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.
221 . These do not turn up in the HTML output, unfortunately. The PDF does get them.
222 . - Worse - they introduce bugus index entries in the HTML, under the
223 . "primary term", a link to the Introduction chapter.
224 . /////////////////////////////////////////////////////////////////////////////
226 .chapter "Introduction" "CHID1"
230 <indexterm role="$2">
231 <primary>$3</primary>
233 <secondary>$5</secondary>
235 <$1><emphasis>$4</emphasis></$1>
240 . NB: for the 4-arg variant the ordering is awkward
242 .seeother see "$1" "$2" "$3" "$4"
245 .seeother seealso "$1" "$2" "$3" "$4"
248 .see variable "<emphasis>$1</emphasis>, <emphasis>$2</emphasis>, etc." "numerical variables"
249 .see concept address rewriting rewriting
250 .see concept "Bounce Address Tag Validation" BATV
251 .see concept "Client SMTP Authorization" CSA
252 .see concept "CR character" "carriage return"
253 .see concept CRL "certificate revocation list"
254 .seealso concept de-tainting "tainted data"
255 .see concept delivery "bounce message" "failure report"
256 .see concept dialup "intermittently connected hosts"
257 .see concept exiscan "content scanning"
258 .see concept fallover fallback
259 .see concept filter "Sieve filter" Sieve
260 .see concept headers "header lines"
261 .see concept ident "RFC 1413"
262 .see concept "LF character" "linefeed"
263 .seealso concept maximum limit
264 .see concept monitor "Exim monitor"
265 .see concept "no_<emphasis>xxx</emphasis>" "entry for xxx"
266 .see concept NUL "binary zero"
267 .see concept "passwd file" "/etc/passwd"
268 .see concept "process id" pid
269 .see concept RBL "DNS list"
270 .see concept redirection "address redirection"
271 .see concept "return path" "envelope sender"
272 .see concept scanning "content scanning"
274 .see concept string expansion expansion
275 .see concept "top bit" "8-bit characters"
276 .see concept variables "expansion, variables"
277 .see concept "zero, binary" "binary zero"
280 . /////////////////////////////////////////////////////////////////////////////
281 . This is the real start of the first chapter. See the comment above as to why
282 . we can't have the .chapter line here.
283 . chapter "Introduction"
284 . /////////////////////////////////////////////////////////////////////////////
286 Exim is a mail transfer agent (MTA) for hosts that are running Unix or
287 Unix-like operating systems. It was designed on the assumption that it would be
288 run on hosts that are permanently connected to the Internet. However, it can be
289 used on intermittently connected hosts with suitable configuration adjustments.
291 Configuration files currently exist for the following operating systems: AIX,
292 BSD/OS (aka BSDI), Darwin (Mac OS X), DGUX, Dragonfly, FreeBSD, GNU/Hurd,
293 GNU/Linux, HI-OSF (Hitachi), HI-UX, HP-UX, IRIX, MIPS RISCOS, NetBSD, OpenBSD,
294 OpenUNIX, QNX, SCO, SCO SVR4.2 (aka UNIX-SV), Solaris (aka SunOS5), SunOS4,
295 Tru64-Unix (formerly Digital UNIX, formerly DEC-OSF1), Ultrix, and UnixWare.
296 Some of these operating systems are no longer current and cannot easily be
297 tested, so the configuration files may no longer work in practice.
299 There are also configuration files for compiling Exim in the Cygwin environment
300 that can be installed on systems running Windows. However, this document does
301 not contain any information about running Exim in the Cygwin environment.
303 The terms and conditions for the use and distribution of Exim are contained in
304 the file &_NOTICE_&. Exim is distributed under the terms of the GNU General
305 Public Licence, a copy of which may be found in the file &_LICENCE_&.
307 The use, supply, or promotion of Exim for the purpose of sending bulk,
308 unsolicited electronic mail is incompatible with the basic aims of Exim,
309 which revolve around the free provision of a service that enhances the quality
310 of personal communications. The author of Exim regards indiscriminate
311 mass-mailing as an antisocial, irresponsible abuse of the Internet.
313 Exim owes a great deal to Smail 3 and its author, Ron Karr. Without the
314 experience of running and working on the Smail 3 code, I could never have
315 contemplated starting to write a new MTA. Many of the ideas and user interfaces
316 were originally taken from Smail 3, though the actual code of Exim is entirely
317 new, and has developed far beyond the initial concept.
319 Many people, both in Cambridge and around the world, have contributed to the
320 development and the testing of Exim, and to porting it to various operating
321 systems. I am grateful to them all. The distribution now contains a file called
322 &_ACKNOWLEDGMENTS_&, in which I have started recording the names of
326 .section "Exim documentation" "SECID1"
327 . Keep this example change bar when updating the documentation!
330 .cindex "documentation"
331 This edition of the Exim specification applies to version &version() of Exim.
332 Substantive changes from the &previousversion; edition are marked in some
333 renditions of this document; this paragraph is so marked if the rendition is
334 capable of showing a change indicator.
337 This document is very much a reference manual; it is not a tutorial. The reader
338 is expected to have some familiarity with the SMTP mail transfer protocol and
339 with general Unix system administration. Although there are some discussions
340 and examples in places, the information is mostly organized in a way that makes
341 it easy to look up, rather than in a natural order for sequential reading.
342 Furthermore, this manual aims to cover every aspect of Exim in detail, including
343 a number of rarely-used, special-purpose features that are unlikely to be of
346 .cindex "books about Exim"
347 An &"easier"& discussion of Exim which provides more in-depth explanatory,
348 introductory, and tutorial material can be found in a book entitled &'The Exim
349 SMTP Mail Server'& (second edition, 2007), published by UIT Cambridge
350 (&url(https://www.uit.co.uk/exim-book/)).
352 The book also contains a chapter that gives a general introduction to SMTP and
353 Internet mail. Inevitably, however, the book is unlikely to be fully up-to-date
354 with the latest release of Exim. (Note that the earlier book about Exim,
355 published by O'Reilly, covers Exim 3, and many things have changed in Exim 4.)
357 .cindex "Debian" "information sources"
358 If you are using a Debian distribution of Exim, you will find information about
359 Debian-specific features in the file
360 &_/usr/share/doc/exim4-base/README.Debian_&.
361 The command &(man update-exim.conf)& is another source of Debian-specific
364 .cindex "&_doc/NewStuff_&"
365 .cindex "&_doc/ChangeLog_&"
367 As Exim develops, there may be features in newer versions that have not
368 yet made it into this document, which is updated only when the most significant
369 digit of the fractional part of the version number changes. Specifications of
370 new features that are not yet in this manual are placed in the file
371 &_doc/NewStuff_& in the Exim distribution.
373 Some features may be classified as &"experimental"&. These may change
374 incompatibly while they are developing, or even be withdrawn. For this reason,
375 they are not documented in this manual. Information about experimental features
376 can be found in the file &_doc/experimental.txt_&.
378 All changes to Exim (whether new features, bug fixes, or other kinds of
379 change) are noted briefly in the file called &_doc/ChangeLog_&.
381 .cindex "&_doc/spec.txt_&"
382 This specification itself is available as an ASCII file in &_doc/spec.txt_& so
383 that it can easily be searched with a text editor. Other files in the &_doc_&
387 .row &_OptionLists.txt_& "list of all options in alphabetical order"
388 .row &_dbm.discuss.txt_& "discussion about DBM libraries"
389 .row &_exim.8_& "a man page of Exim's command line options"
390 .row &_experimental.txt_& "documentation of experimental features"
391 .row &_filter.txt_& "specification of the filter language"
392 .row &_Exim3.upgrade_& "upgrade notes from release 2 to release 3"
393 .row &_Exim4.upgrade_& "upgrade notes from release 3 to release 4"
394 .row &_openssl.txt_& "installing a current OpenSSL release"
397 The main specification and the specification of the filtering language are also
398 available in other formats (HTML, PostScript, PDF, and Texinfo). Section
399 &<<SECTavail>>& below tells you how to get hold of these.
403 .section "FTP site and websites" "SECID2"
406 The primary site for Exim source distributions is the &%exim.org%& FTP site,
407 available over HTTPS, HTTP and FTP. These services, and the &%exim.org%&
408 website, are hosted at the University of Cambridge.
412 As well as Exim distribution tar files, the Exim website contains a number of
413 differently formatted versions of the documentation. A recent addition to the
414 online information is the Exim wiki (&url(https://wiki.exim.org)),
415 which contains what used to be a separate FAQ, as well as various other
416 examples, tips, and know-how that have been contributed by Exim users.
417 The wiki site should always redirect to the correct place, which is currently
418 provided by GitHub, and is open to editing by anyone with a GitHub account.
421 An Exim Bugzilla exists at &url(https://bugs.exim.org). You can use
422 this to report bugs, and also to add items to the wish list. Please search
423 first to check that you are not duplicating a previous entry.
424 Please do not ask for configuration help in the bug-tracker.
427 .section "Mailing lists" "SECID3"
428 .cindex "mailing lists" "for Exim users"
429 The following Exim mailing lists exist:
432 .row &'exim-announce@exim.org'& "Moderated, low volume announcements list"
433 .row &'exim-users@exim.org'& "General discussion list"
434 .row &'exim-dev@exim.org'& "Discussion of bugs, enhancements, etc."
435 .row &'exim-cvs@exim.org'& "Automated commit messages from the VCS"
438 You can subscribe to these lists, change your existing subscriptions, and view
439 or search the archives via the mailing lists link on the Exim home page.
440 .cindex "Debian" "mailing list for"
441 If you are using a Debian distribution of Exim, you may wish to subscribe to
442 the Debian-specific mailing list &'pkg-exim4-users@lists.alioth.debian.org'&
445 &url(https://alioth-lists.debian.net/cgi-bin/mailman/listinfo/pkg-exim4-users)
447 Please ask Debian-specific questions on that list and not on the general Exim
450 .section "Bug reports" "SECID5"
451 .cindex "bug reports"
452 .cindex "reporting bugs"
453 Reports of obvious bugs can be emailed to &'bugs@exim.org'& or reported
454 via the Bugzilla (&url(https://bugs.exim.org)). However, if you are unsure
455 whether some behaviour is a bug or not, the best thing to do is to post a
456 message to the &'exim-dev'& mailing list and have it discussed.
460 .section "Where to find the Exim distribution" "SECTavail"
462 .cindex "HTTPS download site"
463 .cindex "distribution" "FTP site"
464 .cindex "distribution" "https site"
465 The master distribution site for the Exim distribution is
467 &url(https://downloads.exim.org/)
469 The service is available over HTTPS, HTTP and FTP.
470 We encourage people to migrate to HTTPS.
472 The content served at &url(https://downloads.exim.org/) is identical to the
473 content served at &url(https://ftp.exim.org/pub/exim) and
474 &url(ftp://ftp.exim.org/pub/exim).
476 If accessing via a hostname containing &'ftp'&, then the file references that
477 follow are relative to the &_exim_& directories at these sites.
478 If accessing via the hostname &'downloads'& then the subdirectories described
479 here are top-level directories.
481 There are now quite a number of independent mirror sites around
482 the world. Those that I know about are listed in the file called &_Mirrors_&.
484 Within the top exim directory there are subdirectories called &_exim3_& (for
485 previous Exim 3 distributions), &_exim4_& (for the latest Exim 4
486 distributions), and &_Testing_& for testing versions. In the &_exim4_&
487 subdirectory, the current release can always be found in files called
491 &_exim-n.nn.tar.bz2_&
493 where &'n.nn'& is the highest such version number in the directory. The three
494 files contain identical data; the only difference is the type of compression.
495 The &_.xz_& file is usually the smallest, while the &_.gz_& file is the
496 most portable to old systems.
498 .cindex "distribution" "signing details"
499 .cindex "distribution" "public key"
500 .cindex "public key for signed distribution"
501 The distributions will be PGP signed by an individual key of the Release
502 Coordinator. This key will have a uid containing an email address in the
503 &'exim.org'& domain and will have signatures from other people, including
504 other Exim maintainers. We expect that the key will be in the "strong set" of
505 PGP keys. There should be a trust path to that key from the Exim Maintainer's
506 PGP keys, a version of which can be found in the release directory in the file
507 &_Exim-Maintainers-Keyring.asc_&. All keys used will be available in public keyserver pools,
508 such as &'pool.sks-keyservers.net'&.
510 At the time of the last update, releases were being made by Jeremy Harris and signed
511 with key &'0xBCE58C8CE41F32DF'&. Other recent keys used for signing are those
512 of Heiko Schlittermann, &'0x26101B62F69376CE'&,
513 and of Phil Pennock, &'0x4D1E900E14C1CC04'&.
515 The signatures for the tar bundles are in:
517 &_exim-n.nn.tar.xz.asc_&
518 &_exim-n.nn.tar.gz.asc_&
519 &_exim-n.nn.tar.bz2.asc_&
521 For each released version, the log of changes is made available in a
522 separate file in the directory &_ChangeLogs_& so that it is possible to
523 find out what has changed without having to download the entire distribution.
525 .cindex "documentation" "available formats"
526 The main distribution contains ASCII versions of this specification and other
527 documentation; other formats of the documents are available in separate files
528 inside the &_exim4_& directory of the FTP site:
530 &_exim-html-n.nn.tar.gz_&
531 &_exim-pdf-n.nn.tar.gz_&
532 &_exim-postscript-n.nn.tar.gz_&
533 &_exim-texinfo-n.nn.tar.gz_&
535 These tar files contain only the &_doc_& directory, not the complete
536 distribution, and are also available in &_.bz2_& and &_.xz_& forms.
539 .section "Limitations" "SECID6"
541 .cindex "limitations of Exim"
542 .cindex "bang paths" "not handled by Exim"
543 Exim is designed for use as an Internet MTA, and therefore handles addresses in
544 RFC 2822 domain format only. It cannot handle UUCP &"bang paths"&, though
545 simple two-component bang paths can be converted by a straightforward rewriting
546 configuration. This restriction does not prevent Exim from being interfaced to
547 UUCP as a transport mechanism, provided that domain addresses are used.
549 .cindex "domainless addresses"
550 .cindex "address" "without domain"
551 Exim insists that every address it handles has a domain attached. For incoming
552 local messages, domainless addresses are automatically qualified with a
553 configured domain value. Configuration options specify from which remote
554 systems unqualified addresses are acceptable. These are then qualified on
557 .cindex "transport" "external"
558 .cindex "external transports"
559 The only external transport mechanisms that are currently implemented are SMTP
560 and LMTP over a TCP/IP network (including support for IPv6). However, a pipe
561 transport is available, and there are facilities for writing messages to files
562 and pipes, optionally in &'batched SMTP'& format; these facilities can be used
563 to send messages to other transport mechanisms such as UUCP, provided they can
564 handle domain-style addresses. Batched SMTP input is also catered for.
566 Exim is not designed for storing mail for dial-in hosts. When the volumes of
567 such mail are large, it is better to get the messages &"delivered"& into files
568 (that is, off Exim's queue) and subsequently passed on to the dial-in hosts by
571 Although Exim does have basic facilities for scanning incoming messages, these
572 are not comprehensive enough to do full virus or spam scanning. Such operations
573 are best carried out using additional specialized software packages. If you
574 compile Exim with the content-scanning extension, straightforward interfaces to
575 a number of common scanners are provided.
579 .section "Runtime configuration" "SECID7"
580 Exim's runtime configuration is held in a single text file that is divided
581 into a number of sections. The entries in this file consist of keywords and
582 values, in the style of Smail 3 configuration files. A default configuration
583 file which is suitable for simple online installations is provided in the
584 distribution, and is described in chapter &<<CHAPdefconfil>>& below.
587 .section "Calling interface" "SECID8"
588 .cindex "Sendmail compatibility" "command line interface"
589 Like many MTAs, Exim has adopted the Sendmail command line interface so that it
590 can be a straight replacement for &_/usr/lib/sendmail_& or
591 &_/usr/sbin/sendmail_& when sending mail, but you do not need to know anything
592 about Sendmail in order to run Exim. For actions other than sending messages,
593 Sendmail-compatible options also exist, but those that produce output (for
594 example, &%-bp%&, which lists the messages in the queue) do so in Exim's own
595 format. There are also some additional options that are compatible with Smail
596 3, and some further options that are new to Exim. Chapter &<<CHAPcommandline>>&
597 documents all Exim's command line options. This information is automatically
598 made into the man page that forms part of the Exim distribution.
600 Control of messages in the queue can be done via certain privileged command
601 line options. There is also an optional monitor program called &'eximon'&,
602 which displays current information in an X window, and which contains a menu
603 interface to Exim's command line administration options.
607 .section "Terminology" "SECID9"
608 .cindex "terminology definitions"
609 .cindex "body of message" "definition of"
610 The &'body'& of a message is the actual data that the sender wants to transmit.
611 It is the last part of a message and is separated from the &'header'& (see
612 below) by a blank line.
614 .cindex "bounce message" "definition of"
615 When a message cannot be delivered, it is normally returned to the sender in a
616 delivery failure message or a &"non-delivery report"& (NDR). The term
617 &'bounce'& is commonly used for this action, and the error reports are often
618 called &'bounce messages'&. This is a convenient shorthand for &"delivery
619 failure error report"&. Such messages have an empty sender address in the
620 message's &'envelope'& (see below) to ensure that they cannot themselves give
621 rise to further bounce messages.
623 The term &'default'& appears frequently in this manual. It is used to qualify a
624 value which is used in the absence of any setting in the configuration. It may
625 also qualify an action which is taken unless a configuration setting specifies
628 The term &'defer'& is used when the delivery of a message to a specific
629 destination cannot immediately take place for some reason (a remote host may be
630 down, or a user's local mailbox may be full). Such deliveries are &'deferred'&
633 The word &'domain'& is sometimes used to mean all but the first component of a
634 host's name. It is &'not'& used in that sense here, where it normally refers to
635 the part of an email address following the @ sign.
637 .cindex "envelope, definition of"
638 .cindex "sender" "definition of"
639 A message in transit has an associated &'envelope'&, as well as a header and a
640 body. The envelope contains a sender address (to which bounce messages should
641 be delivered), and any number of recipient addresses. References to the
642 sender or the recipients of a message usually mean the addresses in the
643 envelope. An MTA uses these addresses for delivery, and for returning bounce
644 messages, not the addresses that appear in the header lines.
646 .cindex "message" "header, definition of"
647 .cindex "header section" "definition of"
648 The &'header'& of a message is the first part of a message's text, consisting
649 of a number of lines, each of which has a name such as &'From:'&, &'To:'&,
650 &'Subject:'&, etc. Long header lines can be split over several text lines by
651 indenting the continuations. The header is separated from the body by a blank
654 .cindex "local part" "definition of"
655 .cindex "domain" "definition of"
656 The term &'local part'&, which is taken from RFC 2822, is used to refer to the
657 part of an email address that precedes the @ sign. The part that follows the
658 @ sign is called the &'domain'& or &'mail domain'&.
660 .cindex "local delivery" "definition of"
661 .cindex "remote delivery, definition of"
662 The terms &'local delivery'& and &'remote delivery'& are used to distinguish
663 delivery to a file or a pipe on the local host from delivery by SMTP over
664 TCP/IP to another host. As far as Exim is concerned, all hosts other than the
665 host it is running on are &'remote'&.
667 .cindex "return path" "definition of"
668 &'Return path'& is another name that is used for the sender address in a
671 .cindex "queue" "definition of"
672 The term &'queue'& is used to refer to the set of messages awaiting delivery
673 because this term is in widespread use in the context of MTAs. However, in
674 Exim's case, the reality is more like a pool than a queue, because there is
675 normally no ordering of waiting messages.
677 .cindex "queue runner" "definition of"
678 The term &'queue runner'& is used to describe a process that scans the queue
679 and attempts to deliver those messages whose retry times have come. This term
680 is used by other MTAs and also relates to the command &%runq%&, but in Exim
681 the waiting messages are normally processed in an unpredictable order.
683 .cindex "spool directory" "definition of"
684 The term &'spool directory'& is used for a directory in which Exim keeps the
685 messages in its queue &-- that is, those that it is in the process of
686 delivering. This should not be confused with the directory in which local
687 mailboxes are stored, which is called a &"spool directory"& by some people. In
688 the Exim documentation, &"spool"& is always used in the first sense.
695 . ////////////////////////////////////////////////////////////////////////////
696 . ////////////////////////////////////////////////////////////////////////////
698 .chapter "Incorporated code" "CHID2"
699 .cindex "incorporated code"
700 .cindex "regular expressions" "library"
703 A number of pieces of external code are included in the Exim distribution.
706 Regular expressions are supported in the main Exim program and in the
707 Exim monitor using the freely-distributable PCRE2 library, copyright
708 © University of Cambridge. The source to PCRE2 is not longer shipped with
709 Exim, so you will need to use the version of PCRE2 shipped with your system,
710 or obtain and install the full version of the library from
711 &url(https://github.com/PhilipHazel/pcre2/releases).
713 .cindex "cdb" "acknowledgment"
714 Support for the cdb (Constant DataBase) lookup method is provided by code
715 contributed by Nigel Metheringham of (at the time he contributed it) Planet
716 Online Ltd. The implementation is completely contained within the code of Exim.
717 It does not link against an external cdb library. The code contains the
718 following statements:
721 Copyright © 1998 Nigel Metheringham, Planet Online Ltd
723 This program is free software; you can redistribute it and/or modify it under
724 the terms of the GNU General Public License as published by the Free Software
725 Foundation; either version 2 of the License, or (at your option) any later
727 This code implements Dan Bernstein's Constant DataBase (cdb) spec. Information,
728 the spec and sample code for cdb can be obtained from
729 &url(https://cr.yp.to/cdb.html). This implementation borrows
730 some code from Dan Bernstein's implementation (which has no license
731 restrictions applied to it).
734 .cindex "SPA authentication"
735 .cindex "Samba project"
736 .cindex "Microsoft Secure Password Authentication"
737 Client support for Microsoft's &'Secure Password Authentication'& is provided
738 by code contributed by Marc Prud'hommeaux. Server support was contributed by
739 Tom Kistner. This includes code taken from the Samba project, which is released
743 .cindex "&'pwcheck'& daemon"
744 .cindex "&'pwauthd'& daemon"
745 Support for calling the Cyrus &'pwcheck'& and &'saslauthd'& daemons is provided
746 by code taken from the Cyrus-SASL library and adapted by Alexander S.
747 Sabourenkov. The permission notice appears below, in accordance with the
748 conditions expressed therein.
751 Copyright © 2001 Carnegie Mellon University. All rights reserved.
753 Redistribution and use in source and binary forms, with or without
754 modification, are permitted provided that the following conditions
758 Redistributions of source code must retain the above copyright
759 notice, this list of conditions and the following disclaimer.
761 Redistributions in binary form must reproduce the above copyright
762 notice, this list of conditions and the following disclaimer in
763 the documentation and/or other materials provided with the
766 The name &"Carnegie Mellon University"& must not be used to
767 endorse or promote products derived from this software without
768 prior written permission. For permission or any other legal
769 details, please contact
771 Office of Technology Transfer
772 Carnegie Mellon University
774 Pittsburgh, PA 15213-3890
775 (412) 268-4387, fax: (412) 268-7395
776 tech-transfer@andrew.cmu.edu
779 Redistributions of any form whatsoever must retain the following
782 &"This product includes software developed by Computing Services
783 at Carnegie Mellon University (&url(https://www.cmu.edu/computing/)."&
785 CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
786 THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
787 AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
788 FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
789 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
790 AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
791 OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
796 .cindex "Exim monitor" "acknowledgment"
799 The Exim Monitor program, which is an X-Window application, includes
800 modified versions of the Athena StripChart and TextPop widgets.
801 This code is copyright by DEC and MIT, and their permission notice appears
802 below, in accordance with the conditions expressed therein.
805 Copyright 1987, 1988 by Digital Equipment Corporation, Maynard, Massachusetts,
806 and the Massachusetts Institute of Technology, Cambridge, Massachusetts.
810 Permission to use, copy, modify, and distribute this software and its
811 documentation for any purpose and without fee is hereby granted,
812 provided that the above copyright notice appear in all copies and that
813 both that copyright notice and this permission notice appear in
814 supporting documentation, and that the names of Digital or MIT not be
815 used in advertising or publicity pertaining to distribution of the
816 software without specific, written prior permission.
818 DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
819 ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
820 DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
821 ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
822 WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
823 ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
828 .cindex "opendmarc" "acknowledgment"
829 The DMARC implementation uses the OpenDMARC library which is Copyrighted by
830 The Trusted Domain Project. Portions of Exim source which use OpenDMARC
831 derived code are indicated in the respective source files. The full OpenDMARC
832 license is provided in the LICENSE.opendmarc file contained in the distributed
836 Many people have contributed code fragments, some large, some small, that were
837 not covered by any specific license requirements. It is assumed that the
838 contributors are happy to see their code incorporated into Exim under the GPL.
845 . ////////////////////////////////////////////////////////////////////////////
846 . ////////////////////////////////////////////////////////////////////////////
848 .chapter "How Exim receives and delivers mail" "CHID11" &&&
849 "Receiving and delivering mail"
852 .section "Overall philosophy" "SECID10"
853 .cindex "design philosophy"
854 Exim is designed to work efficiently on systems that are permanently connected
855 to the Internet and are handling a general mix of mail. In such circumstances,
856 most messages can be delivered immediately. Consequently, Exim does not
857 maintain independent queues of messages for specific domains or hosts, though
858 it does try to send several messages in a single SMTP connection after a host
859 has been down, and it also maintains per-host retry information.
862 .section "Policy control" "SECID11"
863 .cindex "policy control" "overview"
864 Policy controls are now an important feature of MTAs that are connected to the
865 Internet. Perhaps their most important job is to stop MTAs from being abused as
866 &"open relays"& by misguided individuals who send out vast amounts of
867 unsolicited junk and want to disguise its source. Exim provides flexible
868 facilities for specifying policy controls on incoming mail:
871 .cindex "&ACL;" "introduction"
872 Exim 4 (unlike previous versions of Exim) implements policy controls on
873 incoming mail by means of &'Access Control Lists'& (ACLs). Each list is a
874 series of statements that may either grant or deny access. ACLs can be used at
875 several places in the SMTP dialogue while receiving a message from a remote
876 host. However, the most common places are after each RCPT command, and at the
877 very end of the message. The sysadmin can specify conditions for accepting or
878 rejecting individual recipients or the entire message, respectively, at these
879 two points (see chapter &<<CHAPACL>>&). Denial of access results in an SMTP
882 An ACL is also available for locally generated, non-SMTP messages. In this
883 case, the only available actions are to accept or deny the entire message.
885 When Exim is compiled with the content-scanning extension, facilities are
886 provided in the ACL mechanism for passing the message to external virus and/or
887 spam scanning software. The result of such a scan is passed back to the ACL,
888 which can then use it to decide what to do with the message.
890 When a message has been received, either from a remote host or from the local
891 host, but before the final acknowledgment has been sent, a locally supplied C
892 function called &[local_scan()]& can be run to inspect the message and decide
893 whether to accept it or not (see chapter &<<CHAPlocalscan>>&). If the message
894 is accepted, the list of recipients can be modified by the function.
896 Using the &[local_scan()]& mechanism is another way of calling external scanner
897 software. The &%SA-Exim%& add-on package works this way. It does not require
898 Exim to be compiled with the content-scanning extension.
900 After a message has been accepted, a further checking mechanism is available in
901 the form of the &'system filter'& (see chapter &<<CHAPsystemfilter>>&). This
902 runs at the start of every delivery process.
907 .section "User filters" "SECID12"
908 .cindex "filter" "introduction"
909 .cindex "Sieve filter"
910 In a conventional Exim configuration, users are able to run private filters by
911 setting up appropriate &_.forward_& files in their home directories. See
912 chapter &<<CHAPredirect>>& (about the &(redirect)& router) for the
913 configuration needed to support this, and the separate document entitled
914 &'Exim's interfaces to mail filtering'& for user details. Two different kinds
915 of filtering are available:
918 Sieve filters are written in the standard filtering language that is defined
921 Exim filters are written in a syntax that is unique to Exim, but which is more
922 powerful than Sieve, which it pre-dates.
925 User filters are run as part of the routing process, described below.
929 .section "Message identification" "SECTmessiden"
930 .cindex "message ids" "details of format"
931 .cindex "format" "of message id"
932 .cindex "id of message"
937 Every message handled by Exim is given a &'message id'& which is sixteen
938 characters long. It is divided into three parts, separated by hyphens, for
939 example &`16VDhn-0001bo-D3`&. Each part is a sequence of letters and digits,
940 normally encoding numbers in base 62. However, in the Darwin operating
941 system (Mac OS X) and when Exim is compiled to run under Cygwin, base 36
942 (avoiding the use of lower case letters) is used instead, because the message
943 id is used to construct filenames, and the names of files in those systems are
944 not always case-sensitive.
946 .cindex "pid (process id)" "re-use of"
947 The detail of the contents of the message id have changed as Exim has evolved.
948 Earlier versions relied on the operating system not re-using a process id (pid)
949 within one second. On modern operating systems, this assumption can no longer
950 be made, so the algorithm had to be changed. To retain backward compatibility,
951 the format of the message id was retained, which is why the following rules are
955 The first six characters of the message id are the time at which the message
956 started to be received, to a granularity of one second. That is, this field
957 contains the number of seconds since the start of the epoch (the normal Unix
958 way of representing the date and time of day).
960 After the first hyphen, the next six characters are the id of the process that
961 received the message.
963 There are two different possibilities for the final two characters:
965 .oindex "&%localhost_number%&"
966 If &%localhost_number%& is not set, this value is the fractional part of the
967 time of reception, normally in units of 1/2000 of a second, but for systems
968 that must use base 36 instead of base 62 (because of case-insensitive file
969 systems), the units are 1/1000 of a second.
971 If &%localhost_number%& is set, it is multiplied by 200 (100) and added to
972 the fractional part of the time, which in this case is in units of 1/200
977 After a message has been received, Exim waits for the clock to tick at the
978 appropriate resolution before proceeding, so that if another message is
979 received by the same process, or by another process with the same (re-used)
980 pid, it is guaranteed that the time will be different. In most cases, the clock
981 will already have ticked while the message was being received.
984 .section "Receiving mail" "SECID13"
985 .cindex "receiving mail"
986 .cindex "message" "reception"
987 The only way Exim can receive mail from another host is using SMTP over
988 TCP/IP, in which case the sender and recipient addresses are transferred using
989 SMTP commands. However, from a locally running process (such as a user's MUA),
990 there are several possibilities:
993 If the process runs Exim with the &%-bm%& option, the message is read
994 non-interactively (usually via a pipe), with the recipients taken from the
995 command line, or from the body of the message if &%-t%& is also used.
997 If the process runs Exim with the &%-bS%& option, the message is also read
998 non-interactively, but in this case the recipients are listed at the start of
999 the message in a series of SMTP RCPT commands, terminated by a DATA
1000 command. This is called &"batch SMTP"& format,
1001 but it isn't really SMTP. The SMTP commands are just another way of passing
1002 envelope addresses in a non-interactive submission.
1004 If the process runs Exim with the &%-bs%& option, the message is read
1005 interactively, using the SMTP protocol. A two-way pipe is normally used for
1006 passing data between the local process and the Exim process.
1007 This is &"real"& SMTP and is handled in the same way as SMTP over TCP/IP. For
1008 example, the ACLs for SMTP commands are used for this form of submission.
1010 A local process may also make a TCP/IP call to the host's loopback address
1011 (127.0.0.1) or any other of its IP addresses. When receiving messages, Exim
1012 does not treat the loopback address specially. It treats all such connections
1013 in the same way as connections from other hosts.
1017 .cindex "message sender, constructed by Exim"
1018 .cindex "sender" "constructed by Exim"
1019 In the three cases that do not involve TCP/IP, the sender address is
1020 constructed from the login name of the user that called Exim and a default
1021 qualification domain (which can be set by the &%qualify_domain%& configuration
1022 option). For local or batch SMTP, a sender address that is passed using the
1023 SMTP MAIL command is ignored. However, the system administrator may allow
1024 certain users (&"trusted users"&) to specify a different sender addresses
1025 unconditionally, or all users to specify certain forms of different sender
1026 address. The &%-f%& option or the SMTP MAIL command is used to specify these
1027 different addresses. See section &<<SECTtrustedadmin>>& for details of trusted
1028 users, and the &%untrusted_set_sender%& option for a way of allowing untrusted
1029 users to change sender addresses.
1031 Messages received by either of the non-interactive mechanisms are subject to
1032 checking by the non-SMTP ACL if one is defined. Messages received using SMTP
1033 (either over TCP/IP or interacting with a local process) can be checked by a
1034 number of ACLs that operate at different times during the SMTP session. Either
1035 individual recipients or the entire message can be rejected if local policy
1036 requirements are not met. The &[local_scan()]& function (see chapter
1037 &<<CHAPlocalscan>>&) is run for all incoming messages.
1039 Exim can be configured not to start a delivery process when a message is
1040 received; this can be unconditional, or depend on the number of incoming SMTP
1041 connections or the system load. In these situations, new messages wait on the
1042 queue until a queue runner process picks them up. However, in standard
1043 configurations under normal conditions, delivery is started as soon as a
1044 message is received.
1050 .section "Handling an incoming message" "SECID14"
1051 .cindex "spool directory" "files that hold a message"
1052 .cindex "file" "how a message is held"
1053 When Exim accepts a message, it writes two files in its spool directory. The
1054 first contains the envelope information, the current status of the message, and
1055 the header lines, and the second contains the body of the message. The names of
1056 the two spool files consist of the message id, followed by &`-H`& for the
1057 file containing the envelope and header, and &`-D`& for the data file.
1059 .cindex "spool directory" "&_input_& sub-directory"
1060 By default, all these message files are held in a single directory called
1061 &_input_& inside the general Exim spool directory. Some operating systems do
1062 not perform very well if the number of files in a directory gets large; to
1063 improve performance in such cases, the &%split_spool_directory%& option can be
1064 used. This causes Exim to split up the input files into 62 sub-directories
1065 whose names are single letters or digits. When this is done, the queue is
1066 processed one sub-directory at a time instead of all at once, which can improve
1067 overall performance even when there are not enough files in each directory to
1068 affect file system performance.
1070 The envelope information consists of the address of the message's sender and
1071 the addresses of the recipients. This information is entirely separate from
1072 any addresses contained in the header lines. The status of the message includes
1073 a list of recipients who have already received the message. The format of the
1074 first spool file is described in chapter &<<CHAPspool>>&.
1076 .cindex "rewriting" "addresses"
1077 Address rewriting that is specified in the rewrite section of the configuration
1078 (see chapter &<<CHAPrewrite>>&) is done once and for all on incoming addresses,
1079 both in the header lines and the envelope, at the time the message is accepted.
1080 If during the course of delivery additional addresses are generated (for
1081 example, via aliasing), these new addresses are rewritten as soon as they are
1082 generated. At the time a message is actually delivered (transported) further
1083 rewriting can take place; because this is a transport option, it can be
1084 different for different forms of delivery. It is also possible to specify the
1085 addition or removal of certain header lines at the time the message is
1086 delivered (see chapters &<<CHAProutergeneric>>& and
1087 &<<CHAPtransportgeneric>>&).
1091 .section "Life of a message" "SECID15"
1092 .cindex "message" "life of"
1093 .cindex "message" "frozen"
1094 A message remains in the spool directory until it is completely delivered to
1095 its recipients or to an error address, or until it is deleted by an
1096 administrator or by the user who originally created it. In cases when delivery
1097 cannot proceed &-- for example when a message can neither be delivered to its
1098 recipients nor returned to its sender, the message is marked &"frozen"& on the
1099 spool, and no more deliveries are attempted.
1101 .cindex "frozen messages" "thawing"
1102 .cindex "message" "thawing frozen"
1103 An administrator can &"thaw"& such messages when the problem has been
1104 corrected, and can also freeze individual messages by hand if necessary. In
1105 addition, an administrator can force a delivery error, causing a bounce message
1108 .oindex "&%timeout_frozen_after%&"
1109 .oindex "&%ignore_bounce_errors_after%&"
1110 There are options called &%ignore_bounce_errors_after%& and
1111 &%timeout_frozen_after%&, which discard frozen messages after a certain time.
1112 The first applies only to frozen bounces, the second to all frozen messages.
1114 .cindex "message" "log file for"
1115 .cindex "log" "file for each message"
1116 While Exim is working on a message, it writes information about each delivery
1117 attempt to its main log file. This includes successful, unsuccessful, and
1118 delayed deliveries for each recipient (see chapter &<<CHAPlog>>&). The log
1119 lines are also written to a separate &'message log'& file for each message.
1120 These logs are solely for the benefit of the administrator and are normally
1121 deleted along with the spool files when processing of a message is complete.
1122 The use of individual message logs can be disabled by setting
1123 &%no_message_logs%&; this might give an improvement in performance on very busy
1126 .cindex "journal file"
1127 .cindex "file" "journal"
1128 All the information Exim itself needs to set up a delivery is kept in the first
1129 spool file, along with the header lines. When a successful delivery occurs, the
1130 address is immediately written at the end of a journal file, whose name is the
1131 message id followed by &`-J`&. At the end of a delivery run, if there are some
1132 addresses left to be tried again later, the first spool file (the &`-H`& file)
1133 is updated to indicate which these are, and the journal file is then deleted.
1134 Updating the spool file is done by writing a new file and renaming it, to
1135 minimize the possibility of data loss.
1137 Should the system or Exim crash after a successful delivery but before
1138 the spool file has been updated, the journal is left lying around. The next
1139 time Exim attempts to deliver the message, it reads the journal file and
1140 updates the spool file before proceeding. This minimizes the chances of double
1141 deliveries caused by crashes.
1145 .section "Processing an address for delivery" "SECTprocaddress"
1146 .cindex "drivers" "definition of"
1147 .cindex "router" "definition of"
1148 .cindex "transport" "definition of"
1149 The main delivery processing elements of Exim are called &'routers'& and
1150 &'transports'&, and collectively these are known as &'drivers'&. Code for a
1151 number of them is provided in the source distribution, and compile-time options
1152 specify which ones are included in the binary. Runtime options specify which
1153 ones are actually used for delivering messages.
1155 .cindex "drivers" "instance definition"
1156 Each driver that is specified in the runtime configuration is an &'instance'&
1157 of that particular driver type. Multiple instances are allowed; for example,
1158 you can set up several different &(smtp)& transports, each with different
1159 option values that might specify different ports or different timeouts. Each
1160 instance has its own identifying name. In what follows we will normally use the
1161 instance name when discussing one particular instance (that is, one specific
1162 configuration of the driver), and the generic driver name when discussing
1163 the driver's features in general.
1165 A &'router'& is a driver that operates on an address, either determining how
1166 its delivery should happen, by assigning it to a specific transport, or
1167 converting the address into one or more new addresses (for example, via an
1168 alias file). A router may also explicitly choose to fail an address, causing it
1171 A &'transport'& is a driver that transmits a copy of the message from Exim's
1172 spool to some destination. There are two kinds of transport: for a &'local'&
1173 transport, the destination is a file or a pipe on the local host, whereas for a
1174 &'remote'& transport the destination is some other host. A message is passed
1175 to a specific transport as a result of successful routing. If a message has
1176 several recipients, it may be passed to a number of different transports.
1178 .cindex "preconditions" "definition of"
1179 An address is processed by passing it to each configured router instance in
1180 turn, subject to certain preconditions, until a router accepts the address or
1181 specifies that it should be bounced. We will describe this process in more
1182 detail shortly. First, as a simple example, we consider how each recipient
1183 address in a message is processed in a small configuration of three routers.
1185 To make this a more concrete example, it is described in terms of some actual
1186 routers, but remember, this is only an example. You can configure Exim's
1187 routers in many different ways, and there may be any number of routers in a
1190 The first router that is specified in a configuration is often one that handles
1191 addresses in domains that are not recognized specifically by the local host.
1192 Typically these are addresses for arbitrary domains on the Internet. A precondition
1193 is set up which looks for the special domains known to the host (for example,
1194 its own domain name), and the router is run for addresses that do &'not'&
1195 match. Typically, this is a router that looks up domains in the DNS in order to
1196 find the hosts to which this address routes. If it succeeds, the address is
1197 assigned to a suitable SMTP transport; if it does not succeed, the router is
1198 configured to fail the address.
1200 The second router is reached only when the domain is recognized as one that
1201 &"belongs"& to the local host. This router does redirection &-- also known as
1202 aliasing and forwarding. When it generates one or more new addresses from the
1203 original, each of them is routed independently from the start. Otherwise, the
1204 router may cause an address to fail, or it may simply decline to handle the
1205 address, in which case the address is passed to the next router.
1207 The final router in many configurations is one that checks to see if the
1208 address belongs to a local mailbox. The precondition may involve a check to
1209 see if the local part is the name of a login account, or it may look up the
1210 local part in a file or a database. If its preconditions are not met, or if
1211 the router declines, we have reached the end of the routers. When this happens,
1212 the address is bounced.
1216 .section "Processing an address for verification" "SECID16"
1217 .cindex "router" "for verification"
1218 .cindex "verifying address" "overview"
1219 As well as being used to decide how to deliver to an address, Exim's routers
1220 are also used for &'address verification'&. Verification can be requested as
1221 one of the checks to be performed in an ACL for incoming messages, on both
1222 sender and recipient addresses, and it can be tested using the &%-bv%& and
1223 &%-bvs%& command line options.
1225 When an address is being verified, the routers are run in &"verify mode"&. This
1226 does not affect the way the routers work, but it is a state that can be
1227 detected. By this means, a router can be skipped or made to behave differently
1228 when verifying. A common example is a configuration in which the first router
1229 sends all messages to a message-scanning program unless they have been
1230 previously scanned. Thus, the first router accepts all addresses without any
1231 checking, making it useless for verifying. Normally, the &%no_verify%& option
1232 would be set for such a router, causing it to be skipped in verify mode.
1237 .section "Running an individual router" "SECTrunindrou"
1238 .cindex "router" "running details"
1239 .cindex "preconditions" "checking"
1240 .cindex "router" "result of running"
1241 As explained in the example above, a number of preconditions are checked before
1242 running a router. If any are not met, the router is skipped, and the address is
1243 passed to the next router. When all the preconditions on a router &'are'& met,
1244 the router is run. What happens next depends on the outcome, which is one of
1248 &'accept'&: The router accepts the address, and either assigns it to a
1249 transport or generates one or more &"child"& addresses. Processing the
1250 original address ceases
1251 .oindex "&%unseen%&"
1252 unless the &%unseen%& option is set on the router. This option
1253 can be used to set up multiple deliveries with different routing (for example,
1254 for keeping archive copies of messages). When &%unseen%& is set, the address is
1255 passed to the next router. Normally, however, an &'accept'& return marks the
1258 Any child addresses generated by the router are processed independently,
1259 starting with the first router by default. It is possible to change this by
1260 setting the &%redirect_router%& option to specify which router to start at for
1261 child addresses. Unlike &%pass_router%& (see below) the router specified by
1262 &%redirect_router%& may be anywhere in the router configuration.
1264 &'pass'&: The router recognizes the address, but cannot handle it itself. It
1265 requests that the address be passed to another router. By default, the address
1266 is passed to the next router, but this can be changed by setting the
1267 &%pass_router%& option. However, (unlike &%redirect_router%&) the named router
1268 must be below the current router (to avoid loops).
1270 &'decline'&: The router declines to accept the address because it does not
1271 recognize it at all. By default, the address is passed to the next router, but
1272 this can be prevented by setting the &%no_more%& option. When &%no_more%& is
1273 set, all the remaining routers are skipped. In effect, &%no_more%& converts
1274 &'decline'& into &'fail'&.
1276 &'fail'&: The router determines that the address should fail, and queues it for
1277 the generation of a bounce message. There is no further processing of the
1278 original address unless &%unseen%& is set on the router.
1280 &'defer'&: The router cannot handle the address at the present time. (A
1281 database may be offline, or a DNS lookup may have timed out.) No further
1282 processing of the address happens in this delivery attempt. It is tried again
1283 next time the message is considered for delivery.
1285 &'error'&: There is some error in the router (for example, a syntax error in
1286 its configuration). The action is as for defer.
1289 If an address reaches the end of the routers without having been accepted by
1290 any of them, it is bounced as unrouteable. The default error message in this
1291 situation is &"unrouteable address"&, but you can set your own message by
1292 making use of the &%cannot_route_message%& option. This can be set for any
1293 router; the value from the last router that &"saw"& the address is used.
1295 Sometimes while routing you want to fail a delivery when some conditions are
1296 met but others are not, instead of passing the address on for further routing.
1297 You can do this by having a second router that explicitly fails the delivery
1298 when the relevant conditions are met. The &(redirect)& router has a &"fail"&
1299 facility for this purpose.
1302 .section "Duplicate addresses" "SECID17"
1303 .cindex "case of local parts"
1304 .cindex "address duplicate, discarding"
1305 .cindex "duplicate addresses"
1306 Once routing is complete, Exim scans the addresses that are assigned to local
1307 and remote transports and discards any duplicates that it finds. During this
1308 check, local parts are treated case-sensitively. This happens only when
1309 actually delivering a message; when testing routers with &%-bt%&, all the
1310 routed addresses are shown.
1314 .section "Router preconditions" "SECTrouprecon"
1315 .cindex "router" "preconditions, order of processing"
1316 .cindex "preconditions" "order of processing"
1317 The preconditions that are tested for each router are listed below, in the
1318 order in which they are tested. The individual configuration options are
1319 described in more detail in chapter &<<CHAProutergeneric>>&.
1322 .cindex affix "router precondition"
1323 The &%local_part_prefix%& and &%local_part_suffix%& options can specify that
1324 the local parts handled by the router may or must have certain prefixes and/or
1325 suffixes. If a mandatory affix (prefix or suffix) is not present, the router is
1326 skipped. These conditions are tested first. When an affix is present, it is
1327 removed from the local part before further processing, including the evaluation
1328 of any other conditions.
1330 Routers can be designated for use only when not verifying an address, that is,
1331 only when routing it for delivery (or testing its delivery routing). If the
1332 &%verify%& option is set false, the router is skipped when Exim is verifying an
1334 Setting the &%verify%& option actually sets two options, &%verify_sender%& and
1335 &%verify_recipient%&, which independently control the use of the router for
1336 sender and recipient verification. You can set these options directly if
1337 you want a router to be used for only one type of verification.
1338 Note that cutthrough delivery is classed as a recipient verification for this purpose.
1340 If the &%address_test%& option is set false, the router is skipped when Exim is
1341 run with the &%-bt%& option to test an address routing. This can be helpful
1342 when the first router sends all new messages to a scanner of some sort; it
1343 makes it possible to use &%-bt%& to test subsequent delivery routing without
1344 having to simulate the effect of the scanner.
1346 Routers can be designated for use only when verifying an address, as
1347 opposed to routing it for delivery. The &%verify_only%& option controls this.
1348 Again, cutthrough delivery counts as a verification.
1350 Individual routers can be explicitly skipped when running the routers to
1351 check an address given in the SMTP EXPN command (see the &%expn%& option).
1354 If the &%domains%& option is set, the domain of the address must be in the set
1355 of domains that it defines.
1356 .cindex "tainted data" "de-tainting"
1357 .cindex "de-tainting" "using router domains option"
1358 A match verifies the variable &$domain$& (which carries tainted data)
1359 and assigns an untainted value to the &$domain_data$& variable.
1360 Such an untainted value is often needed in the transport.
1361 For specifics of the matching operation and the resulting untainted value,
1362 refer to section &<<SECTdomainlist>>&.
1364 When an untainted value is wanted, use this option
1365 rather than the generic &%condition%& option.
1368 .vindex "&$local_part_prefix$&"
1369 .vindex "&$local_part_prefix_v$&"
1370 .vindex "&$local_part$&"
1371 .vindex "&$local_part_suffix$&"
1372 .vindex "&$local_part_suffix_v$&"
1373 .cindex affix "router precondition"
1374 If the &%local_parts%& option is set, the local part of the address must be in
1375 the set of local parts that it defines.
1376 A match verifies the variable &$local_part$& (which carries tainted data)
1377 and assigns an untainted value to the &$local_part_data$& variable.
1378 Such an untainted value is often needed in the transport.
1379 For specifics of the matching operation and the resulting untainted value,
1380 refer to section &<<SECTlocparlis>>&.
1382 When an untainted value is wanted, use this option
1383 rather than the generic &%condition%& option.
1385 If &%local_part_prefix%& or
1386 &%local_part_suffix%& is in use, the prefix or suffix is removed from the local
1387 part before this check. If you want to do precondition tests on local parts
1388 that include affixes, you can do so by using a &%condition%& option (see below)
1389 that uses the variables &$local_part$&, &$local_part_prefix$&,
1390 &$local_part_prefix_v$&, &$local_part_suffix$&
1391 and &$local_part_suffix_v$& as necessary.
1394 .vindex "&$local_user_uid$&"
1395 .vindex "&$local_user_gid$&"
1397 If the &%check_local_user%& option is set, the local part must be the name of
1398 an account on the local host. If this check succeeds, the uid and gid of the
1399 local user are placed in &$local_user_uid$& and &$local_user_gid$& and the
1400 user's home directory is placed in &$home$&; these values can be used in the
1401 remaining preconditions.
1404 If the &%router_home_directory%& option is set, it is expanded at this point,
1405 because it overrides the value of &$home$&. If this expansion were left till
1406 later, the value of &$home$& as set by &%check_local_user%& would be used in
1407 subsequent tests. Having two different values of &$home$& in the same router
1408 could lead to confusion.
1411 If the &%senders%& option is set, the envelope sender address must be in the
1412 set of addresses that it defines.
1415 If the &%require_files%& option is set, the existence or non-existence of
1416 specified files is tested.
1419 .cindex "customizing" "precondition"
1420 If the &%condition%& option is set, it is evaluated and tested. This option
1421 uses an expanded string to allow you to set up your own custom preconditions.
1422 Expanded strings are described in chapter &<<CHAPexpand>>&.
1424 Note that while using
1425 this option for address matching technically works,
1426 it does not set any de-tainted values.
1427 Such values are often needed, either for router-specific options or
1428 for transport options.
1429 Using the &%domains%& and &%local_parts%& options is usually the most
1430 convenient way to obtain them.
1434 Note that &%require_files%& comes near the end of the list, so you cannot use
1435 it to check for the existence of a file in which to lookup up a domain, local
1436 part, or sender. However, as these options are all expanded, you can use the
1437 &%exists%& expansion condition to make such tests within each condition. The
1438 &%require_files%& option is intended for checking files that the router may be
1439 going to use internally, or which are needed by a specific transport (for
1440 example, &_.procmailrc_&).
1444 .section "Delivery in detail" "SECID18"
1445 .cindex "delivery" "in detail"
1446 When a message is to be delivered, the sequence of events is as follows:
1449 If a system-wide filter file is specified, the message is passed to it. The
1450 filter may add recipients to the message, replace the recipients, discard the
1451 message, cause a new message to be generated, or cause the message delivery to
1452 fail. The format of the system filter file is the same as for Exim user filter
1453 files, described in the separate document entitled &'Exim's interfaces to mail
1455 .cindex "Sieve filter" "not available for system filter"
1456 (&*Note*&: Sieve cannot be used for system filter files.)
1458 Some additional features are available in system filters &-- see chapter
1459 &<<CHAPsystemfilter>>& for details. Note that a message is passed to the system
1460 filter only once per delivery attempt, however many recipients it has. However,
1461 if there are several delivery attempts because one or more addresses could not
1462 be immediately delivered, the system filter is run each time. The filter
1463 condition &%first_delivery%& can be used to detect the first run of the system
1466 Each recipient address is offered to each configured router, in turn, subject to
1467 its preconditions, until one is able to handle it. If no router can handle the
1468 address, that is, if they all decline, the address is failed. Because routers
1469 can be targeted at particular domains, several locally handled domains can be
1470 processed entirely independently of each other.
1472 .cindex "routing" "loops in"
1473 .cindex "loop" "while routing"
1474 A router that accepts an address may assign it to a local or a remote
1475 transport. However, the transport is not run at this time. Instead, the address
1476 is placed on a list for the particular transport, which will be run later.
1477 Alternatively, the router may generate one or more new addresses (typically
1478 from alias, forward, or filter files). New addresses are fed back into this
1479 process from the top, but in order to avoid loops, a router ignores any address
1480 which has an identically-named ancestor that was processed by itself.
1482 When all the routing has been done, addresses that have been successfully
1483 handled are passed to their assigned transports. When local transports are
1484 doing real local deliveries, they handle only one address at a time, but if a
1485 local transport is being used as a pseudo-remote transport (for example, to
1486 collect batched SMTP messages for transmission by some other means) multiple
1487 addresses can be handled. Remote transports can always handle more than one
1488 address at a time, but can be configured not to do so, or to restrict multiple
1489 addresses to the same domain.
1491 Each local delivery to a file or a pipe runs in a separate process under a
1492 non-privileged uid, and these deliveries are run one at a time. Remote
1493 deliveries also run in separate processes, normally under a uid that is private
1494 to Exim (&"the Exim user"&), but in this case, several remote deliveries can be
1495 run in parallel. The maximum number of simultaneous remote deliveries for any
1496 one message is set by the &%remote_max_parallel%& option.
1497 The order in which deliveries are done is not defined, except that all local
1498 deliveries happen before any remote deliveries.
1500 .cindex "queue runner"
1501 When it encounters a local delivery during a queue run, Exim checks its retry
1502 database to see if there has been a previous temporary delivery failure for the
1503 address before running the local transport. If there was a previous failure,
1504 Exim does not attempt a new delivery until the retry time for the address is
1505 reached. However, this happens only for delivery attempts that are part of a
1506 queue run. Local deliveries are always attempted when delivery immediately
1507 follows message reception, even if retry times are set for them. This makes for
1508 better behaviour if one particular message is causing problems (for example,
1509 causing quota overflow, or provoking an error in a filter file).
1511 .cindex "delivery" "retry in remote transports"
1512 Remote transports do their own retry handling, since an address may be
1513 deliverable to one of a number of hosts, each of which may have a different
1514 retry time. If there have been previous temporary failures and no host has
1515 reached its retry time, no delivery is attempted, whether in a queue run or
1516 not. See chapter &<<CHAPretry>>& for details of retry strategies.
1518 If there were any permanent errors, a bounce message is returned to an
1519 appropriate address (the sender in the common case), with details of the error
1520 for each failing address. Exim can be configured to send copies of bounce
1521 messages to other addresses.
1523 .cindex "delivery" "deferral"
1524 If one or more addresses suffered a temporary failure, the message is left on
1525 the queue, to be tried again later. Delivery of these addresses is said to be
1528 When all the recipient addresses have either been delivered or bounced,
1529 handling of the message is complete. The spool files and message log are
1530 deleted, though the message log can optionally be preserved if required.
1536 .section "Retry mechanism" "SECID19"
1537 .cindex "delivery" "retry mechanism"
1538 .cindex "retry" "description of mechanism"
1539 .cindex "queue runner"
1540 Exim's mechanism for retrying messages that fail to get delivered at the first
1541 attempt is the queue runner process. You must either run an Exim daemon that
1542 uses the &%-q%& option with a time interval to start queue runners at regular
1543 intervals or use some other means (such as &'cron'&) to start them. If you do
1544 not arrange for queue runners to be run, messages that fail temporarily at the
1545 first attempt will remain in your queue forever. A queue runner process works
1546 its way through the queue, one message at a time, trying each delivery that has
1547 passed its retry time.
1548 You can run several queue runners at once.
1550 Exim uses a set of configured rules to determine when next to retry the failing
1551 address (see chapter &<<CHAPretry>>&). These rules also specify when Exim
1552 should give up trying to deliver to the address, at which point it generates a
1553 bounce message. If no retry rules are set for a particular host, address, and
1554 error combination, no retries are attempted, and temporary errors are treated
1559 .section "Temporary delivery failure" "SECID20"
1560 .cindex "delivery" "temporary failure"
1561 There are many reasons why a message may not be immediately deliverable to a
1562 particular address. Failure to connect to a remote machine (because it, or the
1563 connection to it, is down) is one of the most common. Temporary failures may be
1564 detected during routing as well as during the transport stage of delivery.
1565 Local deliveries may be delayed if NFS files are unavailable, or if a mailbox
1566 is on a file system where the user is over quota. Exim can be configured to
1567 impose its own quotas on local mailboxes; where system quotas are set they will
1570 If a host is unreachable for a period of time, a number of messages may be
1571 waiting for it by the time it recovers, and sending them in a single SMTP
1572 connection is clearly beneficial. Whenever a delivery to a remote host is
1574 .cindex "hints database" "deferred deliveries"
1575 Exim makes a note in its hints database, and whenever a successful
1576 SMTP delivery has happened, it looks to see if any other messages are waiting
1577 for the same host. If any are found, they are sent over the same SMTP
1578 connection, subject to a configuration limit as to the maximum number in any
1583 .section "Permanent delivery failure" "SECID21"
1584 .cindex "delivery" "permanent failure"
1585 .cindex "bounce message" "when generated"
1586 When a message cannot be delivered to some or all of its intended recipients, a
1587 bounce message is generated. Temporary delivery failures turn into permanent
1588 errors when their timeout expires. All the addresses that fail in a given
1589 delivery attempt are listed in a single message. If the original message has
1590 many recipients, it is possible for some addresses to fail in one delivery
1591 attempt and others to fail subsequently, giving rise to more than one bounce
1592 message. The wording of bounce messages can be customized by the administrator.
1593 See chapter &<<CHAPemsgcust>>& for details.
1595 .cindex "&'X-Failed-Recipients:'& header line"
1596 Bounce messages contain an &'X-Failed-Recipients:'& header line that lists the
1597 failed addresses, for the benefit of programs that try to analyse such messages
1600 .cindex "bounce message" "recipient of"
1601 A bounce message is normally sent to the sender of the original message, as
1602 obtained from the message's envelope. For incoming SMTP messages, this is the
1603 address given in the MAIL command. However, when an address is expanded via a
1604 forward or alias file, an alternative address can be specified for delivery
1605 failures of the generated addresses. For a mailing list expansion (see section
1606 &<<SECTmailinglists>>&) it is common to direct bounce messages to the manager
1611 .section "Failures to deliver bounce messages" "SECID22"
1612 .cindex "bounce message" "failure to deliver"
1613 If a bounce message (either locally generated or received from a remote host)
1614 itself suffers a permanent delivery failure, the message is left in the queue,
1615 but it is frozen, awaiting the attention of an administrator. There are options
1616 that can be used to make Exim discard such failed messages, or to keep them
1617 for only a short time (see &%timeout_frozen_after%& and
1618 &%ignore_bounce_errors_after%&).
1624 . ////////////////////////////////////////////////////////////////////////////
1625 . ////////////////////////////////////////////////////////////////////////////
1627 .chapter "Building and installing Exim" "CHID3"
1628 .scindex IIDbuex "building Exim"
1630 .section "Unpacking" "SECID23"
1631 Exim is distributed as a gzipped or bzipped tar file which, when unpacked,
1632 creates a directory with the name of the current release (for example,
1633 &_exim-&version()_&) into which the following files are placed:
1636 .irow &_ACKNOWLEDGMENTS_& "contains some acknowledgments"
1637 .irow &_CHANGES_& "contains a reference to where changes are &&&
1639 .irow &_LICENCE_& "the GNU General Public Licence"
1640 .irow &_Makefile_& "top-level make file"
1641 .irow &_NOTICE_& "conditions for the use of Exim"
1642 .irow &_README_& "list of files, directories and simple build &&&
1646 Other files whose names begin with &_README_& may also be present. The
1647 following subdirectories are created:
1650 .irow &_Local_& "an empty directory for local configuration files"
1651 .irow &_OS_& "OS-specific files"
1652 .irow &_doc_& "documentation files"
1653 .irow &_exim_monitor_& "source files for the Exim monitor"
1654 .irow &_scripts_& "scripts used in the build process"
1655 .irow &_src_& "remaining source files"
1656 .irow &_util_& "independent utilities"
1659 The main utility programs are contained in the &_src_& directory and are built
1660 with the Exim binary. The &_util_& directory contains a few optional scripts
1661 that may be useful to some sites.
1664 .section "Multiple machine architectures and operating systems" "SECID24"
1665 .cindex "building Exim" "multiple OS/architectures"
1666 The building process for Exim is arranged to make it easy to build binaries for
1667 a number of different architectures and operating systems from the same set of
1668 source files. Compilation does not take place in the &_src_& directory.
1669 Instead, a &'build directory'& is created for each architecture and operating
1671 .cindex "symbolic link" "to build directory"
1672 Symbolic links to the sources are installed in this directory, which is where
1673 the actual building takes place. In most cases, Exim can discover the machine
1674 architecture and operating system for itself, but the defaults can be
1675 overridden if necessary.
1676 .cindex compiler requirements
1677 .cindex compiler version
1678 A C99-capable compiler will be required for the build.
1681 .section "PCRE2 library" "SECTpcre"
1682 .cindex "PCRE2 library"
1683 Exim no longer has an embedded regular-expression library as the vast majority of
1684 modern systems include PCRE2 as a system library, although you may need to
1685 install the PCRE2 package or the PCRE2 development package for your operating
1686 system. If your system has a normal PCRE2 installation the Exim build
1687 process will need no further configuration. If the library or the
1688 headers are in an unusual location you will need to either set the PCRE2_LIBS
1689 and INCLUDE directives appropriately,
1690 or set PCRE2_CONFIG=yes to use the installed &(pcre-config)& command.
1691 If your operating system has no
1692 PCRE2 support then you will need to obtain and build the current PCRE2
1693 from &url(https://github.com/PhilipHazel/pcre2/releases).
1694 More information on PCRE2 is available at &url(https://www.pcre.org/).
1696 .section "DBM libraries" "SECTdb"
1697 .cindex "DBM libraries" "discussion of"
1698 .cindex "hints database" "DBM files used for"
1699 Even if you do not use any DBM files in your configuration, Exim still needs a
1700 DBM library in order to operate, because it uses indexed files for its hints
1701 databases. Unfortunately, there are a number of DBM libraries in existence, and
1702 different operating systems often have different ones installed.
1704 .cindex "Solaris" "DBM library for"
1705 .cindex "IRIX, DBM library for"
1706 .cindex "BSD, DBM library for"
1707 .cindex "Linux, DBM library for"
1708 If you are using Solaris, IRIX, one of the modern BSD systems, or a modern
1709 Linux distribution, the DBM configuration should happen automatically, and you
1710 may be able to ignore this section. Otherwise, you may have to learn more than
1711 you would like about DBM libraries from what follows.
1713 .cindex "&'ndbm'& DBM library"
1714 Licensed versions of Unix normally contain a library of DBM functions operating
1715 via the &'ndbm'& interface, and this is what Exim expects by default. Free
1716 versions of Unix seem to vary in what they contain as standard. In particular,
1717 some early versions of Linux have no default DBM library, and different
1718 distributors have chosen to bundle different libraries with their packaged
1719 versions. However, the more recent releases seem to have standardized on the
1720 Berkeley DB library.
1722 Different DBM libraries have different conventions for naming the files they
1723 use. When a program opens a file called &_dbmfile_&, there are several
1727 A traditional &'ndbm'& implementation, such as that supplied as part of
1728 Solaris, operates on two files called &_dbmfile.dir_& and &_dbmfile.pag_&.
1730 .cindex "&'gdbm'& DBM library"
1731 The GNU library, &'gdbm'&, operates on a single file. If used via its &'ndbm'&
1732 compatibility interface it makes two different hard links to it with names
1733 &_dbmfile.dir_& and &_dbmfile.pag_&, but if used via its native interface, the
1734 filename is used unmodified.
1736 .cindex "Berkeley DB library"
1737 The Berkeley DB package, if called via its &'ndbm'& compatibility interface,
1738 operates on a single file called &_dbmfile.db_&, but otherwise looks to the
1739 programmer exactly the same as the traditional &'ndbm'& implementation.
1741 If the Berkeley package is used in its native mode, it operates on a single
1742 file called &_dbmfile_&; the programmer's interface is somewhat different to
1743 the traditional &'ndbm'& interface.
1745 To complicate things further, there are several very different versions of the
1746 Berkeley DB package. Version 1.85 was stable for a very long time, releases
1747 2.&'x'& and 3.&'x'& were current for a while,
1748 but the latest versions when Exim last revamped support were numbered 5.&'x'&.
1749 Maintenance of some of the earlier releases has ceased,
1750 and Exim no longer supports versions before 3.&'x'&.
1751 All versions of Berkeley DB could be obtained from
1752 &url(http://www.sleepycat.com/), which is now a redirect to their new owner's
1753 page with far newer versions listed.
1754 It is probably wise to plan to move your storage configurations away from
1755 Berkeley DB format, as today there are smaller and simpler alternatives more
1756 suited to Exim's usage model.
1758 .cindex "&'tdb'& DBM library"
1759 Yet another DBM library, called &'tdb'&, is available from
1760 &url(https://sourceforge.net/projects/tdb/files/). It has its own interface, and also
1761 operates on a single file.
1765 .cindex "DBM libraries" "configuration for building"
1766 Exim and its utilities can be compiled to use any of these interfaces. In order
1767 to use any version of the Berkeley DB package in native mode, you must set
1768 USE_DB in an appropriate configuration file (typically
1769 &_Local/Makefile_&). For example:
1773 Similarly, for gdbm you set USE_GDBM, and for tdb you set USE_TDB. An
1774 error is diagnosed if you set more than one of these.
1775 You can set USE_NDBM if needed to override an operating system default.
1777 At the lowest level, the build-time configuration sets none of these options,
1778 thereby assuming an interface of type (1). However, some operating system
1779 configuration files (for example, those for the BSD operating systems and
1780 Linux) assume type (4) by setting USE_DB as their default, and the
1781 configuration files for Cygwin set USE_GDBM. Anything you set in
1782 &_Local/Makefile_&, however, overrides these system defaults.
1784 As well as setting USE_DB, USE_GDBM, or USE_TDB, it may also be
1785 necessary to set DBMLIB, to cause inclusion of the appropriate library, as
1786 in one of these lines:
1790 DBMLIB = -lgdbm -lgdbm_compat
1792 The last of those was for a Linux having GDBM provide emulated NDBM facilities.
1793 Settings like that will work if the DBM library is installed in the standard
1794 place. Sometimes it is not, and the library's header file may also not be in
1795 the default path. You may need to set INCLUDE to specify where the header
1796 file is, and to specify the path to the library more fully in DBMLIB, as in
1799 INCLUDE=-I/usr/local/include/db-4.1
1800 DBMLIB=/usr/local/lib/db-4.1/libdb.a
1802 There is further detailed discussion about the various DBM libraries in the
1803 file &_doc/dbm.discuss.txt_& in the Exim distribution.
1807 .section "Pre-building configuration" "SECID25"
1808 .cindex "building Exim" "pre-building configuration"
1809 .cindex "configuration for building Exim"
1810 .cindex "&_Local/Makefile_&"
1811 .cindex "&_src/EDITME_&"
1812 Before building Exim, a local configuration file that specifies options
1813 independent of any operating system has to be created with the name
1814 &_Local/Makefile_&. A template for this file is supplied as the file
1815 &_src/EDITME_&, and it contains full descriptions of all the option settings
1816 therein. These descriptions are therefore not repeated here. If you are
1817 building Exim for the first time, the simplest thing to do is to copy
1818 &_src/EDITME_& to &_Local/Makefile_&, then read it and edit it appropriately.
1820 There are three settings that you must supply, because Exim will not build
1821 without them. They are the location of the runtime configuration file
1822 (CONFIGURE_FILE), the directory in which Exim binaries will be installed
1823 (BIN_DIRECTORY), and the identity of the Exim user (EXIM_USER and
1824 maybe EXIM_GROUP as well). The value of CONFIGURE_FILE can in fact be
1825 a colon-separated list of filenames; Exim uses the first of them that exists.
1827 There are a few other parameters that can be specified either at build time or
1828 at runtime, to enable the same binary to be used on a number of different
1829 machines. However, if the locations of Exim's spool directory and log file
1830 directory (if not within the spool directory) are fixed, it is recommended that
1831 you specify them in &_Local/Makefile_& instead of at runtime, so that errors
1832 detected early in Exim's execution (such as a malformed configuration file) can
1835 .cindex "content scanning" "specifying at build time"
1836 Exim's interfaces for calling virus and spam scanning software directly from
1837 access control lists are not compiled by default. If you want to include these
1838 facilities, you need to set
1840 WITH_CONTENT_SCAN=yes
1842 in your &_Local/Makefile_&. For details of the facilities themselves, see
1843 chapter &<<CHAPexiscan>>&.
1846 .cindex "&_Local/eximon.conf_&"
1847 .cindex "&_exim_monitor/EDITME_&"
1848 If you are going to build the Exim monitor, a similar configuration process is
1849 required. The file &_exim_monitor/EDITME_& must be edited appropriately for
1850 your installation and saved under the name &_Local/eximon.conf_&. If you are
1851 happy with the default settings described in &_exim_monitor/EDITME_&,
1852 &_Local/eximon.conf_& can be empty, but it must exist.
1854 This is all the configuration that is needed in straightforward cases for known
1855 operating systems. However, the building process is set up so that it is easy
1856 to override options that are set by default or by operating-system-specific
1857 configuration files, for example, to change the C compiler, which
1858 defaults to &%gcc%&. See section &<<SECToverride>>& below for details of how to
1863 .section "Support for iconv()" "SECID26"
1864 .cindex "&[iconv()]& support"
1866 The contents of header lines in messages may be encoded according to the rules
1867 described RFC 2047. This makes it possible to transmit characters that are not
1868 in the ASCII character set, and to label them as being in a particular
1869 character set. When Exim is inspecting header lines by means of the &%$h_%&
1870 mechanism, it decodes them, and translates them into a specified character set
1871 (default is set at build time). The translation is possible only if the operating system
1872 supports the &[iconv()]& function.
1874 However, some of the operating systems that supply &[iconv()]& do not support
1875 very many conversions. The GNU &%libiconv%& library (available from
1876 &url(https://www.gnu.org/software/libiconv/)) can be installed on such
1877 systems to remedy this deficiency, as well as on systems that do not supply
1878 &[iconv()]& at all. After installing &%libiconv%&, you should add
1882 to your &_Local/Makefile_& and rebuild Exim.
1886 .section "Including TLS/SSL encryption support" "SECTinctlsssl"
1887 .cindex "TLS" "including support for TLS"
1888 .cindex "encryption" "including support for"
1889 .cindex "OpenSSL" "building Exim with"
1890 .cindex "GnuTLS" "building Exim with"
1891 Exim is usually built to support encrypted SMTP connections, using the STARTTLS
1892 command as per RFC 2487. It can also support clients that expect to
1893 start a TLS session immediately on connection to a non-standard port (see the
1894 &%tls_on_connect_ports%& runtime option and the &%-tls-on-connect%& command
1897 If you want to build Exim with TLS support, you must first install either the
1898 OpenSSL or GnuTLS library. There is no cryptographic code in Exim itself for
1901 If you do not want TLS support you should set
1905 in &_Local/Makefile_&.
1907 If OpenSSL is installed, you should set
1910 TLS_LIBS=-lssl -lcrypto
1912 in &_Local/Makefile_&. You may also need to specify the locations of the
1913 OpenSSL library and include files. For example:
1916 TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto
1917 TLS_INCLUDE=-I/usr/local/openssl/include/
1919 .cindex "pkg-config" "OpenSSL"
1920 If you have &'pkg-config'& available, then instead you can just use:
1923 USE_OPENSSL_PC=openssl
1925 .cindex "USE_GNUTLS"
1926 If GnuTLS is installed, you should set
1929 TLS_LIBS=-lgnutls -ltasn1 -lgcrypt
1931 in &_Local/Makefile_&, and again you may need to specify the locations of the
1932 library and include files. For example:
1935 TLS_LIBS=-L/usr/gnu/lib -lgnutls -ltasn1 -lgcrypt
1936 TLS_INCLUDE=-I/usr/gnu/include
1938 .cindex "pkg-config" "GnuTLS"
1939 If you have &'pkg-config'& available, then instead you can just use:
1942 USE_GNUTLS_PC=gnutls
1945 You do not need to set TLS_INCLUDE if the relevant directory is already
1946 specified in INCLUDE. Details of how to configure Exim to make use of TLS are
1947 given in chapter &<<CHAPTLS>>&.
1952 .section "Use of tcpwrappers" "SECID27"
1954 .cindex "tcpwrappers, building Exim to support"
1955 .cindex "USE_TCP_WRAPPERS"
1956 .cindex "TCP_WRAPPERS_DAEMON_NAME"
1957 .cindex "tcp_wrappers_daemon_name"
1958 Exim can be linked with the &'tcpwrappers'& library in order to check incoming
1959 SMTP calls using the &'tcpwrappers'& control files. This may be a convenient
1960 alternative to Exim's own checking facilities for installations that are
1961 already making use of &'tcpwrappers'& for other purposes. To do this, you
1962 should set USE_TCP_WRAPPERS in &_Local/Makefile_&, arrange for the file
1963 &_tcpd.h_& to be available at compile time, and also ensure that the library
1964 &_libwrap.a_& is available at link time, typically by including &%-lwrap%& in
1965 EXTRALIBS_EXIM. For example, if &'tcpwrappers'& is installed in &_/usr/local_&,
1968 USE_TCP_WRAPPERS=yes
1969 CFLAGS=-O -I/usr/local/include
1970 EXTRALIBS_EXIM=-L/usr/local/lib -lwrap
1972 in &_Local/Makefile_&. The daemon name to use in the &'tcpwrappers'& control
1973 files is &"exim"&. For example, the line
1975 exim : LOCAL 192.168.1. .friendly.domain.example
1977 in your &_/etc/hosts.allow_& file allows connections from the local host, from
1978 the subnet 192.168.1.0/24, and from all hosts in &'friendly.domain.example'&.
1979 All other connections are denied. The daemon name used by &'tcpwrappers'&
1980 can be changed at build time by setting TCP_WRAPPERS_DAEMON_NAME in
1981 &_Local/Makefile_&, or by setting tcp_wrappers_daemon_name in the
1982 configure file. Consult the &'tcpwrappers'& documentation for
1986 .section "Including support for IPv6" "SECID28"
1987 .cindex "IPv6" "including support for"
1988 Exim contains code for use on systems that have IPv6 support. Setting
1989 &`HAVE_IPV6=YES`& in &_Local/Makefile_& causes the IPv6 code to be included;
1990 it may also be necessary to set IPV6_INCLUDE and IPV6_LIBS on systems
1991 where the IPv6 support is not fully integrated into the normal include and
1994 Two different types of DNS record for handling IPv6 addresses have been
1995 defined. AAAA records (analogous to A records for IPv4) are in use, and are
1996 currently seen as the mainstream. Another record type called A6 was proposed
1997 as better than AAAA because it had more flexibility. However, it was felt to be
1998 over-complex, and its status was reduced to &"experimental"&.
2000 have a compile option for including A6 record support but this has now been
2005 .section "Dynamically loaded lookup module support" "SECTdynamicmodules"
2006 .cindex "lookup modules"
2007 .cindex "dynamic modules"
2008 .cindex ".so building"
2009 On some platforms, Exim supports not compiling all lookup types directly into
2010 the main binary, instead putting some into external modules which can be loaded
2012 This permits packagers to build Exim with support for lookups with extensive
2013 library dependencies without requiring all users to install all of those
2015 Most, but not all, lookup types can be built this way.
2017 Set &`LOOKUP_MODULE_DIR`& to the directory into which the modules will be
2018 installed; Exim will only load modules from that directory, as a security
2019 measure. You will need to set &`CFLAGS_DYNAMIC`& if not already defined
2020 for your OS; see &_OS/Makefile-Linux_& for an example.
2021 Some other requirements for adjusting &`EXTRALIBS`& may also be necessary,
2022 see &_src/EDITME_& for details.
2024 Then, for each module to be loaded dynamically, define the relevant
2025 &`LOOKUP_`&<&'lookup_type'&> flags to have the value "2" instead of "yes".
2026 For example, this will build in lsearch but load sqlite and mysql support
2035 .section "The building process" "SECID29"
2036 .cindex "build directory"
2037 Once &_Local/Makefile_& (and &_Local/eximon.conf_&, if required) have been
2038 created, run &'make'& at the top level. It determines the architecture and
2039 operating system types, and creates a build directory if one does not exist.
2040 For example, on a Sun system running Solaris 8, the directory
2041 &_build-SunOS5-5.8-sparc_& is created.
2042 .cindex "symbolic link" "to source files"
2043 Symbolic links to relevant source files are installed in the build directory.
2045 If this is the first time &'make'& has been run, it calls a script that builds
2046 a make file inside the build directory, using the configuration files from the
2047 &_Local_& directory. The new make file is then passed to another instance of
2048 &'make'&. This does the real work, building a number of utility scripts, and
2049 then compiling and linking the binaries for the Exim monitor (if configured), a
2050 number of utility programs, and finally Exim itself. The command &`make
2051 makefile`& can be used to force a rebuild of the make file in the build
2052 directory, should this ever be necessary.
2054 If you have problems building Exim, check for any comments there may be in the
2055 &_README_& file concerning your operating system, and also take a look at the
2056 FAQ, where some common problems are covered.
2060 .section 'Output from &"make"&' "SECID283"
2061 The output produced by the &'make'& process for compile lines is often very
2062 unreadable, because these lines can be very long. For this reason, the normal
2063 output is suppressed by default, and instead output similar to that which
2064 appears when compiling the 2.6 Linux kernel is generated: just a short line for
2065 each module that is being compiled or linked. However, it is still possible to
2066 get the full output, by calling &'make'& like this:
2070 The value of FULLECHO defaults to &"@"&, the flag character that suppresses
2071 command reflection in &'make'&. When you ask for the full output, it is
2072 given in addition to the short output.
2076 .section "Overriding build-time options for Exim" "SECToverride"
2077 .cindex "build-time options, overriding"
2078 The main make file that is created at the beginning of the building process
2079 consists of the concatenation of a number of files which set configuration
2080 values, followed by a fixed set of &'make'& instructions. If a value is set
2081 more than once, the last setting overrides any previous ones. This provides a
2082 convenient way of overriding defaults. The files that are concatenated are, in
2085 &_OS/Makefile-Default_&
2086 &_OS/Makefile-_&<&'ostype'&>
2088 &_Local/Makefile-_&<&'ostype'&>
2089 &_Local/Makefile-_&<&'archtype'&>
2090 &_Local/Makefile-_&<&'ostype'&>-<&'archtype'&>
2091 &_OS/Makefile-Base_&
2093 .cindex "&_Local/Makefile_&"
2094 .cindex "building Exim" "operating system type"
2095 .cindex "building Exim" "architecture type"
2096 where <&'ostype'&> is the operating system type and <&'archtype'&> is the
2097 architecture type. &_Local/Makefile_& is required to exist, and the building
2098 process fails if it is absent. The other three &_Local_& files are optional,
2099 and are often not needed.
2101 The values used for <&'ostype'&> and <&'archtype'&> are obtained from scripts
2102 called &_scripts/os-type_& and &_scripts/arch-type_& respectively. If either of
2103 the environment variables EXIM_OSTYPE or EXIM_ARCHTYPE is set, their
2104 values are used, thereby providing a means of forcing particular settings.
2105 Otherwise, the scripts try to get values from the &%uname%& command. If this
2106 fails, the shell variables OSTYPE and ARCHTYPE are inspected. A number
2107 of &'ad hoc'& transformations are then applied, to produce the standard names
2108 that Exim expects. You can run these scripts directly from the shell in order
2109 to find out what values are being used on your system.
2112 &_OS/Makefile-Default_& contains comments about the variables that are set
2113 therein. Some (but not all) are mentioned below. If there is something that
2114 needs changing, review the contents of this file and the contents of the make
2115 file for your operating system (&_OS/Makefile-<ostype>_&) to see what the
2119 .cindex "building Exim" "overriding default settings"
2120 If you need to change any of the values that are set in &_OS/Makefile-Default_&
2121 or in &_OS/Makefile-<ostype>_&, or to add any new definitions, you do not
2122 need to change the original files. Instead, you should make the changes by
2123 putting the new values in an appropriate &_Local_& file. For example,
2124 .cindex "Tru64-Unix build-time settings"
2125 when building Exim in many releases of the Tru64-Unix (formerly Digital UNIX,
2126 formerly DEC-OSF1) operating system, it is necessary to specify that the C
2127 compiler is called &'cc'& rather than &'gcc'&. Also, the compiler must be
2128 called with the option &%-std1%&, to make it recognize some of the features of
2129 Standard C that Exim uses. (Most other compilers recognize Standard C by
2130 default.) To do this, you should create a file called &_Local/Makefile-OSF1_&
2131 containing the lines
2136 If you are compiling for just one operating system, it may be easier to put
2137 these lines directly into &_Local/Makefile_&.
2139 Keeping all your local configuration settings separate from the distributed
2140 files makes it easy to transfer them to new versions of Exim simply by copying
2141 the contents of the &_Local_& directory.
2144 .cindex "NIS lookup type" "including support for"
2145 .cindex "NIS+ lookup type" "including support for"
2146 .cindex "LDAP" "including support for"
2147 .cindex "lookup" "inclusion in binary"
2148 Exim contains support for doing LDAP, NIS, NIS+, and other kinds of file
2149 lookup, but not all systems have these components installed, so the default is
2150 not to include the relevant code in the binary. All the different kinds of file
2151 and database lookup that Exim supports are implemented as separate code modules
2152 which are included only if the relevant compile-time options are set. In the
2153 case of LDAP, NIS, and NIS+, the settings for &_Local/Makefile_& are:
2159 and similar settings apply to the other lookup types. They are all listed in
2160 &_src/EDITME_&. In many cases the relevant include files and interface
2161 libraries need to be installed before compiling Exim.
2162 .cindex "cdb" "including support for"
2163 However, there are some optional lookup types (such as cdb) for which
2164 the code is entirely contained within Exim, and no external include
2165 files or libraries are required. When a lookup type is not included in the
2166 binary, attempts to configure Exim to use it cause runtime configuration
2169 .cindex "pkg-config" "lookups"
2170 .cindex "pkg-config" "authenticators"
2171 Many systems now use a tool called &'pkg-config'& to encapsulate information
2172 about how to compile against a library; Exim has some initial support for
2173 being able to use pkg-config for lookups and authenticators. For any given
2174 makefile variable which starts &`LOOKUP_`& or &`AUTH_`&, you can add a new
2175 variable with the &`_PC`& suffix in the name and assign as the value the
2176 name of the package to be queried. The results of querying via the
2177 &'pkg-config'& command will be added to the appropriate Makefile variables
2178 with &`+=`& directives, so your version of &'make'& will need to support that
2179 syntax. For instance:
2182 LOOKUP_SQLITE_PC=sqlite3
2184 AUTH_GSASL_PC=libgsasl
2185 AUTH_HEIMDAL_GSSAPI=yes
2186 AUTH_HEIMDAL_GSSAPI_PC=heimdal-gssapi
2189 .cindex "Perl" "including support for"
2190 Exim can be linked with an embedded Perl interpreter, allowing Perl
2191 subroutines to be called during string expansion. To enable this facility,
2195 must be defined in &_Local/Makefile_&. Details of this facility are given in
2196 chapter &<<CHAPperl>>&.
2198 .cindex "X11 libraries, location of"
2199 The location of the X11 libraries is something that varies a lot between
2200 operating systems, and there may be different versions of X11 to cope
2201 with. Exim itself makes no use of X11, but if you are compiling the Exim
2202 monitor, the X11 libraries must be available.
2203 The following three variables are set in &_OS/Makefile-Default_&:
2206 XINCLUDE=-I$(X11)/include
2207 XLFLAGS=-L$(X11)/lib
2209 These are overridden in some of the operating-system configuration files. For
2210 example, in &_OS/Makefile-SunOS5_& there is
2213 XINCLUDE=-I$(X11)/include
2214 XLFLAGS=-L$(X11)/lib -R$(X11)/lib
2216 If you need to override the default setting for your operating system, place a
2217 definition of all three of these variables into your
2218 &_Local/Makefile-<ostype>_& file.
2221 If you need to add any extra libraries to the link steps, these can be put in a
2222 variable called EXTRALIBS, which appears in all the link commands, but by
2223 default is not defined. In contrast, EXTRALIBS_EXIM is used only on the
2224 command for linking the main Exim binary, and not for any associated utilities.
2226 .cindex "DBM libraries" "configuration for building"
2227 There is also DBMLIB, which appears in the link commands for binaries that
2228 use DBM functions (see also section &<<SECTdb>>&). Finally, there is
2229 EXTRALIBS_EXIMON, which appears only in the link step for the Exim monitor
2230 binary, and which can be used, for example, to include additional X11
2233 .cindex "configuration file" "editing"
2234 The make file copes with rebuilding Exim correctly if any of the configuration
2235 files are edited. However, if an optional configuration file is deleted, it is
2236 necessary to touch the associated non-optional file (that is,
2237 &_Local/Makefile_& or &_Local/eximon.conf_&) before rebuilding.
2240 .section "OS-specific header files" "SECID30"
2242 .cindex "building Exim" "OS-specific C header files"
2243 The &_OS_& directory contains a number of files with names of the form
2244 &_os.h-<ostype>_&. These are system-specific C header files that should not
2245 normally need to be changed. There is a list of macro settings that are
2246 recognized in the file &_OS/os.configuring_&, which should be consulted if you
2247 are porting Exim to a new operating system.
2251 .section "Overriding build-time options for the monitor" "SECID31"
2252 .cindex "building Eximon"
2253 A similar process is used for overriding things when building the Exim monitor,
2254 where the files that are involved are
2256 &_OS/eximon.conf-Default_&
2257 &_OS/eximon.conf-_&<&'ostype'&>
2258 &_Local/eximon.conf_&
2259 &_Local/eximon.conf-_&<&'ostype'&>
2260 &_Local/eximon.conf-_&<&'archtype'&>
2261 &_Local/eximon.conf-_&<&'ostype'&>-<&'archtype'&>
2263 .cindex "&_Local/eximon.conf_&"
2264 As with Exim itself, the final three files need not exist, and in this case the
2265 &_OS/eximon.conf-<ostype>_& file is also optional. The default values in
2266 &_OS/eximon.conf-Default_& can be overridden dynamically by setting environment
2267 variables of the same name, preceded by EXIMON_. For example, setting
2268 EXIMON_LOG_DEPTH in the environment overrides the value of
2269 LOG_DEPTH at runtime.
2273 .section "Installing Exim binaries and scripts" "SECID32"
2274 .cindex "installing Exim"
2275 .cindex "BIN_DIRECTORY"
2276 The command &`make install`& runs the &(exim_install)& script with no
2277 arguments. The script copies binaries and utility scripts into the directory
2278 whose name is specified by the BIN_DIRECTORY setting in &_Local/Makefile_&.
2279 .cindex "setuid" "installing Exim with"
2280 The install script copies files only if they are newer than the files they are
2281 going to replace. The Exim binary is required to be owned by root and have the
2282 &'setuid'& bit set, for normal configurations. Therefore, you must run &`make
2283 install`& as root so that it can set up the Exim binary in this way. However, in
2284 some special situations (for example, if a host is doing no local deliveries)
2285 it may be possible to run Exim without making the binary setuid root (see
2286 chapter &<<CHAPsecurity>>& for details).
2288 .cindex "CONFIGURE_FILE"
2289 Exim's runtime configuration file is named by the CONFIGURE_FILE setting
2290 in &_Local/Makefile_&. If this names a single file, and the file does not
2291 exist, the default configuration file &_src/configure.default_& is copied there
2292 by the installation script. If a runtime configuration file already exists, it
2293 is left alone. If CONFIGURE_FILE is a colon-separated list, naming several
2294 alternative files, no default is installed.
2296 .cindex "system aliases file"
2297 .cindex "&_/etc/aliases_&"
2298 One change is made to the default configuration file when it is installed: the
2299 default configuration contains a router that references a system aliases file.
2300 The path to this file is set to the value specified by
2301 SYSTEM_ALIASES_FILE in &_Local/Makefile_& (&_/etc/aliases_& by default).
2302 If the system aliases file does not exist, the installation script creates it,
2303 and outputs a comment to the user.
2305 The created file contains no aliases, but it does contain comments about the
2306 aliases a site should normally have. Mail aliases have traditionally been
2307 kept in &_/etc/aliases_&. However, some operating systems are now using
2308 &_/etc/mail/aliases_&. You should check if yours is one of these, and change
2309 Exim's configuration if necessary.
2311 The default configuration uses the local host's name as the only local domain,
2312 and is set up to do local deliveries into the shared directory &_/var/mail_&,
2313 running as the local user. System aliases and &_.forward_& files in users' home
2314 directories are supported, but no NIS or NIS+ support is configured. Domains
2315 other than the name of the local host are routed using the DNS, with delivery
2318 It is possible to install Exim for special purposes (such as building a binary
2319 distribution) in a private part of the file system. You can do this by a
2322 make DESTDIR=/some/directory/ install
2324 This has the effect of pre-pending the specified directory to all the file
2325 paths, except the name of the system aliases file that appears in the default
2326 configuration. (If a default alias file is created, its name &'is'& modified.)
2327 For backwards compatibility, ROOT is used if DESTDIR is not set,
2328 but this usage is deprecated.
2330 .cindex "installing Exim" "what is not installed"
2331 Running &'make install'& does not copy the Exim 4 conversion script
2332 &'convert4r4'&. You will probably run this only once if you are
2333 upgrading from Exim 3. None of the documentation files in the &_doc_&
2334 directory are copied, except for the info files when you have set
2335 INFO_DIRECTORY, as described in section &<<SECTinsinfdoc>>& below.
2337 For the utility programs, old versions are renamed by adding the suffix &_.O_&
2338 to their names. The Exim binary itself, however, is handled differently. It is
2339 installed under a name that includes the version number and the compile number,
2340 for example, &_exim-&version()-1_&. The script then arranges for a symbolic link
2341 called &_exim_& to point to the binary. If you are updating a previous version
2342 of Exim, the script takes care to ensure that the name &_exim_& is never absent
2343 from the directory (as seen by other processes).
2345 .cindex "installing Exim" "testing the script"
2346 If you want to see what the &'make install'& will do before running it for
2347 real, you can pass the &%-n%& option to the installation script by this
2350 make INSTALL_ARG=-n install
2352 The contents of the variable INSTALL_ARG are passed to the installation
2353 script. You do not need to be root to run this test. Alternatively, you can run
2354 the installation script directly, but this must be from within the build
2355 directory. For example, from the top-level Exim directory you could use this
2358 (cd build-SunOS5-5.5.1-sparc; ../scripts/exim_install -n)
2360 .cindex "installing Exim" "install script options"
2361 There are two other options that can be supplied to the installation script.
2364 &%-no_chown%& bypasses the call to change the owner of the installed binary
2365 to root, and the call to make it a setuid binary.
2367 &%-no_symlink%& bypasses the setting up of the symbolic link &_exim_& to the
2371 INSTALL_ARG can be used to pass these options to the script. For example:
2373 make INSTALL_ARG=-no_symlink install
2375 The installation script can also be given arguments specifying which files are
2376 to be copied. For example, to install just the Exim binary, and nothing else,
2377 without creating the symbolic link, you could use:
2379 make INSTALL_ARG='-no_symlink exim' install
2384 .section "Installing info documentation" "SECTinsinfdoc"
2385 .cindex "installing Exim" "&'info'& documentation"
2386 Not all systems use the GNU &'info'& system for documentation, and for this
2387 reason, the Texinfo source of Exim's documentation is not included in the main
2388 distribution. Instead it is available separately from the FTP site (see section
2391 If you have defined INFO_DIRECTORY in &_Local/Makefile_& and the Texinfo
2392 source of the documentation is found in the source tree, running &`make
2393 install`& automatically builds the info files and installs them.
2397 .section "Setting up the spool directory" "SECID33"
2398 .cindex "spool directory" "creating"
2399 When it starts up, Exim tries to create its spool directory if it does not
2400 exist. The Exim uid and gid are used for the owner and group of the spool
2401 directory. Sub-directories are automatically created in the spool directory as
2407 .section "Testing" "SECID34"
2408 .cindex "testing" "installation"
2409 Having installed Exim, you can check that the runtime configuration file is
2410 syntactically valid by running the following command, which assumes that the
2411 Exim binary directory is within your PATH environment variable:
2415 If there are any errors in the configuration file, Exim outputs error messages.
2416 Otherwise it outputs the version number and build date,
2417 the DBM library that is being used, and information about which drivers and
2418 other optional code modules are included in the binary.
2419 Some simple routing tests can be done by using the address testing option. For
2422 &`exim -bt`& <&'local username'&>
2424 should verify that it recognizes a local mailbox, and
2426 &`exim -bt`& <&'remote address'&>
2428 a remote one. Then try getting it to deliver mail, both locally and remotely.
2429 This can be done by passing messages directly to Exim, without going through a
2430 user agent. For example:
2432 exim -v postmaster@your.domain.example
2433 From: user@your.domain.example
2434 To: postmaster@your.domain.example
2435 Subject: Testing Exim
2437 This is a test message.
2440 The &%-v%& option causes Exim to output some verification of what it is doing.
2441 In this case you should see copies of three log lines, one for the message's
2442 arrival, one for its delivery, and one containing &"Completed"&.
2444 .cindex "delivery" "problems with"
2445 If you encounter problems, look at Exim's log files (&'mainlog'& and
2446 &'paniclog'&) to see if there is any relevant information there. Another source
2447 of information is running Exim with debugging turned on, by specifying the
2448 &%-d%& option. If a message is stuck on Exim's spool, you can force a delivery
2449 with debugging turned on by a command of the form
2451 &`exim -d -M`& <&'exim-message-id'&>
2453 You must be root or an &"admin user"& in order to do this. The &%-d%& option
2454 produces rather a lot of output, but you can cut this down to specific areas.
2455 For example, if you use &%-d-all+route%& only the debugging information
2456 relevant to routing is included. (See the &%-d%& option in chapter
2457 &<<CHAPcommandline>>& for more details.)
2459 .cindex '&"sticky"& bit'
2460 .cindex "lock files"
2461 One specific problem that has shown up on some sites is the inability to do
2462 local deliveries into a shared mailbox directory, because it does not have the
2463 &"sticky bit"& set on it. By default, Exim tries to create a lock file before
2464 writing to a mailbox file, and if it cannot create the lock file, the delivery
2465 is deferred. You can get round this either by setting the &"sticky bit"& on the
2466 directory, or by setting a specific group for local deliveries and allowing
2467 that group to create files in the directory (see the comments above the
2468 &(local_delivery)& transport in the default configuration file). Another
2469 approach is to configure Exim not to use lock files, but just to rely on
2470 &[fcntl()]& locking instead. However, you should do this only if all user
2471 agents also use &[fcntl()]& locking. For further discussion of locking issues,
2472 see chapter &<<CHAPappendfile>>&.
2474 One thing that cannot be tested on a system that is already running an MTA is
2475 the receipt of incoming SMTP mail on the standard SMTP port. However, the
2476 &%-oX%& option can be used to run an Exim daemon that listens on some other
2477 port, or &'inetd'& can be used to do this. The &%-bh%& option and the
2478 &'exim_checkaccess'& utility can be used to check out policy controls on
2481 Testing a new version on a system that is already running Exim can most easily
2482 be done by building a binary with a different CONFIGURE_FILE setting. From
2483 within the runtime configuration, all other file and directory names
2484 that Exim uses can be altered, in order to keep it entirely clear of the
2488 .section "Replacing another MTA with Exim" "SECID35"
2489 .cindex "replacing another MTA"
2490 Building and installing Exim for the first time does not of itself put it in
2491 general use. The name by which the system's MTA is called by mail user agents
2492 is either &_/usr/sbin/sendmail_&, or &_/usr/lib/sendmail_& (depending on the
2493 operating system), and it is necessary to make this name point to the &'exim'&
2494 binary in order to get the user agents to pass messages to Exim. This is
2495 normally done by renaming any existing file and making &_/usr/sbin/sendmail_&
2496 or &_/usr/lib/sendmail_&
2497 .cindex "symbolic link" "to &'exim'& binary"
2498 a symbolic link to the &'exim'& binary. It is a good idea to remove any setuid
2499 privilege and executable status from the old MTA. It is then necessary to stop
2500 and restart the mailer daemon, if one is running.
2502 .cindex "FreeBSD, MTA indirection"
2503 .cindex "&_/etc/mail/mailer.conf_&"
2504 Some operating systems have introduced alternative ways of switching MTAs. For
2505 example, if you are running FreeBSD, you need to edit the file
2506 &_/etc/mail/mailer.conf_& instead of setting up a symbolic link as just
2507 described. A typical example of the contents of this file for running Exim is
2510 sendmail /usr/exim/bin/exim
2511 send-mail /usr/exim/bin/exim
2512 mailq /usr/exim/bin/exim -bp
2513 newaliases /usr/bin/true
2515 Once you have set up the symbolic link, or edited &_/etc/mail/mailer.conf_&,
2516 your Exim installation is &"live"&. Check it by sending a message from your
2517 favourite user agent.
2519 You should consider what to tell your users about the change of MTA. Exim may
2520 have different capabilities to what was previously running, and there are
2521 various operational differences such as the text of messages produced by
2522 command line options and in bounce messages. If you allow your users to make
2523 use of Exim's filtering capabilities, you should make the document entitled
2524 &'Exim's interface to mail filtering'& available to them.
2528 .section "Running the daemon" SECTdaemonLaunch
2529 The most common command line for launching the Exim daemon looks like
2533 This starts a daemon which
2535 listens for incoming smtp connections, launching handler processes for
2538 starts a queue-runner process every five minutes, to inspect queued messages
2539 and run delivery attempts on any that have arrived at their retry time
2541 Should a queue run take longer than the time between queue-runner starts,
2542 they will run in parallel.
2543 Numbers of jobs of the various types are subject to policy controls
2544 defined in the configuration.
2547 .section "Upgrading Exim" "SECID36"
2548 .cindex "upgrading Exim"
2549 If you are already running Exim on your host, building and installing a new
2550 version automatically makes it available to MUAs, or any other programs that
2551 call the MTA directly. However, if you are running an Exim daemon, you do need
2552 .cindex restart "on HUP signal"
2553 .cindex signal "HUP, to restart"
2554 to send it a HUP signal, to make it re-execute itself, and thereby pick up the
2555 new binary. You do not need to stop processing mail in order to install a new
2556 version of Exim. The install script does not modify an existing runtime
2562 .section "Stopping the Exim daemon on Solaris" "SECID37"
2563 .cindex "Solaris" "stopping Exim on"
2564 The standard command for stopping the mailer daemon on Solaris is
2566 /etc/init.d/sendmail stop
2568 If &_/usr/lib/sendmail_& has been turned into a symbolic link, this script
2569 fails to stop Exim because it uses the command &'ps -e'& and greps the output
2570 for the text &"sendmail"&; this is not present because the actual program name
2571 (that is, &"exim"&) is given by the &'ps'& command with these options. A
2572 solution is to replace the line that finds the process id with something like
2574 pid=`cat /var/spool/exim/exim-daemon.pid`
2576 to obtain the daemon's pid directly from the file that Exim saves it in.
2578 Note, however, that stopping the daemon does not &"stop Exim"&. Messages can
2579 still be received from local processes, and if automatic delivery is configured
2580 (the normal case), deliveries will still occur.
2585 . ////////////////////////////////////////////////////////////////////////////
2586 . ////////////////////////////////////////////////////////////////////////////
2588 .chapter "The Exim command line" "CHAPcommandline"
2589 .scindex IIDclo1 "command line" "options"
2590 .scindex IIDclo2 "options" "command line"
2591 Exim's command line takes the standard Unix form of a sequence of options,
2592 each starting with a hyphen character, followed by a number of arguments. The
2593 options are compatible with the main options of Sendmail, and there are also
2594 some additional options, some of which are compatible with Smail 3. Certain
2595 combinations of options do not make sense, and provoke an error if used.
2596 The form of the arguments depends on which options are set.
2599 .section "Setting options by program name" "SECID38"
2601 If Exim is called under the name &'mailq'&, it behaves as if the option &%-bp%&
2602 were present before any other options.
2603 The &%-bp%& option requests a listing of the contents of the mail queue on the
2605 This feature is for compatibility with some systems that contain a command of
2606 that name in one of the standard libraries, symbolically linked to
2607 &_/usr/sbin/sendmail_& or &_/usr/lib/sendmail_&.
2610 If Exim is called under the name &'rsmtp'& it behaves as if the option &%-bS%&
2611 were present before any other options, for compatibility with Smail. The
2612 &%-bS%& option is used for reading in a number of messages in batched SMTP
2616 If Exim is called under the name &'rmail'& it behaves as if the &%-i%& and
2617 &%-oee%& options were present before any other options, for compatibility with
2618 Smail. The name &'rmail'& is used as an interface by some UUCP systems.
2621 .cindex "queue runner"
2622 If Exim is called under the name &'runq'& it behaves as if the option &%-q%&
2623 were present before any other options, for compatibility with Smail. The &%-q%&
2624 option causes a single queue runner process to be started.
2626 .cindex "&'newaliases'&"
2627 .cindex "alias file" "building"
2628 .cindex "Sendmail compatibility" "calling Exim as &'newaliases'&"
2629 If Exim is called under the name &'newaliases'& it behaves as if the option
2630 &%-bi%& were present before any other options, for compatibility with Sendmail.
2631 This option is used for rebuilding Sendmail's alias file. Exim does not have
2632 the concept of a single alias file, but can be configured to run a given
2633 command if called with the &%-bi%& option.
2636 .section "Trusted and admin users" "SECTtrustedadmin"
2637 Some Exim options are available only to &'trusted users'& and others are
2638 available only to &'admin users'&. In the description below, the phrases &"Exim
2639 user"& and &"Exim group"& mean the user and group defined by EXIM_USER and
2640 EXIM_GROUP in &_Local/Makefile_& or set by the &%exim_user%& and
2641 &%exim_group%& options. These do not necessarily have to use the name &"exim"&.
2644 .cindex "trusted users" "definition of"
2645 .cindex "user" "trusted definition of"
2646 The trusted users are root, the Exim user, any user listed in the
2647 &%trusted_users%& configuration option, and any user whose current group or any
2648 supplementary group is one of those listed in the &%trusted_groups%&
2649 configuration option. Note that the Exim group is not automatically trusted.
2651 .cindex '&"From"& line'
2652 .cindex "envelope from"
2653 .cindex "envelope sender"
2654 Trusted users are always permitted to use the &%-f%& option or a leading
2655 &"From&~"& line to specify the envelope sender of a message that is passed to
2656 Exim through the local interface (see the &%-bm%& and &%-f%& options below).
2657 See the &%untrusted_set_sender%& option for a way of permitting non-trusted
2658 users to set envelope senders.
2662 For a trusted user, there is never any check on the contents of the &'From:'&
2663 header line, and a &'Sender:'& line is never added. Furthermore, any existing
2664 &'Sender:'& line in incoming local (non-TCP/IP) messages is not removed.
2666 Trusted users may also specify a host name, host address, interface address,
2667 protocol name, ident value, and authentication data when submitting a message
2668 locally. Thus, they are able to insert messages into Exim's queue locally that
2669 have the characteristics of messages received from a remote host. Untrusted
2670 users may in some circumstances use &%-f%&, but can never set the other values
2671 that are available to trusted users.
2673 .cindex "user" "admin definition of"
2674 .cindex "admin user" "definition of"
2675 The admin users are root, the Exim user, and any user that is a member of the
2676 Exim group or of any group listed in the &%admin_groups%& configuration option.
2677 The current group does not have to be one of these groups.
2679 Admin users are permitted to list the queue, and to carry out certain
2680 operations on messages, for example, to force delivery failures. It is also
2681 necessary to be an admin user in order to see the full information provided by
2682 the Exim monitor, and full debugging output.
2684 By default, the use of the &%-M%&, &%-q%&, &%-R%&, and &%-S%& options to cause
2685 Exim to attempt delivery of messages on its queue is restricted to admin users.
2686 However, this restriction can be relaxed by setting the &%prod_requires_admin%&
2687 option false (that is, specifying &%no_prod_requires_admin%&).
2689 Similarly, the use of the &%-bp%& option to list all the messages in the queue
2690 is restricted to admin users unless &%queue_list_requires_admin%& is set
2695 &*Warning*&: If you configure your system so that admin users are able to
2696 edit Exim's configuration file, you are giving those users an easy way of
2697 getting root. There is further discussion of this issue at the start of chapter
2703 .section "Command line options" "SECID39"
2704 Exim's command line options are described in alphabetical order below. If none
2705 of the options that specifies a specific action (such as starting the daemon or
2706 a queue runner, or testing an address, or receiving a message in a specific
2707 format, or listing the queue) are present, and there is at least one argument
2708 on the command line, &%-bm%& (accept a local message on the standard input,
2709 with the arguments specifying the recipients) is assumed. Otherwise, Exim
2710 outputs a brief message about itself and exits.
2712 . ////////////////////////////////////////////////////////////////////////////
2713 . Insert a stylized XML comment here, to identify the start of the command line
2714 . options. This is for the benefit of the Perl script that automatically
2715 . creates a man page for the options.
2716 . ////////////////////////////////////////////////////////////////////////////
2719 <!-- === Start of command line options === -->
2726 .cindex "options" "command line; terminating"
2727 This is a pseudo-option whose only purpose is to terminate the options and
2728 therefore to cause subsequent command line items to be treated as arguments
2729 rather than options, even if they begin with hyphens.
2732 .oindex "&%--help%&"
2733 This option causes Exim to output a few sentences stating what it is.
2734 The same output is generated if the Exim binary is called with no options and
2737 .vitem &%--version%&
2738 .oindex "&%--version%&"
2739 This option is an alias for &%-bV%& and causes version information to be
2746 These options are used by Sendmail for selecting configuration files and are
2749 .vitem &%-B%&<&'type'&>
2751 .cindex "8-bit characters"
2752 .cindex "Sendmail compatibility" "8-bit characters"
2753 This is a Sendmail option for selecting 7 or 8 bit processing. Exim is 8-bit
2754 clean; it ignores this option.
2759 .cindex "SMTP" "listener"
2760 .cindex "queue runner"
2761 This option runs Exim as a daemon, awaiting incoming SMTP connections. Usually
2762 the &%-bd%& option is combined with the &%-q%&<&'time'&> option, to specify
2763 that the daemon should also initiate periodic queue runs.
2765 The &%-bd%& option can be used only by an admin user. If either of the &%-d%&
2766 (debugging) or &%-v%& (verifying) options are set, the daemon does not
2767 disconnect from the controlling terminal. When running this way, it can be
2768 stopped by pressing ctrl-C.
2770 By default, Exim listens for incoming connections to the standard SMTP port on
2771 all the host's running interfaces. However, it is possible to listen on other
2772 ports, on multiple ports, and only on specific interfaces. Chapter
2773 &<<CHAPinterfaces>>& contains a description of the options that control this.
2775 When a listening daemon
2776 .cindex "daemon" "process id (pid)"
2777 .cindex "pid (process id)" "of daemon"
2778 is started without the use of &%-oX%& (that is, without overriding the normal
2779 configuration), it writes its process id to a file called &_exim-daemon.pid_&
2780 in Exim's spool directory. This location can be overridden by setting
2781 PID_FILE_PATH in &_Local/Makefile_&. The file is written while Exim is still
2784 When &%-oX%& is used on the command line to start a listening daemon, the
2785 process id is not written to the normal pid file path. However, &%-oP%& can be
2786 used to specify a path on the command line if a pid file is required.
2790 .cindex restart "on HUP signal"
2791 .cindex signal "HUP, to restart"
2792 .cindex "daemon" "restarting"
2793 .cindex signal "to reload configuration"
2794 .cindex daemon "reload configuration"
2795 .cindex reload configuration
2796 can be used to cause the daemon to re-execute itself. This should be done
2797 whenever Exim's configuration file, or any file that is incorporated into it by
2798 means of the &%.include%& facility, is changed, and also whenever a new version
2799 of Exim is installed. It is not necessary to do this when other files that are
2800 referenced from the configuration (for example, alias files) are changed,
2801 because these are reread each time they are used.
2805 This option has the same effect as &%-bd%& except that it never disconnects
2806 from the controlling terminal, even when no debugging is specified.
2810 .cindex "testing" "string expansion"
2811 .cindex "expansion" "testing"
2812 Run Exim in expansion testing mode. Exim discards its root privilege, to
2813 prevent ordinary users from using this mode to read otherwise inaccessible
2814 files. If no arguments are given, Exim runs interactively, prompting for lines
2815 of data. Otherwise, it processes each argument in turn.
2817 If Exim was built with USE_READLINE=yes in &_Local/Makefile_&, it tries
2818 to load the &%libreadline%& library dynamically whenever the &%-be%& option is
2819 used without command line arguments. If successful, it uses the &[readline()]&
2820 function, which provides extensive line-editing facilities, for reading the
2821 test data. A line history is supported.
2823 Long expansion expressions can be split over several lines by using backslash
2824 continuations. As in Exim's runtime configuration, white space at the start of
2825 continuation lines is ignored. Each argument or data line is passed through the
2826 string expansion mechanism, and the result is output. Variable values from the
2827 configuration file (for example, &$qualify_domain$&) are available, but no
2828 message-specific values (such as &$message_exim_id$&) are set, because no message
2829 is being processed (but see &%-bem%& and &%-Mset%&).
2831 &*Note*&: If you use this mechanism to test lookups, and you change the data
2832 files or databases you are using, you must exit and restart Exim before trying
2833 the same lookup again. Otherwise, because each Exim process caches the results
2834 of lookups, you will just get the same result as before.
2836 Macro processing is done on lines before string-expansion: new macros can be
2837 defined and macros will be expanded.
2838 Because macros in the config file are often used for secrets, those are only
2839 available to admin users.
2842 The word &"set"& at the start of a line, followed by a single space,
2843 is recognised specially as defining a value for a variable.
2844 The syntax is otherwise the same as the ACL modifier &"set ="&.
2847 .vitem &%-bem%&&~<&'filename'&>
2849 .cindex "testing" "string expansion"
2850 .cindex "expansion" "testing"
2851 This option operates like &%-be%& except that it must be followed by the name
2852 of a file. For example:
2854 exim -bem /tmp/testmessage
2856 The file is read as a message (as if receiving a locally-submitted non-SMTP
2857 message) before any of the test expansions are done. Thus, message-specific
2858 variables such as &$message_size$& and &$header_from:$& are available. However,
2859 no &'Received:'& header is added to the message. If the &%-t%& option is set,
2860 recipients are read from the headers in the normal way, and are shown in the
2861 &$recipients$& variable. Note that recipients cannot be given on the command
2862 line, because further arguments are taken as strings to expand (just like
2865 .vitem &%-bF%&&~<&'filename'&>
2867 .cindex "system filter" "testing"
2868 .cindex "testing" "system filter"
2869 This option is the same as &%-bf%& except that it assumes that the filter being
2870 tested is a system filter. The additional commands that are available only in
2871 system filters are recognized.
2873 .vitem &%-bf%&&~<&'filename'&>
2875 .cindex "filter" "testing"
2876 .cindex "testing" "filter file"
2877 .cindex "forward file" "testing"
2878 .cindex "testing" "forward file"
2879 .cindex "Sieve filter" "testing"
2880 This option runs Exim in user filter testing mode; the file is the filter file
2881 to be tested, and a test message must be supplied on the standard input. If
2882 there are no message-dependent tests in the filter, an empty file can be
2885 If you want to test a system filter file, use &%-bF%& instead of &%-bf%&. You
2886 can use both &%-bF%& and &%-bf%& on the same command, in order to test a system
2887 filter and a user filter in the same run. For example:
2889 exim -bF /system/filter -bf /user/filter </test/message
2891 This is helpful when the system filter adds header lines or sets filter
2892 variables that are used by the user filter.
2894 If the test filter file does not begin with one of the special lines
2899 it is taken to be a normal &_.forward_& file, and is tested for validity under
2900 that interpretation. See sections &<<SECTitenonfilred>>& to
2901 &<<SECTspecitredli>>& for a description of the possible contents of non-filter
2904 The result of an Exim command that uses &%-bf%&, provided no errors are
2905 detected, is a list of the actions that Exim would try to take if presented
2906 with the message for real. More details of filter testing are given in the
2907 separate document entitled &'Exim's interfaces to mail filtering'&.
2909 When testing a filter file,
2910 .cindex "&""From""& line"
2911 .cindex "envelope from"
2912 .cindex "envelope sender"
2913 .oindex "&%-f%&" "for filter testing"
2914 the envelope sender can be set by the &%-f%& option,
2915 or by a &"From&~"& line at the start of the test message. Various parameters
2916 that would normally be taken from the envelope recipient address of the message
2917 can be set by means of additional command line options (see the next four
2920 .vitem &%-bfd%&&~<&'domain'&>
2922 .vindex "&$qualify_domain$&"
2923 This sets the domain of the recipient address when a filter file is being
2924 tested by means of the &%-bf%& option. The default is the value of
2927 .vitem &%-bfl%&&~<&'local&~part'&>
2929 This sets the local part of the recipient address when a filter file is being
2930 tested by means of the &%-bf%& option. The default is the username of the
2931 process that calls Exim. A local part should be specified with any prefix or
2932 suffix stripped, because that is how it appears to the filter when a message is
2933 actually being delivered.
2935 .vitem &%-bfp%&&~<&'prefix'&>
2937 .cindex affix "filter testing"
2938 This sets the prefix of the local part of the recipient address when a filter
2939 file is being tested by means of the &%-bf%& option. The default is an empty
2942 .vitem &%-bfs%&&~<&'suffix'&>
2944 .cindex affix "filter testing"
2945 This sets the suffix of the local part of the recipient address when a filter
2946 file is being tested by means of the &%-bf%& option. The default is an empty
2949 .vitem &%-bh%&&~<&'IP&~address'&>
2951 .cindex "testing" "incoming SMTP"
2952 .cindex "SMTP" "testing incoming"
2953 .cindex "testing" "relay control"
2954 .cindex "relaying" "testing configuration"
2955 .cindex "policy control" "testing"
2956 .cindex "debugging" "&%-bh%& option"
2957 This option runs a fake SMTP session as if from the given IP address, using the
2958 standard input and output. The IP address may include a port number at the end,
2959 after a full stop. For example:
2961 exim -bh 10.9.8.7.1234
2962 exim -bh fe80::a00:20ff:fe86:a061.5678
2964 When an IPv6 address is given, it is converted into canonical form. In the case
2965 of the second example above, the value of &$sender_host_address$& after
2966 conversion to the canonical form is
2967 &`fe80:0000:0000:0a00:20ff:fe86:a061.5678`&.
2969 Comments as to what is going on are written to the standard error file. These
2970 include lines beginning with &"LOG"& for anything that would have been logged.
2971 This facility is provided for testing configuration options for incoming
2972 messages, to make sure they implement the required policy. For example, you can
2973 test your relay controls using &%-bh%&.
2977 You can test features of the configuration that rely on ident (RFC 1413)
2978 information by using the &%-oMt%& option. However, Exim cannot actually perform
2979 an ident callout when testing using &%-bh%& because there is no incoming SMTP
2982 &*Warning 2*&: Address verification callouts (see section &<<SECTcallver>>&)
2983 are also skipped when testing using &%-bh%&. If you want these callouts to
2984 occur, use &%-bhc%& instead.
2986 Messages supplied during the testing session are discarded, and nothing is
2987 written to any of the real log files. There may be pauses when DNS (and other)
2988 lookups are taking place, and of course these may time out. The &%-oMi%& option
2989 can be used to specify a specific IP interface and port if this is important,
2990 and &%-oMaa%& and &%-oMai%& can be used to set parameters as if the SMTP
2991 session were authenticated.
2993 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%& whose
2994 output just states whether a given recipient address from a given host is
2995 acceptable or not. See section &<<SECTcheckaccess>>&.
2997 Features such as authentication and encryption, where the client input is not
2998 plain text, cannot easily be tested with &%-bh%&. Instead, you should use a
2999 specialized SMTP test program such as
3000 &url(https://www.jetmore.org/john/code/swaks/,swaks).
3002 .vitem &%-bhc%&&~<&'IP&~address'&>
3004 This option operates in the same way as &%-bh%&, except that address
3005 verification callouts are performed if required. This includes consulting and
3006 updating the callout cache database.
3010 .cindex "alias file" "building"
3011 .cindex "building alias file"
3012 .cindex "Sendmail compatibility" "&%-bi%& option"
3013 Sendmail interprets the &%-bi%& option as a request to rebuild its alias file.
3014 Exim does not have the concept of a single alias file, and so it cannot mimic
3015 this behaviour. However, calls to &_/usr/lib/sendmail_& with the &%-bi%& option
3016 tend to appear in various scripts such as NIS make files, so the option must be
3019 If &%-bi%& is encountered, the command specified by the &%bi_command%&
3020 configuration option is run, under the uid and gid of the caller of Exim. If
3021 the &%-oA%& option is used, its value is passed to the command as an argument.
3022 The command set by &%bi_command%& may not contain arguments. The command can
3023 use the &'exim_dbmbuild'& utility, or some other means, to rebuild alias files
3024 if this is required. If the &%bi_command%& option is not set, calling Exim with
3027 . // Keep :help first, then the rest in alphabetical order
3029 .oindex "&%-bI:help%&"
3030 .cindex "querying exim information"
3031 We shall provide various options starting &`-bI:`& for querying Exim for
3032 information. The output of many of these will be intended for machine
3033 consumption. This one is not. The &%-bI:help%& option asks Exim for a
3034 synopsis of supported options beginning &`-bI:`&. Use of any of these
3035 options shall cause Exim to exit after producing the requested output.
3038 .oindex "&%-bI:dscp%&"
3039 .cindex "DSCP" "values"
3040 This option causes Exim to emit an alphabetically sorted list of all
3041 recognised DSCP names.
3043 .vitem &%-bI:sieve%&
3044 .oindex "&%-bI:sieve%&"
3045 .cindex "Sieve filter" "capabilities"
3046 This option causes Exim to emit an alphabetically sorted list of all supported
3047 Sieve protocol extensions on stdout, one per line. This is anticipated to be
3048 useful for ManageSieve (RFC 5804) implementations, in providing that protocol's
3049 &`SIEVE`& capability response line. As the precise list may depend upon
3050 compile-time build options, which this option will adapt to, this is the only
3051 way to guarantee a correct response.
3055 .cindex "local message reception"
3056 This option runs an Exim receiving process that accepts an incoming,
3057 locally-generated message on the standard input. The recipients are given as the
3058 command arguments (except when &%-t%& is also present &-- see below). Each
3059 argument can be a comma-separated list of RFC 2822 addresses. This is the
3060 default option for selecting the overall action of an Exim call; it is assumed
3061 if no other conflicting option is present.
3063 If any addresses in the message are unqualified (have no domain), they are
3064 qualified by the values of the &%qualify_domain%& or &%qualify_recipient%&
3065 options, as appropriate. The &%-bnq%& option (see below) provides a way of
3066 suppressing this for special cases.
3068 Policy checks on the contents of local messages can be enforced by means of
3069 the non-SMTP ACL. See chapter &<<CHAPACL>>& for details.
3071 .cindex "return code" "for &%-bm%&"
3072 The return code is zero if the message is successfully accepted. Otherwise, the
3073 action is controlled by the &%-oe%&&'x'& option setting &-- see below.
3076 .cindex "message" "format"
3077 .cindex "format" "message"
3078 .cindex "&""From""& line"
3079 .cindex "UUCP" "&""From""& line"
3080 .cindex "Sendmail compatibility" "&""From""& line"
3081 of the message must be as defined in RFC 2822, except that, for
3082 compatibility with Sendmail and Smail, a line in one of the forms
3084 From sender Fri Jan 5 12:55 GMT 1997
3085 From sender Fri, 5 Jan 97 12:55:01
3087 (with the weekday optional, and possibly with additional text after the date)
3088 is permitted to appear at the start of the message. There appears to be no
3089 authoritative specification of the format of this line. Exim recognizes it by
3090 matching against the regular expression defined by the &%uucp_from_pattern%&
3091 option, which can be changed if necessary.
3093 .oindex "&%-f%&" "overriding &""From""& line"
3094 The specified sender is treated as if it were given as the argument to the
3095 &%-f%& option, but if a &%-f%& option is also present, its argument is used in
3096 preference to the address taken from the message. The caller of Exim must be a
3097 trusted user for the sender of a message to be set in this way.
3099 .vitem &%-bmalware%&&~<&'filename'&>
3100 .oindex "&%-bmalware%&"
3101 .cindex "testing", "malware"
3102 .cindex "malware scan test"
3103 This debugging option causes Exim to scan the given file or directory
3104 (depending on the used scanner interface),
3105 using the malware scanning framework. The option of &%av_scanner%& influences
3106 this option, so if &%av_scanner%&'s value is dependent upon an expansion then
3107 the expansion should have defaults which apply to this invocation. ACLs are
3108 not invoked, so if &%av_scanner%& references an ACL variable then that variable
3109 will never be populated and &%-bmalware%& will fail.
3111 Exim will have changed working directory before resolving the filename, so
3112 using fully qualified pathnames is advisable. Exim will be running as the Exim
3113 user when it tries to open the file, rather than as the invoking user.
3114 This option requires admin privileges.
3116 The &%-bmalware%& option will not be extended to be more generally useful,
3117 there are better tools for file-scanning. This option exists to help
3118 administrators verify their Exim and AV scanner configuration.
3122 .cindex "address qualification, suppressing"
3123 By default, Exim automatically qualifies unqualified addresses (those
3124 without domains) that appear in messages that are submitted locally (that
3125 is, not over TCP/IP). This qualification applies both to addresses in
3126 envelopes, and addresses in header lines. Sender addresses are qualified using
3127 &%qualify_domain%&, and recipient addresses using &%qualify_recipient%& (which
3128 defaults to the value of &%qualify_domain%&).
3130 Sometimes, qualification is not wanted. For example, if &%-bS%& (batch SMTP) is
3131 being used to re-submit messages that originally came from remote hosts after
3132 content scanning, you probably do not want to qualify unqualified addresses in
3133 header lines. (Such lines will be present only if you have not enabled a header
3134 syntax check in the appropriate ACL.)
3136 The &%-bnq%& option suppresses all qualification of unqualified addresses in
3137 messages that originate on the local host. When this is used, unqualified
3138 addresses in the envelope provoke errors (causing message rejection) and
3139 unqualified addresses in header lines are left alone.
3144 .cindex "configuration options" "extracting"
3145 .cindex "options" "configuration &-- extracting"
3146 If this option is given with no arguments, it causes the values of all Exim's
3147 main configuration options to be written to the standard output. The values
3148 of one or more specific options can be requested by giving their names as
3149 arguments, for example:
3151 exim -bP qualify_domain hold_domains
3153 .cindex "hiding configuration option values"
3154 .cindex "configuration options" "hiding value of"
3155 .cindex "options" "hiding value of"
3156 However, any option setting that is preceded by the word &"hide"& in the
3157 configuration file is not shown in full, except to an admin user. For other
3158 users, the output is as in this example:
3160 mysql_servers = <value not displayable>
3162 If &%config%& is given as an argument, the config is
3163 output, as it was parsed, any include file resolved, any comment removed.
3165 If &%config_file%& is given as an argument, the name of the runtime
3166 configuration file is output. (&%configure_file%& works too, for
3167 backward compatibility.)
3168 If a list of configuration files was supplied, the value that is output here
3169 is the name of the file that was actually used.
3171 .cindex "options" "hiding name of"
3172 If the &%-n%& flag is given, then for most modes of &%-bP%& operation the
3173 name will not be output.
3175 .cindex "daemon" "process id (pid)"
3176 .cindex "pid (process id)" "of daemon"
3177 If &%log_file_path%& or &%pid_file_path%& are given, the names of the
3178 directories where log files and daemon pid files are written are output,
3179 respectively. If these values are unset, log files are written in a
3180 sub-directory of the spool directory called &%log%&, and the pid file is
3181 written directly into the spool directory.
3183 If &%-bP%& is followed by a name preceded by &`+`&, for example,
3185 exim -bP +local_domains
3187 it searches for a matching named list of any type (domain, host, address, or
3188 local part) and outputs what it finds.
3190 .cindex "options" "router &-- extracting"
3191 .cindex "options" "transport &-- extracting"
3192 .cindex "options" "authenticator &-- extracting"
3193 If one of the words &%router%&, &%transport%&, or &%authenticator%& is given,
3194 followed by the name of an appropriate driver instance, the option settings for
3195 that driver are output. For example:
3197 exim -bP transport local_delivery
3199 The generic driver options are output first, followed by the driver's private
3200 options. A list of the names of drivers of a particular type can be obtained by
3201 using one of the words &%router_list%&, &%transport_list%&, or
3202 &%authenticator_list%&, and a complete list of all drivers with their option
3203 settings can be obtained by using &%routers%&, &%transports%&, or
3206 .cindex "environment"
3207 If &%environment%& is given as an argument, the set of environment
3208 variables is output, line by line. Using the &%-n%& flag suppresses the value of the
3211 .cindex "options" "macro &-- extracting"
3212 If invoked by an admin user, then &%macro%&, &%macro_list%& and &%macros%&
3213 are available, similarly to the drivers. Because macros are sometimes used
3214 for storing passwords, this option is restricted.
3215 The output format is one item per line.
3216 For the "-bP macro <name>" form, if no such macro is found
3217 the exit status will be nonzero.
3221 .cindex "queue" "listing messages in"
3222 .cindex "listing" "messages in the queue"
3223 This option requests a listing of the contents of the mail queue on the
3224 standard output. If the &%-bp%& option is followed by a list of message ids,
3225 just those messages are listed. By default, this option can be used only by an
3226 admin user. However, the &%queue_list_requires_admin%& option can be set false
3227 to allow any user to see the queue.
3229 Each message in the queue is displayed as in the following example:
3231 25m 2.9K 0t5C6f-0000c8-00 <alice@wonderland.fict.example>
3232 red.king@looking-glass.fict.example
3235 .cindex "message" "size in queue listing"
3236 .cindex "size" "of message"
3237 The first line contains the length of time the message has been in the queue
3238 (in this case 25 minutes), the size of the message (2.9K), the unique local
3239 identifier for the message, and the message sender, as contained in the
3240 envelope. For bounce messages, the sender address is empty, and appears as
3241 &"<>"&. If the message was submitted locally by an untrusted user who overrode
3242 the default sender address, the user's login name is shown in parentheses
3243 before the sender address.
3245 .cindex "frozen messages" "in queue listing"
3246 If the message is frozen (attempts to deliver it are suspended) then the text
3247 &"*** frozen ***"& is displayed at the end of this line.
3249 The recipients of the message (taken from the envelope, not the headers) are
3250 displayed on subsequent lines. Those addresses to which the message has already
3251 been delivered are marked with the letter D. If an original address gets
3252 expanded into several addresses via an alias or forward file, the original is
3253 displayed with a D only when deliveries for all of its child addresses are
3259 This option operates like &%-bp%&, but in addition it shows delivered addresses
3260 that were generated from the original top level address(es) in each message by
3261 alias or forwarding operations. These addresses are flagged with &"+D"& instead
3267 .cindex "queue" "count of messages on"
3268 This option counts the number of messages in the queue, and writes the total
3269 to the standard output. It is restricted to admin users, unless
3270 &%queue_list_requires_admin%& is set false.
3275 This option operates like &%-bp%&, but the output is not sorted into
3276 chronological order of message arrival. This can speed it up when there are
3277 lots of messages in the queue, and is particularly useful if the output is
3278 going to be post-processed in a way that doesn't need the sorting.
3282 This option is a combination of &%-bpr%& and &%-bpa%&.
3286 This option is a combination of &%-bpr%& and &%-bpu%&.
3291 This option operates like &%-bp%& but shows only undelivered top-level
3292 addresses for each message displayed. Addresses generated by aliasing or
3293 forwarding are not shown, unless the message was deferred after processing by a
3294 router with the &%one_time%& option set.
3299 .cindex "testing" "retry configuration"
3300 .cindex "retry" "configuration testing"
3301 This option is for testing retry rules, and it must be followed by up to three
3302 arguments. It causes Exim to look for a retry rule that matches the values
3303 and to write it to the standard output. For example:
3305 exim -brt bach.comp.mus.example
3306 Retry rule: *.comp.mus.example F,2h,15m; F,4d,30m;
3308 See chapter &<<CHAPretry>>& for a description of Exim's retry rules. The first
3309 argument, which is required, can be a complete address in the form
3310 &'local_part@domain'&, or it can be just a domain name. If the second argument
3311 contains a dot, it is interpreted as an optional second domain name; if no
3312 retry rule is found for the first argument, the second is tried. This ties in
3313 with Exim's behaviour when looking for retry rules for remote hosts &-- if no
3314 rule is found that matches the host, one that matches the mail domain is
3315 sought. Finally, an argument that is the name of a specific delivery error, as
3316 used in setting up retry rules, can be given. For example:
3318 exim -brt haydn.comp.mus.example quota_3d
3319 Retry rule: *@haydn.comp.mus.example quota_3d F,1h,15m
3324 .cindex "testing" "rewriting"
3325 .cindex "rewriting" "testing"
3326 This option is for testing address rewriting rules, and it must be followed by
3327 a single argument, consisting of either a local part without a domain, or a
3328 complete address with a fully qualified domain. Exim outputs how this address
3329 would be rewritten for each possible place it might appear. See chapter
3330 &<<CHAPrewrite>>& for further details.
3334 .cindex "SMTP" "batched incoming"
3335 .cindex "batched SMTP input"
3336 This option is used for batched SMTP input, which is an alternative interface
3337 for non-interactive local message submission. A number of messages can be
3338 submitted in a single run. However, despite its name, this is not really SMTP
3339 input. Exim reads each message's envelope from SMTP commands on the standard
3340 input, but generates no responses. If the caller is trusted, or
3341 &%untrusted_set_sender%& is set, the senders in the SMTP MAIL commands are
3342 believed; otherwise the sender is always the caller of Exim.
3344 The message itself is read from the standard input, in SMTP format (leading
3345 dots doubled), terminated by a line containing just a single dot. An error is
3346 provoked if the terminating dot is missing. A further message may then follow.
3348 As for other local message submissions, the contents of incoming batch SMTP
3349 messages can be checked using the non-SMTP ACL (see chapter &<<CHAPACL>>&).
3350 Unqualified addresses are automatically qualified using &%qualify_domain%& and
3351 &%qualify_recipient%&, as appropriate, unless the &%-bnq%& option is used.
3353 Some other SMTP commands are recognized in the input. HELO and EHLO act
3354 as RSET; VRFY, EXPN, ETRN, and HELP act as NOOP;
3355 QUIT quits, ignoring the rest of the standard input.
3357 .cindex "return code" "for &%-bS%&"
3358 If any error is encountered, reports are written to the standard output and
3359 error streams, and Exim gives up immediately. The return code is 0 if no error
3360 was detected; it is 1 if one or more messages were accepted before the error
3361 was detected; otherwise it is 2.
3363 More details of input using batched SMTP are given in section
3364 &<<SECTincomingbatchedSMTP>>&.
3368 .cindex "SMTP" "local input"
3369 .cindex "local SMTP input"
3370 This option causes Exim to accept one or more messages by reading SMTP commands
3371 on the standard input, and producing SMTP replies on the standard output. SMTP
3372 policy controls, as defined in ACLs (see chapter &<<CHAPACL>>&) are applied.
3373 Some user agents use this interface as a way of passing locally-generated
3374 messages to the MTA.
3377 .cindex "sender" "source of"
3378 this usage, if the caller of Exim is trusted, or &%untrusted_set_sender%& is
3379 set, the senders of messages are taken from the SMTP MAIL commands.
3380 Otherwise the content of these commands is ignored and the sender is set up as
3381 the calling user. Unqualified addresses are automatically qualified using
3382 &%qualify_domain%& and &%qualify_recipient%&, as appropriate, unless the
3383 &%-bnq%& option is used.
3387 &%-bs%& option is also used to run Exim from &'inetd'&, as an alternative to
3388 using a listening daemon. Exim can distinguish the two cases by checking
3389 whether the standard input is a TCP/IP socket. When Exim is called from
3390 &'inetd'&, the source of the mail is assumed to be remote, and the comments
3391 above concerning senders and qualification do not apply. In this situation,
3392 Exim behaves in exactly the same way as it does when receiving a message via
3393 the listening daemon.
3397 .cindex "testing" "addresses"
3398 .cindex "address" "testing"
3399 This option runs Exim in address testing mode, in which each argument is taken
3400 as a recipient address to be tested for deliverability. The results are
3401 written to the standard output. If a test fails, and the caller is not an admin
3402 user, no details of the failure are output, because these might contain
3403 sensitive information such as usernames and passwords for database lookups.
3405 If no arguments are given, Exim runs in an interactive manner, prompting with a
3406 right angle bracket for addresses to be tested.
3408 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3409 &[readline()]& function, because it is running as &'root'& and there are
3412 Each address is handled as if it were the recipient address of a message
3413 (compare the &%-bv%& option). It is passed to the routers and the result is
3414 written to the standard output. However, any router that has
3415 &%no_address_test%& set is bypassed. This can make &%-bt%& easier to use for
3416 genuine routing tests if your first router passes everything to a scanner
3419 .cindex "return code" "for &%-bt%&"
3420 The return code is 2 if any address failed outright; it is 1 if no address
3421 failed outright but at least one could not be resolved for some reason. Return
3422 code 0 is given only when all addresses succeed.
3424 .cindex "duplicate addresses"
3425 &*Note*&: When actually delivering a message, Exim removes duplicate recipient
3426 addresses after routing is complete, so that only one delivery takes place.
3427 This does not happen when testing with &%-bt%&; the full results of routing are
3430 &*Warning*&: &%-bt%& can only do relatively simple testing. If any of the
3431 routers in the configuration makes any tests on the sender address of a
3433 .oindex "&%-f%&" "for address testing"
3434 you can use the &%-f%& option to set an appropriate sender when running
3435 &%-bt%& tests. Without it, the sender is assumed to be the calling user at the
3436 default qualifying domain. However, if you have set up (for example) routers
3437 whose behaviour depends on the contents of an incoming message, you cannot test
3438 those conditions using &%-bt%&. The &%-N%& option provides a possible way of
3443 .cindex "version number of Exim"
3444 This option causes Exim to write the current version number, compilation
3445 number, and compilation date of the &'exim'& binary to the standard output.
3446 It also lists the DBM library that is being used, the optional modules (such as
3447 specific lookup types), the drivers that are included in the binary, and the
3448 name of the runtime configuration file that is in use.
3450 As part of its operation, &%-bV%& causes Exim to read and syntax check its
3451 configuration file. However, this is a static check only. It cannot check
3452 values that are to be expanded. For example, although a misspelt ACL verb is
3453 detected, an error in the verb's arguments is not. You cannot rely on &%-bV%&
3454 alone to discover (for example) all the typos in the configuration; some
3455 realistic testing is needed. The &%-bh%& and &%-N%& options provide more
3456 dynamic testing facilities.
3460 .cindex "verifying address" "using &%-bv%&"
3461 .cindex "address" "verification"
3462 This option runs Exim in address verification mode, in which each argument is
3463 taken as a recipient address to be verified by the routers. (This does
3464 not involve any verification callouts). During normal operation, verification
3465 happens mostly as a consequence processing a &%verify%& condition in an ACL
3466 (see chapter &<<CHAPACL>>&). If you want to test an entire ACL, possibly
3467 including callouts, see the &%-bh%& and &%-bhc%& options.
3469 If verification fails, and the caller is not an admin user, no details of the
3470 failure are output, because these might contain sensitive information such as
3471 usernames and passwords for database lookups.
3473 If no arguments are given, Exim runs in an interactive manner, prompting with a
3474 right angle bracket for addresses to be verified.
3476 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3477 &[readline()]& function, because it is running as &'exim'& and there are
3480 Verification differs from address testing (the &%-bt%& option) in that routers
3481 that have &%no_verify%& set are skipped, and if the address is accepted by a
3482 router that has &%fail_verify%& set, verification fails. The address is
3483 verified as a recipient if &%-bv%& is used; to test verification for a sender
3484 address, &%-bvs%& should be used.
3486 If the &%-v%& option is not set, the output consists of a single line for each
3487 address, stating whether it was verified or not, and giving a reason in the
3488 latter case. Without &%-v%&, generating more than one address by redirection
3489 causes verification to end successfully, without considering the generated
3490 addresses. However, if just one address is generated, processing continues,
3491 and the generated address must verify successfully for the overall verification
3494 When &%-v%& is set, more details are given of how the address has been handled,
3495 and in the case of address redirection, all the generated addresses are also
3496 considered. Verification may succeed for some and fail for others.
3499 .cindex "return code" "for &%-bv%&"
3500 return code is 2 if any address failed outright; it is 1 if no address
3501 failed outright but at least one could not be resolved for some reason. Return
3502 code 0 is given only when all addresses succeed.
3504 If any of the routers in the configuration makes any tests on the sender
3505 address of a message, you should use the &%-f%& option to set an appropriate
3506 sender when running &%-bv%& tests. Without it, the sender is assumed to be the
3507 calling user at the default qualifying domain.
3511 This option acts like &%-bv%&, but verifies the address as a sender rather
3512 than a recipient address. This affects any rewriting and qualification that
3519 .cindex "inetd" "wait mode"
3520 This option runs Exim as a daemon, awaiting incoming SMTP connections,
3521 similarly to the &%-bd%& option. All port specifications on the command-line
3522 and in the configuration file are ignored. Queue-running may not be specified.
3524 In this mode, Exim expects to be passed a socket as fd 0 (stdin) which is
3525 listening for connections. This permits the system to start up and have
3526 inetd (or equivalent) listen on the SMTP ports, starting an Exim daemon for
3527 each port only when the first connection is received.
3529 If the option is given as &%-bw%&<&'time'&> then the time is a timeout, after
3530 which the daemon will exit, which should cause inetd to listen once more.
3532 .vitem &%-C%&&~<&'filelist'&>
3534 .cindex "configuration file" "alternate"
3535 .cindex "CONFIGURE_FILE"
3536 .cindex "alternate configuration file"
3537 This option causes Exim to find the runtime configuration file from the given
3538 list instead of from the list specified by the CONFIGURE_FILE
3539 compile-time setting. Usually, the list will consist of just a single filename,
3540 but it can be a colon-separated list of names. In this case, the first
3541 file that exists is used. Failure to open an existing file stops Exim from
3542 proceeding any further along the list, and an error is generated.
3544 When this option is used by a caller other than root, and the list is different
3545 from the compiled-in list, Exim gives up its root privilege immediately, and
3546 runs with the real and effective uid and gid set to those of the caller.
3547 However, if a TRUSTED_CONFIG_LIST file is defined in &_Local/Makefile_&, that
3548 file contains a list of full pathnames, one per line, for configuration files
3549 which are trusted. Root privilege is retained for any configuration file so
3550 listed, as long as the caller is the Exim user (or the user specified in the
3551 CONFIGURE_OWNER option, if any), and as long as the configuration file is
3552 not writeable by inappropriate users or groups.
3554 Leaving TRUSTED_CONFIG_LIST unset precludes the possibility of testing a
3555 configuration using &%-C%& right through message reception and delivery,
3556 even if the caller is root. The reception works, but by that time, Exim is
3557 running as the Exim user, so when it re-executes to regain privilege for the
3558 delivery, the use of &%-C%& causes privilege to be lost. However, root can
3559 test reception and delivery using two separate commands (one to put a message
3560 in the queue, using &%-odq%&, and another to do the delivery, using &%-M%&).
3562 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
3563 prefix string with which any file named in a &%-C%& command line option
3564 must start. In addition, the filename must not contain the sequence &`/../`&.
3565 However, if the value of the &%-C%& option is identical to the value of
3566 CONFIGURE_FILE in &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as
3567 usual. There is no default setting for ALT_CONFIG_PREFIX; when it is
3568 unset, any filename can be used with &%-C%&.
3570 ALT_CONFIG_PREFIX can be used to confine alternative configuration files
3571 to a directory to which only root has access. This prevents someone who has
3572 broken into the Exim account from running a privileged Exim with an arbitrary
3575 The &%-C%& facility is useful for ensuring that configuration files are
3576 syntactically correct, but cannot be used for test deliveries, unless the
3577 caller is privileged, or unless it is an exotic configuration that does not
3578 require privilege. No check is made on the owner or group of the files
3579 specified by this option.
3582 .vitem &%-D%&<&'macro'&>=<&'value'&>
3584 .cindex "macro" "setting on command line"
3585 This option can be used to override macro definitions in the configuration file
3586 (see section &<<SECTmacrodefs>>&). However, like &%-C%&, if it is used by an
3587 unprivileged caller, it causes Exim to give up its root privilege.
3588 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
3589 completely disabled, and its use causes an immediate error exit.
3591 If WHITELIST_D_MACROS is defined in &_Local/Makefile_& then it should be a
3592 colon-separated list of macros which are considered safe and, if &%-D%& only
3593 supplies macros from this list, and the values are acceptable, then Exim will
3594 not give up root privilege if the caller is root, the Exim run-time user, or
3595 the CONFIGURE_OWNER, if set. This is a transition mechanism and is expected
3596 to be removed in the future. Acceptable values for the macros satisfy the
3597 regexp: &`^[A-Za-z0-9_/.-]*$`&
3599 The entire option (including equals sign if present) must all be within one
3600 command line item. &%-D%& can be used to set the value of a macro to the empty
3601 string, in which case the equals sign is optional. These two commands are
3607 To include spaces in a macro definition item, quotes must be used. If you use
3608 quotes, spaces are permitted around the macro name and the equals sign. For
3611 exim '-D ABC = something' ...
3613 &%-D%& may be repeated up to 10 times on a command line.
3614 Only macro names up to 22 letters long can be set.
3617 .vitem &%-d%&<&'debug&~options'&>
3619 .cindex "debugging" "list of selectors"
3620 .cindex "debugging" "&%-d%& option"
3621 This option causes debugging information to be written to the standard
3622 error stream. It is restricted to admin users because debugging output may show
3623 database queries that contain password information. Also, the details of users'
3624 filter files should be protected. If a non-admin user uses &%-d%&, Exim
3625 writes an error message to the standard error stream and exits with a non-zero
3628 When &%-d%& is used, &%-v%& is assumed. If &%-d%& is given on its own, a lot of
3629 standard debugging data is output. This can be reduced, or increased to include
3630 some more rarely needed information, by directly following &%-d%& with a string
3631 made up of names preceded by plus or minus characters. These add or remove sets
3632 of debugging data, respectively. For example, &%-d+filter%& adds filter
3633 debugging, whereas &%-d-all+filter%& selects only filter debugging. Note that
3634 no spaces are allowed in the debug setting. The available debugging categories
3636 .itable none 0 0 2 1pt left 1pt left
3637 .irow acl "ACL interpretation"
3638 .irow auth "authenticators"
3639 .irow deliver "general delivery logic"
3640 .irow dns "DNS lookups (see also resolver)"
3641 .irow dnsbl "DNS black list (aka RBL) code"
3642 .irow exec "arguments for &[execv()]& calls"
3643 .irow expand "detailed debugging for string expansions"
3644 .irow filter "filter handling"
3645 .irow hints_lookup "hints data lookups"
3646 .irow host_lookup "all types of name-to-IP address handling"
3647 .irow ident "ident lookup"
3648 .irow interface "lists of local interfaces"
3649 .irow lists "matching things in lists"
3650 .irow load "system load checks"
3651 .irow local_scan "can be used by &[local_scan()]& (see chapter &&&
3652 &<<CHAPlocalscan>>&)"
3653 .irow lookup "general lookup code and all lookups"
3654 .irow memory "memory handling"
3655 .irow noutf8 "modifier: avoid UTF-8 line-drawing"
3656 .irow pid "modifier: add pid to debug output lines"
3657 .irow process_info "setting info for the process log"
3658 .irow queue_run "queue runs"
3659 .irow receive "general message reception logic"
3660 .irow resolver "turn on the DNS resolver's debugging output"
3661 .irow retry "retry handling"
3662 .irow rewrite "address rewriting""
3663 .irow route "address routing"
3664 .irow timestamp "modifier: add timestamp to debug output lines"
3665 .irow tls "TLS logic"
3666 .irow transport "transports"
3667 .irow uid "changes of uid/gid and looking up uid/gid"
3668 .irow verify "address verification logic"
3669 .irow all "almost all of the above (see below), and also &%-v%&"
3671 The &`all`& option excludes &`memory`& when used as &`+all`&, but includes it
3672 for &`-all`&. The reason for this is that &`+all`& is something that people
3673 tend to use when generating debug output for Exim maintainers. If &`+memory`&
3674 is included, an awful lot of output that is very rarely of interest is
3675 generated, so it now has to be explicitly requested. However, &`-all`& does
3676 turn everything off.
3678 .cindex "resolver, debugging output"
3679 .cindex "DNS resolver, debugging output"
3680 The &`resolver`& option produces output only if the DNS resolver was compiled
3681 with DEBUG enabled. This is not the case in some operating systems. Also,
3682 unfortunately, debugging output from the DNS resolver is written to stdout
3685 The default (&%-d%& with no argument) omits &`expand`&, &`filter`&,
3686 &`interface`&, &`load`&, &`memory`&, &`pid`&, &`resolver`&, and &`timestamp`&.
3687 However, the &`pid`& selector is forced when debugging is turned on for a
3688 daemon, which then passes it on to any re-executed Exims. Exim also
3689 automatically adds the pid to debug lines when several remote deliveries are
3692 The &`timestamp`& selector causes the current time to be inserted at the start
3693 of all debug output lines. This can be useful when trying to track down delays
3696 .cindex debugging "UTF-8 in"
3697 .cindex UTF-8 "in debug output"
3698 The &`noutf8`& selector disables the use of
3699 UTF-8 line-drawing characters to group related information.
3700 When disabled. ascii-art is used instead.
3701 Using the &`+all`& option does not set this modifier,
3703 If the &%debug_print%& option is set in any driver, it produces output whenever
3704 any debugging is selected, or if &%-v%& is used.
3706 .vitem &%-dd%&<&'debug&~options'&>
3708 This option behaves exactly like &%-d%& except when used on a command that
3709 starts a daemon process. In that case, debugging is turned off for the
3710 subprocesses that the daemon creates. Thus, it is useful for monitoring the
3711 behaviour of the daemon without creating as much output as full debugging does.
3714 .oindex "&%-dropcr%&"
3715 This is an obsolete option that is now a no-op. It used to affect the way Exim
3716 handled CR and LF characters in incoming messages. What happens now is
3717 described in section &<<SECTlineendings>>&.
3721 .cindex "bounce message" "generating"
3722 This option specifies that an incoming message is a locally-generated delivery
3723 failure report. It is used internally by Exim when handling delivery failures
3724 and is not intended for external use. Its only effect is to stop Exim
3725 generating certain messages to the postmaster, as otherwise message cascades
3726 could occur in some situations. As part of the same option, a message id may
3727 follow the characters &%-E%&. If it does, the log entry for the receipt of the
3728 new message contains the id, following &"R="&, as a cross-reference.
3731 .oindex "&%-e%&&'x'&"
3732 There are a number of Sendmail options starting with &%-oe%& which seem to be
3733 called by various programs without the leading &%o%& in the option. For
3734 example, the &%vacation%& program uses &%-eq%&. Exim treats all options of the
3735 form &%-e%&&'x'& as synonymous with the corresponding &%-oe%&&'x'& options.
3737 .vitem &%-F%&&~<&'string'&>
3739 .cindex "sender" "name"
3740 .cindex "name" "of sender"
3741 This option sets the sender's full name for use when a locally-generated
3742 message is being accepted. In the absence of this option, the user's &'gecos'&
3743 entry from the password data is used. As users are generally permitted to alter
3744 their &'gecos'& entries, no security considerations are involved. White space
3745 between &%-F%& and the <&'string'&> is optional.
3747 .vitem &%-f%&&~<&'address'&>
3749 .cindex "sender" "address"
3750 .cindex "address" "sender"
3751 .cindex "trusted users"
3752 .cindex "envelope from"
3753 .cindex "envelope sender"
3754 .cindex "user" "trusted"
3755 This option sets the address of the envelope sender of a locally-generated
3756 message (also known as the return path). The option can normally be used only
3757 by a trusted user, but &%untrusted_set_sender%& can be set to allow untrusted
3760 Processes running as root or the Exim user are always trusted. Other
3761 trusted users are defined by the &%trusted_users%& or &%trusted_groups%&
3762 options. In the absence of &%-f%&, or if the caller is not trusted, the sender
3763 of a local message is set to the caller's login name at the default qualify
3766 There is one exception to the restriction on the use of &%-f%&: an empty sender
3767 can be specified by any user, trusted or not, to create a message that can
3768 never provoke a bounce. An empty sender can be specified either as an empty
3769 string, or as a pair of angle brackets with nothing between them, as in these
3770 examples of shell commands:
3772 exim -f '<>' user@domain
3773 exim -f "" user@domain
3775 In addition, the use of &%-f%& is not restricted when testing a filter file
3776 with &%-bf%& or when testing or verifying addresses using the &%-bt%& or
3779 Allowing untrusted users to change the sender address does not of itself make
3780 it possible to send anonymous mail. Exim still checks that the &'From:'& header
3781 refers to the local user, and if it does not, it adds a &'Sender:'& header,
3782 though this can be overridden by setting &%no_local_from_check%&.
3785 .cindex "&""From""& line"
3786 space between &%-f%& and the <&'address'&> is optional (that is, they can be
3787 given as two arguments or one combined argument). The sender of a
3788 locally-generated message can also be set (when permitted) by an initial
3789 &"From&~"& line in the message &-- see the description of &%-bm%& above &-- but
3790 if &%-f%& is also present, it overrides &"From&~"&.
3794 .cindex "submission fixups, suppressing (command-line)"
3795 This option is equivalent to an ACL applying:
3797 control = suppress_local_fixups
3799 for every message received. Note that Sendmail will complain about such
3800 bad formatting, where Exim silently just does not fix it up. This may change
3803 As this affects audit information, the caller must be a trusted user to use
3806 .vitem &%-h%&&~<&'number'&>
3808 .cindex "Sendmail compatibility" "&%-h%& option ignored"
3809 This option is accepted for compatibility with Sendmail, but has no effect. (In
3810 Sendmail it overrides the &"hop count"& obtained by counting &'Received:'&
3815 .cindex "Solaris" "&'mail'& command"
3816 .cindex "dot" "in incoming non-SMTP message"
3817 This option, which has the same effect as &%-oi%&, specifies that a dot on a
3818 line by itself should not terminate an incoming, non-SMTP message.
3819 Solaris 2.4 (SunOS 5.4) Sendmail has a similar &%-i%& processing option
3820 &url(https://docs.oracle.com/cd/E19457-01/801-6680-1M/801-6680-1M.pdf),
3821 p. 1M-529), and therefore a &%-oi%& command line option, which both are used
3822 by its &'mailx'& command.
3824 .vitem &%-L%&&~<&'tag'&>
3826 .cindex "syslog" "process name; set with flag"
3827 This option is equivalent to setting &%syslog_processname%& in the config
3828 file and setting &%log_file_path%& to &`syslog`&.
3829 Its use is restricted to administrators. The configuration file has to be
3830 read and parsed, to determine access rights, before this is set and takes
3831 effect, so early configuration file errors will not honour this flag.
3833 The tag should not be longer than 32 characters.
3835 .vitem &%-M%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3837 .cindex "forcing delivery"
3838 .cindex "delivery" "forcing attempt"
3839 .cindex "frozen messages" "forcing delivery"
3840 This option requests Exim to run a delivery attempt on each message in turn. If
3841 any of the messages are frozen, they are automatically thawed before the
3842 delivery attempt. The settings of &%queue_domains%&, &%queue_smtp_domains%&,
3843 and &%hold_domains%& are ignored.
3846 .cindex "hints database" "overriding retry hints"
3847 hints for any of the addresses are overridden &-- Exim tries to deliver even if
3848 the normal retry time has not yet been reached. This option requires the caller
3849 to be an admin user. However, there is an option called &%prod_requires_admin%&
3850 which can be set false to relax this restriction (and also the same requirement
3851 for the &%-q%&, &%-R%&, and &%-S%& options).
3853 The deliveries happen synchronously, that is, the original Exim process does
3854 not terminate until all the delivery attempts have finished. No output is
3855 produced unless there is a serious error. If you want to see what is happening,
3856 use the &%-v%& option as well, or inspect Exim's main log.
3858 .vitem &%-Mar%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3860 .cindex "message" "adding recipients"
3861 .cindex "recipient" "adding"
3862 This option requests Exim to add the addresses to the list of recipients of the
3863 message (&"ar"& for &"add recipients"&). The first argument must be a message
3864 id, and the remaining ones must be email addresses. However, if the message is
3865 active (in the middle of a delivery attempt), it is not altered. This option
3866 can be used only by an admin user.
3868 .vitem "&%-MC%&&~<&'transport'&>&~<&'hostname'&>&&&
3870 &~<&'sequence&~number'&>&&&
3871 &~<&'message&~id'&>"
3873 .cindex "SMTP" "passed connection"
3874 .cindex "SMTP" "multiple deliveries"
3875 .cindex "multiple SMTP deliveries"
3876 This option is not intended for use by external callers. It is used internally
3877 by Exim to invoke another instance of itself to deliver a waiting message using
3878 an existing SMTP connection, which is passed as the standard input. Details are
3879 given in chapter &<<CHAPSMTP>>&. This must be the final option, and the caller
3880 must be root or the Exim user in order to use it.
3884 This option is not intended for use by external callers. It is used internally
3885 by Exim in conjunction with the &%-MC%& option. It signifies that the
3886 connection to the remote host has been authenticated.
3890 This option is not intended for use by external callers. It is used internally
3891 by Exim in conjunction with the &%-MC%& option. It signifies that the
3892 remote host supports the ESMTP &_DSN_& extension.
3896 This option is not intended for use by external callers. It is used internally
3897 by Exim in conjunction with the &%-d%& option
3898 to pass on an information string on the purpose of the process.
3900 .vitem &%-MCG%&&~<&'queue&~name'&>
3902 This option is not intended for use by external callers. It is used internally
3903 by Exim in conjunction with the &%-MC%& option. It signifies that an
3904 alternate queue is used, named by the following argument.
3908 This option is not intended for use by external callers. It is used internally
3909 by Exim in conjunction with the &%-MC%& option. It signifies that a
3910 remote host supports the ESMTP &_CHUNKING_& extension.
3914 This option is not intended for use by external callers. It is used internally
3915 by Exim in conjunction with the &%-MC%& option. It signifies that the server to
3916 which Exim is connected advertised limits on numbers of mails, recipients or
3918 The limits are given by the following three arguments.
3922 This option is not intended for use by external callers. It is used internally
3923 by Exim in conjunction with the &%-MC%& option. It signifies that the server to
3924 which Exim is connected supports pipelining.
3928 This option is not intended for use by external callers. It is used internally
3929 by Exim in conjunction with the &%-MC%& option. It signifies that the connection
3930 t a remote server is via a SOCKS proxy, using addresses and ports given by
3931 the following four arguments.
3933 .vitem &%-MCQ%&&~<&'process&~id'&>&~<&'pipe&~fd'&>
3935 This option is not intended for use by external callers. It is used internally
3936 by Exim in conjunction with the &%-MC%& option when the original delivery was
3937 started by a queue runner. It passes on the process id of the queue runner,
3938 together with the file descriptor number of an open pipe. Closure of the pipe
3939 signals the final completion of the sequence of processes that are passing
3940 messages through the same SMTP connection.
3942 .vitem &%-MCq%&&~<&'recipient&~address'&>&~<&'size'&>
3944 This option is not intended for use by external callers. It is used internally
3945 by Exim to implement quota checking for local users.
3949 This option is not intended for use by external callers. It is used internally
3950 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3951 ESMTP SIZE option should be used on messages delivered down the existing
3956 This option is not intended for use by external callers. It is used internally
3957 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3958 host to which Exim is connected supports TLS encryption.
3960 .vitem &%-MCr%&&~<&'SNI'&> &&&
3964 These options are not intended for use by external callers. It is used internally
3965 by Exim in conjunction with the &%-MCt%& option, and passes on the fact that
3966 a TLS Server Name Indication was sent as part of the channel establishment.
3967 The argument gives the SNI string.
3968 The "r" variant indicates a DANE-verified connection.
3970 .vitem &%-MCt%&&~<&'IP&~address'&>&~<&'port'&>&~<&'cipher'&>
3972 This option is not intended for use by external callers. It is used internally
3973 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3974 connection is being proxied by a parent process for handling TLS encryption.
3975 The arguments give the local address and port being proxied, and the TLS cipher.
3977 .vitem &%-Mc%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3979 .cindex "hints database" "not overridden by &%-Mc%&"
3980 .cindex "delivery" "manually started &-- not forced"
3981 This option requests Exim to run a delivery attempt on each message, in turn,
3982 but unlike the &%-M%& option, it does check for retry hints, and respects any
3983 that are found. This option is not very useful to external callers. It is
3984 provided mainly for internal use by Exim when it needs to re-invoke itself in
3985 order to regain root privilege for a delivery (see chapter &<<CHAPsecurity>>&).
3986 However, &%-Mc%& can be useful when testing, in order to run a delivery that
3987 respects retry times and other options such as &%hold_domains%& that are
3988 overridden when &%-M%& is used. Such a delivery does not count as a queue run.
3989 If you want to run a specific delivery as if in a queue run, you should use
3990 &%-q%& with a message id argument. A distinction between queue run deliveries
3991 and other deliveries is made in one or two places.
3993 .vitem &%-Mes%&&~<&'message&~id'&>&~<&'address'&>
3995 .cindex "message" "changing sender"
3996 .cindex "sender" "changing"
3997 This option requests Exim to change the sender address in the message to the
3998 given address, which must be a fully qualified address or &"<>"& (&"es"& for
3999 &"edit sender"&). There must be exactly two arguments. The first argument must
4000 be a message id, and the second one an email address. However, if the message
4001 is active (in the middle of a delivery attempt), its status is not altered.
4002 This option can be used only by an admin user.
4004 .vitem &%-Mf%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4006 .cindex "freezing messages"
4007 .cindex "message" "manually freezing"
4008 This option requests Exim to mark each listed message as &"frozen"&. This
4009 prevents any delivery attempts taking place until the message is &"thawed"&,
4010 either manually or as a result of the &%auto_thaw%& configuration option.
4011 However, if any of the messages are active (in the middle of a delivery
4012 attempt), their status is not altered. This option can be used only by an admin
4015 .vitem &%-Mg%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4017 .cindex "giving up on messages"
4018 .cindex "message" "abandoning delivery attempts"
4019 .cindex "delivery" "abandoning further attempts"
4020 This option requests Exim to give up trying to deliver the listed messages,
4021 including any that are frozen. However, if any of the messages are active,
4022 their status is not altered. For non-bounce messages, a delivery error message
4023 is sent to the sender, containing the text &"cancelled by administrator"&.
4024 Bounce messages are just discarded. This option can be used only by an admin
4027 .vitem &%-MG%&&~<&'queue&~name'&>&~<&'message&~id'&>&~<&'message&~id'&>&~...
4030 .cindex "named queues" "moving messages"
4031 .cindex "queue" "moving messages"
4032 This option requests that each listed message be moved from its current
4033 queue to the given named queue.
4034 The destination queue name argument is required, but can be an empty
4035 string to define the default queue.
4036 If the messages are not currently located in the default queue,
4037 a &%-qG<name>%& option will be required to define the source queue.
4039 .vitem &%-Mmad%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4041 .cindex "delivery" "cancelling all"
4042 This option requests Exim to mark all the recipient addresses in the messages
4043 as already delivered (&"mad"& for &"mark all delivered"&). However, if any
4044 message is active (in the middle of a delivery attempt), its status is not
4045 altered. This option can be used only by an admin user.
4047 .vitem &%-Mmd%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
4049 .cindex "delivery" "cancelling by address"
4050 .cindex "recipient" "removing"
4051 .cindex "removing recipients"
4052 This option requests Exim to mark the given addresses as already delivered
4053 (&"md"& for &"mark delivered"&). The first argument must be a message id, and
4054 the remaining ones must be email addresses. These are matched to recipient
4055 addresses in the message in a case-sensitive manner. If the message is active
4056 (in the middle of a delivery attempt), its status is not altered. This option
4057 can be used only by an admin user.
4059 .vitem &%-Mrm%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4061 .cindex "removing messages"
4062 .cindex "abandoning mail"
4063 .cindex "message" "manually discarding"
4064 This option requests Exim to remove the given messages from the queue. No
4065 bounce messages are sent; each message is simply forgotten. However, if any of
4066 the messages are active, their status is not altered. This option can be used
4067 only by an admin user or by the user who originally caused the message to be
4068 placed in the queue.
4073 . .cindex REQUIRETLS
4074 . This option is used to request REQUIRETLS processing on the message.
4075 . It is used internally by Exim in conjunction with -E when generating
4079 .vitem &%-Mset%&&~<&'message&~id'&>
4081 .cindex "testing" "string expansion"
4082 .cindex "expansion" "testing"
4083 This option is useful only in conjunction with &%-be%& (that is, when testing
4084 string expansions). Exim loads the given message from its spool before doing
4085 the test expansions, thus setting message-specific variables such as
4086 &$message_size$& and the header variables. The &$recipients$& variable is made
4087 available. This feature is provided to make it easier to test expansions that
4088 make use of these variables. However, this option can be used only by an admin
4089 user. See also &%-bem%&.
4091 .vitem &%-Mt%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4093 .cindex "thawing messages"
4094 .cindex "unfreezing messages"
4095 .cindex "frozen messages" "thawing"
4096 .cindex "message" "thawing frozen"
4097 This option requests Exim to &"thaw"& any of the listed messages that are
4098 &"frozen"&, so that delivery attempts can resume. However, if any of the
4099 messages are active, their status is not altered. This option can be used only
4102 .vitem &%-Mvb%&&~<&'message&~id'&>
4104 .cindex "listing" "message body"
4105 .cindex "message" "listing body of"
4106 This option causes the contents of the message body (-D) spool file to be
4107 written to the standard output. This option can be used only by an admin user.
4109 .vitem &%-Mvc%&&~<&'message&~id'&>
4111 .cindex "message" "listing in RFC 2822 format"
4112 .cindex "listing" "message in RFC 2822 format"
4113 This option causes a copy of the complete message (header lines plus body) to
4114 be written to the standard output in RFC 2822 format. This option can be used
4115 only by an admin user.
4117 .vitem &%-Mvh%&&~<&'message&~id'&>
4119 .cindex "listing" "message headers"
4120 .cindex "header lines" "listing"
4121 .cindex "message" "listing header lines"
4122 This option causes the contents of the message headers (-H) spool file to be
4123 written to the standard output. This option can be used only by an admin user.
4125 .vitem &%-Mvl%&&~<&'message&~id'&>
4127 .cindex "listing" "message log"
4128 .cindex "message" "listing message log"
4129 This option causes the contents of the message log spool file to be written to
4130 the standard output. This option can be used only by an admin user.
4134 This is a synonym for &%-om%& that is accepted by Sendmail
4135 (&url(https://docs.oracle.com/cd/E19457-01/801-6680-1M/801-6680-1M.pdf)
4136 p. 1M-258), so Exim treats it that way too.
4140 .cindex "debugging" "&%-N%& option"
4141 .cindex "debugging" "suppressing delivery"
4142 This is a debugging option that inhibits delivery of a message at the transport
4143 level. It implies &%-v%&. Exim goes through many of the motions of delivery &--
4144 it just doesn't actually transport the message, but instead behaves as if it
4145 had successfully done so. However, it does not make any updates to the retry
4146 database, and the log entries for deliveries are flagged with &"*>"& rather
4149 Because &%-N%& discards any message to which it applies, only root or the Exim
4150 user are allowed to use it with &%-bd%&, &%-q%&, &%-R%& or &%-M%&. In other
4151 words, an ordinary user can use it only when supplying an incoming message to
4152 which it will apply. Although transportation never fails when &%-N%& is set, an
4153 address may be deferred because of a configuration problem on a transport, or a
4154 routing problem. Once &%-N%& has been used for a delivery attempt, it sticks to
4155 the message, and applies to any subsequent delivery attempts that may happen
4160 This option is interpreted by Sendmail to mean &"no aliasing"&.
4161 For normal modes of operation, it is ignored by Exim.
4162 When combined with &%-bP%& it makes the output more terse (suppresses
4163 option names, environment values and config pretty printing).
4165 .vitem &%-O%&&~<&'data'&>
4167 This option is interpreted by Sendmail to mean &`set option`&. It is ignored by
4170 .vitem &%-oA%&&~<&'file&~name'&>
4172 .cindex "Sendmail compatibility" "&%-oA%& option"
4173 This option is used by Sendmail in conjunction with &%-bi%& to specify an
4174 alternative alias filename. Exim handles &%-bi%& differently; see the
4177 .vitem &%-oB%&&~<&'n'&>
4179 .cindex "SMTP" "passed connection"
4180 .cindex "SMTP" "multiple deliveries"
4181 .cindex "multiple SMTP deliveries"
4182 This is a debugging option which limits the maximum number of messages that can
4183 be delivered down one SMTP connection, overriding the value set in any &(smtp)&
4184 transport. If <&'n'&> is omitted, the limit is set to 1.
4188 .cindex "background delivery"
4189 .cindex "delivery" "in the background"
4190 This option applies to all modes in which Exim accepts incoming messages,
4191 including the listening daemon. It requests &"background"& delivery of such
4192 messages, which means that the accepting process automatically starts a
4193 delivery process for each message received, but does not wait for the delivery
4194 processes to finish.
4196 When all the messages have been received, the reception process exits,
4197 leaving the delivery processes to finish in their own time. The standard output
4198 and error streams are closed at the start of each delivery process.
4199 This is the default action if none of the &%-od%& options are present.
4201 If one of the queueing options in the configuration file
4202 (&%queue_only%& or &%queue_only_file%&, for example) is in effect, &%-odb%&
4203 overrides it if &%queue_only_override%& is set true, which is the default
4204 setting. If &%queue_only_override%& is set false, &%-odb%& has no effect.
4208 .cindex "foreground delivery"
4209 .cindex "delivery" "in the foreground"
4210 This option requests &"foreground"& (synchronous) delivery when Exim has
4211 accepted a locally-generated message. (For the daemon it is exactly the same as
4212 &%-odb%&.) A delivery process is automatically started to deliver the message,
4213 and Exim waits for it to complete before proceeding.
4215 The original Exim reception process does not finish until the delivery
4216 process for the final message has ended. The standard error stream is left open
4219 However, like &%-odb%&, this option has no effect if &%queue_only_override%& is
4220 false and one of the queueing options in the configuration file is in effect.
4222 If there is a temporary delivery error during foreground delivery, the
4223 message is left in the queue for later delivery, and the original reception
4224 process exits. See chapter &<<CHAPnonqueueing>>& for a way of setting up a
4225 restricted configuration that never queues messages.
4230 This option is synonymous with &%-odf%&. It is provided for compatibility with
4235 .cindex "non-immediate delivery"
4236 .cindex "delivery" "suppressing immediate"
4237 .cindex "queueing incoming messages"
4238 This option applies to all modes in which Exim accepts incoming messages,
4239 including the listening daemon. It specifies that the accepting process should
4240 not automatically start a delivery process for each message received. Messages
4241 are placed in the queue, and remain there until a subsequent queue runner
4242 process encounters them. There are several configuration options (such as
4243 &%queue_only%&) that can be used to queue incoming messages under certain
4244 conditions. This option overrides all of them and also &%-odqs%&. It always
4249 .cindex "SMTP" "delaying delivery"
4250 .cindex "first pass routing"
4251 This option is a hybrid between &%-odb%&/&%-odi%& and &%-odq%&.
4252 However, like &%-odb%& and &%-odi%&, this option has no effect if
4253 &%queue_only_override%& is false and one of the queueing options in the
4254 configuration file is in effect.
4256 When &%-odqs%& does operate, a delivery process is started for each incoming
4257 message, in the background by default, but in the foreground if &%-odi%& is
4258 also present. The recipient addresses are routed, and local deliveries are done
4259 in the normal way. However, if any SMTP deliveries are required, they are not
4260 done at this time, so the message remains in the queue until a subsequent queue
4261 runner process encounters it. Because routing was done, Exim knows which
4262 messages are waiting for which hosts, and so a number of messages for the same
4263 host can be sent in a single SMTP connection. The &%queue_smtp_domains%&
4264 configuration option has the same effect for specific domains. See also the
4269 .cindex "error" "reporting"
4270 If an error is detected while a non-SMTP message is being received (for
4271 example, a malformed address), the error is reported to the sender in a mail
4274 .cindex "return code" "for &%-oee%&"
4276 this error message is successfully sent, the Exim receiving process
4277 exits with a return code of zero. If not, the return code is 2 if the problem
4278 is that the original message has no recipients, or 1 for any other error.
4279 This is the default &%-oe%&&'x'& option if Exim is called as &'rmail'&.
4283 .cindex "error" "reporting"
4284 .cindex "return code" "for &%-oem%&"
4285 This is the same as &%-oee%&, except that Exim always exits with a non-zero
4286 return code, whether or not the error message was successfully sent.
4287 This is the default &%-oe%&&'x'& option, unless Exim is called as &'rmail'&.
4291 .cindex "error" "reporting"
4292 If an error is detected while a non-SMTP message is being received, the
4293 error is reported by writing a message to the standard error file (stderr).
4294 .cindex "return code" "for &%-oep%&"
4295 The return code is 1 for all errors.
4299 .cindex "error" "reporting"
4300 This option is supported for compatibility with Sendmail, but has the same
4305 .cindex "error" "reporting"
4306 This option is supported for compatibility with Sendmail, but has the same
4311 .cindex "dot" "in incoming non-SMTP message"
4312 This option, which has the same effect as &%-i%&, specifies that a dot on a
4313 line by itself should not terminate an incoming, non-SMTP message. Otherwise, a
4314 single dot does terminate, though Exim does no special processing for other
4315 lines that start with a dot. This option is set by default if Exim is called as
4316 &'rmail'&. See also &%-ti%&.
4319 .oindex "&%-oitrue%&"
4320 This option is treated as synonymous with &%-oi%&.
4322 .vitem &%-oMa%&&~<&'host&~address'&>
4324 .cindex "sender" "host address, specifying for local message"
4325 A number of options starting with &%-oM%& can be used to set values associated
4326 with remote hosts on locally-submitted messages (that is, messages not received
4327 over TCP/IP). These options can be used by any caller in conjunction with the
4328 &%-bh%&, &%-be%&, &%-bf%&, &%-bF%&, &%-bt%&, or &%-bv%& testing options. In
4329 other circumstances, they are ignored unless the caller is trusted.
4331 The &%-oMa%& option sets the sender host address. This may include a port
4332 number at the end, after a full stop (period). For example:
4334 exim -bs -oMa 10.9.8.7.1234
4336 An alternative syntax is to enclose the IP address in square brackets,
4337 followed by a colon and the port number:
4339 exim -bs -oMa [10.9.8.7]:1234
4341 The IP address is placed in the &$sender_host_address$& variable, and the
4342 port, if present, in &$sender_host_port$&. If both &%-oMa%& and &%-bh%&
4343 are present on the command line, the sender host IP address is taken from
4344 whichever one is last.
4346 .vitem &%-oMaa%&&~<&'name'&>
4348 .cindex "authentication" "name, specifying for local message"
4349 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMaa%&
4350 option sets the value of &$sender_host_authenticated$& (the authenticator
4351 name). See chapter &<<CHAPSMTPAUTH>>& for a discussion of SMTP authentication.
4352 This option can be used with &%-bh%& and &%-bs%& to set up an
4353 authenticated SMTP session without actually using the SMTP AUTH command.
4355 .vitem &%-oMai%&&~<&'string'&>
4357 .cindex "authentication" "id, specifying for local message"
4358 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMai%&
4359 option sets the value of &$authenticated_id$& (the id that was authenticated).
4360 This overrides the default value (the caller's login id, except with &%-bh%&,
4361 where there is no default) for messages from local sources. See chapter
4362 &<<CHAPSMTPAUTH>>& for a discussion of authenticated ids.
4364 .vitem &%-oMas%&&~<&'address'&>
4366 .cindex "authentication" "sender, specifying for local message"
4367 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMas%&
4368 option sets the authenticated sender value in &$authenticated_sender$&. It
4369 overrides the sender address that is created from the caller's login id for
4370 messages from local sources, except when &%-bh%& is used, when there is no
4371 default. For both &%-bh%& and &%-bs%&, an authenticated sender that is
4372 specified on a MAIL command overrides this value. See chapter
4373 &<<CHAPSMTPAUTH>>& for a discussion of authenticated senders.
4375 .vitem &%-oMi%&&~<&'interface&~address'&>
4377 .cindex "interface" "address, specifying for local message"
4378 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMi%&
4379 option sets the IP interface address value. A port number may be included,
4380 using the same syntax as for &%-oMa%&. The interface address is placed in
4381 &$received_ip_address$& and the port number, if present, in &$received_port$&.
4383 .vitem &%-oMm%&&~<&'message&~reference'&>
4385 .cindex "message reference" "message reference, specifying for local message"
4386 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMm%&
4387 option sets the message reference, e.g. message-id, and is logged during
4388 delivery. This is useful when some kind of audit trail is required to tie
4389 messages together. The format of the message reference is checked and will
4390 abort if the format is invalid. The option will only be accepted if exim is
4391 running in trusted mode, not as any regular user.
4393 The best example of a message reference is when Exim sends a bounce message.
4394 The message reference is the message-id of the original message for which Exim
4395 is sending the bounce.
4397 .vitem &%-oMr%&&~<&'protocol&~name'&>
4399 .cindex "protocol, specifying for local message"
4400 .vindex "&$received_protocol$&"
4401 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMr%&
4402 option sets the received protocol value that is stored in
4403 &$received_protocol$&. However, it does not apply (and is ignored) when &%-bh%&
4404 or &%-bs%& is used. For &%-bh%&, the protocol is forced to one of the standard
4405 SMTP protocol names (see the description of &$received_protocol$& in section
4406 &<<SECTexpvar>>&). For &%-bs%&, the protocol is always &"local-"& followed by
4407 one of those same names. For &%-bS%& (batched SMTP) however, the protocol can
4408 be set by &%-oMr%&. Repeated use of this option is not supported.
4410 .vitem &%-oMs%&&~<&'host&~name'&>
4412 .cindex "sender" "host name, specifying for local message"
4413 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMs%&
4414 option sets the sender host name in &$sender_host_name$&. When this option is
4415 present, Exim does not attempt to look up a host name from an IP address; it
4416 uses the name it is given.
4418 .vitem &%-oMt%&&~<&'ident&~string'&>
4420 .cindex "sender" "ident string, specifying for local message"
4421 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMt%&
4422 option sets the sender ident value in &$sender_ident$&. The default setting for
4423 local callers is the login id of the calling process, except when &%-bh%& is
4424 used, when there is no default.
4428 .cindex "Sendmail compatibility" "&%-om%& option ignored"
4429 In Sendmail, this option means &"me too"&, indicating that the sender of a
4430 message should receive a copy of the message if the sender appears in an alias
4431 expansion. Exim always does this, so the option does nothing.
4435 .cindex "Sendmail compatibility" "&%-oo%& option ignored"
4436 This option is ignored. In Sendmail it specifies &"old style headers"&,
4437 whatever that means.
4439 .vitem &%-oP%&&~<&'path'&>
4441 .cindex "pid (process id)" "of daemon"
4442 .cindex "daemon" "process id (pid)"
4443 This option is useful only in conjunction with &%-bd%& or &%-q%& with a time
4444 value. The option specifies the file to which the process id of the daemon is
4445 written. When &%-oX%& is used with &%-bd%&, or when &%-q%& with a time is used
4446 without &%-bd%&, this is the only way of causing Exim to write a pid file,
4447 because in those cases, the normal pid file is not used.
4451 .cindex "pid (process id)" "of daemon"
4452 .cindex "daemon" "process id (pid)"
4453 This option is not intended for general use.
4454 The daemon uses it when terminating due to a SIGTEM, possibly in
4455 combination with &%-oP%&&~<&'path'&>.
4456 It causes the pid file to be removed.
4458 .vitem &%-or%&&~<&'time'&>
4460 .cindex "timeout" "for non-SMTP input"
4461 This option sets a timeout value for incoming non-SMTP messages. If it is not
4462 set, Exim will wait forever for the standard input. The value can also be set
4463 by the &%receive_timeout%& option. The format used for specifying times is
4464 described in section &<<SECTtimeformat>>&.
4466 .vitem &%-os%&&~<&'time'&>
4468 .cindex "timeout" "for SMTP input"
4469 .cindex "SMTP" "input timeout"
4470 This option sets a timeout value for incoming SMTP messages. The timeout
4471 applies to each SMTP command and block of data. The value can also be set by
4472 the &%smtp_receive_timeout%& option; it defaults to 5 minutes. The format used
4473 for specifying times is described in section &<<SECTtimeformat>>&.
4477 This option has exactly the same effect as &%-v%&.
4479 .vitem &%-oX%&&~<&'number&~or&~string'&>
4481 .cindex "TCP/IP" "setting listening ports"
4482 .cindex "TCP/IP" "setting listening interfaces"
4483 .cindex "port" "receiving TCP/IP"
4484 This option is relevant only when the &%-bd%& (start listening daemon) option
4485 is also given. It controls which ports and interfaces the daemon uses. Details
4486 of the syntax, and how it interacts with configuration file options, are given
4487 in chapter &<<CHAPinterfaces>>&. When &%-oX%& is used to start a daemon, no pid
4488 file is written unless &%-oP%& is also present to specify a pid filename.
4492 .cindex "daemon notifier socket"
4493 This option controls the creation of an inter-process communications endpoint
4495 It is only relevant when the &%-bd%& (start listening daemon) option is also
4497 Normally the daemon creates this socket, unless a &%-oX%& and &*no*& &%-oP%&
4498 option is also present.
4499 If this option is given then the socket will not be created. This could be
4500 required if the system is running multiple daemons.
4502 The socket is currently used for
4504 fast ramp-up of queue runner processes
4506 obtaining a current queue size
4511 .cindex "Perl" "starting the interpreter"
4512 This option applies when an embedded Perl interpreter is linked with Exim (see
4513 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4514 option, forcing the starting of the interpreter to be delayed until it is
4519 .cindex "Perl" "starting the interpreter"
4520 This option applies when an embedded Perl interpreter is linked with Exim (see
4521 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4522 option, forcing the starting of the interpreter to occur as soon as Exim is
4525 .vitem &%-p%&<&'rval'&>:<&'sval'&>
4527 For compatibility with Sendmail, this option is equivalent to
4529 &`-oMr`& <&'rval'&> &`-oMs`& <&'sval'&>
4531 It sets the incoming protocol and host name (for trusted callers). The
4532 host name and its colon can be omitted when only the protocol is to be set.
4533 Note the Exim already has two private options, &%-pd%& and &%-ps%&, that refer
4534 to embedded Perl. It is therefore impossible to set a protocol value of &`d`&
4535 or &`s`& using this option (but that does not seem a real limitation).
4536 Repeated use of this option is not supported.
4540 .cindex "queue runner" "starting manually"
4541 This option is normally restricted to admin users. However, there is a
4542 configuration option called &%prod_requires_admin%& which can be set false to
4543 relax this restriction (and also the same requirement for the &%-M%&, &%-R%&,
4544 and &%-S%& options).
4546 .cindex "queue runner" "description of operation"
4547 If other commandline options do not specify an action,
4548 the &%-q%& option starts one queue runner process. This scans the queue of
4549 waiting messages, and runs a delivery process for each one in turn. It waits
4550 for each delivery process to finish before starting the next one. A delivery
4551 process may not actually do any deliveries if the retry times for the addresses
4552 have not been reached. Use &%-qf%& (see below) if you want to override this.
4555 .cindex "SMTP" "passed connection"
4556 .cindex "SMTP" "multiple deliveries"
4557 .cindex "multiple SMTP deliveries"
4558 the delivery process spawns other processes to deliver other messages down
4559 passed SMTP connections, the queue runner waits for these to finish before
4562 When all the queued messages have been considered, the original queue runner
4563 process terminates. In other words, a single pass is made over the waiting
4564 mail, one message at a time. Use &%-q%& with a time (see below) if you want
4565 this to be repeated periodically.
4567 Exim processes the waiting messages in an unpredictable order. It isn't very
4568 random, but it is likely to be different each time, which is all that matters.
4569 If one particular message screws up a remote MTA, other messages to the same
4570 MTA have a chance of getting through if they get tried first.
4572 It is possible to cause the messages to be processed in lexical message id
4573 order, which is essentially the order in which they arrived, by setting the
4574 &%queue_run_in_order%& option, but this is not recommended for normal use.
4576 .vitem &%-q%&<&'qflags'&>
4577 The &%-q%& option may be followed by one or more flag letters that change its
4578 behaviour. They are all optional, but if more than one is present, they must
4579 appear in the correct order. Each flag is described in a separate item below.
4583 .cindex "queue" "double scanning"
4584 .cindex "queue" "routing"
4585 .cindex "routing" "whole queue before delivery"
4586 .cindex "first pass routing"
4587 .cindex "queue runner" "two phase"
4588 An option starting with &%-qq%& requests a two-stage queue run. In the first
4589 stage, the queue is scanned as if the &%queue_smtp_domains%& option matched
4590 every domain. Addresses are routed, local deliveries happen, but no remote
4593 Performance will be best if the &%queue_run_in_order%& option is false.
4594 If that is so and the &%queue_fast_ramp%& option is true then
4595 in the first phase of the run,
4596 once a threshold number of messages are routed for a given host,
4597 a delivery process is forked in parallel with the rest of the scan.
4599 .cindex "hints database" "remembering routing"
4600 The hints database that remembers which messages are waiting for specific hosts
4601 is updated, as if delivery to those hosts had been deferred. After this is
4602 complete, a second, normal queue scan happens, with routing and delivery taking
4603 place as normal. Messages that are routed to the same host should mostly be
4604 delivered down a single SMTP
4605 .cindex "SMTP" "passed connection"
4606 .cindex "SMTP" "multiple deliveries"
4607 .cindex "multiple SMTP deliveries"
4608 connection because of the hints that were set up during the first queue scan.
4609 This option may be useful for hosts that are connected to the Internet
4612 .vitem &%-q[q]i...%&
4614 .cindex "queue" "initial delivery"
4615 If the &'i'& flag is present, the queue runner runs delivery processes only for
4616 those messages that haven't previously been tried. (&'i'& stands for &"initial
4617 delivery"&.) This can be helpful if you are putting messages in the queue using
4618 &%-odq%& and want a queue runner just to process the new messages.
4620 .vitem &%-q[q][i]f...%&
4622 .cindex "queue" "forcing delivery"
4623 .cindex "delivery" "forcing in queue run"
4624 If one &'f'& flag is present, a delivery attempt is forced for each non-frozen
4625 message, whereas without &'f'& only those non-frozen addresses that have passed
4626 their retry times are tried.
4628 .vitem &%-q[q][i]ff...%&
4630 .cindex "frozen messages" "forcing delivery"
4631 If &'ff'& is present, a delivery attempt is forced for every message, whether
4634 .vitem &%-q[q][i][f[f]]l%&
4636 .cindex "queue" "local deliveries only"
4637 The &'l'& (the letter &"ell"&) flag specifies that only local deliveries are to
4638 be done. If a message requires any remote deliveries, it remains in the queue
4641 .vitem &%-q[q][i][f[f]][l][G<name>[/<time>]]]%&
4644 .cindex "named queues" "deliver from"
4645 .cindex "queue" "delivering specific messages"
4646 If the &'G'& flag and a name is present, the queue runner operates on the
4647 queue with the given name rather than the default queue.
4648 The name should not contain a &'/'& character.
4649 For a periodic queue run (see below)
4650 append to the name a slash and a time value.
4652 If other commandline options specify an action, a &'-qG<name>'& option
4653 will specify a queue to operate on.
4656 exim -bp -qGquarantine
4658 exim -qGoffpeak -Rf @special.domain.example
4661 .vitem &%-q%&<&'qflags'&>&~<&'start&~id'&>&~<&'end&~id'&>
4662 When scanning the queue, Exim can be made to skip over messages whose ids are
4663 lexically less than a given value by following the &%-q%& option with a
4664 starting message id. For example:
4666 exim -q 0t5C6f-0000c8-00
4668 Messages that arrived earlier than &`0t5C6f-0000c8-00`& are not inspected. If a
4669 second message id is given, messages whose ids are lexically greater than it
4670 are also skipped. If the same id is given twice, for example,
4672 exim -q 0t5C6f-0000c8-00 0t5C6f-0000c8-00
4674 just one delivery process is started, for that message. This differs from
4675 &%-M%& in that retry data is respected, and it also differs from &%-Mc%& in
4676 that it counts as a delivery from a queue run. Note that the selection
4677 mechanism does not affect the order in which the messages are scanned. There
4678 are also other ways of selecting specific sets of messages for delivery in a
4679 queue run &-- see &%-R%& and &%-S%&.
4681 .vitem &%-q%&<&'qflags'&><&'time'&>
4682 .cindex "queue runner" "starting periodically"
4683 .cindex "periodic queue running"
4684 When a time value is present, the &%-q%& option causes Exim to run as a daemon,
4685 starting a queue runner process at intervals specified by the given time value
4686 (whose format is described in section &<<SECTtimeformat>>&). This form of the
4687 &%-q%& option is commonly combined with the &%-bd%& option, in which case a
4688 single daemon process handles both functions. A common way of starting up a
4689 combined daemon at system boot time is to use a command such as
4691 /usr/exim/bin/exim -bd -q30m
4693 Such a daemon listens for incoming SMTP calls, and also starts a queue runner
4694 process every 30 minutes.
4696 When a daemon is started by &%-q%& with a time value, but without &%-bd%&, no
4697 pid file is written unless one is explicitly requested by the &%-oP%& option.
4699 .vitem &%-qR%&<&'rsflags'&>&~<&'string'&>
4701 This option is synonymous with &%-R%&. It is provided for Sendmail
4704 .vitem &%-qS%&<&'rsflags'&>&~<&'string'&>
4706 This option is synonymous with &%-S%&.
4708 .vitem &%-R%&<&'rsflags'&>&~<&'string'&>
4710 .cindex "queue runner" "for specific recipients"
4711 .cindex "delivery" "to given domain"
4712 .cindex "domain" "delivery to"
4713 The <&'rsflags'&> may be empty, in which case the white space before the string
4714 is optional, unless the string is &'f'&, &'ff'&, &'r'&, &'rf'&, or &'rff'&,
4715 which are the possible values for <&'rsflags'&>. White space is required if
4716 <&'rsflags'&> is not empty.
4718 This option is similar to &%-q%& with no time value, that is, it causes Exim to
4719 perform a single queue run, except that, when scanning the messages on the
4720 queue, Exim processes only those that have at least one undelivered recipient
4721 address containing the given string, which is checked in a case-independent
4722 way. If the <&'rsflags'&> start with &'r'&, <&'string'&> is interpreted as a
4723 regular expression; otherwise it is a literal string.
4725 If you want to do periodic queue runs for messages with specific recipients,
4726 you can combine &%-R%& with &%-q%& and a time value. For example:
4728 exim -q25m -R @special.domain.example
4730 This example does a queue run for messages with recipients in the given domain
4731 every 25 minutes. Any additional flags that are specified with &%-q%& are
4732 applied to each queue run.
4734 Once a message is selected for delivery by this mechanism, all its addresses
4735 are processed. For the first selected message, Exim overrides any retry
4736 information and forces a delivery attempt for each undelivered address. This
4737 means that if delivery of any address in the first message is successful, any
4738 existing retry information is deleted, and so delivery attempts for that
4739 address in subsequently selected messages (which are processed without forcing)
4740 will run. However, if delivery of any address does not succeed, the retry
4741 information is updated, and in subsequently selected messages, the failing
4742 address will be skipped.
4744 .cindex "frozen messages" "forcing delivery"
4745 If the <&'rsflags'&> contain &'f'& or &'ff'&, the delivery forcing applies to
4746 all selected messages, not just the first; frozen messages are included when
4749 The &%-R%& option makes it straightforward to initiate delivery of all messages
4750 to a given domain after a host has been down for some time. When the SMTP
4751 command ETRN is accepted by its ACL (see chapter &<<CHAPACL>>&), its default
4752 effect is to run Exim with the &%-R%& option, but it can be configured to run
4753 an arbitrary command instead.
4757 This is a documented (for Sendmail) obsolete alternative name for &%-f%&.
4759 .vitem &%-S%&<&'rsflags'&>&~<&'string'&>
4761 .cindex "delivery" "from given sender"
4762 .cindex "queue runner" "for specific senders"
4763 This option acts like &%-R%& except that it checks the string against each
4764 message's sender instead of against the recipients. If &%-R%& is also set, both
4765 conditions must be met for a message to be selected. If either of the options
4766 has &'f'& or &'ff'& in its flags, the associated action is taken.
4768 .vitem &%-Tqt%&&~<&'times'&>
4770 This is an option that is exclusively for use by the Exim testing suite. It is not
4771 recognized when Exim is run normally. It allows for the setting up of explicit
4772 &"queue times"& so that various warning/retry features can be tested.
4776 .cindex "recipient" "extracting from header lines"
4780 When Exim is receiving a locally-generated, non-SMTP message on its standard
4781 input, the &%-t%& option causes the recipients of the message to be obtained
4782 from the &'To:'&, &'Cc:'&, and &'Bcc:'& header lines in the message instead of
4783 from the command arguments. The addresses are extracted before any rewriting
4784 takes place and the &'Bcc:'& header line, if present, is then removed.
4786 .cindex "Sendmail compatibility" "&%-t%& option"
4787 If the command has any arguments, they specify addresses to which the message
4788 is &'not'& to be delivered. That is, the argument addresses are removed from
4789 the recipients list obtained from the headers. This is compatible with Smail 3
4790 and in accordance with the documented behaviour of several versions of
4791 Sendmail, as described in man pages on a number of operating systems (e.g.
4792 Solaris 8, IRIX 6.5, HP-UX 11). However, some versions of Sendmail &'add'&
4793 argument addresses to those obtained from the headers, and the O'Reilly
4794 Sendmail book documents it that way. Exim can be made to add argument addresses
4795 instead of subtracting them by setting the option
4796 &%extract_addresses_remove_arguments%& false.
4798 .cindex "&%Resent-%& header lines" "with &%-t%&"
4799 If there are any &%Resent-%& header lines in the message, Exim extracts
4800 recipients from all &'Resent-To:'&, &'Resent-Cc:'&, and &'Resent-Bcc:'& header
4801 lines instead of from &'To:'&, &'Cc:'&, and &'Bcc:'&. This is for compatibility
4802 with Sendmail and other MTAs. (Prior to release 4.20, Exim gave an error if
4803 &%-t%& was used in conjunction with &%Resent-%& header lines.)
4805 RFC 2822 talks about different sets of &%Resent-%& header lines (for when a
4806 message is resent several times). The RFC also specifies that they should be
4807 added at the front of the message, and separated by &'Received:'& lines. It is
4808 not at all clear how &%-t%& should operate in the present of multiple sets,
4809 nor indeed exactly what constitutes a &"set"&.
4810 In practice, it seems that MUAs do not follow the RFC. The &%Resent-%& lines
4811 are often added at the end of the header, and if a message is resent more than
4812 once, it is common for the original set of &%Resent-%& headers to be renamed as
4813 &%X-Resent-%& when a new set is added. This removes any possible ambiguity.
4817 This option is exactly equivalent to &%-t%& &%-i%&. It is provided for
4818 compatibility with Sendmail.
4820 .vitem &%-tls-on-connect%&
4821 .oindex "&%-tls-on-connect%&"
4822 .cindex "TLS" "use without STARTTLS"
4823 .cindex "TLS" "automatic start"
4824 This option is available when Exim is compiled with TLS support. It forces all
4825 incoming SMTP connections to behave as if the incoming port is listed in the
4826 &%tls_on_connect_ports%& option. See section &<<SECTsupobssmt>>& and chapter
4827 &<<CHAPTLS>>& for further details.
4832 .cindex "Sendmail compatibility" "&%-U%& option ignored"
4833 Sendmail uses this option for &"initial message submission"&, and its
4834 documentation states that in future releases, it may complain about
4835 syntactically invalid messages rather than fixing them when this flag is not
4836 set. Exim ignores this option.
4840 This option causes Exim to write information to the standard error stream,
4841 describing what it is doing. In particular, it shows the log lines for
4842 receiving and delivering a message, and if an SMTP connection is made, the SMTP
4843 dialogue is shown. Some of the log lines shown may not actually be written to
4844 the log if the setting of &%log_selector%& discards them. Any relevant
4845 selectors are shown with each log line. If none are shown, the logging is
4850 AIX uses &%-x%& for a private purpose (&"mail from a local mail program has
4851 National Language Support extended characters in the body of the mail item"&).
4852 It sets &%-x%& when calling the MTA from its &%mail%& command. Exim ignores
4855 .vitem &%-X%&&~<&'logfile'&>
4857 This option is interpreted by Sendmail to cause debug information to be sent
4858 to the named file. It is ignored by Exim.
4860 .vitem &%-z%&&~<&'log-line'&>
4862 This option writes its argument to Exim's logfile.
4863 Use is restricted to administrators; the intent is for operational notes.
4864 Quotes should be used to maintain a multi-word item as a single argument,
4872 . ////////////////////////////////////////////////////////////////////////////
4873 . Insert a stylized DocBook comment here, to identify the end of the command
4874 . line options. This is for the benefit of the Perl script that automatically
4875 . creates a man page for the options.
4876 . ////////////////////////////////////////////////////////////////////////////
4879 <!-- === End of command line options === -->
4886 . ////////////////////////////////////////////////////////////////////////////
4887 . ////////////////////////////////////////////////////////////////////////////
4890 .chapter "The Exim runtime configuration file" "CHAPconf" &&&
4891 "The runtime configuration file"
4893 .cindex "runtime configuration"
4894 .cindex "configuration file" "general description"
4895 .cindex "CONFIGURE_FILE"
4896 .cindex "configuration file" "errors in"
4897 .cindex "error" "in configuration file"
4898 .cindex "return code" "for bad configuration"
4899 Exim uses a single runtime configuration file that is read whenever an Exim
4900 binary is executed. Note that in normal operation, this happens frequently,
4901 because Exim is designed to operate in a distributed manner, without central
4904 If a syntax error is detected while reading the configuration file, Exim
4905 writes a message on the standard error, and exits with a non-zero return code.
4906 The message is also written to the panic log. &*Note*&: Only simple syntax
4907 errors can be detected at this time. The values of any expanded options are
4908 not checked until the expansion happens, even when the expansion does not
4909 actually alter the string.
4911 The name of the configuration file is compiled into the binary for security
4912 reasons, and is specified by the CONFIGURE_FILE compilation option. In
4913 most configurations, this specifies a single file. However, it is permitted to
4914 give a colon-separated list of filenames, in which case Exim uses the first
4915 existing file in the list.
4918 .cindex "EXIM_GROUP"
4919 .cindex "CONFIGURE_OWNER"
4920 .cindex "CONFIGURE_GROUP"
4921 .cindex "configuration file" "ownership"
4922 .cindex "ownership" "configuration file"
4923 The runtime configuration file must be owned by root or by the user that is
4924 specified at compile time by the CONFIGURE_OWNER option (if set). The
4925 configuration file must not be world-writeable, or group-writeable unless its
4926 group is the root group or the one specified at compile time by the
4927 CONFIGURE_GROUP option.
4929 &*Warning*&: In a conventional configuration, where the Exim binary is setuid
4930 to root, anybody who is able to edit the runtime configuration file has an
4931 easy way to run commands as root. If you specify a user or group in the
4932 CONFIGURE_OWNER or CONFIGURE_GROUP options, then that user and/or any users
4933 who are members of that group will trivially be able to obtain root privileges.
4935 Up to Exim version 4.72, the runtime configuration file was also permitted to
4936 be writeable by the Exim user and/or group. That has been changed in Exim 4.73
4937 since it offered a simple privilege escalation for any attacker who managed to
4938 compromise the Exim user account.
4940 A default configuration file, which will work correctly in simple situations,
4941 is provided in the file &_src/configure.default_&. If CONFIGURE_FILE
4942 defines just one filename, the installation process copies the default
4943 configuration to a new file of that name if it did not previously exist. If
4944 CONFIGURE_FILE is a list, no default is automatically installed. Chapter
4945 &<<CHAPdefconfil>>& is a &"walk-through"& discussion of the default
4950 .section "Using a different configuration file" "SECID40"
4951 .cindex "configuration file" "alternate"
4952 A one-off alternate configuration can be specified by the &%-C%& command line
4953 option, which may specify a single file or a list of files. However, when
4954 &%-C%& is used, Exim gives up its root privilege, unless called by root (or
4955 unless the argument for &%-C%& is identical to the built-in value from
4956 CONFIGURE_FILE), or is listed in the TRUSTED_CONFIG_LIST file and the caller
4957 is the Exim user or the user specified in the CONFIGURE_OWNER setting. &%-C%&
4958 is useful mainly for checking the syntax of configuration files before
4959 installing them. No owner or group checks are done on a configuration file
4960 specified by &%-C%&, if root privilege has been dropped.
4962 Even the Exim user is not trusted to specify an arbitrary configuration file
4963 with the &%-C%& option to be used with root privileges, unless that file is
4964 listed in the TRUSTED_CONFIG_LIST file. This locks out the possibility of
4965 testing a configuration using &%-C%& right through message reception and
4966 delivery, even if the caller is root. The reception works, but by that time,
4967 Exim is running as the Exim user, so when it re-execs to regain privilege for
4968 the delivery, the use of &%-C%& causes privilege to be lost. However, root
4969 can test reception and delivery using two separate commands (one to put a
4970 message in the queue, using &%-odq%&, and another to do the delivery, using
4973 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
4974 prefix string with which any file named in a &%-C%& command line option must
4975 start. In addition, the filename must not contain the sequence &"&`/../`&"&.
4976 There is no default setting for ALT_CONFIG_PREFIX; when it is unset, any
4977 filename can be used with &%-C%&.
4979 One-off changes to a configuration can be specified by the &%-D%& command line
4980 option, which defines and overrides values for macros used inside the
4981 configuration file. However, like &%-C%&, the use of this option by a
4982 non-privileged user causes Exim to discard its root privilege.
4983 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
4984 completely disabled, and its use causes an immediate error exit.
4986 The WHITELIST_D_MACROS option in &_Local/Makefile_& permits the binary builder
4987 to declare certain macro names trusted, such that root privilege will not
4988 necessarily be discarded.
4989 WHITELIST_D_MACROS defines a colon-separated list of macros which are
4990 considered safe and, if &%-D%& only supplies macros from this list, and the
4991 values are acceptable, then Exim will not give up root privilege if the caller
4992 is root, the Exim run-time user, or the CONFIGURE_OWNER, if set. This is a
4993 transition mechanism and is expected to be removed in the future. Acceptable
4994 values for the macros satisfy the regexp: &`^[A-Za-z0-9_/.-]*$`&
4996 Some sites may wish to use the same Exim binary on different machines that
4997 share a file system, but to use different configuration files on each machine.
4998 If CONFIGURE_FILE_USE_NODE is defined in &_Local/Makefile_&, Exim first
4999 looks for a file whose name is the configuration filename followed by a dot
5000 and the machine's node name, as obtained from the &[uname()]& function. If this
5001 file does not exist, the standard name is tried. This processing occurs for
5002 each filename in the list given by CONFIGURE_FILE or &%-C%&.
5004 In some esoteric situations different versions of Exim may be run under
5005 different effective uids and the CONFIGURE_FILE_USE_EUID is defined to
5006 help with this. See the comments in &_src/EDITME_& for details.
5010 .section "Configuration file format" "SECTconffilfor"
5011 .cindex "configuration file" "format of"
5012 .cindex "format" "configuration file"
5013 Exim's configuration file is divided into a number of different parts. General
5014 option settings must always appear at the start of the file. The other parts
5015 are all optional, and may appear in any order. Each part other than the first
5016 is introduced by the word &"begin"& followed by at least one literal
5017 space, and the name of the part. The optional parts are:
5020 &'ACL'&: Access control lists for controlling incoming SMTP mail (see chapter
5023 .cindex "AUTH" "configuration"
5024 &'authenticators'&: Configuration settings for the authenticator drivers. These
5025 are concerned with the SMTP AUTH command (see chapter &<<CHAPSMTPAUTH>>&).
5027 &'routers'&: Configuration settings for the router drivers. Routers process
5028 addresses and determine how the message is to be delivered (see chapters
5029 &<<CHAProutergeneric>>&&--&<<CHAPredirect>>&).
5031 &'transports'&: Configuration settings for the transport drivers. Transports
5032 define mechanisms for copying messages to destinations (see chapters
5033 &<<CHAPtransportgeneric>>&&--&<<CHAPsmtptrans>>&).
5035 &'retry'&: Retry rules, for use when a message cannot be delivered immediately.
5036 If there is no retry section, or if it is empty (that is, no retry rules are
5037 defined), Exim will not retry deliveries. In this situation, temporary errors
5038 are treated the same as permanent errors. Retry rules are discussed in chapter
5041 &'rewrite'&: Global address rewriting rules, for use when a message arrives and
5042 when new addresses are generated during delivery. Rewriting is discussed in
5043 chapter &<<CHAPrewrite>>&.
5045 &'local_scan'&: Private options for the &[local_scan()]& function. If you
5046 want to use this feature, you must set
5048 LOCAL_SCAN_HAS_OPTIONS=yes
5050 in &_Local/Makefile_& before building Exim. Details of the &[local_scan()]&
5051 facility are given in chapter &<<CHAPlocalscan>>&.
5054 .cindex "configuration file" "leading white space in"
5055 .cindex "configuration file" "trailing white space in"
5056 .cindex "white space" "in configuration file"
5057 Leading and trailing white space in configuration lines is always ignored.
5059 Blank lines in the file, and lines starting with a # character (ignoring
5060 leading white space) are treated as comments and are ignored. &*Note*&: A
5061 # character other than at the beginning of a line is not treated specially,
5062 and does not introduce a comment.
5064 Any non-comment line can be continued by ending it with a backslash. Note that
5065 the general rule for white space means that trailing white space after the
5066 backslash and leading white space at the start of continuation
5067 lines is ignored. Comment lines beginning with # (but not empty lines) may
5068 appear in the middle of a sequence of continuation lines.
5070 A convenient way to create a configuration file is to start from the
5071 default, which is supplied in &_src/configure.default_&, and add, delete, or
5072 change settings as required.
5074 The ACLs, retry rules, and rewriting rules have their own syntax which is
5075 described in chapters &<<CHAPACL>>&, &<<CHAPretry>>&, and &<<CHAPrewrite>>&,
5076 respectively. The other parts of the configuration file have some syntactic
5077 items in common, and these are described below, from section &<<SECTcos>>&
5078 onwards. Before that, the inclusion, macro, and conditional facilities are
5083 .section "File inclusions in the configuration file" "SECID41"
5084 .cindex "inclusions in configuration file"
5085 .cindex "configuration file" "including other files"
5086 .cindex "&`.include`& in configuration file"
5087 .cindex "&`.include_if_exists`& in configuration file"
5088 You can include other files inside Exim's runtime configuration file by
5091 &`.include`& <&'filename'&>
5092 &`.include_if_exists`& <&'filename'&>
5094 on a line by itself. Double quotes round the filename are optional. If you use
5095 the first form, a configuration error occurs if the file does not exist; the
5096 second form does nothing for non-existent files.
5097 The first form allows a relative name. It is resolved relative to
5098 the directory of the including file. For the second form an absolute filename
5101 Includes may be nested to any depth, but remember that Exim reads its
5102 configuration file often, so it is a good idea to keep them to a minimum.
5103 If you change the contents of an included file, you must HUP the daemon,
5104 because an included file is read only when the configuration itself is read.
5106 The processing of inclusions happens early, at a physical line level, so, like
5107 comment lines, an inclusion can be used in the middle of an option setting,
5110 hosts_lookup = a.b.c \
5113 Include processing happens after macro processing (see below). Its effect is to
5114 process the lines of the included file as if they occurred inline where the
5119 .section "Macros in the configuration file" "SECTmacrodefs"
5120 .cindex "macro" "description of"
5121 .cindex "configuration file" "macros"
5122 If a line in the main part of the configuration (that is, before the first
5123 &"begin"& line) begins with an upper case letter, it is taken as a macro
5124 definition, and must be of the form
5126 <&'name'&> = <&'rest of line'&>
5128 The name must consist of letters, digits, and underscores, and need not all be
5129 in upper case, though that is recommended. The rest of the line, including any
5130 continuations, is the replacement text, and has leading and trailing white
5131 space removed. Quotes are not removed. The replacement text can never end with
5132 a backslash character, but this doesn't seem to be a serious limitation.
5134 Macros may also be defined between router, transport, authenticator, or ACL
5135 definitions. They may not, however, be defined within an individual driver or
5136 ACL, or in the &%local_scan%&, retry, or rewrite sections of the configuration.
5138 .section "Macro substitution" "SECID42"
5139 Once a macro is defined, all subsequent lines in the file (and any included
5140 files) are scanned for the macro name; if there are several macros, the line is
5141 scanned for each, in turn, in the order in which the macros are defined. The
5142 replacement text is not re-scanned for the current macro, though it is scanned
5143 for subsequently defined macros. For this reason, a macro name may not contain
5144 the name of a previously defined macro as a substring. You could, for example,
5147 &`ABCD_XYZ = `&<&'something'&>
5148 &`ABCD = `&<&'something else'&>
5150 but putting the definitions in the opposite order would provoke a configuration
5151 error. Macro expansion is applied to individual physical lines from the file,
5152 before checking for line continuation or file inclusion (see above). If a line
5153 consists solely of a macro name, and the expansion of the macro is empty, the
5154 line is ignored. A macro at the start of a line may turn the line into a
5155 comment line or a &`.include`& line.
5158 .section "Redefining macros" "SECID43"
5159 Once defined, the value of a macro can be redefined later in the configuration
5160 (or in an included file). Redefinition is specified by using &'=='& instead of
5165 MAC == updated value
5167 Redefinition does not alter the order in which the macros are applied to the
5168 subsequent lines of the configuration file. It is still the same order in which
5169 the macros were originally defined. All that changes is the macro's value.
5170 Redefinition makes it possible to accumulate values. For example:
5174 MAC == MAC and something added
5176 This can be helpful in situations where the configuration file is built
5177 from a number of other files.
5179 .section "Overriding macro values" "SECID44"
5180 The values set for macros in the configuration file can be overridden by the
5181 &%-D%& command line option, but Exim gives up its root privilege when &%-D%& is
5182 used, unless called by root or the Exim user. A definition on the command line
5183 using the &%-D%& option causes all definitions and redefinitions within the
5188 .section "Example of macro usage" "SECID45"
5189 As an example of macro usage, consider a configuration where aliases are looked
5190 up in a MySQL database. It helps to keep the file less cluttered if long
5191 strings such as SQL statements are defined separately as macros, for example:
5193 ALIAS_QUERY = select mailbox from user where \
5194 login='${quote_mysql:$local_part}';
5196 This can then be used in a &(redirect)& router setting like this:
5198 data = ${lookup mysql{ALIAS_QUERY}}
5200 In earlier versions of Exim macros were sometimes used for domain, host, or
5201 address lists. In Exim 4 these are handled better by named lists &-- see
5202 section &<<SECTnamedlists>>&.
5205 .section "Builtin macros" "SECTbuiltinmacros"
5206 Exim defines some macros depending on facilities available, which may
5207 differ due to build-time definitions and from one release to another.
5208 All of these macros start with an underscore.
5209 They can be used to conditionally include parts of a configuration
5212 The following classes of macros are defined:
5214 &` _HAVE_* `& build-time defines
5215 &` _DRIVER_ROUTER_* `& router drivers
5216 &` _DRIVER_TRANSPORT_* `& transport drivers
5217 &` _DRIVER_AUTHENTICATOR_* `& authenticator drivers
5218 &` _LOG_* `& log_selector values
5219 &` _OPT_MAIN_* `& main config options
5220 &` _OPT_ROUTERS_* `& generic router options
5221 &` _OPT_TRANSPORTS_* `& generic transport options
5222 &` _OPT_AUTHENTICATORS_* `& generic authenticator options
5223 &` _OPT_ROUTER_*_* `& private router options
5224 &` _OPT_TRANSPORT_*_* `& private transport options
5225 &` _OPT_AUTHENTICATOR_*_* `& private authenticator options
5228 Use an &"exim -bP macros"& command to get the list of macros.
5231 .section "Conditional skips in the configuration file" "SECID46"
5232 .cindex "configuration file" "conditional skips"
5233 .cindex "&`.ifdef`&"
5234 You can use the directives &`.ifdef`&, &`.ifndef`&, &`.elifdef`&,
5235 &`.elifndef`&, &`.else`&, and &`.endif`& to dynamically include or exclude
5236 portions of the configuration file. The processing happens whenever the file is
5237 read (that is, when an Exim binary starts to run).
5239 The implementation is very simple. Instances of the first four directives must
5240 be followed by text that includes the names of one or macros. The condition
5241 that is tested is whether or not any macro substitution has taken place in the
5245 message_size_limit = 50M
5247 message_size_limit = 100M
5250 sets a message size limit of 50M if the macro &`AAA`& is defined
5251 (or &`A`& or &`AA`&), and 100M
5252 otherwise. If there is more than one macro named on the line, the condition
5253 is true if any of them are defined. That is, it is an &"or"& condition. To
5254 obtain an &"and"& condition, you need to use nested &`.ifdef`&s.
5256 Although you can use a macro expansion to generate one of these directives,
5257 it is not very useful, because the condition &"there was a macro substitution
5258 in this line"& will always be true.
5260 Text following &`.else`& and &`.endif`& is ignored, and can be used as comment
5261 to clarify complicated nestings.
5265 .section "Common option syntax" "SECTcos"
5266 .cindex "common option syntax"
5267 .cindex "syntax of common options"
5268 .cindex "configuration file" "common option syntax"
5269 For the main set of options, driver options, and &[local_scan()]& options,
5270 each setting is on a line by itself, and starts with a name consisting of
5271 lower-case letters and underscores. Many options require a data value, and in
5272 these cases the name must be followed by an equals sign (with optional white
5273 space) and then the value. For example:
5275 qualify_domain = mydomain.example.com
5277 .cindex "hiding configuration option values"
5278 .cindex "configuration options" "hiding value of"
5279 .cindex "options" "hiding value of"
5280 Some option settings may contain sensitive data, for example, passwords for
5281 accessing databases. To stop non-admin users from using the &%-bP%& command
5282 line option to read these values, you can precede the option settings with the
5283 word &"hide"&. For example:
5285 hide mysql_servers = localhost/users/admin/secret-password
5287 For non-admin users, such options are displayed like this:
5289 mysql_servers = <value not displayable>
5291 If &"hide"& is used on a driver option, it hides the value of that option on
5292 all instances of the same driver.
5294 The following sections describe the syntax used for the different data types
5295 that are found in option settings.
5298 .section "Boolean options" "SECID47"
5299 .cindex "format" "boolean"
5300 .cindex "boolean configuration values"
5301 .oindex "&%no_%&&'xxx'&"
5302 .oindex "&%not_%&&'xxx'&"
5303 Options whose type is given as boolean are on/off switches. There are two
5304 different ways of specifying such options: with and without a data value. If
5305 the option name is specified on its own without data, the switch is turned on;
5306 if it is preceded by &"no_"& or &"not_"& the switch is turned off. However,
5307 boolean options may be followed by an equals sign and one of the words
5308 &"true"&, &"false"&, &"yes"&, or &"no"&, as an alternative syntax. For example,
5309 the following two settings have exactly the same effect:
5314 The following two lines also have the same (opposite) effect:
5319 You can use whichever syntax you prefer.
5324 .section "Integer values" "SECID48"
5325 .cindex "integer configuration values"
5326 .cindex "format" "integer"
5327 If an option's type is given as &"integer"&, the value can be given in decimal,
5328 hexadecimal, or octal. If it starts with a digit greater than zero, a decimal
5329 number is assumed. Otherwise, it is treated as an octal number unless it starts
5330 with the characters &"0x"&, in which case the remainder is interpreted as a
5333 If an integer value is followed by the letter K, it is multiplied by 1024; if
5334 it is followed by the letter M, it is multiplied by 1024x1024;
5335 if by the letter G, 1024x1024x1024.
5337 of integer option settings are output, values which are an exact multiple of
5338 1024 or 1024x1024 are sometimes, but not always, printed using the letters K
5339 and M. The printing style is independent of the actual input format that was
5343 .section "Octal integer values" "SECID49"
5344 .cindex "integer format"
5345 .cindex "format" "octal integer"
5346 If an option's type is given as &"octal integer"&, its value is always
5347 interpreted as an octal number, whether or not it starts with the digit zero.
5348 Such options are always output in octal.
5351 .section "Fixed point numbers" "SECID50"
5352 .cindex "fixed point configuration values"
5353 .cindex "format" "fixed point"
5354 If an option's type is given as &"fixed-point"&, its value must be a decimal
5355 integer, optionally followed by a decimal point and up to three further digits.
5359 .section "Time intervals" "SECTtimeformat"
5360 .cindex "time interval" "specifying in configuration"
5361 .cindex "format" "time interval"
5362 A time interval is specified as a sequence of numbers, each followed by one of
5363 the following letters, with no intervening white space:
5373 For example, &"3h50m"& specifies 3 hours and 50 minutes. The values of time
5374 intervals are output in the same format. Exim does not restrict the values; it
5375 is perfectly acceptable, for example, to specify &"90m"& instead of &"1h30m"&.
5379 .section "String values" "SECTstrings"
5380 .cindex "string" "format of configuration values"
5381 .cindex "format" "string"
5382 If an option's type is specified as &"string"&, the value can be specified with
5383 or without double-quotes. If it does not start with a double-quote, the value
5384 consists of the remainder of the line plus any continuation lines, starting at
5385 the first character after any leading white space, with trailing white space
5386 removed, and with no interpretation of the characters in the string. Because
5387 Exim removes comment lines (those beginning with #) at an early stage, they can
5388 appear in the middle of a multi-line string. The following two settings are
5389 therefore equivalent:
5391 trusted_users = uucp:mail
5392 trusted_users = uucp:\
5393 # This comment line is ignored
5396 .cindex "string" "quoted"
5397 .cindex "escape characters in quoted strings"
5398 If a string does start with a double-quote, it must end with a closing
5399 double-quote, and any backslash characters other than those used for line
5400 continuation are interpreted as escape characters, as follows:
5403 .irow &`\\`& "single backslash"
5404 .irow &`\n`& "newline"
5405 .irow &`\r`& "carriage return"
5407 .irow "&`\`&<&'octal digits'&>" "up to 3 octal digits specify one character"
5408 .irow "&`\x`&<&'hex digits'&>" "up to 2 hexadecimal digits specify one &&&
5412 If a backslash is followed by some other character, including a double-quote
5413 character, that character replaces the pair.
5415 Quoting is necessary only if you want to make use of the backslash escapes to
5416 insert special characters, or if you need to specify a value with leading or
5417 trailing spaces. These cases are rare, so quoting is almost never needed in
5418 current versions of Exim. In versions of Exim before 3.14, quoting was required
5419 in order to continue lines, so you may come across older configuration files
5420 and examples that apparently quote unnecessarily.
5423 .section "Expanded strings" "SECID51"
5424 .cindex "expansion" "definition of"
5425 Some strings in the configuration file are subjected to &'string expansion'&,
5426 by which means various parts of the string may be changed according to the
5427 circumstances (see chapter &<<CHAPexpand>>&). The input syntax for such strings
5428 is as just described; in particular, the handling of backslashes in quoted
5429 strings is done as part of the input process, before expansion takes place.
5430 However, backslash is also an escape character for the expander, so any
5431 backslashes that are required for that reason must be doubled if they are
5432 within a quoted configuration string.
5435 .section "User and group names" "SECID52"
5436 .cindex "user name" "format of"
5437 .cindex "format" "user name"
5438 .cindex "groups" "name format"
5439 .cindex "format" "group name"
5440 User and group names are specified as strings, using the syntax described
5441 above, but the strings are interpreted specially. A user or group name must
5442 either consist entirely of digits, or be a name that can be looked up using the
5443 &[getpwnam()]& or &[getgrnam()]& function, as appropriate.
5446 .section "List construction" "SECTlistconstruct"
5447 .cindex "list" "syntax of in configuration"
5448 .cindex "format" "list item in configuration"
5449 .cindex "string" "list, definition of"
5450 The data for some configuration options is a list of items, with colon as the
5451 default separator. Many of these options are shown with type &"string list"& in
5452 the descriptions later in this document. Others are listed as &"domain list"&,
5453 &"host list"&, &"address list"&, or &"local part list"&. Syntactically, they
5454 are all the same; however, those other than &"string list"& are subject to
5455 particular kinds of interpretation, as described in chapter
5456 &<<CHAPdomhosaddlists>>&.
5458 In all these cases, the entire list is treated as a single string as far as the
5459 input syntax is concerned. The &%trusted_users%& setting in section
5460 &<<SECTstrings>>& above is an example. If a colon is actually needed in an item
5461 in a list, it must be entered as two colons. Leading and trailing white space
5462 on each item in a list is ignored. This makes it possible to include items that
5463 start with a colon, and in particular, certain forms of IPv6 address. For
5466 local_interfaces = 127.0.0.1 : ::::1
5468 contains two IP addresses, the IPv4 address 127.0.0.1 and the IPv6 address ::1.
5470 &*Note*&: Although leading and trailing white space is ignored in individual
5471 list items, it is not ignored when parsing the list. The spaces around the first
5472 colon in the example above are necessary. If they were not there, the list would
5473 be interpreted as the two items 127.0.0.1:: and 1.
5475 .section "Changing list separators" "SECTlistsepchange"
5476 .cindex "list separator" "changing"
5477 .cindex "IPv6" "addresses in lists"
5478 Doubling colons in IPv6 addresses is an unwelcome chore, so a mechanism was
5479 introduced to allow the separator character to be changed. If a list begins
5480 with a left angle bracket, followed by any punctuation character, that
5481 character is used instead of colon as the list separator. For example, the list
5482 above can be rewritten to use a semicolon separator like this:
5484 local_interfaces = <; 127.0.0.1 ; ::1
5486 This facility applies to all lists, with the exception of the list in
5487 &%log_file_path%&. It is recommended that the use of non-colon separators be
5488 confined to circumstances where they really are needed.
5490 .cindex "list separator" "newline as"
5491 .cindex "newline" "as list separator"
5492 It is also possible to use newline and other control characters (those with
5493 code values less than 32, plus DEL) as separators in lists. Such separators
5494 must be provided literally at the time the list is processed. For options that
5495 are string-expanded, you can write the separator using a normal escape
5496 sequence. This will be processed by the expander before the string is
5497 interpreted as a list. For example, if a newline-separated list of domains is
5498 generated by a lookup, you can process it directly by a line such as this:
5500 domains = <\n ${lookup mysql{.....}}
5502 This avoids having to change the list separator in such data. You are unlikely
5503 to want to use a control character as a separator in an option that is not
5504 expanded, because the value is literal text. However, it can be done by giving
5505 the value in quotes. For example:
5507 local_interfaces = "<\n 127.0.0.1 \n ::1"
5509 Unlike printing character separators, which can be included in list items by
5510 doubling, it is not possible to include a control character as data when it is
5511 set as the separator. Two such characters in succession are interpreted as
5512 enclosing an empty list item.
5516 .section "Empty items in lists" "SECTempitelis"
5517 .cindex "list" "empty item in"
5518 An empty item at the end of a list is always ignored. In other words, trailing
5519 separator characters are ignored. Thus, the list in
5521 senders = user@domain :
5523 contains only a single item. If you want to include an empty string as one item
5524 in a list, it must not be the last item. For example, this list contains three
5525 items, the second of which is empty:
5527 senders = user1@domain : : user2@domain
5529 &*Note*&: There must be white space between the two colons, as otherwise they
5530 are interpreted as representing a single colon data character (and the list
5531 would then contain just one item). If you want to specify a list that contains
5532 just one, empty item, you can do it as in this example:
5536 In this case, the first item is empty, and the second is discarded because it
5537 is at the end of the list.
5542 .section "Format of driver configurations" "SECTfordricon"
5543 .cindex "drivers" "configuration format"
5544 There are separate parts in the configuration for defining routers, transports,
5545 and authenticators. In each part, you are defining a number of driver
5546 instances, each with its own set of options. Each driver instance is defined by
5547 a sequence of lines like this:
5549 <&'instance name'&>:
5554 In the following example, the instance name is &(localuser)&, and it is
5555 followed by three options settings:
5560 transport = local_delivery
5562 For each driver instance, you specify which Exim code module it uses &-- by the
5563 setting of the &%driver%& option &-- and (optionally) some configuration
5564 settings. For example, in the case of transports, if you want a transport to
5565 deliver with SMTP you would use the &(smtp)& driver; if you want to deliver to
5566 a local file you would use the &(appendfile)& driver. Each of the drivers is
5567 described in detail in its own separate chapter later in this manual.
5569 You can have several routers, transports, or authenticators that are based on
5570 the same underlying driver (each must have a different instance name).
