next ACL statement. For
30950 deny dnslists = blackholes.mail-abuse.org
30952 rejects commands from hosts that are on a DNS black list.
30956 .cindex "&%discard%& ACL verb"
30957 &%discard%&: This verb behaves like &%accept%&, except that it returns
30958 &"discard"& from the ACL instead of &"accept"&. It is permitted only on ACLs
30959 that are concerned with receiving messages. When all the conditions are true,
30960 the sending entity receives a &"success"& response. However, &%discard%& causes
30961 recipients to be discarded. If it is used in an ACL for RCPT, just the one
30962 recipient is discarded; if used for MAIL, DATA or in the non-SMTP ACL, all the
30963 message's recipients are discarded. Recipients that are discarded before DATA
30964 do not appear in the log line when the &%received_recipients%& log selector is set.
30966 If the &%log_message%& modifier is set when &%discard%& operates,
30967 its contents are added to the line that is automatically written to the log.
30968 The &%message%& modifier operates exactly as it does for &%accept%&.
30972 .cindex "&%drop%& ACL verb"
30973 &%drop%&: This verb behaves like &%deny%&, except that an SMTP connection is
30974 forcibly closed after the 5&'xx'& error message has been sent. For example:
30976 drop condition = ${if > {$rcpt_count}{20}}
30977 message = I don't take more than 20 RCPTs
30979 There is no difference between &%deny%& and &%drop%& for the connect-time ACL.
30980 The connection is always dropped after sending a 550 response.
30983 .cindex "&%require%& ACL verb"
30984 &%require%&: If all the conditions are met, control is passed to the next ACL
30985 statement. If any of the conditions are not met, the ACL returns &"deny"&. For
30986 example, when checking a RCPT command,
30988 require message = Sender did not verify
30991 passes control to subsequent statements only if the message's sender can be
30992 verified. Otherwise, it rejects the command. Note the positioning of the
30993 &%message%& modifier, before the &%verify%& condition. The reason for this is
30994 discussed in section &<<SECTcondmodproc>>&.
30997 .cindex "&%warn%& ACL verb"
30998 &%warn%&: If all the conditions are true, a line specified by the
30999 &%log_message%& modifier is written to Exim's main log. Control always passes
31000 to the next ACL statement. If any condition is false, the log line is not
31001 written. If an identical log line is requested several times in the same
31002 message, only one copy is actually written to the log. If you want to force
31003 duplicates to be written, use the &%logwrite%& modifier instead.
31005 If &%log_message%& is not present, a &%warn%& verb just checks its conditions
31006 and obeys any &"immediate"& modifiers (such as &%control%&, &%set%&,
31007 &%logwrite%&, &%add_header%&, and &%remove_header%&) that appear before the
31008 first failing condition. There is more about adding header lines in section
31009 &<<SECTaddheadacl>>&.
31011 If any condition on a &%warn%& statement cannot be completed (that is, there is
31012 some sort of defer), the log line specified by &%log_message%& is not written.
31013 This does not include the case of a forced failure from a lookup, which
31014 is considered to be a successful completion. After a defer, no further
31015 conditions or modifiers in the &%warn%& statement are processed. The incident
31016 is logged, and the ACL continues to be processed, from the next statement
31020 .vindex "&$acl_verify_message$&"
31021 When one of the &%warn%& conditions is an address verification that fails, the
31022 text of the verification failure message is in &$acl_verify_message$&. If you
31023 want this logged, you must set it up explicitly. For example:
31025 warn !verify = sender
31026 log_message = sender verify failed: $acl_verify_message
31030 At the end of each ACL there is an implicit unconditional &%deny%&.
31032 As you can see from the examples above, the conditions and modifiers are
31033 written one to a line, with the first one on the same line as the verb, and
31034 subsequent ones on following lines. If you have a very long condition, you can
31035 continue it onto several physical lines by the usual backslash continuation
31036 mechanism. It is conventional to align the conditions vertically.
31040 .section "ACL variables" "SECTaclvariables"
31041 .cindex "&ACL;" "variables"
31042 There are some special variables that can be set during ACL processing. They
31043 can be used to pass information between different ACLs, different invocations
31044 of the same ACL in the same SMTP connection, and between ACLs and the routers,
31045 transports, and filters that are used to deliver a message. The names of these
31046 variables must begin with &$acl_c$& or &$acl_m$&, followed either by a digit or
31047 an underscore, but the remainder of the name can be any sequence of
31048 alphanumeric characters and underscores that you choose. There is no limit on
31049 the number of ACL variables. The two sets act as follows:
31051 The values of those variables whose names begin with &$acl_c$& persist
31052 throughout an SMTP connection. They are never reset. Thus, a value that is set
31053 while receiving one message is still available when receiving the next message
31054 on the same SMTP connection.
31056 The values of those variables whose names begin with &$acl_m$& persist only
31057 while a message is being received. They are reset afterwards. They are also
31058 reset by MAIL, RSET, EHLO, HELO, and after starting up a TLS session.
31061 When a message is accepted, the current values of all the ACL variables are
31062 preserved with the message and are subsequently made available at delivery
31063 time. The ACL variables are set by a modifier called &%set%&. For example:
31065 accept hosts = whatever
31066 set acl_m4 = some value
31067 accept authenticated = *
31068 set acl_c_auth = yes
31070 &*Note*&: A leading dollar sign is not used when naming a variable that is to
31071 be set. If you want to set a variable without taking any action, you can use a
31072 &%warn%& verb without any other modifiers or conditions.
31074 .oindex &%strict_acl_vars%&
31075 What happens if a syntactically valid but undefined ACL variable is
31076 referenced depends on the setting of the &%strict_acl_vars%& option. If it is
31077 false (the default), an empty string is substituted; if it is true, an
31078 error is generated.
31080 Versions of Exim before 4.64 have a limited set of numbered variables, but
31081 their names are compatible, so there is no problem with upgrading.
31084 .section "Condition and modifier processing" "SECTcondmodproc"
31085 .cindex "&ACL;" "conditions; processing"
31086 .cindex "&ACL;" "modifiers; processing"
31087 An exclamation mark preceding a condition negates its result. For example:
31089 deny domains = *.dom.example
31090 !verify = recipient
31092 causes the ACL to return &"deny"& if the recipient domain ends in
31093 &'dom.example'& and the recipient address cannot be verified. Sometimes
31094 negation can be used on the right-hand side of a condition. For example, these
31095 two statements are equivalent:
31097 deny hosts = !192.168.3.4
31098 deny !hosts = 192.168.3.4
31100 However, for many conditions (&%verify%& being a good example), only left-hand
31101 side negation of the whole condition is possible.
31103 The arguments of conditions and modifiers are expanded. A forced failure
31104 of an expansion causes a condition to be ignored, that is, it behaves as if the
31105 condition is true. Consider these two statements:
31107 accept senders = ${lookup{$host_name}lsearch\
31108 {/some/file}{$value}fail}
31109 accept senders = ${lookup{$host_name}lsearch\
31110 {/some/file}{$value}{}}
31112 Each attempts to look up a list of acceptable senders. If the lookup succeeds,
31113 the returned list is searched, but if the lookup fails the behaviour is
31114 different in the two cases. The &%fail%& in the first statement causes the
31115 condition to be ignored, leaving no further conditions. The &%accept%& verb
31116 therefore succeeds. The second statement, however, generates an empty list when
31117 the lookup fails. No sender can match an empty list, so the condition fails,
31118 and therefore the &%accept%& also fails.
31120 ACL modifiers appear mixed in with conditions in ACL statements. Some of them
31121 specify actions that are taken as the conditions for a statement are checked;
31122 others specify text for messages that are used when access is denied or a
31123 warning is generated. The &%control%& modifier affects the way an incoming
31124 message is handled.
31126 The positioning of the modifiers in an ACL statement is important, because the
31127 processing of a verb ceases as soon as its outcome is known. Only those
31128 modifiers that have already been encountered will take effect. For example,
31129 consider this use of the &%message%& modifier:
31131 require message = Can't verify sender
31133 message = Can't verify recipient
31135 message = This message cannot be used
31137 If sender verification fails, Exim knows that the result of the statement is
31138 &"deny"&, so it goes no further. The first &%message%& modifier has been seen,
31139 so its text is used as the error message. If sender verification succeeds, but
31140 recipient verification fails, the second message is used. If recipient
31141 verification succeeds, the third message becomes &"current"&, but is never used
31142 because there are no more conditions to cause failure.
31144 For the &%deny%& verb, on the other hand, it is always the last &%message%&
31145 modifier that is used, because all the conditions must be true for rejection to
31146 happen. Specifying more than one &%message%& modifier does not make sense, and
31147 the message can even be specified after all the conditions. For example:
31150 !senders = *@my.domain.example
31151 message = Invalid sender from client host
31153 The &"deny"& result does not happen until the end of the statement is reached,
31154 by which time Exim has set up the message.
31158 .section "ACL modifiers" "SECTACLmodi"
31159 .cindex "&ACL;" "modifiers; list of"
31160 The ACL modifiers are as follows:
31163 .vitem &*add_header*&&~=&~<&'text'&>
31164 This modifier specifies one or more header lines that are to be added to an
31165 incoming message, assuming, of course, that the message is ultimately
31166 accepted. For details, see section &<<SECTaddheadacl>>&.
31168 .vitem &*continue*&&~=&~<&'text'&>
31169 .cindex "&%continue%& ACL modifier"
31170 .cindex "database" "updating in ACL"
31171 This modifier does nothing of itself, and processing of the ACL always
31172 continues with the next condition or modifier. The value of &%continue%& is in
31173 the side effects of expanding its argument. Typically this could be used to
31174 update a database. It is really just a syntactic tidiness, to avoid having to
31175 write rather ugly lines like this:
31177 &`condition = ${if eq{0}{`&<&'some expansion'&>&`}{true}{true}}`&
31179 Instead, all you need is
31181 &`continue = `&<&'some expansion'&>
31184 .vitem &*control*&&~=&~<&'text'&>
31185 .cindex "&%control%& ACL modifier"
31186 This modifier affects the subsequent processing of the SMTP connection or of an
31187 incoming message that is accepted. The effect of the first type of control
31188 lasts for the duration of the connection, whereas the effect of the second type
31189 lasts only until the current message has been received. The message-specific
31190 controls always apply to the whole message, not to individual recipients,
31191 even if the &%control%& modifier appears in a RCPT ACL.
31193 As there are now quite a few controls that can be applied, they are described
31194 separately in section &<<SECTcontrols>>&. The &%control%& modifier can be used
31195 in several different ways. For example:
31197 . ==== As this is a nested list, any displays it contains must be indented
31198 . ==== as otherwise they are too far to the left. That comment applies only
31199 . ==== when xmlto and fop are used; formatting with sdop gets it right either
31203 It can be at the end of an &%accept%& statement:
31205 accept ...some conditions
31208 In this case, the control is applied when this statement yields &"accept"&, in
31209 other words, when the conditions are all true.
31212 It can be in the middle of an &%accept%& statement:
31214 accept ...some conditions...
31216 ...some more conditions...
31218 If the first set of conditions are true, the control is applied, even if the
31219 statement does not accept because one of the second set of conditions is false.
31220 In this case, some subsequent statement must yield &"accept"& for the control
31224 It can be used with &%warn%& to apply the control, leaving the
31225 decision about accepting or denying to a subsequent verb. For
31228 warn ...some conditions...
31232 This example of &%warn%& does not contain &%message%&, &%log_message%&, or
31233 &%logwrite%&, so it does not add anything to the message and does not write a
31237 If you want to apply a control unconditionally, you can use it with a
31238 &%require%& verb. For example:
31240 require control = no_multiline_responses
31244 .vitem &*delay*&&~=&~<&'time'&>
31245 .cindex "&%delay%& ACL modifier"
31247 This modifier may appear in any ACL except notquit. It causes Exim to wait for
31248 the time interval before proceeding. However, when testing Exim using the
31249 &%-bh%& option, the delay is not actually imposed (an appropriate message is
31250 output instead). The time is given in the usual Exim notation, and the delay
31251 happens as soon as the modifier is processed. In an SMTP session, pending
31252 output is flushed before the delay is imposed.
31254 Like &%control%&, &%delay%& can be used with &%accept%& or &%deny%&, for
31257 deny ...some conditions...
31260 The delay happens if all the conditions are true, before the statement returns
31261 &"deny"&. Compare this with:
31264 ...some conditions...
31266 which waits for 30s before processing the conditions. The &%delay%& modifier
31267 can also be used with &%warn%& and together with &%control%&:
31269 warn ...some conditions...
31275 If &%delay%& is encountered when the SMTP PIPELINING extension is in use,
31276 responses to several commands are no longer buffered and sent in one packet (as
31277 they would normally be) because all output is flushed before imposing the
31278 delay. This optimization is disabled so that a number of small delays do not
31279 appear to the client as one large aggregated delay that might provoke an
31280 unwanted timeout. You can, however, disable output flushing for &%delay%& by
31281 using a &%control%& modifier to set &%no_delay_flush%&.
31285 .cindex "&%endpass%& ACL modifier"
31286 This modifier, which has no argument, is recognized only in &%accept%& and
31287 &%discard%& statements. It marks the boundary between the conditions whose
31288 failure causes control to pass to the next statement, and the conditions whose
31289 failure causes the ACL to return &"deny"&. This concept has proved to be
31290 confusing to some people, so the use of &%endpass%& is no longer recommended as
31291 &"best practice"&. See the description of &%accept%& above for more details.
31294 .vitem &*log_message*&&~=&~<&'text'&>
31295 .cindex "&%log_message%& ACL modifier"
31296 This modifier sets up a message that is used as part of the log message if the
31297 ACL denies access or a &%warn%& statement's conditions are true. For example:
31299 require log_message = wrong cipher suite $tls_in_cipher
31300 encrypted = DES-CBC3-SHA
31302 &%log_message%& is also used when recipients are discarded by &%discard%&. For
31305 &`discard `&<&'some conditions'&>
31306 &` log_message = Discarded $local_part@$domain because...`&
31308 When access is denied, &%log_message%& adds to any underlying error message
31309 that may exist because of a condition failure. For example, while verifying a
31310 recipient address, a &':fail:'& redirection might have already set up a
31313 The message may be defined before the conditions to which it applies, because
31314 the string expansion does not happen until Exim decides that access is to be
31315 denied. This means that any variables that are set by the condition are
31316 available for inclusion in the message. For example, the &$dnslist_$&<&'xxx'&>
31317 variables are set after a DNS black list lookup succeeds. If the expansion of
31318 &%log_message%& fails, or if the result is an empty string, the modifier is
31321 .vindex "&$acl_verify_message$&"
31322 If you want to use a &%warn%& statement to log the result of an address
31323 verification, you can use &$acl_verify_message$& to include the verification
31326 If &%log_message%& is used with a &%warn%& statement, &"Warning:"& is added to
31327 the start of the logged message. If the same warning log message is requested
31328 more than once while receiving a single email message, only one copy is
31329 actually logged. If you want to log multiple copies, use &%logwrite%& instead
31330 of &%log_message%&. In the absence of &%log_message%& and &%logwrite%&, nothing
31331 is logged for a successful &%warn%& statement.
31333 If &%log_message%& is not present and there is no underlying error message (for
31334 example, from the failure of address verification), but &%message%& is present,
31335 the &%message%& text is used for logging rejections. However, if any text for
31336 logging contains newlines, only the first line is logged. In the absence of
31337 both &%log_message%& and &%message%&, a default built-in message is used for
31338 logging rejections.
31341 .vitem "&*log_reject_target*&&~=&~<&'log name list'&>"
31342 .cindex "&%log_reject_target%& ACL modifier"
31343 .cindex "logging in ACL" "specifying which log"
31344 This modifier makes it possible to specify which logs are used for messages
31345 about ACL rejections. Its argument is a colon-separated list of words that can
31346 be &"main"&, &"reject"&, or &"panic"&. The default is &`main:reject`&. The list
31347 may be empty, in which case a rejection is not logged at all. For example, this
31348 ACL fragment writes no logging information when access is denied:
31350 &`deny `&<&'some conditions'&>
31351 &` log_reject_target =`&
31353 This modifier can be used in SMTP and non-SMTP ACLs. It applies to both
31354 permanent and temporary rejections. Its effect lasts for the rest of the
31358 .vitem &*logwrite*&&~=&~<&'text'&>
31359 .cindex "&%logwrite%& ACL modifier"
31360 .cindex "logging in ACL" "immediate"
31361 This modifier writes a message to a log file as soon as it is encountered when
31362 processing an ACL. (Compare &%log_message%&, which, except in the case of
31363 &%warn%& and &%discard%&, is used only if the ACL statement denies
31364 access.) The &%logwrite%& modifier can be used to log special incidents in
31367 &`accept `&<&'some special conditions'&>
31368 &` control = freeze`&
31369 &` logwrite = froze message because ...`&
31371 By default, the message is written to the main log. However, it may begin
31372 with a colon, followed by a comma-separated list of log names, and then
31373 another colon, to specify exactly which logs are to be written. For
31376 logwrite = :main,reject: text for main and reject logs
31377 logwrite = :panic: text for panic log only
31381 .vitem &*message*&&~=&~<&'text'&>
31382 .cindex "&%message%& ACL modifier"
31383 This modifier sets up a text string that is expanded and used as a response
31384 message when an ACL statement terminates the ACL with an &"accept"&, &"deny"&,
31385 or &"defer"& response. (In the case of the &%accept%& and &%discard%& verbs,
31386 there is some complication if &%endpass%& is involved; see the description of
31387 &%accept%& for details.)
31389 The expansion of the message happens at the time Exim decides that the ACL is
31390 to end, not at the time it processes &%message%&. If the expansion fails, or
31391 generates an empty string, the modifier is ignored. Here is an example where
31392 &%message%& must be specified first, because the ACL ends with a rejection if
31393 the &%hosts%& condition fails:
31395 require message = Host not recognized
31398 (Once a condition has failed, no further conditions or modifiers are
31401 .cindex "SMTP" "error codes"
31402 .oindex "&%smtp_banner%&
31403 For ACLs that are triggered by SMTP commands, the message is returned as part
31404 of the SMTP response. The use of &%message%& with &%accept%& (or &%discard%&)
31405 is meaningful only for SMTP, as no message is returned when a non-SMTP message
31406 is accepted. In the case of the connect ACL, accepting with a message modifier
31407 overrides the value of &%smtp_banner%&. For the EHLO/HELO ACL, a customized
31408 accept message may not contain more than one line (otherwise it will be
31409 truncated at the first newline and a panic logged), and it cannot affect the
31412 When SMTP is involved, the message may begin with an overriding response code,
31413 consisting of three digits optionally followed by an &"extended response code"&
31414 of the form &'n.n.n'&, each code being followed by a space. For example:
31416 deny message = 599 1.2.3 Host not welcome
31417 hosts = 192.168.34.0/24
31419 The first digit of the supplied response code must be the same as would be sent
31420 by default. A panic occurs if it is not. Exim uses a 550 code when it denies
31421 access, but for the predata ACL, note that the default success code is 354, not
31424 Notwithstanding the previous paragraph, for the QUIT ACL, unlike the others,
31425 the message modifier cannot override the 221 response code.
31427 The text in a &%message%& modifier is literal; any quotes are taken as
31428 literals, but because the string is expanded, backslash escapes are processed
31429 anyway. If the message contains newlines, this gives rise to a multi-line SMTP
31432 .vindex "&$acl_verify_message$&"
31433 While the text is being expanded, the &$acl_verify_message$& variable
31434 contains any message previously set.
31435 Afterwards, &$acl_verify_message$& is cleared.
31437 If &%message%& is used on a statement that verifies an address, the message
31438 specified overrides any message that is generated by the verification process.
31439 However, the original message is available in the variable
31440 &$acl_verify_message$&, so you can incorporate it into your message if you
31441 wish. In particular, if you want the text from &%:fail:%& items in &(redirect)&
31442 routers to be passed back as part of the SMTP response, you should either not
31443 use a &%message%& modifier, or make use of &$acl_verify_message$&.
31445 For compatibility with previous releases of Exim, a &%message%& modifier that
31446 is used with a &%warn%& verb behaves in a similar way to the &%add_header%&
31447 modifier, but this usage is now deprecated. However, &%message%& acts only when
31448 all the conditions are true, wherever it appears in an ACL command, whereas
31449 &%add_header%& acts as soon as it is encountered. If &%message%& is used with
31450 &%warn%& in an ACL that is not concerned with receiving a message, it has no
31454 .vitem &*queue*&&~=&~<&'text'&>
31455 .cindex "&%queue%& ACL modifier"
31456 .cindex "named queues" "selecting in ACL"
31457 This modifier specifies the use of a named queue for spool files
31459 It can only be used before the message is received (i.e. not in
31461 This could be used, for example, for known high-volume burst sources
31462 of traffic, or for quarantine of messages.
31463 Separate queue-runner processes will be needed for named queues.
31464 If the text after expansion is empty, the default queue is used.
31467 .vitem &*remove_header*&&~=&~<&'text'&>
31468 This modifier specifies one or more header names in a colon-separated list
31469 that are to be removed from an incoming message, assuming, of course, that
31470 the message is ultimately accepted. For details, see section &<<SECTremoveheadacl>>&.
31473 .vitem &*set*&&~<&'acl_name'&>&~=&~<&'value'&>
31474 .cindex "&%set%& ACL modifier"
31475 This modifier puts a value into one of the ACL variables (see section
31476 &<<SECTaclvariables>>&).
31479 .vitem &*udpsend*&&~=&~<&'parameters'&>
31480 .cindex "UDP communications"
31481 This modifier sends a UDP packet, for purposes such as statistics
31482 collection or behaviour monitoring. The parameters are expanded, and
31483 the result of the expansion must be a colon-separated list consisting
31484 of a destination server, port number, and the packet contents. The
31485 server can be specified as a host name or IPv4 or IPv6 address. The
31486 separator can be changed with the usual angle bracket syntax. For
31487 example, you might want to collect information on which hosts connect
31490 udpsend = <; 2001:dB8::dead:beef ; 1234 ;\
31491 $tod_zulu $sender_host_address
31498 .section "Use of the control modifier" "SECTcontrols"
31499 .cindex "&%control%& ACL modifier"
31500 The &%control%& modifier supports the following settings:
31503 .vitem &*control&~=&~allow_auth_unadvertised*&
31504 This modifier allows a client host to use the SMTP AUTH command even when it
31505 has not been advertised in response to EHLO. Furthermore, because there are
31506 apparently some really broken clients that do this, Exim will accept AUTH after
31507 HELO (rather than EHLO) when this control is set. It should be used only if you
31508 really need it, and you should limit its use to those broken clients that do
31509 not work without it. For example:
31511 warn hosts = 192.168.34.25
31512 control = allow_auth_unadvertised
31514 Normally, when an Exim server receives an AUTH command, it checks the name of
31515 the authentication mechanism that is given in the command to ensure that it
31516 matches an advertised mechanism. When this control is set, the check that a
31517 mechanism has been advertised is bypassed. Any configured mechanism can be used
31518 by the client. This control is permitted only in the connection and HELO ACLs.
31521 .vitem &*control&~=&~caseful_local_part*& &&&
31522 &*control&~=&~caselower_local_part*&
31523 .cindex "&ACL;" "case of local part in"
31524 .cindex "case of local parts"
31525 .vindex "&$local_part$&"
31526 These two controls are permitted only in the ACL specified by &%acl_smtp_rcpt%&
31527 (that is, during RCPT processing). By default, the contents of &$local_part$&
31528 are lower cased before ACL processing. If &"caseful_local_part"& is specified,
31529 any uppercase letters in the original local part are restored in &$local_part$&
31530 for the rest of the ACL, or until a control that sets &"caselower_local_part"&
31533 These controls affect only the current recipient. Moreover, they apply only to
31534 local part handling that takes place directly in the ACL (for example, as a key
31535 in lookups). If a test to verify the recipient is obeyed, the case-related
31536 handling of the local part during the verification is controlled by the router
31537 configuration (see the &%caseful_local_part%& generic router option).
31539 This facility could be used, for example, to add a spam score to local parts
31540 containing upper case letters. For example, using &$acl_m4$& to accumulate the
31543 warn control = caseful_local_part
31544 set acl_m4 = ${eval:\
31546 ${if match{$local_part}{[A-Z]}{1}{0}}\
31548 control = caselower_local_part
31550 Notice that we put back the lower cased version afterwards, assuming that
31551 is what is wanted for subsequent tests.
31554 .vitem &*control&~=&~cutthrough_delivery/*&<&'options'&>
31555 .cindex "&ACL;" "cutthrough routing"
31556 .cindex "cutthrough" "requesting"
31557 This option requests delivery be attempted while the item is being received.
31559 The option is usable in the RCPT ACL.
31560 If enabled for a message received via smtp and routed to an smtp transport,
31561 and only one transport, interface, destination host and port combination
31562 is used for all recipients of the message,
31563 then the delivery connection is made while the receiving connection is open
31564 and data is copied from one to the other.
31566 An attempt to set this option for any recipient but the first
31567 for a mail will be quietly ignored.
31568 If a recipient-verify callout
31570 connection is subsequently
31571 requested in the same ACL it is held open and used for
31572 any subsequent recipients and the data,
31573 otherwise one is made after the initial RCPT ACL completes.
31575 Note that routers are used in verify mode,
31576 and cannot depend on content of received headers.
31577 Note also that headers cannot be
31578 modified by any of the post-data ACLs (DATA, MIME and DKIM).
31579 Headers may be modified by routers (subject to the above) and transports.
31580 The &'Received-By:'& header is generated as soon as the body reception starts,
31581 rather than the traditional time after the full message is received;
31582 this will affect the timestamp.
31584 All the usual ACLs are called; if one results in the message being
31585 rejected, all effort spent in delivery (including the costs on
31586 the ultimate destination) will be wasted.
31587 Note that in the case of data-time ACLs this includes the entire
31590 Cutthrough delivery is not supported via transport-filters or when DKIM signing
31591 of outgoing messages is done, because it sends data to the ultimate destination
31592 before the entire message has been received from the source.
31593 It is not supported for messages received with the SMTP PRDR
31597 Should the ultimate destination system positively accept or reject the mail,
31598 a corresponding indication is given to the source system and nothing is queued.
31599 If the item is successfully delivered in cutthrough mode
31600 the delivery log lines are tagged with ">>" rather than "=>" and appear
31601 before the acceptance "<=" line.
31603 If there is a temporary error the item is queued for later delivery in the
31605 This behaviour can be adjusted by appending the option &*defer=*&<&'value'&>
31606 to the control; the default value is &"spool"& and the alternate value
31607 &"pass"& copies an SMTP defer response from the target back to the initiator
31608 and does not queue the message.
31609 Note that this is independent of any recipient verify conditions in the ACL.
31611 Delivery in this mode avoids the generation of a bounce mail to a
31613 sender when the destination system is doing content-scan based rejection.
31616 .vitem &*control&~=&~debug/*&<&'options'&>
31617 .cindex "&ACL;" "enabling debug logging"
31618 .cindex "debugging" "enabling from an ACL"
31619 This control turns on debug logging, almost as though Exim had been invoked
31620 with &`-d`&, with the output going to a new logfile in the usual logs directory,
31621 by default called &'debuglog'&.
31623 Logging set up by the control will be maintained across spool residency.
31625 Options are a slash-separated list.
31626 If an option takes an argument, the option name and argument are separated by
31627 an equals character.
31628 Several options are supported:
31630 tag=<&'suffix'&> The filename can be adjusted with thise option.
31631 The argument, which may access any variables already defined,
31632 is appended to the default name.
31634 opts=<&'debug&~options'&> The argument specififes what is to be logged,
31635 using the same values as the &`-d`& command-line option.
31637 stop Logging started with this control may be
31638 stopped by using this option.
31640 kill Logging started with this control may be
31641 stopped by using this option.
31642 Additionally the debug file will be removed,
31643 providing one means for speculative debug tracing.
31645 pretrigger=<&'size'&> This option specifies a memory buffuer to be used
31646 for pre-trigger debug capture.
31647 Debug lines are recorded in the buffer until
31648 and if) a trigger occurs; at which time they are
31649 dumped to the debug file. Newer lines displace the
31650 oldest if the buffer is full. After a trigger,
31651 immediate writes to file are done as normal.
31653 trigger=<&'reason'&> This option selects cause for the pretrigger buffer
31654 see above) to be copied to file. A reason of $*now*
31655 take effect immediately; one of &*paniclog*& triggers
31656 on a write to the panic log.
31659 Some examples (which depend on variables that don't exist in all
31663 control = debug/tag=.$sender_host_address
31664 control = debug/opts=+expand+acl
31665 control = debug/tag=.$message_exim_id/opts=+expand
31666 control = debug/kill
31667 control = debug/opts=+all/pretrigger=1024/trigger=paniclog
31668 control = debug/trigger=now
31672 .vitem &*control&~=&~dkim_disable_verify*&
31673 .cindex "disable DKIM verify"
31674 .cindex "DKIM" "disable verify"
31675 This control turns off DKIM verification processing entirely. For details on
31676 the operation and configuration of DKIM, see section &<<SECDKIM>>&.
31679 .vitem &*control&~=&~dmarc_disable_verify*&
31680 .cindex "disable DMARC verify"
31681 .cindex "DMARC" "disable verify"
31682 This control turns off DMARC verification processing entirely. For details on
31683 the operation and configuration of DMARC, see section &<<SECDMARC>>&.
31686 .vitem &*control&~=&~dscp/*&<&'value'&>
31687 .cindex "&ACL;" "setting DSCP value"
31688 .cindex "DSCP" "inbound"
31689 This option causes the DSCP value associated with the socket for the inbound
31690 connection to be adjusted to a given value, given as one of a number of fixed
31691 strings or to numeric value.
31692 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
31693 Common values include &`throughput`&, &`mincost`&, and on newer systems
31694 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
31696 The outbound packets from Exim will be marked with this value in the header
31697 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
31698 that these values will have any effect, not be stripped by networking
31699 equipment, or do much of anything without cooperation with your Network
31700 Engineer and those of all network operators between the source and destination.
31703 .vitem &*control&~=&~enforce_sync*& &&&
31704 &*control&~=&~no_enforce_sync*&
31705 .cindex "SMTP" "synchronization checking"
31706 .cindex "synchronization checking in SMTP"
31707 These controls make it possible to be selective about when SMTP synchronization
31708 is enforced. The global option &%smtp_enforce_sync%& specifies the initial
31709 state of the switch (it is true by default). See the description of this option
31710 in chapter &<<CHAPmainconfig>>& for details of SMTP synchronization checking.
31712 The effect of these two controls lasts for the remainder of the SMTP
31713 connection. They can appear in any ACL except the one for the non-SMTP
31714 messages. The most straightforward place to put them is in the ACL defined by
31715 &%acl_smtp_connect%&, which is run at the start of an incoming SMTP connection,
31716 before the first synchronization check. The expected use is to turn off the
31717 synchronization checks for badly-behaved hosts that you nevertheless need to
31721 .vitem &*control&~=&~fakedefer/*&<&'message'&>
31722 .cindex "fake defer"
31723 .cindex "defer, fake"
31724 This control works in exactly the same way as &%fakereject%& (described below)
31725 except that it causes an SMTP 450 response after the message data instead of a
31726 550 response. You must take care when using &%fakedefer%& because it causes the
31727 messages to be duplicated when the sender retries. Therefore, you should not
31728 use &%fakedefer%& if the message is to be delivered normally.
31730 .vitem &*control&~=&~fakereject/*&<&'message'&>
31731 .cindex "fake rejection"
31732 .cindex "rejection, fake"
31733 This control is permitted only for the MAIL, RCPT, and DATA ACLs, in other
31734 words, only when an SMTP message is being received. If Exim accepts the
31735 message, instead the final 250 response, a 550 rejection message is sent.
31736 However, Exim proceeds to deliver the message as normal. The control applies
31737 only to the current message, not to any subsequent ones that may be received in
31738 the same SMTP connection.
31740 The text for the 550 response is taken from the &%control%& modifier. If no
31741 message is supplied, the following is used:
31743 550-Your message has been rejected but is being
31744 550-kept for evaluation.
31745 550-If it was a legitimate message, it may still be
31746 550 delivered to the target recipient(s).
31748 This facility should be used with extreme caution.
31750 .vitem &*control&~=&~freeze*&
31751 .cindex "frozen messages" "forcing in ACL"
31752 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
31753 other words, only when a message is being received. If the message is accepted,
31754 it is placed on Exim's queue and frozen. The control applies only to the
31755 current message, not to any subsequent ones that may be received in the same
31758 This modifier can optionally be followed by &`/no_tell`&. If the global option
31759 &%freeze_tell%& is set, it is ignored for the current message (that is, nobody
31760 is told about the freezing), provided all the &*control=freeze*& modifiers that
31761 are obeyed for the current message have the &`/no_tell`& option.
31763 .vitem &*control&~=&~no_delay_flush*&
31764 .cindex "SMTP" "output flushing, disabling for delay"
31765 Exim normally flushes SMTP output before implementing a delay in an ACL, to
31766 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
31767 use. This control, as long as it is encountered before the &%delay%& modifier,
31768 disables such output flushing.
31770 .vitem &*control&~=&~no_callout_flush*&
31771 .cindex "SMTP" "output flushing, disabling for callout"
31772 Exim normally flushes SMTP output before performing a callout in an ACL, to
31773 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
31774 use. This control, as long as it is encountered before the &%verify%& condition
31775 that causes the callout, disables such output flushing.
31777 .vitem &*control&~=&~no_mbox_unspool*&
31778 This control is available when Exim is compiled with the content scanning
31779 extension. Content scanning may require a copy of the current message, or parts
31780 of it, to be written in &"mbox format"& to a spool file, for passing to a virus
31781 or spam scanner. Normally, such copies are deleted when they are no longer
31782 needed. If this control is set, the copies are not deleted. The control applies
31783 only to the current message, not to any subsequent ones that may be received in
31784 the same SMTP connection. It is provided for debugging purposes and is unlikely
31785 to be useful in production.
31787 .vitem &*control&~=&~no_multiline_responses*&
31788 .cindex "multiline responses, suppressing"
31789 This control is permitted for any ACL except the one for non-SMTP messages.
31790 It seems that there are broken clients in use that cannot handle multiline
31791 SMTP responses, despite the fact that RFC 821 defined them over 20 years ago.
31793 If this control is set, multiline SMTP responses from ACL rejections are
31794 suppressed. One way of doing this would have been to put out these responses as
31795 one long line. However, RFC 2821 specifies a maximum of 512 bytes per response
31796 (&"use multiline responses for more"& it says &-- ha!), and some of the
31797 responses might get close to that. So this facility, which is after all only a
31798 sop to broken clients, is implemented by doing two very easy things:
31801 Extra information that is normally output as part of a rejection caused by
31802 sender verification failure is omitted. Only the final line (typically &"sender
31803 verification failed"&) is sent.
31805 If a &%message%& modifier supplies a multiline response, only the first
31809 The setting of the switch can, of course, be made conditional on the
31810 calling host. Its effect lasts until the end of the SMTP connection.
31812 .vitem &*control&~=&~no_pipelining*&
31813 .cindex "PIPELINING" "suppressing advertising"
31814 .cindex "ESMTP extensions" PIPELINING
31815 This control turns off the advertising of the PIPELINING extension to SMTP in
31816 the current session. To be useful, it must be obeyed before Exim sends its
31817 response to an EHLO command. Therefore, it should normally appear in an ACL
31818 controlled by &%acl_smtp_connect%& or &%acl_smtp_helo%&. See also
31819 &%pipelining_advertise_hosts%&.
31821 .vitem &*control&~=&~queue/*&<&'options'&>* &&&
31822 &*control&~=&~queue_only*&
31823 .oindex "&%queue%&"
31824 .oindex "&%queue_only%&"
31825 .cindex "queueing incoming messages"
31826 .cindex queueing "forcing in ACL"
31827 .cindex "first pass routing"
31828 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
31829 other words, only when a message is being received. If the message is accepted,
31830 it is placed on Exim's queue and left there for delivery by a subsequent queue
31832 If used with no options set,
31833 no immediate delivery process is started. In other words, it has the
31834 effect as the &%queue_only%& global option or &'-odq'& command-line option.
31836 If the &'first_pass_route'& option is given then
31837 the behaviour is like the command-line &'-oqds'& option;
31838 a delivery process is started which stops short of making
31839 any SMTP delivery. The benefit is that the hints database will be updated for
31840 the message being waiting for a specific host, and a later queue run will be
31841 able to send all such messages on a single connection.
31843 The control only applies to the current message, not to any subsequent ones that
31844 may be received in the same SMTP connection.
31846 .vitem &*control&~=&~submission/*&<&'options'&>
31847 .cindex "message" "submission"
31848 .cindex "submission mode"
31849 This control is permitted only for the MAIL, RCPT, and start of data ACLs (the
31850 latter is the one defined by &%acl_smtp_predata%&). Setting it tells Exim that
31851 the current message is a submission from a local MUA. In this case, Exim
31852 operates in &"submission mode"&, and applies certain fixups to the message if
31853 necessary. For example, it adds a &'Date:'& header line if one is not present.
31854 This control is not permitted in the &%acl_smtp_data%& ACL, because that is too
31855 late (the message has already been created).
31857 Chapter &<<CHAPmsgproc>>& describes the processing that Exim applies to
31858 messages. Section &<<SECTsubmodnon>>& covers the processing that happens in
31859 submission mode; the available options for this control are described there.
31860 The control applies only to the current message, not to any subsequent ones
31861 that may be received in the same SMTP connection.
31863 .vitem &*control&~=&~suppress_local_fixups*&
31864 .cindex "submission fixups, suppressing"
31865 This control applies to locally submitted (non TCP/IP) messages, and is the
31866 complement of &`control = submission`&. It disables the fixups that are
31867 normally applied to locally-submitted messages. Specifically:
31870 Any &'Sender:'& header line is left alone (in this respect, it is a
31871 dynamic version of &%local_sender_retain%&).
31873 No &'Message-ID:'&, &'From:'&, or &'Date:'& header lines are added.
31875 There is no check that &'From:'& corresponds to the actual sender.
31878 This control may be useful when a remotely-originated message is accepted,
31879 passed to some scanning program, and then re-submitted for delivery. It can be
31880 used only in the &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
31881 and &%acl_not_smtp_start%& ACLs, because it has to be set before the message's
31884 &*Note:*& This control applies only to the current message, not to any others
31885 that are being submitted at the same time using &%-bs%& or &%-bS%&.
31887 .vitem &*control&~=&~utf8_downconvert*&
31888 This control enables conversion of UTF-8 in message envelope addresses
31890 For details see section &<<SECTi18nMTA>>&.
31894 .section "Summary of message fixup control" "SECTsummesfix"
31895 All four possibilities for message fixups can be specified:
31898 Locally submitted, fixups applied: the default.
31900 Locally submitted, no fixups applied: use
31901 &`control = suppress_local_fixups`&.
31903 Remotely submitted, no fixups applied: the default.
31905 Remotely submitted, fixups applied: use &`control = submission`&.
31910 .section "Adding header lines in ACLs" "SECTaddheadacl"
31911 .cindex "header lines" "adding in an ACL"
31912 .cindex "header lines" "position of added lines"
31913 .cindex "&%add_header%& ACL modifier"
31914 The &%add_header%& modifier can be used to add one or more extra header lines
31915 to an incoming message, as in this example:
31917 warn dnslists = sbl.spamhaus.org : \
31918 dialup.mail-abuse.org
31919 add_header = X-blacklisted-at: $dnslist_domain
31921 The &%add_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
31922 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
31923 receiving a message). The message must ultimately be accepted for
31924 &%add_header%& to have any significant effect. You can use &%add_header%& with
31925 any ACL verb, including &%deny%& (though this is potentially useful only in a
31928 Headers will not be added to the message if the modifier is used in
31929 DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing.
31931 Leading and trailing newlines are removed from
31932 the data for the &%add_header%& modifier; if it then
31933 contains one or more newlines that
31934 are not followed by a space or a tab, it is assumed to contain multiple header
31935 lines. Each one is checked for valid syntax; &`X-ACL-Warn:`& is added to the
31936 front of any line that is not a valid header line.
31938 Added header lines are accumulated during the MAIL, RCPT, and predata ACLs.
31939 They are added to the message before processing the DATA and MIME ACLs.
31940 However, if an identical header line is requested more than once, only one copy
31941 is actually added to the message. Further header lines may be accumulated
31942 during the DATA and MIME ACLs, after which they are added to the message, again
31943 with duplicates suppressed. Thus, it is possible to add two identical header
31944 lines to an SMTP message, but only if one is added before DATA and one after.
31945 In the case of non-SMTP messages, new headers are accumulated during the
31946 non-SMTP ACLs, and are added to the message after all the ACLs have run. If a
31947 message is rejected after DATA or by the non-SMTP ACL, all added header lines
31948 are included in the entry that is written to the reject log.
31950 .cindex "header lines" "added; visibility of"
31951 Header lines are not visible in string expansions
31953 until they are added to the
31954 message. It follows that header lines defined in the MAIL, RCPT, and predata
31955 ACLs are not visible until the DATA ACL and MIME ACLs are run. Similarly,
31956 header lines that are added by the DATA or MIME ACLs are not visible in those
31957 ACLs. Because of this restriction, you cannot use header lines as a way of
31958 passing data between (for example) the MAIL and RCPT ACLs. If you want to do
31959 this, you can use ACL variables, as described in section
31960 &<<SECTaclvariables>>&.
31962 The list of headers yet to be added is given by the &%$headers_added%& variable.
31964 The &%add_header%& modifier acts immediately as it is encountered during the
31965 processing of an ACL. Notice the difference between these two cases:
31967 &`accept add_header = ADDED: some text`&
31968 &` `&<&'some condition'&>
31970 &`accept `&<&'some condition'&>
31971 &` add_header = ADDED: some text`&
31973 In the first case, the header line is always added, whether or not the
31974 condition is true. In the second case, the header line is added only if the
31975 condition is true. Multiple occurrences of &%add_header%& may occur in the same
31976 ACL statement. All those that are encountered before a condition fails are
31979 .cindex "&%warn%& ACL verb"
31980 For compatibility with previous versions of Exim, a &%message%& modifier for a
31981 &%warn%& verb acts in the same way as &%add_header%&, except that it takes
31982 effect only if all the conditions are true, even if it appears before some of
31983 them. Furthermore, only the last occurrence of &%message%& is honoured. This
31984 usage of &%message%& is now deprecated. If both &%add_header%& and &%message%&
31985 are present on a &%warn%& verb, both are processed according to their
31988 By default, new header lines are added to a message at the end of the existing
31989 header lines. However, you can specify that any particular header line should
31990 be added right at the start (before all the &'Received:'& lines), immediately
31991 after the first block of &'Received:'& lines, or immediately before any line
31992 that is not a &'Received:'& or &'Resent-something:'& header.
31994 This is done by specifying &":at_start:"&, &":after_received:"&, or
31995 &":at_start_rfc:"& (or, for completeness, &":at_end:"&) before the text of the
31996 header line, respectively. (Header text cannot start with a colon, as there has
31997 to be a header name first.) For example:
31999 warn add_header = \
32000 :after_received:X-My-Header: something or other...
32002 If more than one header line is supplied in a single &%add_header%& modifier,
32003 each one is treated independently and can therefore be placed differently. If
32004 you add more than one line at the start, or after the Received: block, they end
32005 up in reverse order.
32007 &*Warning*&: This facility currently applies only to header lines that are
32008 added in an ACL. It does NOT work for header lines that are added in a
32009 system filter or in a router or transport.
32013 .section "Removing header lines in ACLs" "SECTremoveheadacl"
32014 .cindex "header lines" "removing in an ACL"
32015 .cindex "header lines" "position of removed lines"
32016 .cindex "&%remove_header%& ACL modifier"
32017 The &%remove_header%& modifier can be used to remove one or more header lines
32018 from an incoming message, as in this example:
32020 warn message = Remove internal headers
32021 remove_header = x-route-mail1 : x-route-mail2
32023 The &%remove_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
32024 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
32025 receiving a message). The message must ultimately be accepted for
32026 &%remove_header%& to have any significant effect. You can use &%remove_header%&
32027 with any ACL verb, including &%deny%&, though this is really not useful for
32028 any verb that doesn't result in a delivered message.
32030 Headers will not be removed from the message if the modifier is used in
32031 DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing.
32033 More than one header can be removed at the same time by using a colon separated
32034 list of header names. The header matching is case insensitive. Wildcards are
32035 not permitted, nor is list expansion performed, so you cannot use hostlists to
32036 create a list of headers, however both connection and message variable expansion
32037 are performed (&%$acl_c_*%& and &%$acl_m_*%&), illustrated in this example:
32039 warn hosts = +internal_hosts
32040 set acl_c_ihdrs = x-route-mail1 : x-route-mail2
32041 warn message = Remove internal headers
32042 remove_header = $acl_c_ihdrs
32044 Header names for removal are accumulated during the MAIL, RCPT, and predata ACLs.
32045 Matching header lines are removed from the message before processing the DATA and MIME ACLs.
32046 If multiple header lines match, all are removed.
32047 There is no harm in attempting to remove the same header twice nor in removing
32048 a non-existent header. Further header lines to be removed may be accumulated
32049 during the DATA and MIME ACLs, after which they are removed from the message,
32050 if present. In the case of non-SMTP messages, headers to be removed are
32051 accumulated during the non-SMTP ACLs, and are removed from the message after
32052 all the ACLs have run. If a message is rejected after DATA or by the non-SMTP
32053 ACL, there really is no effect because there is no logging of what headers
32054 would have been removed.
32056 .cindex "header lines" "removed; visibility of"
32057 Header lines are not visible in string expansions until the DATA phase when it
32058 is received. Any header lines removed in the MAIL, RCPT, and predata ACLs are
32059 not visible in the DATA ACL and MIME ACLs. Similarly, header lines that are
32060 removed by the DATA or MIME ACLs are still visible in those ACLs. Because of
32061 this restriction, you cannot use header lines as a way of controlling data
32062 passed between (for example) the MAIL and RCPT ACLs. If you want to do this,
32063 you should instead use ACL variables, as described in section
32064 &<<SECTaclvariables>>&.
32066 The &%remove_header%& modifier acts immediately as it is encountered during the
32067 processing of an ACL. Notice the difference between these two cases:
32069 &`accept remove_header = X-Internal`&
32070 &` `&<&'some condition'&>
32072 &`accept `&<&'some condition'&>
32073 &` remove_header = X-Internal`&
32075 In the first case, the header line is always removed, whether or not the
32076 condition is true. In the second case, the header line is removed only if the
32077 condition is true. Multiple occurrences of &%remove_header%& may occur in the
32078 same ACL statement. All those that are encountered before a condition fails
32081 &*Warning*&: This facility currently applies only to header lines that are
32082 present during ACL processing. It does NOT remove header lines that are added
32083 in a system filter or in a router or transport.
32088 .section "ACL conditions" "SECTaclconditions"
32089 .cindex "&ACL;" "conditions; list of"
32090 Some of the conditions listed in this section are available only when Exim is
32091 compiled with the content-scanning extension. They are included here briefly
32092 for completeness. More detailed descriptions can be found in the discussion on
32093 content scanning in chapter &<<CHAPexiscan>>&.
32095 Not all conditions are relevant in all circumstances. For example, testing
32096 senders and recipients does not make sense in an ACL that is being run as the
32097 result of the arrival of an ETRN command, and checks on message headers can be
32098 done only in the ACLs specified by &%acl_smtp_data%& and &%acl_not_smtp%&. You
32099 can use the same condition (with different parameters) more than once in the
32100 same ACL statement. This provides a way of specifying an &"and"& conjunction.
32101 The conditions are as follows:
32105 .vitem &*acl&~=&~*&<&'name&~of&~acl&~or&~ACL&~string&~or&~file&~name&~'&>
32106 .cindex "&ACL;" "nested"
32107 .cindex "&ACL;" "indirect"
32108 .cindex "&ACL;" "arguments"
32109 .cindex "&%acl%& ACL condition"
32110 The possible values of the argument are the same as for the
32111 &%acl_smtp_%&&'xxx'& options. The named or inline ACL is run. If it returns
32112 &"accept"& the condition is true; if it returns &"deny"& the condition is
32113 false. If it returns &"defer"&, the current ACL returns &"defer"& unless the
32114 condition is on a &%warn%& verb. In that case, a &"defer"& return makes the
32115 condition false. This means that further processing of the &%warn%& verb
32116 ceases, but processing of the ACL continues.
32118 If the argument is a named ACL, up to nine space-separated optional values
32119 can be appended; they appear within the called ACL in $acl_arg1 to $acl_arg9,
32120 and $acl_narg is set to the count of values.
32121 Previous values of these variables are restored after the call returns.
32122 The name and values are expanded separately.
32123 Note that spaces in complex expansions which are used as arguments
32124 will act as argument separators.
32126 If the nested &%acl%& returns &"drop"& and the outer condition denies access,
32127 the connection is dropped. If it returns &"discard"&, the verb must be
32128 &%accept%& or &%discard%&, and the action is taken immediately &-- no further
32129 conditions are tested.
32131 ACLs may be nested up to 20 deep; the limit exists purely to catch runaway
32132 loops. This condition allows you to use different ACLs in different
32133 circumstances. For example, different ACLs can be used to handle RCPT commands
32134 for different local users or different local domains.
32136 .vitem &*authenticated&~=&~*&<&'string&~list'&>
32137 .cindex "&%authenticated%& ACL condition"
32138 .cindex "authentication" "ACL checking"
32139 .cindex "&ACL;" "testing for authentication"
32140 If the SMTP connection is not authenticated, the condition is false. Otherwise,
32141 the name of the authenticator is tested against the list. To test for
32142 authentication by any authenticator, you can set
32147 .vitem &*condition&~=&~*&<&'string'&>
32148 .cindex "&%condition%& ACL condition"
32149 .cindex "customizing" "ACL condition"
32150 .cindex "&ACL;" "customized test"
32151 .cindex "&ACL;" "testing, customized"
32152 This feature allows you to make up custom conditions. If the result of
32153 expanding the string is an empty string, the number zero, or one of the strings
32154 &"no"& or &"false"&, the condition is false. If the result is any non-zero
32155 number, or one of the strings &"yes"& or &"true"&, the condition is true. For
32156 any other value, some error is assumed to have occurred, and the ACL returns
32157 &"defer"&. However, if the expansion is forced to fail, the condition is
32158 ignored. The effect is to treat it as true, whether it is positive or
32161 .vitem &*decode&~=&~*&<&'location'&>
32162 .cindex "&%decode%& ACL condition"
32163 This condition is available only when Exim is compiled with the
32164 content-scanning extension, and it is allowed only in the ACL defined by
32165 &%acl_smtp_mime%&. It causes the current MIME part to be decoded into a file.
32166 If all goes well, the condition is true. It is false only if there are
32167 problems such as a syntax error or a memory shortage. For more details, see
32168 chapter &<<CHAPexiscan>>&.
32170 .vitem &*dnslists&~=&~*&<&'list&~of&~domain&~names&~and&~other&~data'&>
32171 .cindex "&%dnslists%& ACL condition"
32172 .cindex "DNS list" "in ACL"
32173 .cindex "black list (DNS)"
32174 .cindex "&ACL;" "testing a DNS list"
32175 This condition checks for entries in DNS black lists. These are also known as
32176 &"RBL lists"&, after the original Realtime Blackhole List, but note that the
32177 use of the lists at &'mail-abuse.org'& now carries a charge. There are too many
32178 different variants of this condition to describe briefly here. See sections
32179 &<<SECTmorednslists>>&&--&<<SECTmorednslistslast>>& for details.
32181 .vitem &*domains&~=&~*&<&'domain&~list'&>
32182 .cindex "&%domains%& ACL condition"
32183 .cindex "domain" "ACL checking"
32184 .cindex "&ACL;" "testing a recipient domain"
32185 .vindex "&$domain_data$&"
32186 This condition is relevant only in a RCPT ACL. It checks that the domain
32187 of the recipient address is in the domain list. If percent-hack processing is
32188 enabled, it is done before this test is done. If the check succeeds with a
32189 lookup, the result of the lookup is placed in &$domain_data$& until the next
32192 &*Note carefully*& (because many people seem to fall foul of this): you cannot
32193 use &%domains%& in a DATA ACL.
32196 .vitem &*encrypted&~=&~*&<&'string&~list'&>
32197 .cindex "&%encrypted%& ACL condition"
32198 .cindex "encryption" "checking in an ACL"
32199 .cindex "&ACL;" "testing for encryption"
32200 If the SMTP connection is not encrypted, the condition is false. Otherwise, the
32201 name of the cipher suite in use is tested against the list. To test for
32202 encryption without testing for any specific cipher suite(s), set
32208 .vitem &*hosts&~=&~*&<&'host&~list'&>
32209 .cindex "&%hosts%& ACL condition"
32210 .cindex "host" "ACL checking"
32211 .cindex "&ACL;" "testing the client host"
32212 This condition tests that the calling host matches the host list. If you have
32213 name lookups or wildcarded host names and IP addresses in the same host list,
32214 you should normally put the IP addresses first. For example, you could have:
32216 accept hosts = 10.9.8.7 : dbm;/etc/friendly/hosts
32218 The lookup in this example uses the host name for its key. This is implied by
32219 the lookup type &"dbm"&. (For a host address lookup you would use &"net-dbm"&
32220 and it wouldn't matter which way round you had these two items.)
32222 The reason for the problem with host names lies in the left-to-right way that
32223 Exim processes lists. It can test IP addresses without doing any DNS lookups,
32224 but when it reaches an item that requires a host name, it fails if it cannot
32225 find a host name to compare with the pattern. If the above list is given in the
32226 opposite order, the &%accept%& statement fails for a host whose name cannot be
32227 found, even if its IP address is 10.9.8.7.
32229 If you really do want to do the name check first, and still recognize the IP
32230 address even if the name lookup fails, you can rewrite the ACL like this:
32232 accept hosts = dbm;/etc/friendly/hosts
32233 accept hosts = 10.9.8.7
32235 The default action on failing to find the host name is to assume that the host
32236 is not in the list, so the first &%accept%& statement fails. The second
32237 statement can then check the IP address.
32239 .vindex "&$host_data$&"
32240 If a &%hosts%& condition is satisfied by means of a lookup, the result
32241 of the lookup is made available in the &$host_data$& variable. This
32242 allows you, for example, to set up a statement like this:
32244 deny hosts = net-lsearch;/some/file
32245 message = $host_data
32247 which gives a custom error message for each denied host.
32249 .vitem &*local_parts&~=&~*&<&'local&~part&~list'&>
32250 .cindex "&%local_parts%& ACL condition"
32251 .cindex "local part" "ACL checking"
32252 .cindex "&ACL;" "testing a local part"
32253 .vindex "&$local_part_data$&"
32254 This condition is relevant only in a RCPT ACL. It checks that the local
32255 part of the recipient address is in the list. If percent-hack processing is
32256 enabled, it is done before this test. If the check succeeds with a lookup, the
32257 result of the lookup is placed in &$local_part_data$&, which remains set until
32258 the next &%local_parts%& test.
32260 .vitem &*malware&~=&~*&<&'option'&>
32261 .cindex "&%malware%& ACL condition"
32262 .cindex "&ACL;" "virus scanning"
32263 .cindex "&ACL;" "scanning for viruses"
32264 This condition is available only when Exim is compiled with the
32265 content-scanning extension
32266 and only after a DATA command.
32267 It causes the incoming message to be scanned for
32268 viruses. For details, see chapter &<<CHAPexiscan>>&.
32270 .vitem &*mime_regex&~=&~*&<&'list&~of&~regular&~expressions'&>
32271 .cindex "&%mime_regex%& ACL condition"
32272 .cindex "&ACL;" "testing by regex matching"
32273 This condition is available only when Exim is compiled with the
32274 content-scanning extension, and it is allowed only in the ACL defined by
32275 &%acl_smtp_mime%&. It causes the current MIME part to be scanned for a match
32276 with any of the regular expressions. For details, see chapter
32279 .vitem &*ratelimit&~=&~*&<&'parameters'&>
32280 .cindex "rate limiting"
32281 This condition can be used to limit the rate at which a user or host submits
32282 messages. Details are given in section &<<SECTratelimiting>>&.
32284 .vitem &*recipients&~=&~*&<&'address&~list'&>
32285 .cindex "&%recipients%& ACL condition"
32286 .cindex "recipient" "ACL checking"
32287 .cindex "&ACL;" "testing a recipient"
32288 This condition is relevant only in a RCPT ACL. It checks the entire
32289 recipient address against a list of recipients.
32291 .vitem &*regex&~=&~*&<&'list&~of&~regular&~expressions'&>
32292 .cindex "&%regex%& ACL condition"
32293 .cindex "&ACL;" "testing by regex matching"
32294 This condition is available only when Exim is compiled with the
32295 content-scanning extension, and is available only in the DATA, MIME, and
32296 non-SMTP ACLs. It causes the incoming message to be scanned for a match with
32297 any of the regular expressions. For details, see chapter &<<CHAPexiscan>>&.
32299 .vitem &*seen&~=&~*&<&'parameters'&>
32300 .cindex "&%seen%& ACL condition"
32301 This condition can be used to test if a situation has been previously met,
32302 for example for greylisting.
32303 Details are given in section &<<SECTseen>>&.
32305 .vitem &*sender_domains&~=&~*&<&'domain&~list'&>
32306 .cindex "&%sender_domains%& ACL condition"
32307 .cindex "sender" "ACL checking"
32308 .cindex "&ACL;" "testing a sender domain"
32309 .vindex "&$domain$&"
32310 .vindex "&$sender_address_domain$&"
32311 This condition tests the domain of the sender of the message against the given
32312 domain list. &*Note*&: The domain of the sender address is in
32313 &$sender_address_domain$&. It is &'not'& put in &$domain$& during the testing
32314 of this condition. This is an exception to the general rule for testing domain
32315 lists. It is done this way so that, if this condition is used in an ACL for a
32316 RCPT command, the recipient's domain (which is in &$domain$&) can be used to
32317 influence the sender checking.
32319 &*Warning*&: It is a bad idea to use this condition on its own as a control on
32320 relaying, because sender addresses are easily, and commonly, forged.
32322 .vitem &*senders&~=&~*&<&'address&~list'&>
32323 .cindex "&%senders%& ACL condition"
32324 .cindex "sender" "ACL checking"
32325 .cindex "&ACL;" "testing a sender"
32326 This condition tests the sender of the message against the given list. To test
32327 for a bounce message, which has an empty sender, set
32331 &*Warning*&: It is a bad idea to use this condition on its own as a control on
32332 relaying, because sender addresses are easily, and commonly, forged.
32334 .vitem &*spam&~=&~*&<&'username'&>
32335 .cindex "&%spam%& ACL condition"
32336 .cindex "&ACL;" "scanning for spam"
32337 This condition is available only when Exim is compiled with the
32338 content-scanning extension. It causes the incoming message to be scanned by
32339 SpamAssassin. For details, see chapter &<<CHAPexiscan>>&.
32341 .vitem &*verify&~=&~certificate*&
32342 .cindex "&%verify%& ACL condition"
32343 .cindex "TLS" "client certificate verification"
32344 .cindex "certificate" "verification of client"
32345 .cindex "&ACL;" "certificate verification"
32346 .cindex "&ACL;" "testing a TLS certificate"
32347 This condition is true in an SMTP session if the session is encrypted, and a
32348 certificate was received from the client, and the certificate was verified. The
32349 server requests a certificate only if the client matches &%tls_verify_hosts%&
32350 or &%tls_try_verify_hosts%& (see chapter &<<CHAPTLS>>&).
32352 .vitem &*verify&~=&~csa*&
32353 .cindex "CSA verification"
32354 This condition checks whether the sending host (the client) is authorized to
32355 send email. Details of how this works are given in section
32356 &<<SECTverifyCSA>>&.
32358 .vitem &*verify&~=&~header_names_ascii*&
32359 .cindex "&%verify%& ACL condition"
32360 .cindex "&ACL;" "verifying header names only ASCII"
32361 .cindex "header lines" "verifying header names only ASCII"
32362 .cindex "verifying" "header names only ASCII"
32363 This condition is relevant only in an ACL that is run after a message has been
32365 This usually means an ACL specified by &%acl_smtp_data%& or &%acl_not_smtp%&.
32366 It checks all header names (not the content) to make sure
32367 there are no non-ASCII characters, also excluding control characters. The
32368 allowable characters are decimal ASCII values 33 through 126.
32370 Exim itself will handle headers with non-ASCII characters, but it can cause
32371 problems for downstream applications, so this option will allow their
32372 detection and rejection in the DATA ACL's.
32374 .vitem &*verify&~=&~header_sender/*&<&'options'&>
32375 .cindex "&%verify%& ACL condition"
32376 .cindex "&ACL;" "verifying sender in the header"
32377 .cindex "header lines" "verifying the sender in"
32378 .cindex "sender" "verifying in header"
32379 .cindex "verifying" "sender in header"
32380 This condition is relevant only in an ACL that is run after a message has been
32381 received, that is, in an ACL specified by &%acl_smtp_data%& or
32382 &%acl_not_smtp%&. It checks that there is a verifiable address in at least one
32383 of the &'Sender:'&, &'Reply-To:'&, or &'From:'& header lines. Such an address
32384 is loosely thought of as a &"sender"& address (hence the name of the test).
32385 However, an address that appears in one of these headers need not be an address
32386 that accepts bounce messages; only sender addresses in envelopes are required
32387 to accept bounces. Therefore, if you use the callout option on this check, you
32388 might want to arrange for a non-empty address in the MAIL command.
