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 "4.95"
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 . This chunk of literal XML implements index entries of the form "x, see y" and
218 . "x, see also y". 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 . /////////////////////////////////////////////////////////////////////////////
224 .chapter "Introduction" "CHID1"
227 <indexterm role="variable">
228 <primary>$1, $2, etc.</primary>
229 <see><emphasis>numerical variables</emphasis></see>
231 <indexterm role="concept">
232 <primary>address</primary>
233 <secondary>rewriting</secondary>
234 <see><emphasis>rewriting</emphasis></see>
236 <indexterm role="concept">
237 <primary>Bounce Address Tag Validation</primary>
238 <see><emphasis>BATV</emphasis></see>
240 <indexterm role="concept">
241 <primary>Client SMTP Authorization</primary>
242 <see><emphasis>CSA</emphasis></see>
244 <indexterm role="concept">
245 <primary>CR character</primary>
246 <see><emphasis>carriage return</emphasis></see>
248 <indexterm role="concept">
249 <primary>CRL</primary>
250 <see><emphasis>certificate revocation list</emphasis></see>
252 <indexterm role="concept">
253 <primary>delivery</primary>
254 <secondary>failure report</secondary>
255 <see><emphasis>bounce message</emphasis></see>
257 <indexterm role="concept">
258 <primary>dialup</primary>
259 <see><emphasis>intermittently connected hosts</emphasis></see>
261 <indexterm role="concept">
262 <primary>exiscan</primary>
263 <see><emphasis>content scanning</emphasis></see>
265 <indexterm role="concept">
266 <primary>failover</primary>
267 <see><emphasis>fallback</emphasis></see>
269 <indexterm role="concept">
270 <primary>fallover</primary>
271 <see><emphasis>fallback</emphasis></see>
273 <indexterm role="concept">
274 <primary>filter</primary>
275 <secondary>Sieve</secondary>
276 <see><emphasis>Sieve filter</emphasis></see>
278 <indexterm role="concept">
279 <primary>ident</primary>
280 <see><emphasis>RFC 1413</emphasis></see>
282 <indexterm role="concept">
283 <primary>LF character</primary>
284 <see><emphasis>linefeed</emphasis></see>
286 <indexterm role="concept">
287 <primary>maximum</primary>
288 <seealso><emphasis>limit</emphasis></seealso>
290 <indexterm role="concept">
291 <primary>monitor</primary>
292 <see><emphasis>Exim monitor</emphasis></see>
294 <indexterm role="concept">
295 <primary>no_<emphasis>xxx</emphasis></primary>
296 <see>entry for xxx</see>
298 <indexterm role="concept">
299 <primary>NUL</primary>
300 <see><emphasis>binary zero</emphasis></see>
302 <indexterm role="concept">
303 <primary>passwd file</primary>
304 <see><emphasis>/etc/passwd</emphasis></see>
306 <indexterm role="concept">
307 <primary>process id</primary>
308 <see><emphasis>pid</emphasis></see>
310 <indexterm role="concept">
311 <primary>RBL</primary>
312 <see><emphasis>DNS list</emphasis></see>
314 <indexterm role="concept">
315 <primary>redirection</primary>
316 <see><emphasis>address redirection</emphasis></see>
318 <indexterm role="concept">
319 <primary>return path</primary>
320 <seealso><emphasis>envelope sender</emphasis></seealso>
322 <indexterm role="concept">
323 <primary>scanning</primary>
324 <see><emphasis>content scanning</emphasis></see>
326 <indexterm role="concept">
327 <primary>SSL</primary>
328 <see><emphasis>TLS</emphasis></see>
330 <indexterm role="concept">
331 <primary>string</primary>
332 <secondary>expansion</secondary>
333 <see><emphasis>expansion</emphasis></see>
335 <indexterm role="concept">
336 <primary>top bit</primary>
337 <see><emphasis>8-bit characters</emphasis></see>
339 <indexterm role="concept">
340 <primary>variables</primary>
341 <see><emphasis>expansion, variables</emphasis></see>
343 <indexterm role="concept">
344 <primary>zero, binary</primary>
345 <see><emphasis>binary zero</emphasis></see>
347 <indexterm role="concept">
348 <primary>headers</primary>
349 <see><emphasis>header lines</emphasis></see>
355 . /////////////////////////////////////////////////////////////////////////////
356 . This is the real start of the first chapter. See the comment above as to why
357 . we can't have the .chapter line here.
358 . chapter "Introduction"
359 . /////////////////////////////////////////////////////////////////////////////
361 Exim is a mail transfer agent (MTA) for hosts that are running Unix or
362 Unix-like operating systems. It was designed on the assumption that it would be
363 run on hosts that are permanently connected to the Internet. However, it can be
364 used on intermittently connected hosts with suitable configuration adjustments.
366 Configuration files currently exist for the following operating systems: AIX,
367 BSD/OS (aka BSDI), Darwin (Mac OS X), DGUX, Dragonfly, FreeBSD, GNU/Hurd,
368 GNU/Linux, HI-OSF (Hitachi), HI-UX, HP-UX, IRIX, MIPS RISCOS, NetBSD, OpenBSD,
369 OpenUNIX, QNX, SCO, SCO SVR4.2 (aka UNIX-SV), Solaris (aka SunOS5), SunOS4,
370 Tru64-Unix (formerly Digital UNIX, formerly DEC-OSF1), Ultrix, and UnixWare.
371 Some of these operating systems are no longer current and cannot easily be
372 tested, so the configuration files may no longer work in practice.
374 There are also configuration files for compiling Exim in the Cygwin environment
375 that can be installed on systems running Windows. However, this document does
376 not contain any information about running Exim in the Cygwin environment.
378 The terms and conditions for the use and distribution of Exim are contained in
379 the file &_NOTICE_&. Exim is distributed under the terms of the GNU General
380 Public Licence, a copy of which may be found in the file &_LICENCE_&.
382 The use, supply, or promotion of Exim for the purpose of sending bulk,
383 unsolicited electronic mail is incompatible with the basic aims of Exim,
384 which revolve around the free provision of a service that enhances the quality
385 of personal communications. The author of Exim regards indiscriminate
386 mass-mailing as an antisocial, irresponsible abuse of the Internet.
388 Exim owes a great deal to Smail 3 and its author, Ron Karr. Without the
389 experience of running and working on the Smail 3 code, I could never have
390 contemplated starting to write a new MTA. Many of the ideas and user interfaces
391 were originally taken from Smail 3, though the actual code of Exim is entirely
392 new, and has developed far beyond the initial concept.
394 Many people, both in Cambridge and around the world, have contributed to the
395 development and the testing of Exim, and to porting it to various operating
396 systems. I am grateful to them all. The distribution now contains a file called
397 &_ACKNOWLEDGMENTS_&, in which I have started recording the names of
401 .section "Exim documentation" "SECID1"
402 . Keep this example change bar when updating the documentation!
405 .cindex "documentation"
406 This edition of the Exim specification applies to version &version() of Exim.
407 Substantive changes from the &previousversion; edition are marked in some
408 renditions of this document; this paragraph is so marked if the rendition is
409 capable of showing a change indicator.
412 This document is very much a reference manual; it is not a tutorial. The reader
413 is expected to have some familiarity with the SMTP mail transfer protocol and
414 with general Unix system administration. Although there are some discussions
415 and examples in places, the information is mostly organized in a way that makes
416 it easy to look up, rather than in a natural order for sequential reading.
417 Furthermore, this manual aims to cover every aspect of Exim in detail, including
418 a number of rarely-used, special-purpose features that are unlikely to be of
421 .cindex "books about Exim"
422 An &"easier"& discussion of Exim which provides more in-depth explanatory,
423 introductory, and tutorial material can be found in a book entitled &'The Exim
424 SMTP Mail Server'& (second edition, 2007), published by UIT Cambridge
425 (&url(https://www.uit.co.uk/exim-book/)).
427 The book also contains a chapter that gives a general introduction to SMTP and
428 Internet mail. Inevitably, however, the book is unlikely to be fully up-to-date
429 with the latest release of Exim. (Note that the earlier book about Exim,
430 published by O'Reilly, covers Exim 3, and many things have changed in Exim 4.)
432 .cindex "Debian" "information sources"
433 If you are using a Debian distribution of Exim, you will find information about
434 Debian-specific features in the file
435 &_/usr/share/doc/exim4-base/README.Debian_&.
436 The command &(man update-exim.conf)& is another source of Debian-specific
439 .cindex "&_doc/NewStuff_&"
440 .cindex "&_doc/ChangeLog_&"
442 As Exim develops, there may be features in newer versions that have not
443 yet made it into this document, which is updated only when the most significant
444 digit of the fractional part of the version number changes. Specifications of
445 new features that are not yet in this manual are placed in the file
446 &_doc/NewStuff_& in the Exim distribution.
448 Some features may be classified as &"experimental"&. These may change
449 incompatibly while they are developing, or even be withdrawn. For this reason,
450 they are not documented in this manual. Information about experimental features
451 can be found in the file &_doc/experimental.txt_&.
453 All changes to Exim (whether new features, bug fixes, or other kinds of
454 change) are noted briefly in the file called &_doc/ChangeLog_&.
456 .cindex "&_doc/spec.txt_&"
457 This specification itself is available as an ASCII file in &_doc/spec.txt_& so
458 that it can easily be searched with a text editor. Other files in the &_doc_&
462 .row &_OptionLists.txt_& "list of all options in alphabetical order"
463 .row &_dbm.discuss.txt_& "discussion about DBM libraries"
464 .row &_exim.8_& "a man page of Exim's command line options"
465 .row &_experimental.txt_& "documentation of experimental features"
466 .row &_filter.txt_& "specification of the filter language"
467 .row &_Exim3.upgrade_& "upgrade notes from release 2 to release 3"
468 .row &_Exim4.upgrade_& "upgrade notes from release 3 to release 4"
469 .row &_openssl.txt_& "installing a current OpenSSL release"
472 The main specification and the specification of the filtering language are also
473 available in other formats (HTML, PostScript, PDF, and Texinfo). Section
474 &<<SECTavail>>& below tells you how to get hold of these.
478 .section "FTP site and websites" "SECID2"
481 The primary site for Exim source distributions is the &%exim.org%& FTP site,
482 available over HTTPS, HTTP and FTP. These services, and the &%exim.org%&
483 website, are hosted at the University of Cambridge.
487 As well as Exim distribution tar files, the Exim website contains a number of
488 differently formatted versions of the documentation. A recent addition to the
489 online information is the Exim wiki (&url(https://wiki.exim.org)),
490 which contains what used to be a separate FAQ, as well as various other
491 examples, tips, and know-how that have been contributed by Exim users.
492 The wiki site should always redirect to the correct place, which is currently
493 provided by GitHub, and is open to editing by anyone with a GitHub account.
496 An Exim Bugzilla exists at &url(https://bugs.exim.org). You can use
497 this to report bugs, and also to add items to the wish list. Please search
498 first to check that you are not duplicating a previous entry.
499 Please do not ask for configuration help in the bug-tracker.
502 .section "Mailing lists" "SECID3"
503 .cindex "mailing lists" "for Exim users"
504 The following Exim mailing lists exist:
507 .row &'exim-announce@exim.org'& "Moderated, low volume announcements list"
508 .row &'exim-users@exim.org'& "General discussion list"
509 .row &'exim-dev@exim.org'& "Discussion of bugs, enhancements, etc."
510 .row &'exim-cvs@exim.org'& "Automated commit messages from the VCS"
513 You can subscribe to these lists, change your existing subscriptions, and view
514 or search the archives via the mailing lists link on the Exim home page.
515 .cindex "Debian" "mailing list for"
516 If you are using a Debian distribution of Exim, you may wish to subscribe to
517 the Debian-specific mailing list &'pkg-exim4-users@lists.alioth.debian.org'&
520 &url(https://alioth-lists.debian.net/cgi-bin/mailman/listinfo/pkg-exim4-users)
522 Please ask Debian-specific questions on that list and not on the general Exim
525 .section "Bug reports" "SECID5"
526 .cindex "bug reports"
527 .cindex "reporting bugs"
528 Reports of obvious bugs can be emailed to &'bugs@exim.org'& or reported
529 via the Bugzilla (&url(https://bugs.exim.org)). However, if you are unsure
530 whether some behaviour is a bug or not, the best thing to do is to post a
531 message to the &'exim-dev'& mailing list and have it discussed.
535 .section "Where to find the Exim distribution" "SECTavail"
537 .cindex "HTTPS download site"
538 .cindex "distribution" "FTP site"
539 .cindex "distribution" "https site"
540 The master distribution site for the Exim distribution is
542 &url(https://downloads.exim.org/)
544 The service is available over HTTPS, HTTP and FTP.
545 We encourage people to migrate to HTTPS.
547 The content served at &url(https://downloads.exim.org/) is identical to the
548 content served at &url(https://ftp.exim.org/pub/exim) and
549 &url(ftp://ftp.exim.org/pub/exim).
551 If accessing via a hostname containing &'ftp'&, then the file references that
552 follow are relative to the &_exim_& directories at these sites.
553 If accessing via the hostname &'downloads'& then the subdirectories described
554 here are top-level directories.
556 There are now quite a number of independent mirror sites around
557 the world. Those that I know about are listed in the file called &_Mirrors_&.
559 Within the top exim directory there are subdirectories called &_exim3_& (for
560 previous Exim 3 distributions), &_exim4_& (for the latest Exim 4
561 distributions), and &_Testing_& for testing versions. In the &_exim4_&
562 subdirectory, the current release can always be found in files called
566 &_exim-n.nn.tar.bz2_&
568 where &'n.nn'& is the highest such version number in the directory. The three
569 files contain identical data; the only difference is the type of compression.
570 The &_.xz_& file is usually the smallest, while the &_.gz_& file is the
571 most portable to old systems.
573 .cindex "distribution" "signing details"
574 .cindex "distribution" "public key"
575 .cindex "public key for signed distribution"
576 The distributions will be PGP signed by an individual key of the Release
577 Coordinator. This key will have a uid containing an email address in the
578 &'exim.org'& domain and will have signatures from other people, including
579 other Exim maintainers. We expect that the key will be in the "strong set" of
580 PGP keys. There should be a trust path to that key from the Exim Maintainer's
581 PGP keys, a version of which can be found in the release directory in the file
582 &_Exim-Maintainers-Keyring.asc_&. All keys used will be available in public keyserver pools,
583 such as &'pool.sks-keyservers.net'&.
585 At the time of the last update, releases were being made by Jeremy Harris and signed
586 with key &'0xBCE58C8CE41F32DF'&. Other recent keys used for signing are those
587 of Heiko Schlittermann, &'0x26101B62F69376CE'&,
588 and of Phil Pennock, &'0x4D1E900E14C1CC04'&.
590 The signatures for the tar bundles are in:
592 &_exim-n.nn.tar.xz.asc_&
593 &_exim-n.nn.tar.gz.asc_&
594 &_exim-n.nn.tar.bz2.asc_&
596 For each released version, the log of changes is made available in a
597 separate file in the directory &_ChangeLogs_& so that it is possible to
598 find out what has changed without having to download the entire distribution.
600 .cindex "documentation" "available formats"
601 The main distribution contains ASCII versions of this specification and other
602 documentation; other formats of the documents are available in separate files
603 inside the &_exim4_& directory of the FTP site:
605 &_exim-html-n.nn.tar.gz_&
606 &_exim-pdf-n.nn.tar.gz_&
607 &_exim-postscript-n.nn.tar.gz_&
608 &_exim-texinfo-n.nn.tar.gz_&
610 These tar files contain only the &_doc_& directory, not the complete
611 distribution, and are also available in &_.bz2_& and &_.xz_& forms.
614 .section "Limitations" "SECID6"
616 .cindex "limitations of Exim"
617 .cindex "bang paths" "not handled by Exim"
618 Exim is designed for use as an Internet MTA, and therefore handles addresses in
619 RFC 2822 domain format only. It cannot handle UUCP &"bang paths"&, though
620 simple two-component bang paths can be converted by a straightforward rewriting
621 configuration. This restriction does not prevent Exim from being interfaced to
622 UUCP as a transport mechanism, provided that domain addresses are used.
624 .cindex "domainless addresses"
625 .cindex "address" "without domain"
626 Exim insists that every address it handles has a domain attached. For incoming
627 local messages, domainless addresses are automatically qualified with a
628 configured domain value. Configuration options specify from which remote
629 systems unqualified addresses are acceptable. These are then qualified on
632 .cindex "transport" "external"
633 .cindex "external transports"
634 The only external transport mechanisms that are currently implemented are SMTP
635 and LMTP over a TCP/IP network (including support for IPv6). However, a pipe
636 transport is available, and there are facilities for writing messages to files
637 and pipes, optionally in &'batched SMTP'& format; these facilities can be used
638 to send messages to other transport mechanisms such as UUCP, provided they can
639 handle domain-style addresses. Batched SMTP input is also catered for.
641 Exim is not designed for storing mail for dial-in hosts. When the volumes of
642 such mail are large, it is better to get the messages &"delivered"& into files
643 (that is, off Exim's queue) and subsequently passed on to the dial-in hosts by
646 Although Exim does have basic facilities for scanning incoming messages, these
647 are not comprehensive enough to do full virus or spam scanning. Such operations
648 are best carried out using additional specialized software packages. If you
649 compile Exim with the content-scanning extension, straightforward interfaces to
650 a number of common scanners are provided.
654 .section "Runtime configuration" "SECID7"
655 Exim's runtime configuration is held in a single text file that is divided
656 into a number of sections. The entries in this file consist of keywords and
657 values, in the style of Smail 3 configuration files. A default configuration
658 file which is suitable for simple online installations is provided in the
659 distribution, and is described in chapter &<<CHAPdefconfil>>& below.
662 .section "Calling interface" "SECID8"
663 .cindex "Sendmail compatibility" "command line interface"
664 Like many MTAs, Exim has adopted the Sendmail command line interface so that it
665 can be a straight replacement for &_/usr/lib/sendmail_& or
666 &_/usr/sbin/sendmail_& when sending mail, but you do not need to know anything
667 about Sendmail in order to run Exim. For actions other than sending messages,
668 Sendmail-compatible options also exist, but those that produce output (for
669 example, &%-bp%&, which lists the messages in the queue) do so in Exim's own
670 format. There are also some additional options that are compatible with Smail
671 3, and some further options that are new to Exim. Chapter &<<CHAPcommandline>>&
672 documents all Exim's command line options. This information is automatically
673 made into the man page that forms part of the Exim distribution.
675 Control of messages in the queue can be done via certain privileged command
676 line options. There is also an optional monitor program called &'eximon'&,
677 which displays current information in an X window, and which contains a menu
678 interface to Exim's command line administration options.
682 .section "Terminology" "SECID9"
683 .cindex "terminology definitions"
684 .cindex "body of message" "definition of"
685 The &'body'& of a message is the actual data that the sender wants to transmit.
686 It is the last part of a message and is separated from the &'header'& (see
687 below) by a blank line.
689 .cindex "bounce message" "definition of"
690 When a message cannot be delivered, it is normally returned to the sender in a
691 delivery failure message or a &"non-delivery report"& (NDR). The term
692 &'bounce'& is commonly used for this action, and the error reports are often
693 called &'bounce messages'&. This is a convenient shorthand for &"delivery
694 failure error report"&. Such messages have an empty sender address in the
695 message's &'envelope'& (see below) to ensure that they cannot themselves give
696 rise to further bounce messages.
698 The term &'default'& appears frequently in this manual. It is used to qualify a
699 value which is used in the absence of any setting in the configuration. It may
700 also qualify an action which is taken unless a configuration setting specifies
703 The term &'defer'& is used when the delivery of a message to a specific
704 destination cannot immediately take place for some reason (a remote host may be
705 down, or a user's local mailbox may be full). Such deliveries are &'deferred'&
708 The word &'domain'& is sometimes used to mean all but the first component of a
709 host's name. It is &'not'& used in that sense here, where it normally refers to
710 the part of an email address following the @ sign.
712 .cindex "envelope, definition of"
713 .cindex "sender" "definition of"
714 A message in transit has an associated &'envelope'&, as well as a header and a
715 body. The envelope contains a sender address (to which bounce messages should
716 be delivered), and any number of recipient addresses. References to the
717 sender or the recipients of a message usually mean the addresses in the
718 envelope. An MTA uses these addresses for delivery, and for returning bounce
719 messages, not the addresses that appear in the header lines.
721 .cindex "message" "header, definition of"
722 .cindex "header section" "definition of"
723 The &'header'& of a message is the first part of a message's text, consisting
724 of a number of lines, each of which has a name such as &'From:'&, &'To:'&,
725 &'Subject:'&, etc. Long header lines can be split over several text lines by
726 indenting the continuations. The header is separated from the body by a blank
729 .cindex "local part" "definition of"
730 .cindex "domain" "definition of"
731 The term &'local part'&, which is taken from RFC 2822, is used to refer to the
732 part of an email address that precedes the @ sign. The part that follows the
733 @ sign is called the &'domain'& or &'mail domain'&.
735 .cindex "local delivery" "definition of"
736 .cindex "remote delivery, definition of"
737 The terms &'local delivery'& and &'remote delivery'& are used to distinguish
738 delivery to a file or a pipe on the local host from delivery by SMTP over
739 TCP/IP to another host. As far as Exim is concerned, all hosts other than the
740 host it is running on are &'remote'&.
742 .cindex "return path" "definition of"
743 &'Return path'& is another name that is used for the sender address in a
746 .cindex "queue" "definition of"
747 The term &'queue'& is used to refer to the set of messages awaiting delivery
748 because this term is in widespread use in the context of MTAs. However, in
749 Exim's case, the reality is more like a pool than a queue, because there is
750 normally no ordering of waiting messages.
752 .cindex "queue runner" "definition of"
753 The term &'queue runner'& is used to describe a process that scans the queue
754 and attempts to deliver those messages whose retry times have come. This term
755 is used by other MTAs and also relates to the command &%runq%&, but in Exim
756 the waiting messages are normally processed in an unpredictable order.
758 .cindex "spool directory" "definition of"
759 The term &'spool directory'& is used for a directory in which Exim keeps the
760 messages in its queue &-- that is, those that it is in the process of
761 delivering. This should not be confused with the directory in which local
762 mailboxes are stored, which is called a &"spool directory"& by some people. In
763 the Exim documentation, &"spool"& is always used in the first sense.
770 . ////////////////////////////////////////////////////////////////////////////
771 . ////////////////////////////////////////////////////////////////////////////
773 .chapter "Incorporated code" "CHID2"
774 .cindex "incorporated code"
775 .cindex "regular expressions" "library"
778 A number of pieces of external code are included in the Exim distribution.
781 Regular expressions are supported in the main Exim program and in the
782 Exim monitor using the freely-distributable PCRE2 library, copyright
783 © University of Cambridge. The source to PCRE2 is not longer shipped with
784 Exim, so you will need to use the version of PCRE2 shipped with your system,
785 or obtain and install the full version of the library from
786 &url(https://github.com/PhilipHazel/pcre2/releases).
788 .cindex "cdb" "acknowledgment"
789 Support for the cdb (Constant DataBase) lookup method is provided by code
790 contributed by Nigel Metheringham of (at the time he contributed it) Planet
791 Online Ltd. The implementation is completely contained within the code of Exim.
792 It does not link against an external cdb library. The code contains the
793 following statements:
796 Copyright © 1998 Nigel Metheringham, Planet Online Ltd
798 This program is free software; you can redistribute it and/or modify it under
799 the terms of the GNU General Public License as published by the Free Software
800 Foundation; either version 2 of the License, or (at your option) any later
802 This code implements Dan Bernstein's Constant DataBase (cdb) spec. Information,
803 the spec and sample code for cdb can be obtained from
804 &url(https://cr.yp.to/cdb.html). This implementation borrows
805 some code from Dan Bernstein's implementation (which has no license
806 restrictions applied to it).
809 .cindex "SPA authentication"
810 .cindex "Samba project"
811 .cindex "Microsoft Secure Password Authentication"
812 Client support for Microsoft's &'Secure Password Authentication'& is provided
813 by code contributed by Marc Prud'hommeaux. Server support was contributed by
814 Tom Kistner. This includes code taken from the Samba project, which is released
818 .cindex "&'pwcheck'& daemon"
819 .cindex "&'pwauthd'& daemon"
820 Support for calling the Cyrus &'pwcheck'& and &'saslauthd'& daemons is provided
821 by code taken from the Cyrus-SASL library and adapted by Alexander S.
822 Sabourenkov. The permission notice appears below, in accordance with the
823 conditions expressed therein.
826 Copyright © 2001 Carnegie Mellon University. All rights reserved.
828 Redistribution and use in source and binary forms, with or without
829 modification, are permitted provided that the following conditions
833 Redistributions of source code must retain the above copyright
834 notice, this list of conditions and the following disclaimer.
836 Redistributions in binary form must reproduce the above copyright
837 notice, this list of conditions and the following disclaimer in
838 the documentation and/or other materials provided with the
841 The name &"Carnegie Mellon University"& must not be used to
842 endorse or promote products derived from this software without
843 prior written permission. For permission or any other legal
844 details, please contact
846 Office of Technology Transfer
847 Carnegie Mellon University
849 Pittsburgh, PA 15213-3890
850 (412) 268-4387, fax: (412) 268-7395
851 tech-transfer@andrew.cmu.edu
854 Redistributions of any form whatsoever must retain the following
857 &"This product includes software developed by Computing Services
858 at Carnegie Mellon University (&url(https://www.cmu.edu/computing/)."&
860 CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
861 THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
862 AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
863 FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
864 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
865 AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
866 OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
871 .cindex "Exim monitor" "acknowledgment"
874 The Exim Monitor program, which is an X-Window application, includes
875 modified versions of the Athena StripChart and TextPop widgets.
876 This code is copyright by DEC and MIT, and their permission notice appears
877 below, in accordance with the conditions expressed therein.
880 Copyright 1987, 1988 by Digital Equipment Corporation, Maynard, Massachusetts,
881 and the Massachusetts Institute of Technology, Cambridge, Massachusetts.
885 Permission to use, copy, modify, and distribute this software and its
886 documentation for any purpose and without fee is hereby granted,
887 provided that the above copyright notice appear in all copies and that
888 both that copyright notice and this permission notice appear in
889 supporting documentation, and that the names of Digital or MIT not be
890 used in advertising or publicity pertaining to distribution of the
891 software without specific, written prior permission.
893 DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
894 ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
895 DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
896 ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
897 WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
898 ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
903 .cindex "opendmarc" "acknowledgment"
904 The DMARC implementation uses the OpenDMARC library which is Copyrighted by
905 The Trusted Domain Project. Portions of Exim source which use OpenDMARC
906 derived code are indicated in the respective source files. The full OpenDMARC
907 license is provided in the LICENSE.opendmarc file contained in the distributed
911 Many people have contributed code fragments, some large, some small, that were
912 not covered by any specific license requirements. It is assumed that the
913 contributors are happy to see their code incorporated into Exim under the GPL.
920 . ////////////////////////////////////////////////////////////////////////////
921 . ////////////////////////////////////////////////////////////////////////////
923 .chapter "How Exim receives and delivers mail" "CHID11" &&&
924 "Receiving and delivering mail"
927 .section "Overall philosophy" "SECID10"
928 .cindex "design philosophy"
929 Exim is designed to work efficiently on systems that are permanently connected
930 to the Internet and are handling a general mix of mail. In such circumstances,
931 most messages can be delivered immediately. Consequently, Exim does not
932 maintain independent queues of messages for specific domains or hosts, though
933 it does try to send several messages in a single SMTP connection after a host
934 has been down, and it also maintains per-host retry information.
937 .section "Policy control" "SECID11"
938 .cindex "policy control" "overview"
939 Policy controls are now an important feature of MTAs that are connected to the
940 Internet. Perhaps their most important job is to stop MTAs from being abused as
941 &"open relays"& by misguided individuals who send out vast amounts of
942 unsolicited junk and want to disguise its source. Exim provides flexible
943 facilities for specifying policy controls on incoming mail:
946 .cindex "&ACL;" "introduction"
947 Exim 4 (unlike previous versions of Exim) implements policy controls on
948 incoming mail by means of &'Access Control Lists'& (ACLs). Each list is a
949 series of statements that may either grant or deny access. ACLs can be used at
950 several places in the SMTP dialogue while receiving a message from a remote
951 host. However, the most common places are after each RCPT command, and at the
952 very end of the message. The sysadmin can specify conditions for accepting or
953 rejecting individual recipients or the entire message, respectively, at these
954 two points (see chapter &<<CHAPACL>>&). Denial of access results in an SMTP
957 An ACL is also available for locally generated, non-SMTP messages. In this
958 case, the only available actions are to accept or deny the entire message.
960 When Exim is compiled with the content-scanning extension, facilities are
961 provided in the ACL mechanism for passing the message to external virus and/or
962 spam scanning software. The result of such a scan is passed back to the ACL,
963 which can then use it to decide what to do with the message.
965 When a message has been received, either from a remote host or from the local
966 host, but before the final acknowledgment has been sent, a locally supplied C
967 function called &[local_scan()]& can be run to inspect the message and decide
968 whether to accept it or not (see chapter &<<CHAPlocalscan>>&). If the message
969 is accepted, the list of recipients can be modified by the function.
971 Using the &[local_scan()]& mechanism is another way of calling external scanner
972 software. The &%SA-Exim%& add-on package works this way. It does not require
973 Exim to be compiled with the content-scanning extension.
975 After a message has been accepted, a further checking mechanism is available in
976 the form of the &'system filter'& (see chapter &<<CHAPsystemfilter>>&). This
977 runs at the start of every delivery process.
982 .section "User filters" "SECID12"
983 .cindex "filter" "introduction"
984 .cindex "Sieve filter"
985 In a conventional Exim configuration, users are able to run private filters by
986 setting up appropriate &_.forward_& files in their home directories. See
987 chapter &<<CHAPredirect>>& (about the &(redirect)& router) for the
988 configuration needed to support this, and the separate document entitled
989 &'Exim's interfaces to mail filtering'& for user details. Two different kinds
990 of filtering are available:
993 Sieve filters are written in the standard filtering language that is defined
996 Exim filters are written in a syntax that is unique to Exim, but which is more
997 powerful than Sieve, which it pre-dates.
1000 User filters are run as part of the routing process, described below.
1004 .section "Message identification" "SECTmessiden"
1005 .cindex "message ids" "details of format"
1006 .cindex "format" "of message id"
1007 .cindex "id of message"
1012 Every message handled by Exim is given a &'message id'& which is sixteen
1013 characters long. It is divided into three parts, separated by hyphens, for
1014 example &`16VDhn-0001bo-D3`&. Each part is a sequence of letters and digits,
1015 normally encoding numbers in base 62. However, in the Darwin operating
1016 system (Mac OS X) and when Exim is compiled to run under Cygwin, base 36
1017 (avoiding the use of lower case letters) is used instead, because the message
1018 id is used to construct filenames, and the names of files in those systems are
1019 not always case-sensitive.
1021 .cindex "pid (process id)" "re-use of"
1022 The detail of the contents of the message id have changed as Exim has evolved.
1023 Earlier versions relied on the operating system not re-using a process id (pid)
1024 within one second. On modern operating systems, this assumption can no longer
1025 be made, so the algorithm had to be changed. To retain backward compatibility,
1026 the format of the message id was retained, which is why the following rules are
1030 The first six characters of the message id are the time at which the message
1031 started to be received, to a granularity of one second. That is, this field
1032 contains the number of seconds since the start of the epoch (the normal Unix
1033 way of representing the date and time of day).
1035 After the first hyphen, the next six characters are the id of the process that
1036 received the message.
1038 There are two different possibilities for the final two characters:
1040 .oindex "&%localhost_number%&"
1041 If &%localhost_number%& is not set, this value is the fractional part of the
1042 time of reception, normally in units of 1/2000 of a second, but for systems
1043 that must use base 36 instead of base 62 (because of case-insensitive file
1044 systems), the units are 1/1000 of a second.
1046 If &%localhost_number%& is set, it is multiplied by 200 (100) and added to
1047 the fractional part of the time, which in this case is in units of 1/200
1048 (1/100) of a second.
1052 After a message has been received, Exim waits for the clock to tick at the
1053 appropriate resolution before proceeding, so that if another message is
1054 received by the same process, or by another process with the same (re-used)
1055 pid, it is guaranteed that the time will be different. In most cases, the clock
1056 will already have ticked while the message was being received.
1059 .section "Receiving mail" "SECID13"
1060 .cindex "receiving mail"
1061 .cindex "message" "reception"
1062 The only way Exim can receive mail from another host is using SMTP over
1063 TCP/IP, in which case the sender and recipient addresses are transferred using
1064 SMTP commands. However, from a locally running process (such as a user's MUA),
1065 there are several possibilities:
1068 If the process runs Exim with the &%-bm%& option, the message is read
1069 non-interactively (usually via a pipe), with the recipients taken from the
1070 command line, or from the body of the message if &%-t%& is also used.
1072 If the process runs Exim with the &%-bS%& option, the message is also read
1073 non-interactively, but in this case the recipients are listed at the start of
1074 the message in a series of SMTP RCPT commands, terminated by a DATA
1075 command. This is called &"batch SMTP"& format,
1076 but it isn't really SMTP. The SMTP commands are just another way of passing
1077 envelope addresses in a non-interactive submission.
1079 If the process runs Exim with the &%-bs%& option, the message is read
1080 interactively, using the SMTP protocol. A two-way pipe is normally used for
1081 passing data between the local process and the Exim process.
1082 This is &"real"& SMTP and is handled in the same way as SMTP over TCP/IP. For
1083 example, the ACLs for SMTP commands are used for this form of submission.
1085 A local process may also make a TCP/IP call to the host's loopback address
1086 (127.0.0.1) or any other of its IP addresses. When receiving messages, Exim
1087 does not treat the loopback address specially. It treats all such connections
1088 in the same way as connections from other hosts.
1092 .cindex "message sender, constructed by Exim"
1093 .cindex "sender" "constructed by Exim"
1094 In the three cases that do not involve TCP/IP, the sender address is
1095 constructed from the login name of the user that called Exim and a default
1096 qualification domain (which can be set by the &%qualify_domain%& configuration
1097 option). For local or batch SMTP, a sender address that is passed using the
1098 SMTP MAIL command is ignored. However, the system administrator may allow
1099 certain users (&"trusted users"&) to specify a different sender addresses
1100 unconditionally, or all users to specify certain forms of different sender
1101 address. The &%-f%& option or the SMTP MAIL command is used to specify these
1102 different addresses. See section &<<SECTtrustedadmin>>& for details of trusted
1103 users, and the &%untrusted_set_sender%& option for a way of allowing untrusted
1104 users to change sender addresses.
1106 Messages received by either of the non-interactive mechanisms are subject to
1107 checking by the non-SMTP ACL if one is defined. Messages received using SMTP
1108 (either over TCP/IP or interacting with a local process) can be checked by a
1109 number of ACLs that operate at different times during the SMTP session. Either
1110 individual recipients or the entire message can be rejected if local policy
1111 requirements are not met. The &[local_scan()]& function (see chapter
1112 &<<CHAPlocalscan>>&) is run for all incoming messages.
1114 Exim can be configured not to start a delivery process when a message is
1115 received; this can be unconditional, or depend on the number of incoming SMTP
1116 connections or the system load. In these situations, new messages wait on the
1117 queue until a queue runner process picks them up. However, in standard
1118 configurations under normal conditions, delivery is started as soon as a
1119 message is received.
1125 .section "Handling an incoming message" "SECID14"
1126 .cindex "spool directory" "files that hold a message"
1127 .cindex "file" "how a message is held"
1128 When Exim accepts a message, it writes two files in its spool directory. The
1129 first contains the envelope information, the current status of the message, and
1130 the header lines, and the second contains the body of the message. The names of
1131 the two spool files consist of the message id, followed by &`-H`& for the
1132 file containing the envelope and header, and &`-D`& for the data file.
1134 .cindex "spool directory" "&_input_& sub-directory"
1135 By default, all these message files are held in a single directory called
1136 &_input_& inside the general Exim spool directory. Some operating systems do
1137 not perform very well if the number of files in a directory gets large; to
1138 improve performance in such cases, the &%split_spool_directory%& option can be
1139 used. This causes Exim to split up the input files into 62 sub-directories
1140 whose names are single letters or digits. When this is done, the queue is
1141 processed one sub-directory at a time instead of all at once, which can improve
1142 overall performance even when there are not enough files in each directory to
1143 affect file system performance.
1145 The envelope information consists of the address of the message's sender and
1146 the addresses of the recipients. This information is entirely separate from
1147 any addresses contained in the header lines. The status of the message includes
1148 a list of recipients who have already received the message. The format of the
1149 first spool file is described in chapter &<<CHAPspool>>&.
1151 .cindex "rewriting" "addresses"
1152 Address rewriting that is specified in the rewrite section of the configuration
1153 (see chapter &<<CHAPrewrite>>&) is done once and for all on incoming addresses,
1154 both in the header lines and the envelope, at the time the message is accepted.
1155 If during the course of delivery additional addresses are generated (for
1156 example, via aliasing), these new addresses are rewritten as soon as they are
1157 generated. At the time a message is actually delivered (transported) further
1158 rewriting can take place; because this is a transport option, it can be
1159 different for different forms of delivery. It is also possible to specify the
1160 addition or removal of certain header lines at the time the message is
1161 delivered (see chapters &<<CHAProutergeneric>>& and
1162 &<<CHAPtransportgeneric>>&).
1166 .section "Life of a message" "SECID15"
1167 .cindex "message" "life of"
1168 .cindex "message" "frozen"
1169 A message remains in the spool directory until it is completely delivered to
1170 its recipients or to an error address, or until it is deleted by an
1171 administrator or by the user who originally created it. In cases when delivery
1172 cannot proceed &-- for example when a message can neither be delivered to its
1173 recipients nor returned to its sender, the message is marked &"frozen"& on the
1174 spool, and no more deliveries are attempted.
1176 .cindex "frozen messages" "thawing"
1177 .cindex "message" "thawing frozen"
1178 An administrator can &"thaw"& such messages when the problem has been
1179 corrected, and can also freeze individual messages by hand if necessary. In
1180 addition, an administrator can force a delivery error, causing a bounce message
1183 .oindex "&%timeout_frozen_after%&"
1184 .oindex "&%ignore_bounce_errors_after%&"
1185 There are options called &%ignore_bounce_errors_after%& and
1186 &%timeout_frozen_after%&, which discard frozen messages after a certain time.
1187 The first applies only to frozen bounces, the second to all frozen messages.
1189 .cindex "message" "log file for"
1190 .cindex "log" "file for each message"
1191 While Exim is working on a message, it writes information about each delivery
1192 attempt to its main log file. This includes successful, unsuccessful, and
1193 delayed deliveries for each recipient (see chapter &<<CHAPlog>>&). The log
1194 lines are also written to a separate &'message log'& file for each message.
1195 These logs are solely for the benefit of the administrator and are normally
1196 deleted along with the spool files when processing of a message is complete.
1197 The use of individual message logs can be disabled by setting
1198 &%no_message_logs%&; this might give an improvement in performance on very busy
1201 .cindex "journal file"
1202 .cindex "file" "journal"
1203 All the information Exim itself needs to set up a delivery is kept in the first
1204 spool file, along with the header lines. When a successful delivery occurs, the
1205 address is immediately written at the end of a journal file, whose name is the
1206 message id followed by &`-J`&. At the end of a delivery run, if there are some
1207 addresses left to be tried again later, the first spool file (the &`-H`& file)
1208 is updated to indicate which these are, and the journal file is then deleted.
1209 Updating the spool file is done by writing a new file and renaming it, to
1210 minimize the possibility of data loss.
1212 Should the system or Exim crash after a successful delivery but before
1213 the spool file has been updated, the journal is left lying around. The next
1214 time Exim attempts to deliver the message, it reads the journal file and
1215 updates the spool file before proceeding. This minimizes the chances of double
1216 deliveries caused by crashes.
1220 .section "Processing an address for delivery" "SECTprocaddress"
1221 .cindex "drivers" "definition of"
1222 .cindex "router" "definition of"
1223 .cindex "transport" "definition of"
1224 The main delivery processing elements of Exim are called &'routers'& and
1225 &'transports'&, and collectively these are known as &'drivers'&. Code for a
1226 number of them is provided in the source distribution, and compile-time options
1227 specify which ones are included in the binary. Runtime options specify which
1228 ones are actually used for delivering messages.
1230 .cindex "drivers" "instance definition"
1231 Each driver that is specified in the runtime configuration is an &'instance'&
1232 of that particular driver type. Multiple instances are allowed; for example,
1233 you can set up several different &(smtp)& transports, each with different
1234 option values that might specify different ports or different timeouts. Each
1235 instance has its own identifying name. In what follows we will normally use the
1236 instance name when discussing one particular instance (that is, one specific
1237 configuration of the driver), and the generic driver name when discussing
1238 the driver's features in general.
1240 A &'router'& is a driver that operates on an address, either determining how
1241 its delivery should happen, by assigning it to a specific transport, or
1242 converting the address into one or more new addresses (for example, via an
1243 alias file). A router may also explicitly choose to fail an address, causing it
1246 A &'transport'& is a driver that transmits a copy of the message from Exim's
1247 spool to some destination. There are two kinds of transport: for a &'local'&
1248 transport, the destination is a file or a pipe on the local host, whereas for a
1249 &'remote'& transport the destination is some other host. A message is passed
1250 to a specific transport as a result of successful routing. If a message has
1251 several recipients, it may be passed to a number of different transports.
1253 .cindex "preconditions" "definition of"
1254 An address is processed by passing it to each configured router instance in
1255 turn, subject to certain preconditions, until a router accepts the address or
1256 specifies that it should be bounced. We will describe this process in more
1257 detail shortly. First, as a simple example, we consider how each recipient
1258 address in a message is processed in a small configuration of three routers.
1260 To make this a more concrete example, it is described in terms of some actual
1261 routers, but remember, this is only an example. You can configure Exim's
1262 routers in many different ways, and there may be any number of routers in a
1265 The first router that is specified in a configuration is often one that handles
1266 addresses in domains that are not recognized specifically by the local host.
1267 Typically these are addresses for arbitrary domains on the Internet. A precondition
1268 is set up which looks for the special domains known to the host (for example,
1269 its own domain name), and the router is run for addresses that do &'not'&
1270 match. Typically, this is a router that looks up domains in the DNS in order to
1271 find the hosts to which this address routes. If it succeeds, the address is
1272 assigned to a suitable SMTP transport; if it does not succeed, the router is
1273 configured to fail the address.
1275 The second router is reached only when the domain is recognized as one that
1276 &"belongs"& to the local host. This router does redirection &-- also known as
1277 aliasing and forwarding. When it generates one or more new addresses from the
1278 original, each of them is routed independently from the start. Otherwise, the
1279 router may cause an address to fail, or it may simply decline to handle the
1280 address, in which case the address is passed to the next router.
1282 The final router in many configurations is one that checks to see if the
1283 address belongs to a local mailbox. The precondition may involve a check to
1284 see if the local part is the name of a login account, or it may look up the
1285 local part in a file or a database. If its preconditions are not met, or if
1286 the router declines, we have reached the end of the routers. When this happens,
1287 the address is bounced.
1291 .section "Processing an address for verification" "SECID16"
1292 .cindex "router" "for verification"
1293 .cindex "verifying address" "overview"
1294 As well as being used to decide how to deliver to an address, Exim's routers
1295 are also used for &'address verification'&. Verification can be requested as
1296 one of the checks to be performed in an ACL for incoming messages, on both
1297 sender and recipient addresses, and it can be tested using the &%-bv%& and
1298 &%-bvs%& command line options.
1300 When an address is being verified, the routers are run in &"verify mode"&. This
1301 does not affect the way the routers work, but it is a state that can be
1302 detected. By this means, a router can be skipped or made to behave differently
1303 when verifying. A common example is a configuration in which the first router
1304 sends all messages to a message-scanning program unless they have been
1305 previously scanned. Thus, the first router accepts all addresses without any
1306 checking, making it useless for verifying. Normally, the &%no_verify%& option
1307 would be set for such a router, causing it to be skipped in verify mode.
1312 .section "Running an individual router" "SECTrunindrou"
1313 .cindex "router" "running details"
1314 .cindex "preconditions" "checking"
1315 .cindex "router" "result of running"
1316 As explained in the example above, a number of preconditions are checked before
1317 running a router. If any are not met, the router is skipped, and the address is
1318 passed to the next router. When all the preconditions on a router &'are'& met,
1319 the router is run. What happens next depends on the outcome, which is one of
1323 &'accept'&: The router accepts the address, and either assigns it to a
1324 transport or generates one or more &"child"& addresses. Processing the
1325 original address ceases
1326 .oindex "&%unseen%&"
1327 unless the &%unseen%& option is set on the router. This option
1328 can be used to set up multiple deliveries with different routing (for example,
1329 for keeping archive copies of messages). When &%unseen%& is set, the address is
1330 passed to the next router. Normally, however, an &'accept'& return marks the
1333 Any child addresses generated by the router are processed independently,
1334 starting with the first router by default. It is possible to change this by
1335 setting the &%redirect_router%& option to specify which router to start at for
1336 child addresses. Unlike &%pass_router%& (see below) the router specified by
1337 &%redirect_router%& may be anywhere in the router configuration.
1339 &'pass'&: The router recognizes the address, but cannot handle it itself. It
1340 requests that the address be passed to another router. By default, the address
1341 is passed to the next router, but this can be changed by setting the
1342 &%pass_router%& option. However, (unlike &%redirect_router%&) the named router
1343 must be below the current router (to avoid loops).
1345 &'decline'&: The router declines to accept the address because it does not
1346 recognize it at all. By default, the address is passed to the next router, but
1347 this can be prevented by setting the &%no_more%& option. When &%no_more%& is
1348 set, all the remaining routers are skipped. In effect, &%no_more%& converts
1349 &'decline'& into &'fail'&.
1351 &'fail'&: The router determines that the address should fail, and queues it for
1352 the generation of a bounce message. There is no further processing of the
1353 original address unless &%unseen%& is set on the router.
1355 &'defer'&: The router cannot handle the address at the present time. (A
1356 database may be offline, or a DNS lookup may have timed out.) No further
1357 processing of the address happens in this delivery attempt. It is tried again
1358 next time the message is considered for delivery.
1360 &'error'&: There is some error in the router (for example, a syntax error in
1361 its configuration). The action is as for defer.
1364 If an address reaches the end of the routers without having been accepted by
1365 any of them, it is bounced as unrouteable. The default error message in this
1366 situation is &"unrouteable address"&, but you can set your own message by
1367 making use of the &%cannot_route_message%& option. This can be set for any
1368 router; the value from the last router that &"saw"& the address is used.
1370 Sometimes while routing you want to fail a delivery when some conditions are
1371 met but others are not, instead of passing the address on for further routing.
1372 You can do this by having a second router that explicitly fails the delivery
1373 when the relevant conditions are met. The &(redirect)& router has a &"fail"&
1374 facility for this purpose.
1377 .section "Duplicate addresses" "SECID17"
1378 .cindex "case of local parts"
1379 .cindex "address duplicate, discarding"
1380 .cindex "duplicate addresses"
1381 Once routing is complete, Exim scans the addresses that are assigned to local
1382 and remote transports and discards any duplicates that it finds. During this
1383 check, local parts are treated case-sensitively. This happens only when
1384 actually delivering a message; when testing routers with &%-bt%&, all the
1385 routed addresses are shown.
1389 .section "Router preconditions" "SECTrouprecon"
1390 .cindex "router" "preconditions, order of processing"
1391 .cindex "preconditions" "order of processing"
1392 The preconditions that are tested for each router are listed below, in the
1393 order in which they are tested. The individual configuration options are
1394 described in more detail in chapter &<<CHAProutergeneric>>&.
1397 .cindex affix "router precondition"
1398 The &%local_part_prefix%& and &%local_part_suffix%& options can specify that
1399 the local parts handled by the router may or must have certain prefixes and/or
1400 suffixes. If a mandatory affix (prefix or suffix) is not present, the router is
1401 skipped. These conditions are tested first. When an affix is present, it is
1402 removed from the local part before further processing, including the evaluation
1403 of any other conditions.
1405 Routers can be designated for use only when not verifying an address, that is,
1406 only when routing it for delivery (or testing its delivery routing). If the
1407 &%verify%& option is set false, the router is skipped when Exim is verifying an
1409 Setting the &%verify%& option actually sets two options, &%verify_sender%& and
1410 &%verify_recipient%&, which independently control the use of the router for
1411 sender and recipient verification. You can set these options directly if
1412 you want a router to be used for only one type of verification.
1413 Note that cutthrough delivery is classed as a recipient verification for this purpose.
1415 If the &%address_test%& option is set false, the router is skipped when Exim is
1416 run with the &%-bt%& option to test an address routing. This can be helpful
1417 when the first router sends all new messages to a scanner of some sort; it
1418 makes it possible to use &%-bt%& to test subsequent delivery routing without
1419 having to simulate the effect of the scanner.
1421 Routers can be designated for use only when verifying an address, as
1422 opposed to routing it for delivery. The &%verify_only%& option controls this.
1423 Again, cutthrough delivery counts as a verification.
1425 Individual routers can be explicitly skipped when running the routers to
1426 check an address given in the SMTP EXPN command (see the &%expn%& option).
1429 If the &%domains%& option is set, the domain of the address must be in the set
1430 of domains that it defines.
1431 .cindex "tainted data" "de-tainting"
1432 A match verifies the variable &$domain$& (which carries tainted data)
1433 and assigns an untainted value to the &$domain_data$& variable.
1434 Such an untainted value is often needed in the transport.
1435 For specifics of the matching operation and the resulting untainted value,
1436 refer to section &<<SECTdomainlist>>&.
1438 When an untainted value is wanted, use this option
1439 rather than the generic &%condition%& option.
1442 .vindex "&$local_part_prefix$&"
1443 .vindex "&$local_part_prefix_v$&"
1444 .vindex "&$local_part$&"
1445 .vindex "&$local_part_suffix$&"
1446 .vindex "&$local_part_suffix_v$&"
1447 .cindex affix "router precondition"
1448 If the &%local_parts%& option is set, the local part of the address must be in
1449 the set of local parts that it defines.
1450 A match verifies the variable &$local_part$& (which carries tainted data)
1451 and assigns an untainted value to the &$local_part_data$& variable.
1452 Such an untainted value is often needed in the transport.
1453 For specifics of the matching operation and the resulting untainted value,
1454 refer to section &<<SECTlocparlis>>&.
1456 When an untainted value is wanted, use this option
1457 rather than the generic &%condition%& option.
1459 If &%local_part_prefix%& or
1460 &%local_part_suffix%& is in use, the prefix or suffix is removed from the local
1461 part before this check. If you want to do precondition tests on local parts
1462 that include affixes, you can do so by using a &%condition%& option (see below)
1463 that uses the variables &$local_part$&, &$local_part_prefix$&,
1464 &$local_part_prefix_v$&, &$local_part_suffix$&
1465 and &$local_part_suffix_v$& as necessary.
1468 .vindex "&$local_user_uid$&"
1469 .vindex "&$local_user_gid$&"
1471 If the &%check_local_user%& option is set, the local part must be the name of
1472 an account on the local host. If this check succeeds, the uid and gid of the
1473 local user are placed in &$local_user_uid$& and &$local_user_gid$& and the
1474 user's home directory is placed in &$home$&; these values can be used in the
1475 remaining preconditions.
1478 If the &%router_home_directory%& option is set, it is expanded at this point,
1479 because it overrides the value of &$home$&. If this expansion were left till
1480 later, the value of &$home$& as set by &%check_local_user%& would be used in
1481 subsequent tests. Having two different values of &$home$& in the same router
1482 could lead to confusion.
1485 If the &%senders%& option is set, the envelope sender address must be in the
1486 set of addresses that it defines.
1489 If the &%require_files%& option is set, the existence or non-existence of
1490 specified files is tested.
1493 .cindex "customizing" "precondition"
1494 If the &%condition%& option is set, it is evaluated and tested. This option
1495 uses an expanded string to allow you to set up your own custom preconditions.
1496 Expanded strings are described in chapter &<<CHAPexpand>>&.
1498 Note that while using
1499 this option for address matching technically works,
1500 it does not set any de-tainted values.
1501 Such values are often needed, either for router-specific options or
1502 for transport options.
1503 Using the &%domains%& and &%local_parts%& options is usually the most
1504 convenient way to obtain them.
1508 Note that &%require_files%& comes near the end of the list, so you cannot use
1509 it to check for the existence of a file in which to lookup up a domain, local
1510 part, or sender. However, as these options are all expanded, you can use the
1511 &%exists%& expansion condition to make such tests within each condition. The
1512 &%require_files%& option is intended for checking files that the router may be
1513 going to use internally, or which are needed by a specific transport (for
1514 example, &_.procmailrc_&).
1518 .section "Delivery in detail" "SECID18"
1519 .cindex "delivery" "in detail"
1520 When a message is to be delivered, the sequence of events is as follows:
1523 If a system-wide filter file is specified, the message is passed to it. The
1524 filter may add recipients to the message, replace the recipients, discard the
1525 message, cause a new message to be generated, or cause the message delivery to
1526 fail. The format of the system filter file is the same as for Exim user filter
1527 files, described in the separate document entitled &'Exim's interfaces to mail
1529 .cindex "Sieve filter" "not available for system filter"
1530 (&*Note*&: Sieve cannot be used for system filter files.)
1532 Some additional features are available in system filters &-- see chapter
1533 &<<CHAPsystemfilter>>& for details. Note that a message is passed to the system
1534 filter only once per delivery attempt, however many recipients it has. However,
1535 if there are several delivery attempts because one or more addresses could not
1536 be immediately delivered, the system filter is run each time. The filter
1537 condition &%first_delivery%& can be used to detect the first run of the system
1540 Each recipient address is offered to each configured router, in turn, subject to
1541 its preconditions, until one is able to handle it. If no router can handle the
1542 address, that is, if they all decline, the address is failed. Because routers
1543 can be targeted at particular domains, several locally handled domains can be
1544 processed entirely independently of each other.
1546 .cindex "routing" "loops in"
1547 .cindex "loop" "while routing"
1548 A router that accepts an address may assign it to a local or a remote
1549 transport. However, the transport is not run at this time. Instead, the address
1550 is placed on a list for the particular transport, which will be run later.
1551 Alternatively, the router may generate one or more new addresses (typically
1552 from alias, forward, or filter files). New addresses are fed back into this
1553 process from the top, but in order to avoid loops, a router ignores any address
1554 which has an identically-named ancestor that was processed by itself.
1556 When all the routing has been done, addresses that have been successfully
1557 handled are passed to their assigned transports. When local transports are
1558 doing real local deliveries, they handle only one address at a time, but if a
1559 local transport is being used as a pseudo-remote transport (for example, to
1560 collect batched SMTP messages for transmission by some other means) multiple
1561 addresses can be handled. Remote transports can always handle more than one
1562 address at a time, but can be configured not to do so, or to restrict multiple
1563 addresses to the same domain.
1565 Each local delivery to a file or a pipe runs in a separate process under a
1566 non-privileged uid, and these deliveries are run one at a time. Remote
1567 deliveries also run in separate processes, normally under a uid that is private
1568 to Exim (&"the Exim user"&), but in this case, several remote deliveries can be
1569 run in parallel. The maximum number of simultaneous remote deliveries for any
1570 one message is set by the &%remote_max_parallel%& option.
1571 The order in which deliveries are done is not defined, except that all local
1572 deliveries happen before any remote deliveries.
1574 .cindex "queue runner"
1575 When it encounters a local delivery during a queue run, Exim checks its retry
1576 database to see if there has been a previous temporary delivery failure for the
1577 address before running the local transport. If there was a previous failure,
1578 Exim does not attempt a new delivery until the retry time for the address is
1579 reached. However, this happens only for delivery attempts that are part of a
1580 queue run. Local deliveries are always attempted when delivery immediately
1581 follows message reception, even if retry times are set for them. This makes for
1582 better behaviour if one particular message is causing problems (for example,
1583 causing quota overflow, or provoking an error in a filter file).
1585 .cindex "delivery" "retry in remote transports"
1586 Remote transports do their own retry handling, since an address may be
1587 deliverable to one of a number of hosts, each of which may have a different
1588 retry time. If there have been previous temporary failures and no host has
1589 reached its retry time, no delivery is attempted, whether in a queue run or
1590 not. See chapter &<<CHAPretry>>& for details of retry strategies.
1592 If there were any permanent errors, a bounce message is returned to an
1593 appropriate address (the sender in the common case), with details of the error
1594 for each failing address. Exim can be configured to send copies of bounce
1595 messages to other addresses.
1597 .cindex "delivery" "deferral"
1598 If one or more addresses suffered a temporary failure, the message is left on
1599 the queue, to be tried again later. Delivery of these addresses is said to be
1602 When all the recipient addresses have either been delivered or bounced,
1603 handling of the message is complete. The spool files and message log are
1604 deleted, though the message log can optionally be preserved if required.
1610 .section "Retry mechanism" "SECID19"
1611 .cindex "delivery" "retry mechanism"
1612 .cindex "retry" "description of mechanism"
1613 .cindex "queue runner"
1614 Exim's mechanism for retrying messages that fail to get delivered at the first
1615 attempt is the queue runner process. You must either run an Exim daemon that
1616 uses the &%-q%& option with a time interval to start queue runners at regular
1617 intervals or use some other means (such as &'cron'&) to start them. If you do
1618 not arrange for queue runners to be run, messages that fail temporarily at the
1619 first attempt will remain in your queue forever. A queue runner process works
1620 its way through the queue, one message at a time, trying each delivery that has
1621 passed its retry time.
1622 You can run several queue runners at once.
1624 Exim uses a set of configured rules to determine when next to retry the failing
1625 address (see chapter &<<CHAPretry>>&). These rules also specify when Exim
1626 should give up trying to deliver to the address, at which point it generates a
1627 bounce message. If no retry rules are set for a particular host, address, and
1628 error combination, no retries are attempted, and temporary errors are treated
1633 .section "Temporary delivery failure" "SECID20"
1634 .cindex "delivery" "temporary failure"
1635 There are many reasons why a message may not be immediately deliverable to a
1636 particular address. Failure to connect to a remote machine (because it, or the
1637 connection to it, is down) is one of the most common. Temporary failures may be
1638 detected during routing as well as during the transport stage of delivery.
1639 Local deliveries may be delayed if NFS files are unavailable, or if a mailbox
1640 is on a file system where the user is over quota. Exim can be configured to
1641 impose its own quotas on local mailboxes; where system quotas are set they will
1644 If a host is unreachable for a period of time, a number of messages may be
1645 waiting for it by the time it recovers, and sending them in a single SMTP
1646 connection is clearly beneficial. Whenever a delivery to a remote host is
1648 .cindex "hints database" "deferred deliveries"
1649 Exim makes a note in its hints database, and whenever a successful
1650 SMTP delivery has happened, it looks to see if any other messages are waiting
1651 for the same host. If any are found, they are sent over the same SMTP
1652 connection, subject to a configuration limit as to the maximum number in any
1657 .section "Permanent delivery failure" "SECID21"
1658 .cindex "delivery" "permanent failure"
1659 .cindex "bounce message" "when generated"
1660 When a message cannot be delivered to some or all of its intended recipients, a
1661 bounce message is generated. Temporary delivery failures turn into permanent
1662 errors when their timeout expires. All the addresses that fail in a given
1663 delivery attempt are listed in a single message. If the original message has
1664 many recipients, it is possible for some addresses to fail in one delivery
1665 attempt and others to fail subsequently, giving rise to more than one bounce
1666 message. The wording of bounce messages can be customized by the administrator.
1667 See chapter &<<CHAPemsgcust>>& for details.
1669 .cindex "&'X-Failed-Recipients:'& header line"
1670 Bounce messages contain an &'X-Failed-Recipients:'& header line that lists the
1671 failed addresses, for the benefit of programs that try to analyse such messages
1674 .cindex "bounce message" "recipient of"
1675 A bounce message is normally sent to the sender of the original message, as
1676 obtained from the message's envelope. For incoming SMTP messages, this is the
1677 address given in the MAIL command. However, when an address is expanded via a
1678 forward or alias file, an alternative address can be specified for delivery
1679 failures of the generated addresses. For a mailing list expansion (see section
1680 &<<SECTmailinglists>>&) it is common to direct bounce messages to the manager
1685 .section "Failures to deliver bounce messages" "SECID22"
1686 .cindex "bounce message" "failure to deliver"
1687 If a bounce message (either locally generated or received from a remote host)
1688 itself suffers a permanent delivery failure, the message is left in the queue,
1689 but it is frozen, awaiting the attention of an administrator. There are options
1690 that can be used to make Exim discard such failed messages, or to keep them
1691 for only a short time (see &%timeout_frozen_after%& and
1692 &%ignore_bounce_errors_after%&).
1698 . ////////////////////////////////////////////////////////////////////////////
1699 . ////////////////////////////////////////////////////////////////////////////
1701 .chapter "Building and installing Exim" "CHID3"
1702 .scindex IIDbuex "building Exim"
1704 .section "Unpacking" "SECID23"
1705 Exim is distributed as a gzipped or bzipped tar file which, when unpacked,
1706 creates a directory with the name of the current release (for example,
1707 &_exim-&version()_&) into which the following files are placed:
1710 .irow &_ACKNOWLEDGMENTS_& "contains some acknowledgments"
1711 .irow &_CHANGES_& "contains a reference to where changes are &&&
1713 .irow &_LICENCE_& "the GNU General Public Licence"
1714 .irow &_Makefile_& "top-level make file"
1715 .irow &_NOTICE_& "conditions for the use of Exim"
1716 .irow &_README_& "list of files, directories and simple build &&&
1720 Other files whose names begin with &_README_& may also be present. The
1721 following subdirectories are created:
1724 .irow &_Local_& "an empty directory for local configuration files"
1725 .irow &_OS_& "OS-specific files"
1726 .irow &_doc_& "documentation files"
1727 .irow &_exim_monitor_& "source files for the Exim monitor"
1728 .irow &_scripts_& "scripts used in the build process"
1729 .irow &_src_& "remaining source files"
1730 .irow &_util_& "independent utilities"
1733 The main utility programs are contained in the &_src_& directory and are built
1734 with the Exim binary. The &_util_& directory contains a few optional scripts
1735 that may be useful to some sites.
1738 .section "Multiple machine architectures and operating systems" "SECID24"
1739 .cindex "building Exim" "multiple OS/architectures"
1740 The building process for Exim is arranged to make it easy to build binaries for
1741 a number of different architectures and operating systems from the same set of
1742 source files. Compilation does not take place in the &_src_& directory.
1743 Instead, a &'build directory'& is created for each architecture and operating
1745 .cindex "symbolic link" "to build directory"
1746 Symbolic links to the sources are installed in this directory, which is where
1747 the actual building takes place. In most cases, Exim can discover the machine
1748 architecture and operating system for itself, but the defaults can be
1749 overridden if necessary.
1750 .cindex compiler requirements
1751 .cindex compiler version
1752 A C99-capable compiler will be required for the build.
1755 .section "PCRE2 library" "SECTpcre"
1756 .cindex "PCRE2 library"
1757 Exim no longer has an embedded regular-expression library as the vast majority of
1758 modern systems include PCRE2 as a system library, although you may need to
1759 install the PCRE2 package or the PCRE2 development package for your operating
1760 system. If your system has a normal PCRE2 installation the Exim build
1761 process will need no further configuration. If the library or the
1762 headers are in an unusual location you will need to either set the PCRE2_LIBS
1763 and INCLUDE directives appropriately,
1764 or set PCRE2_CONFIG=yes to use the installed &(pcre-config)& command.
1765 If your operating system has no
1766 PCRE2 support then you will need to obtain and build the current PCRE2
1767 from &url(https://github.com/PhilipHazel/pcre2/releases).
1768 More information on PCRE2 is available at &url(https://www.pcre.org/).
1770 .section "DBM libraries" "SECTdb"
1771 .cindex "DBM libraries" "discussion of"
1772 .cindex "hints database" "DBM files used for"
1773 Even if you do not use any DBM files in your configuration, Exim still needs a
1774 DBM library in order to operate, because it uses indexed files for its hints
1775 databases. Unfortunately, there are a number of DBM libraries in existence, and
1776 different operating systems often have different ones installed.
1778 .cindex "Solaris" "DBM library for"
1779 .cindex "IRIX, DBM library for"
1780 .cindex "BSD, DBM library for"
1781 .cindex "Linux, DBM library for"
1782 If you are using Solaris, IRIX, one of the modern BSD systems, or a modern
1783 Linux distribution, the DBM configuration should happen automatically, and you
1784 may be able to ignore this section. Otherwise, you may have to learn more than
1785 you would like about DBM libraries from what follows.
1787 .cindex "&'ndbm'& DBM library"
1788 Licensed versions of Unix normally contain a library of DBM functions operating
1789 via the &'ndbm'& interface, and this is what Exim expects by default. Free
1790 versions of Unix seem to vary in what they contain as standard. In particular,
1791 some early versions of Linux have no default DBM library, and different
1792 distributors have chosen to bundle different libraries with their packaged
1793 versions. However, the more recent releases seem to have standardized on the
1794 Berkeley DB library.
1796 Different DBM libraries have different conventions for naming the files they
1797 use. When a program opens a file called &_dbmfile_&, there are several
1801 A traditional &'ndbm'& implementation, such as that supplied as part of
1802 Solaris, operates on two files called &_dbmfile.dir_& and &_dbmfile.pag_&.
1804 .cindex "&'gdbm'& DBM library"
1805 The GNU library, &'gdbm'&, operates on a single file. If used via its &'ndbm'&
1806 compatibility interface it makes two different hard links to it with names
1807 &_dbmfile.dir_& and &_dbmfile.pag_&, but if used via its native interface, the
1808 filename is used unmodified.
1810 .cindex "Berkeley DB library"
1811 The Berkeley DB package, if called via its &'ndbm'& compatibility interface,
1812 operates on a single file called &_dbmfile.db_&, but otherwise looks to the
1813 programmer exactly the same as the traditional &'ndbm'& implementation.
1815 If the Berkeley package is used in its native mode, it operates on a single
1816 file called &_dbmfile_&; the programmer's interface is somewhat different to
1817 the traditional &'ndbm'& interface.
1819 To complicate things further, there are several very different versions of the
1820 Berkeley DB package. Version 1.85 was stable for a very long time, releases
1821 2.&'x'& and 3.&'x'& were current for a while,
1823 but the latest versions when Exim last revamped support were numbered 5.&'x'&.
1824 Maintenance of some of the earlier releases has ceased,
1825 and Exim no longer supports versions before 3.&'x'&.
1827 All versions of Berkeley DB could be obtained from
1828 &url(http://www.sleepycat.com/), which is now a redirect to their new owner's
1829 page with far newer versions listed.
1830 It is probably wise to plan to move your storage configurations away from
1831 Berkeley DB format, as today there are smaller and simpler alternatives more
1832 suited to Exim's usage model.
1834 .cindex "&'tdb'& DBM library"
1835 Yet another DBM library, called &'tdb'&, is available from
1836 &url(https://sourceforge.net/projects/tdb/files/). It has its own interface, and also
1837 operates on a single file.
1841 .cindex "DBM libraries" "configuration for building"
1842 Exim and its utilities can be compiled to use any of these interfaces. In order
1843 to use any version of the Berkeley DB package in native mode, you must set
1844 USE_DB in an appropriate configuration file (typically
1845 &_Local/Makefile_&). For example:
1849 Similarly, for gdbm you set USE_GDBM, and for tdb you set USE_TDB. An
1850 error is diagnosed if you set more than one of these.
1852 You can set USE_NDBM if needed to override an operating system default.
1855 At the lowest level, the build-time configuration sets none of these options,
1856 thereby assuming an interface of type (1). However, some operating system
1857 configuration files (for example, those for the BSD operating systems and
1858 Linux) assume type (4) by setting USE_DB as their default, and the
1859 configuration files for Cygwin set USE_GDBM. Anything you set in
1860 &_Local/Makefile_&, however, overrides these system defaults.
1862 As well as setting USE_DB, USE_GDBM, or USE_TDB, it may also be
1863 necessary to set DBMLIB, to cause inclusion of the appropriate library, as
1864 in one of these lines:
1868 DBMLIB = -lgdbm -lgdbm_compat
1871 The last of those was for a Linux having GDBM provide emulated NDBM facilities.
1873 Settings like that will work if the DBM library is installed in the standard
1874 place. Sometimes it is not, and the library's header file may also not be in
1875 the default path. You may need to set INCLUDE to specify where the header
1876 file is, and to specify the path to the library more fully in DBMLIB, as in
1879 INCLUDE=-I/usr/local/include/db-4.1
1880 DBMLIB=/usr/local/lib/db-4.1/libdb.a
1882 There is further detailed discussion about the various DBM libraries in the
1883 file &_doc/dbm.discuss.txt_& in the Exim distribution.
1887 .section "Pre-building configuration" "SECID25"
1888 .cindex "building Exim" "pre-building configuration"
1889 .cindex "configuration for building Exim"
1890 .cindex "&_Local/Makefile_&"
1891 .cindex "&_src/EDITME_&"
1892 Before building Exim, a local configuration file that specifies options
1893 independent of any operating system has to be created with the name
1894 &_Local/Makefile_&. A template for this file is supplied as the file
1895 &_src/EDITME_&, and it contains full descriptions of all the option settings
1896 therein. These descriptions are therefore not repeated here. If you are
1897 building Exim for the first time, the simplest thing to do is to copy
1898 &_src/EDITME_& to &_Local/Makefile_&, then read it and edit it appropriately.
1900 There are three settings that you must supply, because Exim will not build
1901 without them. They are the location of the runtime configuration file
1902 (CONFIGURE_FILE), the directory in which Exim binaries will be installed
1903 (BIN_DIRECTORY), and the identity of the Exim user (EXIM_USER and
1904 maybe EXIM_GROUP as well). The value of CONFIGURE_FILE can in fact be
1905 a colon-separated list of filenames; Exim uses the first of them that exists.
1907 There are a few other parameters that can be specified either at build time or
1908 at runtime, to enable the same binary to be used on a number of different
1909 machines. However, if the locations of Exim's spool directory and log file
1910 directory (if not within the spool directory) are fixed, it is recommended that
1911 you specify them in &_Local/Makefile_& instead of at runtime, so that errors
1912 detected early in Exim's execution (such as a malformed configuration file) can
1915 .cindex "content scanning" "specifying at build time"
1916 Exim's interfaces for calling virus and spam scanning software directly from
1917 access control lists are not compiled by default. If you want to include these
1918 facilities, you need to set
1920 WITH_CONTENT_SCAN=yes
1922 in your &_Local/Makefile_&. For details of the facilities themselves, see
1923 chapter &<<CHAPexiscan>>&.
1926 .cindex "&_Local/eximon.conf_&"
1927 .cindex "&_exim_monitor/EDITME_&"
1928 If you are going to build the Exim monitor, a similar configuration process is
1929 required. The file &_exim_monitor/EDITME_& must be edited appropriately for
1930 your installation and saved under the name &_Local/eximon.conf_&. If you are
1931 happy with the default settings described in &_exim_monitor/EDITME_&,
1932 &_Local/eximon.conf_& can be empty, but it must exist.
1934 This is all the configuration that is needed in straightforward cases for known
1935 operating systems. However, the building process is set up so that it is easy
1936 to override options that are set by default or by operating-system-specific
1937 configuration files, for example, to change the C compiler, which
1938 defaults to &%gcc%&. See section &<<SECToverride>>& below for details of how to
1943 .section "Support for iconv()" "SECID26"
1944 .cindex "&[iconv()]& support"
1946 The contents of header lines in messages may be encoded according to the rules
1947 described RFC 2047. This makes it possible to transmit characters that are not
1948 in the ASCII character set, and to label them as being in a particular
1949 character set. When Exim is inspecting header lines by means of the &%$h_%&
1950 mechanism, it decodes them, and translates them into a specified character set
1951 (default is set at build time). The translation is possible only if the operating system
1952 supports the &[iconv()]& function.
1954 However, some of the operating systems that supply &[iconv()]& do not support
1955 very many conversions. The GNU &%libiconv%& library (available from
1956 &url(https://www.gnu.org/software/libiconv/)) can be installed on such
1957 systems to remedy this deficiency, as well as on systems that do not supply
1958 &[iconv()]& at all. After installing &%libiconv%&, you should add
1962 to your &_Local/Makefile_& and rebuild Exim.
1966 .section "Including TLS/SSL encryption support" "SECTinctlsssl"
1967 .cindex "TLS" "including support for TLS"
1968 .cindex "encryption" "including support for"
1969 .cindex "OpenSSL" "building Exim with"
1970 .cindex "GnuTLS" "building Exim with"
1971 Exim is usually built to support encrypted SMTP connections, using the STARTTLS
1972 command as per RFC 2487. It can also support clients that expect to
1973 start a TLS session immediately on connection to a non-standard port (see the
1974 &%tls_on_connect_ports%& runtime option and the &%-tls-on-connect%& command
1977 If you want to build Exim with TLS support, you must first install either the
1978 OpenSSL or GnuTLS library. There is no cryptographic code in Exim itself for
1981 If you do not want TLS support you should set
1985 in &_Local/Makefile_&.
1987 If OpenSSL is installed, you should set
1990 TLS_LIBS=-lssl -lcrypto
1992 in &_Local/Makefile_&. You may also need to specify the locations of the
1993 OpenSSL library and include files. For example:
1996 TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto
1997 TLS_INCLUDE=-I/usr/local/openssl/include/
1999 .cindex "pkg-config" "OpenSSL"
2000 If you have &'pkg-config'& available, then instead you can just use:
2003 USE_OPENSSL_PC=openssl
2005 .cindex "USE_GNUTLS"
2006 If GnuTLS is installed, you should set
2009 TLS_LIBS=-lgnutls -ltasn1 -lgcrypt
2011 in &_Local/Makefile_&, and again you may need to specify the locations of the
2012 library and include files. For example:
2015 TLS_LIBS=-L/usr/gnu/lib -lgnutls -ltasn1 -lgcrypt
2016 TLS_INCLUDE=-I/usr/gnu/include
2018 .cindex "pkg-config" "GnuTLS"
2019 If you have &'pkg-config'& available, then instead you can just use:
2022 USE_GNUTLS_PC=gnutls
2025 You do not need to set TLS_INCLUDE if the relevant directory is already
2026 specified in INCLUDE. Details of how to configure Exim to make use of TLS are
2027 given in chapter &<<CHAPTLS>>&.
2032 .section "Use of tcpwrappers" "SECID27"
2034 .cindex "tcpwrappers, building Exim to support"
2035 .cindex "USE_TCP_WRAPPERS"
2036 .cindex "TCP_WRAPPERS_DAEMON_NAME"
2037 .cindex "tcp_wrappers_daemon_name"
2038 Exim can be linked with the &'tcpwrappers'& library in order to check incoming
2039 SMTP calls using the &'tcpwrappers'& control files. This may be a convenient
2040 alternative to Exim's own checking facilities for installations that are
2041 already making use of &'tcpwrappers'& for other purposes. To do this, you
2042 should set USE_TCP_WRAPPERS in &_Local/Makefile_&, arrange for the file
2043 &_tcpd.h_& to be available at compile time, and also ensure that the library
2044 &_libwrap.a_& is available at link time, typically by including &%-lwrap%& in
2045 EXTRALIBS_EXIM. For example, if &'tcpwrappers'& is installed in &_/usr/local_&,
2048 USE_TCP_WRAPPERS=yes
2049 CFLAGS=-O -I/usr/local/include
2050 EXTRALIBS_EXIM=-L/usr/local/lib -lwrap
2052 in &_Local/Makefile_&. The daemon name to use in the &'tcpwrappers'& control
2053 files is &"exim"&. For example, the line
2055 exim : LOCAL 192.168.1. .friendly.domain.example
2057 in your &_/etc/hosts.allow_& file allows connections from the local host, from
2058 the subnet 192.168.1.0/24, and from all hosts in &'friendly.domain.example'&.
2059 All other connections are denied. The daemon name used by &'tcpwrappers'&
2060 can be changed at build time by setting TCP_WRAPPERS_DAEMON_NAME in
2061 &_Local/Makefile_&, or by setting tcp_wrappers_daemon_name in the
2062 configure file. Consult the &'tcpwrappers'& documentation for
2066 .section "Including support for IPv6" "SECID28"
2067 .cindex "IPv6" "including support for"
2068 Exim contains code for use on systems that have IPv6 support. Setting
2069 &`HAVE_IPV6=YES`& in &_Local/Makefile_& causes the IPv6 code to be included;
2070 it may also be necessary to set IPV6_INCLUDE and IPV6_LIBS on systems
2071 where the IPv6 support is not fully integrated into the normal include and
2074 Two different types of DNS record for handling IPv6 addresses have been
2075 defined. AAAA records (analogous to A records for IPv4) are in use, and are
2076 currently seen as the mainstream. Another record type called A6 was proposed
2077 as better than AAAA because it had more flexibility. However, it was felt to be
2078 over-complex, and its status was reduced to &"experimental"&.
2080 have a compile option for including A6 record support but this has now been
2085 .section "Dynamically loaded lookup module support" "SECTdynamicmodules"
2086 .cindex "lookup modules"
2087 .cindex "dynamic modules"
2088 .cindex ".so building"
2089 On some platforms, Exim supports not compiling all lookup types directly into
2090 the main binary, instead putting some into external modules which can be loaded
2092 This permits packagers to build Exim with support for lookups with extensive
2093 library dependencies without requiring all users to install all of those
2095 Most, but not all, lookup types can be built this way.
2097 Set &`LOOKUP_MODULE_DIR`& to the directory into which the modules will be
2098 installed; Exim will only load modules from that directory, as a security
2099 measure. You will need to set &`CFLAGS_DYNAMIC`& if not already defined
2100 for your OS; see &_OS/Makefile-Linux_& for an example.
2101 Some other requirements for adjusting &`EXTRALIBS`& may also be necessary,
2102 see &_src/EDITME_& for details.
2104 Then, for each module to be loaded dynamically, define the relevant
2105 &`LOOKUP_`&<&'lookup_type'&> flags to have the value "2" instead of "yes".
2106 For example, this will build in lsearch but load sqlite and mysql support
2115 .section "The building process" "SECID29"
2116 .cindex "build directory"
2117 Once &_Local/Makefile_& (and &_Local/eximon.conf_&, if required) have been
2118 created, run &'make'& at the top level. It determines the architecture and
2119 operating system types, and creates a build directory if one does not exist.
2120 For example, on a Sun system running Solaris 8, the directory
2121 &_build-SunOS5-5.8-sparc_& is created.
2122 .cindex "symbolic link" "to source files"
2123 Symbolic links to relevant source files are installed in the build directory.
2125 If this is the first time &'make'& has been run, it calls a script that builds
2126 a make file inside the build directory, using the configuration files from the
2127 &_Local_& directory. The new make file is then passed to another instance of
2128 &'make'&. This does the real work, building a number of utility scripts, and
2129 then compiling and linking the binaries for the Exim monitor (if configured), a
2130 number of utility programs, and finally Exim itself. The command &`make
2131 makefile`& can be used to force a rebuild of the make file in the build
2132 directory, should this ever be necessary.
2134 If you have problems building Exim, check for any comments there may be in the
2135 &_README_& file concerning your operating system, and also take a look at the
2136 FAQ, where some common problems are covered.
2140 .section 'Output from &"make"&' "SECID283"
2141 The output produced by the &'make'& process for compile lines is often very
2142 unreadable, because these lines can be very long. For this reason, the normal
2143 output is suppressed by default, and instead output similar to that which
2144 appears when compiling the 2.6 Linux kernel is generated: just a short line for
2145 each module that is being compiled or linked. However, it is still possible to
2146 get the full output, by calling &'make'& like this:
2150 The value of FULLECHO defaults to &"@"&, the flag character that suppresses
2151 command reflection in &'make'&. When you ask for the full output, it is
2152 given in addition to the short output.
2156 .section "Overriding build-time options for Exim" "SECToverride"
2157 .cindex "build-time options, overriding"
2158 The main make file that is created at the beginning of the building process
2159 consists of the concatenation of a number of files which set configuration
2160 values, followed by a fixed set of &'make'& instructions. If a value is set
2161 more than once, the last setting overrides any previous ones. This provides a
2162 convenient way of overriding defaults. The files that are concatenated are, in
2165 &_OS/Makefile-Default_&
2166 &_OS/Makefile-_&<&'ostype'&>
2168 &_Local/Makefile-_&<&'ostype'&>
2169 &_Local/Makefile-_&<&'archtype'&>
2170 &_Local/Makefile-_&<&'ostype'&>-<&'archtype'&>
2171 &_OS/Makefile-Base_&
2173 .cindex "&_Local/Makefile_&"
2174 .cindex "building Exim" "operating system type"
2175 .cindex "building Exim" "architecture type"
2176 where <&'ostype'&> is the operating system type and <&'archtype'&> is the
2177 architecture type. &_Local/Makefile_& is required to exist, and the building
2178 process fails if it is absent. The other three &_Local_& files are optional,
2179 and are often not needed.
2181 The values used for <&'ostype'&> and <&'archtype'&> are obtained from scripts
2182 called &_scripts/os-type_& and &_scripts/arch-type_& respectively. If either of
2183 the environment variables EXIM_OSTYPE or EXIM_ARCHTYPE is set, their
2184 values are used, thereby providing a means of forcing particular settings.
2185 Otherwise, the scripts try to get values from the &%uname%& command. If this
2186 fails, the shell variables OSTYPE and ARCHTYPE are inspected. A number
2187 of &'ad hoc'& transformations are then applied, to produce the standard names
2188 that Exim expects. You can run these scripts directly from the shell in order
2189 to find out what values are being used on your system.
2192 &_OS/Makefile-Default_& contains comments about the variables that are set
2193 therein. Some (but not all) are mentioned below. If there is something that
2194 needs changing, review the contents of this file and the contents of the make
2195 file for your operating system (&_OS/Makefile-<ostype>_&) to see what the
2199 .cindex "building Exim" "overriding default settings"
2200 If you need to change any of the values that are set in &_OS/Makefile-Default_&
2201 or in &_OS/Makefile-<ostype>_&, or to add any new definitions, you do not
2202 need to change the original files. Instead, you should make the changes by
2203 putting the new values in an appropriate &_Local_& file. For example,
2204 .cindex "Tru64-Unix build-time settings"
2205 when building Exim in many releases of the Tru64-Unix (formerly Digital UNIX,
2206 formerly DEC-OSF1) operating system, it is necessary to specify that the C
2207 compiler is called &'cc'& rather than &'gcc'&. Also, the compiler must be
2208 called with the option &%-std1%&, to make it recognize some of the features of
2209 Standard C that Exim uses. (Most other compilers recognize Standard C by
2210 default.) To do this, you should create a file called &_Local/Makefile-OSF1_&
2211 containing the lines
2216 If you are compiling for just one operating system, it may be easier to put
2217 these lines directly into &_Local/Makefile_&.
2219 Keeping all your local configuration settings separate from the distributed
2220 files makes it easy to transfer them to new versions of Exim simply by copying
2221 the contents of the &_Local_& directory.