5572 The order in which routers are defined is important, because addresses are
5573 passed to individual routers one by one, in order. The order in which
5574 transports are defined does not matter at all. The order in which
5575 authenticators are defined is used only when Exim, as a client, is searching
5576 them to find one that matches an authentication mechanism offered by the
5579 .cindex "generic options"
5580 .cindex "options" "generic &-- definition of"
5581 Within a driver instance definition, there are two kinds of option: &'generic'&
5582 and &'private'&. The generic options are those that apply to all drivers of the
5583 same type (that is, all routers, all transports or all authenticators). The
5584 &%driver%& option is a generic option that must appear in every definition.
5585 .cindex "private options"
5586 The private options are special for each driver, and none need appear, because
5587 they all have default values.
5589 The options may appear in any order, except that the &%driver%& option must
5590 precede any private options, since these depend on the particular driver. For
5591 this reason, it is recommended that &%driver%& always be the first option.
5593 Driver instance names, which are used for reference in log entries and
5594 elsewhere, can be any sequence of letters, digits, and underscores (starting
5595 with a letter) and must be unique among drivers of the same type. A router and
5596 a transport (for example) can each have the same name, but no two router
5597 instances can have the same name. The name of a driver instance should not be
5598 confused with the name of the underlying driver module. For example, the
5599 configuration lines:
5604 create an instance of the &(smtp)& transport driver whose name is
5605 &(remote_smtp)&. The same driver code can be used more than once, with
5606 different instance names and different option settings each time. A second
5607 instance of the &(smtp)& transport, with different options, might be defined
5613 command_timeout = 10s
5615 The names &(remote_smtp)& and &(special_smtp)& would be used to reference
5616 these transport instances from routers, and these names would appear in log
5619 Comment lines may be present in the middle of driver specifications. The full
5620 list of option settings for any particular driver instance, including all the
5621 defaulted values, can be extracted by making use of the &%-bP%& command line
5629 . ////////////////////////////////////////////////////////////////////////////
5630 . ////////////////////////////////////////////////////////////////////////////
5632 .chapter "The default configuration file" "CHAPdefconfil"
5633 .scindex IIDconfiwal "configuration file" "default &""walk through""&"
5634 .cindex "default" "configuration file &""walk through""&"
5635 The default configuration file supplied with Exim as &_src/configure.default_&
5636 is sufficient for a host with simple mail requirements. As an introduction to
5637 the way Exim is configured, this chapter &"walks through"& the default
5638 configuration, giving brief explanations of the settings. Detailed descriptions
5639 of the options are given in subsequent chapters. The default configuration file
5640 itself contains extensive comments about ways you might want to modify the
5641 initial settings. However, note that there are many options that are not
5642 mentioned at all in the default configuration.
5646 .section "Macros" "SECTdefconfmacros"
5647 All macros should be defined before any options.
5649 One macro is specified, but commented out, in the default configuration:
5651 # ROUTER_SMARTHOST=MAIL.HOSTNAME.FOR.CENTRAL.SERVER.EXAMPLE
5653 If all off-site mail is expected to be delivered to a "smarthost", then set the
5654 hostname here and uncomment the macro. This will affect which router is used
5655 later on. If this is left commented out, then Exim will perform direct-to-MX
5656 deliveries using a &(dnslookup)& router.
5658 In addition to macros defined here, Exim includes a number of built-in macros
5659 to enable configuration to be guarded by a binary built with support for a
5660 given feature. See section &<<SECTbuiltinmacros>>& for more details.
5663 .section "Main configuration settings" "SECTdefconfmain"
5664 The main (global) configuration option settings section must always come first
5665 in the file, after the macros.
5666 The first thing you'll see in the file, after some initial comments, is the line
5668 # primary_hostname =
5670 This is a commented-out setting of the &%primary_hostname%& option. Exim needs
5671 to know the official, fully qualified name of your host, and this is where you
5672 can specify it. However, in most cases you do not need to set this option. When
5673 it is unset, Exim uses the &[uname()]& system function to obtain the host name.
5675 The first three non-comment configuration lines are as follows:
5677 domainlist local_domains = @
5678 domainlist relay_to_domains =
5679 hostlist relay_from_hosts = 127.0.0.1
5681 These are not, in fact, option settings. They are definitions of two named
5682 domain lists and one named host list. Exim allows you to give names to lists of
5683 domains, hosts, and email addresses, in order to make it easier to manage the
5684 configuration file (see section &<<SECTnamedlists>>&).
5686 The first line defines a domain list called &'local_domains'&; this is used
5687 later in the configuration to identify domains that are to be delivered
5690 .cindex "@ in a domain list"
5691 There is just one item in this list, the string &"@"&. This is a special form
5692 of entry which means &"the name of the local host"&. Thus, if the local host is
5693 called &'a.host.example'&, mail to &'any.user@a.host.example'& is expected to
5694 be delivered locally. Because the local host's name is referenced indirectly,
5695 the same configuration file can be used on different hosts.
5697 The second line defines a domain list called &'relay_to_domains'&, but the
5698 list itself is empty. Later in the configuration we will come to the part that
5699 controls mail relaying through the local host; it allows relaying to any
5700 domains in this list. By default, therefore, no relaying on the basis of a mail
5701 domain is permitted.
5703 The third line defines a host list called &'relay_from_hosts'&. This list is
5704 used later in the configuration to permit relaying from any host or IP address
5705 that matches the list. The default contains just the IP address of the IPv4
5706 loopback interface, which means that processes on the local host are able to
5707 submit mail for relaying by sending it over TCP/IP to that interface. No other
5708 hosts are permitted to submit messages for relaying.
5710 Just to be sure there's no misunderstanding: at this point in the configuration
5711 we aren't actually setting up any controls. We are just defining some domains
5712 and hosts that will be used in the controls that are specified later.
5714 The next two configuration lines are genuine option settings:
5716 acl_smtp_rcpt = acl_check_rcpt
5717 acl_smtp_data = acl_check_data
5719 These options specify &'Access Control Lists'& (ACLs) that are to be used
5720 during an incoming SMTP session for every recipient of a message (every RCPT
5721 command), and after the contents of the message have been received,
5722 respectively. The names of the lists are &'acl_check_rcpt'& and
5723 &'acl_check_data'&, and we will come to their definitions below, in the ACL
5724 section of the configuration. The RCPT ACL controls which recipients are
5725 accepted for an incoming message &-- if a configuration does not provide an ACL
5726 to check recipients, no SMTP mail can be accepted. The DATA ACL allows the
5727 contents of a message to be checked.
5729 Two commented-out option settings are next:
5731 # av_scanner = clamd:/tmp/clamd
5732 # spamd_address = 127.0.0.1 783
5734 These are example settings that can be used when Exim is compiled with the
5735 content-scanning extension. The first specifies the interface to the virus
5736 scanner, and the second specifies the interface to SpamAssassin. Further
5737 details are given in chapter &<<CHAPexiscan>>&.
5739 Three more commented-out option settings follow:
5741 # tls_advertise_hosts = *
5742 # tls_certificate = /etc/ssl/exim.crt
5743 # tls_privatekey = /etc/ssl/exim.pem
5745 These are example settings that can be used when Exim is compiled with
5746 support for TLS (aka SSL) as described in section &<<SECTinctlsssl>>&. The
5747 first one specifies the list of clients that are allowed to use TLS when
5748 connecting to this server; in this case, the wildcard means all clients. The
5749 other options specify where Exim should find its TLS certificate and private
5750 key, which together prove the server's identity to any clients that connect.
5751 More details are given in chapter &<<CHAPTLS>>&.
5753 Another two commented-out option settings follow:
5755 # daemon_smtp_ports = 25 : 465 : 587
5756 # tls_on_connect_ports = 465
5758 .cindex "port" "465 and 587"
5759 .cindex "port" "for message submission"
5760 .cindex "message" "submission, ports for"
5761 .cindex "submissions protocol"
5762 .cindex "smtps protocol"
5763 .cindex "ssmtp protocol"
5764 .cindex "SMTP" "submissions protocol"
5765 .cindex "SMTP" "ssmtp protocol"
5766 .cindex "SMTP" "smtps protocol"
5767 These options provide better support for roaming users who wish to use this
5768 server for message submission. They are not much use unless you have turned on
5769 TLS (as described in the previous paragraph) and authentication (about which
5770 more in section &<<SECTdefconfauth>>&).
5771 Mail submission from mail clients (MUAs) should be separate from inbound mail
5772 to your domain (MX delivery) for various good reasons (eg, ability to impose
5773 much saner TLS protocol and ciphersuite requirements without unintended
5775 RFC 6409 (previously 4409) specifies use of port 587 for SMTP Submission,
5776 which uses STARTTLS, so this is the &"submission"& port.
5777 RFC 8314 specifies use of port 465 as the &"submissions"& protocol,
5778 which should be used in preference to 587.
5779 You should also consider deploying SRV records to help clients find
5781 Older names for &"submissions"& are &"smtps"& and &"ssmtp"&.
5783 Two more commented-out options settings follow:
5786 # qualify_recipient =
5788 The first of these specifies a domain that Exim uses when it constructs a
5789 complete email address from a local login name. This is often needed when Exim
5790 receives a message from a local process. If you do not set &%qualify_domain%&,
5791 the value of &%primary_hostname%& is used. If you set both of these options,
5792 you can have different qualification domains for sender and recipient
5793 addresses. If you set only the first one, its value is used in both cases.
5795 .cindex "domain literal" "recognizing format"
5796 The following line must be uncommented if you want Exim to recognize
5797 addresses of the form &'user@[10.11.12.13]'& that is, with a &"domain literal"&
5798 (an IP address within square brackets) instead of a named domain.
5800 # allow_domain_literals
5802 The RFCs still require this form, but many people think that in the modern
5803 Internet it makes little sense to permit mail to be sent to specific hosts by
5804 quoting their IP addresses. This ancient format has been used by people who
5805 try to abuse hosts by using them for unwanted relaying. However, some
5806 people believe there are circumstances (for example, messages addressed to
5807 &'postmaster'&) where domain literals are still useful.
5809 The next configuration line is a kind of trigger guard:
5813 It specifies that no delivery must ever be run as the root user. The normal
5814 convention is to set up &'root'& as an alias for the system administrator. This
5815 setting is a guard against slips in the configuration.
5816 The list of users specified by &%never_users%& is not, however, the complete
5817 list; the build-time configuration in &_Local/Makefile_& has an option called
5818 FIXED_NEVER_USERS specifying a list that cannot be overridden. The
5819 contents of &%never_users%& are added to this list. By default
5820 FIXED_NEVER_USERS also specifies root.
5822 When a remote host connects to Exim in order to send mail, the only information
5823 Exim has about the host's identity is its IP address. The next configuration
5828 specifies that Exim should do a reverse DNS lookup on all incoming connections,
5829 in order to get a host name. This improves the quality of the logging
5830 information, but if you feel it is too expensive, you can remove it entirely,
5831 or restrict the lookup to hosts on &"nearby"& networks.
5832 Note that it is not always possible to find a host name from an IP address,
5833 because not all DNS reverse zones are maintained, and sometimes DNS servers are
5836 The next two lines are concerned with &'ident'& callbacks, as defined by RFC
5837 1413 (hence their names):
5840 rfc1413_query_timeout = 0s
5842 These settings cause Exim to avoid ident callbacks for all incoming SMTP calls.
5843 Few hosts offer RFC1413 service these days; calls have to be
5844 terminated by a timeout and this needlessly delays the startup
5845 of an incoming SMTP connection.
5846 If you have hosts for which you trust RFC1413 and need this
5847 information, you can change this.
5849 This line enables an efficiency SMTP option. It is negotiated by clients
5850 and not expected to cause problems but can be disabled if needed.
5855 When Exim receives messages over SMTP connections, it expects all addresses to
5856 be fully qualified with a domain, as required by the SMTP definition. However,
5857 if you are running a server to which simple clients submit messages, you may
5858 find that they send unqualified addresses. The two commented-out options:
5860 # sender_unqualified_hosts =
5861 # recipient_unqualified_hosts =
5863 show how you can specify hosts that are permitted to send unqualified sender
5864 and recipient addresses, respectively.
5866 The &%log_selector%& option is used to increase the detail of logging
5869 log_selector = +smtp_protocol_error +smtp_syntax_error \
5870 +tls_certificate_verified
5873 The &%percent_hack_domains%& option is also commented out:
5875 # percent_hack_domains =
5877 It provides a list of domains for which the &"percent hack"& is to operate.
5878 This is an almost obsolete form of explicit email routing. If you do not know
5879 anything about it, you can safely ignore this topic.
5881 The next two settings in the main part of the default configuration are
5882 concerned with messages that have been &"frozen"& on Exim's queue. When a
5883 message is frozen, Exim no longer continues to try to deliver it. Freezing
5884 occurs when a bounce message encounters a permanent failure because the sender
5885 address of the original message that caused the bounce is invalid, so the
5886 bounce cannot be delivered. This is probably the most common case, but there
5887 are also other conditions that cause freezing, and frozen messages are not
5888 always bounce messages.
5890 ignore_bounce_errors_after = 2d
5891 timeout_frozen_after = 7d
5893 The first of these options specifies that failing bounce messages are to be
5894 discarded after 2 days in the queue. The second specifies that any frozen
5895 message (whether a bounce message or not) is to be timed out (and discarded)
5896 after a week. In this configuration, the first setting ensures that no failing
5897 bounce message ever lasts a week.
5899 Exim queues it's messages in a spool directory. If you expect to have
5900 large queues, you may consider using this option. It splits the spool
5901 directory into subdirectories to avoid file system degradation from
5902 many files in a single directory, resulting in better performance.
5903 Manual manipulation of queued messages becomes more complex (though fortunately
5906 # split_spool_directory = true
5909 In an ideal world everybody follows the standards. For non-ASCII
5910 messages RFC 2047 is a standard, allowing a maximum line length of 76
5911 characters. Exim adheres that standard and won't process messages which
5912 violate this standard. (Even ${rfc2047:...} expansions will fail.)
5913 In particular, the Exim maintainers have had multiple reports of
5914 problems from Russian administrators of issues until they disable this
5915 check, because of some popular, yet buggy, mail composition software.
5917 # check_rfc2047_length = false
5920 If you need to be strictly RFC compliant you may wish to disable the
5921 8BITMIME advertisement. Use this, if you exchange mails with systems
5922 that are not 8-bit clean.
5924 # accept_8bitmime = false
5927 Libraries you use may depend on specific environment settings. This
5928 imposes a security risk (e.g. PATH). There are two lists:
5929 &%keep_environment%& for the variables to import as they are, and
5930 &%add_environment%& for variables we want to set to a fixed value.
5931 Note that TZ is handled separately, by the &%timezone%& runtime
5932 option and by the TIMEZONE_DEFAULT buildtime option.
5934 # keep_environment = ^LDAP
5935 # add_environment = PATH=/usr/bin::/bin
5939 .section "ACL configuration" "SECID54"
5940 .cindex "default" "ACLs"
5941 .cindex "&ACL;" "default configuration"
5942 In the default configuration, the ACL section follows the main configuration.
5943 It starts with the line
5947 and it contains the definitions of two ACLs, called &'acl_check_rcpt'& and
5948 &'acl_check_data'&, that were referenced in the settings of &%acl_smtp_rcpt%&
5949 and &%acl_smtp_data%& above.
5951 .cindex "RCPT" "ACL for"
5952 The first ACL is used for every RCPT command in an incoming SMTP message. Each
5953 RCPT command specifies one of the message's recipients. The ACL statements
5954 are considered in order, until the recipient address is either accepted or
5955 rejected. The RCPT command is then accepted or rejected, according to the
5956 result of the ACL processing.
5960 This line, consisting of a name terminated by a colon, marks the start of the
5965 This ACL statement accepts the recipient if the sending host matches the list.
5966 But what does that strange list mean? It doesn't actually contain any host
5967 names or IP addresses. The presence of the colon puts an empty item in the
5968 list; Exim matches this only if the incoming message did not come from a remote
5969 host, because in that case, the remote hostname is empty. The colon is
5970 important. Without it, the list itself is empty, and can never match anything.
5972 What this statement is doing is to accept unconditionally all recipients in
5973 messages that are submitted by SMTP from local processes using the standard
5974 input and output (that is, not using TCP/IP). A number of MUAs operate in this
5977 deny domains = +local_domains
5978 local_parts = ^[.] : ^.*[@%!/|]
5979 message = Restricted characters in address
5981 deny domains = !+local_domains
5982 local_parts = ^[./|] : ^.*[@%!] : ^.*/\\.\\./
5983 message = Restricted characters in address
5985 These statements are concerned with local parts that contain any of the
5986 characters &"@"&, &"%"&, &"!"&, &"/"&, &"|"&, or dots in unusual places.
5987 Although these characters are entirely legal in local parts (in the case of
5988 &"@"& and leading dots, only if correctly quoted), they do not commonly occur
5989 in Internet mail addresses.
5991 The first three have in the past been associated with explicitly routed
5992 addresses (percent is still sometimes used &-- see the &%percent_hack_domains%&
5993 option). Addresses containing these characters are regularly tried by spammers
5994 in an attempt to bypass relaying restrictions, and also by open relay testing
5995 programs. Unless you really need them it is safest to reject these characters
5996 at this early stage. This configuration is heavy-handed in rejecting these
5997 characters for all messages it accepts from remote hosts. This is a deliberate
5998 policy of being as safe as possible.
6000 The first rule above is stricter, and is applied to messages that are addressed
6001 to one of the local domains handled by this host. This is implemented by the
6002 first condition, which restricts it to domains that are listed in the
6003 &'local_domains'& domain list. The &"+"& character is used to indicate a
6004 reference to a named list. In this configuration, there is just one domain in
6005 &'local_domains'&, but in general there may be many.
6007 The second condition on the first statement uses two regular expressions to
6008 block local parts that begin with a dot or contain &"@"&, &"%"&, &"!"&, &"/"&,
6009 or &"|"&. If you have local accounts that include these characters, you will
6010 have to modify this rule.
6012 Empty components (two dots in a row) are not valid in RFC 2822, but Exim
6013 allows them because they have been encountered in practice. (Consider the
6014 common convention of local parts constructed as
6015 &"&'first-initial.second-initial.family-name'&"& when applied to someone like
6016 the author of Exim, who has no second initial.) However, a local part starting
6017 with a dot or containing &"/../"& can cause trouble if it is used as part of a
6018 filename (for example, for a mailing list). This is also true for local parts
6019 that contain slashes. A pipe symbol can also be troublesome if the local part
6020 is incorporated unthinkingly into a shell command line.
6022 The second rule above applies to all other domains, and is less strict. This
6023 allows your own users to send outgoing messages to sites that use slashes
6024 and vertical bars in their local parts. It blocks local parts that begin
6025 with a dot, slash, or vertical bar, but allows these characters within the
6026 local part. However, the sequence &"/../"& is barred. The use of &"@"&, &"%"&,
6027 and &"!"& is blocked, as before. The motivation here is to prevent your users
6028 (or your users' viruses) from mounting certain kinds of attack on remote sites.
6030 accept local_parts = postmaster
6031 domains = +local_domains
6033 This statement, which has two conditions, accepts an incoming address if the
6034 local part is &'postmaster'& and the domain is one of those listed in the
6035 &'local_domains'& domain list. The &"+"& character is used to indicate a
6036 reference to a named list. In this configuration, there is just one domain in
6037 &'local_domains'&, but in general there may be many.
6039 The presence of this statement means that mail to postmaster is never blocked
6040 by any of the subsequent tests. This can be helpful while sorting out problems
6041 in cases where the subsequent tests are incorrectly denying access.
6043 require verify = sender
6045 This statement requires the sender address to be verified before any subsequent
6046 ACL statement can be used. If verification fails, the incoming recipient
6047 address is refused. Verification consists of trying to route the address, to
6048 see if a bounce message could be delivered to it. In the case of remote
6049 addresses, basic verification checks only the domain, but &'callouts'& can be
6050 used for more verification if required. Section &<<SECTaddressverification>>&
6051 discusses the details of address verification.
6053 accept hosts = +relay_from_hosts
6054 control = submission
6056 This statement accepts the address if the message is coming from one of the
6057 hosts that are defined as being allowed to relay through this host. Recipient
6058 verification is omitted here, because in many cases the clients are dumb MUAs
6059 that do not cope well with SMTP error responses. For the same reason, the
6060 second line specifies &"submission mode"& for messages that are accepted. This
6061 is described in detail in section &<<SECTsubmodnon>>&; it causes Exim to fix
6062 messages that are deficient in some way, for example, because they lack a
6063 &'Date:'& header line. If you are actually relaying out from MTAs, you should
6064 probably add recipient verification here, and disable submission mode.
6066 accept authenticated = *
6067 control = submission
6069 This statement accepts the address if the client host has authenticated itself.
6070 Submission mode is again specified, on the grounds that such messages are most
6071 likely to come from MUAs. The default configuration does not define any
6072 authenticators, though it does include some nearly complete commented-out
6073 examples described in &<<SECTdefconfauth>>&. This means that no client can in
6074 fact authenticate until you complete the authenticator definitions.
6076 require message = relay not permitted
6077 domains = +local_domains : +relay_to_domains
6079 This statement rejects the address if its domain is neither a local domain nor
6080 one of the domains for which this host is a relay.
6082 require verify = recipient
6084 This statement requires the recipient address to be verified; if verification
6085 fails, the address is rejected.
6087 # deny dnslists = black.list.example
6088 # message = rejected because $sender_host_address \
6089 # is in a black list at $dnslist_domain\n\
6092 # warn dnslists = black.list.example
6093 # add_header = X-Warning: $sender_host_address is in \
6094 # a black list at $dnslist_domain
6095 # log_message = found in $dnslist_domain
6097 These commented-out lines are examples of how you could configure Exim to check
6098 sending hosts against a DNS black list. The first statement rejects messages
6099 from blacklisted hosts, whereas the second just inserts a warning header
6102 # require verify = csa
6104 This commented-out line is an example of how you could turn on client SMTP
6105 authorization (CSA) checking. Such checks do DNS lookups for special SRV
6110 The final statement in the first ACL unconditionally accepts any recipient
6111 address that has successfully passed all the previous tests.
6115 This line marks the start of the second ACL, and names it. Most of the contents
6116 of this ACL are commented out:
6119 # message = This message contains a virus \
6122 These lines are examples of how to arrange for messages to be scanned for
6123 viruses when Exim has been compiled with the content-scanning extension, and a
6124 suitable virus scanner is installed. If the message is found to contain a
6125 virus, it is rejected with the given custom error message.
6127 # warn spam = nobody
6128 # message = X-Spam_score: $spam_score\n\
6129 # X-Spam_score_int: $spam_score_int\n\
6130 # X-Spam_bar: $spam_bar\n\
6131 # X-Spam_report: $spam_report
6133 These lines are an example of how to arrange for messages to be scanned by
6134 SpamAssassin when Exim has been compiled with the content-scanning extension,
6135 and SpamAssassin has been installed. The SpamAssassin check is run with
6136 &`nobody`& as its user parameter, and the results are added to the message as a
6137 series of extra header line. In this case, the message is not rejected,
6138 whatever the spam score.
6142 This final line in the DATA ACL accepts the message unconditionally.
6145 .section "Router configuration" "SECID55"
6146 .cindex "default" "routers"
6147 .cindex "routers" "default"
6148 The router configuration comes next in the default configuration, introduced
6153 Routers are the modules in Exim that make decisions about where to send
6154 messages. An address is passed to each router, in turn, until it is either
6155 accepted, or failed. This means that the order in which you define the routers
6156 matters. Each router is fully described in its own chapter later in this
6157 manual. Here we give only brief overviews.
6160 # driver = ipliteral
6161 # domains = !+local_domains
6162 # transport = remote_smtp
6164 .cindex "domain literal" "default router"
6165 This router is commented out because the majority of sites do not want to
6166 support domain literal addresses (those of the form &'user@[10.9.8.7]'&). If
6167 you uncomment this router, you also need to uncomment the setting of
6168 &%allow_domain_literals%& in the main part of the configuration.
6170 Which router is used next depends upon whether or not the ROUTER_SMARTHOST
6171 macro has been defined, per
6173 .ifdef ROUTER_SMARTHOST
6182 If ROUTER_SMARTHOST has been defined, either at the top of the file or on the
6183 command-line, then we route all non-local mail to that smarthost; otherwise, we'll
6184 perform DNS lookups for direct-to-MX lookup. Any mail which is to a local domain will
6185 skip these routers because of the &%domains%& option.
6189 driver = manualroute
6190 domains = ! +local_domains
6191 transport = smarthost_smtp
6192 route_data = ROUTER_SMARTHOST
6193 ignore_target_hosts = <; 0.0.0.0 ; 127.0.0.0/8 ; ::1
6196 This router only handles mail which is not to any local domains; this is
6197 specified by the line
6199 domains = ! +local_domains
6201 The &%domains%& option lists the domains to which this router applies, but the
6202 exclamation mark is a negation sign, so the router is used only for domains
6203 that are not in the domain list called &'local_domains'& (which was defined at
6204 the start of the configuration). The plus sign before &'local_domains'&
6205 indicates that it is referring to a named list. Addresses in other domains are
6206 passed on to the following routers.
6208 The name of the router driver is &(manualroute)& because we are manually
6209 specifying how mail should be routed onwards, instead of using DNS MX.
6210 While the name of this router instance is arbitrary, the &%driver%& option must
6211 be one of the driver modules that is in the Exim binary.
6213 With no pre-conditions other than &%domains%&, all mail for non-local domains
6214 will be handled by this router, and the &%no_more%& setting will ensure that no
6215 other routers will be used for messages matching the pre-conditions. See
6216 &<<SECTrouprecon>>& for more on how the pre-conditions apply. For messages which
6217 are handled by this router, we provide a hostname to deliver to in &%route_data%&
6218 and the macro supplies the value; the address is then queued for the
6219 &(smarthost_smtp)& transport.
6224 domains = ! +local_domains
6225 transport = remote_smtp
6226 ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
6229 The &%domains%& option behaves as per smarthost, above.
6231 The name of the router driver is &(dnslookup)&,
6232 and is specified by the &%driver%& option. Do not be confused by the fact that
6233 the name of this router instance is the same as the name of the driver. The
6234 instance name is arbitrary, but the name set in the &%driver%& option must be
6235 one of the driver modules that is in the Exim binary.
6237 The &(dnslookup)& router routes addresses by looking up their domains in the
6238 DNS in order to obtain a list of hosts to which the address is routed. If the
6239 router succeeds, the address is queued for the &(remote_smtp)& transport, as
6240 specified by the &%transport%& option. If the router does not find the domain
6241 in the DNS, no further routers are tried because of the &%no_more%& setting, so
6242 the address fails and is bounced.
6244 The &%ignore_target_hosts%& option specifies a list of IP addresses that are to
6245 be entirely ignored. This option is present because a number of cases have been
6246 encountered where MX records in the DNS point to host names
6247 whose IP addresses are 0.0.0.0 or are in the 127 subnet (typically 127.0.0.1).
6248 Completely ignoring these IP addresses causes Exim to fail to route the
6249 email address, so it bounces. Otherwise, Exim would log a routing problem, and
6250 continue to try to deliver the message periodically until the address timed
6257 data = ${lookup{$local_part}lsearch{/etc/aliases}}
6259 file_transport = address_file
6260 pipe_transport = address_pipe
6262 Control reaches this and subsequent routers only for addresses in the local
6263 domains. This router checks to see whether the local part is defined as an
6264 alias in the &_/etc/aliases_& file, and if so, redirects it according to the
6265 data that it looks up from that file. If no data is found for the local part,
6266 the value of the &%data%& option is empty, causing the address to be passed to
6269 &_/etc/aliases_& is a conventional name for the system aliases file that is
6270 often used. That is why it is referenced by from the default configuration
6271 file. However, you can change this by setting SYSTEM_ALIASES_FILE in
6272 &_Local/Makefile_& before building Exim.
6277 # local_part_suffix = +* : -*
6278 # local_part_suffix_optional
6279 file = $home/.forward
6284 file_transport = address_file
6285 pipe_transport = address_pipe
6286 reply_transport = address_reply
6288 This is the most complicated router in the default configuration. It is another
6289 redirection router, but this time it is looking for forwarding data set up by
6290 individual users. The &%check_local_user%& setting specifies a check that the
6291 local part of the address is the login name of a local user. If it is not, the
6292 router is skipped. The two commented options that follow &%check_local_user%&,
6295 # local_part_suffix = +* : -*
6296 # local_part_suffix_optional
6298 .vindex "&$local_part_suffix$&"
6299 show how you can specify the recognition of local part suffixes. If the first
6300 is uncommented, a suffix beginning with either a plus or a minus sign, followed
6301 by any sequence of characters, is removed from the local part and placed in the
6302 variable &$local_part_suffix$&. The second suffix option specifies that the
6303 presence of a suffix in the local part is optional. When a suffix is present,
6304 the check for a local login uses the local part with the suffix removed.
6306 When a local user account is found, the file called &_.forward_& in the user's
6307 home directory is consulted. If it does not exist, or is empty, the router
6308 declines. Otherwise, the contents of &_.forward_& are interpreted as
6309 redirection data (see chapter &<<CHAPredirect>>& for more details).
6311 .cindex "Sieve filter" "enabling in default router"
6312 Traditional &_.forward_& files contain just a list of addresses, pipes, or
6313 files. Exim supports this by default. However, if &%allow_filter%& is set (it
6314 is commented out by default), the contents of the file are interpreted as a set
6315 of Exim or Sieve filtering instructions, provided the file begins with &"#Exim
6316 filter"& or &"#Sieve filter"&, respectively. User filtering is discussed in the
6317 separate document entitled &'Exim's interfaces to mail filtering'&.
6319 The &%no_verify%& and &%no_expn%& options mean that this router is skipped when
6320 verifying addresses, or when running as a consequence of an SMTP EXPN command.
6321 There are two reasons for doing this:
6324 Whether or not a local user has a &_.forward_& file is not really relevant when
6325 checking an address for validity; it makes sense not to waste resources doing
6328 More importantly, when Exim is verifying addresses or handling an EXPN
6329 command during an SMTP session, it is running as the Exim user, not as root.
6330 The group is the Exim group, and no additional groups are set up.
6331 It may therefore not be possible for Exim to read users' &_.forward_& files at
6335 The setting of &%check_ancestor%& prevents the router from generating a new
6336 address that is the same as any previous address that was redirected. (This
6337 works round a problem concerning a bad interaction between aliasing and
6338 forwarding &-- see section &<<SECTredlocmai>>&).
6340 The final three option settings specify the transports that are to be used when
6341 forwarding generates a direct delivery to a file, or to a pipe, or sets up an
6342 auto-reply, respectively. For example, if a &_.forward_& file contains
6344 a.nother@elsewhere.example, /home/spqr/archive
6346 the delivery to &_/home/spqr/archive_& is done by running the &%address_file%&
6352 # local_part_suffix = +* : -*
6353 # local_part_suffix_optional
6354 transport = local_delivery
6356 The final router sets up delivery into local mailboxes, provided that the local
6357 part is the name of a local login, by accepting the address and assigning it to
6358 the &(local_delivery)& transport. Otherwise, we have reached the end of the
6359 routers, so the address is bounced. The commented suffix settings fulfil the
6360 same purpose as they do for the &(userforward)& router.
6363 .section "Transport configuration" "SECID56"
6364 .cindex "default" "transports"
6365 .cindex "transports" "default"
6366 Transports define mechanisms for actually delivering messages. They operate
6367 only when referenced from routers, so the order in which they are defined does
6368 not matter. The transports section of the configuration starts with
6372 Two remote transports and four local transports are defined.
6376 message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}
6381 This transport is used for delivering messages over SMTP connections.
6382 The list of remote hosts comes from the router.
6383 The &%message_size_limit%& usage is a hack to avoid sending on messages
6384 with over-long lines.
6386 The &%hosts_try_prdr%& option enables an efficiency SMTP option. It is
6387 negotiated between client and server and not expected to cause problems
6388 but can be disabled if needed. The built-in macro _HAVE_PRDR guards the
6389 use of the &%hosts_try_prdr%& configuration option.
6391 The other remote transport is used when delivering to a specific smarthost
6392 with whom there must be some kind of existing relationship, instead of the
6393 usual federated system.
6398 message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}
6402 # Comment out any of these which you have to, then file a Support
6403 # request with your smarthost provider to get things fixed:
6404 hosts_require_tls = *
6405 tls_verify_hosts = *
6406 # As long as tls_verify_hosts is enabled, this this will have no effect,
6407 # but if you have to comment it out then this will at least log whether
6408 # you succeed or not:
6409 tls_try_verify_hosts = *
6411 # The SNI name should match the name which we'll expect to verify;
6412 # many mail systems don't use SNI and this doesn't matter, but if it does,
6413 # we need to send a name which the remote site will recognize.
6414 # This _should_ be the name which the smarthost operators specified as
6415 # the hostname for sending your mail to.
6416 tls_sni = ROUTER_SMARTHOST
6418 .ifdef _HAVE_OPENSSL
6419 tls_require_ciphers = HIGH:!aNULL:@STRENGTH
6422 tls_require_ciphers = SECURE192:-VERS-SSL3.0:-VERS-TLS1.0:-VERS-TLS1.1
6429 After the same &%message_size_limit%& hack, we then specify that this Transport
6430 can handle messages to multiple domains in one run. The assumption here is
6431 that you're routing all non-local mail to the same place and that place is
6432 happy to take all messages from you as quickly as possible.
6433 All other options depend upon built-in macros; if Exim was built without TLS support
6434 then no other options are defined.
6435 If TLS is available, then we configure "stronger than default" TLS ciphersuites
6436 and versions using the &%tls_require_ciphers%& option, where the value to be
6437 used depends upon the library providing TLS.
6438 Beyond that, the options adopt the stance that you should have TLS support available
6439 from your smarthost on today's Internet, so we turn on requiring TLS for the
6440 mail to be delivered, and requiring that the certificate be valid, and match
6441 the expected hostname. The &%tls_sni%& option can be used by service providers
6442 to select an appropriate certificate to present to you and here we re-use the
6443 ROUTER_SMARTHOST macro, because that is unaffected by CNAMEs present in DNS.
6444 You want to specify the hostname which you'll expect to validate for, and that
6445 should not be subject to insecure tampering via DNS results.
6447 For the &%hosts_try_prdr%& option see the previous transport.
6449 All other options are defaulted.
6453 file = /var/mail/$local_part_data
6460 This &(appendfile)& transport is used for local delivery to user mailboxes in
6461 traditional BSD mailbox format.
6463 We prefer to avoid using &$local_part$& directly to define the mailbox filename,
6464 as it is provided by a potential bad actor.
6465 Instead we use &$local_part_data$&,
6466 the result of looking up &$local_part$& in the user database
6467 (done by using &%check_local_user%& in the the router).
6469 By default &(appendfile)& runs under the uid and gid of the
6470 local user, which requires the sticky bit to be set on the &_/var/mail_&
6471 directory. Some systems use the alternative approach of running mail deliveries
6472 under a particular group instead of using the sticky bit. The commented options
6473 show how this can be done.
6475 Exim adds three headers to the message as it delivers it: &'Delivery-date:'&,
6476 &'Envelope-to:'& and &'Return-path:'&. This action is requested by the three
6477 similarly-named options above.
6483 This transport is used for handling deliveries to pipes that are generated by
6484 redirection (aliasing or users' &_.forward_& files). The &%return_output%&
6485 option specifies that any output on stdout or stderr generated by the pipe is to
6486 be returned to the sender.
6494 This transport is used for handling deliveries to files that are generated by
6495 redirection. The name of the file is not specified in this instance of
6496 &(appendfile)&, because it comes from the &(redirect)& router.
6501 This transport is used for handling automatic replies generated by users'
6506 .section "Default retry rule" "SECID57"
6507 .cindex "retry" "default rule"
6508 .cindex "default" "retry rule"
6509 The retry section of the configuration file contains rules which affect the way
6510 Exim retries deliveries that cannot be completed at the first attempt. It is
6511 introduced by the line
6515 In the default configuration, there is just one rule, which applies to all
6518 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
6520 This causes any temporarily failing address to be retried every 15 minutes for
6521 2 hours, then at intervals starting at one hour and increasing by a factor of
6522 1.5 until 16 hours have passed, then every 6 hours up to 4 days. If an address
6523 is not delivered after 4 days of temporary failure, it is bounced. The time is
6524 measured from first failure, not from the time the message was received.
6526 If the retry section is removed from the configuration, or is empty (that is,
6527 if no retry rules are defined), Exim will not retry deliveries. This turns
6528 temporary errors into permanent errors.
6531 .section "Rewriting configuration" "SECID58"
6532 The rewriting section of the configuration, introduced by
6536 contains rules for rewriting addresses in messages as they arrive. There are no
6537 rewriting rules in the default configuration file.
6541 .section "Authenticators configuration" "SECTdefconfauth"
6542 .cindex "AUTH" "configuration"
6543 The authenticators section of the configuration, introduced by
6545 begin authenticators
6547 defines mechanisms for the use of the SMTP AUTH command. The default
6548 configuration file contains two commented-out example authenticators
6549 which support plaintext username/password authentication using the
6550 standard PLAIN mechanism and the traditional but non-standard LOGIN
6551 mechanism, with Exim acting as the server. PLAIN and LOGIN are enough
6552 to support most MUA software.
6554 The example PLAIN authenticator looks like this:
6557 # driver = plaintext
6558 # server_set_id = $auth2
6559 # server_prompts = :
6560 # server_condition = Authentication is not yet configured
6561 # server_advertise_condition = ${if def:tls_in_cipher }
6563 And the example LOGIN authenticator looks like this:
6566 # driver = plaintext
6567 # server_set_id = $auth1
6568 # server_prompts = <| Username: | Password:
6569 # server_condition = Authentication is not yet configured
6570 # server_advertise_condition = ${if def:tls_in_cipher }
6573 The &%server_set_id%& option makes Exim remember the authenticated username
6574 in &$authenticated_id$&, which can be used later in ACLs or routers. The
6575 &%server_prompts%& option configures the &(plaintext)& authenticator so
6576 that it implements the details of the specific authentication mechanism,
6577 i.e. PLAIN or LOGIN. The &%server_advertise_condition%& setting controls
6578 when Exim offers authentication to clients; in the examples, this is only
6579 when TLS or SSL has been started, so to enable the authenticators you also
6580 need to add support for TLS as described in section &<<SECTdefconfmain>>&.
6582 The &%server_condition%& setting defines how to verify that the username and
6583 password are correct. In the examples it just produces an error message.
6584 To make the authenticators work, you can use a string expansion
6585 expression like one of the examples in chapter &<<CHAPplaintext>>&.
6587 Beware that the sequence of the parameters to PLAIN and LOGIN differ; the
6588 usercode and password are in different positions.
6589 Chapter &<<CHAPplaintext>>& covers both.
6591 .ecindex IIDconfiwal
6595 . ////////////////////////////////////////////////////////////////////////////
6596 . ////////////////////////////////////////////////////////////////////////////
6598 .chapter "Regular expressions" "CHAPregexp"
6600 .cindex "regular expressions" "library"
6602 Exim supports the use of regular expressions in many of its options. It
6603 uses the PCRE2 regular expression library; this provides regular expression
6604 matching that is compatible with Perl 5. The syntax and semantics of
6605 regular expressions is discussed in
6606 online Perl manpages, in
6607 many Perl reference books, and also in
6608 Jeffrey Friedl's &'Mastering Regular Expressions'&, which is published by
6609 O'Reilly (see &url(http://www.oreilly.com/catalog/regex2/)).
6610 . --- the http: URL here redirects to another page with the ISBN in the URL
6611 . --- where trying to use https: just redirects back to http:, so sticking
6612 . --- to the old URL for now. 2018-09-07.
6614 The documentation for the syntax and semantics of the regular expressions that
6615 are supported by PCRE2 is included in the PCRE2 distribution, and no further
6616 description is included here. The PCRE2 functions are called from Exim using
6617 the default option settings (that is, with no PCRE2 options set), except that
6618 the PCRE2_CASELESS option is set when the matching is required to be
6621 In most cases, when a regular expression is required in an Exim configuration,
6622 it has to start with a circumflex, in order to distinguish it from plain text
6623 or an &"ends with"& wildcard. In this example of a configuration setting, the
6624 second item in the colon-separated list is a regular expression.
6626 domains = a.b.c : ^\\d{3} : *.y.z : ...
6628 The doubling of the backslash is required because of string expansion that
6629 precedes interpretation &-- see section &<<SECTlittext>>& for more discussion
6630 of this issue, and a way of avoiding the need for doubling backslashes. The
6631 regular expression that is eventually used in this example contains just one
6632 backslash. The circumflex is included in the regular expression, and has the
6633 normal effect of &"anchoring"& it to the start of the string that is being
6636 There are, however, two cases where a circumflex is not required for the
6637 recognition of a regular expression: these are the &%match%& condition in a
6638 string expansion, and the &%matches%& condition in an Exim filter file. In
6639 these cases, the relevant string is always treated as a regular expression; if
6640 it does not start with a circumflex, the expression is not anchored, and can
6641 match anywhere in the subject string.
6643 In all cases, if you want a regular expression to match at the end of a string,
6644 you must code the $ metacharacter to indicate this. For example:
6646 domains = ^\\d{3}\\.example
6648 matches the domain &'123.example'&, but it also matches &'123.example.com'&.
6651 domains = ^\\d{3}\\.example\$
6653 if you want &'example'& to be the top-level domain. The backslash before the
6654 $ is needed because string expansion also interprets dollar characters.
6658 . ////////////////////////////////////////////////////////////////////////////
6659 . ////////////////////////////////////////////////////////////////////////////
6661 .chapter "File and database lookups" "CHAPfdlookup"
6662 .scindex IIDfidalo1 "file" "lookups"
6663 .scindex IIDfidalo2 "database" "lookups"
6664 .cindex "lookup" "description of"
6665 Exim can be configured to look up data in files or databases as it processes
6666 messages. Two different kinds of syntax are used:
6669 A string that is to be expanded may contain explicit lookup requests. These
6670 cause parts of the string to be replaced by data that is obtained from the
6671 lookup. Lookups of this type are conditional expansion items. Different results
6672 can be defined for the cases of lookup success and failure. See chapter
6673 &<<CHAPexpand>>&, where string expansions are described in detail.
6674 The key for the lookup is &*specified*& as part of the string expansion.
6676 Lists of domains, hosts, and email addresses can contain lookup requests as a
6677 way of avoiding excessively long linear lists. In this case, the data that is
6678 returned by the lookup is often (but not always) discarded; whether the lookup
6679 succeeds or fails is what really counts. These kinds of list are described in
6680 chapter &<<CHAPdomhosaddlists>>&.
6681 The key for the lookup is &*implicit*&,
6682 given by the context in which the list is expanded.
6685 String expansions, lists, and lookups interact with each other in such a way
6686 that there is no order in which to describe any one of them that does not
6687 involve references to the others. Each of these three chapters makes more sense
6688 if you have read the other two first. If you are reading this for the first
6689 time, be aware that some of it will make a lot more sense after you have read
6690 chapters &<<CHAPdomhosaddlists>>& and &<<CHAPexpand>>&.
6692 .section "Examples of different lookup syntax" "SECID60"
6693 It is easy to confuse the two different kinds of lookup, especially as the
6694 lists that may contain the second kind are always expanded before being
6695 processed as lists. Therefore, they may also contain lookups of the first kind.
6696 Be careful to distinguish between the following two examples:
6698 domains = ${lookup{$sender_host_address}lsearch{/some/file}}
6699 domains = lsearch;/some/file
6701 The first uses a string expansion, the result of which must be a domain list.
6702 The key for an expansion-style lookup must be given explicitly.
6703 No strings have been specified for a successful or a failing lookup; the
6704 defaults in this case are the looked-up data and an empty string, respectively.
6705 The expansion takes place before the string is processed as a list, and the
6706 file that is searched could contain lines like this:
6708 192.168.3.4: domain1:domain2:...
6709 192.168.1.9: domain3:domain4:...
6711 When the lookup succeeds, the result of the expansion is a list of domains (and
6712 possibly other types of item that are allowed in domain lists).
6713 .cindex "tainted data" "de-tainting"
6714 .cindex "de-tainting" "using a lookup expansion""
6715 The result of the expansion is not tainted.
6717 In the second example, the lookup is a single item in a domain list. It causes
6718 Exim to use a lookup to see if the domain that is being processed can be found
6720 The file could contains lines like this:
6725 Any data that follows the keys is not relevant when checking that the domain
6726 matches the list item.
6728 The key for a list-style lookup is implicit, from the lookup context, if
6729 the lookup is a single-key type (see below).
6730 For query-style lookup types the key must be given explicitly.
6732 It is possible, though no doubt confusing, to use both kinds of lookup at once.
6733 Consider a file containing lines like this:
6735 192.168.5.6: lsearch;/another/file
6737 If the value of &$sender_host_address$& is 192.168.5.6, expansion of the
6738 first &%domains%& setting above generates the second setting, which therefore
6739 causes a second lookup to occur.
6741 The lookup type may optionally be followed by a comma
6742 and a comma-separated list of options.
6743 Each option is a &"name=value"& pair.
6744 Whether an option is meaningful depends on the lookup type.
6746 All lookups support the option &"cache=no_rd"&.
6747 If this is given then the cache that Exim manages for lookup results
6748 is not checked before doing the lookup.
6749 The result of the lookup is still written to the cache.
6751 The rest of this chapter describes the different lookup types that are
6752 available. Any of them can be used in any part of the configuration where a
6753 lookup is permitted.
6756 .section "Lookup types" "SECID61"
6757 .cindex "lookup" "types of"
6758 .cindex "single-key lookup" "definition of"
6759 Two different types of data lookup are implemented:
6762 The &'single-key'& type requires the specification of a file in which to look,
6763 and a single key to search for. The key must be a non-empty string for the
6764 lookup to succeed. The lookup type determines how the file is searched.
6765 .cindex "tainted data" "single-key lookups"
6766 The file string may not be tainted.
6768 .cindex "tainted data" "de-tainting"
6769 .cindex "de-tainting" "using a single-key lookup"
6770 All single-key lookups support the option &"ret=key"&.
6771 If this is given and the lookup
6772 (either underlying implementation or cached value)
6773 returns data, the result is replaced with a non-tainted
6774 version of the lookup key.
6776 .cindex "query-style lookup" "definition of"
6777 The &'query-style'& type accepts a generalized database query. No particular
6778 key value is assumed by Exim for query-style lookups. You can use whichever
6779 Exim variables you need to construct the database query.
6780 .cindex "tainted data" "quoting for lookups"
6781 If tainted data is used in the query then it should be quuted by
6782 using the &*${quote_*&<&'lookup-type'&>&*:*&<&'string'&>&*}*& expansion operator
6783 appropriate for the lookup.
6786 The code for each lookup type is in a separate source file that is included in
6787 the binary of Exim only if the corresponding compile-time option is set. The
6788 default settings in &_src/EDITME_& are:
6793 which means that only linear searching and DBM lookups are included by default.
6794 For some types of lookup (e.g. SQL databases), you need to install appropriate
6795 libraries and header files before building Exim.
6800 .section "Single-key lookup types" "SECTsinglekeylookups"
6801 .cindex "lookup" "single-key types"
6802 .cindex "single-key lookup" "list of types"
6803 The following single-key lookup types are implemented:
6806 .cindex "cdb" "description of"
6807 .cindex "lookup" "cdb"
6808 .cindex "binary zero" "in lookup key"
6809 &(cdb)&: The given file is searched as a Constant DataBase file, using the key
6810 string without a terminating binary zero. The cdb format is designed for
6811 indexed files that are read frequently and never updated, except by total
6812 re-creation. As such, it is particularly suitable for large files containing
6813 aliases or other indexed data referenced by an MTA. Information about cdb and
6814 tools for building the files can be found in several places:
6816 &url(https://cr.yp.to/cdb.html)
6817 &url(https://www.corpit.ru/mjt/tinycdb.html)
6818 &url(https://packages.debian.org/stable/utils/freecdb)
6819 &url(https://github.com/philpennock/cdbtools) (in Go)
6821 A cdb distribution is not needed in order to build Exim with cdb support,
6822 because the code for reading cdb files is included directly in Exim itself.
6823 However, no means of building or testing cdb files is provided with Exim, so
6824 you need to obtain a cdb distribution in order to do this.
6826 .cindex "DBM" "lookup type"
6827 .cindex "lookup" "dbm"
6828 .cindex "binary zero" "in lookup key"
6829 &(dbm)&: Calls to DBM library functions are used to extract data from the given
6830 DBM file by looking up the record with the given key. A terminating binary
6831 zero is included in the key that is passed to the DBM library. See section
6832 &<<SECTdb>>& for a discussion of DBM libraries.
6834 .cindex "Berkeley DB library" "file format"
6835 For all versions of Berkeley DB, Exim uses the DB_HASH style of database
6836 when building DBM files using the &%exim_dbmbuild%& utility. However, when
6837 using Berkeley DB versions 3 or 4, it opens existing databases for reading with
6838 the DB_UNKNOWN option. This enables it to handle any of the types of database
6839 that the library supports, and can be useful for accessing DBM files created by
6840 other applications. (For earlier DB versions, DB_HASH is always used.)
6842 .cindex "lookup" "dbmjz"
6843 .cindex "lookup" "dbm &-- embedded NULs"
6845 .cindex "dbmjz lookup type"
6846 &(dbmjz)&: This is the same as &(dbm)&, except that the lookup key is
6847 interpreted as an Exim list; the elements of the list are joined together with
6848 ASCII NUL characters to form the lookup key. An example usage would be to
6849 authenticate incoming SMTP calls using the passwords from Cyrus SASL's
6850 &_/etc/sasldb2_& file with the &(gsasl)& authenticator or Exim's own
6851 &(cram_md5)& authenticator.
6853 .cindex "lookup" "dbmnz"
6854 .cindex "lookup" "dbm &-- terminating zero"
6855 .cindex "binary zero" "in lookup key"
6857 .cindex "&_/etc/userdbshadow.dat_&"
6858 .cindex "dbmnz lookup type"
6859 &(dbmnz)&: This is the same as &(dbm)&, except that a terminating binary zero
6860 is not included in the key that is passed to the DBM library. You may need this
6861 if you want to look up data in files that are created by or shared with some
6862 other application that does not use terminating zeros. For example, you need to
6863 use &(dbmnz)& rather than &(dbm)& if you want to authenticate incoming SMTP
6864 calls using the passwords from Courier's &_/etc/userdbshadow.dat_& file. Exim's
6865 utility program for creating DBM files (&'exim_dbmbuild'&) includes the zeros
6866 by default, but has an option to omit them (see section &<<SECTdbmbuild>>&).
6868 .cindex "lookup" "dsearch"
6869 .cindex "dsearch lookup type"
6870 &(dsearch)&: The given file must be an
6872 directory path; this is searched for an entry
6873 whose name is the key by calling the &[lstat()]& function.
6875 contain any forward slash characters.
6876 If &[lstat()]& succeeds then so does the lookup.
6877 .cindex "tainted data" "dsearch result"
6878 The result is regarded as untainted.
6880 Options for the lookup can be given by appending them after the word "dsearch",
6881 separated by a comma. Options, if present, are a comma-separated list having
6882 each element starting with a tag name and an equals.
6884 Two options are supported, for the return value and for filtering match
6886 The "ret" option requests an alternate result value of
6887 the entire path for the entry. Example:
6889 ${lookup {passwd} dsearch,ret=full {/etc}}
6891 The default result is just the requested entry.
6892 The "filter" option requests that only directory entries of a given type
6893 are matched. The match value is one of "file", "dir" or "subdir" (the latter
6894 not matching "." or ".."). Example:
6896 ${lookup {passwd} dsearch,filter=file {/etc}}
6898 The default matching is for any entry type, including directories
6901 An example of how this
6902 lookup can be used to support virtual domains is given in section
6903 &<<SECTvirtualdomains>>&.
6905 .cindex "lookup" "iplsearch"
6906 .cindex "iplsearch lookup type"
6907 &(iplsearch)&: The given file is a text file containing keys and data. A key is
6908 terminated by a colon or white space or the end of the line. The keys in the
6909 file must be IP addresses, or IP addresses with CIDR masks. Keys that involve
6910 IPv6 addresses must be enclosed in quotes to prevent the first internal colon
6911 being interpreted as a key terminator. For example:
6913 1.2.3.4: data for 1.2.3.4
6914 192.168.0.0/16: data for 192.168.0.0/16
6915 "abcd::cdab": data for abcd::cdab
6916 "abcd:abcd::/32" data for abcd:abcd::/32
6918 The key for an &(iplsearch)& lookup must be an IP address (without a mask). The
6919 file is searched linearly, using the CIDR masks where present, until a matching
6920 key is found. The first key that matches is used; there is no attempt to find a
6921 &"best"& match. Apart from the way the keys are matched, the processing for
6922 &(iplsearch)& is the same as for &(lsearch)&.
6924 &*Warning 1*&: Unlike most other single-key lookup types, a file of data for
6925 &(iplsearch)& can &'not'& be turned into a DBM or cdb file, because those
6926 lookup types support only literal keys.
6928 &*Warning 2*&: In a host list, you must always use &(net-iplsearch)& so that
6929 the implicit key is the host's IP address rather than its name (see section
6930 &<<SECThoslispatsikey>>&).
6932 &*Warning 3*&: Do not use an IPv4-mapped IPv6 address for a key; use the
6933 IPv4, in dotted-quad form. (Exim converts IPv4-mapped IPv6 addresses to this
6934 notation before executing the lookup.)
6936 One option is supported, "ret=full", to request the return of the entire line
6937 rather than omitting the key portion.
6938 Note however that the key portion will have been de-quoted.
6942 .cindex json "lookup type"
6943 .cindex JSON expansions
6944 &(json)&: The given file is a text file with a JSON structure.
6945 An element of the structure is extracted, defined by the search key.
6946 The key is a list of subelement selectors
6947 (colon-separated by default but changeable in the usual way)
6948 which are applied in turn to select smaller and smaller portions
6949 of the JSON structure.
6950 If a selector is numeric, it must apply to a JSON array; the (zero-based)
6951 nunbered array element is selected.
6952 Otherwise it must apply to a JSON object; the named element is selected.
6953 The final resulting element can be a simple JSON type or a JSON object
6954 or array; for the latter two a string-representation of the JSON
6956 For elements of type string, the returned value is de-quoted.
6962 .cindex database lmdb
6963 &(lmdb)&: The given file is an LMDB database.
6964 LMDB is a memory-mapped key-value store,
6965 with API modeled loosely on that of BerkeleyDB.
6966 See &url(https://symas.com/products/lightning-memory-mapped-database/)
6967 for the feature set and operation modes.
6969 Exim provides read-only access via the LMDB C library.
6970 The library can be obtained from &url(https://github.com/LMDB/lmdb)
6971 or your operating system package repository.
6972 To enable LMDB support in Exim set LOOKUP_LMDB=yes in &_Local/Makefile_&.
6974 You will need to separately create the LMDB database file,
6975 possibly using the &"mdb_load"& utility.
6979 .cindex "linear search"
6980 .cindex "lookup" "lsearch"
6981 .cindex "lsearch lookup type"
6982 .cindex "case sensitivity" "in lsearch lookup"
6983 &(lsearch)&: The given file is a text file that is searched linearly for a
6984 line beginning with the search key, terminated by a colon or white space or the
6985 end of the line. The search is case-insensitive; that is, upper and lower case
6986 letters are treated as the same. The first occurrence of the key that is found
6987 in the file is used.
6989 White space between the key and the colon is permitted. The remainder of the
6990 line, with leading and trailing white space removed, is the data. This can be
6991 continued onto subsequent lines by starting them with any amount of white
6992 space, but only a single space character is included in the data at such a
6993 junction. If the data begins with a colon, the key must be terminated by a
6998 Empty lines and lines beginning with # are ignored, even if they occur in the
6999 middle of an item. This is the traditional textual format of alias files. Note
7000 that the keys in an &(lsearch)& file are literal strings. There is no
7001 wildcarding of any kind.
7003 .cindex "lookup" "lsearch &-- colons in keys"
7004 .cindex "white space" "in lsearch key"
7005 In most &(lsearch)& files, keys are not required to contain colons or #
7006 characters, or white space. However, if you need this feature, it is available.
7007 If a key begins with a doublequote character, it is terminated only by a
7008 matching quote (or end of line), and the normal escaping rules apply to its
7009 contents (see section &<<SECTstrings>>&). An optional colon is permitted after
7010 quoted keys (exactly as for unquoted keys). There is no special handling of
7011 quotes for the data part of an &(lsearch)& line.
7014 .cindex "NIS lookup type"
7015 .cindex "lookup" "NIS"
7016 .cindex "binary zero" "in lookup key"
7017 &(nis)&: The given file is the name of a NIS map, and a NIS lookup is done with
7018 the given key, without a terminating binary zero. There is a variant called
7019 &(nis0)& which does include the terminating binary zero in the key. This is
7020 reportedly needed for Sun-style alias files. Exim does not recognize NIS
7021 aliases; the full map names must be used.
7024 .cindex "wildlsearch lookup type"
7025 .cindex "lookup" "wildlsearch"
7026 .cindex "nwildlsearch lookup type"
7027 .cindex "lookup" "nwildlsearch"
7028 &(wildlsearch)& or &(nwildlsearch)&: These search a file linearly, like
7029 &(lsearch)&, but instead of being interpreted as a literal string, each key in
7030 the file may be wildcarded. The difference between these two lookup types is
7031 that for &(wildlsearch)&, each key in the file is string-expanded before being
7032 used, whereas for &(nwildlsearch)&, no expansion takes place.
7034 .cindex "case sensitivity" "in (n)wildlsearch lookup"
7035 Like &(lsearch)&, the testing is done case-insensitively. However, keys in the
7036 file that are regular expressions can be made case-sensitive by the use of
7037 &`(-i)`& within the pattern. The following forms of wildcard are recognized:
7039 . ==== As this is a nested list, any displays it contains must be indented
7040 . ==== as otherwise they are too far to the left.
7043 The string may begin with an asterisk to mean &"ends with"&. For example:
7045 *.a.b.c data for anything.a.b.c
7046 *fish data for anythingfish
7049 The string may begin with a circumflex to indicate a regular expression. For
7050 example, for &(wildlsearch)&:
7052 ^\N\d+\.a\.b\N data for <digits>.a.b
7054 Note the use of &`\N`& to disable expansion of the contents of the regular
7055 expression. If you are using &(nwildlsearch)&, where the keys are not
7056 string-expanded, the equivalent entry is:
7058 ^\d+\.a\.b data for <digits>.a.b
7060 The case-insensitive flag is set at the start of compiling the regular
7061 expression, but it can be turned off by using &`(-i)`& at an appropriate point.
7062 For example, to make the entire pattern case-sensitive:
7064 ^(?-i)\d+\.a\.b data for <digits>.a.b
7067 If the regular expression contains white space or colon characters, you must
7068 either quote it (see &(lsearch)& above), or represent these characters in other
7069 ways. For example, &`\s`& can be used for white space and &`\x3A`& for a
7070 colon. This may be easier than quoting, because if you quote, you have to
7071 escape all the backslashes inside the quotes.
7073 &*Note*&: It is not possible to capture substrings in a regular expression
7074 match for later use, because the results of all lookups are cached. If a lookup
7075 is repeated, the result is taken from the cache, and no actual pattern matching
7076 takes place. The values of all the numeric variables are unset after a
7077 &((n)wildlsearch)& match.
7080 Although I cannot see it being of much use, the general matching function that
7081 is used to implement &((n)wildlsearch)& means that the string may begin with a
7082 lookup name terminated by a semicolon, and followed by lookup data. For
7085 cdb;/some/file data for keys that match the file
7087 The data that is obtained from the nested lookup is discarded.
7090 Keys that do not match any of these patterns are interpreted literally. The
7091 continuation rules for the data are the same as for &(lsearch)&, and keys may
7092 be followed by optional colons.
7094 &*Warning*&: Unlike most other single-key lookup types, a file of data for
7095 &((n)wildlsearch)& can &'not'& be turned into a DBM or cdb file, because those
7096 lookup types support only literal keys.
7099 .cindex "spf lookup type"
7100 .cindex "lookup" "spf"
7101 &(spf)&: If Exim is built with SPF support, manual lookups can be done
7102 (as opposed to the standard ACL condition method).
7103 For details see section &<<SECSPF>>&.
7107 .section "Query-style lookup types" "SECTquerystylelookups"
7108 .cindex "lookup" "query-style types"
7109 .cindex "query-style lookup" "list of types"
7110 The supported query-style lookup types are listed below. Further details about
7111 many of them are given in later sections.
7114 .cindex "DNS" "as a lookup type"
7115 .cindex "lookup" "DNS"
7116 &(dnsdb)&: This does a DNS search for one or more records whose domain names
7117 are given in the supplied query. The resulting data is the contents of the
7118 records. See section &<<SECTdnsdb>>&.
7120 .cindex "InterBase lookup type"
7121 .cindex "lookup" "InterBase"
7122 &(ibase)&: This does a lookup in an InterBase database.
7124 .cindex "LDAP" "lookup type"
7125 .cindex "lookup" "LDAP"
7126 &(ldap)&: This does an LDAP lookup using a query in the form of a URL, and
7127 returns attributes from a single entry. There is a variant called &(ldapm)&
7128 that permits values from multiple entries to be returned. A third variant
7129 called &(ldapdn)& returns the Distinguished Name of a single entry instead of
7130 any attribute values. See section &<<SECTldap>>&.
7132 .cindex "MySQL" "lookup type"
7133 .cindex "lookup" "MySQL"
7134 &(mysql)&: The format of the query is an SQL statement that is passed to a
7135 MySQL database. See section &<<SECTsql>>&.
7137 .cindex "NIS+ lookup type"
7138 .cindex "lookup" "NIS+"
7139 &(nisplus)&: This does a NIS+ lookup using a query that can specify the name of
7140 the field to be returned. See section &<<SECTnisplus>>&.
7142 .cindex "Oracle" "lookup type"
7143 .cindex "lookup" "Oracle"
7144 &(oracle)&: The format of the query is an SQL statement that is passed to an
7145 Oracle database. See section &<<SECTsql>>&.
7147 .cindex "lookup" "passwd"
7148 .cindex "passwd lookup type"
7149 .cindex "&_/etc/passwd_&"
7150 &(passwd)& is a query-style lookup with queries that are just user names. The
7151 lookup calls &[getpwnam()]& to interrogate the system password data, and on
7152 success, the result string is the same as you would get from an &(lsearch)&
7153 lookup on a traditional &_/etc/passwd file_&, though with &`*`& for the
7154 password value. For example:
7156 *:42:42:King Rat:/home/kr:/bin/bash
7159 .cindex "PostgreSQL lookup type"
7160 .cindex "lookup" "PostgreSQL"
7161 &(pgsql)&: The format of the query is an SQL statement that is passed to a
7162 PostgreSQL database. See section &<<SECTsql>>&.
7165 .cindex "Redis lookup type"
7166 .cindex lookup Redis
7167 &(redis)&: The format of the query is either a simple get or simple set,
7168 passed to a Redis database. See section &<<SECTsql>>&.
7171 .cindex "sqlite lookup type"
7172 .cindex "lookup" "sqlite"
7173 &(sqlite)&: The format of the query is
7174 an SQL statement that is passed to an SQLite database. See section &<<SECTsqlite>>&.
7177 &(testdb)&: This is a lookup type that is used for testing Exim. It is
7178 not likely to be useful in normal operation.
7180 .cindex "whoson lookup type"
7181 .cindex "lookup" "whoson"
7182 . --- still http:-only, 2018-09-07
7183 &(whoson)&: &'Whoson'& (&url(http://whoson.sourceforge.net)) is a protocol that
7184 allows a server to check whether a particular (dynamically allocated) IP
7185 address is currently allocated to a known (trusted) user and, optionally, to
7186 obtain the identity of the said user. For SMTP servers, &'Whoson'& was popular
7187 at one time for &"POP before SMTP"& authentication, but that approach has been
7188 superseded by SMTP authentication. In Exim, &'Whoson'& can be used to implement
7189 &"POP before SMTP"& checking using ACL statements such as
7191 require condition = \
7192 ${lookup whoson {$sender_host_address}{yes}{no}}
7194 The query consists of a single IP address. The value returned is the name of
7195 the authenticated user, which is stored in the variable &$value$&. However, in
7196 this example, the data in &$value$& is not used; the result of the lookup is
7197 one of the fixed strings &"yes"& or &"no"&.
7202 .section "Temporary errors in lookups" "SECID63"
7203 .cindex "lookup" "temporary error in"
7204 Lookup functions can return temporary error codes if the lookup cannot be
7205 completed. For example, an SQL or LDAP database might be unavailable. For this
7206 reason, it is not advisable to use a lookup that might do this for critical
7207 options such as a list of local domains.
7209 When a lookup cannot be completed in a router or transport, delivery
7210 of the message (to the relevant address) is deferred, as for any other
7211 temporary error. In other circumstances Exim may assume the lookup has failed,
7212 or may give up altogether.
7216 .section "Default values in single-key lookups" "SECTdefaultvaluelookups"
7217 .cindex "wildcard lookups"
7218 .cindex "lookup" "default values"
7219 .cindex "lookup" "wildcard"
7220 .cindex "lookup" "* added to type"
7221 .cindex "default" "in single-key lookups"
7222 In this context, a &"default value"& is a value specified by the administrator
7223 that is to be used if a lookup fails.
7225 &*Note:*& This section applies only to single-key lookups. For query-style
7226 lookups, the facilities of the query language must be used. An attempt to
7227 specify a default for a query-style lookup provokes an error.
7229 If &"*"& is added to a single-key lookup type (for example, &%lsearch*%&)
7230 and the initial lookup fails, the key &"*"& is looked up in the file to
7231 provide a default value. See also the section on partial matching below.
7233 .cindex "*@ with single-key lookup"
7234 .cindex "lookup" "*@ added to type"
7235 .cindex "alias file" "per-domain default"
7236 Alternatively, if &"*@"& is added to a single-key lookup type (for example
7237 &%dbm*@%&) then, if the initial lookup fails and the key contains an @
7238 character, a second lookup is done with everything before the last @ replaced
7239 by *. This makes it possible to provide per-domain defaults in alias files
7240 that include the domains in the keys. If the second lookup fails (or doesn't
7241 take place because there is no @ in the key), &"*"& is looked up.
7242 For example, a &(redirect)& router might contain:
7244 data = ${lookup{$local_part@$domain}lsearch*@{/etc/mix-aliases}}
7246 Suppose the address that is being processed is &'jane@eyre.example'&. Exim
7247 looks up these keys, in this order:
7253 The data is taken from whichever key it finds first. &*Note*&: In an
7254 &(lsearch)& file, this does not mean the first of these keys in the file. A
7255 complete scan is done for each key, and only if it is not found at all does
7256 Exim move on to try the next key.
7260 .section "Partial matching in single-key lookups" "SECTpartiallookup"
7261 .cindex "partial matching"
7262 .cindex "wildcard lookups"
7263 .cindex "lookup" "partial matching"
7264 .cindex "lookup" "wildcard"
7265 .cindex "asterisk" "in search type"
7266 The normal operation of a single-key lookup is to search the file for an exact
7267 match with the given key. However, in a number of situations where domains are
7268 being looked up, it is useful to be able to do partial matching. In this case,
7269 information in the file that has a key starting with &"*."& is matched by any
7270 domain that ends with the components that follow the full stop. For example, if
7271 a key in a DBM file is
7273 *.dates.fict.example
7275 then when partial matching is enabled this is matched by (amongst others)
7276 &'2001.dates.fict.example'& and &'1984.dates.fict.example'&. It is also matched
7277 by &'dates.fict.example'&, if that does not appear as a separate key in the
7280 &*Note*&: Partial matching is not available for query-style lookups. It is
7281 also not available for any lookup items in address lists (see section
7282 &<<SECTaddresslist>>&).
7284 Partial matching is implemented by doing a series of separate lookups using
7285 keys constructed by modifying the original subject key. This means that it can
7286 be used with any of the single-key lookup types, provided that
7287 partial matching keys
7288 beginning with a special prefix (default &"*."&) are included in the data file.
7289 Keys in the file that do not begin with the prefix are matched only by
7290 unmodified subject keys when partial matching is in use.
7292 Partial matching is requested by adding the string &"partial-"& to the front of
7293 the name of a single-key lookup type, for example, &%partial-dbm%&. When this
7294 is done, the subject key is first looked up unmodified; if that fails, &"*."&
7295 is added at the start of the subject key, and it is looked up again. If that
7296 fails, further lookups are tried with dot-separated components removed from the
7297 start of the subject key, one-by-one, and &"*."& added on the front of what
7300 A minimum number of two non-* components are required. This can be adjusted
7301 by including a number before the hyphen in the search type. For example,
7302 &%partial3-lsearch%& specifies a minimum of three non-* components in the
7303 modified keys. Omitting the number is equivalent to &"partial2-"&. If the
7304 subject key is &'2250.dates.fict.example'& then the following keys are looked
7305 up when the minimum number of non-* components is two:
7307 2250.dates.fict.example
7308 *.2250.dates.fict.example
7309 *.dates.fict.example
7312 As soon as one key in the sequence is successfully looked up, the lookup
7315 .cindex "lookup" "partial matching &-- changing prefix"
7316 .cindex "prefix" "for partial matching"
7317 The use of &"*."& as the partial matching prefix is a default that can be
7318 changed. The motivation for this feature is to allow Exim to operate with file
7319 formats that are used by other MTAs. A different prefix can be supplied in
7320 parentheses instead of the hyphen after &"partial"&. For example:
7322 domains = partial(.)lsearch;/some/file
7324 In this example, if the domain is &'a.b.c'&, the sequence of lookups is
7325 &`a.b.c`&, &`.a.b.c`&, and &`.b.c`& (the default minimum of 2 non-wild
7326 components is unchanged). The prefix may consist of any punctuation characters
7327 other than a closing parenthesis. It may be empty, for example:
7329 domains = partial1()cdb;/some/file
7331 For this example, if the domain is &'a.b.c'&, the sequence of lookups is
7332 &`a.b.c`&, &`b.c`&, and &`c`&.
7334 If &"partial0"& is specified, what happens at the end (when the lookup with
7335 just one non-wild component has failed, and the original key is shortened right
7336 down to the null string) depends on the prefix:
7339 If the prefix has zero length, the whole lookup fails.
7341 If the prefix has length 1, a lookup for just the prefix is done. For
7342 example, the final lookup for &"partial0(.)"& is for &`.`& alone.
7344 Otherwise, if the prefix ends in a dot, the dot is removed, and the
7345 remainder is looked up. With the default prefix, therefore, the final lookup is
7346 for &"*"& on its own.
7348 Otherwise, the whole prefix is looked up.
7352 If the search type ends in &"*"& or &"*@"& (see section
7353 &<<SECTdefaultvaluelookups>>& above), the search for an ultimate default that
7354 this implies happens after all partial lookups have failed. If &"partial0"& is
7355 specified, adding &"*"& to the search type has no effect with the default
7356 prefix, because the &"*"& key is already included in the sequence of partial
7357 lookups. However, there might be a use for lookup types such as
7358 &"partial0(.)lsearch*"&.
7360 The use of &"*"& in lookup partial matching differs from its use as a wildcard
7361 in domain lists and the like. Partial matching works only in terms of
7362 dot-separated components; a key such as &`*fict.example`&
7363 in a database file is useless, because the asterisk in a partial matching
7364 subject key is always followed by a dot.
7369 .section "Lookup caching" "SECID64"
7370 .cindex "lookup" "caching"
7371 .cindex "caching" "lookup data"
7372 Exim caches all lookup results in order to avoid needless repetition of
7373 lookups. However, because (apart from the daemon) Exim operates as a collection
7374 of independent, short-lived processes, this caching applies only within a
7375 single Exim process. There is no inter-process lookup caching facility.
7377 If an option &"cache=no_rd"& is used on the lookup then
7378 the cache is only written to, cached data is not used for the operation
7379 and a real lookup is done.
7381 For single-key lookups, Exim keeps the relevant files open in case there is
7382 another lookup that needs them. In some types of configuration this can lead to
7383 many files being kept open for messages with many recipients. To avoid hitting
7384 the operating system limit on the number of simultaneously open files, Exim
7385 closes the least recently used file when it needs to open more files than its
7386 own internal limit, which can be changed via the &%lookup_open_max%& option.
7388 The single-key lookup files are closed and the lookup caches are flushed at
7389 strategic points during delivery &-- for example, after all routing is
7395 .section "Quoting lookup data" "SECID65"
7396 .cindex "lookup" "quoting"
7397 .cindex "quoting" "in lookups"
7398 When data from an incoming message is included in a query-style lookup, there
7399 is the possibility of special characters in the data messing up the syntax of
7400 the query. For example, a NIS+ query that contains
7404 will be broken if the local part happens to contain a closing square bracket.
7405 For NIS+, data can be enclosed in double quotes like this:
7407 [name="$local_part"]
7409 but this still leaves the problem of a double quote in the data. The rule for
7410 NIS+ is that double quotes must be doubled. Other lookup types have different
7411 rules, and to cope with the differing requirements, an expansion operator
7412 of the following form is provided:
7414 ${quote_<lookup-type>:<string>}
7416 For example, the safest way to write the NIS+ query is
7418 [name="${quote_nisplus:$local_part}"]
7420 See chapter &<<CHAPexpand>>& for full coverage of string expansions. The quote
7421 operator can be used for all lookup types, but has no effect for single-key
7422 lookups, since no quoting is ever needed in their key strings.
7427 .section "More about dnsdb" "SECTdnsdb"
7428 .cindex "dnsdb lookup"
7429 .cindex "lookup" "dnsdb"
7430 .cindex "DNS" "as a lookup type"
7431 The &(dnsdb)& lookup type uses the DNS as its database. A simple query consists
7432 of a record type and a domain name, separated by an equals sign. For example,
7433 an expansion string could contain:
7435 ${lookup dnsdb{mx=a.b.example}{$value}fail}
7437 If the lookup succeeds, the result is placed in &$value$&, which in this case
7438 is used on its own as the result. If the lookup does not succeed, the
7439 &`fail`& keyword causes a &'forced expansion failure'& &-- see section
7440 &<<SECTforexpfai>>& for an explanation of what this means.
7442 The supported DNS record types are A, CNAME, MX, NS, PTR, SOA, SPF, SRV, TLSA
7443 and TXT, and, when Exim is compiled with IPv6 support, AAAA.
7444 If no type is given, TXT is assumed.
7446 For any record type, if multiple records are found, the data is returned as a
7447 concatenation, with newline as the default separator. The order, of course,
7448 depends on the DNS resolver. You can specify a different separator character
7449 between multiple records by putting a right angle-bracket followed immediately
7450 by the new separator at the start of the query. For example:
7452 ${lookup dnsdb{>: a=host1.example}}
7454 It is permitted to specify a space as the separator character. Further
7455 white space is ignored.
7456 For lookup types that return multiple fields per record,
7457 an alternate field separator can be specified using a comma after the main
7458 separator character, followed immediately by the field separator.
7460 .cindex "PTR record" "in &(dnsdb)& lookup"
7461 When the type is PTR,
7462 the data can be an IP address, written as normal; inversion and the addition of
7463 &%in-addr.arpa%& or &%ip6.arpa%& happens automatically. For example:
7465 ${lookup dnsdb{ptr=192.168.4.5}{$value}fail}
7467 If the data for a PTR record is not a syntactically valid IP address, it is not
7468 altered and nothing is added.
7470 .cindex "MX record" "in &(dnsdb)& lookup"
7471 .cindex "SRV record" "in &(dnsdb)& lookup"
7472 For an MX lookup, both the preference value and the host name are returned for
7473 each record, separated by a space. For an SRV lookup, the priority, weight,
7474 port, and host name are returned for each record, separated by spaces.
7475 The field separator can be modified as above.
7477 .cindex "TXT record" "in &(dnsdb)& lookup"
7478 .cindex "SPF record" "in &(dnsdb)& lookup"
7479 For TXT records with multiple items of data, only the first item is returned,
7480 unless a field separator is specified.
7481 To concatenate items without a separator, use a semicolon instead.
7483 default behaviour is to concatenate multiple items without using a separator.
7485 ${lookup dnsdb{>\n,: txt=a.b.example}}
7486 ${lookup dnsdb{>\n; txt=a.b.example}}
7487 ${lookup dnsdb{spf=example.org}}
7489 It is permitted to specify a space as the separator character. Further
7490 white space is ignored.
7492 .cindex "SOA record" "in &(dnsdb)& lookup"
7493 For an SOA lookup, while no result is obtained the lookup is redone with
7494 successively more leading components dropped from the given domain.
7495 Only the primary-nameserver field is returned unless a field separator is
7498 ${lookup dnsdb{>:,; soa=a.b.example.com}}
7501 .section "Dnsdb lookup modifiers" "SECTdnsdb_mod"
7502 .cindex "dnsdb modifiers"
7503 .cindex "modifiers" "dnsdb"
7504 .cindex "options" "dnsdb"
7505 Modifiers for &(dnsdb)& lookups are given by optional keywords,
7506 each followed by a comma,
7507 that may appear before the record type.
7509 The &(dnsdb)& lookup fails only if all the DNS lookups fail. If there is a
7510 temporary DNS error for any of them, the behaviour is controlled by
7511 a defer-option modifier.
7512 The possible keywords are
7513 &"defer_strict"&, &"defer_never"&, and &"defer_lax"&.
7514 With &"strict"& behaviour, any temporary DNS error causes the
7515 whole lookup to defer. With &"never"& behaviour, a temporary DNS error is
7516 ignored, and the behaviour is as if the DNS lookup failed to find anything.
7517 With &"lax"& behaviour, all the queries are attempted, but a temporary DNS
7518 error causes the whole lookup to defer only if none of the other lookups
7519 succeed. The default is &"lax"&, so the following lookups are equivalent:
7521 ${lookup dnsdb{defer_lax,a=one.host.com:two.host.com}}
7522 ${lookup dnsdb{a=one.host.com:two.host.com}}
7524 Thus, in the default case, as long as at least one of the DNS lookups
7525 yields some data, the lookup succeeds.
7527 .cindex "DNSSEC" "dns lookup"
7528 Use of &(DNSSEC)& is controlled by a dnssec modifier.
7529 The possible keywords are
7530 &"dnssec_strict"&, &"dnssec_lax"&, and &"dnssec_never"&.
7531 With &"strict"& or &"lax"& DNSSEC information is requested
7533 With &"strict"& a response from the DNS resolver that
7534 is not labelled as authenticated data
7535 is treated as equivalent to a temporary DNS error.
7536 The default is &"lax"&.
7538 See also the &$lookup_dnssec_authenticated$& variable.
7540 .cindex timeout "dns lookup"
7541 .cindex "DNS" timeout
7542 Timeout for the dnsdb lookup can be controlled by a retrans modifier.
7543 The form is &"retrans_VAL"& where VAL is an Exim time specification
7545 The default value is set by the main configuration option &%dns_retrans%&.
7547 Retries for the dnsdb lookup can be controlled by a retry modifier.
7548 The form if &"retry_VAL"& where VAL is an integer.
7549 The default count is set by the main configuration option &%dns_retry%&.
7551 .cindex caching "of dns lookup"
7552 .cindex TTL "of dns lookup"
7554 Dnsdb lookup results are cached within a single process (and its children).
7555 The cache entry lifetime is limited to the smallest time-to-live (TTL)
7556 value of the set of returned DNS records.
7559 .section "Pseudo dnsdb record types" "SECID66"
7560 .cindex "MX record" "in &(dnsdb)& lookup"
7561 By default, both the preference value and the host name are returned for
7562 each MX record, separated by a space. If you want only host names, you can use
7563 the pseudo-type MXH:
7565 ${lookup dnsdb{mxh=a.b.example}}
7567 In this case, the preference values are omitted, and just the host names are
7570 .cindex "name server for enclosing domain"
7571 Another pseudo-type is ZNS (for &"zone NS"&). It performs a lookup for NS
7572 records on the given domain, but if none are found, it removes the first
7573 component of the domain name, and tries again. This process continues until NS
7574 records are found or there are no more components left (or there is a DNS
7575 error). In other words, it may return the name servers for a top-level domain,
7576 but it never returns the root name servers. If there are no NS records for the
7577 top-level domain, the lookup fails. Consider these examples:
7579 ${lookup dnsdb{zns=xxx.quercite.com}}
7580 ${lookup dnsdb{zns=xxx.edu}}
7582 Assuming that in each case there are no NS records for the full domain name,
7583 the first returns the name servers for &%quercite.com%&, and the second returns
7584 the name servers for &%edu%&.
7586 You should be careful about how you use this lookup because, unless the
7587 top-level domain does not exist, the lookup always returns some host names. The
7588 sort of use to which this might be put is for seeing if the name servers for a
7589 given domain are on a blacklist. You can probably assume that the name servers
7590 for the high-level domains such as &%com%& or &%co.uk%& are not going to be on
7593 .cindex "CSA" "in &(dnsdb)& lookup"
7594 A third pseudo-type is CSA (Client SMTP Authorization). This looks up SRV
7595 records according to the CSA rules, which are described in section
7596 &<<SECTverifyCSA>>&. Although &(dnsdb)& supports SRV lookups directly, this is
7597 not sufficient because of the extra parent domain search behaviour of CSA. The
7598 result of a successful lookup such as:
7600 ${lookup dnsdb {csa=$sender_helo_name}}
7602 has two space-separated fields: an authorization code and a target host name.
7603 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
7604 authorization required but absent, or &"?"& for unknown.
7606 .cindex "A+" "in &(dnsdb)& lookup"
7607 The pseudo-type A+ performs an AAAA
7608 and then an A lookup. All results are returned; defer processing
7609 (see below) is handled separately for each lookup. Example:
7611 ${lookup dnsdb {>; a+=$sender_helo_name}}
7615 .section "Multiple dnsdb lookups" "SECID67"
7616 In the previous sections, &(dnsdb)& lookups for a single domain are described.
7617 However, you can specify a list of domains or IP addresses in a single
7618 &(dnsdb)& lookup. The list is specified in the normal Exim way, with colon as
7619 the default separator, but with the ability to change this. For example:
7621 ${lookup dnsdb{one.domain.com:two.domain.com}}
7622 ${lookup dnsdb{a=one.host.com:two.host.com}}
7623 ${lookup dnsdb{ptr = <; 1.2.3.4 ; 4.5.6.8}}
7625 In order to retain backwards compatibility, there is one special case: if
7626 the lookup type is PTR and no change of separator is specified, Exim looks
7627 to see if the rest of the string is precisely one IPv6 address. In this
7628 case, it does not treat it as a list.
7630 The data from each lookup is concatenated, with newline separators by default,
7631 in the same way that multiple DNS records for a single item are handled. A
7632 different separator can be specified, as described above.
7637 .section "More about LDAP" "SECTldap"
7638 .cindex "LDAP" "lookup, more about"
7639 .cindex "lookup" "LDAP"
7640 .cindex "Solaris" "LDAP"
7641 The original LDAP implementation came from the University of Michigan; this has
7642 become &"Open LDAP"&, and there are now two different releases. Another
7643 implementation comes from Netscape, and Solaris 7 and subsequent releases
7644 contain inbuilt LDAP support. Unfortunately, though these are all compatible at
7645 the lookup function level, their error handling is different. For this reason
7646 it is necessary to set a compile-time variable when building Exim with LDAP, to
7647 indicate which LDAP library is in use. One of the following should appear in
7648 your &_Local/Makefile_&:
7650 LDAP_LIB_TYPE=UMICHIGAN
7651 LDAP_LIB_TYPE=OPENLDAP1
7652 LDAP_LIB_TYPE=OPENLDAP2
7653 LDAP_LIB_TYPE=NETSCAPE
7654 LDAP_LIB_TYPE=SOLARIS
7656 If LDAP_LIB_TYPE is not set, Exim assumes &`OPENLDAP1`&, which has the
7657 same interface as the University of Michigan version.
7659 There are three LDAP lookup types in Exim. These behave slightly differently in
7660 the way they handle the results of a query:
7663 &(ldap)& requires the result to contain just one entry; if there are more, it
7666 &(ldapdn)& also requires the result to contain just one entry, but it is the
7667 Distinguished Name that is returned rather than any attribute values.
7669 &(ldapm)& permits the result to contain more than one entry; the attributes
7670 from all of them are returned.
7674 For &(ldap)& and &(ldapm)&, if a query finds only entries with no attributes,
7675 Exim behaves as if the entry did not exist, and the lookup fails. The format of
7676 the data returned by a successful lookup is described in the next section.
7677 First we explain how LDAP queries are coded.
7680 .section "Format of LDAP queries" "SECTforldaque"
7681 .cindex "LDAP" "query format"
7682 An LDAP query takes the form of a URL as defined in RFC 2255. For example, in
7683 the configuration of a &(redirect)& router one might have this setting:
7685 data = ${lookup ldap \
7686 {ldap:///cn=$local_part,o=University%20of%20Cambridge,\
7687 c=UK?mailbox?base?}}
7689 .cindex "LDAP" "with TLS"
7690 The URL may begin with &`ldap`& or &`ldaps`& if your LDAP library supports
7691 secure (encrypted) LDAP connections. The second of these ensures that an
7692 encrypted TLS connection is used.
7694 With sufficiently modern LDAP libraries, Exim supports forcing TLS over regular
7695 LDAP connections, rather than the SSL-on-connect &`ldaps`&.
7696 See the &%ldap_start_tls%& option.
7698 Starting with Exim 4.83, the initialization of LDAP with TLS is more tightly
7699 controlled. Every part of the TLS configuration can be configured by settings in
7700 &_exim.conf_&. Depending on the version of the client libraries installed on
7701 your system, some of the initialization may have required setting options in
7702 &_/etc/ldap.conf_& or &_~/.ldaprc_& to get TLS working with self-signed
7703 certificates. This revealed a nuance where the current UID that exim was
7704 running as could affect which config files it read. With Exim 4.83, these
7705 methods become optional, only taking effect if not specifically set in
7709 .section "LDAP quoting" "SECID68"
7710 .cindex "LDAP" "quoting"
7711 Two levels of quoting are required in LDAP queries, the first for LDAP itself
7712 and the second because the LDAP query is represented as a URL. Furthermore,
7713 within an LDAP query, two different kinds of quoting are required. For this
7714 reason, there are two different LDAP-specific quoting operators.
7716 The &%quote_ldap%& operator is designed for use on strings that are part of
7717 filter specifications. Conceptually, it first does the following conversions on
7725 in accordance with RFC 2254. The resulting string is then quoted according
7726 to the rules for URLs, that is, all non-alphanumeric characters except
7730 are converted to their hex values, preceded by a percent sign. For example:
7732 ${quote_ldap: a(bc)*, a<yz>; }
7736 %20a%5C28bc%5C29%5C2A%2C%20a%3Cyz%3E%3B%20
7738 Removing the URL quoting, this is (with a leading and a trailing space):
7740 a\28bc\29\2A, a<yz>;
7742 The &%quote_ldap_dn%& operator is designed for use on strings that are part of
7743 base DN specifications in queries. Conceptually, it first converts the string
7744 by inserting a backslash in front of any of the following characters:
7748 It also inserts a backslash before any leading spaces or # characters, and
7749 before any trailing spaces. (These rules are in RFC 2253.) The resulting string
7750 is then quoted according to the rules for URLs. For example:
7752 ${quote_ldap_dn: a(bc)*, a<yz>; }
7756 %5C%20a(bc)*%5C%2C%20a%5C%3Cyz%5C%3E%5C%3B%5C%20
7758 Removing the URL quoting, this is (with a trailing space):
7760 \ a(bc)*\, a\<yz\>\;\
7762 There are some further comments about quoting in the section on LDAP
7763 authentication below.
7766 .section "LDAP connections" "SECID69"
7767 .cindex "LDAP" "connections"
7768 The connection to an LDAP server may either be over TCP/IP, or, when OpenLDAP
7769 is in use, via a Unix domain socket. The example given above does not specify
7770 an LDAP server. A server that is reached by TCP/IP can be specified in a query
7773 ldap://<hostname>:<port>/...
7775 If the port (and preceding colon) are omitted, the standard LDAP port (389) is
7776 used. When no server is specified in a query, a list of default servers is
7777 taken from the &%ldap_default_servers%& configuration option. This supplies a
7778 colon-separated list of servers which are tried in turn until one successfully
7779 handles a query, or there is a serious error. Successful handling either
7780 returns the requested data, or indicates that it does not exist. Serious errors
7781 are syntactical, or multiple values when only a single value is expected.
7782 Errors which cause the next server to be tried are connection failures, bind
7783 failures, and timeouts.
7785 For each server name in the list, a port number can be given. The standard way
7786 of specifying a host and port is to use a colon separator (RFC 1738). Because
7787 &%ldap_default_servers%& is a colon-separated list, such colons have to be
7788 doubled. For example
7790 ldap_default_servers = ldap1.example.com::145:ldap2.example.com
7792 If &%ldap_default_servers%& is unset, a URL with no server name is passed
7793 to the LDAP library with no server name, and the library's default (normally
7794 the local host) is used.
7796 If you are using the OpenLDAP library, you can connect to an LDAP server using
7797 a Unix domain socket instead of a TCP/IP connection. This is specified by using
7798 &`ldapi`& instead of &`ldap`& in LDAP queries. What follows here applies only
7799 to OpenLDAP. If Exim is compiled with a different LDAP library, this feature is
7802 For this type of connection, instead of a host name for the server, a pathname
7803 for the socket is required, and the port number is not relevant. The pathname
7804 can be specified either as an item in &%ldap_default_servers%&, or inline in
7805 the query. In the former case, you can have settings such as
7807 ldap_default_servers = /tmp/ldap.sock : backup.ldap.your.domain
7809 When the pathname is given in the query, you have to escape the slashes as
7810 &`%2F`& to fit in with the LDAP URL syntax. For example:
7812 ${lookup ldap {ldapi://%2Ftmp%2Fldap.sock/o=...
7814 When Exim processes an LDAP lookup and finds that the &"hostname"& is really
7815 a pathname, it uses the Unix domain socket code, even if the query actually
7816 specifies &`ldap`& or &`ldaps`&. In particular, no encryption is used for a
7817 socket connection. This behaviour means that you can use a setting of
7818 &%ldap_default_servers%& such as in the example above with traditional &`ldap`&
7819 or &`ldaps`& queries, and it will work. First, Exim tries a connection via
7820 the Unix domain socket; if that fails, it tries a TCP/IP connection to the
7823 If an explicit &`ldapi`& type is given in a query when a host name is
7824 specified, an error is diagnosed. However, if there are more items in
7825 &%ldap_default_servers%&, they are tried. In other words:
7828 Using a pathname with &`ldap`& or &`ldaps`& forces the use of the Unix domain
7831 Using &`ldapi`& with a host name causes an error.
7835 Using &`ldapi`& with no host or path in the query, and no setting of
7836 &%ldap_default_servers%&, does whatever the library does by default.
7840 .section "LDAP authentication and control information" "SECID70"
7841 .cindex "LDAP" "authentication"
7842 The LDAP URL syntax provides no way of passing authentication and other control
7843 information to the server. To make this possible, the URL in an LDAP query may
7844 be preceded by any number of <&'name'&>=<&'value'&> settings, separated by
7845 spaces. If a value contains spaces it must be enclosed in double quotes, and
7846 when double quotes are used, backslash is interpreted in the usual way inside
7847 them. The following names are recognized:
7848 .itable none 0 0 2 1pt left 1pt left
7849 .irow DEREFERENCE "set the dereferencing parameter"
7850 .irow NETTIME "set a timeout for a network operation"
7851 .irow USER "set the DN, for authenticating the LDAP bind"
7852 .irow PASS "set the password, likewise"
7853 .irow REFERRALS "set the referrals parameter"
7854 .irow SERVERS "set alternate server list for this query only"
7855 .irow SIZE "set the limit for the number of entries returned"
7856 .irow TIME "set the maximum waiting time for a query"
7858 The value of the DEREFERENCE parameter must be one of the words &"never"&,
7859 &"searching"&, &"finding"&, or &"always"&. The value of the REFERRALS parameter
7860 must be &"follow"& (the default) or &"nofollow"&. The latter stops the LDAP
7861 library from trying to follow referrals issued by the LDAP server.
7863 .cindex LDAP timeout
7864 .cindex timeout "LDAP lookup"
7865 The name CONNECT is an obsolete name for NETTIME, retained for
7866 backwards compatibility. This timeout (specified as a number of seconds) is
7867 enforced from the client end for operations that can be carried out over a
7868 network. Specifically, it applies to network connections and calls to the
7869 &'ldap_result()'& function. If the value is greater than zero, it is used if
7870 LDAP_OPT_NETWORK_TIMEOUT is defined in the LDAP headers (OpenLDAP), or
7871 if LDAP_X_OPT_CONNECT_TIMEOUT is defined in the LDAP headers (Netscape
7872 SDK 4.1). A value of zero forces an explicit setting of &"no timeout"& for
7873 Netscape SDK; for OpenLDAP no action is taken.
7875 The TIME parameter (also a number of seconds) is passed to the server to
7876 set a server-side limit on the time taken to complete a search.
7878 The SERVERS parameter allows you to specify an alternate list of ldap servers
7879 to use for an individual lookup. The global &%ldap_default_servers%& option provides a
7880 default list of ldap servers, and a single lookup can specify a single ldap
7881 server to use. But when you need to do a lookup with a list of servers that is
7882 different than the default list (maybe different order, maybe a completely
7883 different set of servers), the SERVERS parameter allows you to specify this
7884 alternate list (colon-separated).
7886 Here is an example of an LDAP query in an Exim lookup that uses some of these
7887 values. This is a single line, folded to fit on the page:
7890 {user="cn=manager,o=University of Cambridge,c=UK" pass=secret
7891 ldap:///o=University%20of%20Cambridge,c=UK?sn?sub?(cn=foo)}
7894 The encoding of spaces as &`%20`& is a URL thing which should not be done for
7895 any of the auxiliary data. Exim configuration settings that include lookups
7896 which contain password information should be preceded by &"hide"& to prevent
7897 non-admin users from using the &%-bP%& option to see their values.
7899 The auxiliary data items may be given in any order. The default is no
7900 connection timeout (the system timeout is used), no user or password, no limit
7901 on the number of entries returned, and no time limit on queries.
7903 When a DN is quoted in the USER= setting for LDAP authentication, Exim
7904 removes any URL quoting that it may contain before passing it LDAP. Apparently
7905 some libraries do this for themselves, but some do not. Removing the URL
7906 quoting has two advantages:
7909 It makes it possible to use the same &%quote_ldap_dn%& expansion for USER=
7910 DNs as with DNs inside actual queries.
7912 It permits spaces inside USER= DNs.
7915 For example, a setting such as
7917 USER=cn=${quote_ldap_dn:$1}
7919 should work even if &$1$& contains spaces.
7921 Expanded data for the PASS= value should be quoted using the &%quote%&
7922 expansion operator, rather than the LDAP quote operators. The only reason this
7923 field needs quoting is to ensure that it conforms to the Exim syntax, which
7924 does not allow unquoted spaces. For example:
7928 The LDAP authentication mechanism can be used to check passwords as part of
7929 SMTP authentication. See the &%ldapauth%& expansion string condition in chapter
7934 .section "Format of data returned by LDAP" "SECID71"
7935 .cindex "LDAP" "returned data formats"
7936 The &(ldapdn)& lookup type returns the Distinguished Name from a single entry
7937 as a sequence of values, for example
7939 cn=manager,o=University of Cambridge,c=UK
7941 The &(ldap)& lookup type generates an error if more than one entry matches the
7942 search filter, whereas &(ldapm)& permits this case, and inserts a newline in
7943 the result between the data from different entries. It is possible for multiple
7944 values to be returned for both &(ldap)& and &(ldapm)&, but in the former case
7945 you know that whatever values are returned all came from a single entry in the
7948 In the common case where you specify a single attribute in your LDAP query, the
7949 result is not quoted, and does not contain the attribute name. If the attribute
7950 has multiple values, they are separated by commas. Any comma that is
7951 part of an attribute's value is doubled.
7953 If you specify multiple attributes, the result contains space-separated, quoted
7954 strings, each preceded by the attribute name and an equals sign. Within the
7955 quotes, the quote character, backslash, and newline are escaped with
7956 backslashes, and commas are used to separate multiple values for the attribute.
7957 Any commas in attribute values are doubled
7958 (permitting treatment of the values as a comma-separated list).
7959 Apart from the escaping, the string within quotes takes the same form as the
7960 output when a single attribute is requested. Specifying no attributes is the
7961 same as specifying all of an entry's attributes.
7963 Here are some examples of the output format. The first line of each pair is an
7964 LDAP query, and the second is the data that is returned. The attribute called
7965 &%attr1%& has two values, one of them with an embedded comma, whereas
7966 &%attr2%& has only one value. Both attributes are derived from &%attr%&
7967 (they have SUP &%attr%& in their schema definitions).
7970 ldap:///o=base?attr1?sub?(uid=fred)
7973 ldap:///o=base?attr2?sub?(uid=fred)
7976 ldap:///o=base?attr?sub?(uid=fred)
7977 value1.1,value1,,2,value two
7979 ldap:///o=base?attr1,attr2?sub?(uid=fred)
7980 attr1="value1.1,value1,,2" attr2="value two"
7982 ldap:///o=base??sub?(uid=fred)
7983 objectClass="top" attr1="value1.1,value1,,2" attr2="value two"
7986 make use of Exim's &%-be%& option to run expansion tests and thereby check the
7987 results of LDAP lookups.
7988 The &%extract%& operator in string expansions can be used to pick out
7989 individual fields from data that consists of &'key'&=&'value'& pairs.
7990 The &%listextract%& operator should be used to pick out individual values
7991 of attributes, even when only a single value is expected.
7992 The doubling of embedded commas allows you to use the returned data as a
7993 comma separated list (using the "<," syntax for changing the input list separator).
7998 .section "More about NIS+" "SECTnisplus"
7999 .cindex "NIS+ lookup type"
8000 .cindex "lookup" "NIS+"
8001 NIS+ queries consist of a NIS+ &'indexed name'& followed by an optional colon
8002 and field name. If this is given, the result of a successful query is the
8003 contents of the named field; otherwise the result consists of a concatenation
8004 of &'field-name=field-value'& pairs, separated by spaces. Empty values and
8005 values containing spaces are quoted. For example, the query
8007 [name=mg1456],passwd.org_dir
8009 might return the string
8011 name=mg1456 passwd="" uid=999 gid=999 gcos="Martin Guerre"
8012 home=/home/mg1456 shell=/bin/bash shadow=""
8014 (split over two lines here to fit on the page), whereas
8016 [name=mg1456],passwd.org_dir:gcos
8022 with no quotes. A NIS+ lookup fails if NIS+ returns more than one table entry
8023 for the given indexed key. The effect of the &%quote_nisplus%& expansion
8024 operator is to double any quote characters within the text.
8028 .section "SQL lookups" "SECTsql"
8029 .cindex "SQL lookup types"
8030 .cindex "MySQL" "lookup type"
8031 .cindex "PostgreSQL lookup type"
8032 .cindex "lookup" "MySQL"
8033 .cindex "lookup" "PostgreSQL"
8034 .cindex "Oracle" "lookup type"
8035 .cindex "lookup" "Oracle"
8036 .cindex "InterBase lookup type"
8037 .cindex "lookup" "InterBase"
8038 .cindex "Redis lookup type"
8039 .cindex lookup Redis
8040 Exim can support lookups in InterBase, MySQL, Oracle, PostgreSQL, Redis,
8042 databases. Queries for these databases contain SQL statements, so an example
8045 ${lookup mysql{select mailbox from users where id='userx'}\
8048 If the result of the query contains more than one field, the data for each
8049 field in the row is returned, preceded by its name, so the result of
8051 ${lookup pgsql{select home,name from users where id='userx'}\
8056 home=/home/userx name="Mister X"
8058 Empty values and values containing spaces are double quoted, with embedded
8059 quotes escaped by a backslash. If the result of the query contains just one
8060 field, the value is passed back verbatim, without a field name, for example:
8064 If the result of the query yields more than one row, it is all concatenated,
8065 with a newline between the data for each row.
8068 .section "More about MySQL, PostgreSQL, Oracle, InterBase, and Redis" "SECID72"
8069 .cindex "MySQL" "lookup type"
8070 .cindex "PostgreSQL lookup type"
8071 .cindex "lookup" "MySQL"
8072 .cindex "lookup" "PostgreSQL"
8073 .cindex "Oracle" "lookup type"
8074 .cindex "lookup" "Oracle"
8075 .cindex "InterBase lookup type"
8076 .cindex "lookup" "InterBase"
8077 .cindex "Redis lookup type"
8078 .cindex lookup Redis
8079 If any MySQL, PostgreSQL, Oracle, InterBase or Redis lookups are used, the
8080 &%mysql_servers%&, &%pgsql_servers%&, &%oracle_servers%&, &%ibase_servers%&,
8081 or &%redis_servers%&
8082 option (as appropriate) must be set to a colon-separated list of server
8084 .oindex &%mysql_servers%&
8085 .oindex &%pgsql_servers%&
8086 .oindex &%oracle_servers%&
8087 .oindex &%ibase_servers%&
8088 .oindex &%redis_servers%&
8089 (For MySQL and PostgreSQL, the global option need not be set if all
8090 queries contain their own server information &-- see section
8091 &<<SECTspeserque>>&.)
8093 each item in the list is a slash-separated list of four
8094 items: host name, database name, user name, and password. In the case of
8095 Oracle, the host name field is used for the &"service name"&, and the database
8096 name field is not used and should be empty. For example:
8098 hide oracle_servers = oracle.plc.example//userx/abcdwxyz
8100 Because password data is sensitive, you should always precede the setting with
8101 &"hide"&, to prevent non-admin users from obtaining the setting via the &%-bP%&
8102 option. Here is an example where two MySQL servers are listed:
8104 hide mysql_servers = localhost/users/root/secret:\
8105 otherhost/users/root/othersecret
8107 For MySQL and PostgreSQL, a host may be specified as <&'name'&>:<&'port'&> but
8108 because this is a colon-separated list, the colon has to be doubled. For each
8109 query, these parameter groups are tried in order until a connection is made and
8110 a query is successfully processed. The result of a query may be that no data is
8111 found, but that is still a successful query. In other words, the list of
8112 servers provides a backup facility, not a list of different places to look.
8114 For Redis the global option need not be specified if all queries contain their
8115 own server information &-- see section &<<SECTspeserque>>&.
8116 If specified, the option must be set to a colon-separated list of server
8118 Each item in the list is a slash-separated list of three items:
8119 host, database number, and password.
8121 The host is required and may be either an IPv4 address and optional
8122 port number (separated by a colon, which needs doubling due to the
8123 higher-level list), or a Unix socket pathname enclosed in parentheses
8125 The database number is optional; if present that number is selected in the backend
8127 The password is optional; if present it is used to authenticate to the backend
8130 The &%quote_mysql%&, &%quote_pgsql%&, and &%quote_oracle%& expansion operators
8131 convert newline, tab, carriage return, and backspace to \n, \t, \r, and \b
8132 respectively, and the characters single-quote, double-quote, and backslash
8133 itself are escaped with backslashes.
8135 The &%quote_redis%& expansion operator
8136 escapes whitespace and backslash characters with a backslash.
8138 .section "Specifying the server in the query" "SECTspeserque"
8139 For MySQL, PostgreSQL and Redis lookups (but not currently for Oracle and InterBase),
8140 it is possible to specify a list of servers with an individual query. This is
8141 done by appending a comma-separated option to the query type:
8143 &`,servers=`&&'server1:server2:server3:...'&
8145 Each item in the list may take one of two forms:
8147 If it contains no slashes it is assumed to be just a host name. The appropriate
8148 global option (&%mysql_servers%& or &%pgsql_servers%&) is searched for a host
8149 of the same name, and the remaining parameters (database, user, password) are
8152 If it contains any slashes, it is taken as a complete parameter set.
8154 The list of servers is used in exactly the same way as the global list.
8155 Once a connection to a server has happened and a query has been
8156 successfully executed, processing of the lookup ceases.
8158 This feature is intended for use in master/slave situations where updates
8159 are occurring and you want to update the master rather than a slave. If the
8160 master is in the list as a backup for reading, you might have a global setting
8163 mysql_servers = slave1/db/name/pw:\
8167 In an updating lookup, you could then write:
8169 ${lookup mysql,servers=master {UPDATE ...} }
8171 That query would then be sent only to the master server. If, on the other hand,
8172 the master is not to be used for reading, and so is not present in the global
8173 option, you can still update it by a query of this form:
8175 ${lookup pgsql,servers=master/db/name/pw {UPDATE ...} }
8178 An older syntax places the servers specification before the query,
8179 semicolon separated:
8181 ${lookup mysql{servers=master; UPDATE ...} }
8183 The new version avoids potential issues with tainted
8184 arguments in the query, for explicit expansion.
8185 &*Note*&: server specifications in list-style lookups are still problematic.
8188 .section "Special MySQL features" "SECID73"
8189 For MySQL, an empty host name or the use of &"localhost"& in &%mysql_servers%&
8190 causes a connection to the server on the local host by means of a Unix domain
8191 socket. An alternate socket can be specified in parentheses.
8192 An option group name for MySQL option files can be specified in square brackets;
8193 the default value is &"exim"&.
8194 The full syntax of each item in &%mysql_servers%& is:
8196 <&'hostname'&>::<&'port'&>(<&'socket name'&>)[<&'option group'&>]/&&&
8197 <&'database'&>/<&'user'&>/<&'password'&>
8199 Any of the four sub-parts of the first field can be omitted. For normal use on
8200 the local host it can be left blank or set to just &"localhost"&.
8202 No database need be supplied &-- but if it is absent here, it must be given in
8205 If a MySQL query is issued that does not request any data (an insert, update,
8206 or delete command), the result of the lookup is the number of rows affected.
8208 &*Warning*&: This can be misleading. If an update does not actually change
8209 anything (for example, setting a field to the value it already has), the result
8210 is zero because no rows are affected.
8213 .section "Special PostgreSQL features" "SECID74"
8214 PostgreSQL lookups can also use Unix domain socket connections to the database.
8215 This is usually faster and costs less CPU time than a TCP/IP connection.
8216 However it can be used only if the mail server runs on the same machine as the
8217 database server. A configuration line for PostgreSQL via Unix domain sockets
8220 hide pgsql_servers = (/tmp/.s.PGSQL.5432)/db/user/password : ...
8222 In other words, instead of supplying a host name, a path to the socket is
8223 given. The path name is enclosed in parentheses so that its slashes aren't
8224 visually confused with the delimiters for the other server parameters.
8226 If a PostgreSQL query is issued that does not request any data (an insert,
8227 update, or delete command), the result of the lookup is the number of rows
8230 .section "More about SQLite" "SECTsqlite"
8231 .cindex "lookup" "SQLite"
8232 .cindex "sqlite lookup type"
8233 SQLite is different to the other SQL lookups because a filename is required in
8234 addition to the SQL query. An SQLite database is a single file, and there is no
8235 daemon as in the other SQL databases.
8237 .oindex &%sqlite_dbfile%&
8238 There are two ways of
8239 specifying the file.
8240 The first is is by using the &%sqlite_dbfile%& main option.
8241 The second, which allows separate files for each query,
8242 is to use an option appended, comma-separated, to the &"sqlite"&
8243 lookup type word. The option is the word &"file"&, then an equals,
8245 The filename in this case cannot contain whitespace or open-brace charachters.
8247 A deprecated method is available, prefixing the query with the filename
8248 separated by white space.
8250 .cindex "tainted data" "sqlite file"
8251 the query cannot use any tainted values, as that taints
8252 the entire query including the filename - resulting in a refusal to open
8255 In all the above cases the filename must be an absolute path.
8257 Here is a lookup expansion example:
8259 sqlite_dbfile = /some/thing/sqlitedb
8261 ${lookup sqlite {select name from aliases where id='userx';}}
8263 In a list, the syntax is similar. For example:
8265 domainlist relay_to_domains = sqlite;\
8266 select * from relays where ip='$sender_host_address';
8268 The only character affected by the &%quote_sqlite%& operator is a single
8269 quote, which it doubles.
8271 .cindex timeout SQLite
8272 .cindex sqlite "lookup timeout"
8273 The SQLite library handles multiple simultaneous accesses to the database
8274 internally. Multiple readers are permitted, but only one process can
8275 update at once. Attempts to access the database while it is being updated
8276 are rejected after a timeout period, during which the SQLite library
8277 waits for the lock to be released. In Exim, the default timeout is set
8278 to 5 seconds, but it can be changed by means of the &%sqlite_lock_timeout%&
8281 .section "More about Redis" "SECTredis"
8282 .cindex "lookup" "Redis"
8283 .cindex "redis lookup type"
8284 Redis is a non-SQL database. Commands are simple get and set.
8287 ${lookup redis{set keyname ${quote_redis:objvalue plus}}}
8288 ${lookup redis{get keyname}}
8291 As of release 4.91, "lightweight" support for Redis Cluster is available.
8292 Requires &%redis_servers%& list to contain all the servers in the cluster, all
8293 of which must be reachable from the running exim instance. If the cluster has
8294 master/slave replication, the list must contain all the master and slave
8297 When the Redis Cluster returns a "MOVED" response to a query, Exim does not
8298 immediately follow the redirection but treats the response as a DEFER, moving on
8299 to the next server in the &%redis_servers%& list until the correct server is
8306 . ////////////////////////////////////////////////////////////////////////////
8307 . ////////////////////////////////////////////////////////////////////////////
8309 .chapter "Domain, host, address, and local part lists" &&&
8310 "CHAPdomhosaddlists" &&&
8311 "Domain, host, and address lists"
8312 .scindex IIDdohoadli "lists of domains; hosts; etc."
8313 A number of Exim configuration options contain lists of domains, hosts,
8314 email addresses, or local parts. For example, the &%hold_domains%& option
8315 contains a list of domains whose delivery is currently suspended. These lists
8316 are also used as data in ACL statements (see chapter &<<CHAPACL>>&), and as
8317 arguments to expansion conditions such as &%match_domain%&.
8319 Each item in one of these lists is a pattern to be matched against a domain,
8320 host, email address, or local part, respectively. In the sections below, the
8321 different types of pattern for each case are described, but first we cover some
8322 general facilities that apply to all four kinds of list.
8324 Note that other parts of Exim use a &'string list'& which does not
8325 support all the complexity available in
8326 domain, host, address and local part lists.
8330 .section "Expansion of lists" "SECTlistexpand"
8331 .cindex "expansion" "of lists"
8332 Each list is expanded as a single string before it is used.
8334 &'Exception: the router headers_remove option, where list-item
8335 splitting is done before string-expansion.'&
8338 expansion must be a list, possibly containing empty items, which is split up
8339 into separate items for matching. By default, colon is the separator character,
8340 but this can be varied if necessary. See sections &<<SECTlistconstruct>>& and
8341 &<<SECTempitelis>>& for details of the list syntax; the second of these
8342 discusses the way to specify empty list items.
8345 If the string expansion is forced to fail, Exim behaves as if the item it is
8346 testing (domain, host, address, or local part) is not in the list. Other
8347 expansion failures cause temporary errors.
8349 If an item in a list is a regular expression, backslashes, dollars and possibly
8350 other special characters in the expression must be protected against
8351 misinterpretation by the string expander. The easiest way to do this is to use
8352 the &`\N`& expansion feature to indicate that the contents of the regular
8353 expression should not be expanded. For example, in an ACL you might have:
8355 deny senders = \N^\d{8}\w@.*\.baddomain\.example$\N : \
8356 ${lookup{$domain}lsearch{/badsenders/bydomain}}
8358 The first item is a regular expression that is protected from expansion by
8359 &`\N`&, whereas the second uses the expansion to obtain a list of unwanted
8360 senders based on the receiving domain.
8365 .section "Negated items in lists" "SECID76"
8366 .cindex "list" "negation"
8367 .cindex "negation" "in lists"
8368 Items in a list may be positive or negative. Negative items are indicated by a
8369 leading exclamation mark, which may be followed by optional white space. A list
8370 defines a set of items (domains, etc). When Exim processes one of these lists,
8371 it is trying to find out whether a domain, host, address, or local part
8372 (respectively) is in the set that is defined by the list. It works like this:
8374 The list is scanned from left to right. If a positive item is matched, the
8375 subject that is being checked is in the set; if a negative item is matched, the
8376 subject is not in the set. If the end of the list is reached without the
8377 subject having matched any of the patterns, it is in the set if the last item
8378 was a negative one, but not if it was a positive one. For example, the list in
8380 domainlist relay_to_domains = !a.b.c : *.b.c
8382 matches any domain ending in &'.b.c'& except for &'a.b.c'&. Domains that match
8383 neither &'a.b.c'& nor &'*.b.c'& do not match, because the last item in the
8384 list is positive. However, if the setting were
8386 domainlist relay_to_domains = !a.b.c
8388 then all domains other than &'a.b.c'& would match because the last item in the
8389 list is negative. In other words, a list that ends with a negative item behaves
8390 as if it had an extra item &`:*`& on the end.
8392 Another way of thinking about positive and negative items in lists is to read
8393 the connector as &"or"& after a positive item and as &"and"& after a negative
8398 .section "File names in lists" "SECTfilnamlis"
8399 .cindex "list" "filename in"
8400 If an item in a domain, host, address, or local part list is an absolute
8401 filename (beginning with a slash character), each line of the file is read and
8402 processed as if it were an independent item in the list, except that further
8403 filenames are not allowed,
8404 and no expansion of the data from the file takes place.
8405 Empty lines in the file are ignored, and the file may also contain comment
8409 For domain and host lists, if a # character appears anywhere in a line of the
8410 file, it and all following characters are ignored.
8412 Because local parts may legitimately contain # characters, a comment in an
8413 address list or local part list file is recognized only if # is preceded by
8414 white space or the start of the line. For example:
8416 not#comment@x.y.z # but this is a comment
8420 Putting a filename in a list has the same effect as inserting each line of the
8421 file as an item in the list (blank lines and comments excepted). However, there
8422 is one important difference: the file is read each time the list is processed,
8423 so if its contents vary over time, Exim's behaviour changes.
8425 If a filename is preceded by an exclamation mark, the sense of any match
8426 within the file is inverted. For example, if
8428 hold_domains = !/etc/nohold-domains
8430 and the file contains the lines
8435 then &'a.b.c'& is in the set of domains defined by &%hold_domains%&, whereas
8436 any domain matching &`*.b.c`& is not.
8440 .section "An lsearch file is not an out-of-line list" "SECID77"
8441 As will be described in the sections that follow, lookups can be used in lists
8442 to provide indexed methods of checking list membership. There has been some
8443 confusion about the way &(lsearch)& lookups work in lists. Because
8444 an &(lsearch)& file contains plain text and is scanned sequentially, it is
8445 sometimes thought that it is allowed to contain wild cards and other kinds of
8446 non-constant pattern. This is not the case. The keys in an &(lsearch)& file are
8447 always fixed strings, just as for any other single-key lookup type.
8449 If you want to use a file to contain wild-card patterns that form part of a
8450 list, just give the filename on its own, without a search type, as described
8451 in the previous section. You could also use the &(wildlsearch)& or
8452 &(nwildlsearch)&, but there is no advantage in doing this.
8457 .section "Results of list checking" SECTlistresults
8458 The primary result of doing a list check is a truth value.
8459 In some contexts additional information is stored
8460 about the list element that matched:
8463 A &%hosts%& ACL condition
8464 will store a result in the &$host_data$& variable.
8466 A &%local_parts%& router option or &%local_parts%& ACL condition
8467 will store a result in the &$local_part_data$& variable.
8469 A &%domains%& router option or &%domains%& ACL condition
8470 will store a result in the &$domain_data$& variable.
8472 A &%senders%& router option or &%senders%& ACL condition
8473 will store a result in the &$sender_data$& variable.
8475 A &%recipients%& ACL condition
8476 will store a result in the &$recipient_data$& variable.
8479 The detail of the additional information depends on the
8480 type of match and is given below as the &*value*& information.
8485 .section "Named lists" "SECTnamedlists"
8486 .cindex "named lists"
8487 .cindex "list" "named"
8488 A list of domains, hosts, email addresses, or local parts can be given a name
8489 which is then used to refer to the list elsewhere in the configuration. This is
8490 particularly convenient if the same list is required in several different
8491 places. It also allows lists to be given meaningful names, which can improve
8492 the readability of the configuration. For example, it is conventional to define
8493 a domain list called &'local_domains'& for all the domains that are handled
8494 locally on a host, using a configuration line such as
8496 domainlist local_domains = localhost:my.dom.example
8498 Named lists are referenced by giving their name preceded by a plus sign, so,
8499 for example, a router that is intended to handle local domains would be
8500 configured with the line
8502 domains = +local_domains
8504 The first router in a configuration is often one that handles all domains
8505 except the local ones, using a configuration with a negated item like this:
8509 domains = ! +local_domains
8510 transport = remote_smtp
8513 The four kinds of named list are created by configuration lines starting with
8514 the words &%domainlist%&, &%hostlist%&, &%addresslist%&, or &%localpartlist%&,
8515 respectively. Then there follows the name that you are defining, followed by an
8516 equals sign and the list itself. For example:
8518 hostlist relay_from_hosts = 192.168.23.0/24 : my.friend.example
8519 addresslist bad_senders = cdb;/etc/badsenders
8521 A named list may refer to other named lists:
8523 domainlist dom1 = first.example : second.example
8524 domainlist dom2 = +dom1 : third.example
8525 domainlist dom3 = fourth.example : +dom2 : fifth.example
8527 &*Warning*&: If the last item in a referenced list is a negative one, the
8528 effect may not be what you intended, because the negation does not propagate
8529 out to the higher level. For example, consider:
8531 domainlist dom1 = !a.b
8532 domainlist dom2 = +dom1 : *.b
8534 The second list specifies &"either in the &%dom1%& list or &'*.b'&"&. The first
8535 list specifies just &"not &'a.b'&"&, so the domain &'x.y'& matches it. That
8536 means it matches the second list as well. The effect is not the same as
8538 domainlist dom2 = !a.b : *.b
8540 where &'x.y'& does not match. It's best to avoid negation altogether in
8541 referenced lists if you can.
8543 .cindex "hiding named list values"
8544 .cindex "named lists" "hiding value of"
8545 Some named list definitions may contain sensitive data, for example, passwords for
8546 accessing databases. To stop non-admin users from using the &%-bP%& command
8547 line option to read these values, you can precede the definition with the
8548 word &"hide"&. For example:
8550 hide domainlist filter_for_domains = ldap;PASS=secret ldap::/// ...
8554 Named lists may have a performance advantage. When Exim is routing an
8555 address or checking an incoming message, it caches the result of tests on named
8556 lists. So, if you have a setting such as
8558 domains = +local_domains
8560 on several of your routers
8561 or in several ACL statements,
8562 the actual test is done only for the first one. However, the caching works only
8563 if there are no expansions within the list itself or any sublists that it
8564 references. In other words, caching happens only for lists that are known to be
8565 the same each time they are referenced.
8567 By default, there may be up to 16 named lists of each type. This limit can be
8568 extended by changing a compile-time variable. The use of domain and host lists
8569 is recommended for concepts such as local domains, relay domains, and relay
8570 hosts. The default configuration is set up like this.
8574 .section "Named lists compared with macros" "SECID78"
8575 .cindex "list" "named compared with macro"
8576 .cindex "macro" "compared with named list"
8577 At first sight, named lists might seem to be no different from macros in the
8578 configuration file. However, macros are just textual substitutions. If you
8581 ALIST = host1 : host2
8582 auth_advertise_hosts = !ALIST
8584 it probably won't do what you want, because that is exactly the same as
8586 auth_advertise_hosts = !host1 : host2
8588 Notice that the second host name is not negated. However, if you use a host
8591 hostlist alist = host1 : host2
8592 auth_advertise_hosts = ! +alist
8594 the negation applies to the whole list, and so that is equivalent to
8596 auth_advertise_hosts = !host1 : !host2
8600 .section "Named list caching" "SECID79"
8601 .cindex "list" "caching of named"
8602 .cindex "caching" "named lists"
8603 While processing a message, Exim caches the result of checking a named list if
8604 it is sure that the list is the same each time. In practice, this means that
8605 the cache operates only if the list contains no $ characters, which guarantees
8606 that it will not change when it is expanded. Sometimes, however, you may have
8607 an expanded list that you know will be the same each time within a given
8608 message. For example:
8610 domainlist special_domains = \
8611 ${lookup{$sender_host_address}cdb{/some/file}}
8613 This provides a list of domains that depends only on the sending host's IP
8614 address. If this domain list is referenced a number of times (for example,
8615 in several ACL lines, or in several routers) the result of the check is not
8616 cached by default, because Exim does not know that it is going to be the
8617 same list each time.
8619 By appending &`_cache`& to &`domainlist`& you can tell Exim to go ahead and
8620 cache the result anyway. For example:
8622 domainlist_cache special_domains = ${lookup{...
8624 If you do this, you should be absolutely sure that caching is going to do
8625 the right thing in all cases. When in doubt, leave it out.
8629 .section "Domain lists" "SECTdomainlist"
8630 .cindex "domain list" "patterns for"
8631 .cindex "list" "domain list"
8632 Domain lists contain patterns that are to be matched against a mail domain.
8633 The following types of item may appear in domain lists:
8636 .cindex "primary host name"
8637 .cindex "host name" "matched in domain list"
8638 .oindex "&%primary_hostname%&"
8639 .cindex "domain list" "matching primary host name"
8640 .cindex "@ in a domain list"
8641 If a pattern consists of a single @ character, it matches the local host name,
8642 as set by the &%primary_hostname%& option (or defaulted). This makes it
8643 possible to use the same configuration file on several different hosts that
8644 differ only in their names.
8646 The value for a match will be the primary host name.
8650 .cindex "@[] in a domain list"
8651 .cindex "domain list" "matching local IP interfaces"
8652 .cindex "domain literal"
8653 If a pattern consists of the string &`@[]`& it matches an IP address enclosed
8654 in square brackets (as in an email address that contains a domain literal), but
8655 only if that IP address is recognized as local for email routing purposes. The
8656 &%local_interfaces%& and &%extra_local_interfaces%& options can be used to
8657 control which of a host's several IP addresses are treated as local.
8658 In today's Internet, the use of domain literals is controversial;
8659 see the &%allow_domain_literals%& main option.
8661 The value for a match will be the string &`@[]`&.
8666 .cindex "@mx_primary"
8667 .cindex "@mx_secondary"
8668 .cindex "domain list" "matching MX pointers to local host"
8669 If a pattern consists of the string &`@mx_any`& it matches any domain that
8670 has an MX record pointing to the local host or to any host that is listed in
8671 .oindex "&%hosts_treat_as_local%&"
8672 &%hosts_treat_as_local%&. The items &`@mx_primary`& and &`@mx_secondary`&
8673 are similar, except that the first matches only when a primary MX target is the
8674 local host, and the second only when no primary MX target is the local host,
8675 but a secondary MX target is. &"Primary"& means an MX record with the lowest
8676 preference value &-- there may of course be more than one of them.
8678 The MX lookup that takes place when matching a pattern of this type is
8679 performed with the resolver options for widening names turned off. Thus, for
8680 example, a single-component domain will &'not'& be expanded by adding the
8681 resolver's default domain. See the &%qualify_single%& and &%search_parents%&
8682 options of the &(dnslookup)& router for a discussion of domain widening.
8684 Sometimes you may want to ignore certain IP addresses when using one of these
8685 patterns. You can specify this by following the pattern with &`/ignore=`&<&'ip
8686 list'&>, where <&'ip list'&> is a list of IP addresses. These addresses are
8687 ignored when processing the pattern (compare the &%ignore_target_hosts%& option
8688 on a router). For example:
8690 domains = @mx_any/ignore=127.0.0.1
8692 This example matches any domain that has an MX record pointing to one of
8693 the local host's IP addresses other than 127.0.0.1.
8695 The list of IP addresses is in fact processed by the same code that processes
8696 host lists, so it may contain CIDR-coded network specifications and it may also
8697 contain negative items.
8699 Because the list of IP addresses is a sublist within a domain list, you have to
8700 be careful about delimiters if there is more than one address. Like any other
8701 list, the default delimiter can be changed. Thus, you might have:
8703 domains = @mx_any/ignore=<;127.0.0.1;0.0.0.0 : \
8704 an.other.domain : ...
8706 so that the sublist uses semicolons for delimiters. When IPv6 addresses are
8707 involved, it is easiest to change the delimiter for the main list as well:
8709 domains = <? @mx_any/ignore=<;127.0.0.1;::1 ? \
8710 an.other.domain ? ...
8712 The value for a match will be the list element string (starting &`@mx_`&).
8716 .cindex "asterisk" "in domain list"
8717 .cindex "domain list" "asterisk in"
8718 .cindex "domain list" "matching &""ends with""&"
8719 If a pattern starts with an asterisk, the remaining characters of the pattern
8720 are compared with the terminating characters of the domain. The use of &"*"& in
8721 domain lists differs from its use in partial matching lookups. In a domain
8722 list, the character following the asterisk need not be a dot, whereas partial
8723 matching works only in terms of dot-separated components. For example, a domain
8724 list item such as &`*key.ex`& matches &'donkey.ex'& as well as
8727 The value for a match will be the list element string (starting with the asterisk).
8728 Additionally, &$0$& will be set to the matched string
8729 and &$1$& to the variable portion which the asterisk matched.
8732 .cindex "regular expressions" "in domain list"
8733 .cindex "domain list" "matching regular expression"
8734 If a pattern starts with a circumflex character, it is treated as a regular
8735 expression, and matched against the domain using a regular expression matching
8736 function. The circumflex is treated as part of the regular expression.
8737 Email domains are case-independent, so this regular expression match is by
8738 default case-independent, but you can make it case-dependent by starting it
8739 with &`(?-i)`&. References to descriptions of the syntax of regular expressions
8740 are given in chapter &<<CHAPregexp>>&.
8742 &*Warning*&: Because domain lists are expanded before being processed, you
8743 must escape any backslash and dollar characters in the regular expression, or
8744 use the special &`\N`& sequence (see chapter &<<CHAPexpand>>&) to specify that
8745 it is not to be expanded (unless you really do want to build a regular
8746 expression by expansion, of course).
8748 The value for a match will be the list element string (starting with the circumflex).
8749 Additionally, &$0$& will be set to the string matching the regular expression,
8750 and &$1$& (onwards) to any submatches identified by parentheses.
8755 .cindex "lookup" "in domain list"
8756 .cindex "domain list" "matching by lookup"
8757 If a pattern starts with the name of a single-key lookup type followed by a
8758 semicolon (for example, &"dbm;"& or &"lsearch;"&), the remainder of the pattern
8759 must be a filename in a suitable format for the lookup type. For example, for
8760 &"cdb;"& it must be an absolute path:
8762 domains = cdb;/etc/mail/local_domains.cdb
8764 The appropriate type of lookup is done on the file using the domain name as the
8765 key. In most cases, the value resulting from the lookup is not used; Exim is interested
8766 only in whether or not the key is present in the file. However, when a lookup
8767 is used for the &%domains%& option on a router
8768 or a &%domains%& condition in an ACL statement, the value is preserved in the
8769 &$domain_data$& variable and can be referred to in other router options or
8770 other statements in the same ACL.
8771 .cindex "tainted data" "de-tainting"
8772 .cindex "de-tainting" "using ACL domains condition"
8773 The value will be untainted.
8775 &*Note*&: If the data result of the lookup (as opposed to the key)
8776 is empty, then this empty value is stored in &$domain_data$&.
8777 The option to return the key for the lookup, as the value,
8778 may be what is wanted.
8782 Any of the single-key lookup type names may be preceded by
8783 &`partial`&<&'n'&>&`-`&, where the <&'n'&> is optional, for example,
8785 domains = partial-dbm;/partial/domains
8787 This causes partial matching logic to be invoked; a description of how this
8788 works is given in section &<<SECTpartiallookup>>&.
8791 .cindex "asterisk" "in lookup type"
8792 Any of the single-key lookup types may be followed by an asterisk. This causes
8793 a default lookup for a key consisting of a single asterisk to be done if the
8794 original lookup fails. This is not a useful feature when using a domain list to
8795 select particular domains (because any domain would match), but it might have
8796 value if the result of the lookup is being used via the &$domain_data$&
8800 If the pattern starts with the name of a query-style lookup type followed by a
8801 semicolon (for example, &"nisplus;"& or &"ldap;"&), the remainder of the
8802 pattern must be an appropriate query for the lookup type, as described in
8803 chapter &<<CHAPfdlookup>>&. For example:
8805 hold_domains = mysql;select domain from holdlist \
8806 where domain = '${quote_mysql:$domain}';
8808 In most cases, the value resulting from the lookup is not used (so for an SQL query, for
8809 example, it doesn't matter what field you select). Exim is interested only in
8810 whether or not the query succeeds. However, when a lookup is used for the
8811 &%domains%& option on a router, the value is preserved in the &$domain_data$&
8812 variable and can be referred to in other options.
8813 .cindex "tainted data" "de-tainting"
8814 .cindex "de-tainting" "using router domains option"
8815 The value will be untainted.
8818 If the pattern starts with the name of a lookup type
8819 of either kind (single-key or query-style) it may be
8820 followed by a comma and options,
8821 The options are lookup-type specific and consist of a comma-separated list.
8822 Each item starts with a tag and and equals "=" sign.
8825 .cindex "domain list" "matching literal domain name"
8826 If none of the above cases apply, a caseless textual comparison is made
8827 between the pattern and the domain.
8829 The value for a match will be the list element string.
8830 .cindex "tainted data" "de-tainting"
8831 Note that this is commonly untainted
8832 (depending on the way the list was created).
8833 Specifically, explicit text in the configuration file in not tainted.
8834 This is a useful way of obtaining an untainted equivalent to
8835 the domain, for later operations.
8837 However if the list (including one-element lists)
8838 is created by expanding a variable containing tainted data,
8839 it is tainted and so will the match value be.
8843 Here is an example that uses several different kinds of pattern:
8845 domainlist funny_domains = \
8848 *.foundation.fict.example : \
8849 \N^[1-2]\d{3}\.fict\.example$\N : \
8850 partial-dbm;/opt/data/penguin/book : \
8851 nis;domains.byname : \
8852 nisplus;[name=$domain,status=local],domains.org_dir
8854 There are obvious processing trade-offs among the various matching modes. Using
8855 an asterisk is faster than a regular expression, and listing a few names
8856 explicitly probably is too. The use of a file or database lookup is expensive,
8857 but may be the only option if hundreds of names are required. Because the
8858 patterns are tested in order, it makes sense to put the most commonly matched
8863 .section "Host lists" "SECThostlist"
8864 .cindex "host list" "patterns in"
8865 .cindex "list" "host list"
8866 Host lists are used to control what remote hosts are allowed to do. For
8867 example, some hosts may be allowed to use the local host as a relay, and some
8868 may be permitted to use the SMTP ETRN command. Hosts can be identified in
8869 two different ways, by name or by IP address. In a host list, some types of
8870 pattern are matched to a host name, and some are matched to an IP address.
8871 You need to be particularly careful with this when single-key lookups are
8872 involved, to ensure that the right value is being used as the key.
8875 .section "Special host list patterns" "SECID80"
8876 .cindex "empty item in hosts list"
8877 .cindex "host list" "empty string in"
8878 If a host list item is the empty string, it matches only when no remote host is
8879 involved. This is the case when a message is being received from a local
8880 process using SMTP on the standard input, that is, when a TCP/IP connection is
8883 .cindex "asterisk" "in host list"
8884 The special pattern &"*"& in a host list matches any host or no host. Neither
8885 the IP address nor the name is actually inspected.
8889 .section "Host list patterns that match by IP address" "SECThoslispatip"
8890 .cindex "host list" "matching IP addresses"
8891 If an IPv4 host calls an IPv6 host and the call is accepted on an IPv6 socket,
8892 the incoming address actually appears in the IPv6 host as
8893 &`::ffff:`&<&'v4address'&>. When such an address is tested against a host
8894 list, it is converted into a traditional IPv4 address first. (Not all operating
8895 systems accept IPv4 calls on IPv6 sockets, as there have been some security
8898 The following types of pattern in a host list check the remote host by
8899 inspecting its IP address:
8902 If the pattern is a plain domain name (not a regular expression, not starting
8903 with *, not a lookup of any kind), Exim calls the operating system function
8904 to find the associated IP address(es). Exim uses the newer
8905 &[getipnodebyname()]& function when available, otherwise &[gethostbyname()]&.
8906 This typically causes a forward DNS lookup of the name. The result is compared
8907 with the IP address of the subject host.
8909 If there is a temporary problem (such as a DNS timeout) with the host name
8910 lookup, a temporary error occurs. For example, if the list is being used in an
8911 ACL condition, the ACL gives a &"defer"& response, usually leading to a
8912 temporary SMTP error code. If no IP address can be found for the host name,
8913 what happens is described in section &<<SECTbehipnot>>& below.
8916 .cindex "@ in a host list"
8917 If the pattern is &"@"&, the primary host name is substituted and used as a
8918 domain name, as just described.
8921 If the pattern is an IP address, it is matched against the IP address of the
8922 subject host. IPv4 addresses are given in the normal &"dotted-quad"& notation.
8923 IPv6 addresses can be given in colon-separated format, but the colons have to
8924 be doubled so as not to be taken as item separators when the default list
8925 separator is used. IPv6 addresses are recognized even when Exim is compiled
8926 without IPv6 support. This means that if they appear in a host list on an
8927 IPv4-only host, Exim will not treat them as host names. They are just addresses
8928 that can never match a client host.
8931 .cindex "@[] in a host list"
8932 If the pattern is &"@[]"&, it matches the IP address of any IP interface on
8933 the local host. For example, if the local host is an IPv4 host with one
8934 interface address 10.45.23.56, these two ACL statements have the same effect:
8936 accept hosts = 127.0.0.1 : 10.45.23.56
8940 .cindex "CIDR notation"
8941 If the pattern is an IP address followed by a slash and a mask length, for
8946 , it is matched against the IP address of the subject
8947 host under the given mask. This allows an entire network of hosts to be
8948 included (or excluded) by a single item. The mask uses CIDR notation; it
8949 specifies the number of address bits that must match, starting from the most
8950 significant end of the address.
8952 &*Note*&: The mask is &'not'& a count of addresses, nor is it the high number
8953 of a range of addresses. It is the number of bits in the network portion of the
8954 address. The above example specifies a 24-bit netmask, so it matches all 256
8955 addresses in the 10.11.42.0 network. An item such as
8959 matches just two addresses, 192.168.23.236 and 192.168.23.237. A mask value of
8960 32 for an IPv4 address is the same as no mask at all; just a single address
8963 Here is another example which shows an IPv4 and an IPv6 network:
8965 recipient_unqualified_hosts = 192.168.0.0/16: \
8966 3ffe::ffff::836f::::/48
8968 The doubling of list separator characters applies only when these items
8969 appear inline in a host list. It is not required when indirecting via a file.
8972 recipient_unqualified_hosts = /opt/exim/unqualnets
8974 could make use of a file containing
8979 to have exactly the same effect as the previous example. When listing IPv6
8980 addresses inline, it is usually more convenient to use the facility for
8981 changing separator characters. This list contains the same two networks:
8983 recipient_unqualified_hosts = <; 172.16.0.0/12; \
8986 The separator is changed to semicolon by the leading &"<;"& at the start of the
8992 .section "Host list patterns for single-key lookups by host address" &&&
8993 "SECThoslispatsikey"
8994 .cindex "host list" "lookup of IP address"
8995 When a host is to be identified by a single-key lookup of its complete IP
8996 address, the pattern takes this form:
8998 &`net-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
9002 hosts_lookup = net-cdb;/hosts-by-ip.db
9004 The text form of the IP address of the subject host is used as the lookup key.
9005 IPv6 addresses are converted to an unabbreviated form, using lower case
9006 letters, with dots as separators because colon is the key terminator in
9007 &(lsearch)& files. [Colons can in fact be used in keys in &(lsearch)& files by
9008 quoting the keys, but this is a facility that was added later.] The data
9009 returned by the lookup is not used.
9011 .cindex "IP address" "masking"
9012 .cindex "host list" "masked IP address"
9013 Single-key lookups can also be performed using masked IP addresses, using
9014 patterns of this form:
9016 &`net<`&&'number'&&`>-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
9020 net24-dbm;/networks.db
9022 The IP address of the subject host is masked using <&'number'&> as the mask
9023 length. A textual string is constructed from the masked value, followed by the
9024 mask, and this is used as the lookup key. For example, if the host's IP address
9025 is 192.168.34.6, the key that is looked up for the above example is
9026 &"192.168.34.0/24"&.
9028 When an IPv6 address is converted to a string, dots are normally used instead
9029 of colons, so that keys in &(lsearch)& files need not contain colons (which
9030 terminate &(lsearch)& keys). This was implemented some time before the ability
9031 to quote keys was made available in &(lsearch)& files. However, the more
9032 recently implemented &(iplsearch)& files do require colons in IPv6 keys
9033 (notated using the quoting facility) so as to distinguish them from IPv4 keys.
9034 For this reason, when the lookup type is &(iplsearch)&, IPv6 addresses are
9035 converted using colons and not dots.
9036 In all cases except IPv4-mapped IPv6, full, unabbreviated IPv6
9037 addresses are always used.
9038 The latter are converted to IPv4 addresses, in dotted-quad form.
9040 Ideally, it would be nice to tidy up this anomalous situation by changing to
9041 colons in all cases, given that quoting is now available for &(lsearch)&.
9042 However, this would be an incompatible change that might break some existing
9045 &*Warning*&: Specifying &%net32-%& (for an IPv4 address) or &%net128-%& (for an
9046 IPv6 address) is not the same as specifying just &%net-%& without a number. In
9047 the former case the key strings include the mask value, whereas in the latter
9048 case the IP address is used on its own.
9052 .section "Host list patterns that match by host name" "SECThoslispatnam"
9053 .cindex "host" "lookup failures"
9054 .cindex "unknown host name"
9055 .cindex "host list" "matching host name"
9056 There are several types of pattern that require Exim to know the name of the
9057 remote host. These are either wildcard patterns or lookups by name. (If a
9058 complete hostname is given without any wildcarding, it is used to find an IP
9059 address to match against, as described in section &<<SECThoslispatip>>&
9062 If the remote host name is not already known when Exim encounters one of these
9063 patterns, it has to be found from the IP address.
9064 Although many sites on the Internet are conscientious about maintaining reverse
9065 DNS data for their hosts, there are also many that do not do this.
9066 Consequently, a name cannot always be found, and this may lead to unwanted
9067 effects. Take care when configuring host lists with wildcarded name patterns.
9068 Consider what will happen if a name cannot be found.
9070 Because of the problems of determining host names from IP addresses, matching
9071 against host names is not as common as matching against IP addresses.
9073 By default, in order to find a host name, Exim first does a reverse DNS lookup;
9074 if no name is found in the DNS, the system function (&[gethostbyaddr()]& or
9075 &[getipnodebyaddr()]& if available) is tried. The order in which these lookups
9076 are done can be changed by setting the &%host_lookup_order%& option. For
9077 security, once Exim has found one or more names, it looks up the IP addresses
9078 for these names and compares them with the IP address that it started with.
9079 Only those names whose IP addresses match are accepted. Any other names are
9080 discarded. If no names are left, Exim behaves as if the host name cannot be
9081 found. In the most common case there is only one name and one IP address.
9083 There are some options that control what happens if a host name cannot be
9084 found. These are described in section &<<SECTbehipnot>>& below.
9086 .cindex "host" "alias for"
9087 .cindex "alias for host"
9088 As a result of aliasing, hosts may have more than one name. When processing any
9089 of the following types of pattern, all the host's names are checked:
9092 .cindex "asterisk" "in host list"
9093 If a pattern starts with &"*"& the remainder of the item must match the end of
9094 the host name. For example, &`*.b.c`& matches all hosts whose names end in
9095 &'.b.c'&. This special simple form is provided because this is a very common
9096 requirement. Other kinds of wildcarding require the use of a regular
9099 .cindex "regular expressions" "in host list"
9100 .cindex "host list" "regular expression in"
9101 If the item starts with &"^"& it is taken to be a regular expression which is
9102 matched against the host name. Host names are case-independent, so this regular
9103 expression match is by default case-independent, but you can make it
9104 case-dependent by starting it with &`(?-i)`&. References to descriptions of the
9105 syntax of regular expressions are given in chapter &<<CHAPregexp>>&. For
9110 is a regular expression that matches either of the two hosts &'a.c.d'& or
9111 &'b.c.d'&. When a regular expression is used in a host list, you must take care
9112 that backslash and dollar characters are not misinterpreted as part of the
9113 string expansion. The simplest way to do this is to use &`\N`& to mark that
9114 part of the string as non-expandable. For example:
9116 sender_unqualified_hosts = \N^(a|b)\.c\.d$\N : ....
9118 &*Warning*&: If you want to match a complete host name, you must include the
9119 &`$`& terminating metacharacter in the regular expression, as in the above
9120 example. Without it, a match at the start of the host name is all that is
9127 .section "Behaviour when an IP address or name cannot be found" "SECTbehipnot"
9128 .cindex "host" "lookup failures, permanent"
9129 While processing a host list, Exim may need to look up an IP address from a
9130 name (see section &<<SECThoslispatip>>&), or it may need to look up a host name
9131 from an IP address (see section &<<SECThoslispatnam>>&). In either case, the
9132 behaviour when it fails to find the information it is seeking is the same.
9134 &*Note*&: This section applies to permanent lookup failures. It does &'not'&
9135 apply to temporary DNS errors, whose handling is described in the next section.
9137 .cindex "&`+include_unknown`&"
9138 .cindex "&`+ignore_unknown`&"
9139 Exim parses a host list from left to right. If it encounters a permanent
9140 lookup failure in any item in the host list before it has found a match,
9141 Exim treats it as a failure and the default behavior is as if the host
9142 does not match the list. This may not always be what you want to happen.
9143 To change Exim's behaviour, the special items &`+include_unknown`& or
9144 &`+ignore_unknown`& may appear in the list (at top level &-- they are
9145 not recognized in an indirected file).
9148 If any item that follows &`+include_unknown`& requires information that
9149 cannot found, Exim behaves as if the host does match the list. For example,
9151 host_reject_connection = +include_unknown:*.enemy.ex
9153 rejects connections from any host whose name matches &`*.enemy.ex`&, and also
9154 any hosts whose name it cannot find.
9157 If any item that follows &`+ignore_unknown`& requires information that cannot
9158 be found, Exim ignores that item and proceeds to the rest of the list. For
9161 accept hosts = +ignore_unknown : friend.example : \
9164 accepts from any host whose name is &'friend.example'& and from 192.168.4.5,
9165 whether or not its host name can be found. Without &`+ignore_unknown`&, if no
9166 name can be found for 192.168.4.5, it is rejected.
9169 Both &`+include_unknown`& and &`+ignore_unknown`& may appear in the same
9170 list. The effect of each one lasts until the next, or until the end of the
9173 .section "Mixing wildcarded host names and addresses in host lists" &&&
9175 .cindex "host list" "mixing names and addresses in"
9177 This section explains the host/ip processing logic with the same concepts
9178 as the previous section, but specifically addresses what happens when a
9179 wildcarded hostname is one of the items in the hostlist.
9182 If you have name lookups or wildcarded host names and
9183 IP addresses in the same host list, you should normally put the IP
9184 addresses first. For example, in an ACL you could have:
9186 accept hosts = 10.9.8.7 : *.friend.example
9188 The reason you normally would order it this way lies in the
9189 left-to-right way that Exim processes lists. It can test IP addresses
9190 without doing any DNS lookups, but when it reaches an item that requires
9191 a host name, it fails if it cannot find a host name to compare with the
9192 pattern. If the above list is given in the opposite order, the
9193 &%accept%& statement fails for a host whose name cannot be found, even
9194 if its IP address is 10.9.8.7.
9197 If you really do want to do the name check first, and still recognize the IP
9198 address, you can rewrite the ACL like this:
9200 accept hosts = *.friend.example
9201 accept hosts = 10.9.8.7
9203 If the first &%accept%& fails, Exim goes on to try the second one. See chapter
9204 &<<CHAPACL>>& for details of ACLs. Alternatively, you can use
9205 &`+ignore_unknown`&, which was discussed in depth in the first example in
9210 .section "Temporary DNS errors when looking up host information" &&&
9212 .cindex "host" "lookup failures, temporary"
9213 .cindex "&`+include_defer`&"
9214 .cindex "&`+ignore_defer`&"
9215 A temporary DNS lookup failure normally causes a defer action (except when
9216 &%dns_again_means_nonexist%& converts it into a permanent error). However,
9217 host lists can include &`+ignore_defer`& and &`+include_defer`&, analogous to
9218 &`+ignore_unknown`& and &`+include_unknown`&, as described in the previous
9219 section. These options should be used with care, probably only in non-critical
9220 host lists such as whitelists.
9224 .section "Host list patterns for single-key lookups by host name" &&&
9225 "SECThoslispatnamsk"
9226 .cindex "unknown host name"
9227 .cindex "host list" "matching host name"
9228 If a pattern is of the form
9230 <&'single-key-search-type'&>;<&'search-data'&>
9234 dbm;/host/accept/list
9236 a single-key lookup is performed, using the host name as its key. If the
9237 lookup succeeds, the host matches the item. The actual data that is looked up
9240 &*Reminder*&: With this kind of pattern, you must have host &'names'& as
9241 keys in the file, not IP addresses. If you want to do lookups based on IP
9242 addresses, you must precede the search type with &"net-"& (see section
9243 &<<SECThoslispatsikey>>&). There is, however, no reason why you could not use
9244 two items in the same list, one doing an address lookup and one doing a name
9245 lookup, both using the same file.
9249 .section "Host list patterns for query-style lookups" "SECID81"
9250 If a pattern is of the form
9252 <&'query-style-search-type'&>;<&'query'&>
9254 the query is obeyed, and if it succeeds, the host matches the item. The actual
9255 data that is looked up is not used. The variables &$sender_host_address$& and
9256 &$sender_host_name$& can be used in the query. For example:
9258 hosts_lookup = pgsql;\
9259 select ip from hostlist where ip='$sender_host_address'
9261 The value of &$sender_host_address$& for an IPv6 address contains colons. You
9262 can use the &%sg%& expansion item to change this if you need to. If you want to
9263 use masked IP addresses in database queries, you can use the &%mask%& expansion
9266 If the query contains a reference to &$sender_host_name$&, Exim automatically
9267 looks up the host name if it has not already done so. (See section
9268 &<<SECThoslispatnam>>& for comments on finding host names.)
9270 Historical note: prior to release 4.30, Exim would always attempt to find a
9271 host name before running the query, unless the search type was preceded by
9272 &`net-`&. This is no longer the case. For backwards compatibility, &`net-`& is
9273 still recognized for query-style lookups, but its presence or absence has no
9274 effect. (Of course, for single-key lookups, &`net-`& &'is'& important.
9275 See section &<<SECThoslispatsikey>>&.)
9281 .section "Address lists" "SECTaddresslist"
9282 .cindex "list" "address list"
9283 .cindex "address list" "empty item"
9284 .cindex "address list" "patterns"
9285 Address lists contain patterns that are matched against mail addresses. There
9286 is one special case to be considered: the sender address of a bounce message is
9287 always empty. You can test for this by providing an empty item in an address
9288 list. For example, you can set up a router to process bounce messages by
9289 using this option setting:
9293 The presence of the colon creates an empty item. If you do not provide any
9294 data, the list is empty and matches nothing. The empty sender can also be
9295 detected by a regular expression that matches an empty string,
9296 and by a query-style lookup that succeeds when &$sender_address$& is empty.
9298 Non-empty items in an address list can be straightforward email addresses. For
9301 senders = jbc@askone.example : hs@anacreon.example
9303 A certain amount of wildcarding is permitted. If a pattern contains an @
9304 character, but is not a regular expression and does not begin with a
9305 semicolon-terminated lookup type (described below), the local part of the
9306 subject address is compared with the local part of the pattern, which may start
9307 with an asterisk. If the local parts match, the domain is checked in exactly
9308 the same way as for a pattern in a domain list. For example, the domain can be
9309 wildcarded, refer to a named list, or be a lookup:
9311 deny senders = *@*.spamming.site:\
9312 *@+hostile_domains:\
9313 bozo@partial-lsearch;/list/of/dodgy/sites:\
9314 *@dbm;/bad/domains.db
9316 .cindex "local part" "starting with !"
9317 .cindex "address list" "local part starting with !"
9318 If a local part that begins with an exclamation mark is required, it has to be
9319 specified using a regular expression, because otherwise the exclamation mark is
9320 treated as a sign of negation, as is standard in lists.
9322 If a non-empty pattern that is not a regular expression or a lookup does not
9323 contain an @ character, it is matched against the domain part of the subject
9324 address. The only two formats that are recognized this way are a literal
9325 domain, or a domain pattern that starts with *. In both these cases, the effect
9326 is the same as if &`*@`& preceded the pattern. For example:
9328 deny senders = enemy.domain : *.enemy.domain
9331 The following kinds of more complicated address list pattern can match any
9332 address, including the empty address that is characteristic of bounce message
9336 .cindex "regular expressions" "in address list"
9337 .cindex "address list" "regular expression in"
9338 If (after expansion) a pattern starts with &"^"&, a regular expression match is
9339 done against the complete address, with the pattern as the regular expression.
9340 You must take care that backslash and dollar characters are not misinterpreted
9341 as part of the string expansion. The simplest way to do this is to use &`\N`&
9342 to mark that part of the string as non-expandable. For example:
9344 deny senders = \N^.*this.*@example\.com$\N : \
9345 \N^\d{8}.+@spamhaus.example$\N : ...
9347 The &`\N`& sequences are removed by the expansion, so these items do indeed
9348 start with &"^"& by the time they are being interpreted as address patterns.
9351 .cindex "address list" "lookup for complete address"
9352 Complete addresses can be looked up by using a pattern that starts with a
9353 lookup type terminated by a semicolon, followed by the data for the lookup. For
9356 deny senders = cdb;/etc/blocked.senders : \
9357 mysql;select address from blocked where \
9358 address='${quote_mysql:$sender_address}'
9360 Both query-style and single-key lookup types can be used. For a single-key
9361 lookup type, Exim uses the complete address as the key. However, empty keys are
9362 not supported for single-key lookups, so a match against the empty address
9363 always fails. This restriction does not apply to query-style lookups.
9365 Partial matching for single-key lookups (section &<<SECTpartiallookup>>&)
9366 cannot be used, and is ignored if specified, with an entry being written to the
9368 .cindex "*@ with single-key lookup"
9369 However, you can configure lookup defaults, as described in section
9370 &<<SECTdefaultvaluelookups>>&, but this is useful only for the &"*@"& type of
9371 default. For example, with this lookup:
9373 accept senders = lsearch*@;/some/file
9375 the file could contains lines like this:
9377 user1@domain1.example
9380 and for the sender address &'nimrod@jaeger.example'&, the sequence of keys
9383 nimrod@jaeger.example
9387 &*Warning 1*&: Do not include a line keyed by &"*"& in the file, because that
9388 would mean that every address matches, thus rendering the test useless.
9390 &*Warning 2*&: Do not confuse these two kinds of item:
9392 deny recipients = dbm*@;/some/file
9393 deny recipients = *@dbm;/some/file
9395 The first does a whole address lookup, with defaulting, as just described,
9396 because it starts with a lookup type. The second matches the local part and
9397 domain independently, as described in a bullet point below.
9401 The following kinds of address list pattern can match only non-empty addresses.
9402 If the subject address is empty, a match against any of these pattern types
9407 .cindex "@@ with single-key lookup"
9408 .cindex "address list" "@@ lookup type"
9409 .cindex "address list" "split local part and domain"
9410 If a pattern starts with &"@@"& followed by a single-key lookup item
9411 (for example, &`@@lsearch;/some/file`&), the address that is being checked is
9412 split into a local part and a domain. The domain is looked up in the file. If
9413 it is not found, there is no match. If it is found, the data that is looked up
9414 from the file is treated as a colon-separated list of local part patterns, each
9415 of which is matched against the subject local part in turn.
9417 .cindex "asterisk" "in address list"
9418 The lookup may be a partial one, and/or one involving a search for a default
9419 keyed by &"*"& (see section &<<SECTdefaultvaluelookups>>&). The local part
9420 patterns that are looked up can be regular expressions or begin with &"*"&, or
9421 even be further lookups. They may also be independently negated. For example,
9424 deny senders = @@dbm;/etc/reject-by-domain
9426 the data from which the DBM file is built could contain lines like
9428 baddomain.com: !postmaster : *
9430 to reject all senders except &%postmaster%& from that domain.
9432 .cindex "local part" "starting with !"
9433 If a local part that actually begins with an exclamation mark is required, it
9434 has to be specified using a regular expression. In &(lsearch)& files, an entry
9435 may be split over several lines by indenting the second and subsequent lines,
9436 but the separating colon must still be included at line breaks. White space
9437 surrounding the colons is ignored. For example:
9439 aol.com: spammer1 : spammer2 : ^[0-9]+$ :
9442 As in all colon-separated lists in Exim, a colon can be included in an item by
9445 If the last item in the list starts with a right angle-bracket, the remainder
9446 of the item is taken as a new key to look up in order to obtain a continuation
9447 list of local parts. The new key can be any sequence of characters. Thus one
9448 might have entries like
9450 aol.com: spammer1 : spammer 2 : >*
9451 xyz.com: spammer3 : >*
9454 in a file that was searched with &%@@dbm*%&, to specify a match for 8-digit
9455 local parts for all domains, in addition to the specific local parts listed for
9456 each domain. Of course, using this feature costs another lookup each time a
9457 chain is followed, but the effort needed to maintain the data is reduced.
9459 .cindex "loop" "in lookups"
9460 It is possible to construct loops using this facility, and in order to catch
9461 them, the chains may be no more than fifty items long.
9464 The @@<&'lookup'&> style of item can also be used with a query-style
9465 lookup, but in this case, the chaining facility is not available. The lookup
9466 can only return a single list of local parts.
9469 &*Warning*&: There is an important difference between the address list items
9470 in these two examples:
9473 senders = *@+my_list
9475 In the first one, &`my_list`& is a named address list, whereas in the second
9476 example it is a named domain list.
9481 .section "Case of letters in address lists" "SECTcasletadd"
9482 .cindex "case of local parts"
9483 .cindex "address list" "case forcing"
9484 .cindex "case forcing in address lists"
9485 Domains in email addresses are always handled caselessly, but for local parts
9486 case may be significant on some systems (see &%caseful_local_part%& for how
9487 Exim deals with this when routing addresses). However, RFC 2505 (&'Anti-Spam
9488 Recommendations for SMTP MTAs'&) suggests that matching of addresses to
9489 blocking lists should be done in a case-independent manner. Since most address
9490 lists in Exim are used for this kind of control, Exim attempts to do this by
9493 The domain portion of an address is always lowercased before matching it to an
9494 address list. The local part is lowercased by default, and any string
9495 comparisons that take place are done caselessly. This means that the data in
9496 the address list itself, in files included as plain filenames, and in any file
9497 that is looked up using the &"@@"& mechanism, can be in any case. However, the
9498 keys in files that are looked up by a search type other than &(lsearch)& (which
9499 works caselessly) must be in lower case, because these lookups are not
9502 .cindex "&`+caseful`&"
9503 To allow for the possibility of caseful address list matching, if an item in
9504 an address list is the string &"+caseful"&, the original case of the local
9505 part is restored for any comparisons that follow, and string comparisons are no
9506 longer case-independent. This does not affect the domain, which remains in
9507 lower case. However, although independent matches on the domain alone are still
9508 performed caselessly, regular expressions that match against an entire address
9509 become case-sensitive after &"+caseful"& has been seen.
9513 .section "Local part lists" "SECTlocparlis"
9514 .cindex "list" "local part list"
9515 .cindex "local part" "list"
9516 These behave in the same way as domain and host lists, with the following
9519 Case-sensitivity in local part lists is handled in the same way as for address
9520 lists, as just described. The &"+caseful"& item can be used if required. In a
9521 setting of the &%local_parts%& option in a router with &%caseful_local_part%&
9522 set false, the subject is lowercased and the matching is initially
9523 case-insensitive. In this case, &"+caseful"& will restore case-sensitive
9524 matching in the local part list, but not elsewhere in the router. If
9525 &%caseful_local_part%& is set true in a router, matching in the &%local_parts%&
9526 option is case-sensitive from the start.
9528 If a local part list is indirected to a file (see section &<<SECTfilnamlis>>&),
9529 comments are handled in the same way as address lists &-- they are recognized
9530 only if the # is preceded by white space or the start of the line.
9531 Otherwise, local part lists are matched in the same way as domain lists, except
9532 that the special items that refer to the local host (&`@`&, &`@[]`&,
9533 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`&) are not recognized.
9534 Refer to section &<<SECTdomainlist>>& for details of the other available item
9536 .ecindex IIDdohoadli
9541 . ////////////////////////////////////////////////////////////////////////////
9542 . ////////////////////////////////////////////////////////////////////////////
9544 .chapter "String expansions" "CHAPexpand"
9545 .scindex IIDstrexp "expansion" "of strings"
9546 Many strings in Exim's runtime configuration are expanded before use. Some of
9547 them are expanded every time they are used; others are expanded only once.
9549 When a string is being expanded it is copied verbatim from left to right except
9550 .cindex expansion "string concatenation"
9551 when a dollar or backslash character is encountered. A dollar specifies the
9552 start of a portion of the string that is interpreted and replaced as described
9553 below in section &<<SECTexpansionitems>>& onwards. Backslash is used as an
9554 escape character, as described in the following section.
9556 Whether a string is expanded depends upon the context. Usually this is solely
9557 dependent upon the option for which a value is sought; in this documentation,
9558 options for which string expansion is performed are marked with † after
9559 the data type. ACL rules always expand strings. A couple of expansion
9560 conditions do not expand some of the brace-delimited branches, for security
9562 .cindex "tainted data" expansion
9563 .cindex "tainted data" definition
9564 .cindex expansion "tainted data"
9565 and expansion of data deriving from the sender (&"tainted data"&)
9566 is not permitted (including acessing a file using a tainted name).
9568 Common ways of obtaining untainted equivalents of variables with
9570 .cindex "tainted data" "de-tainting"
9571 come down to using the tainted value as a lookup key in a trusted database.
9572 This database could be the filesystem structure,
9573 or the password file,
9574 or accessed via a DBMS.
9575 Specific methods are indexed under &"de-tainting"&.
9579 .section "Literal text in expanded strings" "SECTlittext"
9580 .cindex "expansion" "including literal text"
9581 An uninterpreted dollar can be included in an expanded string by putting a
9582 backslash in front of it. A backslash can be used to prevent any special
9583 character being treated specially in an expansion, including backslash itself.
9584 If the string appears in quotes in the configuration file, two backslashes are
9585 required because the quotes themselves cause interpretation of backslashes when
9586 the string is read in (see section &<<SECTstrings>>&).
9588 .cindex "expansion" "non-expandable substrings"
9589 A portion of the string can specified as non-expandable by placing it between
9590 two occurrences of &`\N`&. This is particularly useful for protecting regular
9591 expressions, which often contain backslashes and dollar signs. For example:
9593 deny senders = \N^\d{8}[a-z]@some\.site\.example$\N
9595 On encountering the first &`\N`&, the expander copies subsequent characters
9596 without interpretation until it reaches the next &`\N`& or the end of the
9601 .section "Character escape sequences in expanded strings" "SECID82"
9602 .cindex "expansion" "escape sequences"
9603 A backslash followed by one of the letters &"n"&, &"r"&, or &"t"& in an
9604 expanded string is recognized as an escape sequence for the character newline,
9605 carriage return, or tab, respectively. A backslash followed by up to three
9606 octal digits is recognized as an octal encoding for a single character, and a
9607 backslash followed by &"x"& and up to two hexadecimal digits is a hexadecimal
9610 These escape sequences are also recognized in quoted strings when they are read
9611 in. Their interpretation in expansions as well is useful for unquoted strings,
9612 and for other cases such as looked-up strings that are then expanded.
9615 .section "Testing string expansions" "SECID83"
9616 .cindex "expansion" "testing"
9617 .cindex "testing" "string expansion"
9619 Many expansions can be tested by calling Exim with the &%-be%& option. This
9620 takes the command arguments, or lines from the standard input if there are no
9621 arguments, runs them through the string expansion code, and writes the results
9622 to the standard output. Variables based on configuration values are set up, but
9623 since no message is being processed, variables such as &$local_part$& have no
9624 value. Nevertheless the &%-be%& option can be useful for checking out file and
9625 database lookups, and the use of expansion operators such as &%sg%&, &%substr%&
9628 Exim gives up its root privilege when it is called with the &%-be%& option, and
9629 instead runs under the uid and gid it was called with, to prevent users from
9630 using &%-be%& for reading files to which they do not have access.
9633 If you want to test expansions that include variables whose values are taken
9634 from a message, there are two other options that can be used. The &%-bem%&
9635 option is like &%-be%& except that it is followed by a filename. The file is
9636 read as a message before doing the test expansions. For example:
9638 exim -bem /tmp/test.message '$h_subject:'
9640 The &%-Mset%& option is used in conjunction with &%-be%& and is followed by an
9641 Exim message identifier. For example:
9643 exim -be -Mset 1GrA8W-0004WS-LQ '$recipients'
9645 This loads the message from Exim's spool before doing the test expansions, and
9646 is therefore restricted to admin users.
9649 .section "Forced expansion failure" "SECTforexpfai"
9650 .cindex "expansion" "forced failure"
9651 A number of expansions that are described in the following section have
9652 alternative &"true"& and &"false"& substrings, enclosed in brace characters
9653 (which are sometimes called &"curly brackets"&). Which of the two strings is
9654 used depends on some condition that is evaluated as part of the expansion. If,
9655 instead of a &"false"& substring, the word &"fail"& is used (not in braces),
9656 the entire string expansion fails in a way that can be detected by the code
9657 that requested the expansion. This is called &"forced expansion failure"&, and
9658 its consequences depend on the circumstances. In some cases it is no different
9659 from any other expansion failure, but in others a different action may be
9660 taken. Such variations are mentioned in the documentation of the option that is
9666 .section "Expansion items" "SECTexpansionitems"
9667 The following items are recognized in expanded strings. White space may be used
9668 between sub-items that are keywords or substrings enclosed in braces inside an
9669 outer set of braces, to improve readability. &*Warning*&: Within braces,
9670 white space is significant.
9673 .vitem &*$*&<&'variable&~name'&>&~or&~&*${*&<&'variable&~name'&>&*}*&
9674 .cindex "expansion" "variables"
9675 Substitute the contents of the named variable, for example:
9680 The second form can be used to separate the name from subsequent alphanumeric
9681 characters. This form (using braces) is available only for variables; it does
9682 &'not'& apply to message headers. The names of the variables are given in
9683 section &<<SECTexpvar>>& below. If the name of a non-existent variable is
9684 given, the expansion fails.
9686 .vitem &*${*&<&'op'&>&*:*&<&'string'&>&*}*&
9687 .cindex "expansion" "operators"
9688 The string is first itself expanded, and then the operation specified by
9689 <&'op'&> is applied to it. For example:
9693 The string starts with the first character after the colon, which may be
9694 leading white space. A list of operators is given in section &<<SECTexpop>>&
9695 below. The operator notation is used for simple expansion items that have just
9696 one argument, because it reduces the number of braces and therefore makes the
9697 string easier to understand.
9699 .vitem &*$bheader_*&<&'header&~name'&>&*:*&&~or&~&*$bh_*&<&'header&~name'&>&*:*&
9700 This item inserts &"basic"& header lines. It is described with the &%header%&
9701 expansion item below.
9704 .vitem "&*${acl{*&<&'name'&>&*}{*&<&'arg'&>&*}...}*&"
9705 .cindex "expansion" "calling an acl"
9706 .cindex "&%acl%&" "call from expansion"
9707 The name and zero to nine argument strings are first expanded separately. The expanded
9708 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
9709 Any unused are made empty. The variable &$acl_narg$& is set to the number of
9710 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
9711 and may use the variables; if another acl expansion is used the values
9712 are restored after it returns. If the ACL sets
9713 a value using a "message =" modifier and returns accept or deny, the value becomes
9714 the result of the expansion.
9715 If no message is set and the ACL returns accept or deny
9716 the expansion result is an empty string.
9717 If the ACL returns defer the result is a forced-fail. Otherwise the expansion fails.
9720 .vitem "&*${authresults{*&<&'authserv-id'&>&*}}*&"
9721 .cindex authentication "results header"
9722 .chindex Authentication-Results:
9723 .cindex authentication "expansion item"
9724 This item returns a string suitable for insertion as an
9725 &'Authentication-Results:'&
9727 The given <&'authserv-id'&> is included in the result; typically this
9728 will be a domain name identifying the system performing the authentications.
9729 Methods that might be present in the result include:
9738 Example use (as an ACL modifier):
9740 add_header = :at_start:${authresults {$primary_hostname}}
9742 This is safe even if no authentication results are available.
9745 .vitem "&*${certextract{*&<&'field'&>&*}{*&<&'certificate'&>&*}&&&
9746 {*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9747 .cindex "expansion" "extracting certificate fields"
9748 .cindex "&%certextract%&" "certificate fields"
9749 .cindex "certificate" "extracting fields"
9750 The <&'certificate'&> must be a variable of type certificate.
9751 The field name is expanded and used to retrieve the relevant field from
9752 the certificate. Supported fields are:
9756 &`subject `& RFC4514 DN
9757 &`issuer `& RFC4514 DN
9762 &`subj_altname `& tagged list
9766 If the field is found,
9767 <&'string2'&> is expanded, and replaces the whole item;
9768 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
9769 variable &$value$& contains the value that has been extracted. Afterwards, it
9770 is restored to any previous value it might have had.
9772 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
9773 key is not found. If {<&'string2'&>} is also omitted, the value that was
9776 Some field names take optional modifiers, appended and separated by commas.
9778 The field selectors marked as "RFC4514" above
9779 output a Distinguished Name string which is
9781 parseable by Exim as a comma-separated tagged list
9782 (the exceptions being elements containing commas).
9783 RDN elements of a single type may be selected by
9784 a modifier of the type label; if so the expansion
9785 result is a list (newline-separated by default).
9786 The separator may be changed by another modifier of
9787 a right angle-bracket followed immediately by the new separator.
9788 Recognised RDN type labels include "CN", "O", "OU" and "DC".
9790 The field selectors marked as "time" above
9791 take an optional modifier of "int"
9792 for which the result is the number of seconds since epoch.
9793 Otherwise the result is a human-readable string
9794 in the timezone selected by the main "timezone" option.
9796 The field selectors marked as "list" above return a list,
9797 newline-separated by default,
9798 (embedded separator characters in elements are doubled).
9799 The separator may be changed by a modifier of
9800 a right angle-bracket followed immediately by the new separator.
9802 The field selectors marked as "tagged" above
9803 prefix each list element with a type string and an equals sign.
9804 Elements of only one type may be selected by a modifier
9805 which is one of "dns", "uri" or "mail";
9806 if so the element tags are omitted.
9808 If not otherwise noted field values are presented in human-readable form.
9810 .vitem "&*${dlfunc{*&<&'file'&>&*}{*&<&'function'&>&*}{*&<&'arg'&>&*}&&&
9811 {*&<&'arg'&>&*}...}*&"
9813 This expansion dynamically loads and then calls a locally-written C function.
9814 This functionality is available only if Exim is compiled with
9818 set in &_Local/Makefile_&. Once loaded, Exim remembers the dynamically loaded
9819 object so that it doesn't reload the same object file in the same Exim process
9820 (but of course Exim does start new processes frequently).
9822 There may be from zero to eight arguments to the function.
9825 a local function that is to be called in this way,
9826 first &_DLFUNC_IMPL_& should be defined,
9827 and second &_local_scan.h_& should be included.
9828 The Exim variables and functions that are defined by that API
9829 are also available for dynamically loaded functions. The function itself
9830 must have the following type:
9832 int dlfunction(uschar **yield, int argc, uschar *argv[])
9834 Where &`uschar`& is a typedef for &`unsigned char`& in &_local_scan.h_&. The
9835 function should return one of the following values:
9837 &`OK`&: Success. The string that is placed in the variable &'yield'& is put
9838 into the expanded string that is being built.
9840 &`FAIL`&: A non-forced expansion failure occurs, with the error message taken
9841 from &'yield'&, if it is set.
9843 &`FAIL_FORCED`&: A forced expansion failure occurs, with the error message
9844 taken from &'yield'& if it is set.
9846 &`ERROR`&: Same as &`FAIL`&, except that a panic log entry is written.
9848 When compiling a function that is to be used in this way with gcc,
9849 you need to add &%-shared%& to the gcc command. Also, in the Exim build-time
9850 configuration, you must add &%-export-dynamic%& to EXTRALIBS.
9853 .vitem "&*${env{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&"
9854 .cindex "expansion" "extracting value from environment"
9855 .cindex "environment" "values from"
9856 The key is first expanded separately, and leading and trailing white space
9858 This is then searched for as a name in the environment.
9859 If a variable is found then its value is placed in &$value$&
9860 and <&'string1'&> is expanded, otherwise <&'string2'&> is expanded.
9862 Instead of {<&'string2'&>} the word &"fail"& (not in curly brackets) can
9863 appear, for example:
9865 ${env{USER}{$value} fail }
9867 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9868 {<&'string1'&>} must be present for &"fail"& to be recognized.
9870 If {<&'string2'&>} is omitted an empty string is substituted on
9872 If {<&'string1'&>} is omitted the search result is substituted on
9875 The environment is adjusted by the &%keep_environment%& and
9876 &%add_environment%& main section options.
9879 .vitem "&*${extract{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9880 {*&<&'string3'&>&*}}*&"
9881 .cindex "expansion" "extracting substrings by key"
9882 .cindex "&%extract%&" "substrings by key"
9883 The key and <&'string1'&> are first expanded separately. Leading and trailing
9884 white space is removed from the key (but not from any of the strings). The key
9885 must not be empty and must not consist entirely of digits.
9886 The expanded <&'string1'&> must be of the form:
9888 <&'key1'&> = <&'value1'&> <&'key2'&> = <&'value2'&> ...
9891 where the equals signs and spaces (but not both) are optional. If any of the
9892 values contain white space, they must be enclosed in double quotes, and any
9893 values that are enclosed in double quotes are subject to escape processing as
9894 described in section &<<SECTstrings>>&. The expanded <&'string1'&> is searched
9895 for the value that corresponds to the key. The search is case-insensitive. If
9896 the key is found, <&'string2'&> is expanded, and replaces the whole item;
9897 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
9898 variable &$value$& contains the value that has been extracted. Afterwards, it
9899 is restored to any previous value it might have had.
9901 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
9902 key is not found. If {<&'string2'&>} is also omitted, the value that was
9903 extracted is used. Thus, for example, these two expansions are identical, and
9906 ${extract{gid}{uid=1984 gid=2001}}
9907 ${extract{gid}{uid=1984 gid=2001}{$value}}
9909 Instead of {<&'string3'&>} the word &"fail"& (not in curly brackets) can
9910 appear, for example:
9912 ${extract{Z}{A=... B=...}{$value} fail }
9914 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9915 {<&'string2'&>} must be present for &"fail"& to be recognized.
9917 .vitem "&*${extract json{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9918 {*&<&'string3'&>&*}}*&" &&&
9919 "&*${extract jsons{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9920 {*&<&'string3'&>&*}}*&"
9921 .cindex "expansion" "extracting from JSON object"
9922 .cindex JSON expansions
9923 The key and <&'string1'&> are first expanded separately. Leading and trailing
9924 white space is removed from the key (but not from any of the strings). The key
9925 must not be empty and must not consist entirely of digits.
9926 The expanded <&'string1'&> must be of the form:
9928 { <&'"key1"'&> : <&'value1'&> , <&'"key2"'&> , <&'value2'&> ... }
9931 The braces, commas and colons, and the quoting of the member name are required;
9932 the spaces are optional.
9933 Matching of the key against the member names is done case-sensitively.
9934 For the &"json"& variant,
9935 if a returned value is a JSON string, it retains its leading and
9937 For the &"jsons"& variant, which is intended for use with JSON strings, the
9938 leading and trailing quotes are removed from the returned value.
9939 . XXX should be a UTF-8 compare
9941 The results of matching are handled as above.
9944 .vitem "&*${extract{*&<&'number'&>&*}{*&<&'separators'&>&*}&&&
9945 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9946 .cindex "expansion" "extracting substrings by number"
9947 .cindex "&%extract%&" "substrings by number"
9948 The <&'number'&> argument must consist entirely of decimal digits,
9949 apart from leading and trailing white space, which is ignored.
9950 This is what distinguishes this form of &%extract%& from the previous kind. It
9951 behaves in the same way, except that, instead of extracting a named field, it
9952 extracts from <&'string1'&> the field whose number is given as the first
9953 argument. You can use &$value$& in <&'string2'&> or &`fail`& instead of
9954 <&'string3'&> as before.
9956 The fields in the string are separated by any one of the characters in the
9957 separator string. These may include space or tab characters.
9958 The first field is numbered one. If the number is negative, the fields are
9959 counted from the end of the string, with the rightmost one numbered -1. If the
9960 number given is zero, the entire string is returned. If the modulus of the
9961 number is greater than the number of fields in the string, the result is the
9962 expansion of <&'string3'&>, or the empty string if <&'string3'&> is not
9963 provided. For example:
9965 ${extract{2}{:}{x:42:99:& Mailer::/bin/bash}}
9969 ${extract{-4}{:}{x:42:99:& Mailer::/bin/bash}}
9971 yields &"99"&. Two successive separators mean that the field between them is
9972 empty (for example, the fifth field above).
9975 .vitem "&*${extract json {*&<&'number'&>&*}}&&&
9976 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&" &&&
9977 "&*${extract jsons{*&<&'number'&>&*}}&&&
9978 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9979 .cindex "expansion" "extracting from JSON array"
9980 .cindex JSON expansions
9981 The <&'number'&> argument must consist entirely of decimal digits,
9982 apart from leading and trailing white space, which is ignored.
9984 Field selection and result handling is as above;
9985 there is no choice of field separator.
9986 For the &"json"& variant,
9987 if a returned value is a JSON string, it retains its leading and
9989 For the &"jsons"& variant, which is intended for use with JSON strings, the
9990 leading and trailing quotes are removed from the returned value.
9993 .vitem &*${filter{*&<&'string'&>&*}{*&<&'condition'&>&*}}*&
9994 .cindex "list" "selecting by condition"
9995 .cindex "expansion" "selecting from list by condition"
9997 After expansion, <&'string'&> is interpreted as a list, colon-separated by
9998 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10000 in this list, its value is place in &$item$&, and then the condition is
10001 evaluated. If the condition is true, &$item$& is added to the output as an
10002 item in a new list; if the condition is false, the item is discarded. The
10003 separator used for the output list is the same as the one used for the
10004 input, but a separator setting is not included in the output. For example:
10006 ${filter{a:b:c}{!eq{$item}{b}}}
10008 yields &`a:c`&. At the end of the expansion, the value of &$item$& is restored
10009 to what it was before. See also the &%map%& and &%reduce%& expansion items.
10012 .vitem &*${hash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10013 .cindex "hash function" "textual"
10014 .cindex "expansion" "textual hash"
10015 This is a textual hashing function, and was the first to be implemented in
10016 early versions of Exim. In current releases, there are other hashing functions
10017 (numeric, MD5, and SHA-1), which are described below.
10019 The first two strings, after expansion, must be numbers. Call them <&'m'&> and
10020 <&'n'&>. If you are using fixed values for these numbers, that is, if
10021 <&'string1'&> and <&'string2'&> do not change when they are expanded, you can
10022 use the simpler operator notation that avoids some of the braces:
10024 ${hash_<n>_<m>:<string>}
10026 The second number is optional (in both notations). If <&'n'&> is greater than
10027 or equal to the length of the string, the expansion item returns the string.
10028 Otherwise it computes a new string of length <&'n'&> by applying a hashing
10029 function to the string. The new string consists of characters taken from the
10030 first <&'m'&> characters of the string
10032 abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQWRSTUVWXYZ0123456789
10034 If <&'m'&> is not present the value 26 is used, so that only lower case
10035 letters appear. For example:
10037 &`$hash{3}{monty}} `& yields &`jmg`&
10038 &`$hash{5}{monty}} `& yields &`monty`&
10039 &`$hash{4}{62}{monty python}}`& yields &`fbWx`&
10042 .vitem "&*$header_*&<&'header&~name'&>&*:*&&~or&~&&&
10043 &*$h_*&<&'header&~name'&>&*:*&" &&&
10044 "&*$bheader_*&<&'header&~name'&>&*:*&&~or&~&&&
10045 &*$bh_*&<&'header&~name'&>&*:*&" &&&
10046 "&*$lheader_*&<&'header&~name'&>&*:*&&~or&~&&&
10047 &*$lh_*&<&'header&~name'&>&*:*&" &&&
10048 "&*$rheader_*&<&'header&~name'&>&*:*&&~or&~&&&
10049 &*$rh_*&<&'header&~name'&>&*:*&"
10050 .cindex "expansion" "header insertion"
10051 .vindex "&$header_$&"
10052 .vindex "&$bheader_$&"
10053 .vindex "&$lheader_$&"
10054 .vindex "&$rheader_$&"
10055 .cindex "header lines" "in expansion strings"
10056 .cindex "header lines" "character sets"
10057 .cindex "header lines" "decoding"
10058 Substitute the contents of the named message header line, for example
10062 The newline that terminates a header line is not included in the expansion, but
10063 internal newlines (caused by splitting the header line over several physical
10064 lines) may be present.
10066 The difference between the four pairs of expansions is in the way
10067 the data in the header line is interpreted.
10070 .cindex "white space" "in header lines"
10071 &%rheader%& gives the original &"raw"& content of the header line, with no
10072 processing at all, and without the removal of leading and trailing white space.
10075 .cindex "list" "of header lines"
10076 &%lheader%& gives a colon-separated list, one element per header when there
10077 are multiple headers with a given name.
10078 Any embedded colon characters within an element are doubled, so normal Exim
10079 list-processing facilities can be used.
10080 The terminating newline of each element is removed; in other respects
10081 the content is &"raw"&.
10084 .cindex "base64 encoding" "in header lines"
10085 &%bheader%& removes leading and trailing white space, and then decodes base64
10086 or quoted-printable MIME &"words"& within the header text, but does no
10087 character set translation. If decoding of what looks superficially like a MIME
10088 &"word"& fails, the raw string is returned. If decoding
10089 .cindex "binary zero" "in header line"
10090 produces a binary zero character, it is replaced by a question mark &-- this is
10091 what Exim does for binary zeros that are actually received in header lines.
10094 &%header%& tries to translate the string as decoded by &%bheader%& to a
10095 standard character set. This is an attempt to produce the same string as would
10096 be displayed on a user's MUA. If translation fails, the &%bheader%& string is
10097 returned. Translation is attempted only on operating systems that support the
10098 &[iconv()]& function. This is indicated by the compile-time macro HAVE_ICONV in
10099 a system Makefile or in &_Local/Makefile_&.
10102 In a filter file, the target character set for &%header%& can be specified by a
10103 command of the following form:
10105 headers charset "UTF-8"
10107 This command affects all references to &$h_$& (or &$header_$&) expansions in
10108 subsequently obeyed filter commands. In the absence of this command, the target
10109 character set in a filter is taken from the setting of the &%headers_charset%&
10110 option in the runtime configuration. The value of this option defaults to the
10111 value of HEADERS_CHARSET in &_Local/Makefile_&. The ultimate default is
10114 Header names follow the syntax of RFC 2822, which states that they may contain
10115 any printing characters except space and colon. Consequently, curly brackets
10116 &'do not'& terminate header names, and should not be used to enclose them as
10117 if they were variables. Attempting to do so causes a syntax error.
10119 Only header lines that are common to all copies of a message are visible to
10120 this mechanism. These are the original header lines that are received with the
10121 message, and any that are added by an ACL statement or by a system
10122 filter. Header lines that are added to a particular copy of a message by a
10123 router or transport are not accessible.
10125 For incoming SMTP messages, no header lines are visible in
10126 ACLs that are obeyed before the data phase completes,
10127 because the header structure is not set up until the message is received.
10128 They are visible in DKIM, PRDR and DATA ACLs.
10129 Header lines that are added in a RCPT ACL (for example)
10130 are saved until the message's incoming header lines are available, at which
10131 point they are added.
10132 When any of the above ACLs are
10133 running, however, header lines added by earlier ACLs are visible.
10135 Upper case and lower case letters are synonymous in header names. If the
10136 following character is white space, the terminating colon may be omitted, but
10137 this is not recommended, because you may then forget it when it is needed. When
10138 white space terminates the header name, this white space is included in the
10139 expanded string. If the message does not contain the given header, the
10140 expansion item is replaced by an empty string. (See the &%def%& condition in
10141 section &<<SECTexpcond>>& for a means of testing for the existence of a
10144 If there is more than one header with the same name, they are all concatenated
10145 to form the substitution string, up to a maximum length of 64K. Unless
10146 &%rheader%& is being used, leading and trailing white space is removed from
10147 each header before concatenation, and a completely empty header is ignored. A
10148 newline character is then inserted between non-empty headers, but there is no
10149 newline at the very end. For the &%header%& and &%bheader%& expansion, for
10150 those headers that contain lists of addresses, a comma is also inserted at the
10151 junctions between headers. This does not happen for the &%rheader%& expansion.
10153 .cindex "tainted data" "message headers"
10154 When the headers are from an incoming message,
10155 the result of expanding any of these variables is tainted.
10158 .vitem &*${hmac{*&<&'hashname'&>&*}{*&<&'secret'&>&*}{*&<&'string'&>&*}}*&
10159 .cindex "expansion" "hmac hashing"
10161 This function uses cryptographic hashing (either MD5 or SHA-1) to convert a
10162 shared secret and some text into a message authentication code, as specified in
10163 RFC 2104. This differs from &`${md5:secret_text...}`& or
10164 &`${sha1:secret_text...}`& in that the hmac step adds a signature to the
10165 cryptographic hash, allowing for authentication that is not possible with MD5
10166 or SHA-1 alone. The hash name must expand to either &`md5`& or &`sha1`& at
10167 present. For example:
10169 ${hmac{md5}{somesecret}{$primary_hostname $tod_log}}
10171 For the hostname &'mail.example.com'& and time 2002-10-17 11:30:59, this
10174 dd97e3ba5d1a61b5006108f8c8252953
10176 As an example of how this might be used, you might put in the main part of
10177 an Exim configuration:
10179 SPAMSCAN_SECRET=cohgheeLei2thahw
10181 In a router or a transport you could then have:
10184 X-Spam-Scanned: ${primary_hostname} ${message_exim_id} \
10185 ${hmac{md5}{SPAMSCAN_SECRET}\
10186 {${primary_hostname},${message_exim_id},$h_message-id:}}
10188 Then given a message, you can check where it was scanned by looking at the
10189 &'X-Spam-Scanned:'& header line. If you know the secret, you can check that
10190 this header line is authentic by recomputing the authentication code from the
10191 host name, message ID and the &'Message-id:'& header line. This can be done
10192 using Exim's &%-be%& option, or by other means, for example, by using the
10193 &'hmac_md5_hex()'& function in Perl.
10196 .vitem &*${if&~*&<&'condition'&>&*&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
10197 .cindex "expansion" "conditional"
10198 .cindex "&%if%&, expansion item"
10199 If <&'condition'&> is true, <&'string1'&> is expanded and replaces the whole
10200 item; otherwise <&'string2'&> is used. The available conditions are described
10201 in section &<<SECTexpcond>>& below. For example:
10203 ${if eq {$local_part}{postmaster} {yes}{no} }
10205 The second string need not be present; if it is not and the condition is not
10206 true, the item is replaced with nothing. Alternatively, the word &"fail"& may
10207 be present instead of the second string (without any curly brackets). In this
10208 case, the expansion is forced to fail if the condition is not true (see section
10209 &<<SECTforexpfai>>&).
10211 If both strings are omitted, the result is the string &`true`& if the condition
10212 is true, and the empty string if the condition is false. This makes it less
10213 cumbersome to write custom ACL and router conditions. For example, instead of
10215 condition = ${if >{$acl_m4}{3}{true}{false}}
10219 condition = ${if >{$acl_m4}{3}}
10224 .vitem &*${imapfolder{*&<&'foldername'&>&*}}*&
10225 .cindex expansion "imap folder"
10226 .cindex "&%imapfolder%& expansion item"
10227 This item converts a (possibly multilevel, or with non-ASCII characters)
10228 folder specification to a Maildir name for filesystem use.
10229 For information on internationalisation support see &<<SECTi18nMDA>>&.
10233 .vitem &*${length{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
10234 .cindex "expansion" "string truncation"
10235 .cindex "&%length%& expansion item"
10236 The &%length%& item is used to extract the initial portion of a string. Both
10237 strings are expanded, and the first one must yield a number, <&'n'&>, say. If
10238 you are using a fixed value for the number, that is, if <&'string1'&> does not
10239 change when expanded, you can use the simpler operator notation that avoids
10240 some of the braces:
10242 ${length_<n>:<string>}
10244 The result of this item is either the first <&'n'&> bytes or the whole
10245 of <&'string2'&>, whichever is the shorter. Do not confuse &%length%& with
10246 &%strlen%&, which gives the length of a string.
10247 All measurement is done in bytes and is not UTF-8 aware.
10250 .vitem "&*${listextract{*&<&'number'&>&*}&&&
10251 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
10252 .cindex "expansion" "extracting list elements by number"
10253 .cindex "&%listextract%&" "extract list elements by number"
10254 .cindex "list" "extracting elements by number"
10255 The <&'number'&> argument must consist entirely of decimal digits,
10256 apart from an optional leading minus,
10257 and leading and trailing white space (which is ignored).
10259 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
10260 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10262 The first field of the list is numbered one.
10263 If the number is negative, the fields are
10264 counted from the end of the list, with the rightmost one numbered -1.
10265 The numbered element of the list is extracted and placed in &$value$&,
10266 then <&'string2'&> is expanded as the result.
10268 If the modulus of the
10269 number is zero or greater than the number of fields in the string,
10270 the result is the expansion of <&'string3'&>.
10274 ${listextract{2}{x:42:99}}
10278 ${listextract{-3}{<, x,42,99,& Mailer,,/bin/bash}{result: $value}}
10280 yields &"result: 42"&.
10282 If {<&'string3'&>} is omitted, an empty string is used for string3.
10283 If {<&'string2'&>} is also omitted, the value that was
10285 You can use &`fail`& instead of {<&'string3'&>} as in a string extract.
10288 .vitem &*${listquote{*&<&'separator'&>&*}{*&<&'string'&>&*}}*&
10289 .cindex quoting "for list"
10290 .cindex list quoting
10291 This item doubles any occurrence of the separator character
10292 in the given string.
10293 An empty string is replaced with a single space.
10294 This converts the string into a safe form for use as a list element,
10295 in a list using the given separator.
10298 .vitem "&*${lookup&~{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&&
10299 {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&" &&&
10300 "&*${lookup&~*&<&'search&~type'&>&*&~{*&<&'query'&>&*}&~&&&
10301 {*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
10302 .cindex "expansion" "lookup in"
10303 .cindex "file" "lookups"
10304 .cindex "lookup" "in expanded string"
10305 The two forms of lookup item specify data lookups in files and databases, as
10306 discussed in chapter &<<CHAPfdlookup>>&. The first form is used for single-key
10307 lookups, and the second is used for query-style lookups. The <&'key'&>,
10308 <&'file'&>, and <&'query'&> strings are expanded before use.
10310 If there is any white space in a lookup item which is part of a filter command,
10311 a retry or rewrite rule, a routing rule for the &(manualroute)& router, or any
10312 other place where white space is significant, the lookup item must be enclosed
10313 in double quotes. The use of data lookups in users' filter files may be locked
10314 out by the system administrator.
10316 .vindex "&$value$&"
10317 If the lookup succeeds, <&'string1'&> is expanded and replaces the entire item.
10318 During its expansion, the variable &$value$& contains the data returned by the
10319 lookup. Afterwards it reverts to the value it had previously (at the outer
10320 level it is empty). If the lookup fails, <&'string2'&> is expanded and replaces
10321 the entire item. If {<&'string2'&>} is omitted, the replacement is the empty
10322 string on failure. If <&'string2'&> is provided, it can itself be a nested
10323 lookup, thus providing a mechanism for looking up a default value when the
10324 original lookup fails.
10326 If a nested lookup is used as part of <&'string1'&>, &$value$& contains the
10327 data for the outer lookup while the parameters of the second lookup are
10328 expanded, and also while <&'string2'&> of the second lookup is expanded, should
10329 the second lookup fail. Instead of {<&'string2'&>} the word &"fail"& can
10330 appear, and in this case, if the lookup fails, the entire expansion is forced
10331 to fail (see section &<<SECTforexpfai>>&). If both {<&'string1'&>} and
10332 {<&'string2'&>} are omitted, the result is the looked up value in the case of a
10333 successful lookup, and nothing in the case of failure.
10335 For single-key lookups, the string &"partial"& is permitted to precede the
10336 search type in order to do partial matching, and * or *@ may follow a search
10337 type to request default lookups if the key does not match (see sections
10338 &<<SECTdefaultvaluelookups>>& and &<<SECTpartiallookup>>& for details).
10340 .cindex "numerical variables (&$1$& &$2$& etc)" "in lookup expansion"
10341 If a partial search is used, the variables &$1$& and &$2$& contain the wild
10342 and non-wild parts of the key during the expansion of the replacement text.
10343 They return to their previous values at the end of the lookup item.
10345 This example looks up the postmaster alias in the conventional alias file:
10347 ${lookup {postmaster} lsearch {/etc/aliases} {$value}}
10349 This example uses NIS+ to look up the full name of the user corresponding to
10350 the local part of an address, forcing the expansion to fail if it is not found:
10352 ${lookup nisplus {[name=$local_part],passwd.org_dir:gcos} \
10357 .vitem &*${map{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
10358 .cindex "expansion" "list creation"
10360 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
10361 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10363 in this list, its value is place in &$item$&, and then <&'string2'&> is
10364 expanded and added to the output as an item in a new list. The separator used
10365 for the output list is the same as the one used for the input, but a separator
10366 setting is not included in the output. For example:
10368 ${map{a:b:c}{[$item]}} ${map{<- x-y-z}{($item)}}
10370 expands to &`[a]:[b]:[c] (x)-(y)-(z)`&. At the end of the expansion, the
10371 value of &$item$& is restored to what it was before. See also the &%filter%&
10372 and &%reduce%& expansion items.
10374 .vitem &*${nhash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10375 .cindex "expansion" "numeric hash"
10376 .cindex "hash function" "numeric"
10377 The three strings are expanded; the first two must yield numbers. Call them
10378 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
10379 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
10380 can use the simpler operator notation that avoids some of the braces:
10382 ${nhash_<n>_<m>:<string>}
10384 The second number is optional (in both notations). If there is only one number,
10385 the result is a number in the range 0&--<&'n'&>-1. Otherwise, the string is
10386 processed by a div/mod hash function that returns two numbers, separated by a
10387 slash, in the ranges 0 to <&'n'&>-1 and 0 to <&'m'&>-1, respectively. For
10390 ${nhash{8}{64}{supercalifragilisticexpialidocious}}
10392 returns the string &"6/33"&.
10396 .vitem &*${perl{*&<&'subroutine'&>&*}{*&<&'arg'&>&*}{*&<&'arg'&>&*}...}*&
10397 .cindex "Perl" "use in expanded string"
10398 .cindex "expansion" "calling Perl from"
10399 This item is available only if Exim has been built to include an embedded Perl
10400 interpreter. The subroutine name and the arguments are first separately
10401 expanded, and then the Perl subroutine is called with those arguments. No
10402 additional arguments need be given; the maximum number permitted, including the
10403 name of the subroutine, is nine.
10405 The return value of the subroutine is inserted into the expanded string, unless
10406 the return value is &%undef%&. In that case, the entire expansion is
10407 forced to fail, in the same way as an explicit &"fail"& on a lookup item
10408 does (see section &<<SECTforexpfai>>&). Whatever you return is evaluated
10409 in a scalar context, thus the return value is a scalar. For example, if you
10410 return a Perl vector, the return value is the size of the vector,
10413 If the subroutine exits by calling Perl's &%die%& function, the expansion fails
10414 with the error message that was passed to &%die%&. More details of the embedded
10415 Perl facility are given in chapter &<<CHAPperl>>&.
10417 The &(redirect)& router has an option called &%forbid_filter_perl%& which locks
10418 out the use of this expansion item in filter files.
10421 .vitem &*${prvs{*&<&'address'&>&*}{*&<&'secret'&>&*}{*&<&'keynumber'&>&*}}*&
10422 .cindex "&%prvs%& expansion item"
10423 The first argument is a complete email address and the second is secret
10424 keystring. The third argument, specifying a key number, is optional. If absent,
10425 it defaults to 0. The result of the expansion is a prvs-signed email address,
10426 to be typically used with the &%return_path%& option on an &(smtp)& transport
10427 as part of a bounce address tag validation (BATV) scheme. For more discussion
10428 and an example, see section &<<SECTverifyPRVS>>&.
10430 .vitem "&*${prvscheck{*&<&'address'&>&*}{*&<&'secret'&>&*}&&&
10431 {*&<&'string'&>&*}}*&"
10432 .cindex "&%prvscheck%& expansion item"
10433 This expansion item is the complement of the &%prvs%& item. It is used for
10434 checking prvs-signed addresses. If the expansion of the first argument does not
10435 yield a syntactically valid prvs-signed address, the whole item expands to the
10436 empty string. When the first argument does expand to a syntactically valid
10437 prvs-signed address, the second argument is expanded, with the prvs-decoded
10438 version of the address and the key number extracted from the address in the
10439 variables &$prvscheck_address$& and &$prvscheck_keynum$&, respectively.
10441 These two variables can be used in the expansion of the second argument to
10442 retrieve the secret. The validity of the prvs-signed address is then checked
10443 against the secret. The result is stored in the variable &$prvscheck_result$&,
10444 which is empty for failure or &"1"& for success.
10446 The third argument is optional; if it is missing, it defaults to an empty
10447 string. This argument is now expanded. If the result is an empty string, the
10448 result of the expansion is the decoded version of the address. This is the case
10449 whether or not the signature was valid. Otherwise, the result of the expansion
10450 is the expansion of the third argument.
10452 All three variables can be used in the expansion of the third argument.
10453 However, once the expansion is complete, only &$prvscheck_result$& remains set.
10454 For more discussion and an example, see section &<<SECTverifyPRVS>>&.
10456 .vitem &*${readfile{*&<&'file&~name'&>&*}{*&<&'eol&~string'&>&*}}*&
10457 .cindex "expansion" "inserting an entire file"
10458 .cindex "file" "inserting into expansion"
10459 .cindex "&%readfile%& expansion item"
10460 The filename and end-of-line (eol) string are first expanded separately. The file is
10461 then read, and its contents replace the entire item. All newline characters in
10462 the file are replaced by the end-of-line string if it is present. Otherwise,
10463 newlines are left in the string.
10464 String expansion is not applied to the contents of the file. If you want this,
10465 you must wrap the item in an &%expand%& operator. If the file cannot be read,
10466 the string expansion fails.
10468 The &(redirect)& router has an option called &%forbid_filter_readfile%& which
10469 locks out the use of this expansion item in filter files.
10473 .vitem "&*${readsocket{*&<&'name'&>&*}{*&<&'request'&>&*}&&&
10474 {*&<&'options'&>&*}{*&<&'eol&~string'&>&*}{*&<&'fail&~string'&>&*}}*&"
10475 .cindex "expansion" "inserting from a socket"
10476 .cindex "socket, use of in expansion"
10477 .cindex "&%readsocket%& expansion item"
10478 This item inserts data from a Unix domain or TCP socket into the expanded
10479 string. The minimal way of using it uses just two arguments, as in these
10482 ${readsocket{/socket/name}{request string}}
10483 ${readsocket{inet:some.host:1234}{request string}}
10485 For a Unix domain socket, the first substring must be the path to the socket.
10486 For an Internet socket, the first substring must contain &`inet:`& followed by
10487 a host name or IP address, followed by a colon and a port, which can be a
10488 number or the name of a TCP port in &_/etc/services_&. An IP address may
10489 optionally be enclosed in square brackets. This is best for IPv6 addresses. For
10492 ${readsocket{inet:[::1]:1234}{request string}}
10494 Only a single host name may be given, but if looking it up yields more than
10495 one IP address, they are each tried in turn until a connection is made. For
10496 both kinds of socket, Exim makes a connection, writes the request string
10497 (unless it is an empty string; no terminating NUL is ever sent)
10498 and reads from the socket until an end-of-file
10499 is read. A timeout of 5 seconds is applied. Additional, optional arguments
10500 extend what can be done. Firstly, you can vary the timeout. For example:
10502 ${readsocket{/socket/name}{request string}{3s}}
10505 The third argument is a list of options, of which the first element is the timeout
10506 and must be present if any options are given.
10507 Further elements are options of form &'name=value'&.
10510 ${readsocket{/socket/name}{request string}{3s:shutdown=no}}
10513 The following option names are recognised:
10516 Defines if the result data can be cached for use by a later identical
10517 request in the same process.
10518 Values are &"yes"& or &"no"& (the default).
10519 If not, all cached results for this connection specification
10520 will be invalidated.
10524 Defines whether or not a write-shutdown is done on the connection after
10525 sending the request. Values are &"yes"& (the default) or &"no"&
10526 (preferred, eg. by some webservers).
10530 Controls the use of TLS on the connection.
10531 Values are &"yes"& or &"no"& (the default).
10532 If it is enabled, a shutdown as described above is never done.
10536 A fourth argument allows you to change any newlines that are in the data
10537 that is read, in the same way as for &%readfile%& (see above). This example
10538 turns them into spaces:
10540 ${readsocket{inet:127.0.0.1:3294}{request string}{3s}{ }}
10542 As with all expansions, the substrings are expanded before the processing
10543 happens. Errors in these sub-expansions cause the expansion to fail. In
10544 addition, the following errors can occur:
10547 Failure to create a socket file descriptor;
10549 Failure to connect the socket;
10551 Failure to write the request string;
10553 Timeout on reading from the socket.
10556 By default, any of these errors causes the expansion to fail. However, if
10557 you supply a fifth substring, it is expanded and used when any of the above
10558 errors occurs. For example:
10560 ${readsocket{/socket/name}{request string}{3s}{\n}\
10563 You can test for the existence of a Unix domain socket by wrapping this
10564 expansion in &`${if exists`&, but there is a race condition between that test
10565 and the actual opening of the socket, so it is safer to use the fifth argument
10566 if you want to be absolutely sure of avoiding an expansion error for a
10567 non-existent Unix domain socket, or a failure to connect to an Internet socket.
10569 The &(redirect)& router has an option called &%forbid_filter_readsocket%& which
10570 locks out the use of this expansion item in filter files.
10573 .vitem &*${reduce{*&<&'string1'&>}{<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10574 .cindex "expansion" "reducing a list to a scalar"
10575 .cindex "list" "reducing to a scalar"
10576 .vindex "&$value$&"
10578 This operation reduces a list to a single, scalar string. After expansion,
10579 <&'string1'&> is interpreted as a list, colon-separated by default, but the
10580 separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10581 Then <&'string2'&> is expanded and
10582 assigned to the &$value$& variable. After this, each item in the <&'string1'&>
10583 list is assigned to &$item$&, in turn, and <&'string3'&> is expanded for each of
10584 them. The result of that expansion is assigned to &$value$& before the next
10585 iteration. When the end of the list is reached, the final value of &$value$& is
10586 added to the expansion output. The &%reduce%& expansion item can be used in a
10587 number of ways. For example, to add up a list of numbers:
10589 ${reduce {<, 1,2,3}{0}{${eval:$value+$item}}}
10591 The result of that expansion would be &`6`&. The maximum of a list of numbers
10594 ${reduce {3:0:9:4:6}{0}{${if >{$item}{$value}{$item}{$value}}}}
10596 At the end of a &*reduce*& expansion, the values of &$item$& and &$value$& are
10597 restored to what they were before. See also the &%filter%& and &%map%&
10600 .vitem &*$rheader_*&<&'header&~name'&>&*:*&&~or&~&*$rh_*&<&'header&~name'&>&*:*&
10601 This item inserts &"raw"& header lines. It is described with the &%header%&
10602 expansion item in section &<<SECTexpansionitems>>& above.
10604 .vitem "&*${run <&'options'&> {*&<&'command&~arg&~list'&>&*}{*&<&'string1'&>&*}&&&
10605 {*&<&'string2'&>&*}}*&"
10606 .cindex "expansion" "running a command"
10607 .cindex "&%run%& expansion item"
10608 This item runs an external command, as a subprocess.
10609 One option is supported after the word &'run'&, comma-separated.
10611 If the option &'preexpand'& is not used,
10612 the command string is split into individual arguments by spaces
10613 and then each argument is expanded.
10614 Then the command is run
10615 in a separate process, but under the same uid and gid. As in other command
10616 executions from Exim, a shell is not used by default. If the command requires
10617 a shell, you must explicitly code it.
10618 The command name may not be tainted, but the remaining arguments can be.
10620 &*Note*&: if tainted arguments are used, they are supplied by a
10621 potential attacker;
10622 a careful assessment for security vulnerabilities should be done.
10624 If the option &'preexpand'& is used,
10625 the command and its arguments are first expanded as one string. The result is
10626 split apart into individual arguments by spaces, and then the command is run
10628 Since the arguments are split by spaces, when there is a variable expansion
10629 which has an empty result, it will cause the situation that the argument will
10630 simply be omitted when the program is actually executed by Exim. If the
10631 script/program requires a specific number of arguments and the expanded
10632 variable could possibly result in this empty expansion, the variable must be
10633 quoted. This is more difficult if the expanded variable itself could result
10634 in a string containing quotes, because it would interfere with the quotes
10635 around the command arguments. A possible guard against this is to wrap the
10636 variable in the &%sg%& operator to change any quote marks to some other
10638 Neither the command nor any argument may be tainted.
10640 The standard input for the command exists, but is empty. The standard output
10641 and standard error are set to the same file descriptor.
10642 .cindex "return code" "from &%run%& expansion"
10643 .vindex "&$value$&"
10644 If the command succeeds (gives a zero return code) <&'string1'&> is expanded
10645 and replaces the entire item; during this expansion, the standard output/error
10646 from the command is in the variable &$value$&. If the command fails,
10647 <&'string2'&>, if present, is expanded and used. Once again, during the
10648 expansion, the standard output/error from the command is in the variable
10651 If <&'string2'&> is absent, the result is empty. Alternatively, <&'string2'&>
10652 can be the word &"fail"& (not in braces) to force expansion failure if the
10653 command does not succeed. If both strings are omitted, the result is contents
10654 of the standard output/error on success, and nothing on failure.
10656 .vindex "&$run_in_acl$&"
10657 The standard output/error of the command is put in the variable &$value$&.
10658 In this ACL example, the output of a command is logged for the admin to
10661 warn condition = ${run{/usr/bin/id}{yes}{no}}
10662 log_message = Output of id: $value
10664 If the command requires shell idioms, such as the > redirect operator, the
10665 shell must be invoked directly, such as with:
10667 ${run{/bin/bash -c "/usr/bin/id >/tmp/id"}{yes}{yes}}
10670 .vindex "&$runrc$&"
10671 The return code from the command is put in the variable &$runrc$&, and this
10672 remains set afterwards, so in a filter file you can do things like this:
10674 if "${run{x y z}{}}$runrc" is 1 then ...
10675 elif $runrc is 2 then ...
10679 If execution of the command fails (for example, the command does not exist),
10680 the return code is 127 &-- the same code that shells use for non-existent
10683 &*Warning*&: In a router or transport, you cannot assume the order in which
10684 option values are expanded, except for those preconditions whose order of
10685 testing is documented. Therefore, you cannot reliably expect to set &$runrc$&
10686 by the expansion of one option, and use it in another.
10688 The &(redirect)& router has an option called &%forbid_filter_run%& which locks
10689 out the use of this expansion item in filter files.
10692 .vitem &*${sg{*&<&'subject'&>&*}{*&<&'regex'&>&*}{*&<&'replacement'&>&*}}*&
10693 .cindex "expansion" "string substitution"
10694 .cindex "&%sg%& expansion item"
10695 This item works like Perl's substitution operator (s) with the global (/g)
10696 option; hence its name. However, unlike the Perl equivalent, Exim does not
10697 modify the subject string; instead it returns the modified string for insertion
10698 into the overall expansion. The item takes three arguments: the subject string,
10699 a regular expression, and a substitution string. For example:
10701 ${sg{abcdefabcdef}{abc}{xyz}}
10703 yields &"xyzdefxyzdef"&. Because all three arguments are expanded before use,
10704 if any $, } or \ characters are required in the regular expression or in the
10705 substitution string, they have to be escaped. For example:
10707 ${sg{abcdef}{^(...)(...)\$}{\$2\$1}}
10709 yields &"defabc"&, and
10711 ${sg{1=A 4=D 3=C}{\N(\d+)=\N}{K\$1=}}
10713 yields &"K1=A K4=D K3=C"&. Note the use of &`\N`& to protect the contents of
10714 the regular expression from string expansion.
10716 The regular expression is compiled in 8-bit mode, working against bytes
10717 rather than any Unicode-aware character handling.
10720 .vitem &*${sort{*&<&'string'&>&*}{*&<&'comparator'&>&*}{*&<&'extractor'&>&*}}*&
10721 .cindex sorting "a list"
10722 .cindex list sorting
10723 .cindex expansion "list sorting"
10724 After expansion, <&'string'&> is interpreted as a list, colon-separated by
10725 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10726 The <&'comparator'&> argument is interpreted as the operator
10727 of a two-argument expansion condition.
10728 The numeric operators plus ge, gt, le, lt (and ~i variants) are supported.
10729 The comparison should return true when applied to two values
10730 if the first value should sort before the second value.
10731 The <&'extractor'&> expansion is applied repeatedly to elements of the list,
10732 the element being placed in &$item$&,
10733 to give values for comparison.
10735 The item result is a sorted list,
10736 with the original list separator,
10737 of the list elements (in full) of the original.
10741 ${sort{3:2:1:4}{<}{$item}}
10743 sorts a list of numbers, and
10745 ${sort {${lookup dnsdb{>:,,mx=example.com}}} {<} {${listextract{1}{<,$item}}}}
10747 will sort an MX lookup into priority order.
10751 .vitem &*${srs_encode&~{*&<&'secret'&>&*}{*&<&'return&~path'&>&*}{*&<&'original&~domain'&>&*}}*&
10752 SRS encoding. See SECT &<<SECTSRS>>& for details.
10756 .vitem &*${substr{*&<&'start'&>&*}{*&<&'len'&>&*}{*&<&'subject'&>&*}}*&
10757 .cindex "&%substr%& expansion item"
10758 .cindex "substring extraction"
10759 .cindex "expansion" "substring extraction"
10760 The three strings are expanded; the first two must yield numbers. Call them
10761 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
10762 if <&'start'&> and <&'len'&> do not change when they are expanded, you
10763 can use the simpler operator notation that avoids some of the braces:
10765 ${substr_<n>_<m>:<subject>}
10767 The second number is optional (in both notations).
10768 If it is absent in the simpler format, the preceding underscore must also be
10771 The &%substr%& item can be used to extract more general substrings than
10772 &%length%&. The first number, <&'n'&>, is a starting offset, and <&'m'&> is the
10773 length required. For example
10775 ${substr{3}{2}{$local_part}}
10777 If the starting offset is greater than the string length the result is the
10778 null string; if the length plus starting offset is greater than the string
10779 length, the result is the right-hand part of the string, starting from the
10780 given offset. The first byte (character) in the string has offset zero.
10782 The &%substr%& expansion item can take negative offset values to count
10783 from the right-hand end of its operand. The last byte (character) is offset -1,
10784 the second-last is offset -2, and so on. Thus, for example,
10786 ${substr{-5}{2}{1234567}}
10788 yields &"34"&. If the absolute value of a negative offset is greater than the
10789 length of the string, the substring starts at the beginning of the string, and
10790 the length is reduced by the amount of overshoot. Thus, for example,
10792 ${substr{-5}{2}{12}}
10794 yields an empty string, but
10796 ${substr{-3}{2}{12}}
10800 When the second number is omitted from &%substr%&, the remainder of the string
10801 is taken if the offset is positive. If it is negative, all bytes (characters) in the
10802 string preceding the offset point are taken. For example, an offset of -1 and
10803 no length, as in these semantically identical examples:
10806 ${substr{-1}{abcde}}
10808 yields all but the last character of the string, that is, &"abcd"&.
10810 All measurement is done in bytes and is not UTF-8 aware.
10814 .vitem "&*${tr{*&<&'subject'&>&*}{*&<&'characters'&>&*}&&&
10815 {*&<&'replacements'&>&*}}*&"
10816 .cindex "expansion" "character translation"
10817 .cindex "&%tr%& expansion item"
10818 This item does single-character (in bytes) translation on its subject string. The second
10819 argument is a list of characters to be translated in the subject string. Each
10820 matching character is replaced by the corresponding character from the
10821 replacement list. For example
10823 ${tr{abcdea}{ac}{13}}
10825 yields &`1b3de1`&. If there are duplicates in the second character string, the
10826 last occurrence is used. If the third string is shorter than the second, its
10827 last character is replicated. However, if it is empty, no translation takes
10830 All character handling is done in bytes and is not UTF-8 aware.
10836 .section "Expansion operators" "SECTexpop"
10837 .cindex "expansion" "operators"
10838 For expansion items that perform transformations on a single argument string,
10839 the &"operator"& notation is used because it is simpler and uses fewer braces.
10840 The substring is first expanded before the operation is applied to it. The
10841 following operations can be performed:
10844 .vitem &*${address:*&<&'string'&>&*}*&
10845 .cindex "expansion" "RFC 2822 address handling"
10846 .cindex "&%address%& expansion item"
10847 The string is interpreted as an RFC 2822 address, as it might appear in a
10848 header line, and the effective address is extracted from it. If the string does
10849 not parse successfully, the result is empty.
10851 The parsing correctly handles SMTPUTF8 Unicode in the string.
10854 .vitem &*${addresses:*&<&'string'&>&*}*&
10855 .cindex "expansion" "RFC 2822 address handling"
10856 .cindex "&%addresses%& expansion item"
10857 The string (after expansion) is interpreted as a list of addresses in RFC
10858 2822 format, such as can be found in a &'To:'& or &'Cc:'& header line. The
10859 operative address (&'local-part@domain'&) is extracted from each item, and the
10860 result of the expansion is a colon-separated list, with appropriate
10861 doubling of colons should any happen to be present in the email addresses.
10862 Syntactically invalid RFC2822 address items are omitted from the output.
10864 It is possible to specify a character other than colon for the output
10865 separator by starting the string with > followed by the new separator
10866 character. For example:
10868 ${addresses:>& Chief <ceo@up.stairs>, sec@base.ment (dogsbody)}
10870 expands to &`ceo@up.stairs&&sec@base.ment`&. The string is expanded
10871 first, so if the expanded string starts with >, it may change the output
10872 separator unintentionally. This can be avoided by setting the output
10873 separator explicitly:
10875 ${addresses:>:$h_from:}
10878 Compare the &%address%& (singular)
10879 expansion item, which extracts the working address from a single RFC2822
10880 address. See the &%filter%&, &%map%&, and &%reduce%& items for ways of
10883 To clarify "list of addresses in RFC 2822 format" mentioned above, Exim follows
10884 a strict interpretation of header line formatting. Exim parses the bare,
10885 unquoted portion of an email address and if it finds a comma, treats it as an
10886 email address separator. For the example header line:
10888 From: =?iso-8859-2?Q?Last=2C_First?= <user@example.com>
10890 The first example below demonstrates that Q-encoded email addresses are parsed
10891 properly if it is given the raw header (in this example, &`$rheader_from:`&).
10892 It does not see the comma because it's still encoded as "=2C". The second
10893 example below is passed the contents of &`$header_from:`&, meaning it gets
10894 de-mimed. Exim sees the decoded "," so it treats it as &*two*& email addresses.
10895 The third example shows that the presence of a comma is skipped when it is
10896 quoted. The fourth example shows SMTPUTF8 handling.
10898 # exim -be '${addresses:From: \
10899 =?iso-8859-2?Q?Last=2C_First?= <user@example.com>}'
10901 # exim -be '${addresses:From: Last, First <user@example.com>}'
10902 Last:user@example.com
10903 # exim -be '${addresses:From: "Last, First" <user@example.com>}'
10905 # exim -be '${addresses:フィル <フィリップ@example.jp>}'
10909 .vitem &*${base32:*&<&'digits'&>&*}*&
10910 .cindex "&%base32%& expansion item"
10911 .cindex "expansion" "conversion to base 32"
10912 The string must consist entirely of decimal digits. The number is converted to
10913 base 32 and output as a (empty, for zero) string of characters.
10914 Only lowercase letters are used.
10916 .vitem &*${base32d:*&<&'base-32&~digits'&>&*}*&
10917 .cindex "&%base32d%& expansion item"
10918 .cindex "expansion" "conversion to base 32"
10919 The string must consist entirely of base-32 digits.
10920 The number is converted to decimal and output as a string.
10922 .vitem &*${base62:*&<&'digits'&>&*}*&
10923 .cindex "&%base62%& expansion item"
10924 .cindex "expansion" "conversion to base 62"
10925 The string must consist entirely of decimal digits. The number is converted to
10926 base 62 and output as a string of six characters, including leading zeros. In
10927 the few operating environments where Exim uses base 36 instead of base 62 for
10928 its message identifiers (because those systems do not have case-sensitive
10929 filenames), base 36 is used by this operator, despite its name. &*Note*&: Just
10930 to be absolutely clear: this is &'not'& base64 encoding.
10932 .vitem &*${base62d:*&<&'base-62&~digits'&>&*}*&
10933 .cindex "&%base62d%& expansion item"
10934 .cindex "expansion" "conversion to base 62"
10935 The string must consist entirely of base-62 digits, or, in operating
10936 environments where Exim uses base 36 instead of base 62 for its message
10937 identifiers, base-36 digits. The number is converted to decimal and output as a
10940 .vitem &*${base64:*&<&'string'&>&*}*&
10941 .cindex "expansion" "base64 encoding"
10942 .cindex "base64 encoding" "in string expansion"
10943 .cindex "&%base64%& expansion item"
10944 .cindex certificate "base64 of DER"
10945 This operator converts a string into one that is base64 encoded.
10947 If the string is a single variable of type certificate,
10948 returns the base64 encoding of the DER form of the certificate.
10951 .vitem &*${base64d:*&<&'string'&>&*}*&
10952 .cindex "expansion" "base64 decoding"
10953 .cindex "base64 decoding" "in string expansion"
10954 .cindex "&%base64d%& expansion item"
10955 This operator converts a base64-encoded string into the un-coded form.
10958 .vitem &*${domain:*&<&'string'&>&*}*&
10959 .cindex "domain" "extraction"
10960 .cindex "expansion" "domain extraction"
10961 The string is interpreted as an RFC 2822 address and the domain is extracted
10962 from it. If the string does not parse successfully, the result is empty.
10965 .vitem &*${escape:*&<&'string'&>&*}*&
10966 .cindex "expansion" "escaping non-printing characters"
10967 .cindex "&%escape%& expansion item"
10968 If the string contains any non-printing characters, they are converted to
10969 escape sequences starting with a backslash. Whether characters with the most
10970 significant bit set (so-called &"8-bit characters"&) count as printing or not
10971 is controlled by the &%print_topbitchars%& option.
10973 .vitem &*${escape8bit:*&<&'string'&>&*}*&
10974 .cindex "expansion" "escaping 8-bit characters"
10975 .cindex "&%escape8bit%& expansion item"
10976 If the string contains any characters with the most significant bit set,
10977 they are converted to escape sequences starting with a backslash.
10978 Backslashes and DEL characters are also converted.
10981 .vitem &*${eval:*&<&'string'&>&*}*&&~and&~&*${eval10:*&<&'string'&>&*}*&
10982 .cindex "expansion" "expression evaluation"
10983 .cindex "expansion" "arithmetic expression"
10984 .cindex "&%eval%& expansion item"
10985 These items supports simple arithmetic and bitwise logical operations in
10986 expansion strings. The string (after expansion) must be a conventional
10987 arithmetic expression, but it is limited to basic arithmetic operators, bitwise
10988 logical operators, and parentheses. All operations are carried out using
10989 integer arithmetic. The operator priorities are as follows (the same as in the
10990 C programming language):
10992 .irow &'highest:'& "not (~), negate (-)"
10993 .irow "" "multiply (*), divide (/), remainder (%)"
10994 .irow "" "plus (+), minus (-)"
10995 .irow "" "shift-left (<<), shift-right (>>)"
10996 .irow "" "and (&&)"
10998 .irow &'lowest:'& "or (|)"
11000 Binary operators with the same priority are evaluated from left to right. White
11001 space is permitted before or after operators.
11003 For &%eval%&, numbers may be decimal, octal (starting with &"0"&) or
11004 hexadecimal (starting with &"0x"&). For &%eval10%&, all numbers are taken as
11005 decimal, even if they start with a leading zero; hexadecimal numbers are not
11006 permitted. This can be useful when processing numbers extracted from dates or
11007 times, which often do have leading zeros.
11009 A number may be followed by &"K"&, &"M"& or &"G"& to multiply it by 1024, 1024*1024
11011 respectively. Negative numbers are supported. The result of the computation is
11012 a decimal representation of the answer (without &"K"&, &"M"& or &"G"&). For example:
11015 &`${eval:1+1} `& yields 2
11016 &`${eval:1+2*3} `& yields 7
11017 &`${eval:(1+2)*3} `& yields 9
11018 &`${eval:2+42%5} `& yields 4
11019 &`${eval:0xc&5} `& yields 4
11020 &`${eval:0xc|5} `& yields 13
11021 &`${eval:0xc^5} `& yields 9
11022 &`${eval:0xc>>1} `& yields 6
11023 &`${eval:0xc<<1} `& yields 24
11024 &`${eval:~255&0x1234} `& yields 4608
11025 &`${eval:-(~255&0x1234)} `& yields -4608
11028 As a more realistic example, in an ACL you might have
11032 {>{$rcpt_count}{10}} \
11035 {$recipients_count} \
11036 {${eval:$rcpt_count/2}} \
11039 message = Too many bad recipients
11041 The condition is true if there have been more than 10 RCPT commands and
11042 fewer than half of them have resulted in a valid recipient.
11045 .vitem &*${expand:*&<&'string'&>&*}*&
11046 .cindex "expansion" "re-expansion of substring"
11047 The &%expand%& operator causes a string to be expanded for a second time. For
11050 ${expand:${lookup{$domain}dbm{/some/file}{$value}}}
11052 first looks up a string in a file while expanding the operand for &%expand%&,
11053 and then re-expands what it has found.
11056 .vitem &*${from_utf8:*&<&'string'&>&*}*&
11058 .cindex "UTF-8" "conversion from"
11059 .cindex "expansion" "UTF-8 conversion"
11060 .cindex "&%from_utf8%& expansion item"
11061 The world is slowly moving towards Unicode, although there are no standards for
11062 email yet. However, other applications (including some databases) are starting
11063 to store data in Unicode, using UTF-8 encoding. This operator converts from a
11064 UTF-8 string to an ISO-8859-1 string. UTF-8 code values greater than 255 are
11065 converted to underscores. The input must be a valid UTF-8 string. If it is not,
11066 the result is an undefined sequence of bytes.
11068 Unicode code points with values less than 256 are compatible with ASCII and
11069 ISO-8859-1 (also known as Latin-1).
11070 For example, character 169 is the copyright symbol in both cases, though the
11071 way it is encoded is different. In UTF-8, more than one byte is needed for
11072 characters with code values greater than 127, whereas ISO-8859-1 is a
11073 single-byte encoding (but thereby limited to 256 characters). This makes
11074 translation from UTF-8 to ISO-8859-1 straightforward.
11077 .vitem &*${hash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
11078 .cindex "hash function" "textual"
11079 .cindex "expansion" "textual hash"
11080 The &%hash%& operator is a simpler interface to the hashing function that can
11081 be used when the two parameters are fixed numbers (as opposed to strings that
11082 change when expanded). The effect is the same as
11084 ${hash{<n>}{<m>}{<string>}}
11086 See the description of the general &%hash%& item above for details. The
11087 abbreviation &%h%& can be used when &%hash%& is used as an operator.
11091 .vitem &*${hex2b64:*&<&'hexstring'&>&*}*&
11092 .cindex "base64 encoding" "conversion from hex"
11093 .cindex "expansion" "hex to base64"
11094 .cindex "&%hex2b64%& expansion item"
11095 This operator converts a hex string into one that is base64 encoded. This can
11096 be useful for processing the output of the various hashing functions.
11100 .vitem &*${hexquote:*&<&'string'&>&*}*&
11101 .cindex "quoting" "hex-encoded unprintable characters"
11102 .cindex "&%hexquote%& expansion item"
11103 This operator converts non-printable characters in a string into a hex
11104 escape form. Byte values between 33 (!) and 126 (~) inclusive are left
11105 as is, and other byte values are converted to &`\xNN`&, for example, a
11106 byte value 127 is converted to &`\x7f`&.