32390 Details of address verification and the options are given later, starting at
32391 section &<<SECTaddressverification>>& (callouts are described in section
32392 &<<SECTcallver>>&). You can combine this condition with the &%senders%&
32393 condition to restrict it to bounce messages only:
32396 !verify = header_sender
32397 message = A valid sender header is required for bounces
32400 .vitem &*verify&~=&~header_syntax*&
32401 .cindex "&%verify%& ACL condition"
32402 .cindex "&ACL;" "verifying header syntax"
32403 .cindex "header lines" "verifying syntax"
32404 .cindex "verifying" "header syntax"
32405 This condition is relevant only in an ACL that is run after a message has been
32406 received, that is, in an ACL specified by &%acl_smtp_data%& or
32407 &%acl_not_smtp%&. It checks the syntax of all header lines that can contain
32408 lists of addresses (&'Sender:'&, &'From:'&, &'Reply-To:'&, &'To:'&, &'Cc:'&,
32409 and &'Bcc:'&), returning true if there are no problems.
32410 Unqualified addresses (local parts without domains) are
32411 permitted only in locally generated messages and from hosts that match
32412 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
32415 Note that this condition is a syntax check only. However, a common spamming
32416 ploy used to be to send syntactically invalid headers such as
32420 and this condition can be used to reject such messages, though they are not as
32421 common as they used to be.
32423 .vitem &*verify&~=&~helo*&
32424 .cindex "&%verify%& ACL condition"
32425 .cindex "&ACL;" "verifying HELO/EHLO"
32426 .cindex "HELO" "verifying"
32427 .cindex "EHLO" "verifying"
32428 .cindex "verifying" "EHLO"
32429 .cindex "verifying" "HELO"
32430 This condition is true if a HELO or EHLO command has been received from the
32431 client host, and its contents have been verified. If there has been no previous
32432 attempt to verify the HELO/EHLO contents, it is carried out when this
32433 condition is encountered. See the description of the &%helo_verify_hosts%& and
32434 &%helo_try_verify_hosts%& options for details of how to request verification
32435 independently of this condition, and for detail of the verification.
32437 For SMTP input that does not come over TCP/IP (the &%-bs%& command line
32438 option), this condition is always true.
32441 .vitem &*verify&~=&~not_blind/*&<&'options'&>
32442 .cindex "verifying" "not blind"
32443 .cindex "bcc recipients, verifying none"
32444 This condition checks that there are no blind (bcc) recipients in the message.
32445 Every envelope recipient must appear either in a &'To:'& header line or in a
32446 &'Cc:'& header line for this condition to be true. Local parts are checked
32447 case-sensitively; domains are checked case-insensitively. If &'Resent-To:'& or
32448 &'Resent-Cc:'& header lines exist, they are also checked. This condition can be
32449 used only in a DATA or non-SMTP ACL.
32451 There is one possible option, &`case_insensitive`&. If this is present then
32452 local parts are checked case-insensitively.
32454 There are, of course, many legitimate messages that make use of blind (bcc)
32455 recipients. This check should not be used on its own for blocking messages.
32458 .vitem &*verify&~=&~recipient/*&<&'options'&>
32459 .cindex "&%verify%& ACL condition"
32460 .cindex "&ACL;" "verifying recipient"
32461 .cindex "recipient" "verifying"
32462 .cindex "verifying" "recipient"
32463 .vindex "&$address_data$&"
32464 This condition is relevant only after a RCPT command. It verifies the current
32465 recipient. Details of address verification are given later, starting at section
32466 &<<SECTaddressverification>>&. After a recipient has been verified, the value
32467 of &$address_data$& is the last value that was set while routing the address.
32468 This applies even if the verification fails. When an address that is being
32469 verified is redirected to a single address, verification continues with the new
32470 address, and in that case, the subsequent value of &$address_data$& is the
32471 value for the child address.
32473 .vitem &*verify&~=&~reverse_host_lookup/*&<&'options'&>
32474 .cindex "&%verify%& ACL condition"
32475 .cindex "&ACL;" "verifying host reverse lookup"
32476 .cindex "host" "verifying reverse lookup"
32477 This condition ensures that a verified host name has been looked up from the IP
32478 address of the client host. (This may have happened already if the host name
32479 was needed for checking a host list, or if the host matched &%host_lookup%&.)
32480 Verification ensures that the host name obtained from a reverse DNS lookup, or
32481 one of its aliases, does, when it is itself looked up in the DNS, yield the
32482 original IP address.
32484 There is one possible option, &`defer_ok`&. If this is present and a
32485 DNS operation returns a temporary error, the verify condition succeeds.
32487 If this condition is used for a locally generated message (that is, when there
32488 is no client host involved), it always succeeds.
32490 .vitem &*verify&~=&~sender/*&<&'options'&>
32491 .cindex "&%verify%& ACL condition"
32492 .cindex "&ACL;" "verifying sender"
32493 .cindex "sender" "verifying"
32494 .cindex "verifying" "sender"
32495 This condition is relevant only after a MAIL or RCPT command, or after a
32496 message has been received (the &%acl_smtp_data%& or &%acl_not_smtp%& ACLs). If
32497 the message's sender is empty (that is, this is a bounce message), the
32498 condition is true. Otherwise, the sender address is verified.
32500 .vindex "&$address_data$&"
32501 .vindex "&$sender_address_data$&"
32502 If there is data in the &$address_data$& variable at the end of routing, its
32503 value is placed in &$sender_address_data$& at the end of verification. This
32504 value can be used in subsequent conditions and modifiers in the same ACL
32505 statement. It does not persist after the end of the current statement. If you
32506 want to preserve the value for longer, you can save it in an ACL variable.
32508 Details of verification are given later, starting at section
32509 &<<SECTaddressverification>>&. Exim caches the result of sender verification,
32510 to avoid doing it more than once per message.
32512 .vitem &*verify&~=&~sender=*&<&'address'&>&*/*&<&'options'&>
32513 .cindex "&%verify%& ACL condition"
32514 This is a variation of the previous option, in which a modified address is
32515 verified as a sender.
32517 Note that '/' is legal in local-parts; if the address may have such
32518 (eg. is generated from the received message)
32519 they must be protected from the options parsing by doubling:
32521 verify = sender=${listquote{/}{${address:$h_sender:}}}
32527 .section "Using DNS lists" "SECTmorednslists"
32528 .cindex "DNS list" "in ACL"
32529 .cindex "black list (DNS)"
32530 .cindex "&ACL;" "testing a DNS list"
32531 In its simplest form, the &%dnslists%& condition tests whether the calling host
32532 is on at least one of a number of DNS lists by looking up the inverted IP
32533 address in one or more DNS domains. (Note that DNS list domains are not mail
32534 domains, so the &`+`& syntax for named lists doesn't work - it is used for
32535 special options instead.) For example, if the calling host's IP
32536 address is 192.168.62.43, and the ACL statement is
32538 deny dnslists = blackholes.mail-abuse.org : \
32539 dialups.mail-abuse.org
32541 the following records are looked up:
32543 43.62.168.192.blackholes.mail-abuse.org
32544 43.62.168.192.dialups.mail-abuse.org
32546 As soon as Exim finds an existing DNS record, processing of the list stops.
32547 Thus, multiple entries on the list provide an &"or"& conjunction. If you want
32548 to test that a host is on more than one list (an &"and"& conjunction), you can
32549 use two separate conditions:
32551 deny dnslists = blackholes.mail-abuse.org
32552 dnslists = dialups.mail-abuse.org
32554 If a DNS lookup times out or otherwise fails to give a decisive answer, Exim
32555 behaves as if the host does not match the list item, that is, as if the DNS
32556 record does not exist. If there are further items in the DNS list, they are
32559 This is usually the required action when &%dnslists%& is used with &%deny%&
32560 (which is the most common usage), because it prevents a DNS failure from
32561 blocking mail. However, you can change this behaviour by putting one of the
32562 following special items in the list:
32563 .itable none 0 0 2 25* left 75* left
32564 .irow "+include_unknown" "behave as if the item is on the list"
32565 .irow "+exclude_unknown" "behave as if the item is not on the list (default)"
32566 .irow "+defer_unknown " "give a temporary error"
32568 .cindex "&`+include_unknown`&"
32569 .cindex "&`+exclude_unknown`&"
32570 .cindex "&`+defer_unknown`&"
32571 Each of these applies to any subsequent items on the list. For example:
32573 deny dnslists = +defer_unknown : foo.bar.example
32575 Testing the list of domains stops as soon as a match is found. If you want to
32576 warn for one list and block for another, you can use two different statements:
32578 deny dnslists = blackholes.mail-abuse.org
32579 warn dnslists = dialups.mail-abuse.org
32580 message = X-Warn: sending host is on dialups list
32582 .cindex caching "of dns lookup"
32584 DNS list lookups are cached by Exim for the duration of the SMTP session
32585 (but limited by the DNS return TTL value),
32586 so a lookup based on the IP address is done at most once for any incoming
32587 connection (assuming long-enough TTL).
32588 Exim does not share information between multiple incoming
32589 connections (but your local name server cache should be active).
32591 There are a number of DNS lists to choose from, some commercial, some free,
32592 or free for small deployments. An overview can be found at
32593 &url(https://en.wikipedia.org/wiki/Comparison_of_DNS_blacklists).
32597 .section "Specifying the IP address for a DNS list lookup" "SECID201"
32598 .cindex "DNS list" "keyed by explicit IP address"
32599 By default, the IP address that is used in a DNS list lookup is the IP address
32600 of the calling host. However, you can specify another IP address by listing it
32601 after the domain name, introduced by a slash. For example:
32603 deny dnslists = black.list.tld/192.168.1.2
32605 This feature is not very helpful with explicit IP addresses; it is intended for
32606 use with IP addresses that are looked up, for example, the IP addresses of the
32607 MX hosts or nameservers of an email sender address. For an example, see section
32608 &<<SECTmulkeyfor>>& below.
32613 .section "DNS lists keyed on domain names" "SECID202"
32614 .cindex "DNS list" "keyed by domain name"
32615 There are some lists that are keyed on domain names rather than inverted IP
32616 addresses (see, e.g., the &'domain based zones'& link at
32617 &url(http://www.rfc-ignorant.org/)). No reversing of components is used
32618 with these lists. You can change the name that is looked up in a DNS list by
32619 listing it after the domain name, introduced by a slash. For example,
32621 deny dnslists = dsn.rfc-ignorant.org/$sender_address_domain
32622 message = Sender's domain is listed at $dnslist_domain
32624 This particular example is useful only in ACLs that are obeyed after the
32625 RCPT or DATA commands, when a sender address is available. If (for
32626 example) the message's sender is &'user@tld.example'& the name that is looked
32627 up by this example is
32629 tld.example.dsn.rfc-ignorant.org
32631 A single &%dnslists%& condition can contain entries for both names and IP
32632 addresses. For example:
32634 deny dnslists = sbl.spamhaus.org : \
32635 dsn.rfc-ignorant.org/$sender_address_domain
32637 The first item checks the sending host's IP address; the second checks a domain
32638 name. The whole condition is true if either of the DNS lookups succeeds.
32643 .section "Multiple explicit keys for a DNS list" "SECTmulkeyfor"
32644 .cindex "DNS list" "multiple keys for"
32645 The syntax described above for looking up explicitly-defined values (either
32646 names or IP addresses) in a DNS blacklist is a simplification. After the domain
32647 name for the DNS list, what follows the slash can in fact be a list of items.
32648 As with all lists in Exim, the default separator is a colon. However, because
32649 this is a sublist within the list of DNS blacklist domains, it is necessary
32650 either to double the separators like this:
32652 dnslists = black.list.tld/name.1::name.2
32654 or to change the separator character, like this:
32656 dnslists = black.list.tld/<;name.1;name.2
32658 If an item in the list is an IP address, it is inverted before the DNS
32659 blacklist domain is appended. If it is not an IP address, no inversion
32660 occurs. Consider this condition:
32662 dnslists = black.list.tld/<;192.168.1.2;a.domain
32664 The DNS lookups that occur are:
32666 2.1.168.192.black.list.tld
32667 a.domain.black.list.tld
32669 Once a DNS record has been found (that matches a specific IP return
32670 address, if specified &-- see section &<<SECTaddmatcon>>&), no further lookups
32671 are done. If there is a temporary DNS error, the rest of the sublist of domains
32672 or IP addresses is tried. A temporary error for the whole dnslists item occurs
32673 only if no other DNS lookup in this sublist succeeds. In other words, a
32674 successful lookup for any of the items in the sublist overrides a temporary
32675 error for a previous item.
32677 The ability to supply a list of items after the slash is in some sense just a
32678 syntactic convenience. These two examples have the same effect:
32680 dnslists = black.list.tld/a.domain : black.list.tld/b.domain
32681 dnslists = black.list.tld/a.domain::b.domain
32683 However, when the data for the list is obtained from a lookup, the second form
32684 is usually much more convenient. Consider this example:
32686 deny dnslists = sbl.spamhaus.org/<|${lookup dnsdb {>|a=<|\
32687 ${lookup dnsdb {>|mxh=\
32688 $sender_address_domain} }} }
32689 message = The mail servers for the domain \
32690 $sender_address_domain \
32691 are listed at $dnslist_domain ($dnslist_value); \
32694 Note the use of &`>|`& in the dnsdb lookup to specify the separator for
32695 multiple DNS records. The inner dnsdb lookup produces a list of MX hosts
32696 and the outer dnsdb lookup finds the IP addresses for these hosts. The result
32697 of expanding the condition might be something like this:
32699 dnslists = sbl.spamhaus.org/<|192.168.2.3|192.168.5.6|...
32701 Thus, this example checks whether or not the IP addresses of the sender
32702 domain's mail servers are on the Spamhaus black list.
32704 The key that was used for a successful DNS list lookup is put into the variable
32705 &$dnslist_matched$& (see section &<<SECID204>>&).
32710 .section "Data returned by DNS lists" "SECID203"
32711 .cindex "DNS list" "data returned from"
32712 DNS lists are constructed using address records in the DNS. The original RBL
32713 just used the address 127.0.0.1 on the right hand side of each record, but the
32714 RBL+ list and some other lists use a number of values with different meanings.
32715 The values used on the RBL+ list are:
32716 .itable none 0 0 2 20* left 80* left
32717 .irow 127.1.0.1 "RBL"
32718 .irow 127.1.0.2 "DUL"
32719 .irow 127.1.0.3 "DUL and RBL"
32720 .irow 127.1.0.4 "RSS"
32721 .irow 127.1.0.5 "RSS and RBL"
32722 .irow 127.1.0.6 "RSS and DUL"
32723 .irow 127.1.0.7 "RSS and DUL and RBL"
32725 Section &<<SECTaddmatcon>>& below describes how you can distinguish between
32726 different values. Some DNS lists may return more than one address record;
32727 see section &<<SECThanmuldnsrec>>& for details of how they are checked.
32729 Values returned by a properly running DBSBL should be in the 127.0.0.0/8
32730 range. If a DNSBL operator loses control of the domain, lookups on it
32731 may start returning other addresses. Because of this, Exim now ignores
32732 returned values outside the 127/8 region.
32735 .section "Variables set from DNS lists" "SECID204"
32736 .cindex "expansion" "variables, set from DNS list"
32737 .cindex "DNS list" "variables set from"
32738 .vindex "&$dnslist_domain$&"
32739 .vindex "&$dnslist_matched$&"
32740 .vindex "&$dnslist_text$&"
32741 .vindex "&$dnslist_value$&"
32742 When an entry is found in a DNS list, the variable &$dnslist_domain$& contains
32743 the name of the overall domain that matched (for example,
32744 &`spamhaus.example`&), &$dnslist_matched$& contains the key within that domain
32745 (for example, &`192.168.5.3`&), and &$dnslist_value$& contains the data from
32746 the DNS record. When the key is an IP address, it is not reversed in
32747 &$dnslist_matched$& (though it is, of course, in the actual lookup). In simple
32748 cases, for example:
32750 deny dnslists = spamhaus.example
32752 the key is also available in another variable (in this case,
32753 &$sender_host_address$&). In more complicated cases, however, this is not true.
32754 For example, using a data lookup (as described in section &<<SECTmulkeyfor>>&)
32755 might generate a dnslists lookup like this:
32757 deny dnslists = spamhaus.example/<|192.168.1.2|192.168.6.7|...
32759 If this condition succeeds, the value in &$dnslist_matched$& might be
32760 &`192.168.6.7`& (for example).
32762 If more than one address record is returned by the DNS lookup, all the IP
32763 addresses are included in &$dnslist_value$&, separated by commas and spaces.
32764 The variable &$dnslist_text$& contains the contents of any associated TXT
32765 record. For lists such as RBL+ the TXT record for a merged entry is often not
32766 very meaningful. See section &<<SECTmordetinf>>& for a way of obtaining more
32769 You can use the DNS list variables in &%message%& or &%log_message%& modifiers
32770 &-- even if these appear before the condition in the ACL, they are not
32771 expanded until after it has failed. For example:
32773 deny hosts = !+local_networks
32774 message = $sender_host_address is listed \
32776 dnslists = rbl-plus.mail-abuse.example
32781 .section "Additional matching conditions for DNS lists" "SECTaddmatcon"
32782 .cindex "DNS list" "matching specific returned data"
32783 You can add an equals sign and an IP address after a &%dnslists%& domain name
32784 in order to restrict its action to DNS records with a matching right hand side.
32787 deny dnslists = rblplus.mail-abuse.org=127.0.0.2
32789 rejects only those hosts that yield 127.0.0.2. Without this additional data,
32790 any address record is considered to be a match. For the moment, we assume
32791 that the DNS lookup returns just one record. Section &<<SECThanmuldnsrec>>&
32792 describes how multiple records are handled.
32794 More than one IP address may be given for checking, using a comma as a
32795 separator. These are alternatives &-- if any one of them matches, the
32796 &%dnslists%& condition is true. For example:
32798 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
32800 If you want to specify a constraining address list and also specify names or IP
32801 addresses to be looked up, the constraining address list must be specified
32802 first. For example:
32804 deny dnslists = dsn.rfc-ignorant.org\
32805 =127.0.0.2/$sender_address_domain
32808 If the character &`&&`& is used instead of &`=`&, the comparison for each
32809 listed IP address is done by a bitwise &"and"& instead of by an equality test.
32810 In other words, the listed addresses are used as bit masks. The comparison is
32811 true if all the bits in the mask are present in the address that is being
32812 tested. For example:
32814 dnslists = a.b.c&0.0.0.3
32816 matches if the address is &'x.x.x.'&3, &'x.x.x.'&7, &'x.x.x.'&11, etc. If you
32817 want to test whether one bit or another bit is present (as opposed to both
32818 being present), you must use multiple values. For example:
32820 dnslists = a.b.c&0.0.0.1,0.0.0.2
32822 matches if the final component of the address is an odd number or two times
32827 .section "Negated DNS matching conditions" "SECID205"
32828 You can supply a negative list of IP addresses as part of a &%dnslists%&
32831 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
32833 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
32834 IP address yielded by the list is either 127.0.0.2 or 127.0.0.3"&,
32836 deny dnslists = a.b.c!=127.0.0.2,127.0.0.3
32838 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
32839 IP address yielded by the list is not 127.0.0.2 and not 127.0.0.3"&. In other
32840 words, the result of the test is inverted if an exclamation mark appears before
32841 the &`=`& (or the &`&&`&) sign.
32843 &*Note*&: This kind of negation is not the same as negation in a domain,
32844 host, or address list (which is why the syntax is different).
32846 If you are using just one list, the negation syntax does not gain you much. The
32847 previous example is precisely equivalent to
32849 deny dnslists = a.b.c
32850 !dnslists = a.b.c=127.0.0.2,127.0.0.3
32852 However, if you are using multiple lists, the negation syntax is clearer.
32853 Consider this example:
32855 deny dnslists = sbl.spamhaus.org : \
32857 dnsbl.njabl.org!=127.0.0.3 : \
32860 Using only positive lists, this would have to be:
32862 deny dnslists = sbl.spamhaus.org : \
32864 deny dnslists = dnsbl.njabl.org
32865 !dnslists = dnsbl.njabl.org=127.0.0.3
32866 deny dnslists = relays.ordb.org
32868 which is less clear, and harder to maintain.
32870 Negation can also be used with a bitwise-and restriction.
32871 The dnslists condition with only be trus if a result is returned
32872 by the lookup which, anded with the restriction, is all zeroes.
32875 deny dnslists = zen.spamhaus.org!&0.255.255.0
32881 .section "Handling multiple DNS records from a DNS list" "SECThanmuldnsrec"
32882 A DNS lookup for a &%dnslists%& condition may return more than one DNS record,
32883 thereby providing more than one IP address. When an item in a &%dnslists%& list
32884 is followed by &`=`& or &`&&`& and a list of IP addresses, in order to restrict
32885 the match to specific results from the DNS lookup, there are two ways in which
32886 the checking can be handled. For example, consider the condition:
32888 dnslists = a.b.c=127.0.0.1
32890 What happens if the DNS lookup for the incoming IP address yields both
32891 127.0.0.1 and 127.0.0.2 by means of two separate DNS records? Is the
32892 condition true because at least one given value was found, or is it false
32893 because at least one of the found values was not listed? And how does this
32894 affect negated conditions? Both possibilities are provided for with the help of
32895 additional separators &`==`& and &`=&&`&.
32898 If &`=`& or &`&&`& is used, the condition is true if any one of the looked up
32899 IP addresses matches one of the listed addresses. For the example above, the
32900 condition is true because 127.0.0.1 matches.
32902 If &`==`& or &`=&&`& is used, the condition is true only if every one of the
32903 looked up IP addresses matches one of the listed addresses. If the condition is
32906 dnslists = a.b.c==127.0.0.1
32908 and the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
32909 false because 127.0.0.2 is not listed. You would need to have:
32911 dnslists = a.b.c==127.0.0.1,127.0.0.2
32913 for the condition to be true.
32916 When &`!`& is used to negate IP address matching, it inverts the result, giving
32917 the precise opposite of the behaviour above. Thus:
32919 If &`!=`& or &`!&&`& is used, the condition is true if none of the looked up IP
32920 addresses matches one of the listed addresses. Consider:
32922 dnslists = a.b.c!&0.0.0.1
32924 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
32925 false because 127.0.0.1 matches.
32927 If &`!==`& or &`!=&&`& is used, the condition is true if there is at least one
32928 looked up IP address that does not match. Consider:
32930 dnslists = a.b.c!=&0.0.0.1
32932 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
32933 true, because 127.0.0.2 does not match. You would need to have:
32935 dnslists = a.b.c!=&0.0.0.1,0.0.0.2
32937 for the condition to be false.
32939 When the DNS lookup yields only a single IP address, there is no difference
32940 between &`=`& and &`==`& and between &`&&`& and &`=&&`&.
32945 .section "Detailed information from merged DNS lists" "SECTmordetinf"
32946 .cindex "DNS list" "information from merged"
32947 When the facility for restricting the matching IP values in a DNS list is used,
32948 the text from the TXT record that is set in &$dnslist_text$& may not reflect
32949 the true reason for rejection. This happens when lists are merged and the IP
32950 address in the A record is used to distinguish them; unfortunately there is
32951 only one TXT record. One way round this is not to use merged lists, but that
32952 can be inefficient because it requires multiple DNS lookups where one would do
32953 in the vast majority of cases when the host of interest is not on any of the
32956 A less inefficient way of solving this problem is available. If
32957 two domain names, comma-separated, are given, the second is used first to
32958 do an initial check, making use of any IP value restrictions that are set.
32959 If there is a match, the first domain is used, without any IP value
32960 restrictions, to get the TXT record. As a byproduct of this, there is also
32961 a check that the IP being tested is indeed on the first list. The first
32962 domain is the one that is put in &$dnslist_domain$&. For example:
32965 sbl.spamhaus.org,sbl-xbl.spamhaus.org=127.0.0.2 : \
32966 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
32968 rejected because $sender_host_address is blacklisted \
32969 at $dnslist_domain\n$dnslist_text
32971 For the first blacklist item, this starts by doing a lookup in
32972 &'sbl-xbl.spamhaus.org'& and testing for a 127.0.0.2 return. If there is a
32973 match, it then looks in &'sbl.spamhaus.org'&, without checking the return
32974 value, and as long as something is found, it looks for the corresponding TXT
32975 record. If there is no match in &'sbl-xbl.spamhaus.org'&, nothing more is done.
32976 The second blacklist item is processed similarly.
32978 If you are interested in more than one merged list, the same list must be
32979 given several times, but because the results of the DNS lookups are cached,
32980 the DNS calls themselves are not repeated. For example:
32983 http.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.2 : \
32984 socks.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.3 : \
32985 misc.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.4 : \
32986 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
32988 In this case there is one lookup in &'dnsbl.sorbs.net'&, and if none of the IP
32989 values matches (or if no record is found), this is the only lookup that is
32990 done. Only if there is a match is one of the more specific lists consulted.
32994 .section "DNS lists and IPv6" "SECTmorednslistslast"
32995 .cindex "IPv6" "DNS black lists"
32996 .cindex "DNS list" "IPv6 usage"
32997 If Exim is asked to do a dnslist lookup for an IPv6 address, it inverts it
32998 nibble by nibble. For example, if the calling host's IP address is
32999 3ffe:ffff:836f:0a00:000a:0800:200a:c031, Exim might look up
33001 1.3.0.c.a.0.0.2.0.0.8.0.a.0.0.0.0.0.a.0.f.6.3.8.
33002 f.f.f.f.e.f.f.3.blackholes.mail-abuse.org
33004 (split over two lines here to fit on the page). Unfortunately, some of the DNS
33005 lists contain wildcard records, intended for IPv4, that interact badly with
33006 IPv6. For example, the DNS entry
33008 *.3.some.list.example. A 127.0.0.1
33010 is probably intended to put the entire 3.0.0.0/8 IPv4 network on the list.
33011 Unfortunately, it also matches the entire 3::/4 IPv6 network.
33013 You can exclude IPv6 addresses from DNS lookups by making use of a suitable
33014 &%condition%& condition, as in this example:
33016 deny condition = ${if isip4{$sender_host_address}}
33017 dnslists = some.list.example
33020 If an explicit key is being used for a DNS lookup and it may be an IPv6
33021 address you should specify alternate list separators for both the outer
33022 (DNS list name) list and inner (lookup keys) list:
33024 dnslists = <; dnsbl.example.com/<|$acl_m_addrslist
33028 .section "Previously seen user and hosts" "SECTseen"
33029 .cindex "&%een%& ACL condition"
33030 .cindex greylisting
33031 The &%seen%& ACL condition can be used to test whether a
33032 situation has been previously met.
33033 It uses a hints database to record a timestamp against a key.
33034 host. The syntax of the condition is:
33036 &`seen =`& <&'optional flag'&><&'time interval'&> &`/`& <&'options'&>
33041 defer seen = -5m / key=${sender_host_address}_$local_part@$domain
33043 in a RCPT ACL will implement simple greylisting.
33045 The parameters for the condition are
33046 a possible minus sign,
33048 then, slash-separated, a list of options.
33049 The interval is taken as an offset before the current time,
33050 and used for the test.
33051 If the interval is preceded by a minus sign then the condition returns
33052 whether a record is found which is before the test time.
33053 Otherwise, the condition returns whether one is found which is since the
33056 Options are read in order with later ones overriding earlier ones.
33058 The default key is &$sender_host_address$&.
33059 An explicit key can be set using a &%key=value%& option.
33061 If a &%readonly%& option is given then
33062 no record create or update is done.
33063 If a &%write%& option is given then
33064 a record create or update is always done.
33065 An update is done if the test is for &"since"&.
33066 If none of those hold and there was no existing record,
33067 a record is created.
33069 Creates and updates are marked with the current time.
33071 Finally, a &"before"& test which succeeds, and for which the record
33072 is old enough, will be refreshed with a timestamp of the test time.
33073 This can prevent tidying of the database from removing the entry.
33074 The interval for this is, by default, 10 days.
33075 An explicit interval can be set using a
33076 &%refresh=value%& option.
33078 Note that &"seen"& should be added to the list of hints databases
33079 for maintenance if this ACL condition is used.
33082 .section "Rate limiting incoming messages" "SECTratelimiting"
33083 .cindex "rate limiting" "client sending"
33084 .cindex "limiting client sending rates"
33085 .oindex "&%smtp_ratelimit_*%&"
33086 The &%ratelimit%& ACL condition can be used to measure and control the rate at
33087 which clients can send email. This is more powerful than the
33088 &%smtp_ratelimit_*%& options, because those options control the rate of
33089 commands in a single SMTP session only, whereas the &%ratelimit%& condition
33090 works across all connections (concurrent and sequential) from the same client
33091 host. The syntax of the &%ratelimit%& condition is:
33093 &`ratelimit =`& <&'m'&> &`/`& <&'p'&> &`/`& <&'options'&> &`/`& <&'key'&>
33095 If the average client sending rate is less than &'m'& messages per time
33096 period &'p'& then the condition is false; otherwise it is true.
33098 As a side-effect, the &%ratelimit%& condition sets the expansion variable
33099 &$sender_rate$& to the client's computed rate, &$sender_rate_limit$& to the
33100 configured value of &'m'&, and &$sender_rate_period$& to the configured value
33103 The parameter &'p'& is the smoothing time constant, in the form of an Exim
33104 time interval, for example, &`8h`& for eight hours. A larger time constant
33105 means that it takes Exim longer to forget a client's past behaviour. The
33106 parameter &'m'& is the maximum number of messages that a client is permitted to
33107 send in each time interval. It also specifies the number of messages permitted
33108 in a fast burst. By increasing both &'m'& and &'p'& but keeping &'m/p'&
33109 constant, you can allow a client to send more messages in a burst without
33110 changing its long-term sending rate limit. Conversely, if &'m'& and &'p'& are
33111 both small, messages must be sent at an even rate.
33113 There is a script in &_util/ratelimit.pl_& which extracts sending rates from
33114 log files, to assist with choosing appropriate settings for &'m'& and &'p'&
33115 when deploying the &%ratelimit%& ACL condition. The script prints usage
33116 instructions when it is run with no arguments.
33118 The key is used to look up the data for calculating the client's average
33119 sending rate. This data is stored in Exim's spool directory, alongside the
33120 retry and other hints databases. The default key is &$sender_host_address$&,
33121 which means Exim computes the sending rate of each client host IP address.
33122 By changing the key you can change how Exim identifies clients for the purpose
33123 of ratelimiting. For example, to limit the sending rate of each authenticated
33124 user, independent of the computer they are sending from, set the key to
33125 &$authenticated_id$&. You must ensure that the lookup key is meaningful; for
33126 example, &$authenticated_id$& is only meaningful if the client has
33127 authenticated (which you can check with the &%authenticated%& ACL condition).
33129 The lookup key does not have to identify clients: If you want to limit the
33130 rate at which a recipient receives messages, you can use the key
33131 &`$local_part@$domain`& with the &%per_rcpt%& option (see below) in a RCPT
33134 Each &%ratelimit%& condition can have up to four options. A &%per_*%& option
33135 specifies what Exim measures the rate of, for example, messages or recipients
33136 or bytes. You can adjust the measurement using the &%unique=%& and/or
33137 &%count=%& options. You can also control when Exim updates the recorded rate
33138 using a &%strict%&, &%leaky%&, or &%readonly%& option. The options are
33139 separated by a slash, like the other parameters. They may appear in any order.
33141 Internally, Exim appends the smoothing constant &'p'& onto the lookup key with
33142 any options that alter the meaning of the stored data. The limit &'m'& is not
33143 stored, so you can alter the configured maximum rate and Exim will still
33144 remember clients' past behaviour. If you change the &%per_*%& mode or add or
33145 remove the &%unique=%& option, the lookup key changes so Exim will forget past
33146 behaviour. The lookup key is not affected by changes to the update mode and
33147 the &%count=%& option.
33150 .section "Ratelimit options for what is being measured" "ratoptmea"
33151 .cindex "rate limiting" "per_* options"
33152 The &%per_conn%& option limits the client's connection rate. It is not
33153 normally used in the &%acl_not_smtp%&, &%acl_not_smtp_mime%&, or
33154 &%acl_not_smtp_start%& ACLs.
33156 The &%per_mail%& option limits the client's rate of sending messages. This is
33157 the default if none of the &%per_*%& options is specified. It can be used in
33158 &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&, &%acl_smtp_mime%&,
33159 &%acl_smtp_data%&, or &%acl_not_smtp%&.
33161 The &%per_byte%& option limits the sender's email bandwidth. It can be used in
33162 the same ACLs as the &%per_mail%& option, though it is best to use this option
33163 in the &%acl_smtp_mime%&, &%acl_smtp_data%& or &%acl_not_smtp%& ACLs; if it is
33164 used in an earlier ACL, Exim relies on the SIZE parameter given by the client
33165 in its MAIL command, which may be inaccurate or completely missing. You can
33166 follow the limit &'m'& in the configuration with K, M, or G to specify limits
33167 in kilobytes, megabytes, or gigabytes, respectively.
33169 The &%per_rcpt%& option causes Exim to limit the rate at which recipients are
33170 accepted. It can be used in the &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
33171 &%acl_smtp_mime%&, or &%acl_smtp_data%& ACLs. In
33172 &%acl_smtp_rcpt%& the rate is updated one recipient at a time; in the other
33173 ACLs the rate is updated with the total (accepted) recipient count in one go. Note that
33174 in either case the rate limiting engine will see a message with many
33175 recipients as a large high-speed burst.
33177 The &%per_addr%& option is like the &%per_rcpt%& option, except it counts the
33178 number of different recipients that the client has sent messages to in the
33179 last time period. That is, if the client repeatedly sends messages to the same
33180 recipient, its measured rate is not increased. This option can only be used in
33183 The &%per_cmd%& option causes Exim to recompute the rate every time the
33184 condition is processed. This can be used to limit the rate of any SMTP
33185 command. If it is used in multiple ACLs it can limit the aggregate rate of
33186 multiple different commands.
33188 The &%count=%& option can be used to alter how much Exim adds to the client's
33189 measured rate. For example, the &%per_byte%& option is equivalent to
33190 &`per_mail/count=$message_size`&. If there is no &%count=%& option, Exim
33191 increases the measured rate by one (except for the &%per_rcpt%& option in ACLs
33192 other than &%acl_smtp_rcpt%&). The count does not have to be an integer.
33194 The &%unique=%& option is described in section &<<ratoptuniq>>& below.
33197 .section "Ratelimit update modes" "ratoptupd"
33198 .cindex "rate limiting" "reading data without updating"
33199 You can specify one of three options with the &%ratelimit%& condition to
33200 control when its database is updated. This section describes the &%readonly%&
33201 mode, and the next section describes the &%strict%& and &%leaky%& modes.
33203 If the &%ratelimit%& condition is used in &%readonly%& mode, Exim looks up a
33204 previously-computed rate to check against the limit.
33206 For example, you can test the client's sending rate and deny it access (when
33207 it is too fast) in the connect ACL. If the client passes this check then it
33208 can go on to send a message, in which case its recorded rate will be updated
33209 in the MAIL ACL. Subsequent connections from the same client will check this
33213 deny ratelimit = 100 / 5m / readonly
33214 log_message = RATE CHECK: $sender_rate/$sender_rate_period \
33215 (max $sender_rate_limit)
33218 warn ratelimit = 100 / 5m / strict
33219 log_message = RATE UPDATE: $sender_rate/$sender_rate_period \
33220 (max $sender_rate_limit)
33223 If Exim encounters multiple &%ratelimit%& conditions with the same key when
33224 processing a message then it may increase the client's measured rate more than
33225 it should. For example, this will happen if you check the &%per_rcpt%& option
33226 in both &%acl_smtp_rcpt%& and &%acl_smtp_data%&. However it's OK to check the
33227 same &%ratelimit%& condition multiple times in the same ACL. You can avoid any
33228 multiple update problems by using the &%readonly%& option on later ratelimit
33231 The &%per_*%& options described above do not make sense in some ACLs. If you
33232 use a &%per_*%& option in an ACL where it is not normally permitted then the
33233 update mode defaults to &%readonly%& and you cannot specify the &%strict%& or
33234 &%leaky%& modes. In other ACLs the default update mode is &%leaky%& (see the
33235 next section) so you must specify the &%readonly%& option explicitly.
33238 .section "Ratelimit options for handling fast clients" "ratoptfast"
33239 .cindex "rate limiting" "strict and leaky modes"
33240 If a client's average rate is greater than the maximum, the rate limiting
33241 engine can react in two possible ways, depending on the presence of the
33242 &%strict%& or &%leaky%& update modes. This is independent of the other
33243 counter-measures (such as rejecting the message) that may be specified by the
33246 The &%leaky%& (default) option means that the client's recorded rate is not
33247 updated if it is above the limit. The effect of this is that Exim measures the
33248 client's average rate of successfully sent email,
33249 up to the given limit.
33250 This is appropriate if the countermeasure when the condition is true
33251 consists of refusing the message, and
33252 is generally the better choice if you have clients that retry automatically.
33253 If the action when true is anything more complex then this option is
33254 likely not what is wanted.
33256 The &%strict%& option means that the client's recorded rate is always
33257 updated. The effect of this is that Exim measures the client's average rate
33258 of attempts to send email, which can be much higher than the maximum it is
33259 actually allowed. If the client is over the limit it may be subjected to
33260 counter-measures by the ACL. It must slow down and allow sufficient time to
33261 pass that its computed rate falls below the maximum before it can send email
33262 again. The time (the number of smoothing periods) it must wait and not
33263 attempt to send mail can be calculated with this formula:
33265 ln(peakrate/maxrate)
33269 .section "Limiting the rate of different events" "ratoptuniq"
33270 .cindex "rate limiting" "counting unique events"
33271 The &%ratelimit%& &%unique=%& option controls a mechanism for counting the
33272 rate of different events. For example, the &%per_addr%& option uses this
33273 mechanism to count the number of different recipients that the client has
33274 sent messages to in the last time period; it is equivalent to
33275 &`per_rcpt/unique=$local_part@$domain`&. You could use this feature to
33276 measure the rate that a client uses different sender addresses with the
33277 options &`per_mail/unique=$sender_address`&.
33279 For each &%ratelimit%& key Exim stores the set of &%unique=%& values that it
33280 has seen for that key. The whole set is thrown away when it is older than the
33281 rate smoothing period &'p'&, so each different event is counted at most once
33282 per period. In the &%leaky%& update mode, an event that causes the client to
33283 go over the limit is not added to the set, in the same way that the client's
33284 recorded rate is not updated in the same situation.
33286 When you combine the &%unique=%& and &%readonly%& options, the specific
33287 &%unique=%& value is ignored, and Exim just retrieves the client's stored
33290 The &%unique=%& mechanism needs more space in the ratelimit database than the
33291 other &%ratelimit%& options in order to store the event set. The number of
33292 unique values is potentially as large as the rate limit, so the extra space
33293 required increases with larger limits.
33295 The uniqueification is not perfect: there is a small probability that Exim
33296 will think a new event has happened before. If the sender's rate is less than
33297 the limit, Exim should be more than 99.9% correct. However in &%strict%& mode
33298 the measured rate can go above the limit, in which case Exim may under-count
33299 events by a significant margin. Fortunately, if the rate is high enough (2.7
33300 times the limit) that the false positive rate goes above 9%, then Exim will
33301 throw away the over-full event set before the measured rate falls below the
33302 limit. Therefore the only harm should be that exceptionally high sending rates
33303 are logged incorrectly; any countermeasures you configure will be as effective
33307 .section "Using rate limiting" "useratlim"
33308 Exim's other ACL facilities are used to define what counter-measures are taken
33309 when the rate limit is exceeded. This might be anything from logging a warning
33310 (for example, while measuring existing sending rates in order to define
33311 policy), through time delays to slow down fast senders, up to rejecting the
33312 message. For example:
33314 # Log all senders' rates
33315 warn ratelimit = 0 / 1h / strict
33316 log_message = Sender rate $sender_rate / $sender_rate_period
33318 # Slow down fast senders; note the need to truncate $sender_rate
33319 # at the decimal point.
33320 warn ratelimit = 100 / 1h / per_rcpt / strict
33321 delay = ${eval: ${sg{$sender_rate}{[.].*}{}} - \
33322 $sender_rate_limit }s
33324 # Keep authenticated users under control
33325 deny authenticated = *
33326 ratelimit = 100 / 1d / strict / $authenticated_id
33328 # System-wide rate limit
33329 defer ratelimit = 10 / 1s / $primary_hostname
33330 message = Sorry, too busy. Try again later.
33332 # Restrict incoming rate from each host, with a default
33333 # set using a macro and special cases looked up in a table.
33334 defer ratelimit = ${lookup {$sender_host_address} \
33335 cdb {DB/ratelimits.cdb} \
33336 {$value} {RATELIMIT} }
33337 message = Sender rate exceeds $sender_rate_limit \
33338 messages per $sender_rate_period
33340 &*Warning*&: If you have a busy server with a lot of &%ratelimit%& tests,
33341 especially with the &%per_rcpt%& option, you may suffer from a performance
33342 bottleneck caused by locking on the ratelimit hints database. Apart from
33343 making your ACLs less complicated, you can reduce the problem by using a
33344 RAM disk for Exim's hints directory (usually &_/var/spool/exim/db/_&). However
33345 this means that Exim will lose its hints data after a reboot (including retry
33346 hints, the callout cache, and ratelimit data).
33350 .section "Address verification" "SECTaddressverification"
33351 .cindex "verifying address" "options for"
33352 .cindex "policy control" "address verification"
33353 Several of the &%verify%& conditions described in section
33354 &<<SECTaclconditions>>& cause addresses to be verified. Section
33355 &<<SECTsenaddver>>& discusses the reporting of sender verification failures.
33356 The verification conditions can be followed by options that modify the
33357 verification process. The options are separated from the keyword and from each
33358 other by slashes, and some of them contain parameters. For example:
33360 verify = sender/callout
33361 verify = recipient/defer_ok/callout=10s,defer_ok
33363 The first stage of address verification, which always happens, is to run the
33364 address through the routers, in &"verify mode"&. Routers can detect the
33365 difference between verification and routing for delivery, and their actions can
33366 be varied by a number of generic options such as &%verify%& and &%verify_only%&
33367 (see chapter &<<CHAProutergeneric>>&). If routing fails, verification fails.
33368 The available options are as follows:
33371 If the &%callout%& option is specified, successful routing to one or more
33372 remote hosts is followed by a &"callout"& to those hosts as an additional
33373 check. Callouts and their sub-options are discussed in the next section.
33375 If there is a defer error while doing verification routing, the ACL
33376 normally returns &"defer"&. However, if you include &%defer_ok%& in the
33377 options, the condition is forced to be true instead. Note that this is a main
33378 verification option as well as a suboption for callouts.
33380 The &%no_details%& option is covered in section &<<SECTsenaddver>>&, which
33381 discusses the reporting of sender address verification failures.
33383 The &%success_on_redirect%& option causes verification always to succeed
33384 immediately after a successful redirection. By default, if a redirection
33385 generates just one address, that address is also verified. See further
33386 discussion in section &<<SECTredirwhilveri>>&.
33388 If the &%quota%& option is specified for recipient verify,
33389 successful routing to an appendfile transport is followed by a call into
33390 the transport to evaluate the quota status for the recipient.
33391 No actual delivery is done, but verification will succeed if the quota
33392 is sufficient for the message (if the sender gave a message size) or
33393 not already exceeded (otherwise).
33396 .cindex "verifying address" "differentiating failures"
33397 .vindex "&$recipient_verify_failure$&"
33398 .vindex "&$sender_verify_failure$&"
33399 .vindex "&$acl_verify_message$&"
33400 After an address verification failure, &$acl_verify_message$& contains the
33401 error message that is associated with the failure. It can be preserved by
33404 warn !verify = sender
33405 set acl_m0 = $acl_verify_message
33407 If you are writing your own custom rejection message or log message when
33408 denying access, you can use this variable to include information about the
33409 verification failure.
33410 This variable is cleared at the end of processing the ACL verb.
33412 In addition, &$sender_verify_failure$& or &$recipient_verify_failure$& (as
33413 appropriate) contains one of the following words:
33416 &%qualify%&: The address was unqualified (no domain), and the message
33417 was neither local nor came from an exempted host.
33419 &%route%&: Routing failed.
33421 &%mail%&: Routing succeeded, and a callout was attempted; rejection
33422 occurred at or before the MAIL command (that is, on initial
33423 connection, HELO, or MAIL).
33425 &%recipient%&: The RCPT command in a callout was rejected.
33427 &%postmaster%&: The postmaster check in a callout was rejected.
33429 &%quota%&: The quota check for a local recipient did non pass.
33432 The main use of these variables is expected to be to distinguish between
33433 rejections of MAIL and rejections of RCPT in callouts.
33435 The above variables may also be set after a &*successful*&
33436 address verification to:
33439 &%random%&: A random local-part callout succeeded
33445 .section "Callout verification" "SECTcallver"
33446 .cindex "verifying address" "by callout"
33447 .cindex "callout" "verification"
33448 .cindex "SMTP" "callout verification"
33449 For non-local addresses, routing verifies the domain, but is unable to do any
33450 checking of the local part. There are situations where some means of verifying
33451 the local part is desirable. One way this can be done is to make an SMTP
33452 &'callback'& to a delivery host for the sender address or a &'callforward'& to
33453 a subsequent host for a recipient address, to see if the host accepts the
33454 address. We use the term &'callout'& to cover both cases. Note that for a
33455 sender address, the callback is not to the client host that is trying to
33456 deliver the message, but to one of the hosts that accepts incoming mail for the
33459 Exim does not do callouts by default. If you want them to happen, you must
33460 request them by setting appropriate options on the &%verify%& condition, as
33461 described below. This facility should be used with care, because it can add a
33462 lot of resource usage to the cost of verifying an address. However, Exim does
33463 cache the results of callouts, which helps to reduce the cost. Details of
33464 caching are in section &<<SECTcallvercache>>&.
33466 Recipient callouts are usually used only between hosts that are controlled by
33467 the same administration. For example, a corporate gateway host could use
33468 callouts to check for valid recipients on an internal mailserver. A successful
33469 callout does not guarantee that a real delivery to the address would succeed;
33470 on the other hand, a failing callout does guarantee that a delivery would fail.
33472 If the &%callout%& option is present on a condition that verifies an address, a
33473 second stage of verification occurs if the address is successfully routed to
33474 one or more remote hosts. The usual case is routing by a &(dnslookup)& or a
33475 &(manualroute)& router, where the router specifies the hosts. However, if a
33476 router that does not set up hosts routes to an &(smtp)& transport with a
33477 &%hosts%& setting, the transport's hosts are used. If an &(smtp)& transport has
33478 &%hosts_override%& set, its hosts are always used, whether or not the router
33479 supplies a host list.
33480 Callouts are only supported on &(smtp)& transports.
33482 The port that is used is taken from the transport, if it is specified and is a
33483 remote transport. (For routers that do verification only, no transport need be
33484 specified.) Otherwise, the default SMTP port is used. If a remote transport
33485 specifies an outgoing interface, this is used; otherwise the interface is not
33486 specified. Likewise, the text that is used for the HELO command is taken from
33487 the transport's &%helo_data%& option; if there is no transport, the value of
33488 &$smtp_active_hostname$& is used.
33490 For a sender callout check, Exim makes SMTP connections to the remote hosts, to
33491 test whether a bounce message could be delivered to the sender address. The
33492 following SMTP commands are sent:
33494 &`HELO `&<&'local host name'&>
33496 &`RCPT TO:`&<&'the address to be tested'&>
33499 LHLO is used instead of HELO if the transport's &%protocol%& option is
33502 The callout may use EHLO, AUTH and/or STARTTLS given appropriate option
33505 A recipient callout check is similar. By default, it also uses an empty address
33506 for the sender. This default is chosen because most hosts do not make use of
33507 the sender address when verifying a recipient. Using the same address means
33508 that a single cache entry can be used for each recipient. Some sites, however,
33509 do make use of the sender address when verifying. These are catered for by the
33510 &%use_sender%& and &%use_postmaster%& options, described in the next section.
33512 If the response to the RCPT command is a 2&'xx'& code, the verification
33513 succeeds. If it is 5&'xx'&, the verification fails. For any other condition,
33514 Exim tries the next host, if any. If there is a problem with all the remote
33515 hosts, the ACL yields &"defer"&, unless the &%defer_ok%& parameter of the
33516 &%callout%& option is given, in which case the condition is forced to succeed.
33518 .cindex "SMTP" "output flushing, disabling for callout"
33519 A callout may take a little time. For this reason, Exim normally flushes SMTP
33520 output before performing a callout in an ACL, to avoid unexpected timeouts in
33521 clients when the SMTP PIPELINING extension is in use. The flushing can be
33522 disabled by using a &%control%& modifier to set &%no_callout_flush%&.
33524 .cindex "tainted data" "de-tainting"
33525 .cindex "de-tainting" "using recipient verify"
33526 A recipient callout which gets a 2&'xx'& code
33527 will assign untainted values to the
33528 &$domain_data$& and &$local_part_data$& variables,
33529 corresponding to the domain and local parts of the recipient address.
33534 .section "Additional parameters for callouts" "CALLaddparcall"
33535 .cindex "callout" "additional parameters for"
33536 The &%callout%& option can be followed by an equals sign and a number of
33537 optional parameters, separated by commas. For example:
33539 verify = recipient/callout=10s,defer_ok
33541 The old syntax, which had &%callout_defer_ok%& and &%check_postmaster%& as
33542 separate verify options, is retained for backwards compatibility, but is now
33543 deprecated. The additional parameters for &%callout%& are as follows:
33547 .vitem <&'a&~time&~interval'&>
33548 .cindex "callout" "timeout, specifying"
33549 This specifies the timeout that applies for the callout attempt to each host.
33552 verify = sender/callout=5s
33554 The default is 30 seconds. The timeout is used for each response from the
33555 remote host. It is also used for the initial connection, unless overridden by
33556 the &%connect%& parameter.
33559 .vitem &*connect&~=&~*&<&'time&~interval'&>
33560 .cindex "callout" "connection timeout, specifying"
33561 This parameter makes it possible to set a different (usually smaller) timeout
33562 for making the SMTP connection. For example:
33564 verify = sender/callout=5s,connect=1s
33566 If not specified, this timeout defaults to the general timeout value.
33568 .vitem &*defer_ok*&
33569 .cindex "callout" "defer, action on"
33570 When this parameter is present, failure to contact any host, or any other kind
33571 of temporary error, is treated as success by the ACL. However, the cache is not
33572 updated in this circumstance.
33574 .vitem &*fullpostmaster*&
33575 .cindex "callout" "full postmaster check"
33576 This operates like the &%postmaster%& option (see below), but if the check for
33577 &'postmaster@domain'& fails, it tries just &'postmaster'&, without a domain, in
33578 accordance with the specification in RFC 2821. The RFC states that the
33579 unqualified address &'postmaster'& should be accepted.
33582 .vitem &*mailfrom&~=&~*&<&'email&~address'&>
33583 .cindex "callout" "sender when verifying header"
33584 When verifying addresses in header lines using the &%header_sender%&
33585 verification option, Exim behaves by default as if the addresses are envelope
33586 sender addresses from a message. Callout verification therefore tests to see
33587 whether a bounce message could be delivered, by using an empty address in the
33588 MAIL command. However, it is arguable that these addresses might never be used
33589 as envelope senders, and could therefore justifiably reject bounce messages
33590 (empty senders). The &%mailfrom%& callout parameter allows you to specify what
33591 address to use in the MAIL command. For example:
33593 require verify = header_sender/callout=mailfrom=abcd@x.y.z
33595 This parameter is available only for the &%header_sender%& verification option.
33598 .vitem &*maxwait&~=&~*&<&'time&~interval'&>
33599 .cindex "callout" "overall timeout, specifying"
33600 This parameter sets an overall timeout for performing a callout verification.
33603 verify = sender/callout=5s,maxwait=30s
33605 This timeout defaults to four times the callout timeout for individual SMTP
33606 commands. The overall timeout applies when there is more than one host that can
33607 be tried. The timeout is checked before trying the next host. This prevents
33608 very long delays if there are a large number of hosts and all are timing out
33609 (for example, when network connections are timing out).
33612 .vitem &*no_cache*&
33613 .cindex "callout" "cache, suppressing"
33614 .cindex "caching callout, suppressing"
33615 When this parameter is given, the callout cache is neither read nor updated.
33617 .vitem &*postmaster*&
33618 .cindex "callout" "postmaster; checking"
33619 When this parameter is set, a successful callout check is followed by a similar
33620 check for the local part &'postmaster'& at the same domain. If this address is
33621 rejected, the callout fails (but see &%fullpostmaster%& above). The result of
33622 the postmaster check is recorded in a cache record; if it is a failure, this is
33623 used to fail subsequent callouts for the domain without a connection being
33624 made, until the cache record expires.
33626 .vitem &*postmaster_mailfrom&~=&~*&<&'email&~address'&>
33627 The postmaster check uses an empty sender in the MAIL command by default.
33628 You can use this parameter to do a postmaster check using a different address.
33631 require verify = sender/callout=postmaster_mailfrom=abc@x.y.z
33633 If both &%postmaster%& and &%postmaster_mailfrom%& are present, the rightmost
33634 one overrides. The &%postmaster%& parameter is equivalent to this example:
33636 require verify = sender/callout=postmaster_mailfrom=
33638 &*Warning*&: The caching arrangements for postmaster checking do not take
33639 account of the sender address. It is assumed that either the empty address or
33640 a fixed non-empty address will be used. All that Exim remembers is that the
33641 postmaster check for the domain succeeded or failed.
33645 .cindex "callout" "&""random""& check"
33646 When this parameter is set, before doing the normal callout check, Exim does a
33647 check for a &"random"& local part at the same domain. The local part is not
33648 really random &-- it is defined by the expansion of the option
33649 &%callout_random_local_part%&, which defaults to
33651 $primary_hostname-$tod_epoch-testing
33653 The idea here is to try to determine whether the remote host accepts all local
33654 parts without checking. If it does, there is no point in doing callouts for
33655 specific local parts. If the &"random"& check succeeds, the result is saved in
33656 a cache record, and used to force the current and subsequent callout checks to
33657 succeed without a connection being made, until the cache record expires.
33659 .vitem &*use_postmaster*&
33660 .cindex "callout" "sender for recipient check"
33661 This parameter applies to recipient callouts only. For example:
33663 deny !verify = recipient/callout=use_postmaster
33665 .vindex "&$qualify_domain$&"
33666 It causes a non-empty postmaster address to be used in the MAIL command when
33667 performing the callout for the recipient, and also for a &"random"& check if
33668 that is configured. The local part of the address is &`postmaster`& and the
33669 domain is the contents of &$qualify_domain$&.
33671 .vitem &*use_sender*&
33672 This option applies to recipient callouts only. For example:
33674 require verify = recipient/callout=use_sender
33676 It causes the message's actual sender address to be used in the MAIL
33677 command when performing the callout, instead of an empty address. There is no
33678 need to use this option unless you know that the called hosts make use of the
33679 sender when checking recipients. If used indiscriminately, it reduces the
33680 usefulness of callout caching.
33683 This option applies to recipient callouts only. For example:
33685 require verify = recipient/callout=use_sender,hold
33687 It causes the connection to be held open and used for any further recipients
33688 and for eventual delivery (should that be done quickly).
33689 Doing this saves on TCP and SMTP startup costs, and TLS costs also
33690 when that is used for the connections.
33691 The advantage is only gained if there are no callout cache hits
33692 (which could be enforced by the no_cache option),
33693 if the use_sender option is used,
33694 if neither the random nor the use_postmaster option is used,
33695 and if no other callouts intervene.
33698 If you use any of the parameters that set a non-empty sender for the MAIL
33699 command (&%mailfrom%&, &%postmaster_mailfrom%&, &%use_postmaster%&, or
33700 &%use_sender%&), you should think about possible loops. Recipient checking is
33701 usually done between two hosts that are under the same management, and the host
33702 that receives the callouts is not normally configured to do callouts itself.
33703 Therefore, it is normally safe to use &%use_postmaster%& or &%use_sender%& in
33704 these circumstances.
33706 However, if you use a non-empty sender address for a callout to an arbitrary
33707 host, there is the likelihood that the remote host will itself initiate a
33708 callout check back to your host. As it is checking what appears to be a message
33709 sender, it is likely to use an empty address in MAIL, thus avoiding a
33710 callout loop. However, to be on the safe side it would be best to set up your
33711 own ACLs so that they do not do sender verification checks when the recipient
33712 is the address you use for header sender or postmaster callout checking.
33714 Another issue to think about when using non-empty senders for callouts is
33715 caching. When you set &%mailfrom%& or &%use_sender%&, the cache record is keyed
33716 by the sender/recipient combination; thus, for any given recipient, many more
33717 actual callouts are performed than when an empty sender or postmaster is used.
33722 .section "Callout caching" "SECTcallvercache"
33723 .cindex "hints database" "callout cache"
33724 .cindex "callout" "cache, description of"
33725 .cindex "caching" "callout"
33726 Exim caches the results of callouts in order to reduce the amount of resources
33727 used, unless you specify the &%no_cache%& parameter with the &%callout%&
33728 option. A hints database called &"callout"& is used for the cache. Two
33729 different record types are used: one records the result of a callout check for
33730 a specific address, and the other records information that applies to the
33731 entire domain (for example, that it accepts the local part &'postmaster'&).
33733 When an original callout fails, a detailed SMTP error message is given about
33734 the failure. However, for subsequent failures use the cache data, this message
33737 The expiry times for negative and positive address cache records are
33738 independent, and can be set by the global options &%callout_negative_expire%&
33739 (default 2h) and &%callout_positive_expire%& (default 24h), respectively.
33741 If a host gives a negative response to an SMTP connection, or rejects any
33742 commands up to and including
33746 (but not including the MAIL command with a non-empty address),
33747 any callout attempt is bound to fail. Exim remembers such failures in a
33748 domain cache record, which it uses to fail callouts for the domain without
33749 making new connections, until the domain record times out. There are two
33750 separate expiry times for domain cache records:
33751 &%callout_domain_negative_expire%& (default 3h) and
33752 &%callout_domain_positive_expire%& (default 7d).
33754 Domain records expire when the negative expiry time is reached if callouts
33755 cannot be made for the domain, or if the postmaster check failed.
33756 Otherwise, they expire when the positive expiry time is reached. This
33757 ensures that, for example, a host that stops accepting &"random"& local parts
33758 will eventually be noticed.
33760 The callout caching mechanism is based on the domain of the address that is
33761 being tested. If the domain routes to several hosts, it is assumed that their
33762 behaviour will be the same.
33766 .section "Quota caching" "SECTquotacache"
33767 .cindex "hints database" "quota cache"
33768 .cindex "quota" "cache, description of"
33769 .cindex "caching" "quota"
33770 Exim caches the results of quota verification
33771 in order to reduce the amount of resources used.
33772 The &"callout"& hints database is used.
33774 The default cache periods are five minutes for a positive (good) result
33775 and one hour for a negative result.
33776 To change the periods the &%quota%& option can be followed by an equals sign
33777 and a number of optional paramemters, separated by commas.
33780 verify = recipient/quota=cachepos=1h,cacheneg=1d
33782 Possible parameters are:
33784 .vitem &*cachepos&~=&~*&<&'time&~interval'&>
33785 .cindex "quota cache" "positive entry expiry, specifying"
33786 Set the lifetime for a positive cache entry.
33787 A value of zero seconds is legitimate.
33789 .vitem &*cacheneg&~=&~*&<&'time&~interval'&>
33790 .cindex "quota cache" "negative entry expiry, specifying"
33791 As above, for a negative entry.
33793 .vitem &*no_cache*&
33794 Set both positive and negative lifetimes to zero.
33796 .section "Sender address verification reporting" "SECTsenaddver"
33797 .cindex "verifying" "suppressing error details"
33798 See section &<<SECTaddressverification>>& for a general discussion of
33799 verification. When sender verification fails in an ACL, the details of the
33800 failure are given as additional output lines before the 550 response to the
33801 relevant SMTP command (RCPT or DATA). For example, if sender callout is in use,
33804 MAIL FROM:<xyz@abc.example>
33806 RCPT TO:<pqr@def.example>
33807 550-Verification failed for <xyz@abc.example>
33808 550-Called: 192.168.34.43
33809 550-Sent: RCPT TO:<xyz@abc.example>
33810 550-Response: 550 Unknown local part xyz in <xyz@abc.example>
33811 550 Sender verification failed
33813 If more than one RCPT command fails in the same way, the details are given
33814 only for the first of them. However, some administrators do not want to send
33815 out this much information. You can suppress the details by adding
33816 &`/no_details`& to the ACL statement that requests sender verification. For
33819 verify = sender/no_details
33822 .section "Redirection while verifying" "SECTredirwhilveri"
33823 .cindex "verifying" "redirection while"
33824 .cindex "address redirection" "while verifying"
33825 A dilemma arises when a local address is redirected by aliasing or forwarding
33826 during verification: should the generated addresses themselves be verified,
33827 or should the successful expansion of the original address be enough to verify
33828 it? By default, Exim takes the following pragmatic approach:
33831 When an incoming address is redirected to just one child address, verification
33832 continues with the child address, and if that fails to verify, the original
33833 verification also fails.
33835 When an incoming address is redirected to more than one child address,
33836 verification does not continue. A success result is returned.
33839 This seems the most reasonable behaviour for the common use of aliasing as a
33840 way of redirecting different local parts to the same mailbox. It means, for
33841 example, that a pair of alias entries of the form
33844 aw123: :fail: Gone away, no forwarding address
33846 work as expected, with both local parts causing verification failure. When a
33847 redirection generates more than one address, the behaviour is more like a
33848 mailing list, where the existence of the alias itself is sufficient for
33849 verification to succeed.
33851 It is possible, however, to change the default behaviour so that all successful
33852 redirections count as successful verifications, however many new addresses are
33853 generated. This is specified by the &%success_on_redirect%& verification
33854 option. For example:
33856 require verify = recipient/success_on_redirect/callout=10s
33858 In this example, verification succeeds if a router generates a new address, and
33859 the callout does not occur, because no address was routed to a remote host.