2224 .cindex "NIS lookup type" "including support for"
2225 .cindex "NIS+ lookup type" "including support for"
2226 .cindex "LDAP" "including support for"
2227 .cindex "lookup" "inclusion in binary"
2228 Exim contains support for doing LDAP, NIS, NIS+, and other kinds of file
2229 lookup, but not all systems have these components installed, so the default is
2230 not to include the relevant code in the binary. All the different kinds of file
2231 and database lookup that Exim supports are implemented as separate code modules
2232 which are included only if the relevant compile-time options are set. In the
2233 case of LDAP, NIS, and NIS+, the settings for &_Local/Makefile_& are:
2239 and similar settings apply to the other lookup types. They are all listed in
2240 &_src/EDITME_&. In many cases the relevant include files and interface
2241 libraries need to be installed before compiling Exim.
2242 .cindex "cdb" "including support for"
2243 However, there are some optional lookup types (such as cdb) for which
2244 the code is entirely contained within Exim, and no external include
2245 files or libraries are required. When a lookup type is not included in the
2246 binary, attempts to configure Exim to use it cause runtime configuration
2249 .cindex "pkg-config" "lookups"
2250 .cindex "pkg-config" "authenticators"
2251 Many systems now use a tool called &'pkg-config'& to encapsulate information
2252 about how to compile against a library; Exim has some initial support for
2253 being able to use pkg-config for lookups and authenticators. For any given
2254 makefile variable which starts &`LOOKUP_`& or &`AUTH_`&, you can add a new
2255 variable with the &`_PC`& suffix in the name and assign as the value the
2256 name of the package to be queried. The results of querying via the
2257 &'pkg-config'& command will be added to the appropriate Makefile variables
2258 with &`+=`& directives, so your version of &'make'& will need to support that
2259 syntax. For instance:
2262 LOOKUP_SQLITE_PC=sqlite3
2264 AUTH_GSASL_PC=libgsasl
2265 AUTH_HEIMDAL_GSSAPI=yes
2266 AUTH_HEIMDAL_GSSAPI_PC=heimdal-gssapi
2269 .cindex "Perl" "including support for"
2270 Exim can be linked with an embedded Perl interpreter, allowing Perl
2271 subroutines to be called during string expansion. To enable this facility,
2275 must be defined in &_Local/Makefile_&. Details of this facility are given in
2276 chapter &<<CHAPperl>>&.
2278 .cindex "X11 libraries, location of"
2279 The location of the X11 libraries is something that varies a lot between
2280 operating systems, and there may be different versions of X11 to cope
2281 with. Exim itself makes no use of X11, but if you are compiling the Exim
2282 monitor, the X11 libraries must be available.
2283 The following three variables are set in &_OS/Makefile-Default_&:
2286 XINCLUDE=-I$(X11)/include
2287 XLFLAGS=-L$(X11)/lib
2289 These are overridden in some of the operating-system configuration files. For
2290 example, in &_OS/Makefile-SunOS5_& there is
2293 XINCLUDE=-I$(X11)/include
2294 XLFLAGS=-L$(X11)/lib -R$(X11)/lib
2296 If you need to override the default setting for your operating system, place a
2297 definition of all three of these variables into your
2298 &_Local/Makefile-<ostype>_& file.
2301 If you need to add any extra libraries to the link steps, these can be put in a
2302 variable called EXTRALIBS, which appears in all the link commands, but by
2303 default is not defined. In contrast, EXTRALIBS_EXIM is used only on the
2304 command for linking the main Exim binary, and not for any associated utilities.
2306 .cindex "DBM libraries" "configuration for building"
2307 There is also DBMLIB, which appears in the link commands for binaries that
2308 use DBM functions (see also section &<<SECTdb>>&). Finally, there is
2309 EXTRALIBS_EXIMON, which appears only in the link step for the Exim monitor
2310 binary, and which can be used, for example, to include additional X11
2313 .cindex "configuration file" "editing"
2314 The make file copes with rebuilding Exim correctly if any of the configuration
2315 files are edited. However, if an optional configuration file is deleted, it is
2316 necessary to touch the associated non-optional file (that is,
2317 &_Local/Makefile_& or &_Local/eximon.conf_&) before rebuilding.
2320 .section "OS-specific header files" "SECID30"
2322 .cindex "building Exim" "OS-specific C header files"
2323 The &_OS_& directory contains a number of files with names of the form
2324 &_os.h-<ostype>_&. These are system-specific C header files that should not
2325 normally need to be changed. There is a list of macro settings that are
2326 recognized in the file &_OS/os.configuring_&, which should be consulted if you
2327 are porting Exim to a new operating system.
2331 .section "Overriding build-time options for the monitor" "SECID31"
2332 .cindex "building Eximon"
2333 A similar process is used for overriding things when building the Exim monitor,
2334 where the files that are involved are
2336 &_OS/eximon.conf-Default_&
2337 &_OS/eximon.conf-_&<&'ostype'&>
2338 &_Local/eximon.conf_&
2339 &_Local/eximon.conf-_&<&'ostype'&>
2340 &_Local/eximon.conf-_&<&'archtype'&>
2341 &_Local/eximon.conf-_&<&'ostype'&>-<&'archtype'&>
2343 .cindex "&_Local/eximon.conf_&"
2344 As with Exim itself, the final three files need not exist, and in this case the
2345 &_OS/eximon.conf-<ostype>_& file is also optional. The default values in
2346 &_OS/eximon.conf-Default_& can be overridden dynamically by setting environment
2347 variables of the same name, preceded by EXIMON_. For example, setting
2348 EXIMON_LOG_DEPTH in the environment overrides the value of
2349 LOG_DEPTH at runtime.
2353 .section "Installing Exim binaries and scripts" "SECID32"
2354 .cindex "installing Exim"
2355 .cindex "BIN_DIRECTORY"
2356 The command &`make install`& runs the &(exim_install)& script with no
2357 arguments. The script copies binaries and utility scripts into the directory
2358 whose name is specified by the BIN_DIRECTORY setting in &_Local/Makefile_&.
2359 .cindex "setuid" "installing Exim with"
2360 The install script copies files only if they are newer than the files they are
2361 going to replace. The Exim binary is required to be owned by root and have the
2362 &'setuid'& bit set, for normal configurations. Therefore, you must run &`make
2363 install`& as root so that it can set up the Exim binary in this way. However, in
2364 some special situations (for example, if a host is doing no local deliveries)
2365 it may be possible to run Exim without making the binary setuid root (see
2366 chapter &<<CHAPsecurity>>& for details).
2368 .cindex "CONFIGURE_FILE"
2369 Exim's runtime configuration file is named by the CONFIGURE_FILE setting
2370 in &_Local/Makefile_&. If this names a single file, and the file does not
2371 exist, the default configuration file &_src/configure.default_& is copied there
2372 by the installation script. If a runtime configuration file already exists, it
2373 is left alone. If CONFIGURE_FILE is a colon-separated list, naming several
2374 alternative files, no default is installed.
2376 .cindex "system aliases file"
2377 .cindex "&_/etc/aliases_&"
2378 One change is made to the default configuration file when it is installed: the
2379 default configuration contains a router that references a system aliases file.
2380 The path to this file is set to the value specified by
2381 SYSTEM_ALIASES_FILE in &_Local/Makefile_& (&_/etc/aliases_& by default).
2382 If the system aliases file does not exist, the installation script creates it,
2383 and outputs a comment to the user.
2385 The created file contains no aliases, but it does contain comments about the
2386 aliases a site should normally have. Mail aliases have traditionally been
2387 kept in &_/etc/aliases_&. However, some operating systems are now using
2388 &_/etc/mail/aliases_&. You should check if yours is one of these, and change
2389 Exim's configuration if necessary.
2391 The default configuration uses the local host's name as the only local domain,
2392 and is set up to do local deliveries into the shared directory &_/var/mail_&,
2393 running as the local user. System aliases and &_.forward_& files in users' home
2394 directories are supported, but no NIS or NIS+ support is configured. Domains
2395 other than the name of the local host are routed using the DNS, with delivery
2398 It is possible to install Exim for special purposes (such as building a binary
2399 distribution) in a private part of the file system. You can do this by a
2402 make DESTDIR=/some/directory/ install
2404 This has the effect of pre-pending the specified directory to all the file
2405 paths, except the name of the system aliases file that appears in the default
2406 configuration. (If a default alias file is created, its name &'is'& modified.)
2407 For backwards compatibility, ROOT is used if DESTDIR is not set,
2408 but this usage is deprecated.
2410 .cindex "installing Exim" "what is not installed"
2411 Running &'make install'& does not copy the Exim 4 conversion script
2412 &'convert4r4'&. You will probably run this only once if you are
2413 upgrading from Exim 3. None of the documentation files in the &_doc_&
2414 directory are copied, except for the info files when you have set
2415 INFO_DIRECTORY, as described in section &<<SECTinsinfdoc>>& below.
2417 For the utility programs, old versions are renamed by adding the suffix &_.O_&
2418 to their names. The Exim binary itself, however, is handled differently. It is
2419 installed under a name that includes the version number and the compile number,
2420 for example, &_exim-&version()-1_&. The script then arranges for a symbolic link
2421 called &_exim_& to point to the binary. If you are updating a previous version
2422 of Exim, the script takes care to ensure that the name &_exim_& is never absent
2423 from the directory (as seen by other processes).
2425 .cindex "installing Exim" "testing the script"
2426 If you want to see what the &'make install'& will do before running it for
2427 real, you can pass the &%-n%& option to the installation script by this
2430 make INSTALL_ARG=-n install
2432 The contents of the variable INSTALL_ARG are passed to the installation
2433 script. You do not need to be root to run this test. Alternatively, you can run
2434 the installation script directly, but this must be from within the build
2435 directory. For example, from the top-level Exim directory you could use this
2438 (cd build-SunOS5-5.5.1-sparc; ../scripts/exim_install -n)
2440 .cindex "installing Exim" "install script options"
2441 There are two other options that can be supplied to the installation script.
2444 &%-no_chown%& bypasses the call to change the owner of the installed binary
2445 to root, and the call to make it a setuid binary.
2447 &%-no_symlink%& bypasses the setting up of the symbolic link &_exim_& to the
2451 INSTALL_ARG can be used to pass these options to the script. For example:
2453 make INSTALL_ARG=-no_symlink install
2455 The installation script can also be given arguments specifying which files are
2456 to be copied. For example, to install just the Exim binary, and nothing else,
2457 without creating the symbolic link, you could use:
2459 make INSTALL_ARG='-no_symlink exim' install
2464 .section "Installing info documentation" "SECTinsinfdoc"
2465 .cindex "installing Exim" "&'info'& documentation"
2466 Not all systems use the GNU &'info'& system for documentation, and for this
2467 reason, the Texinfo source of Exim's documentation is not included in the main
2468 distribution. Instead it is available separately from the FTP site (see section
2471 If you have defined INFO_DIRECTORY in &_Local/Makefile_& and the Texinfo
2472 source of the documentation is found in the source tree, running &`make
2473 install`& automatically builds the info files and installs them.
2477 .section "Setting up the spool directory" "SECID33"
2478 .cindex "spool directory" "creating"
2479 When it starts up, Exim tries to create its spool directory if it does not
2480 exist. The Exim uid and gid are used for the owner and group of the spool
2481 directory. Sub-directories are automatically created in the spool directory as
2487 .section "Testing" "SECID34"
2488 .cindex "testing" "installation"
2489 Having installed Exim, you can check that the runtime configuration file is
2490 syntactically valid by running the following command, which assumes that the
2491 Exim binary directory is within your PATH environment variable:
2495 If there are any errors in the configuration file, Exim outputs error messages.
2496 Otherwise it outputs the version number and build date,
2497 the DBM library that is being used, and information about which drivers and
2498 other optional code modules are included in the binary.
2499 Some simple routing tests can be done by using the address testing option. For
2502 &`exim -bt`& <&'local username'&>
2504 should verify that it recognizes a local mailbox, and
2506 &`exim -bt`& <&'remote address'&>
2508 a remote one. Then try getting it to deliver mail, both locally and remotely.
2509 This can be done by passing messages directly to Exim, without going through a
2510 user agent. For example:
2512 exim -v postmaster@your.domain.example
2513 From: user@your.domain.example
2514 To: postmaster@your.domain.example
2515 Subject: Testing Exim
2517 This is a test message.
2520 The &%-v%& option causes Exim to output some verification of what it is doing.
2521 In this case you should see copies of three log lines, one for the message's
2522 arrival, one for its delivery, and one containing &"Completed"&.
2524 .cindex "delivery" "problems with"
2525 If you encounter problems, look at Exim's log files (&'mainlog'& and
2526 &'paniclog'&) to see if there is any relevant information there. Another source
2527 of information is running Exim with debugging turned on, by specifying the
2528 &%-d%& option. If a message is stuck on Exim's spool, you can force a delivery
2529 with debugging turned on by a command of the form
2531 &`exim -d -M`& <&'exim-message-id'&>
2533 You must be root or an &"admin user"& in order to do this. The &%-d%& option
2534 produces rather a lot of output, but you can cut this down to specific areas.
2535 For example, if you use &%-d-all+route%& only the debugging information
2536 relevant to routing is included. (See the &%-d%& option in chapter
2537 &<<CHAPcommandline>>& for more details.)
2539 .cindex '&"sticky"& bit'
2540 .cindex "lock files"
2541 One specific problem that has shown up on some sites is the inability to do
2542 local deliveries into a shared mailbox directory, because it does not have the
2543 &"sticky bit"& set on it. By default, Exim tries to create a lock file before
2544 writing to a mailbox file, and if it cannot create the lock file, the delivery
2545 is deferred. You can get round this either by setting the &"sticky bit"& on the
2546 directory, or by setting a specific group for local deliveries and allowing
2547 that group to create files in the directory (see the comments above the
2548 &(local_delivery)& transport in the default configuration file). Another
2549 approach is to configure Exim not to use lock files, but just to rely on
2550 &[fcntl()]& locking instead. However, you should do this only if all user
2551 agents also use &[fcntl()]& locking. For further discussion of locking issues,
2552 see chapter &<<CHAPappendfile>>&.
2554 One thing that cannot be tested on a system that is already running an MTA is
2555 the receipt of incoming SMTP mail on the standard SMTP port. However, the
2556 &%-oX%& option can be used to run an Exim daemon that listens on some other
2557 port, or &'inetd'& can be used to do this. The &%-bh%& option and the
2558 &'exim_checkaccess'& utility can be used to check out policy controls on
2561 Testing a new version on a system that is already running Exim can most easily
2562 be done by building a binary with a different CONFIGURE_FILE setting. From
2563 within the runtime configuration, all other file and directory names
2564 that Exim uses can be altered, in order to keep it entirely clear of the
2568 .section "Replacing another MTA with Exim" "SECID35"
2569 .cindex "replacing another MTA"
2570 Building and installing Exim for the first time does not of itself put it in
2571 general use. The name by which the system's MTA is called by mail user agents
2572 is either &_/usr/sbin/sendmail_&, or &_/usr/lib/sendmail_& (depending on the
2573 operating system), and it is necessary to make this name point to the &'exim'&
2574 binary in order to get the user agents to pass messages to Exim. This is
2575 normally done by renaming any existing file and making &_/usr/sbin/sendmail_&
2576 or &_/usr/lib/sendmail_&
2577 .cindex "symbolic link" "to &'exim'& binary"
2578 a symbolic link to the &'exim'& binary. It is a good idea to remove any setuid
2579 privilege and executable status from the old MTA. It is then necessary to stop
2580 and restart the mailer daemon, if one is running.
2582 .cindex "FreeBSD, MTA indirection"
2583 .cindex "&_/etc/mail/mailer.conf_&"
2584 Some operating systems have introduced alternative ways of switching MTAs. For
2585 example, if you are running FreeBSD, you need to edit the file
2586 &_/etc/mail/mailer.conf_& instead of setting up a symbolic link as just
2587 described. A typical example of the contents of this file for running Exim is
2590 sendmail /usr/exim/bin/exim
2591 send-mail /usr/exim/bin/exim
2592 mailq /usr/exim/bin/exim -bp
2593 newaliases /usr/bin/true
2595 Once you have set up the symbolic link, or edited &_/etc/mail/mailer.conf_&,
2596 your Exim installation is &"live"&. Check it by sending a message from your
2597 favourite user agent.
2599 You should consider what to tell your users about the change of MTA. Exim may
2600 have different capabilities to what was previously running, and there are
2601 various operational differences such as the text of messages produced by
2602 command line options and in bounce messages. If you allow your users to make
2603 use of Exim's filtering capabilities, you should make the document entitled
2604 &'Exim's interface to mail filtering'& available to them.
2608 .section "Running the daemon" SECTdaemonLaunch
2609 The most common command line for launching the Exim daemon looks like
2613 This starts a daemon which
2615 listens for incoming smtp connections, launching handler processes for
2618 starts a queue-runner process every five minutes, to inspect queued messages
2619 and run delivery attempts on any that have arrived at their retry time
2621 Should a queue run take longer than the time between queue-runner starts,
2622 they will run in parallel.
2623 Numbers of jobs of the various types are subject to policy controls
2624 defined in the configuration.
2627 .section "Upgrading Exim" "SECID36"
2628 .cindex "upgrading Exim"
2629 If you are already running Exim on your host, building and installing a new
2630 version automatically makes it available to MUAs, or any other programs that
2631 call the MTA directly. However, if you are running an Exim daemon, you do need
2632 .cindex restart "on HUP signal"
2633 .cindex signal "HUP, to restart"
2634 to send it a HUP signal, to make it re-execute itself, and thereby pick up the
2635 new binary. You do not need to stop processing mail in order to install a new
2636 version of Exim. The install script does not modify an existing runtime
2642 .section "Stopping the Exim daemon on Solaris" "SECID37"
2643 .cindex "Solaris" "stopping Exim on"
2644 The standard command for stopping the mailer daemon on Solaris is
2646 /etc/init.d/sendmail stop
2648 If &_/usr/lib/sendmail_& has been turned into a symbolic link, this script
2649 fails to stop Exim because it uses the command &'ps -e'& and greps the output
2650 for the text &"sendmail"&; this is not present because the actual program name
2651 (that is, &"exim"&) is given by the &'ps'& command with these options. A
2652 solution is to replace the line that finds the process id with something like
2654 pid=`cat /var/spool/exim/exim-daemon.pid`
2656 to obtain the daemon's pid directly from the file that Exim saves it in.
2658 Note, however, that stopping the daemon does not &"stop Exim"&. Messages can
2659 still be received from local processes, and if automatic delivery is configured
2660 (the normal case), deliveries will still occur.
2665 . ////////////////////////////////////////////////////////////////////////////
2666 . ////////////////////////////////////////////////////////////////////////////
2668 .chapter "The Exim command line" "CHAPcommandline"
2669 .scindex IIDclo1 "command line" "options"
2670 .scindex IIDclo2 "options" "command line"
2671 Exim's command line takes the standard Unix form of a sequence of options,
2672 each starting with a hyphen character, followed by a number of arguments. The
2673 options are compatible with the main options of Sendmail, and there are also
2674 some additional options, some of which are compatible with Smail 3. Certain
2675 combinations of options do not make sense, and provoke an error if used.
2676 The form of the arguments depends on which options are set.
2679 .section "Setting options by program name" "SECID38"
2681 If Exim is called under the name &'mailq'&, it behaves as if the option &%-bp%&
2682 were present before any other options.
2683 The &%-bp%& option requests a listing of the contents of the mail queue on the
2685 This feature is for compatibility with some systems that contain a command of
2686 that name in one of the standard libraries, symbolically linked to
2687 &_/usr/sbin/sendmail_& or &_/usr/lib/sendmail_&.
2690 If Exim is called under the name &'rsmtp'& it behaves as if the option &%-bS%&
2691 were present before any other options, for compatibility with Smail. The
2692 &%-bS%& option is used for reading in a number of messages in batched SMTP
2696 If Exim is called under the name &'rmail'& it behaves as if the &%-i%& and
2697 &%-oee%& options were present before any other options, for compatibility with
2698 Smail. The name &'rmail'& is used as an interface by some UUCP systems.
2701 .cindex "queue runner"
2702 If Exim is called under the name &'runq'& it behaves as if the option &%-q%&
2703 were present before any other options, for compatibility with Smail. The &%-q%&
2704 option causes a single queue runner process to be started.
2706 .cindex "&'newaliases'&"
2707 .cindex "alias file" "building"
2708 .cindex "Sendmail compatibility" "calling Exim as &'newaliases'&"
2709 If Exim is called under the name &'newaliases'& it behaves as if the option
2710 &%-bi%& were present before any other options, for compatibility with Sendmail.
2711 This option is used for rebuilding Sendmail's alias file. Exim does not have
2712 the concept of a single alias file, but can be configured to run a given
2713 command if called with the &%-bi%& option.
2716 .section "Trusted and admin users" "SECTtrustedadmin"
2717 Some Exim options are available only to &'trusted users'& and others are
2718 available only to &'admin users'&. In the description below, the phrases &"Exim
2719 user"& and &"Exim group"& mean the user and group defined by EXIM_USER and
2720 EXIM_GROUP in &_Local/Makefile_& or set by the &%exim_user%& and
2721 &%exim_group%& options. These do not necessarily have to use the name &"exim"&.
2724 .cindex "trusted users" "definition of"
2725 .cindex "user" "trusted definition of"
2726 The trusted users are root, the Exim user, any user listed in the
2727 &%trusted_users%& configuration option, and any user whose current group or any
2728 supplementary group is one of those listed in the &%trusted_groups%&
2729 configuration option. Note that the Exim group is not automatically trusted.
2731 .cindex '&"From"& line'
2732 .cindex "envelope from"
2733 .cindex "envelope sender"
2734 Trusted users are always permitted to use the &%-f%& option or a leading
2735 &"From&~"& line to specify the envelope sender of a message that is passed to
2736 Exim through the local interface (see the &%-bm%& and &%-f%& options below).
2737 See the &%untrusted_set_sender%& option for a way of permitting non-trusted
2738 users to set envelope senders.
2742 For a trusted user, there is never any check on the contents of the &'From:'&
2743 header line, and a &'Sender:'& line is never added. Furthermore, any existing
2744 &'Sender:'& line in incoming local (non-TCP/IP) messages is not removed.
2746 Trusted users may also specify a host name, host address, interface address,
2747 protocol name, ident value, and authentication data when submitting a message
2748 locally. Thus, they are able to insert messages into Exim's queue locally that
2749 have the characteristics of messages received from a remote host. Untrusted
2750 users may in some circumstances use &%-f%&, but can never set the other values
2751 that are available to trusted users.
2753 .cindex "user" "admin definition of"
2754 .cindex "admin user" "definition of"
2755 The admin users are root, the Exim user, and any user that is a member of the
2756 Exim group or of any group listed in the &%admin_groups%& configuration option.
2757 The current group does not have to be one of these groups.
2759 Admin users are permitted to list the queue, and to carry out certain
2760 operations on messages, for example, to force delivery failures. It is also
2761 necessary to be an admin user in order to see the full information provided by
2762 the Exim monitor, and full debugging output.
2764 By default, the use of the &%-M%&, &%-q%&, &%-R%&, and &%-S%& options to cause
2765 Exim to attempt delivery of messages on its queue is restricted to admin users.
2766 However, this restriction can be relaxed by setting the &%prod_requires_admin%&
2767 option false (that is, specifying &%no_prod_requires_admin%&).
2769 Similarly, the use of the &%-bp%& option to list all the messages in the queue
2770 is restricted to admin users unless &%queue_list_requires_admin%& is set
2775 &*Warning*&: If you configure your system so that admin users are able to
2776 edit Exim's configuration file, you are giving those users an easy way of
2777 getting root. There is further discussion of this issue at the start of chapter
2783 .section "Command line options" "SECID39"
2784 Exim's command line options are described in alphabetical order below. If none
2785 of the options that specifies a specific action (such as starting the daemon or
2786 a queue runner, or testing an address, or receiving a message in a specific
2787 format, or listing the queue) are present, and there is at least one argument
2788 on the command line, &%-bm%& (accept a local message on the standard input,
2789 with the arguments specifying the recipients) is assumed. Otherwise, Exim
2790 outputs a brief message about itself and exits.
2792 . ////////////////////////////////////////////////////////////////////////////
2793 . Insert a stylized XML comment here, to identify the start of the command line
2794 . options. This is for the benefit of the Perl script that automatically
2795 . creates a man page for the options.
2796 . ////////////////////////////////////////////////////////////////////////////
2799 <!-- === Start of command line options === -->
2806 .cindex "options" "command line; terminating"
2807 This is a pseudo-option whose only purpose is to terminate the options and
2808 therefore to cause subsequent command line items to be treated as arguments
2809 rather than options, even if they begin with hyphens.
2812 .oindex "&%--help%&"
2813 This option causes Exim to output a few sentences stating what it is.
2814 The same output is generated if the Exim binary is called with no options and
2817 .vitem &%--version%&
2818 .oindex "&%--version%&"
2819 This option is an alias for &%-bV%& and causes version information to be
2826 These options are used by Sendmail for selecting configuration files and are
2829 .vitem &%-B%&<&'type'&>
2831 .cindex "8-bit characters"
2832 .cindex "Sendmail compatibility" "8-bit characters"
2833 This is a Sendmail option for selecting 7 or 8 bit processing. Exim is 8-bit
2834 clean; it ignores this option.
2839 .cindex "SMTP" "listener"
2840 .cindex "queue runner"
2841 This option runs Exim as a daemon, awaiting incoming SMTP connections. Usually
2842 the &%-bd%& option is combined with the &%-q%&<&'time'&> option, to specify
2843 that the daemon should also initiate periodic queue runs.
2845 The &%-bd%& option can be used only by an admin user. If either of the &%-d%&
2846 (debugging) or &%-v%& (verifying) options are set, the daemon does not
2847 disconnect from the controlling terminal. When running this way, it can be
2848 stopped by pressing ctrl-C.
2850 By default, Exim listens for incoming connections to the standard SMTP port on
2851 all the host's running interfaces. However, it is possible to listen on other
2852 ports, on multiple ports, and only on specific interfaces. Chapter
2853 &<<CHAPinterfaces>>& contains a description of the options that control this.
2855 When a listening daemon
2856 .cindex "daemon" "process id (pid)"
2857 .cindex "pid (process id)" "of daemon"
2858 is started without the use of &%-oX%& (that is, without overriding the normal
2859 configuration), it writes its process id to a file called &_exim-daemon.pid_&
2860 in Exim's spool directory. This location can be overridden by setting
2861 PID_FILE_PATH in &_Local/Makefile_&. The file is written while Exim is still
2864 When &%-oX%& is used on the command line to start a listening daemon, the
2865 process id is not written to the normal pid file path. However, &%-oP%& can be
2866 used to specify a path on the command line if a pid file is required.
2870 .cindex restart "on HUP signal"
2871 .cindex signal "HUP, to restart"
2872 .cindex "daemon" "restarting"
2873 .cindex signal "to reload configuration"
2874 .cindex daemon "reload configuration"
2875 .cindex reload configuration
2876 can be used to cause the daemon to re-execute itself. This should be done
2877 whenever Exim's configuration file, or any file that is incorporated into it by
2878 means of the &%.include%& facility, is changed, and also whenever a new version
2879 of Exim is installed. It is not necessary to do this when other files that are
2880 referenced from the configuration (for example, alias files) are changed,
2881 because these are reread each time they are used.
2885 This option has the same effect as &%-bd%& except that it never disconnects
2886 from the controlling terminal, even when no debugging is specified.
2890 .cindex "testing" "string expansion"
2891 .cindex "expansion" "testing"
2892 Run Exim in expansion testing mode. Exim discards its root privilege, to
2893 prevent ordinary users from using this mode to read otherwise inaccessible
2894 files. If no arguments are given, Exim runs interactively, prompting for lines
2895 of data. Otherwise, it processes each argument in turn.
2897 If Exim was built with USE_READLINE=yes in &_Local/Makefile_&, it tries
2898 to load the &%libreadline%& library dynamically whenever the &%-be%& option is
2899 used without command line arguments. If successful, it uses the &[readline()]&
2900 function, which provides extensive line-editing facilities, for reading the
2901 test data. A line history is supported.
2903 Long expansion expressions can be split over several lines by using backslash
2904 continuations. As in Exim's runtime configuration, white space at the start of
2905 continuation lines is ignored. Each argument or data line is passed through the
2906 string expansion mechanism, and the result is output. Variable values from the
2907 configuration file (for example, &$qualify_domain$&) are available, but no
2908 message-specific values (such as &$message_exim_id$&) are set, because no message
2909 is being processed (but see &%-bem%& and &%-Mset%&).
2911 &*Note*&: If you use this mechanism to test lookups, and you change the data
2912 files or databases you are using, you must exit and restart Exim before trying
2913 the same lookup again. Otherwise, because each Exim process caches the results
2914 of lookups, you will just get the same result as before.
2916 Macro processing is done on lines before string-expansion: new macros can be
2917 defined and macros will be expanded.
2918 Because macros in the config file are often used for secrets, those are only
2919 available to admin users.
2921 .vitem &%-bem%&&~<&'filename'&>
2923 .cindex "testing" "string expansion"
2924 .cindex "expansion" "testing"
2925 This option operates like &%-be%& except that it must be followed by the name
2926 of a file. For example:
2928 exim -bem /tmp/testmessage
2930 The file is read as a message (as if receiving a locally-submitted non-SMTP
2931 message) before any of the test expansions are done. Thus, message-specific
2932 variables such as &$message_size$& and &$header_from:$& are available. However,
2933 no &'Received:'& header is added to the message. If the &%-t%& option is set,
2934 recipients are read from the headers in the normal way, and are shown in the
2935 &$recipients$& variable. Note that recipients cannot be given on the command
2936 line, because further arguments are taken as strings to expand (just like
2939 .vitem &%-bF%&&~<&'filename'&>
2941 .cindex "system filter" "testing"
2942 .cindex "testing" "system filter"
2943 This option is the same as &%-bf%& except that it assumes that the filter being
2944 tested is a system filter. The additional commands that are available only in
2945 system filters are recognized.
2947 .vitem &%-bf%&&~<&'filename'&>
2949 .cindex "filter" "testing"
2950 .cindex "testing" "filter file"
2951 .cindex "forward file" "testing"
2952 .cindex "testing" "forward file"
2953 .cindex "Sieve filter" "testing"
2954 This option runs Exim in user filter testing mode; the file is the filter file
2955 to be tested, and a test message must be supplied on the standard input. If
2956 there are no message-dependent tests in the filter, an empty file can be
2959 If you want to test a system filter file, use &%-bF%& instead of &%-bf%&. You
2960 can use both &%-bF%& and &%-bf%& on the same command, in order to test a system
2961 filter and a user filter in the same run. For example:
2963 exim -bF /system/filter -bf /user/filter </test/message
2965 This is helpful when the system filter adds header lines or sets filter
2966 variables that are used by the user filter.
2968 If the test filter file does not begin with one of the special lines
2973 it is taken to be a normal &_.forward_& file, and is tested for validity under
2974 that interpretation. See sections &<<SECTitenonfilred>>& to
2975 &<<SECTspecitredli>>& for a description of the possible contents of non-filter
2978 The result of an Exim command that uses &%-bf%&, provided no errors are
2979 detected, is a list of the actions that Exim would try to take if presented
2980 with the message for real. More details of filter testing are given in the
2981 separate document entitled &'Exim's interfaces to mail filtering'&.
2983 When testing a filter file,
2984 .cindex "&""From""& line"
2985 .cindex "envelope from"
2986 .cindex "envelope sender"
2987 .oindex "&%-f%&" "for filter testing"
2988 the envelope sender can be set by the &%-f%& option,
2989 or by a &"From&~"& line at the start of the test message. Various parameters
2990 that would normally be taken from the envelope recipient address of the message
2991 can be set by means of additional command line options (see the next four
2994 .vitem &%-bfd%&&~<&'domain'&>
2996 .vindex "&$qualify_domain$&"
2997 This sets the domain of the recipient address when a filter file is being
2998 tested by means of the &%-bf%& option. The default is the value of
3001 .vitem &%-bfl%&&~<&'local&~part'&>
3003 This sets the local part of the recipient address when a filter file is being
3004 tested by means of the &%-bf%& option. The default is the username of the
3005 process that calls Exim. A local part should be specified with any prefix or
3006 suffix stripped, because that is how it appears to the filter when a message is
3007 actually being delivered.
3009 .vitem &%-bfp%&&~<&'prefix'&>
3011 .cindex affix "filter testing"
3012 This sets the prefix of the local part of the recipient address when a filter
3013 file is being tested by means of the &%-bf%& option. The default is an empty
3016 .vitem &%-bfs%&&~<&'suffix'&>
3018 .cindex affix "filter testing"
3019 This sets the suffix of the local part of the recipient address when a filter
3020 file is being tested by means of the &%-bf%& option. The default is an empty
3023 .vitem &%-bh%&&~<&'IP&~address'&>
3025 .cindex "testing" "incoming SMTP"
3026 .cindex "SMTP" "testing incoming"
3027 .cindex "testing" "relay control"
3028 .cindex "relaying" "testing configuration"
3029 .cindex "policy control" "testing"
3030 .cindex "debugging" "&%-bh%& option"
3031 This option runs a fake SMTP session as if from the given IP address, using the
3032 standard input and output. The IP address may include a port number at the end,
3033 after a full stop. For example:
3035 exim -bh 10.9.8.7.1234
3036 exim -bh fe80::a00:20ff:fe86:a061.5678
3038 When an IPv6 address is given, it is converted into canonical form. In the case
3039 of the second example above, the value of &$sender_host_address$& after
3040 conversion to the canonical form is
3041 &`fe80:0000:0000:0a00:20ff:fe86:a061.5678`&.
3043 Comments as to what is going on are written to the standard error file. These
3044 include lines beginning with &"LOG"& for anything that would have been logged.
3045 This facility is provided for testing configuration options for incoming
3046 messages, to make sure they implement the required policy. For example, you can
3047 test your relay controls using &%-bh%&.
3051 You can test features of the configuration that rely on ident (RFC 1413)
3052 information by using the &%-oMt%& option. However, Exim cannot actually perform
3053 an ident callout when testing using &%-bh%& because there is no incoming SMTP
3056 &*Warning 2*&: Address verification callouts (see section &<<SECTcallver>>&)
3057 are also skipped when testing using &%-bh%&. If you want these callouts to
3058 occur, use &%-bhc%& instead.
3060 Messages supplied during the testing session are discarded, and nothing is
3061 written to any of the real log files. There may be pauses when DNS (and other)
3062 lookups are taking place, and of course these may time out. The &%-oMi%& option
3063 can be used to specify a specific IP interface and port if this is important,
3064 and &%-oMaa%& and &%-oMai%& can be used to set parameters as if the SMTP
3065 session were authenticated.
3067 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%& whose
3068 output just states whether a given recipient address from a given host is
3069 acceptable or not. See section &<<SECTcheckaccess>>&.
3071 Features such as authentication and encryption, where the client input is not
3072 plain text, cannot easily be tested with &%-bh%&. Instead, you should use a
3073 specialized SMTP test program such as
3074 &url(https://www.jetmore.org/john/code/swaks/,swaks).
3076 .vitem &%-bhc%&&~<&'IP&~address'&>
3078 This option operates in the same way as &%-bh%&, except that address
3079 verification callouts are performed if required. This includes consulting and
3080 updating the callout cache database.
3084 .cindex "alias file" "building"
3085 .cindex "building alias file"
3086 .cindex "Sendmail compatibility" "&%-bi%& option"
3087 Sendmail interprets the &%-bi%& option as a request to rebuild its alias file.
3088 Exim does not have the concept of a single alias file, and so it cannot mimic
3089 this behaviour. However, calls to &_/usr/lib/sendmail_& with the &%-bi%& option
3090 tend to appear in various scripts such as NIS make files, so the option must be
3093 If &%-bi%& is encountered, the command specified by the &%bi_command%&
3094 configuration option is run, under the uid and gid of the caller of Exim. If
3095 the &%-oA%& option is used, its value is passed to the command as an argument.
3096 The command set by &%bi_command%& may not contain arguments. The command can
3097 use the &'exim_dbmbuild'& utility, or some other means, to rebuild alias files
3098 if this is required. If the &%bi_command%& option is not set, calling Exim with
3101 . // Keep :help first, then the rest in alphabetical order
3103 .oindex "&%-bI:help%&"
3104 .cindex "querying exim information"
3105 We shall provide various options starting &`-bI:`& for querying Exim for
3106 information. The output of many of these will be intended for machine
3107 consumption. This one is not. The &%-bI:help%& option asks Exim for a
3108 synopsis of supported options beginning &`-bI:`&. Use of any of these
3109 options shall cause Exim to exit after producing the requested output.
3112 .oindex "&%-bI:dscp%&"
3113 .cindex "DSCP" "values"
3114 This option causes Exim to emit an alphabetically sorted list of all
3115 recognised DSCP names.
3117 .vitem &%-bI:sieve%&
3118 .oindex "&%-bI:sieve%&"
3119 .cindex "Sieve filter" "capabilities"
3120 This option causes Exim to emit an alphabetically sorted list of all supported
3121 Sieve protocol extensions on stdout, one per line. This is anticipated to be
3122 useful for ManageSieve (RFC 5804) implementations, in providing that protocol's
3123 &`SIEVE`& capability response line. As the precise list may depend upon
3124 compile-time build options, which this option will adapt to, this is the only
3125 way to guarantee a correct response.
3129 .cindex "local message reception"
3130 This option runs an Exim receiving process that accepts an incoming,
3131 locally-generated message on the standard input. The recipients are given as the
3132 command arguments (except when &%-t%& is also present &-- see below). Each
3133 argument can be a comma-separated list of RFC 2822 addresses. This is the
3134 default option for selecting the overall action of an Exim call; it is assumed
3135 if no other conflicting option is present.
3137 If any addresses in the message are unqualified (have no domain), they are
3138 qualified by the values of the &%qualify_domain%& or &%qualify_recipient%&
3139 options, as appropriate. The &%-bnq%& option (see below) provides a way of
3140 suppressing this for special cases.
3142 Policy checks on the contents of local messages can be enforced by means of
3143 the non-SMTP ACL. See chapter &<<CHAPACL>>& for details.
3145 .cindex "return code" "for &%-bm%&"
3146 The return code is zero if the message is successfully accepted. Otherwise, the
3147 action is controlled by the &%-oe%&&'x'& option setting &-- see below.
3150 .cindex "message" "format"
3151 .cindex "format" "message"
3152 .cindex "&""From""& line"
3153 .cindex "UUCP" "&""From""& line"
3154 .cindex "Sendmail compatibility" "&""From""& line"
3155 of the message must be as defined in RFC 2822, except that, for
3156 compatibility with Sendmail and Smail, a line in one of the forms
3158 From sender Fri Jan 5 12:55 GMT 1997
3159 From sender Fri, 5 Jan 97 12:55:01
3161 (with the weekday optional, and possibly with additional text after the date)
3162 is permitted to appear at the start of the message. There appears to be no
3163 authoritative specification of the format of this line. Exim recognizes it by
3164 matching against the regular expression defined by the &%uucp_from_pattern%&
3165 option, which can be changed if necessary.
3167 .oindex "&%-f%&" "overriding &""From""& line"
3168 The specified sender is treated as if it were given as the argument to the
3169 &%-f%& option, but if a &%-f%& option is also present, its argument is used in
3170 preference to the address taken from the message. The caller of Exim must be a
3171 trusted user for the sender of a message to be set in this way.
3173 .vitem &%-bmalware%&&~<&'filename'&>
3174 .oindex "&%-bmalware%&"
3175 .cindex "testing", "malware"
3176 .cindex "malware scan test"
3177 This debugging option causes Exim to scan the given file or directory
3178 (depending on the used scanner interface),
3179 using the malware scanning framework. The option of &%av_scanner%& influences
3180 this option, so if &%av_scanner%&'s value is dependent upon an expansion then
3181 the expansion should have defaults which apply to this invocation. ACLs are
3182 not invoked, so if &%av_scanner%& references an ACL variable then that variable
3183 will never be populated and &%-bmalware%& will fail.
3185 Exim will have changed working directory before resolving the filename, so
3186 using fully qualified pathnames is advisable. Exim will be running as the Exim
3187 user when it tries to open the file, rather than as the invoking user.
3188 This option requires admin privileges.
3190 The &%-bmalware%& option will not be extended to be more generally useful,
3191 there are better tools for file-scanning. This option exists to help
3192 administrators verify their Exim and AV scanner configuration.
3196 .cindex "address qualification, suppressing"
3197 By default, Exim automatically qualifies unqualified addresses (those
3198 without domains) that appear in messages that are submitted locally (that
3199 is, not over TCP/IP). This qualification applies both to addresses in
3200 envelopes, and addresses in header lines. Sender addresses are qualified using
3201 &%qualify_domain%&, and recipient addresses using &%qualify_recipient%& (which
3202 defaults to the value of &%qualify_domain%&).
3204 Sometimes, qualification is not wanted. For example, if &%-bS%& (batch SMTP) is
3205 being used to re-submit messages that originally came from remote hosts after
3206 content scanning, you probably do not want to qualify unqualified addresses in
3207 header lines. (Such lines will be present only if you have not enabled a header
3208 syntax check in the appropriate ACL.)
3210 The &%-bnq%& option suppresses all qualification of unqualified addresses in
3211 messages that originate on the local host. When this is used, unqualified
3212 addresses in the envelope provoke errors (causing message rejection) and
3213 unqualified addresses in header lines are left alone.
3218 .cindex "configuration options" "extracting"
3219 .cindex "options" "configuration &-- extracting"
3220 If this option is given with no arguments, it causes the values of all Exim's
3221 main configuration options to be written to the standard output. The values
3222 of one or more specific options can be requested by giving their names as
3223 arguments, for example:
3225 exim -bP qualify_domain hold_domains
3227 .cindex "hiding configuration option values"
3228 .cindex "configuration options" "hiding value of"
3229 .cindex "options" "hiding value of"
3230 However, any option setting that is preceded by the word &"hide"& in the
3231 configuration file is not shown in full, except to an admin user. For other
3232 users, the output is as in this example:
3234 mysql_servers = <value not displayable>
3236 If &%config%& is given as an argument, the config is
3237 output, as it was parsed, any include file resolved, any comment removed.
3239 If &%config_file%& is given as an argument, the name of the runtime
3240 configuration file is output. (&%configure_file%& works too, for
3241 backward compatibility.)
3242 If a list of configuration files was supplied, the value that is output here
3243 is the name of the file that was actually used.
3245 .cindex "options" "hiding name of"
3246 If the &%-n%& flag is given, then for most modes of &%-bP%& operation the
3247 name will not be output.
3249 .cindex "daemon" "process id (pid)"
3250 .cindex "pid (process id)" "of daemon"
3251 If &%log_file_path%& or &%pid_file_path%& are given, the names of the
3252 directories where log files and daemon pid files are written are output,
3253 respectively. If these values are unset, log files are written in a
3254 sub-directory of the spool directory called &%log%&, and the pid file is
3255 written directly into the spool directory.
3257 If &%-bP%& is followed by a name preceded by &`+`&, for example,
3259 exim -bP +local_domains
3261 it searches for a matching named list of any type (domain, host, address, or
3262 local part) and outputs what it finds.
3264 .cindex "options" "router &-- extracting"
3265 .cindex "options" "transport &-- extracting"
3266 .cindex "options" "authenticator &-- extracting"
3267 If one of the words &%router%&, &%transport%&, or &%authenticator%& is given,
3268 followed by the name of an appropriate driver instance, the option settings for
3269 that driver are output. For example:
3271 exim -bP transport local_delivery
3273 The generic driver options are output first, followed by the driver's private
3274 options. A list of the names of drivers of a particular type can be obtained by
3275 using one of the words &%router_list%&, &%transport_list%&, or
3276 &%authenticator_list%&, and a complete list of all drivers with their option
3277 settings can be obtained by using &%routers%&, &%transports%&, or
3280 .cindex "environment"
3281 If &%environment%& is given as an argument, the set of environment
3282 variables is output, line by line. Using the &%-n%& flag suppresses the value of the
3285 .cindex "options" "macro &-- extracting"
3286 If invoked by an admin user, then &%macro%&, &%macro_list%& and &%macros%&
3287 are available, similarly to the drivers. Because macros are sometimes used
3288 for storing passwords, this option is restricted.
3289 The output format is one item per line.
3290 For the "-bP macro <name>" form, if no such macro is found
3291 the exit status will be nonzero.
3295 .cindex "queue" "listing messages in"
3296 .cindex "listing" "messages in the queue"
3297 This option requests a listing of the contents of the mail queue on the
3298 standard output. If the &%-bp%& option is followed by a list of message ids,
3299 just those messages are listed. By default, this option can be used only by an
3300 admin user. However, the &%queue_list_requires_admin%& option can be set false
3301 to allow any user to see the queue.
3303 Each message in the queue is displayed as in the following example:
3305 25m 2.9K 0t5C6f-0000c8-00 <alice@wonderland.fict.example>
3306 red.king@looking-glass.fict.example
3309 .cindex "message" "size in queue listing"
3310 .cindex "size" "of message"
3311 The first line contains the length of time the message has been in the queue
3312 (in this case 25 minutes), the size of the message (2.9K), the unique local
3313 identifier for the message, and the message sender, as contained in the
3314 envelope. For bounce messages, the sender address is empty, and appears as
3315 &"<>"&. If the message was submitted locally by an untrusted user who overrode
3316 the default sender address, the user's login name is shown in parentheses
3317 before the sender address.
3319 .cindex "frozen messages" "in queue listing"
3320 If the message is frozen (attempts to deliver it are suspended) then the text
3321 &"*** frozen ***"& is displayed at the end of this line.
3323 The recipients of the message (taken from the envelope, not the headers) are
3324 displayed on subsequent lines. Those addresses to which the message has already
3325 been delivered are marked with the letter D. If an original address gets
3326 expanded into several addresses via an alias or forward file, the original is
3327 displayed with a D only when deliveries for all of its child addresses are
3333 This option operates like &%-bp%&, but in addition it shows delivered addresses
3334 that were generated from the original top level address(es) in each message by
3335 alias or forwarding operations. These addresses are flagged with &"+D"& instead
3341 .cindex "queue" "count of messages on"
3342 This option counts the number of messages in the queue, and writes the total
3343 to the standard output. It is restricted to admin users, unless
3344 &%queue_list_requires_admin%& is set false.
3349 This option operates like &%-bp%&, but the output is not sorted into
3350 chronological order of message arrival. This can speed it up when there are
3351 lots of messages in the queue, and is particularly useful if the output is
3352 going to be post-processed in a way that doesn't need the sorting.
3356 This option is a combination of &%-bpr%& and &%-bpa%&.
3360 This option is a combination of &%-bpr%& and &%-bpu%&.
3365 This option operates like &%-bp%& but shows only undelivered top-level
3366 addresses for each message displayed. Addresses generated by aliasing or
3367 forwarding are not shown, unless the message was deferred after processing by a
3368 router with the &%one_time%& option set.
3373 .cindex "testing" "retry configuration"
3374 .cindex "retry" "configuration testing"
3375 This option is for testing retry rules, and it must be followed by up to three
3376 arguments. It causes Exim to look for a retry rule that matches the values
3377 and to write it to the standard output. For example:
3379 exim -brt bach.comp.mus.example
3380 Retry rule: *.comp.mus.example F,2h,15m; F,4d,30m;
3382 See chapter &<<CHAPretry>>& for a description of Exim's retry rules. The first
3383 argument, which is required, can be a complete address in the form
3384 &'local_part@domain'&, or it can be just a domain name. If the second argument
3385 contains a dot, it is interpreted as an optional second domain name; if no
3386 retry rule is found for the first argument, the second is tried. This ties in
3387 with Exim's behaviour when looking for retry rules for remote hosts &-- if no
3388 rule is found that matches the host, one that matches the mail domain is
3389 sought. Finally, an argument that is the name of a specific delivery error, as
3390 used in setting up retry rules, can be given. For example:
3392 exim -brt haydn.comp.mus.example quota_3d
3393 Retry rule: *@haydn.comp.mus.example quota_3d F,1h,15m
3398 .cindex "testing" "rewriting"
3399 .cindex "rewriting" "testing"
3400 This option is for testing address rewriting rules, and it must be followed by
3401 a single argument, consisting of either a local part without a domain, or a
3402 complete address with a fully qualified domain. Exim outputs how this address
3403 would be rewritten for each possible place it might appear. See chapter
3404 &<<CHAPrewrite>>& for further details.
3408 .cindex "SMTP" "batched incoming"
3409 .cindex "batched SMTP input"
3410 This option is used for batched SMTP input, which is an alternative interface
3411 for non-interactive local message submission. A number of messages can be
3412 submitted in a single run. However, despite its name, this is not really SMTP
3413 input. Exim reads each message's envelope from SMTP commands on the standard
3414 input, but generates no responses. If the caller is trusted, or
3415 &%untrusted_set_sender%& is set, the senders in the SMTP MAIL commands are
3416 believed; otherwise the sender is always the caller of Exim.
3418 The message itself is read from the standard input, in SMTP format (leading
3419 dots doubled), terminated by a line containing just a single dot. An error is
3420 provoked if the terminating dot is missing. A further message may then follow.
3422 As for other local message submissions, the contents of incoming batch SMTP
3423 messages can be checked using the non-SMTP ACL (see chapter &<<CHAPACL>>&).
3424 Unqualified addresses are automatically qualified using &%qualify_domain%& and
3425 &%qualify_recipient%&, as appropriate, unless the &%-bnq%& option is used.
3427 Some other SMTP commands are recognized in the input. HELO and EHLO act
3428 as RSET; VRFY, EXPN, ETRN, and HELP act as NOOP;
3429 QUIT quits, ignoring the rest of the standard input.
3431 .cindex "return code" "for &%-bS%&"
3432 If any error is encountered, reports are written to the standard output and
3433 error streams, and Exim gives up immediately. The return code is 0 if no error
3434 was detected; it is 1 if one or more messages were accepted before the error
3435 was detected; otherwise it is 2.
3437 More details of input using batched SMTP are given in section
3438 &<<SECTincomingbatchedSMTP>>&.
3442 .cindex "SMTP" "local input"
3443 .cindex "local SMTP input"
3444 This option causes Exim to accept one or more messages by reading SMTP commands
3445 on the standard input, and producing SMTP replies on the standard output. SMTP
3446 policy controls, as defined in ACLs (see chapter &<<CHAPACL>>&) are applied.
3447 Some user agents use this interface as a way of passing locally-generated
3448 messages to the MTA.
3451 .cindex "sender" "source of"
3452 this usage, if the caller of Exim is trusted, or &%untrusted_set_sender%& is
3453 set, the senders of messages are taken from the SMTP MAIL commands.
3454 Otherwise the content of these commands is ignored and the sender is set up as
3455 the calling user. Unqualified addresses are automatically qualified using
3456 &%qualify_domain%& and &%qualify_recipient%&, as appropriate, unless the
3457 &%-bnq%& option is used.
3461 &%-bs%& option is also used to run Exim from &'inetd'&, as an alternative to
3462 using a listening daemon. Exim can distinguish the two cases by checking
3463 whether the standard input is a TCP/IP socket. When Exim is called from
3464 &'inetd'&, the source of the mail is assumed to be remote, and the comments
3465 above concerning senders and qualification do not apply. In this situation,
3466 Exim behaves in exactly the same way as it does when receiving a message via
3467 the listening daemon.
3471 .cindex "testing" "addresses"
3472 .cindex "address" "testing"
3473 This option runs Exim in address testing mode, in which each argument is taken
3474 as a recipient address to be tested for deliverability. The results are
3475 written to the standard output. If a test fails, and the caller is not an admin
3476 user, no details of the failure are output, because these might contain
3477 sensitive information such as usernames and passwords for database lookups.
3479 If no arguments are given, Exim runs in an interactive manner, prompting with a
3480 right angle bracket for addresses to be tested.
3482 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3483 &[readline()]& function, because it is running as &'root'& and there are
3486 Each address is handled as if it were the recipient address of a message
3487 (compare the &%-bv%& option). It is passed to the routers and the result is
3488 written to the standard output. However, any router that has
3489 &%no_address_test%& set is bypassed. This can make &%-bt%& easier to use for
3490 genuine routing tests if your first router passes everything to a scanner
3493 .cindex "return code" "for &%-bt%&"
3494 The return code is 2 if any address failed outright; it is 1 if no address
3495 failed outright but at least one could not be resolved for some reason. Return
3496 code 0 is given only when all addresses succeed.
3498 .cindex "duplicate addresses"
3499 &*Note*&: When actually delivering a message, Exim removes duplicate recipient
3500 addresses after routing is complete, so that only one delivery takes place.
3501 This does not happen when testing with &%-bt%&; the full results of routing are
3504 &*Warning*&: &%-bt%& can only do relatively simple testing. If any of the
3505 routers in the configuration makes any tests on the sender address of a
3507 .oindex "&%-f%&" "for address testing"
3508 you can use the &%-f%& option to set an appropriate sender when running
3509 &%-bt%& tests. Without it, the sender is assumed to be the calling user at the
3510 default qualifying domain. However, if you have set up (for example) routers
3511 whose behaviour depends on the contents of an incoming message, you cannot test
3512 those conditions using &%-bt%&. The &%-N%& option provides a possible way of
3517 .cindex "version number of Exim"
3518 This option causes Exim to write the current version number, compilation
3519 number, and compilation date of the &'exim'& binary to the standard output.
3520 It also lists the DBM library that is being used, the optional modules (such as
3521 specific lookup types), the drivers that are included in the binary, and the
3522 name of the runtime configuration file that is in use.
3524 As part of its operation, &%-bV%& causes Exim to read and syntax check its
3525 configuration file. However, this is a static check only. It cannot check
3526 values that are to be expanded. For example, although a misspelt ACL verb is
3527 detected, an error in the verb's arguments is not. You cannot rely on &%-bV%&
3528 alone to discover (for example) all the typos in the configuration; some
3529 realistic testing is needed. The &%-bh%& and &%-N%& options provide more
3530 dynamic testing facilities.
3534 .cindex "verifying address" "using &%-bv%&"
3535 .cindex "address" "verification"
3536 This option runs Exim in address verification mode, in which each argument is
3537 taken as a recipient address to be verified by the routers. (This does
3538 not involve any verification callouts). During normal operation, verification
3539 happens mostly as a consequence processing a &%verify%& condition in an ACL
3540 (see chapter &<<CHAPACL>>&). If you want to test an entire ACL, possibly
3541 including callouts, see the &%-bh%& and &%-bhc%& options.
3543 If verification fails, and the caller is not an admin user, no details of the
3544 failure are output, because these might contain sensitive information such as
3545 usernames and passwords for database lookups.
3547 If no arguments are given, Exim runs in an interactive manner, prompting with a
3548 right angle bracket for addresses to be verified.
3550 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3551 &[readline()]& function, because it is running as &'exim'& and there are
3554 Verification differs from address testing (the &%-bt%& option) in that routers
3555 that have &%no_verify%& set are skipped, and if the address is accepted by a
3556 router that has &%fail_verify%& set, verification fails. The address is
3557 verified as a recipient if &%-bv%& is used; to test verification for a sender
3558 address, &%-bvs%& should be used.
3560 If the &%-v%& option is not set, the output consists of a single line for each
3561 address, stating whether it was verified or not, and giving a reason in the
3562 latter case. Without &%-v%&, generating more than one address by redirection
3563 causes verification to end successfully, without considering the generated
3564 addresses. However, if just one address is generated, processing continues,
3565 and the generated address must verify successfully for the overall verification
3568 When &%-v%& is set, more details are given of how the address has been handled,
3569 and in the case of address redirection, all the generated addresses are also
3570 considered. Verification may succeed for some and fail for others.
3573 .cindex "return code" "for &%-bv%&"
3574 return code is 2 if any address failed outright; it is 1 if no address
3575 failed outright but at least one could not be resolved for some reason. Return
3576 code 0 is given only when all addresses succeed.
3578 If any of the routers in the configuration makes any tests on the sender
3579 address of a message, you should use the &%-f%& option to set an appropriate
3580 sender when running &%-bv%& tests. Without it, the sender is assumed to be the
3581 calling user at the default qualifying domain.
3585 This option acts like &%-bv%&, but verifies the address as a sender rather
3586 than a recipient address. This affects any rewriting and qualification that
3593 .cindex "inetd" "wait mode"
3594 This option runs Exim as a daemon, awaiting incoming SMTP connections,
3595 similarly to the &%-bd%& option. All port specifications on the command-line
3596 and in the configuration file are ignored. Queue-running may not be specified.
3598 In this mode, Exim expects to be passed a socket as fd 0 (stdin) which is
3599 listening for connections. This permits the system to start up and have
3600 inetd (or equivalent) listen on the SMTP ports, starting an Exim daemon for
3601 each port only when the first connection is received.
3603 If the option is given as &%-bw%&<&'time'&> then the time is a timeout, after
3604 which the daemon will exit, which should cause inetd to listen once more.
3606 .vitem &%-C%&&~<&'filelist'&>
3608 .cindex "configuration file" "alternate"
3609 .cindex "CONFIGURE_FILE"
3610 .cindex "alternate configuration file"
3611 This option causes Exim to find the runtime configuration file from the given
3612 list instead of from the list specified by the CONFIGURE_FILE
3613 compile-time setting. Usually, the list will consist of just a single filename,
3614 but it can be a colon-separated list of names. In this case, the first
3615 file that exists is used. Failure to open an existing file stops Exim from
3616 proceeding any further along the list, and an error is generated.
3618 When this option is used by a caller other than root, and the list is different
3619 from the compiled-in list, Exim gives up its root privilege immediately, and
3620 runs with the real and effective uid and gid set to those of the caller.
3621 However, if a TRUSTED_CONFIG_LIST file is defined in &_Local/Makefile_&, that
3622 file contains a list of full pathnames, one per line, for configuration files
3623 which are trusted. Root privilege is retained for any configuration file so
3624 listed, as long as the caller is the Exim user (or the user specified in the
3625 CONFIGURE_OWNER option, if any), and as long as the configuration file is
3626 not writeable by inappropriate users or groups.
3628 Leaving TRUSTED_CONFIG_LIST unset precludes the possibility of testing a
3629 configuration using &%-C%& right through message reception and delivery,
3630 even if the caller is root. The reception works, but by that time, Exim is
3631 running as the Exim user, so when it re-executes to regain privilege for the
3632 delivery, the use of &%-C%& causes privilege to be lost. However, root can
3633 test reception and delivery using two separate commands (one to put a message
3634 in the queue, using &%-odq%&, and another to do the delivery, using &%-M%&).
3636 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
3637 prefix string with which any file named in a &%-C%& command line option
3638 must start. In addition, the filename must not contain the sequence &`/../`&.
3639 However, if the value of the &%-C%& option is identical to the value of
3640 CONFIGURE_FILE in &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as
3641 usual. There is no default setting for ALT_CONFIG_PREFIX; when it is
3642 unset, any filename can be used with &%-C%&.
3644 ALT_CONFIG_PREFIX can be used to confine alternative configuration files
3645 to a directory to which only root has access. This prevents someone who has
3646 broken into the Exim account from running a privileged Exim with an arbitrary
3649 The &%-C%& facility is useful for ensuring that configuration files are
3650 syntactically correct, but cannot be used for test deliveries, unless the
3651 caller is privileged, or unless it is an exotic configuration that does not
3652 require privilege. No check is made on the owner or group of the files
3653 specified by this option.
3656 .vitem &%-D%&<&'macro'&>=<&'value'&>
3658 .cindex "macro" "setting on command line"
3659 This option can be used to override macro definitions in the configuration file
3660 (see section &<<SECTmacrodefs>>&). However, like &%-C%&, if it is used by an
3661 unprivileged caller, it causes Exim to give up its root privilege.
3662 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
3663 completely disabled, and its use causes an immediate error exit.
3665 If WHITELIST_D_MACROS is defined in &_Local/Makefile_& then it should be a
3666 colon-separated list of macros which are considered safe and, if &%-D%& only
3667 supplies macros from this list, and the values are acceptable, then Exim will
3668 not give up root privilege if the caller is root, the Exim run-time user, or
3669 the CONFIGURE_OWNER, if set. This is a transition mechanism and is expected
3670 to be removed in the future. Acceptable values for the macros satisfy the
3671 regexp: &`^[A-Za-z0-9_/.-]*$`&
3673 The entire option (including equals sign if present) must all be within one
3674 command line item. &%-D%& can be used to set the value of a macro to the empty
3675 string, in which case the equals sign is optional. These two commands are
3681 To include spaces in a macro definition item, quotes must be used. If you use
3682 quotes, spaces are permitted around the macro name and the equals sign. For
3685 exim '-D ABC = something' ...
3687 &%-D%& may be repeated up to 10 times on a command line.
3688 Only macro names up to 22 letters long can be set.
3691 .vitem &%-d%&<&'debug&~options'&>
3693 .cindex "debugging" "list of selectors"
3694 .cindex "debugging" "&%-d%& option"
3695 This option causes debugging information to be written to the standard
3696 error stream. It is restricted to admin users because debugging output may show
3697 database queries that contain password information. Also, the details of users'
3698 filter files should be protected. If a non-admin user uses &%-d%&, Exim
3699 writes an error message to the standard error stream and exits with a non-zero
3702 When &%-d%& is used, &%-v%& is assumed. If &%-d%& is given on its own, a lot of
3703 standard debugging data is output. This can be reduced, or increased to include
3704 some more rarely needed information, by directly following &%-d%& with a string
3705 made up of names preceded by plus or minus characters. These add or remove sets
3706 of debugging data, respectively. For example, &%-d+filter%& adds filter
3707 debugging, whereas &%-d-all+filter%& selects only filter debugging. Note that
3708 no spaces are allowed in the debug setting. The available debugging categories
3711 &`acl `& ACL interpretation
3712 &`auth `& authenticators
3713 &`deliver `& general delivery logic
3714 &`dns `& DNS lookups (see also resolver)
3715 &`dnsbl `& DNS black list (aka RBL) code
3716 &`exec `& arguments for &[execv()]& calls
3717 &`expand `& detailed debugging for string expansions
3718 &`filter `& filter handling
3719 &`hints_lookup `& hints data lookups
3720 &`host_lookup `& all types of name-to-IP address handling
3721 &`ident `& ident lookup
3722 &`interface `& lists of local interfaces
3723 &`lists `& matching things in lists
3724 &`load `& system load checks
3725 &`local_scan `& can be used by &[local_scan()]& (see chapter &&&
3726 &<<CHAPlocalscan>>&)
3727 &`lookup `& general lookup code and all lookups
3728 &`memory `& memory handling
3729 &`noutf8 `& modifier: avoid UTF-8 line-drawing
3730 &`pid `& modifier: add pid to debug output lines
3731 &`process_info `& setting info for the process log
3732 &`queue_run `& queue runs
3733 &`receive `& general message reception logic
3734 &`resolver `& turn on the DNS resolver's debugging output
3735 &`retry `& retry handling
3736 &`rewrite `& address rewriting
3737 &`route `& address routing
3738 &`timestamp `& modifier: add timestamp to debug output lines
3740 &`transport `& transports
3741 &`uid `& changes of uid/gid and looking up uid/gid
3742 &`verify `& address verification logic
3743 &`all `& almost all of the above (see below), and also &%-v%&
3745 The &`all`& option excludes &`memory`& when used as &`+all`&, but includes it
3746 for &`-all`&. The reason for this is that &`+all`& is something that people
3747 tend to use when generating debug output for Exim maintainers. If &`+memory`&
3748 is included, an awful lot of output that is very rarely of interest is
3749 generated, so it now has to be explicitly requested. However, &`-all`& does
3750 turn everything off.
3752 .cindex "resolver, debugging output"
3753 .cindex "DNS resolver, debugging output"
3754 The &`resolver`& option produces output only if the DNS resolver was compiled
3755 with DEBUG enabled. This is not the case in some operating systems. Also,
3756 unfortunately, debugging output from the DNS resolver is written to stdout
3759 The default (&%-d%& with no argument) omits &`expand`&, &`filter`&,
3760 &`interface`&, &`load`&, &`memory`&, &`pid`&, &`resolver`&, and &`timestamp`&.
3761 However, the &`pid`& selector is forced when debugging is turned on for a
3762 daemon, which then passes it on to any re-executed Exims. Exim also
3763 automatically adds the pid to debug lines when several remote deliveries are
3766 The &`timestamp`& selector causes the current time to be inserted at the start
3767 of all debug output lines. This can be useful when trying to track down delays
3770 .cindex debugging "UTF-8 in"
3771 .cindex UTF-8 "in debug output"
3772 The &`noutf8`& selector disables the use of
3773 UTF-8 line-drawing characters to group related information.
3774 When disabled. ascii-art is used instead.
3775 Using the &`+all`& option does not set this modifier,
3777 If the &%debug_print%& option is set in any driver, it produces output whenever
3778 any debugging is selected, or if &%-v%& is used.
3780 .vitem &%-dd%&<&'debug&~options'&>
3782 This option behaves exactly like &%-d%& except when used on a command that
3783 starts a daemon process. In that case, debugging is turned off for the
3784 subprocesses that the daemon creates. Thus, it is useful for monitoring the
3785 behaviour of the daemon without creating as much output as full debugging does.
3788 .oindex "&%-dropcr%&"
3789 This is an obsolete option that is now a no-op. It used to affect the way Exim
3790 handled CR and LF characters in incoming messages. What happens now is
3791 described in section &<<SECTlineendings>>&.
3795 .cindex "bounce message" "generating"
3796 This option specifies that an incoming message is a locally-generated delivery
3797 failure report. It is used internally by Exim when handling delivery failures
3798 and is not intended for external use. Its only effect is to stop Exim
3799 generating certain messages to the postmaster, as otherwise message cascades
3800 could occur in some situations. As part of the same option, a message id may
3801 follow the characters &%-E%&. If it does, the log entry for the receipt of the
3802 new message contains the id, following &"R="&, as a cross-reference.
3805 .oindex "&%-e%&&'x'&"
3806 There are a number of Sendmail options starting with &%-oe%& which seem to be
3807 called by various programs without the leading &%o%& in the option. For
3808 example, the &%vacation%& program uses &%-eq%&. Exim treats all options of the
3809 form &%-e%&&'x'& as synonymous with the corresponding &%-oe%&&'x'& options.
3811 .vitem &%-F%&&~<&'string'&>
3813 .cindex "sender" "name"
3814 .cindex "name" "of sender"
3815 This option sets the sender's full name for use when a locally-generated
3816 message is being accepted. In the absence of this option, the user's &'gecos'&
3817 entry from the password data is used. As users are generally permitted to alter
3818 their &'gecos'& entries, no security considerations are involved. White space
3819 between &%-F%& and the <&'string'&> is optional.
3821 .vitem &%-f%&&~<&'address'&>
3823 .cindex "sender" "address"
3824 .cindex "address" "sender"
3825 .cindex "trusted users"
3826 .cindex "envelope from"
3827 .cindex "envelope sender"
3828 .cindex "user" "trusted"
3829 This option sets the address of the envelope sender of a locally-generated
3830 message (also known as the return path). The option can normally be used only
3831 by a trusted user, but &%untrusted_set_sender%& can be set to allow untrusted
3834 Processes running as root or the Exim user are always trusted. Other
3835 trusted users are defined by the &%trusted_users%& or &%trusted_groups%&
3836 options. In the absence of &%-f%&, or if the caller is not trusted, the sender
3837 of a local message is set to the caller's login name at the default qualify
3840 There is one exception to the restriction on the use of &%-f%&: an empty sender
3841 can be specified by any user, trusted or not, to create a message that can
3842 never provoke a bounce. An empty sender can be specified either as an empty
3843 string, or as a pair of angle brackets with nothing between them, as in these
3844 examples of shell commands:
3846 exim -f '<>' user@domain
3847 exim -f "" user@domain
3849 In addition, the use of &%-f%& is not restricted when testing a filter file
3850 with &%-bf%& or when testing or verifying addresses using the &%-bt%& or
3853 Allowing untrusted users to change the sender address does not of itself make
3854 it possible to send anonymous mail. Exim still checks that the &'From:'& header
3855 refers to the local user, and if it does not, it adds a &'Sender:'& header,
3856 though this can be overridden by setting &%no_local_from_check%&.
3859 .cindex "&""From""& line"
3860 space between &%-f%& and the <&'address'&> is optional (that is, they can be
3861 given as two arguments or one combined argument). The sender of a
3862 locally-generated message can also be set (when permitted) by an initial
3863 &"From&~"& line in the message &-- see the description of &%-bm%& above &-- but
3864 if &%-f%& is also present, it overrides &"From&~"&.
3868 .cindex "submission fixups, suppressing (command-line)"
3869 This option is equivalent to an ACL applying:
3871 control = suppress_local_fixups
3873 for every message received. Note that Sendmail will complain about such
3874 bad formatting, where Exim silently just does not fix it up. This may change
3877 As this affects audit information, the caller must be a trusted user to use
3880 .vitem &%-h%&&~<&'number'&>
3882 .cindex "Sendmail compatibility" "&%-h%& option ignored"
3883 This option is accepted for compatibility with Sendmail, but has no effect. (In
3884 Sendmail it overrides the &"hop count"& obtained by counting &'Received:'&
3889 .cindex "Solaris" "&'mail'& command"
3890 .cindex "dot" "in incoming non-SMTP message"
3891 This option, which has the same effect as &%-oi%&, specifies that a dot on a
3892 line by itself should not terminate an incoming, non-SMTP message.
3893 Solaris 2.4 (SunOS 5.4) Sendmail has a similar &%-i%& processing option
3894 &url(https://docs.oracle.com/cd/E19457-01/801-6680-1M/801-6680-1M.pdf),
3895 p. 1M-529), and therefore a &%-oi%& command line option, which both are used
3896 by its &'mailx'& command.
3898 .vitem &%-L%&&~<&'tag'&>
3900 .cindex "syslog" "process name; set with flag"
3901 This option is equivalent to setting &%syslog_processname%& in the config
3902 file and setting &%log_file_path%& to &`syslog`&.
3903 Its use is restricted to administrators. The configuration file has to be
3904 read and parsed, to determine access rights, before this is set and takes
3905 effect, so early configuration file errors will not honour this flag.
3907 The tag should not be longer than 32 characters.
3909 .vitem &%-M%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3911 .cindex "forcing delivery"
3912 .cindex "delivery" "forcing attempt"
3913 .cindex "frozen messages" "forcing delivery"
3914 This option requests Exim to run a delivery attempt on each message in turn. If
3915 any of the messages are frozen, they are automatically thawed before the
3916 delivery attempt. The settings of &%queue_domains%&, &%queue_smtp_domains%&,
3917 and &%hold_domains%& are ignored.
3920 .cindex "hints database" "overriding retry hints"
3921 hints for any of the addresses are overridden &-- Exim tries to deliver even if
3922 the normal retry time has not yet been reached. This option requires the caller
3923 to be an admin user. However, there is an option called &%prod_requires_admin%&
3924 which can be set false to relax this restriction (and also the same requirement
3925 for the &%-q%&, &%-R%&, and &%-S%& options).
3927 The deliveries happen synchronously, that is, the original Exim process does
3928 not terminate until all the delivery attempts have finished. No output is
3929 produced unless there is a serious error. If you want to see what is happening,
3930 use the &%-v%& option as well, or inspect Exim's main log.
3932 .vitem &%-Mar%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3934 .cindex "message" "adding recipients"
3935 .cindex "recipient" "adding"
3936 This option requests Exim to add the addresses to the list of recipients of the
3937 message (&"ar"& for &"add recipients"&). The first argument must be a message
3938 id, and the remaining ones must be email addresses. However, if the message is
3939 active (in the middle of a delivery attempt), it is not altered. This option
3940 can be used only by an admin user.
3942 .vitem "&%-MC%&&~<&'transport'&>&~<&'hostname'&>&&&
3944 &~<&'sequence&~number'&>&&&
3945 &~<&'message&~id'&>"
3947 .cindex "SMTP" "passed connection"
3948 .cindex "SMTP" "multiple deliveries"
3949 .cindex "multiple SMTP deliveries"
3950 This option is not intended for use by external callers. It is used internally
3951 by Exim to invoke another instance of itself to deliver a waiting message using
3952 an existing SMTP connection, which is passed as the standard input. Details are
3953 given in chapter &<<CHAPSMTP>>&. This must be the final option, and the caller
3954 must be root or the Exim user in order to use it.
3958 This option is not intended for use by external callers. It is used internally
3959 by Exim in conjunction with the &%-MC%& option. It signifies that the
3960 connection to the remote host has been authenticated.
3964 This option is not intended for use by external callers. It is used internally
3965 by Exim in conjunction with the &%-MC%& option. It signifies that the
3966 remote host supports the ESMTP &_DSN_& extension.
3970 This option is not intended for use by external callers. It is used internally
3971 by Exim in conjunction with the &%-d%& option
3972 to pass on an information string on the purpose of the process.
3974 .vitem &%-MCG%&&~<&'queue&~name'&>
3976 This option is not intended for use by external callers. It is used internally
3977 by Exim in conjunction with the &%-MC%& option. It signifies that an
3978 alternate queue is used, named by the following argument.
3982 This option is not intended for use by external callers. It is used internally
3983 by Exim in conjunction with the &%-MC%& option. It signifies that a
3984 remote host supports the ESMTP &_CHUNKING_& extension.
3988 This option is not intended for use by external callers. It is used internally
3989 by Exim in conjunction with the &%-MC%& option. It signifies that the server to
3990 which Exim is connected advertised limits on numbers of mails, recipients or
3992 The limits are given by the following three arguments.
3996 This option is not intended for use by external callers. It is used internally
3997 by Exim in conjunction with the &%-MC%& option. It signifies that the server to
3998 which Exim is connected supports pipelining.
4002 This option is not intended for use by external callers. It is used internally
4003 by Exim in conjunction with the &%-MC%& option. It signifies that the connection
4004 t a remote server is via a SOCKS proxy, using addresses and ports given by
4005 the following four arguments.
4007 .vitem &%-MCQ%&&~<&'process&~id'&>&~<&'pipe&~fd'&>
4009 This option is not intended for use by external callers. It is used internally
4010 by Exim in conjunction with the &%-MC%& option when the original delivery was
4011 started by a queue runner. It passes on the process id of the queue runner,
4012 together with the file descriptor number of an open pipe. Closure of the pipe
4013 signals the final completion of the sequence of processes that are passing
4014 messages through the same SMTP connection.
4016 .vitem &%-MCq%&&~<&'recipient&~address'&>&~<&'size'&>
4018 This option is not intended for use by external callers. It is used internally
4019 by Exim to implement quota checking for local users.
4023 This option is not intended for use by external callers. It is used internally
4024 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
4025 ESMTP SIZE option should be used on messages delivered down the existing
4030 This option is not intended for use by external callers. It is used internally
4031 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
4032 host to which Exim is connected supports TLS encryption.
4034 .vitem &%-MCr%&&~<&'SNI'&> &&&
4038 These options are not intended for use by external callers. It is used internally
4039 by Exim in conjunction with the &%-MCt%& option, and passes on the fact that
4040 a TLS Server Name Indication was sent as part of the channel establishment.
4041 The argument gives the SNI string.
4042 The "r" variant indicates a DANE-verified connection.
4044 .vitem &%-MCt%&&~<&'IP&~address'&>&~<&'port'&>&~<&'cipher'&>
4046 This option is not intended for use by external callers. It is used internally
4047 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
4048 connection is being proxied by a parent process for handling TLS encryption.
4049 The arguments give the local address and port being proxied, and the TLS cipher.
4051 .vitem &%-Mc%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4053 .cindex "hints database" "not overridden by &%-Mc%&"
4054 .cindex "delivery" "manually started &-- not forced"
4055 This option requests Exim to run a delivery attempt on each message, in turn,
4056 but unlike the &%-M%& option, it does check for retry hints, and respects any
4057 that are found. This option is not very useful to external callers. It is
4058 provided mainly for internal use by Exim when it needs to re-invoke itself in
4059 order to regain root privilege for a delivery (see chapter &<<CHAPsecurity>>&).
4060 However, &%-Mc%& can be useful when testing, in order to run a delivery that
4061 respects retry times and other options such as &%hold_domains%& that are
4062 overridden when &%-M%& is used. Such a delivery does not count as a queue run.
4063 If you want to run a specific delivery as if in a queue run, you should use
4064 &%-q%& with a message id argument. A distinction between queue run deliveries
4065 and other deliveries is made in one or two places.
4067 .vitem &%-Mes%&&~<&'message&~id'&>&~<&'address'&>
4069 .cindex "message" "changing sender"
4070 .cindex "sender" "changing"
4071 This option requests Exim to change the sender address in the message to the
4072 given address, which must be a fully qualified address or &"<>"& (&"es"& for
4073 &"edit sender"&). There must be exactly two arguments. The first argument must
4074 be a message id, and the second one an email address. However, if the message
4075 is active (in the middle of a delivery attempt), its status is not altered.
4076 This option can be used only by an admin user.
4078 .vitem &%-Mf%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4080 .cindex "freezing messages"
4081 .cindex "message" "manually freezing"
4082 This option requests Exim to mark each listed message as &"frozen"&. This
4083 prevents any delivery attempts taking place until the message is &"thawed"&,
4084 either manually or as a result of the &%auto_thaw%& configuration option.
4085 However, if any of the messages are active (in the middle of a delivery
4086 attempt), their status is not altered. This option can be used only by an admin
4089 .vitem &%-Mg%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4091 .cindex "giving up on messages"
4092 .cindex "message" "abandoning delivery attempts"
4093 .cindex "delivery" "abandoning further attempts"
4094 This option requests Exim to give up trying to deliver the listed messages,
4095 including any that are frozen. However, if any of the messages are active,
4096 their status is not altered. For non-bounce messages, a delivery error message
4097 is sent to the sender, containing the text &"cancelled by administrator"&.
4098 Bounce messages are just discarded. This option can be used only by an admin
4101 .vitem &%-MG%&&~<&'queue&~name'&>&~<&'message&~id'&>&~<&'message&~id'&>&~...
4104 .cindex "named queues" "moving messages"
4105 .cindex "queue" "moving messages"
4106 This option requests that each listed message be moved from its current
4107 queue to the given named queue.
4108 The destination queue name argument is required, but can be an empty
4109 string to define the default queue.
4110 If the messages are not currently located in the default queue,
4111 a &%-qG<name>%& option will be required to define the source queue.
4113 .vitem &%-Mmad%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4115 .cindex "delivery" "cancelling all"
4116 This option requests Exim to mark all the recipient addresses in the messages
4117 as already delivered (&"mad"& for &"mark all delivered"&). However, if any
4118 message is active (in the middle of a delivery attempt), its status is not
4119 altered. This option can be used only by an admin user.
4121 .vitem &%-Mmd%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
4123 .cindex "delivery" "cancelling by address"
4124 .cindex "recipient" "removing"
4125 .cindex "removing recipients"
4126 This option requests Exim to mark the given addresses as already delivered
4127 (&"md"& for &"mark delivered"&). The first argument must be a message id, and
4128 the remaining ones must be email addresses. These are matched to recipient
4129 addresses in the message in a case-sensitive manner. If the message is active
4130 (in the middle of a delivery attempt), its status is not altered. This option
4131 can be used only by an admin user.
4133 .vitem &%-Mrm%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4135 .cindex "removing messages"
4136 .cindex "abandoning mail"
4137 .cindex "message" "manually discarding"
4138 This option requests Exim to remove the given messages from the queue. No
4139 bounce messages are sent; each message is simply forgotten. However, if any of
4140 the messages are active, their status is not altered. This option can be used
4141 only by an admin user or by the user who originally caused the message to be
4142 placed in the queue.
4147 . .cindex REQUIRETLS
4148 . This option is used to request REQUIRETLS processing on the message.
4149 . It is used internally by Exim in conjunction with -E when generating
4153 .vitem &%-Mset%&&~<&'message&~id'&>
4155 .cindex "testing" "string expansion"
4156 .cindex "expansion" "testing"
4157 This option is useful only in conjunction with &%-be%& (that is, when testing
4158 string expansions). Exim loads the given message from its spool before doing
4159 the test expansions, thus setting message-specific variables such as
4160 &$message_size$& and the header variables. The &$recipients$& variable is made
4161 available. This feature is provided to make it easier to test expansions that
4162 make use of these variables. However, this option can be used only by an admin
4163 user. See also &%-bem%&.
4165 .vitem &%-Mt%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4167 .cindex "thawing messages"
4168 .cindex "unfreezing messages"
4169 .cindex "frozen messages" "thawing"
4170 .cindex "message" "thawing frozen"
4171 This option requests Exim to &"thaw"& any of the listed messages that are
4172 &"frozen"&, so that delivery attempts can resume. However, if any of the
4173 messages are active, their status is not altered. This option can be used only
4176 .vitem &%-Mvb%&&~<&'message&~id'&>
4178 .cindex "listing" "message body"
4179 .cindex "message" "listing body of"
4180 This option causes the contents of the message body (-D) spool file to be
4181 written to the standard output. This option can be used only by an admin user.
4183 .vitem &%-Mvc%&&~<&'message&~id'&>
4185 .cindex "message" "listing in RFC 2822 format"
4186 .cindex "listing" "message in RFC 2822 format"
4187 This option causes a copy of the complete message (header lines plus body) to
4188 be written to the standard output in RFC 2822 format. This option can be used
4189 only by an admin user.
4191 .vitem &%-Mvh%&&~<&'message&~id'&>
4193 .cindex "listing" "message headers"
4194 .cindex "header lines" "listing"
4195 .cindex "message" "listing header lines"
4196 This option causes the contents of the message headers (-H) spool file to be
4197 written to the standard output. This option can be used only by an admin user.
4199 .vitem &%-Mvl%&&~<&'message&~id'&>
4201 .cindex "listing" "message log"
4202 .cindex "message" "listing message log"
4203 This option causes the contents of the message log spool file to be written to
4204 the standard output. This option can be used only by an admin user.
4208 This is a synonym for &%-om%& that is accepted by Sendmail
4209 (&url(https://docs.oracle.com/cd/E19457-01/801-6680-1M/801-6680-1M.pdf)
4210 p. 1M-258), so Exim treats it that way too.
4214 .cindex "debugging" "&%-N%& option"
4215 .cindex "debugging" "suppressing delivery"
4216 This is a debugging option that inhibits delivery of a message at the transport
4217 level. It implies &%-v%&. Exim goes through many of the motions of delivery &--
4218 it just doesn't actually transport the message, but instead behaves as if it
4219 had successfully done so. However, it does not make any updates to the retry
4220 database, and the log entries for deliveries are flagged with &"*>"& rather
4223 Because &%-N%& discards any message to which it applies, only root or the Exim
4224 user are allowed to use it with &%-bd%&, &%-q%&, &%-R%& or &%-M%&. In other
4225 words, an ordinary user can use it only when supplying an incoming message to
4226 which it will apply. Although transportation never fails when &%-N%& is set, an
4227 address may be deferred because of a configuration problem on a transport, or a
4228 routing problem. Once &%-N%& has been used for a delivery attempt, it sticks to
4229 the message, and applies to any subsequent delivery attempts that may happen
4234 This option is interpreted by Sendmail to mean &"no aliasing"&.
4235 For normal modes of operation, it is ignored by Exim.
4236 When combined with &%-bP%& it makes the output more terse (suppresses
4237 option names, environment values and config pretty printing).