11109 .vitem &*${ipv6denorm:*&<&'string'&>&*}*&
11110 .cindex "&%ipv6denorm%& expansion item"
11111 .cindex "IP address" normalisation
11112 This expands an IPv6 address to a full eight-element colon-separated set
11113 of hex digits including leading zeroes.
11114 A trailing ipv4-style dotted-decimal set is converted to hex.
11115 Pure IPv4 addresses are converted to IPv4-mapped IPv6.
11117 .vitem &*${ipv6norm:*&<&'string'&>&*}*&
11118 .cindex "&%ipv6norm%& expansion item"
11119 .cindex "IP address" normalisation
11120 .cindex "IP address" "canonical form"
11121 This converts an IPv6 address to canonical form.
11122 Leading zeroes of groups are omitted, and the longest
11123 set of zero-valued groups is replaced with a double colon.
11124 A trailing ipv4-style dotted-decimal set is converted to hex.
11125 Pure IPv4 addresses are converted to IPv4-mapped IPv6.
11128 .vitem &*${lc:*&<&'string'&>&*}*&
11129 .cindex "case forcing in strings"
11130 .cindex "string" "case forcing"
11131 .cindex "lower casing"
11132 .cindex "expansion" "case forcing"
11133 .cindex "&%lc%& expansion item"
11134 This forces the letters in the string into lower-case, for example:
11138 Case is defined per the system C locale.
11140 .vitem &*${length_*&<&'number'&>&*:*&<&'string'&>&*}*&
11141 .cindex "expansion" "string truncation"
11142 .cindex "&%length%& expansion item"
11143 The &%length%& operator is a simpler interface to the &%length%& function that
11144 can be used when the parameter is a fixed number (as opposed to a string that
11145 changes when expanded). The effect is the same as
11147 ${length{<number>}{<string>}}
11149 See the description of the general &%length%& item above for details. Note that
11150 &%length%& is not the same as &%strlen%&. The abbreviation &%l%& can be used
11151 when &%length%& is used as an operator.
11152 All measurement is done in bytes and is not UTF-8 aware.
11155 .vitem &*${listcount:*&<&'string'&>&*}*&
11156 .cindex "expansion" "list item count"
11157 .cindex "list" "item count"
11158 .cindex "list" "count of items"
11159 .cindex "&%listcount%& expansion item"
11160 The string is interpreted as a list and the number of items is returned.
11163 .vitem &*${listnamed:*&<&'name'&>&*}*&&~and&~&*${listnamed_*&<&'type'&>&*:*&<&'name'&>&*}*&
11164 .cindex "expansion" "named list"
11165 .cindex "&%listnamed%& expansion item"
11166 The name is interpreted as a named list and the content of the list is returned,
11167 expanding any referenced lists, re-quoting as needed for colon-separation.
11168 If the optional type is given it must be one of "a", "d", "h" or "l"
11169 and selects address-, domain-, host- or localpart- lists to search among respectively.
11170 Otherwise all types are searched in an undefined order and the first
11171 matching list is returned.
11172 &*Note*&: Neither string-expansion of lists referenced by named-list syntax elements,
11173 nor expansion of lookup elements, is done by the &%listnamed%& operator.
11176 .vitem &*${local_part:*&<&'string'&>&*}*&
11177 .cindex "expansion" "local part extraction"
11178 .cindex "&%local_part%& expansion item"
11179 The string is interpreted as an RFC 2822 address and the local part is
11180 extracted from it. If the string does not parse successfully, the result is
11182 The parsing correctly handles SMTPUTF8 Unicode in the string.
11185 .vitem &*${mask:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*& &&&
11186 &*${mask_n:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*&
11187 .cindex "masked IP address"
11188 .cindex "IP address" "masking"
11189 .cindex "CIDR notation"
11190 .cindex "expansion" "IP address masking"
11191 .cindex "&%mask%& expansion item"
11192 If the form of the string to be operated on is not an IP address followed by a
11193 slash and an integer (that is, a network address in CIDR notation), the
11194 expansion fails. Otherwise, this operator converts the IP address to binary,
11195 masks off the least significant bits according to the bit count, and converts
11196 the result back to text, with mask appended. For example,
11198 ${mask:10.111.131.206/28}
11200 returns the string &"10.111.131.192/28"&.
11202 Since this operation is expected to
11203 be mostly used for looking up masked addresses in files, the
11206 address uses dots to separate components instead of colons, because colon
11207 terminates a key string in lsearch files. So, for example,
11209 ${mask:3ffe:ffff:836f:0a00:000a:0800:200a:c031/99}
11213 3ffe.ffff.836f.0a00.000a.0800.2000.0000/99
11215 If the optional form &*mask_n*& is used, IPv6 address result are instead
11216 returned in normailsed form, using colons and with zero-compression.
11217 Letters in IPv6 addresses are always output in lower case.
11220 .vitem &*${md5:*&<&'string'&>&*}*&
11222 .cindex "expansion" "MD5 hash"
11223 .cindex certificate fingerprint
11224 .cindex "&%md5%& expansion item"
11225 The &%md5%& operator computes the MD5 hash value of the string, and returns it
11226 as a 32-digit hexadecimal number, in which any letters are in lower case.
11228 If the string is a single variable of type certificate,
11229 returns the MD5 hash fingerprint of the certificate.
11232 .vitem &*${nhash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
11233 .cindex "expansion" "numeric hash"
11234 .cindex "hash function" "numeric"
11235 The &%nhash%& operator is a simpler interface to the numeric hashing function
11236 that can be used when the two parameters are fixed numbers (as opposed to
11237 strings that change when expanded). The effect is the same as
11239 ${nhash{<n>}{<m>}{<string>}}
11241 See the description of the general &%nhash%& item above for details.
11244 .vitem &*${quote:*&<&'string'&>&*}*&
11245 .cindex "quoting" "in string expansions"
11246 .cindex "expansion" "quoting"
11247 .cindex "&%quote%& expansion item"
11248 The &%quote%& operator puts its argument into double quotes if it
11249 is an empty string or
11250 contains anything other than letters, digits, underscores, dots, and hyphens.
11251 Any occurrences of double quotes and backslashes are escaped with a backslash.
11252 Newlines and carriage returns are converted to &`\n`& and &`\r`&,
11253 respectively For example,
11261 The place where this is useful is when the argument is a substitution from a
11262 variable or a message header.
11264 .vitem &*${quote_local_part:*&<&'string'&>&*}*&
11265 .cindex "&%quote_local_part%& expansion item"
11266 This operator is like &%quote%&, except that it quotes the string only if
11267 required to do so by the rules of RFC 2822 for quoting local parts. For
11268 example, a plus sign would not cause quoting (but it would for &%quote%&).
11269 If you are creating a new email address from the contents of &$local_part$&
11270 (or any other unknown data), you should always use this operator.
11272 This quoting determination is not SMTPUTF8-aware, thus quoting non-ASCII data
11273 will likely use the quoting form.
11274 Thus &'${quote_local_part:フィル}'& will always become &'"フィル"'&.
11277 .vitem &*${quote_*&<&'lookup-type'&>&*:*&<&'string'&>&*}*&
11278 .cindex "quoting" "lookup-specific"
11279 This operator applies lookup-specific quoting rules to the string. Each
11280 query-style lookup type has its own quoting rules which are described with
11281 the lookups in chapter &<<CHAPfdlookup>>&. For example,
11283 ${quote_ldap:two * two}
11289 For single-key lookup types, no quoting is ever necessary and this operator
11290 yields an unchanged string.
11293 .vitem &*${randint:*&<&'n'&>&*}*&
11294 .cindex "random number"
11295 This operator returns a somewhat random number which is less than the
11296 supplied number and is at least 0. The quality of this randomness depends
11297 on how Exim was built; the values are not suitable for keying material.
11298 If Exim is linked against OpenSSL then RAND_pseudo_bytes() is used.
11299 If Exim is linked against GnuTLS then gnutls_rnd(GNUTLS_RND_NONCE) is used,
11300 for versions of GnuTLS with that function.
11301 Otherwise, the implementation may be arc4random(), random() seeded by
11302 srandomdev() or srandom(), or a custom implementation even weaker than
11306 .vitem &*${reverse_ip:*&<&'ipaddr'&>&*}*&
11307 .cindex "expansion" "IP address"
11308 This operator reverses an IP address; for IPv4 addresses, the result is in
11309 dotted-quad decimal form, while for IPv6 addresses the result is in
11310 dotted-nibble hexadecimal form. In both cases, this is the "natural" form
11311 for DNS. For example,
11313 ${reverse_ip:192.0.2.4}
11314 ${reverse_ip:2001:0db8:c42:9:1:abcd:192.0.2.127}
11319 f.7.2.0.0.0.0.c.d.c.b.a.1.0.0.0.9.0.0.0.2.4.c.0.8.b.d.0.1.0.0.2
11323 .vitem &*${rfc2047:*&<&'string'&>&*}*&
11324 .cindex "expansion" "RFC 2047"
11325 .cindex "RFC 2047" "expansion operator"
11326 .cindex "&%rfc2047%& expansion item"
11327 This operator encodes text according to the rules of RFC 2047. This is an
11328 encoding that is used in header lines to encode non-ASCII characters. It is
11329 assumed that the input string is in the encoding specified by the
11330 &%headers_charset%& option, which gets its default at build time. If the string
11331 contains only characters in the range 33&--126, and no instances of the
11334 ? = ( ) < > @ , ; : \ " . [ ] _
11336 it is not modified. Otherwise, the result is the RFC 2047 encoding of the
11337 string, using as many &"encoded words"& as necessary to encode all the
11341 .vitem &*${rfc2047d:*&<&'string'&>&*}*&
11342 .cindex "expansion" "RFC 2047"
11343 .cindex "RFC 2047" "decoding"
11344 .cindex "&%rfc2047d%& expansion item"
11345 This operator decodes strings that are encoded as per RFC 2047. Binary zero
11346 bytes are replaced by question marks. Characters are converted into the
11347 character set defined by &%headers_charset%&. Overlong RFC 2047 &"words"& are
11348 not recognized unless &%check_rfc2047_length%& is set false.
11350 &*Note*&: If you use &%$header%&_&'xxx'&&*:*& (or &%$h%&_&'xxx'&&*:*&) to
11351 access a header line, RFC 2047 decoding is done automatically. You do not need
11352 to use this operator as well.
11356 .vitem &*${rxquote:*&<&'string'&>&*}*&
11357 .cindex "quoting" "in regular expressions"
11358 .cindex "regular expressions" "quoting"
11359 .cindex "&%rxquote%& expansion item"
11360 The &%rxquote%& operator inserts a backslash before any non-alphanumeric
11361 characters in its argument. This is useful when substituting the values of
11362 variables or headers inside regular expressions.
11365 .vitem &*${sha1:*&<&'string'&>&*}*&
11366 .cindex "SHA-1 hash"
11367 .cindex "expansion" "SHA-1 hashing"
11368 .cindex certificate fingerprint
11369 .cindex "&%sha1%& expansion item"
11370 The &%sha1%& operator computes the SHA-1 hash value of the string, and returns
11371 it as a 40-digit hexadecimal number, in which any letters are in upper case.
11373 If the string is a single variable of type certificate,
11374 returns the SHA-1 hash fingerprint of the certificate.
11377 .vitem &*${sha256:*&<&'string'&>&*}*& &&&
11378 &*${sha2:*&<&'string'&>&*}*& &&&
11379 &*${sha2_<n>:*&<&'string'&>&*}*&
11380 .cindex "SHA-256 hash"
11381 .cindex "SHA-2 hash"
11382 .cindex certificate fingerprint
11383 .cindex "expansion" "SHA-256 hashing"
11384 .cindex "&%sha256%& expansion item"
11385 .cindex "&%sha2%& expansion item"
11386 The &%sha256%& operator computes the SHA-256 hash value of the string
11388 it as a 64-digit hexadecimal number, in which any letters are in upper case.
11390 If the string is a single variable of type certificate,
11391 returns the SHA-256 hash fingerprint of the certificate.
11393 The operator can also be spelled &%sha2%& and does the same as &%sha256%&
11394 (except for certificates, which are not supported).
11395 Finally, if an underbar
11396 and a number is appended it specifies the output length, selecting a
11397 member of the SHA-2 family of hash functions.
11398 Values of 256, 384 and 512 are accepted, with 256 being the default.
11401 .vitem &*${sha3:*&<&'string'&>&*}*& &&&
11402 &*${sha3_<n>:*&<&'string'&>&*}*&
11403 .cindex "SHA3 hash"
11404 .cindex "expansion" "SHA3 hashing"
11405 .cindex "&%sha3%& expansion item"
11406 The &%sha3%& operator computes the SHA3-256 hash value of the string
11408 it as a 64-digit hexadecimal number, in which any letters are in upper case.
11410 If a number is appended, separated by an underbar, it specifies
11411 the output length. Values of 224, 256, 384 and 512 are accepted;
11412 with 256 being the default.
11414 The &%sha3%& expansion item is only supported if Exim has been
11415 compiled with GnuTLS 3.5.0 or later,
11416 or OpenSSL 1.1.1 or later.
11417 The macro "_CRYPTO_HASH_SHA3" will be defined if it is supported.
11420 .vitem &*${stat:*&<&'string'&>&*}*&
11421 .cindex "expansion" "statting a file"
11422 .cindex "file" "extracting characteristics"
11423 .cindex "&%stat%& expansion item"
11424 The string, after expansion, must be a file path. A call to the &[stat()]&
11425 function is made for this path. If &[stat()]& fails, an error occurs and the
11426 expansion fails. If it succeeds, the data from the stat replaces the item, as a
11427 series of <&'name'&>=<&'value'&> pairs, where the values are all numerical,
11428 except for the value of &"smode"&. The names are: &"mode"& (giving the mode as
11429 a 4-digit octal number), &"smode"& (giving the mode in symbolic format as a
11430 10-character string, as for the &'ls'& command), &"inode"&, &"device"&,
11431 &"links"&, &"uid"&, &"gid"&, &"size"&, &"atime"&, &"mtime"&, and &"ctime"&. You
11432 can extract individual fields using the &%extract%& expansion item.
11434 The use of the &%stat%& expansion in users' filter files can be locked out by
11435 the system administrator. &*Warning*&: The file size may be incorrect on 32-bit
11436 systems for files larger than 2GB.
11438 .vitem &*${str2b64:*&<&'string'&>&*}*&
11439 .cindex "&%str2b64%& expansion item"
11440 Now deprecated, a synonym for the &%base64%& expansion operator.
11444 .vitem &*${strlen:*&<&'string'&>&*}*&
11445 .cindex "expansion" "string length"
11446 .cindex "string" "length in expansion"
11447 .cindex "&%strlen%& expansion item"
11448 The item is replaced by the length of the expanded string, expressed as a
11449 decimal number. &*Note*&: Do not confuse &%strlen%& with &%length%&.
11450 All measurement is done in bytes and is not UTF-8 aware.
11453 .vitem &*${substr_*&<&'start'&>&*_*&<&'length'&>&*:*&<&'string'&>&*}*&
11454 .cindex "&%substr%& expansion item"
11455 .cindex "substring extraction"
11456 .cindex "expansion" "substring expansion"
11457 The &%substr%& operator is a simpler interface to the &%substr%& function that
11458 can be used when the two parameters are fixed numbers (as opposed to strings
11459 that change when expanded). The effect is the same as
11461 ${substr{<start>}{<length>}{<string>}}
11463 See the description of the general &%substr%& item above for details. The
11464 abbreviation &%s%& can be used when &%substr%& is used as an operator.
11465 All measurement is done in bytes and is not UTF-8 aware.
11467 .vitem &*${time_eval:*&<&'string'&>&*}*&
11468 .cindex "&%time_eval%& expansion item"
11469 .cindex "time interval" "decoding"
11470 This item converts an Exim time interval such as &`2d4h5m`& into a number of
11473 .vitem &*${time_interval:*&<&'string'&>&*}*&
11474 .cindex "&%time_interval%& expansion item"
11475 .cindex "time interval" "formatting"
11476 The argument (after sub-expansion) must be a sequence of decimal digits that
11477 represents an interval of time as a number of seconds. It is converted into a
11478 number of larger units and output in Exim's normal time format, for example,
11481 .vitem &*${uc:*&<&'string'&>&*}*&
11482 .cindex "case forcing in strings"
11483 .cindex "string" "case forcing"
11484 .cindex "upper casing"
11485 .cindex "expansion" "case forcing"
11486 .cindex "&%uc%& expansion item"
11487 This forces the letters in the string into upper-case.
11488 Case is defined per the system C locale.
11490 .vitem &*${utf8clean:*&<&'string'&>&*}*&
11491 .cindex "correction of invalid utf-8 sequences in strings"
11492 .cindex "utf-8" "utf-8 sequences"
11493 .cindex "incorrect utf-8"
11494 .cindex "expansion" "utf-8 forcing"
11495 .cindex "&%utf8clean%& expansion item"
11496 This replaces any invalid utf-8 sequence in the string by the character &`?`&.
11497 In versions of Exim before 4.92, this did not correctly do so for a truncated
11498 final codepoint's encoding, and the character would be silently dropped.
11499 If you must handle detection of this scenario across both sets of Exim behavior,
11500 the complexity will depend upon the task.
11501 For instance, to detect if the first character is multibyte and a 1-byte
11502 extraction can be successfully used as a path component (as is common for
11503 dividing up delivery folders), you might use:
11505 condition = ${if inlist{${utf8clean:${length_1:$local_part}}}{:?}{yes}{no}}
11507 (which will false-positive if the first character of the local part is a
11508 literal question mark).
11510 .vitem "&*${utf8_domain_to_alabel:*&<&'string'&>&*}*&" &&&
11511 "&*${utf8_domain_from_alabel:*&<&'string'&>&*}*&" &&&
11512 "&*${utf8_localpart_to_alabel:*&<&'string'&>&*}*&" &&&
11513 "&*${utf8_localpart_from_alabel:*&<&'string'&>&*}*&"
11514 .cindex expansion UTF-8
11515 .cindex UTF-8 expansion
11517 .cindex internationalisation
11518 .cindex "&%utf8_domain_to_alabel%& expansion item"
11519 .cindex "&%utf8_domain_from_alabel%& expansion item"
11520 .cindex "&%utf8_localpart_to_alabel%& expansion item"
11521 .cindex "&%utf8_localpart_from_alabel%& expansion item"
11522 These convert EAI mail name components between UTF-8 and a-label forms.
11523 For information on internationalisation support see &<<SECTi18nMTA>>&.
11531 .section "Expansion conditions" "SECTexpcond"
11532 .scindex IIDexpcond "expansion" "conditions"
11533 The following conditions are available for testing by the &%${if%& construct
11534 while expanding strings:
11537 .vitem &*!*&<&'condition'&>
11538 .cindex "expansion" "negating a condition"
11539 .cindex "negation" "in expansion condition"
11540 Preceding any condition with an exclamation mark negates the result of the
11543 .vitem <&'symbolic&~operator'&>&~&*{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11544 .cindex "numeric comparison"
11545 .cindex "expansion" "numeric comparison"
11546 There are a number of symbolic operators for doing numeric comparisons. They
11548 .itable none 0 0 2 1pt left 1pt left
11550 .irow "== " "equal"
11551 .irow "> " "greater"
11552 .irow ">= " "greater or equal"
11554 .irow "<= " "less or equal"
11558 ${if >{$message_size}{10M} ...
11560 Note that the general negation operator provides for inequality testing. The
11561 two strings must take the form of optionally signed decimal integers,
11562 optionally followed by one of the letters &"K"&, &"M"& or &"G"& (in either upper or
11563 lower case), signifying multiplication by 1024, 1024*1024 or 1024*1024*1024, respectively.
11564 As a special case, the numerical value of an empty string is taken as
11567 In all cases, a relative comparator OP is testing if <&'string1'&> OP
11568 <&'string2'&>; the above example is checking if &$message_size$& is larger than
11569 10M, not if 10M is larger than &$message_size$&.
11572 .vitem &*acl&~{{*&<&'name'&>&*}{*&<&'arg1'&>&*}&&&
11573 {*&<&'arg2'&>&*}...}*&
11574 .cindex "expansion" "calling an acl"
11575 .cindex "&%acl%&" "expansion condition"
11576 The name and zero to nine argument strings are first expanded separately. The expanded
11577 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
11578 Any unused are made empty. The variable &$acl_narg$& is set to the number of
11579 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
11580 and may use the variables; if another acl expansion is used the values
11581 are restored after it returns. If the ACL sets
11582 a value using a "message =" modifier the variable $value becomes
11583 the result of the expansion, otherwise it is empty.
11584 If the ACL returns accept the condition is true; if deny, false.
11585 If the ACL returns defer the result is a forced-fail.
11587 .vitem &*bool&~{*&<&'string'&>&*}*&
11588 .cindex "expansion" "boolean parsing"
11589 .cindex "&%bool%& expansion condition"
11590 This condition turns a string holding a true or false representation into
11591 a boolean state. It parses &"true"&, &"false"&, &"yes"& and &"no"&
11592 (case-insensitively); also integer numbers map to true if non-zero,
11594 An empty string is treated as false.
11595 Leading and trailing whitespace is ignored;
11596 thus a string consisting only of whitespace is false.
11597 All other string values will result in expansion failure.
11599 When combined with ACL variables, this expansion condition will let you
11600 make decisions in one place and act on those decisions in another place.
11603 ${if bool{$acl_m_privileged_sender} ...
11607 .vitem &*bool_lax&~{*&<&'string'&>&*}*&
11608 .cindex "expansion" "boolean parsing"
11609 .cindex "&%bool_lax%& expansion condition"
11610 Like &%bool%&, this condition turns a string into a boolean state. But
11611 where &%bool%& accepts a strict set of strings, &%bool_lax%& uses the same
11612 loose definition that the Router &%condition%& option uses. The empty string
11613 and the values &"false"&, &"no"& and &"0"& map to false, all others map to
11614 true. Leading and trailing whitespace is ignored.
11616 Note that where &"bool{00}"& is false, &"bool_lax{00}"& is true.
11618 .vitem &*crypteq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11619 .cindex "expansion" "encrypted comparison"
11620 .cindex "encrypted strings, comparing"
11621 .cindex "&%crypteq%& expansion condition"
11622 This condition is included in the Exim binary if it is built to support any
11623 authentication mechanisms (see chapter &<<CHAPSMTPAUTH>>&). Otherwise, it is
11624 necessary to define SUPPORT_CRYPTEQ in &_Local/Makefile_& to get &%crypteq%&
11625 included in the binary.
11627 The &%crypteq%& condition has two arguments. The first is encrypted and
11628 compared against the second, which is already encrypted. The second string may
11629 be in the LDAP form for storing encrypted strings, which starts with the
11630 encryption type in curly brackets, followed by the data. If the second string
11631 does not begin with &"{"& it is assumed to be encrypted with &[crypt()]& or
11632 &[crypt16()]& (see below), since such strings cannot begin with &"{"&.
11633 Typically this will be a field from a password file. An example of an encrypted
11634 string in LDAP form is:
11636 {md5}CY9rzUYh03PK3k6DJie09g==
11638 If such a string appears directly in an expansion, the curly brackets have to
11639 be quoted, because they are part of the expansion syntax. For example:
11641 ${if crypteq {test}{\{md5\}CY9rzUYh03PK3k6DJie09g==}{yes}{no}}
11643 The following encryption types (whose names are matched case-independently) are
11648 .cindex "base64 encoding" "in encrypted password"
11649 &%{md5}%& computes the MD5 digest of the first string, and expresses this as
11650 printable characters to compare with the remainder of the second string. If the
11651 length of the comparison string is 24, Exim assumes that it is base64 encoded
11652 (as in the above example). If the length is 32, Exim assumes that it is a
11653 hexadecimal encoding of the MD5 digest. If the length not 24 or 32, the
11657 .cindex "SHA-1 hash"
11658 &%{sha1}%& computes the SHA-1 digest of the first string, and expresses this as
11659 printable characters to compare with the remainder of the second string. If the
11660 length of the comparison string is 28, Exim assumes that it is base64 encoded.
11661 If the length is 40, Exim assumes that it is a hexadecimal encoding of the
11662 SHA-1 digest. If the length is not 28 or 40, the comparison fails.
11665 .cindex "&[crypt()]&"
11666 &%{crypt}%& calls the &[crypt()]& function, which traditionally used to use
11667 only the first eight characters of the password. However, in modern operating
11668 systems this is no longer true, and in many cases the entire password is used,
11669 whatever its length.
11672 .cindex "&[crypt16()]&"
11673 &%{crypt16}%& calls the &[crypt16()]& function, which was originally created to
11674 use up to 16 characters of the password in some operating systems. Again, in
11675 modern operating systems, more characters may be used.
11677 Exim has its own version of &[crypt16()]&, which is just a double call to
11678 &[crypt()]&. For operating systems that have their own version, setting
11679 HAVE_CRYPT16 in &_Local/Makefile_& when building Exim causes it to use the
11680 operating system version instead of its own. This option is set by default in
11681 the OS-dependent &_Makefile_& for those operating systems that are known to
11682 support &[crypt16()]&.
11684 Some years after Exim's &[crypt16()]& was implemented, a user discovered that
11685 it was not using the same algorithm as some operating systems' versions. It
11686 turns out that as well as &[crypt16()]& there is a function called
11687 &[bigcrypt()]& in some operating systems. This may or may not use the same
11688 algorithm, and both of them may be different to Exim's built-in &[crypt16()]&.
11690 However, since there is now a move away from the traditional &[crypt()]&
11691 functions towards using SHA1 and other algorithms, tidying up this area of
11692 Exim is seen as very low priority.
11694 If you do not put a encryption type (in curly brackets) in a &%crypteq%&
11695 comparison, the default is usually either &`{crypt}`& or &`{crypt16}`&, as
11696 determined by the setting of DEFAULT_CRYPT in &_Local/Makefile_&. The default
11697 default is &`{crypt}`&. Whatever the default, you can always use either
11698 function by specifying it explicitly in curly brackets.
11700 .vitem &*def:*&<&'variable&~name'&>
11701 .cindex "expansion" "checking for empty variable"
11702 .cindex "&%def%& expansion condition"
11703 The &%def%& condition must be followed by the name of one of the expansion
11704 variables defined in section &<<SECTexpvar>>&. The condition is true if the
11705 variable does not contain the empty string. For example:
11707 ${if def:sender_ident {from $sender_ident}}
11709 Note that the variable name is given without a leading &%$%& character. If the
11710 variable does not exist, the expansion fails.
11712 .vitem "&*def:header_*&<&'header&~name'&>&*:*&&~&~or&~&&&
11713 &~&*def:h_*&<&'header&~name'&>&*:*&"
11714 .cindex "expansion" "checking header line existence"
11715 This condition is true if a message is being processed and the named header
11716 exists in the message. For example,
11718 ${if def:header_reply-to:{$h_reply-to:}{$h_from:}}
11720 &*Note*&: No &%$%& appears before &%header_%& or &%h_%& in the condition, and
11721 the header name must be terminated by a colon if white space does not follow.
11723 .vitem &*eq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11724 &*eqi&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11725 .cindex "string" "comparison"
11726 .cindex "expansion" "string comparison"
11727 .cindex "&%eq%& expansion condition"
11728 .cindex "&%eqi%& expansion condition"
11729 The two substrings are first expanded. The condition is true if the two
11730 resulting strings are identical. For &%eq%& the comparison includes the case of
11731 letters, whereas for &%eqi%& the comparison is case-independent, where
11732 case is defined per the system C locale.
11734 .vitem &*exists&~{*&<&'file&~name'&>&*}*&
11735 .cindex "expansion" "file existence test"
11736 .cindex "file" "existence test"
11737 .cindex "&%exists%&, expansion condition"
11738 The substring is first expanded and then interpreted as an absolute path. The
11739 condition is true if the named file (or directory) exists. The existence test
11740 is done by calling the &[stat()]& function. The use of the &%exists%& test in
11741 users' filter files may be locked out by the system administrator.
11743 &*Note:*& Testing a path using this condition is not a sufficient way of
11745 Consider using a dsearch lookup.
11747 .vitem &*first_delivery*&
11748 .cindex "delivery" "first"
11749 .cindex "first delivery"
11750 .cindex "expansion" "first delivery test"
11751 .cindex "&%first_delivery%& expansion condition"
11752 This condition, which has no data, is true during a message's first delivery
11753 attempt. It is false during any subsequent delivery attempts.
11756 .vitem "&*forall{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&" &&&
11757 "&*forany{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&"
11758 .cindex "list" "iterative conditions"
11759 .cindex "expansion" "&*forall*& condition"
11760 .cindex "expansion" "&*forany*& condition"
11762 These conditions iterate over a list. The first argument is expanded to form
11763 the list. By default, the list separator is a colon, but it can be changed by
11764 the normal method (&<<SECTlistsepchange>>&).
11765 The second argument is interpreted as a condition that is to
11766 be applied to each item in the list in turn. During the interpretation of the
11767 condition, the current list item is placed in a variable called &$item$&.
11769 For &*forany*&, interpretation stops if the condition is true for any item, and
11770 the result of the whole condition is true. If the condition is false for all
11771 items in the list, the overall condition is false.
11773 For &*forall*&, interpretation stops if the condition is false for any item,
11774 and the result of the whole condition is false. If the condition is true for
11775 all items in the list, the overall condition is true.
11777 Note that negation of &*forany*& means that the condition must be false for all
11778 items for the overall condition to succeed, and negation of &*forall*& means
11779 that the condition must be false for at least one item. In this example, the
11780 list separator is changed to a comma:
11782 ${if forany{<, $recipients}{match{$item}{^user3@}}{yes}{no}}
11784 The value of &$item$& is saved and restored while &%forany%& or &%forall%& is
11785 being processed, to enable these expansion items to be nested.
11787 To scan a named list, expand it with the &*listnamed*& operator.
11789 .vitem "&*forall_json{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
11790 "&*forany_json{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
11791 "&*forall_jsons{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
11792 "&*forany_jsons{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&"
11793 .cindex JSON "iterative conditions"
11794 .cindex JSON expansions
11795 .cindex expansion "&*forall_json*& condition"
11796 .cindex expansion "&*forany_json*& condition"
11797 .cindex expansion "&*forall_jsons*& condition"
11798 .cindex expansion "&*forany_jsons*& condition"
11799 As for the above, except that the first argument must, after expansion,
11801 The array separator is not changeable.
11802 For the &"jsons"& variants the elements are expected to be JSON strings
11803 and have their quotes removed before the evaluation of the condition.
11807 .vitem &*ge&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11808 &*gei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11809 .cindex "string" "comparison"
11810 .cindex "expansion" "string comparison"
11811 .cindex "&%ge%& expansion condition"
11812 .cindex "&%gei%& expansion condition"
11813 The two substrings are first expanded. The condition is true if the first
11814 string is lexically greater than or equal to the second string. For &%ge%& the
11815 comparison includes the case of letters, whereas for &%gei%& the comparison is
11817 Case and collation order are defined per the system C locale.
11819 .vitem &*gt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11820 &*gti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11821 .cindex "string" "comparison"
11822 .cindex "expansion" "string comparison"
11823 .cindex "&%gt%& expansion condition"
11824 .cindex "&%gti%& expansion condition"
11825 The two substrings are first expanded. The condition is true if the first
11826 string is lexically greater than the second string. For &%gt%& the comparison
11827 includes the case of letters, whereas for &%gti%& the comparison is
11829 Case and collation order are defined per the system C locale.
11832 .vitem &*inbound_srs&~{*&<&'local&~part'&>&*}{*&<&'secret'&>&*}*&
11833 SRS decode. See SECT &<<SECTSRS>>& for details.
11836 .vitem &*inlist&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11837 &*inlisti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11838 .cindex "string" "comparison"
11839 .cindex "list" "iterative conditions"
11840 Both strings are expanded; the second string is treated as a list of simple
11841 strings; if the first string is a member of the second, then the condition
11843 For the case-independent &%inlisti%& condition, case is defined per the system C locale.
11845 These are simpler to use versions of the more powerful &*forany*& condition.
11846 Examples, and the &*forany*& equivalents:
11848 ${if inlist{needle}{foo:needle:bar}}
11849 ${if forany{foo:needle:bar}{eq{$item}{needle}}}
11850 ${if inlisti{Needle}{fOo:NeeDLE:bAr}}
11851 ${if forany{fOo:NeeDLE:bAr}{eqi{$item}{Needle}}}
11854 The variable &$value$& will be set for a successful match and can be
11855 used in the success clause of an &%if%& expansion item using the condition.
11856 .cindex "tainted data" "de-tainting"
11857 .cindex "de-tainting" "using an inlist expansion condition"
11858 It will have the same taint status as the list; expansions such as
11860 ${if inlist {$h_mycode:} {0 : 1 : 42} {$value}}
11862 can be used for de-tainting.
11863 Any previous &$value$& is restored after the if.
11866 .vitem &*isip&~{*&<&'string'&>&*}*& &&&
11867 &*isip4&~{*&<&'string'&>&*}*& &&&
11868 &*isip6&~{*&<&'string'&>&*}*&
11869 .cindex "IP address" "testing string format"
11870 .cindex "string" "testing for IP address"
11871 .cindex "&%isip%& expansion condition"
11872 .cindex "&%isip4%& expansion condition"
11873 .cindex "&%isip6%& expansion condition"
11874 The substring is first expanded, and then tested to see if it has the form of
11875 an IP address. Both IPv4 and IPv6 addresses are valid for &%isip%&, whereas
11876 &%isip4%& and &%isip6%& test specifically for IPv4 or IPv6 addresses.
11878 For an IPv4 address, the test is for four dot-separated components, each of
11879 which consists of from one to three digits. For an IPv6 address, up to eight
11880 colon-separated components are permitted, each containing from one to four
11881 hexadecimal digits. There may be fewer than eight components if an empty
11882 component (adjacent colons) is present. Only one empty component is permitted.
11884 &*Note*&: The checks used to be just on the form of the address; actual numerical
11885 values were not considered. Thus, for example, 999.999.999.999 passed the IPv4
11887 This is no longer the case.
11889 The main use of these tests is to distinguish between IP addresses and
11890 host names, or between IPv4 and IPv6 addresses. For example, you could use
11892 ${if isip4{$sender_host_address}...
11894 to test which IP version an incoming SMTP connection is using.
11896 .vitem &*ldapauth&~{*&<&'ldap&~query'&>&*}*&
11897 .cindex "LDAP" "use for authentication"
11898 .cindex "expansion" "LDAP authentication test"
11899 .cindex "&%ldapauth%& expansion condition"
11900 This condition supports user authentication using LDAP. See section
11901 &<<SECTldap>>& for details of how to use LDAP in lookups and the syntax of
11902 queries. For this use, the query must contain a user name and password. The
11903 query itself is not used, and can be empty. The condition is true if the
11904 password is not empty, and the user name and password are accepted by the LDAP
11905 server. An empty password is rejected without calling LDAP because LDAP binds
11906 with an empty password are considered anonymous regardless of the username, and
11907 will succeed in most configurations. See chapter &<<CHAPSMTPAUTH>>& for details
11908 of SMTP authentication, and chapter &<<CHAPplaintext>>& for an example of how
11912 .vitem &*le&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11913 &*lei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11914 .cindex "string" "comparison"
11915 .cindex "expansion" "string comparison"
11916 .cindex "&%le%& expansion condition"
11917 .cindex "&%lei%& expansion condition"
11918 The two substrings are first expanded. The condition is true if the first
11919 string is lexically less than or equal to the second string. For &%le%& the
11920 comparison includes the case of letters, whereas for &%lei%& the comparison is
11922 Case and collation order are defined per the system C locale.
11924 .vitem &*lt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11925 &*lti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11926 .cindex "string" "comparison"
11927 .cindex "expansion" "string comparison"
11928 .cindex "&%lt%& expansion condition"
11929 .cindex "&%lti%& expansion condition"
11930 The two substrings are first expanded. The condition is true if the first
11931 string is lexically less than the second string. For &%lt%& the comparison
11932 includes the case of letters, whereas for &%lti%& the comparison is
11934 Case and collation order are defined per the system C locale.
11937 .vitem &*match&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11938 .cindex "expansion" "regular expression comparison"
11939 .cindex "regular expressions" "match in expanded string"
11940 .cindex "&%match%& expansion condition"
11941 The two substrings are first expanded. The second is then treated as a regular
11942 expression and applied to the first. Because of the pre-expansion, if the
11943 regular expression contains dollar, or backslash characters, they must be
11944 escaped. Care must also be taken if the regular expression contains braces
11945 (curly brackets). A closing brace must be escaped so that it is not taken as a
11946 premature termination of <&'string2'&>. The easiest approach is to use the
11947 &`\N`& feature to disable expansion of the regular expression.
11950 ${if match {$local_part}{\N^\d{3}\N} ...
11952 If the whole expansion string is in double quotes, further escaping of
11953 backslashes is also required.
11955 The condition is true if the regular expression match succeeds.
11956 The regular expression is not required to begin with a circumflex
11957 metacharacter, but if there is no circumflex, the expression is not anchored,
11958 and it may match anywhere in the subject, not just at the start. If you want
11959 the pattern to match at the end of the subject, you must include the &`$`&
11960 metacharacter at an appropriate point.
11961 All character handling is done in bytes and is not UTF-8 aware,
11962 but we might change this in a future Exim release.
11964 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%if%& expansion"
11965 At the start of an &%if%& expansion the values of the numeric variable
11966 substitutions &$1$& etc. are remembered. Obeying a &%match%& condition that
11967 succeeds causes them to be reset to the substrings of that condition and they
11968 will have these values during the expansion of the success string. At the end
11969 of the &%if%& expansion, the previous values are restored. After testing a
11970 combination of conditions using &%or%&, the subsequent values of the numeric
11971 variables are those of the condition that succeeded.
11973 .vitem &*match_address&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11974 .cindex "&%match_address%& expansion condition"
11975 See &*match_local_part*&.
11977 .vitem &*match_domain&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11978 .cindex "&%match_domain%& expansion condition"
11979 See &*match_local_part*&.
11981 .vitem &*match_ip&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11982 .cindex "&%match_ip%& expansion condition"
11983 This condition matches an IP address to a list of IP address patterns. It must
11984 be followed by two argument strings. The first (after expansion) must be an IP
11985 address or an empty string. The second (not expanded) is a restricted host
11986 list that can match only an IP address, not a host name. For example:
11988 ${if match_ip{$sender_host_address}{1.2.3.4:5.6.7.8}{...}{...}}
11990 The specific types of host list item that are permitted in the list are:
11993 An IP address, optionally with a CIDR mask.
11995 A single asterisk, which matches any IP address.
11997 An empty item, which matches only if the IP address is empty. This could be
11998 useful for testing for a locally submitted message or one from specific hosts
11999 in a single test such as
12000 . ==== As this is a nested list, any displays it contains must be indented
12001 . ==== as otherwise they are too far to the left. This comment applies to
12002 . ==== the use of xmlto plus fop. There's no problem when formatting with
12003 . ==== sdop, with or without the extra indent.
12005 ${if match_ip{$sender_host_address}{:4.3.2.1:...}{...}{...}}
12007 where the first item in the list is the empty string.
12009 The item @[] matches any of the local host's interface addresses.
12011 Single-key lookups are assumed to be like &"net-"& style lookups in host lists,
12012 even if &`net-`& is not specified. There is never any attempt to turn the IP
12013 address into a host name. The most common type of linear search for
12014 &*match_ip*& is likely to be &*iplsearch*&, in which the file can contain CIDR
12015 masks. For example:
12017 ${if match_ip{$sender_host_address}{iplsearch;/some/file}...
12019 It is of course possible to use other kinds of lookup, and in such a case, you
12020 do need to specify the &`net-`& prefix if you want to specify a specific
12021 address mask, for example:
12023 ${if match_ip{$sender_host_address}{net24-dbm;/some/file}...
12025 However, unless you are combining a &%match_ip%& condition with others, it is
12026 just as easy to use the fact that a lookup is itself a condition, and write:
12028 ${lookup{${mask:$sender_host_address/24}}dbm{/a/file}...
12032 Note that <&'string2'&> is not itself subject to string expansion, unless
12033 Exim was built with the EXPAND_LISTMATCH_RHS option.
12035 Consult section &<<SECThoslispatip>>& for further details of these patterns.
12037 .vitem &*match_local_part&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
12038 .cindex "domain list" "in expansion condition"
12039 .cindex "address list" "in expansion condition"
12040 .cindex "local part" "list, in expansion condition"
12041 .cindex "&%match_local_part%& expansion condition"
12042 This condition, together with &%match_address%& and &%match_domain%&, make it
12043 possible to test domain, address, and local part lists within expansions. Each
12044 condition requires two arguments: an item and a list to match. A trivial
12047 ${if match_domain{a.b.c}{x.y.z:a.b.c:p.q.r}{yes}{no}}
12049 In each case, the second argument may contain any of the allowable items for a
12050 list of the appropriate type. Also, because the second argument
12051 is a standard form of list, it is possible to refer to a named list.
12052 Thus, you can use conditions like this:
12054 ${if match_domain{$domain}{+local_domains}{...
12056 .cindex "&`+caseful`&"
12057 For address lists, the matching starts off caselessly, but the &`+caseful`&
12058 item can be used, as in all address lists, to cause subsequent items to
12059 have their local parts matched casefully. Domains are always matched
12062 The variable &$value$& will be set for a successful match and can be
12063 used in the success clause of an &%if%& expansion item using the condition.
12064 .cindex "tainted data" "de-tainting"
12065 .cindex "de-tainting" "using a match_local_part expansion condition"
12066 It will have the same taint status as the list; expansions such as
12068 ${if match_local_part {$local_part} {alice : bill : charlotte : dave} {$value}}
12070 can be used for de-tainting.
12071 Any previous &$value$& is restored after the if.
12073 Note that <&'string2'&> is not itself subject to string expansion, unless
12074 Exim was built with the EXPAND_LISTMATCH_RHS option.
12076 &*Note*&: Host lists are &'not'& supported in this way. This is because
12077 hosts have two identities: a name and an IP address, and it is not clear
12078 how to specify cleanly how such a test would work. However, IP addresses can be
12079 matched using &%match_ip%&.
12081 .vitem &*pam&~{*&<&'string1'&>&*:*&<&'string2'&>&*:...}*&
12082 .cindex "PAM authentication"
12083 .cindex "AUTH" "with PAM"
12084 .cindex "Solaris" "PAM support"
12085 .cindex "expansion" "PAM authentication test"
12086 .cindex "&%pam%& expansion condition"
12087 &'Pluggable Authentication Modules'&
12088 (&url(https://mirrors.edge.kernel.org/pub/linux/libs/pam/)) are a facility that is
12089 available in Solaris
12090 and in some GNU/Linux distributions.
12091 The Exim support, which is intended for use in conjunction with
12092 the SMTP AUTH command, is available only if Exim is compiled with
12096 in &_Local/Makefile_&. You probably need to add &%-lpam%& to EXTRALIBS, and
12097 in some releases of GNU/Linux &%-ldl%& is also needed.
12099 The argument string is first expanded, and the result must be a
12100 colon-separated list of strings. Leading and trailing white space is ignored.
12101 The PAM module is initialized with the service name &"exim"& and the user name
12102 taken from the first item in the colon-separated data string (<&'string1'&>).
12103 The remaining items in the data string are passed over in response to requests
12104 from the authentication function. In the simple case there will only be one
12105 request, for a password, so the data consists of just two strings.
12107 There can be problems if any of the strings are permitted to contain colon
12108 characters. In the usual way, these have to be doubled to avoid being taken as
12110 The &%listquote%& expansion item can be used for this.
12111 For example, the configuration
12112 of a LOGIN authenticator might contain this setting:
12114 server_condition = ${if pam{$auth1:${listquote{:}{$auth2}}}}
12116 In some operating systems, PAM authentication can be done only from a process
12117 running as root. Since Exim is running as the Exim user when receiving
12118 messages, this means that PAM cannot be used directly in those systems.
12119 . --- 2018-09-07: the pam_exim modified variant has gone, removed claims re using Exim via that
12122 .vitem &*pwcheck&~{*&<&'string1'&>&*:*&<&'string2'&>&*}*&
12123 .cindex "&'pwcheck'& daemon"
12125 .cindex "expansion" "&'pwcheck'& authentication test"
12126 .cindex "&%pwcheck%& expansion condition"
12127 This condition supports user authentication using the Cyrus &'pwcheck'& daemon.
12128 This is one way of making it possible for passwords to be checked by a process
12129 that is not running as root. &*Note*&: The use of &'pwcheck'& is now
12130 deprecated. Its replacement is &'saslauthd'& (see below).
12132 The pwcheck support is not included in Exim by default. You need to specify
12133 the location of the pwcheck daemon's socket in &_Local/Makefile_& before
12134 building Exim. For example:
12136 CYRUS_PWCHECK_SOCKET=/var/pwcheck/pwcheck
12138 You do not need to install the full Cyrus software suite in order to use
12139 the pwcheck daemon. You can compile and install just the daemon alone
12140 from the Cyrus SASL library. Ensure that &'exim'& is the only user that has
12141 access to the &_/var/pwcheck_& directory.
12143 The &%pwcheck%& condition takes one argument, which must be the user name and
12144 password, separated by a colon. For example, in a LOGIN authenticator
12145 configuration, you might have this:
12147 server_condition = ${if pwcheck{$auth1:$auth2}}
12149 Again, for a PLAIN authenticator configuration, this would be:
12151 server_condition = ${if pwcheck{$auth2:$auth3}}
12153 .vitem &*queue_running*&
12154 .cindex "queue runner" "detecting when delivering from"
12155 .cindex "expansion" "queue runner test"
12156 .cindex "&%queue_running%& expansion condition"
12157 This condition, which has no data, is true during delivery attempts that are
12158 initiated by queue runner processes, and false otherwise.
12161 .vitem &*radius&~{*&<&'authentication&~string'&>&*}*&
12163 .cindex "expansion" "Radius authentication"
12164 .cindex "&%radius%& expansion condition"
12165 Radius authentication (RFC 2865) is supported in a similar way to PAM. You must
12166 set RADIUS_CONFIG_FILE in &_Local/Makefile_& to specify the location of
12167 the Radius client configuration file in order to build Exim with Radius
12170 With just that one setting, Exim expects to be linked with the &%radiusclient%&
12171 library, using the original API. If you are using release 0.4.0 or later of
12172 this library, you need to set
12174 RADIUS_LIB_TYPE=RADIUSCLIENTNEW
12176 in &_Local/Makefile_& when building Exim. You can also link Exim with the
12177 &%libradius%& library that comes with FreeBSD. To do this, set
12179 RADIUS_LIB_TYPE=RADLIB
12181 in &_Local/Makefile_&, in addition to setting RADIUS_CONFIGURE_FILE.
12182 You may also have to supply a suitable setting in EXTRALIBS so that the
12183 Radius library can be found when Exim is linked.
12185 The string specified by RADIUS_CONFIG_FILE is expanded and passed to the
12186 Radius client library, which calls the Radius server. The condition is true if
12187 the authentication is successful. For example:
12189 server_condition = ${if radius{<arguments>}}
12193 .vitem "&*saslauthd&~{{*&<&'user'&>&*}{*&<&'password'&>&*}&&&
12194 {*&<&'service'&>&*}{*&<&'realm'&>&*}}*&"
12195 .cindex "&'saslauthd'& daemon"
12197 .cindex "expansion" "&'saslauthd'& authentication test"
12198 .cindex "&%saslauthd%& expansion condition"
12199 This condition supports user authentication using the Cyrus &'saslauthd'&
12200 daemon. This replaces the older &'pwcheck'& daemon, which is now deprecated.
12201 Using this daemon is one way of making it possible for passwords to be checked
12202 by a process that is not running as root.
12204 The saslauthd support is not included in Exim by default. You need to specify
12205 the location of the saslauthd daemon's socket in &_Local/Makefile_& before
12206 building Exim. For example:
12208 CYRUS_SASLAUTHD_SOCKET=/var/state/saslauthd/mux
12210 You do not need to install the full Cyrus software suite in order to use
12211 the saslauthd daemon. You can compile and install just the daemon alone
12212 from the Cyrus SASL library.
12214 Up to four arguments can be supplied to the &%saslauthd%& condition, but only
12215 two are mandatory. For example:
12217 server_condition = ${if saslauthd{{$auth1}{$auth2}}}
12219 The service and the realm are optional (which is why the arguments are enclosed
12220 in their own set of braces). For details of the meaning of the service and
12221 realm, and how to run the daemon, consult the Cyrus documentation.
12226 .section "Combining expansion conditions" "SECID84"
12227 .cindex "expansion" "combining conditions"
12228 Several conditions can be tested at once by combining them using the &%and%&
12229 and &%or%& combination conditions. Note that &%and%& and &%or%& are complete
12230 conditions on their own, and precede their lists of sub-conditions. Each
12231 sub-condition must be enclosed in braces within the overall braces that contain
12232 the list. No repetition of &%if%& is used.
12236 .vitem &*or&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
12237 .cindex "&""or""& expansion condition"
12238 .cindex "expansion" "&""or""& of conditions"
12239 The sub-conditions are evaluated from left to right. The condition is true if
12240 any one of the sub-conditions is true.
12243 ${if or {{eq{$local_part}{spqr}}{eq{$domain}{testing.com}}}...
12245 When a true sub-condition is found, the following ones are parsed but not
12246 evaluated. If there are several &"match"& sub-conditions the values of the
12247 numeric variables afterwards are taken from the first one that succeeds.
12249 .vitem &*and&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
12250 .cindex "&""and""& expansion condition"
12251 .cindex "expansion" "&""and""& of conditions"
12252 The sub-conditions are evaluated from left to right. The condition is true if
12253 all of the sub-conditions are true. If there are several &"match"&
12254 sub-conditions, the values of the numeric variables afterwards are taken from
12255 the last one. When a false sub-condition is found, the following ones are
12256 parsed but not evaluated.
12258 .ecindex IIDexpcond
12263 .section "Expansion variables" "SECTexpvar"
12264 .cindex "expansion" "variables, list of"
12265 This section contains an alphabetical list of all the expansion variables. Some
12266 of them are available only when Exim is compiled with specific options such as
12267 support for TLS or the content scanning extension.
12268 .cindex "tainted data"
12269 Variables marked as &'tainted'& are likely to carry data supplied by
12270 a potential attacker.
12271 Variables without such marking may also, depending on how their
12272 values are created.
12273 Such variables should not be further expanded,
12275 or used as command-line arguments for external commands.
12278 .vitem "&$0$&, &$1$&, etc"
12279 .cindex "numerical variables (&$1$& &$2$& etc)"
12280 When a &%match%& expansion condition succeeds, these variables contain the
12281 captured substrings identified by the regular expression during subsequent
12282 processing of the success string of the containing &%if%& expansion item.
12283 In the expansion condition case
12284 they do not retain their values afterwards; in fact, their previous
12285 values are restored at the end of processing an &%if%& item. The numerical
12286 variables may also be set externally by some other matching process which
12287 precedes the expansion of the string. For example, the commands available in
12288 Exim filter files include an &%if%& command with its own regular expression
12289 matching condition.
12290 If the subject string was tainted then any captured substring will also be.
12292 .vitem "&$acl_arg1$&, &$acl_arg2$&, etc"
12293 Within an acl condition, expansion condition or expansion item
12294 any arguments are copied to these variables,
12295 any unused variables being made empty.
12297 .vitem "&$acl_c...$&"
12298 Values can be placed in these variables by the &%set%& modifier in an ACL. They
12299 can be given any name that starts with &$acl_c$& and is at least six characters
12300 long, but the sixth character must be either a digit or an underscore. For
12301 example: &$acl_c5$&, &$acl_c_mycount$&. The values of the &$acl_c...$&
12302 variables persist throughout the lifetime of an SMTP connection. They can be
12303 used to pass information between ACLs and between different invocations of the
12304 same ACL. When a message is received, the values of these variables are saved
12305 with the message, and can be accessed by filters, routers, and transports
12306 during subsequent delivery.
12308 .vitem "&$acl_m...$&"
12309 These variables are like the &$acl_c...$& variables, except that their values
12310 are reset after a message has been received. Thus, if several messages are
12311 received in one SMTP connection, &$acl_m...$& values are not passed on from one
12312 message to the next, as &$acl_c...$& values are. The &$acl_m...$& variables are
12313 also reset by MAIL, RSET, EHLO, HELO, and after starting a TLS session. When a
12314 message is received, the values of these variables are saved with the message,
12315 and can be accessed by filters, routers, and transports during subsequent
12318 .vitem &$acl_narg$&
12319 Within an acl condition, expansion condition or expansion item
12320 this variable has the number of arguments.
12322 .vitem &$acl_verify_message$&
12323 .vindex "&$acl_verify_message$&"
12324 After an address verification has failed, this variable contains the failure
12325 message. It retains its value for use in subsequent modifiers of the verb.
12326 The message can be preserved by coding like this:
12328 warn !verify = sender
12329 set acl_m0 = $acl_verify_message
12331 You can use &$acl_verify_message$& during the expansion of the &%message%& or
12332 &%log_message%& modifiers, to include information about the verification
12334 &*Note*&: The variable is cleared at the end of processing the ACL verb.
12336 .vitem &$address_data$&
12337 .vindex "&$address_data$&"
12338 This variable is set by means of the &%address_data%& option in routers. The
12339 value then remains with the address while it is processed by subsequent routers
12340 and eventually a transport. If the transport is handling multiple addresses,
12341 the value from the first address is used. See chapter &<<CHAProutergeneric>>&
12342 for more details. &*Note*&: The contents of &$address_data$& are visible in
12345 If &$address_data$& is set when the routers are called from an ACL to verify
12346 a recipient address, the final value is still in the variable for subsequent
12347 conditions and modifiers of the ACL statement. If routing the address caused it
12348 to be redirected to just one address, the child address is also routed as part
12349 of the verification, and in this case the final value of &$address_data$& is
12350 from the child's routing.
12352 If &$address_data$& is set when the routers are called from an ACL to verify a
12353 sender address, the final value is also preserved, but this time in
12354 &$sender_address_data$&, to distinguish it from data from a recipient
12357 In both cases (recipient and sender verification), the value does not persist
12358 after the end of the current ACL statement. If you want to preserve
12359 these values for longer, you can save them in ACL variables.
12361 .vitem &$address_file$&
12362 .vindex "&$address_file$&"
12363 When, as a result of aliasing, forwarding, or filtering, a message is directed
12364 to a specific file, this variable holds the name of the file when the transport
12365 is running. At other times, the variable is empty. For example, using the
12366 default configuration, if user &%r2d2%& has a &_.forward_& file containing
12368 /home/r2d2/savemail
12370 then when the &(address_file)& transport is running, &$address_file$&
12371 contains the text string &`/home/r2d2/savemail`&.
12372 .cindex "Sieve filter" "value of &$address_file$&"
12373 For Sieve filters, the value may be &"inbox"& or a relative folder name. It is
12374 then up to the transport configuration to generate an appropriate absolute path
12375 to the relevant file.
12377 .vitem &$address_pipe$&
12378 .vindex "&$address_pipe$&"
12379 When, as a result of aliasing or forwarding, a message is directed to a pipe,
12380 this variable holds the pipe command when the transport is running.
12382 .vitem "&$auth1$& &-- &$auth4$&"
12383 .vindex "&$auth1$&, &$auth2$&, etc"
12384 These variables are used in SMTP authenticators (see chapters
12385 &<<CHAPplaintext>>&&--&<<CHAPtlsauth>>&). Elsewhere, they are empty.
12387 .vitem &$authenticated_id$&
12388 .cindex "authentication" "id"
12389 .vindex "&$authenticated_id$&"
12390 When a server successfully authenticates a client it may be configured to
12391 preserve some of the authentication information in the variable
12392 &$authenticated_id$& (see chapter &<<CHAPSMTPAUTH>>&). For example, a
12393 user/password authenticator configuration might preserve the user name for use
12394 in the routers. Note that this is not the same information that is saved in
12395 &$sender_host_authenticated$&.
12397 When a message is submitted locally (that is, not over a TCP connection)
12398 the value of &$authenticated_id$& is normally the login name of the calling
12399 process. However, a trusted user can override this by means of the &%-oMai%&
12400 command line option.
12401 This second case also sets up information used by the
12402 &$authresults$& expansion item.
12404 .vitem &$authenticated_fail_id$&
12405 .cindex "authentication" "fail" "id"
12406 .vindex "&$authenticated_fail_id$&"
12407 When an authentication attempt fails, the variable &$authenticated_fail_id$&
12408 will contain the failed authentication id. If more than one authentication
12409 id is attempted, it will contain only the last one. The variable is
12410 available for processing in the ACL's, generally the quit or notquit ACL.
12411 A message to a local recipient could still be accepted without requiring
12412 authentication, which means this variable could also be visible in all of
12416 .tvar &$authenticated_sender$&
12417 .cindex "sender" "authenticated"
12418 .cindex "authentication" "sender"
12419 .cindex "AUTH" "on MAIL command"
12420 When acting as a server, Exim takes note of the AUTH= parameter on an incoming
12421 SMTP MAIL command if it believes the sender is sufficiently trusted, as
12422 described in section &<<SECTauthparamail>>&. Unless the data is the string
12423 &"<>"&, it is set as the authenticated sender of the message, and the value is
12424 available during delivery in the &$authenticated_sender$& variable. If the
12425 sender is not trusted, Exim accepts the syntax of AUTH=, but ignores the data.
12427 .vindex "&$qualify_domain$&"
12428 When a message is submitted locally (that is, not over a TCP connection), the
12429 value of &$authenticated_sender$& is an address constructed from the login
12430 name of the calling process and &$qualify_domain$&, except that a trusted user
12431 can override this by means of the &%-oMas%& command line option.
12434 .vitem &$authentication_failed$&
12435 .cindex "authentication" "failure"
12436 .vindex "&$authentication_failed$&"
12437 This variable is set to &"1"& in an Exim server if a client issues an AUTH
12438 command that does not succeed. Otherwise it is set to &"0"&. This makes it
12439 possible to distinguish between &"did not try to authenticate"&
12440 (&$sender_host_authenticated$& is empty and &$authentication_failed$& is set to
12441 &"0"&) and &"tried to authenticate but failed"& (&$sender_host_authenticated$&
12442 is empty and &$authentication_failed$& is set to &"1"&).
12443 Failure includes cancellation of a authentication attempt,
12444 and any negative response to an AUTH command,
12445 (including, for example, an attempt to use an undefined mechanism).
12447 .vitem &$av_failed$&
12448 .cindex "content scanning" "AV scanner failure"
12449 This variable is available when Exim is compiled with the content-scanning
12450 extension. It is set to &"0"& by default, but will be set to &"1"& if any
12451 problem occurs with the virus scanner (specified by &%av_scanner%&) during
12452 the ACL malware condition.
12454 .vitem &$body_linecount$&
12455 .cindex "message body" "line count"
12456 .cindex "body of message" "line count"
12457 .vindex "&$body_linecount$&"
12458 When a message is being received or delivered, this variable contains the
12459 number of lines in the message's body. See also &$message_linecount$&.
12461 .vitem &$body_zerocount$&
12462 .cindex "message body" "binary zero count"
12463 .cindex "body of message" "binary zero count"
12464 .cindex "binary zero" "in message body"
12465 .vindex "&$body_zerocount$&"
12466 When a message is being received or delivered, this variable contains the
12467 number of binary zero bytes (ASCII NULs) in the message's body.
12469 .vitem &$bounce_recipient$&
12470 .vindex "&$bounce_recipient$&"
12471 This is set to the recipient address of a bounce message while Exim is creating
12472 it. It is useful if a customized bounce message text file is in use (see
12473 chapter &<<CHAPemsgcust>>&).
12475 .vitem &$bounce_return_size_limit$&
12476 .vindex "&$bounce_return_size_limit$&"
12477 This contains the value set in the &%bounce_return_size_limit%& option, rounded
12478 up to a multiple of 1000. It is useful when a customized error message text
12479 file is in use (see chapter &<<CHAPemsgcust>>&).
12481 .vitem &$caller_gid$&
12482 .cindex "gid (group id)" "caller"
12483 .vindex "&$caller_gid$&"
12484 The real group id under which the process that called Exim was running. This is
12485 not the same as the group id of the originator of a message (see
12486 &$originator_gid$&). If Exim re-execs itself, this variable in the new
12487 incarnation normally contains the Exim gid.
12489 .vitem &$caller_uid$&
12490 .cindex "uid (user id)" "caller"
12491 .vindex "&$caller_uid$&"
12492 The real user id under which the process that called Exim was running. This is
12493 not the same as the user id of the originator of a message (see
12494 &$originator_uid$&). If Exim re-execs itself, this variable in the new
12495 incarnation normally contains the Exim uid.
12497 .vitem &$callout_address$&
12498 .vindex "&$callout_address$&"
12499 After a callout for verification, spamd or malware daemon service, the
12500 address that was connected to.
12502 .vitem &$compile_number$&
12503 .vindex "&$compile_number$&"
12504 The building process for Exim keeps a count of the number
12505 of times it has been compiled. This serves to distinguish different
12506 compilations of the same version of Exim.
12508 .vitem &$config_dir$&
12509 .vindex "&$config_dir$&"
12510 The directory name of the main configuration file. That is, the content of
12511 &$config_file$& with the last component stripped. The value does not
12512 contain the trailing slash. If &$config_file$& does not contain a slash,
12513 &$config_dir$& is ".".
12515 .vitem &$config_file$&
12516 .vindex "&$config_file$&"
12517 The name of the main configuration file Exim is using.
12519 .vitem &$dkim_verify_status$&
12520 Results of DKIM verification.
12521 For details see section &<<SECDKIMVFY>>&.
12523 .vitem &$dkim_cur_signer$& &&&
12524 &$dkim_verify_reason$& &&&
12525 &$dkim_domain$& &&&
12526 &$dkim_identity$& &&&
12527 &$dkim_selector$& &&&
12529 &$dkim_canon_body$& &&&
12530 &$dkim_canon_headers$& &&&
12531 &$dkim_copiedheaders$& &&&
12532 &$dkim_bodylength$& &&&
12533 &$dkim_created$& &&&
12534 &$dkim_expires$& &&&
12535 &$dkim_headernames$& &&&
12536 &$dkim_key_testing$& &&&
12537 &$dkim_key_nosubdomains$& &&&
12538 &$dkim_key_srvtype$& &&&
12539 &$dkim_key_granularity$& &&&
12540 &$dkim_key_notes$& &&&
12541 &$dkim_key_length$&
12542 These variables are only available within the DKIM ACL.
12543 For details see section &<<SECDKIMVFY>>&.
12545 .vitem &$dkim_signers$&
12546 .vindex &$dkim_signers$&
12547 When a message has been received this variable contains
12548 a colon-separated list of signer domains and identities for the message.
12549 For details see section &<<SECDKIMVFY>>&.
12551 .vitem &$dmarc_domain_policy$& &&&
12552 &$dmarc_status$& &&&
12553 &$dmarc_status_text$& &&&
12554 &$dmarc_used_domains$&
12555 Results of DMARC verification.
12556 For details see section &<<SECDMARC>>&.
12558 .vitem &$dnslist_domain$& &&&
12559 &$dnslist_matched$& &&&
12560 &$dnslist_text$& &&&
12562 .vindex "&$dnslist_domain$&"
12563 .vindex "&$dnslist_matched$&"
12564 .vindex "&$dnslist_text$&"
12565 .vindex "&$dnslist_value$&"
12566 .cindex "black list (DNS)"
12567 When a DNS (black) list lookup succeeds, these variables are set to contain
12568 the following data from the lookup: the list's domain name, the key that was
12569 looked up, the contents of any associated TXT record, and the value from the
12570 main A record. See section &<<SECID204>>& for more details.
12573 When an address is being routed, or delivered on its own, this variable
12574 contains the domain. Uppercase letters in the domain are converted into lower
12575 case for &$domain$&.
12577 Global address rewriting happens when a message is received, so the value of
12578 &$domain$& during routing and delivery is the value after rewriting. &$domain$&
12579 is set during user filtering, but not during system filtering, because a
12580 message may have many recipients and the system filter is called just once.
12582 When more than one address is being delivered at once (for example, several
12583 RCPT commands in one SMTP delivery), &$domain$& is set only if they all
12584 have the same domain. Transports can be restricted to handling only one domain
12585 at a time if the value of &$domain$& is required at transport time &-- this is
12586 the default for local transports. For further details of the environment in
12587 which local transports are run, see chapter &<<CHAPenvironment>>&.
12589 .oindex "&%delay_warning_condition%&"
12590 At the end of a delivery, if all deferred addresses have the same domain, it is
12591 set in &$domain$& during the expansion of &%delay_warning_condition%&.
12593 The &$domain$& variable is also used in some other circumstances:
12596 When an ACL is running for a RCPT command, &$domain$& contains the domain of
12597 the recipient address. The domain of the &'sender'& address is in
12598 &$sender_address_domain$& at both MAIL time and at RCPT time. &$domain$& is not
12599 normally set during the running of the MAIL ACL. However, if the sender address
12600 is verified with a callout during the MAIL ACL, the sender domain is placed in
12601 &$domain$& during the expansions of &%hosts%&, &%interface%&, and &%port%& in
12602 the &(smtp)& transport.
12605 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
12606 &$domain$& contains the domain portion of the address that is being rewritten;
12607 it can be used in the expansion of the replacement address, for example, to
12608 rewrite domains by file lookup.
12611 With one important exception, whenever a domain list is being scanned,
12612 &$domain$& contains the subject domain. &*Exception*&: When a domain list in
12613 a &%sender_domains%& condition in an ACL is being processed, the subject domain
12614 is in &$sender_address_domain$& and not in &$domain$&. It works this way so
12615 that, in a RCPT ACL, the sender domain list can be dependent on the
12616 recipient domain (which is what is in &$domain$& at this time).
12619 .cindex "ETRN" "value of &$domain$&"
12620 .oindex "&%smtp_etrn_command%&"
12621 When the &%smtp_etrn_command%& option is being expanded, &$domain$& contains
12622 the complete argument of the ETRN command (see section &<<SECTETRN>>&).
12625 .cindex "tainted data"
12626 If the origin of the data is an incoming message,
12627 the result of expanding this variable is tainted and may not
12628 be further expanded or used as a filename.
12629 When an untainted version is needed, one should be obtained from
12630 looking up the value in a local (therefore trusted) database.
12631 Often &$domain_data$& is usable in this role.
12634 .vitem &$domain_data$&
12635 .vindex "&$domain_data$&"
12636 When the &%domains%& condition on a router
12639 against a list, the match value is copied to &$domain_data$&.
12640 This is an enhancement over previous versions of Exim, when it only
12641 applied to the data read by a lookup.
12642 For details on match values see section &<<SECTlistresults>>& et. al.
12644 If the router routes the
12645 address to a transport, the value is available in that transport. If the
12646 transport is handling multiple addresses, the value from the first address is
12649 &$domain_data$& set in an ACL is available during
12650 the rest of the ACL statement.
12652 .vitem &$exim_gid$&
12653 .vindex "&$exim_gid$&"
12654 This variable contains the numerical value of the Exim group id.
12656 .vitem &$exim_path$&
12657 .vindex "&$exim_path$&"
12658 This variable contains the path to the Exim binary.
12660 .vitem &$exim_uid$&
12661 .vindex "&$exim_uid$&"
12662 This variable contains the numerical value of the Exim user id.
12664 .vitem &$exim_version$&
12665 .vindex "&$exim_version$&"
12666 This variable contains the version string of the Exim build.
12667 The first character is a major version number, currently 4.
12668 Then after a dot, the next group of digits is a minor version number.
12669 There may be other characters following the minor version.
12670 This value may be overridden by the &%exim_version%& main config option.
12672 .vitem &$header_$&<&'name'&>
12674 This is not strictly an expansion variable. It is expansion syntax for
12675 inserting the message header line with the given name. Note that the name must
12676 be terminated by colon or white space, because it may contain a wide variety of
12677 characters. Note also that braces must &'not'& be used.
12678 See the full description in section &<<SECTexpansionitems>>& above.
12680 .vitem &$headers_added$&
12681 .vindex "&$headers_added$&"
12682 Within an ACL this variable contains the headers added so far by
12683 the ACL modifier add_header (section &<<SECTaddheadacl>>&).
12684 The headers are a newline-separated list.
12688 When the &%check_local_user%& option is set for a router, the user's home
12689 directory is placed in &$home$& when the check succeeds. In particular, this
12690 means it is set during the running of users' filter files. A router may also
12691 explicitly set a home directory for use by a transport; this can be overridden
12692 by a setting on the transport itself.
12694 When running a filter test via the &%-bf%& option, &$home$& is set to the value
12695 of the environment variable HOME, which is subject to the
12696 &%keep_environment%& and &%add_environment%& main config options.
12700 If a router assigns an address to a transport (any transport), and passes a
12701 list of hosts with the address, the value of &$host$& when the transport starts
12702 to run is the name of the first host on the list. Note that this applies both
12703 to local and remote transports.
12705 .cindex "transport" "filter"
12706 .cindex "filter" "transport filter"
12707 For the &(smtp)& transport, if there is more than one host, the value of
12708 &$host$& changes as the transport works its way through the list. In
12709 particular, when the &(smtp)& transport is expanding its options for encryption
12710 using TLS, or for specifying a transport filter (see chapter
12711 &<<CHAPtransportgeneric>>&), &$host$& contains the name of the host to which it
12714 When used in the client part of an authenticator configuration (see chapter
12715 &<<CHAPSMTPAUTH>>&), &$host$& contains the name of the server to which the
12716 client is connected.
12719 .vitem &$host_address$&
12720 .vindex "&$host_address$&"
12721 This variable is set to the remote host's IP address whenever &$host$& is set
12722 for a remote connection. It is also set to the IP address that is being checked
12723 when the &%ignore_target_hosts%& option is being processed.
12725 .vitem &$host_data$&
12726 .vindex "&$host_data$&"
12727 If a &%hosts%& condition in an ACL is satisfied by means of a lookup, the
12728 result of the lookup is made available in the &$host_data$& variable. This
12729 allows you, for example, to do things like this:
12731 deny hosts = net-lsearch;/some/file
12732 message = $host_data
12735 .vitem &$host_lookup_deferred$&
12736 .cindex "host name" "lookup, failure of"
12737 .vindex "&$host_lookup_deferred$&"
12738 This variable normally contains &"0"&, as does &$host_lookup_failed$&. When a
12739 message comes from a remote host and there is an attempt to look up the host's
12740 name from its IP address, and the attempt is not successful, one of these
12741 variables is set to &"1"&.
12744 If the lookup receives a definite negative response (for example, a DNS lookup
12745 succeeded, but no records were found), &$host_lookup_failed$& is set to &"1"&.
12748 If there is any kind of problem during the lookup, such that Exim cannot
12749 tell whether or not the host name is defined (for example, a timeout for a DNS
12750 lookup), &$host_lookup_deferred$& is set to &"1"&.
12753 Looking up a host's name from its IP address consists of more than just a
12754 single reverse lookup. Exim checks that a forward lookup of at least one of the
12755 names it receives from a reverse lookup yields the original IP address. If this
12756 is not the case, Exim does not accept the looked up name(s), and
12757 &$host_lookup_failed$& is set to &"1"&. Thus, being able to find a name from an
12758 IP address (for example, the existence of a PTR record in the DNS) is not
12759 sufficient on its own for the success of a host name lookup. If the reverse
12760 lookup succeeds, but there is a lookup problem such as a timeout when checking
12761 the result, the name is not accepted, and &$host_lookup_deferred$& is set to
12762 &"1"&. See also &$sender_host_name$&.
12764 .cindex authentication "expansion item"
12765 Performing these checks sets up information used by the
12766 &%authresults%& expansion item.
12769 .vitem &$host_lookup_failed$&
12770 .vindex "&$host_lookup_failed$&"
12771 See &$host_lookup_deferred$&.
12773 .vitem &$host_port$&
12774 .vindex "&$host_port$&"
12775 This variable is set to the remote host's TCP port whenever &$host$& is set
12776 for an outbound connection.
12778 .vitem &$initial_cwd$&
12779 .vindex "&$initial_cwd$&
12780 This variable contains the full path name of the initial working
12781 directory of the current Exim process. This may differ from the current
12782 working directory, as Exim changes this to "/" during early startup, and
12783 to &$spool_directory$& later.
12786 .vindex "&$inode$&"
12787 The only time this variable is set is while expanding the &%directory_file%&
12788 option in the &(appendfile)& transport. The variable contains the inode number
12789 of the temporary file which is about to be renamed. It can be used to construct
12790 a unique name for the file.
12792 .vitem &$interface_address$& &&&
12794 .vindex "&$interface_address$&"
12795 .vindex "&$interface_port$&"
12796 These are obsolete names for &$received_ip_address$& and &$received_port$&.
12800 This variable is used during the expansion of &*forall*& and &*forany*&
12801 conditions (see section &<<SECTexpcond>>&), and &*filter*&, &*map*&, and
12802 &*reduce*& items (see section &<<SECTexpcond>>&). In other circumstances, it is
12806 .vindex "&$ldap_dn$&"
12807 This variable, which is available only when Exim is compiled with LDAP support,
12808 contains the DN from the last entry in the most recently successful LDAP
12811 .vitem &$load_average$&
12812 .vindex "&$load_average$&"
12813 This variable contains the system load average, multiplied by 1000 so that it
12814 is an integer. For example, if the load average is 0.21, the value of the
12815 variable is 210. The value is recomputed every time the variable is referenced.
12817 .tvar &$local_part$&
12818 When an address is being routed, or delivered on its own, this
12819 variable contains the local part. When a number of addresses are being
12820 delivered together (for example, multiple RCPT commands in an SMTP
12821 session), &$local_part$& is not set.
12823 Global address rewriting happens when a message is received, so the value of
12824 &$local_part$& during routing and delivery is the value after rewriting.
12825 &$local_part$& is set during user filtering, but not during system filtering,
12826 because a message may have many recipients and the system filter is called just
12829 .cindex "tainted data"
12830 If the origin of the data is an incoming message,
12831 the result of expanding this variable is tainted and
12832 may not be further expanded or used as a filename.
12834 &*Warning*&: the content of this variable is usually provided by a potential
12836 Consider carefully the implications of using it unvalidated as a name
12838 This presents issues for users' &_.forward_& and filter files.
12839 For traditional full user accounts, use &%check_local_users%& and the
12840 &$local_part_data$& variable rather than this one.
12841 For virtual users, store a suitable pathname component in the database
12842 which is used for account name validation, and use that retrieved value
12843 rather than this variable.
12844 Often &$local_part_data$& is usable in this role.
12845 If needed, use a router &%address_data%& or &%set%& option for
12846 the retrieved data.
12848 When a message is being delivered to a file, pipe, or autoreply transport as a
12849 result of aliasing or forwarding, &$local_part$& is set to the local part of
12850 the parent address, not to the filename or command (see &$address_file$& and
12853 When an ACL is running for a RCPT command, &$local_part$& contains the
12854 local part of the recipient address.
12856 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
12857 &$local_part$& contains the local part of the address that is being rewritten;
12858 it can be used in the expansion of the replacement address, for example.
12860 In all cases, all quoting is removed from the local part. For example, for both
12863 "abc:xyz"@test.example
12864 abc\:xyz@test.example
12866 the value of &$local_part$& is
12870 If you use &$local_part$& to create another address, you should always wrap it
12871 inside a quoting operator. For example, in a &(redirect)& router you could
12874 data = ${quote_local_part:$local_part}@new.domain.example
12876 &*Note*&: The value of &$local_part$& is normally lower cased. If you want
12877 to process local parts in a case-dependent manner in a router, you can set the
12878 &%caseful_local_part%& option (see chapter &<<CHAProutergeneric>>&).
12880 .vitem &$local_part_data$&
12881 .vindex "&$local_part_data$&"
12882 When the &%local_parts%& condition on a router or ACL
12883 matches a local part list
12884 the match value is copied to &$local_part_data$&.
12885 This is an enhancement over previous versions of Exim, when it only
12886 applied to the data read by a lookup.
12887 For details on match values see section &<<SECTlistresults>>& et. al.
12889 The &%check_local_user%& router option also sets this variable.
12891 .vindex &$local_part_prefix$& &&&
12892 &$local_part_prefix_v$& &&&
12893 &$local_part_suffix$& &&&
12894 &$local_part_suffix_v$&
12895 .cindex affix variables
12896 If a local part prefix or suffix has been recognized, it is not included in the
12897 value of &$local_part$& during routing and subsequent delivery. The values of
12898 any prefix or suffix are in &$local_part_prefix$& and
12899 &$local_part_suffix$&, respectively.
12900 .cindex "tainted data"
12901 If the specification did not include a wildcard then
12902 the affix variable value is not tainted.
12904 If the affix specification included a wildcard then the portion of
12905 the affix matched by the wildcard is in
12906 &$local_part_prefix_v$& or &$local_part_suffix_v$& as appropriate,
12907 and both the whole and varying values are tainted.
12909 .vitem &$local_scan_data$&
12910 .vindex "&$local_scan_data$&"
12911 This variable contains the text returned by the &[local_scan()]& function when
12912 a message is received. See chapter &<<CHAPlocalscan>>& for more details.
12914 .vitem &$local_user_gid$&
12915 .vindex "&$local_user_gid$&"
12916 See &$local_user_uid$&.
12918 .vitem &$local_user_uid$&
12919 .vindex "&$local_user_uid$&"
12920 This variable and &$local_user_gid$& are set to the uid and gid after the
12921 &%check_local_user%& router precondition succeeds. This means that their values
12922 are available for the remaining preconditions (&%senders%&, &%require_files%&,
12923 and &%condition%&), for the &%address_data%& expansion, and for any
12924 router-specific expansions. At all other times, the values in these variables
12925 are &`(uid_t)(-1)`& and &`(gid_t)(-1)`&, respectively.
12927 .vitem &$localhost_number$&
12928 .vindex "&$localhost_number$&"
12929 This contains the expanded value of the
12930 &%localhost_number%& option. The expansion happens after the main options have
12933 .vitem &$log_inodes$&
12934 .vindex "&$log_inodes$&"
12935 The number of free inodes in the disk partition where Exim's
12936 log files are being written. The value is recalculated whenever the variable is
12937 referenced. If the relevant file system does not have the concept of inodes,
12938 the value of is -1. See also the &%check_log_inodes%& option.
12940 .vitem &$log_space$&
12941 .vindex "&$log_space$&"
12942 The amount of free space (as a number of kilobytes) in the disk
12943 partition where Exim's log files are being written. The value is recalculated
12944 whenever the variable is referenced. If the operating system does not have the
12945 ability to find the amount of free space (only true for experimental systems),
12946 the space value is -1. See also the &%check_log_space%& option.
12949 .vitem &$lookup_dnssec_authenticated$&
12950 .vindex "&$lookup_dnssec_authenticated$&"
12951 This variable is set after a DNS lookup done by
12952 a dnsdb lookup expansion, dnslookup router or smtp transport.
12953 .cindex "DNS" "DNSSEC"
12954 It will be empty if &(DNSSEC)& was not requested,
12955 &"no"& if the result was not labelled as authenticated data
12956 and &"yes"& if it was.
12957 Results that are labelled as authoritative answer that match
12958 the &%dns_trust_aa%& configuration variable count also
12959 as authenticated data.
12961 .vitem &$mailstore_basename$&
12962 .vindex "&$mailstore_basename$&"
12963 This variable is set only when doing deliveries in &"mailstore"& format in the
12964 &(appendfile)& transport. During the expansion of the &%mailstore_prefix%&,
12965 &%mailstore_suffix%&, &%message_prefix%&, and &%message_suffix%& options, it
12966 contains the basename of the files that are being written, that is, the name
12967 without the &".tmp"&, &".env"&, or &".msg"& suffix. At all other times, this
12970 .vitem &$malware_name$&
12971 .vindex "&$malware_name$&"
12972 This variable is available when Exim is compiled with the
12973 content-scanning extension. It is set to the name of the virus that was found
12974 when the ACL &%malware%& condition is true (see section &<<SECTscanvirus>>&).
12976 .vitem &$max_received_linelength$&
12977 .vindex "&$max_received_linelength$&"
12978 .cindex "maximum" "line length"
12979 .cindex "line length" "maximum"
12980 This variable contains the number of bytes in the longest line that was
12981 received as part of the message, not counting the line termination
12983 It is not valid if the &%spool_wireformat%& option is used.
12985 .vitem &$message_age$&
12986 .cindex "message" "age of"
12987 .vindex "&$message_age$&"
12988 This variable is set at the start of a delivery attempt to contain the number
12989 of seconds since the message was received. It does not change during a single
12992 .tvar &$message_body$&
12993 .cindex "body of message" "expansion variable"
12994 .cindex "message body" "in expansion"
12995 .cindex "binary zero" "in message body"
12996 .oindex "&%message_body_visible%&"
12997 This variable contains the initial portion of a message's body while it is
12998 being delivered, and is intended mainly for use in filter files. The maximum
12999 number of characters of the body that are put into the variable is set by the
13000 &%message_body_visible%& configuration option; the default is 500.
13002 .oindex "&%message_body_newlines%&"
13003 By default, newlines are converted into spaces in &$message_body$&, to make it
13004 easier to search for phrases that might be split over a line break. However,
13005 this can be disabled by setting &%message_body_newlines%& to be true. Binary
13006 zeros are always converted into spaces.
13008 .tvar &$message_body_end$&
13009 .cindex "body of message" "expansion variable"
13010 .cindex "message body" "in expansion"
13011 This variable contains the final portion of a message's
13012 body while it is being delivered. The format and maximum size are as for
13015 .vitem &$message_body_size$&
13016 .cindex "body of message" "size"
13017 .cindex "message body" "size"
13018 .vindex "&$message_body_size$&"
13019 When a message is being delivered, this variable contains the size of the body
13020 in bytes. The count starts from the character after the blank line that
13021 separates the body from the header. Newlines are included in the count. See
13022 also &$message_size$&, &$body_linecount$&, and &$body_zerocount$&.
13024 If the spool file is wireformat
13025 (see the &%spool_wireformat%& main option)
13026 the CRLF line-terminators are included in the count.
13028 .vitem &$message_exim_id$&
13029 .vindex "&$message_exim_id$&"
13030 When a message is being received or delivered, this variable contains the
13031 unique message id that is generated and used by Exim to identify the message.
13032 An id is not created for a message until after its header has been successfully
13033 received. &*Note*&: This is &'not'& the contents of the &'Message-ID:'& header
13034 line; it is the local id that Exim assigns to the message, for example:
13035 &`1BXTIK-0001yO-VA`&.
13037 .tvar &$message_headers$&
13038 This variable contains a concatenation of all the header lines when a message
13039 is being processed, except for lines added by routers or transports. The header
13040 lines are separated by newline characters. Their contents are decoded in the
13041 same way as a header line that is inserted by &%bheader%&.
13043 .tvar &$message_headers_raw$&
13044 This variable is like &$message_headers$& except that no processing of the
13045 contents of header lines is done.
13047 .vitem &$message_id$&
13048 This is an old name for &$message_exim_id$&. It is now deprecated.
13050 .vitem &$message_linecount$&
13051 .vindex "&$message_linecount$&"
13052 This variable contains the total number of lines in the header and body of the
13053 message. Compare &$body_linecount$&, which is the count for the body only.
13054 During the DATA and content-scanning ACLs, &$message_linecount$& contains the
13055 number of lines received. Before delivery happens (that is, before filters,
13056 routers, and transports run) the count is increased to include the
13057 &'Received:'& header line that Exim standardly adds, and also any other header
13058 lines that are added by ACLs. The blank line that separates the message header
13059 from the body is not counted.
13061 As with the special case of &$message_size$&, during the expansion of the
13062 appendfile transport's maildir_tag option in maildir format, the value of
13063 &$message_linecount$& is the precise size of the number of newlines in the
13064 file that has been written (minus one for the blank line between the
13065 header and the body).
13067 Here is an example of the use of this variable in a DATA ACL:
13070 ${if <{250}{${eval:$message_linecount - $body_linecount}}}
13071 message = Too many lines in message header
13073 In the MAIL and RCPT ACLs, the value is zero because at that stage the
13074 message has not yet been received.
13076 This variable is not valid if the &%spool_wireformat%& option is used.
13078 .vitem &$message_size$&
13079 .cindex "size" "of message"
13080 .cindex "message" "size"
13081 .vindex "&$message_size$&"
13082 When a message is being processed, this variable contains its size in bytes. In
13083 most cases, the size includes those headers that were received with the
13084 message, but not those (such as &'Envelope-to:'&) that are added to individual
13085 deliveries as they are written. However, there is one special case: during the
13086 expansion of the &%maildir_tag%& option in the &(appendfile)& transport while
13087 doing a delivery in maildir format, the value of &$message_size$& is the
13088 precise size of the file that has been written. See also
13089 &$message_body_size$&, &$body_linecount$&, and &$body_zerocount$&.
13091 .cindex "RCPT" "value of &$message_size$&"
13092 While running a per message ACL (mail/rcpt/predata), &$message_size$&
13093 contains the size supplied on the MAIL command, or -1 if no size was given. The
13094 value may not, of course, be truthful.
13096 .vitem &$mime_anomaly_level$& &&&
13097 &$mime_anomaly_text$& &&&
13098 &$mime_boundary$& &&&
13099 &$mime_charset$& &&&
13100 &$mime_content_description$& &&&
13101 &$mime_content_disposition$& &&&
13102 &$mime_content_id$& &&&
13103 &$mime_content_size$& &&&
13104 &$mime_content_transfer_encoding$& &&&
13105 &$mime_content_type$& &&&
13106 &$mime_decoded_filename$& &&&
13107 &$mime_filename$& &&&
13108 &$mime_is_coverletter$& &&&
13109 &$mime_is_multipart$& &&&
13110 &$mime_is_rfc822$& &&&
13111 &$mime_part_count$&
13112 A number of variables whose names start with &$mime$& are
13113 available when Exim is compiled with the content-scanning extension. For
13114 details, see section &<<SECTscanmimepart>>&.
13116 .vitem "&$n0$& &-- &$n9$&"
13117 These variables are counters that can be incremented by means
13118 of the &%add%& command in filter files.
13120 .tvar &$original_domain$&
13121 .vindex "&$domain$&"
13122 When a top-level address is being processed for delivery, this contains the
13123 same value as &$domain$&. However, if a &"child"& address (for example,
13124 generated by an alias, forward, or filter file) is being processed, this
13125 variable contains the domain of the original address (lower cased). This
13126 differs from &$parent_domain$& only when there is more than one level of
13127 aliasing or forwarding. When more than one address is being delivered in a
13128 single transport run, &$original_domain$& is not set.
13130 If a new address is created by means of a &%deliver%& command in a system
13131 filter, it is set up with an artificial &"parent"& address. This has the local
13132 part &'system-filter'& and the default qualify domain.
13134 .tvar &$original_local_part$&
13135 .vindex "&$local_part$&"
13136 When a top-level address is being processed for delivery, this contains the
13137 same value as &$local_part$&, unless a prefix or suffix was removed from the
13138 local part, because &$original_local_part$& always contains the full local
13139 part. When a &"child"& address (for example, generated by an alias, forward, or
13140 filter file) is being processed, this variable contains the full local part of
13141 the original address.
13143 If the router that did the redirection processed the local part
13144 case-insensitively, the value in &$original_local_part$& is in lower case.
13145 This variable differs from &$parent_local_part$& only when there is more than
13146 one level of aliasing or forwarding. When more than one address is being
13147 delivered in a single transport run, &$original_local_part$& is not set.
13149 If a new address is created by means of a &%deliver%& command in a system
13150 filter, it is set up with an artificial &"parent"& address. This has the local
13151 part &'system-filter'& and the default qualify domain.
13153 .vitem &$originator_gid$&
13154 .cindex "gid (group id)" "of originating user"
13155 .cindex "sender" "gid"
13156 .vindex "&$caller_gid$&"
13157 .vindex "&$originator_gid$&"
13158 This variable contains the value of &$caller_gid$& that was set when the
13159 message was received. For messages received via the command line, this is the
13160 gid of the sending user. For messages received by SMTP over TCP/IP, this is
13161 normally the gid of the Exim user.
13163 .vitem &$originator_uid$&
13164 .cindex "uid (user id)" "of originating user"
13165 .cindex "sender" "uid"
13166 .vindex "&$caller_uid$&"
13167 .vindex "&$originator_uid$&"
13168 The value of &$caller_uid$& that was set when the message was received. For
13169 messages received via the command line, this is the uid of the sending user.
13170 For messages received by SMTP over TCP/IP, this is normally the uid of the Exim
13173 .tvar &$parent_domain$&
13174 This variable is similar to &$original_domain$& (see
13175 above), except that it refers to the immediately preceding parent address.
13177 .tvar &$parent_local_part$&
13178 This variable is similar to &$original_local_part$&
13179 (see above), except that it refers to the immediately preceding parent address.
13182 .cindex "pid (process id)" "of current process"
13184 This variable contains the current process id.
13186 .vitem &$pipe_addresses$&
13187 .cindex "filter" "transport filter"
13188 .cindex "transport" "filter"
13189 .vindex "&$pipe_addresses$&"
13190 This is not an expansion variable, but is mentioned here because the string
13191 &`$pipe_addresses`& is handled specially in the command specification for the
13192 &(pipe)& transport (chapter &<<CHAPpipetransport>>&) and in transport filters
13193 (described under &%transport_filter%& in chapter &<<CHAPtransportgeneric>>&).
13194 It cannot be used in general expansion strings, and provokes an &"unknown
13195 variable"& error if encountered.
13196 &*Note*&: This value permits data supplied by a potential attacker to
13197 be used in the command for a &(pipe)& transport.
13198 Such configurations should be carefully assessed for security vulnerbilities.
13200 .vitem &$primary_hostname$&
13201 .vindex "&$primary_hostname$&"
13202 This variable contains the value set by &%primary_hostname%& in the
13203 configuration file, or read by the &[uname()]& function. If &[uname()]& returns
13204 a single-component name, Exim calls &[gethostbyname()]& (or
13205 &[getipnodebyname()]& where available) in an attempt to acquire a fully
13206 qualified host name. See also &$smtp_active_hostname$&.
13209 .vitem &$proxy_external_address$& &&&
13210 &$proxy_external_port$& &&&
13211 &$proxy_local_address$& &&&
13212 &$proxy_local_port$& &&&
13214 These variables are only available when built with Proxy Protocol
13216 For details see chapter &<<SECTproxyInbound>>&.
13218 .vitem &$prdr_requested$&
13219 .cindex "PRDR" "variable for"
13220 This variable is set to &"yes"& if PRDR was requested by the client for the
13221 current message, otherwise &"no"&.
13223 .vitem &$prvscheck_address$& &&&
13224 &$prvscheck_keynum$& &&&
13225 &$prvscheck_result$&
13226 These variables are used in conjunction with the &%prvscheck%& expansion item,
13227 which is described in sections &<<SECTexpansionitems>>& and
13228 &<<SECTverifyPRVS>>&.
13230 .vitem &$qualify_domain$&
13231 .vindex "&$qualify_domain$&"
13232 The value set for the &%qualify_domain%& option in the configuration file.
13234 .vitem &$qualify_recipient$&
13235 .vindex "&$qualify_recipient$&"
13236 The value set for the &%qualify_recipient%& option in the configuration file,
13237 or if not set, the value of &$qualify_domain$&.
13239 .vitem &$queue_name$&
13240 .vindex &$queue_name$&
13241 .cindex "named queues" variable
13242 .cindex queues named
13243 The name of the spool queue in use; empty for the default queue.
13245 .vitem &$queue_size$&
13246 .vindex "&$queue_size$&"
13247 .cindex "queue" "size of"
13248 .cindex "spool" "number of messages"
13249 This variable contains the number of messages queued.
13250 It is evaluated on demand, but no more often than once every minute.
13251 If there is no daemon notifier socket open, the value will be
13256 .cindex router variables
13257 Values can be placed in these variables by the &%set%& option of a router.
13258 They can be given any name that starts with &$r_$&.
13259 The values persist for the address being handled through subsequent routers
13260 and the eventual transport.
13262 .vitem &$rcpt_count$&
13263 .vindex "&$rcpt_count$&"
13264 When a message is being received by SMTP, this variable contains the number of
13265 RCPT commands received for the current message. If this variable is used in a
13266 RCPT ACL, its value includes the current command.
13268 .vitem &$rcpt_defer_count$&
13269 .vindex "&$rcpt_defer_count$&"
13270 .cindex "4&'xx'& responses" "count of"
13271 When a message is being received by SMTP, this variable contains the number of
13272 RCPT commands in the current message that have previously been rejected with a
13273 temporary (4&'xx'&) response.
13275 .vitem &$rcpt_fail_count$&
13276 .vindex "&$rcpt_fail_count$&"
13277 When a message is being received by SMTP, this variable contains the number of
13278 RCPT commands in the current message that have previously been rejected with a
13279 permanent (5&'xx'&) response.
13281 .vitem &$received_count$&
13282 .vindex "&$received_count$&"
13283 This variable contains the number of &'Received:'& header lines in the message,
13284 including the one added by Exim (so its value is always greater than zero). It
13285 is available in the DATA ACL, the non-SMTP ACL, and while routing and
13288 .tvar &$received_for$&
13289 If there is only a single recipient address in an incoming message, this
13290 variable contains that address when the &'Received:'& header line is being
13291 built. The value is copied after recipient rewriting has happened, but before
13292 the &[local_scan()]& function is run.
13294 .vitem &$received_ip_address$& &&&
13296 .vindex "&$received_ip_address$&"
13297 .vindex "&$received_port$&"
13298 As soon as an Exim server starts processing an incoming TCP/IP connection, these
13299 variables are set to the address and port on the local IP interface.
13300 (The remote IP address and port are in
13301 &$sender_host_address$& and &$sender_host_port$&.) When testing with &%-bh%&,
13302 the port value is -1 unless it has been set using the &%-oMi%& command line
13305 As well as being useful in ACLs (including the &"connect"& ACL), these variable
13306 could be used, for example, to make the filename for a TLS certificate depend
13307 on which interface and/or port is being used for the incoming connection. The
13308 values of &$received_ip_address$& and &$received_port$& are saved with any
13309 messages that are received, thus making these variables available at delivery
13311 For outbound connections see &$sending_ip_address$&.
13313 .vitem &$received_protocol$&
13314 .vindex "&$received_protocol$&"
13315 When a message is being processed, this variable contains the name of the
13316 protocol by which it was received. Most of the names used by Exim are defined
13317 by RFCs 821, 2821, and 3848. They start with &"smtp"& (the client used HELO) or
13318 &"esmtp"& (the client used EHLO). This can be followed by &"s"& for secure
13319 (encrypted) and/or &"a"& for authenticated. Thus, for example, if the protocol
13320 is set to &"esmtpsa"&, the message was received over an encrypted SMTP
13321 connection and the client was successfully authenticated.
13323 Exim uses the protocol name &"smtps"& for the case when encryption is
13324 automatically set up on connection without the use of STARTTLS (see
13325 &%tls_on_connect_ports%&), and the client uses HELO to initiate the
13326 encrypted SMTP session. The name &"smtps"& is also used for the rare situation
13327 where the client initially uses EHLO, sets up an encrypted connection using
13328 STARTTLS, and then uses HELO afterwards.
13330 The &%-oMr%& option provides a way of specifying a custom protocol name for
13331 messages that are injected locally by trusted callers. This is commonly used to
13332 identify messages that are being re-injected after some kind of scanning.
13334 .vitem &$received_time$&
13335 .vindex "&$received_time$&"
13336 This variable contains the date and time when the current message was received,
13337 as a number of seconds since the start of the Unix epoch.
13339 .vitem &$recipient_data$&
13340 .vindex "&$recipient_data$&"
13341 This variable is set after an indexing lookup success in an ACL &%recipients%&
13342 condition. It contains the data from the lookup, and the value remains set
13343 until the next &%recipients%& test. Thus, you can do things like this:
13345 &`require recipients = cdb*@;/some/file`&
13346 &`deny `&&'some further test involving'& &`$recipient_data`&
13348 &*Warning*&: This variable is set only when a lookup is used as an indexing
13349 method in the address list, using the semicolon syntax as in the example above.
13350 The variable is not set for a lookup that is used as part of the string
13351 expansion that all such lists undergo before being interpreted.
13353 .vitem &$recipient_verify_failure$&
13354 .vindex "&$recipient_verify_failure$&"
13355 In an ACL, when a recipient verification fails, this variable contains
13356 information about the failure. It is set to one of the following words:
13359 &"qualify"&: The address was unqualified (no domain), and the message
13360 was neither local nor came from an exempted host.
13363 &"route"&: Routing failed.
13366 &"mail"&: Routing succeeded, and a callout was attempted; rejection occurred at
13367 or before the MAIL command (that is, on initial connection, HELO, or
13371 &"recipient"&: The RCPT command in a callout was rejected.
13374 &"postmaster"&: The postmaster check in a callout was rejected.
13377 The main use of this variable is expected to be to distinguish between
13378 rejections of MAIL and rejections of RCPT.
13380 .tvar &$recipients$&
13381 This variable contains a list of envelope recipients for a message. A comma and
13382 a space separate the addresses in the replacement text. However, the variable
13383 is not generally available, to prevent exposure of Bcc recipients in
13384 unprivileged users' filter files. You can use &$recipients$& only in these
13388 In a system filter file.
13390 In the ACLs associated with the DATA command and with non-SMTP messages, that
13391 is, the ACLs defined by &%acl_smtp_predata%&, &%acl_smtp_data%&,
13392 &%acl_smtp_mime%&, &%acl_not_smtp_start%&, &%acl_not_smtp%&, and
13393 &%acl_not_smtp_mime%&.
13395 From within a &[local_scan()]& function.
13399 .vitem &$recipients_count$&
13400 .vindex "&$recipients_count$&"
13401 When a message is being processed, this variable contains the number of
13402 envelope recipients that came with the message. Duplicates are not excluded
13403 from the count. While a message is being received over SMTP, the number
13404 increases for each accepted recipient. It can be referenced in an ACL.
13407 .vitem &$regex_match_string$&
13408 .vindex "&$regex_match_string$&"
13409 This variable is set to contain the matching regular expression after a
13410 &%regex%& ACL condition has matched (see section &<<SECTscanregex>>&).
13412 .vitem "&$regex1$&, &$regex2$&, etc"
13413 .cindex "regex submatch variables (&$1regex$& &$2regex$& etc)"
13414 When a &%regex%& or &%mime_regex%& ACL condition succeeds,
13415 these variables contain the
13416 captured substrings identified by the regular expression.
13417 If the subject string was tainted then so will any captured substring.
13420 .tvar &$reply_address$&
13421 When a message is being processed, this variable contains the contents of the
13422 &'Reply-To:'& header line if one exists and it is not empty, or otherwise the
13423 contents of the &'From:'& header line. Apart from the removal of leading
13424 white space, the value is not processed in any way. In particular, no RFC 2047
13425 decoding or character code translation takes place.
13427 .vitem &$return_path$&
13428 .vindex "&$return_path$&"
13429 When a message is being delivered, this variable contains the return path &--
13430 the sender field that will be sent as part of the envelope. It is not enclosed
13431 in <> characters. At the start of routing an address, &$return_path$& has the
13432 same value as &$sender_address$&, but if, for example, an incoming message to a
13433 mailing list has been expanded by a router which specifies a different address
13434 for bounce messages, &$return_path$& subsequently contains the new bounce
13435 address, whereas &$sender_address$& always contains the original sender address
13436 that was received with the message. In other words, &$sender_address$& contains
13437 the incoming envelope sender, and &$return_path$& contains the outgoing
13440 .vitem &$return_size_limit$&
13441 .vindex "&$return_size_limit$&"
13442 This is an obsolete name for &$bounce_return_size_limit$&.
13444 .vitem &$router_name$&
13445 .cindex "router" "name"
13446 .cindex "name" "of router"
13447 .vindex "&$router_name$&"
13448 During the running of a router this variable contains its name.
13451 .cindex "return code" "from &%run%& expansion"
13452 .vindex "&$runrc$&"
13453 This variable contains the return code from a command that is run by the
13454 &%${run...}%& expansion item. &*Warning*&: In a router or transport, you cannot
13455 assume the order in which option values are expanded, except for those
13456 preconditions whose order of testing is documented. Therefore, you cannot
13457 reliably expect to set &$runrc$& by the expansion of one option, and use it in
13460 .vitem &$self_hostname$&
13461 .oindex "&%self%&" "value of host name"
13462 .vindex "&$self_hostname$&"
13463 When an address is routed to a supposedly remote host that turns out to be the
13464 local host, what happens is controlled by the &%self%& generic router option.
13465 One of its values causes the address to be passed to another router. When this
13466 happens, &$self_hostname$& is set to the name of the local host that the
13467 original router encountered. In other circumstances its contents are null.
13469 .tvar &$sender_address$&
13470 When a message is being processed, this variable contains the sender's address
13471 that was received in the message's envelope. The case of letters in the address
13472 is retained, in both the local part and the domain. For bounce messages, the
13473 value of this variable is the empty string. See also &$return_path$&.
13475 .vitem &$sender_address_data$&
13476 .vindex "&$address_data$&"
13477 .vindex "&$sender_address_data$&"
13478 If &$address_data$& is set when the routers are called from an ACL to verify a
13479 sender address, the final value is preserved in &$sender_address_data$&, to
13480 distinguish it from data from a recipient address. The value does not persist
13481 after the end of the current ACL statement. If you want to preserve it for
13482 longer, you can save it in an ACL variable.
13484 .tvar &$sender_address_domain$&
13485 The domain portion of &$sender_address$&.
13487 .tvar &$sender_address_local_part$&
13488 The local part portion of &$sender_address$&.
13490 .vitem &$sender_data$&
13491 .vindex "&$sender_data$&"
13492 This variable is set after a lookup success in an ACL &%senders%& condition or
13493 in a router &%senders%& option. It contains the data from the lookup, and the
13494 value remains set until the next &%senders%& test. Thus, you can do things like
13497 &`require senders = cdb*@;/some/file`&
13498 &`deny `&&'some further test involving'& &`$sender_data`&
13500 &*Warning*&: This variable is set only when a lookup is used as an indexing
13501 method in the address list, using the semicolon syntax as in the example above.
13502 The variable is not set for a lookup that is used as part of the string
13503 expansion that all such lists undergo before being interpreted.
13505 .vitem &$sender_fullhost$&
13506 .vindex "&$sender_fullhost$&"
13507 When a message is received from a remote host, this variable contains the host
13508 name and IP address in a single string. It ends with the IP address in square
13509 brackets, followed by a colon and a port number if the logging of ports is
13510 enabled. The format of the rest of the string depends on whether the host
13511 issued a HELO or EHLO SMTP command, and whether the host name was verified by
13512 looking up its IP address. (Looking up the IP address can be forced by the
13513 &%host_lookup%& option, independent of verification.) A plain host name at the
13514 start of the string is a verified host name; if this is not present,
13515 verification either failed or was not requested. A host name in parentheses is
13516 the argument of a HELO or EHLO command. This is omitted if it is identical to
13517 the verified host name or to the host's IP address in square brackets.
13519 .vitem &$sender_helo_dnssec$&
13520 .vindex "&$sender_helo_dnssec$&"
13521 This boolean variable is true if a successful HELO verification was
13522 .cindex "DNS" "DNSSEC"
13523 done using DNS information the resolver library stated was authenticated data.
13525 .tvar &$sender_helo_name$&
13526 When a message is received from a remote host that has issued a HELO or EHLO
13527 command, the argument of that command is placed in this variable. It is also
13528 set if HELO or EHLO is used when a message is received using SMTP locally via
13529 the &%-bs%& or &%-bS%& options.
13531 .vitem &$sender_host_address$&
13532 .vindex "&$sender_host_address$&"
13533 When a message is received from a remote host using SMTP,
13534 this variable contains that
13535 host's IP address. For locally non-SMTP submitted messages, it is empty.
13537 .vitem &$sender_host_authenticated$&
13538 .vindex "&$sender_host_authenticated$&"
13539 This variable contains the name (not the public name) of the authenticator
13540 driver that successfully authenticated the client from which the message was
13541 received. It is empty if there was no successful authentication. See also
13542 &$authenticated_id$&.
13544 .vitem &$sender_host_dnssec$&
13545 .vindex "&$sender_host_dnssec$&"
13546 If an attempt to populate &$sender_host_name$& has been made
13547 (by reference, &%hosts_lookup%& or
13548 otherwise) then this boolean will have been set true if, and only if, the
13549 resolver library states that both
13550 the reverse and forward DNS were authenticated data. At all
13551 other times, this variable is false.
13553 .cindex "DNS" "DNSSEC"
13554 It is likely that you will need to coerce DNSSEC support on in the resolver
13555 library, by setting:
13560 In addition, on Linux with glibc 2.31 or newer the resolver library will
13561 default to stripping out a successful validation status.
13562 This will break a previously working Exim installation.
13563 Provided that you do trust the resolver (ie, is on localhost) you can tell
13564 glibc to pass through any successful validation with a new option in
13565 &_/etc/resolv.conf_&:
13570 Exim does not perform DNSSEC validation itself, instead leaving that to a
13571 validating resolver (e.g. unbound, or bind with suitable configuration).
13573 If you have changed &%host_lookup_order%& so that &`bydns`& is not the first
13574 mechanism in the list, then this variable will be false.
13576 This requires that your system resolver library support EDNS0 (and that
13577 DNSSEC flags exist in the system headers). If the resolver silently drops
13578 all EDNS0 options, then this will have no effect. OpenBSD's asr resolver
13579 is known to currently ignore EDNS0, documented in CAVEATS of asr_run(3).
13582 .tvar &$sender_host_name$&
13583 When a message is received from a remote host, this variable contains the
13584 host's name as obtained by looking up its IP address. For messages received by
13585 other means, this variable is empty.
13587 .vindex "&$host_lookup_failed$&"
13588 If the host name has not previously been looked up, a reference to
13589 &$sender_host_name$& triggers a lookup (for messages from remote hosts).
13590 A looked up name is accepted only if it leads back to the original IP address
13591 via a forward lookup. If either the reverse or the forward lookup fails to find
13592 any data, or if the forward lookup does not yield the original IP address,
13593 &$sender_host_name$& remains empty, and &$host_lookup_failed$& is set to &"1"&.
13595 .vindex "&$host_lookup_deferred$&"
13596 However, if either of the lookups cannot be completed (for example, there is a
13597 DNS timeout), &$host_lookup_deferred$& is set to &"1"&, and
13598 &$host_lookup_failed$& remains set to &"0"&.
13600 Once &$host_lookup_failed$& is set to &"1"&, Exim does not try to look up the
13601 host name again if there is a subsequent reference to &$sender_host_name$&
13602 in the same Exim process, but it does try again if &$host_lookup_deferred$&
13605 Exim does not automatically look up every calling host's name. If you want
13606 maximum efficiency, you should arrange your configuration so that it avoids
13607 these lookups altogether. The lookup happens only if one or more of the
13608 following are true:
13611 A string containing &$sender_host_name$& is expanded.
13613 The calling host matches the list in &%host_lookup%&. In the default
13614 configuration, this option is set to *, so it must be changed if lookups are
13615 to be avoided. (In the code, the default for &%host_lookup%& is unset.)
13617 Exim needs the host name in order to test an item in a host list. The items
13618 that require this are described in sections &<<SECThoslispatnam>>& and
13619 &<<SECThoslispatnamsk>>&.
13621 The calling host matches &%helo_try_verify_hosts%& or &%helo_verify_hosts%&.
13622 In this case, the host name is required to compare with the name quoted in any
13623 EHLO or HELO commands that the client issues.
13625 The remote host issues a EHLO or HELO command that quotes one of the
13626 domains in &%helo_lookup_domains%&. The default value of this option is
13627 . ==== As this is a nested list, any displays it contains must be indented
13628 . ==== as otherwise they are too far to the left.
13630 helo_lookup_domains = @ : @[]
13632 which causes a lookup if a remote host (incorrectly) gives the server's name or
13633 IP address in an EHLO or HELO command.
13637 .vitem &$sender_host_port$&
13638 .vindex "&$sender_host_port$&"
13639 When a message is received from a remote host, this variable contains the port
13640 number that was used on the remote host.
13642 .vitem &$sender_ident$&
13643 .vindex "&$sender_ident$&"
13644 When a message is received from a remote host, this variable contains the
13645 identification received in response to an RFC 1413 request. When a message has
13646 been received locally, this variable contains the login name of the user that
13649 .vitem &$sender_rate_$&&'xxx'&
13650 A number of variables whose names begin &$sender_rate_$& are set as part of the
13651 &%ratelimit%& ACL condition. Details are given in section
13652 &<<SECTratelimiting>>&.
13654 .vitem &$sender_rcvhost$&
13655 .cindex "DNS" "reverse lookup"
13656 .cindex "reverse DNS lookup"
13657 .vindex "&$sender_rcvhost$&"
13658 This is provided specifically for use in &'Received:'& headers. It starts with
13659 either the verified host name (as obtained from a reverse DNS lookup) or, if
13660 there is no verified host name, the IP address in square brackets. After that
13661 there may be text in parentheses. When the first item is a verified host name,
13662 the first thing in the parentheses is the IP address in square brackets,
13663 followed by a colon and a port number if port logging is enabled. When the
13664 first item is an IP address, the port is recorded as &"port=&'xxxx'&"& inside
13667 There may also be items of the form &"helo=&'xxxx'&"& if HELO or EHLO
13668 was used and its argument was not identical to the real host name or IP
13669 address, and &"ident=&'xxxx'&"& if an RFC 1413 ident string is available. If
13670 all three items are present in the parentheses, a newline and tab are inserted
13671 into the string, to improve the formatting of the &'Received:'& header.
13673 .vitem &$sender_verify_failure$&
13674 .vindex "&$sender_verify_failure$&"
13675 In an ACL, when a sender verification fails, this variable contains information
13676 about the failure. The details are the same as for
13677 &$recipient_verify_failure$&.
13679 .vitem &$sending_ip_address$&
13680 .vindex "&$sending_ip_address$&"
13681 This variable is set whenever an outgoing SMTP connection to another host has
13682 been set up. It contains the IP address of the local interface that is being
13683 used. This is useful if a host that has more than one IP address wants to take
13684 on different personalities depending on which one is being used. For incoming
13685 connections, see &$received_ip_address$&.
13687 .vitem &$sending_port$&
13688 .vindex "&$sending_port$&"
13689 This variable is set whenever an outgoing SMTP connection to another host has
13690 been set up. It contains the local port that is being used. For incoming
13691 connections, see &$received_port$&.
13693 .vitem &$smtp_active_hostname$&
13694 .vindex "&$smtp_active_hostname$&"
13695 During an incoming SMTP session, this variable contains the value of the active
13696 host name, as specified by the &%smtp_active_hostname%& option. The value of
13697 &$smtp_active_hostname$& is saved with any message that is received, so its
13698 value can be consulted during routing and delivery.
13700 .tvar &$smtp_command$&
13701 During the processing of an incoming SMTP command, this variable contains the
13702 entire command. This makes it possible to distinguish between HELO and EHLO in
13703 the HELO ACL, and also to distinguish between commands such as these:
13708 For a MAIL command, extra parameters such as SIZE can be inspected. For a RCPT
13709 command, the address in &$smtp_command$& is the original address before any
13710 rewriting, whereas the values in &$local_part$& and &$domain$& are taken from
13711 the address after SMTP-time rewriting.
13713 .tvar &$smtp_command_argument$&
13714 .cindex "SMTP" "command, argument for"
13715 While an ACL is running to check an SMTP command, this variable contains the
13716 argument, that is, the text that follows the command name, with leading white
13717 space removed. Following the introduction of &$smtp_command$&, this variable is
13718 somewhat redundant, but is retained for backwards compatibility.
13720 .vitem &$smtp_command_history$&
13721 .cindex SMTP "command history"
13722 .vindex "&$smtp_command_history$&"
13723 A comma-separated list (with no whitespace) of the most-recent SMTP commands
13724 received, in time-order left to right. Only a limited number of commands
13727 .vitem &$smtp_count_at_connection_start$&
13728 .vindex "&$smtp_count_at_connection_start$&"
13729 This variable is set greater than zero only in processes spawned by the Exim
13730 daemon for handling incoming SMTP connections. The name is deliberately long,
13731 in order to emphasize what the contents are. When the daemon accepts a new
13732 connection, it increments this variable. A copy of the variable is passed to
13733 the child process that handles the connection, but its value is fixed, and
13734 never changes. It is only an approximation of how many incoming connections
13735 there actually are, because many other connections may come and go while a
13736 single connection is being processed. When a child process terminates, the
13737 daemon decrements its copy of the variable.
13739 .vitem "&$sn0$& &-- &$sn9$&"
13740 These variables are copies of the values of the &$n0$& &-- &$n9$& accumulators
13741 that were current at the end of the system filter file. This allows a system
13742 filter file to set values that can be tested in users' filter files. For
13743 example, a system filter could set a value indicating how likely it is that a
13744 message is junk mail.
13746 .vitem &$spam_score$& &&&
13747 &$spam_score_int$& &&&
13749 &$spam_report$& &&&
13751 A number of variables whose names start with &$spam$& are available when Exim
13752 is compiled with the content-scanning extension. For details, see section
13753 &<<SECTscanspamass>>&.
13755 .vitem &$spf_header_comment$& &&&
13756 &$spf_received$& &&&
13758 &$spf_result_guessed$& &&&
13759 &$spf_smtp_comment$&
13760 These variables are only available if Exim is built with SPF support.
13761 For details see section &<<SECSPF>>&.
13763 .vitem &$spool_directory$&
13764 .vindex "&$spool_directory$&"
13765 The name of Exim's spool directory.
13767 .vitem &$spool_inodes$&
13768 .vindex "&$spool_inodes$&"
13769 The number of free inodes in the disk partition where Exim's spool files are
13770 being written. The value is recalculated whenever the variable is referenced.
13771 If the relevant file system does not have the concept of inodes, the value of
13772 is -1. See also the &%check_spool_inodes%& option.
13774 .vitem &$spool_space$&
13775 .vindex "&$spool_space$&"
13776 The amount of free space (as a number of kilobytes) in the disk partition where
13777 Exim's spool files are being written. The value is recalculated whenever the
13778 variable is referenced. If the operating system does not have the ability to
13779 find the amount of free space (only true for experimental systems), the space
13780 value is -1. For example, to check in an ACL that there is at least 50
13781 megabytes free on the spool, you could write:
13783 condition = ${if > {$spool_space}{50000}}
13785 See also the &%check_spool_space%& option.
13788 .vitem &$thisaddress$&
13789 .vindex "&$thisaddress$&"
13790 This variable is set only during the processing of the &%foranyaddress%&
13791 command in a filter file. Its use is explained in the description of that
13792 command, which can be found in the separate document entitled &'Exim's
13793 interfaces to mail filtering'&.
13795 .vitem &$tls_in_bits$&
13796 .vindex "&$tls_in_bits$&"
13797 Contains an approximation of the TLS cipher's bit-strength
13798 on the inbound connection; the meaning of
13799 this depends upon the TLS implementation used.
13800 If TLS has not been negotiated, the value will be 0.
13801 The value of this is automatically fed into the Cyrus SASL authenticator
13802 when acting as a server, to specify the "external SSF" (a SASL term).
13804 The deprecated &$tls_bits$& variable refers to the inbound side
13805 except when used in the context of an outbound SMTP delivery, when it refers to
13808 .vitem &$tls_out_bits$&
13809 .vindex "&$tls_out_bits$&"
13810 Contains an approximation of the TLS cipher's bit-strength
13811 on an outbound SMTP connection; the meaning of
13812 this depends upon the TLS implementation used.
13813 If TLS has not been negotiated, the value will be 0.
13815 .vitem &$tls_in_ourcert$&
13816 .vindex "&$tls_in_ourcert$&"
13817 .cindex certificate variables
13818 This variable refers to the certificate presented to the peer of an
13819 inbound connection when the message was received.
13820 It is only useful as the argument of a
13821 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13822 or a &%def%& condition.
13824 &*Note*&: Under versions of OpenSSL preceding 1.1.1,
13825 when a list of more than one
13826 file is used for &%tls_certificate%&, this variable is not reliable.
13827 The macro "_TLS_BAD_MULTICERT_IN_OURCERT" will be defined for those versions.
13829 .vitem &$tls_in_peercert$&
13830 .vindex "&$tls_in_peercert$&"
13831 This variable refers to the certificate presented by the peer of an
13832 inbound connection when the message was received.
13833 It is only useful as the argument of a
13834 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13835 or a &%def%& condition.
13836 If certificate verification fails it may refer to a failing chain element
13837 which is not the leaf.
13839 .vitem &$tls_out_ourcert$&
13840 .vindex "&$tls_out_ourcert$&"
13841 This variable refers to the certificate presented to the peer of an
13842 outbound connection. It is only useful as the argument of a
13843 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13844 or a &%def%& condition.
13846 .vitem &$tls_out_peercert$&
13847 .vindex "&$tls_out_peercert$&"
13848 This variable refers to the certificate presented by the peer of an
13849 outbound connection. It is only useful as the argument of a
13850 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13851 or a &%def%& condition.
13852 If certificate verification fails it may refer to a failing chain element
13853 which is not the leaf.
13855 .vitem &$tls_in_certificate_verified$&
13856 .vindex "&$tls_in_certificate_verified$&"
13857 This variable is set to &"1"& if a TLS certificate was verified when the
13858 message was received, and &"0"& otherwise.
13860 The deprecated &$tls_certificate_verified$& variable refers to the inbound side
13861 except when used in the context of an outbound SMTP delivery, when it refers to
13864 .vitem &$tls_out_certificate_verified$&
13865 .vindex "&$tls_out_certificate_verified$&"
13866 This variable is set to &"1"& if a TLS certificate was verified when an
13867 outbound SMTP connection was made,
13868 and &"0"& otherwise.
13870 .vitem &$tls_in_cipher$&
13871 .vindex "&$tls_in_cipher$&"
13872 .vindex "&$tls_cipher$&"
13873 When a message is received from a remote host over an encrypted SMTP
13874 connection, this variable is set to the cipher suite that was negotiated, for
13875 example DES-CBC3-SHA. In other circumstances, in particular, for message
13876 received over unencrypted connections, the variable is empty. Testing
13877 &$tls_in_cipher$& for emptiness is one way of distinguishing between encrypted and
13878 non-encrypted connections during ACL processing.
13880 The deprecated &$tls_cipher$& variable is the same as &$tls_in_cipher$& during message reception,
13881 but in the context of an outward SMTP delivery taking place via the &(smtp)& transport
13882 becomes the same as &$tls_out_cipher$&.
13884 .vitem &$tls_in_cipher_std$&
13885 .vindex "&$tls_in_cipher_std$&"
13886 As above, but returning the RFC standard name for the cipher suite.
13888 .vitem &$tls_out_cipher$&
13889 .vindex "&$tls_out_cipher$&"
13891 cleared before any outgoing SMTP connection is made,
13892 and then set to the outgoing cipher suite if one is negotiated. See chapter
13893 &<<CHAPTLS>>& for details of TLS support and chapter &<<CHAPsmtptrans>>& for
13894 details of the &(smtp)& transport.
13896 .vitem &$tls_out_cipher_std$&
13897 .vindex "&$tls_out_cipher_std$&"
13898 As above, but returning the RFC standard name for the cipher suite.
13900 .vitem &$tls_out_dane$&
13901 .vindex &$tls_out_dane$&
13902 DANE active status. See section &<<SECDANE>>&.
13904 .vitem &$tls_in_ocsp$&
13905 .vindex "&$tls_in_ocsp$&"
13906 When a message is received from a remote client connection
13907 the result of any OCSP request from the client is encoded in this variable:
13909 0 OCSP proof was not requested (default value)
13910 1 No response to request
13911 2 Response not verified
13912 3 Verification failed
13913 4 Verification succeeded
13916 .vitem &$tls_out_ocsp$&
13917 .vindex "&$tls_out_ocsp$&"
13918 When a message is sent to a remote host connection
13919 the result of any OCSP request made is encoded in this variable.
13920 See &$tls_in_ocsp$& for values.
13922 .vitem &$tls_in_peerdn$&
13923 .vindex "&$tls_in_peerdn$&"
13924 .vindex "&$tls_peerdn$&"
13925 .cindex certificate "extracting fields"
13926 When a message is received from a remote host over an encrypted SMTP
13927 connection, and Exim is configured to request a certificate from the client,
13928 the value of the Distinguished Name of the certificate is made available in the
13929 &$tls_in_peerdn$& during subsequent processing.
13930 If certificate verification fails it may refer to a failing chain element
13931 which is not the leaf.
13933 The deprecated &$tls_peerdn$& variable refers to the inbound side
13934 except when used in the context of an outbound SMTP delivery, when it refers to
13937 .vitem &$tls_out_peerdn$&
13938 .vindex "&$tls_out_peerdn$&"
13939 When a message is being delivered to a remote host over an encrypted SMTP
13940 connection, and Exim is configured to request a certificate from the server,
13941 the value of the Distinguished Name of the certificate is made available in the
13942 &$tls_out_peerdn$& during subsequent processing.
13943 If certificate verification fails it may refer to a failing chain element
13944 which is not the leaf.
13947 .vitem &$tls_in_resumption$& &&&
13948 &$tls_out_resumption$&
13949 .vindex &$tls_in_resumption$&
13950 .vindex &$tls_out_resumption$&
13951 .cindex TLS resumption
13952 Observability for TLS session resumption. See &<<SECTresumption>>& for details.
13955 .tvar &$tls_in_sni$&
13956 .vindex "&$tls_sni$&"
13957 .cindex "TLS" "Server Name Indication"
13959 .cindex SNI "observability on server"
13960 When a TLS session is being established, if the client sends the Server
13961 Name Indication extension, the value will be placed in this variable.
13962 If the variable appears in &%tls_certificate%& then this option and
13963 some others, described in &<<SECTtlssni>>&,
13964 will be re-expanded early in the TLS session, to permit
13965 a different certificate to be presented (and optionally a different key to be
13966 used) to the client, based upon the value of the SNI extension.
13968 The deprecated &$tls_sni$& variable refers to the inbound side
13969 except when used in the context of an outbound SMTP delivery, when it refers to
13972 .vitem &$tls_out_sni$&
13973 .vindex "&$tls_out_sni$&"
13974 .cindex "TLS" "Server Name Indication"
13976 .cindex SNI "observability in client"
13978 SMTP deliveries, this variable reflects the value of the &%tls_sni%& option on
13981 .vitem &$tls_out_tlsa_usage$&
13982 .vindex &$tls_out_tlsa_usage$&
13983 Bitfield of TLSA record types found. See section &<<SECDANE>>&.
13985 .vitem &$tls_in_ver$&
13986 .vindex "&$tls_in_ver$&"
13987 When a message is received from a remote host over an encrypted SMTP connection
13988 this variable is set to the protocol version, eg &'TLS1.2'&.
13990 .vitem &$tls_out_ver$&
13991 .vindex "&$tls_out_ver$&"
13992 When a message is being delivered to a remote host over an encrypted SMTP connection
13993 this variable is set to the protocol version.
13996 .vitem &$tod_bsdinbox$&
13997 .vindex "&$tod_bsdinbox$&"
13998 The time of day and the date, in the format required for BSD-style mailbox
13999 files, for example: Thu Oct 17 17:14:09 1995.
14001 .vitem &$tod_epoch$&
14002 .vindex "&$tod_epoch$&"
14003 The time and date as a number of seconds since the start of the Unix epoch.
14005 .vitem &$tod_epoch_l$&
14006 .vindex "&$tod_epoch_l$&"
14007 The time and date as a number of microseconds since the start of the Unix epoch.
14009 .vitem &$tod_full$&
14010 .vindex "&$tod_full$&"
14011 A full version of the time and date, for example: Wed, 16 Oct 1995 09:51:40
14012 +0100. The timezone is always given as a numerical offset from UTC, with
14013 positive values used for timezones that are ahead (east) of UTC, and negative
14014 values for those that are behind (west).
14017 .vindex "&$tod_log$&"
14018 The time and date in the format used for writing Exim's log files, for example:
14019 1995-10-12 15:32:29, but without a timezone.
14021 .vitem &$tod_logfile$&
14022 .vindex "&$tod_logfile$&"
14023 This variable contains the date in the format yyyymmdd. This is the format that
14024 is used for datestamping log files when &%log_file_path%& contains the &`%D`&
14027 .vitem &$tod_zone$&
14028 .vindex "&$tod_zone$&"
14029 This variable contains the numerical value of the local timezone, for example:
14032 .vitem &$tod_zulu$&
14033 .vindex "&$tod_zulu$&"
14034 This variable contains the UTC date and time in &"Zulu"& format, as specified
14035 by ISO 8601, for example: 20030221154023Z.
14037 .vitem &$transport_name$&
14038 .cindex "transport" "name"
14039 .cindex "name" "of transport"
14040 .vindex "&$transport_name$&"
14041 During the running of a transport, this variable contains its name.
14044 .vindex "&$value$&"
14045 This variable contains the result of an expansion lookup, extraction operation,
14046 or external command, as described above. It is also used during a
14047 &*reduce*& expansion.
14049 .vitem &$verify_mode$&
14050 .vindex "&$verify_mode$&"
14051 While a router or transport is being run in verify mode or for cutthrough delivery,
14052 contains "S" for sender-verification or "R" for recipient-verification.
14055 .vitem &$version_number$&
14056 .vindex "&$version_number$&"
14057 The version number of Exim. Same as &$exim_version$&, may be overridden
14058 by the &%exim_version%& main config option.
14060 .vitem &$warn_message_delay$&
14061 .vindex "&$warn_message_delay$&"
14062 This variable is set only during the creation of a message warning about a
14063 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
14065 .vitem &$warn_message_recipients$&
14066 .vindex "&$warn_message_recipients$&"
14067 This variable is set only during the creation of a message warning about a
14068 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
14074 . ////////////////////////////////////////////////////////////////////////////
14075 . ////////////////////////////////////////////////////////////////////////////
14077 .chapter "Embedded Perl" "CHAPperl"
14078 .scindex IIDperl "Perl" "calling from Exim"
14079 Exim can be built to include an embedded Perl interpreter. When this is done,
14080 Perl subroutines can be called as part of the string expansion process. To make
14081 use of the Perl support, you need version 5.004 or later of Perl installed on
14082 your system. To include the embedded interpreter in the Exim binary, include
14087 in your &_Local/Makefile_& and then build Exim in the normal way.
14090 .section "Setting up so Perl can be used" "SECID85"
14091 .oindex "&%perl_startup%&"
14092 Access to Perl subroutines is via a global configuration option called
14093 &%perl_startup%& and an expansion string operator &%${perl ...}%&. If there is
14094 no &%perl_startup%& option in the Exim configuration file then no Perl
14095 interpreter is started and there is almost no overhead for Exim (since none of
14096 the Perl library will be paged in unless used). If there is a &%perl_startup%&
14097 option then the associated value is taken to be Perl code which is executed in
14098 a newly created Perl interpreter.
14100 The value of &%perl_startup%& is not expanded in the Exim sense, so you do not
14101 need backslashes before any characters to escape special meanings. The option
14102 should usually be something like
14104 perl_startup = do '/etc/exim.pl'
14106 where &_/etc/exim.pl_& is Perl code which defines any subroutines you want to
14107 use from Exim. Exim can be configured either to start up a Perl interpreter as
14108 soon as it is entered, or to wait until the first time it is needed. Starting
14109 the interpreter at the beginning ensures that it is done while Exim still has
14110 its setuid privilege, but can impose an unnecessary overhead if Perl is not in
14111 fact used in a particular run. Also, note that this does not mean that Exim is
14112 necessarily running as root when Perl is called at a later time. By default,
14113 the interpreter is started only when it is needed, but this can be changed in
14117 .oindex "&%perl_at_start%&"
14118 Setting &%perl_at_start%& (a boolean option) in the configuration requests
14119 a startup when Exim is entered.
14121 The command line option &%-ps%& also requests a startup when Exim is entered,
14122 overriding the setting of &%perl_at_start%&.
14125 There is also a command line option &%-pd%& (for delay) which suppresses the
14126 initial startup, even if &%perl_at_start%& is set.
14129 .oindex "&%perl_taintmode%&"
14130 .cindex "Perl" "taintmode"
14131 To provide more security executing Perl code via the embedded Perl
14132 interpreter, the &%perl_taintmode%& option can be set. This enables the
14133 taint mode of the Perl interpreter. You are encouraged to set this
14134 option to a true value. To avoid breaking existing installations, it
14137 &*Note*&: This is entirely separate from Exim's tainted-data tracking.
14140 .section "Calling Perl subroutines" "SECID86"
14141 When the configuration file includes a &%perl_startup%& option you can make use
14142 of the string expansion item to call the Perl subroutines that are defined
14143 by the &%perl_startup%& code. The operator is used in any of the following
14147 ${perl{foo}{argument}}
14148 ${perl{foo}{argument1}{argument2} ... }
14150 which calls the subroutine &%foo%& with the given arguments. A maximum of eight
14151 arguments may be passed. Passing more than this results in an expansion failure
14152 with an error message of the form
14154 Too many arguments passed to Perl subroutine "foo" (max is 8)
14156 The return value of the Perl subroutine is evaluated in a scalar context before
14157 it is passed back to Exim to be inserted into the expanded string. If the
14158 return value is &'undef'&, the expansion is forced to fail in the same way as
14159 an explicit &"fail"& on an &%if%& or &%lookup%& item. If the subroutine aborts
14160 by obeying Perl's &%die%& function, the expansion fails with the error message
14161 that was passed to &%die%&.
14164 .section "Calling Exim functions from Perl" "SECID87"
14165 Within any Perl code called from Exim, the function &'Exim::expand_string()'&
14166 is available to call back into Exim's string expansion function. For example,
14169 my $lp = Exim::expand_string('$local_part');
14171 makes the current Exim &$local_part$& available in the Perl variable &$lp$&.
14172 Note those are single quotes and not double quotes to protect against
14173 &$local_part$& being interpolated as a Perl variable.
14175 If the string expansion is forced to fail by a &"fail"& item, the result of
14176 &'Exim::expand_string()'& is &%undef%&. If there is a syntax error in the
14177 expansion string, the Perl call from the original expansion string fails with
14178 an appropriate error message, in the same way as if &%die%& were used.
14180 .cindex "debugging" "from embedded Perl"
14181 .cindex "log" "writing from embedded Perl"
14182 Two other Exim functions are available for use from within Perl code.
14183 &'Exim::debug_write()'& writes a string to the standard error stream if Exim's
14184 debugging is enabled. If you want a newline at the end, you must supply it.
14185 &'Exim::log_write()'& writes a string to Exim's main log, adding a leading
14186 timestamp. In this case, you should not supply a terminating newline.
14189 .section "Use of standard output and error by Perl" "SECID88"
14190 .cindex "Perl" "standard output and error"
14191 You should not write to the standard error or output streams from within your
14192 Perl code, as it is not defined how these are set up. In versions of Exim
14193 before 4.50, it is possible for the standard output or error to refer to the
14194 SMTP connection during message reception via the daemon. Writing to this stream
14195 is certain to cause chaos. From Exim 4.50 onwards, the standard output and
14196 error streams are connected to &_/dev/null_& in the daemon. The chaos is
14197 avoided, but the output is lost.
14199 .cindex "Perl" "use of &%warn%&"
14200 The Perl &%warn%& statement writes to the standard error stream by default.
14201 Calls to &%warn%& may be embedded in Perl modules that you use, but over which
14202 you have no control. When Exim starts up the Perl interpreter, it arranges for
14203 output from the &%warn%& statement to be written to the Exim main log. You can
14204 change this by including appropriate Perl magic somewhere in your Perl code.
14205 For example, to discard &%warn%& output completely, you need this:
14207 $SIG{__WARN__} = sub { };
14209 Whenever a &%warn%& is obeyed, the anonymous subroutine is called. In this
14210 example, the code for the subroutine is empty, so it does nothing, but you can
14211 include any Perl code that you like. The text of the &%warn%& message is passed
14212 as the first subroutine argument.
14216 . ////////////////////////////////////////////////////////////////////////////
14217 . ////////////////////////////////////////////////////////////////////////////
14219 .chapter "Starting the daemon and the use of network interfaces" &&&
14220 "CHAPinterfaces" &&&
14221 "Starting the daemon"
14222 .cindex "daemon" "starting"
14223 .cindex "interface" "listening"
14224 .cindex "network interface"
14225 .cindex "interface" "network"
14226 .cindex "IP address" "for listening"
14227 .cindex "daemon" "listening IP addresses"
14228 .cindex "TCP/IP" "setting listening interfaces"
14229 .cindex "TCP/IP" "setting listening ports"
14230 A host that is connected to a TCP/IP network may have one or more physical
14231 hardware network interfaces. Each of these interfaces may be configured as one
14232 or more &"logical"& interfaces, which are the entities that a program actually
14233 works with. Each of these logical interfaces is associated with an IP address.
14234 In addition, TCP/IP software supports &"loopback"& interfaces (127.0.0.1 in
14235 IPv4 and ::1 in IPv6), which do not use any physical hardware. Exim requires
14236 knowledge about the host's interfaces for use in three different circumstances:
14239 When a listening daemon is started, Exim needs to know which interfaces
14240 and ports to listen on.
14242 When Exim is routing an address, it needs to know which IP addresses
14243 are associated with local interfaces. This is required for the correct
14244 processing of MX lists by removing the local host and others with the
14245 same or higher priority values. Also, Exim needs to detect cases
14246 when an address is routed to an IP address that in fact belongs to the
14247 local host. Unless the &%self%& router option or the &%allow_localhost%&
14248 option of the smtp transport is set (as appropriate), this is treated
14249 as an error situation.
14251 When Exim connects to a remote host, it may need to know which interface to use
14252 for the outgoing connection.
14256 Exim's default behaviour is likely to be appropriate in the vast majority
14257 of cases. If your host has only one interface, and you want all its IP
14258 addresses to be treated in the same way, and you are using only the
14259 standard SMTP port, you should not need to take any special action. The
14260 rest of this chapter does not apply to you.
14262 In a more complicated situation you may want to listen only on certain
14263 interfaces, or on different ports, and for this reason there are a number of
14264 options that can be used to influence Exim's behaviour. The rest of this
14265 chapter describes how they operate.
14267 When a message is received over TCP/IP, the interface and port that were
14268 actually used are set in &$received_ip_address$& and &$received_port$&.
14272 .section "Starting a listening daemon" "SECID89"
14273 When a listening daemon is started (by means of the &%-bd%& command line
14274 option), the interfaces and ports on which it listens are controlled by the
14278 &%daemon_smtp_ports%& contains a list of default ports
14280 (For backward compatibility, this option can also be specified in the singular.)
14282 &%local_interfaces%& contains list of interface IP addresses on which to
14283 listen. Each item may optionally also specify a port.
14286 The default list separator in both cases is a colon, but this can be changed as
14287 described in section &<<SECTlistsepchange>>&. When IPv6 addresses are involved,
14288 it is usually best to change the separator to avoid having to double all the
14289 colons. For example:
14291 local_interfaces = <; 127.0.0.1 ; \
14294 3ffe:ffff:836f::fe86:a061
14296 There are two different formats for specifying a port along with an IP address
14297 in &%local_interfaces%&:
14300 The port is added onto the address with a dot separator. For example, to listen
14301 on port 1234 on two different IP addresses:
14303 local_interfaces = <; 192.168.23.65.1234 ; \
14304 3ffe:ffff:836f::fe86:a061.1234
14307 The IP address is enclosed in square brackets, and the port is added
14308 with a colon separator, for example:
14310 local_interfaces = <; [192.168.23.65]:1234 ; \
14311 [3ffe:ffff:836f::fe86:a061]:1234
14315 When a port is not specified, the value of &%daemon_smtp_ports%& is used. The
14316 default setting contains just one port:
14318 daemon_smtp_ports = smtp
14320 If more than one port is listed, each interface that does not have its own port
14321 specified listens on all of them. Ports that are listed in
14322 &%daemon_smtp_ports%& can be identified either by name (defined in
14323 &_/etc/services_&) or by number. However, when ports are given with individual
14324 IP addresses in &%local_interfaces%&, only numbers (not names) can be used.
14328 .section "Special IP listening addresses" "SECID90"
14329 The addresses 0.0.0.0 and ::0 are treated specially. They are interpreted
14330 as &"all IPv4 interfaces"& and &"all IPv6 interfaces"&, respectively. In each
14331 case, Exim tells the TCP/IP stack to &"listen on all IPv&'x'& interfaces"&
14332 instead of setting up separate listening sockets for each interface. The
14333 default value of &%local_interfaces%& is
14335 local_interfaces = 0.0.0.0
14337 when Exim is built without IPv6 support; otherwise it is:
14339 local_interfaces = <; ::0 ; 0.0.0.0
14341 Thus, by default, Exim listens on all available interfaces, on the SMTP port.
14345 .section "Overriding local_interfaces and daemon_smtp_ports" "SECID91"
14346 The &%-oX%& command line option can be used to override the values of
14347 &%daemon_smtp_ports%& and/or &%local_interfaces%& for a particular daemon
14348 instance. Another way of doing this would be to use macros and the &%-D%&
14349 option. However, &%-oX%& can be used by any admin user, whereas modification of
14350 the runtime configuration by &%-D%& is allowed only when the caller is root or
14353 The value of &%-oX%& is a list of items. The default colon separator can be
14354 changed in the usual way (&<<SECTlistsepchange>>&) if required.
14355 If there are any items that do not
14356 contain dots or colons (that is, are not IP addresses), the value of
14357 &%daemon_smtp_ports%& is replaced by the list of those items. If there are any
14358 items that do contain dots or colons, the value of &%local_interfaces%& is
14359 replaced by those items. Thus, for example,
14363 overrides &%daemon_smtp_ports%&, but leaves &%local_interfaces%& unchanged,
14366 -oX 192.168.34.5.1125
14368 overrides &%local_interfaces%&, leaving &%daemon_smtp_ports%& unchanged.
14369 (However, since &%local_interfaces%& now contains no items without ports, the
14370 value of &%daemon_smtp_ports%& is no longer relevant in this example.)
14374 .section "Support for the submissions (aka SSMTP or SMTPS) protocol" "SECTsupobssmt"
14375 .cindex "submissions protocol"
14376 .cindex "ssmtp protocol"
14377 .cindex "smtps protocol"
14378 .cindex "SMTP" "ssmtp protocol"
14379 .cindex "SMTP" "smtps protocol"
14380 Exim supports the use of TLS-on-connect, used by mail clients in the
14381 &"submissions"& protocol, historically also known as SMTPS or SSMTP.
14382 For some years, IETF Standards Track documents only blessed the
14383 STARTTLS-based Submission service (port 587) while common practice was to support
14384 the same feature set on port 465, but using TLS-on-connect.
14385 If your installation needs to provide service to mail clients
14386 (Mail User Agents, MUAs) then you should provide service on both the 587 and
14389 If the &%tls_on_connect_ports%& option is set to a list of port numbers or
14390 service names, connections to those ports must first establish TLS, before
14391 proceeding to the application layer use of the SMTP protocol.
14393 The common use of this option is expected to be
14395 tls_on_connect_ports = 465
14398 There is also a command line option &%-tls-on-connect%&, which forces all ports
14399 to behave in this way when a daemon is started.
14401 &*Warning*&: Setting &%tls_on_connect_ports%& does not of itself cause the
14402 daemon to listen on those ports. You must still specify them in
14403 &%daemon_smtp_ports%&, &%local_interfaces%&, or the &%-oX%& option. (This is
14404 because &%tls_on_connect_ports%& applies to &%inetd%& connections as well as to
14405 connections via the daemon.)
14410 .section "IPv6 address scopes" "SECID92"
14411 .cindex "IPv6" "address scopes"
14412 IPv6 addresses have &"scopes"&, and a host with multiple hardware interfaces
14413 can, in principle, have the same link-local IPv6 address on different
14414 interfaces. Thus, additional information is needed, over and above the IP
14415 address, to distinguish individual interfaces. A convention of using a
14416 percent sign followed by something (often the interface name) has been
14417 adopted in some cases, leading to addresses like this:
14419 fe80::202:b3ff:fe03:45c1%eth0
14421 To accommodate this usage, a percent sign followed by an arbitrary string is
14422 allowed at the end of an IPv6 address. By default, Exim calls &[getaddrinfo()]&
14423 to convert a textual IPv6 address for actual use. This function recognizes the
14424 percent convention in operating systems that support it, and it processes the
14425 address appropriately. Unfortunately, some older libraries have problems with
14426 &[getaddrinfo()]&. If
14428 IPV6_USE_INET_PTON=yes
14430 is set in &_Local/Makefile_& (or an OS-dependent Makefile) when Exim is built,
14431 Exim uses &'inet_pton()'& to convert a textual IPv6 address for actual use,
14432 instead of &[getaddrinfo()]&. (Before version 4.14, it always used this
14433 function.) Of course, this means that the additional functionality of
14434 &[getaddrinfo()]& &-- recognizing scoped addresses &-- is lost.
14436 .section "Disabling IPv6" "SECID93"
14437 .cindex "IPv6" "disabling"
14438 Sometimes it happens that an Exim binary that was compiled with IPv6 support is
14439 run on a host whose kernel does not support IPv6. The binary will fall back to
14440 using IPv4, but it may waste resources looking up AAAA records, and trying to
14441 connect to IPv6 addresses, causing delays to mail delivery. If you set the
14442 .oindex "&%disable_ipv6%&"
14443 &%disable_ipv6%& option true, even if the Exim binary has IPv6 support, no IPv6
14444 activities take place. AAAA records are never looked up, and any IPv6 addresses
14445 that are listed in &%local_interfaces%&, data for the &(manualroute)& router,
14446 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
14447 to handle IPv6 literal addresses.
14449 On the other hand, when IPv6 is in use, there may be times when you want to
14450 disable it for certain hosts or domains. You can use the &%dns_ipv4_lookup%&
14451 option to globally suppress the lookup of AAAA records for specified domains,
14452 and you can use the &%ignore_target_hosts%& generic router option to ignore
14453 IPv6 addresses in an individual router.
14457 .section "Examples of starting a listening daemon" "SECID94"
14458 The default case in an IPv6 environment is
14460 daemon_smtp_ports = smtp
14461 local_interfaces = <; ::0 ; 0.0.0.0
14463 This specifies listening on the smtp port on all IPv6 and IPv4 interfaces.
14464 Either one or two sockets may be used, depending on the characteristics of
14465 the TCP/IP stack. (This is complicated and messy; for more information,
14466 read the comments in the &_daemon.c_& source file.)
14468 To specify listening on ports 25 and 26 on all interfaces:
14470 daemon_smtp_ports = 25 : 26
14472 (leaving &%local_interfaces%& at the default setting) or, more explicitly:
14474 local_interfaces = <; ::0.25 ; ::0.26 \
14475 0.0.0.0.25 ; 0.0.0.0.26
14477 To listen on the default port on all IPv4 interfaces, and on port 26 on the
14478 IPv4 loopback address only:
14480 local_interfaces = 0.0.0.0 : 127.0.0.1.26
14482 To specify listening on the default port on specific interfaces only:
14484 local_interfaces = 10.0.0.67 : 192.168.34.67
14486 &*Warning*&: Such a setting excludes listening on the loopback interfaces.
14490 .section "Recognizing the local host" "SECTreclocipadd"
14491 The &%local_interfaces%& option is also used when Exim needs to determine
14492 whether or not an IP address refers to the local host. That is, the IP
14493 addresses of all the interfaces on which a daemon is listening are always
14496 For this usage, port numbers in &%local_interfaces%& are ignored. If either of
14497 the items 0.0.0.0 or ::0 are encountered, Exim gets a complete list of
14498 available interfaces from the operating system, and extracts the relevant
14499 (that is, IPv4 or IPv6) addresses to use for checking.
14501 Some systems set up large numbers of virtual interfaces in order to provide
14502 many virtual web servers. In this situation, you may want to listen for
14503 email on only a few of the available interfaces, but nevertheless treat all
14504 interfaces as local when routing. You can do this by setting
14505 &%extra_local_interfaces%& to a list of IP addresses, possibly including the
14506 &"all"& wildcard values. These addresses are recognized as local, but are not
14507 used for listening. Consider this example:
14509 local_interfaces = <; 127.0.0.1 ; ::1 ; \
14511 3ffe:2101:12:1:a00:20ff:fe86:a061
14513 extra_local_interfaces = <; ::0 ; 0.0.0.0
14515 The daemon listens on the loopback interfaces and just one IPv4 and one IPv6
14516 address, but all available interface addresses are treated as local when
14519 In some environments the local host name may be in an MX list, but with an IP
14520 address that is not assigned to any local interface. In other cases it may be
14521 desirable to treat other host names as if they referred to the local host. Both
14522 these cases can be handled by setting the &%hosts_treat_as_local%& option.
14523 This contains host names rather than IP addresses. When a host is referenced
14524 during routing, either via an MX record or directly, it is treated as the local
14525 host if its name matches &%hosts_treat_as_local%&, or if any of its IP
14526 addresses match &%local_interfaces%& or &%extra_local_interfaces%&.
14530 .section "Delivering to a remote host" "SECID95"
14531 Delivery to a remote host is handled by the smtp transport. By default, it
14532 allows the system's TCP/IP functions to choose which interface to use (if
14533 there is more than one) when connecting to a remote host. However, the
14534 &%interface%& option can be set to specify which interface is used. See the
14535 description of the smtp transport in chapter &<<CHAPsmtptrans>>& for more
14541 . ////////////////////////////////////////////////////////////////////////////
14542 . ////////////////////////////////////////////////////////////////////////////
14544 .chapter "Main configuration" "CHAPmainconfig"
14545 .scindex IIDconfima "configuration file" "main section"
14546 .scindex IIDmaiconf "main configuration"
14547 The first part of the runtime configuration file contains three types of item:
14550 Macro definitions: These lines start with an upper case letter. See section
14551 &<<SECTmacrodefs>>& for details of macro processing.
14553 Named list definitions: These lines start with one of the words &"domainlist"&,
14554 &"hostlist"&, &"addresslist"&, or &"localpartlist"&. Their use is described in
14555 section &<<SECTnamedlists>>&.
14557 Main configuration settings: Each setting occupies one line of the file
14558 (with possible continuations). If any setting is preceded by the word
14559 &"hide"&, the &%-bP%& command line option displays its value to admin users
14560 only. See section &<<SECTcos>>& for a description of the syntax of these option
14564 This chapter specifies all the main configuration options, along with their
14565 types and default values. For ease of finding a particular option, they appear
14566 in alphabetical order in section &<<SECTalomo>>& below. However, because there
14567 are now so many options, they are first listed briefly in functional groups, as
14568 an aid to finding the name of the option you are looking for. Some options are
14569 listed in more than one group.
14571 .section "Miscellaneous" "SECID96"
14573 .row &%add_environment%& "environment variables"
14574 .row &%bi_command%& "to run for &%-bi%& command line option"
14575 .row &%debug_store%& "do extra internal checks"
14576 .row &%disable_ipv6%& "do no IPv6 processing"
14577 .row &%keep_environment%& "environment variables"
14578 .row &%keep_malformed%& "for broken files &-- should not happen"
14579 .row &%localhost_number%& "for unique message ids in clusters"
14580 .row &%message_body_newlines%& "retain newlines in &$message_body$&"
14581 .row &%message_body_visible%& "how much to show in &$message_body$&"
14582 .row &%mua_wrapper%& "run in &""MUA wrapper""& mode"
14583 .row &%print_topbitchars%& "top-bit characters are printing"
14584 .row &%spool_wireformat%& "use wire-format spool data files when possible"
14585 .row &%timezone%& "force time zone"
14589 .section "Exim parameters" "SECID97"
14591 .row &%exim_group%& "override compiled-in value"
14592 .row &%exim_path%& "override compiled-in value"
14593 .row &%exim_user%& "override compiled-in value"
14594 .row &%primary_hostname%& "default from &[uname()]&"
14595 .row &%split_spool_directory%& "use multiple directories"
14596 .row &%spool_directory%& "override compiled-in value"
14601 .section "Privilege controls" "SECID98"
14603 .row &%admin_groups%& "groups that are Exim admin users"
14604 .row &%commandline_checks_require_admin%& "require admin for various checks"
14605 .row &%deliver_drop_privilege%& "drop root for delivery processes"
14606 .row &%local_from_check%& "insert &'Sender:'& if necessary"
14607 .row &%local_from_prefix%& "for testing &'From:'& for local sender"
14608 .row &%local_from_suffix%& "for testing &'From:'& for local sender"
14609 .row &%local_sender_retain%& "keep &'Sender:'& from untrusted user"
14610 .row &%never_users%& "do not run deliveries as these"
14611 .row &%prod_requires_admin%& "forced delivery requires admin user"
14612 .row &%queue_list_requires_admin%& "queue listing requires admin user"
14613 .row &%trusted_groups%& "groups that are trusted"
14614 .row &%trusted_users%& "users that are trusted"
14619 .section "Logging" "SECID99"
14621 .row &%event_action%& "custom logging"
14622 .row &%hosts_connection_nolog%& "exemption from connect logging"
14623 .row &%log_file_path%& "override compiled-in value"
14624 .row &%log_selector%& "set/unset optional logging"
14625 .row &%log_timezone%& "add timezone to log lines"
14626 .row &%message_logs%& "create per-message logs"
14627 .row &%preserve_message_logs%& "after message completion"
14628 .row &%panic_coredump%& "request coredump on fatal errors"
14629 .row &%process_log_path%& "for SIGUSR1 and &'exiwhat'&"
14630 .row &%slow_lookup_log%& "control logging of slow DNS lookups"
14631 .row &%syslog_duplication%& "controls duplicate log lines on syslog"
14632 .row &%syslog_facility%& "set syslog &""facility""& field"
14633 .row &%syslog_pid%& "pid in syslog lines"
14634 .row &%syslog_processname%& "set syslog &""ident""& field"
14635 .row &%syslog_timestamp%& "timestamp syslog lines"
14636 .row &%write_rejectlog%& "control use of message log"
14641 .section "Frozen messages" "SECID100"
14643 .row &%auto_thaw%& "sets time for retrying frozen messages"
14644 .row &%freeze_tell%& "send message when freezing"
14645 .row &%move_frozen_messages%& "to another directory"
14646 .row &%timeout_frozen_after%& "keep frozen messages only so long"
14651 .section "Data lookups" "SECID101"
14653 .row &%ibase_servers%& "InterBase servers"
14654 .row &%ldap_ca_cert_dir%& "dir of CA certs to verify LDAP server's"
14655 .row &%ldap_ca_cert_file%& "file of CA certs to verify LDAP server's"
14656 .row &%ldap_cert_file%& "client cert file for LDAP"
14657 .row &%ldap_cert_key%& "client key file for LDAP"
14658 .row &%ldap_cipher_suite%& "TLS negotiation preference control"
14659 .row &%ldap_default_servers%& "used if no server in query"
14660 .row &%ldap_require_cert%& "action to take without LDAP server cert"
14661 .row &%ldap_start_tls%& "require TLS within LDAP"
14662 .row &%ldap_version%& "set protocol version"
14663 .row &%lookup_open_max%& "lookup files held open"
14664 .row &%mysql_servers%& "default MySQL servers"
14665 .row &%oracle_servers%& "Oracle servers"
14666 .row &%pgsql_servers%& "default PostgreSQL servers"
14667 .row &%sqlite_lock_timeout%& "as it says"
14672 .section "Message ids" "SECID102"
14674 .row &%message_id_header_domain%& "used to build &'Message-ID:'& header"
14675 .row &%message_id_header_text%& "ditto"
14680 .section "Embedded Perl Startup" "SECID103"
14682 .row &%perl_at_start%& "always start the interpreter"
14683 .row &%perl_startup%& "code to obey when starting Perl"
14684 .row &%perl_taintmode%& "enable taint mode in Perl"
14689 .section "Daemon" "SECID104"
14691 .row &%daemon_smtp_ports%& "default ports"
14692 .row &%daemon_startup_retries%& "number of times to retry"
14693 .row &%daemon_startup_sleep%& "time to sleep between tries"
14694 .row &%extra_local_interfaces%& "not necessarily listened on"
14695 .row &%local_interfaces%& "on which to listen, with optional ports"
14696 .row &%notifier_socket%& "override compiled-in value"
14697 .row &%pid_file_path%& "override compiled-in value"
14698 .row &%queue_run_max%& "maximum simultaneous queue runners"
14699 .row &%smtp_backlog_monitor%& "level to log listen backlog"
14704 .section "Resource control" "SECID105"
14706 .row &%check_log_inodes%& "before accepting a message"
14707 .row &%check_log_space%& "before accepting a message"
14708 .row &%check_spool_inodes%& "before accepting a message"
14709 .row &%check_spool_space%& "before accepting a message"
14710 .row &%deliver_queue_load_max%& "no queue deliveries if load high"
14711 .row &%queue_only_load%& "queue incoming if load high"
14712 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
14713 .row &%queue_run_max%& "maximum simultaneous queue runners"
14714 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
14715 .row &%smtp_accept_max%& "simultaneous incoming connections"
14716 .row &%smtp_accept_max_nonmail%& "non-mail commands"
14717 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
14718 .row &%smtp_accept_max_per_connection%& "messages per connection"
14719 .row &%smtp_accept_max_per_host%& "connections from one host"
14720 .row &%smtp_accept_queue%& "queue mail if more connections"
14721 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
14723 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
14724 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
14725 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
14726 .row &%smtp_load_reserve%& "SMTP from reserved hosts if load high"
14727 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
14732 .section "Policy controls" "SECID106"
14734 .row &%acl_not_smtp%& "ACL for non-SMTP messages"
14735 .row &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
14736 .row &%acl_not_smtp_start%& "ACL for start of non-SMTP message"
14737 .row &%acl_smtp_auth%& "ACL for AUTH"
14738 .row &%acl_smtp_connect%& "ACL for connection"
14739 .row &%acl_smtp_data%& "ACL for DATA"
14740 .row &%acl_smtp_data_prdr%& "ACL for DATA, per-recipient"
14741 .row &%acl_smtp_dkim%& "ACL for DKIM verification"
14742 .row &%acl_smtp_etrn%& "ACL for ETRN"
14743 .row &%acl_smtp_expn%& "ACL for EXPN"
14744 .row &%acl_smtp_helo%& "ACL for EHLO or HELO"
14745 .row &%acl_smtp_mail%& "ACL for MAIL"
14746 .row &%acl_smtp_mailauth%& "ACL for AUTH on MAIL command"
14747 .row &%acl_smtp_mime%& "ACL for MIME parts"
14748 .row &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
14749 .row &%acl_smtp_predata%& "ACL for start of data"
14750 .row &%acl_smtp_quit%& "ACL for QUIT"
14751 .row &%acl_smtp_rcpt%& "ACL for RCPT"
14752 .row &%acl_smtp_starttls%& "ACL for STARTTLS"
14753 .row &%acl_smtp_vrfy%& "ACL for VRFY"
14754 .row &%av_scanner%& "specify virus scanner"
14755 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
14757 .row &%dns_cname_loops%& "follow CNAMEs returned by resolver"
14758 .row &%dns_csa_search_limit%& "control CSA parent search depth"
14759 .row &%dns_csa_use_reverse%& "en/disable CSA IP reverse search"
14760 .row &%header_maxsize%& "total size of message header"
14761 .row &%header_line_maxsize%& "individual header line limit"
14762 .row &%helo_accept_junk_hosts%& "allow syntactic junk from these hosts"
14763 .row &%helo_allow_chars%& "allow illegal chars in HELO names"
14764 .row &%helo_lookup_domains%& "lookup hostname for these HELO names"
14765 .row &%helo_try_verify_hosts%& "HELO soft-checked for these hosts"
14766 .row &%helo_verify_hosts%& "HELO hard-checked for these hosts"
14767 .row &%host_lookup%& "host name looked up for these hosts"
14768 .row &%host_lookup_order%& "order of DNS and local name lookups"
14769 .row &%hosts_proxy%& "use proxy protocol for these hosts"
14770 .row &%host_reject_connection%& "reject connection from these hosts"
14771 .row &%hosts_treat_as_local%& "useful in some cluster configurations"
14772 .row &%local_scan_timeout%& "timeout for &[local_scan()]&"
14773 .row &%message_size_limit%& "for all messages"
14774 .row &%percent_hack_domains%& "recognize %-hack for these domains"
14775 .row &%proxy_protocol_timeout%& "timeout for proxy protocol negotiation"
14776 .row &%spamd_address%& "set interface to SpamAssassin"
14777 .row &%strict_acl_vars%& "object to unset ACL variables"
14778 .row &%spf_smtp_comment_template%& "template for &$spf_smtp_comment$&"
14783 .section "Callout cache" "SECID107"
14785 .row &%callout_domain_negative_expire%& "timeout for negative domain cache &&&
14787 .row &%callout_domain_positive_expire%& "timeout for positive domain cache &&&
14789 .row &%callout_negative_expire%& "timeout for negative address cache item"
14790 .row &%callout_positive_expire%& "timeout for positive address cache item"
14791 .row &%callout_random_local_part%& "string to use for &""random""& testing"
14796 .section "TLS" "SECID108"
14798 .row &%gnutls_compat_mode%& "use GnuTLS compatibility mode"
14799 .row &%gnutls_allow_auto_pkcs11%& "allow GnuTLS to autoload PKCS11 modules"
14800 .row &%hosts_require_alpn%& "mandatory ALPN"
14801 .row &%hosts_require_helo%& "mandatory HELO/EHLO"
14802 .row &%openssl_options%& "adjust OpenSSL compatibility options"
14803 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
14804 .row &%tls_alpn%& "acceptable protocol names"
14805 .row &%tls_certificate%& "location of server certificate"
14806 .row &%tls_crl%& "certificate revocation list"
14807 .row &%tls_dh_max_bits%& "clamp D-H bit count suggestion"
14808 .row &%tls_dhparam%& "DH parameters for server"
14809 .row &%tls_eccurve%& "EC curve selection for server"
14810 .row &%tls_ocsp_file%& "location of server certificate status proof"
14811 .row &%tls_on_connect_ports%& "specify SSMTP (SMTPS) ports"
14812 .row &%tls_privatekey%& "location of server private key"
14813 .row &%tls_remember_esmtp%& "don't reset after starting TLS"
14814 .row &%tls_require_ciphers%& "specify acceptable ciphers"
14815 .row &%tls_try_verify_hosts%& "try to verify client certificate"
14816 .row &%tls_verify_certificates%& "expected client certificates"
14817 .row &%tls_verify_hosts%& "insist on client certificate verify"
14822 .section "Local user handling" "SECID109"
14824 .row &%finduser_retries%& "useful in NIS environments"
14825 .row &%gecos_name%& "used when creating &'Sender:'&"
14826 .row &%gecos_pattern%& "ditto"
14827 .row &%max_username_length%& "for systems that truncate"
14828 .row &%unknown_login%& "used when no login name found"
14829 .row &%unknown_username%& "ditto"
14830 .row &%uucp_from_pattern%& "for recognizing &""From ""& lines"
14831 .row &%uucp_from_sender%& "ditto"
14836 .section "All incoming messages (SMTP and non-SMTP)" "SECID110"
14838 .row &%header_maxsize%& "total size of message header"
14839 .row &%header_line_maxsize%& "individual header line limit"
14840 .row &%message_size_limit%& "applies to all messages"
14841 .row &%percent_hack_domains%& "recognize %-hack for these domains"
14842 .row &%received_header_text%& "expanded to make &'Received:'&"
14843 .row &%received_headers_max%& "for mail loop detection"
14844 .row &%recipients_max%& "limit per message"
14845 .row &%recipients_max_reject%& "permanently reject excess recipients"
14851 .section "Non-SMTP incoming messages" "SECID111"
14853 .row &%receive_timeout%& "for non-SMTP messages"
14860 .section "Incoming SMTP messages" "SECID112"
14861 See also the &'Policy controls'& section above.
14864 .row &%dkim_verify_hashes%& "DKIM hash methods accepted for signatures"
14865 .row &%dkim_verify_keytypes%& "DKIM key types accepted for signatures"
14866 .row &%dkim_verify_min_keysizes%& "DKIM key sizes accepted for signatures"
14867 .row &%dkim_verify_signers%& "DKIM domains for which DKIM ACL is run"
14868 .row &%dmarc_forensic_sender%& "DMARC sender for report messages"
14869 .row &%dmarc_history_file%& "DMARC results log"
14870 .row &%dmarc_tld_file%& "DMARC toplevel domains file"
14871 .row &%host_lookup%& "host name looked up for these hosts"
14872 .row &%host_lookup_order%& "order of DNS and local name lookups"
14873 .row &%recipient_unqualified_hosts%& "may send unqualified recipients"
14874 .row &%rfc1413_hosts%& "make ident calls to these hosts"
14875 .row &%rfc1413_query_timeout%& "zero disables ident calls"
14876 .row &%sender_unqualified_hosts%& "may send unqualified senders"
14877 .row &%smtp_accept_keepalive%& "some TCP/IP magic"
14878 .row &%smtp_accept_max%& "simultaneous incoming connections"
14879 .row &%smtp_accept_max_nonmail%& "non-mail commands"
14880 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
14881 .row &%smtp_accept_max_per_connection%& "messages per connection"
14882 .row &%smtp_accept_max_per_host%& "connections from one host"
14883 .row &%smtp_accept_queue%& "queue mail if more connections"
14884 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
14886 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
14887 .row &%smtp_active_hostname%& "host name to use in messages"
14888 .row &%smtp_banner%& "text for welcome banner"
14889 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
14890 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
14891 .row &%smtp_enforce_sync%& "of SMTP command/responses"
14892 .row &%smtp_etrn_command%& "what to run for ETRN"
14893 .row &%smtp_etrn_serialize%& "only one at once"
14894 .row &%smtp_load_reserve%& "only reserve hosts if this load"
14895 .row &%smtp_max_unknown_commands%& "before dropping connection"
14896 .row &%smtp_ratelimit_hosts%& "apply ratelimiting to these hosts"
14897 .row &%smtp_ratelimit_mail%& "ratelimit for MAIL commands"
14898 .row &%smtp_ratelimit_rcpt%& "ratelimit for RCPT commands"
14899 .row &%smtp_receive_timeout%& "per command or data line"
14900 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
14901 .row &%smtp_return_error_details%& "give detail on rejections"
14906 .section "SMTP extensions" "SECID113"
14908 .row &%accept_8bitmime%& "advertise 8BITMIME"
14909 .row &%auth_advertise_hosts%& "advertise AUTH to these hosts"
14910 .row &%chunking_advertise_hosts%& "advertise CHUNKING to these hosts"
14911 .row &%dsn_advertise_hosts%& "advertise DSN extensions to these hosts"
14912 .row &%ignore_fromline_hosts%& "allow &""From ""& from these hosts"
14913 .row &%ignore_fromline_local%& "allow &""From ""& from local SMTP"
14914 .row &%pipelining_advertise_hosts%& "advertise pipelining to these hosts"
14915 .row &%pipelining_connect_advertise_hosts%& "advertise pipelining to these hosts"
14916 .row &%prdr_enable%& "advertise PRDR to all hosts"
14917 .row &%smtputf8_advertise_hosts%& "advertise SMTPUTF8 to these hosts"
14918 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
14923 .section "Processing messages" "SECID114"
14925 .row &%allow_domain_literals%& "recognize domain literal syntax"
14926 .row &%allow_mx_to_ip%& "allow MX to point to IP address"
14927 .row &%allow_utf8_domains%& "in addresses"
14928 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
14930 .row &%delivery_date_remove%& "from incoming messages"
14931 .row &%envelope_to_remove%& "from incoming messages"
14932 .row &%extract_addresses_remove_arguments%& "affects &%-t%& processing"
14933 .row &%headers_charset%& "default for translations"
14934 .row &%qualify_domain%& "default for senders"
14935 .row &%qualify_recipient%& "default for recipients"
14936 .row &%return_path_remove%& "from incoming messages"
14937 .row &%strip_excess_angle_brackets%& "in addresses"
14938 .row &%strip_trailing_dot%& "at end of addresses"
14939 .row &%untrusted_set_sender%& "untrusted can set envelope sender"
14944 .section "System filter" "SECID115"
14946 .row &%system_filter%& "locate system filter"
14947 .row &%system_filter_directory_transport%& "transport for delivery to a &&&
14949 .row &%system_filter_file_transport%& "transport for delivery to a file"
14950 .row &%system_filter_group%& "group for filter running"
14951 .row &%system_filter_pipe_transport%& "transport for delivery to a pipe"
14952 .row &%system_filter_reply_transport%& "transport for autoreply delivery"
14953 .row &%system_filter_user%& "user for filter running"
14958 .section "Routing and delivery" "SECID116"
14960 .row &%disable_ipv6%& "do no IPv6 processing"
14961 .row &%dns_again_means_nonexist%& "for broken domains"
14962 .row &%dns_check_names_pattern%& "pre-DNS syntax check"
14963 .row &%dns_dnssec_ok%& "parameter for resolver"
14964 .row &%dns_ipv4_lookup%& "only v4 lookup for these domains"
14965 .row &%dns_retrans%& "parameter for resolver"
14966 .row &%dns_retry%& "parameter for resolver"
14967 .row &%dns_trust_aa%& "DNS zones trusted as authentic"
14968 .row &%dns_use_edns0%& "parameter for resolver"
14969 .row &%hold_domains%& "hold delivery for these domains"
14970 .row &%local_interfaces%& "for routing checks"
14971 .row &%queue_domains%& "no immediate delivery for these"
14972 .row &%queue_fast_ramp%& "parallel delivery with 2-phase queue run"
14973 .row &%queue_only%& "no immediate delivery at all"
14974 .row &%queue_only_file%& "no immediate delivery if file exists"
14975 .row &%queue_only_load%& "no immediate delivery if load is high"
14976 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
14977 .row &%queue_only_override%& "allow command line to override"
14978 .row &%queue_run_in_order%& "order of arrival"
14979 .row &%queue_run_max%& "of simultaneous queue runners"
14980 .row &%queue_smtp_domains%& "no immediate SMTP delivery for these"
14981 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
14982 .row &%remote_sort_domains%& "order of remote deliveries"
14983 .row &%retry_data_expire%& "timeout for retry data"
14984 .row &%retry_interval_max%& "safety net for retry rules"
14989 .section "Bounce and warning messages" "SECID117"
14991 .row &%bounce_message_file%& "content of bounce"
14992 .row &%bounce_message_text%& "content of bounce"
14993 .row &%bounce_return_body%& "include body if returning message"
14994 .row &%bounce_return_linesize_limit%& "limit on returned message line length"
14995 .row &%bounce_return_message%& "include original message in bounce"
14996 .row &%bounce_return_size_limit%& "limit on returned message"
14997 .row &%bounce_sender_authentication%& "send authenticated sender with bounce"
14998 .row &%dsn_from%& "set &'From:'& contents in bounces"
14999 .row &%errors_copy%& "copy bounce messages"
15000 .row &%errors_reply_to%& "&'Reply-to:'& in bounces"
15001 .row &%delay_warning%& "time schedule"
15002 .row &%delay_warning_condition%& "condition for warning messages"
15003 .row &%ignore_bounce_errors_after%& "discard undeliverable bounces"
15004 .row &%smtp_return_error_details%& "give detail on rejections"
15005 .row &%warn_message_file%& "content of warning message"
15010 .section "Alphabetical list of main options" "SECTalomo"
15011 Those options that undergo string expansion before use are marked with
15014 .option accept_8bitmime main boolean true
15016 .cindex "8-bit characters"
15017 .cindex "log" "selectors"
15018 .cindex "log" "8BITMIME"
15019 .cindex "ESMTP extensions" 8BITMIME
15020 This option causes Exim to send 8BITMIME in its response to an SMTP
15021 EHLO command, and to accept the BODY= parameter on MAIL commands.
15022 However, though Exim is 8-bit clean, it is not a protocol converter, and it
15023 takes no steps to do anything special with messages received by this route.
15025 Historically Exim kept this option off by default, but the maintainers
15026 feel that in today's Internet, this causes more problems than it solves.
15027 It now defaults to true.
15028 A more detailed analysis of the issues is provided by Dan Bernstein:
15030 &url(https://cr.yp.to/smtp/8bitmime.html)
15033 To log received 8BITMIME status use
15035 log_selector = +8bitmime
15038 .option acl_not_smtp main string&!! unset
15039 .cindex "&ACL;" "for non-SMTP messages"
15040 .cindex "non-SMTP messages" "ACLs for"
15041 This option defines the ACL that is run when a non-SMTP message has been
15042 read and is on the point of being accepted. See chapter &<<CHAPACL>>& for
15045 .option acl_not_smtp_mime main string&!! unset
15046 This option defines the ACL that is run for individual MIME parts of non-SMTP
15047 messages. It operates in exactly the same way as &%acl_smtp_mime%& operates for
15050 .option acl_not_smtp_start main string&!! unset
15051 .cindex "&ACL;" "at start of non-SMTP message"
15052 .cindex "non-SMTP messages" "ACLs for"
15053 This option defines the ACL that is run before Exim starts reading a
15054 non-SMTP message. See chapter &<<CHAPACL>>& for further details.
15056 .option acl_smtp_auth main string&!! unset
15057 .cindex "&ACL;" "setting up for SMTP commands"
15058 .cindex "AUTH" "ACL for"
15059 This option defines the ACL that is run when an SMTP AUTH command is
15060 received. See chapter &<<CHAPACL>>& for further details.
15062 .option acl_smtp_connect main string&!! unset
15063 .cindex "&ACL;" "on SMTP connection"
15064 This option defines the ACL that is run when an SMTP connection is received.
15065 See chapter &<<CHAPACL>>& for further details.
15067 .option acl_smtp_data main string&!! unset
15068 .cindex "DATA" "ACL for"
15069 This option defines the ACL that is run after an SMTP DATA command has been
15070 processed and the message itself has been received, but before the final
15071 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
15073 .option acl_smtp_data_prdr main string&!! accept
15074 .cindex "PRDR" "ACL for"
15075 .cindex "DATA" "PRDR ACL for"
15076 .cindex "&ACL;" "PRDR-related"
15077 .cindex "&ACL;" "per-user data processing"
15078 This option defines the ACL that,
15079 if the PRDR feature has been negotiated,
15080 is run for each recipient after an SMTP DATA command has been
15081 processed and the message itself has been received, but before the
15082 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
15084 .option acl_smtp_dkim main string&!! unset
15085 .cindex DKIM "ACL for"
15086 This option defines the ACL that is run for each DKIM signature
15087 (by default, or as specified in the dkim_verify_signers option)
15088 of a received message.
15089 See section &<<SECDKIMVFY>>& for further details.
15091 .option acl_smtp_etrn main string&!! unset
15092 .cindex "ETRN" "ACL for"
15093 This option defines the ACL that is run when an SMTP ETRN command is
15094 received. See chapter &<<CHAPACL>>& for further details.
15096 .option acl_smtp_expn main string&!! unset
15097 .cindex "EXPN" "ACL for"
15098 This option defines the ACL that is run when an SMTP EXPN command is
15099 received. See chapter &<<CHAPACL>>& for further details.
15101 .option acl_smtp_helo main string&!! unset
15102 .cindex "EHLO" "ACL for"
15103 .cindex "HELO" "ACL for"
15104 This option defines the ACL that is run when an SMTP EHLO or HELO
15105 command is received. See chapter &<<CHAPACL>>& for further details.
15108 .option acl_smtp_mail main string&!! unset
15109 .cindex "MAIL" "ACL for"
15110 This option defines the ACL that is run when an SMTP MAIL command is
15111 received. See chapter &<<CHAPACL>>& for further details.
15113 .option acl_smtp_mailauth main string&!! unset
15114 .cindex "AUTH" "on MAIL command"
15115 This option defines the ACL that is run when there is an AUTH parameter on
15116 a MAIL command. See chapter &<<CHAPACL>>& for details of ACLs, and chapter
15117 &<<CHAPSMTPAUTH>>& for details of authentication.
15119 .option acl_smtp_mime main string&!! unset
15120 .cindex "MIME content scanning" "ACL for"
15121 This option is available when Exim is built with the content-scanning
15122 extension. It defines the ACL that is run for each MIME part in a message. See
15123 section &<<SECTscanmimepart>>& for details.
15125 .option acl_smtp_notquit main string&!! unset
15126 .cindex "not-QUIT, ACL for"
15127 This option defines the ACL that is run when an SMTP session
15128 ends without a QUIT command being received.
15129 See chapter &<<CHAPACL>>& for further details.
15131 .option acl_smtp_predata main string&!! unset
15132 This option defines the ACL that is run when an SMTP DATA command is
15133 received, before the message itself is received. See chapter &<<CHAPACL>>& for
15136 .option acl_smtp_quit main string&!! unset
15137 .cindex "QUIT, ACL for"
15138 This option defines the ACL that is run when an SMTP QUIT command is
15139 received. See chapter &<<CHAPACL>>& for further details.
15141 .option acl_smtp_rcpt main string&!! unset
15142 .cindex "RCPT" "ACL for"
15143 This option defines the ACL that is run when an SMTP RCPT command is
15144 received. See chapter &<<CHAPACL>>& for further details.
15146 .option acl_smtp_starttls main string&!! unset
15147 .cindex "STARTTLS, ACL for"
15148 This option defines the ACL that is run when an SMTP STARTTLS command is
15149 received. See chapter &<<CHAPACL>>& for further details.
15151 .option acl_smtp_vrfy main string&!! unset
15152 .cindex "VRFY" "ACL for"
15153 This option defines the ACL that is run when an SMTP VRFY command is
15154 received. See chapter &<<CHAPACL>>& for further details.
15156 .option add_environment main "string list" empty
15157 .cindex "environment" "set values"
15158 This option adds individual environment variables that the
15159 currently linked libraries and programs in child processes may use.
15160 Each list element should be of the form &"name=value"&.
15162 See &<<SECTpipeenv>>& for the environment of &(pipe)& transports.
15164 .option admin_groups main "string list&!!" unset
15165 .cindex "admin user"
15166 This option is expanded just once, at the start of Exim's processing. If the
15167 current group or any of the supplementary groups of an Exim caller is in this
15168 colon-separated list, the caller has admin privileges. If all your system
15169 programmers are in a specific group, for example, you can give them all Exim
15170 admin privileges by putting that group in &%admin_groups%&. However, this does
15171 not permit them to read Exim's spool files (whose group owner is the Exim gid).
15172 To permit this, you have to add individuals to the Exim group.
15174 .option allow_domain_literals main boolean false
15175 .cindex "domain literal"
15176 If this option is set, the RFC 2822 domain literal format is permitted in
15177 email addresses. The option is not set by default, because the domain literal
15178 format is not normally required these days, and few people know about it. It
15179 has, however, been exploited by mail abusers.
15181 Unfortunately, it seems that some DNS black list maintainers are using this
15182 format to report black listing to postmasters. If you want to accept messages
15183 addressed to your hosts by IP address, you need to set
15184 &%allow_domain_literals%& true, and also to add &`@[]`& to the list of local
15185 domains (defined in the named domain list &%local_domains%& in the default
15186 configuration). This &"magic string"& matches the domain literal form of all
15187 the local host's IP addresses.
15189 .option allow_mx_to_ip main boolean false
15190 .cindex "MX record" "pointing to IP address"
15191 It appears that more and more DNS zone administrators are breaking the rules
15192 and putting domain names that look like IP addresses on the right hand side of
15193 MX records. Exim follows the rules and rejects this, giving an error message
15194 that explains the misconfiguration. However, some other MTAs support this
15195 practice, so to avoid &"Why can't Exim do this?"& complaints,
15196 &%allow_mx_to_ip%& exists, in order to enable this heinous activity. It is not
15197 recommended, except when you have no other choice.
15199 .option allow_utf8_domains main boolean false
15200 .cindex "domain" "UTF-8 characters in"
15201 .cindex "UTF-8" "in domain name"
15202 Lots of discussion is going on about internationalized domain names. One
15203 camp is strongly in favour of just using UTF-8 characters, and it seems
15204 that at least two other MTAs permit this.
15205 This option allows Exim users to experiment if they wish.
15207 If it is set true, Exim's domain parsing function allows valid
15208 UTF-8 multicharacters to appear in domain name components, in addition to
15209 letters, digits, and hyphens.
15211 If Exim is built with internationalization support
15212 and the SMTPUTF8 ESMTP option is in use (see chapter &<<CHAPi18n>>&)
15213 this option can be left as default.
15215 if you want to look up such domain names in the DNS, you must also
15216 adjust the value of &%dns_check_names_pattern%& to match the extended form. A
15217 suitable setting is:
15219 dns_check_names_pattern = (?i)^(?>(?(1)\.|())[a-z0-9\xc0-\xff]\
15220 (?>[-a-z0-9\x80-\xff]*[a-z0-9\x80-\xbf])?)+$
15222 Alternatively, you can just disable this feature by setting
15224 dns_check_names_pattern =
15226 That is, set the option to an empty string so that no check is done.
15229 .option auth_advertise_hosts main "host list&!!" *
15230 .cindex "authentication" "advertising"
15231 .cindex "AUTH" "advertising"
15232 .cindex "ESMTP extensions" AUTH
15233 If any server authentication mechanisms are configured, Exim advertises them in
15234 response to an EHLO command only if the calling host matches this list.
15235 Otherwise, Exim does not advertise AUTH.
15236 Exim does not accept AUTH commands from clients to which it has not
15237 advertised the availability of AUTH. The advertising of individual
15238 authentication mechanisms can be controlled by the use of the
15239 &%server_advertise_condition%& generic authenticator option on the individual
15240 authenticators. See chapter &<<CHAPSMTPAUTH>>& for further details.
15242 Certain mail clients (for example, Netscape) require the user to provide a name
15243 and password for authentication if AUTH is advertised, even though it may
15244 not be needed (the host may accept messages from hosts on its local LAN without
15245 authentication, for example). The &%auth_advertise_hosts%& option can be used
15246 to make these clients more friendly by excluding them from the set of hosts to
15247 which Exim advertises AUTH.
15249 .cindex "AUTH" "advertising when encrypted"
15250 If you want to advertise the availability of AUTH only when the connection
15251 is encrypted using TLS, you can make use of the fact that the value of this
15252 option is expanded, with a setting like this:
15254 auth_advertise_hosts = ${if eq{$tls_in_cipher}{}{}{*}}
15256 .vindex "&$tls_in_cipher$&"
15257 If &$tls_in_cipher$& is empty, the session is not encrypted, and the result of
15258 the expansion is empty, thus matching no hosts. Otherwise, the result of the
15259 expansion is *, which matches all hosts.
15262 .option auto_thaw main time 0s
15263 .cindex "thawing messages"
15264 .cindex "unfreezing messages"
15265 If this option is set to a time greater than zero, a queue runner will try a
15266 new delivery attempt on any frozen message, other than a bounce message, if
15267 this much time has passed since it was frozen. This may result in the message
15268 being re-frozen if nothing has changed since the last attempt. It is a way of
15269 saying &"keep on trying, even though there are big problems"&.
15271 &*Note*&: This is an old option, which predates &%timeout_frozen_after%& and
15272 &%ignore_bounce_errors_after%&. It is retained for compatibility, but it is not
15273 thought to be very useful any more, and its use should probably be avoided.
15276 .option av_scanner main string "see below"
15277 This option is available if Exim is built with the content-scanning extension.
15278 It specifies which anti-virus scanner to use. The default value is:
15280 sophie:/var/run/sophie
15282 If the value of &%av_scanner%& starts with a dollar character, it is expanded
15283 before use. See section &<<SECTscanvirus>>& for further details.
15286 .option bi_command main string unset
15288 This option supplies the name of a command that is run when Exim is called with
15289 the &%-bi%& option (see chapter &<<CHAPcommandline>>&). The string value is
15290 just the command name, it is not a complete command line. If an argument is
15291 required, it must come from the &%-oA%& command line option.
15294 .option bounce_message_file main string&!! unset
15295 .cindex "bounce message" "customizing"
15296 .cindex "customizing" "bounce message"
15297 This option defines a template file containing paragraphs of text to be used
15298 for constructing bounce messages. Details of the file's contents are given in
15299 chapter &<<CHAPemsgcust>>&.
15300 .cindex bounce_message_file "tainted data"
15301 The option is expanded to give the file path, which must be
15302 absolute and untainted.
15303 See also &%warn_message_file%&.
15306 .option bounce_message_text main string unset
15307 When this option is set, its contents are included in the default bounce
15308 message immediately after &"This message was created automatically by mail
15309 delivery software."& It is not used if &%bounce_message_file%& is set.
15311 .option bounce_return_body main boolean true
15312 .cindex "bounce message" "including body"
15313 This option controls whether the body of an incoming message is included in a
15314 bounce message when &%bounce_return_message%& is true. The default setting
15315 causes the entire message, both header and body, to be returned (subject to the
15316 value of &%bounce_return_size_limit%&). If this option is false, only the
15317 message header is included. In the case of a non-SMTP message containing an
15318 error that is detected during reception, only those header lines preceding the
15319 point at which the error was detected are returned.
15320 .cindex "bounce message" "including original"
15322 .option bounce_return_linesize_limit main integer 998
15323 .cindex "size" "of bounce lines, limit"
15324 .cindex "bounce message" "line length limit"
15325 .cindex "limit" "bounce message line length"
15326 This option sets a limit in bytes on the line length of messages
15327 that are returned to senders due to delivery problems,
15328 when &%bounce_return_message%& is true.
15329 The default value corresponds to RFC limits.
15330 If the message being returned has lines longer than this value it is
15331 treated as if the &%bounce_return_size_limit%& (below) restriction was exceeded.
15333 The option also applies to bounces returned when an error is detected
15334 during reception of a message.
15335 In this case lines from the original are truncated.
15337 The option does not apply to messages generated by an &(autoreply)& transport.
15340 .option bounce_return_message main boolean true
15341 If this option is set false, none of the original message is included in
15342 bounce messages generated by Exim. See also &%bounce_return_size_limit%& and
15343 &%bounce_return_body%&.
15346 .option bounce_return_size_limit main integer 100K
15347 .cindex "size" "of bounce, limit"
15348 .cindex "bounce message" "size limit"
15349 .cindex "limit" "bounce message size"
15350 This option sets a limit in bytes on the size of messages that are returned to
15351 senders as part of bounce messages when &%bounce_return_message%& is true. The
15352 limit should be less than the value of the global &%message_size_limit%& and of
15353 any &%message_size_limit%& settings on transports, to allow for the bounce text
15354 that Exim generates. If this option is set to zero there is no limit.
15356 When the body of any message that is to be included in a bounce message is
15357 greater than the limit, it is truncated, and a comment pointing this out is
15358 added at the top. The actual cutoff may be greater than the value given, owing
15359 to the use of buffering for transferring the message in chunks (typically 8K in
15360 size). The idea is to save bandwidth on those undeliverable 15-megabyte
15363 .option bounce_sender_authentication main string unset
15364 .cindex "bounce message" "sender authentication"
15365 .cindex "authentication" "bounce message"
15366 .cindex "AUTH" "on bounce message"
15367 This option provides an authenticated sender address that is sent with any
15368 bounce messages generated by Exim that are sent over an authenticated SMTP
15369 connection. A typical setting might be:
15371 bounce_sender_authentication = mailer-daemon@my.domain.example
15373 which would cause bounce messages to be sent using the SMTP command:
15375 MAIL FROM:<> AUTH=mailer-daemon@my.domain.example
15377 The value of &%bounce_sender_authentication%& must always be a complete email
15380 .option callout_domain_negative_expire main time 3h
15381 .cindex "caching" "callout timeouts"
15382 .cindex "callout" "caching timeouts"
15383 This option specifies the expiry time for negative callout cache data for a
15384 domain. See section &<<SECTcallver>>& for details of callout verification, and
15385 section &<<SECTcallvercache>>& for details of the caching.
15388 .option callout_domain_positive_expire main time 7d
15389 This option specifies the expiry time for positive callout cache data for a
15390 domain. See section &<<SECTcallver>>& for details of callout verification, and
15391 section &<<SECTcallvercache>>& for details of the caching.
15394 .option callout_negative_expire main time 2h
15395 This option specifies the expiry time for negative callout cache data for an
15396 address. See section &<<SECTcallver>>& for details of callout verification, and
15397 section &<<SECTcallvercache>>& for details of the caching.
15400 .option callout_positive_expire main time 24h
15401 This option specifies the expiry time for positive callout cache data for an
15402 address. See section &<<SECTcallver>>& for details of callout verification, and
15403 section &<<SECTcallvercache>>& for details of the caching.
15406 .option callout_random_local_part main string&!! "see below"
15407 This option defines the &"random"& local part that can be used as part of
15408 callout verification. The default value is
15410 $primary_hostname-$tod_epoch-testing
15412 See section &<<CALLaddparcall>>& for details of how this value is used.
15415 .option check_log_inodes main integer 100
15416 See &%check_spool_space%& below.
15419 .option check_log_space main integer 10M
15420 See &%check_spool_space%& below.
15422 .oindex "&%check_rfc2047_length%&"
15423 .cindex "RFC 2047" "disabling length check"
15424 .option check_rfc2047_length main boolean true
15425 RFC 2047 defines a way of encoding non-ASCII characters in headers using a
15426 system of &"encoded words"&. The RFC specifies a maximum length for an encoded
15427 word; strings to be encoded that exceed this length are supposed to use
15428 multiple encoded words. By default, Exim does not recognize encoded words that
15429 exceed the maximum length. However, it seems that some software, in violation
15430 of the RFC, generates overlong encoded words. If &%check_rfc2047_length%& is
15431 set false, Exim recognizes encoded words of any length.
15434 .option check_spool_inodes main integer 100
15435 See &%check_spool_space%& below.
15438 .option check_spool_space main integer 10M
15439 .cindex "checking disk space"
15440 .cindex "disk space, checking"
15441 .cindex "spool directory" "checking space"
15442 The four &%check_...%& options allow for checking of disk resources before a
15443 message is accepted.
15445 .vindex "&$log_inodes$&"
15446 .vindex "&$log_space$&"
15447 .vindex "&$spool_inodes$&"
15448 .vindex "&$spool_space$&"
15449 When any of these options are nonzero, they apply to all incoming messages. If you
15450 want to apply different checks to different kinds of message, you can do so by
15451 testing the variables &$log_inodes$&, &$log_space$&, &$spool_inodes$&, and
15452 &$spool_space$& in an ACL with appropriate additional conditions.
15455 &%check_spool_space%& and &%check_spool_inodes%& check the spool partition if
15456 either value is greater than zero, for example:
15458 check_spool_space = 100M
15459 check_spool_inodes = 100
15461 The spool partition is the one that contains the directory defined by
15462 SPOOL_DIRECTORY in &_Local/Makefile_&. It is used for holding messages in
15465 &%check_log_space%& and &%check_log_inodes%& check the partition in which log
15466 files are written if either is greater than zero. These should be set only if
15467 &%log_file_path%& and &%spool_directory%& refer to different partitions.
15469 If there is less space or fewer inodes than requested, Exim refuses to accept
15470 incoming mail. In the case of SMTP input this is done by giving a 452 temporary
15471 error response to the MAIL command. If ESMTP is in use and there was a
15472 SIZE parameter on the MAIL command, its value is added to the
15473 &%check_spool_space%& value, and the check is performed even if
15474 &%check_spool_space%& is zero, unless &%no_smtp_check_spool_space%& is set.
15476 The values for &%check_spool_space%& and &%check_log_space%& are held as a
15477 number of kilobytes (though specified in bytes).
15478 If a non-multiple of 1024 is specified, it is rounded up.
15480 For non-SMTP input and for batched SMTP input, the test is done at start-up; on
15481 failure a message is written to stderr and Exim exits with a non-zero code, as
15482 it obviously cannot send an error message of any kind.
15484 There is a slight performance penalty for these checks.
15485 Versions of Exim preceding 4.88 had these disabled by default;
15486 high-rate installations confident they will never run out of resources
15487 may wish to deliberately disable them.
15489 .option chunking_advertise_hosts main "host list&!!" *
15490 .cindex CHUNKING advertisement
15491 .cindex "RFC 3030" "CHUNKING"
15492 .cindex "ESMTP extensions" CHUNKING
15493 The CHUNKING extension (RFC3030) will be advertised in the EHLO message to
15495 Hosts may use the BDAT command as an alternate to DATA.
15497 .option commandline_checks_require_admin main boolean &`false`&
15498 .cindex "restricting access to features"
15499 This option restricts various basic checking features to require an
15500 administrative user.
15501 This affects most of the &%-b*%& options, such as &%-be%&.
15503 .option debug_store main boolean &`false`&
15504 .cindex debugging "memory corruption"
15505 .cindex memory debugging
15506 This option, when true, enables extra checking in Exim's internal memory
15507 management. For use when a memory corruption issue is being investigated,
15508 it should normally be left as default.
15510 .option daemon_smtp_ports main string &`smtp`&
15511 .cindex "port" "for daemon"
15512 .cindex "TCP/IP" "setting listening ports"
15513 This option specifies one or more default SMTP ports on which the Exim daemon
15514 listens. See chapter &<<CHAPinterfaces>>& for details of how it is used. For
15515 backward compatibility, &%daemon_smtp_port%& (singular) is a synonym.
15517 .option daemon_startup_retries main integer 9
15518 .cindex "daemon startup, retrying"
15519 This option, along with &%daemon_startup_sleep%&, controls the retrying done by
15520 the daemon at startup when it cannot immediately bind a listening socket
15521 (typically because the socket is already in use): &%daemon_startup_retries%&
15522 defines the number of retries after the first failure, and
15523 &%daemon_startup_sleep%& defines the length of time to wait between retries.
15525 .option daemon_startup_sleep main time 30s
15526 See &%daemon_startup_retries%&.
15528 .option delay_warning main "time list" 24h
15529 .cindex "warning of delay"
15530 .cindex "delay warning, specifying"
15531 .cindex "queue" "delay warning"
15532 When a message is delayed, Exim sends a warning message to the sender at
15533 intervals specified by this option. The data is a colon-separated list of times
15534 after which to send warning messages. If the value of the option is an empty
15535 string or a zero time, no warnings are sent. Up to 10 times may be given. If a
15536 message has been in the queue for longer than the last time, the last interval
15537 between the times is used to compute subsequent warning times. For example,
15540 delay_warning = 4h:8h:24h
15542 the first message is sent after 4 hours, the second after 8 hours, and
15543 the third one after 24 hours. After that, messages are sent every 16 hours,
15544 because that is the interval between the last two times on the list. If you set
15545 just one time, it specifies the repeat interval. For example, with:
15549 messages are repeated every six hours. To stop warnings after a given time, set
15550 a very large time at the end of the list. For example:
15552 delay_warning = 2h:12h:99d
15554 Note that the option is only evaluated at the time a delivery attempt fails,
15555 which depends on retry and queue-runner configuration.
15556 Typically retries will be configured more frequently than warning messages.
15558 .option delay_warning_condition main string&!! "see below"
15559 .vindex "&$domain$&"
15560 The string is expanded at the time a warning message might be sent. If all the
15561 deferred addresses have the same domain, it is set in &$domain$& during the
15562 expansion. Otherwise &$domain$& is empty. If the result of the expansion is a
15563 forced failure, an empty string, or a string matching any of &"0"&, &"no"& or
15564 &"false"& (the comparison being done caselessly) then the warning message is
15565 not sent. The default is:
15567 delay_warning_condition = ${if or {\
15568 { !eq{$h_list-id:$h_list-post:$h_list-subscribe:}{} }\
15569 { match{$h_precedence:}{(?i)bulk|list|junk} }\
15570 { match{$h_auto-submitted:}{(?i)auto-generated|auto-replied} }\
15573 This suppresses the sending of warnings for messages that contain &'List-ID:'&,
15574 &'List-Post:'&, or &'List-Subscribe:'& headers, or have &"bulk"&, &"list"& or
15575 &"junk"& in a &'Precedence:'& header, or have &"auto-generated"& or
15576 &"auto-replied"& in an &'Auto-Submitted:'& header.
15578 .option deliver_drop_privilege main boolean false
15579 .cindex "unprivileged delivery"
15580 .cindex "delivery" "unprivileged"
15581 If this option is set true, Exim drops its root privilege at the start of a
15582 delivery process, and runs as the Exim user throughout. This severely restricts
15583 the kinds of local delivery that are possible, but is viable in certain types
15584 of configuration. There is a discussion about the use of root privilege in
15585 chapter &<<CHAPsecurity>>&.
15587 .option deliver_queue_load_max main fixed-point unset
15588 .cindex "load average"
15589 .cindex "queue runner" "abandoning"
15590 When this option is set, a queue run is abandoned if the system load average
15591 becomes greater than the value of the option. The option has no effect on
15592 ancient operating systems on which Exim cannot determine the load average.
15593 See also &%queue_only_load%& and &%smtp_load_reserve%&.
15596 .option delivery_date_remove main boolean true
15597 .cindex "&'Delivery-date:'& header line"
15598 Exim's transports have an option for adding a &'Delivery-date:'& header to a
15599 message when it is delivered, in exactly the same way as &'Return-path:'& is
15600 handled. &'Delivery-date:'& records the actual time of delivery. Such headers
15601 should not be present in incoming messages, and this option causes them to be
15602 removed at the time the message is received, to avoid any problems that might
15603 occur when a delivered message is subsequently sent on to some other recipient.
15605 .option disable_fsync main boolean false
15606 .cindex "&[fsync()]&, disabling"
15607 This option is available only if Exim was built with the compile-time option
15608 ENABLE_DISABLE_FSYNC. When this is not set, a reference to &%disable_fsync%& in
15609 a runtime configuration generates an &"unknown option"& error. You should not
15610 build Exim with ENABLE_DISABLE_FSYNC or set &%disable_fsync%& unless you
15611 really, really, really understand what you are doing. &'No pre-compiled
15612 distributions of Exim should ever make this option available.'&
15614 When &%disable_fsync%& is set true, Exim no longer calls &[fsync()]& to force
15615 updated files' data to be written to disc before continuing. Unexpected events
15616 such as crashes and power outages may cause data to be lost or scrambled.
15617 Here be Dragons. &*Beware.*&
15620 .option disable_ipv6 main boolean false
15621 .cindex "IPv6" "disabling"
15622 If this option is set true, even if the Exim binary has IPv6 support, no IPv6
15623 activities take place. AAAA records are never looked up, and any IPv6 addresses
15624 that are listed in &%local_interfaces%&, data for the &%manualroute%& router,
15625 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
15626 to handle IPv6 literal addresses.
15629 .option dkim_verify_hashes main "string list" "sha256 : sha512"
15630 .cindex DKIM "selecting signature algorithms"
15631 This option gives a list of hash types which are acceptable in signatures,
15632 and an order of processing.
15633 Signatures with algorithms not in the list will be ignored.
15635 Acceptable values include:
15642 Note that the acceptance of sha1 violates RFC 8301.
15644 .option dkim_verify_keytypes main "string list" "ed25519 : rsa"
15645 This option gives a list of key types which are acceptable in signatures,
15646 and an order of processing.
15647 Signatures with algorithms not in the list will be ignored.
15650 .option dkim_verify_min_keysizes main "string list" "rsa=1024 ed25519=250"
15651 This option gives a list of key sizes which are acceptable in signatures.
15652 The list is keyed by the algorithm type for the key; the values are in bits.
15653 Signatures with keys smaller than given by this option will fail verification.
15655 The default enforces the RFC 8301 minimum key size for RSA signatures.
15657 .option dkim_verify_minimal main boolean false
15658 If set to true, verification of signatures will terminate after the
15661 .option dkim_verify_signers main "domain list&!!" $dkim_signers
15662 .cindex DKIM "controlling calls to the ACL"
15663 This option gives a list of DKIM domains for which the DKIM ACL is run.
15664 It is expanded after the message is received; by default it runs
15665 the ACL once for each signature in the message.
15666 See section &<<SECDKIMVFY>>&.
15669 .option dmarc_forensic_sender main string&!! unset
15670 .option dmarc_history_file main string unset
15671 .option dmarc_tld_file main string unset
15672 .cindex DMARC "main section options"
15673 These options control DMARC processing.
15674 See section &<<SECDMARC>>& for details.
15677 .option dns_again_means_nonexist main "domain list&!!" unset
15678 .cindex "DNS" "&""try again""& response; overriding"
15679 DNS lookups give a &"try again"& response for the DNS errors
15680 &"non-authoritative host not found"& and &"SERVERFAIL"&. This can cause Exim to
15681 keep trying to deliver a message, or to give repeated temporary errors to
15682 incoming mail. Sometimes the effect is caused by a badly set up name server and
15683 may persist for a long time. If a domain which exhibits this problem matches
15684 anything in &%dns_again_means_nonexist%&, it is treated as if it did not exist.
15685 This option should be used with care. You can make it apply to reverse lookups
15686 by a setting such as this:
15688 dns_again_means_nonexist = *.in-addr.arpa
15690 This option applies to all DNS lookups that Exim does. It also applies when the
15691 &[gethostbyname()]& or &[getipnodebyname()]& functions give temporary errors,
15692 since these are most likely to be caused by DNS lookup problems. The
15693 &(dnslookup)& router has some options of its own for controlling what happens
15694 when lookups for MX or SRV records give temporary errors. These more specific
15695 options are applied after this global option.
15697 .option dns_check_names_pattern main string "see below"
15698 .cindex "DNS" "pre-check of name syntax"
15699 When this option is set to a non-empty string, it causes Exim to check domain
15700 names for characters that are not allowed in host names before handing them to
15701 the DNS resolver, because some resolvers give temporary errors for names that
15702 contain unusual characters. If a domain name contains any unwanted characters,
15703 a &"not found"& result is forced, and the resolver is not called. The check is
15704 done by matching the domain name against a regular expression, which is the
15705 value of this option. The default pattern is
15707 dns_check_names_pattern = \
15708 (?i)^(?>(?(1)\.|())[^\W_](?>[a-z0-9/-]*[^\W_])?)+$
15710 which permits only letters, digits, slashes, and hyphens in components, but
15711 they must start and end with a letter or digit. Slashes are not, in fact,
15712 permitted in host names, but they are found in certain NS records (which can be
15713 accessed in Exim by using a &%dnsdb%& lookup). If you set
15714 &%allow_utf8_domains%&, you must modify this pattern, or set the option to an
15717 .option dns_csa_search_limit main integer 5
15718 This option controls the depth of parental searching for CSA SRV records in the
15719 DNS, as described in more detail in section &<<SECTverifyCSA>>&.
15721 .option dns_csa_use_reverse main boolean true
15722 This option controls whether or not an IP address, given as a CSA domain, is
15723 reversed and looked up in the reverse DNS, as described in more detail in
15724 section &<<SECTverifyCSA>>&.
15726 .option dns_cname_loops main integer 1
15727 .cindex DNS "CNAME following"
15728 This option controls the following of CNAME chains, needed if the resolver does
15729 not do it internally.
15730 As of 2018 most should, and the default can be left.
15731 If you have an ancient one, a value of 10 is likely needed.
15733 The default value of one CNAME-follow is needed
15734 thanks to the observed return for an MX request,
15735 given no MX presence but a CNAME to an A, of the CNAME.
15738 .option dns_dnssec_ok main integer -1
15739 .cindex "DNS" "resolver options"
15740 .cindex "DNS" "DNSSEC"
15741 If this option is set to a non-negative number then Exim will initialise the
15742 DNS resolver library to either use or not use DNSSEC, overriding the system
15743 default. A value of 0 coerces DNSSEC off, a value of 1 coerces DNSSEC on.
15745 If the resolver library does not support DNSSEC then this option has no effect.
15747 On Linux with glibc 2.31 or newer this is insufficient, the resolver library
15748 will default to stripping out a successful validation status.
15749 This will break a previously working Exim installation.
15750 Provided that you do trust the resolver (ie, is on localhost) you can tell
15751 glibc to pass through any successful validation with a new option in
15752 &_/etc/resolv.conf_&:
15758 .option dns_ipv4_lookup main "domain list&!!" unset
15759 .cindex "IPv6" "DNS lookup for AAAA records"
15760 .cindex "DNS" "IPv6 lookup for AAAA records"
15761 .cindex DNS "IPv6 disabling"
15762 When Exim is compiled with IPv6 support and &%disable_ipv6%& is not set, it
15763 looks for IPv6 address records (AAAA records) as well as IPv4 address records
15764 (A records) when trying to find IP addresses for hosts, unless the host's
15765 domain matches this list.
15767 This is a fudge to help with name servers that give big delays or otherwise do
15768 not work for the AAAA record type. In due course, when the world's name
15769 servers have all been upgraded, there should be no need for this option.
15770 Note that all lookups, including those done for verification, are affected;
15771 this will result in verify failure for IPv6 connections or ones using names
15772 only valid for IPv6 addresses.
15775 .option dns_retrans main time 0s
15776 .cindex "DNS" "resolver options"
15777 .cindex timeout "dns lookup"
15778 .cindex "DNS" timeout
15779 The options &%dns_retrans%& and &%dns_retry%& can be used to set the
15780 retransmission and retry parameters for DNS lookups. Values of zero (the
15781 defaults) leave the system default settings unchanged. The first value is the
15782 time between retries, and the second is the number of retries. It isn't
15783 totally clear exactly how these settings affect the total time a DNS lookup may
15784 take. I haven't found any documentation about timeouts on DNS lookups; these
15785 parameter values are available in the external resolver interface structure,
15786 but nowhere does it seem to describe how they are used or what you might want
15788 See also the &%slow_lookup_log%& option.
15791 .option dns_retry main integer 0
15792 See &%dns_retrans%& above.
15795 .option dns_trust_aa main "domain list&!!" unset
15796 .cindex "DNS" "resolver options"
15797 .cindex "DNS" "DNSSEC"
15798 If this option is set then lookup results marked with the AA bit
15799 (Authoritative Answer) are trusted the same way as if they were
15800 DNSSEC-verified. The authority section's name of the answer must
15801 match with this expanded domain list.
15803 Use this option only if you talk directly to a resolver that is
15804 authoritative for some zones and does not set the AD (Authentic Data)
15805 bit in the answer. Some DNS servers may have an configuration option to
15806 mark the answers from their own zones as verified (they set the AD bit).
15807 Others do not have this option. It is considered as poor practice using
15808 a resolver that is an authoritative server for some zones.
15810 Use this option only if you really have to (e.g. if you want
15811 to use DANE for remote delivery to a server that is listed in the DNS
15812 zones that your resolver is authoritative for).
15814 If the DNS answer packet has the AA bit set and contains resource record
15815 in the answer section, the name of the first NS record appearing in the
15816 authority section is compared against the list. If the answer packet is
15817 authoritative but the answer section is empty, the name of the first SOA
15818 record in the authoritative section is used instead.
15820 .cindex "DNS" "resolver options"
15821 .option dns_use_edns0 main integer -1
15822 .cindex "DNS" "resolver options"
15823 .cindex "DNS" "EDNS0"
15824 .cindex "DNS" "OpenBSD
15825 If this option is set to a non-negative number then Exim will initialise the
15826 DNS resolver library to either use or not use EDNS0 extensions, overriding
15827 the system default. A value of 0 coerces EDNS0 off, a value of 1 coerces EDNS0
15830 If the resolver library does not support EDNS0 then this option has no effect.
15832 OpenBSD's asr resolver routines are known to ignore the EDNS0 option; this
15833 means that DNSSEC will not work with Exim on that platform either, unless Exim
15834 is linked against an alternative DNS client library.
15837 .option drop_cr main boolean false
15838 This is an obsolete option that is now a no-op. It used to affect the way Exim
15839 handled CR and LF characters in incoming messages. What happens now is
15840 described in section &<<SECTlineendings>>&.
15842 .option dsn_advertise_hosts main "host list&!!" unset
15843 .cindex "bounce messages" "success"
15844 .cindex "DSN" "success"
15845 .cindex "Delivery Status Notification" "success"
15846 .cindex "ESMTP extensions" DSN
15847 DSN extensions (RFC3461) will be advertised in the EHLO message to,
15848 and accepted from, these hosts.
15849 Hosts may use the NOTIFY and ORCPT options on RCPT TO commands,
15850 and RET and ENVID options on MAIL FROM commands.
15851 A NOTIFY=SUCCESS option requests success-DSN messages.
15852 A NOTIFY= option with no argument requests that no delay or failure DSNs
15854 &*Note*&: Supplying success-DSN messages has been criticised
15855 on privacy grounds; it can leak details of internal forwarding.
15857 .option dsn_from main "string&!!" "see below"
15858 .cindex "&'From:'& header line" "in bounces"
15859 .cindex "bounce messages" "&'From:'& line, specifying"
15860 This option can be used to vary the contents of &'From:'& header lines in
15861 bounces and other automatically generated messages (&"Delivery Status
15862 Notifications"& &-- hence the name of the option). The default setting is:
15864 dsn_from = Mail Delivery System <Mailer-Daemon@$qualify_domain>
15866 The value is expanded every time it is needed. If the expansion fails, a
15867 panic is logged, and the default value is used.
15869 .option envelope_to_remove main boolean true
15870 .cindex "&'Envelope-to:'& header line"
15871 Exim's transports have an option for adding an &'Envelope-to:'& header to a
15872 message when it is delivered, in exactly the same way as &'Return-path:'& is
15873 handled. &'Envelope-to:'& records the original recipient address from the
15874 message's envelope that caused the delivery to happen. Such headers should not
15875 be present in incoming messages, and this option causes them to be removed at
15876 the time the message is received, to avoid any problems that might occur when a
15877 delivered message is subsequently sent on to some other recipient.
15880 .option errors_copy main "string list&!!" unset
15881 .cindex "bounce message" "copy to other address"
15882 .cindex "copy of bounce message"
15883 Setting this option causes Exim to send bcc copies of bounce messages that it
15884 generates to other addresses. &*Note*&: This does not apply to bounce messages
15885 coming from elsewhere. The value of the option is a colon-separated list of
15886 items. Each item consists of a pattern, terminated by white space, followed by
15887 a comma-separated list of email addresses. If a pattern contains spaces, it
15888 must be enclosed in double quotes.
15890 Each pattern is processed in the same way as a single item in an address list
15891 (see section &<<SECTaddresslist>>&). When a pattern matches the recipient of
15892 the bounce message, the message is copied to the addresses on the list. The
15893 items are scanned in order, and once a matching one is found, no further items
15894 are examined. For example:
15896 errors_copy = spqr@mydomain postmaster@mydomain.example :\
15897 rqps@mydomain hostmaster@mydomain.example,\
15898 postmaster@mydomain.example
15900 .vindex "&$domain$&"
15901 .vindex "&$local_part$&"
15902 The address list is expanded before use. The expansion variables &$local_part$&
15903 and &$domain$& are set from the original recipient of the error message, and if
15904 there was any wildcard matching in the pattern, the expansion
15905 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%errors_copy%&"
15906 variables &$0$&, &$1$&, etc. are set in the normal way.
15909 .option errors_reply_to main string unset
15910 .cindex "bounce message" "&'Reply-to:'& in"
15911 By default, Exim's bounce and delivery warning messages contain the header line
15913 &`From: Mail Delivery System <Mailer-Daemon@`&&'qualify-domain'&&`>`&
15915 .oindex &%quota_warn_message%&
15916 where &'qualify-domain'& is the value of the &%qualify_domain%& option.
15917 A warning message that is generated by the &%quota_warn_message%& option in an
15918 &(appendfile)& transport may contain its own &'From:'& header line that
15919 overrides the default.
15921 Experience shows that people reply to bounce messages. If the
15922 &%errors_reply_to%& option is set, a &'Reply-To:'& header is added to bounce
15923 and warning messages. For example:
15925 errors_reply_to = postmaster@my.domain.example
15927 The value of the option is not expanded. It must specify a valid RFC 2822
15928 address. However, if a warning message that is generated by the
15929 &%quota_warn_message%& option in an &(appendfile)& transport contain its
15930 own &'Reply-To:'& header line, the value of the &%errors_reply_to%& option is
15934 .option event_action main string&!! unset
15936 This option declares a string to be expanded for Exim's events mechanism.
15937 For details see chapter &<<CHAPevents>>&.
15940 .option exim_group main string "compile-time configured"
15941 .cindex "gid (group id)" "Exim's own"
15942 .cindex "Exim group"
15943 This option changes the gid under which Exim runs when it gives up root
15944 privilege. The default value is compiled into the binary. The value of this
15945 option is used only when &%exim_user%& is also set. Unless it consists entirely
15946 of digits, the string is looked up using &[getgrnam()]&, and failure causes a
15947 configuration error. See chapter &<<CHAPsecurity>>& for a discussion of
15951 .option exim_path main string "see below"
15952 .cindex "Exim binary, path name"
15953 This option specifies the path name of the Exim binary, which is used when Exim
15954 needs to re-exec itself. The default is set up to point to the file &'exim'& in
15955 the directory configured at compile time by the BIN_DIRECTORY setting. It
15956 is necessary to change &%exim_path%& if, exceptionally, Exim is run from some
15958 &*Warning*&: Do not use a macro to define the value of this option, because
15959 you will break those Exim utilities that scan the configuration file to find
15960 where the binary is. (They then use the &%-bP%& option to extract option
15961 settings such as the value of &%spool_directory%&.)
15964 .option exim_user main string "compile-time configured"
15965 .cindex "uid (user id)" "Exim's own"
15966 .cindex "Exim user"
15967 This option changes the uid under which Exim runs when it gives up root
15968 privilege. The default value is compiled into the binary. Ownership of the run
15969 time configuration file and the use of the &%-C%& and &%-D%& command line
15970 options is checked against the values in the binary, not what is set here.
15972 Unless it consists entirely of digits, the string is looked up using
15973 &[getpwnam()]&, and failure causes a configuration error. If &%exim_group%& is
15974 not also supplied, the gid is taken from the result of &[getpwnam()]& if it is
15975 used. See chapter &<<CHAPsecurity>>& for a discussion of security issues.
15978 .option exim_version main string "current version"
15979 .cindex "Exim version"
15980 .cindex customizing "version number"
15981 .cindex "version number of Exim" override
15982 This option overrides the &$version_number$&/&$exim_version$& that Exim reports in
15983 various places. Use with care; this may fool stupid security scanners.
15986 .option extra_local_interfaces main "string list" unset
15987 This option defines network interfaces that are to be considered local when
15988 routing, but which are not used for listening by the daemon. See section
15989 &<<SECTreclocipadd>>& for details.
15992 . Allow this long option name to split; give it unsplit as a fifth argument
15993 . for the automatic .oindex that is generated by .option.
15995 .option "extract_addresses_remove_arguments" main boolean true &&&
15996 extract_addresses_remove_arguments
15998 .cindex "command line" "addresses with &%-t%&"
15999 .cindex "Sendmail compatibility" "&%-t%& option"
16000 According to some Sendmail documentation (Sun, IRIX, HP-UX), if any addresses
16001 are present on the command line when the &%-t%& option is used to build an
16002 envelope from a message's &'To:'&, &'Cc:'& and &'Bcc:'& headers, the command
16003 line addresses are removed from the recipients list. This is also how Smail
16004 behaves. However, other Sendmail documentation (the O'Reilly book) states that
16005 command line addresses are added to those obtained from the header lines. When
16006 &%extract_addresses_remove_arguments%& is true (the default), Exim subtracts
16007 argument headers. If it is set false, Exim adds rather than removes argument
16011 .option finduser_retries main integer 0
16012 .cindex "NIS, retrying user lookups"
16013 On systems running NIS or other schemes in which user and group information is
16014 distributed from a remote system, there can be times when &[getpwnam()]& and
16015 related functions fail, even when given valid data, because things time out.
16016 Unfortunately these failures cannot be distinguished from genuine &"not found"&
16017 errors. If &%finduser_retries%& is set greater than zero, Exim will try that
16018 many extra times to find a user or a group, waiting for one second between
16021 .cindex "&_/etc/passwd_&" "multiple reading of"
16022 You should not set this option greater than zero if your user information is in
16023 a traditional &_/etc/passwd_& file, because it will cause Exim needlessly to
16024 search the file multiple times for non-existent users, and also cause delay.
16028 .option freeze_tell main "string list, comma separated" unset
16029 .cindex "freezing messages" "sending a message when freezing"
16030 On encountering certain errors, or when configured to do so in a system filter,
16031 ACL, or special router, Exim freezes a message. This means that no further
16032 delivery attempts take place until an administrator thaws the message, or the
16033 &%auto_thaw%&, &%ignore_bounce_errors_after%&, or &%timeout_frozen_after%&
16034 feature cause it to be processed. If &%freeze_tell%& is set, Exim generates a
16035 warning message whenever it freezes something, unless the message it is
16036 freezing is a locally-generated bounce message. (Without this exception there
16037 is the possibility of looping.) The warning message is sent to the addresses
16038 supplied as the comma-separated value of this option. If several of the
16039 message's addresses cause freezing, only a single message is sent. If the
16040 freezing was automatic, the reason(s) for freezing can be found in the message
16041 log. If you configure freezing in a filter or ACL, you must arrange for any
16042 logging that you require.
16045 .option gecos_name main string&!! unset
16047 .cindex "&""gecos""& field, parsing"
16048 Some operating systems, notably HP-UX, use the &"gecos"& field in the system
16049 password file to hold other information in addition to users' real names. Exim
16050 looks up this field for use when it is creating &'Sender:'& or &'From:'&
16051 headers. If either &%gecos_pattern%& or &%gecos_name%& are unset, the contents
16052 of the field are used unchanged, except that, if an ampersand is encountered,
16053 it is replaced by the user's login name with the first character forced to
16054 upper case, since this is a convention that is observed on many systems.
16056 When these options are set, &%gecos_pattern%& is treated as a regular
16057 expression that is to be applied to the field (again with && replaced by the
16058 login name), and if it matches, &%gecos_name%& is expanded and used as the
16061 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%gecos_name%&"
16062 Numeric variables such as &$1$&, &$2$&, etc. can be used in the expansion to
16063 pick up sub-fields that were matched by the pattern. In HP-UX, where the user's
16064 name terminates at the first comma, the following can be used:
16066 gecos_pattern = ([^,]*)
16070 .option gecos_pattern main string unset
16071 See &%gecos_name%& above.
16074 .option gnutls_compat_mode main boolean unset
16075 This option controls whether GnuTLS is used in compatibility mode in an Exim
16076 server. This reduces security slightly, but improves interworking with older
16077 implementations of TLS.
16080 .option gnutls_allow_auto_pkcs11 main boolean unset
16081 This option will let GnuTLS (2.12.0 or later) autoload PKCS11 modules with
16082 the p11-kit configuration files in &_/etc/pkcs11/modules/_&.
16085 &url(https://www.gnutls.org/manual/gnutls.html#Smart-cards-and-HSMs)
16090 .option headers_charset main string "see below"
16091 This option sets a default character set for translating from encoded MIME
16092 &"words"& in header lines, when referenced by an &$h_xxx$& expansion item. The
16093 default is the value of HEADERS_CHARSET in &_Local/Makefile_&. The
16094 ultimate default is ISO-8859-1. For more details see the description of header
16095 insertions in section &<<SECTexpansionitems>>&.
16099 .option header_maxsize main integer "see below"
16100 .cindex "header section" "maximum size of"
16101 .cindex "limit" "size of message header section"
16102 This option controls the overall maximum size of a message's header
16103 section. The default is the value of HEADER_MAXSIZE in
16104 &_Local/Makefile_&; the default for that is 1M. Messages with larger header
16105 sections are rejected.
16108 .option header_line_maxsize main integer 0
16109 .cindex "header lines" "maximum size of"
16110 .cindex "limit" "size of one header line"
16111 This option limits the length of any individual header line in a message, after
16112 all the continuations have been joined together. Messages with individual
16113 header lines that are longer than the limit are rejected. The default value of
16114 zero means &"no limit"&.
16119 .option helo_accept_junk_hosts main "host list&!!" unset
16120 .cindex "HELO" "accepting junk data"
16121 .cindex "EHLO" "accepting junk data"
16122 Exim checks the syntax of HELO and EHLO commands for incoming SMTP
16123 mail, and gives an error response for invalid data. Unfortunately, there are
16124 some SMTP clients that send syntactic junk. They can be accommodated by setting
16125 this option. Note that this is a syntax check only. See &%helo_verify_hosts%&
16126 if you want to do semantic checking.
16127 See also &%helo_allow_chars%& for a way of extending the permitted character
16131 .option helo_allow_chars main string unset
16132 .cindex "HELO" "underscores in"
16133 .cindex "EHLO" "underscores in"
16134 .cindex "underscore in EHLO/HELO"
16135 This option can be set to a string of rogue characters that are permitted in
16136 all EHLO and HELO names in addition to the standard letters, digits,
16137 hyphens, and dots. If you really must allow underscores, you can set
16139 helo_allow_chars = _
16141 Note that the value is one string, not a list.
16144 .option helo_lookup_domains main "domain list&!!" &`@:@[]`&
16145 .cindex "HELO" "forcing reverse lookup"
16146 .cindex "EHLO" "forcing reverse lookup"
16147 If the domain given by a client in a HELO or EHLO command matches this
16148 list, a reverse lookup is done in order to establish the host's true name. The
16149 default forces a lookup if the client host gives the server's name or any of
16150 its IP addresses (in brackets), something that broken clients have been seen to
16154 .option helo_try_verify_hosts main "host list&!!" unset
16155 .cindex "HELO verifying" "optional"
16156 .cindex "EHLO" "verifying, optional"
16157 By default, Exim just checks the syntax of HELO and EHLO commands (see
16158 &%helo_accept_junk_hosts%& and &%helo_allow_chars%&). However, some sites like
16159 to do more extensive checking of the data supplied by these commands. The ACL
16160 condition &`verify = helo`& is provided to make this possible.
16161 Formerly, it was necessary also to set this option (&%helo_try_verify_hosts%&)
16162 to force the check to occur. From release 4.53 onwards, this is no longer
16163 necessary. If the check has not been done before &`verify = helo`& is
16164 encountered, it is done at that time. Consequently, this option is obsolete.
16165 Its specification is retained here for backwards compatibility.
16167 When an EHLO or HELO command is received, if the calling host matches
16168 &%helo_try_verify_hosts%&, Exim checks that the host name given in the HELO or
16169 EHLO command either:
16172 is an IP literal matching the calling address of the host, or
16174 .cindex "DNS" "reverse lookup"
16175 .cindex "reverse DNS lookup"
16176 matches the host name that Exim obtains by doing a reverse lookup of the
16177 calling host address, or
16179 when looked up in DNS yields the calling host address.
16182 However, the EHLO or HELO command is not rejected if any of the checks
16183 fail. Processing continues, but the result of the check is remembered, and can
16184 be detected later in an ACL by the &`verify = helo`& condition.
16186 If DNS was used for successful verification, the variable
16187 .cindex "DNS" "DNSSEC"
16188 &$helo_verify_dnssec$& records the DNSSEC status of the lookups.
16190 .option helo_verify_hosts main "host list&!!" unset
16191 .cindex "HELO verifying" "mandatory"
16192 .cindex "EHLO" "verifying, mandatory"
16193 Like &%helo_try_verify_hosts%&, this option is obsolete, and retained only for
16194 backwards compatibility. For hosts that match this option, Exim checks the host
16195 name given in the HELO or EHLO in the same way as for
16196 &%helo_try_verify_hosts%&. If the check fails, the HELO or EHLO command is
16197 rejected with a 550 error, and entries are written to the main and reject logs.
16198 If a MAIL command is received before EHLO or HELO, it is rejected with a 503
16201 .option hold_domains main "domain list&!!" unset
16202 .cindex "domain" "delaying delivery"
16203 .cindex "delivery" "delaying certain domains"
16204 This option allows mail for particular domains to be held in the queue
16205 manually. The option is overridden if a message delivery is forced with the
16206 &%-M%&, &%-qf%&, &%-Rf%& or &%-Sf%& options, and also while testing or
16207 verifying addresses using &%-bt%& or &%-bv%&. Otherwise, if a domain matches an
16208 item in &%hold_domains%&, no routing or delivery for that address is done, and
16209 it is deferred every time the message is looked at.
16211 This option is intended as a temporary operational measure for delaying the
16212 delivery of mail while some problem is being sorted out, or some new
16213 configuration tested. If you just want to delay the processing of some
16214 domains until a queue run occurs, you should use &%queue_domains%& or
16215 &%queue_smtp_domains%&, not &%hold_domains%&.
16217 A setting of &%hold_domains%& does not override Exim's code for removing
16218 messages from the queue if they have been there longer than the longest retry
16219 time in any retry rule. If you want to hold messages for longer than the normal
16220 retry times, insert a dummy retry rule with a long retry time.
16223 .option host_lookup main "host list&!!" unset
16224 .cindex "host name" "lookup, forcing"
16225 Exim does not look up the name of a calling host from its IP address unless it
16226 is required to compare against some host list, or the host matches
16227 &%helo_try_verify_hosts%& or &%helo_verify_hosts%&, or the host matches this
16228 option (which normally contains IP addresses rather than host names). The
16229 default configuration file contains
16233 which causes a lookup to happen for all hosts. If the expense of these lookups
16234 is felt to be too great, the setting can be changed or removed.
16236 After a successful reverse lookup, Exim does a forward lookup on the name it
16237 has obtained, to verify that it yields the IP address that it started with. If
16238 this check fails, Exim behaves as if the name lookup failed.