33861 When verification is being tested via the &%-bv%& option, the treatment of
33862 redirections is as just described, unless the &%-v%& or any debugging option is
33863 also specified. In that case, full verification is done for every generated
33864 address and a report is output for each of them.
33868 .section "Client SMTP authorization (CSA)" "SECTverifyCSA"
33869 .cindex "CSA" "verifying"
33870 Client SMTP Authorization is a system that allows a site to advertise
33871 which machines are and are not permitted to send email. This is done by placing
33872 special SRV records in the DNS; these are looked up using the client's HELO
33873 domain. At the time of writing, CSA is still an Internet Draft. Client SMTP
33874 Authorization checks in Exim are performed by the ACL condition:
33878 This fails if the client is not authorized. If there is a DNS problem, or if no
33879 valid CSA SRV record is found, or if the client is authorized, the condition
33880 succeeds. These three cases can be distinguished using the expansion variable
33881 &$csa_status$&, which can take one of the values &"fail"&, &"defer"&,
33882 &"unknown"&, or &"ok"&. The condition does not itself defer because that would
33883 be likely to cause problems for legitimate email.
33885 The error messages produced by the CSA code include slightly more
33886 detail. If &$csa_status$& is &"defer"&, this may be because of problems
33887 looking up the CSA SRV record, or problems looking up the CSA target
33888 address record. There are four reasons for &$csa_status$& being &"fail"&:
33891 The client's host name is explicitly not authorized.
33893 The client's IP address does not match any of the CSA target IP addresses.
33895 The client's host name is authorized but it has no valid target IP addresses
33896 (for example, the target's addresses are IPv6 and the client is using IPv4).
33898 The client's host name has no CSA SRV record but a parent domain has asserted
33899 that all subdomains must be explicitly authorized.
33902 The &%csa%& verification condition can take an argument which is the domain to
33903 use for the DNS query. The default is:
33905 verify = csa/$sender_helo_name
33907 This implementation includes an extension to CSA. If the query domain
33908 is an address literal such as [192.0.2.95], or if it is a bare IP
33909 address, Exim searches for CSA SRV records in the reverse DNS as if
33910 the HELO domain was (for example) &'95.2.0.192.in-addr.arpa'&. Therefore it is
33913 verify = csa/$sender_host_address
33915 In fact, this is the check that Exim performs if the client does not say HELO.
33916 This extension can be turned off by setting the main configuration option
33917 &%dns_csa_use_reverse%& to be false.
33919 If a CSA SRV record is not found for the domain itself, a search
33920 is performed through its parent domains for a record which might be
33921 making assertions about subdomains. The maximum depth of this search is limited
33922 using the main configuration option &%dns_csa_search_limit%&, which is 5 by
33923 default. Exim does not look for CSA SRV records in a top level domain, so the
33924 default settings handle HELO domains as long as seven
33925 (&'hostname.five.four.three.two.one.com'&). This encompasses the vast majority
33926 of legitimate HELO domains.
33928 The &'dnsdb'& lookup also has support for CSA. Although &'dnsdb'& also supports
33929 direct SRV lookups, this is not sufficient because of the extra parent domain
33930 search behaviour of CSA, and (as with PTR lookups) &'dnsdb'& also turns IP
33931 addresses into lookups in the reverse DNS space. The result of a successful
33934 ${lookup dnsdb {csa=$sender_helo_name}}
33936 has two space-separated fields: an authorization code and a target host name.
33937 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
33938 authorization required but absent, or &"?"& for unknown.
33943 .section "Bounce address tag validation" "SECTverifyPRVS"
33944 .cindex "BATV, verifying"
33945 Bounce address tag validation (BATV) is a scheme whereby the envelope senders
33946 of outgoing messages have a cryptographic, timestamped &"tag"& added to them.
33947 Genuine incoming bounce messages should therefore always be addressed to
33948 recipients that have a valid tag. This scheme is a way of detecting unwanted
33949 bounce messages caused by sender address forgeries (often called &"collateral
33950 spam"&), because the recipients of such messages do not include valid tags.
33952 There are two expansion items to help with the implementation of the BATV
33953 &"prvs"& (private signature) scheme in an Exim configuration. This scheme signs
33954 the original envelope sender address by using a simple key to add a hash of the
33955 address and some time-based randomizing information. The &%prvs%& expansion
33956 item creates a signed address, and the &%prvscheck%& expansion item checks one.
33957 The syntax of these expansion items is described in section
33958 &<<SECTexpansionitems>>&.
33959 The validity period on signed addresses is seven days.
33961 As an example, suppose the secret per-address keys are stored in an MySQL
33962 database. A query to look up the key for an address could be defined as a macro
33965 PRVSCHECK_SQL = ${lookup mysql{SELECT secret FROM batv_prvs \
33966 WHERE sender='${quote_mysql:$prvscheck_address}'\
33969 Suppose also that the senders who make use of BATV are defined by an address
33970 list called &%batv_senders%&. Then, in the ACL for RCPT commands, you could
33973 # Bounces: drop unsigned addresses for BATV senders
33975 recipients = +batv_senders
33976 message = This address does not send an unsigned reverse path
33978 # Bounces: In case of prvs-signed address, check signature.
33980 condition = ${prvscheck {$local_part@$domain}\
33981 {PRVSCHECK_SQL}{1}}
33982 !condition = $prvscheck_result
33983 message = Invalid reverse path signature.
33985 The first statement rejects recipients for bounce messages that are addressed
33986 to plain BATV sender addresses, because it is known that BATV senders do not
33987 send out messages with plain sender addresses. The second statement rejects
33988 recipients that are prvs-signed, but with invalid signatures (either because
33989 the key is wrong, or the signature has timed out).
33991 A non-prvs-signed address is not rejected by the second statement, because the
33992 &%prvscheck%& expansion yields an empty string if its first argument is not a
33993 prvs-signed address, thus causing the &%condition%& condition to be false. If
33994 the first argument is a syntactically valid prvs-signed address, the yield is
33995 the third string (in this case &"1"&), whether or not the cryptographic and
33996 timeout checks succeed. The &$prvscheck_result$& variable contains the result
33997 of the checks (empty for failure, &"1"& for success).
33999 There is one more issue you must consider when implementing prvs-signing:
34000 you have to ensure that the routers accept prvs-signed addresses and
34001 deliver them correctly. The easiest way to handle this is to use a &(redirect)&
34002 router to remove the signature with a configuration along these lines:
34006 data = ${prvscheck {$local_part@$domain}{PRVSCHECK_SQL}}
34008 This works because, if the third argument of &%prvscheck%& is empty, the result
34009 of the expansion of a prvs-signed address is the decoded value of the original
34010 address. This router should probably be the first of your routers that handles
34013 To create BATV-signed addresses in the first place, a transport of this form
34016 external_smtp_batv:
34018 return_path = ${prvs {$return_path} \
34019 {${lookup mysql{SELECT \
34020 secret FROM batv_prvs WHERE \
34021 sender='${quote_mysql:$sender_address}'} \
34024 If no key can be found for the existing return path, no signing takes place.
34028 .section "Using an ACL to control relaying" "SECTrelaycontrol"
34029 .cindex "&ACL;" "relay control"
34030 .cindex "relaying" "control by ACL"
34031 .cindex "policy control" "relay control"
34032 An MTA is said to &'relay'& a message if it receives it from some host and
34033 delivers it directly to another host as a result of a remote address contained
34034 within it. Redirecting a local address via an alias or forward file and then
34035 passing the message on to another host is not relaying,
34036 .cindex "&""percent hack""&"
34037 but a redirection as a result of the &"percent hack"& is.
34039 Two kinds of relaying exist, which are termed &"incoming"& and &"outgoing"&.
34040 A host which is acting as a gateway or an MX backup is concerned with incoming
34041 relaying from arbitrary hosts to a specific set of domains. On the other hand,
34042 a host which is acting as a smart host for a number of clients is concerned
34043 with outgoing relaying from those clients to the Internet at large. Often the
34044 same host is fulfilling both functions,
34046 . as illustrated in the diagram below,
34048 but in principle these two kinds of relaying are entirely independent. What is
34049 not wanted is the transmission of mail from arbitrary remote hosts through your
34050 system to arbitrary domains.
34053 You can implement relay control by means of suitable statements in the ACL that
34054 runs for each RCPT command. For convenience, it is often easiest to use
34055 Exim's named list facility to define the domains and hosts involved. For
34056 example, suppose you want to do the following:
34059 Deliver a number of domains to mailboxes on the local host (or process them
34060 locally in some other way). Let's say these are &'my.dom1.example'& and
34061 &'my.dom2.example'&.
34063 Relay mail for a number of other domains for which you are the secondary MX.
34064 These might be &'friend1.example'& and &'friend2.example'&.
34066 Relay mail from the hosts on your local LAN, to whatever domains are involved.
34067 Suppose your LAN is 192.168.45.0/24.
34071 In the main part of the configuration, you put the following definitions:
34073 domainlist local_domains = my.dom1.example : my.dom2.example
34074 domainlist relay_to_domains = friend1.example : friend2.example
34075 hostlist relay_from_hosts = 192.168.45.0/24
34077 Now you can use these definitions in the ACL that is run for every RCPT
34081 accept domains = +local_domains : +relay_to_domains
34082 accept hosts = +relay_from_hosts
34084 The first statement accepts any RCPT command that contains an address in
34085 the local or relay domains. For any other domain, control passes to the second
34086 statement, which accepts the command only if it comes from one of the relay
34087 hosts. In practice, you will probably want to make your ACL more sophisticated
34088 than this, for example, by including sender and recipient verification. The
34089 default configuration includes a more comprehensive example, which is described
34090 in chapter &<<CHAPdefconfil>>&.
34094 .section "Checking a relay configuration" "SECTcheralcon"
34095 .cindex "relaying" "checking control of"
34096 You can check the relay characteristics of your configuration in the same way
34097 that you can test any ACL behaviour for an incoming SMTP connection, by using
34098 the &%-bh%& option to run a fake SMTP session with which you interact.
34103 . ////////////////////////////////////////////////////////////////////////////
34104 . ////////////////////////////////////////////////////////////////////////////
34106 .chapter "Content scanning at ACL time" "CHAPexiscan"
34107 .scindex IIDcosca "content scanning" "at ACL time"
34108 The extension of Exim to include content scanning at ACL time, formerly known
34109 as &"exiscan"&, was originally implemented as a patch by Tom Kistner. The code
34110 was integrated into the main source for Exim release 4.50, and Tom continues to
34111 maintain it. Most of the wording of this chapter is taken from Tom's
34114 It is also possible to scan the content of messages at other times. The
34115 &[local_scan()]& function (see chapter &<<CHAPlocalscan>>&) allows for content
34116 scanning after all the ACLs have run. A transport filter can be used to scan
34117 messages at delivery time (see the &%transport_filter%& option, described in
34118 chapter &<<CHAPtransportgeneric>>&).
34120 If you want to include the ACL-time content-scanning features when you compile
34121 Exim, you need to arrange for WITH_CONTENT_SCAN to be defined in your
34122 &_Local/Makefile_&. When you do that, the Exim binary is built with:
34125 Two additional ACLs (&%acl_smtp_mime%& and &%acl_not_smtp_mime%&) that are run
34126 for all MIME parts for SMTP and non-SMTP messages, respectively.
34128 Additional ACL conditions and modifiers: &%decode%&, &%malware%&,
34129 &%mime_regex%&, &%regex%&, and &%spam%&. These can be used in the ACL that is
34130 run at the end of message reception (the &%acl_smtp_data%& ACL).
34132 An additional control feature (&"no_mbox_unspool"&) that saves spooled copies
34133 of messages, or parts of messages, for debugging purposes.
34135 Additional expansion variables that are set in the new ACL and by the new
34138 Two new main configuration options: &%av_scanner%& and &%spamd_address%&.
34141 Content-scanning is continually evolving, and new features are still being
34142 added. While such features are still unstable and liable to incompatible
34143 changes, they are made available in Exim by setting options whose names begin
34144 EXPERIMENTAL_ in &_Local/Makefile_&. Such features are not documented in
34145 this manual. You can find out about them by reading the file called
34146 &_doc/experimental.txt_&.
34148 All the content-scanning facilities work on a MBOX copy of the message that is
34149 temporarily created in a file called:
34151 <&'spool_directory'&>&`/scan/`&<&'message_id'&>/<&'message_id'&>&`.eml`&
34153 The &_.eml_& extension is a friendly hint to virus scanners that they can
34154 expect an MBOX-like structure inside that file. The file is created when the
34155 first content scanning facility is called. Subsequent calls to content
34156 scanning conditions open the same file again. The directory is recursively
34157 removed when the &%acl_smtp_data%& ACL has finished running, unless
34159 control = no_mbox_unspool
34161 has been encountered. When the MIME ACL decodes files, they are put into the
34162 same directory by default.
34166 .section "Scanning for viruses" "SECTscanvirus"
34167 .cindex "virus scanning"
34168 .cindex "content scanning" "for viruses"
34169 .cindex "content scanning" "the &%malware%& condition"
34170 The &%malware%& ACL condition lets you connect virus scanner software to Exim.
34171 It supports a &"generic"& interface to scanners called via the shell, and
34172 specialized interfaces for &"daemon"& type virus scanners, which are resident
34173 in memory and thus are much faster.
34175 Since message data needs to have arrived,
34176 the condition may be only called in ACL defined by
34178 &%acl_smtp_data_prdr%&,
34179 &%acl_smtp_mime%& or
34182 A timeout of 2 minutes is applied to a scanner call (by default);
34183 if it expires then a defer action is taken.
34185 .oindex "&%av_scanner%&"
34186 You can set the &%av_scanner%& option in the main part of the configuration
34187 to specify which scanner to use, together with any additional options that
34188 are needed. The basic syntax is as follows:
34190 &`av_scanner = <`&&'scanner-type'&&`>:<`&&'option1'&&`>:<`&&'option2'&&`>:[...]`&
34192 If you do not set &%av_scanner%&, it defaults to
34194 av_scanner = sophie:/var/run/sophie
34196 If the value of &%av_scanner%& starts with a dollar character, it is expanded
34198 The usual list-parsing of the content (see &<<SECTlistconstruct>>&) applies.
34199 The following scanner types are supported in this release,
34200 though individual ones can be included or not at build time:
34204 .cindex "virus scanners" "avast"
34205 This is the scanner daemon of Avast. It has been tested with Avast Core
34206 Security (currently at version 2.2.0).
34207 You can get a trial version at &url(https://www.avast.com) or for Linux
34208 at &url(https://www.avast.com/linux-server-antivirus).
34209 This scanner type takes one option,
34210 which can be either a full path to a UNIX socket,
34211 or host and port specifiers separated by white space.
34212 The host may be a name or an IP address; the port is either a
34213 single number or a pair of numbers with a dash between.
34214 A list of options may follow. These options are interpreted on the
34215 Exim's side of the malware scanner, or are given on separate lines to
34216 the daemon as options before the main scan command.
34218 .cindex &`pass_unscanned`& "avast"
34219 If &`pass_unscanned`&
34220 is set, any files the Avast scanner can't scan (e.g.
34221 decompression bombs, or invalid archives) are considered clean. Use with
34226 av_scanner = avast:/var/run/avast/scan.sock:FLAGS -fullfiles:SENSITIVITY -pup
34227 av_scanner = avast:/var/run/avast/scan.sock:pass_unscanned:FLAGS -fullfiles:SENSITIVITY -pup
34228 av_scanner = avast:192.168.2.22 5036
34230 If you omit the argument, the default path
34231 &_/var/run/avast/scan.sock_&
34233 If you use a remote host,
34234 you need to make Exim's spool directory available to it,
34235 as the scanner is passed a file path, not file contents.
34236 For information about available commands and their options you may use
34238 $ socat UNIX:/var/run/avast/scan.sock STDIO:
34244 If the scanner returns a temporary failure (e.g. license issues, or
34245 permission problems), the message is deferred and a paniclog entry is
34246 written. The usual &`defer_ok`& option is available.
34248 .vitem &%aveserver%&
34249 .cindex "virus scanners" "Kaspersky"
34250 This is the scanner daemon of Kaspersky Version 5. You can get a trial version
34251 at &url(https://www.kaspersky.com/). This scanner type takes one option,
34252 which is the path to the daemon's UNIX socket. The default is shown in this
34255 av_scanner = aveserver:/var/run/aveserver
34260 .cindex "virus scanners" "clamd"
34261 This daemon-type scanner is GPL and free. You can get it at
34262 &url(https://www.clamav.net/). Some older versions of clamd do not seem to
34263 unpack MIME containers, so it used to be recommended to unpack MIME attachments
34264 in the MIME ACL. This is no longer believed to be necessary.
34266 The options are a list of server specifiers, which may be
34267 a UNIX socket specification,
34268 a TCP socket specification,
34269 or a (global) option.
34271 A socket specification consists of a space-separated list.
34272 For a Unix socket the first element is a full path for the socket,
34273 for a TCP socket the first element is the IP address
34274 and the second a port number,
34275 Any further elements are per-server (non-global) options.
34276 These per-server options are supported:
34278 retry=<timespec> Retry on connect fail
34281 The &`retry`& option specifies a time after which a single retry for
34282 a failed connect is made. The default is to not retry.
34284 If a Unix socket file is specified, only one server is supported.
34288 av_scanner = clamd:/opt/clamd/socket
34289 av_scanner = clamd:192.0.2.3 1234
34290 av_scanner = clamd:192.0.2.3 1234:local
34291 av_scanner = clamd:192.0.2.3 1234 retry=10s
34292 av_scanner = clamd:192.0.2.3 1234 : 192.0.2.4 1234
34294 If the value of av_scanner points to a UNIX socket file or contains the
34296 option, then the ClamAV interface will pass a filename containing the data
34297 to be scanned, which should normally result in less I/O happening and be
34298 more efficient. Normally in the TCP case, the data is streamed to ClamAV as
34299 Exim does not assume that there is a common filesystem with the remote host.
34301 The final example shows that multiple TCP targets can be specified. Exim will
34302 randomly use one for each incoming email (i.e. it load balances them). Note
34303 that only TCP targets may be used if specifying a list of scanners; a UNIX
34304 socket cannot be mixed in with TCP targets. If one of the servers becomes
34305 unavailable, Exim will try the remaining one(s) until it finds one that works.
34306 When a clamd server becomes unreachable, Exim will log a message. Exim does
34307 not keep track of scanner state between multiple messages, and the scanner
34308 selection is random, so the message will get logged in the mainlog for each
34309 email that the down scanner gets chosen first (message wrapped to be readable):
34311 2013-10-09 14:30:39 1VTumd-0000Y8-BQ malware acl condition:
34312 clamd: connection to localhost, port 3310 failed
34313 (Connection refused)
34316 If the option is unset, the default is &_/tmp/clamd_&. Thanks to David Saez for
34317 contributing the code for this scanner.
34320 .cindex "virus scanners" "command line interface"
34321 This is the keyword for the generic command line scanner interface. It can be
34322 used to attach virus scanners that are invoked from the shell. This scanner
34323 type takes 3 mandatory options:
34326 The full path and name of the scanner binary, with all command line options,
34327 and a placeholder (&`%s`&) for the directory to scan.
34330 A regular expression to match against the STDOUT and STDERR output of the
34331 virus scanner. If the expression matches, a virus was found. You must make
34332 absolutely sure that this expression matches on &"virus found"&. This is called
34333 the &"trigger"& expression.
34336 Another regular expression, containing exactly one pair of parentheses, to
34337 match the name of the virus found in the scanners output. This is called the
34338 &"name"& expression.
34341 For example, Sophos Sweep reports a virus on a line like this:
34343 Virus 'W32/Magistr-B' found in file ./those.bat
34345 For the trigger expression, we can match the phrase &"found in file"&. For the
34346 name expression, we want to extract the W32/Magistr-B string, so we can match
34347 for the single quotes left and right of it. Altogether, this makes the
34348 configuration setting:
34350 av_scanner = cmdline:\
34351 /path/to/sweep -ss -all -rec -archive %s:\
34352 found in file:'(.+)'
34355 .cindex "virus scanners" "DrWeb"
34356 The DrWeb daemon scanner (&url(https://www.sald.ru/)) interface
34358 either a full path to a UNIX socket,
34359 or host and port specifiers separated by white space.
34360 The host may be a name or an IP address; the port is either a
34361 single number or a pair of numbers with a dash between.
34364 av_scanner = drweb:/var/run/drwebd.sock
34365 av_scanner = drweb:192.168.2.20 31337
34367 If you omit the argument, the default path &_/usr/local/drweb/run/drwebd.sock_&
34368 is used. Thanks to Alex Miller for contributing the code for this scanner.
34371 .cindex "virus scanners" "f-protd"
34372 The f-protd scanner is accessed via HTTP over TCP.
34373 One argument is taken, being a space-separated hostname and port number
34377 av_scanner = f-protd:localhost 10200-10204
34379 If you omit the argument, the default values shown above are used.
34381 .vitem &%f-prot6d%&
34382 .cindex "virus scanners" "f-prot6d"
34383 The f-prot6d scanner is accessed using the FPSCAND protocol over TCP.
34384 One argument is taken, being a space-separated hostname and port number.
34387 av_scanner = f-prot6d:localhost 10200
34389 If you omit the argument, the default values show above are used.
34392 .cindex "virus scanners" "F-Secure"
34393 The F-Secure daemon scanner (&url(https://www.f-secure.com/)) takes one
34394 argument which is the path to a UNIX socket. For example:
34396 av_scanner = fsecure:/path/to/.fsav
34398 If no argument is given, the default is &_/var/run/.fsav_&. Thanks to Johan
34399 Thelmen for contributing the code for this scanner.
34401 .vitem &%kavdaemon%&
34402 .cindex "virus scanners" "Kaspersky"
34403 This is the scanner daemon of Kaspersky Version 4. This version of the
34404 Kaspersky scanner is outdated. Please upgrade (see &%aveserver%& above). This
34405 scanner type takes one option, which is the path to the daemon's UNIX socket.
34408 av_scanner = kavdaemon:/opt/AVP/AvpCtl
34410 The default path is &_/var/run/AvpCtl_&.
34413 .cindex "virus scanners" "mksd"
34414 This was a daemon type scanner that is aimed mainly at Polish users,
34415 though some documentation was available in English.
34416 The history can be shown at &url(https://en.wikipedia.org/wiki/Mks_vir)
34417 and this appears to be a candidate for removal from Exim, unless
34418 we are informed of other virus scanners which use the same protocol
34420 The only option for this scanner type is
34421 the maximum number of processes used simultaneously to scan the attachments,
34422 provided that mksd has
34423 been run with at least the same number of child processes. For example:
34425 av_scanner = mksd:2
34427 You can safely omit this option (the default value is 1).
34430 .cindex "virus scanners" "simple socket-connected"
34431 This is a general-purpose way of talking to simple scanner daemons
34432 running on the local machine.
34433 There are four options:
34434 an address (which may be an IP address and port, or the path of a Unix socket),
34435 a commandline to send (may include a single %s which will be replaced with
34436 the path to the mail file to be scanned),
34437 an RE to trigger on from the returned data,
34438 and an RE to extract malware_name from the returned data.
34441 av_scanner = sock:127.0.0.1 6001:%s:(SPAM|VIRUS):(.*)$
34443 Note that surrounding whitespace is stripped from each option, meaning
34444 there is no way to specify a trailing newline.
34445 The socket specifier and both regular-expressions are required.
34446 Default for the commandline is &_%s\n_& (note this does have a trailing newline);
34447 specify an empty element to get this.
34450 .cindex "virus scanners" "Sophos and Sophie"
34451 Sophie is a daemon that uses Sophos' &%libsavi%& library to scan for viruses.
34452 You can get Sophie at &url(http://sophie.sourceforge.net/). The only option
34453 for this scanner type is the path to the UNIX socket that Sophie uses for
34454 client communication. For example:
34456 av_scanner = sophie:/tmp/sophie
34458 The default path is &_/var/run/sophie_&, so if you are using this, you can omit
34462 When &%av_scanner%& is correctly set, you can use the &%malware%& condition in
34463 the DATA ACL. &*Note*&: You cannot use the &%malware%& condition in the MIME
34466 The &%av_scanner%& option is expanded each time &%malware%& is called. This
34467 makes it possible to use different scanners. See further below for an example.
34468 The &%malware%& condition caches its results, so when you use it multiple times
34469 for the same message, the actual scanning process is only carried out once.
34470 However, using expandable items in &%av_scanner%& disables this caching, in
34471 which case each use of the &%malware%& condition causes a new scan of the
34474 The &%malware%& condition takes a right-hand argument that is expanded before
34475 use and taken as a list, slash-separated by default.
34476 The first element can then be one of
34479 &"true"&, &"*"&, or &"1"&, in which case the message is scanned for viruses.
34480 The condition succeeds if a virus was found, and fail otherwise. This is the
34483 &"false"& or &"0"& or an empty string, in which case no scanning is done and
34484 the condition fails immediately.
34486 A regular expression, in which case the message is scanned for viruses. The
34487 condition succeeds if a virus is found and its name matches the regular
34488 expression. This allows you to take special actions on certain types of virus.
34489 Note that &"/"& characters in the RE must be doubled due to the list-processing,
34490 unless the separator is changed (in the usual way &<<SECTlistsepchange>>&).
34493 You can append a &`defer_ok`& element to the &%malware%& argument list to accept
34494 messages even if there is a problem with the virus scanner.
34495 Otherwise, such a problem causes the ACL to defer.
34497 You can append a &`tmo=<val>`& element to the &%malware%& argument list to
34498 specify a non-default timeout. The default is two minutes.
34501 malware = * / defer_ok / tmo=10s
34503 A timeout causes the ACL to defer.
34505 .vindex "&$callout_address$&"
34506 When a connection is made to the scanner the expansion variable &$callout_address$&
34507 is set to record the actual address used.
34509 .vindex "&$malware_name$&"
34510 When a virus is found, the condition sets up an expansion variable called
34511 &$malware_name$& that contains the name of the virus. You can use it in a
34512 &%message%& modifier that specifies the error returned to the sender, and/or in
34515 Beware the interaction of Exim's &%message_size_limit%& with any size limits
34516 imposed by your anti-virus scanner.
34518 Here is a very simple scanning example:
34521 message = This message contains malware ($malware_name)
34523 The next example accepts messages when there is a problem with the scanner:
34525 deny malware = */defer_ok
34526 message = This message contains malware ($malware_name)
34528 The next example shows how to use an ACL variable to scan with both sophie and
34529 aveserver. It assumes you have set:
34531 av_scanner = $acl_m0
34533 in the main Exim configuration.
34535 deny set acl_m0 = sophie
34537 message = This message contains malware ($malware_name)
34539 deny set acl_m0 = aveserver
34541 message = This message contains malware ($malware_name)
34545 .section "Scanning with SpamAssassin and Rspamd" "SECTscanspamass"
34546 .cindex "content scanning" "for spam"
34547 .cindex "spam scanning"
34548 .cindex "SpamAssassin"
34550 The &%spam%& ACL condition calls SpamAssassin's &%spamd%& daemon to get a spam
34551 score and a report for the message.
34552 Support is also provided for Rspamd.
34554 For more information about installation and configuration of SpamAssassin or
34555 Rspamd refer to their respective websites at
34556 &url(https://spamassassin.apache.org/) and &url(https://www.rspamd.com/)
34558 SpamAssassin can be installed with CPAN by running:
34560 perl -MCPAN -e 'install Mail::SpamAssassin'
34562 SpamAssassin has its own set of configuration files. Please review its
34563 documentation to see how you can tweak it. The default installation should work
34566 .oindex "&%spamd_address%&"
34567 By default, SpamAssassin listens on 127.0.0.1, TCP port 783 and if you
34568 intend to use an instance running on the local host you do not need to set
34569 &%spamd_address%&. If you intend to use another host or port for SpamAssassin,
34570 you must set the &%spamd_address%& option in the global part of the Exim
34571 configuration as follows (example):
34573 spamd_address = 192.168.99.45 783
34575 The SpamAssassin protocol relies on a TCP half-close from the client.
34576 If your SpamAssassin client side is running a Linux system with an
34577 iptables firewall, consider setting
34578 &%net.netfilter.nf_conntrack_tcp_timeout_close_wait%& to at least the
34579 timeout, Exim uses when waiting for a response from the SpamAssassin
34580 server (currently defaulting to 120s). With a lower value the Linux
34581 connection tracking may consider your half-closed connection as dead too
34585 To use Rspamd (which by default listens on all local addresses
34587 you should add &%variant=rspamd%& after the address/port pair, for example:
34589 spamd_address = 127.0.0.1 11333 variant=rspamd
34592 As of version 2.60, &%SpamAssassin%& also supports communication over UNIX
34593 sockets. If you want to us these, supply &%spamd_address%& with an absolute
34594 filename instead of an address/port pair:
34596 spamd_address = /var/run/spamd_socket
34598 You can have multiple &%spamd%& servers to improve scalability. These can
34599 reside on other hardware reachable over the network. To specify multiple
34600 &%spamd%& servers, put multiple address/port pairs in the &%spamd_address%&
34601 option, separated with colons (the separator can be changed in the usual way &<<SECTlistsepchange>>&):
34603 spamd_address = 192.168.2.10 783 : \
34604 192.168.2.11 783 : \
34607 Up to 32 &%spamd%& servers are supported.
34608 When a server fails to respond to the connection attempt, all other
34609 servers are tried until one succeeds. If no server responds, the &%spam%&
34612 Unix and TCP socket specifications may be mixed in any order.
34613 Each element of the list is a list itself, space-separated by default
34614 and changeable in the usual way (&<<SECTlistsepchange>>&);
34615 take care to not double the separator.
34617 For TCP socket specifications a host name or IP (v4 or v6, but
34618 subject to list-separator quoting rules) address can be used,
34619 and the port can be one or a dash-separated pair.
34620 In the latter case, the range is tried in strict order.
34622 Elements after the first for Unix sockets, or second for TCP socket,
34624 The supported options are:
34626 pri=<priority> Selection priority
34627 weight=<value> Selection bias
34628 time=<start>-<end> Use only between these times of day
34629 retry=<timespec> Retry on connect fail
34630 tmo=<timespec> Connection time limit
34631 variant=rspamd Use Rspamd rather than SpamAssassin protocol
34634 The &`pri`& option specifies a priority for the server within the list,
34635 higher values being tried first.
34636 The default priority is 1.
34638 The &`weight`& option specifies a selection bias.
34639 Within a priority set
34640 servers are queried in a random fashion, weighted by this value.
34641 The default value for selection bias is 1.
34643 Time specifications for the &`time`& option are <hour>.<minute>.<second>
34644 in the local time zone; each element being one or more digits.
34645 Either the seconds or both minutes and seconds, plus the leading &`.`&
34646 characters, may be omitted and will be taken as zero.
34648 Timeout specifications for the &`retry`& and &`tmo`& options
34649 are the usual Exim time interval standard, e.g. &`20s`& or &`1m`&.
34651 The &`tmo`& option specifies an overall timeout for communication.
34652 The default value is two minutes.
34654 The &`retry`& option specifies a time after which a single retry for
34655 a failed connect is made.
34656 The default is to not retry.
34658 The &%spamd_address%& variable is expanded before use if it starts with
34659 a dollar sign. In this case, the expansion may return a string that is
34660 used as the list so that multiple spamd servers can be the result of an
34663 .vindex "&$callout_address$&"
34664 When a connection is made to the server the expansion variable &$callout_address$&
34665 is set to record the actual address used.
34667 .section "Calling SpamAssassin from an Exim ACL" "SECID206"
34668 Here is a simple example of the use of the &%spam%& condition in a DATA ACL:
34671 message = This message was classified as SPAM
34673 The right-hand side of the &%spam%& condition specifies a name. This is
34674 relevant if you have set up multiple SpamAssassin profiles. If you do not want
34675 to scan using a specific profile, but rather use the SpamAssassin system-wide
34676 default profile, you can scan for an unknown name, or simply use &"nobody"&.
34677 Rspamd does not use this setting. However, you must put something on the
34680 The name allows you to use per-domain or per-user antispam profiles in
34681 principle, but this is not straightforward in practice, because a message may
34682 have multiple recipients, not necessarily all in the same domain. Because the
34683 &%spam%& condition has to be called from a DATA-time ACL in order to be able to
34684 read the contents of the message, the variables &$local_part$& and &$domain$&
34686 Careful enforcement of single-recipient messages
34687 (e.g. by responding with defer in the recipient ACL for all recipients
34689 or the use of PRDR,
34690 .cindex "PRDR" "use for per-user SpamAssassin profiles"
34691 are needed to use this feature.
34693 The right-hand side of the &%spam%& condition is expanded before being used, so
34694 you can put lookups or conditions there. When the right-hand side evaluates to
34695 &"0"& or &"false"&, no scanning is done and the condition fails immediately.
34698 Scanning with SpamAssassin uses a lot of resources. If you scan every message,
34699 large ones may cause significant performance degradation. As most spam messages
34700 are quite small, it is recommended that you do not scan the big ones. For
34703 deny condition = ${if < {$message_size}{10K}}
34705 message = This message was classified as SPAM
34708 The &%spam%& condition returns true if the threshold specified in the user's
34709 SpamAssassin profile has been matched or exceeded. If you want to use the
34710 &%spam%& condition for its side effects (see the variables below), you can make
34711 it always return &"true"& by appending &`:true`& to the username.
34713 .cindex "spam scanning" "returned variables"
34714 When the &%spam%& condition is run, it sets up a number of expansion
34716 Except for &$spam_report$&,
34717 these variables are saved with the received message so are
34718 available for use at delivery time.
34721 .vitem &$spam_score$&
34722 The spam score of the message, for example, &"3.4"& or &"30.5"&. This is useful
34723 for inclusion in log or reject messages.
34725 .vitem &$spam_score_int$&
34726 The spam score of the message, multiplied by ten, as an integer value. For
34727 example &"34"& or &"305"&. It may appear to disagree with &$spam_score$&
34728 because &$spam_score$& is rounded and &$spam_score_int$& is truncated.
34729 The integer value is useful for numeric comparisons in conditions.
34731 .vitem &$spam_bar$&
34732 A string consisting of a number of &"+"& or &"-"& characters, representing the
34733 integer part of the spam score value. A spam score of 4.4 would have a
34734 &$spam_bar$& value of &"++++"&. This is useful for inclusion in warning
34735 headers, since MUAs can match on such strings. The maximum length of the
34736 spam bar is 50 characters.
34738 .vitem &$spam_report$&
34739 A multiline text table, containing the full SpamAssassin report for the
34740 message. Useful for inclusion in headers or reject messages.
34741 This variable is only usable in a DATA-time ACL.
34742 Beware that SpamAssassin may return non-ASCII characters, especially
34743 when running in country-specific locales, which are not legal
34744 unencoded in headers.
34746 .vitem &$spam_action$&
34747 For SpamAssassin either 'reject' or 'no action' depending on the
34748 spam score versus threshold.
34749 For Rspamd, the recommended action.
34753 The &%spam%& condition caches its results unless expansion in
34754 spamd_address was used. If you call it again with the same user name, it
34755 does not scan again, but rather returns the same values as before.
34757 The &%spam%& condition returns DEFER if there is any error while running
34758 the message through SpamAssassin or if the expansion of spamd_address
34759 failed. If you want to treat DEFER as FAIL (to pass on to the next ACL
34760 statement block), append &`/defer_ok`& to the right-hand side of the
34761 spam condition, like this:
34763 deny spam = joe/defer_ok
34764 message = This message was classified as SPAM
34766 This causes messages to be accepted even if there is a problem with &%spamd%&.
34768 Here is a longer, commented example of the use of the &%spam%&
34771 # put headers in all messages (no matter if spam or not)
34772 warn spam = nobody:true
34773 add_header = X-Spam-Score: $spam_score ($spam_bar)
34774 add_header = X-Spam-Report: $spam_report
34776 # add second subject line with *SPAM* marker when message
34777 # is over threshold
34779 add_header = Subject: *SPAM* $h_Subject:
34781 # reject spam at high scores (> 12)
34782 deny spam = nobody:true
34783 condition = ${if >{$spam_score_int}{120}{1}{0}}
34784 message = This message scored $spam_score spam points.
34789 .section "Scanning MIME parts" "SECTscanmimepart"
34790 .cindex "content scanning" "MIME parts"
34791 .cindex "MIME content scanning"
34792 .oindex "&%acl_smtp_mime%&"
34793 .oindex "&%acl_not_smtp_mime%&"
34794 The &%acl_smtp_mime%& global option specifies an ACL that is called once for
34795 each MIME part of an SMTP message, including multipart types, in the sequence
34796 of their position in the message. Similarly, the &%acl_not_smtp_mime%& option
34797 specifies an ACL that is used for the MIME parts of non-SMTP messages. These
34798 options may both refer to the same ACL if you want the same processing in both
34801 These ACLs are called (possibly many times) just before the &%acl_smtp_data%&
34802 ACL in the case of an SMTP message, or just before the &%acl_not_smtp%& ACL in
34803 the case of a non-SMTP message. However, a MIME ACL is called only if the
34804 message contains a &'Content-Type:'& header line. When a call to a MIME
34805 ACL does not yield &"accept"&, ACL processing is aborted and the appropriate
34806 result code is sent to the client. In the case of an SMTP message, the
34807 &%acl_smtp_data%& ACL is not called when this happens.
34809 You cannot use the &%malware%& or &%spam%& conditions in a MIME ACL; these can
34810 only be used in the DATA or non-SMTP ACLs. However, you can use the &%regex%&
34811 condition to match against the raw MIME part. You can also use the
34812 &%mime_regex%& condition to match against the decoded MIME part (see section
34813 &<<SECTscanregex>>&).
34815 At the start of a MIME ACL, a number of variables are set from the header
34816 information for the relevant MIME part. These are described below. The contents
34817 of the MIME part are not by default decoded into a disk file except for MIME
34818 parts whose content-type is &"message/rfc822"&. If you want to decode a MIME
34819 part into a disk file, you can use the &%decode%& condition. The general
34822 &`decode = [/`&<&'path'&>&`/]`&<&'filename'&>
34824 The right hand side is expanded before use. After expansion,
34828 &"0"& or &"false"&, in which case no decoding is done.
34830 The string &"default"&. In that case, the file is put in the temporary
34831 &"default"& directory <&'spool_directory'&>&_/scan/_&<&'message_id'&>&_/_& with
34832 a sequential filename consisting of the message id and a sequence number. The
34833 full path and name is available in &$mime_decoded_filename$& after decoding.
34835 A full path name starting with a slash. If the full name is an existing
34836 directory, it is used as a replacement for the default directory. The filename
34837 is then sequentially assigned. If the path does not exist, it is used as
34838 the full path and filename.
34840 If the string does not start with a slash, it is used as the
34841 filename, and the default path is then used.
34843 The &%decode%& condition normally succeeds. It is only false for syntax
34844 errors or unusual circumstances such as memory shortages. You can easily decode
34845 a file with its original, proposed filename using
34847 decode = $mime_filename
34849 However, you should keep in mind that &$mime_filename$& might contain
34850 anything. If you place files outside of the default path, they are not
34851 automatically unlinked.
34853 For RFC822 attachments (these are messages attached to messages, with a
34854 content-type of &"message/rfc822"&), the ACL is called again in the same manner
34855 as for the primary message, only that the &$mime_is_rfc822$& expansion
34856 variable is set (see below). Attached messages are always decoded to disk
34857 before being checked, and the files are unlinked once the check is done.
34859 The MIME ACL supports the &%regex%& and &%mime_regex%& conditions. These can be
34860 used to match regular expressions against raw and decoded MIME parts,
34861 respectively. They are described in section &<<SECTscanregex>>&.
34863 .cindex "MIME content scanning" "returned variables"
34864 The following list describes all expansion variables that are
34865 available in the MIME ACL:
34868 .vitem &$mime_anomaly_level$& &&&
34869 &$mime_anomaly_text$&
34870 .vindex &$mime_anomaly_level$&
34871 .vindex &$mime_anomaly_text$&
34872 If there are problems decoding, these variables contain information on
34873 the detected issue.
34875 .vitem &$mime_boundary$&
34876 .vindex &$mime_boundary$&
34877 If the current part is a multipart (see &$mime_is_multipart$& below), it should
34878 have a boundary string, which is stored in this variable. If the current part
34879 has no boundary parameter in the &'Content-Type:'& header, this variable
34880 contains the empty string.
34882 .vitem &$mime_charset$&
34883 .vindex &$mime_charset$&
34884 This variable contains the character set identifier, if one was found in the
34885 &'Content-Type:'& header. Examples for charset identifiers are:
34891 Please note that this value is not normalized, so you should do matches
34892 case-insensitively.
34894 .vitem &$mime_content_description$&
34895 .vindex &$mime_content_description$&
34896 This variable contains the normalized content of the &'Content-Description:'&
34897 header. It can contain a human-readable description of the parts content. Some
34898 implementations repeat the filename for attachments here, but they are usually
34899 only used for display purposes.
34901 .vitem &$mime_content_disposition$&
34902 .vindex &$mime_content_disposition$&
34903 This variable contains the normalized content of the &'Content-Disposition:'&
34904 header. You can expect strings like &"attachment"& or &"inline"& here.
34906 .vitem &$mime_content_id$&
34907 .vindex &$mime_content_id$&
34908 This variable contains the normalized content of the &'Content-ID:'& header.
34909 This is a unique ID that can be used to reference a part from another part.
34911 .vitem &$mime_content_size$&
34912 .vindex &$mime_content_size$&
34913 This variable is set only after the &%decode%& modifier (see above) has been
34914 successfully run. It contains the size of the decoded part in kilobytes. The
34915 size is always rounded up to full kilobytes, so only a completely empty part
34916 has a &$mime_content_size$& of zero.
34918 .vitem &$mime_content_transfer_encoding$&
34919 .vindex &$mime_content_transfer_encoding$&
34920 This variable contains the normalized content of the
34921 &'Content-transfer-encoding:'& header. This is a symbolic name for an encoding
34922 type. Typical values are &"base64"& and &"quoted-printable"&.
34924 .vitem &$mime_content_type$&
34925 .vindex &$mime_content_type$&
34926 If the MIME part has a &'Content-Type:'& header, this variable contains its
34927 value, lowercased, and without any options (like &"name"& or &"charset"&). Here
34928 are some examples of popular MIME types, as they may appear in this variable:
34932 application/octet-stream
34936 If the MIME part has no &'Content-Type:'& header, this variable contains the
34939 .vitem &$mime_decoded_filename$&
34940 .vindex &$mime_decoded_filename$&
34941 This variable is set only after the &%decode%& modifier (see above) has been
34942 successfully run. It contains the full path and filename of the file
34943 containing the decoded data.
34948 .vitem &$mime_filename$&
34949 .vindex &$mime_filename$&
34950 This is perhaps the most important of the MIME variables. It contains a
34951 proposed filename for an attachment, if one was found in either the
34952 &'Content-Type:'& or &'Content-Disposition:'& headers. The filename will be
34955 decoded, but no additional sanity checks are done.
34957 found, this variable contains the empty string.
34959 .vitem &$mime_is_coverletter$&
34960 .vindex &$mime_is_coverletter$&
34961 This variable attempts to differentiate the &"cover letter"& of an e-mail from
34962 attached data. It can be used to clamp down on flashy or unnecessarily encoded
34963 content in the cover letter, while not restricting attachments at all.
34965 The variable contains 1 (true) for a MIME part believed to be part of the
34966 cover letter, and 0 (false) for an attachment. At present, the algorithm is as
34970 The outermost MIME part of a message is always a cover letter.
34973 If a multipart/alternative or multipart/related MIME part is a cover letter,
34974 so are all MIME subparts within that multipart.
34977 If any other multipart is a cover letter, the first subpart is a cover letter,
34978 and the rest are attachments.
34981 All parts contained within an attachment multipart are attachments.
34984 As an example, the following will ban &"HTML mail"& (including that sent with
34985 alternative plain text), while allowing HTML files to be attached. HTML
34986 coverletter mail attached to non-HTML coverletter mail will also be allowed:
34988 deny !condition = $mime_is_rfc822
34989 condition = $mime_is_coverletter
34990 condition = ${if eq{$mime_content_type}{text/html}{1}{0}}
34991 message = HTML mail is not accepted here
34994 .vitem &$mime_is_multipart$&
34995 .vindex &$mime_is_multipart$&
34996 This variable has the value 1 (true) when the current part has the main type
34997 &"multipart"&, for example, &"multipart/alternative"& or &"multipart/mixed"&.
34998 Since multipart entities only serve as containers for other parts, you may not
34999 want to carry out specific actions on them.
35001 .vitem &$mime_is_rfc822$&
35002 .vindex &$mime_is_rfc822$&
35003 This variable has the value 1 (true) if the current part is not a part of the
35004 checked message itself, but part of an attached message. Attached message
35005 decoding is fully recursive.
35007 .vitem &$mime_part_count$&
35008 .vindex &$mime_part_count$&
35009 This variable is a counter that is raised for each processed MIME part. It
35010 starts at zero for the very first part (which is usually a multipart). The
35011 counter is per-message, so it is reset when processing RFC822 attachments (see
35012 &$mime_is_rfc822$&). The counter stays set after &%acl_smtp_mime%& is
35013 complete, so you can use it in the DATA ACL to determine the number of MIME
35014 parts of a message. For non-MIME messages, this variable contains the value -1.
35019 .section "Scanning with regular expressions" "SECTscanregex"
35020 .cindex "content scanning" "with regular expressions"
35021 .cindex "regular expressions" "content scanning with"
35022 You can specify your own custom regular expression matches on the full body of
35023 the message, or on individual MIME parts.
35025 The &%regex%& condition takes one or more regular expressions as arguments and
35026 matches them against the full message (when called in the DATA ACL) or a raw
35027 MIME part (when called in the MIME ACL). The &%regex%& condition matches
35028 linewise, with a maximum line length of 32K characters. That means you cannot
35029 have multiline matches with the &%regex%& condition.
35031 The &%mime_regex%& condition can be called only in the MIME ACL. It matches up
35032 to 32K of decoded content (the whole content at once, not linewise). If the
35033 part has not been decoded with the &%decode%& modifier earlier in the ACL, it
35034 is decoded automatically when &%mime_regex%& is executed (using default path
35035 and filename values). If the decoded data is larger than 32K, only the first
35036 32K characters are checked.
35038 The regular expressions are passed as a colon-separated list. To include a
35039 literal colon, you must double it. Since the whole right-hand side string is
35040 expanded before being used, you must also escape dollar signs and backslashes
35041 with more backslashes, or use the &`\N`& facility to disable expansion.
35042 Here is a simple example that contains two regular expressions:
35044 deny regex = [Mm]ortgage : URGENT BUSINESS PROPOSAL
35045 message = contains blacklisted regex ($regex_match_string)
35047 The conditions returns true if any one of the regular expressions matches. The
35048 &$regex_match_string$& expansion variable is then set up and contains the
35049 matching regular expression.
35050 The expansion variables &$regex1$& &$regex2$& etc
35051 are set to any substrings captured by the regular expression.
35053 &*Warning*&: With large messages, these conditions can be fairly
35061 . ////////////////////////////////////////////////////////////////////////////
35062 . ////////////////////////////////////////////////////////////////////////////
35064 .chapter "Adding a local scan function to Exim" "CHAPlocalscan" &&&
35065 "Local scan function"
35066 .scindex IIDlosca "&[local_scan()]& function" "description of"
35067 .cindex "customizing" "input scan using C function"
35068 .cindex "policy control" "by local scan function"
35069 In these days of email worms, viruses, and ever-increasing spam, some sites
35070 want to apply a lot of checking to messages before accepting them.
35072 The content scanning extension (chapter &<<CHAPexiscan>>&) has facilities for
35073 passing messages to external virus and spam scanning software. You can also do
35074 a certain amount in Exim itself through string expansions and the &%condition%&
35075 condition in the ACL that runs after the SMTP DATA command or the ACL for
35076 non-SMTP messages (see chapter &<<CHAPACL>>&), but this has its limitations.
35078 To allow for further customization to a site's own requirements, there is the
35079 possibility of linking Exim with a private message scanning function, written
35080 in C. If you want to run code that is written in something other than C, you
35081 can of course use a little C stub to call it.
35083 The local scan function is run once for every incoming message, at the point
35084 when Exim is just about to accept the message.
35085 It can therefore be used to control non-SMTP messages from local processes as
35086 well as messages arriving via SMTP.
35088 Exim applies a timeout to calls of the local scan function, and there is an
35089 option called &%local_scan_timeout%& for setting it. The default is 5 minutes.
35090 Zero means &"no timeout"&.
35091 Exim also sets up signal handlers for SIGSEGV, SIGILL, SIGFPE, and SIGBUS
35092 before calling the local scan function, so that the most common types of crash
35093 are caught. If the timeout is exceeded or one of those signals is caught, the
35094 incoming message is rejected with a temporary error if it is an SMTP message.
35095 For a non-SMTP message, the message is dropped and Exim ends with a non-zero
35096 code. The incident is logged on the main and reject logs.
35100 .section "Building Exim to use a local scan function" "SECID207"
35101 .cindex "&[local_scan()]& function" "building Exim to use"
35102 To make use of the local scan function feature, you must tell Exim where your
35103 function is before building Exim, by setting
35104 both HAVE_LOCAL_SCAN and
35105 LOCAL_SCAN_SOURCE in your
35106 &_Local/Makefile_&. A recommended place to put it is in the &_Local_&
35107 directory, so you might set
35109 HAVE_LOCAL_SCAN=yes
35110 LOCAL_SCAN_SOURCE=Local/local_scan.c
35112 for example. The function must be called &[local_scan()]&;
35113 the source file(s) for it should first #define LOCAL_SCAN
35114 and then #include "local_scan.h".
35116 Exim after it has received a message, when the success return code is about to
35117 be sent. This is after all the ACLs have been run. The return code from your
35118 function controls whether the message is actually accepted or not. There is a
35119 commented template function (that just accepts the message) in the file
35120 _src/local_scan.c_.
35122 If you want to make use of Exim's runtime configuration file to set options
35123 for your &[local_scan()]& function, you must also set
35125 LOCAL_SCAN_HAS_OPTIONS=yes
35127 in &_Local/Makefile_& (see section &<<SECTconoptloc>>& below).
35132 .section "API for local_scan()" "SECTapiforloc"
35133 .cindex "&[local_scan()]& function" "API description"
35134 .cindex &%dlfunc%& "API description"
35135 You must include this line near the start of your code:
35138 #include "local_scan.h"
35140 This header file defines a number of variables and other values, and the
35141 prototype for the function itself. Exim is coded to use unsigned char values
35142 almost exclusively, and one of the things this header defines is a shorthand
35143 for &`unsigned char`& called &`uschar`&.
35144 It also makes available the following macro definitions, to simplify casting character
35145 strings and pointers to character strings:
35147 #define CS (char *)
35148 #define CCS (const char *)
35149 #define CSS (char **)
35150 #define US (unsigned char *)
35151 #define CUS (const unsigned char *)
35152 #define USS (unsigned char **)
35154 The function prototype for &[local_scan()]& is:
35156 extern int local_scan(int fd, uschar **return_text);
35158 The arguments are as follows:
35161 &%fd%& is a file descriptor for the file that contains the body of the message
35162 (the -D file). The file is open for reading and writing, but updating it is not
35163 recommended. &*Warning*&: You must &'not'& close this file descriptor.
35165 The descriptor is positioned at character 19 of the file, which is the first
35166 character of the body itself, because the first 19 characters are the message
35167 id followed by &`-D`& and a newline. If you rewind the file, you should use the
35168 macro SPOOL_DATA_START_OFFSET to reset to the start of the data, just in
35169 case this changes in some future version.
35171 &%return_text%& is an address which you can use to return a pointer to a text
35172 string at the end of the function. The value it points to on entry is NULL.
35175 The function must return an &%int%& value which is one of the following macros:
35178 .vitem &`LOCAL_SCAN_ACCEPT`&
35179 .vindex "&$local_scan_data$&"
35180 The message is accepted. If you pass back a string of text, it is saved with
35181 the message, and made available in the variable &$local_scan_data$&. No
35182 newlines are permitted (if there are any, they are turned into spaces) and the
35183 maximum length of text is 1000 characters.
35185 .vitem &`LOCAL_SCAN_ACCEPT_FREEZE`&
35186 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
35187 queued without immediate delivery, and is frozen.
35189 .vitem &`LOCAL_SCAN_ACCEPT_QUEUE`&
35190 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
35191 queued without immediate delivery.
35193 .vitem &`LOCAL_SCAN_REJECT`&
35194 The message is rejected; the returned text is used as an error message which is
35195 passed back to the sender and which is also logged. Newlines are permitted &--
35196 they cause a multiline response for SMTP rejections, but are converted to
35197 &`\n`& in log lines. If no message is given, &"Administrative prohibition"& is
35200 .vitem &`LOCAL_SCAN_TEMPREJECT`&
35201 The message is temporarily rejected; the returned text is used as an error
35202 message as for LOCAL_SCAN_REJECT. If no message is given, &"Temporary local
35205 .vitem &`LOCAL_SCAN_REJECT_NOLOGHDR`&
35206 This behaves as LOCAL_SCAN_REJECT, except that the header of the rejected
35207 message is not written to the reject log. It has the effect of unsetting the
35208 &%rejected_header%& log selector for just this rejection. If
35209 &%rejected_header%& is already unset (see the discussion of the
35210 &%log_selection%& option in section &<<SECTlogselector>>&), this code is the
35211 same as LOCAL_SCAN_REJECT.
35213 .vitem &`LOCAL_SCAN_TEMPREJECT_NOLOGHDR`&
35214 This code is a variation of LOCAL_SCAN_TEMPREJECT in the same way that
35215 LOCAL_SCAN_REJECT_NOLOGHDR is a variation of LOCAL_SCAN_REJECT.
35218 If the message is not being received by interactive SMTP, rejections are
35219 reported by writing to &%stderr%& or by sending an email, as configured by the
35220 &%-oe%& command line options.
35224 .section "Configuration options for local_scan()" "SECTconoptloc"
35225 .cindex "&[local_scan()]& function" "configuration options"
35226 It is possible to have option settings in the main configuration file
35227 that set values in static variables in the &[local_scan()]& module. If you
35228 want to do this, you must have the line
35230 LOCAL_SCAN_HAS_OPTIONS=yes
35232 in your &_Local/Makefile_& when you build Exim. (This line is in
35233 &_OS/Makefile-Default_&, commented out). Then, in the &[local_scan()]& source
35234 file, you must define static variables to hold the option values, and a table
35237 The table must be a vector called &%local_scan_options%&, of type
35238 &`optionlist`&. Each entry is a triplet, consisting of a name, an option type,
35239 and a pointer to the variable that holds the value. The entries must appear in
35240 alphabetical order. Following &%local_scan_options%& you must also define a
35241 variable called &%local_scan_options_count%& that contains the number of
35242 entries in the table. Here is a short example, showing two kinds of option:
35244 static int my_integer_option = 42;
35245 static uschar *my_string_option = US"a default string";
35247 optionlist local_scan_options[] = {
35248 { "my_integer", opt_int, &my_integer_option },
35249 { "my_string", opt_stringptr, &my_string_option }
35252 int local_scan_options_count =
35253 sizeof(local_scan_options)/sizeof(optionlist);
35255 The values of the variables can now be changed from Exim's runtime
35256 configuration file by including a local scan section as in this example:
35260 my_string = some string of text...
35262 The available types of option data are as follows:
35265 .vitem &*opt_bool*&
35266 This specifies a boolean (true/false) option. The address should point to a
35267 variable of type &`BOOL`&, which will be set to TRUE or FALSE, which are macros
35268 that are defined as &"1"& and &"0"&, respectively. If you want to detect
35269 whether such a variable has been set at all, you can initialize it to
35270 TRUE_UNSET. (BOOL variables are integers underneath, so can hold more than two
35273 .vitem &*opt_fixed*&
35274 This specifies a fixed point number, such as is used for load averages.
35275 The address should point to a variable of type &`int`&. The value is stored
35276 multiplied by 1000, so, for example, 1.4142 is truncated and stored as 1414.
35279 This specifies an integer; the address should point to a variable of type
35280 &`int`&. The value may be specified in any of the integer formats accepted by
35283 .vitem &*opt_mkint*&
35284 This is the same as &%opt_int%&, except that when such a value is output in a
35285 &%-bP%& listing, if it is an exact number of kilobytes or megabytes, it is
35286 printed with the suffix K or M.
35288 .vitem &*opt_octint*&
35289 This also specifies an integer, but the value is always interpreted as an
35290 octal integer, whether or not it starts with the digit zero, and it is
35291 always output in octal.
35293 .vitem &*opt_stringptr*&
35294 This specifies a string value; the address must be a pointer to a
35295 variable that points to a string (for example, of type &`uschar *`&).
35297 .vitem &*opt_time*&
35298 This specifies a time interval value. The address must point to a variable of
35299 type &`int`&. The value that is placed there is a number of seconds.
35302 If the &%-bP%& command line option is followed by &`local_scan`&, Exim prints
35303 out the values of all the &[local_scan()]& options.
35307 .section "Available Exim variables" "SECID208"
35308 .cindex "&[local_scan()]& function" "available Exim variables"
35309 The header &_local_scan.h_& gives you access to a number of C variables. These
35310 are the only ones that are guaranteed to be maintained from release to release.
35311 Note, however, that you can obtain the value of any Exim expansion variable,
35312 including &$recipients$&, by calling &'expand_string()'&. The exported
35313 C variables are as follows:
35316 .vitem &*int&~body_linecount*&
35317 This variable contains the number of lines in the message's body.
35318 It is not valid if the &%spool_wireformat%& option is used.
35320 .vitem &*int&~body_zerocount*&
35321 This variable contains the number of binary zero bytes in the message's body.
35322 It is not valid if the &%spool_wireformat%& option is used.
35324 .vitem &*unsigned&~int&~debug_selector*&
35325 This variable is set to zero when no debugging is taking place. Otherwise, it
35326 is a bitmap of debugging selectors. Two bits are identified for use in
35327 &[local_scan()]&; they are defined as macros:
35330 The &`D_v`& bit is set when &%-v%& was present on the command line. This is a
35331 testing option that is not privileged &-- any caller may set it. All the
35332 other selector bits can be set only by admin users.
35335 The &`D_local_scan`& bit is provided for use by &[local_scan()]&; it is set
35336 by the &`+local_scan`& debug selector. It is not included in the default set
35340 Thus, to write to the debugging output only when &`+local_scan`& has been
35341 selected, you should use code like this:
35343 if ((debug_selector & D_local_scan) != 0)
35344 debug_printf("xxx", ...);
35346 .vitem &*uschar&~*expand_string_message*&
35347 After a failing call to &'expand_string()'& (returned value NULL), the
35348 variable &%expand_string_message%& contains the error message, zero-terminated.
35350 .vitem &*header_line&~*header_list*&
35351 A pointer to a chain of header lines. The &%header_line%& structure is
35354 .vitem &*header_line&~*header_last*&
35355 A pointer to the last of the header lines.
35357 .vitem &*const&~uschar&~*headers_charset*&
35358 The value of the &%headers_charset%& configuration option.
35360 .vitem &*BOOL&~host_checking*&
35361 This variable is TRUE during a host checking session that is initiated by the
35362 &%-bh%& command line option.
35364 .vitem &*uschar&~*interface_address*&
35365 The IP address of the interface that received the message, as a string. This
35366 is NULL for locally submitted messages.
35368 .vitem &*int&~interface_port*&
35369 The port on which this message was received. When testing with the &%-bh%&
35370 command line option, the value of this variable is -1 unless a port has been
35371 specified via the &%-oMi%& option.
35373 .vitem &*uschar&~*message_id*&
35374 This variable contains Exim's message id for the incoming message (the value of
35375 &$message_exim_id$&) as a zero-terminated string.
35377 .vitem &*uschar&~*received_protocol*&
35378 The name of the protocol by which the message was received.
35380 .vitem &*int&~recipients_count*&
35381 The number of accepted recipients.
35383 .vitem &*recipient_item&~*recipients_list*&
35384 .cindex "recipient" "adding in local scan"
35385 .cindex "recipient" "removing in local scan"
35386 The list of accepted recipients, held in a vector of length
35387 &%recipients_count%&. The &%recipient_item%& structure is discussed below. You
35388 can add additional recipients by calling &'receive_add_recipient()'& (see
35389 below). You can delete recipients by removing them from the vector and
35390 adjusting the value in &%recipients_count%&. In particular, by setting
35391 &%recipients_count%& to zero you remove all recipients. If you then return the
35392 value &`LOCAL_SCAN_ACCEPT`&, the message is accepted, but immediately
35393 blackholed. To replace the recipients, you can set &%recipients_count%& to zero
35394 and then call &'receive_add_recipient()'& as often as needed.
35396 .vitem &*uschar&~*sender_address*&
35397 The envelope sender address. For bounce messages this is the empty string.
35399 .vitem &*uschar&~*sender_host_address*&
35400 The IP address of the sending host, as a string. This is NULL for
35401 locally-submitted messages.
35403 .vitem &*uschar&~*sender_host_authenticated*&
35404 The name of the authentication mechanism that was used, or NULL if the message
35405 was not received over an authenticated SMTP connection.
35407 .vitem &*uschar&~*sender_host_name*&
35408 The name of the sending host, if known.
35410 .vitem &*int&~sender_host_port*&
35411 The port on the sending host.
35413 .vitem &*BOOL&~smtp_input*&
35414 This variable is TRUE for all SMTP input, including BSMTP.
35416 .vitem &*BOOL&~smtp_batched_input*&
35417 This variable is TRUE for BSMTP input.
35419 .vitem &*int&~store_pool*&
35420 The contents of this variable control which pool of memory is used for new
35421 requests. See section &<<SECTmemhanloc>>& for details.