4239 .vitem &%-O%&&~<&'data'&>
4241 This option is interpreted by Sendmail to mean &`set option`&. It is ignored by
4244 .vitem &%-oA%&&~<&'file&~name'&>
4246 .cindex "Sendmail compatibility" "&%-oA%& option"
4247 This option is used by Sendmail in conjunction with &%-bi%& to specify an
4248 alternative alias filename. Exim handles &%-bi%& differently; see the
4251 .vitem &%-oB%&&~<&'n'&>
4253 .cindex "SMTP" "passed connection"
4254 .cindex "SMTP" "multiple deliveries"
4255 .cindex "multiple SMTP deliveries"
4256 This is a debugging option which limits the maximum number of messages that can
4257 be delivered down one SMTP connection, overriding the value set in any &(smtp)&
4258 transport. If <&'n'&> is omitted, the limit is set to 1.
4262 .cindex "background delivery"
4263 .cindex "delivery" "in the background"
4264 This option applies to all modes in which Exim accepts incoming messages,
4265 including the listening daemon. It requests &"background"& delivery of such
4266 messages, which means that the accepting process automatically starts a
4267 delivery process for each message received, but does not wait for the delivery
4268 processes to finish.
4270 When all the messages have been received, the reception process exits,
4271 leaving the delivery processes to finish in their own time. The standard output
4272 and error streams are closed at the start of each delivery process.
4273 This is the default action if none of the &%-od%& options are present.
4275 If one of the queueing options in the configuration file
4276 (&%queue_only%& or &%queue_only_file%&, for example) is in effect, &%-odb%&
4277 overrides it if &%queue_only_override%& is set true, which is the default
4278 setting. If &%queue_only_override%& is set false, &%-odb%& has no effect.
4282 .cindex "foreground delivery"
4283 .cindex "delivery" "in the foreground"
4284 This option requests &"foreground"& (synchronous) delivery when Exim has
4285 accepted a locally-generated message. (For the daemon it is exactly the same as
4286 &%-odb%&.) A delivery process is automatically started to deliver the message,
4287 and Exim waits for it to complete before proceeding.
4289 The original Exim reception process does not finish until the delivery
4290 process for the final message has ended. The standard error stream is left open
4293 However, like &%-odb%&, this option has no effect if &%queue_only_override%& is
4294 false and one of the queueing options in the configuration file is in effect.
4296 If there is a temporary delivery error during foreground delivery, the
4297 message is left in the queue for later delivery, and the original reception
4298 process exits. See chapter &<<CHAPnonqueueing>>& for a way of setting up a
4299 restricted configuration that never queues messages.
4304 This option is synonymous with &%-odf%&. It is provided for compatibility with
4309 .cindex "non-immediate delivery"
4310 .cindex "delivery" "suppressing immediate"
4311 .cindex "queueing incoming messages"
4312 This option applies to all modes in which Exim accepts incoming messages,
4313 including the listening daemon. It specifies that the accepting process should
4314 not automatically start a delivery process for each message received. Messages
4315 are placed in the queue, and remain there until a subsequent queue runner
4316 process encounters them. There are several configuration options (such as
4317 &%queue_only%&) that can be used to queue incoming messages under certain
4318 conditions. This option overrides all of them and also &%-odqs%&. It always
4323 .cindex "SMTP" "delaying delivery"
4324 .cindex "first pass routing"
4325 This option is a hybrid between &%-odb%&/&%-odi%& and &%-odq%&.
4326 However, like &%-odb%& and &%-odi%&, this option has no effect if
4327 &%queue_only_override%& is false and one of the queueing options in the
4328 configuration file is in effect.
4330 When &%-odqs%& does operate, a delivery process is started for each incoming
4331 message, in the background by default, but in the foreground if &%-odi%& is
4332 also present. The recipient addresses are routed, and local deliveries are done
4333 in the normal way. However, if any SMTP deliveries are required, they are not
4334 done at this time, so the message remains in the queue until a subsequent queue
4335 runner process encounters it. Because routing was done, Exim knows which
4336 messages are waiting for which hosts, and so a number of messages for the same
4337 host can be sent in a single SMTP connection. The &%queue_smtp_domains%&
4338 configuration option has the same effect for specific domains. See also the
4343 .cindex "error" "reporting"
4344 If an error is detected while a non-SMTP message is being received (for
4345 example, a malformed address), the error is reported to the sender in a mail
4348 .cindex "return code" "for &%-oee%&"
4350 this error message is successfully sent, the Exim receiving process
4351 exits with a return code of zero. If not, the return code is 2 if the problem
4352 is that the original message has no recipients, or 1 for any other error.
4353 This is the default &%-oe%&&'x'& option if Exim is called as &'rmail'&.
4357 .cindex "error" "reporting"
4358 .cindex "return code" "for &%-oem%&"
4359 This is the same as &%-oee%&, except that Exim always exits with a non-zero
4360 return code, whether or not the error message was successfully sent.
4361 This is the default &%-oe%&&'x'& option, unless Exim is called as &'rmail'&.
4365 .cindex "error" "reporting"
4366 If an error is detected while a non-SMTP message is being received, the
4367 error is reported by writing a message to the standard error file (stderr).
4368 .cindex "return code" "for &%-oep%&"
4369 The return code is 1 for all errors.
4373 .cindex "error" "reporting"
4374 This option is supported for compatibility with Sendmail, but has the same
4379 .cindex "error" "reporting"
4380 This option is supported for compatibility with Sendmail, but has the same
4385 .cindex "dot" "in incoming non-SMTP message"
4386 This option, which has the same effect as &%-i%&, specifies that a dot on a
4387 line by itself should not terminate an incoming, non-SMTP message. Otherwise, a
4388 single dot does terminate, though Exim does no special processing for other
4389 lines that start with a dot. This option is set by default if Exim is called as
4390 &'rmail'&. See also &%-ti%&.
4393 .oindex "&%-oitrue%&"
4394 This option is treated as synonymous with &%-oi%&.
4396 .vitem &%-oMa%&&~<&'host&~address'&>
4398 .cindex "sender" "host address, specifying for local message"
4399 A number of options starting with &%-oM%& can be used to set values associated
4400 with remote hosts on locally-submitted messages (that is, messages not received
4401 over TCP/IP). These options can be used by any caller in conjunction with the
4402 &%-bh%&, &%-be%&, &%-bf%&, &%-bF%&, &%-bt%&, or &%-bv%& testing options. In
4403 other circumstances, they are ignored unless the caller is trusted.
4405 The &%-oMa%& option sets the sender host address. This may include a port
4406 number at the end, after a full stop (period). For example:
4408 exim -bs -oMa 10.9.8.7.1234
4410 An alternative syntax is to enclose the IP address in square brackets,
4411 followed by a colon and the port number:
4413 exim -bs -oMa [10.9.8.7]:1234
4415 The IP address is placed in the &$sender_host_address$& variable, and the
4416 port, if present, in &$sender_host_port$&. If both &%-oMa%& and &%-bh%&
4417 are present on the command line, the sender host IP address is taken from
4418 whichever one is last.
4420 .vitem &%-oMaa%&&~<&'name'&>
4422 .cindex "authentication" "name, specifying for local message"
4423 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMaa%&
4424 option sets the value of &$sender_host_authenticated$& (the authenticator
4425 name). See chapter &<<CHAPSMTPAUTH>>& for a discussion of SMTP authentication.
4426 This option can be used with &%-bh%& and &%-bs%& to set up an
4427 authenticated SMTP session without actually using the SMTP AUTH command.
4429 .vitem &%-oMai%&&~<&'string'&>
4431 .cindex "authentication" "id, specifying for local message"
4432 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMai%&
4433 option sets the value of &$authenticated_id$& (the id that was authenticated).
4434 This overrides the default value (the caller's login id, except with &%-bh%&,
4435 where there is no default) for messages from local sources. See chapter
4436 &<<CHAPSMTPAUTH>>& for a discussion of authenticated ids.
4438 .vitem &%-oMas%&&~<&'address'&>
4440 .cindex "authentication" "sender, specifying for local message"
4441 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMas%&
4442 option sets the authenticated sender value in &$authenticated_sender$&. It
4443 overrides the sender address that is created from the caller's login id for
4444 messages from local sources, except when &%-bh%& is used, when there is no
4445 default. For both &%-bh%& and &%-bs%&, an authenticated sender that is
4446 specified on a MAIL command overrides this value. See chapter
4447 &<<CHAPSMTPAUTH>>& for a discussion of authenticated senders.
4449 .vitem &%-oMi%&&~<&'interface&~address'&>
4451 .cindex "interface" "address, specifying for local message"
4452 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMi%&
4453 option sets the IP interface address value. A port number may be included,
4454 using the same syntax as for &%-oMa%&. The interface address is placed in
4455 &$received_ip_address$& and the port number, if present, in &$received_port$&.
4457 .vitem &%-oMm%&&~<&'message&~reference'&>
4459 .cindex "message reference" "message reference, specifying for local message"
4460 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMm%&
4461 option sets the message reference, e.g. message-id, and is logged during
4462 delivery. This is useful when some kind of audit trail is required to tie
4463 messages together. The format of the message reference is checked and will
4464 abort if the format is invalid. The option will only be accepted if exim is
4465 running in trusted mode, not as any regular user.
4467 The best example of a message reference is when Exim sends a bounce message.
4468 The message reference is the message-id of the original message for which Exim
4469 is sending the bounce.
4471 .vitem &%-oMr%&&~<&'protocol&~name'&>
4473 .cindex "protocol, specifying for local message"
4474 .vindex "&$received_protocol$&"
4475 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMr%&
4476 option sets the received protocol value that is stored in
4477 &$received_protocol$&. However, it does not apply (and is ignored) when &%-bh%&
4478 or &%-bs%& is used. For &%-bh%&, the protocol is forced to one of the standard
4479 SMTP protocol names (see the description of &$received_protocol$& in section
4480 &<<SECTexpvar>>&). For &%-bs%&, the protocol is always &"local-"& followed by
4481 one of those same names. For &%-bS%& (batched SMTP) however, the protocol can
4482 be set by &%-oMr%&. Repeated use of this option is not supported.
4484 .vitem &%-oMs%&&~<&'host&~name'&>
4486 .cindex "sender" "host name, specifying for local message"
4487 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMs%&
4488 option sets the sender host name in &$sender_host_name$&. When this option is
4489 present, Exim does not attempt to look up a host name from an IP address; it
4490 uses the name it is given.
4492 .vitem &%-oMt%&&~<&'ident&~string'&>
4494 .cindex "sender" "ident string, specifying for local message"
4495 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMt%&
4496 option sets the sender ident value in &$sender_ident$&. The default setting for
4497 local callers is the login id of the calling process, except when &%-bh%& is
4498 used, when there is no default.
4502 .cindex "Sendmail compatibility" "&%-om%& option ignored"
4503 In Sendmail, this option means &"me too"&, indicating that the sender of a
4504 message should receive a copy of the message if the sender appears in an alias
4505 expansion. Exim always does this, so the option does nothing.
4509 .cindex "Sendmail compatibility" "&%-oo%& option ignored"
4510 This option is ignored. In Sendmail it specifies &"old style headers"&,
4511 whatever that means.
4513 .vitem &%-oP%&&~<&'path'&>
4515 .cindex "pid (process id)" "of daemon"
4516 .cindex "daemon" "process id (pid)"
4517 This option is useful only in conjunction with &%-bd%& or &%-q%& with a time
4518 value. The option specifies the file to which the process id of the daemon is
4519 written. When &%-oX%& is used with &%-bd%&, or when &%-q%& with a time is used
4520 without &%-bd%&, this is the only way of causing Exim to write a pid file,
4521 because in those cases, the normal pid file is not used.
4525 .cindex "pid (process id)" "of daemon"
4526 .cindex "daemon" "process id (pid)"
4527 This option is not intended for general use.
4528 The daemon uses it when terminating due to a SIGTEM, possibly in
4529 combination with &%-oP%&&~<&'path'&>.
4530 It causes the pid file to be removed.
4532 .vitem &%-or%&&~<&'time'&>
4534 .cindex "timeout" "for non-SMTP input"
4535 This option sets a timeout value for incoming non-SMTP messages. If it is not
4536 set, Exim will wait forever for the standard input. The value can also be set
4537 by the &%receive_timeout%& option. The format used for specifying times is
4538 described in section &<<SECTtimeformat>>&.
4540 .vitem &%-os%&&~<&'time'&>
4542 .cindex "timeout" "for SMTP input"
4543 .cindex "SMTP" "input timeout"
4544 This option sets a timeout value for incoming SMTP messages. The timeout
4545 applies to each SMTP command and block of data. The value can also be set by
4546 the &%smtp_receive_timeout%& option; it defaults to 5 minutes. The format used
4547 for specifying times is described in section &<<SECTtimeformat>>&.
4551 This option has exactly the same effect as &%-v%&.
4553 .vitem &%-oX%&&~<&'number&~or&~string'&>
4555 .cindex "TCP/IP" "setting listening ports"
4556 .cindex "TCP/IP" "setting listening interfaces"
4557 .cindex "port" "receiving TCP/IP"
4558 This option is relevant only when the &%-bd%& (start listening daemon) option
4559 is also given. It controls which ports and interfaces the daemon uses. Details
4560 of the syntax, and how it interacts with configuration file options, are given
4561 in chapter &<<CHAPinterfaces>>&. When &%-oX%& is used to start a daemon, no pid
4562 file is written unless &%-oP%& is also present to specify a pid filename.
4566 .cindex "daemon notifier socket"
4567 This option controls the creation of an inter-process communications endpoint
4569 It is only relevant when the &%-bd%& (start listening daemon) option is also
4571 Normally the daemon creates this socket, unless a &%-oX%& and &*no*& &%-oP%&
4572 option is also present.
4573 If this option is given then the socket will not be created. This could be
4574 required if the system is running multiple daemons.
4576 The socket is currently used for
4578 fast ramp-up of queue runner processes
4580 obtaining a current queue size
4585 .cindex "Perl" "starting the interpreter"
4586 This option applies when an embedded Perl interpreter is linked with Exim (see
4587 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4588 option, forcing the starting of the interpreter to be delayed until it is
4593 .cindex "Perl" "starting the interpreter"
4594 This option applies when an embedded Perl interpreter is linked with Exim (see
4595 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4596 option, forcing the starting of the interpreter to occur as soon as Exim is
4599 .vitem &%-p%&<&'rval'&>:<&'sval'&>
4601 For compatibility with Sendmail, this option is equivalent to
4603 &`-oMr`& <&'rval'&> &`-oMs`& <&'sval'&>
4605 It sets the incoming protocol and host name (for trusted callers). The
4606 host name and its colon can be omitted when only the protocol is to be set.
4607 Note the Exim already has two private options, &%-pd%& and &%-ps%&, that refer
4608 to embedded Perl. It is therefore impossible to set a protocol value of &`d`&
4609 or &`s`& using this option (but that does not seem a real limitation).
4610 Repeated use of this option is not supported.
4614 .cindex "queue runner" "starting manually"
4615 This option is normally restricted to admin users. However, there is a
4616 configuration option called &%prod_requires_admin%& which can be set false to
4617 relax this restriction (and also the same requirement for the &%-M%&, &%-R%&,
4618 and &%-S%& options).
4620 .cindex "queue runner" "description of operation"
4621 If other commandline options do not specify an action,
4622 the &%-q%& option starts one queue runner process. This scans the queue of
4623 waiting messages, and runs a delivery process for each one in turn. It waits
4624 for each delivery process to finish before starting the next one. A delivery
4625 process may not actually do any deliveries if the retry times for the addresses
4626 have not been reached. Use &%-qf%& (see below) if you want to override this.
4629 .cindex "SMTP" "passed connection"
4630 .cindex "SMTP" "multiple deliveries"
4631 .cindex "multiple SMTP deliveries"
4632 the delivery process spawns other processes to deliver other messages down
4633 passed SMTP connections, the queue runner waits for these to finish before
4636 When all the queued messages have been considered, the original queue runner
4637 process terminates. In other words, a single pass is made over the waiting
4638 mail, one message at a time. Use &%-q%& with a time (see below) if you want
4639 this to be repeated periodically.
4641 Exim processes the waiting messages in an unpredictable order. It isn't very
4642 random, but it is likely to be different each time, which is all that matters.
4643 If one particular message screws up a remote MTA, other messages to the same
4644 MTA have a chance of getting through if they get tried first.
4646 It is possible to cause the messages to be processed in lexical message id
4647 order, which is essentially the order in which they arrived, by setting the
4648 &%queue_run_in_order%& option, but this is not recommended for normal use.
4650 .vitem &%-q%&<&'qflags'&>
4651 The &%-q%& option may be followed by one or more flag letters that change its
4652 behaviour. They are all optional, but if more than one is present, they must
4653 appear in the correct order. Each flag is described in a separate item below.
4657 .cindex "queue" "double scanning"
4658 .cindex "queue" "routing"
4659 .cindex "routing" "whole queue before delivery"
4660 .cindex "first pass routing"
4661 .cindex "queue runner" "two phase"
4662 An option starting with &%-qq%& requests a two-stage queue run. In the first
4663 stage, the queue is scanned as if the &%queue_smtp_domains%& option matched
4664 every domain. Addresses are routed, local deliveries happen, but no remote
4667 Performance will be best if the &%queue_run_in_order%& option is false.
4668 If that is so and the &%queue_fast_ramp%& option is true then
4669 in the first phase of the run,
4670 once a threshold number of messages are routed for a given host,
4671 a delivery process is forked in parallel with the rest of the scan.
4673 .cindex "hints database" "remembering routing"
4674 The hints database that remembers which messages are waiting for specific hosts
4675 is updated, as if delivery to those hosts had been deferred. After this is
4676 complete, a second, normal queue scan happens, with routing and delivery taking
4677 place as normal. Messages that are routed to the same host should mostly be
4678 delivered down a single SMTP
4679 .cindex "SMTP" "passed connection"
4680 .cindex "SMTP" "multiple deliveries"
4681 .cindex "multiple SMTP deliveries"
4682 connection because of the hints that were set up during the first queue scan.
4683 This option may be useful for hosts that are connected to the Internet
4686 .vitem &%-q[q]i...%&
4688 .cindex "queue" "initial delivery"
4689 If the &'i'& flag is present, the queue runner runs delivery processes only for
4690 those messages that haven't previously been tried. (&'i'& stands for &"initial
4691 delivery"&.) This can be helpful if you are putting messages in the queue using
4692 &%-odq%& and want a queue runner just to process the new messages.
4694 .vitem &%-q[q][i]f...%&
4696 .cindex "queue" "forcing delivery"
4697 .cindex "delivery" "forcing in queue run"
4698 If one &'f'& flag is present, a delivery attempt is forced for each non-frozen
4699 message, whereas without &'f'& only those non-frozen addresses that have passed
4700 their retry times are tried.
4702 .vitem &%-q[q][i]ff...%&
4704 .cindex "frozen messages" "forcing delivery"
4705 If &'ff'& is present, a delivery attempt is forced for every message, whether
4708 .vitem &%-q[q][i][f[f]]l%&
4710 .cindex "queue" "local deliveries only"
4711 The &'l'& (the letter &"ell"&) flag specifies that only local deliveries are to
4712 be done. If a message requires any remote deliveries, it remains in the queue
4715 .vitem &%-q[q][i][f[f]][l][G<name>[/<time>]]]%&
4718 .cindex "named queues" "deliver from"
4719 .cindex "queue" "delivering specific messages"
4720 If the &'G'& flag and a name is present, the queue runner operates on the
4721 queue with the given name rather than the default queue.
4722 The name should not contain a &'/'& character.
4723 For a periodic queue run (see below)
4724 append to the name a slash and a time value.
4726 If other commandline options specify an action, a &'-qG<name>'& option
4727 will specify a queue to operate on.
4730 exim -bp -qGquarantine
4732 exim -qGoffpeak -Rf @special.domain.example
4735 .vitem &%-q%&<&'qflags'&>&~<&'start&~id'&>&~<&'end&~id'&>
4736 When scanning the queue, Exim can be made to skip over messages whose ids are
4737 lexically less than a given value by following the &%-q%& option with a
4738 starting message id. For example:
4740 exim -q 0t5C6f-0000c8-00
4742 Messages that arrived earlier than &`0t5C6f-0000c8-00`& are not inspected. If a
4743 second message id is given, messages whose ids are lexically greater than it
4744 are also skipped. If the same id is given twice, for example,
4746 exim -q 0t5C6f-0000c8-00 0t5C6f-0000c8-00
4748 just one delivery process is started, for that message. This differs from
4749 &%-M%& in that retry data is respected, and it also differs from &%-Mc%& in
4750 that it counts as a delivery from a queue run. Note that the selection
4751 mechanism does not affect the order in which the messages are scanned. There
4752 are also other ways of selecting specific sets of messages for delivery in a
4753 queue run &-- see &%-R%& and &%-S%&.
4755 .vitem &%-q%&<&'qflags'&><&'time'&>
4756 .cindex "queue runner" "starting periodically"
4757 .cindex "periodic queue running"
4758 When a time value is present, the &%-q%& option causes Exim to run as a daemon,
4759 starting a queue runner process at intervals specified by the given time value
4760 (whose format is described in section &<<SECTtimeformat>>&). This form of the
4761 &%-q%& option is commonly combined with the &%-bd%& option, in which case a
4762 single daemon process handles both functions. A common way of starting up a
4763 combined daemon at system boot time is to use a command such as
4765 /usr/exim/bin/exim -bd -q30m
4767 Such a daemon listens for incoming SMTP calls, and also starts a queue runner
4768 process every 30 minutes.
4770 When a daemon is started by &%-q%& with a time value, but without &%-bd%&, no
4771 pid file is written unless one is explicitly requested by the &%-oP%& option.
4773 .vitem &%-qR%&<&'rsflags'&>&~<&'string'&>
4775 This option is synonymous with &%-R%&. It is provided for Sendmail
4778 .vitem &%-qS%&<&'rsflags'&>&~<&'string'&>
4780 This option is synonymous with &%-S%&.
4782 .vitem &%-R%&<&'rsflags'&>&~<&'string'&>
4784 .cindex "queue runner" "for specific recipients"
4785 .cindex "delivery" "to given domain"
4786 .cindex "domain" "delivery to"
4787 The <&'rsflags'&> may be empty, in which case the white space before the string
4788 is optional, unless the string is &'f'&, &'ff'&, &'r'&, &'rf'&, or &'rff'&,
4789 which are the possible values for <&'rsflags'&>. White space is required if
4790 <&'rsflags'&> is not empty.
4792 This option is similar to &%-q%& with no time value, that is, it causes Exim to
4793 perform a single queue run, except that, when scanning the messages on the
4794 queue, Exim processes only those that have at least one undelivered recipient
4795 address containing the given string, which is checked in a case-independent
4796 way. If the <&'rsflags'&> start with &'r'&, <&'string'&> is interpreted as a
4797 regular expression; otherwise it is a literal string.
4799 If you want to do periodic queue runs for messages with specific recipients,
4800 you can combine &%-R%& with &%-q%& and a time value. For example:
4802 exim -q25m -R @special.domain.example
4804 This example does a queue run for messages with recipients in the given domain
4805 every 25 minutes. Any additional flags that are specified with &%-q%& are
4806 applied to each queue run.
4808 Once a message is selected for delivery by this mechanism, all its addresses
4809 are processed. For the first selected message, Exim overrides any retry
4810 information and forces a delivery attempt for each undelivered address. This
4811 means that if delivery of any address in the first message is successful, any
4812 existing retry information is deleted, and so delivery attempts for that
4813 address in subsequently selected messages (which are processed without forcing)
4814 will run. However, if delivery of any address does not succeed, the retry
4815 information is updated, and in subsequently selected messages, the failing
4816 address will be skipped.
4818 .cindex "frozen messages" "forcing delivery"
4819 If the <&'rsflags'&> contain &'f'& or &'ff'&, the delivery forcing applies to
4820 all selected messages, not just the first; frozen messages are included when
4823 The &%-R%& option makes it straightforward to initiate delivery of all messages
4824 to a given domain after a host has been down for some time. When the SMTP
4825 command ETRN is accepted by its ACL (see chapter &<<CHAPACL>>&), its default
4826 effect is to run Exim with the &%-R%& option, but it can be configured to run
4827 an arbitrary command instead.
4831 This is a documented (for Sendmail) obsolete alternative name for &%-f%&.
4833 .vitem &%-S%&<&'rsflags'&>&~<&'string'&>
4835 .cindex "delivery" "from given sender"
4836 .cindex "queue runner" "for specific senders"
4837 This option acts like &%-R%& except that it checks the string against each
4838 message's sender instead of against the recipients. If &%-R%& is also set, both
4839 conditions must be met for a message to be selected. If either of the options
4840 has &'f'& or &'ff'& in its flags, the associated action is taken.
4842 .vitem &%-Tqt%&&~<&'times'&>
4844 This is an option that is exclusively for use by the Exim testing suite. It is not
4845 recognized when Exim is run normally. It allows for the setting up of explicit
4846 &"queue times"& so that various warning/retry features can be tested.
4850 .cindex "recipient" "extracting from header lines"
4854 When Exim is receiving a locally-generated, non-SMTP message on its standard
4855 input, the &%-t%& option causes the recipients of the message to be obtained
4856 from the &'To:'&, &'Cc:'&, and &'Bcc:'& header lines in the message instead of
4857 from the command arguments. The addresses are extracted before any rewriting
4858 takes place and the &'Bcc:'& header line, if present, is then removed.
4860 .cindex "Sendmail compatibility" "&%-t%& option"
4861 If the command has any arguments, they specify addresses to which the message
4862 is &'not'& to be delivered. That is, the argument addresses are removed from
4863 the recipients list obtained from the headers. This is compatible with Smail 3
4864 and in accordance with the documented behaviour of several versions of
4865 Sendmail, as described in man pages on a number of operating systems (e.g.
4866 Solaris 8, IRIX 6.5, HP-UX 11). However, some versions of Sendmail &'add'&
4867 argument addresses to those obtained from the headers, and the O'Reilly
4868 Sendmail book documents it that way. Exim can be made to add argument addresses
4869 instead of subtracting them by setting the option
4870 &%extract_addresses_remove_arguments%& false.
4872 .cindex "&%Resent-%& header lines" "with &%-t%&"
4873 If there are any &%Resent-%& header lines in the message, Exim extracts
4874 recipients from all &'Resent-To:'&, &'Resent-Cc:'&, and &'Resent-Bcc:'& header
4875 lines instead of from &'To:'&, &'Cc:'&, and &'Bcc:'&. This is for compatibility
4876 with Sendmail and other MTAs. (Prior to release 4.20, Exim gave an error if
4877 &%-t%& was used in conjunction with &%Resent-%& header lines.)
4879 RFC 2822 talks about different sets of &%Resent-%& header lines (for when a
4880 message is resent several times). The RFC also specifies that they should be
4881 added at the front of the message, and separated by &'Received:'& lines. It is
4882 not at all clear how &%-t%& should operate in the present of multiple sets,
4883 nor indeed exactly what constitutes a &"set"&.
4884 In practice, it seems that MUAs do not follow the RFC. The &%Resent-%& lines
4885 are often added at the end of the header, and if a message is resent more than
4886 once, it is common for the original set of &%Resent-%& headers to be renamed as
4887 &%X-Resent-%& when a new set is added. This removes any possible ambiguity.
4891 This option is exactly equivalent to &%-t%& &%-i%&. It is provided for
4892 compatibility with Sendmail.
4894 .vitem &%-tls-on-connect%&
4895 .oindex "&%-tls-on-connect%&"
4896 .cindex "TLS" "use without STARTTLS"
4897 .cindex "TLS" "automatic start"
4898 This option is available when Exim is compiled with TLS support. It forces all
4899 incoming SMTP connections to behave as if the incoming port is listed in the
4900 &%tls_on_connect_ports%& option. See section &<<SECTsupobssmt>>& and chapter
4901 &<<CHAPTLS>>& for further details.
4906 .cindex "Sendmail compatibility" "&%-U%& option ignored"
4907 Sendmail uses this option for &"initial message submission"&, and its
4908 documentation states that in future releases, it may complain about
4909 syntactically invalid messages rather than fixing them when this flag is not
4910 set. Exim ignores this option.
4914 This option causes Exim to write information to the standard error stream,
4915 describing what it is doing. In particular, it shows the log lines for
4916 receiving and delivering a message, and if an SMTP connection is made, the SMTP
4917 dialogue is shown. Some of the log lines shown may not actually be written to
4918 the log if the setting of &%log_selector%& discards them. Any relevant
4919 selectors are shown with each log line. If none are shown, the logging is
4924 AIX uses &%-x%& for a private purpose (&"mail from a local mail program has
4925 National Language Support extended characters in the body of the mail item"&).
4926 It sets &%-x%& when calling the MTA from its &%mail%& command. Exim ignores
4929 .vitem &%-X%&&~<&'logfile'&>
4931 This option is interpreted by Sendmail to cause debug information to be sent
4932 to the named file. It is ignored by Exim.
4934 .vitem &%-z%&&~<&'log-line'&>
4936 This option writes its argument to Exim's logfile.
4937 Use is restricted to administrators; the intent is for operational notes.
4938 Quotes should be used to maintain a multi-word item as a single argument,
4946 . ////////////////////////////////////////////////////////////////////////////
4947 . Insert a stylized DocBook comment here, to identify the end of the command
4948 . line options. This is for the benefit of the Perl script that automatically
4949 . creates a man page for the options.
4950 . ////////////////////////////////////////////////////////////////////////////
4953 <!-- === End of command line options === -->
4960 . ////////////////////////////////////////////////////////////////////////////
4961 . ////////////////////////////////////////////////////////////////////////////
4964 .chapter "The Exim runtime configuration file" "CHAPconf" &&&
4965 "The runtime configuration file"
4967 .cindex "runtime configuration"
4968 .cindex "configuration file" "general description"
4969 .cindex "CONFIGURE_FILE"
4970 .cindex "configuration file" "errors in"
4971 .cindex "error" "in configuration file"
4972 .cindex "return code" "for bad configuration"
4973 Exim uses a single runtime configuration file that is read whenever an Exim
4974 binary is executed. Note that in normal operation, this happens frequently,
4975 because Exim is designed to operate in a distributed manner, without central
4978 If a syntax error is detected while reading the configuration file, Exim
4979 writes a message on the standard error, and exits with a non-zero return code.
4980 The message is also written to the panic log. &*Note*&: Only simple syntax
4981 errors can be detected at this time. The values of any expanded options are
4982 not checked until the expansion happens, even when the expansion does not
4983 actually alter the string.
4985 The name of the configuration file is compiled into the binary for security
4986 reasons, and is specified by the CONFIGURE_FILE compilation option. In
4987 most configurations, this specifies a single file. However, it is permitted to
4988 give a colon-separated list of filenames, in which case Exim uses the first
4989 existing file in the list.
4992 .cindex "EXIM_GROUP"
4993 .cindex "CONFIGURE_OWNER"
4994 .cindex "CONFIGURE_GROUP"
4995 .cindex "configuration file" "ownership"
4996 .cindex "ownership" "configuration file"
4997 The runtime configuration file must be owned by root or by the user that is
4998 specified at compile time by the CONFIGURE_OWNER option (if set). The
4999 configuration file must not be world-writeable, or group-writeable unless its
5000 group is the root group or the one specified at compile time by the
5001 CONFIGURE_GROUP option.
5003 &*Warning*&: In a conventional configuration, where the Exim binary is setuid
5004 to root, anybody who is able to edit the runtime configuration file has an
5005 easy way to run commands as root. If you specify a user or group in the
5006 CONFIGURE_OWNER or CONFIGURE_GROUP options, then that user and/or any users
5007 who are members of that group will trivially be able to obtain root privileges.
5009 Up to Exim version 4.72, the runtime configuration file was also permitted to
5010 be writeable by the Exim user and/or group. That has been changed in Exim 4.73
5011 since it offered a simple privilege escalation for any attacker who managed to
5012 compromise the Exim user account.
5014 A default configuration file, which will work correctly in simple situations,
5015 is provided in the file &_src/configure.default_&. If CONFIGURE_FILE
5016 defines just one filename, the installation process copies the default
5017 configuration to a new file of that name if it did not previously exist. If
5018 CONFIGURE_FILE is a list, no default is automatically installed. Chapter
5019 &<<CHAPdefconfil>>& is a &"walk-through"& discussion of the default
5024 .section "Using a different configuration file" "SECID40"
5025 .cindex "configuration file" "alternate"
5026 A one-off alternate configuration can be specified by the &%-C%& command line
5027 option, which may specify a single file or a list of files. However, when
5028 &%-C%& is used, Exim gives up its root privilege, unless called by root (or
5029 unless the argument for &%-C%& is identical to the built-in value from
5030 CONFIGURE_FILE), or is listed in the TRUSTED_CONFIG_LIST file and the caller
5031 is the Exim user or the user specified in the CONFIGURE_OWNER setting. &%-C%&
5032 is useful mainly for checking the syntax of configuration files before
5033 installing them. No owner or group checks are done on a configuration file
5034 specified by &%-C%&, if root privilege has been dropped.
5036 Even the Exim user is not trusted to specify an arbitrary configuration file
5037 with the &%-C%& option to be used with root privileges, unless that file is
5038 listed in the TRUSTED_CONFIG_LIST file. This locks out the possibility of
5039 testing a configuration using &%-C%& right through message reception and
5040 delivery, even if the caller is root. The reception works, but by that time,
5041 Exim is running as the Exim user, so when it re-execs to regain privilege for
5042 the delivery, the use of &%-C%& causes privilege to be lost. However, root
5043 can test reception and delivery using two separate commands (one to put a
5044 message in the queue, using &%-odq%&, and another to do the delivery, using
5047 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
5048 prefix string with which any file named in a &%-C%& command line option must
5049 start. In addition, the filename must not contain the sequence &"&`/../`&"&.
5050 There is no default setting for ALT_CONFIG_PREFIX; when it is unset, any
5051 filename can be used with &%-C%&.
5053 One-off changes to a configuration can be specified by the &%-D%& command line
5054 option, which defines and overrides values for macros used inside the
5055 configuration file. However, like &%-C%&, the use of this option by a
5056 non-privileged user causes Exim to discard its root privilege.
5057 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
5058 completely disabled, and its use causes an immediate error exit.
5060 The WHITELIST_D_MACROS option in &_Local/Makefile_& permits the binary builder
5061 to declare certain macro names trusted, such that root privilege will not
5062 necessarily be discarded.
5063 WHITELIST_D_MACROS defines a colon-separated list of macros which are
5064 considered safe and, if &%-D%& only supplies macros from this list, and the
5065 values are acceptable, then Exim will not give up root privilege if the caller
5066 is root, the Exim run-time user, or the CONFIGURE_OWNER, if set. This is a
5067 transition mechanism and is expected to be removed in the future. Acceptable
5068 values for the macros satisfy the regexp: &`^[A-Za-z0-9_/.-]*$`&
5070 Some sites may wish to use the same Exim binary on different machines that
5071 share a file system, but to use different configuration files on each machine.
5072 If CONFIGURE_FILE_USE_NODE is defined in &_Local/Makefile_&, Exim first
5073 looks for a file whose name is the configuration filename followed by a dot
5074 and the machine's node name, as obtained from the &[uname()]& function. If this
5075 file does not exist, the standard name is tried. This processing occurs for
5076 each filename in the list given by CONFIGURE_FILE or &%-C%&.
5078 In some esoteric situations different versions of Exim may be run under
5079 different effective uids and the CONFIGURE_FILE_USE_EUID is defined to
5080 help with this. See the comments in &_src/EDITME_& for details.
5084 .section "Configuration file format" "SECTconffilfor"
5085 .cindex "configuration file" "format of"
5086 .cindex "format" "configuration file"
5087 Exim's configuration file is divided into a number of different parts. General
5088 option settings must always appear at the start of the file. The other parts
5089 are all optional, and may appear in any order. Each part other than the first
5090 is introduced by the word &"begin"& followed by at least one literal
5091 space, and the name of the part. The optional parts are:
5094 &'ACL'&: Access control lists for controlling incoming SMTP mail (see chapter
5097 .cindex "AUTH" "configuration"
5098 &'authenticators'&: Configuration settings for the authenticator drivers. These
5099 are concerned with the SMTP AUTH command (see chapter &<<CHAPSMTPAUTH>>&).
5101 &'routers'&: Configuration settings for the router drivers. Routers process
5102 addresses and determine how the message is to be delivered (see chapters
5103 &<<CHAProutergeneric>>&&--&<<CHAPredirect>>&).
5105 &'transports'&: Configuration settings for the transport drivers. Transports
5106 define mechanisms for copying messages to destinations (see chapters
5107 &<<CHAPtransportgeneric>>&&--&<<CHAPsmtptrans>>&).
5109 &'retry'&: Retry rules, for use when a message cannot be delivered immediately.
5110 If there is no retry section, or if it is empty (that is, no retry rules are
5111 defined), Exim will not retry deliveries. In this situation, temporary errors
5112 are treated the same as permanent errors. Retry rules are discussed in chapter
5115 &'rewrite'&: Global address rewriting rules, for use when a message arrives and
5116 when new addresses are generated during delivery. Rewriting is discussed in
5117 chapter &<<CHAPrewrite>>&.
5119 &'local_scan'&: Private options for the &[local_scan()]& function. If you
5120 want to use this feature, you must set
5122 LOCAL_SCAN_HAS_OPTIONS=yes
5124 in &_Local/Makefile_& before building Exim. Details of the &[local_scan()]&
5125 facility are given in chapter &<<CHAPlocalscan>>&.
5128 .cindex "configuration file" "leading white space in"
5129 .cindex "configuration file" "trailing white space in"
5130 .cindex "white space" "in configuration file"
5131 Leading and trailing white space in configuration lines is always ignored.
5133 Blank lines in the file, and lines starting with a # character (ignoring
5134 leading white space) are treated as comments and are ignored. &*Note*&: A
5135 # character other than at the beginning of a line is not treated specially,
5136 and does not introduce a comment.
5138 Any non-comment line can be continued by ending it with a backslash. Note that
5139 the general rule for white space means that trailing white space after the
5140 backslash and leading white space at the start of continuation
5141 lines is ignored. Comment lines beginning with # (but not empty lines) may
5142 appear in the middle of a sequence of continuation lines.
5144 A convenient way to create a configuration file is to start from the
5145 default, which is supplied in &_src/configure.default_&, and add, delete, or
5146 change settings as required.
5148 The ACLs, retry rules, and rewriting rules have their own syntax which is
5149 described in chapters &<<CHAPACL>>&, &<<CHAPretry>>&, and &<<CHAPrewrite>>&,
5150 respectively. The other parts of the configuration file have some syntactic
5151 items in common, and these are described below, from section &<<SECTcos>>&
5152 onwards. Before that, the inclusion, macro, and conditional facilities are
5157 .section "File inclusions in the configuration file" "SECID41"
5158 .cindex "inclusions in configuration file"
5159 .cindex "configuration file" "including other files"
5160 .cindex "&`.include`& in configuration file"
5161 .cindex "&`.include_if_exists`& in configuration file"
5162 You can include other files inside Exim's runtime configuration file by
5165 &`.include`& <&'filename'&>
5166 &`.include_if_exists`& <&'filename'&>
5168 on a line by itself. Double quotes round the filename are optional. If you use
5169 the first form, a configuration error occurs if the file does not exist; the
5170 second form does nothing for non-existent files.
5171 The first form allows a relative name. It is resolved relative to
5172 the directory of the including file. For the second form an absolute filename
5175 Includes may be nested to any depth, but remember that Exim reads its
5176 configuration file often, so it is a good idea to keep them to a minimum.
5177 If you change the contents of an included file, you must HUP the daemon,
5178 because an included file is read only when the configuration itself is read.
5180 The processing of inclusions happens early, at a physical line level, so, like
5181 comment lines, an inclusion can be used in the middle of an option setting,
5184 hosts_lookup = a.b.c \
5187 Include processing happens after macro processing (see below). Its effect is to
5188 process the lines of the included file as if they occurred inline where the
5193 .section "Macros in the configuration file" "SECTmacrodefs"
5194 .cindex "macro" "description of"
5195 .cindex "configuration file" "macros"
5196 If a line in the main part of the configuration (that is, before the first
5197 &"begin"& line) begins with an upper case letter, it is taken as a macro
5198 definition, and must be of the form
5200 <&'name'&> = <&'rest of line'&>
5202 The name must consist of letters, digits, and underscores, and need not all be
5203 in upper case, though that is recommended. The rest of the line, including any
5204 continuations, is the replacement text, and has leading and trailing white
5205 space removed. Quotes are not removed. The replacement text can never end with
5206 a backslash character, but this doesn't seem to be a serious limitation.
5208 Macros may also be defined between router, transport, authenticator, or ACL
5209 definitions. They may not, however, be defined within an individual driver or
5210 ACL, or in the &%local_scan%&, retry, or rewrite sections of the configuration.
5212 .section "Macro substitution" "SECID42"
5213 Once a macro is defined, all subsequent lines in the file (and any included
5214 files) are scanned for the macro name; if there are several macros, the line is
5215 scanned for each, in turn, in the order in which the macros are defined. The
5216 replacement text is not re-scanned for the current macro, though it is scanned
5217 for subsequently defined macros. For this reason, a macro name may not contain
5218 the name of a previously defined macro as a substring. You could, for example,
5221 &`ABCD_XYZ = `&<&'something'&>
5222 &`ABCD = `&<&'something else'&>
5224 but putting the definitions in the opposite order would provoke a configuration
5225 error. Macro expansion is applied to individual physical lines from the file,
5226 before checking for line continuation or file inclusion (see above). If a line
5227 consists solely of a macro name, and the expansion of the macro is empty, the
5228 line is ignored. A macro at the start of a line may turn the line into a
5229 comment line or a &`.include`& line.
5232 .section "Redefining macros" "SECID43"
5233 Once defined, the value of a macro can be redefined later in the configuration
5234 (or in an included file). Redefinition is specified by using &'=='& instead of
5239 MAC == updated value
5241 Redefinition does not alter the order in which the macros are applied to the
5242 subsequent lines of the configuration file. It is still the same order in which
5243 the macros were originally defined. All that changes is the macro's value.
5244 Redefinition makes it possible to accumulate values. For example:
5248 MAC == MAC and something added
5250 This can be helpful in situations where the configuration file is built
5251 from a number of other files.
5253 .section "Overriding macro values" "SECID44"
5254 The values set for macros in the configuration file can be overridden by the
5255 &%-D%& command line option, but Exim gives up its root privilege when &%-D%& is
5256 used, unless called by root or the Exim user. A definition on the command line
5257 using the &%-D%& option causes all definitions and redefinitions within the
5262 .section "Example of macro usage" "SECID45"
5263 As an example of macro usage, consider a configuration where aliases are looked
5264 up in a MySQL database. It helps to keep the file less cluttered if long
5265 strings such as SQL statements are defined separately as macros, for example:
5267 ALIAS_QUERY = select mailbox from user where \
5268 login='${quote_mysql:$local_part}';
5270 This can then be used in a &(redirect)& router setting like this:
5272 data = ${lookup mysql{ALIAS_QUERY}}
5274 In earlier versions of Exim macros were sometimes used for domain, host, or
5275 address lists. In Exim 4 these are handled better by named lists &-- see
5276 section &<<SECTnamedlists>>&.
5279 .section "Builtin macros" "SECTbuiltinmacros"
5280 Exim defines some macros depending on facilities available, which may
5281 differ due to build-time definitions and from one release to another.
5282 All of these macros start with an underscore.
5283 They can be used to conditionally include parts of a configuration
5286 The following classes of macros are defined:
5288 &` _HAVE_* `& build-time defines
5289 &` _DRIVER_ROUTER_* `& router drivers
5290 &` _DRIVER_TRANSPORT_* `& transport drivers
5291 &` _DRIVER_AUTHENTICATOR_* `& authenticator drivers
5292 &` _LOG_* `& log_selector values
5293 &` _OPT_MAIN_* `& main config options
5294 &` _OPT_ROUTERS_* `& generic router options
5295 &` _OPT_TRANSPORTS_* `& generic transport options
5296 &` _OPT_AUTHENTICATORS_* `& generic authenticator options
5297 &` _OPT_ROUTER_*_* `& private router options
5298 &` _OPT_TRANSPORT_*_* `& private transport options
5299 &` _OPT_AUTHENTICATOR_*_* `& private authenticator options
5302 Use an &"exim -bP macros"& command to get the list of macros.
5305 .section "Conditional skips in the configuration file" "SECID46"
5306 .cindex "configuration file" "conditional skips"
5307 .cindex "&`.ifdef`&"
5308 You can use the directives &`.ifdef`&, &`.ifndef`&, &`.elifdef`&,
5309 &`.elifndef`&, &`.else`&, and &`.endif`& to dynamically include or exclude
5310 portions of the configuration file. The processing happens whenever the file is
5311 read (that is, when an Exim binary starts to run).
5313 The implementation is very simple. Instances of the first four directives must
5314 be followed by text that includes the names of one or macros. The condition
5315 that is tested is whether or not any macro substitution has taken place in the
5319 message_size_limit = 50M
5321 message_size_limit = 100M
5324 sets a message size limit of 50M if the macro &`AAA`& is defined
5325 (or &`A`& or &`AA`&), and 100M
5326 otherwise. If there is more than one macro named on the line, the condition
5327 is true if any of them are defined. That is, it is an &"or"& condition. To
5328 obtain an &"and"& condition, you need to use nested &`.ifdef`&s.
5330 Although you can use a macro expansion to generate one of these directives,
5331 it is not very useful, because the condition &"there was a macro substitution
5332 in this line"& will always be true.
5334 Text following &`.else`& and &`.endif`& is ignored, and can be used as comment
5335 to clarify complicated nestings.
5339 .section "Common option syntax" "SECTcos"
5340 .cindex "common option syntax"
5341 .cindex "syntax of common options"
5342 .cindex "configuration file" "common option syntax"
5343 For the main set of options, driver options, and &[local_scan()]& options,
5344 each setting is on a line by itself, and starts with a name consisting of
5345 lower-case letters and underscores. Many options require a data value, and in
5346 these cases the name must be followed by an equals sign (with optional white
5347 space) and then the value. For example:
5349 qualify_domain = mydomain.example.com
5351 .cindex "hiding configuration option values"
5352 .cindex "configuration options" "hiding value of"
5353 .cindex "options" "hiding value of"
5354 Some option settings may contain sensitive data, for example, passwords for
5355 accessing databases. To stop non-admin users from using the &%-bP%& command
5356 line option to read these values, you can precede the option settings with the
5357 word &"hide"&. For example:
5359 hide mysql_servers = localhost/users/admin/secret-password
5361 For non-admin users, such options are displayed like this:
5363 mysql_servers = <value not displayable>
5365 If &"hide"& is used on a driver option, it hides the value of that option on
5366 all instances of the same driver.
5368 The following sections describe the syntax used for the different data types
5369 that are found in option settings.
5372 .section "Boolean options" "SECID47"
5373 .cindex "format" "boolean"
5374 .cindex "boolean configuration values"
5375 .oindex "&%no_%&&'xxx'&"
5376 .oindex "&%not_%&&'xxx'&"
5377 Options whose type is given as boolean are on/off switches. There are two
5378 different ways of specifying such options: with and without a data value. If
5379 the option name is specified on its own without data, the switch is turned on;
5380 if it is preceded by &"no_"& or &"not_"& the switch is turned off. However,
5381 boolean options may be followed by an equals sign and one of the words
5382 &"true"&, &"false"&, &"yes"&, or &"no"&, as an alternative syntax. For example,
5383 the following two settings have exactly the same effect:
5388 The following two lines also have the same (opposite) effect:
5393 You can use whichever syntax you prefer.
5398 .section "Integer values" "SECID48"
5399 .cindex "integer configuration values"
5400 .cindex "format" "integer"
5401 If an option's type is given as &"integer"&, the value can be given in decimal,
5402 hexadecimal, or octal. If it starts with a digit greater than zero, a decimal
5403 number is assumed. Otherwise, it is treated as an octal number unless it starts
5404 with the characters &"0x"&, in which case the remainder is interpreted as a
5407 If an integer value is followed by the letter K, it is multiplied by 1024; if
5408 it is followed by the letter M, it is multiplied by 1024x1024;
5409 if by the letter G, 1024x1024x1024.
5411 of integer option settings are output, values which are an exact multiple of
5412 1024 or 1024x1024 are sometimes, but not always, printed using the letters K
5413 and M. The printing style is independent of the actual input format that was
5417 .section "Octal integer values" "SECID49"
5418 .cindex "integer format"
5419 .cindex "format" "octal integer"
5420 If an option's type is given as &"octal integer"&, its value is always
5421 interpreted as an octal number, whether or not it starts with the digit zero.
5422 Such options are always output in octal.
5425 .section "Fixed point numbers" "SECID50"
5426 .cindex "fixed point configuration values"
5427 .cindex "format" "fixed point"
5428 If an option's type is given as &"fixed-point"&, its value must be a decimal
5429 integer, optionally followed by a decimal point and up to three further digits.
5433 .section "Time intervals" "SECTtimeformat"
5434 .cindex "time interval" "specifying in configuration"
5435 .cindex "format" "time interval"
5436 A time interval is specified as a sequence of numbers, each followed by one of
5437 the following letters, with no intervening white space:
5447 For example, &"3h50m"& specifies 3 hours and 50 minutes. The values of time
5448 intervals are output in the same format. Exim does not restrict the values; it
5449 is perfectly acceptable, for example, to specify &"90m"& instead of &"1h30m"&.
5453 .section "String values" "SECTstrings"
5454 .cindex "string" "format of configuration values"
5455 .cindex "format" "string"
5456 If an option's type is specified as &"string"&, the value can be specified with
5457 or without double-quotes. If it does not start with a double-quote, the value
5458 consists of the remainder of the line plus any continuation lines, starting at
5459 the first character after any leading white space, with trailing white space
5460 removed, and with no interpretation of the characters in the string. Because
5461 Exim removes comment lines (those beginning with #) at an early stage, they can
5462 appear in the middle of a multi-line string. The following two settings are
5463 therefore equivalent:
5465 trusted_users = uucp:mail
5466 trusted_users = uucp:\
5467 # This comment line is ignored
5470 .cindex "string" "quoted"
5471 .cindex "escape characters in quoted strings"
5472 If a string does start with a double-quote, it must end with a closing
5473 double-quote, and any backslash characters other than those used for line
5474 continuation are interpreted as escape characters, as follows:
5477 .irow &`\\`& "single backslash"
5478 .irow &`\n`& "newline"
5479 .irow &`\r`& "carriage return"
5481 .irow "&`\`&<&'octal digits'&>" "up to 3 octal digits specify one character"
5482 .irow "&`\x`&<&'hex digits'&>" "up to 2 hexadecimal digits specify one &&&
5486 If a backslash is followed by some other character, including a double-quote
5487 character, that character replaces the pair.
5489 Quoting is necessary only if you want to make use of the backslash escapes to
5490 insert special characters, or if you need to specify a value with leading or
5491 trailing spaces. These cases are rare, so quoting is almost never needed in
5492 current versions of Exim. In versions of Exim before 3.14, quoting was required
5493 in order to continue lines, so you may come across older configuration files
5494 and examples that apparently quote unnecessarily.
5497 .section "Expanded strings" "SECID51"
5498 .cindex "expansion" "definition of"
5499 Some strings in the configuration file are subjected to &'string expansion'&,
5500 by which means various parts of the string may be changed according to the
5501 circumstances (see chapter &<<CHAPexpand>>&). The input syntax for such strings
5502 is as just described; in particular, the handling of backslashes in quoted
5503 strings is done as part of the input process, before expansion takes place.
5504 However, backslash is also an escape character for the expander, so any
5505 backslashes that are required for that reason must be doubled if they are
5506 within a quoted configuration string.
5509 .section "User and group names" "SECID52"
5510 .cindex "user name" "format of"
5511 .cindex "format" "user name"
5512 .cindex "groups" "name format"
5513 .cindex "format" "group name"
5514 User and group names are specified as strings, using the syntax described
5515 above, but the strings are interpreted specially. A user or group name must
5516 either consist entirely of digits, or be a name that can be looked up using the
5517 &[getpwnam()]& or &[getgrnam()]& function, as appropriate.
5520 .section "List construction" "SECTlistconstruct"
5521 .cindex "list" "syntax of in configuration"
5522 .cindex "format" "list item in configuration"
5523 .cindex "string" "list, definition of"
5524 The data for some configuration options is a list of items, with colon as the
5525 default separator. Many of these options are shown with type &"string list"& in
5526 the descriptions later in this document. Others are listed as &"domain list"&,
5527 &"host list"&, &"address list"&, or &"local part list"&. Syntactically, they
5528 are all the same; however, those other than &"string list"& are subject to
5529 particular kinds of interpretation, as described in chapter
5530 &<<CHAPdomhosaddlists>>&.
5532 In all these cases, the entire list is treated as a single string as far as the
5533 input syntax is concerned. The &%trusted_users%& setting in section
5534 &<<SECTstrings>>& above is an example. If a colon is actually needed in an item
5535 in a list, it must be entered as two colons. Leading and trailing white space
5536 on each item in a list is ignored. This makes it possible to include items that
5537 start with a colon, and in particular, certain forms of IPv6 address. For
5540 local_interfaces = 127.0.0.1 : ::::1
5542 contains two IP addresses, the IPv4 address 127.0.0.1 and the IPv6 address ::1.
5544 &*Note*&: Although leading and trailing white space is ignored in individual
5545 list items, it is not ignored when parsing the list. The spaces around the first
5546 colon in the example above are necessary. If they were not there, the list would
5547 be interpreted as the two items 127.0.0.1:: and 1.
5549 .section "Changing list separators" "SECTlistsepchange"
5550 .cindex "list separator" "changing"
5551 .cindex "IPv6" "addresses in lists"
5552 Doubling colons in IPv6 addresses is an unwelcome chore, so a mechanism was
5553 introduced to allow the separator character to be changed. If a list begins
5554 with a left angle bracket, followed by any punctuation character, that
5555 character is used instead of colon as the list separator. For example, the list
5556 above can be rewritten to use a semicolon separator like this:
5558 local_interfaces = <; 127.0.0.1 ; ::1
5560 This facility applies to all lists, with the exception of the list in
5561 &%log_file_path%&. It is recommended that the use of non-colon separators be
5562 confined to circumstances where they really are needed.
5564 .cindex "list separator" "newline as"
5565 .cindex "newline" "as list separator"
5566 It is also possible to use newline and other control characters (those with
5567 code values less than 32, plus DEL) as separators in lists. Such separators
5568 must be provided literally at the time the list is processed. For options that
5569 are string-expanded, you can write the separator using a normal escape
5570 sequence. This will be processed by the expander before the string is
5571 interpreted as a list. For example, if a newline-separated list of domains is
5572 generated by a lookup, you can process it directly by a line such as this:
5574 domains = <\n ${lookup mysql{.....}}
5576 This avoids having to change the list separator in such data. You are unlikely
5577 to want to use a control character as a separator in an option that is not
5578 expanded, because the value is literal text. However, it can be done by giving
5579 the value in quotes. For example:
5581 local_interfaces = "<\n 127.0.0.1 \n ::1"
5583 Unlike printing character separators, which can be included in list items by
5584 doubling, it is not possible to include a control character as data when it is
5585 set as the separator. Two such characters in succession are interpreted as
5586 enclosing an empty list item.
5590 .section "Empty items in lists" "SECTempitelis"
5591 .cindex "list" "empty item in"
5592 An empty item at the end of a list is always ignored. In other words, trailing
5593 separator characters are ignored. Thus, the list in
5595 senders = user@domain :
5597 contains only a single item. If you want to include an empty string as one item
5598 in a list, it must not be the last item. For example, this list contains three
5599 items, the second of which is empty:
5601 senders = user1@domain : : user2@domain
5603 &*Note*&: There must be white space between the two colons, as otherwise they
5604 are interpreted as representing a single colon data character (and the list
5605 would then contain just one item). If you want to specify a list that contains
5606 just one, empty item, you can do it as in this example:
5610 In this case, the first item is empty, and the second is discarded because it
5611 is at the end of the list.
5616 .section "Format of driver configurations" "SECTfordricon"
5617 .cindex "drivers" "configuration format"
5618 There are separate parts in the configuration for defining routers, transports,
5619 and authenticators. In each part, you are defining a number of driver
5620 instances, each with its own set of options. Each driver instance is defined by
5621 a sequence of lines like this:
5623 <&'instance name'&>:
5628 In the following example, the instance name is &(localuser)&, and it is
5629 followed by three options settings:
5634 transport = local_delivery
5636 For each driver instance, you specify which Exim code module it uses &-- by the
5637 setting of the &%driver%& option &-- and (optionally) some configuration
5638 settings. For example, in the case of transports, if you want a transport to
5639 deliver with SMTP you would use the &(smtp)& driver; if you want to deliver to
5640 a local file you would use the &(appendfile)& driver. Each of the drivers is
5641 described in detail in its own separate chapter later in this manual.
5643 You can have several routers, transports, or authenticators that are based on
5644 the same underlying driver (each must have a different instance name).
5646 The order in which routers are defined is important, because addresses are
5647 passed to individual routers one by one, in order. The order in which
5648 transports are defined does not matter at all. The order in which
5649 authenticators are defined is used only when Exim, as a client, is searching
5650 them to find one that matches an authentication mechanism offered by the
5653 .cindex "generic options"
5654 .cindex "options" "generic &-- definition of"
5655 Within a driver instance definition, there are two kinds of option: &'generic'&
5656 and &'private'&. The generic options are those that apply to all drivers of the
5657 same type (that is, all routers, all transports or all authenticators). The
5658 &%driver%& option is a generic option that must appear in every definition.
5659 .cindex "private options"
5660 The private options are special for each driver, and none need appear, because
5661 they all have default values.
5663 The options may appear in any order, except that the &%driver%& option must
5664 precede any private options, since these depend on the particular driver. For
5665 this reason, it is recommended that &%driver%& always be the first option.
5667 Driver instance names, which are used for reference in log entries and
5668 elsewhere, can be any sequence of letters, digits, and underscores (starting
5669 with a letter) and must be unique among drivers of the same type. A router and
5670 a transport (for example) can each have the same name, but no two router
5671 instances can have the same name. The name of a driver instance should not be
5672 confused with the name of the underlying driver module. For example, the
5673 configuration lines:
5678 create an instance of the &(smtp)& transport driver whose name is
5679 &(remote_smtp)&. The same driver code can be used more than once, with
5680 different instance names and different option settings each time. A second
5681 instance of the &(smtp)& transport, with different options, might be defined
5687 command_timeout = 10s
5689 The names &(remote_smtp)& and &(special_smtp)& would be used to reference
5690 these transport instances from routers, and these names would appear in log
5693 Comment lines may be present in the middle of driver specifications. The full
5694 list of option settings for any particular driver instance, including all the
5695 defaulted values, can be extracted by making use of the &%-bP%& command line
5703 . ////////////////////////////////////////////////////////////////////////////
5704 . ////////////////////////////////////////////////////////////////////////////
5706 .chapter "The default configuration file" "CHAPdefconfil"
5707 .scindex IIDconfiwal "configuration file" "default &""walk through""&"
5708 .cindex "default" "configuration file &""walk through""&"
5709 The default configuration file supplied with Exim as &_src/configure.default_&
5710 is sufficient for a host with simple mail requirements. As an introduction to
5711 the way Exim is configured, this chapter &"walks through"& the default
5712 configuration, giving brief explanations of the settings. Detailed descriptions
5713 of the options are given in subsequent chapters. The default configuration file
5714 itself contains extensive comments about ways you might want to modify the
5715 initial settings. However, note that there are many options that are not
5716 mentioned at all in the default configuration.
5720 .section "Macros" "SECTdefconfmacros"
5721 All macros should be defined before any options.
5723 One macro is specified, but commented out, in the default configuration:
5725 # ROUTER_SMARTHOST=MAIL.HOSTNAME.FOR.CENTRAL.SERVER.EXAMPLE
5727 If all off-site mail is expected to be delivered to a "smarthost", then set the
5728 hostname here and uncomment the macro. This will affect which router is used
5729 later on. If this is left commented out, then Exim will perform direct-to-MX
5730 deliveries using a &(dnslookup)& router.
5732 In addition to macros defined here, Exim includes a number of built-in macros
5733 to enable configuration to be guarded by a binary built with support for a
5734 given feature. See section &<<SECTbuiltinmacros>>& for more details.
5737 .section "Main configuration settings" "SECTdefconfmain"
5738 The main (global) configuration option settings section must always come first
5739 in the file, after the macros.
5740 The first thing you'll see in the file, after some initial comments, is the line
5742 # primary_hostname =
5744 This is a commented-out setting of the &%primary_hostname%& option. Exim needs
5745 to know the official, fully qualified name of your host, and this is where you
5746 can specify it. However, in most cases you do not need to set this option. When
5747 it is unset, Exim uses the &[uname()]& system function to obtain the host name.
5749 The first three non-comment configuration lines are as follows:
5751 domainlist local_domains = @
5752 domainlist relay_to_domains =
5753 hostlist relay_from_hosts = 127.0.0.1
5755 These are not, in fact, option settings. They are definitions of two named
5756 domain lists and one named host list. Exim allows you to give names to lists of
5757 domains, hosts, and email addresses, in order to make it easier to manage the
5758 configuration file (see section &<<SECTnamedlists>>&).
5760 The first line defines a domain list called &'local_domains'&; this is used
5761 later in the configuration to identify domains that are to be delivered
5764 .cindex "@ in a domain list"
5765 There is just one item in this list, the string &"@"&. This is a special form
5766 of entry which means &"the name of the local host"&. Thus, if the local host is
5767 called &'a.host.example'&, mail to &'any.user@a.host.example'& is expected to
5768 be delivered locally. Because the local host's name is referenced indirectly,
5769 the same configuration file can be used on different hosts.
5771 The second line defines a domain list called &'relay_to_domains'&, but the
5772 list itself is empty. Later in the configuration we will come to the part that
5773 controls mail relaying through the local host; it allows relaying to any
5774 domains in this list. By default, therefore, no relaying on the basis of a mail
5775 domain is permitted.
5777 The third line defines a host list called &'relay_from_hosts'&. This list is
5778 used later in the configuration to permit relaying from any host or IP address
5779 that matches the list. The default contains just the IP address of the IPv4
5780 loopback interface, which means that processes on the local host are able to
5781 submit mail for relaying by sending it over TCP/IP to that interface. No other
5782 hosts are permitted to submit messages for relaying.
5784 Just to be sure there's no misunderstanding: at this point in the configuration
5785 we aren't actually setting up any controls. We are just defining some domains
5786 and hosts that will be used in the controls that are specified later.
5788 The next two configuration lines are genuine option settings:
5790 acl_smtp_rcpt = acl_check_rcpt
5791 acl_smtp_data = acl_check_data
5793 These options specify &'Access Control Lists'& (ACLs) that are to be used
5794 during an incoming SMTP session for every recipient of a message (every RCPT
5795 command), and after the contents of the message have been received,
5796 respectively. The names of the lists are &'acl_check_rcpt'& and
5797 &'acl_check_data'&, and we will come to their definitions below, in the ACL
5798 section of the configuration. The RCPT ACL controls which recipients are
5799 accepted for an incoming message &-- if a configuration does not provide an ACL
5800 to check recipients, no SMTP mail can be accepted. The DATA ACL allows the
5801 contents of a message to be checked.
5803 Two commented-out option settings are next:
5805 # av_scanner = clamd:/tmp/clamd
5806 # spamd_address = 127.0.0.1 783
5808 These are example settings that can be used when Exim is compiled with the
5809 content-scanning extension. The first specifies the interface to the virus
5810 scanner, and the second specifies the interface to SpamAssassin. Further
5811 details are given in chapter &<<CHAPexiscan>>&.
5813 Three more commented-out option settings follow:
5815 # tls_advertise_hosts = *
5816 # tls_certificate = /etc/ssl/exim.crt
5817 # tls_privatekey = /etc/ssl/exim.pem
5819 These are example settings that can be used when Exim is compiled with
5820 support for TLS (aka SSL) as described in section &<<SECTinctlsssl>>&. The
5821 first one specifies the list of clients that are allowed to use TLS when
5822 connecting to this server; in this case, the wildcard means all clients. The
5823 other options specify where Exim should find its TLS certificate and private
5824 key, which together prove the server's identity to any clients that connect.
5825 More details are given in chapter &<<CHAPTLS>>&.
5827 Another two commented-out option settings follow:
5829 # daemon_smtp_ports = 25 : 465 : 587
5830 # tls_on_connect_ports = 465
5832 .cindex "port" "465 and 587"
5833 .cindex "port" "for message submission"
5834 .cindex "message" "submission, ports for"
5835 .cindex "submissions protocol"
5836 .cindex "smtps protocol"
5837 .cindex "ssmtp protocol"
5838 .cindex "SMTP" "submissions protocol"
5839 .cindex "SMTP" "ssmtp protocol"
5840 .cindex "SMTP" "smtps protocol"
5841 These options provide better support for roaming users who wish to use this
5842 server for message submission. They are not much use unless you have turned on
5843 TLS (as described in the previous paragraph) and authentication (about which
5844 more in section &<<SECTdefconfauth>>&).
5845 Mail submission from mail clients (MUAs) should be separate from inbound mail
5846 to your domain (MX delivery) for various good reasons (eg, ability to impose
5847 much saner TLS protocol and ciphersuite requirements without unintended
5849 RFC 6409 (previously 4409) specifies use of port 587 for SMTP Submission,
5850 which uses STARTTLS, so this is the &"submission"& port.
5851 RFC 8314 specifies use of port 465 as the &"submissions"& protocol,
5852 which should be used in preference to 587.
5853 You should also consider deploying SRV records to help clients find
5855 Older names for &"submissions"& are &"smtps"& and &"ssmtp"&.
5857 Two more commented-out options settings follow:
5860 # qualify_recipient =
5862 The first of these specifies a domain that Exim uses when it constructs a
5863 complete email address from a local login name. This is often needed when Exim
5864 receives a message from a local process. If you do not set &%qualify_domain%&,
5865 the value of &%primary_hostname%& is used. If you set both of these options,
5866 you can have different qualification domains for sender and recipient
5867 addresses. If you set only the first one, its value is used in both cases.
5869 .cindex "domain literal" "recognizing format"
5870 The following line must be uncommented if you want Exim to recognize
5871 addresses of the form &'user@[10.11.12.13]'& that is, with a &"domain literal"&
5872 (an IP address within square brackets) instead of a named domain.
5874 # allow_domain_literals
5876 The RFCs still require this form, but many people think that in the modern
5877 Internet it makes little sense to permit mail to be sent to specific hosts by
5878 quoting their IP addresses. This ancient format has been used by people who
5879 try to abuse hosts by using them for unwanted relaying. However, some
5880 people believe there are circumstances (for example, messages addressed to
5881 &'postmaster'&) where domain literals are still useful.
5883 The next configuration line is a kind of trigger guard:
5887 It specifies that no delivery must ever be run as the root user. The normal
5888 convention is to set up &'root'& as an alias for the system administrator. This
5889 setting is a guard against slips in the configuration.
5890 The list of users specified by &%never_users%& is not, however, the complete
5891 list; the build-time configuration in &_Local/Makefile_& has an option called
5892 FIXED_NEVER_USERS specifying a list that cannot be overridden. The
5893 contents of &%never_users%& are added to this list. By default
5894 FIXED_NEVER_USERS also specifies root.
5896 When a remote host connects to Exim in order to send mail, the only information
5897 Exim has about the host's identity is its IP address. The next configuration
5902 specifies that Exim should do a reverse DNS lookup on all incoming connections,
5903 in order to get a host name. This improves the quality of the logging
5904 information, but if you feel it is too expensive, you can remove it entirely,
5905 or restrict the lookup to hosts on &"nearby"& networks.
5906 Note that it is not always possible to find a host name from an IP address,
5907 because not all DNS reverse zones are maintained, and sometimes DNS servers are
5910 The next two lines are concerned with &'ident'& callbacks, as defined by RFC
5911 1413 (hence their names):
5914 rfc1413_query_timeout = 0s
5916 These settings cause Exim to avoid ident callbacks for all incoming SMTP calls.
5917 Few hosts offer RFC1413 service these days; calls have to be
5918 terminated by a timeout and this needlessly delays the startup
5919 of an incoming SMTP connection.
5920 If you have hosts for which you trust RFC1413 and need this
5921 information, you can change this.
5923 This line enables an efficiency SMTP option. It is negotiated by clients
5924 and not expected to cause problems but can be disabled if needed.
5929 When Exim receives messages over SMTP connections, it expects all addresses to
5930 be fully qualified with a domain, as required by the SMTP definition. However,
5931 if you are running a server to which simple clients submit messages, you may
5932 find that they send unqualified addresses. The two commented-out options:
5934 # sender_unqualified_hosts =
5935 # recipient_unqualified_hosts =
5937 show how you can specify hosts that are permitted to send unqualified sender
5938 and recipient addresses, respectively.
5940 The &%log_selector%& option is used to increase the detail of logging
5943 log_selector = +smtp_protocol_error +smtp_syntax_error \
5944 +tls_certificate_verified
5947 The &%percent_hack_domains%& option is also commented out:
5949 # percent_hack_domains =
5951 It provides a list of domains for which the &"percent hack"& is to operate.
5952 This is an almost obsolete form of explicit email routing. If you do not know
5953 anything about it, you can safely ignore this topic.
5955 The next two settings in the main part of the default configuration are
5956 concerned with messages that have been &"frozen"& on Exim's queue. When a
5957 message is frozen, Exim no longer continues to try to deliver it. Freezing
5958 occurs when a bounce message encounters a permanent failure because the sender
5959 address of the original message that caused the bounce is invalid, so the
5960 bounce cannot be delivered. This is probably the most common case, but there
5961 are also other conditions that cause freezing, and frozen messages are not
5962 always bounce messages.
5964 ignore_bounce_errors_after = 2d
5965 timeout_frozen_after = 7d
5967 The first of these options specifies that failing bounce messages are to be
5968 discarded after 2 days in the queue. The second specifies that any frozen
5969 message (whether a bounce message or not) is to be timed out (and discarded)
5970 after a week. In this configuration, the first setting ensures that no failing
5971 bounce message ever lasts a week.
5973 Exim queues it's messages in a spool directory. If you expect to have
5974 large queues, you may consider using this option. It splits the spool
5975 directory into subdirectories to avoid file system degradation from
5976 many files in a single directory, resulting in better performance.
5977 Manual manipulation of queued messages becomes more complex (though fortunately
5980 # split_spool_directory = true
5983 In an ideal world everybody follows the standards. For non-ASCII
5984 messages RFC 2047 is a standard, allowing a maximum line length of 76
5985 characters. Exim adheres that standard and won't process messages which
5986 violate this standard. (Even ${rfc2047:...} expansions will fail.)
5987 In particular, the Exim maintainers have had multiple reports of
5988 problems from Russian administrators of issues until they disable this
5989 check, because of some popular, yet buggy, mail composition software.
5991 # check_rfc2047_length = false
5994 If you need to be strictly RFC compliant you may wish to disable the
5995 8BITMIME advertisement. Use this, if you exchange mails with systems
5996 that are not 8-bit clean.
5998 # accept_8bitmime = false
6001 Libraries you use may depend on specific environment settings. This
6002 imposes a security risk (e.g. PATH). There are two lists:
6003 &%keep_environment%& for the variables to import as they are, and
6004 &%add_environment%& for variables we want to set to a fixed value.
6005 Note that TZ is handled separately, by the &%timezone%& runtime
6006 option and by the TIMEZONE_DEFAULT buildtime option.
6008 # keep_environment = ^LDAP
6009 # add_environment = PATH=/usr/bin::/bin
6013 .section "ACL configuration" "SECID54"
6014 .cindex "default" "ACLs"
6015 .cindex "&ACL;" "default configuration"
6016 In the default configuration, the ACL section follows the main configuration.
6017 It starts with the line
6021 and it contains the definitions of two ACLs, called &'acl_check_rcpt'& and
6022 &'acl_check_data'&, that were referenced in the settings of &%acl_smtp_rcpt%&
6023 and &%acl_smtp_data%& above.
6025 .cindex "RCPT" "ACL for"
6026 The first ACL is used for every RCPT command in an incoming SMTP message. Each
6027 RCPT command specifies one of the message's recipients. The ACL statements
6028 are considered in order, until the recipient address is either accepted or
6029 rejected. The RCPT command is then accepted or rejected, according to the
6030 result of the ACL processing.
6034 This line, consisting of a name terminated by a colon, marks the start of the
6039 This ACL statement accepts the recipient if the sending host matches the list.
6040 But what does that strange list mean? It doesn't actually contain any host
6041 names or IP addresses. The presence of the colon puts an empty item in the
6042 list; Exim matches this only if the incoming message did not come from a remote
6043 host, because in that case, the remote hostname is empty. The colon is
6044 important. Without it, the list itself is empty, and can never match anything.
6046 What this statement is doing is to accept unconditionally all recipients in
6047 messages that are submitted by SMTP from local processes using the standard
6048 input and output (that is, not using TCP/IP). A number of MUAs operate in this
6051 deny domains = +local_domains
6052 local_parts = ^[.] : ^.*[@%!/|]
6053 message = Restricted characters in address
6055 deny domains = !+local_domains
6056 local_parts = ^[./|] : ^.*[@%!] : ^.*/\\.\\./
6057 message = Restricted characters in address
6059 These statements are concerned with local parts that contain any of the
6060 characters &"@"&, &"%"&, &"!"&, &"/"&, &"|"&, or dots in unusual places.
6061 Although these characters are entirely legal in local parts (in the case of
6062 &"@"& and leading dots, only if correctly quoted), they do not commonly occur
6063 in Internet mail addresses.
6065 The first three have in the past been associated with explicitly routed
6066 addresses (percent is still sometimes used &-- see the &%percent_hack_domains%&
6067 option). Addresses containing these characters are regularly tried by spammers
6068 in an attempt to bypass relaying restrictions, and also by open relay testing
6069 programs. Unless you really need them it is safest to reject these characters
6070 at this early stage. This configuration is heavy-handed in rejecting these
6071 characters for all messages it accepts from remote hosts. This is a deliberate
6072 policy of being as safe as possible.
6074 The first rule above is stricter, and is applied to messages that are addressed
6075 to one of the local domains handled by this host. This is implemented by the
6076 first condition, which restricts it to domains that are listed in the
6077 &'local_domains'& domain list. The &"+"& character is used to indicate a
6078 reference to a named list. In this configuration, there is just one domain in
6079 &'local_domains'&, but in general there may be many.
6081 The second condition on the first statement uses two regular expressions to
6082 block local parts that begin with a dot or contain &"@"&, &"%"&, &"!"&, &"/"&,
6083 or &"|"&. If you have local accounts that include these characters, you will
6084 have to modify this rule.
6086 Empty components (two dots in a row) are not valid in RFC 2822, but Exim
6087 allows them because they have been encountered in practice. (Consider the
6088 common convention of local parts constructed as
6089 &"&'first-initial.second-initial.family-name'&"& when applied to someone like
6090 the author of Exim, who has no second initial.) However, a local part starting
6091 with a dot or containing &"/../"& can cause trouble if it is used as part of a
6092 filename (for example, for a mailing list). This is also true for local parts
6093 that contain slashes. A pipe symbol can also be troublesome if the local part
6094 is incorporated unthinkingly into a shell command line.
6096 The second rule above applies to all other domains, and is less strict. This
6097 allows your own users to send outgoing messages to sites that use slashes
6098 and vertical bars in their local parts. It blocks local parts that begin
6099 with a dot, slash, or vertical bar, but allows these characters within the
6100 local part. However, the sequence &"/../"& is barred. The use of &"@"&, &"%"&,
6101 and &"!"& is blocked, as before. The motivation here is to prevent your users
6102 (or your users' viruses) from mounting certain kinds of attack on remote sites.
6104 accept local_parts = postmaster
6105 domains = +local_domains
6107 This statement, which has two conditions, accepts an incoming address if the
6108 local part is &'postmaster'& and the domain is one of those listed in the
6109 &'local_domains'& domain list. The &"+"& character is used to indicate a
6110 reference to a named list. In this configuration, there is just one domain in
6111 &'local_domains'&, but in general there may be many.
6113 The presence of this statement means that mail to postmaster is never blocked
6114 by any of the subsequent tests. This can be helpful while sorting out problems
6115 in cases where the subsequent tests are incorrectly denying access.
6117 require verify = sender
6119 This statement requires the sender address to be verified before any subsequent
6120 ACL statement can be used. If verification fails, the incoming recipient
6121 address is refused. Verification consists of trying to route the address, to
6122 see if a bounce message could be delivered to it. In the case of remote
6123 addresses, basic verification checks only the domain, but &'callouts'& can be
6124 used for more verification if required. Section &<<SECTaddressverification>>&
6125 discusses the details of address verification.
6127 accept hosts = +relay_from_hosts
6128 control = submission
6130 This statement accepts the address if the message is coming from one of the
6131 hosts that are defined as being allowed to relay through this host. Recipient
6132 verification is omitted here, because in many cases the clients are dumb MUAs
6133 that do not cope well with SMTP error responses. For the same reason, the
6134 second line specifies &"submission mode"& for messages that are accepted. This
6135 is described in detail in section &<<SECTsubmodnon>>&; it causes Exim to fix
6136 messages that are deficient in some way, for example, because they lack a
6137 &'Date:'& header line. If you are actually relaying out from MTAs, you should
6138 probably add recipient verification here, and disable submission mode.
6140 accept authenticated = *
6141 control = submission
6143 This statement accepts the address if the client host has authenticated itself.
6144 Submission mode is again specified, on the grounds that such messages are most
6145 likely to come from MUAs. The default configuration does not define any
6146 authenticators, though it does include some nearly complete commented-out
6147 examples described in &<<SECTdefconfauth>>&. This means that no client can in
6148 fact authenticate until you complete the authenticator definitions.
6150 require message = relay not permitted
6151 domains = +local_domains : +relay_to_domains
6153 This statement rejects the address if its domain is neither a local domain nor
6154 one of the domains for which this host is a relay.
6156 require verify = recipient
6158 This statement requires the recipient address to be verified; if verification
6159 fails, the address is rejected.
6161 # deny dnslists = black.list.example
6162 # message = rejected because $sender_host_address \
6163 # is in a black list at $dnslist_domain\n\
6166 # warn dnslists = black.list.example
6167 # add_header = X-Warning: $sender_host_address is in \
6168 # a black list at $dnslist_domain
6169 # log_message = found in $dnslist_domain
6171 These commented-out lines are examples of how you could configure Exim to check
6172 sending hosts against a DNS black list. The first statement rejects messages
6173 from blacklisted hosts, whereas the second just inserts a warning header
6176 # require verify = csa
6178 This commented-out line is an example of how you could turn on client SMTP
6179 authorization (CSA) checking. Such checks do DNS lookups for special SRV
6184 The final statement in the first ACL unconditionally accepts any recipient
6185 address that has successfully passed all the previous tests.
6189 This line marks the start of the second ACL, and names it. Most of the contents
6190 of this ACL are commented out:
6193 # message = This message contains a virus \
6196 These lines are examples of how to arrange for messages to be scanned for
6197 viruses when Exim has been compiled with the content-scanning extension, and a
6198 suitable virus scanner is installed. If the message is found to contain a
6199 virus, it is rejected with the given custom error message.
6201 # warn spam = nobody
6202 # message = X-Spam_score: $spam_score\n\
6203 # X-Spam_score_int: $spam_score_int\n\
6204 # X-Spam_bar: $spam_bar\n\
6205 # X-Spam_report: $spam_report
6207 These lines are an example of how to arrange for messages to be scanned by
6208 SpamAssassin when Exim has been compiled with the content-scanning extension,
6209 and SpamAssassin has been installed. The SpamAssassin check is run with
6210 &`nobody`& as its user parameter, and the results are added to the message as a
6211 series of extra header line. In this case, the message is not rejected,
6212 whatever the spam score.
6216 This final line in the DATA ACL accepts the message unconditionally.
6219 .section "Router configuration" "SECID55"
6220 .cindex "default" "routers"
6221 .cindex "routers" "default"
6222 The router configuration comes next in the default configuration, introduced
6227 Routers are the modules in Exim that make decisions about where to send
6228 messages. An address is passed to each router, in turn, until it is either
6229 accepted, or failed. This means that the order in which you define the routers
6230 matters. Each router is fully described in its own chapter later in this
6231 manual. Here we give only brief overviews.
6234 # driver = ipliteral
6235 # domains = !+local_domains
6236 # transport = remote_smtp
6238 .cindex "domain literal" "default router"
6239 This router is commented out because the majority of sites do not want to
6240 support domain literal addresses (those of the form &'user@[10.9.8.7]'&). If
6241 you uncomment this router, you also need to uncomment the setting of
6242 &%allow_domain_literals%& in the main part of the configuration.
6244 Which router is used next depends upon whether or not the ROUTER_SMARTHOST
6245 macro has been defined, per
6247 .ifdef ROUTER_SMARTHOST
6256 If ROUTER_SMARTHOST has been defined, either at the top of the file or on the
6257 command-line, then we route all non-local mail to that smarthost; otherwise, we'll
6258 perform DNS lookups for direct-to-MX lookup. Any mail which is to a local domain will
6259 skip these routers because of the &%domains%& option.
6263 driver = manualroute
6264 domains = ! +local_domains
6265 transport = smarthost_smtp
6266 route_data = ROUTER_SMARTHOST
6267 ignore_target_hosts = <; 0.0.0.0 ; 127.0.0.0/8 ; ::1
6270 This router only handles mail which is not to any local domains; this is
6271 specified by the line
6273 domains = ! +local_domains
6275 The &%domains%& option lists the domains to which this router applies, but the
6276 exclamation mark is a negation sign, so the router is used only for domains
6277 that are not in the domain list called &'local_domains'& (which was defined at
6278 the start of the configuration). The plus sign before &'local_domains'&
6279 indicates that it is referring to a named list. Addresses in other domains are
6280 passed on to the following routers.
6282 The name of the router driver is &(manualroute)& because we are manually
6283 specifying how mail should be routed onwards, instead of using DNS MX.
6284 While the name of this router instance is arbitrary, the &%driver%& option must
6285 be one of the driver modules that is in the Exim binary.
6287 With no pre-conditions other than &%domains%&, all mail for non-local domains
6288 will be handled by this router, and the &%no_more%& setting will ensure that no
6289 other routers will be used for messages matching the pre-conditions. See
6290 &<<SECTrouprecon>>& for more on how the pre-conditions apply. For messages which
6291 are handled by this router, we provide a hostname to deliver to in &%route_data%&
6292 and the macro supplies the value; the address is then queued for the
6293 &(smarthost_smtp)& transport.
6298 domains = ! +local_domains
6299 transport = remote_smtp
6300 ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
6303 The &%domains%& option behaves as per smarthost, above.
6305 The name of the router driver is &(dnslookup)&,
6306 and is specified by the &%driver%& option. Do not be confused by the fact that
6307 the name of this router instance is the same as the name of the driver. The
6308 instance name is arbitrary, but the name set in the &%driver%& option must be
6309 one of the driver modules that is in the Exim binary.