16240 .vindex "&$host_lookup_failed$&"
16241 .vindex "&$sender_host_name$&"
16242 After any kind of failure, the host name (in &$sender_host_name$&) remains
16243 unset, and &$host_lookup_failed$& is set to the string &"1"&. See also
16244 &%dns_again_means_nonexist%&, &%helo_lookup_domains%&, and
16245 &`verify = reverse_host_lookup`& in ACLs.
16248 .option host_lookup_order main "string list" &`bydns:byaddr`&
16249 This option specifies the order of different lookup methods when Exim is trying
16250 to find a host name from an IP address. The default is to do a DNS lookup
16251 first, and then to try a local lookup (using &[gethostbyaddr()]& or equivalent)
16252 if that fails. You can change the order of these lookups, or omit one entirely,
16255 &*Warning*&: The &"byaddr"& method does not always yield aliases when there are
16256 multiple PTR records in the DNS and the IP address is not listed in
16257 &_/etc/hosts_&. Different operating systems give different results in this
16258 case. That is why the default tries a DNS lookup first.
16262 .option host_reject_connection main "host list&!!" unset
16263 .cindex "host" "rejecting connections from"
16264 If this option is set, incoming SMTP calls from the hosts listed are rejected
16265 as soon as the connection is made.
16266 This option is obsolete, and retained only for backward compatibility, because
16267 nowadays the ACL specified by &%acl_smtp_connect%& can also reject incoming
16268 connections immediately.
16270 The ability to give an immediate rejection (either by this option or using an
16271 ACL) is provided for use in unusual cases. Many hosts will just try again,
16272 sometimes without much delay. Normally, it is better to use an ACL to reject
16273 incoming messages at a later stage, such as after RCPT commands. See
16274 chapter &<<CHAPACL>>&.
16277 .option hosts_connection_nolog main "host list&!!" unset
16278 .cindex "host" "not logging connections from"
16279 This option defines a list of hosts for which connection logging does not
16280 happen, even though the &%smtp_connection%& log selector is set. For example,
16281 you might want not to log SMTP connections from local processes, or from
16282 127.0.0.1, or from your local LAN. This option is consulted in the main loop of
16283 the daemon; you should therefore strive to restrict its value to a short inline
16284 list of IP addresses and networks. To disable logging SMTP connections from
16285 local processes, you must create a host list with an empty item. For example:
16287 hosts_connection_nolog = :
16290 The hosts affected by this option also do not log "no MAIL in SMTP connection"
16291 lines, as may commonly be produced by a monitoring system.
16295 .option hosts_require_alpn main "host list&!!" unset
16296 .cindex ALPN "require negotiation in server"
16298 .cindex TLS "Application Layer Protocol Names"
16299 If the TLS library supports ALPN
16300 then a successful negotiation of ALPN will be required for any client
16301 matching the list, for TLS to be used.
16302 See also the &%tls_alpn%& option.
16304 &*Note*&: prevention of fallback to in-clear connection is not
16305 managed by this option, and should be done separately.
16308 .option hosts_require_helo main "host list&!!" *
16309 .cindex "HELO/EHLO" requiring
16310 Exim will require an accepted HELO or EHLO command from a host matching
16311 this list, before accepting a MAIL command.
16314 .option hosts_proxy main "host list&!!" unset
16315 .cindex proxy "proxy protocol"
16316 This option enables use of Proxy Protocol proxies for incoming
16317 connections. For details see section &<<SECTproxyInbound>>&.
16320 .option hosts_treat_as_local main "domain list&!!" unset
16321 .cindex "local host" "domains treated as"
16322 .cindex "host" "treated as local"
16323 If this option is set, any host names that match the domain list are treated as
16324 if they were the local host when Exim is scanning host lists obtained from MX
16326 or other sources. Note that the value of this option is a domain list, not a
16327 host list, because it is always used to check host names, not IP addresses.
16329 This option also applies when Exim is matching the special items
16330 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`& in a domain list (see
16331 section &<<SECTdomainlist>>&), and when checking the &%hosts%& option in the
16332 &(smtp)& transport for the local host (see the &%allow_localhost%& option in
16333 that transport). See also &%local_interfaces%&, &%extra_local_interfaces%&, and
16334 chapter &<<CHAPinterfaces>>&, which contains a discussion about local network
16335 interfaces and recognizing the local host.
16338 .option ibase_servers main "string list" unset
16339 .cindex "InterBase" "server list"
16340 This option provides a list of InterBase servers and associated connection data,
16341 to be used in conjunction with &(ibase)& lookups (see section &<<SECID72>>&).
16342 The option is available only if Exim has been built with InterBase support.
16346 .option ignore_bounce_errors_after main time 10w
16347 .cindex "bounce message" "discarding"
16348 .cindex "discarding bounce message"
16349 This option affects the processing of bounce messages that cannot be delivered,
16350 that is, those that suffer a permanent delivery failure. (Bounce messages that
16351 suffer temporary delivery failures are of course retried in the usual way.)
16353 After a permanent delivery failure, bounce messages are frozen,
16354 because there is no sender to whom they can be returned. When a frozen bounce
16355 message has been in the queue for more than the given time, it is unfrozen at
16356 the next queue run, and a further delivery is attempted. If delivery fails
16357 again, the bounce message is discarded. This makes it possible to keep failed
16358 bounce messages around for a shorter time than the normal maximum retry time
16359 for frozen messages. For example,
16361 ignore_bounce_errors_after = 12h
16363 retries failed bounce message deliveries after 12 hours, discarding any further
16364 failures. If the value of this option is set to a zero time period, bounce
16365 failures are discarded immediately. Setting a very long time (as in the default
16366 value) has the effect of disabling this option. For ways of automatically
16367 dealing with other kinds of frozen message, see &%auto_thaw%& and
16368 &%timeout_frozen_after%&.
16371 .option ignore_fromline_hosts main "host list&!!" unset
16372 .cindex "&""From""& line"
16373 .cindex "UUCP" "&""From""& line"
16374 Some broken SMTP clients insist on sending a UUCP-like &"From&~"& line before
16375 the headers of a message. By default this is treated as the start of the
16376 message's body, which means that any following headers are not recognized as
16377 such. Exim can be made to ignore it by setting &%ignore_fromline_hosts%& to
16378 match those hosts that insist on sending it. If the sender is actually a local
16379 process rather than a remote host, and is using &%-bs%& to inject the messages,
16380 &%ignore_fromline_local%& must be set to achieve this effect.
16383 .option ignore_fromline_local main boolean false
16384 See &%ignore_fromline_hosts%& above.
16386 .option keep_environment main "string list" unset
16387 .cindex "environment" "values from"
16388 This option contains a string list of environment variables to keep.
16389 You have to trust these variables or you have to be sure that
16390 these variables do not impose any security risk. Keep in mind that
16391 during the startup phase Exim is running with an effective UID 0 in most
16392 installations. As the default value is an empty list, the default
16393 environment for using libraries, running embedded Perl code, or running
16394 external binaries is empty, and does not not even contain PATH or HOME.
16396 Actually the list is interpreted as a list of patterns
16397 (&<<SECTlistexpand>>&), except that it is not expanded first.
16399 WARNING: Macro substitution is still done first, so having a macro
16400 FOO and having FOO_HOME in your &%keep_environment%& option may have
16401 unexpected results. You may work around this using a regular expression
16402 that does not match the macro name: ^[F]OO_HOME$.
16404 Current versions of Exim issue a warning during startup if you do not mention
16405 &%keep_environment%& in your runtime configuration file and if your
16406 current environment is not empty. Future versions may not issue that warning
16409 See the &%add_environment%& main config option for a way to set
16410 environment variables to a fixed value. The environment for &(pipe)&
16411 transports is handled separately, see section &<<SECTpipeenv>>& for
16415 .option keep_malformed main time 4d
16416 This option specifies the length of time to keep messages whose spool files
16417 have been corrupted in some way. This should, of course, never happen. At the
16418 next attempt to deliver such a message, it gets removed. The incident is
16422 .option ldap_ca_cert_dir main string unset
16423 .cindex "LDAP", "TLS CA certificate directory"
16424 .cindex certificate "directory for LDAP"
16425 This option indicates which directory contains CA certificates for verifying
16426 a TLS certificate presented by an LDAP server.
16427 While Exim does not provide a default value, your SSL library may.
16428 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
16429 and constrained to be a directory.
16432 .option ldap_ca_cert_file main string unset
16433 .cindex "LDAP", "TLS CA certificate file"
16434 .cindex certificate "file for LDAP"
16435 This option indicates which file contains CA certificates for verifying
16436 a TLS certificate presented by an LDAP server.
16437 While Exim does not provide a default value, your SSL library may.
16438 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
16439 and constrained to be a file.
16442 .option ldap_cert_file main string unset
16443 .cindex "LDAP" "TLS client certificate file"
16444 .cindex certificate "file for LDAP"
16445 This option indicates which file contains an TLS client certificate which
16446 Exim should present to the LDAP server during TLS negotiation.
16447 Should be used together with &%ldap_cert_key%&.
16450 .option ldap_cert_key main string unset
16451 .cindex "LDAP" "TLS client key file"
16452 .cindex certificate "key for LDAP"
16453 This option indicates which file contains the secret/private key to use
16454 to prove identity to the LDAP server during TLS negotiation.
16455 Should be used together with &%ldap_cert_file%&, which contains the
16456 identity to be proven.
16459 .option ldap_cipher_suite main string unset
16460 .cindex "LDAP" "TLS cipher suite"
16461 This controls the TLS cipher-suite negotiation during TLS negotiation with
16462 the LDAP server. See &<<SECTreqciphssl>>& for more details of the format of
16463 cipher-suite options with OpenSSL (as used by LDAP client libraries).
16466 .option ldap_default_servers main "string list" unset
16467 .cindex "LDAP" "default servers"
16468 This option provides a list of LDAP servers which are tried in turn when an
16469 LDAP query does not contain a server. See section &<<SECTforldaque>>& for
16470 details of LDAP queries. This option is available only when Exim has been built
16474 .option ldap_require_cert main string unset.
16475 .cindex "LDAP" "policy for LDAP server TLS cert presentation"
16476 This should be one of the values "hard", "demand", "allow", "try" or "never".
16477 A value other than one of these is interpreted as "never".
16478 See the entry "TLS_REQCERT" in your system man page for ldap.conf(5).
16479 Although Exim does not set a default, the LDAP library probably defaults
16483 .option ldap_start_tls main boolean false
16484 .cindex "LDAP" "whether or not to negotiate TLS"
16485 If set, Exim will attempt to negotiate TLS with the LDAP server when
16486 connecting on a regular LDAP port. This is the LDAP equivalent of SMTP's
16487 "STARTTLS". This is distinct from using "ldaps", which is the LDAP form
16489 In the event of failure to negotiate TLS, the action taken is controlled
16490 by &%ldap_require_cert%&.
16491 This option is ignored for &`ldapi`& connections.
16494 .option ldap_version main integer unset
16495 .cindex "LDAP" "protocol version, forcing"
16496 This option can be used to force Exim to set a specific protocol version for
16497 LDAP. If it option is unset, it is shown by the &%-bP%& command line option as
16498 -1. When this is the case, the default is 3 if LDAP_VERSION3 is defined in
16499 the LDAP headers; otherwise it is 2. This option is available only when Exim
16500 has been built with LDAP support.
16504 .option local_from_check main boolean true
16505 .cindex "&'Sender:'& header line" "disabling addition of"
16506 .cindex "&'From:'& header line" "disabling checking of"
16507 When a message is submitted locally (that is, not over a TCP/IP connection) by
16508 an untrusted user, Exim removes any existing &'Sender:'& header line, and
16509 checks that the &'From:'& header line matches the login of the calling user and
16510 the domain specified by &%qualify_domain%&.
16512 &*Note*&: An unqualified address (no domain) in the &'From:'& header in a
16513 locally submitted message is automatically qualified by Exim, unless the
16514 &%-bnq%& command line option is used.
16516 You can use &%local_from_prefix%& and &%local_from_suffix%& to permit affixes
16517 on the local part. If the &'From:'& header line does not match, Exim adds a
16518 &'Sender:'& header with an address constructed from the calling user's login
16519 and the default qualify domain.
16521 If &%local_from_check%& is set false, the &'From:'& header check is disabled,
16522 and no &'Sender:'& header is ever added. If, in addition, you want to retain
16523 &'Sender:'& header lines supplied by untrusted users, you must also set
16524 &%local_sender_retain%& to be true.
16526 .cindex "envelope from"
16527 .cindex "envelope sender"
16528 These options affect only the header lines in the message. The envelope sender
16529 is still forced to be the login id at the qualify domain unless
16530 &%untrusted_set_sender%& permits the user to supply an envelope sender.
16532 For messages received over TCP/IP, an ACL can specify &"submission mode"& to
16533 request similar header line checking. See section &<<SECTthesenhea>>&, which
16534 has more details about &'Sender:'& processing.
16539 .option local_from_prefix main string unset
16540 When Exim checks the &'From:'& header line of locally submitted messages for
16541 matching the login id (see &%local_from_check%& above), it can be configured to
16542 ignore certain prefixes and suffixes in the local part of the address. This is
16543 done by setting &%local_from_prefix%& and/or &%local_from_suffix%& to
16544 appropriate lists, in the same form as the &%local_part_prefix%& and
16545 &%local_part_suffix%& router options (see chapter &<<CHAProutergeneric>>&). For
16548 local_from_prefix = *-
16550 is set, a &'From:'& line containing
16552 From: anything-user@your.domain.example
16554 will not cause a &'Sender:'& header to be added if &'user@your.domain.example'&
16555 matches the actual sender address that is constructed from the login name and
16559 .option local_from_suffix main string unset
16560 See &%local_from_prefix%& above.
16563 .option local_interfaces main "string list" "see below"
16564 This option controls which network interfaces are used by the daemon for
16565 listening; they are also used to identify the local host when routing. Chapter
16566 &<<CHAPinterfaces>>& contains a full description of this option and the related
16567 options &%daemon_smtp_ports%&, &%extra_local_interfaces%&,
16568 &%hosts_treat_as_local%&, and &%tls_on_connect_ports%&. The default value for
16569 &%local_interfaces%& is
16571 local_interfaces = 0.0.0.0
16573 when Exim is built without IPv6 support; otherwise it is
16575 local_interfaces = <; ::0 ; 0.0.0.0
16578 .option local_scan_timeout main time 5m
16579 .cindex "timeout" "for &[local_scan()]& function"
16580 .cindex "&[local_scan()]& function" "timeout"
16581 This timeout applies to the &[local_scan()]& function (see chapter
16582 &<<CHAPlocalscan>>&). Zero means &"no timeout"&. If the timeout is exceeded,
16583 the incoming message is rejected with a temporary error if it is an SMTP
16584 message. For a non-SMTP message, the message is dropped and Exim ends with a
16585 non-zero code. The incident is logged on the main and reject logs.
16589 .option local_sender_retain main boolean false
16590 .cindex "&'Sender:'& header line" "retaining from local submission"
16591 When a message is submitted locally (that is, not over a TCP/IP connection) by
16592 an untrusted user, Exim removes any existing &'Sender:'& header line. If you
16593 do not want this to happen, you must set &%local_sender_retain%&, and you must
16594 also set &%local_from_check%& to be false (Exim will complain if you do not).
16595 See also the ACL modifier &`control = suppress_local_fixups`&. Section
16596 &<<SECTthesenhea>>& has more details about &'Sender:'& processing.
16601 .option localhost_number main string&!! unset
16602 .cindex "host" "locally unique number for"
16603 .cindex "message ids" "with multiple hosts"
16604 .vindex "&$localhost_number$&"
16605 Exim's message ids are normally unique only within the local host. If
16606 uniqueness among a set of hosts is required, each host must set a different
16607 value for the &%localhost_number%& option. The string is expanded immediately
16608 after reading the configuration file (so that a number can be computed from the
16609 host name, for example) and the result of the expansion must be a number in the
16610 range 0&--16 (or 0&--10 on operating systems with case-insensitive file
16611 systems). This is available in subsequent string expansions via the variable
16612 &$localhost_number$&. When &%localhost_number is set%&, the final two
16613 characters of the message id, instead of just being a fractional part of the
16614 time, are computed from the time and the local host number as described in
16615 section &<<SECTmessiden>>&.
16619 .option log_file_path main "string list&!!" "set at compile time"
16620 .cindex "log" "file path for"
16621 This option sets the path which is used to determine the names of Exim's log
16622 files, or indicates that logging is to be to syslog, or both. It is expanded
16623 when Exim is entered, so it can, for example, contain a reference to the host
16624 name. If no specific path is set for the log files at compile or runtime,
16625 or if the option is unset at runtime (i.e. &`log_file_path = `&)
16626 they are written in a sub-directory called &_log_& in Exim's spool directory.
16627 A path must start with a slash.
16628 To send to syslog, use the word &"syslog"&.
16629 Chapter &<<CHAPlog>>& contains further details about Exim's logging, and
16630 section &<<SECTwhelogwri>>& describes how the contents of &%log_file_path%& are
16631 used. If this string is fixed at your installation (contains no expansion
16632 variables) it is recommended that you do not set this option in the
16633 configuration file, but instead supply the path using LOG_FILE_PATH in
16634 &_Local/Makefile_& so that it is available to Exim for logging errors detected
16635 early on &-- in particular, failure to read the configuration file.
16638 .option log_selector main string unset
16639 .cindex "log" "selectors"
16640 This option can be used to reduce or increase the number of things that Exim
16641 writes to its log files. Its argument is made up of names preceded by plus or
16642 minus characters. For example:
16644 log_selector = +arguments -retry_defer
16646 A list of possible names and what they control is given in the chapter on
16647 logging, in section &<<SECTlogselector>>&.
16650 .option log_timezone main boolean false
16651 .cindex "log" "timezone for entries"
16652 .vindex "&$tod_log$&"
16653 .vindex "&$tod_zone$&"
16654 By default, the timestamps on log lines are in local time without the
16655 timezone. This means that if your timezone changes twice a year, the timestamps
16656 in log lines are ambiguous for an hour when the clocks go back. One way of
16657 avoiding this problem is to set the timezone to UTC. An alternative is to set
16658 &%log_timezone%& true. This turns on the addition of the timezone offset to
16659 timestamps in log lines. Turning on this option can add quite a lot to the size
16660 of log files because each line is extended by 6 characters. Note that the
16661 &$tod_log$& variable contains the log timestamp without the zone, but there is
16662 another variable called &$tod_zone$& that contains just the timezone offset.
16665 .option lookup_open_max main integer 25
16666 .cindex "too many open files"
16667 .cindex "open files, too many"
16668 .cindex "file" "too many open"
16669 .cindex "lookup" "maximum open files"
16670 .cindex "limit" "open files for lookups"
16671 This option limits the number of simultaneously open files for single-key
16672 lookups that use regular files (that is, &(lsearch)&, &(dbm)&, and &(cdb)&).
16673 Exim normally keeps these files open during routing, because often the same
16674 file is required several times. If the limit is reached, Exim closes the least
16675 recently used file. Note that if you are using the &'ndbm'& library, it
16676 actually opens two files for each logical DBM database, though it still counts
16677 as one for the purposes of &%lookup_open_max%&. If you are getting &"too many
16678 open files"& errors with NDBM, you need to reduce the value of
16679 &%lookup_open_max%&.
16682 .option max_username_length main integer 0
16683 .cindex "length of login name"
16684 .cindex "user name" "maximum length"
16685 .cindex "limit" "user name length"
16686 Some operating systems are broken in that they truncate long arguments to
16687 &[getpwnam()]& to eight characters, instead of returning &"no such user"&. If
16688 this option is set greater than zero, any attempt to call &[getpwnam()]& with
16689 an argument that is longer behaves as if &[getpwnam()]& failed.
16692 .option message_body_newlines main bool false
16693 .cindex "message body" "newlines in variables"
16694 .cindex "newline" "in message body variables"
16695 .vindex "&$message_body$&"
16696 .vindex "&$message_body_end$&"
16697 By default, newlines in the message body are replaced by spaces when setting
16698 the &$message_body$& and &$message_body_end$& expansion variables. If this
16699 option is set true, this no longer happens.
16702 .option message_body_visible main integer 500
16703 .cindex "body of message" "visible size"
16704 .cindex "message body" "visible size"
16705 .vindex "&$message_body$&"
16706 .vindex "&$message_body_end$&"
16707 This option specifies how much of a message's body is to be included in the
16708 &$message_body$& and &$message_body_end$& expansion variables.
16711 .option message_id_header_domain main string&!! unset
16712 .cindex "&'Message-ID:'& header line"
16713 If this option is set, the string is expanded and used as the right hand side
16714 (domain) of the &'Message-ID:'& header that Exim creates if a
16715 locally-originated incoming message does not have one. &"Locally-originated"&
16716 means &"not received over TCP/IP."&
16717 Otherwise, the primary host name is used.
16718 Only letters, digits, dot and hyphen are accepted; any other characters are
16719 replaced by hyphens. If the expansion is forced to fail, or if the result is an
16720 empty string, the option is ignored.
16723 .option message_id_header_text main string&!! unset
16724 If this variable is set, the string is expanded and used to augment the text of
16725 the &'Message-id:'& header that Exim creates if a locally-originated incoming
16726 message does not have one. The text of this header is required by RFC 2822 to
16727 take the form of an address. By default, Exim uses its internal message id as
16728 the local part, and the primary host name as the domain. If this option is set,
16729 it is expanded, and provided the expansion is not forced to fail, and does not
16730 yield an empty string, the result is inserted into the header immediately
16731 before the @, separated from the internal message id by a dot. Any characters
16732 that are illegal in an address are automatically converted into hyphens. This
16733 means that variables such as &$tod_log$& can be used, because the spaces and
16734 colons will become hyphens.
16737 .option message_logs main boolean true
16738 .cindex "message logs" "disabling"
16739 .cindex "log" "message log; disabling"
16740 If this option is turned off, per-message log files are not created in the
16741 &_msglog_& spool sub-directory. This reduces the amount of disk I/O required by
16742 Exim, by reducing the number of files involved in handling a message from a
16743 minimum of four (header spool file, body spool file, delivery journal, and
16744 per-message log) to three. The other major I/O activity is Exim's main log,
16745 which is not affected by this option.
16748 .option message_size_limit main string&!! 50M
16749 .cindex "message" "size limit"
16750 .cindex "limit" "message size"
16751 .cindex "size" "of message, limit"
16752 This option limits the maximum size of message that Exim will process. The
16753 value is expanded for each incoming connection so, for example, it can be made
16754 to depend on the IP address of the remote host for messages arriving via
16755 TCP/IP. After expansion, the value must be a sequence of decimal digits,
16756 optionally followed by K or M.
16758 .cindex "SIZE" "ESMTP extension, advertising"
16759 .cindex "ESMTP extensions" SIZE
16760 If nonzero the value will be advertised as a parameter to the ESMTP SIZE
16761 service extension keyword.
16763 &*Note*&: This limit cannot be made to depend on a message's sender or any
16764 other properties of an individual message, because it has to be advertised in
16765 the server's response to EHLO. String expansion failure causes a temporary
16766 error. A value of zero means no limit, but its use is not recommended. See also
16767 &%bounce_return_size_limit%&.
16769 Incoming SMTP messages are failed with a 552 error if the limit is
16770 exceeded; locally-generated messages either get a stderr message or a delivery
16771 failure message to the sender, depending on the &%-oe%& setting. Rejection of
16772 an oversized message is logged in both the main and the reject logs. See also
16773 the generic transport option &%message_size_limit%&, which limits the size of
16774 message that an individual transport can process.
16776 If you use a virus-scanner and set this option to to a value larger than the
16777 maximum size that your virus-scanner is configured to support, you may get
16778 failures triggered by large mails. The right size to configure for the
16779 virus-scanner depends upon what data is passed and the options in use but it's
16780 probably safest to just set it to a little larger than this value. E.g., with a
16781 default Exim message size of 50M and a default ClamAV StreamMaxLength of 10M,
16782 some problems may result.
16784 A value of 0 will disable size limit checking; Exim will still advertise the
16785 SIZE extension in an EHLO response, but without a limit, so as to permit
16786 SMTP clients to still indicate the message size along with the MAIL verb.
16789 .option move_frozen_messages main boolean false
16790 .cindex "frozen messages" "moving"
16791 This option, which is available only if Exim has been built with the setting
16793 SUPPORT_MOVE_FROZEN_MESSAGES=yes
16795 in &_Local/Makefile_&, causes frozen messages and their message logs to be
16796 moved from the &_input_& and &_msglog_& directories on the spool to &_Finput_&
16797 and &_Fmsglog_&, respectively. There is currently no support in Exim or the
16798 standard utilities for handling such moved messages, and they do not show up in
16799 lists generated by &%-bp%& or by the Exim monitor.
16802 .option mua_wrapper main boolean false
16803 Setting this option true causes Exim to run in a very restrictive mode in which
16804 it passes messages synchronously to a smart host. Chapter &<<CHAPnonqueueing>>&
16805 contains a full description of this facility.
16809 .option mysql_servers main "string list" unset
16810 .cindex "MySQL" "server list"
16811 This option provides a list of MySQL servers and associated connection data, to
16812 be used in conjunction with &(mysql)& lookups (see section &<<SECID72>>&). The
16813 option is available only if Exim has been built with MySQL support.
16816 .option never_users main "string list&!!" unset
16817 This option is expanded just once, at the start of Exim's processing. Local
16818 message deliveries are normally run in processes that are setuid to the
16819 recipient, and remote deliveries are normally run under Exim's own uid and gid.
16820 It is usually desirable to prevent any deliveries from running as root, as a
16823 When Exim is built, an option called FIXED_NEVER_USERS can be set to a
16824 list of users that must not be used for local deliveries. This list is fixed in
16825 the binary and cannot be overridden by the configuration file. By default, it
16826 contains just the single user name &"root"&. The &%never_users%& runtime option
16827 can be used to add more users to the fixed list.
16829 If a message is to be delivered as one of the users on the fixed list or the
16830 &%never_users%& list, an error occurs, and delivery is deferred. A common
16833 never_users = root:daemon:bin
16835 Including root is redundant if it is also on the fixed list, but it does no
16836 harm. This option overrides the &%pipe_as_creator%& option of the &(pipe)&
16840 .option notifier_socket main string "$spool_directory/exim_daemon_notify"
16841 This option gives the name for a unix-domain socket on which the daemon
16842 listens for work and information-requests.
16843 Only installations running multiple daemons sharing a spool directory
16844 should need to modify the default.
16846 The option is expanded before use.
16847 If the platform supports Linux-style abstract socket names, the result
16848 is used with a nul byte prefixed.
16850 it should be a full path name and use a directory accessible
16853 If this option is set as empty,
16854 or the command line &%-oY%& option is used, or
16855 the command line uses a &%-oX%& option and does not use &%-oP%&,
16856 then a notifier socket is not created.
16859 .option openssl_options main "string list" "+no_sslv2 +no_sslv3 +single_dh_use +no_ticket +no_renegotiation"
16860 .cindex "OpenSSL "compatibility options"
16861 This option allows an administrator to adjust the SSL options applied
16862 by OpenSSL to connections. It is given as a space-separated list of items,
16863 each one to be +added or -subtracted from the current value.
16865 This option is only available if Exim is built against OpenSSL. The values
16866 available for this option vary according to the age of your OpenSSL install.
16867 The &"all"& value controls a subset of flags which are available, typically
16868 the bug workaround options. The &'SSL_CTX_set_options'& man page will
16869 list the values known on your system and Exim should support all the
16870 &"bug workaround"& options and many of the &"modifying"& options. The Exim
16871 names lose the leading &"SSL_OP_"& and are lower-cased.
16873 Note that adjusting the options can have severe impact upon the security of
16874 SSL as used by Exim. It is possible to disable safety checks and shoot
16875 yourself in the foot in various unpleasant ways. This option should not be
16876 adjusted lightly. An unrecognised item will be detected at startup, by
16877 invoking Exim with the &%-bV%& flag.
16879 The option affects Exim operating both as a server and as a client.
16881 Historical note: prior to release 4.80, Exim defaulted this value to
16882 "+dont_insert_empty_fragments", which may still be needed for compatibility
16883 with some clients, but which lowers security by increasing exposure to
16884 some now infamous attacks.
16888 # Make both old MS and old Eudora happy:
16889 openssl_options = -all +microsoft_big_sslv3_buffer \
16890 +dont_insert_empty_fragments
16892 # Disable older protocol versions:
16893 openssl_options = +no_sslv2 +no_sslv3
16896 Possible options may include:
16900 &`allow_unsafe_legacy_renegotiation`&
16902 &`cipher_server_preference`&
16904 &`dont_insert_empty_fragments`&
16908 &`legacy_server_connect`&
16910 &`microsoft_big_sslv3_buffer`&
16912 &`microsoft_sess_id_bug`&
16914 &`msie_sslv2_rsa_padding`&
16916 &`netscape_challenge_bug`&
16918 &`netscape_reuse_cipher_change_bug`&
16922 &`no_session_resumption_on_renegotiation`&
16936 &`safari_ecdhe_ecdsa_bug`&
16940 &`single_ecdh_use`&
16942 &`ssleay_080_client_dh_bug`&
16944 &`sslref2_reuse_cert_type_bug`&
16946 &`tls_block_padding_bug`&
16950 &`tls_rollback_bug`&
16953 As an aside, the &`safari_ecdhe_ecdsa_bug`& item is a misnomer and affects
16954 all clients connecting using the MacOS SecureTransport TLS facility prior
16955 to MacOS 10.8.4, including email clients. If you see old MacOS clients failing
16956 to negotiate TLS then this option value might help, provided that your OpenSSL
16957 release is new enough to contain this work-around. This may be a situation
16958 where you have to upgrade OpenSSL to get buggy clients working.
16961 .option oracle_servers main "string list" unset
16962 .cindex "Oracle" "server list"
16963 This option provides a list of Oracle servers and associated connection data,
16964 to be used in conjunction with &(oracle)& lookups (see section &<<SECID72>>&).
16965 The option is available only if Exim has been built with Oracle support.
16969 .option panic_coredump main boolean false
16970 This option is rarely needed but can help for some debugging investigations.
16971 If set, when an internal error is detected by Exim which is sufficient
16972 to terminate the process
16973 (all such are logged in the paniclog)
16974 then a coredump is requested.
16976 Note that most systems require additional administrative configuration
16977 to permit write a core file for a setuid program, which is Exim's
16978 common installed configuration.
16981 .option percent_hack_domains main "domain list&!!" unset
16982 .cindex "&""percent hack""&"
16983 .cindex "source routing" "in email address"
16984 .cindex "address" "source-routed"
16985 The &"percent hack"& is the convention whereby a local part containing a
16986 percent sign is re-interpreted as a new email address, with the percent
16987 replaced by @. This is sometimes called &"source routing"&, though that term is
16988 also applied to RFC 2822 addresses that begin with an @ character. If this
16989 option is set, Exim implements the percent facility for those domains listed,
16990 but no others. This happens before an incoming SMTP address is tested against
16993 &*Warning*&: The &"percent hack"& has often been abused by people who are
16994 trying to get round relaying restrictions. For this reason, it is best avoided
16995 if at all possible. Unfortunately, a number of less security-conscious MTAs
16996 implement it unconditionally. If you are running Exim on a gateway host, and
16997 routing mail through to internal MTAs without processing the local parts, it is
16998 a good idea to reject recipient addresses with percent characters in their
16999 local parts. Exim's default configuration does this.
17002 .option perl_at_start main boolean false
17004 This option is available only when Exim is built with an embedded Perl
17005 interpreter. See chapter &<<CHAPperl>>& for details of its use.
17008 .option perl_startup main string unset
17010 This option is available only when Exim is built with an embedded Perl
17011 interpreter. See chapter &<<CHAPperl>>& for details of its use.
17013 .option perl_taintmode main boolean false
17015 This option enables the taint mode of the embedded Perl interpreter.
17018 .option pgsql_servers main "string list" unset
17019 .cindex "PostgreSQL lookup type" "server list"
17020 This option provides a list of PostgreSQL servers and associated connection
17021 data, to be used in conjunction with &(pgsql)& lookups (see section
17022 &<<SECID72>>&). The option is available only if Exim has been built with
17023 PostgreSQL support.
17026 .option pid_file_path main string&!! "set at compile time"
17027 .cindex "daemon" "pid file path"
17028 .cindex "pid file, path for"
17029 This option sets the name of the file to which the Exim daemon writes its
17030 process id. The string is expanded, so it can contain, for example, references
17033 pid_file_path = /var/log/$primary_hostname/exim.pid
17035 If no path is set, the pid is written to the file &_exim-daemon.pid_& in Exim's
17037 The value set by the option can be overridden by the &%-oP%& command line
17038 option. A pid file is not written if a &"non-standard"& daemon is run by means
17039 of the &%-oX%& option, unless a path is explicitly supplied by &%-oP%&.
17042 .option pipelining_advertise_hosts main "host list&!!" *
17043 .cindex "PIPELINING" "suppressing advertising"
17044 .cindex "ESMTP extensions" PIPELINING
17045 This option can be used to suppress the advertisement of the SMTP
17046 PIPELINING extension to specific hosts. See also the &*no_pipelining*&
17047 control in section &<<SECTcontrols>>&. When PIPELINING is not advertised and
17048 &%smtp_enforce_sync%& is true, an Exim server enforces strict synchronization
17049 for each SMTP command and response. When PIPELINING is advertised, Exim assumes
17050 that clients will use it; &"out of order"& commands that are &"expected"& do
17051 not count as protocol errors (see &%smtp_max_synprot_errors%&).
17053 .option pipelining_connect_advertise_hosts main "host list&!!" *
17054 .cindex "pipelining" "early connection"
17055 .cindex "pipelining" PIPECONNECT
17056 .cindex "ESMTP extensions" PIPECONNECT
17057 If Exim is built without the DISABLE_PIPE_CONNECT build option
17058 this option controls which hosts the facility is advertised to
17059 and from which pipeline early-connection (before MAIL) SMTP
17060 commands are acceptable.
17061 When used, the pipelining saves on roundtrip times.
17063 See also the &%hosts_pipe_connect%& smtp transport option.
17065 The SMTP service extension keyword advertised is &"PIPECONNECT"&;
17066 it permits the client to pipeline
17067 TCP connection and hello command (inclear phase),
17068 or TLS-establishment and hello command (encrypted phase),
17069 on later connections to the same host.
17072 .option prdr_enable main boolean false
17073 .cindex "PRDR" "enabling on server"
17074 .cindex "ESMTP extensions" PRDR
17075 This option can be used to enable the Per-Recipient Data Response extension
17076 to SMTP, defined by Eric Hall.
17077 If the option is set, PRDR is advertised by Exim when operating as a server.
17078 If the client requests PRDR, and more than one recipient, for a message
17079 an additional ACL is called for each recipient after the message content
17080 is received. See section &<<SECTPRDRACL>>&.
17082 .option preserve_message_logs main boolean false
17083 .cindex "message logs" "preserving"
17084 If this option is set, message log files are not deleted when messages are
17085 completed. Instead, they are moved to a sub-directory of the spool directory
17086 called &_msglog.OLD_&, where they remain available for statistical or debugging
17087 purposes. This is a dangerous option to set on systems with any appreciable
17088 volume of mail. Use with care!
17091 .option primary_hostname main string "see below"
17092 .cindex "name" "of local host"
17093 .cindex "host" "name of local"
17094 .cindex "local host" "name of"
17095 .vindex "&$primary_hostname$&"
17096 This specifies the name of the current host. It is used in the default EHLO or
17097 HELO command for outgoing SMTP messages (changeable via the &%helo_data%&
17098 option in the &(smtp)& transport), and as the default for &%qualify_domain%&.
17099 The value is also used by default in some SMTP response messages from an Exim
17100 server. This can be changed dynamically by setting &%smtp_active_hostname%&.
17102 If &%primary_hostname%& is not set, Exim calls &[uname()]& to find the host
17103 name. If this fails, Exim panics and dies. If the name returned by &[uname()]&
17104 contains only one component, Exim passes it to &[gethostbyname()]& (or
17105 &[getipnodebyname()]& when available) in order to obtain the fully qualified
17106 version. The variable &$primary_hostname$& contains the host name, whether set
17107 explicitly by this option, or defaulted.
17110 .option print_topbitchars main boolean false
17111 .cindex "printing characters"
17112 .cindex "8-bit characters"
17113 By default, Exim considers only those characters whose codes lie in the range
17114 32&--126 to be printing characters. In a number of circumstances (for example,
17115 when writing log entries) non-printing characters are converted into escape
17116 sequences, primarily to avoid messing up the layout. If &%print_topbitchars%&
17117 is set, code values of 128 and above are also considered to be printing
17120 This option also affects the header syntax checks performed by the
17121 &(autoreply)& transport, and whether Exim uses RFC 2047 encoding of
17122 the user's full name when constructing From: and Sender: addresses (as
17123 described in section &<<SECTconstr>>&). Setting this option can cause
17124 Exim to generate eight bit message headers that do not conform to the
17128 .option process_log_path main string unset
17129 .cindex "process log path"
17130 .cindex "log" "process log"
17131 .cindex "&'exiwhat'&"
17132 This option sets the name of the file to which an Exim process writes its
17133 &"process log"& when sent a USR1 signal. This is used by the &'exiwhat'&
17134 utility script. If this option is unset, the file called &_exim-process.info_&
17135 in Exim's spool directory is used. The ability to specify the name explicitly
17136 can be useful in environments where two different Exims are running, using
17137 different spool directories.
17140 .option prod_requires_admin main boolean true
17141 .cindex "restricting access to features"
17145 The &%-M%&, &%-R%&, and &%-q%& command-line options require the caller to be an
17146 admin user unless &%prod_requires_admin%& is set false. See also
17147 &%queue_list_requires_admin%& and &%commandline_checks_require_admin%&.
17150 .option proxy_protocol_timeout main time 3s
17151 .cindex proxy "proxy protocol"
17152 This option sets the timeout for proxy protocol negotiation.
17153 For details see section &<<SECTproxyInbound>>&.
17156 .option qualify_domain main string "see below"
17157 .cindex "domain" "for qualifying addresses"
17158 .cindex "address" "qualification"
17159 This option specifies the domain name that is added to any envelope sender
17160 addresses that do not have a domain qualification. It also applies to
17161 recipient addresses if &%qualify_recipient%& is not set. Unqualified addresses
17162 are accepted by default only for locally-generated messages. Qualification is
17163 also applied to addresses in header lines such as &'From:'& and &'To:'& for
17164 locally-generated messages, unless the &%-bnq%& command line option is used.
17166 Messages from external sources must always contain fully qualified addresses,
17167 unless the sending host matches &%sender_unqualified_hosts%& or
17168 &%recipient_unqualified_hosts%& (as appropriate), in which case incoming
17169 addresses are qualified with &%qualify_domain%& or &%qualify_recipient%& as
17170 necessary. Internally, Exim always works with fully qualified envelope
17171 addresses. If &%qualify_domain%& is not set, it defaults to the
17172 &%primary_hostname%& value.
17175 .option qualify_recipient main string "see below"
17176 This option allows you to specify a different domain for qualifying recipient
17177 addresses to the one that is used for senders. See &%qualify_domain%& above.
17181 .option queue_domains main "domain list&!!" unset
17182 .cindex "domain" "specifying non-immediate delivery"
17183 .cindex "queueing incoming messages"
17184 .cindex "message" "queueing certain domains"
17185 This option lists domains for which immediate delivery is not required.
17186 A delivery process is started whenever a message is received, but only those
17187 domains that do not match are processed. All other deliveries wait until the
17188 next queue run. See also &%hold_domains%& and &%queue_smtp_domains%&.
17191 .option queue_fast_ramp main boolean true
17192 .cindex "queue runner" "two phase"
17193 .cindex "queue" "double scanning"
17194 If set to true, two-phase queue runs, initiated using &%-qq%& on the
17195 command line, may start parallel delivery processes during their first
17196 phase. This will be done when a threshold number of messages have been
17197 routed for a single host.
17200 .option queue_list_requires_admin main boolean true
17201 .cindex "restricting access to features"
17203 The &%-bp%& command-line option, which lists the messages that are on the
17204 queue, requires the caller to be an admin user unless
17205 &%queue_list_requires_admin%& is set false.
17206 See also &%prod_requires_admin%& and &%commandline_checks_require_admin%&.
17209 .option queue_only main boolean false
17210 .cindex "queueing incoming messages"
17211 .cindex "message" "queueing unconditionally"
17212 If &%queue_only%& is set, a delivery process is not automatically started
17213 whenever a message is received. Instead, the message waits in the queue for the
17214 next queue run. Even if &%queue_only%& is false, incoming messages may not get
17215 delivered immediately when certain conditions (such as heavy load) occur.
17217 The &%-odq%& command line has the same effect as &%queue_only%&. The &%-odb%&
17218 and &%-odi%& command line options override &%queue_only%& unless
17219 &%queue_only_override%& is set false. See also &%queue_only_file%&,
17220 &%queue_only_load%&, and &%smtp_accept_queue%&.
17223 .option queue_only_file main string unset
17224 .cindex "queueing incoming messages"
17225 .cindex "message" "queueing by file existence"
17226 This option can be set to a colon-separated list of absolute path names, each
17227 one optionally preceded by &"smtp"&. When Exim is receiving a message,
17228 it tests for the existence of each listed path using a call to &[stat()]&. For
17229 each path that exists, the corresponding queueing option is set.
17230 For paths with no prefix, &%queue_only%& is set; for paths prefixed by
17231 &"smtp"&, &%queue_smtp_domains%& is set to match all domains. So, for example,
17233 queue_only_file = smtp/some/file
17235 causes Exim to behave as if &%queue_smtp_domains%& were set to &"*"& whenever
17236 &_/some/file_& exists.
17239 .option queue_only_load main fixed-point unset
17240 .cindex "load average"
17241 .cindex "queueing incoming messages"
17242 .cindex "message" "queueing by load"
17243 If the system load average is higher than this value, incoming messages from
17244 all sources are queued, and no automatic deliveries are started. If this
17245 happens during local or remote SMTP input, all subsequent messages received on
17246 the same SMTP connection are queued by default, whatever happens to the load in
17247 the meantime, but this can be changed by setting &%queue_only_load_latch%&
17250 Deliveries will subsequently be performed by queue runner processes. This
17251 option has no effect on ancient operating systems on which Exim cannot
17252 determine the load average. See also &%deliver_queue_load_max%& and
17253 &%smtp_load_reserve%&.
17256 .option queue_only_load_latch main boolean true
17257 .cindex "load average" "re-evaluating per message"
17258 When this option is true (the default), once one message has been queued
17259 because the load average is higher than the value set by &%queue_only_load%&,
17260 all subsequent messages received on the same SMTP connection are also queued.
17261 This is a deliberate choice; even though the load average may fall below the
17262 threshold, it doesn't seem right to deliver later messages on the same
17263 connection when not delivering earlier ones. However, there are special
17264 circumstances such as very long-lived connections from scanning appliances
17265 where this is not the best strategy. In such cases, &%queue_only_load_latch%&
17266 should be set false. This causes the value of the load average to be
17267 re-evaluated for each message.
17270 .option queue_only_override main boolean true
17271 .cindex "queueing incoming messages"
17272 When this option is true, the &%-od%&&'x'& command line options override the
17273 setting of &%queue_only%& or &%queue_only_file%& in the configuration file. If
17274 &%queue_only_override%& is set false, the &%-od%&&'x'& options cannot be used
17275 to override; they are accepted, but ignored.
17278 .option queue_run_in_order main boolean false
17279 .cindex "queue runner" "processing messages in order"
17280 If this option is set, queue runs happen in order of message arrival instead of
17281 in an arbitrary order. For this to happen, a complete list of the entire queue
17282 must be set up before the deliveries start. When the queue is all held in a
17283 single directory (the default), a single list is created for both the ordered
17284 and the non-ordered cases. However, if &%split_spool_directory%& is set, a
17285 single list is not created when &%queue_run_in_order%& is false. In this case,
17286 the sub-directories are processed one at a time (in a random order), and this
17287 avoids setting up one huge list for the whole queue. Thus, setting
17288 &%queue_run_in_order%& with &%split_spool_directory%& may degrade performance
17289 when the queue is large, because of the extra work in setting up the single,
17290 large list. In most situations, &%queue_run_in_order%& should not be set.
17294 .option queue_run_max main integer&!! 5
17295 .cindex "queue runner" "maximum number of"
17296 This controls the maximum number of queue runner processes that an Exim daemon
17297 can run simultaneously. This does not mean that it starts them all at once,
17298 but rather that if the maximum number are still running when the time comes to
17299 start another one, it refrains from starting another one. This can happen with
17300 very large queues and/or very sluggish deliveries. This option does not,
17301 however, interlock with other processes, so additional queue runners can be
17302 started by other means, or by killing and restarting the daemon.
17304 Setting this option to zero does not suppress queue runs; rather, it disables
17305 the limit, allowing any number of simultaneous queue runner processes to be
17306 run. If you do not want queue runs to occur, omit the &%-q%&&'xx'& setting on
17307 the daemon's command line.
17309 .cindex queues named
17310 .cindex "named queues" "resource limit"
17311 To set limits for different named queues use
17312 an expansion depending on the &$queue_name$& variable.
17314 .option queue_smtp_domains main "domain list&!!" unset
17315 .cindex "queueing incoming messages"
17316 .cindex "message" "queueing remote deliveries"
17317 .cindex "first pass routing"
17318 When this option is set, a delivery process is started whenever a message is
17319 received, routing is performed, and local deliveries take place.
17320 However, if any SMTP deliveries are required for domains that match
17321 &%queue_smtp_domains%&, they are not immediately delivered, but instead the
17322 message waits in the queue for the next queue run. Since routing of the message
17323 has taken place, Exim knows to which remote hosts it must be delivered, and so
17324 when the queue run happens, multiple messages for the same host are delivered
17325 over a single SMTP connection. The &%-odqs%& command line option causes all
17326 SMTP deliveries to be queued in this way, and is equivalent to setting
17327 &%queue_smtp_domains%& to &"*"&. See also &%hold_domains%& and
17331 .option receive_timeout main time 0s
17332 .cindex "timeout" "for non-SMTP input"
17333 This option sets the timeout for accepting a non-SMTP message, that is, the
17334 maximum time that Exim waits when reading a message on the standard input. If
17335 the value is zero, it will wait forever. This setting is overridden by the
17336 &%-or%& command line option. The timeout for incoming SMTP messages is
17337 controlled by &%smtp_receive_timeout%&.
17339 .option received_header_text main string&!! "see below"
17340 .cindex "customizing" "&'Received:'& header"
17341 .cindex "&'Received:'& header line" "customizing"
17342 This string defines the contents of the &'Received:'& message header that is
17343 added to each message, except for the timestamp, which is automatically added
17344 on at the end (preceded by a semicolon). The string is expanded each time it is
17345 used. If the expansion yields an empty string, no &'Received:'& header line is
17346 added to the message. Otherwise, the string should start with the text
17347 &"Received:"& and conform to the RFC 2822 specification for &'Received:'&
17349 The default setting is:
17352 received_header_text = Received: \
17353 ${if def:sender_rcvhost {from $sender_rcvhost\n\t}\
17354 {${if def:sender_ident \
17355 {from ${quote_local_part:$sender_ident} }}\
17356 ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\
17357 by $primary_hostname \
17358 ${if def:received_protocol {with $received_protocol }}\
17359 ${if def:tls_in_ver { ($tls_in_ver)}}\
17360 ${if def:tls_in_cipher_std { tls $tls_in_cipher_std\n\t}}\
17361 (Exim $version_number)\n\t\
17362 ${if def:sender_address \
17363 {(envelope-from <$sender_address>)\n\t}}\
17364 id $message_exim_id\
17365 ${if def:received_for {\n\tfor $received_for}}
17368 The references to the TLS version and cipher are
17369 omitted when Exim is built without TLS
17370 support. The use of conditional expansions ensures that this works for both
17371 locally generated messages and messages received from remote hosts, giving
17372 header lines such as the following:
17374 Received: from scrooge.carol.example ([192.168.12.25] ident=root)
17375 by marley.carol.example with esmtp (Exim 4.00)
17376 (envelope-from <bob@carol.example>)
17377 id 16IOWa-00019l-00
17378 for chas@dickens.example; Tue, 25 Dec 2001 14:43:44 +0000
17379 Received: by scrooge.carol.example with local (Exim 4.00)
17380 id 16IOWW-000083-00; Tue, 25 Dec 2001 14:43:41 +0000
17382 Until the body of the message has been received, the timestamp is the time when
17383 the message started to be received. Once the body has arrived, and all policy
17384 checks have taken place, the timestamp is updated to the time at which the
17385 message was accepted.
17388 .option received_headers_max main integer 30
17389 .cindex "loop" "prevention"
17390 .cindex "mail loop prevention"
17391 .cindex "&'Received:'& header line" "counting"
17392 When a message is to be delivered, the number of &'Received:'& headers is
17393 counted, and if it is greater than this parameter, a mail loop is assumed to
17394 have occurred, the delivery is abandoned, and an error message is generated.
17395 This applies to both local and remote deliveries.
17398 .option recipient_unqualified_hosts main "host list&!!" unset
17399 .cindex "unqualified addresses"
17400 .cindex "host" "unqualified addresses from"
17401 This option lists those hosts from which Exim is prepared to accept unqualified
17402 recipient addresses in message envelopes. The addresses are made fully
17403 qualified by the addition of the &%qualify_recipient%& value. This option also
17404 affects message header lines. Exim does not reject unqualified recipient
17405 addresses in headers, but it qualifies them only if the message came from a
17406 host that matches &%recipient_unqualified_hosts%&,
17407 or if the message was submitted locally (not using TCP/IP), and the &%-bnq%&
17408 option was not set.
17411 .option recipients_max main integer 50000
17412 .cindex "limit" "number of recipients"
17413 .cindex "recipient" "maximum number"
17414 If this option is set greater than zero, it specifies the maximum number of
17415 original recipients for any message. Additional recipients that are generated
17416 by aliasing or forwarding do not count. SMTP messages get a 452 response for
17417 all recipients over the limit; earlier recipients are delivered as normal.
17418 Non-SMTP messages with too many recipients are failed, and no deliveries are
17421 .cindex "RCPT" "maximum number of incoming"
17422 &*Note*&: The RFCs specify that an SMTP server should accept at least 100
17423 RCPT commands in a single message.
17426 .option recipients_max_reject main boolean false
17427 If this option is set true, Exim rejects SMTP messages containing too many
17428 recipients by giving 552 errors to the surplus RCPT commands, and a 554
17429 error to the eventual DATA command. Otherwise (the default) it gives a 452
17430 error to the surplus RCPT commands and accepts the message on behalf of the
17431 initial set of recipients. The remote server should then re-send the message
17432 for the remaining recipients at a later time.
17435 .option remote_max_parallel main integer 4
17436 .cindex "delivery" "parallelism for remote"
17437 This option controls parallel delivery of one message to a number of remote
17438 hosts. If the value is less than 2, parallel delivery is disabled, and Exim
17439 does all the remote deliveries for a message one by one. Otherwise, if a single
17440 message has to be delivered to more than one remote host, or if several copies
17441 have to be sent to the same remote host, up to &%remote_max_parallel%&
17442 deliveries are done simultaneously. If more than &%remote_max_parallel%&
17443 deliveries are required, the maximum number of processes are started, and as
17444 each one finishes, another is begun. The order of starting processes is the
17445 same as if sequential delivery were being done, and can be controlled by the
17446 &%remote_sort_domains%& option. If parallel delivery takes place while running
17447 with debugging turned on, the debugging output from each delivery process is
17448 tagged with its process id.
17450 This option controls only the maximum number of parallel deliveries for one
17451 message in one Exim delivery process. Because Exim has no central queue
17452 manager, there is no way of controlling the total number of simultaneous
17453 deliveries if the configuration allows a delivery attempt as soon as a message
17456 See also the &%max_parallel%& generic transport option,
17457 and the &%serialize_hosts%& smtp transport option.
17459 .cindex "number of deliveries"
17460 .cindex "delivery" "maximum number of"
17461 If you want to control the total number of deliveries on the system, you
17462 need to set the &%queue_only%& option. This ensures that all incoming messages
17463 are added to the queue without starting a delivery process. Then set up an Exim
17464 daemon to start queue runner processes at appropriate intervals (probably
17465 fairly often, for example, every minute), and limit the total number of queue
17466 runners by setting the &%queue_run_max%& parameter. Because each queue runner
17467 delivers only one message at a time, the maximum number of deliveries that can
17468 then take place at once is &%queue_run_max%& multiplied by
17469 &%remote_max_parallel%&.
17471 If it is purely remote deliveries you want to control, use
17472 &%queue_smtp_domains%& instead of &%queue_only%&. This has the added benefit of
17473 doing the SMTP routing before queueing, so that several messages for the same
17474 host will eventually get delivered down the same connection.
17477 .option remote_sort_domains main "domain list&!!" unset
17478 .cindex "sorting remote deliveries"
17479 .cindex "delivery" "sorting remote"
17480 When there are a number of remote deliveries for a message, they are sorted by
17481 domain into the order given by this list. For example,
17483 remote_sort_domains = *.cam.ac.uk:*.uk
17485 would attempt to deliver to all addresses in the &'cam.ac.uk'& domain first,
17486 then to those in the &%uk%& domain, then to any others.
17489 .option retry_data_expire main time 7d
17490 .cindex "hints database" "data expiry"
17491 This option sets a &"use before"& time on retry information in Exim's hints
17492 database. Any older retry data is ignored. This means that, for example, once a
17493 host has not been tried for 7 days, Exim behaves as if it has no knowledge of
17497 .option retry_interval_max main time 24h
17498 .cindex "retry" "limit on interval"
17499 .cindex "limit" "on retry interval"
17500 Chapter &<<CHAPretry>>& describes Exim's mechanisms for controlling the
17501 intervals between delivery attempts for messages that cannot be delivered
17502 straight away. This option sets an overall limit to the length of time between
17503 retries. It cannot be set greater than 24 hours; any attempt to do so forces
17507 .option return_path_remove main boolean true
17508 .cindex "&'Return-path:'& header line" "removing"
17509 RFC 2821, section 4.4, states that an SMTP server must insert a
17510 &'Return-path:'& header line into a message when it makes a &"final delivery"&.
17511 The &'Return-path:'& header preserves the sender address as received in the
17512 MAIL command. This description implies that this header should not be present
17513 in an incoming message. If &%return_path_remove%& is true, any existing
17514 &'Return-path:'& headers are removed from messages at the time they are
17515 received. Exim's transports have options for adding &'Return-path:'& headers at
17516 the time of delivery. They are normally used only for final local deliveries.
17519 .option return_size_limit main integer 100K
17520 This option is an obsolete synonym for &%bounce_return_size_limit%&.
17523 .option rfc1413_hosts main "host list&!!" @[]
17525 .cindex "host" "for RFC 1413 calls"
17526 RFC 1413 identification calls are made to any client host which matches
17527 an item in the list.
17528 The default value specifies just this host, being any local interface
17531 .option rfc1413_query_timeout main time 0s
17532 .cindex "RFC 1413" "query timeout"
17533 .cindex "timeout" "for RFC 1413 call"
17534 This sets the timeout on RFC 1413 identification calls. If it is set to zero,
17535 no RFC 1413 calls are ever made.
17538 .option sender_unqualified_hosts main "host list&!!" unset
17539 .cindex "unqualified addresses"
17540 .cindex "host" "unqualified addresses from"
17541 This option lists those hosts from which Exim is prepared to accept unqualified
17542 sender addresses. The addresses are made fully qualified by the addition of
17543 &%qualify_domain%&. This option also affects message header lines. Exim does
17544 not reject unqualified addresses in headers that contain sender addresses, but
17545 it qualifies them only if the message came from a host that matches
17546 &%sender_unqualified_hosts%&, or if the message was submitted locally (not
17547 using TCP/IP), and the &%-bnq%& option was not set.
17550 .option slow_lookup_log main integer 0
17551 .cindex "logging" "slow lookups"
17552 .cindex "dns" "logging slow lookups"
17553 This option controls logging of slow lookups.
17554 If the value is nonzero it is taken as a number of milliseconds
17555 and lookups taking longer than this are logged.
17556 Currently this applies only to DNS lookups.
17560 .option smtp_accept_keepalive main boolean true
17561 .cindex "keepalive" "on incoming connection"
17562 This option controls the setting of the SO_KEEPALIVE option on incoming
17563 TCP/IP socket connections. When set, it causes the kernel to probe idle
17564 connections periodically, by sending packets with &"old"& sequence numbers. The
17565 other end of the connection should send an acknowledgment if the connection is
17566 still okay or a reset if the connection has been aborted. The reason for doing
17567 this is that it has the beneficial effect of freeing up certain types of
17568 connection that can get stuck when the remote host is disconnected without
17569 tidying up the TCP/IP call properly. The keepalive mechanism takes several
17570 hours to detect unreachable hosts.
17574 .option smtp_accept_max main integer 20
17575 .cindex "limit" "incoming SMTP connections"
17576 .cindex "SMTP" "incoming connection count"
17578 This option specifies the maximum number of simultaneous incoming SMTP calls
17579 that Exim will accept. It applies only to the listening daemon; there is no
17580 control (in Exim) when incoming SMTP is being handled by &'inetd'&. If the
17581 value is set to zero, no limit is applied. However, it is required to be
17582 non-zero if either &%smtp_accept_max_per_host%& or &%smtp_accept_queue%& is
17583 set. See also &%smtp_accept_reserve%& and &%smtp_load_reserve%&.
17585 A new SMTP connection is immediately rejected if the &%smtp_accept_max%& limit
17586 has been reached. If not, Exim first checks &%smtp_accept_max_per_host%&. If
17587 that limit has not been reached for the client host, &%smtp_accept_reserve%&
17588 and &%smtp_load_reserve%& are then checked before accepting the connection.
17591 .option smtp_accept_max_nonmail main integer 10
17592 .cindex "limit" "non-mail SMTP commands"
17593 .cindex "SMTP" "limiting non-mail commands"
17594 Exim counts the number of &"non-mail"& commands in an SMTP session, and drops
17595 the connection if there are too many. This option defines &"too many"&. The
17596 check catches some denial-of-service attacks, repeated failing AUTHs, or a mad
17597 client looping sending EHLO, for example. The check is applied only if the
17598 client host matches &%smtp_accept_max_nonmail_hosts%&.
17600 When a new message is expected, one occurrence of RSET is not counted. This
17601 allows a client to send one RSET between messages (this is not necessary,
17602 but some clients do it). Exim also allows one uncounted occurrence of HELO
17603 or EHLO, and one occurrence of STARTTLS between messages. After
17604 starting up a TLS session, another EHLO is expected, and so it too is not
17605 counted. The first occurrence of AUTH in a connection, or immediately
17606 following STARTTLS is not counted. Otherwise, all commands other than
17607 MAIL, RCPT, DATA, and QUIT are counted.
17610 .option smtp_accept_max_nonmail_hosts main "host list&!!" *
17611 You can control which hosts are subject to the &%smtp_accept_max_nonmail%&
17612 check by setting this option. The default value makes it apply to all hosts. By
17613 changing the value, you can exclude any badly-behaved hosts that you have to
17617 . Allow this long option name to split; give it unsplit as a fifth argument
17618 . for the automatic .oindex that is generated by .option.
17619 . We insert " &~&~" which is both pretty nasty visually and results in
17620 . non-searchable text. HowItWorks.txt mentions an option for inserting
17621 . zero-width-space, which would be nicer visually and results in (at least)
17622 . html that Firefox will split on when it's forced to reflow (rather than
17623 . inserting a horizontal scrollbar). However, the text is still not
17624 . searchable. NM changed this occurrence for bug 1197 to no longer allow
17625 . the option name to split.
17627 .option "smtp_accept_max_per_connection" main integer&!! 1000 &&&
17628 smtp_accept_max_per_connection
17629 .cindex "SMTP" "limiting incoming message count"
17630 .cindex "limit" "messages per SMTP connection"
17631 The value of this option limits the number of MAIL commands that Exim is
17632 prepared to accept over a single SMTP connection, whether or not each command
17633 results in the transfer of a message. After the limit is reached, a 421
17634 response is given to subsequent MAIL commands. This limit is a safety
17635 precaution against a client that goes mad (incidents of this type have been
17637 The option is expanded after the HELO or EHLO is received
17638 and may depend on values available at that time.
17639 An empty or zero value after expansion removes the limit.
17642 .option smtp_accept_max_per_host main string&!! unset
17643 .cindex "limit" "SMTP connections from one host"
17644 .cindex "host" "limiting SMTP connections from"
17645 This option restricts the number of simultaneous IP connections from a single
17646 host (strictly, from a single IP address) to the Exim daemon. The option is
17647 expanded, to enable different limits to be applied to different hosts by
17648 reference to &$sender_host_address$&. Once the limit is reached, additional
17649 connection attempts from the same host are rejected with error code 421. This
17650 is entirely independent of &%smtp_accept_reserve%&. The option's default value
17651 of zero imposes no limit. If this option is set greater than zero, it is
17652 required that &%smtp_accept_max%& be non-zero.
17654 &*Warning*&: When setting this option you should not use any expansion
17655 constructions that take an appreciable amount of time. The expansion and test
17656 happen in the main daemon loop, in order to reject additional connections
17657 without forking additional processes (otherwise a denial-of-service attack
17658 could cause a vast number or processes to be created). While the daemon is
17659 doing this processing, it cannot accept any other incoming connections.
17663 .option smtp_accept_queue main integer 0
17664 .cindex "SMTP" "incoming connection count"
17665 .cindex "queueing incoming messages"
17666 .cindex "message" "queueing by SMTP connection count"
17667 If the number of simultaneous incoming SMTP connections being handled via the
17668 listening daemon exceeds this value, messages received by SMTP are just placed
17669 in the queue; no delivery processes are started automatically. The count is
17670 fixed at the start of an SMTP connection. It cannot be updated in the
17671 subprocess that receives messages, and so the queueing or not queueing applies
17672 to all messages received in the same connection.
17674 A value of zero implies no limit, and clearly any non-zero value is useful only
17675 if it is less than the &%smtp_accept_max%& value (unless that is zero). See
17676 also &%queue_only%&, &%queue_only_load%&, &%queue_smtp_domains%&, and the
17677 various &%-od%&&'x'& command line options.
17680 . See the comment on smtp_accept_max_per_connection
17682 .option "smtp_accept_queue_per_connection" main integer 10 &&&
17683 smtp_accept_queue_per_connection
17684 .cindex "queueing incoming messages"
17685 .cindex "message" "queueing by message count"
17686 This option limits the number of delivery processes that Exim starts
17687 automatically when receiving messages via SMTP, whether via the daemon or by
17688 the use of &%-bs%& or &%-bS%&. If the value of the option is greater than zero,
17689 and the number of messages received in a single SMTP session exceeds this
17690 number, subsequent messages are placed in the queue, but no delivery processes
17691 are started. This helps to limit the number of Exim processes when a server
17692 restarts after downtime and there is a lot of mail waiting for it on other
17693 systems. On large systems, the default should probably be increased, and on
17694 dial-in client systems it should probably be set to zero (that is, disabled).
17697 .option smtp_accept_reserve main integer 0
17698 .cindex "SMTP" "incoming call count"
17699 .cindex "host" "reserved"
17700 When &%smtp_accept_max%& is set greater than zero, this option specifies a
17701 number of SMTP connections that are reserved for connections from the hosts
17702 that are specified in &%smtp_reserve_hosts%&. The value set in
17703 &%smtp_accept_max%& includes this reserve pool. The specified hosts are not
17704 restricted to this number of connections; the option specifies a minimum number
17705 of connection slots for them, not a maximum. It is a guarantee that this group
17706 of hosts can always get at least &%smtp_accept_reserve%& connections. However,
17707 the limit specified by &%smtp_accept_max_per_host%& is still applied to each
17710 For example, if &%smtp_accept_max%& is set to 50 and &%smtp_accept_reserve%& is
17711 set to 5, once there are 45 active connections (from any hosts), new
17712 connections are accepted only from hosts listed in &%smtp_reserve_hosts%&,
17713 provided the other criteria for acceptance are met.
17716 .option smtp_active_hostname main string&!! unset
17717 .cindex "host" "name in SMTP responses"
17718 .cindex "SMTP" "host name in responses"
17719 .vindex "&$primary_hostname$&"
17720 This option is provided for multi-homed servers that want to masquerade as
17721 several different hosts. At the start of an incoming SMTP connection, its value
17722 is expanded and used instead of the value of &$primary_hostname$& in SMTP
17723 responses. For example, it is used as domain name in the response to an
17724 incoming HELO or EHLO command.
17726 .vindex "&$smtp_active_hostname$&"
17727 The active hostname is placed in the &$smtp_active_hostname$& variable, which
17728 is saved with any messages that are received. It is therefore available for use
17729 in routers and transports when the message is later delivered.
17731 If this option is unset, or if its expansion is forced to fail, or if the
17732 expansion results in an empty string, the value of &$primary_hostname$& is
17733 used. Other expansion failures cause a message to be written to the main and
17734 panic logs, and the SMTP command receives a temporary error. Typically, the
17735 value of &%smtp_active_hostname%& depends on the incoming interface address.
17738 smtp_active_hostname = ${if eq{$received_ip_address}{10.0.0.1}\
17739 {cox.mydomain}{box.mydomain}}
17742 Although &$smtp_active_hostname$& is primarily concerned with incoming
17743 messages, it is also used as the default for HELO commands in callout
17744 verification if there is no remote transport from which to obtain a
17745 &%helo_data%& value.
17747 .option smtp_backlog_monitor main integer 0
17748 .cindex "connection backlog" monitoring
17749 If this option is set to greater than zero, and the backlog of available
17750 TCP connections on a socket listening for SMTP is larger than it, a line
17751 is logged giving the value and the socket address and port.
17752 The value is retrived jsut before an accept call.
17753 This facility is only available on Linux.
17755 .option smtp_banner main string&!! "see below"
17756 .cindex "SMTP" "welcome banner"
17757 .cindex "banner for SMTP"
17758 .cindex "welcome banner for SMTP"
17759 .cindex "customizing" "SMTP banner"
17760 This string, which is expanded every time it is used, is output as the initial
17761 positive response to an SMTP connection. The default setting is:
17763 smtp_banner = $smtp_active_hostname ESMTP Exim \
17764 $version_number $tod_full
17766 Failure to expand the string causes a panic error. If you want to create a
17767 multiline response to the initial SMTP connection, use &"\n"& in the string at
17768 appropriate points, but not at the end. Note that the 220 code is not included
17769 in this string. Exim adds it automatically (several times in the case of a
17770 multiline response).
17773 .option smtp_check_spool_space main boolean true
17774 .cindex "checking disk space"
17775 .cindex "disk space, checking"
17776 .cindex "spool directory" "checking space"
17777 When this option is set, if an incoming SMTP session encounters the SIZE
17778 option on a MAIL command, it checks that there is enough space in the
17779 spool directory's partition to accept a message of that size, while still
17780 leaving free the amount specified by &%check_spool_space%& (even if that value
17781 is zero). If there isn't enough space, a temporary error code is returned.
17784 .option smtp_connect_backlog main integer 20
17785 .cindex "connection backlog" "set maximum"
17786 .cindex "SMTP" "connection backlog"
17787 .cindex "backlog of connections"
17788 This option specifies a maximum number of waiting SMTP connections. Exim passes
17789 this value to the TCP/IP system when it sets up its listener. Once this number
17790 of connections are waiting for the daemon's attention, subsequent connection
17791 attempts are refused at the TCP/IP level. At least, that is what the manuals
17792 say; in some circumstances such connection attempts have been observed to time
17793 out instead. For large systems it is probably a good idea to increase the
17794 value (to 50, say). It also gives some protection against denial-of-service
17795 attacks by SYN flooding.
17798 .option smtp_enforce_sync main boolean true
17799 .cindex "SMTP" "synchronization checking"
17800 .cindex "synchronization checking in SMTP"
17801 The SMTP protocol specification requires the client to wait for a response from
17802 the server at certain points in the dialogue. Without PIPELINING these
17803 synchronization points are after every command; with PIPELINING they are
17804 fewer, but they still exist.
17806 Some spamming sites send out a complete set of SMTP commands without waiting
17807 for any response. Exim protects against this by rejecting a message if the
17808 client has sent further input when it should not have. The error response &"554
17809 SMTP synchronization error"& is sent, and the connection is dropped. Testing
17810 for this error cannot be perfect because of transmission delays (unexpected
17811 input may be on its way but not yet received when Exim checks). However, it
17812 does detect many instances.
17814 The check can be globally disabled by setting &%smtp_enforce_sync%& false.
17815 If you want to disable the check selectively (for example, only for certain
17816 hosts), you can do so by an appropriate use of a &%control%& modifier in an ACL
17817 (see section &<<SECTcontrols>>&). See also &%pipelining_advertise_hosts%&.
17821 .option smtp_etrn_command main string&!! unset
17822 .cindex "ETRN" "command to be run"
17823 .cindex "ESMTP extensions" ETRN
17824 .vindex "&$domain$&"
17825 If this option is set, the given command is run whenever an SMTP ETRN
17826 command is received from a host that is permitted to issue such commands (see
17827 chapter &<<CHAPACL>>&). The string is split up into separate arguments which
17828 are independently expanded. The expansion variable &$domain$& is set to the
17829 argument of the ETRN command, and no syntax checking is done on it. For
17832 smtp_etrn_command = /etc/etrn_command $domain \
17833 $sender_host_address
17835 If the option is not set, the argument for the ETRN command must
17836 be a &'#'& followed by an address string.
17837 In this case an &'exim -R <string>'& command is used;
17838 if the ETRN ACL has set up a named-queue then &'-MCG <queue>'& is appended.
17840 A new process is created to run the command, but Exim does not wait for it to
17841 complete. Consequently, its status cannot be checked. If the command cannot be
17842 run, a line is written to the panic log, but the ETRN caller still receives
17843 a 250 success response. Exim is normally running under its own uid when
17844 receiving SMTP, so it is not possible for it to change the uid before running
17848 .option smtp_etrn_serialize main boolean true
17849 .cindex "ETRN" "serializing"
17850 When this option is set, it prevents the simultaneous execution of more than
17851 one identical command as a result of ETRN in an SMTP connection. See
17852 section &<<SECTETRN>>& for details.
17855 .option smtp_load_reserve main fixed-point unset
17856 .cindex "load average"
17857 If the system load average ever gets higher than this, incoming SMTP calls are
17858 accepted only from those hosts that match an entry in &%smtp_reserve_hosts%&.
17859 If &%smtp_reserve_hosts%& is not set, no incoming SMTP calls are accepted when
17860 the load is over the limit. The option has no effect on ancient operating
17861 systems on which Exim cannot determine the load average. See also
17862 &%deliver_queue_load_max%& and &%queue_only_load%&.
17866 .option smtp_max_synprot_errors main integer 3
17867 .cindex "SMTP" "limiting syntax and protocol errors"
17868 .cindex "limit" "SMTP syntax and protocol errors"
17869 Exim rejects SMTP commands that contain syntax or protocol errors. In
17870 particular, a syntactically invalid email address, as in this command:
17872 RCPT TO:<abc xyz@a.b.c>
17874 causes immediate rejection of the command, before any other tests are done.
17875 (The ACL cannot be run if there is no valid address to set up for it.) An
17876 example of a protocol error is receiving RCPT before MAIL. If there are
17877 too many syntax or protocol errors in one SMTP session, the connection is
17878 dropped. The limit is set by this option.
17880 .cindex "PIPELINING" "expected errors"
17881 When the PIPELINING extension to SMTP is in use, some protocol errors are
17882 &"expected"&, for instance, a RCPT command after a rejected MAIL command.
17883 Exim assumes that PIPELINING will be used if it advertises it (see
17884 &%pipelining_advertise_hosts%&), and in this situation, &"expected"& errors do
17885 not count towards the limit.
17889 .option smtp_max_unknown_commands main integer 3
17890 .cindex "SMTP" "limiting unknown commands"
17891 .cindex "limit" "unknown SMTP commands"
17892 If there are too many unrecognized commands in an incoming SMTP session, an
17893 Exim server drops the connection. This is a defence against some kinds of abuse
17896 into making connections to SMTP ports; in these circumstances, a number of
17897 non-SMTP command lines are sent first.
17901 .option smtp_ratelimit_hosts main "host list&!!" unset
17902 .cindex "SMTP" "rate limiting"
17903 .cindex "limit" "rate of message arrival"
17904 .cindex "RCPT" "rate limiting"
17905 Some sites find it helpful to be able to limit the rate at which certain hosts
17906 can send them messages, and the rate at which an individual message can specify
17909 Exim has two rate-limiting facilities. This section describes the older
17910 facility, which can limit rates within a single connection. The newer
17911 &%ratelimit%& ACL condition can limit rates across all connections. See section
17912 &<<SECTratelimiting>>& for details of the newer facility.
17914 When a host matches &%smtp_ratelimit_hosts%&, the values of
17915 &%smtp_ratelimit_mail%& and &%smtp_ratelimit_rcpt%& are used to control the
17916 rate of acceptance of MAIL and RCPT commands in a single SMTP session,
17917 respectively. Each option, if set, must contain a set of four comma-separated
17921 A threshold, before which there is no rate limiting.
17923 An initial time delay. Unlike other times in Exim, numbers with decimal
17924 fractional parts are allowed here.
17926 A factor by which to increase the delay each time.
17928 A maximum value for the delay. This should normally be less than 5 minutes,
17929 because after that time, the client is liable to timeout the SMTP command.
17932 For example, these settings have been used successfully at the site which
17933 first suggested this feature, for controlling mail from their customers:
17935 smtp_ratelimit_mail = 2,0.5s,1.05,4m
17936 smtp_ratelimit_rcpt = 4,0.25s,1.015,4m
17938 The first setting specifies delays that are applied to MAIL commands after
17939 two have been received over a single connection. The initial delay is 0.5
17940 seconds, increasing by a factor of 1.05 each time. The second setting applies
17941 delays to RCPT commands when more than four occur in a single message.
17944 .option smtp_ratelimit_mail main string unset
17945 See &%smtp_ratelimit_hosts%& above.
17948 .option smtp_ratelimit_rcpt main string unset
17949 See &%smtp_ratelimit_hosts%& above.
17952 .option smtp_receive_timeout main time&!! 5m
17953 .cindex "timeout" "for SMTP input"
17954 .cindex "SMTP" "input timeout"
17955 This sets a timeout value for SMTP reception. It applies to all forms of SMTP
17956 input, including batch SMTP. If a line of input (either an SMTP command or a
17957 data line) is not received within this time, the SMTP connection is dropped and
17958 the message is abandoned.
17959 A line is written to the log containing one of the following messages:
17961 SMTP command timeout on connection from...
17962 SMTP data timeout on connection from...
17964 The former means that Exim was expecting to read an SMTP command; the latter
17965 means that it was in the DATA phase, reading the contents of a message.
17967 If the first character of the option is a &"$"& the option is
17968 expanded before use and may depend on
17969 &$sender_host_name$&, &$sender_host_address$& and &$sender_host_port$&.
17973 The value set by this option can be overridden by the
17974 &%-os%& command-line option. A setting of zero time disables the timeout, but
17975 this should never be used for SMTP over TCP/IP. (It can be useful in some cases
17976 of local input using &%-bs%& or &%-bS%&.) For non-SMTP input, the reception
17977 timeout is controlled by &%receive_timeout%& and &%-or%&.
17980 .option smtp_reserve_hosts main "host list&!!" unset
17981 This option defines hosts for which SMTP connections are reserved; see
17982 &%smtp_accept_reserve%& and &%smtp_load_reserve%& above.
17985 .option smtp_return_error_details main boolean false
17986 .cindex "SMTP" "details policy failures"
17987 .cindex "policy control" "rejection, returning details"
17988 In the default state, Exim uses bland messages such as
17989 &"Administrative prohibition"& when it rejects SMTP commands for policy
17990 reasons. Many sysadmins like this because it gives away little information
17991 to spammers. However, some other sysadmins who are applying strict checking
17992 policies want to give out much fuller information about failures. Setting
17993 &%smtp_return_error_details%& true causes Exim to be more forthcoming. For
17994 example, instead of &"Administrative prohibition"&, it might give:
17996 550-Rejected after DATA: '>' missing at end of address:
17997 550 failing address in "From" header is: <user@dom.ain
18001 .option smtputf8_advertise_hosts main "host list&!!" *
18002 .cindex "SMTPUTF8" "ESMTP extension, advertising"
18003 .cindex "ESMTP extensions" SMTPUTF8
18004 When Exim is built with support for internationalised mail names,
18005 the availability thereof is advertised in
18006 response to EHLO only to those client hosts that match this option. See
18007 chapter &<<CHAPi18n>>& for details of Exim's support for internationalisation.
18010 .option spamd_address main string "127.0.0.1 783"
18011 This option is available when Exim is compiled with the content-scanning
18012 extension. It specifies how Exim connects to SpamAssassin's &%spamd%& daemon.
18013 See section &<<SECTscanspamass>>& for more details.
18017 .option spf_guess main string "v=spf1 a/24 mx/24 ptr ?all"
18018 This option is available when Exim is compiled with SPF support.
18019 See section &<<SECSPF>>& for more details.
18021 .option spf_smtp_comment_template main string&!! "Please%_see%_http://www.open-spf.org/Why"
18022 This option is available when Exim is compiled with SPF support. It
18023 allows the customisation of the SMTP comment that the SPF library
18024 generates. You are strongly encouraged to link to your own explanative
18025 site. The template must not contain spaces. If you need spaces in the
18026 output, use the proper placeholder. If libspf2 can not parse the
18027 template, it uses a built-in default broken link. The following placeholders
18028 (along with Exim variables (but see below)) are allowed in the template:
18032 &*%{L}*&: Envelope sender's local part.
18034 &*%{S}*&: Envelope sender.
18036 &*%{O}*&: Envelope sender's domain.
18038 &*%{D}*&: Current(?) domain.
18040 &*%{I}*&: SMTP client Ip.
18042 &*%{C}*&: SMTP client pretty IP.
18044 &*%{T}*&: Epoch time (UTC).
18046 &*%{P}*&: SMTP client domain name.
18048 &*%{V}*&: IP version.
18050 &*%{H}*&: EHLO/HELO domain.
18052 &*%{R}*&: Receiving domain.
18054 The capitalized placeholders do proper URL encoding, if you use them
18055 lowercased, no encoding takes place. This list was compiled from the
18058 A note on using Exim variables: As
18059 currently the SPF library is initialized before the SMTP EHLO phase,
18060 the variables useful for expansion are quite limited.
18063 .option split_spool_directory main boolean false
18064 .cindex "multiple spool directories"
18065 .cindex "spool directory" "split"
18066 .cindex "directories, multiple"
18067 If this option is set, it causes Exim to split its input directory into 62
18068 subdirectories, each with a single alphanumeric character as its name. The
18069 sixth character of the message id is used to allocate messages to
18070 subdirectories; this is the least significant base-62 digit of the time of
18071 arrival of the message.
18073 Splitting up the spool in this way may provide better performance on systems
18074 where there are long mail queues, by reducing the number of files in any one
18075 directory. The msglog directory is also split up in a similar way to the input
18076 directory; however, if &%preserve_message_logs%& is set, all old msglog files
18077 are still placed in the single directory &_msglog.OLD_&.
18079 It is not necessary to take any special action for existing messages when
18080 changing &%split_spool_directory%&. Exim notices messages that are in the
18081 &"wrong"& place, and continues to process them. If the option is turned off
18082 after a period of being on, the subdirectories will eventually empty and be
18083 automatically deleted.
18085 When &%split_spool_directory%& is set, the behaviour of queue runner processes
18086 changes. Instead of creating a list of all messages in the queue, and then
18087 trying to deliver each one, in turn, it constructs a list of those in one
18088 sub-directory and tries to deliver them, before moving on to the next
18089 sub-directory. The sub-directories are processed in a random order. This
18090 spreads out the scanning of the input directories, and uses less memory. It is
18091 particularly beneficial when there are lots of messages in the queue. However,
18092 if &%queue_run_in_order%& is set, none of this new processing happens. The
18093 entire queue has to be scanned and sorted before any deliveries can start.
18096 .option spool_directory main string&!! "set at compile time"
18097 .cindex "spool directory" "path to"
18098 This defines the directory in which Exim keeps its spool, that is, the messages
18099 it is waiting to deliver. The default value is taken from the compile-time
18100 configuration setting, if there is one. If not, this option must be set. The
18101 string is expanded, so it can contain, for example, a reference to
18102 &$primary_hostname$&.
18104 If the spool directory name is fixed on your installation, it is recommended
18105 that you set it at build time rather than from this option, particularly if the
18106 log files are being written to the spool directory (see &%log_file_path%&).
18107 Otherwise log files cannot be used for errors that are detected early on, such
18108 as failures in the configuration file.
18110 By using this option to override the compiled-in path, it is possible to run
18111 tests of Exim without using the standard spool.
18113 .option spool_wireformat main boolean false
18114 .cindex "spool directory" "file formats"
18115 If this option is set, Exim may for some messages use an alternative format
18116 for data-files in the spool which matches the wire format.
18117 Doing this permits more efficient message reception and transmission.
18118 Currently it is only done for messages received using the ESMTP CHUNKING
18121 The following variables will not have useful values:
18123 $max_received_linelength
18128 Users of the local_scan() API (see &<<CHAPlocalscan>>&),
18129 and any external programs which are passed a reference to a message data file
18130 (except via the &"regex"&, &"malware"& or &"spam"&) ACL conditions)
18131 will need to be aware of the different formats potentially available.
18133 Using any of the ACL conditions noted will negate the reception benefit
18134 (as a Unix-mbox-format file is constructed for them).
18135 The transmission benefit is maintained.
18137 .option sqlite_lock_timeout main time 5s
18138 .cindex "sqlite lookup type" "lock timeout"
18139 This option controls the timeout that the &(sqlite)& lookup uses when trying to
18140 access an SQLite database. See section &<<SECTsqlite>>& for more details.
18142 .option strict_acl_vars main boolean false
18143 .cindex "&ACL;" "variables, handling unset"
18144 This option controls what happens if a syntactically valid but undefined ACL
18145 variable is referenced. If it is false (the default), an empty string
18146 is substituted; if it is true, an error is generated. See section
18147 &<<SECTaclvariables>>& for details of ACL variables.
18149 .option strip_excess_angle_brackets main boolean false
18150 .cindex "angle brackets, excess"
18151 If this option is set, redundant pairs of angle brackets round &"route-addr"&
18152 items in addresses are stripped. For example, &'<<xxx@a.b.c.d>>'& is
18153 treated as &'<xxx@a.b.c.d>'&. If this is in the envelope and the message is
18154 passed on to another MTA, the excess angle brackets are not passed on. If this
18155 option is not set, multiple pairs of angle brackets cause a syntax error.
18158 .option strip_trailing_dot main boolean false
18159 .cindex "trailing dot on domain"
18160 .cindex "dot" "trailing on domain"
18161 If this option is set, a trailing dot at the end of a domain in an address is
18162 ignored. If this is in the envelope and the message is passed on to another
18163 MTA, the dot is not passed on. If this option is not set, a dot at the end of a
18164 domain causes a syntax error.
18165 However, addresses in header lines are checked only when an ACL requests header
18169 .option syslog_duplication main boolean true
18170 .cindex "syslog" "duplicate log lines; suppressing"
18171 When Exim is logging to syslog, it writes the log lines for its three
18172 separate logs at different syslog priorities so that they can in principle
18173 be separated on the logging hosts. Some installations do not require this
18174 separation, and in those cases, the duplication of certain log lines is a
18175 nuisance. If &%syslog_duplication%& is set false, only one copy of any
18176 particular log line is written to syslog. For lines that normally go to
18177 both the main log and the reject log, the reject log version (possibly
18178 containing message header lines) is written, at LOG_NOTICE priority.
18179 Lines that normally go to both the main and the panic log are written at
18180 the LOG_ALERT priority.
18183 .option syslog_facility main string unset
18184 .cindex "syslog" "facility; setting"
18185 This option sets the syslog &"facility"& name, used when Exim is logging to
18186 syslog. The value must be one of the strings &"mail"&, &"user"&, &"news"&,
18187 &"uucp"&, &"daemon"&, or &"local&'x'&"& where &'x'& is a digit between 0 and 7.
18188 If this option is unset, &"mail"& is used. See chapter &<<CHAPlog>>& for
18189 details of Exim's logging.
18192 .option syslog_pid main boolean true
18193 .cindex "syslog" "pid"
18194 If &%syslog_pid%& is set false, the PID on Exim's log lines are
18195 omitted when these lines are sent to syslog. (Syslog normally prefixes
18196 the log lines with the PID of the logging process automatically.) You need
18197 to enable the &`+pid`& log selector item, if you want Exim to write it's PID
18198 into the logs.) See chapter &<<CHAPlog>>& for details of Exim's logging.
18202 .option syslog_processname main string &`exim`&
18203 .cindex "syslog" "process name; setting"
18204 This option sets the syslog &"ident"& name, used when Exim is logging to
18205 syslog. The value must be no longer than 32 characters. See chapter
18206 &<<CHAPlog>>& for details of Exim's logging.
18210 .option syslog_timestamp main boolean true
18211 .cindex "syslog" "timestamps"
18212 .cindex timestamps syslog
18213 If &%syslog_timestamp%& is set false, the timestamps on Exim's log lines are
18214 omitted when these lines are sent to syslog. See chapter &<<CHAPlog>>& for
18215 details of Exim's logging.
18218 .option system_filter main string&!! unset
18219 .cindex "filter" "system filter"
18220 .cindex "system filter" "specifying"
18221 .cindex "Sieve filter" "not available for system filter"
18222 This option specifies an Exim filter file that is applied to all messages at
18223 the start of each delivery attempt, before any routing is done. System filters
18224 must be Exim filters; they cannot be Sieve filters. If the system filter
18225 generates any deliveries to files or pipes, or any new mail messages, the
18226 appropriate &%system_filter_..._transport%& option(s) must be set, to define
18227 which transports are to be used. Details of this facility are given in chapter
18228 &<<CHAPsystemfilter>>&.
18229 A forced expansion failure results in no filter operation.
18232 .option system_filter_directory_transport main string&!! unset
18233 .vindex "&$address_file$&"
18234 This sets the name of the transport driver that is to be used when the
18235 &%save%& command in a system message filter specifies a path ending in &"/"&,
18236 implying delivery of each message into a separate file in some directory.
18237 During the delivery, the variable &$address_file$& contains the path name.
18240 .option system_filter_file_transport main string&!! unset
18241 .cindex "file" "transport for system filter"
18242 This sets the name of the transport driver that is to be used when the &%save%&
18243 command in a system message filter specifies a path not ending in &"/"&. During
18244 the delivery, the variable &$address_file$& contains the path name.
18246 .option system_filter_group main string unset
18247 .cindex "gid (group id)" "system filter"
18248 This option is used only when &%system_filter_user%& is also set. It sets the
18249 gid under which the system filter is run, overriding any gid that is associated
18250 with the user. The value may be numerical or symbolic.
18252 .option system_filter_pipe_transport main string&!! unset
18253 .cindex "&(pipe)& transport" "for system filter"
18254 .vindex "&$address_pipe$&"
18255 This specifies the transport driver that is to be used when a &%pipe%& command
18256 is used in a system filter. During the delivery, the variable &$address_pipe$&
18257 contains the pipe command.
18260 .option system_filter_reply_transport main string&!! unset
18261 .cindex "&(autoreply)& transport" "for system filter"
18262 This specifies the transport driver that is to be used when a &%mail%& command
18263 is used in a system filter.
18266 .option system_filter_user main string unset
18267 .cindex "uid (user id)" "system filter"
18268 If this option is set to root, the system filter is run in the main Exim
18269 delivery process, as root. Otherwise, the system filter runs in a separate
18270 process, as the given user, defaulting to the Exim run-time user.
18271 Unless the string consists entirely of digits, it
18272 is looked up in the password data. Failure to find the named user causes a
18273 configuration error. The gid is either taken from the password data, or
18274 specified by &%system_filter_group%&. When the uid is specified numerically,
18275 &%system_filter_group%& is required to be set.
18277 If the system filter generates any pipe, file, or reply deliveries, the uid
18278 under which the filter is run is used when transporting them, unless a
18279 transport option overrides.
18282 .option tcp_nodelay main boolean true
18283 .cindex "daemon" "TCP_NODELAY on sockets"
18284 .cindex "Nagle algorithm"
18285 .cindex "TCP_NODELAY on listening sockets"
18286 If this option is set false, it stops the Exim daemon setting the
18287 TCP_NODELAY option on its listening sockets. Setting TCP_NODELAY
18288 turns off the &"Nagle algorithm"&, which is a way of improving network
18289 performance in interactive (character-by-character) situations. Turning it off
18290 should improve Exim's performance a bit, so that is what happens by default.
18291 However, it appears that some broken clients cannot cope, and time out. Hence
18292 this option. It affects only those sockets that are set up for listening by the
18293 daemon. Sockets created by the smtp transport for delivering mail always set
18297 .option timeout_frozen_after main time 0s
18298 .cindex "frozen messages" "timing out"
18299 .cindex "timeout" "frozen messages"
18300 If &%timeout_frozen_after%& is set to a time greater than zero, a frozen
18301 message of any kind that has been in the queue for longer than the given time
18302 is automatically cancelled at the next queue run. If the frozen message is a
18303 bounce message, it is just discarded; otherwise, a bounce is sent to the
18304 sender, in a similar manner to cancellation by the &%-Mg%& command line option.
18305 If you want to timeout frozen bounce messages earlier than other kinds of
18306 frozen message, see &%ignore_bounce_errors_after%&.
18308 &*Note:*& the default value of zero means no timeouts; with this setting,
18309 frozen messages remain in the queue forever (except for any frozen bounce
18310 messages that are released by &%ignore_bounce_errors_after%&).
18313 .option timezone main string unset
18314 .cindex "timezone, setting"
18315 .cindex "environment" "values from"
18316 The value of &%timezone%& is used to set the environment variable TZ while
18317 running Exim (if it is different on entry). This ensures that all timestamps
18318 created by Exim are in the required timezone. If you want all your timestamps
18319 to be in UTC (aka GMT) you should set
18323 The default value is taken from TIMEZONE_DEFAULT in &_Local/Makefile_&,
18324 or, if that is not set, from the value of the TZ environment variable when Exim
18325 is built. If &%timezone%& is set to the empty string, either at build or run
18326 time, any existing TZ variable is removed from the environment when Exim
18327 runs. This is appropriate behaviour for obtaining wall-clock time on some, but
18328 unfortunately not all, operating systems.
18331 .option tls_advertise_hosts main "host list&!!" *
18332 .cindex "TLS" "advertising"
18333 .cindex "encryption" "on SMTP connection"
18334 .cindex "SMTP" "encrypted connection"
18335 .cindex "ESMTP extensions" STARTTLS
18336 When Exim is built with support for TLS encrypted connections, the availability
18337 of the STARTTLS command to set up an encrypted session is advertised in
18338 response to EHLO only to those client hosts that match this option. See
18339 chapter &<<CHAPTLS>>& for details of Exim's support for TLS.
18340 Note that the default value requires that a certificate be supplied
18341 using the &%tls_certificate%& option. If TLS support for incoming connections
18342 is not required the &%tls_advertise_hosts%& option should be set empty.
18345 .option tls_alpn main "string list&!!" "smtp : esmtp"
18346 .cindex TLS "Application Layer Protocol Names"
18348 .cindex ALPN "set acceptable names for server"
18349 If this option is set,
18350 the TLS library supports ALPN,
18351 and the client offers either more than
18352 ALPN name or a name which does not match the list,
18353 the TLS connection is declined.
18356 .option tls_certificate main "string list&!!" unset
18357 .cindex "TLS" "server certificate; location of"
18358 .cindex "certificate" "server, location of"
18359 The value of this option is expanded, and must then be a list of absolute paths to
18360 files which contain the server's certificates (in PEM format).
18361 Commonly only one file is needed.
18362 The server's private key is also
18363 assumed to be in this file if &%tls_privatekey%& is unset. See chapter
18364 &<<CHAPTLS>>& for further details.
18366 &*Note*&: The certificates defined by this option are used only when Exim is
18367 receiving incoming messages as a server. If you want to supply certificates for
18368 use when sending messages as a client, you must set the &%tls_certificate%&
18369 option in the relevant &(smtp)& transport.
18371 &*Note*&: If you use filenames based on IP addresses, change the list
18372 separator in the usual way (&<<SECTlistsepchange>>&) to avoid confusion under IPv6.
18374 &*Note*&: Under versions of OpenSSL preceding 1.1.1,
18375 when a list of more than one
18376 file is used, the &$tls_in_ourcert$& variable is unreliable.
18377 The macro "_TLS_BAD_MULTICERT_IN_OURCERT" will be defined for those versions.
18379 .cindex SNI "selecting server certificate based on"
18380 If the option contains &$tls_out_sni$& and Exim is built against OpenSSL, then
18381 if the OpenSSL build supports TLS extensions and the TLS client sends the
18382 Server Name Indication extension, then this option and others documented in
18383 &<<SECTtlssni>>& will be re-expanded.
18385 If this option is unset or empty a self-signed certificate will be
18387 Under Linux this is generated at daemon startup; on other platforms it will be
18388 generated fresh for every connection.
18390 .option tls_crl main string&!! unset
18391 .cindex "TLS" "server certificate revocation list"
18392 .cindex "certificate" "revocation list for server"
18393 This option specifies a certificate revocation list. The expanded value must
18394 be the name of a file that contains CRLs in PEM format.
18396 Under OpenSSL the option can specify a directory with CRL files.
18398 &*Note:*& Under OpenSSL the option must, if given, supply a CRL
18399 for each signing element of the certificate chain (i.e. all but the leaf).
18400 For the file variant this can be multiple PEM blocks in the one file.
18402 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
18405 .option tls_dh_max_bits main integer 2236
18406 .cindex "TLS" "D-H bit count"
18407 The number of bits used for Diffie-Hellman key-exchange may be suggested by
18408 the chosen TLS library. That value might prove to be too high for
18409 interoperability. This option provides a maximum clamp on the value
18410 suggested, trading off security for interoperability.
18412 The value must be at least 1024.
18414 The value 2236 was chosen because, at time of adding the option, it was the
18415 hard-coded maximum value supported by the NSS cryptographic library, as used
18416 by Thunderbird, while GnuTLS was suggesting 2432 bits as normal.
18418 If you prefer more security and are willing to break some clients, raise this
18421 Note that the value passed to GnuTLS for *generating* a new prime may be a
18422 little less than this figure, because GnuTLS is inexact and may produce a
18423 larger prime than requested.
18426 .option tls_dhparam main string&!! unset
18427 .cindex "TLS" "D-H parameters for server"
18428 The value of this option is expanded and indicates the source of DH parameters
18429 to be used by Exim.
18431 &*Note: The Exim Maintainers strongly recommend using a filename with site-generated
18432 local DH parameters*&, which has been supported across all versions of Exim. The
18433 other specific constants available are a fallback so that even when
18434 "unconfigured", Exim can offer Perfect Forward Secrecy in older ciphersuites in TLS.
18436 If &%tls_dhparam%& is a filename starting with a &`/`&,
18437 then it names a file from which DH
18438 parameters should be loaded. If the file exists, it should hold a PEM-encoded
18439 PKCS#3 representation of the DH prime. If the file does not exist, for
18440 OpenSSL it is an error. For GnuTLS, Exim will attempt to create the file and
18441 fill it with a generated DH prime. For OpenSSL, if the DH bit-count from
18442 loading the file is greater than &%tls_dh_max_bits%& then it will be ignored,
18443 and treated as though the &%tls_dhparam%& were set to "none".
18445 If this option expands to the string "none", then no DH parameters will be
18448 If this option expands to the string "historic" and Exim is using GnuTLS, then
18449 Exim will attempt to load a file from inside the spool directory. If the file
18450 does not exist, Exim will attempt to create it.
18451 See section &<<SECTgnutlsparam>>& for further details.
18453 If Exim is using OpenSSL and this option is empty or unset, then Exim will load
18454 a default DH prime; the default is Exim-specific but lacks verifiable provenance.
18456 In older versions of Exim the default was the 2048 bit prime described in section
18457 2.2 of RFC 5114, "2048-bit MODP Group with 224-bit Prime Order Subgroup", which
18458 in IKE is assigned number 23.
18460 Otherwise, the option must expand to the name used by Exim for any of a number
18461 of DH primes specified in RFC 2409, RFC 3526, RFC 5114, RFC 7919, or from other
18462 sources. As names, Exim uses a standard specified name, else "ike" followed by
18463 the number used by IKE, or "default" which corresponds to
18464 &`exim.dev.20160529.3`&.
18466 The available standard primes are:
18467 &`ffdhe2048`&, &`ffdhe3072`&, &`ffdhe4096`&, &`ffdhe6144`&, &`ffdhe8192`&,
18468 &`ike1`&, &`ike2`&, &`ike5`&,
18469 &`ike14`&, &`ike15`&, &`ike16`&, &`ike17`&, &`ike18`&,
18470 &`ike22`&, &`ike23`& and &`ike24`&.
18472 The available additional primes are:
18473 &`exim.dev.20160529.1`&, &`exim.dev.20160529.2`& and &`exim.dev.20160529.3`&.
18475 Some of these will be too small to be accepted by clients.
18476 Some may be too large to be accepted by clients.
18477 The open cryptographic community has suspicions about the integrity of some
18478 of the later IKE values, which led into RFC7919 providing new fixed constants
18479 (the "ffdhe" identifiers).
18481 At this point, all of the "ike" values should be considered obsolete;
18482 they are still in Exim to avoid breaking unusual configurations, but are
18483 candidates for removal the next time we have backwards-incompatible changes.
18484 Two of them in particular (&`ike1`& and &`ike22`&) are called out by RFC 8247
18485 as MUST NOT use for IPSEC, and two more (&`ike23`& and &`ike24`&) as
18487 Because of this, Exim regards them as deprecated; if either of the first pair
18488 are used, warnings will be logged in the paniclog, and if any are used then
18489 warnings will be logged in the mainlog.
18490 All four will be removed in a future Exim release.
18492 The TLS protocol does not negotiate an acceptable size for this; clients tend
18493 to hard-drop connections if what is offered by the server is unacceptable,
18494 whether too large or too small, and there's no provision for the client to
18495 tell the server what these constraints are. Thus, as a server operator, you
18496 need to make an educated guess as to what is most likely to work for your
18499 Some known size constraints suggest that a bit-size in the range 2048 to 2236
18500 is most likely to maximise interoperability. The upper bound comes from
18501 applications using the Mozilla Network Security Services (NSS) library, which
18502 used to set its &`DH_MAX_P_BITS`& upper-bound to 2236. This affects many
18503 mail user agents (MUAs). The lower bound comes from Debian installs of Exim4
18504 prior to the 4.80 release, as Debian used to patch Exim to raise the minimum
18505 acceptable bound from 1024 to 2048.
18508 .option tls_eccurve main string&!! &`auto`&
18509 .cindex TLS "EC cryptography"
18510 This option selects a EC curve for use by Exim when used with OpenSSL.
18511 It has no effect when Exim is used with GnuTLS.
18513 After expansion it must contain a valid EC curve parameter, such as
18514 &`prime256v1`&, &`secp384r1`&, or &`P-512`&. Consult your OpenSSL manual
18515 for valid selections.
18517 For OpenSSL versions before (and not including) 1.0.2, the string
18518 &`auto`& selects &`prime256v1`&. For more recent OpenSSL versions
18519 &`auto`& tells the library to choose.
18521 If the option expands to an empty string, no EC curves will be enabled.
18524 .option tls_ocsp_file main string&!! unset
18525 .cindex TLS "certificate status"
18526 .cindex TLS "OCSP proof file"
18528 must if set expand to the absolute path to a file which contains a current
18529 status proof for the server's certificate, as obtained from the
18530 Certificate Authority.
18532 Usable for GnuTLS 3.4.4 or 3.3.17 or OpenSSL 1.1.0 (or later).
18533 The macro "_HAVE_TLS_OCSP" will be defined for those versions.
18535 For OpenSSL 1.1.0 or later, and
18536 for GnuTLS 3.5.6 or later the expanded value of this option can be a list
18537 of files, to match a list given for the &%tls_certificate%& option.
18538 The ordering of the two lists must match.
18539 The macro "_HAVE_TLS_OCSP_LIST" will be defined for those versions.
18541 The file(s) should be in DER format,
18542 except for GnuTLS 3.6.3 or later
18544 when an optional filetype prefix can be used.
18545 The prefix must be one of "DER" or "PEM", followed by
18546 a single space. If one is used it sets the format for subsequent
18547 files in the list; the initial format is DER.
18548 If multiple proofs are wanted, for multiple chain elements
18549 (this only works under TLS1.3)
18550 they must be coded as a combined OCSP response.
18552 Although GnuTLS will accept PEM files with multiple separate
18553 PEM blobs (ie. separate OCSP responses), it sends them in the
18554 TLS Certificate record interleaved with the certificates of the chain;
18555 although a GnuTLS client is happy with that, an OpenSSL client is not.
18557 .option tls_on_connect_ports main "string list" unset
18560 This option specifies a list of incoming SSMTP (aka SMTPS) ports that should
18561 operate the SSMTP (SMTPS) protocol, where a TLS session is immediately
18562 set up without waiting for the client to issue a STARTTLS command. For
18563 further details, see section &<<SECTsupobssmt>>&.
18567 .option tls_privatekey main "string list&!!" unset
18568 .cindex "TLS" "server private key; location of"
18569 The value of this option is expanded, and must then be a list of absolute paths to
18570 files which contains the server's private keys.
18571 If this option is unset, or if
18572 the expansion is forced to fail, or the result is an empty string, the private
18573 key is assumed to be in the same file as the server's certificates. See chapter
18574 &<<CHAPTLS>>& for further details.
18576 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
18579 .option tls_remember_esmtp main boolean false
18580 .cindex "TLS" "esmtp state; remembering"
18581 .cindex "TLS" "broken clients"
18582 If this option is set true, Exim violates the RFCs by remembering that it is in
18583 &"esmtp"& state after successfully negotiating a TLS session. This provides
18584 support for broken clients that fail to send a new EHLO after starting a
18588 .option tls_require_ciphers main string&!! unset
18589 .cindex "TLS" "requiring specific ciphers"
18590 .cindex "cipher" "requiring specific"
18591 This option controls which ciphers can be used for incoming TLS connections.
18592 The &(smtp)& transport has an option of the same name for controlling outgoing
18593 connections. This option is expanded for each connection, so can be varied for
18594 different clients if required. The value of this option must be a list of
18595 permitted cipher suites. The OpenSSL and GnuTLS libraries handle cipher control
18596 in somewhat different ways. If GnuTLS is being used, the client controls the
18597 preference order of the available ciphers. Details are given in sections
18598 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
18601 .option tls_resumption_hosts main "host list&!!" unset
18602 .cindex TLS resumption
18603 This option controls which connections to offer the TLS resumption feature.
18604 See &<<SECTresumption>>& for details.
18607 .option tls_try_verify_hosts main "host list&!!" unset
18608 .cindex "TLS" "client certificate verification"
18609 .cindex "certificate" "verification of client"
18610 See &%tls_verify_hosts%& below.
18613 .option tls_verify_certificates main string&!! system
18614 .cindex "TLS" "client certificate verification"
18615 .cindex "certificate" "verification of client"
18616 The value of this option is expanded, and must then be either the
18618 or the absolute path to
18619 a file or directory containing permitted certificates for clients that
18620 match &%tls_verify_hosts%& or &%tls_try_verify_hosts%&.
18622 The "system" value for the option will use a
18623 system default location compiled into the SSL library.
18624 This is not available for GnuTLS versions preceding 3.0.20,
18625 and will be taken as empty; an explicit location
18628 The use of a directory for the option value is not available for GnuTLS versions
18629 preceding 3.3.6 and a single file must be used.
18631 With OpenSSL the certificates specified
18633 either by file or directory
18634 are added to those given by the system default location.
18636 These certificates should be for the certificate authorities trusted, rather
18637 than the public cert of individual clients. With both OpenSSL and GnuTLS, if
18638 the value is a file then the certificates are sent by Exim as a server to
18639 connecting clients, defining the list of accepted certificate authorities.
18640 Thus the values defined should be considered public data. To avoid this,
18641 use the explicit directory version. (If your peer is Exim up to 4.85,
18642 using GnuTLS, you may need to send the CAs (thus using the file
18643 variant). Otherwise the peer doesn't send its certificate.)
18645 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
18647 A forced expansion failure or setting to an empty string is equivalent to
18651 .option tls_verify_hosts main "host list&!!" unset
18652 .cindex "TLS" "client certificate verification"
18653 .cindex "certificate" "verification of client"
18654 This option, along with &%tls_try_verify_hosts%&, controls the checking of
18655 certificates from clients. The expected certificates are defined by
18656 &%tls_verify_certificates%&, which must be set. A configuration error occurs if
18657 either &%tls_verify_hosts%& or &%tls_try_verify_hosts%& is set and
18658 &%tls_verify_certificates%& is not set.
18660 Any client that matches &%tls_verify_hosts%& is constrained by
18661 &%tls_verify_certificates%&. When the client initiates a TLS session, it must
18662 present one of the listed certificates. If it does not, the connection is
18664 &*Warning*&: Including a host in &%tls_verify_hosts%& does not require
18665 the host to use TLS. It can still send SMTP commands through unencrypted
18666 connections. Forcing a client to use TLS has to be done separately using an
18667 ACL to reject inappropriate commands when the connection is not encrypted.
18669 A weaker form of checking is provided by &%tls_try_verify_hosts%&. If a client
18670 matches this option (but not &%tls_verify_hosts%&), Exim requests a
18671 certificate and checks it against &%tls_verify_certificates%&, but does not
18672 abort the connection if there is no certificate or if it does not match. This
18673 state can be detected in an ACL, which makes it possible to implement policies
18674 such as &"accept for relay only if a verified certificate has been received,
18675 but accept for local delivery if encrypted, even without a verified
18678 Client hosts that match neither of these lists are not asked to present
18682 .option trusted_groups main "string list&!!" unset
18683 .cindex "trusted groups"
18684 .cindex "groups" "trusted"
18685 This option is expanded just once, at the start of Exim's processing. If this
18686 option is set, any process that is running in one of the listed groups, or
18687 which has one of them as a supplementary group, is trusted. The groups can be
18688 specified numerically or by name. See section &<<SECTtrustedadmin>>& for
18689 details of what trusted callers are permitted to do. If neither
18690 &%trusted_groups%& nor &%trusted_users%& is set, only root and the Exim user
18693 .option trusted_users main "string list&!!" unset
18694 .cindex "trusted users"
18695 .cindex "user" "trusted"
18696 This option is expanded just once, at the start of Exim's processing. If this
18697 option is set, any process that is running as one of the listed users is
18698 trusted. The users can be specified numerically or by name. See section
18699 &<<SECTtrustedadmin>>& for details of what trusted callers are permitted to do.
18700 If neither &%trusted_groups%& nor &%trusted_users%& is set, only root and the
18701 Exim user are trusted.
18703 .option unknown_login main string&!! unset
18704 .cindex "uid (user id)" "unknown caller"
18705 .vindex "&$caller_uid$&"
18706 This is a specialized feature for use in unusual configurations. By default, if
18707 the uid of the caller of Exim cannot be looked up using &[getpwuid()]&, Exim
18708 gives up. The &%unknown_login%& option can be used to set a login name to be
18709 used in this circumstance. It is expanded, so values like &%user$caller_uid%&
18710 can be set. When &%unknown_login%& is used, the value of &%unknown_username%&
18711 is used for the user's real name (gecos field), unless this has been set by the
18714 .option unknown_username main string unset
18715 See &%unknown_login%&.
18717 .option untrusted_set_sender main "address list&!!" unset
18718 .cindex "trusted users"
18719 .cindex "sender" "setting by untrusted user"
18720 .cindex "untrusted user setting sender"
18721 .cindex "user" "untrusted setting sender"
18722 .cindex "envelope from"
18723 .cindex "envelope sender"
18724 When an untrusted user submits a message to Exim using the standard input, Exim
18725 normally creates an envelope sender address from the user's login and the
18726 default qualification domain. Data from the &%-f%& option (for setting envelope
18727 senders on non-SMTP messages) or the SMTP MAIL command (if &%-bs%& or &%-bS%&
18728 is used) is ignored.
18730 However, untrusted users are permitted to set an empty envelope sender address,
18731 to declare that a message should never generate any bounces. For example:
18733 exim -f '<>' user@domain.example
18735 .vindex "&$sender_ident$&"
18736 The &%untrusted_set_sender%& option allows you to permit untrusted users to set
18737 other envelope sender addresses in a controlled way. When it is set, untrusted
18738 users are allowed to set envelope sender addresses that match any of the
18739 patterns in the list. Like all address lists, the string is expanded. The
18740 identity of the user is in &$sender_ident$&, so you can, for example, restrict
18741 users to setting senders that start with their login ids
18742 followed by a hyphen
18743 by a setting like this:
18745 untrusted_set_sender = ^$sender_ident-
18747 If you want to allow untrusted users to set envelope sender addresses without
18748 restriction, you can use
18750 untrusted_set_sender = *
18752 The &%untrusted_set_sender%& option applies to all forms of local input, but
18753 only to the setting of the envelope sender. It does not permit untrusted users
18754 to use the other options which trusted user can use to override message
18755 parameters. Furthermore, it does not stop Exim from removing an existing
18756 &'Sender:'& header in the message, or from adding a &'Sender:'& header if
18757 necessary. See &%local_sender_retain%& and &%local_from_check%& for ways of
18758 overriding these actions. The handling of the &'Sender:'& header is also
18759 described in section &<<SECTthesenhea>>&.
18761 The log line for a message's arrival shows the envelope sender following
18762 &"<="&. For local messages, the user's login always follows, after &"U="&. In
18763 &%-bp%& displays, and in the Exim monitor, if an untrusted user sets an
18764 envelope sender address, the user's login is shown in parentheses after the
18768 .option uucp_from_pattern main string "see below"
18769 .cindex "&""From""& line"
18770 .cindex "UUCP" "&""From""& line"
18771 Some applications that pass messages to an MTA via a command line interface use
18772 an initial line starting with &"From&~"& to pass the envelope sender. In
18773 particular, this is used by UUCP software. Exim recognizes such a line by means
18774 of a regular expression that is set in &%uucp_from_pattern%&. When the pattern
18775 matches, the sender address is constructed by expanding the contents of
18776 &%uucp_from_sender%&, provided that the caller of Exim is a trusted user. The
18777 default pattern recognizes lines in the following two forms:
18779 From ph10 Fri Jan 5 12:35 GMT 1996
18780 From ph10 Fri, 7 Jan 97 14:00:00 GMT
18782 The pattern can be seen by running
18784 exim -bP uucp_from_pattern
18786 It checks only up to the hours and minutes, and allows for a 2-digit or 4-digit
18787 year in the second case. The first word after &"From&~"& is matched in the
18788 regular expression by a parenthesized subpattern. The default value for
18789 &%uucp_from_sender%& is &"$1"&, which therefore just uses this first word
18790 (&"ph10"& in the example above) as the message's sender. See also
18791 &%ignore_fromline_hosts%&.
18794 .option uucp_from_sender main string&!! &`$1`&
18795 See &%uucp_from_pattern%& above.
18798 .option warn_message_file main string&!! unset
18799 .cindex "warning of delay" "customizing the message"
18800 .cindex "customizing" "warning message"
18801 This option defines a template file containing paragraphs of text to be used
18802 for constructing the warning message which is sent by Exim when a message has
18803 been in the queue for a specified amount of time, as specified by
18804 &%delay_warning%&. Details of the file's contents are given in chapter
18805 &<<CHAPemsgcust>>&.
18806 .cindex warn_message_file "tainted data"
18807 The option is expanded to give the file path, which must be
18808 absolute and untainted.
18809 See also &%bounce_message_file%&.
18812 .option write_rejectlog main boolean true
18813 .cindex "reject log" "disabling"
18814 If this option is set false, Exim no longer writes anything to the reject log.
18815 See chapter &<<CHAPlog>>& for details of what Exim writes to its logs.
18816 .ecindex IIDconfima
18817 .ecindex IIDmaiconf
18822 . ////////////////////////////////////////////////////////////////////////////
18823 . ////////////////////////////////////////////////////////////////////////////
18825 .chapter "Generic options for routers" "CHAProutergeneric"
18826 .scindex IIDgenoprou1 "options" "generic; for routers"
18827 .scindex IIDgenoprou2 "generic options" "router"
18828 This chapter describes the generic options that apply to all routers.
18829 Those that are preconditions are marked with ‡ in the &"use"& field.
18831 For a general description of how a router operates, see sections
18832 &<<SECTrunindrou>>& and &<<SECTrouprecon>>&. The latter specifies the order in
18833 which the preconditions are tested. The order of expansion of the options that
18834 provide data for a transport is: &%errors_to%&, &%headers_add%&,
18835 &%headers_remove%&, &%transport%&.
18837 The name of a router is limited to be &drivernamemax; ASCII characters long;
18838 prior to Exim 4.95 names would be silently truncated at this length, but now
18842 .option address_data routers string&!! unset
18843 .cindex "router" "data attached to address"
18844 The string is expanded just before the router is run, that is, after all the
18845 precondition tests have succeeded. If the expansion is forced to fail, the
18846 router declines, the value of &%address_data%& remains unchanged, and the
18847 &%more%& option controls what happens next. Other expansion failures cause
18848 delivery of the address to be deferred.
18850 .vindex "&$address_data$&"
18851 When the expansion succeeds, the value is retained with the address, and can be
18852 accessed using the variable &$address_data$& in the current router, subsequent
18853 routers, and the eventual transport.
18855 &*Warning*&: If the current or any subsequent router is a &(redirect)& router
18856 that runs a user's filter file, the contents of &$address_data$& are accessible
18857 in the filter. This is not normally a problem, because such data is usually
18858 either not confidential or it &"belongs"& to the current user, but if you do
18859 put confidential data into &$address_data$& you need to remember this point.
18861 Even if the router declines or passes, the value of &$address_data$& remains
18862 with the address, though it can be changed by another &%address_data%& setting
18863 on a subsequent router. If a router generates child addresses, the value of
18864 &$address_data$& propagates to them. This also applies to the special kind of
18865 &"child"& that is generated by a router with the &%unseen%& option.
18867 The idea of &%address_data%& is that you can use it to look up a lot of data
18868 for the address once, and then pick out parts of the data later. For example,
18869 you could use a single LDAP lookup to return a string of the form
18871 uid=1234 gid=5678 mailbox=/mail/xyz forward=/home/xyz/.forward
18873 In the transport you could pick out the mailbox by a setting such as
18875 file = ${extract{mailbox}{$address_data}}
18877 This makes the configuration file less messy, and also reduces the number of
18878 lookups (though Exim does cache lookups).
18880 See also the &%set%& option below.
18882 .vindex "&$sender_address_data$&"
18883 .vindex "&$address_data$&"
18884 The &%address_data%& facility is also useful as a means of passing information
18885 from one router to another, and from a router to a transport. In addition, if
18886 &$address_data$& is set by a router when verifying a recipient address from an
18887 ACL, it remains available for use in the rest of the ACL statement. After
18888 verifying a sender, the value is transferred to &$sender_address_data$&.
18892 .option address_test routers&!? boolean true
18894 .cindex "router" "skipping when address testing"
18895 If this option is set false, the router is skipped when routing is being tested
18896 by means of the &%-bt%& command line option. This can be a convenience when
18897 your first router sends messages to an external scanner, because it saves you
18898 having to set the &"already scanned"& indicator when testing real address
18903 .option cannot_route_message routers string&!! unset
18904 .cindex "router" "customizing &""cannot route""& message"
18905 .cindex "customizing" "&""cannot route""& message"
18906 This option specifies a text message that is used when an address cannot be
18907 routed because Exim has run out of routers. The default message is
18908 &"Unrouteable address"&. This option is useful only on routers that have
18909 &%more%& set false, or on the very last router in a configuration, because the
18910 value that is used is taken from the last router that is considered. This
18911 includes a router that is skipped because its preconditions are not met, as
18912 well as a router that declines. For example, using the default configuration,
18915 cannot_route_message = Remote domain not found in DNS
18917 on the first router, which is a &(dnslookup)& router with &%more%& set false,
18920 cannot_route_message = Unknown local user
18922 on the final router that checks for local users. If string expansion fails for
18923 this option, the default message is used. Unless the expansion failure was
18924 explicitly forced, a message about the failure is written to the main and panic
18925 logs, in addition to the normal message about the routing failure.
18928 .option caseful_local_part routers boolean false
18929 .cindex "case of local parts"
18930 .cindex "router" "case of local parts"
18931 By default, routers handle the local parts of addresses in a case-insensitive
18932 manner, though the actual case is preserved for transmission with the message.
18933 If you want the case of letters to be significant in a router, you must set
18934 this option true. For individual router options that contain address or local
18935 part lists (for example, &%local_parts%&), case-sensitive matching can be
18936 turned on by &"+caseful"& as a list item. See section &<<SECTcasletadd>>& for
18939 .vindex "&$local_part$&"
18940 .vindex "&$original_local_part$&"
18941 .vindex "&$parent_local_part$&"
18942 The value of the &$local_part$& variable is forced to lower case while a
18943 router is running unless &%caseful_local_part%& is set. When a router assigns
18944 an address to a transport, the value of &$local_part$& when the transport runs
18945 is the same as it was in the router. Similarly, when a router generates child
18946 addresses by aliasing or forwarding, the values of &$original_local_part$&
18947 and &$parent_local_part$& are those that were used by the redirecting router.
18949 This option applies to the processing of an address by a router. When a
18950 recipient address is being processed in an ACL, there is a separate &%control%&
18951 modifier that can be used to specify case-sensitive processing within the ACL
18952 (see section &<<SECTcontrols>>&).
18956 .option check_local_user routers&!? boolean false
18957 .cindex "local user, checking in router"
18958 .cindex "router" "checking for local user"
18959 .cindex "&_/etc/passwd_&"
18961 When this option is true, Exim checks that the local part of the recipient
18962 address (with affixes removed if relevant) is the name of an account on the
18963 local system. The check is done by calling the &[getpwnam()]& function rather
18964 than trying to read &_/etc/passwd_& directly. This means that other methods of
18965 holding password data (such as NIS) are supported. If the local part is a local
18967 .cindex "tainted data" "de-tainting"
18968 .cindex "de-tainting" "using router check_local_user option"
18969 &$local_part_data$& is set to an untainted version of the local part and
18970 &$home$& is set from the password data. The latter can be tested in other
18971 preconditions that are evaluated after this one (the order of evaluation is
18972 given in section &<<SECTrouprecon>>&). However, the value of &$home$& can be
18973 overridden by &%router_home_directory%&. If the local part is not a local user,
18974 the router is skipped.
18976 If you want to check that the local part is either the name of a local user
18977 or matches something else, you cannot combine &%check_local_user%& with a
18978 setting of &%local_parts%&, because that specifies the logical &'and'& of the
18979 two conditions. However, you can use a &(passwd)& lookup in a &%local_parts%&
18980 setting to achieve this. For example:
18982 local_parts = passwd;$local_part : lsearch;/etc/other/users
18984 Note, however, that the side effects of &%check_local_user%& (such as setting
18985 up a home directory) do not occur when a &(passwd)& lookup is used in a
18986 &%local_parts%& (or any other) precondition.
18990 .option condition routers&!? string&!! unset
18991 .cindex "router" "customized precondition"
18992 This option specifies a general precondition test that has to succeed for the
18993 router to be called. The &%condition%& option is the last precondition to be
18994 evaluated (see section &<<SECTrouprecon>>&). The string is expanded, and if the
18995 result is a forced failure, or an empty string, or one of the strings &"0"& or
18996 &"no"& or &"false"& (checked without regard to the case of the letters), the
18997 router is skipped, and the address is offered to the next one.
18999 If the result is any other value, the router is run (as this is the last
19000 precondition to be evaluated, all the other preconditions must be true).
19002 This option is unusual in that multiple &%condition%& options may be present.
19003 All &%condition%& options must succeed.
19005 The &%condition%& option provides a means of applying custom conditions to the
19006 running of routers. Note that in the case of a simple conditional expansion,
19007 the default expansion values are exactly what is wanted. For example:
19009 condition = ${if >{$message_age}{600}}
19011 Because of the default behaviour of the string expansion, this is equivalent to
19013 condition = ${if >{$message_age}{600}{true}{}}
19016 A multiple condition example, which succeeds:
19018 condition = ${if >{$message_age}{600}}
19019 condition = ${if !eq{${lc:$local_part}}{postmaster}}
19023 If the expansion fails (other than forced failure) delivery is deferred. Some
19024 of the other precondition options are common special cases that could in fact
19025 be specified using &%condition%&.
19027 Historical note: We have &%condition%& on ACLs and on Routers. Routers
19028 are far older, and use one set of semantics. ACLs are newer and when
19029 they were created, the ACL &%condition%& process was given far stricter
19030 parse semantics. The &%bool{}%& expansion condition uses the same rules as
19031 ACLs. The &%bool_lax{}%& expansion condition uses the same rules as
19032 Routers. More pointedly, the &%bool_lax{}%& was written to match the existing
19033 Router rules processing behavior.
19035 This is best illustrated in an example:
19037 # If used in an ACL condition will fail with a syntax error, but
19038 # in a router condition any extra characters are treated as a string
19040 $ exim -be '${if eq {${lc:GOOGLE.com}} {google.com}} {yes} {no}}'
19043 $ exim -be '${if eq {${lc:WHOIS.com}} {google.com}} {yes} {no}}'
19046 In each example above, the &%if%& statement actually ends after
19047 &"{google.com}}"&. Since no true or false braces were defined, the
19048 default &%if%& behavior is to return a boolean true or a null answer
19049 (which evaluates to false). The rest of the line is then treated as a
19050 string. So the first example resulted in the boolean answer &"true"&
19051 with the string &" {yes} {no}}"& appended to it. The second example
19052 resulted in the null output (indicating false) with the string
19053 &" {yes} {no}}"& appended to it.
19055 In fact you can put excess forward braces in too. In the router
19056 &%condition%&, Exim's parser only looks for &"{"& symbols when they
19057 mean something, like after a &"$"& or when required as part of a
19058 conditional. But otherwise &"{"& and &"}"& are treated as ordinary
19061 Thus, in a Router, the above expansion strings will both always evaluate
19062 true, as the result of expansion is a non-empty string which doesn't
19063 match an explicit false value. This can be tricky to debug. By
19064 contrast, in an ACL either of those strings will always result in an
19065 expansion error because the result doesn't look sufficiently boolean.
19068 .option debug_print routers string&!! unset
19069 .cindex "testing" "variables in drivers"
19070 If this option is set and debugging is enabled (see the &%-d%& command line
19071 option) or in address-testing mode (see the &%-bt%& command line option),
19072 the string is expanded and included in the debugging output.
19073 If expansion of the string fails, the error message is written to the debugging
19074 output, and Exim carries on processing.
19075 This option is provided to help with checking out the values of variables and
19076 so on when debugging router configurations. For example, if a &%condition%&
19077 option appears not to be working, &%debug_print%& can be used to output the
19078 variables it references. The output happens after checks for &%domains%&,
19079 &%local_parts%&, and &%check_local_user%& but before any other preconditions
19080 are tested. A newline is added to the text if it does not end with one.
19081 The variable &$router_name$& contains the name of the router.
19085 .option disable_logging routers boolean false
19086 If this option is set true, nothing is logged for any routing errors
19087 or for any deliveries caused by this router. You should not set this option
19088 unless you really, really know what you are doing. See also the generic
19089 transport option of the same name.
19091 .option dnssec_request_domains routers "domain list&!!" *
19092 .cindex "MX record" "security"
19093 .cindex "DNSSEC" "MX lookup"
19094 .cindex "security" "MX lookup"
19095 .cindex "DNS" "DNSSEC"
19096 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
19097 the DNSSEC request bit set.
19098 This applies to all of the SRV, MX, AAAA, A lookup sequence.
19100 .option dnssec_require_domains routers "domain list&!!" unset
19101 .cindex "MX record" "security"
19102 .cindex "DNSSEC" "MX lookup"
19103 .cindex "security" "MX lookup"
19104 .cindex "DNS" "DNSSEC"
19105 DNS lookups for domains matching &%dnssec_require_domains%& will be done with
19106 the DNSSEC request bit set. Any returns not having the Authenticated Data bit
19107 (AD bit) set will be ignored and logged as a host-lookup failure.
19108 This applies to all of the SRV, MX, AAAA, A lookup sequence.
19111 .option domains routers&!? "domain list&!!" unset
19112 .cindex "router" "restricting to specific domains"
19113 .vindex "&$domain_data$&"
19114 If this option is set, the router is skipped unless the current domain matches
19115 the list. If the match is achieved by means of a file lookup, the data that the
19116 lookup returned for the domain is placed in &$domain_data$& for use in string
19117 expansions of the driver's private options and in the transport.
19118 See section &<<SECTrouprecon>>& for
19119 a list of the order in which preconditions are evaluated.
19123 .option driver routers string unset
19124 This option must always be set. It specifies which of the available routers is
19128 .option dsn_lasthop routers boolean false
19129 .cindex "DSN" "success"
19130 .cindex "Delivery Status Notification" "success"
19131 If this option is set true, and extended DSN (RFC3461) processing is in effect,
19132 Exim will not pass on DSN requests to downstream DSN-aware hosts but will
19133 instead send a success DSN as if the next hop does not support DSN.
19134 Not effective on redirect routers.
19138 .option errors_to routers string&!! unset
19139 .cindex "envelope from"
19140 .cindex "envelope sender"
19141 .cindex "router" "changing address for errors"
19142 If a router successfully handles an address, it may assign the address to a
19143 transport for delivery or it may generate child addresses. In both cases, if
19144 there is a delivery problem during later processing, the resulting bounce
19145 message is sent to the address that results from expanding this string,
19146 provided that the address verifies successfully. The &%errors_to%& option is
19147 expanded before &%headers_add%&, &%headers_remove%&, and &%transport%&.
19149 The &%errors_to%& setting associated with an address can be overridden if it
19150 subsequently passes through other routers that have their own &%errors_to%&
19151 settings, or if the message is delivered by a transport with a &%return_path%&
19154 If &%errors_to%& is unset, or the expansion is forced to fail, or the result of
19155 the expansion fails to verify, the errors address associated with the incoming
19156 address is used. At top level, this is the envelope sender. A non-forced
19157 expansion failure causes delivery to be deferred.
19159 If an address for which &%errors_to%& has been set ends up being delivered over
19160 SMTP, the envelope sender for that delivery is the &%errors_to%& value, so that
19161 any bounces that are generated by other MTAs on the delivery route are also
19162 sent there. You can set &%errors_to%& to the empty string by either of these
19168 An expansion item that yields an empty string has the same effect. If you do
19169 this, a locally detected delivery error for addresses processed by this router
19170 no longer gives rise to a bounce message; the error is discarded. If the
19171 address is delivered to a remote host, the return path is set to &`<>`&, unless
19172 overridden by the &%return_path%& option on the transport.
19174 .vindex "&$address_data$&"
19175 If for some reason you want to discard local errors, but use a non-empty
19176 MAIL command for remote delivery, you can preserve the original return
19177 path in &$address_data$& in the router, and reinstate it in the transport by
19178 setting &%return_path%&.
19180 The most common use of &%errors_to%& is to direct mailing list bounces to the
19181 manager of the list, as described in section &<<SECTmailinglists>>&, or to
19182 implement VERP (Variable Envelope Return Paths) (see section &<<SECTverp>>&).
19186 .option expn routers&!? boolean true
19187 .cindex "address" "testing"
19188 .cindex "testing" "addresses"
19189 .cindex "EXPN" "router skipping"
19190 .cindex "router" "skipping for EXPN"
19191 If this option is turned off, the router is skipped when testing an address
19192 as a result of processing an SMTP EXPN command. You might, for example,
19193 want to turn it off on a router for users' &_.forward_& files, while leaving it
19194 on for the system alias file.
19195 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19198 The use of the SMTP EXPN command is controlled by an ACL (see chapter
19199 &<<CHAPACL>>&). When Exim is running an EXPN command, it is similar to testing
19200 an address with &%-bt%&. Compare VRFY, whose counterpart is &%-bv%&.
19204 .option fail_verify routers boolean false
19205 .cindex "router" "forcing verification failure"
19206 Setting this option has the effect of setting both &%fail_verify_sender%& and
19207 &%fail_verify_recipient%& to the same value.
19211 .option fail_verify_recipient routers boolean false
19212 If this option is true and an address is accepted by this router when
19213 verifying a recipient, verification fails.
19217 .option fail_verify_sender routers boolean false
19218 If this option is true and an address is accepted by this router when
19219 verifying a sender, verification fails.
19223 .option fallback_hosts routers "string list" unset
19224 .cindex "router" "fallback hosts"
19225 .cindex "fallback" "hosts specified on router"
19226 String expansion is not applied to this option. The argument must be a
19227 colon-separated list of host names or IP addresses. The list separator can be
19228 changed (see section &<<SECTlistsepchange>>&), and a port can be specified with
19229 each name or address. In fact, the format of each item is exactly the same as
19230 defined for the list of hosts in a &(manualroute)& router (see section
19231 &<<SECTformatonehostitem>>&).
19233 If a router queues an address for a remote transport, this host list is
19234 associated with the address, and used instead of the transport's fallback host
19235 list. If &%hosts_randomize%& is set on the transport, the order of the list is
19236 randomized for each use. See the &%fallback_hosts%& option of the &(smtp)&
19237 transport for further details.
19240 .option group routers string&!! "see below"
19241 .cindex "gid (group id)" "local delivery"
19242 .cindex "local transports" "uid and gid"
19243 .cindex "transport" "local"
19244 .cindex "router" "setting group"
19245 When a router queues an address for a transport, and the transport does not
19246 specify a group, the group given here is used when running the delivery
19248 The group may be specified numerically or by name. If expansion fails, the
19249 error is logged and delivery is deferred.
19250 The default is unset, unless &%check_local_user%& is set, when the default
19251 is taken from the password information. See also &%initgroups%& and &%user%&
19252 and the discussion in chapter &<<CHAPenvironment>>&.
19256 .option headers_add routers list&!! unset
19257 .cindex "header lines" "adding"
19258 .cindex "router" "adding header lines"
19259 This option specifies a list of text headers,
19260 newline-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
19261 that is associated with any addresses that are accepted by the router.
19262 Each item is separately expanded, at routing time. However, this
19263 option has no effect when an address is just being verified. The way in which
19264 the text is used to add header lines at transport time is described in section
19265 &<<SECTheadersaddrem>>&. New header lines are not actually added until the
19266 message is in the process of being transported. This means that references to
19267 header lines in string expansions in the transport's configuration do not
19268 &"see"& the added header lines.
19270 The &%headers_add%& option is expanded after &%errors_to%&, but before
19271 &%headers_remove%& and &%transport%&. If an item is empty, or if
19272 an item expansion is forced to fail, the item has no effect. Other expansion
19273 failures are treated as configuration errors.
19275 Unlike most options, &%headers_add%& can be specified multiple times
19276 for a router; all listed headers are added.
19278 &*Warning 1*&: The &%headers_add%& option cannot be used for a &(redirect)&
19279 router that has the &%one_time%& option set.
19281 .cindex "duplicate addresses"
19282 .oindex "&%unseen%&"
19283 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
19284 additions are deleted when the address is passed on to subsequent routers.
19285 For a &%redirect%& router, if a generated address is the same as the incoming
19286 address, this can lead to duplicate addresses with different header
19287 modifications. Exim does not do duplicate deliveries (except, in certain
19288 circumstances, to pipes -- see section &<<SECTdupaddr>>&), but it is undefined
19289 which of the duplicates is discarded, so this ambiguous situation should be
19290 avoided. The &%repeat_use%& option of the &%redirect%& router may be of help.
19294 .option headers_remove routers list&!! unset
19295 .cindex "header lines" "removing"
19296 .cindex "router" "removing header lines"
19297 This option specifies a list of text headers,
19298 colon-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
19299 that is associated with any addresses that are accepted by the router.
19300 However, the option has no effect when an address is just being verified.
19301 Each list item is separately expanded, at transport time.
19302 If an item ends in *, it will match any header with the given prefix.
19304 the text is used to remove header lines at transport time is described in
19305 section &<<SECTheadersaddrem>>&. Header lines are not actually removed until
19306 the message is in the process of being transported. This means that references
19307 to header lines in string expansions in the transport's configuration still
19308 &"see"& the original header lines.
19310 The &%headers_remove%& option is handled after &%errors_to%& and
19311 &%headers_add%&, but before &%transport%&. If an item expansion is forced to fail,
19312 the item has no effect. Other expansion failures are treated as configuration
19315 Unlike most options, &%headers_remove%& can be specified multiple times
19316 for a router; all listed headers are removed.
19318 &*Warning 1*&: The &%headers_remove%& option cannot be used for a &(redirect)&
19319 router that has the &%one_time%& option set.
19321 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
19322 removal requests are deleted when the address is passed on to subsequent
19323 routers, and this can lead to problems with duplicates -- see the similar
19324 warning for &%headers_add%& above.
19326 &*Warning 3*&: Because of the separate expansion of the list items,
19327 items that contain a list separator must have it doubled.
19328 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
19332 .option ignore_target_hosts routers "host list&!!" unset
19333 .cindex "IP address" "discarding"
19334 .cindex "router" "discarding IP addresses"
19335 Although this option is a host list, it should normally contain IP address
19336 entries rather than names. If any host that is looked up by the router has an
19337 IP address that matches an item in this list, Exim behaves as if that IP
19338 address did not exist. This option allows you to cope with rogue DNS entries
19341 remote.domain.example. A 127.0.0.1
19345 ignore_target_hosts = 127.0.0.1
19347 on the relevant router. If all the hosts found by a &(dnslookup)& router are
19348 discarded in this way, the router declines. In a conventional configuration, an
19349 attempt to mail to such a domain would normally provoke the &"unrouteable
19350 domain"& error, and an attempt to verify an address in the domain would fail.
19351 Similarly, if &%ignore_target_hosts%& is set on an &(ipliteral)& router, the
19352 router declines if presented with one of the listed addresses.
19354 You can use this option to disable the use of IPv4 or IPv6 for mail delivery by
19355 means of the first or the second of the following settings, respectively:
19357 ignore_target_hosts = 0.0.0.0/0
19358 ignore_target_hosts = <; 0::0/0
19360 The pattern in the first line matches all IPv4 addresses, whereas the pattern
19361 in the second line matches all IPv6 addresses.
19363 This option may also be useful for ignoring link-local and site-local IPv6
19364 addresses. Because, like all host lists, the value of &%ignore_target_hosts%&
19365 is expanded before use as a list, it is possible to make it dependent on the
19366 domain that is being routed.
19368 .vindex "&$host_address$&"
19369 During its expansion, &$host_address$& is set to the IP address that is being
19372 .option initgroups routers boolean false
19373 .cindex "additional groups"
19374 .cindex "groups" "additional"
19375 .cindex "local transports" "uid and gid"
19376 .cindex "transport" "local"
19377 If the router queues an address for a transport, and this option is true, and
19378 the uid supplied by the router is not overridden by the transport, the
19379 &[initgroups()]& function is called when running the transport to ensure that
19380 any additional groups associated with the uid are set up. See also &%group%&
19381 and &%user%& and the discussion in chapter &<<CHAPenvironment>>&.
19385 .option local_part_prefix routers&!? "string list" unset
19386 .cindex affix "router precondition"
19387 .cindex "router" "prefix for local part"
19388 .cindex "prefix" "for local part, used in router"
19389 If this option is set, the router is skipped unless the local part starts with
19390 one of the given strings, or &%local_part_prefix_optional%& is true. See
19391 section &<<SECTrouprecon>>& for a list of the order in which preconditions are
19394 The list is scanned from left to right, and the first prefix that matches is
19395 used. A limited form of wildcard is available; if the prefix begins with an
19396 asterisk, it matches the longest possible sequence of arbitrary characters at
19397 the start of the local part. An asterisk should therefore always be followed by
19398 some character that does not occur in normal local parts.
19399 .cindex "multiple mailboxes"
19400 .cindex "mailbox" "multiple"
19401 Wildcarding can be used to set up multiple user mailboxes, as described in
19402 section &<<SECTmulbox>>&.
19404 .vindex "&$local_part$&"
19405 .vindex "&$local_part_prefix$&"
19406 During the testing of the &%local_parts%& option, and while the router is
19407 running, the prefix is removed from the local part, and is available in the
19408 expansion variable &$local_part_prefix$&. When a message is being delivered, if
19409 the router accepts the address, this remains true during subsequent delivery by
19410 a transport. In particular, the local part that is transmitted in the RCPT
19411 command for LMTP, SMTP, and BSMTP deliveries has the prefix removed by default.
19412 This behaviour can be overridden by setting &%rcpt_include_affixes%& true on
19413 the relevant transport.
19415 .vindex &$local_part_prefix_v$&
19416 If wildcarding (above) was used then the part of the prefix matching the
19417 wildcard is available in &$local_part_prefix_v$&.
19419 When an address is being verified, &%local_part_prefix%& affects only the
19420 behaviour of the router. If the callout feature of verification is in use, this
19421 means that the full address, including the prefix, will be used during the
19424 The prefix facility is commonly used to handle local parts of the form
19425 &%owner-something%&. Another common use is to support local parts of the form
19426 &%real-username%& to bypass a user's &_.forward_& file &-- helpful when trying
19427 to tell a user their forwarding is broken &-- by placing a router like this one
19428 immediately before the router that handles &_.forward_& files:
19432 local_part_prefix = real-
19434 transport = local_delivery
19436 For security, it would probably be a good idea to restrict the use of this
19437 router to locally-generated messages, using a condition such as this:
19439 condition = ${if match {$sender_host_address}\
19440 {\N^(|127\.0\.0\.1)$\N}}
19443 If both &%local_part_prefix%& and &%local_part_suffix%& are set for a router,
19444 both conditions must be met if not optional. Care must be taken if wildcards
19445 are used in both a prefix and a suffix on the same router. Different
19446 separator characters must be used to avoid ambiguity.
19449 .option local_part_prefix_optional routers boolean false
19450 See &%local_part_prefix%& above.
19454 .option local_part_suffix routers&!? "string list" unset
19455 .cindex "router" "suffix for local part"
19456 .cindex "suffix for local part" "used in router"
19457 This option operates in the same way as &%local_part_prefix%&, except that the
19458 local part must end (rather than start) with the given string, the
19459 &%local_part_suffix_optional%& option determines whether the suffix is
19460 mandatory, and the wildcard * character, if present, must be the last
19461 character of the suffix. This option facility is commonly used to handle local
19462 parts of the form &%something-request%& and multiple user mailboxes of the form
19466 .option local_part_suffix_optional routers boolean false
19467 See &%local_part_suffix%& above.
19471 .option local_parts routers&!? "local part list&!!" unset
19472 .cindex "router" "restricting to specific local parts"
19473 .cindex "local part" "checking in router"
19474 The router is run only if the local part of the address matches the list.
19475 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19477 section &<<SECTlocparlis>>& for a discussion of local part lists. Because the
19478 string is expanded, it is possible to make it depend on the domain, for
19481 local_parts = dbm;/usr/local/specials/$domain_data
19483 .vindex "&$local_part_data$&"
19484 If the match is achieved by a lookup, the data that the lookup returned
19485 for the local part is placed in the variable &$local_part_data$& for use in
19486 expansions of the router's private options or in the transport.
19487 You might use this option, for
19488 example, if you have a large number of local virtual domains, and you want to
19489 send all postmaster mail to the same place without having to set up an alias in
19490 each virtual domain:
19494 local_parts = postmaster
19495 data = postmaster@real.domain.example
19499 .option log_as_local routers boolean "see below"
19500 .cindex "log" "delivery line"
19501 .cindex "delivery" "log line format"
19502 Exim has two logging styles for delivery, the idea being to make local
19503 deliveries stand out more visibly from remote ones. In the &"local"& style, the
19504 recipient address is given just as the local part, without a domain. The use of
19505 this style is controlled by this option. It defaults to true for the &(accept)&
19506 router, and false for all the others. This option applies only when a
19507 router assigns an address to a transport. It has no effect on routers that
19508 redirect addresses.
19512 .option more routers boolean&!! true
19513 The result of string expansion for this option must be a valid boolean value,
19514 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
19515 result causes an error, and delivery is deferred. If the expansion is forced to
19516 fail, the default value for the option (true) is used. Other failures cause
19517 delivery to be deferred.
19519 If this option is set false, and the router declines to handle the address, no
19520 further routers are tried, routing fails, and the address is bounced.
19522 However, if the router explicitly passes an address to the following router by
19523 means of the setting
19527 or otherwise, the setting of &%more%& is ignored. Also, the setting of &%more%&
19528 does not affect the behaviour if one of the precondition tests fails. In that
19529 case, the address is always passed to the next router.
19531 Note that &%address_data%& is not considered to be a precondition. If its
19532 expansion is forced to fail, the router declines, and the value of &%more%&
19533 controls what happens next.
19536 .option pass_on_timeout routers boolean false
19537 .cindex "timeout" "of router"
19538 .cindex "router" "timeout"
19539 If a router times out during a host lookup, it normally causes deferral of the
19540 address. If &%pass_on_timeout%& is set, the address is passed on to the next
19541 router, overriding &%no_more%&. This may be helpful for systems that are
19542 intermittently connected to the Internet, or those that want to pass to a smart
19543 host any messages that cannot immediately be delivered.
19545 There are occasional other temporary errors that can occur while doing DNS
19546 lookups. They are treated in the same way as a timeout, and this option
19547 applies to all of them.
19551 .option pass_router routers string unset
19552 .cindex "router" "go to after &""pass""&"
19553 Routers that recognize the generic &%self%& option (&(dnslookup)&,
19554 &(ipliteral)&, and &(manualroute)&) are able to return &"pass"&, forcing
19555 routing to continue, and overriding a false setting of &%more%&. When one of
19556 these routers returns &"pass"&, the address is normally handed on to the next
19557 router in sequence. This can be changed by setting &%pass_router%& to the name
19558 of another router. However (unlike &%redirect_router%&) the named router must
19559 be below the current router, to avoid loops. Note that this option applies only
19560 to the special case of &"pass"&. It does not apply when a router returns
19561 &"decline"& because it cannot handle an address.
19565 .option redirect_router routers string unset
19566 .cindex "router" "start at after redirection"
19567 Sometimes an administrator knows that it is pointless to reprocess addresses
19568 generated from alias or forward files with the same router again. For
19569 example, if an alias file translates real names into login ids there is no
19570 point searching the alias file a second time, especially if it is a large file.
19572 The &%redirect_router%& option can be set to the name of any router instance.
19573 It causes the routing of any generated addresses to start at the named router
19574 instead of at the first router. This option has no effect if the router in
19575 which it is set does not generate new addresses.
19579 .option require_files routers&!? "string list&!!" unset
19580 .cindex "file" "requiring for router"
19581 .cindex "router" "requiring file existence"
19582 This option provides a general mechanism for predicating the running of a
19583 router on the existence or non-existence of certain files or directories.
19584 Before running a router, as one of its precondition tests, Exim works its way
19585 through the &%require_files%& list, expanding each item separately.
19587 Because the list is split before expansion, any colons in expansion items must
19588 be doubled, or the facility for using a different list separator must be used
19589 (&<<SECTlistsepchange>>&).
19590 If any expansion is forced to fail, the item is ignored. Other expansion
19591 failures cause routing of the address to be deferred.
19593 If any expanded string is empty, it is ignored. Otherwise, except as described
19594 below, each string must be a fully qualified file path, optionally preceded by
19595 &"!"&. The paths are passed to the &[stat()]& function to test for the
19596 existence of the files or directories. The router is skipped if any paths not
19597 preceded by &"!"& do not exist, or if any paths preceded by &"!"& do exist.
19600 If &[stat()]& cannot determine whether a file exists or not, delivery of
19601 the message is deferred. This can happen when NFS-mounted filesystems are
19604 This option is checked after the &%domains%&, &%local_parts%&, and &%senders%&
19605 options, so you cannot use it to check for the existence of a file in which to
19606 look up a domain, local part, or sender. (See section &<<SECTrouprecon>>& for a
19607 full list of the order in which preconditions are evaluated.) However, as
19608 these options are all expanded, you can use the &%exists%& expansion condition
19609 to make such tests. The &%require_files%& option is intended for checking files
19610 that the router may be going to use internally, or which are needed by a
19611 transport (e.g., &_.procmailrc_&).
19613 During delivery, the &[stat()]& function is run as root, but there is a
19614 facility for some checking of the accessibility of a file by another user.
19615 This is not a proper permissions check, but just a &"rough"& check that
19616 operates as follows:
19618 If an item in a &%require_files%& list does not contain any forward slash
19619 characters, it is taken to be the user (and optional group, separated by a
19620 comma) to be checked for subsequent files in the list. If no group is specified
19621 but the user is specified symbolically, the gid associated with the uid is
19624 require_files = mail:/some/file
19625 require_files = $local_part_data:$home/.procmailrc
19627 If a user or group name in a &%require_files%& list does not exist, the
19628 &%require_files%& condition fails.
19630 Exim performs the check by scanning along the components of the file path, and
19631 checking the access for the given uid and gid. It checks for &"x"& access on
19632 directories, and &"r"& access on the final file. Note that this means that file
19633 access control lists, if the operating system has them, are ignored.
19635 &*Warning 1*&: When the router is being run to verify addresses for an
19636 incoming SMTP message, Exim is not running as root, but under its own uid. This
19637 may affect the result of a &%require_files%& check. In particular, &[stat()]&
19638 may yield the error EACCES (&"Permission denied"&). This means that the Exim
19639 user is not permitted to read one of the directories on the file's path.
19641 &*Warning 2*&: Even when Exim is running as root while delivering a message,
19642 &[stat()]& can yield EACCES for a file in an NFS directory that is mounted
19643 without root access. In this case, if a check for access by a particular user
19644 is requested, Exim creates a subprocess that runs as that user, and tries the
19645 check again in that process.
19647 The default action for handling an unresolved EACCES is to consider it to
19648 be caused by a configuration error, and routing is deferred because the
19649 existence or non-existence of the file cannot be determined. However, in some
19650 circumstances it may be desirable to treat this condition as if the file did
19651 not exist. If the filename (or the exclamation mark that precedes the filename
19652 for non-existence) is preceded by a plus sign, the EACCES error is treated
19653 as if the file did not exist. For example:
19655 require_files = +/some/file
19657 If the router is not an essential part of verification (for example, it
19658 handles users' &_.forward_& files), another solution is to set the &%verify%&
19659 option false so that the router is skipped when verifying.
19663 .option retry_use_local_part routers boolean "see below"
19664 .cindex "hints database" "retry keys"
19665 .cindex "local part" "in retry keys"
19666 When a delivery suffers a temporary routing failure, a retry record is created
19667 in Exim's hints database. For addresses whose routing depends only on the
19668 domain, the key for the retry record should not involve the local part, but for
19669 other addresses, both the domain and the local part should be included.
19670 Usually, remote routing is of the former kind, and local routing is of the
19673 This option controls whether the local part is used to form the key for retry
19674 hints for addresses that suffer temporary errors while being handled by this
19675 router. The default value is true for any router that has any of
19676 &%check_local_user%&,
19679 &%local_part_prefix%&,
19680 &%local_part_suffix%&,
19683 set, and false otherwise. Note that this option does not apply to hints keys
19684 for transport delays; they are controlled by a generic transport option of the
19687 Failing to set this option when it is needed
19688 (because a remote router handles only some of the local-parts for a domain)
19689 can result in incorrect error messages being generated.
19691 The setting of &%retry_use_local_part%& applies only to the router on which it
19692 appears. If the router generates child addresses, they are routed
19693 independently; this setting does not become attached to them.
19697 .option router_home_directory routers string&!! unset
19698 .cindex "router" "home directory for"
19699 .cindex "home directory" "for router"
19701 This option sets a home directory for use while the router is running. (Compare
19702 &%transport_home_directory%&, which sets a home directory for later
19703 transporting.) In particular, if used on a &(redirect)& router, this option
19704 sets a value for &$home$& while a filter is running. The value is expanded;
19705 forced expansion failure causes the option to be ignored &-- other failures
19706 cause the router to defer.
19708 Expansion of &%router_home_directory%& happens immediately after the
19709 &%check_local_user%& test (if configured), before any further expansions take
19711 (See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19713 While the router is running, &%router_home_directory%& overrides the value of
19714 &$home$& that came from &%check_local_user%&.
19716 When a router accepts an address and assigns it to a local transport (including
19717 the cases when a &(redirect)& router generates a pipe, file, or autoreply
19718 delivery), the home directory setting for the transport is taken from the first
19719 of these values that is set:
19722 The &%home_directory%& option on the transport;
19724 The &%transport_home_directory%& option on the router;
19726 The password data if &%check_local_user%& is set on the router;
19728 The &%router_home_directory%& option on the router.
19731 In other words, &%router_home_directory%& overrides the password data for the
19732 router, but not for the transport.
19736 .option self routers string freeze
19737 .cindex "MX record" "pointing to local host"
19738 .cindex "local host" "MX pointing to"
19739 This option applies to those routers that use a recipient address to find a
19740 list of remote hosts. Currently, these are the &(dnslookup)&, &(ipliteral)&,
19741 and &(manualroute)& routers.
19742 Certain configurations of the &(queryprogram)& router can also specify a list
19744 Usually such routers are configured to send the message to a remote host via an
19745 &(smtp)& transport. The &%self%& option specifies what happens when the first
19746 host on the list turns out to be the local host.
19747 The way in which Exim checks for the local host is described in section
19748 &<<SECTreclocipadd>>&.
19750 Normally this situation indicates either an error in Exim's configuration (for
19751 example, the router should be configured not to process this domain), or an
19752 error in the DNS (for example, the MX should not point to this host). For this
19753 reason, the default action is to log the incident, defer the address, and
19754 freeze the message. The following alternatives are provided for use in special
19759 Delivery of the message is tried again later, but the message is not frozen.
19761 .vitem "&%reroute%&: <&'domain'&>"
19762 The domain is changed to the given domain, and the address is passed back to
19763 be reprocessed by the routers. No rewriting of headers takes place. This
19764 behaviour is essentially a redirection.
19766 .vitem "&%reroute: rewrite:%& <&'domain'&>"
19767 The domain is changed to the given domain, and the address is passed back to be
19768 reprocessed by the routers. Any headers that contain the original domain are
19773 .vindex "&$self_hostname$&"
19774 The router passes the address to the next router, or to the router named in the
19775 &%pass_router%& option if it is set. This overrides &%no_more%&. During
19776 subsequent routing and delivery, the variable &$self_hostname$& contains the
19777 name of the local host that the router encountered. This can be used to
19778 distinguish between different cases for hosts with multiple names. The
19784 ensures that only those addresses that routed to the local host are passed on.
19785 Without &%no_more%&, addresses that were declined for other reasons would also
19786 be passed to the next router.
19789 Delivery fails and an error report is generated.
19792 .cindex "local host" "sending to"
19793 The anomaly is ignored and the address is queued for the transport. This
19794 setting should be used with extreme caution. For an &(smtp)& transport, it
19795 makes sense only in cases where the program that is listening on the SMTP port
19796 is not this version of Exim. That is, it must be some other MTA, or Exim with a
19797 different configuration file that handles the domain in another way.
19802 .option senders routers&!? "address list&!!" unset
19803 .cindex "router" "checking senders"
19804 If this option is set, the router is skipped unless the message's sender
19805 address matches something on the list.
19806 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19809 There are issues concerning verification when the running of routers is
19810 dependent on the sender. When Exim is verifying the address in an &%errors_to%&
19811 setting, it sets the sender to the null string. When using the &%-bt%& option
19812 to check a configuration file, it is necessary also to use the &%-f%& option to
19813 set an appropriate sender. For incoming mail, the sender is unset when
19814 verifying the sender, but is available when verifying any recipients. If the
19815 SMTP VRFY command is enabled, it must be used after MAIL if the sender address
19819 .option set routers "string list" unset
19820 .cindex router variables
19821 This option may be used multiple times on a router;
19822 because of this the list aspect is mostly irrelevant.
19823 The list separator is a semicolon but can be changed in the
19826 Each list-element given must be of the form &"name = value"&
19827 and the names used must start with the string &"r_"&.
19828 Values containing a list-separator should have them doubled.
19829 When a router runs, the strings are evaluated in order,
19830 to create variables which are added to the set associated with
19832 This is done immediately after all the preconditions, before the
19833 evaluation of the &%address_data%& option.
19834 The variable is set with the expansion of the value.
19835 The variables can be used by the router options
19836 (not including any preconditions)
19837 and by the transport.
19838 Later definitions of a given named variable will override former ones.
19839 Variable use is via the usual &$r_...$& syntax.
19841 This is similar to the &%address_data%& option, except that
19842 many independent variables can be used, with choice of naming.
19845 .option translate_ip_address routers string&!! unset
19846 .cindex "IP address" "translating"
19847 .cindex "packet radio"
19848 .cindex "router" "IP address translation"
19849 There exist some rare networking situations (for example, packet radio) where
19850 it is helpful to be able to translate IP addresses generated by normal routing
19851 mechanisms into other IP addresses, thus performing a kind of manual IP
19852 routing. This should be done only if the normal IP routing of the TCP/IP stack
19853 is inadequate or broken. Because this is an extremely uncommon requirement, the
19854 code to support this option is not included in the Exim binary unless
19855 SUPPORT_TRANSLATE_IP_ADDRESS=yes is set in &_Local/Makefile_&.
19857 .vindex "&$host_address$&"
19858 The &%translate_ip_address%& string is expanded for every IP address generated
19859 by the router, with the generated address set in &$host_address$&. If the
19860 expansion is forced to fail, no action is taken.
19861 For any other expansion error, delivery of the message is deferred.
19862 If the result of the expansion is an IP address, that replaces the original
19863 address; otherwise the result is assumed to be a host name &-- this is looked
19864 up using &[gethostbyname()]& (or &[getipnodebyname()]& when available) to
19865 produce one or more replacement IP addresses. For example, to subvert all IP
19866 addresses in some specific networks, this could be added to a router:
19868 translate_ip_address = \
19869 ${lookup{${mask:$host_address/26}}lsearch{/some/file}\
19872 The file would contain lines like
19874 10.2.3.128/26 some.host
19875 10.8.4.34/26 10.44.8.15
19877 You should not make use of this facility unless you really understand what you
19882 .option transport routers string&!! unset
19883 This option specifies the transport to be used when a router accepts an address
19884 and sets it up for delivery. A transport is never needed if a router is used
19885 only for verification. The value of the option is expanded at routing time,
19886 after the expansion of &%errors_to%&, &%headers_add%&, and &%headers_remove%&,
19887 and result must be the name of one of the configured transports. If it is not,
19888 delivery is deferred.
19890 The &%transport%& option is not used by the &(redirect)& router, but it does
19891 have some private options that set up transports for pipe and file deliveries
19892 (see chapter &<<CHAPredirect>>&).
19896 .option transport_current_directory routers string&!! unset
19897 .cindex "current directory for local transport"
19898 This option associates a current directory with any address that is routed
19899 to a local transport. This can happen either because a transport is
19900 explicitly configured for the router, or because it generates a delivery to a
19901 file or a pipe. During the delivery process (that is, at transport time), this
19902 option string is expanded and is set as the current directory, unless
19903 overridden by a setting on the transport.
19904 If the expansion fails for any reason, including forced failure, an error is
19905 logged, and delivery is deferred.
19906 See chapter &<<CHAPenvironment>>& for details of the local delivery
19912 .option transport_home_directory routers string&!! "see below"
19913 .cindex "home directory" "for local transport"
19914 This option associates a home directory with any address that is routed to a
19915 local transport. This can happen either because a transport is explicitly
19916 configured for the router, or because it generates a delivery to a file or a
19917 pipe. During the delivery process (that is, at transport time), the option
19918 string is expanded and is set as the home directory, unless overridden by a
19919 setting of &%home_directory%& on the transport.
19920 If the expansion fails for any reason, including forced failure, an error is
19921 logged, and delivery is deferred.
19923 If the transport does not specify a home directory, and
19924 &%transport_home_directory%& is not set for the router, the home directory for
19925 the transport is taken from the password data if &%check_local_user%& is set for
19926 the router. Otherwise it is taken from &%router_home_directory%& if that option
19927 is set; if not, no home directory is set for the transport.
19929 See chapter &<<CHAPenvironment>>& for further details of the local delivery
19935 .option unseen routers boolean&!! false
19936 .cindex "router" "carrying on after success"
19937 The result of string expansion for this option must be a valid boolean value,
19938 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
19939 result causes an error, and delivery is deferred. If the expansion is forced to
19940 fail, the default value for the option (false) is used. Other failures cause
19941 delivery to be deferred.
19943 When this option is set true, routing does not cease if the router accepts the
19944 address. Instead, a copy of the incoming address is passed to the next router,
19945 overriding a false setting of &%more%&. There is little point in setting
19946 &%more%& false if &%unseen%& is always true, but it may be useful in cases when
19947 the value of &%unseen%& contains expansion items (and therefore, presumably, is
19948 sometimes true and sometimes false).
19950 .cindex "copy of message (&%unseen%& option)"
19951 Setting the &%unseen%& option has a similar effect to the &%unseen%& command
19952 qualifier in filter files. It can be used to cause copies of messages to be
19953 delivered to some other destination, while also carrying out a normal delivery.
19954 In effect, the current address is made into a &"parent"& that has two children
19955 &-- one that is delivered as specified by this router, and a clone that goes on
19956 to be routed further. For this reason, &%unseen%& may not be combined with the
19957 &%one_time%& option in a &(redirect)& router.
19959 &*Warning*&: Header lines added to the address (or specified for removal) by
19960 this router or by previous routers affect the &"unseen"& copy of the message
19961 only. The clone that continues to be processed by further routers starts with
19962 no added headers and none specified for removal. For a &%redirect%& router, if
19963 a generated address is the same as the incoming address, this can lead to
19964 duplicate addresses with different header modifications. Exim does not do
19965 duplicate deliveries (except, in certain circumstances, to pipes -- see section
19966 &<<SECTdupaddr>>&), but it is undefined which of the duplicates is discarded,
19967 so this ambiguous situation should be avoided. The &%repeat_use%& option of the
19968 &%redirect%& router may be of help.
19970 Unlike the handling of header modifications, any data that was set by the
19971 &%address_data%& option in the current or previous routers &'is'& passed on to
19972 subsequent routers.
19975 .option user routers string&!! "see below"
19976 .cindex "uid (user id)" "local delivery"
19977 .cindex "local transports" "uid and gid"
19978 .cindex "transport" "local"
19979 .cindex "router" "user for filter processing"
19980 .cindex "filter" "user for processing"
19981 When a router queues an address for a transport, and the transport does not
19982 specify a user, the user given here is used when running the delivery process.
19983 The user may be specified numerically or by name. If expansion fails, the
19984 error is logged and delivery is deferred.
19985 This user is also used by the &(redirect)& router when running a filter file.
19986 The default is unset, except when &%check_local_user%& is set. In this case,
19987 the default is taken from the password information. If the user is specified as
19988 a name, and &%group%& is not set, the group associated with the user is used.
19989 See also &%initgroups%& and &%group%& and the discussion in chapter
19990 &<<CHAPenvironment>>&.
19994 .option verify routers&!? boolean true
19995 Setting this option has the effect of setting &%verify_sender%& and
19996 &%verify_recipient%& to the same value.
19999 .option verify_only routers&!? boolean false
20000 .cindex "EXPN" "with &%verify_only%&"
20002 .cindex "router" "used only when verifying"
20003 If this option is set, the router is used only when verifying an address,
20004 delivering in cutthrough mode or
20005 testing with the &%-bv%& option, not when actually doing a delivery, testing
20006 with the &%-bt%& option, or running the SMTP EXPN command. It can be further
20007 restricted to verifying only senders or recipients by means of
20008 &%verify_sender%& and &%verify_recipient%&.
20010 &*Warning*&: When the router is being run to verify addresses for an incoming
20011 SMTP message, Exim is not running as root, but under its own uid. If the router
20012 accesses any files, you need to make sure that they are accessible to the Exim
20016 .option verify_recipient routers&!? boolean true
20017 If this option is false, the router is skipped when verifying recipient
20019 delivering in cutthrough mode
20020 or testing recipient verification using &%-bv%&.
20021 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
20023 See also the &$verify_mode$& variable.
20026 .option verify_sender routers&!? boolean true
20027 If this option is false, the router is skipped when verifying sender addresses
20028 or testing sender verification using &%-bvs%&.
20029 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
20031 See also the &$verify_mode$& variable.
20032 .ecindex IIDgenoprou1
20033 .ecindex IIDgenoprou2
20040 . ////////////////////////////////////////////////////////////////////////////
20041 . ////////////////////////////////////////////////////////////////////////////
20043 .chapter "The accept router" "CHID4"
20044 .cindex "&(accept)& router"
20045 .cindex "routers" "&(accept)&"
20046 The &(accept)& router has no private options of its own. Unless it is being
20047 used purely for verification (see &%verify_only%&) a transport is required to
20048 be defined by the generic &%transport%& option. If the preconditions that are
20049 specified by generic options are met, the router accepts the address and queues
20050 it for the given transport. The most common use of this router is for setting
20051 up deliveries to local mailboxes. For example:
20055 domains = mydomain.example
20057 transport = local_delivery
20059 The &%domains%& condition in this example checks the domain of the address, and
20060 &%check_local_user%& checks that the local part is the login of a local user.
20061 When both preconditions are met, the &(accept)& router runs, and queues the
20062 address for the &(local_delivery)& transport.
20069 . ////////////////////////////////////////////////////////////////////////////
20070 . ////////////////////////////////////////////////////////////////////////////
20072 .chapter "The dnslookup router" "CHAPdnslookup"
20073 .scindex IIDdnsrou1 "&(dnslookup)& router"
20074 .scindex IIDdnsrou2 "routers" "&(dnslookup)&"
20075 The &(dnslookup)& router looks up the hosts that handle mail for the
20076 recipient's domain in the DNS. A transport must always be set for this router,
20077 unless &%verify_only%& is set.
20079 If SRV support is configured (see &%check_srv%& below), Exim first searches for
20080 SRV records. If none are found, or if SRV support is not configured,
20081 MX records are looked up. If no MX records exist, address records are sought.
20082 However, &%mx_domains%& can be set to disable the direct use of address
20085 MX records of equal priority are sorted by Exim into a random order. Exim then
20086 looks for address records for the host names obtained from MX or SRV records.
20087 When a host has more than one IP address, they are sorted into a random order,
20088 except that IPv6 addresses are sorted before IPv4 addresses. If all the
20089 IP addresses found are discarded by a setting of the &%ignore_target_hosts%&
20090 generic option, the router declines.
20092 Unless they have the highest priority (lowest MX value), MX records that point
20093 to the local host, or to any host name that matches &%hosts_treat_as_local%&,
20094 are discarded, together with any other MX records of equal or lower priority.
20096 .cindex "MX record" "pointing to local host"
20097 .cindex "local host" "MX pointing to"
20098 .oindex "&%self%&" "in &(dnslookup)& router"
20099 If the host pointed to by the highest priority MX record, or looked up as an
20100 address record, is the local host, or matches &%hosts_treat_as_local%&, what
20101 happens is controlled by the generic &%self%& option.
20104 .section "Problems with DNS lookups" "SECTprowitdnsloo"
20105 There have been problems with DNS servers when SRV records are looked up.
20106 Some misbehaving servers return a DNS error or timeout when a non-existent
20107 SRV record is sought. Similar problems have in the past been reported for
20108 MX records. The global &%dns_again_means_nonexist%& option can help with this
20109 problem, but it is heavy-handed because it is a global option.
20111 For this reason, there are two options, &%srv_fail_domains%& and
20112 &%mx_fail_domains%&, that control what happens when a DNS lookup in a
20113 &(dnslookup)& router results in a DNS failure or a &"try again"& response. If
20114 an attempt to look up an SRV or MX record causes one of these results, and the
20115 domain matches the relevant list, Exim behaves as if the DNS had responded &"no
20116 such record"&. In the case of an SRV lookup, this means that the router
20117 proceeds to look for MX records; in the case of an MX lookup, it proceeds to
20118 look for A or AAAA records, unless the domain matches &%mx_domains%&, in which
20119 case routing fails.
20122 .section "Declining addresses by dnslookup" "SECTdnslookupdecline"
20123 .cindex "&(dnslookup)& router" "declines"
20124 There are a few cases where a &(dnslookup)& router will decline to accept
20125 an address; if such a router is expected to handle "all remaining non-local
20126 domains", then it is important to set &%no_more%&.
20128 The router will defer rather than decline if the domain
20129 is found in the &%fail_defer_domains%& router option.
20131 Reasons for a &(dnslookup)& router to decline currently include:
20133 The domain does not exist in DNS
20135 The domain exists but the MX record's host part is just "."; this is a common
20136 convention (borrowed from SRV) used to indicate that there is no such service
20137 for this domain and to not fall back to trying A/AAAA records.
20139 Ditto, but for SRV records, when &%check_srv%& is set on this router.
20141 MX record points to a non-existent host.
20143 MX record points to an IP address and the main section option
20144 &%allow_mx_to_ip%& is not set.
20146 MX records exist and point to valid hosts, but all hosts resolve only to
20147 addresses blocked by the &%ignore_target_hosts%& generic option on this router.
20149 The domain is not syntactically valid (see also &%allow_utf8_domains%& and
20150 &%dns_check_names_pattern%& for handling one variant of this)
20152 &%check_secondary_mx%& is set on this router but the local host can
20153 not be found in the MX records (see below)
20159 .section "Private options for dnslookup" "SECID118"
20160 .cindex "options" "&(dnslookup)& router"
20161 The private options for the &(dnslookup)& router are as follows:
20163 .option check_secondary_mx dnslookup boolean false
20164 .cindex "MX record" "checking for secondary"
20165 If this option is set, the router declines unless the local host is found in
20166 (and removed from) the list of hosts obtained by MX lookup. This can be used to
20167 process domains for which the local host is a secondary mail exchanger
20168 differently to other domains. The way in which Exim decides whether a host is
20169 the local host is described in section &<<SECTreclocipadd>>&.
20172 .option check_srv dnslookup string&!! unset
20173 .cindex "SRV record" "enabling use of"
20174 The &(dnslookup)& router supports the use of SRV records (see RFC 2782) in
20175 addition to MX and address records. The support is disabled by default. To
20176 enable SRV support, set the &%check_srv%& option to the name of the service
20177 required. For example,
20181 looks for SRV records that refer to the normal smtp service. The option is
20182 expanded, so the service name can vary from message to message or address
20183 to address. This might be helpful if SRV records are being used for a
20184 submission service. If the expansion is forced to fail, the &%check_srv%&
20185 option is ignored, and the router proceeds to look for MX records in the
20188 When the expansion succeeds, the router searches first for SRV records for
20189 the given service (it assumes TCP protocol). A single SRV record with a
20190 host name that consists of just a single dot indicates &"no such service for
20191 this domain"&; if this is encountered, the router declines. If other kinds of
20192 SRV record are found, they are used to construct a host list for delivery
20193 according to the rules of RFC 2782. MX records are not sought in this case.
20195 When no SRV records are found, MX records (and address records) are sought in
20196 the traditional way. In other words, SRV records take precedence over MX
20197 records, just as MX records take precedence over address records. Note that
20198 this behaviour is not sanctioned by RFC 2782, though a previous draft RFC
20199 defined it. It is apparently believed that MX records are sufficient for email
20200 and that SRV records should not be used for this purpose. However, SRV records
20201 have an additional &"weight"& feature which some people might find useful when
20202 trying to split an SMTP load between hosts of different power.
20204 See section &<<SECTprowitdnsloo>>& above for a discussion of Exim's behaviour
20205 when there is a DNS lookup error.
20210 .option fail_defer_domains dnslookup "domain list&!!" unset
20211 .cindex "MX record" "not found"
20212 DNS lookups for domains matching &%fail_defer_domains%&
20213 which find no matching record will cause the router to defer
20214 rather than the default behaviour of decline.
20215 This maybe be useful for queueing messages for a newly created
20216 domain while the DNS configuration is not ready.
20217 However, it will result in any message with mistyped domains
20221 .option ipv4_only "string&!!" unset
20222 .cindex IPv6 disabling
20223 .cindex DNS "IPv6 disabling"
20224 The string is expanded, and if the result is anything but a forced failure,
20225 or an empty string, or one of the strings “0” or “no” or “false”
20226 (checked without regard to the case of the letters),
20227 only A records are used.
20229 .option ipv4_prefer "string&!!" unset
20230 .cindex IPv4 preference
20231 .cindex DNS "IPv4 preference"
20232 The string is expanded, and if the result is anything but a forced failure,
20233 or an empty string, or one of the strings “0” or “no” or “false”
20234 (checked without regard to the case of the letters),
20235 A records are sorted before AAAA records (inverting the default).
20237 .option mx_domains dnslookup "domain list&!!" unset
20238 .cindex "MX record" "required to exist"
20239 .cindex "SRV record" "required to exist"
20240 A domain that matches &%mx_domains%& is required to have either an MX or an SRV
20241 record in order to be recognized. (The name of this option could be improved.)
20242 For example, if all the mail hosts in &'fict.example'& are known to have MX
20243 records, except for those in &'discworld.fict.example'&, you could use this
20246 mx_domains = ! *.discworld.fict.example : *.fict.example
20248 This specifies that messages addressed to a domain that matches the list but
20249 has no MX record should be bounced immediately instead of being routed using
20250 the address record.
20253 .option mx_fail_domains dnslookup "domain list&!!" unset
20254 If the DNS lookup for MX records for one of the domains in this list causes a
20255 DNS lookup error, Exim behaves as if no MX records were found. See section
20256 &<<SECTprowitdnsloo>>& for more discussion.
20261 .option qualify_single dnslookup boolean true
20262 .cindex "DNS" "resolver options"
20263 .cindex "DNS" "qualifying single-component names"
20264 When this option is true, the resolver option RES_DEFNAMES is set for DNS
20265 lookups. Typically, but not standardly, this causes the resolver to qualify
20266 single-component names with the default domain. For example, on a machine
20267 called &'dictionary.ref.example'&, the domain &'thesaurus'& would be changed to
20268 &'thesaurus.ref.example'& inside the resolver. For details of what your
20269 resolver actually does, consult your man pages for &'resolver'& and
20274 .option rewrite_headers dnslookup boolean true
20275 .cindex "rewriting" "header lines"
20276 .cindex "header lines" "rewriting"
20277 If the domain name in the address that is being processed is not fully
20278 qualified, it may be expanded to its full form by a DNS lookup. For example, if
20279 an address is specified as &'dormouse@teaparty'&, the domain might be
20280 expanded to &'teaparty.wonderland.fict.example'&. Domain expansion can also
20281 occur as a result of setting the &%widen_domains%& option. If
20282 &%rewrite_headers%& is true, all occurrences of the abbreviated domain name in
20283 any &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-to:'&, &'Sender:'&, and &'To:'&
20284 header lines of the message are rewritten with the full domain name.
20286 This option should be turned off only when it is known that no message is
20287 ever going to be sent outside an environment where the abbreviation makes
20290 When an MX record is looked up in the DNS and matches a wildcard record, name
20291 servers normally return a record containing the name that has been looked up,
20292 making it impossible to detect whether a wildcard was present or not. However,
20293 some name servers have recently been seen to return the wildcard entry. If the
20294 name returned by a DNS lookup begins with an asterisk, it is not used for
20298 .option same_domain_copy_routing dnslookup boolean false
20299 .cindex "address" "copying routing"
20300 Addresses with the same domain are normally routed by the &(dnslookup)& router
20301 to the same list of hosts. However, this cannot be presumed, because the router
20302 options and preconditions may refer to the local part of the address. By
20303 default, therefore, Exim routes each address in a message independently. DNS
20304 servers run caches, so repeated DNS lookups are not normally expensive, and in
20305 any case, personal messages rarely have more than a few recipients.
20307 If you are running mailing lists with large numbers of subscribers at the same
20308 domain, and you are using a &(dnslookup)& router which is independent of the
20309 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
20310 lookups for identical domains in one message. In this case, when &(dnslookup)&
20311 routes an address to a remote transport, any other unrouted addresses in the
20312 message that have the same domain are automatically given the same routing
20313 without processing them independently,
20314 provided the following conditions are met:
20317 No router that processed the address specified &%headers_add%& or
20318 &%headers_remove%&.
20320 The router did not change the address in any way, for example, by &"widening"&
20327 .option search_parents dnslookup boolean false
20328 .cindex "DNS" "resolver options"
20329 When this option is true, the resolver option RES_DNSRCH is set for DNS
20330 lookups. This is different from the &%qualify_single%& option in that it
20331 applies to domains containing dots. Typically, but not standardly, it causes
20332 the resolver to search for the name in the current domain and in parent
20333 domains. For example, on a machine in the &'fict.example'& domain, if looking
20334 up &'teaparty.wonderland'& failed, the resolver would try
20335 &'teaparty.wonderland.fict.example'&. For details of what your resolver
20336 actually does, consult your man pages for &'resolver'& and &'resolv.conf'&.
20338 Setting this option true can cause problems in domains that have a wildcard MX
20339 record, because any domain that does not have its own MX record matches the
20344 .option srv_fail_domains dnslookup "domain list&!!" unset
20345 If the DNS lookup for SRV records for one of the domains in this list causes a
20346 DNS lookup error, Exim behaves as if no SRV records were found. See section
20347 &<<SECTprowitdnsloo>>& for more discussion.
20352 .option widen_domains dnslookup "string list" unset
20353 .cindex "domain" "partial; widening"
20354 If a DNS lookup fails and this option is set, each of its strings in turn is
20355 added onto the end of the domain, and the lookup is tried again. For example,
20358 widen_domains = fict.example:ref.example
20360 is set and a lookup of &'klingon.dictionary'& fails,
20361 &'klingon.dictionary.fict.example'& is looked up, and if this fails,
20362 &'klingon.dictionary.ref.example'& is tried. Note that the &%qualify_single%&
20363 and &%search_parents%& options can cause some widening to be undertaken inside
20364 the DNS resolver. &%widen_domains%& is not applied to sender addresses
20365 when verifying, unless &%rewrite_headers%& is false (not the default).
20368 .section "Effect of qualify_single and search_parents" "SECID119"
20369 When a domain from an envelope recipient is changed by the resolver as a result
20370 of the &%qualify_single%& or &%search_parents%& options, Exim rewrites the
20371 corresponding address in the message's header lines unless &%rewrite_headers%&
20372 is set false. Exim then re-routes the address, using the full domain.
20374 These two options affect only the DNS lookup that takes place inside the router
20375 for the domain of the address that is being routed. They do not affect lookups
20376 such as that implied by
20380 that may happen while processing a router precondition before the router is
20381 entered. No widening ever takes place for these lookups.
20382 .ecindex IIDdnsrou1
20383 .ecindex IIDdnsrou2
20393 . ////////////////////////////////////////////////////////////////////////////
20394 . ////////////////////////////////////////////////////////////////////////////
20396 .chapter "The ipliteral router" "CHID5"
20397 .cindex "&(ipliteral)& router"
20398 .cindex "domain literal" "routing"
20399 .cindex "routers" "&(ipliteral)&"
20400 This router has no private options. Unless it is being used purely for
20401 verification (see &%verify_only%&) a transport is required to be defined by the
20402 generic &%transport%& option. The router accepts the address if its domain part
20403 takes the form of an RFC 2822 domain literal. For example, the &(ipliteral)&
20404 router handles the address
20408 by setting up delivery to the host with that IP address. IPv4 domain literals
20409 consist of an IPv4 address enclosed in square brackets. IPv6 domain literals
20410 are similar, but the address is preceded by &`ipv6:`&. For example:
20412 postmaster@[ipv6:fe80::a00:20ff:fe86:a061.5678]
20414 Exim allows &`ipv4:`& before IPv4 addresses, for consistency, and on the
20415 grounds that sooner or later somebody will try it.
20417 .oindex "&%self%&" "in &(ipliteral)& router"
20418 If the IP address matches something in &%ignore_target_hosts%&, the router
20419 declines. If an IP literal turns out to refer to the local host, the generic
20420 &%self%& option determines what happens.
20422 The RFCs require support for domain literals; however, their use is
20423 controversial in today's Internet. If you want to use this router, you must
20424 also set the main configuration option &%allow_domain_literals%&. Otherwise,
20425 Exim will not recognize the domain literal syntax in addresses.
20429 . ////////////////////////////////////////////////////////////////////////////
20430 . ////////////////////////////////////////////////////////////////////////////
20432 .chapter "The iplookup router" "CHID6"
20433 .cindex "&(iplookup)& router"
20434 .cindex "routers" "&(iplookup)&"
20435 The &(iplookup)& router was written to fulfil a specific requirement in
20436 Cambridge University (which in fact no longer exists). For this reason, it is
20437 not included in the binary of Exim by default. If you want to include it, you
20440 ROUTER_IPLOOKUP=yes
20442 in your &_Local/Makefile_& configuration file.
20444 The &(iplookup)& router routes an address by sending it over a TCP or UDP
20445 connection to one or more specific hosts. The host can then return the same or
20446 a different address &-- in effect rewriting the recipient address in the
20447 message's envelope. The new address is then passed on to subsequent routers. If
20448 this process fails, the address can be passed on to other routers, or delivery
20449 can be deferred. Since &(iplookup)& is just a rewriting router, a transport
20450 must not be specified for it.
20452 .cindex "options" "&(iplookup)& router"
20453 .option hosts iplookup string unset
20454 This option must be supplied. Its value is a colon-separated list of host
20455 names. The hosts are looked up using &[gethostbyname()]&
20456 (or &[getipnodebyname()]& when available)
20457 and are tried in order until one responds to the query. If none respond, what
20458 happens is controlled by &%optional%&.
20461 .option optional iplookup boolean false
20462 If &%optional%& is true, if no response is obtained from any host, the address
20463 is passed to the next router, overriding &%no_more%&. If &%optional%& is false,
20464 delivery to the address is deferred.
20467 .option port iplookup integer 0
20468 .cindex "port" "&(iplookup)& router"
20469 This option must be supplied. It specifies the port number for the TCP or UDP
20473 .option protocol iplookup string udp
20474 This option can be set to &"udp"& or &"tcp"& to specify which of the two
20475 protocols is to be used.
20478 .option query iplookup string&!! "see below"
20479 This defines the content of the query that is sent to the remote hosts. The
20482 $local_part@$domain $local_part@$domain
20484 The repetition serves as a way of checking that a response is to the correct
20485 query in the default case (see &%response_pattern%& below).
20488 .option reroute iplookup string&!! unset
20489 If this option is not set, the rerouted address is precisely the byte string
20490 returned by the remote host, up to the first white space, if any. If set, the
20491 string is expanded to form the rerouted address. It can include parts matched
20492 in the response by &%response_pattern%& by means of numeric variables such as
20493 &$1$&, &$2$&, etc. The variable &$0$& refers to the entire input string,
20494 whether or not a pattern is in use. In all cases, the rerouted address must end
20495 up in the form &'local_part@domain'&.
20498 .option response_pattern iplookup string unset
20499 This option can be set to a regular expression that is applied to the string
20500 returned from the remote host. If the pattern does not match the response, the
20501 router declines. If &%response_pattern%& is not set, no checking of the
20502 response is done, unless the query was defaulted, in which case there is a
20503 check that the text returned after the first white space is the original
20504 address. This checks that the answer that has been received is in response to
20505 the correct question. For example, if the response is just a new domain, the
20506 following could be used:
20508 response_pattern = ^([^@]+)$
20509 reroute = $local_part@$1
20512 .option timeout iplookup time 5s
20513 This specifies the amount of time to wait for a response from the remote
20514 machine. The same timeout is used for the &[connect()]& function for a TCP
20515 call. It does not apply to UDP.
20520 . ////////////////////////////////////////////////////////////////////////////
20521 . ////////////////////////////////////////////////////////////////////////////
20523 .chapter "The manualroute router" "CHID7"
20524 .scindex IIDmanrou1 "&(manualroute)& router"
20525 .scindex IIDmanrou2 "routers" "&(manualroute)&"
20526 .cindex "domain" "manually routing"
20527 The &(manualroute)& router is so-called because it provides a way of manually
20528 routing an address according to its domain. It is mainly used when you want to
20529 route addresses to remote hosts according to your own rules, bypassing the
20530 normal DNS routing that looks up MX records. However, &(manualroute)& can also
20531 route to local transports, a facility that may be useful if you want to save
20532 messages for dial-in hosts in local files.
20534 The &(manualroute)& router compares a list of domain patterns with the domain
20535 it is trying to route. If there is no match, the router declines. Each pattern
20536 has associated with it a list of hosts and some other optional data, which may
20537 include a transport. The combination of a pattern and its data is called a
20538 &"routing rule"&. For patterns that do not have an associated transport, the
20539 generic &%transport%& option must specify a transport, unless the router is
20540 being used purely for verification (see &%verify_only%&).
20543 In the case of verification, matching the domain pattern is sufficient for the
20544 router to accept the address. When actually routing an address for delivery,
20545 an address that matches a domain pattern is queued for the associated
20546 transport. If the transport is not a local one, a host list must be associated
20547 with the pattern; IP addresses are looked up for the hosts, and these are
20548 passed to the transport along with the mail address. For local transports, a
20549 host list is optional. If it is present, it is passed in &$host$& as a single
20552 The list of routing rules can be provided as an inline string in
20553 &%route_list%&, or the data can be obtained by looking up the domain in a file
20554 or database by setting &%route_data%&. Only one of these settings may appear in
20555 any one instance of &(manualroute)&. The format of routing rules is described
20556 below, following the list of private options.
20559 .section "Private options for manualroute" "SECTprioptman"
20561 .cindex "options" "&(manualroute)& router"
20562 The private options for the &(manualroute)& router are as follows:
20564 .option host_all_ignored manualroute string defer
20565 See &%host_find_failed%&.
20567 .option host_find_failed manualroute string freeze
20568 This option controls what happens when &(manualroute)& tries to find an IP
20569 address for a host, and the host does not exist. The option can be set to one
20570 of the following values:
20579 The default (&"freeze"&) assumes that this state is a serious configuration
20580 error. The difference between &"pass"& and &"decline"& is that the former
20581 forces the address to be passed to the next router (or the router defined by
20584 overriding &%no_more%&, whereas the latter passes the address to the next
20585 router only if &%more%& is true.
20587 The value &"ignore"& causes Exim to completely ignore a host whose IP address
20588 cannot be found. If all the hosts in the list are ignored, the behaviour is
20589 controlled by the &%host_all_ignored%& option. This takes the same values
20590 as &%host_find_failed%&, except that it cannot be set to &"ignore"&.
20592 The &%host_find_failed%& option applies only to a definite &"does not exist"&
20593 state; if a host lookup gets a temporary error, delivery is deferred unless the
20594 generic &%pass_on_timeout%& option is set.
20597 .option hosts_randomize manualroute boolean false
20598 .cindex "randomized host list"
20599 .cindex "host" "list of; randomized"
20600 If this option is set, the order of the items in a host list in a routing rule
20601 is randomized each time the list is used, unless an option in the routing rule
20602 overrides (see below). Randomizing the order of a host list can be used to do
20603 crude load sharing. However, if more than one mail address is routed by the
20604 same router to the same host list, the host lists are considered to be the same
20605 (even though they may be randomized into different orders) for the purpose of
20606 deciding whether to batch the deliveries into a single SMTP transaction.
20608 When &%hosts_randomize%& is true, a host list may be split
20609 into groups whose order is separately randomized. This makes it possible to
20610 set up MX-like behaviour. The boundaries between groups are indicated by an
20611 item that is just &`+`& in the host list. For example:
20613 route_list = * host1:host2:host3:+:host4:host5
20615 The order of the first three hosts and the order of the last two hosts is
20616 randomized for each use, but the first three always end up before the last two.
20617 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored. If a
20618 randomized host list is passed to an &(smtp)& transport that also has
20619 &%hosts_randomize set%&, the list is not re-randomized.
20622 .option route_data manualroute string&!! unset
20623 If this option is set, it must expand to yield the data part of a routing rule.
20624 Typically, the expansion string includes a lookup based on the domain. For
20627 route_data = ${lookup{$domain}dbm{/etc/routes}}
20629 If the expansion is forced to fail, or the result is an empty string, the
20630 router declines. Other kinds of expansion failure cause delivery to be
20634 .option route_list manualroute "string list" unset
20635 This string is a list of routing rules, in the form defined below. Note that,
20636 unlike most string lists, the items are separated by semicolons. This is so
20637 that they may contain colon-separated host lists.
20640 .option same_domain_copy_routing manualroute boolean false
20641 .cindex "address" "copying routing"
20642 Addresses with the same domain are normally routed by the &(manualroute)&
20643 router to the same list of hosts. However, this cannot be presumed, because the
20644 router options and preconditions may refer to the local part of the address. By
20645 default, therefore, Exim routes each address in a message independently. DNS
20646 servers run caches, so repeated DNS lookups are not normally expensive, and in
20647 any case, personal messages rarely have more than a few recipients.
20649 If you are running mailing lists with large numbers of subscribers at the same
20650 domain, and you are using a &(manualroute)& router which is independent of the
20651 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
20652 lookups for identical domains in one message. In this case, when
20653 &(manualroute)& routes an address to a remote transport, any other unrouted
20654 addresses in the message that have the same domain are automatically given the
20655 same routing without processing them independently. However, this is only done
20656 if &%headers_add%& and &%headers_remove%& are unset.
20661 .section "Routing rules in route_list" "SECID120"
20662 The value of &%route_list%& is a string consisting of a sequence of routing
20663 rules, separated by semicolons. If a semicolon is needed in a rule, it can be
20664 entered as two semicolons. Alternatively, the list separator can be changed as
20665 described (for colon-separated lists) in section &<<SECTlistconstruct>>&.
20666 Empty rules are ignored. The format of each rule is
20668 <&'domain pattern'&> <&'list of hosts'&> <&'options'&>
20670 The following example contains two rules, each with a simple domain pattern and
20674 dict.ref.example mail-1.ref.example:mail-2.ref.example ; \
20675 thes.ref.example mail-3.ref.example:mail-4.ref.example
20677 The three parts of a rule are separated by white space. The pattern and the
20678 list of hosts can be enclosed in quotes if necessary, and if they are, the
20679 usual quoting rules apply. Each rule in a &%route_list%& must start with a
20680 single domain pattern, which is the only mandatory item in the rule. The
20681 pattern is in the same format as one item in a domain list (see section
20682 &<<SECTdomainlist>>&),
20683 except that it may not be the name of an interpolated file.
20684 That is, it may be wildcarded, or a regular expression, or a file or database
20685 lookup (with semicolons doubled, because of the use of semicolon as a separator
20686 in a &%route_list%&).
20688 The rules in &%route_list%& are searched in order until one of the patterns
20689 matches the domain that is being routed. The list of hosts and then options are
20690 then used as described below. If there is no match, the router declines. When
20691 &%route_list%& is set, &%route_data%& must not be set.
20695 .section "Routing rules in route_data" "SECID121"
20696 The use of &%route_list%& is convenient when there are only a small number of
20697 routing rules. For larger numbers, it is easier to use a file or database to
20698 hold the routing information, and use the &%route_data%& option instead.
20699 The value of &%route_data%& is a list of hosts, followed by (optional) options.
20700 Most commonly, &%route_data%& is set as a string that contains an
20701 expansion lookup. For example, suppose we place two routing rules in a file
20704 dict.ref.example: mail-1.ref.example:mail-2.ref.example
20705 thes.ref.example: mail-3.ref.example:mail-4.ref.example
20707 This data can be accessed by setting
20709 route_data = ${lookup{$domain}lsearch{/the/file/name}}
20711 Failure of the lookup results in an empty string, causing the router to
20712 decline. However, you do not have to use a lookup in &%route_data%&. The only
20713 requirement is that the result of expanding the string is a list of hosts,
20714 possibly followed by options, separated by white space. The list of hosts must
20715 be enclosed in quotes if it contains white space.
20720 .section "Format of the list of hosts" "SECID122"
20721 A list of hosts, whether obtained via &%route_data%& or &%route_list%&, is
20722 always separately expanded before use. If the expansion fails, the router
20723 declines. The result of the expansion must be a colon-separated list of names
20724 and/or IP addresses, optionally also including ports.
20725 If the list is written with spaces, it must be protected with quotes.
20726 The format of each item
20727 in the list is described in the next section. The list separator can be changed
20728 as described in section &<<SECTlistsepchange>>&.
20730 If the list of hosts was obtained from a &%route_list%& item, the following
20731 variables are set during its expansion:
20734 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(manualroute)& router"
20735 If the domain was matched against a regular expression, the numeric variables
20736 &$1$&, &$2$&, etc. may be set. For example:
20738 route_list = ^domain(\d+) host-$1.text.example
20741 &$0$& is always set to the entire domain.
20743 &$1$& is also set when partial matching is done in a file lookup.
20746 .vindex "&$value$&"
20747 If the pattern that matched the domain was a lookup item, the data that was
20748 looked up is available in the expansion variable &$value$&. For example:
20750 route_list = lsearch;;/some/file.routes $value
20754 Note the doubling of the semicolon in the pattern that is necessary because
20755 semicolon is the default route list separator.
20759 .section "Format of one host item" "SECTformatonehostitem"
20760 Each item in the list of hosts can be either a host name or an IP address,
20761 optionally with an attached port number, or it can be a single "+"
20762 (see &%hosts_randomize%&).
20763 When no port is given, an IP address
20764 is not enclosed in brackets. When a port is specified, it overrides the port
20765 specification on the transport. The port is separated from the name or address
20766 by a colon. This leads to some complications:
20769 Because colon is the default separator for the list of hosts, either
20770 the colon that specifies a port must be doubled, or the list separator must
20771 be changed. The following two examples have the same effect:
20773 route_list = * "host1.tld::1225 : host2.tld::1226"
20774 route_list = * "<+ host1.tld:1225 + host2.tld:1226"
20777 When IPv6 addresses are involved, it gets worse, because they contain
20778 colons of their own. To make this case easier, it is permitted to
20779 enclose an IP address (either v4 or v6) in square brackets if a port
20780 number follows. For example:
20782 route_list = * "</ [10.1.1.1]:1225 / [::1]:1226"
20786 .section "How the list of hosts is used" "SECThostshowused"
20787 When an address is routed to an &(smtp)& transport by &(manualroute)&, each of
20788 the hosts is tried, in the order specified, when carrying out the SMTP
20789 delivery. However, the order can be changed by setting the &%hosts_randomize%&
20790 option, either on the router (see section &<<SECTprioptman>>& above), or on the
20793 Hosts may be listed by name or by IP address. An unadorned name in the list of
20794 hosts is interpreted as a host name. A name that is followed by &`/MX`& is
20795 interpreted as an indirection to a sublist of hosts obtained by looking up MX
20796 records in the DNS. For example:
20798 route_list = * x.y.z:p.q.r/MX:e.f.g
20800 If this feature is used with a port specifier, the port must come last. For
20803 route_list = * dom1.tld/mx::1225
20805 If the &%hosts_randomize%& option is set, the order of the items in the list is
20806 randomized before any lookups are done. Exim then scans the list; for any name
20807 that is not followed by &`/MX`& it looks up an IP address. If this turns out to
20808 be an interface on the local host and the item is not the first in the list,
20809 Exim discards it and any subsequent items. If it is the first item, what
20810 happens is controlled by the
20811 .oindex "&%self%&" "in &(manualroute)& router"
20812 &%self%& option of the router.
20814 A name on the list that is followed by &`/MX`& is replaced with the list of
20815 hosts obtained by looking up MX records for the name. This is always a DNS
20816 lookup; the &%bydns%& and &%byname%& options (see section &<<SECThowoptused>>&
20817 below) are not relevant here. The order of these hosts is determined by the
20818 preference values in the MX records, according to the usual rules. Because
20819 randomizing happens before the MX lookup, it does not affect the order that is
20820 defined by MX preferences.
20822 If the local host is present in the sublist obtained from MX records, but is
20823 not the most preferred host in that list, it and any equally or less
20824 preferred hosts are removed before the sublist is inserted into the main list.
20826 If the local host is the most preferred host in the MX list, what happens
20827 depends on where in the original list of hosts the &`/MX`& item appears. If it
20828 is not the first item (that is, there are previous hosts in the main list),
20829 Exim discards this name and any subsequent items in the main list.
20831 If the MX item is first in the list of hosts, and the local host is the
20832 most preferred host, what happens is controlled by the &%self%& option of the
20835 DNS failures when lookup up the MX records are treated in the same way as DNS
20836 failures when looking up IP addresses: &%pass_on_timeout%& and
20837 &%host_find_failed%& are used when relevant.
20839 The generic &%ignore_target_hosts%& option applies to all hosts in the list,
20840 whether obtained from an MX lookup or not.
20844 .section "How the options are used" "SECThowoptused"
20845 The options are a sequence of words, space-separated.
20846 One of the words can be the name of a transport; this overrides the
20847 &%transport%& option on the router for this particular routing rule only. The
20848 other words (if present) control randomization of the list of hosts on a
20849 per-rule basis, and how the IP addresses of the hosts are to be found when
20850 routing to a remote transport. These options are as follows:
20853 &%randomize%&: randomize the order of the hosts in this list, overriding the
20854 setting of &%hosts_randomize%& for this routing rule only.
20856 &%no_randomize%&: do not randomize the order of the hosts in this list,
20857 overriding the setting of &%hosts_randomize%& for this routing rule only.
20859 &%byname%&: use &[getipnodebyname()]& (&[gethostbyname()]& on older systems) to
20860 find IP addresses. This function may ultimately cause a DNS lookup, but it may
20861 also look in &_/etc/hosts_& or other sources of information.
20863 &%bydns%&: look up address records for the hosts directly in the DNS; fail if
20864 no address records are found. If there is a temporary DNS error (such as a
20865 timeout), delivery is deferred.
20867 &%ipv4_only%&: in direct DNS lookups, look up only A records.
20869 &%ipv4_prefer%&: in direct DNS lookups, sort A records before AAAA records.
20874 route_list = domain1 host1:host2:host3 randomize bydns;\
20875 domain2 host4:host5
20877 If neither &%byname%& nor &%bydns%& is given, Exim behaves as follows: First, a
20878 DNS lookup is done. If this yields anything other than HOST_NOT_FOUND, that
20879 result is used. Otherwise, Exim goes on to try a call to &[getipnodebyname()]&
20880 or &[gethostbyname()]&, and the result of the lookup is the result of that
20883 &*Warning*&: It has been discovered that on some systems, if a DNS lookup
20884 called via &[getipnodebyname()]& times out, HOST_NOT_FOUND is returned
20885 instead of TRY_AGAIN. That is why the default action is to try a DNS
20886 lookup first. Only if that gives a definite &"no such host"& is the local
20889 &*Compatibility*&: From Exim 4.85 until fixed for 4.90, there was an
20890 inadvertent constraint that a transport name as an option had to be the last
20895 If no IP address for a host can be found, what happens is controlled by the
20896 &%host_find_failed%& option.
20899 When an address is routed to a local transport, IP addresses are not looked up.
20900 The host list is passed to the transport in the &$host$& variable.
20904 .section "Manualroute examples" "SECID123"
20905 In some of the examples that follow, the presence of the &%remote_smtp%&
20906 transport, as defined in the default configuration file, is assumed:
20909 .cindex "smart host" "example router"
20910 The &(manualroute)& router can be used to forward all external mail to a
20911 &'smart host'&. If you have set up, in the main part of the configuration, a
20912 named domain list that contains your local domains, for example:
20914 domainlist local_domains = my.domain.example
20916 You can arrange for all other domains to be routed to a smart host by making
20917 your first router something like this:
20920 driver = manualroute
20921 domains = !+local_domains
20922 transport = remote_smtp
20923 route_list = * smarthost.ref.example
20925 This causes all non-local addresses to be sent to the single host
20926 &'smarthost.ref.example'&. If a colon-separated list of smart hosts is given,
20927 they are tried in order
20928 (but you can use &%hosts_randomize%& to vary the order each time).
20929 Another way of configuring the same thing is this:
20932 driver = manualroute
20933 transport = remote_smtp
20934 route_list = !+local_domains smarthost.ref.example
20936 There is no difference in behaviour between these two routers as they stand.
20937 However, they behave differently if &%no_more%& is added to them. In the first
20938 example, the router is skipped if the domain does not match the &%domains%&
20939 precondition; the following router is always tried. If the router runs, it
20940 always matches the domain and so can never decline. Therefore, &%no_more%&
20941 would have no effect. In the second case, the router is never skipped; it
20942 always runs. However, if it doesn't match the domain, it declines. In this case
20943 &%no_more%& would prevent subsequent routers from running.
20946 .cindex "mail hub example"
20947 A &'mail hub'& is a host which receives mail for a number of domains via MX
20948 records in the DNS and delivers it via its own private routing mechanism. Often
20949 the final destinations are behind a firewall, with the mail hub being the one
20950 machine that can connect to machines both inside and outside the firewall. The
20951 &(manualroute)& router is usually used on a mail hub to route incoming messages
20952 to the correct hosts. For a small number of domains, the routing can be inline,
20953 using the &%route_list%& option, but for a larger number a file or database
20954 lookup is easier to manage.
20956 If the domain names are in fact the names of the machines to which the mail is
20957 to be sent by the mail hub, the configuration can be quite simple. For
20961 driver = manualroute
20962 transport = remote_smtp
20963 route_list = *.rhodes.tvs.example $domain
20965 This configuration routes domains that match &`*.rhodes.tvs.example`& to hosts
20966 whose names are the same as the mail domains. A similar approach can be taken
20967 if the host name can be obtained from the domain name by a string manipulation
20968 that the expansion facilities can handle. Otherwise, a lookup based on the
20969 domain can be used to find the host:
20972 driver = manualroute
20973 transport = remote_smtp
20974 route_data = ${lookup {$domain} cdb {/internal/host/routes}}
20976 The result of the lookup must be the name or IP address of the host (or
20977 hosts) to which the address is to be routed. If the lookup fails, the route
20978 data is empty, causing the router to decline. The address then passes to the
20982 .cindex "batched SMTP output example"
20983 .cindex "SMTP" "batched outgoing; example"
20984 You can use &(manualroute)& to deliver messages to pipes or files in batched
20985 SMTP format for onward transportation by some other means. This is one way of
20986 storing mail for a dial-up host when it is not connected. The route list entry
20987 can be as simple as a single domain name in a configuration like this:
20990 driver = manualroute
20991 transport = batchsmtp_appendfile
20992 route_list = saved.domain.example
20994 though often a pattern is used to pick up more than one domain. If there are
20995 several domains or groups of domains with different transport requirements,
20996 different transports can be listed in the routing information:
20999 driver = manualroute
21001 *.saved.domain1.example $domain batch_appendfile; \
21002 *.saved.domain2.example \
21003 ${lookup{$domain}dbm{/domain2/hosts}{$value}fail} \
21006 .vindex "&$domain$&"
21008 The first of these just passes the domain in the &$host$& variable, which
21009 doesn't achieve much (since it is also in &$domain$&), but the second does a
21010 file lookup to find a value to pass, causing the router to decline to handle
21011 the address if the lookup fails.
21014 .cindex "UUCP" "example of router for"
21015 Routing mail directly to UUCP software is a specific case of the use of
21016 &(manualroute)& in a gateway to another mail environment. This is an example of
21017 one way it can be done:
21023 command = /usr/local/bin/uux -r - \
21024 ${substr_-5:$host}!rmail ${local_part}
21025 return_fail_output = true
21030 driver = manualroute
21032 ${lookup{$domain}lsearch{/usr/local/exim/uucphosts}}
21034 The file &_/usr/local/exim/uucphosts_& contains entries like
21036 darksite.ethereal.example: darksite.UUCP
21038 It can be set up more simply without adding and removing &".UUCP"& but this way
21039 makes clear the distinction between the domain name
21040 &'darksite.ethereal.example'& and the UUCP host name &'darksite'&.
21042 .ecindex IIDmanrou1
21043 .ecindex IIDmanrou2
21052 . ////////////////////////////////////////////////////////////////////////////
21053 . ////////////////////////////////////////////////////////////////////////////
21055 .chapter "The queryprogram router" "CHAPdriverlast"
21056 .scindex IIDquerou1 "&(queryprogram)& router"
21057 .scindex IIDquerou2 "routers" "&(queryprogram)&"
21058 .cindex "routing" "by external program"
21059 The &(queryprogram)& router routes an address by running an external command
21060 and acting on its output. This is an expensive way to route, and is intended
21061 mainly for use in lightly-loaded systems, or for performing experiments.
21062 However, if it is possible to use the precondition options (&%domains%&,
21063 &%local_parts%&, etc) to skip this router for most addresses, it could sensibly
21064 be used in special cases, even on a busy host. There are the following private
21066 .cindex "options" "&(queryprogram)& router"
21068 .option command queryprogram string&!! unset
21069 This option must be set. It specifies the command that is to be run. The
21070 command is split up into a command name and arguments, and then each is
21071 expanded separately (exactly as for a &(pipe)& transport, described in chapter
21072 &<<CHAPpipetransport>>&).
21075 .option command_group queryprogram string unset
21076 .cindex "gid (group id)" "in &(queryprogram)& router"
21077 This option specifies a gid to be set when running the command while routing an
21078 address for deliver. It must be set if &%command_user%& specifies a numerical
21079 uid. If it begins with a digit, it is interpreted as the numerical value of the
21080 gid. Otherwise it is looked up using &[getgrnam()]&.
21083 .option command_user queryprogram string unset
21084 .cindex "uid (user id)" "for &(queryprogram)&"
21085 This option must be set. It specifies the uid which is set when running the
21086 command while routing an address for delivery. If the value begins with a digit,
21087 it is interpreted as the numerical value of the uid. Otherwise, it is looked up
21088 using &[getpwnam()]& to obtain a value for the uid and, if &%command_group%& is
21089 not set, a value for the gid also.
21091 &*Warning:*& Changing uid and gid is possible only when Exim is running as
21092 root, which it does during a normal delivery in a conventional configuration.
21093 However, when an address is being verified during message reception, Exim is
21094 usually running as the Exim user, not as root. If the &(queryprogram)& router
21095 is called from a non-root process, Exim cannot change uid or gid before running
21096 the command. In this circumstance the command runs under the current uid and
21100 .option current_directory queryprogram string /
21101 This option specifies an absolute path which is made the current directory
21102 before running the command.
21105 .option timeout queryprogram time 1h
21106 If the command does not complete within the timeout period, its process group
21107 is killed and the message is frozen. A value of zero time specifies no
21111 The standard output of the command is connected to a pipe, which is read when
21112 the command terminates. It should consist of a single line of output,
21113 containing up to five fields, separated by white space. The maximum length of
21114 the line is 1023 characters. Longer lines are silently truncated. The first
21115 field is one of the following words (case-insensitive):
21118 &'Accept'&: routing succeeded; the remaining fields specify what to do (see
21121 &'Decline'&: the router declines; pass the address to the next router, unless
21122 &%no_more%& is set.
21124 &'Fail'&: routing failed; do not pass the address to any more routers. Any
21125 subsequent text on the line is an error message. If the router is run as part
21126 of address verification during an incoming SMTP message, the message is
21127 included in the SMTP response.
21129 &'Defer'&: routing could not be completed at this time; try again later. Any
21130 subsequent text on the line is an error message which is logged. It is not
21131 included in any SMTP response.
21133 &'Freeze'&: the same as &'defer'&, except that the message is frozen.
21135 &'Pass'&: pass the address to the next router (or the router specified by
21136 &%pass_router%&), overriding &%no_more%&.
21138 &'Redirect'&: the message is redirected. The remainder of the line is a list of
21139 new addresses, which are routed independently, starting with the first router,
21140 or the router specified by &%redirect_router%&, if set.
21143 When the first word is &'accept'&, the remainder of the line consists of a
21144 number of keyed data values, as follows (split into two lines here, to fit on
21147 ACCEPT TRANSPORT=<transport> HOSTS=<list of hosts>
21148 LOOKUP=byname|bydns DATA=<text>
21150 The data items can be given in any order, and all are optional. If no transport
21151 is included, the transport specified by the generic &%transport%& option is
21152 used. The list of hosts and the lookup type are needed only if the transport is
21153 an &(smtp)& transport that does not itself supply a list of hosts.
21155 The format of the list of hosts is the same as for the &(manualroute)& router.
21156 As well as host names and IP addresses with optional port numbers, as described
21157 in section &<<SECTformatonehostitem>>&, it may contain names followed by
21158 &`/MX`& to specify sublists of hosts that are obtained by looking up MX records
21159 (see section &<<SECThostshowused>>&).
21161 If the lookup type is not specified, Exim behaves as follows when trying to
21162 find an IP address for each host: First, a DNS lookup is done. If this yields
21163 anything other than HOST_NOT_FOUND, that result is used. Otherwise, Exim
21164 goes on to try a call to &[getipnodebyname()]& or &[gethostbyname()]&, and the
21165 result of the lookup is the result of that call.
21167 .vindex "&$address_data$&"
21168 If the DATA field is set, its value is placed in the &$address_data$&
21169 variable. For example, this return line
21171 accept hosts=x1.y.example:x2.y.example data="rule1"
21173 routes the address to the default transport, passing a list of two hosts. When
21174 the transport runs, the string &"rule1"& is in &$address_data$&.
21175 .ecindex IIDquerou1
21176 .ecindex IIDquerou2
21181 . ////////////////////////////////////////////////////////////////////////////
21182 . ////////////////////////////////////////////////////////////////////////////
21184 .chapter "The redirect router" "CHAPredirect"
21185 .scindex IIDredrou1 "&(redirect)& router"
21186 .scindex IIDredrou2 "routers" "&(redirect)&"
21187 .cindex "alias file" "in a &(redirect)& router"
21188 .cindex "address redirection" "&(redirect)& router"
21189 The &(redirect)& router handles several kinds of address redirection. Its most
21190 common uses are for resolving local part aliases from a central alias file
21191 (usually called &_/etc/aliases_&) and for handling users' personal &_.forward_&
21192 files, but it has many other potential uses. The incoming address can be
21193 redirected in several different ways:
21196 It can be replaced by one or more new addresses which are themselves routed
21199 It can be routed to be delivered to a given file or directory.
21201 It can be routed to be delivered to a specified pipe command.
21203 It can cause an automatic reply to be generated.
21205 It can be forced to fail, optionally with a custom error message.
21207 It can be temporarily deferred, optionally with a custom message.
21209 It can be discarded.
21212 The generic &%transport%& option must not be set for &(redirect)& routers.
21213 However, there are some private options which define transports for delivery to
21214 files and pipes, and for generating autoreplies. See the &%file_transport%&,
21215 &%pipe_transport%& and &%reply_transport%& descriptions below.
21217 If success DSNs have been requested
21218 .cindex "DSN" "success"
21219 .cindex "Delivery Status Notification" "success"
21220 redirection triggers one and the DSN options are not passed any further.
21224 .section "Redirection data" "SECID124"
21225 The router operates by interpreting a text string which it obtains either by
21226 expanding the contents of the &%data%& option, or by reading the entire
21227 contents of a file whose name is given in the &%file%& option. These two
21228 options are mutually exclusive. The first is commonly used for handling system
21229 aliases, in a configuration like this:
21233 data = ${lookup{$local_part}lsearch{/etc/aliases}}
21235 If the lookup fails, the expanded string in this example is empty. When the
21236 expansion of &%data%& results in an empty string, the router declines. A forced
21237 expansion failure also causes the router to decline; other expansion failures
21238 cause delivery to be deferred.
21240 A configuration using &%file%& is commonly used for handling users'
21241 &_.forward_& files, like this:
21246 file = $home/.forward
21249 If the file does not exist, or causes no action to be taken (for example, it is
21250 empty or consists only of comments), the router declines. &*Warning*&: This
21251 is not the case when the file contains syntactically valid items that happen to
21252 yield empty addresses, for example, items containing only RFC 2822 address
21255 .cindex "tainted data" "in filenames"
21256 .cindex redirect "tainted data"
21257 Tainted data may not be used for a filename.
21259 &*Warning*&: It is unwise to use &$local_part$& or &$domain$&
21260 directly for redirection,
21261 as they are provided by a potential attacker.
21262 In the examples above, &$local_part$& is used for looking up data held locally
21263 on the system, and not used directly (the second example derives &$home$& via
21264 the passsword file or database, using &$local_part$&).
21268 .section "Forward files and address verification" "SECID125"
21269 .cindex "address redirection" "while verifying"
21270 It is usual to set &%no_verify%& on &(redirect)& routers which handle users'
21271 &_.forward_& files, as in the example above. There are two reasons for this:
21274 When Exim is receiving an incoming SMTP message from a remote host, it is
21275 running under the Exim uid, not as root. Exim is unable to change uid to read
21276 the file as the user, and it may not be able to read it as the Exim user. So in
21277 practice the router may not be able to operate.
21279 However, even when the router can operate, the existence of a &_.forward_& file
21280 is unimportant when verifying an address. What should be checked is whether the
21281 local part is a valid user name or not. Cutting out the redirection processing
21282 saves some resources.
21290 .section "Interpreting redirection data" "SECID126"
21291 .cindex "Sieve filter" "specifying in redirection data"
21292 .cindex "filter" "specifying in redirection data"
21293 The contents of the data string, whether obtained from &%data%& or &%file%&,
21294 can be interpreted in two different ways:
21297 If the &%allow_filter%& option is set true, and the data begins with the text
21298 &"#Exim filter"& or &"#Sieve filter"&, it is interpreted as a list of
21299 &'filtering'& instructions in the form of an Exim or Sieve filter file,
21300 respectively. Details of the syntax and semantics of filter files are described
21301 in a separate document entitled &'Exim's interfaces to mail filtering'&; this
21302 document is intended for use by end users.
21304 Otherwise, the data must be a comma-separated list of redirection items, as
21305 described in the next section.
21308 When a message is redirected to a file (a &"mail folder"&), the filename given
21309 in a non-filter redirection list must always be an absolute path. A filter may
21310 generate a relative path &-- how this is handled depends on the transport's
21311 configuration. See section &<<SECTfildiropt>>& for a discussion of this issue
21312 for the &(appendfile)& transport.
21316 .section "Items in a non-filter redirection list" "SECTitenonfilred"
21317 .cindex "address redirection" "non-filter list items"
21318 When the redirection data is not an Exim or Sieve filter, for example, if it
21319 comes from a conventional alias or forward file, it consists of a list of
21320 addresses, filenames, pipe commands, or certain special items (see section
21321 &<<SECTspecitredli>>& below). The special items can be individually enabled or
21322 disabled by means of options whose names begin with &%allow_%& or &%forbid_%&,
21323 depending on their default values. The items in the list are separated by
21324 commas or newlines.
21325 If a comma is required in an item, the entire item must be enclosed in double
21328 Lines starting with a # character are comments, and are ignored, and # may
21329 also appear following a comma, in which case everything between the # and the
21330 next newline character is ignored.
21332 If an item is entirely enclosed in double quotes, these are removed. Otherwise
21333 double quotes are retained because some forms of mail address require their use
21334 (but never to enclose the entire address). In the following description,
21335 &"item"& refers to what remains after any surrounding double quotes have been
21338 .vindex "&$local_part$&"
21339 &*Warning*&: If you use an Exim expansion to construct a redirection address,
21340 and the expansion contains a reference to &$local_part$&, you should make use
21341 of the &%quote_local_part%& expansion operator, in case the local part contains
21342 special characters. For example, to redirect all mail for the domain
21343 &'obsolete.example'&, retaining the existing local part, you could use this
21346 data = ${quote_local_part:$local_part}@newdomain.example
21350 .section "Redirecting to a local mailbox" "SECTredlocmai"
21351 .cindex "routing" "loops in"
21352 .cindex "loop" "while routing, avoidance of"
21353 .cindex "address redirection" "to local mailbox"
21354 A redirection item may safely be the same as the address currently under
21355 consideration. This does not cause a routing loop, because a router is
21356 automatically skipped if any ancestor of the address that is being processed
21357 is the same as the current address and was processed by the current router.
21358 Such an address is therefore passed to the following routers, so it is handled
21359 as if there were no redirection. When making this loop-avoidance test, the
21360 complete local part, including any prefix or suffix, is used.
21362 .cindex "address redirection" "local part without domain"
21363 Specifying the same local part without a domain is a common usage in personal
21364 filter files when the user wants to have messages delivered to the local
21365 mailbox and also forwarded elsewhere. For example, the user whose login is
21366 &'cleo'& might have a &_.forward_& file containing this:
21368 cleo, cleopatra@egypt.example
21370 .cindex "backslash in alias file"
21371 .cindex "alias file" "backslash in"
21372 For compatibility with other MTAs, such unqualified local parts may be
21373 preceded by &"\"&, but this is not a requirement for loop prevention. However,
21374 it does make a difference if more than one domain is being handled
21377 If an item begins with &"\"& and the rest of the item parses as a valid RFC
21378 2822 address that does not include a domain, the item is qualified using the
21379 domain of the incoming address. In the absence of a leading &"\"&, unqualified
21380 addresses are qualified using the value in &%qualify_recipient%&, but you can
21381 force the incoming domain to be used by setting &%qualify_preserve_domain%&.
21383 Care must be taken if there are alias names for local users.
21384 Consider an MTA handling a single local domain where the system alias file
21389 Now suppose that Sam (whose login id is &'spqr'&) wants to save copies of
21390 messages in the local mailbox, and also forward copies elsewhere. He creates
21393 Sam.Reman, spqr@reme.elsewhere.example
21395 With these settings, an incoming message addressed to &'Sam.Reman'& fails. The
21396 &(redirect)& router for system aliases does not process &'Sam.Reman'& the
21397 second time round, because it has previously routed it,
21398 and the following routers presumably cannot handle the alias. The forward file
21399 should really contain
21401 spqr, spqr@reme.elsewhere.example
21403 but because this is such a common error, the &%check_ancestor%& option (see
21404 below) exists to provide a way to get round it. This is normally set on a
21405 &(redirect)& router that is handling users' &_.forward_& files.
21409 .section "Special items in redirection lists" "SECTspecitredli"
21410 In addition to addresses, the following types of item may appear in redirection
21411 lists (that is, in non-filter redirection data):
21414 .cindex "pipe" "in redirection list"
21415 .cindex "address redirection" "to pipe"
21416 An item is treated as a pipe command if it begins with &"|"& and does not parse
21417 as a valid RFC 2822 address that includes a domain. A transport for running the
21418 command must be specified by the &%pipe_transport%& option.
21419 Normally, either the router or the transport specifies a user and a group under
21420 which to run the delivery. The default is to use the Exim user and group.
21422 Single or double quotes can be used for enclosing the individual arguments of
21423 the pipe command; no interpretation of escapes is done for single quotes. If
21424 the command contains a comma character, it is necessary to put the whole item
21425 in double quotes, for example:
21427 "|/some/command ready,steady,go"
21429 since items in redirection lists are terminated by commas. Do not, however,
21430 quote just the command. An item such as
21432 |"/some/command ready,steady,go"
21434 is interpreted as a pipe with a rather strange command name, and no arguments.
21436 Note that the above example assumes that the text comes from a lookup source
21437 of some sort, so that the quotes are part of the data. If composing a
21438 redirect router with a &%data%& option directly specifying this command, the
21439 quotes will be used by the configuration parser to define the extent of one
21440 string, but will not be passed down into the redirect router itself. There
21441 are two main approaches to get around this: escape quotes to be part of the
21442 data itself, or avoid using this mechanism and instead create a custom
21443 transport with the &%command%& option set and reference that transport from
21444 an &%accept%& router.
21447 .cindex "file" "in redirection list"
21448 .cindex "address redirection" "to file"
21449 An item is interpreted as a path name if it begins with &"/"& and does not
21450 parse as a valid RFC 2822 address that includes a domain. For example,
21452 /home/world/minbari
21454 is treated as a filename, but
21456 /s=molari/o=babylon/@x400gate.way
21458 is treated as an address. For a filename, a transport must be specified using
21459 the &%file_transport%& option. However, if the generated path name ends with a
21460 forward slash character, it is interpreted as a directory name rather than a
21461 filename, and &%directory_transport%& is used instead.
21463 Normally, either the router or the transport specifies a user and a group under
21464 which to run the delivery. The default is to use the Exim user and group.
21466 .cindex "&_/dev/null_&"
21467 However, if a redirection item is the path &_/dev/null_&, delivery to it is
21468 bypassed at a high level, and the log entry shows &"**bypassed**"&
21469 instead of a transport name. In this case the user and group are not used.
21472 .cindex "included address list"
21473 .cindex "address redirection" "included external list"
21474 If an item is of the form
21476 :include:<path name>
21478 a list of further items is taken from the given file and included at that
21479 point. &*Note*&: Such a file can not be a filter file; it is just an
21480 out-of-line addition to the list. The items in the included list are separated
21481 by commas or newlines and are not subject to expansion. If this is the first
21482 item in an alias list in an &(lsearch)& file, a colon must be used to terminate
21483 the alias name. This example is incorrect:
21485 list1 :include:/opt/lists/list1
21487 It must be given as
21489 list1: :include:/opt/lists/list1
21491 .cindex "tainted data" "in filenames"
21492 .cindex redirect "tainted data"
21493 Tainted data may not be used for a filename.
21495 .cindex "address redirection" "to black hole"
21496 .cindex "delivery" "discard"
21497 .cindex "delivery" "blackhole"
21498 .cindex "black hole"
21499 .cindex "abandoning mail"
21500 Sometimes you want to throw away mail to a particular local part. Making the
21501 &%data%& option expand to an empty string does not work, because that causes
21502 the router to decline. Instead, the alias item
21506 can be used. It does what its name implies. No delivery is
21507 done, and no error message is generated. This has the same effect as specifying
21508 &_/dev/null_& as a destination, but it can be independently disabled.
21510 &*Warning*&: If &':blackhole:'& appears anywhere in a redirection list, no
21511 delivery is done for the original local part, even if other redirection items
21512 are present. If you are generating a multi-item list (for example, by reading a
21513 database) and need the ability to provide a no-op item, you must use
21517 .cindex "delivery" "forcing failure"
21518 .cindex "delivery" "forcing deferral"
21519 .cindex "failing delivery" "forcing"
21520 .cindex "deferred delivery, forcing"
21521 .cindex "customizing" "failure message"
21522 An attempt to deliver a particular address can be deferred or forced to fail by
21523 redirection items of the form
21528 respectively. When a redirection list contains such an item, it applies
21529 to the entire redirection; any other items in the list are ignored. Any
21530 text following &':fail:'& or &':defer:'& is placed in the error text
21531 associated with the failure. For example, an alias file might contain:
21533 X.Employee: :fail: Gone away, no forwarding address
21535 In the case of an address that is being verified from an ACL or as the subject
21537 .cindex "VRFY" "error text, display of"
21538 VRFY command, the text is included in the SMTP error response by
21540 .cindex "EXPN" "error text, display of"
21541 The text is not included in the response to an EXPN command. In non-SMTP cases
21542 the text is included in the error message that Exim generates.
21544 .cindex "SMTP" "error codes"
21545 By default for verify, Exim sends a 451 SMTP code for a &':defer:'&, and 550 for
21546 &':fail:'&. However, if the message starts with three digits followed by a
21547 space, optionally followed by an extended code of the form &'n.n.n'&, also
21548 followed by a space, and the very first digit is the same as the default error
21549 code, the code from the message is used instead. If the very first digit is
21550 incorrect, a panic error is logged, and the default code is used. You can
21551 suppress the use of the supplied code in a redirect router by setting the
21552 &%forbid_smtp_code%& option true. In this case, any SMTP code is quietly
21555 .vindex "&$acl_verify_message$&"
21556 In an ACL, an explicitly provided message overrides the default, but the
21557 default message is available in the variable &$acl_verify_message$& and can
21558 therefore be included in a custom message if this is desired.
21560 Normally the error text is the rest of the redirection list &-- a comma does
21561 not terminate it &-- but a newline does act as a terminator. Newlines are not
21562 normally present in alias expansions. In &(lsearch)& lookups they are removed
21563 as part of the continuation process, but they may exist in other kinds of
21564 lookup and in &':include:'& files.
21566 During routing for message delivery (as opposed to verification), a redirection
21567 containing &':fail:'& causes an immediate failure of the incoming address,
21568 whereas &':defer:'& causes the message to remain in the queue so that a
21569 subsequent delivery attempt can happen at a later time. If an address is
21570 deferred for too long, it will ultimately fail, because the normal retry
21574 .cindex "alias file" "exception to default"
21575 Sometimes it is useful to use a single-key search type with a default (see
21576 chapter &<<CHAPfdlookup>>&) to look up aliases. However, there may be a need
21577 for exceptions to the default. These can be handled by aliasing them to
21578 &':unknown:'&. This differs from &':fail:'& in that it causes the &(redirect)&
21579 router to decline, whereas &':fail:'& forces routing to fail. A lookup which
21580 results in an empty redirection list has the same effect.