35425 .section "Structure of header lines" "SECID209"
35426 The &%header_line%& structure contains the members listed below.
35427 You can add additional header lines by calling the &'header_add()'& function
35428 (see below). You can cause header lines to be ignored (deleted) by setting
35433 .vitem &*struct&~header_line&~*next*&
35434 A pointer to the next header line, or NULL for the last line.
35436 .vitem &*int&~type*&
35437 A code identifying certain headers that Exim recognizes. The codes are printing
35438 characters, and are documented in chapter &<<CHAPspool>>& of this manual.
35439 Notice in particular that any header line whose type is * is not transmitted
35440 with the message. This flagging is used for header lines that have been
35441 rewritten, or are to be removed (for example, &'Envelope-sender:'& header
35442 lines.) Effectively, * means &"deleted"&.
35444 .vitem &*int&~slen*&
35445 The number of characters in the header line, including the terminating and any
35448 .vitem &*uschar&~*text*&
35449 A pointer to the text of the header. It always ends with a newline, followed by
35450 a zero byte. Internal newlines are preserved.
35455 .section "Structure of recipient items" "SECID210"
35456 The &%recipient_item%& structure contains these members:
35459 .vitem &*uschar&~*address*&
35460 This is a pointer to the recipient address as it was received.
35462 .vitem &*int&~pno*&
35463 This is used in later Exim processing when top level addresses are created by
35464 the &%one_time%& option. It is not relevant at the time &[local_scan()]& is run
35465 and must always contain -1 at this stage.
35467 .vitem &*uschar&~*errors_to*&
35468 If this value is not NULL, bounce messages caused by failing to deliver to the
35469 recipient are sent to the address it contains. In other words, it overrides the
35470 envelope sender for this one recipient. (Compare the &%errors_to%& generic
35471 router option.) If a &[local_scan()]& function sets an &%errors_to%& field to
35472 an unqualified address, Exim qualifies it using the domain from
35473 &%qualify_recipient%&. When &[local_scan()]& is called, the &%errors_to%& field
35474 is NULL for all recipients.
35479 .section "Available Exim functions" "SECID211"
35480 .cindex "&[local_scan()]& function" "available Exim functions"
35481 The header &_local_scan.h_& gives you access to a number of Exim functions.
35482 These are the only ones that are guaranteed to be maintained from release to
35486 .vitem "&*pid_t&~child_open(uschar&~**argv,&~uschar&~**envp,&~int&~newumask,&&&
35487 &~int&~*infdptr,&~int&~*outfdptr, &~&~BOOL&~make_leader)*&"
35489 This function creates a child process that runs the command specified by
35490 &%argv%&. The environment for the process is specified by &%envp%&, which can
35491 be NULL if no environment variables are to be passed. A new umask is supplied
35492 for the process in &%newumask%&.
35494 Pipes to the standard input and output of the new process are set up
35495 and returned to the caller via the &%infdptr%& and &%outfdptr%& arguments. The
35496 standard error is cloned to the standard output. If there are any file
35497 descriptors &"in the way"& in the new process, they are closed. If the final
35498 argument is TRUE, the new process is made into a process group leader.
35500 The function returns the pid of the new process, or -1 if things go wrong.
35502 .vitem &*int&~child_close(pid_t&~pid,&~int&~timeout)*&
35503 This function waits for a child process to terminate, or for a timeout (in
35504 seconds) to expire. A timeout value of zero means wait as long as it takes. The
35505 return value is as follows:
35510 The process terminated by a normal exit and the value is the process
35516 The process was terminated by a signal and the value is the negation of the
35522 The process timed out.
35526 The was some other error in wait(); &%errno%& is still set.
35529 .vitem &*pid_t&~child_open_exim(int&~*fd)*&
35530 This function provide you with a means of submitting a new message to
35531 Exim. (Of course, you can also call &_/usr/sbin/sendmail_& yourself if you
35532 want, but this packages it all up for you.) The function creates a pipe,
35533 forks a subprocess that is running
35535 exim -t -oem -oi -f <>
35537 and returns to you (via the &`int *`& argument) a file descriptor for the pipe
35538 that is connected to the standard input. The yield of the function is the PID
35539 of the subprocess. You can then write a message to the file descriptor, with
35540 recipients in &'To:'&, &'Cc:'&, and/or &'Bcc:'& header lines.
35542 When you have finished, call &'child_close()'& to wait for the process to
35543 finish and to collect its ending status. A timeout value of zero is usually
35544 fine in this circumstance. Unless you have made a mistake with the recipient
35545 addresses, you should get a return code of zero.
35548 .vitem &*pid_t&~child_open_exim2(int&~*fd,&~uschar&~*sender,&~uschar&~&&&
35549 *sender_authentication)*&
35550 This function is a more sophisticated version of &'child_open()'&. The command
35553 &`exim -t -oem -oi -f `&&'sender'&&` -oMas `&&'sender_authentication'&
35555 The third argument may be NULL, in which case the &%-oMas%& option is omitted.
35558 .vitem &*void&~debug_printf(char&~*,&~...)*&
35559 This is Exim's debugging function, with arguments as for &'(printf()'&. The
35560 output is written to the standard error stream. If no debugging is selected,
35561 calls to &'debug_printf()'& have no effect. Normally, you should make calls
35562 conditional on the &`local_scan`& debug selector by coding like this:
35564 if ((debug_selector & D_local_scan) != 0)
35565 debug_printf("xxx", ...);
35568 .vitem &*uschar&~*expand_string(uschar&~*string)*&
35569 This is an interface to Exim's string expansion code. The return value is the
35570 expanded string, or NULL if there was an expansion failure.
35571 The C variable &%expand_string_message%& contains an error message after an
35572 expansion failure. If expansion does not change the string, the return value is
35573 the pointer to the input string. Otherwise, the return value points to a new
35574 block of memory that was obtained by a call to &'store_get()'&. See section
35575 &<<SECTmemhanloc>>& below for a discussion of memory handling.
35577 .vitem &*void&~header_add(int&~type,&~char&~*format,&~...)*&
35578 This function allows you to an add additional header line at the end of the
35579 existing ones. The first argument is the type, and should normally be a space
35580 character. The second argument is a format string and any number of
35581 substitution arguments as for &[sprintf()]&. You may include internal newlines
35582 if you want, and you must ensure that the string ends with a newline.
35584 .vitem "&*void&~header_add_at_position(BOOL&~after,&~uschar&~*name,&~&&&
35585 BOOL&~topnot,&~int&~type,&~char&~*format, &~&~...)*&"
35586 This function adds a new header line at a specified point in the header
35587 chain. The header itself is specified as for &'header_add()'&.
35589 If &%name%& is NULL, the new header is added at the end of the chain if
35590 &%after%& is true, or at the start if &%after%& is false. If &%name%& is not
35591 NULL, the header lines are searched for the first non-deleted header that
35592 matches the name. If one is found, the new header is added before it if
35593 &%after%& is false. If &%after%& is true, the new header is added after the
35594 found header and any adjacent subsequent ones with the same name (even if
35595 marked &"deleted"&). If no matching non-deleted header is found, the &%topnot%&
35596 option controls where the header is added. If it is true, addition is at the
35597 top; otherwise at the bottom. Thus, to add a header after all the &'Received:'&
35598 headers, or at the top if there are no &'Received:'& headers, you could use
35600 header_add_at_position(TRUE, US"Received", TRUE,
35601 ' ', "X-xxx: ...");
35603 Normally, there is always at least one non-deleted &'Received:'& header, but
35604 there may not be if &%received_header_text%& expands to an empty string.
35607 .vitem &*void&~header_remove(int&~occurrence,&~uschar&~*name)*&
35608 This function removes header lines. If &%occurrence%& is zero or negative, all
35609 occurrences of the header are removed. If occurrence is greater than zero, that
35610 particular instance of the header is removed. If no header(s) can be found that
35611 match the specification, the function does nothing.
35614 .vitem "&*BOOL&~header_testname(header_line&~*hdr,&~uschar&~*name,&~&&&
35615 int&~length,&~BOOL&~notdel)*&"
35616 This function tests whether the given header has the given name. It is not just
35617 a string comparison, because white space is permitted between the name and the
35618 colon. If the &%notdel%& argument is true, a false return is forced for all
35619 &"deleted"& headers; otherwise they are not treated specially. For example:
35621 if (header_testname(h, US"X-Spam", 6, TRUE)) ...
35623 .vitem &*uschar&~*lss_b64encode(uschar&~*cleartext,&~int&~length)*&
35624 .cindex "base64 encoding" "functions for &[local_scan()]& use"
35625 This function base64-encodes a string, which is passed by address and length.
35626 The text may contain bytes of any value, including zero. The result is passed
35627 back in dynamic memory that is obtained by calling &'store_get()'&. It is
35630 .vitem &*int&~lss_b64decode(uschar&~*codetext,&~uschar&~**cleartext)*&
35631 This function decodes a base64-encoded string. Its arguments are a
35632 zero-terminated base64-encoded string and the address of a variable that is set
35633 to point to the result, which is in dynamic memory. The length of the decoded
35634 string is the yield of the function. If the input is invalid base64 data, the
35635 yield is -1. A zero byte is added to the end of the output string to make it
35636 easy to interpret as a C string (assuming it contains no zeros of its own). The
35637 added zero byte is not included in the returned count.
35639 .vitem &*int&~lss_match_domain(uschar&~*domain,&~uschar&~*list)*&
35640 This function checks for a match in a domain list. Domains are always
35641 matched caselessly. The return value is one of the following:
35642 .itable none 0 0 2 15* left 85* left
35643 .irow &`OK`& "match succeeded"
35644 .irow &`FAIL`& "match failed"
35645 .irow &`DEFER`& "match deferred"
35647 DEFER is usually caused by some kind of lookup defer, such as the
35648 inability to contact a database.
35650 .vitem "&*int&~lss_match_local_part(uschar&~*localpart,&~uschar&~*list,&~&&&
35652 This function checks for a match in a local part list. The third argument
35653 controls case-sensitivity. The return values are as for
35654 &'lss_match_domain()'&.
35656 .vitem "&*int&~lss_match_address(uschar&~*address,&~uschar&~*list,&~&&&
35658 This function checks for a match in an address list. The third argument
35659 controls the case-sensitivity of the local part match. The domain is always
35660 matched caselessly. The return values are as for &'lss_match_domain()'&.
35662 .vitem "&*int&~lss_match_host(uschar&~*host_name,&~uschar&~*host_address,&~&&&
35664 This function checks for a match in a host list. The most common usage is
35667 lss_match_host(sender_host_name, sender_host_address, ...)
35669 .vindex "&$sender_host_address$&"
35670 An empty address field matches an empty item in the host list. If the host name
35671 is NULL, the name corresponding to &$sender_host_address$& is automatically
35672 looked up if a host name is required to match an item in the list. The return
35673 values are as for &'lss_match_domain()'&, but in addition, &'lss_match_host()'&
35674 returns ERROR in the case when it had to look up a host name, but the lookup
35677 .vitem "&*void&~log_write(unsigned&~int&~selector,&~int&~which,&~char&~&&&
35679 This function writes to Exim's log files. The first argument should be zero (it
35680 is concerned with &%log_selector%&). The second argument can be &`LOG_MAIN`& or
35681 &`LOG_REJECT`& or &`LOG_PANIC`& or the inclusive &"or"& of any combination of
35682 them. It specifies to which log or logs the message is written. The remaining
35683 arguments are a format and relevant insertion arguments. The string should not
35684 contain any newlines, not even at the end.
35687 .vitem &*void&~receive_add_recipient(uschar&~*address,&~int&~pno)*&
35688 This function adds an additional recipient to the message. The first argument
35689 is the recipient address. If it is unqualified (has no domain), it is qualified
35690 with the &%qualify_recipient%& domain. The second argument must always be -1.
35692 This function does not allow you to specify a private &%errors_to%& address (as
35693 described with the structure of &%recipient_item%& above), because it pre-dates
35694 the addition of that field to the structure. However, it is easy to add such a
35695 value afterwards. For example:
35697 receive_add_recipient(US"monitor@mydom.example", -1);
35698 recipients_list[recipients_count-1].errors_to =
35699 US"postmaster@mydom.example";
35702 .vitem &*BOOL&~receive_remove_recipient(uschar&~*recipient)*&
35703 This is a convenience function to remove a named recipient from the list of
35704 recipients. It returns true if a recipient was removed, and false if no
35705 matching recipient could be found. The argument must be a complete email
35712 .vitem "&*uschar&~rfc2047_decode(uschar&~*string,&~BOOL&~lencheck,&&&
35713 &~uschar&~*target,&~int&~zeroval,&~int&~*lenptr, &~&~uschar&~**error)*&"
35714 This function decodes strings that are encoded according to RFC 2047. Typically
35715 these are the contents of header lines. First, each &"encoded word"& is decoded
35716 from the Q or B encoding into a byte-string. Then, if provided with the name of
35717 a charset encoding, and if the &[iconv()]& function is available, an attempt is
35718 made to translate the result to the named character set. If this fails, the
35719 binary string is returned with an error message.
35721 The first argument is the string to be decoded. If &%lencheck%& is TRUE, the
35722 maximum MIME word length is enforced. The third argument is the target
35723 encoding, or NULL if no translation is wanted.
35725 .cindex "binary zero" "in RFC 2047 decoding"
35726 .cindex "RFC 2047" "binary zero in"
35727 If a binary zero is encountered in the decoded string, it is replaced by the
35728 contents of the &%zeroval%& argument. For use with Exim headers, the value must
35729 not be 0 because header lines are handled as zero-terminated strings.
35731 The function returns the result of processing the string, zero-terminated; if
35732 &%lenptr%& is not NULL, the length of the result is set in the variable to
35733 which it points. When &%zeroval%& is 0, &%lenptr%& should not be NULL.
35735 If an error is encountered, the function returns NULL and uses the &%error%&
35736 argument to return an error message. The variable pointed to by &%error%& is
35737 set to NULL if there is no error; it may be set non-NULL even when the function
35738 returns a non-NULL value if decoding was successful, but there was a problem
35742 .vitem &*int&~smtp_fflush(void)*&
35743 This function is used in conjunction with &'smtp_printf()'&, as described
35746 .vitem &*void&~smtp_printf(char&~*,BOOL,&~...)*&
35747 The arguments of this function are almost like &[printf()]&; it writes to the SMTP
35748 output stream. You should use this function only when there is an SMTP output
35749 stream, that is, when the incoming message is being received via interactive
35750 SMTP. This is the case when &%smtp_input%& is TRUE and &%smtp_batched_input%&
35751 is FALSE. If you want to test for an incoming message from another host (as
35752 opposed to a local process that used the &%-bs%& command line option), you can
35753 test the value of &%sender_host_address%&, which is non-NULL when a remote host
35756 If an SMTP TLS connection is established, &'smtp_printf()'& uses the TLS
35757 output function, so it can be used for all forms of SMTP connection.
35759 The second argument is used to request that the data be buffered
35760 (when TRUE) or flushed (along with any previously buffered, when FALSE).
35761 This is advisory only, but likely to save on system-calls and packets
35762 sent when a sequence of calls to the function are made.
35764 The argument was added in Exim version 4.90 - changing the API/ABI.
35765 Nobody noticed until 4.93 was imminent, at which point the
35766 ABI version number was incremented.
35768 Strings that are written by &'smtp_printf()'& from within &[local_scan()]&
35769 must start with an appropriate response code: 550 if you are going to return
35770 LOCAL_SCAN_REJECT, 451 if you are going to return
35771 LOCAL_SCAN_TEMPREJECT, and 250 otherwise. Because you are writing the
35772 initial lines of a multi-line response, the code must be followed by a hyphen
35773 to indicate that the line is not the final response line. You must also ensure
35774 that the lines you write terminate with CRLF. For example:
35776 smtp_printf("550-this is some extra info\r\n");
35777 return LOCAL_SCAN_REJECT;
35779 Note that you can also create multi-line responses by including newlines in
35780 the data returned via the &%return_text%& argument. The added value of using
35781 &'smtp_printf()'& is that, for instance, you could introduce delays between
35782 multiple output lines.
35784 The &'smtp_printf()'& function does not return any error indication, because it
35786 guarantee a flush of
35787 pending output, and therefore does not test
35788 the state of the stream. (In the main code of Exim, flushing and error
35789 detection is done when Exim is ready for the next SMTP input command.) If
35790 you want to flush the output and check for an error (for example, the
35791 dropping of a TCP/IP connection), you can call &'smtp_fflush()'&, which has no
35792 arguments. It flushes the output stream, and returns a non-zero value if there
35795 .vitem &*void&~*store_get(int,BOOL)*&
35796 This function accesses Exim's internal store (memory) manager. It gets a new
35797 chunk of memory whose size is given by the first argument.
35798 The second argument should be given as TRUE if the memory will be used for
35799 data possibly coming from an attacker (eg. the message content),
35800 FALSE if it is locally-sourced.
35801 Exim bombs out if it ever
35802 runs out of memory. See the next section for a discussion of memory handling.
35804 .vitem &*void&~*store_get_perm(int,BOOL)*&
35805 This function is like &'store_get()'&, but it always gets memory from the
35806 permanent pool. See the next section for a discussion of memory handling.
35808 .vitem &*uschar&~*string_copy(uschar&~*string)*&
35811 .vitem &*uschar&~*string_copyn(uschar&~*string,&~int&~length)*&
35814 .vitem &*uschar&~*string_sprintf(char&~*format,&~...)*&
35815 These three functions create strings using Exim's dynamic memory facilities.
35816 The first makes a copy of an entire string. The second copies up to a maximum
35817 number of characters, indicated by the second argument. The third uses a format
35818 and insertion arguments to create a new string. In each case, the result is a
35819 pointer to a new string in the current memory pool. See the next section for
35825 .section "More about Exim's memory handling" "SECTmemhanloc"
35826 .cindex "&[local_scan()]& function" "memory handling"
35827 No function is provided for freeing memory, because that is never needed.
35828 The dynamic memory that Exim uses when receiving a message is automatically
35829 recycled if another message is received by the same process (this applies only
35830 to incoming SMTP connections &-- other input methods can supply only one
35831 message at a time). After receiving the last message, a reception process
35834 Because it is recycled, the normal dynamic memory cannot be used for holding
35835 data that must be preserved over a number of incoming messages on the same SMTP
35836 connection. However, Exim in fact uses two pools of dynamic memory; the second
35837 one is not recycled, and can be used for this purpose.
35839 If you want to allocate memory that remains available for subsequent messages
35840 in the same SMTP connection, you should set
35842 store_pool = POOL_PERM
35844 before calling the function that does the allocation. There is no need to
35845 restore the value if you do not need to; however, if you do want to revert to
35846 the normal pool, you can either restore the previous value of &%store_pool%& or
35847 set it explicitly to POOL_MAIN.
35849 The pool setting applies to all functions that get dynamic memory, including
35850 &'expand_string()'&, &'store_get()'&, and the &'string_xxx()'& functions.
35851 There is also a convenience function called &'store_get_perm()'& that gets a
35852 block of memory from the permanent pool while preserving the value of
35859 . ////////////////////////////////////////////////////////////////////////////
35860 . ////////////////////////////////////////////////////////////////////////////
35862 .chapter "System-wide message filtering" "CHAPsystemfilter"
35863 .scindex IIDsysfil1 "filter" "system filter"
35864 .scindex IIDsysfil2 "filtering all mail"
35865 .scindex IIDsysfil3 "system filter"
35866 The previous chapters (on ACLs and the local scan function) describe checks
35867 that can be applied to messages before they are accepted by a host. There is
35868 also a mechanism for checking messages once they have been received, but before
35869 they are delivered. This is called the &'system filter'&.
35871 The system filter operates in a similar manner to users' filter files, but it
35872 is run just once per message (however many recipients the message has).
35873 It should not normally be used as a substitute for routing, because &%deliver%&
35874 commands in a system router provide new envelope recipient addresses.
35875 The system filter must be an Exim filter. It cannot be a Sieve filter.
35877 The system filter is run at the start of a delivery attempt, before any routing
35878 is done. If a message fails to be completely delivered at the first attempt,
35879 the system filter is run again at the start of every retry.
35880 If you want your filter to do something only once per message, you can make use
35881 of the &%first_delivery%& condition in an &%if%& command in the filter to
35882 prevent it happening on retries.
35884 .vindex "&$domain$&"
35885 .vindex "&$local_part$&"
35886 &*Warning*&: Because the system filter runs just once, variables that are
35887 specific to individual recipient addresses, such as &$local_part$& and
35888 &$domain$&, are not set, and the &"personal"& condition is not meaningful. If
35889 you want to run a centrally-specified filter for each recipient address
35890 independently, you can do so by setting up a suitable &(redirect)& router, as
35891 described in section &<<SECTperaddfil>>& below.
35894 .section "Specifying a system filter" "SECID212"
35895 .cindex "uid (user id)" "system filter"
35896 .cindex "gid (group id)" "system filter"
35897 The name of the file that contains the system filter must be specified by
35898 setting &%system_filter%&. If you want the filter to run under a uid and gid
35899 other than root, you must also set &%system_filter_user%& and
35900 &%system_filter_group%& as appropriate. For example:
35902 system_filter = /etc/mail/exim.filter
35903 system_filter_user = exim
35905 If a system filter generates any deliveries directly to files or pipes (via the
35906 &%save%& or &%pipe%& commands), transports to handle these deliveries must be
35907 specified by setting &%system_filter_file_transport%& and
35908 &%system_filter_pipe_transport%&, respectively. Similarly,
35909 &%system_filter_reply_transport%& must be set to handle any messages generated
35910 by the &%reply%& command.
35913 .section "Testing a system filter" "SECID213"
35914 You can run simple tests of a system filter in the same way as for a user
35915 filter, but you should use &%-bF%& rather than &%-bf%&, so that features that
35916 are permitted only in system filters are recognized.
35918 If you want to test the combined effect of a system filter and a user filter,
35919 you can use both &%-bF%& and &%-bf%& on the same command line.
35923 .section "Contents of a system filter" "SECID214"
35924 The language used to specify system filters is the same as for users' filter
35925 files. It is described in the separate end-user document &'Exim's interface to
35926 mail filtering'&. However, there are some additional features that are
35927 available only in system filters; these are described in subsequent sections.
35928 If they are encountered in a user's filter file or when testing with &%-bf%&,
35931 .cindex "frozen messages" "manual thaw; testing in filter"
35932 There are two special conditions which, though available in users' filter
35933 files, are designed for use in system filters. The condition &%first_delivery%&
35934 is true only for the first attempt at delivering a message, and
35935 &%manually_thawed%& is true only if the message has been frozen, and
35936 subsequently thawed by an admin user. An explicit forced delivery counts as a
35937 manual thaw, but thawing as a result of the &%auto_thaw%& setting does not.
35939 &*Warning*&: If a system filter uses the &%first_delivery%& condition to
35940 specify an &"unseen"& (non-significant) delivery, and that delivery does not
35941 succeed, it will not be tried again.
35942 If you want Exim to retry an unseen delivery until it succeeds, you should
35943 arrange to set it up every time the filter runs.
35945 When a system filter finishes running, the values of the variables &$n0$& &--
35946 &$n9$& are copied into &$sn0$& &-- &$sn9$& and are thereby made available to
35947 users' filter files. Thus a system filter can, for example, set up &"scores"&
35948 to which users' filter files can refer.
35952 .section "Additional variable for system filters" "SECID215"
35953 .vindex "&$recipients$&"
35954 The expansion variable &$recipients$&, containing a list of all the recipients
35955 of the message (separated by commas and white space), is available in system
35956 filters. It is not available in users' filters for privacy reasons.
35960 .section "Defer, freeze, and fail commands for system filters" "SECID216"
35961 .cindex "freezing messages"
35962 .cindex "message" "freezing"
35963 .cindex "message" "forced failure"
35964 .cindex "&%fail%&" "in system filter"
35965 .cindex "&%freeze%& in system filter"
35966 .cindex "&%defer%& in system filter"
35967 There are three extra commands (&%defer%&, &%freeze%& and &%fail%&) which are
35968 always available in system filters, but are not normally enabled in users'
35969 filters. (See the &%allow_defer%&, &%allow_freeze%& and &%allow_fail%& options
35970 for the &(redirect)& router.) These commands can optionally be followed by the
35971 word &%text%& and a string containing an error message, for example:
35973 fail text "this message looks like spam to me"
35975 The keyword &%text%& is optional if the next character is a double quote.
35977 The &%defer%& command defers delivery of the original recipients of the
35978 message. The &%fail%& command causes all the original recipients to be failed,
35979 and a bounce message to be created. The &%freeze%& command suspends all
35980 delivery attempts for the original recipients. In all cases, any new deliveries
35981 that are specified by the filter are attempted as normal after the filter has
35984 The &%freeze%& command is ignored if the message has been manually unfrozen and
35985 not manually frozen since. This means that automatic freezing by a system
35986 filter can be used as a way of checking out suspicious messages. If a message
35987 is found to be all right, manually unfreezing it allows it to be delivered.
35989 .cindex "log" "&%fail%& command log line"
35990 .cindex "&%fail%&" "log line; reducing"
35991 The text given with a fail command is used as part of the bounce message as
35992 well as being written to the log. If the message is quite long, this can fill
35993 up a lot of log space when such failures are common. To reduce the size of the
35994 log message, Exim interprets the text in a special way if it starts with the
35995 two characters &`<<`& and contains &`>>`& later. The text between these two
35996 strings is written to the log, and the rest of the text is used in the bounce
35997 message. For example:
35999 fail "<<filter test 1>>Your message is rejected \
36000 because it contains attachments that we are \
36001 not prepared to receive."
36004 .cindex "loop" "caused by &%fail%&"
36005 Take great care with the &%fail%& command when basing the decision to fail on
36006 the contents of the message, because the bounce message will of course include
36007 the contents of the original message and will therefore trigger the &%fail%&
36008 command again (causing a mail loop) unless steps are taken to prevent this.
36009 Testing the &%error_message%& condition is one way to prevent this. You could
36012 if $message_body contains "this is spam" and not error_message
36013 then fail text "spam is not wanted here" endif
36015 though of course that might let through unwanted bounce messages. The
36016 alternative is clever checking of the body and/or headers to detect bounces
36017 generated by the filter.
36019 The interpretation of a system filter file ceases after a
36021 &%freeze%&, or &%fail%& command is obeyed. However, any deliveries that were
36022 set up earlier in the filter file are honoured, so you can use a sequence such
36028 to send a specified message when the system filter is freezing (or deferring or
36029 failing) a message. The normal deliveries for the message do not, of course,
36034 .section "Adding and removing headers in a system filter" "SECTaddremheasys"
36035 .cindex "header lines" "adding; in system filter"
36036 .cindex "header lines" "removing; in system filter"
36037 .cindex "filter" "header lines; adding/removing"
36038 Two filter commands that are available only in system filters are:
36040 headers add <string>
36041 headers remove <string>
36043 The argument for the &%headers add%& is a string that is expanded and then
36044 added to the end of the message's headers. It is the responsibility of the
36045 filter maintainer to make sure it conforms to RFC 2822 syntax. Leading white
36046 space is ignored, and if the string is otherwise empty, or if the expansion is
36047 forced to fail, the command has no effect.
36049 You can use &"\n"& within the string, followed by white space, to specify
36050 continued header lines. More than one header may be added in one command by
36051 including &"\n"& within the string without any following white space. For
36054 headers add "X-header-1: ....\n \
36055 continuation of X-header-1 ...\n\
36058 Note that the header line continuation white space after the first newline must
36059 be placed before the backslash that continues the input string, because white
36060 space after input continuations is ignored.
36062 The argument for &%headers remove%& is a colon-separated list of header names.
36063 This command applies only to those headers that are stored with the message;
36064 those that are added at delivery time (such as &'Envelope-To:'& and
36065 &'Return-Path:'&) cannot be removed by this means. If there is more than one
36066 header with the same name, they are all removed.
36068 The &%headers%& command in a system filter makes an immediate change to the set
36069 of header lines that was received with the message (with possible additions
36070 from ACL processing). Subsequent commands in the system filter operate on the
36071 modified set, which also forms the basis for subsequent message delivery.
36072 Unless further modified during routing or transporting, this set of headers is
36073 used for all recipients of the message.
36075 During routing and transporting, the variables that refer to the contents of
36076 header lines refer only to those lines that are in this set. Thus, header lines
36077 that are added by a system filter are visible to users' filter files and to all
36078 routers and transports. This contrasts with the manipulation of header lines by
36079 routers and transports, which is not immediate, but which instead is saved up
36080 until the message is actually being written (see section
36081 &<<SECTheadersaddrem>>&).
36083 If the message is not delivered at the first attempt, header lines that were
36084 added by the system filter are stored with the message, and so are still
36085 present at the next delivery attempt. Header lines that were removed are still
36086 present, but marked &"deleted"& so that they are not transported with the
36087 message. For this reason, it is usual to make the &%headers%& command
36088 conditional on &%first_delivery%& so that the set of header lines is not
36089 modified more than once.
36091 Because header modification in a system filter acts immediately, you have to
36092 use an indirect approach if you want to modify the contents of a header line.
36095 headers add "Old-Subject: $h_subject:"
36096 headers remove "Subject"
36097 headers add "Subject: new subject (was: $h_old-subject:)"
36098 headers remove "Old-Subject"
36103 .section "Setting an errors address in a system filter" "SECID217"
36104 .cindex "envelope from"
36105 .cindex "envelope sender"
36106 In a system filter, if a &%deliver%& command is followed by
36108 errors_to <some address>
36110 in order to change the envelope sender (and hence the error reporting) for that
36111 delivery, any address may be specified. (In a user filter, only the current
36112 user's address can be set.) For example, if some mail is being monitored, you
36115 unseen deliver monitor@spying.example errors_to root@local.example
36117 to take a copy which would not be sent back to the normal error reporting
36118 address if its delivery failed.
36122 .section "Per-address filtering" "SECTperaddfil"
36123 .vindex "&$domain_data$&"
36124 .vindex "&$local_part_data$&"
36125 In contrast to the system filter, which is run just once per message for each
36126 delivery attempt, it is also possible to set up a system-wide filtering
36127 operation that runs once for each recipient address. In this case, variables
36128 such as &$local_part_data$& and &$domain_data$& can be used,
36129 and indeed, the choice of filter file could be made dependent on them.
36130 This is an example of a router which implements such a filter:
36135 domains = +local_domains
36136 file = /central/filters/$local_part_data
36141 The filter is run in a separate process under its own uid. Therefore, either
36142 &%check_local_user%& must be set (as above), in which case the filter is run as
36143 the local user, or the &%user%& option must be used to specify which user to
36144 use. If both are set, &%user%& overrides.
36146 Care should be taken to ensure that none of the commands in the filter file
36147 specify a significant delivery if the message is to go on to be delivered to
36148 its intended recipient. The router will not then claim to have dealt with the
36149 address, so it will be passed on to subsequent routers to be delivered in the
36151 .ecindex IIDsysfil1
36152 .ecindex IIDsysfil2
36153 .ecindex IIDsysfil3
36160 . ////////////////////////////////////////////////////////////////////////////
36161 . ////////////////////////////////////////////////////////////////////////////
36163 .chapter "Message processing" "CHAPmsgproc"
36164 .scindex IIDmesproc "message" "general processing"
36165 Exim performs various transformations on the sender and recipient addresses of
36166 all messages that it handles, and also on the messages' header lines. Some of
36167 these are optional and configurable, while others always take place. All of
36168 this processing, except rewriting as a result of routing, and the addition or
36169 removal of header lines while delivering, happens when a message is received,
36170 before it is placed on Exim's queue.
36172 Some of the automatic processing takes place by default only for
36173 &"locally-originated"& messages. This adjective is used to describe messages
36174 that are not received over TCP/IP, but instead are passed to an Exim process on
36175 its standard input. This includes the interactive &"local SMTP"& case that is
36176 set up by the &%-bs%& command line option.
36178 &*Note*&: Messages received over TCP/IP on the loopback interface (127.0.0.1
36179 or ::1) are not considered to be locally-originated. Exim does not treat the
36180 loopback interface specially in any way.
36182 If you want the loopback interface to be treated specially, you must ensure
36183 that there are appropriate entries in your ACLs.
36188 .section "Submission mode for non-local messages" "SECTsubmodnon"
36189 .cindex "message" "submission"
36190 .cindex "submission mode"
36191 Processing that happens automatically for locally-originated messages (unless
36192 &%suppress_local_fixups%& is set) can also be requested for messages that are
36193 received over TCP/IP. The term &"submission mode"& is used to describe this
36194 state. Submission mode is set by the modifier
36196 control = submission
36198 in a MAIL, RCPT, or pre-data ACL for an incoming message (see sections
36199 &<<SECTACLmodi>>& and &<<SECTcontrols>>&). This makes Exim treat the message as
36200 a local submission, and is normally used when the source of the message is
36201 known to be an MUA running on a client host (as opposed to an MTA). For
36202 example, to set submission mode for messages originating on the IPv4 loopback
36203 interface, you could include the following in the MAIL ACL:
36205 warn hosts = 127.0.0.1
36206 control = submission
36208 .cindex "&%sender_retain%& submission option"
36209 There are some options that can be used when setting submission mode. A slash
36210 is used to separate options. For example:
36212 control = submission/sender_retain
36214 Specifying &%sender_retain%& has the effect of setting &%local_sender_retain%&
36215 true and &%local_from_check%& false for the current incoming message. The first
36216 of these allows an existing &'Sender:'& header in the message to remain, and
36217 the second suppresses the check to ensure that &'From:'& matches the
36218 authenticated sender. With this setting, Exim still fixes up messages by adding
36219 &'Date:'& and &'Message-ID:'& header lines if they are missing, but makes no
36220 attempt to check sender authenticity in header lines.
36222 When &%sender_retain%& is not set, a submission mode setting may specify a
36223 domain to be used when generating a &'From:'& or &'Sender:'& header line. For
36226 control = submission/domain=some.domain
36228 The domain may be empty. How this value is used is described in sections
36229 &<<SECTthefrohea>>& and &<<SECTthesenhea>>&. There is also a &%name%& option
36230 that allows you to specify the user's full name for inclusion in a created
36231 &'Sender:'& or &'From:'& header line. For example:
36233 accept authenticated = *
36234 control = submission/domain=wonderland.example/\
36235 name=${lookup {$authenticated_id} \
36236 lsearch {/etc/exim/namelist}}
36238 Because the name may contain any characters, including slashes, the &%name%&
36239 option must be given last. The remainder of the string is used as the name. For
36240 the example above, if &_/etc/exim/namelist_& contains:
36242 bigegg: Humpty Dumpty
36244 then when the sender has authenticated as &'bigegg'&, the generated &'Sender:'&
36247 Sender: Humpty Dumpty <bigegg@wonderland.example>
36249 .cindex "return path" "in submission mode"
36250 By default, submission mode forces the return path to the same address as is
36251 used to create the &'Sender:'& header. However, if &%sender_retain%& is
36252 specified, the return path is also left unchanged.
36254 &*Note*&: The changes caused by submission mode take effect after the predata
36255 ACL. This means that any sender checks performed before the fix-ups use the
36256 untrusted sender address specified by the user, not the trusted sender address
36257 specified by submission mode. Although this might be slightly unexpected, it
36258 does mean that you can configure ACL checks to spot that a user is trying to
36259 spoof another's address.
36261 .section "Line endings" "SECTlineendings"
36262 .cindex "line endings"
36263 .cindex "carriage return"
36265 RFC 2821 specifies that CRLF (two characters: carriage-return, followed by
36266 linefeed) is the line ending for messages transmitted over the Internet using
36267 SMTP over TCP/IP. However, within individual operating systems, different
36268 conventions are used. For example, Unix-like systems use just LF, but others
36269 use CRLF or just CR.
36271 Exim was designed for Unix-like systems, and internally, it stores messages
36272 using the system's convention of a single LF as a line terminator. When
36273 receiving a message, all line endings are translated to this standard format.
36274 Originally, it was thought that programs that passed messages directly to an
36275 MTA within an operating system would use that system's convention. Experience
36276 has shown that this is not the case; for example, there are Unix applications
36277 that use CRLF in this circumstance. For this reason, and for compatibility with
36278 other MTAs, the way Exim handles line endings for all messages is now as
36282 LF not preceded by CR is treated as a line ending.
36284 CR is treated as a line ending; if it is immediately followed by LF, the LF
36287 The sequence &"CR, dot, CR"& does not terminate an incoming SMTP message,
36288 nor a local message in the state where a line containing only a dot is a
36291 If a bare CR is encountered within a header line, an extra space is added after
36292 the line terminator so as not to end the header line. The reasoning behind this
36293 is that bare CRs in header lines are most likely either to be mistakes, or
36294 people trying to play silly games.
36296 If the first header line received in a message ends with CRLF, a subsequent
36297 bare LF in a header line is treated in the same way as a bare CR in a header
36305 .section "Unqualified addresses" "SECID218"
36306 .cindex "unqualified addresses"
36307 .cindex "address" "qualification"
36308 By default, Exim expects every envelope address it receives from an external
36309 host to be fully qualified. Unqualified addresses cause negative responses to
36310 SMTP commands. However, because SMTP is used as a means of transporting
36311 messages from MUAs running on personal workstations, there is sometimes a
36312 requirement to accept unqualified addresses from specific hosts or IP networks.
36314 Exim has two options that separately control which hosts may send unqualified
36315 sender or recipient addresses in SMTP commands, namely
36316 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&. In both
36317 cases, if an unqualified address is accepted, it is qualified by adding the
36318 value of &%qualify_domain%& or &%qualify_recipient%&, as appropriate.
36320 .oindex "&%qualify_domain%&"
36321 .oindex "&%qualify_recipient%&"
36322 Unqualified addresses in header lines are automatically qualified for messages
36323 that are locally originated, unless the &%-bnq%& option is given on the command
36324 line. For messages received over SMTP, unqualified addresses in header lines
36325 are qualified only if unqualified addresses are permitted in SMTP commands. In
36326 other words, such qualification is also controlled by
36327 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&,
36332 .section "The UUCP From line" "SECID219"
36333 .cindex "&""From""& line"
36334 .cindex "UUCP" "&""From""& line"
36335 .cindex "sender" "address"
36336 .oindex "&%uucp_from_pattern%&"
36337 .oindex "&%uucp_from_sender%&"
36338 .cindex "envelope from"
36339 .cindex "envelope sender"
36340 .cindex "Sendmail compatibility" "&""From""& line"
36341 Messages that have come from UUCP (and some other applications) often begin
36342 with a line containing the envelope sender and a timestamp, following the word
36343 &"From"&. Examples of two common formats are:
36345 From a.oakley@berlin.mus Fri Jan 5 12:35 GMT 1996
36346 From f.butler@berlin.mus Fri, 7 Jan 97 14:00:00 GMT
36348 This line precedes the RFC 2822 header lines. For compatibility with Sendmail,
36349 Exim recognizes such lines at the start of messages that are submitted to it
36350 via the command line (that is, on the standard input). It does not recognize
36351 such lines in incoming SMTP messages, unless the sending host matches
36352 &%ignore_fromline_hosts%& or the &%-bs%& option was used for a local message
36353 and &%ignore_fromline_local%& is set. The recognition is controlled by a
36354 regular expression that is defined by the &%uucp_from_pattern%& option, whose
36355 default value matches the two common cases shown above and puts the address
36356 that follows &"From"& into &$1$&.
36358 .cindex "numerical variables (&$1$& &$2$& etc)" "in &""From ""& line handling"
36359 When the caller of Exim for a non-SMTP message that contains a &"From"& line is
36360 a trusted user, the message's sender address is constructed by expanding the
36361 contents of &%uucp_sender_address%&, whose default value is &"$1"&. This is
36362 then parsed as an RFC 2822 address. If there is no domain, the local part is
36363 qualified with &%qualify_domain%& unless it is the empty string. However, if
36364 the command line &%-f%& option is used, it overrides the &"From"& line.
36366 If the caller of Exim is not trusted, the &"From"& line is recognized, but the
36367 sender address is not changed. This is also the case for incoming SMTP messages
36368 that are permitted to contain &"From"& lines.
36370 Only one &"From"& line is recognized. If there is more than one, the second is
36371 treated as a data line that starts the body of the message, as it is not valid
36372 as a header line. This also happens if a &"From"& line is present in an
36373 incoming SMTP message from a source that is not permitted to send them.
36377 .section "Resent- header lines" "SECID220"
36379 RFC 2822 makes provision for sets of header lines starting with the string
36380 &`Resent-`& to be added to a message when it is resent by the original
36381 recipient to somebody else. These headers are &'Resent-Date:'&,
36382 &'Resent-From:'&, &'Resent-Sender:'&, &'Resent-To:'&, &'Resent-Cc:'&,
36383 &'Resent-Bcc:'& and &'Resent-Message-ID:'&. The RFC says:
36386 &'Resent fields are strictly informational. They MUST NOT be used in the normal
36387 processing of replies or other such automatic actions on messages.'&
36390 This leaves things a bit vague as far as other processing actions such as
36391 address rewriting are concerned. Exim treats &%Resent-%& header lines as
36395 A &'Resent-From:'& line that just contains the login id of the submitting user
36396 is automatically rewritten in the same way as &'From:'& (see below).
36398 If there's a rewriting rule for a particular header line, it is also applied to
36399 &%Resent-%& header lines of the same type. For example, a rule that rewrites
36400 &'From:'& also rewrites &'Resent-From:'&.
36402 For local messages, if &'Sender:'& is removed on input, &'Resent-Sender:'& is
36405 For a locally-submitted message,
36406 if there are any &%Resent-%& header lines but no &'Resent-Date:'&,
36407 &'Resent-From:'&, or &'Resent-Message-Id:'&, they are added as necessary. It is
36408 the contents of &'Resent-Message-Id:'& (rather than &'Message-Id:'&) which are
36409 included in log lines in this case.
36411 The logic for adding &'Sender:'& is duplicated for &'Resent-Sender:'& when any
36412 &%Resent-%& header lines are present.
36418 .section "The Auto-Submitted: header line" "SECID221"
36419 Whenever Exim generates an autoreply, a bounce, or a delay warning message, it
36420 includes the header line:
36422 Auto-Submitted: auto-replied
36425 .section "The Bcc: header line" "SECID222"
36426 .cindex "&'Bcc:'& header line"
36427 If Exim is called with the &%-t%& option, to take recipient addresses from a
36428 message's header, it removes any &'Bcc:'& header line that may exist (after
36429 extracting its addresses). If &%-t%& is not present on the command line, any
36430 existing &'Bcc:'& is not removed.
36433 .section "The Date: header line" "SECID223"
36435 If a locally-generated or submission-mode message has no &'Date:'& header line,
36436 Exim adds one, using the current date and time, unless the
36437 &%suppress_local_fixups%& control has been specified.
36439 .section "The Delivery-date: header line" "SECID224"
36440 .cindex "&'Delivery-date:'& header line"
36441 .oindex "&%delivery_date_remove%&"
36442 &'Delivery-date:'& header lines are not part of the standard RFC 2822 header
36443 set. Exim can be configured to add them to the final delivery of messages. (See
36444 the generic &%delivery_date_add%& transport option.) They should not be present
36445 in messages in transit. If the &%delivery_date_remove%& configuration option is
36446 set (the default), Exim removes &'Delivery-date:'& header lines from incoming
36450 .section "The Envelope-to: header line" "SECID225"
36451 .chindex Envelope-to:
36452 .oindex "&%envelope_to_remove%&"
36453 &'Envelope-to:'& header lines are not part of the standard RFC 2822 header set.
36454 Exim can be configured to add them to the final delivery of messages. (See the
36455 generic &%envelope_to_add%& transport option.) They should not be present in
36456 messages in transit. If the &%envelope_to_remove%& configuration option is set
36457 (the default), Exim removes &'Envelope-to:'& header lines from incoming
36461 .section "The From: header line" "SECTthefrohea"
36463 .cindex "Sendmail compatibility" "&""From""& line"
36464 .cindex "message" "submission"
36465 .cindex "submission mode"
36466 If a submission-mode message does not contain a &'From:'& header line, Exim
36467 adds one if either of the following conditions is true:
36470 The envelope sender address is not empty (that is, this is not a bounce
36471 message). The added header line copies the envelope sender address.
36473 .vindex "&$authenticated_id$&"
36474 The SMTP session is authenticated and &$authenticated_id$& is not empty.
36476 .vindex "&$qualify_domain$&"
36477 If no domain is specified by the submission control, the local part is
36478 &$authenticated_id$& and the domain is &$qualify_domain$&.
36480 If a non-empty domain is specified by the submission control, the local
36481 part is &$authenticated_id$&, and the domain is the specified domain.
36483 If an empty domain is specified by the submission control,
36484 &$authenticated_id$& is assumed to be the complete address.
36488 A non-empty envelope sender takes precedence.
36490 If a locally-generated incoming message does not contain a &'From:'& header
36491 line, and the &%suppress_local_fixups%& control is not set, Exim adds one
36492 containing the sender's address. The calling user's login name and full name
36493 are used to construct the address, as described in section &<<SECTconstr>>&.
36494 They are obtained from the password data by calling &[getpwuid()]& (but see the
36495 &%unknown_login%& configuration option). The address is qualified with
36496 &%qualify_domain%&.
36498 For compatibility with Sendmail, if an incoming, non-SMTP message has a
36499 &'From:'& header line containing just the unqualified login name of the calling
36500 user, this is replaced by an address containing the user's login name and full
36501 name as described in section &<<SECTconstr>>&.
36504 .section "The Message-ID: header line" "SECID226"
36505 .chindex Message-ID:
36506 .cindex "message" "submission"
36507 .oindex "&%message_id_header_text%&"
36508 If a locally-generated or submission-mode incoming message does not contain a
36509 &'Message-ID:'& or &'Resent-Message-ID:'& header line, and the
36510 &%suppress_local_fixups%& control is not set, Exim adds a suitable header line
36511 to the message. If there are any &'Resent-:'& headers in the message, it
36512 creates &'Resent-Message-ID:'&. The id is constructed from Exim's internal
36513 message id, preceded by the letter E to ensure it starts with a letter, and
36514 followed by @ and the primary host name. Additional information can be included
36515 in this header line by setting the &%message_id_header_text%& and/or
36516 &%message_id_header_domain%& options.
36519 .section "The Received: header line" "SECID227"
36521 A &'Received:'& header line is added at the start of every message. The
36522 contents are defined by the &%received_header_text%& configuration option, and
36523 Exim automatically adds a semicolon and a timestamp to the configured string.
36525 The &'Received:'& header is generated as soon as the message's header lines
36526 have been received. At this stage, the timestamp in the &'Received:'& header
36527 line is the time that the message started to be received. This is the value
36528 that is seen by the DATA ACL and by the &[local_scan()]& function.
36530 Once a message is accepted, the timestamp in the &'Received:'& header line is
36531 changed to the time of acceptance, which is (apart from a small delay while the
36532 -H spool file is written) the earliest time at which delivery could start.
36535 .section "The References: header line" "SECID228"
36536 .chindex References:
36537 Messages created by the &(autoreply)& transport include a &'References:'&
36538 header line. This is constructed according to the rules that are described in
36539 section 3.64 of RFC 2822 (which states that replies should contain such a
36540 header line), and section 3.14 of RFC 3834 (which states that automatic
36541 responses are not different in this respect). However, because some mail
36542 processing software does not cope well with very long header lines, no more
36543 than 12 message IDs are copied from the &'References:'& header line in the
36544 incoming message. If there are more than 12, the first one and then the final
36545 11 are copied, before adding the message ID of the incoming message.
36549 .section "The Return-path: header line" "SECID229"
36550 .chindex Return-path:
36551 .oindex "&%return_path_remove%&"
36552 &'Return-path:'& header lines are defined as something an MTA may insert when
36553 it does the final delivery of messages. (See the generic &%return_path_add%&
36554 transport option.) Therefore, they should not be present in messages in
36555 transit. If the &%return_path_remove%& configuration option is set (the
36556 default), Exim removes &'Return-path:'& header lines from incoming messages.
36560 .section "The Sender: header line" "SECTthesenhea"
36561 .cindex "&'Sender:'& header line"
36562 .cindex "message" "submission"
36564 For a locally-originated message from an untrusted user, Exim may remove an
36565 existing &'Sender:'& header line, and it may add a new one. You can modify
36566 these actions by setting the &%local_sender_retain%& option true, the
36567 &%local_from_check%& option false, or by using the &%suppress_local_fixups%&
36570 When a local message is received from an untrusted user and
36571 &%local_from_check%& is true (the default), and the &%suppress_local_fixups%&
36572 control has not been set, a check is made to see if the address given in the
36573 &'From:'& header line is the correct (local) sender of the message. The address
36574 that is expected has the login name as the local part and the value of
36575 &%qualify_domain%& as the domain. Prefixes and suffixes for the local part can
36576 be permitted by setting &%local_from_prefix%& and &%local_from_suffix%&
36577 appropriately. If &'From:'& does not contain the correct sender, a &'Sender:'&
36578 line is added to the message.
36580 If you set &%local_from_check%& false, this checking does not occur. However,
36581 the removal of an existing &'Sender:'& line still happens, unless you also set
36582 &%local_sender_retain%& to be true. It is not possible to set both of these
36583 options true at the same time.
36585 .cindex "submission mode"
36586 By default, no processing of &'Sender:'& header lines is done for messages
36587 received over TCP/IP or for messages submitted by trusted users. However, when
36588 a message is received over TCP/IP in submission mode, and &%sender_retain%& is
36589 not specified on the submission control, the following processing takes place:
36591 .vindex "&$authenticated_id$&"
36592 First, any existing &'Sender:'& lines are removed. Then, if the SMTP session is
36593 authenticated, and &$authenticated_id$& is not empty, a sender address is
36594 created as follows:
36597 .vindex "&$qualify_domain$&"
36598 If no domain is specified by the submission control, the local part is
36599 &$authenticated_id$& and the domain is &$qualify_domain$&.
36601 If a non-empty domain is specified by the submission control, the local part
36602 is &$authenticated_id$&, and the domain is the specified domain.
36604 If an empty domain is specified by the submission control,
36605 &$authenticated_id$& is assumed to be the complete address.
36608 This address is compared with the address in the &'From:'& header line. If they
36609 are different, a &'Sender:'& header line containing the created address is
36610 added. Prefixes and suffixes for the local part in &'From:'& can be permitted
36611 by setting &%local_from_prefix%& and &%local_from_suffix%& appropriately.
36613 .cindex "return path" "created from &'Sender:'&"
36614 &*Note*&: Whenever a &'Sender:'& header line is created, the return path for
36615 the message (the envelope sender address) is changed to be the same address,
36616 except in the case of submission mode when &%sender_retain%& is specified.
36620 .section "Adding and removing header lines in routers and transports" &&&
36621 "SECTheadersaddrem"
36622 .cindex "header lines" "adding; in router or transport"
36623 .cindex "header lines" "removing; in router or transport"
36624 When a message is delivered, the addition and removal of header lines can be
36625 specified in a system filter, or on any of the routers and transports that
36626 process the message. Section &<<SECTaddremheasys>>& contains details about
36627 modifying headers in a system filter. Header lines can also be added in an ACL
36628 as a message is received (see section &<<SECTaddheadacl>>&).
36630 In contrast to what happens in a system filter, header modifications that are
36631 specified on routers and transports apply only to the particular recipient
36632 addresses that are being processed by those routers and transports. These
36633 changes do not actually take place until a copy of the message is being
36634 transported. Therefore, they do not affect the basic set of header lines, and
36635 they do not affect the values of the variables that refer to header lines.
36637 &*Note*&: In particular, this means that any expansions in the configuration of
36638 the transport cannot refer to the modified header lines, because such
36639 expansions all occur before the message is actually transported.
36641 For both routers and transports, the argument of a &%headers_add%&
36642 option must be in the form of one or more RFC 2822 header lines, separated by
36643 newlines (coded as &"\n"&). For example:
36645 headers_add = X-added-header: added by $primary_hostname\n\
36646 X-added-second: another added header line
36648 Exim does not check the syntax of these added header lines.
36650 Multiple &%headers_add%& options for a single router or transport can be
36651 specified; the values will append to a single list of header lines.
36652 Each header-line is separately expanded.
36654 The argument of a &%headers_remove%& option must consist of a colon-separated
36655 list of header names. This is confusing, because header names themselves are
36656 often terminated by colons. In this case, the colons are the list separators,
36657 not part of the names. For example:
36659 headers_remove = return-receipt-to:acknowledge-to
36662 Multiple &%headers_remove%& options for a single router or transport can be
36663 specified; the arguments will append to a single header-names list.
36664 Each item is separately expanded.
36665 Note that colons in complex expansions which are used to
36666 form all or part of a &%headers_remove%& list
36667 will act as list separators.
36669 When &%headers_add%& or &%headers_remove%& is specified on a router,
36670 items are expanded at routing time,
36671 and then associated with all addresses that are
36672 accepted by that router, and also with any new addresses that it generates. If
36673 an address passes through several routers as a result of aliasing or
36674 forwarding, the changes are cumulative.
36676 .oindex "&%unseen%&"
36677 However, this does not apply to multiple routers that result from the use of
36678 the &%unseen%& option. Any header modifications that were specified by the
36679 &"unseen"& router or its predecessors apply only to the &"unseen"& delivery.
36681 Addresses that end up with different &%headers_add%& or &%headers_remove%&
36682 settings cannot be delivered together in a batch, so a transport is always
36683 dealing with a set of addresses that have the same header-processing
36686 The transport starts by writing the original set of header lines that arrived
36687 with the message, possibly modified by the system filter. As it writes out
36688 these lines, it consults the list of header names that were attached to the
36689 recipient address(es) by &%headers_remove%& options in routers, and it also
36690 consults the transport's own &%headers_remove%& option. Header lines whose
36691 names are on either of these lists are not written out. If there are multiple
36692 instances of any listed header, they are all skipped.
36694 After the remaining original header lines have been written, new header
36695 lines that were specified by routers' &%headers_add%& options are written, in
36696 the order in which they were attached to the address. These are followed by any
36697 header lines specified by the transport's &%headers_add%& option.
36699 This way of handling header line modifications in routers and transports has
36700 the following consequences:
36703 The original set of header lines, possibly modified by the system filter,
36704 remains &"visible"&, in the sense that the &$header_$&&'xxx'& variables refer
36705 to it, at all times.
36707 Header lines that are added by a router's
36708 &%headers_add%& option are not accessible by means of the &$header_$&&'xxx'&
36709 expansion syntax in subsequent routers or the transport.
36711 Conversely, header lines that are specified for removal by &%headers_remove%&
36712 in a router remain visible to subsequent routers and the transport.
36714 Headers added to an address by &%headers_add%& in a router cannot be removed by
36715 a later router or by a transport.
36717 An added header can refer to the contents of an original header that is to be
36718 removed, even it has the same name as the added header. For example:
36720 headers_remove = subject
36721 headers_add = Subject: new subject (was: $h_subject:)
36725 &*Warning*&: The &%headers_add%& and &%headers_remove%& options cannot be used
36726 for a &(redirect)& router that has the &%one_time%& option set.
36732 .section "Constructed addresses" "SECTconstr"
36733 .cindex "address" "constructed"
36734 .cindex "constructed address"
36735 When Exim constructs a sender address for a locally-generated message, it uses
36738 <&'user name'&>&~&~<&'login'&&`@`&&'qualify_domain'&>
36742 Zaphod Beeblebrox <zaphod@end.univ.example>
36744 The user name is obtained from the &%-F%& command line option if set, or
36745 otherwise by looking up the calling user by &[getpwuid()]& and extracting the
36746 &"gecos"& field from the password entry. If the &"gecos"& field contains an
36747 ampersand character, this is replaced by the login name with the first letter
36748 upper cased, as is conventional in a number of operating systems. See the
36749 &%gecos_name%& option for a way to tailor the handling of the &"gecos"& field.
36750 The &%unknown_username%& option can be used to specify user names in cases when
36751 there is no password file entry.
36754 In all cases, the user name is made to conform to RFC 2822 by quoting all or
36755 parts of it if necessary. In addition, if it contains any non-printing
36756 characters, it is encoded as described in RFC 2047, which defines a way of
36757 including non-ASCII characters in header lines. The value of the
36758 &%headers_charset%& option specifies the name of the encoding that is used (the
36759 characters are assumed to be in this encoding). The setting of
36760 &%print_topbitchars%& controls whether characters with the top bit set (that
36761 is, with codes greater than 127) count as printing characters or not.
36765 .section "Case of local parts" "SECID230"
36766 .cindex "case of local parts"
36767 .cindex "local part" "case of"
36768 RFC 2822 states that the case of letters in the local parts of addresses cannot
36769 be assumed to be non-significant. Exim preserves the case of local parts of
36770 addresses, but by default it uses a lower-cased form when it is routing,
36771 because on most Unix systems, usernames are in lower case and case-insensitive
36772 routing is required. However, any particular router can be made to use the
36773 original case for local parts by setting the &%caseful_local_part%& generic
36776 .cindex "mixed-case login names"
36777 If you must have mixed-case user names on your system, the best way to proceed,
36778 assuming you want case-independent handling of incoming email, is to set up
36779 your first router to convert incoming local parts in your domains to the
36780 correct case by means of a file lookup. For example:
36784 domains = +local_domains
36785 data = ${lookup{$local_part}cdb\
36786 {/etc/usercased.cdb}{$value}fail}\
36789 For this router, the local part is forced to lower case by the default action
36790 (&%caseful_local_part%& is not set). The lower-cased local part is used to look
36791 up a new local part in the correct case. If you then set &%caseful_local_part%&
36792 on any subsequent routers which process your domains, they will operate on
36793 local parts with the correct case in a case-sensitive manner.
36797 .section "Dots in local parts" "SECID231"
36798 .cindex "dot" "in local part"
36799 .cindex "local part" "dots in"
36800 RFC 2822 forbids empty components in local parts. That is, an unquoted local
36801 part may not begin or end with a dot, nor have two consecutive dots in the
36802 middle. However, it seems that many MTAs do not enforce this, so Exim permits
36803 empty components for compatibility.
36807 .section "Rewriting addresses" "SECID232"
36808 .cindex "rewriting" "addresses"
36809 Rewriting of sender and recipient addresses, and addresses in headers, can
36810 happen automatically, or as the result of configuration options, as described
36811 in chapter &<<CHAPrewrite>>&. The headers that may be affected by this are
36812 &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-To:'&, &'Sender:'&, and &'To:'&.
36814 Automatic rewriting includes qualification, as mentioned above. The other case
36815 in which it can happen is when an incomplete non-local domain is given. The
36816 routing process may cause this to be expanded into the full domain name. For
36817 example, a header such as
36821 might get rewritten as
36823 To: hare@teaparty.wonderland.fict.example
36825 Rewriting as a result of routing is the one kind of message processing that
36826 does not happen at input time, as it cannot be done until the address has
36829 Strictly, one should not do &'any'& deliveries of a message until all its
36830 addresses have been routed, in case any of the headers get changed as a
36831 result of routing. However, doing this in practice would hold up many
36832 deliveries for unreasonable amounts of time, just because one address could not
36833 immediately be routed. Exim therefore does not delay other deliveries when
36834 routing of one or more addresses is deferred.
36835 .ecindex IIDmesproc
36839 . ////////////////////////////////////////////////////////////////////////////
36840 . ////////////////////////////////////////////////////////////////////////////
36842 .chapter "SMTP processing" "CHAPSMTP"
36843 .scindex IIDsmtpproc1 "SMTP" "processing details"
36844 .scindex IIDsmtpproc2 "LMTP" "processing details"
36845 Exim supports a number of different ways of using the SMTP protocol, and its
36846 LMTP variant, which is an interactive protocol for transferring messages into a
36847 closed mail store application. This chapter contains details of how SMTP is
36848 processed. For incoming mail, the following are available:
36851 SMTP over TCP/IP (Exim daemon or &'inetd'&);
36853 SMTP over the standard input and output (the &%-bs%& option);
36855 Batched SMTP on the standard input (the &%-bS%& option).
36858 For mail delivery, the following are available:
36861 SMTP over TCP/IP (the &(smtp)& transport);
36863 LMTP over TCP/IP (the &(smtp)& transport with the &%protocol%& option set to
36866 LMTP over a pipe to a process running in the local host (the &(lmtp)&
36869 Batched SMTP to a file or pipe (the &(appendfile)& and &(pipe)& transports with
36870 the &%use_bsmtp%& option set).
36873 &'Batched SMTP'& is the name for a process in which batches of messages are
36874 stored in or read from files (or pipes), in a format in which SMTP commands are
36875 used to contain the envelope information.
36879 .section "Outgoing SMTP and LMTP over TCP/IP" "SECToutSMTPTCP"
36880 .cindex "SMTP" "outgoing over TCP/IP"
36881 .cindex "outgoing SMTP over TCP/IP"
36882 .cindex "LMTP" "over TCP/IP"
36883 .cindex "outgoing LMTP over TCP/IP"
36886 .cindex "SIZE" "option on MAIL command"
36887 Outgoing SMTP and LMTP over TCP/IP is implemented by the &(smtp)& transport.
36888 The &%protocol%& option selects which protocol is to be used, but the actual
36889 processing is the same in both cases.
36891 .cindex "ESMTP extensions" SIZE
36892 If, in response to its EHLO command, Exim is told that the SIZE
36893 extension is supported, it adds SIZE=<&'n'&> to each subsequent MAIL
36894 command. The value of <&'n'&> is the message size plus the value of the
36895 &%size_addition%& option (default 1024) to allow for additions to the message
36896 such as per-transport header lines, or changes made in a
36897 .cindex "transport" "filter"
36898 .cindex "filter" "transport filter"
36899 transport filter. If &%size_addition%& is set negative, the use of SIZE is
36902 If the remote server advertises support for PIPELINING, Exim uses the
36903 pipelining extension to SMTP (RFC 2197) to reduce the number of TCP/IP packets
36904 required for the transaction.