6311 The &(dnslookup)& router routes addresses by looking up their domains in the
6312 DNS in order to obtain a list of hosts to which the address is routed. If the
6313 router succeeds, the address is queued for the &(remote_smtp)& transport, as
6314 specified by the &%transport%& option. If the router does not find the domain
6315 in the DNS, no further routers are tried because of the &%no_more%& setting, so
6316 the address fails and is bounced.
6318 The &%ignore_target_hosts%& option specifies a list of IP addresses that are to
6319 be entirely ignored. This option is present because a number of cases have been
6320 encountered where MX records in the DNS point to host names
6321 whose IP addresses are 0.0.0.0 or are in the 127 subnet (typically 127.0.0.1).
6322 Completely ignoring these IP addresses causes Exim to fail to route the
6323 email address, so it bounces. Otherwise, Exim would log a routing problem, and
6324 continue to try to deliver the message periodically until the address timed
6331 data = ${lookup{$local_part}lsearch{/etc/aliases}}
6333 file_transport = address_file
6334 pipe_transport = address_pipe
6336 Control reaches this and subsequent routers only for addresses in the local
6337 domains. This router checks to see whether the local part is defined as an
6338 alias in the &_/etc/aliases_& file, and if so, redirects it according to the
6339 data that it looks up from that file. If no data is found for the local part,
6340 the value of the &%data%& option is empty, causing the address to be passed to
6343 &_/etc/aliases_& is a conventional name for the system aliases file that is
6344 often used. That is why it is referenced by from the default configuration
6345 file. However, you can change this by setting SYSTEM_ALIASES_FILE in
6346 &_Local/Makefile_& before building Exim.
6351 # local_part_suffix = +* : -*
6352 # local_part_suffix_optional
6353 file = $home/.forward
6358 file_transport = address_file
6359 pipe_transport = address_pipe
6360 reply_transport = address_reply
6362 This is the most complicated router in the default configuration. It is another
6363 redirection router, but this time it is looking for forwarding data set up by
6364 individual users. The &%check_local_user%& setting specifies a check that the
6365 local part of the address is the login name of a local user. If it is not, the
6366 router is skipped. The two commented options that follow &%check_local_user%&,
6369 # local_part_suffix = +* : -*
6370 # local_part_suffix_optional
6372 .vindex "&$local_part_suffix$&"
6373 show how you can specify the recognition of local part suffixes. If the first
6374 is uncommented, a suffix beginning with either a plus or a minus sign, followed
6375 by any sequence of characters, is removed from the local part and placed in the
6376 variable &$local_part_suffix$&. The second suffix option specifies that the
6377 presence of a suffix in the local part is optional. When a suffix is present,
6378 the check for a local login uses the local part with the suffix removed.
6380 When a local user account is found, the file called &_.forward_& in the user's
6381 home directory is consulted. If it does not exist, or is empty, the router
6382 declines. Otherwise, the contents of &_.forward_& are interpreted as
6383 redirection data (see chapter &<<CHAPredirect>>& for more details).
6385 .cindex "Sieve filter" "enabling in default router"
6386 Traditional &_.forward_& files contain just a list of addresses, pipes, or
6387 files. Exim supports this by default. However, if &%allow_filter%& is set (it
6388 is commented out by default), the contents of the file are interpreted as a set
6389 of Exim or Sieve filtering instructions, provided the file begins with &"#Exim
6390 filter"& or &"#Sieve filter"&, respectively. User filtering is discussed in the
6391 separate document entitled &'Exim's interfaces to mail filtering'&.
6393 The &%no_verify%& and &%no_expn%& options mean that this router is skipped when
6394 verifying addresses, or when running as a consequence of an SMTP EXPN command.
6395 There are two reasons for doing this:
6398 Whether or not a local user has a &_.forward_& file is not really relevant when
6399 checking an address for validity; it makes sense not to waste resources doing
6402 More importantly, when Exim is verifying addresses or handling an EXPN
6403 command during an SMTP session, it is running as the Exim user, not as root.
6404 The group is the Exim group, and no additional groups are set up.
6405 It may therefore not be possible for Exim to read users' &_.forward_& files at
6409 The setting of &%check_ancestor%& prevents the router from generating a new
6410 address that is the same as any previous address that was redirected. (This
6411 works round a problem concerning a bad interaction between aliasing and
6412 forwarding &-- see section &<<SECTredlocmai>>&).
6414 The final three option settings specify the transports that are to be used when
6415 forwarding generates a direct delivery to a file, or to a pipe, or sets up an
6416 auto-reply, respectively. For example, if a &_.forward_& file contains
6418 a.nother@elsewhere.example, /home/spqr/archive
6420 the delivery to &_/home/spqr/archive_& is done by running the &%address_file%&
6426 # local_part_suffix = +* : -*
6427 # local_part_suffix_optional
6428 transport = local_delivery
6430 The final router sets up delivery into local mailboxes, provided that the local
6431 part is the name of a local login, by accepting the address and assigning it to
6432 the &(local_delivery)& transport. Otherwise, we have reached the end of the
6433 routers, so the address is bounced. The commented suffix settings fulfil the
6434 same purpose as they do for the &(userforward)& router.
6437 .section "Transport configuration" "SECID56"
6438 .cindex "default" "transports"
6439 .cindex "transports" "default"
6440 Transports define mechanisms for actually delivering messages. They operate
6441 only when referenced from routers, so the order in which they are defined does
6442 not matter. The transports section of the configuration starts with
6446 Two remote transports and four local transports are defined.
6450 message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}
6455 This transport is used for delivering messages over SMTP connections.
6456 The list of remote hosts comes from the router.
6457 The &%message_size_limit%& usage is a hack to avoid sending on messages
6458 with over-long lines.
6460 The &%hosts_try_prdr%& option enables an efficiency SMTP option. It is
6461 negotiated between client and server and not expected to cause problems
6462 but can be disabled if needed. The built-in macro _HAVE_PRDR guards the
6463 use of the &%hosts_try_prdr%& configuration option.
6465 The other remote transport is used when delivering to a specific smarthost
6466 with whom there must be some kind of existing relationship, instead of the
6467 usual federated system.
6472 message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}
6476 # Comment out any of these which you have to, then file a Support
6477 # request with your smarthost provider to get things fixed:
6478 hosts_require_tls = *
6479 tls_verify_hosts = *
6480 # As long as tls_verify_hosts is enabled, this this will have no effect,
6481 # but if you have to comment it out then this will at least log whether
6482 # you succeed or not:
6483 tls_try_verify_hosts = *
6485 # The SNI name should match the name which we'll expect to verify;
6486 # many mail systems don't use SNI and this doesn't matter, but if it does,
6487 # we need to send a name which the remote site will recognize.
6488 # This _should_ be the name which the smarthost operators specified as
6489 # the hostname for sending your mail to.
6490 tls_sni = ROUTER_SMARTHOST
6492 .ifdef _HAVE_OPENSSL
6493 tls_require_ciphers = HIGH:!aNULL:@STRENGTH
6496 tls_require_ciphers = SECURE192:-VERS-SSL3.0:-VERS-TLS1.0:-VERS-TLS1.1
6503 After the same &%message_size_limit%& hack, we then specify that this Transport
6504 can handle messages to multiple domains in one run. The assumption here is
6505 that you're routing all non-local mail to the same place and that place is
6506 happy to take all messages from you as quickly as possible.
6507 All other options depend upon built-in macros; if Exim was built without TLS support
6508 then no other options are defined.
6509 If TLS is available, then we configure "stronger than default" TLS ciphersuites
6510 and versions using the &%tls_require_ciphers%& option, where the value to be
6511 used depends upon the library providing TLS.
6512 Beyond that, the options adopt the stance that you should have TLS support available
6513 from your smarthost on today's Internet, so we turn on requiring TLS for the
6514 mail to be delivered, and requiring that the certificate be valid, and match
6515 the expected hostname. The &%tls_sni%& option can be used by service providers
6516 to select an appropriate certificate to present to you and here we re-use the
6517 ROUTER_SMARTHOST macro, because that is unaffected by CNAMEs present in DNS.
6518 You want to specify the hostname which you'll expect to validate for, and that
6519 should not be subject to insecure tampering via DNS results.
6521 For the &%hosts_try_prdr%& option see the previous transport.
6523 All other options are defaulted.
6527 file = /var/mail/$local_part_data
6534 This &(appendfile)& transport is used for local delivery to user mailboxes in
6535 traditional BSD mailbox format.
6537 We prefer to avoid using &$local_part$& directly to define the mailbox filename,
6538 as it is provided by a potential bad actor.
6539 Instead we use &$local_part_data$&,
6540 the result of looking up &$local_part$& in the user database
6541 (done by using &%check_local_user%& in the the router).
6543 By default &(appendfile)& runs under the uid and gid of the
6544 local user, which requires the sticky bit to be set on the &_/var/mail_&
6545 directory. Some systems use the alternative approach of running mail deliveries
6546 under a particular group instead of using the sticky bit. The commented options
6547 show how this can be done.
6549 Exim adds three headers to the message as it delivers it: &'Delivery-date:'&,
6550 &'Envelope-to:'& and &'Return-path:'&. This action is requested by the three
6551 similarly-named options above.
6557 This transport is used for handling deliveries to pipes that are generated by
6558 redirection (aliasing or users' &_.forward_& files). The &%return_output%&
6559 option specifies that any output on stdout or stderr generated by the pipe is to
6560 be returned to the sender.
6568 This transport is used for handling deliveries to files that are generated by
6569 redirection. The name of the file is not specified in this instance of
6570 &(appendfile)&, because it comes from the &(redirect)& router.
6575 This transport is used for handling automatic replies generated by users'
6580 .section "Default retry rule" "SECID57"
6581 .cindex "retry" "default rule"
6582 .cindex "default" "retry rule"
6583 The retry section of the configuration file contains rules which affect the way
6584 Exim retries deliveries that cannot be completed at the first attempt. It is
6585 introduced by the line
6589 In the default configuration, there is just one rule, which applies to all
6592 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
6594 This causes any temporarily failing address to be retried every 15 minutes for
6595 2 hours, then at intervals starting at one hour and increasing by a factor of
6596 1.5 until 16 hours have passed, then every 6 hours up to 4 days. If an address
6597 is not delivered after 4 days of temporary failure, it is bounced. The time is
6598 measured from first failure, not from the time the message was received.
6600 If the retry section is removed from the configuration, or is empty (that is,
6601 if no retry rules are defined), Exim will not retry deliveries. This turns
6602 temporary errors into permanent errors.
6605 .section "Rewriting configuration" "SECID58"
6606 The rewriting section of the configuration, introduced by
6610 contains rules for rewriting addresses in messages as they arrive. There are no
6611 rewriting rules in the default configuration file.
6615 .section "Authenticators configuration" "SECTdefconfauth"
6616 .cindex "AUTH" "configuration"
6617 The authenticators section of the configuration, introduced by
6619 begin authenticators
6621 defines mechanisms for the use of the SMTP AUTH command. The default
6622 configuration file contains two commented-out example authenticators
6623 which support plaintext username/password authentication using the
6624 standard PLAIN mechanism and the traditional but non-standard LOGIN
6625 mechanism, with Exim acting as the server. PLAIN and LOGIN are enough
6626 to support most MUA software.
6628 The example PLAIN authenticator looks like this:
6631 # driver = plaintext
6632 # server_set_id = $auth2
6633 # server_prompts = :
6634 # server_condition = Authentication is not yet configured
6635 # server_advertise_condition = ${if def:tls_in_cipher }
6637 And the example LOGIN authenticator looks like this:
6640 # driver = plaintext
6641 # server_set_id = $auth1
6642 # server_prompts = <| Username: | Password:
6643 # server_condition = Authentication is not yet configured
6644 # server_advertise_condition = ${if def:tls_in_cipher }
6647 The &%server_set_id%& option makes Exim remember the authenticated username
6648 in &$authenticated_id$&, which can be used later in ACLs or routers. The
6649 &%server_prompts%& option configures the &(plaintext)& authenticator so
6650 that it implements the details of the specific authentication mechanism,
6651 i.e. PLAIN or LOGIN. The &%server_advertise_condition%& setting controls
6652 when Exim offers authentication to clients; in the examples, this is only
6653 when TLS or SSL has been started, so to enable the authenticators you also
6654 need to add support for TLS as described in section &<<SECTdefconfmain>>&.
6656 The &%server_condition%& setting defines how to verify that the username and
6657 password are correct. In the examples it just produces an error message.
6658 To make the authenticators work, you can use a string expansion
6659 expression like one of the examples in chapter &<<CHAPplaintext>>&.
6661 Beware that the sequence of the parameters to PLAIN and LOGIN differ; the
6662 usercode and password are in different positions.
6663 Chapter &<<CHAPplaintext>>& covers both.
6665 .ecindex IIDconfiwal
6669 . ////////////////////////////////////////////////////////////////////////////
6670 . ////////////////////////////////////////////////////////////////////////////
6672 .chapter "Regular expressions" "CHAPregexp"
6674 .cindex "regular expressions" "library"
6676 Exim supports the use of regular expressions in many of its options. It
6677 uses the PCRE2 regular expression library; this provides regular expression
6678 matching that is compatible with Perl 5. The syntax and semantics of
6679 regular expressions is discussed in
6680 online Perl manpages, in
6681 many Perl reference books, and also in
6682 Jeffrey Friedl's &'Mastering Regular Expressions'&, which is published by
6683 O'Reilly (see &url(http://www.oreilly.com/catalog/regex2/)).
6684 . --- the http: URL here redirects to another page with the ISBN in the URL
6685 . --- where trying to use https: just redirects back to http:, so sticking
6686 . --- to the old URL for now. 2018-09-07.
6688 The documentation for the syntax and semantics of the regular expressions that
6689 are supported by PCRE2 is included in the PCRE2 distribution, and no further
6690 description is included here. The PCRE2 functions are called from Exim using
6691 the default option settings (that is, with no PCRE2 options set), except that
6692 the PCRE2_CASELESS option is set when the matching is required to be
6695 In most cases, when a regular expression is required in an Exim configuration,
6696 it has to start with a circumflex, in order to distinguish it from plain text
6697 or an &"ends with"& wildcard. In this example of a configuration setting, the
6698 second item in the colon-separated list is a regular expression.
6700 domains = a.b.c : ^\\d{3} : *.y.z : ...
6702 The doubling of the backslash is required because of string expansion that
6703 precedes interpretation &-- see section &<<SECTlittext>>& for more discussion
6704 of this issue, and a way of avoiding the need for doubling backslashes. The
6705 regular expression that is eventually used in this example contains just one
6706 backslash. The circumflex is included in the regular expression, and has the
6707 normal effect of &"anchoring"& it to the start of the string that is being
6710 There are, however, two cases where a circumflex is not required for the
6711 recognition of a regular expression: these are the &%match%& condition in a
6712 string expansion, and the &%matches%& condition in an Exim filter file. In
6713 these cases, the relevant string is always treated as a regular expression; if
6714 it does not start with a circumflex, the expression is not anchored, and can
6715 match anywhere in the subject string.
6717 In all cases, if you want a regular expression to match at the end of a string,
6718 you must code the $ metacharacter to indicate this. For example:
6720 domains = ^\\d{3}\\.example
6722 matches the domain &'123.example'&, but it also matches &'123.example.com'&.
6725 domains = ^\\d{3}\\.example\$
6727 if you want &'example'& to be the top-level domain. The backslash before the
6728 $ is needed because string expansion also interprets dollar characters.
6732 . ////////////////////////////////////////////////////////////////////////////
6733 . ////////////////////////////////////////////////////////////////////////////
6735 .chapter "File and database lookups" "CHAPfdlookup"
6736 .scindex IIDfidalo1 "file" "lookups"
6737 .scindex IIDfidalo2 "database" "lookups"
6738 .cindex "lookup" "description of"
6739 Exim can be configured to look up data in files or databases as it processes
6740 messages. Two different kinds of syntax are used:
6743 A string that is to be expanded may contain explicit lookup requests. These
6744 cause parts of the string to be replaced by data that is obtained from the
6745 lookup. Lookups of this type are conditional expansion items. Different results
6746 can be defined for the cases of lookup success and failure. See chapter
6747 &<<CHAPexpand>>&, where string expansions are described in detail.
6748 The key for the lookup is &*specified*& as part of the string expansion.
6750 Lists of domains, hosts, and email addresses can contain lookup requests as a
6751 way of avoiding excessively long linear lists. In this case, the data that is
6752 returned by the lookup is often (but not always) discarded; whether the lookup
6753 succeeds or fails is what really counts. These kinds of list are described in
6754 chapter &<<CHAPdomhosaddlists>>&.
6755 The key for the lookup is &*implicit*&,
6756 given by the context in which the list is expanded.
6759 String expansions, lists, and lookups interact with each other in such a way
6760 that there is no order in which to describe any one of them that does not
6761 involve references to the others. Each of these three chapters makes more sense
6762 if you have read the other two first. If you are reading this for the first
6763 time, be aware that some of it will make a lot more sense after you have read
6764 chapters &<<CHAPdomhosaddlists>>& and &<<CHAPexpand>>&.
6766 .section "Examples of different lookup syntax" "SECID60"
6767 It is easy to confuse the two different kinds of lookup, especially as the
6768 lists that may contain the second kind are always expanded before being
6769 processed as lists. Therefore, they may also contain lookups of the first kind.
6770 Be careful to distinguish between the following two examples:
6772 domains = ${lookup{$sender_host_address}lsearch{/some/file}}
6773 domains = lsearch;/some/file
6775 The first uses a string expansion, the result of which must be a domain list.
6777 The key for an expansion-style lookup must be given explicitly.
6779 No strings have been specified for a successful or a failing lookup; the
6780 defaults in this case are the looked-up data and an empty string, respectively.
6781 The expansion takes place before the string is processed as a list, and the
6782 file that is searched could contain lines like this:
6784 192.168.3.4: domain1:domain2:...
6785 192.168.1.9: domain3:domain4:...
6787 When the lookup succeeds, the result of the expansion is a list of domains (and
6788 possibly other types of item that are allowed in domain lists).
6789 .cindex "tainted data" "de-tainting"
6790 The result of the expansion is not tainted.
6792 In the second example, the lookup is a single item in a domain list. It causes
6793 Exim to use a lookup to see if the domain that is being processed can be found
6795 The file could contains lines like this:
6800 Any data that follows the keys is not relevant when checking that the domain
6801 matches the list item.
6804 The key for a list-style lookup is implicit, from the lookup context, if
6805 the lookup is a single-key type (see below).
6806 For query-style lookup types the key must be given explicitly.
6809 It is possible, though no doubt confusing, to use both kinds of lookup at once.
6810 Consider a file containing lines like this:
6812 192.168.5.6: lsearch;/another/file
6814 If the value of &$sender_host_address$& is 192.168.5.6, expansion of the
6815 first &%domains%& setting above generates the second setting, which therefore
6816 causes a second lookup to occur.
6818 The lookup type may optionally be followed by a comma
6819 and a comma-separated list of options.
6820 Each option is a &"name=value"& pair.
6821 Whether an option is meaningful depends on the lookup type.
6823 All lookups support the option &"cache=no_rd"&.
6824 If this is given then the cache that Exim manages for lookup results
6825 is not checked before doing the lookup.
6826 The result of the lookup is still written to the cache.
6828 The rest of this chapter describes the different lookup types that are
6829 available. Any of them can be used in any part of the configuration where a
6830 lookup is permitted.
6833 .section "Lookup types" "SECID61"
6834 .cindex "lookup" "types of"
6835 .cindex "single-key lookup" "definition of"
6836 Two different types of data lookup are implemented:
6839 The &'single-key'& type requires the specification of a file in which to look,
6840 and a single key to search for. The key must be a non-empty string for the
6841 lookup to succeed. The lookup type determines how the file is searched.
6842 .cindex "tainted data" "single-key lookups"
6843 The file string may not be tainted.
6845 .cindex "tainted data" "de-tainting"
6846 All single-key lookups support the option &"ret=key"&.
6847 If this is given and the lookup
6848 (either underlying implementation or cached value)
6849 returns data, the result is replaced with a non-tainted
6850 version of the lookup key.
6851 .cindex "tainted data" "de-tainting"
6853 .cindex "query-style lookup" "definition of"
6854 The &'query-style'& type accepts a generalized database query. No particular
6855 key value is assumed by Exim for query-style lookups. You can use whichever
6856 Exim variables you need to construct the database query.
6857 .cindex "tainted data" "quoting for lookups"
6859 If tainted data is used in the query then it should be quuted by
6860 using the &*${quote_*&<&'lookup-type'&>&*:*&<&'string'&>&*}*& expansion operator
6861 appropriate for the lookup.
6865 The code for each lookup type is in a separate source file that is included in
6866 the binary of Exim only if the corresponding compile-time option is set. The
6867 default settings in &_src/EDITME_& are:
6872 which means that only linear searching and DBM lookups are included by default.
6873 For some types of lookup (e.g. SQL databases), you need to install appropriate
6874 libraries and header files before building Exim.
6879 .section "Single-key lookup types" "SECTsinglekeylookups"
6880 .cindex "lookup" "single-key types"
6881 .cindex "single-key lookup" "list of types"
6882 The following single-key lookup types are implemented:
6885 .cindex "cdb" "description of"
6886 .cindex "lookup" "cdb"
6887 .cindex "binary zero" "in lookup key"
6888 &(cdb)&: The given file is searched as a Constant DataBase file, using the key
6889 string without a terminating binary zero. The cdb format is designed for
6890 indexed files that are read frequently and never updated, except by total
6891 re-creation. As such, it is particularly suitable for large files containing
6892 aliases or other indexed data referenced by an MTA. Information about cdb and
6893 tools for building the files can be found in several places:
6895 &url(https://cr.yp.to/cdb.html)
6896 &url(https://www.corpit.ru/mjt/tinycdb.html)
6897 &url(https://packages.debian.org/stable/utils/freecdb)
6898 &url(https://github.com/philpennock/cdbtools) (in Go)
6900 A cdb distribution is not needed in order to build Exim with cdb support,
6901 because the code for reading cdb files is included directly in Exim itself.
6902 However, no means of building or testing cdb files is provided with Exim, so
6903 you need to obtain a cdb distribution in order to do this.
6905 .cindex "DBM" "lookup type"
6906 .cindex "lookup" "dbm"
6907 .cindex "binary zero" "in lookup key"
6908 &(dbm)&: Calls to DBM library functions are used to extract data from the given
6909 DBM file by looking up the record with the given key. A terminating binary
6910 zero is included in the key that is passed to the DBM library. See section
6911 &<<SECTdb>>& for a discussion of DBM libraries.
6913 .cindex "Berkeley DB library" "file format"
6914 For all versions of Berkeley DB, Exim uses the DB_HASH style of database
6915 when building DBM files using the &%exim_dbmbuild%& utility. However, when
6916 using Berkeley DB versions 3 or 4, it opens existing databases for reading with
6917 the DB_UNKNOWN option. This enables it to handle any of the types of database
6918 that the library supports, and can be useful for accessing DBM files created by
6919 other applications. (For earlier DB versions, DB_HASH is always used.)
6921 .cindex "lookup" "dbmjz"
6922 .cindex "lookup" "dbm &-- embedded NULs"
6924 .cindex "dbmjz lookup type"
6925 &(dbmjz)&: This is the same as &(dbm)&, except that the lookup key is
6926 interpreted as an Exim list; the elements of the list are joined together with
6927 ASCII NUL characters to form the lookup key. An example usage would be to
6928 authenticate incoming SMTP calls using the passwords from Cyrus SASL's
6929 &_/etc/sasldb2_& file with the &(gsasl)& authenticator or Exim's own
6930 &(cram_md5)& authenticator.
6932 .cindex "lookup" "dbmnz"
6933 .cindex "lookup" "dbm &-- terminating zero"
6934 .cindex "binary zero" "in lookup key"
6936 .cindex "&_/etc/userdbshadow.dat_&"
6937 .cindex "dbmnz lookup type"
6938 &(dbmnz)&: This is the same as &(dbm)&, except that a terminating binary zero
6939 is not included in the key that is passed to the DBM library. You may need this
6940 if you want to look up data in files that are created by or shared with some
6941 other application that does not use terminating zeros. For example, you need to
6942 use &(dbmnz)& rather than &(dbm)& if you want to authenticate incoming SMTP
6943 calls using the passwords from Courier's &_/etc/userdbshadow.dat_& file. Exim's
6944 utility program for creating DBM files (&'exim_dbmbuild'&) includes the zeros
6945 by default, but has an option to omit them (see section &<<SECTdbmbuild>>&).
6947 .cindex "lookup" "dsearch"
6948 .cindex "dsearch lookup type"
6949 &(dsearch)&: The given file must be an
6951 directory path; this is searched for an entry
6952 whose name is the key by calling the &[lstat()]& function.
6954 contain any forward slash characters.
6955 If &[lstat()]& succeeds then so does the lookup.
6956 .cindex "tainted data" "dsearch result"
6957 The result is regarded as untainted.
6959 Options for the lookup can be given by appending them after the word "dsearch",
6960 separated by a comma. Options, if present, are a comma-separated list having
6961 each element starting with a tag name and an equals.
6963 Two options are supported, for the return value and for filtering match
6965 The "ret" option requests an alternate result value of
6966 the entire path for the entry. Example:
6968 ${lookup {passwd} dsearch,ret=full {/etc}}
6970 The default result is just the requested entry.
6971 The "filter" option requests that only directory entries of a given type
6972 are matched. The match value is one of "file", "dir" or "subdir" (the latter
6973 not matching "." or ".."). Example:
6975 ${lookup {passwd} dsearch,filter=file {/etc}}
6977 The default matching is for any entry type, including directories
6980 An example of how this
6981 lookup can be used to support virtual domains is given in section
6982 &<<SECTvirtualdomains>>&.
6984 .cindex "lookup" "iplsearch"
6985 .cindex "iplsearch lookup type"
6986 &(iplsearch)&: The given file is a text file containing keys and data. A key is
6987 terminated by a colon or white space or the end of the line. The keys in the
6988 file must be IP addresses, or IP addresses with CIDR masks. Keys that involve
6989 IPv6 addresses must be enclosed in quotes to prevent the first internal colon
6990 being interpreted as a key terminator. For example:
6992 1.2.3.4: data for 1.2.3.4
6993 192.168.0.0/16: data for 192.168.0.0/16
6994 "abcd::cdab": data for abcd::cdab
6995 "abcd:abcd::/32" data for abcd:abcd::/32
6997 The key for an &(iplsearch)& lookup must be an IP address (without a mask). The
6998 file is searched linearly, using the CIDR masks where present, until a matching
6999 key is found. The first key that matches is used; there is no attempt to find a
7000 &"best"& match. Apart from the way the keys are matched, the processing for
7001 &(iplsearch)& is the same as for &(lsearch)&.
7003 &*Warning 1*&: Unlike most other single-key lookup types, a file of data for
7004 &(iplsearch)& can &'not'& be turned into a DBM or cdb file, because those
7005 lookup types support only literal keys.
7007 &*Warning 2*&: In a host list, you must always use &(net-iplsearch)& so that
7008 the implicit key is the host's IP address rather than its name (see section
7009 &<<SECThoslispatsikey>>&).
7011 &*Warning 3*&: Do not use an IPv4-mapped IPv6 address for a key; use the
7012 IPv4, in dotted-quad form. (Exim converts IPv4-mapped IPv6 addresses to this
7013 notation before executing the lookup.)
7015 One option is supported, "ret=full", to request the return of the entire line
7016 rather than omitting the key portion.
7017 Note however that the key portion will have been de-quoted.
7021 .cindex json "lookup type"
7022 .cindex JSON expansions
7023 &(json)&: The given file is a text file with a JSON structure.
7024 An element of the structure is extracted, defined by the search key.
7025 The key is a list of subelement selectors
7026 (colon-separated by default but changeable in the usual way)
7027 which are applied in turn to select smaller and smaller portions
7028 of the JSON structure.
7029 If a selector is numeric, it must apply to a JSON array; the (zero-based)
7030 nunbered array element is selected.
7031 Otherwise it must apply to a JSON object; the named element is selected.
7032 The final resulting element can be a simple JSON type or a JSON object
7033 or array; for the latter two a string-representation of the JSON
7035 For elements of type string, the returned value is de-quoted.
7041 .cindex database lmdb
7042 &(lmdb)&: The given file is an LMDB database.
7043 LMDB is a memory-mapped key-value store,
7044 with API modeled loosely on that of BerkeleyDB.
7045 See &url(https://symas.com/products/lightning-memory-mapped-database/)
7046 for the feature set and operation modes.
7048 Exim provides read-only access via the LMDB C library.
7049 The library can be obtained from &url(https://github.com/LMDB/lmdb)
7050 or your operating system package repository.
7051 To enable LMDB support in Exim set LOOKUP_LMDB=yes in &_Local/Makefile_&.
7053 You will need to separately create the LMDB database file,
7054 possibly using the &"mdb_load"& utility.
7058 .cindex "linear search"
7059 .cindex "lookup" "lsearch"
7060 .cindex "lsearch lookup type"
7061 .cindex "case sensitivity" "in lsearch lookup"
7062 &(lsearch)&: The given file is a text file that is searched linearly for a
7063 line beginning with the search key, terminated by a colon or white space or the
7064 end of the line. The search is case-insensitive; that is, upper and lower case
7065 letters are treated as the same. The first occurrence of the key that is found
7066 in the file is used.
7068 White space between the key and the colon is permitted. The remainder of the
7069 line, with leading and trailing white space removed, is the data. This can be
7070 continued onto subsequent lines by starting them with any amount of white
7071 space, but only a single space character is included in the data at such a
7072 junction. If the data begins with a colon, the key must be terminated by a
7077 Empty lines and lines beginning with # are ignored, even if they occur in the
7078 middle of an item. This is the traditional textual format of alias files. Note
7079 that the keys in an &(lsearch)& file are literal strings. There is no
7080 wildcarding of any kind.
7082 .cindex "lookup" "lsearch &-- colons in keys"
7083 .cindex "white space" "in lsearch key"
7084 In most &(lsearch)& files, keys are not required to contain colons or #
7085 characters, or white space. However, if you need this feature, it is available.
7086 If a key begins with a doublequote character, it is terminated only by a
7087 matching quote (or end of line), and the normal escaping rules apply to its
7088 contents (see section &<<SECTstrings>>&). An optional colon is permitted after
7089 quoted keys (exactly as for unquoted keys). There is no special handling of
7090 quotes for the data part of an &(lsearch)& line.
7093 .cindex "NIS lookup type"
7094 .cindex "lookup" "NIS"
7095 .cindex "binary zero" "in lookup key"
7096 &(nis)&: The given file is the name of a NIS map, and a NIS lookup is done with
7097 the given key, without a terminating binary zero. There is a variant called
7098 &(nis0)& which does include the terminating binary zero in the key. This is
7099 reportedly needed for Sun-style alias files. Exim does not recognize NIS
7100 aliases; the full map names must be used.
7103 .cindex "wildlsearch lookup type"
7104 .cindex "lookup" "wildlsearch"
7105 .cindex "nwildlsearch lookup type"
7106 .cindex "lookup" "nwildlsearch"
7107 &(wildlsearch)& or &(nwildlsearch)&: These search a file linearly, like
7108 &(lsearch)&, but instead of being interpreted as a literal string, each key in
7109 the file may be wildcarded. The difference between these two lookup types is
7110 that for &(wildlsearch)&, each key in the file is string-expanded before being
7111 used, whereas for &(nwildlsearch)&, no expansion takes place.
7113 .cindex "case sensitivity" "in (n)wildlsearch lookup"
7114 Like &(lsearch)&, the testing is done case-insensitively. However, keys in the
7115 file that are regular expressions can be made case-sensitive by the use of
7116 &`(-i)`& within the pattern. The following forms of wildcard are recognized:
7118 . ==== As this is a nested list, any displays it contains must be indented
7119 . ==== as otherwise they are too far to the left.
7122 The string may begin with an asterisk to mean &"ends with"&. For example:
7124 *.a.b.c data for anything.a.b.c
7125 *fish data for anythingfish
7128 The string may begin with a circumflex to indicate a regular expression. For
7129 example, for &(wildlsearch)&:
7131 ^\N\d+\.a\.b\N data for <digits>.a.b
7133 Note the use of &`\N`& to disable expansion of the contents of the regular
7134 expression. If you are using &(nwildlsearch)&, where the keys are not
7135 string-expanded, the equivalent entry is:
7137 ^\d+\.a\.b data for <digits>.a.b
7139 The case-insensitive flag is set at the start of compiling the regular
7140 expression, but it can be turned off by using &`(-i)`& at an appropriate point.
7141 For example, to make the entire pattern case-sensitive:
7143 ^(?-i)\d+\.a\.b data for <digits>.a.b
7146 If the regular expression contains white space or colon characters, you must
7147 either quote it (see &(lsearch)& above), or represent these characters in other
7148 ways. For example, &`\s`& can be used for white space and &`\x3A`& for a
7149 colon. This may be easier than quoting, because if you quote, you have to
7150 escape all the backslashes inside the quotes.
7152 &*Note*&: It is not possible to capture substrings in a regular expression
7153 match for later use, because the results of all lookups are cached. If a lookup
7154 is repeated, the result is taken from the cache, and no actual pattern matching
7155 takes place. The values of all the numeric variables are unset after a
7156 &((n)wildlsearch)& match.
7159 Although I cannot see it being of much use, the general matching function that
7160 is used to implement &((n)wildlsearch)& means that the string may begin with a
7161 lookup name terminated by a semicolon, and followed by lookup data. For
7164 cdb;/some/file data for keys that match the file
7166 The data that is obtained from the nested lookup is discarded.
7169 Keys that do not match any of these patterns are interpreted literally. The
7170 continuation rules for the data are the same as for &(lsearch)&, and keys may
7171 be followed by optional colons.
7173 &*Warning*&: Unlike most other single-key lookup types, a file of data for
7174 &((n)wildlsearch)& can &'not'& be turned into a DBM or cdb file, because those
7175 lookup types support only literal keys.
7178 .cindex "spf lookup type"
7179 .cindex "lookup" "spf"
7180 &(spf)&: If Exim is built with SPF support, manual lookups can be done
7181 (as opposed to the standard ACL condition method).
7182 For details see section &<<SECSPF>>&.
7186 .section "Query-style lookup types" "SECTquerystylelookups"
7187 .cindex "lookup" "query-style types"
7188 .cindex "query-style lookup" "list of types"
7189 The supported query-style lookup types are listed below. Further details about
7190 many of them are given in later sections.
7193 .cindex "DNS" "as a lookup type"
7194 .cindex "lookup" "DNS"
7195 &(dnsdb)&: This does a DNS search for one or more records whose domain names
7196 are given in the supplied query. The resulting data is the contents of the
7197 records. See section &<<SECTdnsdb>>&.
7199 .cindex "InterBase lookup type"
7200 .cindex "lookup" "InterBase"
7201 &(ibase)&: This does a lookup in an InterBase database.
7203 .cindex "LDAP" "lookup type"
7204 .cindex "lookup" "LDAP"
7205 &(ldap)&: This does an LDAP lookup using a query in the form of a URL, and
7206 returns attributes from a single entry. There is a variant called &(ldapm)&
7207 that permits values from multiple entries to be returned. A third variant
7208 called &(ldapdn)& returns the Distinguished Name of a single entry instead of
7209 any attribute values. See section &<<SECTldap>>&.
7211 .cindex "MySQL" "lookup type"
7212 .cindex "lookup" "MySQL"
7213 &(mysql)&: The format of the query is an SQL statement that is passed to a
7214 MySQL database. See section &<<SECTsql>>&.
7216 .cindex "NIS+ lookup type"
7217 .cindex "lookup" "NIS+"
7218 &(nisplus)&: This does a NIS+ lookup using a query that can specify the name of
7219 the field to be returned. See section &<<SECTnisplus>>&.
7221 .cindex "Oracle" "lookup type"
7222 .cindex "lookup" "Oracle"
7223 &(oracle)&: The format of the query is an SQL statement that is passed to an
7224 Oracle database. See section &<<SECTsql>>&.
7226 .cindex "lookup" "passwd"
7227 .cindex "passwd lookup type"
7228 .cindex "&_/etc/passwd_&"
7229 &(passwd)& is a query-style lookup with queries that are just user names. The
7230 lookup calls &[getpwnam()]& to interrogate the system password data, and on
7231 success, the result string is the same as you would get from an &(lsearch)&
7232 lookup on a traditional &_/etc/passwd file_&, though with &`*`& for the
7233 password value. For example:
7235 *:42:42:King Rat:/home/kr:/bin/bash
7238 .cindex "PostgreSQL lookup type"
7239 .cindex "lookup" "PostgreSQL"
7240 &(pgsql)&: The format of the query is an SQL statement that is passed to a
7241 PostgreSQL database. See section &<<SECTsql>>&.
7244 .cindex "Redis lookup type"
7245 .cindex lookup Redis
7246 &(redis)&: The format of the query is either a simple get or simple set,
7247 passed to a Redis database. See section &<<SECTsql>>&.
7250 .cindex "sqlite lookup type"
7251 .cindex "lookup" "sqlite"
7252 &(sqlite)&: The format of the query is
7253 an SQL statement that is passed to an SQLite database. See section &<<SECTsqlite>>&.
7256 &(testdb)&: This is a lookup type that is used for testing Exim. It is
7257 not likely to be useful in normal operation.
7259 .cindex "whoson lookup type"
7260 .cindex "lookup" "whoson"
7261 . --- still http:-only, 2018-09-07
7262 &(whoson)&: &'Whoson'& (&url(http://whoson.sourceforge.net)) is a protocol that
7263 allows a server to check whether a particular (dynamically allocated) IP
7264 address is currently allocated to a known (trusted) user and, optionally, to
7265 obtain the identity of the said user. For SMTP servers, &'Whoson'& was popular
7266 at one time for &"POP before SMTP"& authentication, but that approach has been
7267 superseded by SMTP authentication. In Exim, &'Whoson'& can be used to implement
7268 &"POP before SMTP"& checking using ACL statements such as
7270 require condition = \
7271 ${lookup whoson {$sender_host_address}{yes}{no}}
7273 The query consists of a single IP address. The value returned is the name of
7274 the authenticated user, which is stored in the variable &$value$&. However, in
7275 this example, the data in &$value$& is not used; the result of the lookup is
7276 one of the fixed strings &"yes"& or &"no"&.
7281 .section "Temporary errors in lookups" "SECID63"
7282 .cindex "lookup" "temporary error in"
7283 Lookup functions can return temporary error codes if the lookup cannot be
7284 completed. For example, an SQL or LDAP database might be unavailable. For this
7285 reason, it is not advisable to use a lookup that might do this for critical
7286 options such as a list of local domains.
7288 When a lookup cannot be completed in a router or transport, delivery
7289 of the message (to the relevant address) is deferred, as for any other
7290 temporary error. In other circumstances Exim may assume the lookup has failed,
7291 or may give up altogether.
7295 .section "Default values in single-key lookups" "SECTdefaultvaluelookups"
7296 .cindex "wildcard lookups"
7297 .cindex "lookup" "default values"
7298 .cindex "lookup" "wildcard"
7299 .cindex "lookup" "* added to type"
7300 .cindex "default" "in single-key lookups"
7301 In this context, a &"default value"& is a value specified by the administrator
7302 that is to be used if a lookup fails.
7304 &*Note:*& This section applies only to single-key lookups. For query-style
7305 lookups, the facilities of the query language must be used. An attempt to
7306 specify a default for a query-style lookup provokes an error.
7308 If &"*"& is added to a single-key lookup type (for example, &%lsearch*%&)
7309 and the initial lookup fails, the key &"*"& is looked up in the file to
7310 provide a default value. See also the section on partial matching below.
7312 .cindex "*@ with single-key lookup"
7313 .cindex "lookup" "*@ added to type"
7314 .cindex "alias file" "per-domain default"
7315 Alternatively, if &"*@"& is added to a single-key lookup type (for example
7316 &%dbm*@%&) then, if the initial lookup fails and the key contains an @
7317 character, a second lookup is done with everything before the last @ replaced
7318 by *. This makes it possible to provide per-domain defaults in alias files
7319 that include the domains in the keys. If the second lookup fails (or doesn't
7320 take place because there is no @ in the key), &"*"& is looked up.
7321 For example, a &(redirect)& router might contain:
7323 data = ${lookup{$local_part@$domain}lsearch*@{/etc/mix-aliases}}
7325 Suppose the address that is being processed is &'jane@eyre.example'&. Exim
7326 looks up these keys, in this order:
7332 The data is taken from whichever key it finds first. &*Note*&: In an
7333 &(lsearch)& file, this does not mean the first of these keys in the file. A
7334 complete scan is done for each key, and only if it is not found at all does
7335 Exim move on to try the next key.
7339 .section "Partial matching in single-key lookups" "SECTpartiallookup"
7340 .cindex "partial matching"
7341 .cindex "wildcard lookups"
7342 .cindex "lookup" "partial matching"
7343 .cindex "lookup" "wildcard"
7344 .cindex "asterisk" "in search type"
7345 The normal operation of a single-key lookup is to search the file for an exact
7346 match with the given key. However, in a number of situations where domains are
7347 being looked up, it is useful to be able to do partial matching. In this case,
7348 information in the file that has a key starting with &"*."& is matched by any
7349 domain that ends with the components that follow the full stop. For example, if
7350 a key in a DBM file is
7352 *.dates.fict.example
7354 then when partial matching is enabled this is matched by (amongst others)
7355 &'2001.dates.fict.example'& and &'1984.dates.fict.example'&. It is also matched
7356 by &'dates.fict.example'&, if that does not appear as a separate key in the
7359 &*Note*&: Partial matching is not available for query-style lookups. It is
7360 also not available for any lookup items in address lists (see section
7361 &<<SECTaddresslist>>&).
7363 Partial matching is implemented by doing a series of separate lookups using
7364 keys constructed by modifying the original subject key. This means that it can
7365 be used with any of the single-key lookup types, provided that
7366 partial matching keys
7367 beginning with a special prefix (default &"*."&) are included in the data file.
7368 Keys in the file that do not begin with the prefix are matched only by
7369 unmodified subject keys when partial matching is in use.
7371 Partial matching is requested by adding the string &"partial-"& to the front of
7372 the name of a single-key lookup type, for example, &%partial-dbm%&. When this
7373 is done, the subject key is first looked up unmodified; if that fails, &"*."&
7374 is added at the start of the subject key, and it is looked up again. If that
7375 fails, further lookups are tried with dot-separated components removed from the
7376 start of the subject key, one-by-one, and &"*."& added on the front of what
7379 A minimum number of two non-* components are required. This can be adjusted
7380 by including a number before the hyphen in the search type. For example,
7381 &%partial3-lsearch%& specifies a minimum of three non-* components in the
7382 modified keys. Omitting the number is equivalent to &"partial2-"&. If the
7383 subject key is &'2250.dates.fict.example'& then the following keys are looked
7384 up when the minimum number of non-* components is two:
7386 2250.dates.fict.example
7387 *.2250.dates.fict.example
7388 *.dates.fict.example
7391 As soon as one key in the sequence is successfully looked up, the lookup
7394 .cindex "lookup" "partial matching &-- changing prefix"
7395 .cindex "prefix" "for partial matching"
7396 The use of &"*."& as the partial matching prefix is a default that can be
7397 changed. The motivation for this feature is to allow Exim to operate with file
7398 formats that are used by other MTAs. A different prefix can be supplied in
7399 parentheses instead of the hyphen after &"partial"&. For example:
7401 domains = partial(.)lsearch;/some/file
7403 In this example, if the domain is &'a.b.c'&, the sequence of lookups is
7404 &`a.b.c`&, &`.a.b.c`&, and &`.b.c`& (the default minimum of 2 non-wild
7405 components is unchanged). The prefix may consist of any punctuation characters
7406 other than a closing parenthesis. It may be empty, for example:
7408 domains = partial1()cdb;/some/file
7410 For this example, if the domain is &'a.b.c'&, the sequence of lookups is
7411 &`a.b.c`&, &`b.c`&, and &`c`&.
7413 If &"partial0"& is specified, what happens at the end (when the lookup with
7414 just one non-wild component has failed, and the original key is shortened right
7415 down to the null string) depends on the prefix:
7418 If the prefix has zero length, the whole lookup fails.
7420 If the prefix has length 1, a lookup for just the prefix is done. For
7421 example, the final lookup for &"partial0(.)"& is for &`.`& alone.
7423 Otherwise, if the prefix ends in a dot, the dot is removed, and the
7424 remainder is looked up. With the default prefix, therefore, the final lookup is
7425 for &"*"& on its own.
7427 Otherwise, the whole prefix is looked up.
7431 If the search type ends in &"*"& or &"*@"& (see section
7432 &<<SECTdefaultvaluelookups>>& above), the search for an ultimate default that
7433 this implies happens after all partial lookups have failed. If &"partial0"& is
7434 specified, adding &"*"& to the search type has no effect with the default
7435 prefix, because the &"*"& key is already included in the sequence of partial
7436 lookups. However, there might be a use for lookup types such as
7437 &"partial0(.)lsearch*"&.
7439 The use of &"*"& in lookup partial matching differs from its use as a wildcard
7440 in domain lists and the like. Partial matching works only in terms of
7441 dot-separated components; a key such as &`*fict.example`&
7442 in a database file is useless, because the asterisk in a partial matching
7443 subject key is always followed by a dot.
7448 .section "Lookup caching" "SECID64"
7449 .cindex "lookup" "caching"
7450 .cindex "caching" "lookup data"
7451 Exim caches all lookup results in order to avoid needless repetition of
7452 lookups. However, because (apart from the daemon) Exim operates as a collection
7453 of independent, short-lived processes, this caching applies only within a
7454 single Exim process. There is no inter-process lookup caching facility.
7456 If an option &"cache=no_rd"& is used on the lookup then
7457 the cache is only written to, cached data is not used for the operation
7458 and a real lookup is done.
7460 For single-key lookups, Exim keeps the relevant files open in case there is
7461 another lookup that needs them. In some types of configuration this can lead to
7462 many files being kept open for messages with many recipients. To avoid hitting
7463 the operating system limit on the number of simultaneously open files, Exim
7464 closes the least recently used file when it needs to open more files than its
7465 own internal limit, which can be changed via the &%lookup_open_max%& option.
7467 The single-key lookup files are closed and the lookup caches are flushed at
7468 strategic points during delivery &-- for example, after all routing is
7474 .section "Quoting lookup data" "SECID65"
7475 .cindex "lookup" "quoting"
7476 .cindex "quoting" "in lookups"
7477 When data from an incoming message is included in a query-style lookup, there
7478 is the possibility of special characters in the data messing up the syntax of
7479 the query. For example, a NIS+ query that contains
7483 will be broken if the local part happens to contain a closing square bracket.
7484 For NIS+, data can be enclosed in double quotes like this:
7486 [name="$local_part"]
7488 but this still leaves the problem of a double quote in the data. The rule for
7489 NIS+ is that double quotes must be doubled. Other lookup types have different
7490 rules, and to cope with the differing requirements, an expansion operator
7491 of the following form is provided:
7493 ${quote_<lookup-type>:<string>}
7495 For example, the safest way to write the NIS+ query is
7497 [name="${quote_nisplus:$local_part}"]
7499 See chapter &<<CHAPexpand>>& for full coverage of string expansions. The quote
7500 operator can be used for all lookup types, but has no effect for single-key
7501 lookups, since no quoting is ever needed in their key strings.
7506 .section "More about dnsdb" "SECTdnsdb"
7507 .cindex "dnsdb lookup"
7508 .cindex "lookup" "dnsdb"
7509 .cindex "DNS" "as a lookup type"
7510 The &(dnsdb)& lookup type uses the DNS as its database. A simple query consists
7511 of a record type and a domain name, separated by an equals sign. For example,
7512 an expansion string could contain:
7514 ${lookup dnsdb{mx=a.b.example}{$value}fail}
7516 If the lookup succeeds, the result is placed in &$value$&, which in this case
7517 is used on its own as the result. If the lookup does not succeed, the
7518 &`fail`& keyword causes a &'forced expansion failure'& &-- see section
7519 &<<SECTforexpfai>>& for an explanation of what this means.
7521 The supported DNS record types are A, CNAME, MX, NS, PTR, SOA, SPF, SRV, TLSA
7522 and TXT, and, when Exim is compiled with IPv6 support, AAAA.
7523 If no type is given, TXT is assumed.
7525 For any record type, if multiple records are found, the data is returned as a
7526 concatenation, with newline as the default separator. The order, of course,
7527 depends on the DNS resolver. You can specify a different separator character
7528 between multiple records by putting a right angle-bracket followed immediately
7529 by the new separator at the start of the query. For example:
7531 ${lookup dnsdb{>: a=host1.example}}
7533 It is permitted to specify a space as the separator character. Further
7534 white space is ignored.
7535 For lookup types that return multiple fields per record,
7536 an alternate field separator can be specified using a comma after the main
7537 separator character, followed immediately by the field separator.
7539 .cindex "PTR record" "in &(dnsdb)& lookup"
7540 When the type is PTR,
7541 the data can be an IP address, written as normal; inversion and the addition of
7542 &%in-addr.arpa%& or &%ip6.arpa%& happens automatically. For example:
7544 ${lookup dnsdb{ptr=192.168.4.5}{$value}fail}
7546 If the data for a PTR record is not a syntactically valid IP address, it is not
7547 altered and nothing is added.
7549 .cindex "MX record" "in &(dnsdb)& lookup"
7550 .cindex "SRV record" "in &(dnsdb)& lookup"
7551 For an MX lookup, both the preference value and the host name are returned for
7552 each record, separated by a space. For an SRV lookup, the priority, weight,
7553 port, and host name are returned for each record, separated by spaces.
7554 The field separator can be modified as above.
7556 .cindex "TXT record" "in &(dnsdb)& lookup"
7557 .cindex "SPF record" "in &(dnsdb)& lookup"
7558 For TXT records with multiple items of data, only the first item is returned,
7559 unless a field separator is specified.
7560 To concatenate items without a separator, use a semicolon instead.
7562 default behaviour is to concatenate multiple items without using a separator.
7564 ${lookup dnsdb{>\n,: txt=a.b.example}}
7565 ${lookup dnsdb{>\n; txt=a.b.example}}
7566 ${lookup dnsdb{spf=example.org}}
7568 It is permitted to specify a space as the separator character. Further
7569 white space is ignored.
7571 .cindex "SOA record" "in &(dnsdb)& lookup"
7572 For an SOA lookup, while no result is obtained the lookup is redone with
7573 successively more leading components dropped from the given domain.
7574 Only the primary-nameserver field is returned unless a field separator is
7577 ${lookup dnsdb{>:,; soa=a.b.example.com}}
7580 .section "Dnsdb lookup modifiers" "SECTdnsdb_mod"
7581 .cindex "dnsdb modifiers"
7582 .cindex "modifiers" "dnsdb"
7583 .cindex "options" "dnsdb"
7584 Modifiers for &(dnsdb)& lookups are given by optional keywords,
7585 each followed by a comma,
7586 that may appear before the record type.
7588 The &(dnsdb)& lookup fails only if all the DNS lookups fail. If there is a
7589 temporary DNS error for any of them, the behaviour is controlled by
7590 a defer-option modifier.
7591 The possible keywords are
7592 &"defer_strict"&, &"defer_never"&, and &"defer_lax"&.
7593 With &"strict"& behaviour, any temporary DNS error causes the
7594 whole lookup to defer. With &"never"& behaviour, a temporary DNS error is
7595 ignored, and the behaviour is as if the DNS lookup failed to find anything.
7596 With &"lax"& behaviour, all the queries are attempted, but a temporary DNS
7597 error causes the whole lookup to defer only if none of the other lookups
7598 succeed. The default is &"lax"&, so the following lookups are equivalent:
7600 ${lookup dnsdb{defer_lax,a=one.host.com:two.host.com}}
7601 ${lookup dnsdb{a=one.host.com:two.host.com}}
7603 Thus, in the default case, as long as at least one of the DNS lookups
7604 yields some data, the lookup succeeds.
7606 .cindex "DNSSEC" "dns lookup"
7607 Use of &(DNSSEC)& is controlled by a dnssec modifier.
7608 The possible keywords are
7609 &"dnssec_strict"&, &"dnssec_lax"&, and &"dnssec_never"&.
7610 With &"strict"& or &"lax"& DNSSEC information is requested
7612 With &"strict"& a response from the DNS resolver that
7613 is not labelled as authenticated data
7614 is treated as equivalent to a temporary DNS error.
7615 The default is &"lax"&.
7617 See also the &$lookup_dnssec_authenticated$& variable.
7619 .cindex timeout "dns lookup"
7620 .cindex "DNS" timeout
7621 Timeout for the dnsdb lookup can be controlled by a retrans modifier.
7622 The form is &"retrans_VAL"& where VAL is an Exim time specification
7624 The default value is set by the main configuration option &%dns_retrans%&.
7626 Retries for the dnsdb lookup can be controlled by a retry modifier.
7627 The form if &"retry_VAL"& where VAL is an integer.
7628 The default count is set by the main configuration option &%dns_retry%&.
7630 .cindex caching "of dns lookup"
7631 .cindex TTL "of dns lookup"
7633 Dnsdb lookup results are cached within a single process (and its children).
7634 The cache entry lifetime is limited to the smallest time-to-live (TTL)
7635 value of the set of returned DNS records.
7638 .section "Pseudo dnsdb record types" "SECID66"
7639 .cindex "MX record" "in &(dnsdb)& lookup"
7640 By default, both the preference value and the host name are returned for
7641 each MX record, separated by a space. If you want only host names, you can use
7642 the pseudo-type MXH:
7644 ${lookup dnsdb{mxh=a.b.example}}
7646 In this case, the preference values are omitted, and just the host names are
7649 .cindex "name server for enclosing domain"
7650 Another pseudo-type is ZNS (for &"zone NS"&). It performs a lookup for NS
7651 records on the given domain, but if none are found, it removes the first
7652 component of the domain name, and tries again. This process continues until NS
7653 records are found or there are no more components left (or there is a DNS
7654 error). In other words, it may return the name servers for a top-level domain,
7655 but it never returns the root name servers. If there are no NS records for the
7656 top-level domain, the lookup fails. Consider these examples:
7658 ${lookup dnsdb{zns=xxx.quercite.com}}
7659 ${lookup dnsdb{zns=xxx.edu}}
7661 Assuming that in each case there are no NS records for the full domain name,
7662 the first returns the name servers for &%quercite.com%&, and the second returns
7663 the name servers for &%edu%&.
7665 You should be careful about how you use this lookup because, unless the
7666 top-level domain does not exist, the lookup always returns some host names. The
7667 sort of use to which this might be put is for seeing if the name servers for a
7668 given domain are on a blacklist. You can probably assume that the name servers
7669 for the high-level domains such as &%com%& or &%co.uk%& are not going to be on
7672 .cindex "CSA" "in &(dnsdb)& lookup"
7673 A third pseudo-type is CSA (Client SMTP Authorization). This looks up SRV
7674 records according to the CSA rules, which are described in section
7675 &<<SECTverifyCSA>>&. Although &(dnsdb)& supports SRV lookups directly, this is
7676 not sufficient because of the extra parent domain search behaviour of CSA. The
7677 result of a successful lookup such as:
7679 ${lookup dnsdb {csa=$sender_helo_name}}
7681 has two space-separated fields: an authorization code and a target host name.
7682 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
7683 authorization required but absent, or &"?"& for unknown.
7685 .cindex "A+" "in &(dnsdb)& lookup"
7686 The pseudo-type A+ performs an AAAA
7687 and then an A lookup. All results are returned; defer processing
7688 (see below) is handled separately for each lookup. Example:
7690 ${lookup dnsdb {>; a+=$sender_helo_name}}
7694 .section "Multiple dnsdb lookups" "SECID67"
7695 In the previous sections, &(dnsdb)& lookups for a single domain are described.
7696 However, you can specify a list of domains or IP addresses in a single
7697 &(dnsdb)& lookup. The list is specified in the normal Exim way, with colon as
7698 the default separator, but with the ability to change this. For example:
7700 ${lookup dnsdb{one.domain.com:two.domain.com}}
7701 ${lookup dnsdb{a=one.host.com:two.host.com}}
7702 ${lookup dnsdb{ptr = <; 1.2.3.4 ; 4.5.6.8}}
7704 In order to retain backwards compatibility, there is one special case: if
7705 the lookup type is PTR and no change of separator is specified, Exim looks
7706 to see if the rest of the string is precisely one IPv6 address. In this
7707 case, it does not treat it as a list.
7709 The data from each lookup is concatenated, with newline separators by default,
7710 in the same way that multiple DNS records for a single item are handled. A
7711 different separator can be specified, as described above.
7716 .section "More about LDAP" "SECTldap"
7717 .cindex "LDAP" "lookup, more about"
7718 .cindex "lookup" "LDAP"
7719 .cindex "Solaris" "LDAP"
7720 The original LDAP implementation came from the University of Michigan; this has
7721 become &"Open LDAP"&, and there are now two different releases. Another
7722 implementation comes from Netscape, and Solaris 7 and subsequent releases
7723 contain inbuilt LDAP support. Unfortunately, though these are all compatible at
7724 the lookup function level, their error handling is different. For this reason
7725 it is necessary to set a compile-time variable when building Exim with LDAP, to
7726 indicate which LDAP library is in use. One of the following should appear in
7727 your &_Local/Makefile_&:
7729 LDAP_LIB_TYPE=UMICHIGAN
7730 LDAP_LIB_TYPE=OPENLDAP1
7731 LDAP_LIB_TYPE=OPENLDAP2
7732 LDAP_LIB_TYPE=NETSCAPE
7733 LDAP_LIB_TYPE=SOLARIS
7735 If LDAP_LIB_TYPE is not set, Exim assumes &`OPENLDAP1`&, which has the
7736 same interface as the University of Michigan version.
7738 There are three LDAP lookup types in Exim. These behave slightly differently in
7739 the way they handle the results of a query:
7742 &(ldap)& requires the result to contain just one entry; if there are more, it
7745 &(ldapdn)& also requires the result to contain just one entry, but it is the
7746 Distinguished Name that is returned rather than any attribute values.
7748 &(ldapm)& permits the result to contain more than one entry; the attributes
7749 from all of them are returned.
7753 For &(ldap)& and &(ldapm)&, if a query finds only entries with no attributes,
7754 Exim behaves as if the entry did not exist, and the lookup fails. The format of
7755 the data returned by a successful lookup is described in the next section.
7756 First we explain how LDAP queries are coded.
7759 .section "Format of LDAP queries" "SECTforldaque"
7760 .cindex "LDAP" "query format"
7761 An LDAP query takes the form of a URL as defined in RFC 2255. For example, in
7762 the configuration of a &(redirect)& router one might have this setting:
7764 data = ${lookup ldap \
7765 {ldap:///cn=$local_part,o=University%20of%20Cambridge,\
7766 c=UK?mailbox?base?}}
7768 .cindex "LDAP" "with TLS"
7769 The URL may begin with &`ldap`& or &`ldaps`& if your LDAP library supports
7770 secure (encrypted) LDAP connections. The second of these ensures that an
7771 encrypted TLS connection is used.
7773 With sufficiently modern LDAP libraries, Exim supports forcing TLS over regular
7774 LDAP connections, rather than the SSL-on-connect &`ldaps`&.
7775 See the &%ldap_start_tls%& option.
7777 Starting with Exim 4.83, the initialization of LDAP with TLS is more tightly
7778 controlled. Every part of the TLS configuration can be configured by settings in
7779 &_exim.conf_&. Depending on the version of the client libraries installed on
7780 your system, some of the initialization may have required setting options in
7781 &_/etc/ldap.conf_& or &_~/.ldaprc_& to get TLS working with self-signed
7782 certificates. This revealed a nuance where the current UID that exim was
7783 running as could affect which config files it read. With Exim 4.83, these
7784 methods become optional, only taking effect if not specifically set in
7788 .section "LDAP quoting" "SECID68"
7789 .cindex "LDAP" "quoting"
7790 Two levels of quoting are required in LDAP queries, the first for LDAP itself
7791 and the second because the LDAP query is represented as a URL. Furthermore,
7792 within an LDAP query, two different kinds of quoting are required. For this
7793 reason, there are two different LDAP-specific quoting operators.
7795 The &%quote_ldap%& operator is designed for use on strings that are part of
7796 filter specifications. Conceptually, it first does the following conversions on
7804 in accordance with RFC 2254. The resulting string is then quoted according
7805 to the rules for URLs, that is, all non-alphanumeric characters except
7809 are converted to their hex values, preceded by a percent sign. For example:
7811 ${quote_ldap: a(bc)*, a<yz>; }
7815 %20a%5C28bc%5C29%5C2A%2C%20a%3Cyz%3E%3B%20
7817 Removing the URL quoting, this is (with a leading and a trailing space):
7819 a\28bc\29\2A, a<yz>;
7821 The &%quote_ldap_dn%& operator is designed for use on strings that are part of
7822 base DN specifications in queries. Conceptually, it first converts the string
7823 by inserting a backslash in front of any of the following characters:
7827 It also inserts a backslash before any leading spaces or # characters, and
7828 before any trailing spaces. (These rules are in RFC 2253.) The resulting string
7829 is then quoted according to the rules for URLs. For example:
7831 ${quote_ldap_dn: a(bc)*, a<yz>; }
7835 %5C%20a(bc)*%5C%2C%20a%5C%3Cyz%5C%3E%5C%3B%5C%20
7837 Removing the URL quoting, this is (with a trailing space):
7839 \ a(bc)*\, a\<yz\>\;\
7841 There are some further comments about quoting in the section on LDAP
7842 authentication below.
7845 .section "LDAP connections" "SECID69"
7846 .cindex "LDAP" "connections"
7847 The connection to an LDAP server may either be over TCP/IP, or, when OpenLDAP
7848 is in use, via a Unix domain socket. The example given above does not specify
7849 an LDAP server. A server that is reached by TCP/IP can be specified in a query
7852 ldap://<hostname>:<port>/...
7854 If the port (and preceding colon) are omitted, the standard LDAP port (389) is
7855 used. When no server is specified in a query, a list of default servers is
7856 taken from the &%ldap_default_servers%& configuration option. This supplies a
7857 colon-separated list of servers which are tried in turn until one successfully
7858 handles a query, or there is a serious error. Successful handling either
7859 returns the requested data, or indicates that it does not exist. Serious errors
7860 are syntactical, or multiple values when only a single value is expected.
7861 Errors which cause the next server to be tried are connection failures, bind
7862 failures, and timeouts.
7864 For each server name in the list, a port number can be given. The standard way
7865 of specifying a host and port is to use a colon separator (RFC 1738). Because
7866 &%ldap_default_servers%& is a colon-separated list, such colons have to be
7867 doubled. For example
7869 ldap_default_servers = ldap1.example.com::145:ldap2.example.com
7871 If &%ldap_default_servers%& is unset, a URL with no server name is passed
7872 to the LDAP library with no server name, and the library's default (normally
7873 the local host) is used.
7875 If you are using the OpenLDAP library, you can connect to an LDAP server using
7876 a Unix domain socket instead of a TCP/IP connection. This is specified by using
7877 &`ldapi`& instead of &`ldap`& in LDAP queries. What follows here applies only
7878 to OpenLDAP. If Exim is compiled with a different LDAP library, this feature is
7881 For this type of connection, instead of a host name for the server, a pathname
7882 for the socket is required, and the port number is not relevant. The pathname
7883 can be specified either as an item in &%ldap_default_servers%&, or inline in
7884 the query. In the former case, you can have settings such as
7886 ldap_default_servers = /tmp/ldap.sock : backup.ldap.your.domain
7888 When the pathname is given in the query, you have to escape the slashes as
7889 &`%2F`& to fit in with the LDAP URL syntax. For example:
7891 ${lookup ldap {ldapi://%2Ftmp%2Fldap.sock/o=...
7893 When Exim processes an LDAP lookup and finds that the &"hostname"& is really
7894 a pathname, it uses the Unix domain socket code, even if the query actually
7895 specifies &`ldap`& or &`ldaps`&. In particular, no encryption is used for a
7896 socket connection. This behaviour means that you can use a setting of
7897 &%ldap_default_servers%& such as in the example above with traditional &`ldap`&
7898 or &`ldaps`& queries, and it will work. First, Exim tries a connection via
7899 the Unix domain socket; if that fails, it tries a TCP/IP connection to the
7902 If an explicit &`ldapi`& type is given in a query when a host name is
7903 specified, an error is diagnosed. However, if there are more items in
7904 &%ldap_default_servers%&, they are tried. In other words:
7907 Using a pathname with &`ldap`& or &`ldaps`& forces the use of the Unix domain
7910 Using &`ldapi`& with a host name causes an error.
7914 Using &`ldapi`& with no host or path in the query, and no setting of
7915 &%ldap_default_servers%&, does whatever the library does by default.
7919 .section "LDAP authentication and control information" "SECID70"
7920 .cindex "LDAP" "authentication"
7921 The LDAP URL syntax provides no way of passing authentication and other control
7922 information to the server. To make this possible, the URL in an LDAP query may
7923 be preceded by any number of <&'name'&>=<&'value'&> settings, separated by
7924 spaces. If a value contains spaces it must be enclosed in double quotes, and
7925 when double quotes are used, backslash is interpreted in the usual way inside
7926 them. The following names are recognized:
7928 &`DEREFERENCE`& set the dereferencing parameter
7929 &`NETTIME `& set a timeout for a network operation
7930 &`USER `& set the DN, for authenticating the LDAP bind
7931 &`PASS `& set the password, likewise
7932 &`REFERRALS `& set the referrals parameter
7933 &`SERVERS `& set alternate server list for this query only
7934 &`SIZE `& set the limit for the number of entries returned
7935 &`TIME `& set the maximum waiting time for a query
7937 The value of the DEREFERENCE parameter must be one of the words &"never"&,
7938 &"searching"&, &"finding"&, or &"always"&. The value of the REFERRALS parameter
7939 must be &"follow"& (the default) or &"nofollow"&. The latter stops the LDAP
7940 library from trying to follow referrals issued by the LDAP server.
7942 .cindex LDAP timeout
7943 .cindex timeout "LDAP lookup"
7944 The name CONNECT is an obsolete name for NETTIME, retained for
7945 backwards compatibility. This timeout (specified as a number of seconds) is
7946 enforced from the client end for operations that can be carried out over a
7947 network. Specifically, it applies to network connections and calls to the
7948 &'ldap_result()'& function. If the value is greater than zero, it is used if
7949 LDAP_OPT_NETWORK_TIMEOUT is defined in the LDAP headers (OpenLDAP), or
7950 if LDAP_X_OPT_CONNECT_TIMEOUT is defined in the LDAP headers (Netscape
7951 SDK 4.1). A value of zero forces an explicit setting of &"no timeout"& for
7952 Netscape SDK; for OpenLDAP no action is taken.
7954 The TIME parameter (also a number of seconds) is passed to the server to
7955 set a server-side limit on the time taken to complete a search.
7957 The SERVERS parameter allows you to specify an alternate list of ldap servers
7958 to use for an individual lookup. The global &%ldap_default_servers%& option provides a
7959 default list of ldap servers, and a single lookup can specify a single ldap
7960 server to use. But when you need to do a lookup with a list of servers that is
7961 different than the default list (maybe different order, maybe a completely
7962 different set of servers), the SERVERS parameter allows you to specify this
7963 alternate list (colon-separated).
7965 Here is an example of an LDAP query in an Exim lookup that uses some of these
7966 values. This is a single line, folded to fit on the page:
7969 {user="cn=manager,o=University of Cambridge,c=UK" pass=secret
7970 ldap:///o=University%20of%20Cambridge,c=UK?sn?sub?(cn=foo)}
7973 The encoding of spaces as &`%20`& is a URL thing which should not be done for
7974 any of the auxiliary data. Exim configuration settings that include lookups
7975 which contain password information should be preceded by &"hide"& to prevent
7976 non-admin users from using the &%-bP%& option to see their values.
7978 The auxiliary data items may be given in any order. The default is no
7979 connection timeout (the system timeout is used), no user or password, no limit
7980 on the number of entries returned, and no time limit on queries.
7982 When a DN is quoted in the USER= setting for LDAP authentication, Exim
7983 removes any URL quoting that it may contain before passing it LDAP. Apparently
7984 some libraries do this for themselves, but some do not. Removing the URL
7985 quoting has two advantages:
7988 It makes it possible to use the same &%quote_ldap_dn%& expansion for USER=
7989 DNs as with DNs inside actual queries.
7991 It permits spaces inside USER= DNs.
7994 For example, a setting such as
7996 USER=cn=${quote_ldap_dn:$1}
7998 should work even if &$1$& contains spaces.
8000 Expanded data for the PASS= value should be quoted using the &%quote%&
8001 expansion operator, rather than the LDAP quote operators. The only reason this
8002 field needs quoting is to ensure that it conforms to the Exim syntax, which
8003 does not allow unquoted spaces. For example:
8007 The LDAP authentication mechanism can be used to check passwords as part of
8008 SMTP authentication. See the &%ldapauth%& expansion string condition in chapter
8013 .section "Format of data returned by LDAP" "SECID71"
8014 .cindex "LDAP" "returned data formats"
8015 The &(ldapdn)& lookup type returns the Distinguished Name from a single entry
8016 as a sequence of values, for example
8018 cn=manager,o=University of Cambridge,c=UK
8020 The &(ldap)& lookup type generates an error if more than one entry matches the
8021 search filter, whereas &(ldapm)& permits this case, and inserts a newline in
8022 the result between the data from different entries. It is possible for multiple
8023 values to be returned for both &(ldap)& and &(ldapm)&, but in the former case
8024 you know that whatever values are returned all came from a single entry in the
8027 In the common case where you specify a single attribute in your LDAP query, the
8028 result is not quoted, and does not contain the attribute name. If the attribute
8029 has multiple values, they are separated by commas. Any comma that is
8030 part of an attribute's value is doubled.
8032 If you specify multiple attributes, the result contains space-separated, quoted
8033 strings, each preceded by the attribute name and an equals sign. Within the
8034 quotes, the quote character, backslash, and newline are escaped with
8035 backslashes, and commas are used to separate multiple values for the attribute.
8036 Any commas in attribute values are doubled
8037 (permitting treatment of the values as a comma-separated list).
8038 Apart from the escaping, the string within quotes takes the same form as the
8039 output when a single attribute is requested. Specifying no attributes is the
8040 same as specifying all of an entry's attributes.
8042 Here are some examples of the output format. The first line of each pair is an
8043 LDAP query, and the second is the data that is returned. The attribute called
8044 &%attr1%& has two values, one of them with an embedded comma, whereas
8045 &%attr2%& has only one value. Both attributes are derived from &%attr%&
8046 (they have SUP &%attr%& in their schema definitions).
8049 ldap:///o=base?attr1?sub?(uid=fred)
8052 ldap:///o=base?attr2?sub?(uid=fred)
8055 ldap:///o=base?attr?sub?(uid=fred)
8056 value1.1,value1,,2,value two
8058 ldap:///o=base?attr1,attr2?sub?(uid=fred)
8059 attr1="value1.1,value1,,2" attr2="value two"
8061 ldap:///o=base??sub?(uid=fred)
8062 objectClass="top" attr1="value1.1,value1,,2" attr2="value two"
8065 make use of Exim's &%-be%& option to run expansion tests and thereby check the
8066 results of LDAP lookups.
8067 The &%extract%& operator in string expansions can be used to pick out
8068 individual fields from data that consists of &'key'&=&'value'& pairs.
8069 The &%listextract%& operator should be used to pick out individual values
8070 of attributes, even when only a single value is expected.
8071 The doubling of embedded commas allows you to use the returned data as a
8072 comma separated list (using the "<," syntax for changing the input list separator).
8077 .section "More about NIS+" "SECTnisplus"
8078 .cindex "NIS+ lookup type"
8079 .cindex "lookup" "NIS+"
8080 NIS+ queries consist of a NIS+ &'indexed name'& followed by an optional colon
8081 and field name. If this is given, the result of a successful query is the
8082 contents of the named field; otherwise the result consists of a concatenation
8083 of &'field-name=field-value'& pairs, separated by spaces. Empty values and
8084 values containing spaces are quoted. For example, the query
8086 [name=mg1456],passwd.org_dir
8088 might return the string
8090 name=mg1456 passwd="" uid=999 gid=999 gcos="Martin Guerre"
8091 home=/home/mg1456 shell=/bin/bash shadow=""
8093 (split over two lines here to fit on the page), whereas
8095 [name=mg1456],passwd.org_dir:gcos
8101 with no quotes. A NIS+ lookup fails if NIS+ returns more than one table entry
8102 for the given indexed key. The effect of the &%quote_nisplus%& expansion
8103 operator is to double any quote characters within the text.
8107 .section "SQL lookups" "SECTsql"
8108 .cindex "SQL lookup types"
8109 .cindex "MySQL" "lookup type"
8110 .cindex "PostgreSQL lookup type"
8111 .cindex "lookup" "MySQL"
8112 .cindex "lookup" "PostgreSQL"
8113 .cindex "Oracle" "lookup type"
8114 .cindex "lookup" "Oracle"
8115 .cindex "InterBase lookup type"
8116 .cindex "lookup" "InterBase"
8117 .cindex "Redis lookup type"
8118 .cindex lookup Redis
8119 Exim can support lookups in InterBase, MySQL, Oracle, PostgreSQL, Redis,
8121 databases. Queries for these databases contain SQL statements, so an example
8124 ${lookup mysql{select mailbox from users where id='userx'}\
8127 If the result of the query contains more than one field, the data for each
8128 field in the row is returned, preceded by its name, so the result of
8130 ${lookup pgsql{select home,name from users where id='userx'}\
8135 home=/home/userx name="Mister X"
8137 Empty values and values containing spaces are double quoted, with embedded
8138 quotes escaped by a backslash. If the result of the query contains just one
8139 field, the value is passed back verbatim, without a field name, for example:
8143 If the result of the query yields more than one row, it is all concatenated,
8144 with a newline between the data for each row.
8147 .section "More about MySQL, PostgreSQL, Oracle, InterBase, and Redis" "SECID72"
8148 .cindex "MySQL" "lookup type"
8149 .cindex "PostgreSQL lookup type"
8150 .cindex "lookup" "MySQL"
8151 .cindex "lookup" "PostgreSQL"
8152 .cindex "Oracle" "lookup type"
8153 .cindex "lookup" "Oracle"
8154 .cindex "InterBase lookup type"
8155 .cindex "lookup" "InterBase"
8156 .cindex "Redis lookup type"
8157 .cindex lookup Redis
8158 If any MySQL, PostgreSQL, Oracle, InterBase or Redis lookups are used, the
8159 &%mysql_servers%&, &%pgsql_servers%&, &%oracle_servers%&, &%ibase_servers%&,
8160 or &%redis_servers%&
8161 option (as appropriate) must be set to a colon-separated list of server
8163 .oindex &%mysql_servers%&
8164 .oindex &%pgsql_servers%&
8165 .oindex &%oracle_servers%&
8166 .oindex &%ibase_servers%&
8167 .oindex &%redis_servers%&
8168 (For MySQL and PostgreSQL, the global option need not be set if all
8169 queries contain their own server information &-- see section
8170 &<<SECTspeserque>>&.)
8172 each item in the list is a slash-separated list of four
8173 items: host name, database name, user name, and password. In the case of
8174 Oracle, the host name field is used for the &"service name"&, and the database
8175 name field is not used and should be empty. For example:
8177 hide oracle_servers = oracle.plc.example//userx/abcdwxyz
8179 Because password data is sensitive, you should always precede the setting with
8180 &"hide"&, to prevent non-admin users from obtaining the setting via the &%-bP%&
8181 option. Here is an example where two MySQL servers are listed:
8183 hide mysql_servers = localhost/users/root/secret:\
8184 otherhost/users/root/othersecret
8186 For MySQL and PostgreSQL, a host may be specified as <&'name'&>:<&'port'&> but
8187 because this is a colon-separated list, the colon has to be doubled. For each
8188 query, these parameter groups are tried in order until a connection is made and
8189 a query is successfully processed. The result of a query may be that no data is
8190 found, but that is still a successful query. In other words, the list of
8191 servers provides a backup facility, not a list of different places to look.
8193 For Redis the global option need not be specified if all queries contain their
8194 own server information &-- see section &<<SECTspeserque>>&.
8195 If specified, the option must be set to a colon-separated list of server
8197 Each item in the list is a slash-separated list of three items:
8198 host, database number, and password.
8200 The host is required and may be either an IPv4 address and optional
8201 port number (separated by a colon, which needs doubling due to the
8202 higher-level list), or a Unix socket pathname enclosed in parentheses
8204 The database number is optional; if present that number is selected in the backend
8206 The password is optional; if present it is used to authenticate to the backend
8209 The &%quote_mysql%&, &%quote_pgsql%&, and &%quote_oracle%& expansion operators
8210 convert newline, tab, carriage return, and backspace to \n, \t, \r, and \b
8211 respectively, and the characters single-quote, double-quote, and backslash
8212 itself are escaped with backslashes.
8214 The &%quote_redis%& expansion operator
8215 escapes whitespace and backslash characters with a backslash.
8217 .section "Specifying the server in the query" "SECTspeserque"
8218 For MySQL, PostgreSQL and Redis lookups (but not currently for Oracle and InterBase),
8219 it is possible to specify a list of servers with an individual query. This is
8220 done by appending a comma-separated option to the query type:
8222 &`,servers=`&&'server1:server2:server3:...'&
8224 Each item in the list may take one of two forms:
8226 If it contains no slashes it is assumed to be just a host name. The appropriate
8227 global option (&%mysql_servers%& or &%pgsql_servers%&) is searched for a host
8228 of the same name, and the remaining parameters (database, user, password) are
8231 If it contains any slashes, it is taken as a complete parameter set.
8233 The list of servers is used in exactly the same way as the global list.
8234 Once a connection to a server has happened and a query has been
8235 successfully executed, processing of the lookup ceases.
8237 This feature is intended for use in master/slave situations where updates
8238 are occurring and you want to update the master rather than a slave. If the
8239 master is in the list as a backup for reading, you might have a global setting
8242 mysql_servers = slave1/db/name/pw:\
8246 In an updating lookup, you could then write:
8248 ${lookup mysql,servers=master {UPDATE ...} }
8250 That query would then be sent only to the master server. If, on the other hand,
8251 the master is not to be used for reading, and so is not present in the global
8252 option, you can still update it by a query of this form:
8254 ${lookup pgsql,servers=master/db/name/pw {UPDATE ...} }
8257 An older syntax places the servers specification before the query,
8258 semicolon separated:
8260 ${lookup mysql{servers=master; UPDATE ...} }
8262 The new version avoids potential issues with tainted
8263 arguments in the query, for explicit expansion.
8264 &*Note*&: server specifications in list-style lookups are still problematic.
8267 .section "Special MySQL features" "SECID73"
8268 For MySQL, an empty host name or the use of &"localhost"& in &%mysql_servers%&
8269 causes a connection to the server on the local host by means of a Unix domain
8270 socket. An alternate socket can be specified in parentheses.
8271 An option group name for MySQL option files can be specified in square brackets;
8272 the default value is &"exim"&.
8273 The full syntax of each item in &%mysql_servers%& is:
8275 <&'hostname'&>::<&'port'&>(<&'socket name'&>)[<&'option group'&>]/&&&
8276 <&'database'&>/<&'user'&>/<&'password'&>
8278 Any of the four sub-parts of the first field can be omitted. For normal use on
8279 the local host it can be left blank or set to just &"localhost"&.
8281 No database need be supplied &-- but if it is absent here, it must be given in
8284 If a MySQL query is issued that does not request any data (an insert, update,
8285 or delete command), the result of the lookup is the number of rows affected.
8287 &*Warning*&: This can be misleading. If an update does not actually change
8288 anything (for example, setting a field to the value it already has), the result
8289 is zero because no rows are affected.
8292 .section "Special PostgreSQL features" "SECID74"
8293 PostgreSQL lookups can also use Unix domain socket connections to the database.
8294 This is usually faster and costs less CPU time than a TCP/IP connection.
8295 However it can be used only if the mail server runs on the same machine as the
8296 database server. A configuration line for PostgreSQL via Unix domain sockets
8299 hide pgsql_servers = (/tmp/.s.PGSQL.5432)/db/user/password : ...
8301 In other words, instead of supplying a host name, a path to the socket is
8302 given. The path name is enclosed in parentheses so that its slashes aren't
8303 visually confused with the delimiters for the other server parameters.
8305 If a PostgreSQL query is issued that does not request any data (an insert,
8306 update, or delete command), the result of the lookup is the number of rows
8309 .section "More about SQLite" "SECTsqlite"
8310 .cindex "lookup" "SQLite"
8311 .cindex "sqlite lookup type"
8312 SQLite is different to the other SQL lookups because a filename is required in
8313 addition to the SQL query. An SQLite database is a single file, and there is no
8314 daemon as in the other SQL databases.
8316 .oindex &%sqlite_dbfile%&
8317 There are two ways of
8318 specifying the file.
8319 The first is is by using the &%sqlite_dbfile%& main option.
8320 The second, which allows separate files for each query,
8321 is to use an option appended, comma-separated, to the &"sqlite"&
8322 lookup type word. The option is the word &"file"&, then an equals,
8324 The filename in this case cannot contain whitespace or open-brace charachters.
8326 A deprecated method is available, prefixing the query with the filename
8327 separated by white space.
8329 .cindex "tainted data" "sqlite file"
8330 the query cannot use any tainted values, as that taints
8331 the entire query including the filename - resulting in a refusal to open
8334 In all the above cases the filename must be an absolute path.
8336 Here is a lookup expansion example:
8338 sqlite_dbfile = /some/thing/sqlitedb
8340 ${lookup sqlite {select name from aliases where id='userx';}}
8342 In a list, the syntax is similar. For example:
8344 domainlist relay_to_domains = sqlite;\
8345 select * from relays where ip='$sender_host_address';
8347 The only character affected by the &%quote_sqlite%& operator is a single
8348 quote, which it doubles.
8350 .cindex timeout SQLite
8351 .cindex sqlite "lookup timeout"
8352 The SQLite library handles multiple simultaneous accesses to the database
8353 internally. Multiple readers are permitted, but only one process can
8354 update at once. Attempts to access the database while it is being updated
8355 are rejected after a timeout period, during which the SQLite library
8356 waits for the lock to be released. In Exim, the default timeout is set
8357 to 5 seconds, but it can be changed by means of the &%sqlite_lock_timeout%&
8360 .section "More about Redis" "SECTredis"
8361 .cindex "lookup" "Redis"
8362 .cindex "redis lookup type"
8363 Redis is a non-SQL database. Commands are simple get and set.
8366 ${lookup redis{set keyname ${quote_redis:objvalue plus}}}
8367 ${lookup redis{get keyname}}
8370 As of release 4.91, "lightweight" support for Redis Cluster is available.
8371 Requires &%redis_servers%& list to contain all the servers in the cluster, all
8372 of which must be reachable from the running exim instance. If the cluster has
8373 master/slave replication, the list must contain all the master and slave
8376 When the Redis Cluster returns a "MOVED" response to a query, Exim does not
8377 immediately follow the redirection but treats the response as a DEFER, moving on
8378 to the next server in the &%redis_servers%& list until the correct server is
8385 . ////////////////////////////////////////////////////////////////////////////
8386 . ////////////////////////////////////////////////////////////////////////////
8388 .chapter "Domain, host, address, and local part lists" &&&
8389 "CHAPdomhosaddlists" &&&
8390 "Domain, host, and address lists"
8391 .scindex IIDdohoadli "lists of domains; hosts; etc."