21584 .section "Duplicate addresses" "SECTdupaddr"
21585 .cindex "duplicate addresses"
21586 .cindex "address duplicate, discarding"
21587 .cindex "pipe" "duplicated"
21588 Exim removes duplicate addresses from the list to which it is delivering, so as
21589 to deliver just one copy to each address. This does not apply to deliveries
21590 routed to pipes by different immediate parent addresses, but an indirect
21591 aliasing scheme of the type
21593 pipe: |/some/command $local_part
21597 does not work with a message that is addressed to both local parts, because
21598 when the second is aliased to the intermediate local part &"pipe"& it gets
21599 discarded as being the same as a previously handled address. However, a scheme
21602 localpart1: |/some/command $local_part
21603 localpart2: |/some/command $local_part
21605 does result in two different pipe deliveries, because the immediate parents of
21606 the pipes are distinct.
21610 .section "Repeated redirection expansion" "SECID128"
21611 .cindex "repeated redirection expansion"
21612 .cindex "address redirection" "repeated for each delivery attempt"
21613 When a message cannot be delivered to all of its recipients immediately,
21614 leading to two or more delivery attempts, redirection expansion is carried out
21615 afresh each time for those addresses whose children were not all previously
21616 delivered. If redirection is being used as a mailing list, this can lead to new
21617 members of the list receiving copies of old messages. The &%one_time%& option
21618 can be used to avoid this.
21621 .section "Errors in redirection lists" "SECID129"
21622 .cindex "address redirection" "errors"
21623 If &%skip_syntax_errors%& is set, a malformed address that causes a parsing
21624 error is skipped, and an entry is written to the main log. This may be useful
21625 for mailing lists that are automatically managed. Otherwise, if an error is
21626 detected while generating the list of new addresses, the original address is
21627 deferred. See also &%syntax_errors_to%&.
21631 .section "Private options for the redirect router" "SECID130"
21633 .cindex "options" "&(redirect)& router"
21634 The private options for the &(redirect)& router are as follows:
21637 .option allow_defer redirect boolean false
21638 Setting this option allows the use of &':defer:'& in non-filter redirection
21639 data, or the &%defer%& command in an Exim filter file.
21642 .option allow_fail redirect boolean false
21643 .cindex "failing delivery" "from filter"
21644 If this option is true, the &':fail:'& item can be used in a redirection list,
21645 and the &%fail%& command may be used in an Exim filter file.
21648 .option allow_filter redirect boolean false
21649 .cindex "filter" "enabling use of"
21650 .cindex "Sieve filter" "enabling use of"
21651 Setting this option allows Exim to interpret redirection data that starts with
21652 &"#Exim filter"& or &"#Sieve filter"& as a set of filtering instructions. There
21653 are some features of Exim filter files that some administrators may wish to
21654 lock out; see the &%forbid_filter_%&&'xxx'& options below.
21656 It is also possible to lock out Exim filters or Sieve filters while allowing
21657 the other type; see &%forbid_exim_filter%& and &%forbid_sieve_filter%&.
21660 The filter is run using the uid and gid set by the generic &%user%& and
21661 &%group%& options. These take their defaults from the password data if
21662 &%check_local_user%& is set, so in the normal case of users' personal filter
21663 files, the filter is run as the relevant user. When &%allow_filter%& is set
21664 true, Exim insists that either &%check_local_user%& or &%user%& is set.
21668 .option allow_freeze redirect boolean false
21669 .cindex "freezing messages" "allowing in filter"
21670 Setting this option allows the use of the &%freeze%& command in an Exim filter.
21671 This command is more normally encountered in system filters, and is disabled by
21672 default for redirection filters because it isn't something you usually want to
21673 let ordinary users do.
21677 .option check_ancestor redirect boolean false
21678 This option is concerned with handling generated addresses that are the same
21679 as some address in the list of redirection ancestors of the current address.
21680 Although it is turned off by default in the code, it is set in the default
21681 configuration file for handling users' &_.forward_& files. It is recommended
21682 for this use of the &(redirect)& router.
21684 When &%check_ancestor%& is set, if a generated address (including the domain)
21685 is the same as any ancestor of the current address, it is replaced by a copy of
21686 the current address. This helps in the case where local part A is aliased to B,
21687 and B has a &_.forward_& file pointing back to A. For example, within a single
21688 domain, the local part &"Joe.Bloggs"& is aliased to &"jb"& and
21689 &_&~jb/.forward_& contains:
21691 \Joe.Bloggs, <other item(s)>
21693 Without the &%check_ancestor%& setting, either local part (&"jb"& or
21694 &"joe.bloggs"&) gets processed once by each router and so ends up as it was
21695 originally. If &"jb"& is the real mailbox name, mail to &"jb"& gets delivered
21696 (having been turned into &"joe.bloggs"& by the &_.forward_& file and back to
21697 &"jb"& by the alias), but mail to &"joe.bloggs"& fails. Setting
21698 &%check_ancestor%& on the &(redirect)& router that handles the &_.forward_&
21699 file prevents it from turning &"jb"& back into &"joe.bloggs"& when that was the
21700 original address. See also the &%repeat_use%& option below.
21703 .option check_group redirect boolean "see below"
21704 When the &%file%& option is used, the group owner of the file is checked only
21705 when this option is set. The permitted groups are those listed in the
21706 &%owngroups%& option, together with the user's default group if
21707 &%check_local_user%& is set. If the file has the wrong group, routing is
21708 deferred. The default setting for this option is true if &%check_local_user%&
21709 is set and the &%modemask%& option permits the group write bit, or if the
21710 &%owngroups%& option is set. Otherwise it is false, and no group check occurs.
21714 .option check_owner redirect boolean "see below"
21715 When the &%file%& option is used, the owner of the file is checked only when
21716 this option is set. If &%check_local_user%& is set, the local user is
21717 permitted; otherwise the owner must be one of those listed in the &%owners%&
21718 option. The default value for this option is true if &%check_local_user%& or
21719 &%owners%& is set. Otherwise the default is false, and no owner check occurs.
21722 .option data redirect string&!! unset
21723 This option is mutually exclusive with &%file%&. One or other of them must be
21724 set, but not both. The contents of &%data%& are expanded, and then used as the
21725 list of forwarding items, or as a set of filtering instructions. If the
21726 expansion is forced to fail, or the result is an empty string or a string that
21727 has no effect (consists entirely of comments), the router declines.
21729 When filtering instructions are used, the string must begin with &"#Exim
21730 filter"&, and all comments in the string, including this initial one, must be
21731 terminated with newline characters. For example:
21733 data = #Exim filter\n\
21734 if $h_to: contains Exim then save $home/mail/exim endif
21736 If you are reading the data from a database where newlines cannot be included,
21737 you can use the &${sg}$& expansion item to turn the escape string of your
21738 choice into a newline.
21741 .option directory_transport redirect string&!! unset
21742 A &(redirect)& router sets up a direct delivery to a directory when a path name
21743 ending with a slash is specified as a new &"address"&. The transport used is
21744 specified by this option, which, after expansion, must be the name of a
21745 configured transport. This should normally be an &(appendfile)& transport.
21748 .option file redirect string&!! unset
21749 This option specifies the name of a file that contains the redirection data. It
21750 is mutually exclusive with the &%data%& option. The string is expanded before
21751 use; if the expansion is forced to fail, the router declines. Other expansion
21752 failures cause delivery to be deferred. The result of a successful expansion
21753 must be an absolute path. The entire file is read and used as the redirection
21754 data. If the data is an empty string or a string that has no effect (consists
21755 entirely of comments), the router declines.
21757 .cindex "NFS" "checking for file existence"
21758 If the attempt to open the file fails with a &"does not exist"& error, Exim
21759 runs a check on the containing directory,
21760 unless &%ignore_enotdir%& is true (see below).
21761 If the directory does not appear to exist, delivery is deferred. This can
21762 happen when users' &_.forward_& files are in NFS-mounted directories, and there
21763 is a mount problem. If the containing directory does exist, but the file does
21764 not, the router declines.
21767 .option file_transport redirect string&!! unset
21768 .vindex "&$address_file$&"
21769 A &(redirect)& router sets up a direct delivery to a file when a path name not
21770 ending in a slash is specified as a new &"address"&. The transport used is
21771 specified by this option, which, after expansion, must be the name of a
21772 configured transport. This should normally be an &(appendfile)& transport. When
21773 it is running, the filename is in &$address_file$&.
21776 .option filter_prepend_home redirect boolean true
21777 When this option is true, if a &(save)& command in an Exim filter specifies a
21778 relative path, and &$home$& is defined, it is automatically prepended to the
21779 relative path. If this option is set false, this action does not happen. The
21780 relative path is then passed to the transport unmodified.
21783 .option forbid_blackhole redirect boolean false
21784 .cindex "restricting access to features"
21785 .cindex "filter" "locking out certain features"
21786 If this option is true, the &':blackhole:'& item may not appear in a
21790 .option forbid_exim_filter redirect boolean false
21791 .cindex "restricting access to features"
21792 .cindex "filter" "locking out certain features"
21793 If this option is set true, only Sieve filters are permitted when
21794 &%allow_filter%& is true.
21799 .option forbid_file redirect boolean false
21800 .cindex "restricting access to features"
21801 .cindex "delivery" "to file; forbidding"
21802 .cindex "filter" "locking out certain features"
21803 .cindex "Sieve filter" "forbidding delivery to a file"
21804 .cindex "Sieve filter" "&""keep""& facility; disabling"
21805 If this option is true, this router may not generate a new address that
21806 specifies delivery to a local file or directory, either from a filter or from a
21807 conventional forward file. This option is forced to be true if &%one_time%& is
21808 set. It applies to Sieve filters as well as to Exim filters, but if true, it
21809 locks out the Sieve's &"keep"& facility.
21812 .option forbid_filter_dlfunc redirect boolean false
21813 .cindex "restricting access to features"
21814 .cindex "filter" "locking out certain features"
21815 If this option is true, string expansions in Exim filters are not allowed to
21816 make use of the &%dlfunc%& expansion facility to run dynamically loaded
21819 .option forbid_filter_existstest redirect boolean false
21820 .cindex "restricting access to features"
21821 .cindex "filter" "locking out certain features"
21822 .cindex "expansion" "statting a file"
21823 If this option is true, string expansions in Exim filters are not allowed to
21824 make use of the &%exists%& condition or the &%stat%& expansion item.
21826 .option forbid_filter_logwrite redirect boolean false
21827 .cindex "restricting access to features"
21828 .cindex "filter" "locking out certain features"
21829 If this option is true, use of the logging facility in Exim filters is not
21830 permitted. Logging is in any case available only if the filter is being run
21831 under some unprivileged uid (which is normally the case for ordinary users'
21832 &_.forward_& files).
21835 .option forbid_filter_lookup redirect boolean false
21836 .cindex "restricting access to features"
21837 .cindex "filter" "locking out certain features"
21838 If this option is true, string expansions in Exim filter files are not allowed
21839 to make use of &%lookup%& items.
21842 .option forbid_filter_perl redirect boolean false
21843 .cindex "restricting access to features"
21844 .cindex "filter" "locking out certain features"
21845 This option has an effect only if Exim is built with embedded Perl support. If
21846 it is true, string expansions in Exim filter files are not allowed to make use
21847 of the embedded Perl support.
21850 .option forbid_filter_readfile redirect boolean false
21851 .cindex "restricting access to features"
21852 .cindex "filter" "locking out certain features"
21853 If this option is true, string expansions in Exim filter files are not allowed
21854 to make use of &%readfile%& items.
21857 .option forbid_filter_readsocket redirect boolean false
21858 .cindex "restricting access to features"
21859 .cindex "filter" "locking out certain features"
21860 If this option is true, string expansions in Exim filter files are not allowed
21861 to make use of &%readsocket%& items.
21864 .option forbid_filter_reply redirect boolean false
21865 .cindex "restricting access to features"
21866 .cindex "filter" "locking out certain features"
21867 If this option is true, this router may not generate an automatic reply
21868 message. Automatic replies can be generated only from Exim or Sieve filter
21869 files, not from traditional forward files. This option is forced to be true if
21870 &%one_time%& is set.
21873 .option forbid_filter_run redirect boolean false
21874 .cindex "restricting access to features"
21875 .cindex "filter" "locking out certain features"
21876 If this option is true, string expansions in Exim filter files are not allowed
21877 to make use of &%run%& items.
21880 .option forbid_include redirect boolean false
21881 .cindex "restricting access to features"
21882 .cindex "filter" "locking out certain features"
21883 If this option is true, items of the form
21885 :include:<path name>
21887 are not permitted in non-filter redirection lists.
21890 .option forbid_pipe redirect boolean false
21891 .cindex "restricting access to features"
21892 .cindex "filter" "locking out certain features"
21893 .cindex "delivery" "to pipe; forbidding"
21894 If this option is true, this router may not generate a new address which
21895 specifies delivery to a pipe, either from an Exim filter or from a conventional
21896 forward file. This option is forced to be true if &%one_time%& is set.
21899 .option forbid_sieve_filter redirect boolean false
21900 .cindex "restricting access to features"
21901 .cindex "filter" "locking out certain features"
21902 If this option is set true, only Exim filters are permitted when
21903 &%allow_filter%& is true.
21906 .cindex "SMTP" "error codes"
21907 .option forbid_smtp_code redirect boolean false
21908 If this option is set true, any SMTP error codes that are present at the start
21909 of messages specified for &`:defer:`& or &`:fail:`& are quietly ignored, and
21910 the default codes (451 and 550, respectively) are always used.
21915 .option hide_child_in_errmsg redirect boolean false
21916 .cindex "bounce message" "redirection details; suppressing"
21917 If this option is true, it prevents Exim from quoting a child address if it
21918 generates a bounce or delay message for it. Instead it says &"an address
21919 generated from <&'the top level address'&>"&. Of course, this applies only to
21920 bounces generated locally. If a message is forwarded to another host, &'its'&
21921 bounce may well quote the generated address.
21924 .option ignore_eacces redirect boolean false
21926 If this option is set and an attempt to open a redirection file yields the
21927 EACCES error (permission denied), the &(redirect)& router behaves as if the
21928 file did not exist.
21931 .option ignore_enotdir redirect boolean false
21933 If this option is set and an attempt to open a redirection file yields the
21934 ENOTDIR error (something on the path is not a directory), the &(redirect)&
21935 router behaves as if the file did not exist.
21937 Setting &%ignore_enotdir%& has another effect as well: When a &(redirect)&
21938 router that has the &%file%& option set discovers that the file does not exist
21939 (the ENOENT error), it tries to &[stat()]& the parent directory, as a check
21940 against unmounted NFS directories. If the parent can not be statted, delivery
21941 is deferred. However, it seems wrong to do this check when &%ignore_enotdir%&
21942 is set, because that option tells Exim to ignore &"something on the path is not
21943 a directory"& (the ENOTDIR error). This is a confusing area, because it seems
21944 that some operating systems give ENOENT where others give ENOTDIR.
21948 .option include_directory redirect string unset
21949 If this option is set, the path names of any &':include:'& items in a
21950 redirection list must start with this directory.
21953 .option modemask redirect "octal integer" 022
21954 This specifies mode bits which must not be set for a file specified by the
21955 &%file%& option. If any of the forbidden bits are set, delivery is deferred.
21958 .option one_time redirect boolean false
21959 .cindex "one-time aliasing/forwarding expansion"
21960 .cindex "alias file" "one-time expansion"
21961 .cindex "forward file" "one-time expansion"
21962 .cindex "mailing lists" "one-time expansion"
21963 .cindex "address redirection" "one-time expansion"
21964 Sometimes the fact that Exim re-evaluates aliases and reprocesses redirection
21965 files each time it tries to deliver a message causes a problem when one or more
21966 of the generated addresses fails be delivered at the first attempt. The problem
21967 is not one of duplicate delivery &-- Exim is clever enough to handle that &--
21968 but of what happens when the redirection list changes during the time that the
21969 message is on Exim's queue. This is particularly true in the case of mailing
21970 lists, where new subscribers might receive copies of messages that were posted
21971 before they subscribed.
21973 If &%one_time%& is set and any addresses generated by the router fail to
21974 deliver at the first attempt, the failing addresses are added to the message as
21975 &"top level"& addresses, and the parent address that generated them is marked
21976 &"delivered"&. Thus, redirection does not happen again at the next delivery
21979 &*Warning 1*&: Any header line addition or removal that is specified by this
21980 router would be lost if delivery did not succeed at the first attempt. For this
21981 reason, the &%headers_add%& and &%headers_remove%& generic options are not
21982 permitted when &%one_time%& is set.
21984 &*Warning 2*&: To ensure that the router generates only addresses (as opposed
21985 to pipe or file deliveries or auto-replies) &%forbid_file%&, &%forbid_pipe%&,
21986 and &%forbid_filter_reply%& are forced to be true when &%one_time%& is set.
21988 &*Warning 3*&: The &%unseen%& generic router option may not be set with
21991 The original top-level address is remembered with each of the generated
21992 addresses, and is output in any log messages. However, any intermediate parent
21993 addresses are not recorded. This makes a difference to the log only if
21994 &%all_parents%& log selector is set. It is expected that &%one_time%& will
21995 typically be used for mailing lists, where there is normally just one level of
21999 .option owners redirect "string list" unset
22000 .cindex "ownership" "alias file"
22001 .cindex "ownership" "forward file"
22002 .cindex "alias file" "ownership"
22003 .cindex "forward file" "ownership"
22004 This specifies a list of permitted owners for the file specified by &%file%&.
22005 This list is in addition to the local user when &%check_local_user%& is set.
22006 See &%check_owner%& above.
22009 .option owngroups redirect "string list" unset
22010 This specifies a list of permitted groups for the file specified by &%file%&.
22011 The list is in addition to the local user's primary group when
22012 &%check_local_user%& is set. See &%check_group%& above.
22015 .option pipe_transport redirect string&!! unset
22016 .vindex "&$address_pipe$&"
22017 A &(redirect)& router sets up a direct delivery to a pipe when a string
22018 starting with a vertical bar character is specified as a new &"address"&. The
22019 transport used is specified by this option, which, after expansion, must be the
22020 name of a configured transport. This should normally be a &(pipe)& transport.
22021 When the transport is run, the pipe command is in &$address_pipe$&.
22024 .option qualify_domain redirect string&!! unset
22025 .vindex "&$qualify_recipient$&"
22026 If this option is set, and an unqualified address (one without a domain) is
22027 generated, and that address would normally be qualified by the global setting
22028 in &%qualify_recipient%&, it is instead qualified with the domain specified by
22029 expanding this string. If the expansion fails, the router declines. If you want
22030 to revert to the default, you can have the expansion generate
22031 &$qualify_recipient$&.
22033 This option applies to all unqualified addresses generated by Exim filters,
22034 but for traditional &_.forward_& files, it applies only to addresses that are
22035 not preceded by a backslash. Sieve filters cannot generate unqualified
22038 .option qualify_preserve_domain redirect boolean false
22039 .cindex "domain" "in redirection; preserving"
22040 .cindex "preserving domain in redirection"
22041 .cindex "address redirection" "domain; preserving"
22042 If this option is set, the router's local &%qualify_domain%& option must not be
22043 set (a configuration error occurs if it is). If an unqualified address (one
22044 without a domain) is generated, it is qualified with the domain of the parent
22045 address (the immediately preceding ancestor) instead of the global
22046 &%qualify_recipient%& value. In the case of a traditional &_.forward_& file,
22047 this applies whether or not the address is preceded by a backslash.
22050 .option repeat_use redirect boolean true
22051 If this option is set false, the router is skipped for a child address that has
22052 any ancestor that was routed by this router. This test happens before any of
22053 the other preconditions are tested. Exim's default anti-looping rules skip
22054 only when the ancestor is the same as the current address. See also
22055 &%check_ancestor%& above and the generic &%redirect_router%& option.
22058 .option reply_transport redirect string&!! unset
22059 A &(redirect)& router sets up an automatic reply when a &%mail%& or
22060 &%vacation%& command is used in a filter file. The transport used is specified
22061 by this option, which, after expansion, must be the name of a configured
22062 transport. This should normally be an &(autoreply)& transport. Other transports
22063 are unlikely to do anything sensible or useful.
22066 .option rewrite redirect boolean true
22067 .cindex "address redirection" "disabling rewriting"
22068 If this option is set false, addresses generated by the router are not
22069 subject to address rewriting. Otherwise, they are treated like new addresses
22070 and are rewritten according to the global rewriting rules.
22073 .option sieve_subaddress redirect string&!! unset
22074 The value of this option is passed to a Sieve filter to specify the
22075 :subaddress part of an address.
22077 .option sieve_useraddress redirect string&!! unset
22078 The value of this option is passed to a Sieve filter to specify the :user part
22079 of an address. However, if it is unset, the entire original local part
22080 (including any prefix or suffix) is used for :user.
22083 .option sieve_vacation_directory redirect string&!! unset
22084 .cindex "Sieve filter" "vacation directory"
22085 To enable the &"vacation"& extension for Sieve filters, you must set
22086 &%sieve_vacation_directory%& to the directory where vacation databases are held
22087 (do not put anything else in that directory), and ensure that the
22088 &%reply_transport%& option refers to an &(autoreply)& transport. Each user
22089 needs their own directory; Exim will create it if necessary.
22093 .option skip_syntax_errors redirect boolean false
22094 .cindex "forward file" "broken"
22095 .cindex "address redirection" "broken files"
22096 .cindex "alias file" "broken"
22097 .cindex "broken alias or forward files"
22098 .cindex "ignoring faulty addresses"
22099 .cindex "skipping faulty addresses"
22100 .cindex "error" "skipping bad syntax"
22101 If &%skip_syntax_errors%& is set, syntactically malformed addresses in
22102 non-filter redirection data are skipped, and each failing address is logged. If
22103 &%syntax_errors_to%& is set, a message is sent to the address it defines,
22104 giving details of the failures. If &%syntax_errors_text%& is set, its contents
22105 are expanded and placed at the head of the error message generated by
22106 &%syntax_errors_to%&. Usually it is appropriate to set &%syntax_errors_to%& to
22107 be the same address as the generic &%errors_to%& option. The
22108 &%skip_syntax_errors%& option is often used when handling mailing lists.
22110 If all the addresses in a redirection list are skipped because of syntax
22111 errors, the router declines to handle the original address, and it is passed to
22112 the following routers.
22114 If &%skip_syntax_errors%& is set when an Exim filter is interpreted, any syntax
22115 error in the filter causes filtering to be abandoned without any action being
22116 taken. The incident is logged, and the router declines to handle the address,
22117 so it is passed to the following routers.
22119 .cindex "Sieve filter" "syntax errors in"
22120 Syntax errors in a Sieve filter file cause the &"keep"& action to occur. This
22121 action is specified by RFC 3028. The values of &%skip_syntax_errors%&,
22122 &%syntax_errors_to%&, and &%syntax_errors_text%& are not used.
22124 &%skip_syntax_errors%& can be used to specify that errors in users' forward
22125 lists or filter files should not prevent delivery. The &%syntax_errors_to%&
22126 option, used with an address that does not get redirected, can be used to
22127 notify users of these errors, by means of a router like this:
22133 file = $home/.forward
22134 file_transport = address_file
22135 pipe_transport = address_pipe
22136 reply_transport = address_reply
22139 syntax_errors_to = real-$local_part@$domain
22140 syntax_errors_text = \
22141 This is an automatically generated message. An error has\n\
22142 been found in your .forward file. Details of the error are\n\
22143 reported below. While this error persists, you will receive\n\
22144 a copy of this message for every message that is addressed\n\
22145 to you. If your .forward file is a filter file, or if it is\n\
22146 a non-filter file containing no valid forwarding addresses,\n\
22147 a copy of each incoming message will be put in your normal\n\
22148 mailbox. If a non-filter file contains at least one valid\n\
22149 forwarding address, forwarding to the valid addresses will\n\
22150 happen, and those will be the only deliveries that occur.
22152 You also need a router to ensure that local addresses that are prefixed by
22153 &`real-`& are recognized, but not forwarded or filtered. For example, you could
22154 put this immediately before the &(userforward)& router:
22159 local_part_prefix = real-
22160 transport = local_delivery
22162 For security, it would probably be a good idea to restrict the use of this
22163 router to locally-generated messages, using a condition such as this:
22165 condition = ${if match {$sender_host_address}\
22166 {\N^(|127\.0\.0\.1)$\N}}
22170 .option syntax_errors_text redirect string&!! unset
22171 See &%skip_syntax_errors%& above.
22174 .option syntax_errors_to redirect string unset
22175 See &%skip_syntax_errors%& above.
22176 .ecindex IIDredrou1
22177 .ecindex IIDredrou2
22184 . ////////////////////////////////////////////////////////////////////////////
22185 . ////////////////////////////////////////////////////////////////////////////
22187 .chapter "Environment for running local transports" "CHAPenvironment" &&&
22188 "Environment for local transports"
22189 .scindex IIDenvlotra1 "local transports" "environment for"
22190 .scindex IIDenvlotra2 "environment" "local transports"
22191 .scindex IIDenvlotra3 "transport" "local; environment for"
22192 Local transports handle deliveries to files and pipes. (The &(autoreply)&
22193 transport can be thought of as similar to a pipe.) Exim always runs transports
22194 in subprocesses, under specified uids and gids. Typical deliveries to local
22195 mailboxes run under the uid and gid of the local user.
22197 Exim also sets a specific current directory while running the transport; for
22198 some transports a home directory setting is also relevant. The &(pipe)&
22199 transport is the only one that sets up environment variables; see section
22200 &<<SECTpipeenv>>& for details.
22202 The values used for the uid, gid, and the directories may come from several
22203 different places. In many cases, the router that handles the address associates
22204 settings with that address as a result of its &%check_local_user%&, &%group%&,
22205 or &%user%& options. However, values may also be given in the transport's own
22206 configuration, and these override anything that comes from the router.
22210 .section "Concurrent deliveries" "SECID131"
22211 .cindex "concurrent deliveries"
22212 .cindex "simultaneous deliveries"
22213 If two different messages for the same local recipient arrive more or less
22214 simultaneously, the two delivery processes are likely to run concurrently. When
22215 the &(appendfile)& transport is used to write to a file, Exim applies locking
22216 rules to stop concurrent processes from writing to the same file at the same
22219 However, when you use a &(pipe)& transport, it is up to you to arrange any
22220 locking that is needed. Here is a silly example:
22224 command = /bin/sh -c 'cat >>/some/file'
22226 This is supposed to write the message at the end of the file. However, if two
22227 messages arrive at the same time, the file will be scrambled. You can use the
22228 &%exim_lock%& utility program (see section &<<SECTmailboxmaint>>&) to lock a
22229 file using the same algorithm that Exim itself uses.
22234 .section "Uids and gids" "SECTenvuidgid"
22235 .cindex "local transports" "uid and gid"
22236 .cindex "transport" "local; uid and gid"
22237 All transports have the options &%group%& and &%user%&. If &%group%& is set, it
22238 overrides any group that the router set in the address, even if &%user%& is not
22239 set for the transport. This makes it possible, for example, to run local mail
22240 delivery under the uid of the recipient (set by the router), but in a special
22241 group (set by the transport). For example:
22244 # User/group are set by check_local_user in this router
22248 transport = group_delivery
22251 # This transport overrides the group
22253 driver = appendfile
22254 file = /var/spool/mail/$local_part_data
22257 If &%user%& is set for a transport, its value overrides what is set in the
22258 address by the router. If &%user%& is non-numeric and &%group%& is not set, the
22259 gid associated with the user is used. If &%user%& is numeric, &%group%& must be
22262 .oindex "&%initgroups%&"
22263 When the uid is taken from the transport's configuration, the &[initgroups()]&
22264 function is called for the groups associated with that uid if the
22265 &%initgroups%& option is set for the transport. When the uid is not specified
22266 by the transport, but is associated with the address by a router, the option
22267 for calling &[initgroups()]& is taken from the router configuration.
22269 .cindex "&(pipe)& transport" "uid for"
22270 The &(pipe)& transport contains the special option &%pipe_as_creator%&. If this
22271 is set and &%user%& is not set, the uid of the process that called Exim to
22272 receive the message is used, and if &%group%& is not set, the corresponding
22273 original gid is also used.
22275 This is the detailed preference order for obtaining a gid; the first of the
22276 following that is set is used:
22279 A &%group%& setting of the transport;
22281 A &%group%& setting of the router;
22283 A gid associated with a user setting of the router, either as a result of
22284 &%check_local_user%& or an explicit non-numeric &%user%& setting;
22286 The group associated with a non-numeric &%user%& setting of the transport;
22288 In a &(pipe)& transport, the creator's gid if &%deliver_as_creator%& is set and
22289 the uid is the creator's uid;
22291 The Exim gid if the Exim uid is being used as a default.
22294 If, for example, the user is specified numerically on the router and there are
22295 no group settings, no gid is available. In this situation, an error occurs.
22296 This is different for the uid, for which there always is an ultimate default.
22297 The first of the following that is set is used:
22300 A &%user%& setting of the transport;
22302 In a &(pipe)& transport, the creator's uid if &%deliver_as_creator%& is set;
22304 A &%user%& setting of the router;
22306 A &%check_local_user%& setting of the router;
22311 Of course, an error will still occur if the uid that is chosen is on the
22312 &%never_users%& list.
22318 .section "Current and home directories" "SECID132"
22319 .cindex "current directory for local transport"
22320 .cindex "home directory" "for local transport"
22321 .cindex "transport" "local; home directory for"
22322 .cindex "transport" "local; current directory for"
22323 Routers may set current and home directories for local transports by means of
22324 the &%transport_current_directory%& and &%transport_home_directory%& options.
22325 However, if the transport's &%current_directory%& or &%home_directory%& options
22326 are set, they override the router's values. In detail, the home directory
22327 for a local transport is taken from the first of these values that is set:
22330 The &%home_directory%& option on the transport;
22332 The &%transport_home_directory%& option on the router;
22334 The password data if &%check_local_user%& is set on the router;
22336 The &%router_home_directory%& option on the router.
22339 The current directory is taken from the first of these values that is set:
22342 The &%current_directory%& option on the transport;
22344 The &%transport_current_directory%& option on the router.
22348 If neither the router nor the transport sets a current directory, Exim uses the
22349 value of the home directory, if it is set. Otherwise it sets the current
22350 directory to &_/_& before running a local transport.
22354 .section "Expansion variables derived from the address" "SECID133"
22355 .vindex "&$domain$&"
22356 .vindex "&$local_part$&"
22357 .vindex "&$original_domain$&"
22358 Normally a local delivery is handling a single address, and in that case the
22359 variables such as &$domain$& and &$local_part$& are set during local
22360 deliveries. However, in some circumstances more than one address may be handled
22361 at once (for example, while writing batch SMTP for onward transmission by some
22362 other means). In this case, the variables associated with the local part are
22363 never set, &$domain$& is set only if all the addresses have the same domain,
22364 and &$original_domain$& is never set.
22365 .ecindex IIDenvlotra1
22366 .ecindex IIDenvlotra2
22367 .ecindex IIDenvlotra3
22375 . ////////////////////////////////////////////////////////////////////////////
22376 . ////////////////////////////////////////////////////////////////////////////
22378 .chapter "Generic options for transports" "CHAPtransportgeneric"
22379 .scindex IIDgenoptra1 "generic options" "transport"
22380 .scindex IIDgenoptra2 "options" "generic; for transports"
22381 .scindex IIDgenoptra3 "transport" "generic options for"
22382 The name of a transport is limited to be &drivernamemax; ASCII characters long;
22383 prior to Exim 4.95 names would be silently truncated at this length, but now
22386 The following generic options apply to all transports:
22389 .option body_only transports boolean false
22390 .cindex "transport" "body only"
22391 .cindex "message" "transporting body only"
22392 .cindex "body of message" "transporting"
22393 If this option is set, the message's headers are not transported. It is
22394 mutually exclusive with &%headers_only%&. If it is used with the &(appendfile)&
22395 or &(pipe)& transports, the settings of &%message_prefix%& and
22396 &%message_suffix%& should be checked, because this option does not
22397 automatically suppress them.
22400 .option current_directory transports string&!! unset
22401 .cindex "transport" "current directory for"
22402 This specifies the current directory that is to be set while running the
22403 transport, overriding any value that may have been set by the router.
22404 If the expansion fails for any reason, including forced failure, an error is
22405 logged, and delivery is deferred.
22408 .option disable_logging transports boolean false
22409 If this option is set true, nothing is logged for any
22410 deliveries by the transport or for any
22411 transport errors. You should not set this option unless you really, really know
22412 what you are doing.
22415 .option debug_print transports string&!! unset
22416 .cindex "testing" "variables in drivers"
22417 If this option is set and debugging is enabled (see the &%-d%& command line
22418 option), the string is expanded and included in the debugging output when the
22420 If expansion of the string fails, the error message is written to the debugging
22421 output, and Exim carries on processing.
22422 This facility is provided to help with checking out the values of variables and
22423 so on when debugging driver configurations. For example, if a &%headers_add%&
22424 option is not working properly, &%debug_print%& could be used to output the
22425 variables it references. A newline is added to the text if it does not end with
22427 The variables &$transport_name$& and &$router_name$& contain the name of the
22428 transport and the router that called it.
22430 .option delivery_date_add transports boolean false
22431 .cindex "&'Delivery-date:'& header line"
22432 If this option is true, a &'Delivery-date:'& header is added to the message.
22433 This gives the actual time the delivery was made. As this is not a standard
22434 header, Exim has a configuration option (&%delivery_date_remove%&) which
22435 requests its removal from incoming messages, so that delivered messages can
22436 safely be resent to other recipients.
22439 .option driver transports string unset
22440 This specifies which of the available transport drivers is to be used.
22441 There is no default, and this option must be set for every transport.
22444 .option envelope_to_add transports boolean false
22445 .cindex "&'Envelope-to:'& header line"
22446 If this option is true, an &'Envelope-to:'& header is added to the message.
22447 This gives the original address(es) in the incoming envelope that caused this
22448 delivery to happen. More than one address may be present if the transport is
22449 configured to handle several addresses at once, or if more than one original
22450 address was redirected to the same final address. As this is not a standard
22451 header, Exim has a configuration option (&%envelope_to_remove%&) which requests
22452 its removal from incoming messages, so that delivered messages can safely be
22453 resent to other recipients.
22455 &*Note:*& If used on a transport handling multiple recipients
22456 (the smtp transport unless &%rcpt_max%& is 1, the appendfile, pipe or lmtp
22457 transport if &%batch_max%& is greater than 1)
22458 then information about Bcc recipients will be leaked.
22459 Doing so is generally not advised.
22462 .option event_action transports string&!! unset
22464 This option declares a string to be expanded for Exim's events mechanism.
22465 For details see chapter &<<CHAPevents>>&.
22468 .option group transports string&!! "Exim group"
22469 .cindex "transport" "group; specifying"
22470 This option specifies a gid for running the transport process, overriding any
22471 value that the router supplies, and also overriding any value associated with
22472 &%user%& (see below).
22475 .option headers_add transports list&!! unset
22476 .cindex "header lines" "adding in transport"
22477 .cindex "transport" "header lines; adding"
22478 This option specifies a list of text headers,
22479 newline-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
22480 which are (separately) expanded and added to the header
22481 portion of a message as it is transported, as described in section
22482 &<<SECTheadersaddrem>>&. Additional header lines can also be specified by
22483 routers. If the result of the expansion is an empty string, or if the expansion
22484 is forced to fail, no action is taken. Other expansion failures are treated as
22485 errors and cause the delivery to be deferred.
22487 Unlike most options, &%headers_add%& can be specified multiple times
22488 for a transport; all listed headers are added.
22491 .option headers_only transports boolean false
22492 .cindex "transport" "header lines only"
22493 .cindex "message" "transporting headers only"
22494 .cindex "header lines" "transporting"
22495 If this option is set, the message's body is not transported. It is mutually
22496 exclusive with &%body_only%&. If it is used with the &(appendfile)& or &(pipe)&
22497 transports, the settings of &%message_prefix%& and &%message_suffix%& should be
22498 checked, since this option does not automatically suppress them.
22501 .option headers_remove transports list&!! unset
22502 .cindex "header lines" "removing"
22503 .cindex "transport" "header lines; removing"
22504 This option specifies a list of text headers,
22505 colon-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
22506 to be removed from the message.
22507 However, the option has no effect when an address is just being verified.
22508 Each list item is separately expanded.
22509 If the result of the expansion is an empty string, or if the expansion
22510 is forced to fail, no action is taken. Other expansion failures are treated as
22511 errors and cause the delivery to be deferred.
22512 If an item ends in *, it will match any header with the given prefix.
22514 Matching headers are omitted from the message as it is transported, as described
22515 in section &<<SECTheadersaddrem>>&. Header removal can also be specified by
22518 Unlike most options, &%headers_remove%& can be specified multiple times
22519 for a transport; all listed headers are removed.
22521 &*Warning*&: Because of the separate expansion of the list items,
22522 items that contain a list separator must have it doubled.
22523 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
22527 .option headers_rewrite transports string unset
22528 .cindex "transport" "header lines; rewriting"
22529 .cindex "rewriting" "at transport time"
22530 This option allows addresses in header lines to be rewritten at transport time,
22531 that is, as the message is being copied to its destination. The contents of the
22532 option are a colon-separated list of rewriting rules. Each rule is in exactly
22533 the same form as one of the general rewriting rules that are applied when a
22534 message is received. These are described in chapter &<<CHAPrewrite>>&. For
22537 headers_rewrite = a@b c@d f : \
22540 changes &'a@b'& into &'c@d'& in &'From:'& header lines, and &'x@y'& into
22541 &'w@z'& in all address-bearing header lines. The rules are applied to the
22542 header lines just before they are written out at transport time, so they affect
22543 only those copies of the message that pass through the transport. However, only
22544 the message's original header lines, and any that were added by a system
22545 filter, are rewritten. If a router or transport adds header lines, they are not
22546 affected by this option. These rewriting rules are &'not'& applied to the
22547 envelope. You can change the return path using &%return_path%&, but you cannot
22548 change envelope recipients at this time.
22551 .option home_directory transports string&!! unset
22552 .cindex "transport" "home directory for"
22554 This option specifies a home directory setting for a local transport,
22555 overriding any value that may be set by the router. The home directory is
22556 placed in &$home$& while expanding the transport's private options. It is also
22557 used as the current directory if no current directory is set by the
22558 &%current_directory%& option on the transport or the
22559 &%transport_current_directory%& option on the router. If the expansion fails
22560 for any reason, including forced failure, an error is logged, and delivery is
22564 .option initgroups transports boolean false
22565 .cindex "additional groups"
22566 .cindex "groups" "additional"
22567 .cindex "transport" "group; additional"
22568 If this option is true and the uid for the delivery process is provided by the
22569 transport, the &[initgroups()]& function is called when running the transport
22570 to ensure that any additional groups associated with the uid are set up.
22573 .option max_parallel transports integer&!! unset
22574 .cindex limit "transport parallelism"
22575 .cindex transport "parallel processes"
22576 .cindex transport "concurrency limit"
22577 .cindex "delivery" "parallelism for transport"
22578 If this option is set and expands to an integer greater than zero
22579 it limits the number of concurrent runs of the transport.
22580 The control does not apply to shadow transports.
22582 .cindex "hints database" "transport concurrency control"
22583 Exim implements this control by means of a hints database in which a record is
22584 incremented whenever a transport process is being created. The record
22585 is decremented and possibly removed when the process terminates.
22586 Obviously there is scope for
22587 records to get left lying around if there is a system or program crash. To
22588 guard against this, Exim ignores any records that are more than six hours old.
22590 If you use this option, you should also arrange to delete the
22591 relevant hints database whenever your system reboots. The names of the files
22592 start with &_misc_& and they are kept in the &_spool/db_& directory. There
22593 may be one or two files, depending on the type of DBM in use. The same files
22594 are used for ETRN and smtp transport serialization.
22597 .option message_size_limit transports string&!! 0
22598 .cindex "limit" "message size per transport"
22599 .cindex "size" "of message, limit"
22600 .cindex "transport" "message size; limiting"
22601 This option controls the size of messages passed through the transport. It is
22602 expanded before use; the result of the expansion must be a sequence of decimal
22603 digits, optionally followed by K or M. If the expansion fails for any reason,
22604 including forced failure, or if the result is not of the required form,
22605 delivery is deferred. If the value is greater than zero and the size of a
22606 message exceeds this limit, the address is failed. If there is any chance that
22607 the resulting bounce message could be routed to the same transport, you should
22608 ensure that &%return_size_limit%& is less than the transport's
22609 &%message_size_limit%&, as otherwise the bounce message will fail to get
22614 .option rcpt_include_affixes transports boolean false
22615 .cindex "prefix" "for local part, including in envelope"
22616 .cindex "suffix for local part" "including in envelope"
22617 .cindex "local part" "prefix"
22618 .cindex "local part" "suffix"
22619 When this option is false (the default), and an address that has had any
22620 affixes (prefixes or suffixes) removed from the local part is delivered by any
22621 form of SMTP or LMTP, the affixes are not included. For example, if a router
22624 local_part_prefix = *-
22626 routes the address &'abc-xyz@some.domain'& to an SMTP transport, the envelope
22629 RCPT TO:<xyz@some.domain>
22631 This is also the case when an ACL-time callout is being used to verify a
22632 recipient address. However, if &%rcpt_include_affixes%& is set true, the
22633 whole local part is included in the RCPT command. This option applies to BSMTP
22634 deliveries by the &(appendfile)& and &(pipe)& transports as well as to the
22635 &(lmtp)& and &(smtp)& transports.
22638 .option retry_use_local_part transports boolean "see below"
22639 .cindex "hints database" "retry keys"
22640 When a delivery suffers a temporary failure, a retry record is created
22641 in Exim's hints database. For remote deliveries, the key for the retry record
22642 is based on the name and/or IP address of the failing remote host. For local
22643 deliveries, the key is normally the entire address, including both the local
22644 part and the domain. This is suitable for most common cases of local delivery
22645 temporary failure &-- for example, exceeding a mailbox quota should delay only
22646 deliveries to that mailbox, not to the whole domain.
22648 However, in some special cases you may want to treat a temporary local delivery
22649 as a failure associated with the domain, and not with a particular local part.
22650 (For example, if you are storing all mail for some domain in files.) You can do
22651 this by setting &%retry_use_local_part%& false.
22653 For all the local transports, its default value is true. For remote transports,
22654 the default value is false for tidiness, but changing the value has no effect
22655 on a remote transport in the current implementation.
22658 .option return_path transports string&!! unset
22659 .cindex "envelope sender"
22660 .cindex "envelope from"
22661 .cindex "transport" "return path; changing"
22662 .cindex "return path" "changing in transport"
22663 If this option is set, the string is expanded at transport time and replaces
22664 the existing return path (envelope sender) value in the copy of the message
22665 that is being delivered. An empty return path is permitted. This feature is
22666 designed for remote deliveries, where the value of this option is used in the
22667 SMTP MAIL command. If you set &%return_path%& for a local transport, the
22668 only effect is to change the address that is placed in the &'Return-path:'&
22669 header line, if one is added to the message (see the next option).
22671 &*Note:*& A changed return path is not logged unless you add
22672 &%return_path_on_delivery%& to the log selector.
22674 .vindex "&$return_path$&"
22675 The expansion can refer to the existing value via &$return_path$&. This is
22676 either the message's envelope sender, or an address set by the
22677 &%errors_to%& option on a router. If the expansion is forced to fail, no
22678 replacement occurs; if it fails for another reason, delivery is deferred. This
22679 option can be used to support VERP (Variable Envelope Return Paths) &-- see
22680 section &<<SECTverp>>&.
22682 &*Note*&: If a delivery error is detected locally, including the case when a
22683 remote server rejects a message at SMTP time, the bounce message is not sent to
22684 the value of this option. It is sent to the previously set errors address.
22685 This defaults to the incoming sender address, but can be changed by setting
22686 &%errors_to%& in a router.
22690 .option return_path_add transports boolean false
22691 .chindex Return-path:
22692 If this option is true, a &'Return-path:'& header is added to the message.
22693 Although the return path is normally available in the prefix line of BSD
22694 mailboxes, this is commonly not displayed by MUAs, and so the user does not
22695 have easy access to it.
22697 RFC 2821 states that the &'Return-path:'& header is added to a message &"when
22698 the delivery SMTP server makes the final delivery"&. This implies that this
22699 header should not be present in incoming messages. Exim has a configuration
22700 option, &%return_path_remove%&, which requests removal of this header from
22701 incoming messages, so that delivered messages can safely be resent to other
22705 .option shadow_condition transports string&!! unset
22706 See &%shadow_transport%& below.
22709 .option shadow_transport transports string unset
22710 .cindex "shadow transport"
22711 .cindex "transport" "shadow"
22712 A local transport may set the &%shadow_transport%& option to the name of
22713 another local transport. Shadow remote transports are not supported.
22715 Whenever a delivery to the main transport succeeds, and either
22716 &%shadow_condition%& is unset, or its expansion does not result in the empty
22717 string or one of the strings &"0"& or &"no"& or &"false"&, the message is also
22718 passed to the shadow transport, with the same delivery address or addresses. If
22719 expansion fails, no action is taken except that non-forced expansion failures
22720 cause a log line to be written.
22722 The result of the shadow transport is discarded and does not affect the
22723 subsequent processing of the message. Only a single level of shadowing is
22724 provided; the &%shadow_transport%& option is ignored on any transport when it
22725 is running as a shadow. Options concerned with output from pipes are also
22726 ignored. The log line for the successful delivery has an item added on the end,
22729 ST=<shadow transport name>
22731 If the shadow transport did not succeed, the error message is put in
22732 parentheses afterwards. Shadow transports can be used for a number of different
22733 purposes, including keeping more detailed log information than Exim normally
22734 provides, and implementing automatic acknowledgment policies based on message
22735 headers that some sites insist on.
22738 .option transport_filter transports string&!! unset
22739 .cindex "transport" "filter"
22740 .cindex "filter" "transport filter"
22741 This option sets up a filtering (in the Unix shell sense) process for messages
22742 at transport time. It should not be confused with mail filtering as set up by
22743 individual users or via a system filter.
22744 If unset, or expanding to an empty string, no filtering is done.
22746 When the message is about to be written out, the command specified by
22747 &%transport_filter%& is started up in a separate, parallel process, and
22748 the entire message, including the header lines, is passed to it on its standard
22749 input (this in fact is done from a third process, to avoid deadlock). The
22750 command must be specified as an absolute path.
22752 The lines of the message that are written to the transport filter are
22753 terminated by newline (&"\n"&). The message is passed to the filter before any
22754 SMTP-specific processing, such as turning &"\n"& into &"\r\n"& and escaping
22755 lines beginning with a dot, and also before any processing implied by the
22756 settings of &%check_string%& and &%escape_string%& in the &(appendfile)& or
22757 &(pipe)& transports.
22759 The standard error for the filter process is set to the same destination as its
22760 standard output; this is read and written to the message's ultimate
22761 destination. The process that writes the message to the filter, the
22762 filter itself, and the original process that reads the result and delivers it
22763 are all run in parallel, like a shell pipeline.
22765 The filter can perform any transformations it likes, but of course should take
22766 care not to break RFC 2822 syntax. Exim does not check the result, except to
22767 test for a final newline when SMTP is in use. All messages transmitted over
22768 SMTP must end with a newline, so Exim supplies one if it is missing.
22770 .cindex "content scanning" "per user"
22771 A transport filter can be used to provide content-scanning on a per-user basis
22772 at delivery time if the only required effect of the scan is to modify the
22773 message. For example, a content scan could insert a new header line containing
22774 a spam score. This could be interpreted by a filter in the user's MUA. It is
22775 not possible to discard a message at this stage.
22777 .cindex "SIZE" "ESMTP extension"
22778 A problem might arise if the filter increases the size of a message that is
22779 being sent down an SMTP connection. If the receiving SMTP server has indicated
22780 support for the SIZE parameter, Exim will have sent the size of the message
22781 at the start of the SMTP session. If what is actually sent is substantially
22782 more, the server might reject the message. This can be worked round by setting
22783 the &%size_addition%& option on the &(smtp)& transport, either to allow for
22784 additions to the message, or to disable the use of SIZE altogether.
22786 .vindex "&$pipe_addresses$&"
22787 The value of the &%transport_filter%& option is the command string for starting
22788 the filter, which is run directly from Exim, not under a shell. The string is
22789 parsed by Exim in the same way as a command string for the &(pipe)& transport:
22790 Exim breaks it up into arguments and then expands each argument separately (see
22791 section &<<SECThowcommandrun>>&). Any kind of expansion failure causes delivery
22792 to be deferred. The special argument &$pipe_addresses$& is replaced by a number
22793 of arguments, one for each address that applies to this delivery. (This isn't
22794 an ideal name for this feature here, but as it was already implemented for the
22795 &(pipe)& transport, it seemed sensible not to change it.)
22798 .vindex "&$host_address$&"
22799 The expansion variables &$host$& and &$host_address$& are available when the
22800 transport is a remote one. They contain the name and IP address of the host to
22801 which the message is being sent. For example:
22802 . used to have $sender_address in this cmdline, but it's tainted
22804 transport_filter = /some/directory/transport-filter.pl \
22805 $host $host_address $pipe_addresses
22808 Two problems arise if you want to use more complicated expansion items to
22809 generate transport filter commands, both of which due to the fact that the
22810 command is split up &'before'& expansion.
22812 If an expansion item contains white space, you must quote it, so that it is all
22813 part of the same command item. If the entire option setting is one such
22814 expansion item, you have to take care what kind of quoting you use. For
22817 transport_filter = '/bin/cmd${if eq{$host}{a.b.c}{1}{2}}'
22819 This runs the command &(/bin/cmd1)& if the host name is &'a.b.c'&, and
22820 &(/bin/cmd2)& otherwise. If double quotes had been used, they would have been
22821 stripped by Exim when it read the option's value. When the value is used, if
22822 the single quotes were missing, the line would be split into two items,
22823 &`/bin/cmd${if`& and &`eq{$host}{a.b.c}{1}{2}`&, and an error would occur when
22824 Exim tried to expand the first one.
22826 Except for the special case of &$pipe_addresses$& that is mentioned above, an
22827 expansion cannot generate multiple arguments, or a command name followed by
22828 arguments. Consider this example:
22830 transport_filter = ${lookup{$host}lsearch{/a/file}\
22831 {$value}{/bin/cat}}
22833 The result of the lookup is interpreted as the name of the command, even
22834 if it contains white space. The simplest way round this is to use a shell:
22836 transport_filter = /bin/sh -c ${lookup{$host}lsearch{/a/file}\
22837 {$value}{/bin/cat}}
22841 The filter process is run under the same uid and gid as the normal delivery.
22842 For remote deliveries this is the Exim uid/gid by default. The command should
22843 normally yield a zero return code. Transport filters are not supposed to fail.
22844 A non-zero code is taken to mean that the transport filter encountered some
22845 serious problem. Delivery of the message is deferred; the message remains on
22846 the queue and is tried again later. It is not possible to cause a message to be
22847 bounced from a transport filter.
22849 If a transport filter is set on an autoreply transport, the original message is
22850 passed through the filter as it is being copied into the newly generated
22851 message, which happens if the &%return_message%& option is set.
22854 .option transport_filter_timeout transports time 5m
22855 .cindex "transport" "filter, timeout"
22856 When Exim is reading the output of a transport filter, it applies a timeout
22857 that can be set by this option. Exceeding the timeout is normally treated as a
22858 temporary delivery failure. However, if a transport filter is used with a
22859 &(pipe)& transport, a timeout in the transport filter is treated in the same
22860 way as a timeout in the pipe command itself. By default, a timeout is a hard
22861 error, but if the &(pipe)& transport's &%timeout_defer%& option is set true, it
22862 becomes a temporary error.
22865 .option user transports string&!! "Exim user"
22866 .cindex "uid (user id)" "local delivery"
22867 .cindex "transport" "user, specifying"
22868 This option specifies the user under whose uid the delivery process is to be
22869 run, overriding any uid that may have been set by the router. If the user is
22870 given as a name, the uid is looked up from the password data, and the
22871 associated group is taken as the value of the gid to be used if the &%group%&
22874 For deliveries that use local transports, a user and group are normally
22875 specified explicitly or implicitly (for example, as a result of
22876 &%check_local_user%&) by the router or transport.
22878 .cindex "hints database" "access by remote transport"
22879 For remote transports, you should leave this option unset unless you really are
22880 sure you know what you are doing. When a remote transport is running, it needs
22881 to be able to access Exim's hints databases, because each host may have its own
22883 .ecindex IIDgenoptra1
22884 .ecindex IIDgenoptra2
22885 .ecindex IIDgenoptra3
22892 . ////////////////////////////////////////////////////////////////////////////
22893 . ////////////////////////////////////////////////////////////////////////////
22895 .chapter "Address batching in local transports" "CHAPbatching" &&&
22897 .cindex "transport" "local; address batching in"
22898 The only remote transport (&(smtp)&) is normally configured to handle more than
22899 one address at a time, so that when several addresses are routed to the same
22900 remote host, just one copy of the message is sent. Local transports, however,
22901 normally handle one address at a time. That is, a separate instance of the
22902 transport is run for each address that is routed to the transport. A separate
22903 copy of the message is delivered each time.
22905 .cindex "batched local delivery"
22906 .oindex "&%batch_max%&"
22907 .oindex "&%batch_id%&"
22908 In special cases, it may be desirable to handle several addresses at once in a
22909 local transport, for example:
22912 In an &(appendfile)& transport, when storing messages in files for later
22913 delivery by some other means, a single copy of the message with multiple
22914 recipients saves space.
22916 In an &(lmtp)& transport, when delivering over &"local SMTP"& to some process,
22917 a single copy saves time, and is the normal way LMTP is expected to work.
22919 In a &(pipe)& transport, when passing the message
22920 to a scanner program or
22921 to some other delivery mechanism such as UUCP, multiple recipients may be
22925 These three local transports all have the same options for controlling multiple
22926 (&"batched"&) deliveries, namely &%batch_max%& and &%batch_id%&. To save
22927 repeating the information for each transport, these options are described here.
22929 The &%batch_max%& option specifies the maximum number of addresses that can be
22930 delivered together in a single run of the transport. Its default value is one
22931 (no batching). When more than one address is routed to a transport that has a
22932 &%batch_max%& value greater than one, the addresses are delivered in a batch
22933 (that is, in a single run of the transport with multiple recipients), subject
22934 to certain conditions:
22937 .vindex "&$local_part$&"
22938 If any of the transport's options contain a reference to &$local_part$&, no
22939 batching is possible.
22941 .vindex "&$domain$&"
22942 If any of the transport's options contain a reference to &$domain$&, only
22943 addresses with the same domain are batched.
22945 .cindex "customizing" "batching condition"
22946 If &%batch_id%& is set, it is expanded for each address, and only those
22947 addresses with the same expanded value are batched. This allows you to specify
22948 customized batching conditions. Failure of the expansion for any reason,
22949 including forced failure, disables batching, but it does not stop the delivery
22952 Batched addresses must also have the same errors address (where to send
22953 delivery errors), the same header additions and removals, the same user and
22954 group for the transport, and if a host list is present, the first host must
22958 In the case of the &(appendfile)& and &(pipe)& transports, batching applies
22959 both when the file or pipe command is specified in the transport, and when it
22960 is specified by a &(redirect)& router, but all the batched addresses must of
22961 course be routed to the same file or pipe command. These two transports have an
22962 option called &%use_bsmtp%&, which causes them to deliver the message in
22963 &"batched SMTP"& format, with the envelope represented as SMTP commands. The
22964 &%check_string%& and &%escape_string%& options are forced to the values
22967 escape_string = ".."
22969 when batched SMTP is in use. A full description of the batch SMTP mechanism is
22970 given in section &<<SECTbatchSMTP>>&. The &(lmtp)& transport does not have a
22971 &%use_bsmtp%& option, because it always delivers using the SMTP protocol.
22973 .cindex "&'Envelope-to:'& header line"
22974 If the generic &%envelope_to_add%& option is set for a batching transport, the
22975 &'Envelope-to:'& header that is added to the message contains all the addresses
22976 that are being processed together. If you are using a batching &(appendfile)&
22977 transport without &%use_bsmtp%&, the only way to preserve the recipient
22978 addresses is to set the &%envelope_to_add%& option.
22980 .cindex "&(pipe)& transport" "with multiple addresses"
22981 .vindex "&$pipe_addresses$&"
22982 If you are using a &(pipe)& transport without BSMTP, and setting the
22983 transport's &%command%& option, you can include &$pipe_addresses$& as part of
22984 the command. This is not a true variable; it is a bit of magic that causes each
22985 of the recipient addresses to be inserted into the command as a separate
22986 argument. This provides a way of accessing all the addresses that are being
22987 delivered in the batch. &*Note:*& This is not possible for pipe commands that
22988 are specified by a &(redirect)& router.
22993 . ////////////////////////////////////////////////////////////////////////////
22994 . ////////////////////////////////////////////////////////////////////////////
22996 .chapter "The appendfile transport" "CHAPappendfile"
22997 .scindex IIDapptra1 "&(appendfile)& transport"
22998 .scindex IIDapptra2 "transports" "&(appendfile)&"
22999 .cindex "directory creation"
23000 .cindex "creating directories"
23001 The &(appendfile)& transport delivers a message by appending it to an existing
23002 file, or by creating an entirely new file in a specified directory. Single
23003 files to which messages are appended can be in the traditional Unix mailbox
23004 format, or optionally in the MBX format supported by the Pine MUA and
23005 University of Washington IMAP daemon, &'inter alia'&. When each message is
23006 being delivered as a separate file, &"maildir"& format can optionally be used
23007 to give added protection against failures that happen part-way through the
23008 delivery. A third form of separate-file delivery known as &"mailstore"& is also
23009 supported. For all file formats, Exim attempts to create as many levels of
23010 directory as necessary, provided that &%create_directory%& is set.
23012 The code for the optional formats is not included in the Exim binary by
23013 default. It is necessary to set SUPPORT_MBX, SUPPORT_MAILDIR and/or
23014 SUPPORT_MAILSTORE in &_Local/Makefile_& to have the appropriate code
23017 .cindex "quota" "system"
23018 Exim recognizes system quota errors, and generates an appropriate message. Exim
23019 also supports its own quota control within the transport, for use when the
23020 system facility is unavailable or cannot be used for some reason.
23022 If there is an error while appending to a file (for example, quota exceeded or
23023 partition filled), Exim attempts to reset the file's length and last
23024 modification time back to what they were before. If there is an error while
23025 creating an entirely new file, the new file is removed.
23027 Before appending to a file, a number of security checks are made, and the
23028 file is locked. A detailed description is given below, after the list of
23031 The &(appendfile)& transport is most commonly used for local deliveries to
23032 users' mailboxes. However, it can also be used as a pseudo-remote transport for
23033 putting messages into files for remote delivery by some means other than Exim.
23034 &"Batch SMTP"& format is often used in this case (see the &%use_bsmtp%&
23039 .section "The file and directory options" "SECTfildiropt"
23040 The &%file%& option specifies a single file, to which the message is appended;
23041 the &%directory%& option specifies a directory, in which a new file containing
23042 the message is created. Only one of these two options can be set, and for
23043 normal deliveries to mailboxes, one of them &'must'& be set.
23045 .vindex "&$address_file$&"
23046 .vindex "&$local_part$&"
23047 However, &(appendfile)& is also used for delivering messages to files or
23048 directories whose names (or parts of names) are obtained from alias,
23049 forwarding, or filtering operations (for example, a &%save%& command in a
23050 user's Exim filter). When such a transport is running, &$local_part$& contains
23051 the local part that was aliased or forwarded, and &$address_file$& contains the
23052 name (or partial name) of the file or directory generated by the redirection
23053 operation. There are two cases:
23056 If neither &%file%& nor &%directory%& is set, the redirection operation
23057 must specify an absolute path (one that begins with &`/`&). This is the most
23058 common case when users with local accounts use filtering to sort mail into
23059 different folders. See for example, the &(address_file)& transport in the
23060 default configuration. If the path ends with a slash, it is assumed to be the
23061 name of a directory. A delivery to a directory can also be forced by setting
23062 &%maildir_format%& or &%mailstore_format%&.
23064 If &%file%& or &%directory%& is set for a delivery from a redirection, it is
23065 used to determine the file or directory name for the delivery. Normally, the
23066 contents of &$address_file$& are used in some way in the string expansion.
23068 If the &%create_file%& option is set to a path which
23069 matches (see the option definition below for details)
23070 a file or directory name
23071 for the delivery, that name becomes de-tainted.
23073 .cindex "tainted data" "in filenames"
23074 .cindex appendfile "tainted data"
23075 Tainted data may not be used for a file or directory name.
23076 This means that, for instance, &$local_part$& cannot be used directly
23077 as a component of a path. It can however be used as the key for a lookup
23078 which returns a path (or component).
23081 .cindex "Sieve filter" "configuring &(appendfile)&"
23082 .cindex "Sieve filter" "relative mailbox path handling"
23083 As an example of the second case, consider an environment where users do not
23084 have home directories. They may be permitted to use Exim filter commands of the
23089 or Sieve filter commands of the form:
23091 require "fileinto";
23092 fileinto "folder23";
23094 In this situation, the expansion of &%file%& or &%directory%& in the transport
23095 must transform the relative path into an appropriate absolute filename. In the
23096 case of Sieve filters, the name &'inbox'& must be handled. It is the name that
23097 is used as a result of a &"keep"& action in the filter. This example shows one
23098 way of handling this requirement:
23100 file = ${if eq{$address_file}{inbox} \
23101 {/var/mail/$local_part_data} \
23102 {${if eq{${substr_0_1:$address_file}}{/} \
23104 {$home/mail/$address_file} \
23108 With this setting of &%file%&, &'inbox'& refers to the standard mailbox
23109 location, absolute paths are used without change, and other folders are in the
23110 &_mail_& directory within the home directory.
23112 &*Note 1*&: While processing an Exim filter, a relative path such as
23113 &_folder23_& is turned into an absolute path if a home directory is known to
23114 the router. In particular, this is the case if &%check_local_user%& is set. If
23115 you want to prevent this happening at routing time, you can set
23116 &%router_home_directory%& empty. This forces the router to pass the relative
23117 path to the transport.
23119 &*Note 2*&: An absolute path in &$address_file$& is not treated specially;
23120 the &%file%& or &%directory%& option is still used if it is set.
23125 .section "Private options for appendfile" "SECID134"
23126 .cindex "options" "&(appendfile)& transport"
23130 .option allow_fifo appendfile boolean false
23131 .cindex "fifo (named pipe)"
23132 .cindex "named pipe (fifo)"
23133 .cindex "pipe" "named (fifo)"
23134 Setting this option permits delivery to named pipes (FIFOs) as well as to
23135 regular files. If no process is reading the named pipe at delivery time, the
23136 delivery is deferred.
23139 .option allow_symlink appendfile boolean false
23140 .cindex "symbolic link" "to mailbox"
23141 .cindex "mailbox" "symbolic link"
23142 By default, &(appendfile)& will not deliver if the path name for the file is
23143 that of a symbolic link. Setting this option relaxes that constraint, but there
23144 are security issues involved in the use of symbolic links. Be sure you know
23145 what you are doing if you set this. Details of exactly what this option affects
23146 are included in the discussion which follows this list of options.
23149 .option batch_id appendfile string&!! unset
23150 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
23151 However, batching is automatically disabled for &(appendfile)& deliveries that
23152 happen as a result of forwarding or aliasing or other redirection directly to a
23156 .option batch_max appendfile integer 1
23157 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
23160 .option check_group appendfile boolean false
23161 When this option is set, the group owner of the file defined by the &%file%&
23162 option is checked to see that it is the same as the group under which the
23163 delivery process is running. The default setting is false because the default
23164 file mode is 0600, which means that the group is irrelevant.
23167 .option check_owner appendfile boolean true
23168 When this option is set, the owner of the file defined by the &%file%& option
23169 is checked to ensure that it is the same as the user under which the delivery
23170 process is running.
23173 .option check_string appendfile string "see below"
23174 .cindex "&""From""& line"
23175 As &(appendfile)& writes the message, the start of each line is tested for
23176 matching &%check_string%&, and if it does, the initial matching characters are
23177 replaced by the contents of &%escape_string%&. The value of &%check_string%& is
23178 a literal string, not a regular expression, and the case of any letters it
23179 contains is significant.
23181 If &%use_bsmtp%& is set the values of &%check_string%& and &%escape_string%&
23182 are forced to &"."& and &".."& respectively, and any settings in the
23183 configuration are ignored. Otherwise, they default to &"From&~"& and
23184 &">From&~"& when the &%file%& option is set, and unset when any of the
23185 &%directory%&, &%maildir%&, or &%mailstore%& options are set.
23187 The default settings, along with &%message_prefix%& and &%message_suffix%&, are
23188 suitable for traditional &"BSD"& mailboxes, where a line beginning with
23189 &"From&~"& indicates the start of a new message. All four options need changing
23190 if another format is used. For example, to deliver to mailboxes in MMDF format:
23191 .cindex "MMDF format mailbox"
23192 .cindex "mailbox" "MMDF format"
23194 check_string = "\1\1\1\1\n"
23195 escape_string = "\1\1\1\1 \n"
23196 message_prefix = "\1\1\1\1\n"
23197 message_suffix = "\1\1\1\1\n"
23199 .option create_directory appendfile boolean true
23200 .cindex "directory creation"
23201 When this option is true, Exim attempts to create any missing superior
23202 directories for the file that it is about to write. A created directory's mode
23203 is given by the &%directory_mode%& option.
23205 The group ownership of a newly created directory is highly dependent on the
23206 operating system (and possibly the file system) that is being used. For
23207 example, in Solaris, if the parent directory has the setgid bit set, its group
23208 is propagated to the child; if not, the currently set group is used. However,
23209 in FreeBSD, the parent's group is always used.
23213 .option create_file appendfile string anywhere
23214 This option constrains the location of files and directories that are created
23215 by this transport. It applies to files defined by the &%file%& option and
23216 directories defined by the &%directory%& option. In the case of maildir
23217 delivery, it applies to the top level directory, not the maildir directories
23220 The option must be set to one of the words &"anywhere"&, &"inhome"&, or
23221 &"belowhome"&, or to an absolute path.
23223 In the second and third cases, a home directory must have been
23224 set for the transport, and the file or directory being created must
23226 The "belowhome" checking additionally checks for attempts to use "../"
23227 to evade the testing.
23228 This option is not useful when an explicit filename is
23229 given for normal mailbox deliveries. It is intended for the case when filenames
23230 are generated from users' &_.forward_& files. These are usually handled
23231 by an &(appendfile)& transport called &%address_file%&. See also
23232 &%file_must_exist%&.
23234 In the fourth case,
23235 the value given for this option must be an absolute path for an
23236 existing directory.
23237 The value is used for checking instead of a home directory;
23238 checking is done in "belowhome" mode.
23240 .cindex "tainted data" "de-tainting"
23241 .cindex "de-tainting" "using appendfile create_file option"
23242 If "belowhome" checking is used, the file or directory path
23243 becomes de-tainted.
23246 .option directory appendfile string&!! unset
23247 This option is mutually exclusive with the &%file%& option, but one of &%file%&
23248 or &%directory%& must be set, unless the delivery is the direct result of a
23249 redirection (see section &<<SECTfildiropt>>&).
23251 When &%directory%& is set, the string is expanded, and the message is delivered
23252 into a new file or files in or below the given directory, instead of being
23253 appended to a single mailbox file. A number of different formats are provided
23254 (see &%maildir_format%& and &%mailstore_format%&), and see section
23255 &<<SECTopdir>>& for further details of this form of delivery.
23257 The result of expansion must not be tainted, unless the &%create_file%& option
23261 .option directory_file appendfile string&!! "see below"
23263 .vindex "&$inode$&"
23264 When &%directory%& is set, but neither &%maildir_format%& nor
23265 &%mailstore_format%& is set, &(appendfile)& delivers each message into a file
23266 whose name is obtained by expanding this string. The default value is:
23268 q${base62:$tod_epoch}-$inode
23270 This generates a unique name from the current time, in base 62 form, and the
23271 inode of the file. The variable &$inode$& is available only when expanding this
23275 .option directory_mode appendfile "octal integer" 0700
23276 If &(appendfile)& creates any directories as a result of the
23277 &%create_directory%& option, their mode is specified by this option.
23280 .option escape_string appendfile string "see description"
23281 See &%check_string%& above.
23284 .option file appendfile string&!! unset
23285 This option is mutually exclusive with the &%directory%& option, but one of
23286 &%file%& or &%directory%& must be set, unless the delivery is the direct result
23287 of a redirection (see section &<<SECTfildiropt>>&). The &%file%& option
23288 specifies a single file, to which the message is appended. One or more of
23289 &%use_fcntl_lock%&, &%use_flock_lock%&, or &%use_lockfile%& must be set with
23292 The result of expansion must not be tainted, unless the &%create_file%& option
23295 .cindex "NFS" "lock file"
23296 .cindex "locking files"
23297 .cindex "lock files"
23298 If you are using more than one host to deliver over NFS into the same
23299 mailboxes, you should always use lock files.
23301 The string value is expanded for each delivery, and must yield an absolute
23302 path. The most common settings of this option are variations on one of these
23305 file = /var/spool/mail/$local_part_data
23306 file = /home/$local_part_data/inbox
23309 .cindex "&""sticky""& bit"
23310 In the first example, all deliveries are done into the same directory. If Exim
23311 is configured to use lock files (see &%use_lockfile%& below) it must be able to
23312 create a file in the directory, so the &"sticky"& bit must be turned on for
23313 deliveries to be possible, or alternatively the &%group%& option can be used to
23314 run the delivery under a group id which has write access to the directory.
23318 .option file_format appendfile string unset
23319 .cindex "file" "mailbox; checking existing format"
23320 This option requests the transport to check the format of an existing file
23321 before adding to it. The check consists of matching a specific string at the
23322 start of the file. The value of the option consists of an even number of
23323 colon-separated strings. The first of each pair is the test string, and the
23324 second is the name of a transport. If the transport associated with a matched
23325 string is not the current transport, control is passed over to the other
23326 transport. For example, suppose the standard &(local_delivery)& transport has
23329 file_format = "From : local_delivery :\
23330 \1\1\1\1\n : local_mmdf_delivery"
23332 Mailboxes that begin with &"From"& are still handled by this transport, but if
23333 a mailbox begins with four binary ones followed by a newline, control is passed
23334 to a transport called &%local_mmdf_delivery%&, which presumably is configured
23335 to do the delivery in MMDF format. If a mailbox does not exist or is empty, it
23336 is assumed to match the current transport. If the start of a mailbox doesn't
23337 match any string, or if the transport named for a given string is not defined,
23338 delivery is deferred.
23341 .option file_must_exist appendfile boolean false
23342 If this option is true, the file specified by the &%file%& option must exist.
23343 A temporary error occurs if it does not, causing delivery to be deferred.
23344 If this option is false, the file is created if it does not exist.
23347 .option lock_fcntl_timeout appendfile time 0s
23348 .cindex "timeout" "mailbox locking"
23349 .cindex "mailbox" "locking, blocking and non-blocking"
23350 .cindex "locking files"
23351 By default, the &(appendfile)& transport uses non-blocking calls to &[fcntl()]&
23352 when locking an open mailbox file. If the call fails, the delivery process
23353 sleeps for &%lock_interval%& and tries again, up to &%lock_retries%& times.
23354 Non-blocking calls are used so that the file is not kept open during the wait
23355 for the lock; the reason for this is to make it as safe as possible for
23356 deliveries over NFS in the case when processes might be accessing an NFS
23357 mailbox without using a lock file. This should not be done, but
23358 misunderstandings and hence misconfigurations are not unknown.
23360 On a busy system, however, the performance of a non-blocking lock approach is
23361 not as good as using a blocking lock with a timeout. In this case, the waiting
23362 is done inside the system call, and Exim's delivery process acquires the lock
23363 and can proceed as soon as the previous lock holder releases it.
23365 If &%lock_fcntl_timeout%& is set to a non-zero time, blocking locks, with that
23366 timeout, are used. There may still be some retrying: the maximum number of
23369 (lock_retries * lock_interval) / lock_fcntl_timeout
23371 rounded up to the next whole number. In other words, the total time during
23372 which &(appendfile)& is trying to get a lock is roughly the same, unless
23373 &%lock_fcntl_timeout%& is set very large.
23375 You should consider setting this option if you are getting a lot of delayed
23376 local deliveries because of errors of the form
23378 failed to lock mailbox /some/file (fcntl)
23381 .option lock_flock_timeout appendfile time 0s
23382 This timeout applies to file locking when using &[flock()]& (see
23383 &%use_flock%&); the timeout operates in a similar manner to
23384 &%lock_fcntl_timeout%&.
23387 .option lock_interval appendfile time 3s
23388 This specifies the time to wait between attempts to lock the file. See below
23389 for details of locking.
23392 .option lock_retries appendfile integer 10
23393 This specifies the maximum number of attempts to lock the file. A value of zero
23394 is treated as 1. See below for details of locking.
23397 .option lockfile_mode appendfile "octal integer" 0600
23398 This specifies the mode of the created lock file, when a lock file is being
23399 used (see &%use_lockfile%& and &%use_mbx_lock%&).
23402 .option lockfile_timeout appendfile time 30m
23403 .cindex "timeout" "mailbox locking"
23404 When a lock file is being used (see &%use_lockfile%&), if a lock file already
23405 exists and is older than this value, it is assumed to have been left behind by
23406 accident, and Exim attempts to remove it.
23409 .option mailbox_filecount appendfile string&!! unset
23410 .cindex "mailbox" "specifying size of"
23411 .cindex "size" "of mailbox"
23412 If this option is set, it is expanded, and the result is taken as the current
23413 number of files in the mailbox. It must be a decimal number, optionally
23414 followed by K or M. This provides a way of obtaining this information from an
23415 external source that maintains the data.
23418 .option mailbox_size appendfile string&!! unset
23419 .cindex "mailbox" "specifying size of"
23420 .cindex "size" "of mailbox"
23421 If this option is set, it is expanded, and the result is taken as the current
23422 size the mailbox. It must be a decimal number, optionally followed by K or M.
23423 This provides a way of obtaining this information from an external source that
23424 maintains the data. This is likely to be helpful for maildir deliveries where
23425 it is computationally expensive to compute the size of a mailbox.
23429 .option maildir_format appendfile boolean false
23430 .cindex "maildir format" "specifying"
23431 If this option is set with the &%directory%& option, the delivery is into a new
23432 file, in the &"maildir"& format that is used by other mail software. When the
23433 transport is activated directly from a &(redirect)& router (for example, the
23434 &(address_file)& transport in the default configuration), setting
23435 &%maildir_format%& causes the path received from the router to be treated as a
23436 directory, whether or not it ends with &`/`&. This option is available only if
23437 SUPPORT_MAILDIR is present in &_Local/Makefile_&. See section
23438 &<<SECTmaildirdelivery>>& below for further details.
23441 .option maildir_quota_directory_regex appendfile string "See below"
23442 .cindex "maildir format" "quota; directories included in"
23443 .cindex "quota" "maildir; directories included in"
23444 This option is relevant only when &%maildir_use_size_file%& is set. It defines
23445 a regular expression for specifying directories, relative to the quota
23446 directory (see &%quota_directory%&), that should be included in the quota
23447 calculation. The default value is:
23449 maildir_quota_directory_regex = ^(?:cur|new|\..*)$
23451 This includes the &_cur_& and &_new_& directories, and any maildir++ folders
23452 (directories whose names begin with a dot). If you want to exclude the
23454 folder from the count (as some sites do), you need to change this setting to
23456 maildir_quota_directory_regex = ^(?:cur|new|\.(?!Trash).*)$
23458 This uses a negative lookahead in the regular expression to exclude the
23459 directory whose name is &_.Trash_&. When a directory is excluded from quota
23460 calculations, quota processing is bypassed for any messages that are delivered
23461 directly into that directory.
23464 .option maildir_retries appendfile integer 10
23465 This option specifies the number of times to retry when writing a file in
23466 &"maildir"& format. See section &<<SECTmaildirdelivery>>& below.
23469 .option maildir_tag appendfile string&!! unset
23470 This option applies only to deliveries in maildir format, and is described in
23471 section &<<SECTmaildirdelivery>>& below.
23474 .option maildir_use_size_file appendfile&!! boolean false
23475 .cindex "maildir format" "&_maildirsize_& file"
23476 The result of string expansion for this option must be a valid boolean value.
23477 If it is true, it enables support for &_maildirsize_& files. Exim
23478 creates a &_maildirsize_& file in a maildir if one does not exist, taking the
23479 quota from the &%quota%& option of the transport. If &%quota%& is unset, the
23480 value is zero. See &%maildir_quota_directory_regex%& above and section
23481 &<<SECTmaildirdelivery>>& below for further details.
23483 .option maildirfolder_create_regex appendfile string unset
23484 .cindex "maildir format" "&_maildirfolder_& file"
23485 .cindex "&_maildirfolder_&, creating"
23486 The value of this option is a regular expression. If it is unset, it has no
23487 effect. Otherwise, before a maildir delivery takes place, the pattern is
23488 matched against the name of the maildir directory, that is, the directory
23489 containing the &_new_& and &_tmp_& subdirectories that will be used for the
23490 delivery. If there is a match, Exim checks for the existence of a file called
23491 &_maildirfolder_& in the directory, and creates it if it does not exist.
23492 See section &<<SECTmaildirdelivery>>& for more details.
23495 .option mailstore_format appendfile boolean false
23496 .cindex "mailstore format" "specifying"
23497 If this option is set with the &%directory%& option, the delivery is into two
23498 new files in &"mailstore"& format. The option is available only if
23499 SUPPORT_MAILSTORE is present in &_Local/Makefile_&. See section &<<SECTopdir>>&
23500 below for further details.
23503 .option mailstore_prefix appendfile string&!! unset
23504 This option applies only to deliveries in mailstore format, and is described in
23505 section &<<SECTopdir>>& below.
23508 .option mailstore_suffix appendfile string&!! unset
23509 This option applies only to deliveries in mailstore format, and is described in
23510 section &<<SECTopdir>>& below.
23513 .option mbx_format appendfile boolean false
23514 .cindex "locking files"
23515 .cindex "file" "locking"
23516 .cindex "file" "MBX format"
23517 .cindex "MBX format, specifying"
23518 This option is available only if Exim has been compiled with SUPPORT_MBX
23519 set in &_Local/Makefile_&. If &%mbx_format%& is set with the &%file%& option,
23520 the message is appended to the mailbox file in MBX format instead of
23521 traditional Unix format. This format is supported by Pine4 and its associated
23522 IMAP and POP daemons, by means of the &'c-client'& library that they all use.
23524 &*Note*&: The &%message_prefix%& and &%message_suffix%& options are not
23525 automatically changed by the use of &%mbx_format%&. They should normally be set
23526 empty when using MBX format, so this option almost always appears in this
23533 If none of the locking options are mentioned in the configuration,
23534 &%use_mbx_lock%& is assumed and the other locking options default to false. It
23535 is possible to specify the other kinds of locking with &%mbx_format%&, but
23536 &%use_fcntl_lock%& and &%use_mbx_lock%& are mutually exclusive. MBX locking
23537 interworks with &'c-client'&, providing for shared access to the mailbox. It
23538 should not be used if any program that does not use this form of locking is
23539 going to access the mailbox, nor should it be used if the mailbox file is NFS
23540 mounted, because it works only when the mailbox is accessed from a single host.
23542 If you set &%use_fcntl_lock%& with an MBX-format mailbox, you cannot use
23543 the standard version of &'c-client'&, because as long as it has a mailbox open
23544 (this means for the whole of a Pine or IMAP session), Exim will not be able to
23545 append messages to it.
23548 .option message_prefix appendfile string&!! "see below"
23549 .cindex "&""From""& line"
23550 The string specified here is expanded and output at the start of every message.
23551 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
23552 in which case it is:
23554 message_prefix = "From ${if def:return_path{$return_path}\
23555 {MAILER-DAEMON}} $tod_bsdinbox\n"
23557 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
23558 &`\n`& to &`\r\n`& in &%message_prefix%&.
23560 .option message_suffix appendfile string&!! "see below"
23561 The string specified here is expanded and output at the end of every message.
23562 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
23563 in which case it is a single newline character. The suffix can be suppressed by
23568 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
23569 &`\n`& to &`\r\n`& in &%message_suffix%&.
23571 .option mode appendfile "octal integer" 0600
23572 If the output file is created, it is given this mode. If it already exists and
23573 has wider permissions, they are reduced to this mode. If it has narrower
23574 permissions, an error occurs unless &%mode_fail_narrower%& is false. However,
23575 if the delivery is the result of a &%save%& command in a filter file specifying
23576 a particular mode, the mode of the output file is always forced to take that
23577 value, and this option is ignored.
23580 .option mode_fail_narrower appendfile boolean true
23581 This option applies in the case when an existing mailbox file has a narrower
23582 mode than that specified by the &%mode%& option. If &%mode_fail_narrower%& is
23583 true, the delivery is deferred (&"mailbox has the wrong mode"&); otherwise Exim
23584 continues with the delivery attempt, using the existing mode of the file.
23587 .option notify_comsat appendfile boolean false
23588 If this option is true, the &'comsat'& daemon is notified after every
23589 successful delivery to a user mailbox. This is the daemon that notifies logged
23590 on users about incoming mail.
23593 .option quota appendfile string&!! unset
23594 .cindex "quota" "imposed by Exim"
23595 This option imposes a limit on the size of the file to which Exim is appending,
23596 or to the total space used in the directory tree when the &%directory%& option
23597 is set. In the latter case, computation of the space used is expensive, because
23598 all the files in the directory (and any sub-directories) have to be
23599 individually inspected and their sizes summed. (See &%quota_size_regex%& and
23600 &%maildir_use_size_file%& for ways to avoid this in environments where users
23601 have no shell access to their mailboxes).
23603 As there is no interlock against two simultaneous deliveries into a
23604 multi-file mailbox, it is possible for the quota to be overrun in this case.
23605 For single-file mailboxes, of course, an interlock is a necessity.
23607 A file's size is taken as its &'used'& value. Because of blocking effects, this
23608 may be a lot less than the actual amount of disk space allocated to the file.
23609 If the sizes of a number of files are being added up, the rounding effect can
23610 become quite noticeable, especially on systems that have large block sizes.
23611 Nevertheless, it seems best to stick to the &'used'& figure, because this is
23612 the obvious value which users understand most easily.
23614 The value of the option is expanded, and must then be a numerical value
23615 (decimal point allowed), optionally followed by one of the letters K, M, or G,
23616 for kilobytes, megabytes, or gigabytes, optionally followed by a slash
23617 and further option modifiers. If Exim is running on a system with
23618 large file support (Linux and FreeBSD have this), mailboxes larger than 2G can
23621 The option modifier &%no_check%& can be used to force delivery even if the over
23622 quota condition is met. The quota gets updated as usual.
23624 &*Note*&: A value of zero is interpreted as &"no quota"&.
23626 The expansion happens while Exim is running as root, before it changes uid for
23627 the delivery. This means that files that are inaccessible to the end user can
23628 be used to hold quota values that are looked up in the expansion. When delivery
23629 fails because this quota is exceeded, the handling of the error is as for
23630 system quota failures.
23632 By default, Exim's quota checking mimics system quotas, and restricts the
23633 mailbox to the specified maximum size, though the value is not accurate to the
23634 last byte, owing to separator lines and additional headers that may get added
23635 during message delivery. When a mailbox is nearly full, large messages may get
23636 refused even though small ones are accepted, because the size of the current
23637 message is added to the quota when the check is made. This behaviour can be
23638 changed by setting &%quota_is_inclusive%& false. When this is done, the check
23639 for exceeding the quota does not include the current message. Thus, deliveries
23640 continue until the quota has been exceeded; thereafter, no further messages are
23641 delivered. See also &%quota_warn_threshold%&.
23644 .option quota_directory appendfile string&!! unset
23645 This option defines the directory to check for quota purposes when delivering
23646 into individual files. The default is the delivery directory, or, if a file
23647 called &_maildirfolder_& exists in a maildir directory, the parent of the
23648 delivery directory.
23651 .option quota_filecount appendfile string&!! 0
23652 This option applies when the &%directory%& option is set. It limits the total
23653 number of files in the directory (compare the inode limit in system quotas). It
23654 can only be used if &%quota%& is also set. The value is expanded; an expansion
23655 failure causes delivery to be deferred. A value of zero is interpreted as
23658 The option modifier &%no_check%& can be used to force delivery even if the over
23659 quota condition is met. The quota gets updated as usual.
23661 .option quota_is_inclusive appendfile boolean true
23662 See &%quota%& above.
23665 .option quota_size_regex appendfile string unset
23666 This option applies when one of the delivery modes that writes a separate file
23667 for each message is being used. When Exim wants to find the size of one of
23668 these files in order to test the quota, it first checks &%quota_size_regex%&.
23669 If this is set to a regular expression that matches the filename, and it
23670 captures one string, that string is interpreted as a representation of the
23671 file's size. The value of &%quota_size_regex%& is not expanded.
23673 This feature is useful only when users have no shell access to their mailboxes
23674 &-- otherwise they could defeat the quota simply by renaming the files. This
23675 facility can be used with maildir deliveries, by setting &%maildir_tag%& to add
23676 the file length to the filename. For example:
23678 maildir_tag = ,S=$message_size
23679 quota_size_regex = ,S=(\d+)
23681 An alternative to &$message_size$& is &$message_linecount$&, which contains the
23682 number of lines in the message.
23684 The regular expression should not assume that the length is at the end of the
23685 filename (even though &%maildir_tag%& puts it there) because maildir MUAs
23686 sometimes add other information onto the ends of message filenames.
23688 Section &<<SECID136>>& contains further information.
23690 This option should not be used when other message-handling software
23691 may duplicate messages by making hardlinks to the files. When that is done Exim
23692 will count the message size once for each filename, in contrast with the actual
23693 disk usage. When the option is not set, calculating total usage requires
23694 a system-call per file to get the size; the number of links is then available also
23695 as is used to adjust the effective size.
23698 .option quota_warn_message appendfile string&!! "see below"
23699 See below for the use of this option. If it is not set when
23700 &%quota_warn_threshold%& is set, it defaults to
23702 quota_warn_message = "\
23703 To: $local_part@$domain\n\
23704 Subject: Your mailbox\n\n\
23705 This message is automatically created \
23706 by mail delivery software.\n\n\
23707 The size of your mailbox has exceeded \
23708 a warning threshold that is\n\
23709 set by the system administrator.\n"
23713 .option quota_warn_threshold appendfile string&!! 0
23714 .cindex "quota" "warning threshold"
23715 .cindex "mailbox" "size warning"
23716 .cindex "size" "of mailbox"
23717 This option is expanded in the same way as &%quota%& (see above). If the
23718 resulting value is greater than zero, and delivery of the message causes the
23719 size of the file or total space in the directory tree to cross the given
23720 threshold, a warning message is sent. If &%quota%& is also set, the threshold
23721 may be specified as a percentage of it by following the value with a percent
23725 quota_warn_threshold = 75%
23727 If &%quota%& is not set, a setting of &%quota_warn_threshold%& that ends with a
23728 percent sign is ignored.
23730 The warning message itself is specified by the &%quota_warn_message%& option,
23731 and it must start with a &'To:'& header line containing the recipient(s) of the
23732 warning message. These do not necessarily have to include the recipient(s) of
23733 the original message. A &'Subject:'& line should also normally be supplied. You
23734 can include any other header lines that you want. If you do not include a
23735 &'From:'& line, the default is:
23737 From: Mail Delivery System <mailer-daemon@$qualify_domain_sender>
23739 .oindex &%errors_reply_to%&
23740 If you supply a &'Reply-To:'& line, it overrides the global &%errors_reply_to%&
23743 The &%quota%& option does not have to be set in order to use this option; they
23744 are independent of one another except when the threshold is specified as a
23748 .option use_bsmtp appendfile boolean false
23749 .cindex "envelope from"
23750 .cindex "envelope sender"
23751 If this option is set true, &(appendfile)& writes messages in &"batch SMTP"&
23752 format, with the envelope sender and recipient(s) included as SMTP commands. If
23753 you want to include a leading HELO command with such messages, you can do
23754 so by setting the &%message_prefix%& option. See section &<<SECTbatchSMTP>>&
23755 for details of batch SMTP.
23758 .option use_crlf appendfile boolean false
23759 .cindex "carriage return"
23761 This option causes lines to be terminated with the two-character CRLF sequence
23762 (carriage return, linefeed) instead of just a linefeed character. In the case
23763 of batched SMTP, the byte sequence written to the file is then an exact image
23764 of what would be sent down a real SMTP connection.
23766 &*Note:*& The contents of the &%message_prefix%& and &%message_suffix%& options
23767 (which are used to supply the traditional &"From&~"& and blank line separators
23768 in Berkeley-style mailboxes) are written verbatim, so must contain their own
23769 carriage return characters if these are needed. In cases where these options
23770 have non-empty defaults, the values end with a single linefeed, so they must be
23771 changed to end with &`\r\n`& if &%use_crlf%& is set.
23774 .option use_fcntl_lock appendfile boolean "see below"
23775 This option controls the use of the &[fcntl()]& function to lock a file for
23776 exclusive use when a message is being appended. It is set by default unless
23777 &%use_flock_lock%& is set. Otherwise, it should be turned off only if you know
23778 that all your MUAs use lock file locking. When both &%use_fcntl_lock%& and
23779 &%use_flock_lock%& are unset, &%use_lockfile%& must be set.
23782 .option use_flock_lock appendfile boolean false
23783 This option is provided to support the use of &[flock()]& for file locking, for
23784 the few situations where it is needed. Most modern operating systems support
23785 &[fcntl()]& and &[lockf()]& locking, and these two functions interwork with
23786 each other. Exim uses &[fcntl()]& locking by default.
23788 This option is required only if you are using an operating system where
23789 &[flock()]& is used by programs that access mailboxes (typically MUAs), and
23790 where &[flock()]& does not correctly interwork with &[fcntl()]&. You can use
23791 both &[fcntl()]& and &[flock()]& locking simultaneously if you want.
23793 .cindex "Solaris" "&[flock()]& support"
23794 Not all operating systems provide &[flock()]&. Some versions of Solaris do not
23795 have it (and some, I think, provide a not quite right version built on top of
23796 &[lockf()]&). If the OS does not have &[flock()]&, Exim will be built without
23797 the ability to use it, and any attempt to do so will cause a configuration
23800 &*Warning*&: &[flock()]& locks do not work on NFS files (unless &[flock()]&
23801 is just being mapped onto &[fcntl()]& by the OS).
23804 .option use_lockfile appendfile boolean "see below"
23805 If this option is turned off, Exim does not attempt to create a lock file when
23806 appending to a mailbox file. In this situation, the only locking is by
23807 &[fcntl()]&. You should only turn &%use_lockfile%& off if you are absolutely
23808 sure that every MUA that is ever going to look at your users' mailboxes uses
23809 &[fcntl()]& rather than a lock file, and even then only when you are not
23810 delivering over NFS from more than one host.
23812 .cindex "NFS" "lock file"
23813 In order to append to an NFS file safely from more than one host, it is
23814 necessary to take out a lock &'before'& opening the file, and the lock file
23815 achieves this. Otherwise, even with &[fcntl()]& locking, there is a risk of
23818 The &%use_lockfile%& option is set by default unless &%use_mbx_lock%& is set.
23819 It is not possible to turn both &%use_lockfile%& and &%use_fcntl_lock%& off,
23820 except when &%mbx_format%& is set.
23823 .option use_mbx_lock appendfile boolean "see below"
23824 This option is available only if Exim has been compiled with SUPPORT_MBX
23825 set in &_Local/Makefile_&. Setting the option specifies that special MBX
23826 locking rules be used. It is set by default if &%mbx_format%& is set and none
23827 of the locking options are mentioned in the configuration. The locking rules
23828 are the same as are used by the &'c-client'& library that underlies Pine and
23829 the IMAP4 and POP daemons that come with it (see the discussion below). The
23830 rules allow for shared access to the mailbox. However, this kind of locking
23831 does not work when the mailbox is NFS mounted.
23833 You can set &%use_mbx_lock%& with either (or both) of &%use_fcntl_lock%& and
23834 &%use_flock_lock%& to control what kind of locking is used in implementing the
23835 MBX locking rules. The default is to use &[fcntl()]& if &%use_mbx_lock%& is set
23836 without &%use_fcntl_lock%& or &%use_flock_lock%&.
23841 .section "Operational details for appending" "SECTopappend"
23842 .cindex "appending to a file"
23843 .cindex "file" "appending"
23844 Before appending to a file, the following preparations are made:
23847 If the name of the file is &_/dev/null_&, no action is taken, and a success
23851 .cindex "directory creation"
23852 If any directories on the file's path are missing, Exim creates them if the
23853 &%create_directory%& option is set. A created directory's mode is given by the
23854 &%directory_mode%& option.
23857 If &%file_format%& is set, the format of an existing file is checked. If this
23858 indicates that a different transport should be used, control is passed to that
23862 .cindex "file" "locking"
23863 .cindex "locking files"
23864 .cindex "NFS" "lock file"
23865 If &%use_lockfile%& is set, a lock file is built in a way that will work
23866 reliably over NFS, as follows:
23869 Create a &"hitching post"& file whose name is that of the lock file with the
23870 current time, primary host name, and process id added, by opening for writing
23871 as a new file. If this fails with an access error, delivery is deferred.
23873 Close the hitching post file, and hard link it to the lock filename.
23875 If the call to &[link()]& succeeds, creation of the lock file has succeeded.
23876 Unlink the hitching post name.
23878 Otherwise, use &[stat()]& to get information about the hitching post file, and
23879 then unlink hitching post name. If the number of links is exactly two, creation
23880 of the lock file succeeded but something (for example, an NFS server crash and
23881 restart) caused this fact not to be communicated to the &[link()]& call.
23883 If creation of the lock file failed, wait for &%lock_interval%& and try again,
23884 up to &%lock_retries%& times. However, since any program that writes to a
23885 mailbox should complete its task very quickly, it is reasonable to time out old
23886 lock files that are normally the result of user agent and system crashes. If an
23887 existing lock file is older than &%lockfile_timeout%& Exim attempts to unlink
23888 it before trying again.
23892 A call is made to &[lstat()]& to discover whether the main file exists, and if
23893 so, what its characteristics are. If &[lstat()]& fails for any reason other
23894 than non-existence, delivery is deferred.
23897 .cindex "symbolic link" "to mailbox"
23898 .cindex "mailbox" "symbolic link"
23899 If the file does exist and is a symbolic link, delivery is deferred, unless the
23900 &%allow_symlink%& option is set, in which case the ownership of the link is
23901 checked, and then &[stat()]& is called to find out about the real file, which
23902 is then subjected to the checks below. The check on the top-level link
23903 ownership prevents one user creating a link for another's mailbox in a sticky
23904 directory, though allowing symbolic links in this case is definitely not a good
23905 idea. If there is a chain of symbolic links, the intermediate ones are not
23909 If the file already exists but is not a regular file, or if the file's owner
23910 and group (if the group is being checked &-- see &%check_group%& above) are
23911 different from the user and group under which the delivery is running,
23912 delivery is deferred.
23915 If the file's permissions are more generous than specified, they are reduced.
23916 If they are insufficient, delivery is deferred, unless &%mode_fail_narrower%&
23917 is set false, in which case the delivery is tried using the existing
23921 The file's inode number is saved, and the file is then opened for appending.
23922 If this fails because the file has vanished, &(appendfile)& behaves as if it
23923 hadn't existed (see below). For any other failures, delivery is deferred.
23926 If the file is opened successfully, check that the inode number hasn't
23927 changed, that it is still a regular file, and that the owner and permissions
23928 have not changed. If anything is wrong, defer delivery and freeze the message.
23931 If the file did not exist originally, defer delivery if the &%file_must_exist%&
23932 option is set. Otherwise, check that the file is being created in a permitted
23933 directory if the &%create_file%& option is set (deferring on failure), and then
23934 open for writing as a new file, with the O_EXCL and O_CREAT options,
23935 except when dealing with a symbolic link (the &%allow_symlink%& option must be
23936 set). In this case, which can happen if the link points to a non-existent file,
23937 the file is opened for writing using O_CREAT but not O_EXCL, because
23938 that prevents link following.
23941 .cindex "loop" "while file testing"
23942 If opening fails because the file exists, obey the tests given above for
23943 existing files. However, to avoid looping in a situation where the file is
23944 being continuously created and destroyed, the exists/not-exists loop is broken
23945 after 10 repetitions, and the message is then frozen.
23948 If opening fails with any other error, defer delivery.
23951 .cindex "file" "locking"
23952 .cindex "locking files"
23953 Once the file is open, unless both &%use_fcntl_lock%& and &%use_flock_lock%&
23954 are false, it is locked using &[fcntl()]& or &[flock()]& or both. If
23955 &%use_mbx_lock%& is false, an exclusive lock is requested in each case.
23956 However, if &%use_mbx_lock%& is true, Exim takes out a shared lock on the open
23957 file, and an exclusive lock on the file whose name is
23959 /tmp/.<device-number>.<inode-number>
23961 using the device and inode numbers of the open mailbox file, in accordance with
23962 the MBX locking rules. This file is created with a mode that is specified by
23963 the &%lockfile_mode%& option.
23965 If Exim fails to lock the file, there are two possible courses of action,
23966 depending on the value of the locking timeout. This is obtained from
23967 &%lock_fcntl_timeout%& or &%lock_flock_timeout%&, as appropriate.
23969 If the timeout value is zero, the file is closed, Exim waits for
23970 &%lock_interval%&, and then goes back and re-opens the file as above and tries
23971 to lock it again. This happens up to &%lock_retries%& times, after which the
23972 delivery is deferred.
23974 If the timeout has a value greater than zero, blocking calls to &[fcntl()]& or
23975 &[flock()]& are used (with the given timeout), so there has already been some
23976 waiting involved by the time locking fails. Nevertheless, Exim does not give up
23977 immediately. It retries up to
23979 (lock_retries * lock_interval) / <timeout>
23981 times (rounded up).
23984 At the end of delivery, Exim closes the file (which releases the &[fcntl()]&
23985 and/or &[flock()]& locks) and then deletes the lock file if one was created.
23988 .section "Operational details for delivery to a new file" "SECTopdir"
23989 .cindex "delivery" "to single file"
23990 .cindex "&""From""& line"
23991 When the &%directory%& option is set instead of &%file%&, each message is
23992 delivered into a newly-created file or set of files. When &(appendfile)& is
23993 activated directly from a &(redirect)& router, neither &%file%& nor
23994 &%directory%& is normally set, because the path for delivery is supplied by the
23995 router. (See for example, the &(address_file)& transport in the default
23996 configuration.) In this case, delivery is to a new file if either the path name
23997 ends in &`/`&, or the &%maildir_format%& or &%mailstore_format%& option is set.
23999 No locking is required while writing the message to a new file, so the various
24000 locking options of the transport are ignored. The &"From"& line that by default
24001 separates messages in a single file is not normally needed, nor is the escaping
24002 of message lines that start with &"From"&, and there is no need to ensure a
24003 newline at the end of each message. Consequently, the default values for
24004 &%check_string%&, &%message_prefix%&, and &%message_suffix%& are all unset when
24005 any of &%directory%&, &%maildir_format%&, or &%mailstore_format%& is set.
24007 If Exim is required to check a &%quota%& setting, it adds up the sizes of all
24008 the files in the delivery directory by default. However, you can specify a
24009 different directory by setting &%quota_directory%&. Also, for maildir
24010 deliveries (see below) the &_maildirfolder_& convention is honoured.
24013 .cindex "maildir format"
24014 .cindex "mailstore format"
24015 There are three different ways in which delivery to individual files can be
24016 done, controlled by the settings of the &%maildir_format%& and
24017 &%mailstore_format%& options. Note that code to support maildir or mailstore
24018 formats is not included in the binary unless SUPPORT_MAILDIR or
24019 SUPPORT_MAILSTORE, respectively, is set in &_Local/Makefile_&.
24021 .cindex "directory creation"
24022 In all three cases an attempt is made to create the directory and any necessary
24023 sub-directories if they do not exist, provided that the &%create_directory%&
24024 option is set (the default). The location of a created directory can be
24025 constrained by setting &%create_file%&. A created directory's mode is given by
24026 the &%directory_mode%& option. If creation fails, or if the
24027 &%create_directory%& option is not set when creation is required, delivery is
24032 .section "Maildir delivery" "SECTmaildirdelivery"
24033 .cindex "maildir format" "description of"
24034 If the &%maildir_format%& option is true, Exim delivers each message by writing
24035 it to a file whose name is &_tmp/<stime>.H<mtime>P<pid>.<host>_& in the
24036 directory that is defined by the &%directory%& option (the &"delivery
24037 directory"&). If the delivery is successful, the file is renamed into the
24038 &_new_& subdirectory.
24040 In the filename, <&'stime'&> is the current time of day in seconds, and
24041 <&'mtime'&> is the microsecond fraction of the time. After a maildir delivery,
24042 Exim checks that the time-of-day clock has moved on by at least one microsecond
24043 before terminating the delivery process. This guarantees uniqueness for the
24044 filename. However, as a precaution, Exim calls &[stat()]& for the file before
24045 opening it. If any response other than ENOENT (does not exist) is given,
24046 Exim waits 2 seconds and tries again, up to &%maildir_retries%& times.
24048 Before Exim carries out a maildir delivery, it ensures that subdirectories
24049 called &_new_&, &_cur_&, and &_tmp_& exist in the delivery directory. If they
24050 do not exist, Exim tries to create them and any superior directories in their
24051 path, subject to the &%create_directory%& and &%create_file%& options. If the
24052 &%maildirfolder_create_regex%& option is set, and the regular expression it
24053 contains matches the delivery directory, Exim also ensures that a file called
24054 &_maildirfolder_& exists in the delivery directory. If a missing directory or
24055 &_maildirfolder_& file cannot be created, delivery is deferred.
24057 These features make it possible to use Exim to create all the necessary files
24058 and directories in a maildir mailbox, including subdirectories for maildir++
24059 folders. Consider this example:
24061 maildir_format = true
24062 directory = /var/mail/$local_part_data\
24063 ${if eq{$local_part_suffix}{}{}\
24064 {/.${substr_1:$local_part_suffix}}}
24065 maildirfolder_create_regex = /\.[^/]+$
24067 If &$local_part_suffix$& is empty (there was no suffix for the local part),
24068 delivery is into a toplevel maildir with a name like &_/var/mail/pimbo_& (for
24069 the user called &'pimbo'&). The pattern in &%maildirfolder_create_regex%& does
24070 not match this name, so Exim will not look for or create the file
24071 &_/var/mail/pimbo/maildirfolder_&, though it will create
24072 &_/var/mail/pimbo/{cur,new,tmp}_& if necessary.
24074 However, if &$local_part_suffix$& contains &`-eximusers`& (for example),
24075 delivery is into the maildir++ folder &_/var/mail/pimbo/.eximusers_&, which
24076 does match &%maildirfolder_create_regex%&. In this case, Exim will create
24077 &_/var/mail/pimbo/.eximusers/maildirfolder_& as well as the three maildir
24078 directories &_/var/mail/pimbo/.eximusers/{cur,new,tmp}_&.
24080 &*Warning:*& Take care when setting &%maildirfolder_create_regex%& that it does
24081 not inadvertently match the toplevel maildir directory, because a
24082 &_maildirfolder_& file at top level would completely break quota calculations.
24084 .cindex "quota" "in maildir delivery"
24085 .cindex "maildir++"
24086 If Exim is required to check a &%quota%& setting before a maildir delivery, and
24087 &%quota_directory%& is not set, it looks for a file called &_maildirfolder_& in
24088 the maildir directory (alongside &_new_&, &_cur_&, &_tmp_&). If this exists,
24089 Exim assumes the directory is a maildir++ folder directory, which is one level
24090 down from the user's top level mailbox directory. This causes it to start at
24091 the parent directory instead of the current directory when calculating the
24092 amount of space used.
24094 One problem with delivering into a multi-file mailbox is that it is
24095 computationally expensive to compute the size of the mailbox for quota
24096 checking. Various approaches have been taken to reduce the amount of work
24097 needed. The next two sections describe two of them. A third alternative is to
24098 use some external process for maintaining the size data, and use the expansion
24099 of the &%mailbox_size%& option as a way of importing it into Exim.
24104 .section "Using tags to record message sizes" "SECID135"
24105 If &%maildir_tag%& is set, the string is expanded for each delivery.
24106 When the maildir file is renamed into the &_new_& sub-directory, the
24107 tag is added to its name. However, if adding the tag takes the length of the
24108 name to the point where the test &[stat()]& call fails with ENAMETOOLONG,
24109 the tag is dropped and the maildir file is created with no tag.
24112 .vindex "&$message_size$&"
24113 Tags can be used to encode the size of files in their names; see
24114 &%quota_size_regex%& above for an example. The expansion of &%maildir_tag%&
24115 happens after the message has been written. The value of the &$message_size$&
24116 variable is set to the number of bytes actually written. If the expansion is
24117 forced to fail, the tag is ignored, but a non-forced failure causes delivery to
24118 be deferred. The expanded tag may contain any printing characters except &"/"&.
24119 Non-printing characters in the string are ignored; if the resulting string is
24120 empty, it is ignored. If it starts with an alphanumeric character, a leading
24121 colon is inserted; this default has not proven to be the path that popular
24122 maildir implementations have chosen (but changing it in Exim would break
24123 backwards compatibility).
24125 For one common implementation, you might set:
24127 maildir_tag = ,S=${message_size}
24129 but you should check the documentation of the other software to be sure.
24131 It is advisable to also set &%quota_size_regex%& when setting &%maildir_tag%&
24132 as this allows Exim to extract the size from your tag, instead of having to
24133 &[stat()]& each message file.
24136 .section "Using a maildirsize file" "SECID136"
24137 .cindex "quota" "in maildir delivery"
24138 .cindex "maildir format" "&_maildirsize_& file"
24139 If &%maildir_use_size_file%& is true, Exim implements the maildir++ rules for
24140 storing quota and message size information in a file called &_maildirsize_&
24141 within the toplevel maildir directory. If this file does not exist, Exim
24142 creates it, setting the quota from the &%quota%& option of the transport. If
24143 the maildir directory itself does not exist, it is created before any attempt
24144 to write a &_maildirsize_& file.
24146 The &_maildirsize_& file is used to hold information about the sizes of
24147 messages in the maildir, thus speeding up quota calculations. The quota value
24148 in the file is just a cache; if the quota is changed in the transport, the new
24149 value overrides the cached value when the next message is delivered. The cache
24150 is maintained for the benefit of other programs that access the maildir and
24151 need to know the quota.
24153 If the &%quota%& option in the transport is unset or zero, the &_maildirsize_&
24154 file is maintained (with a zero quota setting), but no quota is imposed.
24156 A regular expression is available for controlling which directories in the
24157 maildir participate in quota calculations when a &_maildirsizefile_& is in use.
24158 See the description of the &%maildir_quota_directory_regex%& option above for
24162 .section "Mailstore delivery" "SECID137"
24163 .cindex "mailstore format" "description of"
24164 If the &%mailstore_format%& option is true, each message is written as two
24165 files in the given directory. A unique base name is constructed from the
24166 message id and the current delivery process, and the files that are written use
24167 this base name plus the suffixes &_.env_& and &_.msg_&. The &_.env_& file
24168 contains the message's envelope, and the &_.msg_& file contains the message
24169 itself. The base name is placed in the variable &$mailstore_basename$&.
24171 During delivery, the envelope is first written to a file with the suffix
24172 &_.tmp_&. The &_.msg_& file is then written, and when it is complete, the
24173 &_.tmp_& file is renamed as the &_.env_& file. Programs that access messages in
24174 mailstore format should wait for the presence of both a &_.msg_& and a &_.env_&
24175 file before accessing either of them. An alternative approach is to wait for
24176 the absence of a &_.tmp_& file.
24178 The envelope file starts with any text defined by the &%mailstore_prefix%&
24179 option, expanded and terminated by a newline if there isn't one. Then follows
24180 the sender address on one line, then all the recipient addresses, one per line.
24181 There can be more than one recipient only if the &%batch_max%& option is set
24182 greater than one. Finally, &%mailstore_suffix%& is expanded and the result
24183 appended to the file, followed by a newline if it does not end with one.
24185 If expansion of &%mailstore_prefix%& or &%mailstore_suffix%& ends with a forced
24186 failure, it is ignored. Other expansion errors are treated as serious
24187 configuration errors, and delivery is deferred. The variable
24188 &$mailstore_basename$& is available for use during these expansions.
24191 .section "Non-special new file delivery" "SECID138"
24192 If neither &%maildir_format%& nor &%mailstore_format%& is set, a single new
24193 file is created directly in the named directory. For example, when delivering
24194 messages into files in batched SMTP format for later delivery to some host (see
24195 section &<<SECTbatchSMTP>>&), a setting such as
24197 directory = /var/bsmtp/$host
24199 might be used. A message is written to a file with a temporary name, which is
24200 then renamed when the delivery is complete. The final name is obtained by
24201 expanding the contents of the &%directory_file%& option.
24202 .ecindex IIDapptra1
24203 .ecindex IIDapptra2
24210 . ////////////////////////////////////////////////////////////////////////////
24211 . ////////////////////////////////////////////////////////////////////////////
24213 .chapter "The autoreply transport" "CHID8"
24214 .scindex IIDauttra1 "transports" "&(autoreply)&"
24215 .scindex IIDauttra2 "&(autoreply)& transport"
24216 The &(autoreply)& transport is not a true transport in that it does not cause
24217 the message to be transmitted. Instead, it generates a new mail message as an
24218 automatic reply to the incoming message. &'References:'& and
24219 &'Auto-Submitted:'& header lines are included. These are constructed according
24220 to the rules in RFCs 2822 and 3834, respectively.
24222 If the router that passes the message to this transport does not have the
24223 &%unseen%& option set, the original message (for the current recipient) is not
24224 delivered anywhere. However, when the &%unseen%& option is set on the router
24225 that passes the message to this transport, routing of the address continues, so
24226 another router can set up a normal message delivery.
24229 The &(autoreply)& transport is usually run as the result of mail filtering, a
24230 &"vacation"& message being the standard example. However, it can also be run
24231 directly from a router like any other transport. To reduce the possibility of
24232 message cascades, messages created by the &(autoreply)& transport always have
24233 empty envelope sender addresses, like bounce messages.
24235 The parameters of the message to be sent can be specified in the configuration
24236 by options described below. However, these are used only when the address
24237 passed to the transport does not contain its own reply information. When the
24238 transport is run as a consequence of a
24240 or &%vacation%& command in a filter file, the parameters of the message are
24241 supplied by the filter, and passed with the address. The transport's options
24242 that define the message are then ignored (so they are not usually set in this
24243 case). The message is specified entirely by the filter or by the transport; it
24244 is never built from a mixture of options. However, the &%file_optional%&,
24245 &%mode%&, and &%return_message%& options apply in all cases.
24247 &(Autoreply)& is implemented as a local transport. When used as a result of a
24248 command in a user's filter file, &(autoreply)& normally runs under the uid and
24249 gid of the user, and with appropriate current and home directories (see chapter
24250 &<<CHAPenvironment>>&).
24252 There is a subtle difference between routing a message to a &(pipe)& transport
24253 that generates some text to be returned to the sender, and routing it to an
24254 &(autoreply)& transport. This difference is noticeable only if more than one
24255 address from the same message is so handled. In the case of a pipe, the
24256 separate outputs from the different addresses are gathered up and returned to
24257 the sender in a single message, whereas if &(autoreply)& is used, a separate
24258 message is generated for each address that is passed to it.
24260 Non-printing characters are not permitted in the header lines generated for the
24261 message that &(autoreply)& creates, with the exception of newlines that are
24262 immediately followed by white space. If any non-printing characters are found,
24263 the transport defers.
24264 Whether characters with the top bit set count as printing characters or not is
24265 controlled by the &%print_topbitchars%& global option.
24267 If any of the generic options for manipulating headers (for example,
24268 &%headers_add%&) are set on an &(autoreply)& transport, they apply to the copy
24269 of the original message that is included in the generated message when
24270 &%return_message%& is set. They do not apply to the generated message itself.
24272 .vindex "&$sender_address$&"
24273 If the &(autoreply)& transport receives return code 2 from Exim when it submits
24274 the message, indicating that there were no recipients, it does not treat this
24275 as an error. This means that autoreplies sent to &$sender_address$& when this
24276 is empty (because the incoming message is a bounce message) do not cause
24277 problems. They are just discarded.
24281 .section "Private options for autoreply" "SECID139"
24282 .cindex "options" "&(autoreply)& transport"
24284 .option bcc autoreply string&!! unset
24285 This specifies the addresses that are to receive &"blind carbon copies"& of the
24286 message when the message is specified by the transport.
24289 .option cc autoreply string&!! unset
24290 This specifies recipients of the message and the contents of the &'Cc:'& header
24291 when the message is specified by the transport.
24294 .option file autoreply string&!! unset
24295 The contents of the file are sent as the body of the message when the message
24296 is specified by the transport. If both &%file%& and &%text%& are set, the text
24297 string comes first.
24300 .option file_expand autoreply boolean false
24301 If this is set, the contents of the file named by the &%file%& option are
24302 subjected to string expansion as they are added to the message.
24305 .option file_optional autoreply boolean false
24306 If this option is true, no error is generated if the file named by the &%file%&
24307 option or passed with the address does not exist or cannot be read.
24310 .option from autoreply string&!! unset
24311 This specifies the contents of the &'From:'& header when the message is
24312 specified by the transport.
24315 .option headers autoreply string&!! unset
24316 This specifies additional RFC 2822 headers that are to be added to the message
24317 when the message is specified by the transport. Several can be given by using
24318 &"\n"& to separate them. There is no check on the format.
24321 .option log autoreply string&!! unset
24322 This option names a file in which a record of every message sent is logged when
24323 the message is specified by the transport.
24326 .option mode autoreply "octal integer" 0600
24327 If either the log file or the &"once"& file has to be created, this mode is
24331 .option never_mail autoreply "address list&!!" unset
24332 If any run of the transport creates a message with a recipient that matches any
24333 item in the list, that recipient is quietly discarded. If all recipients are
24334 discarded, no message is created. This applies both when the recipients are
24335 generated by a filter and when they are specified in the transport.
24339 .option once autoreply string&!! unset
24340 This option names a file or DBM database in which a record of each &'To:'&
24341 recipient is kept when the message is specified by the transport. &*Note*&:
24342 This does not apply to &'Cc:'& or &'Bcc:'& recipients.
24344 If &%once%& is unset, or is set to an empty string, the message is always sent.
24345 By default, if &%once%& is set to a non-empty filename, the message
24346 is not sent if a potential recipient is already listed in the database.
24347 However, if the &%once_repeat%& option specifies a time greater than zero, the
24348 message is sent if that much time has elapsed since a message was last sent to
24349 this recipient. A setting of zero time for &%once_repeat%& (the default)
24350 prevents a message from being sent a second time &-- in this case, zero means
24353 If &%once_file_size%& is zero, a DBM database is used to remember recipients,
24354 and it is allowed to grow as large as necessary. If &%once_file_size%& is set
24355 greater than zero, it changes the way Exim implements the &%once%& option.
24356 Instead of using a DBM file to record every recipient it sends to, it uses a
24357 regular file, whose size will never get larger than the given value.
24359 In the file, Exim keeps a linear list of recipient addresses and the times at
24360 which they were sent messages. If the file is full when a new address needs to
24361 be added, the oldest address is dropped. If &%once_repeat%& is not set, this
24362 means that a given recipient may receive multiple messages, but at
24363 unpredictable intervals that depend on the rate of turnover of addresses in the
24364 file. If &%once_repeat%& is set, it specifies a maximum time between repeats.
24367 .option once_file_size autoreply integer 0
24368 See &%once%& above.
24371 .option once_repeat autoreply time&!! 0s
24372 See &%once%& above.
24373 After expansion, the value of this option must be a valid time value.
24376 .option reply_to autoreply string&!! unset
24377 This specifies the contents of the &'Reply-To:'& header when the message is
24378 specified by the transport.
24381 .option return_message autoreply boolean false
24382 If this is set, a copy of the original message is returned with the new
24383 message, subject to the maximum size set in the &%return_size_limit%& global
24384 configuration option.
24387 .option subject autoreply string&!! unset
24388 This specifies the contents of the &'Subject:'& header when the message is
24389 specified by the transport. It is tempting to quote the original subject in
24390 automatic responses. For example:
24392 subject = Re: $h_subject:
24394 There is a danger in doing this, however. It may allow a third party to
24395 subscribe your users to an opt-in mailing list, provided that the list accepts
24396 bounce messages as subscription confirmations. Well-managed lists require a
24397 non-bounce message to confirm a subscription, so the danger is relatively
24402 .option text autoreply string&!! unset
24403 This specifies a single string to be used as the body of the message when the
24404 message is specified by the transport. If both &%text%& and &%file%& are set,
24405 the text comes first.
24408 .option to autoreply string&!! unset
24409 This specifies recipients of the message and the contents of the &'To:'& header
24410 when the message is specified by the transport.
24411 .ecindex IIDauttra1
24412 .ecindex IIDauttra2
24417 . ////////////////////////////////////////////////////////////////////////////
24418 . ////////////////////////////////////////////////////////////////////////////
24420 .chapter "The lmtp transport" "CHAPLMTP"
24421 .cindex "transports" "&(lmtp)&"
24422 .cindex "&(lmtp)& transport"
24423 .cindex "LMTP" "over a pipe"
24424 .cindex "LMTP" "over a socket"
24425 The &(lmtp)& transport runs the LMTP protocol (RFC 2033) over a pipe to a
24427 or by interacting with a Unix domain socket.
24428 This transport is something of a cross between the &(pipe)& and &(smtp)&
24429 transports. Exim also has support for using LMTP over TCP/IP; this is
24430 implemented as an option for the &(smtp)& transport. Because LMTP is expected
24431 to be of minority interest, the default build-time configure in &_src/EDITME_&
24432 has it commented out. You need to ensure that
24436 .cindex "options" "&(lmtp)& transport"
24437 is present in your &_Local/Makefile_& in order to have the &(lmtp)& transport
24438 included in the Exim binary. The private options of the &(lmtp)& transport are
24441 .option batch_id lmtp string&!! unset
24442 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
24445 .option batch_max lmtp integer 1
24446 This limits the number of addresses that can be handled in a single delivery.
24447 Most LMTP servers can handle several addresses at once, so it is normally a
24448 good idea to increase this value. See the description of local delivery
24449 batching in chapter &<<CHAPbatching>>&.
24452 .option command lmtp string&!! unset
24453 This option must be set if &%socket%& is not set. The string is a command which
24454 is run in a separate process. It is split up into a command name and list of
24455 arguments, each of which is separately expanded (so expansion cannot change the
24456 number of arguments). The command is run directly, not via a shell. The message
24457 is passed to the new process using the standard input and output to operate the
24460 .option ignore_quota lmtp boolean false
24461 .cindex "LMTP" "ignoring quota errors"
24462 If this option is set true, the string &`IGNOREQUOTA`& is added to RCPT
24463 commands, provided that the LMTP server has advertised support for IGNOREQUOTA
24464 in its response to the LHLO command.
24466 .option socket lmtp string&!! unset
24467 This option must be set if &%command%& is not set. The result of expansion must
24468 be the name of a Unix domain socket. The transport connects to the socket and
24469 delivers the message to it using the LMTP protocol.
24472 .option timeout lmtp time 5m
24473 The transport is aborted if the created process or Unix domain socket does not
24474 respond to LMTP commands or message input within this timeout. Delivery
24475 is deferred, and will be tried again later. Here is an example of a typical
24480 command = /some/local/lmtp/delivery/program
24484 This delivers up to 20 addresses at a time, in a mixture of domains if
24485 necessary, running as the user &'exim'&.
24489 . ////////////////////////////////////////////////////////////////////////////
24490 . ////////////////////////////////////////////////////////////////////////////
24492 .chapter "The pipe transport" "CHAPpipetransport"
24493 .scindex IIDpiptra1 "transports" "&(pipe)&"
24494 .scindex IIDpiptra2 "&(pipe)& transport"
24495 The &(pipe)& transport is used to deliver messages via a pipe to a command
24496 running in another process. One example is the use of &(pipe)& as a
24497 pseudo-remote transport for passing messages to some other delivery mechanism
24498 (such as UUCP). Another is the use by individual users to automatically process
24499 their incoming messages. The &(pipe)& transport can be used in one of the
24503 .vindex "&$local_part$&"
24504 A router routes one address to a transport in the normal way, and the
24505 transport is configured as a &(pipe)& transport. In this case, &$local_part$&
24506 contains the local part of the address (as usual), and the command that is run
24507 is specified by the &%command%& option on the transport.
24509 .vindex "&$pipe_addresses$&"
24510 If the &%batch_max%& option is set greater than 1 (the default is 1), the
24511 transport can handle more than one address in a single run. In this case, when
24512 more than one address is routed to the transport, &$local_part$& is not set
24513 (because it is not unique). However, the pseudo-variable &$pipe_addresses$&
24514 (described in section &<<SECThowcommandrun>>& below) contains all the addresses
24515 that are routed to the transport.
24517 .vindex "&$address_pipe$&"
24518 A router redirects an address directly to a pipe command (for example, from an
24519 alias or forward file). In this case, &$address_pipe$& contains the text of the
24520 pipe command, and the &%command%& option on the transport is ignored unless
24521 &%force_command%& is set. If only one address is being transported
24522 (&%batch_max%& is not greater than one, or only one address was redirected to
24523 this pipe command), &$local_part$& contains the local part that was redirected.
24527 The &(pipe)& transport is a non-interactive delivery method. Exim can also
24528 deliver messages over pipes using the LMTP interactive protocol. This is
24529 implemented by the &(lmtp)& transport.
24531 In the case when &(pipe)& is run as a consequence of an entry in a local user's
24532 &_.forward_& file, the command runs under the uid and gid of that user. In
24533 other cases, the uid and gid have to be specified explicitly, either on the
24534 transport or on the router that handles the address. Current and &"home"&
24535 directories are also controllable. See chapter &<<CHAPenvironment>>& for
24536 details of the local delivery environment and chapter &<<CHAPbatching>>&
24537 for a discussion of local delivery batching.
24539 .cindex "tainted data" "in pipe command"
24540 .cindex pipe "tainted data"
24541 Tainted data may not be used for the command name.
24544 .section "Concurrent delivery" "SECID140"
24545 If two messages arrive at almost the same time, and both are routed to a pipe
24546 delivery, the two pipe transports may be run concurrently. You must ensure that
24547 any pipe commands you set up are robust against this happening. If the commands
24548 write to a file, the &%exim_lock%& utility might be of use.
24549 Alternatively the &%max_parallel%& option could be used with a value
24550 of "1" to enforce serialization.
24555 .section "Returned status and data" "SECID141"
24556 .cindex "&(pipe)& transport" "returned data"
24557 If the command exits with a non-zero return code, the delivery is deemed to
24558 have failed, unless either the &%ignore_status%& option is set (in which case
24559 the return code is treated as zero), or the return code is one of those listed
24560 in the &%temp_errors%& option, which are interpreted as meaning &"try again
24561 later"&. In this case, delivery is deferred. Details of a permanent failure are
24562 logged, but are not included in the bounce message, which merely contains
24563 &"local delivery failed"&.
24565 If the command exits on a signal and the &%freeze_signal%& option is set then
24566 the message will be frozen in the queue. If that option is not set, a bounce
24567 will be sent as normal.
24569 If the return code is greater than 128 and the command being run is a shell
24570 script, it normally means that the script was terminated by a signal whose
24571 value is the return code minus 128. The &%freeze_signal%& option does not
24572 apply in this case.
24574 If Exim is unable to run the command (that is, if &[execve()]& fails), the
24575 return code is set to 127. This is the value that a shell returns if it is
24576 asked to run a non-existent command. The wording for the log line suggests that
24577 a non-existent command may be the problem.
24579 The &%return_output%& option can affect the result of a pipe delivery. If it is
24580 set and the command produces any output on its standard output or standard
24581 error streams, the command is considered to have failed, even if it gave a zero
24582 return code or if &%ignore_status%& is set. The output from the command is
24583 included as part of the bounce message. The &%return_fail_output%& option is
24584 similar, except that output is returned only when the command exits with a
24585 failure return code, that is, a value other than zero or a code that matches
24590 .section "How the command is run" "SECThowcommandrun"
24591 .cindex "&(pipe)& transport" "path for command"
24592 The command line is (by default) broken down into a command name and arguments
24593 by the &(pipe)& transport itself. The &%allow_commands%& and
24594 &%restrict_to_path%& options can be used to restrict the commands that may be
24597 .cindex "quoting" "in pipe command"
24598 Unquoted arguments are delimited by white space. If an argument appears in
24599 double quotes, backslash is interpreted as an escape character in the usual
24600 way. If an argument appears in single quotes, no escaping is done.
24602 String expansion is applied to the command line except when it comes from a
24603 traditional &_.forward_& file (commands from a filter file are expanded). The
24604 expansion is applied to each argument in turn rather than to the whole line.
24605 For this reason, any string expansion item that contains white space must be
24606 quoted so as to be contained within a single argument. A setting such as
24608 command = /some/path ${if eq{$local_part}{postmaster}{xx}{yy}}
24610 will not work, because the expansion item gets split between several
24611 arguments. You have to write
24613 command = /some/path "${if eq{$local_part}{postmaster}{xx}{yy}}"
24615 to ensure that it is all in one argument. The expansion is done in this way,
24616 argument by argument, so that the number of arguments cannot be changed as a
24617 result of expansion, and quotes or backslashes in inserted variables do not
24618 interact with external quoting. However, this leads to problems if you want to
24619 generate multiple arguments (or the command name plus arguments) from a single
24620 expansion. In this situation, the simplest solution is to use a shell. For
24623 command = /bin/sh -c ${lookup{$local_part}lsearch{/some/file}}
24626 .cindex "transport" "filter"
24627 .cindex "filter" "transport filter"
24628 .vindex "&$pipe_addresses$&"
24629 Special handling takes place when an argument consists of precisely the text
24630 &`$pipe_addresses`& (no quotes).
24631 This is not a general expansion variable; the only
24632 place this string is recognized is when it appears as an argument for a pipe or
24633 transport filter command. It causes each address that is being handled to be
24634 inserted in the argument list at that point &'as a separate argument'&. This
24635 avoids any problems with spaces or shell metacharacters, and is of use when a
24636 &(pipe)& transport is handling groups of addresses in a batch.
24638 If &%force_command%& is enabled on the transport, special handling takes place
24639 for an argument that consists of precisely the text &`$address_pipe`&. It
24640 is handled similarly to &$pipe_addresses$& above. It is expanded and each
24641 argument is inserted in the argument list at that point
24642 &'as a separate argument'&. The &`$address_pipe`& item does not need to be
24643 the only item in the argument; in fact, if it were then &%force_command%&
24644 should behave as a no-op. Rather, it should be used to adjust the command
24645 run while preserving the argument vector separation.
24647 After splitting up into arguments and expansion, the resulting command is run
24648 in a subprocess directly from the transport, &'not'& under a shell. The
24649 message that is being delivered is supplied on the standard input, and the
24650 standard output and standard error are both connected to a single pipe that is
24651 read by Exim. The &%max_output%& option controls how much output the command
24652 may produce, and the &%return_output%& and &%return_fail_output%& options
24653 control what is done with it.
24655 Not running the command under a shell (by default) lessens the security risks
24656 in cases when a command from a user's filter file is built out of data that was
24657 taken from an incoming message. If a shell is required, it can of course be
24658 explicitly specified as the command to be run. However, there are circumstances
24659 where existing commands (for example, in &_.forward_& files) expect to be run
24660 under a shell and cannot easily be modified. To allow for these cases, there is
24661 an option called &%use_shell%&, which changes the way the &(pipe)& transport
24662 works. Instead of breaking up the command line as just described, it expands it
24663 as a single string and passes the result to &_/bin/sh_&. The
24664 &%restrict_to_path%& option and the &$pipe_addresses$& facility cannot be used
24665 with &%use_shell%&, and the whole mechanism is inherently less secure.
24669 .section "Environment variables" "SECTpipeenv"
24670 .cindex "&(pipe)& transport" "environment for command"
24671 .cindex "environment" "&(pipe)& transport"
24672 The environment variables listed below are set up when the command is invoked.
24673 This list is a compromise for maximum compatibility with other MTAs. Note that
24674 the &%environment%& option can be used to add additional variables to this
24675 environment. The environment for the &(pipe)& transport is not subject
24676 to the &%add_environment%& and &%keep_environment%& main config options.
24677 &*Note*&: Using enviroment variables loses track of tainted data.
24678 Writers of &(pipe)& transport commands should be wary of data supplied
24679 by potential attackers.
24681 &`DOMAIN `& the domain of the address
24682 &`HOME `& the home directory, if set
24683 &`HOST `& the host name when called from a router (see below)
24684 &`LOCAL_PART `& see below
24685 &`LOCAL_PART_PREFIX `& see below
24686 &`LOCAL_PART_SUFFIX `& see below
24687 &`LOGNAME `& see below
24688 &`MESSAGE_ID `& Exim's local ID for the message
24689 &`PATH `& as specified by the &%path%& option below
24690 &`QUALIFY_DOMAIN `& the sender qualification domain
24691 &`RECIPIENT `& the complete recipient address
24692 &`SENDER `& the sender of the message (empty if a bounce)
24693 &`SHELL `& &`/bin/sh`&
24694 &`TZ `& the value of the &%timezone%& option, if set
24695 &`USER `& see below
24697 When a &(pipe)& transport is called directly from (for example) an &(accept)&
24698 router, LOCAL_PART is set to the local part of the address. When it is
24699 called as a result of a forward or alias expansion, LOCAL_PART is set to
24700 the local part of the address that was expanded. In both cases, any affixes are
24701 removed from the local part, and made available in LOCAL_PART_PREFIX and
24702 LOCAL_PART_SUFFIX, respectively. LOGNAME and USER are set to the
24703 same value as LOCAL_PART for compatibility with other MTAs.
24706 HOST is set only when a &(pipe)& transport is called from a router that
24707 associates hosts with an address, typically when using &(pipe)& as a
24708 pseudo-remote transport. HOST is set to the first host name specified by
24712 If the transport's generic &%home_directory%& option is set, its value is used
24713 for the HOME environment variable. Otherwise, a home directory may be set
24714 by the router's &%transport_home_directory%& option, which defaults to the
24715 user's home directory if &%check_local_user%& is set.
24718 .section "Private options for pipe" "SECID142"
24719 .cindex "options" "&(pipe)& transport"
24723 .option allow_commands pipe "string list&!!" unset
24724 .cindex "&(pipe)& transport" "permitted commands"
24725 The string is expanded, and is then interpreted as a colon-separated list of
24726 permitted commands. If &%restrict_to_path%& is not set, the only commands
24727 permitted are those in the &%allow_commands%& list. They need not be absolute
24728 paths; the &%path%& option is still used for relative paths. If
24729 &%restrict_to_path%& is set with &%allow_commands%&, the command must either be
24730 in the &%allow_commands%& list, or a name without any slashes that is found on
24731 the path. In other words, if neither &%allow_commands%& nor
24732 &%restrict_to_path%& is set, there is no restriction on the command, but
24733 otherwise only commands that are permitted by one or the other are allowed. For
24736 allow_commands = /usr/bin/vacation
24738 and &%restrict_to_path%& is not set, the only permitted command is
24739 &_/usr/bin/vacation_&. The &%allow_commands%& option may not be set if
24740 &%use_shell%& is set.
24743 .option batch_id pipe string&!! unset
24744 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
24747 .option batch_max pipe integer 1
24748 This limits the number of addresses that can be handled in a single delivery.
24749 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
24752 .option check_string pipe string unset
24753 As &(pipe)& writes the message, the start of each line is tested for matching
24754 &%check_string%&, and if it does, the initial matching characters are replaced
24755 by the contents of &%escape_string%&, provided both are set. The value of
24756 &%check_string%& is a literal string, not a regular expression, and the case of
24757 any letters it contains is significant. When &%use_bsmtp%& is set, the contents
24758 of &%check_string%& and &%escape_string%& are forced to values that implement
24759 the SMTP escaping protocol. Any settings made in the configuration file are
24763 .option command pipe string&!! unset
24764 This option need not be set when &(pipe)& is being used to deliver to pipes
24765 obtained directly from address redirections. In other cases, the option must be
24766 set, to provide a command to be run. It need not yield an absolute path (see
24767 the &%path%& option below). The command is split up into separate arguments by
24768 Exim, and each argument is separately expanded, as described in section
24769 &<<SECThowcommandrun>>& above.
24771 .cindex "tainted data"
24772 No part of the resulting command may be tainted.
24775 .option environment pipe string&!! unset
24776 .cindex "&(pipe)& transport" "environment for command"
24777 .cindex "environment" "&(pipe)& transport"
24778 This option is used to add additional variables to the environment in which the
24779 command runs (see section &<<SECTpipeenv>>& for the default list). Its value is
24780 a string which is expanded, and then interpreted as a colon-separated list of
24781 environment settings of the form <&'name'&>=<&'value'&>.
24784 .option escape_string pipe string unset
24785 See &%check_string%& above.
24788 .option freeze_exec_fail pipe boolean false
24789 .cindex "exec failure"
24790 .cindex "failure of exec"
24791 .cindex "&(pipe)& transport" "failure of exec"
24792 Failure to exec the command in a pipe transport is by default treated like
24793 any other failure while running the command. However, if &%freeze_exec_fail%&
24794 is set, failure to exec is treated specially, and causes the message to be
24795 frozen, whatever the setting of &%ignore_status%&.
24798 .option freeze_signal pipe boolean false
24799 .cindex "signal exit"
24800 .cindex "&(pipe)& transport", "signal exit"
24801 Normally if the process run by a command in a pipe transport exits on a signal,
24802 a bounce message is sent. If &%freeze_signal%& is set, the message will be
24803 frozen in Exim's queue instead.
24806 .option force_command pipe boolean false
24807 .cindex "force command"
24808 .cindex "&(pipe)& transport", "force command"
24809 Normally when a router redirects an address directly to a pipe command
24810 the &%command%& option on the transport is ignored. If &%force_command%&
24811 is set, the &%command%& option will used. This is especially
24812 useful for forcing a wrapper or additional argument to be added to the
24813 command. For example:
24815 command = /usr/bin/remote_exec myhost -- $address_pipe
24819 Note that &$address_pipe$& is handled specially in &%command%& when
24820 &%force_command%& is set, expanding out to the original argument vector as
24821 separate items, similarly to a Unix shell &`"$@"`& construct.
24824 .option ignore_status pipe boolean false
24825 If this option is true, the status returned by the subprocess that is set up to
24826 run the command is ignored, and Exim behaves as if zero had been returned.
24827 Otherwise, a non-zero status or termination by signal causes an error return
24828 from the transport unless the status value is one of those listed in
24829 &%temp_errors%&; these cause the delivery to be deferred and tried again later.
24831 &*Note*&: This option does not apply to timeouts, which do not return a status.
24832 See the &%timeout_defer%& option for how timeouts are handled.
24835 .option log_defer_output pipe boolean false
24836 .cindex "&(pipe)& transport" "logging output"
24837 If this option is set, and the status returned by the command is
24838 one of the codes listed in &%temp_errors%& (that is, delivery was deferred),
24839 and any output was produced on stdout or stderr, the first line of it is
24840 written to the main log.
24843 .option log_fail_output pipe boolean false
24844 If this option is set, and the command returns any output on stdout or
24845 stderr, and also ends with a return code that is neither zero nor one of
24846 the return codes listed in &%temp_errors%& (that is, the delivery
24847 failed), the first line of output is written to the main log. This
24848 option and &%log_output%& are mutually exclusive. Only one of them may
24852 .option log_output pipe boolean false
24853 If this option is set and the command returns any output on stdout or
24854 stderr, the first line of output is written to the main log, whatever
24855 the return code. This option and &%log_fail_output%& are mutually
24856 exclusive. Only one of them may be set.
24859 .option max_output pipe integer 20K
24860 This specifies the maximum amount of output that the command may produce on its
24861 standard output and standard error file combined. If the limit is exceeded, the
24862 process running the command is killed. This is intended as a safety measure to
24863 catch runaway processes. The limit is applied independently of the settings of
24864 the options that control what is done with such output (for example,
24865 &%return_output%&). Because of buffering effects, the amount of output may
24866 exceed the limit by a small amount before Exim notices.
24869 .option message_prefix pipe string&!! "see below"
24870 The string specified here is expanded and output at the start of every message.
24871 The default is unset if &%use_bsmtp%& is set. Otherwise it is
24874 From ${if def:return_path{$return_path}{MAILER-DAEMON}}\
24878 .cindex "&%tmail%&"
24879 .cindex "&""From""& line"
24880 This is required by the commonly used &_/usr/bin/vacation_& program.
24881 However, it must &'not'& be present if delivery is to the Cyrus IMAP server,
24882 or to the &%tmail%& local delivery agent. The prefix can be suppressed by
24887 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
24888 &`\n`& to &`\r\n`& in &%message_prefix%&.
24891 .option message_suffix pipe string&!! "see below"
24892 The string specified here is expanded and output at the end of every message.
24893 The default is unset if &%use_bsmtp%& is set. Otherwise it is a single newline.
24894 The suffix can be suppressed by setting
24898 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
24899 &`\n`& to &`\r\n`& in &%message_suffix%&.
24902 .option path pipe string&!! "/bin:/usr/bin"
24903 This option is expanded and
24904 specifies the string that is set up in the PATH environment
24905 variable of the subprocess.
24906 If the &%command%& option does not yield an absolute path name, the command is
24907 sought in the PATH directories, in the usual way. &*Warning*&: This does not
24908 apply to a command specified as a transport filter.
24911 .option permit_coredump pipe boolean false
24912 Normally Exim inhibits core-dumps during delivery. If you have a need to get
24913 a core-dump of a pipe command, enable this command. This enables core-dumps
24914 during delivery and affects both the Exim binary and the pipe command run.
24915 It is recommended that this option remain off unless and until you have a need
24916 for it and that this only be enabled when needed, as the risk of excessive
24917 resource consumption can be quite high. Note also that Exim is typically
24918 installed as a setuid binary and most operating systems will inhibit coredumps
24919 of these by default, so further OS-specific action may be required.
24922 .option pipe_as_creator pipe boolean false
24923 .cindex "uid (user id)" "local delivery"
24924 If the generic &%user%& option is not set and this option is true, the delivery
24925 process is run under the uid that was in force when Exim was originally called
24926 to accept the message. If the group id is not otherwise set (via the generic
24927 &%group%& option), the gid that was in force when Exim was originally called to
24928 accept the message is used.
24931 .option restrict_to_path pipe boolean false
24932 When this option is set, any command name not listed in &%allow_commands%& must
24933 contain no slashes. The command is searched for only in the directories listed
24934 in the &%path%& option. This option is intended for use in the case when a pipe
24935 command has been generated from a user's &_.forward_& file. This is usually
24936 handled by a &(pipe)& transport called &%address_pipe%&.
24939 .option return_fail_output pipe boolean false
24940 If this option is true, and the command produced any output and ended with a
24941 return code other than zero or one of the codes listed in &%temp_errors%& (that
24942 is, the delivery failed), the output is returned in the bounce message.
24943 However, if the message has a null sender (that is, it is itself a bounce
24944 message), output from the command is discarded. This option and
24945 &%return_output%& are mutually exclusive. Only one of them may be set.
24949 .option return_output pipe boolean false
24950 If this option is true, and the command produced any output, the delivery is
24951 deemed to have failed whatever the return code from the command, and the output
24952 is returned in the bounce message. Otherwise, the output is just discarded.
24953 However, if the message has a null sender (that is, it is a bounce message),
24954 output from the command is always discarded, whatever the setting of this
24955 option. This option and &%return_fail_output%& are mutually exclusive. Only one
24956 of them may be set.
24960 .option temp_errors pipe "string list" "see below"
24961 .cindex "&(pipe)& transport" "temporary failure"
24962 This option contains either a colon-separated list of numbers, or a single
24963 asterisk. If &%ignore_status%& is false
24964 and &%return_output%& is not set,
24965 and the command exits with a non-zero return code, the failure is treated as
24966 temporary and the delivery is deferred if the return code matches one of the
24967 numbers, or if the setting is a single asterisk. Otherwise, non-zero return
24968 codes are treated as permanent errors. The default setting contains the codes
24969 defined by EX_TEMPFAIL and EX_CANTCREAT in &_sysexits.h_&. If Exim is
24970 compiled on a system that does not define these macros, it assumes values of 75
24971 and 73, respectively.
24974 .option timeout pipe time 1h
24975 If the command fails to complete within this time, it is killed. This normally
24976 causes the delivery to fail (but see &%timeout_defer%&). A zero time interval
24977 specifies no timeout. In order to ensure that any subprocesses created by the
24978 command are also killed, Exim makes the initial process a process group leader,
24979 and kills the whole process group on a timeout. However, this can be defeated
24980 if one of the processes starts a new process group.
24982 .option timeout_defer pipe boolean false
24983 A timeout in a &(pipe)& transport, either in the command that the transport
24984 runs, or in a transport filter that is associated with it, is by default
24985 treated as a hard error, and the delivery fails. However, if &%timeout_defer%&
24986 is set true, both kinds of timeout become temporary errors, causing the
24987 delivery to be deferred.
24989 .option umask pipe "octal integer" 022
24990 This specifies the umask setting for the subprocess that runs the command.
24993 .option use_bsmtp pipe boolean false
24994 .cindex "envelope sender"
24995 If this option is set true, the &(pipe)& transport writes messages in &"batch
24996 SMTP"& format, with the envelope sender and recipient(s) included as SMTP
24997 commands. If you want to include a leading HELO command with such messages,
24998 you can do so by setting the &%message_prefix%& option. See section
24999 &<<SECTbatchSMTP>>& for details of batch SMTP.
25001 .option use_classresources pipe boolean false
25002 .cindex "class resources (BSD)"
25003 This option is available only when Exim is running on FreeBSD, NetBSD, or
25004 BSD/OS. If it is set true, the &[setclassresources()]& function is used to set
25005 resource limits when a &(pipe)& transport is run to perform a delivery. The
25006 limits for the uid under which the pipe is to run are obtained from the login
25010 .option use_crlf pipe boolean false
25011 .cindex "carriage return"
25013 This option causes lines to be terminated with the two-character CRLF sequence
25014 (carriage return, linefeed) instead of just a linefeed character. In the case
25015 of batched SMTP, the byte sequence written to the pipe is then an exact image
25016 of what would be sent down a real SMTP connection.
25018 The contents of the &%message_prefix%& and &%message_suffix%& options are
25019 written verbatim, so must contain their own carriage return characters if these
25020 are needed. When &%use_bsmtp%& is not set, the default values for both
25021 &%message_prefix%& and &%message_suffix%& end with a single linefeed, so their
25022 values must be changed to end with &`\r\n`& if &%use_crlf%& is set.
25025 .option use_shell pipe boolean false
25026 .vindex "&$pipe_addresses$&"
25027 If this option is set, it causes the command to be passed to &_/bin/sh_&
25028 instead of being run directly from the transport, as described in section
25029 &<<SECThowcommandrun>>&. This is less secure, but is needed in some situations
25030 where the command is expected to be run under a shell and cannot easily be
25031 modified. The &%allow_commands%& and &%restrict_to_path%& options, and the
25032 &`$pipe_addresses`& facility are incompatible with &%use_shell%&. The
25033 command is expanded as a single string, and handed to &_/bin/sh_& as data for
25038 .section "Using an external local delivery agent" "SECID143"
25039 .cindex "local delivery" "using an external agent"
25040 .cindex "&'procmail'&"
25041 .cindex "external local delivery"
25042 .cindex "delivery" "&'procmail'&"
25043 .cindex "delivery" "by external agent"
25044 The &(pipe)& transport can be used to pass all messages that require local
25045 delivery to a separate local delivery agent such as &%procmail%&. When doing
25046 this, care must be taken to ensure that the pipe is run under an appropriate
25047 uid and gid. In some configurations one wants this to be a uid that is trusted
25048 by the delivery agent to supply the correct sender of the message. It may be
25049 necessary to recompile or reconfigure the delivery agent so that it trusts an
25050 appropriate user. The following is an example transport and router
25051 configuration for &%procmail%&:
25056 command = /usr/local/bin/procmail -d $local_part_data
25060 check_string = "From "
25061 escape_string = ">From "
25063 user = $local_part_data
25070 transport = procmail_pipe
25072 In this example, the pipe is run as the local user, but with the group set to
25073 &'mail'&. An alternative is to run the pipe as a specific user such as &'mail'&
25074 or &'exim'&, but in this case you must arrange for &%procmail%& to trust that
25075 user to supply a correct sender address. If you do not specify either a
25076 &%group%& or a &%user%& option, the pipe command is run as the local user. The
25077 home directory is the user's home directory by default.
25079 &*Note*&: The command that the pipe transport runs does &'not'& begin with
25083 as shown in some &%procmail%& documentation, because Exim does not by default
25084 use a shell to run pipe commands.
25087 The next example shows a transport and a router for a system where local
25088 deliveries are handled by the Cyrus IMAP server.
25089 . Used to have R: local_part_suffix = .* + T: -m $local_part_suffix_v
25090 . but that suffix is tainted so cannot be used in a command arg
25091 . Really, you'd want to use a lookup for acceptable suffixes to do real detainting
25094 local_delivery_cyrus:
25096 command = /usr/cyrus/bin/deliver \
25097 -- $local_part_data
25109 transport = local_delivery_cyrus
25111 Note the unsetting of &%message_prefix%& and &%message_suffix%&, and the use of
25112 &%return_output%& to cause any text written by Cyrus to be returned to the
25114 .ecindex IIDpiptra1
25115 .ecindex IIDpiptra2
25118 . ////////////////////////////////////////////////////////////////////////////
25119 . ////////////////////////////////////////////////////////////////////////////
25121 .chapter "The smtp transport" "CHAPsmtptrans"
25122 .scindex IIDsmttra1 "transports" "&(smtp)&"
25123 .scindex IIDsmttra2 "&(smtp)& transport"
25124 The &(smtp)& transport delivers messages over TCP/IP connections using the SMTP
25125 or LMTP protocol. The list of hosts to try can either be taken from the address
25126 that is being processed (having been set up by the router), or specified
25127 explicitly for the transport. Timeout and retry processing (see chapter
25128 &<<CHAPretry>>&) is applied to each IP address independently.
25131 .section "Multiple messages on a single connection" "SECID144"
25132 The sending of multiple messages over a single TCP/IP connection can arise in
25136 If a message contains more than &%max_rcpt%& (see below) addresses that are
25137 routed to the same host, more than one copy of the message has to be sent to
25138 that host. In this situation, multiple copies may be sent in a single run of
25139 the &(smtp)& transport over a single TCP/IP connection. (What Exim actually
25140 does when it has too many addresses to send in one message also depends on the
25141 value of the global &%remote_max_parallel%& option. Details are given in
25142 section &<<SECToutSMTPTCP>>&.)
25144 .cindex "hints database" "remembering routing"
25145 When a message has been successfully delivered over a TCP/IP connection, Exim
25146 looks in its hints database to see if there are any other messages awaiting a
25147 connection to the same host. If there are, a new delivery process is started
25148 for one of them, and the current TCP/IP connection is passed on to it. The new
25149 process may in turn send multiple copies and possibly create yet another
25154 For each copy sent over the same TCP/IP connection, a sequence counter is
25155 incremented, and if it ever gets to the value of &%connection_max_messages%&,
25156 no further messages are sent over that connection.
25160 .section "Use of the $host and $host_address variables" "SECID145"
25162 .vindex "&$host_address$&"
25163 At the start of a run of the &(smtp)& transport, the values of &$host$& and
25164 &$host_address$& are the name and IP address of the first host on the host list
25165 passed by the router. However, when the transport is about to connect to a
25166 specific host, and while it is connected to that host, &$host$& and
25167 &$host_address$& are set to the values for that host. These are the values
25168 that are in force when the &%helo_data%&, &%hosts_try_auth%&, &%interface%&,
25169 &%serialize_hosts%&, and the various TLS options are expanded.
25172 .section "Use of $tls_cipher and $tls_peerdn" "usecippeer"
25173 .vindex &$tls_bits$&
25174 .vindex &$tls_cipher$&
25175 .vindex &$tls_peerdn$&
25176 .vindex &$tls_sni$&
25177 At the start of a run of the &(smtp)& transport, the values of &$tls_bits$&,
25178 &$tls_cipher$&, &$tls_peerdn$& and &$tls_sni$&
25179 are the values that were set when the message was received.
25180 These are the values that are used for options that are expanded before any
25181 SMTP connections are made. Just before each connection is made, these four
25182 variables are emptied. If TLS is subsequently started, they are set to the
25183 appropriate values for the outgoing connection, and these are the values that
25184 are in force when any authenticators are run and when the
25185 &%authenticated_sender%& option is expanded.
25187 These variables are deprecated in favour of &$tls_in_cipher$& et. al.
25188 and will be removed in a future release.
25191 .section "Private options for smtp" "SECID146"
25192 .cindex "options" "&(smtp)& transport"
25193 The private options of the &(smtp)& transport are as follows:
25196 .option address_retry_include_sender smtp boolean true
25197 .cindex "4&'xx'& responses" "retrying after"
25198 When an address is delayed because of a 4&'xx'& response to a RCPT command, it
25199 is the combination of sender and recipient that is delayed in subsequent queue
25200 runs until the retry time is reached. You can delay the recipient without
25201 reference to the sender (which is what earlier versions of Exim did), by
25202 setting &%address_retry_include_sender%& false. However, this can lead to
25203 problems with servers that regularly issue 4&'xx'& responses to RCPT commands.
25205 .option allow_localhost smtp boolean false
25206 .cindex "local host" "sending to"
25207 .cindex "fallback" "hosts specified on transport"
25208 When a host specified in &%hosts%& or &%fallback_hosts%& (see below) turns out
25209 to be the local host, or is listed in &%hosts_treat_as_local%&, delivery is
25210 deferred by default. However, if &%allow_localhost%& is set, Exim goes on to do
25211 the delivery anyway. This should be used only in special cases when the
25212 configuration ensures that no looping will result (for example, a differently
25213 configured Exim is listening on the port to which the message is sent).
25216 .option authenticated_sender smtp string&!! unset
25218 When Exim has authenticated as a client, or if &%authenticated_sender_force%&
25219 is true, this option sets a value for the AUTH= item on outgoing MAIL commands,
25220 overriding any existing authenticated sender value. If the string expansion is
25221 forced to fail, the option is ignored. Other expansion failures cause delivery
25222 to be deferred. If the result of expansion is an empty string, that is also
25225 The expansion happens after the outgoing connection has been made and TLS
25226 started, if required. This means that the &$host$&, &$host_address$&,
25227 &$tls_out_cipher$&, and &$tls_out_peerdn$& variables are set according to the
25228 particular connection.
25230 If the SMTP session is not authenticated, the expansion of
25231 &%authenticated_sender%& still happens (and can cause the delivery to be
25232 deferred if it fails), but no AUTH= item is added to MAIL commands
25233 unless &%authenticated_sender_force%& is true.
25235 This option allows you to use the &(smtp)& transport in LMTP mode to
25236 deliver mail to Cyrus IMAP and provide the proper local part as the
25237 &"authenticated sender"&, via a setting such as:
25239 authenticated_sender = $local_part
25241 This removes the need for IMAP subfolders to be assigned special ACLs to
25242 allow direct delivery to those subfolders.
25244 Because of expected uses such as that just described for Cyrus (when no
25245 domain is involved), there is no checking on the syntax of the provided
25249 .option authenticated_sender_force smtp boolean false
25250 If this option is set true, the &%authenticated_sender%& option's value
25251 is used for the AUTH= item on outgoing MAIL commands, even if Exim has not
25252 authenticated as a client.
25255 .option command_timeout smtp time 5m
25256 .cindex timeout "smtp transport command"
25257 This sets a timeout for receiving a response to an SMTP command that has been
25258 sent out. It is also used when waiting for the initial banner line from the
25259 remote host. Its value must not be zero.
25262 .option connect_timeout smtp time 5m
25263 .cindex timeout "smtp transport connect"
25264 This sets a timeout for the &[connect()]& function, which sets up a TCP/IP call
25265 to a remote host. A setting of zero allows the system timeout (typically
25266 several minutes) to act. To have any effect, the value of this option must be
25267 less than the system timeout. However, it has been observed that on some
25268 systems there is no system timeout, which is why the default value for this
25269 option is 5 minutes, a value recommended by RFC 1123.
25272 .option connection_max_messages smtp integer 500
25273 .cindex "SMTP" "passed connection"
25274 .cindex "SMTP" "multiple deliveries"
25275 .cindex "multiple SMTP deliveries"
25276 This controls the maximum number of separate message deliveries that are sent
25277 over a single TCP/IP connection. If the value is zero, there is no limit.
25278 For testing purposes, this value can be overridden by the &%-oB%& command line
25282 .option dane_require_tls_ciphers smtp string&!! unset
25283 .cindex "TLS" "requiring specific ciphers for DANE"
25284 .cindex "cipher" "requiring specific"
25285 .cindex DANE "TLS ciphers"
25286 This option may be used to override &%tls_require_ciphers%& for connections
25287 where DANE has been determined to be in effect.
25288 If not set, then &%tls_require_ciphers%& will be used.
25289 Normal SMTP delivery is not able to make strong demands of TLS cipher
25290 configuration, because delivery will fall back to plaintext. Once DANE has
25291 been determined to be in effect, there is no plaintext fallback and making the
25292 TLS cipherlist configuration stronger will increase security, rather than
25293 counter-intuitively decreasing it.
25294 If the option expands to be empty or is forced to fail, then it will
25295 be treated as unset and &%tls_require_ciphers%& will be used instead.
25298 .option data_timeout smtp time 5m
25299 .cindex timeout "for transmitted SMTP data blocks"
25300 This sets a timeout for the transmission of each block in the data portion of
25301 the message. As a result, the overall timeout for a message depends on the size
25302 of the message. Its value must not be zero. See also &%final_timeout%&.
25305 .option dkim_canon smtp string&!! unset
25306 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25307 .option dkim_domain smtp "string list&!!" unset
25308 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25309 .option dkim_hash smtp string&!! sha256
25310 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25311 .option dkim_identity smtp string&!! unset
25312 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25313 .option dkim_private_key smtp string&!! unset
25314 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25315 .option dkim_selector smtp string&!! unset
25316 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25317 .option dkim_strict smtp string&!! unset
25318 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25319 .option dkim_sign_headers smtp string&!! "per RFC"
25320 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25321 .option dkim_timestamps smtp string&!! unset
25322 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25325 .option delay_after_cutoff smtp boolean true
25326 .cindex "final cutoff" "retries, controlling"
25327 .cindex retry "final cutoff"
25328 This option controls what happens when all remote IP addresses for a given
25329 domain have been inaccessible for so long that they have passed their retry
25332 In the default state, if the next retry time has not been reached for any of
25333 them, the address is bounced without trying any deliveries. In other words,
25334 Exim delays retrying an IP address after the final cutoff time until a new
25335 retry time is reached, and can therefore bounce an address without ever trying
25336 a delivery, when machines have been down for a long time. Some people are
25337 unhappy at this prospect, so...
25339 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
25340 addresses are past their final cutoff time, Exim tries to deliver to those
25341 IP addresses that have not been tried since the message arrived. If there are
25342 none, of if they all fail, the address is bounced. In other words, it does not
25343 delay when a new message arrives, but immediately tries those expired IP
25344 addresses that haven't been tried since the message arrived. If there is a
25345 continuous stream of messages for the dead hosts, unsetting
25346 &%delay_after_cutoff%& means that there will be many more attempts to deliver
25350 .option dns_qualify_single smtp boolean true
25351 If the &%hosts%& or &%fallback_hosts%& option is being used,
25352 and the &%gethostbyname%& option is false,
25353 the RES_DEFNAMES resolver option is set. See the &%qualify_single%& option
25354 in chapter &<<CHAPdnslookup>>& for more details.
25357 .option dns_search_parents smtp boolean false
25358 If the &%hosts%& or &%fallback_hosts%& option is being used, and the
25359 &%gethostbyname%& option is false, the RES_DNSRCH resolver option is set.
25360 See the &%search_parents%& option in chapter &<<CHAPdnslookup>>& for more
25364 .option dnssec_request_domains smtp "domain list&!!" *
25365 .cindex "MX record" "security"
25366 .cindex "DNSSEC" "MX lookup"
25367 .cindex "security" "MX lookup"
25368 .cindex "DNS" "DNSSEC"
25369 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
25370 the DNSSEC request bit set. Setting this transport option is only useful if the
25371 transport overrides or sets the host names. See the &%dnssec_request_domains%&
25376 .option dnssec_require_domains smtp "domain list&!!" unset
25377 .cindex "MX record" "security"
25378 .cindex "DNSSEC" "MX lookup"
25379 .cindex "security" "MX lookup"
25380 .cindex "DNS" "DNSSEC"
25381 DNS lookups for domains matching &%dnssec_require_domains%& will be done with
25382 the DNSSEC request bit set. Setting this transport option is only
25383 useful if the transport overrides or sets the host names. See the
25384 &%dnssec_require_domains%& router option.
25388 .option dscp smtp string&!! unset
25389 .cindex "DCSP" "outbound"
25390 This option causes the DSCP value associated with a socket to be set to one
25391 of a number of fixed strings or to numeric value.
25392 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
25393 Common values include &`throughput`&, &`mincost`&, and on newer systems
25394 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
25396 The outbound packets from Exim will be marked with this value in the header
25397 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
25398 that these values will have any effect, not be stripped by networking
25399 equipment, or do much of anything without cooperation with your Network
25400 Engineer and those of all network operators between the source and destination.
25403 .option fallback_hosts smtp "string list" unset
25404 .cindex "fallback" "hosts specified on transport"
25405 String expansion is not applied to this option. The argument must be a
25406 colon-separated list of host names or IP addresses, optionally also including
25407 port numbers, though the separator can be changed, as described in section
25408 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
25409 item in a &%route_list%& setting for the &(manualroute)& router, as described
25410 in section &<<SECTformatonehostitem>>&.
25412 Fallback hosts can also be specified on routers, which associate them with the
25413 addresses they process. As for the &%hosts%& option without &%hosts_override%&,
25414 &%fallback_hosts%& specified on the transport is used only if the address does
25415 not have its own associated fallback host list. Unlike &%hosts%&, a setting of
25416 &%fallback_hosts%& on an address is not overridden by &%hosts_override%&.
25417 However, &%hosts_randomize%& does apply to fallback host lists.
25419 If Exim is unable to deliver to any of the hosts for a particular address, and
25420 the errors are not permanent rejections, the address is put on a separate
25421 transport queue with its host list replaced by the fallback hosts, unless the
25422 address was routed via MX records and the current host was in the original MX
25423 list. In that situation, the fallback host list is not used.
25425 Once normal deliveries are complete, the fallback queue is delivered by
25426 re-running the same transports with the new host lists. If several failing
25427 addresses have the same fallback hosts (and &%max_rcpt%& permits it), a single
25428 copy of the message is sent.
25430 The resolution of the host names on the fallback list is controlled by the
25431 &%gethostbyname%& option, as for the &%hosts%& option. Fallback hosts apply
25432 both to cases when the host list comes with the address and when it is taken
25433 from &%hosts%&. This option provides a &"use a smart host only if delivery
25437 .option final_timeout smtp time 10m
25438 .cindex timeout "for transmitted SMTP data accept"
25439 This is the timeout that applies while waiting for the response to the final
25440 line containing just &"."& that terminates a message. Its value must not be
25443 .option gethostbyname smtp boolean false
25444 If this option is true when the &%hosts%& and/or &%fallback_hosts%& options are
25445 being used, names are looked up using &[gethostbyname()]&
25446 (or &[getipnodebyname()]& when available)
25447 instead of using the DNS. Of course, that function may in fact use the DNS, but
25448 it may also consult other sources of information such as &_/etc/hosts_&.
25450 .option gnutls_compat_mode smtp boolean unset
25451 This option controls whether GnuTLS is used in compatibility mode in an Exim
25452 server. This reduces security slightly, but improves interworking with older
25453 implementations of TLS.
25455 .option helo_data smtp string&!! "see below"
25456 .cindex "HELO" "argument, setting"
25457 .cindex "EHLO" "argument, setting"
25458 .cindex "LHLO argument setting"
25459 The value of this option is expanded after a connection to a another host has
25460 been set up. The result is used as the argument for the EHLO, HELO, or LHLO
25461 command that starts the outgoing SMTP or LMTP session. The default value of the
25466 During the expansion, the variables &$host$& and &$host_address$& are set to
25467 the identity of the remote host, and the variables &$sending_ip_address$& and
25468 &$sending_port$& are set to the local IP address and port number that are being
25469 used. These variables can be used to generate different values for different
25470 servers or different local IP addresses. For example, if you want the string
25471 that is used for &%helo_data%& to be obtained by a DNS lookup of the outgoing
25472 interface address, you could use this:
25474 helo_data = ${lookup dnsdb{ptr=$sending_ip_address} \
25475 {${listextract{1}{<\n $value}}} \
25476 {$primary_hostname}}
25478 The use of &%helo_data%& applies both to sending messages and when doing
25481 .option host_name_extract smtp "string list&!!" "see below"
25482 .cindex "load balancer" "hosts behind"
25483 .cindex TLS resumption
25484 Some mail-accepting sites
25485 (notably Microsoft)
25486 operate many servers behind a network load-balancer. When this is done,
25487 with separated TLS session caches, TLS session resuption becomes problematic.
25488 It will only succeed when the same server happens to be selected by the
25489 load-balancer, matching the session stored in the client's cache.
25491 Exim can pull out a server name, if there is one, from the response to the
25492 client's SMTP EHLO command.
25493 The default value of this option:
25495 ${if and { {match {$host} {.outlook.com\$}} \
25496 {match {$item} {\N^250-([\w.]+)\s\N}} \
25499 suffices for one known case.
25500 During the expansion of this option the &$item$& variable will have the
25501 server's EHLO response.
25502 The result of the option expansion is included in the key used to store and
25503 retrieve the TLS session, for session resumption.
25505 Operators of high-load sites may wish to evaluate their logs for indications
25506 of other destination sites operating load-balancers, and develop a suitable
25507 expression for this option.
25508 The smtp:ehlo event and the &$tls_out_resumption$& variable
25509 will be useful for such work.
25511 .option hosts smtp "string list&!!" unset
25512 Hosts are associated with an address by a router such as &(dnslookup)&, which
25513 finds the hosts by looking up the address domain in the DNS, or by
25514 &(manualroute)&, which has lists of hosts in its configuration. However,
25515 email addresses can be passed to the &(smtp)& transport by any router, and not
25516 all of them can provide an associated list of hosts.
25518 The &%hosts%& option specifies a list of hosts to be used if the address being
25519 processed does not have any hosts associated with it. The hosts specified by
25520 &%hosts%& are also used, whether or not the address has its own hosts, if
25521 &%hosts_override%& is set.
25523 The string is first expanded, before being interpreted as a colon-separated
25524 list of host names or IP addresses, possibly including port numbers. The
25525 separator may be changed to something other than colon, as described in section
25526 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
25527 item in a &%route_list%& setting for the &(manualroute)& router, as described
25528 in section &<<SECTformatonehostitem>>&. However, note that the &`/MX`& facility
25529 of the &(manualroute)& router is not available here.
25531 If the expansion fails, delivery is deferred. Unless the failure was caused by
25532 the inability to complete a lookup, the error is logged to the panic log as
25533 well as the main log. Host names are looked up either by searching directly for
25534 address records in the DNS or by calling &[gethostbyname()]& (or
25535 &[getipnodebyname()]& when available), depending on the setting of the
25536 &%gethostbyname%& option. When Exim is compiled with IPv6 support, if a host
25537 that is looked up in the DNS has both IPv4 and IPv6 addresses, both types of
25540 During delivery, the hosts are tried in order, subject to their retry status,
25541 unless &%hosts_randomize%& is set.
25544 .option hosts_avoid_esmtp smtp "host list&!!" unset
25545 .cindex "ESMTP, avoiding use of"
25546 .cindex "HELO" "forcing use of"
25547 .cindex "EHLO" "avoiding use of"
25548 .cindex "PIPELINING" "avoiding the use of"
25549 This option is for use with broken hosts that announce ESMTP facilities (for
25550 example, PIPELINING) and then fail to implement them properly. When a host
25551 matches &%hosts_avoid_esmtp%&, Exim sends HELO rather than EHLO at the
25552 start of the SMTP session. This means that it cannot use any of the ESMTP
25553 facilities such as AUTH, PIPELINING, SIZE, and STARTTLS.
25556 .option hosts_avoid_pipelining smtp "host list&!!" unset
25557 .cindex "PIPELINING" "avoiding the use of"
25558 .cindex "ESMTP extensions" PIPELINING
25559 Exim will not use the ESMTP PIPELINING extension when delivering to any host
25560 that matches this list, even if the server host advertises PIPELINING support.
25562 .option hosts_pipe_connect smtp "host list&!!" unset
25563 .cindex "pipelining" "early connection"
25564 .cindex "pipelining" PIPECONNECT
25565 If Exim is built with the SUPPORT_PIPE_CONNECT build option
25566 this option controls which to hosts the facility watched for
25567 and recorded, and used for subsequent connections.
25569 The retry hints database is used for the record,
25570 and records are subject to the &%retry_data_expire%& option.
25571 When used, the pipelining saves on roundtrip times.
25572 It also turns SMTP into a client-first protocol
25573 so combines well with TCP Fast Open.
25575 See also the &%pipelining_connect_advertise_hosts%& main option.
25578 When the facility is used, if the transport &%interface%& option is unset
25579 the &%helo_data%& option
25580 will be expanded before the &$sending_ip_address$& variable
25582 A check is made for the use of that variable, without the
25583 presence of a &"def:"& test on it, but suitably complex coding
25584 can avoid the check and produce unexpected results.
25585 You have been warned.
25588 .option hosts_avoid_tls smtp "host list&!!" unset
25589 .cindex "TLS" "avoiding for certain hosts"
25590 Exim will not try to start a TLS session when delivering to any host that
25591 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
25593 .option hosts_verify_avoid_tls smtp "host list&!!" unset
25594 .cindex "TLS" "avoiding for certain hosts"
25595 Exim will not try to start a TLS session for a verify callout,
25596 or when delivering in cutthrough mode,
25597 to any host that matches this list.
25600 .option hosts_max_try smtp integer 5
25601 .cindex "host" "maximum number to try"
25602 .cindex "limit" "number of hosts tried"
25603 .cindex "limit" "number of MX tried"
25604 .cindex "MX record" "maximum tried"
25605 This option limits the number of IP addresses that are tried for any one
25606 delivery in cases where there are temporary delivery errors. Section
25607 &<<SECTvalhosmax>>& describes in detail how the value of this option is used.
25610 .option hosts_max_try_hardlimit smtp integer 50
25611 This is an additional check on the maximum number of IP addresses that Exim
25612 tries for any one delivery. Section &<<SECTvalhosmax>>& describes its use and
25617 .option hosts_nopass_tls smtp "host list&!!" unset
25618 .cindex "TLS" "passing connection"
25619 .cindex "multiple SMTP deliveries"
25620 .cindex "TLS" "multiple message deliveries"
25621 For any host that matches this list, a connection on which a TLS session has
25622 been started will not be passed to a new delivery process for sending another
25623 message on the same connection. See section &<<SECTmulmessam>>& for an
25624 explanation of when this might be needed.
25626 .option hosts_noproxy_tls smtp "host list&!!" unset
25627 .cindex "TLS" "passing connection"
25628 .cindex "multiple SMTP deliveries"
25629 .cindex "TLS" "multiple message deliveries"
25630 For any host that matches this list, a TLS session which has
25631 been started will not be passed to a new delivery process for sending another
25632 message on the same session.
25634 The traditional implementation closes down TLS and re-starts it in the new
25635 process, on the same open TCP connection, for each successive message
25636 sent. If permitted by this option a pipe to to the new process is set up
25637 instead, and the original process maintains the TLS connection and proxies
25638 the SMTP connection from and to the new process and any subsequents.
25639 The new process has no access to TLS information, so cannot include it in
25644 .option hosts_override smtp boolean false
25645 If this option is set and the &%hosts%& option is also set, any hosts that are
25646 attached to the address are ignored, and instead the hosts specified by the
25647 &%hosts%& option are always used. This option does not apply to
25648 &%fallback_hosts%&.
25651 .option hosts_randomize smtp boolean false
25652 .cindex "randomized host list"
25653 .cindex "host" "list of; randomized"
25654 .cindex "fallback" "randomized hosts"
25655 If this option is set, and either the list of hosts is taken from the
25656 &%hosts%& or the &%fallback_hosts%& option, or the hosts supplied by the router
25657 were not obtained from MX records (this includes fallback hosts from the
25658 router), and were not randomized by the router, the order of trying the hosts
25659 is randomized each time the transport runs. Randomizing the order of a host
25660 list can be used to do crude load sharing.
25662 When &%hosts_randomize%& is true, a host list may be split into groups whose
25663 order is separately randomized. This makes it possible to set up MX-like
25664 behaviour. The boundaries between groups are indicated by an item that is just
25665 &`+`& in the host list. For example:
25667 hosts = host1:host2:host3:+:host4:host5
25669 The order of the first three hosts and the order of the last two hosts is
25670 randomized for each use, but the first three always end up before the last two.
25671 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored.
25673 .option hosts_require_auth smtp "host list&!!" unset
25674 .cindex "authentication" "required by client"
25675 This option provides a list of servers for which authentication must succeed
25676 before Exim will try to transfer a message. If authentication fails for
25677 servers which are not in this list, Exim tries to send unauthenticated. If
25678 authentication fails for one of these servers, delivery is deferred. This
25679 temporary error is detectable in the retry rules, so it can be turned into a
25680 hard failure if required. See also &%hosts_try_auth%&, and chapter
25681 &<<CHAPSMTPAUTH>>& for details of authentication.
25684 .option hosts_request_ocsp smtp "host list&!!" *
25685 .cindex "TLS" "requiring for certain servers"
25686 Exim will request a Certificate Status on a
25687 TLS session for any host that matches this list.
25688 &%tls_verify_certificates%& should also be set for the transport.
25690 .option hosts_require_alpn smtp "host list&!!" unset
25691 .cindex ALPN "require negotiation in client"
25693 .cindex TLS "Application Layer Protocol Names"
25694 If the TLS library supports ALPN
25695 then a successful negotiation of ALPN will be required for any host
25696 matching the list, for TLS to be used.
25697 See also the &%tls_alpn%& option.
25699 &*Note*&: prevention of fallback to in-clear connection is not
25700 managed by this option; see &%hosts_require_tls%&.
25702 .option hosts_require_dane smtp "host list&!!" unset
25703 .cindex DANE "transport options"
25704 .cindex DANE "requiring for certain servers"
25705 If built with DANE support, Exim will require that a DNSSEC-validated
25706 TLSA record is present for any host matching the list,
25707 and that a DANE-verified TLS connection is made.
25708 There will be no fallback to in-clear communication.
25709 See the &%dnssec_request_domains%& router and transport options.
25710 See section &<<SECDANE>>&.
25712 .option hosts_require_ocsp smtp "host list&!!" unset
25713 .cindex "TLS" "requiring for certain servers"
25714 Exim will request, and check for a valid Certificate Status being given, on a
25715 TLS session for any host that matches this list.
25716 &%tls_verify_certificates%& should also be set for the transport.
25718 .option hosts_require_tls smtp "host list&!!" unset
25719 .cindex "TLS" "requiring for certain servers"
25720 Exim will insist on using a TLS session when delivering to any host that
25721 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
25722 &*Note*&: This option affects outgoing mail only. To insist on TLS for
25723 incoming messages, use an appropriate ACL.
25725 .option hosts_try_auth smtp "host list&!!" unset
25726 .cindex "authentication" "optional in client"
25727 This option provides a list of servers to which, provided they announce
25728 authentication support, Exim will attempt to authenticate as a client when it
25729 connects. If authentication fails
25730 and &%hosts_require_auth%& permits,
25731 Exim will try to transfer the message unauthenticated.
25732 See also chapter &<<CHAPSMTPAUTH>>& for details of authentication.
25734 .option hosts_try_chunking smtp "host list&!!" *
25735 .cindex CHUNKING "enabling, in client"
25736 .cindex BDAT "SMTP command"
25737 .cindex "RFC 3030" "CHUNKING"
25738 This option provides a list of servers to which, provided they announce
25739 CHUNKING support, Exim will attempt to use BDAT commands rather than DATA.
25740 Unless DKIM signing is being done,
25741 BDAT will not be used in conjunction with a transport filter.
25743 .option hosts_try_dane smtp "host list&!!" *
25744 .cindex DANE "transport options"
25745 .cindex DANE "attempting for certain servers"
25746 If built with DANE support, Exim will look up a
25747 TLSA record for any host matching the list,
25748 If one is found and that lookup was DNSSEC-validated,
25749 then Exim requires that a DANE-verified TLS connection is made for that host;
25750 there will be no fallback to in-clear communication.
25751 See the &%dnssec_request_domains%& router and transport options.
25752 See section &<<SECDANE>>&.
25754 .option hosts_try_fastopen smtp "host list&!!" *
25755 .cindex "fast open, TCP" "enabling, in client"
25756 .cindex "TCP Fast Open" "enabling, in client"
25757 .cindex "RFC 7413" "TCP Fast Open"
25758 This option provides a list of servers to which, provided
25759 the facility is supported by this system, Exim will attempt to
25760 perform a TCP Fast Open.
25761 No data is sent on the SYN segment but, if the remote server also
25762 supports the facility, it can send its SMTP banner immediately after
25763 the SYN,ACK segment. This can save up to one round-trip time.
25765 The facility is only active for previously-contacted servers,
25766 as the initiator must present a cookie in the SYN segment.
25768 On (at least some) current Linux distributions the facility must be enabled
25769 in the kernel by the sysadmin before the support is usable.
25770 There is no option for control of the server side; if the system supports
25771 it it is always enabled. Note that lengthy operations in the connect ACL,
25772 such as DNSBL lookups, will still delay the emission of the SMTP banner.
25774 .option hosts_try_prdr smtp "host list&!!" *
25775 .cindex "PRDR" "enabling, optional in client"
25776 .cindex "ESMTP extensions" PRDR
25777 This option provides a list of servers to which, provided they announce
25778 PRDR support, Exim will attempt to negotiate PRDR
25779 for multi-recipient messages.
25780 The option can usually be left as default.
25782 .option interface smtp "string list&!!" unset
25783 .cindex "bind IP address"
25784 .cindex "IP address" "binding"
25786 .vindex "&$host_address$&"
25787 This option specifies which interface to bind to when making an outgoing SMTP
25788 call. The value is an IP address, not an interface name such as
25789 &`eth0`&. Do not confuse this with the interface address that was used when a
25790 message was received, which is in &$received_ip_address$&, formerly known as
25791 &$interface_address$&. The name was changed to minimize confusion with the
25792 outgoing interface address. There is no variable that contains an outgoing
25793 interface address because, unless it is set by this option, its value is
25796 During the expansion of the &%interface%& option the variables &$host$& and
25797 &$host_address$& refer to the host to which a connection is about to be made
25798 during the expansion of the string. Forced expansion failure, or an empty
25799 string result causes the option to be ignored. Otherwise, after expansion, the
25800 string must be a list of IP addresses, colon-separated by default, but the
25801 separator can be changed in the usual way (&<<SECTlistsepchange>>&).
25804 interface = <; 192.168.123.123 ; 3ffe:ffff:836f::fe86:a061
25806 The first interface of the correct type (IPv4 or IPv6) is used for the outgoing
25807 connection. If none of them are the correct type, the option is ignored. If
25808 &%interface%& is not set, or is ignored, the system's IP functions choose which
25809 interface to use if the host has more than one.
25812 .option keepalive smtp boolean true
25813 .cindex "keepalive" "on outgoing connection"
25814 This option controls the setting of SO_KEEPALIVE on outgoing TCP/IP socket
25815 connections. When set, it causes the kernel to probe idle connections
25816 periodically, by sending packets with &"old"& sequence numbers. The other end
25817 of the connection should send a acknowledgment if the connection is still okay
25818 or a reset if the connection has been aborted. The reason for doing this is
25819 that it has the beneficial effect of freeing up certain types of connection
25820 that can get stuck when the remote host is disconnected without tidying up the
25821 TCP/IP call properly. The keepalive mechanism takes several hours to detect
25825 .option lmtp_ignore_quota smtp boolean false
25826 .cindex "LMTP" "ignoring quota errors"
25827 If this option is set true when the &%protocol%& option is set to &"lmtp"&, the
25828 string &`IGNOREQUOTA`& is added to RCPT commands, provided that the LMTP server
25829 has advertised support for IGNOREQUOTA in its response to the LHLO command.
25831 .option max_rcpt smtp integer 100
25832 .cindex "RCPT" "maximum number of outgoing"
25833 This option limits the number of RCPT commands that are sent in a single
25834 SMTP message transaction. Each set of addresses is treated independently, and
25835 so can cause parallel connections to the same host if &%remote_max_parallel%&
25836 permits this. A value setting of zero disables the limit.
25839 .option message_linelength_limit smtp integer 998
25840 .cindex "line length" limit
25841 This option sets the maximum line length, in bytes, that the transport
25842 will send. Any messages with lines exceeding the given value
25843 will fail and a failure-DSN ("bounce") message will if possible be returned
25845 The default value is that defined by the SMTP standards.
25847 It is generally wise to also check in the data ACL so that messages
25848 received via SMTP can be refused without producing a bounce.
25851 .option multi_domain smtp boolean&!! true
25852 .vindex "&$domain$&"
25853 When this option is set, the &(smtp)& transport can handle a number of
25854 addresses containing a mixture of different domains provided they all resolve
25855 to the same list of hosts. Turning the option off restricts the transport to
25856 handling only one domain at a time. This is useful if you want to use
25857 &$domain$& in an expansion for the transport, because it is set only when there
25858 is a single domain involved in a remote delivery.
25860 It is expanded per-address and can depend on any of
25861 &$address_data$&, &$domain_data$&, &$local_part_data$&,
25862 &$host$&, &$host_address$& and &$host_port$&.
25864 If the connection is DANE-enabled then this option is ignored;
25865 only messages having the domain used for the DANE TLSA lookup are
25866 sent on the connection.
25868 .option port smtp string&!! "see below"
25869 .cindex "port" "sending TCP/IP"
25870 .cindex "TCP/IP" "setting outgoing port"
25871 This option specifies the TCP/IP port on the server to which Exim connects.
25872 &*Note:*& Do not confuse this with the port that was used when a message was
25873 received, which is in &$received_port$&, formerly known as &$interface_port$&.
25874 The name was changed to minimize confusion with the outgoing port. There is no
25875 variable that contains an outgoing port.
25877 If the value of this option begins with a digit it is taken as a port number;
25878 otherwise it is looked up using &[getservbyname()]&. The default value is
25880 but if &%protocol%& is set to &"lmtp"& the default is &"lmtp"&
25881 and if &%protocol%& is set to &"smtps"& the default is &"smtps"&.
25882 If the expansion fails, or if a port number cannot be found, delivery
25885 Note that at least one Linux distribution has been seen failing
25886 to put &"smtps"& in its &"/etc/services"& file, resulting is such deferrals.
25890 .option protocol smtp string smtp
25891 .cindex "LMTP" "over TCP/IP"
25892 .cindex "ssmtp protocol" "outbound"
25893 .cindex "TLS" "SSL-on-connect outbound"
25895 If this option is set to &"lmtp"& instead of &"smtp"&, the default value for
25896 the &%port%& option changes to &"lmtp"&, and the transport operates the LMTP
25897 protocol (RFC 2033) instead of SMTP. This protocol is sometimes used for local
25898 deliveries into closed message stores. Exim also has support for running LMTP
25899 over a pipe to a local process &-- see chapter &<<CHAPLMTP>>&.
25901 If this option is set to &"smtps"&, the default value for the &%port%& option
25902 changes to &"smtps"&, and the transport initiates TLS immediately after
25903 connecting, as an outbound SSL-on-connect, instead of using STARTTLS to upgrade.
25904 The Internet standards bodies used to strongly discourage use of this mode,
25905 but as of RFC 8314 it is preferred over STARTTLS for message submission
25906 (as distinct from MTA-MTA communication).
25909 .option retry_include_ip_address smtp boolean&!! true
25910 Exim normally includes both the host name and the IP address in the key it
25911 constructs for indexing retry data after a temporary delivery failure. This
25912 means that when one of several IP addresses for a host is failing, it gets
25913 tried periodically (controlled by the retry rules), but use of the other IP
25914 addresses is not affected.
25916 However, in some dialup environments hosts are assigned a different IP address
25917 each time they connect. In this situation the use of the IP address as part of
25918 the retry key leads to undesirable behaviour. Setting this option false causes
25919 Exim to use only the host name.
25920 Since it is expanded it can be made to depend on the host or domain.
25923 .option serialize_hosts smtp "host list&!!" unset
25924 .cindex "serializing connections"
25925 .cindex "host" "serializing connections"
25926 Because Exim operates in a distributed manner, if several messages for the same
25927 host arrive at around the same time, more than one simultaneous connection to
25928 the remote host can occur. This is not usually a problem except when there is a
25929 slow link between the hosts. In that situation it may be helpful to restrict
25930 Exim to one connection at a time. This can be done by setting
25931 &%serialize_hosts%& to match the relevant hosts.
25933 .cindex "hints database" "serializing deliveries to a host"
25934 Exim implements serialization by means of a hints database in which a record is
25935 written whenever a process connects to one of the restricted hosts. The record
25936 is deleted when the connection is completed. Obviously there is scope for
25937 records to get left lying around if there is a system or program crash. To
25938 guard against this, Exim ignores any records that are more than six hours old.
25940 If you set up this kind of serialization, you should also arrange to delete the
25941 relevant hints database whenever your system reboots. The names of the files
25942 start with &_misc_& and they are kept in the &_spool/db_& directory. There
25943 may be one or two files, depending on the type of DBM in use. The same files
25944 are used for ETRN serialization.
25946 See also the &%max_parallel%& generic transport option.
25949 .option size_addition smtp integer 1024
25950 .cindex "SIZE" "ESMTP extension"
25951 .cindex "message" "size issue for transport filter"
25952 .cindex "size" "of message"
25953 .cindex "transport" "filter"
25954 .cindex "filter" "transport filter"
25955 If a remote SMTP server indicates that it supports the SIZE option of the
25956 MAIL command, Exim uses this to pass over the message size at the start of
25957 an SMTP transaction. It adds the value of &%size_addition%& to the value it
25958 sends, to allow for headers and other text that may be added during delivery by
25959 configuration options or in a transport filter. It may be necessary to increase
25960 this if a lot of text is added to messages.
25962 Alternatively, if the value of &%size_addition%& is set negative, it disables
25963 the use of the SIZE option altogether.
25966 .option socks_proxy smtp string&!! unset
25967 .cindex proxy SOCKS
25968 This option enables use of SOCKS proxies for connections made by the
25969 transport. For details see section &<<SECTproxySOCKS>>&.
25972 .option tls_alpn smtp string&!! unset
25973 .cindex TLS "Application Layer Protocol Names"
25975 .cindex ALPN "set name in client"
25976 If this option is set
25977 and the TLS library supports ALPN,
25978 the value given is used.
25980 As of writing no value has been standardised for email use.
25981 The authors suggest using &"smtp"&.
25985 .option tls_certificate smtp string&!! unset
25986 .cindex "TLS" "client certificate, location of"
25987 .cindex "certificate" "client, location of"
25989 .vindex "&$host_address$&"
25990 The value of this option must be the absolute path to a file which contains the
25991 client's certificate, for possible use when sending a message over an encrypted
25992 connection. The values of &$host$& and &$host_address$& are set to the name and
25993 address of the server during the expansion. See chapter &<<CHAPTLS>>& for
25996 &*Note*&: This option must be set if you want Exim to be able to use a TLS
25997 certificate when sending messages as a client. The global option of the same
25998 name specifies the certificate for Exim as a server; it is not automatically
25999 assumed that the same certificate should be used when Exim is operating as a
26003 .option tls_crl smtp string&!! unset
26004 .cindex "TLS" "client certificate revocation list"
26005 .cindex "certificate" "revocation list for client"
26006 This option specifies a certificate revocation list. The expanded value must
26007 be the name of a file that contains a CRL in PEM format.
26010 .option tls_dh_min_bits smtp integer 1024
26011 .cindex "TLS" "Diffie-Hellman minimum acceptable size"
26012 When establishing a TLS session, if a ciphersuite which uses Diffie-Hellman
26013 key agreement is negotiated, the server will provide a large prime number
26014 for use. This option establishes the minimum acceptable size of that number.
26015 If the parameter offered by the server is too small, then the TLS handshake
26018 Only supported when using GnuTLS.
26021 .option tls_privatekey smtp string&!! unset
26022 .cindex "TLS" "client private key, location of"
26024 .vindex "&$host_address$&"
26025 The value of this option must be the absolute path to a file which contains the
26026 client's private key. This is used when sending a message over an encrypted
26027 connection using a client certificate. The values of &$host$& and
26028 &$host_address$& are set to the name and address of the server during the
26029 expansion. If this option is unset, or the expansion is forced to fail, or the
26030 result is an empty string, the private key is assumed to be in the same file as
26031 the certificate. See chapter &<<CHAPTLS>>& for details of TLS.
26034 .option tls_require_ciphers smtp string&!! unset
26035 .cindex "TLS" "requiring specific ciphers"
26036 .cindex "cipher" "requiring specific"
26038 .vindex "&$host_address$&"
26039 The value of this option must be a list of permitted cipher suites, for use
26040 when setting up an outgoing encrypted connection. (There is a global option of
26041 the same name for controlling incoming connections.) The values of &$host$& and
26042 &$host_address$& are set to the name and address of the server during the
26043 expansion. See chapter &<<CHAPTLS>>& for details of TLS; note that this option
26044 is used in different ways by OpenSSL and GnuTLS (see sections
26045 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&). For GnuTLS, the order of the
26046 ciphers is a preference order.
26049 .option tls_resumption_hosts smtp "host list&!!" unset
26050 .cindex TLS resumption
26051 This option controls which connections to use the TLS resumption feature.
26052 See &<<SECTresumption>>& for details.
26056 .option tls_sni smtp string&!! unset
26057 .cindex "TLS" "Server Name Indication"
26059 .cindex SNI "setting in client"
26060 .vindex "&$tls_sni$&"
26061 If this option is set
26062 and the connection is not DANE-validated
26063 then it sets the $tls_out_sni variable and causes any
26064 TLS session to pass this value as the Server Name Indication extension to
26065 the remote side, which can be used by the remote side to select an appropriate
26066 certificate and private key for the session.
26068 See &<<SECTtlssni>>& for more information.
26070 Note that for OpenSSL, this feature requires a build of OpenSSL that supports
26076 .option tls_tempfail_tryclear smtp boolean true
26077 .cindex "4&'xx'& responses" "to STARTTLS"
26078 When the server host is not in &%hosts_require_tls%&, and there is a problem in
26079 setting up a TLS session, this option determines whether or not Exim should try
26080 to deliver the message unencrypted. If it is set false, delivery to the
26081 current host is deferred; if there are other hosts, they are tried. If this
26082 option is set true, Exim attempts to deliver unencrypted after a 4&'xx'&
26083 response to STARTTLS. Also, if STARTTLS is accepted, but the subsequent
26084 TLS negotiation fails, Exim closes the current connection (because it is in an
26085 unknown state), opens a new one to the same host, and then tries the delivery
26089 .option tls_try_verify_hosts smtp "host list&!!" *
26090 .cindex "TLS" "server certificate verification"
26091 .cindex "certificate" "verification of server"
26092 This option gives a list of hosts for which, on encrypted connections,
26093 certificate verification will be tried but need not succeed.
26094 The &%tls_verify_certificates%& option must also be set.
26095 Note that unless the host is in this list
26096 TLS connections will be denied to hosts using self-signed certificates
26097 when &%tls_verify_certificates%& is matched.
26098 The &$tls_out_certificate_verified$& variable is set when
26099 certificate verification succeeds.
26102 .option tls_verify_cert_hostnames smtp "host list&!!" *
26103 .cindex "TLS" "server certificate hostname verification"
26104 .cindex "certificate" "verification of server"
26105 This option give a list of hosts for which,
26106 while verifying the server certificate,
26107 checks will be included on the host name
26108 (note that this will generally be the result of a DNS MX lookup)
26109 versus Subject and Subject-Alternate-Name fields. Wildcard names are permitted
26110 limited to being the initial component of a 3-or-more component FQDN.
26112 There is no equivalent checking on client certificates.
26115 .option tls_verify_certificates smtp string&!! system
26116 .cindex "TLS" "server certificate verification"
26117 .cindex "certificate" "verification of server"
26119 .vindex "&$host_address$&"
26120 The value of this option must be either the
26122 or the absolute path to
26123 a file or directory containing permitted certificates for servers,
26124 for use when setting up an encrypted connection.
26126 The "system" value for the option will use a location compiled into the SSL library.
26127 This is not available for GnuTLS versions preceding 3.0.20; a value of "system"
26128 is taken as empty and an explicit location
26131 The use of a directory for the option value is not available for GnuTLS versions
26132 preceding 3.3.6 and a single file must be used.
26134 With OpenSSL the certificates specified
26136 either by file or directory
26137 are added to those given by the system default location.
26139 The values of &$host$& and
26140 &$host_address$& are set to the name and address of the server during the
26141 expansion of this option. See chapter &<<CHAPTLS>>& for details of TLS.
26143 For back-compatibility,
26144 if neither tls_verify_hosts nor tls_try_verify_hosts are set
26145 (a single-colon empty list counts as being set)
26146 and certificate verification fails the TLS connection is closed.
26149 .option tls_verify_hosts smtp "host list&!!" unset
26150 .cindex "TLS" "server certificate verification"
26151 .cindex "certificate" "verification of server"
26152 This option gives a list of hosts for which, on encrypted connections,
26153 certificate verification must succeed.
26154 The &%tls_verify_certificates%& option must also be set.
26155 If both this option and &%tls_try_verify_hosts%& are unset
26156 operation is as if this option selected all hosts.
26157 &*Warning*&: Including a host in &%tls_verify_hosts%& does not require
26158 that connections use TLS.
26159 Fallback to in-clear communication will be done unless restricted by
26160 the &%hosts_require_tls%& option.
26162 .option utf8_downconvert smtp integer&!! -1
26163 .cindex utf8 "address downconversion"
26164 .cindex i18n "utf8 address downconversion"
26165 If built with internationalization support,
26166 this option controls conversion of UTF-8 in message envelope addresses
26168 If, after expansion, the value is 1, 0, or -1 then this value overrides
26169 any value previously set for the message. Otherwise, any previously
26170 set value is used. To permit use of a previous value,
26171 set this option to an empty string.
26172 For details on the values see section &<<SECTi18nMTA>>&.
26177 .section "How the limits for the number of hosts to try are used" &&&
26179 .cindex "host" "maximum number to try"
26180 .cindex "limit" "hosts; maximum number tried"
26181 There are two options that are concerned with the number of hosts that are
26182 tried when an SMTP delivery takes place. They are &%hosts_max_try%& and
26183 &%hosts_max_try_hardlimit%&.
26186 The &%hosts_max_try%& option limits the number of hosts that are tried
26187 for a single delivery. However, despite the term &"host"& in its name, the
26188 option actually applies to each IP address independently. In other words, a
26189 multihomed host is treated as several independent hosts, just as it is for
26192 Many of the larger ISPs have multiple MX records which often point to
26193 multihomed hosts. As a result, a list of a dozen or more IP addresses may be
26194 created as a result of routing one of these domains.
26196 Trying every single IP address on such a long list does not seem sensible; if
26197 several at the top of the list fail, it is reasonable to assume there is some
26198 problem that is likely to affect all of them. Roughly speaking, the value of
26199 &%hosts_max_try%& is the maximum number that are tried before deferring the
26200 delivery. However, the logic cannot be quite that simple.
26202 Firstly, IP addresses that are skipped because their retry times have not
26203 arrived do not count, and in addition, addresses that are past their retry
26204 limits are also not counted, even when they are tried. This means that when
26205 some IP addresses are past their retry limits, more than the value of
26206 &%hosts_max_retry%& may be tried. The reason for this behaviour is to ensure
26207 that all IP addresses are considered before timing out an email address (but
26208 see below for an exception).
26210 Secondly, when the &%hosts_max_try%& limit is reached, Exim looks down the host
26211 list to see if there is a subsequent host with a different (higher valued) MX.
26212 If there is, that host is considered next, and the current IP address is used
26213 but not counted. This behaviour helps in the case of a domain with a retry rule
26214 that hardly ever delays any hosts, as is now explained:
26216 Consider the case of a long list of hosts with one MX value, and a few with a
26217 higher MX value. If &%hosts_max_try%& is small (the default is 5) only a few
26218 hosts at the top of the list are tried at first. With the default retry rule,
26219 which specifies increasing retry times, the higher MX hosts are eventually
26220 tried when those at the top of the list are skipped because they have not
26221 reached their retry times.
26223 However, it is common practice to put a fixed short retry time on domains for
26224 large ISPs, on the grounds that their servers are rarely down for very long.
26225 Unfortunately, these are exactly the domains that tend to resolve to long lists
26226 of hosts. The short retry time means that the lowest MX hosts are tried every
26227 time. The attempts may be in a different order because of random sorting, but
26228 without the special MX check, the higher MX hosts would never be tried until
26229 all the lower MX hosts had timed out (which might be several days), because
26230 there are always some lower MX hosts that have reached their retry times. With
26231 the special check, Exim considers at least one IP address from each MX value at
26232 every delivery attempt, even if the &%hosts_max_try%& limit has already been
26235 The above logic means that &%hosts_max_try%& is not a hard limit, and in
26236 particular, Exim normally eventually tries all the IP addresses before timing
26237 out an email address. When &%hosts_max_try%& was implemented, this seemed a
26238 reasonable thing to do. Recently, however, some lunatic DNS configurations have
26239 been set up with hundreds of IP addresses for some domains. It can
26240 take a very long time indeed for an address to time out in these cases.
26242 The &%hosts_max_try_hardlimit%& option was added to help with this problem.
26243 Exim never tries more than this number of IP addresses; if it hits this limit
26244 and they are all timed out, the email address is bounced, even though not all
26245 possible IP addresses have been tried.
26246 .ecindex IIDsmttra1
26247 .ecindex IIDsmttra2
26253 . ////////////////////////////////////////////////////////////////////////////
26254 . ////////////////////////////////////////////////////////////////////////////
26256 .chapter "Address rewriting" "CHAPrewrite"
26257 .scindex IIDaddrew "rewriting" "addresses"
26258 There are some circumstances in which Exim automatically rewrites domains in
26259 addresses. The two most common are when an address is given without a domain
26260 (referred to as an &"unqualified address"&) or when an address contains an
26261 abbreviated domain that is expanded by DNS lookup.
26263 Unqualified envelope addresses are accepted only for locally submitted
26264 messages, or for messages that are received from hosts matching
26265 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
26266 appropriate. Unqualified addresses in header lines are qualified if they are in
26267 locally submitted messages, or messages from hosts that are permitted to send
26268 unqualified envelope addresses. Otherwise, unqualified addresses in header
26269 lines are neither qualified nor rewritten.
26271 One situation in which Exim does &'not'& automatically rewrite a domain is
26272 when it is the name of a CNAME record in the DNS. The older RFCs suggest that
26273 such a domain should be rewritten using the &"canonical"& name, and some MTAs
26274 do this. The new RFCs do not contain this suggestion.
26277 .section "Explicitly configured address rewriting" "SECID147"
26278 This chapter describes the rewriting rules that can be used in the
26279 main rewrite section of the configuration file, and also in the generic
26280 &%headers_rewrite%& option that can be set on any transport.
26282 Some people believe that configured address rewriting is a Mortal Sin.
26283 Others believe that life is not possible without it. Exim provides the
26284 facility; you do not have to use it.
26286 The main rewriting rules that appear in the &"rewrite"& section of the
26287 configuration file are applied to addresses in incoming messages, both envelope
26288 addresses and addresses in header lines. Each rule specifies the types of
26289 address to which it applies.
26291 Whether or not addresses in header lines are rewritten depends on the origin of
26292 the headers and the type of rewriting. Global rewriting, that is, rewriting
26293 rules from the rewrite section of the configuration file, is applied only to
26294 those headers that were received with the message. Header lines that are added
26295 by ACLs or by a system filter or by individual routers or transports (which
26296 are specific to individual recipient addresses) are not rewritten by the global
26299 Rewriting at transport time, by means of the &%headers_rewrite%& option,
26300 applies all headers except those added by routers and transports. That is, as
26301 well as the headers that were received with the message, it also applies to
26302 headers that were added by an ACL or a system filter.
26305 In general, rewriting addresses from your own system or domain has some
26306 legitimacy. Rewriting other addresses should be done only with great care and
26307 in special circumstances. The author of Exim believes that rewriting should be
26308 used sparingly, and mainly for &"regularizing"& addresses in your own domains.
26309 Although it can sometimes be used as a routing tool, this is very strongly
26312 There are two commonly encountered circumstances where rewriting is used, as
26313 illustrated by these examples:
26316 The company whose domain is &'hitch.fict.example'& has a number of hosts that
26317 exchange mail with each other behind a firewall, but there is only a single
26318 gateway to the outer world. The gateway rewrites &'*.hitch.fict.example'& as
26319 &'hitch.fict.example'& when sending mail off-site.
26321 A host rewrites the local parts of its own users so that, for example,
26322 &'fp42@hitch.fict.example'& becomes &'Ford.Prefect@hitch.fict.example'&.
26327 .section "When does rewriting happen?" "SECID148"
26328 .cindex "rewriting" "timing of"
26329 .cindex "&ACL;" "rewriting addresses in"
26330 Configured address rewriting can take place at several different stages of a
26331 message's processing.
26333 .vindex "&$sender_address$&"
26334 At the start of an ACL for MAIL, the sender address may have been rewritten
26335 by a special SMTP-time rewrite rule (see section &<<SECTrewriteS>>&), but no
26336 ordinary rewrite rules have yet been applied. If, however, the sender address
26337 is verified in the ACL, it is rewritten before verification, and remains
26338 rewritten thereafter. The subsequent value of &$sender_address$& is the
26339 rewritten address. This also applies if sender verification happens in a
26340 RCPT ACL. Otherwise, when the sender address is not verified, it is
26341 rewritten as soon as a message's header lines have been received.
26343 .vindex "&$domain$&"
26344 .vindex "&$local_part$&"
26345 Similarly, at the start of an ACL for RCPT, the current recipient's address
26346 may have been rewritten by a special SMTP-time rewrite rule, but no ordinary
26347 rewrite rules have yet been applied to it. However, the behaviour is different
26348 from the sender address when a recipient is verified. The address is rewritten
26349 for the verification, but the rewriting is not remembered at this stage. The
26350 value of &$local_part$& and &$domain$& after verification are always the same
26351 as they were before (that is, they contain the unrewritten &-- except for
26352 SMTP-time rewriting &-- address).
26354 As soon as a message's header lines have been received, all the envelope
26355 recipient addresses are permanently rewritten, and rewriting is also applied to
26356 the addresses in the header lines (if configured). This happens before adding
26357 any header lines that were specified in MAIL or RCPT ACLs, and
26358 .cindex "&[local_scan()]& function" "address rewriting; timing of"
26359 before the DATA ACL and &[local_scan()]& functions are run.
26361 When an address is being routed, either for delivery or for verification,
26362 rewriting is applied immediately to child addresses that are generated by
26363 redirection, unless &%no_rewrite%& is set on the router.
26365 .cindex "envelope from"
26366 .cindex "envelope sender" "rewriting at transport time"
26367 .cindex "rewriting" "at transport time"
26368 .cindex "header lines" "rewriting at transport time"
26369 At transport time, additional rewriting of addresses in header lines can be
26370 specified by setting the generic &%headers_rewrite%& option on a transport.
26371 This option contains rules that are identical in form to those in the rewrite
26372 section of the configuration file. They are applied to the original message
26373 header lines and any that were added by ACLs or a system filter. They are not
26374 applied to header lines that are added by routers or the transport.
26376 The outgoing envelope sender can be rewritten by means of the &%return_path%&
26377 transport option. However, it is not possible to rewrite envelope recipients at
26383 .section "Testing the rewriting rules that apply on input" "SECID149"
26384 .cindex "rewriting" "testing"
26385 .cindex "testing" "rewriting"
26386 Exim's input rewriting configuration appears in a part of the runtime
26387 configuration file headed by &"begin rewrite"&. It can be tested by the
26388 &%-brw%& command line option. This takes an address (which can be a full RFC
26389 2822 address) as its argument. The output is a list of how the address would be
26390 transformed by the rewriting rules for each of the different places it might
26391 appear in an incoming message, that is, for each different header and for the
26392 envelope sender and recipient fields. For example,
26394 exim -brw ph10@exim.workshop.example
26396 might produce the output
26398 sender: Philip.Hazel@exim.workshop.example
26399 from: Philip.Hazel@exim.workshop.example
26400 to: ph10@exim.workshop.example
26401 cc: ph10@exim.workshop.example
26402 bcc: ph10@exim.workshop.example
26403 reply-to: Philip.Hazel@exim.workshop.example
26404 env-from: Philip.Hazel@exim.workshop.example
26405 env-to: ph10@exim.workshop.example
26407 which shows that rewriting has been set up for that address when used in any of
26408 the source fields, but not when it appears as a recipient address. At the
26409 present time, there is no equivalent way of testing rewriting rules that are
26410 set for a particular transport.
26413 .section "Rewriting rules" "SECID150"
26414 .cindex "rewriting" "rules"
26415 The rewrite section of the configuration file consists of lines of rewriting
26418 <&'source pattern'&> <&'replacement'&> <&'flags'&>
26420 Rewriting rules that are specified for the &%headers_rewrite%& generic
26421 transport option are given as a colon-separated list. Each item in the list
26422 takes the same form as a line in the main rewriting configuration (except that
26423 any colons must be doubled, of course).
26425 The formats of source patterns and replacement strings are described below.
26426 Each is terminated by white space, unless enclosed in double quotes, in which
26427 case normal quoting conventions apply inside the quotes. The flags are single
26428 characters which may appear in any order. Spaces and tabs between them are
26431 For each address that could potentially be rewritten, the rules are scanned in
26432 order, and replacements for the address from earlier rules can themselves be
26433 replaced by later rules (but see the &"q"& and &"R"& flags).
26435 The order in which addresses are rewritten is undefined, may change between
26436 releases, and must not be relied on, with one exception: when a message is
26437 received, the envelope sender is always rewritten first, before any header
26438 lines are rewritten. For example, the replacement string for a rewrite of an
26439 address in &'To:'& must not assume that the message's address in &'From:'& has
26440 (or has not) already been rewritten. However, a rewrite of &'From:'& may assume
26441 that the envelope sender has already been rewritten.
26443 .vindex "&$domain$&"
26444 .vindex "&$local_part$&"
26445 The variables &$local_part$& and &$domain$& can be used in the replacement
26446 string to refer to the address that is being rewritten. Note that lookup-driven
26447 rewriting can be done by a rule of the form
26451 where the lookup key uses &$1$& and &$2$& or &$local_part$& and &$domain$& to
26452 refer to the address that is being rewritten.
26455 .section "Rewriting patterns" "SECID151"
26456 .cindex "rewriting" "patterns"
26457 .cindex "address list" "in a rewriting pattern"
26458 The source pattern in a rewriting rule is any item which may appear in an
26459 address list (see section &<<SECTaddresslist>>&). It is in fact processed as a
26460 single-item address list, which means that it is expanded before being tested
26461 against the address. As always, if you use a regular expression as a pattern,
26462 you must take care to escape dollar and backslash characters, or use the &`\N`&
26463 facility to suppress string expansion within the regular expression.
26465 Domains in patterns should be given in lower case. Local parts in patterns are
26466 case-sensitive. If you want to do case-insensitive matching of local parts, you
26467 can use a regular expression that starts with &`^(?i)`&.
26469 .cindex "numerical variables (&$1$& &$2$& etc)" "in rewriting rules"
26470 After matching, the numerical variables &$1$&, &$2$&, etc. may be set,
26471 depending on the type of match which occurred. These can be used in the
26472 replacement string to insert portions of the incoming address. &$0$& always
26473 refers to the complete incoming address. When a regular expression is used, the
26474 numerical variables are set from its capturing subexpressions. For other types
26475 of pattern they are set as follows:
26478 If a local part or domain starts with an asterisk, the numerical variables
26479 refer to the character strings matched by asterisks, with &$1$& associated with
26480 the first asterisk, and &$2$& with the second, if present. For example, if the
26483 *queen@*.fict.example
26485 is matched against the address &'hearts-queen@wonderland.fict.example'& then
26487 $0 = hearts-queen@wonderland.fict.example
26491 Note that if the local part does not start with an asterisk, but the domain
26492 does, it is &$1$& that contains the wild part of the domain.
26495 If the domain part of the pattern is a partial lookup, the wild and fixed parts
26496 of the domain are placed in the next available numerical variables. Suppose,
26497 for example, that the address &'foo@bar.baz.example'& is processed by a
26498 rewriting rule of the form
26500 &`*@partial-dbm;/some/dbm/file`& <&'replacement string'&>
26502 and the key in the file that matches the domain is &`*.baz.example`&. Then
26508 If the address &'foo@baz.example'& is looked up, this matches the same
26509 wildcard file entry, and in this case &$2$& is set to the empty string, but
26510 &$3$& is still set to &'baz.example'&. If a non-wild key is matched in a
26511 partial lookup, &$2$& is again set to the empty string and &$3$& is set to the
26512 whole domain. For non-partial domain lookups, no numerical variables are set.
26516 .section "Rewriting replacements" "SECID152"
26517 .cindex "rewriting" "replacements"
26518 If the replacement string for a rule is a single asterisk, addresses that
26519 match the pattern and the flags are &'not'& rewritten, and no subsequent
26520 rewriting rules are scanned. For example,
26522 hatta@lookingglass.fict.example * f
26524 specifies that &'hatta@lookingglass.fict.example'& is never to be rewritten in
26527 .vindex "&$domain$&"
26528 .vindex "&$local_part$&"
26529 If the replacement string is not a single asterisk, it is expanded, and must
26530 yield a fully qualified address. Within the expansion, the variables
26531 &$local_part$& and &$domain$& refer to the address that is being rewritten.
26532 Any letters they contain retain their original case &-- they are not lower
26533 cased. The numerical variables are set up according to the type of pattern that
26534 matched the address, as described above. If the expansion is forced to fail by
26535 the presence of &"fail"& in a conditional or lookup item, rewriting by the
26536 current rule is abandoned, but subsequent rules may take effect. Any other
26537 expansion failure causes the entire rewriting operation to be abandoned, and an
26538 entry written to the panic log.
26542 .section "Rewriting flags" "SECID153"
26543 There are three different kinds of flag that may appear on rewriting rules:
26546 Flags that specify which headers and envelope addresses to rewrite: E, F, T, b,
26549 A flag that specifies rewriting at SMTP time: S.
26551 Flags that control the rewriting process: Q, q, R, w.
26554 For rules that are part of the &%headers_rewrite%& generic transport option,
26555 E, F, T, and S are not permitted.
26559 .section "Flags specifying which headers and envelope addresses to rewrite" &&&
26561 .cindex "rewriting" "flags"
26562 If none of the following flag letters, nor the &"S"& flag (see section
26563 &<<SECTrewriteS>>&) are present, a main rewriting rule applies to all headers
26564 and to both the sender and recipient fields of the envelope, whereas a
26565 transport-time rewriting rule just applies to all headers. Otherwise, the
26566 rewriting rule is skipped unless the relevant addresses are being processed.
26568 &`E`& rewrite all envelope fields
26569 &`F`& rewrite the envelope From field
26570 &`T`& rewrite the envelope To field
26571 &`b`& rewrite the &'Bcc:'& header
26572 &`c`& rewrite the &'Cc:'& header
26573 &`f`& rewrite the &'From:'& header
26574 &`h`& rewrite all headers
26575 &`r`& rewrite the &'Reply-To:'& header
26576 &`s`& rewrite the &'Sender:'& header
26577 &`t`& rewrite the &'To:'& header
26579 "All headers" means all of the headers listed above that can be selected
26580 individually, plus their &'Resent-'& versions. It does not include
26581 other headers such as &'Subject:'& etc.
26583 You should be particularly careful about rewriting &'Sender:'& headers, and
26584 restrict this to special known cases in your own domains.
26587 .section "The SMTP-time rewriting flag" "SECTrewriteS"
26588 .cindex "SMTP" "rewriting malformed addresses"
26589 .cindex "RCPT" "rewriting argument of"
26590 .cindex "MAIL" "rewriting argument of"
26591 The rewrite flag &"S"& specifies a rewrite of incoming envelope addresses at
26592 SMTP time, as soon as an address is received in a MAIL or RCPT command, and
26593 before any other processing; even before syntax checking. The pattern is
26594 required to be a regular expression, and it is matched against the whole of the
26595 data for the command, including any surrounding angle brackets.
26597 .vindex "&$domain$&"
26598 .vindex "&$local_part$&"
26599 This form of rewrite rule allows for the handling of addresses that are not
26600 compliant with RFCs 2821 and 2822 (for example, &"bang paths"& in batched SMTP
26601 input). Because the input is not required to be a syntactically valid address,
26602 the variables &$local_part$& and &$domain$& are not available during the
26603 expansion of the replacement string. The result of rewriting replaces the
26604 original address in the MAIL or RCPT command.
26607 .section "Flags controlling the rewriting process" "SECID155"
26608 There are four flags which control the way the rewriting process works. These
26609 take effect only when a rule is invoked, that is, when the address is of the
26610 correct type (matches the flags) and matches the pattern:
26613 If the &"Q"& flag is set on a rule, the rewritten address is permitted to be an
26614 unqualified local part. It is qualified with &%qualify_recipient%&. In the
26615 absence of &"Q"& the rewritten address must always include a domain.
26617 If the &"q"& flag is set on a rule, no further rewriting rules are considered,
26618 even if no rewriting actually takes place because of a &"fail"& in the
26619 expansion. The &"q"& flag is not effective if the address is of the wrong type
26620 (does not match the flags) or does not match the pattern.
26622 The &"R"& flag causes a successful rewriting rule to be re-applied to the new
26623 address, up to ten times. It can be combined with the &"q"& flag, to stop
26624 rewriting once it fails to match (after at least one successful rewrite).
26626 .cindex "rewriting" "whole addresses"
26627 When an address in a header is rewritten, the rewriting normally applies only
26628 to the working part of the address, with any comments and RFC 2822 &"phrase"&
26629 left unchanged. For example, rewriting might change
26631 From: Ford Prefect <fp42@restaurant.hitch.fict.example>
26635 From: Ford Prefect <prefectf@hitch.fict.example>
26638 Sometimes there is a need to replace the whole address item, and this can be
26639 done by adding the flag letter &"w"& to a rule. If this is set on a rule that
26640 causes an address in a header line to be rewritten, the entire address is
26641 replaced, not just the working part. The replacement must be a complete RFC
26642 2822 address, including the angle brackets if necessary. If text outside angle
26643 brackets contains a character whose value is greater than 126 or less than 32
26644 (except for tab), the text is encoded according to RFC 2047. The character set
26645 is taken from &%headers_charset%&, which gets its default at build time.
26647 When the &"w"& flag is set on a rule that causes an envelope address to be
26648 rewritten, all but the working part of the replacement address is discarded.
26652 .section "Rewriting examples" "SECID156"
26653 Here is an example of the two common rewriting paradigms:
26655 *@*.hitch.fict.example $1@hitch.fict.example
26656 *@hitch.fict.example ${lookup{$1}dbm{/etc/realnames}\
26657 {$value}fail}@hitch.fict.example bctfrF
26659 Note the use of &"fail"& in the lookup expansion in the second rule, forcing
26660 the string expansion to fail if the lookup does not succeed. In this context it
26661 has the effect of leaving the original address unchanged, but Exim goes on to
26662 consider subsequent rewriting rules, if any, because the &"q"& flag is not
26663 present in that rule. An alternative to &"fail"& would be to supply &$1$&
26664 explicitly, which would cause the rewritten address to be the same as before,
26665 at the cost of a small bit of processing. Not supplying either of these is an
26666 error, since the rewritten address would then contain no local part.
26668 The first example above replaces the domain with a superior, more general
26669 domain. This may not be desirable for certain local parts. If the rule
26671 root@*.hitch.fict.example *
26673 were inserted before the first rule, rewriting would be suppressed for the
26674 local part &'root'& at any domain ending in &'hitch.fict.example'&.
26676 Rewriting can be made conditional on a number of tests, by making use of
26677 &${if$& in the expansion item. For example, to apply a rewriting rule only to
26678 messages that originate outside the local host:
26680 *@*.hitch.fict.example "${if !eq {$sender_host_address}{}\
26681 {$1@hitch.fict.example}fail}"
26683 The replacement string is quoted in this example because it contains white
26686 .cindex "rewriting" "bang paths"
26687 .cindex "bang paths" "rewriting"
26688 Exim does not handle addresses in the form of &"bang paths"&. If it sees such
26689 an address it treats it as an unqualified local part which it qualifies with
26690 the local qualification domain (if the source of the message is local or if the
26691 remote host is permitted to send unqualified addresses). Rewriting can
26692 sometimes be used to handle simple bang paths with a fixed number of
26693 components. For example, the rule
26695 \N^([^!]+)!(.*)@your.domain.example$\N $2@$1
26697 rewrites a two-component bang path &'host.name!user'& as the domain address
26698 &'user@host.name'&. However, there is a security implication in using this as
26699 a global rewriting rule for envelope addresses. It can provide a backdoor
26700 method for using your system as a relay, because the incoming addresses appear
26701 to be local. If the bang path addresses are received via SMTP, it is safer to
26702 use the &"S"& flag to rewrite them as they are received, so that relay checking
26703 can be done on the rewritten addresses.
26710 . ////////////////////////////////////////////////////////////////////////////
26711 . ////////////////////////////////////////////////////////////////////////////
26713 .chapter "Retry configuration" "CHAPretry"
26714 .scindex IIDretconf1 "retry" "configuration, description of"
26715 .scindex IIDregconf2 "configuration file" "retry section"
26716 The &"retry"& section of the runtime configuration file contains a list of
26717 retry rules that control how often Exim tries to deliver messages that cannot
26718 be delivered at the first attempt. If there are no retry rules (the section is
26719 empty or not present), there are no retries. In this situation, temporary
26720 errors are treated as permanent. The default configuration contains a single,
26721 general-purpose retry rule (see section &<<SECID57>>&). The &%-brt%& command
26722 line option can be used to test which retry rule will be used for a given
26723 address, domain and error.
26725 The most common cause of retries is temporary failure to deliver to a remote
26726 host because the host is down, or inaccessible because of a network problem.
26727 Exim's retry processing in this case is applied on a per-host (strictly, per IP
26728 address) basis, not on a per-message basis. Thus, if one message has recently
26729 been delayed, delivery of a new message to the same host is not immediately
26730 tried, but waits for the host's retry time to arrive. If the &%retry_defer%&
26731 log selector is set, the message
26732 .cindex "retry" "time not reached"
26733 &"retry time not reached"& is written to the main log whenever a delivery is
26734 skipped for this reason. Section &<<SECToutSMTPerr>>& contains more details of
26735 the handling of errors during remote deliveries.
26737 Retry processing applies to routing as well as to delivering, except as covered
26738 in the next paragraph. The retry rules do not distinguish between these
26739 actions. It is not possible, for example, to specify different behaviour for
26740 failures to route the domain &'snark.fict.example'& and failures to deliver to
26741 the host &'snark.fict.example'&. I didn't think anyone would ever need this
26742 added complication, so did not implement it. However, although they share the
26743 same retry rule, the actual retry times for routing and transporting a given
26744 domain are maintained independently.
26746 When a delivery is not part of a queue run (typically an immediate delivery on
26747 receipt of a message), the routers are always run, and local deliveries are
26748 always attempted, even if retry times are set for them. This makes for better
26749 behaviour if one particular message is causing problems (for example, causing
26750 quota overflow, or provoking an error in a filter file). If such a delivery
26751 suffers a temporary failure, the retry data is updated as normal, and
26752 subsequent delivery attempts from queue runs occur only when the retry time for
26753 the local address is reached.
26755 .section "Changing retry rules" "SECID157"
26756 If you change the retry rules in your configuration, you should consider
26757 whether or not to delete the retry data that is stored in Exim's spool area in
26758 files with names like &_db/retry_&. Deleting any of Exim's hints files is
26759 always safe; that is why they are called &"hints"&.
26761 The hints retry data contains suggested retry times based on the previous
26762 rules. In the case of a long-running problem with a remote host, it might
26763 record the fact that the host has timed out. If your new rules increase the
26764 timeout time for such a host, you should definitely remove the old retry data
26765 and let Exim recreate it, based on the new rules. Otherwise Exim might bounce
26766 messages that it should now be retaining.
26770 .section "Format of retry rules" "SECID158"
26771 .cindex "retry" "rules"
26772 Each retry rule occupies one line and consists of three or four parts,
26773 separated by white space: a pattern, an error name, an optional list of sender
26774 addresses, and a list of retry parameters. The pattern and sender lists must be
26775 enclosed in double quotes if they contain white space. The rules are searched
26776 in order until one is found where the pattern, error name, and sender list (if
26777 present) match the failing host or address, the error that occurred, and the
26778 message's sender, respectively.
26781 The pattern is any single item that may appear in an address list (see section
26782 &<<SECTaddresslist>>&). It is in fact processed as a one-item address list,
26783 which means that it is expanded before being tested against the address that
26784 has been delayed. A negated address list item is permitted. Address
26785 list processing treats a plain domain name as if it were preceded by &"*@"&,
26786 which makes it possible for many retry rules to start with just a domain. For
26789 lookingglass.fict.example * F,24h,30m;
26791 provides a rule for any address in the &'lookingglass.fict.example'& domain,
26794 alice@lookingglass.fict.example * F,24h,30m;
26796 applies only to temporary failures involving the local part &%alice%&.
26797 In practice, almost all rules start with a domain name pattern without a local
26800 .cindex "regular expressions" "in retry rules"
26801 &*Warning*&: If you use a regular expression in a retry rule pattern, it
26802 must match a complete address, not just a domain, because that is how regular
26803 expressions work in address lists.
26805 &`^\Nxyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Wrong%&
26806 &`^\N[^@]+@xyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Right%&
26810 .section "Choosing which retry rule to use for address errors" "SECID159"
26811 When Exim is looking for a retry rule after a routing attempt has failed (for
26812 example, after a DNS timeout), each line in the retry configuration is tested
26813 against the complete address only if &%retry_use_local_part%& is set for the
26814 router. Otherwise, only the domain is used, except when matching against a
26815 regular expression, when the local part of the address is replaced with &"*"&.
26816 A domain on its own can match a domain pattern, or a pattern that starts with
26817 &"*@"&. By default, &%retry_use_local_part%& is true for routers where
26818 &%check_local_user%& is true, and false for other routers.
26820 Similarly, when Exim is looking for a retry rule after a local delivery has
26821 failed (for example, after a mailbox full error), each line in the retry
26822 configuration is tested against the complete address only if
26823 &%retry_use_local_part%& is set for the transport (it defaults true for all
26826 .cindex "4&'xx'& responses" "retry rules for"
26827 However, when Exim is looking for a retry rule after a remote delivery attempt
26828 suffers an address error (a 4&'xx'& SMTP response for a recipient address), the
26829 whole address is always used as the key when searching the retry rules. The
26830 rule that is found is used to create a retry time for the combination of the
26831 failing address and the message's sender. It is the combination of sender and
26832 recipient that is delayed in subsequent queue runs until its retry time is
26833 reached. You can delay the recipient without regard to the sender by setting
26834 &%address_retry_include_sender%& false in the &(smtp)& transport but this can
26835 lead to problems with servers that regularly issue 4&'xx'& responses to RCPT
26840 .section "Choosing which retry rule to use for host and message errors" &&&
26842 For a temporary error that is not related to an individual address (for
26843 example, a connection timeout), each line in the retry configuration is checked
26844 twice. First, the name of the remote host is used as a domain name (preceded by
26845 &"*@"& when matching a regular expression). If this does not match the line,
26846 the domain from the email address is tried in a similar fashion. For example,
26847 suppose the MX records for &'a.b.c.example'& are
26849 a.b.c.example MX 5 x.y.z.example
26853 and the retry rules are
26855 p.q.r.example * F,24h,30m;
26856 a.b.c.example * F,4d,45m;
26858 and a delivery to the host &'x.y.z.example'& suffers a connection failure. The
26859 first rule matches neither the host nor the domain, so Exim looks at the second
26860 rule. This does not match the host, but it does match the domain, so it is used
26861 to calculate the retry time for the host &'x.y.z.example'&. Meanwhile, Exim
26862 tries to deliver to &'p.q.r.example'&. If this also suffers a host error, the
26863 first retry rule is used, because it matches the host.