36906 If the remote server advertises support for the STARTTLS command, and Exim
36907 was built to support TLS encryption, it tries to start a TLS session unless the
36908 server matches &%hosts_avoid_tls%&. See chapter &<<CHAPTLS>>& for more details.
36909 Either a match in that or &%hosts_verify_avoid_tls%& apply when the transport
36910 is called for verification.
36912 If the remote server advertises support for the AUTH command, Exim scans
36913 the authenticators configuration for any suitable client settings, as described
36914 in chapter &<<CHAPSMTPAUTH>>&.
36916 .cindex "carriage return"
36918 Responses from the remote host are supposed to be terminated by CR followed by
36919 LF. However, there are known to be hosts that do not send CR characters, so in
36920 order to be able to interwork with such hosts, Exim treats LF on its own as a
36923 If a message contains a number of different addresses, all those with the same
36924 characteristics (for example, the same envelope sender) that resolve to the
36925 same set of hosts, in the same order, are sent in a single SMTP transaction,
36926 even if they are for different domains, unless there are more than the setting
36927 of the &%max_rcpt%&s option in the &(smtp)& transport allows, in which case
36928 they are split into groups containing no more than &%max_rcpt%&s addresses
36929 each. If &%remote_max_parallel%& is greater than one, such groups may be sent
36930 in parallel sessions. The order of hosts with identical MX values is not
36931 significant when checking whether addresses can be batched in this way.
36933 When the &(smtp)& transport suffers a temporary failure that is not
36934 message-related, Exim updates its transport-specific database, which contains
36935 records indexed by host name that remember which messages are waiting for each
36936 particular host. It also updates the retry database with new retry times.
36938 .cindex "hints database" "retry keys"
36939 Exim's retry hints are based on host name plus IP address, so if one address of
36940 a multi-homed host is broken, it will soon be skipped most of the time.
36941 See the next section for more detail about error handling.
36943 .cindex "SMTP" "passed connection"
36944 .cindex "SMTP" "batching over TCP/IP"
36945 When a message is successfully delivered over a TCP/IP SMTP connection, Exim
36946 looks in the hints database for the transport to see if there are any queued
36947 messages waiting for the host to which it is connected. If it finds one, it
36948 creates a new Exim process using the &%-MC%& option (which can only be used by
36949 a process running as root or the Exim user) and passes the TCP/IP socket to it
36950 so that it can deliver another message using the same socket. The new process
36951 does only those deliveries that are routed to the connected host, and may in
36952 turn pass the socket on to a third process, and so on.
36954 The &%connection_max_messages%& option of the &(smtp)& transport can be used to
36955 limit the number of messages sent down a single TCP/IP connection.
36957 .cindex "asterisk" "after IP address"
36958 The second and subsequent messages delivered down an existing connection are
36959 identified in the main log by the addition of an asterisk after the closing
36960 square bracket of the IP address.
36965 .section "Errors in outgoing SMTP" "SECToutSMTPerr"
36966 .cindex "error" "in outgoing SMTP"
36967 .cindex "SMTP" "errors in outgoing"
36968 .cindex "host" "error"
36969 Three different kinds of error are recognized for outgoing SMTP: host errors,
36970 message errors, and recipient errors.
36973 .vitem "&*Host errors*&"
36974 A host error is not associated with a particular message or with a
36975 particular recipient of a message. The host errors are:
36978 Connection refused or timed out,
36980 Any error response code on connection,
36982 Any error response code to EHLO or HELO,
36984 Loss of connection at any time, except after &"."&,
36986 I/O errors at any time,
36988 Timeouts during the session, other than in response to MAIL, RCPT or
36989 the &"."& at the end of the data.
36992 For a host error, a permanent error response on connection, or in response to
36993 EHLO, causes all addresses routed to the host to be failed. Any other host
36994 error causes all addresses to be deferred, and retry data to be created for the
36995 host. It is not tried again, for any message, until its retry time arrives. If
36996 the current set of addresses are not all delivered in this run (to some
36997 alternative host), the message is added to the list of those waiting for this
36998 host, so if it is still undelivered when a subsequent successful delivery is
36999 made to the host, it will be sent down the same SMTP connection.
37001 .vitem "&*Message errors*&"
37002 .cindex "message" "error"
37003 A message error is associated with a particular message when sent to a
37004 particular host, but not with a particular recipient of the message. The
37005 message errors are:
37008 Any error response code to MAIL, DATA, or the &"."& that terminates
37011 Timeout after MAIL,
37013 Timeout or loss of connection after the &"."& that terminates the data. A
37014 timeout after the DATA command itself is treated as a host error, as is loss of
37015 connection at any other time.
37018 For a message error, a permanent error response (5&'xx'&) causes all addresses
37019 to be failed, and a delivery error report to be returned to the sender. A
37020 temporary error response (4&'xx'&), or one of the timeouts, causes all
37021 addresses to be deferred. Retry data is not created for the host, but instead,
37022 a retry record for the combination of host plus message id is created. The
37023 message is not added to the list of those waiting for this host. This ensures
37024 that the failing message will not be sent to this host again until the retry
37025 time arrives. However, other messages that are routed to the host are not
37026 affected, so if it is some property of the message that is causing the error,
37027 it will not stop the delivery of other mail.
37029 If the remote host specified support for the SIZE parameter in its response
37030 to EHLO, Exim adds SIZE=&'nnn'& to the MAIL command, so an
37031 over-large message will cause a message error because the error arrives as a
37034 .vitem "&*Recipient errors*&"
37035 .cindex "recipient" "error"
37036 A recipient error is associated with a particular recipient of a message. The
37037 recipient errors are:
37040 Any error response to RCPT,
37042 Timeout after RCPT.
37045 For a recipient error, a permanent error response (5&'xx'&) causes the
37046 recipient address to be failed, and a bounce message to be returned to the
37047 sender. A temporary error response (4&'xx'&) or a timeout causes the failing
37048 address to be deferred, and routing retry data to be created for it. This is
37049 used to delay processing of the address in subsequent queue runs, until its
37050 routing retry time arrives. This applies to all messages, but because it
37051 operates only in queue runs, one attempt will be made to deliver a new message
37052 to the failing address before the delay starts to operate. This ensures that,
37053 if the failure is really related to the message rather than the recipient
37054 (&"message too big for this recipient"& is a possible example), other messages
37055 have a chance of getting delivered. If a delivery to the address does succeed,
37056 the retry information gets cleared, so all stuck messages get tried again, and
37057 the retry clock is reset.
37059 The message is not added to the list of those waiting for this host. Use of the
37060 host for other messages is unaffected, and except in the case of a timeout,
37061 other recipients are processed independently, and may be successfully delivered
37062 in the current SMTP session. After a timeout it is of course impossible to
37063 proceed with the session, so all addresses get deferred. However, those other
37064 than the one that failed do not suffer any subsequent retry delays. Therefore,
37065 if one recipient is causing trouble, the others have a chance of getting
37066 through when a subsequent delivery attempt occurs before the failing
37067 recipient's retry time.
37070 In all cases, if there are other hosts (or IP addresses) available for the
37071 current set of addresses (for example, from multiple MX records), they are
37072 tried in this run for any undelivered addresses, subject of course to their
37073 own retry data. In other words, recipient error retry data does not take effect
37074 until the next delivery attempt.
37076 Some hosts have been observed to give temporary error responses to every
37077 MAIL command at certain times (&"insufficient space"& has been seen). It
37078 would be nice if such circumstances could be recognized, and defer data for the
37079 host itself created, but this is not possible within the current Exim design.
37080 What actually happens is that retry data for every (host, message) combination
37083 The reason that timeouts after MAIL and RCPT are treated specially is that
37084 these can sometimes arise as a result of the remote host's verification
37085 procedures. Exim makes this assumption, and treats them as if a temporary error
37086 response had been received. A timeout after &"."& is treated specially because
37087 it is known that some broken implementations fail to recognize the end of the
37088 message if the last character of the last line is a binary zero. Thus, it is
37089 helpful to treat this case as a message error.
37091 Timeouts at other times are treated as host errors, assuming a problem with the
37092 host, or the connection to it. If a timeout after MAIL, RCPT,
37093 or &"."& is really a connection problem, the assumption is that at the next try
37094 the timeout is likely to occur at some other point in the dialogue, causing it
37095 then to be treated as a host error.
37097 There is experimental evidence that some MTAs drop the connection after the
37098 terminating &"."& if they do not like the contents of the message for some
37099 reason, in contravention of the RFC, which indicates that a 5&'xx'& response
37100 should be given. That is why Exim treats this case as a message rather than a
37101 host error, in order not to delay other messages to the same host.
37106 .section "Incoming SMTP messages over TCP/IP" "SECID233"
37107 .cindex "SMTP" "incoming over TCP/IP"
37108 .cindex "incoming SMTP over TCP/IP"
37111 Incoming SMTP messages can be accepted in one of two ways: by running a
37112 listening daemon, or by using &'inetd'&. In the latter case, the entry in
37113 &_/etc/inetd.conf_& should be like this:
37115 smtp stream tcp nowait exim /opt/exim/bin/exim in.exim -bs
37117 Exim distinguishes between this case and the case of a locally running user
37118 agent using the &%-bs%& option by checking whether or not the standard input is
37119 a socket. When it is, either the port must be privileged (less than 1024), or
37120 the caller must be root or the Exim user. If any other user passes a socket
37121 with an unprivileged port number, Exim prints a message on the standard error
37122 stream and exits with an error code.
37124 By default, Exim does not make a log entry when a remote host connects or
37125 disconnects (either via the daemon or &'inetd'&), unless the disconnection is
37126 unexpected. It can be made to write such log entries by setting the
37127 &%smtp_connection%& log selector.
37129 .cindex "carriage return"
37131 Commands from the remote host are supposed to be terminated by CR followed by
37132 LF. However, there are known to be hosts that do not send CR characters. In
37133 order to be able to interwork with such hosts, Exim treats LF on its own as a
37135 Furthermore, because common code is used for receiving messages from all
37136 sources, a CR on its own is also interpreted as a line terminator. However, the
37137 sequence &"CR, dot, CR"& does not terminate incoming SMTP data.
37139 .cindex "EHLO" "invalid data"
37140 .cindex "HELO" "invalid data"
37141 One area that sometimes gives rise to problems concerns the EHLO or
37142 HELO commands. Some clients send syntactically invalid versions of these
37143 commands, which Exim rejects by default. (This is nothing to do with verifying
37144 the data that is sent, so &%helo_verify_hosts%& is not relevant.) You can tell
37145 Exim not to apply a syntax check by setting &%helo_accept_junk_hosts%& to
37146 match the broken hosts that send invalid commands.
37148 .cindex "SIZE option on MAIL command"
37149 .cindex "MAIL" "SIZE option"
37150 The amount of disk space available is checked whenever SIZE is received on
37151 a MAIL command, independently of whether &%message_size_limit%& or
37152 &%check_spool_space%& is configured, unless &%smtp_check_spool_space%& is set
37153 false. A temporary error is given if there is not enough space. If
37154 &%check_spool_space%& is set, the check is for that amount of space plus the
37155 value given with SIZE, that is, it checks that the addition of the incoming
37156 message will not reduce the space below the threshold.
37158 When a message is successfully received, Exim includes the local message id in
37159 its response to the final &"."& that terminates the data. If the remote host
37160 logs this text it can help with tracing what has happened to a message.
37162 The Exim daemon can limit the number of simultaneous incoming connections it is
37163 prepared to handle (see the &%smtp_accept_max%& option). It can also limit the
37164 number of simultaneous incoming connections from a single remote host (see the
37165 &%smtp_accept_max_per_host%& option). Additional connection attempts are
37166 rejected using the SMTP temporary error code 421.
37168 The Exim daemon does not rely on the SIGCHLD signal to detect when a
37169 subprocess has finished, as this can get lost at busy times. Instead, it looks
37170 for completed subprocesses every time it wakes up. Provided there are other
37171 things happening (new incoming calls, starts of queue runs), completed
37172 processes will be noticed and tidied away. On very quiet systems you may
37173 sometimes see a &"defunct"& Exim process hanging about. This is not a problem;
37174 it will be noticed when the daemon next wakes up.
37176 When running as a daemon, Exim can reserve some SMTP slots for specific hosts,
37177 and can also be set up to reject SMTP calls from non-reserved hosts at times of
37178 high system load &-- for details see the &%smtp_accept_reserve%&,
37179 &%smtp_load_reserve%&, and &%smtp_reserve_hosts%& options. The load check
37180 applies in both the daemon and &'inetd'& cases.
37182 Exim normally starts a delivery process for each message received, though this
37183 can be varied by means of the &%-odq%& command line option and the
37184 &%queue_only%&, &%queue_only_file%&, and &%queue_only_load%& options. The
37185 number of simultaneously running delivery processes started in this way from
37186 SMTP input can be limited by the &%smtp_accept_queue%& and
37187 &%smtp_accept_queue_per_connection%& options. When either limit is reached,
37188 subsequently received messages are just put on the input queue without starting
37189 a delivery process.
37191 The controls that involve counts of incoming SMTP calls (&%smtp_accept_max%&,
37192 &%smtp_accept_queue%&, &%smtp_accept_reserve%&) are not available when Exim is
37193 started up from the &'inetd'& daemon, because in that case each connection is
37194 handled by an entirely independent Exim process. Control by load average is,
37195 however, available with &'inetd'&.
37197 Exim can be configured to verify addresses in incoming SMTP commands as they
37198 are received. See chapter &<<CHAPACL>>& for details. It can also be configured
37199 to rewrite addresses at this time &-- before any syntax checking is done. See
37200 section &<<SECTrewriteS>>&.
37202 Exim can also be configured to limit the rate at which a client host submits
37203 MAIL and RCPT commands in a single SMTP session. See the
37204 &%smtp_ratelimit_hosts%& option.
37208 .section "Unrecognized SMTP commands" "SECID234"
37209 .cindex "SMTP" "unrecognized commands"
37210 If Exim receives more than &%smtp_max_unknown_commands%& unrecognized SMTP
37211 commands during a single SMTP connection, it drops the connection after sending
37212 the error response to the last command. The default value for
37213 &%smtp_max_unknown_commands%& is 3. This is a defence against some kinds of
37214 abuse that subvert web servers into making connections to SMTP ports; in these
37215 circumstances, a number of non-SMTP lines are sent first.
37218 .section "Syntax and protocol errors in SMTP commands" "SECID235"
37219 .cindex "SMTP" "syntax errors"
37220 .cindex "SMTP" "protocol errors"
37221 A syntax error is detected if an SMTP command is recognized, but there is
37222 something syntactically wrong with its data, for example, a malformed email
37223 address in a RCPT command. Protocol errors include invalid command
37224 sequencing such as RCPT before MAIL. If Exim receives more than
37225 &%smtp_max_synprot_errors%& such commands during a single SMTP connection, it
37226 drops the connection after sending the error response to the last command. The
37227 default value for &%smtp_max_synprot_errors%& is 3. This is a defence against
37228 broken clients that loop sending bad commands (yes, it has been seen).
37232 .section "Use of non-mail SMTP commands" "SECID236"
37233 .cindex "SMTP" "non-mail commands"
37234 The &"non-mail"& SMTP commands are those other than MAIL, RCPT, and
37235 DATA. Exim counts such commands, and drops the connection if there are too
37236 many of them in a single SMTP session. This action catches some
37237 denial-of-service attempts and things like repeated failing AUTHs, or a mad
37238 client looping sending EHLO. The global option &%smtp_accept_max_nonmail%&
37239 defines what &"too many"& means. Its default value is 10.
37241 When a new message is expected, one occurrence of RSET is not counted. This
37242 allows a client to send one RSET between messages (this is not necessary,
37243 but some clients do it). Exim also allows one uncounted occurrence of HELO
37244 or EHLO, and one occurrence of STARTTLS between messages. After
37245 starting up a TLS session, another EHLO is expected, and so it too is not
37248 The first occurrence of AUTH in a connection, or immediately following
37249 STARTTLS is also not counted. Otherwise, all commands other than MAIL,
37250 RCPT, DATA, and QUIT are counted.
37252 You can control which hosts are subject to the limit set by
37253 &%smtp_accept_max_nonmail%& by setting
37254 &%smtp_accept_max_nonmail_hosts%&. The default value is &`*`&, which makes
37255 the limit apply to all hosts. This option means that you can exclude any
37256 specific badly-behaved hosts that you have to live with.
37261 .section "The VRFY and EXPN commands" "SECID237"
37262 When Exim receives a VRFY or EXPN command on a TCP/IP connection, it
37263 runs the ACL specified by &%acl_smtp_vrfy%& or &%acl_smtp_expn%& (as
37264 appropriate) in order to decide whether the command should be accepted or not.
37266 .cindex "VRFY" "processing"
37267 When no ACL is defined for VRFY, or if it rejects without
37268 setting an explicit response code, the command is accepted
37269 (with a 252 SMTP response code)
37270 in order to support awkward clients that do a VRFY before every RCPT.
37271 When VRFY is accepted, it runs exactly the same code as when Exim is
37272 called with the &%-bv%& option, and returns 250/451/550
37273 SMTP response codes.
37275 .cindex "EXPN" "processing"
37276 If no ACL for EXPN is defined, the command is rejected.
37277 When EXPN is accepted, a single-level expansion of the address is done.
37278 EXPN is treated as an &"address test"& (similar to the &%-bt%& option) rather
37279 than a verification (the &%-bv%& option). If an unqualified local part is given
37280 as the argument to EXPN, it is qualified with &%qualify_domain%&. Rejections
37281 of VRFY and EXPN commands are logged on the main and reject logs, and
37282 VRFY verification failures are logged on the main log for consistency with
37287 .section "The ETRN command" "SECTETRN"
37288 .cindex "ETRN" "processing"
37289 .cindex "ESMTP extensions" ETRN
37290 RFC 1985 describes an ESMTP command called ETRN that is designed to
37291 overcome the security problems of the TURN command (which has fallen into
37292 disuse). When Exim receives an ETRN command on a TCP/IP connection, it runs
37293 the ACL specified by &%acl_smtp_etrn%& in order to decide whether the command
37294 should be accepted or not. If no ACL is defined, the command is rejected.
37296 The ETRN command is concerned with &"releasing"& messages that are awaiting
37297 delivery to certain hosts. As Exim does not organize its message queue by host,
37298 the only form of ETRN that is supported by default is the one where the
37299 text starts with the &"#"& prefix, in which case the remainder of the text is
37300 specific to the SMTP server. A valid ETRN command causes a run of Exim with
37301 the &%-R%& option to happen, with the remainder of the ETRN text as its
37302 argument. For example,
37310 which causes a delivery attempt on all messages with undelivered addresses
37311 containing the text &"brigadoon"&. When &%smtp_etrn_serialize%& is set (the
37312 default), Exim prevents the simultaneous execution of more than one queue run
37313 for the same argument string as a result of an ETRN command. This stops
37314 a misbehaving client from starting more than one queue runner at once.
37316 .cindex "hints database" "ETRN serialization"
37317 Exim implements the serialization by means of a hints database in which a
37318 record is written whenever a process is started by ETRN, and deleted when
37319 the process completes. However, Exim does not keep the SMTP session waiting for
37320 the ETRN process to complete. Once ETRN is accepted, the client is sent
37321 a &"success"& return code. Obviously there is scope for hints records to get
37322 left lying around if there is a system or program crash. To guard against this,
37323 Exim ignores any records that are more than six hours old.
37325 .oindex "&%smtp_etrn_command%&"
37326 For more control over what ETRN does, the &%smtp_etrn_command%& option can
37327 used. This specifies a command that is run whenever ETRN is received,
37328 whatever the form of its argument. For
37331 smtp_etrn_command = /etc/etrn_command $domain \
37332 $sender_host_address
37334 .vindex "&$domain$&"
37335 The string is split up into arguments which are independently expanded. The
37336 expansion variable &$domain$& is set to the argument of the ETRN command,
37337 and no syntax checking is done on the contents of this argument. Exim does not
37338 wait for the command to complete, so its status code is not checked. Exim runs
37339 under its own uid and gid when receiving incoming SMTP, so it is not possible
37340 for it to change them before running the command.
37344 .section "Incoming local SMTP" "SECID238"
37345 .cindex "SMTP" "local incoming"
37346 Some user agents use SMTP to pass messages to their local MTA using the
37347 standard input and output, as opposed to passing the envelope on the command
37348 line and writing the message to the standard input. This is supported by the
37349 &%-bs%& option. This form of SMTP is handled in the same way as incoming
37350 messages over TCP/IP (including the use of ACLs), except that the envelope
37351 sender given in a MAIL command is ignored unless the caller is trusted. In
37352 an ACL you can detect this form of SMTP input by testing for an empty host
37353 identification. It is common to have this as the first line in the ACL that
37354 runs for RCPT commands:
37358 This accepts SMTP messages from local processes without doing any other tests.
37362 .section "Outgoing batched SMTP" "SECTbatchSMTP"
37363 .cindex "SMTP" "batched outgoing"
37364 .cindex "batched SMTP output"
37365 Both the &(appendfile)& and &(pipe)& transports can be used for handling
37366 batched SMTP. Each has an option called &%use_bsmtp%& which causes messages to
37367 be output in BSMTP format. No SMTP responses are possible for this form of
37368 delivery. All it is doing is using SMTP commands as a way of transmitting the
37369 envelope along with the message.
37371 The message is written to the file or pipe preceded by the SMTP commands
37372 MAIL and RCPT, and followed by a line containing a single dot. Lines in
37373 the message that start with a dot have an extra dot added. The SMTP command
37374 HELO is not normally used. If it is required, the &%message_prefix%& option
37375 can be used to specify it.
37377 Because &(appendfile)& and &(pipe)& are both local transports, they accept only
37378 one recipient address at a time by default. However, you can arrange for them
37379 to handle several addresses at once by setting the &%batch_max%& option. When
37380 this is done for BSMTP, messages may contain multiple RCPT commands. See
37381 chapter &<<CHAPbatching>>& for more details.
37384 When one or more addresses are routed to a BSMTP transport by a router that
37385 sets up a host list, the name of the first host on the list is available to the
37386 transport in the variable &$host$&. Here is an example of such a transport and
37391 driver = manualroute
37392 transport = smtp_appendfile
37393 route_list = domain.example batch.host.example
37397 driver = appendfile
37398 directory = /var/bsmtp/$host
37403 This causes messages addressed to &'domain.example'& to be written in BSMTP
37404 format to &_/var/bsmtp/batch.host.example_&, with only a single copy of each
37405 message (unless there are more than 1000 recipients).
37409 .section "Incoming batched SMTP" "SECTincomingbatchedSMTP"
37410 .cindex "SMTP" "batched incoming"
37411 .cindex "batched SMTP input"
37412 The &%-bS%& command line option causes Exim to accept one or more messages by
37413 reading SMTP on the standard input, but to generate no responses. If the caller
37414 is trusted, the senders in the MAIL commands are believed; otherwise the
37415 sender is always the caller of Exim. Unqualified senders and receivers are not
37416 rejected (there seems little point) but instead just get qualified. HELO
37417 and EHLO act as RSET; VRFY, EXPN, ETRN and HELP, act
37418 as NOOP; QUIT quits.
37420 Minimal policy checking is done for BSMTP input. Only the non-SMTP
37421 ACL is run in the same way as for non-SMTP local input.
37423 If an error is detected while reading a message, including a missing &"."& at
37424 the end, Exim gives up immediately. It writes details of the error to the
37425 standard output in a stylized way that the calling program should be able to
37426 make some use of automatically, for example:
37428 554 Unexpected end of file
37429 Transaction started in line 10
37430 Error detected in line 14
37432 It writes a more verbose version, for human consumption, to the standard error
37435 An error was detected while processing a file of BSMTP input.
37436 The error message was:
37438 501 '>' missing at end of address
37440 The SMTP transaction started in line 10.
37441 The error was detected in line 12.
37442 The SMTP command at fault was:
37444 rcpt to:<malformed@in.com.plete
37446 1 previous message was successfully processed.
37447 The rest of the batch was abandoned.
37449 The return code from Exim is zero only if there were no errors. It is 1 if some
37450 messages were accepted before an error was detected, and 2 if no messages were
37452 .ecindex IIDsmtpproc1
37453 .ecindex IIDsmtpproc2
37457 . ////////////////////////////////////////////////////////////////////////////
37458 . ////////////////////////////////////////////////////////////////////////////
37460 .chapter "Customizing bounce and warning messages" "CHAPemsgcust" &&&
37461 "Customizing messages"
37462 When a message fails to be delivered, or remains in the queue for more than a
37463 configured amount of time, Exim sends a message to the original sender, or
37464 to an alternative configured address. The text of these messages is built into
37465 the code of Exim, but it is possible to change it, either by adding a single
37466 string, or by replacing each of the paragraphs by text supplied in a file.
37468 The &'From:'& and &'To:'& header lines are automatically generated; you can
37469 cause a &'Reply-To:'& line to be added by setting the &%errors_reply_to%&
37470 option. Exim also adds the line
37472 Auto-Submitted: auto-generated
37474 to all warning and bounce messages,
37477 .section "Customizing bounce messages" "SECID239"
37478 .cindex "customizing" "bounce message"
37479 .cindex "bounce message" "customizing"
37480 If &%bounce_message_text%& is set, its contents are included in the default
37481 message immediately after &"This message was created automatically by mail
37482 delivery software."& The string is not expanded. It is not used if
37483 &%bounce_message_file%& is set.
37485 When &%bounce_message_file%& is set, it must point to a template file for
37486 constructing error messages. The file consists of a series of text items,
37487 separated by lines consisting of exactly four asterisks. If the file cannot be
37488 opened, default text is used and a message is written to the main and panic
37489 logs. If any text item in the file is empty, default text is used for that
37492 .vindex "&$bounce_recipient$&"
37493 .vindex "&$bounce_return_size_limit$&"
37494 Each item of text that is read from the file is expanded, and there are two
37495 expansion variables which can be of use here: &$bounce_recipient$& is set to
37496 the recipient of an error message while it is being created, and
37497 &$bounce_return_size_limit$& contains the value of the &%return_size_limit%&
37498 option, rounded to a whole number.
37500 The items must appear in the file in the following order:
37503 The first item is included in the headers, and should include at least a
37504 &'Subject:'& header. Exim does not check the syntax of these headers.
37506 The second item forms the start of the error message. After it, Exim lists the
37507 failing addresses with their error messages.
37509 The third item is used to introduce any text from pipe transports that is to be
37510 returned to the sender. It is omitted if there is no such text.
37512 The fourth, fifth and sixth items will be ignored and may be empty.
37513 The fields exist for back-compatibility
37516 The default state (&%bounce_message_file%& unset) is equivalent to the
37517 following file, in which the sixth item is empty. The &'Subject:'& and some
37518 other lines have been split in order to fit them on the page:
37520 Subject: Mail delivery failed
37521 ${if eq{$sender_address}{$bounce_recipient}
37522 {: returning message to sender}}
37524 This message was created automatically by mail delivery software.
37526 A message ${if eq{$sender_address}{$bounce_recipient}
37527 {that you sent }{sent by
37531 }}could not be delivered to all of its recipients.
37532 This is a permanent error. The following address(es) failed:
37534 The following text was generated during the delivery attempt(s):
37536 ------ This is a copy of the message, including all the headers.
37539 ------ The body of the message is $message_size characters long;
37541 ------ $bounce_return_size_limit or so are included here.
37544 .section "Customizing warning messages" "SECTcustwarn"
37545 .cindex "customizing" "warning message"
37546 .cindex "warning of delay" "customizing the message"
37547 The option &%warn_message_file%& can be pointed at a template file for use when
37548 warnings about message delays are created. In this case there are only three
37552 The first item is included in the headers, and should include at least a
37553 &'Subject:'& header. Exim does not check the syntax of these headers.
37555 The second item forms the start of the warning message. After it, Exim lists
37556 the delayed addresses.
37558 The third item then ends the message.
37561 The default state is equivalent to the following file, except that some lines
37562 have been split here, in order to fit them on the page:
37564 Subject: Warning: message $message_exim_id delayed
37565 $warn_message_delay
37567 This message was created automatically by mail delivery software.
37569 A message ${if eq{$sender_address}{$warn_message_recipients}
37570 {that you sent }{sent by
37574 }}has not been delivered to all of its recipients after
37575 more than $warn_message_delay in the queue on $primary_hostname.
37577 The message identifier is: $message_exim_id
37578 The subject of the message is: $h_subject
37579 The date of the message is: $h_date
37581 The following address(es) have not yet been delivered:
37583 No action is required on your part. Delivery attempts will
37584 continue for some time, and this warning may be repeated at
37585 intervals if the message remains undelivered. Eventually the
37586 mail delivery software will give up, and when that happens,
37587 the message will be returned to you.
37589 .vindex "&$warn_message_delay$&"
37590 .vindex "&$warn_message_recipients$&"
37591 However, in the default state the subject and date lines are omitted if no
37592 appropriate headers exist. During the expansion of this file,
37593 &$warn_message_delay$& is set to the delay time in one of the forms &"<&'n'&>
37594 minutes"& or &"<&'n'&> hours"&, and &$warn_message_recipients$& contains a list
37595 of recipients for the warning message. There may be more than one if there are
37596 multiple addresses with different &%errors_to%& settings on the routers that
37602 . ////////////////////////////////////////////////////////////////////////////
37603 . ////////////////////////////////////////////////////////////////////////////
37605 .chapter "Some common configuration settings" "CHAPcomconreq"
37606 This chapter discusses some configuration settings that seem to be fairly
37607 common. More examples and discussion can be found in the Exim book.
37611 .section "Sending mail to a smart host" "SECID240"
37612 .cindex "smart host" "example router"
37613 If you want to send all mail for non-local domains to a &"smart host"&, you
37614 should replace the default &(dnslookup)& router with a router which does the
37615 routing explicitly:
37617 send_to_smart_host:
37618 driver = manualroute
37619 route_list = !+local_domains smart.host.name
37620 transport = remote_smtp
37622 You can use the smart host's IP address instead of the name if you wish.
37623 If you are using Exim only to submit messages to a smart host, and not for
37624 receiving incoming messages, you can arrange for it to do the submission
37625 synchronously by setting the &%mua_wrapper%& option (see chapter
37626 &<<CHAPnonqueueing>>&).
37631 .section "Using Exim to handle mailing lists" "SECTmailinglists"
37632 .cindex "mailing lists"
37633 Exim can be used to run simple mailing lists, but for large and/or complicated
37634 requirements, the use of additional specialized mailing list software such as
37635 Majordomo or Mailman is recommended.
37637 The &(redirect)& router can be used to handle mailing lists where each list
37638 is maintained in a separate file, which can therefore be managed by an
37639 independent manager. The &%domains%& router option can be used to run these
37640 lists in a separate domain from normal mail. For example:
37644 domains = lists.example
37645 file = ${lookup {$local_part} dsearch,ret=full {/usr/lists}}
37648 errors_to = ${quote_local_part:$local_part-request}@lists.example
37651 This router is skipped for domains other than &'lists.example'&. For addresses
37652 in that domain, it looks for a file that matches the local part. If there is no
37653 such file, the router declines, but because &%no_more%& is set, no subsequent
37654 routers are tried, and so the whole delivery fails.
37656 The &%forbid_pipe%& and &%forbid_file%& options prevent a local part from being
37657 expanded into a filename or a pipe delivery, which is usually inappropriate in
37660 .oindex "&%errors_to%&"
37661 The &%errors_to%& option specifies that any delivery errors caused by addresses
37662 taken from a mailing list are to be sent to the given address rather than the
37663 original sender of the message. However, before acting on this, Exim verifies
37664 the error address, and ignores it if verification fails.
37666 For example, using the configuration above, mail sent to
37667 &'dicts@lists.example'& is passed on to those addresses contained in
37668 &_/usr/lists/dicts_&, with error reports directed to
37669 &'dicts-request@lists.example'&, provided that this address can be verified.
37670 There could be a file called &_/usr/lists/dicts-request_& containing
37671 the address(es) of this particular list's manager(s), but other approaches,
37672 such as setting up an earlier router (possibly using the &%local_part_prefix%&
37673 or &%local_part_suffix%& options) to handle addresses of the form
37674 &%owner-%&&'xxx'& or &%xxx-%&&'request'&, are also possible.
37678 .section "Syntax errors in mailing lists" "SECID241"
37679 .cindex "mailing lists" "syntax errors in"
37680 If an entry in redirection data contains a syntax error, Exim normally defers
37681 delivery of the original address. That means that a syntax error in a mailing
37682 list holds up all deliveries to the list. This may not be appropriate when a
37683 list is being maintained automatically from data supplied by users, and the
37684 addresses are not rigorously checked.
37686 If the &%skip_syntax_errors%& option is set, the &(redirect)& router just skips
37687 entries that fail to parse, noting the incident in the log. If in addition
37688 &%syntax_errors_to%& is set to a verifiable address, a message is sent to it
37689 whenever a broken address is skipped. It is usually appropriate to set
37690 &%syntax_errors_to%& to the same address as &%errors_to%&.
37694 .section "Re-expansion of mailing lists" "SECID242"
37695 .cindex "mailing lists" "re-expansion of"
37696 Exim remembers every individual address to which a message has been delivered,
37697 in order to avoid duplication, but it normally stores only the original
37698 recipient addresses with a message. If all the deliveries to a mailing list
37699 cannot be done at the first attempt, the mailing list is re-expanded when the
37700 delivery is next tried. This means that alterations to the list are taken into
37701 account at each delivery attempt, so addresses that have been added to
37702 the list since the message arrived will therefore receive a copy of the
37703 message, even though it pre-dates their subscription.
37705 If this behaviour is felt to be undesirable, the &%one_time%& option can be set
37706 on the &(redirect)& router. If this is done, any addresses generated by the
37707 router that fail to deliver at the first attempt are added to the message as
37708 &"top level"& addresses, and the parent address that generated them is marked
37709 &"delivered"&. Thus, expansion of the mailing list does not happen again at the
37710 subsequent delivery attempts. The disadvantage of this is that if any of the
37711 failing addresses are incorrect, correcting them in the file has no effect on
37712 pre-existing messages.
37714 The original top-level address is remembered with each of the generated
37715 addresses, and is output in any log messages. However, any intermediate parent
37716 addresses are not recorded. This makes a difference to the log only if the
37717 &%all_parents%& selector is set, but for mailing lists there is normally only
37718 one level of expansion anyway.
37722 .section "Closed mailing lists" "SECID243"
37723 .cindex "mailing lists" "closed"
37724 The examples so far have assumed open mailing lists, to which anybody may
37725 send mail. It is also possible to set up closed lists, where mail is accepted
37726 from specified senders only. This is done by making use of the generic
37727 &%senders%& option to restrict the router that handles the list.
37729 The following example uses the same file as a list of recipients and as a list
37730 of permitted senders. It requires three routers:
37734 domains = lists.example
37735 local_part_suffix = -request
37736 local_parts = ${lookup {$local_part} dsearch,filter=file {/usr/lists}}
37737 file = /usr/lists/${local_part_data}-request
37742 domains = lists.example
37743 local_parts = ${lookup {$local_part} dsearch,filter=file,ret=full {/usr/lists}}
37744 senders = ${if exists {$local_part_data} {lsearch;$local_part_data}{*}}
37745 file = ${lookup {$local_part} dsearch,ret=full {/usr/lists}}
37748 errors_to = ${quote_local_part:$local_part-request}@lists.example
37753 domains = lists.example
37755 data = :fail: $local_part@lists.example is a closed mailing list
37757 All three routers have the same &%domains%& setting, so for any other domains,
37758 they are all skipped. The first router runs only if the local part ends in
37759 &%-request%&. It handles messages to the list manager(s) by means of an open
37762 The second router runs only if the &%senders%& precondition is satisfied. It
37763 checks for the existence of a list that corresponds to the local part, and then
37764 checks that the sender is on the list by means of a linear search. It is
37765 necessary to check for the existence of the file before trying to search it,
37766 because otherwise Exim thinks there is a configuration error. If the file does
37767 not exist, the expansion of &%senders%& is *, which matches all senders. This
37768 means that the router runs, but because there is no list, declines, and
37769 &%no_more%& ensures that no further routers are run. The address fails with an
37770 &"unrouteable address"& error.
37772 The third router runs only if the second router is skipped, which happens when
37773 a mailing list exists, but the sender is not on it. This router forcibly fails
37774 the address, giving a suitable error message.
37779 .section "Variable Envelope Return Paths (VERP)" "SECTverp"
37781 .cindex "Variable Envelope Return Paths"
37782 .cindex "envelope from"
37783 .cindex "envelope sender"
37784 Variable Envelope Return Paths &-- see &url(https://cr.yp.to/proto/verp.txt) &--
37785 are a way of helping mailing list administrators discover which subscription
37786 address is the cause of a particular delivery failure. The idea is to encode
37787 the original recipient address in the outgoing envelope sender address, so that
37788 if the message is forwarded by another host and then subsequently bounces, the
37789 original recipient can be extracted from the recipient address of the bounce.
37791 .oindex &%errors_to%&
37792 .oindex &%return_path%&
37793 Envelope sender addresses can be modified by Exim using two different
37794 facilities: the &%errors_to%& option on a router (as shown in previous mailing
37795 list examples), or the &%return_path%& option on a transport. The second of
37796 these is effective only if the message is successfully delivered to another
37797 host; it is not used for errors detected on the local host (see the description
37798 of &%return_path%& in chapter &<<CHAPtransportgeneric>>&). Here is an example
37799 of the use of &%return_path%& to implement VERP on an &(smtp)& transport:
37805 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
37806 {${quote_local_part:$1-request+$local_part=$domain}@your.dom.example}fail}
37808 This has the effect of rewriting the return path (envelope sender) on outgoing
37809 SMTP messages, if the local part of the original return path ends in
37810 &"-request"&, and the domain is &'your.dom.example'&. The rewriting inserts the
37811 local part and domain of the recipient into the return path. Suppose, for
37812 example, that a message whose return path has been set to
37813 &'somelist-request@your.dom.example'& is sent to
37814 &'subscriber@other.dom.example'&. In the transport, the return path is
37817 somelist-request+subscriber=other.dom.example@your.dom.example
37819 .vindex "&$local_part$&"
37820 For this to work, you must tell Exim to send multiple copies of messages that
37821 have more than one recipient, so that each copy has just one recipient. This is
37822 achieved by setting &%max_rcpt%& to 1. Without this, a single copy of a message
37823 might be sent to several different recipients in the same domain, in which case
37824 &$local_part$& is not available in the transport, because it is not unique.
37826 Unless your host is doing nothing but mailing list deliveries, you should
37827 probably use a separate transport for the VERP deliveries, so as not to use
37828 extra resources in making one-per-recipient copies for other deliveries. This
37829 can easily be done by expanding the &%transport%& option in the router:
37833 domains = ! +local_domains
37835 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
37836 {verp_smtp}{remote_smtp}}
37839 If you want to change the return path using &%errors_to%& in a router instead
37840 of using &%return_path%& in the transport, you need to set &%errors_to%& on all
37841 routers that handle mailing list addresses. This will ensure that all delivery
37842 errors, including those detected on the local host, are sent to the VERP
37845 On a host that does no local deliveries and has no manual routing, only the
37846 &(dnslookup)& router needs to be changed. A special transport is not needed for
37847 SMTP deliveries. Every mailing list recipient has its own return path value,
37848 and so Exim must hand them to the transport one at a time. Here is an example
37849 of a &(dnslookup)& router that implements VERP:
37853 domains = ! +local_domains
37854 transport = remote_smtp
37856 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}}
37857 {${quote_local_part:$1-request+$local_part=$domain}@your.dom.example}fail}
37860 Before you start sending out messages with VERPed return paths, you must also
37861 configure Exim to accept the bounce messages that come back to those paths.
37862 Typically this is done by setting a &%local_part_suffix%& option for a
37863 router, and using this to route the messages to wherever you want to handle
37866 The overhead incurred in using VERP depends very much on the size of the
37867 message, the number of recipient addresses that resolve to the same remote
37868 host, and the speed of the connection over which the message is being sent. If
37869 a lot of addresses resolve to the same host and the connection is slow, sending
37870 a separate copy of the message for each address may take substantially longer
37871 than sending a single copy with many recipients (for which VERP cannot be
37879 .section "Virtual domains" "SECTvirtualdomains"
37880 .cindex "virtual domains"
37881 .cindex "domain" "virtual"
37882 The phrase &'virtual domain'& is unfortunately used with two rather different
37886 A domain for which there are no real mailboxes; all valid local parts are
37887 aliases for other email addresses. Common examples are organizational
37888 top-level domains and &"vanity"& domains.
37890 One of a number of independent domains that are all handled by the same host,
37891 with mailboxes on that host, but where the mailbox owners do not necessarily
37892 have login accounts on that host.
37895 The first usage is probably more common, and does seem more &"virtual"& than
37896 the second. This kind of domain can be handled in Exim with a straightforward
37897 aliasing router. One approach is to create a separate alias file for each
37898 virtual domain. Exim can test for the existence of the alias file to determine
37899 whether the domain exists. The &(dsearch)& lookup type is useful here, leading
37900 to a router of this form:
37904 domains = dsearch;/etc/mail/virtual
37905 data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain_data}}
37908 The &%domains%& option specifies that the router is to be skipped, unless there
37909 is a file in the &_/etc/mail/virtual_& directory whose name is the same as the
37910 domain that is being processed.
37911 The &(dsearch)& lookup used results in an untainted version of &$domain$&
37912 being placed into the &$domain_data$& variable.
37914 When the router runs, it looks up the local
37915 part in the file to find a new address (or list of addresses). The &%no_more%&
37916 setting ensures that if the lookup fails (leading to &%data%& being an empty
37917 string), Exim gives up on the address without trying any subsequent routers.
37919 This one router can handle all the virtual domains because the alias filenames
37920 follow a fixed pattern. Permissions can be arranged so that appropriate people
37921 can edit the different alias files. A successful aliasing operation results in
37922 a new envelope recipient address, which is then routed from scratch.
37924 The other kind of &"virtual"& domain can also be handled in a straightforward
37925 way. One approach is to create a file for each domain containing a list of
37926 valid local parts, and use it in a router like this:
37930 domains = dsearch;/etc/mail/domains
37931 local_parts = lsearch;/etc/mail/domains/$domain
37932 transport = my_mailboxes
37934 The address is accepted if there is a file for the domain, and the local part
37935 can be found in the file. The &%domains%& option is used to check for the
37936 file's existence because &%domains%& is tested before the &%local_parts%&
37937 option (see section &<<SECTrouprecon>>&). You cannot use &%require_files%&,
37938 because that option is tested after &%local_parts%&. The transport is as
37942 driver = appendfile
37943 file = /var/mail/$domain_data/$local_part_data
37946 This uses a directory of mailboxes for each domain. The &%user%& setting is
37947 required, to specify which uid is to be used for writing to the mailboxes.
37949 The configuration shown here is just one example of how you might support this
37950 requirement. There are many other ways this kind of configuration can be set
37951 up, for example, by using a database instead of separate files to hold all the
37952 information about the domains.
37956 .section "Multiple user mailboxes" "SECTmulbox"
37957 .cindex "multiple mailboxes"
37958 .cindex "mailbox" "multiple"
37959 .cindex "local part" "prefix"
37960 .cindex "local part" "suffix"
37961 Heavy email users often want to operate with multiple mailboxes, into which
37962 incoming mail is automatically sorted. A popular way of handling this is to
37963 allow users to use multiple sender addresses, so that replies can easily be
37964 identified. Users are permitted to add prefixes or suffixes to their local
37965 parts for this purpose. The wildcard facility of the generic router options
37966 &%local_part_prefix%& and &%local_part_suffix%& can be used for this. For
37967 example, consider this router:
37972 file = $home/.forward
37973 local_part_suffix = -*
37974 local_part_suffix_optional
37977 .vindex "&$local_part_suffix$&"
37978 It runs a user's &_.forward_& file for all local parts of the form
37979 &'username-*'&. Within the filter file the user can distinguish different
37980 cases by testing the variable &$local_part_suffix$&. For example:
37982 if $local_part_suffix contains -special then
37983 save /home/$local_part_data/Mail/special
37986 If the filter file does not exist, or does not deal with such addresses, they
37987 fall through to subsequent routers, and, assuming no subsequent use of the
37988 &%local_part_suffix%& option is made, they presumably fail. Thus, users have
37989 control over which suffixes are valid.
37991 Alternatively, a suffix can be used to trigger the use of a different
37992 &_.forward_& file &-- which is the way a similar facility is implemented in
37998 local_part_suffix = -*
37999 local_part_suffix_optional
38000 file = ${lookup {.forward$local_part_suffix} dsearch,ret=full {$home} {$value}fail}
38003 If there is no suffix, &_.forward_& is used; if the suffix is &'-special'&, for
38004 example, &_.forward-special_& is used. Once again, if the appropriate file
38005 does not exist, or does not deal with the address, it is passed on to
38006 subsequent routers, which could, if required, look for an unqualified
38007 &_.forward_& file to use as a default.
38011 .section "Simplified vacation processing" "SECID244"
38012 .cindex "vacation processing"
38013 The traditional way of running the &'vacation'& program is for a user to set up
38014 a pipe command in a &_.forward_& file
38015 (see section &<<SECTspecitredli>>& for syntax details).
38016 This is prone to error by inexperienced users. There are two features of Exim
38017 that can be used to make this process simpler for users:
38020 A local part prefix such as &"vacation-"& can be specified on a router which
38021 can cause the message to be delivered directly to the &'vacation'& program, or
38022 alternatively can use Exim's &(autoreply)& transport. The contents of a user's
38023 &_.forward_& file are then much simpler. For example:
38025 spqr, vacation-spqr
38028 The &%require_files%& generic router option can be used to trigger a
38029 vacation delivery by checking for the existence of a certain file in the
38030 user's home directory. The &%unseen%& generic option should also be used, to
38031 ensure that the original delivery also proceeds. In this case, all the user has
38032 to do is to create a file called, say, &_.vacation_&, containing a vacation
38036 Another advantage of both these methods is that they both work even when the
38037 use of arbitrary pipes by users is locked out.
38041 .section "Taking copies of mail" "SECID245"
38042 .cindex "message" "copying every"
38043 Some installations have policies that require archive copies of all messages to
38044 be made. A single copy of each message can easily be taken by an appropriate
38045 command in a system filter, which could, for example, use a different file for
38046 each day's messages.
38048 There is also a shadow transport mechanism that can be used to take copies of
38049 messages that are successfully delivered by local transports, one copy per
38050 delivery. This could be used, &'inter alia'&, to implement automatic
38051 notification of delivery by sites that insist on doing such things.
38055 .section "Intermittently connected hosts" "SECID246"
38056 .cindex "intermittently connected hosts"
38057 It has become quite common (because it is cheaper) for hosts to connect to the
38058 Internet periodically rather than remain connected all the time. The normal
38059 arrangement is that mail for such hosts accumulates on a system that is
38060 permanently connected.
38062 Exim was designed for use on permanently connected hosts, and so it is not
38063 particularly well-suited to use in an intermittently connected environment.
38064 Nevertheless there are some features that can be used.
38067 .section "Exim on the upstream server host" "SECID247"
38068 It is tempting to arrange for incoming mail for the intermittently connected
38069 host to remain in Exim's queue until the client connects. However, this
38070 approach does not scale very well. Two different kinds of waiting message are
38071 being mixed up in the same queue &-- those that cannot be delivered because of
38072 some temporary problem, and those that are waiting for their destination host
38073 to connect. This makes it hard to manage the queue, as well as wasting
38074 resources, because each queue runner scans the entire queue.
38076 A better approach is to separate off those messages that are waiting for an
38077 intermittently connected host. This can be done by delivering these messages
38078 into local files in batch SMTP, &"mailstore"&, or other envelope-preserving
38079 format, from where they are transmitted by other software when their
38080 destination connects. This makes it easy to collect all the mail for one host
38081 in a single directory, and to apply local timeout rules on a per-message basis
38084 On a very small scale, leaving the mail on Exim's queue can be made to work. If
38085 you are doing this, you should configure Exim with a long retry period for the
38086 intermittent host. For example:
38088 cheshire.wonderland.fict.example * F,5d,24h
38090 This stops a lot of failed delivery attempts from occurring, but Exim remembers
38091 which messages it has queued up for that host. Once the intermittent host comes
38092 online, forcing delivery of one message (either by using the &%-M%& or &%-R%&
38093 options, or by using the ETRN SMTP command (see section &<<SECTETRN>>&)
38094 causes all the queued up messages to be delivered, often down a single SMTP
38095 connection. While the host remains connected, any new messages get delivered
38098 If the connecting hosts do not have fixed IP addresses, that is, if a host is
38099 issued with a different IP address each time it connects, Exim's retry
38100 mechanisms on the holding host get confused, because the IP address is normally
38101 used as part of the key string for holding retry information. This can be
38102 avoided by unsetting &%retry_include_ip_address%& on the &(smtp)& transport.
38103 Since this has disadvantages for permanently connected hosts, it is best to
38104 arrange a separate transport for the intermittently connected ones.
38108 .section "Exim on the intermittently connected client host" "SECID248"
38109 The value of &%smtp_accept_queue_per_connection%& should probably be
38110 increased, or even set to zero (that is, disabled) on the intermittently
38111 connected host, so that all incoming messages down a single connection get
38112 delivered immediately.
38114 .cindex "SMTP" "passed connection"
38115 .cindex "SMTP" "multiple deliveries"
38116 .cindex "multiple SMTP deliveries"
38117 .cindex "first pass routing"
38118 Mail waiting to be sent from an intermittently connected host will probably
38119 not have been routed, because without a connection DNS lookups are not
38120 possible. This means that if a normal queue run is done at connection time,
38121 each message is likely to be sent in a separate SMTP session. This can be
38122 avoided by starting the queue run with a command line option beginning with
38123 &%-qq%& instead of &%-q%&. In this case, the queue is scanned twice. In the
38124 first pass, routing is done but no deliveries take place. The second pass is a
38125 normal queue run; since all the messages have been previously routed, those
38126 destined for the same host are likely to get sent as multiple deliveries in a
38127 single SMTP connection.
38131 . ////////////////////////////////////////////////////////////////////////////
38132 . ////////////////////////////////////////////////////////////////////////////
38134 .chapter "Using Exim as a non-queueing client" "CHAPnonqueueing" &&&
38135 "Exim as a non-queueing client"
38136 .cindex "client, non-queueing"
38137 .cindex "smart host" "suppressing queueing"
38138 On a personal computer, it is a common requirement for all
38139 email to be sent to a &"smart host"&. There are plenty of MUAs that can be
38140 configured to operate that way, for all the popular operating systems.
38141 However, there are some MUAs for Unix-like systems that cannot be so
38142 configured: they submit messages using the command line interface of
38143 &_/usr/sbin/sendmail_&. Furthermore, utility programs such as &'cron'& submit
38146 If the personal computer runs continuously, there is no problem, because it can
38147 run a conventional MTA that handles delivery to the smart host, and deal with
38148 any delays via its queueing mechanism. However, if the computer does not run
38149 continuously or runs different operating systems at different times, queueing
38150 email is not desirable.
38152 There is therefore a requirement for something that can provide the
38153 &_/usr/sbin/sendmail_& interface but deliver messages to a smart host without
38154 any queueing or retrying facilities. Furthermore, the delivery to the smart
38155 host should be synchronous, so that if it fails, the sending MUA is immediately
38156 informed. In other words, we want something that extends an MUA that submits
38157 to a local MTA via the command line so that it behaves like one that submits
38158 to a remote smart host using TCP/SMTP.
38160 There are a number of applications (for example, there is one called &'ssmtp'&)
38161 that do this job. However, people have found them to be lacking in various
38162 ways. For instance, you might want to allow aliasing and forwarding to be done
38163 before sending a message to the smart host.
38165 Exim already had the necessary infrastructure for doing this job. Just a few
38166 tweaks were needed to make it behave as required, though it is somewhat of an
38167 overkill to use a fully-featured MTA for this purpose.
38169 .oindex "&%mua_wrapper%&"
38170 There is a Boolean global option called &%mua_wrapper%&, defaulting false.
38171 Setting &%mua_wrapper%& true causes Exim to run in a special mode where it
38172 assumes that it is being used to &"wrap"& a command-line MUA in the manner
38173 just described. As well as setting &%mua_wrapper%&, you also need to provide a
38174 compatible router and transport configuration. Typically there will be just one
38175 router and one transport, sending everything to a smart host.
38177 When run in MUA wrapping mode, the behaviour of Exim changes in the
38181 A daemon cannot be run, nor will Exim accept incoming messages from &'inetd'&.
38182 In other words, the only way to submit messages is via the command line.
38184 Each message is synchronously delivered as soon as it is received (&%-odi%& is
38185 assumed). All queueing options (&%queue_only%&, &%queue_smtp_domains%&,
38186 &%control%& in an ACL, etc.) are quietly ignored. The Exim reception process
38187 does not finish until the delivery attempt is complete. If the delivery is
38188 successful, a zero return code is given.
38190 Address redirection is permitted, but the final routing for all addresses must
38191 be to the same remote transport, and to the same list of hosts. Furthermore,
38192 the return address (envelope sender) must be the same for all recipients, as
38193 must any added or deleted header lines. In other words, it must be possible to
38194 deliver the message in a single SMTP transaction, however many recipients there
38197 If these conditions are not met, or if routing any address results in a
38198 failure or defer status, or if Exim is unable to deliver all the recipients
38199 successfully to one of the smart hosts, delivery of the entire message fails.
38201 Because no queueing is allowed, all failures are treated as permanent; there
38202 is no distinction between 4&'xx'& and 5&'xx'& SMTP response codes from the
38203 smart host. Furthermore, because only a single yes/no response can be given to
38204 the caller, it is not possible to deliver to some recipients and not others. If
38205 there is an error (temporary or permanent) for any recipient, all are failed.
38207 If more than one smart host is listed, Exim will try another host after a
38208 connection failure or a timeout, in the normal way. However, if this kind of
38209 failure happens for all the hosts, the delivery fails.
38211 When delivery fails, an error message is written to the standard error stream
38212 (as well as to Exim's log), and Exim exits to the caller with a return code
38213 value 1. The message is expunged from Exim's spool files. No bounce messages
38214 are ever generated.
38216 No retry data is maintained, and any retry rules are ignored.
38218 A number of Exim options are overridden: &%deliver_drop_privilege%& is forced
38219 true, &%max_rcpt%& in the &(smtp)& transport is forced to &"unlimited"&,
38220 &%remote_max_parallel%& is forced to one, and fallback hosts are ignored.
38223 The overall effect is that Exim makes a single synchronous attempt to deliver
38224 the message, failing if there is any kind of problem. Because no local
38225 deliveries are done and no daemon can be run, Exim does not need root
38226 privilege. It should be possible to run it setuid to &'exim'& instead of setuid
38227 to &'root'&. See section &<<SECTrunexiwitpri>>& for a general discussion about
38228 the advantages and disadvantages of running without root privilege.
38233 . ////////////////////////////////////////////////////////////////////////////
38234 . ////////////////////////////////////////////////////////////////////////////
38236 .chapter "Log files" "CHAPlog"
38237 .scindex IIDloggen "log" "general description"
38238 .cindex "log" "types of"
38239 Exim writes three different logs, referred to as the main log, the reject log,
38244 The main log records the arrival of each message and each delivery in a single
38245 line in each case. The format is as compact as possible, in an attempt to keep
38246 down the size of log files. Two-character flag sequences make it easy to pick
38247 out these lines. A number of other events are recorded in the main log. Some of
38248 them are optional, in which case the &%log_selector%& option controls whether
38249 they are included or not. A Perl script called &'eximstats'&, which does simple
38250 analysis of main log files, is provided in the Exim distribution (see section
38251 &<<SECTmailstat>>&).
38253 .cindex "reject log"
38254 The reject log records information from messages that are rejected as a result
38255 of a configuration option (that is, for policy reasons).
38256 The first line of each rejection is a copy of the line that is also written to
38257 the main log. Then, if the message's header has been read at the time the log
38258 is written, its contents are written to this log. Only the original header
38259 lines are available; header lines added by ACLs are not logged. You can use the
38260 reject log to check that your policy controls are working correctly; on a busy
38261 host this may be easier than scanning the main log for rejection messages. You
38262 can suppress the writing of the reject log by setting &%write_rejectlog%&
38265 .cindex "panic log"
38266 .cindex "system log"
38267 When certain serious errors occur, Exim writes entries to its panic log. If the
38268 error is sufficiently disastrous, Exim bombs out afterwards. Panic log entries
38269 are usually written to the main log as well, but can get lost amid the mass of
38270 other entries. The panic log should be empty under normal circumstances. It is
38271 therefore a good idea to check it (or to have a &'cron'& script check it)
38272 regularly, in order to become aware of any problems. When Exim cannot open its
38273 panic log, it tries as a last resort to write to the system log (syslog). This
38274 is opened with LOG_PID+LOG_CONS and the facility code of LOG_MAIL. The
38275 message itself is written at priority LOG_CRIT.
38278 Every log line starts with a timestamp, in the format shown in the following
38279 example. Note that many of the examples shown in this chapter are line-wrapped.
38280 In the log file, this would be all on one line:
38282 2001-09-16 16:09:47 SMTP connection from [127.0.0.1] closed
38285 By default, the timestamps are in the local timezone. There are two
38286 ways of changing this:
38289 You can set the &%timezone%& option to a different time zone; in particular, if
38294 the timestamps will be in UTC (aka GMT).
38296 If you set &%log_timezone%& true, the time zone is added to the timestamp, for
38299 2003-04-25 11:17:07 +0100 Start queue run: pid=12762
38303 .cindex "log" "process ids in"
38304 .cindex "pid (process id)" "in log lines"
38305 Exim does not include its process id in log lines by default, but you can
38306 request that it does so by specifying the &`pid`& log selector (see section
38307 &<<SECTlogselector>>&). When this is set, the process id is output, in square
38308 brackets, immediately after the time and date.
38313 .section "Where the logs are written" "SECTwhelogwri"
38314 .cindex "log" "destination"
38315 .cindex "log" "to file"
38316 .cindex "log" "to syslog"
38318 The logs may be written to local files, or to syslog, or both. However, it
38319 should be noted that many syslog implementations use UDP as a transport, and
38320 are therefore unreliable in the sense that messages are not guaranteed to
38321 arrive at the loghost, nor is the ordering of messages necessarily maintained.
38322 It has also been reported that on large log files (tens of megabytes) you may
38323 need to tweak syslog to prevent it syncing the file with each write &-- on
38324 Linux this has been seen to make syslog take 90% plus of CPU time.
38326 The destination for Exim's logs is configured by setting LOG_FILE_PATH in
38327 &_Local/Makefile_& or by setting &%log_file_path%& in the runtime
38328 configuration. This latter string is expanded, so it can contain, for example,
38329 references to the host name:
38331 log_file_path = /var/log/$primary_hostname/exim_%slog
38333 It is generally advisable, however, to set the string in &_Local/Makefile_&
38334 rather than at runtime, because then the setting is available right from the
38335 start of Exim's execution. Otherwise, if there's something it wants to log
38336 before it has read the configuration file (for example, an error in the
38337 configuration file) it will not use the path you want, and may not be able to
38340 The value of LOG_FILE_PATH or &%log_file_path%& is a colon-separated
38341 list, currently limited to at most two items. This is one option where the
38342 facility for changing a list separator may not be used. The list must always be
38343 colon-separated. If an item in the list is &"syslog"& then syslog is used;
38344 otherwise the item must either be an absolute path, containing &`%s`& at the
38345 point where &"main"&, &"reject"&, or &"panic"& is to be inserted, or be empty,
38346 implying the use of a default path.
38348 When Exim encounters an empty item in the list, it searches the list defined by
38349 LOG_FILE_PATH, and uses the first item it finds that is neither empty nor
38350 &"syslog"&. This means that an empty item in &%log_file_path%& can be used to
38351 mean &"use the path specified at build time"&. If no such item exists, log
38352 files are written in the &_log_& subdirectory of the spool directory. This is
38353 equivalent to the configuration file setting:
38355 log_file_path = $spool_directory/log/%slog
38357 If you do not specify anything at build time or runtime,
38358 or if you unset the option at runtime (i.e. &`log_file_path = `&),
38359 that is where the logs are written.
38361 A log file path may also contain &`%D`& or &`%M`& if datestamped log filenames
38362 are in use &-- see section &<<SECTdatlogfil>>& below.
38364 Here are some examples of possible Makefile settings:
38366 &`LOG_FILE_PATH=syslog `& syslog only
38367 &`LOG_FILE_PATH=:syslog `& syslog and default path
38368 &`LOG_FILE_PATH=syslog : /usr/log/exim_%s `& syslog and specified path
38369 &`LOG_FILE_PATH=/usr/log/exim_%s `& specified path only
38371 If there are more than two paths in the list, the first is used and a panic
38376 .section "Logging to local files that are periodically &""cycled""&" "SECID285"
38377 .cindex "log" "cycling local files"
38378 .cindex "cycling logs"
38379 .cindex "&'exicyclog'&"
38380 .cindex "log" "local files; writing to"
38381 Some operating systems provide centralized and standardized methods for cycling
38382 log files. For those that do not, a utility script called &'exicyclog'& is
38383 provided (see section &<<SECTcyclogfil>>&). This renames and compresses the
38384 main and reject logs each time it is called. The maximum number of old logs to
38385 keep can be set. It is suggested this script is run as a daily &'cron'& job.