8392 A number of Exim configuration options contain lists of domains, hosts,
8393 email addresses, or local parts. For example, the &%hold_domains%& option
8394 contains a list of domains whose delivery is currently suspended. These lists
8395 are also used as data in ACL statements (see chapter &<<CHAPACL>>&), and as
8396 arguments to expansion conditions such as &%match_domain%&.
8398 Each item in one of these lists is a pattern to be matched against a domain,
8399 host, email address, or local part, respectively. In the sections below, the
8400 different types of pattern for each case are described, but first we cover some
8401 general facilities that apply to all four kinds of list.
8403 Note that other parts of Exim use a &'string list'& which does not
8404 support all the complexity available in
8405 domain, host, address and local part lists.
8409 .section "Expansion of lists" "SECTlistexpand"
8410 .cindex "expansion" "of lists"
8411 Each list is expanded as a single string before it is used.
8413 &'Exception: the router headers_remove option, where list-item
8414 splitting is done before string-expansion.'&
8417 expansion must be a list, possibly containing empty items, which is split up
8418 into separate items for matching. By default, colon is the separator character,
8419 but this can be varied if necessary. See sections &<<SECTlistconstruct>>& and
8420 &<<SECTempitelis>>& for details of the list syntax; the second of these
8421 discusses the way to specify empty list items.
8424 If the string expansion is forced to fail, Exim behaves as if the item it is
8425 testing (domain, host, address, or local part) is not in the list. Other
8426 expansion failures cause temporary errors.
8428 If an item in a list is a regular expression, backslashes, dollars and possibly
8429 other special characters in the expression must be protected against
8430 misinterpretation by the string expander. The easiest way to do this is to use
8431 the &`\N`& expansion feature to indicate that the contents of the regular
8432 expression should not be expanded. For example, in an ACL you might have:
8434 deny senders = \N^\d{8}\w@.*\.baddomain\.example$\N : \
8435 ${lookup{$domain}lsearch{/badsenders/bydomain}}
8437 The first item is a regular expression that is protected from expansion by
8438 &`\N`&, whereas the second uses the expansion to obtain a list of unwanted
8439 senders based on the receiving domain.
8444 .section "Negated items in lists" "SECID76"
8445 .cindex "list" "negation"
8446 .cindex "negation" "in lists"
8447 Items in a list may be positive or negative. Negative items are indicated by a
8448 leading exclamation mark, which may be followed by optional white space. A list
8449 defines a set of items (domains, etc). When Exim processes one of these lists,
8450 it is trying to find out whether a domain, host, address, or local part
8451 (respectively) is in the set that is defined by the list. It works like this:
8453 The list is scanned from left to right. If a positive item is matched, the
8454 subject that is being checked is in the set; if a negative item is matched, the
8455 subject is not in the set. If the end of the list is reached without the
8456 subject having matched any of the patterns, it is in the set if the last item
8457 was a negative one, but not if it was a positive one. For example, the list in
8459 domainlist relay_to_domains = !a.b.c : *.b.c
8461 matches any domain ending in &'.b.c'& except for &'a.b.c'&. Domains that match
8462 neither &'a.b.c'& nor &'*.b.c'& do not match, because the last item in the
8463 list is positive. However, if the setting were
8465 domainlist relay_to_domains = !a.b.c
8467 then all domains other than &'a.b.c'& would match because the last item in the
8468 list is negative. In other words, a list that ends with a negative item behaves
8469 as if it had an extra item &`:*`& on the end.
8471 Another way of thinking about positive and negative items in lists is to read
8472 the connector as &"or"& after a positive item and as &"and"& after a negative
8477 .section "File names in lists" "SECTfilnamlis"
8478 .cindex "list" "filename in"
8479 If an item in a domain, host, address, or local part list is an absolute
8480 filename (beginning with a slash character), each line of the file is read and
8481 processed as if it were an independent item in the list, except that further
8482 filenames are not allowed,
8483 and no expansion of the data from the file takes place.
8484 Empty lines in the file are ignored, and the file may also contain comment
8488 For domain and host lists, if a # character appears anywhere in a line of the
8489 file, it and all following characters are ignored.
8491 Because local parts may legitimately contain # characters, a comment in an
8492 address list or local part list file is recognized only if # is preceded by
8493 white space or the start of the line. For example:
8495 not#comment@x.y.z # but this is a comment
8499 Putting a filename in a list has the same effect as inserting each line of the
8500 file as an item in the list (blank lines and comments excepted). However, there
8501 is one important difference: the file is read each time the list is processed,
8502 so if its contents vary over time, Exim's behaviour changes.
8504 If a filename is preceded by an exclamation mark, the sense of any match
8505 within the file is inverted. For example, if
8507 hold_domains = !/etc/nohold-domains
8509 and the file contains the lines
8514 then &'a.b.c'& is in the set of domains defined by &%hold_domains%&, whereas
8515 any domain matching &`*.b.c`& is not.
8519 .section "An lsearch file is not an out-of-line list" "SECID77"
8520 As will be described in the sections that follow, lookups can be used in lists
8521 to provide indexed methods of checking list membership. There has been some
8522 confusion about the way &(lsearch)& lookups work in lists. Because
8523 an &(lsearch)& file contains plain text and is scanned sequentially, it is
8524 sometimes thought that it is allowed to contain wild cards and other kinds of
8525 non-constant pattern. This is not the case. The keys in an &(lsearch)& file are
8526 always fixed strings, just as for any other single-key lookup type.
8528 If you want to use a file to contain wild-card patterns that form part of a
8529 list, just give the filename on its own, without a search type, as described
8530 in the previous section. You could also use the &(wildlsearch)& or
8531 &(nwildlsearch)&, but there is no advantage in doing this.
8536 .section "Results of list checking" SECTlistresults
8537 The primary result of doing a list check is a truth value.
8538 In some contexts additional information is stored
8539 about the list element that matched:
8542 A &%hosts%& ACL condition
8543 will store a result in the &$host_data$& variable.
8545 A &%local_parts%& router option or &%local_parts%& ACL condition
8546 will store a result in the &$local_part_data$& variable.
8548 A &%domains%& router option or &%domains%& ACL condition
8549 will store a result in the &$domain_data$& variable.
8551 A &%senders%& router option or &%senders%& ACL condition
8552 will store a result in the &$sender_data$& variable.
8554 A &%recipients%& ACL condition
8555 will store a result in the &$recipient_data$& variable.
8558 The detail of the additional information depends on the
8559 type of match and is given below as the &*value*& information.
8564 .section "Named lists" "SECTnamedlists"
8565 .cindex "named lists"
8566 .cindex "list" "named"
8567 A list of domains, hosts, email addresses, or local parts can be given a name
8568 which is then used to refer to the list elsewhere in the configuration. This is
8569 particularly convenient if the same list is required in several different
8570 places. It also allows lists to be given meaningful names, which can improve
8571 the readability of the configuration. For example, it is conventional to define
8572 a domain list called &'local_domains'& for all the domains that are handled
8573 locally on a host, using a configuration line such as
8575 domainlist local_domains = localhost:my.dom.example
8577 Named lists are referenced by giving their name preceded by a plus sign, so,
8578 for example, a router that is intended to handle local domains would be
8579 configured with the line
8581 domains = +local_domains
8583 The first router in a configuration is often one that handles all domains
8584 except the local ones, using a configuration with a negated item like this:
8588 domains = ! +local_domains
8589 transport = remote_smtp
8592 The four kinds of named list are created by configuration lines starting with
8593 the words &%domainlist%&, &%hostlist%&, &%addresslist%&, or &%localpartlist%&,
8594 respectively. Then there follows the name that you are defining, followed by an
8595 equals sign and the list itself. For example:
8597 hostlist relay_from_hosts = 192.168.23.0/24 : my.friend.example
8598 addresslist bad_senders = cdb;/etc/badsenders
8600 A named list may refer to other named lists:
8602 domainlist dom1 = first.example : second.example
8603 domainlist dom2 = +dom1 : third.example
8604 domainlist dom3 = fourth.example : +dom2 : fifth.example
8606 &*Warning*&: If the last item in a referenced list is a negative one, the
8607 effect may not be what you intended, because the negation does not propagate
8608 out to the higher level. For example, consider:
8610 domainlist dom1 = !a.b
8611 domainlist dom2 = +dom1 : *.b
8613 The second list specifies &"either in the &%dom1%& list or &'*.b'&"&. The first
8614 list specifies just &"not &'a.b'&"&, so the domain &'x.y'& matches it. That
8615 means it matches the second list as well. The effect is not the same as
8617 domainlist dom2 = !a.b : *.b
8619 where &'x.y'& does not match. It's best to avoid negation altogether in
8620 referenced lists if you can.
8622 .cindex "hiding named list values"
8623 .cindex "named lists" "hiding value of"
8624 Some named list definitions may contain sensitive data, for example, passwords for
8625 accessing databases. To stop non-admin users from using the &%-bP%& command
8626 line option to read these values, you can precede the definition with the
8627 word &"hide"&. For example:
8629 hide domainlist filter_for_domains = ldap;PASS=secret ldap::/// ...
8633 Named lists may have a performance advantage. When Exim is routing an
8634 address or checking an incoming message, it caches the result of tests on named
8635 lists. So, if you have a setting such as
8637 domains = +local_domains
8639 on several of your routers
8640 or in several ACL statements,
8641 the actual test is done only for the first one. However, the caching works only
8642 if there are no expansions within the list itself or any sublists that it
8643 references. In other words, caching happens only for lists that are known to be
8644 the same each time they are referenced.
8646 By default, there may be up to 16 named lists of each type. This limit can be
8647 extended by changing a compile-time variable. The use of domain and host lists
8648 is recommended for concepts such as local domains, relay domains, and relay
8649 hosts. The default configuration is set up like this.
8653 .section "Named lists compared with macros" "SECID78"
8654 .cindex "list" "named compared with macro"
8655 .cindex "macro" "compared with named list"
8656 At first sight, named lists might seem to be no different from macros in the
8657 configuration file. However, macros are just textual substitutions. If you
8660 ALIST = host1 : host2
8661 auth_advertise_hosts = !ALIST
8663 it probably won't do what you want, because that is exactly the same as
8665 auth_advertise_hosts = !host1 : host2
8667 Notice that the second host name is not negated. However, if you use a host
8670 hostlist alist = host1 : host2
8671 auth_advertise_hosts = ! +alist
8673 the negation applies to the whole list, and so that is equivalent to
8675 auth_advertise_hosts = !host1 : !host2
8679 .section "Named list caching" "SECID79"
8680 .cindex "list" "caching of named"
8681 .cindex "caching" "named lists"
8682 While processing a message, Exim caches the result of checking a named list if
8683 it is sure that the list is the same each time. In practice, this means that
8684 the cache operates only if the list contains no $ characters, which guarantees
8685 that it will not change when it is expanded. Sometimes, however, you may have
8686 an expanded list that you know will be the same each time within a given
8687 message. For example:
8689 domainlist special_domains = \
8690 ${lookup{$sender_host_address}cdb{/some/file}}
8692 This provides a list of domains that depends only on the sending host's IP
8693 address. If this domain list is referenced a number of times (for example,
8694 in several ACL lines, or in several routers) the result of the check is not
8695 cached by default, because Exim does not know that it is going to be the
8696 same list each time.
8698 By appending &`_cache`& to &`domainlist`& you can tell Exim to go ahead and
8699 cache the result anyway. For example:
8701 domainlist_cache special_domains = ${lookup{...
8703 If you do this, you should be absolutely sure that caching is going to do
8704 the right thing in all cases. When in doubt, leave it out.
8708 .section "Domain lists" "SECTdomainlist"
8709 .cindex "domain list" "patterns for"
8710 .cindex "list" "domain list"
8711 Domain lists contain patterns that are to be matched against a mail domain.
8712 The following types of item may appear in domain lists:
8715 .cindex "primary host name"
8716 .cindex "host name" "matched in domain list"
8717 .oindex "&%primary_hostname%&"
8718 .cindex "domain list" "matching primary host name"
8719 .cindex "@ in a domain list"
8720 If a pattern consists of a single @ character, it matches the local host name,
8721 as set by the &%primary_hostname%& option (or defaulted). This makes it
8722 possible to use the same configuration file on several different hosts that
8723 differ only in their names.
8725 The value for a match will be the primary host name.
8729 .cindex "@[] in a domain list"
8730 .cindex "domain list" "matching local IP interfaces"
8731 .cindex "domain literal"
8732 If a pattern consists of the string &`@[]`& it matches an IP address enclosed
8733 in square brackets (as in an email address that contains a domain literal), but
8734 only if that IP address is recognized as local for email routing purposes. The
8735 &%local_interfaces%& and &%extra_local_interfaces%& options can be used to
8736 control which of a host's several IP addresses are treated as local.
8737 In today's Internet, the use of domain literals is controversial;
8738 see the &%allow_domain_literals%& main option.
8740 The value for a match will be the string &`@[]`&.
8745 .cindex "@mx_primary"
8746 .cindex "@mx_secondary"
8747 .cindex "domain list" "matching MX pointers to local host"
8748 If a pattern consists of the string &`@mx_any`& it matches any domain that
8749 has an MX record pointing to the local host or to any host that is listed in
8750 .oindex "&%hosts_treat_as_local%&"
8751 &%hosts_treat_as_local%&. The items &`@mx_primary`& and &`@mx_secondary`&
8752 are similar, except that the first matches only when a primary MX target is the
8753 local host, and the second only when no primary MX target is the local host,
8754 but a secondary MX target is. &"Primary"& means an MX record with the lowest
8755 preference value &-- there may of course be more than one of them.
8757 The MX lookup that takes place when matching a pattern of this type is
8758 performed with the resolver options for widening names turned off. Thus, for
8759 example, a single-component domain will &'not'& be expanded by adding the
8760 resolver's default domain. See the &%qualify_single%& and &%search_parents%&
8761 options of the &(dnslookup)& router for a discussion of domain widening.
8763 Sometimes you may want to ignore certain IP addresses when using one of these
8764 patterns. You can specify this by following the pattern with &`/ignore=`&<&'ip
8765 list'&>, where <&'ip list'&> is a list of IP addresses. These addresses are
8766 ignored when processing the pattern (compare the &%ignore_target_hosts%& option
8767 on a router). For example:
8769 domains = @mx_any/ignore=127.0.0.1
8771 This example matches any domain that has an MX record pointing to one of
8772 the local host's IP addresses other than 127.0.0.1.
8774 The list of IP addresses is in fact processed by the same code that processes
8775 host lists, so it may contain CIDR-coded network specifications and it may also
8776 contain negative items.
8778 Because the list of IP addresses is a sublist within a domain list, you have to
8779 be careful about delimiters if there is more than one address. Like any other
8780 list, the default delimiter can be changed. Thus, you might have:
8782 domains = @mx_any/ignore=<;127.0.0.1;0.0.0.0 : \
8783 an.other.domain : ...
8785 so that the sublist uses semicolons for delimiters. When IPv6 addresses are
8786 involved, it is easiest to change the delimiter for the main list as well:
8788 domains = <? @mx_any/ignore=<;127.0.0.1;::1 ? \
8789 an.other.domain ? ...
8791 The value for a match will be the list element string (starting &`@mx_`&).
8795 .cindex "asterisk" "in domain list"
8796 .cindex "domain list" "asterisk in"
8797 .cindex "domain list" "matching &""ends with""&"
8798 If a pattern starts with an asterisk, the remaining characters of the pattern
8799 are compared with the terminating characters of the domain. The use of &"*"& in
8800 domain lists differs from its use in partial matching lookups. In a domain
8801 list, the character following the asterisk need not be a dot, whereas partial
8802 matching works only in terms of dot-separated components. For example, a domain
8803 list item such as &`*key.ex`& matches &'donkey.ex'& as well as
8806 The value for a match will be the list element string (starting with the asterisk).
8807 Additionally, &$0$& will be set to the matched string
8808 and &$1$& to the variable portion which the asterisk matched.
8811 .cindex "regular expressions" "in domain list"
8812 .cindex "domain list" "matching regular expression"
8813 If a pattern starts with a circumflex character, it is treated as a regular
8814 expression, and matched against the domain using a regular expression matching
8815 function. The circumflex is treated as part of the regular expression.
8816 Email domains are case-independent, so this regular expression match is by
8817 default case-independent, but you can make it case-dependent by starting it
8818 with &`(?-i)`&. References to descriptions of the syntax of regular expressions
8819 are given in chapter &<<CHAPregexp>>&.
8821 &*Warning*&: Because domain lists are expanded before being processed, you
8822 must escape any backslash and dollar characters in the regular expression, or
8823 use the special &`\N`& sequence (see chapter &<<CHAPexpand>>&) to specify that
8824 it is not to be expanded (unless you really do want to build a regular
8825 expression by expansion, of course).
8827 The value for a match will be the list element string (starting with the circumflex).
8828 Additionally, &$0$& will be set to the string matching the regular expression,
8829 and &$1$& (onwards) to any submatches identified by parentheses.
8834 .cindex "lookup" "in domain list"
8835 .cindex "domain list" "matching by lookup"
8836 If a pattern starts with the name of a single-key lookup type followed by a
8837 semicolon (for example, &"dbm;"& or &"lsearch;"&), the remainder of the pattern
8838 must be a filename in a suitable format for the lookup type. For example, for
8839 &"cdb;"& it must be an absolute path:
8841 domains = cdb;/etc/mail/local_domains.cdb
8843 The appropriate type of lookup is done on the file using the domain name as the
8844 key. In most cases, the value resulting from the lookup is not used; Exim is interested
8845 only in whether or not the key is present in the file. However, when a lookup
8846 is used for the &%domains%& option on a router
8847 or a &%domains%& condition in an ACL statement, the value is preserved in the
8848 &$domain_data$& variable and can be referred to in other router options or
8849 other statements in the same ACL.
8850 .cindex "tainted data" "de-tainting"
8851 The value will be untainted.
8853 &*Note*&: If the data result of the lookup (as opposed to the key)
8854 is empty, then this empty value is stored in &$domain_data$&.
8855 The option to return the key for the lookup, as the value,
8856 may be what is wanted.
8860 Any of the single-key lookup type names may be preceded by
8861 &`partial`&<&'n'&>&`-`&, where the <&'n'&> is optional, for example,
8863 domains = partial-dbm;/partial/domains
8865 This causes partial matching logic to be invoked; a description of how this
8866 works is given in section &<<SECTpartiallookup>>&.
8869 .cindex "asterisk" "in lookup type"
8870 Any of the single-key lookup types may be followed by an asterisk. This causes
8871 a default lookup for a key consisting of a single asterisk to be done if the
8872 original lookup fails. This is not a useful feature when using a domain list to
8873 select particular domains (because any domain would match), but it might have
8874 value if the result of the lookup is being used via the &$domain_data$&
8878 If the pattern starts with the name of a query-style lookup type followed by a
8879 semicolon (for example, &"nisplus;"& or &"ldap;"&), the remainder of the
8880 pattern must be an appropriate query for the lookup type, as described in
8881 chapter &<<CHAPfdlookup>>&. For example:
8883 hold_domains = mysql;select domain from holdlist \
8884 where domain = '${quote_mysql:$domain}';
8886 In most cases, the value resulting from the lookup is not used (so for an SQL query, for
8887 example, it doesn't matter what field you select). Exim is interested only in
8888 whether or not the query succeeds. However, when a lookup is used for the
8889 &%domains%& option on a router, the value is preserved in the &$domain_data$&
8890 variable and can be referred to in other options.
8891 .cindex "tainted data" "de-tainting"
8892 The value will be untainted.
8895 If the pattern starts with the name of a lookup type
8896 of either kind (single-key or query-style) it may be
8897 followed by a comma and options,
8898 The options are lookup-type specific and consist of a comma-separated list.
8899 Each item starts with a tag and and equals "=" sign.
8902 .cindex "domain list" "matching literal domain name"
8903 If none of the above cases apply, a caseless textual comparison is made
8904 between the pattern and the domain.
8906 The value for a match will be the list element string.
8907 .cindex "tainted data" "de-tainting"
8908 Note that this is commonly untainted
8909 (depending on the way the list was created).
8910 Specifically, explicit text in the configuration file in not tainted.
8911 This is a useful way of obtaining an untainted equivalent to
8912 the domain, for later operations.
8914 However if the list (including one-element lists)
8915 is created by expanding a variable containing tainted data,
8916 it is tainted and so will the match value be.
8920 Here is an example that uses several different kinds of pattern:
8922 domainlist funny_domains = \
8925 *.foundation.fict.example : \
8926 \N^[1-2]\d{3}\.fict\.example$\N : \
8927 partial-dbm;/opt/data/penguin/book : \
8928 nis;domains.byname : \
8929 nisplus;[name=$domain,status=local],domains.org_dir
8931 There are obvious processing trade-offs among the various matching modes. Using
8932 an asterisk is faster than a regular expression, and listing a few names
8933 explicitly probably is too. The use of a file or database lookup is expensive,
8934 but may be the only option if hundreds of names are required. Because the
8935 patterns are tested in order, it makes sense to put the most commonly matched
8940 .section "Host lists" "SECThostlist"
8941 .cindex "host list" "patterns in"
8942 .cindex "list" "host list"
8943 Host lists are used to control what remote hosts are allowed to do. For
8944 example, some hosts may be allowed to use the local host as a relay, and some
8945 may be permitted to use the SMTP ETRN command. Hosts can be identified in
8946 two different ways, by name or by IP address. In a host list, some types of
8947 pattern are matched to a host name, and some are matched to an IP address.
8948 You need to be particularly careful with this when single-key lookups are
8949 involved, to ensure that the right value is being used as the key.
8952 .section "Special host list patterns" "SECID80"
8953 .cindex "empty item in hosts list"
8954 .cindex "host list" "empty string in"
8955 If a host list item is the empty string, it matches only when no remote host is
8956 involved. This is the case when a message is being received from a local
8957 process using SMTP on the standard input, that is, when a TCP/IP connection is
8960 .cindex "asterisk" "in host list"
8961 The special pattern &"*"& in a host list matches any host or no host. Neither
8962 the IP address nor the name is actually inspected.
8966 .section "Host list patterns that match by IP address" "SECThoslispatip"
8967 .cindex "host list" "matching IP addresses"
8968 If an IPv4 host calls an IPv6 host and the call is accepted on an IPv6 socket,
8969 the incoming address actually appears in the IPv6 host as
8970 &`::ffff:`&<&'v4address'&>. When such an address is tested against a host
8971 list, it is converted into a traditional IPv4 address first. (Not all operating
8972 systems accept IPv4 calls on IPv6 sockets, as there have been some security
8975 The following types of pattern in a host list check the remote host by
8976 inspecting its IP address:
8979 If the pattern is a plain domain name (not a regular expression, not starting
8980 with *, not a lookup of any kind), Exim calls the operating system function
8981 to find the associated IP address(es). Exim uses the newer
8982 &[getipnodebyname()]& function when available, otherwise &[gethostbyname()]&.
8983 This typically causes a forward DNS lookup of the name. The result is compared
8984 with the IP address of the subject host.
8986 If there is a temporary problem (such as a DNS timeout) with the host name
8987 lookup, a temporary error occurs. For example, if the list is being used in an
8988 ACL condition, the ACL gives a &"defer"& response, usually leading to a
8989 temporary SMTP error code. If no IP address can be found for the host name,
8990 what happens is described in section &<<SECTbehipnot>>& below.
8993 .cindex "@ in a host list"
8994 If the pattern is &"@"&, the primary host name is substituted and used as a
8995 domain name, as just described.
8998 If the pattern is an IP address, it is matched against the IP address of the
8999 subject host. IPv4 addresses are given in the normal &"dotted-quad"& notation.
9000 IPv6 addresses can be given in colon-separated format, but the colons have to
9001 be doubled so as not to be taken as item separators when the default list
9002 separator is used. IPv6 addresses are recognized even when Exim is compiled
9003 without IPv6 support. This means that if they appear in a host list on an
9004 IPv4-only host, Exim will not treat them as host names. They are just addresses
9005 that can never match a client host.
9008 .cindex "@[] in a host list"
9009 If the pattern is &"@[]"&, it matches the IP address of any IP interface on
9010 the local host. For example, if the local host is an IPv4 host with one
9011 interface address 10.45.23.56, these two ACL statements have the same effect:
9013 accept hosts = 127.0.0.1 : 10.45.23.56
9017 .cindex "CIDR notation"
9018 If the pattern is an IP address followed by a slash and a mask length, for
9023 , it is matched against the IP address of the subject
9024 host under the given mask. This allows an entire network of hosts to be
9025 included (or excluded) by a single item. The mask uses CIDR notation; it
9026 specifies the number of address bits that must match, starting from the most
9027 significant end of the address.
9029 &*Note*&: The mask is &'not'& a count of addresses, nor is it the high number
9030 of a range of addresses. It is the number of bits in the network portion of the
9031 address. The above example specifies a 24-bit netmask, so it matches all 256
9032 addresses in the 10.11.42.0 network. An item such as
9036 matches just two addresses, 192.168.23.236 and 192.168.23.237. A mask value of
9037 32 for an IPv4 address is the same as no mask at all; just a single address
9040 Here is another example which shows an IPv4 and an IPv6 network:
9042 recipient_unqualified_hosts = 192.168.0.0/16: \
9043 3ffe::ffff::836f::::/48
9045 The doubling of list separator characters applies only when these items
9046 appear inline in a host list. It is not required when indirecting via a file.
9049 recipient_unqualified_hosts = /opt/exim/unqualnets
9051 could make use of a file containing
9056 to have exactly the same effect as the previous example. When listing IPv6
9057 addresses inline, it is usually more convenient to use the facility for
9058 changing separator characters. This list contains the same two networks:
9060 recipient_unqualified_hosts = <; 172.16.0.0/12; \
9063 The separator is changed to semicolon by the leading &"<;"& at the start of the
9069 .section "Host list patterns for single-key lookups by host address" &&&
9070 "SECThoslispatsikey"
9071 .cindex "host list" "lookup of IP address"
9072 When a host is to be identified by a single-key lookup of its complete IP
9073 address, the pattern takes this form:
9075 &`net-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
9079 hosts_lookup = net-cdb;/hosts-by-ip.db
9081 The text form of the IP address of the subject host is used as the lookup key.
9082 IPv6 addresses are converted to an unabbreviated form, using lower case
9083 letters, with dots as separators because colon is the key terminator in
9084 &(lsearch)& files. [Colons can in fact be used in keys in &(lsearch)& files by
9085 quoting the keys, but this is a facility that was added later.] The data
9086 returned by the lookup is not used.
9088 .cindex "IP address" "masking"
9089 .cindex "host list" "masked IP address"
9090 Single-key lookups can also be performed using masked IP addresses, using
9091 patterns of this form:
9093 &`net<`&&'number'&&`>-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
9097 net24-dbm;/networks.db
9099 The IP address of the subject host is masked using <&'number'&> as the mask
9100 length. A textual string is constructed from the masked value, followed by the
9101 mask, and this is used as the lookup key. For example, if the host's IP address
9102 is 192.168.34.6, the key that is looked up for the above example is
9103 &"192.168.34.0/24"&.
9105 When an IPv6 address is converted to a string, dots are normally used instead
9106 of colons, so that keys in &(lsearch)& files need not contain colons (which
9107 terminate &(lsearch)& keys). This was implemented some time before the ability
9108 to quote keys was made available in &(lsearch)& files. However, the more
9109 recently implemented &(iplsearch)& files do require colons in IPv6 keys
9110 (notated using the quoting facility) so as to distinguish them from IPv4 keys.
9111 For this reason, when the lookup type is &(iplsearch)&, IPv6 addresses are
9112 converted using colons and not dots.
9113 In all cases except IPv4-mapped IPv6, full, unabbreviated IPv6
9114 addresses are always used.
9115 The latter are converted to IPv4 addresses, in dotted-quad form.
9117 Ideally, it would be nice to tidy up this anomalous situation by changing to
9118 colons in all cases, given that quoting is now available for &(lsearch)&.
9119 However, this would be an incompatible change that might break some existing
9122 &*Warning*&: Specifying &%net32-%& (for an IPv4 address) or &%net128-%& (for an
9123 IPv6 address) is not the same as specifying just &%net-%& without a number. In
9124 the former case the key strings include the mask value, whereas in the latter
9125 case the IP address is used on its own.
9129 .section "Host list patterns that match by host name" "SECThoslispatnam"
9130 .cindex "host" "lookup failures"
9131 .cindex "unknown host name"
9132 .cindex "host list" "matching host name"
9133 There are several types of pattern that require Exim to know the name of the
9134 remote host. These are either wildcard patterns or lookups by name. (If a
9135 complete hostname is given without any wildcarding, it is used to find an IP
9136 address to match against, as described in section &<<SECThoslispatip>>&
9139 If the remote host name is not already known when Exim encounters one of these
9140 patterns, it has to be found from the IP address.
9141 Although many sites on the Internet are conscientious about maintaining reverse
9142 DNS data for their hosts, there are also many that do not do this.
9143 Consequently, a name cannot always be found, and this may lead to unwanted
9144 effects. Take care when configuring host lists with wildcarded name patterns.
9145 Consider what will happen if a name cannot be found.
9147 Because of the problems of determining host names from IP addresses, matching
9148 against host names is not as common as matching against IP addresses.
9150 By default, in order to find a host name, Exim first does a reverse DNS lookup;
9151 if no name is found in the DNS, the system function (&[gethostbyaddr()]& or
9152 &[getipnodebyaddr()]& if available) is tried. The order in which these lookups
9153 are done can be changed by setting the &%host_lookup_order%& option. For
9154 security, once Exim has found one or more names, it looks up the IP addresses
9155 for these names and compares them with the IP address that it started with.
9156 Only those names whose IP addresses match are accepted. Any other names are
9157 discarded. If no names are left, Exim behaves as if the host name cannot be
9158 found. In the most common case there is only one name and one IP address.
9160 There are some options that control what happens if a host name cannot be
9161 found. These are described in section &<<SECTbehipnot>>& below.
9163 .cindex "host" "alias for"
9164 .cindex "alias for host"
9165 As a result of aliasing, hosts may have more than one name. When processing any
9166 of the following types of pattern, all the host's names are checked:
9169 .cindex "asterisk" "in host list"
9170 If a pattern starts with &"*"& the remainder of the item must match the end of
9171 the host name. For example, &`*.b.c`& matches all hosts whose names end in
9172 &'.b.c'&. This special simple form is provided because this is a very common
9173 requirement. Other kinds of wildcarding require the use of a regular
9176 .cindex "regular expressions" "in host list"
9177 .cindex "host list" "regular expression in"
9178 If the item starts with &"^"& it is taken to be a regular expression which is
9179 matched against the host name. Host names are case-independent, so this regular
9180 expression match is by default case-independent, but you can make it
9181 case-dependent by starting it with &`(?-i)`&. References to descriptions of the
9182 syntax of regular expressions are given in chapter &<<CHAPregexp>>&. For
9187 is a regular expression that matches either of the two hosts &'a.c.d'& or
9188 &'b.c.d'&. When a regular expression is used in a host list, you must take care
9189 that backslash and dollar characters are not misinterpreted as part of the
9190 string expansion. The simplest way to do this is to use &`\N`& to mark that
9191 part of the string as non-expandable. For example:
9193 sender_unqualified_hosts = \N^(a|b)\.c\.d$\N : ....
9195 &*Warning*&: If you want to match a complete host name, you must include the
9196 &`$`& terminating metacharacter in the regular expression, as in the above
9197 example. Without it, a match at the start of the host name is all that is
9204 .section "Behaviour when an IP address or name cannot be found" "SECTbehipnot"
9205 .cindex "host" "lookup failures, permanent"
9206 While processing a host list, Exim may need to look up an IP address from a
9207 name (see section &<<SECThoslispatip>>&), or it may need to look up a host name
9208 from an IP address (see section &<<SECThoslispatnam>>&). In either case, the
9209 behaviour when it fails to find the information it is seeking is the same.
9211 &*Note*&: This section applies to permanent lookup failures. It does &'not'&
9212 apply to temporary DNS errors, whose handling is described in the next section.
9214 .cindex "&`+include_unknown`&"
9215 .cindex "&`+ignore_unknown`&"
9216 Exim parses a host list from left to right. If it encounters a permanent
9217 lookup failure in any item in the host list before it has found a match,
9218 Exim treats it as a failure and the default behavior is as if the host
9219 does not match the list. This may not always be what you want to happen.
9220 To change Exim's behaviour, the special items &`+include_unknown`& or
9221 &`+ignore_unknown`& may appear in the list (at top level &-- they are
9222 not recognized in an indirected file).
9225 If any item that follows &`+include_unknown`& requires information that
9226 cannot found, Exim behaves as if the host does match the list. For example,
9228 host_reject_connection = +include_unknown:*.enemy.ex
9230 rejects connections from any host whose name matches &`*.enemy.ex`&, and also
9231 any hosts whose name it cannot find.
9234 If any item that follows &`+ignore_unknown`& requires information that cannot
9235 be found, Exim ignores that item and proceeds to the rest of the list. For
9238 accept hosts = +ignore_unknown : friend.example : \
9241 accepts from any host whose name is &'friend.example'& and from 192.168.4.5,
9242 whether or not its host name can be found. Without &`+ignore_unknown`&, if no
9243 name can be found for 192.168.4.5, it is rejected.
9246 Both &`+include_unknown`& and &`+ignore_unknown`& may appear in the same
9247 list. The effect of each one lasts until the next, or until the end of the
9250 .section "Mixing wildcarded host names and addresses in host lists" &&&
9252 .cindex "host list" "mixing names and addresses in"
9254 This section explains the host/ip processing logic with the same concepts
9255 as the previous section, but specifically addresses what happens when a
9256 wildcarded hostname is one of the items in the hostlist.
9259 If you have name lookups or wildcarded host names and
9260 IP addresses in the same host list, you should normally put the IP
9261 addresses first. For example, in an ACL you could have:
9263 accept hosts = 10.9.8.7 : *.friend.example
9265 The reason you normally would order it this way lies in the
9266 left-to-right way that Exim processes lists. It can test IP addresses
9267 without doing any DNS lookups, but when it reaches an item that requires
9268 a host name, it fails if it cannot find a host name to compare with the
9269 pattern. If the above list is given in the opposite order, the
9270 &%accept%& statement fails for a host whose name cannot be found, even
9271 if its IP address is 10.9.8.7.
9274 If you really do want to do the name check first, and still recognize the IP
9275 address, you can rewrite the ACL like this:
9277 accept hosts = *.friend.example
9278 accept hosts = 10.9.8.7
9280 If the first &%accept%& fails, Exim goes on to try the second one. See chapter
9281 &<<CHAPACL>>& for details of ACLs. Alternatively, you can use
9282 &`+ignore_unknown`&, which was discussed in depth in the first example in
9287 .section "Temporary DNS errors when looking up host information" &&&
9289 .cindex "host" "lookup failures, temporary"
9290 .cindex "&`+include_defer`&"
9291 .cindex "&`+ignore_defer`&"
9292 A temporary DNS lookup failure normally causes a defer action (except when
9293 &%dns_again_means_nonexist%& converts it into a permanent error). However,
9294 host lists can include &`+ignore_defer`& and &`+include_defer`&, analogous to
9295 &`+ignore_unknown`& and &`+include_unknown`&, as described in the previous
9296 section. These options should be used with care, probably only in non-critical
9297 host lists such as whitelists.
9301 .section "Host list patterns for single-key lookups by host name" &&&
9302 "SECThoslispatnamsk"
9303 .cindex "unknown host name"
9304 .cindex "host list" "matching host name"
9305 If a pattern is of the form
9307 <&'single-key-search-type'&>;<&'search-data'&>
9311 dbm;/host/accept/list
9313 a single-key lookup is performed, using the host name as its key. If the
9314 lookup succeeds, the host matches the item. The actual data that is looked up
9317 &*Reminder*&: With this kind of pattern, you must have host &'names'& as
9318 keys in the file, not IP addresses. If you want to do lookups based on IP
9319 addresses, you must precede the search type with &"net-"& (see section
9320 &<<SECThoslispatsikey>>&). There is, however, no reason why you could not use
9321 two items in the same list, one doing an address lookup and one doing a name
9322 lookup, both using the same file.
9326 .section "Host list patterns for query-style lookups" "SECID81"
9327 If a pattern is of the form
9329 <&'query-style-search-type'&>;<&'query'&>
9331 the query is obeyed, and if it succeeds, the host matches the item. The actual
9332 data that is looked up is not used. The variables &$sender_host_address$& and
9333 &$sender_host_name$& can be used in the query. For example:
9335 hosts_lookup = pgsql;\
9336 select ip from hostlist where ip='$sender_host_address'
9338 The value of &$sender_host_address$& for an IPv6 address contains colons. You
9339 can use the &%sg%& expansion item to change this if you need to. If you want to
9340 use masked IP addresses in database queries, you can use the &%mask%& expansion
9343 If the query contains a reference to &$sender_host_name$&, Exim automatically
9344 looks up the host name if it has not already done so. (See section
9345 &<<SECThoslispatnam>>& for comments on finding host names.)
9347 Historical note: prior to release 4.30, Exim would always attempt to find a
9348 host name before running the query, unless the search type was preceded by
9349 &`net-`&. This is no longer the case. For backwards compatibility, &`net-`& is
9350 still recognized for query-style lookups, but its presence or absence has no
9351 effect. (Of course, for single-key lookups, &`net-`& &'is'& important.
9352 See section &<<SECThoslispatsikey>>&.)
9358 .section "Address lists" "SECTaddresslist"
9359 .cindex "list" "address list"
9360 .cindex "address list" "empty item"
9361 .cindex "address list" "patterns"
9362 Address lists contain patterns that are matched against mail addresses. There
9363 is one special case to be considered: the sender address of a bounce message is
9364 always empty. You can test for this by providing an empty item in an address
9365 list. For example, you can set up a router to process bounce messages by
9366 using this option setting:
9370 The presence of the colon creates an empty item. If you do not provide any
9371 data, the list is empty and matches nothing. The empty sender can also be
9372 detected by a regular expression that matches an empty string,
9373 and by a query-style lookup that succeeds when &$sender_address$& is empty.
9375 Non-empty items in an address list can be straightforward email addresses. For
9378 senders = jbc@askone.example : hs@anacreon.example
9380 A certain amount of wildcarding is permitted. If a pattern contains an @
9381 character, but is not a regular expression and does not begin with a
9382 semicolon-terminated lookup type (described below), the local part of the
9383 subject address is compared with the local part of the pattern, which may start
9384 with an asterisk. If the local parts match, the domain is checked in exactly
9385 the same way as for a pattern in a domain list. For example, the domain can be
9386 wildcarded, refer to a named list, or be a lookup:
9388 deny senders = *@*.spamming.site:\
9389 *@+hostile_domains:\
9390 bozo@partial-lsearch;/list/of/dodgy/sites:\
9391 *@dbm;/bad/domains.db
9393 .cindex "local part" "starting with !"
9394 .cindex "address list" "local part starting with !"
9395 If a local part that begins with an exclamation mark is required, it has to be
9396 specified using a regular expression, because otherwise the exclamation mark is
9397 treated as a sign of negation, as is standard in lists.
9399 If a non-empty pattern that is not a regular expression or a lookup does not
9400 contain an @ character, it is matched against the domain part of the subject
9401 address. The only two formats that are recognized this way are a literal
9402 domain, or a domain pattern that starts with *. In both these cases, the effect
9403 is the same as if &`*@`& preceded the pattern. For example:
9405 deny senders = enemy.domain : *.enemy.domain
9408 The following kinds of more complicated address list pattern can match any
9409 address, including the empty address that is characteristic of bounce message
9413 .cindex "regular expressions" "in address list"
9414 .cindex "address list" "regular expression in"
9415 If (after expansion) a pattern starts with &"^"&, a regular expression match is
9416 done against the complete address, with the pattern as the regular expression.
9417 You must take care that backslash and dollar characters are not misinterpreted
9418 as part of the string expansion. The simplest way to do this is to use &`\N`&
9419 to mark that part of the string as non-expandable. For example:
9421 deny senders = \N^.*this.*@example\.com$\N : \
9422 \N^\d{8}.+@spamhaus.example$\N : ...
9424 The &`\N`& sequences are removed by the expansion, so these items do indeed
9425 start with &"^"& by the time they are being interpreted as address patterns.
9428 .cindex "address list" "lookup for complete address"
9429 Complete addresses can be looked up by using a pattern that starts with a
9430 lookup type terminated by a semicolon, followed by the data for the lookup. For
9433 deny senders = cdb;/etc/blocked.senders : \
9434 mysql;select address from blocked where \
9435 address='${quote_mysql:$sender_address}'
9437 Both query-style and single-key lookup types can be used. For a single-key
9438 lookup type, Exim uses the complete address as the key. However, empty keys are
9439 not supported for single-key lookups, so a match against the empty address
9440 always fails. This restriction does not apply to query-style lookups.
9442 Partial matching for single-key lookups (section &<<SECTpartiallookup>>&)
9443 cannot be used, and is ignored if specified, with an entry being written to the
9445 .cindex "*@ with single-key lookup"
9446 However, you can configure lookup defaults, as described in section
9447 &<<SECTdefaultvaluelookups>>&, but this is useful only for the &"*@"& type of
9448 default. For example, with this lookup:
9450 accept senders = lsearch*@;/some/file
9452 the file could contains lines like this:
9454 user1@domain1.example
9457 and for the sender address &'nimrod@jaeger.example'&, the sequence of keys
9460 nimrod@jaeger.example
9464 &*Warning 1*&: Do not include a line keyed by &"*"& in the file, because that
9465 would mean that every address matches, thus rendering the test useless.
9467 &*Warning 2*&: Do not confuse these two kinds of item:
9469 deny recipients = dbm*@;/some/file
9470 deny recipients = *@dbm;/some/file
9472 The first does a whole address lookup, with defaulting, as just described,
9473 because it starts with a lookup type. The second matches the local part and
9474 domain independently, as described in a bullet point below.
9478 The following kinds of address list pattern can match only non-empty addresses.
9479 If the subject address is empty, a match against any of these pattern types
9484 .cindex "@@ with single-key lookup"
9485 .cindex "address list" "@@ lookup type"
9486 .cindex "address list" "split local part and domain"
9487 If a pattern starts with &"@@"& followed by a single-key lookup item
9488 (for example, &`@@lsearch;/some/file`&), the address that is being checked is
9489 split into a local part and a domain. The domain is looked up in the file. If
9490 it is not found, there is no match. If it is found, the data that is looked up
9491 from the file is treated as a colon-separated list of local part patterns, each
9492 of which is matched against the subject local part in turn.
9494 .cindex "asterisk" "in address list"
9495 The lookup may be a partial one, and/or one involving a search for a default
9496 keyed by &"*"& (see section &<<SECTdefaultvaluelookups>>&). The local part
9497 patterns that are looked up can be regular expressions or begin with &"*"&, or
9498 even be further lookups. They may also be independently negated. For example,
9501 deny senders = @@dbm;/etc/reject-by-domain
9503 the data from which the DBM file is built could contain lines like
9505 baddomain.com: !postmaster : *
9507 to reject all senders except &%postmaster%& from that domain.
9509 .cindex "local part" "starting with !"
9510 If a local part that actually begins with an exclamation mark is required, it
9511 has to be specified using a regular expression. In &(lsearch)& files, an entry
9512 may be split over several lines by indenting the second and subsequent lines,
9513 but the separating colon must still be included at line breaks. White space
9514 surrounding the colons is ignored. For example:
9516 aol.com: spammer1 : spammer2 : ^[0-9]+$ :
9519 As in all colon-separated lists in Exim, a colon can be included in an item by
9522 If the last item in the list starts with a right angle-bracket, the remainder
9523 of the item is taken as a new key to look up in order to obtain a continuation
9524 list of local parts. The new key can be any sequence of characters. Thus one
9525 might have entries like
9527 aol.com: spammer1 : spammer 2 : >*
9528 xyz.com: spammer3 : >*
9531 in a file that was searched with &%@@dbm*%&, to specify a match for 8-digit
9532 local parts for all domains, in addition to the specific local parts listed for
9533 each domain. Of course, using this feature costs another lookup each time a
9534 chain is followed, but the effort needed to maintain the data is reduced.
9536 .cindex "loop" "in lookups"
9537 It is possible to construct loops using this facility, and in order to catch
9538 them, the chains may be no more than fifty items long.
9541 The @@<&'lookup'&> style of item can also be used with a query-style
9542 lookup, but in this case, the chaining facility is not available. The lookup
9543 can only return a single list of local parts.
9546 &*Warning*&: There is an important difference between the address list items
9547 in these two examples:
9550 senders = *@+my_list
9552 In the first one, &`my_list`& is a named address list, whereas in the second
9553 example it is a named domain list.
9558 .section "Case of letters in address lists" "SECTcasletadd"
9559 .cindex "case of local parts"
9560 .cindex "address list" "case forcing"
9561 .cindex "case forcing in address lists"
9562 Domains in email addresses are always handled caselessly, but for local parts
9563 case may be significant on some systems (see &%caseful_local_part%& for how
9564 Exim deals with this when routing addresses). However, RFC 2505 (&'Anti-Spam
9565 Recommendations for SMTP MTAs'&) suggests that matching of addresses to
9566 blocking lists should be done in a case-independent manner. Since most address
9567 lists in Exim are used for this kind of control, Exim attempts to do this by
9570 The domain portion of an address is always lowercased before matching it to an
9571 address list. The local part is lowercased by default, and any string
9572 comparisons that take place are done caselessly. This means that the data in
9573 the address list itself, in files included as plain filenames, and in any file
9574 that is looked up using the &"@@"& mechanism, can be in any case. However, the
9575 keys in files that are looked up by a search type other than &(lsearch)& (which
9576 works caselessly) must be in lower case, because these lookups are not
9579 .cindex "&`+caseful`&"
9580 To allow for the possibility of caseful address list matching, if an item in
9581 an address list is the string &"+caseful"&, the original case of the local
9582 part is restored for any comparisons that follow, and string comparisons are no
9583 longer case-independent. This does not affect the domain, which remains in
9584 lower case. However, although independent matches on the domain alone are still
9585 performed caselessly, regular expressions that match against an entire address
9586 become case-sensitive after &"+caseful"& has been seen.
9590 .section "Local part lists" "SECTlocparlis"
9591 .cindex "list" "local part list"
9592 .cindex "local part" "list"
9593 These behave in the same way as domain and host lists, with the following
9596 Case-sensitivity in local part lists is handled in the same way as for address
9597 lists, as just described. The &"+caseful"& item can be used if required. In a
9598 setting of the &%local_parts%& option in a router with &%caseful_local_part%&
9599 set false, the subject is lowercased and the matching is initially
9600 case-insensitive. In this case, &"+caseful"& will restore case-sensitive
9601 matching in the local part list, but not elsewhere in the router. If
9602 &%caseful_local_part%& is set true in a router, matching in the &%local_parts%&
9603 option is case-sensitive from the start.
9605 If a local part list is indirected to a file (see section &<<SECTfilnamlis>>&),
9606 comments are handled in the same way as address lists &-- they are recognized
9607 only if the # is preceded by white space or the start of the line.
9608 Otherwise, local part lists are matched in the same way as domain lists, except
9609 that the special items that refer to the local host (&`@`&, &`@[]`&,
9610 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`&) are not recognized.
9611 Refer to section &<<SECTdomainlist>>& for details of the other available item
9613 .ecindex IIDdohoadli
9618 . ////////////////////////////////////////////////////////////////////////////
9619 . ////////////////////////////////////////////////////////////////////////////
9621 .chapter "String expansions" "CHAPexpand"
9622 .scindex IIDstrexp "expansion" "of strings"
9623 Many strings in Exim's runtime configuration are expanded before use. Some of
9624 them are expanded every time they are used; others are expanded only once.
9626 When a string is being expanded it is copied verbatim from left to right except
9627 .cindex expansion "string concatenation"
9628 when a dollar or backslash character is encountered. A dollar specifies the
9629 start of a portion of the string that is interpreted and replaced as described
9630 below in section &<<SECTexpansionitems>>& onwards. Backslash is used as an
9631 escape character, as described in the following section.
9633 Whether a string is expanded depends upon the context. Usually this is solely
9634 dependent upon the option for which a value is sought; in this documentation,
9635 options for which string expansion is performed are marked with † after
9636 the data type. ACL rules always expand strings. A couple of expansion
9637 conditions do not expand some of the brace-delimited branches, for security
9639 .cindex "tainted data" expansion
9640 .cindex "tainted data" definition
9641 .cindex expansion "tainted data"
9642 and expansion of data deriving from the sender (&"tainted data"&)
9643 is not permitted (including acessing a file using a tainted name).
9645 Common ways of obtaining untainted equivalents of variables with
9647 .cindex "tainted data" "de-tainting"
9648 come down to using the tainted value as a lookup key in a trusted database.
9649 This database could be the filesystem structure,
9650 or the password file,
9651 or accessed via a DBMS.
9652 Specific methods are indexed under &"de-tainting"&.
9656 .section "Literal text in expanded strings" "SECTlittext"
9657 .cindex "expansion" "including literal text"
9658 An uninterpreted dollar can be included in an expanded string by putting a
9659 backslash in front of it. A backslash can be used to prevent any special
9660 character being treated specially in an expansion, including backslash itself.
9661 If the string appears in quotes in the configuration file, two backslashes are
9662 required because the quotes themselves cause interpretation of backslashes when
9663 the string is read in (see section &<<SECTstrings>>&).
9665 .cindex "expansion" "non-expandable substrings"
9666 A portion of the string can specified as non-expandable by placing it between
9667 two occurrences of &`\N`&. This is particularly useful for protecting regular
9668 expressions, which often contain backslashes and dollar signs. For example:
9670 deny senders = \N^\d{8}[a-z]@some\.site\.example$\N
9672 On encountering the first &`\N`&, the expander copies subsequent characters
9673 without interpretation until it reaches the next &`\N`& or the end of the
9678 .section "Character escape sequences in expanded strings" "SECID82"
9679 .cindex "expansion" "escape sequences"
9680 A backslash followed by one of the letters &"n"&, &"r"&, or &"t"& in an
9681 expanded string is recognized as an escape sequence for the character newline,
9682 carriage return, or tab, respectively. A backslash followed by up to three
9683 octal digits is recognized as an octal encoding for a single character, and a
9684 backslash followed by &"x"& and up to two hexadecimal digits is a hexadecimal
9687 These escape sequences are also recognized in quoted strings when they are read
9688 in. Their interpretation in expansions as well is useful for unquoted strings,
9689 and for other cases such as looked-up strings that are then expanded.
9692 .section "Testing string expansions" "SECID83"
9693 .cindex "expansion" "testing"
9694 .cindex "testing" "string expansion"
9696 Many expansions can be tested by calling Exim with the &%-be%& option. This
9697 takes the command arguments, or lines from the standard input if there are no
9698 arguments, runs them through the string expansion code, and writes the results
9699 to the standard output. Variables based on configuration values are set up, but
9700 since no message is being processed, variables such as &$local_part$& have no
9701 value. Nevertheless the &%-be%& option can be useful for checking out file and
9702 database lookups, and the use of expansion operators such as &%sg%&, &%substr%&
9705 Exim gives up its root privilege when it is called with the &%-be%& option, and
9706 instead runs under the uid and gid it was called with, to prevent users from
9707 using &%-be%& for reading files to which they do not have access.
9710 If you want to test expansions that include variables whose values are taken
9711 from a message, there are two other options that can be used. The &%-bem%&
9712 option is like &%-be%& except that it is followed by a filename. The file is
9713 read as a message before doing the test expansions. For example:
9715 exim -bem /tmp/test.message '$h_subject:'
9717 The &%-Mset%& option is used in conjunction with &%-be%& and is followed by an
9718 Exim message identifier. For example:
9720 exim -be -Mset 1GrA8W-0004WS-LQ '$recipients'
9722 This loads the message from Exim's spool before doing the test expansions, and
9723 is therefore restricted to admin users.
9726 .section "Forced expansion failure" "SECTforexpfai"
9727 .cindex "expansion" "forced failure"
9728 A number of expansions that are described in the following section have
9729 alternative &"true"& and &"false"& substrings, enclosed in brace characters
9730 (which are sometimes called &"curly brackets"&). Which of the two strings is
9731 used depends on some condition that is evaluated as part of the expansion. If,
9732 instead of a &"false"& substring, the word &"fail"& is used (not in braces),
9733 the entire string expansion fails in a way that can be detected by the code
9734 that requested the expansion. This is called &"forced expansion failure"&, and
9735 its consequences depend on the circumstances. In some cases it is no different
9736 from any other expansion failure, but in others a different action may be
9737 taken. Such variations are mentioned in the documentation of the option that is
9743 .section "Expansion items" "SECTexpansionitems"
9744 The following items are recognized in expanded strings. White space may be used
9745 between sub-items that are keywords or substrings enclosed in braces inside an
9746 outer set of braces, to improve readability. &*Warning*&: Within braces,
9747 white space is significant.
9750 .vitem &*$*&<&'variable&~name'&>&~or&~&*${*&<&'variable&~name'&>&*}*&
9751 .cindex "expansion" "variables"
9752 Substitute the contents of the named variable, for example:
9757 The second form can be used to separate the name from subsequent alphanumeric
9758 characters. This form (using braces) is available only for variables; it does
9759 &'not'& apply to message headers. The names of the variables are given in
9760 section &<<SECTexpvar>>& below. If the name of a non-existent variable is
9761 given, the expansion fails.
9763 .vitem &*${*&<&'op'&>&*:*&<&'string'&>&*}*&
9764 .cindex "expansion" "operators"
9765 The string is first itself expanded, and then the operation specified by
9766 <&'op'&> is applied to it. For example:
9770 The string starts with the first character after the colon, which may be
9771 leading white space. A list of operators is given in section &<<SECTexpop>>&
9772 below. The operator notation is used for simple expansion items that have just
9773 one argument, because it reduces the number of braces and therefore makes the
9774 string easier to understand.
9776 .vitem &*$bheader_*&<&'header&~name'&>&*:*&&~or&~&*$bh_*&<&'header&~name'&>&*:*&
9777 This item inserts &"basic"& header lines. It is described with the &%header%&
9778 expansion item below.
9781 .vitem "&*${acl{*&<&'name'&>&*}{*&<&'arg'&>&*}...}*&"
9782 .cindex "expansion" "calling an acl"
9783 .cindex "&%acl%&" "call from expansion"
9784 The name and zero to nine argument strings are first expanded separately. The expanded
9785 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
9786 Any unused are made empty. The variable &$acl_narg$& is set to the number of
9787 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
9788 and may use the variables; if another acl expansion is used the values
9789 are restored after it returns. If the ACL sets
9790 a value using a "message =" modifier and returns accept or deny, the value becomes
9791 the result of the expansion.
9792 If no message is set and the ACL returns accept or deny
9793 the expansion result is an empty string.
9794 If the ACL returns defer the result is a forced-fail. Otherwise the expansion fails.
9797 .vitem "&*${authresults{*&<&'authserv-id'&>&*}}*&"
9798 .cindex authentication "results header"
9799 .chindex Authentication-Results:
9800 .cindex authentication "expansion item"
9801 This item returns a string suitable for insertion as an
9802 &'Authentication-Results:'&
9804 The given <&'authserv-id'&> is included in the result; typically this
9805 will be a domain name identifying the system performing the authentications.
9806 Methods that might be present in the result include:
9815 Example use (as an ACL modifier):
9817 add_header = :at_start:${authresults {$primary_hostname}}
9819 This is safe even if no authentication results are available.
9822 .vitem "&*${certextract{*&<&'field'&>&*}{*&<&'certificate'&>&*}&&&
9823 {*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9824 .cindex "expansion" "extracting certificate fields"
9825 .cindex "&%certextract%&" "certificate fields"
9826 .cindex "certificate" "extracting fields"
9827 The <&'certificate'&> must be a variable of type certificate.
9828 The field name is expanded and used to retrieve the relevant field from
9829 the certificate. Supported fields are:
9833 &`subject `& RFC4514 DN
9834 &`issuer `& RFC4514 DN
9839 &`subj_altname `& tagged list
9843 If the field is found,
9844 <&'string2'&> is expanded, and replaces the whole item;
9845 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
9846 variable &$value$& contains the value that has been extracted. Afterwards, it
9847 is restored to any previous value it might have had.
9849 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
9850 key is not found. If {<&'string2'&>} is also omitted, the value that was
9853 Some field names take optional modifiers, appended and separated by commas.
9855 The field selectors marked as "RFC4514" above
9856 output a Distinguished Name string which is
9858 parseable by Exim as a comma-separated tagged list
9859 (the exceptions being elements containing commas).
9860 RDN elements of a single type may be selected by
9861 a modifier of the type label; if so the expansion
9862 result is a list (newline-separated by default).
9863 The separator may be changed by another modifier of
9864 a right angle-bracket followed immediately by the new separator.
9865 Recognised RDN type labels include "CN", "O", "OU" and "DC".
9867 The field selectors marked as "time" above
9868 take an optional modifier of "int"
9869 for which the result is the number of seconds since epoch.
9870 Otherwise the result is a human-readable string
9871 in the timezone selected by the main "timezone" option.
9873 The field selectors marked as "list" above return a list,
9874 newline-separated by default,
9875 (embedded separator characters in elements are doubled).
9876 The separator may be changed by a modifier of
9877 a right angle-bracket followed immediately by the new separator.
9879 The field selectors marked as "tagged" above
9880 prefix each list element with a type string and an equals sign.
9881 Elements of only one type may be selected by a modifier
9882 which is one of "dns", "uri" or "mail";
9883 if so the element tags are omitted.
9885 If not otherwise noted field values are presented in human-readable form.
9887 .vitem "&*${dlfunc{*&<&'file'&>&*}{*&<&'function'&>&*}{*&<&'arg'&>&*}&&&
9888 {*&<&'arg'&>&*}...}*&"
9890 This expansion dynamically loads and then calls a locally-written C function.
9891 This functionality is available only if Exim is compiled with
9895 set in &_Local/Makefile_&. Once loaded, Exim remembers the dynamically loaded
9896 object so that it doesn't reload the same object file in the same Exim process
9897 (but of course Exim does start new processes frequently).
9899 There may be from zero to eight arguments to the function.
9902 a local function that is to be called in this way,
9903 first &_DLFUNC_IMPL_& should be defined,
9904 and second &_local_scan.h_& should be included.
9905 The Exim variables and functions that are defined by that API
9906 are also available for dynamically loaded functions. The function itself
9907 must have the following type:
9909 int dlfunction(uschar **yield, int argc, uschar *argv[])
9911 Where &`uschar`& is a typedef for &`unsigned char`& in &_local_scan.h_&. The
9912 function should return one of the following values:
9914 &`OK`&: Success. The string that is placed in the variable &'yield'& is put
9915 into the expanded string that is being built.
9917 &`FAIL`&: A non-forced expansion failure occurs, with the error message taken
9918 from &'yield'&, if it is set.
9920 &`FAIL_FORCED`&: A forced expansion failure occurs, with the error message
9921 taken from &'yield'& if it is set.
9923 &`ERROR`&: Same as &`FAIL`&, except that a panic log entry is written.
9925 When compiling a function that is to be used in this way with gcc,
9926 you need to add &%-shared%& to the gcc command. Also, in the Exim build-time
9927 configuration, you must add &%-export-dynamic%& to EXTRALIBS.
9930 .vitem "&*${env{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&"
9931 .cindex "expansion" "extracting value from environment"
9932 .cindex "environment" "values from"
9933 The key is first expanded separately, and leading and trailing white space
9935 This is then searched for as a name in the environment.
9936 If a variable is found then its value is placed in &$value$&
9937 and <&'string1'&> is expanded, otherwise <&'string2'&> is expanded.
9939 Instead of {<&'string2'&>} the word &"fail"& (not in curly brackets) can
9940 appear, for example:
9942 ${env{USER}{$value} fail }
9944 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9945 {<&'string1'&>} must be present for &"fail"& to be recognized.
9947 If {<&'string2'&>} is omitted an empty string is substituted on
9949 If {<&'string1'&>} is omitted the search result is substituted on
9952 The environment is adjusted by the &%keep_environment%& and
9953 &%add_environment%& main section options.
9956 .vitem "&*${extract{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9957 {*&<&'string3'&>&*}}*&"
9958 .cindex "expansion" "extracting substrings by key"
9959 .cindex "&%extract%&" "substrings by key"
9960 The key and <&'string1'&> are first expanded separately. Leading and trailing
9961 white space is removed from the key (but not from any of the strings). The key
9962 must not be empty and must not consist entirely of digits.
9963 The expanded <&'string1'&> must be of the form:
9965 <&'key1'&> = <&'value1'&> <&'key2'&> = <&'value2'&> ...
9968 where the equals signs and spaces (but not both) are optional. If any of the
9969 values contain white space, they must be enclosed in double quotes, and any
9970 values that are enclosed in double quotes are subject to escape processing as
9971 described in section &<<SECTstrings>>&. The expanded <&'string1'&> is searched
9972 for the value that corresponds to the key. The search is case-insensitive. If
9973 the key is found, <&'string2'&> is expanded, and replaces the whole item;
9974 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
9975 variable &$value$& contains the value that has been extracted. Afterwards, it
9976 is restored to any previous value it might have had.
9978 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
9979 key is not found. If {<&'string2'&>} is also omitted, the value that was
9980 extracted is used. Thus, for example, these two expansions are identical, and
9983 ${extract{gid}{uid=1984 gid=2001}}
9984 ${extract{gid}{uid=1984 gid=2001}{$value}}
9986 Instead of {<&'string3'&>} the word &"fail"& (not in curly brackets) can
9987 appear, for example:
9989 ${extract{Z}{A=... B=...}{$value} fail }
9991 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9992 {<&'string2'&>} must be present for &"fail"& to be recognized.
9994 .vitem "&*${extract json{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9995 {*&<&'string3'&>&*}}*&" &&&
9996 "&*${extract jsons{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9997 {*&<&'string3'&>&*}}*&"
9998 .cindex "expansion" "extracting from JSON object"
9999 .cindex JSON expansions
10000 The key and <&'string1'&> are first expanded separately. Leading and trailing
10001 white space is removed from the key (but not from any of the strings). The key
10002 must not be empty and must not consist entirely of digits.
10003 The expanded <&'string1'&> must be of the form:
10005 { <&'"key1"'&> : <&'value1'&> , <&'"key2"'&> , <&'value2'&> ... }
10007 .vindex "&$value$&"
10008 The braces, commas and colons, and the quoting of the member name are required;
10009 the spaces are optional.
10010 Matching of the key against the member names is done case-sensitively.
10011 For the &"json"& variant,
10012 if a returned value is a JSON string, it retains its leading and
10014 For the &"jsons"& variant, which is intended for use with JSON strings, the
10015 leading and trailing quotes are removed from the returned value.
10016 . XXX should be a UTF-8 compare
10018 The results of matching are handled as above.
10021 .vitem "&*${extract{*&<&'number'&>&*}{*&<&'separators'&>&*}&&&
10022 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
10023 .cindex "expansion" "extracting substrings by number"
10024 .cindex "&%extract%&" "substrings by number"
10025 The <&'number'&> argument must consist entirely of decimal digits,
10026 apart from leading and trailing white space, which is ignored.
10027 This is what distinguishes this form of &%extract%& from the previous kind. It
10028 behaves in the same way, except that, instead of extracting a named field, it
10029 extracts from <&'string1'&> the field whose number is given as the first
10030 argument. You can use &$value$& in <&'string2'&> or &`fail`& instead of
10031 <&'string3'&> as before.
10033 The fields in the string are separated by any one of the characters in the
10034 separator string. These may include space or tab characters.
10035 The first field is numbered one. If the number is negative, the fields are
10036 counted from the end of the string, with the rightmost one numbered -1. If the
10037 number given is zero, the entire string is returned. If the modulus of the
10038 number is greater than the number of fields in the string, the result is the
10039 expansion of <&'string3'&>, or the empty string if <&'string3'&> is not
10040 provided. For example:
10042 ${extract{2}{:}{x:42:99:& Mailer::/bin/bash}}
10046 ${extract{-4}{:}{x:42:99:& Mailer::/bin/bash}}
10048 yields &"99"&. Two successive separators mean that the field between them is
10049 empty (for example, the fifth field above).
10052 .vitem "&*${extract json {*&<&'number'&>&*}}&&&
10053 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&" &&&
10054 "&*${extract jsons{*&<&'number'&>&*}}&&&
10055 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
10056 .cindex "expansion" "extracting from JSON array"
10057 .cindex JSON expansions
10058 The <&'number'&> argument must consist entirely of decimal digits,
10059 apart from leading and trailing white space, which is ignored.
10061 Field selection and result handling is as above;
10062 there is no choice of field separator.
10063 For the &"json"& variant,
10064 if a returned value is a JSON string, it retains its leading and
10066 For the &"jsons"& variant, which is intended for use with JSON strings, the
10067 leading and trailing quotes are removed from the returned value.
10070 .vitem &*${filter{*&<&'string'&>&*}{*&<&'condition'&>&*}}*&
10071 .cindex "list" "selecting by condition"
10072 .cindex "expansion" "selecting from list by condition"
10074 After expansion, <&'string'&> is interpreted as a list, colon-separated by
10075 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10077 in this list, its value is place in &$item$&, and then the condition is
10078 evaluated. If the condition is true, &$item$& is added to the output as an
10079 item in a new list; if the condition is false, the item is discarded. The
10080 separator used for the output list is the same as the one used for the
10081 input, but a separator setting is not included in the output. For example:
10083 ${filter{a:b:c}{!eq{$item}{b}}}
10085 yields &`a:c`&. At the end of the expansion, the value of &$item$& is restored
10086 to what it was before. See also the &%map%& and &%reduce%& expansion items.
10089 .vitem &*${hash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10090 .cindex "hash function" "textual"
10091 .cindex "expansion" "textual hash"
10092 This is a textual hashing function, and was the first to be implemented in
10093 early versions of Exim. In current releases, there are other hashing functions
10094 (numeric, MD5, and SHA-1), which are described below.
10096 The first two strings, after expansion, must be numbers. Call them <&'m'&> and
10097 <&'n'&>. If you are using fixed values for these numbers, that is, if
10098 <&'string1'&> and <&'string2'&> do not change when they are expanded, you can
10099 use the simpler operator notation that avoids some of the braces:
10101 ${hash_<n>_<m>:<string>}
10103 The second number is optional (in both notations). If <&'n'&> is greater than
10104 or equal to the length of the string, the expansion item returns the string.
10105 Otherwise it computes a new string of length <&'n'&> by applying a hashing
10106 function to the string. The new string consists of characters taken from the
10107 first <&'m'&> characters of the string
10109 abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQWRSTUVWXYZ0123456789
10111 If <&'m'&> is not present the value 26 is used, so that only lower case
10112 letters appear. For example:
10114 &`$hash{3}{monty}} `& yields &`jmg`&
10115 &`$hash{5}{monty}} `& yields &`monty`&
10116 &`$hash{4}{62}{monty python}}`& yields &`fbWx`&
10119 .vitem "&*$header_*&<&'header&~name'&>&*:*&&~or&~&&&
10120 &*$h_*&<&'header&~name'&>&*:*&" &&&
10121 "&*$bheader_*&<&'header&~name'&>&*:*&&~or&~&&&
10122 &*$bh_*&<&'header&~name'&>&*:*&" &&&
10123 "&*$lheader_*&<&'header&~name'&>&*:*&&~or&~&&&
10124 &*$lh_*&<&'header&~name'&>&*:*&" &&&
10125 "&*$rheader_*&<&'header&~name'&>&*:*&&~or&~&&&
10126 &*$rh_*&<&'header&~name'&>&*:*&"
10127 .cindex "expansion" "header insertion"
10128 .vindex "&$header_$&"
10129 .vindex "&$bheader_$&"
10130 .vindex "&$lheader_$&"
10131 .vindex "&$rheader_$&"
10132 .cindex "header lines" "in expansion strings"
10133 .cindex "header lines" "character sets"
10134 .cindex "header lines" "decoding"
10135 Substitute the contents of the named message header line, for example
10139 The newline that terminates a header line is not included in the expansion, but
10140 internal newlines (caused by splitting the header line over several physical
10141 lines) may be present.
10143 The difference between the four pairs of expansions is in the way
10144 the data in the header line is interpreted.
10147 .cindex "white space" "in header lines"
10148 &%rheader%& gives the original &"raw"& content of the header line, with no
10149 processing at all, and without the removal of leading and trailing white space.
10152 .cindex "list" "of header lines"
10153 &%lheader%& gives a colon-separated list, one element per header when there
10154 are multiple headers with a given name.
10155 Any embedded colon characters within an element are doubled, so normal Exim
10156 list-processing facilities can be used.
10157 The terminating newline of each element is removed; in other respects
10158 the content is &"raw"&.
10161 .cindex "base64 encoding" "in header lines"
10162 &%bheader%& removes leading and trailing white space, and then decodes base64
10163 or quoted-printable MIME &"words"& within the header text, but does no
10164 character set translation. If decoding of what looks superficially like a MIME
10165 &"word"& fails, the raw string is returned. If decoding
10166 .cindex "binary zero" "in header line"
10167 produces a binary zero character, it is replaced by a question mark &-- this is
10168 what Exim does for binary zeros that are actually received in header lines.
10171 &%header%& tries to translate the string as decoded by &%bheader%& to a
10172 standard character set. This is an attempt to produce the same string as would
10173 be displayed on a user's MUA. If translation fails, the &%bheader%& string is
10174 returned. Translation is attempted only on operating systems that support the
10175 &[iconv()]& function. This is indicated by the compile-time macro HAVE_ICONV in
10176 a system Makefile or in &_Local/Makefile_&.
10179 In a filter file, the target character set for &%header%& can be specified by a
10180 command of the following form:
10182 headers charset "UTF-8"
10184 This command affects all references to &$h_$& (or &$header_$&) expansions in
10185 subsequently obeyed filter commands. In the absence of this command, the target
10186 character set in a filter is taken from the setting of the &%headers_charset%&
10187 option in the runtime configuration. The value of this option defaults to the
10188 value of HEADERS_CHARSET in &_Local/Makefile_&. The ultimate default is
10191 Header names follow the syntax of RFC 2822, which states that they may contain
10192 any printing characters except space and colon. Consequently, curly brackets
10193 &'do not'& terminate header names, and should not be used to enclose them as
10194 if they were variables. Attempting to do so causes a syntax error.
10196 Only header lines that are common to all copies of a message are visible to
10197 this mechanism. These are the original header lines that are received with the
10198 message, and any that are added by an ACL statement or by a system
10199 filter. Header lines that are added to a particular copy of a message by a
10200 router or transport are not accessible.
10202 For incoming SMTP messages, no header lines are visible in
10203 ACLs that are obeyed before the data phase completes,
10204 because the header structure is not set up until the message is received.
10205 They are visible in DKIM, PRDR and DATA ACLs.
10206 Header lines that are added in a RCPT ACL (for example)
10207 are saved until the message's incoming header lines are available, at which
10208 point they are added.
10209 When any of the above ACLs are
10210 running, however, header lines added by earlier ACLs are visible.
10212 Upper case and lower case letters are synonymous in header names. If the
10213 following character is white space, the terminating colon may be omitted, but
10214 this is not recommended, because you may then forget it when it is needed. When
10215 white space terminates the header name, this white space is included in the
10216 expanded string. If the message does not contain the given header, the
10217 expansion item is replaced by an empty string. (See the &%def%& condition in
10218 section &<<SECTexpcond>>& for a means of testing for the existence of a
10221 If there is more than one header with the same name, they are all concatenated
10222 to form the substitution string, up to a maximum length of 64K. Unless
10223 &%rheader%& is being used, leading and trailing white space is removed from
10224 each header before concatenation, and a completely empty header is ignored. A
10225 newline character is then inserted between non-empty headers, but there is no
10226 newline at the very end. For the &%header%& and &%bheader%& expansion, for
10227 those headers that contain lists of addresses, a comma is also inserted at the
10228 junctions between headers. This does not happen for the &%rheader%& expansion.
10230 .cindex "tainted data" "message headers"
10231 When the headers are from an incoming message,
10232 the result of expanding any of these variables is tainted.
10235 .vitem &*${hmac{*&<&'hashname'&>&*}{*&<&'secret'&>&*}{*&<&'string'&>&*}}*&
10236 .cindex "expansion" "hmac hashing"
10238 This function uses cryptographic hashing (either MD5 or SHA-1) to convert a
10239 shared secret and some text into a message authentication code, as specified in
10240 RFC 2104. This differs from &`${md5:secret_text...}`& or
10241 &`${sha1:secret_text...}`& in that the hmac step adds a signature to the
10242 cryptographic hash, allowing for authentication that is not possible with MD5
10243 or SHA-1 alone. The hash name must expand to either &`md5`& or &`sha1`& at
10244 present. For example:
10246 ${hmac{md5}{somesecret}{$primary_hostname $tod_log}}
10248 For the hostname &'mail.example.com'& and time 2002-10-17 11:30:59, this
10251 dd97e3ba5d1a61b5006108f8c8252953
10253 As an example of how this might be used, you might put in the main part of
10254 an Exim configuration:
10256 SPAMSCAN_SECRET=cohgheeLei2thahw
10258 In a router or a transport you could then have:
10261 X-Spam-Scanned: ${primary_hostname} ${message_exim_id} \
10262 ${hmac{md5}{SPAMSCAN_SECRET}\
10263 {${primary_hostname},${message_exim_id},$h_message-id:}}
10265 Then given a message, you can check where it was scanned by looking at the
10266 &'X-Spam-Scanned:'& header line. If you know the secret, you can check that
10267 this header line is authentic by recomputing the authentication code from the
10268 host name, message ID and the &'Message-id:'& header line. This can be done
10269 using Exim's &%-be%& option, or by other means, for example, by using the
10270 &'hmac_md5_hex()'& function in Perl.
10273 .vitem &*${if&~*&<&'condition'&>&*&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
10274 .cindex "expansion" "conditional"
10275 .cindex "&%if%&, expansion item"
10276 If <&'condition'&> is true, <&'string1'&> is expanded and replaces the whole
10277 item; otherwise <&'string2'&> is used. The available conditions are described
10278 in section &<<SECTexpcond>>& below. For example:
10280 ${if eq {$local_part}{postmaster} {yes}{no} }
10282 The second string need not be present; if it is not and the condition is not
10283 true, the item is replaced with nothing. Alternatively, the word &"fail"& may
10284 be present instead of the second string (without any curly brackets). In this
10285 case, the expansion is forced to fail if the condition is not true (see section
10286 &<<SECTforexpfai>>&).
10288 If both strings are omitted, the result is the string &`true`& if the condition
10289 is true, and the empty string if the condition is false. This makes it less
10290 cumbersome to write custom ACL and router conditions. For example, instead of
10292 condition = ${if >{$acl_m4}{3}{true}{false}}
10296 condition = ${if >{$acl_m4}{3}}
10301 .vitem &*${imapfolder{*&<&'foldername'&>&*}}*&
10302 .cindex expansion "imap folder"
10303 .cindex "&%imapfolder%& expansion item"
10304 This item converts a (possibly multilevel, or with non-ASCII characters)
10305 folder specification to a Maildir name for filesystem use.
10306 For information on internationalisation support see &<<SECTi18nMDA>>&.
10310 .vitem &*${length{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
10311 .cindex "expansion" "string truncation"
10312 .cindex "&%length%& expansion item"
10313 The &%length%& item is used to extract the initial portion of a string. Both
10314 strings are expanded, and the first one must yield a number, <&'n'&>, say. If
10315 you are using a fixed value for the number, that is, if <&'string1'&> does not
10316 change when expanded, you can use the simpler operator notation that avoids
10317 some of the braces:
10319 ${length_<n>:<string>}
10321 The result of this item is either the first <&'n'&> bytes or the whole
10322 of <&'string2'&>, whichever is the shorter. Do not confuse &%length%& with
10323 &%strlen%&, which gives the length of a string.
10324 All measurement is done in bytes and is not UTF-8 aware.
10327 .vitem "&*${listextract{*&<&'number'&>&*}&&&
10328 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
10329 .cindex "expansion" "extracting list elements by number"
10330 .cindex "&%listextract%&" "extract list elements by number"
10331 .cindex "list" "extracting elements by number"
10332 The <&'number'&> argument must consist entirely of decimal digits,
10333 apart from an optional leading minus,
10334 and leading and trailing white space (which is ignored).
10336 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
10337 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10339 The first field of the list is numbered one.
10340 If the number is negative, the fields are
10341 counted from the end of the list, with the rightmost one numbered -1.
10342 The numbered element of the list is extracted and placed in &$value$&,
10343 then <&'string2'&> is expanded as the result.
10345 If the modulus of the
10346 number is zero or greater than the number of fields in the string,
10347 the result is the expansion of <&'string3'&>.
10351 ${listextract{2}{x:42:99}}
10355 ${listextract{-3}{<, x,42,99,& Mailer,,/bin/bash}{result: $value}}
10357 yields &"result: 42"&.
10359 If {<&'string3'&>} is omitted, an empty string is used for string3.
10360 If {<&'string2'&>} is also omitted, the value that was
10362 You can use &`fail`& instead of {<&'string3'&>} as in a string extract.
10365 .vitem &*${listquote{*&<&'separator'&>&*}{*&<&'string'&>&*}}*&
10366 .cindex quoting "for list"
10367 .cindex list quoting
10368 This item doubles any occurrence of the separator character
10369 in the given string.
10370 An empty string is replaced with a single space.
10371 This converts the string into a safe form for use as a list element,
10372 in a list using the given separator.
10375 .vitem "&*${lookup&~{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&&
10376 {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&" &&&
10377 "&*${lookup&~*&<&'search&~type'&>&*&~{*&<&'query'&>&*}&~&&&
10378 {*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
10379 .cindex "expansion" "lookup in"
10380 .cindex "file" "lookups"
10381 .cindex "lookup" "in expanded string"
10382 The two forms of lookup item specify data lookups in files and databases, as
10383 discussed in chapter &<<CHAPfdlookup>>&. The first form is used for single-key
10384 lookups, and the second is used for query-style lookups. The <&'key'&>,
10385 <&'file'&>, and <&'query'&> strings are expanded before use.
10387 If there is any white space in a lookup item which is part of a filter command,
10388 a retry or rewrite rule, a routing rule for the &(manualroute)& router, or any
10389 other place where white space is significant, the lookup item must be enclosed
10390 in double quotes. The use of data lookups in users' filter files may be locked
10391 out by the system administrator.
10393 .vindex "&$value$&"
10394 If the lookup succeeds, <&'string1'&> is expanded and replaces the entire item.
10395 During its expansion, the variable &$value$& contains the data returned by the
10396 lookup. Afterwards it reverts to the value it had previously (at the outer
10397 level it is empty). If the lookup fails, <&'string2'&> is expanded and replaces
10398 the entire item. If {<&'string2'&>} is omitted, the replacement is the empty
10399 string on failure. If <&'string2'&> is provided, it can itself be a nested
10400 lookup, thus providing a mechanism for looking up a default value when the
10401 original lookup fails.
10403 If a nested lookup is used as part of <&'string1'&>, &$value$& contains the
10404 data for the outer lookup while the parameters of the second lookup are
10405 expanded, and also while <&'string2'&> of the second lookup is expanded, should
10406 the second lookup fail. Instead of {<&'string2'&>} the word &"fail"& can
10407 appear, and in this case, if the lookup fails, the entire expansion is forced
10408 to fail (see section &<<SECTforexpfai>>&). If both {<&'string1'&>} and
10409 {<&'string2'&>} are omitted, the result is the looked up value in the case of a
10410 successful lookup, and nothing in the case of failure.
10412 For single-key lookups, the string &"partial"& is permitted to precede the
10413 search type in order to do partial matching, and * or *@ may follow a search
10414 type to request default lookups if the key does not match (see sections
10415 &<<SECTdefaultvaluelookups>>& and &<<SECTpartiallookup>>& for details).
10417 .cindex "numerical variables (&$1$& &$2$& etc)" "in lookup expansion"
10418 If a partial search is used, the variables &$1$& and &$2$& contain the wild
10419 and non-wild parts of the key during the expansion of the replacement text.
10420 They return to their previous values at the end of the lookup item.
10422 This example looks up the postmaster alias in the conventional alias file:
10424 ${lookup {postmaster} lsearch {/etc/aliases} {$value}}
10426 This example uses NIS+ to look up the full name of the user corresponding to
10427 the local part of an address, forcing the expansion to fail if it is not found:
10429 ${lookup nisplus {[name=$local_part],passwd.org_dir:gcos} \
10434 .vitem &*${map{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
10435 .cindex "expansion" "list creation"
10437 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
10438 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10440 in this list, its value is place in &$item$&, and then <&'string2'&> is
10441 expanded and added to the output as an item in a new list. The separator used
10442 for the output list is the same as the one used for the input, but a separator
10443 setting is not included in the output. For example:
10445 ${map{a:b:c}{[$item]}} ${map{<- x-y-z}{($item)}}
10447 expands to &`[a]:[b]:[c] (x)-(y)-(z)`&. At the end of the expansion, the
10448 value of &$item$& is restored to what it was before. See also the &%filter%&
10449 and &%reduce%& expansion items.
10451 .vitem &*${nhash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10452 .cindex "expansion" "numeric hash"
10453 .cindex "hash function" "numeric"
10454 The three strings are expanded; the first two must yield numbers. Call them
10455 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
10456 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
10457 can use the simpler operator notation that avoids some of the braces:
10459 ${nhash_<n>_<m>:<string>}
10461 The second number is optional (in both notations). If there is only one number,
10462 the result is a number in the range 0&--<&'n'&>-1. Otherwise, the string is
10463 processed by a div/mod hash function that returns two numbers, separated by a
10464 slash, in the ranges 0 to <&'n'&>-1 and 0 to <&'m'&>-1, respectively. For
10467 ${nhash{8}{64}{supercalifragilisticexpialidocious}}
10469 returns the string &"6/33"&.
10473 .vitem &*${perl{*&<&'subroutine'&>&*}{*&<&'arg'&>&*}{*&<&'arg'&>&*}...}*&
10474 .cindex "Perl" "use in expanded string"
10475 .cindex "expansion" "calling Perl from"
10476 This item is available only if Exim has been built to include an embedded Perl
10477 interpreter. The subroutine name and the arguments are first separately
10478 expanded, and then the Perl subroutine is called with those arguments. No
10479 additional arguments need be given; the maximum number permitted, including the
10480 name of the subroutine, is nine.
10482 The return value of the subroutine is inserted into the expanded string, unless
10483 the return value is &%undef%&. In that case, the entire expansion is
10484 forced to fail, in the same way as an explicit &"fail"& on a lookup item
10485 does (see section &<<SECTforexpfai>>&). Whatever you return is evaluated
10486 in a scalar context, thus the return value is a scalar. For example, if you
10487 return a Perl vector, the return value is the size of the vector,
10490 If the subroutine exits by calling Perl's &%die%& function, the expansion fails
10491 with the error message that was passed to &%die%&. More details of the embedded
10492 Perl facility are given in chapter &<<CHAPperl>>&.
10494 The &(redirect)& router has an option called &%forbid_filter_perl%& which locks
10495 out the use of this expansion item in filter files.