26865 In other words, temporary failures to deliver to host &'p.q.r.example'& use the
26866 first rule to determine retry times, but for all the other hosts for the domain
26867 &'a.b.c.example'&, the second rule is used. The second rule is also used if
26868 routing to &'a.b.c.example'& suffers a temporary failure.
26870 &*Note*&: The host name is used when matching the patterns, not its IP address.
26871 However, if a message is routed directly to an IP address without the use of a
26872 host name, for example, if a &(manualroute)& router contains a setting such as:
26874 route_list = *.a.example 192.168.34.23
26876 then the &"host name"& that is used when searching for a retry rule is the
26877 textual form of the IP address.
26879 .section "Retry rules for specific errors" "SECID161"
26880 .cindex "retry" "specific errors; specifying"
26881 The second field in a retry rule is the name of a particular error, or an
26882 asterisk, which matches any error. The errors that can be tested for are:
26885 .vitem &%auth_failed%&
26886 Authentication failed when trying to send to a host in the
26887 &%hosts_require_auth%& list in an &(smtp)& transport.
26889 .vitem &%data_4xx%&
26890 A 4&'xx'& error was received for an outgoing DATA command, either immediately
26891 after the command, or after sending the message's data.
26893 .vitem &%mail_4xx%&
26894 A 4&'xx'& error was received for an outgoing MAIL command.
26896 .vitem &%rcpt_4xx%&
26897 A 4&'xx'& error was received for an outgoing RCPT command.
26900 For the three 4&'xx'& errors, either the first or both of the x's can be given
26901 as specific digits, for example: &`mail_45x`& or &`rcpt_436`&. For example, to
26902 recognize 452 errors given to RCPT commands for addresses in a certain domain,
26903 and have retries every ten minutes with a one-hour timeout, you could set up a
26904 retry rule of this form:
26906 the.domain.name rcpt_452 F,1h,10m
26908 These errors apply to both outgoing SMTP (the &(smtp)& transport) and outgoing
26909 LMTP (either the &(lmtp)& transport, or the &(smtp)& transport in LMTP mode).
26912 .vitem &%lost_connection%&
26913 A server unexpectedly closed the SMTP connection. There may, of course,
26914 legitimate reasons for this (host died, network died), but if it repeats a lot
26915 for the same host, it indicates something odd.
26918 A DNS lookup for a host failed.
26919 Note that a &%dnslookup%& router will need to have matched
26920 its &%fail_defer_domains%& option for this retry type to be usable.
26921 Also note that a &%manualroute%& router will probably need
26922 its &%host_find_failed%& option set to &%defer%&.
26924 .vitem &%refused_MX%&
26925 A connection to a host obtained from an MX record was refused.
26927 .vitem &%refused_A%&
26928 A connection to a host not obtained from an MX record was refused.
26931 A connection was refused.
26933 .vitem &%timeout_connect_MX%&
26934 A connection attempt to a host obtained from an MX record timed out.
26936 .vitem &%timeout_connect_A%&
26937 A connection attempt to a host not obtained from an MX record timed out.
26939 .vitem &%timeout_connect%&
26940 A connection attempt timed out.
26942 .vitem &%timeout_MX%&
26943 There was a timeout while connecting or during an SMTP session with a host
26944 obtained from an MX record.
26946 .vitem &%timeout_A%&
26947 There was a timeout while connecting or during an SMTP session with a host not
26948 obtained from an MX record.
26951 There was a timeout while connecting or during an SMTP session.
26953 .vitem &%tls_required%&
26954 The server was required to use TLS (it matched &%hosts_require_tls%& in the
26955 &(smtp)& transport), but either did not offer TLS, or it responded with 4&'xx'&
26956 to STARTTLS, or there was a problem setting up the TLS connection.
26959 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
26962 .vitem &%quota_%&<&'time'&>
26963 .cindex "quota" "error testing in retry rule"
26964 .cindex "retry" "quota error testing"
26965 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
26966 transport, and the mailbox has not been accessed for <&'time'&>. For example,
26967 &'quota_4d'& applies to a quota error when the mailbox has not been accessed
26971 .cindex "mailbox" "time of last read"
26972 The idea of &%quota_%&<&'time'&> is to make it possible to have shorter
26973 timeouts when the mailbox is full and is not being read by its owner. Ideally,
26974 it should be based on the last time that the user accessed the mailbox.
26975 However, it is not always possible to determine this. Exim uses the following
26979 If the mailbox is a single file, the time of last access (the &"atime"&) is
26980 used. As no new messages are being delivered (because the mailbox is over
26981 quota), Exim does not access the file, so this is the time of last user access.
26983 .cindex "maildir format" "time of last read"
26984 For a maildir delivery, the time of last modification of the &_new_&
26985 subdirectory is used. As the mailbox is over quota, no new files are created in
26986 the &_new_& subdirectory, because no new messages are being delivered. Any
26987 change to the &_new_& subdirectory is therefore assumed to be the result of an
26988 MUA moving a new message to the &_cur_& directory when it is first read. The
26989 time that is used is therefore the last time that the user read a new message.
26991 For other kinds of multi-file mailbox, the time of last access cannot be
26992 obtained, so a retry rule that uses this type of error field is never matched.
26995 The quota errors apply both to system-enforced quotas and to Exim's own quota
26996 mechanism in the &(appendfile)& transport. The &'quota'& error also applies
26997 when a local delivery is deferred because a partition is full (the ENOSPC
27002 .section "Retry rules for specified senders" "SECID162"
27003 .cindex "retry" "rules; sender-specific"
27004 You can specify retry rules that apply only when the failing message has a
27005 specific sender. In particular, this can be used to define retry rules that
27006 apply only to bounce messages. The third item in a retry rule can be of this
27009 &`senders=`&<&'address list'&>
27011 The retry timings themselves are then the fourth item. For example:
27013 * rcpt_4xx senders=: F,1h,30m
27015 matches recipient 4&'xx'& errors for bounce messages sent to any address at any
27016 host. If the address list contains white space, it must be enclosed in quotes.
27019 a.domain rcpt_452 senders="xb.dom : yc.dom" G,8h,10m,1.5
27021 &*Warning*&: This facility can be unhelpful if it is used for host errors
27022 (which do not depend on the recipient). The reason is that the sender is used
27023 only to match the retry rule. Once the rule has been found for a host error,
27024 its contents are used to set a retry time for the host, and this will apply to
27025 all messages, not just those with specific senders.
27027 When testing retry rules using &%-brt%&, you can supply a sender using the
27028 &%-f%& command line option, like this:
27030 exim -f "" -brt user@dom.ain
27032 If you do not set &%-f%& with &%-brt%&, a retry rule that contains a senders
27033 list is never matched.
27039 .section "Retry parameters" "SECID163"
27040 .cindex "retry" "parameters in rules"
27041 The third (or fourth, if a senders list is present) field in a retry rule is a
27042 sequence of retry parameter sets, separated by semicolons. Each set consists of
27044 <&'letter'&>,<&'cutoff time'&>,<&'arguments'&>
27046 The letter identifies the algorithm for computing a new retry time; the cutoff
27047 time is the time beyond which this algorithm no longer applies, and the
27048 arguments vary the algorithm's action. The cutoff time is measured from the
27049 time that the first failure for the domain (combined with the local part if
27050 relevant) was detected, not from the time the message was received.
27052 .cindex "retry" "algorithms"
27053 .cindex "retry" "fixed intervals"
27054 .cindex "retry" "increasing intervals"
27055 .cindex "retry" "random intervals"
27056 The available algorithms are:
27059 &'F'&: retry at fixed intervals. There is a single time parameter specifying
27062 &'G'&: retry at geometrically increasing intervals. The first argument
27063 specifies a starting value for the interval, and the second a multiplier, which
27064 is used to increase the size of the interval at each retry.
27066 &'H'&: retry at randomized intervals. The arguments are as for &'G'&. For each
27067 retry, the previous interval is multiplied by the factor in order to get a
27068 maximum for the next interval. The minimum interval is the first argument of
27069 the parameter, and an actual interval is chosen randomly between them. Such a
27070 rule has been found to be helpful in cluster configurations when all the
27071 members of the cluster restart at once, and may therefore synchronize their
27072 queue processing times.
27075 When computing the next retry time, the algorithm definitions are scanned in
27076 order until one whose cutoff time has not yet passed is reached. This is then
27077 used to compute a new retry time that is later than the current time. In the
27078 case of fixed interval retries, this simply means adding the interval to the
27079 current time. For geometrically increasing intervals, retry intervals are
27080 computed from the rule's parameters until one that is greater than the previous
27081 interval is found. The main configuration variable
27082 .cindex "limit" "retry interval"
27083 .cindex "retry" "interval, maximum"
27084 .oindex "&%retry_interval_max%&"
27085 &%retry_interval_max%& limits the maximum interval between retries. It
27086 cannot be set greater than &`24h`&, which is its default value.
27088 A single remote domain may have a number of hosts associated with it, and each
27089 host may have more than one IP address. Retry algorithms are selected on the
27090 basis of the domain name, but are applied to each IP address independently. If,
27091 for example, a host has two IP addresses and one is unusable, Exim will
27092 generate retry times for it and will not try to use it until its next retry
27093 time comes. Thus the good IP address is likely to be tried first most of the
27096 .cindex "hints database" "use for retrying"
27097 Retry times are hints rather than promises. Exim does not make any attempt to
27098 run deliveries exactly at the computed times. Instead, a queue runner process
27099 starts delivery processes for delayed messages periodically, and these attempt
27100 new deliveries only for those addresses that have passed their next retry time.
27101 If a new message arrives for a deferred address, an immediate delivery attempt
27102 occurs only if the address has passed its retry time. In the absence of new
27103 messages, the minimum time between retries is the interval between queue runner
27104 processes. There is not much point in setting retry times of five minutes if
27105 your queue runners happen only once an hour, unless there are a significant
27106 number of incoming messages (which might be the case on a system that is
27107 sending everything to a smart host, for example).
27109 The data in the retry hints database can be inspected by using the
27110 &'exim_dumpdb'& or &'exim_fixdb'& utility programs (see chapter
27111 &<<CHAPutils>>&). The latter utility can also be used to change the data. The
27112 &'exinext'& utility script can be used to find out what the next retry times
27113 are for the hosts associated with a particular mail domain, and also for local
27114 deliveries that have been deferred.
27117 .section "Retry rule examples" "SECID164"
27118 Here are some example retry rules:
27120 alice@wonderland.fict.example quota_5d F,7d,3h
27121 wonderland.fict.example quota_5d
27122 wonderland.fict.example * F,1h,15m; G,2d,1h,2;
27123 lookingglass.fict.example * F,24h,30m;
27124 * refused_A F,2h,20m;
27125 * * F,2h,15m; G,16h,1h,1.5; F,5d,8h
27127 The first rule sets up special handling for mail to
27128 &'alice@wonderland.fict.example'& when there is an over-quota error and the
27129 mailbox has not been read for at least 5 days. Retries continue every three
27130 hours for 7 days. The second rule handles over-quota errors for all other local
27131 parts at &'wonderland.fict.example'&; the absence of a local part has the same
27132 effect as supplying &"*@"&. As no retry algorithms are supplied, messages that
27133 fail are bounced immediately if the mailbox has not been read for at least 5
27136 The third rule handles all other errors at &'wonderland.fict.example'&; retries
27137 happen every 15 minutes for an hour, then with geometrically increasing
27138 intervals until two days have passed since a delivery first failed. After the
27139 first hour there is a delay of one hour, then two hours, then four hours, and
27140 so on (this is a rather extreme example).
27142 The fourth rule controls retries for the domain &'lookingglass.fict.example'&.
27143 They happen every 30 minutes for 24 hours only. The remaining two rules handle
27144 all other domains, with special action for connection refusal from hosts that
27145 were not obtained from an MX record.
27147 The final rule in a retry configuration should always have asterisks in the
27148 first two fields so as to provide a general catch-all for any addresses that do
27149 not have their own special handling. This example tries every 15 minutes for 2
27150 hours, then with intervals starting at one hour and increasing by a factor of
27151 1.5 up to 16 hours, then every 8 hours up to 5 days.
27155 .section "Timeout of retry data" "SECID165"
27156 .cindex "timeout" "of retry data"
27157 .oindex "&%retry_data_expire%&"
27158 .cindex "hints database" "data expiry"
27159 .cindex "retry" "timeout of data"
27160 Exim timestamps the data that it writes to its retry hints database. When it
27161 consults the data during a delivery it ignores any that is older than the value
27162 set in &%retry_data_expire%& (default 7 days). If, for example, a host hasn't
27163 been tried for 7 days, Exim will try to deliver to it immediately a message
27164 arrives, and if that fails, it will calculate a retry time as if it were
27165 failing for the first time.
27167 This improves the behaviour for messages routed to rarely-used hosts such as MX
27168 backups. If such a host was down at one time, and happens to be down again when
27169 Exim tries a month later, using the old retry data would imply that it had been
27170 down all the time, which is not a justified assumption.
27172 If a host really is permanently dead, this behaviour causes a burst of retries
27173 every now and again, but only if messages routed to it are rare. If there is a
27174 message at least once every 7 days the retry data never expires.
27179 .section "Long-term failures" "SECID166"
27180 .cindex "delivery failure, long-term"
27181 .cindex "retry" "after long-term failure"
27182 Special processing happens when an email address has been failing for so long
27183 that the cutoff time for the last algorithm is reached. For example, using the
27184 default retry rule:
27186 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
27188 the cutoff time is four days. Reaching the retry cutoff is independent of how
27189 long any specific message has been failing; it is the length of continuous
27190 failure for the recipient address that counts.
27192 When the cutoff time is reached for a local delivery, or for all the IP
27193 addresses associated with a remote delivery, a subsequent delivery failure
27194 causes Exim to give up on the address, and a bounce message is generated.
27195 In order to cater for new messages that use the failing address, a next retry
27196 time is still computed from the final algorithm, and is used as follows:
27198 For local deliveries, one delivery attempt is always made for any subsequent
27199 messages. If this delivery fails, the address fails immediately. The
27200 post-cutoff retry time is not used.
27202 .cindex "final cutoff" "retries, controlling"
27203 .cindex retry "final cutoff"
27204 If the delivery is remote, there are two possibilities, controlled by the
27205 .oindex "&%delay_after_cutoff%&"
27206 &%delay_after_cutoff%& option of the &(smtp)& transport. The option is true by
27207 default. Until the post-cutoff retry time for one of the IP addresses,
27208 as set by the &%retry_data_expire%& option, is
27209 reached, the failing email address is bounced immediately, without a delivery
27210 attempt taking place. After that time, one new delivery attempt is made to
27211 those IP addresses that are past their retry times, and if that still fails,
27212 the address is bounced and new retry times are computed.
27214 In other words, when all the hosts for a given email address have been failing
27215 for a long time, Exim bounces rather then defers until one of the hosts' retry
27216 times is reached. Then it tries once, and bounces if that attempt fails. This
27217 behaviour ensures that few resources are wasted in repeatedly trying to deliver
27218 to a broken destination, but if the host does recover, Exim will eventually
27221 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
27222 addresses are past their final cutoff time, Exim tries to deliver to those IP
27223 addresses that have not been tried since the message arrived. If there are
27224 no suitable IP addresses, or if they all fail, the address is bounced. In other
27225 words, it does not delay when a new message arrives, but tries the expired
27226 addresses immediately, unless they have been tried since the message arrived.
27227 If there is a continuous stream of messages for the failing domains, setting
27228 &%delay_after_cutoff%& false means that there will be many more attempts to
27229 deliver to permanently failing IP addresses than when &%delay_after_cutoff%& is
27232 .section "Deliveries that work intermittently" "SECID167"
27233 .cindex "retry" "intermittently working deliveries"
27234 Some additional logic is needed to cope with cases where a host is
27235 intermittently available, or when a message has some attribute that prevents
27236 its delivery when others to the same address get through. In this situation,
27237 because some messages are successfully delivered, the &"retry clock"& for the
27238 host or address keeps getting reset by the successful deliveries, and so
27239 failing messages remain in the queue for ever because the cutoff time is never
27242 Two exceptional actions are applied to prevent this happening. The first
27243 applies to errors that are related to a message rather than a remote host.
27244 Section &<<SECToutSMTPerr>>& has a discussion of the different kinds of error;
27245 examples of message-related errors are 4&'xx'& responses to MAIL or DATA
27246 commands, and quota failures. For this type of error, if a message's arrival
27247 time is earlier than the &"first failed"& time for the error, the earlier time
27248 is used when scanning the retry rules to decide when to try next and when to
27249 time out the address.
27251 The exceptional second action applies in all cases. If a message has been on
27252 the queue for longer than the cutoff time of any applicable retry rule for a
27253 given address, a delivery is attempted for that address, even if it is not yet
27254 time, and if this delivery fails, the address is timed out. A new retry time is
27255 not computed in this case, so that other messages for the same address are
27256 considered immediately.
27257 .ecindex IIDretconf1
27258 .ecindex IIDregconf2
27265 . ////////////////////////////////////////////////////////////////////////////
27266 . ////////////////////////////////////////////////////////////////////////////
27268 .chapter "SMTP authentication" "CHAPSMTPAUTH"
27269 .scindex IIDauthconf1 "SMTP" "authentication configuration"
27270 .scindex IIDauthconf2 "authentication"
27271 The &"authenticators"& section of Exim's runtime configuration is concerned
27272 with SMTP authentication. This facility is an extension to the SMTP protocol,
27273 described in RFC 2554, which allows a client SMTP host to authenticate itself
27274 to a server. This is a common way for a server to recognize clients that are
27275 permitted to use it as a relay. SMTP authentication is not of relevance to the
27276 transfer of mail between servers that have no managerial connection with each
27279 The name of an authenticator is limited to be &drivernamemax; ASCII characters long;
27280 prior to Exim 4.95 names would be silently truncated at this length, but now
27283 .cindex "AUTH" "description of"
27284 .cindex "ESMTP extensions" AUTH
27285 Very briefly, the way SMTP authentication works is as follows:
27288 The server advertises a number of authentication &'mechanisms'& in response to
27289 the client's EHLO command.
27291 The client issues an AUTH command, naming a specific mechanism. The command
27292 may, optionally, contain some authentication data.
27294 The server may issue one or more &'challenges'&, to which the client must send
27295 appropriate responses. In simple authentication mechanisms, the challenges are
27296 just prompts for user names and passwords. The server does not have to issue
27297 any challenges &-- in some mechanisms the relevant data may all be transmitted
27298 with the AUTH command.
27300 The server either accepts or denies authentication.
27302 If authentication succeeds, the client may optionally make use of the AUTH
27303 option on the MAIL command to pass an authenticated sender in subsequent
27304 mail transactions. Authentication lasts for the remainder of the SMTP
27307 If authentication fails, the client may give up, or it may try a different
27308 authentication mechanism, or it may try transferring mail over the
27309 unauthenticated connection.
27312 If you are setting up a client, and want to know which authentication
27313 mechanisms the server supports, you can use Telnet to connect to port 25 (the
27314 SMTP port) on the server, and issue an EHLO command. The response to this
27315 includes the list of supported mechanisms. For example:
27317 &`$ `&&*&`telnet server.example 25`&*&
27318 &`Trying 192.168.34.25...`&
27319 &`Connected to server.example.`&
27320 &`Escape character is '^]'.`&
27321 &`220 server.example ESMTP Exim 4.20 ...`&
27322 &*&`ehlo client.example`&*&
27323 &`250-server.example Hello client.example [10.8.4.5]`&
27324 &`250-SIZE 52428800`&
27329 The second-last line of this example output shows that the server supports
27330 authentication using the PLAIN mechanism. In Exim, the different authentication
27331 mechanisms are configured by specifying &'authenticator'& drivers. Like the
27332 routers and transports, which authenticators are included in the binary is
27333 controlled by build-time definitions. The following are currently available,
27334 included by setting
27337 AUTH_CYRUS_SASL=yes
27341 AUTH_HEIMDAL_GSSAPI=yes
27346 in &_Local/Makefile_&, respectively. The first of these supports the CRAM-MD5
27347 authentication mechanism (RFC 2195), and the second provides an interface to
27348 the Cyrus SASL authentication library.
27349 The third is an interface to Dovecot's authentication system, delegating the
27350 work via a socket interface.
27351 The fourth provides for negotiation of authentication done via non-SMTP means,
27352 as defined by RFC 4422 Appendix A.
27353 The fifth provides an interface to the GNU SASL authentication library, which
27354 provides mechanisms but typically not data sources.
27355 The sixth provides direct access to Heimdal GSSAPI, geared for Kerberos, but
27356 supporting setting a server keytab.
27357 The seventh can be configured to support
27358 the PLAIN authentication mechanism (RFC 2595) or the LOGIN mechanism, which is
27359 not formally documented, but used by several MUAs.
27360 The eighth authenticator
27361 supports Microsoft's &'Secure Password Authentication'& mechanism.
27362 The last is an Exim authenticator but not an SMTP one;
27363 instead it can use information from a TLS negotiation.
27365 The authenticators are configured using the same syntax as other drivers (see
27366 section &<<SECTfordricon>>&). If no authenticators are required, no
27367 authentication section need be present in the configuration file. Each
27368 authenticator can in principle have both server and client functions. When Exim
27369 is receiving SMTP mail, it is acting as a server; when it is sending out
27370 messages over SMTP, it is acting as a client. Authenticator configuration
27371 options are provided for use in both these circumstances.
27373 To make it clear which options apply to which situation, the prefixes
27374 &%server_%& and &%client_%& are used on option names that are specific to
27375 either the server or the client function, respectively. Server and client
27376 functions are disabled if none of their options are set. If an authenticator is
27377 to be used for both server and client functions, a single definition, using
27378 both sets of options, is required. For example:
27382 public_name = CRAM-MD5
27383 server_secret = ${if eq{$auth1}{ph10}{secret1}fail}
27385 client_secret = secret2
27387 The &%server_%& option is used when Exim is acting as a server, and the
27388 &%client_%& options when it is acting as a client.
27390 Descriptions of the individual authenticators are given in subsequent chapters.
27391 The remainder of this chapter covers the generic options for the
27392 authenticators, followed by general discussion of the way authentication works
27395 &*Beware:*& the meaning of &$auth1$&, &$auth2$&, ... varies on a per-driver and
27396 per-mechanism basis. Please read carefully to determine which variables hold
27397 account labels such as usercodes and which hold passwords or other
27398 authenticating data.
27400 Note that some mechanisms support two different identifiers for accounts: the
27401 &'authentication id'& and the &'authorization id'&. The contractions &'authn'&
27402 and &'authz'& are commonly encountered. The American spelling is standard here.
27403 Conceptually, authentication data such as passwords are tied to the identifier
27404 used to authenticate; servers may have rules to permit one user to act as a
27405 second user, so that after login the session is treated as though that second
27406 user had logged in. That second user is the &'authorization id'&. A robust
27407 configuration might confirm that the &'authz'& field is empty or matches the
27408 &'authn'& field. Often this is just ignored. The &'authn'& can be considered
27409 as verified data, the &'authz'& as an unverified request which the server might
27412 A &'realm'& is a text string, typically a domain name, presented by a server
27413 to a client to help it select an account and credentials to use. In some
27414 mechanisms, the client and server provably agree on the realm, but clients
27415 typically can not treat the realm as secure data to be blindly trusted.
27419 .section "Generic options for authenticators" "SECID168"
27420 .cindex "authentication" "generic options"
27421 .cindex "options" "generic; for authenticators"
27423 .option client_condition authenticators string&!! unset
27424 When Exim is authenticating as a client, it skips any authenticator whose
27425 &%client_condition%& expansion yields &"0"&, &"no"&, or &"false"&. This can be
27426 used, for example, to skip plain text authenticators when the connection is not
27427 encrypted by a setting such as:
27429 client_condition = ${if !eq{$tls_out_cipher}{}}
27433 .option client_set_id authenticators string&!! unset
27434 When client authentication succeeds, this condition is expanded; the
27435 result is used in the log lines for outbound messages.
27436 Typically it will be the user name used for authentication.
27439 .option driver authenticators string unset
27440 This option must always be set. It specifies which of the available
27441 authenticators is to be used.
27444 .option public_name authenticators string unset
27445 This option specifies the name of the authentication mechanism that the driver
27446 implements, and by which it is known to the outside world. These names should
27447 contain only upper case letters, digits, underscores, and hyphens (RFC 2222),
27448 but Exim in fact matches them caselessly. If &%public_name%& is not set, it
27449 defaults to the driver's instance name.
27452 .option server_advertise_condition authenticators string&!! unset
27453 When a server is about to advertise an authentication mechanism, the condition
27454 is expanded. If it yields the empty string, &"0"&, &"no"&, or &"false"&, the
27455 mechanism is not advertised.
27456 If the expansion fails, the mechanism is not advertised. If the failure was not
27457 forced, and was not caused by a lookup defer, the incident is logged.
27458 See section &<<SECTauthexiser>>& below for further discussion.
27461 .option server_condition authenticators string&!! unset
27462 This option must be set for a &%plaintext%& server authenticator, where it
27463 is used directly to control authentication. See section &<<SECTplainserver>>&
27466 For the &(gsasl)& authenticator, this option is required for various
27467 mechanisms; see chapter &<<CHAPgsasl>>& for details.
27469 For the other authenticators, &%server_condition%& can be used as an additional
27470 authentication or authorization mechanism that is applied after the other
27471 authenticator conditions succeed. If it is set, it is expanded when the
27472 authenticator would otherwise return a success code. If the expansion is forced
27473 to fail, authentication fails. Any other expansion failure causes a temporary
27474 error code to be returned. If the result of a successful expansion is an empty
27475 string, &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
27476 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds. For any
27477 other result, a temporary error code is returned, with the expanded string as
27481 .option server_debug_print authenticators string&!! unset
27482 If this option is set and authentication debugging is enabled (see the &%-d%&
27483 command line option), the string is expanded and included in the debugging
27484 output when the authenticator is run as a server. This can help with checking
27485 out the values of variables.
27486 If expansion of the string fails, the error message is written to the debugging
27487 output, and Exim carries on processing.
27490 .option server_set_id authenticators string&!! unset
27491 .vindex "&$authenticated_id$&"
27492 .vindex "&$authenticated_fail_id$&"
27493 When an Exim server successfully authenticates a client, this string is
27494 expanded using data from the authentication, and preserved for any incoming
27495 messages in the variable &$authenticated_id$&. It is also included in the log
27496 lines for incoming messages. For example, a user/password authenticator
27497 configuration might preserve the user name that was used to authenticate, and
27498 refer to it subsequently during delivery of the message.
27499 On a failing authentication the expansion result is instead saved in
27500 the &$authenticated_fail_id$& variable.
27501 If expansion fails, the option is ignored.
27504 .option server_mail_auth_condition authenticators string&!! unset
27505 This option allows a server to discard authenticated sender addresses supplied
27506 as part of MAIL commands in SMTP connections that are authenticated by the
27507 driver on which &%server_mail_auth_condition%& is set. The option is not used
27508 as part of the authentication process; instead its (unexpanded) value is
27509 remembered for later use.
27510 How it is used is described in the following section.
27516 .section "The AUTH parameter on MAIL commands" "SECTauthparamail"
27517 .cindex "authentication" "sender; authenticated"
27518 .cindex "AUTH" "on MAIL command"
27519 When a client supplied an AUTH= item on a MAIL command, Exim applies
27520 the following checks before accepting it as the authenticated sender of the
27524 If the connection is not using extended SMTP (that is, HELO was used rather
27525 than EHLO), the use of AUTH= is a syntax error.
27527 If the value of the AUTH= parameter is &"<>"&, it is ignored.
27529 .vindex "&$authenticated_sender$&"
27530 If &%acl_smtp_mailauth%& is defined, the ACL it specifies is run. While it is
27531 running, the value of &$authenticated_sender$& is set to the value obtained
27532 from the AUTH= parameter. If the ACL does not yield &"accept"&, the value of
27533 &$authenticated_sender$& is deleted. The &%acl_smtp_mailauth%& ACL may not
27534 return &"drop"& or &"discard"&. If it defers, a temporary error code (451) is
27535 given for the MAIL command.
27537 If &%acl_smtp_mailauth%& is not defined, the value of the AUTH= parameter
27538 is accepted and placed in &$authenticated_sender$& only if the client has
27541 If the AUTH= value was accepted by either of the two previous rules, and
27542 the client has authenticated, and the authenticator has a setting for the
27543 &%server_mail_auth_condition%&, the condition is checked at this point. The
27544 valued that was saved from the authenticator is expanded. If the expansion
27545 fails, or yields an empty string, &"0"&, &"no"&, or &"false"&, the value of
27546 &$authenticated_sender$& is deleted. If the expansion yields any other value,
27547 the value of &$authenticated_sender$& is retained and passed on with the
27552 When &$authenticated_sender$& is set for a message, it is passed on to other
27553 hosts to which Exim authenticates as a client. Do not confuse this value with
27554 &$authenticated_id$&, which is a string obtained from the authentication
27555 process, and which is not usually a complete email address.
27557 .vindex "&$sender_address$&"
27558 Whenever an AUTH= value is ignored, the incident is logged. The ACL for
27559 MAIL, if defined, is run after AUTH= is accepted or ignored. It can
27560 therefore make use of &$authenticated_sender$&. The converse is not true: the
27561 value of &$sender_address$& is not yet set up when the &%acl_smtp_mailauth%&
27566 .section "Authentication on an Exim server" "SECTauthexiser"
27567 .cindex "authentication" "on an Exim server"
27568 When Exim receives an EHLO command, it advertises the public names of those
27569 authenticators that are configured as servers, subject to the following
27573 The client host must match &%auth_advertise_hosts%& (default *).
27575 If the &%server_advertise_condition%& option is set, its expansion must not
27576 yield the empty string, &"0"&, &"no"&, or &"false"&.
27579 The order in which the authenticators are defined controls the order in which
27580 the mechanisms are advertised.
27582 Some mail clients (for example, some versions of Netscape) require the user to
27583 provide a name and password for authentication whenever AUTH is advertised,
27584 even though authentication may not in fact be needed (for example, Exim may be
27585 set up to allow unconditional relaying from the client by an IP address check).
27586 You can make such clients more friendly by not advertising AUTH to them.
27587 For example, if clients on the 10.9.8.0/24 network are permitted (by the ACL
27588 that runs for RCPT) to relay without authentication, you should set
27590 auth_advertise_hosts = ! 10.9.8.0/24
27592 so that no authentication mechanisms are advertised to them.
27594 The &%server_advertise_condition%& controls the advertisement of individual
27595 authentication mechanisms. For example, it can be used to restrict the
27596 advertisement of a particular mechanism to encrypted connections, by a setting
27599 server_advertise_condition = ${if eq{$tls_in_cipher}{}{no}{yes}}
27601 .vindex "&$tls_in_cipher$&"
27602 If the session is encrypted, &$tls_in_cipher$& is not empty, and so the expansion
27603 yields &"yes"&, which allows the advertisement to happen.
27605 When an Exim server receives an AUTH command from a client, it rejects it
27606 immediately if AUTH was not advertised in response to an earlier EHLO
27607 command. This is the case if
27610 The client host does not match &%auth_advertise_hosts%&; or
27612 No authenticators are configured with server options; or
27614 Expansion of &%server_advertise_condition%& blocked the advertising of all the
27615 server authenticators.
27619 Otherwise, Exim runs the ACL specified by &%acl_smtp_auth%& in order
27620 to decide whether to accept the command. If &%acl_smtp_auth%& is not set,
27621 AUTH is accepted from any client host.
27623 If AUTH is not rejected by the ACL, Exim searches its configuration for a
27624 server authentication mechanism that was advertised in response to EHLO and
27625 that matches the one named in the AUTH command. If it finds one, it runs
27626 the appropriate authentication protocol, and authentication either succeeds or
27627 fails. If there is no matching advertised mechanism, the AUTH command is
27628 rejected with a 504 error.
27630 .vindex "&$received_protocol$&"
27631 .vindex "&$sender_host_authenticated$&"
27632 When a message is received from an authenticated host, the value of
27633 &$received_protocol$& is set to &"esmtpa"& or &"esmtpsa"& instead of &"esmtp"&
27634 or &"esmtps"&, and &$sender_host_authenticated$& contains the name (not the
27635 public name) of the authenticator driver that successfully authenticated the
27636 client from which the message was received. This variable is empty if there was
27637 no successful authentication.
27639 .cindex authentication "expansion item"
27640 Successful authentication sets up information used by the
27641 &%authresults%& expansion item.
27646 .section "Testing server authentication" "SECID169"
27647 .cindex "authentication" "testing a server"
27648 .cindex "AUTH" "testing a server"
27649 .cindex "base64 encoding" "creating authentication test data"
27650 Exim's &%-bh%& option can be useful for testing server authentication
27651 configurations. The data for the AUTH command has to be sent using base64
27652 encoding. A quick way to produce such data for testing is the following Perl
27656 printf ("%s", encode_base64(eval "\"$ARGV[0]\""));
27658 .cindex "binary zero" "in authentication data"
27659 This interprets its argument as a Perl string, and then encodes it. The
27660 interpretation as a Perl string allows binary zeros, which are required for
27661 some kinds of authentication, to be included in the data. For example, a
27662 command line to run this script on such data might be
27664 encode '\0user\0password'
27666 Note the use of single quotes to prevent the shell interpreting the
27667 backslashes, so that they can be interpreted by Perl to specify characters
27668 whose code value is zero.
27670 &*Warning 1*&: If either of the user or password strings starts with an octal
27671 digit, you must use three zeros instead of one after the leading backslash. If
27672 you do not, the octal digit that starts your string will be incorrectly
27673 interpreted as part of the code for the first character.
27675 &*Warning 2*&: If there are characters in the strings that Perl interprets
27676 specially, you must use a Perl escape to prevent them being misinterpreted. For
27677 example, a command such as
27679 encode '\0user@domain.com\0pas$$word'
27681 gives an incorrect answer because of the unescaped &"@"& and &"$"& characters.
27683 If you have the &%mimencode%& command installed, another way to produce
27684 base64-encoded strings is to run the command
27686 echo -e -n `\0user\0password' | mimencode
27688 The &%-e%& option of &%echo%& enables the interpretation of backslash escapes
27689 in the argument, and the &%-n%& option specifies no newline at the end of its
27690 output. However, not all versions of &%echo%& recognize these options, so you
27691 should check your version before relying on this suggestion.
27695 .section "Authentication by an Exim client" "SECID170"
27696 .cindex "authentication" "on an Exim client"
27697 The &(smtp)& transport has two options called &%hosts_require_auth%& and
27698 &%hosts_try_auth%&. When the &(smtp)& transport connects to a server that
27699 announces support for authentication, and the host matches an entry in either
27700 of these options, Exim (as a client) tries to authenticate as follows:
27703 For each authenticator that is configured as a client, in the order in which
27704 they are defined in the configuration, it searches the authentication
27705 mechanisms announced by the server for one whose name matches the public name
27706 of the authenticator.
27709 .vindex "&$host_address$&"
27710 When it finds one that matches, it runs the authenticator's client code. The
27711 variables &$host$& and &$host_address$& are available for any string expansions
27712 that the client might do. They are set to the server's name and IP address. If
27713 any expansion is forced to fail, the authentication attempt is abandoned, and
27714 Exim moves on to the next authenticator. Otherwise an expansion failure causes
27715 delivery to be deferred.
27717 If the result of the authentication attempt is a temporary error or a timeout,
27718 Exim abandons trying to send the message to the host for the moment. It will
27719 try again later. If there are any backup hosts available, they are tried in the
27722 If the response to authentication is a permanent error (5&'xx'& code), Exim
27723 carries on searching the list of authenticators and tries another one if
27724 possible. If all authentication attempts give permanent errors, or if there are
27725 no attempts because no mechanisms match (or option expansions force failure),
27726 what happens depends on whether the host matches &%hosts_require_auth%& or
27727 &%hosts_try_auth%&. In the first case, a temporary error is generated, and
27728 delivery is deferred. The error can be detected in the retry rules, and thereby
27729 turned into a permanent error if you wish. In the second case, Exim tries to
27730 deliver the message unauthenticated.
27733 Note that the hostlist test for whether to do authentication can be
27734 confused if name-IP lookups change between the time the peer is decided
27735 upon and the time that the transport runs. For example, with a manualroute
27736 router given a host name, and with DNS "round-robin" used by that name: if
27737 the local resolver cache times out between the router and the transport
27738 running, the transport may get an IP for the name for its authentication
27739 check which does not match the connection peer IP.
27740 No authentication will then be done, despite the names being identical.
27742 For such cases use a separate transport which always authenticates.
27744 .cindex "AUTH" "on MAIL command"
27745 When Exim has authenticated itself to a remote server, it adds the AUTH
27746 parameter to the MAIL commands it sends, if it has an authenticated sender for
27747 the message. If the message came from a remote host, the authenticated sender
27748 is the one that was receiving on an incoming MAIL command, provided that the
27749 incoming connection was authenticated and the &%server_mail_auth%& condition
27750 allowed the authenticated sender to be retained. If a local process calls Exim
27751 to send a message, the sender address that is built from the login name and
27752 &%qualify_domain%& is treated as authenticated. However, if the
27753 &%authenticated_sender%& option is set on the &(smtp)& transport, it overrides
27754 the authenticated sender that was received with the message.
27755 .ecindex IIDauthconf1
27756 .ecindex IIDauthconf2
27763 . ////////////////////////////////////////////////////////////////////////////
27764 . ////////////////////////////////////////////////////////////////////////////
27766 .chapter "The plaintext authenticator" "CHAPplaintext"
27767 .scindex IIDplaiauth1 "&(plaintext)& authenticator"
27768 .scindex IIDplaiauth2 "authenticators" "&(plaintext)&"
27769 The &(plaintext)& authenticator can be configured to support the PLAIN and
27770 LOGIN authentication mechanisms, both of which transfer authentication data as
27771 plain (unencrypted) text (though base64 encoded). The use of plain text is a
27772 security risk; you are strongly advised to insist on the use of SMTP encryption
27773 (see chapter &<<CHAPTLS>>&) if you use the PLAIN or LOGIN mechanisms. If you do
27774 use unencrypted plain text, you should not use the same passwords for SMTP
27775 connections as you do for login accounts.
27777 .section "Avoiding cleartext use" "SECTplain_TLS"
27778 The following generic option settings will disable &(plaintext)& authenticators when
27779 TLS is not being used:
27781 server_advertise_condition = ${if def:tls_in_cipher }
27782 client_condition = ${if def:tls_out_cipher}
27785 &*Note*&: a plaintext SMTP AUTH done inside TLS is not vulnerable to casual snooping,
27786 but is still vulnerable to a Man In The Middle attack unless certificates
27787 (including their names) have been properly verified.
27789 .section "Plaintext server options" "SECID171"
27790 .cindex "options" "&(plaintext)& authenticator (server)"
27791 When configured as a server, &(plaintext)& uses the following options:
27793 .option server_condition authenticators string&!! unset
27794 This is actually a global authentication option, but it must be set in order to
27795 configure the &(plaintext)& driver as a server. Its use is described below.
27797 .option server_prompts plaintext "string list&!!" unset
27798 The contents of this option, after expansion, must be a colon-separated list of
27799 prompt strings. If expansion fails, a temporary authentication rejection is
27802 .section "Using plaintext in a server" "SECTplainserver"
27803 .cindex "AUTH" "in &(plaintext)& authenticator"
27804 .cindex "binary zero" "in &(plaintext)& authenticator"
27805 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
27806 "in &(plaintext)& authenticator"
27807 .vindex "&$auth1$&, &$auth2$&, etc"
27808 .cindex "base64 encoding" "in &(plaintext)& authenticator"
27810 When running as a server, &(plaintext)& performs the authentication test by
27811 expanding a string. The data sent by the client with the AUTH command, or in
27812 response to subsequent prompts, is base64 encoded, and so may contain any byte
27813 values when decoded. If any data is supplied with the command, it is treated as
27814 a list of strings, separated by NULs (binary zeros), the first three of which
27815 are placed in the expansion variables &$auth1$&, &$auth2$&, and &$auth3$&
27816 (neither LOGIN nor PLAIN uses more than three strings).
27818 For compatibility with previous releases of Exim, the values are also placed in
27819 the expansion variables &$1$&, &$2$&, and &$3$&. However, the use of these
27820 variables for this purpose is now deprecated, as it can lead to confusion in
27821 string expansions that also use them for other things.
27823 If there are more strings in &%server_prompts%& than the number of strings
27824 supplied with the AUTH command, the remaining prompts are used to obtain more
27825 data. Each response from the client may be a list of NUL-separated strings.
27827 .vindex "&$authenticated_id$&"
27828 Once a sufficient number of data strings have been received,
27829 &%server_condition%& is expanded. If the expansion is forced to fail,
27830 authentication fails. Any other expansion failure causes a temporary error code
27831 to be returned. If the result of a successful expansion is an empty string,
27832 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
27833 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
27834 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
27835 For any other result, a temporary error code is returned, with the expanded
27836 string as the error text.
27838 &*Warning*&: If you use a lookup in the expansion to find the user's
27839 password, be sure to make the authentication fail if the user is unknown.
27840 There are good and bad examples at the end of the next section.
27844 .section "The PLAIN authentication mechanism" "SECID172"
27845 .cindex "PLAIN authentication mechanism"
27846 .cindex authentication PLAIN
27847 .cindex "binary zero" "in &(plaintext)& authenticator"
27848 The PLAIN authentication mechanism (RFC 2595) specifies that three strings be
27849 sent as one item of data (that is, one combined string containing two NUL
27850 separators). The data is sent either as part of the AUTH command, or
27851 subsequently in response to an empty prompt from the server.
27853 The second and third strings are a user name and a corresponding password.
27854 Using a single fixed user name and password as an example, this could be
27855 configured as follows:
27859 public_name = PLAIN
27861 server_condition = \
27862 ${if and {{eq{$auth2}{username}}{eq{$auth3}{mysecret}}}}
27863 server_set_id = $auth2
27865 Note that the default result strings from &%if%& (&"true"& or an empty string)
27866 are exactly what we want here, so they need not be specified. Obviously, if the
27867 password contains expansion-significant characters such as dollar, backslash,
27868 or closing brace, they have to be escaped.
27870 The &%server_prompts%& setting specifies a single, empty prompt (empty items at
27871 the end of a string list are ignored). If all the data comes as part of the
27872 AUTH command, as is commonly the case, the prompt is not used. This
27873 authenticator is advertised in the response to EHLO as
27877 and a client host can authenticate itself by sending the command
27879 AUTH PLAIN AHVzZXJuYW1lAG15c2VjcmV0
27881 As this contains three strings (more than the number of prompts), no further
27882 data is required from the client. Alternatively, the client may just send
27886 to initiate authentication, in which case the server replies with an empty
27887 prompt. The client must respond with the combined data string.
27889 The data string is base64 encoded, as required by the RFC. This example,
27890 when decoded, is <&'NUL'&>&`username`&<&'NUL'&>&`mysecret`&, where <&'NUL'&>
27891 represents a zero byte. This is split up into three strings, the first of which
27892 is empty. The &%server_condition%& option in the authenticator checks that the
27893 second two are &`username`& and &`mysecret`& respectively.
27895 Having just one fixed user name and password, as in this example, is not very
27896 realistic, though for a small organization with only a handful of
27897 authenticating clients it could make sense.
27899 A more sophisticated instance of this authenticator could use the user name in
27900 &$auth2$& to look up a password in a file or database, and maybe do an encrypted
27901 comparison (see &%crypteq%& in chapter &<<CHAPexpand>>&). Here is a example of
27902 this approach, where the passwords are looked up in a DBM file. &*Warning*&:
27903 This is an incorrect example:
27905 server_condition = \
27906 ${if eq{$auth3}{${lookup{$auth2}dbm{/etc/authpwd}}}}
27908 The expansion uses the user name (&$auth2$&) as the key to look up a password,
27909 which it then compares to the supplied password (&$auth3$&). Why is this example
27910 incorrect? It works fine for existing users, but consider what happens if a
27911 non-existent user name is given. The lookup fails, but as no success/failure
27912 strings are given for the lookup, it yields an empty string. Thus, to defeat
27913 the authentication, all a client has to do is to supply a non-existent user
27914 name and an empty password. The correct way of writing this test is:
27916 server_condition = ${lookup{$auth2}dbm{/etc/authpwd}\
27917 {${if eq{$value}{$auth3}}} {false}}
27919 In this case, if the lookup succeeds, the result is checked; if the lookup
27920 fails, &"false"& is returned and authentication fails. If &%crypteq%& is being
27921 used instead of &%eq%&, the first example is in fact safe, because &%crypteq%&
27922 always fails if its second argument is empty. However, the second way of
27923 writing the test makes the logic clearer.
27926 .section "The LOGIN authentication mechanism" "SECID173"
27927 .cindex "LOGIN authentication mechanism"
27928 .cindex authentication LOGIN
27929 The LOGIN authentication mechanism is not documented in any RFC, but is in use
27930 in a number of programs. No data is sent with the AUTH command. Instead, a
27931 user name and password are supplied separately, in response to prompts. The
27932 plaintext authenticator can be configured to support this as in this example:
27936 public_name = LOGIN
27937 server_prompts = User Name : Password
27938 server_condition = \
27939 ${if and {{eq{$auth1}{username}}{eq{$auth2}{mysecret}}}}
27940 server_set_id = $auth1
27942 Because of the way plaintext operates, this authenticator accepts data supplied
27943 with the AUTH command (in contravention of the specification of LOGIN), but
27944 if the client does not supply it (as is the case for LOGIN clients), the prompt
27945 strings are used to obtain two data items.
27947 Some clients are very particular about the precise text of the prompts. For
27948 example, Outlook Express is reported to recognize only &"Username:"& and
27949 &"Password:"&. Here is an example of a LOGIN authenticator that uses those
27950 strings. It uses the &%ldapauth%& expansion condition to check the user
27951 name and password by binding to an LDAP server:
27955 public_name = LOGIN
27956 server_prompts = Username:: : Password::
27957 server_condition = ${if and{{ \
27960 user="uid=${quote_ldap_dn:$auth1},ou=people,o=example.org" \
27961 pass=${quote:$auth2} \
27962 ldap://ldap.example.org/} }} }
27963 server_set_id = uid=$auth1,ou=people,o=example.org
27965 We have to check that the username is not empty before using it, because LDAP
27966 does not permit empty DN components. We must also use the &%quote_ldap_dn%&
27967 operator to correctly quote the DN for authentication. However, the basic
27968 &%quote%& operator, rather than any of the LDAP quoting operators, is the
27969 correct one to use for the password, because quoting is needed only to make
27970 the password conform to the Exim syntax. At the LDAP level, the password is an
27971 uninterpreted string.
27974 .section "Support for different kinds of authentication" "SECID174"
27975 A number of string expansion features are provided for the purpose of
27976 interfacing to different ways of user authentication. These include checking
27977 traditionally encrypted passwords from &_/etc/passwd_& (or equivalent), PAM,
27978 Radius, &%ldapauth%&, &'pwcheck'&, and &'saslauthd'&. For details see section
27984 .section "Using plaintext in a client" "SECID175"
27985 .cindex "options" "&(plaintext)& authenticator (client)"
27986 The &(plaintext)& authenticator has two client options:
27988 .option client_ignore_invalid_base64 plaintext boolean false
27989 If the client receives a server prompt that is not a valid base64 string,
27990 authentication is abandoned by default. However, if this option is set true,
27991 the error in the challenge is ignored and the client sends the response as
27994 .option client_send plaintext string&!! unset
27995 The string is a colon-separated list of authentication data strings. Each
27996 string is independently expanded before being sent to the server. The first
27997 string is sent with the AUTH command; any more strings are sent in response
27998 to prompts from the server. Before each string is expanded, the value of the
27999 most recent prompt is placed in the next &$auth$&<&'n'&> variable, starting
28000 with &$auth1$& for the first prompt. Up to three prompts are stored in this
28001 way. Thus, the prompt that is received in response to sending the first string
28002 (with the AUTH command) can be used in the expansion of the second string, and
28003 so on. If an invalid base64 string is received when
28004 &%client_ignore_invalid_base64%& is set, an empty string is put in the
28005 &$auth$&<&'n'&> variable.
28007 &*Note*&: You cannot use expansion to create multiple strings, because
28008 splitting takes priority and happens first.
28010 Because the PLAIN authentication mechanism requires NUL (binary zero) bytes in
28011 the data, further processing is applied to each string before it is sent. If
28012 there are any single circumflex characters in the string, they are converted to
28013 NULs. Should an actual circumflex be required as data, it must be doubled in
28016 This is an example of a client configuration that implements the PLAIN
28017 authentication mechanism with a fixed user name and password:
28021 public_name = PLAIN
28022 client_send = ^username^mysecret
28024 The lack of colons means that the entire text is sent with the AUTH
28025 command, with the circumflex characters converted to NULs.
28026 Note that due to the ambiguity of parsing three consectutive circumflex characters
28027 there is no way to provide a password having a leading circumflex.
28031 that uses the LOGIN mechanism is:
28035 public_name = LOGIN
28036 client_send = : username : mysecret
28038 The initial colon means that the first string is empty, so no data is sent with
28039 the AUTH command itself. The remaining strings are sent in response to
28041 .ecindex IIDplaiauth1
28042 .ecindex IIDplaiauth2
28047 . ////////////////////////////////////////////////////////////////////////////
28048 . ////////////////////////////////////////////////////////////////////////////
28050 .chapter "The cram_md5 authenticator" "CHID9"
28051 .scindex IIDcramauth1 "&(cram_md5)& authenticator"
28052 .scindex IIDcramauth2 "authenticators" "&(cram_md5)&"
28053 .cindex "CRAM-MD5 authentication mechanism"
28054 .cindex authentication CRAM-MD5
28055 The CRAM-MD5 authentication mechanism is described in RFC 2195. The server
28056 sends a challenge string to the client, and the response consists of a user
28057 name and the CRAM-MD5 digest of the challenge string combined with a secret
28058 string (password) which is known to both server and client. Thus, the secret
28059 is not sent over the network as plain text, which makes this authenticator more
28060 secure than &(plaintext)&. However, the downside is that the secret has to be
28061 available in plain text at either end.
28064 .section "Using cram_md5 as a server" "SECID176"
28065 .cindex "options" "&(cram_md5)& authenticator (server)"
28066 This authenticator has one server option, which must be set to configure the
28067 authenticator as a server:
28069 .option server_secret cram_md5 string&!! unset
28070 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(cram_md5)& authenticator"
28071 When the server receives the client's response, the user name is placed in
28072 the expansion variable &$auth1$&, and &%server_secret%& is expanded to
28073 obtain the password for that user. The server then computes the CRAM-MD5 digest
28074 that the client should have sent, and checks that it received the correct
28075 string. If the expansion of &%server_secret%& is forced to fail, authentication
28076 fails. If the expansion fails for some other reason, a temporary error code is
28077 returned to the client.
28079 For compatibility with previous releases of Exim, the user name is also placed
28080 in &$1$&. However, the use of this variables for this purpose is now
28081 deprecated, as it can lead to confusion in string expansions that also use
28082 numeric variables for other things.
28084 For example, the following authenticator checks that the user name given by the
28085 client is &"ph10"&, and if so, uses &"secret"& as the password. For any other
28086 user name, authentication fails.
28090 public_name = CRAM-MD5
28091 server_secret = ${if eq{$auth1}{ph10}{secret}fail}
28092 server_set_id = $auth1
28094 .vindex "&$authenticated_id$&"
28095 If authentication succeeds, the setting of &%server_set_id%& preserves the user
28096 name in &$authenticated_id$&. A more typical configuration might look up the
28097 secret string in a file, using the user name as the key. For example:
28101 public_name = CRAM-MD5
28102 server_secret = ${lookup{$auth1}lsearch{/etc/authpwd}\
28104 server_set_id = $auth1
28106 Note that this expansion explicitly forces failure if the lookup fails
28107 because &$auth1$& contains an unknown user name.
28109 As another example, if you wish to re-use a Cyrus SASL sasldb2 file without
28110 using the relevant libraries, you need to know the realm to specify in the
28111 lookup and then ask for the &"userPassword"& attribute for that user in that
28116 public_name = CRAM-MD5
28117 server_secret = ${lookup{$auth1:mail.example.org:userPassword}\
28118 dbmjz{/etc/sasldb2}{$value}fail}
28119 server_set_id = $auth1
28122 .section "Using cram_md5 as a client" "SECID177"
28123 .cindex "options" "&(cram_md5)& authenticator (client)"
28124 When used as a client, the &(cram_md5)& authenticator has two options:
28128 .option client_name cram_md5 string&!! "the primary host name"
28129 This string is expanded, and the result used as the user name data when
28130 computing the response to the server's challenge.
28133 .option client_secret cram_md5 string&!! unset
28134 This option must be set for the authenticator to work as a client. Its value is
28135 expanded and the result used as the secret string when computing the response.
28139 .vindex "&$host_address$&"
28140 Different user names and secrets can be used for different servers by referring
28141 to &$host$& or &$host_address$& in the options. Forced failure of either
28142 expansion string is treated as an indication that this authenticator is not
28143 prepared to handle this case. Exim moves on to the next configured client
28144 authenticator. Any other expansion failure causes Exim to give up trying to
28145 send the message to the current server.
28147 A simple example configuration of a &(cram_md5)& authenticator, using fixed
28152 public_name = CRAM-MD5
28154 client_secret = secret
28156 .ecindex IIDcramauth1
28157 .ecindex IIDcramauth2
28161 . ////////////////////////////////////////////////////////////////////////////
28162 . ////////////////////////////////////////////////////////////////////////////
28164 .chapter "The cyrus_sasl authenticator" "CHID10"
28165 .scindex IIDcyrauth1 "&(cyrus_sasl)& authenticator"
28166 .scindex IIDcyrauth2 "authenticators" "&(cyrus_sasl)&"
28167 .cindex "Cyrus" "SASL library"
28169 The code for this authenticator was provided by Matthew Byng-Maddick while
28170 at A L Digital Ltd.
28172 The &(cyrus_sasl)& authenticator provides server support for the Cyrus SASL
28173 library implementation of the RFC 2222 (&"Simple Authentication and Security
28174 Layer"&). This library supports a number of authentication mechanisms,
28175 including PLAIN and LOGIN, but also several others that Exim does not support
28176 directly. In particular, there is support for Kerberos authentication.
28178 The &(cyrus_sasl)& authenticator provides a gatewaying mechanism directly to
28179 the Cyrus interface, so if your Cyrus library can do, for example, CRAM-MD5,
28180 then so can the &(cyrus_sasl)& authenticator. By default it uses the public
28181 name of the driver to determine which mechanism to support.
28183 Where access to some kind of secret file is required, for example, in GSSAPI
28184 or CRAM-MD5, it is worth noting that the authenticator runs as the Exim
28185 user, and that the Cyrus SASL library has no way of escalating privileges
28186 by default. You may also find you need to set environment variables,
28187 depending on the driver you are using.
28189 The application name provided by Exim is &"exim"&, so various SASL options may
28190 be set in &_exim.conf_& in your SASL directory. If you are using GSSAPI for
28191 Kerberos, note that because of limitations in the GSSAPI interface,
28192 changing the server keytab might need to be communicated down to the Kerberos
28193 layer independently. The mechanism for doing so is dependent upon the Kerberos
28196 For example, for older releases of Heimdal, the environment variable KRB5_KTNAME
28197 may be set to point to an alternative keytab file. Exim will pass this
28198 variable through from its own inherited environment when started as root or the
28199 Exim user. The keytab file needs to be readable by the Exim user.
28200 With newer releases of Heimdal, a setuid Exim may cause Heimdal to discard the
28201 environment variable. In practice, for those releases, the Cyrus authenticator
28202 is not a suitable interface for GSSAPI (Kerberos) support. Instead, consider
28203 the &(heimdal_gssapi)& authenticator, described in chapter &<<CHAPheimdalgss>>&
28206 .section "Using cyrus_sasl as a server" "SECID178"
28207 The &(cyrus_sasl)& authenticator has four private options. It puts the username
28208 (on a successful authentication) into &$auth1$&. For compatibility with
28209 previous releases of Exim, the username is also placed in &$1$&. However, the
28210 use of this variable for this purpose is now deprecated, as it can lead to
28211 confusion in string expansions that also use numeric variables for other
28215 .option server_hostname cyrus_sasl string&!! "see below"
28216 This option selects the hostname that is used when communicating with the
28217 library. The default value is &`$primary_hostname`&. It is up to the underlying
28218 SASL plug-in what it does with this data.
28221 .option server_mech cyrus_sasl string "see below"
28222 This option selects the authentication mechanism this driver should use. The
28223 default is the value of the generic &%public_name%& option. This option allows
28224 you to use a different underlying mechanism from the advertised name. For
28228 driver = cyrus_sasl
28229 public_name = X-ANYTHING
28230 server_mech = CRAM-MD5
28231 server_set_id = $auth1
28234 .option server_realm cyrus_sasl string&!! unset
28235 This specifies the SASL realm that the server claims to be in.
28238 .option server_service cyrus_sasl string &`smtp`&
28239 This is the SASL service that the server claims to implement.
28242 For straightforward cases, you do not need to set any of the authenticator's
28243 private options. All you need to do is to specify an appropriate mechanism as
28244 the public name. Thus, if you have a SASL library that supports CRAM-MD5 and
28245 PLAIN, you could have two authenticators as follows:
28248 driver = cyrus_sasl
28249 public_name = CRAM-MD5
28250 server_set_id = $auth1
28253 driver = cyrus_sasl
28254 public_name = PLAIN
28255 server_set_id = $auth2
28257 Cyrus SASL does implement the LOGIN authentication method, even though it is
28258 not a standard method. It is disabled by default in the source distribution,
28259 but it is present in many binary distributions.
28260 .ecindex IIDcyrauth1
28261 .ecindex IIDcyrauth2
28266 . ////////////////////////////////////////////////////////////////////////////
28267 . ////////////////////////////////////////////////////////////////////////////
28268 .chapter "The dovecot authenticator" "CHAPdovecot"
28269 .scindex IIDdcotauth1 "&(dovecot)& authenticator"
28270 .scindex IIDdcotauth2 "authenticators" "&(dovecot)&"
28271 This authenticator is an interface to the authentication facility of the
28272 Dovecot 2 POP/IMAP server, which can support a number of authentication methods.
28273 Note that Dovecot must be configured to use auth-client not auth-userdb.
28274 If you are using Dovecot to authenticate POP/IMAP clients, it might be helpful
28275 to use the same mechanisms for SMTP authentication. This is a server
28276 authenticator only. There is only one option:
28278 .option server_socket dovecot string unset
28280 This option must specify the UNIX socket that is the interface to Dovecot
28281 authentication. The &%public_name%& option must specify an authentication
28282 mechanism that Dovecot is configured to support. You can have several
28283 authenticators for different mechanisms. For example:
28287 public_name = PLAIN
28288 server_socket = /var/run/dovecot/auth-client
28289 server_set_id = $auth1
28294 server_socket = /var/run/dovecot/auth-client
28295 server_set_id = $auth1
28297 If the SMTP connection is encrypted, or if &$sender_host_address$& is equal to
28298 &$received_ip_address$& (that is, the connection is local), the &"secured"&
28299 option is passed in the Dovecot authentication command. If, for a TLS
28300 connection, a client certificate has been verified, the &"valid-client-cert"&
28301 option is passed. When authentication succeeds, the identity of the user
28302 who authenticated is placed in &$auth1$&.
28304 The Dovecot configuration to match the above will look
28307 conf.d/10-master.conf :-
28312 unix_listener auth-client {
28319 conf.d/10-auth.conf :-
28321 auth_mechanisms = plain login ntlm
28324 .ecindex IIDdcotauth1
28325 .ecindex IIDdcotauth2
28328 . ////////////////////////////////////////////////////////////////////////////
28329 . ////////////////////////////////////////////////////////////////////////////
28330 .chapter "The gsasl authenticator" "CHAPgsasl"
28331 .scindex IIDgsaslauth1 "&(gsasl)& authenticator"
28332 .scindex IIDgsaslauth2 "authenticators" "&(gsasl)&"
28333 .cindex "authentication" "GNU SASL"
28334 .cindex "authentication" "SASL"
28335 .cindex "authentication" "EXTERNAL"
28336 .cindex "authentication" "ANONYMOUS"
28337 .cindex "authentication" "PLAIN"
28338 .cindex "authentication" "LOGIN"
28339 .cindex "authentication" "DIGEST-MD5"
28340 .cindex "authentication" "CRAM-MD5"
28341 .cindex "authentication" "SCRAM family"
28342 The &(gsasl)& authenticator provides integration for the GNU SASL
28343 library and the mechanisms it provides. This is new as of the 4.80 release
28344 and there are a few areas where the library does not let Exim smoothly
28345 scale to handle future authentication mechanisms, so no guarantee can be
28346 made that any particular new authentication mechanism will be supported
28347 without code changes in Exim.
28349 The library is expected to add support in an upcoming
28350 realease for the SCRAM-SHA-256 method.
28351 The macro _HAVE_AUTH_GSASL_SCRAM_SHA_256 will be defined
28354 To see the list of mechanisms supported by the library run Exim with "auth" debug
28355 enabled and look for a line containing "GNU SASL supports".
28356 Note however that some may not have been tested from Exim.
28359 .option client_authz gsasl string&!! unset
28360 This option can be used to supply an &'authorization id'&
28361 which is different to the &'authentication_id'& provided
28362 by &%client_username%& option.
28363 If unset or (after expansion) empty it is not used,
28364 which is the common case.
28366 .option client_channelbinding gsasl boolean false
28367 See &%server_channelbinding%& below.
28369 .option client_password gsasl string&!! unset
28370 This option is exapanded before use, and should result in
28371 the password to be used, in clear.
28373 .option client_username gsasl string&!! unset
28374 This option is exapanded before use, and should result in
28375 the account name to be used.
28378 .option client_spassword gsasl string&!! unset
28379 This option is only supported for library versions 1.9.1 and greater.
28380 The macro _HAVE_AUTH_GSASL_SCRAM_S_KEY will be defined when this is so.
28382 If a SCRAM mechanism is being used and this option is set
28383 and correctly sized
28384 it is used in preference to &%client_password%&.
28385 The value after expansion should be
28386 a 40 (for SHA-1) or 64 (for SHA-256) character string
28387 with the PBKDF2-prepared password, hex-encoded.
28389 Note that this value will depend on the salt and iteration-count
28390 supplied by the server.
28391 The option is expanded before use.
28392 During the expansion &$auth1$& is set with the client username,
28393 &$auth2$& with the iteration count, and
28394 &$auth3$& with the salt.
28396 The intent of this option
28397 is to support clients that can cache thes salted password
28398 to save on recalculation costs.
28399 The cache lookup should return an unusable value
28400 (eg. an empty string)
28401 if the salt or iteration count has changed
28403 If the authentication succeeds then the above variables are set,
28404 .vindex "&$auth4$&"
28405 plus the calculated salted password value value in &$auth4$&,
28406 during the expansion of the &%client_set_id%& option.
28407 A side-effect of this expansion can be used to prime the cache.
28410 .option server_channelbinding gsasl boolean false
28411 Some authentication mechanisms are able to use external context at both ends
28412 of the session to bind the authentication to that context, and fail the
28413 authentication process if that context differs. Specifically, some TLS
28414 ciphersuites can provide identifying information about the cryptographic
28417 This should have meant that certificate identity and verification becomes a
28418 non-issue, as a man-in-the-middle attack will cause the correct client and
28419 server to see different identifiers and authentication will fail.
28422 only usable by mechanisms which support "channel binding"; at time of
28423 writing, that's the SCRAM family.
28424 When using this feature the "-PLUS" variants of the method names need to be used.
28426 This defaults off to ensure smooth upgrade across Exim releases, in case
28427 this option causes some clients to start failing. Some future release
28428 of Exim might have switched the default to be true.
28430 . However, Channel Binding in TLS has proven to be vulnerable in current versions.
28431 . Do not plan to rely upon this feature for security, ever, without consulting
28432 . with a subject matter expert (a cryptographic engineer).
28434 This option was deprecated in previous releases due to doubts over
28435 the "Triple Handshake" vulnerability.
28436 Exim takes suitable precausions (requiring Extended Master Secret if TLS
28437 Session Resumption was used) for safety.
28440 .option server_hostname gsasl string&!! "see below"
28441 This option selects the hostname that is used when communicating with the
28442 library. The default value is &`$primary_hostname`&.
28443 Some mechanisms will use this data.
28446 .option server_mech gsasl string "see below"
28447 This option selects the authentication mechanism this driver should use. The
28448 default is the value of the generic &%public_name%& option. This option allows
28449 you to use a different underlying mechanism from the advertised name. For
28454 public_name = X-ANYTHING
28455 server_mech = CRAM-MD5
28456 server_set_id = $auth1
28460 .option server_password gsasl string&!! unset
28461 Various mechanisms need access to the cleartext password on the server, so
28462 that proof-of-possession can be demonstrated on the wire, without sending
28463 the password itself.
28465 The data available for lookup varies per mechanism.
28466 In all cases, &$auth1$& is set to the &'authentication id'&.
28467 The &$auth2$& variable will always be the &'authorization id'& (&'authz'&)
28468 if available, else the empty string.
28469 The &$auth3$& variable will always be the &'realm'& if available,
28470 else the empty string.
28472 A forced failure will cause authentication to defer.
28474 If using this option, it may make sense to set the &%server_condition%&
28475 option to be simply "true".
28478 .option server_realm gsasl string&!! unset
28479 This specifies the SASL realm that the server claims to be in.
28480 Some mechanisms will use this data.
28483 .option server_scram_iter gsasl string&!! 4096
28484 This option provides data for the SCRAM family of mechanisms.
28485 The &$auth1$&, &$auth2$& and &$auth3$& variables are available
28486 when this option is expanded.
28488 The result of expansion should be a decimal number,
28489 and represents both a lower-bound on the security, and
28490 a compute cost factor imposed on the client
28491 (if it does not cache results, or the server changes
28492 either the iteration count or the salt).
28493 A minimum value of 4096 is required by the standards
28494 for all current SCRAM mechanism variants.
28496 .option server_scram_salt gsasl string&!! unset
28497 This option provides data for the SCRAM family of mechanisms.
28498 The &$auth1$&, &$auth2$& and &$auth3$& variables are available
28499 when this option is expanded.
28500 The value should be a base64-encoded string,
28501 of random data typically 4-to-16 bytes long.
28502 If unset or empty after expansion the library will provides a value for the
28503 protocol conversation.
28506 .option server_key gsasl string&!! unset
28507 .option server_skey gsasl string&!! unset
28508 These options can be used for the SCRAM family of mechanisms
28509 to provide stored information related to a password,
28510 the storage of which is preferable to plaintext.
28512 &%server_key%& is the value defined in the SCRAM standards as ServerKey;
28513 &%server_skey%& is StoredKey.
28515 They are only available for version 1.9.0 (or later) of the gsasl library.
28516 When this is so, the macros
28517 _OPT_AUTHENTICATOR_GSASL_SERVER_KEY
28518 and _HAVE_AUTH_GSASL_SCRAM_S_KEY
28521 The &$authN$& variables are available when these options are expanded.
28523 If set, the results of expansion should for each
28524 should be a 28 (for SHA-1) or 44 (for SHA-256) character string
28525 of base64-coded data, and will be used in preference to the
28526 &%server_password%& option.
28527 If unset or not of the right length, &%server_password%& will be used.
28529 The libgsasl library release includes a utility &'gsasl'& which can be used
28530 to generate these values.
28533 .option server_service gsasl string &`smtp`&
28534 This is the SASL service that the server claims to implement.
28535 Some mechanisms will use this data.
28538 .section "&(gsasl)& auth variables" "SECTgsaslauthvar"
28539 .vindex "&$auth1$&, &$auth2$&, etc"
28540 These may be set when evaluating specific options, as detailed above.
28541 They will also be set when evaluating &%server_condition%&.
28543 Unless otherwise stated below, the &(gsasl)& integration will use the following
28544 meanings for these variables:
28547 .vindex "&$auth1$&"
28548 &$auth1$&: the &'authentication id'&
28550 .vindex "&$auth2$&"
28551 &$auth2$&: the &'authorization id'&
28553 .vindex "&$auth3$&"
28554 &$auth3$&: the &'realm'&
28557 On a per-mechanism basis:
28560 .cindex "authentication" "EXTERNAL"
28561 EXTERNAL: only &$auth1$& is set, to the possibly empty &'authorization id'&;
28562 the &%server_condition%& option must be present.
28564 .cindex "authentication" "ANONYMOUS"
28565 ANONYMOUS: only &$auth1$& is set, to the possibly empty &'anonymous token'&;
28566 the &%server_condition%& option must be present.
28568 .cindex "authentication" "GSSAPI"
28569 GSSAPI: &$auth1$& will be set to the &'GSSAPI Display Name'&;
28570 &$auth2$& will be set to the &'authorization id'&,
28571 the &%server_condition%& option must be present.
28574 An &'anonymous token'& is something passed along as an unauthenticated
28575 identifier; this is analogous to FTP anonymous authentication passing an
28576 email address, or software-identifier@, as the "password".
28579 An example showing the password having the realm specified in the callback
28580 and demonstrating a Cyrus SASL to GSASL migration approach is:
28582 gsasl_cyrusless_crammd5:
28584 public_name = CRAM-MD5
28585 server_realm = imap.example.org
28586 server_password = ${lookup{$auth1:$auth3:userPassword}\
28587 dbmjz{/etc/sasldb2}{$value}fail}
28588 server_set_id = ${quote:$auth1}
28589 server_condition = yes
28593 . ////////////////////////////////////////////////////////////////////////////
28594 . ////////////////////////////////////////////////////////////////////////////
28596 .chapter "The heimdal_gssapi authenticator" "CHAPheimdalgss"
28597 .scindex IIDheimdalgssauth1 "&(heimdal_gssapi)& authenticator"
28598 .scindex IIDheimdalgssauth2 "authenticators" "&(heimdal_gssapi)&"
28599 .cindex "authentication" "GSSAPI"
28600 .cindex "authentication" "Kerberos"
28601 The &(heimdal_gssapi)& authenticator provides server integration for the
28602 Heimdal GSSAPI/Kerberos library, permitting Exim to set a keytab pathname
28605 .option server_hostname heimdal_gssapi string&!! "see below"
28606 This option selects the hostname that is used, with &%server_service%&,
28607 for constructing the GSS server name, as a &'GSS_C_NT_HOSTBASED_SERVICE'&
28608 identifier. The default value is &`$primary_hostname`&.
28610 .option server_keytab heimdal_gssapi string&!! unset
28611 If set, then Heimdal will not use the system default keytab (typically
28612 &_/etc/krb5.keytab_&) but instead the pathname given in this option.
28613 The value should be a pathname, with no &"file:"& prefix.
28615 .option server_service heimdal_gssapi string&!! "smtp"
28616 This option specifies the service identifier used, in conjunction with
28617 &%server_hostname%&, for building the identifier for finding credentials
28621 .section "&(heimdal_gssapi)& auth variables" "SECTheimdalgssauthvar"
28622 Beware that these variables will typically include a realm, thus will appear
28623 to be roughly like an email address already. The &'authzid'& in &$auth2$& is
28624 not verified, so a malicious client can set it to anything.
28626 The &$auth1$& field should be safely trustable as a value from the Key
28627 Distribution Center. Note that these are not quite email addresses.
28628 Each identifier is for a role, and so the left-hand-side may include a
28629 role suffix. For instance, &"joe/admin@EXAMPLE.ORG"&.
28631 .vindex "&$auth1$&, &$auth2$&, etc"
28633 .vindex "&$auth1$&"
28634 &$auth1$&: the &'authentication id'&, set to the GSS Display Name.
28636 .vindex "&$auth2$&"
28637 &$auth2$&: the &'authorization id'&, sent within SASL encapsulation after
28638 authentication. If that was empty, this will also be set to the
28643 . ////////////////////////////////////////////////////////////////////////////
28644 . ////////////////////////////////////////////////////////////////////////////
28646 .chapter "The spa authenticator" "CHAPspa"
28647 .scindex IIDspaauth1 "&(spa)& authenticator"
28648 .scindex IIDspaauth2 "authenticators" "&(spa)&"
28649 .cindex "authentication" "Microsoft Secure Password"
28650 .cindex "authentication" "NTLM"
28651 .cindex "Microsoft Secure Password Authentication"
28652 .cindex "NTLM authentication"
28653 The &(spa)& authenticator provides client support for Microsoft's &'Secure
28654 Password Authentication'& mechanism,
28655 which is also sometimes known as NTLM (NT LanMan). The code for client side of
28656 this authenticator was contributed by Marc Prud'hommeaux, and much of it is
28657 taken from the Samba project (&url(https://www.samba.org/)). The code for the
28658 server side was subsequently contributed by Tom Kistner. The mechanism works as
28662 After the AUTH command has been accepted, the client sends an SPA
28663 authentication request based on the user name and optional domain.
28665 The server sends back a challenge.
28667 The client builds a challenge response which makes use of the user's password
28668 and sends it to the server, which then accepts or rejects it.
28671 Encryption is used to protect the password in transit.
28675 .section "Using spa as a server" "SECID179"
28676 .cindex "options" "&(spa)& authenticator (server)"
28677 The &(spa)& authenticator has just one server option:
28679 .option server_password spa string&!! unset
28680 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(spa)& authenticator"
28681 This option is expanded, and the result must be the cleartext password for the
28682 authenticating user, whose name is at this point in &$auth1$&. For
28683 compatibility with previous releases of Exim, the user name is also placed in
28684 &$1$&. However, the use of this variable for this purpose is now deprecated, as
28685 it can lead to confusion in string expansions that also use numeric variables
28686 for other things. For example:
28691 server_password = \
28692 ${lookup{$auth1}lsearch{/etc/exim/spa_clearpass}{$value}fail}
28694 If the expansion is forced to fail, authentication fails. Any other expansion
28695 failure causes a temporary error code to be returned.
28701 .section "Using spa as a client" "SECID180"
28702 .cindex "options" "&(spa)& authenticator (client)"
28703 The &(spa)& authenticator has the following client options:
28707 .option client_domain spa string&!! unset
28708 This option specifies an optional domain for the authentication.
28711 .option client_password spa string&!! unset
28712 This option specifies the user's password, and must be set.
28715 .option client_username spa string&!! unset
28716 This option specifies the user name, and must be set. Here is an example of a
28717 configuration of this authenticator for use with the mail servers at
28723 client_username = msn/msn_username
28724 client_password = msn_plaintext_password
28725 client_domain = DOMAIN_OR_UNSET
28727 .ecindex IIDspaauth1
28728 .ecindex IIDspaauth2
28734 . ////////////////////////////////////////////////////////////////////////////
28735 . ////////////////////////////////////////////////////////////////////////////
28737 .chapter "The external authenticator" "CHAPexternauth"
28738 .scindex IIDexternauth1 "&(external)& authenticator"
28739 .scindex IIDexternauth2 "authenticators" "&(external)&"
28740 .cindex "authentication" "Client Certificate"
28741 .cindex "authentication" "X509"
28742 .cindex "Certificate-based authentication"
28743 The &(external)& authenticator provides support for
28744 authentication based on non-SMTP information.
28745 The specification is in RFC 4422 Appendix A
28746 (&url(https://tools.ietf.org/html/rfc4422)).
28747 It is only a transport and negotiation mechanism;
28748 the process of authentication is entirely controlled
28749 by the server configuration.
28751 The client presents an identity in-clear.
28752 It is probably wise for a server to only advertise,
28753 and for clients to only attempt,
28754 this authentication method on a secure (eg. under TLS) connection.
28756 One possible use, compatible with the
28757 K-9 Mail Android client (&url(https://k9mail.github.io/)),
28758 is for using X509 client certificates.
28760 It thus overlaps in function with the TLS authenticator
28761 (see &<<CHAPtlsauth>>&)
28762 but is a full SMTP SASL authenticator
28763 rather than being implicit for TLS-connection carried
28764 client certificates only.
28766 The examples and discussion in this chapter assume that
28767 client-certificate authentication is being done.
28769 The client must present a certificate,
28770 for which it must have been requested via the
28771 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& main options
28772 (see &<<CHAPTLS>>&).
28773 For authentication to be effective the certificate should be
28774 verifiable against a trust-anchor certificate known to the server.
28776 .section "External options" "SECTexternsoptions"
28777 .cindex "options" "&(external)& authenticator (server)"
28778 The &(external)& authenticator has two server options:
28780 .option server_param2 external string&!! unset
28781 .option server_param3 external string&!! unset
28782 .cindex "variables (&$auth1$& &$auth2$& etc)" "in &(external)& authenticator"
28783 These options are expanded before the &%server_condition%& option
28784 and the result are placed in &$auth2$& and &$auth3$& resectively.
28785 If the expansion is forced to fail, authentication fails. Any other expansion
28786 failure causes a temporary error code to be returned.
28788 They can be used to clarify the coding of a complex &%server_condition%&.
28790 .section "Using external in a server" "SECTexternserver"
28791 .cindex "AUTH" "in &(external)& authenticator"
28792 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
28793 "in &(external)& authenticator"
28794 .vindex "&$auth1$&, &$auth2$&, etc"
28795 .cindex "base64 encoding" "in &(external)& authenticator"
28797 When running as a server, &(external)& performs the authentication test by
28798 expanding a string. The data sent by the client with the AUTH command, or in
28799 response to subsequent prompts, is base64 encoded, and so may contain any byte
28800 values when decoded. The decoded value is treated as
28801 an identity for authentication and
28802 placed in the expansion variable &$auth1$&.
28804 For compatibility with previous releases of Exim, the value is also placed in
28805 the expansion variable &$1$&. However, the use of this
28806 variable for this purpose is now deprecated, as it can lead to confusion in
28807 string expansions that also use them for other things.
28809 .vindex "&$authenticated_id$&"
28810 Once an identity has been received,
28811 &%server_condition%& is expanded. If the expansion is forced to fail,
28812 authentication fails. Any other expansion failure causes a temporary error code
28813 to be returned. If the result of a successful expansion is an empty string,
28814 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
28815 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
28816 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
28817 For any other result, a temporary error code is returned, with the expanded
28818 string as the error text.
28822 ext_ccert_san_mail:
28824 public_name = EXTERNAL
28826 server_advertise_condition = $tls_in_certificate_verified
28827 server_param2 = ${certextract {subj_altname,mail,>:} \
28828 {$tls_in_peercert}}
28829 server_condition = ${if forany {$auth2} \
28830 {eq {$item}{$auth1}}}
28831 server_set_id = $auth1
28833 This accepts a client certificate that is verifiable against any
28834 of your configured trust-anchors
28835 (which usually means the full set of public CAs)
28836 and which has a mail-SAN matching the claimed identity sent by the client.
28838 &*Note*&: up to TLS1.2, the client cert is on the wire in-clear, including the SAN.
28839 The account name is therefore guessable by an opponent.
28840 TLS 1.3 protects both server and client certificates, and is not vulnerable
28844 .section "Using external in a client" "SECTexternclient"
28845 .cindex "options" "&(external)& authenticator (client)"
28846 The &(external)& authenticator has one client option:
28848 .option client_send external string&!! unset
28849 This option is expanded and sent with the AUTH command as the
28850 identity being asserted.
28856 public_name = EXTERNAL
28858 client_condition = ${if !eq{$tls_out_cipher}{}}
28859 client_send = myaccount@smarthost.example.net
28863 .ecindex IIDexternauth1
28864 .ecindex IIDexternauth2
28870 . ////////////////////////////////////////////////////////////////////////////
28871 . ////////////////////////////////////////////////////////////////////////////
28873 .chapter "The tls authenticator" "CHAPtlsauth"
28874 .scindex IIDtlsauth1 "&(tls)& authenticator"
28875 .scindex IIDtlsauth2 "authenticators" "&(tls)&"
28876 .cindex "authentication" "Client Certificate"
28877 .cindex "authentication" "X509"
28878 .cindex "Certificate-based authentication"
28879 The &(tls)& authenticator provides server support for
28880 authentication based on client certificates.
28882 It is not an SMTP authentication mechanism and is not
28883 advertised by the server as part of the SMTP EHLO response.
28884 It is an Exim authenticator in the sense that it affects
28885 the protocol element of the log line, can be tested for
28886 by the &%authenticated%& ACL condition, and can set
28887 the &$authenticated_id$& variable.
28889 The client must present a verifiable certificate,
28890 for which it must have been requested via the
28891 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& main options
28892 (see &<<CHAPTLS>>&).
28894 If an authenticator of this type is configured it is
28895 run before any SMTP-level communication is done,
28896 and can authenticate the connection.
28897 If it does, SMTP authentication is not offered.
28899 A maximum of one authenticator of this type may be present.
28902 .cindex "options" "&(tls)& authenticator (server)"
28903 The &(tls)& authenticator has three server options:
28905 .option server_param1 tls string&!! unset
28906 .cindex "variables (&$auth1$& &$auth2$& etc)" "in &(tls)& authenticator"
28907 This option is expanded after the TLS negotiation and
28908 the result is placed in &$auth1$&.
28909 If the expansion is forced to fail, authentication fails. Any other expansion
28910 failure causes a temporary error code to be returned.
28912 .option server_param2 tls string&!! unset
28913 .option server_param3 tls string&!! unset
28914 As above, for &$auth2$& and &$auth3$&.
28916 &%server_param1%& may also be spelled &%server_param%&.
28923 server_param1 = ${certextract {subj_altname,mail,>:} \
28924 {$tls_in_peercert}}
28925 server_condition = ${if and { {eq{$tls_in_certificate_verified}{1}} \
28928 {${lookup ldap{ldap:///\
28929 mailname=${quote_ldap_dn:${lc:$item}},\
28930 ou=users,LDAP_DC?mailid} {$value}{0} \
28932 server_set_id = ${if = {1}{${listcount:$auth1}} {$auth1}{}}
28934 This accepts a client certificate that is verifiable against any
28935 of your configured trust-anchors
28936 (which usually means the full set of public CAs)
28937 and which has a SAN with a good account name.
28939 Note that, up to TLS1.2, the client cert is on the wire in-clear, including the SAN,
28940 The account name is therefore guessable by an opponent.
28941 TLS 1.3 protects both server and client certificates, and is not vulnerable
28943 Likewise, a traditional plaintext SMTP AUTH done inside TLS is not.
28945 . An alternative might use
28947 . server_param1 = ${sha256:$tls_in_peercert}
28949 . to require one of a set of specific certs that define a given account
28950 . (the verification is still required, but mostly irrelevant).
28951 . This would help for per-device use.
28953 . However, for the future we really need support for checking a
28954 . user cert in LDAP - which probably wants a base-64 DER.
28956 .ecindex IIDtlsauth1
28957 .ecindex IIDtlsauth2
28960 Note that because authentication is traditionally an SMTP operation,
28961 the &%authenticated%& ACL condition cannot be used in
28962 a connect- or helo-ACL.
28966 . ////////////////////////////////////////////////////////////////////////////
28967 . ////////////////////////////////////////////////////////////////////////////
28969 .chapter "Encrypted SMTP connections using TLS/SSL" "CHAPTLS" &&&
28970 "Encrypted SMTP connections"
28971 .scindex IIDencsmtp1 "encryption" "on SMTP connection"
28972 .scindex IIDencsmtp2 "SMTP" "encryption"
28973 .cindex "TLS" "on SMTP connection"
28976 Support for TLS (Transport Layer Security), formerly known as SSL (Secure
28977 Sockets Layer), is implemented by making use of the OpenSSL library or the
28978 GnuTLS library (Exim requires GnuTLS release 1.0 or later). There is no
28979 cryptographic code in the Exim distribution itself for implementing TLS. In
28980 order to use this feature you must install OpenSSL or GnuTLS, and then build a
28981 version of Exim that includes TLS support (see section &<<SECTinctlsssl>>&).
28982 You also need to understand the basic concepts of encryption at a managerial
28983 level, and in particular, the way that public keys, private keys, and
28984 certificates are used.
28986 RFC 3207 defines how SMTP connections can make use of encryption. Once a
28987 connection is established, the client issues a STARTTLS command. If the
28988 server accepts this, the client and the server negotiate an encryption
28989 mechanism. If the negotiation succeeds, the data that subsequently passes
28990 between them is encrypted.
28992 Exim's ACLs can detect whether the current SMTP session is encrypted or not,
28993 and if so, what cipher suite is in use, whether the client supplied a
28994 certificate, and whether or not that certificate was verified. This makes it
28995 possible for an Exim server to deny or accept certain commands based on the
28998 &*Warning*&: Certain types of firewall and certain anti-virus products can
28999 disrupt TLS connections. You need to turn off SMTP scanning for these products
29000 in order to get TLS to work.
29004 .section "Support for the &""submissions""& (aka &""ssmtp""& and &""smtps""&) protocol" &&&
29006 .cindex "submissions protocol"
29007 .cindex "ssmtp protocol"
29008 .cindex "smtps protocol"
29009 .cindex "SMTP" "submissions protocol"
29010 .cindex "SMTP" "ssmtp protocol"
29011 .cindex "SMTP" "smtps protocol"
29012 The history of port numbers for TLS in SMTP is a little messy and has been
29013 contentious. As of RFC 8314, the common practice of using the historically
29014 allocated port 465 for "email submission but with TLS immediately upon connect
29015 instead of using STARTTLS" is officially blessed by the IETF, and recommended
29016 by them in preference to STARTTLS.
29018 The name originally assigned to the port was &"ssmtp"& or &"smtps"&, but as
29019 clarity emerged over the dual roles of SMTP, for MX delivery and Email
29020 Submission, nomenclature has shifted. The modern name is now &"submissions"&.
29022 This approach was, for a while, officially abandoned when encrypted SMTP was
29023 standardized, but many clients kept using it, even as the TCP port number was
29024 reassigned for other use.
29025 Thus you may encounter guidance claiming that you shouldn't enable use of
29027 In practice, a number of mail-clients have only ever supported submissions,
29028 not submission with STARTTLS upgrade.
29029 Ideally, offer both submission (587) and submissions (465) service.
29031 Exim supports TLS-on-connect by means of the &%tls_on_connect_ports%&
29032 global option. Its value must be a list of port numbers;
29033 the most common use is expected to be:
29035 tls_on_connect_ports = 465
29037 The port numbers specified by this option apply to all SMTP connections, both
29038 via the daemon and via &'inetd'&. You still need to specify all the ports that
29039 the daemon uses (by setting &%daemon_smtp_ports%& or &%local_interfaces%& or
29040 the &%-oX%& command line option) because &%tls_on_connect_ports%& does not add
29041 an extra port &-- rather, it specifies different behaviour on a port that is
29044 There is also a &%-tls-on-connect%& command line option. This overrides
29045 &%tls_on_connect_ports%&; it forces the TLS-only behaviour for all ports.
29052 .section "OpenSSL vs GnuTLS" "SECTopenvsgnu"
29053 .cindex "TLS" "OpenSSL &'vs'& GnuTLS"
29054 TLS is supported in Exim using either the OpenSSL or GnuTLS library.
29055 To build Exim to use OpenSSL you need to set
29061 To build Exim to use GnuTLS, you need to set
29067 You must also set TLS_LIBS and TLS_INCLUDE appropriately, so that the
29068 include files and libraries for GnuTLS can be found.
29070 There are some differences in usage when using GnuTLS instead of OpenSSL:
29073 The &%tls_verify_certificates%& option
29074 cannot be the path of a directory
29075 for GnuTLS versions before 3.3.6
29076 (for later versions, or OpenSSL, it can be either).
29078 The default value for &%tls_dhparam%& differs for historical reasons.
29080 .vindex "&$tls_in_peerdn$&"
29081 .vindex "&$tls_out_peerdn$&"
29082 Distinguished Name (DN) strings reported by the OpenSSL library use a slash for
29083 separating fields; GnuTLS uses commas, in accordance with RFC 2253. This
29084 affects the value of the &$tls_in_peerdn$& and &$tls_out_peerdn$& variables.
29086 OpenSSL identifies cipher suites using hyphens as separators, for example:
29087 DES-CBC3-SHA. GnuTLS historically used underscores, for example:
29088 RSA_ARCFOUR_SHA. What is more, OpenSSL complains if underscores are present
29089 in a cipher list. To make life simpler, Exim changes underscores to hyphens
29090 for OpenSSL and passes the string unchanged to GnuTLS (expecting the library
29091 to handle its own older variants) when processing lists of cipher suites in the
29092 &%tls_require_ciphers%& options (the global option and the &(smtp)& transport
29095 The &%tls_require_ciphers%& options operate differently, as described in the
29096 sections &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
29098 The &%tls_dh_min_bits%& SMTP transport option is only honoured by GnuTLS.
29099 When using OpenSSL, this option is ignored.
29100 (If an API is found to let OpenSSL be configured in this way,
29101 let the Exim Maintainers know and we'll likely use it).
29103 With GnuTLS, if an explicit list is used for the &%tls_privatekey%& main option
29104 main option, it must be ordered to match the &%tls_certificate%& list.
29106 Some other recently added features may only be available in one or the other.
29107 This should be documented with the feature. If the documentation does not
29108 explicitly state that the feature is infeasible in the other TLS
29109 implementation, then patches are welcome.
29111 The output from "exim -bV" will show which (if any) support was included
29113 Also, the macro "_HAVE_OPENSSL" or "_HAVE_GNUTLS" will be defined.
29117 .section "GnuTLS parameter computation" "SECTgnutlsparam"
29118 This section only applies if &%tls_dhparam%& is set to &`historic`& or to
29119 an explicit path; if the latter, then the text about generation still applies,
29120 but not the chosen filename.
29121 By default, as of Exim 4.80 a hard-coded D-H prime is used.
29122 See the documentation of &%tls_dhparam%& for more information.
29124 GnuTLS uses D-H parameters that may take a substantial amount of time
29125 to compute. It is unreasonable to re-compute them for every TLS session.
29126 Therefore, Exim keeps this data in a file in its spool directory, called
29127 &_gnutls-params-NNNN_& for some value of NNNN, corresponding to the number
29129 The file is owned by the Exim user and is readable only by
29130 its owner. Every Exim process that start up GnuTLS reads the D-H
29131 parameters from this file. If the file does not exist, the first Exim process
29132 that needs it computes the data and writes it to a temporary file which is
29133 renamed once it is complete. It does not matter if several Exim processes do
29134 this simultaneously (apart from wasting a few resources). Once a file is in
29135 place, new Exim processes immediately start using it.
29137 For maximum security, the parameters that are stored in this file should be
29138 recalculated periodically, the frequency depending on your paranoia level.
29139 If you are avoiding using the fixed D-H primes published in RFCs, then you
29140 are concerned about some advanced attacks and will wish to do this; if you do
29141 not regenerate then you might as well stick to the standard primes.
29143 Arranging this is easy in principle; just delete the file when you want new
29144 values to be computed. However, there may be a problem. The calculation of new
29145 parameters needs random numbers, and these are obtained from &_/dev/random_&.
29146 If the system is not very active, &_/dev/random_& may delay returning data
29147 until enough randomness (entropy) is available. This may cause Exim to hang for
29148 a substantial amount of time, causing timeouts on incoming connections.
29150 The solution is to generate the parameters externally to Exim. They are stored
29151 in &_gnutls-params-N_& in PEM format, which means that they can be
29152 generated externally using the &(certtool)& command that is part of GnuTLS.
29154 To replace the parameters with new ones, instead of deleting the file
29155 and letting Exim re-create it, you can generate new parameters using
29156 &(certtool)& and, when this has been done, replace Exim's cache file by
29157 renaming. The relevant commands are something like this:
29160 [ look for file; assume gnutls-params-2236 is the most recent ]
29163 # chown exim:exim new-params
29164 # chmod 0600 new-params
29165 # certtool --generate-dh-params --bits 2236 >>new-params
29166 # openssl dhparam -noout -text -in new-params | head
29167 [ check the first line, make sure it's not more than 2236;
29168 if it is, then go back to the start ("rm") and repeat
29169 until the size generated is at most the size requested ]
29170 # chmod 0400 new-params
29171 # mv new-params gnutls-params-2236
29173 If Exim never has to generate the parameters itself, the possibility of
29174 stalling is removed.
29176 The filename changed in Exim 4.80, to gain the -bits suffix. The value which
29177 Exim will choose depends upon the version of GnuTLS in use. For older GnuTLS,
29178 the value remains hard-coded in Exim as 1024. As of GnuTLS 2.12.x, there is
29179 a way for Exim to ask for the "normal" number of bits for D-H public-key usage,
29180 and Exim does so. This attempt to remove Exim from TLS policy decisions
29181 failed, as GnuTLS 2.12 returns a value higher than the current hard-coded limit
29182 of the NSS library. Thus Exim gains the &%tls_dh_max_bits%& global option,
29183 which applies to all D-H usage, client or server. If the value returned by
29184 GnuTLS is greater than &%tls_dh_max_bits%& then the value will be clamped down
29185 to &%tls_dh_max_bits%&. The default value has been set at the current NSS
29186 limit, which is still much higher than Exim historically used.
29188 The filename and bits used will change as the GnuTLS maintainers change the
29189 value for their parameter &`GNUTLS_SEC_PARAM_NORMAL`&, as clamped by
29190 &%tls_dh_max_bits%&. At the time of writing (mid 2012), GnuTLS 2.12 recommends
29191 2432 bits, while NSS is limited to 2236 bits.
29193 In fact, the requested value will be *lower* than &%tls_dh_max_bits%&, to
29194 increase the chance of the generated prime actually being within acceptable
29195 bounds, as GnuTLS has been observed to overshoot. Note the check step in the
29196 procedure above. There is no sane procedure available to Exim to double-check
29197 the size of the generated prime, so it might still be too large.
29200 .section "Requiring specific ciphers in OpenSSL" "SECTreqciphssl"
29201 .cindex "TLS" "requiring specific ciphers (OpenSSL)"
29202 .oindex "&%tls_require_ciphers%&" "OpenSSL"
29203 There is a function in the OpenSSL library that can be passed a list of cipher
29204 suites before the cipher negotiation takes place. This specifies which ciphers
29205 are acceptable for TLS versions prior to 1.3.
29206 The list is colon separated and may contain names like
29207 DES-CBC3-SHA. Exim passes the expanded value of &%tls_require_ciphers%&
29208 directly to this function call.
29209 Many systems will install the OpenSSL manual-pages, so you may have
29210 &'ciphers(1)'& available to you.
29211 The following quotation from the OpenSSL
29212 documentation specifies what forms of item are allowed in the cipher string:
29215 It can consist of a single cipher suite such as RC4-SHA.
29217 It can represent a list of cipher suites containing a certain algorithm,
29218 or cipher suites of a certain type. For example SHA1 represents all
29219 ciphers suites using the digest algorithm SHA1 and SSLv3 represents all
29222 Lists of cipher suites can be combined in a single cipher string using
29223 the + character. This is used as a logical and operation. For example
29224 SHA1+DES represents all cipher suites containing the SHA1 and the DES
29228 Each cipher string can be optionally preceded by one of the characters &`!`&,
29231 If &`!`& is used, the ciphers are permanently deleted from the list. The
29232 ciphers deleted can never reappear in the list even if they are explicitly
29235 If &`-`& is used, the ciphers are deleted from the list, but some or all
29236 of the ciphers can be added again by later options.
29238 If &`+`& is used, the ciphers are moved to the end of the list. This
29239 option does not add any new ciphers; it just moves matching existing ones.
29242 If none of these characters is present, the string is interpreted as
29243 a list of ciphers to be appended to the current preference list. If the list
29244 includes any ciphers already present they will be ignored: that is, they will
29245 not be moved to the end of the list.
29248 The OpenSSL &'ciphers(1)'& command may be used to test the results of a given
29251 # note single-quotes to get ! past any shell history expansion
29252 $ openssl ciphers 'HIGH:!MD5:!SHA1'
29255 This example will let the library defaults be permitted on the MX port, where
29256 there's probably no identity verification anyway, but ups the ante on the
29257 submission ports where the administrator might have some influence on the
29258 choice of clients used:
29260 # OpenSSL variant; see man ciphers(1)
29261 tls_require_ciphers = ${if =={$received_port}{25}\
29266 This example will prefer ECDSA-authenticated ciphers over RSA ones:
29268 tls_require_ciphers = ECDSA:RSA:!COMPLEMENTOFDEFAULT
29271 For TLS version 1.3 the control available is less fine-grained
29272 and Exim does not provide access to it at present.
29273 The value of the &%tls_require_ciphers%& option is ignored when
29274 TLS version 1.3 is negotiated.
29276 As of writing the library default cipher suite list for TLSv1.3 is
29278 TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256
29282 .section "Requiring specific ciphers or other parameters in GnuTLS" &&&
29284 .cindex "GnuTLS" "specifying parameters for"
29285 .cindex "TLS" "specifying ciphers (GnuTLS)"
29286 .cindex "TLS" "specifying key exchange methods (GnuTLS)"
29287 .cindex "TLS" "specifying MAC algorithms (GnuTLS)"
29288 .cindex "TLS" "specifying protocols (GnuTLS)"
29289 .cindex "TLS" "specifying priority string (GnuTLS)"
29290 .oindex "&%tls_require_ciphers%&" "GnuTLS"
29291 The GnuTLS library allows the caller to provide a "priority string", documented
29292 as part of the &[gnutls_priority_init]& function. This is very similar to the
29293 ciphersuite specification in OpenSSL.
29295 The &%tls_require_ciphers%& option is treated as the GnuTLS priority string
29296 and controls both protocols and ciphers.
29298 The &%tls_require_ciphers%& option is available both as an global option,
29299 controlling how Exim behaves as a server, and also as an option of the
29300 &(smtp)& transport, controlling how Exim behaves as a client. In both cases
29301 the value is string expanded. The resulting string is not an Exim list and
29302 the string is given to the GnuTLS library, so that Exim does not need to be
29303 aware of future feature enhancements of GnuTLS.
29305 Documentation of the strings accepted may be found in the GnuTLS manual, under
29306 "Priority strings". This is online as
29307 &url(https://www.gnutls.org/manual/html_node/Priority-Strings.html),
29308 but beware that this relates to GnuTLS 3, which may be newer than the version
29309 installed on your system. If you are using GnuTLS 3,
29310 then the example code
29311 &url(https://www.gnutls.org/manual/gnutls.html#Listing-the-ciphersuites-in-a-priority-string)
29312 on that site can be used to test a given string.
29316 # Disable older versions of protocols
29317 tls_require_ciphers = NORMAL:%LATEST_RECORD_VERSION:-VERS-SSL3.0
29320 Prior to Exim 4.80, an older API of GnuTLS was used, and Exim supported three
29321 additional options, "&%gnutls_require_kx%&", "&%gnutls_require_mac%&" and
29322 "&%gnutls_require_protocols%&". &%tls_require_ciphers%& was an Exim list.
29324 This example will let the library defaults be permitted on the MX port, where
29325 there's probably no identity verification anyway, and lowers security further
29326 by increasing compatibility; but this ups the ante on the submission ports
29327 where the administrator might have some influence on the choice of clients
29331 tls_require_ciphers = ${if =={$received_port}{25}\
29337 .section "Configuring an Exim server to use TLS" "SECID182"
29338 .cindex "TLS" "configuring an Exim server"
29339 .cindex "ESMTP extensions" STARTTLS
29340 When Exim has been built with TLS support, it advertises the availability of
29341 the STARTTLS command to client hosts that match &%tls_advertise_hosts%&,
29342 but not to any others. The default value of this option is *, which means
29343 that STARTTLS is always advertised. Set it to blank to never advertise;
29344 this is reasonable for systems that want to use TLS only as a client.
29346 If STARTTLS is to be used you
29347 need to set some other options in order to make TLS available.
29349 If a client issues a STARTTLS command and there is some configuration
29350 problem in the server, the command is rejected with a 454 error. If the client
29351 persists in trying to issue SMTP commands, all except QUIT are rejected
29354 554 Security failure
29356 If a STARTTLS command is issued within an existing TLS session, it is
29357 rejected with a 554 error code.
29359 To enable TLS operations on a server, the &%tls_advertise_hosts%& option
29360 must be set to match some hosts. The default is * which matches all hosts.
29362 If this is all you do, TLS encryption will be enabled but not authentication -
29363 meaning that the peer has no assurance it is actually you he is talking to.
29364 You gain protection from a passive sniffer listening on the wire but not
29365 from someone able to intercept the communication.
29367 Further protection requires some further configuration at the server end.
29369 To make TLS work you need to set, in the server,
29371 tls_certificate = /some/file/name
29372 tls_privatekey = /some/file/name
29374 These options are, in fact, expanded strings, so you can make them depend on
29375 the identity of the client that is connected if you wish. The first file
29376 contains the server's X509 certificate, and the second contains the private key
29377 that goes with it. These files need to be
29378 PEM format and readable by the Exim user, and must
29379 always be given as full path names.
29380 The key must not be password-protected.
29381 They can be the same file if both the
29382 certificate and the key are contained within it. If &%tls_privatekey%& is not
29383 set, or if its expansion is forced to fail or results in an empty string, this
29384 is assumed to be the case. The certificate file may also contain intermediate
29385 certificates that need to be sent to the client to enable it to authenticate
29386 the server's certificate.
29388 For dual-stack (eg. RSA and ECDSA) configurations, these options can be
29389 colon-separated lists of file paths. Ciphers using given authentication
29390 algorithms require the presence of a suitable certificate to supply the
29391 public-key. The server selects among the certificates to present to the
29392 client depending on the selected cipher, hence the priority ordering for
29393 ciphers will affect which certificate is used.
29395 If you do not understand about certificates and keys, please try to find a
29396 source of this background information, which is not Exim-specific. (There are a
29397 few comments below in section &<<SECTcerandall>>&.)
29399 &*Note*&: These options do not apply when Exim is operating as a client &--
29400 they apply only in the case of a server. If you need to use a certificate in an
29401 Exim client, you must set the options of the same names in an &(smtp)&
29404 With just these options, an Exim server will be able to use TLS. It does not
29405 require the client to have a certificate (but see below for how to insist on
29406 this). There is one other option that may be needed in other situations. If
29408 tls_dhparam = /some/file/name
29410 is set, the SSL library is initialized for the use of Diffie-Hellman ciphers
29411 with the parameters contained in the file.
29412 Set this to &`none`& to disable use of DH entirely, by making no prime
29417 This may also be set to a string identifying a standard prime to be used for
29418 DH; if it is set to &`default`& or, for OpenSSL, is unset, then the prime
29419 used is &`ike23`&. There are a few standard primes available, see the
29420 documentation for &%tls_dhparam%& for the complete list.
29426 for a way of generating file data.
29428 The strings supplied for these three options are expanded every time a client
29429 host connects. It is therefore possible to use different certificates and keys
29430 for different hosts, if you so wish, by making use of the client's IP address
29431 in &$sender_host_address$& to control the expansion. If a string expansion is
29432 forced to fail, Exim behaves as if the option is not set.
29434 .cindex "cipher" "logging"
29435 .cindex "log" "TLS cipher"
29436 .vindex "&$tls_in_cipher$&"
29437 The variable &$tls_in_cipher$& is set to the cipher suite that was negotiated for
29438 an incoming TLS connection. It is included in the &'Received:'& header of an
29439 incoming message (by default &-- you can, of course, change this), and it is
29440 also included in the log line that records a message's arrival, keyed by
29441 &"X="&, unless the &%tls_cipher%& log selector is turned off. The &%encrypted%&
29442 condition can be used to test for specific cipher suites in ACLs.
29444 Once TLS has been established, the ACLs that run for subsequent SMTP commands
29445 can check the name of the cipher suite and vary their actions accordingly. The
29446 cipher suite names vary, depending on which TLS library is being used. For
29447 example, OpenSSL uses the name DES-CBC3-SHA for the cipher suite which in other
29448 contexts is known as TLS_RSA_WITH_3DES_EDE_CBC_SHA. Check the OpenSSL or GnuTLS
29449 documentation for more details.
29451 For outgoing SMTP deliveries, &$tls_out_cipher$& is used and logged
29452 (again depending on the &%tls_cipher%& log selector).
29455 .section "Requesting and verifying client certificates" "SECID183"
29456 .cindex "certificate" "verification of client"
29457 .cindex "TLS" "client certificate verification"
29458 If you want an Exim server to request a certificate when negotiating a TLS
29459 session with a client, you must set either &%tls_verify_hosts%& or
29460 &%tls_try_verify_hosts%&. You can, of course, set either of them to * to
29461 apply to all TLS connections. For any host that matches one of these options,
29462 Exim requests a certificate as part of the setup of the TLS session. The
29463 contents of the certificate are verified by comparing it with a list of
29464 expected trust-anchors or certificates.
29465 These may be the system default set (depending on library version),
29466 an explicit file or,
29467 depending on library version, a directory, identified by
29468 &%tls_verify_certificates%&.
29470 A file can contain multiple certificates, concatenated end to end. If a
29473 each certificate must be in a separate file, with a name (or a symbolic link)
29474 of the form <&'hash'&>.0, where <&'hash'&> is a hash value constructed from the
29475 certificate. You can compute the relevant hash by running the command
29477 openssl x509 -hash -noout -in /cert/file
29479 where &_/cert/file_& contains a single certificate.
29481 There is no checking of names of the client against the certificate
29482 Subject Name or Subject Alternate Names.
29484 The difference between &%tls_verify_hosts%& and &%tls_try_verify_hosts%& is
29485 what happens if the client does not supply a certificate, or if the certificate
29486 does not match any of the certificates in the collection named by
29487 &%tls_verify_certificates%&. If the client matches &%tls_verify_hosts%&, the
29488 attempt to set up a TLS session is aborted, and the incoming connection is
29489 dropped. If the client matches &%tls_try_verify_hosts%&, the (encrypted) SMTP
29490 session continues. ACLs that run for subsequent SMTP commands can detect the
29491 fact that no certificate was verified, and vary their actions accordingly. For
29492 example, you can insist on a certificate before accepting a message for
29493 relaying, but not when the message is destined for local delivery.
29495 .vindex "&$tls_in_peerdn$&"
29496 When a client supplies a certificate (whether it verifies or not), the value of
29497 the Distinguished Name of the certificate is made available in the variable
29498 &$tls_in_peerdn$& during subsequent processing of the message.
29500 .cindex "log" "distinguished name"
29501 Because it is often a long text string, it is not included in the log line or
29502 &'Received:'& header by default. You can arrange for it to be logged, keyed by
29503 &"DN="&, by setting the &%tls_peerdn%& log selector, and you can use
29504 &%received_header_text%& to change the &'Received:'& header. When no
29505 certificate is supplied, &$tls_in_peerdn$& is empty.
29508 .section "Revoked certificates" "SECID184"
29509 .cindex "TLS" "revoked certificates"
29510 .cindex "revocation list"
29511 .cindex "certificate" "revocation list"
29512 .cindex "OCSP" "stapling"
29513 Certificate issuing authorities issue Certificate Revocation Lists (CRLs) when
29514 certificates are revoked. If you have such a list, you can pass it to an Exim
29515 server using the global option called &%tls_crl%& and to an Exim client using
29516 an identically named option for the &(smtp)& transport. In each case, the value
29517 of the option is expanded and must then be the name of a file that contains a
29519 The downside is that clients have to periodically re-download a potentially huge
29520 file from every certificate authority they know of.
29522 The way with most moving parts at query time is Online Certificate
29523 Status Protocol (OCSP), where the client verifies the certificate
29524 against an OCSP server run by the CA. This lets the CA track all
29525 usage of the certs. It requires running software with access to the
29526 private key of the CA, to sign the responses to the OCSP queries. OCSP
29527 is based on HTTP and can be proxied accordingly.
29529 The only widespread OCSP server implementation (known to this writer)
29530 comes as part of OpenSSL and aborts on an invalid request, such as
29531 connecting to the port and then disconnecting. This requires
29532 re-entering the passphrase each time some random client does this.
29534 The third way is OCSP Stapling; in this, the server using a certificate
29535 issued by the CA periodically requests an OCSP proof of validity from
29536 the OCSP server, then serves it up inline as part of the TLS
29537 negotiation. This approach adds no extra round trips, does not let the
29538 CA track users, scales well with number of certs issued by the CA and is
29539 resilient to temporary OCSP server failures, as long as the server
29540 starts retrying to fetch an OCSP proof some time before its current
29541 proof expires. The downside is that it requires server support.
29543 Unless Exim is built with the support disabled,
29544 or with GnuTLS earlier than version 3.3.16 / 3.4.8
29545 support for OCSP stapling is included.
29547 There is a global option called &%tls_ocsp_file%&.
29548 The file specified therein is expected to be in DER format, and contain
29549 an OCSP proof. Exim will serve it as part of the TLS handshake. This
29550 option will be re-expanded for SNI, if the &%tls_certificate%& option
29551 contains &`tls_in_sni`&, as per other TLS options.
29553 Exim does not at this time implement any support for fetching a new OCSP
29554 proof. The burden is on the administrator to handle this, outside of
29555 Exim. The file specified should be replaced atomically, so that the
29556 contents are always valid. Exim will expand the &%tls_ocsp_file%& option
29557 on each connection, so a new file will be handled transparently on the
29560 When built with OpenSSL Exim will check for a valid next update timestamp
29561 in the OCSP proof; if not present, or if the proof has expired, it will be
29564 For the client to be able to verify the stapled OCSP the server must
29565 also supply, in its stapled information, any intermediate
29566 certificates for the chain leading to the OCSP proof from the signer
29567 of the server certificate. There may be zero or one such. These
29568 intermediate certificates should be added to the server OCSP stapling
29569 file named by &%tls_ocsp_file%&.
29571 Note that the proof only covers the terminal server certificate,
29572 not any of the chain from CA to it.
29574 There is no current way to staple a proof for a client certificate.
29577 A helper script "ocsp_fetch.pl" for fetching a proof from a CA
29578 OCSP server is supplied. The server URL may be included in the
29579 server certificate, if the CA is helpful.
29581 One failure mode seen was the OCSP Signer cert expiring before the end
29582 of validity of the OCSP proof. The checking done by Exim/OpenSSL
29583 noted this as invalid overall, but the re-fetch script did not.
29587 .section "Caching of static server configuration items" "SECTserverTLScache"
29588 .cindex certificate caching
29589 .cindex privatekey caching
29590 .cindex crl caching
29591 .cindex ocsp caching
29592 .cindex ciphers caching
29593 .cindex "CA bundle" caching
29594 .cindex "certificate authorities" caching
29595 .cindex tls_certificate caching
29596 .cindex tls_privatekey caching
29597 .cindex tls_crl caching
29598 .cindex tls_ocsp_file caching
29599 .cindex tls_require_ciphers caching
29600 .cindex tls_verify_certificate caching
29601 .cindex caching certificate
29602 .cindex caching privatekey
29603 .cindex caching crl
29604 .cindex caching ocsp
29605 .cindex caching ciphers
29606 .cindex caching "certificate authorities
29607 If any of the main configuration options &%tls_certificate%&, &%tls_privatekey%&,
29608 &%tls_crl%& and &%tls_ocsp_file%& have values with no
29609 expandable elements,
29610 then the associated information is loaded at daemon startup.
29611 It is made available
29612 to child processes forked for handling received SMTP connections.
29614 This caching is currently only supported under Linux and FreeBSD.
29616 If caching is not possible, for example if an item has to be dependent
29617 on the peer host so contains a &$sender_host_name$& expansion, the load
29618 of the associated information is done at the startup of the TLS connection.
29620 The cache is invalidated and reloaded after any changes to the directories
29621 containing files specified by these options.
29623 The information specified by the main option &%tls_verify_certificates%&
29624 is similarly cached so long as it specifies files explicitly
29625 or (under GnuTLS) is the string &"system,cache"&.
29626 The latter case is not automatically invalidated;
29627 it is the operator's responsibility to arrange for a daemon restart
29628 any time the system certificate authority bundle is updated.
29629 A HUP signal is sufficient for this.
29630 The value &"system"& results in no caching under GnuTLS.
29632 The macro _HAVE_TLS_CA_CACHE will be defined if the suffix for "system"
29633 is acceptable in configurations for the Exim executavble.
29635 Caching of the system Certificate Authorities bundle can
29636 save siginificant time and processing on every TLS connection
29642 .section "Configuring an Exim client to use TLS" "SECTclientTLS"
29643 .cindex "cipher" "logging"
29644 .cindex "log" "TLS cipher"
29645 .cindex "log" "distinguished name"
29646 .cindex "TLS" "configuring an Exim client"
29647 The &%tls_cipher%& and &%tls_peerdn%& log selectors apply to outgoing SMTP
29648 deliveries as well as to incoming, the latter one causing logging of the
29649 server certificate's DN. The remaining client configuration for TLS is all
29650 within the &(smtp)& transport.
29652 .cindex "ESMTP extensions" STARTTLS
29653 It is not necessary to set any options to have TLS work in the &(smtp)&
29654 transport. If Exim is built with TLS support, and TLS is advertised by a
29655 server, the &(smtp)& transport always tries to start a TLS session. However,
29656 this can be prevented by setting &%hosts_avoid_tls%& (an option of the
29657 transport) to a list of server hosts for which TLS should not be used.
29659 If you do not want Exim to attempt to send messages unencrypted when an attempt
29660 to set up an encrypted connection fails in any way, you can set
29661 &%hosts_require_tls%& to a list of hosts for which encryption is mandatory. For
29662 those hosts, delivery is always deferred if an encrypted connection cannot be
29663 set up. If there are any other hosts for the address, they are tried in the
29666 When the server host is not in &%hosts_require_tls%&, Exim may try to deliver
29667 the message unencrypted. It always does this if the response to STARTTLS is
29668 a 5&'xx'& code. For a temporary error code, or for a failure to negotiate a TLS
29669 session after a success response code, what happens is controlled by the
29670 &%tls_tempfail_tryclear%& option of the &(smtp)& transport. If it is false,
29671 delivery to this host is deferred, and other hosts (if available) are tried. If
29672 it is true, Exim attempts to deliver unencrypted after a 4&'xx'& response to
29673 STARTTLS, and if STARTTLS is accepted, but the subsequent TLS
29674 negotiation fails, Exim closes the current connection (because it is in an
29675 unknown state), opens a new one to the same host, and then tries the delivery
29678 The &%tls_certificate%& and &%tls_privatekey%& options of the &(smtp)&
29679 transport provide the client with a certificate, which is passed to the server
29681 This is an optional thing for TLS connections, although either end
29683 If the server is Exim, it will request a certificate only if
29684 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client.
29686 &*Note*&: Do not use a certificate which has the OCSP-must-staple extension,
29687 for client use (they are usable for server use).
29688 As the TLS protocol has no means for the client to staple before TLS 1.3 it will result
29689 in failed connections.
29691 If the &%tls_verify_certificates%& option is set on the &(smtp)& transport, it
29692 specifies a collection of expected server certificates.
29694 the system default set (depending on library version),
29696 or (depending on library version) a directory.
29697 The client verifies the server's certificate
29698 against this collection, taking into account any revoked certificates that are
29699 in the list defined by &%tls_crl%&.
29700 Failure to verify fails the TLS connection unless either of the
29701 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& options are set.
29703 The &%tls_verify_hosts%& and &%tls_try_verify_hosts%& options restrict
29704 certificate verification to the listed servers. Verification either must
29705 or need not succeed respectively.
29707 The &%tls_verify_cert_hostnames%& option lists hosts for which additional
29708 name checks are made on the server certificate.
29709 The match against this list is, as per other Exim usage, the
29710 IP for the host. That is most closely associated with the
29711 name on the DNS A (or AAAA) record for the host.
29712 However, the name that needs to be in the certificate
29713 is the one at the head of any CNAME chain leading to the A record.
29714 The option defaults to always checking.
29716 The &(smtp)& transport has two OCSP-related options:
29717 &%hosts_require_ocsp%&; a host-list for which a Certificate Status
29718 is requested and required for the connection to proceed. The default
29720 &%hosts_request_ocsp%&; a host-list for which (additionally)
29721 a Certificate Status is requested (but not necessarily verified). The default
29722 value is "*" meaning that requests are made unless configured
29725 The host(s) should also be in &%hosts_require_tls%&, and
29726 &%tls_verify_certificates%& configured for the transport,
29727 for OCSP to be relevant.
29730 &%tls_require_ciphers%& is set on the &(smtp)& transport, it must contain a
29731 list of permitted cipher suites. If either of these checks fails, delivery to
29732 the current host is abandoned, and the &(smtp)& transport tries to deliver to
29733 alternative hosts, if any.
29736 These options must be set in the &(smtp)& transport for Exim to use TLS when it
29737 is operating as a client. Exim does not assume that a server certificate (set
29738 by the global options of the same name) should also be used when operating as a
29742 .vindex "&$host_address$&"
29743 All the TLS options in the &(smtp)& transport are expanded before use, with
29744 &$host$& and &$host_address$& containing the name and address of the server to
29745 which the client is connected. Forced failure of an expansion causes Exim to
29746 behave as if the relevant option were unset.
29748 .vindex &$tls_out_bits$&
29749 .vindex &$tls_out_cipher$&
29750 .vindex &$tls_out_peerdn$&
29751 .vindex &$tls_out_sni$&
29752 Before an SMTP connection is established, the
29753 &$tls_out_bits$&, &$tls_out_cipher$&, &$tls_out_peerdn$& and &$tls_out_sni$&
29754 variables are emptied. (Until the first connection, they contain the values
29755 that were set when the message was received.) If STARTTLS is subsequently
29756 successfully obeyed, these variables are set to the relevant values for the
29757 outgoing connection.
29761 .section "Caching of static client configuration items" "SECTclientTLScache"
29762 .cindex certificate caching
29763 .cindex privatekey caching
29764 .cindex crl caching
29765 .cindex ciphers caching
29766 .cindex "CA bundle" caching
29767 .cindex "certificate authorities" caching
29768 .cindex tls_certificate caching
29769 .cindex tls_privatekey caching
29770 .cindex tls_crl caching
29771 .cindex tls_require_ciphers caching
29772 .cindex tls_verify_certificate caching
29773 .cindex caching certificate
29774 .cindex caching privatekey
29775 .cindex caching crl
29776 .cindex caching ciphers
29777 .cindex caching "certificate authorities
29778 If any of the transport configuration options &%tls_certificate%&, &%tls_privatekey%&
29779 and &%tls_crl%& have values with no
29780 expandable elements,
29781 then the associated information is loaded per smtp transport
29782 at daemon startup, at the start of a queue run, or on a
29783 command-line specified message delivery.
29784 It is made available
29785 to child processes forked for handling making SMTP connections.
29787 This caching is currently only supported under Linux.
29789 If caching is not possible, the load
29790 of the associated information is done at the startup of the TLS connection.
29792 The cache is invalidated in the daemon
29793 and reloaded after any changes to the directories
29794 containing files specified by these options.
29796 The information specified by the main option &%tls_verify_certificates%&
29797 is similarly cached so long as it specifies files explicitly
29798 or (under GnuTLS) is the string &"system,cache"&.
29799 The latter case is not automatically invaludated;
29800 it is the operator's responsibility to arrange for a daemon restart
29801 any time the system certificate authority bundle is updated.
29802 A HUP signal is sufficient for this.
29803 The value &"system"& results in no caching under GnuTLS.
29805 The macro _HAVE_TLS_CA_CACHE will be defined if the suffix for "system"
29806 is acceptable in configurations for the Exim executavble.
29808 Caching of the system Certificate Authorities bundle can
29809 save siginificant time and processing on every TLS connection
29815 .section "Use of TLS Server Name Indication" "SECTtlssni"
29816 .cindex "TLS" "Server Name Indication"
29819 .vindex "&$tls_in_sni$&"
29820 .oindex "&%tls_in_sni%&"
29821 With TLS1.0 or above, there is an extension mechanism by which extra
29822 information can be included at various points in the protocol. One of these
29823 extensions, documented in RFC 6066 (and before that RFC 4366) is
29824 &"Server Name Indication"&, commonly &"SNI"&. This extension is sent by the
29825 client in the initial handshake, so that the server can examine the servername
29826 within and possibly choose to use different certificates and keys (and more)
29829 This is analogous to HTTP's &"Host:"& header, and is the main mechanism by
29830 which HTTPS-enabled web-sites can be virtual-hosted, many sites to one IP
29833 With SMTP to MX, there are the same problems here as in choosing the identity
29834 against which to validate a certificate: you can't rely on insecure DNS to
29835 provide the identity which you then cryptographically verify. So this will
29836 be of limited use in that environment.
29838 With SMTP to Submission, there is a well-defined hostname which clients are
29839 connecting to and can validate certificates against. Thus clients &*can*&
29840 choose to include this information in the TLS negotiation. If this becomes
29841 wide-spread, then hosters can choose to present different certificates to
29842 different clients. Or even negotiate different cipher suites.
29844 The &%tls_sni%& option on an SMTP transport is an expanded string; the result,
29845 if not empty, will be sent on a TLS session as part of the handshake. There's
29846 nothing more to it. Choosing a sensible value not derived insecurely is the
29847 only point of caution. The &$tls_out_sni$& variable will be set to this string
29848 for the lifetime of the client connection (including during authentication).
29850 If DANE validated the connection attempt then the value of the &%tls_sni%& option
29851 is forced to the name of the destination host, after any MX- or CNAME-following.
29853 Except during SMTP client sessions, if &$tls_in_sni$& is set then it is a string
29854 received from a client.
29855 It can be logged with the &%log_selector%& item &`+tls_sni`&.
29857 If the string &`tls_in_sni`& appears in the main section's &%tls_certificate%&
29858 option (prior to expansion) then the following options will be re-expanded
29859 during TLS session handshake, to permit alternative values to be chosen:
29862 &%tls_certificate%&
29868 &%tls_verify_certificates%&
29873 Great care should be taken to deal with matters of case, various injection
29874 attacks in the string (&`../`& or SQL), and ensuring that a valid filename
29875 can always be referenced; it is important to remember that &$tls_in_sni$& is
29876 arbitrary unverified data provided prior to authentication.
29877 Further, the initial certificate is loaded before SNI has arrived, so
29878 an expansion for &%tls_certificate%& must have a default which is used
29879 when &$tls_in_sni$& is empty.
29881 The Exim developers are proceeding cautiously and so far no other TLS options
29884 When Exim is built against OpenSSL, OpenSSL must have been built with support
29885 for TLS Extensions. This holds true for OpenSSL 1.0.0+ and 0.9.8+ with
29886 enable-tlsext in EXTRACONFIGURE. If you invoke &(openssl s_client -h)& and
29887 see &`-servername`& in the output, then OpenSSL has support.
29889 When Exim is built against GnuTLS, SNI support is available as of GnuTLS
29890 0.5.10. (Its presence predates the current API which Exim uses, so if Exim
29891 built, then you have SNI support).
29894 .cindex ALPN "general information"
29895 .cindex TLS "Application Layer Protocol Names"
29896 There is a TLS feature related to SNI
29897 called Application Layer Protocol Name (ALPN).
29898 This is intended to declare, or select, what protocol layer will be using a TLS
29900 The client for the connection proposes a set of protocol names, and
29901 the server responds with a selected one.
29902 It is not, as of 2021, commonly used for SMTP connections.
29903 However, to guard against misirected or malicious use of web clients
29904 (which often do use ALPN) against MTA ports, Exim by default check that
29905 there is no incompatible ALPN specified by a client for a TLS connection.
29906 If there is, the connection is rejected.
29908 As a client Exim does not supply ALPN by default.
29909 The behaviour of both client and server can be configured using the options
29910 &%tls_alpn%& and &%hosts_require_alpn%&.
29911 There are no variables providing observability.
29912 Some feature-specific logging may appear on denied connections, but this
29913 depends on the behavious of the peer
29914 (not all peers can send a feature-specific TLS Alert).
29916 This feature is available when Exim is built with
29917 OpenSSL 1.1.0 or later or GnuTLS 3.2.0 or later;
29918 the macro _HAVE_TLS_ALPN will be defined when this is so.
29922 .section "Multiple messages on the same encrypted TCP/IP connection" &&&
29924 .cindex "multiple SMTP deliveries with TLS"
29925 .cindex "TLS" "multiple message deliveries"
29926 Exim sends multiple messages down the same TCP/IP connection by starting up
29927 an entirely new delivery process for each message, passing the socket from
29928 one process to the next. This implementation does not fit well with the use
29929 of TLS, because there is quite a lot of state information associated with a TLS
29930 connection, not just a socket identification. Passing all the state information
29931 to a new process is not feasible. Consequently, for sending using TLS Exim
29932 starts an additional proxy process for handling the encryption, piping the
29933 unencrypted data stream from and to the delivery processes.
29935 An older mode of operation can be enabled on a per-host basis by the
29936 &%hosts_noproxy_tls%& option on the &(smtp)& transport. If the host matches
29937 this list the proxy process described above is not used; instead Exim
29938 shuts down an existing TLS session being run by the delivery process
29939 before passing the socket to a new process. The new process may then
29940 try to start a new TLS session, and if successful, may try to re-authenticate
29941 if AUTH is in use, before sending the next message.
29943 The RFC is not clear as to whether or not an SMTP session continues in clear
29944 after TLS has been shut down, or whether TLS may be restarted again later, as
29945 just described. However, if the server is Exim, this shutdown and
29946 reinitialization works. It is not known which (if any) other servers operate
29947 successfully if the client closes a TLS session and continues with unencrypted
29948 SMTP, but there are certainly some that do not work. For such servers, Exim
29949 should not pass the socket to another process, because the failure of the
29950 subsequent attempt to use it would cause Exim to record a temporary host error,
29951 and delay other deliveries to that host.
29953 To test for this case, Exim sends an EHLO command to the server after
29954 closing down the TLS session. If this fails in any way, the connection is
29955 closed instead of being passed to a new delivery process, but no retry
29956 information is recorded.
29958 There is also a manual override; you can set &%hosts_nopass_tls%& on the
29959 &(smtp)& transport to match those hosts for which Exim should not pass
29960 connections to new processes if TLS has been used.
29965 .section "Certificates and all that" "SECTcerandall"
29966 .cindex "certificate" "references to discussion"
29967 In order to understand fully how TLS works, you need to know about
29968 certificates, certificate signing, and certificate authorities.
29969 This is a large topic and an introductory guide is unsuitable for the Exim
29970 reference manual, so instead we provide pointers to existing documentation.
29972 The Apache web-server was for a long time the canonical guide, so their
29973 documentation is a good place to start; their SSL module's Introduction
29974 document is currently at
29976 &url(https://httpd.apache.org/docs/current/ssl/ssl_intro.html)
29978 and their FAQ is at
29980 &url(https://httpd.apache.org/docs/current/ssl/ssl_faq.html)
29983 Eric Rescorla's book, &'SSL and TLS'&, published by Addison-Wesley (ISBN
29984 0-201-61598-3) in 2001, contains both introductory and more in-depth
29986 More recently Ivan Ristić's book &'Bulletproof SSL and TLS'&,
29987 published by Feisty Duck (ISBN 978-1907117046) in 2013 is good.
29988 Ivan is the author of the popular TLS testing tools at
29989 &url(https://www.ssllabs.com/).
29992 .section "Certificate chains" "SECID186"
29993 A file named by &%tls_certificate%& may contain more than one
29994 certificate. This is useful in the case where the certificate that is being
29995 sent is validated by an intermediate certificate which the other end does
29996 not have. Multiple certificates must be in the correct order in the file.
29997 First the host's certificate itself, then the first intermediate
29998 certificate to validate the issuer of the host certificate, then the next
29999 intermediate certificate to validate the issuer of the first intermediate
30000 certificate, and so on, until finally (optionally) the root certificate.
30001 The root certificate must already be trusted by the recipient for
30002 validation to succeed, of course, but if it's not preinstalled, sending the
30003 root certificate along with the rest makes it available for the user to
30004 install if the receiving end is a client MUA that can interact with a user.
30006 Note that certificates using MD5 are unlikely to work on today's Internet;
30007 even if your libraries allow loading them for use in Exim when acting as a
30008 server, increasingly clients will not accept such certificates. The error
30009 diagnostics in such a case can be frustratingly vague.
30013 .section "Self-signed certificates" "SECID187"
30014 .cindex "certificate" "self-signed"
30015 You can create a self-signed certificate using the &'req'& command provided
30016 with OpenSSL, like this:
30017 . ==== Do not shorten the duration here without reading and considering
30018 . ==== the text below. Please leave it at 9999 days.
30020 openssl req -x509 -newkey rsa:1024 -keyout file1 -out file2 \
30023 &_file1_& and &_file2_& can be the same file; the key and the certificate are
30024 delimited and so can be identified independently. The &%-days%& option
30025 specifies a period for which the certificate is valid. The &%-nodes%& option is
30026 important: if you do not set it, the key is encrypted with a passphrase
30027 that you are prompted for, and any use that is made of the key causes more
30028 prompting for the passphrase. This is not helpful if you are going to use
30029 this certificate and key in an MTA, where prompting is not possible.
30031 . ==== I expect to still be working 26 years from now. The less technical
30032 . ==== debt I create, in terms of storing up trouble for my later years, the
30033 . ==== happier I will be then. We really have reached the point where we
30034 . ==== should start, at the very least, provoking thought and making folks
30035 . ==== pause before proceeding, instead of leaving all the fixes until two
30036 . ==== years before 2^31 seconds after the 1970 Unix epoch.
30038 NB: we are now past the point where 9999 days takes us past the 32-bit Unix
30039 epoch. If your system uses unsigned time_t (most do) and is 32-bit, then
30040 the above command might produce a date in the past. Think carefully about
30041 the lifetime of the systems you're deploying, and either reduce the duration
30042 of the certificate or reconsider your platform deployment. (At time of
30043 writing, reducing the duration is the most likely choice, but the inexorable
30044 progression of time takes us steadily towards an era where this will not
30045 be a sensible resolution).
30047 A self-signed certificate made in this way is sufficient for testing, and
30048 may be adequate for all your requirements if you are mainly interested in
30049 encrypting transfers, and not in secure identification.
30051 However, many clients require that the certificate presented by the server be a
30052 user (also called &"leaf"& or &"site"&) certificate, and not a self-signed
30053 certificate. In this situation, the self-signed certificate described above
30054 must be installed on the client host as a trusted root &'certification
30055 authority'& (CA), and the certificate used by Exim must be a user certificate
30056 signed with that self-signed certificate.
30058 For information on creating self-signed CA certificates and using them to sign
30059 user certificates, see the &'General implementation overview'& chapter of the
30060 Open-source PKI book, available online at
30061 &url(https://sourceforge.net/projects/ospkibook/).
30062 .ecindex IIDencsmtp1
30063 .ecindex IIDencsmtp2
30066 .section "TLS Resumption" "SECTresumption"
30067 .cindex TLS resumption
30068 TLS Session Resumption for TLS 1.2 and TLS 1.3 connections can be used (defined
30069 in RFC 5077 for 1.2). The support for this requires GnuTLS 3.6.3 or OpenSSL 1.1.1
30072 Session resumption (this is the "stateless" variant) involves the server sending
30073 a "session ticket" to the client on one connection, which can be stored by the
30074 client and used for a later session. The ticket contains sufficient state for
30075 the server to reconstruct the TLS session, avoiding some expensive crypto
30076 calculation and (on TLS1.2) one full packet roundtrip time.
30079 Operational cost/benefit:
30081 The extra data being transmitted costs a minor amount, and the client has
30082 extra costs in storing and retrieving the data.
30084 In the Exim/Gnutls implementation the extra cost on an initial connection
30085 which is TLS1.2 over a loopback path is about 6ms on 2017-laptop class hardware.
30086 The saved cost on a subsequent connection is about 4ms; three or more
30087 connections become a net win. On longer network paths, two or more
30088 connections will have an average lower startup time thanks to the one
30089 saved packet roundtrip. TLS1.3 will save the crypto cpu costs but not any
30092 .cindex "hints database" tls
30093 Since a new hints DB is used on the TLS client,
30094 the hints DB maintenance should be updated to additionally handle "tls".
30099 The session ticket is encrypted, but is obviously an additional security
30100 vulnarability surface. An attacker able to decrypt it would have access
30101 all connections using the resumed session.
30102 The session ticket encryption key is not committed to storage by the server
30103 and is rotated regularly (OpenSSL: 1hr, and one previous key is used for
30104 overlap; GnuTLS 6hr but does not specify any overlap).
30105 Tickets have limited lifetime (2hr, and new ones issued after 1hr under
30106 OpenSSL. GnuTLS 2hr, appears to not do overlap).
30108 There is a question-mark over the security of the Diffie-Helman parameters
30109 used for session negotiation.
30114 The &%log_selector%& "tls_resumption" appends an asterisk to the tls_cipher "X="
30117 The variables &$tls_in_resumption$& and &$tls_out_resumption$&
30118 have bits 0-4 indicating respectively
30119 support built, client requested ticket, client offered session,
30120 server issued ticket, resume used. A suitable decode list is provided
30121 in the builtin macro _RESUME_DECODE for in &%listextract%& expansions.
30126 The &%tls_resumption_hosts%& main option specifies a hostlist for which
30127 exim, operating as a server, will offer resumption to clients.
30128 Current best practice is to not offer the feature to MUA connection.
30129 Commonly this can be done like this:
30131 tls_resumption_hosts = ${if inlist {$received_port}{587:465} {:}{*}}
30133 If the peer host matches the list after expansion then resumption
30134 is offered and/or accepted.
30136 The &%tls_resumption_hosts%& smtp transport option performs the
30137 equivalent function for operation as a client.
30138 If the peer host matches the list after expansion then resumption
30139 is attempted (if a stored session is available) or the information
30140 stored (if supplied by the peer).
30146 In a resumed session:
30148 The variables &$tls_{in,out}_cipher$& will have values different
30149 to the original (under GnuTLS).
30151 The variables &$tls_{in,out}_ocsp$& will be "not requested" or "no response",
30152 and the &%hosts_require_ocsp%& smtp trasnport option will fail.
30153 . XXX need to do something with that hosts_require_ocsp
30159 .section DANE "SECDANE"
30161 DNS-based Authentication of Named Entities, as applied to SMTP over TLS, provides assurance to a client that
30162 it is actually talking to the server it wants to rather than some attacker operating a Man In The Middle (MITM)
30163 operation. The latter can terminate the TLS connection you make, and make another one to the server (so both
30164 you and the server still think you have an encrypted connection) and, if one of the "well known" set of
30165 Certificate Authorities has been suborned - something which *has* been seen already (2014), a verifiable
30166 certificate (if you're using normal root CAs, eg. the Mozilla set, as your trust anchors).
30168 What DANE does is replace the CAs with the DNS as the trust anchor. The assurance is limited to a) the possibility
30169 that the DNS has been suborned, b) mistakes made by the admins of the target server. The attack surface presented
30170 by (a) is thought to be smaller than that of the set of root CAs.
30172 It also allows the server to declare (implicitly) that connections to it should use TLS. An MITM could simply
30173 fail to pass on a server's STARTTLS.
30175 DANE scales better than having to maintain (and communicate via side-channel) copies of server certificates
30176 for every possible target server. It also scales (slightly) better than having to maintain on an SMTP
30177 client a copy of the standard CAs bundle. It also means not having to pay a CA for certificates.
30179 DANE requires a server operator to do three things: 1) run DNSSEC. This provides assurance to clients
30180 that DNS lookups they do for the server have not been tampered with. The domain MX record applying
30181 to this server, its A record, its TLSA record and any associated CNAME records must all be covered by
30183 2) add TLSA DNS records. These say what the server certificate for a TLS connection should be.
30184 3) offer a server certificate, or certificate chain, in TLS connections which is is anchored by one of the TLSA records.
30186 There are no changes to Exim specific to server-side operation of DANE.
30187 Support for client-side operation of DANE can be included at compile time by defining SUPPORT_DANE=yes
30188 in &_Local/Makefile_&.
30189 If it has been included, the macro "_HAVE_DANE" will be defined.
30191 A TLSA record consist of 4 fields, the "Certificate Usage", the
30192 "Selector", the "Matching type", and the "Certificate Association Data".
30193 For a detailed description of the TLSA record see
30194 &url(https://tools.ietf.org/html/rfc7671#page-5,RFC 7671).
30196 The TLSA record for the server may have "Certificate Usage" (1st) field of DANE-TA(2) or DANE-EE(3).
30197 These are the "Trust Anchor" and "End Entity" variants.
30198 The latter specifies the End Entity directly, i.e. the certificate involved is that of the server
30199 (and if only DANE-EE is used then it should be the sole one transmitted during the TLS handshake);
30200 this is appropriate for a single system, using a self-signed certificate.
30201 DANE-TA usage is effectively declaring a specific CA to be used; this might be a private CA or a public,
30203 A private CA at simplest is just a self-signed certificate (with certain
30204 attributes) which is used to sign server certificates, but running one securely
30205 does require careful arrangement.
30206 With DANE-TA, as implemented in Exim and commonly in other MTAs,
30207 the server TLS handshake must transmit the entire certificate chain from CA to server-certificate.
30208 DANE-TA is commonly used for several services and/or servers, each having a TLSA query-domain CNAME record,
30209 all of which point to a single TLSA record.
30210 DANE-TA and DANE-EE can both be used together.
30212 Our recommendation is to use DANE with a certificate from a public CA,
30213 because this enables a variety of strategies for remote clients to verify
30215 You can then publish information both via DANE and another technology,
30216 "MTA-STS", described below.
30218 When you use DANE-TA to publish trust anchor information, you ask entities
30219 outside your administrative control to trust the Certificate Authority for
30220 connections to you.
30221 If using a private CA then you should expect others to still apply the
30222 technical criteria they'd use for a public CA to your certificates.
30223 In particular, you should probably try to follow current best practices for CA
30224 operation around hash algorithms and key sizes.
30225 Do not expect other organizations to lower their security expectations just
30226 because a particular profile might be reasonable for your own internal use.
30228 When this text was last updated, this in practice means to avoid use of SHA-1
30229 and MD5; if using RSA to use key sizes of at least 2048 bits (and no larger
30230 than 4096, for interoperability); to use keyUsage fields correctly; to use
30231 random serial numbers.
30232 The list of requirements is subject to change as best practices evolve.
30233 If you're not already using a private CA, or it doesn't meet these
30234 requirements, then we encourage you to avoid all these issues and use a public
30235 CA such as &url(https://letsencrypt.org/,Let's Encrypt) instead.
30237 The TLSA record should have a "Selector" (2nd) field of SPKI(1) and
30238 a "Matching Type" (3rd) field of SHA2-512(2).
30240 For the "Certificate Authority Data" (4th) field, commands like
30243 openssl x509 -pubkey -noout <certificate.pem \
30244 | openssl rsa -outform der -pubin 2>/dev/null \
30249 are workable to create a hash of the certificate's public key.
30251 An example TLSA record for DANE-EE(3), SPKI(1), and SHA-512 (2) looks like
30254 _25._tcp.mail.example.com. TLSA 3 1 2 8BA8A336E...
30257 At the time of writing, &url(https://www.huque.com/bin/gen_tlsa)
30258 is useful for quickly generating TLSA records.
30261 For use with the DANE-TA model, server certificates must have a correct name (SubjectName or SubjectAltName).
30263 The Certificate issued by the CA published in the DANE-TA model should be
30264 issued using a strong hash algorithm.
30265 Exim, and importantly various other MTAs sending to you, will not
30266 re-enable hash algorithms which have been disabled by default in TLS
30268 This means no MD5 and no SHA-1. SHA2-256 is the minimum for reliable
30269 interoperability (and probably the maximum too, in 2018).
30271 The use of OCSP-stapling should be considered, allowing for fast revocation of certificates (which would otherwise
30272 be limited by the DNS TTL on the TLSA records). However, this is likely to only be usable with DANE-TA. NOTE: the
30273 default of requesting OCSP for all hosts is modified iff DANE is in use, to:
30276 hosts_request_ocsp = ${if or { {= {0}{$tls_out_tlsa_usage}} \
30277 {= {4}{$tls_out_tlsa_usage}} } \
30281 The (new) variable &$tls_out_tlsa_usage$& is a bitfield with numbered bits set for TLSA record usage codes.
30282 The zero above means DANE was not in use, the four means that only DANE-TA usage TLSA records were
30283 found. If the definition of &%hosts_request_ocsp%& includes the
30284 string "tls_out_tlsa_usage", they are re-expanded in time to
30285 control the OCSP request.
30287 This modification of hosts_request_ocsp is only done if it has the default value of "*". Admins who change it, and
30288 those who use &%hosts_require_ocsp%&, should consider the interaction with DANE in their OCSP settings.
30291 For client-side DANE there are three new smtp transport options, &%hosts_try_dane%&, &%hosts_require_dane%&
30292 and &%dane_require_tls_ciphers%&.
30293 The &"require"& variant will result in failure if the target host is not
30294 DNSSEC-secured. To get DNSSEC-secured hostname resolution, use
30295 the &%dnssec_request_domains%& router or transport option.
30297 DANE will only be usable if the target host has DNSSEC-secured MX, A and TLSA records.
30299 A TLSA lookup will be done if either of the above options match and the host-lookup succeeded using DNSSEC.
30300 If a TLSA lookup is done and succeeds, a DANE-verified TLS connection
30301 will be required for the host. If it does not, the host will not
30302 be used; there is no fallback to non-DANE or non-TLS.
30304 If DANE is requested and usable, then the TLS cipher list configuration
30305 prefers to use the option &%dane_require_tls_ciphers%& and falls
30306 back to &%tls_require_ciphers%& only if that is unset.
30307 This lets you configure "decent crypto" for DANE and "better than nothing
30308 crypto" as the default. Note though that while GnuTLS lets the string control
30309 which versions of TLS/SSL will be negotiated, OpenSSL does not and you're
30310 limited to ciphersuite constraints.
30312 If DANE is requested and useable (see above) the following transport options are ignored:
30316 tls_try_verify_hosts
30317 tls_verify_certificates
30319 tls_verify_cert_hostnames
30323 If DANE is not usable, whether requested or not, and CA-anchored
30324 verification evaluation is wanted, the above variables should be set appropriately.
30326 The router and transport option &%dnssec_request_domains%& must not be
30327 set to &"never"&, and &%dnssec_require_domains%& is ignored.
30329 If verification was successful using DANE then the "CV" item in the delivery log line will show as "CV=dane".
30331 There is a new variable &$tls_out_dane$& which will have "yes" if
30332 verification succeeded using DANE and "no" otherwise (only useful
30333 in combination with events; see &<<CHAPevents>>&),
30334 and a new variable &$tls_out_tlsa_usage$& (detailed above).
30336 .cindex DANE reporting
30337 An event (see &<<CHAPevents>>&) of type "dane:fail" will be raised on failures
30338 to achieve DANE-verified connection, if one was either requested and offered, or
30339 required. This is intended to support TLS-reporting as defined in
30340 &url(https://tools.ietf.org/html/draft-ietf-uta-smtp-tlsrpt-17).
30341 The &$event_data$& will be one of the Result Types defined in
30342 Section 4.3 of that document.
30344 Under GnuTLS, DANE is only supported from version 3.0.0 onwards.
30346 DANE is specified in published RFCs and decouples certificate authority trust
30347 selection from a "race to the bottom" of "you must trust everything for mail
30348 to get through". There is an alternative technology called MTA-STS, which
30349 instead publishes MX trust anchor information on an HTTPS website. At the
30350 time this text was last updated, MTA-STS was still a draft, not yet an RFC.
30351 Exim has no support for MTA-STS as a client, but Exim mail server operators
30352 can choose to publish information describing their TLS configuration using
30353 MTA-STS to let those clients who do use that protocol derive trust
30356 The MTA-STS design requires a certificate from a public Certificate Authority
30357 which is recognized by clients sending to you.
30358 That selection of which CAs are trusted by others is outside your control.
30360 The most interoperable course of action is probably to use
30361 &url(https://letsencrypt.org/,Let's Encrypt), with automated certificate
30362 renewal; to publish the anchor information in DNSSEC-secured DNS via TLSA
30363 records for DANE clients (such as Exim and Postfix) and to publish anchor
30364 information for MTA-STS as well. This is what is done for the &'exim.org'&
30365 domain itself (with caveats around occasionally broken MTA-STS because of
30366 incompatible specification changes prior to reaching RFC status).
30370 . ////////////////////////////////////////////////////////////////////////////
30371 . ////////////////////////////////////////////////////////////////////////////
30373 .chapter "Access control lists" "CHAPACL"
30374 .scindex IIDacl "&ACL;" "description"
30375 .cindex "control of incoming mail"
30376 .cindex "message" "controlling incoming"
30377 .cindex "policy control" "access control lists"
30378 Access Control Lists (ACLs) are defined in a separate section of the runtime
30379 configuration file, headed by &"begin acl"&. Each ACL definition starts with a
30380 name, terminated by a colon. Here is a complete ACL section that contains just
30381 one very small ACL:
30385 accept hosts = one.host.only
30387 You can have as many lists as you like in the ACL section, and the order in
30388 which they appear does not matter. The lists are self-terminating.
30390 The majority of ACLs are used to control Exim's behaviour when it receives
30391 certain SMTP commands. This applies both to incoming TCP/IP connections, and
30392 when a local process submits a message using SMTP by specifying the &%-bs%&
30393 option. The most common use is for controlling which recipients are accepted
30394 in incoming messages. In addition, you can define an ACL that is used to check
30395 local non-SMTP messages. The default configuration file contains an example of
30396 a realistic ACL for checking RCPT commands. This is discussed in chapter
30397 &<<CHAPdefconfil>>&.
30400 .section "Testing ACLs" "SECID188"
30401 The &%-bh%& command line option provides a way of testing your ACL
30402 configuration locally by running a fake SMTP session with which you interact.
30405 .section "Specifying when ACLs are used" "SECID189"
30406 .cindex "&ACL;" "options for specifying"
30407 In order to cause an ACL to be used, you have to name it in one of the relevant
30408 options in the main part of the configuration. These options are:
30409 .cindex "AUTH" "ACL for"
30410 .cindex "DATA" "ACLs for"
30411 .cindex "ETRN" "ACL for"
30412 .cindex "EXPN" "ACL for"
30413 .cindex "HELO" "ACL for"
30414 .cindex "EHLO" "ACL for"
30415 .cindex "DKIM" "ACL for"
30416 .cindex "MAIL" "ACL for"
30417 .cindex "QUIT, ACL for"
30418 .cindex "RCPT" "ACL for"
30419 .cindex "STARTTLS, ACL for"
30420 .cindex "VRFY" "ACL for"
30421 .cindex "SMTP" "connection, ACL for"
30422 .cindex "non-SMTP messages" "ACLs for"
30423 .cindex "MIME content scanning" "ACL for"
30424 .cindex "PRDR" "ACL for"
30427 .irow &%acl_not_smtp%& "ACL for non-SMTP messages"
30428 .irow &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
30429 .irow &%acl_not_smtp_start%& "ACL at start of non-SMTP message"
30430 .irow &%acl_smtp_auth%& "ACL for AUTH"
30431 .irow &%acl_smtp_connect%& "ACL for start of SMTP connection"
30432 .irow &%acl_smtp_data%& "ACL after DATA is complete"
30433 .irow &%acl_smtp_data_prdr%& "ACL for each recipient, after DATA is complete"
30434 .irow &%acl_smtp_dkim%& "ACL for each DKIM signer"
30435 .irow &%acl_smtp_etrn%& "ACL for ETRN"
30436 .irow &%acl_smtp_expn%& "ACL for EXPN"
30437 .irow &%acl_smtp_helo%& "ACL for HELO or EHLO"
30438 .irow &%acl_smtp_mail%& "ACL for MAIL"
30439 .irow &%acl_smtp_mailauth%& "ACL for the AUTH parameter of MAIL"
30440 .irow &%acl_smtp_mime%& "ACL for content-scanning MIME parts"
30441 .irow &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
30442 .irow &%acl_smtp_predata%& "ACL at start of DATA command"
30443 .irow &%acl_smtp_quit%& "ACL for QUIT"
30444 .irow &%acl_smtp_rcpt%& "ACL for RCPT"
30445 .irow &%acl_smtp_starttls%& "ACL for STARTTLS"
30446 .irow &%acl_smtp_vrfy%& "ACL for VRFY"
30449 For example, if you set
30451 acl_smtp_rcpt = small_acl
30453 the little ACL defined above is used whenever Exim receives a RCPT command
30454 in an SMTP dialogue. The majority of policy tests on incoming messages can be
30455 done when RCPT commands arrive. A rejection of RCPT should cause the
30456 sending MTA to give up on the recipient address contained in the RCPT
30457 command, whereas rejection at other times may cause the client MTA to keep on
30458 trying to deliver the message. It is therefore recommended that you do as much
30459 testing as possible at RCPT time.
30462 .section "The non-SMTP ACLs" "SECID190"
30463 .cindex "non-SMTP messages" "ACLs for"
30464 The non-SMTP ACLs apply to all non-interactive incoming messages, that is, they
30465 apply to batched SMTP as well as to non-SMTP messages. (Batched SMTP is not
30466 really SMTP.) Many of the ACL conditions (for example, host tests, and tests on
30467 the state of the SMTP connection such as encryption and authentication) are not
30468 relevant and are forbidden in these ACLs. However, the sender and recipients
30469 are known, so the &%senders%& and &%sender_domains%& conditions and the
30470 &$sender_address$& and &$recipients$& variables can be used. Variables such as
30471 &$authenticated_sender$& are also available. You can specify added header lines
30472 in any of these ACLs.
30474 The &%acl_not_smtp_start%& ACL is run right at the start of receiving a
30475 non-SMTP message, before any of the message has been read. (This is the
30476 analogue of the &%acl_smtp_predata%& ACL for SMTP input.) In the case of
30477 batched SMTP input, it runs after the DATA command has been reached. The
30478 result of this ACL is ignored; it cannot be used to reject a message. If you
30479 really need to, you could set a value in an ACL variable here and reject based
30480 on that in the &%acl_not_smtp%& ACL. However, this ACL can be used to set
30481 controls, and in particular, it can be used to set
30483 control = suppress_local_fixups
30485 This cannot be used in the other non-SMTP ACLs because by the time they are
30486 run, it is too late.
30488 The &%acl_not_smtp_mime%& ACL is available only when Exim is compiled with the
30489 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
30491 The &%acl_not_smtp%& ACL is run just before the &[local_scan()]& function. Any
30492 kind of rejection is treated as permanent, because there is no way of sending a
30493 temporary error for these kinds of message.
30496 .section "The SMTP connect ACL" "SECID191"
30497 .cindex "SMTP" "connection, ACL for"
30498 .oindex &%smtp_banner%&
30499 The ACL test specified by &%acl_smtp_connect%& happens at the start of an SMTP
30500 session, after the test specified by &%host_reject_connection%& (which is now
30501 an anomaly) and any TCP Wrappers testing (if configured). If the connection is
30502 accepted by an &%accept%& verb that has a &%message%& modifier, the contents of
30503 the message override the banner message that is otherwise specified by the
30504 &%smtp_banner%& option.
30506 For tls-on-connect connections, the ACL is run after the TLS connection
30507 is accepted (however, &%host_reject_connection%& is tested before).
30510 .section "The EHLO/HELO ACL" "SECID192"
30511 .cindex "EHLO" "ACL for"
30512 .cindex "HELO" "ACL for"
30513 The ACL test specified by &%acl_smtp_helo%& happens when the client issues an
30514 EHLO or HELO command, after the tests specified by &%helo_accept_junk_hosts%&,
30515 &%helo_allow_chars%&, &%helo_verify_hosts%&, and &%helo_try_verify_hosts%&.
30516 Note that a client may issue more than one EHLO or HELO command in an SMTP
30517 session, and indeed is required to issue a new EHLO or HELO after successfully
30518 setting up encryption following a STARTTLS command.
30520 Note also that a deny neither forces the client to go away nor means that
30521 mail will be refused on the connection. Consider checking for
30522 &$sender_helo_name$& being defined in a MAIL or RCPT ACL to do that.
30524 If the command is accepted by an &%accept%& verb that has a &%message%&
30525 modifier, the message may not contain more than one line (it will be truncated
30526 at the first newline and a panic logged if it does). Such a message cannot
30527 affect the EHLO options that are listed on the second and subsequent lines of
30531 .section "The DATA ACLs" "SECID193"
30532 .cindex "DATA" "ACLs for"
30533 Two ACLs are associated with the DATA command, because it is two-stage
30534 command, with two responses being sent to the client.
30535 When the DATA command is received, the ACL defined by &%acl_smtp_predata%&
30536 is obeyed. This gives you control after all the RCPT commands, but before
30537 the message itself is received. It offers the opportunity to give a negative
30538 response to the DATA command before the data is transmitted. Header lines
30539 added by MAIL or RCPT ACLs are not visible at this time, but any that
30540 are defined here are visible when the &%acl_smtp_data%& ACL is run.
30542 You cannot test the contents of the message, for example, to verify addresses
30543 in the headers, at RCPT time or when the DATA command is received. Such
30544 tests have to appear in the ACL that is run after the message itself has been
30545 received, before the final response to the DATA command is sent. This is
30546 the ACL specified by &%acl_smtp_data%&, which is the second ACL that is
30547 associated with the DATA command.
30549 .cindex CHUNKING "BDAT command"
30550 .cindex BDAT "SMTP command"
30551 .cindex "RFC 3030" CHUNKING
30552 If CHUNKING was advertised and a BDAT command sequence is received,
30553 the &%acl_smtp_predata%& ACL is not run.
30554 . XXX why not? It should be possible, for the first BDAT.
30555 The &%acl_smtp_data%& is run after the last BDAT command and all of
30556 the data specified is received.
30558 For both of these ACLs, it is not possible to reject individual recipients. An
30559 error response rejects the entire message. Unfortunately, it is known that some
30560 MTAs do not treat hard (5&'xx'&) responses to the DATA command (either
30561 before or after the data) correctly &-- they keep the message on their queues
30562 and try again later, but that is their problem, though it does waste some of
30565 The &%acl_smtp_data%& ACL is run after
30566 the &%acl_smtp_data_prdr%&,
30567 the &%acl_smtp_dkim%&
30568 and the &%acl_smtp_mime%& ACLs.
30570 .section "The SMTP DKIM ACL" "SECTDKIMACL"
30571 The &%acl_smtp_dkim%& ACL is available only when Exim is compiled with DKIM support
30572 enabled (which is the default).
30574 The ACL test specified by &%acl_smtp_dkim%& happens after a message has been
30575 received, and is executed for each DKIM signature found in a message. If not
30576 otherwise specified, the default action is to accept.
30578 This ACL is evaluated before &%acl_smtp_mime%& and &%acl_smtp_data%&.
30580 For details on the operation of DKIM, see section &<<SECDKIM>>&.
30583 .section "The SMTP MIME ACL" "SECID194"
30584 The &%acl_smtp_mime%& option is available only when Exim is compiled with the
30585 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
30587 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
30590 .section "The SMTP PRDR ACL" "SECTPRDRACL"
30591 .cindex "PRDR" "ACL for"
30592 .oindex "&%prdr_enable%&"
30593 The &%acl_smtp_data_prdr%& ACL is available only when Exim is compiled
30594 with PRDR support enabled (which is the default).
30595 It becomes active only when the PRDR feature is negotiated between
30596 client and server for a message, and more than one recipient
30599 The ACL test specified by &%acl_smtp_data_prdr%& happens after a message
30600 has been received, and is executed once for each recipient of the message
30601 with &$local_part$& and &$domain$& valid.
30602 The test may accept, defer or deny for individual recipients.
30603 The &%acl_smtp_data%& will still be called after this ACL and
30604 can reject the message overall, even if this ACL has accepted it
30605 for some or all recipients.
30607 PRDR may be used to support per-user content filtering. Without it
30608 one must defer any recipient after the first that has a different
30609 content-filter configuration. With PRDR, the RCPT-time check
30610 .cindex "PRDR" "variable for"
30611 for this can be disabled when the variable &$prdr_requested$&
30613 Any required difference in behaviour of the main DATA-time
30614 ACL should however depend on the PRDR-time ACL having run, as Exim
30615 will avoid doing so in some situations (e.g. single-recipient mails).
30617 See also the &%prdr_enable%& global option
30618 and the &%hosts_try_prdr%& smtp transport option.
30620 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
30621 If the ACL is not defined, processing completes as if
30622 the feature was not requested by the client.
30624 .section "The QUIT ACL" "SECTQUITACL"
30625 .cindex "QUIT, ACL for"
30626 The ACL for the SMTP QUIT command is anomalous, in that the outcome of the ACL
30627 does not affect the response code to QUIT, which is always 221. Thus, the ACL
30628 does not in fact control any access.
30629 For this reason, it may only accept
30630 or warn as its final result.
30632 This ACL can be used for tasks such as custom logging at the end of an SMTP
30633 session. For example, you can use ACL variables in other ACLs to count
30634 messages, recipients, etc., and log the totals at QUIT time using one or
30635 more &%logwrite%& modifiers on a &%warn%& verb.
30637 &*Warning*&: Only the &$acl_c$&&'x'& variables can be used for this, because
30638 the &$acl_m$&&'x'& variables are reset at the end of each incoming message.
30640 You do not need to have a final &%accept%&, but if you do, you can use a
30641 &%message%& modifier to specify custom text that is sent as part of the 221
30644 This ACL is run only for a &"normal"& QUIT. For certain kinds of disastrous
30645 failure (for example, failure to open a log file, or when Exim is bombing out
30646 because it has detected an unrecoverable error), all SMTP commands from the
30647 client are given temporary error responses until QUIT is received or the
30648 connection is closed. In these special cases, the QUIT ACL does not run.
30651 .section "The not-QUIT ACL" "SECTNOTQUITACL"
30652 .vindex &$acl_smtp_notquit$&
30653 The not-QUIT ACL, specified by &%acl_smtp_notquit%&, is run in most cases when
30654 an SMTP session ends without sending QUIT. However, when Exim itself is in bad
30655 trouble, such as being unable to write to its log files, this ACL is not run,
30656 because it might try to do things (such as write to log files) that make the
30657 situation even worse.
30659 Like the QUIT ACL, this ACL is provided to make it possible to do customized
30660 logging or to gather statistics, and its outcome is ignored. The &%delay%&
30661 modifier is forbidden in this ACL, and the only permitted verbs are &%accept%&
30664 .vindex &$smtp_notquit_reason$&
30665 When the not-QUIT ACL is running, the variable &$smtp_notquit_reason$& is set
30666 to a string that indicates the reason for the termination of the SMTP
30667 connection. The possible values are:
30669 .irow &`acl-drop`& "Another ACL issued a &%drop%& command"
30670 .irow &`bad-commands`& "Too many unknown or non-mail commands"
30671 .irow &`command-timeout`& "Timeout while reading SMTP commands"
30672 .irow &`connection-lost`& "The SMTP connection has been lost"
30673 .irow &`data-timeout`& "Timeout while reading message data"
30674 .irow &`local-scan-error`& "The &[local_scan()]& function crashed"
30675 .irow &`local-scan-timeout`& "The &[local_scan()]& function timed out"
30676 .irow &`signal-exit`& "SIGTERM or SIGINT"
30677 .irow &`synchronization-error`& "SMTP synchronization error"
30678 .irow &`tls-failed`& "TLS failed to start"
30680 In most cases when an SMTP connection is closed without having received QUIT,
30681 Exim sends an SMTP response message before actually closing the connection.
30682 With the exception of the &`acl-drop`& case, the default message can be
30683 overridden by the &%message%& modifier in the not-QUIT ACL. In the case of a
30684 &%drop%& verb in another ACL, it is the message from the other ACL that is
30688 .section "Finding an ACL to use" "SECID195"
30689 .cindex "&ACL;" "finding which to use"
30690 The value of an &%acl_smtp_%&&'xxx'& option is expanded before use, so
30691 you can use different ACLs in different circumstances. For example,
30693 acl_smtp_rcpt = ${if ={25}{$interface_port} \
30694 {acl_check_rcpt} {acl_check_rcpt_submit} }
30696 In the default configuration file there are some example settings for
30697 providing an RFC 4409 message &"submission"& service on port 587 and
30698 an RFC 8314 &"submissions"& service on port 465. You can use a string
30699 expansion like this to choose an ACL for MUAs on these ports which is
30700 more appropriate for this purpose than the default ACL on port 25.
30702 The expanded string does not have to be the name of an ACL in the
30703 configuration file; there are other possibilities. Having expanded the
30704 string, Exim searches for an ACL as follows:
30707 If the string begins with a slash, Exim uses it as a filename, and reads its
30708 contents as an ACL. The lines are processed in the same way as lines in the
30709 Exim configuration file. In particular, continuation lines are supported, blank
30710 lines are ignored, as are lines whose first non-whitespace character is &"#"&.
30711 If the file does not exist or cannot be read, an error occurs (typically
30712 causing a temporary failure of whatever caused the ACL to be run). For example:
30714 acl_smtp_data = /etc/acls/\
30715 ${lookup{$sender_host_address}lsearch\
30716 {/etc/acllist}{$value}{default}}
30718 This looks up an ACL file to use on the basis of the host's IP address, falling
30719 back to a default if the lookup fails. If an ACL is successfully read from a
30720 file, it is retained in memory for the duration of the Exim process, so that it
30721 can be re-used without having to re-read the file.
30723 If the string does not start with a slash, and does not contain any spaces,
30724 Exim searches the ACL section of the configuration for an ACL whose name
30725 matches the string.
30727 If no named ACL is found, or if the string contains spaces, Exim parses
30728 the string as an inline ACL. This can save typing in cases where you just
30729 want to have something like
30731 acl_smtp_vrfy = accept
30733 in order to allow free use of the VRFY command. Such a string may contain
30734 newlines; it is processed in the same way as an ACL that is read from a file.
30740 .section "ACL return codes" "SECID196"
30741 .cindex "&ACL;" "return codes"
30742 Except for the QUIT ACL, which does not affect the SMTP return code (see
30743 section &<<SECTQUITACL>>& above), the result of running an ACL is either
30744 &"accept"& or &"deny"&, or, if some test cannot be completed (for example, if a
30745 database is down), &"defer"&. These results cause 2&'xx'&, 5&'xx'&, and 4&'xx'&
30746 return codes, respectively, to be used in the SMTP dialogue. A fourth return,
30747 &"error"&, occurs when there is an error such as invalid syntax in the ACL.
30748 This also causes a 4&'xx'& return code.
30750 For the non-SMTP ACL, &"defer"& and &"error"& are treated in the same way as
30751 &"deny"&, because there is no mechanism for passing temporary errors to the
30752 submitters of non-SMTP messages.
30755 ACLs that are relevant to message reception may also return &"discard"&. This
30756 has the effect of &"accept"&, but causes either the entire message or an
30757 individual recipient address to be discarded. In other words, it is a
30758 blackholing facility. Use it with care.
30760 If the ACL for MAIL returns &"discard"&, all recipients are discarded, and no
30761 ACL is run for subsequent RCPT commands. The effect of &"discard"& in a
30762 RCPT ACL is to discard just the one recipient address. If there are no
30763 recipients left when the message's data is received, the DATA ACL is not
30764 run. A &"discard"& return from the DATA or the non-SMTP ACL discards all the
30765 remaining recipients. The &"discard"& return is not permitted for the
30766 &%acl_smtp_predata%& ACL.
30768 If the ACL for VRFY returns &"accept"&, a recipient verify (without callout)
30769 is done on the address and the result determines the SMTP response.
30772 .cindex "&[local_scan()]& function" "when all recipients discarded"
30773 The &[local_scan()]& function is always run, even if there are no remaining
30774 recipients; it may create new recipients.
30778 .section "Unset ACL options" "SECID197"
30779 .cindex "&ACL;" "unset options"
30780 The default actions when any of the &%acl_%&&'xxx'& options are unset are not
30781 all the same. &*Note*&: These defaults apply only when the relevant ACL is
30782 not defined at all. For any defined ACL, the default action when control
30783 reaches the end of the ACL statements is &"deny"&.
30785 For &%acl_smtp_quit%& and &%acl_not_smtp_start%& there is no default because
30786 these two are ACLs that are used only for their side effects. They cannot be
30787 used to accept or reject anything.
30789 For &%acl_not_smtp%&, &%acl_smtp_auth%&, &%acl_smtp_connect%&,
30790 &%acl_smtp_data%&, &%acl_smtp_helo%&, &%acl_smtp_mail%&, &%acl_smtp_mailauth%&,
30791 &%acl_smtp_mime%&, &%acl_smtp_predata%&, and &%acl_smtp_starttls%&, the action
30792 when the ACL is not defined is &"accept"&.
30794 For the others (&%acl_smtp_etrn%&, &%acl_smtp_expn%&, &%acl_smtp_rcpt%&, and
30795 &%acl_smtp_vrfy%&), the action when the ACL is not defined is &"deny"&.
30796 This means that &%acl_smtp_rcpt%& must be defined in order to receive any
30797 messages over an SMTP connection. For an example, see the ACL in the default
30798 configuration file.
30803 .section "Data for message ACLs" "SECID198"
30804 .cindex "&ACL;" "data for message ACL"
30806 .vindex &$local_part$&
30807 .vindex &$sender_address$&
30808 .vindex &$sender_host_address$&
30809 .vindex &$smtp_command$&
30810 When a MAIL or RCPT ACL, or either of the DATA ACLs, is running, the variables
30811 that contain information about the host and the message's sender (for example,
30812 &$sender_host_address$& and &$sender_address$&) are set, and can be used in ACL
30813 statements. In the case of RCPT (but not MAIL or DATA), &$domain$& and
30814 &$local_part$& are set from the argument address. The entire SMTP command
30815 is available in &$smtp_command$&.
30817 When an ACL for the AUTH parameter of MAIL is running, the variables that
30818 contain information about the host are set, but &$sender_address$& is not yet
30819 set. Section &<<SECTauthparamail>>& contains a discussion of this parameter and
30822 .vindex "&$message_size$&"
30823 The &$message_size$& variable is set to the value of the SIZE parameter on
30824 the MAIL command at MAIL, RCPT and pre-data time, or to -1 if
30825 that parameter is not given. The value is updated to the true message size by
30826 the time the final DATA ACL is run (after the message data has been
30829 .vindex "&$rcpt_count$&"
30830 .vindex "&$recipients_count$&"
30831 The &$rcpt_count$& variable increases by one for each RCPT command received.
30832 The &$recipients_count$& variable increases by one each time a RCPT command is
30833 accepted, so while an ACL for RCPT is being processed, it contains the number
30834 of previously accepted recipients. At DATA time (for both the DATA ACLs),
30835 &$rcpt_count$& contains the total number of RCPT commands, and
30836 &$recipients_count$& contains the total number of accepted recipients.
30842 .section "Data for non-message ACLs" "SECTdatfornon"
30843 .cindex "&ACL;" "data for non-message ACL"
30844 .vindex &$smtp_command_argument$&
30845 .vindex &$smtp_command$&
30846 When an ACL is being run for AUTH, EHLO, ETRN, EXPN, HELO, STARTTLS, or VRFY,
30847 the remainder of the SMTP command line is placed in &$smtp_command_argument$&,
30848 and the entire SMTP command is available in &$smtp_command$&.
30849 These variables can be tested using a &%condition%& condition. For example,
30850 here is an ACL for use with AUTH, which insists that either the session is
30851 encrypted, or the CRAM-MD5 authentication method is used. In other words, it
30852 does not permit authentication methods that use cleartext passwords on
30853 unencrypted connections.
30856 accept encrypted = *
30857 accept condition = ${if eq{${uc:$smtp_command_argument}}\
30859 deny message = TLS encryption or CRAM-MD5 required
30861 (Another way of applying this restriction is to arrange for the authenticators
30862 that use cleartext passwords not to be advertised when the connection is not
30863 encrypted. You can use the generic &%server_advertise_condition%& authenticator
30864 option to do this.)
30868 .section "Format of an ACL" "SECID199"
30869 .cindex "&ACL;" "format of"
30870 .cindex "&ACL;" "verbs, definition of"
30871 An individual ACL consists of a number of statements. Each statement starts
30872 with a verb, optionally followed by a number of conditions and &"modifiers"&.
30873 Modifiers can change the way the verb operates, define error and log messages,
30874 set variables, insert delays, and vary the processing of accepted messages.
30876 If all the conditions are met, the verb is obeyed. The same condition may be
30877 used (with different arguments) more than once in the same statement. This
30878 provides a means of specifying an &"and"& conjunction between conditions. For
30881 deny dnslists = list1.example
30882 dnslists = list2.example
30884 If there are no conditions, the verb is always obeyed. Exim stops evaluating
30885 the conditions and modifiers when it reaches a condition that fails. What
30886 happens then depends on the verb (and in one case, on a special modifier). Not
30887 all the conditions make sense at every testing point. For example, you cannot
30888 test a sender address in the ACL that is run for a VRFY command.
30891 .section "ACL verbs" "SECID200"
30892 The ACL verbs are as follows:
30895 .cindex "&%accept%& ACL verb"
30896 &%accept%&: If all the conditions are met, the ACL returns &"accept"&. If any
30897 of the conditions are not met, what happens depends on whether &%endpass%&
30898 appears among the conditions (for syntax see below). If the failing condition
30899 is before &%endpass%&, control is passed to the next ACL statement; if it is
30900 after &%endpass%&, the ACL returns &"deny"&. Consider this statement, used to
30901 check a RCPT command:
30903 accept domains = +local_domains
30907 If the recipient domain does not match the &%domains%& condition, control
30908 passes to the next statement. If it does match, the recipient is verified, and
30909 the command is accepted if verification succeeds. However, if verification
30910 fails, the ACL yields &"deny"&, because the failing condition is after
30913 The &%endpass%& feature has turned out to be confusing to many people, so its
30914 use is not recommended nowadays. It is always possible to rewrite an ACL so
30915 that &%endpass%& is not needed, and it is no longer used in the default
30918 .cindex "&%message%& ACL modifier" "with &%accept%&"
30919 If a &%message%& modifier appears on an &%accept%& statement, its action
30920 depends on whether or not &%endpass%& is present. In the absence of &%endpass%&
30921 (when an &%accept%& verb either accepts or passes control to the next
30922 statement), &%message%& can be used to vary the message that is sent when an
30923 SMTP command is accepted. For example, in a RCPT ACL you could have:
30925 &`accept `&<&'some conditions'&>
30926 &` message = OK, I will allow you through today`&
30928 You can specify an SMTP response code, optionally followed by an &"extended
30929 response code"& at the start of the message, but the first digit must be the
30930 same as would be sent by default, which is 2 for an &%accept%& verb.
30932 If &%endpass%& is present in an &%accept%& statement, &%message%& specifies
30933 an error message that is used when access is denied. This behaviour is retained
30934 for backward compatibility, but current &"best practice"& is to avoid the use
30939 .cindex "&%defer%& ACL verb"
30940 &%defer%&: If all the conditions are true, the ACL returns &"defer"& which, in
30941 an SMTP session, causes a 4&'xx'& response to be given. For a non-SMTP ACL,
30942 &%defer%& is the same as &%deny%&, because there is no way of sending a
30943 temporary error. For a RCPT command, &%defer%& is much the same as using a
30944 &(redirect)& router and &`:defer:`& while verifying, but the &%defer%& verb can
30945 be used in any ACL, and even for a recipient it might be a simpler approach.
30949 .cindex "&%deny%& ACL verb"
30950 &%deny%&: If all the conditions are met, the ACL returns &"deny"&. If any of
30951 the conditions are not met, control is passed to the next ACL statement. For
30954 deny dnslists = blackholes.mail-abuse.org
30956 rejects commands from hosts that are on a DNS black list.
30960 .cindex "&%discard%& ACL verb"
30961 &%discard%&: This verb behaves like &%accept%&, except that it returns
30962 &"discard"& from the ACL instead of &"accept"&. It is permitted only on ACLs
30963 that are concerned with receiving messages. When all the conditions are true,
30964 the sending entity receives a &"success"& response. However, &%discard%& causes
30965 recipients to be discarded. If it is used in an ACL for RCPT, just the one
30966 recipient is discarded; if used for MAIL, DATA or in the non-SMTP ACL, all the
30967 message's recipients are discarded. Recipients that are discarded before DATA
30968 do not appear in the log line when the &%received_recipients%& log selector is set.
30970 If the &%log_message%& modifier is set when &%discard%& operates,
30971 its contents are added to the line that is automatically written to the log.
30972 The &%message%& modifier operates exactly as it does for &%accept%&.
30976 .cindex "&%drop%& ACL verb"
30977 &%drop%&: This verb behaves like &%deny%&, except that an SMTP connection is
30978 forcibly closed after the 5&'xx'& error message has been sent. For example:
30980 drop condition = ${if > {$rcpt_count}{20}}
30981 message = I don't take more than 20 RCPTs
30983 There is no difference between &%deny%& and &%drop%& for the connect-time ACL.
30984 The connection is always dropped after sending a 550 response.
30987 .cindex "&%require%& ACL verb"
30988 &%require%&: If all the conditions are met, control is passed to the next ACL
30989 statement. If any of the conditions are not met, the ACL returns &"deny"&. For
30990 example, when checking a RCPT command,
30992 require message = Sender did not verify
30995 passes control to subsequent statements only if the message's sender can be
30996 verified. Otherwise, it rejects the command. Note the positioning of the
30997 &%message%& modifier, before the &%verify%& condition. The reason for this is
30998 discussed in section &<<SECTcondmodproc>>&.
31001 .cindex "&%warn%& ACL verb"
31002 &%warn%&: If all the conditions are true, a line specified by the
31003 &%log_message%& modifier is written to Exim's main log. Control always passes
31004 to the next ACL statement. If any condition is false, the log line is not
31005 written. If an identical log line is requested several times in the same
31006 message, only one copy is actually written to the log. If you want to force
31007 duplicates to be written, use the &%logwrite%& modifier instead.
31009 If &%log_message%& is not present, a &%warn%& verb just checks its conditions
31010 and obeys any &"immediate"& modifiers (such as &%control%&, &%set%&,
31011 &%logwrite%&, &%add_header%&, and &%remove_header%&) that appear before the
31012 first failing condition. There is more about adding header lines in section
31013 &<<SECTaddheadacl>>&.
31015 If any condition on a &%warn%& statement cannot be completed (that is, there is
31016 some sort of defer), the log line specified by &%log_message%& is not written.
31017 This does not include the case of a forced failure from a lookup, which
31018 is considered to be a successful completion. After a defer, no further
31019 conditions or modifiers in the &%warn%& statement are processed. The incident
31020 is logged, and the ACL continues to be processed, from the next statement
31024 .vindex "&$acl_verify_message$&"
31025 When one of the &%warn%& conditions is an address verification that fails, the
31026 text of the verification failure message is in &$acl_verify_message$&. If you
31027 want this logged, you must set it up explicitly. For example:
31029 warn !verify = sender
31030 log_message = sender verify failed: $acl_verify_message
31034 At the end of each ACL there is an implicit unconditional &%deny%&.
31036 As you can see from the examples above, the conditions and modifiers are
31037 written one to a line, with the first one on the same line as the verb, and
31038 subsequent ones on following lines. If you have a very long condition, you can
31039 continue it onto several physical lines by the usual backslash continuation
31040 mechanism. It is conventional to align the conditions vertically.
31044 .section "ACL variables" "SECTaclvariables"
31045 .cindex "&ACL;" "variables"
31046 There are some special variables that can be set during ACL processing. They
31047 can be used to pass information between different ACLs, different invocations
31048 of the same ACL in the same SMTP connection, and between ACLs and the routers,
31049 transports, and filters that are used to deliver a message. The names of these
31050 variables must begin with &$acl_c$& or &$acl_m$&, followed either by a digit or
31051 an underscore, but the remainder of the name can be any sequence of
31052 alphanumeric characters and underscores that you choose. There is no limit on
31053 the number of ACL variables. The two sets act as follows:
31055 The values of those variables whose names begin with &$acl_c$& persist
31056 throughout an SMTP connection. They are never reset. Thus, a value that is set
31057 while receiving one message is still available when receiving the next message
31058 on the same SMTP connection.
31060 The values of those variables whose names begin with &$acl_m$& persist only
31061 while a message is being received. They are reset afterwards. They are also
31062 reset by MAIL, RSET, EHLO, HELO, and after starting up a TLS session.
31065 When a message is accepted, the current values of all the ACL variables are
31066 preserved with the message and are subsequently made available at delivery
31067 time. The ACL variables are set by a modifier called &%set%&. For example:
31069 accept hosts = whatever
31070 set acl_m4 = some value
31071 accept authenticated = *
31072 set acl_c_auth = yes
31074 &*Note*&: A leading dollar sign is not used when naming a variable that is to
31075 be set. If you want to set a variable without taking any action, you can use a
31076 &%warn%& verb without any other modifiers or conditions.
31078 .oindex &%strict_acl_vars%&
31079 What happens if a syntactically valid but undefined ACL variable is
31080 referenced depends on the setting of the &%strict_acl_vars%& option. If it is
31081 false (the default), an empty string is substituted; if it is true, an
31082 error is generated.
31084 Versions of Exim before 4.64 have a limited set of numbered variables, but
31085 their names are compatible, so there is no problem with upgrading.
31088 .section "Condition and modifier processing" "SECTcondmodproc"
31089 .cindex "&ACL;" "conditions; processing"
31090 .cindex "&ACL;" "modifiers; processing"
31091 An exclamation mark preceding a condition negates its result. For example:
31093 deny domains = *.dom.example
31094 !verify = recipient
31096 causes the ACL to return &"deny"& if the recipient domain ends in
31097 &'dom.example'& and the recipient address cannot be verified. Sometimes
31098 negation can be used on the right-hand side of a condition. For example, these
31099 two statements are equivalent:
31101 deny hosts = !192.168.3.4
31102 deny !hosts = 192.168.3.4
31104 However, for many conditions (&%verify%& being a good example), only left-hand
31105 side negation of the whole condition is possible.
31107 The arguments of conditions and modifiers are expanded. A forced failure
31108 of an expansion causes a condition to be ignored, that is, it behaves as if the
31109 condition is true. Consider these two statements:
31111 accept senders = ${lookup{$host_name}lsearch\
31112 {/some/file}{$value}fail}
31113 accept senders = ${lookup{$host_name}lsearch\
31114 {/some/file}{$value}{}}
31116 Each attempts to look up a list of acceptable senders. If the lookup succeeds,
31117 the returned list is searched, but if the lookup fails the behaviour is
31118 different in the two cases. The &%fail%& in the first statement causes the
31119 condition to be ignored, leaving no further conditions. The &%accept%& verb
31120 therefore succeeds. The second statement, however, generates an empty list when
31121 the lookup fails. No sender can match an empty list, so the condition fails,
31122 and therefore the &%accept%& also fails.
31124 ACL modifiers appear mixed in with conditions in ACL statements. Some of them
31125 specify actions that are taken as the conditions for a statement are checked;
31126 others specify text for messages that are used when access is denied or a
31127 warning is generated. The &%control%& modifier affects the way an incoming
31128 message is handled.
31130 The positioning of the modifiers in an ACL statement is important, because the
31131 processing of a verb ceases as soon as its outcome is known. Only those
31132 modifiers that have already been encountered will take effect. For example,
31133 consider this use of the &%message%& modifier:
31135 require message = Can't verify sender
31137 message = Can't verify recipient
31139 message = This message cannot be used
31141 If sender verification fails, Exim knows that the result of the statement is
31142 &"deny"&, so it goes no further. The first &%message%& modifier has been seen,
31143 so its text is used as the error message. If sender verification succeeds, but
31144 recipient verification fails, the second message is used. If recipient
31145 verification succeeds, the third message becomes &"current"&, but is never used
31146 because there are no more conditions to cause failure.
31148 For the &%deny%& verb, on the other hand, it is always the last &%message%&
31149 modifier that is used, because all the conditions must be true for rejection to
31150 happen. Specifying more than one &%message%& modifier does not make sense, and
31151 the message can even be specified after all the conditions. For example:
31154 !senders = *@my.domain.example
31155 message = Invalid sender from client host
31157 The &"deny"& result does not happen until the end of the statement is reached,
31158 by which time Exim has set up the message.
31162 .section "ACL modifiers" "SECTACLmodi"
31163 .cindex "&ACL;" "modifiers; list of"
31164 The ACL modifiers are as follows:
31167 .vitem &*add_header*&&~=&~<&'text'&>
31168 This modifier specifies one or more header lines that are to be added to an
31169 incoming message, assuming, of course, that the message is ultimately
31170 accepted. For details, see section &<<SECTaddheadacl>>&.
31172 .vitem &*continue*&&~=&~<&'text'&>
31173 .cindex "&%continue%& ACL modifier"
31174 .cindex "database" "updating in ACL"
31175 This modifier does nothing of itself, and processing of the ACL always
31176 continues with the next condition or modifier. The value of &%continue%& is in
31177 the side effects of expanding its argument. Typically this could be used to
31178 update a database. It is really just a syntactic tidiness, to avoid having to
31179 write rather ugly lines like this:
31181 &`condition = ${if eq{0}{`&<&'some expansion'&>&`}{true}{true}}`&
31183 Instead, all you need is
31185 &`continue = `&<&'some expansion'&>
31188 .vitem &*control*&&~=&~<&'text'&>
31189 .cindex "&%control%& ACL modifier"
31190 This modifier affects the subsequent processing of the SMTP connection or of an
31191 incoming message that is accepted. The effect of the first type of control
31192 lasts for the duration of the connection, whereas the effect of the second type
31193 lasts only until the current message has been received. The message-specific
31194 controls always apply to the whole message, not to individual recipients,
31195 even if the &%control%& modifier appears in a RCPT ACL.
31197 As there are now quite a few controls that can be applied, they are described
31198 separately in section &<<SECTcontrols>>&. The &%control%& modifier can be used
31199 in several different ways. For example:
31201 . ==== As this is a nested list, any displays it contains must be indented
31202 . ==== as otherwise they are too far to the left. That comment applies only
31203 . ==== when xmlto and fop are used; formatting with sdop gets it right either
31207 It can be at the end of an &%accept%& statement:
31209 accept ...some conditions
31212 In this case, the control is applied when this statement yields &"accept"&, in
31213 other words, when the conditions are all true.
31216 It can be in the middle of an &%accept%& statement:
31218 accept ...some conditions...
31220 ...some more conditions...
31222 If the first set of conditions are true, the control is applied, even if the
31223 statement does not accept because one of the second set of conditions is false.
31224 In this case, some subsequent statement must yield &"accept"& for the control
31228 It can be used with &%warn%& to apply the control, leaving the
31229 decision about accepting or denying to a subsequent verb. For
31232 warn ...some conditions...
31236 This example of &%warn%& does not contain &%message%&, &%log_message%&, or
31237 &%logwrite%&, so it does not add anything to the message and does not write a
31241 If you want to apply a control unconditionally, you can use it with a
31242 &%require%& verb. For example:
31244 require control = no_multiline_responses
31248 .vitem &*delay*&&~=&~<&'time'&>
31249 .cindex "&%delay%& ACL modifier"
31251 This modifier may appear in any ACL except notquit. It causes Exim to wait for
31252 the time interval before proceeding. However, when testing Exim using the
31253 &%-bh%& option, the delay is not actually imposed (an appropriate message is
31254 output instead). The time is given in the usual Exim notation, and the delay
31255 happens as soon as the modifier is processed. In an SMTP session, pending
31256 output is flushed before the delay is imposed.
31258 Like &%control%&, &%delay%& can be used with &%accept%& or &%deny%&, for
31261 deny ...some conditions...
31264 The delay happens if all the conditions are true, before the statement returns
31265 &"deny"&. Compare this with:
31268 ...some conditions...
31270 which waits for 30s before processing the conditions. The &%delay%& modifier
31271 can also be used with &%warn%& and together with &%control%&:
31273 warn ...some conditions...
31279 If &%delay%& is encountered when the SMTP PIPELINING extension is in use,
31280 responses to several commands are no longer buffered and sent in one packet (as
31281 they would normally be) because all output is flushed before imposing the
31282 delay. This optimization is disabled so that a number of small delays do not
31283 appear to the client as one large aggregated delay that might provoke an
31284 unwanted timeout. You can, however, disable output flushing for &%delay%& by
31285 using a &%control%& modifier to set &%no_delay_flush%&.
31289 .cindex "&%endpass%& ACL modifier"
31290 This modifier, which has no argument, is recognized only in &%accept%& and
31291 &%discard%& statements. It marks the boundary between the conditions whose
31292 failure causes control to pass to the next statement, and the conditions whose
31293 failure causes the ACL to return &"deny"&. This concept has proved to be
31294 confusing to some people, so the use of &%endpass%& is no longer recommended as
31295 &"best practice"&. See the description of &%accept%& above for more details.
31298 .vitem &*log_message*&&~=&~<&'text'&>
31299 .cindex "&%log_message%& ACL modifier"
31300 This modifier sets up a message that is used as part of the log message if the
31301 ACL denies access or a &%warn%& statement's conditions are true. For example:
31303 require log_message = wrong cipher suite $tls_in_cipher
31304 encrypted = DES-CBC3-SHA
31306 &%log_message%& is also used when recipients are discarded by &%discard%&. For
31309 &`discard `&<&'some conditions'&>
31310 &` log_message = Discarded $local_part@$domain because...`&
31312 When access is denied, &%log_message%& adds to any underlying error message
31313 that may exist because of a condition failure. For example, while verifying a
31314 recipient address, a &':fail:'& redirection might have already set up a
31317 The message may be defined before the conditions to which it applies, because
31318 the string expansion does not happen until Exim decides that access is to be
31319 denied. This means that any variables that are set by the condition are
31320 available for inclusion in the message. For example, the &$dnslist_$&<&'xxx'&>
31321 variables are set after a DNS black list lookup succeeds. If the expansion of
31322 &%log_message%& fails, or if the result is an empty string, the modifier is
31325 .vindex "&$acl_verify_message$&"
31326 If you want to use a &%warn%& statement to log the result of an address
31327 verification, you can use &$acl_verify_message$& to include the verification
31330 If &%log_message%& is used with a &%warn%& statement, &"Warning:"& is added to
31331 the start of the logged message. If the same warning log message is requested
31332 more than once while receiving a single email message, only one copy is
31333 actually logged. If you want to log multiple copies, use &%logwrite%& instead
31334 of &%log_message%&. In the absence of &%log_message%& and &%logwrite%&, nothing
31335 is logged for a successful &%warn%& statement.
31337 If &%log_message%& is not present and there is no underlying error message (for
31338 example, from the failure of address verification), but &%message%& is present,
31339 the &%message%& text is used for logging rejections. However, if any text for
31340 logging contains newlines, only the first line is logged. In the absence of
31341 both &%log_message%& and &%message%&, a default built-in message is used for
31342 logging rejections.
31345 .vitem "&*log_reject_target*&&~=&~<&'log name list'&>"
31346 .cindex "&%log_reject_target%& ACL modifier"
31347 .cindex "logging in ACL" "specifying which log"
31348 This modifier makes it possible to specify which logs are used for messages
31349 about ACL rejections. Its argument is a colon-separated list of words that can
31350 be &"main"&, &"reject"&, or &"panic"&. The default is &`main:reject`&. The list
31351 may be empty, in which case a rejection is not logged at all. For example, this
31352 ACL fragment writes no logging information when access is denied:
31354 &`deny `&<&'some conditions'&>
31355 &` log_reject_target =`&
31357 This modifier can be used in SMTP and non-SMTP ACLs. It applies to both
31358 permanent and temporary rejections. Its effect lasts for the rest of the
31362 .vitem &*logwrite*&&~=&~<&'text'&>
31363 .cindex "&%logwrite%& ACL modifier"
31364 .cindex "logging in ACL" "immediate"
31365 This modifier writes a message to a log file as soon as it is encountered when
31366 processing an ACL. (Compare &%log_message%&, which, except in the case of
31367 &%warn%& and &%discard%&, is used only if the ACL statement denies
31368 access.) The &%logwrite%& modifier can be used to log special incidents in
31371 &`accept `&<&'some special conditions'&>
31372 &` control = freeze`&
31373 &` logwrite = froze message because ...`&
31375 By default, the message is written to the main log. However, it may begin
31376 with a colon, followed by a comma-separated list of log names, and then
31377 another colon, to specify exactly which logs are to be written. For
31380 logwrite = :main,reject: text for main and reject logs
31381 logwrite = :panic: text for panic log only
31385 .vitem &*message*&&~=&~<&'text'&>
31386 .cindex "&%message%& ACL modifier"
31387 This modifier sets up a text string that is expanded and used as a response
31388 message when an ACL statement terminates the ACL with an &"accept"&, &"deny"&,
31389 or &"defer"& response. (In the case of the &%accept%& and &%discard%& verbs,
31390 there is some complication if &%endpass%& is involved; see the description of
31391 &%accept%& for details.)
31393 The expansion of the message happens at the time Exim decides that the ACL is
31394 to end, not at the time it processes &%message%&. If the expansion fails, or
31395 generates an empty string, the modifier is ignored. Here is an example where
31396 &%message%& must be specified first, because the ACL ends with a rejection if
31397 the &%hosts%& condition fails:
31399 require message = Host not recognized
31402 (Once a condition has failed, no further conditions or modifiers are
31405 .cindex "SMTP" "error codes"
31406 .oindex "&%smtp_banner%&
31407 For ACLs that are triggered by SMTP commands, the message is returned as part
31408 of the SMTP response. The use of &%message%& with &%accept%& (or &%discard%&)
31409 is meaningful only for SMTP, as no message is returned when a non-SMTP message
31410 is accepted. In the case of the connect ACL, accepting with a message modifier
31411 overrides the value of &%smtp_banner%&. For the EHLO/HELO ACL, a customized
31412 accept message may not contain more than one line (otherwise it will be
31413 truncated at the first newline and a panic logged), and it cannot affect the
31416 When SMTP is involved, the message may begin with an overriding response code,
31417 consisting of three digits optionally followed by an &"extended response code"&
31418 of the form &'n.n.n'&, each code being followed by a space. For example:
31420 deny message = 599 1.2.3 Host not welcome
31421 hosts = 192.168.34.0/24
31423 The first digit of the supplied response code must be the same as would be sent
31424 by default. A panic occurs if it is not. Exim uses a 550 code when it denies
31425 access, but for the predata ACL, note that the default success code is 354, not
31428 Notwithstanding the previous paragraph, for the QUIT ACL, unlike the others,
31429 the message modifier cannot override the 221 response code.
31431 The text in a &%message%& modifier is literal; any quotes are taken as
31432 literals, but because the string is expanded, backslash escapes are processed
31433 anyway. If the message contains newlines, this gives rise to a multi-line SMTP
31436 .vindex "&$acl_verify_message$&"
31437 While the text is being expanded, the &$acl_verify_message$& variable
31438 contains any message previously set.
31439 Afterwards, &$acl_verify_message$& is cleared.
31441 If &%message%& is used on a statement that verifies an address, the message
31442 specified overrides any message that is generated by the verification process.
31443 However, the original message is available in the variable
31444 &$acl_verify_message$&, so you can incorporate it into your message if you
31445 wish. In particular, if you want the text from &%:fail:%& items in &(redirect)&
31446 routers to be passed back as part of the SMTP response, you should either not
31447 use a &%message%& modifier, or make use of &$acl_verify_message$&.
31449 For compatibility with previous releases of Exim, a &%message%& modifier that
31450 is used with a &%warn%& verb behaves in a similar way to the &%add_header%&
31451 modifier, but this usage is now deprecated. However, &%message%& acts only when
31452 all the conditions are true, wherever it appears in an ACL command, whereas
31453 &%add_header%& acts as soon as it is encountered. If &%message%& is used with
31454 &%warn%& in an ACL that is not concerned with receiving a message, it has no
31458 .vitem &*queue*&&~=&~<&'text'&>
31459 .cindex "&%queue%& ACL modifier"
31460 .cindex "named queues" "selecting in ACL"
31461 This modifier specifies the use of a named queue for spool files
31463 It can only be used before the message is received (i.e. not in
31465 This could be used, for example, for known high-volume burst sources
31466 of traffic, or for quarantine of messages.
31467 Separate queue-runner processes will be needed for named queues.
31468 If the text after expansion is empty, the default queue is used.
31471 .vitem &*remove_header*&&~=&~<&'text'&>
31472 This modifier specifies one or more header names in a colon-separated list
31473 that are to be removed from an incoming message, assuming, of course, that
31474 the message is ultimately accepted. For details, see section &<<SECTremoveheadacl>>&.
31477 .vitem &*set*&&~<&'acl_name'&>&~=&~<&'value'&>
31478 .cindex "&%set%& ACL modifier"
31479 This modifier puts a value into one of the ACL variables (see section
31480 &<<SECTaclvariables>>&).
31483 .vitem &*udpsend*&&~=&~<&'parameters'&>
31484 .cindex "UDP communications"
31485 This modifier sends a UDP packet, for purposes such as statistics
31486 collection or behaviour monitoring. The parameters are expanded, and
31487 the result of the expansion must be a colon-separated list consisting
31488 of a destination server, port number, and the packet contents. The
31489 server can be specified as a host name or IPv4 or IPv6 address. The
31490 separator can be changed with the usual angle bracket syntax. For
31491 example, you might want to collect information on which hosts connect
31494 udpsend = <; 2001:dB8::dead:beef ; 1234 ;\
31495 $tod_zulu $sender_host_address
31502 .section "Use of the control modifier" "SECTcontrols"
31503 .cindex "&%control%& ACL modifier"
31504 The &%control%& modifier supports the following settings:
31507 .vitem &*control&~=&~allow_auth_unadvertised*&
31508 This modifier allows a client host to use the SMTP AUTH command even when it
31509 has not been advertised in response to EHLO. Furthermore, because there are
31510 apparently some really broken clients that do this, Exim will accept AUTH after
31511 HELO (rather than EHLO) when this control is set. It should be used only if you
31512 really need it, and you should limit its use to those broken clients that do
31513 not work without it. For example:
31515 warn hosts = 192.168.34.25
31516 control = allow_auth_unadvertised
31518 Normally, when an Exim server receives an AUTH command, it checks the name of
31519 the authentication mechanism that is given in the command to ensure that it
31520 matches an advertised mechanism. When this control is set, the check that a
31521 mechanism has been advertised is bypassed. Any configured mechanism can be used
31522 by the client. This control is permitted only in the connection and HELO ACLs.
31525 .vitem &*control&~=&~caseful_local_part*& &&&
31526 &*control&~=&~caselower_local_part*&
31527 .cindex "&ACL;" "case of local part in"
31528 .cindex "case of local parts"
31529 .vindex "&$local_part$&"
31530 These two controls are permitted only in the ACL specified by &%acl_smtp_rcpt%&
31531 (that is, during RCPT processing). By default, the contents of &$local_part$&
31532 are lower cased before ACL processing. If &"caseful_local_part"& is specified,
31533 any uppercase letters in the original local part are restored in &$local_part$&
31534 for the rest of the ACL, or until a control that sets &"caselower_local_part"&
31537 These controls affect only the current recipient. Moreover, they apply only to
31538 local part handling that takes place directly in the ACL (for example, as a key
31539 in lookups). If a test to verify the recipient is obeyed, the case-related
31540 handling of the local part during the verification is controlled by the router
31541 configuration (see the &%caseful_local_part%& generic router option).
31543 This facility could be used, for example, to add a spam score to local parts
31544 containing upper case letters. For example, using &$acl_m4$& to accumulate the
31547 warn control = caseful_local_part
31548 set acl_m4 = ${eval:\
31550 ${if match{$local_part}{[A-Z]}{1}{0}}\
31552 control = caselower_local_part
31554 Notice that we put back the lower cased version afterwards, assuming that
31555 is what is wanted for subsequent tests.
31558 .vitem &*control&~=&~cutthrough_delivery/*&<&'options'&>
31559 .cindex "&ACL;" "cutthrough routing"
31560 .cindex "cutthrough" "requesting"
31561 This option requests delivery be attempted while the item is being received.
31563 The option is usable in the RCPT ACL.
31564 If enabled for a message received via smtp and routed to an smtp transport,
31565 and only one transport, interface, destination host and port combination
31566 is used for all recipients of the message,
31567 then the delivery connection is made while the receiving connection is open
31568 and data is copied from one to the other.
31570 An attempt to set this option for any recipient but the first
31571 for a mail will be quietly ignored.
31572 If a recipient-verify callout
31574 connection is subsequently
31575 requested in the same ACL it is held open and used for
31576 any subsequent recipients and the data,
31577 otherwise one is made after the initial RCPT ACL completes.
31579 Note that routers are used in verify mode,
31580 and cannot depend on content of received headers.
31581 Note also that headers cannot be
31582 modified by any of the post-data ACLs (DATA, MIME and DKIM).
31583 Headers may be modified by routers (subject to the above) and transports.
31584 The &'Received-By:'& header is generated as soon as the body reception starts,
31585 rather than the traditional time after the full message is received;
31586 this will affect the timestamp.
31588 All the usual ACLs are called; if one results in the message being
31589 rejected, all effort spent in delivery (including the costs on
31590 the ultimate destination) will be wasted.
31591 Note that in the case of data-time ACLs this includes the entire
31594 Cutthrough delivery is not supported via transport-filters or when DKIM signing
31595 of outgoing messages is done, because it sends data to the ultimate destination
31596 before the entire message has been received from the source.
31597 It is not supported for messages received with the SMTP PRDR
31601 Should the ultimate destination system positively accept or reject the mail,
31602 a corresponding indication is given to the source system and nothing is queued.
31603 If the item is successfully delivered in cutthrough mode
31604 the delivery log lines are tagged with ">>" rather than "=>" and appear
31605 before the acceptance "<=" line.
31607 If there is a temporary error the item is queued for later delivery in the
31609 This behaviour can be adjusted by appending the option &*defer=*&<&'value'&>
31610 to the control; the default value is &"spool"& and the alternate value
31611 &"pass"& copies an SMTP defer response from the target back to the initiator
31612 and does not queue the message.
31613 Note that this is independent of any recipient verify conditions in the ACL.
31615 Delivery in this mode avoids the generation of a bounce mail to a
31617 sender when the destination system is doing content-scan based rejection.
31620 .vitem &*control&~=&~debug/*&<&'options'&>
31621 .cindex "&ACL;" "enabling debug logging"
31622 .cindex "debugging" "enabling from an ACL"
31623 This control turns on debug logging, almost as though Exim had been invoked
31624 with &`-d`&, with the output going to a new logfile in the usual logs directory,
31625 by default called &'debuglog'&.
31627 Logging set up by the control will be maintained across spool residency.
31629 Options are a slash-separated list.
31630 If an option takes an argument, the option name and argument are separated by
31631 an equals character.
31632 Several options are supported:
31634 tag=<&'suffix'&> The filename can be adjusted with thise option.
31635 The argument, which may access any variables already defined,
31636 is appended to the default name.
31638 opts=<&'debug&~options'&> The argument specififes what is to be logged,
31639 using the same values as the &`-d`& command-line option.
31641 stop Logging started with this control may be
31642 stopped by using this option.
31644 kill Logging started with this control may be
31645 stopped by using this option.
31646 Additionally the debug file will be removed,
31647 providing one means for speculative debug tracing.
31649 pretrigger=<&'size'&> This option specifies a memory buffuer to be used
31650 for pre-trigger debug capture.
31651 Debug lines are recorded in the buffer until
31652 and if) a trigger occurs; at which time they are
31653 dumped to the debug file. Newer lines displace the
31654 oldest if the buffer is full. After a trigger,
31655 immediate writes to file are done as normal.
31657 trigger=<&'reason'&> This option selects cause for the pretrigger buffer
31658 see above) to be copied to file. A reason of $*now*
31659 take effect immediately; one of &*paniclog*& triggers
31660 on a write to the panic log.
31663 Some examples (which depend on variables that don't exist in all
31667 control = debug/tag=.$sender_host_address
31668 control = debug/opts=+expand+acl
31669 control = debug/tag=.$message_exim_id/opts=+expand
31670 control = debug/kill
31671 control = debug/opts=+all/pretrigger=1024/trigger=paniclog
31672 control = debug/trigger=now
31676 .vitem &*control&~=&~dkim_disable_verify*&
31677 .cindex "disable DKIM verify"
31678 .cindex "DKIM" "disable verify"
31679 This control turns off DKIM verification processing entirely. For details on
31680 the operation and configuration of DKIM, see section &<<SECDKIM>>&.
31683 .vitem &*control&~=&~dmarc_disable_verify*&
31684 .cindex "disable DMARC verify"
31685 .cindex "DMARC" "disable verify"
31686 This control turns off DMARC verification processing entirely. For details on
31687 the operation and configuration of DMARC, see section &<<SECDMARC>>&.
31690 .vitem &*control&~=&~dscp/*&<&'value'&>
31691 .cindex "&ACL;" "setting DSCP value"
31692 .cindex "DSCP" "inbound"
31693 This option causes the DSCP value associated with the socket for the inbound
31694 connection to be adjusted to a given value, given as one of a number of fixed
31695 strings or to numeric value.
31696 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
31697 Common values include &`throughput`&, &`mincost`&, and on newer systems
31698 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
31700 The outbound packets from Exim will be marked with this value in the header
31701 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
31702 that these values will have any effect, not be stripped by networking
31703 equipment, or do much of anything without cooperation with your Network
31704 Engineer and those of all network operators between the source and destination.
31707 .vitem &*control&~=&~enforce_sync*& &&&
31708 &*control&~=&~no_enforce_sync*&
31709 .cindex "SMTP" "synchronization checking"
31710 .cindex "synchronization checking in SMTP"
31711 These controls make it possible to be selective about when SMTP synchronization
31712 is enforced. The global option &%smtp_enforce_sync%& specifies the initial
31713 state of the switch (it is true by default). See the description of this option
31714 in chapter &<<CHAPmainconfig>>& for details of SMTP synchronization checking.
31716 The effect of these two controls lasts for the remainder of the SMTP
31717 connection. They can appear in any ACL except the one for the non-SMTP
31718 messages. The most straightforward place to put them is in the ACL defined by
31719 &%acl_smtp_connect%&, which is run at the start of an incoming SMTP connection,
31720 before the first synchronization check. The expected use is to turn off the
31721 synchronization checks for badly-behaved hosts that you nevertheless need to
31725 .vitem &*control&~=&~fakedefer/*&<&'message'&>
31726 .cindex "fake defer"
31727 .cindex "defer, fake"
31728 This control works in exactly the same way as &%fakereject%& (described below)
31729 except that it causes an SMTP 450 response after the message data instead of a
31730 550 response. You must take care when using &%fakedefer%& because it causes the
31731 messages to be duplicated when the sender retries. Therefore, you should not
31732 use &%fakedefer%& if the message is to be delivered normally.
31734 .vitem &*control&~=&~fakereject/*&<&'message'&>
31735 .cindex "fake rejection"
31736 .cindex "rejection, fake"
31737 This control is permitted only for the MAIL, RCPT, and DATA ACLs, in other
31738 words, only when an SMTP message is being received. If Exim accepts the
31739 message, instead the final 250 response, a 550 rejection message is sent.
31740 However, Exim proceeds to deliver the message as normal. The control applies
31741 only to the current message, not to any subsequent ones that may be received in
31742 the same SMTP connection.
31744 The text for the 550 response is taken from the &%control%& modifier. If no
31745 message is supplied, the following is used:
31747 550-Your message has been rejected but is being
31748 550-kept for evaluation.
31749 550-If it was a legitimate message, it may still be
31750 550 delivered to the target recipient(s).
31752 This facility should be used with extreme caution.
31754 .vitem &*control&~=&~freeze*&
31755 .cindex "frozen messages" "forcing in ACL"
31756 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
31757 other words, only when a message is being received. If the message is accepted,
31758 it is placed on Exim's queue and frozen. The control applies only to the
31759 current message, not to any subsequent ones that may be received in the same
31762 This modifier can optionally be followed by &`/no_tell`&. If the global option
31763 &%freeze_tell%& is set, it is ignored for the current message (that is, nobody
31764 is told about the freezing), provided all the &*control=freeze*& modifiers that
31765 are obeyed for the current message have the &`/no_tell`& option.
31767 .vitem &*control&~=&~no_delay_flush*&
31768 .cindex "SMTP" "output flushing, disabling for delay"
31769 Exim normally flushes SMTP output before implementing a delay in an ACL, to
31770 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
31771 use. This control, as long as it is encountered before the &%delay%& modifier,
31772 disables such output flushing.
31774 .vitem &*control&~=&~no_callout_flush*&
31775 .cindex "SMTP" "output flushing, disabling for callout"
31776 Exim normally flushes SMTP output before performing a callout in an ACL, to
31777 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
31778 use. This control, as long as it is encountered before the &%verify%& condition
31779 that causes the callout, disables such output flushing.
31781 .vitem &*control&~=&~no_mbox_unspool*&
31782 This control is available when Exim is compiled with the content scanning
31783 extension. Content scanning may require a copy of the current message, or parts
31784 of it, to be written in &"mbox format"& to a spool file, for passing to a virus
31785 or spam scanner. Normally, such copies are deleted when they are no longer
31786 needed. If this control is set, the copies are not deleted. The control applies
31787 only to the current message, not to any subsequent ones that may be received in
31788 the same SMTP connection. It is provided for debugging purposes and is unlikely
31789 to be useful in production.
31791 .vitem &*control&~=&~no_multiline_responses*&
31792 .cindex "multiline responses, suppressing"
31793 This control is permitted for any ACL except the one for non-SMTP messages.
31794 It seems that there are broken clients in use that cannot handle multiline
31795 SMTP responses, despite the fact that RFC 821 defined them over 20 years ago.
31797 If this control is set, multiline SMTP responses from ACL rejections are
31798 suppressed. One way of doing this would have been to put out these responses as
31799 one long line. However, RFC 2821 specifies a maximum of 512 bytes per response
31800 (&"use multiline responses for more"& it says &-- ha!), and some of the
31801 responses might get close to that. So this facility, which is after all only a
31802 sop to broken clients, is implemented by doing two very easy things:
31805 Extra information that is normally output as part of a rejection caused by
31806 sender verification failure is omitted. Only the final line (typically &"sender
31807 verification failed"&) is sent.
31809 If a &%message%& modifier supplies a multiline response, only the first
31813 The setting of the switch can, of course, be made conditional on the
31814 calling host. Its effect lasts until the end of the SMTP connection.
31816 .vitem &*control&~=&~no_pipelining*&
31817 .cindex "PIPELINING" "suppressing advertising"
31818 .cindex "ESMTP extensions" PIPELINING
31819 This control turns off the advertising of the PIPELINING extension to SMTP in
31820 the current session. To be useful, it must be obeyed before Exim sends its
31821 response to an EHLO command. Therefore, it should normally appear in an ACL
31822 controlled by &%acl_smtp_connect%& or &%acl_smtp_helo%&. See also
31823 &%pipelining_advertise_hosts%&.
31825 .vitem &*control&~=&~queue/*&<&'options'&>* &&&
31826 &*control&~=&~queue_only*&
31827 .oindex "&%queue%&"
31828 .oindex "&%queue_only%&"
31829 .cindex "queueing incoming messages"
31830 .cindex queueing "forcing in ACL"
31831 .cindex "first pass routing"
31832 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
31833 other words, only when a message is being received. If the message is accepted,
31834 it is placed on Exim's queue and left there for delivery by a subsequent queue
31836 If used with no options set,
31837 no immediate delivery process is started. In other words, it has the
31838 effect as the &%queue_only%& global option or &'-odq'& command-line option.
31840 If the &'first_pass_route'& option is given then
31841 the behaviour is like the command-line &'-oqds'& option;
31842 a delivery process is started which stops short of making
31843 any SMTP delivery. The benefit is that the hints database will be updated for
31844 the message being waiting for a specific host, and a later queue run will be
31845 able to send all such messages on a single connection.
31847 The control only applies to the current message, not to any subsequent ones that
31848 may be received in the same SMTP connection.
31850 .vitem &*control&~=&~submission/*&<&'options'&>
31851 .cindex "message" "submission"
31852 .cindex "submission mode"
31853 This control is permitted only for the MAIL, RCPT, and start of data ACLs (the
31854 latter is the one defined by &%acl_smtp_predata%&). Setting it tells Exim that
31855 the current message is a submission from a local MUA. In this case, Exim
31856 operates in &"submission mode"&, and applies certain fixups to the message if
31857 necessary. For example, it adds a &'Date:'& header line if one is not present.
31858 This control is not permitted in the &%acl_smtp_data%& ACL, because that is too
31859 late (the message has already been created).
31861 Chapter &<<CHAPmsgproc>>& describes the processing that Exim applies to
31862 messages. Section &<<SECTsubmodnon>>& covers the processing that happens in
31863 submission mode; the available options for this control are described there.
31864 The control applies only to the current message, not to any subsequent ones
31865 that may be received in the same SMTP connection.
31867 .vitem &*control&~=&~suppress_local_fixups*&
31868 .cindex "submission fixups, suppressing"
31869 This control applies to locally submitted (non TCP/IP) messages, and is the
31870 complement of &`control = submission`&. It disables the fixups that are
31871 normally applied to locally-submitted messages. Specifically:
31874 Any &'Sender:'& header line is left alone (in this respect, it is a
31875 dynamic version of &%local_sender_retain%&).
31877 No &'Message-ID:'&, &'From:'&, or &'Date:'& header lines are added.
31879 There is no check that &'From:'& corresponds to the actual sender.
31882 This control may be useful when a remotely-originated message is accepted,
31883 passed to some scanning program, and then re-submitted for delivery. It can be
31884 used only in the &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
31885 and &%acl_not_smtp_start%& ACLs, because it has to be set before the message's
31888 &*Note:*& This control applies only to the current message, not to any others
31889 that are being submitted at the same time using &%-bs%& or &%-bS%&.
31891 .vitem &*control&~=&~utf8_downconvert*&
31892 This control enables conversion of UTF-8 in message envelope addresses
31894 For details see section &<<SECTi18nMTA>>&.
31898 .section "Summary of message fixup control" "SECTsummesfix"
31899 All four possibilities for message fixups can be specified:
31902 Locally submitted, fixups applied: the default.
31904 Locally submitted, no fixups applied: use
31905 &`control = suppress_local_fixups`&.
31907 Remotely submitted, no fixups applied: the default.
31909 Remotely submitted, fixups applied: use &`control = submission`&.
31914 .section "Adding header lines in ACLs" "SECTaddheadacl"
31915 .cindex "header lines" "adding in an ACL"
31916 .cindex "header lines" "position of added lines"
31917 .cindex "&%add_header%& ACL modifier"
31918 The &%add_header%& modifier can be used to add one or more extra header lines
31919 to an incoming message, as in this example:
31921 warn dnslists = sbl.spamhaus.org : \
31922 dialup.mail-abuse.org
31923 add_header = X-blacklisted-at: $dnslist_domain
31925 The &%add_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
31926 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
31927 receiving a message). The message must ultimately be accepted for
31928 &%add_header%& to have any significant effect. You can use &%add_header%& with
31929 any ACL verb, including &%deny%& (though this is potentially useful only in a
31932 Headers will not be added to the message if the modifier is used in
31933 DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing.
31935 Leading and trailing newlines are removed from
31936 the data for the &%add_header%& modifier; if it then
31937 contains one or more newlines that
31938 are not followed by a space or a tab, it is assumed to contain multiple header
31939 lines. Each one is checked for valid syntax; &`X-ACL-Warn:`& is added to the
31940 front of any line that is not a valid header line.
31942 Added header lines are accumulated during the MAIL, RCPT, and predata ACLs.
31943 They are added to the message before processing the DATA and MIME ACLs.
31944 However, if an identical header line is requested more than once, only one copy
31945 is actually added to the message. Further header lines may be accumulated
31946 during the DATA and MIME ACLs, after which they are added to the message, again
31947 with duplicates suppressed. Thus, it is possible to add two identical header
31948 lines to an SMTP message, but only if one is added before DATA and one after.
31949 In the case of non-SMTP messages, new headers are accumulated during the
31950 non-SMTP ACLs, and are added to the message after all the ACLs have run. If a
31951 message is rejected after DATA or by the non-SMTP ACL, all added header lines
31952 are included in the entry that is written to the reject log.
31954 .cindex "header lines" "added; visibility of"
31955 Header lines are not visible in string expansions
31957 until they are added to the
31958 message. It follows that header lines defined in the MAIL, RCPT, and predata
31959 ACLs are not visible until the DATA ACL and MIME ACLs are run. Similarly,
31960 header lines that are added by the DATA or MIME ACLs are not visible in those
31961 ACLs. Because of this restriction, you cannot use header lines as a way of
31962 passing data between (for example) the MAIL and RCPT ACLs. If you want to do
31963 this, you can use ACL variables, as described in section
31964 &<<SECTaclvariables>>&.
31966 The list of headers yet to be added is given by the &%$headers_added%& variable.
31968 The &%add_header%& modifier acts immediately as it is encountered during the
31969 processing of an ACL. Notice the difference between these two cases:
31971 &`accept add_header = ADDED: some text`&
31972 &` `&<&'some condition'&>
31974 &`accept `&<&'some condition'&>
31975 &` add_header = ADDED: some text`&
31977 In the first case, the header line is always added, whether or not the
31978 condition is true. In the second case, the header line is added only if the
31979 condition is true. Multiple occurrences of &%add_header%& may occur in the same
31980 ACL statement. All those that are encountered before a condition fails are
31983 .cindex "&%warn%& ACL verb"
31984 For compatibility with previous versions of Exim, a &%message%& modifier for a
31985 &%warn%& verb acts in the same way as &%add_header%&, except that it takes
31986 effect only if all the conditions are true, even if it appears before some of
31987 them. Furthermore, only the last occurrence of &%message%& is honoured. This
31988 usage of &%message%& is now deprecated. If both &%add_header%& and &%message%&
31989 are present on a &%warn%& verb, both are processed according to their
31992 By default, new header lines are added to a message at the end of the existing
31993 header lines. However, you can specify that any particular header line should
31994 be added right at the start (before all the &'Received:'& lines), immediately
31995 after the first block of &'Received:'& lines, or immediately before any line
31996 that is not a &'Received:'& or &'Resent-something:'& header.
31998 This is done by specifying &":at_start:"&, &":after_received:"&, or
31999 &":at_start_rfc:"& (or, for completeness, &":at_end:"&) before the text of the
32000 header line, respectively. (Header text cannot start with a colon, as there has
32001 to be a header name first.) For example:
32003 warn add_header = \
32004 :after_received:X-My-Header: something or other...
32006 If more than one header line is supplied in a single &%add_header%& modifier,
32007 each one is treated independently and can therefore be placed differently. If
32008 you add more than one line at the start, or after the Received: block, they end
32009 up in reverse order.
32011 &*Warning*&: This facility currently applies only to header lines that are
32012 added in an ACL. It does NOT work for header lines that are added in a
32013 system filter or in a router or transport.
32017 .section "Removing header lines in ACLs" "SECTremoveheadacl"
32018 .cindex "header lines" "removing in an ACL"
32019 .cindex "header lines" "position of removed lines"
32020 .cindex "&%remove_header%& ACL modifier"
32021 The &%remove_header%& modifier can be used to remove one or more header lines
32022 from an incoming message, as in this example:
32024 warn message = Remove internal headers
32025 remove_header = x-route-mail1 : x-route-mail2
32027 The &%remove_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
32028 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
32029 receiving a message). The message must ultimately be accepted for
32030 &%remove_header%& to have any significant effect. You can use &%remove_header%&
32031 with any ACL verb, including &%deny%&, though this is really not useful for
32032 any verb that doesn't result in a delivered message.
32034 Headers will not be removed from the message if the modifier is used in
32035 DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing.
32037 More than one header can be removed at the same time by using a colon separated
32038 list of header names. The header matching is case insensitive. Wildcards are
32039 not permitted, nor is list expansion performed, so you cannot use hostlists to
32040 create a list of headers, however both connection and message variable expansion
32041 are performed (&%$acl_c_*%& and &%$acl_m_*%&), illustrated in this example:
32043 warn hosts = +internal_hosts
32044 set acl_c_ihdrs = x-route-mail1 : x-route-mail2
32045 warn message = Remove internal headers
32046 remove_header = $acl_c_ihdrs
32048 Header names for removal are accumulated during the MAIL, RCPT, and predata ACLs.
32049 Matching header lines are removed from the message before processing the DATA and MIME ACLs.
32050 If multiple header lines match, all are removed.
32051 There is no harm in attempting to remove the same header twice nor in removing
32052 a non-existent header. Further header lines to be removed may be accumulated
32053 during the DATA and MIME ACLs, after which they are removed from the message,
32054 if present. In the case of non-SMTP messages, headers to be removed are
32055 accumulated during the non-SMTP ACLs, and are removed from the message after
32056 all the ACLs have run. If a message is rejected after DATA or by the non-SMTP
32057 ACL, there really is no effect because there is no logging of what headers
32058 would have been removed.
32060 .cindex "header lines" "removed; visibility of"
32061 Header lines are not visible in string expansions until the DATA phase when it
32062 is received. Any header lines removed in the MAIL, RCPT, and predata ACLs are
32063 not visible in the DATA ACL and MIME ACLs. Similarly, header lines that are
32064 removed by the DATA or MIME ACLs are still visible in those ACLs. Because of
32065 this restriction, you cannot use header lines as a way of controlling data
32066 passed between (for example) the MAIL and RCPT ACLs. If you want to do this,
32067 you should instead use ACL variables, as described in section
32068 &<<SECTaclvariables>>&.
32070 The &%remove_header%& modifier acts immediately as it is encountered during the
32071 processing of an ACL. Notice the difference between these two cases:
32073 &`accept remove_header = X-Internal`&
32074 &` `&<&'some condition'&>
32076 &`accept `&<&'some condition'&>
32077 &` remove_header = X-Internal`&
32079 In the first case, the header line is always removed, whether or not the
32080 condition is true. In the second case, the header line is removed only if the
32081 condition is true. Multiple occurrences of &%remove_header%& may occur in the
32082 same ACL statement. All those that are encountered before a condition fails
32085 &*Warning*&: This facility currently applies only to header lines that are
32086 present during ACL processing. It does NOT remove header lines that are added
32087 in a system filter or in a router or transport.
32092 .section "ACL conditions" "SECTaclconditions"
32093 .cindex "&ACL;" "conditions; list of"
32094 Some of the conditions listed in this section are available only when Exim is
32095 compiled with the content-scanning extension. They are included here briefly
32096 for completeness. More detailed descriptions can be found in the discussion on
32097 content scanning in chapter &<<CHAPexiscan>>&.
32099 Not all conditions are relevant in all circumstances. For example, testing
32100 senders and recipients does not make sense in an ACL that is being run as the
32101 result of the arrival of an ETRN command, and checks on message headers can be
32102 done only in the ACLs specified by &%acl_smtp_data%& and &%acl_not_smtp%&. You
32103 can use the same condition (with different parameters) more than once in the
32104 same ACL statement. This provides a way of specifying an &"and"& conjunction.
32105 The conditions are as follows:
32109 .vitem &*acl&~=&~*&<&'name&~of&~acl&~or&~ACL&~string&~or&~file&~name&~'&>
32110 .cindex "&ACL;" "nested"
32111 .cindex "&ACL;" "indirect"
32112 .cindex "&ACL;" "arguments"
32113 .cindex "&%acl%& ACL condition"
32114 The possible values of the argument are the same as for the
32115 &%acl_smtp_%&&'xxx'& options. The named or inline ACL is run. If it returns
32116 &"accept"& the condition is true; if it returns &"deny"& the condition is
32117 false. If it returns &"defer"&, the current ACL returns &"defer"& unless the
32118 condition is on a &%warn%& verb. In that case, a &"defer"& return makes the
32119 condition false. This means that further processing of the &%warn%& verb
32120 ceases, but processing of the ACL continues.
32122 If the argument is a named ACL, up to nine space-separated optional values
32123 can be appended; they appear within the called ACL in $acl_arg1 to $acl_arg9,
32124 and $acl_narg is set to the count of values.
32125 Previous values of these variables are restored after the call returns.
32126 The name and values are expanded separately.
32127 Note that spaces in complex expansions which are used as arguments
32128 will act as argument separators.
32130 If the nested &%acl%& returns &"drop"& and the outer condition denies access,
32131 the connection is dropped. If it returns &"discard"&, the verb must be
32132 &%accept%& or &%discard%&, and the action is taken immediately &-- no further
32133 conditions are tested.
32135 ACLs may be nested up to 20 deep; the limit exists purely to catch runaway
32136 loops. This condition allows you to use different ACLs in different
32137 circumstances. For example, different ACLs can be used to handle RCPT commands
32138 for different local users or different local domains.
32140 .vitem &*authenticated&~=&~*&<&'string&~list'&>
32141 .cindex "&%authenticated%& ACL condition"
32142 .cindex "authentication" "ACL checking"
32143 .cindex "&ACL;" "testing for authentication"
32144 If the SMTP connection is not authenticated, the condition is false. Otherwise,
32145 the name of the authenticator is tested against the list. To test for
32146 authentication by any authenticator, you can set
32151 .vitem &*condition&~=&~*&<&'string'&>
32152 .cindex "&%condition%& ACL condition"
32153 .cindex "customizing" "ACL condition"
32154 .cindex "&ACL;" "customized test"
32155 .cindex "&ACL;" "testing, customized"
32156 This feature allows you to make up custom conditions. If the result of
32157 expanding the string is an empty string, the number zero, or one of the strings
32158 &"no"& or &"false"&, the condition is false. If the result is any non-zero
32159 number, or one of the strings &"yes"& or &"true"&, the condition is true. For
32160 any other value, some error is assumed to have occurred, and the ACL returns
32161 &"defer"&. However, if the expansion is forced to fail, the condition is
32162 ignored. The effect is to treat it as true, whether it is positive or
32165 .vitem &*decode&~=&~*&<&'location'&>
32166 .cindex "&%decode%& ACL condition"
32167 This condition is available only when Exim is compiled with the
32168 content-scanning extension, and it is allowed only in the ACL defined by
32169 &%acl_smtp_mime%&. It causes the current MIME part to be decoded into a file.