38387 An Exim delivery process opens the main log when it first needs to write to it,
38388 and it keeps the file open in case subsequent entries are required &-- for
38389 example, if a number of different deliveries are being done for the same
38390 message. However, remote SMTP deliveries can take a long time, and this means
38391 that the file may be kept open long after it is renamed if &'exicyclog'& or
38392 something similar is being used to rename log files on a regular basis. To
38393 ensure that a switch of log files is noticed as soon as possible, Exim calls
38394 &[stat()]& on the main log's name before reusing an open file, and if the file
38395 does not exist, or its inode has changed, the old file is closed and Exim
38396 tries to open the main log from scratch. Thus, an old log file may remain open
38397 for quite some time, but no Exim processes should write to it once it has been
38402 .section "Datestamped log files" "SECTdatlogfil"
38403 .cindex "log" "datestamped files"
38404 Instead of cycling the main and reject log files by renaming them
38405 periodically, some sites like to use files whose names contain a datestamp,
38406 for example, &_mainlog-20031225_&. The datestamp is in the form &_yyyymmdd_& or
38407 &_yyyymm_&. Exim has support for this way of working. It is enabled by setting
38408 the &%log_file_path%& option to a path that includes &`%D`& or &`%M`& at the
38409 point where the datestamp is required. For example:
38411 log_file_path = /var/spool/exim/log/%slog-%D
38412 log_file_path = /var/log/exim-%s-%D.log
38413 log_file_path = /var/spool/exim/log/%D-%slog
38414 log_file_path = /var/log/exim/%s.%M
38416 As before, &`%s`& is replaced by &"main"& or &"reject"&; the following are
38417 examples of names generated by the above examples:
38419 /var/spool/exim/log/mainlog-20021225
38420 /var/log/exim-reject-20021225.log
38421 /var/spool/exim/log/20021225-mainlog
38422 /var/log/exim/main.200212
38424 When this form of log file is specified, Exim automatically switches to new
38425 files at midnight. It does not make any attempt to compress old logs; you
38426 will need to write your own script if you require this. You should not
38427 run &'exicyclog'& with this form of logging.
38429 The location of the panic log is also determined by &%log_file_path%&, but it
38430 is not datestamped, because rotation of the panic log does not make sense.
38431 When generating the name of the panic log, &`%D`& or &`%M`& are removed from
38432 the string. In addition, if it immediately follows a slash, a following
38433 non-alphanumeric character is removed; otherwise a preceding non-alphanumeric
38434 character is removed. Thus, the four examples above would give these panic
38437 /var/spool/exim/log/paniclog
38438 /var/log/exim-panic.log
38439 /var/spool/exim/log/paniclog
38440 /var/log/exim/panic
38444 .section "Logging to syslog" "SECID249"
38445 .cindex "log" "syslog; writing to"
38446 The use of syslog does not change what Exim logs or the format of its messages,
38447 except in one respect. If &%syslog_timestamp%& is set false, the timestamps on
38448 Exim's log lines are omitted when these lines are sent to syslog. Apart from
38449 that, the same strings are written to syslog as to log files. The syslog
38450 &"facility"& is set to LOG_MAIL, and the program name to &"exim"&
38451 by default, but you can change these by setting the &%syslog_facility%& and
38452 &%syslog_processname%& options, respectively. If Exim was compiled with
38453 SYSLOG_LOG_PID set in &_Local/Makefile_& (this is the default in
38454 &_src/EDITME_&), then, on systems that permit it (all except ULTRIX), the
38455 LOG_PID flag is set so that the &[syslog()]& call adds the pid as well as
38456 the time and host name to each line.
38457 The three log streams are mapped onto syslog priorities as follows:
38460 &'mainlog'& is mapped to LOG_INFO
38462 &'rejectlog'& is mapped to LOG_NOTICE
38464 &'paniclog'& is mapped to LOG_ALERT
38467 Many log lines are written to both &'mainlog'& and &'rejectlog'&, and some are
38468 written to both &'mainlog'& and &'paniclog'&, so there will be duplicates if
38469 these are routed by syslog to the same place. You can suppress this duplication
38470 by setting &%syslog_duplication%& false.
38472 Exim's log lines can sometimes be very long, and some of its &'rejectlog'&
38473 entries contain multiple lines when headers are included. To cope with both
38474 these cases, entries written to syslog are split into separate &[syslog()]&
38475 calls at each internal newline, and also after a maximum of
38476 870 data characters. (This allows for a total syslog line length of 1024, when
38477 additions such as timestamps are added.) If you are running a syslog
38478 replacement that can handle lines longer than the 1024 characters allowed by
38479 RFC 3164, you should set
38481 SYSLOG_LONG_LINES=yes
38483 in &_Local/Makefile_& before building Exim. That stops Exim from splitting long
38484 lines, but it still splits at internal newlines in &'reject'& log entries.
38486 To make it easy to re-assemble split lines later, each component of a split
38487 entry starts with a string of the form [<&'n'&>/<&'m'&>] or [<&'n'&>\<&'m'&>]
38488 where <&'n'&> is the component number and <&'m'&> is the total number of
38489 components in the entry. The / delimiter is used when the line was split
38490 because it was too long; if it was split because of an internal newline, the \
38491 delimiter is used. For example, supposing the length limit to be 50 instead of
38492 870, the following would be the result of a typical rejection message to
38493 &'mainlog'& (LOG_INFO), each line in addition being preceded by the time, host
38494 name, and pid as added by syslog:
38496 [1/5] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected from
38497 [2/5] [127.0.0.1] (ph10): syntax error in 'From' header
38498 [3/5] when scanning for sender: missing or malformed lo
38499 [4/5] cal part in "<>" (envelope sender is <ph10@cam.exa
38502 The same error might cause the following lines to be written to &"rejectlog"&
38505 [1/18] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected fro
38506 [2/18] m [127.0.0.1] (ph10): syntax error in 'From' head
38507 [3/18] er when scanning for sender: missing or malformed
38508 [4/18] local part in "<>" (envelope sender is <ph10@cam
38510 [6\18] Recipients: ph10@some.domain.cam.example
38511 [7\18] P Received: from [127.0.0.1] (ident=ph10)
38512 [8\18] by xxxxx.cam.example with smtp (Exim 4.00)
38513 [9\18] id 16RdAL-0006pc-00
38514 [10/18] for ph10@cam.example; Mon, 16 Sep 2002 16:
38515 [11\18] 09:43 +0100
38517 [13\18] Subject: this is a test header
38518 [18\18] X-something: this is another header
38519 [15/18] I Message-Id: <E16RdAL-0006pc-00@xxxxx.cam.examp
38522 [18/18] Date: Mon, 16 Sep 2002 16:09:43 +0100
38524 Log lines that are neither too long nor contain newlines are written to syslog
38525 without modification.
38527 If only syslog is being used, the Exim monitor is unable to provide a log tail
38528 display, unless syslog is routing &'mainlog'& to a file on the local host and
38529 the environment variable EXIMON_LOG_FILE_PATH is set to tell the monitor
38534 .section "Log line flags" "SECID250"
38535 One line is written to the main log for each message received, and for each
38536 successful, unsuccessful, and delayed delivery. These lines can readily be
38537 picked out by the distinctive two-character flags that immediately follow the
38538 timestamp. The flags are:
38539 .itable none 0 0 2 10* left 90* left
38540 .irow &%<=%& "message arrival"
38541 .irow &%(=%& "message fakereject"
38542 .irow &%=>%& "normal message delivery"
38543 .irow &%->%& "additional address in same delivery"
38544 .irow &%>>%& "cutthrough message delivery"
38545 .irow &%*>%& "delivery suppressed by &%-N%&"
38546 .irow &%**%& "delivery failed; address bounced"
38547 .irow &%==%& "delivery deferred; temporary problem"
38551 .section "Logging message reception" "SECID251"
38552 .cindex "log" "reception line"
38553 The format of the single-line entry in the main log that is written for every
38554 message received is shown in the basic example below, which is split over
38555 several lines in order to fit it on the page:
38557 2002-10-31 08:57:53 16ZCW1-0005MB-00 <= kryten@dwarf.fict.example
38558 H=mailer.fict.example [192.168.123.123] U=exim
38559 P=smtp S=5678 id=<incoming message id>
38561 The address immediately following &"<="& is the envelope sender address. A
38562 bounce message is shown with the sender address &"<>"&, and if it is locally
38563 generated, this is followed by an item of the form
38567 which is a reference to the message that caused the bounce to be sent.
38571 For messages from other hosts, the H and U fields identify the remote host and
38572 record the RFC 1413 identity of the user that sent the message, if one was
38573 received. The number given in square brackets is the IP address of the sending
38574 host. If there is a single, unparenthesized host name in the H field, as
38575 above, it has been verified to correspond to the IP address (see the
38576 &%host_lookup%& option). If the name is in parentheses, it was the name quoted
38577 by the remote host in the SMTP HELO or EHLO command, and has not been
38578 verified. If verification yields a different name to that given for HELO or
38579 EHLO, the verified name appears first, followed by the HELO or EHLO
38580 name in parentheses.
38582 Misconfigured hosts (and mail forgers) sometimes put an IP address, with or
38583 without brackets, in the HELO or EHLO command, leading to entries in
38584 the log containing text like these examples:
38586 H=(10.21.32.43) [192.168.8.34]
38587 H=([10.21.32.43]) [192.168.8.34]
38589 This can be confusing. Only the final address in square brackets can be relied
38592 For locally generated messages (that is, messages not received over TCP/IP),
38593 the H field is omitted, and the U field contains the login name of the caller
38596 .cindex "authentication" "logging"
38597 .cindex "AUTH" "logging"
38598 For all messages, the P field specifies the protocol used to receive the
38599 message. This is the value that is stored in &$received_protocol$&. In the case
38600 of incoming SMTP messages, the value indicates whether or not any SMTP
38601 extensions (ESMTP), encryption, or authentication were used. If the SMTP
38602 session was encrypted, there is an additional X field that records the cipher
38603 suite that was used.
38605 .cindex log protocol
38606 The protocol is set to &"esmtpsa"& or &"esmtpa"& for messages received from
38607 hosts that have authenticated themselves using the SMTP AUTH command. The first
38608 value is used when the SMTP connection was encrypted (&"secure"&). In this case
38609 there is an additional item A= followed by the name of the authenticator that
38610 was used. If an authenticated identification was set up by the authenticator's
38611 &%server_set_id%& option, this is logged too, separated by a colon from the
38612 authenticator name.
38614 .cindex "size" "of message"
38615 The id field records the existing message id, if present. The size of the
38616 received message is given by the S field. When the message is delivered,
38617 headers may be removed or added, so that the size of delivered copies of the
38618 message may not correspond with this value (and indeed may be different to each
38621 The &%log_selector%& option can be used to request the logging of additional
38622 data when a message is received. See section &<<SECTlogselector>>& below.
38626 .section "Logging deliveries" "SECID252"
38627 .cindex "log" "delivery line"
38628 The format of the single-line entry in the main log that is written for every
38629 delivery is shown in one of the examples below, for local and remote
38630 deliveries, respectively. Each example has been split into multiple lines in order
38631 to fit it on the page:
38633 2002-10-31 08:59:13 16ZCW1-0005MB-00 => marv
38634 <marv@hitch.fict.example> R=localuser T=local_delivery
38635 2002-10-31 09:00:10 16ZCW1-0005MB-00 =>
38636 monk@holistic.fict.example R=dnslookup T=remote_smtp
38637 H=holistic.fict.example [192.168.234.234]
38639 For ordinary local deliveries, the original address is given in angle brackets
38640 after the final delivery address, which might be a pipe or a file. If
38641 intermediate address(es) exist between the original and the final address, the
38642 last of these is given in parentheses after the final address. The R and T
38643 fields record the router and transport that were used to process the address.
38645 If SMTP AUTH was used for the delivery there is an additional item A=
38646 followed by the name of the authenticator that was used.
38647 If an authenticated identification was set up by the authenticator's &%client_set_id%&
38648 option, this is logged too, as a second colon-separated list item.
38649 Optionally (see the &%smtp_mailauth%& &%log_selector%&) there may be a third list item.
38651 If a shadow transport was run after a successful local delivery, the log line
38652 for the successful delivery has an item added on the end, of the form
38654 &`ST=<`&&'shadow transport name'&&`>`&
38656 If the shadow transport did not succeed, the error message is put in
38657 parentheses afterwards.
38659 .cindex "asterisk" "after IP address"
38660 When more than one address is included in a single delivery (for example, two
38661 SMTP RCPT commands in one transaction) the second and subsequent addresses are
38662 flagged with &`->`& instead of &`=>`&. When two or more messages are delivered
38663 down a single SMTP connection, an asterisk follows the
38664 remote IP address (and port if enabled)
38665 in the log lines for the second and subsequent messages.
38666 When two or more messages are delivered down a single TLS connection, the
38667 DNS and some TLS-related information logged for the first message delivered
38668 will not be present in the log lines for the second and subsequent messages.
38669 TLS cipher information is still available.
38671 .cindex "delivery" "cutthrough; logging"
38672 .cindex "cutthrough" "logging"
38673 When delivery is done in cutthrough mode it is flagged with &`>>`& and the log
38674 line precedes the reception line, since cutthrough waits for a possible
38675 rejection from the destination in case it can reject the sourced item.
38677 The generation of a reply message by a filter file gets logged as a
38678 &"delivery"& to the addressee, preceded by &">"&.
38680 The &%log_selector%& option can be used to request the logging of additional
38681 data when a message is delivered. See section &<<SECTlogselector>>& below.
38684 .section "Discarded deliveries" "SECID253"
38685 .cindex "discarded messages"
38686 .cindex "message" "discarded"
38687 .cindex "delivery" "discarded; logging"
38688 When a message is discarded as a result of the command &"seen finish"& being
38689 obeyed in a filter file which generates no deliveries, a log entry of the form
38691 2002-12-10 00:50:49 16auJc-0001UB-00 => discarded
38692 <low.club@bridge.example> R=userforward
38694 is written, to record why no deliveries are logged. When a message is discarded
38695 because it is aliased to &":blackhole:"& the log line is like this:
38697 1999-03-02 09:44:33 10HmaX-0005vi-00 => :blackhole:
38698 <hole@nowhere.example> R=blackhole_router
38702 .section "Deferred deliveries" "SECID254"
38703 When a delivery is deferred, a line of the following form is logged:
38705 2002-12-19 16:20:23 16aiQz-0002Q5-00 == marvin@endrest.example
38706 R=dnslookup T=smtp defer (146): Connection refused
38708 In the case of remote deliveries, the error is the one that was given for the
38709 last IP address that was tried. Details of individual SMTP failures are also
38710 written to the log, so the above line would be preceded by something like
38712 2002-12-19 16:20:23 16aiQz-0002Q5-00 Failed to connect to
38713 mail1.endrest.example [192.168.239.239]: Connection refused
38715 When a deferred address is skipped because its retry time has not been reached,
38716 a message is written to the log, but this can be suppressed by setting an
38717 appropriate value in &%log_selector%&.
38721 .section "Delivery failures" "SECID255"
38722 .cindex "delivery" "failure; logging"
38723 If a delivery fails because an address cannot be routed, a line of the
38724 following form is logged:
38726 1995-12-19 16:20:23 0tRiQz-0002Q5-00 ** jim@trek99.example
38727 <jim@trek99.example>: unknown mail domain
38729 If a delivery fails at transport time, the router and transport are shown, and
38730 the response from the remote host is included, as in this example:
38732 2002-07-11 07:14:17 17SXDU-000189-00 ** ace400@pb.example
38733 R=dnslookup T=remote_smtp: SMTP error from remote mailer
38734 after pipelined RCPT TO:<ace400@pb.example>: host
38735 pbmail3.py.example [192.168.63.111]: 553 5.3.0
38736 <ace400@pb.example>...Addressee unknown
38738 The word &"pipelined"& indicates that the SMTP PIPELINING extension was being
38739 used. See &%hosts_avoid_esmtp%& in the &(smtp)& transport for a way of
38740 disabling PIPELINING. The log lines for all forms of delivery failure are
38741 flagged with &`**`&.
38745 .section "Fake deliveries" "SECID256"
38746 .cindex "delivery" "fake; logging"
38747 If a delivery does not actually take place because the &%-N%& option has been
38748 used to suppress it, a normal delivery line is written to the log, except that
38749 &"=>"& is replaced by &"*>"&.
38753 .section "Completion" "SECID257"
38756 2002-10-31 09:00:11 16ZCW1-0005MB-00 Completed
38758 is written to the main log when a message is about to be removed from the spool
38759 at the end of its processing.
38764 .section "Summary of Fields in Log Lines" "SECID258"
38765 .cindex "log" "summary of fields"
38766 A summary of the field identifiers that are used in log lines is shown in
38767 the following table:
38769 &`A `& authenticator name (and optional id and sender)
38770 &`C `& SMTP confirmation on delivery
38771 &` `& command list for &"no mail in SMTP session"&
38772 &`CV `& certificate verification status
38773 &`D `& duration of &"no mail in SMTP session"&
38774 &`DKIM`& domain verified in incoming message
38775 &`DN `& distinguished name from peer certificate
38776 &`DS `& DNSSEC secured lookups
38777 &`DT `& on &`=>`&, &'=='& and &'**'& lines: time taken for, or to attempt, a delivery
38778 &`F `& sender address (on delivery lines)
38779 &`H `& host name and IP address
38780 &`I `& local interface used
38781 &`id `& message id (from header) for incoming message
38782 &`K `& CHUNKING extension used
38783 &`L `& on &`<=`& and &`=>`& lines: PIPELINING extension used
38784 &`M8S `& 8BITMIME status for incoming message
38785 &`P `& on &`<=`& lines: protocol used
38786 &` `& on &`=>`& and &`**`& lines: return path
38787 &`PRDR`& PRDR extension used
38788 &`PRX `& on &`<=`& and &`=>`& lines: proxy address
38789 &`Q `& alternate queue name
38790 &`QT `& on &`=>`& lines: time spent on queue so far
38791 &` `& on &"Completed"& lines: time spent on queue
38792 &`R `& on &`<=`& lines: reference for local bounce
38793 &` `& on &`=>`& &`>>`& &`**`& and &`==`& lines: router name
38794 &`RT `& on &`<=`& lines: time taken for reception
38795 &`S `& size of message in bytes
38796 &`SNI `& server name indication from TLS client hello
38797 &`ST `& shadow transport name
38798 &`T `& on &`<=`& lines: message subject (topic)
38799 &`TFO `& connection took advantage of TCP Fast Open
38800 &` `& on &`=>`& &`**`& and &`==`& lines: transport name
38801 &`U `& local user or RFC 1413 identity
38802 &`X `& TLS cipher suite
38806 .section "Other log entries" "SECID259"
38807 Various other types of log entry are written from time to time. Most should be
38808 self-explanatory. Among the more common are:
38811 .cindex "retry" "time not reached"
38812 &'retry time not reached'&&~&~An address previously suffered a temporary error
38813 during routing or local delivery, and the time to retry has not yet arrived.
38814 This message is not written to an individual message log file unless it happens
38815 during the first delivery attempt.
38817 &'retry time not reached for any host'&&~&~An address previously suffered
38818 temporary errors during remote delivery, and the retry time has not yet arrived
38819 for any of the hosts to which it is routed.
38821 .cindex "spool directory" "file locked"
38822 &'spool file locked'&&~&~An attempt to deliver a message cannot proceed because
38823 some other Exim process is already working on the message. This can be quite
38824 common if queue running processes are started at frequent intervals. The
38825 &'exiwhat'& utility script can be used to find out what Exim processes are
38828 .cindex "error" "ignored"
38829 &'error ignored'&&~&~There are several circumstances that give rise to this
38832 Exim failed to deliver a bounce message whose age was greater than
38833 &%ignore_bounce_errors_after%&. The bounce was discarded.
38835 A filter file set up a delivery using the &"noerror"& option, and the delivery
38836 failed. The delivery was discarded.
38838 A delivery set up by a router configured with
38839 . ==== As this is a nested list, any displays it contains must be indented
38840 . ==== as otherwise they are too far to the left.
38844 failed. The delivery was discarded.
38847 .cindex DKIM "log line"
38848 &'DKIM: d='&&~&~Verbose results of a DKIM verification attempt, if enabled for
38849 logging and the message has a DKIM signature header.
38856 .section "Reducing or increasing what is logged" "SECTlogselector"
38857 .cindex "log" "selectors"
38858 By setting the &%log_selector%& global option, you can disable some of Exim's
38859 default logging, or you can request additional logging. The value of
38860 &%log_selector%& is made up of names preceded by plus or minus characters. For
38863 log_selector = +arguments -retry_defer
38865 The list of optional log items is in the following table, with the default
38866 selection marked by asterisks:
38867 .itable none 0 0 3 2.8in left 10pt center 3in left
38868 .irow &`8bitmime`& "received 8BITMIME status"
38869 .irow &`acl_warn_skipped`& * "skipped &%warn%& statement in ACL"
38870 .irow &`address_rewrite`& "address rewriting"
38871 .irow &`all_parents`& "all parents in => lines"
38872 .irow &`arguments`& "command line arguments"
38873 .irow &`connection_reject`& * "connection rejections"
38874 .irow &`delay_delivery`& * "immediate delivery delayed"
38875 .irow &`deliver_time`& "time taken to attempt delivery"
38876 .irow &`delivery_size`& "add &`S=`&&'nnn'& to => lines"
38877 .irow &`dkim`& * "DKIM verified domain on <= lines"
38878 .irow &`dkim_verbose`& "separate full DKIM verification result line, per signature"
38879 .irow &`dnslist_defer`& * "defers of DNS list (aka RBL) lookups"
38880 .irow &`dnssec`& "DNSSEC secured lookups"
38881 .irow &`etrn`& * "ETRN commands"
38882 .irow &`host_lookup_failed`& * "as it says"
38883 .irow &`ident_timeout`& "timeout for ident connection"
38884 .irow &`incoming_interface`& "local interface on <= and => lines"
38885 .irow &`incoming_port`& "remote port on <= lines"
38886 .irow &`lost_incoming_connection`& * "as it says (includes timeouts)"
38887 .irow &`millisec`& "millisecond timestamps and RT,QT,DT,D times"
38888 .irow &`msg_id`& * "on <= lines, Message-ID: header value"
38889 .irow &`msg_id_created`& "on <= lines, Message-ID: header value when one had to be added"
38890 .irow &`outgoing_interface`& "local interface on => lines"
38891 .irow &`outgoing_port`& "add remote port to => lines"
38892 .irow &`queue_run`& * "start and end queue runs"
38893 .irow &`queue_time`& "time on queue for one recipient"
38894 .irow &`queue_time_exclusive`& "exclude recieve time from QT times"
38895 .irow &`queue_time_overall`& "time on queue for whole message"
38896 .irow &`pid`& "Exim process id"
38897 .irow &`pipelining`& "PIPELINING use, on <= and => lines"
38898 .irow &`proxy`& "proxy address on <= and => lines"
38899 .irow &`receive_time`& "time taken to receive message"
38900 .irow &`received_recipients`& "recipients on <= lines"
38901 .irow &`received_sender`& "sender on <= lines"
38902 .irow &`rejected_header`& * "header contents on reject log"
38903 .irow &`retry_defer`& * "&<quote>&retry time not reached&</quote>&"
38904 .irow &`return_path_on_delivery`& "put return path on => and ** lines"
38905 .irow &`sender_on_delivery`& "add sender to => lines"
38906 .irow &`sender_verify_fail`& * "sender verification failures"
38907 .irow &`size_reject`& * "rejection because too big"
38908 .irow &`skip_delivery`& * "delivery skipped in a queue run"
38909 .irow &`smtp_confirmation`& * "SMTP confirmation on => lines"
38910 .irow &`smtp_connection`& "incoming SMTP connections"
38911 .irow &`smtp_incomplete_transaction`& "incomplete SMTP transactions"
38912 .irow &`smtp_mailauth`& "AUTH argument to MAIL commands"
38913 .irow &`smtp_no_mail`& "session with no MAIL commands"
38914 .irow &`smtp_protocol_error`& "SMTP protocol errors"
38915 .irow &`smtp_syntax_error`& "SMTP syntax errors"
38916 .irow &`subject`& "contents of &'Subject:'& on <= lines"
38917 .irow &`tls_certificate_verified`& * "certificate verification status"
38918 .irow &`tls_cipher`& * "TLS cipher suite on <= and => lines"
38919 .irow &`tls_peerdn`& "TLS peer DN on <= and => lines"
38920 .irow &`tls_resumption`& "append * to cipher field"
38921 .irow &`tls_sni`& "TLS SNI on <= lines"
38922 .irow &`unknown_in_list`& "DNS lookup failed in list match"
38923 .irow &`all`& "&*all of the above*&"
38925 See also the &%slow_lookup_log%& main configuration option,
38926 section &<<SECID99>>&
38928 More details on each of these items follows:
38932 .cindex "log" "8BITMIME"
38933 &%8bitmime%&: This causes Exim to log any 8BITMIME status of received messages,
38934 which may help in tracking down interoperability issues with ancient MTAs
38935 that are not 8bit clean. This is added to the &"<="& line, tagged with
38936 &`M8S=`& and a value of &`0`&, &`7`& or &`8`&, corresponding to "not given",
38937 &`7BIT`& and &`8BITMIME`& respectively.
38939 .cindex "&%warn%& ACL verb" "log when skipping"
38940 &%acl_warn_skipped%&: When an ACL &%warn%& statement is skipped because one of
38941 its conditions cannot be evaluated, a log line to this effect is written if
38942 this log selector is set.
38944 .cindex "log" "rewriting"
38945 .cindex "rewriting" "logging"
38946 &%address_rewrite%&: This applies both to global rewrites and per-transport
38947 rewrites, but not to rewrites in filters run as an unprivileged user (because
38948 such users cannot access the log).
38950 .cindex "log" "full parentage"
38951 &%all_parents%&: Normally only the original and final addresses are logged on
38952 delivery lines; with this selector, intermediate parents are given in
38953 parentheses between them.
38955 .cindex "log" "Exim arguments"
38956 .cindex "Exim arguments, logging"
38957 &%arguments%&: This causes Exim to write the arguments with which it was called
38958 to the main log, preceded by the current working directory. This is a debugging
38959 feature, added to make it easier to find out how certain MUAs call
38960 &_/usr/sbin/sendmail_&. The logging does not happen if Exim has given up root
38961 privilege because it was called with the &%-C%& or &%-D%& options. Arguments
38962 that are empty or that contain white space are quoted. Non-printing characters
38963 are shown as escape sequences. This facility cannot log unrecognized arguments,
38964 because the arguments are checked before the configuration file is read. The
38965 only way to log such cases is to interpose a script such as &_util/logargs.sh_&
38966 between the caller and Exim.
38968 .cindex "log" "connection rejections"
38969 &%connection_reject%&: A log entry is written whenever an incoming SMTP
38970 connection is rejected, for whatever reason.
38972 .cindex "log" "delayed delivery"
38973 .cindex "delayed delivery, logging"
38974 &%delay_delivery%&: A log entry is written whenever a delivery process is not
38975 started for an incoming message because the load is too high or too many
38976 messages were received on one connection. Logging does not occur if no delivery
38977 process is started because &%queue_only%& is set or &%-odq%& was used.
38979 .cindex "log" "delivery duration"
38980 &%deliver_time%&: For each delivery, the amount of real time it has taken to
38981 perform the actual delivery is logged as DT=<&'time'&>, for example, &`DT=1s`&.
38982 If millisecond logging is enabled, short times will be shown with greater
38983 precision, eg. &`DT=0.304s`&.
38985 .cindex "log" "message size on delivery"
38986 .cindex "size" "of message"
38987 &%delivery_size%&: For each delivery, the size of message delivered is added to
38988 the &"=>"& line, tagged with S=.
38990 .cindex log "DKIM verification"
38991 .cindex DKIM "verification logging"
38992 &%dkim%&: For message acceptance log lines, when an DKIM signature in the header
38993 verifies successfully a tag of DKIM is added, with one of the verified domains.
38995 .cindex log "DKIM verification"
38996 .cindex DKIM "verification logging"
38997 &%dkim_verbose%&: A log entry is written for each attempted DKIM verification.
38999 .cindex "log" "dnslist defer"
39000 .cindex "DNS list" "logging defer"
39001 .cindex "black list (DNS)"
39002 &%dnslist_defer%&: A log entry is written if an attempt to look up a host in a
39003 DNS black list suffers a temporary error.
39006 .cindex dnssec logging
39007 &%dnssec%&: For message acceptance and (attempted) delivery log lines, when
39008 dns lookups gave secure results a tag of DS is added.
39009 For acceptance this covers the reverse and forward lookups for host name verification.
39010 It does not cover helo-name verification.
39011 For delivery this covers the SRV, MX, A and/or AAAA lookups.
39013 .cindex "log" "ETRN commands"
39014 .cindex "ETRN" "logging"
39015 &%etrn%&: Every valid ETRN command that is received is logged, before the ACL
39016 is run to determine whether or not it is actually accepted. An invalid ETRN
39017 command, or one received within a message transaction is not logged by this
39018 selector (see &%smtp_syntax_error%& and &%smtp_protocol_error%&).
39020 .cindex "log" "host lookup failure"
39021 &%host_lookup_failed%&: When a lookup of a host's IP addresses fails to find
39022 any addresses, or when a lookup of an IP address fails to find a host name, a
39023 log line is written. This logging does not apply to direct DNS lookups when
39024 routing email addresses, but it does apply to &"byname"& lookups.
39026 .cindex "log" "ident timeout"
39027 .cindex "RFC 1413" "logging timeout"
39028 &%ident_timeout%&: A log line is written whenever an attempt to connect to a
39029 client's ident port times out.
39031 .cindex "log" "incoming interface"
39032 .cindex "log" "outgoing interface"
39033 .cindex "log" "local interface"
39034 .cindex "log" "local address and port"
39035 .cindex "TCP/IP" "logging local address and port"
39036 .cindex "interface" "logging"
39037 &%incoming_interface%&: The interface on which a message was received is added
39038 to the &"<="& line as an IP address in square brackets, tagged by I= and
39039 followed by a colon and the port number. The local interface and port are also
39040 added to other SMTP log lines, for example, &"SMTP connection from"&, to
39041 rejection lines, and (despite the name) to outgoing
39042 &"=>"&, &"->"&, &"=="& and &"**"& lines.
39043 The latter can be disabled by turning off the &%outgoing_interface%& option.
39045 .cindex log "incoming proxy address"
39046 .cindex proxy "logging proxy address"
39047 .cindex "TCP/IP" "logging proxy address"
39048 &%proxy%&: The internal (closest to the system running Exim) IP address
39049 of the proxy, tagged by PRX=, on the &"<="& line for a message accepted
39050 on a proxied connection
39051 or the &"=>"& line for a message delivered on a proxied connection.
39052 See &<<SECTproxyInbound>>& for more information.
39054 .cindex "log" "incoming remote port"
39055 .cindex "port" "logging remote"
39056 .cindex "TCP/IP" "logging incoming remote port"
39057 .vindex "&$sender_fullhost$&"
39058 .vindex "&$sender_rcvhost$&"
39059 &%incoming_port%&: The remote port number from which a message was received is
39060 added to log entries and &'Received:'& header lines, following the IP address
39061 in square brackets, and separated from it by a colon. This is implemented by
39062 changing the value that is put in the &$sender_fullhost$& and
39063 &$sender_rcvhost$& variables. Recording the remote port number has become more
39064 important with the widening use of NAT (see RFC 2505).
39066 .cindex "log" "dropped connection"
39067 &%lost_incoming_connection%&: A log line is written when an incoming SMTP
39068 connection is unexpectedly dropped.
39070 .cindex "log" "millisecond timestamps"
39071 .cindex millisecond logging
39072 .cindex timestamps "millisecond, in logs"
39073 &%millisec%&: Timestamps have a period and three decimal places of finer granularity
39074 appended to the seconds value.
39076 .cindex "log" "message id"
39077 &%msg_id%&: The value of the Message-ID: header.
39079 &%msg_id_created%&: The value of the Message-ID: header, when one had to be created.
39080 This will be either because the message is a bounce, or was submitted locally
39081 (submission mode) without one.
39082 The field identifier will have an asterix appended: &"id*="&.
39084 .cindex "log" "outgoing interface"
39085 .cindex "log" "local interface"
39086 .cindex "log" "local address and port"
39087 .cindex "TCP/IP" "logging local address and port"
39088 .cindex "interface" "logging"
39089 &%outgoing_interface%&: If &%incoming_interface%& is turned on, then the
39090 interface on which a message was sent is added to delivery lines as an I= tag
39091 followed by IP address in square brackets. You can disable this by turning
39092 off the &%outgoing_interface%& option.
39094 .cindex "log" "outgoing remote port"
39095 .cindex "port" "logging outgoing remote"
39096 .cindex "TCP/IP" "logging outgoing remote port"
39097 &%outgoing_port%&: The remote port number is added to delivery log lines (those
39098 containing => tags) following the IP address.
39099 The local port is also added if &%incoming_interface%& and
39100 &%outgoing_interface%& are both enabled.
39101 This option is not included in the default setting, because for most ordinary
39102 configurations, the remote port number is always 25 (the SMTP port), and the
39103 local port is a random ephemeral port.
39105 .cindex "log" "process ids in"
39106 .cindex "pid (process id)" "in log lines"
39107 &%pid%&: The current process id is added to every log line, in square brackets,
39108 immediately after the time and date.
39110 .cindex log pipelining
39111 .cindex pipelining "logging outgoing"
39112 &%pipelining%&: A field is added to delivery and accept
39113 log lines when the ESMTP PIPELINING extension was used.
39114 The field is a single "L".
39116 On accept lines, where PIPELINING was offered but not used by the client,
39117 the field has a minus appended.
39119 .cindex "pipelining" "early connection"
39120 If Exim is built without the DISABLE_PIPE_CONNECT build option
39121 accept "L" fields have a period appended if the feature was
39122 offered but not used, or an asterisk appended if used.
39123 Delivery "L" fields have an asterisk appended if used.
39126 .cindex "log" "queue run"
39127 .cindex "queue runner" "logging"
39128 &%queue_run%&: The start and end of every queue run are logged.
39130 .cindex "log" "queue time"
39131 &%queue_time%&: The amount of time the message has been in the queue on the
39132 local host is logged as QT=<&'time'&> on delivery (&`=>`&) lines, for example,
39134 If millisecond logging is enabled, short times will be shown with greater
39135 precision, eg. &`QT=1.578s`&.
39137 &%queue_time_overall%&: The amount of time the message has been in the queue on
39138 the local host is logged as QT=<&'time'&> on &"Completed"& lines, for
39139 example, &`QT=3m45s`&.
39141 .cindex "log" "receive duration"
39142 &%receive_time%&: For each message, the amount of real time it has taken to
39143 perform the reception is logged as RT=<&'time'&>, for example, &`RT=1s`&.
39144 If millisecond logging is enabled, short times will be shown with greater
39145 precision, eg. &`RT=0.204s`&.
39147 .cindex "log" "recipients"
39148 &%received_recipients%&: The recipients of a message are listed in the main log
39149 as soon as the message is received. The list appears at the end of the log line
39150 that is written when a message is received, preceded by the word &"for"&. The
39151 addresses are listed after they have been qualified, but before any rewriting
39153 Recipients that were discarded by an ACL for MAIL or RCPT do not appear
39156 .cindex "log" "sender reception"
39157 &%received_sender%&: The unrewritten original sender of a message is added to
39158 the end of the log line that records the message's arrival, after the word
39159 &"from"& (before the recipients if &%received_recipients%& is also set).
39161 .cindex "log" "header lines for rejection"
39162 &%rejected_header%&: If a message's header has been received at the time a
39163 rejection is written to the reject log, the complete header is added to the
39164 log. Header logging can be turned off individually for messages that are
39165 rejected by the &[local_scan()]& function (see section &<<SECTapiforloc>>&).
39167 .cindex "log" "retry defer"
39168 &%retry_defer%&: A log line is written if a delivery is deferred because a
39169 retry time has not yet been reached. However, this &"retry time not reached"&
39170 message is always omitted from individual message logs after the first delivery
39173 .cindex "log" "return path"
39174 &%return_path_on_delivery%&: The return path that is being transmitted with
39175 the message is included in delivery and bounce lines, using the tag P=.
39176 This is omitted if no delivery actually happens, for example, if routing fails,
39177 or if delivery is to &_/dev/null_& or to &`:blackhole:`&.
39179 .cindex "log" "sender on delivery"
39180 &%sender_on_delivery%&: The message's sender address is added to every delivery
39181 and bounce line, tagged by F= (for &"from"&).
39182 This is the original sender that was received with the message; it is not
39183 necessarily the same as the outgoing return path.
39185 .cindex "log" "sender verify failure"
39186 &%sender_verify_fail%&: If this selector is unset, the separate log line that
39187 gives details of a sender verification failure is not written. Log lines for
39188 the rejection of SMTP commands contain just &"sender verify failed"&, so some
39191 .cindex "log" "size rejection"
39192 &%size_reject%&: A log line is written whenever a message is rejected because
39195 .cindex "log" "frozen messages; skipped"
39196 .cindex "frozen messages" "logging skipping"
39197 &%skip_delivery%&: A log line is written whenever a message is skipped during a
39198 queue run because it another process is already delivering it or because
39200 .cindex "&""spool file is locked""&"
39201 .cindex "&""message is frozen""&"
39202 The message that is written is either &"spool file is locked"& or
39203 &"message is frozen"&.
39205 .cindex "log" "smtp confirmation"
39206 .cindex "SMTP" "logging confirmation"
39207 .cindex "LMTP" "logging confirmation"
39208 &%smtp_confirmation%&: The response to the final &"."& in the SMTP or LMTP dialogue for
39209 outgoing messages is added to delivery log lines in the form &`C=`&<&'text'&>.
39210 A number of MTAs (including Exim) return an identifying string in this
39213 .cindex "log" "SMTP connections"
39214 .cindex "SMTP" "logging connections"
39215 &%smtp_connection%&: A log line is written whenever an incoming SMTP connection is
39216 established or closed, unless the connection is from a host that matches
39217 &%hosts_connection_nolog%&. (In contrast, &%lost_incoming_connection%& applies
39218 only when the closure is unexpected.) This applies to connections from local
39219 processes that use &%-bs%& as well as to TCP/IP connections. If a connection is
39220 dropped in the middle of a message, a log line is always written, whether or
39221 not this selector is set, but otherwise nothing is written at the start and end
39222 of connections unless this selector is enabled.
39224 For TCP/IP connections to an Exim daemon, the current number of connections is
39225 included in the log message for each new connection, but note that the count is
39226 reset if the daemon is restarted.
39227 Also, because connections are closed (and the closure is logged) in
39228 subprocesses, the count may not include connections that have been closed but
39229 whose termination the daemon has not yet noticed. Thus, while it is possible to
39230 match up the opening and closing of connections in the log, the value of the
39231 logged counts may not be entirely accurate.
39233 .cindex "log" "SMTP transaction; incomplete"
39234 .cindex "SMTP" "logging incomplete transactions"
39235 &%smtp_incomplete_transaction%&: When a mail transaction is aborted by
39236 RSET, QUIT, loss of connection, or otherwise, the incident is logged,
39237 and the message sender plus any accepted recipients are included in the log
39238 line. This can provide evidence of dictionary attacks.
39240 .cindex "log" "non-MAIL SMTP sessions"
39241 .cindex "MAIL" "logging session without"
39242 &%smtp_no_mail%&: A line is written to the main log whenever an accepted SMTP
39243 connection terminates without having issued a MAIL command. This includes both
39244 the case when the connection is dropped, and the case when QUIT is used. It
39245 does not include cases where the connection is rejected right at the start (by
39246 an ACL, or because there are too many connections, or whatever). These cases
39247 already have their own log lines.
39249 The log line that is written contains the identity of the client in the usual
39250 way, followed by D= and a time, which records the duration of the connection.
39251 If the connection was authenticated, this fact is logged exactly as it is for
39252 an incoming message, with an A= item. If the connection was encrypted, CV=,
39253 DN=, and X= items may appear as they do for an incoming message, controlled by
39254 the same logging options.
39256 Finally, if any SMTP commands were issued during the connection, a C= item
39257 is added to the line, listing the commands that were used. For example,
39261 shows that the client issued QUIT straight after EHLO. If there were fewer
39262 than 20 commands, they are all listed. If there were more than 20 commands,
39263 the last 20 are listed, preceded by &"..."&. However, with the default
39264 setting of 10 for &%smtp_accept_max_nonmail%&, the connection will in any case
39265 have been aborted before 20 non-mail commands are processed.
39267 &%smtp_mailauth%&: A third subfield with the authenticated sender,
39268 colon-separated, is appended to the A= item for a message arrival or delivery
39269 log line, if an AUTH argument to the SMTP MAIL command (see &<<SECTauthparamail>>&)
39270 was accepted or used.
39272 .cindex "log" "SMTP protocol error"
39273 .cindex "SMTP" "logging protocol error"
39274 &%smtp_protocol_error%&: A log line is written for every SMTP protocol error
39275 encountered. Exim does not have perfect detection of all protocol errors
39276 because of transmission delays and the use of pipelining. If PIPELINING has
39277 been advertised to a client, an Exim server assumes that the client will use
39278 it, and therefore it does not count &"expected"& errors (for example, RCPT
39279 received after rejecting MAIL) as protocol errors.
39281 .cindex "SMTP" "logging syntax errors"
39282 .cindex "SMTP" "syntax errors; logging"
39283 .cindex "SMTP" "unknown command; logging"
39284 .cindex "log" "unknown SMTP command"
39285 .cindex "log" "SMTP syntax error"
39286 &%smtp_syntax_error%&: A log line is written for every SMTP syntax error
39287 encountered. An unrecognized command is treated as a syntax error. For an
39288 external connection, the host identity is given; for an internal connection
39289 using &%-bs%& the sender identification (normally the calling user) is given.
39291 .cindex "log" "subject"
39292 .cindex "subject, logging"
39293 &%subject%&: The subject of the message is added to the arrival log line,
39294 preceded by &"T="& (T for &"topic"&, since S is already used for &"size"&).
39295 Any MIME &"words"& in the subject are decoded. The &%print_topbitchars%& option
39296 specifies whether characters with values greater than 127 should be logged
39297 unchanged, or whether they should be rendered as escape sequences.
39299 .cindex "log" "certificate verification"
39301 .cindex DANE logging
39302 &%tls_certificate_verified%&: An extra item is added to <= and => log lines
39303 when TLS is in use. The item is &`CV=yes`& if the peer's certificate was
39305 using a CA trust anchor,
39306 &`CV=dane`& if using a DNS trust anchor,
39307 and &`CV=no`& if not.
39309 .cindex "log" "TLS cipher"
39310 .cindex "TLS" "logging cipher"
39311 &%tls_cipher%&: When a message is sent or received over an encrypted
39312 connection, the cipher suite used is added to the log line, preceded by X=.
39314 .cindex "log" "TLS peer DN"
39315 .cindex "TLS" "logging peer DN"
39316 &%tls_peerdn%&: When a message is sent or received over an encrypted
39317 connection, and a certificate is supplied by the remote host, the peer DN is
39318 added to the log line, preceded by DN=.
39320 .cindex "log" "TLS resumption"
39321 .cindex "TLS" "logging session resumption"
39322 &%tls_resumption%&: When a message is sent or received over an encrypted
39323 connection and the TLS session resumed one used on a previous TCP connection,
39324 an asterisk is appended to the X= cipher field in the log line.
39326 .cindex "log" "TLS SNI"
39327 .cindex "TLS" "logging SNI"
39328 .cindex SNI logging
39329 &%tls_sni%&: When a message is received over an encrypted connection, and
39330 the remote host provided the Server Name Indication extension, the SNI is
39331 added to the log line, preceded by SNI=.
39333 .cindex "log" "DNS failure in list"
39334 &%unknown_in_list%&: This setting causes a log entry to be written when the
39335 result of a list match is failure because a DNS lookup failed.
39339 .section "Message log" "SECID260"
39340 .cindex "message" "log file for"
39341 .cindex "log" "message log; description of"
39342 .cindex "&_msglog_& directory"
39343 .oindex "&%preserve_message_logs%&"
39344 In addition to the general log files, Exim writes a log file for each message
39345 that it handles. The names of these per-message logs are the message ids, and
39346 they are kept in the &_msglog_& sub-directory of the spool directory. Each
39347 message log contains copies of the log lines that apply to the message. This
39348 makes it easier to inspect the status of an individual message without having
39349 to search the main log. A message log is deleted when processing of the message
39350 is complete, unless &%preserve_message_logs%& is set, but this should be used
39351 only with great care because they can fill up your disk very quickly.
39353 On a heavily loaded system, it may be desirable to disable the use of
39354 per-message logs, in order to reduce disk I/O. This can be done by setting the
39355 &%message_logs%& option false.
39361 . ////////////////////////////////////////////////////////////////////////////
39362 . ////////////////////////////////////////////////////////////////////////////
39364 .chapter "Exim utilities" "CHAPutils"
39365 .scindex IIDutils "utilities"
39366 A number of utility scripts and programs are supplied with Exim and are
39367 described in this chapter. There is also the Exim Monitor, which is covered in
39368 the next chapter. The utilities described here are:
39370 .itable none 0 0 3 7* left 15* left 40* left
39371 .irow &<<SECTfinoutwha>>& &'exiwhat'& &&&
39372 "list what Exim processes are doing"
39373 .irow &<<SECTgreptheque>>& &'exiqgrep'& "grep the queue"
39374 .irow &<<SECTsumtheque>>& &'exiqsumm'& "summarize the queue"
39375 .irow &<<SECTextspeinf>>& &'exigrep'& "search the main log"
39376 .irow &<<SECTexipick>>& &'exipick'& "select messages on &&&
39378 .irow &<<SECTcyclogfil>>& &'exicyclog'& "cycle (rotate) log files"
39379 .irow &<<SECTmailstat>>& &'eximstats'& &&&
39380 "extract statistics from the log"
39381 .irow &<<SECTcheckaccess>>& &'exim_checkaccess'& &&&
39382 "check address acceptance from given IP"
39383 .irow &<<SECTdbmbuild>>& &'exim_dbmbuild'& "build a DBM file"
39384 .irow &<<SECTfinindret>>& &'exinext'& "extract retry information"
39385 .irow &<<SECTdumpdb>>& &'exim_dumpdb'& "dump a hints database"
39386 .irow &<<SECTtidydb>>& &'exim_tidydb'& "clean up a hints database"
39387 .irow &<<SECTfixdb>>& &'exim_fixdb'& "patch a hints database"
39388 .irow &<<SECTmailboxmaint>>& &'exim_lock'& "lock a mailbox file"
39391 Another utility that might be of use to sites with many MTAs is Tom Kistner's
39392 &'exilog'&. It provides log visualizations across multiple Exim servers. See
39393 &url(https://duncanthrax.net/exilog/) for details.
39398 .section "Finding out what Exim processes are doing (exiwhat)" "SECTfinoutwha"
39399 .cindex "&'exiwhat'&"
39400 .cindex "process, querying"
39402 On operating systems that can restart a system call after receiving a signal
39403 (most modern OS), an Exim process responds to the SIGUSR1 signal by writing
39404 a line describing what it is doing to the file &_exim-process.info_& in the
39405 Exim spool directory. The &'exiwhat'& script sends the signal to all Exim
39406 processes it can find, having first emptied the file. It then waits for one
39407 second to allow the Exim processes to react before displaying the results. In
39408 order to run &'exiwhat'& successfully you have to have sufficient privilege to
39409 send the signal to the Exim processes, so it is normally run as root.
39411 &*Warning*&: This is not an efficient process. It is intended for occasional
39412 use by system administrators. It is not sensible, for example, to set up a
39413 script that sends SIGUSR1 signals to Exim processes at short intervals.
39416 Unfortunately, the &'ps'& command that &'exiwhat'& uses to find Exim processes
39417 varies in different operating systems. Not only are different options used,
39418 but the format of the output is different. For this reason, there are some
39419 system configuration options that configure exactly how &'exiwhat'& works. If
39420 it doesn't seem to be working for you, check the following compile-time
39422 .itable none 0 0 2 30* left 70* left
39423 .irow &`EXIWHAT_PS_CMD`& "the command for running &'ps'&"
39424 .irow &`EXIWHAT_PS_ARG`& "the argument for &'ps'&"
39425 .irow &`EXIWHAT_EGREP_ARG`& "the argument for &'egrep'& to select from &'ps'& output"
39426 .irow &`EXIWHAT_KILL_ARG`& "the argument for the &'kill'& command"
39428 An example of typical output from &'exiwhat'& is
39430 164 daemon: -q1h, listening on port 25
39431 10483 running queue: waiting for 0tAycK-0002ij-00 (10492)
39432 10492 delivering 0tAycK-0002ij-00 to mail.ref.example
39433 [10.19.42.42] (editor@ref.example)
39434 10592 handling incoming call from [192.168.243.242]
39435 10628 accepting a local non-SMTP message
39437 The first number in the output line is the process number. The third line has
39438 been split here, in order to fit it on the page.
39442 .section "Selective queue listing (exiqgrep)" "SECTgreptheque"
39443 .cindex "&'exiqgrep'&"
39444 .cindex "queue" "grepping"
39445 This utility is a Perl script contributed by Matt Hubbard. It runs
39449 or (in case &*-a*& switch is specified)
39453 to obtain a queue listing, and then greps the output to select messages
39454 that match given criteria. The following selection options are available:
39457 .vitem &*-f*&&~<&'regex'&>
39458 Match the sender address using a case-insensitive search. The field that is
39459 tested is enclosed in angle brackets, so you can test for bounce messages with
39463 .vitem &*-r*&&~<&'regex'&>
39464 Match a recipient address using a case-insensitive search. The field that is
39465 tested is not enclosed in angle brackets.
39467 .vitem &*-s*&&~<&'regex'&>
39468 Match against the size field.
39470 .vitem &*-y*&&~<&'seconds'&>
39471 Match messages that are younger than the given time.
39473 .vitem &*-o*&&~<&'seconds'&>
39474 Match messages that are older than the given time.
39477 Match only frozen messages.
39480 Match only non-frozen messages.
39482 .vitem &*-G*&&~<&'queuename'&>
39483 Match only messages in the given queue. Without this, the default queue is searched.
39486 The following options control the format of the output:
39490 Display only the count of matching messages.
39493 Long format &-- display the full message information as output by Exim. This is
39497 Display message ids only.
39500 Brief format &-- one line per message.
39503 Display messages in reverse order.
39506 Include delivered recipients in queue listing.
39509 The following options give alternates for configuration:
39512 .vitem &*-C*&&~<&'config&~file'&>
39513 is used to specify an alternate &_exim.conf_& which might
39514 contain alternate exim configuration the queue management might be using.
39516 .vitem &*-E*&&~<&'path'&>
39517 can be used to specify a path for the exim binary,
39518 overriding the built-in one.
39521 There is one more option, &%-h%&, which outputs a list of options.
39522 At least one selection option, or either the &*-c*& or &*-h*& option, must be given.
39526 .section "Summarizing the queue (exiqsumm)" "SECTsumtheque"
39527 .cindex "&'exiqsumm'&"
39528 .cindex "queue" "summary"
39529 The &'exiqsumm'& utility is a Perl script which reads the output of &`exim
39530 -bp`& and produces a summary of the messages in the queue. Thus, you use it by
39531 running a command such as
39533 exim -bp | exiqsumm
39535 The output consists of one line for each domain that has messages waiting for
39536 it, as in the following example:
39538 3 2322 74m 66m msn.com.example
39540 Each line lists the number of pending deliveries for a domain, their total
39541 volume, and the length of time that the oldest and the newest messages have
39542 been waiting. Note that the number of pending deliveries is greater than the
39543 number of messages when messages have more than one recipient.
39545 A summary line is output at the end. By default the output is sorted on the
39546 domain name, but &'exiqsumm'& has the options &%-a%& and &%-c%&, which cause
39547 the output to be sorted by oldest message and by count of messages,
39548 respectively. There are also three options that split the messages for each
39549 domain into two or more subcounts: &%-b%& separates bounce messages, &%-f%&
39550 separates frozen messages, and &%-s%& separates messages according to their
39553 The output of &'exim -bp'& contains the original addresses in the message, so
39554 this also applies to the output from &'exiqsumm'&. No domains from addresses
39555 generated by aliasing or forwarding are included (unless the &%one_time%&
39556 option of the &(redirect)& router has been used to convert them into &"top
39557 level"& addresses).
39562 .section "Extracting specific information from the log (exigrep)" &&&
39564 .cindex "&'exigrep'&"
39565 .cindex "log" "extracts; grepping for"
39566 The &'exigrep'& utility is a Perl script that searches one or more main log
39567 files for entries that match a given pattern. When it finds a match, it
39568 extracts all the log entries for the relevant message, not just those that
39569 match the pattern. Thus, &'exigrep'& can extract complete log entries for a
39570 given message, or all mail for a given user, or for a given host, for example.
39571 The input files can be in Exim log format or syslog format.
39572 If a matching log line is not associated with a specific message, it is
39573 included in &'exigrep'&'s output without any additional lines. The usage is:
39575 &`exigrep [-t<`&&'n'&&`>] [-I] [-l] [-M] [-v] <`&&'pattern'&&`> [<`&&'log file'&&`>] ...`&
39577 If no log filenames are given on the command line, the standard input is read.
39579 The &%-t%& argument specifies a number of seconds. It adds an additional
39580 condition for message selection. Messages that are complete are shown only if
39581 they spent more than <&'n'&> seconds in the queue.
39583 By default, &'exigrep'& does case-insensitive matching. The &%-I%& option
39584 makes it case-sensitive. This may give a performance improvement when searching
39585 large log files. Without &%-I%&, the Perl pattern matches use Perl's &`/i`&
39586 option; with &%-I%& they do not. In both cases it is possible to change the
39587 case sensitivity within the pattern by using &`(?i)`& or &`(?-i)`&.
39589 The &%-l%& option means &"literal"&, that is, treat all characters in the
39590 pattern as standing for themselves. Otherwise the pattern must be a Perl
39591 regular expression.
39593 The &%-v%& option inverts the matching condition. That is, a line is selected
39594 if it does &'not'& match the pattern.
39596 The &%-M%& options means &"related messages"&. &'exigrep'& will show messages
39597 that are generated as a result/response to a message that &'exigrep'& matched
39601 user_a sends a message to user_b, which generates a bounce back to user_b. If
39602 &'exigrep'& is used to search for &"user_a"&, only the first message will be
39603 displayed. But if &'exigrep'& is used to search for &"user_b"&, the first and
39604 the second (bounce) message will be displayed. Using &%-M%& with &'exigrep'&
39605 when searching for &"user_a"& will show both messages since the bounce is
39606 &"related"& to or a &"result"& of the first message that was found by the
39609 If the location of a &'zcat'& command is known from the definition of
39610 ZCAT_COMMAND in &_Local/Makefile_&, &'exigrep'& automatically passes any file
39611 whose name ends in COMPRESS_SUFFIX through &'zcat'& as it searches it.
39612 If the ZCAT_COMMAND is not executable, &'exigrep'& tries to use
39613 autodetection of some well known compression extensions.
39616 .section "Selecting messages by various criteria (exipick)" "SECTexipick"
39617 .cindex "&'exipick'&"
39618 John Jetmore's &'exipick'& utility is included in the Exim distribution. It
39619 lists messages from the queue according to a variety of criteria. For details
39620 of &'exipick'&'s facilities, run &'exipick'& with
39621 the &%--help%& option.
39624 .section "Cycling log files (exicyclog)" "SECTcyclogfil"
39625 .cindex "log" "cycling local files"
39626 .cindex "cycling logs"
39627 .cindex "&'exicyclog'&"
39628 The &'exicyclog'& script can be used to cycle (rotate) &'mainlog'& and
39629 &'rejectlog'& files. This is not necessary if only syslog is being used, or if
39630 you are using log files with datestamps in their names (see section
39631 &<<SECTdatlogfil>>&). Some operating systems have their own standard mechanisms
39632 for log cycling, and these can be used instead of &'exicyclog'& if preferred.
39633 There are two command line options for &'exicyclog'&:
39635 &%-k%& <&'count'&> specifies the number of log files to keep, overriding the
39636 default that is set when Exim is built. The default default is 10.
39638 &%-l%& <&'path'&> specifies the log file path, in the same format as Exim's
39639 &%log_file_path%& option (for example, &`/var/log/exim_%slog`&), again
39640 overriding the script's default, which is to find the setting from Exim's
39644 Each time &'exicyclog'& is run the filenames get &"shuffled down"& by one. If
39645 the main log filename is &_mainlog_& (the default) then when &'exicyclog'& is
39646 run &_mainlog_& becomes &_mainlog.01_&, the previous &_mainlog.01_& becomes
39647 &_mainlog.02_& and so on, up to the limit that is set in the script or by the
39648 &%-k%& option. Log files whose numbers exceed the limit are discarded. Reject
39649 logs are handled similarly.
39651 If the limit is greater than 99, the script uses 3-digit numbers such as
39652 &_mainlog.001_&, &_mainlog.002_&, etc. If you change from a number less than 99
39653 to one that is greater, or &'vice versa'&, you will have to fix the names of
39654 any existing log files.
39656 If no &_mainlog_& file exists, the script does nothing. Files that &"drop off"&
39657 the end are deleted. All files with numbers greater than 01 are compressed,
39658 using a compression command which is configured by the COMPRESS_COMMAND
39659 setting in &_Local/Makefile_&. It is usual to run &'exicyclog'& daily from a
39660 root &%crontab%& entry of the form
39662 1 0 * * * su exim -c /usr/exim/bin/exicyclog
39664 assuming you have used the name &"exim"& for the Exim user. You can run
39665 &'exicyclog'& as root if you wish, but there is no need.
39669 .section "Mail statistics (eximstats)" "SECTmailstat"
39670 .cindex "statistics"
39671 .cindex "&'eximstats'&"
39672 A Perl script called &'eximstats'& is provided for extracting statistical
39673 information from log files. The output is either plain text, or HTML.
39674 . --- 2018-09-07: LogReport's Lire appears to be dead; website is a Yahoo Japan
39675 . --- 404 error and everything else points to that.
39677 The &'eximstats'& script has been hacked about quite a bit over time. The
39678 latest version is the result of some extensive revision by Steve Campbell. A
39679 lot of information is given by default, but there are options for suppressing
39680 various parts of it. Following any options, the arguments to the script are a
39681 list of files, which should be main log files. For example:
39683 eximstats -nr /var/spool/exim/log/mainlog.01
39685 By default, &'eximstats'& extracts information about the number and volume of
39686 messages received from or delivered to various hosts. The information is sorted
39687 both by message count and by volume, and the top fifty hosts in each category
39688 are listed on the standard output. Similar information, based on email
39689 addresses or domains instead of hosts can be requested by means of various
39690 options. For messages delivered and received locally, similar statistics are
39691 also produced per user.
39693 The output also includes total counts and statistics about delivery errors, and
39694 histograms showing the number of messages received and deliveries made in each
39695 hour of the day. A delivery with more than one address in its envelope (for
39696 example, an SMTP transaction with more than one RCPT command) is counted
39697 as a single delivery by &'eximstats'&.
39699 Though normally more deliveries than receipts are reported (as messages may
39700 have multiple recipients), it is possible for &'eximstats'& to report more
39701 messages received than delivered, even though the queue is empty at the start
39702 and end of the period in question. If an incoming message contains no valid
39703 recipients, no deliveries are recorded for it. A bounce message is handled as
39704 an entirely separate message.
39706 &'eximstats'& always outputs a grand total summary giving the volume and number
39707 of messages received and deliveries made, and the number of hosts involved in
39708 each case. It also outputs the number of messages that were delayed (that is,
39709 not completely delivered at the first attempt), and the number that had at
39710 least one address that failed.
39712 The remainder of the output is in sections that can be independently disabled
39713 or modified by various options. It consists of a summary of deliveries by
39714 transport, histograms of messages received and delivered per time interval
39715 (default per hour), information about the time messages spent in the queue,
39716 a list of relayed messages, lists of the top fifty sending hosts, local
39717 senders, destination hosts, and destination local users by count and by volume,
39718 and a list of delivery errors that occurred.
39720 The relay information lists messages that were actually relayed, that is, they
39721 came from a remote host and were directly delivered to some other remote host,
39722 without being processed (for example, for aliasing or forwarding) locally.
39724 There are quite a few options for &'eximstats'& to control exactly what it
39725 outputs. These are documented in the Perl script itself, and can be extracted
39726 by running the command &(perldoc)& on the script. For example:
39728 perldoc /usr/exim/bin/eximstats
39731 .section "Checking access policy (exim_checkaccess)" "SECTcheckaccess"
39732 .cindex "&'exim_checkaccess'&"
39733 .cindex "policy control" "checking access"
39734 .cindex "checking access"
39735 The &%-bh%& command line argument allows you to run a fake SMTP session with
39736 debugging output, in order to check what Exim is doing when it is applying
39737 policy controls to incoming SMTP mail. However, not everybody is sufficiently
39738 familiar with the SMTP protocol to be able to make full use of &%-bh%&, and
39739 sometimes you just want to answer the question &"Does this address have
39740 access?"& without bothering with any further details.
39742 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%&. It takes
39743 two arguments, an IP address and an email address:
39745 exim_checkaccess 10.9.8.7 A.User@a.domain.example
39747 The utility runs a call to Exim with the &%-bh%& option, to test whether the
39748 given email address would be accepted in a RCPT command in a TCP/IP
39749 connection from the host with the given IP address. The output of the utility
39750 is either the word &"accepted"&, or the SMTP error response, for example:
39753 550 Relay not permitted
39755 When running this test, the utility uses &`<>`& as the envelope sender address
39756 for the MAIL command, but you can change this by providing additional
39757 options. These are passed directly to the Exim command. For example, to specify
39758 that the test is to be run with the sender address &'himself@there.example'&
39761 exim_checkaccess 10.9.8.7 A.User@a.domain.example \
39762 -f himself@there.example
39764 Note that these additional Exim command line items must be given after the two
39765 mandatory arguments.