10498 .vitem &*${prvs{*&<&'address'&>&*}{*&<&'secret'&>&*}{*&<&'keynumber'&>&*}}*&
10499 .cindex "&%prvs%& expansion item"
10500 The first argument is a complete email address and the second is secret
10501 keystring. The third argument, specifying a key number, is optional. If absent,
10502 it defaults to 0. The result of the expansion is a prvs-signed email address,
10503 to be typically used with the &%return_path%& option on an &(smtp)& transport
10504 as part of a bounce address tag validation (BATV) scheme. For more discussion
10505 and an example, see section &<<SECTverifyPRVS>>&.
10507 .vitem "&*${prvscheck{*&<&'address'&>&*}{*&<&'secret'&>&*}&&&
10508 {*&<&'string'&>&*}}*&"
10509 .cindex "&%prvscheck%& expansion item"
10510 This expansion item is the complement of the &%prvs%& item. It is used for
10511 checking prvs-signed addresses. If the expansion of the first argument does not
10512 yield a syntactically valid prvs-signed address, the whole item expands to the
10513 empty string. When the first argument does expand to a syntactically valid
10514 prvs-signed address, the second argument is expanded, with the prvs-decoded
10515 version of the address and the key number extracted from the address in the
10516 variables &$prvscheck_address$& and &$prvscheck_keynum$&, respectively.
10518 These two variables can be used in the expansion of the second argument to
10519 retrieve the secret. The validity of the prvs-signed address is then checked
10520 against the secret. The result is stored in the variable &$prvscheck_result$&,
10521 which is empty for failure or &"1"& for success.
10523 The third argument is optional; if it is missing, it defaults to an empty
10524 string. This argument is now expanded. If the result is an empty string, the
10525 result of the expansion is the decoded version of the address. This is the case
10526 whether or not the signature was valid. Otherwise, the result of the expansion
10527 is the expansion of the third argument.
10529 All three variables can be used in the expansion of the third argument.
10530 However, once the expansion is complete, only &$prvscheck_result$& remains set.
10531 For more discussion and an example, see section &<<SECTverifyPRVS>>&.
10533 .vitem &*${readfile{*&<&'file&~name'&>&*}{*&<&'eol&~string'&>&*}}*&
10534 .cindex "expansion" "inserting an entire file"
10535 .cindex "file" "inserting into expansion"
10536 .cindex "&%readfile%& expansion item"
10537 The filename and end-of-line (eol) string are first expanded separately. The file is
10538 then read, and its contents replace the entire item. All newline characters in
10539 the file are replaced by the end-of-line string if it is present. Otherwise,
10540 newlines are left in the string.
10541 String expansion is not applied to the contents of the file. If you want this,
10542 you must wrap the item in an &%expand%& operator. If the file cannot be read,
10543 the string expansion fails.
10545 The &(redirect)& router has an option called &%forbid_filter_readfile%& which
10546 locks out the use of this expansion item in filter files.
10550 .vitem "&*${readsocket{*&<&'name'&>&*}{*&<&'request'&>&*}&&&
10551 {*&<&'options'&>&*}{*&<&'eol&~string'&>&*}{*&<&'fail&~string'&>&*}}*&"
10552 .cindex "expansion" "inserting from a socket"
10553 .cindex "socket, use of in expansion"
10554 .cindex "&%readsocket%& expansion item"
10555 This item inserts data from a Unix domain or TCP socket into the expanded
10556 string. The minimal way of using it uses just two arguments, as in these
10559 ${readsocket{/socket/name}{request string}}
10560 ${readsocket{inet:some.host:1234}{request string}}
10562 For a Unix domain socket, the first substring must be the path to the socket.
10563 For an Internet socket, the first substring must contain &`inet:`& followed by
10564 a host name or IP address, followed by a colon and a port, which can be a
10565 number or the name of a TCP port in &_/etc/services_&. An IP address may
10566 optionally be enclosed in square brackets. This is best for IPv6 addresses. For
10569 ${readsocket{inet:[::1]:1234}{request string}}
10571 Only a single host name may be given, but if looking it up yields more than
10572 one IP address, they are each tried in turn until a connection is made. For
10573 both kinds of socket, Exim makes a connection, writes the request string
10574 (unless it is an empty string; no terminating NUL is ever sent)
10575 and reads from the socket until an end-of-file
10576 is read. A timeout of 5 seconds is applied. Additional, optional arguments
10577 extend what can be done. Firstly, you can vary the timeout. For example:
10579 ${readsocket{/socket/name}{request string}{3s}}
10582 The third argument is a list of options, of which the first element is the timeout
10583 and must be present if any options are given.
10584 Further elements are options of form &'name=value'&.
10587 ${readsocket{/socket/name}{request string}{3s:shutdown=no}}
10590 The following option names are recognised:
10593 Defines if the result data can be cached for use by a later identical
10594 request in the same process.
10595 Values are &"yes"& or &"no"& (the default).
10596 If not, all cached results for this connection specification
10597 will be invalidated.
10601 Defines whether or not a write-shutdown is done on the connection after
10602 sending the request. Values are &"yes"& (the default) or &"no"&
10603 (preferred, eg. by some webservers).
10607 Controls the use of TLS on the connection.
10608 Values are &"yes"& or &"no"& (the default).
10609 If it is enabled, a shutdown as described above is never done.
10613 A fourth argument allows you to change any newlines that are in the data
10614 that is read, in the same way as for &%readfile%& (see above). This example
10615 turns them into spaces:
10617 ${readsocket{inet:127.0.0.1:3294}{request string}{3s}{ }}
10619 As with all expansions, the substrings are expanded before the processing
10620 happens. Errors in these sub-expansions cause the expansion to fail. In
10621 addition, the following errors can occur:
10624 Failure to create a socket file descriptor;
10626 Failure to connect the socket;
10628 Failure to write the request string;
10630 Timeout on reading from the socket.
10633 By default, any of these errors causes the expansion to fail. However, if
10634 you supply a fifth substring, it is expanded and used when any of the above
10635 errors occurs. For example:
10637 ${readsocket{/socket/name}{request string}{3s}{\n}\
10640 You can test for the existence of a Unix domain socket by wrapping this
10641 expansion in &`${if exists`&, but there is a race condition between that test
10642 and the actual opening of the socket, so it is safer to use the fifth argument
10643 if you want to be absolutely sure of avoiding an expansion error for a
10644 non-existent Unix domain socket, or a failure to connect to an Internet socket.
10646 The &(redirect)& router has an option called &%forbid_filter_readsocket%& which
10647 locks out the use of this expansion item in filter files.
10650 .vitem &*${reduce{*&<&'string1'&>}{<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10651 .cindex "expansion" "reducing a list to a scalar"
10652 .cindex "list" "reducing to a scalar"
10653 .vindex "&$value$&"
10655 This operation reduces a list to a single, scalar string. After expansion,
10656 <&'string1'&> is interpreted as a list, colon-separated by default, but the
10657 separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10658 Then <&'string2'&> is expanded and
10659 assigned to the &$value$& variable. After this, each item in the <&'string1'&>
10660 list is assigned to &$item$&, in turn, and <&'string3'&> is expanded for each of
10661 them. The result of that expansion is assigned to &$value$& before the next
10662 iteration. When the end of the list is reached, the final value of &$value$& is
10663 added to the expansion output. The &%reduce%& expansion item can be used in a
10664 number of ways. For example, to add up a list of numbers:
10666 ${reduce {<, 1,2,3}{0}{${eval:$value+$item}}}
10668 The result of that expansion would be &`6`&. The maximum of a list of numbers
10671 ${reduce {3:0:9:4:6}{0}{${if >{$item}{$value}{$item}{$value}}}}
10673 At the end of a &*reduce*& expansion, the values of &$item$& and &$value$& are
10674 restored to what they were before. See also the &%filter%& and &%map%&
10677 .vitem &*$rheader_*&<&'header&~name'&>&*:*&&~or&~&*$rh_*&<&'header&~name'&>&*:*&
10678 This item inserts &"raw"& header lines. It is described with the &%header%&
10679 expansion item in section &<<SECTexpansionitems>>& above.
10681 .vitem "&*${run <&'options'&> {*&<&'command&~arg&~list'&>&*}{*&<&'string1'&>&*}&&&
10682 {*&<&'string2'&>&*}}*&"
10683 .cindex "expansion" "running a command"
10684 .cindex "&%run%& expansion item"
10685 This item runs an external command, as a subprocess.
10687 One option is supported after the word &'run'&, comma-separated.
10689 If the option &'preexpand'& is not used,
10690 the command string is split into individual arguments by spaces
10691 and then each argument is expanded.
10692 Then the command is run
10693 in a separate process, but under the same uid and gid. As in other command
10694 executions from Exim, a shell is not used by default. If the command requires
10695 a shell, you must explicitly code it.
10696 The command name may not be tainted, but the remaining arguments can be.
10698 &*Note*&: if tainted arguments are used, they are supplied by a
10699 potential attacker;
10700 a careful assessment for security vulnerabilities should be done.
10702 If the option &'preexpand'& is used,
10704 the command and its arguments are first expanded as one string. The result is
10705 split apart into individual arguments by spaces, and then the command is run
10707 Since the arguments are split by spaces, when there is a variable expansion
10708 which has an empty result, it will cause the situation that the argument will
10709 simply be omitted when the program is actually executed by Exim. If the
10710 script/program requires a specific number of arguments and the expanded
10711 variable could possibly result in this empty expansion, the variable must be
10712 quoted. This is more difficult if the expanded variable itself could result
10713 in a string containing quotes, because it would interfere with the quotes
10714 around the command arguments. A possible guard against this is to wrap the
10715 variable in the &%sg%& operator to change any quote marks to some other
10718 Neither the command nor any argument may be tainted.
10721 The standard input for the command exists, but is empty. The standard output
10722 and standard error are set to the same file descriptor.
10723 .cindex "return code" "from &%run%& expansion"
10724 .vindex "&$value$&"
10725 If the command succeeds (gives a zero return code) <&'string1'&> is expanded
10726 and replaces the entire item; during this expansion, the standard output/error
10727 from the command is in the variable &$value$&. If the command fails,
10728 <&'string2'&>, if present, is expanded and used. Once again, during the
10729 expansion, the standard output/error from the command is in the variable
10732 If <&'string2'&> is absent, the result is empty. Alternatively, <&'string2'&>
10733 can be the word &"fail"& (not in braces) to force expansion failure if the
10734 command does not succeed. If both strings are omitted, the result is contents
10735 of the standard output/error on success, and nothing on failure.
10737 .vindex "&$run_in_acl$&"
10738 The standard output/error of the command is put in the variable &$value$&.
10739 In this ACL example, the output of a command is logged for the admin to
10742 warn condition = ${run{/usr/bin/id}{yes}{no}}
10743 log_message = Output of id: $value
10745 If the command requires shell idioms, such as the > redirect operator, the
10746 shell must be invoked directly, such as with:
10748 ${run{/bin/bash -c "/usr/bin/id >/tmp/id"}{yes}{yes}}
10751 .vindex "&$runrc$&"
10752 The return code from the command is put in the variable &$runrc$&, and this
10753 remains set afterwards, so in a filter file you can do things like this:
10755 if "${run{x y z}{}}$runrc" is 1 then ...
10756 elif $runrc is 2 then ...
10760 If execution of the command fails (for example, the command does not exist),
10761 the return code is 127 &-- the same code that shells use for non-existent
10764 &*Warning*&: In a router or transport, you cannot assume the order in which
10765 option values are expanded, except for those preconditions whose order of
10766 testing is documented. Therefore, you cannot reliably expect to set &$runrc$&
10767 by the expansion of one option, and use it in another.
10769 The &(redirect)& router has an option called &%forbid_filter_run%& which locks
10770 out the use of this expansion item in filter files.
10773 .vitem &*${sg{*&<&'subject'&>&*}{*&<&'regex'&>&*}{*&<&'replacement'&>&*}}*&
10774 .cindex "expansion" "string substitution"
10775 .cindex "&%sg%& expansion item"
10776 This item works like Perl's substitution operator (s) with the global (/g)
10777 option; hence its name. However, unlike the Perl equivalent, Exim does not
10778 modify the subject string; instead it returns the modified string for insertion
10779 into the overall expansion. The item takes three arguments: the subject string,
10780 a regular expression, and a substitution string. For example:
10782 ${sg{abcdefabcdef}{abc}{xyz}}
10784 yields &"xyzdefxyzdef"&. Because all three arguments are expanded before use,
10785 if any $, } or \ characters are required in the regular expression or in the
10786 substitution string, they have to be escaped. For example:
10788 ${sg{abcdef}{^(...)(...)\$}{\$2\$1}}
10790 yields &"defabc"&, and
10792 ${sg{1=A 4=D 3=C}{\N(\d+)=\N}{K\$1=}}
10794 yields &"K1=A K4=D K3=C"&. Note the use of &`\N`& to protect the contents of
10795 the regular expression from string expansion.
10797 The regular expression is compiled in 8-bit mode, working against bytes
10798 rather than any Unicode-aware character handling.
10801 .vitem &*${sort{*&<&'string'&>&*}{*&<&'comparator'&>&*}{*&<&'extractor'&>&*}}*&
10802 .cindex sorting "a list"
10803 .cindex list sorting
10804 .cindex expansion "list sorting"
10805 After expansion, <&'string'&> is interpreted as a list, colon-separated by
10806 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10807 The <&'comparator'&> argument is interpreted as the operator
10808 of a two-argument expansion condition.
10809 The numeric operators plus ge, gt, le, lt (and ~i variants) are supported.
10810 The comparison should return true when applied to two values
10811 if the first value should sort before the second value.
10812 The <&'extractor'&> expansion is applied repeatedly to elements of the list,
10813 the element being placed in &$item$&,
10814 to give values for comparison.
10816 The item result is a sorted list,
10817 with the original list separator,
10818 of the list elements (in full) of the original.
10822 ${sort{3:2:1:4}{<}{$item}}
10824 sorts a list of numbers, and
10826 ${sort {${lookup dnsdb{>:,,mx=example.com}}} {<} {${listextract{1}{<,$item}}}}
10828 will sort an MX lookup into priority order.
10832 .vitem &*${srs_encode&~{*&<&'secret'&>&*}{*&<&'return&~path'&>&*}{*&<&'original&~domain'&>&*}}*&
10833 SRS encoding. See SECT &<<SECTSRS>>& for details.
10837 .vitem &*${substr{*&<&'start'&>&*}{*&<&'len'&>&*}{*&<&'subject'&>&*}}*&
10838 .cindex "&%substr%& expansion item"
10839 .cindex "substring extraction"
10840 .cindex "expansion" "substring extraction"
10841 The three strings are expanded; the first two must yield numbers. Call them
10842 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
10843 if <&'start'&> and <&'len'&> do not change when they are expanded, you
10844 can use the simpler operator notation that avoids some of the braces:
10846 ${substr_<n>_<m>:<subject>}
10848 The second number is optional (in both notations).
10849 If it is absent in the simpler format, the preceding underscore must also be
10852 The &%substr%& item can be used to extract more general substrings than
10853 &%length%&. The first number, <&'n'&>, is a starting offset, and <&'m'&> is the
10854 length required. For example
10856 ${substr{3}{2}{$local_part}}
10858 If the starting offset is greater than the string length the result is the
10859 null string; if the length plus starting offset is greater than the string
10860 length, the result is the right-hand part of the string, starting from the
10861 given offset. The first byte (character) in the string has offset zero.
10863 The &%substr%& expansion item can take negative offset values to count
10864 from the right-hand end of its operand. The last byte (character) is offset -1,
10865 the second-last is offset -2, and so on. Thus, for example,
10867 ${substr{-5}{2}{1234567}}
10869 yields &"34"&. If the absolute value of a negative offset is greater than the
10870 length of the string, the substring starts at the beginning of the string, and
10871 the length is reduced by the amount of overshoot. Thus, for example,
10873 ${substr{-5}{2}{12}}
10875 yields an empty string, but
10877 ${substr{-3}{2}{12}}
10881 When the second number is omitted from &%substr%&, the remainder of the string
10882 is taken if the offset is positive. If it is negative, all bytes (characters) in the
10883 string preceding the offset point are taken. For example, an offset of -1 and
10884 no length, as in these semantically identical examples:
10887 ${substr{-1}{abcde}}
10889 yields all but the last character of the string, that is, &"abcd"&.
10891 All measurement is done in bytes and is not UTF-8 aware.
10895 .vitem "&*${tr{*&<&'subject'&>&*}{*&<&'characters'&>&*}&&&
10896 {*&<&'replacements'&>&*}}*&"
10897 .cindex "expansion" "character translation"
10898 .cindex "&%tr%& expansion item"
10899 This item does single-character (in bytes) translation on its subject string. The second
10900 argument is a list of characters to be translated in the subject string. Each
10901 matching character is replaced by the corresponding character from the
10902 replacement list. For example
10904 ${tr{abcdea}{ac}{13}}
10906 yields &`1b3de1`&. If there are duplicates in the second character string, the
10907 last occurrence is used. If the third string is shorter than the second, its
10908 last character is replicated. However, if it is empty, no translation takes
10911 All character handling is done in bytes and is not UTF-8 aware.
10917 .section "Expansion operators" "SECTexpop"
10918 .cindex "expansion" "operators"
10919 For expansion items that perform transformations on a single argument string,
10920 the &"operator"& notation is used because it is simpler and uses fewer braces.
10921 The substring is first expanded before the operation is applied to it. The
10922 following operations can be performed:
10925 .vitem &*${address:*&<&'string'&>&*}*&
10926 .cindex "expansion" "RFC 2822 address handling"
10927 .cindex "&%address%& expansion item"
10928 The string is interpreted as an RFC 2822 address, as it might appear in a
10929 header line, and the effective address is extracted from it. If the string does
10930 not parse successfully, the result is empty.
10932 The parsing correctly handles SMTPUTF8 Unicode in the string.
10935 .vitem &*${addresses:*&<&'string'&>&*}*&
10936 .cindex "expansion" "RFC 2822 address handling"
10937 .cindex "&%addresses%& expansion item"
10938 The string (after expansion) is interpreted as a list of addresses in RFC
10939 2822 format, such as can be found in a &'To:'& or &'Cc:'& header line. The
10940 operative address (&'local-part@domain'&) is extracted from each item, and the
10941 result of the expansion is a colon-separated list, with appropriate
10942 doubling of colons should any happen to be present in the email addresses.
10943 Syntactically invalid RFC2822 address items are omitted from the output.
10945 It is possible to specify a character other than colon for the output
10946 separator by starting the string with > followed by the new separator
10947 character. For example:
10949 ${addresses:>& Chief <ceo@up.stairs>, sec@base.ment (dogsbody)}
10951 expands to &`ceo@up.stairs&&sec@base.ment`&. The string is expanded
10952 first, so if the expanded string starts with >, it may change the output
10953 separator unintentionally. This can be avoided by setting the output
10954 separator explicitly:
10956 ${addresses:>:$h_from:}
10959 Compare the &%address%& (singular)
10960 expansion item, which extracts the working address from a single RFC2822
10961 address. See the &%filter%&, &%map%&, and &%reduce%& items for ways of
10964 To clarify "list of addresses in RFC 2822 format" mentioned above, Exim follows
10965 a strict interpretation of header line formatting. Exim parses the bare,
10966 unquoted portion of an email address and if it finds a comma, treats it as an
10967 email address separator. For the example header line:
10969 From: =?iso-8859-2?Q?Last=2C_First?= <user@example.com>
10971 The first example below demonstrates that Q-encoded email addresses are parsed
10972 properly if it is given the raw header (in this example, &`$rheader_from:`&).
10973 It does not see the comma because it's still encoded as "=2C". The second
10974 example below is passed the contents of &`$header_from:`&, meaning it gets
10975 de-mimed. Exim sees the decoded "," so it treats it as &*two*& email addresses.
10976 The third example shows that the presence of a comma is skipped when it is
10977 quoted. The fourth example shows SMTPUTF8 handling.
10979 # exim -be '${addresses:From: \
10980 =?iso-8859-2?Q?Last=2C_First?= <user@example.com>}'
10982 # exim -be '${addresses:From: Last, First <user@example.com>}'
10983 Last:user@example.com
10984 # exim -be '${addresses:From: "Last, First" <user@example.com>}'
10986 # exim -be '${addresses:フィル <フィリップ@example.jp>}'
10990 .vitem &*${base32:*&<&'digits'&>&*}*&
10991 .cindex "&%base32%& expansion item"
10992 .cindex "expansion" "conversion to base 32"
10993 The string must consist entirely of decimal digits. The number is converted to
10994 base 32 and output as a (empty, for zero) string of characters.
10995 Only lowercase letters are used.
10997 .vitem &*${base32d:*&<&'base-32&~digits'&>&*}*&
10998 .cindex "&%base32d%& expansion item"
10999 .cindex "expansion" "conversion to base 32"
11000 The string must consist entirely of base-32 digits.
11001 The number is converted to decimal and output as a string.
11003 .vitem &*${base62:*&<&'digits'&>&*}*&
11004 .cindex "&%base62%& expansion item"
11005 .cindex "expansion" "conversion to base 62"
11006 The string must consist entirely of decimal digits. The number is converted to
11007 base 62 and output as a string of six characters, including leading zeros. In
11008 the few operating environments where Exim uses base 36 instead of base 62 for
11009 its message identifiers (because those systems do not have case-sensitive
11010 filenames), base 36 is used by this operator, despite its name. &*Note*&: Just
11011 to be absolutely clear: this is &'not'& base64 encoding.
11013 .vitem &*${base62d:*&<&'base-62&~digits'&>&*}*&
11014 .cindex "&%base62d%& expansion item"
11015 .cindex "expansion" "conversion to base 62"
11016 The string must consist entirely of base-62 digits, or, in operating
11017 environments where Exim uses base 36 instead of base 62 for its message
11018 identifiers, base-36 digits. The number is converted to decimal and output as a
11021 .vitem &*${base64:*&<&'string'&>&*}*&
11022 .cindex "expansion" "base64 encoding"
11023 .cindex "base64 encoding" "in string expansion"
11024 .cindex "&%base64%& expansion item"
11025 .cindex certificate "base64 of DER"
11026 This operator converts a string into one that is base64 encoded.
11028 If the string is a single variable of type certificate,
11029 returns the base64 encoding of the DER form of the certificate.
11032 .vitem &*${base64d:*&<&'string'&>&*}*&
11033 .cindex "expansion" "base64 decoding"
11034 .cindex "base64 decoding" "in string expansion"
11035 .cindex "&%base64d%& expansion item"
11036 This operator converts a base64-encoded string into the un-coded form.
11039 .vitem &*${domain:*&<&'string'&>&*}*&
11040 .cindex "domain" "extraction"
11041 .cindex "expansion" "domain extraction"
11042 The string is interpreted as an RFC 2822 address and the domain is extracted
11043 from it. If the string does not parse successfully, the result is empty.
11046 .vitem &*${escape:*&<&'string'&>&*}*&
11047 .cindex "expansion" "escaping non-printing characters"
11048 .cindex "&%escape%& expansion item"
11049 If the string contains any non-printing characters, they are converted to
11050 escape sequences starting with a backslash. Whether characters with the most
11051 significant bit set (so-called &"8-bit characters"&) count as printing or not
11052 is controlled by the &%print_topbitchars%& option.
11054 .vitem &*${escape8bit:*&<&'string'&>&*}*&
11055 .cindex "expansion" "escaping 8-bit characters"
11056 .cindex "&%escape8bit%& expansion item"
11057 If the string contains any characters with the most significant bit set,
11058 they are converted to escape sequences starting with a backslash.
11059 Backslashes and DEL characters are also converted.
11062 .vitem &*${eval:*&<&'string'&>&*}*&&~and&~&*${eval10:*&<&'string'&>&*}*&
11063 .cindex "expansion" "expression evaluation"
11064 .cindex "expansion" "arithmetic expression"
11065 .cindex "&%eval%& expansion item"
11066 These items supports simple arithmetic and bitwise logical operations in
11067 expansion strings. The string (after expansion) must be a conventional
11068 arithmetic expression, but it is limited to basic arithmetic operators, bitwise
11069 logical operators, and parentheses. All operations are carried out using
11070 integer arithmetic. The operator priorities are as follows (the same as in the
11071 C programming language):
11073 .irow &'highest:'& "not (~), negate (-)"
11074 .irow "" "multiply (*), divide (/), remainder (%)"
11075 .irow "" "plus (+), minus (-)"
11076 .irow "" "shift-left (<<), shift-right (>>)"
11077 .irow "" "and (&&)"
11079 .irow &'lowest:'& "or (|)"
11081 Binary operators with the same priority are evaluated from left to right. White
11082 space is permitted before or after operators.
11084 For &%eval%&, numbers may be decimal, octal (starting with &"0"&) or
11085 hexadecimal (starting with &"0x"&). For &%eval10%&, all numbers are taken as
11086 decimal, even if they start with a leading zero; hexadecimal numbers are not
11087 permitted. This can be useful when processing numbers extracted from dates or
11088 times, which often do have leading zeros.
11090 A number may be followed by &"K"&, &"M"& or &"G"& to multiply it by 1024, 1024*1024
11092 respectively. Negative numbers are supported. The result of the computation is
11093 a decimal representation of the answer (without &"K"&, &"M"& or &"G"&). For example:
11096 &`${eval:1+1} `& yields 2
11097 &`${eval:1+2*3} `& yields 7
11098 &`${eval:(1+2)*3} `& yields 9
11099 &`${eval:2+42%5} `& yields 4
11100 &`${eval:0xc&5} `& yields 4
11101 &`${eval:0xc|5} `& yields 13
11102 &`${eval:0xc^5} `& yields 9
11103 &`${eval:0xc>>1} `& yields 6
11104 &`${eval:0xc<<1} `& yields 24
11105 &`${eval:~255&0x1234} `& yields 4608
11106 &`${eval:-(~255&0x1234)} `& yields -4608
11109 As a more realistic example, in an ACL you might have
11113 {>{$rcpt_count}{10}} \
11116 {$recipients_count} \
11117 {${eval:$rcpt_count/2}} \
11120 message = Too many bad recipients
11122 The condition is true if there have been more than 10 RCPT commands and
11123 fewer than half of them have resulted in a valid recipient.
11126 .vitem &*${expand:*&<&'string'&>&*}*&
11127 .cindex "expansion" "re-expansion of substring"
11128 The &%expand%& operator causes a string to be expanded for a second time. For
11131 ${expand:${lookup{$domain}dbm{/some/file}{$value}}}
11133 first looks up a string in a file while expanding the operand for &%expand%&,
11134 and then re-expands what it has found.
11137 .vitem &*${from_utf8:*&<&'string'&>&*}*&
11139 .cindex "UTF-8" "conversion from"
11140 .cindex "expansion" "UTF-8 conversion"
11141 .cindex "&%from_utf8%& expansion item"
11142 The world is slowly moving towards Unicode, although there are no standards for
11143 email yet. However, other applications (including some databases) are starting
11144 to store data in Unicode, using UTF-8 encoding. This operator converts from a
11145 UTF-8 string to an ISO-8859-1 string. UTF-8 code values greater than 255 are
11146 converted to underscores. The input must be a valid UTF-8 string. If it is not,
11147 the result is an undefined sequence of bytes.
11149 Unicode code points with values less than 256 are compatible with ASCII and
11150 ISO-8859-1 (also known as Latin-1).
11151 For example, character 169 is the copyright symbol in both cases, though the
11152 way it is encoded is different. In UTF-8, more than one byte is needed for
11153 characters with code values greater than 127, whereas ISO-8859-1 is a
11154 single-byte encoding (but thereby limited to 256 characters). This makes
11155 translation from UTF-8 to ISO-8859-1 straightforward.
11158 .vitem &*${hash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
11159 .cindex "hash function" "textual"
11160 .cindex "expansion" "textual hash"
11161 The &%hash%& operator is a simpler interface to the hashing function that can
11162 be used when the two parameters are fixed numbers (as opposed to strings that
11163 change when expanded). The effect is the same as
11165 ${hash{<n>}{<m>}{<string>}}
11167 See the description of the general &%hash%& item above for details. The
11168 abbreviation &%h%& can be used when &%hash%& is used as an operator.
11172 .vitem &*${hex2b64:*&<&'hexstring'&>&*}*&
11173 .cindex "base64 encoding" "conversion from hex"
11174 .cindex "expansion" "hex to base64"
11175 .cindex "&%hex2b64%& expansion item"
11176 This operator converts a hex string into one that is base64 encoded. This can
11177 be useful for processing the output of the various hashing functions.
11181 .vitem &*${hexquote:*&<&'string'&>&*}*&
11182 .cindex "quoting" "hex-encoded unprintable characters"
11183 .cindex "&%hexquote%& expansion item"
11184 This operator converts non-printable characters in a string into a hex
11185 escape form. Byte values between 33 (!) and 126 (~) inclusive are left
11186 as is, and other byte values are converted to &`\xNN`&, for example, a
11187 byte value 127 is converted to &`\x7f`&.
11190 .vitem &*${ipv6denorm:*&<&'string'&>&*}*&
11191 .cindex "&%ipv6denorm%& expansion item"
11192 .cindex "IP address" normalisation
11193 This expands an IPv6 address to a full eight-element colon-separated set
11194 of hex digits including leading zeroes.
11195 A trailing ipv4-style dotted-decimal set is converted to hex.
11196 Pure IPv4 addresses are converted to IPv4-mapped IPv6.
11198 .vitem &*${ipv6norm:*&<&'string'&>&*}*&
11199 .cindex "&%ipv6norm%& expansion item"
11200 .cindex "IP address" normalisation
11201 .cindex "IP address" "canonical form"
11202 This converts an IPv6 address to canonical form.
11203 Leading zeroes of groups are omitted, and the longest
11204 set of zero-valued groups is replaced with a double colon.
11205 A trailing ipv4-style dotted-decimal set is converted to hex.
11206 Pure IPv4 addresses are converted to IPv4-mapped IPv6.
11209 .vitem &*${lc:*&<&'string'&>&*}*&
11210 .cindex "case forcing in strings"
11211 .cindex "string" "case forcing"
11212 .cindex "lower casing"
11213 .cindex "expansion" "case forcing"
11214 .cindex "&%lc%& expansion item"
11215 This forces the letters in the string into lower-case, for example:
11219 Case is defined per the system C locale.
11221 .vitem &*${length_*&<&'number'&>&*:*&<&'string'&>&*}*&
11222 .cindex "expansion" "string truncation"
11223 .cindex "&%length%& expansion item"
11224 The &%length%& operator is a simpler interface to the &%length%& function that
11225 can be used when the parameter is a fixed number (as opposed to a string that
11226 changes when expanded). The effect is the same as
11228 ${length{<number>}{<string>}}
11230 See the description of the general &%length%& item above for details. Note that
11231 &%length%& is not the same as &%strlen%&. The abbreviation &%l%& can be used
11232 when &%length%& is used as an operator.
11233 All measurement is done in bytes and is not UTF-8 aware.
11236 .vitem &*${listcount:*&<&'string'&>&*}*&
11237 .cindex "expansion" "list item count"
11238 .cindex "list" "item count"
11239 .cindex "list" "count of items"
11240 .cindex "&%listcount%& expansion item"
11241 The string is interpreted as a list and the number of items is returned.
11244 .vitem &*${listnamed:*&<&'name'&>&*}*&&~and&~&*${listnamed_*&<&'type'&>&*:*&<&'name'&>&*}*&
11245 .cindex "expansion" "named list"
11246 .cindex "&%listnamed%& expansion item"
11247 The name is interpreted as a named list and the content of the list is returned,
11248 expanding any referenced lists, re-quoting as needed for colon-separation.
11249 If the optional type is given it must be one of "a", "d", "h" or "l"
11250 and selects address-, domain-, host- or localpart- lists to search among respectively.
11251 Otherwise all types are searched in an undefined order and the first
11252 matching list is returned.
11253 &*Note*&: Neither string-expansion of lists referenced by named-list syntax elements,
11254 nor expansion of lookup elements, is done by the &%listnamed%& operator.
11257 .vitem &*${local_part:*&<&'string'&>&*}*&
11258 .cindex "expansion" "local part extraction"
11259 .cindex "&%local_part%& expansion item"
11260 The string is interpreted as an RFC 2822 address and the local part is
11261 extracted from it. If the string does not parse successfully, the result is
11263 The parsing correctly handles SMTPUTF8 Unicode in the string.
11266 .vitem &*${mask:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*& &&&
11267 &*${mask_n:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*&
11268 .cindex "masked IP address"
11269 .cindex "IP address" "masking"
11270 .cindex "CIDR notation"
11271 .cindex "expansion" "IP address masking"
11272 .cindex "&%mask%& expansion item"
11273 If the form of the string to be operated on is not an IP address followed by a
11274 slash and an integer (that is, a network address in CIDR notation), the
11275 expansion fails. Otherwise, this operator converts the IP address to binary,
11276 masks off the least significant bits according to the bit count, and converts
11277 the result back to text, with mask appended. For example,
11279 ${mask:10.111.131.206/28}
11281 returns the string &"10.111.131.192/28"&.
11283 Since this operation is expected to
11284 be mostly used for looking up masked addresses in files, the
11289 address uses dots to separate components instead of colons, because colon
11290 terminates a key string in lsearch files. So, for example,
11292 ${mask:3ffe:ffff:836f:0a00:000a:0800:200a:c031/99}
11296 3ffe.ffff.836f.0a00.000a.0800.2000.0000/99
11299 If the optional form &*mask_n*& is used, IPv6 address result are instead
11300 returned in normailsed form, using colons and with zero-compression.
11302 Letters in IPv6 addresses are always output in lower case.
11305 .vitem &*${md5:*&<&'string'&>&*}*&
11307 .cindex "expansion" "MD5 hash"
11308 .cindex certificate fingerprint
11309 .cindex "&%md5%& expansion item"
11310 The &%md5%& operator computes the MD5 hash value of the string, and returns it
11311 as a 32-digit hexadecimal number, in which any letters are in lower case.
11313 If the string is a single variable of type certificate,
11314 returns the MD5 hash fingerprint of the certificate.
11317 .vitem &*${nhash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
11318 .cindex "expansion" "numeric hash"
11319 .cindex "hash function" "numeric"
11320 The &%nhash%& operator is a simpler interface to the numeric hashing function
11321 that can be used when the two parameters are fixed numbers (as opposed to
11322 strings that change when expanded). The effect is the same as
11324 ${nhash{<n>}{<m>}{<string>}}
11326 See the description of the general &%nhash%& item above for details.
11329 .vitem &*${quote:*&<&'string'&>&*}*&
11330 .cindex "quoting" "in string expansions"
11331 .cindex "expansion" "quoting"
11332 .cindex "&%quote%& expansion item"
11333 The &%quote%& operator puts its argument into double quotes if it
11334 is an empty string or
11335 contains anything other than letters, digits, underscores, dots, and hyphens.
11336 Any occurrences of double quotes and backslashes are escaped with a backslash.
11337 Newlines and carriage returns are converted to &`\n`& and &`\r`&,
11338 respectively For example,
11346 The place where this is useful is when the argument is a substitution from a
11347 variable or a message header.
11349 .vitem &*${quote_local_part:*&<&'string'&>&*}*&
11350 .cindex "&%quote_local_part%& expansion item"
11351 This operator is like &%quote%&, except that it quotes the string only if
11352 required to do so by the rules of RFC 2822 for quoting local parts. For
11353 example, a plus sign would not cause quoting (but it would for &%quote%&).
11354 If you are creating a new email address from the contents of &$local_part$&
11355 (or any other unknown data), you should always use this operator.
11357 This quoting determination is not SMTPUTF8-aware, thus quoting non-ASCII data
11358 will likely use the quoting form.
11359 Thus &'${quote_local_part:フィル}'& will always become &'"フィル"'&.
11362 .vitem &*${quote_*&<&'lookup-type'&>&*:*&<&'string'&>&*}*&
11363 .cindex "quoting" "lookup-specific"
11364 This operator applies lookup-specific quoting rules to the string. Each
11365 query-style lookup type has its own quoting rules which are described with
11366 the lookups in chapter &<<CHAPfdlookup>>&. For example,
11368 ${quote_ldap:two * two}
11374 For single-key lookup types, no quoting is ever necessary and this operator
11375 yields an unchanged string.
11378 .vitem &*${randint:*&<&'n'&>&*}*&
11379 .cindex "random number"
11380 This operator returns a somewhat random number which is less than the
11381 supplied number and is at least 0. The quality of this randomness depends
11382 on how Exim was built; the values are not suitable for keying material.
11383 If Exim is linked against OpenSSL then RAND_pseudo_bytes() is used.
11384 If Exim is linked against GnuTLS then gnutls_rnd(GNUTLS_RND_NONCE) is used,
11385 for versions of GnuTLS with that function.
11386 Otherwise, the implementation may be arc4random(), random() seeded by
11387 srandomdev() or srandom(), or a custom implementation even weaker than
11391 .vitem &*${reverse_ip:*&<&'ipaddr'&>&*}*&
11392 .cindex "expansion" "IP address"
11393 This operator reverses an IP address; for IPv4 addresses, the result is in
11394 dotted-quad decimal form, while for IPv6 addresses the result is in
11395 dotted-nibble hexadecimal form. In both cases, this is the "natural" form
11396 for DNS. For example,
11398 ${reverse_ip:192.0.2.4}
11399 ${reverse_ip:2001:0db8:c42:9:1:abcd:192.0.2.127}
11404 f.7.2.0.0.0.0.c.d.c.b.a.1.0.0.0.9.0.0.0.2.4.c.0.8.b.d.0.1.0.0.2
11408 .vitem &*${rfc2047:*&<&'string'&>&*}*&
11409 .cindex "expansion" "RFC 2047"
11410 .cindex "RFC 2047" "expansion operator"
11411 .cindex "&%rfc2047%& expansion item"
11412 This operator encodes text according to the rules of RFC 2047. This is an
11413 encoding that is used in header lines to encode non-ASCII characters. It is
11414 assumed that the input string is in the encoding specified by the
11415 &%headers_charset%& option, which gets its default at build time. If the string
11416 contains only characters in the range 33&--126, and no instances of the
11419 ? = ( ) < > @ , ; : \ " . [ ] _
11421 it is not modified. Otherwise, the result is the RFC 2047 encoding of the
11422 string, using as many &"encoded words"& as necessary to encode all the
11426 .vitem &*${rfc2047d:*&<&'string'&>&*}*&
11427 .cindex "expansion" "RFC 2047"
11428 .cindex "RFC 2047" "decoding"
11429 .cindex "&%rfc2047d%& expansion item"
11430 This operator decodes strings that are encoded as per RFC 2047. Binary zero
11431 bytes are replaced by question marks. Characters are converted into the
11432 character set defined by &%headers_charset%&. Overlong RFC 2047 &"words"& are
11433 not recognized unless &%check_rfc2047_length%& is set false.
11435 &*Note*&: If you use &%$header%&_&'xxx'&&*:*& (or &%$h%&_&'xxx'&&*:*&) to
11436 access a header line, RFC 2047 decoding is done automatically. You do not need
11437 to use this operator as well.
11441 .vitem &*${rxquote:*&<&'string'&>&*}*&
11442 .cindex "quoting" "in regular expressions"
11443 .cindex "regular expressions" "quoting"
11444 .cindex "&%rxquote%& expansion item"
11445 The &%rxquote%& operator inserts a backslash before any non-alphanumeric
11446 characters in its argument. This is useful when substituting the values of
11447 variables or headers inside regular expressions.
11450 .vitem &*${sha1:*&<&'string'&>&*}*&
11451 .cindex "SHA-1 hash"
11452 .cindex "expansion" "SHA-1 hashing"
11453 .cindex certificate fingerprint
11454 .cindex "&%sha1%& expansion item"
11455 The &%sha1%& operator computes the SHA-1 hash value of the string, and returns
11456 it as a 40-digit hexadecimal number, in which any letters are in upper case.
11458 If the string is a single variable of type certificate,
11459 returns the SHA-1 hash fingerprint of the certificate.
11462 .vitem &*${sha256:*&<&'string'&>&*}*& &&&
11463 &*${sha2:*&<&'string'&>&*}*& &&&
11464 &*${sha2_<n>:*&<&'string'&>&*}*&
11465 .cindex "SHA-256 hash"
11466 .cindex "SHA-2 hash"
11467 .cindex certificate fingerprint
11468 .cindex "expansion" "SHA-256 hashing"
11469 .cindex "&%sha256%& expansion item"
11470 .cindex "&%sha2%& expansion item"
11471 The &%sha256%& operator computes the SHA-256 hash value of the string
11473 it as a 64-digit hexadecimal number, in which any letters are in upper case.
11475 If the string is a single variable of type certificate,
11476 returns the SHA-256 hash fingerprint of the certificate.
11478 The operator can also be spelled &%sha2%& and does the same as &%sha256%&
11479 (except for certificates, which are not supported).
11480 Finally, if an underbar
11481 and a number is appended it specifies the output length, selecting a
11482 member of the SHA-2 family of hash functions.
11483 Values of 256, 384 and 512 are accepted, with 256 being the default.
11486 .vitem &*${sha3:*&<&'string'&>&*}*& &&&
11487 &*${sha3_<n>:*&<&'string'&>&*}*&
11488 .cindex "SHA3 hash"
11489 .cindex "expansion" "SHA3 hashing"
11490 .cindex "&%sha3%& expansion item"
11491 The &%sha3%& operator computes the SHA3-256 hash value of the string
11493 it as a 64-digit hexadecimal number, in which any letters are in upper case.
11495 If a number is appended, separated by an underbar, it specifies
11496 the output length. Values of 224, 256, 384 and 512 are accepted;
11497 with 256 being the default.
11499 The &%sha3%& expansion item is only supported if Exim has been
11500 compiled with GnuTLS 3.5.0 or later,
11501 or OpenSSL 1.1.1 or later.
11502 The macro "_CRYPTO_HASH_SHA3" will be defined if it is supported.
11505 .vitem &*${stat:*&<&'string'&>&*}*&
11506 .cindex "expansion" "statting a file"
11507 .cindex "file" "extracting characteristics"
11508 .cindex "&%stat%& expansion item"
11509 The string, after expansion, must be a file path. A call to the &[stat()]&
11510 function is made for this path. If &[stat()]& fails, an error occurs and the
11511 expansion fails. If it succeeds, the data from the stat replaces the item, as a
11512 series of <&'name'&>=<&'value'&> pairs, where the values are all numerical,
11513 except for the value of &"smode"&. The names are: &"mode"& (giving the mode as
11514 a 4-digit octal number), &"smode"& (giving the mode in symbolic format as a
11515 10-character string, as for the &'ls'& command), &"inode"&, &"device"&,
11516 &"links"&, &"uid"&, &"gid"&, &"size"&, &"atime"&, &"mtime"&, and &"ctime"&. You
11517 can extract individual fields using the &%extract%& expansion item.
11519 The use of the &%stat%& expansion in users' filter files can be locked out by
11520 the system administrator. &*Warning*&: The file size may be incorrect on 32-bit
11521 systems for files larger than 2GB.
11523 .vitem &*${str2b64:*&<&'string'&>&*}*&
11524 .cindex "&%str2b64%& expansion item"
11525 Now deprecated, a synonym for the &%base64%& expansion operator.
11529 .vitem &*${strlen:*&<&'string'&>&*}*&
11530 .cindex "expansion" "string length"
11531 .cindex "string" "length in expansion"
11532 .cindex "&%strlen%& expansion item"
11533 The item is replaced by the length of the expanded string, expressed as a
11534 decimal number. &*Note*&: Do not confuse &%strlen%& with &%length%&.
11535 All measurement is done in bytes and is not UTF-8 aware.
11538 .vitem &*${substr_*&<&'start'&>&*_*&<&'length'&>&*:*&<&'string'&>&*}*&
11539 .cindex "&%substr%& expansion item"
11540 .cindex "substring extraction"
11541 .cindex "expansion" "substring expansion"
11542 The &%substr%& operator is a simpler interface to the &%substr%& function that
11543 can be used when the two parameters are fixed numbers (as opposed to strings
11544 that change when expanded). The effect is the same as
11546 ${substr{<start>}{<length>}{<string>}}
11548 See the description of the general &%substr%& item above for details. The
11549 abbreviation &%s%& can be used when &%substr%& is used as an operator.
11550 All measurement is done in bytes and is not UTF-8 aware.
11552 .vitem &*${time_eval:*&<&'string'&>&*}*&
11553 .cindex "&%time_eval%& expansion item"
11554 .cindex "time interval" "decoding"
11555 This item converts an Exim time interval such as &`2d4h5m`& into a number of
11558 .vitem &*${time_interval:*&<&'string'&>&*}*&
11559 .cindex "&%time_interval%& expansion item"
11560 .cindex "time interval" "formatting"
11561 The argument (after sub-expansion) must be a sequence of decimal digits that
11562 represents an interval of time as a number of seconds. It is converted into a
11563 number of larger units and output in Exim's normal time format, for example,
11566 .vitem &*${uc:*&<&'string'&>&*}*&
11567 .cindex "case forcing in strings"
11568 .cindex "string" "case forcing"
11569 .cindex "upper casing"
11570 .cindex "expansion" "case forcing"
11571 .cindex "&%uc%& expansion item"
11572 This forces the letters in the string into upper-case.
11573 Case is defined per the system C locale.
11575 .vitem &*${utf8clean:*&<&'string'&>&*}*&
11576 .cindex "correction of invalid utf-8 sequences in strings"
11577 .cindex "utf-8" "utf-8 sequences"
11578 .cindex "incorrect utf-8"
11579 .cindex "expansion" "utf-8 forcing"
11580 .cindex "&%utf8clean%& expansion item"
11581 This replaces any invalid utf-8 sequence in the string by the character &`?`&.
11582 In versions of Exim before 4.92, this did not correctly do so for a truncated
11583 final codepoint's encoding, and the character would be silently dropped.
11584 If you must handle detection of this scenario across both sets of Exim behavior,
11585 the complexity will depend upon the task.
11586 For instance, to detect if the first character is multibyte and a 1-byte
11587 extraction can be successfully used as a path component (as is common for
11588 dividing up delivery folders), you might use:
11590 condition = ${if inlist{${utf8clean:${length_1:$local_part}}}{:?}{yes}{no}}
11592 (which will false-positive if the first character of the local part is a
11593 literal question mark).
11595 .vitem "&*${utf8_domain_to_alabel:*&<&'string'&>&*}*&" &&&
11596 "&*${utf8_domain_from_alabel:*&<&'string'&>&*}*&" &&&
11597 "&*${utf8_localpart_to_alabel:*&<&'string'&>&*}*&" &&&
11598 "&*${utf8_localpart_from_alabel:*&<&'string'&>&*}*&"
11599 .cindex expansion UTF-8
11600 .cindex UTF-8 expansion
11602 .cindex internationalisation
11603 .cindex "&%utf8_domain_to_alabel%& expansion item"
11604 .cindex "&%utf8_domain_from_alabel%& expansion item"
11605 .cindex "&%utf8_localpart_to_alabel%& expansion item"
11606 .cindex "&%utf8_localpart_from_alabel%& expansion item"
11607 These convert EAI mail name components between UTF-8 and a-label forms.
11608 For information on internationalisation support see &<<SECTi18nMTA>>&.
11616 .section "Expansion conditions" "SECTexpcond"
11617 .scindex IIDexpcond "expansion" "conditions"
11618 The following conditions are available for testing by the &%${if%& construct
11619 while expanding strings:
11622 .vitem &*!*&<&'condition'&>
11623 .cindex "expansion" "negating a condition"
11624 .cindex "negation" "in expansion condition"
11625 Preceding any condition with an exclamation mark negates the result of the
11628 .vitem <&'symbolic&~operator'&>&~&*{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11629 .cindex "numeric comparison"
11630 .cindex "expansion" "numeric comparison"
11631 There are a number of symbolic operators for doing numeric comparisons. They
11637 &`>= `& greater or equal
11639 &`<= `& less or equal
11643 ${if >{$message_size}{10M} ...
11645 Note that the general negation operator provides for inequality testing. The
11646 two strings must take the form of optionally signed decimal integers,
11647 optionally followed by one of the letters &"K"&, &"M"& or &"G"& (in either upper or
11648 lower case), signifying multiplication by 1024, 1024*1024 or 1024*1024*1024, respectively.
11649 As a special case, the numerical value of an empty string is taken as
11652 In all cases, a relative comparator OP is testing if <&'string1'&> OP
11653 <&'string2'&>; the above example is checking if &$message_size$& is larger than
11654 10M, not if 10M is larger than &$message_size$&.
11657 .vitem &*acl&~{{*&<&'name'&>&*}{*&<&'arg1'&>&*}&&&
11658 {*&<&'arg2'&>&*}...}*&
11659 .cindex "expansion" "calling an acl"
11660 .cindex "&%acl%&" "expansion condition"
11661 The name and zero to nine argument strings are first expanded separately. The expanded
11662 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
11663 Any unused are made empty. The variable &$acl_narg$& is set to the number of
11664 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
11665 and may use the variables; if another acl expansion is used the values
11666 are restored after it returns. If the ACL sets
11667 a value using a "message =" modifier the variable $value becomes
11668 the result of the expansion, otherwise it is empty.
11669 If the ACL returns accept the condition is true; if deny, false.
11670 If the ACL returns defer the result is a forced-fail.
11672 .vitem &*bool&~{*&<&'string'&>&*}*&
11673 .cindex "expansion" "boolean parsing"
11674 .cindex "&%bool%& expansion condition"
11675 This condition turns a string holding a true or false representation into
11676 a boolean state. It parses &"true"&, &"false"&, &"yes"& and &"no"&
11677 (case-insensitively); also integer numbers map to true if non-zero,
11679 An empty string is treated as false.
11680 Leading and trailing whitespace is ignored;
11681 thus a string consisting only of whitespace is false.
11682 All other string values will result in expansion failure.
11684 When combined with ACL variables, this expansion condition will let you
11685 make decisions in one place and act on those decisions in another place.
11688 ${if bool{$acl_m_privileged_sender} ...
11692 .vitem &*bool_lax&~{*&<&'string'&>&*}*&
11693 .cindex "expansion" "boolean parsing"
11694 .cindex "&%bool_lax%& expansion condition"
11695 Like &%bool%&, this condition turns a string into a boolean state. But
11696 where &%bool%& accepts a strict set of strings, &%bool_lax%& uses the same
11697 loose definition that the Router &%condition%& option uses. The empty string
11698 and the values &"false"&, &"no"& and &"0"& map to false, all others map to
11699 true. Leading and trailing whitespace is ignored.
11701 Note that where &"bool{00}"& is false, &"bool_lax{00}"& is true.
11703 .vitem &*crypteq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11704 .cindex "expansion" "encrypted comparison"
11705 .cindex "encrypted strings, comparing"
11706 .cindex "&%crypteq%& expansion condition"
11707 This condition is included in the Exim binary if it is built to support any
11708 authentication mechanisms (see chapter &<<CHAPSMTPAUTH>>&). Otherwise, it is
11709 necessary to define SUPPORT_CRYPTEQ in &_Local/Makefile_& to get &%crypteq%&
11710 included in the binary.
11712 The &%crypteq%& condition has two arguments. The first is encrypted and
11713 compared against the second, which is already encrypted. The second string may
11714 be in the LDAP form for storing encrypted strings, which starts with the
11715 encryption type in curly brackets, followed by the data. If the second string
11716 does not begin with &"{"& it is assumed to be encrypted with &[crypt()]& or
11717 &[crypt16()]& (see below), since such strings cannot begin with &"{"&.
11718 Typically this will be a field from a password file. An example of an encrypted
11719 string in LDAP form is:
11721 {md5}CY9rzUYh03PK3k6DJie09g==
11723 If such a string appears directly in an expansion, the curly brackets have to
11724 be quoted, because they are part of the expansion syntax. For example:
11726 ${if crypteq {test}{\{md5\}CY9rzUYh03PK3k6DJie09g==}{yes}{no}}
11728 The following encryption types (whose names are matched case-independently) are
11733 .cindex "base64 encoding" "in encrypted password"
11734 &%{md5}%& computes the MD5 digest of the first string, and expresses this as
11735 printable characters to compare with the remainder of the second string. If the
11736 length of the comparison string is 24, Exim assumes that it is base64 encoded
11737 (as in the above example). If the length is 32, Exim assumes that it is a
11738 hexadecimal encoding of the MD5 digest. If the length not 24 or 32, the
11742 .cindex "SHA-1 hash"
11743 &%{sha1}%& computes the SHA-1 digest of the first string, and expresses this as
11744 printable characters to compare with the remainder of the second string. If the
11745 length of the comparison string is 28, Exim assumes that it is base64 encoded.
11746 If the length is 40, Exim assumes that it is a hexadecimal encoding of the
11747 SHA-1 digest. If the length is not 28 or 40, the comparison fails.
11750 .cindex "&[crypt()]&"
11751 &%{crypt}%& calls the &[crypt()]& function, which traditionally used to use
11752 only the first eight characters of the password. However, in modern operating
11753 systems this is no longer true, and in many cases the entire password is used,
11754 whatever its length.
11757 .cindex "&[crypt16()]&"
11758 &%{crypt16}%& calls the &[crypt16()]& function, which was originally created to
11759 use up to 16 characters of the password in some operating systems. Again, in
11760 modern operating systems, more characters may be used.
11762 Exim has its own version of &[crypt16()]&, which is just a double call to
11763 &[crypt()]&. For operating systems that have their own version, setting
11764 HAVE_CRYPT16 in &_Local/Makefile_& when building Exim causes it to use the
11765 operating system version instead of its own. This option is set by default in
11766 the OS-dependent &_Makefile_& for those operating systems that are known to
11767 support &[crypt16()]&.
11769 Some years after Exim's &[crypt16()]& was implemented, a user discovered that
11770 it was not using the same algorithm as some operating systems' versions. It
11771 turns out that as well as &[crypt16()]& there is a function called
11772 &[bigcrypt()]& in some operating systems. This may or may not use the same
11773 algorithm, and both of them may be different to Exim's built-in &[crypt16()]&.
11775 However, since there is now a move away from the traditional &[crypt()]&
11776 functions towards using SHA1 and other algorithms, tidying up this area of
11777 Exim is seen as very low priority.
11779 If you do not put a encryption type (in curly brackets) in a &%crypteq%&
11780 comparison, the default is usually either &`{crypt}`& or &`{crypt16}`&, as
11781 determined by the setting of DEFAULT_CRYPT in &_Local/Makefile_&. The default
11782 default is &`{crypt}`&. Whatever the default, you can always use either
11783 function by specifying it explicitly in curly brackets.
11785 .vitem &*def:*&<&'variable&~name'&>
11786 .cindex "expansion" "checking for empty variable"
11787 .cindex "&%def%& expansion condition"
11788 The &%def%& condition must be followed by the name of one of the expansion
11789 variables defined in section &<<SECTexpvar>>&. The condition is true if the
11790 variable does not contain the empty string. For example:
11792 ${if def:sender_ident {from $sender_ident}}
11794 Note that the variable name is given without a leading &%$%& character. If the
11795 variable does not exist, the expansion fails.
11797 .vitem "&*def:header_*&<&'header&~name'&>&*:*&&~&~or&~&&&
11798 &~&*def:h_*&<&'header&~name'&>&*:*&"
11799 .cindex "expansion" "checking header line existence"
11800 This condition is true if a message is being processed and the named header
11801 exists in the message. For example,
11803 ${if def:header_reply-to:{$h_reply-to:}{$h_from:}}
11805 &*Note*&: No &%$%& appears before &%header_%& or &%h_%& in the condition, and
11806 the header name must be terminated by a colon if white space does not follow.
11808 .vitem &*eq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11809 &*eqi&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11810 .cindex "string" "comparison"
11811 .cindex "expansion" "string comparison"
11812 .cindex "&%eq%& expansion condition"
11813 .cindex "&%eqi%& expansion condition"
11814 The two substrings are first expanded. The condition is true if the two
11815 resulting strings are identical. For &%eq%& the comparison includes the case of
11816 letters, whereas for &%eqi%& the comparison is case-independent, where
11817 case is defined per the system C locale.
11819 .vitem &*exists&~{*&<&'file&~name'&>&*}*&
11820 .cindex "expansion" "file existence test"
11821 .cindex "file" "existence test"
11822 .cindex "&%exists%&, expansion condition"
11823 The substring is first expanded and then interpreted as an absolute path. The
11824 condition is true if the named file (or directory) exists. The existence test
11825 is done by calling the &[stat()]& function. The use of the &%exists%& test in
11826 users' filter files may be locked out by the system administrator.
11828 &*Note:*& Testing a path using this condition is not a sufficient way of
11830 Consider using a dsearch lookup.
11832 .vitem &*first_delivery*&
11833 .cindex "delivery" "first"
11834 .cindex "first delivery"
11835 .cindex "expansion" "first delivery test"
11836 .cindex "&%first_delivery%& expansion condition"
11837 This condition, which has no data, is true during a message's first delivery
11838 attempt. It is false during any subsequent delivery attempts.
11841 .vitem "&*forall{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&" &&&
11842 "&*forany{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&"
11843 .cindex "list" "iterative conditions"
11844 .cindex "expansion" "&*forall*& condition"
11845 .cindex "expansion" "&*forany*& condition"
11847 These conditions iterate over a list. The first argument is expanded to form
11848 the list. By default, the list separator is a colon, but it can be changed by
11849 the normal method (&<<SECTlistsepchange>>&).
11850 The second argument is interpreted as a condition that is to
11851 be applied to each item in the list in turn. During the interpretation of the
11852 condition, the current list item is placed in a variable called &$item$&.
11854 For &*forany*&, interpretation stops if the condition is true for any item, and
11855 the result of the whole condition is true. If the condition is false for all
11856 items in the list, the overall condition is false.
11858 For &*forall*&, interpretation stops if the condition is false for any item,
11859 and the result of the whole condition is false. If the condition is true for
11860 all items in the list, the overall condition is true.
11862 Note that negation of &*forany*& means that the condition must be false for all
11863 items for the overall condition to succeed, and negation of &*forall*& means
11864 that the condition must be false for at least one item. In this example, the
11865 list separator is changed to a comma:
11867 ${if forany{<, $recipients}{match{$item}{^user3@}}{yes}{no}}
11869 The value of &$item$& is saved and restored while &%forany%& or &%forall%& is
11870 being processed, to enable these expansion items to be nested.
11872 To scan a named list, expand it with the &*listnamed*& operator.
11874 .vitem "&*forall_json{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
11875 "&*forany_json{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
11876 "&*forall_jsons{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
11877 "&*forany_jsons{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&"
11878 .cindex JSON "iterative conditions"
11879 .cindex JSON expansions
11880 .cindex expansion "&*forall_json*& condition"
11881 .cindex expansion "&*forany_json*& condition"
11882 .cindex expansion "&*forall_jsons*& condition"
11883 .cindex expansion "&*forany_jsons*& condition"
11884 As for the above, except that the first argument must, after expansion,
11886 The array separator is not changeable.
11887 For the &"jsons"& variants the elements are expected to be JSON strings
11888 and have their quotes removed before the evaluation of the condition.
11892 .vitem &*ge&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11893 &*gei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11894 .cindex "string" "comparison"
11895 .cindex "expansion" "string comparison"
11896 .cindex "&%ge%& expansion condition"
11897 .cindex "&%gei%& expansion condition"
11898 The two substrings are first expanded. The condition is true if the first
11899 string is lexically greater than or equal to the second string. For &%ge%& the
11900 comparison includes the case of letters, whereas for &%gei%& the comparison is
11902 Case and collation order are defined per the system C locale.
11904 .vitem &*gt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11905 &*gti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11906 .cindex "string" "comparison"
11907 .cindex "expansion" "string comparison"
11908 .cindex "&%gt%& expansion condition"
11909 .cindex "&%gti%& expansion condition"
11910 The two substrings are first expanded. The condition is true if the first
11911 string is lexically greater than the second string. For &%gt%& the comparison
11912 includes the case of letters, whereas for &%gti%& the comparison is
11914 Case and collation order are defined per the system C locale.
11917 .vitem &*inbound_srs&~{*&<&'local&~part'&>&*}{*&<&'secret'&>&*}*&
11918 SRS decode. See SECT &<<SECTSRS>>& for details.
11921 .vitem &*inlist&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11922 &*inlisti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11923 .cindex "string" "comparison"
11924 .cindex "list" "iterative conditions"
11925 Both strings are expanded; the second string is treated as a list of simple
11926 strings; if the first string is a member of the second, then the condition
11928 For the case-independent &%inlisti%& condition, case is defined per the system C locale.
11930 These are simpler to use versions of the more powerful &*forany*& condition.
11931 Examples, and the &*forany*& equivalents:
11933 ${if inlist{needle}{foo:needle:bar}}
11934 ${if forany{foo:needle:bar}{eq{$item}{needle}}}
11935 ${if inlisti{Needle}{fOo:NeeDLE:bAr}}
11936 ${if forany{fOo:NeeDLE:bAr}{eqi{$item}{Needle}}}
11940 The variable &$value$& will be set for a successful match and can be
11941 used in the success clause of an &%if%& expansion item using the condition.
11942 .cindex "tainted data" "de-tainting"
11943 It will have the same taint status as the list; expansions such as
11945 ${if inlist {$h_mycode:} {0 : 1 : 42} {$value}}
11947 can be used for de-tainting.
11948 Any previous &$value$& is restored after the if.
11952 .vitem &*isip&~{*&<&'string'&>&*}*& &&&
11953 &*isip4&~{*&<&'string'&>&*}*& &&&
11954 &*isip6&~{*&<&'string'&>&*}*&
11955 .cindex "IP address" "testing string format"
11956 .cindex "string" "testing for IP address"
11957 .cindex "&%isip%& expansion condition"
11958 .cindex "&%isip4%& expansion condition"
11959 .cindex "&%isip6%& expansion condition"
11960 The substring is first expanded, and then tested to see if it has the form of
11961 an IP address. Both IPv4 and IPv6 addresses are valid for &%isip%&, whereas
11962 &%isip4%& and &%isip6%& test specifically for IPv4 or IPv6 addresses.
11964 For an IPv4 address, the test is for four dot-separated components, each of
11965 which consists of from one to three digits. For an IPv6 address, up to eight
11966 colon-separated components are permitted, each containing from one to four
11967 hexadecimal digits. There may be fewer than eight components if an empty
11968 component (adjacent colons) is present. Only one empty component is permitted.
11970 &*Note*&: The checks used to be just on the form of the address; actual numerical
11971 values were not considered. Thus, for example, 999.999.999.999 passed the IPv4
11973 This is no longer the case.
11975 The main use of these tests is to distinguish between IP addresses and
11976 host names, or between IPv4 and IPv6 addresses. For example, you could use
11978 ${if isip4{$sender_host_address}...
11980 to test which IP version an incoming SMTP connection is using.
11982 .vitem &*ldapauth&~{*&<&'ldap&~query'&>&*}*&
11983 .cindex "LDAP" "use for authentication"
11984 .cindex "expansion" "LDAP authentication test"
11985 .cindex "&%ldapauth%& expansion condition"
11986 This condition supports user authentication using LDAP. See section
11987 &<<SECTldap>>& for details of how to use LDAP in lookups and the syntax of
11988 queries. For this use, the query must contain a user name and password. The
11989 query itself is not used, and can be empty. The condition is true if the
11990 password is not empty, and the user name and password are accepted by the LDAP
11991 server. An empty password is rejected without calling LDAP because LDAP binds
11992 with an empty password are considered anonymous regardless of the username, and
11993 will succeed in most configurations. See chapter &<<CHAPSMTPAUTH>>& for details
11994 of SMTP authentication, and chapter &<<CHAPplaintext>>& for an example of how
11998 .vitem &*le&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11999 &*lei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
12000 .cindex "string" "comparison"
12001 .cindex "expansion" "string comparison"
12002 .cindex "&%le%& expansion condition"
12003 .cindex "&%lei%& expansion condition"
12004 The two substrings are first expanded. The condition is true if the first
12005 string is lexically less than or equal to the second string. For &%le%& the
12006 comparison includes the case of letters, whereas for &%lei%& the comparison is
12008 Case and collation order are defined per the system C locale.
12010 .vitem &*lt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
12011 &*lti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
12012 .cindex "string" "comparison"
12013 .cindex "expansion" "string comparison"
12014 .cindex "&%lt%& expansion condition"
12015 .cindex "&%lti%& expansion condition"
12016 The two substrings are first expanded. The condition is true if the first
12017 string is lexically less than the second string. For &%lt%& the comparison
12018 includes the case of letters, whereas for &%lti%& the comparison is
12020 Case and collation order are defined per the system C locale.
12023 .vitem &*match&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
12024 .cindex "expansion" "regular expression comparison"
12025 .cindex "regular expressions" "match in expanded string"
12026 .cindex "&%match%& expansion condition"
12027 The two substrings are first expanded. The second is then treated as a regular
12028 expression and applied to the first. Because of the pre-expansion, if the
12029 regular expression contains dollar, or backslash characters, they must be
12030 escaped. Care must also be taken if the regular expression contains braces
12031 (curly brackets). A closing brace must be escaped so that it is not taken as a
12032 premature termination of <&'string2'&>. The easiest approach is to use the
12033 &`\N`& feature to disable expansion of the regular expression.
12036 ${if match {$local_part}{\N^\d{3}\N} ...
12038 If the whole expansion string is in double quotes, further escaping of
12039 backslashes is also required.
12041 The condition is true if the regular expression match succeeds.
12042 The regular expression is not required to begin with a circumflex
12043 metacharacter, but if there is no circumflex, the expression is not anchored,
12044 and it may match anywhere in the subject, not just at the start. If you want
12045 the pattern to match at the end of the subject, you must include the &`$`&
12046 metacharacter at an appropriate point.
12047 All character handling is done in bytes and is not UTF-8 aware,
12048 but we might change this in a future Exim release.
12050 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%if%& expansion"
12051 At the start of an &%if%& expansion the values of the numeric variable
12052 substitutions &$1$& etc. are remembered. Obeying a &%match%& condition that
12053 succeeds causes them to be reset to the substrings of that condition and they
12054 will have these values during the expansion of the success string. At the end
12055 of the &%if%& expansion, the previous values are restored. After testing a
12056 combination of conditions using &%or%&, the subsequent values of the numeric
12057 variables are those of the condition that succeeded.
12059 .vitem &*match_address&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
12060 .cindex "&%match_address%& expansion condition"
12061 See &*match_local_part*&.
12063 .vitem &*match_domain&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
12064 .cindex "&%match_domain%& expansion condition"
12065 See &*match_local_part*&.
12067 .vitem &*match_ip&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
12068 .cindex "&%match_ip%& expansion condition"
12069 This condition matches an IP address to a list of IP address patterns. It must
12070 be followed by two argument strings. The first (after expansion) must be an IP
12071 address or an empty string. The second (not expanded) is a restricted host
12072 list that can match only an IP address, not a host name. For example:
12074 ${if match_ip{$sender_host_address}{1.2.3.4:5.6.7.8}{...}{...}}
12076 The specific types of host list item that are permitted in the list are:
12079 An IP address, optionally with a CIDR mask.
12081 A single asterisk, which matches any IP address.
12083 An empty item, which matches only if the IP address is empty. This could be
12084 useful for testing for a locally submitted message or one from specific hosts
12085 in a single test such as
12086 . ==== As this is a nested list, any displays it contains must be indented
12087 . ==== as otherwise they are too far to the left. This comment applies to
12088 . ==== the use of xmlto plus fop. There's no problem when formatting with
12089 . ==== sdop, with or without the extra indent.
12091 ${if match_ip{$sender_host_address}{:4.3.2.1:...}{...}{...}}
12093 where the first item in the list is the empty string.
12095 The item @[] matches any of the local host's interface addresses.
12097 Single-key lookups are assumed to be like &"net-"& style lookups in host lists,
12098 even if &`net-`& is not specified. There is never any attempt to turn the IP
12099 address into a host name. The most common type of linear search for
12100 &*match_ip*& is likely to be &*iplsearch*&, in which the file can contain CIDR
12101 masks. For example:
12103 ${if match_ip{$sender_host_address}{iplsearch;/some/file}...
12105 It is of course possible to use other kinds of lookup, and in such a case, you
12106 do need to specify the &`net-`& prefix if you want to specify a specific
12107 address mask, for example:
12109 ${if match_ip{$sender_host_address}{net24-dbm;/some/file}...
12111 However, unless you are combining a &%match_ip%& condition with others, it is
12112 just as easy to use the fact that a lookup is itself a condition, and write:
12114 ${lookup{${mask:$sender_host_address/24}}dbm{/a/file}...
12118 Note that <&'string2'&> is not itself subject to string expansion, unless
12119 Exim was built with the EXPAND_LISTMATCH_RHS option.
12121 Consult section &<<SECThoslispatip>>& for further details of these patterns.
12123 .vitem &*match_local_part&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
12124 .cindex "domain list" "in expansion condition"
12125 .cindex "address list" "in expansion condition"
12126 .cindex "local part" "list, in expansion condition"
12127 .cindex "&%match_local_part%& expansion condition"
12128 This condition, together with &%match_address%& and &%match_domain%&, make it
12129 possible to test domain, address, and local part lists within expansions. Each
12130 condition requires two arguments: an item and a list to match. A trivial
12133 ${if match_domain{a.b.c}{x.y.z:a.b.c:p.q.r}{yes}{no}}
12135 In each case, the second argument may contain any of the allowable items for a
12136 list of the appropriate type. Also, because the second argument
12137 is a standard form of list, it is possible to refer to a named list.
12138 Thus, you can use conditions like this:
12140 ${if match_domain{$domain}{+local_domains}{...
12142 .cindex "&`+caseful`&"
12143 For address lists, the matching starts off caselessly, but the &`+caseful`&
12144 item can be used, as in all address lists, to cause subsequent items to
12145 have their local parts matched casefully. Domains are always matched
12149 The variable &$value$& will be set for a successful match and can be
12150 used in the success clause of an &%if%& expansion item using the condition.
12151 .cindex "tainted data" "de-tainting"
12152 It will have the same taint status as the list; expansions such as
12154 ${if match_local_part {$local_part} {alice : bill : charlotte : dave} {$value}}
12156 can be used for de-tainting.
12157 Any previous &$value$& is restored after the if.
12160 Note that <&'string2'&> is not itself subject to string expansion, unless
12161 Exim was built with the EXPAND_LISTMATCH_RHS option.
12163 &*Note*&: Host lists are &'not'& supported in this way. This is because
12164 hosts have two identities: a name and an IP address, and it is not clear
12165 how to specify cleanly how such a test would work. However, IP addresses can be
12166 matched using &%match_ip%&.
12168 .vitem &*pam&~{*&<&'string1'&>&*:*&<&'string2'&>&*:...}*&
12169 .cindex "PAM authentication"
12170 .cindex "AUTH" "with PAM"
12171 .cindex "Solaris" "PAM support"
12172 .cindex "expansion" "PAM authentication test"
12173 .cindex "&%pam%& expansion condition"
12174 &'Pluggable Authentication Modules'&
12175 (&url(https://mirrors.edge.kernel.org/pub/linux/libs/pam/)) are a facility that is
12176 available in Solaris
12177 and in some GNU/Linux distributions.
12178 The Exim support, which is intended for use in conjunction with
12179 the SMTP AUTH command, is available only if Exim is compiled with
12183 in &_Local/Makefile_&. You probably need to add &%-lpam%& to EXTRALIBS, and
12184 in some releases of GNU/Linux &%-ldl%& is also needed.
12186 The argument string is first expanded, and the result must be a
12187 colon-separated list of strings. Leading and trailing white space is ignored.
12188 The PAM module is initialized with the service name &"exim"& and the user name
12189 taken from the first item in the colon-separated data string (<&'string1'&>).
12190 The remaining items in the data string are passed over in response to requests
12191 from the authentication function. In the simple case there will only be one
12192 request, for a password, so the data consists of just two strings.
12194 There can be problems if any of the strings are permitted to contain colon
12195 characters. In the usual way, these have to be doubled to avoid being taken as
12197 The &%listquote%& expansion item can be used for this.
12198 For example, the configuration
12199 of a LOGIN authenticator might contain this setting:
12201 server_condition = ${if pam{$auth1:${listquote{:}{$auth2}}}}
12203 In some operating systems, PAM authentication can be done only from a process
12204 running as root. Since Exim is running as the Exim user when receiving
12205 messages, this means that PAM cannot be used directly in those systems.
12206 . --- 2018-09-07: the pam_exim modified variant has gone, removed claims re using Exim via that
12209 .vitem &*pwcheck&~{*&<&'string1'&>&*:*&<&'string2'&>&*}*&
12210 .cindex "&'pwcheck'& daemon"
12212 .cindex "expansion" "&'pwcheck'& authentication test"
12213 .cindex "&%pwcheck%& expansion condition"
12214 This condition supports user authentication using the Cyrus &'pwcheck'& daemon.
12215 This is one way of making it possible for passwords to be checked by a process
12216 that is not running as root. &*Note*&: The use of &'pwcheck'& is now
12217 deprecated. Its replacement is &'saslauthd'& (see below).
12219 The pwcheck support is not included in Exim by default. You need to specify
12220 the location of the pwcheck daemon's socket in &_Local/Makefile_& before
12221 building Exim. For example:
12223 CYRUS_PWCHECK_SOCKET=/var/pwcheck/pwcheck
12225 You do not need to install the full Cyrus software suite in order to use
12226 the pwcheck daemon. You can compile and install just the daemon alone
12227 from the Cyrus SASL library. Ensure that &'exim'& is the only user that has
12228 access to the &_/var/pwcheck_& directory.
12230 The &%pwcheck%& condition takes one argument, which must be the user name and
12231 password, separated by a colon. For example, in a LOGIN authenticator
12232 configuration, you might have this:
12234 server_condition = ${if pwcheck{$auth1:$auth2}}
12236 Again, for a PLAIN authenticator configuration, this would be:
12238 server_condition = ${if pwcheck{$auth2:$auth3}}
12240 .vitem &*queue_running*&
12241 .cindex "queue runner" "detecting when delivering from"
12242 .cindex "expansion" "queue runner test"
12243 .cindex "&%queue_running%& expansion condition"
12244 This condition, which has no data, is true during delivery attempts that are
12245 initiated by queue runner processes, and false otherwise.
12248 .vitem &*radius&~{*&<&'authentication&~string'&>&*}*&
12250 .cindex "expansion" "Radius authentication"
12251 .cindex "&%radius%& expansion condition"
12252 Radius authentication (RFC 2865) is supported in a similar way to PAM. You must
12253 set RADIUS_CONFIG_FILE in &_Local/Makefile_& to specify the location of
12254 the Radius client configuration file in order to build Exim with Radius
12257 With just that one setting, Exim expects to be linked with the &%radiusclient%&
12258 library, using the original API. If you are using release 0.4.0 or later of
12259 this library, you need to set
12261 RADIUS_LIB_TYPE=RADIUSCLIENTNEW
12263 in &_Local/Makefile_& when building Exim. You can also link Exim with the
12264 &%libradius%& library that comes with FreeBSD. To do this, set
12266 RADIUS_LIB_TYPE=RADLIB
12268 in &_Local/Makefile_&, in addition to setting RADIUS_CONFIGURE_FILE.
12269 You may also have to supply a suitable setting in EXTRALIBS so that the
12270 Radius library can be found when Exim is linked.
12272 The string specified by RADIUS_CONFIG_FILE is expanded and passed to the
12273 Radius client library, which calls the Radius server. The condition is true if
12274 the authentication is successful. For example:
12276 server_condition = ${if radius{<arguments>}}
12280 .vitem "&*saslauthd&~{{*&<&'user'&>&*}{*&<&'password'&>&*}&&&
12281 {*&<&'service'&>&*}{*&<&'realm'&>&*}}*&"
12282 .cindex "&'saslauthd'& daemon"
12284 .cindex "expansion" "&'saslauthd'& authentication test"
12285 .cindex "&%saslauthd%& expansion condition"
12286 This condition supports user authentication using the Cyrus &'saslauthd'&
12287 daemon. This replaces the older &'pwcheck'& daemon, which is now deprecated.
12288 Using this daemon is one way of making it possible for passwords to be checked
12289 by a process that is not running as root.
12291 The saslauthd support is not included in Exim by default. You need to specify
12292 the location of the saslauthd daemon's socket in &_Local/Makefile_& before
12293 building Exim. For example:
12295 CYRUS_SASLAUTHD_SOCKET=/var/state/saslauthd/mux
12297 You do not need to install the full Cyrus software suite in order to use
12298 the saslauthd daemon. You can compile and install just the daemon alone
12299 from the Cyrus SASL library.
12301 Up to four arguments can be supplied to the &%saslauthd%& condition, but only
12302 two are mandatory. For example:
12304 server_condition = ${if saslauthd{{$auth1}{$auth2}}}
12306 The service and the realm are optional (which is why the arguments are enclosed
12307 in their own set of braces). For details of the meaning of the service and
12308 realm, and how to run the daemon, consult the Cyrus documentation.
12313 .section "Combining expansion conditions" "SECID84"
12314 .cindex "expansion" "combining conditions"
12315 Several conditions can be tested at once by combining them using the &%and%&
12316 and &%or%& combination conditions. Note that &%and%& and &%or%& are complete
12317 conditions on their own, and precede their lists of sub-conditions. Each
12318 sub-condition must be enclosed in braces within the overall braces that contain
12319 the list. No repetition of &%if%& is used.
12323 .vitem &*or&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
12324 .cindex "&""or""& expansion condition"
12325 .cindex "expansion" "&""or""& of conditions"
12326 The sub-conditions are evaluated from left to right. The condition is true if
12327 any one of the sub-conditions is true.
12330 ${if or {{eq{$local_part}{spqr}}{eq{$domain}{testing.com}}}...
12332 When a true sub-condition is found, the following ones are parsed but not
12333 evaluated. If there are several &"match"& sub-conditions the values of the
12334 numeric variables afterwards are taken from the first one that succeeds.
12336 .vitem &*and&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
12337 .cindex "&""and""& expansion condition"
12338 .cindex "expansion" "&""and""& of conditions"
12339 The sub-conditions are evaluated from left to right. The condition is true if
12340 all of the sub-conditions are true. If there are several &"match"&
12341 sub-conditions, the values of the numeric variables afterwards are taken from
12342 the last one. When a false sub-condition is found, the following ones are
12343 parsed but not evaluated.
12345 .ecindex IIDexpcond
12350 .section "Expansion variables" "SECTexpvar"
12351 .cindex "expansion" "variables, list of"
12352 This section contains an alphabetical list of all the expansion variables. Some
12353 of them are available only when Exim is compiled with specific options such as
12354 support for TLS or the content scanning extension.
12356 .cindex "tainted data"
12357 Variables marked as &'tainted'& are likely to carry data supplied by
12358 a potential attacker.
12359 Variables without such marking may also, depending on how their
12360 values are created.
12361 Such variables should not be further expanded,
12363 or used as command-line arguments for external commands.
12367 .vitem "&$0$&, &$1$&, etc"
12368 .cindex "numerical variables (&$1$& &$2$& etc)"
12369 When a &%match%& expansion condition succeeds, these variables contain the
12370 captured substrings identified by the regular expression during subsequent
12371 processing of the success string of the containing &%if%& expansion item.
12372 In the expansion condition case
12373 they do not retain their values afterwards; in fact, their previous
12374 values are restored at the end of processing an &%if%& item. The numerical
12375 variables may also be set externally by some other matching process which
12376 precedes the expansion of the string. For example, the commands available in
12377 Exim filter files include an &%if%& command with its own regular expression
12378 matching condition.
12380 If the subject string was tainted then any captured substring will also be.
12383 .vitem "&$acl_arg1$&, &$acl_arg2$&, etc"
12384 Within an acl condition, expansion condition or expansion item
12385 any arguments are copied to these variables,
12386 any unused variables being made empty.
12388 .vitem "&$acl_c...$&"
12389 Values can be placed in these variables by the &%set%& modifier in an ACL. They
12390 can be given any name that starts with &$acl_c$& and is at least six characters
12391 long, but the sixth character must be either a digit or an underscore. For
12392 example: &$acl_c5$&, &$acl_c_mycount$&. The values of the &$acl_c...$&
12393 variables persist throughout the lifetime of an SMTP connection. They can be
12394 used to pass information between ACLs and between different invocations of the
12395 same ACL. When a message is received, the values of these variables are saved
12396 with the message, and can be accessed by filters, routers, and transports
12397 during subsequent delivery.
12399 .vitem "&$acl_m...$&"
12400 These variables are like the &$acl_c...$& variables, except that their values
12401 are reset after a message has been received. Thus, if several messages are
12402 received in one SMTP connection, &$acl_m...$& values are not passed on from one
12403 message to the next, as &$acl_c...$& values are. The &$acl_m...$& variables are
12404 also reset by MAIL, RSET, EHLO, HELO, and after starting a TLS session. When a
12405 message is received, the values of these variables are saved with the message,
12406 and can be accessed by filters, routers, and transports during subsequent
12409 .vitem &$acl_narg$&
12410 Within an acl condition, expansion condition or expansion item
12411 this variable has the number of arguments.
12413 .vitem &$acl_verify_message$&
12414 .vindex "&$acl_verify_message$&"
12415 After an address verification has failed, this variable contains the failure
12416 message. It retains its value for use in subsequent modifiers of the verb.
12417 The message can be preserved by coding like this:
12419 warn !verify = sender
12420 set acl_m0 = $acl_verify_message
12422 You can use &$acl_verify_message$& during the expansion of the &%message%& or
12423 &%log_message%& modifiers, to include information about the verification
12425 &*Note*&: The variable is cleared at the end of processing the ACL verb.
12427 .vitem &$address_data$&
12428 .vindex "&$address_data$&"
12429 This variable is set by means of the &%address_data%& option in routers. The
12430 value then remains with the address while it is processed by subsequent routers
12431 and eventually a transport. If the transport is handling multiple addresses,
12432 the value from the first address is used. See chapter &<<CHAProutergeneric>>&
12433 for more details. &*Note*&: The contents of &$address_data$& are visible in
12436 If &$address_data$& is set when the routers are called from an ACL to verify
12437 a recipient address, the final value is still in the variable for subsequent
12438 conditions and modifiers of the ACL statement. If routing the address caused it
12439 to be redirected to just one address, the child address is also routed as part
12440 of the verification, and in this case the final value of &$address_data$& is
12441 from the child's routing.
12443 If &$address_data$& is set when the routers are called from an ACL to verify a
12444 sender address, the final value is also preserved, but this time in
12445 &$sender_address_data$&, to distinguish it from data from a recipient
12448 In both cases (recipient and sender verification), the value does not persist
12449 after the end of the current ACL statement. If you want to preserve
12450 these values for longer, you can save them in ACL variables.
12452 .vitem &$address_file$&
12453 .vindex "&$address_file$&"
12454 When, as a result of aliasing, forwarding, or filtering, a message is directed
12455 to a specific file, this variable holds the name of the file when the transport
12456 is running. At other times, the variable is empty. For example, using the
12457 default configuration, if user &%r2d2%& has a &_.forward_& file containing
12459 /home/r2d2/savemail
12461 then when the &(address_file)& transport is running, &$address_file$&
12462 contains the text string &`/home/r2d2/savemail`&.
12463 .cindex "Sieve filter" "value of &$address_file$&"
12464 For Sieve filters, the value may be &"inbox"& or a relative folder name. It is
12465 then up to the transport configuration to generate an appropriate absolute path
12466 to the relevant file.