32170 If all goes well, the condition is true. It is false only if there are
32171 problems such as a syntax error or a memory shortage. For more details, see
32172 chapter &<<CHAPexiscan>>&.
32174 .vitem &*dnslists&~=&~*&<&'list&~of&~domain&~names&~and&~other&~data'&>
32175 .cindex "&%dnslists%& ACL condition"
32176 .cindex "DNS list" "in ACL"
32177 .cindex "black list (DNS)"
32178 .cindex "&ACL;" "testing a DNS list"
32179 This condition checks for entries in DNS black lists. These are also known as
32180 &"RBL lists"&, after the original Realtime Blackhole List, but note that the
32181 use of the lists at &'mail-abuse.org'& now carries a charge. There are too many
32182 different variants of this condition to describe briefly here. See sections
32183 &<<SECTmorednslists>>&&--&<<SECTmorednslistslast>>& for details.
32185 .vitem &*domains&~=&~*&<&'domain&~list'&>
32186 .cindex "&%domains%& ACL condition"
32187 .cindex "domain" "ACL checking"
32188 .cindex "&ACL;" "testing a recipient domain"
32189 .vindex "&$domain_data$&"
32190 This condition is relevant only in a RCPT ACL. It checks that the domain
32191 of the recipient address is in the domain list. If percent-hack processing is
32192 enabled, it is done before this test is done. If the check succeeds with a
32193 lookup, the result of the lookup is placed in &$domain_data$& until the next
32196 &*Note carefully*& (because many people seem to fall foul of this): you cannot
32197 use &%domains%& in a DATA ACL.
32200 .vitem &*encrypted&~=&~*&<&'string&~list'&>
32201 .cindex "&%encrypted%& ACL condition"
32202 .cindex "encryption" "checking in an ACL"
32203 .cindex "&ACL;" "testing for encryption"
32204 If the SMTP connection is not encrypted, the condition is false. Otherwise, the
32205 name of the cipher suite in use is tested against the list. To test for
32206 encryption without testing for any specific cipher suite(s), set
32212 .vitem &*hosts&~=&~*&<&'host&~list'&>
32213 .cindex "&%hosts%& ACL condition"
32214 .cindex "host" "ACL checking"
32215 .cindex "&ACL;" "testing the client host"
32216 This condition tests that the calling host matches the host list. If you have
32217 name lookups or wildcarded host names and IP addresses in the same host list,
32218 you should normally put the IP addresses first. For example, you could have:
32220 accept hosts = 10.9.8.7 : dbm;/etc/friendly/hosts
32222 The lookup in this example uses the host name for its key. This is implied by
32223 the lookup type &"dbm"&. (For a host address lookup you would use &"net-dbm"&
32224 and it wouldn't matter which way round you had these two items.)
32226 The reason for the problem with host names lies in the left-to-right way that
32227 Exim processes lists. It can test IP addresses without doing any DNS lookups,
32228 but when it reaches an item that requires a host name, it fails if it cannot
32229 find a host name to compare with the pattern. If the above list is given in the
32230 opposite order, the &%accept%& statement fails for a host whose name cannot be
32231 found, even if its IP address is 10.9.8.7.
32233 If you really do want to do the name check first, and still recognize the IP
32234 address even if the name lookup fails, you can rewrite the ACL like this:
32236 accept hosts = dbm;/etc/friendly/hosts
32237 accept hosts = 10.9.8.7
32239 The default action on failing to find the host name is to assume that the host
32240 is not in the list, so the first &%accept%& statement fails. The second
32241 statement can then check the IP address.
32243 .vindex "&$host_data$&"
32244 If a &%hosts%& condition is satisfied by means of a lookup, the result
32245 of the lookup is made available in the &$host_data$& variable. This
32246 allows you, for example, to set up a statement like this:
32248 deny hosts = net-lsearch;/some/file
32249 message = $host_data
32251 which gives a custom error message for each denied host.
32253 .vitem &*local_parts&~=&~*&<&'local&~part&~list'&>
32254 .cindex "&%local_parts%& ACL condition"
32255 .cindex "local part" "ACL checking"
32256 .cindex "&ACL;" "testing a local part"
32257 .vindex "&$local_part_data$&"
32258 This condition is relevant only in a RCPT ACL. It checks that the local
32259 part of the recipient address is in the list. If percent-hack processing is
32260 enabled, it is done before this test. If the check succeeds with a lookup, the
32261 result of the lookup is placed in &$local_part_data$&, which remains set until
32262 the next &%local_parts%& test.
32264 .vitem &*malware&~=&~*&<&'option'&>
32265 .cindex "&%malware%& ACL condition"
32266 .cindex "&ACL;" "virus scanning"
32267 .cindex "&ACL;" "scanning for viruses"
32268 This condition is available only when Exim is compiled with the
32269 content-scanning extension
32270 and only after a DATA command.
32271 It causes the incoming message to be scanned for
32272 viruses. For details, see chapter &<<CHAPexiscan>>&.
32274 .vitem &*mime_regex&~=&~*&<&'list&~of&~regular&~expressions'&>
32275 .cindex "&%mime_regex%& ACL condition"
32276 .cindex "&ACL;" "testing by regex matching"
32277 This condition is available only when Exim is compiled with the
32278 content-scanning extension, and it is allowed only in the ACL defined by
32279 &%acl_smtp_mime%&. It causes the current MIME part to be scanned for a match
32280 with any of the regular expressions. For details, see chapter
32283 .vitem &*ratelimit&~=&~*&<&'parameters'&>
32284 .cindex "rate limiting"
32285 This condition can be used to limit the rate at which a user or host submits
32286 messages. Details are given in section &<<SECTratelimiting>>&.
32288 .vitem &*recipients&~=&~*&<&'address&~list'&>
32289 .cindex "&%recipients%& ACL condition"
32290 .cindex "recipient" "ACL checking"
32291 .cindex "&ACL;" "testing a recipient"
32292 This condition is relevant only in a RCPT ACL. It checks the entire
32293 recipient address against a list of recipients.
32295 .vitem &*regex&~=&~*&<&'list&~of&~regular&~expressions'&>
32296 .cindex "&%regex%& ACL condition"
32297 .cindex "&ACL;" "testing by regex matching"
32298 This condition is available only when Exim is compiled with the
32299 content-scanning extension, and is available only in the DATA, MIME, and
32300 non-SMTP ACLs. It causes the incoming message to be scanned for a match with
32301 any of the regular expressions. For details, see chapter &<<CHAPexiscan>>&.
32303 .vitem &*seen&~=&~*&<&'parameters'&>
32304 .cindex "&%seen%& ACL condition"
32305 This condition can be used to test if a situation has been previously met,
32306 for example for greylisting.
32307 Details are given in section &<<SECTseen>>&.
32309 .vitem &*sender_domains&~=&~*&<&'domain&~list'&>
32310 .cindex "&%sender_domains%& ACL condition"
32311 .cindex "sender" "ACL checking"
32312 .cindex "&ACL;" "testing a sender domain"
32313 .vindex "&$domain$&"
32314 .vindex "&$sender_address_domain$&"
32315 This condition tests the domain of the sender of the message against the given
32316 domain list. &*Note*&: The domain of the sender address is in
32317 &$sender_address_domain$&. It is &'not'& put in &$domain$& during the testing
32318 of this condition. This is an exception to the general rule for testing domain
32319 lists. It is done this way so that, if this condition is used in an ACL for a
32320 RCPT command, the recipient's domain (which is in &$domain$&) can be used to
32321 influence the sender checking.
32323 &*Warning*&: It is a bad idea to use this condition on its own as a control on
32324 relaying, because sender addresses are easily, and commonly, forged.
32326 .vitem &*senders&~=&~*&<&'address&~list'&>
32327 .cindex "&%senders%& ACL condition"
32328 .cindex "sender" "ACL checking"
32329 .cindex "&ACL;" "testing a sender"
32330 This condition tests the sender of the message against the given list. To test
32331 for a bounce message, which has an empty sender, set
32335 &*Warning*&: It is a bad idea to use this condition on its own as a control on
32336 relaying, because sender addresses are easily, and commonly, forged.
32338 .vitem &*spam&~=&~*&<&'username'&>
32339 .cindex "&%spam%& ACL condition"
32340 .cindex "&ACL;" "scanning for spam"
32341 This condition is available only when Exim is compiled with the
32342 content-scanning extension. It causes the incoming message to be scanned by
32343 SpamAssassin. For details, see chapter &<<CHAPexiscan>>&.
32345 .vitem &*verify&~=&~certificate*&
32346 .cindex "&%verify%& ACL condition"
32347 .cindex "TLS" "client certificate verification"
32348 .cindex "certificate" "verification of client"
32349 .cindex "&ACL;" "certificate verification"
32350 .cindex "&ACL;" "testing a TLS certificate"
32351 This condition is true in an SMTP session if the session is encrypted, and a
32352 certificate was received from the client, and the certificate was verified. The
32353 server requests a certificate only if the client matches &%tls_verify_hosts%&
32354 or &%tls_try_verify_hosts%& (see chapter &<<CHAPTLS>>&).
32356 .vitem &*verify&~=&~csa*&
32357 .cindex "CSA verification"
32358 This condition checks whether the sending host (the client) is authorized to
32359 send email. Details of how this works are given in section
32360 &<<SECTverifyCSA>>&.
32362 .vitem &*verify&~=&~header_names_ascii*&
32363 .cindex "&%verify%& ACL condition"
32364 .cindex "&ACL;" "verifying header names only ASCII"
32365 .cindex "header lines" "verifying header names only ASCII"
32366 .cindex "verifying" "header names only ASCII"
32367 This condition is relevant only in an ACL that is run after a message has been
32369 This usually means an ACL specified by &%acl_smtp_data%& or &%acl_not_smtp%&.
32370 It checks all header names (not the content) to make sure
32371 there are no non-ASCII characters, also excluding control characters. The
32372 allowable characters are decimal ASCII values 33 through 126.
32374 Exim itself will handle headers with non-ASCII characters, but it can cause
32375 problems for downstream applications, so this option will allow their
32376 detection and rejection in the DATA ACL's.
32378 .vitem &*verify&~=&~header_sender/*&<&'options'&>
32379 .cindex "&%verify%& ACL condition"
32380 .cindex "&ACL;" "verifying sender in the header"
32381 .cindex "header lines" "verifying the sender in"
32382 .cindex "sender" "verifying in header"
32383 .cindex "verifying" "sender in header"
32384 This condition is relevant only in an ACL that is run after a message has been
32385 received, that is, in an ACL specified by &%acl_smtp_data%& or
32386 &%acl_not_smtp%&. It checks that there is a verifiable address in at least one
32387 of the &'Sender:'&, &'Reply-To:'&, or &'From:'& header lines. Such an address
32388 is loosely thought of as a &"sender"& address (hence the name of the test).
32389 However, an address that appears in one of these headers need not be an address
32390 that accepts bounce messages; only sender addresses in envelopes are required
32391 to accept bounces. Therefore, if you use the callout option on this check, you
32392 might want to arrange for a non-empty address in the MAIL command.
32394 Details of address verification and the options are given later, starting at
32395 section &<<SECTaddressverification>>& (callouts are described in section
32396 &<<SECTcallver>>&). You can combine this condition with the &%senders%&
32397 condition to restrict it to bounce messages only:
32400 !verify = header_sender
32401 message = A valid sender header is required for bounces
32404 .vitem &*verify&~=&~header_syntax*&
32405 .cindex "&%verify%& ACL condition"
32406 .cindex "&ACL;" "verifying header syntax"
32407 .cindex "header lines" "verifying syntax"
32408 .cindex "verifying" "header syntax"
32409 This condition is relevant only in an ACL that is run after a message has been
32410 received, that is, in an ACL specified by &%acl_smtp_data%& or
32411 &%acl_not_smtp%&. It checks the syntax of all header lines that can contain
32412 lists of addresses (&'Sender:'&, &'From:'&, &'Reply-To:'&, &'To:'&, &'Cc:'&,
32413 and &'Bcc:'&), returning true if there are no problems.
32414 Unqualified addresses (local parts without domains) are
32415 permitted only in locally generated messages and from hosts that match
32416 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
32419 Note that this condition is a syntax check only. However, a common spamming
32420 ploy used to be to send syntactically invalid headers such as
32424 and this condition can be used to reject such messages, though they are not as
32425 common as they used to be.
32427 .vitem &*verify&~=&~helo*&
32428 .cindex "&%verify%& ACL condition"
32429 .cindex "&ACL;" "verifying HELO/EHLO"
32430 .cindex "HELO" "verifying"
32431 .cindex "EHLO" "verifying"
32432 .cindex "verifying" "EHLO"
32433 .cindex "verifying" "HELO"
32434 This condition is true if a HELO or EHLO command has been received from the
32435 client host, and its contents have been verified. If there has been no previous
32436 attempt to verify the HELO/EHLO contents, it is carried out when this
32437 condition is encountered. See the description of the &%helo_verify_hosts%& and
32438 &%helo_try_verify_hosts%& options for details of how to request verification
32439 independently of this condition, and for detail of the verification.
32441 For SMTP input that does not come over TCP/IP (the &%-bs%& command line
32442 option), this condition is always true.
32445 .vitem &*verify&~=&~not_blind/*&<&'options'&>
32446 .cindex "verifying" "not blind"
32447 .cindex "bcc recipients, verifying none"
32448 This condition checks that there are no blind (bcc) recipients in the message.
32449 Every envelope recipient must appear either in a &'To:'& header line or in a
32450 &'Cc:'& header line for this condition to be true. Local parts are checked
32451 case-sensitively; domains are checked case-insensitively. If &'Resent-To:'& or
32452 &'Resent-Cc:'& header lines exist, they are also checked. This condition can be
32453 used only in a DATA or non-SMTP ACL.
32455 There is one possible option, &`case_insensitive`&. If this is present then
32456 local parts are checked case-insensitively.
32458 There are, of course, many legitimate messages that make use of blind (bcc)
32459 recipients. This check should not be used on its own for blocking messages.
32462 .vitem &*verify&~=&~recipient/*&<&'options'&>
32463 .cindex "&%verify%& ACL condition"
32464 .cindex "&ACL;" "verifying recipient"
32465 .cindex "recipient" "verifying"
32466 .cindex "verifying" "recipient"
32467 .vindex "&$address_data$&"
32468 This condition is relevant only after a RCPT command. It verifies the current
32469 recipient. Details of address verification are given later, starting at section
32470 &<<SECTaddressverification>>&. After a recipient has been verified, the value
32471 of &$address_data$& is the last value that was set while routing the address.
32472 This applies even if the verification fails. When an address that is being
32473 verified is redirected to a single address, verification continues with the new
32474 address, and in that case, the subsequent value of &$address_data$& is the
32475 value for the child address.
32477 .vitem &*verify&~=&~reverse_host_lookup/*&<&'options'&>
32478 .cindex "&%verify%& ACL condition"
32479 .cindex "&ACL;" "verifying host reverse lookup"
32480 .cindex "host" "verifying reverse lookup"
32481 This condition ensures that a verified host name has been looked up from the IP
32482 address of the client host. (This may have happened already if the host name
32483 was needed for checking a host list, or if the host matched &%host_lookup%&.)
32484 Verification ensures that the host name obtained from a reverse DNS lookup, or
32485 one of its aliases, does, when it is itself looked up in the DNS, yield the
32486 original IP address.
32488 There is one possible option, &`defer_ok`&. If this is present and a
32489 DNS operation returns a temporary error, the verify condition succeeds.
32491 If this condition is used for a locally generated message (that is, when there
32492 is no client host involved), it always succeeds.
32494 .vitem &*verify&~=&~sender/*&<&'options'&>
32495 .cindex "&%verify%& ACL condition"
32496 .cindex "&ACL;" "verifying sender"
32497 .cindex "sender" "verifying"
32498 .cindex "verifying" "sender"
32499 This condition is relevant only after a MAIL or RCPT command, or after a
32500 message has been received (the &%acl_smtp_data%& or &%acl_not_smtp%& ACLs). If
32501 the message's sender is empty (that is, this is a bounce message), the
32502 condition is true. Otherwise, the sender address is verified.
32504 .vindex "&$address_data$&"
32505 .vindex "&$sender_address_data$&"
32506 If there is data in the &$address_data$& variable at the end of routing, its
32507 value is placed in &$sender_address_data$& at the end of verification. This
32508 value can be used in subsequent conditions and modifiers in the same ACL
32509 statement. It does not persist after the end of the current statement. If you
32510 want to preserve the value for longer, you can save it in an ACL variable.
32512 Details of verification are given later, starting at section
32513 &<<SECTaddressverification>>&. Exim caches the result of sender verification,
32514 to avoid doing it more than once per message.
32516 .vitem &*verify&~=&~sender=*&<&'address'&>&*/*&<&'options'&>
32517 .cindex "&%verify%& ACL condition"
32518 This is a variation of the previous option, in which a modified address is
32519 verified as a sender.
32521 Note that '/' is legal in local-parts; if the address may have such
32522 (eg. is generated from the received message)
32523 they must be protected from the options parsing by doubling:
32525 verify = sender=${listquote{/}{${address:$h_sender:}}}
32531 .section "Using DNS lists" "SECTmorednslists"
32532 .cindex "DNS list" "in ACL"
32533 .cindex "black list (DNS)"
32534 .cindex "&ACL;" "testing a DNS list"
32535 In its simplest form, the &%dnslists%& condition tests whether the calling host
32536 is on at least one of a number of DNS lists by looking up the inverted IP
32537 address in one or more DNS domains. (Note that DNS list domains are not mail
32538 domains, so the &`+`& syntax for named lists doesn't work - it is used for
32539 special options instead.) For example, if the calling host's IP
32540 address is 192.168.62.43, and the ACL statement is
32542 deny dnslists = blackholes.mail-abuse.org : \
32543 dialups.mail-abuse.org
32545 the following records are looked up:
32547 43.62.168.192.blackholes.mail-abuse.org
32548 43.62.168.192.dialups.mail-abuse.org
32550 As soon as Exim finds an existing DNS record, processing of the list stops.
32551 Thus, multiple entries on the list provide an &"or"& conjunction. If you want
32552 to test that a host is on more than one list (an &"and"& conjunction), you can
32553 use two separate conditions:
32555 deny dnslists = blackholes.mail-abuse.org
32556 dnslists = dialups.mail-abuse.org
32558 If a DNS lookup times out or otherwise fails to give a decisive answer, Exim
32559 behaves as if the host does not match the list item, that is, as if the DNS
32560 record does not exist. If there are further items in the DNS list, they are
32563 This is usually the required action when &%dnslists%& is used with &%deny%&
32564 (which is the most common usage), because it prevents a DNS failure from
32565 blocking mail. However, you can change this behaviour by putting one of the
32566 following special items in the list:
32567 .itable none 0 0 2 1pt left 1pt left
32568 .irow "+include_unknown" "behave as if the item is on the list"
32569 .irow "+exclude_unknown" "behave as if the item is not on the list (default)"
32570 .irow "+defer_unknown " "give a temporary error"
32572 .cindex "&`+include_unknown`&"
32573 .cindex "&`+exclude_unknown`&"
32574 .cindex "&`+defer_unknown`&"
32575 Each of these applies to any subsequent items on the list. For example:
32577 deny dnslists = +defer_unknown : foo.bar.example
32579 Testing the list of domains stops as soon as a match is found. If you want to
32580 warn for one list and block for another, you can use two different statements:
32582 deny dnslists = blackholes.mail-abuse.org
32583 warn dnslists = dialups.mail-abuse.org
32584 message = X-Warn: sending host is on dialups list
32586 .cindex caching "of dns lookup"
32588 DNS list lookups are cached by Exim for the duration of the SMTP session
32589 (but limited by the DNS return TTL value),
32590 so a lookup based on the IP address is done at most once for any incoming
32591 connection (assuming long-enough TTL).
32592 Exim does not share information between multiple incoming
32593 connections (but your local name server cache should be active).
32595 There are a number of DNS lists to choose from, some commercial, some free,
32596 or free for small deployments. An overview can be found at
32597 &url(https://en.wikipedia.org/wiki/Comparison_of_DNS_blacklists).
32601 .section "Specifying the IP address for a DNS list lookup" "SECID201"
32602 .cindex "DNS list" "keyed by explicit IP address"
32603 By default, the IP address that is used in a DNS list lookup is the IP address
32604 of the calling host. However, you can specify another IP address by listing it
32605 after the domain name, introduced by a slash. For example:
32607 deny dnslists = black.list.tld/192.168.1.2
32609 This feature is not very helpful with explicit IP addresses; it is intended for
32610 use with IP addresses that are looked up, for example, the IP addresses of the
32611 MX hosts or nameservers of an email sender address. For an example, see section
32612 &<<SECTmulkeyfor>>& below.
32617 .section "DNS lists keyed on domain names" "SECID202"
32618 .cindex "DNS list" "keyed by domain name"
32619 There are some lists that are keyed on domain names rather than inverted IP
32620 addresses (see, e.g., the &'domain based zones'& link at
32621 &url(http://www.rfc-ignorant.org/)). No reversing of components is used
32622 with these lists. You can change the name that is looked up in a DNS list by
32623 listing it after the domain name, introduced by a slash. For example,
32625 deny dnslists = dsn.rfc-ignorant.org/$sender_address_domain
32626 message = Sender's domain is listed at $dnslist_domain
32628 This particular example is useful only in ACLs that are obeyed after the
32629 RCPT or DATA commands, when a sender address is available. If (for
32630 example) the message's sender is &'user@tld.example'& the name that is looked
32631 up by this example is
32633 tld.example.dsn.rfc-ignorant.org
32635 A single &%dnslists%& condition can contain entries for both names and IP
32636 addresses. For example:
32638 deny dnslists = sbl.spamhaus.org : \
32639 dsn.rfc-ignorant.org/$sender_address_domain
32641 The first item checks the sending host's IP address; the second checks a domain
32642 name. The whole condition is true if either of the DNS lookups succeeds.
32647 .section "Multiple explicit keys for a DNS list" "SECTmulkeyfor"
32648 .cindex "DNS list" "multiple keys for"
32649 The syntax described above for looking up explicitly-defined values (either
32650 names or IP addresses) in a DNS blacklist is a simplification. After the domain
32651 name for the DNS list, what follows the slash can in fact be a list of items.
32652 As with all lists in Exim, the default separator is a colon. However, because
32653 this is a sublist within the list of DNS blacklist domains, it is necessary
32654 either to double the separators like this:
32656 dnslists = black.list.tld/name.1::name.2
32658 or to change the separator character, like this:
32660 dnslists = black.list.tld/<;name.1;name.2
32662 If an item in the list is an IP address, it is inverted before the DNS
32663 blacklist domain is appended. If it is not an IP address, no inversion
32664 occurs. Consider this condition:
32666 dnslists = black.list.tld/<;192.168.1.2;a.domain
32668 The DNS lookups that occur are:
32670 2.1.168.192.black.list.tld
32671 a.domain.black.list.tld
32673 Once a DNS record has been found (that matches a specific IP return
32674 address, if specified &-- see section &<<SECTaddmatcon>>&), no further lookups
32675 are done. If there is a temporary DNS error, the rest of the sublist of domains
32676 or IP addresses is tried. A temporary error for the whole dnslists item occurs
32677 only if no other DNS lookup in this sublist succeeds. In other words, a
32678 successful lookup for any of the items in the sublist overrides a temporary
32679 error for a previous item.
32681 The ability to supply a list of items after the slash is in some sense just a
32682 syntactic convenience. These two examples have the same effect:
32684 dnslists = black.list.tld/a.domain : black.list.tld/b.domain
32685 dnslists = black.list.tld/a.domain::b.domain
32687 However, when the data for the list is obtained from a lookup, the second form
32688 is usually much more convenient. Consider this example:
32690 deny dnslists = sbl.spamhaus.org/<|${lookup dnsdb {>|a=<|\
32691 ${lookup dnsdb {>|mxh=\
32692 $sender_address_domain} }} }
32693 message = The mail servers for the domain \
32694 $sender_address_domain \
32695 are listed at $dnslist_domain ($dnslist_value); \
32698 Note the use of &`>|`& in the dnsdb lookup to specify the separator for
32699 multiple DNS records. The inner dnsdb lookup produces a list of MX hosts
32700 and the outer dnsdb lookup finds the IP addresses for these hosts. The result
32701 of expanding the condition might be something like this:
32703 dnslists = sbl.spamhaus.org/<|192.168.2.3|192.168.5.6|...
32705 Thus, this example checks whether or not the IP addresses of the sender
32706 domain's mail servers are on the Spamhaus black list.
32708 The key that was used for a successful DNS list lookup is put into the variable
32709 &$dnslist_matched$& (see section &<<SECID204>>&).
32714 .section "Data returned by DNS lists" "SECID203"
32715 .cindex "DNS list" "data returned from"
32716 DNS lists are constructed using address records in the DNS. The original RBL
32717 just used the address 127.0.0.1 on the right hand side of each record, but the
32718 RBL+ list and some other lists use a number of values with different meanings.
32719 The values used on the RBL+ list are:
32720 .itable none 0 0 2 1pt left 1pt left
32721 .irow 127.1.0.1 "RBL"
32722 .irow 127.1.0.2 "DUL"
32723 .irow 127.1.0.3 "DUL and RBL"
32724 .irow 127.1.0.4 "RSS"
32725 .irow 127.1.0.5 "RSS and RBL"
32726 .irow 127.1.0.6 "RSS and DUL"
32727 .irow 127.1.0.7 "RSS and DUL and RBL"
32729 Section &<<SECTaddmatcon>>& below describes how you can distinguish between
32730 different values. Some DNS lists may return more than one address record;
32731 see section &<<SECThanmuldnsrec>>& for details of how they are checked.
32733 Values returned by a properly running DBSBL should be in the 127.0.0.0/8
32734 range. If a DNSBL operator loses control of the domain, lookups on it
32735 may start returning other addresses. Because of this, Exim now ignores
32736 returned values outside the 127/8 region.
32739 .section "Variables set from DNS lists" "SECID204"
32740 .cindex "expansion" "variables, set from DNS list"
32741 .cindex "DNS list" "variables set from"
32742 .vindex "&$dnslist_domain$&"
32743 .vindex "&$dnslist_matched$&"
32744 .vindex "&$dnslist_text$&"
32745 .vindex "&$dnslist_value$&"
32746 When an entry is found in a DNS list, the variable &$dnslist_domain$& contains
32747 the name of the overall domain that matched (for example,
32748 &`spamhaus.example`&), &$dnslist_matched$& contains the key within that domain
32749 (for example, &`192.168.5.3`&), and &$dnslist_value$& contains the data from
32750 the DNS record. When the key is an IP address, it is not reversed in
32751 &$dnslist_matched$& (though it is, of course, in the actual lookup). In simple
32752 cases, for example:
32754 deny dnslists = spamhaus.example
32756 the key is also available in another variable (in this case,
32757 &$sender_host_address$&). In more complicated cases, however, this is not true.
32758 For example, using a data lookup (as described in section &<<SECTmulkeyfor>>&)
32759 might generate a dnslists lookup like this:
32761 deny dnslists = spamhaus.example/<|192.168.1.2|192.168.6.7|...
32763 If this condition succeeds, the value in &$dnslist_matched$& might be
32764 &`192.168.6.7`& (for example).
32766 If more than one address record is returned by the DNS lookup, all the IP
32767 addresses are included in &$dnslist_value$&, separated by commas and spaces.
32768 The variable &$dnslist_text$& contains the contents of any associated TXT
32769 record. For lists such as RBL+ the TXT record for a merged entry is often not
32770 very meaningful. See section &<<SECTmordetinf>>& for a way of obtaining more
32773 You can use the DNS list variables in &%message%& or &%log_message%& modifiers
32774 &-- even if these appear before the condition in the ACL, they are not
32775 expanded until after it has failed. For example:
32777 deny hosts = !+local_networks
32778 message = $sender_host_address is listed \
32780 dnslists = rbl-plus.mail-abuse.example
32785 .section "Additional matching conditions for DNS lists" "SECTaddmatcon"
32786 .cindex "DNS list" "matching specific returned data"
32787 You can add an equals sign and an IP address after a &%dnslists%& domain name
32788 in order to restrict its action to DNS records with a matching right hand side.
32791 deny dnslists = rblplus.mail-abuse.org=127.0.0.2
32793 rejects only those hosts that yield 127.0.0.2. Without this additional data,
32794 any address record is considered to be a match. For the moment, we assume
32795 that the DNS lookup returns just one record. Section &<<SECThanmuldnsrec>>&
32796 describes how multiple records are handled.
32798 More than one IP address may be given for checking, using a comma as a
32799 separator. These are alternatives &-- if any one of them matches, the
32800 &%dnslists%& condition is true. For example:
32802 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
32804 If you want to specify a constraining address list and also specify names or IP
32805 addresses to be looked up, the constraining address list must be specified
32806 first. For example:
32808 deny dnslists = dsn.rfc-ignorant.org\
32809 =127.0.0.2/$sender_address_domain
32812 If the character &`&&`& is used instead of &`=`&, the comparison for each
32813 listed IP address is done by a bitwise &"and"& instead of by an equality test.
32814 In other words, the listed addresses are used as bit masks. The comparison is
32815 true if all the bits in the mask are present in the address that is being
32816 tested. For example:
32818 dnslists = a.b.c&0.0.0.3
32820 matches if the address is &'x.x.x.'&3, &'x.x.x.'&7, &'x.x.x.'&11, etc. If you
32821 want to test whether one bit or another bit is present (as opposed to both
32822 being present), you must use multiple values. For example:
32824 dnslists = a.b.c&0.0.0.1,0.0.0.2
32826 matches if the final component of the address is an odd number or two times
32831 .section "Negated DNS matching conditions" "SECID205"
32832 You can supply a negative list of IP addresses as part of a &%dnslists%&
32835 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
32837 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
32838 IP address yielded by the list is either 127.0.0.2 or 127.0.0.3"&,
32840 deny dnslists = a.b.c!=127.0.0.2,127.0.0.3
32842 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
32843 IP address yielded by the list is not 127.0.0.2 and not 127.0.0.3"&. In other
32844 words, the result of the test is inverted if an exclamation mark appears before
32845 the &`=`& (or the &`&&`&) sign.
32847 &*Note*&: This kind of negation is not the same as negation in a domain,
32848 host, or address list (which is why the syntax is different).
32850 If you are using just one list, the negation syntax does not gain you much. The
32851 previous example is precisely equivalent to
32853 deny dnslists = a.b.c
32854 !dnslists = a.b.c=127.0.0.2,127.0.0.3
32856 However, if you are using multiple lists, the negation syntax is clearer.
32857 Consider this example:
32859 deny dnslists = sbl.spamhaus.org : \
32861 dnsbl.njabl.org!=127.0.0.3 : \
32864 Using only positive lists, this would have to be:
32866 deny dnslists = sbl.spamhaus.org : \
32868 deny dnslists = dnsbl.njabl.org
32869 !dnslists = dnsbl.njabl.org=127.0.0.3
32870 deny dnslists = relays.ordb.org
32872 which is less clear, and harder to maintain.
32874 Negation can also be used with a bitwise-and restriction.
32875 The dnslists condition with only be trus if a result is returned
32876 by the lookup which, anded with the restriction, is all zeroes.
32879 deny dnslists = zen.spamhaus.org!&0.255.255.0
32885 .section "Handling multiple DNS records from a DNS list" "SECThanmuldnsrec"
32886 A DNS lookup for a &%dnslists%& condition may return more than one DNS record,
32887 thereby providing more than one IP address. When an item in a &%dnslists%& list
32888 is followed by &`=`& or &`&&`& and a list of IP addresses, in order to restrict
32889 the match to specific results from the DNS lookup, there are two ways in which
32890 the checking can be handled. For example, consider the condition:
32892 dnslists = a.b.c=127.0.0.1
32894 What happens if the DNS lookup for the incoming IP address yields both
32895 127.0.0.1 and 127.0.0.2 by means of two separate DNS records? Is the
32896 condition true because at least one given value was found, or is it false
32897 because at least one of the found values was not listed? And how does this
32898 affect negated conditions? Both possibilities are provided for with the help of
32899 additional separators &`==`& and &`=&&`&.
32902 If &`=`& or &`&&`& is used, the condition is true if any one of the looked up
32903 IP addresses matches one of the listed addresses. For the example above, the
32904 condition is true because 127.0.0.1 matches.
32906 If &`==`& or &`=&&`& is used, the condition is true only if every one of the
32907 looked up IP addresses matches one of the listed addresses. If the condition is
32910 dnslists = a.b.c==127.0.0.1
32912 and the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
32913 false because 127.0.0.2 is not listed. You would need to have:
32915 dnslists = a.b.c==127.0.0.1,127.0.0.2
32917 for the condition to be true.
32920 When &`!`& is used to negate IP address matching, it inverts the result, giving
32921 the precise opposite of the behaviour above. Thus:
32923 If &`!=`& or &`!&&`& is used, the condition is true if none of the looked up IP
32924 addresses matches one of the listed addresses. Consider:
32926 dnslists = a.b.c!&0.0.0.1
32928 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
32929 false because 127.0.0.1 matches.
32931 If &`!==`& or &`!=&&`& is used, the condition is true if there is at least one
32932 looked up IP address that does not match. Consider:
32934 dnslists = a.b.c!=&0.0.0.1
32936 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
32937 true, because 127.0.0.2 does not match. You would need to have:
32939 dnslists = a.b.c!=&0.0.0.1,0.0.0.2
32941 for the condition to be false.
32943 When the DNS lookup yields only a single IP address, there is no difference
32944 between &`=`& and &`==`& and between &`&&`& and &`=&&`&.
32949 .section "Detailed information from merged DNS lists" "SECTmordetinf"
32950 .cindex "DNS list" "information from merged"
32951 When the facility for restricting the matching IP values in a DNS list is used,
32952 the text from the TXT record that is set in &$dnslist_text$& may not reflect
32953 the true reason for rejection. This happens when lists are merged and the IP
32954 address in the A record is used to distinguish them; unfortunately there is
32955 only one TXT record. One way round this is not to use merged lists, but that
32956 can be inefficient because it requires multiple DNS lookups where one would do
32957 in the vast majority of cases when the host of interest is not on any of the
32960 A less inefficient way of solving this problem is available. If
32961 two domain names, comma-separated, are given, the second is used first to
32962 do an initial check, making use of any IP value restrictions that are set.
32963 If there is a match, the first domain is used, without any IP value
32964 restrictions, to get the TXT record. As a byproduct of this, there is also
32965 a check that the IP being tested is indeed on the first list. The first
32966 domain is the one that is put in &$dnslist_domain$&. For example:
32969 sbl.spamhaus.org,sbl-xbl.spamhaus.org=127.0.0.2 : \
32970 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
32972 rejected because $sender_host_address is blacklisted \
32973 at $dnslist_domain\n$dnslist_text
32975 For the first blacklist item, this starts by doing a lookup in
32976 &'sbl-xbl.spamhaus.org'& and testing for a 127.0.0.2 return. If there is a
32977 match, it then looks in &'sbl.spamhaus.org'&, without checking the return
32978 value, and as long as something is found, it looks for the corresponding TXT
32979 record. If there is no match in &'sbl-xbl.spamhaus.org'&, nothing more is done.
32980 The second blacklist item is processed similarly.
32982 If you are interested in more than one merged list, the same list must be
32983 given several times, but because the results of the DNS lookups are cached,
32984 the DNS calls themselves are not repeated. For example:
32987 http.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.2 : \
32988 socks.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.3 : \
32989 misc.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.4 : \
32990 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
32992 In this case there is one lookup in &'dnsbl.sorbs.net'&, and if none of the IP
32993 values matches (or if no record is found), this is the only lookup that is
32994 done. Only if there is a match is one of the more specific lists consulted.
32998 .section "DNS lists and IPv6" "SECTmorednslistslast"
32999 .cindex "IPv6" "DNS black lists"
33000 .cindex "DNS list" "IPv6 usage"
33001 If Exim is asked to do a dnslist lookup for an IPv6 address, it inverts it
33002 nibble by nibble. For example, if the calling host's IP address is
33003 3ffe:ffff:836f:0a00:000a:0800:200a:c031, Exim might look up
33005 1.3.0.c.a.0.0.2.0.0.8.0.a.0.0.0.0.0.a.0.f.6.3.8.
33006 f.f.f.f.e.f.f.3.blackholes.mail-abuse.org
33008 (split over two lines here to fit on the page). Unfortunately, some of the DNS
33009 lists contain wildcard records, intended for IPv4, that interact badly with
33010 IPv6. For example, the DNS entry
33012 *.3.some.list.example. A 127.0.0.1
33014 is probably intended to put the entire 3.0.0.0/8 IPv4 network on the list.
33015 Unfortunately, it also matches the entire 3::/4 IPv6 network.
33017 You can exclude IPv6 addresses from DNS lookups by making use of a suitable
33018 &%condition%& condition, as in this example:
33020 deny condition = ${if isip4{$sender_host_address}}
33021 dnslists = some.list.example
33024 If an explicit key is being used for a DNS lookup and it may be an IPv6
33025 address you should specify alternate list separators for both the outer
33026 (DNS list name) list and inner (lookup keys) list:
33028 dnslists = <; dnsbl.example.com/<|$acl_m_addrslist
33032 .section "Previously seen user and hosts" "SECTseen"
33033 .cindex "&%een%& ACL condition"
33034 .cindex greylisting
33035 The &%seen%& ACL condition can be used to test whether a
33036 situation has been previously met.
33037 It uses a hints database to record a timestamp against a key.
33038 host. The syntax of the condition is:
33040 &`seen =`& <&'optional flag'&><&'time interval'&> &`/`& <&'options'&>
33045 defer seen = -5m / key=${sender_host_address}_$local_part@$domain
33047 in a RCPT ACL will implement simple greylisting.
33049 The parameters for the condition are
33050 a possible minus sign,
33052 then, slash-separated, a list of options.
33053 The interval is taken as an offset before the current time,
33054 and used for the test.
33055 If the interval is preceded by a minus sign then the condition returns
33056 whether a record is found which is before the test time.
33057 Otherwise, the condition returns whether one is found which is since the
33060 Options are read in order with later ones overriding earlier ones.
33062 The default key is &$sender_host_address$&.
33063 An explicit key can be set using a &%key=value%& option.
33065 If a &%readonly%& option is given then
33066 no record create or update is done.
33067 If a &%write%& option is given then
33068 a record create or update is always done.
33069 An update is done if the test is for &"since"&.
33070 If none of those hold and there was no existing record,
33071 a record is created.
33073 Creates and updates are marked with the current time.
33075 Finally, a &"before"& test which succeeds, and for which the record
33076 is old enough, will be refreshed with a timestamp of the test time.
33077 This can prevent tidying of the database from removing the entry.
33078 The interval for this is, by default, 10 days.
33079 An explicit interval can be set using a
33080 &%refresh=value%& option.
33082 Note that &"seen"& should be added to the list of hints databases
33083 for maintenance if this ACL condition is used.
33086 .section "Rate limiting incoming messages" "SECTratelimiting"
33087 .cindex "rate limiting" "client sending"
33088 .cindex "limiting client sending rates"
33089 .oindex "&%smtp_ratelimit_*%&"
33090 The &%ratelimit%& ACL condition can be used to measure and control the rate at
33091 which clients can send email. This is more powerful than the
33092 &%smtp_ratelimit_*%& options, because those options control the rate of
33093 commands in a single SMTP session only, whereas the &%ratelimit%& condition
33094 works across all connections (concurrent and sequential) from the same client
33095 host. The syntax of the &%ratelimit%& condition is:
33097 &`ratelimit =`& <&'m'&> &`/`& <&'p'&> &`/`& <&'options'&> &`/`& <&'key'&>
33099 If the average client sending rate is less than &'m'& messages per time
33100 period &'p'& then the condition is false; otherwise it is true.
33102 As a side-effect, the &%ratelimit%& condition sets the expansion variable
33103 &$sender_rate$& to the client's computed rate, &$sender_rate_limit$& to the
33104 configured value of &'m'&, and &$sender_rate_period$& to the configured value
33107 The parameter &'p'& is the smoothing time constant, in the form of an Exim
33108 time interval, for example, &`8h`& for eight hours. A larger time constant
33109 means that it takes Exim longer to forget a client's past behaviour. The
33110 parameter &'m'& is the maximum number of messages that a client is permitted to
33111 send in each time interval. It also specifies the number of messages permitted
33112 in a fast burst. By increasing both &'m'& and &'p'& but keeping &'m/p'&
33113 constant, you can allow a client to send more messages in a burst without
33114 changing its long-term sending rate limit. Conversely, if &'m'& and &'p'& are
33115 both small, messages must be sent at an even rate.
33117 There is a script in &_util/ratelimit.pl_& which extracts sending rates from
33118 log files, to assist with choosing appropriate settings for &'m'& and &'p'&
33119 when deploying the &%ratelimit%& ACL condition. The script prints usage
33120 instructions when it is run with no arguments.
33122 The key is used to look up the data for calculating the client's average
33123 sending rate. This data is stored in Exim's spool directory, alongside the
33124 retry and other hints databases. The default key is &$sender_host_address$&,
33125 which means Exim computes the sending rate of each client host IP address.
33126 By changing the key you can change how Exim identifies clients for the purpose
33127 of ratelimiting. For example, to limit the sending rate of each authenticated
33128 user, independent of the computer they are sending from, set the key to
33129 &$authenticated_id$&. You must ensure that the lookup key is meaningful; for
33130 example, &$authenticated_id$& is only meaningful if the client has
33131 authenticated (which you can check with the &%authenticated%& ACL condition).
33133 The lookup key does not have to identify clients: If you want to limit the
33134 rate at which a recipient receives messages, you can use the key
33135 &`$local_part@$domain`& with the &%per_rcpt%& option (see below) in a RCPT
33138 Each &%ratelimit%& condition can have up to four options. A &%per_*%& option
33139 specifies what Exim measures the rate of, for example, messages or recipients
33140 or bytes. You can adjust the measurement using the &%unique=%& and/or
33141 &%count=%& options. You can also control when Exim updates the recorded rate
33142 using a &%strict%&, &%leaky%&, or &%readonly%& option. The options are
33143 separated by a slash, like the other parameters. They may appear in any order.
33145 Internally, Exim appends the smoothing constant &'p'& onto the lookup key with
33146 any options that alter the meaning of the stored data. The limit &'m'& is not
33147 stored, so you can alter the configured maximum rate and Exim will still
33148 remember clients' past behaviour. If you change the &%per_*%& mode or add or
33149 remove the &%unique=%& option, the lookup key changes so Exim will forget past
33150 behaviour. The lookup key is not affected by changes to the update mode and
33151 the &%count=%& option.
33154 .section "Ratelimit options for what is being measured" "ratoptmea"
33155 .cindex "rate limiting" "per_* options"
33156 The &%per_conn%& option limits the client's connection rate. It is not
33157 normally used in the &%acl_not_smtp%&, &%acl_not_smtp_mime%&, or
33158 &%acl_not_smtp_start%& ACLs.
33160 The &%per_mail%& option limits the client's rate of sending messages. This is
33161 the default if none of the &%per_*%& options is specified. It can be used in
33162 &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&, &%acl_smtp_mime%&,
33163 &%acl_smtp_data%&, or &%acl_not_smtp%&.
33165 The &%per_byte%& option limits the sender's email bandwidth. It can be used in
33166 the same ACLs as the &%per_mail%& option, though it is best to use this option
33167 in the &%acl_smtp_mime%&, &%acl_smtp_data%& or &%acl_not_smtp%& ACLs; if it is
33168 used in an earlier ACL, Exim relies on the SIZE parameter given by the client
33169 in its MAIL command, which may be inaccurate or completely missing. You can
33170 follow the limit &'m'& in the configuration with K, M, or G to specify limits
33171 in kilobytes, megabytes, or gigabytes, respectively.
33173 The &%per_rcpt%& option causes Exim to limit the rate at which recipients are
33174 accepted. It can be used in the &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
33175 &%acl_smtp_mime%&, or &%acl_smtp_data%& ACLs. In
33176 &%acl_smtp_rcpt%& the rate is updated one recipient at a time; in the other
33177 ACLs the rate is updated with the total (accepted) recipient count in one go. Note that
33178 in either case the rate limiting engine will see a message with many
33179 recipients as a large high-speed burst.
33181 The &%per_addr%& option is like the &%per_rcpt%& option, except it counts the
33182 number of different recipients that the client has sent messages to in the
33183 last time period. That is, if the client repeatedly sends messages to the same
33184 recipient, its measured rate is not increased. This option can only be used in
33187 The &%per_cmd%& option causes Exim to recompute the rate every time the
33188 condition is processed. This can be used to limit the rate of any SMTP
33189 command. If it is used in multiple ACLs it can limit the aggregate rate of
33190 multiple different commands.
33192 The &%count=%& option can be used to alter how much Exim adds to the client's
33193 measured rate. For example, the &%per_byte%& option is equivalent to
33194 &`per_mail/count=$message_size`&. If there is no &%count=%& option, Exim
33195 increases the measured rate by one (except for the &%per_rcpt%& option in ACLs
33196 other than &%acl_smtp_rcpt%&). The count does not have to be an integer.
33198 The &%unique=%& option is described in section &<<ratoptuniq>>& below.
33201 .section "Ratelimit update modes" "ratoptupd"
33202 .cindex "rate limiting" "reading data without updating"
33203 You can specify one of three options with the &%ratelimit%& condition to
33204 control when its database is updated. This section describes the &%readonly%&
33205 mode, and the next section describes the &%strict%& and &%leaky%& modes.
33207 If the &%ratelimit%& condition is used in &%readonly%& mode, Exim looks up a
33208 previously-computed rate to check against the limit.
33210 For example, you can test the client's sending rate and deny it access (when
33211 it is too fast) in the connect ACL. If the client passes this check then it
33212 can go on to send a message, in which case its recorded rate will be updated
33213 in the MAIL ACL. Subsequent connections from the same client will check this
33217 deny ratelimit = 100 / 5m / readonly
33218 log_message = RATE CHECK: $sender_rate/$sender_rate_period \
33219 (max $sender_rate_limit)
33222 warn ratelimit = 100 / 5m / strict
33223 log_message = RATE UPDATE: $sender_rate/$sender_rate_period \
33224 (max $sender_rate_limit)
33227 If Exim encounters multiple &%ratelimit%& conditions with the same key when
33228 processing a message then it may increase the client's measured rate more than
33229 it should. For example, this will happen if you check the &%per_rcpt%& option
33230 in both &%acl_smtp_rcpt%& and &%acl_smtp_data%&. However it's OK to check the
33231 same &%ratelimit%& condition multiple times in the same ACL. You can avoid any
33232 multiple update problems by using the &%readonly%& option on later ratelimit
33235 The &%per_*%& options described above do not make sense in some ACLs. If you
33236 use a &%per_*%& option in an ACL where it is not normally permitted then the
33237 update mode defaults to &%readonly%& and you cannot specify the &%strict%& or
33238 &%leaky%& modes. In other ACLs the default update mode is &%leaky%& (see the
33239 next section) so you must specify the &%readonly%& option explicitly.
33242 .section "Ratelimit options for handling fast clients" "ratoptfast"
33243 .cindex "rate limiting" "strict and leaky modes"
33244 If a client's average rate is greater than the maximum, the rate limiting
33245 engine can react in two possible ways, depending on the presence of the
33246 &%strict%& or &%leaky%& update modes. This is independent of the other
33247 counter-measures (such as rejecting the message) that may be specified by the
33250 The &%leaky%& (default) option means that the client's recorded rate is not
33251 updated if it is above the limit. The effect of this is that Exim measures the
33252 client's average rate of successfully sent email,
33253 up to the given limit.
33254 This is appropriate if the countermeasure when the condition is true
33255 consists of refusing the message, and
33256 is generally the better choice if you have clients that retry automatically.
33257 If the action when true is anything more complex then this option is
33258 likely not what is wanted.
33260 The &%strict%& option means that the client's recorded rate is always
33261 updated. The effect of this is that Exim measures the client's average rate
33262 of attempts to send email, which can be much higher than the maximum it is
33263 actually allowed. If the client is over the limit it may be subjected to
33264 counter-measures by the ACL. It must slow down and allow sufficient time to
33265 pass that its computed rate falls below the maximum before it can send email
33266 again. The time (the number of smoothing periods) it must wait and not
33267 attempt to send mail can be calculated with this formula:
33269 ln(peakrate/maxrate)
33273 .section "Limiting the rate of different events" "ratoptuniq"
33274 .cindex "rate limiting" "counting unique events"
33275 The &%ratelimit%& &%unique=%& option controls a mechanism for counting the
33276 rate of different events. For example, the &%per_addr%& option uses this
33277 mechanism to count the number of different recipients that the client has
33278 sent messages to in the last time period; it is equivalent to
33279 &`per_rcpt/unique=$local_part@$domain`&. You could use this feature to
33280 measure the rate that a client uses different sender addresses with the
33281 options &`per_mail/unique=$sender_address`&.
33283 For each &%ratelimit%& key Exim stores the set of &%unique=%& values that it
33284 has seen for that key. The whole set is thrown away when it is older than the
33285 rate smoothing period &'p'&, so each different event is counted at most once
33286 per period. In the &%leaky%& update mode, an event that causes the client to
33287 go over the limit is not added to the set, in the same way that the client's
33288 recorded rate is not updated in the same situation.
33290 When you combine the &%unique=%& and &%readonly%& options, the specific
33291 &%unique=%& value is ignored, and Exim just retrieves the client's stored
33294 The &%unique=%& mechanism needs more space in the ratelimit database than the
33295 other &%ratelimit%& options in order to store the event set. The number of
33296 unique values is potentially as large as the rate limit, so the extra space
33297 required increases with larger limits.
33299 The uniqueification is not perfect: there is a small probability that Exim
33300 will think a new event has happened before. If the sender's rate is less than
33301 the limit, Exim should be more than 99.9% correct. However in &%strict%& mode
33302 the measured rate can go above the limit, in which case Exim may under-count
33303 events by a significant margin. Fortunately, if the rate is high enough (2.7
33304 times the limit) that the false positive rate goes above 9%, then Exim will
33305 throw away the over-full event set before the measured rate falls below the
33306 limit. Therefore the only harm should be that exceptionally high sending rates
33307 are logged incorrectly; any countermeasures you configure will be as effective
33311 .section "Using rate limiting" "useratlim"
33312 Exim's other ACL facilities are used to define what counter-measures are taken
33313 when the rate limit is exceeded. This might be anything from logging a warning
33314 (for example, while measuring existing sending rates in order to define
33315 policy), through time delays to slow down fast senders, up to rejecting the
33316 message. For example:
33318 # Log all senders' rates
33319 warn ratelimit = 0 / 1h / strict
33320 log_message = Sender rate $sender_rate / $sender_rate_period
33322 # Slow down fast senders; note the need to truncate $sender_rate
33323 # at the decimal point.
33324 warn ratelimit = 100 / 1h / per_rcpt / strict
33325 delay = ${eval: ${sg{$sender_rate}{[.].*}{}} - \
33326 $sender_rate_limit }s
33328 # Keep authenticated users under control
33329 deny authenticated = *
33330 ratelimit = 100 / 1d / strict / $authenticated_id
33332 # System-wide rate limit
33333 defer ratelimit = 10 / 1s / $primary_hostname
33334 message = Sorry, too busy. Try again later.
33336 # Restrict incoming rate from each host, with a default
33337 # set using a macro and special cases looked up in a table.
33338 defer ratelimit = ${lookup {$sender_host_address} \
33339 cdb {DB/ratelimits.cdb} \
33340 {$value} {RATELIMIT} }
33341 message = Sender rate exceeds $sender_rate_limit \
33342 messages per $sender_rate_period
33344 &*Warning*&: If you have a busy server with a lot of &%ratelimit%& tests,
33345 especially with the &%per_rcpt%& option, you may suffer from a performance
33346 bottleneck caused by locking on the ratelimit hints database. Apart from
33347 making your ACLs less complicated, you can reduce the problem by using a
33348 RAM disk for Exim's hints directory (usually &_/var/spool/exim/db/_&). However
33349 this means that Exim will lose its hints data after a reboot (including retry
33350 hints, the callout cache, and ratelimit data).
33354 .section "Address verification" "SECTaddressverification"
33355 .cindex "verifying address" "options for"
33356 .cindex "policy control" "address verification"
33357 Several of the &%verify%& conditions described in section
33358 &<<SECTaclconditions>>& cause addresses to be verified. Section
33359 &<<SECTsenaddver>>& discusses the reporting of sender verification failures.
33360 The verification conditions can be followed by options that modify the
33361 verification process. The options are separated from the keyword and from each
33362 other by slashes, and some of them contain parameters. For example:
33364 verify = sender/callout
33365 verify = recipient/defer_ok/callout=10s,defer_ok
33367 The first stage of address verification, which always happens, is to run the
33368 address through the routers, in &"verify mode"&. Routers can detect the
33369 difference between verification and routing for delivery, and their actions can
33370 be varied by a number of generic options such as &%verify%& and &%verify_only%&
33371 (see chapter &<<CHAProutergeneric>>&). If routing fails, verification fails.
33372 The available options are as follows:
33375 If the &%callout%& option is specified, successful routing to one or more
33376 remote hosts is followed by a &"callout"& to those hosts as an additional
33377 check. Callouts and their sub-options are discussed in the next section.
33379 If there is a defer error while doing verification routing, the ACL
33380 normally returns &"defer"&. However, if you include &%defer_ok%& in the
33381 options, the condition is forced to be true instead. Note that this is a main
33382 verification option as well as a suboption for callouts.
33384 The &%no_details%& option is covered in section &<<SECTsenaddver>>&, which
33385 discusses the reporting of sender address verification failures.
33387 The &%success_on_redirect%& option causes verification always to succeed
33388 immediately after a successful redirection. By default, if a redirection
33389 generates just one address, that address is also verified. See further
33390 discussion in section &<<SECTredirwhilveri>>&.
33392 If the &%quota%& option is specified for recipient verify,
33393 successful routing to an appendfile transport is followed by a call into
33394 the transport to evaluate the quota status for the recipient.
33395 No actual delivery is done, but verification will succeed if the quota
33396 is sufficient for the message (if the sender gave a message size) or
33397 not already exceeded (otherwise).
33400 .cindex "verifying address" "differentiating failures"
33401 .vindex "&$recipient_verify_failure$&"
33402 .vindex "&$sender_verify_failure$&"
33403 .vindex "&$acl_verify_message$&"
33404 After an address verification failure, &$acl_verify_message$& contains the
33405 error message that is associated with the failure. It can be preserved by
33408 warn !verify = sender
33409 set acl_m0 = $acl_verify_message
33411 If you are writing your own custom rejection message or log message when
33412 denying access, you can use this variable to include information about the
33413 verification failure.
33414 This variable is cleared at the end of processing the ACL verb.
33416 In addition, &$sender_verify_failure$& or &$recipient_verify_failure$& (as
33417 appropriate) contains one of the following words:
33420 &%qualify%&: The address was unqualified (no domain), and the message
33421 was neither local nor came from an exempted host.
33423 &%route%&: Routing failed.
33425 &%mail%&: Routing succeeded, and a callout was attempted; rejection
33426 occurred at or before the MAIL command (that is, on initial
33427 connection, HELO, or MAIL).
33429 &%recipient%&: The RCPT command in a callout was rejected.
33431 &%postmaster%&: The postmaster check in a callout was rejected.
33433 &%quota%&: The quota check for a local recipient did non pass.
33436 The main use of these variables is expected to be to distinguish between
33437 rejections of MAIL and rejections of RCPT in callouts.
33439 The above variables may also be set after a &*successful*&
33440 address verification to:
33443 &%random%&: A random local-part callout succeeded
33449 .section "Callout verification" "SECTcallver"
33450 .cindex "verifying address" "by callout"
33451 .cindex "callout" "verification"
33452 .cindex "SMTP" "callout verification"
33453 For non-local addresses, routing verifies the domain, but is unable to do any
33454 checking of the local part. There are situations where some means of verifying
33455 the local part is desirable. One way this can be done is to make an SMTP
33456 &'callback'& to a delivery host for the sender address or a &'callforward'& to
33457 a subsequent host for a recipient address, to see if the host accepts the
33458 address. We use the term &'callout'& to cover both cases. Note that for a
33459 sender address, the callback is not to the client host that is trying to
33460 deliver the message, but to one of the hosts that accepts incoming mail for the
33463 Exim does not do callouts by default. If you want them to happen, you must
33464 request them by setting appropriate options on the &%verify%& condition, as
33465 described below. This facility should be used with care, because it can add a
33466 lot of resource usage to the cost of verifying an address. However, Exim does
33467 cache the results of callouts, which helps to reduce the cost. Details of
33468 caching are in section &<<SECTcallvercache>>&.
33470 Recipient callouts are usually used only between hosts that are controlled by
33471 the same administration. For example, a corporate gateway host could use
33472 callouts to check for valid recipients on an internal mailserver. A successful
33473 callout does not guarantee that a real delivery to the address would succeed;
33474 on the other hand, a failing callout does guarantee that a delivery would fail.
33476 If the &%callout%& option is present on a condition that verifies an address, a
33477 second stage of verification occurs if the address is successfully routed to
33478 one or more remote hosts. The usual case is routing by a &(dnslookup)& or a
33479 &(manualroute)& router, where the router specifies the hosts. However, if a
33480 router that does not set up hosts routes to an &(smtp)& transport with a
33481 &%hosts%& setting, the transport's hosts are used. If an &(smtp)& transport has
33482 &%hosts_override%& set, its hosts are always used, whether or not the router
33483 supplies a host list.
33484 Callouts are only supported on &(smtp)& transports.
33486 The port that is used is taken from the transport, if it is specified and is a
33487 remote transport. (For routers that do verification only, no transport need be
33488 specified.) Otherwise, the default SMTP port is used. If a remote transport
33489 specifies an outgoing interface, this is used; otherwise the interface is not
33490 specified. Likewise, the text that is used for the HELO command is taken from
33491 the transport's &%helo_data%& option; if there is no transport, the value of
33492 &$smtp_active_hostname$& is used.
33494 For a sender callout check, Exim makes SMTP connections to the remote hosts, to
33495 test whether a bounce message could be delivered to the sender address. The
33496 following SMTP commands are sent:
33498 &`HELO `&<&'local host name'&>
33500 &`RCPT TO:`&<&'the address to be tested'&>
33503 LHLO is used instead of HELO if the transport's &%protocol%& option is
33506 The callout may use EHLO, AUTH and/or STARTTLS given appropriate option
33509 A recipient callout check is similar. By default, it also uses an empty address
33510 for the sender. This default is chosen because most hosts do not make use of
33511 the sender address when verifying a recipient. Using the same address means
33512 that a single cache entry can be used for each recipient. Some sites, however,
33513 do make use of the sender address when verifying. These are catered for by the
33514 &%use_sender%& and &%use_postmaster%& options, described in the next section.
33516 If the response to the RCPT command is a 2&'xx'& code, the verification
33517 succeeds. If it is 5&'xx'&, the verification fails. For any other condition,
33518 Exim tries the next host, if any. If there is a problem with all the remote
33519 hosts, the ACL yields &"defer"&, unless the &%defer_ok%& parameter of the
33520 &%callout%& option is given, in which case the condition is forced to succeed.
33522 .cindex "SMTP" "output flushing, disabling for callout"
33523 A callout may take a little time. For this reason, Exim normally flushes SMTP
33524 output before performing a callout in an ACL, to avoid unexpected timeouts in
33525 clients when the SMTP PIPELINING extension is in use. The flushing can be
33526 disabled by using a &%control%& modifier to set &%no_callout_flush%&.
33528 .cindex "tainted data" "de-tainting"
33529 .cindex "de-tainting" "using recipient verify"
33530 A recipient callout which gets a 2&'xx'& code
33531 will assign untainted values to the
33532 &$domain_data$& and &$local_part_data$& variables,
33533 corresponding to the domain and local parts of the recipient address.
33538 .section "Additional parameters for callouts" "CALLaddparcall"
33539 .cindex "callout" "additional parameters for"
33540 The &%callout%& option can be followed by an equals sign and a number of
33541 optional parameters, separated by commas. For example:
33543 verify = recipient/callout=10s,defer_ok
33545 The old syntax, which had &%callout_defer_ok%& and &%check_postmaster%& as
33546 separate verify options, is retained for backwards compatibility, but is now
33547 deprecated. The additional parameters for &%callout%& are as follows:
33551 .vitem <&'a&~time&~interval'&>
33552 .cindex "callout" "timeout, specifying"
33553 This specifies the timeout that applies for the callout attempt to each host.
33556 verify = sender/callout=5s
33558 The default is 30 seconds. The timeout is used for each response from the
33559 remote host. It is also used for the initial connection, unless overridden by
33560 the &%connect%& parameter.
33563 .vitem &*connect&~=&~*&<&'time&~interval'&>
33564 .cindex "callout" "connection timeout, specifying"
33565 This parameter makes it possible to set a different (usually smaller) timeout
33566 for making the SMTP connection. For example:
33568 verify = sender/callout=5s,connect=1s
33570 If not specified, this timeout defaults to the general timeout value.
33572 .vitem &*defer_ok*&
33573 .cindex "callout" "defer, action on"
33574 When this parameter is present, failure to contact any host, or any other kind
33575 of temporary error, is treated as success by the ACL. However, the cache is not
33576 updated in this circumstance.
33578 .vitem &*fullpostmaster*&
33579 .cindex "callout" "full postmaster check"
33580 This operates like the &%postmaster%& option (see below), but if the check for
33581 &'postmaster@domain'& fails, it tries just &'postmaster'&, without a domain, in
33582 accordance with the specification in RFC 2821. The RFC states that the
33583 unqualified address &'postmaster'& should be accepted.
33586 .vitem &*mailfrom&~=&~*&<&'email&~address'&>
33587 .cindex "callout" "sender when verifying header"
33588 When verifying addresses in header lines using the &%header_sender%&
33589 verification option, Exim behaves by default as if the addresses are envelope
33590 sender addresses from a message. Callout verification therefore tests to see
33591 whether a bounce message could be delivered, by using an empty address in the
33592 MAIL command. However, it is arguable that these addresses might never be used
33593 as envelope senders, and could therefore justifiably reject bounce messages
33594 (empty senders). The &%mailfrom%& callout parameter allows you to specify what
33595 address to use in the MAIL command. For example:
33597 require verify = header_sender/callout=mailfrom=abcd@x.y.z
33599 This parameter is available only for the &%header_sender%& verification option.
33602 .vitem &*maxwait&~=&~*&<&'time&~interval'&>
33603 .cindex "callout" "overall timeout, specifying"
33604 This parameter sets an overall timeout for performing a callout verification.
33607 verify = sender/callout=5s,maxwait=30s
33609 This timeout defaults to four times the callout timeout for individual SMTP
33610 commands. The overall timeout applies when there is more than one host that can
33611 be tried. The timeout is checked before trying the next host. This prevents
33612 very long delays if there are a large number of hosts and all are timing out
33613 (for example, when network connections are timing out).
33616 .vitem &*no_cache*&
33617 .cindex "callout" "cache, suppressing"
33618 .cindex "caching callout, suppressing"
33619 When this parameter is given, the callout cache is neither read nor updated.
33621 .vitem &*postmaster*&
33622 .cindex "callout" "postmaster; checking"
33623 When this parameter is set, a successful callout check is followed by a similar
33624 check for the local part &'postmaster'& at the same domain. If this address is
33625 rejected, the callout fails (but see &%fullpostmaster%& above). The result of
33626 the postmaster check is recorded in a cache record; if it is a failure, this is
33627 used to fail subsequent callouts for the domain without a connection being
33628 made, until the cache record expires.
33630 .vitem &*postmaster_mailfrom&~=&~*&<&'email&~address'&>
33631 The postmaster check uses an empty sender in the MAIL command by default.
33632 You can use this parameter to do a postmaster check using a different address.
33635 require verify = sender/callout=postmaster_mailfrom=abc@x.y.z
33637 If both &%postmaster%& and &%postmaster_mailfrom%& are present, the rightmost
33638 one overrides. The &%postmaster%& parameter is equivalent to this example:
33640 require verify = sender/callout=postmaster_mailfrom=
33642 &*Warning*&: The caching arrangements for postmaster checking do not take
33643 account of the sender address. It is assumed that either the empty address or
33644 a fixed non-empty address will be used. All that Exim remembers is that the
33645 postmaster check for the domain succeeded or failed.
33649 .cindex "callout" "&""random""& check"
33650 When this parameter is set, before doing the normal callout check, Exim does a
33651 check for a &"random"& local part at the same domain. The local part is not
33652 really random &-- it is defined by the expansion of the option
33653 &%callout_random_local_part%&, which defaults to
33655 $primary_hostname-$tod_epoch-testing
33657 The idea here is to try to determine whether the remote host accepts all local
33658 parts without checking. If it does, there is no point in doing callouts for
33659 specific local parts. If the &"random"& check succeeds, the result is saved in
33660 a cache record, and used to force the current and subsequent callout checks to
33661 succeed without a connection being made, until the cache record expires.
33663 .vitem &*use_postmaster*&
33664 .cindex "callout" "sender for recipient check"
33665 This parameter applies to recipient callouts only. For example:
33667 deny !verify = recipient/callout=use_postmaster
33669 .vindex "&$qualify_domain$&"
33670 It causes a non-empty postmaster address to be used in the MAIL command when
33671 performing the callout for the recipient, and also for a &"random"& check if
33672 that is configured. The local part of the address is &`postmaster`& and the
33673 domain is the contents of &$qualify_domain$&.
33675 .vitem &*use_sender*&
33676 This option applies to recipient callouts only. For example:
33678 require verify = recipient/callout=use_sender
33680 It causes the message's actual sender address to be used in the MAIL
33681 command when performing the callout, instead of an empty address. There is no
33682 need to use this option unless you know that the called hosts make use of the
33683 sender when checking recipients. If used indiscriminately, it reduces the
33684 usefulness of callout caching.
33687 This option applies to recipient callouts only. For example:
33689 require verify = recipient/callout=use_sender,hold
33691 It causes the connection to be held open and used for any further recipients
33692 and for eventual delivery (should that be done quickly).
33693 Doing this saves on TCP and SMTP startup costs, and TLS costs also
33694 when that is used for the connections.
33695 The advantage is only gained if there are no callout cache hits
33696 (which could be enforced by the no_cache option),
33697 if the use_sender option is used,
33698 if neither the random nor the use_postmaster option is used,
33699 and if no other callouts intervene.
33702 If you use any of the parameters that set a non-empty sender for the MAIL
33703 command (&%mailfrom%&, &%postmaster_mailfrom%&, &%use_postmaster%&, or
33704 &%use_sender%&), you should think about possible loops. Recipient checking is
33705 usually done between two hosts that are under the same management, and the host
33706 that receives the callouts is not normally configured to do callouts itself.
33707 Therefore, it is normally safe to use &%use_postmaster%& or &%use_sender%& in
33708 these circumstances.
33710 However, if you use a non-empty sender address for a callout to an arbitrary
33711 host, there is the likelihood that the remote host will itself initiate a
33712 callout check back to your host. As it is checking what appears to be a message
33713 sender, it is likely to use an empty address in MAIL, thus avoiding a
33714 callout loop. However, to be on the safe side it would be best to set up your
33715 own ACLs so that they do not do sender verification checks when the recipient
33716 is the address you use for header sender or postmaster callout checking.
33718 Another issue to think about when using non-empty senders for callouts is
33719 caching. When you set &%mailfrom%& or &%use_sender%&, the cache record is keyed
33720 by the sender/recipient combination; thus, for any given recipient, many more
33721 actual callouts are performed than when an empty sender or postmaster is used.
33726 .section "Callout caching" "SECTcallvercache"
33727 .cindex "hints database" "callout cache"
33728 .cindex "callout" "cache, description of"
33729 .cindex "caching" "callout"
33730 Exim caches the results of callouts in order to reduce the amount of resources
33731 used, unless you specify the &%no_cache%& parameter with the &%callout%&
33732 option. A hints database called &"callout"& is used for the cache. Two
33733 different record types are used: one records the result of a callout check for
33734 a specific address, and the other records information that applies to the
33735 entire domain (for example, that it accepts the local part &'postmaster'&).
33737 When an original callout fails, a detailed SMTP error message is given about
33738 the failure. However, for subsequent failures use the cache data, this message
33741 The expiry times for negative and positive address cache records are
33742 independent, and can be set by the global options &%callout_negative_expire%&
33743 (default 2h) and &%callout_positive_expire%& (default 24h), respectively.
33745 If a host gives a negative response to an SMTP connection, or rejects any
33746 commands up to and including
33750 (but not including the MAIL command with a non-empty address),
33751 any callout attempt is bound to fail. Exim remembers such failures in a
33752 domain cache record, which it uses to fail callouts for the domain without
33753 making new connections, until the domain record times out. There are two
33754 separate expiry times for domain cache records:
33755 &%callout_domain_negative_expire%& (default 3h) and
33756 &%callout_domain_positive_expire%& (default 7d).
33758 Domain records expire when the negative expiry time is reached if callouts
33759 cannot be made for the domain, or if the postmaster check failed.
33760 Otherwise, they expire when the positive expiry time is reached. This
33761 ensures that, for example, a host that stops accepting &"random"& local parts
33762 will eventually be noticed.
33764 The callout caching mechanism is based on the domain of the address that is
33765 being tested. If the domain routes to several hosts, it is assumed that their
33766 behaviour will be the same.
33770 .section "Quota caching" "SECTquotacache"
33771 .cindex "hints database" "quota cache"
33772 .cindex "quota" "cache, description of"
33773 .cindex "caching" "quota"
33774 Exim caches the results of quota verification
33775 in order to reduce the amount of resources used.
33776 The &"callout"& hints database is used.
33778 The default cache periods are five minutes for a positive (good) result
33779 and one hour for a negative result.
33780 To change the periods the &%quota%& option can be followed by an equals sign
33781 and a number of optional paramemters, separated by commas.
33784 verify = recipient/quota=cachepos=1h,cacheneg=1d
33786 Possible parameters are:
33788 .vitem &*cachepos&~=&~*&<&'time&~interval'&>
33789 .cindex "quota cache" "positive entry expiry, specifying"
33790 Set the lifetime for a positive cache entry.
33791 A value of zero seconds is legitimate.
33793 .vitem &*cacheneg&~=&~*&<&'time&~interval'&>
33794 .cindex "quota cache" "negative entry expiry, specifying"
33795 As above, for a negative entry.
33797 .vitem &*no_cache*&
33798 Set both positive and negative lifetimes to zero.
33800 .section "Sender address verification reporting" "SECTsenaddver"
33801 .cindex "verifying" "suppressing error details"
33802 See section &<<SECTaddressverification>>& for a general discussion of
33803 verification. When sender verification fails in an ACL, the details of the
33804 failure are given as additional output lines before the 550 response to the
33805 relevant SMTP command (RCPT or DATA). For example, if sender callout is in use,
33808 MAIL FROM:<xyz@abc.example>
33810 RCPT TO:<pqr@def.example>
33811 550-Verification failed for <xyz@abc.example>
33812 550-Called: 192.168.34.43
33813 550-Sent: RCPT TO:<xyz@abc.example>
33814 550-Response: 550 Unknown local part xyz in <xyz@abc.example>
33815 550 Sender verification failed
33817 If more than one RCPT command fails in the same way, the details are given
33818 only for the first of them. However, some administrators do not want to send
33819 out this much information. You can suppress the details by adding
33820 &`/no_details`& to the ACL statement that requests sender verification. For
33823 verify = sender/no_details
33826 .section "Redirection while verifying" "SECTredirwhilveri"
33827 .cindex "verifying" "redirection while"
33828 .cindex "address redirection" "while verifying"
33829 A dilemma arises when a local address is redirected by aliasing or forwarding
33830 during verification: should the generated addresses themselves be verified,
33831 or should the successful expansion of the original address be enough to verify
33832 it? By default, Exim takes the following pragmatic approach:
33835 When an incoming address is redirected to just one child address, verification
33836 continues with the child address, and if that fails to verify, the original
33837 verification also fails.
33839 When an incoming address is redirected to more than one child address,
33840 verification does not continue. A success result is returned.
33843 This seems the most reasonable behaviour for the common use of aliasing as a
33844 way of redirecting different local parts to the same mailbox. It means, for
33845 example, that a pair of alias entries of the form
33848 aw123: :fail: Gone away, no forwarding address
33850 work as expected, with both local parts causing verification failure. When a
33851 redirection generates more than one address, the behaviour is more like a
33852 mailing list, where the existence of the alias itself is sufficient for
33853 verification to succeed.
33855 It is possible, however, to change the default behaviour so that all successful
33856 redirections count as successful verifications, however many new addresses are
33857 generated. This is specified by the &%success_on_redirect%& verification
33858 option. For example:
33860 require verify = recipient/success_on_redirect/callout=10s
33862 In this example, verification succeeds if a router generates a new address, and
33863 the callout does not occur, because no address was routed to a remote host.
33865 When verification is being tested via the &%-bv%& option, the treatment of
33866 redirections is as just described, unless the &%-v%& or any debugging option is
33867 also specified. In that case, full verification is done for every generated
33868 address and a report is output for each of them.
33872 .section "Client SMTP authorization (CSA)" "SECTverifyCSA"
33873 .cindex "CSA" "verifying"
33874 Client SMTP Authorization is a system that allows a site to advertise
33875 which machines are and are not permitted to send email. This is done by placing
33876 special SRV records in the DNS; these are looked up using the client's HELO
33877 domain. At the time of writing, CSA is still an Internet Draft. Client SMTP
33878 Authorization checks in Exim are performed by the ACL condition:
33882 This fails if the client is not authorized. If there is a DNS problem, or if no
33883 valid CSA SRV record is found, or if the client is authorized, the condition
33884 succeeds. These three cases can be distinguished using the expansion variable
33885 &$csa_status$&, which can take one of the values &"fail"&, &"defer"&,
33886 &"unknown"&, or &"ok"&. The condition does not itself defer because that would
33887 be likely to cause problems for legitimate email.
33889 The error messages produced by the CSA code include slightly more
33890 detail. If &$csa_status$& is &"defer"&, this may be because of problems
33891 looking up the CSA SRV record, or problems looking up the CSA target
33892 address record. There are four reasons for &$csa_status$& being &"fail"&:
33895 The client's host name is explicitly not authorized.
33897 The client's IP address does not match any of the CSA target IP addresses.
33899 The client's host name is authorized but it has no valid target IP addresses
33900 (for example, the target's addresses are IPv6 and the client is using IPv4).
33902 The client's host name has no CSA SRV record but a parent domain has asserted
33903 that all subdomains must be explicitly authorized.
33906 The &%csa%& verification condition can take an argument which is the domain to
33907 use for the DNS query. The default is:
33909 verify = csa/$sender_helo_name
33911 This implementation includes an extension to CSA. If the query domain
33912 is an address literal such as [192.0.2.95], or if it is a bare IP
33913 address, Exim searches for CSA SRV records in the reverse DNS as if
33914 the HELO domain was (for example) &'95.2.0.192.in-addr.arpa'&. Therefore it is
33917 verify = csa/$sender_host_address
33919 In fact, this is the check that Exim performs if the client does not say HELO.
33920 This extension can be turned off by setting the main configuration option
33921 &%dns_csa_use_reverse%& to be false.
33923 If a CSA SRV record is not found for the domain itself, a search
33924 is performed through its parent domains for a record which might be
33925 making assertions about subdomains. The maximum depth of this search is limited
33926 using the main configuration option &%dns_csa_search_limit%&, which is 5 by
33927 default. Exim does not look for CSA SRV records in a top level domain, so the
33928 default settings handle HELO domains as long as seven
33929 (&'hostname.five.four.three.two.one.com'&). This encompasses the vast majority
33930 of legitimate HELO domains.
33932 The &'dnsdb'& lookup also has support for CSA. Although &'dnsdb'& also supports
33933 direct SRV lookups, this is not sufficient because of the extra parent domain
33934 search behaviour of CSA, and (as with PTR lookups) &'dnsdb'& also turns IP
33935 addresses into lookups in the reverse DNS space. The result of a successful
33938 ${lookup dnsdb {csa=$sender_helo_name}}
33940 has two space-separated fields: an authorization code and a target host name.
33941 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
33942 authorization required but absent, or &"?"& for unknown.
33947 .section "Bounce address tag validation" "SECTverifyPRVS"
33948 .cindex "BATV, verifying"
33949 Bounce address tag validation (BATV) is a scheme whereby the envelope senders
33950 of outgoing messages have a cryptographic, timestamped &"tag"& added to them.
33951 Genuine incoming bounce messages should therefore always be addressed to
33952 recipients that have a valid tag. This scheme is a way of detecting unwanted
33953 bounce messages caused by sender address forgeries (often called &"collateral
33954 spam"&), because the recipients of such messages do not include valid tags.
33956 There are two expansion items to help with the implementation of the BATV
33957 &"prvs"& (private signature) scheme in an Exim configuration. This scheme signs
33958 the original envelope sender address by using a simple key to add a hash of the
33959 address and some time-based randomizing information. The &%prvs%& expansion
33960 item creates a signed address, and the &%prvscheck%& expansion item checks one.
33961 The syntax of these expansion items is described in section
33962 &<<SECTexpansionitems>>&.
33963 The validity period on signed addresses is seven days.
33965 As an example, suppose the secret per-address keys are stored in an MySQL
33966 database. A query to look up the key for an address could be defined as a macro
33969 PRVSCHECK_SQL = ${lookup mysql{SELECT secret FROM batv_prvs \
33970 WHERE sender='${quote_mysql:$prvscheck_address}'\
33973 Suppose also that the senders who make use of BATV are defined by an address
33974 list called &%batv_senders%&. Then, in the ACL for RCPT commands, you could
33977 # Bounces: drop unsigned addresses for BATV senders
33979 recipients = +batv_senders
33980 message = This address does not send an unsigned reverse path
33982 # Bounces: In case of prvs-signed address, check signature.
33984 condition = ${prvscheck {$local_part@$domain}\
33985 {PRVSCHECK_SQL}{1}}
33986 !condition = $prvscheck_result
33987 message = Invalid reverse path signature.
33989 The first statement rejects recipients for bounce messages that are addressed
33990 to plain BATV sender addresses, because it is known that BATV senders do not
33991 send out messages with plain sender addresses. The second statement rejects
33992 recipients that are prvs-signed, but with invalid signatures (either because
33993 the key is wrong, or the signature has timed out).
33995 A non-prvs-signed address is not rejected by the second statement, because the
33996 &%prvscheck%& expansion yields an empty string if its first argument is not a
33997 prvs-signed address, thus causing the &%condition%& condition to be false. If
33998 the first argument is a syntactically valid prvs-signed address, the yield is
33999 the third string (in this case &"1"&), whether or not the cryptographic and
34000 timeout checks succeed. The &$prvscheck_result$& variable contains the result
34001 of the checks (empty for failure, &"1"& for success).
34003 There is one more issue you must consider when implementing prvs-signing:
34004 you have to ensure that the routers accept prvs-signed addresses and
34005 deliver them correctly. The easiest way to handle this is to use a &(redirect)&
34006 router to remove the signature with a configuration along these lines:
34010 data = ${prvscheck {$local_part@$domain}{PRVSCHECK_SQL}}
34012 This works because, if the third argument of &%prvscheck%& is empty, the result
34013 of the expansion of a prvs-signed address is the decoded value of the original
34014 address. This router should probably be the first of your routers that handles
34017 To create BATV-signed addresses in the first place, a transport of this form
34020 external_smtp_batv:
34022 return_path = ${prvs {$return_path} \
34023 {${lookup mysql{SELECT \
34024 secret FROM batv_prvs WHERE \
34025 sender='${quote_mysql:$sender_address}'} \
34028 If no key can be found for the existing return path, no signing takes place.
34032 .section "Using an ACL to control relaying" "SECTrelaycontrol"
34033 .cindex "&ACL;" "relay control"
34034 .cindex "relaying" "control by ACL"
34035 .cindex "policy control" "relay control"
34036 An MTA is said to &'relay'& a message if it receives it from some host and
34037 delivers it directly to another host as a result of a remote address contained
34038 within it. Redirecting a local address via an alias or forward file and then
34039 passing the message on to another host is not relaying,
34040 .cindex "&""percent hack""&"
34041 but a redirection as a result of the &"percent hack"& is.
34043 Two kinds of relaying exist, which are termed &"incoming"& and &"outgoing"&.
34044 A host which is acting as a gateway or an MX backup is concerned with incoming
34045 relaying from arbitrary hosts to a specific set of domains. On the other hand,
34046 a host which is acting as a smart host for a number of clients is concerned
34047 with outgoing relaying from those clients to the Internet at large. Often the
34048 same host is fulfilling both functions,
34050 . as illustrated in the diagram below,
34052 but in principle these two kinds of relaying are entirely independent. What is
34053 not wanted is the transmission of mail from arbitrary remote hosts through your
34054 system to arbitrary domains.
34057 You can implement relay control by means of suitable statements in the ACL that
34058 runs for each RCPT command. For convenience, it is often easiest to use
34059 Exim's named list facility to define the domains and hosts involved. For
34060 example, suppose you want to do the following:
34063 Deliver a number of domains to mailboxes on the local host (or process them
34064 locally in some other way). Let's say these are &'my.dom1.example'& and
34065 &'my.dom2.example'&.
34067 Relay mail for a number of other domains for which you are the secondary MX.
34068 These might be &'friend1.example'& and &'friend2.example'&.
34070 Relay mail from the hosts on your local LAN, to whatever domains are involved.
34071 Suppose your LAN is 192.168.45.0/24.
34075 In the main part of the configuration, you put the following definitions:
34077 domainlist local_domains = my.dom1.example : my.dom2.example
34078 domainlist relay_to_domains = friend1.example : friend2.example
34079 hostlist relay_from_hosts = 192.168.45.0/24
34081 Now you can use these definitions in the ACL that is run for every RCPT
34085 accept domains = +local_domains : +relay_to_domains
34086 accept hosts = +relay_from_hosts
34088 The first statement accepts any RCPT command that contains an address in
34089 the local or relay domains. For any other domain, control passes to the second
34090 statement, which accepts the command only if it comes from one of the relay
34091 hosts. In practice, you will probably want to make your ACL more sophisticated
34092 than this, for example, by including sender and recipient verification. The
34093 default configuration includes a more comprehensive example, which is described
34094 in chapter &<<CHAPdefconfil>>&.
34098 .section "Checking a relay configuration" "SECTcheralcon"
34099 .cindex "relaying" "checking control of"
34100 You can check the relay characteristics of your configuration in the same way
34101 that you can test any ACL behaviour for an incoming SMTP connection, by using
34102 the &%-bh%& option to run a fake SMTP session with which you interact.
34107 . ////////////////////////////////////////////////////////////////////////////
34108 . ////////////////////////////////////////////////////////////////////////////
34110 .chapter "Content scanning at ACL time" "CHAPexiscan"
34111 .scindex IIDcosca "content scanning" "at ACL time"
34112 The extension of Exim to include content scanning at ACL time, formerly known
34113 as &"exiscan"&, was originally implemented as a patch by Tom Kistner. The code
34114 was integrated into the main source for Exim release 4.50, and Tom continues to
34115 maintain it. Most of the wording of this chapter is taken from Tom's
34118 It is also possible to scan the content of messages at other times. The
34119 &[local_scan()]& function (see chapter &<<CHAPlocalscan>>&) allows for content
34120 scanning after all the ACLs have run. A transport filter can be used to scan
34121 messages at delivery time (see the &%transport_filter%& option, described in
34122 chapter &<<CHAPtransportgeneric>>&).
34124 If you want to include the ACL-time content-scanning features when you compile
34125 Exim, you need to arrange for WITH_CONTENT_SCAN to be defined in your
34126 &_Local/Makefile_&. When you do that, the Exim binary is built with:
34129 Two additional ACLs (&%acl_smtp_mime%& and &%acl_not_smtp_mime%&) that are run
34130 for all MIME parts for SMTP and non-SMTP messages, respectively.
34132 Additional ACL conditions and modifiers: &%decode%&, &%malware%&,
34133 &%mime_regex%&, &%regex%&, and &%spam%&. These can be used in the ACL that is
34134 run at the end of message reception (the &%acl_smtp_data%& ACL).
34136 An additional control feature (&"no_mbox_unspool"&) that saves spooled copies
34137 of messages, or parts of messages, for debugging purposes.
34139 Additional expansion variables that are set in the new ACL and by the new
34142 Two new main configuration options: &%av_scanner%& and &%spamd_address%&.
34145 Content-scanning is continually evolving, and new features are still being
34146 added. While such features are still unstable and liable to incompatible
34147 changes, they are made available in Exim by setting options whose names begin
34148 EXPERIMENTAL_ in &_Local/Makefile_&. Such features are not documented in
34149 this manual. You can find out about them by reading the file called
34150 &_doc/experimental.txt_&.
34152 All the content-scanning facilities work on a MBOX copy of the message that is
34153 temporarily created in a file called:
34155 <&'spool_directory'&>&`/scan/`&<&'message_id'&>/<&'message_id'&>&`.eml`&
34157 The &_.eml_& extension is a friendly hint to virus scanners that they can
34158 expect an MBOX-like structure inside that file. The file is created when the
34159 first content scanning facility is called. Subsequent calls to content
34160 scanning conditions open the same file again. The directory is recursively
34161 removed when the &%acl_smtp_data%& ACL has finished running, unless
34163 control = no_mbox_unspool
34165 has been encountered. When the MIME ACL decodes files, they are put into the
34166 same directory by default.
34170 .section "Scanning for viruses" "SECTscanvirus"
34171 .cindex "virus scanning"
34172 .cindex "content scanning" "for viruses"
34173 .cindex "content scanning" "the &%malware%& condition"
34174 The &%malware%& ACL condition lets you connect virus scanner software to Exim.
34175 It supports a &"generic"& interface to scanners called via the shell, and
34176 specialized interfaces for &"daemon"& type virus scanners, which are resident
34177 in memory and thus are much faster.
34179 Since message data needs to have arrived,
34180 the condition may be only called in ACL defined by
34182 &%acl_smtp_data_prdr%&,
34183 &%acl_smtp_mime%& or
34186 A timeout of 2 minutes is applied to a scanner call (by default);
34187 if it expires then a defer action is taken.
34189 .oindex "&%av_scanner%&"
34190 You can set the &%av_scanner%& option in the main part of the configuration
34191 to specify which scanner to use, together with any additional options that
34192 are needed. The basic syntax is as follows:
34194 &`av_scanner = <`&&'scanner-type'&&`>:<`&&'option1'&&`>:<`&&'option2'&&`>:[...]`&
34196 If you do not set &%av_scanner%&, it defaults to
34198 av_scanner = sophie:/var/run/sophie
34200 If the value of &%av_scanner%& starts with a dollar character, it is expanded
34202 The usual list-parsing of the content (see &<<SECTlistconstruct>>&) applies.
34203 The following scanner types are supported in this release,
34204 though individual ones can be included or not at build time:
34208 .cindex "virus scanners" "avast"
34209 This is the scanner daemon of Avast. It has been tested with Avast Core
34210 Security (currently at version 2.2.0).
34211 You can get a trial version at &url(https://www.avast.com) or for Linux
34212 at &url(https://www.avast.com/linux-server-antivirus).
34213 This scanner type takes one option,
34214 which can be either a full path to a UNIX socket,
34215 or host and port specifiers separated by white space.
34216 The host may be a name or an IP address; the port is either a
34217 single number or a pair of numbers with a dash between.
34218 A list of options may follow. These options are interpreted on the
34219 Exim's side of the malware scanner, or are given on separate lines to
34220 the daemon as options before the main scan command.
34222 .cindex &`pass_unscanned`& "avast"
34223 If &`pass_unscanned`&
34224 is set, any files the Avast scanner can't scan (e.g.
34225 decompression bombs, or invalid archives) are considered clean. Use with
34230 av_scanner = avast:/var/run/avast/scan.sock:FLAGS -fullfiles:SENSITIVITY -pup
34231 av_scanner = avast:/var/run/avast/scan.sock:pass_unscanned:FLAGS -fullfiles:SENSITIVITY -pup
34232 av_scanner = avast:192.168.2.22 5036
34234 If you omit the argument, the default path
34235 &_/var/run/avast/scan.sock_&
34237 If you use a remote host,
34238 you need to make Exim's spool directory available to it,
34239 as the scanner is passed a file path, not file contents.
34240 For information about available commands and their options you may use
34242 $ socat UNIX:/var/run/avast/scan.sock STDIO:
34248 If the scanner returns a temporary failure (e.g. license issues, or
34249 permission problems), the message is deferred and a paniclog entry is
34250 written. The usual &`defer_ok`& option is available.
34252 .vitem &%aveserver%&
34253 .cindex "virus scanners" "Kaspersky"
34254 This is the scanner daemon of Kaspersky Version 5. You can get a trial version
34255 at &url(https://www.kaspersky.com/). This scanner type takes one option,
34256 which is the path to the daemon's UNIX socket. The default is shown in this
34259 av_scanner = aveserver:/var/run/aveserver
34264 .cindex "virus scanners" "clamd"
34265 This daemon-type scanner is GPL and free. You can get it at
34266 &url(https://www.clamav.net/). Some older versions of clamd do not seem to
34267 unpack MIME containers, so it used to be recommended to unpack MIME attachments
34268 in the MIME ACL. This is no longer believed to be necessary.
34270 The options are a list of server specifiers, which may be
34271 a UNIX socket specification,
34272 a TCP socket specification,
34273 or a (global) option.
34275 A socket specification consists of a space-separated list.
34276 For a Unix socket the first element is a full path for the socket,
34277 for a TCP socket the first element is the IP address
34278 and the second a port number,
34279 Any further elements are per-server (non-global) options.
34280 These per-server options are supported:
34282 retry=<timespec> Retry on connect fail
34285 The &`retry`& option specifies a time after which a single retry for
34286 a failed connect is made. The default is to not retry.
34288 If a Unix socket file is specified, only one server is supported.
34292 av_scanner = clamd:/opt/clamd/socket
34293 av_scanner = clamd:192.0.2.3 1234
34294 av_scanner = clamd:192.0.2.3 1234:local
34295 av_scanner = clamd:192.0.2.3 1234 retry=10s
34296 av_scanner = clamd:192.0.2.3 1234 : 192.0.2.4 1234
34298 If the value of av_scanner points to a UNIX socket file or contains the
34300 option, then the ClamAV interface will pass a filename containing the data
34301 to be scanned, which should normally result in less I/O happening and be
34302 more efficient. Normally in the TCP case, the data is streamed to ClamAV as
34303 Exim does not assume that there is a common filesystem with the remote host.
34305 The final example shows that multiple TCP targets can be specified. Exim will
34306 randomly use one for each incoming email (i.e. it load balances them). Note
34307 that only TCP targets may be used if specifying a list of scanners; a UNIX
34308 socket cannot be mixed in with TCP targets. If one of the servers becomes
34309 unavailable, Exim will try the remaining one(s) until it finds one that works.
34310 When a clamd server becomes unreachable, Exim will log a message. Exim does
34311 not keep track of scanner state between multiple messages, and the scanner
34312 selection is random, so the message will get logged in the mainlog for each
34313 email that the down scanner gets chosen first (message wrapped to be readable):
34315 2013-10-09 14:30:39 1VTumd-0000Y8-BQ malware acl condition:
34316 clamd: connection to localhost, port 3310 failed
34317 (Connection refused)
34320 If the option is unset, the default is &_/tmp/clamd_&. Thanks to David Saez for
34321 contributing the code for this scanner.
34324 .cindex "virus scanners" "command line interface"
34325 This is the keyword for the generic command line scanner interface. It can be
34326 used to attach virus scanners that are invoked from the shell. This scanner
34327 type takes 3 mandatory options:
34330 The full path and name of the scanner binary, with all command line options,
34331 and a placeholder (&`%s`&) for the directory to scan.
34334 A regular expression to match against the STDOUT and STDERR output of the
34335 virus scanner. If the expression matches, a virus was found. You must make
34336 absolutely sure that this expression matches on &"virus found"&. This is called
34337 the &"trigger"& expression.
34340 Another regular expression, containing exactly one pair of parentheses, to
34341 match the name of the virus found in the scanners output. This is called the
34342 &"name"& expression.
34345 For example, Sophos Sweep reports a virus on a line like this:
34347 Virus 'W32/Magistr-B' found in file ./those.bat
34349 For the trigger expression, we can match the phrase &"found in file"&. For the
34350 name expression, we want to extract the W32/Magistr-B string, so we can match
34351 for the single quotes left and right of it. Altogether, this makes the
34352 configuration setting:
34354 av_scanner = cmdline:\
34355 /path/to/sweep -ss -all -rec -archive %s:\
34356 found in file:'(.+)'
34359 .cindex "virus scanners" "DrWeb"
34360 The DrWeb daemon scanner (&url(https://www.sald.ru/)) interface
34362 either a full path to a UNIX socket,
34363 or host and port specifiers separated by white space.
34364 The host may be a name or an IP address; the port is either a
34365 single number or a pair of numbers with a dash between.
34368 av_scanner = drweb:/var/run/drwebd.sock
34369 av_scanner = drweb:192.168.2.20 31337
34371 If you omit the argument, the default path &_/usr/local/drweb/run/drwebd.sock_&
34372 is used. Thanks to Alex Miller for contributing the code for this scanner.
34375 .cindex "virus scanners" "f-protd"
34376 The f-protd scanner is accessed via HTTP over TCP.
34377 One argument is taken, being a space-separated hostname and port number
34381 av_scanner = f-protd:localhost 10200-10204
34383 If you omit the argument, the default values shown above are used.
34385 .vitem &%f-prot6d%&
34386 .cindex "virus scanners" "f-prot6d"
34387 The f-prot6d scanner is accessed using the FPSCAND protocol over TCP.
34388 One argument is taken, being a space-separated hostname and port number.
34391 av_scanner = f-prot6d:localhost 10200
34393 If you omit the argument, the default values show above are used.
34396 .cindex "virus scanners" "F-Secure"
34397 The F-Secure daemon scanner (&url(https://www.f-secure.com/)) takes one
34398 argument which is the path to a UNIX socket. For example:
34400 av_scanner = fsecure:/path/to/.fsav
34402 If no argument is given, the default is &_/var/run/.fsav_&. Thanks to Johan
34403 Thelmen for contributing the code for this scanner.
34405 .vitem &%kavdaemon%&
34406 .cindex "virus scanners" "Kaspersky"
34407 This is the scanner daemon of Kaspersky Version 4. This version of the
34408 Kaspersky scanner is outdated. Please upgrade (see &%aveserver%& above). This
34409 scanner type takes one option, which is the path to the daemon's UNIX socket.
34412 av_scanner = kavdaemon:/opt/AVP/AvpCtl
34414 The default path is &_/var/run/AvpCtl_&.
34417 .cindex "virus scanners" "mksd"
34418 This was a daemon type scanner that is aimed mainly at Polish users,
34419 though some documentation was available in English.
34420 The history can be shown at &url(https://en.wikipedia.org/wiki/Mks_vir)
34421 and this appears to be a candidate for removal from Exim, unless
34422 we are informed of other virus scanners which use the same protocol
34424 The only option for this scanner type is
34425 the maximum number of processes used simultaneously to scan the attachments,
34426 provided that mksd has
34427 been run with at least the same number of child processes. For example:
34429 av_scanner = mksd:2
34431 You can safely omit this option (the default value is 1).
34434 .cindex "virus scanners" "simple socket-connected"
34435 This is a general-purpose way of talking to simple scanner daemons
34436 running on the local machine.
34437 There are four options:
34438 an address (which may be an IP address and port, or the path of a Unix socket),
34439 a commandline to send (may include a single %s which will be replaced with
34440 the path to the mail file to be scanned),
34441 an RE to trigger on from the returned data,
34442 and an RE to extract malware_name from the returned data.
34445 av_scanner = sock:127.0.0.1 6001:%s:(SPAM|VIRUS):(.*)$
34447 Note that surrounding whitespace is stripped from each option, meaning
34448 there is no way to specify a trailing newline.
34449 The socket specifier and both regular-expressions are required.
34450 Default for the commandline is &_%s\n_& (note this does have a trailing newline);
34451 specify an empty element to get this.
34454 .cindex "virus scanners" "Sophos and Sophie"
34455 Sophie is a daemon that uses Sophos' &%libsavi%& library to scan for viruses.
34456 You can get Sophie at &url(http://sophie.sourceforge.net/). The only option
34457 for this scanner type is the path to the UNIX socket that Sophie uses for
34458 client communication. For example:
34460 av_scanner = sophie:/tmp/sophie
34462 The default path is &_/var/run/sophie_&, so if you are using this, you can omit
34466 When &%av_scanner%& is correctly set, you can use the &%malware%& condition in
34467 the DATA ACL. &*Note*&: You cannot use the &%malware%& condition in the MIME
34470 The &%av_scanner%& option is expanded each time &%malware%& is called. This
34471 makes it possible to use different scanners. See further below for an example.
34472 The &%malware%& condition caches its results, so when you use it multiple times
34473 for the same message, the actual scanning process is only carried out once.
34474 However, using expandable items in &%av_scanner%& disables this caching, in
34475 which case each use of the &%malware%& condition causes a new scan of the
34478 The &%malware%& condition takes a right-hand argument that is expanded before
34479 use and taken as a list, slash-separated by default.
34480 The first element can then be one of
34483 &"true"&, &"*"&, or &"1"&, in which case the message is scanned for viruses.
34484 The condition succeeds if a virus was found, and fail otherwise. This is the
34487 &"false"& or &"0"& or an empty string, in which case no scanning is done and
34488 the condition fails immediately.
34490 A regular expression, in which case the message is scanned for viruses. The
34491 condition succeeds if a virus is found and its name matches the regular
34492 expression. This allows you to take special actions on certain types of virus.
34493 Note that &"/"& characters in the RE must be doubled due to the list-processing,
34494 unless the separator is changed (in the usual way &<<SECTlistsepchange>>&).
34497 You can append a &`defer_ok`& element to the &%malware%& argument list to accept
34498 messages even if there is a problem with the virus scanner.
34499 Otherwise, such a problem causes the ACL to defer.
34501 You can append a &`tmo=<val>`& element to the &%malware%& argument list to
34502 specify a non-default timeout. The default is two minutes.
34505 malware = * / defer_ok / tmo=10s
34507 A timeout causes the ACL to defer.
34509 .vindex "&$callout_address$&"
34510 When a connection is made to the scanner the expansion variable &$callout_address$&
34511 is set to record the actual address used.
34513 .vindex "&$malware_name$&"
34514 When a virus is found, the condition sets up an expansion variable called
34515 &$malware_name$& that contains the name of the virus. You can use it in a
34516 &%message%& modifier that specifies the error returned to the sender, and/or in
34519 Beware the interaction of Exim's &%message_size_limit%& with any size limits
34520 imposed by your anti-virus scanner.
34522 Here is a very simple scanning example:
34525 message = This message contains malware ($malware_name)
34527 The next example accepts messages when there is a problem with the scanner:
34529 deny malware = */defer_ok
34530 message = This message contains malware ($malware_name)
34532 The next example shows how to use an ACL variable to scan with both sophie and
34533 aveserver. It assumes you have set:
34535 av_scanner = $acl_m0
34537 in the main Exim configuration.
34539 deny set acl_m0 = sophie
34541 message = This message contains malware ($malware_name)
34543 deny set acl_m0 = aveserver
34545 message = This message contains malware ($malware_name)
34549 .section "Scanning with SpamAssassin and Rspamd" "SECTscanspamass"
34550 .cindex "content scanning" "for spam"
34551 .cindex "spam scanning"
34552 .cindex "SpamAssassin"
34554 The &%spam%& ACL condition calls SpamAssassin's &%spamd%& daemon to get a spam
34555 score and a report for the message.
34556 Support is also provided for Rspamd.
34558 For more information about installation and configuration of SpamAssassin or
34559 Rspamd refer to their respective websites at
34560 &url(https://spamassassin.apache.org/) and &url(https://www.rspamd.com/)
34562 SpamAssassin can be installed with CPAN by running:
34564 perl -MCPAN -e 'install Mail::SpamAssassin'
34566 SpamAssassin has its own set of configuration files. Please review its
34567 documentation to see how you can tweak it. The default installation should work
34570 .oindex "&%spamd_address%&"
34571 By default, SpamAssassin listens on 127.0.0.1, TCP port 783 and if you
34572 intend to use an instance running on the local host you do not need to set
34573 &%spamd_address%&. If you intend to use another host or port for SpamAssassin,
34574 you must set the &%spamd_address%& option in the global part of the Exim
34575 configuration as follows (example):
34577 spamd_address = 192.168.99.45 783
34579 The SpamAssassin protocol relies on a TCP half-close from the client.
34580 If your SpamAssassin client side is running a Linux system with an
34581 iptables firewall, consider setting
34582 &%net.netfilter.nf_conntrack_tcp_timeout_close_wait%& to at least the
34583 timeout, Exim uses when waiting for a response from the SpamAssassin
34584 server (currently defaulting to 120s). With a lower value the Linux
34585 connection tracking may consider your half-closed connection as dead too
34589 To use Rspamd (which by default listens on all local addresses
34591 you should add &%variant=rspamd%& after the address/port pair, for example:
34593 spamd_address = 127.0.0.1 11333 variant=rspamd
34596 As of version 2.60, &%SpamAssassin%& also supports communication over UNIX
34597 sockets. If you want to us these, supply &%spamd_address%& with an absolute
34598 filename instead of an address/port pair:
34600 spamd_address = /var/run/spamd_socket
34602 You can have multiple &%spamd%& servers to improve scalability. These can
34603 reside on other hardware reachable over the network. To specify multiple
34604 &%spamd%& servers, put multiple address/port pairs in the &%spamd_address%&
34605 option, separated with colons (the separator can be changed in the usual way &<<SECTlistsepchange>>&):
34607 spamd_address = 192.168.2.10 783 : \
34608 192.168.2.11 783 : \
34611 Up to 32 &%spamd%& servers are supported.
34612 When a server fails to respond to the connection attempt, all other
34613 servers are tried until one succeeds. If no server responds, the &%spam%&
34616 Unix and TCP socket specifications may be mixed in any order.
34617 Each element of the list is a list itself, space-separated by default
34618 and changeable in the usual way (&<<SECTlistsepchange>>&);
34619 take care to not double the separator.
34621 For TCP socket specifications a host name or IP (v4 or v6, but
34622 subject to list-separator quoting rules) address can be used,
34623 and the port can be one or a dash-separated pair.
34624 In the latter case, the range is tried in strict order.
34626 Elements after the first for Unix sockets, or second for TCP socket,
34628 The supported options are:
34630 pri=<priority> Selection priority
34631 weight=<value> Selection bias
34632 time=<start>-<end> Use only between these times of day
34633 retry=<timespec> Retry on connect fail
34634 tmo=<timespec> Connection time limit
34635 variant=rspamd Use Rspamd rather than SpamAssassin protocol
34638 The &`pri`& option specifies a priority for the server within the list,
34639 higher values being tried first.
34640 The default priority is 1.
34642 The &`weight`& option specifies a selection bias.
34643 Within a priority set
34644 servers are queried in a random fashion, weighted by this value.
34645 The default value for selection bias is 1.
34647 Time specifications for the &`time`& option are <hour>.<minute>.<second>
34648 in the local time zone; each element being one or more digits.
34649 Either the seconds or both minutes and seconds, plus the leading &`.`&
34650 characters, may be omitted and will be taken as zero.
34652 Timeout specifications for the &`retry`& and &`tmo`& options
34653 are the usual Exim time interval standard, e.g. &`20s`& or &`1m`&.
34655 The &`tmo`& option specifies an overall timeout for communication.
34656 The default value is two minutes.
34658 The &`retry`& option specifies a time after which a single retry for
34659 a failed connect is made.
34660 The default is to not retry.
34662 The &%spamd_address%& variable is expanded before use if it starts with
34663 a dollar sign. In this case, the expansion may return a string that is
34664 used as the list so that multiple spamd servers can be the result of an
34667 .vindex "&$callout_address$&"
34668 When a connection is made to the server the expansion variable &$callout_address$&
34669 is set to record the actual address used.
34671 .section "Calling SpamAssassin from an Exim ACL" "SECID206"
34672 Here is a simple example of the use of the &%spam%& condition in a DATA ACL:
34675 message = This message was classified as SPAM
34677 The right-hand side of the &%spam%& condition specifies a name. This is
34678 relevant if you have set up multiple SpamAssassin profiles. If you do not want
34679 to scan using a specific profile, but rather use the SpamAssassin system-wide
34680 default profile, you can scan for an unknown name, or simply use &"nobody"&.
34681 Rspamd does not use this setting. However, you must put something on the
34684 The name allows you to use per-domain or per-user antispam profiles in
34685 principle, but this is not straightforward in practice, because a message may
34686 have multiple recipients, not necessarily all in the same domain. Because the
34687 &%spam%& condition has to be called from a DATA-time ACL in order to be able to
34688 read the contents of the message, the variables &$local_part$& and &$domain$&
34690 Careful enforcement of single-recipient messages
34691 (e.g. by responding with defer in the recipient ACL for all recipients
34693 or the use of PRDR,
34694 .cindex "PRDR" "use for per-user SpamAssassin profiles"
34695 are needed to use this feature.
34697 The right-hand side of the &%spam%& condition is expanded before being used, so
34698 you can put lookups or conditions there. When the right-hand side evaluates to
34699 &"0"& or &"false"&, no scanning is done and the condition fails immediately.
34702 Scanning with SpamAssassin uses a lot of resources. If you scan every message,
34703 large ones may cause significant performance degradation. As most spam messages
34704 are quite small, it is recommended that you do not scan the big ones. For
34707 deny condition = ${if < {$message_size}{10K}}
34709 message = This message was classified as SPAM
34712 The &%spam%& condition returns true if the threshold specified in the user's
34713 SpamAssassin profile has been matched or exceeded. If you want to use the
34714 &%spam%& condition for its side effects (see the variables below), you can make
34715 it always return &"true"& by appending &`:true`& to the username.
34717 .cindex "spam scanning" "returned variables"
34718 When the &%spam%& condition is run, it sets up a number of expansion
34720 Except for &$spam_report$&,
34721 these variables are saved with the received message so are
34722 available for use at delivery time.
34725 .vitem &$spam_score$&
34726 The spam score of the message, for example, &"3.4"& or &"30.5"&. This is useful
34727 for inclusion in log or reject messages.
34729 .vitem &$spam_score_int$&
34730 The spam score of the message, multiplied by ten, as an integer value. For
34731 example &"34"& or &"305"&. It may appear to disagree with &$spam_score$&
34732 because &$spam_score$& is rounded and &$spam_score_int$& is truncated.
34733 The integer value is useful for numeric comparisons in conditions.
34735 .vitem &$spam_bar$&
34736 A string consisting of a number of &"+"& or &"-"& characters, representing the
34737 integer part of the spam score value. A spam score of 4.4 would have a
34738 &$spam_bar$& value of &"++++"&. This is useful for inclusion in warning
34739 headers, since MUAs can match on such strings. The maximum length of the
34740 spam bar is 50 characters.
34742 .vitem &$spam_report$&
34743 A multiline text table, containing the full SpamAssassin report for the
34744 message. Useful for inclusion in headers or reject messages.
34745 This variable is only usable in a DATA-time ACL.
34746 Beware that SpamAssassin may return non-ASCII characters, especially
34747 when running in country-specific locales, which are not legal
34748 unencoded in headers.
34750 .vitem &$spam_action$&
34751 For SpamAssassin either 'reject' or 'no action' depending on the
34752 spam score versus threshold.
34753 For Rspamd, the recommended action.
34757 The &%spam%& condition caches its results unless expansion in
34758 spamd_address was used. If you call it again with the same user name, it
34759 does not scan again, but rather returns the same values as before.
34761 The &%spam%& condition returns DEFER if there is any error while running
34762 the message through SpamAssassin or if the expansion of spamd_address
34763 failed. If you want to treat DEFER as FAIL (to pass on to the next ACL
34764 statement block), append &`/defer_ok`& to the right-hand side of the
34765 spam condition, like this:
34767 deny spam = joe/defer_ok
34768 message = This message was classified as SPAM
34770 This causes messages to be accepted even if there is a problem with &%spamd%&.
34772 Here is a longer, commented example of the use of the &%spam%&
34775 # put headers in all messages (no matter if spam or not)
34776 warn spam = nobody:true
34777 add_header = X-Spam-Score: $spam_score ($spam_bar)
34778 add_header = X-Spam-Report: $spam_report
34780 # add second subject line with *SPAM* marker when message
34781 # is over threshold
34783 add_header = Subject: *SPAM* $h_Subject:
34785 # reject spam at high scores (> 12)
34786 deny spam = nobody:true
34787 condition = ${if >{$spam_score_int}{120}{1}{0}}
34788 message = This message scored $spam_score spam points.
34793 .section "Scanning MIME parts" "SECTscanmimepart"
34794 .cindex "content scanning" "MIME parts"
34795 .cindex "MIME content scanning"
34796 .oindex "&%acl_smtp_mime%&"
34797 .oindex "&%acl_not_smtp_mime%&"
34798 The &%acl_smtp_mime%& global option specifies an ACL that is called once for
34799 each MIME part of an SMTP message, including multipart types, in the sequence
34800 of their position in the message. Similarly, the &%acl_not_smtp_mime%& option
34801 specifies an ACL that is used for the MIME parts of non-SMTP messages. These
34802 options may both refer to the same ACL if you want the same processing in both
34805 These ACLs are called (possibly many times) just before the &%acl_smtp_data%&
34806 ACL in the case of an SMTP message, or just before the &%acl_not_smtp%& ACL in
34807 the case of a non-SMTP message. However, a MIME ACL is called only if the
34808 message contains a &'Content-Type:'& header line. When a call to a MIME
34809 ACL does not yield &"accept"&, ACL processing is aborted and the appropriate
34810 result code is sent to the client. In the case of an SMTP message, the
34811 &%acl_smtp_data%& ACL is not called when this happens.
34813 You cannot use the &%malware%& or &%spam%& conditions in a MIME ACL; these can
34814 only be used in the DATA or non-SMTP ACLs. However, you can use the &%regex%&
34815 condition to match against the raw MIME part. You can also use the
34816 &%mime_regex%& condition to match against the decoded MIME part (see section
34817 &<<SECTscanregex>>&).
34819 At the start of a MIME ACL, a number of variables are set from the header
34820 information for the relevant MIME part. These are described below. The contents
34821 of the MIME part are not by default decoded into a disk file except for MIME
34822 parts whose content-type is &"message/rfc822"&. If you want to decode a MIME
34823 part into a disk file, you can use the &%decode%& condition. The general
34826 &`decode = [/`&<&'path'&>&`/]`&<&'filename'&>
34828 The right hand side is expanded before use. After expansion,
34832 &"0"& or &"false"&, in which case no decoding is done.
34834 The string &"default"&. In that case, the file is put in the temporary
34835 &"default"& directory <&'spool_directory'&>&_/scan/_&<&'message_id'&>&_/_& with
34836 a sequential filename consisting of the message id and a sequence number. The
34837 full path and name is available in &$mime_decoded_filename$& after decoding.
34839 A full path name starting with a slash. If the full name is an existing
34840 directory, it is used as a replacement for the default directory. The filename
34841 is then sequentially assigned. If the path does not exist, it is used as
34842 the full path and filename.
34844 If the string does not start with a slash, it is used as the
34845 filename, and the default path is then used.
34847 The &%decode%& condition normally succeeds. It is only false for syntax
34848 errors or unusual circumstances such as memory shortages. You can easily decode
34849 a file with its original, proposed filename using
34851 decode = $mime_filename
34853 However, you should keep in mind that &$mime_filename$& might contain
34854 anything. If you place files outside of the default path, they are not
34855 automatically unlinked.
34857 For RFC822 attachments (these are messages attached to messages, with a
34858 content-type of &"message/rfc822"&), the ACL is called again in the same manner
34859 as for the primary message, only that the &$mime_is_rfc822$& expansion
34860 variable is set (see below). Attached messages are always decoded to disk
34861 before being checked, and the files are unlinked once the check is done.
34863 The MIME ACL supports the &%regex%& and &%mime_regex%& conditions. These can be
34864 used to match regular expressions against raw and decoded MIME parts,
34865 respectively. They are described in section &<<SECTscanregex>>&.
34867 .cindex "MIME content scanning" "returned variables"
34868 The following list describes all expansion variables that are
34869 available in the MIME ACL:
34872 .vitem &$mime_anomaly_level$& &&&
34873 &$mime_anomaly_text$&
34874 .vindex &$mime_anomaly_level$&
34875 .vindex &$mime_anomaly_text$&
34876 If there are problems decoding, these variables contain information on
34877 the detected issue.
34879 .vitem &$mime_boundary$&
34880 .vindex &$mime_boundary$&
34881 If the current part is a multipart (see &$mime_is_multipart$& below), it should
34882 have a boundary string, which is stored in this variable. If the current part
34883 has no boundary parameter in the &'Content-Type:'& header, this variable
34884 contains the empty string.
34886 .vitem &$mime_charset$&
34887 .vindex &$mime_charset$&
34888 This variable contains the character set identifier, if one was found in the
34889 &'Content-Type:'& header. Examples for charset identifiers are:
34895 Please note that this value is not normalized, so you should do matches
34896 case-insensitively.
34898 .vitem &$mime_content_description$&
34899 .vindex &$mime_content_description$&
34900 This variable contains the normalized content of the &'Content-Description:'&
34901 header. It can contain a human-readable description of the parts content. Some
34902 implementations repeat the filename for attachments here, but they are usually
34903 only used for display purposes.
34905 .vitem &$mime_content_disposition$&
34906 .vindex &$mime_content_disposition$&
34907 This variable contains the normalized content of the &'Content-Disposition:'&
34908 header. You can expect strings like &"attachment"& or &"inline"& here.
34910 .vitem &$mime_content_id$&
34911 .vindex &$mime_content_id$&
34912 This variable contains the normalized content of the &'Content-ID:'& header.
34913 This is a unique ID that can be used to reference a part from another part.
34915 .vitem &$mime_content_size$&
34916 .vindex &$mime_content_size$&
34917 This variable is set only after the &%decode%& modifier (see above) has been
34918 successfully run. It contains the size of the decoded part in kilobytes. The
34919 size is always rounded up to full kilobytes, so only a completely empty part
34920 has a &$mime_content_size$& of zero.
34922 .vitem &$mime_content_transfer_encoding$&
34923 .vindex &$mime_content_transfer_encoding$&
34924 This variable contains the normalized content of the
34925 &'Content-transfer-encoding:'& header. This is a symbolic name for an encoding
34926 type. Typical values are &"base64"& and &"quoted-printable"&.
34928 .vitem &$mime_content_type$&
34929 .vindex &$mime_content_type$&
34930 If the MIME part has a &'Content-Type:'& header, this variable contains its
34931 value, lowercased, and without any options (like &"name"& or &"charset"&). Here
34932 are some examples of popular MIME types, as they may appear in this variable:
34936 application/octet-stream
34940 If the MIME part has no &'Content-Type:'& header, this variable contains the
34943 .vitem &$mime_decoded_filename$&
34944 .vindex &$mime_decoded_filename$&
34945 This variable is set only after the &%decode%& modifier (see above) has been
34946 successfully run. It contains the full path and filename of the file
34947 containing the decoded data.
34952 .vitem &$mime_filename$&
34953 .vindex &$mime_filename$&
34954 This is perhaps the most important of the MIME variables. It contains a
34955 proposed filename for an attachment, if one was found in either the
34956 &'Content-Type:'& or &'Content-Disposition:'& headers. The filename will be
34959 decoded, but no additional sanity checks are done.
34961 found, this variable contains the empty string.
34963 .vitem &$mime_is_coverletter$&
34964 .vindex &$mime_is_coverletter$&
34965 This variable attempts to differentiate the &"cover letter"& of an e-mail from
34966 attached data. It can be used to clamp down on flashy or unnecessarily encoded
34967 content in the cover letter, while not restricting attachments at all.
34969 The variable contains 1 (true) for a MIME part believed to be part of the
34970 cover letter, and 0 (false) for an attachment. At present, the algorithm is as
34974 The outermost MIME part of a message is always a cover letter.
34977 If a multipart/alternative or multipart/related MIME part is a cover letter,
34978 so are all MIME subparts within that multipart.
34981 If any other multipart is a cover letter, the first subpart is a cover letter,
34982 and the rest are attachments.
34985 All parts contained within an attachment multipart are attachments.
34988 As an example, the following will ban &"HTML mail"& (including that sent with
34989 alternative plain text), while allowing HTML files to be attached. HTML
34990 coverletter mail attached to non-HTML coverletter mail will also be allowed:
34992 deny !condition = $mime_is_rfc822
34993 condition = $mime_is_coverletter
34994 condition = ${if eq{$mime_content_type}{text/html}{1}{0}}
34995 message = HTML mail is not accepted here
34998 .vitem &$mime_is_multipart$&
34999 .vindex &$mime_is_multipart$&
35000 This variable has the value 1 (true) when the current part has the main type
35001 &"multipart"&, for example, &"multipart/alternative"& or &"multipart/mixed"&.
35002 Since multipart entities only serve as containers for other parts, you may not
35003 want to carry out specific actions on them.
35005 .vitem &$mime_is_rfc822$&
35006 .vindex &$mime_is_rfc822$&
35007 This variable has the value 1 (true) if the current part is not a part of the
35008 checked message itself, but part of an attached message. Attached message
35009 decoding is fully recursive.
35011 .vitem &$mime_part_count$&
35012 .vindex &$mime_part_count$&
35013 This variable is a counter that is raised for each processed MIME part. It
35014 starts at zero for the very first part (which is usually a multipart). The
35015 counter is per-message, so it is reset when processing RFC822 attachments (see
35016 &$mime_is_rfc822$&). The counter stays set after &%acl_smtp_mime%& is
35017 complete, so you can use it in the DATA ACL to determine the number of MIME
35018 parts of a message. For non-MIME messages, this variable contains the value -1.
35023 .section "Scanning with regular expressions" "SECTscanregex"
35024 .cindex "content scanning" "with regular expressions"
35025 .cindex "regular expressions" "content scanning with"
35026 You can specify your own custom regular expression matches on the full body of
35027 the message, or on individual MIME parts.
35029 The &%regex%& condition takes one or more regular expressions as arguments and
35030 matches them against the full message (when called in the DATA ACL) or a raw
35031 MIME part (when called in the MIME ACL). The &%regex%& condition matches
35032 linewise, with a maximum line length of 32K characters. That means you cannot
35033 have multiline matches with the &%regex%& condition.
35035 The &%mime_regex%& condition can be called only in the MIME ACL. It matches up
35036 to 32K of decoded content (the whole content at once, not linewise). If the
35037 part has not been decoded with the &%decode%& modifier earlier in the ACL, it
35038 is decoded automatically when &%mime_regex%& is executed (using default path
35039 and filename values). If the decoded data is larger than 32K, only the first
35040 32K characters are checked.
35042 The regular expressions are passed as a colon-separated list. To include a
35043 literal colon, you must double it. Since the whole right-hand side string is
35044 expanded before being used, you must also escape dollar signs and backslashes
35045 with more backslashes, or use the &`\N`& facility to disable expansion.
35046 Here is a simple example that contains two regular expressions:
35048 deny regex = [Mm]ortgage : URGENT BUSINESS PROPOSAL
35049 message = contains blacklisted regex ($regex_match_string)
35051 The conditions returns true if any one of the regular expressions matches. The
35052 &$regex_match_string$& expansion variable is then set up and contains the
35053 matching regular expression.
35054 The expansion variables &$regex1$& &$regex2$& etc
35055 are set to any substrings captured by the regular expression.
35057 &*Warning*&: With large messages, these conditions can be fairly
35065 . ////////////////////////////////////////////////////////////////////////////
35066 . ////////////////////////////////////////////////////////////////////////////
35068 .chapter "Adding a local scan function to Exim" "CHAPlocalscan" &&&
35069 "Local scan function"
35070 .scindex IIDlosca "&[local_scan()]& function" "description of"
35071 .cindex "customizing" "input scan using C function"
35072 .cindex "policy control" "by local scan function"
35073 In these days of email worms, viruses, and ever-increasing spam, some sites
35074 want to apply a lot of checking to messages before accepting them.
35076 The content scanning extension (chapter &<<CHAPexiscan>>&) has facilities for
35077 passing messages to external virus and spam scanning software. You can also do
35078 a certain amount in Exim itself through string expansions and the &%condition%&
35079 condition in the ACL that runs after the SMTP DATA command or the ACL for
35080 non-SMTP messages (see chapter &<<CHAPACL>>&), but this has its limitations.
35082 To allow for further customization to a site's own requirements, there is the
35083 possibility of linking Exim with a private message scanning function, written
35084 in C. If you want to run code that is written in something other than C, you
35085 can of course use a little C stub to call it.
35087 The local scan function is run once for every incoming message, at the point
35088 when Exim is just about to accept the message.
35089 It can therefore be used to control non-SMTP messages from local processes as
35090 well as messages arriving via SMTP.
35092 Exim applies a timeout to calls of the local scan function, and there is an
35093 option called &%local_scan_timeout%& for setting it. The default is 5 minutes.
35094 Zero means &"no timeout"&.
35095 Exim also sets up signal handlers for SIGSEGV, SIGILL, SIGFPE, and SIGBUS
35096 before calling the local scan function, so that the most common types of crash
35097 are caught. If the timeout is exceeded or one of those signals is caught, the
35098 incoming message is rejected with a temporary error if it is an SMTP message.
35099 For a non-SMTP message, the message is dropped and Exim ends with a non-zero
35100 code. The incident is logged on the main and reject logs.
35104 .section "Building Exim to use a local scan function" "SECID207"
35105 .cindex "&[local_scan()]& function" "building Exim to use"
35106 To make use of the local scan function feature, you must tell Exim where your
35107 function is before building Exim, by setting
35108 both HAVE_LOCAL_SCAN and
35109 LOCAL_SCAN_SOURCE in your
35110 &_Local/Makefile_&. A recommended place to put it is in the &_Local_&
35111 directory, so you might set
35113 HAVE_LOCAL_SCAN=yes
35114 LOCAL_SCAN_SOURCE=Local/local_scan.c
35116 for example. The function must be called &[local_scan()]&;
35117 the source file(s) for it should first #define LOCAL_SCAN
35118 and then #include "local_scan.h".
35120 Exim after it has received a message, when the success return code is about to
35121 be sent. This is after all the ACLs have been run. The return code from your
35122 function controls whether the message is actually accepted or not. There is a
35123 commented template function (that just accepts the message) in the file
35124 _src/local_scan.c_.
35126 If you want to make use of Exim's runtime configuration file to set options
35127 for your &[local_scan()]& function, you must also set
35129 LOCAL_SCAN_HAS_OPTIONS=yes
35131 in &_Local/Makefile_& (see section &<<SECTconoptloc>>& below).
35136 .section "API for local_scan()" "SECTapiforloc"
35137 .cindex "&[local_scan()]& function" "API description"
35138 .cindex &%dlfunc%& "API description"
35139 You must include this line near the start of your code:
35142 #include "local_scan.h"
35144 This header file defines a number of variables and other values, and the
35145 prototype for the function itself. Exim is coded to use unsigned char values
35146 almost exclusively, and one of the things this header defines is a shorthand
35147 for &`unsigned char`& called &`uschar`&.
35148 It also makes available the following macro definitions, to simplify casting character
35149 strings and pointers to character strings:
35151 #define CS (char *)
35152 #define CCS (const char *)
35153 #define CSS (char **)
35154 #define US (unsigned char *)
35155 #define CUS (const unsigned char *)
35156 #define USS (unsigned char **)
35158 The function prototype for &[local_scan()]& is:
35160 extern int local_scan(int fd, uschar **return_text);
35162 The arguments are as follows:
35165 &%fd%& is a file descriptor for the file that contains the body of the message
35166 (the -D file). The file is open for reading and writing, but updating it is not
35167 recommended. &*Warning*&: You must &'not'& close this file descriptor.
35169 The descriptor is positioned at character 19 of the file, which is the first
35170 character of the body itself, because the first 19 characters are the message
35171 id followed by &`-D`& and a newline. If you rewind the file, you should use the
35172 macro SPOOL_DATA_START_OFFSET to reset to the start of the data, just in
35173 case this changes in some future version.
35175 &%return_text%& is an address which you can use to return a pointer to a text
35176 string at the end of the function. The value it points to on entry is NULL.
35179 The function must return an &%int%& value which is one of the following macros:
35182 .vitem &`LOCAL_SCAN_ACCEPT`&
35183 .vindex "&$local_scan_data$&"
35184 The message is accepted. If you pass back a string of text, it is saved with
35185 the message, and made available in the variable &$local_scan_data$&. No
35186 newlines are permitted (if there are any, they are turned into spaces) and the
35187 maximum length of text is 1000 characters.
35189 .vitem &`LOCAL_SCAN_ACCEPT_FREEZE`&
35190 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
35191 queued without immediate delivery, and is frozen.
35193 .vitem &`LOCAL_SCAN_ACCEPT_QUEUE`&
35194 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
35195 queued without immediate delivery.
35197 .vitem &`LOCAL_SCAN_REJECT`&
35198 The message is rejected; the returned text is used as an error message which is
35199 passed back to the sender and which is also logged. Newlines are permitted &--
35200 they cause a multiline response for SMTP rejections, but are converted to
35201 &`\n`& in log lines. If no message is given, &"Administrative prohibition"& is
35204 .vitem &`LOCAL_SCAN_TEMPREJECT`&
35205 The message is temporarily rejected; the returned text is used as an error
35206 message as for LOCAL_SCAN_REJECT. If no message is given, &"Temporary local
35209 .vitem &`LOCAL_SCAN_REJECT_NOLOGHDR`&
35210 This behaves as LOCAL_SCAN_REJECT, except that the header of the rejected
35211 message is not written to the reject log. It has the effect of unsetting the
35212 &%rejected_header%& log selector for just this rejection. If
35213 &%rejected_header%& is already unset (see the discussion of the
35214 &%log_selection%& option in section &<<SECTlogselector>>&), this code is the
35215 same as LOCAL_SCAN_REJECT.
35217 .vitem &`LOCAL_SCAN_TEMPREJECT_NOLOGHDR`&
35218 This code is a variation of LOCAL_SCAN_TEMPREJECT in the same way that
35219 LOCAL_SCAN_REJECT_NOLOGHDR is a variation of LOCAL_SCAN_REJECT.
35222 If the message is not being received by interactive SMTP, rejections are
35223 reported by writing to &%stderr%& or by sending an email, as configured by the
35224 &%-oe%& command line options.
35228 .section "Configuration options for local_scan()" "SECTconoptloc"
35229 .cindex "&[local_scan()]& function" "configuration options"
35230 It is possible to have option settings in the main configuration file
35231 that set values in static variables in the &[local_scan()]& module. If you
35232 want to do this, you must have the line
35234 LOCAL_SCAN_HAS_OPTIONS=yes
35236 in your &_Local/Makefile_& when you build Exim. (This line is in
35237 &_OS/Makefile-Default_&, commented out). Then, in the &[local_scan()]& source
35238 file, you must define static variables to hold the option values, and a table
35241 The table must be a vector called &%local_scan_options%&, of type
35242 &`optionlist`&. Each entry is a triplet, consisting of a name, an option type,
35243 and a pointer to the variable that holds the value. The entries must appear in
35244 alphabetical order. Following &%local_scan_options%& you must also define a
35245 variable called &%local_scan_options_count%& that contains the number of
35246 entries in the table. Here is a short example, showing two kinds of option:
35248 static int my_integer_option = 42;
35249 static uschar *my_string_option = US"a default string";
35251 optionlist local_scan_options[] = {
35252 { "my_integer", opt_int, &my_integer_option },
35253 { "my_string", opt_stringptr, &my_string_option }
35256 int local_scan_options_count =
35257 sizeof(local_scan_options)/sizeof(optionlist);
35259 The values of the variables can now be changed from Exim's runtime
35260 configuration file by including a local scan section as in this example:
35264 my_string = some string of text...
35266 The available types of option data are as follows:
35269 .vitem &*opt_bool*&
35270 This specifies a boolean (true/false) option. The address should point to a
35271 variable of type &`BOOL`&, which will be set to TRUE or FALSE, which are macros
35272 that are defined as &"1"& and &"0"&, respectively. If you want to detect
35273 whether such a variable has been set at all, you can initialize it to
35274 TRUE_UNSET. (BOOL variables are integers underneath, so can hold more than two
35277 .vitem &*opt_fixed*&
35278 This specifies a fixed point number, such as is used for load averages.
35279 The address should point to a variable of type &`int`&. The value is stored
35280 multiplied by 1000, so, for example, 1.4142 is truncated and stored as 1414.
35283 This specifies an integer; the address should point to a variable of type
35284 &`int`&. The value may be specified in any of the integer formats accepted by
35287 .vitem &*opt_mkint*&
35288 This is the same as &%opt_int%&, except that when such a value is output in a
35289 &%-bP%& listing, if it is an exact number of kilobytes or megabytes, it is
35290 printed with the suffix K or M.
35292 .vitem &*opt_octint*&
35293 This also specifies an integer, but the value is always interpreted as an
35294 octal integer, whether or not it starts with the digit zero, and it is
35295 always output in octal.
35297 .vitem &*opt_stringptr*&
35298 This specifies a string value; the address must be a pointer to a
35299 variable that points to a string (for example, of type &`uschar *`&).
35301 .vitem &*opt_time*&
35302 This specifies a time interval value. The address must point to a variable of
35303 type &`int`&. The value that is placed there is a number of seconds.
35306 If the &%-bP%& command line option is followed by &`local_scan`&, Exim prints
35307 out the values of all the &[local_scan()]& options.
35311 .section "Available Exim variables" "SECID208"
35312 .cindex "&[local_scan()]& function" "available Exim variables"
35313 The header &_local_scan.h_& gives you access to a number of C variables. These
35314 are the only ones that are guaranteed to be maintained from release to release.
35315 Note, however, that you can obtain the value of any Exim expansion variable,
35316 including &$recipients$&, by calling &'expand_string()'&. The exported
35317 C variables are as follows:
35320 .vitem &*int&~body_linecount*&
35321 This variable contains the number of lines in the message's body.
35322 It is not valid if the &%spool_wireformat%& option is used.
35324 .vitem &*int&~body_zerocount*&
35325 This variable contains the number of binary zero bytes in the message's body.
35326 It is not valid if the &%spool_wireformat%& option is used.
35328 .vitem &*unsigned&~int&~debug_selector*&
35329 This variable is set to zero when no debugging is taking place. Otherwise, it
35330 is a bitmap of debugging selectors. Two bits are identified for use in
35331 &[local_scan()]&; they are defined as macros:
35334 The &`D_v`& bit is set when &%-v%& was present on the command line. This is a
35335 testing option that is not privileged &-- any caller may set it. All the
35336 other selector bits can be set only by admin users.
35339 The &`D_local_scan`& bit is provided for use by &[local_scan()]&; it is set
35340 by the &`+local_scan`& debug selector. It is not included in the default set
35344 Thus, to write to the debugging output only when &`+local_scan`& has been
35345 selected, you should use code like this:
35347 if ((debug_selector & D_local_scan) != 0)
35348 debug_printf("xxx", ...);
35350 .vitem &*uschar&~*expand_string_message*&
35351 After a failing call to &'expand_string()'& (returned value NULL), the
35352 variable &%expand_string_message%& contains the error message, zero-terminated.
35354 .vitem &*header_line&~*header_list*&
35355 A pointer to a chain of header lines. The &%header_line%& structure is
35358 .vitem &*header_line&~*header_last*&
35359 A pointer to the last of the header lines.
35361 .vitem &*const&~uschar&~*headers_charset*&
35362 The value of the &%headers_charset%& configuration option.
35364 .vitem &*BOOL&~host_checking*&
35365 This variable is TRUE during a host checking session that is initiated by the
35366 &%-bh%& command line option.
35368 .vitem &*uschar&~*interface_address*&
35369 The IP address of the interface that received the message, as a string. This
35370 is NULL for locally submitted messages.
35372 .vitem &*int&~interface_port*&
35373 The port on which this message was received. When testing with the &%-bh%&
35374 command line option, the value of this variable is -1 unless a port has been
35375 specified via the &%-oMi%& option.
35377 .vitem &*uschar&~*message_id*&
35378 This variable contains Exim's message id for the incoming message (the value of
35379 &$message_exim_id$&) as a zero-terminated string.
35381 .vitem &*uschar&~*received_protocol*&
35382 The name of the protocol by which the message was received.
35384 .vitem &*int&~recipients_count*&
35385 The number of accepted recipients.
35387 .vitem &*recipient_item&~*recipients_list*&
35388 .cindex "recipient" "adding in local scan"
35389 .cindex "recipient" "removing in local scan"
35390 The list of accepted recipients, held in a vector of length
35391 &%recipients_count%&. The &%recipient_item%& structure is discussed below. You
35392 can add additional recipients by calling &'receive_add_recipient()'& (see
35393 below). You can delete recipients by removing them from the vector and
35394 adjusting the value in &%recipients_count%&. In particular, by setting
35395 &%recipients_count%& to zero you remove all recipients. If you then return the
35396 value &`LOCAL_SCAN_ACCEPT`&, the message is accepted, but immediately
35397 blackholed. To replace the recipients, you can set &%recipients_count%& to zero
35398 and then call &'receive_add_recipient()'& as often as needed.
35400 .vitem &*uschar&~*sender_address*&
35401 The envelope sender address. For bounce messages this is the empty string.
35403 .vitem &*uschar&~*sender_host_address*&
35404 The IP address of the sending host, as a string. This is NULL for
35405 locally-submitted messages.
35407 .vitem &*uschar&~*sender_host_authenticated*&
35408 The name of the authentication mechanism that was used, or NULL if the message
35409 was not received over an authenticated SMTP connection.
35411 .vitem &*uschar&~*sender_host_name*&
35412 The name of the sending host, if known.
35414 .vitem &*int&~sender_host_port*&
35415 The port on the sending host.
35417 .vitem &*BOOL&~smtp_input*&
35418 This variable is TRUE for all SMTP input, including BSMTP.
35420 .vitem &*BOOL&~smtp_batched_input*&
35421 This variable is TRUE for BSMTP input.
35423 .vitem &*int&~store_pool*&
35424 The contents of this variable control which pool of memory is used for new
35425 requests. See section &<<SECTmemhanloc>>& for details.
35429 .section "Structure of header lines" "SECID209"
35430 The &%header_line%& structure contains the members listed below.
35431 You can add additional header lines by calling the &'header_add()'& function
35432 (see below). You can cause header lines to be ignored (deleted) by setting
35437 .vitem &*struct&~header_line&~*next*&
35438 A pointer to the next header line, or NULL for the last line.
35440 .vitem &*int&~type*&
35441 A code identifying certain headers that Exim recognizes. The codes are printing
35442 characters, and are documented in chapter &<<CHAPspool>>& of this manual.
35443 Notice in particular that any header line whose type is * is not transmitted
35444 with the message. This flagging is used for header lines that have been
35445 rewritten, or are to be removed (for example, &'Envelope-sender:'& header
35446 lines.) Effectively, * means &"deleted"&.
35448 .vitem &*int&~slen*&
35449 The number of characters in the header line, including the terminating and any
35452 .vitem &*uschar&~*text*&
35453 A pointer to the text of the header. It always ends with a newline, followed by
35454 a zero byte. Internal newlines are preserved.
35459 .section "Structure of recipient items" "SECID210"
35460 The &%recipient_item%& structure contains these members:
35463 .vitem &*uschar&~*address*&
35464 This is a pointer to the recipient address as it was received.
35466 .vitem &*int&~pno*&
35467 This is used in later Exim processing when top level addresses are created by
35468 the &%one_time%& option. It is not relevant at the time &[local_scan()]& is run
35469 and must always contain -1 at this stage.
35471 .vitem &*uschar&~*errors_to*&
35472 If this value is not NULL, bounce messages caused by failing to deliver to the
35473 recipient are sent to the address it contains. In other words, it overrides the
35474 envelope sender for this one recipient. (Compare the &%errors_to%& generic
35475 router option.) If a &[local_scan()]& function sets an &%errors_to%& field to
35476 an unqualified address, Exim qualifies it using the domain from
35477 &%qualify_recipient%&. When &[local_scan()]& is called, the &%errors_to%& field
35478 is NULL for all recipients.
35483 .section "Available Exim functions" "SECID211"
35484 .cindex "&[local_scan()]& function" "available Exim functions"
35485 The header &_local_scan.h_& gives you access to a number of Exim functions.
35486 These are the only ones that are guaranteed to be maintained from release to
35490 .vitem "&*pid_t&~child_open(uschar&~**argv,&~uschar&~**envp,&~int&~newumask,&&&
35491 &~int&~*infdptr,&~int&~*outfdptr, &~&~BOOL&~make_leader)*&"
35493 This function creates a child process that runs the command specified by
35494 &%argv%&. The environment for the process is specified by &%envp%&, which can
35495 be NULL if no environment variables are to be passed. A new umask is supplied
35496 for the process in &%newumask%&.
35498 Pipes to the standard input and output of the new process are set up
35499 and returned to the caller via the &%infdptr%& and &%outfdptr%& arguments. The
35500 standard error is cloned to the standard output. If there are any file
35501 descriptors &"in the way"& in the new process, they are closed. If the final
35502 argument is TRUE, the new process is made into a process group leader.
35504 The function returns the pid of the new process, or -1 if things go wrong.
35506 .vitem &*int&~child_close(pid_t&~pid,&~int&~timeout)*&
35507 This function waits for a child process to terminate, or for a timeout (in
35508 seconds) to expire. A timeout value of zero means wait as long as it takes. The
35509 return value is as follows:
35514 The process terminated by a normal exit and the value is the process
35520 The process was terminated by a signal and the value is the negation of the
35526 The process timed out.
35530 The was some other error in wait(); &%errno%& is still set.
35533 .vitem &*pid_t&~child_open_exim(int&~*fd)*&
35534 This function provide you with a means of submitting a new message to
35535 Exim. (Of course, you can also call &_/usr/sbin/sendmail_& yourself if you
35536 want, but this packages it all up for you.) The function creates a pipe,
35537 forks a subprocess that is running
35539 exim -t -oem -oi -f <>
35541 and returns to you (via the &`int *`& argument) a file descriptor for the pipe
35542 that is connected to the standard input. The yield of the function is the PID
35543 of the subprocess. You can then write a message to the file descriptor, with
35544 recipients in &'To:'&, &'Cc:'&, and/or &'Bcc:'& header lines.
35546 When you have finished, call &'child_close()'& to wait for the process to
35547 finish and to collect its ending status. A timeout value of zero is usually
35548 fine in this circumstance. Unless you have made a mistake with the recipient
35549 addresses, you should get a return code of zero.
35552 .vitem &*pid_t&~child_open_exim2(int&~*fd,&~uschar&~*sender,&~uschar&~&&&
35553 *sender_authentication)*&
35554 This function is a more sophisticated version of &'child_open()'&. The command
35557 &`exim -t -oem -oi -f `&&'sender'&&` -oMas `&&'sender_authentication'&
35559 The third argument may be NULL, in which case the &%-oMas%& option is omitted.
35562 .vitem &*void&~debug_printf(char&~*,&~...)*&
35563 This is Exim's debugging function, with arguments as for &'(printf()'&. The
35564 output is written to the standard error stream. If no debugging is selected,
35565 calls to &'debug_printf()'& have no effect. Normally, you should make calls
35566 conditional on the &`local_scan`& debug selector by coding like this:
35568 if ((debug_selector & D_local_scan) != 0)
35569 debug_printf("xxx", ...);
35572 .vitem &*uschar&~*expand_string(uschar&~*string)*&
35573 This is an interface to Exim's string expansion code. The return value is the
35574 expanded string, or NULL if there was an expansion failure.
35575 The C variable &%expand_string_message%& contains an error message after an
35576 expansion failure. If expansion does not change the string, the return value is
35577 the pointer to the input string. Otherwise, the return value points to a new
35578 block of memory that was obtained by a call to &'store_get()'&. See section
35579 &<<SECTmemhanloc>>& below for a discussion of memory handling.
35581 .vitem &*void&~header_add(int&~type,&~char&~*format,&~...)*&
35582 This function allows you to an add additional header line at the end of the
35583 existing ones. The first argument is the type, and should normally be a space
35584 character. The second argument is a format string and any number of
35585 substitution arguments as for &[sprintf()]&. You may include internal newlines
35586 if you want, and you must ensure that the string ends with a newline.
35588 .vitem "&*void&~header_add_at_position(BOOL&~after,&~uschar&~*name,&~&&&
35589 BOOL&~topnot,&~int&~type,&~char&~*format, &~&~...)*&"
35590 This function adds a new header line at a specified point in the header
35591 chain. The header itself is specified as for &'header_add()'&.
35593 If &%name%& is NULL, the new header is added at the end of the chain if
35594 &%after%& is true, or at the start if &%after%& is false. If &%name%& is not
35595 NULL, the header lines are searched for the first non-deleted header that
35596 matches the name. If one is found, the new header is added before it if
35597 &%after%& is false. If &%after%& is true, the new header is added after the
35598 found header and any adjacent subsequent ones with the same name (even if
35599 marked &"deleted"&). If no matching non-deleted header is found, the &%topnot%&
35600 option controls where the header is added. If it is true, addition is at the
35601 top; otherwise at the bottom. Thus, to add a header after all the &'Received:'&
35602 headers, or at the top if there are no &'Received:'& headers, you could use
35604 header_add_at_position(TRUE, US"Received", TRUE,
35605 ' ', "X-xxx: ...");
35607 Normally, there is always at least one non-deleted &'Received:'& header, but
35608 there may not be if &%received_header_text%& expands to an empty string.
35611 .vitem &*void&~header_remove(int&~occurrence,&~uschar&~*name)*&
35612 This function removes header lines. If &%occurrence%& is zero or negative, all
35613 occurrences of the header are removed. If occurrence is greater than zero, that
35614 particular instance of the header is removed. If no header(s) can be found that
35615 match the specification, the function does nothing.
35618 .vitem "&*BOOL&~header_testname(header_line&~*hdr,&~uschar&~*name,&~&&&
35619 int&~length,&~BOOL&~notdel)*&"
35620 This function tests whether the given header has the given name. It is not just
35621 a string comparison, because white space is permitted between the name and the
35622 colon. If the &%notdel%& argument is true, a false return is forced for all
35623 &"deleted"& headers; otherwise they are not treated specially. For example:
35625 if (header_testname(h, US"X-Spam", 6, TRUE)) ...
35627 .vitem &*uschar&~*lss_b64encode(uschar&~*cleartext,&~int&~length)*&
35628 .cindex "base64 encoding" "functions for &[local_scan()]& use"
35629 This function base64-encodes a string, which is passed by address and length.
35630 The text may contain bytes of any value, including zero. The result is passed
35631 back in dynamic memory that is obtained by calling &'store_get()'&. It is
35634 .vitem &*int&~lss_b64decode(uschar&~*codetext,&~uschar&~**cleartext)*&
35635 This function decodes a base64-encoded string. Its arguments are a
35636 zero-terminated base64-encoded string and the address of a variable that is set
35637 to point to the result, which is in dynamic memory. The length of the decoded
35638 string is the yield of the function. If the input is invalid base64 data, the
35639 yield is -1. A zero byte is added to the end of the output string to make it
35640 easy to interpret as a C string (assuming it contains no zeros of its own). The
35641 added zero byte is not included in the returned count.
35643 .vitem &*int&~lss_match_domain(uschar&~*domain,&~uschar&~*list)*&
35644 This function checks for a match in a domain list. Domains are always
35645 matched caselessly. The return value is one of the following:
35646 .itable none 0 0 2 1pt left 1pt left
35647 .irow &`OK`& "match succeeded"
35648 .irow &`FAIL`& "match failed"
35649 .irow &`DEFER`& "match deferred"
35651 DEFER is usually caused by some kind of lookup defer, such as the
35652 inability to contact a database.
35654 .vitem "&*int&~lss_match_local_part(uschar&~*localpart,&~uschar&~*list,&~&&&
35656 This function checks for a match in a local part list. The third argument
35657 controls case-sensitivity. The return values are as for
35658 &'lss_match_domain()'&.
35660 .vitem "&*int&~lss_match_address(uschar&~*address,&~uschar&~*list,&~&&&
35662 This function checks for a match in an address list. The third argument
35663 controls the case-sensitivity of the local part match. The domain is always
35664 matched caselessly. The return values are as for &'lss_match_domain()'&.
35666 .vitem "&*int&~lss_match_host(uschar&~*host_name,&~uschar&~*host_address,&~&&&
35668 This function checks for a match in a host list. The most common usage is
35671 lss_match_host(sender_host_name, sender_host_address, ...)
35673 .vindex "&$sender_host_address$&"
35674 An empty address field matches an empty item in the host list. If the host name
35675 is NULL, the name corresponding to &$sender_host_address$& is automatically
35676 looked up if a host name is required to match an item in the list. The return
35677 values are as for &'lss_match_domain()'&, but in addition, &'lss_match_host()'&
35678 returns ERROR in the case when it had to look up a host name, but the lookup
35681 .vitem "&*void&~log_write(unsigned&~int&~selector,&~int&~which,&~char&~&&&
35683 This function writes to Exim's log files. The first argument should be zero (it
35684 is concerned with &%log_selector%&). The second argument can be &`LOG_MAIN`& or
35685 &`LOG_REJECT`& or &`LOG_PANIC`& or the inclusive &"or"& of any combination of
35686 them. It specifies to which log or logs the message is written. The remaining
35687 arguments are a format and relevant insertion arguments. The string should not
35688 contain any newlines, not even at the end.
35691 .vitem &*void&~receive_add_recipient(uschar&~*address,&~int&~pno)*&
35692 This function adds an additional recipient to the message. The first argument
35693 is the recipient address. If it is unqualified (has no domain), it is qualified
35694 with the &%qualify_recipient%& domain. The second argument must always be -1.
35696 This function does not allow you to specify a private &%errors_to%& address (as
35697 described with the structure of &%recipient_item%& above), because it pre-dates
35698 the addition of that field to the structure. However, it is easy to add such a
35699 value afterwards. For example:
35701 receive_add_recipient(US"monitor@mydom.example", -1);
35702 recipients_list[recipients_count-1].errors_to =
35703 US"postmaster@mydom.example";
35706 .vitem &*BOOL&~receive_remove_recipient(uschar&~*recipient)*&
35707 This is a convenience function to remove a named recipient from the list of
35708 recipients. It returns true if a recipient was removed, and false if no
35709 matching recipient could be found. The argument must be a complete email
35716 .vitem "&*uschar&~rfc2047_decode(uschar&~*string,&~BOOL&~lencheck,&&&
35717 &~uschar&~*target,&~int&~zeroval,&~int&~*lenptr, &~&~uschar&~**error)*&"
35718 This function decodes strings that are encoded according to RFC 2047. Typically
35719 these are the contents of header lines. First, each &"encoded word"& is decoded
35720 from the Q or B encoding into a byte-string. Then, if provided with the name of
35721 a charset encoding, and if the &[iconv()]& function is available, an attempt is
35722 made to translate the result to the named character set. If this fails, the
35723 binary string is returned with an error message.
35725 The first argument is the string to be decoded. If &%lencheck%& is TRUE, the
35726 maximum MIME word length is enforced. The third argument is the target
35727 encoding, or NULL if no translation is wanted.
35729 .cindex "binary zero" "in RFC 2047 decoding"
35730 .cindex "RFC 2047" "binary zero in"
35731 If a binary zero is encountered in the decoded string, it is replaced by the
35732 contents of the &%zeroval%& argument. For use with Exim headers, the value must
35733 not be 0 because header lines are handled as zero-terminated strings.
35735 The function returns the result of processing the string, zero-terminated; if
35736 &%lenptr%& is not NULL, the length of the result is set in the variable to
35737 which it points. When &%zeroval%& is 0, &%lenptr%& should not be NULL.
35739 If an error is encountered, the function returns NULL and uses the &%error%&
35740 argument to return an error message. The variable pointed to by &%error%& is
35741 set to NULL if there is no error; it may be set non-NULL even when the function
35742 returns a non-NULL value if decoding was successful, but there was a problem
35746 .vitem &*int&~smtp_fflush(void)*&
35747 This function is used in conjunction with &'smtp_printf()'&, as described
35750 .vitem &*void&~smtp_printf(char&~*,BOOL,&~...)*&
35751 The arguments of this function are almost like &[printf()]&; it writes to the SMTP
35752 output stream. You should use this function only when there is an SMTP output
35753 stream, that is, when the incoming message is being received via interactive
35754 SMTP. This is the case when &%smtp_input%& is TRUE and &%smtp_batched_input%&
35755 is FALSE. If you want to test for an incoming message from another host (as
35756 opposed to a local process that used the &%-bs%& command line option), you can
35757 test the value of &%sender_host_address%&, which is non-NULL when a remote host
35760 If an SMTP TLS connection is established, &'smtp_printf()'& uses the TLS
35761 output function, so it can be used for all forms of SMTP connection.
35763 The second argument is used to request that the data be buffered
35764 (when TRUE) or flushed (along with any previously buffered, when FALSE).
35765 This is advisory only, but likely to save on system-calls and packets
35766 sent when a sequence of calls to the function are made.
35768 The argument was added in Exim version 4.90 - changing the API/ABI.
35769 Nobody noticed until 4.93 was imminent, at which point the
35770 ABI version number was incremented.
35772 Strings that are written by &'smtp_printf()'& from within &[local_scan()]&
35773 must start with an appropriate response code: 550 if you are going to return
35774 LOCAL_SCAN_REJECT, 451 if you are going to return
35775 LOCAL_SCAN_TEMPREJECT, and 250 otherwise. Because you are writing the
35776 initial lines of a multi-line response, the code must be followed by a hyphen
35777 to indicate that the line is not the final response line. You must also ensure
35778 that the lines you write terminate with CRLF. For example:
35780 smtp_printf("550-this is some extra info\r\n");
35781 return LOCAL_SCAN_REJECT;
35783 Note that you can also create multi-line responses by including newlines in
35784 the data returned via the &%return_text%& argument. The added value of using
35785 &'smtp_printf()'& is that, for instance, you could introduce delays between
35786 multiple output lines.
35788 The &'smtp_printf()'& function does not return any error indication, because it
35790 guarantee a flush of
35791 pending output, and therefore does not test
35792 the state of the stream. (In the main code of Exim, flushing and error
35793 detection is done when Exim is ready for the next SMTP input command.) If
35794 you want to flush the output and check for an error (for example, the
35795 dropping of a TCP/IP connection), you can call &'smtp_fflush()'&, which has no
35796 arguments. It flushes the output stream, and returns a non-zero value if there
35799 .vitem &*void&~*store_get(int,BOOL)*&
35800 This function accesses Exim's internal store (memory) manager. It gets a new
35801 chunk of memory whose size is given by the first argument.
35802 The second argument should be given as TRUE if the memory will be used for
35803 data possibly coming from an attacker (eg. the message content),
35804 FALSE if it is locally-sourced.
35805 Exim bombs out if it ever
35806 runs out of memory. See the next section for a discussion of memory handling.
35808 .vitem &*void&~*store_get_perm(int,BOOL)*&
35809 This function is like &'store_get()'&, but it always gets memory from the
35810 permanent pool. See the next section for a discussion of memory handling.
35812 .vitem &*uschar&~*string_copy(uschar&~*string)*&
35815 .vitem &*uschar&~*string_copyn(uschar&~*string,&~int&~length)*&
35818 .vitem &*uschar&~*string_sprintf(char&~*format,&~...)*&
35819 These three functions create strings using Exim's dynamic memory facilities.
35820 The first makes a copy of an entire string. The second copies up to a maximum
35821 number of characters, indicated by the second argument. The third uses a format
35822 and insertion arguments to create a new string. In each case, the result is a
35823 pointer to a new string in the current memory pool. See the next section for
35829 .section "More about Exim's memory handling" "SECTmemhanloc"
35830 .cindex "&[local_scan()]& function" "memory handling"
35831 No function is provided for freeing memory, because that is never needed.
35832 The dynamic memory that Exim uses when receiving a message is automatically
35833 recycled if another message is received by the same process (this applies only
35834 to incoming SMTP connections &-- other input methods can supply only one
35835 message at a time). After receiving the last message, a reception process
35838 Because it is recycled, the normal dynamic memory cannot be used for holding
35839 data that must be preserved over a number of incoming messages on the same SMTP
35840 connection. However, Exim in fact uses two pools of dynamic memory; the second
35841 one is not recycled, and can be used for this purpose.
35843 If you want to allocate memory that remains available for subsequent messages
35844 in the same SMTP connection, you should set
35846 store_pool = POOL_PERM
35848 before calling the function that does the allocation. There is no need to
35849 restore the value if you do not need to; however, if you do want to revert to
35850 the normal pool, you can either restore the previous value of &%store_pool%& or
35851 set it explicitly to POOL_MAIN.
35853 The pool setting applies to all functions that get dynamic memory, including
35854 &'expand_string()'&, &'store_get()'&, and the &'string_xxx()'& functions.
35855 There is also a convenience function called &'store_get_perm()'& that gets a
35856 block of memory from the permanent pool while preserving the value of
35863 . ////////////////////////////////////////////////////////////////////////////
35864 . ////////////////////////////////////////////////////////////////////////////
35866 .chapter "System-wide message filtering" "CHAPsystemfilter"
35867 .scindex IIDsysfil1 "filter" "system filter"
35868 .scindex IIDsysfil2 "filtering all mail"
35869 .scindex IIDsysfil3 "system filter"
35870 The previous chapters (on ACLs and the local scan function) describe checks
35871 that can be applied to messages before they are accepted by a host. There is
35872 also a mechanism for checking messages once they have been received, but before
35873 they are delivered. This is called the &'system filter'&.
35875 The system filter operates in a similar manner to users' filter files, but it
35876 is run just once per message (however many recipients the message has).
35877 It should not normally be used as a substitute for routing, because &%deliver%&
35878 commands in a system router provide new envelope recipient addresses.
35879 The system filter must be an Exim filter. It cannot be a Sieve filter.
35881 The system filter is run at the start of a delivery attempt, before any routing
35882 is done. If a message fails to be completely delivered at the first attempt,
35883 the system filter is run again at the start of every retry.
35884 If you want your filter to do something only once per message, you can make use
35885 of the &%first_delivery%& condition in an &%if%& command in the filter to
35886 prevent it happening on retries.
35888 .vindex "&$domain$&"
35889 .vindex "&$local_part$&"
35890 &*Warning*&: Because the system filter runs just once, variables that are
35891 specific to individual recipient addresses, such as &$local_part$& and
35892 &$domain$&, are not set, and the &"personal"& condition is not meaningful. If
35893 you want to run a centrally-specified filter for each recipient address
35894 independently, you can do so by setting up a suitable &(redirect)& router, as
35895 described in section &<<SECTperaddfil>>& below.
35898 .section "Specifying a system filter" "SECID212"
35899 .cindex "uid (user id)" "system filter"
35900 .cindex "gid (group id)" "system filter"
35901 The name of the file that contains the system filter must be specified by
35902 setting &%system_filter%&. If you want the filter to run under a uid and gid
35903 other than root, you must also set &%system_filter_user%& and
35904 &%system_filter_group%& as appropriate. For example:
35906 system_filter = /etc/mail/exim.filter
35907 system_filter_user = exim
35909 If a system filter generates any deliveries directly to files or pipes (via the
35910 &%save%& or &%pipe%& commands), transports to handle these deliveries must be
35911 specified by setting &%system_filter_file_transport%& and
35912 &%system_filter_pipe_transport%&, respectively. Similarly,
35913 &%system_filter_reply_transport%& must be set to handle any messages generated
35914 by the &%reply%& command.
35917 .section "Testing a system filter" "SECID213"
35918 You can run simple tests of a system filter in the same way as for a user
35919 filter, but you should use &%-bF%& rather than &%-bf%&, so that features that
35920 are permitted only in system filters are recognized.
35922 If you want to test the combined effect of a system filter and a user filter,
35923 you can use both &%-bF%& and &%-bf%& on the same command line.
35927 .section "Contents of a system filter" "SECID214"
35928 The language used to specify system filters is the same as for users' filter
35929 files. It is described in the separate end-user document &'Exim's interface to
35930 mail filtering'&. However, there are some additional features that are
35931 available only in system filters; these are described in subsequent sections.
35932 If they are encountered in a user's filter file or when testing with &%-bf%&,
35935 .cindex "frozen messages" "manual thaw; testing in filter"
35936 There are two special conditions which, though available in users' filter
35937 files, are designed for use in system filters. The condition &%first_delivery%&
35938 is true only for the first attempt at delivering a message, and
35939 &%manually_thawed%& is true only if the message has been frozen, and
35940 subsequently thawed by an admin user. An explicit forced delivery counts as a
35941 manual thaw, but thawing as a result of the &%auto_thaw%& setting does not.
35943 &*Warning*&: If a system filter uses the &%first_delivery%& condition to
35944 specify an &"unseen"& (non-significant) delivery, and that delivery does not
35945 succeed, it will not be tried again.
35946 If you want Exim to retry an unseen delivery until it succeeds, you should
35947 arrange to set it up every time the filter runs.
35949 When a system filter finishes running, the values of the variables &$n0$& &--
35950 &$n9$& are copied into &$sn0$& &-- &$sn9$& and are thereby made available to
35951 users' filter files. Thus a system filter can, for example, set up &"scores"&
35952 to which users' filter files can refer.
35956 .section "Additional variable for system filters" "SECID215"
35957 .vindex "&$recipients$&"
35958 The expansion variable &$recipients$&, containing a list of all the recipients
35959 of the message (separated by commas and white space), is available in system
35960 filters. It is not available in users' filters for privacy reasons.
35964 .section "Defer, freeze, and fail commands for system filters" "SECID216"
35965 .cindex "freezing messages"
35966 .cindex "message" "freezing"
35967 .cindex "message" "forced failure"
35968 .cindex "&%fail%&" "in system filter"
35969 .cindex "&%freeze%& in system filter"
35970 .cindex "&%defer%& in system filter"
35971 There are three extra commands (&%defer%&, &%freeze%& and &%fail%&) which are
35972 always available in system filters, but are not normally enabled in users'
35973 filters. (See the &%allow_defer%&, &%allow_freeze%& and &%allow_fail%& options
35974 for the &(redirect)& router.) These commands can optionally be followed by the
35975 word &%text%& and a string containing an error message, for example:
35977 fail text "this message looks like spam to me"
35979 The keyword &%text%& is optional if the next character is a double quote.
35981 The &%defer%& command defers delivery of the original recipients of the
35982 message. The &%fail%& command causes all the original recipients to be failed,
35983 and a bounce message to be created. The &%freeze%& command suspends all
35984 delivery attempts for the original recipients. In all cases, any new deliveries
35985 that are specified by the filter are attempted as normal after the filter has
35988 The &%freeze%& command is ignored if the message has been manually unfrozen and
35989 not manually frozen since. This means that automatic freezing by a system
35990 filter can be used as a way of checking out suspicious messages. If a message
35991 is found to be all right, manually unfreezing it allows it to be delivered.
35993 .cindex "log" "&%fail%& command log line"
35994 .cindex "&%fail%&" "log line; reducing"
35995 The text given with a fail command is used as part of the bounce message as
35996 well as being written to the log. If the message is quite long, this can fill
35997 up a lot of log space when such failures are common. To reduce the size of the
35998 log message, Exim interprets the text in a special way if it starts with the
35999 two characters &`<<`& and contains &`>>`& later. The text between these two
36000 strings is written to the log, and the rest of the text is used in the bounce
36001 message. For example:
36003 fail "<<filter test 1>>Your message is rejected \
36004 because it contains attachments that we are \
36005 not prepared to receive."
36008 .cindex "loop" "caused by &%fail%&"
36009 Take great care with the &%fail%& command when basing the decision to fail on
36010 the contents of the message, because the bounce message will of course include
36011 the contents of the original message and will therefore trigger the &%fail%&
36012 command again (causing a mail loop) unless steps are taken to prevent this.
36013 Testing the &%error_message%& condition is one way to prevent this. You could
36016 if $message_body contains "this is spam" and not error_message
36017 then fail text "spam is not wanted here" endif
36019 though of course that might let through unwanted bounce messages. The
36020 alternative is clever checking of the body and/or headers to detect bounces
36021 generated by the filter.
36023 The interpretation of a system filter file ceases after a
36025 &%freeze%&, or &%fail%& command is obeyed. However, any deliveries that were
36026 set up earlier in the filter file are honoured, so you can use a sequence such
36032 to send a specified message when the system filter is freezing (or deferring or
36033 failing) a message. The normal deliveries for the message do not, of course,
36038 .section "Adding and removing headers in a system filter" "SECTaddremheasys"
36039 .cindex "header lines" "adding; in system filter"
36040 .cindex "header lines" "removing; in system filter"
36041 .cindex "filter" "header lines; adding/removing"
36042 Two filter commands that are available only in system filters are:
36044 headers add <string>
36045 headers remove <string>
36047 The argument for the &%headers add%& is a string that is expanded and then
36048 added to the end of the message's headers. It is the responsibility of the
36049 filter maintainer to make sure it conforms to RFC 2822 syntax. Leading white
36050 space is ignored, and if the string is otherwise empty, or if the expansion is
36051 forced to fail, the command has no effect.
36053 You can use &"\n"& within the string, followed by white space, to specify
36054 continued header lines. More than one header may be added in one command by
36055 including &"\n"& within the string without any following white space. For
36058 headers add "X-header-1: ....\n \
36059 continuation of X-header-1 ...\n\
36062 Note that the header line continuation white space after the first newline must
36063 be placed before the backslash that continues the input string, because white
36064 space after input continuations is ignored.
36066 The argument for &%headers remove%& is a colon-separated list of header names.
36067 This command applies only to those headers that are stored with the message;
36068 those that are added at delivery time (such as &'Envelope-To:'& and
36069 &'Return-Path:'&) cannot be removed by this means. If there is more than one
36070 header with the same name, they are all removed.
36072 The &%headers%& command in a system filter makes an immediate change to the set
36073 of header lines that was received with the message (with possible additions
36074 from ACL processing). Subsequent commands in the system filter operate on the
36075 modified set, which also forms the basis for subsequent message delivery.
36076 Unless further modified during routing or transporting, this set of headers is
36077 used for all recipients of the message.
36079 During routing and transporting, the variables that refer to the contents of
36080 header lines refer only to those lines that are in this set. Thus, header lines
36081 that are added by a system filter are visible to users' filter files and to all
36082 routers and transports. This contrasts with the manipulation of header lines by
36083 routers and transports, which is not immediate, but which instead is saved up
36084 until the message is actually being written (see section
36085 &<<SECTheadersaddrem>>&).
36087 If the message is not delivered at the first attempt, header lines that were
36088 added by the system filter are stored with the message, and so are still
36089 present at the next delivery attempt. Header lines that were removed are still
36090 present, but marked &"deleted"& so that they are not transported with the
36091 message. For this reason, it is usual to make the &%headers%& command
36092 conditional on &%first_delivery%& so that the set of header lines is not
36093 modified more than once.
36095 Because header modification in a system filter acts immediately, you have to
36096 use an indirect approach if you want to modify the contents of a header line.
36099 headers add "Old-Subject: $h_subject:"
36100 headers remove "Subject"
36101 headers add "Subject: new subject (was: $h_old-subject:)"
36102 headers remove "Old-Subject"
36107 .section "Setting an errors address in a system filter" "SECID217"
36108 .cindex "envelope from"
36109 .cindex "envelope sender"
36110 In a system filter, if a &%deliver%& command is followed by
36112 errors_to <some address>
36114 in order to change the envelope sender (and hence the error reporting) for that
36115 delivery, any address may be specified. (In a user filter, only the current
36116 user's address can be set.) For example, if some mail is being monitored, you
36119 unseen deliver monitor@spying.example errors_to root@local.example
36121 to take a copy which would not be sent back to the normal error reporting
36122 address if its delivery failed.
36126 .section "Per-address filtering" "SECTperaddfil"
36127 .vindex "&$domain_data$&"
36128 .vindex "&$local_part_data$&"
36129 In contrast to the system filter, which is run just once per message for each
36130 delivery attempt, it is also possible to set up a system-wide filtering
36131 operation that runs once for each recipient address. In this case, variables
36132 such as &$local_part_data$& and &$domain_data$& can be used,
36133 and indeed, the choice of filter file could be made dependent on them.
36134 This is an example of a router which implements such a filter:
36139 domains = +local_domains
36140 file = /central/filters/$local_part_data
36145 The filter is run in a separate process under its own uid. Therefore, either
36146 &%check_local_user%& must be set (as above), in which case the filter is run as
36147 the local user, or the &%user%& option must be used to specify which user to
36148 use. If both are set, &%user%& overrides.
36150 Care should be taken to ensure that none of the commands in the filter file
36151 specify a significant delivery if the message is to go on to be delivered to
36152 its intended recipient. The router will not then claim to have dealt with the
36153 address, so it will be passed on to subsequent routers to be delivered in the
36155 .ecindex IIDsysfil1
36156 .ecindex IIDsysfil2
36157 .ecindex IIDsysfil3
36164 . ////////////////////////////////////////////////////////////////////////////
36165 . ////////////////////////////////////////////////////////////////////////////
36167 .chapter "Message processing" "CHAPmsgproc"
36168 .scindex IIDmesproc "message" "general processing"
36169 Exim performs various transformations on the sender and recipient addresses of
36170 all messages that it handles, and also on the messages' header lines. Some of
36171 these are optional and configurable, while others always take place. All of
36172 this processing, except rewriting as a result of routing, and the addition or
36173 removal of header lines while delivering, happens when a message is received,
36174 before it is placed on Exim's queue.
36176 Some of the automatic processing takes place by default only for
36177 &"locally-originated"& messages. This adjective is used to describe messages
36178 that are not received over TCP/IP, but instead are passed to an Exim process on
36179 its standard input. This includes the interactive &"local SMTP"& case that is
36180 set up by the &%-bs%& command line option.
36182 &*Note*&: Messages received over TCP/IP on the loopback interface (127.0.0.1
36183 or ::1) are not considered to be locally-originated. Exim does not treat the
36184 loopback interface specially in any way.
36186 If you want the loopback interface to be treated specially, you must ensure
36187 that there are appropriate entries in your ACLs.
36192 .section "Submission mode for non-local messages" "SECTsubmodnon"
36193 .cindex "message" "submission"
36194 .cindex "submission mode"
36195 Processing that happens automatically for locally-originated messages (unless
36196 &%suppress_local_fixups%& is set) can also be requested for messages that are
36197 received over TCP/IP. The term &"submission mode"& is used to describe this
36198 state. Submission mode is set by the modifier
36200 control = submission
36202 in a MAIL, RCPT, or pre-data ACL for an incoming message (see sections
36203 &<<SECTACLmodi>>& and &<<SECTcontrols>>&). This makes Exim treat the message as
36204 a local submission, and is normally used when the source of the message is
36205 known to be an MUA running on a client host (as opposed to an MTA). For
36206 example, to set submission mode for messages originating on the IPv4 loopback
36207 interface, you could include the following in the MAIL ACL:
36209 warn hosts = 127.0.0.1
36210 control = submission
36212 .cindex "&%sender_retain%& submission option"
36213 There are some options that can be used when setting submission mode. A slash
36214 is used to separate options. For example:
36216 control = submission/sender_retain
36218 Specifying &%sender_retain%& has the effect of setting &%local_sender_retain%&
36219 true and &%local_from_check%& false for the current incoming message. The first
36220 of these allows an existing &'Sender:'& header in the message to remain, and
36221 the second suppresses the check to ensure that &'From:'& matches the
36222 authenticated sender. With this setting, Exim still fixes up messages by adding
36223 &'Date:'& and &'Message-ID:'& header lines if they are missing, but makes no
36224 attempt to check sender authenticity in header lines.
36226 When &%sender_retain%& is not set, a submission mode setting may specify a
36227 domain to be used when generating a &'From:'& or &'Sender:'& header line. For
36230 control = submission/domain=some.domain
36232 The domain may be empty. How this value is used is described in sections
36233 &<<SECTthefrohea>>& and &<<SECTthesenhea>>&. There is also a &%name%& option
36234 that allows you to specify the user's full name for inclusion in a created
36235 &'Sender:'& or &'From:'& header line. For example:
36237 accept authenticated = *
36238 control = submission/domain=wonderland.example/\
36239 name=${lookup {$authenticated_id} \
36240 lsearch {/etc/exim/namelist}}
36242 Because the name may contain any characters, including slashes, the &%name%&
36243 option must be given last. The remainder of the string is used as the name. For
36244 the example above, if &_/etc/exim/namelist_& contains:
36246 bigegg: Humpty Dumpty
36248 then when the sender has authenticated as &'bigegg'&, the generated &'Sender:'&
36251 Sender: Humpty Dumpty <bigegg@wonderland.example>
36253 .cindex "return path" "in submission mode"
36254 By default, submission mode forces the return path to the same address as is
36255 used to create the &'Sender:'& header. However, if &%sender_retain%& is
36256 specified, the return path is also left unchanged.
36258 &*Note*&: The changes caused by submission mode take effect after the predata
36259 ACL. This means that any sender checks performed before the fix-ups use the
36260 untrusted sender address specified by the user, not the trusted sender address
36261 specified by submission mode. Although this might be slightly unexpected, it
36262 does mean that you can configure ACL checks to spot that a user is trying to
36263 spoof another's address.
36265 .section "Line endings" "SECTlineendings"
36266 .cindex "line endings"
36267 .cindex "carriage return"
36269 RFC 2821 specifies that CRLF (two characters: carriage-return, followed by
36270 linefeed) is the line ending for messages transmitted over the Internet using
36271 SMTP over TCP/IP. However, within individual operating systems, different
36272 conventions are used. For example, Unix-like systems use just LF, but others
36273 use CRLF or just CR.
36275 Exim was designed for Unix-like systems, and internally, it stores messages
36276 using the system's convention of a single LF as a line terminator. When
36277 receiving a message, all line endings are translated to this standard format.
36278 Originally, it was thought that programs that passed messages directly to an
36279 MTA within an operating system would use that system's convention. Experience
36280 has shown that this is not the case; for example, there are Unix applications
36281 that use CRLF in this circumstance. For this reason, and for compatibility with
36282 other MTAs, the way Exim handles line endings for all messages is now as
36286 LF not preceded by CR is treated as a line ending.
36288 CR is treated as a line ending; if it is immediately followed by LF, the LF
36291 The sequence &"CR, dot, CR"& does not terminate an incoming SMTP message,
36292 nor a local message in the state where a line containing only a dot is a
36295 If a bare CR is encountered within a header line, an extra space is added after
36296 the line terminator so as not to end the header line. The reasoning behind this
36297 is that bare CRs in header lines are most likely either to be mistakes, or
36298 people trying to play silly games.
36300 If the first header line received in a message ends with CRLF, a subsequent
36301 bare LF in a header line is treated in the same way as a bare CR in a header
36309 .section "Unqualified addresses" "SECID218"
36310 .cindex "unqualified addresses"
36311 .cindex "address" "qualification"
36312 By default, Exim expects every envelope address it receives from an external
36313 host to be fully qualified. Unqualified addresses cause negative responses to
36314 SMTP commands. However, because SMTP is used as a means of transporting
36315 messages from MUAs running on personal workstations, there is sometimes a
36316 requirement to accept unqualified addresses from specific hosts or IP networks.
36318 Exim has two options that separately control which hosts may send unqualified
36319 sender or recipient addresses in SMTP commands, namely
36320 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&. In both
36321 cases, if an unqualified address is accepted, it is qualified by adding the
36322 value of &%qualify_domain%& or &%qualify_recipient%&, as appropriate.
36324 .oindex "&%qualify_domain%&"
36325 .oindex "&%qualify_recipient%&"
36326 Unqualified addresses in header lines are automatically qualified for messages
36327 that are locally originated, unless the &%-bnq%& option is given on the command
36328 line. For messages received over SMTP, unqualified addresses in header lines
36329 are qualified only if unqualified addresses are permitted in SMTP commands. In
36330 other words, such qualification is also controlled by
36331 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&,
36336 .section "The UUCP From line" "SECID219"
36337 .cindex "&""From""& line"
36338 .cindex "UUCP" "&""From""& line"
36339 .cindex "sender" "address"
36340 .oindex "&%uucp_from_pattern%&"
36341 .oindex "&%uucp_from_sender%&"
36342 .cindex "envelope from"
36343 .cindex "envelope sender"
36344 .cindex "Sendmail compatibility" "&""From""& line"
36345 Messages that have come from UUCP (and some other applications) often begin
36346 with a line containing the envelope sender and a timestamp, following the word
36347 &"From"&. Examples of two common formats are:
36349 From a.oakley@berlin.mus Fri Jan 5 12:35 GMT 1996
36350 From f.butler@berlin.mus Fri, 7 Jan 97 14:00:00 GMT
36352 This line precedes the RFC 2822 header lines. For compatibility with Sendmail,
36353 Exim recognizes such lines at the start of messages that are submitted to it
36354 via the command line (that is, on the standard input). It does not recognize
36355 such lines in incoming SMTP messages, unless the sending host matches
36356 &%ignore_fromline_hosts%& or the &%-bs%& option was used for a local message
36357 and &%ignore_fromline_local%& is set. The recognition is controlled by a
36358 regular expression that is defined by the &%uucp_from_pattern%& option, whose
36359 default value matches the two common cases shown above and puts the address
36360 that follows &"From"& into &$1$&.
36362 .cindex "numerical variables (&$1$& &$2$& etc)" "in &""From ""& line handling"
36363 When the caller of Exim for a non-SMTP message that contains a &"From"& line is
36364 a trusted user, the message's sender address is constructed by expanding the
36365 contents of &%uucp_sender_address%&, whose default value is &"$1"&. This is
36366 then parsed as an RFC 2822 address. If there is no domain, the local part is
36367 qualified with &%qualify_domain%& unless it is the empty string. However, if
36368 the command line &%-f%& option is used, it overrides the &"From"& line.
36370 If the caller of Exim is not trusted, the &"From"& line is recognized, but the
36371 sender address is not changed. This is also the case for incoming SMTP messages
36372 that are permitted to contain &"From"& lines.
36374 Only one &"From"& line is recognized. If there is more than one, the second is
36375 treated as a data line that starts the body of the message, as it is not valid
36376 as a header line. This also happens if a &"From"& line is present in an
36377 incoming SMTP message from a source that is not permitted to send them.
36381 .section "Resent- header lines" "SECID220"
36383 RFC 2822 makes provision for sets of header lines starting with the string
36384 &`Resent-`& to be added to a message when it is resent by the original
36385 recipient to somebody else. These headers are &'Resent-Date:'&,
36386 &'Resent-From:'&, &'Resent-Sender:'&, &'Resent-To:'&, &'Resent-Cc:'&,
36387 &'Resent-Bcc:'& and &'Resent-Message-ID:'&. The RFC says:
36390 &'Resent fields are strictly informational. They MUST NOT be used in the normal
36391 processing of replies or other such automatic actions on messages.'&
36394 This leaves things a bit vague as far as other processing actions such as
36395 address rewriting are concerned. Exim treats &%Resent-%& header lines as
36399 A &'Resent-From:'& line that just contains the login id of the submitting user
36400 is automatically rewritten in the same way as &'From:'& (see below).
36402 If there's a rewriting rule for a particular header line, it is also applied to
36403 &%Resent-%& header lines of the same type. For example, a rule that rewrites
36404 &'From:'& also rewrites &'Resent-From:'&.
36406 For local messages, if &'Sender:'& is removed on input, &'Resent-Sender:'& is
36409 For a locally-submitted message,
36410 if there are any &%Resent-%& header lines but no &'Resent-Date:'&,
36411 &'Resent-From:'&, or &'Resent-Message-Id:'&, they are added as necessary. It is
36412 the contents of &'Resent-Message-Id:'& (rather than &'Message-Id:'&) which are
36413 included in log lines in this case.
36415 The logic for adding &'Sender:'& is duplicated for &'Resent-Sender:'& when any
36416 &%Resent-%& header lines are present.
36422 .section "The Auto-Submitted: header line" "SECID221"
36423 Whenever Exim generates an autoreply, a bounce, or a delay warning message, it
36424 includes the header line:
36426 Auto-Submitted: auto-replied
36429 .section "The Bcc: header line" "SECID222"
36430 .cindex "&'Bcc:'& header line"
36431 If Exim is called with the &%-t%& option, to take recipient addresses from a
36432 message's header, it removes any &'Bcc:'& header line that may exist (after
36433 extracting its addresses). If &%-t%& is not present on the command line, any
36434 existing &'Bcc:'& is not removed.
36437 .section "The Date: header line" "SECID223"
36439 If a locally-generated or submission-mode message has no &'Date:'& header line,
36440 Exim adds one, using the current date and time, unless the
36441 &%suppress_local_fixups%& control has been specified.
36443 .section "The Delivery-date: header line" "SECID224"
36444 .cindex "&'Delivery-date:'& header line"
36445 .oindex "&%delivery_date_remove%&"
36446 &'Delivery-date:'& header lines are not part of the standard RFC 2822 header
36447 set. Exim can be configured to add them to the final delivery of messages. (See
36448 the generic &%delivery_date_add%& transport option.) They should not be present
36449 in messages in transit. If the &%delivery_date_remove%& configuration option is
36450 set (the default), Exim removes &'Delivery-date:'& header lines from incoming
36454 .section "The Envelope-to: header line" "SECID225"
36455 .chindex Envelope-to:
36456 .oindex "&%envelope_to_remove%&"
36457 &'Envelope-to:'& header lines are not part of the standard RFC 2822 header set.
36458 Exim can be configured to add them to the final delivery of messages. (See the
36459 generic &%envelope_to_add%& transport option.) They should not be present in
36460 messages in transit. If the &%envelope_to_remove%& configuration option is set
36461 (the default), Exim removes &'Envelope-to:'& header lines from incoming
36465 .section "The From: header line" "SECTthefrohea"
36467 .cindex "Sendmail compatibility" "&""From""& line"
36468 .cindex "message" "submission"
36469 .cindex "submission mode"
36470 If a submission-mode message does not contain a &'From:'& header line, Exim
36471 adds one if either of the following conditions is true:
36474 The envelope sender address is not empty (that is, this is not a bounce
36475 message). The added header line copies the envelope sender address.
36477 .vindex "&$authenticated_id$&"
36478 The SMTP session is authenticated and &$authenticated_id$& is not empty.
36480 .vindex "&$qualify_domain$&"
36481 If no domain is specified by the submission control, the local part is
36482 &$authenticated_id$& and the domain is &$qualify_domain$&.
36484 If a non-empty domain is specified by the submission control, the local
36485 part is &$authenticated_id$&, and the domain is the specified domain.
36487 If an empty domain is specified by the submission control,
36488 &$authenticated_id$& is assumed to be the complete address.
36492 A non-empty envelope sender takes precedence.
36494 If a locally-generated incoming message does not contain a &'From:'& header
36495 line, and the &%suppress_local_fixups%& control is not set, Exim adds one
36496 containing the sender's address. The calling user's login name and full name
36497 are used to construct the address, as described in section &<<SECTconstr>>&.
36498 They are obtained from the password data by calling &[getpwuid()]& (but see the
36499 &%unknown_login%& configuration option). The address is qualified with
36500 &%qualify_domain%&.
36502 For compatibility with Sendmail, if an incoming, non-SMTP message has a
36503 &'From:'& header line containing just the unqualified login name of the calling
36504 user, this is replaced by an address containing the user's login name and full
36505 name as described in section &<<SECTconstr>>&.
36508 .section "The Message-ID: header line" "SECID226"
36509 .chindex Message-ID:
36510 .cindex "message" "submission"
36511 .oindex "&%message_id_header_text%&"
36512 If a locally-generated or submission-mode incoming message does not contain a
36513 &'Message-ID:'& or &'Resent-Message-ID:'& header line, and the
36514 &%suppress_local_fixups%& control is not set, Exim adds a suitable header line
36515 to the message. If there are any &'Resent-:'& headers in the message, it
36516 creates &'Resent-Message-ID:'&. The id is constructed from Exim's internal
36517 message id, preceded by the letter E to ensure it starts with a letter, and
36518 followed by @ and the primary host name. Additional information can be included
36519 in this header line by setting the &%message_id_header_text%& and/or
36520 &%message_id_header_domain%& options.
36523 .section "The Received: header line" "SECID227"
36525 A &'Received:'& header line is added at the start of every message. The
36526 contents are defined by the &%received_header_text%& configuration option, and
36527 Exim automatically adds a semicolon and a timestamp to the configured string.
36529 The &'Received:'& header is generated as soon as the message's header lines
36530 have been received. At this stage, the timestamp in the &'Received:'& header
36531 line is the time that the message started to be received. This is the value
36532 that is seen by the DATA ACL and by the &[local_scan()]& function.
36534 Once a message is accepted, the timestamp in the &'Received:'& header line is
36535 changed to the time of acceptance, which is (apart from a small delay while the
36536 -H spool file is written) the earliest time at which delivery could start.
36539 .section "The References: header line" "SECID228"
36540 .chindex References:
36541 Messages created by the &(autoreply)& transport include a &'References:'&
36542 header line. This is constructed according to the rules that are described in
36543 section 3.64 of RFC 2822 (which states that replies should contain such a
36544 header line), and section 3.14 of RFC 3834 (which states that automatic
36545 responses are not different in this respect). However, because some mail
36546 processing software does not cope well with very long header lines, no more
36547 than 12 message IDs are copied from the &'References:'& header line in the
36548 incoming message. If there are more than 12, the first one and then the final
36549 11 are copied, before adding the message ID of the incoming message.
36553 .section "The Return-path: header line" "SECID229"
36554 .chindex Return-path:
36555 .oindex "&%return_path_remove%&"
36556 &'Return-path:'& header lines are defined as something an MTA may insert when
36557 it does the final delivery of messages. (See the generic &%return_path_add%&
36558 transport option.) Therefore, they should not be present in messages in
36559 transit. If the &%return_path_remove%& configuration option is set (the
36560 default), Exim removes &'Return-path:'& header lines from incoming messages.
36564 .section "The Sender: header line" "SECTthesenhea"
36565 .cindex "&'Sender:'& header line"
36566 .cindex "message" "submission"
36568 For a locally-originated message from an untrusted user, Exim may remove an
36569 existing &'Sender:'& header line, and it may add a new one. You can modify
36570 these actions by setting the &%local_sender_retain%& option true, the
36571 &%local_from_check%& option false, or by using the &%suppress_local_fixups%&
36574 When a local message is received from an untrusted user and
36575 &%local_from_check%& is true (the default), and the &%suppress_local_fixups%&
36576 control has not been set, a check is made to see if the address given in the
36577 &'From:'& header line is the correct (local) sender of the message. The address
36578 that is expected has the login name as the local part and the value of
36579 &%qualify_domain%& as the domain. Prefixes and suffixes for the local part can
36580 be permitted by setting &%local_from_prefix%& and &%local_from_suffix%&
36581 appropriately. If &'From:'& does not contain the correct sender, a &'Sender:'&
36582 line is added to the message.
36584 If you set &%local_from_check%& false, this checking does not occur. However,
36585 the removal of an existing &'Sender:'& line still happens, unless you also set
36586 &%local_sender_retain%& to be true. It is not possible to set both of these
36587 options true at the same time.
36589 .cindex "submission mode"
36590 By default, no processing of &'Sender:'& header lines is done for messages
36591 received over TCP/IP or for messages submitted by trusted users. However, when
36592 a message is received over TCP/IP in submission mode, and &%sender_retain%& is
36593 not specified on the submission control, the following processing takes place:
36595 .vindex "&$authenticated_id$&"
36596 First, any existing &'Sender:'& lines are removed. Then, if the SMTP session is
36597 authenticated, and &$authenticated_id$& is not empty, a sender address is
36598 created as follows:
36601 .vindex "&$qualify_domain$&"
36602 If no domain is specified by the submission control, the local part is
36603 &$authenticated_id$& and the domain is &$qualify_domain$&.
36605 If a non-empty domain is specified by the submission control, the local part
36606 is &$authenticated_id$&, and the domain is the specified domain.
36608 If an empty domain is specified by the submission control,
36609 &$authenticated_id$& is assumed to be the complete address.
36612 This address is compared with the address in the &'From:'& header line. If they
36613 are different, a &'Sender:'& header line containing the created address is
36614 added. Prefixes and suffixes for the local part in &'From:'& can be permitted
36615 by setting &%local_from_prefix%& and &%local_from_suffix%& appropriately.
36617 .cindex "return path" "created from &'Sender:'&"
36618 &*Note*&: Whenever a &'Sender:'& header line is created, the return path for
36619 the message (the envelope sender address) is changed to be the same address,
36620 except in the case of submission mode when &%sender_retain%& is specified.
36624 .section "Adding and removing header lines in routers and transports" &&&
36625 "SECTheadersaddrem"
36626 .cindex "header lines" "adding; in router or transport"
36627 .cindex "header lines" "removing; in router or transport"
36628 When a message is delivered, the addition and removal of header lines can be
36629 specified in a system filter, or on any of the routers and transports that
36630 process the message. Section &<<SECTaddremheasys>>& contains details about
36631 modifying headers in a system filter. Header lines can also be added in an ACL
36632 as a message is received (see section &<<SECTaddheadacl>>&).
36634 In contrast to what happens in a system filter, header modifications that are
36635 specified on routers and transports apply only to the particular recipient
36636 addresses that are being processed by those routers and transports. These
36637 changes do not actually take place until a copy of the message is being
36638 transported. Therefore, they do not affect the basic set of header lines, and
36639 they do not affect the values of the variables that refer to header lines.
36641 &*Note*&: In particular, this means that any expansions in the configuration of
36642 the transport cannot refer to the modified header lines, because such
36643 expansions all occur before the message is actually transported.
36645 For both routers and transports, the argument of a &%headers_add%&
36646 option must be in the form of one or more RFC 2822 header lines, separated by
36647 newlines (coded as &"\n"&). For example:
36649 headers_add = X-added-header: added by $primary_hostname\n\
36650 X-added-second: another added header line
36652 Exim does not check the syntax of these added header lines.
36654 Multiple &%headers_add%& options for a single router or transport can be
36655 specified; the values will append to a single list of header lines.
36656 Each header-line is separately expanded.
36658 The argument of a &%headers_remove%& option must consist of a colon-separated
36659 list of header names. This is confusing, because header names themselves are
36660 often terminated by colons. In this case, the colons are the list separators,
36661 not part of the names. For example:
36663 headers_remove = return-receipt-to:acknowledge-to
36666 Multiple &%headers_remove%& options for a single router or transport can be
36667 specified; the arguments will append to a single header-names list.
36668 Each item is separately expanded.
36669 Note that colons in complex expansions which are used to
36670 form all or part of a &%headers_remove%& list
36671 will act as list separators.
36673 When &%headers_add%& or &%headers_remove%& is specified on a router,
36674 items are expanded at routing time,
36675 and then associated with all addresses that are
36676 accepted by that router, and also with any new addresses that it generates. If
36677 an address passes through several routers as a result of aliasing or
36678 forwarding, the changes are cumulative.
36680 .oindex "&%unseen%&"
36681 However, this does not apply to multiple routers that result from the use of
36682 the &%unseen%& option. Any header modifications that were specified by the
36683 &"unseen"& router or its predecessors apply only to the &"unseen"& delivery.
36685 Addresses that end up with different &%headers_add%& or &%headers_remove%&
36686 settings cannot be delivered together in a batch, so a transport is always
36687 dealing with a set of addresses that have the same header-processing
36690 The transport starts by writing the original set of header lines that arrived
36691 with the message, possibly modified by the system filter. As it writes out
36692 these lines, it consults the list of header names that were attached to the
36693 recipient address(es) by &%headers_remove%& options in routers, and it also
36694 consults the transport's own &%headers_remove%& option. Header lines whose
36695 names are on either of these lists are not written out. If there are multiple
36696 instances of any listed header, they are all skipped.
36698 After the remaining original header lines have been written, new header
36699 lines that were specified by routers' &%headers_add%& options are written, in
36700 the order in which they were attached to the address. These are followed by any
36701 header lines specified by the transport's &%headers_add%& option.
36703 This way of handling header line modifications in routers and transports has
36704 the following consequences:
36707 The original set of header lines, possibly modified by the system filter,
36708 remains &"visible"&, in the sense that the &$header_$&&'xxx'& variables refer
36709 to it, at all times.
36711 Header lines that are added by a router's
36712 &%headers_add%& option are not accessible by means of the &$header_$&&'xxx'&
36713 expansion syntax in subsequent routers or the transport.
36715 Conversely, header lines that are specified for removal by &%headers_remove%&
36716 in a router remain visible to subsequent routers and the transport.
36718 Headers added to an address by &%headers_add%& in a router cannot be removed by
36719 a later router or by a transport.
36721 An added header can refer to the contents of an original header that is to be
36722 removed, even it has the same name as the added header. For example:
36724 headers_remove = subject
36725 headers_add = Subject: new subject (was: $h_subject:)
36729 &*Warning*&: The &%headers_add%& and &%headers_remove%& options cannot be used
36730 for a &(redirect)& router that has the &%one_time%& option set.
36736 .section "Constructed addresses" "SECTconstr"
36737 .cindex "address" "constructed"
36738 .cindex "constructed address"
36739 When Exim constructs a sender address for a locally-generated message, it uses
36742 <&'user name'&>&~&~<&'login'&&`@`&&'qualify_domain'&>
36746 Zaphod Beeblebrox <zaphod@end.univ.example>
36748 The user name is obtained from the &%-F%& command line option if set, or
36749 otherwise by looking up the calling user by &[getpwuid()]& and extracting the
36750 &"gecos"& field from the password entry. If the &"gecos"& field contains an
36751 ampersand character, this is replaced by the login name with the first letter
36752 upper cased, as is conventional in a number of operating systems. See the
36753 &%gecos_name%& option for a way to tailor the handling of the &"gecos"& field.
36754 The &%unknown_username%& option can be used to specify user names in cases when
36755 there is no password file entry.
36758 In all cases, the user name is made to conform to RFC 2822 by quoting all or
36759 parts of it if necessary. In addition, if it contains any non-printing
36760 characters, it is encoded as described in RFC 2047, which defines a way of
36761 including non-ASCII characters in header lines. The value of the
36762 &%headers_charset%& option specifies the name of the encoding that is used (the
36763 characters are assumed to be in this encoding). The setting of
36764 &%print_topbitchars%& controls whether characters with the top bit set (that
36765 is, with codes greater than 127) count as printing characters or not.
36769 .section "Case of local parts" "SECID230"
36770 .cindex "case of local parts"
36771 .cindex "local part" "case of"
36772 RFC 2822 states that the case of letters in the local parts of addresses cannot
36773 be assumed to be non-significant. Exim preserves the case of local parts of
36774 addresses, but by default it uses a lower-cased form when it is routing,
36775 because on most Unix systems, usernames are in lower case and case-insensitive
36776 routing is required. However, any particular router can be made to use the
36777 original case for local parts by setting the &%caseful_local_part%& generic
36780 .cindex "mixed-case login names"
36781 If you must have mixed-case user names on your system, the best way to proceed,
36782 assuming you want case-independent handling of incoming email, is to set up
36783 your first router to convert incoming local parts in your domains to the
36784 correct case by means of a file lookup. For example:
36788 domains = +local_domains
36789 data = ${lookup{$local_part}cdb\
36790 {/etc/usercased.cdb}{$value}fail}\
36793 For this router, the local part is forced to lower case by the default action
36794 (&%caseful_local_part%& is not set). The lower-cased local part is used to look
36795 up a new local part in the correct case. If you then set &%caseful_local_part%&
36796 on any subsequent routers which process your domains, they will operate on
36797 local parts with the correct case in a case-sensitive manner.
36801 .section "Dots in local parts" "SECID231"
36802 .cindex "dot" "in local part"
36803 .cindex "local part" "dots in"
36804 RFC 2822 forbids empty components in local parts. That is, an unquoted local
36805 part may not begin or end with a dot, nor have two consecutive dots in the
36806 middle. However, it seems that many MTAs do not enforce this, so Exim permits
36807 empty components for compatibility.
36811 .section "Rewriting addresses" "SECID232"
36812 .cindex "rewriting" "addresses"
36813 Rewriting of sender and recipient addresses, and addresses in headers, can
36814 happen automatically, or as the result of configuration options, as described
36815 in chapter &<<CHAPrewrite>>&. The headers that may be affected by this are
36816 &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-To:'&, &'Sender:'&, and &'To:'&.
36818 Automatic rewriting includes qualification, as mentioned above. The other case
36819 in which it can happen is when an incomplete non-local domain is given. The
36820 routing process may cause this to be expanded into the full domain name. For
36821 example, a header such as
36825 might get rewritten as
36827 To: hare@teaparty.wonderland.fict.example
36829 Rewriting as a result of routing is the one kind of message processing that
36830 does not happen at input time, as it cannot be done until the address has
36833 Strictly, one should not do &'any'& deliveries of a message until all its
36834 addresses have been routed, in case any of the headers get changed as a
36835 result of routing. However, doing this in practice would hold up many
36836 deliveries for unreasonable amounts of time, just because one address could not
36837 immediately be routed. Exim therefore does not delay other deliveries when
36838 routing of one or more addresses is deferred.
36839 .ecindex IIDmesproc
36843 . ////////////////////////////////////////////////////////////////////////////
36844 . ////////////////////////////////////////////////////////////////////////////
36846 .chapter "SMTP processing" "CHAPSMTP"
36847 .scindex IIDsmtpproc1 "SMTP" "processing details"
36848 .scindex IIDsmtpproc2 "LMTP" "processing details"
36849 Exim supports a number of different ways of using the SMTP protocol, and its
36850 LMTP variant, which is an interactive protocol for transferring messages into a
36851 closed mail store application. This chapter contains details of how SMTP is
36852 processed. For incoming mail, the following are available:
36855 SMTP over TCP/IP (Exim daemon or &'inetd'&);
36857 SMTP over the standard input and output (the &%-bs%& option);
36859 Batched SMTP on the standard input (the &%-bS%& option).
36862 For mail delivery, the following are available:
36865 SMTP over TCP/IP (the &(smtp)& transport);
36867 LMTP over TCP/IP (the &(smtp)& transport with the &%protocol%& option set to
36870 LMTP over a pipe to a process running in the local host (the &(lmtp)&
36873 Batched SMTP to a file or pipe (the &(appendfile)& and &(pipe)& transports with
36874 the &%use_bsmtp%& option set).
36877 &'Batched SMTP'& is the name for a process in which batches of messages are
36878 stored in or read from files (or pipes), in a format in which SMTP commands are
36879 used to contain the envelope information.
36883 .section "Outgoing SMTP and LMTP over TCP/IP" "SECToutSMTPTCP"
36884 .cindex "SMTP" "outgoing over TCP/IP"
36885 .cindex "outgoing SMTP over TCP/IP"
36886 .cindex "LMTP" "over TCP/IP"
36887 .cindex "outgoing LMTP over TCP/IP"
36890 .cindex "SIZE" "option on MAIL command"
36891 Outgoing SMTP and LMTP over TCP/IP is implemented by the &(smtp)& transport.
36892 The &%protocol%& option selects which protocol is to be used, but the actual
36893 processing is the same in both cases.
36895 .cindex "ESMTP extensions" SIZE
36896 If, in response to its EHLO command, Exim is told that the SIZE
36897 extension is supported, it adds SIZE=<&'n'&> to each subsequent MAIL
36898 command. The value of <&'n'&> is the message size plus the value of the
36899 &%size_addition%& option (default 1024) to allow for additions to the message
36900 such as per-transport header lines, or changes made in a
36901 .cindex "transport" "filter"
36902 .cindex "filter" "transport filter"
36903 transport filter. If &%size_addition%& is set negative, the use of SIZE is
36906 If the remote server advertises support for PIPELINING, Exim uses the
36907 pipelining extension to SMTP (RFC 2197) to reduce the number of TCP/IP packets
36908 required for the transaction.
36910 If the remote server advertises support for the STARTTLS command, and Exim
36911 was built to support TLS encryption, it tries to start a TLS session unless the
36912 server matches &%hosts_avoid_tls%&. See chapter &<<CHAPTLS>>& for more details.
36913 Either a match in that or &%hosts_verify_avoid_tls%& apply when the transport
36914 is called for verification.
36916 If the remote server advertises support for the AUTH command, Exim scans
36917 the authenticators configuration for any suitable client settings, as described
36918 in chapter &<<CHAPSMTPAUTH>>&.
36920 .cindex "carriage return"
36922 Responses from the remote host are supposed to be terminated by CR followed by
36923 LF. However, there are known to be hosts that do not send CR characters, so in
36924 order to be able to interwork with such hosts, Exim treats LF on its own as a
36927 If a message contains a number of different addresses, all those with the same
36928 characteristics (for example, the same envelope sender) that resolve to the
36929 same set of hosts, in the same order, are sent in a single SMTP transaction,
36930 even if they are for different domains, unless there are more than the setting
36931 of the &%max_rcpt%&s option in the &(smtp)& transport allows, in which case
36932 they are split into groups containing no more than &%max_rcpt%&s addresses
36933 each. If &%remote_max_parallel%& is greater than one, such groups may be sent
36934 in parallel sessions. The order of hosts with identical MX values is not
36935 significant when checking whether addresses can be batched in this way.
36937 When the &(smtp)& transport suffers a temporary failure that is not
36938 message-related, Exim updates its transport-specific database, which contains
36939 records indexed by host name that remember which messages are waiting for each
36940 particular host. It also updates the retry database with new retry times.
36942 .cindex "hints database" "retry keys"
36943 Exim's retry hints are based on host name plus IP address, so if one address of
36944 a multi-homed host is broken, it will soon be skipped most of the time.
36945 See the next section for more detail about error handling.
36947 .cindex "SMTP" "passed connection"
36948 .cindex "SMTP" "batching over TCP/IP"
36949 When a message is successfully delivered over a TCP/IP SMTP connection, Exim
36950 looks in the hints database for the transport to see if there are any queued
36951 messages waiting for the host to which it is connected. If it finds one, it
36952 creates a new Exim process using the &%-MC%& option (which can only be used by
36953 a process running as root or the Exim user) and passes the TCP/IP socket to it
36954 so that it can deliver another message using the same socket. The new process
36955 does only those deliveries that are routed to the connected host, and may in
36956 turn pass the socket on to a third process, and so on.
36958 The &%connection_max_messages%& option of the &(smtp)& transport can be used to
36959 limit the number of messages sent down a single TCP/IP connection.
36961 .cindex "asterisk" "after IP address"
36962 The second and subsequent messages delivered down an existing connection are
36963 identified in the main log by the addition of an asterisk after the closing
36964 square bracket of the IP address.
36969 .section "Errors in outgoing SMTP" "SECToutSMTPerr"
36970 .cindex "error" "in outgoing SMTP"
36971 .cindex "SMTP" "errors in outgoing"
36972 .cindex "host" "error"
36973 Three different kinds of error are recognized for outgoing SMTP: host errors,
36974 message errors, and recipient errors.
36977 .vitem "&*Host errors*&"
36978 A host error is not associated with a particular message or with a
36979 particular recipient of a message. The host errors are:
36982 Connection refused or timed out,
36984 Any error response code on connection,
36986 Any error response code to EHLO or HELO,
36988 Loss of connection at any time, except after &"."&,
36990 I/O errors at any time,
36992 Timeouts during the session, other than in response to MAIL, RCPT or
36993 the &"."& at the end of the data.
36996 For a host error, a permanent error response on connection, or in response to
36997 EHLO, causes all addresses routed to the host to be failed. Any other host
36998 error causes all addresses to be deferred, and retry data to be created for the
36999 host. It is not tried again, for any message, until its retry time arrives. If
37000 the current set of addresses are not all delivered in this run (to some
37001 alternative host), the message is added to the list of those waiting for this
37002 host, so if it is still undelivered when a subsequent successful delivery is
37003 made to the host, it will be sent down the same SMTP connection.
37005 .vitem "&*Message errors*&"
37006 .cindex "message" "error"
37007 A message error is associated with a particular message when sent to a
37008 particular host, but not with a particular recipient of the message. The
37009 message errors are:
37012 Any error response code to MAIL, DATA, or the &"."& that terminates
37015 Timeout after MAIL,
37017 Timeout or loss of connection after the &"."& that terminates the data. A
37018 timeout after the DATA command itself is treated as a host error, as is loss of
37019 connection at any other time.
37022 For a message error, a permanent error response (5&'xx'&) causes all addresses
37023 to be failed, and a delivery error report to be returned to the sender. A
37024 temporary error response (4&'xx'&), or one of the timeouts, causes all
37025 addresses to be deferred. Retry data is not created for the host, but instead,
37026 a retry record for the combination of host plus message id is created. The
37027 message is not added to the list of those waiting for this host. This ensures
37028 that the failing message will not be sent to this host again until the retry
37029 time arrives. However, other messages that are routed to the host are not
37030 affected, so if it is some property of the message that is causing the error,
37031 it will not stop the delivery of other mail.
37033 If the remote host specified support for the SIZE parameter in its response
37034 to EHLO, Exim adds SIZE=&'nnn'& to the MAIL command, so an
37035 over-large message will cause a message error because the error arrives as a
37038 .vitem "&*Recipient errors*&"
37039 .cindex "recipient" "error"
37040 A recipient error is associated with a particular recipient of a message. The
37041 recipient errors are:
37044 Any error response to RCPT,
37046 Timeout after RCPT.
37049 For a recipient error, a permanent error response (5&'xx'&) causes the
37050 recipient address to be failed, and a bounce message to be returned to the
37051 sender. A temporary error response (4&'xx'&) or a timeout causes the failing
37052 address to be deferred, and routing retry data to be created for it. This is
37053 used to delay processing of the address in subsequent queue runs, until its
37054 routing retry time arrives. This applies to all messages, but because it
37055 operates only in queue runs, one attempt will be made to deliver a new message
37056 to the failing address before the delay starts to operate. This ensures that,
37057 if the failure is really related to the message rather than the recipient
37058 (&"message too big for this recipient"& is a possible example), other messages
37059 have a chance of getting delivered. If a delivery to the address does succeed,
37060 the retry information gets cleared, so all stuck messages get tried again, and
37061 the retry clock is reset.
37063 The message is not added to the list of those waiting for this host. Use of the
37064 host for other messages is unaffected, and except in the case of a timeout,
37065 other recipients are processed independently, and may be successfully delivered
37066 in the current SMTP session. After a timeout it is of course impossible to
37067 proceed with the session, so all addresses get deferred. However, those other
37068 than the one that failed do not suffer any subsequent retry delays. Therefore,
37069 if one recipient is causing trouble, the others have a chance of getting
37070 through when a subsequent delivery attempt occurs before the failing
37071 recipient's retry time.
37074 In all cases, if there are other hosts (or IP addresses) available for the
37075 current set of addresses (for example, from multiple MX records), they are
37076 tried in this run for any undelivered addresses, subject of course to their
37077 own retry data. In other words, recipient error retry data does not take effect
37078 until the next delivery attempt.
37080 Some hosts have been observed to give temporary error responses to every
37081 MAIL command at certain times (&"insufficient space"& has been seen). It
37082 would be nice if such circumstances could be recognized, and defer data for the
37083 host itself created, but this is not possible within the current Exim design.
37084 What actually happens is that retry data for every (host, message) combination
37087 The reason that timeouts after MAIL and RCPT are treated specially is that
37088 these can sometimes arise as a result of the remote host's verification
37089 procedures. Exim makes this assumption, and treats them as if a temporary error
37090 response had been received. A timeout after &"."& is treated specially because
37091 it is known that some broken implementations fail to recognize the end of the
37092 message if the last character of the last line is a binary zero. Thus, it is
37093 helpful to treat this case as a message error.
37095 Timeouts at other times are treated as host errors, assuming a problem with the
37096 host, or the connection to it. If a timeout after MAIL, RCPT,
37097 or &"."& is really a connection problem, the assumption is that at the next try
37098 the timeout is likely to occur at some other point in the dialogue, causing it
37099 then to be treated as a host error.
37101 There is experimental evidence that some MTAs drop the connection after the
37102 terminating &"."& if they do not like the contents of the message for some
37103 reason, in contravention of the RFC, which indicates that a 5&'xx'& response
37104 should be given. That is why Exim treats this case as a message rather than a
37105 host error, in order not to delay other messages to the same host.
37110 .section "Incoming SMTP messages over TCP/IP" "SECID233"
37111 .cindex "SMTP" "incoming over TCP/IP"
37112 .cindex "incoming SMTP over TCP/IP"
37115 Incoming SMTP messages can be accepted in one of two ways: by running a
37116 listening daemon, or by using &'inetd'&. In the latter case, the entry in
37117 &_/etc/inetd.conf_& should be like this:
37119 smtp stream tcp nowait exim /opt/exim/bin/exim in.exim -bs
37121 Exim distinguishes between this case and the case of a locally running user
37122 agent using the &%-bs%& option by checking whether or not the standard input is
37123 a socket. When it is, either the port must be privileged (less than 1024), or
37124 the caller must be root or the Exim user. If any other user passes a socket
37125 with an unprivileged port number, Exim prints a message on the standard error
37126 stream and exits with an error code.
37128 By default, Exim does not make a log entry when a remote host connects or
37129 disconnects (either via the daemon or &'inetd'&), unless the disconnection is
37130 unexpected. It can be made to write such log entries by setting the
37131 &%smtp_connection%& log selector.
37133 .cindex "carriage return"
37135 Commands from the remote host are supposed to be terminated by CR followed by
37136 LF. However, there are known to be hosts that do not send CR characters. In
37137 order to be able to interwork with such hosts, Exim treats LF on its own as a
37139 Furthermore, because common code is used for receiving messages from all
37140 sources, a CR on its own is also interpreted as a line terminator. However, the
37141 sequence &"CR, dot, CR"& does not terminate incoming SMTP data.
37143 .cindex "EHLO" "invalid data"
37144 .cindex "HELO" "invalid data"
37145 One area that sometimes gives rise to problems concerns the EHLO or
37146 HELO commands. Some clients send syntactically invalid versions of these
37147 commands, which Exim rejects by default. (This is nothing to do with verifying
37148 the data that is sent, so &%helo_verify_hosts%& is not relevant.) You can tell
37149 Exim not to apply a syntax check by setting &%helo_accept_junk_hosts%& to
37150 match the broken hosts that send invalid commands.
37152 .cindex "SIZE option on MAIL command"
37153 .cindex "MAIL" "SIZE option"
37154 The amount of disk space available is checked whenever SIZE is received on
37155 a MAIL command, independently of whether &%message_size_limit%& or
37156 &%check_spool_space%& is configured, unless &%smtp_check_spool_space%& is set
37157 false. A temporary error is given if there is not enough space. If
37158 &%check_spool_space%& is set, the check is for that amount of space plus the
37159 value given with SIZE, that is, it checks that the addition of the incoming
37160 message will not reduce the space below the threshold.
37162 When a message is successfully received, Exim includes the local message id in
37163 its response to the final &"."& that terminates the data. If the remote host
37164 logs this text it can help with tracing what has happened to a message.
37166 The Exim daemon can limit the number of simultaneous incoming connections it is
37167 prepared to handle (see the &%smtp_accept_max%& option). It can also limit the
37168 number of simultaneous incoming connections from a single remote host (see the
37169 &%smtp_accept_max_per_host%& option). Additional connection attempts are
37170 rejected using the SMTP temporary error code 421.
37172 The Exim daemon does not rely on the SIGCHLD signal to detect when a
37173 subprocess has finished, as this can get lost at busy times. Instead, it looks
37174 for completed subprocesses every time it wakes up. Provided there are other
37175 things happening (new incoming calls, starts of queue runs), completed
37176 processes will be noticed and tidied away. On very quiet systems you may
37177 sometimes see a &"defunct"& Exim process hanging about. This is not a problem;
37178 it will be noticed when the daemon next wakes up.
37180 When running as a daemon, Exim can reserve some SMTP slots for specific hosts,
37181 and can also be set up to reject SMTP calls from non-reserved hosts at times of
37182 high system load &-- for details see the &%smtp_accept_reserve%&,
37183 &%smtp_load_reserve%&, and &%smtp_reserve_hosts%& options. The load check
37184 applies in both the daemon and &'inetd'& cases.
37186 Exim normally starts a delivery process for each message received, though this
37187 can be varied by means of the &%-odq%& command line option and the
37188 &%queue_only%&, &%queue_only_file%&, and &%queue_only_load%& options. The
37189 number of simultaneously running delivery processes started in this way from
37190 SMTP input can be limited by the &%smtp_accept_queue%& and
37191 &%smtp_accept_queue_per_connection%& options. When either limit is reached,
37192 subsequently received messages are just put on the input queue without starting
37193 a delivery process.
37195 The controls that involve counts of incoming SMTP calls (&%smtp_accept_max%&,
37196 &%smtp_accept_queue%&, &%smtp_accept_reserve%&) are not available when Exim is
37197 started up from the &'inetd'& daemon, because in that case each connection is
37198 handled by an entirely independent Exim process. Control by load average is,
37199 however, available with &'inetd'&.
37201 Exim can be configured to verify addresses in incoming SMTP commands as they
37202 are received. See chapter &<<CHAPACL>>& for details. It can also be configured
37203 to rewrite addresses at this time &-- before any syntax checking is done. See
37204 section &<<SECTrewriteS>>&.
37206 Exim can also be configured to limit the rate at which a client host submits
37207 MAIL and RCPT commands in a single SMTP session. See the
37208 &%smtp_ratelimit_hosts%& option.
37212 .section "Unrecognized SMTP commands" "SECID234"
37213 .cindex "SMTP" "unrecognized commands"
37214 If Exim receives more than &%smtp_max_unknown_commands%& unrecognized SMTP
37215 commands during a single SMTP connection, it drops the connection after sending
37216 the error response to the last command. The default value for
37217 &%smtp_max_unknown_commands%& is 3. This is a defence against some kinds of
37218 abuse that subvert web servers into making connections to SMTP ports; in these
37219 circumstances, a number of non-SMTP lines are sent first.
37222 .section "Syntax and protocol errors in SMTP commands" "SECID235"
37223 .cindex "SMTP" "syntax errors"
37224 .cindex "SMTP" "protocol errors"
37225 A syntax error is detected if an SMTP command is recognized, but there is
37226 something syntactically wrong with its data, for example, a malformed email
37227 address in a RCPT command. Protocol errors include invalid command
37228 sequencing such as RCPT before MAIL. If Exim receives more than
37229 &%smtp_max_synprot_errors%& such commands during a single SMTP connection, it
37230 drops the connection after sending the error response to the last command. The
37231 default value for &%smtp_max_synprot_errors%& is 3. This is a defence against
37232 broken clients that loop sending bad commands (yes, it has been seen).
37236 .section "Use of non-mail SMTP commands" "SECID236"
37237 .cindex "SMTP" "non-mail commands"
37238 The &"non-mail"& SMTP commands are those other than MAIL, RCPT, and
37239 DATA. Exim counts such commands, and drops the connection if there are too
37240 many of them in a single SMTP session. This action catches some
37241 denial-of-service attempts and things like repeated failing AUTHs, or a mad
37242 client looping sending EHLO. The global option &%smtp_accept_max_nonmail%&
37243 defines what &"too many"& means. Its default value is 10.
37245 When a new message is expected, one occurrence of RSET is not counted. This
37246 allows a client to send one RSET between messages (this is not necessary,
37247 but some clients do it). Exim also allows one uncounted occurrence of HELO
37248 or EHLO, and one occurrence of STARTTLS between messages. After
37249 starting up a TLS session, another EHLO is expected, and so it too is not
37252 The first occurrence of AUTH in a connection, or immediately following
37253 STARTTLS is also not counted. Otherwise, all commands other than MAIL,
37254 RCPT, DATA, and QUIT are counted.
37256 You can control which hosts are subject to the limit set by
37257 &%smtp_accept_max_nonmail%& by setting
37258 &%smtp_accept_max_nonmail_hosts%&. The default value is &`*`&, which makes
37259 the limit apply to all hosts. This option means that you can exclude any
37260 specific badly-behaved hosts that you have to live with.
37265 .section "The VRFY and EXPN commands" "SECID237"
37266 When Exim receives a VRFY or EXPN command on a TCP/IP connection, it
37267 runs the ACL specified by &%acl_smtp_vrfy%& or &%acl_smtp_expn%& (as
37268 appropriate) in order to decide whether the command should be accepted or not.
37270 .cindex "VRFY" "processing"
37271 When no ACL is defined for VRFY, or if it rejects without
37272 setting an explicit response code, the command is accepted
37273 (with a 252 SMTP response code)
37274 in order to support awkward clients that do a VRFY before every RCPT.
37275 When VRFY is accepted, it runs exactly the same code as when Exim is
37276 called with the &%-bv%& option, and returns 250/451/550
37277 SMTP response codes.
37279 .cindex "EXPN" "processing"
37280 If no ACL for EXPN is defined, the command is rejected.
37281 When EXPN is accepted, a single-level expansion of the address is done.
37282 EXPN is treated as an &"address test"& (similar to the &%-bt%& option) rather
37283 than a verification (the &%-bv%& option). If an unqualified local part is given
37284 as the argument to EXPN, it is qualified with &%qualify_domain%&. Rejections
37285 of VRFY and EXPN commands are logged on the main and reject logs, and
37286 VRFY verification failures are logged on the main log for consistency with
37291 .section "The ETRN command" "SECTETRN"
37292 .cindex "ETRN" "processing"
37293 .cindex "ESMTP extensions" ETRN
37294 RFC 1985 describes an ESMTP command called ETRN that is designed to
37295 overcome the security problems of the TURN command (which has fallen into
37296 disuse). When Exim receives an ETRN command on a TCP/IP connection, it runs
37297 the ACL specified by &%acl_smtp_etrn%& in order to decide whether the command
37298 should be accepted or not. If no ACL is defined, the command is rejected.
37300 The ETRN command is concerned with &"releasing"& messages that are awaiting
37301 delivery to certain hosts. As Exim does not organize its message queue by host,
37302 the only form of ETRN that is supported by default is the one where the
37303 text starts with the &"#"& prefix, in which case the remainder of the text is
37304 specific to the SMTP server. A valid ETRN command causes a run of Exim with
37305 the &%-R%& option to happen, with the remainder of the ETRN text as its
37306 argument. For example,
37314 which causes a delivery attempt on all messages with undelivered addresses
37315 containing the text &"brigadoon"&. When &%smtp_etrn_serialize%& is set (the
37316 default), Exim prevents the simultaneous execution of more than one queue run
37317 for the same argument string as a result of an ETRN command. This stops
37318 a misbehaving client from starting more than one queue runner at once.
37320 .cindex "hints database" "ETRN serialization"
37321 Exim implements the serialization by means of a hints database in which a
37322 record is written whenever a process is started by ETRN, and deleted when
37323 the process completes. However, Exim does not keep the SMTP session waiting for
37324 the ETRN process to complete. Once ETRN is accepted, the client is sent
37325 a &"success"& return code. Obviously there is scope for hints records to get
37326 left lying around if there is a system or program crash. To guard against this,
37327 Exim ignores any records that are more than six hours old.
37329 .oindex "&%smtp_etrn_command%&"
37330 For more control over what ETRN does, the &%smtp_etrn_command%& option can
37331 used. This specifies a command that is run whenever ETRN is received,
37332 whatever the form of its argument. For
37335 smtp_etrn_command = /etc/etrn_command $domain \
37336 $sender_host_address
37338 .vindex "&$domain$&"
37339 The string is split up into arguments which are independently expanded. The
37340 expansion variable &$domain$& is set to the argument of the ETRN command,
37341 and no syntax checking is done on the contents of this argument. Exim does not
37342 wait for the command to complete, so its status code is not checked. Exim runs
37343 under its own uid and gid when receiving incoming SMTP, so it is not possible
37344 for it to change them before running the command.
37348 .section "Incoming local SMTP" "SECID238"
37349 .cindex "SMTP" "local incoming"
37350 Some user agents use SMTP to pass messages to their local MTA using the
37351 standard input and output, as opposed to passing the envelope on the command
37352 line and writing the message to the standard input. This is supported by the
37353 &%-bs%& option. This form of SMTP is handled in the same way as incoming
37354 messages over TCP/IP (including the use of ACLs), except that the envelope
37355 sender given in a MAIL command is ignored unless the caller is trusted. In
37356 an ACL you can detect this form of SMTP input by testing for an empty host
37357 identification. It is common to have this as the first line in the ACL that
37358 runs for RCPT commands:
37362 This accepts SMTP messages from local processes without doing any other tests.
37366 .section "Outgoing batched SMTP" "SECTbatchSMTP"
37367 .cindex "SMTP" "batched outgoing"
37368 .cindex "batched SMTP output"
37369 Both the &(appendfile)& and &(pipe)& transports can be used for handling
37370 batched SMTP. Each has an option called &%use_bsmtp%& which causes messages to
37371 be output in BSMTP format. No SMTP responses are possible for this form of
37372 delivery. All it is doing is using SMTP commands as a way of transmitting the
37373 envelope along with the message.
37375 The message is written to the file or pipe preceded by the SMTP commands
37376 MAIL and RCPT, and followed by a line containing a single dot. Lines in
37377 the message that start with a dot have an extra dot added. The SMTP command
37378 HELO is not normally used. If it is required, the &%message_prefix%& option
37379 can be used to specify it.
37381 Because &(appendfile)& and &(pipe)& are both local transports, they accept only
37382 one recipient address at a time by default. However, you can arrange for them
37383 to handle several addresses at once by setting the &%batch_max%& option. When
37384 this is done for BSMTP, messages may contain multiple RCPT commands. See
37385 chapter &<<CHAPbatching>>& for more details.
37388 When one or more addresses are routed to a BSMTP transport by a router that
37389 sets up a host list, the name of the first host on the list is available to the
37390 transport in the variable &$host$&. Here is an example of such a transport and
37395 driver = manualroute
37396 transport = smtp_appendfile
37397 route_list = domain.example batch.host.example
37401 driver = appendfile
37402 directory = /var/bsmtp/$host
37407 This causes messages addressed to &'domain.example'& to be written in BSMTP
37408 format to &_/var/bsmtp/batch.host.example_&, with only a single copy of each
37409 message (unless there are more than 1000 recipients).
37413 .section "Incoming batched SMTP" "SECTincomingbatchedSMTP"
37414 .cindex "SMTP" "batched incoming"
37415 .cindex "batched SMTP input"
37416 The &%-bS%& command line option causes Exim to accept one or more messages by
37417 reading SMTP on the standard input, but to generate no responses. If the caller
37418 is trusted, the senders in the MAIL commands are believed; otherwise the
37419 sender is always the caller of Exim. Unqualified senders and receivers are not
37420 rejected (there seems little point) but instead just get qualified. HELO
37421 and EHLO act as RSET; VRFY, EXPN, ETRN and HELP, act
37422 as NOOP; QUIT quits.
37424 Minimal policy checking is done for BSMTP input. Only the non-SMTP
37425 ACL is run in the same way as for non-SMTP local input.
37427 If an error is detected while reading a message, including a missing &"."& at
37428 the end, Exim gives up immediately. It writes details of the error to the
37429 standard output in a stylized way that the calling program should be able to
37430 make some use of automatically, for example:
37432 554 Unexpected end of file
37433 Transaction started in line 10
37434 Error detected in line 14
37436 It writes a more verbose version, for human consumption, to the standard error
37439 An error was detected while processing a file of BSMTP input.
37440 The error message was:
37442 501 '>' missing at end of address
37444 The SMTP transaction started in line 10.
37445 The error was detected in line 12.
37446 The SMTP command at fault was:
37448 rcpt to:<malformed@in.com.plete
37450 1 previous message was successfully processed.
37451 The rest of the batch was abandoned.
37453 The return code from Exim is zero only if there were no errors. It is 1 if some
37454 messages were accepted before an error was detected, and 2 if no messages were
37456 .ecindex IIDsmtpproc1
37457 .ecindex IIDsmtpproc2
37461 . ////////////////////////////////////////////////////////////////////////////
37462 . ////////////////////////////////////////////////////////////////////////////
37464 .chapter "Customizing bounce and warning messages" "CHAPemsgcust" &&&
37465 "Customizing messages"
37466 When a message fails to be delivered, or remains in the queue for more than a
37467 configured amount of time, Exim sends a message to the original sender, or
37468 to an alternative configured address. The text of these messages is built into
37469 the code of Exim, but it is possible to change it, either by adding a single
37470 string, or by replacing each of the paragraphs by text supplied in a file.
37472 The &'From:'& and &'To:'& header lines are automatically generated; you can
37473 cause a &'Reply-To:'& line to be added by setting the &%errors_reply_to%&
37474 option. Exim also adds the line
37476 Auto-Submitted: auto-generated
37478 to all warning and bounce messages,
37481 .section "Customizing bounce messages" "SECID239"
37482 .cindex "customizing" "bounce message"
37483 .cindex "bounce message" "customizing"
37484 If &%bounce_message_text%& is set, its contents are included in the default
37485 message immediately after &"This message was created automatically by mail
37486 delivery software."& The string is not expanded. It is not used if
37487 &%bounce_message_file%& is set.