39767 Because the &%exim_checkaccess%& uses &%-bh%&, it does not perform callouts
39768 while running its checks. You can run checks that include callouts by using
39769 &%-bhc%&, but this is not yet available in a &"packaged"& form.
39773 .section "Making DBM files (exim_dbmbuild)" "SECTdbmbuild"
39774 .cindex "DBM" "building dbm files"
39775 .cindex "building DBM files"
39776 .cindex "&'exim_dbmbuild'&"
39777 .cindex "lower casing"
39778 .cindex "binary zero" "in lookup key"
39779 The &'exim_dbmbuild'& program reads an input file containing keys and data in
39780 the format used by the &(lsearch)& lookup (see section
39781 &<<SECTsinglekeylookups>>&). It writes a DBM file using the lower-cased alias
39782 names as keys and the remainder of the information as data. The lower-casing
39783 can be prevented by calling the program with the &%-nolc%& option.
39785 A terminating zero is included as part of the key string. This is expected by
39786 the &(dbm)& lookup type. However, if the option &%-nozero%& is given,
39787 &'exim_dbmbuild'& creates files without terminating zeroes in either the key
39788 strings or the data strings. The &(dbmnz)& lookup type can be used with such
39791 The program requires two arguments: the name of the input file (which can be a
39792 single hyphen to indicate the standard input), and the name of the output file.
39793 It creates the output under a temporary name, and then renames it if all went
39797 If the native DB interface is in use (USE_DB is set in a compile-time
39798 configuration file &-- this is common in free versions of Unix) the two
39799 filenames must be different, because in this mode the Berkeley DB functions
39800 create a single output file using exactly the name given. For example,
39802 exim_dbmbuild /etc/aliases /etc/aliases.db
39804 reads the system alias file and creates a DBM version of it in
39805 &_/etc/aliases.db_&.
39807 In systems that use the &'ndbm'& routines (mostly proprietary versions of
39808 Unix), two files are used, with the suffixes &_.dir_& and &_.pag_&. In this
39809 environment, the suffixes are added to the second argument of
39810 &'exim_dbmbuild'&, so it can be the same as the first. This is also the case
39811 when the Berkeley functions are used in compatibility mode (though this is not
39812 recommended), because in that case it adds a &_.db_& suffix to the filename.
39814 If a duplicate key is encountered, the program outputs a warning, and when it
39815 finishes, its return code is 1 rather than zero, unless the &%-noduperr%&
39816 option is used. By default, only the first of a set of duplicates is used &--
39817 this makes it compatible with &(lsearch)& lookups. There is an option
39818 &%-lastdup%& which causes it to use the data for the last duplicate instead.
39819 There is also an option &%-nowarn%&, which stops it listing duplicate keys to
39820 &%stderr%&. For other errors, where it doesn't actually make a new file, the
39826 .section "Finding individual retry times (exinext)" "SECTfinindret"
39827 .cindex "retry" "times"
39828 .cindex "&'exinext'&"
39829 A utility called &'exinext'& (mostly a Perl script) provides the ability to
39830 fish specific information out of the retry database. Given a mail domain (or a
39831 complete address), it looks up the hosts for that domain, and outputs any retry
39832 information for the hosts or for the domain. At present, the retry information
39833 is obtained by running &'exim_dumpdb'& (see below) and post-processing the
39834 output. For example:
39836 $ exinext piglet@milne.fict.example
39837 kanga.milne.example:192.168.8.1 error 146: Connection refused
39838 first failed: 21-Feb-1996 14:57:34
39839 last tried: 21-Feb-1996 14:57:34
39840 next try at: 21-Feb-1996 15:02:34
39841 roo.milne.example:192.168.8.3 error 146: Connection refused
39842 first failed: 20-Jan-1996 13:12:08
39843 last tried: 21-Feb-1996 11:42:03
39844 next try at: 21-Feb-1996 19:42:03
39845 past final cutoff time
39847 You can also give &'exinext'& a local part, without a domain, and it
39848 will give any retry information for that local part in your default domain.
39849 A message id can be used to obtain retry information pertaining to a specific
39850 message. This exists only when an attempt to deliver a message to a remote host
39851 suffers a message-specific error (see section &<<SECToutSMTPerr>>&).
39852 &'exinext'& is not particularly efficient, but then it is not expected to be
39855 The &'exinext'& utility calls Exim to find out information such as the location
39856 of the spool directory. The utility has &%-C%& and &%-D%& options, which are
39857 passed on to the &'exim'& commands. The first specifies an alternate Exim
39858 configuration file, and the second sets macros for use within the configuration
39859 file. These features are mainly to help in testing, but might also be useful in
39860 environments where more than one configuration file is in use.
39864 .section "Hints database maintenance" "SECThindatmai"
39865 .cindex "hints database" "maintenance"
39866 .cindex "maintaining Exim's hints database"
39867 Three utility programs are provided for maintaining the DBM files that Exim
39868 uses to contain its delivery hint information. Each program requires two
39869 arguments. The first specifies the name of Exim's spool directory, and the
39870 second is the name of the database it is to operate on. These are as follows:
39873 &'retry'&: the database of retry information
39875 &'wait-'&<&'transport name'&>: databases of information about messages waiting
39878 &'callout'&: the callout cache
39880 &'ratelimit'&: the data for implementing the ratelimit ACL condition
39882 &'tls'&: TLS session resumption data
39884 &'misc'&: other hints data
39887 The &'misc'& database is used for
39890 Serializing ETRN runs (when &%smtp_etrn_serialize%& is set)
39892 Serializing delivery to a specific host (when &%serialize_hosts%& is set in an
39893 &(smtp)& transport)
39895 Limiting the concurrency of specific transports (when &%max_parallel%& is set
39901 .section "exim_dumpdb" "SECTdumpdb"
39902 .cindex "&'exim_dumpdb'&"
39903 The entire contents of a database are written to the standard output by the
39904 &'exim_dumpdb'& program,
39905 taking as arguments the spool and database names.
39906 An option &'-z'& may be given to request times in UTC;
39907 otherwise times are in the local timezone.
39908 An option &'-k'& may be given to dump only the record keys.
39909 For example, to dump the retry database:
39911 exim_dumpdb /var/spool/exim retry
39913 For the retry database
39914 two lines of output are produced for each entry:
39916 T:mail.ref.example:192.168.242.242 146 77 Connection refused
39917 31-Oct-1995 12:00:12 02-Nov-1995 12:21:39 02-Nov-1995 20:21:39 *
39919 The first item on the first line is the key of the record. It starts with one
39920 of the letters R, or T, depending on whether it refers to a routing or
39921 transport retry. For a local delivery, the next part is the local address; for
39922 a remote delivery it is the name of the remote host, followed by its failing IP
39923 address (unless &%retry_include_ip_address%& is set false on the &(smtp)&
39924 transport). If the remote port is not the standard one (port 25), it is added
39925 to the IP address. Then there follows an error code, an additional error code,
39926 and a textual description of the error.
39928 The three times on the second line are the time of first failure, the time of
39929 the last delivery attempt, and the computed time for the next attempt. The line
39930 ends with an asterisk if the cutoff time for the last retry rule has been
39933 Each output line from &'exim_dumpdb'& for the &'wait-xxx'& databases
39934 consists of a host name followed by a list of ids for messages that are or were
39935 waiting to be delivered to that host. If there are a very large number for any
39936 one host, continuation records, with a sequence number added to the host name,
39937 may be seen. The data in these records is often out of date, because a message
39938 may be routed to several alternative hosts, and Exim makes no effort to keep
39943 .section "exim_tidydb" "SECTtidydb"
39944 .cindex "&'exim_tidydb'&"
39945 The &'exim_tidydb'& utility program is used to tidy up the contents of a hints
39946 database. If run with no options, it removes all records that are more than 30
39947 days old. The age is calculated from the date and time that the record was last
39948 updated. Note that, in the case of the retry database, it is &'not'& the time
39949 since the first delivery failure. Information about a host that has been down
39950 for more than 30 days will remain in the database, provided that the record is
39951 updated sufficiently often.
39953 The cutoff date can be altered by means of the &%-t%& option, which must be
39954 followed by a time. For example, to remove all records older than a week from
39955 the retry database:
39957 exim_tidydb -t 7d /var/spool/exim retry
39959 Both the &'wait-xxx'& and &'retry'& databases contain items that involve
39960 message ids. In the former these appear as data in records keyed by host &--
39961 they were messages that were waiting for that host &-- and in the latter they
39962 are the keys for retry information for messages that have suffered certain
39963 types of error. When &'exim_tidydb'& is run, a check is made to ensure that
39964 message ids in database records are those of messages that are still on the
39965 queue. Message ids for messages that no longer exist are removed from
39966 &'wait-xxx'& records, and if this leaves any records empty, they are deleted.
39967 For the &'retry'& database, records whose keys are non-existent message ids are
39968 removed. The &'exim_tidydb'& utility outputs comments on the standard output
39969 whenever it removes information from the database.
39971 Certain records are automatically removed by Exim when they are no longer
39972 needed, but others are not. For example, if all the MX hosts for a domain are
39973 down, a retry record is created for each one. If the primary MX host comes back
39974 first, its record is removed when Exim successfully delivers to it, but the
39975 records for the others remain because Exim has not tried to use those hosts.
39977 It is important, therefore, to run &'exim_tidydb'& periodically on all the
39978 hints databases. You should do this at a quiet time of day, because it requires
39979 a database to be locked (and therefore inaccessible to Exim) while it does its
39980 work. Removing records from a DBM file does not normally make the file smaller,
39981 but all the common DBM libraries are able to re-use the space that is released.
39982 After an initial phase of increasing in size, the databases normally reach a
39983 point at which they no longer get any bigger, as long as they are regularly
39986 &*Warning*&: If you never run &'exim_tidydb'&, the space used by the hints
39987 databases is likely to keep on increasing.
39992 .section "exim_fixdb" "SECTfixdb"
39993 .cindex "&'exim_fixdb'&"
39994 The &'exim_fixdb'& program is a utility for interactively modifying databases.
39995 Its main use is for testing Exim, but it might also be occasionally useful for
39996 getting round problems in a live system. Its interface
39997 is somewhat crude. On entry, it prompts for input with a right angle-bracket. A
39998 key of a database record can then be entered, and the data for that record is
40001 If &"d"& is typed at the next prompt, the entire record is deleted. For all
40002 except the &'retry'& database, that is the only operation that can be carried
40003 out. For the &'retry'& database, each field is output preceded by a number, and
40004 data for individual fields can be changed by typing the field number followed
40005 by new data, for example:
40009 resets the time of the next delivery attempt. Time values are given as a
40010 sequence of digit pairs for year, month, day, hour, and minute. Colons can be
40011 used as optional separators.
40013 Both displayed and input times are in the local timezone by default.
40014 If an option &'-z'& is used on the command line, displayed times
40020 .section "Mailbox maintenance (exim_lock)" "SECTmailboxmaint"
40021 .cindex "mailbox" "maintenance"
40022 .cindex "&'exim_lock'&"
40023 .cindex "locking mailboxes"
40024 The &'exim_lock'& utility locks a mailbox file using the same algorithm as
40025 Exim. For a discussion of locking issues, see section &<<SECTopappend>>&.
40026 &'Exim_lock'& can be used to prevent any modification of a mailbox by Exim or
40027 a user agent while investigating a problem. The utility requires the name of
40028 the file as its first argument. If the locking is successful, the second
40029 argument is run as a command (using C's &[system()]& function); if there is no
40030 second argument, the value of the SHELL environment variable is used; if this
40031 is unset or empty, &_/bin/sh_& is run. When the command finishes, the mailbox
40032 is unlocked and the utility ends. The following options are available:
40036 Use &[fcntl()]& locking on the open mailbox.
40039 Use &[flock()]& locking on the open mailbox, provided the operating system
40042 .vitem &%-interval%&
40043 This must be followed by a number, which is a number of seconds; it sets the
40044 interval to sleep between retries (default 3).
40046 .vitem &%-lockfile%&
40047 Create a lock file before opening the mailbox.
40050 Lock the mailbox using MBX rules.
40053 Suppress verification output.
40055 .vitem &%-retries%&
40056 This must be followed by a number; it sets the number of times to try to get
40057 the lock (default 10).
40059 .vitem &%-restore_time%&
40060 This option causes &%exim_lock%& to restore the modified and read times to the
40061 locked file before exiting. This allows you to access a locked mailbox (for
40062 example, to take a backup copy) without disturbing the times that the user
40065 .vitem &%-timeout%&
40066 This must be followed by a number, which is a number of seconds; it sets a
40067 timeout to be used with a blocking &[fcntl()]& lock. If it is not set (the
40068 default), a non-blocking call is used.
40071 Generate verbose output.
40074 If none of &%-fcntl%&, &%-flock%&, &%-lockfile%& or &%-mbx%& are given, the
40075 default is to create a lock file and also to use &[fcntl()]& locking on the
40076 mailbox, which is the same as Exim's default. The use of &%-flock%& or
40077 &%-fcntl%& requires that the file be writeable; the use of &%-lockfile%&
40078 requires that the directory containing the file be writeable. Locking by lock
40079 file does not last forever; Exim assumes that a lock file is expired if it is
40080 more than 30 minutes old.
40082 The &%-mbx%& option can be used with either or both of &%-fcntl%& or
40083 &%-flock%&. It assumes &%-fcntl%& by default. MBX locking causes a shared lock
40084 to be taken out on the open mailbox, and an exclusive lock on the file
40085 &_/tmp/.n.m_& where &'n'& and &'m'& are the device number and inode
40086 number of the mailbox file. When the locking is released, if an exclusive lock
40087 can be obtained for the mailbox, the file in &_/tmp_& is deleted.
40089 The default output contains verification of the locking that takes place. The
40090 &%-v%& option causes some additional information to be given. The &%-q%& option
40091 suppresses all output except error messages.
40095 exim_lock /var/spool/mail/spqr
40097 runs an interactive shell while the file is locked, whereas
40099 &`exim_lock -q /var/spool/mail/spqr <<End`&
40100 <&'some commands'&>
40103 runs a specific non-interactive sequence of commands while the file is locked,
40104 suppressing all verification output. A single command can be run by a command
40107 exim_lock -q /var/spool/mail/spqr \
40108 "cp /var/spool/mail/spqr /some/where"
40110 Note that if a command is supplied, it must be entirely contained within the
40111 second argument &-- hence the quotes.
40115 . ////////////////////////////////////////////////////////////////////////////
40116 . ////////////////////////////////////////////////////////////////////////////
40118 .chapter "The Exim monitor" "CHAPeximon"
40119 .scindex IIDeximon "Exim monitor" "description"
40120 .cindex "X-windows"
40121 .cindex "&'eximon'&"
40122 .cindex "Local/eximon.conf"
40123 .cindex "&_exim_monitor/EDITME_&"
40124 The Exim monitor is an application which displays in an X window information
40125 about the state of Exim's queue and what Exim is doing. An admin user can
40126 perform certain operations on messages from this GUI interface; however all
40127 such facilities are also available from the command line, and indeed, the
40128 monitor itself makes use of the command line to perform any actions requested.
40132 .section "Running the monitor" "SECID264"
40133 The monitor is started by running the script called &'eximon'&. This is a shell
40134 script that sets up a number of environment variables, and then runs the
40135 binary called &_eximon.bin_&. The default appearance of the monitor window can
40136 be changed by editing the &_Local/eximon.conf_& file created by editing
40137 &_exim_monitor/EDITME_&. Comments in that file describe what the various
40138 parameters are for.
40140 The parameters that get built into the &'eximon'& script can be overridden for
40141 a particular invocation by setting up environment variables of the same names,
40142 preceded by &`EXIMON_`&. For example, a shell command such as
40144 EXIMON_LOG_DEPTH=400 eximon
40146 (in a Bourne-compatible shell) runs &'eximon'& with an overriding setting of
40147 the LOG_DEPTH parameter. If EXIMON_LOG_FILE_PATH is set in the environment, it
40148 overrides the Exim log file configuration. This makes it possible to have
40149 &'eximon'& tailing log data that is written to syslog, provided that MAIL.INFO
40150 syslog messages are routed to a file on the local host.
40152 X resources can be used to change the appearance of the window in the normal
40153 way. For example, a resource setting of the form
40155 Eximon*background: gray94
40157 changes the colour of the background to light grey rather than white. The
40158 stripcharts are drawn with both the data lines and the reference lines in
40159 black. This means that the reference lines are not visible when on top of the
40160 data. However, their colour can be changed by setting a resource called
40161 &"highlight"& (an odd name, but that's what the Athena stripchart widget uses).
40162 For example, if your X server is running Unix, you could set up lighter
40163 reference lines in the stripcharts by obeying
40166 Eximon*highlight: gray
40169 .cindex "admin user"
40170 In order to see the contents of messages in the queue, and to operate on them,
40171 &'eximon'& must either be run as root or by an admin user.
40173 The command-line parameters of &'eximon'& are passed to &_eximon.bin_& and may
40174 contain X11 resource parameters interpreted by the X11 library. In addition,
40175 if the first parameter starts with the string "gdb" then it is removed and the
40176 binary is invoked under gdb (the parameter is used as the gdb command-name, so
40177 versioned variants of gdb can be invoked).
40179 The monitor's window is divided into three parts. The first contains one or
40180 more stripcharts and two action buttons, the second contains a &"tail"& of the
40181 main log file, and the third is a display of the queue of messages awaiting
40182 delivery, with two more action buttons. The following sections describe these
40183 different parts of the display.
40188 .section "The stripcharts" "SECID265"
40189 .cindex "stripchart"
40190 The first stripchart is always a count of messages in the queue. Its name can
40191 be configured by setting QUEUE_STRIPCHART_NAME in the
40192 &_Local/eximon.conf_& file. The remaining stripcharts are defined in the
40193 configuration script by regular expression matches on log file entries, making
40194 it possible to display, for example, counts of messages delivered to certain
40195 hosts or using certain transports. The supplied defaults display counts of
40196 received and delivered messages, and of local and SMTP deliveries. The default
40197 period between stripchart updates is one minute; this can be adjusted by a
40198 parameter in the &_Local/eximon.conf_& file.
40200 The stripchart displays rescale themselves automatically as the value they are
40201 displaying changes. There are always 10 horizontal lines in each chart; the
40202 title string indicates the value of each division when it is greater than one.
40203 For example, &"x2"& means that each division represents a value of 2.
40205 It is also possible to have a stripchart which shows the percentage fullness of
40206 a particular disk partition, which is useful when local deliveries are confined
40207 to a single partition.
40209 .cindex "&%statvfs%& function"
40210 This relies on the availability of the &[statvfs()]& function or equivalent in
40211 the operating system. Most, but not all versions of Unix that support Exim have
40212 this. For this particular stripchart, the top of the chart always represents
40213 100%, and the scale is given as &"x10%"&. This chart is configured by setting
40214 SIZE_STRIPCHART and (optionally) SIZE_STRIPCHART_NAME in the
40215 &_Local/eximon.conf_& file.
40220 .section "Main action buttons" "SECID266"
40221 .cindex "size" "of monitor window"
40222 .cindex "Exim monitor" "window size"
40223 .cindex "window size"
40224 Below the stripcharts there is an action button for quitting the monitor. Next
40225 to this is another button marked &"Size"&. They are placed here so that
40226 shrinking the window to its default minimum size leaves just the queue count
40227 stripchart and these two buttons visible. Pressing the &"Size"& button causes
40228 the window to expand to its maximum size, unless it is already at the maximum,
40229 in which case it is reduced to its minimum.
40231 When expanding to the maximum, if the window cannot be fully seen where it
40232 currently is, it is moved back to where it was the last time it was at full
40233 size. When it is expanding from its minimum size, the old position is
40234 remembered, and next time it is reduced to the minimum it is moved back there.
40236 The idea is that you can keep a reduced window just showing one or two
40237 stripcharts at a convenient place on your screen, easily expand it to show
40238 the full window when required, and just as easily put it back to what it was.
40239 The idea is copied from what the &'twm'& window manager does for its
40240 &'f.fullzoom'& action. The minimum size of the window can be changed by setting
40241 the MIN_HEIGHT and MIN_WIDTH values in &_Local/eximon.conf_&.
40243 Normally, the monitor starts up with the window at its full size, but it can be
40244 built so that it starts up with the window at its smallest size, by setting
40245 START_SMALL=yes in &_Local/eximon.conf_&.
40249 .section "The log display" "SECID267"
40250 .cindex "log" "tail of; in monitor"
40251 The second section of the window is an area in which a display of the tail of
40252 the main log is maintained.
40253 To save space on the screen, the timestamp on each log line is shortened by
40254 removing the date and, if &%log_timezone%& is set, the timezone.
40255 The log tail is not available when the only destination for logging data is
40256 syslog, unless the syslog lines are routed to a local file whose name is passed
40257 to &'eximon'& via the EXIMON_LOG_FILE_PATH environment variable.
40259 The log sub-window has a scroll bar at its lefthand side which can be used to
40260 move back to look at earlier text, and the up and down arrow keys also have a
40261 scrolling effect. The amount of log that is kept depends on the setting of
40262 LOG_BUFFER in &_Local/eximon.conf_&, which specifies the amount of memory
40263 to use. When this is full, the earlier 50% of data is discarded &-- this is
40264 much more efficient than throwing it away line by line. The sub-window also has
40265 a horizontal scroll bar for accessing the ends of long log lines. This is the
40266 only means of horizontal scrolling; the right and left arrow keys are not
40267 available. Text can be cut from this part of the window using the mouse in the
40268 normal way. The size of this subwindow is controlled by parameters in the
40269 configuration file &_Local/eximon.conf_&.
40271 Searches of the text in the log window can be carried out by means of the ^R
40272 and ^S keystrokes, which default to a reverse and a forward search,
40273 respectively. The search covers only the text that is displayed in the window.
40274 It cannot go further back up the log.
40276 The point from which the search starts is indicated by a caret marker. This is
40277 normally at the end of the text in the window, but can be positioned explicitly
40278 by pointing and clicking with the left mouse button, and is moved automatically
40279 by a successful search. If new text arrives in the window when it is scrolled
40280 back, the caret remains where it is, but if the window is not scrolled back,
40281 the caret is moved to the end of the new text.
40283 Pressing ^R or ^S pops up a window into which the search text can be typed.
40284 There are buttons for selecting forward or reverse searching, for carrying out
40285 the search, and for cancelling. If the &"Search"& button is pressed, the search
40286 happens and the window remains so that further searches can be done. If the
40287 &"Return"& key is pressed, a single search is done and the window is closed. If
40288 ^C is typed the search is cancelled.
40290 The searching facility is implemented using the facilities of the Athena text
40291 widget. By default this pops up a window containing both &"search"& and
40292 &"replace"& options. In order to suppress the unwanted &"replace"& portion for
40293 eximon, a modified version of the &%TextPop%& widget is distributed with Exim.
40294 However, the linkers in BSDI and HP-UX seem unable to handle an externally
40295 provided version of &%TextPop%& when the remaining parts of the text widget
40296 come from the standard libraries. The compile-time option EXIMON_TEXTPOP can be
40297 unset to cut out the modified &%TextPop%&, making it possible to build Eximon
40298 on these systems, at the expense of having unwanted items in the search popup
40303 .section "The queue display" "SECID268"
40304 .cindex "queue" "display in monitor"
40305 The bottom section of the monitor window contains a list of all messages that
40306 are in the queue, which includes those currently being received or delivered,
40307 as well as those awaiting delivery. The size of this subwindow is controlled by
40308 parameters in the configuration file &_Local/eximon.conf_&, and the frequency
40309 at which it is updated is controlled by another parameter in the same file &--
40310 the default is 5 minutes, since queue scans can be quite expensive. However,
40311 there is an &"Update"& action button just above the display which can be used
40312 to force an update of the queue display at any time.
40314 When a host is down for some time, a lot of pending mail can build up for it,
40315 and this can make it hard to deal with other messages in the queue. To help
40316 with this situation there is a button next to &"Update"& called &"Hide"&. If
40317 pressed, a dialogue box called &"Hide addresses ending with"& is put up. If you
40318 type anything in here and press &"Return"&, the text is added to a chain of
40319 such texts, and if every undelivered address in a message matches at least one
40320 of the texts, the message is not displayed.
40322 If there is an address that does not match any of the texts, all the addresses
40323 are displayed as normal. The matching happens on the ends of addresses so, for
40324 example, &'cam.ac.uk'& specifies all addresses in Cambridge, while
40325 &'xxx@foo.com.example'& specifies just one specific address. When any hiding
40326 has been set up, a button called &"Unhide"& is displayed. If pressed, it
40327 cancels all hiding. Also, to ensure that hidden messages do not get forgotten,
40328 a hide request is automatically cancelled after one hour.
40330 While the dialogue box is displayed, you can't press any buttons or do anything
40331 else to the monitor window. For this reason, if you want to cut text from the
40332 queue display to use in the dialogue box, you have to do the cutting before
40333 pressing the &"Hide"& button.
40335 The queue display contains, for each unhidden queued message, the length of
40336 time it has been in the queue, the size of the message, the message id, the
40337 message sender, and the first undelivered recipient, all on one line. If it is
40338 a bounce message, the sender is shown as &"<>"&. If there is more than one
40339 recipient to which the message has not yet been delivered, subsequent ones are
40340 listed on additional lines, up to a maximum configured number, following which
40341 an ellipsis is displayed. Recipients that have already received the message are
40344 .cindex "frozen messages" "display"
40345 If a message is frozen, an asterisk is displayed at the left-hand side.
40347 The queue display has a vertical scroll bar, and can also be scrolled by means
40348 of the arrow keys. Text can be cut from it using the mouse in the normal way.
40349 The text searching facilities, as described above for the log window, are also
40350 available, but the caret is always moved to the end of the text when the queue
40351 display is updated.
40355 .section "The queue menu" "SECID269"
40356 .cindex "queue" "menu in monitor"
40357 If the &%shift%& key is held down and the left button is clicked when the mouse
40358 pointer is over the text for any message, an action menu pops up, and the first
40359 line of the queue display for the message is highlighted. This does not affect
40362 If you want to use some other event for popping up the menu, you can set the
40363 MENU_EVENT parameter in &_Local/eximon.conf_& to change the default, or
40364 set EXIMON_MENU_EVENT in the environment before starting the monitor. The
40365 value set in this parameter is a standard X event description. For example, to
40366 run eximon using &%ctrl%& rather than &%shift%& you could use
40368 EXIMON_MENU_EVENT='Ctrl<Btn1Down>' eximon
40370 The title of the menu is the message id, and it contains entries which act as
40374 &'message log'&: The contents of the message log for the message are displayed
40375 in a new text window.
40377 &'headers'&: Information from the spool file that contains the envelope
40378 information and headers is displayed in a new text window. See chapter
40379 &<<CHAPspool>>& for a description of the format of spool files.
40381 &'body'&: The contents of the spool file containing the body of the message are
40382 displayed in a new text window. There is a default limit of 20,000 bytes to the
40383 amount of data displayed. This can be changed by setting the BODY_MAX
40384 option at compile time, or the EXIMON_BODY_MAX option at runtime.
40386 &'deliver message'&: A call to Exim is made using the &%-M%& option to request
40387 delivery of the message. This causes an automatic thaw if the message is
40388 frozen. The &%-v%& option is also set, and the output from Exim is displayed in
40389 a new text window. The delivery is run in a separate process, to avoid holding
40390 up the monitor while the delivery proceeds.
40392 &'freeze message'&: A call to Exim is made using the &%-Mf%& option to request
40393 that the message be frozen.
40395 .cindex "thawing messages"
40396 .cindex "unfreezing messages"
40397 .cindex "frozen messages" "thawing"
40398 &'thaw message'&: A call to Exim is made using the &%-Mt%& option to request
40399 that the message be thawed.
40401 .cindex "delivery" "forcing failure"
40402 &'give up on msg'&: A call to Exim is made using the &%-Mg%& option to request
40403 that Exim gives up trying to deliver the message. A bounce message is generated
40404 for any remaining undelivered addresses.
40406 &'remove message'&: A call to Exim is made using the &%-Mrm%& option to request
40407 that the message be deleted from the system without generating a bounce
40410 &'add recipient'&: A dialog box is displayed into which a recipient address can
40411 be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
40412 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
40413 Otherwise it must be entered as a fully qualified address. Pressing RETURN
40414 causes a call to Exim to be made using the &%-Mar%& option to request that an
40415 additional recipient be added to the message, unless the entry box is empty, in
40416 which case no action is taken.
40418 &'mark delivered'&: A dialog box is displayed into which a recipient address
40419 can be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
40420 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
40421 Otherwise it must be entered as a fully qualified address. Pressing RETURN
40422 causes a call to Exim to be made using the &%-Mmd%& option to mark the given
40423 recipient address as already delivered, unless the entry box is empty, in which
40424 case no action is taken.
40426 &'mark all delivered'&: A call to Exim is made using the &%-Mmad%& option to
40427 mark all recipient addresses as already delivered.
40429 &'edit sender'&: A dialog box is displayed initialized with the current
40430 sender's address. Pressing RETURN causes a call to Exim to be made using the
40431 &%-Mes%& option to replace the sender address, unless the entry box is empty,
40432 in which case no action is taken. If you want to set an empty sender (as in
40433 bounce messages), you must specify it as &"<>"&. Otherwise, if the address is
40434 not qualified and the QUALIFY_DOMAIN parameter is set in &_Local/eximon.conf_&,
40435 the address is qualified with that domain.
40438 When a delivery is forced, a window showing the &%-v%& output is displayed. In
40439 other cases when a call to Exim is made, if there is any output from Exim (in
40440 particular, if the command fails) a window containing the command and the
40441 output is displayed. Otherwise, the results of the action are normally apparent
40442 from the log and queue displays. However, if you set ACTION_OUTPUT=yes in
40443 &_Local/eximon.conf_&, a window showing the Exim command is always opened, even
40444 if no output is generated.
40446 The queue display is automatically updated for actions such as freezing and
40447 thawing, unless ACTION_QUEUE_UPDATE=no has been set in
40448 &_Local/eximon.conf_&. In this case the &"Update"& button has to be used to
40449 force an update of the display after one of these actions.
40451 In any text window that is displayed as result of a menu action, the normal
40452 cut-and-paste facility is available, and searching can be carried out using ^R
40453 and ^S, as described above for the log tail window.
40460 . ////////////////////////////////////////////////////////////////////////////
40461 . ////////////////////////////////////////////////////////////////////////////
40463 .chapter "Security considerations" "CHAPsecurity"
40464 .scindex IIDsecurcon "security" "discussion of"
40465 This chapter discusses a number of issues concerned with security, some of
40466 which are also covered in other parts of this manual.
40468 For reasons that this author does not understand, some people have promoted
40469 Exim as a &"particularly secure"& mailer. Perhaps it is because of the
40470 existence of this chapter in the documentation. However, the intent of the
40471 chapter is simply to describe the way Exim works in relation to certain
40472 security concerns, not to make any specific claims about the effectiveness of
40473 its security as compared with other MTAs.
40475 What follows is a description of the way Exim is supposed to be. Best efforts
40476 have been made to try to ensure that the code agrees with the theory, but an
40477 absence of bugs can never be guaranteed. Any that are reported will get fixed
40478 as soon as possible.
40481 .section "Building a more &""hardened""& Exim" "SECID286"
40482 .cindex "security" "build-time features"
40483 There are a number of build-time options that can be set in &_Local/Makefile_&
40484 to create Exim binaries that are &"harder"& to attack, in particular by a rogue
40485 Exim administrator who does not have the root password, or by someone who has
40486 penetrated the Exim (but not the root) account. These options are as follows:
40489 ALT_CONFIG_PREFIX can be set to a string that is required to match the
40490 start of any filenames used with the &%-C%& option. When it is set, these
40491 filenames are also not allowed to contain the sequence &"/../"&. (However, if
40492 the value of the &%-C%& option is identical to the value of CONFIGURE_FILE in
40493 &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as usual.) There is no
40494 default setting for &%ALT_CONFIG_PREFIX%&.
40496 If the permitted configuration files are confined to a directory to
40497 which only root has access, this guards against someone who has broken
40498 into the Exim account from running a privileged Exim with an arbitrary
40499 configuration file, and using it to break into other accounts.
40502 If a non-trusted configuration file (i.e. not the default configuration file
40503 or one which is trusted by virtue of being listed in the TRUSTED_CONFIG_LIST
40504 file) is specified with &%-C%&, or if macros are given with &%-D%& (but see
40505 the next item), then root privilege is retained only if the caller of Exim is
40506 root. This locks out the possibility of testing a configuration using &%-C%&
40507 right through message reception and delivery, even if the caller is root. The
40508 reception works, but by that time, Exim is running as the Exim user, so when
40509 it re-execs to regain privilege for the delivery, the use of &%-C%& causes
40510 privilege to be lost. However, root can test reception and delivery using two
40514 The WHITELIST_D_MACROS build option declares some macros to be safe to override
40515 with &%-D%& if the real uid is one of root, the Exim run-time user or the
40516 CONFIGURE_OWNER, if defined. The potential impact of this option is limited by
40517 requiring the run-time value supplied to &%-D%& to match a regex that errs on
40518 the restrictive side. Requiring build-time selection of safe macros is onerous
40519 but this option is intended solely as a transition mechanism to permit
40520 previously-working configurations to continue to work after release 4.73.
40522 If DISABLE_D_OPTION is defined, the use of the &%-D%& command line option
40525 FIXED_NEVER_USERS can be set to a colon-separated list of users that are
40526 never to be used for any deliveries. This is like the &%never_users%& runtime
40527 option, but it cannot be overridden; the runtime option adds additional users
40528 to the list. The default setting is &"root"&; this prevents a non-root user who
40529 is permitted to modify the runtime file from using Exim as a way to get root.
40534 .section "Root privilege" "SECID270"
40536 .cindex "root privilege"
40537 The Exim binary is normally setuid to root, which means that it gains root
40538 privilege (runs as root) when it starts execution. In some special cases (for
40539 example, when the daemon is not in use and there are no local deliveries), it
40540 may be possible to run Exim setuid to some user other than root. This is
40541 discussed in the next section. However, in most installations, root privilege
40542 is required for two things:
40545 To set up a socket connected to the standard SMTP port (25) when initialising
40546 the listening daemon. If Exim is run from &'inetd'&, this privileged action is
40549 To be able to change uid and gid in order to read users' &_.forward_& files and
40550 perform local deliveries as the receiving user or as specified in the
40554 It is not necessary to be root to do any of the other things Exim does, such as
40555 receiving messages and delivering them externally over SMTP, and it is
40556 obviously more secure if Exim does not run as root except when necessary.
40557 For this reason, a user and group for Exim to use must be defined in
40558 &_Local/Makefile_&. These are known as &"the Exim user"& and &"the Exim
40559 group"&. Their values can be changed by the runtime configuration, though this
40560 is not recommended. Often a user called &'exim'& is used, but some sites use
40561 &'mail'& or another user name altogether.
40563 Exim uses &[setuid()]& whenever it gives up root privilege. This is a permanent
40564 abdication; the process cannot regain root afterwards. Prior to release 4.00,
40565 &[seteuid()]& was used in some circumstances, but this is no longer the case.
40567 After a new Exim process has interpreted its command line options, it changes
40568 uid and gid in the following cases:
40573 If the &%-C%& option is used to specify an alternate configuration file, or if
40574 the &%-D%& option is used to define macro values for the configuration, and the
40575 calling process is not running as root, the uid and gid are changed to those of
40576 the calling process.
40577 However, if DISABLE_D_OPTION is defined in &_Local/Makefile_&, the &%-D%&
40578 option may not be used at all.
40579 If WHITELIST_D_MACROS is defined in &_Local/Makefile_&, then some macro values
40580 can be supplied if the calling process is running as root, the Exim run-time
40581 user or CONFIGURE_OWNER, if defined.
40586 If the expansion test option (&%-be%&) or one of the filter testing options
40587 (&%-bf%& or &%-bF%&) are used, the uid and gid are changed to those of the
40590 If the process is not a daemon process or a queue runner process or a delivery
40591 process or a process for testing address routing (started with &%-bt%&), the
40592 uid and gid are changed to the Exim user and group. This means that Exim always
40593 runs under its own uid and gid when receiving messages. This also applies when
40594 testing address verification
40597 (the &%-bv%& option) and testing incoming message policy controls (the &%-bh%&
40600 For a daemon, queue runner, delivery, or address testing process, the uid
40601 remains as root at this stage, but the gid is changed to the Exim group.
40604 The processes that initially retain root privilege behave as follows:
40607 A daemon process changes the gid to the Exim group and the uid to the Exim
40608 user after setting up one or more listening sockets. The &[initgroups()]&
40609 function is called, so that if the Exim user is in any additional groups, they
40610 will be used during message reception.
40612 A queue runner process retains root privilege throughout its execution. Its
40613 job is to fork a controlled sequence of delivery processes.
40615 A delivery process retains root privilege throughout most of its execution,
40616 but any actual deliveries (that is, the transports themselves) are run in
40617 subprocesses which always change to a non-root uid and gid. For local
40618 deliveries this is typically the uid and gid of the owner of the mailbox; for
40619 remote deliveries, the Exim uid and gid are used. Once all the delivery
40620 subprocesses have been run, a delivery process changes to the Exim uid and gid
40621 while doing post-delivery tidying up such as updating the retry database and
40622 generating bounce and warning messages.
40624 While the recipient addresses in a message are being routed, the delivery
40625 process runs as root. However, if a user's filter file has to be processed,
40626 this is done in a subprocess that runs under the individual user's uid and
40627 gid. A system filter is run as root unless &%system_filter_user%& is set.
40629 A process that is testing addresses (the &%-bt%& option) runs as root so that
40630 the routing is done in the same environment as a message delivery.
40636 .section "Running Exim without privilege" "SECTrunexiwitpri"
40637 .cindex "privilege, running without"
40638 .cindex "unprivileged running"
40639 .cindex "root privilege" "running without"
40640 Some installations like to run Exim in an unprivileged state for more of its
40641 operation, for added security. Support for this mode of operation is provided
40642 by the global option &%deliver_drop_privilege%&. When this is set, the uid and
40643 gid are changed to the Exim user and group at the start of a delivery process
40644 (and also queue runner and address testing processes). This means that address
40645 routing is no longer run as root, and the deliveries themselves cannot change
40649 .cindex "daemon" "restarting"
40650 Leaving the binary setuid to root, but setting &%deliver_drop_privilege%& means
40651 that the daemon can still be started in the usual way, and it can respond
40652 correctly to SIGHUP because the re-invocation regains root privilege.
40654 An alternative approach is to make Exim setuid to the Exim user and also setgid
40655 to the Exim group. If you do this, the daemon must be started from a root
40656 process. (Calling Exim from a root process makes it behave in the way it does
40657 when it is setuid root.) However, the daemon cannot restart itself after a
40658 SIGHUP signal because it cannot regain privilege.
40660 It is still useful to set &%deliver_drop_privilege%& in this case, because it
40661 stops Exim from trying to re-invoke itself to do a delivery after a message has
40662 been received. Such a re-invocation is a waste of resources because it has no
40665 If restarting the daemon is not an issue (for example, if &%mua_wrapper%& is
40666 set, or &'inetd'& is being used instead of a daemon), having the binary setuid
40667 to the Exim user seems a clean approach, but there is one complication:
40669 In this style of operation, Exim is running with the real uid and gid set to
40670 those of the calling process, and the effective uid/gid set to Exim's values.
40671 Ideally, any association with the calling process' uid/gid should be dropped,
40672 that is, the real uid/gid should be reset to the effective values so as to
40673 discard any privileges that the caller may have. While some operating systems
40674 have a function that permits this action for a non-root effective uid, quite a
40675 number of them do not. Because of this lack of standardization, Exim does not
40676 address this problem at this time.
40678 For this reason, the recommended approach for &"mostly unprivileged"& running
40679 is to keep the Exim binary setuid to root, and to set
40680 &%deliver_drop_privilege%&. This also has the advantage of allowing a daemon to
40681 be used in the most straightforward way.
40683 If you configure Exim not to run delivery processes as root, there are a
40684 number of restrictions on what you can do:
40687 You can deliver only as the Exim user/group. You should explicitly use the
40688 &%user%& and &%group%& options to override routers or local transports that
40689 normally deliver as the recipient. This makes sure that configurations that
40690 work in this mode function the same way in normal mode. Any implicit or
40691 explicit specification of another user causes an error.
40693 Use of &_.forward_& files is severely restricted, such that it is usually
40694 not worthwhile to include them in the configuration.
40696 Users who wish to use &_.forward_& would have to make their home directory and
40697 the file itself accessible to the Exim user. Pipe and append-to-file entries,
40698 and their equivalents in Exim filters, cannot be used. While they could be
40699 enabled in the Exim user's name, that would be insecure and not very useful.
40701 Unless the local user mailboxes are all owned by the Exim user (possible in
40702 some POP3 or IMAP-only environments):
40705 They must be owned by the Exim group and be writeable by that group. This
40706 implies you must set &%mode%& in the appendfile configuration, as well as the
40707 mode of the mailbox files themselves.
40709 You must set &%no_check_owner%&, since most or all of the files will not be
40710 owned by the Exim user.
40712 You must set &%file_must_exist%&, because Exim cannot set the owner correctly
40713 on a newly created mailbox when unprivileged. This also implies that new
40714 mailboxes need to be created manually.
40719 These restrictions severely restrict what can be done in local deliveries.
40720 However, there are no restrictions on remote deliveries. If you are running a
40721 gateway host that does no local deliveries, setting &%deliver_drop_privilege%&
40722 gives more security at essentially no cost.
40724 If you are using the &%mua_wrapper%& facility (see chapter
40725 &<<CHAPnonqueueing>>&), &%deliver_drop_privilege%& is forced to be true.
40730 .section "Delivering to local files" "SECID271"
40731 Full details of the checks applied by &(appendfile)& before it writes to a file
40732 are given in chapter &<<CHAPappendfile>>&.
40736 .section "Running local commands" "SECTsecconslocalcmds"
40737 .cindex "security" "local commands"
40738 .cindex "security" "command injection attacks"
40739 There are a number of ways in which an administrator can configure Exim to run
40740 commands based upon received, untrustworthy, data. Further, in some
40741 configurations a user who can control a &_.forward_& file can also arrange to
40742 run commands. Configuration to check includes, but is not limited to:
40745 Use of &%use_shell%& in the pipe transport: various forms of shell command
40746 injection may be possible with this option present. It is dangerous and should
40747 be used only with considerable caution. Consider constraints which whitelist
40748 allowed characters in a variable which is to be used in a pipe transport that
40749 has &%use_shell%& enabled.
40751 A number of options such as &%forbid_filter_run%&, &%forbid_filter_perl%&,
40752 &%forbid_filter_dlfunc%& and so forth which restrict facilities available to
40753 &_.forward_& files in a redirect router. If Exim is running on a central mail
40754 hub to which ordinary users do not have shell access, but home directories are
40755 NFS mounted (for instance) then administrators should review the list of these
40756 forbid options available, and should bear in mind that the options that may
40757 need forbidding can change as new features are added between releases.
40759 The &%${run...}%& expansion item does not use a shell by default, but
40760 administrators can configure use of &_/bin/sh_& as part of the command.
40761 Such invocations should be viewed with prejudicial suspicion.
40763 Administrators who use embedded Perl are advised to explore how Perl's
40764 taint checking might apply to their usage.
40766 Use of &%${expand...}%& is somewhat analogous to shell's eval builtin and
40767 administrators are well advised to view its use with suspicion, in case (for
40768 instance) it allows a local-part to contain embedded Exim directives.
40770 Use of &%${match_local_part...}%& and friends becomes more dangerous if
40771 Exim was built with EXPAND_LISTMATCH_RHS defined: the second string in
40772 each can reference arbitrary lists and files, rather than just being a list
40774 The EXPAND_LISTMATCH_RHS option was added and set false by default because of
40775 real-world security vulnerabilities caused by its use with untrustworthy data
40776 injected in, for SQL injection attacks.
40777 Consider the use of the &%inlisti%& expansion condition instead.
40783 .section "Trust in configuration data" "SECTsecconfdata"
40784 .cindex "security" "data sources"
40785 .cindex "security" "regular expressions"
40786 .cindex "regular expressions" "security"
40787 .cindex "PCRE2" "security"
40788 If configuration data for Exim can come from untrustworthy sources, there
40789 are some issues to be aware of:
40792 Use of &%${expand...}%& may provide a path for shell injection attacks.
40794 Letting untrusted data provide a regular expression is unwise.
40796 Using &%${match...}%& to apply a fixed regular expression against untrusted
40797 data may result in pathological behaviour within PCRE2. Be aware of what
40798 "backtracking" means and consider options for being more strict with a regular
40799 expression. Avenues to explore include limiting what can match (avoiding &`.`&
40800 when &`[a-z0-9]`& or other character class will do), use of atomic grouping and
40801 possessive quantifiers or just not using regular expressions against untrusted
40804 It can be important to correctly use &%${quote:...}%&,
40805 &%${quote_local_part:...}%& and &%${quote_%&<&'lookup-type'&>&%:...}%& expansion
40806 items to ensure that data is correctly constructed.
40808 Some lookups might return multiple results, even though normal usage is only
40809 expected to yield one result.
40815 .section "IPv4 source routing" "SECID272"
40816 .cindex "source routing" "in IP packets"
40817 .cindex "IP source routing"
40818 Many operating systems suppress IP source-routed packets in the kernel, but
40819 some cannot be made to do this, so Exim does its own check. It logs incoming
40820 IPv4 source-routed TCP calls, and then drops them. Things are all different in
40821 IPv6. No special checking is currently done.
40825 .section "The VRFY, EXPN, and ETRN commands in SMTP" "SECID273"
40826 Support for these SMTP commands is disabled by default. If required, they can
40827 be enabled by defining suitable ACLs.
40832 .section "Privileged users" "SECID274"
40833 .cindex "trusted users"
40834 .cindex "admin user"
40835 .cindex "privileged user"
40836 .cindex "user" "trusted"
40837 .cindex "user" "admin"
40838 Exim recognizes two sets of users with special privileges. Trusted users are
40839 able to submit new messages to Exim locally, but supply their own sender
40840 addresses and information about a sending host. For other users submitting
40841 local messages, Exim sets up the sender address from the uid, and doesn't
40842 permit a remote host to be specified.
40845 However, an untrusted user is permitted to use the &%-f%& command line option
40846 in the special form &%-f <>%& to indicate that a delivery failure for the
40847 message should not cause an error report. This affects the message's envelope,
40848 but it does not affect the &'Sender:'& header. Untrusted users may also be
40849 permitted to use specific forms of address with the &%-f%& option by setting
40850 the &%untrusted_set_sender%& option.
40852 Trusted users are used to run processes that receive mail messages from some
40853 other mail domain and pass them on to Exim for delivery either locally, or over
40854 the Internet. Exim trusts a caller that is running as root, as the Exim user,
40855 as any user listed in the &%trusted_users%& configuration option, or under any
40856 group listed in the &%trusted_groups%& option.
40858 Admin users are permitted to do things to the messages on Exim's queue. They
40859 can freeze or thaw messages, cause them to be returned to their senders, remove
40860 them entirely, or modify them in various ways. In addition, admin users can run
40861 the Exim monitor and see all the information it is capable of providing, which
40862 includes the contents of files on the spool.
40866 By default, the use of the &%-M%& and &%-q%& options to cause Exim to attempt
40867 delivery of messages on its queue is restricted to admin users. This
40868 restriction can be relaxed by setting the &%no_prod_requires_admin%& option.
40869 Similarly, the use of &%-bp%& (and its variants) to list the contents of the
40870 queue is also restricted to admin users. This restriction can be relaxed by
40871 setting &%no_queue_list_requires_admin%&.
40873 Exim recognizes an admin user if the calling process is running as root or as
40874 the Exim user or if any of the groups associated with the calling process is
40875 the Exim group. It is not necessary actually to be running under the Exim
40876 group. However, if admin users who are not root or the Exim user are to access
40877 the contents of files on the spool via the Exim monitor (which runs
40878 unprivileged), Exim must be built to allow group read access to its spool
40881 By default, regular users are trusted to perform basic testing and
40882 introspection commands, as themselves. This setting can be tightened by
40883 setting the &%commandline_checks_require_admin%& option.
40884 This affects most of the checking options,
40885 such as &%-be%& and anything else &%-b*%&.
40888 .section "Spool files" "SECID275"
40889 .cindex "spool directory" "files"
40890 Exim's spool directory and everything it contains is owned by the Exim user and
40891 set to the Exim group. The mode for spool files is defined in the
40892 &_Local/Makefile_& configuration file, and defaults to 0640. This means that
40893 any user who is a member of the Exim group can access these files.
40897 .section "Use of argv[0]" "SECID276"
40898 Exim examines the last component of &%argv[0]%&, and if it matches one of a set
40899 of specific strings, Exim assumes certain options. For example, calling Exim
40900 with the last component of &%argv[0]%& set to &"rsmtp"& is exactly equivalent
40901 to calling it with the option &%-bS%&. There are no security implications in
40906 .section "Use of %f formatting" "SECID277"
40907 The only use made of &"%f"& by Exim is in formatting load average values. These
40908 are actually stored in integer variables as 1000 times the load average.
40909 Consequently, their range is limited and so therefore is the length of the
40914 .section "Embedded Exim path" "SECID278"
40915 Exim uses its own path name, which is embedded in the code, only when it needs
40916 to re-exec in order to regain root privilege. Therefore, it is not root when it
40917 does so. If some bug allowed the path to get overwritten, it would lead to an
40918 arbitrary program's being run as exim, not as root.
40922 .section "Dynamic module directory" "SECTdynmoddir"
40923 Any dynamically loadable modules must be installed into the directory
40924 defined in &`LOOKUP_MODULE_DIR`& in &_Local/Makefile_& for Exim to permit
40928 .section "Use of sprintf()" "SECID279"
40929 .cindex "&[sprintf()]&"
40930 A large number of occurrences of &"sprintf"& in the code are actually calls to
40931 &'string_sprintf()'&, a function that returns the result in malloc'd store.
40932 The intermediate formatting is done into a large fixed buffer by a function
40933 that runs through the format string itself, and checks the length of each
40934 conversion before performing it, thus preventing buffer overruns.
40936 The remaining uses of &[sprintf()]& happen in controlled circumstances where
40937 the output buffer is known to be sufficiently long to contain the converted
40942 .section "Use of debug_printf() and log_write()" "SECID280"
40943 Arbitrary strings are passed to both these functions, but they do their
40944 formatting by calling the function &'string_vformat()'&, which runs through
40945 the format string itself, and checks the length of each conversion.
40949 .section "Use of strcat() and strcpy()" "SECID281"
40950 These are used only in cases where the output buffer is known to be large
40951 enough to hold the result.
40952 .ecindex IIDsecurcon
40957 . ////////////////////////////////////////////////////////////////////////////
40958 . ////////////////////////////////////////////////////////////////////////////
40960 .chapter "Format of spool files" "CHAPspool"
40961 .scindex IIDforspo1 "format" "spool files"
40962 .scindex IIDforspo2 "spool directory" "format of files"
40963 .scindex IIDforspo3 "spool files" "format of"
40964 .cindex "spool files" "editing"
40965 A message on Exim's queue consists of two files, whose names are the message id
40966 followed by -D and -H, respectively. The data portion of the message is kept in
40967 the -D file on its own. The message's envelope, status, and headers are all
40968 kept in the -H file, whose format is described in this chapter. Each of these
40969 two files contains the final component of its own name as its first line. This
40970 is insurance against disk crashes where the directory is lost but the files
40971 themselves are recoverable.
40973 The file formats may be changed, or new formats added, at any release.
40974 Spool files are not intended as an interface to other programs
40975 and should not be used as such.
40977 Some people are tempted into editing -D files in order to modify messages. You
40978 need to be extremely careful if you do this; it is not recommended and you are
40979 on your own if you do it. Here are some of the pitfalls:
40982 You must ensure that Exim does not try to deliver the message while you are
40983 fiddling with it. The safest way is to take out a write lock on the -D file,
40984 which is what Exim itself does, using &[fcntl()]&. If you update the file in
40985 place, the lock will be retained. If you write a new file and rename it, the
40986 lock will be lost at the instant of rename.
40988 .vindex "&$body_linecount$&"
40989 If you change the number of lines in the file, the value of
40990 &$body_linecount$&, which is stored in the -H file, will be incorrect and can
40991 cause incomplete transmission of messages or undeliverable messages.
40993 If the message is in MIME format, you must take care not to break it.
40995 If the message is cryptographically signed, any change will invalidate the
40998 All in all, modifying -D files is fraught with danger.
41000 Files whose names end with -J may also be seen in the &_input_& directory (or
41001 its subdirectories when &%split_spool_directory%& is set). These are journal
41002 files, used to record addresses to which the message has been delivered during
41003 the course of a delivery attempt. If there are still undelivered recipients at
41004 the end, the -H file is updated, and the -J file is deleted. If, however, there
41005 is some kind of crash (for example, a power outage) before this happens, the -J
41006 file remains in existence. When Exim next processes the message, it notices the
41007 -J file and uses it to update the -H file before starting the next delivery
41010 Files whose names end with -K or .eml may also be seen in the spool.
41011 These are temporaries used for DKIM or malware processing, when that is used.
41012 They should be tidied up by normal operations; any old ones are probably
41013 relics of crashes and can be removed.
41015 .section "Format of the -H file" "SECID282"
41016 .cindex "uid (user id)" "in spool file"
41017 .cindex "gid (group id)" "in spool file"
41018 The second line of the -H file contains the login name for the uid of the
41019 process that called Exim to read the message, followed by the numerical uid and
41020 gid. For a locally generated message, this is normally the user who sent the
41021 message. For a message received over TCP/IP via the daemon, it is
41022 normally the Exim user.
41024 The third line of the file contains the address of the message's sender as
41025 transmitted in the envelope, contained in angle brackets. The sender address is
41026 empty for bounce messages. For incoming SMTP mail, the sender address is given
41027 in the MAIL command. For locally generated mail, the sender address is
41028 created by Exim from the login name of the current user and the configured
41029 &%qualify_domain%&. However, this can be overridden by the &%-f%& option or a
41030 leading &"From&~"& line if the caller is trusted, or if the supplied address is
41031 &"<>"& or an address that matches &%untrusted_set_senders%&.
41033 The fourth line contains two numbers. The first is the time that the message
41034 was received, in the conventional Unix form &-- the number of seconds since the
41035 start of the epoch. The second number is a count of the number of messages
41036 warning of delayed delivery that have been sent to the sender.
41038 There follow a number of lines starting with a hyphen.
41039 These contain variables, can appear in any
41040 order, and are omitted when not relevant.
41042 If there is a second hyphen after the first,
41043 the corresponding data is tainted.
41044 If there is a value in parentheses, the data is quoted for a lookup.
41046 The following word specifies a variable,
41047 and the remainder of the item depends on the variable.
41050 .vitem "&%-acl%&&~<&'number'&>&~<&'length'&>"
41051 This item is obsolete, and is not generated from Exim release 4.61 onwards;
41052 &%-aclc%& and &%-aclm%& are used instead. However, &%-acl%& is still
41053 recognized, to provide backward compatibility. In the old format, a line of
41054 this form is present for every ACL variable that is not empty. The number
41055 identifies the variable; the &%acl_c%&&*x*& variables are numbered 0&--9 and
41056 the &%acl_m%&&*x*& variables are numbered 10&--19. The length is the length of
41057 the data string for the variable. The string itself starts at the beginning of
41058 the next line, and is followed by a newline character. It may contain internal
41061 .vitem "&%-aclc%&&~<&'rest-of-name'&>&~<&'length'&>"
41062 A line of this form is present for every ACL connection variable that is
41063 defined. Note that there is a space between &%-aclc%& and the rest of the name.
41064 The length is the length of the data string for the variable. The string itself
41065 starts at the beginning of the next line, and is followed by a newline
41066 character. It may contain internal newlines.
41068 .vitem "&%-aclm%&&~<&'rest-of-name'&>&~<&'length'&>"
41069 A line of this form is present for every ACL message variable that is defined.
41070 Note that there is a space between &%-aclm%& and the rest of the name. The
41071 length is the length of the data string for the variable. The string itself
41072 starts at the beginning of the next line, and is followed by a newline
41073 character. It may contain internal newlines.
41075 .vitem "&%-active_hostname%&&~<&'hostname'&>"
41076 This is present if, when the message was received over SMTP, the value of
41077 &$smtp_active_hostname$& was different to the value of &$primary_hostname$&.
41079 .vitem &%-allow_unqualified_recipient%&
41080 This is present if unqualified recipient addresses are permitted in header
41081 lines (to stop such addresses from being qualified if rewriting occurs at
41082 transport time). Local messages that were input using &%-bnq%& and remote
41083 messages from hosts that match &%recipient_unqualified_hosts%& set this flag.
41085 .vitem &%-allow_unqualified_sender%&
41086 This is present if unqualified sender addresses are permitted in header lines
41087 (to stop such addresses from being qualified if rewriting occurs at transport
41088 time). Local messages that were input using &%-bnq%& and remote messages from
41089 hosts that match &%sender_unqualified_hosts%& set this flag.
41091 .vitem "&%-auth_id%&&~<&'text'&>"
41092 The id information for a message received on an authenticated SMTP connection
41093 &-- the value of the &$authenticated_id$& variable.
41095 .vitem "&%-auth_sender%&&~<&'address'&>"
41096 The address of an authenticated sender &-- the value of the
41097 &$authenticated_sender$& variable.
41099 .vitem "&%-body_linecount%&&~<&'number'&>"
41100 This records the number of lines in the body of the message, and is
41101 present unless &%-spool_file_wireformat%& is.
41103 .vitem "&%-body_zerocount%&&~<&'number'&>"
41104 This records the number of binary zero bytes in the body of the message, and is
41105 present if the number is greater than zero.
41107 .vitem &%-deliver_firsttime%&
41108 This is written when a new message is first added to the spool. When the spool
41109 file is updated after a deferral, it is omitted.
41111 .vitem "&%-frozen%&&~<&'time'&>"
41112 .cindex "frozen messages" "spool data"
41113 The message is frozen, and the freezing happened at <&'time'&>.
41115 .vitem "&%-helo_name%&&~<&'text'&>"
41116 This records the host name as specified by a remote host in a HELO or EHLO
41119 .vitem "&%-host_address%&&~<&'address'&>.<&'port'&>"
41120 This records the IP address of the host from which the message was received and
41121 the remote port number that was used. It is omitted for locally generated
41124 .vitem "&%-host_auth%&&~<&'text'&>"
41125 If the message was received on an authenticated SMTP connection, this records
41126 the name of the authenticator &-- the value of the
41127 &$sender_host_authenticated$& variable.
41129 .vitem &%-host_lookup_failed%&
41130 This is present if an attempt to look up the sending host's name from its IP
41131 address failed. It corresponds to the &$host_lookup_failed$& variable.
41133 .vitem "&%-host_name%&&~<&'text'&>"
41134 .cindex "reverse DNS lookup"
41135 .cindex "DNS" "reverse lookup"
41136 This records the name of the remote host from which the message was received,
41137 if the host name was looked up from the IP address when the message was being
41138 received. It is not present if no reverse lookup was done.
41140 .vitem "&%-ident%&&~<&'text'&>"
41141 For locally submitted messages, this records the login of the originating user,
41142 unless it was a trusted user and the &%-oMt%& option was used to specify an
41143 ident value. For messages received over TCP/IP, this records the ident string
41144 supplied by the remote host, if any.
41146 .vitem "&%-interface_address%&&~<&'address'&>.<&'port'&>"
41147 This records the IP address of the local interface and the port number through
41148 which a message was received from a remote host. It is omitted for locally
41149 generated messages.
41152 The message is from a local sender.
41154 .vitem &%-localerror%&
41155 The message is a locally-generated bounce message.
41157 .vitem "&%-local_scan%&&~<&'string'&>"
41158 This records the data string that was returned by the &[local_scan()]& function
41159 when the message was received &-- the value of the &$local_scan_data$&
41160 variable. It is omitted if no data was returned.
41162 .vitem &%-manual_thaw%&
41163 The message was frozen but has been thawed manually, that is, by an explicit
41164 Exim command rather than via the auto-thaw process.
41167 A testing delivery process was started using the &%-N%& option to suppress any
41168 actual deliveries, but delivery was deferred. At any further delivery attempts,
41171 .vitem &%-received_protocol%&
41172 This records the value of the &$received_protocol$& variable, which contains
41173 the name of the protocol by which the message was received.
41175 .vitem &%-sender_set_untrusted%&
41176 The envelope sender of this message was set by an untrusted local caller (used
41177 to ensure that the caller is displayed in queue listings).
41179 .vitem "&%-spam_score_int%&&~<&'number'&>"
41180 If a message was scanned by SpamAssassin, this is present. It records the value
41181 of &$spam_score_int$&.
41183 .vitem &%-spool_file_wireformat%&
41184 The -D file for this message is in wire-format (for ESMTP CHUNKING)
41185 rather than Unix-format.
41186 The line-ending is CRLF rather than newline.
41187 There is still, however, no leading-dot-stuffing.
41189 .vitem &%-tls_certificate_verified%&
41190 A TLS certificate was received from the client that sent this message, and the
41191 certificate was verified by the server.
41193 .vitem "&%-tls_cipher%&&~<&'cipher name'&>"
41194 When the message was received over an encrypted connection, this records the
41195 name of the cipher suite that was used.