12468 .vitem &$address_pipe$&
12469 .vindex "&$address_pipe$&"
12470 When, as a result of aliasing or forwarding, a message is directed to a pipe,
12471 this variable holds the pipe command when the transport is running.
12473 .vitem "&$auth1$& &-- &$auth4$&"
12474 .vindex "&$auth1$&, &$auth2$&, etc"
12475 These variables are used in SMTP authenticators (see chapters
12476 &<<CHAPplaintext>>&&--&<<CHAPtlsauth>>&). Elsewhere, they are empty.
12478 .vitem &$authenticated_id$&
12479 .cindex "authentication" "id"
12480 .vindex "&$authenticated_id$&"
12481 When a server successfully authenticates a client it may be configured to
12482 preserve some of the authentication information in the variable
12483 &$authenticated_id$& (see chapter &<<CHAPSMTPAUTH>>&). For example, a
12484 user/password authenticator configuration might preserve the user name for use
12485 in the routers. Note that this is not the same information that is saved in
12486 &$sender_host_authenticated$&.
12488 When a message is submitted locally (that is, not over a TCP connection)
12489 the value of &$authenticated_id$& is normally the login name of the calling
12490 process. However, a trusted user can override this by means of the &%-oMai%&
12491 command line option.
12492 This second case also sets up information used by the
12493 &$authresults$& expansion item.
12495 .vitem &$authenticated_fail_id$&
12496 .cindex "authentication" "fail" "id"
12497 .vindex "&$authenticated_fail_id$&"
12498 When an authentication attempt fails, the variable &$authenticated_fail_id$&
12499 will contain the failed authentication id. If more than one authentication
12500 id is attempted, it will contain only the last one. The variable is
12501 available for processing in the ACL's, generally the quit or notquit ACL.
12502 A message to a local recipient could still be accepted without requiring
12503 authentication, which means this variable could also be visible in all of
12507 .tvar &$authenticated_sender$&
12508 .cindex "sender" "authenticated"
12509 .cindex "authentication" "sender"
12510 .cindex "AUTH" "on MAIL command"
12511 When acting as a server, Exim takes note of the AUTH= parameter on an incoming
12512 SMTP MAIL command if it believes the sender is sufficiently trusted, as
12513 described in section &<<SECTauthparamail>>&. Unless the data is the string
12514 &"<>"&, it is set as the authenticated sender of the message, and the value is
12515 available during delivery in the &$authenticated_sender$& variable. If the
12516 sender is not trusted, Exim accepts the syntax of AUTH=, but ignores the data.
12518 .vindex "&$qualify_domain$&"
12519 When a message is submitted locally (that is, not over a TCP connection), the
12520 value of &$authenticated_sender$& is an address constructed from the login
12521 name of the calling process and &$qualify_domain$&, except that a trusted user
12522 can override this by means of the &%-oMas%& command line option.
12525 .vitem &$authentication_failed$&
12526 .cindex "authentication" "failure"
12527 .vindex "&$authentication_failed$&"
12528 This variable is set to &"1"& in an Exim server if a client issues an AUTH
12529 command that does not succeed. Otherwise it is set to &"0"&. This makes it
12530 possible to distinguish between &"did not try to authenticate"&
12531 (&$sender_host_authenticated$& is empty and &$authentication_failed$& is set to
12532 &"0"&) and &"tried to authenticate but failed"& (&$sender_host_authenticated$&
12533 is empty and &$authentication_failed$& is set to &"1"&). Failure includes any
12534 negative response to an AUTH command, including (for example) an attempt to use
12535 an undefined mechanism.
12537 .vitem &$av_failed$&
12538 .cindex "content scanning" "AV scanner failure"
12539 This variable is available when Exim is compiled with the content-scanning
12540 extension. It is set to &"0"& by default, but will be set to &"1"& if any
12541 problem occurs with the virus scanner (specified by &%av_scanner%&) during
12542 the ACL malware condition.
12544 .vitem &$body_linecount$&
12545 .cindex "message body" "line count"
12546 .cindex "body of message" "line count"
12547 .vindex "&$body_linecount$&"
12548 When a message is being received or delivered, this variable contains the
12549 number of lines in the message's body. See also &$message_linecount$&.
12551 .vitem &$body_zerocount$&
12552 .cindex "message body" "binary zero count"
12553 .cindex "body of message" "binary zero count"
12554 .cindex "binary zero" "in message body"
12555 .vindex "&$body_zerocount$&"
12556 When a message is being received or delivered, this variable contains the
12557 number of binary zero bytes (ASCII NULs) in the message's body.
12559 .vitem &$bounce_recipient$&
12560 .vindex "&$bounce_recipient$&"
12561 This is set to the recipient address of a bounce message while Exim is creating
12562 it. It is useful if a customized bounce message text file is in use (see
12563 chapter &<<CHAPemsgcust>>&).
12565 .vitem &$bounce_return_size_limit$&
12566 .vindex "&$bounce_return_size_limit$&"
12567 This contains the value set in the &%bounce_return_size_limit%& option, rounded
12568 up to a multiple of 1000. It is useful when a customized error message text
12569 file is in use (see chapter &<<CHAPemsgcust>>&).
12571 .vitem &$caller_gid$&
12572 .cindex "gid (group id)" "caller"
12573 .vindex "&$caller_gid$&"
12574 The real group id under which the process that called Exim was running. This is
12575 not the same as the group id of the originator of a message (see
12576 &$originator_gid$&). If Exim re-execs itself, this variable in the new
12577 incarnation normally contains the Exim gid.
12579 .vitem &$caller_uid$&
12580 .cindex "uid (user id)" "caller"
12581 .vindex "&$caller_uid$&"
12582 The real user id under which the process that called Exim was running. This is
12583 not the same as the user id of the originator of a message (see
12584 &$originator_uid$&). If Exim re-execs itself, this variable in the new
12585 incarnation normally contains the Exim uid.
12587 .vitem &$callout_address$&
12588 .vindex "&$callout_address$&"
12589 After a callout for verification, spamd or malware daemon service, the
12590 address that was connected to.
12592 .vitem &$compile_number$&
12593 .vindex "&$compile_number$&"
12594 The building process for Exim keeps a count of the number
12595 of times it has been compiled. This serves to distinguish different
12596 compilations of the same version of Exim.
12598 .vitem &$config_dir$&
12599 .vindex "&$config_dir$&"
12600 The directory name of the main configuration file. That is, the content of
12601 &$config_file$& with the last component stripped. The value does not
12602 contain the trailing slash. If &$config_file$& does not contain a slash,
12603 &$config_dir$& is ".".
12605 .vitem &$config_file$&
12606 .vindex "&$config_file$&"
12607 The name of the main configuration file Exim is using.
12609 .vitem &$dkim_verify_status$&
12610 Results of DKIM verification.
12611 For details see section &<<SECDKIMVFY>>&.
12613 .vitem &$dkim_cur_signer$& &&&
12614 &$dkim_verify_reason$& &&&
12615 &$dkim_domain$& &&&
12616 &$dkim_identity$& &&&
12617 &$dkim_selector$& &&&
12619 &$dkim_canon_body$& &&&
12620 &$dkim_canon_headers$& &&&
12621 &$dkim_copiedheaders$& &&&
12622 &$dkim_bodylength$& &&&
12623 &$dkim_created$& &&&
12624 &$dkim_expires$& &&&
12625 &$dkim_headernames$& &&&
12626 &$dkim_key_testing$& &&&
12627 &$dkim_key_nosubdomains$& &&&
12628 &$dkim_key_srvtype$& &&&
12629 &$dkim_key_granularity$& &&&
12630 &$dkim_key_notes$& &&&
12631 &$dkim_key_length$&
12632 These variables are only available within the DKIM ACL.
12633 For details see section &<<SECDKIMVFY>>&.
12635 .vitem &$dkim_signers$&
12636 .vindex &$dkim_signers$&
12637 When a message has been received this variable contains
12638 a colon-separated list of signer domains and identities for the message.
12639 For details see section &<<SECDKIMVFY>>&.
12641 .vitem &$dmarc_domain_policy$& &&&
12642 &$dmarc_status$& &&&
12643 &$dmarc_status_text$& &&&
12644 &$dmarc_used_domains$&
12645 Results of DMARC verification.
12646 For details see section &<<SECDMARC>>&.
12648 .vitem &$dnslist_domain$& &&&
12649 &$dnslist_matched$& &&&
12650 &$dnslist_text$& &&&
12652 .vindex "&$dnslist_domain$&"
12653 .vindex "&$dnslist_matched$&"
12654 .vindex "&$dnslist_text$&"
12655 .vindex "&$dnslist_value$&"
12656 .cindex "black list (DNS)"
12657 When a DNS (black) list lookup succeeds, these variables are set to contain
12658 the following data from the lookup: the list's domain name, the key that was
12659 looked up, the contents of any associated TXT record, and the value from the
12660 main A record. See section &<<SECID204>>& for more details.
12663 When an address is being routed, or delivered on its own, this variable
12664 contains the domain. Uppercase letters in the domain are converted into lower
12665 case for &$domain$&.
12667 Global address rewriting happens when a message is received, so the value of
12668 &$domain$& during routing and delivery is the value after rewriting. &$domain$&
12669 is set during user filtering, but not during system filtering, because a
12670 message may have many recipients and the system filter is called just once.
12672 When more than one address is being delivered at once (for example, several
12673 RCPT commands in one SMTP delivery), &$domain$& is set only if they all
12674 have the same domain. Transports can be restricted to handling only one domain
12675 at a time if the value of &$domain$& is required at transport time &-- this is
12676 the default for local transports. For further details of the environment in
12677 which local transports are run, see chapter &<<CHAPenvironment>>&.
12679 .oindex "&%delay_warning_condition%&"
12680 At the end of a delivery, if all deferred addresses have the same domain, it is
12681 set in &$domain$& during the expansion of &%delay_warning_condition%&.
12683 The &$domain$& variable is also used in some other circumstances:
12686 When an ACL is running for a RCPT command, &$domain$& contains the domain of
12687 the recipient address. The domain of the &'sender'& address is in
12688 &$sender_address_domain$& at both MAIL time and at RCPT time. &$domain$& is not
12689 normally set during the running of the MAIL ACL. However, if the sender address
12690 is verified with a callout during the MAIL ACL, the sender domain is placed in
12691 &$domain$& during the expansions of &%hosts%&, &%interface%&, and &%port%& in
12692 the &(smtp)& transport.
12695 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
12696 &$domain$& contains the domain portion of the address that is being rewritten;
12697 it can be used in the expansion of the replacement address, for example, to
12698 rewrite domains by file lookup.
12701 With one important exception, whenever a domain list is being scanned,
12702 &$domain$& contains the subject domain. &*Exception*&: When a domain list in
12703 a &%sender_domains%& condition in an ACL is being processed, the subject domain
12704 is in &$sender_address_domain$& and not in &$domain$&. It works this way so
12705 that, in a RCPT ACL, the sender domain list can be dependent on the
12706 recipient domain (which is what is in &$domain$& at this time).
12709 .cindex "ETRN" "value of &$domain$&"
12710 .oindex "&%smtp_etrn_command%&"
12711 When the &%smtp_etrn_command%& option is being expanded, &$domain$& contains
12712 the complete argument of the ETRN command (see section &<<SECTETRN>>&).
12715 .cindex "tainted data"
12716 If the origin of the data is an incoming message,
12717 the result of expanding this variable is tainted and may not
12718 be further expanded or used as a filename.
12719 When an untainted version is needed, one should be obtained from
12720 looking up the value in a local (therefore trusted) database.
12721 Often &$domain_data$& is usable in this role.
12724 .vitem &$domain_data$&
12725 .vindex "&$domain_data$&"
12726 When the &%domains%& condition on a router
12729 against a list, the match value is copied to &$domain_data$&.
12730 This is an enhancement over previous versions of Exim, when it only
12731 applied to the data read by a lookup.
12732 For details on match values see section &<<SECTlistresults>>& et. al.
12734 If the router routes the
12735 address to a transport, the value is available in that transport. If the
12736 transport is handling multiple addresses, the value from the first address is
12739 &$domain_data$& set in an ACL is available during
12740 the rest of the ACL statement.
12742 .vitem &$exim_gid$&
12743 .vindex "&$exim_gid$&"
12744 This variable contains the numerical value of the Exim group id.
12746 .vitem &$exim_path$&
12747 .vindex "&$exim_path$&"
12748 This variable contains the path to the Exim binary.
12750 .vitem &$exim_uid$&
12751 .vindex "&$exim_uid$&"
12752 This variable contains the numerical value of the Exim user id.
12754 .vitem &$exim_version$&
12755 .vindex "&$exim_version$&"
12756 This variable contains the version string of the Exim build.
12757 The first character is a major version number, currently 4.
12758 Then after a dot, the next group of digits is a minor version number.
12759 There may be other characters following the minor version.
12760 This value may be overridden by the &%exim_version%& main config option.
12762 .vitem &$header_$&<&'name'&>
12764 This is not strictly an expansion variable. It is expansion syntax for
12765 inserting the message header line with the given name. Note that the name must
12766 be terminated by colon or white space, because it may contain a wide variety of
12767 characters. Note also that braces must &'not'& be used.
12768 See the full description in section &<<SECTexpansionitems>>& above.
12770 .vitem &$headers_added$&
12771 .vindex "&$headers_added$&"
12772 Within an ACL this variable contains the headers added so far by
12773 the ACL modifier add_header (section &<<SECTaddheadacl>>&).
12774 The headers are a newline-separated list.
12778 When the &%check_local_user%& option is set for a router, the user's home
12779 directory is placed in &$home$& when the check succeeds. In particular, this
12780 means it is set during the running of users' filter files. A router may also
12781 explicitly set a home directory for use by a transport; this can be overridden
12782 by a setting on the transport itself.
12784 When running a filter test via the &%-bf%& option, &$home$& is set to the value
12785 of the environment variable HOME, which is subject to the
12786 &%keep_environment%& and &%add_environment%& main config options.
12790 If a router assigns an address to a transport (any transport), and passes a
12791 list of hosts with the address, the value of &$host$& when the transport starts
12792 to run is the name of the first host on the list. Note that this applies both
12793 to local and remote transports.
12795 .cindex "transport" "filter"
12796 .cindex "filter" "transport filter"
12797 For the &(smtp)& transport, if there is more than one host, the value of
12798 &$host$& changes as the transport works its way through the list. In
12799 particular, when the &(smtp)& transport is expanding its options for encryption
12800 using TLS, or for specifying a transport filter (see chapter
12801 &<<CHAPtransportgeneric>>&), &$host$& contains the name of the host to which it
12804 When used in the client part of an authenticator configuration (see chapter
12805 &<<CHAPSMTPAUTH>>&), &$host$& contains the name of the server to which the
12806 client is connected.
12809 .vitem &$host_address$&
12810 .vindex "&$host_address$&"
12811 This variable is set to the remote host's IP address whenever &$host$& is set
12812 for a remote connection. It is also set to the IP address that is being checked
12813 when the &%ignore_target_hosts%& option is being processed.
12815 .vitem &$host_data$&
12816 .vindex "&$host_data$&"
12817 If a &%hosts%& condition in an ACL is satisfied by means of a lookup, the
12818 result of the lookup is made available in the &$host_data$& variable. This
12819 allows you, for example, to do things like this:
12821 deny hosts = net-lsearch;/some/file
12822 message = $host_data
12825 .vitem &$host_lookup_deferred$&
12826 .cindex "host name" "lookup, failure of"
12827 .vindex "&$host_lookup_deferred$&"
12828 This variable normally contains &"0"&, as does &$host_lookup_failed$&. When a
12829 message comes from a remote host and there is an attempt to look up the host's
12830 name from its IP address, and the attempt is not successful, one of these
12831 variables is set to &"1"&.
12834 If the lookup receives a definite negative response (for example, a DNS lookup
12835 succeeded, but no records were found), &$host_lookup_failed$& is set to &"1"&.
12838 If there is any kind of problem during the lookup, such that Exim cannot
12839 tell whether or not the host name is defined (for example, a timeout for a DNS
12840 lookup), &$host_lookup_deferred$& is set to &"1"&.
12843 Looking up a host's name from its IP address consists of more than just a
12844 single reverse lookup. Exim checks that a forward lookup of at least one of the
12845 names it receives from a reverse lookup yields the original IP address. If this
12846 is not the case, Exim does not accept the looked up name(s), and
12847 &$host_lookup_failed$& is set to &"1"&. Thus, being able to find a name from an
12848 IP address (for example, the existence of a PTR record in the DNS) is not
12849 sufficient on its own for the success of a host name lookup. If the reverse
12850 lookup succeeds, but there is a lookup problem such as a timeout when checking
12851 the result, the name is not accepted, and &$host_lookup_deferred$& is set to
12852 &"1"&. See also &$sender_host_name$&.
12854 .cindex authentication "expansion item"
12855 Performing these checks sets up information used by the
12856 &%authresults%& expansion item.
12859 .vitem &$host_lookup_failed$&
12860 .vindex "&$host_lookup_failed$&"
12861 See &$host_lookup_deferred$&.
12863 .vitem &$host_port$&
12864 .vindex "&$host_port$&"
12865 This variable is set to the remote host's TCP port whenever &$host$& is set
12866 for an outbound connection.
12868 .vitem &$initial_cwd$&
12869 .vindex "&$initial_cwd$&
12870 This variable contains the full path name of the initial working
12871 directory of the current Exim process. This may differ from the current
12872 working directory, as Exim changes this to "/" during early startup, and
12873 to &$spool_directory$& later.
12876 .vindex "&$inode$&"
12877 The only time this variable is set is while expanding the &%directory_file%&
12878 option in the &(appendfile)& transport. The variable contains the inode number
12879 of the temporary file which is about to be renamed. It can be used to construct
12880 a unique name for the file.
12882 .vitem &$interface_address$& &&&
12884 .vindex "&$interface_address$&"
12885 .vindex "&$interface_port$&"
12886 These are obsolete names for &$received_ip_address$& and &$received_port$&.
12890 This variable is used during the expansion of &*forall*& and &*forany*&
12891 conditions (see section &<<SECTexpcond>>&), and &*filter*&, &*map*&, and
12892 &*reduce*& items (see section &<<SECTexpcond>>&). In other circumstances, it is
12896 .vindex "&$ldap_dn$&"
12897 This variable, which is available only when Exim is compiled with LDAP support,
12898 contains the DN from the last entry in the most recently successful LDAP
12901 .vitem &$load_average$&
12902 .vindex "&$load_average$&"
12903 This variable contains the system load average, multiplied by 1000 so that it
12904 is an integer. For example, if the load average is 0.21, the value of the
12905 variable is 210. The value is recomputed every time the variable is referenced.
12907 .tvar &$local_part$&
12908 When an address is being routed, or delivered on its own, this
12909 variable contains the local part. When a number of addresses are being
12910 delivered together (for example, multiple RCPT commands in an SMTP
12911 session), &$local_part$& is not set.
12913 Global address rewriting happens when a message is received, so the value of
12914 &$local_part$& during routing and delivery is the value after rewriting.
12915 &$local_part$& is set during user filtering, but not during system filtering,
12916 because a message may have many recipients and the system filter is called just
12919 .cindex "tainted data"
12920 If the origin of the data is an incoming message,
12921 the result of expanding this variable is tainted and
12922 may not be further expanded or used as a filename.
12924 &*Warning*&: the content of this variable is usually provided by a potential
12926 Consider carefully the implications of using it unvalidated as a name
12928 This presents issues for users' &_.forward_& and filter files.
12929 For traditional full user accounts, use &%check_local_users%& and the
12930 &$local_part_data$& variable rather than this one.
12931 For virtual users, store a suitable pathname component in the database
12932 which is used for account name validation, and use that retrieved value
12933 rather than this variable.
12934 Often &$local_part_data$& is usable in this role.
12935 If needed, use a router &%address_data%& or &%set%& option for
12936 the retrieved data.
12938 When a message is being delivered to a file, pipe, or autoreply transport as a
12939 result of aliasing or forwarding, &$local_part$& is set to the local part of
12940 the parent address, not to the filename or command (see &$address_file$& and
12943 When an ACL is running for a RCPT command, &$local_part$& contains the
12944 local part of the recipient address.
12946 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
12947 &$local_part$& contains the local part of the address that is being rewritten;
12948 it can be used in the expansion of the replacement address, for example.
12950 In all cases, all quoting is removed from the local part. For example, for both
12953 "abc:xyz"@test.example
12954 abc\:xyz@test.example
12956 the value of &$local_part$& is
12960 If you use &$local_part$& to create another address, you should always wrap it
12961 inside a quoting operator. For example, in a &(redirect)& router you could
12964 data = ${quote_local_part:$local_part}@new.domain.example
12966 &*Note*&: The value of &$local_part$& is normally lower cased. If you want
12967 to process local parts in a case-dependent manner in a router, you can set the
12968 &%caseful_local_part%& option (see chapter &<<CHAProutergeneric>>&).
12970 .vitem &$local_part_data$&
12971 .vindex "&$local_part_data$&"
12972 When the &%local_parts%& condition on a router or ACL
12973 matches a local part list
12974 the match value is copied to &$local_part_data$&.
12975 This is an enhancement over previous versions of Exim, when it only
12976 applied to the data read by a lookup.
12977 For details on match values see section &<<SECTlistresults>>& et. al.
12979 The &%check_local_user%& router option also sets this variable.
12981 .vindex &$local_part_prefix$& &&&
12982 &$local_part_prefix_v$& &&&
12983 &$local_part_suffix$& &&&
12984 &$local_part_suffix_v$&
12985 .cindex affix variables
12986 If a local part prefix or suffix has been recognized, it is not included in the
12987 value of &$local_part$& during routing and subsequent delivery. The values of
12988 any prefix or suffix are in &$local_part_prefix$& and
12989 &$local_part_suffix$&, respectively.
12990 .cindex "tainted data"
12991 If the specification did not include a wildcard then
12992 the affix variable value is not tainted.
12994 If the affix specification included a wildcard then the portion of
12995 the affix matched by the wildcard is in
12996 &$local_part_prefix_v$& or &$local_part_suffix_v$& as appropriate,
12997 and both the whole and varying values are tainted.
12999 .vitem &$local_scan_data$&
13000 .vindex "&$local_scan_data$&"
13001 This variable contains the text returned by the &[local_scan()]& function when
13002 a message is received. See chapter &<<CHAPlocalscan>>& for more details.
13004 .vitem &$local_user_gid$&
13005 .vindex "&$local_user_gid$&"
13006 See &$local_user_uid$&.
13008 .vitem &$local_user_uid$&
13009 .vindex "&$local_user_uid$&"
13010 This variable and &$local_user_gid$& are set to the uid and gid after the
13011 &%check_local_user%& router precondition succeeds. This means that their values
13012 are available for the remaining preconditions (&%senders%&, &%require_files%&,
13013 and &%condition%&), for the &%address_data%& expansion, and for any
13014 router-specific expansions. At all other times, the values in these variables
13015 are &`(uid_t)(-1)`& and &`(gid_t)(-1)`&, respectively.
13017 .vitem &$localhost_number$&
13018 .vindex "&$localhost_number$&"
13019 This contains the expanded value of the
13020 &%localhost_number%& option. The expansion happens after the main options have
13023 .vitem &$log_inodes$&
13024 .vindex "&$log_inodes$&"
13025 The number of free inodes in the disk partition where Exim's
13026 log files are being written. The value is recalculated whenever the variable is
13027 referenced. If the relevant file system does not have the concept of inodes,
13028 the value of is -1. See also the &%check_log_inodes%& option.
13030 .vitem &$log_space$&
13031 .vindex "&$log_space$&"
13032 The amount of free space (as a number of kilobytes) in the disk
13033 partition where Exim's log files are being written. The value is recalculated
13034 whenever the variable is referenced. If the operating system does not have the
13035 ability to find the amount of free space (only true for experimental systems),
13036 the space value is -1. See also the &%check_log_space%& option.
13039 .vitem &$lookup_dnssec_authenticated$&
13040 .vindex "&$lookup_dnssec_authenticated$&"
13041 This variable is set after a DNS lookup done by
13042 a dnsdb lookup expansion, dnslookup router or smtp transport.
13043 .cindex "DNS" "DNSSEC"
13044 It will be empty if &(DNSSEC)& was not requested,
13045 &"no"& if the result was not labelled as authenticated data
13046 and &"yes"& if it was.
13047 Results that are labelled as authoritative answer that match
13048 the &%dns_trust_aa%& configuration variable count also
13049 as authenticated data.
13051 .vitem &$mailstore_basename$&
13052 .vindex "&$mailstore_basename$&"
13053 This variable is set only when doing deliveries in &"mailstore"& format in the
13054 &(appendfile)& transport. During the expansion of the &%mailstore_prefix%&,
13055 &%mailstore_suffix%&, &%message_prefix%&, and &%message_suffix%& options, it
13056 contains the basename of the files that are being written, that is, the name
13057 without the &".tmp"&, &".env"&, or &".msg"& suffix. At all other times, this
13060 .vitem &$malware_name$&
13061 .vindex "&$malware_name$&"
13062 This variable is available when Exim is compiled with the
13063 content-scanning extension. It is set to the name of the virus that was found
13064 when the ACL &%malware%& condition is true (see section &<<SECTscanvirus>>&).
13066 .vitem &$max_received_linelength$&
13067 .vindex "&$max_received_linelength$&"
13068 .cindex "maximum" "line length"
13069 .cindex "line length" "maximum"
13070 This variable contains the number of bytes in the longest line that was
13071 received as part of the message, not counting the line termination
13073 It is not valid if the &%spool_wireformat%& option is used.
13075 .vitem &$message_age$&
13076 .cindex "message" "age of"
13077 .vindex "&$message_age$&"
13078 This variable is set at the start of a delivery attempt to contain the number
13079 of seconds since the message was received. It does not change during a single
13082 .tvar &$message_body$&
13083 .cindex "body of message" "expansion variable"
13084 .cindex "message body" "in expansion"
13085 .cindex "binary zero" "in message body"
13086 .oindex "&%message_body_visible%&"
13087 This variable contains the initial portion of a message's body while it is
13088 being delivered, and is intended mainly for use in filter files. The maximum
13089 number of characters of the body that are put into the variable is set by the
13090 &%message_body_visible%& configuration option; the default is 500.
13092 .oindex "&%message_body_newlines%&"
13093 By default, newlines are converted into spaces in &$message_body$&, to make it
13094 easier to search for phrases that might be split over a line break. However,
13095 this can be disabled by setting &%message_body_newlines%& to be true. Binary
13096 zeros are always converted into spaces.
13098 .tvar &$message_body_end$&
13099 .cindex "body of message" "expansion variable"
13100 .cindex "message body" "in expansion"
13101 This variable contains the final portion of a message's
13102 body while it is being delivered. The format and maximum size are as for
13105 .vitem &$message_body_size$&
13106 .cindex "body of message" "size"
13107 .cindex "message body" "size"
13108 .vindex "&$message_body_size$&"
13109 When a message is being delivered, this variable contains the size of the body
13110 in bytes. The count starts from the character after the blank line that
13111 separates the body from the header. Newlines are included in the count. See
13112 also &$message_size$&, &$body_linecount$&, and &$body_zerocount$&.
13114 If the spool file is wireformat
13115 (see the &%spool_wireformat%& main option)
13116 the CRLF line-terminators are included in the count.
13118 .vitem &$message_exim_id$&
13119 .vindex "&$message_exim_id$&"
13120 When a message is being received or delivered, this variable contains the
13121 unique message id that is generated and used by Exim to identify the message.
13122 An id is not created for a message until after its header has been successfully
13123 received. &*Note*&: This is &'not'& the contents of the &'Message-ID:'& header
13124 line; it is the local id that Exim assigns to the message, for example:
13125 &`1BXTIK-0001yO-VA`&.
13127 .tvar &$message_headers$&
13128 This variable contains a concatenation of all the header lines when a message
13129 is being processed, except for lines added by routers or transports. The header
13130 lines are separated by newline characters. Their contents are decoded in the
13131 same way as a header line that is inserted by &%bheader%&.
13133 .tvar &$message_headers_raw$&
13134 This variable is like &$message_headers$& except that no processing of the
13135 contents of header lines is done.
13137 .vitem &$message_id$&
13138 This is an old name for &$message_exim_id$&. It is now deprecated.
13140 .vitem &$message_linecount$&
13141 .vindex "&$message_linecount$&"
13142 This variable contains the total number of lines in the header and body of the
13143 message. Compare &$body_linecount$&, which is the count for the body only.
13144 During the DATA and content-scanning ACLs, &$message_linecount$& contains the
13145 number of lines received. Before delivery happens (that is, before filters,
13146 routers, and transports run) the count is increased to include the
13147 &'Received:'& header line that Exim standardly adds, and also any other header
13148 lines that are added by ACLs. The blank line that separates the message header
13149 from the body is not counted.
13151 As with the special case of &$message_size$&, during the expansion of the
13152 appendfile transport's maildir_tag option in maildir format, the value of
13153 &$message_linecount$& is the precise size of the number of newlines in the
13154 file that has been written (minus one for the blank line between the
13155 header and the body).
13157 Here is an example of the use of this variable in a DATA ACL:
13160 ${if <{250}{${eval:$message_linecount - $body_linecount}}}
13161 message = Too many lines in message header
13163 In the MAIL and RCPT ACLs, the value is zero because at that stage the
13164 message has not yet been received.
13166 This variable is not valid if the &%spool_wireformat%& option is used.
13168 .vitem &$message_size$&
13169 .cindex "size" "of message"
13170 .cindex "message" "size"
13171 .vindex "&$message_size$&"
13172 When a message is being processed, this variable contains its size in bytes. In
13173 most cases, the size includes those headers that were received with the
13174 message, but not those (such as &'Envelope-to:'&) that are added to individual
13175 deliveries as they are written. However, there is one special case: during the
13176 expansion of the &%maildir_tag%& option in the &(appendfile)& transport while
13177 doing a delivery in maildir format, the value of &$message_size$& is the
13178 precise size of the file that has been written. See also
13179 &$message_body_size$&, &$body_linecount$&, and &$body_zerocount$&.
13181 .cindex "RCPT" "value of &$message_size$&"
13182 While running a per message ACL (mail/rcpt/predata), &$message_size$&
13183 contains the size supplied on the MAIL command, or -1 if no size was given. The
13184 value may not, of course, be truthful.
13186 .vitem &$mime_anomaly_level$& &&&
13187 &$mime_anomaly_text$& &&&
13188 &$mime_boundary$& &&&
13189 &$mime_charset$& &&&
13190 &$mime_content_description$& &&&
13191 &$mime_content_disposition$& &&&
13192 &$mime_content_id$& &&&
13193 &$mime_content_size$& &&&
13194 &$mime_content_transfer_encoding$& &&&
13195 &$mime_content_type$& &&&
13196 &$mime_decoded_filename$& &&&
13197 &$mime_filename$& &&&
13198 &$mime_is_coverletter$& &&&
13199 &$mime_is_multipart$& &&&
13200 &$mime_is_rfc822$& &&&
13201 &$mime_part_count$&
13202 A number of variables whose names start with &$mime$& are
13203 available when Exim is compiled with the content-scanning extension. For
13204 details, see section &<<SECTscanmimepart>>&.
13206 .vitem "&$n0$& &-- &$n9$&"
13207 These variables are counters that can be incremented by means
13208 of the &%add%& command in filter files.
13210 .tvar &$original_domain$&
13211 .vindex "&$domain$&"
13212 When a top-level address is being processed for delivery, this contains the
13213 same value as &$domain$&. However, if a &"child"& address (for example,
13214 generated by an alias, forward, or filter file) is being processed, this
13215 variable contains the domain of the original address (lower cased). This
13216 differs from &$parent_domain$& only when there is more than one level of
13217 aliasing or forwarding. When more than one address is being delivered in a
13218 single transport run, &$original_domain$& is not set.
13220 If a new address is created by means of a &%deliver%& command in a system
13221 filter, it is set up with an artificial &"parent"& address. This has the local
13222 part &'system-filter'& and the default qualify domain.
13224 .tvar &$original_local_part$&
13225 .vindex "&$local_part$&"
13226 When a top-level address is being processed for delivery, this contains the
13227 same value as &$local_part$&, unless a prefix or suffix was removed from the
13228 local part, because &$original_local_part$& always contains the full local
13229 part. When a &"child"& address (for example, generated by an alias, forward, or
13230 filter file) is being processed, this variable contains the full local part of
13231 the original address.
13233 If the router that did the redirection processed the local part
13234 case-insensitively, the value in &$original_local_part$& is in lower case.
13235 This variable differs from &$parent_local_part$& only when there is more than
13236 one level of aliasing or forwarding. When more than one address is being
13237 delivered in a single transport run, &$original_local_part$& is not set.
13239 If a new address is created by means of a &%deliver%& command in a system
13240 filter, it is set up with an artificial &"parent"& address. This has the local
13241 part &'system-filter'& and the default qualify domain.
13243 .vitem &$originator_gid$&
13244 .cindex "gid (group id)" "of originating user"
13245 .cindex "sender" "gid"
13246 .vindex "&$caller_gid$&"
13247 .vindex "&$originator_gid$&"
13248 This variable contains the value of &$caller_gid$& that was set when the
13249 message was received. For messages received via the command line, this is the
13250 gid of the sending user. For messages received by SMTP over TCP/IP, this is
13251 normally the gid of the Exim user.
13253 .vitem &$originator_uid$&
13254 .cindex "uid (user id)" "of originating user"
13255 .cindex "sender" "uid"
13256 .vindex "&$caller_uid$&"
13257 .vindex "&$originator_uid$&"
13258 The value of &$caller_uid$& that was set when the message was received. For
13259 messages received via the command line, this is the uid of the sending user.
13260 For messages received by SMTP over TCP/IP, this is normally the uid of the Exim
13263 .tvar &$parent_domain$&
13264 This variable is similar to &$original_domain$& (see
13265 above), except that it refers to the immediately preceding parent address.
13267 .tvar &$parent_local_part$&
13268 This variable is similar to &$original_local_part$&
13269 (see above), except that it refers to the immediately preceding parent address.
13272 .cindex "pid (process id)" "of current process"
13274 This variable contains the current process id.
13276 .vitem &$pipe_addresses$&
13277 .cindex "filter" "transport filter"
13278 .cindex "transport" "filter"
13279 .vindex "&$pipe_addresses$&"
13280 This is not an expansion variable, but is mentioned here because the string
13281 &`$pipe_addresses`& is handled specially in the command specification for the
13282 &(pipe)& transport (chapter &<<CHAPpipetransport>>&) and in transport filters
13283 (described under &%transport_filter%& in chapter &<<CHAPtransportgeneric>>&).
13284 It cannot be used in general expansion strings, and provokes an &"unknown
13285 variable"& error if encountered.
13287 &*Note*&: This value permits data supplied by a potential attacker to
13288 be used in the command for a &(pipe)& transport.
13289 Such configurations should be carefully assessed for security vulnerbilities.
13292 .vitem &$primary_hostname$&
13293 .vindex "&$primary_hostname$&"
13294 This variable contains the value set by &%primary_hostname%& in the
13295 configuration file, or read by the &[uname()]& function. If &[uname()]& returns
13296 a single-component name, Exim calls &[gethostbyname()]& (or
13297 &[getipnodebyname()]& where available) in an attempt to acquire a fully
13298 qualified host name. See also &$smtp_active_hostname$&.
13301 .vitem &$proxy_external_address$& &&&
13302 &$proxy_external_port$& &&&
13303 &$proxy_local_address$& &&&
13304 &$proxy_local_port$& &&&
13306 These variables are only available when built with Proxy Protocol
13308 For details see chapter &<<SECTproxyInbound>>&.
13310 .vitem &$prdr_requested$&
13311 .cindex "PRDR" "variable for"
13312 This variable is set to &"yes"& if PRDR was requested by the client for the
13313 current message, otherwise &"no"&.
13315 .vitem &$prvscheck_address$& &&&
13316 &$prvscheck_keynum$& &&&
13317 &$prvscheck_result$&
13318 These variables are used in conjunction with the &%prvscheck%& expansion item,
13319 which is described in sections &<<SECTexpansionitems>>& and
13320 &<<SECTverifyPRVS>>&.
13322 .vitem &$qualify_domain$&
13323 .vindex "&$qualify_domain$&"
13324 The value set for the &%qualify_domain%& option in the configuration file.
13326 .vitem &$qualify_recipient$&
13327 .vindex "&$qualify_recipient$&"
13328 The value set for the &%qualify_recipient%& option in the configuration file,
13329 or if not set, the value of &$qualify_domain$&.
13331 .vitem &$queue_name$&
13332 .vindex &$queue_name$&
13333 .cindex "named queues" variable
13334 .cindex queues named
13335 The name of the spool queue in use; empty for the default queue.
13337 .vitem &$queue_size$&
13338 .vindex "&$queue_size$&"
13339 .cindex "queue" "size of"
13340 .cindex "spool" "number of messages"
13341 This variable contains the number of messages queued.
13342 It is evaluated on demand, but no more often than once every minute.
13343 If there is no daemon notifier socket open, the value will be
13348 .cindex router variables
13349 Values can be placed in these variables by the &%set%& option of a router.
13350 They can be given any name that starts with &$r_$&.
13351 The values persist for the address being handled through subsequent routers
13352 and the eventual transport.
13354 .vitem &$rcpt_count$&
13355 .vindex "&$rcpt_count$&"
13356 When a message is being received by SMTP, this variable contains the number of
13357 RCPT commands received for the current message. If this variable is used in a
13358 RCPT ACL, its value includes the current command.
13360 .vitem &$rcpt_defer_count$&
13361 .vindex "&$rcpt_defer_count$&"
13362 .cindex "4&'xx'& responses" "count of"
13363 When a message is being received by SMTP, this variable contains the number of
13364 RCPT commands in the current message that have previously been rejected with a
13365 temporary (4&'xx'&) response.
13367 .vitem &$rcpt_fail_count$&
13368 .vindex "&$rcpt_fail_count$&"
13369 When a message is being received by SMTP, this variable contains the number of
13370 RCPT commands in the current message that have previously been rejected with a
13371 permanent (5&'xx'&) response.
13373 .vitem &$received_count$&
13374 .vindex "&$received_count$&"
13375 This variable contains the number of &'Received:'& header lines in the message,
13376 including the one added by Exim (so its value is always greater than zero). It
13377 is available in the DATA ACL, the non-SMTP ACL, and while routing and
13380 .tvar &$received_for$&
13381 If there is only a single recipient address in an incoming message, this
13382 variable contains that address when the &'Received:'& header line is being
13383 built. The value is copied after recipient rewriting has happened, but before
13384 the &[local_scan()]& function is run.
13386 .vitem &$received_ip_address$& &&&
13388 .vindex "&$received_ip_address$&"
13389 .vindex "&$received_port$&"
13390 As soon as an Exim server starts processing an incoming TCP/IP connection, these
13391 variables are set to the address and port on the local IP interface.
13392 (The remote IP address and port are in
13393 &$sender_host_address$& and &$sender_host_port$&.) When testing with &%-bh%&,
13394 the port value is -1 unless it has been set using the &%-oMi%& command line
13397 As well as being useful in ACLs (including the &"connect"& ACL), these variable
13398 could be used, for example, to make the filename for a TLS certificate depend
13399 on which interface and/or port is being used for the incoming connection. The
13400 values of &$received_ip_address$& and &$received_port$& are saved with any
13401 messages that are received, thus making these variables available at delivery
13403 For outbound connections see &$sending_ip_address$&.
13405 .vitem &$received_protocol$&
13406 .vindex "&$received_protocol$&"
13407 When a message is being processed, this variable contains the name of the
13408 protocol by which it was received. Most of the names used by Exim are defined
13409 by RFCs 821, 2821, and 3848. They start with &"smtp"& (the client used HELO) or
13410 &"esmtp"& (the client used EHLO). This can be followed by &"s"& for secure
13411 (encrypted) and/or &"a"& for authenticated. Thus, for example, if the protocol
13412 is set to &"esmtpsa"&, the message was received over an encrypted SMTP
13413 connection and the client was successfully authenticated.
13415 Exim uses the protocol name &"smtps"& for the case when encryption is
13416 automatically set up on connection without the use of STARTTLS (see
13417 &%tls_on_connect_ports%&), and the client uses HELO to initiate the
13418 encrypted SMTP session. The name &"smtps"& is also used for the rare situation
13419 where the client initially uses EHLO, sets up an encrypted connection using
13420 STARTTLS, and then uses HELO afterwards.
13422 The &%-oMr%& option provides a way of specifying a custom protocol name for
13423 messages that are injected locally by trusted callers. This is commonly used to
13424 identify messages that are being re-injected after some kind of scanning.
13426 .vitem &$received_time$&
13427 .vindex "&$received_time$&"
13428 This variable contains the date and time when the current message was received,
13429 as a number of seconds since the start of the Unix epoch.
13431 .vitem &$recipient_data$&
13432 .vindex "&$recipient_data$&"
13433 This variable is set after an indexing lookup success in an ACL &%recipients%&
13434 condition. It contains the data from the lookup, and the value remains set
13435 until the next &%recipients%& test. Thus, you can do things like this:
13437 &`require recipients = cdb*@;/some/file`&
13438 &`deny `&&'some further test involving'& &`$recipient_data`&
13440 &*Warning*&: This variable is set only when a lookup is used as an indexing
13441 method in the address list, using the semicolon syntax as in the example above.
13442 The variable is not set for a lookup that is used as part of the string
13443 expansion that all such lists undergo before being interpreted.
13445 .vitem &$recipient_verify_failure$&
13446 .vindex "&$recipient_verify_failure$&"
13447 In an ACL, when a recipient verification fails, this variable contains
13448 information about the failure. It is set to one of the following words:
13451 &"qualify"&: The address was unqualified (no domain), and the message
13452 was neither local nor came from an exempted host.
13455 &"route"&: Routing failed.
13458 &"mail"&: Routing succeeded, and a callout was attempted; rejection occurred at
13459 or before the MAIL command (that is, on initial connection, HELO, or
13463 &"recipient"&: The RCPT command in a callout was rejected.
13466 &"postmaster"&: The postmaster check in a callout was rejected.
13469 The main use of this variable is expected to be to distinguish between
13470 rejections of MAIL and rejections of RCPT.
13472 .tvar &$recipients$&
13473 This variable contains a list of envelope recipients for a message. A comma and
13474 a space separate the addresses in the replacement text. However, the variable
13475 is not generally available, to prevent exposure of Bcc recipients in
13476 unprivileged users' filter files. You can use &$recipients$& only in these
13480 In a system filter file.
13482 In the ACLs associated with the DATA command and with non-SMTP messages, that
13483 is, the ACLs defined by &%acl_smtp_predata%&, &%acl_smtp_data%&,
13484 &%acl_smtp_mime%&, &%acl_not_smtp_start%&, &%acl_not_smtp%&, and
13485 &%acl_not_smtp_mime%&.
13487 From within a &[local_scan()]& function.
13491 .vitem &$recipients_count$&
13492 .vindex "&$recipients_count$&"
13493 When a message is being processed, this variable contains the number of
13494 envelope recipients that came with the message. Duplicates are not excluded
13495 from the count. While a message is being received over SMTP, the number
13496 increases for each accepted recipient. It can be referenced in an ACL.
13499 .vitem &$regex_match_string$&
13500 .vindex "&$regex_match_string$&"
13501 This variable is set to contain the matching regular expression after a
13502 &%regex%& ACL condition has matched (see section &<<SECTscanregex>>&).
13504 .vitem "&$regex1$&, &$regex2$&, etc"
13505 .cindex "regex submatch variables (&$1regex$& &$2regex$& etc)"
13506 When a &%regex%& or &%mime_regex%& ACL condition succeeds,
13507 these variables contain the
13508 captured substrings identified by the regular expression.
13510 If the subject string was tainted then so will any captured substring.
13514 .tvar &$reply_address$&
13515 When a message is being processed, this variable contains the contents of the
13516 &'Reply-To:'& header line if one exists and it is not empty, or otherwise the
13517 contents of the &'From:'& header line. Apart from the removal of leading
13518 white space, the value is not processed in any way. In particular, no RFC 2047
13519 decoding or character code translation takes place.
13521 .vitem &$return_path$&
13522 .vindex "&$return_path$&"
13523 When a message is being delivered, this variable contains the return path &--
13524 the sender field that will be sent as part of the envelope. It is not enclosed
13525 in <> characters. At the start of routing an address, &$return_path$& has the
13526 same value as &$sender_address$&, but if, for example, an incoming message to a
13527 mailing list has been expanded by a router which specifies a different address
13528 for bounce messages, &$return_path$& subsequently contains the new bounce
13529 address, whereas &$sender_address$& always contains the original sender address
13530 that was received with the message. In other words, &$sender_address$& contains
13531 the incoming envelope sender, and &$return_path$& contains the outgoing
13534 .vitem &$return_size_limit$&
13535 .vindex "&$return_size_limit$&"
13536 This is an obsolete name for &$bounce_return_size_limit$&.
13538 .vitem &$router_name$&
13539 .cindex "router" "name"
13540 .cindex "name" "of router"
13541 .vindex "&$router_name$&"
13542 During the running of a router this variable contains its name.
13545 .cindex "return code" "from &%run%& expansion"
13546 .vindex "&$runrc$&"
13547 This variable contains the return code from a command that is run by the
13548 &%${run...}%& expansion item. &*Warning*&: In a router or transport, you cannot
13549 assume the order in which option values are expanded, except for those
13550 preconditions whose order of testing is documented. Therefore, you cannot
13551 reliably expect to set &$runrc$& by the expansion of one option, and use it in
13554 .vitem &$self_hostname$&
13555 .oindex "&%self%&" "value of host name"
13556 .vindex "&$self_hostname$&"
13557 When an address is routed to a supposedly remote host that turns out to be the
13558 local host, what happens is controlled by the &%self%& generic router option.
13559 One of its values causes the address to be passed to another router. When this
13560 happens, &$self_hostname$& is set to the name of the local host that the
13561 original router encountered. In other circumstances its contents are null.
13563 .tvar &$sender_address$&
13564 When a message is being processed, this variable contains the sender's address
13565 that was received in the message's envelope. The case of letters in the address
13566 is retained, in both the local part and the domain. For bounce messages, the
13567 value of this variable is the empty string. See also &$return_path$&.
13569 .vitem &$sender_address_data$&
13570 .vindex "&$address_data$&"
13571 .vindex "&$sender_address_data$&"
13572 If &$address_data$& is set when the routers are called from an ACL to verify a
13573 sender address, the final value is preserved in &$sender_address_data$&, to
13574 distinguish it from data from a recipient address. The value does not persist
13575 after the end of the current ACL statement. If you want to preserve it for
13576 longer, you can save it in an ACL variable.
13578 .tvar &$sender_address_domain$&
13579 The domain portion of &$sender_address$&.
13581 .tvar &$sender_address_local_part$&
13582 The local part portion of &$sender_address$&.
13584 .vitem &$sender_data$&
13585 .vindex "&$sender_data$&"
13586 This variable is set after a lookup success in an ACL &%senders%& condition or
13587 in a router &%senders%& option. It contains the data from the lookup, and the
13588 value remains set until the next &%senders%& test. Thus, you can do things like
13591 &`require senders = cdb*@;/some/file`&
13592 &`deny `&&'some further test involving'& &`$sender_data`&
13594 &*Warning*&: This variable is set only when a lookup is used as an indexing
13595 method in the address list, using the semicolon syntax as in the example above.
13596 The variable is not set for a lookup that is used as part of the string
13597 expansion that all such lists undergo before being interpreted.
13599 .vitem &$sender_fullhost$&
13600 .vindex "&$sender_fullhost$&"
13601 When a message is received from a remote host, this variable contains the host
13602 name and IP address in a single string. It ends with the IP address in square
13603 brackets, followed by a colon and a port number if the logging of ports is
13604 enabled. The format of the rest of the string depends on whether the host
13605 issued a HELO or EHLO SMTP command, and whether the host name was verified by
13606 looking up its IP address. (Looking up the IP address can be forced by the
13607 &%host_lookup%& option, independent of verification.) A plain host name at the
13608 start of the string is a verified host name; if this is not present,
13609 verification either failed or was not requested. A host name in parentheses is
13610 the argument of a HELO or EHLO command. This is omitted if it is identical to
13611 the verified host name or to the host's IP address in square brackets.
13613 .vitem &$sender_helo_dnssec$&
13614 .vindex "&$sender_helo_dnssec$&"
13615 This boolean variable is true if a successful HELO verification was
13616 .cindex "DNS" "DNSSEC"
13617 done using DNS information the resolver library stated was authenticated data.
13619 .tvar &$sender_helo_name$&
13620 When a message is received from a remote host that has issued a HELO or EHLO
13621 command, the argument of that command is placed in this variable. It is also
13622 set if HELO or EHLO is used when a message is received using SMTP locally via
13623 the &%-bs%& or &%-bS%& options.
13625 .vitem &$sender_host_address$&
13626 .vindex "&$sender_host_address$&"
13627 When a message is received from a remote host using SMTP,
13628 this variable contains that
13629 host's IP address. For locally non-SMTP submitted messages, it is empty.
13631 .vitem &$sender_host_authenticated$&
13632 .vindex "&$sender_host_authenticated$&"
13633 This variable contains the name (not the public name) of the authenticator
13634 driver that successfully authenticated the client from which the message was
13635 received. It is empty if there was no successful authentication. See also
13636 &$authenticated_id$&.
13638 .vitem &$sender_host_dnssec$&
13639 .vindex "&$sender_host_dnssec$&"
13640 If an attempt to populate &$sender_host_name$& has been made
13641 (by reference, &%hosts_lookup%& or
13642 otherwise) then this boolean will have been set true if, and only if, the
13643 resolver library states that both
13644 the reverse and forward DNS were authenticated data. At all
13645 other times, this variable is false.
13647 .cindex "DNS" "DNSSEC"
13648 It is likely that you will need to coerce DNSSEC support on in the resolver
13649 library, by setting:
13654 In addition, on Linux with glibc 2.31 or newer the resolver library will
13655 default to stripping out a successful validation status.
13656 This will break a previously working Exim installation.
13657 Provided that you do trust the resolver (ie, is on localhost) you can tell
13658 glibc to pass through any successful validation with a new option in
13659 &_/etc/resolv.conf_&:
13664 Exim does not perform DNSSEC validation itself, instead leaving that to a
13665 validating resolver (e.g. unbound, or bind with suitable configuration).
13667 If you have changed &%host_lookup_order%& so that &`bydns`& is not the first
13668 mechanism in the list, then this variable will be false.
13670 This requires that your system resolver library support EDNS0 (and that
13671 DNSSEC flags exist in the system headers). If the resolver silently drops
13672 all EDNS0 options, then this will have no effect. OpenBSD's asr resolver
13673 is known to currently ignore EDNS0, documented in CAVEATS of asr_run(3).
13676 .tvar &$sender_host_name$&
13677 When a message is received from a remote host, this variable contains the
13678 host's name as obtained by looking up its IP address. For messages received by
13679 other means, this variable is empty.
13681 .vindex "&$host_lookup_failed$&"
13682 If the host name has not previously been looked up, a reference to
13683 &$sender_host_name$& triggers a lookup (for messages from remote hosts).
13684 A looked up name is accepted only if it leads back to the original IP address
13685 via a forward lookup. If either the reverse or the forward lookup fails to find
13686 any data, or if the forward lookup does not yield the original IP address,
13687 &$sender_host_name$& remains empty, and &$host_lookup_failed$& is set to &"1"&.
13689 .vindex "&$host_lookup_deferred$&"
13690 However, if either of the lookups cannot be completed (for example, there is a
13691 DNS timeout), &$host_lookup_deferred$& is set to &"1"&, and
13692 &$host_lookup_failed$& remains set to &"0"&.
13694 Once &$host_lookup_failed$& is set to &"1"&, Exim does not try to look up the
13695 host name again if there is a subsequent reference to &$sender_host_name$&
13696 in the same Exim process, but it does try again if &$host_lookup_deferred$&
13699 Exim does not automatically look up every calling host's name. If you want
13700 maximum efficiency, you should arrange your configuration so that it avoids
13701 these lookups altogether. The lookup happens only if one or more of the
13702 following are true:
13705 A string containing &$sender_host_name$& is expanded.
13707 The calling host matches the list in &%host_lookup%&. In the default
13708 configuration, this option is set to *, so it must be changed if lookups are
13709 to be avoided. (In the code, the default for &%host_lookup%& is unset.)
13711 Exim needs the host name in order to test an item in a host list. The items
13712 that require this are described in sections &<<SECThoslispatnam>>& and
13713 &<<SECThoslispatnamsk>>&.
13715 The calling host matches &%helo_try_verify_hosts%& or &%helo_verify_hosts%&.
13716 In this case, the host name is required to compare with the name quoted in any
13717 EHLO or HELO commands that the client issues.
13719 The remote host issues a EHLO or HELO command that quotes one of the
13720 domains in &%helo_lookup_domains%&. The default value of this option is
13721 . ==== As this is a nested list, any displays it contains must be indented
13722 . ==== as otherwise they are too far to the left.
13724 helo_lookup_domains = @ : @[]
13726 which causes a lookup if a remote host (incorrectly) gives the server's name or
13727 IP address in an EHLO or HELO command.
13731 .vitem &$sender_host_port$&
13732 .vindex "&$sender_host_port$&"
13733 When a message is received from a remote host, this variable contains the port
13734 number that was used on the remote host.
13736 .vitem &$sender_ident$&
13737 .vindex "&$sender_ident$&"
13738 When a message is received from a remote host, this variable contains the
13739 identification received in response to an RFC 1413 request. When a message has
13740 been received locally, this variable contains the login name of the user that
13743 .vitem &$sender_rate_$&&'xxx'&
13744 A number of variables whose names begin &$sender_rate_$& are set as part of the
13745 &%ratelimit%& ACL condition. Details are given in section
13746 &<<SECTratelimiting>>&.
13748 .vitem &$sender_rcvhost$&
13749 .cindex "DNS" "reverse lookup"
13750 .cindex "reverse DNS lookup"
13751 .vindex "&$sender_rcvhost$&"
13752 This is provided specifically for use in &'Received:'& headers. It starts with
13753 either the verified host name (as obtained from a reverse DNS lookup) or, if
13754 there is no verified host name, the IP address in square brackets. After that
13755 there may be text in parentheses. When the first item is a verified host name,
13756 the first thing in the parentheses is the IP address in square brackets,
13757 followed by a colon and a port number if port logging is enabled. When the
13758 first item is an IP address, the port is recorded as &"port=&'xxxx'&"& inside
13761 There may also be items of the form &"helo=&'xxxx'&"& if HELO or EHLO
13762 was used and its argument was not identical to the real host name or IP
13763 address, and &"ident=&'xxxx'&"& if an RFC 1413 ident string is available. If
13764 all three items are present in the parentheses, a newline and tab are inserted
13765 into the string, to improve the formatting of the &'Received:'& header.
13767 .vitem &$sender_verify_failure$&
13768 .vindex "&$sender_verify_failure$&"
13769 In an ACL, when a sender verification fails, this variable contains information
13770 about the failure. The details are the same as for
13771 &$recipient_verify_failure$&.
13773 .vitem &$sending_ip_address$&
13774 .vindex "&$sending_ip_address$&"
13775 This variable is set whenever an outgoing SMTP connection to another host has
13776 been set up. It contains the IP address of the local interface that is being
13777 used. This is useful if a host that has more than one IP address wants to take
13778 on different personalities depending on which one is being used. For incoming
13779 connections, see &$received_ip_address$&.
13781 .vitem &$sending_port$&
13782 .vindex "&$sending_port$&"
13783 This variable is set whenever an outgoing SMTP connection to another host has
13784 been set up. It contains the local port that is being used. For incoming
13785 connections, see &$received_port$&.
13787 .vitem &$smtp_active_hostname$&
13788 .vindex "&$smtp_active_hostname$&"
13789 During an incoming SMTP session, this variable contains the value of the active
13790 host name, as specified by the &%smtp_active_hostname%& option. The value of
13791 &$smtp_active_hostname$& is saved with any message that is received, so its
13792 value can be consulted during routing and delivery.
13794 .tvar &$smtp_command$&
13795 During the processing of an incoming SMTP command, this variable contains the
13796 entire command. This makes it possible to distinguish between HELO and EHLO in
13797 the HELO ACL, and also to distinguish between commands such as these:
13802 For a MAIL command, extra parameters such as SIZE can be inspected. For a RCPT
13803 command, the address in &$smtp_command$& is the original address before any
13804 rewriting, whereas the values in &$local_part$& and &$domain$& are taken from
13805 the address after SMTP-time rewriting.
13807 .tvar &$smtp_command_argument$&
13808 .cindex "SMTP" "command, argument for"
13809 While an ACL is running to check an SMTP command, this variable contains the
13810 argument, that is, the text that follows the command name, with leading white
13811 space removed. Following the introduction of &$smtp_command$&, this variable is
13812 somewhat redundant, but is retained for backwards compatibility.
13814 .vitem &$smtp_command_history$&
13815 .cindex SMTP "command history"
13816 .vindex "&$smtp_command_history$&"
13817 A comma-separated list (with no whitespace) of the most-recent SMTP commands
13818 received, in time-order left to right. Only a limited number of commands
13821 .vitem &$smtp_count_at_connection_start$&
13822 .vindex "&$smtp_count_at_connection_start$&"
13823 This variable is set greater than zero only in processes spawned by the Exim
13824 daemon for handling incoming SMTP connections. The name is deliberately long,
13825 in order to emphasize what the contents are. When the daemon accepts a new
13826 connection, it increments this variable. A copy of the variable is passed to
13827 the child process that handles the connection, but its value is fixed, and
13828 never changes. It is only an approximation of how many incoming connections
13829 there actually are, because many other connections may come and go while a
13830 single connection is being processed. When a child process terminates, the
13831 daemon decrements its copy of the variable.
13833 .vitem "&$sn0$& &-- &$sn9$&"
13834 These variables are copies of the values of the &$n0$& &-- &$n9$& accumulators
13835 that were current at the end of the system filter file. This allows a system
13836 filter file to set values that can be tested in users' filter files. For
13837 example, a system filter could set a value indicating how likely it is that a
13838 message is junk mail.
13840 .vitem &$spam_score$& &&&
13841 &$spam_score_int$& &&&
13843 &$spam_report$& &&&
13845 A number of variables whose names start with &$spam$& are available when Exim
13846 is compiled with the content-scanning extension. For details, see section
13847 &<<SECTscanspamass>>&.
13849 .vitem &$spf_header_comment$& &&&
13850 &$spf_received$& &&&
13852 &$spf_result_guessed$& &&&
13853 &$spf_smtp_comment$&
13854 These variables are only available if Exim is built with SPF support.
13855 For details see section &<<SECSPF>>&.
13857 .vitem &$spool_directory$&
13858 .vindex "&$spool_directory$&"
13859 The name of Exim's spool directory.
13861 .vitem &$spool_inodes$&
13862 .vindex "&$spool_inodes$&"
13863 The number of free inodes in the disk partition where Exim's spool files are
13864 being written. The value is recalculated whenever the variable is referenced.
13865 If the relevant file system does not have the concept of inodes, the value of
13866 is -1. See also the &%check_spool_inodes%& option.
13868 .vitem &$spool_space$&
13869 .vindex "&$spool_space$&"
13870 The amount of free space (as a number of kilobytes) in the disk partition where
13871 Exim's spool files are being written. The value is recalculated whenever the
13872 variable is referenced. If the operating system does not have the ability to
13873 find the amount of free space (only true for experimental systems), the space
13874 value is -1. For example, to check in an ACL that there is at least 50
13875 megabytes free on the spool, you could write:
13877 condition = ${if > {$spool_space}{50000}}
13879 See also the &%check_spool_space%& option.
13882 .vitem &$thisaddress$&
13883 .vindex "&$thisaddress$&"
13884 This variable is set only during the processing of the &%foranyaddress%&
13885 command in a filter file. Its use is explained in the description of that
13886 command, which can be found in the separate document entitled &'Exim's
13887 interfaces to mail filtering'&.
13889 .vitem &$tls_in_bits$&
13890 .vindex "&$tls_in_bits$&"
13891 Contains an approximation of the TLS cipher's bit-strength
13892 on the inbound connection; the meaning of
13893 this depends upon the TLS implementation used.
13894 If TLS has not been negotiated, the value will be 0.
13895 The value of this is automatically fed into the Cyrus SASL authenticator
13896 when acting as a server, to specify the "external SSF" (a SASL term).
13898 The deprecated &$tls_bits$& variable refers to the inbound side
13899 except when used in the context of an outbound SMTP delivery, when it refers to
13902 .vitem &$tls_out_bits$&
13903 .vindex "&$tls_out_bits$&"
13904 Contains an approximation of the TLS cipher's bit-strength
13905 on an outbound SMTP connection; the meaning of
13906 this depends upon the TLS implementation used.
13907 If TLS has not been negotiated, the value will be 0.
13909 .vitem &$tls_in_ourcert$&
13910 .vindex "&$tls_in_ourcert$&"
13911 .cindex certificate variables
13912 This variable refers to the certificate presented to the peer of an
13913 inbound connection when the message was received.
13914 It is only useful as the argument of a
13915 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13916 or a &%def%& condition.
13918 &*Note*&: Under versions of OpenSSL preceding 1.1.1,
13919 when a list of more than one
13920 file is used for &%tls_certificate%&, this variable is not reliable.
13921 The macro "_TLS_BAD_MULTICERT_IN_OURCERT" will be defined for those versions.
13923 .vitem &$tls_in_peercert$&
13924 .vindex "&$tls_in_peercert$&"
13925 This variable refers to the certificate presented by the peer of an
13926 inbound connection when the message was received.
13927 It is only useful as the argument of a
13928 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13929 or a &%def%& condition.
13930 If certificate verification fails it may refer to a failing chain element
13931 which is not the leaf.
13933 .vitem &$tls_out_ourcert$&
13934 .vindex "&$tls_out_ourcert$&"
13935 This variable refers to the certificate presented to the peer of an
13936 outbound connection. It is only useful as the argument of a
13937 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13938 or a &%def%& condition.
13940 .vitem &$tls_out_peercert$&
13941 .vindex "&$tls_out_peercert$&"
13942 This variable refers to the certificate presented by the peer of an
13943 outbound connection. It is only useful as the argument of a
13944 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13945 or a &%def%& condition.
13946 If certificate verification fails it may refer to a failing chain element
13947 which is not the leaf.
13949 .vitem &$tls_in_certificate_verified$&
13950 .vindex "&$tls_in_certificate_verified$&"
13951 This variable is set to &"1"& if a TLS certificate was verified when the
13952 message was received, and &"0"& otherwise.
13954 The deprecated &$tls_certificate_verified$& variable refers to the inbound side
13955 except when used in the context of an outbound SMTP delivery, when it refers to
13958 .vitem &$tls_out_certificate_verified$&
13959 .vindex "&$tls_out_certificate_verified$&"
13960 This variable is set to &"1"& if a TLS certificate was verified when an
13961 outbound SMTP connection was made,
13962 and &"0"& otherwise.
13964 .vitem &$tls_in_cipher$&
13965 .vindex "&$tls_in_cipher$&"
13966 .vindex "&$tls_cipher$&"
13967 When a message is received from a remote host over an encrypted SMTP
13968 connection, this variable is set to the cipher suite that was negotiated, for
13969 example DES-CBC3-SHA. In other circumstances, in particular, for message
13970 received over unencrypted connections, the variable is empty. Testing
13971 &$tls_in_cipher$& for emptiness is one way of distinguishing between encrypted and
13972 non-encrypted connections during ACL processing.
13974 The deprecated &$tls_cipher$& variable is the same as &$tls_in_cipher$& during message reception,
13975 but in the context of an outward SMTP delivery taking place via the &(smtp)& transport
13976 becomes the same as &$tls_out_cipher$&.
13978 .vitem &$tls_in_cipher_std$&
13979 .vindex "&$tls_in_cipher_std$&"
13980 As above, but returning the RFC standard name for the cipher suite.
13982 .vitem &$tls_out_cipher$&
13983 .vindex "&$tls_out_cipher$&"
13985 cleared before any outgoing SMTP connection is made,
13986 and then set to the outgoing cipher suite if one is negotiated. See chapter
13987 &<<CHAPTLS>>& for details of TLS support and chapter &<<CHAPsmtptrans>>& for
13988 details of the &(smtp)& transport.
13990 .vitem &$tls_out_cipher_std$&
13991 .vindex "&$tls_out_cipher_std$&"
13992 As above, but returning the RFC standard name for the cipher suite.
13994 .vitem &$tls_out_dane$&
13995 .vindex &$tls_out_dane$&
13996 DANE active status. See section &<<SECDANE>>&.
13998 .vitem &$tls_in_ocsp$&
13999 .vindex "&$tls_in_ocsp$&"
14000 When a message is received from a remote client connection
14001 the result of any OCSP request from the client is encoded in this variable:
14003 0 OCSP proof was not requested (default value)
14004 1 No response to request
14005 2 Response not verified
14006 3 Verification failed
14007 4 Verification succeeded
14010 .vitem &$tls_out_ocsp$&
14011 .vindex "&$tls_out_ocsp$&"
14012 When a message is sent to a remote host connection
14013 the result of any OCSP request made is encoded in this variable.
14014 See &$tls_in_ocsp$& for values.
14016 .vitem &$tls_in_peerdn$&
14017 .vindex "&$tls_in_peerdn$&"
14018 .vindex "&$tls_peerdn$&"
14019 .cindex certificate "extracting fields"
14020 When a message is received from a remote host over an encrypted SMTP
14021 connection, and Exim is configured to request a certificate from the client,
14022 the value of the Distinguished Name of the certificate is made available in the
14023 &$tls_in_peerdn$& during subsequent processing.
14024 If certificate verification fails it may refer to a failing chain element
14025 which is not the leaf.
14027 The deprecated &$tls_peerdn$& variable refers to the inbound side
14028 except when used in the context of an outbound SMTP delivery, when it refers to
14031 .vitem &$tls_out_peerdn$&
14032 .vindex "&$tls_out_peerdn$&"
14033 When a message is being delivered to a remote host over an encrypted SMTP
14034 connection, and Exim is configured to request a certificate from the server,
14035 the value of the Distinguished Name of the certificate is made available in the
14036 &$tls_out_peerdn$& during subsequent processing.
14037 If certificate verification fails it may refer to a failing chain element
14038 which is not the leaf.
14041 .vitem &$tls_in_resumption$& &&&
14042 &$tls_out_resumption$&
14043 .vindex &$tls_in_resumption$&
14044 .vindex &$tls_out_resumption$&
14045 .cindex TLS resumption
14046 Observability for TLS session resumption. See &<<SECTresumption>>& for details.
14049 .tvar &$tls_in_sni$&
14050 .vindex "&$tls_sni$&"
14051 .cindex "TLS" "Server Name Indication"
14053 .cindex SNI "observability on server"
14054 When a TLS session is being established, if the client sends the Server
14055 Name Indication extension, the value will be placed in this variable.
14056 If the variable appears in &%tls_certificate%& then this option and
14057 some others, described in &<<SECTtlssni>>&,
14058 will be re-expanded early in the TLS session, to permit
14059 a different certificate to be presented (and optionally a different key to be
14060 used) to the client, based upon the value of the SNI extension.
14062 The deprecated &$tls_sni$& variable refers to the inbound side
14063 except when used in the context of an outbound SMTP delivery, when it refers to
14066 .vitem &$tls_out_sni$&
14067 .vindex "&$tls_out_sni$&"
14068 .cindex "TLS" "Server Name Indication"
14070 .cindex SNI "observability in client"
14072 SMTP deliveries, this variable reflects the value of the &%tls_sni%& option on
14075 .vitem &$tls_out_tlsa_usage$&
14076 .vindex &$tls_out_tlsa_usage$&
14077 Bitfield of TLSA record types found. See section &<<SECDANE>>&.
14079 .vitem &$tls_in_ver$&
14080 .vindex "&$tls_in_ver$&"
14081 When a message is received from a remote host over an encrypted SMTP connection
14082 this variable is set to the protocol version, eg &'TLS1.2'&.
14084 .vitem &$tls_out_ver$&
14085 .vindex "&$tls_out_ver$&"
14086 When a message is being delivered to a remote host over an encrypted SMTP connection
14087 this variable is set to the protocol version.
14090 .vitem &$tod_bsdinbox$&
14091 .vindex "&$tod_bsdinbox$&"
14092 The time of day and the date, in the format required for BSD-style mailbox
14093 files, for example: Thu Oct 17 17:14:09 1995.
14095 .vitem &$tod_epoch$&
14096 .vindex "&$tod_epoch$&"
14097 The time and date as a number of seconds since the start of the Unix epoch.
14099 .vitem &$tod_epoch_l$&
14100 .vindex "&$tod_epoch_l$&"
14101 The time and date as a number of microseconds since the start of the Unix epoch.
14103 .vitem &$tod_full$&
14104 .vindex "&$tod_full$&"
14105 A full version of the time and date, for example: Wed, 16 Oct 1995 09:51:40
14106 +0100. The timezone is always given as a numerical offset from UTC, with
14107 positive values used for timezones that are ahead (east) of UTC, and negative
14108 values for those that are behind (west).
14111 .vindex "&$tod_log$&"
14112 The time and date in the format used for writing Exim's log files, for example:
14113 1995-10-12 15:32:29, but without a timezone.
14115 .vitem &$tod_logfile$&
14116 .vindex "&$tod_logfile$&"
14117 This variable contains the date in the format yyyymmdd. This is the format that
14118 is used for datestamping log files when &%log_file_path%& contains the &`%D`&
14121 .vitem &$tod_zone$&
14122 .vindex "&$tod_zone$&"
14123 This variable contains the numerical value of the local timezone, for example:
14126 .vitem &$tod_zulu$&
14127 .vindex "&$tod_zulu$&"
14128 This variable contains the UTC date and time in &"Zulu"& format, as specified
14129 by ISO 8601, for example: 20030221154023Z.
14131 .vitem &$transport_name$&
14132 .cindex "transport" "name"
14133 .cindex "name" "of transport"
14134 .vindex "&$transport_name$&"
14135 During the running of a transport, this variable contains its name.
14138 .vindex "&$value$&"
14139 This variable contains the result of an expansion lookup, extraction operation,
14140 or external command, as described above. It is also used during a
14141 &*reduce*& expansion.
14143 .vitem &$verify_mode$&
14144 .vindex "&$verify_mode$&"
14145 While a router or transport is being run in verify mode or for cutthrough delivery,
14146 contains "S" for sender-verification or "R" for recipient-verification.
14149 .vitem &$version_number$&
14150 .vindex "&$version_number$&"
14151 The version number of Exim. Same as &$exim_version$&, may be overridden
14152 by the &%exim_version%& main config option.
14154 .vitem &$warn_message_delay$&
14155 .vindex "&$warn_message_delay$&"
14156 This variable is set only during the creation of a message warning about a
14157 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
14159 .vitem &$warn_message_recipients$&
14160 .vindex "&$warn_message_recipients$&"
14161 This variable is set only during the creation of a message warning about a
14162 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
14168 . ////////////////////////////////////////////////////////////////////////////
14169 . ////////////////////////////////////////////////////////////////////////////
14171 .chapter "Embedded Perl" "CHAPperl"
14172 .scindex IIDperl "Perl" "calling from Exim"
14173 Exim can be built to include an embedded Perl interpreter. When this is done,
14174 Perl subroutines can be called as part of the string expansion process. To make
14175 use of the Perl support, you need version 5.004 or later of Perl installed on
14176 your system. To include the embedded interpreter in the Exim binary, include
14181 in your &_Local/Makefile_& and then build Exim in the normal way.
14184 .section "Setting up so Perl can be used" "SECID85"
14185 .oindex "&%perl_startup%&"
14186 Access to Perl subroutines is via a global configuration option called
14187 &%perl_startup%& and an expansion string operator &%${perl ...}%&. If there is
14188 no &%perl_startup%& option in the Exim configuration file then no Perl
14189 interpreter is started and there is almost no overhead for Exim (since none of
14190 the Perl library will be paged in unless used). If there is a &%perl_startup%&
14191 option then the associated value is taken to be Perl code which is executed in
14192 a newly created Perl interpreter.
14194 The value of &%perl_startup%& is not expanded in the Exim sense, so you do not
14195 need backslashes before any characters to escape special meanings. The option
14196 should usually be something like
14198 perl_startup = do '/etc/exim.pl'
14200 where &_/etc/exim.pl_& is Perl code which defines any subroutines you want to
14201 use from Exim. Exim can be configured either to start up a Perl interpreter as
14202 soon as it is entered, or to wait until the first time it is needed. Starting
14203 the interpreter at the beginning ensures that it is done while Exim still has
14204 its setuid privilege, but can impose an unnecessary overhead if Perl is not in
14205 fact used in a particular run. Also, note that this does not mean that Exim is
14206 necessarily running as root when Perl is called at a later time. By default,
14207 the interpreter is started only when it is needed, but this can be changed in
14211 .oindex "&%perl_at_start%&"
14212 Setting &%perl_at_start%& (a boolean option) in the configuration requests
14213 a startup when Exim is entered.
14215 The command line option &%-ps%& also requests a startup when Exim is entered,
14216 overriding the setting of &%perl_at_start%&.
14219 There is also a command line option &%-pd%& (for delay) which suppresses the
14220 initial startup, even if &%perl_at_start%& is set.
14223 .oindex "&%perl_taintmode%&"
14224 .cindex "Perl" "taintmode"
14225 To provide more security executing Perl code via the embedded Perl
14226 interpreter, the &%perl_taintmode%& option can be set. This enables the
14227 taint mode of the Perl interpreter. You are encouraged to set this
14228 option to a true value. To avoid breaking existing installations, it
14231 &*Note*&: This is entirely separate from Exim's tainted-data tracking.
14234 .section "Calling Perl subroutines" "SECID86"
14235 When the configuration file includes a &%perl_startup%& option you can make use
14236 of the string expansion item to call the Perl subroutines that are defined
14237 by the &%perl_startup%& code. The operator is used in any of the following
14241 ${perl{foo}{argument}}
14242 ${perl{foo}{argument1}{argument2} ... }
14244 which calls the subroutine &%foo%& with the given arguments. A maximum of eight
14245 arguments may be passed. Passing more than this results in an expansion failure
14246 with an error message of the form
14248 Too many arguments passed to Perl subroutine "foo" (max is 8)
14250 The return value of the Perl subroutine is evaluated in a scalar context before
14251 it is passed back to Exim to be inserted into the expanded string. If the
14252 return value is &'undef'&, the expansion is forced to fail in the same way as
14253 an explicit &"fail"& on an &%if%& or &%lookup%& item. If the subroutine aborts
14254 by obeying Perl's &%die%& function, the expansion fails with the error message
14255 that was passed to &%die%&.
14258 .section "Calling Exim functions from Perl" "SECID87"
14259 Within any Perl code called from Exim, the function &'Exim::expand_string()'&
14260 is available to call back into Exim's string expansion function. For example,
14263 my $lp = Exim::expand_string('$local_part');
14265 makes the current Exim &$local_part$& available in the Perl variable &$lp$&.
14266 Note those are single quotes and not double quotes to protect against
14267 &$local_part$& being interpolated as a Perl variable.
14269 If the string expansion is forced to fail by a &"fail"& item, the result of
14270 &'Exim::expand_string()'& is &%undef%&. If there is a syntax error in the
14271 expansion string, the Perl call from the original expansion string fails with
14272 an appropriate error message, in the same way as if &%die%& were used.
14274 .cindex "debugging" "from embedded Perl"
14275 .cindex "log" "writing from embedded Perl"
14276 Two other Exim functions are available for use from within Perl code.
14277 &'Exim::debug_write()'& writes a string to the standard error stream if Exim's
14278 debugging is enabled. If you want a newline at the end, you must supply it.
14279 &'Exim::log_write()'& writes a string to Exim's main log, adding a leading
14280 timestamp. In this case, you should not supply a terminating newline.
14283 .section "Use of standard output and error by Perl" "SECID88"
14284 .cindex "Perl" "standard output and error"
14285 You should not write to the standard error or output streams from within your
14286 Perl code, as it is not defined how these are set up. In versions of Exim
14287 before 4.50, it is possible for the standard output or error to refer to the
14288 SMTP connection during message reception via the daemon. Writing to this stream
14289 is certain to cause chaos. From Exim 4.50 onwards, the standard output and
14290 error streams are connected to &_/dev/null_& in the daemon. The chaos is
14291 avoided, but the output is lost.
14293 .cindex "Perl" "use of &%warn%&"
14294 The Perl &%warn%& statement writes to the standard error stream by default.
14295 Calls to &%warn%& may be embedded in Perl modules that you use, but over which
14296 you have no control. When Exim starts up the Perl interpreter, it arranges for
14297 output from the &%warn%& statement to be written to the Exim main log. You can
14298 change this by including appropriate Perl magic somewhere in your Perl code.
14299 For example, to discard &%warn%& output completely, you need this:
14301 $SIG{__WARN__} = sub { };
14303 Whenever a &%warn%& is obeyed, the anonymous subroutine is called. In this
14304 example, the code for the subroutine is empty, so it does nothing, but you can
14305 include any Perl code that you like. The text of the &%warn%& message is passed
14306 as the first subroutine argument.
14310 . ////////////////////////////////////////////////////////////////////////////
14311 . ////////////////////////////////////////////////////////////////////////////
14313 .chapter "Starting the daemon and the use of network interfaces" &&&
14314 "CHAPinterfaces" &&&
14315 "Starting the daemon"
14316 .cindex "daemon" "starting"
14317 .cindex "interface" "listening"
14318 .cindex "network interface"
14319 .cindex "interface" "network"
14320 .cindex "IP address" "for listening"
14321 .cindex "daemon" "listening IP addresses"
14322 .cindex "TCP/IP" "setting listening interfaces"
14323 .cindex "TCP/IP" "setting listening ports"
14324 A host that is connected to a TCP/IP network may have one or more physical
14325 hardware network interfaces. Each of these interfaces may be configured as one
14326 or more &"logical"& interfaces, which are the entities that a program actually
14327 works with. Each of these logical interfaces is associated with an IP address.
14328 In addition, TCP/IP software supports &"loopback"& interfaces (127.0.0.1 in
14329 IPv4 and ::1 in IPv6), which do not use any physical hardware. Exim requires
14330 knowledge about the host's interfaces for use in three different circumstances:
14333 When a listening daemon is started, Exim needs to know which interfaces
14334 and ports to listen on.
14336 When Exim is routing an address, it needs to know which IP addresses
14337 are associated with local interfaces. This is required for the correct
14338 processing of MX lists by removing the local host and others with the
14339 same or higher priority values. Also, Exim needs to detect cases
14340 when an address is routed to an IP address that in fact belongs to the
14341 local host. Unless the &%self%& router option or the &%allow_localhost%&
14342 option of the smtp transport is set (as appropriate), this is treated
14343 as an error situation.
14345 When Exim connects to a remote host, it may need to know which interface to use
14346 for the outgoing connection.
14350 Exim's default behaviour is likely to be appropriate in the vast majority
14351 of cases. If your host has only one interface, and you want all its IP
14352 addresses to be treated in the same way, and you are using only the
14353 standard SMTP port, you should not need to take any special action. The
14354 rest of this chapter does not apply to you.
14356 In a more complicated situation you may want to listen only on certain
14357 interfaces, or on different ports, and for this reason there are a number of
14358 options that can be used to influence Exim's behaviour. The rest of this
14359 chapter describes how they operate.
14361 When a message is received over TCP/IP, the interface and port that were
14362 actually used are set in &$received_ip_address$& and &$received_port$&.
14366 .section "Starting a listening daemon" "SECID89"
14367 When a listening daemon is started (by means of the &%-bd%& command line
14368 option), the interfaces and ports on which it listens are controlled by the
14372 &%daemon_smtp_ports%& contains a list of default ports
14374 (For backward compatibility, this option can also be specified in the singular.)
14376 &%local_interfaces%& contains list of interface IP addresses on which to
14377 listen. Each item may optionally also specify a port.
14380 The default list separator in both cases is a colon, but this can be changed as
14381 described in section &<<SECTlistsepchange>>&. When IPv6 addresses are involved,
14382 it is usually best to change the separator to avoid having to double all the
14383 colons. For example:
14385 local_interfaces = <; 127.0.0.1 ; \
14388 3ffe:ffff:836f::fe86:a061
14390 There are two different formats for specifying a port along with an IP address
14391 in &%local_interfaces%&:
14394 The port is added onto the address with a dot separator. For example, to listen
14395 on port 1234 on two different IP addresses:
14397 local_interfaces = <; 192.168.23.65.1234 ; \
14398 3ffe:ffff:836f::fe86:a061.1234
14401 The IP address is enclosed in square brackets, and the port is added
14402 with a colon separator, for example:
14404 local_interfaces = <; [192.168.23.65]:1234 ; \
14405 [3ffe:ffff:836f::fe86:a061]:1234
14409 When a port is not specified, the value of &%daemon_smtp_ports%& is used. The
14410 default setting contains just one port:
14412 daemon_smtp_ports = smtp
14414 If more than one port is listed, each interface that does not have its own port
14415 specified listens on all of them. Ports that are listed in
14416 &%daemon_smtp_ports%& can be identified either by name (defined in
14417 &_/etc/services_&) or by number. However, when ports are given with individual
14418 IP addresses in &%local_interfaces%&, only numbers (not names) can be used.
14422 .section "Special IP listening addresses" "SECID90"
14423 The addresses 0.0.0.0 and ::0 are treated specially. They are interpreted
14424 as &"all IPv4 interfaces"& and &"all IPv6 interfaces"&, respectively. In each
14425 case, Exim tells the TCP/IP stack to &"listen on all IPv&'x'& interfaces"&
14426 instead of setting up separate listening sockets for each interface. The
14427 default value of &%local_interfaces%& is
14429 local_interfaces = 0.0.0.0
14431 when Exim is built without IPv6 support; otherwise it is:
14433 local_interfaces = <; ::0 ; 0.0.0.0
14435 Thus, by default, Exim listens on all available interfaces, on the SMTP port.
14439 .section "Overriding local_interfaces and daemon_smtp_ports" "SECID91"
14440 The &%-oX%& command line option can be used to override the values of
14441 &%daemon_smtp_ports%& and/or &%local_interfaces%& for a particular daemon
14442 instance. Another way of doing this would be to use macros and the &%-D%&
14443 option. However, &%-oX%& can be used by any admin user, whereas modification of
14444 the runtime configuration by &%-D%& is allowed only when the caller is root or
14447 The value of &%-oX%& is a list of items. The default colon separator can be
14448 changed in the usual way (&<<SECTlistsepchange>>&) if required.
14449 If there are any items that do not
14450 contain dots or colons (that is, are not IP addresses), the value of
14451 &%daemon_smtp_ports%& is replaced by the list of those items. If there are any
14452 items that do contain dots or colons, the value of &%local_interfaces%& is
14453 replaced by those items. Thus, for example,
14457 overrides &%daemon_smtp_ports%&, but leaves &%local_interfaces%& unchanged,
14460 -oX 192.168.34.5.1125
14462 overrides &%local_interfaces%&, leaving &%daemon_smtp_ports%& unchanged.