37489 When &%bounce_message_file%& is set, it must point to a template file for
37490 constructing error messages. The file consists of a series of text items,
37491 separated by lines consisting of exactly four asterisks. If the file cannot be
37492 opened, default text is used and a message is written to the main and panic
37493 logs. If any text item in the file is empty, default text is used for that
37496 .vindex "&$bounce_recipient$&"
37497 .vindex "&$bounce_return_size_limit$&"
37498 Each item of text that is read from the file is expanded, and there are two
37499 expansion variables which can be of use here: &$bounce_recipient$& is set to
37500 the recipient of an error message while it is being created, and
37501 &$bounce_return_size_limit$& contains the value of the &%return_size_limit%&
37502 option, rounded to a whole number.
37504 The items must appear in the file in the following order:
37507 The first item is included in the headers, and should include at least a
37508 &'Subject:'& header. Exim does not check the syntax of these headers.
37510 The second item forms the start of the error message. After it, Exim lists the
37511 failing addresses with their error messages.
37513 The third item is used to introduce any text from pipe transports that is to be
37514 returned to the sender. It is omitted if there is no such text.
37516 The fourth, fifth and sixth items will be ignored and may be empty.
37517 The fields exist for back-compatibility
37520 The default state (&%bounce_message_file%& unset) is equivalent to the
37521 following file, in which the sixth item is empty. The &'Subject:'& and some
37522 other lines have been split in order to fit them on the page:
37524 Subject: Mail delivery failed
37525 ${if eq{$sender_address}{$bounce_recipient}
37526 {: returning message to sender}}
37528 This message was created automatically by mail delivery software.
37530 A message ${if eq{$sender_address}{$bounce_recipient}
37531 {that you sent }{sent by
37535 }}could not be delivered to all of its recipients.
37536 This is a permanent error. The following address(es) failed:
37538 The following text was generated during the delivery attempt(s):
37540 ------ This is a copy of the message, including all the headers.
37543 ------ The body of the message is $message_size characters long;
37545 ------ $bounce_return_size_limit or so are included here.
37548 .section "Customizing warning messages" "SECTcustwarn"
37549 .cindex "customizing" "warning message"
37550 .cindex "warning of delay" "customizing the message"
37551 The option &%warn_message_file%& can be pointed at a template file for use when
37552 warnings about message delays are created. In this case there are only three
37556 The first item is included in the headers, and should include at least a
37557 &'Subject:'& header. Exim does not check the syntax of these headers.
37559 The second item forms the start of the warning message. After it, Exim lists
37560 the delayed addresses.
37562 The third item then ends the message.
37565 The default state is equivalent to the following file, except that some lines
37566 have been split here, in order to fit them on the page:
37568 Subject: Warning: message $message_exim_id delayed
37569 $warn_message_delay
37571 This message was created automatically by mail delivery software.
37573 A message ${if eq{$sender_address}{$warn_message_recipients}
37574 {that you sent }{sent by
37578 }}has not been delivered to all of its recipients after
37579 more than $warn_message_delay in the queue on $primary_hostname.
37581 The message identifier is: $message_exim_id
37582 The subject of the message is: $h_subject
37583 The date of the message is: $h_date
37585 The following address(es) have not yet been delivered:
37587 No action is required on your part. Delivery attempts will
37588 continue for some time, and this warning may be repeated at
37589 intervals if the message remains undelivered. Eventually the
37590 mail delivery software will give up, and when that happens,
37591 the message will be returned to you.
37593 .vindex "&$warn_message_delay$&"
37594 .vindex "&$warn_message_recipients$&"
37595 However, in the default state the subject and date lines are omitted if no
37596 appropriate headers exist. During the expansion of this file,
37597 &$warn_message_delay$& is set to the delay time in one of the forms &"<&'n'&>
37598 minutes"& or &"<&'n'&> hours"&, and &$warn_message_recipients$& contains a list
37599 of recipients for the warning message. There may be more than one if there are
37600 multiple addresses with different &%errors_to%& settings on the routers that
37606 . ////////////////////////////////////////////////////////////////////////////
37607 . ////////////////////////////////////////////////////////////////////////////
37609 .chapter "Some common configuration settings" "CHAPcomconreq"
37610 This chapter discusses some configuration settings that seem to be fairly
37611 common. More examples and discussion can be found in the Exim book.
37615 .section "Sending mail to a smart host" "SECID240"
37616 .cindex "smart host" "example router"
37617 If you want to send all mail for non-local domains to a &"smart host"&, you
37618 should replace the default &(dnslookup)& router with a router which does the
37619 routing explicitly:
37621 send_to_smart_host:
37622 driver = manualroute
37623 route_list = !+local_domains smart.host.name
37624 transport = remote_smtp
37626 You can use the smart host's IP address instead of the name if you wish.
37627 If you are using Exim only to submit messages to a smart host, and not for
37628 receiving incoming messages, you can arrange for it to do the submission
37629 synchronously by setting the &%mua_wrapper%& option (see chapter
37630 &<<CHAPnonqueueing>>&).
37635 .section "Using Exim to handle mailing lists" "SECTmailinglists"
37636 .cindex "mailing lists"
37637 Exim can be used to run simple mailing lists, but for large and/or complicated
37638 requirements, the use of additional specialized mailing list software such as
37639 Majordomo or Mailman is recommended.
37641 The &(redirect)& router can be used to handle mailing lists where each list
37642 is maintained in a separate file, which can therefore be managed by an
37643 independent manager. The &%domains%& router option can be used to run these
37644 lists in a separate domain from normal mail. For example:
37648 domains = lists.example
37649 file = ${lookup {$local_part} dsearch,ret=full {/usr/lists}}
37652 errors_to = ${quote_local_part:$local_part-request}@lists.example
37655 This router is skipped for domains other than &'lists.example'&. For addresses
37656 in that domain, it looks for a file that matches the local part. If there is no
37657 such file, the router declines, but because &%no_more%& is set, no subsequent
37658 routers are tried, and so the whole delivery fails.
37660 The &%forbid_pipe%& and &%forbid_file%& options prevent a local part from being
37661 expanded into a filename or a pipe delivery, which is usually inappropriate in
37664 .oindex "&%errors_to%&"
37665 The &%errors_to%& option specifies that any delivery errors caused by addresses
37666 taken from a mailing list are to be sent to the given address rather than the
37667 original sender of the message. However, before acting on this, Exim verifies
37668 the error address, and ignores it if verification fails.
37670 For example, using the configuration above, mail sent to
37671 &'dicts@lists.example'& is passed on to those addresses contained in
37672 &_/usr/lists/dicts_&, with error reports directed to
37673 &'dicts-request@lists.example'&, provided that this address can be verified.
37674 There could be a file called &_/usr/lists/dicts-request_& containing
37675 the address(es) of this particular list's manager(s), but other approaches,
37676 such as setting up an earlier router (possibly using the &%local_part_prefix%&
37677 or &%local_part_suffix%& options) to handle addresses of the form
37678 &%owner-%&&'xxx'& or &%xxx-%&&'request'&, are also possible.
37682 .section "Syntax errors in mailing lists" "SECID241"
37683 .cindex "mailing lists" "syntax errors in"
37684 If an entry in redirection data contains a syntax error, Exim normally defers
37685 delivery of the original address. That means that a syntax error in a mailing
37686 list holds up all deliveries to the list. This may not be appropriate when a
37687 list is being maintained automatically from data supplied by users, and the
37688 addresses are not rigorously checked.
37690 If the &%skip_syntax_errors%& option is set, the &(redirect)& router just skips
37691 entries that fail to parse, noting the incident in the log. If in addition
37692 &%syntax_errors_to%& is set to a verifiable address, a message is sent to it
37693 whenever a broken address is skipped. It is usually appropriate to set
37694 &%syntax_errors_to%& to the same address as &%errors_to%&.
37698 .section "Re-expansion of mailing lists" "SECID242"
37699 .cindex "mailing lists" "re-expansion of"
37700 Exim remembers every individual address to which a message has been delivered,
37701 in order to avoid duplication, but it normally stores only the original
37702 recipient addresses with a message. If all the deliveries to a mailing list
37703 cannot be done at the first attempt, the mailing list is re-expanded when the
37704 delivery is next tried. This means that alterations to the list are taken into
37705 account at each delivery attempt, so addresses that have been added to
37706 the list since the message arrived will therefore receive a copy of the
37707 message, even though it pre-dates their subscription.
37709 If this behaviour is felt to be undesirable, the &%one_time%& option can be set
37710 on the &(redirect)& router. If this is done, any addresses generated by the
37711 router that fail to deliver at the first attempt are added to the message as
37712 &"top level"& addresses, and the parent address that generated them is marked
37713 &"delivered"&. Thus, expansion of the mailing list does not happen again at the
37714 subsequent delivery attempts. The disadvantage of this is that if any of the
37715 failing addresses are incorrect, correcting them in the file has no effect on
37716 pre-existing messages.
37718 The original top-level address is remembered with each of the generated
37719 addresses, and is output in any log messages. However, any intermediate parent
37720 addresses are not recorded. This makes a difference to the log only if the
37721 &%all_parents%& selector is set, but for mailing lists there is normally only
37722 one level of expansion anyway.
37726 .section "Closed mailing lists" "SECID243"
37727 .cindex "mailing lists" "closed"
37728 The examples so far have assumed open mailing lists, to which anybody may
37729 send mail. It is also possible to set up closed lists, where mail is accepted
37730 from specified senders only. This is done by making use of the generic
37731 &%senders%& option to restrict the router that handles the list.
37733 The following example uses the same file as a list of recipients and as a list
37734 of permitted senders. It requires three routers:
37738 domains = lists.example
37739 local_part_suffix = -request
37740 local_parts = ${lookup {$local_part} dsearch,filter=file {/usr/lists}}
37741 file = /usr/lists/${local_part_data}-request
37746 domains = lists.example
37747 local_parts = ${lookup {$local_part} dsearch,filter=file,ret=full {/usr/lists}}
37748 senders = ${if exists {$local_part_data} {lsearch;$local_part_data}{*}}
37749 file = ${lookup {$local_part} dsearch,ret=full {/usr/lists}}
37752 errors_to = ${quote_local_part:$local_part-request}@lists.example
37757 domains = lists.example
37759 data = :fail: $local_part@lists.example is a closed mailing list
37761 All three routers have the same &%domains%& setting, so for any other domains,
37762 they are all skipped. The first router runs only if the local part ends in
37763 &%-request%&. It handles messages to the list manager(s) by means of an open
37766 The second router runs only if the &%senders%& precondition is satisfied. It
37767 checks for the existence of a list that corresponds to the local part, and then
37768 checks that the sender is on the list by means of a linear search. It is
37769 necessary to check for the existence of the file before trying to search it,
37770 because otherwise Exim thinks there is a configuration error. If the file does
37771 not exist, the expansion of &%senders%& is *, which matches all senders. This
37772 means that the router runs, but because there is no list, declines, and
37773 &%no_more%& ensures that no further routers are run. The address fails with an
37774 &"unrouteable address"& error.
37776 The third router runs only if the second router is skipped, which happens when
37777 a mailing list exists, but the sender is not on it. This router forcibly fails
37778 the address, giving a suitable error message.
37783 .section "Variable Envelope Return Paths (VERP)" "SECTverp"
37785 .cindex "Variable Envelope Return Paths"
37786 .cindex "envelope from"
37787 .cindex "envelope sender"
37788 Variable Envelope Return Paths &-- see &url(https://cr.yp.to/proto/verp.txt) &--
37789 are a way of helping mailing list administrators discover which subscription
37790 address is the cause of a particular delivery failure. The idea is to encode
37791 the original recipient address in the outgoing envelope sender address, so that
37792 if the message is forwarded by another host and then subsequently bounces, the
37793 original recipient can be extracted from the recipient address of the bounce.
37795 .oindex &%errors_to%&
37796 .oindex &%return_path%&
37797 Envelope sender addresses can be modified by Exim using two different
37798 facilities: the &%errors_to%& option on a router (as shown in previous mailing
37799 list examples), or the &%return_path%& option on a transport. The second of
37800 these is effective only if the message is successfully delivered to another
37801 host; it is not used for errors detected on the local host (see the description
37802 of &%return_path%& in chapter &<<CHAPtransportgeneric>>&). Here is an example
37803 of the use of &%return_path%& to implement VERP on an &(smtp)& transport:
37809 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
37810 {${quote_local_part:$1-request+$local_part=$domain}@your.dom.example}fail}
37812 This has the effect of rewriting the return path (envelope sender) on outgoing
37813 SMTP messages, if the local part of the original return path ends in
37814 &"-request"&, and the domain is &'your.dom.example'&. The rewriting inserts the
37815 local part and domain of the recipient into the return path. Suppose, for
37816 example, that a message whose return path has been set to
37817 &'somelist-request@your.dom.example'& is sent to
37818 &'subscriber@other.dom.example'&. In the transport, the return path is
37821 somelist-request+subscriber=other.dom.example@your.dom.example
37823 .vindex "&$local_part$&"
37824 For this to work, you must tell Exim to send multiple copies of messages that
37825 have more than one recipient, so that each copy has just one recipient. This is
37826 achieved by setting &%max_rcpt%& to 1. Without this, a single copy of a message
37827 might be sent to several different recipients in the same domain, in which case
37828 &$local_part$& is not available in the transport, because it is not unique.
37830 Unless your host is doing nothing but mailing list deliveries, you should
37831 probably use a separate transport for the VERP deliveries, so as not to use
37832 extra resources in making one-per-recipient copies for other deliveries. This
37833 can easily be done by expanding the &%transport%& option in the router:
37837 domains = ! +local_domains
37839 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
37840 {verp_smtp}{remote_smtp}}
37843 If you want to change the return path using &%errors_to%& in a router instead
37844 of using &%return_path%& in the transport, you need to set &%errors_to%& on all
37845 routers that handle mailing list addresses. This will ensure that all delivery
37846 errors, including those detected on the local host, are sent to the VERP
37849 On a host that does no local deliveries and has no manual routing, only the
37850 &(dnslookup)& router needs to be changed. A special transport is not needed for
37851 SMTP deliveries. Every mailing list recipient has its own return path value,
37852 and so Exim must hand them to the transport one at a time. Here is an example
37853 of a &(dnslookup)& router that implements VERP:
37857 domains = ! +local_domains
37858 transport = remote_smtp
37860 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}}
37861 {${quote_local_part:$1-request+$local_part=$domain}@your.dom.example}fail}
37864 Before you start sending out messages with VERPed return paths, you must also
37865 configure Exim to accept the bounce messages that come back to those paths.
37866 Typically this is done by setting a &%local_part_suffix%& option for a
37867 router, and using this to route the messages to wherever you want to handle
37870 The overhead incurred in using VERP depends very much on the size of the
37871 message, the number of recipient addresses that resolve to the same remote
37872 host, and the speed of the connection over which the message is being sent. If
37873 a lot of addresses resolve to the same host and the connection is slow, sending
37874 a separate copy of the message for each address may take substantially longer
37875 than sending a single copy with many recipients (for which VERP cannot be
37883 .section "Virtual domains" "SECTvirtualdomains"
37884 .cindex "virtual domains"
37885 .cindex "domain" "virtual"
37886 The phrase &'virtual domain'& is unfortunately used with two rather different
37890 A domain for which there are no real mailboxes; all valid local parts are
37891 aliases for other email addresses. Common examples are organizational
37892 top-level domains and &"vanity"& domains.
37894 One of a number of independent domains that are all handled by the same host,
37895 with mailboxes on that host, but where the mailbox owners do not necessarily
37896 have login accounts on that host.
37899 The first usage is probably more common, and does seem more &"virtual"& than
37900 the second. This kind of domain can be handled in Exim with a straightforward
37901 aliasing router. One approach is to create a separate alias file for each
37902 virtual domain. Exim can test for the existence of the alias file to determine
37903 whether the domain exists. The &(dsearch)& lookup type is useful here, leading
37904 to a router of this form:
37908 domains = dsearch;/etc/mail/virtual
37909 data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain_data}}
37912 The &%domains%& option specifies that the router is to be skipped, unless there
37913 is a file in the &_/etc/mail/virtual_& directory whose name is the same as the
37914 domain that is being processed.
37915 The &(dsearch)& lookup used results in an untainted version of &$domain$&
37916 being placed into the &$domain_data$& variable.
37918 When the router runs, it looks up the local
37919 part in the file to find a new address (or list of addresses). The &%no_more%&
37920 setting ensures that if the lookup fails (leading to &%data%& being an empty
37921 string), Exim gives up on the address without trying any subsequent routers.
37923 This one router can handle all the virtual domains because the alias filenames
37924 follow a fixed pattern. Permissions can be arranged so that appropriate people
37925 can edit the different alias files. A successful aliasing operation results in
37926 a new envelope recipient address, which is then routed from scratch.
37928 The other kind of &"virtual"& domain can also be handled in a straightforward
37929 way. One approach is to create a file for each domain containing a list of
37930 valid local parts, and use it in a router like this:
37934 domains = dsearch;/etc/mail/domains
37935 local_parts = lsearch;/etc/mail/domains/$domain
37936 transport = my_mailboxes
37938 The address is accepted if there is a file for the domain, and the local part
37939 can be found in the file. The &%domains%& option is used to check for the
37940 file's existence because &%domains%& is tested before the &%local_parts%&
37941 option (see section &<<SECTrouprecon>>&). You cannot use &%require_files%&,
37942 because that option is tested after &%local_parts%&. The transport is as
37946 driver = appendfile
37947 file = /var/mail/$domain_data/$local_part_data
37950 This uses a directory of mailboxes for each domain. The &%user%& setting is
37951 required, to specify which uid is to be used for writing to the mailboxes.
37953 The configuration shown here is just one example of how you might support this
37954 requirement. There are many other ways this kind of configuration can be set
37955 up, for example, by using a database instead of separate files to hold all the
37956 information about the domains.
37960 .section "Multiple user mailboxes" "SECTmulbox"
37961 .cindex "multiple mailboxes"
37962 .cindex "mailbox" "multiple"
37963 .cindex "local part" "prefix"
37964 .cindex "local part" "suffix"
37965 Heavy email users often want to operate with multiple mailboxes, into which
37966 incoming mail is automatically sorted. A popular way of handling this is to
37967 allow users to use multiple sender addresses, so that replies can easily be
37968 identified. Users are permitted to add prefixes or suffixes to their local
37969 parts for this purpose. The wildcard facility of the generic router options
37970 &%local_part_prefix%& and &%local_part_suffix%& can be used for this. For
37971 example, consider this router:
37976 file = $home/.forward
37977 local_part_suffix = -*
37978 local_part_suffix_optional
37981 .vindex "&$local_part_suffix$&"
37982 It runs a user's &_.forward_& file for all local parts of the form
37983 &'username-*'&. Within the filter file the user can distinguish different
37984 cases by testing the variable &$local_part_suffix$&. For example:
37986 if $local_part_suffix contains -special then
37987 save /home/$local_part_data/Mail/special
37990 If the filter file does not exist, or does not deal with such addresses, they
37991 fall through to subsequent routers, and, assuming no subsequent use of the
37992 &%local_part_suffix%& option is made, they presumably fail. Thus, users have
37993 control over which suffixes are valid.
37995 Alternatively, a suffix can be used to trigger the use of a different
37996 &_.forward_& file &-- which is the way a similar facility is implemented in
38002 local_part_suffix = -*
38003 local_part_suffix_optional
38004 file = ${lookup {.forward$local_part_suffix} dsearch,ret=full {$home} {$value}fail}
38007 If there is no suffix, &_.forward_& is used; if the suffix is &'-special'&, for
38008 example, &_.forward-special_& is used. Once again, if the appropriate file
38009 does not exist, or does not deal with the address, it is passed on to
38010 subsequent routers, which could, if required, look for an unqualified
38011 &_.forward_& file to use as a default.
38015 .section "Simplified vacation processing" "SECID244"
38016 .cindex "vacation processing"
38017 The traditional way of running the &'vacation'& program is for a user to set up
38018 a pipe command in a &_.forward_& file
38019 (see section &<<SECTspecitredli>>& for syntax details).
38020 This is prone to error by inexperienced users. There are two features of Exim
38021 that can be used to make this process simpler for users:
38024 A local part prefix such as &"vacation-"& can be specified on a router which
38025 can cause the message to be delivered directly to the &'vacation'& program, or
38026 alternatively can use Exim's &(autoreply)& transport. The contents of a user's
38027 &_.forward_& file are then much simpler. For example:
38029 spqr, vacation-spqr
38032 The &%require_files%& generic router option can be used to trigger a
38033 vacation delivery by checking for the existence of a certain file in the
38034 user's home directory. The &%unseen%& generic option should also be used, to
38035 ensure that the original delivery also proceeds. In this case, all the user has
38036 to do is to create a file called, say, &_.vacation_&, containing a vacation
38040 Another advantage of both these methods is that they both work even when the
38041 use of arbitrary pipes by users is locked out.
38045 .section "Taking copies of mail" "SECID245"
38046 .cindex "message" "copying every"
38047 Some installations have policies that require archive copies of all messages to
38048 be made. A single copy of each message can easily be taken by an appropriate
38049 command in a system filter, which could, for example, use a different file for
38050 each day's messages.
38052 There is also a shadow transport mechanism that can be used to take copies of
38053 messages that are successfully delivered by local transports, one copy per
38054 delivery. This could be used, &'inter alia'&, to implement automatic
38055 notification of delivery by sites that insist on doing such things.
38059 .section "Intermittently connected hosts" "SECID246"
38060 .cindex "intermittently connected hosts"
38061 It has become quite common (because it is cheaper) for hosts to connect to the
38062 Internet periodically rather than remain connected all the time. The normal
38063 arrangement is that mail for such hosts accumulates on a system that is
38064 permanently connected.
38066 Exim was designed for use on permanently connected hosts, and so it is not
38067 particularly well-suited to use in an intermittently connected environment.
38068 Nevertheless there are some features that can be used.
38071 .section "Exim on the upstream server host" "SECID247"
38072 It is tempting to arrange for incoming mail for the intermittently connected
38073 host to remain in Exim's queue until the client connects. However, this
38074 approach does not scale very well. Two different kinds of waiting message are
38075 being mixed up in the same queue &-- those that cannot be delivered because of
38076 some temporary problem, and those that are waiting for their destination host
38077 to connect. This makes it hard to manage the queue, as well as wasting
38078 resources, because each queue runner scans the entire queue.
38080 A better approach is to separate off those messages that are waiting for an
38081 intermittently connected host. This can be done by delivering these messages
38082 into local files in batch SMTP, &"mailstore"&, or other envelope-preserving
38083 format, from where they are transmitted by other software when their
38084 destination connects. This makes it easy to collect all the mail for one host
38085 in a single directory, and to apply local timeout rules on a per-message basis
38088 On a very small scale, leaving the mail on Exim's queue can be made to work. If
38089 you are doing this, you should configure Exim with a long retry period for the
38090 intermittent host. For example:
38092 cheshire.wonderland.fict.example * F,5d,24h
38094 This stops a lot of failed delivery attempts from occurring, but Exim remembers
38095 which messages it has queued up for that host. Once the intermittent host comes
38096 online, forcing delivery of one message (either by using the &%-M%& or &%-R%&
38097 options, or by using the ETRN SMTP command (see section &<<SECTETRN>>&)
38098 causes all the queued up messages to be delivered, often down a single SMTP
38099 connection. While the host remains connected, any new messages get delivered
38102 If the connecting hosts do not have fixed IP addresses, that is, if a host is
38103 issued with a different IP address each time it connects, Exim's retry
38104 mechanisms on the holding host get confused, because the IP address is normally
38105 used as part of the key string for holding retry information. This can be
38106 avoided by unsetting &%retry_include_ip_address%& on the &(smtp)& transport.
38107 Since this has disadvantages for permanently connected hosts, it is best to
38108 arrange a separate transport for the intermittently connected ones.
38112 .section "Exim on the intermittently connected client host" "SECID248"
38113 The value of &%smtp_accept_queue_per_connection%& should probably be
38114 increased, or even set to zero (that is, disabled) on the intermittently
38115 connected host, so that all incoming messages down a single connection get
38116 delivered immediately.
38118 .cindex "SMTP" "passed connection"
38119 .cindex "SMTP" "multiple deliveries"
38120 .cindex "multiple SMTP deliveries"
38121 .cindex "first pass routing"
38122 Mail waiting to be sent from an intermittently connected host will probably
38123 not have been routed, because without a connection DNS lookups are not
38124 possible. This means that if a normal queue run is done at connection time,
38125 each message is likely to be sent in a separate SMTP session. This can be
38126 avoided by starting the queue run with a command line option beginning with
38127 &%-qq%& instead of &%-q%&. In this case, the queue is scanned twice. In the
38128 first pass, routing is done but no deliveries take place. The second pass is a
38129 normal queue run; since all the messages have been previously routed, those
38130 destined for the same host are likely to get sent as multiple deliveries in a
38131 single SMTP connection.
38135 . ////////////////////////////////////////////////////////////////////////////
38136 . ////////////////////////////////////////////////////////////////////////////
38138 .chapter "Using Exim as a non-queueing client" "CHAPnonqueueing" &&&
38139 "Exim as a non-queueing client"
38140 .cindex "client, non-queueing"
38141 .cindex "smart host" "suppressing queueing"
38142 On a personal computer, it is a common requirement for all
38143 email to be sent to a &"smart host"&. There are plenty of MUAs that can be
38144 configured to operate that way, for all the popular operating systems.
38145 However, there are some MUAs for Unix-like systems that cannot be so
38146 configured: they submit messages using the command line interface of
38147 &_/usr/sbin/sendmail_&. Furthermore, utility programs such as &'cron'& submit
38150 If the personal computer runs continuously, there is no problem, because it can
38151 run a conventional MTA that handles delivery to the smart host, and deal with
38152 any delays via its queueing mechanism. However, if the computer does not run
38153 continuously or runs different operating systems at different times, queueing
38154 email is not desirable.
38156 There is therefore a requirement for something that can provide the
38157 &_/usr/sbin/sendmail_& interface but deliver messages to a smart host without
38158 any queueing or retrying facilities. Furthermore, the delivery to the smart
38159 host should be synchronous, so that if it fails, the sending MUA is immediately
38160 informed. In other words, we want something that extends an MUA that submits
38161 to a local MTA via the command line so that it behaves like one that submits
38162 to a remote smart host using TCP/SMTP.
38164 There are a number of applications (for example, there is one called &'ssmtp'&)
38165 that do this job. However, people have found them to be lacking in various
38166 ways. For instance, you might want to allow aliasing and forwarding to be done
38167 before sending a message to the smart host.
38169 Exim already had the necessary infrastructure for doing this job. Just a few
38170 tweaks were needed to make it behave as required, though it is somewhat of an
38171 overkill to use a fully-featured MTA for this purpose.
38173 .oindex "&%mua_wrapper%&"
38174 There is a Boolean global option called &%mua_wrapper%&, defaulting false.
38175 Setting &%mua_wrapper%& true causes Exim to run in a special mode where it
38176 assumes that it is being used to &"wrap"& a command-line MUA in the manner
38177 just described. As well as setting &%mua_wrapper%&, you also need to provide a
38178 compatible router and transport configuration. Typically there will be just one
38179 router and one transport, sending everything to a smart host.
38181 When run in MUA wrapping mode, the behaviour of Exim changes in the
38185 A daemon cannot be run, nor will Exim accept incoming messages from &'inetd'&.
38186 In other words, the only way to submit messages is via the command line.
38188 Each message is synchronously delivered as soon as it is received (&%-odi%& is
38189 assumed). All queueing options (&%queue_only%&, &%queue_smtp_domains%&,
38190 &%control%& in an ACL, etc.) are quietly ignored. The Exim reception process
38191 does not finish until the delivery attempt is complete. If the delivery is
38192 successful, a zero return code is given.
38194 Address redirection is permitted, but the final routing for all addresses must
38195 be to the same remote transport, and to the same list of hosts. Furthermore,
38196 the return address (envelope sender) must be the same for all recipients, as
38197 must any added or deleted header lines. In other words, it must be possible to
38198 deliver the message in a single SMTP transaction, however many recipients there
38201 If these conditions are not met, or if routing any address results in a
38202 failure or defer status, or if Exim is unable to deliver all the recipients
38203 successfully to one of the smart hosts, delivery of the entire message fails.
38205 Because no queueing is allowed, all failures are treated as permanent; there
38206 is no distinction between 4&'xx'& and 5&'xx'& SMTP response codes from the
38207 smart host. Furthermore, because only a single yes/no response can be given to
38208 the caller, it is not possible to deliver to some recipients and not others. If
38209 there is an error (temporary or permanent) for any recipient, all are failed.
38211 If more than one smart host is listed, Exim will try another host after a
38212 connection failure or a timeout, in the normal way. However, if this kind of
38213 failure happens for all the hosts, the delivery fails.
38215 When delivery fails, an error message is written to the standard error stream
38216 (as well as to Exim's log), and Exim exits to the caller with a return code
38217 value 1. The message is expunged from Exim's spool files. No bounce messages
38218 are ever generated.
38220 No retry data is maintained, and any retry rules are ignored.
38222 A number of Exim options are overridden: &%deliver_drop_privilege%& is forced
38223 true, &%max_rcpt%& in the &(smtp)& transport is forced to &"unlimited"&,
38224 &%remote_max_parallel%& is forced to one, and fallback hosts are ignored.
38227 The overall effect is that Exim makes a single synchronous attempt to deliver
38228 the message, failing if there is any kind of problem. Because no local
38229 deliveries are done and no daemon can be run, Exim does not need root
38230 privilege. It should be possible to run it setuid to &'exim'& instead of setuid
38231 to &'root'&. See section &<<SECTrunexiwitpri>>& for a general discussion about
38232 the advantages and disadvantages of running without root privilege.
38237 . ////////////////////////////////////////////////////////////////////////////
38238 . ////////////////////////////////////////////////////////////////////////////
38240 .chapter "Log files" "CHAPlog"
38241 .scindex IIDloggen "log" "general description"
38242 .cindex "log" "types of"
38243 Exim writes three different logs, referred to as the main log, the reject log,
38248 The main log records the arrival of each message and each delivery in a single
38249 line in each case. The format is as compact as possible, in an attempt to keep
38250 down the size of log files. Two-character flag sequences make it easy to pick
38251 out these lines. A number of other events are recorded in the main log. Some of
38252 them are optional, in which case the &%log_selector%& option controls whether
38253 they are included or not. A Perl script called &'eximstats'&, which does simple
38254 analysis of main log files, is provided in the Exim distribution (see section
38255 &<<SECTmailstat>>&).
38257 .cindex "reject log"
38258 The reject log records information from messages that are rejected as a result
38259 of a configuration option (that is, for policy reasons).
38260 The first line of each rejection is a copy of the line that is also written to
38261 the main log. Then, if the message's header has been read at the time the log
38262 is written, its contents are written to this log. Only the original header
38263 lines are available; header lines added by ACLs are not logged. You can use the
38264 reject log to check that your policy controls are working correctly; on a busy
38265 host this may be easier than scanning the main log for rejection messages. You
38266 can suppress the writing of the reject log by setting &%write_rejectlog%&
38269 .cindex "panic log"
38270 .cindex "system log"
38271 When certain serious errors occur, Exim writes entries to its panic log. If the
38272 error is sufficiently disastrous, Exim bombs out afterwards. Panic log entries
38273 are usually written to the main log as well, but can get lost amid the mass of
38274 other entries. The panic log should be empty under normal circumstances. It is
38275 therefore a good idea to check it (or to have a &'cron'& script check it)
38276 regularly, in order to become aware of any problems. When Exim cannot open its
38277 panic log, it tries as a last resort to write to the system log (syslog). This
38278 is opened with LOG_PID+LOG_CONS and the facility code of LOG_MAIL. The
38279 message itself is written at priority LOG_CRIT.
38282 Every log line starts with a timestamp, in the format shown in the following
38283 example. Note that many of the examples shown in this chapter are line-wrapped.
38284 In the log file, this would be all on one line:
38286 2001-09-16 16:09:47 SMTP connection from [127.0.0.1] closed
38289 By default, the timestamps are in the local timezone. There are two
38290 ways of changing this:
38293 You can set the &%timezone%& option to a different time zone; in particular, if
38298 the timestamps will be in UTC (aka GMT).
38300 If you set &%log_timezone%& true, the time zone is added to the timestamp, for
38303 2003-04-25 11:17:07 +0100 Start queue run: pid=12762
38307 .cindex "log" "process ids in"
38308 .cindex "pid (process id)" "in log lines"
38309 Exim does not include its process id in log lines by default, but you can
38310 request that it does so by specifying the &`pid`& log selector (see section
38311 &<<SECTlogselector>>&). When this is set, the process id is output, in square
38312 brackets, immediately after the time and date.
38317 .section "Where the logs are written" "SECTwhelogwri"
38318 .cindex "log" "destination"
38319 .cindex "log" "to file"
38320 .cindex "log" "to syslog"
38322 The logs may be written to local files, or to syslog, or both. However, it
38323 should be noted that many syslog implementations use UDP as a transport, and
38324 are therefore unreliable in the sense that messages are not guaranteed to
38325 arrive at the loghost, nor is the ordering of messages necessarily maintained.
38326 It has also been reported that on large log files (tens of megabytes) you may
38327 need to tweak syslog to prevent it syncing the file with each write &-- on
38328 Linux this has been seen to make syslog take 90% plus of CPU time.
38330 The destination for Exim's logs is configured by setting LOG_FILE_PATH in
38331 &_Local/Makefile_& or by setting &%log_file_path%& in the runtime
38332 configuration. This latter string is expanded, so it can contain, for example,
38333 references to the host name:
38335 log_file_path = /var/log/$primary_hostname/exim_%slog
38337 It is generally advisable, however, to set the string in &_Local/Makefile_&
38338 rather than at runtime, because then the setting is available right from the
38339 start of Exim's execution. Otherwise, if there's something it wants to log
38340 before it has read the configuration file (for example, an error in the
38341 configuration file) it will not use the path you want, and may not be able to
38344 The value of LOG_FILE_PATH or &%log_file_path%& is a colon-separated
38345 list, currently limited to at most two items. This is one option where the
38346 facility for changing a list separator may not be used. The list must always be
38347 colon-separated. If an item in the list is &"syslog"& then syslog is used;
38348 otherwise the item must either be an absolute path, containing &`%s`& at the
38349 point where &"main"&, &"reject"&, or &"panic"& is to be inserted, or be empty,
38350 implying the use of a default path.
38352 When Exim encounters an empty item in the list, it searches the list defined by
38353 LOG_FILE_PATH, and uses the first item it finds that is neither empty nor
38354 &"syslog"&. This means that an empty item in &%log_file_path%& can be used to
38355 mean &"use the path specified at build time"&. If no such item exists, log
38356 files are written in the &_log_& subdirectory of the spool directory. This is
38357 equivalent to the configuration file setting:
38359 log_file_path = $spool_directory/log/%slog
38361 If you do not specify anything at build time or runtime,
38362 or if you unset the option at runtime (i.e. &`log_file_path = `&),
38363 that is where the logs are written.
38365 A log file path may also contain &`%D`& or &`%M`& if datestamped log filenames
38366 are in use &-- see section &<<SECTdatlogfil>>& below.
38368 Here are some examples of possible Makefile settings:
38370 &`LOG_FILE_PATH=syslog `& syslog only
38371 &`LOG_FILE_PATH=:syslog `& syslog and default path
38372 &`LOG_FILE_PATH=syslog : /usr/log/exim_%s `& syslog and specified path
38373 &`LOG_FILE_PATH=/usr/log/exim_%s `& specified path only
38375 If there are more than two paths in the list, the first is used and a panic
38380 .section "Logging to local files that are periodically &""cycled""&" "SECID285"
38381 .cindex "log" "cycling local files"
38382 .cindex "cycling logs"
38383 .cindex "&'exicyclog'&"
38384 .cindex "log" "local files; writing to"
38385 Some operating systems provide centralized and standardized methods for cycling
38386 log files. For those that do not, a utility script called &'exicyclog'& is
38387 provided (see section &<<SECTcyclogfil>>&). This renames and compresses the
38388 main and reject logs each time it is called. The maximum number of old logs to
38389 keep can be set. It is suggested this script is run as a daily &'cron'& job.
38391 An Exim delivery process opens the main log when it first needs to write to it,
38392 and it keeps the file open in case subsequent entries are required &-- for
38393 example, if a number of different deliveries are being done for the same
38394 message. However, remote SMTP deliveries can take a long time, and this means
38395 that the file may be kept open long after it is renamed if &'exicyclog'& or
38396 something similar is being used to rename log files on a regular basis. To
38397 ensure that a switch of log files is noticed as soon as possible, Exim calls
38398 &[stat()]& on the main log's name before reusing an open file, and if the file
38399 does not exist, or its inode has changed, the old file is closed and Exim
38400 tries to open the main log from scratch. Thus, an old log file may remain open
38401 for quite some time, but no Exim processes should write to it once it has been
38406 .section "Datestamped log files" "SECTdatlogfil"
38407 .cindex "log" "datestamped files"
38408 Instead of cycling the main and reject log files by renaming them
38409 periodically, some sites like to use files whose names contain a datestamp,
38410 for example, &_mainlog-20031225_&. The datestamp is in the form &_yyyymmdd_& or
38411 &_yyyymm_&. Exim has support for this way of working. It is enabled by setting
38412 the &%log_file_path%& option to a path that includes &`%D`& or &`%M`& at the
38413 point where the datestamp is required. For example:
38415 log_file_path = /var/spool/exim/log/%slog-%D
38416 log_file_path = /var/log/exim-%s-%D.log
38417 log_file_path = /var/spool/exim/log/%D-%slog
38418 log_file_path = /var/log/exim/%s.%M
38420 As before, &`%s`& is replaced by &"main"& or &"reject"&; the following are
38421 examples of names generated by the above examples:
38423 /var/spool/exim/log/mainlog-20021225
38424 /var/log/exim-reject-20021225.log
38425 /var/spool/exim/log/20021225-mainlog
38426 /var/log/exim/main.200212
38428 When this form of log file is specified, Exim automatically switches to new
38429 files at midnight. It does not make any attempt to compress old logs; you
38430 will need to write your own script if you require this. You should not
38431 run &'exicyclog'& with this form of logging.
38433 The location of the panic log is also determined by &%log_file_path%&, but it
38434 is not datestamped, because rotation of the panic log does not make sense.
38435 When generating the name of the panic log, &`%D`& or &`%M`& are removed from
38436 the string. In addition, if it immediately follows a slash, a following
38437 non-alphanumeric character is removed; otherwise a preceding non-alphanumeric
38438 character is removed. Thus, the four examples above would give these panic
38441 /var/spool/exim/log/paniclog
38442 /var/log/exim-panic.log
38443 /var/spool/exim/log/paniclog
38444 /var/log/exim/panic
38448 .section "Logging to syslog" "SECID249"
38449 .cindex "log" "syslog; writing to"
38450 The use of syslog does not change what Exim logs or the format of its messages,
38451 except in one respect. If &%syslog_timestamp%& is set false, the timestamps on
38452 Exim's log lines are omitted when these lines are sent to syslog. Apart from
38453 that, the same strings are written to syslog as to log files. The syslog
38454 &"facility"& is set to LOG_MAIL, and the program name to &"exim"&
38455 by default, but you can change these by setting the &%syslog_facility%& and
38456 &%syslog_processname%& options, respectively. If Exim was compiled with
38457 SYSLOG_LOG_PID set in &_Local/Makefile_& (this is the default in
38458 &_src/EDITME_&), then, on systems that permit it (all except ULTRIX), the
38459 LOG_PID flag is set so that the &[syslog()]& call adds the pid as well as
38460 the time and host name to each line.
38461 The three log streams are mapped onto syslog priorities as follows:
38464 &'mainlog'& is mapped to LOG_INFO
38466 &'rejectlog'& is mapped to LOG_NOTICE
38468 &'paniclog'& is mapped to LOG_ALERT
38471 Many log lines are written to both &'mainlog'& and &'rejectlog'&, and some are
38472 written to both &'mainlog'& and &'paniclog'&, so there will be duplicates if
38473 these are routed by syslog to the same place. You can suppress this duplication
38474 by setting &%syslog_duplication%& false.
38476 Exim's log lines can sometimes be very long, and some of its &'rejectlog'&
38477 entries contain multiple lines when headers are included. To cope with both
38478 these cases, entries written to syslog are split into separate &[syslog()]&
38479 calls at each internal newline, and also after a maximum of
38480 870 data characters. (This allows for a total syslog line length of 1024, when
38481 additions such as timestamps are added.) If you are running a syslog
38482 replacement that can handle lines longer than the 1024 characters allowed by
38483 RFC 3164, you should set
38485 SYSLOG_LONG_LINES=yes
38487 in &_Local/Makefile_& before building Exim. That stops Exim from splitting long
38488 lines, but it still splits at internal newlines in &'reject'& log entries.
38490 To make it easy to re-assemble split lines later, each component of a split
38491 entry starts with a string of the form [<&'n'&>/<&'m'&>] or [<&'n'&>\<&'m'&>]
38492 where <&'n'&> is the component number and <&'m'&> is the total number of
38493 components in the entry. The / delimiter is used when the line was split
38494 because it was too long; if it was split because of an internal newline, the \
38495 delimiter is used. For example, supposing the length limit to be 50 instead of
38496 870, the following would be the result of a typical rejection message to
38497 &'mainlog'& (LOG_INFO), each line in addition being preceded by the time, host
38498 name, and pid as added by syslog:
38500 [1/5] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected from
38501 [2/5] [127.0.0.1] (ph10): syntax error in 'From' header
38502 [3/5] when scanning for sender: missing or malformed lo
38503 [4/5] cal part in "<>" (envelope sender is <ph10@cam.exa
38506 The same error might cause the following lines to be written to &"rejectlog"&
38509 [1/18] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected fro
38510 [2/18] m [127.0.0.1] (ph10): syntax error in 'From' head
38511 [3/18] er when scanning for sender: missing or malformed
38512 [4/18] local part in "<>" (envelope sender is <ph10@cam
38514 [6\18] Recipients: ph10@some.domain.cam.example
38515 [7\18] P Received: from [127.0.0.1] (ident=ph10)
38516 [8\18] by xxxxx.cam.example with smtp (Exim 4.00)
38517 [9\18] id 16RdAL-0006pc-00
38518 [10/18] for ph10@cam.example; Mon, 16 Sep 2002 16:
38519 [11\18] 09:43 +0100
38521 [13\18] Subject: this is a test header
38522 [18\18] X-something: this is another header
38523 [15/18] I Message-Id: <E16RdAL-0006pc-00@xxxxx.cam.examp
38526 [18/18] Date: Mon, 16 Sep 2002 16:09:43 +0100
38528 Log lines that are neither too long nor contain newlines are written to syslog
38529 without modification.
38531 If only syslog is being used, the Exim monitor is unable to provide a log tail
38532 display, unless syslog is routing &'mainlog'& to a file on the local host and
38533 the environment variable EXIMON_LOG_FILE_PATH is set to tell the monitor
38538 .section "Log line flags" "SECID250"
38539 One line is written to the main log for each message received, and for each
38540 successful, unsuccessful, and delayed delivery. These lines can readily be
38541 picked out by the distinctive two-character flags that immediately follow the
38542 timestamp. The flags are:
38543 .itable none 0 0 2 1pt left 1pt left
38544 .irow &%<=%& "message arrival"
38545 .irow &%(=%& "message fakereject"
38546 .irow &%=>%& "normal message delivery"
38547 .irow &%->%& "additional address in same delivery"
38548 .irow &%>>%& "cutthrough message delivery"
38549 .irow &%*>%& "delivery suppressed by &%-N%&"
38550 .irow &%**%& "delivery failed; address bounced"
38551 .irow &%==%& "delivery deferred; temporary problem"
38555 .section "Logging message reception" "SECID251"
38556 .cindex "log" "reception line"
38557 The format of the single-line entry in the main log that is written for every
38558 message received is shown in the basic example below, which is split over
38559 several lines in order to fit it on the page:
38561 2002-10-31 08:57:53 16ZCW1-0005MB-00 <= kryten@dwarf.fict.example
38562 H=mailer.fict.example [192.168.123.123] U=exim
38563 P=smtp S=5678 id=<incoming message id>
38565 The address immediately following &"<="& is the envelope sender address. A
38566 bounce message is shown with the sender address &"<>"&, and if it is locally
38567 generated, this is followed by an item of the form
38571 which is a reference to the message that caused the bounce to be sent.
38575 For messages from other hosts, the H and U fields identify the remote host and
38576 record the RFC 1413 identity of the user that sent the message, if one was
38577 received. The number given in square brackets is the IP address of the sending
38578 host. If there is a single, unparenthesized host name in the H field, as
38579 above, it has been verified to correspond to the IP address (see the
38580 &%host_lookup%& option). If the name is in parentheses, it was the name quoted
38581 by the remote host in the SMTP HELO or EHLO command, and has not been
38582 verified. If verification yields a different name to that given for HELO or
38583 EHLO, the verified name appears first, followed by the HELO or EHLO
38584 name in parentheses.
38586 Misconfigured hosts (and mail forgers) sometimes put an IP address, with or
38587 without brackets, in the HELO or EHLO command, leading to entries in
38588 the log containing text like these examples:
38590 H=(10.21.32.43) [192.168.8.34]
38591 H=([10.21.32.43]) [192.168.8.34]
38593 This can be confusing. Only the final address in square brackets can be relied
38596 For locally generated messages (that is, messages not received over TCP/IP),
38597 the H field is omitted, and the U field contains the login name of the caller
38600 .cindex "authentication" "logging"
38601 .cindex "AUTH" "logging"
38602 For all messages, the P field specifies the protocol used to receive the
38603 message. This is the value that is stored in &$received_protocol$&. In the case
38604 of incoming SMTP messages, the value indicates whether or not any SMTP
38605 extensions (ESMTP), encryption, or authentication were used. If the SMTP
38606 session was encrypted, there is an additional X field that records the cipher
38607 suite that was used.
38609 .cindex log protocol
38610 The protocol is set to &"esmtpsa"& or &"esmtpa"& for messages received from
38611 hosts that have authenticated themselves using the SMTP AUTH command. The first
38612 value is used when the SMTP connection was encrypted (&"secure"&). In this case
38613 there is an additional item A= followed by the name of the authenticator that
38614 was used. If an authenticated identification was set up by the authenticator's
38615 &%server_set_id%& option, this is logged too, separated by a colon from the
38616 authenticator name.
38618 .cindex "size" "of message"
38619 The id field records the existing message id, if present. The size of the
38620 received message is given by the S field. When the message is delivered,
38621 headers may be removed or added, so that the size of delivered copies of the
38622 message may not correspond with this value (and indeed may be different to each
38625 The &%log_selector%& option can be used to request the logging of additional
38626 data when a message is received. See section &<<SECTlogselector>>& below.
38630 .section "Logging deliveries" "SECID252"
38631 .cindex "log" "delivery line"
38632 The format of the single-line entry in the main log that is written for every
38633 delivery is shown in one of the examples below, for local and remote
38634 deliveries, respectively. Each example has been split into multiple lines in order
38635 to fit it on the page:
38637 2002-10-31 08:59:13 16ZCW1-0005MB-00 => marv
38638 <marv@hitch.fict.example> R=localuser T=local_delivery
38639 2002-10-31 09:00:10 16ZCW1-0005MB-00 =>
38640 monk@holistic.fict.example R=dnslookup T=remote_smtp
38641 H=holistic.fict.example [192.168.234.234]
38643 For ordinary local deliveries, the original address is given in angle brackets
38644 after the final delivery address, which might be a pipe or a file. If
38645 intermediate address(es) exist between the original and the final address, the
38646 last of these is given in parentheses after the final address. The R and T
38647 fields record the router and transport that were used to process the address.
38649 If SMTP AUTH was used for the delivery there is an additional item A=
38650 followed by the name of the authenticator that was used.
38651 If an authenticated identification was set up by the authenticator's &%client_set_id%&
38652 option, this is logged too, as a second colon-separated list item.
38653 Optionally (see the &%smtp_mailauth%& &%log_selector%&) there may be a third list item.
38655 If a shadow transport was run after a successful local delivery, the log line
38656 for the successful delivery has an item added on the end, of the form
38658 &`ST=<`&&'shadow transport name'&&`>`&
38660 If the shadow transport did not succeed, the error message is put in
38661 parentheses afterwards.
38663 .cindex "asterisk" "after IP address"
38664 When more than one address is included in a single delivery (for example, two
38665 SMTP RCPT commands in one transaction) the second and subsequent addresses are
38666 flagged with &`->`& instead of &`=>`&. When two or more messages are delivered
38667 down a single SMTP connection, an asterisk follows the
38668 remote IP address (and port if enabled)
38669 in the log lines for the second and subsequent messages.
38670 When two or more messages are delivered down a single TLS connection, the
38671 DNS and some TLS-related information logged for the first message delivered
38672 will not be present in the log lines for the second and subsequent messages.
38673 TLS cipher information is still available.
38675 .cindex "delivery" "cutthrough; logging"
38676 .cindex "cutthrough" "logging"
38677 When delivery is done in cutthrough mode it is flagged with &`>>`& and the log
38678 line precedes the reception line, since cutthrough waits for a possible
38679 rejection from the destination in case it can reject the sourced item.
38681 The generation of a reply message by a filter file gets logged as a
38682 &"delivery"& to the addressee, preceded by &">"&.
38684 The &%log_selector%& option can be used to request the logging of additional
38685 data when a message is delivered. See section &<<SECTlogselector>>& below.
38688 .section "Discarded deliveries" "SECID253"
38689 .cindex "discarded messages"
38690 .cindex "message" "discarded"
38691 .cindex "delivery" "discarded; logging"
38692 When a message is discarded as a result of the command &"seen finish"& being
38693 obeyed in a filter file which generates no deliveries, a log entry of the form
38695 2002-12-10 00:50:49 16auJc-0001UB-00 => discarded
38696 <low.club@bridge.example> R=userforward
38698 is written, to record why no deliveries are logged. When a message is discarded
38699 because it is aliased to &":blackhole:"& the log line is like this:
38701 1999-03-02 09:44:33 10HmaX-0005vi-00 => :blackhole:
38702 <hole@nowhere.example> R=blackhole_router
38706 .section "Deferred deliveries" "SECID254"
38707 When a delivery is deferred, a line of the following form is logged:
38709 2002-12-19 16:20:23 16aiQz-0002Q5-00 == marvin@endrest.example
38710 R=dnslookup T=smtp defer (146): Connection refused
38712 In the case of remote deliveries, the error is the one that was given for the
38713 last IP address that was tried. Details of individual SMTP failures are also
38714 written to the log, so the above line would be preceded by something like
38716 2002-12-19 16:20:23 16aiQz-0002Q5-00 Failed to connect to
38717 mail1.endrest.example [192.168.239.239]: Connection refused
38719 When a deferred address is skipped because its retry time has not been reached,
38720 a message is written to the log, but this can be suppressed by setting an
38721 appropriate value in &%log_selector%&.
38725 .section "Delivery failures" "SECID255"
38726 .cindex "delivery" "failure; logging"
38727 If a delivery fails because an address cannot be routed, a line of the
38728 following form is logged:
38730 1995-12-19 16:20:23 0tRiQz-0002Q5-00 ** jim@trek99.example
38731 <jim@trek99.example>: unknown mail domain
38733 If a delivery fails at transport time, the router and transport are shown, and
38734 the response from the remote host is included, as in this example:
38736 2002-07-11 07:14:17 17SXDU-000189-00 ** ace400@pb.example
38737 R=dnslookup T=remote_smtp: SMTP error from remote mailer
38738 after pipelined RCPT TO:<ace400@pb.example>: host
38739 pbmail3.py.example [192.168.63.111]: 553 5.3.0
38740 <ace400@pb.example>...Addressee unknown
38742 The word &"pipelined"& indicates that the SMTP PIPELINING extension was being
38743 used. See &%hosts_avoid_esmtp%& in the &(smtp)& transport for a way of
38744 disabling PIPELINING. The log lines for all forms of delivery failure are
38745 flagged with &`**`&.
38749 .section "Fake deliveries" "SECID256"
38750 .cindex "delivery" "fake; logging"
38751 If a delivery does not actually take place because the &%-N%& option has been
38752 used to suppress it, a normal delivery line is written to the log, except that
38753 &"=>"& is replaced by &"*>"&.
38757 .section "Completion" "SECID257"
38760 2002-10-31 09:00:11 16ZCW1-0005MB-00 Completed
38762 is written to the main log when a message is about to be removed from the spool
38763 at the end of its processing.
38768 .section "Summary of Fields in Log Lines" "SECID258"
38769 .cindex "log" "summary of fields"
38770 A summary of the field identifiers that are used in log lines is shown in
38771 the following table:
38773 &`A `& authenticator name (and optional id and sender)
38774 &`C `& SMTP confirmation on delivery
38775 &` `& command list for &"no mail in SMTP session"&
38776 &`CV `& certificate verification status
38777 &`D `& duration of &"no mail in SMTP session"&
38778 &`DKIM`& domain verified in incoming message
38779 &`DN `& distinguished name from peer certificate
38780 &`DS `& DNSSEC secured lookups
38781 &`DT `& on &`=>`&, &'=='& and &'**'& lines: time taken for, or to attempt, a delivery
38782 &`F `& sender address (on delivery lines)
38783 &`H `& host name and IP address
38784 &`I `& local interface used
38785 &`id `& message id (from header) for incoming message
38786 &`K `& CHUNKING extension used
38787 &`L `& on &`<=`& and &`=>`& lines: PIPELINING extension used
38788 &`M8S `& 8BITMIME status for incoming message
38789 &`P `& on &`<=`& lines: protocol used
38790 &` `& on &`=>`& and &`**`& lines: return path
38791 &`PRDR`& PRDR extension used
38792 &`PRX `& on &`<=`& and &`=>`& lines: proxy address
38793 &`Q `& alternate queue name
38794 &`QT `& on &`=>`& lines: time spent on queue so far
38795 &` `& on &"Completed"& lines: time spent on queue
38796 &`R `& on &`<=`& lines: reference for local bounce
38797 &` `& on &`=>`& &`>>`& &`**`& and &`==`& lines: router name
38798 &`RT `& on &`<=`& lines: time taken for reception
38799 &`S `& size of message in bytes
38800 &`SNI `& server name indication from TLS client hello
38801 &`ST `& shadow transport name
38802 &`T `& on &`<=`& lines: message subject (topic)
38803 &`TFO `& connection took advantage of TCP Fast Open
38804 &` `& on &`=>`& &`**`& and &`==`& lines: transport name
38805 &`U `& local user or RFC 1413 identity
38806 &`X `& TLS cipher suite
38810 .section "Other log entries" "SECID259"
38811 Various other types of log entry are written from time to time. Most should be
38812 self-explanatory. Among the more common are:
38815 .cindex "retry" "time not reached"
38816 &'retry time not reached'&&~&~An address previously suffered a temporary error
38817 during routing or local delivery, and the time to retry has not yet arrived.
38818 This message is not written to an individual message log file unless it happens
38819 during the first delivery attempt.
38821 &'retry time not reached for any host'&&~&~An address previously suffered
38822 temporary errors during remote delivery, and the retry time has not yet arrived
38823 for any of the hosts to which it is routed.
38825 .cindex "spool directory" "file locked"
38826 &'spool file locked'&&~&~An attempt to deliver a message cannot proceed because
38827 some other Exim process is already working on the message. This can be quite
38828 common if queue running processes are started at frequent intervals. The
38829 &'exiwhat'& utility script can be used to find out what Exim processes are
38832 .cindex "error" "ignored"
38833 &'error ignored'&&~&~There are several circumstances that give rise to this
38836 Exim failed to deliver a bounce message whose age was greater than
38837 &%ignore_bounce_errors_after%&. The bounce was discarded.
38839 A filter file set up a delivery using the &"noerror"& option, and the delivery
38840 failed. The delivery was discarded.
38842 A delivery set up by a router configured with
38843 . ==== As this is a nested list, any displays it contains must be indented
38844 . ==== as otherwise they are too far to the left.
38848 failed. The delivery was discarded.
38851 .cindex DKIM "log line"
38852 &'DKIM: d='&&~&~Verbose results of a DKIM verification attempt, if enabled for
38853 logging and the message has a DKIM signature header.
38860 .section "Reducing or increasing what is logged" "SECTlogselector"
38861 .cindex "log" "selectors"
38862 By setting the &%log_selector%& global option, you can disable some of Exim's
38863 default logging, or you can request additional logging. The value of
38864 &%log_selector%& is made up of names preceded by plus or minus characters. For
38867 log_selector = +arguments -retry_defer
38869 The list of optional log items is in the following table, with the default
38870 selection marked by asterisks:
38871 .itable none 0 0 3 1pt left 10pt center 1pt left
38872 .irow &`8bitmime`& "received 8BITMIME status"
38873 .irow &`acl_warn_skipped`& * "skipped &%warn%& statement in ACL"
38874 .irow &`address_rewrite`& "address rewriting"
38875 .irow &`all_parents`& "all parents in => lines"
38876 .irow &`arguments`& "command line arguments"
38877 .irow &`connection_reject`& * "connection rejections"
38878 .irow &`delay_delivery`& * "immediate delivery delayed"
38879 .irow &`deliver_time`& "time taken to attempt delivery"
38880 .irow &`delivery_size`& "add &`S=`&&'nnn'& to => lines"
38881 .irow &`dkim`& * "DKIM verified domain on <= lines"
38882 .irow &`dkim_verbose`& "separate full DKIM verification result line, per signature"
38883 .irow &`dnslist_defer`& * "defers of DNS list (aka RBL) lookups"
38884 .irow &`dnssec`& "DNSSEC secured lookups"
38885 .irow &`etrn`& * "ETRN commands"
38886 .irow &`host_lookup_failed`& * "as it says"
38887 .irow &`ident_timeout`& "timeout for ident connection"
38888 .irow &`incoming_interface`& "local interface on <= and => lines"
38889 .irow &`incoming_port`& "remote port on <= lines"
38890 .irow &`lost_incoming_connection`& * "as it says (includes timeouts)"
38891 .irow &`millisec`& "millisecond timestamps and RT,QT,DT,D times"
38892 .irow &`msg_id`& * "on <= lines, Message-ID: header value"
38893 .irow &`msg_id_created`& "on <= lines, Message-ID: header value when one had to be added"
38894 .irow &`outgoing_interface`& "local interface on => lines"
38895 .irow &`outgoing_port`& "add remote port to => lines"
38896 .irow &`queue_run`& * "start and end queue runs"
38897 .irow &`queue_time`& "time on queue for one recipient"
38898 .irow &`queue_time_exclusive`& "exclude recieve time from QT times"
38899 .irow &`queue_time_overall`& "time on queue for whole message"
38900 .irow &`pid`& "Exim process id"
38901 .irow &`pipelining`& "PIPELINING use, on <= and => lines"
38902 .irow &`proxy`& "proxy address on <= and => lines"
38903 .irow &`receive_time`& "time taken to receive message"
38904 .irow &`received_recipients`& "recipients on <= lines"
38905 .irow &`received_sender`& "sender on <= lines"
38906 .irow &`rejected_header`& * "header contents on reject log"
38907 .irow &`retry_defer`& * "&<quote>&retry time not reached&</quote>&"
38908 .irow &`return_path_on_delivery`& "put return path on => and ** lines"
38909 .irow &`sender_on_delivery`& "add sender to => lines"
38910 .irow &`sender_verify_fail`& * "sender verification failures"
38911 .irow &`size_reject`& * "rejection because too big"
38912 .irow &`skip_delivery`& * "delivery skipped in a queue run"
38913 .irow &`smtp_confirmation`& * "SMTP confirmation on => lines"
38914 .irow &`smtp_connection`& "incoming SMTP connections"
38915 .irow &`smtp_incomplete_transaction`& "incomplete SMTP transactions"
38916 .irow &`smtp_mailauth`& "AUTH argument to MAIL commands"
38917 .irow &`smtp_no_mail`& "session with no MAIL commands"
38918 .irow &`smtp_protocol_error`& "SMTP protocol errors"
38919 .irow &`smtp_syntax_error`& "SMTP syntax errors"
38920 .irow &`subject`& "contents of &'Subject:'& on <= lines"
38921 .irow &`tls_certificate_verified`& * "certificate verification status"
38922 .irow &`tls_cipher`& * "TLS cipher suite on <= and => lines"
38923 .irow &`tls_peerdn`& "TLS peer DN on <= and => lines"
38924 .irow &`tls_resumption`& "append * to cipher field"
38925 .irow &`tls_sni`& "TLS SNI on <= lines"
38926 .irow &`unknown_in_list`& "DNS lookup failed in list match"
38927 .irow &`all`& "&*all of the above*&"
38929 See also the &%slow_lookup_log%& main configuration option,
38930 section &<<SECID99>>&
38932 More details on each of these items follows:
38936 .cindex "log" "8BITMIME"
38937 &%8bitmime%&: This causes Exim to log any 8BITMIME status of received messages,
38938 which may help in tracking down interoperability issues with ancient MTAs
38939 that are not 8bit clean. This is added to the &"<="& line, tagged with
38940 &`M8S=`& and a value of &`0`&, &`7`& or &`8`&, corresponding to "not given",
38941 &`7BIT`& and &`8BITMIME`& respectively.
38943 .cindex "&%warn%& ACL verb" "log when skipping"
38944 &%acl_warn_skipped%&: When an ACL &%warn%& statement is skipped because one of
38945 its conditions cannot be evaluated, a log line to this effect is written if
38946 this log selector is set.
38948 .cindex "log" "rewriting"
38949 .cindex "rewriting" "logging"
38950 &%address_rewrite%&: This applies both to global rewrites and per-transport
38951 rewrites, but not to rewrites in filters run as an unprivileged user (because
38952 such users cannot access the log).
38954 .cindex "log" "full parentage"
38955 &%all_parents%&: Normally only the original and final addresses are logged on
38956 delivery lines; with this selector, intermediate parents are given in
38957 parentheses between them.
38959 .cindex "log" "Exim arguments"
38960 .cindex "Exim arguments, logging"
38961 &%arguments%&: This causes Exim to write the arguments with which it was called
38962 to the main log, preceded by the current working directory. This is a debugging
38963 feature, added to make it easier to find out how certain MUAs call
38964 &_/usr/sbin/sendmail_&. The logging does not happen if Exim has given up root
38965 privilege because it was called with the &%-C%& or &%-D%& options. Arguments
38966 that are empty or that contain white space are quoted. Non-printing characters
38967 are shown as escape sequences. This facility cannot log unrecognized arguments,
38968 because the arguments are checked before the configuration file is read. The
38969 only way to log such cases is to interpose a script such as &_util/logargs.sh_&
38970 between the caller and Exim.
38972 .cindex "log" "connection rejections"
38973 &%connection_reject%&: A log entry is written whenever an incoming SMTP
38974 connection is rejected, for whatever reason.
38976 .cindex "log" "delayed delivery"
38977 .cindex "delayed delivery, logging"
38978 &%delay_delivery%&: A log entry is written whenever a delivery process is not
38979 started for an incoming message because the load is too high or too many
38980 messages were received on one connection. Logging does not occur if no delivery
38981 process is started because &%queue_only%& is set or &%-odq%& was used.
38983 .cindex "log" "delivery duration"
38984 &%deliver_time%&: For each delivery, the amount of real time it has taken to
38985 perform the actual delivery is logged as DT=<&'time'&>, for example, &`DT=1s`&.
38986 If millisecond logging is enabled, short times will be shown with greater
38987 precision, eg. &`DT=0.304s`&.
38989 .cindex "log" "message size on delivery"
38990 .cindex "size" "of message"
38991 &%delivery_size%&: For each delivery, the size of message delivered is added to
38992 the &"=>"& line, tagged with S=.
38994 .cindex log "DKIM verification"
38995 .cindex DKIM "verification logging"
38996 &%dkim%&: For message acceptance log lines, when an DKIM signature in the header
38997 verifies successfully a tag of DKIM is added, with one of the verified domains.
38999 .cindex log "DKIM verification"
39000 .cindex DKIM "verification logging"
39001 &%dkim_verbose%&: A log entry is written for each attempted DKIM verification.
39003 .cindex "log" "dnslist defer"
39004 .cindex "DNS list" "logging defer"
39005 .cindex "black list (DNS)"
39006 &%dnslist_defer%&: A log entry is written if an attempt to look up a host in a
39007 DNS black list suffers a temporary error.
39010 .cindex dnssec logging
39011 &%dnssec%&: For message acceptance and (attempted) delivery log lines, when
39012 dns lookups gave secure results a tag of DS is added.
39013 For acceptance this covers the reverse and forward lookups for host name verification.
39014 It does not cover helo-name verification.
39015 For delivery this covers the SRV, MX, A and/or AAAA lookups.
39017 .cindex "log" "ETRN commands"
39018 .cindex "ETRN" "logging"
39019 &%etrn%&: Every valid ETRN command that is received is logged, before the ACL
39020 is run to determine whether or not it is actually accepted. An invalid ETRN
39021 command, or one received within a message transaction is not logged by this
39022 selector (see &%smtp_syntax_error%& and &%smtp_protocol_error%&).
39024 .cindex "log" "host lookup failure"
39025 &%host_lookup_failed%&: When a lookup of a host's IP addresses fails to find
39026 any addresses, or when a lookup of an IP address fails to find a host name, a
39027 log line is written. This logging does not apply to direct DNS lookups when
39028 routing email addresses, but it does apply to &"byname"& lookups.
39030 .cindex "log" "ident timeout"
39031 .cindex "RFC 1413" "logging timeout"
39032 &%ident_timeout%&: A log line is written whenever an attempt to connect to a
39033 client's ident port times out.
39035 .cindex "log" "incoming interface"
39036 .cindex "log" "outgoing interface"
39037 .cindex "log" "local interface"
39038 .cindex "log" "local address and port"
39039 .cindex "TCP/IP" "logging local address and port"
39040 .cindex "interface" "logging"
39041 &%incoming_interface%&: The interface on which a message was received is added
39042 to the &"<="& line as an IP address in square brackets, tagged by I= and
39043 followed by a colon and the port number. The local interface and port are also
39044 added to other SMTP log lines, for example, &"SMTP connection from"&, to
39045 rejection lines, and (despite the name) to outgoing
39046 &"=>"&, &"->"&, &"=="& and &"**"& lines.
39047 The latter can be disabled by turning off the &%outgoing_interface%& option.
39049 .cindex log "incoming proxy address"
39050 .cindex proxy "logging proxy address"
39051 .cindex "TCP/IP" "logging proxy address"
39052 &%proxy%&: The internal (closest to the system running Exim) IP address
39053 of the proxy, tagged by PRX=, on the &"<="& line for a message accepted
39054 on a proxied connection
39055 or the &"=>"& line for a message delivered on a proxied connection.
39056 See &<<SECTproxyInbound>>& for more information.
39058 .cindex "log" "incoming remote port"
39059 .cindex "port" "logging remote"
39060 .cindex "TCP/IP" "logging incoming remote port"
39061 .vindex "&$sender_fullhost$&"
39062 .vindex "&$sender_rcvhost$&"
39063 &%incoming_port%&: The remote port number from which a message was received is
39064 added to log entries and &'Received:'& header lines, following the IP address
39065 in square brackets, and separated from it by a colon. This is implemented by
39066 changing the value that is put in the &$sender_fullhost$& and
39067 &$sender_rcvhost$& variables. Recording the remote port number has become more
39068 important with the widening use of NAT (see RFC 2505).
39070 .cindex "log" "dropped connection"
39071 &%lost_incoming_connection%&: A log line is written when an incoming SMTP
39072 connection is unexpectedly dropped.
39074 .cindex "log" "millisecond timestamps"
39075 .cindex millisecond logging
39076 .cindex timestamps "millisecond, in logs"
39077 &%millisec%&: Timestamps have a period and three decimal places of finer granularity
39078 appended to the seconds value.
39080 .cindex "log" "message id"
39081 &%msg_id%&: The value of the Message-ID: header.
39083 &%msg_id_created%&: The value of the Message-ID: header, when one had to be created.
39084 This will be either because the message is a bounce, or was submitted locally
39085 (submission mode) without one.
39086 The field identifier will have an asterix appended: &"id*="&.
39088 .cindex "log" "outgoing interface"
39089 .cindex "log" "local interface"
39090 .cindex "log" "local address and port"
39091 .cindex "TCP/IP" "logging local address and port"
39092 .cindex "interface" "logging"
39093 &%outgoing_interface%&: If &%incoming_interface%& is turned on, then the
39094 interface on which a message was sent is added to delivery lines as an I= tag
39095 followed by IP address in square brackets. You can disable this by turning
39096 off the &%outgoing_interface%& option.
39098 .cindex "log" "outgoing remote port"
39099 .cindex "port" "logging outgoing remote"
39100 .cindex "TCP/IP" "logging outgoing remote port"
39101 &%outgoing_port%&: The remote port number is added to delivery log lines (those
39102 containing => tags) following the IP address.
39103 The local port is also added if &%incoming_interface%& and
39104 &%outgoing_interface%& are both enabled.
39105 This option is not included in the default setting, because for most ordinary
39106 configurations, the remote port number is always 25 (the SMTP port), and the
39107 local port is a random ephemeral port.
39109 .cindex "log" "process ids in"
39110 .cindex "pid (process id)" "in log lines"
39111 &%pid%&: The current process id is added to every log line, in square brackets,
39112 immediately after the time and date.
39114 .cindex log pipelining
39115 .cindex pipelining "logging outgoing"
39116 &%pipelining%&: A field is added to delivery and accept
39117 log lines when the ESMTP PIPELINING extension was used.
39118 The field is a single "L".
39120 On accept lines, where PIPELINING was offered but not used by the client,
39121 the field has a minus appended.
39123 .cindex "pipelining" "early connection"
39124 If Exim is built without the DISABLE_PIPE_CONNECT build option
39125 accept "L" fields have a period appended if the feature was
39126 offered but not used, or an asterisk appended if used.
39127 Delivery "L" fields have an asterisk appended if used.
39130 .cindex "log" "queue run"
39131 .cindex "queue runner" "logging"
39132 &%queue_run%&: The start and end of every queue run are logged.
39134 .cindex "log" "queue time"
39135 &%queue_time%&: The amount of time the message has been in the queue on the
39136 local host is logged as QT=<&'time'&> on delivery (&`=>`&) lines, for example,
39138 If millisecond logging is enabled, short times will be shown with greater
39139 precision, eg. &`QT=1.578s`&.
39141 &%queue_time_overall%&: The amount of time the message has been in the queue on
39142 the local host is logged as QT=<&'time'&> on &"Completed"& lines, for
39143 example, &`QT=3m45s`&.
39145 .cindex "log" "receive duration"
39146 &%receive_time%&: For each message, the amount of real time it has taken to
39147 perform the reception is logged as RT=<&'time'&>, for example, &`RT=1s`&.
39148 If millisecond logging is enabled, short times will be shown with greater
39149 precision, eg. &`RT=0.204s`&.
39151 .cindex "log" "recipients"
39152 &%received_recipients%&: The recipients of a message are listed in the main log
39153 as soon as the message is received. The list appears at the end of the log line
39154 that is written when a message is received, preceded by the word &"for"&. The
39155 addresses are listed after they have been qualified, but before any rewriting
39157 Recipients that were discarded by an ACL for MAIL or RCPT do not appear
39160 .cindex "log" "sender reception"
39161 &%received_sender%&: The unrewritten original sender of a message is added to
39162 the end of the log line that records the message's arrival, after the word
39163 &"from"& (before the recipients if &%received_recipients%& is also set).
39165 .cindex "log" "header lines for rejection"
39166 &%rejected_header%&: If a message's header has been received at the time a
39167 rejection is written to the reject log, the complete header is added to the
39168 log. Header logging can be turned off individually for messages that are
39169 rejected by the &[local_scan()]& function (see section &<<SECTapiforloc>>&).
39171 .cindex "log" "retry defer"
39172 &%retry_defer%&: A log line is written if a delivery is deferred because a
39173 retry time has not yet been reached. However, this &"retry time not reached"&
39174 message is always omitted from individual message logs after the first delivery
39177 .cindex "log" "return path"
39178 &%return_path_on_delivery%&: The return path that is being transmitted with
39179 the message is included in delivery and bounce lines, using the tag P=.
39180 This is omitted if no delivery actually happens, for example, if routing fails,
39181 or if delivery is to &_/dev/null_& or to &`:blackhole:`&.
39183 .cindex "log" "sender on delivery"
39184 &%sender_on_delivery%&: The message's sender address is added to every delivery
39185 and bounce line, tagged by F= (for &"from"&).
39186 This is the original sender that was received with the message; it is not
39187 necessarily the same as the outgoing return path.
39189 .cindex "log" "sender verify failure"
39190 &%sender_verify_fail%&: If this selector is unset, the separate log line that
39191 gives details of a sender verification failure is not written. Log lines for
39192 the rejection of SMTP commands contain just &"sender verify failed"&, so some
39195 .cindex "log" "size rejection"
39196 &%size_reject%&: A log line is written whenever a message is rejected because
39199 .cindex "log" "frozen messages; skipped"
39200 .cindex "frozen messages" "logging skipping"
39201 &%skip_delivery%&: A log line is written whenever a message is skipped during a
39202 queue run because it another process is already delivering it or because
39204 .cindex "&""spool file is locked""&"
39205 .cindex "&""message is frozen""&"
39206 The message that is written is either &"spool file is locked"& or
39207 &"message is frozen"&.
39209 .cindex "log" "smtp confirmation"
39210 .cindex "SMTP" "logging confirmation"
39211 .cindex "LMTP" "logging confirmation"
39212 &%smtp_confirmation%&: The response to the final &"."& in the SMTP or LMTP dialogue for
39213 outgoing messages is added to delivery log lines in the form &`C=`&<&'text'&>.
39214 A number of MTAs (including Exim) return an identifying string in this
39217 .cindex "log" "SMTP connections"
39218 .cindex "SMTP" "logging connections"
39219 &%smtp_connection%&: A log line is written whenever an incoming SMTP connection is
39220 established or closed, unless the connection is from a host that matches
39221 &%hosts_connection_nolog%&. (In contrast, &%lost_incoming_connection%& applies
39222 only when the closure is unexpected.) This applies to connections from local
39223 processes that use &%-bs%& as well as to TCP/IP connections. If a connection is
39224 dropped in the middle of a message, a log line is always written, whether or
39225 not this selector is set, but otherwise nothing is written at the start and end
39226 of connections unless this selector is enabled.
39228 For TCP/IP connections to an Exim daemon, the current number of connections is
39229 included in the log message for each new connection, but note that the count is
39230 reset if the daemon is restarted.
39231 Also, because connections are closed (and the closure is logged) in
39232 subprocesses, the count may not include connections that have been closed but
39233 whose termination the daemon has not yet noticed. Thus, while it is possible to
39234 match up the opening and closing of connections in the log, the value of the
39235 logged counts may not be entirely accurate.
39237 .cindex "log" "SMTP transaction; incomplete"
39238 .cindex "SMTP" "logging incomplete transactions"
39239 &%smtp_incomplete_transaction%&: When a mail transaction is aborted by
39240 RSET, QUIT, loss of connection, or otherwise, the incident is logged,
39241 and the message sender plus any accepted recipients are included in the log
39242 line. This can provide evidence of dictionary attacks.
39244 .cindex "log" "non-MAIL SMTP sessions"
39245 .cindex "MAIL" "logging session without"
39246 &%smtp_no_mail%&: A line is written to the main log whenever an accepted SMTP
39247 connection terminates without having issued a MAIL command. This includes both
39248 the case when the connection is dropped, and the case when QUIT is used. It
39249 does not include cases where the connection is rejected right at the start (by
39250 an ACL, or because there are too many connections, or whatever). These cases
39251 already have their own log lines.
39253 The log line that is written contains the identity of the client in the usual
39254 way, followed by D= and a time, which records the duration of the connection.
39255 If the connection was authenticated, this fact is logged exactly as it is for
39256 an incoming message, with an A= item. If the connection was encrypted, CV=,
39257 DN=, and X= items may appear as they do for an incoming message, controlled by
39258 the same logging options.
39260 Finally, if any SMTP commands were issued during the connection, a C= item
39261 is added to the line, listing the commands that were used. For example,
39265 shows that the client issued QUIT straight after EHLO. If there were fewer
39266 than 20 commands, they are all listed. If there were more than 20 commands,
39267 the last 20 are listed, preceded by &"..."&. However, with the default
39268 setting of 10 for &%smtp_accept_max_nonmail%&, the connection will in any case
39269 have been aborted before 20 non-mail commands are processed.
39271 &%smtp_mailauth%&: A third subfield with the authenticated sender,
39272 colon-separated, is appended to the A= item for a message arrival or delivery
39273 log line, if an AUTH argument to the SMTP MAIL command (see &<<SECTauthparamail>>&)
39274 was accepted or used.
39276 .cindex "log" "SMTP protocol error"
39277 .cindex "SMTP" "logging protocol error"
39278 &%smtp_protocol_error%&: A log line is written for every SMTP protocol error
39279 encountered. Exim does not have perfect detection of all protocol errors
39280 because of transmission delays and the use of pipelining. If PIPELINING has
39281 been advertised to a client, an Exim server assumes that the client will use
39282 it, and therefore it does not count &"expected"& errors (for example, RCPT
39283 received after rejecting MAIL) as protocol errors.
39285 .cindex "SMTP" "logging syntax errors"
39286 .cindex "SMTP" "syntax errors; logging"
39287 .cindex "SMTP" "unknown command; logging"
39288 .cindex "log" "unknown SMTP command"
39289 .cindex "log" "SMTP syntax error"
39290 &%smtp_syntax_error%&: A log line is written for every SMTP syntax error
39291 encountered. An unrecognized command is treated as a syntax error. For an
39292 external connection, the host identity is given; for an internal connection
39293 using &%-bs%& the sender identification (normally the calling user) is given.
39295 .cindex "log" "subject"
39296 .cindex "subject, logging"
39297 &%subject%&: The subject of the message is added to the arrival log line,
39298 preceded by &"T="& (T for &"topic"&, since S is already used for &"size"&).
39299 Any MIME &"words"& in the subject are decoded. The &%print_topbitchars%& option
39300 specifies whether characters with values greater than 127 should be logged
39301 unchanged, or whether they should be rendered as escape sequences.
39303 .cindex "log" "certificate verification"
39305 .cindex DANE logging
39306 &%tls_certificate_verified%&: An extra item is added to <= and => log lines
39307 when TLS is in use. The item is &`CV=yes`& if the peer's certificate was
39309 using a CA trust anchor,
39310 &`CV=dane`& if using a DNS trust anchor,
39311 and &`CV=no`& if not.
39313 .cindex "log" "TLS cipher"
39314 .cindex "TLS" "logging cipher"
39315 &%tls_cipher%&: When a message is sent or received over an encrypted
39316 connection, the cipher suite used is added to the log line, preceded by X=.
39318 .cindex "log" "TLS peer DN"
39319 .cindex "TLS" "logging peer DN"
39320 &%tls_peerdn%&: When a message is sent or received over an encrypted
39321 connection, and a certificate is supplied by the remote host, the peer DN is
39322 added to the log line, preceded by DN=.
39324 .cindex "log" "TLS resumption"
39325 .cindex "TLS" "logging session resumption"
39326 &%tls_resumption%&: When a message is sent or received over an encrypted
39327 connection and the TLS session resumed one used on a previous TCP connection,
39328 an asterisk is appended to the X= cipher field in the log line.
39330 .cindex "log" "TLS SNI"
39331 .cindex "TLS" "logging SNI"
39332 .cindex SNI logging
39333 &%tls_sni%&: When a message is received over an encrypted connection, and
39334 the remote host provided the Server Name Indication extension, the SNI is
39335 added to the log line, preceded by SNI=.
39337 .cindex "log" "DNS failure in list"
39338 &%unknown_in_list%&: This setting causes a log entry to be written when the
39339 result of a list match is failure because a DNS lookup failed.
39343 .section "Message log" "SECID260"
39344 .cindex "message" "log file for"
39345 .cindex "log" "message log; description of"
39346 .cindex "&_msglog_& directory"
39347 .oindex "&%preserve_message_logs%&"
39348 In addition to the general log files, Exim writes a log file for each message
39349 that it handles. The names of these per-message logs are the message ids, and
39350 they are kept in the &_msglog_& sub-directory of the spool directory. Each
39351 message log contains copies of the log lines that apply to the message. This
39352 makes it easier to inspect the status of an individual message without having
39353 to search the main log. A message log is deleted when processing of the message
39354 is complete, unless &%preserve_message_logs%& is set, but this should be used
39355 only with great care because they can fill up your disk very quickly.
39357 On a heavily loaded system, it may be desirable to disable the use of
39358 per-message logs, in order to reduce disk I/O. This can be done by setting the
39359 &%message_logs%& option false.
39365 . ////////////////////////////////////////////////////////////////////////////
39366 . ////////////////////////////////////////////////////////////////////////////
39368 .chapter "Exim utilities" "CHAPutils"
39369 .scindex IIDutils "utilities"
39370 A number of utility scripts and programs are supplied with Exim and are
39371 described in this chapter. There is also the Exim Monitor, which is covered in
39372 the next chapter. The utilities described here are:
39374 .itable none 0 0 3 7* left 15* left 40* left
39375 .irow &<<SECTfinoutwha>>& &'exiwhat'& &&&
39376 "list what Exim processes are doing"
39377 .irow &<<SECTgreptheque>>& &'exiqgrep'& "grep the queue"
39378 .irow &<<SECTsumtheque>>& &'exiqsumm'& "summarize the queue"
39379 .irow &<<SECTextspeinf>>& &'exigrep'& "search the main log"
39380 .irow &<<SECTexipick>>& &'exipick'& "select messages on &&&
39382 .irow &<<SECTcyclogfil>>& &'exicyclog'& "cycle (rotate) log files"
39383 .irow &<<SECTmailstat>>& &'eximstats'& &&&
39384 "extract statistics from the log"
39385 .irow &<<SECTcheckaccess>>& &'exim_checkaccess'& &&&
39386 "check address acceptance from given IP"
39387 .irow &<<SECTdbmbuild>>& &'exim_dbmbuild'& "build a DBM file"
39388 .irow &<<SECTfinindret>>& &'exinext'& "extract retry information"
39389 .irow &<<SECTdumpdb>>& &'exim_dumpdb'& "dump a hints database"
39390 .irow &<<SECTtidydb>>& &'exim_tidydb'& "clean up a hints database"
39391 .irow &<<SECTfixdb>>& &'exim_fixdb'& "patch a hints database"
39392 .irow &<<SECTmailboxmaint>>& &'exim_lock'& "lock a mailbox file"
39395 Another utility that might be of use to sites with many MTAs is Tom Kistner's
39396 &'exilog'&. It provides log visualizations across multiple Exim servers. See
39397 &url(https://duncanthrax.net/exilog/) for details.
39402 .section "Finding out what Exim processes are doing (exiwhat)" "SECTfinoutwha"
39403 .cindex "&'exiwhat'&"
39404 .cindex "process, querying"
39406 On operating systems that can restart a system call after receiving a signal
39407 (most modern OS), an Exim process responds to the SIGUSR1 signal by writing
39408 a line describing what it is doing to the file &_exim-process.info_& in the
39409 Exim spool directory. The &'exiwhat'& script sends the signal to all Exim
39410 processes it can find, having first emptied the file. It then waits for one
39411 second to allow the Exim processes to react before displaying the results. In
39412 order to run &'exiwhat'& successfully you have to have sufficient privilege to
39413 send the signal to the Exim processes, so it is normally run as root.
39415 &*Warning*&: This is not an efficient process. It is intended for occasional
39416 use by system administrators. It is not sensible, for example, to set up a
39417 script that sends SIGUSR1 signals to Exim processes at short intervals.
39420 Unfortunately, the &'ps'& command that &'exiwhat'& uses to find Exim processes
39421 varies in different operating systems. Not only are different options used,
39422 but the format of the output is different. For this reason, there are some
39423 system configuration options that configure exactly how &'exiwhat'& works. If
39424 it doesn't seem to be working for you, check the following compile-time
39426 .itable none 0 0 2 1pt left 1pt left
39427 .irow &`EXIWHAT_PS_CMD`& "the command for running &'ps'&"
39428 .irow &`EXIWHAT_PS_ARG`& "the argument for &'ps'&"
39429 .irow &`EXIWHAT_EGREP_ARG`& "the argument for &'egrep'& to select from &'ps'& output"
39430 .irow &`EXIWHAT_KILL_ARG`& "the argument for the &'kill'& command"
39432 An example of typical output from &'exiwhat'& is
39434 164 daemon: -q1h, listening on port 25
39435 10483 running queue: waiting for 0tAycK-0002ij-00 (10492)
39436 10492 delivering 0tAycK-0002ij-00 to mail.ref.example
39437 [10.19.42.42] (editor@ref.example)
39438 10592 handling incoming call from [192.168.243.242]
39439 10628 accepting a local non-SMTP message
39441 The first number in the output line is the process number. The third line has
39442 been split here, in order to fit it on the page.
39446 .section "Selective queue listing (exiqgrep)" "SECTgreptheque"
39447 .cindex "&'exiqgrep'&"
39448 .cindex "queue" "grepping"
39449 This utility is a Perl script contributed by Matt Hubbard. It runs
39453 or (in case &*-a*& switch is specified)
39457 to obtain a queue listing, and then greps the output to select messages
39458 that match given criteria. The following selection options are available:
39461 .vitem &*-f*&&~<&'regex'&>
39462 Match the sender address using a case-insensitive search. The field that is
39463 tested is enclosed in angle brackets, so you can test for bounce messages with
39467 .vitem &*-r*&&~<&'regex'&>
39468 Match a recipient address using a case-insensitive search. The field that is
39469 tested is not enclosed in angle brackets.
39471 .vitem &*-s*&&~<&'regex'&>
39472 Match against the size field.
39474 .vitem &*-y*&&~<&'seconds'&>
39475 Match messages that are younger than the given time.
39477 .vitem &*-o*&&~<&'seconds'&>
39478 Match messages that are older than the given time.
39481 Match only frozen messages.
39484 Match only non-frozen messages.
39486 .vitem &*-G*&&~<&'queuename'&>
39487 Match only messages in the given queue. Without this, the default queue is searched.
39490 The following options control the format of the output:
39494 Display only the count of matching messages.
39497 Long format &-- display the full message information as output by Exim. This is
39501 Display message ids only.
39504 Brief format &-- one line per message.
39507 Display messages in reverse order.
39510 Include delivered recipients in queue listing.
39513 The following options give alternates for configuration:
39516 .vitem &*-C*&&~<&'config&~file'&>
39517 is used to specify an alternate &_exim.conf_& which might
39518 contain alternate exim configuration the queue management might be using.
39520 .vitem &*-E*&&~<&'path'&>
39521 can be used to specify a path for the exim binary,
39522 overriding the built-in one.
39525 There is one more option, &%-h%&, which outputs a list of options.
39526 At least one selection option, or either the &*-c*& or &*-h*& option, must be given.
39530 .section "Summarizing the queue (exiqsumm)" "SECTsumtheque"
39531 .cindex "&'exiqsumm'&"
39532 .cindex "queue" "summary"
39533 The &'exiqsumm'& utility is a Perl script which reads the output of &`exim
39534 -bp`& and produces a summary of the messages in the queue. Thus, you use it by
39535 running a command such as
39537 exim -bp | exiqsumm
39539 The output consists of one line for each domain that has messages waiting for
39540 it, as in the following example:
39542 3 2322 74m 66m msn.com.example
39544 Each line lists the number of pending deliveries for a domain, their total
39545 volume, and the length of time that the oldest and the newest messages have
39546 been waiting. Note that the number of pending deliveries is greater than the
39547 number of messages when messages have more than one recipient.
39549 A summary line is output at the end. By default the output is sorted on the
39550 domain name, but &'exiqsumm'& has the options &%-a%& and &%-c%&, which cause
39551 the output to be sorted by oldest message and by count of messages,
39552 respectively. There are also three options that split the messages for each
39553 domain into two or more subcounts: &%-b%& separates bounce messages, &%-f%&
39554 separates frozen messages, and &%-s%& separates messages according to their
39557 The output of &'exim -bp'& contains the original addresses in the message, so
39558 this also applies to the output from &'exiqsumm'&. No domains from addresses
39559 generated by aliasing or forwarding are included (unless the &%one_time%&
39560 option of the &(redirect)& router has been used to convert them into &"top
39561 level"& addresses).
39566 .section "Extracting specific information from the log (exigrep)" &&&
39568 .cindex "&'exigrep'&"
39569 .cindex "log" "extracts; grepping for"
39570 The &'exigrep'& utility is a Perl script that searches one or more main log
39571 files for entries that match a given pattern. When it finds a match, it
39572 extracts all the log entries for the relevant message, not just those that
39573 match the pattern. Thus, &'exigrep'& can extract complete log entries for a
39574 given message, or all mail for a given user, or for a given host, for example.
39575 The input files can be in Exim log format or syslog format.
39576 If a matching log line is not associated with a specific message, it is
39577 included in &'exigrep'&'s output without any additional lines. The usage is:
39579 &`exigrep [-t<`&&'n'&&`>] [-I] [-l] [-M] [-v] <`&&'pattern'&&`> [<`&&'log file'&&`>] ...`&
39581 If no log filenames are given on the command line, the standard input is read.
39583 The &%-t%& argument specifies a number of seconds. It adds an additional
39584 condition for message selection. Messages that are complete are shown only if
39585 they spent more than <&'n'&> seconds in the queue.
39587 By default, &'exigrep'& does case-insensitive matching. The &%-I%& option
39588 makes it case-sensitive. This may give a performance improvement when searching
39589 large log files. Without &%-I%&, the Perl pattern matches use Perl's &`/i`&
39590 option; with &%-I%& they do not. In both cases it is possible to change the
39591 case sensitivity within the pattern by using &`(?i)`& or &`(?-i)`&.
39593 The &%-l%& option means &"literal"&, that is, treat all characters in the
39594 pattern as standing for themselves. Otherwise the pattern must be a Perl
39595 regular expression.
39597 The &%-v%& option inverts the matching condition. That is, a line is selected
39598 if it does &'not'& match the pattern.
39600 The &%-M%& options means &"related messages"&. &'exigrep'& will show messages
39601 that are generated as a result/response to a message that &'exigrep'& matched
39605 user_a sends a message to user_b, which generates a bounce back to user_b. If
39606 &'exigrep'& is used to search for &"user_a"&, only the first message will be
39607 displayed. But if &'exigrep'& is used to search for &"user_b"&, the first and
39608 the second (bounce) message will be displayed. Using &%-M%& with &'exigrep'&
39609 when searching for &"user_a"& will show both messages since the bounce is
39610 &"related"& to or a &"result"& of the first message that was found by the
39613 If the location of a &'zcat'& command is known from the definition of
39614 ZCAT_COMMAND in &_Local/Makefile_&, &'exigrep'& automatically passes any file
39615 whose name ends in COMPRESS_SUFFIX through &'zcat'& as it searches it.
39616 If the ZCAT_COMMAND is not executable, &'exigrep'& tries to use
39617 autodetection of some well known compression extensions.
39620 .section "Selecting messages by various criteria (exipick)" "SECTexipick"
39621 .cindex "&'exipick'&"
39622 John Jetmore's &'exipick'& utility is included in the Exim distribution. It
39623 lists messages from the queue according to a variety of criteria. For details
39624 of &'exipick'&'s facilities, run &'exipick'& with
39625 the &%--help%& option.
39628 .section "Cycling log files (exicyclog)" "SECTcyclogfil"
39629 .cindex "log" "cycling local files"
39630 .cindex "cycling logs"
39631 .cindex "&'exicyclog'&"
39632 The &'exicyclog'& script can be used to cycle (rotate) &'mainlog'& and
39633 &'rejectlog'& files. This is not necessary if only syslog is being used, or if
39634 you are using log files with datestamps in their names (see section
39635 &<<SECTdatlogfil>>&). Some operating systems have their own standard mechanisms
39636 for log cycling, and these can be used instead of &'exicyclog'& if preferred.
39637 There are two command line options for &'exicyclog'&:
39639 &%-k%& <&'count'&> specifies the number of log files to keep, overriding the
39640 default that is set when Exim is built. The default default is 10.
39642 &%-l%& <&'path'&> specifies the log file path, in the same format as Exim's
39643 &%log_file_path%& option (for example, &`/var/log/exim_%slog`&), again
39644 overriding the script's default, which is to find the setting from Exim's
39648 Each time &'exicyclog'& is run the filenames get &"shuffled down"& by one. If
39649 the main log filename is &_mainlog_& (the default) then when &'exicyclog'& is
39650 run &_mainlog_& becomes &_mainlog.01_&, the previous &_mainlog.01_& becomes
39651 &_mainlog.02_& and so on, up to the limit that is set in the script or by the
39652 &%-k%& option. Log files whose numbers exceed the limit are discarded. Reject
39653 logs are handled similarly.
39655 If the limit is greater than 99, the script uses 3-digit numbers such as
39656 &_mainlog.001_&, &_mainlog.002_&, etc. If you change from a number less than 99
39657 to one that is greater, or &'vice versa'&, you will have to fix the names of
39658 any existing log files.
39660 If no &_mainlog_& file exists, the script does nothing. Files that &"drop off"&
39661 the end are deleted. All files with numbers greater than 01 are compressed,
39662 using a compression command which is configured by the COMPRESS_COMMAND
39663 setting in &_Local/Makefile_&. It is usual to run &'exicyclog'& daily from a
39664 root &%crontab%& entry of the form
39666 1 0 * * * su exim -c /usr/exim/bin/exicyclog
39668 assuming you have used the name &"exim"& for the Exim user. You can run
39669 &'exicyclog'& as root if you wish, but there is no need.
39673 .section "Mail statistics (eximstats)" "SECTmailstat"
39674 .cindex "statistics"
39675 .cindex "&'eximstats'&"
39676 A Perl script called &'eximstats'& is provided for extracting statistical
39677 information from log files. The output is either plain text, or HTML.
39678 . --- 2018-09-07: LogReport's Lire appears to be dead; website is a Yahoo Japan
39679 . --- 404 error and everything else points to that.
39681 The &'eximstats'& script has been hacked about quite a bit over time. The
39682 latest version is the result of some extensive revision by Steve Campbell. A
39683 lot of information is given by default, but there are options for suppressing
39684 various parts of it. Following any options, the arguments to the script are a
39685 list of files, which should be main log files. For example:
39687 eximstats -nr /var/spool/exim/log/mainlog.01
39689 By default, &'eximstats'& extracts information about the number and volume of
39690 messages received from or delivered to various hosts. The information is sorted
39691 both by message count and by volume, and the top fifty hosts in each category
39692 are listed on the standard output. Similar information, based on email
39693 addresses or domains instead of hosts can be requested by means of various
39694 options. For messages delivered and received locally, similar statistics are
39695 also produced per user.
39697 The output also includes total counts and statistics about delivery errors, and
39698 histograms showing the number of messages received and deliveries made in each
39699 hour of the day. A delivery with more than one address in its envelope (for
39700 example, an SMTP transaction with more than one RCPT command) is counted
39701 as a single delivery by &'eximstats'&.
39703 Though normally more deliveries than receipts are reported (as messages may
39704 have multiple recipients), it is possible for &'eximstats'& to report more
39705 messages received than delivered, even though the queue is empty at the start
39706 and end of the period in question. If an incoming message contains no valid
39707 recipients, no deliveries are recorded for it. A bounce message is handled as
39708 an entirely separate message.
39710 &'eximstats'& always outputs a grand total summary giving the volume and number
39711 of messages received and deliveries made, and the number of hosts involved in
39712 each case. It also outputs the number of messages that were delayed (that is,
39713 not completely delivered at the first attempt), and the number that had at
39714 least one address that failed.
39716 The remainder of the output is in sections that can be independently disabled
39717 or modified by various options. It consists of a summary of deliveries by
39718 transport, histograms of messages received and delivered per time interval
39719 (default per hour), information about the time messages spent in the queue,
39720 a list of relayed messages, lists of the top fifty sending hosts, local
39721 senders, destination hosts, and destination local users by count and by volume,
39722 and a list of delivery errors that occurred.
39724 The relay information lists messages that were actually relayed, that is, they
39725 came from a remote host and were directly delivered to some other remote host,
39726 without being processed (for example, for aliasing or forwarding) locally.
39728 There are quite a few options for &'eximstats'& to control exactly what it
39729 outputs. These are documented in the Perl script itself, and can be extracted
39730 by running the command &(perldoc)& on the script. For example:
39732 perldoc /usr/exim/bin/eximstats
39735 .section "Checking access policy (exim_checkaccess)" "SECTcheckaccess"
39736 .cindex "&'exim_checkaccess'&"
39737 .cindex "policy control" "checking access"
39738 .cindex "checking access"
39739 The &%-bh%& command line argument allows you to run a fake SMTP session with
39740 debugging output, in order to check what Exim is doing when it is applying
39741 policy controls to incoming SMTP mail. However, not everybody is sufficiently
39742 familiar with the SMTP protocol to be able to make full use of &%-bh%&, and
39743 sometimes you just want to answer the question &"Does this address have
39744 access?"& without bothering with any further details.
39746 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%&. It takes
39747 two arguments, an IP address and an email address:
39749 exim_checkaccess 10.9.8.7 A.User@a.domain.example
39751 The utility runs a call to Exim with the &%-bh%& option, to test whether the
39752 given email address would be accepted in a RCPT command in a TCP/IP
39753 connection from the host with the given IP address. The output of the utility
39754 is either the word &"accepted"&, or the SMTP error response, for example:
39757 550 Relay not permitted
39759 When running this test, the utility uses &`<>`& as the envelope sender address
39760 for the MAIL command, but you can change this by providing additional
39761 options. These are passed directly to the Exim command. For example, to specify
39762 that the test is to be run with the sender address &'himself@there.example'&
39765 exim_checkaccess 10.9.8.7 A.User@a.domain.example \
39766 -f himself@there.example
39768 Note that these additional Exim command line items must be given after the two
39769 mandatory arguments.
39771 Because the &%exim_checkaccess%& uses &%-bh%&, it does not perform callouts
39772 while running its checks. You can run checks that include callouts by using
39773 &%-bhc%&, but this is not yet available in a &"packaged"& form.
39777 .section "Making DBM files (exim_dbmbuild)" "SECTdbmbuild"
39778 .cindex "DBM" "building dbm files"
39779 .cindex "building DBM files"
39780 .cindex "&'exim_dbmbuild'&"
39781 .cindex "lower casing"
39782 .cindex "binary zero" "in lookup key"
39783 The &'exim_dbmbuild'& program reads an input file containing keys and data in
39784 the format used by the &(lsearch)& lookup (see section
39785 &<<SECTsinglekeylookups>>&). It writes a DBM file using the lower-cased alias
39786 names as keys and the remainder of the information as data. The lower-casing
39787 can be prevented by calling the program with the &%-nolc%& option.
39789 A terminating zero is included as part of the key string. This is expected by
39790 the &(dbm)& lookup type. However, if the option &%-nozero%& is given,
39791 &'exim_dbmbuild'& creates files without terminating zeroes in either the key
39792 strings or the data strings. The &(dbmnz)& lookup type can be used with such
39795 The program requires two arguments: the name of the input file (which can be a
39796 single hyphen to indicate the standard input), and the name of the output file.
39797 It creates the output under a temporary name, and then renames it if all went
39801 If the native DB interface is in use (USE_DB is set in a compile-time
39802 configuration file &-- this is common in free versions of Unix) the two
39803 filenames must be different, because in this mode the Berkeley DB functions
39804 create a single output file using exactly the name given. For example,
39806 exim_dbmbuild /etc/aliases /etc/aliases.db
39808 reads the system alias file and creates a DBM version of it in
39809 &_/etc/aliases.db_&.
39811 In systems that use the &'ndbm'& routines (mostly proprietary versions of
39812 Unix), two files are used, with the suffixes &_.dir_& and &_.pag_&. In this
39813 environment, the suffixes are added to the second argument of
39814 &'exim_dbmbuild'&, so it can be the same as the first. This is also the case
39815 when the Berkeley functions are used in compatibility mode (though this is not
39816 recommended), because in that case it adds a &_.db_& suffix to the filename.
39818 If a duplicate key is encountered, the program outputs a warning, and when it
39819 finishes, its return code is 1 rather than zero, unless the &%-noduperr%&
39820 option is used. By default, only the first of a set of duplicates is used &--
39821 this makes it compatible with &(lsearch)& lookups. There is an option
39822 &%-lastdup%& which causes it to use the data for the last duplicate instead.
39823 There is also an option &%-nowarn%&, which stops it listing duplicate keys to
39824 &%stderr%&. For other errors, where it doesn't actually make a new file, the
39830 .section "Finding individual retry times (exinext)" "SECTfinindret"
39831 .cindex "retry" "times"
39832 .cindex "&'exinext'&"
39833 A utility called &'exinext'& (mostly a Perl script) provides the ability to
39834 fish specific information out of the retry database. Given a mail domain (or a
39835 complete address), it looks up the hosts for that domain, and outputs any retry
39836 information for the hosts or for the domain. At present, the retry information
39837 is obtained by running &'exim_dumpdb'& (see below) and post-processing the
39838 output. For example:
39840 $ exinext piglet@milne.fict.example
39841 kanga.milne.example:192.168.8.1 error 146: Connection refused
39842 first failed: 21-Feb-1996 14:57:34
39843 last tried: 21-Feb-1996 14:57:34
39844 next try at: 21-Feb-1996 15:02:34
39845 roo.milne.example:192.168.8.3 error 146: Connection refused
39846 first failed: 20-Jan-1996 13:12:08
39847 last tried: 21-Feb-1996 11:42:03
39848 next try at: 21-Feb-1996 19:42:03
39849 past final cutoff time
39851 You can also give &'exinext'& a local part, without a domain, and it
39852 will give any retry information for that local part in your default domain.
39853 A message id can be used to obtain retry information pertaining to a specific
39854 message. This exists only when an attempt to deliver a message to a remote host
39855 suffers a message-specific error (see section &<<SECToutSMTPerr>>&).
39856 &'exinext'& is not particularly efficient, but then it is not expected to be
39859 The &'exinext'& utility calls Exim to find out information such as the location
39860 of the spool directory. The utility has &%-C%& and &%-D%& options, which are
39861 passed on to the &'exim'& commands. The first specifies an alternate Exim
39862 configuration file, and the second sets macros for use within the configuration
39863 file. These features are mainly to help in testing, but might also be useful in
39864 environments where more than one configuration file is in use.
39868 .section "Hints database maintenance" "SECThindatmai"
39869 .cindex "hints database" "maintenance"
39870 .cindex "maintaining Exim's hints database"
39871 Three utility programs are provided for maintaining the DBM files that Exim
39872 uses to contain its delivery hint information. Each program requires two
39873 arguments. The first specifies the name of Exim's spool directory, and the
39874 second is the name of the database it is to operate on. These are as follows:
39877 &'retry'&: the database of retry information
39879 &'wait-'&<&'transport name'&>: databases of information about messages waiting
39882 &'callout'&: the callout cache
39884 &'ratelimit'&: the data for implementing the ratelimit ACL condition
39886 &'tls'&: TLS session resumption data
39888 &'misc'&: other hints data
39891 The &'misc'& database is used for
39894 Serializing ETRN runs (when &%smtp_etrn_serialize%& is set)
39896 Serializing delivery to a specific host (when &%serialize_hosts%& is set in an
39897 &(smtp)& transport)
39899 Limiting the concurrency of specific transports (when &%max_parallel%& is set
39905 .section "exim_dumpdb" "SECTdumpdb"
39906 .cindex "&'exim_dumpdb'&"
39907 The entire contents of a database are written to the standard output by the
39908 &'exim_dumpdb'& program,
39909 taking as arguments the spool and database names.
39910 An option &'-z'& may be given to request times in UTC;
39911 otherwise times are in the local timezone.
39912 An option &'-k'& may be given to dump only the record keys.
39913 For example, to dump the retry database:
39915 exim_dumpdb /var/spool/exim retry
39917 For the retry database
39918 two lines of output are produced for each entry:
39920 T:mail.ref.example:192.168.242.242 146 77 Connection refused
39921 31-Oct-1995 12:00:12 02-Nov-1995 12:21:39 02-Nov-1995 20:21:39 *
39923 The first item on the first line is the key of the record. It starts with one
39924 of the letters R, or T, depending on whether it refers to a routing or
39925 transport retry. For a local delivery, the next part is the local address; for
39926 a remote delivery it is the name of the remote host, followed by its failing IP
39927 address (unless &%retry_include_ip_address%& is set false on the &(smtp)&
39928 transport). If the remote port is not the standard one (port 25), it is added
39929 to the IP address. Then there follows an error code, an additional error code,
39930 and a textual description of the error.
39932 The three times on the second line are the time of first failure, the time of
39933 the last delivery attempt, and the computed time for the next attempt. The line
39934 ends with an asterisk if the cutoff time for the last retry rule has been
39937 Each output line from &'exim_dumpdb'& for the &'wait-xxx'& databases
39938 consists of a host name followed by a list of ids for messages that are or were
39939 waiting to be delivered to that host. If there are a very large number for any
39940 one host, continuation records, with a sequence number added to the host name,
39941 may be seen. The data in these records is often out of date, because a message
39942 may be routed to several alternative hosts, and Exim makes no effort to keep
39947 .section "exim_tidydb" "SECTtidydb"
39948 .cindex "&'exim_tidydb'&"
39949 The &'exim_tidydb'& utility program is used to tidy up the contents of a hints
39950 database. If run with no options, it removes all records that are more than 30
39951 days old. The age is calculated from the date and time that the record was last
39952 updated. Note that, in the case of the retry database, it is &'not'& the time
39953 since the first delivery failure. Information about a host that has been down
39954 for more than 30 days will remain in the database, provided that the record is
39955 updated sufficiently often.
39957 The cutoff date can be altered by means of the &%-t%& option, which must be
39958 followed by a time. For example, to remove all records older than a week from
39959 the retry database:
39961 exim_tidydb -t 7d /var/spool/exim retry
39963 Both the &'wait-xxx'& and &'retry'& databases contain items that involve
39964 message ids. In the former these appear as data in records keyed by host &--
39965 they were messages that were waiting for that host &-- and in the latter they
39966 are the keys for retry information for messages that have suffered certain
39967 types of error. When &'exim_tidydb'& is run, a check is made to ensure that
39968 message ids in database records are those of messages that are still on the
39969 queue. Message ids for messages that no longer exist are removed from
39970 &'wait-xxx'& records, and if this leaves any records empty, they are deleted.
39971 For the &'retry'& database, records whose keys are non-existent message ids are
39972 removed. The &'exim_tidydb'& utility outputs comments on the standard output
39973 whenever it removes information from the database.
39975 Certain records are automatically removed by Exim when they are no longer
39976 needed, but others are not. For example, if all the MX hosts for a domain are
39977 down, a retry record is created for each one. If the primary MX host comes back
39978 first, its record is removed when Exim successfully delivers to it, but the
39979 records for the others remain because Exim has not tried to use those hosts.
39981 It is important, therefore, to run &'exim_tidydb'& periodically on all the
39982 hints databases. You should do this at a quiet time of day, because it requires
39983 a database to be locked (and therefore inaccessible to Exim) while it does its
39984 work. Removing records from a DBM file does not normally make the file smaller,
39985 but all the common DBM libraries are able to re-use the space that is released.
39986 After an initial phase of increasing in size, the databases normally reach a
39987 point at which they no longer get any bigger, as long as they are regularly
39990 &*Warning*&: If you never run &'exim_tidydb'&, the space used by the hints
39991 databases is likely to keep on increasing.
39996 .section "exim_fixdb" "SECTfixdb"
39997 .cindex "&'exim_fixdb'&"
39998 The &'exim_fixdb'& program is a utility for interactively modifying databases.
39999 Its main use is for testing Exim, but it might also be occasionally useful for
40000 getting round problems in a live system. Its interface
40001 is somewhat crude. On entry, it prompts for input with a right angle-bracket. A
40002 key of a database record can then be entered, and the data for that record is
40005 If &"d"& is typed at the next prompt, the entire record is deleted. For all
40006 except the &'retry'& database, that is the only operation that can be carried
40007 out. For the &'retry'& database, each field is output preceded by a number, and
40008 data for individual fields can be changed by typing the field number followed
40009 by new data, for example:
40013 resets the time of the next delivery attempt. Time values are given as a
40014 sequence of digit pairs for year, month, day, hour, and minute. Colons can be
40015 used as optional separators.
40017 Both displayed and input times are in the local timezone by default.
40018 If an option &'-z'& is used on the command line, displayed times
40024 .section "Mailbox maintenance (exim_lock)" "SECTmailboxmaint"
40025 .cindex "mailbox" "maintenance"
40026 .cindex "&'exim_lock'&"
40027 .cindex "locking mailboxes"
40028 The &'exim_lock'& utility locks a mailbox file using the same algorithm as
40029 Exim. For a discussion of locking issues, see section &<<SECTopappend>>&.
40030 &'Exim_lock'& can be used to prevent any modification of a mailbox by Exim or
40031 a user agent while investigating a problem. The utility requires the name of
40032 the file as its first argument. If the locking is successful, the second
40033 argument is run as a command (using C's &[system()]& function); if there is no
40034 second argument, the value of the SHELL environment variable is used; if this
40035 is unset or empty, &_/bin/sh_& is run. When the command finishes, the mailbox
40036 is unlocked and the utility ends. The following options are available:
40040 Use &[fcntl()]& locking on the open mailbox.
40043 Use &[flock()]& locking on the open mailbox, provided the operating system
40046 .vitem &%-interval%&
40047 This must be followed by a number, which is a number of seconds; it sets the
40048 interval to sleep between retries (default 3).
40050 .vitem &%-lockfile%&
40051 Create a lock file before opening the mailbox.
40054 Lock the mailbox using MBX rules.
40057 Suppress verification output.
40059 .vitem &%-retries%&
40060 This must be followed by a number; it sets the number of times to try to get
40061 the lock (default 10).
40063 .vitem &%-restore_time%&
40064 This option causes &%exim_lock%& to restore the modified and read times to the
40065 locked file before exiting. This allows you to access a locked mailbox (for
40066 example, to take a backup copy) without disturbing the times that the user
40069 .vitem &%-timeout%&
40070 This must be followed by a number, which is a number of seconds; it sets a
40071 timeout to be used with a blocking &[fcntl()]& lock. If it is not set (the
40072 default), a non-blocking call is used.
40075 Generate verbose output.
40078 If none of &%-fcntl%&, &%-flock%&, &%-lockfile%& or &%-mbx%& are given, the
40079 default is to create a lock file and also to use &[fcntl()]& locking on the
40080 mailbox, which is the same as Exim's default. The use of &%-flock%& or
40081 &%-fcntl%& requires that the file be writeable; the use of &%-lockfile%&
40082 requires that the directory containing the file be writeable. Locking by lock
40083 file does not last forever; Exim assumes that a lock file is expired if it is
40084 more than 30 minutes old.
40086 The &%-mbx%& option can be used with either or both of &%-fcntl%& or
40087 &%-flock%&. It assumes &%-fcntl%& by default. MBX locking causes a shared lock
40088 to be taken out on the open mailbox, and an exclusive lock on the file
40089 &_/tmp/.n.m_& where &'n'& and &'m'& are the device number and inode
40090 number of the mailbox file. When the locking is released, if an exclusive lock
40091 can be obtained for the mailbox, the file in &_/tmp_& is deleted.
40093 The default output contains verification of the locking that takes place. The
40094 &%-v%& option causes some additional information to be given. The &%-q%& option
40095 suppresses all output except error messages.
40099 exim_lock /var/spool/mail/spqr
40101 runs an interactive shell while the file is locked, whereas
40103 &`exim_lock -q /var/spool/mail/spqr <<End`&
40104 <&'some commands'&>
40107 runs a specific non-interactive sequence of commands while the file is locked,
40108 suppressing all verification output. A single command can be run by a command
40111 exim_lock -q /var/spool/mail/spqr \
40112 "cp /var/spool/mail/spqr /some/where"
40114 Note that if a command is supplied, it must be entirely contained within the
40115 second argument &-- hence the quotes.
40119 . ////////////////////////////////////////////////////////////////////////////
40120 . ////////////////////////////////////////////////////////////////////////////
40122 .chapter "The Exim monitor" "CHAPeximon"
40123 .scindex IIDeximon "Exim monitor" "description"
40124 .cindex "X-windows"
40125 .cindex "&'eximon'&"
40126 .cindex "Local/eximon.conf"
40127 .cindex "&_exim_monitor/EDITME_&"
40128 The Exim monitor is an application which displays in an X window information
40129 about the state of Exim's queue and what Exim is doing. An admin user can
40130 perform certain operations on messages from this GUI interface; however all
40131 such facilities are also available from the command line, and indeed, the
40132 monitor itself makes use of the command line to perform any actions requested.
40136 .section "Running the monitor" "SECID264"
40137 The monitor is started by running the script called &'eximon'&. This is a shell
40138 script that sets up a number of environment variables, and then runs the
40139 binary called &_eximon.bin_&. The default appearance of the monitor window can
40140 be changed by editing the &_Local/eximon.conf_& file created by editing
40141 &_exim_monitor/EDITME_&. Comments in that file describe what the various
40142 parameters are for.
40144 The parameters that get built into the &'eximon'& script can be overridden for
40145 a particular invocation by setting up environment variables of the same names,
40146 preceded by &`EXIMON_`&. For example, a shell command such as
40148 EXIMON_LOG_DEPTH=400 eximon
40150 (in a Bourne-compatible shell) runs &'eximon'& with an overriding setting of
40151 the LOG_DEPTH parameter. If EXIMON_LOG_FILE_PATH is set in the environment, it
40152 overrides the Exim log file configuration. This makes it possible to have
40153 &'eximon'& tailing log data that is written to syslog, provided that MAIL.INFO
40154 syslog messages are routed to a file on the local host.
40156 X resources can be used to change the appearance of the window in the normal
40157 way. For example, a resource setting of the form
40159 Eximon*background: gray94
40161 changes the colour of the background to light grey rather than white. The
40162 stripcharts are drawn with both the data lines and the reference lines in
40163 black. This means that the reference lines are not visible when on top of the
40164 data. However, their colour can be changed by setting a resource called
40165 &"highlight"& (an odd name, but that's what the Athena stripchart widget uses).
40166 For example, if your X server is running Unix, you could set up lighter
40167 reference lines in the stripcharts by obeying
40170 Eximon*highlight: gray
40173 .cindex "admin user"
40174 In order to see the contents of messages in the queue, and to operate on them,
40175 &'eximon'& must either be run as root or by an admin user.
40177 The command-line parameters of &'eximon'& are passed to &_eximon.bin_& and may
40178 contain X11 resource parameters interpreted by the X11 library. In addition,
40179 if the first parameter starts with the string "gdb" then it is removed and the
40180 binary is invoked under gdb (the parameter is used as the gdb command-name, so
40181 versioned variants of gdb can be invoked).
40183 The monitor's window is divided into three parts. The first contains one or
40184 more stripcharts and two action buttons, the second contains a &"tail"& of the
40185 main log file, and the third is a display of the queue of messages awaiting
40186 delivery, with two more action buttons. The following sections describe these
40187 different parts of the display.
40192 .section "The stripcharts" "SECID265"
40193 .cindex "stripchart"
40194 The first stripchart is always a count of messages in the queue. Its name can
40195 be configured by setting QUEUE_STRIPCHART_NAME in the
40196 &_Local/eximon.conf_& file. The remaining stripcharts are defined in the
40197 configuration script by regular expression matches on log file entries, making
40198 it possible to display, for example, counts of messages delivered to certain
40199 hosts or using certain transports. The supplied defaults display counts of
40200 received and delivered messages, and of local and SMTP deliveries. The default
40201 period between stripchart updates is one minute; this can be adjusted by a
40202 parameter in the &_Local/eximon.conf_& file.
40204 The stripchart displays rescale themselves automatically as the value they are
40205 displaying changes. There are always 10 horizontal lines in each chart; the
40206 title string indicates the value of each division when it is greater than one.
40207 For example, &"x2"& means that each division represents a value of 2.
40209 It is also possible to have a stripchart which shows the percentage fullness of
40210 a particular disk partition, which is useful when local deliveries are confined
40211 to a single partition.
40213 .cindex "&%statvfs%& function"
40214 This relies on the availability of the &[statvfs()]& function or equivalent in
40215 the operating system. Most, but not all versions of Unix that support Exim have
40216 this. For this particular stripchart, the top of the chart always represents
40217 100%, and the scale is given as &"x10%"&. This chart is configured by setting
40218 SIZE_STRIPCHART and (optionally) SIZE_STRIPCHART_NAME in the
40219 &_Local/eximon.conf_& file.
40224 .section "Main action buttons" "SECID266"
40225 .cindex "size" "of monitor window"
40226 .cindex "Exim monitor" "window size"
40227 .cindex "window size"
40228 Below the stripcharts there is an action button for quitting the monitor. Next
40229 to this is another button marked &"Size"&. They are placed here so that
40230 shrinking the window to its default minimum size leaves just the queue count
40231 stripchart and these two buttons visible. Pressing the &"Size"& button causes
40232 the window to expand to its maximum size, unless it is already at the maximum,
40233 in which case it is reduced to its minimum.
40235 When expanding to the maximum, if the window cannot be fully seen where it
40236 currently is, it is moved back to where it was the last time it was at full
40237 size. When it is expanding from its minimum size, the old position is
40238 remembered, and next time it is reduced to the minimum it is moved back there.
40240 The idea is that you can keep a reduced window just showing one or two
40241 stripcharts at a convenient place on your screen, easily expand it to show
40242 the full window when required, and just as easily put it back to what it was.
40243 The idea is copied from what the &'twm'& window manager does for its
40244 &'f.fullzoom'& action. The minimum size of the window can be changed by setting
40245 the MIN_HEIGHT and MIN_WIDTH values in &_Local/eximon.conf_&.
40247 Normally, the monitor starts up with the window at its full size, but it can be
40248 built so that it starts up with the window at its smallest size, by setting
40249 START_SMALL=yes in &_Local/eximon.conf_&.
40253 .section "The log display" "SECID267"
40254 .cindex "log" "tail of; in monitor"
40255 The second section of the window is an area in which a display of the tail of
40256 the main log is maintained.
40257 To save space on the screen, the timestamp on each log line is shortened by
40258 removing the date and, if &%log_timezone%& is set, the timezone.
40259 The log tail is not available when the only destination for logging data is
40260 syslog, unless the syslog lines are routed to a local file whose name is passed
40261 to &'eximon'& via the EXIMON_LOG_FILE_PATH environment variable.
40263 The log sub-window has a scroll bar at its lefthand side which can be used to
40264 move back to look at earlier text, and the up and down arrow keys also have a
40265 scrolling effect. The amount of log that is kept depends on the setting of
40266 LOG_BUFFER in &_Local/eximon.conf_&, which specifies the amount of memory
40267 to use. When this is full, the earlier 50% of data is discarded &-- this is
40268 much more efficient than throwing it away line by line. The sub-window also has
40269 a horizontal scroll bar for accessing the ends of long log lines. This is the
40270 only means of horizontal scrolling; the right and left arrow keys are not
40271 available. Text can be cut from this part of the window using the mouse in the
40272 normal way. The size of this subwindow is controlled by parameters in the
40273 configuration file &_Local/eximon.conf_&.
40275 Searches of the text in the log window can be carried out by means of the ^R
40276 and ^S keystrokes, which default to a reverse and a forward search,
40277 respectively. The search covers only the text that is displayed in the window.
40278 It cannot go further back up the log.
40280 The point from which the search starts is indicated by a caret marker. This is
40281 normally at the end of the text in the window, but can be positioned explicitly
40282 by pointing and clicking with the left mouse button, and is moved automatically
40283 by a successful search. If new text arrives in the window when it is scrolled
40284 back, the caret remains where it is, but if the window is not scrolled back,
40285 the caret is moved to the end of the new text.
40287 Pressing ^R or ^S pops up a window into which the search text can be typed.
40288 There are buttons for selecting forward or reverse searching, for carrying out
40289 the search, and for cancelling. If the &"Search"& button is pressed, the search
40290 happens and the window remains so that further searches can be done. If the
40291 &"Return"& key is pressed, a single search is done and the window is closed. If
40292 ^C is typed the search is cancelled.
40294 The searching facility is implemented using the facilities of the Athena text
40295 widget. By default this pops up a window containing both &"search"& and
40296 &"replace"& options. In order to suppress the unwanted &"replace"& portion for
40297 eximon, a modified version of the &%TextPop%& widget is distributed with Exim.
40298 However, the linkers in BSDI and HP-UX seem unable to handle an externally
40299 provided version of &%TextPop%& when the remaining parts of the text widget
40300 come from the standard libraries. The compile-time option EXIMON_TEXTPOP can be
40301 unset to cut out the modified &%TextPop%&, making it possible to build Eximon
40302 on these systems, at the expense of having unwanted items in the search popup
40307 .section "The queue display" "SECID268"
40308 .cindex "queue" "display in monitor"
40309 The bottom section of the monitor window contains a list of all messages that
40310 are in the queue, which includes those currently being received or delivered,
40311 as well as those awaiting delivery. The size of this subwindow is controlled by
40312 parameters in the configuration file &_Local/eximon.conf_&, and the frequency
40313 at which it is updated is controlled by another parameter in the same file &--
40314 the default is 5 minutes, since queue scans can be quite expensive. However,
40315 there is an &"Update"& action button just above the display which can be used
40316 to force an update of the queue display at any time.
40318 When a host is down for some time, a lot of pending mail can build up for it,
40319 and this can make it hard to deal with other messages in the queue. To help
40320 with this situation there is a button next to &"Update"& called &"Hide"&. If
40321 pressed, a dialogue box called &"Hide addresses ending with"& is put up. If you
40322 type anything in here and press &"Return"&, the text is added to a chain of
40323 such texts, and if every undelivered address in a message matches at least one
40324 of the texts, the message is not displayed.
40326 If there is an address that does not match any of the texts, all the addresses
40327 are displayed as normal. The matching happens on the ends of addresses so, for
40328 example, &'cam.ac.uk'& specifies all addresses in Cambridge, while
40329 &'xxx@foo.com.example'& specifies just one specific address. When any hiding
40330 has been set up, a button called &"Unhide"& is displayed. If pressed, it
40331 cancels all hiding. Also, to ensure that hidden messages do not get forgotten,
40332 a hide request is automatically cancelled after one hour.
40334 While the dialogue box is displayed, you can't press any buttons or do anything
40335 else to the monitor window. For this reason, if you want to cut text from the
40336 queue display to use in the dialogue box, you have to do the cutting before
40337 pressing the &"Hide"& button.
40339 The queue display contains, for each unhidden queued message, the length of
40340 time it has been in the queue, the size of the message, the message id, the
40341 message sender, and the first undelivered recipient, all on one line. If it is
40342 a bounce message, the sender is shown as &"<>"&. If there is more than one
40343 recipient to which the message has not yet been delivered, subsequent ones are
40344 listed on additional lines, up to a maximum configured number, following which
40345 an ellipsis is displayed. Recipients that have already received the message are
40348 .cindex "frozen messages" "display"
40349 If a message is frozen, an asterisk is displayed at the left-hand side.
40351 The queue display has a vertical scroll bar, and can also be scrolled by means
40352 of the arrow keys. Text can be cut from it using the mouse in the normal way.
40353 The text searching facilities, as described above for the log window, are also
40354 available, but the caret is always moved to the end of the text when the queue
40355 display is updated.
40359 .section "The queue menu" "SECID269"
40360 .cindex "queue" "menu in monitor"
40361 If the &%shift%& key is held down and the left button is clicked when the mouse
40362 pointer is over the text for any message, an action menu pops up, and the first
40363 line of the queue display for the message is highlighted. This does not affect
40366 If you want to use some other event for popping up the menu, you can set the
40367 MENU_EVENT parameter in &_Local/eximon.conf_& to change the default, or
40368 set EXIMON_MENU_EVENT in the environment before starting the monitor. The
40369 value set in this parameter is a standard X event description. For example, to
40370 run eximon using &%ctrl%& rather than &%shift%& you could use
40372 EXIMON_MENU_EVENT='Ctrl<Btn1Down>' eximon
40374 The title of the menu is the message id, and it contains entries which act as
40378 &'message log'&: The contents of the message log for the message are displayed
40379 in a new text window.
40381 &'headers'&: Information from the spool file that contains the envelope
40382 information and headers is displayed in a new text window. See chapter
40383 &<<CHAPspool>>& for a description of the format of spool files.
40385 &'body'&: The contents of the spool file containing the body of the message are
40386 displayed in a new text window. There is a default limit of 20,000 bytes to the
40387 amount of data displayed. This can be changed by setting the BODY_MAX
40388 option at compile time, or the EXIMON_BODY_MAX option at runtime.
40390 &'deliver message'&: A call to Exim is made using the &%-M%& option to request
40391 delivery of the message. This causes an automatic thaw if the message is
40392 frozen. The &%-v%& option is also set, and the output from Exim is displayed in
40393 a new text window. The delivery is run in a separate process, to avoid holding
40394 up the monitor while the delivery proceeds.
40396 &'freeze message'&: A call to Exim is made using the &%-Mf%& option to request
40397 that the message be frozen.
40399 .cindex "thawing messages"
40400 .cindex "unfreezing messages"
40401 .cindex "frozen messages" "thawing"
40402 &'thaw message'&: A call to Exim is made using the &%-Mt%& option to request
40403 that the message be thawed.
40405 .cindex "delivery" "forcing failure"
40406 &'give up on msg'&: A call to Exim is made using the &%-Mg%& option to request
40407 that Exim gives up trying to deliver the message. A bounce message is generated
40408 for any remaining undelivered addresses.
40410 &'remove message'&: A call to Exim is made using the &%-Mrm%& option to request
40411 that the message be deleted from the system without generating a bounce
40414 &'add recipient'&: A dialog box is displayed into which a recipient address can
40415 be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
40416 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
40417 Otherwise it must be entered as a fully qualified address. Pressing RETURN
40418 causes a call to Exim to be made using the &%-Mar%& option to request that an
40419 additional recipient be added to the message, unless the entry box is empty, in
40420 which case no action is taken.
40422 &'mark delivered'&: A dialog box is displayed into which a recipient address
40423 can be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
40424 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
40425 Otherwise it must be entered as a fully qualified address. Pressing RETURN
40426 causes a call to Exim to be made using the &%-Mmd%& option to mark the given
40427 recipient address as already delivered, unless the entry box is empty, in which
40428 case no action is taken.
40430 &'mark all delivered'&: A call to Exim is made using the &%-Mmad%& option to
40431 mark all recipient addresses as already delivered.
40433 &'edit sender'&: A dialog box is displayed initialized with the current
40434 sender's address. Pressing RETURN causes a call to Exim to be made using the
40435 &%-Mes%& option to replace the sender address, unless the entry box is empty,
40436 in which case no action is taken. If you want to set an empty sender (as in
40437 bounce messages), you must specify it as &"<>"&. Otherwise, if the address is
40438 not qualified and the QUALIFY_DOMAIN parameter is set in &_Local/eximon.conf_&,
40439 the address is qualified with that domain.
40442 When a delivery is forced, a window showing the &%-v%& output is displayed. In
40443 other cases when a call to Exim is made, if there is any output from Exim (in
40444 particular, if the command fails) a window containing the command and the
40445 output is displayed. Otherwise, the results of the action are normally apparent
40446 from the log and queue displays. However, if you set ACTION_OUTPUT=yes in
40447 &_Local/eximon.conf_&, a window showing the Exim command is always opened, even
40448 if no output is generated.
40450 The queue display is automatically updated for actions such as freezing and
40451 thawing, unless ACTION_QUEUE_UPDATE=no has been set in
40452 &_Local/eximon.conf_&. In this case the &"Update"& button has to be used to
40453 force an update of the display after one of these actions.
40455 In any text window that is displayed as result of a menu action, the normal
40456 cut-and-paste facility is available, and searching can be carried out using ^R
40457 and ^S, as described above for the log tail window.
40464 . ////////////////////////////////////////////////////////////////////////////
40465 . ////////////////////////////////////////////////////////////////////////////
40467 .chapter "Security considerations" "CHAPsecurity"
40468 .scindex IIDsecurcon "security" "discussion of"
40469 This chapter discusses a number of issues concerned with security, some of
40470 which are also covered in other parts of this manual.
40472 For reasons that this author does not understand, some people have promoted
40473 Exim as a &"particularly secure"& mailer. Perhaps it is because of the
40474 existence of this chapter in the documentation. However, the intent of the
40475 chapter is simply to describe the way Exim works in relation to certain
40476 security concerns, not to make any specific claims about the effectiveness of
40477 its security as compared with other MTAs.
40479 What follows is a description of the way Exim is supposed to be. Best efforts
40480 have been made to try to ensure that the code agrees with the theory, but an
40481 absence of bugs can never be guaranteed. Any that are reported will get fixed
40482 as soon as possible.
40485 .section "Building a more &""hardened""& Exim" "SECID286"
40486 .cindex "security" "build-time features"
40487 There are a number of build-time options that can be set in &_Local/Makefile_&
40488 to create Exim binaries that are &"harder"& to attack, in particular by a rogue
40489 Exim administrator who does not have the root password, or by someone who has
40490 penetrated the Exim (but not the root) account. These options are as follows:
40493 ALT_CONFIG_PREFIX can be set to a string that is required to match the
40494 start of any filenames used with the &%-C%& option. When it is set, these
40495 filenames are also not allowed to contain the sequence &"/../"&. (However, if
40496 the value of the &%-C%& option is identical to the value of CONFIGURE_FILE in
40497 &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as usual.) There is no
40498 default setting for &%ALT_CONFIG_PREFIX%&.
40500 If the permitted configuration files are confined to a directory to
40501 which only root has access, this guards against someone who has broken
40502 into the Exim account from running a privileged Exim with an arbitrary
40503 configuration file, and using it to break into other accounts.
40506 If a non-trusted configuration file (i.e. not the default configuration file
40507 or one which is trusted by virtue of being listed in the TRUSTED_CONFIG_LIST
40508 file) is specified with &%-C%&, or if macros are given with &%-D%& (but see
40509 the next item), then root privilege is retained only if the caller of Exim is
40510 root. This locks out the possibility of testing a configuration using &%-C%&
40511 right through message reception and delivery, even if the caller is root. The
40512 reception works, but by that time, Exim is running as the Exim user, so when
40513 it re-execs to regain privilege for the delivery, the use of &%-C%& causes
40514 privilege to be lost. However, root can test reception and delivery using two
40518 The WHITELIST_D_MACROS build option declares some macros to be safe to override
40519 with &%-D%& if the real uid is one of root, the Exim run-time user or the
40520 CONFIGURE_OWNER, if defined. The potential impact of this option is limited by
40521 requiring the run-time value supplied to &%-D%& to match a regex that errs on
40522 the restrictive side. Requiring build-time selection of safe macros is onerous
40523 but this option is intended solely as a transition mechanism to permit
40524 previously-working configurations to continue to work after release 4.73.
40526 If DISABLE_D_OPTION is defined, the use of the &%-D%& command line option
40529 FIXED_NEVER_USERS can be set to a colon-separated list of users that are
40530 never to be used for any deliveries. This is like the &%never_users%& runtime
40531 option, but it cannot be overridden; the runtime option adds additional users
40532 to the list. The default setting is &"root"&; this prevents a non-root user who
40533 is permitted to modify the runtime file from using Exim as a way to get root.
40538 .section "Root privilege" "SECID270"
40540 .cindex "root privilege"
40541 The Exim binary is normally setuid to root, which means that it gains root
40542 privilege (runs as root) when it starts execution. In some special cases (for
40543 example, when the daemon is not in use and there are no local deliveries), it
40544 may be possible to run Exim setuid to some user other than root. This is
40545 discussed in the next section. However, in most installations, root privilege
40546 is required for two things:
40549 To set up a socket connected to the standard SMTP port (25) when initialising
40550 the listening daemon. If Exim is run from &'inetd'&, this privileged action is
40553 To be able to change uid and gid in order to read users' &_.forward_& files and
40554 perform local deliveries as the receiving user or as specified in the
40558 It is not necessary to be root to do any of the other things Exim does, such as
40559 receiving messages and delivering them externally over SMTP, and it is
40560 obviously more secure if Exim does not run as root except when necessary.
40561 For this reason, a user and group for Exim to use must be defined in
40562 &_Local/Makefile_&. These are known as &"the Exim user"& and &"the Exim
40563 group"&. Their values can be changed by the runtime configuration, though this
40564 is not recommended. Often a user called &'exim'& is used, but some sites use
40565 &'mail'& or another user name altogether.
40567 Exim uses &[setuid()]& whenever it gives up root privilege. This is a permanent
40568 abdication; the process cannot regain root afterwards. Prior to release 4.00,
40569 &[seteuid()]& was used in some circumstances, but this is no longer the case.
40571 After a new Exim process has interpreted its command line options, it changes
40572 uid and gid in the following cases:
40577 If the &%-C%& option is used to specify an alternate configuration file, or if
40578 the &%-D%& option is used to define macro values for the configuration, and the
40579 calling process is not running as root, the uid and gid are changed to those of
40580 the calling process.
40581 However, if DISABLE_D_OPTION is defined in &_Local/Makefile_&, the &%-D%&
40582 option may not be used at all.
40583 If WHITELIST_D_MACROS is defined in &_Local/Makefile_&, then some macro values
40584 can be supplied if the calling process is running as root, the Exim run-time
40585 user or CONFIGURE_OWNER, if defined.
40590 If the expansion test option (&%-be%&) or one of the filter testing options
40591 (&%-bf%& or &%-bF%&) are used, the uid and gid are changed to those of the
40594 If the process is not a daemon process or a queue runner process or a delivery
40595 process or a process for testing address routing (started with &%-bt%&), the
40596 uid and gid are changed to the Exim user and group. This means that Exim always
40597 runs under its own uid and gid when receiving messages. This also applies when
40598 testing address verification
40601 (the &%-bv%& option) and testing incoming message policy controls (the &%-bh%&
40604 For a daemon, queue runner, delivery, or address testing process, the uid
40605 remains as root at this stage, but the gid is changed to the Exim group.
40608 The processes that initially retain root privilege behave as follows:
40611 A daemon process changes the gid to the Exim group and the uid to the Exim
40612 user after setting up one or more listening sockets. The &[initgroups()]&
40613 function is called, so that if the Exim user is in any additional groups, they
40614 will be used during message reception.
40616 A queue runner process retains root privilege throughout its execution. Its
40617 job is to fork a controlled sequence of delivery processes.
40619 A delivery process retains root privilege throughout most of its execution,
40620 but any actual deliveries (that is, the transports themselves) are run in
40621 subprocesses which always change to a non-root uid and gid. For local
40622 deliveries this is typically the uid and gid of the owner of the mailbox; for
40623 remote deliveries, the Exim uid and gid are used. Once all the delivery
40624 subprocesses have been run, a delivery process changes to the Exim uid and gid
40625 while doing post-delivery tidying up such as updating the retry database and
40626 generating bounce and warning messages.
40628 While the recipient addresses in a message are being routed, the delivery
40629 process runs as root. However, if a user's filter file has to be processed,
40630 this is done in a subprocess that runs under the individual user's uid and
40631 gid. A system filter is run as root unless &%system_filter_user%& is set.
40633 A process that is testing addresses (the &%-bt%& option) runs as root so that
40634 the routing is done in the same environment as a message delivery.
40640 .section "Running Exim without privilege" "SECTrunexiwitpri"
40641 .cindex "privilege, running without"
40642 .cindex "unprivileged running"
40643 .cindex "root privilege" "running without"
40644 Some installations like to run Exim in an unprivileged state for more of its
40645 operation, for added security. Support for this mode of operation is provided
40646 by the global option &%deliver_drop_privilege%&. When this is set, the uid and
40647 gid are changed to the Exim user and group at the start of a delivery process
40648 (and also queue runner and address testing processes). This means that address
40649 routing is no longer run as root, and the deliveries themselves cannot change
40653 .cindex "daemon" "restarting"
40654 Leaving the binary setuid to root, but setting &%deliver_drop_privilege%& means
40655 that the daemon can still be started in the usual way, and it can respond
40656 correctly to SIGHUP because the re-invocation regains root privilege.
40658 An alternative approach is to make Exim setuid to the Exim user and also setgid
40659 to the Exim group. If you do this, the daemon must be started from a root
40660 process. (Calling Exim from a root process makes it behave in the way it does
40661 when it is setuid root.) However, the daemon cannot restart itself after a
40662 SIGHUP signal because it cannot regain privilege.
40664 It is still useful to set &%deliver_drop_privilege%& in this case, because it
40665 stops Exim from trying to re-invoke itself to do a delivery after a message has
40666 been received. Such a re-invocation is a waste of resources because it has no
40669 If restarting the daemon is not an issue (for example, if &%mua_wrapper%& is
40670 set, or &'inetd'& is being used instead of a daemon), having the binary setuid
40671 to the Exim user seems a clean approach, but there is one complication:
40673 In this style of operation, Exim is running with the real uid and gid set to
40674 those of the calling process, and the effective uid/gid set to Exim's values.
40675 Ideally, any association with the calling process' uid/gid should be dropped,
40676 that is, the real uid/gid should be reset to the effective values so as to
40677 discard any privileges that the caller may have. While some operating systems
40678 have a function that permits this action for a non-root effective uid, quite a
40679 number of them do not. Because of this lack of standardization, Exim does not
40680 address this problem at this time.
40682 For this reason, the recommended approach for &"mostly unprivileged"& running
40683 is to keep the Exim binary setuid to root, and to set
40684 &%deliver_drop_privilege%&. This also has the advantage of allowing a daemon to
40685 be used in the most straightforward way.
40687 If you configure Exim not to run delivery processes as root, there are a
40688 number of restrictions on what you can do:
40691 You can deliver only as the Exim user/group. You should explicitly use the
40692 &%user%& and &%group%& options to override routers or local transports that
40693 normally deliver as the recipient. This makes sure that configurations that
40694 work in this mode function the same way in normal mode. Any implicit or
40695 explicit specification of another user causes an error.
40697 Use of &_.forward_& files is severely restricted, such that it is usually
40698 not worthwhile to include them in the configuration.
40700 Users who wish to use &_.forward_& would have to make their home directory and
40701 the file itself accessible to the Exim user. Pipe and append-to-file entries,
40702 and their equivalents in Exim filters, cannot be used. While they could be
40703 enabled in the Exim user's name, that would be insecure and not very useful.
40705 Unless the local user mailboxes are all owned by the Exim user (possible in
40706 some POP3 or IMAP-only environments):
40709 They must be owned by the Exim group and be writeable by that group. This
40710 implies you must set &%mode%& in the appendfile configuration, as well as the
40711 mode of the mailbox files themselves.
40713 You must set &%no_check_owner%&, since most or all of the files will not be
40714 owned by the Exim user.
40716 You must set &%file_must_exist%&, because Exim cannot set the owner correctly
40717 on a newly created mailbox when unprivileged. This also implies that new
40718 mailboxes need to be created manually.
40723 These restrictions severely restrict what can be done in local deliveries.
40724 However, there are no restrictions on remote deliveries. If you are running a
40725 gateway host that does no local deliveries, setting &%deliver_drop_privilege%&
40726 gives more security at essentially no cost.
40728 If you are using the &%mua_wrapper%& facility (see chapter
40729 &<<CHAPnonqueueing>>&), &%deliver_drop_privilege%& is forced to be true.
40734 .section "Delivering to local files" "SECID271"
40735 Full details of the checks applied by &(appendfile)& before it writes to a file
40736 are given in chapter &<<CHAPappendfile>>&.
40740 .section "Running local commands" "SECTsecconslocalcmds"
40741 .cindex "security" "local commands"
40742 .cindex "security" "command injection attacks"
40743 There are a number of ways in which an administrator can configure Exim to run
40744 commands based upon received, untrustworthy, data. Further, in some
40745 configurations a user who can control a &_.forward_& file can also arrange to
40746 run commands. Configuration to check includes, but is not limited to:
40749 Use of &%use_shell%& in the pipe transport: various forms of shell command
40750 injection may be possible with this option present. It is dangerous and should
40751 be used only with considerable caution. Consider constraints which whitelist
40752 allowed characters in a variable which is to be used in a pipe transport that
40753 has &%use_shell%& enabled.
40755 A number of options such as &%forbid_filter_run%&, &%forbid_filter_perl%&,
40756 &%forbid_filter_dlfunc%& and so forth which restrict facilities available to
40757 &_.forward_& files in a redirect router. If Exim is running on a central mail
40758 hub to which ordinary users do not have shell access, but home directories are
40759 NFS mounted (for instance) then administrators should review the list of these
40760 forbid options available, and should bear in mind that the options that may
40761 need forbidding can change as new features are added between releases.
40763 The &%${run...}%& expansion item does not use a shell by default, but
40764 administrators can configure use of &_/bin/sh_& as part of the command.
40765 Such invocations should be viewed with prejudicial suspicion.
40767 Administrators who use embedded Perl are advised to explore how Perl's
40768 taint checking might apply to their usage.
40770 Use of &%${expand...}%& is somewhat analogous to shell's eval builtin and
40771 administrators are well advised to view its use with suspicion, in case (for
40772 instance) it allows a local-part to contain embedded Exim directives.
40774 Use of &%${match_local_part...}%& and friends becomes more dangerous if
40775 Exim was built with EXPAND_LISTMATCH_RHS defined: the second string in
40776 each can reference arbitrary lists and files, rather than just being a list
40778 The EXPAND_LISTMATCH_RHS option was added and set false by default because of
40779 real-world security vulnerabilities caused by its use with untrustworthy data
40780 injected in, for SQL injection attacks.
40781 Consider the use of the &%inlisti%& expansion condition instead.
40787 .section "Trust in configuration data" "SECTsecconfdata"
40788 .cindex "security" "data sources"
40789 .cindex "security" "regular expressions"
40790 .cindex "regular expressions" "security"
40791 .cindex "PCRE2" "security"
40792 If configuration data for Exim can come from untrustworthy sources, there
40793 are some issues to be aware of:
40796 Use of &%${expand...}%& may provide a path for shell injection attacks.
40798 Letting untrusted data provide a regular expression is unwise.
40800 Using &%${match...}%& to apply a fixed regular expression against untrusted
40801 data may result in pathological behaviour within PCRE2. Be aware of what
40802 "backtracking" means and consider options for being more strict with a regular
40803 expression. Avenues to explore include limiting what can match (avoiding &`.`&
40804 when &`[a-z0-9]`& or other character class will do), use of atomic grouping and
40805 possessive quantifiers or just not using regular expressions against untrusted
40808 It can be important to correctly use &%${quote:...}%&,
40809 &%${quote_local_part:...}%& and &%${quote_%&<&'lookup-type'&>&%:...}%& expansion
40810 items to ensure that data is correctly constructed.
40812 Some lookups might return multiple results, even though normal usage is only
40813 expected to yield one result.
40819 .section "IPv4 source routing" "SECID272"
40820 .cindex "source routing" "in IP packets"
40821 .cindex "IP source routing"
40822 Many operating systems suppress IP source-routed packets in the kernel, but
40823 some cannot be made to do this, so Exim does its own check. It logs incoming
40824 IPv4 source-routed TCP calls, and then drops them. Things are all different in
40825 IPv6. No special checking is currently done.
40829 .section "The VRFY, EXPN, and ETRN commands in SMTP" "SECID273"
40830 Support for these SMTP commands is disabled by default. If required, they can
40831 be enabled by defining suitable ACLs.
40836 .section "Privileged users" "SECID274"
40837 .cindex "trusted users"
40838 .cindex "admin user"
40839 .cindex "privileged user"
40840 .cindex "user" "trusted"
40841 .cindex "user" "admin"
40842 Exim recognizes two sets of users with special privileges. Trusted users are
40843 able to submit new messages to Exim locally, but supply their own sender
40844 addresses and information about a sending host. For other users submitting
40845 local messages, Exim sets up the sender address from the uid, and doesn't
40846 permit a remote host to be specified.
40849 However, an untrusted user is permitted to use the &%-f%& command line option
40850 in the special form &%-f <>%& to indicate that a delivery failure for the
40851 message should not cause an error report. This affects the message's envelope,
40852 but it does not affect the &'Sender:'& header. Untrusted users may also be
40853 permitted to use specific forms of address with the &%-f%& option by setting
40854 the &%untrusted_set_sender%& option.
40856 Trusted users are used to run processes that receive mail messages from some
40857 other mail domain and pass them on to Exim for delivery either locally, or over
40858 the Internet. Exim trusts a caller that is running as root, as the Exim user,
40859 as any user listed in the &%trusted_users%& configuration option, or under any
40860 group listed in the &%trusted_groups%& option.
40862 Admin users are permitted to do things to the messages on Exim's queue. They
40863 can freeze or thaw messages, cause them to be returned to their senders, remove
40864 them entirely, or modify them in various ways. In addition, admin users can run
40865 the Exim monitor and see all the information it is capable of providing, which
40866 includes the contents of files on the spool.
40870 By default, the use of the &%-M%& and &%-q%& options to cause Exim to attempt
40871 delivery of messages on its queue is restricted to admin users. This
40872 restriction can be relaxed by setting the &%no_prod_requires_admin%& option.
40873 Similarly, the use of &%-bp%& (and its variants) to list the contents of the
40874 queue is also restricted to admin users. This restriction can be relaxed by
40875 setting &%no_queue_list_requires_admin%&.
40877 Exim recognizes an admin user if the calling process is running as root or as
40878 the Exim user or if any of the groups associated with the calling process is
40879 the Exim group. It is not necessary actually to be running under the Exim
40880 group. However, if admin users who are not root or the Exim user are to access
40881 the contents of files on the spool via the Exim monitor (which runs
40882 unprivileged), Exim must be built to allow group read access to its spool
40885 By default, regular users are trusted to perform basic testing and
40886 introspection commands, as themselves. This setting can be tightened by
40887 setting the &%commandline_checks_require_admin%& option.
40888 This affects most of the checking options,
40889 such as &%-be%& and anything else &%-b*%&.
40892 .section "Spool files" "SECID275"
40893 .cindex "spool directory" "files"
40894 Exim's spool directory and everything it contains is owned by the Exim user and
40895 set to the Exim group. The mode for spool files is defined in the
40896 &_Local/Makefile_& configuration file, and defaults to 0640. This means that
40897 any user who is a member of the Exim group can access these files.
40901 .section "Use of argv[0]" "SECID276"
40902 Exim examines the last component of &%argv[0]%&, and if it matches one of a set
40903 of specific strings, Exim assumes certain options. For example, calling Exim
40904 with the last component of &%argv[0]%& set to &"rsmtp"& is exactly equivalent
40905 to calling it with the option &%-bS%&. There are no security implications in
40910 .section "Use of %f formatting" "SECID277"
40911 The only use made of &"%f"& by Exim is in formatting load average values. These
40912 are actually stored in integer variables as 1000 times the load average.
40913 Consequently, their range is limited and so therefore is the length of the
40918 .section "Embedded Exim path" "SECID278"
40919 Exim uses its own path name, which is embedded in the code, only when it needs
40920 to re-exec in order to regain root privilege. Therefore, it is not root when it
40921 does so. If some bug allowed the path to get overwritten, it would lead to an
40922 arbitrary program's being run as exim, not as root.
40926 .section "Dynamic module directory" "SECTdynmoddir"
40927 Any dynamically loadable modules must be installed into the directory
40928 defined in &`LOOKUP_MODULE_DIR`& in &_Local/Makefile_& for Exim to permit
40932 .section "Use of sprintf()" "SECID279"
40933 .cindex "&[sprintf()]&"
40934 A large number of occurrences of &"sprintf"& in the code are actually calls to
40935 &'string_sprintf()'&, a function that returns the result in malloc'd store.
40936 The intermediate formatting is done into a large fixed buffer by a function
40937 that runs through the format string itself, and checks the length of each
40938 conversion before performing it, thus preventing buffer overruns.
40940 The remaining uses of &[sprintf()]& happen in controlled circumstances where
40941 the output buffer is known to be sufficiently long to contain the converted
40946 .section "Use of debug_printf() and log_write()" "SECID280"
40947 Arbitrary strings are passed to both these functions, but they do their
40948 formatting by calling the function &'string_vformat()'&, which runs through
40949 the format string itself, and checks the length of each conversion.
40953 .section "Use of strcat() and strcpy()" "SECID281"
40954 These are used only in cases where the output buffer is known to be large
40955 enough to hold the result.
40956 .ecindex IIDsecurcon
40961 . ////////////////////////////////////////////////////////////////////////////
40962 . ////////////////////////////////////////////////////////////////////////////
40964 .chapter "Format of spool files" "CHAPspool"
40965 .scindex IIDforspo1 "format" "spool files"
40966 .scindex IIDforspo2 "spool directory" "format of files"
40967 .scindex IIDforspo3 "spool files" "format of"
40968 .cindex "spool files" "editing"
40969 A message on Exim's queue consists of two files, whose names are the message id
40970 followed by -D and -H, respectively. The data portion of the message is kept in
40971 the -D file on its own. The message's envelope, status, and headers are all
40972 kept in the -H file, whose format is described in this chapter. Each of these
40973 two files contains the final component of its own name as its first line. This
40974 is insurance against disk crashes where the directory is lost but the files
40975 themselves are recoverable.
40977 The file formats may be changed, or new formats added, at any release.
40978 Spool files are not intended as an interface to other programs
40979 and should not be used as such.
40981 Some people are tempted into editing -D files in order to modify messages. You
40982 need to be extremely careful if you do this; it is not recommended and you are
40983 on your own if you do it. Here are some of the pitfalls:
40986 You must ensure that Exim does not try to deliver the message while you are
40987 fiddling with it. The safest way is to take out a write lock on the -D file,
40988 which is what Exim itself does, using &[fcntl()]&. If you update the file in
40989 place, the lock will be retained. If you write a new file and rename it, the
40990 lock will be lost at the instant of rename.
40992 .vindex "&$body_linecount$&"
40993 If you change the number of lines in the file, the value of
40994 &$body_linecount$&, which is stored in the -H file, will be incorrect and can
40995 cause incomplete transmission of messages or undeliverable messages.
40997 If the message is in MIME format, you must take care not to break it.
40999 If the message is cryptographically signed, any change will invalidate the
41002 All in all, modifying -D files is fraught with danger.
41004 Files whose names end with -J may also be seen in the &_input_& directory (or
41005 its subdirectories when &%split_spool_directory%& is set). These are journal
41006 files, used to record addresses to which the message has been delivered during
41007 the course of a delivery attempt. If there are still undelivered recipients at
41008 the end, the -H file is updated, and the -J file is deleted. If, however, there
41009 is some kind of crash (for example, a power outage) before this happens, the -J
41010 file remains in existence. When Exim next processes the message, it notices the
41011 -J file and uses it to update the -H file before starting the next delivery
41014 Files whose names end with -K or .eml may also be seen in the spool.
41015 These are temporaries used for DKIM or malware processing, when that is used.
41016 They should be tidied up by normal operations; any old ones are probably
41017 relics of crashes and can be removed.
41019 .section "Format of the -H file" "SECID282"
41020 .cindex "uid (user id)" "in spool file"
41021 .cindex "gid (group id)" "in spool file"
41022 The second line of the -H file contains the login name for the uid of the
41023 process that called Exim to read the message, followed by the numerical uid and
41024 gid. For a locally generated message, this is normally the user who sent the
41025 message. For a message received over TCP/IP via the daemon, it is
41026 normally the Exim user.
41028 The third line of the file contains the address of the message's sender as
41029 transmitted in the envelope, contained in angle brackets. The sender address is
41030 empty for bounce messages. For incoming SMTP mail, the sender address is given
41031 in the MAIL command. For locally generated mail, the sender address is
41032 created by Exim from the login name of the current user and the configured
41033 &%qualify_domain%&. However, this can be overridden by the &%-f%& option or a
41034 leading &"From&~"& line if the caller is trusted, or if the supplied address is
41035 &"<>"& or an address that matches &%untrusted_set_senders%&.
41037 The fourth line contains two numbers. The first is the time that the message
41038 was received, in the conventional Unix form &-- the number of seconds since the
41039 start of the epoch. The second number is a count of the number of messages
41040 warning of delayed delivery that have been sent to the sender.
41042 There follow a number of lines starting with a hyphen.
41043 These contain variables, can appear in any
41044 order, and are omitted when not relevant.
41046 If there is a second hyphen after the first,
41047 the corresponding data is tainted.
41048 If there is a value in parentheses, the data is quoted for a lookup.
41050 The following word specifies a variable,
41051 and the remainder of the item depends on the variable.
41054 .vitem "&%-acl%&&~<&'number'&>&~<&'length'&>"
41055 This item is obsolete, and is not generated from Exim release 4.61 onwards;
41056 &%-aclc%& and &%-aclm%& are used instead. However, &%-acl%& is still
41057 recognized, to provide backward compatibility. In the old format, a line of
41058 this form is present for every ACL variable that is not empty. The number
41059 identifies the variable; the &%acl_c%&&*x*& variables are numbered 0&--9 and
41060 the &%acl_m%&&*x*& variables are numbered 10&--19. The length is the length of
41061 the data string for the variable. The string itself starts at the beginning of
41062 the next line, and is followed by a newline character. It may contain internal
41065 .vitem "&%-aclc%&&~<&'rest-of-name'&>&~<&'length'&>"
41066 A line of this form is present for every ACL connection variable that is
41067 defined. Note that there is a space between &%-aclc%& and the rest of the name.
41068 The length is the length of the data string for the variable. The string itself
41069 starts at the beginning of the next line, and is followed by a newline
41070 character. It may contain internal newlines.
41072 .vitem "&%-aclm%&&~<&'rest-of-name'&>&~<&'length'&>"
41073 A line of this form is present for every ACL message variable that is defined.
41074 Note that there is a space between &%-aclm%& and the rest of the name. The
41075 length is the length of the data string for the variable. The string itself
41076 starts at the beginning of the next line, and is followed by a newline
41077 character. It may contain internal newlines.
41079 .vitem "&%-active_hostname%&&~<&'hostname'&>"
41080 This is present if, when the message was received over SMTP, the value of
41081 &$smtp_active_hostname$& was different to the value of &$primary_hostname$&.
41083 .vitem &%-allow_unqualified_recipient%&
41084 This is present if unqualified recipient addresses are permitted in header
41085 lines (to stop such addresses from being qualified if rewriting occurs at
41086 transport time). Local messages that were input using &%-bnq%& and remote
41087 messages from hosts that match &%recipient_unqualified_hosts%& set this flag.
41089 .vitem &%-allow_unqualified_sender%&
41090 This is present if unqualified sender addresses are permitted in header lines
41091 (to stop such addresses from being qualified if rewriting occurs at transport
41092 time). Local messages that were input using &%-bnq%& and remote messages from
41093 hosts that match &%sender_unqualified_hosts%& set this flag.
41095 .vitem "&%-auth_id%&&~<&'text'&>"
41096 The id information for a message received on an authenticated SMTP connection
41097 &-- the value of the &$authenticated_id$& variable.
41099 .vitem "&%-auth_sender%&&~<&'address'&>"
41100 The address of an authenticated sender &-- the value of the
41101 &$authenticated_sender$& variable.
41103 .vitem "&%-body_linecount%&&~<&'number'&>"
41104 This records the number of lines in the body of the message, and is
41105 present unless &%-spool_file_wireformat%& is.
41107 .vitem "&%-body_zerocount%&&~<&'number'&>"
41108 This records the number of binary zero bytes in the body of the message, and is
41109 present if the number is greater than zero.
41111 .vitem &%-deliver_firsttime%&
41112 This is written when a new message is first added to the spool. When the spool
41113 file is updated after a deferral, it is omitted.
41115 .vitem "&%-frozen%&&~<&'time'&>"
41116 .cindex "frozen messages" "spool data"
41117 The message is frozen, and the freezing happened at <&'time'&>.
41119 .vitem "&%-helo_name%&&~<&'text'&>"
41120 This records the host name as specified by a remote host in a HELO or EHLO
41123 .vitem "&%-host_address%&&~<&'address'&>.<&'port'&>"
41124 This records the IP address of the host from which the message was received and
41125 the remote port number that was used. It is omitted for locally generated
41128 .vitem "&%-host_auth%&&~<&'text'&>"
41129 If the message was received on an authenticated SMTP connection, this records
41130 the name of the authenticator &-- the value of the
41131 &$sender_host_authenticated$& variable.
41133 .vitem &%-host_lookup_failed%&
41134 This is present if an attempt to look up the sending host's name from its IP
41135 address failed. It corresponds to the &$host_lookup_failed$& variable.
41137 .vitem "&%-host_name%&&~<&'text'&>"
41138 .cindex "reverse DNS lookup"
41139 .cindex "DNS" "reverse lookup"
41140 This records the name of the remote host from which the message was received,
41141 if the host name was looked up from the IP address when the message was being
41142 received. It is not present if no reverse lookup was done.
41144 .vitem "&%-ident%&&~<&'text'&>"
41145 For locally submitted messages, this records the login of the originating user,
41146 unless it was a trusted user and the &%-oMt%& option was used to specify an
41147 ident value. For messages received over TCP/IP, this records the ident string
41148 supplied by the remote host, if any.
41150 .vitem "&%-interface_address%&&~<&'address'&>.<&'port'&>"
41151 This records the IP address of the local interface and the port number through
41152 which a message was received from a remote host. It is omitted for locally
41153 generated messages.
41156 The message is from a local sender.
41158 .vitem &%-localerror%&
41159 The message is a locally-generated bounce message.
41161 .vitem "&%-local_scan%&&~<&'string'&>"
41162 This records the data string that was returned by the &[local_scan()]& function
41163 when the message was received &-- the value of the &$local_scan_data$&
41164 variable. It is omitted if no data was returned.
41166 .vitem &%-manual_thaw%&
41167 The message was frozen but has been thawed manually, that is, by an explicit
41168 Exim command rather than via the auto-thaw process.
41171 A testing delivery process was started using the &%-N%& option to suppress any
41172 actual deliveries, but delivery was deferred. At any further delivery attempts,
41175 .vitem &%-received_protocol%&
41176 This records the value of the &$received_protocol$& variable, which contains
41177 the name of the protocol by which the message was received.
41179 .vitem &%-sender_set_untrusted%&
41180 The envelope sender of this message was set by an untrusted local caller (used
41181 to ensure that the caller is displayed in queue listings).
41183 .vitem "&%-spam_score_int%&&~<&'number'&>"
41184 If a message was scanned by SpamAssassin, this is present. It records the value
41185 of &$spam_score_int$&.
41187 .vitem &%-spool_file_wireformat%&
41188 The -D file for this message is in wire-format (for ESMTP CHUNKING)
41189 rather than Unix-format.
41190 The line-ending is CRLF rather than newline.
41191 There is still, however, no leading-dot-stuffing.
41193 .vitem &%-tls_certificate_verified%&
41194 A TLS certificate was received from the client that sent this message, and the
41195 certificate was verified by the server.
41197 .vitem "&%-tls_cipher%&&~<&'cipher name'&>"
41198 When the message was received over an encrypted connection, this records the
41199 name of the cipher suite that was used.
41201 .vitem "&%-tls_peerdn%&&~<&'peer DN'&>"
41202 When the message was received over an encrypted connection, and a certificate
41203 was received from the client, this records the Distinguished Name from that
41207 Following the options there is a list of those addresses to which the message
41208 is not to be delivered. This set of addresses is initialized from the command
41209 line when the &%-t%& option is used and &%extract_addresses_remove_arguments%&
41210 is set; otherwise it starts out empty. Whenever a successful delivery is made,
41211 the address is added to this set. The addresses are kept internally as a
41212 balanced binary tree, and it is a representation of that tree which is written
41213 to the spool file. If an address is expanded via an alias or forward file, the
41214 original address is added to the tree when deliveries to all its child
41215 addresses are complete.
41217 If the tree is empty, there is a single line in the spool file containing just
41218 the text &"XX"&. Otherwise, each line consists of two letters, which are either
41219 Y or N, followed by an address. The address is the value for the node of the
41220 tree, and the letters indicate whether the node has a left branch and/or a
41221 right branch attached to it, respectively. If branches exist, they immediately
41222 follow. Here is an example of a three-node tree:
41224 YY darcy@austen.fict.example
41225 NN alice@wonderland.fict.example
41226 NN editor@thesaurus.ref.example
41228 After the non-recipients tree, there is a list of the message's recipients.
41229 This is a simple list, preceded by a count. It includes all the original
41230 recipients of the message, including those to whom the message has already been
41231 delivered. In the simplest case, the list contains one address per line. For
41235 editor@thesaurus.ref.example
41236 darcy@austen.fict.example
41238 alice@wonderland.fict.example
41240 However, when a child address has been added to the top-level addresses as a
41241 result of the use of the &%one_time%& option on a &(redirect)& router, each
41242 line is of the following form:
41244 <&'top-level address'&> <&'errors_to address'&> &&&
41245 <&'length'&>,<&'parent number'&>#<&'flag bits'&>
41247 The 01 flag bit indicates the presence of the three other fields that follow
41248 the top-level address. Other bits may be used in future to support additional
41249 fields. The <&'parent number'&> is the offset in the recipients list of the
41250 original parent of the &"one time"& address. The first two fields are the
41251 envelope sender that is associated with this address and its length. If the
41252 length is zero, there is no special envelope sender (there are then two space
41253 characters in the line). A non-empty field can arise from a &(redirect)& router
41254 that has an &%errors_to%& setting.
41257 A blank line separates the envelope and status information from the headers
41258 which follow. A header may occupy several lines of the file, and to save effort
41259 when reading it in, each header is preceded by a number and an identifying
41260 character. The number is the number of characters in the header, including any
41261 embedded newlines and the terminating newline. The character is one of the
41265 .row <&'blank'&> "header in which Exim has no special interest"
41266 .row &`B`& "&'Bcc:'& header"
41267 .row &`C`& "&'Cc:'& header"
41268 .row &`F`& "&'From:'& header"
41269 .row &`I`& "&'Message-id:'& header"
41270 .row &`P`& "&'Received:'& header &-- P for &""postmark""&"
41271 .row &`R`& "&'Reply-To:'& header"
41272 .row &`S`& "&'Sender:'& header"
41273 .row &`T`& "&'To:'& header"
41274 .row &`*`& "replaced or deleted header"
41277 Deleted or replaced (rewritten) headers remain in the spool file for debugging
41278 purposes. They are not transmitted when the message is delivered. Here is a
41279 typical set of headers:
41281 111P Received: by hobbit.fict.example with local (Exim 4.00)
41282 id 14y9EI-00026G-00; Fri, 11 May 2001 10:28:59 +0100
41283 049 Message-Id: <E14y9EI-00026G-00@hobbit.fict.example>
41284 038* X-rewrote-sender: bb@hobbit.fict.example
41285 042* From: Bilbo Baggins <bb@hobbit.fict.example>
41286 049F From: Bilbo Baggins <B.Baggins@hobbit.fict.example>
41287 099* To: alice@wonderland.fict.example, rdo@foundation,
41288 darcy@austen.fict.example, editor@thesaurus.ref.example
41289 104T To: alice@wonderland.fict.example, rdo@foundation.example,
41290 darcy@austen.fict.example, editor@thesaurus.ref.example
41291 038 Date: Fri, 11 May 2001 10:28:59 +0100
41293 The asterisked headers indicate that the envelope sender, &'From:'& header, and
41294 &'To:'& header have been rewritten, the last one because routing expanded the
41295 unqualified domain &'foundation'&.
41296 .ecindex IIDforspo1
41297 .ecindex IIDforspo2
41298 .ecindex IIDforspo3
41300 .section "Format of the -D file" "SECID282a"
41301 The data file is traditionally in Unix-standard format: lines are ended with
41302 an ASCII newline character.
41303 However, when the &%spool_wireformat%& main option is used some -D files
41304 can have an alternate format.
41305 This is flagged by a &%-spool_file_wireformat%& line in the corresponding -H file.
41306 The -D file lines (not including the first name-component line) are
41307 suitable for direct copying to the wire when transmitting using the
41308 ESMTP CHUNKING option, meaning lower processing overhead.
41309 Lines are terminated with an ASCII CRLF pair.
41310 There is no dot-stuffing (and no dot-termination).
41312 . ////////////////////////////////////////////////////////////////////////////
41313 . ////////////////////////////////////////////////////////////////////////////
41315 .chapter "DKIM, SPF, SRS and DMARC" "CHAPdkim" &&&
41316 "DKIM, SPF, SRS and DMARC Support"
41318 .section "DKIM (DomainKeys Identified Mail)" SECDKIM
41321 DKIM is a mechanism by which messages sent by some entity can be provably
41322 linked to a domain which that entity controls. It permits reputation to
41323 be tracked on a per-domain basis, rather than merely upon source IP address.
41324 DKIM is documented in RFC 6376.
41326 As DKIM relies on the message being unchanged in transit, messages handled
41327 by a mailing-list (which traditionally adds to the message) will not match
41328 any original DKIM signature.
41330 DKIM support is compiled into Exim by default if TLS support is present.
41331 It can be disabled by setting DISABLE_DKIM=yes in &_Local/Makefile_&.
41333 Exim's DKIM implementation allows for
41335 Signing outgoing messages: This function is implemented in the SMTP transport.
41336 It can co-exist with all other Exim features
41337 (including transport filters)
41338 except cutthrough delivery.
41340 Verifying signatures in incoming messages: This is implemented by an additional
41341 ACL (acl_smtp_dkim), which can be called several times per message, with
41342 different signature contexts.
41345 In typical Exim style, the verification implementation does not include any
41346 default "policy". Instead it enables you to build your own policy using
41347 Exim's standard controls.
41349 Please note that verification of DKIM signatures in incoming mail is turned
41350 on by default for logging (in the <= line) purposes.
41352 Additional log detail can be enabled using the &%dkim_verbose%& log_selector.
41353 When set, for each signature in incoming email,
41354 exim will log a line displaying the most important signature details, and the
41355 signature status. Here is an example (with line-breaks added for clarity):
41357 2009-09-09 10:22:28 1MlIRf-0003LU-U3 DKIM:
41358 d=facebookmail.com s=q1-2009b
41359 c=relaxed/relaxed a=rsa-sha1
41360 i=@facebookmail.com t=1252484542 [verification succeeded]
41363 You might want to turn off DKIM verification processing entirely for internal
41364 or relay mail sources. To do that, set the &%dkim_disable_verify%& ACL
41365 control modifier. This should typically be done in the RCPT ACL, at points
41366 where you accept mail from relay sources (internal hosts or authenticated
41370 .section "Signing outgoing messages" "SECDKIMSIGN"
41371 .cindex "DKIM" "signing"
41373 For signing to be usable you must have published a DKIM record in DNS.
41374 Note that RFC 8301 (which does not cover EC keys) says:
41376 rsa-sha1 MUST NOT be used for signing or verifying.
41378 Signers MUST use RSA keys of at least 1024 bits for all keys.
41379 Signers SHOULD use RSA keys of at least 2048 bits.
41382 Note also that the key content (the 'p=' field)
41383 in the DNS record is different between RSA and EC keys;
41384 for the former it is the base64 of the ASN.1 for the RSA public key
41385 (equivalent to the private-key .pem with the header/trailer stripped)
41386 but for EC keys it is the base64 of the pure key; no ASN.1 wrapping.
41388 Signing is enabled by setting private options on the SMTP transport.
41389 These options take (expandable) strings as arguments.
41391 .option dkim_domain smtp "string list&!!" unset
41392 The domain(s) you want to sign with.
41393 After expansion, this can be a list.
41394 Each element in turn,
41396 .vindex "&$dkim_domain$&"
41397 is put into the &%$dkim_domain%& expansion variable
41398 while expanding the remaining signing options.
41399 If it is empty after expansion, DKIM signing is not done,
41400 and no error will result even if &%dkim_strict%& is set.
41402 .option dkim_selector smtp "string list&!!" unset
41403 This sets the key selector string.
41404 After expansion, which can use &$dkim_domain$&, this can be a list.
41405 Each element in turn is put in the expansion
41406 .vindex "&$dkim_selector$&"
41407 variable &%$dkim_selector%& which may be used in the &%dkim_private_key%&
41408 option along with &%$dkim_domain%&.
41409 If the option is empty after expansion, DKIM signing is not done for this domain,
41410 and no error will result even if &%dkim_strict%& is set.
41412 To do, for example, dual-signing with RSA and EC keys
41413 this could be be used:
41415 dkim_selector = ec_sel : rsa_sel
41416 dkim_private_key = KEYS_DIR/$dkim_selector
41419 .option dkim_private_key smtp string&!! unset
41420 This sets the private key to use.
41421 You can use the &%$dkim_domain%& and
41422 &%$dkim_selector%& expansion variables to determine the private key to use.
41423 The result can either
41425 be a valid RSA private key in ASCII armor (.pem file), including line breaks
41427 with GnuTLS 3.6.0 or OpenSSL 1.1.1 or later,
41428 be a valid Ed25519 private key (same format as above)
41430 start with a slash, in which case it is treated as a file that contains
41433 be "0", "false" or the empty string, in which case the message will not
41434 be signed. This case will not result in an error, even if &%dkim_strict%&
41438 To generate keys under OpenSSL:
41440 openssl genrsa -out dkim_rsa.private 2048
41441 openssl rsa -in dkim_rsa.private -out /dev/stdout -pubout -outform PEM
41443 The result file from the first command should be retained, and
41444 this option set to use it.
41445 Take the base-64 lines from the output of the second command, concatenated,
41446 for the DNS TXT record.
41447 See section 3.6 of RFC6376 for the record specification.
41451 certtool --generate-privkey --rsa --bits=2048 --password='' -8 --outfile=dkim_rsa.private
41452 certtool --load-privkey=dkim_rsa.private --pubkey-info
41455 Note that RFC 8301 says:
41457 Signers MUST use RSA keys of at least 1024 bits for all keys.
41458 Signers SHOULD use RSA keys of at least 2048 bits.
41461 EC keys for DKIM are defined by RFC 8463.
41462 They are considerably smaller than RSA keys for equivalent protection.
41463 As they are a recent development, users should consider dual-signing
41464 (by setting a list of selectors, and an expansion for this option)
41465 for some transition period.
41466 The "_CRYPTO_SIGN_ED25519" macro will be defined if support is present
41469 OpenSSL 1.1.1 and GnuTLS 3.6.0 can create Ed25519 private keys:
41471 openssl genpkey -algorithm ed25519 -out dkim_ed25519.private
41472 certtool --generate-privkey --key-type=ed25519 --outfile=dkim_ed25519.private
41475 To produce the required public key value for a DNS record:
41477 openssl pkey -outform DER -pubout -in dkim_ed25519.private | tail -c +13 | base64
41478 certtool --load_privkey=dkim_ed25519.private --pubkey_info --outder | tail -c +13 | base64
41481 Exim also supports an alternate format
41482 of Ed25519 keys in DNS which was a candidate during development
41483 of the standard, but not adopted.
41484 A future release will probably drop that support.
41486 .option dkim_hash smtp string&!! sha256
41487 Can be set to any one of the supported hash methods, which are:
41489 &`sha1`& &-- should not be used, is old and insecure
41491 &`sha256`& &-- the default
41493 &`sha512`& &-- possibly more secure but less well supported
41496 Note that RFC 8301 says:
41498 rsa-sha1 MUST NOT be used for signing or verifying.
41501 .option dkim_identity smtp string&!! unset
41502 If set after expansion, the value is used to set an "i=" tag in
41503 the signing header. The DKIM standards restrict the permissible
41504 syntax of this optional tag to a mail address, with possibly-empty
41505 local part, an @, and a domain identical to or subdomain of the "d="
41506 tag value. Note that Exim does not check the value.
41508 .option dkim_canon smtp string&!! unset
41509 This option sets the canonicalization method used when signing a message.
41510 The DKIM RFC currently supports two methods: "simple" and "relaxed".
41511 The option defaults to "relaxed" when unset. Note: the current implementation
41512 only supports signing with the same canonicalization method for both headers and body.
41514 .option dkim_strict smtp string&!! unset
41515 This option defines how Exim behaves when signing a message that
41516 should be signed fails for some reason. When the expansion evaluates to
41517 either &"1"& or &"true"&, Exim will defer. Otherwise Exim will send the message
41518 unsigned. You can use the &%$dkim_domain%& and &%$dkim_selector%& expansion
41521 .option dkim_sign_headers smtp string&!! "see below"
41522 If set, this option must expand to a colon-separated
41523 list of header names.
41524 Headers with these names, or the absence or such a header, will be included
41525 in the message signature.
41526 When unspecified, the header names listed in RFC4871 will be used,
41527 whether or not each header is present in the message.
41528 The default list is available for the expansion in the macro
41529 &"_DKIM_SIGN_HEADERS"&
41530 and an oversigning variant is in &"_DKIM_OVERSIGN_HEADERS"&.
41532 If a name is repeated, multiple headers by that name (or the absence thereof)
41533 will be signed. The textually later headers in the headers part of the
41534 message are signed first, if there are multiples.
41536 A name can be prefixed with either an &"="& or a &"+"& character.
41537 If an &"="& prefix is used, all headers that are present with this name
41539 If a &"+"& prefix if used, all headers that are present with this name
41540 will be signed, and one signature added for a missing header with the
41541 name will be appended.
41543 .option dkim_timestamps smtp integer&!! unset
41544 This option controls the inclusion of timestamp information in the signature.
41545 If not set, no such information will be included.
41546 Otherwise, must be an unsigned number giving an offset in seconds from the current time
41548 (eg. 1209600 for two weeks);
41549 both creation (t=) and expiry (x=) tags will be included.
41551 RFC 6376 lists these tags as RECOMMENDED.
41554 .section "Verifying DKIM signatures in incoming mail" "SECDKIMVFY"
41555 .cindex "DKIM" "verification"
41557 Verification of DKIM signatures in SMTP incoming email is done for all
41558 messages for which an ACL control &%dkim_disable_verify%& has not been set.
41559 .cindex DKIM "selecting signature algorithms"
41560 Individual classes of signature algorithm can be ignored by changing
41561 the main options &%dkim_verify_hashes%& or &%dkim_verify_keytypes%&.
41562 The &%dkim_verify_minimal%& option can be set to cease verification
41563 processing for a message once the first passing signature is found.
41565 .cindex authentication "expansion item"
41566 Performing verification sets up information used by the
41567 &%authresults%& expansion item.
41569 For most purposes the default option settings suffice and the remainder
41570 of this section can be ignored.
41572 The results of verification are made available to the
41573 &%acl_smtp_dkim%& ACL, which can examine and modify them.
41574 A missing ACL definition defaults to accept.
41575 By default, the ACL is called once for each
41576 syntactically(!) correct signature in the incoming message.
41577 If any ACL call does not accept, the message is not accepted.
41578 If a cutthrough delivery was in progress for the message, that is
41579 summarily dropped (having wasted the transmission effort).
41581 To evaluate the verification result in the ACL
41582 a large number of expansion variables
41583 containing the signature status and its details are set up during the
41584 runtime of the ACL.
41586 Calling the ACL only for existing signatures is not sufficient to build
41587 more advanced policies. For that reason, the main option
41588 &%dkim_verify_signers%&, and an expansion variable
41589 &%$dkim_signers%& exist.
41591 The main option &%dkim_verify_signers%& can be set to a colon-separated
41592 list of DKIM domains or identities for which the ACL &%acl_smtp_dkim%& is
41593 called. It is expanded when the message has been received. At this point,
41594 the expansion variable &%$dkim_signers%& already contains a colon-separated
41595 list of signer domains and identities for the message. When
41596 &%dkim_verify_signers%& is not specified in the main configuration,
41599 dkim_verify_signers = $dkim_signers
41601 This leads to the default behaviour of calling &%acl_smtp_dkim%& for each
41602 DKIM signature in the message. Current DKIM verifiers may want to explicitly
41603 call the ACL for known domains or identities. This would be achieved as follows:
41605 dkim_verify_signers = paypal.com:ebay.com:$dkim_signers
41607 This would result in &%acl_smtp_dkim%& always being called for "paypal.com"
41608 and "ebay.com", plus all domains and identities that have signatures in the message.
41609 You can also be more creative in constructing your policy. For example:
41611 dkim_verify_signers = $sender_address_domain:$dkim_signers
41614 If a domain or identity is listed several times in the (expanded) value of
41615 &%dkim_verify_signers%&, the ACL is only called once for that domain or identity.
41617 Note that if the option is set using untrustworthy data
41618 (such as the From: header)
41619 care should be taken to force lowercase for domains
41620 and for the domain part if identities.
41621 The default setting can be regarded as trustworthy in this respect.
41623 If multiple signatures match a domain (or identity), the ACL is called once
41624 for each matching signature.
41627 Inside the DKIM ACL, the following expansion variables are
41628 available (from most to least important):
41632 .vitem &%$dkim_cur_signer%&
41633 The signer that is being evaluated in this ACL run. This can be a domain or
41634 an identity. This is one of the list items from the expanded main option
41635 &%dkim_verify_signers%& (see above).
41637 .vitem &%$dkim_verify_status%&
41638 Within the DKIM ACL,
41639 a string describing the general status of the signature. One of
41641 &%none%&: There is no signature in the message for the current domain or
41642 identity (as reflected by &%$dkim_cur_signer%&).
41644 &%invalid%&: The signature could not be verified due to a processing error.
41645 More detail is available in &%$dkim_verify_reason%&.
41647 &%fail%&: Verification of the signature failed. More detail is
41648 available in &%$dkim_verify_reason%&.
41650 &%pass%&: The signature passed verification. It is valid.
41653 This variable can be overwritten using an ACL 'set' modifier.
41654 This might, for instance, be done to enforce a policy restriction on
41655 hash-method or key-size:
41657 warn condition = ${if eq {$dkim_verify_status}{pass}}
41658 condition = ${if eq {${length_3:$dkim_algo}}{rsa}}
41659 condition = ${if or {{eq {$dkim_algo}{rsa-sha1}} \
41660 {< {$dkim_key_length}{1024}}}}
41661 logwrite = NOTE: forcing DKIM verify fail (was pass)
41662 set dkim_verify_status = fail
41663 set dkim_verify_reason = hash too weak or key too short
41666 So long as a DKIM ACL is defined (it need do no more than accept),
41667 after all the DKIM ACL runs have completed, the value becomes a
41668 colon-separated list of the values after each run.
41669 This is maintained for the mime, prdr and data ACLs.
41671 .vitem &%$dkim_verify_reason%&
41672 A string giving a little bit more detail when &%$dkim_verify_status%& is either
41673 "fail" or "invalid". One of
41675 &%pubkey_unavailable%& (when &%$dkim_verify_status%&="invalid"): The public
41676 key for the domain could not be retrieved. This may be a temporary problem.
41678 &%pubkey_syntax%& (when &%$dkim_verify_status%&="invalid"): The public key
41679 record for the domain is syntactically invalid.
41681 &%bodyhash_mismatch%& (when &%$dkim_verify_status%&="fail"): The calculated
41682 body hash does not match the one specified in the signature header. This
41683 means that the message body was modified in transit.
41685 &%signature_incorrect%& (when &%$dkim_verify_status%&="fail"): The signature
41686 could not be verified. This may mean that headers were modified,
41687 re-written or otherwise changed in a way which is incompatible with
41688 DKIM verification. It may of course also mean that the signature is forged.
41691 This variable can be overwritten, with any value, using an ACL 'set' modifier.
41693 .vitem &%$dkim_domain%&
41694 The signing domain. IMPORTANT: This variable is only populated if there is
41695 an actual signature in the message for the current domain or identity (as
41696 reflected by &%$dkim_cur_signer%&).
41698 .vitem &%$dkim_identity%&
41699 The signing identity, if present. IMPORTANT: This variable is only populated
41700 if there is an actual signature in the message for the current domain or
41701 identity (as reflected by &%$dkim_cur_signer%&).
41703 .vitem &%$dkim_selector%&
41704 The key record selector string.
41706 .vitem &%$dkim_algo%&
41707 The algorithm used. One of 'rsa-sha1' or 'rsa-sha256'.
41708 If running under GnuTLS 3.6.0 or OpenSSL 1.1.1 or later,
41709 may also be 'ed25519-sha256'.
41710 The "_CRYPTO_SIGN_ED25519" macro will be defined if support is present
41713 Note that RFC 8301 says:
41715 rsa-sha1 MUST NOT be used for signing or verifying.
41717 DKIM signatures identified as having been signed with historic
41718 algorithms (currently, rsa-sha1) have permanently failed evaluation
41721 To enforce this you must either have a DKIM ACL which checks this variable
41722 and overwrites the &$dkim_verify_status$& variable as discussed above,
41723 or have set the main option &%dkim_verify_hashes%& to exclude
41724 processing of such signatures.
41726 .vitem &%$dkim_canon_body%&
41727 The body canonicalization method. One of 'relaxed' or 'simple'.
41729 .vitem &%$dkim_canon_headers%&
41730 The header canonicalization method. One of 'relaxed' or 'simple'.
41732 .vitem &%$dkim_copiedheaders%&
41733 A transcript of headers and their values which are included in the signature
41734 (copied from the 'z=' tag of the signature).
41735 Note that RFC6376 requires that verification fail if the From: header is
41736 not included in the signature. Exim does not enforce this; sites wishing
41737 strict enforcement should code the check explicitly.
41739 .vitem &%$dkim_bodylength%&
41740 The number of signed body bytes. If zero ("0"), the body is unsigned. If no
41741 limit was set by the signer, "9999999999999" is returned. This makes sure
41742 that this variable always expands to an integer value.
41743 &*Note:*& The presence of the signature tag specifying a signing body length
41744 is one possible route to spoofing of valid DKIM signatures.
41745 A paranoid implementation might wish to regard signature where this variable
41746 shows less than the "no limit" return as being invalid.
41748 .vitem &%$dkim_created%&
41749 UNIX timestamp reflecting the date and time when the signature was created.
41750 When this was not specified by the signer, "0" is returned.
41752 .vitem &%$dkim_expires%&
41753 UNIX timestamp reflecting the date and time when the signer wants the
41754 signature to be treated as "expired". When this was not specified by the
41755 signer, "9999999999999" is returned. This makes it possible to do useful
41756 integer size comparisons against this value.
41757 Note that Exim does not check this value.
41759 .vitem &%$dkim_headernames%&
41760 A colon-separated list of names of headers included in the signature.
41762 .vitem &%$dkim_key_testing%&
41763 "1" if the key record has the "testing" flag set, "0" if not.
41765 .vitem &%$dkim_key_nosubdomains%&
41766 "1" if the key record forbids subdomaining, "0" otherwise.
41768 .vitem &%$dkim_key_srvtype%&
41769 Service type (tag s=) from the key record. Defaults to "*" if not specified
41772 .vitem &%$dkim_key_granularity%&
41773 Key granularity (tag g=) from the key record. Defaults to "*" if not specified
41776 .vitem &%$dkim_key_notes%&
41777 Notes from the key record (tag n=).
41779 .vitem &%$dkim_key_length%&
41780 Number of bits in the key.
41781 Valid only once the key is loaded, which is at the time the header signature
41782 is verified, which is after the body hash is.
41784 Note that RFC 8301 says:
41786 Verifiers MUST NOT consider signatures using RSA keys of
41787 less than 1024 bits as valid signatures.
41790 This is enforced by the default setting for the &%dkim_verify_min_keysizes%&
41795 In addition, two ACL conditions are provided:
41798 .vitem &%dkim_signers%&
41799 ACL condition that checks a colon-separated list of domains or identities
41800 for a match against the domain or identity that the ACL is currently verifying
41801 (reflected by &%$dkim_cur_signer%&). This is typically used to restrict an ACL
41802 verb to a group of domains or identities. For example:
41805 # Warn when Mail purportedly from GMail has no gmail signature
41806 warn sender_domains = gmail.com
41807 dkim_signers = gmail.com
41809 log_message = GMail sender without gmail.com DKIM signature
41812 Note that the above does not check for a total lack of DKIM signing;
41813 for that check for empty &$h_DKIM-Signature:$& in the data ACL.
41815 .vitem &%dkim_status%&
41816 ACL condition that checks a colon-separated list of possible DKIM verification
41817 results against the actual result of verification. This is typically used
41818 to restrict an ACL verb to a list of verification outcomes, for example:
41821 deny sender_domains = paypal.com:paypal.de
41822 dkim_signers = paypal.com:paypal.de
41823 dkim_status = none:invalid:fail
41824 message = Mail from Paypal with invalid/missing signature
41827 The possible status keywords are: 'none','invalid','fail' and 'pass'. Please
41828 see the documentation of the &%$dkim_verify_status%& expansion variable above
41829 for more information of what they mean.
41835 .section "SPF (Sender Policy Framework)" SECSPF
41836 .cindex SPF verification
41838 SPF is a mechanism whereby a domain may assert which IP addresses may transmit
41839 messages with its domain in the envelope from, documented by RFC 7208.
41840 For more information on SPF see &url(http://www.open-spf.org), a static copy of
41841 the &url(http://openspf.org).
41842 . --- 2019-10-28: still not https, open-spf.org is told to be a
41843 . --- web-archive copy of the now dead openspf.org site
41844 . --- See https://www.mail-archive.com/mailop@mailop.org/msg08019.html for a
41847 Messages sent by a system not authorised will fail checking of such assertions.
41848 This includes retransmissions done by traditional forwarders.
41850 SPF verification support is built into Exim if SUPPORT_SPF=yes is set in
41851 &_Local/Makefile_&. The support uses the &_libspf2_& library
41852 &url(https://www.libspf2.org/).
41853 There is no Exim involvement in the transmission of messages;
41854 publishing certain DNS records is all that is required.
41856 For verification, an ACL condition and an expansion lookup are provided.
41857 .cindex authentication "expansion item"
41858 Performing verification sets up information used by the
41859 &%authresults%& expansion item.
41862 .cindex SPF "ACL condition"
41863 .cindex ACL "spf condition"
41864 The ACL condition "spf" can be used at or after the MAIL ACL.
41865 It takes as an argument a list of strings giving the outcome of the SPF check,
41866 and will succeed for any matching outcome.
41870 The SPF check passed, the sending host is positively verified by SPF.
41873 The SPF check failed, the sending host is NOT allowed to send mail for the
41874 domain in the envelope-from address.
41876 .vitem &%softfail%&
41877 The SPF check failed, but the queried domain can't absolutely confirm that this
41881 The queried domain does not publish SPF records.
41884 The SPF check returned a "neutral" state. This means the queried domain has
41885 published a SPF record, but wants to allow outside servers to send mail under
41886 its domain as well. This should be treated like "none".
41888 .vitem &%permerror%&
41889 This indicates a syntax error in the SPF record of the queried domain.
41890 You may deny messages when this occurs.
41892 .vitem &%temperror%&
41893 This indicates a temporary error during all processing, including Exim's
41894 SPF processing. You may defer messages when this occurs.
41897 There was an error during processing of the SPF lookup
41900 You can prefix each string with an exclamation mark to invert
41901 its meaning, for example "!fail" will match all results but
41902 "fail". The string list is evaluated left-to-right, in a
41903 short-circuit fashion.
41908 message = $sender_host_address is not allowed to send mail from \
41909 ${if def:sender_address_domain \
41910 {$sender_address_domain}{$sender_helo_name}}. \
41911 Please see http://www.open-spf.org/Why;\
41912 identity=${if def:sender_address_domain \
41913 {$sender_address}{$sender_helo_name}};\
41914 ip=$sender_host_address
41917 Note: The above mentioned URL may not be as helpful as expected. You are
41918 encouraged to replace the link with a link to a site with more
41921 When the spf condition has run, it sets up several expansion
41924 .cindex SPF "verification variables"
41926 .vitem &$spf_header_comment$&
41927 .vindex &$spf_header_comment$&
41928 This contains a human-readable string describing the outcome
41929 of the SPF check. You can add it to a custom header or use
41930 it for logging purposes.
41932 .vitem &$spf_received$&
41933 .vindex &$spf_received$&
41934 This contains a complete Received-SPF: header (name and
41935 content) that can be added to the message. Please note that
41936 according to the SPF draft, this header must be added at the
41937 top of the header list, i.e. with
41939 add_header = :at_start:$spf_received
41941 See section &<<SECTaddheadacl>>& for further details.
41943 Note: in case of "Best-guess" (see below), the convention is
41944 to put this string in a header called X-SPF-Guess: instead.
41946 .vitem &$spf_result$&
41947 .vindex &$spf_result$&
41948 This contains the outcome of the SPF check in string form,
41949 currently one of pass, fail, softfail, none, neutral, permerror,
41950 temperror, or &"(invalid)"&.
41952 .vitem &$spf_result_guessed$&
41953 .vindex &$spf_result_guessed$&
41954 This boolean is true only if a best-guess operation was used
41955 and required in order to obtain a result.
41957 .vitem &$spf_smtp_comment$&
41958 .vindex &$spf_smtp_comment$&
41959 .vindex &%spf_smtp_comment_template%&
41960 This contains a string that can be used in a SMTP response
41961 to the calling party. Useful for "fail".
41962 The string is generated by the SPF library from the template configured in the main config
41963 option &%spf_smtp_comment_template%&.
41967 .cindex SPF "ACL condition"
41968 .cindex ACL "spf_guess condition"
41969 .cindex SPF "best guess"
41970 In addition to SPF, you can also perform checks for so-called
41971 "Best-guess". Strictly speaking, "Best-guess" is not standard
41972 SPF, but it is supported by the same framework that enables SPF
41974 Refer to &url(http://www.open-spf.org/FAQ/Best_guess_record)
41975 for a description of what it means.
41976 . --- 2019-10-28: still not https:
41978 To access this feature, simply use the spf_guess condition in place
41979 of the spf one. For example:
41982 deny spf_guess = fail
41983 message = $sender_host_address doesn't look trustworthy to me
41986 In case you decide to reject messages based on this check, you
41987 should note that although it uses the same framework, "Best-guess"
41988 is not SPF, and therefore you should not mention SPF at all in your
41991 When the spf_guess condition has run, it sets up the same expansion
41992 variables as when spf condition is run, described above.
41994 Additionally, since Best-guess is not standardized, you may redefine
41995 what "Best-guess" means to you by redefining the main configuration
41996 &%spf_guess%& option.
41997 For example, the following:
42000 spf_guess = v=spf1 a/16 mx/16 ptr ?all
42003 would relax host matching rules to a broader network range.
42006 .cindex SPF "lookup expansion"
42008 A lookup expansion is also available. It takes an email
42009 address as the key and an IP address
42014 ${lookup {username@domain} spf {ip.ip.ip.ip}}
42017 The lookup will return the same result strings as can appear in
42018 &$spf_result$& (pass,fail,softfail,neutral,none,err_perm,err_temp).
42024 .section "SRS (Sender Rewriting Scheme)" SECTSRS
42025 .cindex SRS "sender rewriting scheme"
42027 SRS can be used to modify sender addresses when forwarding so that
42028 SPF verification does not object to them.
42029 It operates by encoding the original envelope sender in a new
42030 sender local part and using a domain run by the forwarding site
42031 as the new domain for the sender. Any DSN message should be returned
42032 to this new sender at the forwarding site, which can extract the
42033 original sender from the coded local part and forward the DSN to
42036 This is a way of avoiding the breakage that SPF does to forwarding.
42037 The constructed local-part will be longer than the original,
42038 leading to possible problems with very long addresses.
42039 The changing of the sender address also hinders the tracing of mail
42042 Exim can be built to include native SRS support. To do this
42043 SUPPORT_SRS=yes must be defined in &_Local/Makefile_&.
42044 If this has been done, the macros _HAVE_SRS and _HAVE_NATIVE_SRS
42046 The support is limited to SRS0-encoding; SRS1 is not supported.
42048 .cindex SRS excoding
42049 To encode an address use this expansion item:
42051 .vitem &*${srs_encode&~{*&<&'secret'&>&*}{*&<&'return&~path'&>&*}{*&<&'original&~domain'&>&*}}*&
42052 .cindex "&%srs_encode%& expansion item"
42053 .cindex SRS "expansion item"
42054 The first argument should be a secret known and used by all systems
42055 handling the recipient domain for the original message.
42056 There is no need to periodically change this key; a timestamp is also
42058 The second argument should be given as the envelope sender address before this
42059 encoding operation.
42060 If this value is empty the the expansion result will be empty.
42061 The third argument should be the recipient domain of the message when
42062 it arrived at this system.
42065 .cindex SRS decoding
42066 To decode an address use this expansion condition:
42068 .vitem &*inbound_srs&~{*&<&'local&~part'&>&*}{*&<&'secret'&>&*}*&
42069 The first argument should be the recipient local prt as is was received.
42070 The second argument is the site secret.
42072 If the messages is not for an SRS-encoded recipient the condition will
42073 return false. If it is, the condition will return true and the variable
42074 &$srs_recipient$& will be set to the decoded (original) value.
42080 SRS_SECRET = <pick something unique for your site for this. Use on all MXs.>
42086 # if outbound, and forwarding has been done, use an alternate transport
42087 domains = ! +my_domains
42088 transport = ${if eq {$local_part@$domain} \
42089 {$original_local_part@$original_domain} \
42090 {remote_smtp} {remote_forwarded_smtp}}
42095 domains = +my_domains
42096 # detect inbound bounces which are SRS'd, and decode them
42097 condition = ${if inbound_srs {$local_part} {SRS_SECRET}}
42098 data = $srs_recipient
42100 inbound_srs_failure:
42103 domains = +my_domains
42104 # detect inbound bounces which look SRS'd but are invalid
42105 condition = ${if inbound_srs {$local_part} {}}
42107 data = :fail: Invalid SRS recipient address
42109 #... further routers here
42112 # transport; should look like the non-forward outbound
42113 # one, plus the max_rcpt and return_path options
42114 remote_forwarded_smtp:
42116 # modify the envelope from, for mails that we forward
42118 return_path = ${srs_encode {SRS_SECRET} {$return_path} {$original_domain}}
42125 .section DMARC SECDMARC
42126 .cindex DMARC verification
42128 DMARC combines feedback from SPF, DKIM, and header From: in order
42129 to attempt to provide better indicators of the authenticity of an
42130 email. This document does not explain the fundamentals; you
42131 should read and understand how it works by visiting the website at
42132 &url(http://www.dmarc.org/).
42134 If Exim is built with DMARC support,
42135 the libopendmarc library is used.
42137 For building Exim yourself, obtain the library from
42138 &url(http://sourceforge.net/projects/opendmarc/)
42139 to obtain a copy, or find it in your favorite package
42140 repository. You will need to attend to the local/Makefile feature
42141 SUPPORT_DMARC and the associated LDFLAGS addition.
42142 This description assumes
42143 that headers will be in /usr/local/include, and that the libraries
42144 are in /usr/local/lib.
42148 There are three main-configuration options:
42149 .cindex DMARC "configuration options"
42151 The &%dmarc_tld_file%& option
42152 .oindex &%dmarc_tld_file%&
42153 defines the location of a text file of valid
42154 top level domains the opendmarc library uses
42155 during domain parsing. Maintained by Mozilla,
42156 the most current version can be downloaded
42157 from a link at &url(https://publicsuffix.org/list/public_suffix_list.dat).
42158 See also the util/renew-opendmarc-tlds.sh script.
42159 The default for the option is unset.
42160 If not set, DMARC processing is disabled.
42163 The &%dmarc_history_file%& option, if set
42164 .oindex &%dmarc_history_file%&
42165 defines the location of a file to log results
42166 of dmarc verification on inbound emails. The
42167 contents are importable by the opendmarc tools
42168 which will manage the data, send out DMARC
42169 reports, and expire the data. Make sure the
42170 directory of this file is writable by the user
42172 The default is unset.
42174 The &%dmarc_forensic_sender%& option
42175 .oindex &%dmarc_forensic_sender%&
42176 defines an alternate email address to use when sending a
42177 forensic report detailing alignment failures
42178 if a sender domain's dmarc record specifies it
42179 and you have configured Exim to send them.
42180 If set, this is expanded and used for the
42181 From: header line; the address is extracted
42182 from it and used for the envelope from.
42183 If not set (the default), the From: header is expanded from
42184 the dsn_from option, and <> is used for the
42187 . I wish we had subsections...
42189 .cindex DMARC controls
42190 By default, the DMARC processing will run for any remote,
42191 non-authenticated user. It makes sense to only verify DMARC
42192 status of messages coming from remote, untrusted sources. You can
42193 use standard conditions such as hosts, senders, etc, to decide that
42194 DMARC verification should *not* be performed for them and disable
42195 DMARC with an ACL control modifier:
42197 control = dmarc_disable_verify
42199 A DMARC record can also specify a "forensic address", which gives
42200 exim an email address to submit reports about failed alignment.
42201 Exim does not do this by default because in certain conditions it
42202 results in unintended information leakage (what lists a user might
42203 be subscribed to, etc). You must configure exim to submit forensic
42204 reports to the owner of the domain. If the DMARC record contains a
42205 forensic address and you specify the control statement below, then
42206 exim will send these forensic emails. It is also advised that you
42207 configure a &%dmarc_forensic_sender%& because the default sender address
42208 construction might be inadequate.
42210 control = dmarc_enable_forensic
42212 (AGAIN: You can choose not to send these forensic reports by simply
42213 not putting the dmarc_enable_forensic control line at any point in
42214 your exim config. If you don't tell exim to send them, it will not
42217 There are no options to either control. Both must appear before
42222 DMARC checks cam be run on incoming SMTP messages by using the
42223 &"dmarc_status"& ACL condition in the DATA ACL. You are required to
42224 call the &"spf"& condition first in the ACLs, then the &"dmarc_status"&
42225 condition. Putting this condition in the ACLs is required in order
42226 for a DMARC check to actually occur. All of the variables are set
42227 up before the DATA ACL, but there is no actual DMARC check that
42228 occurs until a &"dmarc_status"& condition is encountered in the ACLs.
42230 The &"dmarc_status"& condition takes a list of strings on its
42231 right-hand side. These strings describe recommended action based
42232 on the DMARC check. To understand what the policy recommendations
42233 mean, refer to the DMARC website above. Valid strings are:
42234 .itable none 0 0 2 1pt left 1pt left
42235 .irow &'accept'& "The DMARC check passed and the library recommends accepting the email"
42236 .irow &'reject'& "The DMARC check failed and the library recommends rejecting the email"
42237 .irow &'quarantine'& "The DMARC check failed and the library recommends keeping it for further inspection"
42238 .irow &'none'& "The DMARC check passed and the library recommends no specific action, neutral"
42239 .irow &'norecord'& "No policy section in the DMARC record for this RFC5322.From field"
42240 .irow &'nofrom'& "Unable to determine the domain of the sender"
42241 .irow &'temperror'& "Library error or dns error"
42242 .irow &'off'& "The DMARC check was disabled for this email"
42244 You can prefix each string with an exclamation mark to invert its
42245 meaning, for example "!accept" will match all results but
42246 "accept". The string list is evaluated left-to-right in a
42247 short-circuit fashion. When a string matches the outcome of the
42248 DMARC check, the condition succeeds. If none of the listed
42249 strings matches the outcome of the DMARC check, the condition
42252 Of course, you can also use any other lookup method that Exim
42253 supports, including LDAP, Postgres, MySQL, etc, as long as the
42254 result is a list of colon-separated strings.
42256 Performing the check sets up information used by the
42257 &%authresults%& expansion item.
42259 Several expansion variables are set before the DATA ACL is
42260 processed, and you can use them in this ACL. The following
42261 expansion variables are available:
42264 .vitem &$dmarc_status$&
42265 .vindex &$dmarc_status$&
42266 .cindex DMARC result
42267 A one word status indicating what the DMARC library
42268 thinks of the email. It is a combination of the results of
42269 DMARC record lookup and the SPF/DKIM/DMARC processing results
42270 (if a DMARC record was found). The actual policy declared
42271 in the DMARC record is in a separate expansion variable.
42273 .vitem &$dmarc_status_text$&
42274 .vindex &$dmarc_status_text$&
42275 Slightly longer, human readable status.
42277 .vitem &$dmarc_used_domain$&
42278 .vindex &$dmarc_used_domain$&
42279 The domain which DMARC used to look up the DMARC policy record.
42281 .vitem &$dmarc_domain_policy$&
42282 .vindex &$dmarc_domain_policy$&
42283 The policy declared in the DMARC record. Valid values
42284 are "none", "reject" and "quarantine". It is blank when there
42285 is any error, including no DMARC record.
42290 By default, Exim's DMARC configuration is intended to be
42291 non-intrusive and conservative. To facilitate this, Exim will not
42292 create any type of logging files without explicit configuration by
42293 you, the admin. Nor will Exim send out any emails/reports about
42294 DMARC issues without explicit configuration by you, the admin (other
42295 than typical bounce messages that may come about due to ACL
42296 processing or failure delivery issues).
42298 In order to log statistics suitable to be imported by the opendmarc
42299 tools, you need to:
42301 Configure the global option &%dmarc_history_file%&
42303 Configure cron jobs to call the appropriate opendmarc history
42304 import scripts and truncating the dmarc_history_file
42307 In order to send forensic reports, you need to:
42309 Configure the global option &%dmarc_forensic_sender%&
42311 Configure, somewhere before the DATA ACL, the control option to
42312 enable sending DMARC forensic reports
42320 warn domains = +local_domains
42321 hosts = +local_hosts
42322 control = dmarc_disable_verify
42324 warn !domains = +screwed_up_dmarc_records
42325 control = dmarc_enable_forensic
42327 warn condition = (lookup if destined to mailing list)
42328 set acl_m_mailing_list = 1
42331 warn dmarc_status = accept : none : off
42333 log_message = DMARC DEBUG: $dmarc_status $dmarc_used_domain
42335 warn dmarc_status = !accept
42337 log_message = DMARC DEBUG: '$dmarc_status' for $dmarc_used_domain
42339 warn dmarc_status = quarantine
42341 set $acl_m_quarantine = 1
42342 # Do something in a transport with this flag variable
42344 deny condition = ${if eq{$dmarc_domain_policy}{reject}}
42345 condition = ${if eq{$acl_m_mailing_list}{1}}
42346 message = Messages from $dmarc_used_domain break mailing lists
42348 deny dmarc_status = reject
42350 message = Message from $dmarc_used_domain failed sender's DMARC policy, REJECT
42352 warn add_header = :at_start:${authresults {$primary_hostname}}
42359 . ////////////////////////////////////////////////////////////////////////////
42360 . ////////////////////////////////////////////////////////////////////////////
42362 .chapter "Proxies" "CHAPproxies" &&&
42364 .cindex "proxy support"
42365 .cindex "proxy" "access via"
42367 A proxy is an intermediate system through which communication is passed.
42368 Proxies may provide a security, availability or load-distribution function.
42371 .section "Inbound proxies" SECTproxyInbound
42372 .cindex proxy inbound
42373 .cindex proxy "server side"
42374 .cindex proxy "Proxy protocol"
42375 .cindex "Proxy protocol" proxy
42377 Exim has support for receiving inbound SMTP connections via a proxy
42378 that uses &"Proxy Protocol"& to speak to it.
42379 To include this support, include &"SUPPORT_PROXY=yes"&
42382 It was built on the HAProxy specification, found at
42383 &url(https://www.haproxy.org/download/1.8/doc/proxy-protocol.txt).
42385 The purpose of this facility is so that an application load balancer,
42386 such as HAProxy, can sit in front of several Exim servers
42387 to distribute load.
42388 Exim uses the local protocol communication with the proxy to obtain
42389 the remote SMTP system IP address and port information.
42390 There is no logging if a host passes or
42391 fails Proxy Protocol negotiation, but it can easily be determined and
42392 recorded in an ACL (example is below).
42394 Use of a proxy is enabled by setting the &%hosts_proxy%&
42395 main configuration option to a hostlist; connections from these
42396 hosts will use Proxy Protocol.
42397 Exim supports both version 1 and version 2 of the Proxy Protocol and
42398 automatically determines which version is in use.
42400 The Proxy Protocol header is the first data received on a TCP connection
42401 and is inserted before any TLS-on-connect handshake from the client; Exim
42402 negotiates TLS between Exim-as-server and the remote client, not between
42403 Exim and the proxy server. The Proxy Protocol header must be received
42404 within &%proxy_protocol_timeout%&, which defaults to 3s.
42406 The following expansion variables are usable
42407 (&"internal"& and &"external"& here refer to the interfaces
42409 .itable none 0 0 2 1pt left 1pt left
42410 .irow $proxy_external_address "IP of host being proxied or IP of remote interface of proxy"
42411 .irow $proxy_external_port "Port of host being proxied or Port on remote interface of proxy"
42412 .irow $proxy_local_address "IP of proxy server inbound or IP of local interface of proxy"
42413 .irow $proxy_local_port "Port of proxy server inbound or Port on local interface of proxy"
42414 .irow $proxy_session "boolean: SMTP connection via proxy"
42416 If &$proxy_session$& is set but &$proxy_external_address$& is empty
42417 there was a protocol error.
42418 The variables &$sender_host_address$& and &$sender_host_port$&
42419 will have values for the actual client system, not the proxy.
42421 Since the real connections are all coming from the proxy, and the
42422 per host connection tracking is done before Proxy Protocol is
42423 evaluated, &%smtp_accept_max_per_host%& must be set high enough to
42424 handle all of the parallel volume you expect per inbound proxy.
42425 With the option set so high, you lose the ability
42426 to protect your server from many connections from one IP.
42427 In order to prevent your server from overload, you
42428 need to add a per connection ratelimit to your connect ACL.
42429 A possible solution is:
42431 # Set max number of connections per host
42433 # Or do some kind of IP lookup in a flat file or database
42434 # LIMIT = ${lookup{$sender_host_address}iplsearch{/etc/exim/proxy_limits}}
42436 defer ratelimit = LIMIT / 5s / per_conn / strict
42437 message = Too many connections from this IP right now
42442 .section "Outbound proxies" SECTproxySOCKS
42443 .cindex proxy outbound
42444 .cindex proxy "client side"
42445 .cindex proxy SOCKS
42446 .cindex SOCKS proxy
42447 Exim has support for sending outbound SMTP via a proxy
42448 using a protocol called SOCKS5 (defined by RFC1928).
42449 The support can be optionally included by defining SUPPORT_SOCKS=yes in
42452 Use of a proxy is enabled by setting the &%socks_proxy%& option
42453 on an smtp transport.
42454 The option value is expanded and should then be a list
42455 (colon-separated by default) of proxy specifiers.
42456 Each proxy specifier is a list
42457 (space-separated by default) where the initial element
42458 is an IP address and any subsequent elements are options.
42460 Options are a string <name>=<value>.
42461 The list of options is in the following table:
42462 .itable none 0 0 2 1pt left 1pt left
42463 .irow &'auth'& "authentication method"
42464 .irow &'name'& "authentication username"
42465 .irow &'pass'& "authentication password"
42466 .irow &'port'& "tcp port"
42467 .irow &'tmo'& "connection timeout"
42468 .irow &'pri'& "priority"
42469 .irow &'weight'& "selection bias"
42472 More details on each of these options follows:
42475 .cindex authentication "to proxy"
42476 .cindex proxy authentication
42477 &%auth%&: Either &"none"& (default) or &"name"&.
42478 Using &"name"& selects username/password authentication per RFC 1929
42479 for access to the proxy.
42480 Default is &"none"&.
42482 &%name%&: sets the username for the &"name"& authentication method.
42485 &%pass%&: sets the password for the &"name"& authentication method.
42488 &%port%&: the TCP port number to use for the connection to the proxy.
42491 &%tmo%&: sets a connection timeout in seconds for this proxy.
42494 &%pri%&: specifies a priority for the proxy within the list,
42495 higher values being tried first.
42496 The default priority is 1.
42498 &%weight%&: specifies a selection bias.
42499 Within a priority set servers are queried in a random fashion,
42500 weighted by this value.
42501 The default value for selection bias is 1.
42504 Proxies from the list are tried according to their priority
42505 and weight settings until one responds. The timeout for the
42506 overall connection applies to the set of proxied attempts.
42508 .section Logging SECTproxyLog
42509 To log the (local) IP of a proxy in the incoming or delivery logline,
42510 add &"+proxy"& to the &%log_selector%& option.
42511 This will add a component tagged with &"PRX="& to the line.
42513 . ////////////////////////////////////////////////////////////////////////////
42514 . ////////////////////////////////////////////////////////////////////////////
42516 .chapter "Internationalisation" "CHAPi18n" &&&
42517 "Internationalisation""
42518 .cindex internationalisation "email address"
42521 .cindex utf8 "mail name handling"
42523 Exim has support for Internationalised mail names.
42524 To include this it must be built with SUPPORT_I18N and the libidn library.
42525 Standards supported are RFCs 2060, 5890, 6530 and 6533.
42527 If Exim is built with SUPPORT_I18N_2008 (in addition to SUPPORT_I18N, not
42528 instead of it) then IDNA2008 is supported; this adds an extra library
42529 requirement, upon libidn2.
42531 .section "MTA operations" SECTi18nMTA
42532 .cindex SMTPUTF8 "ESMTP option"
42533 .cindex "ESMTP extensions" SMTPUTF8
42534 The main configuration option &%smtputf8_advertise_hosts%& specifies
42535 a host list. If this matches the sending host and
42536 accept_8bitmime is true (the default) then the ESMTP option
42537 SMTPUTF8 will be advertised.
42539 If the sender specifies the SMTPUTF8 option on a MAIL command
42540 international handling for the message is enabled and
42541 the expansion variable &$message_smtputf8$& will have value TRUE.
42543 The option &%allow_utf8_domains%& is set to true for this
42544 message. All DNS lookups are converted to a-label form
42545 whatever the setting of &%allow_utf8_domains%&
42546 when Exim is built with SUPPORT_I18N.
42548 Both localparts and domain are maintained as the original
42549 UTF-8 form internally; any comparison or regular-expression use will
42550 require appropriate care. Filenames created, eg. by
42551 the appendfile transport, will have UTF-8 names.
42553 HELO names sent by the smtp transport will have any UTF-8
42554 components expanded to a-label form,
42555 and any certificate name checks will be done using the a-label
42558 .cindex log protocol
42559 .cindex SMTPUTF8 logging
42560 .cindex i18n logging
42561 Log lines and Received-by: header lines will acquire a "utf8"
42562 prefix on the protocol element, eg. utf8esmtp.
42564 The following expansion operators can be used:
42566 ${utf8_domain_to_alabel:str}
42567 ${utf8_domain_from_alabel:str}
42568 ${utf8_localpart_to_alabel:str}
42569 ${utf8_localpart_from_alabel:str}
42572 .cindex utf8 "address downconversion"
42573 .cindex i18n "utf8 address downconversion"
42575 may use the following modifier:
42577 control = utf8_downconvert
42578 control = utf8_downconvert/<value>
42580 This sets a flag requiring that envelope addresses are converted to
42581 a-label form before smtp delivery.
42582 This is usually for use in a Message Submission Agent context,
42583 but could be used for any message.
42585 If a value is appended it may be:
42586 .itable none 0 0 2 1pt right 1pt left
42587 .irow &`1`& "mandatory downconversion"
42588 .irow &`0`& "no downconversion"
42589 .irow &`-1`& "if SMTPUTF8 not supported by destination host"
42591 If no value is given, 1 is used.
42593 If mua_wrapper is set, the utf8_downconvert control
42594 is initially set to -1.
42596 The smtp transport has an option &%utf8_downconvert%&.
42597 If set it must expand to one of the three values described above,
42598 or an empty string.
42599 If non-empty it overrides value previously set
42600 (due to mua_wrapper or by an ACL control).
42603 There is no explicit support for VRFY and EXPN.
42604 Configurations supporting these should inspect
42605 &$smtp_command_argument$& for an SMTPUTF8 argument.
42607 There is no support for LMTP on Unix sockets.
42608 Using the "lmtp" protocol option on an smtp transport,
42609 for LMTP over TCP, should work as expected.
42611 There is no support for DSN unitext handling,
42612 and no provision for converting logging from or to UTF-8.
42616 .section "MDA operations" SECTi18nMDA
42617 To aid in constructing names suitable for IMAP folders
42618 the following expansion operator can be used:
42620 ${imapfolder {<string>} {<sep>} {<specials>}}
42623 The string is converted from the charset specified by
42624 the "headers charset" command (in a filter file)
42625 or &%headers_charset%& main configuration option (otherwise),
42627 modified UTF-7 encoding specified by RFC 2060,
42628 with the following exception: All occurrences of <sep>
42629 (which has to be a single character)
42630 are replaced with periods ("."), and all periods and slashes that are not
42631 <sep> and are not in the <specials> string are BASE64 encoded.
42633 The third argument can be omitted, defaulting to an empty string.
42634 The second argument can be omitted, defaulting to "/".
42636 This is the encoding used by Courier for Maildir names on disk, and followed
42637 by many other IMAP servers.
42641 &`${imapfolder {Foo/Bar}} `& yields &`Foo.Bar`&
42642 &`${imapfolder {Foo/Bar}{.}{/}} `& yields &`Foo&&AC8-Bar`&
42643 &`${imapfolder {Räksmörgås}} `& yields &`R&&AOQ-ksm&&APY-rg&&AOU-s`&
42646 Note that the source charset setting is vital, and also that characters
42647 must be representable in UTF-16.
42650 . ////////////////////////////////////////////////////////////////////////////
42651 . ////////////////////////////////////////////////////////////////////////////
42653 .chapter "Events" "CHAPevents" &&&
42657 The events mechanism in Exim can be used to intercept processing at a number
42658 of points. It was originally invented to give a way to do customised logging
42659 actions (for example, to a database) but can also be used to modify some
42660 processing actions.
42662 Most installations will never need to use Events.
42663 The support can be left out of a build by defining DISABLE_EVENT=yes
42664 in &_Local/Makefile_&.
42666 There are two major classes of events: main and transport.
42667 The main configuration option &%event_action%& controls reception events;
42668 a transport option &%event_action%& controls delivery events.
42670 Both options are a string which is expanded when the event fires.
42671 An example might look like:
42672 .cindex logging custom
42674 event_action = ${if eq {msg:delivery}{$event_name} \
42675 {${lookup pgsql {SELECT * FROM record_Delivery( \
42676 '${quote_pgsql:$sender_address_domain}',\
42677 '${quote_pgsql:${lc:$sender_address_local_part}}', \
42678 '${quote_pgsql:$domain}', \
42679 '${quote_pgsql:${lc:$local_part}}', \
42680 '${quote_pgsql:$host_address}', \
42681 '${quote_pgsql:${lc:$host}}', \
42682 '${quote_pgsql:$message_exim_id}')}} \
42686 Events have names which correspond to the point in process at which they fire.
42687 The name is placed in the variable &$event_name$& and the event action
42688 expansion must check this, as it will be called for every possible event type.
42690 The current list of events is:
42691 .itable all 0 0 4 1pt left 1pt center 1pt center 1pt left
42692 .irow dane:fail after transport "per connection"
42693 .irow msg:complete after main "per message"
42694 .irow msg:defer after transport "per message per delivery try"
42695 .irow msg:delivery after transport "per recipient"
42696 .irow msg:rcpt:host:defer after transport "per recipient per host"
42697 .irow msg:rcpt:defer after transport "per recipient"
42698 .irow msg:host:defer after transport "per host per delivery try; host errors"
42699 .irow msg:fail:delivery after transport "per recipient"
42700 .irow msg:fail:internal after main "per recipient"
42701 .irow tcp:connect before transport "per connection"
42702 .irow tcp:close after transport "per connection"
42703 .irow tls:cert before both "per certificate in verification chain"
42704 .irow tls:fail:connect after main "per connection"
42705 .irow smtp:connect after transport "per connection"
42706 .irow smtp:ehlo after transport "per connection"
42708 New event types may be added in future.
42710 The event name is a colon-separated list, defining the type of
42711 event in a tree of possibilities. It may be used as a list
42712 or just matched on as a whole. There will be no spaces in the name.
42714 The second column in the table above describes whether the event fires
42715 before or after the action is associates with. Those which fire before
42716 can be used to affect that action (more on this below).
42718 The third column in the table above says what section of the configuration
42719 should define the event action.
42721 An additional variable, &$event_data$&, is filled with information varying
42722 with the event type:
42723 .itable all 0 0 2 1pt left 1pt left
42724 .irow dane:fail "failure reason"
42725 .irow msg:defer "error string"
42726 .irow msg:delivery "smtp confirmation message"
42727 .irow msg:fail:internal "failure reason"
42728 .irow msg:fail:delivery "smtp error message"
42729 .irow msg:host:defer "error string"
42730 .irow msg:rcpt:host:defer "error string"
42731 .irow msg:rcpt:defer "error string"
42732 .irow tls:cert "verification chain depth"
42733 .irow tls:fail:connect "error string"
42734 .irow smtp:connect "smtp banner"
42735 .irow smtp:ehlo "smtp ehlo response"
42738 The :defer events populate one extra variable: &$event_defer_errno$&.
42740 For complex operations an ACL expansion can be used in &%event_action%&,
42741 however due to the multiple contexts that Exim operates in during
42742 the course of its processing:
42744 variables set in transport events will not be visible outside that
42747 acl_m variables in a server context are lost on a new connection,
42748 and after smtp helo/ehlo/mail/starttls/rset commands
42750 Using an ACL expansion with the logwrite modifier can be
42751 a useful way of writing to the main log.
42753 The expansion of the event_action option should normally
42754 return an empty string. Should it return anything else the
42755 following will be forced:
42756 .itable all 0 0 2 1pt left 1pt left
42757 .irow tcp:connect "do not connect"
42758 .irow tls:cert "refuse verification"
42759 .irow smtp:connect "close connection"
42761 All other message types ignore the result string, and
42762 no other use is made of it.
42764 For a tcp:connect event, if the connection is being made to a proxy
42765 then the address and port variables will be that of the proxy and not
42768 For tls:cert events, if GnuTLS is in use this will trigger only per
42769 chain element received on the connection.
42770 For OpenSSL it will trigger for every chain element including those
42773 . ////////////////////////////////////////////////////////////////////////////
42774 . ////////////////////////////////////////////////////////////////////////////
42776 .chapter "Adding new drivers or lookup types" "CHID13" &&&
42777 "Adding drivers or lookups"
42778 .cindex "adding drivers"
42779 .cindex "new drivers, adding"
42780 .cindex "drivers" "adding new"
42781 The following actions have to be taken in order to add a new router, transport,
42782 authenticator, or lookup type to Exim:
42785 Choose a name for the driver or lookup type that does not conflict with any
42786 existing name; I will use &"newdriver"& in what follows.
42788 Add to &_src/EDITME_& the line:
42790 <&'type'&>&`_NEWDRIVER=yes`&
42792 where <&'type'&> is ROUTER, TRANSPORT, AUTH, or LOOKUP. If the
42793 code is not to be included in the binary by default, comment this line out. You
42794 should also add any relevant comments about the driver or lookup type.
42796 Add to &_src/config.h.defaults_& the line:
42798 #define <type>_NEWDRIVER
42801 Edit &_src/drtables.c_&, adding conditional code to pull in the private header
42802 and create a table entry as is done for all the other drivers and lookup types.
42804 Edit &_scripts/lookups-Makefile_& if this is a new lookup; there is a for-loop
42805 near the bottom, ranging the &`name_mod`& variable over a list of all lookups.
42806 Add your &`NEWDRIVER`& to that list.
42807 As long as the dynamic module would be named &_newdriver.so_&, you can use the
42808 simple form that most lookups have.
42810 Edit &_Makefile_& in the appropriate sub-directory (&_src/routers_&,
42811 &_src/transports_&, &_src/auths_&, or &_src/lookups_&); add a line for the new
42812 driver or lookup type and add it to the definition of OBJ.
42814 Edit &_OS/Makefile-Base_& adding a &_.o_& file for the predefined-macros, to the
42815 definition of OBJ_MACRO. Add a set of line to do the compile also.
42817 Create &_newdriver.h_& and &_newdriver.c_& in the appropriate sub-directory of
42820 Edit &_scripts/MakeLinks_& and add commands to link the &_.h_& and &_.c_& files
42821 as for other drivers and lookups.
42824 Then all you need to do is write the code! A good way to start is to make a
42825 proforma by copying an existing module of the same type, globally changing all
42826 occurrences of the name, and cutting out most of the code. Note that any
42827 options you create must be listed in alphabetical order, because the tables are
42828 searched using a binary chop procedure.
42830 There is a &_README_& file in each of the sub-directories of &_src_& describing
42831 the interface that is expected.
42836 . ////////////////////////////////////////////////////////////////////////////
42837 . ////////////////////////////////////////////////////////////////////////////
42839 . /////////////////////////////////////////////////////////////////////////////
42840 . These lines are processing instructions for the Simple DocBook Processor that
42841 . Philip Hazel has developed as a less cumbersome way of making PostScript and
42842 . PDFs than using xmlto and fop. They will be ignored by all other XML
42844 . /////////////////////////////////////////////////////////////////////////////
42849 foot_right_recto="&chaptertitle;"
42850 foot_right_verso="&chaptertitle;"
42854 .makeindex "Options index" "option"
42855 .makeindex "Variables index" "variable"
42856 .makeindex "Concept index" "concept"
42859 . /////////////////////////////////////////////////////////////////////////////
42860 . /////////////////////////////////////////////////////////////////////////////