41197 .vitem "&%-tls_peerdn%&&~<&'peer DN'&>"
41198 When the message was received over an encrypted connection, and a certificate
41199 was received from the client, this records the Distinguished Name from that
41203 Following the options there is a list of those addresses to which the message
41204 is not to be delivered. This set of addresses is initialized from the command
41205 line when the &%-t%& option is used and &%extract_addresses_remove_arguments%&
41206 is set; otherwise it starts out empty. Whenever a successful delivery is made,
41207 the address is added to this set. The addresses are kept internally as a
41208 balanced binary tree, and it is a representation of that tree which is written
41209 to the spool file. If an address is expanded via an alias or forward file, the
41210 original address is added to the tree when deliveries to all its child
41211 addresses are complete.
41213 If the tree is empty, there is a single line in the spool file containing just
41214 the text &"XX"&. Otherwise, each line consists of two letters, which are either
41215 Y or N, followed by an address. The address is the value for the node of the
41216 tree, and the letters indicate whether the node has a left branch and/or a
41217 right branch attached to it, respectively. If branches exist, they immediately
41218 follow. Here is an example of a three-node tree:
41220 YY darcy@austen.fict.example
41221 NN alice@wonderland.fict.example
41222 NN editor@thesaurus.ref.example
41224 After the non-recipients tree, there is a list of the message's recipients.
41225 This is a simple list, preceded by a count. It includes all the original
41226 recipients of the message, including those to whom the message has already been
41227 delivered. In the simplest case, the list contains one address per line. For
41231 editor@thesaurus.ref.example
41232 darcy@austen.fict.example
41234 alice@wonderland.fict.example
41236 However, when a child address has been added to the top-level addresses as a
41237 result of the use of the &%one_time%& option on a &(redirect)& router, each
41238 line is of the following form:
41240 <&'top-level address'&> <&'errors_to address'&> &&&
41241 <&'length'&>,<&'parent number'&>#<&'flag bits'&>
41243 The 01 flag bit indicates the presence of the three other fields that follow
41244 the top-level address. Other bits may be used in future to support additional
41245 fields. The <&'parent number'&> is the offset in the recipients list of the
41246 original parent of the &"one time"& address. The first two fields are the
41247 envelope sender that is associated with this address and its length. If the
41248 length is zero, there is no special envelope sender (there are then two space
41249 characters in the line). A non-empty field can arise from a &(redirect)& router
41250 that has an &%errors_to%& setting.
41253 A blank line separates the envelope and status information from the headers
41254 which follow. A header may occupy several lines of the file, and to save effort
41255 when reading it in, each header is preceded by a number and an identifying
41256 character. The number is the number of characters in the header, including any
41257 embedded newlines and the terminating newline. The character is one of the
41261 .row <&'blank'&> "header in which Exim has no special interest"
41262 .row &`B`& "&'Bcc:'& header"
41263 .row &`C`& "&'Cc:'& header"
41264 .row &`F`& "&'From:'& header"
41265 .row &`I`& "&'Message-id:'& header"
41266 .row &`P`& "&'Received:'& header &-- P for &""postmark""&"
41267 .row &`R`& "&'Reply-To:'& header"
41268 .row &`S`& "&'Sender:'& header"
41269 .row &`T`& "&'To:'& header"
41270 .row &`*`& "replaced or deleted header"
41273 Deleted or replaced (rewritten) headers remain in the spool file for debugging
41274 purposes. They are not transmitted when the message is delivered. Here is a
41275 typical set of headers:
41277 111P Received: by hobbit.fict.example with local (Exim 4.00)
41278 id 14y9EI-00026G-00; Fri, 11 May 2001 10:28:59 +0100
41279 049 Message-Id: <E14y9EI-00026G-00@hobbit.fict.example>
41280 038* X-rewrote-sender: bb@hobbit.fict.example
41281 042* From: Bilbo Baggins <bb@hobbit.fict.example>
41282 049F From: Bilbo Baggins <B.Baggins@hobbit.fict.example>
41283 099* To: alice@wonderland.fict.example, rdo@foundation,
41284 darcy@austen.fict.example, editor@thesaurus.ref.example
41285 104T To: alice@wonderland.fict.example, rdo@foundation.example,
41286 darcy@austen.fict.example, editor@thesaurus.ref.example
41287 038 Date: Fri, 11 May 2001 10:28:59 +0100
41289 The asterisked headers indicate that the envelope sender, &'From:'& header, and
41290 &'To:'& header have been rewritten, the last one because routing expanded the
41291 unqualified domain &'foundation'&.
41292 .ecindex IIDforspo1
41293 .ecindex IIDforspo2
41294 .ecindex IIDforspo3
41296 .section "Format of the -D file" "SECID282a"
41297 The data file is traditionally in Unix-standard format: lines are ended with
41298 an ASCII newline character.
41299 However, when the &%spool_wireformat%& main option is used some -D files
41300 can have an alternate format.
41301 This is flagged by a &%-spool_file_wireformat%& line in the corresponding -H file.
41302 The -D file lines (not including the first name-component line) are
41303 suitable for direct copying to the wire when transmitting using the
41304 ESMTP CHUNKING option, meaning lower processing overhead.
41305 Lines are terminated with an ASCII CRLF pair.
41306 There is no dot-stuffing (and no dot-termination).
41308 . ////////////////////////////////////////////////////////////////////////////
41309 . ////////////////////////////////////////////////////////////////////////////
41311 .chapter "DKIM, SPF, SRS and DMARC" "CHAPdkim" &&&
41312 "DKIM, SPF, SRS and DMARC Support"
41314 .section "DKIM (DomainKeys Identified Mail)" SECDKIM
41317 DKIM is a mechanism by which messages sent by some entity can be provably
41318 linked to a domain which that entity controls. It permits reputation to
41319 be tracked on a per-domain basis, rather than merely upon source IP address.
41320 DKIM is documented in RFC 6376.
41322 As DKIM relies on the message being unchanged in transit, messages handled
41323 by a mailing-list (which traditionally adds to the message) will not match
41324 any original DKIM signature.
41326 DKIM support is compiled into Exim by default if TLS support is present.
41327 It can be disabled by setting DISABLE_DKIM=yes in &_Local/Makefile_&.
41329 Exim's DKIM implementation allows for
41331 Signing outgoing messages: This function is implemented in the SMTP transport.
41332 It can co-exist with all other Exim features
41333 (including transport filters)
41334 except cutthrough delivery.
41336 Verifying signatures in incoming messages: This is implemented by an additional
41337 ACL (acl_smtp_dkim), which can be called several times per message, with
41338 different signature contexts.
41341 In typical Exim style, the verification implementation does not include any
41342 default "policy". Instead it enables you to build your own policy using
41343 Exim's standard controls.
41345 Please note that verification of DKIM signatures in incoming mail is turned
41346 on by default for logging (in the <= line) purposes.
41348 Additional log detail can be enabled using the &%dkim_verbose%& log_selector.
41349 When set, for each signature in incoming email,
41350 exim will log a line displaying the most important signature details, and the
41351 signature status. Here is an example (with line-breaks added for clarity):
41353 2009-09-09 10:22:28 1MlIRf-0003LU-U3 DKIM:
41354 d=facebookmail.com s=q1-2009b
41355 c=relaxed/relaxed a=rsa-sha1
41356 i=@facebookmail.com t=1252484542 [verification succeeded]
41359 You might want to turn off DKIM verification processing entirely for internal
41360 or relay mail sources. To do that, set the &%dkim_disable_verify%& ACL
41361 control modifier. This should typically be done in the RCPT ACL, at points
41362 where you accept mail from relay sources (internal hosts or authenticated
41366 .section "Signing outgoing messages" "SECDKIMSIGN"
41367 .cindex "DKIM" "signing"
41369 For signing to be usable you must have published a DKIM record in DNS.
41370 Note that RFC 8301 (which does not cover EC keys) says:
41372 rsa-sha1 MUST NOT be used for signing or verifying.
41374 Signers MUST use RSA keys of at least 1024 bits for all keys.
41375 Signers SHOULD use RSA keys of at least 2048 bits.
41378 Note also that the key content (the 'p=' field)
41379 in the DNS record is different between RSA and EC keys;
41380 for the former it is the base64 of the ASN.1 for the RSA public key
41381 (equivalent to the private-key .pem with the header/trailer stripped)
41382 but for EC keys it is the base64 of the pure key; no ASN.1 wrapping.
41384 Signing is enabled by setting private options on the SMTP transport.
41385 These options take (expandable) strings as arguments.
41387 .option dkim_domain smtp "string list&!!" unset
41388 The domain(s) you want to sign with.
41389 After expansion, this can be a list.
41390 Each element in turn,
41392 .vindex "&$dkim_domain$&"
41393 is put into the &%$dkim_domain%& expansion variable
41394 while expanding the remaining signing options.
41395 If it is empty after expansion, DKIM signing is not done,
41396 and no error will result even if &%dkim_strict%& is set.
41398 .option dkim_selector smtp "string list&!!" unset
41399 This sets the key selector string.
41400 After expansion, which can use &$dkim_domain$&, this can be a list.
41401 Each element in turn is put in the expansion
41402 .vindex "&$dkim_selector$&"
41403 variable &%$dkim_selector%& which may be used in the &%dkim_private_key%&
41404 option along with &%$dkim_domain%&.
41405 If the option is empty after expansion, DKIM signing is not done for this domain,
41406 and no error will result even if &%dkim_strict%& is set.
41408 To do, for example, dual-signing with RSA and EC keys
41409 this could be be used:
41411 dkim_selector = ec_sel : rsa_sel
41412 dkim_private_key = KEYS_DIR/$dkim_selector
41415 .option dkim_private_key smtp string&!! unset
41416 This sets the private key to use.
41417 You can use the &%$dkim_domain%& and
41418 &%$dkim_selector%& expansion variables to determine the private key to use.
41419 The result can either
41421 be a valid RSA private key in ASCII armor (.pem file), including line breaks
41423 with GnuTLS 3.6.0 or OpenSSL 1.1.1 or later,
41424 be a valid Ed25519 private key (same format as above)
41426 start with a slash, in which case it is treated as a file that contains
41429 be "0", "false" or the empty string, in which case the message will not
41430 be signed. This case will not result in an error, even if &%dkim_strict%&
41434 To generate keys under OpenSSL:
41436 openssl genrsa -out dkim_rsa.private 2048
41437 openssl rsa -in dkim_rsa.private -out /dev/stdout -pubout -outform PEM
41439 The result file from the first command should be retained, and
41440 this option set to use it.
41441 Take the base-64 lines from the output of the second command, concatenated,
41442 for the DNS TXT record.
41443 See section 3.6 of RFC6376 for the record specification.
41447 certtool --generate-privkey --rsa --bits=2048 --password='' -8 --outfile=dkim_rsa.private
41448 certtool --load-privkey=dkim_rsa.private --pubkey-info
41451 Note that RFC 8301 says:
41453 Signers MUST use RSA keys of at least 1024 bits for all keys.
41454 Signers SHOULD use RSA keys of at least 2048 bits.
41457 EC keys for DKIM are defined by RFC 8463.
41458 They are considerably smaller than RSA keys for equivalent protection.
41459 As they are a recent development, users should consider dual-signing
41460 (by setting a list of selectors, and an expansion for this option)
41461 for some transition period.
41462 The "_CRYPTO_SIGN_ED25519" macro will be defined if support is present
41465 OpenSSL 1.1.1 and GnuTLS 3.6.0 can create Ed25519 private keys:
41467 openssl genpkey -algorithm ed25519 -out dkim_ed25519.private
41468 certtool --generate-privkey --key-type=ed25519 --outfile=dkim_ed25519.private
41471 To produce the required public key value for a DNS record:
41473 openssl pkey -outform DER -pubout -in dkim_ed25519.private | tail -c +13 | base64
41474 certtool --load_privkey=dkim_ed25519.private --pubkey_info --outder | tail -c +13 | base64
41477 Exim also supports an alternate format
41478 of Ed25519 keys in DNS which was a candidate during development
41479 of the standard, but not adopted.
41480 A future release will probably drop that support.
41482 .option dkim_hash smtp string&!! sha256
41483 Can be set to any one of the supported hash methods, which are:
41485 &`sha1`& &-- should not be used, is old and insecure
41487 &`sha256`& &-- the default
41489 &`sha512`& &-- possibly more secure but less well supported
41492 Note that RFC 8301 says:
41494 rsa-sha1 MUST NOT be used for signing or verifying.
41497 .option dkim_identity smtp string&!! unset
41498 If set after expansion, the value is used to set an "i=" tag in
41499 the signing header. The DKIM standards restrict the permissible
41500 syntax of this optional tag to a mail address, with possibly-empty
41501 local part, an @, and a domain identical to or subdomain of the "d="
41502 tag value. Note that Exim does not check the value.
41504 .option dkim_canon smtp string&!! unset
41505 This option sets the canonicalization method used when signing a message.
41506 The DKIM RFC currently supports two methods: "simple" and "relaxed".
41507 The option defaults to "relaxed" when unset. Note: the current implementation
41508 only supports signing with the same canonicalization method for both headers and body.
41510 .option dkim_strict smtp string&!! unset
41511 This option defines how Exim behaves when signing a message that
41512 should be signed fails for some reason. When the expansion evaluates to
41513 either &"1"& or &"true"&, Exim will defer. Otherwise Exim will send the message
41514 unsigned. You can use the &%$dkim_domain%& and &%$dkim_selector%& expansion
41517 .option dkim_sign_headers smtp string&!! "see below"
41518 If set, this option must expand to a colon-separated
41519 list of header names.
41520 Headers with these names, or the absence or such a header, will be included
41521 in the message signature.
41522 When unspecified, the header names listed in RFC4871 will be used,
41523 whether or not each header is present in the message.
41524 The default list is available for the expansion in the macro
41525 &"_DKIM_SIGN_HEADERS"&
41526 and an oversigning variant is in &"_DKIM_OVERSIGN_HEADERS"&.
41528 If a name is repeated, multiple headers by that name (or the absence thereof)
41529 will be signed. The textually later headers in the headers part of the
41530 message are signed first, if there are multiples.
41532 A name can be prefixed with either an &"="& or a &"+"& character.
41533 If an &"="& prefix is used, all headers that are present with this name
41535 If a &"+"& prefix if used, all headers that are present with this name
41536 will be signed, and one signature added for a missing header with the
41537 name will be appended.
41539 .option dkim_timestamps smtp integer&!! unset
41540 This option controls the inclusion of timestamp information in the signature.
41541 If not set, no such information will be included.
41542 Otherwise, must be an unsigned number giving an offset in seconds from the current time
41544 (eg. 1209600 for two weeks);
41545 both creation (t=) and expiry (x=) tags will be included.
41547 RFC 6376 lists these tags as RECOMMENDED.
41550 .section "Verifying DKIM signatures in incoming mail" "SECDKIMVFY"
41551 .cindex "DKIM" "verification"
41553 Verification of DKIM signatures in SMTP incoming email is done for all
41554 messages for which an ACL control &%dkim_disable_verify%& has not been set.
41555 .cindex DKIM "selecting signature algorithms"
41556 Individual classes of signature algorithm can be ignored by changing
41557 the main options &%dkim_verify_hashes%& or &%dkim_verify_keytypes%&.
41558 The &%dkim_verify_minimal%& option can be set to cease verification
41559 processing for a message once the first passing signature is found.
41561 .cindex authentication "expansion item"
41562 Performing verification sets up information used by the
41563 &%authresults%& expansion item.
41565 For most purposes the default option settings suffice and the remainder
41566 of this section can be ignored.
41568 The results of verification are made available to the
41569 &%acl_smtp_dkim%& ACL, which can examine and modify them.
41570 A missing ACL definition defaults to accept.
41571 By default, the ACL is called once for each
41572 syntactically(!) correct signature in the incoming message.
41573 If any ACL call does not accept, the message is not accepted.
41574 If a cutthrough delivery was in progress for the message, that is
41575 summarily dropped (having wasted the transmission effort).
41577 To evaluate the verification result in the ACL
41578 a large number of expansion variables
41579 containing the signature status and its details are set up during the
41580 runtime of the ACL.
41582 Calling the ACL only for existing signatures is not sufficient to build
41583 more advanced policies. For that reason, the main option
41584 &%dkim_verify_signers%&, and an expansion variable
41585 &%$dkim_signers%& exist.
41587 The main option &%dkim_verify_signers%& can be set to a colon-separated
41588 list of DKIM domains or identities for which the ACL &%acl_smtp_dkim%& is
41589 called. It is expanded when the message has been received. At this point,
41590 the expansion variable &%$dkim_signers%& already contains a colon-separated
41591 list of signer domains and identities for the message. When
41592 &%dkim_verify_signers%& is not specified in the main configuration,
41595 dkim_verify_signers = $dkim_signers
41597 This leads to the default behaviour of calling &%acl_smtp_dkim%& for each
41598 DKIM signature in the message. Current DKIM verifiers may want to explicitly
41599 call the ACL for known domains or identities. This would be achieved as follows:
41601 dkim_verify_signers = paypal.com:ebay.com:$dkim_signers
41603 This would result in &%acl_smtp_dkim%& always being called for "paypal.com"
41604 and "ebay.com", plus all domains and identities that have signatures in the message.
41605 You can also be more creative in constructing your policy. For example:
41607 dkim_verify_signers = $sender_address_domain:$dkim_signers
41610 If a domain or identity is listed several times in the (expanded) value of
41611 &%dkim_verify_signers%&, the ACL is only called once for that domain or identity.
41613 Note that if the option is set using untrustworthy data
41614 (such as the From: header)
41615 care should be taken to force lowercase for domains
41616 and for the domain part if identities.
41617 The default setting can be regarded as trustworthy in this respect.
41619 If multiple signatures match a domain (or identity), the ACL is called once
41620 for each matching signature.
41623 Inside the DKIM ACL, the following expansion variables are
41624 available (from most to least important):
41628 .vitem &%$dkim_cur_signer%&
41629 The signer that is being evaluated in this ACL run. This can be a domain or
41630 an identity. This is one of the list items from the expanded main option
41631 &%dkim_verify_signers%& (see above).
41633 .vitem &%$dkim_verify_status%&
41634 Within the DKIM ACL,
41635 a string describing the general status of the signature. One of
41637 &%none%&: There is no signature in the message for the current domain or
41638 identity (as reflected by &%$dkim_cur_signer%&).
41640 &%invalid%&: The signature could not be verified due to a processing error.
41641 More detail is available in &%$dkim_verify_reason%&.
41643 &%fail%&: Verification of the signature failed. More detail is
41644 available in &%$dkim_verify_reason%&.
41646 &%pass%&: The signature passed verification. It is valid.
41649 This variable can be overwritten using an ACL 'set' modifier.
41650 This might, for instance, be done to enforce a policy restriction on
41651 hash-method or key-size:
41653 warn condition = ${if eq {$dkim_verify_status}{pass}}
41654 condition = ${if eq {${length_3:$dkim_algo}}{rsa}}
41655 condition = ${if or {{eq {$dkim_algo}{rsa-sha1}} \
41656 {< {$dkim_key_length}{1024}}}}
41657 logwrite = NOTE: forcing DKIM verify fail (was pass)
41658 set dkim_verify_status = fail
41659 set dkim_verify_reason = hash too weak or key too short
41662 So long as a DKIM ACL is defined (it need do no more than accept),
41663 after all the DKIM ACL runs have completed, the value becomes a
41664 colon-separated list of the values after each run.
41665 This is maintained for the mime, prdr and data ACLs.
41667 .vitem &%$dkim_verify_reason%&
41668 A string giving a little bit more detail when &%$dkim_verify_status%& is either
41669 "fail" or "invalid". One of
41671 &%pubkey_unavailable%& (when &%$dkim_verify_status%&="invalid"): The public
41672 key for the domain could not be retrieved. This may be a temporary problem.
41674 &%pubkey_syntax%& (when &%$dkim_verify_status%&="invalid"): The public key
41675 record for the domain is syntactically invalid.
41677 &%bodyhash_mismatch%& (when &%$dkim_verify_status%&="fail"): The calculated
41678 body hash does not match the one specified in the signature header. This
41679 means that the message body was modified in transit.
41681 &%signature_incorrect%& (when &%$dkim_verify_status%&="fail"): The signature
41682 could not be verified. This may mean that headers were modified,
41683 re-written or otherwise changed in a way which is incompatible with
41684 DKIM verification. It may of course also mean that the signature is forged.
41687 This variable can be overwritten, with any value, using an ACL 'set' modifier.
41689 .vitem &%$dkim_domain%&
41690 The signing domain. IMPORTANT: This variable is only populated if there is
41691 an actual signature in the message for the current domain or identity (as
41692 reflected by &%$dkim_cur_signer%&).
41694 .vitem &%$dkim_identity%&
41695 The signing identity, if present. IMPORTANT: This variable is only populated
41696 if there is an actual signature in the message for the current domain or
41697 identity (as reflected by &%$dkim_cur_signer%&).
41699 .vitem &%$dkim_selector%&
41700 The key record selector string.
41702 .vitem &%$dkim_algo%&
41703 The algorithm used. One of 'rsa-sha1' or 'rsa-sha256'.
41704 If running under GnuTLS 3.6.0 or OpenSSL 1.1.1 or later,
41705 may also be 'ed25519-sha256'.
41706 The "_CRYPTO_SIGN_ED25519" macro will be defined if support is present
41709 Note that RFC 8301 says:
41711 rsa-sha1 MUST NOT be used for signing or verifying.
41713 DKIM signatures identified as having been signed with historic
41714 algorithms (currently, rsa-sha1) have permanently failed evaluation
41717 To enforce this you must either have a DKIM ACL which checks this variable
41718 and overwrites the &$dkim_verify_status$& variable as discussed above,
41719 or have set the main option &%dkim_verify_hashes%& to exclude
41720 processing of such signatures.
41722 .vitem &%$dkim_canon_body%&
41723 The body canonicalization method. One of 'relaxed' or 'simple'.
41725 .vitem &%$dkim_canon_headers%&
41726 The header canonicalization method. One of 'relaxed' or 'simple'.
41728 .vitem &%$dkim_copiedheaders%&
41729 A transcript of headers and their values which are included in the signature
41730 (copied from the 'z=' tag of the signature).
41731 Note that RFC6376 requires that verification fail if the From: header is
41732 not included in the signature. Exim does not enforce this; sites wishing
41733 strict enforcement should code the check explicitly.
41735 .vitem &%$dkim_bodylength%&
41736 The number of signed body bytes. If zero ("0"), the body is unsigned. If no
41737 limit was set by the signer, "9999999999999" is returned. This makes sure
41738 that this variable always expands to an integer value.
41739 &*Note:*& The presence of the signature tag specifying a signing body length
41740 is one possible route to spoofing of valid DKIM signatures.
41741 A paranoid implementation might wish to regard signature where this variable
41742 shows less than the "no limit" return as being invalid.
41744 .vitem &%$dkim_created%&
41745 UNIX timestamp reflecting the date and time when the signature was created.
41746 When this was not specified by the signer, "0" is returned.
41748 .vitem &%$dkim_expires%&
41749 UNIX timestamp reflecting the date and time when the signer wants the
41750 signature to be treated as "expired". When this was not specified by the
41751 signer, "9999999999999" is returned. This makes it possible to do useful
41752 integer size comparisons against this value.
41753 Note that Exim does not check this value.
41755 .vitem &%$dkim_headernames%&
41756 A colon-separated list of names of headers included in the signature.
41758 .vitem &%$dkim_key_testing%&
41759 "1" if the key record has the "testing" flag set, "0" if not.
41761 .vitem &%$dkim_key_nosubdomains%&
41762 "1" if the key record forbids subdomaining, "0" otherwise.
41764 .vitem &%$dkim_key_srvtype%&
41765 Service type (tag s=) from the key record. Defaults to "*" if not specified
41768 .vitem &%$dkim_key_granularity%&
41769 Key granularity (tag g=) from the key record. Defaults to "*" if not specified
41772 .vitem &%$dkim_key_notes%&
41773 Notes from the key record (tag n=).
41775 .vitem &%$dkim_key_length%&
41776 Number of bits in the key.
41777 Valid only once the key is loaded, which is at the time the header signature
41778 is verified, which is after the body hash is.
41780 Note that RFC 8301 says:
41782 Verifiers MUST NOT consider signatures using RSA keys of
41783 less than 1024 bits as valid signatures.
41786 This is enforced by the default setting for the &%dkim_verify_min_keysizes%&
41791 In addition, two ACL conditions are provided:
41794 .vitem &%dkim_signers%&
41795 ACL condition that checks a colon-separated list of domains or identities
41796 for a match against the domain or identity that the ACL is currently verifying
41797 (reflected by &%$dkim_cur_signer%&). This is typically used to restrict an ACL
41798 verb to a group of domains or identities. For example:
41801 # Warn when Mail purportedly from GMail has no gmail signature
41802 warn sender_domains = gmail.com
41803 dkim_signers = gmail.com
41805 log_message = GMail sender without gmail.com DKIM signature
41808 Note that the above does not check for a total lack of DKIM signing;
41809 for that check for empty &$h_DKIM-Signature:$& in the data ACL.
41811 .vitem &%dkim_status%&
41812 ACL condition that checks a colon-separated list of possible DKIM verification
41813 results against the actual result of verification. This is typically used
41814 to restrict an ACL verb to a list of verification outcomes, for example:
41817 deny sender_domains = paypal.com:paypal.de
41818 dkim_signers = paypal.com:paypal.de
41819 dkim_status = none:invalid:fail
41820 message = Mail from Paypal with invalid/missing signature
41823 The possible status keywords are: 'none','invalid','fail' and 'pass'. Please
41824 see the documentation of the &%$dkim_verify_status%& expansion variable above
41825 for more information of what they mean.
41831 .section "SPF (Sender Policy Framework)" SECSPF
41832 .cindex SPF verification
41834 SPF is a mechanism whereby a domain may assert which IP addresses may transmit
41835 messages with its domain in the envelope from, documented by RFC 7208.
41836 For more information on SPF see &url(http://www.open-spf.org), a static copy of
41837 the &url(http://openspf.org).
41838 . --- 2019-10-28: still not https, open-spf.org is told to be a
41839 . --- web-archive copy of the now dead openspf.org site
41840 . --- See https://www.mail-archive.com/mailop@mailop.org/msg08019.html for a
41843 Messages sent by a system not authorised will fail checking of such assertions.
41844 This includes retransmissions done by traditional forwarders.
41846 SPF verification support is built into Exim if SUPPORT_SPF=yes is set in
41847 &_Local/Makefile_&. The support uses the &_libspf2_& library
41848 &url(https://www.libspf2.org/).
41849 There is no Exim involvement in the transmission of messages;
41850 publishing certain DNS records is all that is required.
41852 For verification, an ACL condition and an expansion lookup are provided.
41853 .cindex authentication "expansion item"
41854 Performing verification sets up information used by the
41855 &%authresults%& expansion item.
41858 .cindex SPF "ACL condition"
41859 .cindex ACL "spf condition"
41860 The ACL condition "spf" can be used at or after the MAIL ACL.
41861 It takes as an argument a list of strings giving the outcome of the SPF check,
41862 and will succeed for any matching outcome.
41866 The SPF check passed, the sending host is positively verified by SPF.
41869 The SPF check failed, the sending host is NOT allowed to send mail for the
41870 domain in the envelope-from address.
41872 .vitem &%softfail%&
41873 The SPF check failed, but the queried domain can't absolutely confirm that this
41877 The queried domain does not publish SPF records.
41880 The SPF check returned a "neutral" state. This means the queried domain has
41881 published a SPF record, but wants to allow outside servers to send mail under
41882 its domain as well. This should be treated like "none".
41884 .vitem &%permerror%&
41885 This indicates a syntax error in the SPF record of the queried domain.
41886 You may deny messages when this occurs.
41888 .vitem &%temperror%&
41889 This indicates a temporary error during all processing, including Exim's
41890 SPF processing. You may defer messages when this occurs.
41893 There was an error during processing of the SPF lookup
41896 You can prefix each string with an exclamation mark to invert
41897 its meaning, for example "!fail" will match all results but
41898 "fail". The string list is evaluated left-to-right, in a
41899 short-circuit fashion.
41904 message = $sender_host_address is not allowed to send mail from \
41905 ${if def:sender_address_domain \
41906 {$sender_address_domain}{$sender_helo_name}}. \
41907 Please see http://www.open-spf.org/Why;\
41908 identity=${if def:sender_address_domain \
41909 {$sender_address}{$sender_helo_name}};\
41910 ip=$sender_host_address
41913 Note: The above mentioned URL may not be as helpful as expected. You are
41914 encouraged to replace the link with a link to a site with more
41917 When the spf condition has run, it sets up several expansion
41920 .cindex SPF "verification variables"
41922 .vitem &$spf_header_comment$&
41923 .vindex &$spf_header_comment$&
41924 This contains a human-readable string describing the outcome
41925 of the SPF check. You can add it to a custom header or use
41926 it for logging purposes.
41928 .vitem &$spf_received$&
41929 .vindex &$spf_received$&
41930 This contains a complete Received-SPF: header (name and
41931 content) that can be added to the message. Please note that
41932 according to the SPF draft, this header must be added at the
41933 top of the header list, i.e. with
41935 add_header = :at_start:$spf_received
41937 See section &<<SECTaddheadacl>>& for further details.
41939 Note: in case of "Best-guess" (see below), the convention is
41940 to put this string in a header called X-SPF-Guess: instead.
41942 .vitem &$spf_result$&
41943 .vindex &$spf_result$&
41944 This contains the outcome of the SPF check in string form,
41945 currently one of pass, fail, softfail, none, neutral, permerror,
41946 temperror, or &"(invalid)"&.
41948 .vitem &$spf_result_guessed$&
41949 .vindex &$spf_result_guessed$&
41950 This boolean is true only if a best-guess operation was used
41951 and required in order to obtain a result.
41953 .vitem &$spf_smtp_comment$&
41954 .vindex &$spf_smtp_comment$&
41955 .vindex &%spf_smtp_comment_template%&
41956 This contains a string that can be used in a SMTP response
41957 to the calling party. Useful for "fail".
41958 The string is generated by the SPF library from the template configured in the main config
41959 option &%spf_smtp_comment_template%&.
41963 .cindex SPF "ACL condition"
41964 .cindex ACL "spf_guess condition"
41965 .cindex SPF "best guess"
41966 In addition to SPF, you can also perform checks for so-called
41967 "Best-guess". Strictly speaking, "Best-guess" is not standard
41968 SPF, but it is supported by the same framework that enables SPF
41970 Refer to &url(http://www.open-spf.org/FAQ/Best_guess_record)
41971 for a description of what it means.
41972 . --- 2019-10-28: still not https:
41974 To access this feature, simply use the spf_guess condition in place
41975 of the spf one. For example:
41978 deny spf_guess = fail
41979 message = $sender_host_address doesn't look trustworthy to me
41982 In case you decide to reject messages based on this check, you
41983 should note that although it uses the same framework, "Best-guess"
41984 is not SPF, and therefore you should not mention SPF at all in your
41987 When the spf_guess condition has run, it sets up the same expansion
41988 variables as when spf condition is run, described above.
41990 Additionally, since Best-guess is not standardized, you may redefine
41991 what "Best-guess" means to you by redefining the main configuration
41992 &%spf_guess%& option.
41993 For example, the following:
41996 spf_guess = v=spf1 a/16 mx/16 ptr ?all
41999 would relax host matching rules to a broader network range.
42002 .cindex SPF "lookup expansion"
42004 A lookup expansion is also available. It takes an email
42005 address as the key and an IP address
42010 ${lookup {username@domain} spf {ip.ip.ip.ip}}
42013 The lookup will return the same result strings as can appear in
42014 &$spf_result$& (pass,fail,softfail,neutral,none,err_perm,err_temp).
42020 .section "SRS (Sender Rewriting Scheme)" SECTSRS
42021 .cindex SRS "sender rewriting scheme"
42023 SRS can be used to modify sender addresses when forwarding so that
42024 SPF verification does not object to them.
42025 It operates by encoding the original envelope sender in a new
42026 sender local part and using a domain run by the forwarding site
42027 as the new domain for the sender. Any DSN message should be returned
42028 to this new sender at the forwarding site, which can extract the
42029 original sender from the coded local part and forward the DSN to
42032 This is a way of avoiding the breakage that SPF does to forwarding.
42033 The constructed local-part will be longer than the original,
42034 leading to possible problems with very long addresses.
42035 The changing of the sender address also hinders the tracing of mail
42038 Exim can be built to include native SRS support. To do this
42039 SUPPORT_SRS=yes must be defined in &_Local/Makefile_&.
42040 If this has been done, the macros _HAVE_SRS and _HAVE_NATIVE_SRS
42042 The support is limited to SRS0-encoding; SRS1 is not supported.
42044 .cindex SRS excoding
42045 To encode an address use this expansion item:
42047 .vitem &*${srs_encode&~{*&<&'secret'&>&*}{*&<&'return&~path'&>&*}{*&<&'original&~domain'&>&*}}*&
42048 .cindex "&%srs_encode%& expansion item"
42049 .cindex SRS "expansion item"
42050 The first argument should be a secret known and used by all systems
42051 handling the recipient domain for the original message.
42052 There is no need to periodically change this key; a timestamp is also
42054 The second argument should be given as the envelope sender address before this
42055 encoding operation.
42056 If this value is empty the the expansion result will be empty.
42057 The third argument should be the recipient domain of the message when
42058 it arrived at this system.
42061 .cindex SRS decoding
42062 To decode an address use this expansion condition:
42064 .vitem &*inbound_srs&~{*&<&'local&~part'&>&*}{*&<&'secret'&>&*}*&
42065 The first argument should be the recipient local prt as is was received.
42066 The second argument is the site secret.
42068 If the messages is not for an SRS-encoded recipient the condition will
42069 return false. If it is, the condition will return true and the variable
42070 &$srs_recipient$& will be set to the decoded (original) value.
42076 SRS_SECRET = <pick something unique for your site for this. Use on all MXs.>
42082 # if outbound, and forwarding has been done, use an alternate transport
42083 domains = ! +my_domains
42084 transport = ${if eq {$local_part@$domain} \
42085 {$original_local_part@$original_domain} \
42086 {remote_smtp} {remote_forwarded_smtp}}
42091 domains = +my_domains
42092 # detect inbound bounces which are SRS'd, and decode them
42093 condition = ${if inbound_srs {$local_part} {SRS_SECRET}}
42094 data = $srs_recipient
42096 inbound_srs_failure:
42099 domains = +my_domains
42100 # detect inbound bounces which look SRS'd but are invalid
42101 condition = ${if inbound_srs {$local_part} {}}
42103 data = :fail: Invalid SRS recipient address
42105 #... further routers here
42108 # transport; should look like the non-forward outbound
42109 # one, plus the max_rcpt and return_path options
42110 remote_forwarded_smtp:
42112 # modify the envelope from, for mails that we forward
42114 return_path = ${srs_encode {SRS_SECRET} {$return_path} {$original_domain}}
42121 .section DMARC SECDMARC
42122 .cindex DMARC verification
42124 DMARC combines feedback from SPF, DKIM, and header From: in order
42125 to attempt to provide better indicators of the authenticity of an
42126 email. This document does not explain the fundamentals; you
42127 should read and understand how it works by visiting the website at
42128 &url(http://www.dmarc.org/).
42130 If Exim is built with DMARC support,
42131 the libopendmarc library is used.
42133 For building Exim yourself, obtain the library from
42134 &url(http://sourceforge.net/projects/opendmarc/)
42135 to obtain a copy, or find it in your favorite package
42136 repository. You will need to attend to the local/Makefile feature
42137 SUPPORT_DMARC and the associated LDFLAGS addition.
42138 This description assumes
42139 that headers will be in /usr/local/include, and that the libraries
42140 are in /usr/local/lib.
42144 There are three main-configuration options:
42145 .cindex DMARC "configuration options"
42147 The &%dmarc_tld_file%& option
42148 .oindex &%dmarc_tld_file%&
42149 defines the location of a text file of valid
42150 top level domains the opendmarc library uses
42151 during domain parsing. Maintained by Mozilla,
42152 the most current version can be downloaded
42153 from a link at &url(https://publicsuffix.org/list/public_suffix_list.dat).
42154 See also the util/renew-opendmarc-tlds.sh script.
42155 The default for the option is unset.
42156 If not set, DMARC processing is disabled.
42159 The &%dmarc_history_file%& option, if set
42160 .oindex &%dmarc_history_file%&
42161 defines the location of a file to log results
42162 of dmarc verification on inbound emails. The
42163 contents are importable by the opendmarc tools
42164 which will manage the data, send out DMARC
42165 reports, and expire the data. Make sure the
42166 directory of this file is writable by the user
42168 The default is unset.
42170 The &%dmarc_forensic_sender%& option
42171 .oindex &%dmarc_forensic_sender%&
42172 defines an alternate email address to use when sending a
42173 forensic report detailing alignment failures
42174 if a sender domain's dmarc record specifies it
42175 and you have configured Exim to send them.
42176 If set, this is expanded and used for the
42177 From: header line; the address is extracted
42178 from it and used for the envelope from.
42179 If not set (the default), the From: header is expanded from
42180 the dsn_from option, and <> is used for the
42183 . I wish we had subsections...
42185 .cindex DMARC controls
42186 By default, the DMARC processing will run for any remote,
42187 non-authenticated user. It makes sense to only verify DMARC
42188 status of messages coming from remote, untrusted sources. You can
42189 use standard conditions such as hosts, senders, etc, to decide that
42190 DMARC verification should *not* be performed for them and disable
42191 DMARC with an ACL control modifier:
42193 control = dmarc_disable_verify
42195 A DMARC record can also specify a "forensic address", which gives
42196 exim an email address to submit reports about failed alignment.
42197 Exim does not do this by default because in certain conditions it
42198 results in unintended information leakage (what lists a user might
42199 be subscribed to, etc). You must configure exim to submit forensic
42200 reports to the owner of the domain. If the DMARC record contains a
42201 forensic address and you specify the control statement below, then
42202 exim will send these forensic emails. It is also advised that you
42203 configure a &%dmarc_forensic_sender%& because the default sender address
42204 construction might be inadequate.
42206 control = dmarc_enable_forensic
42208 (AGAIN: You can choose not to send these forensic reports by simply
42209 not putting the dmarc_enable_forensic control line at any point in
42210 your exim config. If you don't tell exim to send them, it will not
42213 There are no options to either control. Both must appear before
42218 DMARC checks cam be run on incoming SMTP messages by using the
42219 &"dmarc_status"& ACL condition in the DATA ACL. You are required to
42220 call the &"spf"& condition first in the ACLs, then the &"dmarc_status"&
42221 condition. Putting this condition in the ACLs is required in order
42222 for a DMARC check to actually occur. All of the variables are set
42223 up before the DATA ACL, but there is no actual DMARC check that
42224 occurs until a &"dmarc_status"& condition is encountered in the ACLs.
42226 The &"dmarc_status"& condition takes a list of strings on its
42227 right-hand side. These strings describe recommended action based
42228 on the DMARC check. To understand what the policy recommendations
42229 mean, refer to the DMARC website above. Valid strings are:
42230 .itable none 0 0 2 20* left 80* left
42231 .irow &'accept'& "The DMARC check passed and the library recommends accepting the email"
42232 .irow &'reject'& "The DMARC check failed and the library recommends rejecting the email"
42233 .irow &'quarantine'& "The DMARC check failed and the library recommends keeping it for further inspection"
42234 .irow &'none'& "The DMARC check passed and the library recommends no specific action, neutral"
42235 .irow &'norecord'& "No policy section in the DMARC record for this RFC5322.From field"
42236 .irow &'nofrom'& "Unable to determine the domain of the sender"
42237 .irow &'temperror'& "Library error or dns error"
42238 .irow &'off'& "The DMARC check was disabled for this email"
42240 You can prefix each string with an exclamation mark to invert its
42241 meaning, for example "!accept" will match all results but
42242 "accept". The string list is evaluated left-to-right in a
42243 short-circuit fashion. When a string matches the outcome of the
42244 DMARC check, the condition succeeds. If none of the listed
42245 strings matches the outcome of the DMARC check, the condition
42248 Of course, you can also use any other lookup method that Exim
42249 supports, including LDAP, Postgres, MySQL, etc, as long as the
42250 result is a list of colon-separated strings.
42252 Performing the check sets up information used by the
42253 &%authresults%& expansion item.
42255 Several expansion variables are set before the DATA ACL is
42256 processed, and you can use them in this ACL. The following
42257 expansion variables are available:
42260 .vitem &$dmarc_status$&
42261 .vindex &$dmarc_status$&
42262 .cindex DMARC result
42263 A one word status indicating what the DMARC library
42264 thinks of the email. It is a combination of the results of
42265 DMARC record lookup and the SPF/DKIM/DMARC processing results
42266 (if a DMARC record was found). The actual policy declared
42267 in the DMARC record is in a separate expansion variable.
42269 .vitem &$dmarc_status_text$&
42270 .vindex &$dmarc_status_text$&
42271 Slightly longer, human readable status.
42273 .vitem &$dmarc_used_domain$&
42274 .vindex &$dmarc_used_domain$&
42275 The domain which DMARC used to look up the DMARC policy record.
42277 .vitem &$dmarc_domain_policy$&
42278 .vindex &$dmarc_domain_policy$&
42279 The policy declared in the DMARC record. Valid values
42280 are "none", "reject" and "quarantine". It is blank when there
42281 is any error, including no DMARC record.
42286 By default, Exim's DMARC configuration is intended to be
42287 non-intrusive and conservative. To facilitate this, Exim will not
42288 create any type of logging files without explicit configuration by
42289 you, the admin. Nor will Exim send out any emails/reports about
42290 DMARC issues without explicit configuration by you, the admin (other
42291 than typical bounce messages that may come about due to ACL
42292 processing or failure delivery issues).
42294 In order to log statistics suitable to be imported by the opendmarc
42295 tools, you need to:
42297 Configure the global option &%dmarc_history_file%&
42299 Configure cron jobs to call the appropriate opendmarc history
42300 import scripts and truncating the dmarc_history_file
42303 In order to send forensic reports, you need to:
42305 Configure the global option &%dmarc_forensic_sender%&
42307 Configure, somewhere before the DATA ACL, the control option to
42308 enable sending DMARC forensic reports
42316 warn domains = +local_domains
42317 hosts = +local_hosts
42318 control = dmarc_disable_verify
42320 warn !domains = +screwed_up_dmarc_records
42321 control = dmarc_enable_forensic
42323 warn condition = (lookup if destined to mailing list)
42324 set acl_m_mailing_list = 1
42327 warn dmarc_status = accept : none : off
42329 log_message = DMARC DEBUG: $dmarc_status $dmarc_used_domain
42331 warn dmarc_status = !accept
42333 log_message = DMARC DEBUG: '$dmarc_status' for $dmarc_used_domain
42335 warn dmarc_status = quarantine
42337 set $acl_m_quarantine = 1
42338 # Do something in a transport with this flag variable
42340 deny condition = ${if eq{$dmarc_domain_policy}{reject}}
42341 condition = ${if eq{$acl_m_mailing_list}{1}}
42342 message = Messages from $dmarc_used_domain break mailing lists
42344 deny dmarc_status = reject
42346 message = Message from $dmarc_used_domain failed sender's DMARC policy, REJECT
42348 warn add_header = :at_start:${authresults {$primary_hostname}}
42355 . ////////////////////////////////////////////////////////////////////////////
42356 . ////////////////////////////////////////////////////////////////////////////
42358 .chapter "Proxies" "CHAPproxies" &&&
42360 .cindex "proxy support"
42361 .cindex "proxy" "access via"
42363 A proxy is an intermediate system through which communication is passed.
42364 Proxies may provide a security, availability or load-distribution function.
42367 .section "Inbound proxies" SECTproxyInbound
42368 .cindex proxy inbound
42369 .cindex proxy "server side"
42370 .cindex proxy "Proxy protocol"
42371 .cindex "Proxy protocol" proxy
42373 Exim has support for receiving inbound SMTP connections via a proxy
42374 that uses &"Proxy Protocol"& to speak to it.
42375 To include this support, include &"SUPPORT_PROXY=yes"&
42378 It was built on the HAProxy specification, found at
42379 &url(https://www.haproxy.org/download/1.8/doc/proxy-protocol.txt).
42381 The purpose of this facility is so that an application load balancer,
42382 such as HAProxy, can sit in front of several Exim servers
42383 to distribute load.
42384 Exim uses the local protocol communication with the proxy to obtain
42385 the remote SMTP system IP address and port information.
42386 There is no logging if a host passes or
42387 fails Proxy Protocol negotiation, but it can easily be determined and
42388 recorded in an ACL (example is below).
42390 Use of a proxy is enabled by setting the &%hosts_proxy%&
42391 main configuration option to a hostlist; connections from these
42392 hosts will use Proxy Protocol.
42393 Exim supports both version 1 and version 2 of the Proxy Protocol and
42394 automatically determines which version is in use.
42396 The Proxy Protocol header is the first data received on a TCP connection
42397 and is inserted before any TLS-on-connect handshake from the client; Exim
42398 negotiates TLS between Exim-as-server and the remote client, not between
42399 Exim and the proxy server. The Proxy Protocol header must be received
42400 within &%proxy_protocol_timeout%&, which defaults to 3s.
42402 The following expansion variables are usable
42403 (&"internal"& and &"external"& here refer to the interfaces
42405 .itable none 0 0 2 30* left 70* left
42406 .irow $proxy_external_address "IP of host being proxied or IP of remote interface of proxy"
42407 .irow $proxy_external_port "Port of host being proxied or Port on remote interface of proxy"
42408 .irow $proxy_local_address "IP of proxy server inbound or IP of local interface of proxy"
42409 .irow $proxy_local_port "Port of proxy server inbound or Port on local interface of proxy"
42410 .irow $proxy_session "boolean: SMTP connection via proxy"
42412 If &$proxy_session$& is set but &$proxy_external_address$& is empty
42413 there was a protocol error.
42414 The variables &$sender_host_address$& and &$sender_host_port$&
42415 will have values for the actual client system, not the proxy.
42417 Since the real connections are all coming from the proxy, and the
42418 per host connection tracking is done before Proxy Protocol is
42419 evaluated, &%smtp_accept_max_per_host%& must be set high enough to
42420 handle all of the parallel volume you expect per inbound proxy.
42421 With the option set so high, you lose the ability
42422 to protect your server from many connections from one IP.
42423 In order to prevent your server from overload, you
42424 need to add a per connection ratelimit to your connect ACL.
42425 A possible solution is:
42427 # Set max number of connections per host
42429 # Or do some kind of IP lookup in a flat file or database
42430 # LIMIT = ${lookup{$sender_host_address}iplsearch{/etc/exim/proxy_limits}}
42432 defer ratelimit = LIMIT / 5s / per_conn / strict
42433 message = Too many connections from this IP right now
42438 .section "Outbound proxies" SECTproxySOCKS
42439 .cindex proxy outbound
42440 .cindex proxy "client side"
42441 .cindex proxy SOCKS
42442 .cindex SOCKS proxy
42443 Exim has support for sending outbound SMTP via a proxy
42444 using a protocol called SOCKS5 (defined by RFC1928).
42445 The support can be optionally included by defining SUPPORT_SOCKS=yes in
42448 Use of a proxy is enabled by setting the &%socks_proxy%& option
42449 on an smtp transport.
42450 The option value is expanded and should then be a list
42451 (colon-separated by default) of proxy specifiers.
42452 Each proxy specifier is a list
42453 (space-separated by default) where the initial element
42454 is an IP address and any subsequent elements are options.
42456 Options are a string <name>=<value>.
42457 The list of options is in the following table:
42458 .itable none 0 0 2 10* left 90* left
42459 .irow &'auth'& "authentication method"
42460 .irow &'name'& "authentication username"
42461 .irow &'pass'& "authentication password"
42462 .irow &'port'& "tcp port"
42463 .irow &'tmo'& "connection timeout"
42464 .irow &'pri'& "priority"
42465 .irow &'weight'& "selection bias"
42468 More details on each of these options follows:
42471 .cindex authentication "to proxy"
42472 .cindex proxy authentication
42473 &%auth%&: Either &"none"& (default) or &"name"&.
42474 Using &"name"& selects username/password authentication per RFC 1929
42475 for access to the proxy.
42476 Default is &"none"&.
42478 &%name%&: sets the username for the &"name"& authentication method.
42481 &%pass%&: sets the password for the &"name"& authentication method.
42484 &%port%&: the TCP port number to use for the connection to the proxy.
42487 &%tmo%&: sets a connection timeout in seconds for this proxy.
42490 &%pri%&: specifies a priority for the proxy within the list,
42491 higher values being tried first.
42492 The default priority is 1.
42494 &%weight%&: specifies a selection bias.
42495 Within a priority set servers are queried in a random fashion,
42496 weighted by this value.
42497 The default value for selection bias is 1.
42500 Proxies from the list are tried according to their priority
42501 and weight settings until one responds. The timeout for the
42502 overall connection applies to the set of proxied attempts.
42504 .section Logging SECTproxyLog
42505 To log the (local) IP of a proxy in the incoming or delivery logline,
42506 add &"+proxy"& to the &%log_selector%& option.
42507 This will add a component tagged with &"PRX="& to the line.
42509 . ////////////////////////////////////////////////////////////////////////////
42510 . ////////////////////////////////////////////////////////////////////////////
42512 .chapter "Internationalisation" "CHAPi18n" &&&
42513 "Internationalisation""
42514 .cindex internationalisation "email address"
42517 .cindex utf8 "mail name handling"
42519 Exim has support for Internationalised mail names.
42520 To include this it must be built with SUPPORT_I18N and the libidn library.
42521 Standards supported are RFCs 2060, 5890, 6530 and 6533.
42523 If Exim is built with SUPPORT_I18N_2008 (in addition to SUPPORT_I18N, not
42524 instead of it) then IDNA2008 is supported; this adds an extra library
42525 requirement, upon libidn2.
42527 .section "MTA operations" SECTi18nMTA
42528 .cindex SMTPUTF8 "ESMTP option"
42529 .cindex "ESMTP extensions" SMTPUTF8
42530 The main configuration option &%smtputf8_advertise_hosts%& specifies
42531 a host list. If this matches the sending host and
42532 accept_8bitmime is true (the default) then the ESMTP option
42533 SMTPUTF8 will be advertised.
42535 If the sender specifies the SMTPUTF8 option on a MAIL command
42536 international handling for the message is enabled and
42537 the expansion variable &$message_smtputf8$& will have value TRUE.
42539 The option &%allow_utf8_domains%& is set to true for this
42540 message. All DNS lookups are converted to a-label form
42541 whatever the setting of &%allow_utf8_domains%&
42542 when Exim is built with SUPPORT_I18N.
42544 Both localparts and domain are maintained as the original
42545 UTF-8 form internally; any comparison or regular-expression use will
42546 require appropriate care. Filenames created, eg. by
42547 the appendfile transport, will have UTF-8 names.
42549 HELO names sent by the smtp transport will have any UTF-8
42550 components expanded to a-label form,
42551 and any certificate name checks will be done using the a-label
42554 .cindex log protocol
42555 .cindex SMTPUTF8 logging
42556 .cindex i18n logging
42557 Log lines and Received-by: header lines will acquire a "utf8"
42558 prefix on the protocol element, eg. utf8esmtp.
42560 The following expansion operators can be used:
42562 ${utf8_domain_to_alabel:str}
42563 ${utf8_domain_from_alabel:str}
42564 ${utf8_localpart_to_alabel:str}
42565 ${utf8_localpart_from_alabel:str}
42568 .cindex utf8 "address downconversion"
42569 .cindex i18n "utf8 address downconversion"
42571 may use the following modifier:
42573 control = utf8_downconvert
42574 control = utf8_downconvert/<value>
42576 This sets a flag requiring that envelope addresses are converted to
42577 a-label form before smtp delivery.
42578 This is usually for use in a Message Submission Agent context,
42579 but could be used for any message.
42581 If a value is appended it may be:
42582 .itable none 0 0 2 5* right 95* left
42583 .irow &`1`& "mandatory downconversion"
42584 .irow &`0`& "no downconversion"
42585 .irow &`-1`& "if SMTPUTF8 not supported by destination host"
42587 If no value is given, 1 is used.
42589 If mua_wrapper is set, the utf8_downconvert control
42590 is initially set to -1.
42592 The smtp transport has an option &%utf8_downconvert%&.
42593 If set it must expand to one of the three values described above,
42594 or an empty string.
42595 If non-empty it overrides value previously set
42596 (due to mua_wrapper or by an ACL control).
42599 There is no explicit support for VRFY and EXPN.
42600 Configurations supporting these should inspect
42601 &$smtp_command_argument$& for an SMTPUTF8 argument.
42603 There is no support for LMTP on Unix sockets.
42604 Using the "lmtp" protocol option on an smtp transport,
42605 for LMTP over TCP, should work as expected.
42607 There is no support for DSN unitext handling,
42608 and no provision for converting logging from or to UTF-8.
42612 .section "MDA operations" SECTi18nMDA
42613 To aid in constructing names suitable for IMAP folders
42614 the following expansion operator can be used:
42616 ${imapfolder {<string>} {<sep>} {<specials>}}
42619 The string is converted from the charset specified by
42620 the "headers charset" command (in a filter file)
42621 or &%headers_charset%& main configuration option (otherwise),
42623 modified UTF-7 encoding specified by RFC 2060,
42624 with the following exception: All occurrences of <sep>
42625 (which has to be a single character)
42626 are replaced with periods ("."), and all periods and slashes that are not
42627 <sep> and are not in the <specials> string are BASE64 encoded.
42629 The third argument can be omitted, defaulting to an empty string.
42630 The second argument can be omitted, defaulting to "/".
42632 This is the encoding used by Courier for Maildir names on disk, and followed
42633 by many other IMAP servers.
42637 &`${imapfolder {Foo/Bar}} `& yields &`Foo.Bar`&
42638 &`${imapfolder {Foo/Bar}{.}{/}} `& yields &`Foo&&AC8-Bar`&
42639 &`${imapfolder {Räksmörgås}} `& yields &`R&&AOQ-ksm&&APY-rg&&AOU-s`&
42642 Note that the source charset setting is vital, and also that characters
42643 must be representable in UTF-16.
42646 . ////////////////////////////////////////////////////////////////////////////
42647 . ////////////////////////////////////////////////////////////////////////////
42649 .chapter "Events" "CHAPevents" &&&
42653 The events mechanism in Exim can be used to intercept processing at a number
42654 of points. It was originally invented to give a way to do customised logging
42655 actions (for example, to a database) but can also be used to modify some
42656 processing actions.
42658 Most installations will never need to use Events.
42659 The support can be left out of a build by defining DISABLE_EVENT=yes
42660 in &_Local/Makefile_&.
42662 There are two major classes of events: main and transport.
42663 The main configuration option &%event_action%& controls reception events;
42664 a transport option &%event_action%& controls delivery events.
42666 Both options are a string which is expanded when the event fires.
42667 An example might look like:
42668 .cindex logging custom
42670 event_action = ${if eq {msg:delivery}{$event_name} \
42671 {${lookup pgsql {SELECT * FROM record_Delivery( \
42672 '${quote_pgsql:$sender_address_domain}',\
42673 '${quote_pgsql:${lc:$sender_address_local_part}}', \
42674 '${quote_pgsql:$domain}', \
42675 '${quote_pgsql:${lc:$local_part}}', \
42676 '${quote_pgsql:$host_address}', \
42677 '${quote_pgsql:${lc:$host}}', \
42678 '${quote_pgsql:$message_exim_id}')}} \
42682 Events have names which correspond to the point in process at which they fire.
42683 The name is placed in the variable &$event_name$& and the event action
42684 expansion must check this, as it will be called for every possible event type.
42686 The current list of events is:
42687 .itable all 0 0 4 25* left 10* center 15* center 50* left
42688 .row dane:fail after transport "per connection"
42689 .row msg:complete after main "per message"
42690 .row msg:defer after transport "per message per delivery try"
42691 .row msg:delivery after transport "per recipient"
42692 .row msg:rcpt:host:defer after transport "per recipient per host"
42693 .row msg:rcpt:defer after transport "per recipient"
42694 .row msg:host:defer after transport "per host per delivery try; host errors"
42695 .row msg:fail:delivery after transport "per recipient"
42696 .row msg:fail:internal after main "per recipient"
42697 .row tcp:connect before transport "per connection"
42698 .row tcp:close after transport "per connection"
42699 .row tls:cert before both "per certificate in verification chain"
42700 .row tls:fail:connect after main "per connection"
42701 .row smtp:connect after transport "per connection"
42702 .row smtp:ehlo after transport "per connection"
42704 New event types may be added in future.
42706 The event name is a colon-separated list, defining the type of
42707 event in a tree of possibilities. It may be used as a list
42708 or just matched on as a whole. There will be no spaces in the name.
42710 The second column in the table above describes whether the event fires
42711 before or after the action is associates with. Those which fire before
42712 can be used to affect that action (more on this below).
42714 The third column in the table above says what section of the configuration
42715 should define the event action.
42717 An additional variable, &$event_data$&, is filled with information varying
42718 with the event type:
42719 .itable all 0 0 2 20* left 80* left
42720 .row dane:fail "failure reason"
42721 .row msg:defer "error string"
42722 .row msg:delivery "smtp confirmation message"
42723 .row msg:fail:internal "failure reason"
42724 .row msg:fail:delivery "smtp error message"
42725 .row msg:host:defer "error string"
42726 .row msg:rcpt:host:defer "error string"
42727 .row msg:rcpt:defer "error string"
42728 .row tls:cert "verification chain depth"
42729 .row tls:fail:connect "error string"
42730 .row smtp:connect "smtp banner"
42731 .row smtp:ehlo "smtp ehlo response"
42734 The :defer events populate one extra variable: &$event_defer_errno$&.
42736 For complex operations an ACL expansion can be used in &%event_action%&,
42737 however due to the multiple contexts that Exim operates in during
42738 the course of its processing:
42740 variables set in transport events will not be visible outside that
42743 acl_m variables in a server context are lost on a new connection,
42744 and after smtp helo/ehlo/mail/starttls/rset commands
42746 Using an ACL expansion with the logwrite modifier can be
42747 a useful way of writing to the main log.
42749 The expansion of the event_action option should normally
42750 return an empty string. Should it return anything else the
42751 following will be forced:
42752 .itable all 0 0 2 20* left 80* left
42753 .row tcp:connect "do not connect"
42754 .row tls:cert "refuse verification"
42755 .row smtp:connect "close connection"
42757 All other message types ignore the result string, and
42758 no other use is made of it.
42760 For a tcp:connect event, if the connection is being made to a proxy
42761 then the address and port variables will be that of the proxy and not
42764 For tls:cert events, if GnuTLS is in use this will trigger only per
42765 chain element received on the connection.
42766 For OpenSSL it will trigger for every chain element including those
42769 . ////////////////////////////////////////////////////////////////////////////
42770 . ////////////////////////////////////////////////////////////////////////////
42772 .chapter "Adding new drivers or lookup types" "CHID13" &&&
42773 "Adding drivers or lookups"
42774 .cindex "adding drivers"
42775 .cindex "new drivers, adding"
42776 .cindex "drivers" "adding new"
42777 The following actions have to be taken in order to add a new router, transport,
42778 authenticator, or lookup type to Exim:
42781 Choose a name for the driver or lookup type that does not conflict with any
42782 existing name; I will use &"newdriver"& in what follows.
42784 Add to &_src/EDITME_& the line:
42786 <&'type'&>&`_NEWDRIVER=yes`&
42788 where <&'type'&> is ROUTER, TRANSPORT, AUTH, or LOOKUP. If the
42789 code is not to be included in the binary by default, comment this line out. You
42790 should also add any relevant comments about the driver or lookup type.
42792 Add to &_src/config.h.defaults_& the line:
42794 #define <type>_NEWDRIVER
42797 Edit &_src/drtables.c_&, adding conditional code to pull in the private header
42798 and create a table entry as is done for all the other drivers and lookup types.
42800 Edit &_scripts/lookups-Makefile_& if this is a new lookup; there is a for-loop
42801 near the bottom, ranging the &`name_mod`& variable over a list of all lookups.
42802 Add your &`NEWDRIVER`& to that list.
42803 As long as the dynamic module would be named &_newdriver.so_&, you can use the
42804 simple form that most lookups have.
42806 Edit &_Makefile_& in the appropriate sub-directory (&_src/routers_&,
42807 &_src/transports_&, &_src/auths_&, or &_src/lookups_&); add a line for the new
42808 driver or lookup type and add it to the definition of OBJ.
42810 Edit &_OS/Makefile-Base_& adding a &_.o_& file for the predefined-macros, to the
42811 definition of OBJ_MACRO. Add a set of line to do the compile also.
42813 Create &_newdriver.h_& and &_newdriver.c_& in the appropriate sub-directory of
42816 Edit &_scripts/MakeLinks_& and add commands to link the &_.h_& and &_.c_& files
42817 as for other drivers and lookups.
42820 Then all you need to do is write the code! A good way to start is to make a
42821 proforma by copying an existing module of the same type, globally changing all
42822 occurrences of the name, and cutting out most of the code. Note that any
42823 options you create must be listed in alphabetical order, because the tables are
42824 searched using a binary chop procedure.
42826 There is a &_README_& file in each of the sub-directories of &_src_& describing
42827 the interface that is expected.
42832 . ////////////////////////////////////////////////////////////////////////////
42833 . ////////////////////////////////////////////////////////////////////////////
42835 . /////////////////////////////////////////////////////////////////////////////
42836 . These lines are processing instructions for the Simple DocBook Processor that
42837 . Philip Hazel has developed as a less cumbersome way of making PostScript and
42838 . PDFs than using xmlto and fop. They will be ignored by all other XML
42840 . /////////////////////////////////////////////////////////////////////////////
42845 foot_right_recto="&chaptertitle;"
42846 foot_right_verso="&chaptertitle;"
42850 .makeindex "Options index" "option"
42851 .makeindex "Variables index" "variable"
42852 .makeindex "Concept index" "concept"
42855 . /////////////////////////////////////////////////////////////////////////////
42856 . /////////////////////////////////////////////////////////////////////////////