14463 (However, since &%local_interfaces%& now contains no items without ports, the
14464 value of &%daemon_smtp_ports%& is no longer relevant in this example.)
14468 .section "Support for the submissions (aka SSMTP or SMTPS) protocol" "SECTsupobssmt"
14469 .cindex "submissions protocol"
14470 .cindex "ssmtp protocol"
14471 .cindex "smtps protocol"
14472 .cindex "SMTP" "ssmtp protocol"
14473 .cindex "SMTP" "smtps protocol"
14474 Exim supports the use of TLS-on-connect, used by mail clients in the
14475 &"submissions"& protocol, historically also known as SMTPS or SSMTP.
14476 For some years, IETF Standards Track documents only blessed the
14477 STARTTLS-based Submission service (port 587) while common practice was to support
14478 the same feature set on port 465, but using TLS-on-connect.
14479 If your installation needs to provide service to mail clients
14480 (Mail User Agents, MUAs) then you should provide service on both the 587 and
14483 If the &%tls_on_connect_ports%& option is set to a list of port numbers or
14484 service names, connections to those ports must first establish TLS, before
14485 proceeding to the application layer use of the SMTP protocol.
14487 The common use of this option is expected to be
14489 tls_on_connect_ports = 465
14492 There is also a command line option &%-tls-on-connect%&, which forces all ports
14493 to behave in this way when a daemon is started.
14495 &*Warning*&: Setting &%tls_on_connect_ports%& does not of itself cause the
14496 daemon to listen on those ports. You must still specify them in
14497 &%daemon_smtp_ports%&, &%local_interfaces%&, or the &%-oX%& option. (This is
14498 because &%tls_on_connect_ports%& applies to &%inetd%& connections as well as to
14499 connections via the daemon.)
14504 .section "IPv6 address scopes" "SECID92"
14505 .cindex "IPv6" "address scopes"
14506 IPv6 addresses have &"scopes"&, and a host with multiple hardware interfaces
14507 can, in principle, have the same link-local IPv6 address on different
14508 interfaces. Thus, additional information is needed, over and above the IP
14509 address, to distinguish individual interfaces. A convention of using a
14510 percent sign followed by something (often the interface name) has been
14511 adopted in some cases, leading to addresses like this:
14513 fe80::202:b3ff:fe03:45c1%eth0
14515 To accommodate this usage, a percent sign followed by an arbitrary string is
14516 allowed at the end of an IPv6 address. By default, Exim calls &[getaddrinfo()]&
14517 to convert a textual IPv6 address for actual use. This function recognizes the
14518 percent convention in operating systems that support it, and it processes the
14519 address appropriately. Unfortunately, some older libraries have problems with
14520 &[getaddrinfo()]&. If
14522 IPV6_USE_INET_PTON=yes
14524 is set in &_Local/Makefile_& (or an OS-dependent Makefile) when Exim is built,
14525 Exim uses &'inet_pton()'& to convert a textual IPv6 address for actual use,
14526 instead of &[getaddrinfo()]&. (Before version 4.14, it always used this
14527 function.) Of course, this means that the additional functionality of
14528 &[getaddrinfo()]& &-- recognizing scoped addresses &-- is lost.
14530 .section "Disabling IPv6" "SECID93"
14531 .cindex "IPv6" "disabling"
14532 Sometimes it happens that an Exim binary that was compiled with IPv6 support is
14533 run on a host whose kernel does not support IPv6. The binary will fall back to
14534 using IPv4, but it may waste resources looking up AAAA records, and trying to
14535 connect to IPv6 addresses, causing delays to mail delivery. If you set the
14536 .oindex "&%disable_ipv6%&"
14537 &%disable_ipv6%& option true, even if the Exim binary has IPv6 support, no IPv6
14538 activities take place. AAAA records are never looked up, and any IPv6 addresses
14539 that are listed in &%local_interfaces%&, data for the &(manualroute)& router,
14540 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
14541 to handle IPv6 literal addresses.
14543 On the other hand, when IPv6 is in use, there may be times when you want to
14544 disable it for certain hosts or domains. You can use the &%dns_ipv4_lookup%&
14545 option to globally suppress the lookup of AAAA records for specified domains,
14546 and you can use the &%ignore_target_hosts%& generic router option to ignore
14547 IPv6 addresses in an individual router.
14551 .section "Examples of starting a listening daemon" "SECID94"
14552 The default case in an IPv6 environment is
14554 daemon_smtp_ports = smtp
14555 local_interfaces = <; ::0 ; 0.0.0.0
14557 This specifies listening on the smtp port on all IPv6 and IPv4 interfaces.
14558 Either one or two sockets may be used, depending on the characteristics of
14559 the TCP/IP stack. (This is complicated and messy; for more information,
14560 read the comments in the &_daemon.c_& source file.)
14562 To specify listening on ports 25 and 26 on all interfaces:
14564 daemon_smtp_ports = 25 : 26
14566 (leaving &%local_interfaces%& at the default setting) or, more explicitly:
14568 local_interfaces = <; ::0.25 ; ::0.26 \
14569 0.0.0.0.25 ; 0.0.0.0.26
14571 To listen on the default port on all IPv4 interfaces, and on port 26 on the
14572 IPv4 loopback address only:
14574 local_interfaces = 0.0.0.0 : 127.0.0.1.26
14576 To specify listening on the default port on specific interfaces only:
14578 local_interfaces = 10.0.0.67 : 192.168.34.67
14580 &*Warning*&: Such a setting excludes listening on the loopback interfaces.
14584 .section "Recognizing the local host" "SECTreclocipadd"
14585 The &%local_interfaces%& option is also used when Exim needs to determine
14586 whether or not an IP address refers to the local host. That is, the IP
14587 addresses of all the interfaces on which a daemon is listening are always
14590 For this usage, port numbers in &%local_interfaces%& are ignored. If either of
14591 the items 0.0.0.0 or ::0 are encountered, Exim gets a complete list of
14592 available interfaces from the operating system, and extracts the relevant
14593 (that is, IPv4 or IPv6) addresses to use for checking.
14595 Some systems set up large numbers of virtual interfaces in order to provide
14596 many virtual web servers. In this situation, you may want to listen for
14597 email on only a few of the available interfaces, but nevertheless treat all
14598 interfaces as local when routing. You can do this by setting
14599 &%extra_local_interfaces%& to a list of IP addresses, possibly including the
14600 &"all"& wildcard values. These addresses are recognized as local, but are not
14601 used for listening. Consider this example:
14603 local_interfaces = <; 127.0.0.1 ; ::1 ; \
14605 3ffe:2101:12:1:a00:20ff:fe86:a061
14607 extra_local_interfaces = <; ::0 ; 0.0.0.0
14609 The daemon listens on the loopback interfaces and just one IPv4 and one IPv6
14610 address, but all available interface addresses are treated as local when
14613 In some environments the local host name may be in an MX list, but with an IP
14614 address that is not assigned to any local interface. In other cases it may be
14615 desirable to treat other host names as if they referred to the local host. Both
14616 these cases can be handled by setting the &%hosts_treat_as_local%& option.
14617 This contains host names rather than IP addresses. When a host is referenced
14618 during routing, either via an MX record or directly, it is treated as the local
14619 host if its name matches &%hosts_treat_as_local%&, or if any of its IP
14620 addresses match &%local_interfaces%& or &%extra_local_interfaces%&.
14624 .section "Delivering to a remote host" "SECID95"
14625 Delivery to a remote host is handled by the smtp transport. By default, it
14626 allows the system's TCP/IP functions to choose which interface to use (if
14627 there is more than one) when connecting to a remote host. However, the
14628 &%interface%& option can be set to specify which interface is used. See the
14629 description of the smtp transport in chapter &<<CHAPsmtptrans>>& for more
14635 . ////////////////////////////////////////////////////////////////////////////
14636 . ////////////////////////////////////////////////////////////////////////////
14638 .chapter "Main configuration" "CHAPmainconfig"
14639 .scindex IIDconfima "configuration file" "main section"
14640 .scindex IIDmaiconf "main configuration"
14641 The first part of the runtime configuration file contains three types of item:
14644 Macro definitions: These lines start with an upper case letter. See section
14645 &<<SECTmacrodefs>>& for details of macro processing.
14647 Named list definitions: These lines start with one of the words &"domainlist"&,
14648 &"hostlist"&, &"addresslist"&, or &"localpartlist"&. Their use is described in
14649 section &<<SECTnamedlists>>&.
14651 Main configuration settings: Each setting occupies one line of the file
14652 (with possible continuations). If any setting is preceded by the word
14653 &"hide"&, the &%-bP%& command line option displays its value to admin users
14654 only. See section &<<SECTcos>>& for a description of the syntax of these option
14658 This chapter specifies all the main configuration options, along with their
14659 types and default values. For ease of finding a particular option, they appear
14660 in alphabetical order in section &<<SECTalomo>>& below. However, because there
14661 are now so many options, they are first listed briefly in functional groups, as
14662 an aid to finding the name of the option you are looking for. Some options are
14663 listed in more than one group.
14665 .section "Miscellaneous" "SECID96"
14667 .row &%add_environment%& "environment variables"
14668 .row &%bi_command%& "to run for &%-bi%& command line option"
14669 .row &%debug_store%& "do extra internal checks"
14670 .row &%disable_ipv6%& "do no IPv6 processing"
14671 .row &%keep_environment%& "environment variables"
14672 .row &%keep_malformed%& "for broken files &-- should not happen"
14673 .row &%localhost_number%& "for unique message ids in clusters"
14674 .row &%message_body_newlines%& "retain newlines in &$message_body$&"
14675 .row &%message_body_visible%& "how much to show in &$message_body$&"
14676 .row &%mua_wrapper%& "run in &""MUA wrapper""& mode"
14677 .row &%print_topbitchars%& "top-bit characters are printing"
14678 .row &%spool_wireformat%& "use wire-format spool data files when possible"
14679 .row &%timezone%& "force time zone"
14683 .section "Exim parameters" "SECID97"
14685 .row &%exim_group%& "override compiled-in value"
14686 .row &%exim_path%& "override compiled-in value"
14687 .row &%exim_user%& "override compiled-in value"
14688 .row &%primary_hostname%& "default from &[uname()]&"
14689 .row &%split_spool_directory%& "use multiple directories"
14690 .row &%spool_directory%& "override compiled-in value"
14695 .section "Privilege controls" "SECID98"
14697 .row &%admin_groups%& "groups that are Exim admin users"
14698 .row &%commandline_checks_require_admin%& "require admin for various checks"
14699 .row &%deliver_drop_privilege%& "drop root for delivery processes"
14700 .row &%local_from_check%& "insert &'Sender:'& if necessary"
14701 .row &%local_from_prefix%& "for testing &'From:'& for local sender"
14702 .row &%local_from_suffix%& "for testing &'From:'& for local sender"
14703 .row &%local_sender_retain%& "keep &'Sender:'& from untrusted user"
14704 .row &%never_users%& "do not run deliveries as these"
14705 .row &%prod_requires_admin%& "forced delivery requires admin user"
14706 .row &%queue_list_requires_admin%& "queue listing requires admin user"
14707 .row &%trusted_groups%& "groups that are trusted"
14708 .row &%trusted_users%& "users that are trusted"
14713 .section "Logging" "SECID99"
14715 .row &%event_action%& "custom logging"
14716 .row &%hosts_connection_nolog%& "exemption from connect logging"
14717 .row &%log_file_path%& "override compiled-in value"
14718 .row &%log_selector%& "set/unset optional logging"
14719 .row &%log_timezone%& "add timezone to log lines"
14720 .row &%message_logs%& "create per-message logs"
14721 .row &%preserve_message_logs%& "after message completion"
14722 .row &%process_log_path%& "for SIGUSR1 and &'exiwhat'&"
14723 .row &%slow_lookup_log%& "control logging of slow DNS lookups"
14724 .row &%syslog_duplication%& "controls duplicate log lines on syslog"
14725 .row &%syslog_facility%& "set syslog &""facility""& field"
14726 .row &%syslog_pid%& "pid in syslog lines"
14727 .row &%syslog_processname%& "set syslog &""ident""& field"
14728 .row &%syslog_timestamp%& "timestamp syslog lines"
14729 .row &%write_rejectlog%& "control use of message log"
14734 .section "Frozen messages" "SECID100"
14736 .row &%auto_thaw%& "sets time for retrying frozen messages"
14737 .row &%freeze_tell%& "send message when freezing"
14738 .row &%move_frozen_messages%& "to another directory"
14739 .row &%timeout_frozen_after%& "keep frozen messages only so long"
14744 .section "Data lookups" "SECID101"
14746 .row &%ibase_servers%& "InterBase servers"
14747 .row &%ldap_ca_cert_dir%& "dir of CA certs to verify LDAP server's"
14748 .row &%ldap_ca_cert_file%& "file of CA certs to verify LDAP server's"
14749 .row &%ldap_cert_file%& "client cert file for LDAP"
14750 .row &%ldap_cert_key%& "client key file for LDAP"
14751 .row &%ldap_cipher_suite%& "TLS negotiation preference control"
14752 .row &%ldap_default_servers%& "used if no server in query"
14753 .row &%ldap_require_cert%& "action to take without LDAP server cert"
14754 .row &%ldap_start_tls%& "require TLS within LDAP"
14755 .row &%ldap_version%& "set protocol version"
14756 .row &%lookup_open_max%& "lookup files held open"
14757 .row &%mysql_servers%& "default MySQL servers"
14758 .row &%oracle_servers%& "Oracle servers"
14759 .row &%pgsql_servers%& "default PostgreSQL servers"
14760 .row &%sqlite_lock_timeout%& "as it says"
14765 .section "Message ids" "SECID102"
14767 .row &%message_id_header_domain%& "used to build &'Message-ID:'& header"
14768 .row &%message_id_header_text%& "ditto"
14773 .section "Embedded Perl Startup" "SECID103"
14775 .row &%perl_at_start%& "always start the interpreter"
14776 .row &%perl_startup%& "code to obey when starting Perl"
14777 .row &%perl_taintmode%& "enable taint mode in Perl"
14782 .section "Daemon" "SECID104"
14784 .row &%daemon_smtp_ports%& "default ports"
14785 .row &%daemon_startup_retries%& "number of times to retry"
14786 .row &%daemon_startup_sleep%& "time to sleep between tries"
14787 .row &%extra_local_interfaces%& "not necessarily listened on"
14788 .row &%local_interfaces%& "on which to listen, with optional ports"
14789 .row &%notifier_socket%& "override compiled-in value"
14790 .row &%pid_file_path%& "override compiled-in value"
14791 .row &%queue_run_max%& "maximum simultaneous queue runners"
14792 .row &%smtp_backlog_monitor%& "level to log listen backlog"
14797 .section "Resource control" "SECID105"
14799 .row &%check_log_inodes%& "before accepting a message"
14800 .row &%check_log_space%& "before accepting a message"
14801 .row &%check_spool_inodes%& "before accepting a message"
14802 .row &%check_spool_space%& "before accepting a message"
14803 .row &%deliver_queue_load_max%& "no queue deliveries if load high"
14804 .row &%queue_only_load%& "queue incoming if load high"
14805 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
14806 .row &%queue_run_max%& "maximum simultaneous queue runners"
14807 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
14808 .row &%smtp_accept_max%& "simultaneous incoming connections"
14809 .row &%smtp_accept_max_nonmail%& "non-mail commands"
14810 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
14811 .row &%smtp_accept_max_per_connection%& "messages per connection"
14812 .row &%smtp_accept_max_per_host%& "connections from one host"
14813 .row &%smtp_accept_queue%& "queue mail if more connections"
14814 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
14816 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
14817 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
14818 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
14819 .row &%smtp_load_reserve%& "SMTP from reserved hosts if load high"
14820 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
14825 .section "Policy controls" "SECID106"
14827 .row &%acl_not_smtp%& "ACL for non-SMTP messages"
14828 .row &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
14829 .row &%acl_not_smtp_start%& "ACL for start of non-SMTP message"
14830 .row &%acl_smtp_auth%& "ACL for AUTH"
14831 .row &%acl_smtp_connect%& "ACL for connection"
14832 .row &%acl_smtp_data%& "ACL for DATA"
14833 .row &%acl_smtp_data_prdr%& "ACL for DATA, per-recipient"
14834 .row &%acl_smtp_dkim%& "ACL for DKIM verification"
14835 .row &%acl_smtp_etrn%& "ACL for ETRN"
14836 .row &%acl_smtp_expn%& "ACL for EXPN"
14837 .row &%acl_smtp_helo%& "ACL for EHLO or HELO"
14838 .row &%acl_smtp_mail%& "ACL for MAIL"
14839 .row &%acl_smtp_mailauth%& "ACL for AUTH on MAIL command"
14840 .row &%acl_smtp_mime%& "ACL for MIME parts"
14841 .row &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
14842 .row &%acl_smtp_predata%& "ACL for start of data"
14843 .row &%acl_smtp_quit%& "ACL for QUIT"
14844 .row &%acl_smtp_rcpt%& "ACL for RCPT"
14845 .row &%acl_smtp_starttls%& "ACL for STARTTLS"
14846 .row &%acl_smtp_vrfy%& "ACL for VRFY"
14847 .row &%av_scanner%& "specify virus scanner"
14848 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
14850 .row &%dns_cname_loops%& "follow CNAMEs returned by resolver"
14851 .row &%dns_csa_search_limit%& "control CSA parent search depth"
14852 .row &%dns_csa_use_reverse%& "en/disable CSA IP reverse search"
14853 .row &%header_maxsize%& "total size of message header"
14854 .row &%header_line_maxsize%& "individual header line limit"
14855 .row &%helo_accept_junk_hosts%& "allow syntactic junk from these hosts"
14856 .row &%helo_allow_chars%& "allow illegal chars in HELO names"
14857 .row &%helo_lookup_domains%& "lookup hostname for these HELO names"
14858 .row &%helo_try_verify_hosts%& "HELO soft-checked for these hosts"
14859 .row &%helo_verify_hosts%& "HELO hard-checked for these hosts"
14860 .row &%host_lookup%& "host name looked up for these hosts"
14861 .row &%host_lookup_order%& "order of DNS and local name lookups"
14862 .row &%hosts_proxy%& "use proxy protocol for these hosts"
14863 .row &%host_reject_connection%& "reject connection from these hosts"
14864 .row &%hosts_treat_as_local%& "useful in some cluster configurations"
14865 .row &%local_scan_timeout%& "timeout for &[local_scan()]&"
14866 .row &%message_size_limit%& "for all messages"
14867 .row &%percent_hack_domains%& "recognize %-hack for these domains"
14868 .row &%proxy_protocol_timeout%& "timeout for proxy protocol negotiation"
14869 .row &%spamd_address%& "set interface to SpamAssassin"
14870 .row &%strict_acl_vars%& "object to unset ACL variables"
14871 .row &%spf_smtp_comment_template%& "template for &$spf_smtp_comment$&"
14876 .section "Callout cache" "SECID107"
14878 .row &%callout_domain_negative_expire%& "timeout for negative domain cache &&&
14880 .row &%callout_domain_positive_expire%& "timeout for positive domain cache &&&
14882 .row &%callout_negative_expire%& "timeout for negative address cache item"
14883 .row &%callout_positive_expire%& "timeout for positive address cache item"
14884 .row &%callout_random_local_part%& "string to use for &""random""& testing"
14889 .section "TLS" "SECID108"
14891 .row &%gnutls_compat_mode%& "use GnuTLS compatibility mode"
14892 .row &%gnutls_allow_auto_pkcs11%& "allow GnuTLS to autoload PKCS11 modules"
14893 .row &%hosts_require_alpn%& "mandatory ALPN"
14894 .row &%openssl_options%& "adjust OpenSSL compatibility options"
14895 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
14896 .row &%tls_alpn%& "acceptable protocol names"
14897 .row &%tls_certificate%& "location of server certificate"
14898 .row &%tls_crl%& "certificate revocation list"
14899 .row &%tls_dh_max_bits%& "clamp D-H bit count suggestion"
14900 .row &%tls_dhparam%& "DH parameters for server"
14901 .row &%tls_eccurve%& "EC curve selection for server"
14902 .row &%tls_ocsp_file%& "location of server certificate status proof"
14903 .row &%tls_on_connect_ports%& "specify SSMTP (SMTPS) ports"
14904 .row &%tls_privatekey%& "location of server private key"
14905 .row &%tls_remember_esmtp%& "don't reset after starting TLS"
14906 .row &%tls_require_ciphers%& "specify acceptable ciphers"
14907 .row &%tls_try_verify_hosts%& "try to verify client certificate"
14908 .row &%tls_verify_certificates%& "expected client certificates"
14909 .row &%tls_verify_hosts%& "insist on client certificate verify"
14914 .section "Local user handling" "SECID109"
14916 .row &%finduser_retries%& "useful in NIS environments"
14917 .row &%gecos_name%& "used when creating &'Sender:'&"
14918 .row &%gecos_pattern%& "ditto"
14919 .row &%max_username_length%& "for systems that truncate"
14920 .row &%unknown_login%& "used when no login name found"
14921 .row &%unknown_username%& "ditto"
14922 .row &%uucp_from_pattern%& "for recognizing &""From ""& lines"
14923 .row &%uucp_from_sender%& "ditto"
14928 .section "All incoming messages (SMTP and non-SMTP)" "SECID110"
14930 .row &%header_maxsize%& "total size of message header"
14931 .row &%header_line_maxsize%& "individual header line limit"
14932 .row &%message_size_limit%& "applies to all messages"
14933 .row &%percent_hack_domains%& "recognize %-hack for these domains"
14934 .row &%received_header_text%& "expanded to make &'Received:'&"
14935 .row &%received_headers_max%& "for mail loop detection"
14936 .row &%recipients_max%& "limit per message"
14937 .row &%recipients_max_reject%& "permanently reject excess recipients"
14943 .section "Non-SMTP incoming messages" "SECID111"
14945 .row &%receive_timeout%& "for non-SMTP messages"
14952 .section "Incoming SMTP messages" "SECID112"
14953 See also the &'Policy controls'& section above.
14956 .row &%dkim_verify_hashes%& "DKIM hash methods accepted for signatures"
14957 .row &%dkim_verify_keytypes%& "DKIM key types accepted for signatures"
14958 .row &%dkim_verify_min_keysizes%& "DKIM key sizes accepted for signatures"
14959 .row &%dkim_verify_signers%& "DKIM domains for which DKIM ACL is run"
14960 .row &%dmarc_forensic_sender%& "DMARC sender for report messages"
14961 .row &%dmarc_history_file%& "DMARC results log"
14962 .row &%dmarc_tld_file%& "DMARC toplevel domains file"
14963 .row &%host_lookup%& "host name looked up for these hosts"
14964 .row &%host_lookup_order%& "order of DNS and local name lookups"
14965 .row &%recipient_unqualified_hosts%& "may send unqualified recipients"
14966 .row &%rfc1413_hosts%& "make ident calls to these hosts"
14967 .row &%rfc1413_query_timeout%& "zero disables ident calls"
14968 .row &%sender_unqualified_hosts%& "may send unqualified senders"
14969 .row &%smtp_accept_keepalive%& "some TCP/IP magic"
14970 .row &%smtp_accept_max%& "simultaneous incoming connections"
14971 .row &%smtp_accept_max_nonmail%& "non-mail commands"
14972 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
14973 .row &%smtp_accept_max_per_connection%& "messages per connection"
14974 .row &%smtp_accept_max_per_host%& "connections from one host"
14975 .row &%smtp_accept_queue%& "queue mail if more connections"
14976 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
14978 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
14979 .row &%smtp_active_hostname%& "host name to use in messages"
14980 .row &%smtp_banner%& "text for welcome banner"
14981 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
14982 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
14983 .row &%smtp_enforce_sync%& "of SMTP command/responses"
14984 .row &%smtp_etrn_command%& "what to run for ETRN"
14985 .row &%smtp_etrn_serialize%& "only one at once"
14986 .row &%smtp_load_reserve%& "only reserve hosts if this load"
14987 .row &%smtp_max_unknown_commands%& "before dropping connection"
14988 .row &%smtp_ratelimit_hosts%& "apply ratelimiting to these hosts"
14989 .row &%smtp_ratelimit_mail%& "ratelimit for MAIL commands"
14990 .row &%smtp_ratelimit_rcpt%& "ratelimit for RCPT commands"
14991 .row &%smtp_receive_timeout%& "per command or data line"
14992 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
14993 .row &%smtp_return_error_details%& "give detail on rejections"
14998 .section "SMTP extensions" "SECID113"
15000 .row &%accept_8bitmime%& "advertise 8BITMIME"
15001 .row &%auth_advertise_hosts%& "advertise AUTH to these hosts"
15002 .row &%chunking_advertise_hosts%& "advertise CHUNKING to these hosts"
15003 .row &%dsn_advertise_hosts%& "advertise DSN extensions to these hosts"
15004 .row &%ignore_fromline_hosts%& "allow &""From ""& from these hosts"
15005 .row &%ignore_fromline_local%& "allow &""From ""& from local SMTP"
15006 .row &%pipelining_advertise_hosts%& "advertise pipelining to these hosts"
15007 .row &%pipelining_connect_advertise_hosts%& "advertise pipelining to these hosts"
15008 .row &%prdr_enable%& "advertise PRDR to all hosts"
15009 .row &%smtputf8_advertise_hosts%& "advertise SMTPUTF8 to these hosts"
15010 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
15015 .section "Processing messages" "SECID114"
15017 .row &%allow_domain_literals%& "recognize domain literal syntax"
15018 .row &%allow_mx_to_ip%& "allow MX to point to IP address"
15019 .row &%allow_utf8_domains%& "in addresses"
15020 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
15022 .row &%delivery_date_remove%& "from incoming messages"
15023 .row &%envelope_to_remove%& "from incoming messages"
15024 .row &%extract_addresses_remove_arguments%& "affects &%-t%& processing"
15025 .row &%headers_charset%& "default for translations"
15026 .row &%qualify_domain%& "default for senders"
15027 .row &%qualify_recipient%& "default for recipients"
15028 .row &%return_path_remove%& "from incoming messages"
15029 .row &%strip_excess_angle_brackets%& "in addresses"
15030 .row &%strip_trailing_dot%& "at end of addresses"
15031 .row &%untrusted_set_sender%& "untrusted can set envelope sender"
15036 .section "System filter" "SECID115"
15038 .row &%system_filter%& "locate system filter"
15039 .row &%system_filter_directory_transport%& "transport for delivery to a &&&
15041 .row &%system_filter_file_transport%& "transport for delivery to a file"
15042 .row &%system_filter_group%& "group for filter running"
15043 .row &%system_filter_pipe_transport%& "transport for delivery to a pipe"
15044 .row &%system_filter_reply_transport%& "transport for autoreply delivery"
15045 .row &%system_filter_user%& "user for filter running"
15050 .section "Routing and delivery" "SECID116"
15052 .row &%disable_ipv6%& "do no IPv6 processing"
15053 .row &%dns_again_means_nonexist%& "for broken domains"
15054 .row &%dns_check_names_pattern%& "pre-DNS syntax check"
15055 .row &%dns_dnssec_ok%& "parameter for resolver"
15056 .row &%dns_ipv4_lookup%& "only v4 lookup for these domains"
15057 .row &%dns_retrans%& "parameter for resolver"
15058 .row &%dns_retry%& "parameter for resolver"
15059 .row &%dns_trust_aa%& "DNS zones trusted as authentic"
15060 .row &%dns_use_edns0%& "parameter for resolver"
15061 .row &%hold_domains%& "hold delivery for these domains"
15062 .row &%local_interfaces%& "for routing checks"
15063 .row &%queue_domains%& "no immediate delivery for these"
15064 .row &%queue_fast_ramp%& "parallel delivery with 2-phase queue run"
15065 .row &%queue_only%& "no immediate delivery at all"
15066 .row &%queue_only_file%& "no immediate delivery if file exists"
15067 .row &%queue_only_load%& "no immediate delivery if load is high"
15068 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
15069 .row &%queue_only_override%& "allow command line to override"
15070 .row &%queue_run_in_order%& "order of arrival"
15071 .row &%queue_run_max%& "of simultaneous queue runners"
15072 .row &%queue_smtp_domains%& "no immediate SMTP delivery for these"
15073 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
15074 .row &%remote_sort_domains%& "order of remote deliveries"
15075 .row &%retry_data_expire%& "timeout for retry data"
15076 .row &%retry_interval_max%& "safety net for retry rules"
15081 .section "Bounce and warning messages" "SECID117"
15083 .row &%bounce_message_file%& "content of bounce"
15084 .row &%bounce_message_text%& "content of bounce"
15085 .row &%bounce_return_body%& "include body if returning message"
15086 .row &%bounce_return_linesize_limit%& "limit on returned message line length"
15087 .row &%bounce_return_message%& "include original message in bounce"
15088 .row &%bounce_return_size_limit%& "limit on returned message"
15089 .row &%bounce_sender_authentication%& "send authenticated sender with bounce"
15090 .row &%dsn_from%& "set &'From:'& contents in bounces"
15091 .row &%errors_copy%& "copy bounce messages"
15092 .row &%errors_reply_to%& "&'Reply-to:'& in bounces"
15093 .row &%delay_warning%& "time schedule"
15094 .row &%delay_warning_condition%& "condition for warning messages"
15095 .row &%ignore_bounce_errors_after%& "discard undeliverable bounces"
15096 .row &%smtp_return_error_details%& "give detail on rejections"
15097 .row &%warn_message_file%& "content of warning message"
15102 .section "Alphabetical list of main options" "SECTalomo"
15103 Those options that undergo string expansion before use are marked with
15106 .option accept_8bitmime main boolean true
15108 .cindex "8-bit characters"
15109 .cindex "log" "selectors"
15110 .cindex "log" "8BITMIME"
15111 .cindex "ESMTP extensions" 8BITMIME
15112 This option causes Exim to send 8BITMIME in its response to an SMTP
15113 EHLO command, and to accept the BODY= parameter on MAIL commands.
15114 However, though Exim is 8-bit clean, it is not a protocol converter, and it
15115 takes no steps to do anything special with messages received by this route.
15117 Historically Exim kept this option off by default, but the maintainers
15118 feel that in today's Internet, this causes more problems than it solves.
15119 It now defaults to true.
15120 A more detailed analysis of the issues is provided by Dan Bernstein:
15122 &url(https://cr.yp.to/smtp/8bitmime.html)
15125 To log received 8BITMIME status use
15127 log_selector = +8bitmime
15130 .option acl_not_smtp main string&!! unset
15131 .cindex "&ACL;" "for non-SMTP messages"
15132 .cindex "non-SMTP messages" "ACLs for"
15133 This option defines the ACL that is run when a non-SMTP message has been
15134 read and is on the point of being accepted. See chapter &<<CHAPACL>>& for
15137 .option acl_not_smtp_mime main string&!! unset
15138 This option defines the ACL that is run for individual MIME parts of non-SMTP
15139 messages. It operates in exactly the same way as &%acl_smtp_mime%& operates for
15142 .option acl_not_smtp_start main string&!! unset
15143 .cindex "&ACL;" "at start of non-SMTP message"
15144 .cindex "non-SMTP messages" "ACLs for"
15145 This option defines the ACL that is run before Exim starts reading a
15146 non-SMTP message. See chapter &<<CHAPACL>>& for further details.
15148 .option acl_smtp_auth main string&!! unset
15149 .cindex "&ACL;" "setting up for SMTP commands"
15150 .cindex "AUTH" "ACL for"
15151 This option defines the ACL that is run when an SMTP AUTH command is
15152 received. See chapter &<<CHAPACL>>& for further details.
15154 .option acl_smtp_connect main string&!! unset
15155 .cindex "&ACL;" "on SMTP connection"
15156 This option defines the ACL that is run when an SMTP connection is received.
15157 See chapter &<<CHAPACL>>& for further details.
15159 .option acl_smtp_data main string&!! unset
15160 .cindex "DATA" "ACL for"
15161 This option defines the ACL that is run after an SMTP DATA command has been
15162 processed and the message itself has been received, but before the final
15163 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
15165 .option acl_smtp_data_prdr main string&!! accept
15166 .cindex "PRDR" "ACL for"
15167 .cindex "DATA" "PRDR ACL for"
15168 .cindex "&ACL;" "PRDR-related"
15169 .cindex "&ACL;" "per-user data processing"
15170 This option defines the ACL that,
15171 if the PRDR feature has been negotiated,
15172 is run for each recipient after an SMTP DATA command has been
15173 processed and the message itself has been received, but before the
15174 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
15176 .option acl_smtp_dkim main string&!! unset
15177 .cindex DKIM "ACL for"
15178 This option defines the ACL that is run for each DKIM signature
15179 (by default, or as specified in the dkim_verify_signers option)
15180 of a received message.
15181 See section &<<SECDKIMVFY>>& for further details.
15183 .option acl_smtp_etrn main string&!! unset
15184 .cindex "ETRN" "ACL for"
15185 This option defines the ACL that is run when an SMTP ETRN command is
15186 received. See chapter &<<CHAPACL>>& for further details.
15188 .option acl_smtp_expn main string&!! unset
15189 .cindex "EXPN" "ACL for"
15190 This option defines the ACL that is run when an SMTP EXPN command is
15191 received. See chapter &<<CHAPACL>>& for further details.
15193 .option acl_smtp_helo main string&!! unset
15194 .cindex "EHLO" "ACL for"
15195 .cindex "HELO" "ACL for"
15196 This option defines the ACL that is run when an SMTP EHLO or HELO
15197 command is received. See chapter &<<CHAPACL>>& for further details.
15200 .option acl_smtp_mail main string&!! unset
15201 .cindex "MAIL" "ACL for"
15202 This option defines the ACL that is run when an SMTP MAIL command is
15203 received. See chapter &<<CHAPACL>>& for further details.
15205 .option acl_smtp_mailauth main string&!! unset
15206 .cindex "AUTH" "on MAIL command"
15207 This option defines the ACL that is run when there is an AUTH parameter on
15208 a MAIL command. See chapter &<<CHAPACL>>& for details of ACLs, and chapter
15209 &<<CHAPSMTPAUTH>>& for details of authentication.
15211 .option acl_smtp_mime main string&!! unset
15212 .cindex "MIME content scanning" "ACL for"
15213 This option is available when Exim is built with the content-scanning
15214 extension. It defines the ACL that is run for each MIME part in a message. See
15215 section &<<SECTscanmimepart>>& for details.
15217 .option acl_smtp_notquit main string&!! unset
15218 .cindex "not-QUIT, ACL for"
15219 This option defines the ACL that is run when an SMTP session
15220 ends without a QUIT command being received.
15221 See chapter &<<CHAPACL>>& for further details.
15223 .option acl_smtp_predata main string&!! unset
15224 This option defines the ACL that is run when an SMTP DATA command is
15225 received, before the message itself is received. See chapter &<<CHAPACL>>& for
15228 .option acl_smtp_quit main string&!! unset
15229 .cindex "QUIT, ACL for"
15230 This option defines the ACL that is run when an SMTP QUIT command is
15231 received. See chapter &<<CHAPACL>>& for further details.
15233 .option acl_smtp_rcpt main string&!! unset
15234 .cindex "RCPT" "ACL for"
15235 This option defines the ACL that is run when an SMTP RCPT command is
15236 received. See chapter &<<CHAPACL>>& for further details.
15238 .option acl_smtp_starttls main string&!! unset
15239 .cindex "STARTTLS, ACL for"
15240 This option defines the ACL that is run when an SMTP STARTTLS command is
15241 received. See chapter &<<CHAPACL>>& for further details.
15243 .option acl_smtp_vrfy main string&!! unset
15244 .cindex "VRFY" "ACL for"
15245 This option defines the ACL that is run when an SMTP VRFY command is
15246 received. See chapter &<<CHAPACL>>& for further details.
15248 .option add_environment main "string list" empty
15249 .cindex "environment" "set values"
15250 This option adds individual environment variables that the
15251 currently linked libraries and programs in child processes may use.
15252 Each list element should be of the form &"name=value"&.
15254 See &<<SECTpipeenv>>& for the environment of &(pipe)& transports.
15256 .option admin_groups main "string list&!!" unset
15257 .cindex "admin user"
15258 This option is expanded just once, at the start of Exim's processing. If the
15259 current group or any of the supplementary groups of an Exim caller is in this
15260 colon-separated list, the caller has admin privileges. If all your system
15261 programmers are in a specific group, for example, you can give them all Exim
15262 admin privileges by putting that group in &%admin_groups%&. However, this does
15263 not permit them to read Exim's spool files (whose group owner is the Exim gid).
15264 To permit this, you have to add individuals to the Exim group.
15266 .option allow_domain_literals main boolean false
15267 .cindex "domain literal"
15268 If this option is set, the RFC 2822 domain literal format is permitted in
15269 email addresses. The option is not set by default, because the domain literal
15270 format is not normally required these days, and few people know about it. It
15271 has, however, been exploited by mail abusers.
15273 Unfortunately, it seems that some DNS black list maintainers are using this
15274 format to report black listing to postmasters. If you want to accept messages
15275 addressed to your hosts by IP address, you need to set
15276 &%allow_domain_literals%& true, and also to add &`@[]`& to the list of local
15277 domains (defined in the named domain list &%local_domains%& in the default
15278 configuration). This &"magic string"& matches the domain literal form of all
15279 the local host's IP addresses.
15281 .option allow_mx_to_ip main boolean false
15282 .cindex "MX record" "pointing to IP address"
15283 It appears that more and more DNS zone administrators are breaking the rules
15284 and putting domain names that look like IP addresses on the right hand side of
15285 MX records. Exim follows the rules and rejects this, giving an error message
15286 that explains the misconfiguration. However, some other MTAs support this
15287 practice, so to avoid &"Why can't Exim do this?"& complaints,
15288 &%allow_mx_to_ip%& exists, in order to enable this heinous activity. It is not
15289 recommended, except when you have no other choice.
15291 .option allow_utf8_domains main boolean false
15292 .cindex "domain" "UTF-8 characters in"
15293 .cindex "UTF-8" "in domain name"
15294 Lots of discussion is going on about internationalized domain names. One
15295 camp is strongly in favour of just using UTF-8 characters, and it seems
15296 that at least two other MTAs permit this.
15297 This option allows Exim users to experiment if they wish.
15299 If it is set true, Exim's domain parsing function allows valid
15300 UTF-8 multicharacters to appear in domain name components, in addition to
15301 letters, digits, and hyphens.
15303 If Exim is built with internationalization support
15304 and the SMTPUTF8 ESMTP option is in use (see chapter &<<CHAPi18n>>&)
15305 this option can be left as default.
15307 if you want to look up such domain names in the DNS, you must also
15308 adjust the value of &%dns_check_names_pattern%& to match the extended form. A
15309 suitable setting is:
15311 dns_check_names_pattern = (?i)^(?>(?(1)\.|())[a-z0-9\xc0-\xff]\
15312 (?>[-a-z0-9\x80-\xff]*[a-z0-9\x80-\xbf])?)+$
15314 Alternatively, you can just disable this feature by setting
15316 dns_check_names_pattern =
15318 That is, set the option to an empty string so that no check is done.
15321 .option auth_advertise_hosts main "host list&!!" *
15322 .cindex "authentication" "advertising"
15323 .cindex "AUTH" "advertising"
15324 .cindex "ESMTP extensions" AUTH
15325 If any server authentication mechanisms are configured, Exim advertises them in
15326 response to an EHLO command only if the calling host matches this list.
15327 Otherwise, Exim does not advertise AUTH.
15328 Exim does not accept AUTH commands from clients to which it has not
15329 advertised the availability of AUTH. The advertising of individual
15330 authentication mechanisms can be controlled by the use of the
15331 &%server_advertise_condition%& generic authenticator option on the individual
15332 authenticators. See chapter &<<CHAPSMTPAUTH>>& for further details.
15334 Certain mail clients (for example, Netscape) require the user to provide a name
15335 and password for authentication if AUTH is advertised, even though it may
15336 not be needed (the host may accept messages from hosts on its local LAN without
15337 authentication, for example). The &%auth_advertise_hosts%& option can be used
15338 to make these clients more friendly by excluding them from the set of hosts to
15339 which Exim advertises AUTH.
15341 .cindex "AUTH" "advertising when encrypted"
15342 If you want to advertise the availability of AUTH only when the connection
15343 is encrypted using TLS, you can make use of the fact that the value of this
15344 option is expanded, with a setting like this:
15346 auth_advertise_hosts = ${if eq{$tls_in_cipher}{}{}{*}}
15348 .vindex "&$tls_in_cipher$&"
15349 If &$tls_in_cipher$& is empty, the session is not encrypted, and the result of
15350 the expansion is empty, thus matching no hosts. Otherwise, the result of the
15351 expansion is *, which matches all hosts.
15354 .option auto_thaw main time 0s
15355 .cindex "thawing messages"
15356 .cindex "unfreezing messages"
15357 If this option is set to a time greater than zero, a queue runner will try a
15358 new delivery attempt on any frozen message, other than a bounce message, if
15359 this much time has passed since it was frozen. This may result in the message
15360 being re-frozen if nothing has changed since the last attempt. It is a way of
15361 saying &"keep on trying, even though there are big problems"&.
15363 &*Note*&: This is an old option, which predates &%timeout_frozen_after%& and
15364 &%ignore_bounce_errors_after%&. It is retained for compatibility, but it is not
15365 thought to be very useful any more, and its use should probably be avoided.
15368 .option av_scanner main string "see below"
15369 This option is available if Exim is built with the content-scanning extension.
15370 It specifies which anti-virus scanner to use. The default value is:
15372 sophie:/var/run/sophie
15374 If the value of &%av_scanner%& starts with a dollar character, it is expanded
15375 before use. See section &<<SECTscanvirus>>& for further details.
15378 .option bi_command main string unset
15380 This option supplies the name of a command that is run when Exim is called with
15381 the &%-bi%& option (see chapter &<<CHAPcommandline>>&). The string value is
15382 just the command name, it is not a complete command line. If an argument is
15383 required, it must come from the &%-oA%& command line option.
15386 .option bounce_message_file main string&!! unset
15387 .cindex "bounce message" "customizing"
15388 .cindex "customizing" "bounce message"
15389 This option defines a template file containing paragraphs of text to be used
15390 for constructing bounce messages. Details of the file's contents are given in
15391 chapter &<<CHAPemsgcust>>&.
15392 .cindex bounce_message_file "tainted data"
15393 The option is expanded to give the file path, which must be
15394 absolute and untainted.
15395 See also &%warn_message_file%&.
15398 .option bounce_message_text main string unset
15399 When this option is set, its contents are included in the default bounce
15400 message immediately after &"This message was created automatically by mail
15401 delivery software."& It is not used if &%bounce_message_file%& is set.
15403 .option bounce_return_body main boolean true
15404 .cindex "bounce message" "including body"
15405 This option controls whether the body of an incoming message is included in a
15406 bounce message when &%bounce_return_message%& is true. The default setting
15407 causes the entire message, both header and body, to be returned (subject to the
15408 value of &%bounce_return_size_limit%&). If this option is false, only the
15409 message header is included. In the case of a non-SMTP message containing an
15410 error that is detected during reception, only those header lines preceding the
15411 point at which the error was detected are returned.
15412 .cindex "bounce message" "including original"
15414 .option bounce_return_linesize_limit main integer 998
15415 .cindex "size" "of bounce lines, limit"
15416 .cindex "bounce message" "line length limit"
15417 .cindex "limit" "bounce message line length"
15418 This option sets a limit in bytes on the line length of messages
15419 that are returned to senders due to delivery problems,
15420 when &%bounce_return_message%& is true.
15421 The default value corresponds to RFC limits.
15422 If the message being returned has lines longer than this value it is
15423 treated as if the &%bounce_return_size_limit%& (below) restriction was exceeded.
15425 The option also applies to bounces returned when an error is detected
15426 during reception of a message.
15427 In this case lines from the original are truncated.
15429 The option does not apply to messages generated by an &(autoreply)& transport.
15432 .option bounce_return_message main boolean true
15433 If this option is set false, none of the original message is included in
15434 bounce messages generated by Exim. See also &%bounce_return_size_limit%& and
15435 &%bounce_return_body%&.
15438 .option bounce_return_size_limit main integer 100K
15439 .cindex "size" "of bounce, limit"
15440 .cindex "bounce message" "size limit"
15441 .cindex "limit" "bounce message size"
15442 This option sets a limit in bytes on the size of messages that are returned to
15443 senders as part of bounce messages when &%bounce_return_message%& is true. The
15444 limit should be less than the value of the global &%message_size_limit%& and of
15445 any &%message_size_limit%& settings on transports, to allow for the bounce text
15446 that Exim generates. If this option is set to zero there is no limit.
15448 When the body of any message that is to be included in a bounce message is
15449 greater than the limit, it is truncated, and a comment pointing this out is
15450 added at the top. The actual cutoff may be greater than the value given, owing
15451 to the use of buffering for transferring the message in chunks (typically 8K in
15452 size). The idea is to save bandwidth on those undeliverable 15-megabyte
15455 .option bounce_sender_authentication main string unset
15456 .cindex "bounce message" "sender authentication"
15457 .cindex "authentication" "bounce message"
15458 .cindex "AUTH" "on bounce message"
15459 This option provides an authenticated sender address that is sent with any
15460 bounce messages generated by Exim that are sent over an authenticated SMTP
15461 connection. A typical setting might be:
15463 bounce_sender_authentication = mailer-daemon@my.domain.example
15465 which would cause bounce messages to be sent using the SMTP command:
15467 MAIL FROM:<> AUTH=mailer-daemon@my.domain.example
15469 The value of &%bounce_sender_authentication%& must always be a complete email
15472 .option callout_domain_negative_expire main time 3h
15473 .cindex "caching" "callout timeouts"
15474 .cindex "callout" "caching timeouts"
15475 This option specifies the expiry time for negative callout cache data for a
15476 domain. See section &<<SECTcallver>>& for details of callout verification, and
15477 section &<<SECTcallvercache>>& for details of the caching.
15480 .option callout_domain_positive_expire main time 7d
15481 This option specifies the expiry time for positive callout cache data for a
15482 domain. See section &<<SECTcallver>>& for details of callout verification, and
15483 section &<<SECTcallvercache>>& for details of the caching.
15486 .option callout_negative_expire main time 2h
15487 This option specifies the expiry time for negative callout cache data for an
15488 address. See section &<<SECTcallver>>& for details of callout verification, and
15489 section &<<SECTcallvercache>>& for details of the caching.
15492 .option callout_positive_expire main time 24h
15493 This option specifies the expiry time for positive callout cache data for an
15494 address. See section &<<SECTcallver>>& for details of callout verification, and
15495 section &<<SECTcallvercache>>& for details of the caching.
15498 .option callout_random_local_part main string&!! "see below"
15499 This option defines the &"random"& local part that can be used as part of
15500 callout verification. The default value is
15502 $primary_hostname-$tod_epoch-testing
15504 See section &<<CALLaddparcall>>& for details of how this value is used.
15507 .option check_log_inodes main integer 100
15508 See &%check_spool_space%& below.
15511 .option check_log_space main integer 10M
15512 See &%check_spool_space%& below.
15514 .oindex "&%check_rfc2047_length%&"
15515 .cindex "RFC 2047" "disabling length check"
15516 .option check_rfc2047_length main boolean true
15517 RFC 2047 defines a way of encoding non-ASCII characters in headers using a
15518 system of &"encoded words"&. The RFC specifies a maximum length for an encoded
15519 word; strings to be encoded that exceed this length are supposed to use
15520 multiple encoded words. By default, Exim does not recognize encoded words that
15521 exceed the maximum length. However, it seems that some software, in violation
15522 of the RFC, generates overlong encoded words. If &%check_rfc2047_length%& is
15523 set false, Exim recognizes encoded words of any length.
15526 .option check_spool_inodes main integer 100
15527 See &%check_spool_space%& below.
15530 .option check_spool_space main integer 10M
15531 .cindex "checking disk space"
15532 .cindex "disk space, checking"
15533 .cindex "spool directory" "checking space"
15534 The four &%check_...%& options allow for checking of disk resources before a
15535 message is accepted.
15537 .vindex "&$log_inodes$&"
15538 .vindex "&$log_space$&"
15539 .vindex "&$spool_inodes$&"
15540 .vindex "&$spool_space$&"
15541 When any of these options are nonzero, they apply to all incoming messages. If you
15542 want to apply different checks to different kinds of message, you can do so by
15543 testing the variables &$log_inodes$&, &$log_space$&, &$spool_inodes$&, and
15544 &$spool_space$& in an ACL with appropriate additional conditions.
15547 &%check_spool_space%& and &%check_spool_inodes%& check the spool partition if
15548 either value is greater than zero, for example:
15550 check_spool_space = 100M
15551 check_spool_inodes = 100
15553 The spool partition is the one that contains the directory defined by
15554 SPOOL_DIRECTORY in &_Local/Makefile_&. It is used for holding messages in
15557 &%check_log_space%& and &%check_log_inodes%& check the partition in which log
15558 files are written if either is greater than zero. These should be set only if
15559 &%log_file_path%& and &%spool_directory%& refer to different partitions.
15561 If there is less space or fewer inodes than requested, Exim refuses to accept
15562 incoming mail. In the case of SMTP input this is done by giving a 452 temporary
15563 error response to the MAIL command. If ESMTP is in use and there was a
15564 SIZE parameter on the MAIL command, its value is added to the
15565 &%check_spool_space%& value, and the check is performed even if
15566 &%check_spool_space%& is zero, unless &%no_smtp_check_spool_space%& is set.
15568 The values for &%check_spool_space%& and &%check_log_space%& are held as a
15569 number of kilobytes (though specified in bytes).
15570 If a non-multiple of 1024 is specified, it is rounded up.
15572 For non-SMTP input and for batched SMTP input, the test is done at start-up; on
15573 failure a message is written to stderr and Exim exits with a non-zero code, as
15574 it obviously cannot send an error message of any kind.
15576 There is a slight performance penalty for these checks.
15577 Versions of Exim preceding 4.88 had these disabled by default;
15578 high-rate installations confident they will never run out of resources
15579 may wish to deliberately disable them.
15581 .option chunking_advertise_hosts main "host list&!!" *
15582 .cindex CHUNKING advertisement
15583 .cindex "RFC 3030" "CHUNKING"
15584 .cindex "ESMTP extensions" CHUNKING
15585 The CHUNKING extension (RFC3030) will be advertised in the EHLO message to
15587 Hosts may use the BDAT command as an alternate to DATA.
15589 .option commandline_checks_require_admin main boolean &`false`&
15590 .cindex "restricting access to features"
15591 This option restricts various basic checking features to require an
15592 administrative user.
15593 This affects most of the &%-b*%& options, such as &%-be%&.
15595 .option debug_store main boolean &`false`&
15596 .cindex debugging "memory corruption"
15597 .cindex memory debugging
15598 This option, when true, enables extra checking in Exim's internal memory
15599 management. For use when a memory corruption issue is being investigated,
15600 it should normally be left as default.
15602 .option daemon_smtp_ports main string &`smtp`&
15603 .cindex "port" "for daemon"
15604 .cindex "TCP/IP" "setting listening ports"
15605 This option specifies one or more default SMTP ports on which the Exim daemon
15606 listens. See chapter &<<CHAPinterfaces>>& for details of how it is used. For
15607 backward compatibility, &%daemon_smtp_port%& (singular) is a synonym.
15609 .option daemon_startup_retries main integer 9
15610 .cindex "daemon startup, retrying"
15611 This option, along with &%daemon_startup_sleep%&, controls the retrying done by
15612 the daemon at startup when it cannot immediately bind a listening socket
15613 (typically because the socket is already in use): &%daemon_startup_retries%&
15614 defines the number of retries after the first failure, and
15615 &%daemon_startup_sleep%& defines the length of time to wait between retries.
15617 .option daemon_startup_sleep main time 30s
15618 See &%daemon_startup_retries%&.
15620 .option delay_warning main "time list" 24h
15621 .cindex "warning of delay"
15622 .cindex "delay warning, specifying"
15623 .cindex "queue" "delay warning"
15624 When a message is delayed, Exim sends a warning message to the sender at
15625 intervals specified by this option. The data is a colon-separated list of times
15626 after which to send warning messages. If the value of the option is an empty
15627 string or a zero time, no warnings are sent. Up to 10 times may be given. If a
15628 message has been in the queue for longer than the last time, the last interval
15629 between the times is used to compute subsequent warning times. For example,
15632 delay_warning = 4h:8h:24h
15634 the first message is sent after 4 hours, the second after 8 hours, and
15635 the third one after 24 hours. After that, messages are sent every 16 hours,
15636 because that is the interval between the last two times on the list. If you set
15637 just one time, it specifies the repeat interval. For example, with:
15641 messages are repeated every six hours. To stop warnings after a given time, set
15642 a very large time at the end of the list. For example:
15644 delay_warning = 2h:12h:99d
15646 Note that the option is only evaluated at the time a delivery attempt fails,
15647 which depends on retry and queue-runner configuration.
15648 Typically retries will be configured more frequently than warning messages.
15650 .option delay_warning_condition main string&!! "see below"
15651 .vindex "&$domain$&"
15652 The string is expanded at the time a warning message might be sent. If all the
15653 deferred addresses have the same domain, it is set in &$domain$& during the
15654 expansion. Otherwise &$domain$& is empty. If the result of the expansion is a
15655 forced failure, an empty string, or a string matching any of &"0"&, &"no"& or
15656 &"false"& (the comparison being done caselessly) then the warning message is
15657 not sent. The default is:
15659 delay_warning_condition = ${if or {\
15660 { !eq{$h_list-id:$h_list-post:$h_list-subscribe:}{} }\
15661 { match{$h_precedence:}{(?i)bulk|list|junk} }\
15662 { match{$h_auto-submitted:}{(?i)auto-generated|auto-replied} }\
15665 This suppresses the sending of warnings for messages that contain &'List-ID:'&,
15666 &'List-Post:'&, or &'List-Subscribe:'& headers, or have &"bulk"&, &"list"& or
15667 &"junk"& in a &'Precedence:'& header, or have &"auto-generated"& or
15668 &"auto-replied"& in an &'Auto-Submitted:'& header.
15670 .option deliver_drop_privilege main boolean false
15671 .cindex "unprivileged delivery"
15672 .cindex "delivery" "unprivileged"
15673 If this option is set true, Exim drops its root privilege at the start of a
15674 delivery process, and runs as the Exim user throughout. This severely restricts
15675 the kinds of local delivery that are possible, but is viable in certain types
15676 of configuration. There is a discussion about the use of root privilege in
15677 chapter &<<CHAPsecurity>>&.
15679 .option deliver_queue_load_max main fixed-point unset
15680 .cindex "load average"
15681 .cindex "queue runner" "abandoning"
15682 When this option is set, a queue run is abandoned if the system load average
15683 becomes greater than the value of the option. The option has no effect on
15684 ancient operating systems on which Exim cannot determine the load average.
15685 See also &%queue_only_load%& and &%smtp_load_reserve%&.
15688 .option delivery_date_remove main boolean true
15689 .cindex "&'Delivery-date:'& header line"
15690 Exim's transports have an option for adding a &'Delivery-date:'& header to a
15691 message when it is delivered, in exactly the same way as &'Return-path:'& is
15692 handled. &'Delivery-date:'& records the actual time of delivery. Such headers
15693 should not be present in incoming messages, and this option causes them to be
15694 removed at the time the message is received, to avoid any problems that might
15695 occur when a delivered message is subsequently sent on to some other recipient.
15697 .option disable_fsync main boolean false
15698 .cindex "&[fsync()]&, disabling"
15699 This option is available only if Exim was built with the compile-time option
15700 ENABLE_DISABLE_FSYNC. When this is not set, a reference to &%disable_fsync%& in
15701 a runtime configuration generates an &"unknown option"& error. You should not
15702 build Exim with ENABLE_DISABLE_FSYNC or set &%disable_fsync%& unless you
15703 really, really, really understand what you are doing. &'No pre-compiled
15704 distributions of Exim should ever make this option available.'&
15706 When &%disable_fsync%& is set true, Exim no longer calls &[fsync()]& to force
15707 updated files' data to be written to disc before continuing. Unexpected events
15708 such as crashes and power outages may cause data to be lost or scrambled.
15709 Here be Dragons. &*Beware.*&
15712 .option disable_ipv6 main boolean false
15713 .cindex "IPv6" "disabling"
15714 If this option is set true, even if the Exim binary has IPv6 support, no IPv6
15715 activities take place. AAAA records are never looked up, and any IPv6 addresses
15716 that are listed in &%local_interfaces%&, data for the &%manualroute%& router,
15717 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
15718 to handle IPv6 literal addresses.
15721 .option dkim_verify_hashes main "string list" "sha256 : sha512"
15722 .cindex DKIM "selecting signature algorithms"
15723 This option gives a list of hash types which are acceptable in signatures,
15724 and an order of processing.
15725 Signatures with algorithms not in the list will be ignored.
15727 Acceptable values include:
15734 Note that the acceptance of sha1 violates RFC 8301.
15736 .option dkim_verify_keytypes main "string list" "ed25519 : rsa"
15737 This option gives a list of key types which are acceptable in signatures,
15738 and an order of processing.
15739 Signatures with algorithms not in the list will be ignored.
15742 .option dkim_verify_min_keysizes main "string list" "rsa=1024 ed25519=250"
15743 This option gives a list of key sizes which are acceptable in signatures.
15744 The list is keyed by the algorithm type for the key; the values are in bits.
15745 Signatures with keys smaller than given by this option will fail verification.
15747 The default enforces the RFC 8301 minimum key size for RSA signatures.
15749 .option dkim_verify_minimal main boolean false
15750 If set to true, verification of signatures will terminate after the
15753 .option dkim_verify_signers main "domain list&!!" $dkim_signers
15754 .cindex DKIM "controlling calls to the ACL"
15755 This option gives a list of DKIM domains for which the DKIM ACL is run.
15756 It is expanded after the message is received; by default it runs
15757 the ACL once for each signature in the message.
15758 See section &<<SECDKIMVFY>>&.
15761 .option dmarc_forensic_sender main string&!! unset
15762 .option dmarc_history_file main string unset
15763 .option dmarc_tld_file main string unset
15764 .cindex DMARC "main section options"
15765 These options control DMARC processing.
15766 See section &<<SECDMARC>>& for details.
15769 .option dns_again_means_nonexist main "domain list&!!" unset
15770 .cindex "DNS" "&""try again""& response; overriding"
15771 DNS lookups give a &"try again"& response for the DNS errors
15772 &"non-authoritative host not found"& and &"SERVERFAIL"&. This can cause Exim to
15773 keep trying to deliver a message, or to give repeated temporary errors to
15774 incoming mail. Sometimes the effect is caused by a badly set up name server and
15775 may persist for a long time. If a domain which exhibits this problem matches
15776 anything in &%dns_again_means_nonexist%&, it is treated as if it did not exist.
15777 This option should be used with care. You can make it apply to reverse lookups
15778 by a setting such as this:
15780 dns_again_means_nonexist = *.in-addr.arpa
15782 This option applies to all DNS lookups that Exim does. It also applies when the
15783 &[gethostbyname()]& or &[getipnodebyname()]& functions give temporary errors,
15784 since these are most likely to be caused by DNS lookup problems. The
15785 &(dnslookup)& router has some options of its own for controlling what happens
15786 when lookups for MX or SRV records give temporary errors. These more specific
15787 options are applied after this global option.
15789 .option dns_check_names_pattern main string "see below"
15790 .cindex "DNS" "pre-check of name syntax"
15791 When this option is set to a non-empty string, it causes Exim to check domain
15792 names for characters that are not allowed in host names before handing them to
15793 the DNS resolver, because some resolvers give temporary errors for names that
15794 contain unusual characters. If a domain name contains any unwanted characters,
15795 a &"not found"& result is forced, and the resolver is not called. The check is
15796 done by matching the domain name against a regular expression, which is the
15797 value of this option. The default pattern is
15799 dns_check_names_pattern = \
15800 (?i)^(?>(?(1)\.|())[^\W_](?>[a-z0-9/-]*[^\W_])?)+$
15802 which permits only letters, digits, slashes, and hyphens in components, but
15803 they must start and end with a letter or digit. Slashes are not, in fact,
15804 permitted in host names, but they are found in certain NS records (which can be
15805 accessed in Exim by using a &%dnsdb%& lookup). If you set
15806 &%allow_utf8_domains%&, you must modify this pattern, or set the option to an
15809 .option dns_csa_search_limit main integer 5
15810 This option controls the depth of parental searching for CSA SRV records in the
15811 DNS, as described in more detail in section &<<SECTverifyCSA>>&.
15813 .option dns_csa_use_reverse main boolean true
15814 This option controls whether or not an IP address, given as a CSA domain, is
15815 reversed and looked up in the reverse DNS, as described in more detail in
15816 section &<<SECTverifyCSA>>&.
15818 .option dns_cname_loops main integer 1
15819 .cindex DNS "CNAME following"
15820 This option controls the following of CNAME chains, needed if the resolver does
15821 not do it internally.
15822 As of 2018 most should, and the default can be left.
15823 If you have an ancient one, a value of 10 is likely needed.
15825 The default value of one CNAME-follow is needed
15826 thanks to the observed return for an MX request,
15827 given no MX presence but a CNAME to an A, of the CNAME.
15830 .option dns_dnssec_ok main integer -1
15831 .cindex "DNS" "resolver options"
15832 .cindex "DNS" "DNSSEC"
15833 If this option is set to a non-negative number then Exim will initialise the
15834 DNS resolver library to either use or not use DNSSEC, overriding the system
15835 default. A value of 0 coerces DNSSEC off, a value of 1 coerces DNSSEC on.
15837 If the resolver library does not support DNSSEC then this option has no effect.
15839 On Linux with glibc 2.31 or newer this is insufficient, the resolver library
15840 will default to stripping out a successful validation status.
15841 This will break a previously working Exim installation.
15842 Provided that you do trust the resolver (ie, is on localhost) you can tell
15843 glibc to pass through any successful validation with a new option in
15844 &_/etc/resolv.conf_&:
15850 .option dns_ipv4_lookup main "domain list&!!" unset
15851 .cindex "IPv6" "DNS lookup for AAAA records"
15852 .cindex "DNS" "IPv6 lookup for AAAA records"
15853 .cindex DNS "IPv6 disabling"
15854 When Exim is compiled with IPv6 support and &%disable_ipv6%& is not set, it
15855 looks for IPv6 address records (AAAA records) as well as IPv4 address records
15856 (A records) when trying to find IP addresses for hosts, unless the host's
15857 domain matches this list.
15859 This is a fudge to help with name servers that give big delays or otherwise do
15860 not work for the AAAA record type. In due course, when the world's name
15861 servers have all been upgraded, there should be no need for this option.
15862 Note that all lookups, including those done for verification, are affected;
15863 this will result in verify failure for IPv6 connections or ones using names
15864 only valid for IPv6 addresses.
15867 .option dns_retrans main time 0s
15868 .cindex "DNS" "resolver options"
15869 .cindex timeout "dns lookup"
15870 .cindex "DNS" timeout
15871 The options &%dns_retrans%& and &%dns_retry%& can be used to set the
15872 retransmission and retry parameters for DNS lookups. Values of zero (the
15873 defaults) leave the system default settings unchanged. The first value is the
15874 time between retries, and the second is the number of retries. It isn't
15875 totally clear exactly how these settings affect the total time a DNS lookup may
15876 take. I haven't found any documentation about timeouts on DNS lookups; these
15877 parameter values are available in the external resolver interface structure,
15878 but nowhere does it seem to describe how they are used or what you might want
15880 See also the &%slow_lookup_log%& option.
15883 .option dns_retry main integer 0
15884 See &%dns_retrans%& above.
15887 .option dns_trust_aa main "domain list&!!" unset
15888 .cindex "DNS" "resolver options"
15889 .cindex "DNS" "DNSSEC"
15890 If this option is set then lookup results marked with the AA bit
15891 (Authoritative Answer) are trusted the same way as if they were
15892 DNSSEC-verified. The authority section's name of the answer must
15893 match with this expanded domain list.
15895 Use this option only if you talk directly to a resolver that is
15896 authoritative for some zones and does not set the AD (Authentic Data)
15897 bit in the answer. Some DNS servers may have an configuration option to
15898 mark the answers from their own zones as verified (they set the AD bit).
15899 Others do not have this option. It is considered as poor practice using
15900 a resolver that is an authoritative server for some zones.
15902 Use this option only if you really have to (e.g. if you want
15903 to use DANE for remote delivery to a server that is listed in the DNS
15904 zones that your resolver is authoritative for).
15906 If the DNS answer packet has the AA bit set and contains resource record
15907 in the answer section, the name of the first NS record appearing in the
15908 authority section is compared against the list. If the answer packet is
15909 authoritative but the answer section is empty, the name of the first SOA
15910 record in the authoritative section is used instead.
15912 .cindex "DNS" "resolver options"
15913 .option dns_use_edns0 main integer -1
15914 .cindex "DNS" "resolver options"
15915 .cindex "DNS" "EDNS0"
15916 .cindex "DNS" "OpenBSD
15917 If this option is set to a non-negative number then Exim will initialise the
15918 DNS resolver library to either use or not use EDNS0 extensions, overriding
15919 the system default. A value of 0 coerces EDNS0 off, a value of 1 coerces EDNS0
15922 If the resolver library does not support EDNS0 then this option has no effect.
15924 OpenBSD's asr resolver routines are known to ignore the EDNS0 option; this
15925 means that DNSSEC will not work with Exim on that platform either, unless Exim
15926 is linked against an alternative DNS client library.
15929 .option drop_cr main boolean false
15930 This is an obsolete option that is now a no-op. It used to affect the way Exim
15931 handled CR and LF characters in incoming messages. What happens now is
15932 described in section &<<SECTlineendings>>&.
15934 .option dsn_advertise_hosts main "host list&!!" unset
15935 .cindex "bounce messages" "success"
15936 .cindex "DSN" "success"
15937 .cindex "Delivery Status Notification" "success"
15938 .cindex "ESMTP extensions" DSN
15939 DSN extensions (RFC3461) will be advertised in the EHLO message to,
15940 and accepted from, these hosts.
15941 Hosts may use the NOTIFY and ORCPT options on RCPT TO commands,
15942 and RET and ENVID options on MAIL FROM commands.
15943 A NOTIFY=SUCCESS option requests success-DSN messages.
15944 A NOTIFY= option with no argument requests that no delay or failure DSNs
15946 &*Note*&: Supplying success-DSN messages has been criticised
15947 on privacy grounds; it can leak details of internal forwarding.
15949 .option dsn_from main "string&!!" "see below"
15950 .cindex "&'From:'& header line" "in bounces"
15951 .cindex "bounce messages" "&'From:'& line, specifying"
15952 This option can be used to vary the contents of &'From:'& header lines in
15953 bounces and other automatically generated messages (&"Delivery Status
15954 Notifications"& &-- hence the name of the option). The default setting is:
15956 dsn_from = Mail Delivery System <Mailer-Daemon@$qualify_domain>
15958 The value is expanded every time it is needed. If the expansion fails, a
15959 panic is logged, and the default value is used.
15961 .option envelope_to_remove main boolean true
15962 .cindex "&'Envelope-to:'& header line"
15963 Exim's transports have an option for adding an &'Envelope-to:'& header to a
15964 message when it is delivered, in exactly the same way as &'Return-path:'& is
15965 handled. &'Envelope-to:'& records the original recipient address from the
15966 message's envelope that caused the delivery to happen. Such headers should not
15967 be present in incoming messages, and this option causes them to be removed at
15968 the time the message is received, to avoid any problems that might occur when a
15969 delivered message is subsequently sent on to some other recipient.
15972 .option errors_copy main "string list&!!" unset
15973 .cindex "bounce message" "copy to other address"
15974 .cindex "copy of bounce message"
15975 Setting this option causes Exim to send bcc copies of bounce messages that it
15976 generates to other addresses. &*Note*&: This does not apply to bounce messages
15977 coming from elsewhere. The value of the option is a colon-separated list of
15978 items. Each item consists of a pattern, terminated by white space, followed by
15979 a comma-separated list of email addresses. If a pattern contains spaces, it
15980 must be enclosed in double quotes.
15982 Each pattern is processed in the same way as a single item in an address list
15983 (see section &<<SECTaddresslist>>&). When a pattern matches the recipient of
15984 the bounce message, the message is copied to the addresses on the list. The
15985 items are scanned in order, and once a matching one is found, no further items
15986 are examined. For example:
15988 errors_copy = spqr@mydomain postmaster@mydomain.example :\
15989 rqps@mydomain hostmaster@mydomain.example,\
15990 postmaster@mydomain.example
15992 .vindex "&$domain$&"
15993 .vindex "&$local_part$&"
15994 The address list is expanded before use. The expansion variables &$local_part$&
15995 and &$domain$& are set from the original recipient of the error message, and if
15996 there was any wildcard matching in the pattern, the expansion
15997 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%errors_copy%&"
15998 variables &$0$&, &$1$&, etc. are set in the normal way.
16001 .option errors_reply_to main string unset
16002 .cindex "bounce message" "&'Reply-to:'& in"
16003 By default, Exim's bounce and delivery warning messages contain the header line
16005 &`From: Mail Delivery System <Mailer-Daemon@`&&'qualify-domain'&&`>`&
16007 .oindex &%quota_warn_message%&
16008 where &'qualify-domain'& is the value of the &%qualify_domain%& option.
16009 A warning message that is generated by the &%quota_warn_message%& option in an
16010 &(appendfile)& transport may contain its own &'From:'& header line that
16011 overrides the default.
16013 Experience shows that people reply to bounce messages. If the
16014 &%errors_reply_to%& option is set, a &'Reply-To:'& header is added to bounce
16015 and warning messages. For example:
16017 errors_reply_to = postmaster@my.domain.example
16019 The value of the option is not expanded. It must specify a valid RFC 2822
16020 address. However, if a warning message that is generated by the
16021 &%quota_warn_message%& option in an &(appendfile)& transport contain its
16022 own &'Reply-To:'& header line, the value of the &%errors_reply_to%& option is
16026 .option event_action main string&!! unset
16028 This option declares a string to be expanded for Exim's events mechanism.
16029 For details see chapter &<<CHAPevents>>&.
16032 .option exim_group main string "compile-time configured"
16033 .cindex "gid (group id)" "Exim's own"
16034 .cindex "Exim group"
16035 This option changes the gid under which Exim runs when it gives up root
16036 privilege. The default value is compiled into the binary. The value of this
16037 option is used only when &%exim_user%& is also set. Unless it consists entirely
16038 of digits, the string is looked up using &[getgrnam()]&, and failure causes a
16039 configuration error. See chapter &<<CHAPsecurity>>& for a discussion of
16043 .option exim_path main string "see below"
16044 .cindex "Exim binary, path name"
16045 This option specifies the path name of the Exim binary, which is used when Exim
16046 needs to re-exec itself. The default is set up to point to the file &'exim'& in
16047 the directory configured at compile time by the BIN_DIRECTORY setting. It
16048 is necessary to change &%exim_path%& if, exceptionally, Exim is run from some
16050 &*Warning*&: Do not use a macro to define the value of this option, because
16051 you will break those Exim utilities that scan the configuration file to find
16052 where the binary is. (They then use the &%-bP%& option to extract option
16053 settings such as the value of &%spool_directory%&.)
16056 .option exim_user main string "compile-time configured"
16057 .cindex "uid (user id)" "Exim's own"
16058 .cindex "Exim user"
16059 This option changes the uid under which Exim runs when it gives up root
16060 privilege. The default value is compiled into the binary. Ownership of the run
16061 time configuration file and the use of the &%-C%& and &%-D%& command line
16062 options is checked against the values in the binary, not what is set here.
16064 Unless it consists entirely of digits, the string is looked up using
16065 &[getpwnam()]&, and failure causes a configuration error. If &%exim_group%& is
16066 not also supplied, the gid is taken from the result of &[getpwnam()]& if it is
16067 used. See chapter &<<CHAPsecurity>>& for a discussion of security issues.
16070 .option exim_version main string "current version"
16071 .cindex "Exim version"
16072 .cindex customizing "version number"
16073 .cindex "version number of Exim" override
16074 This option overrides the &$version_number$&/&$exim_version$& that Exim reports in
16075 various places. Use with care; this may fool stupid security scanners.
16078 .option extra_local_interfaces main "string list" unset
16079 This option defines network interfaces that are to be considered local when
16080 routing, but which are not used for listening by the daemon. See section
16081 &<<SECTreclocipadd>>& for details.
16084 . Allow this long option name to split; give it unsplit as a fifth argument
16085 . for the automatic .oindex that is generated by .option.
16087 .option "extract_addresses_remove_arguments" main boolean true &&&
16088 extract_addresses_remove_arguments
16090 .cindex "command line" "addresses with &%-t%&"
16091 .cindex "Sendmail compatibility" "&%-t%& option"
16092 According to some Sendmail documentation (Sun, IRIX, HP-UX), if any addresses
16093 are present on the command line when the &%-t%& option is used to build an
16094 envelope from a message's &'To:'&, &'Cc:'& and &'Bcc:'& headers, the command
16095 line addresses are removed from the recipients list. This is also how Smail
16096 behaves. However, other Sendmail documentation (the O'Reilly book) states that
16097 command line addresses are added to those obtained from the header lines. When
16098 &%extract_addresses_remove_arguments%& is true (the default), Exim subtracts
16099 argument headers. If it is set false, Exim adds rather than removes argument
16103 .option finduser_retries main integer 0
16104 .cindex "NIS, retrying user lookups"
16105 On systems running NIS or other schemes in which user and group information is
16106 distributed from a remote system, there can be times when &[getpwnam()]& and
16107 related functions fail, even when given valid data, because things time out.
16108 Unfortunately these failures cannot be distinguished from genuine &"not found"&
16109 errors. If &%finduser_retries%& is set greater than zero, Exim will try that
16110 many extra times to find a user or a group, waiting for one second between
16113 .cindex "&_/etc/passwd_&" "multiple reading of"
16114 You should not set this option greater than zero if your user information is in
16115 a traditional &_/etc/passwd_& file, because it will cause Exim needlessly to
16116 search the file multiple times for non-existent users, and also cause delay.
16120 .option freeze_tell main "string list, comma separated" unset
16121 .cindex "freezing messages" "sending a message when freezing"
16122 On encountering certain errors, or when configured to do so in a system filter,
16123 ACL, or special router, Exim freezes a message. This means that no further
16124 delivery attempts take place until an administrator thaws the message, or the
16125 &%auto_thaw%&, &%ignore_bounce_errors_after%&, or &%timeout_frozen_after%&
16126 feature cause it to be processed. If &%freeze_tell%& is set, Exim generates a
16127 warning message whenever it freezes something, unless the message it is
16128 freezing is a locally-generated bounce message. (Without this exception there
16129 is the possibility of looping.) The warning message is sent to the addresses
16130 supplied as the comma-separated value of this option. If several of the
16131 message's addresses cause freezing, only a single message is sent. If the
16132 freezing was automatic, the reason(s) for freezing can be found in the message
16133 log. If you configure freezing in a filter or ACL, you must arrange for any
16134 logging that you require.
16137 .option gecos_name main string&!! unset
16139 .cindex "&""gecos""& field, parsing"
16140 Some operating systems, notably HP-UX, use the &"gecos"& field in the system
16141 password file to hold other information in addition to users' real names. Exim
16142 looks up this field for use when it is creating &'Sender:'& or &'From:'&
16143 headers. If either &%gecos_pattern%& or &%gecos_name%& are unset, the contents
16144 of the field are used unchanged, except that, if an ampersand is encountered,
16145 it is replaced by the user's login name with the first character forced to
16146 upper case, since this is a convention that is observed on many systems.
16148 When these options are set, &%gecos_pattern%& is treated as a regular
16149 expression that is to be applied to the field (again with && replaced by the
16150 login name), and if it matches, &%gecos_name%& is expanded and used as the
16153 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%gecos_name%&"
16154 Numeric variables such as &$1$&, &$2$&, etc. can be used in the expansion to
16155 pick up sub-fields that were matched by the pattern. In HP-UX, where the user's
16156 name terminates at the first comma, the following can be used:
16158 gecos_pattern = ([^,]*)
16162 .option gecos_pattern main string unset
16163 See &%gecos_name%& above.
16166 .option gnutls_compat_mode main boolean unset
16167 This option controls whether GnuTLS is used in compatibility mode in an Exim
16168 server. This reduces security slightly, but improves interworking with older
16169 implementations of TLS.
16172 .option gnutls_allow_auto_pkcs11 main boolean unset
16173 This option will let GnuTLS (2.12.0 or later) autoload PKCS11 modules with
16174 the p11-kit configuration files in &_/etc/pkcs11/modules/_&.
16177 &url(https://www.gnutls.org/manual/gnutls.html#Smart-cards-and-HSMs)
16182 .option headers_charset main string "see below"
16183 This option sets a default character set for translating from encoded MIME
16184 &"words"& in header lines, when referenced by an &$h_xxx$& expansion item. The
16185 default is the value of HEADERS_CHARSET in &_Local/Makefile_&. The
16186 ultimate default is ISO-8859-1. For more details see the description of header
16187 insertions in section &<<SECTexpansionitems>>&.
16191 .option header_maxsize main integer "see below"
16192 .cindex "header section" "maximum size of"
16193 .cindex "limit" "size of message header section"
16194 This option controls the overall maximum size of a message's header
16195 section. The default is the value of HEADER_MAXSIZE in
16196 &_Local/Makefile_&; the default for that is 1M. Messages with larger header
16197 sections are rejected.
16200 .option header_line_maxsize main integer 0
16201 .cindex "header lines" "maximum size of"
16202 .cindex "limit" "size of one header line"
16203 This option limits the length of any individual header line in a message, after
16204 all the continuations have been joined together. Messages with individual
16205 header lines that are longer than the limit are rejected. The default value of
16206 zero means &"no limit"&.
16211 .option helo_accept_junk_hosts main "host list&!!" unset
16212 .cindex "HELO" "accepting junk data"
16213 .cindex "EHLO" "accepting junk data"
16214 Exim checks the syntax of HELO and EHLO commands for incoming SMTP
16215 mail, and gives an error response for invalid data. Unfortunately, there are
16216 some SMTP clients that send syntactic junk. They can be accommodated by setting
16217 this option. Note that this is a syntax check only. See &%helo_verify_hosts%&
16218 if you want to do semantic checking.
16219 See also &%helo_allow_chars%& for a way of extending the permitted character
16223 .option helo_allow_chars main string unset
16224 .cindex "HELO" "underscores in"
16225 .cindex "EHLO" "underscores in"
16226 .cindex "underscore in EHLO/HELO"
16227 This option can be set to a string of rogue characters that are permitted in
16228 all EHLO and HELO names in addition to the standard letters, digits,
16229 hyphens, and dots. If you really must allow underscores, you can set
16231 helo_allow_chars = _
16233 Note that the value is one string, not a list.
16236 .option helo_lookup_domains main "domain list&!!" &`@:@[]`&
16237 .cindex "HELO" "forcing reverse lookup"
16238 .cindex "EHLO" "forcing reverse lookup"
16239 If the domain given by a client in a HELO or EHLO command matches this
16240 list, a reverse lookup is done in order to establish the host's true name. The
16241 default forces a lookup if the client host gives the server's name or any of
16242 its IP addresses (in brackets), something that broken clients have been seen to
16246 .option helo_try_verify_hosts main "host list&!!" unset
16247 .cindex "HELO verifying" "optional"
16248 .cindex "EHLO" "verifying, optional"
16249 By default, Exim just checks the syntax of HELO and EHLO commands (see
16250 &%helo_accept_junk_hosts%& and &%helo_allow_chars%&). However, some sites like
16251 to do more extensive checking of the data supplied by these commands. The ACL
16252 condition &`verify = helo`& is provided to make this possible.
16253 Formerly, it was necessary also to set this option (&%helo_try_verify_hosts%&)
16254 to force the check to occur. From release 4.53 onwards, this is no longer
16255 necessary. If the check has not been done before &`verify = helo`& is
16256 encountered, it is done at that time. Consequently, this option is obsolete.
16257 Its specification is retained here for backwards compatibility.
16259 When an EHLO or HELO command is received, if the calling host matches
16260 &%helo_try_verify_hosts%&, Exim checks that the host name given in the HELO or
16261 EHLO command either:
16264 is an IP literal matching the calling address of the host, or
16266 .cindex "DNS" "reverse lookup"
16267 .cindex "reverse DNS lookup"
16268 matches the host name that Exim obtains by doing a reverse lookup of the
16269 calling host address, or
16271 when looked up in DNS yields the calling host address.
16274 However, the EHLO or HELO command is not rejected if any of the checks
16275 fail. Processing continues, but the result of the check is remembered, and can
16276 be detected later in an ACL by the &`verify = helo`& condition.
16278 If DNS was used for successful verification, the variable
16279 .cindex "DNS" "DNSSEC"
16280 &$helo_verify_dnssec$& records the DNSSEC status of the lookups.
16282 .option helo_verify_hosts main "host list&!!" unset
16283 .cindex "HELO verifying" "mandatory"
16284 .cindex "EHLO" "verifying, mandatory"
16285 Like &%helo_try_verify_hosts%&, this option is obsolete, and retained only for
16286 backwards compatibility. For hosts that match this option, Exim checks the host
16287 name given in the HELO or EHLO in the same way as for
16288 &%helo_try_verify_hosts%&. If the check fails, the HELO or EHLO command is
16289 rejected with a 550 error, and entries are written to the main and reject logs.
16290 If a MAIL command is received before EHLO or HELO, it is rejected with a 503
16293 .option hold_domains main "domain list&!!" unset
16294 .cindex "domain" "delaying delivery"
16295 .cindex "delivery" "delaying certain domains"
16296 This option allows mail for particular domains to be held in the queue
16297 manually. The option is overridden if a message delivery is forced with the
16298 &%-M%&, &%-qf%&, &%-Rf%& or &%-Sf%& options, and also while testing or
16299 verifying addresses using &%-bt%& or &%-bv%&. Otherwise, if a domain matches an
16300 item in &%hold_domains%&, no routing or delivery for that address is done, and
16301 it is deferred every time the message is looked at.
16303 This option is intended as a temporary operational measure for delaying the
16304 delivery of mail while some problem is being sorted out, or some new
16305 configuration tested. If you just want to delay the processing of some
16306 domains until a queue run occurs, you should use &%queue_domains%& or
16307 &%queue_smtp_domains%&, not &%hold_domains%&.
16309 A setting of &%hold_domains%& does not override Exim's code for removing
16310 messages from the queue if they have been there longer than the longest retry
16311 time in any retry rule. If you want to hold messages for longer than the normal
16312 retry times, insert a dummy retry rule with a long retry time.
16315 .option host_lookup main "host list&!!" unset
16316 .cindex "host name" "lookup, forcing"
16317 Exim does not look up the name of a calling host from its IP address unless it
16318 is required to compare against some host list, or the host matches
16319 &%helo_try_verify_hosts%& or &%helo_verify_hosts%&, or the host matches this
16320 option (which normally contains IP addresses rather than host names). The
16321 default configuration file contains
16325 which causes a lookup to happen for all hosts. If the expense of these lookups
16326 is felt to be too great, the setting can be changed or removed.
16328 After a successful reverse lookup, Exim does a forward lookup on the name it
16329 has obtained, to verify that it yields the IP address that it started with. If
16330 this check fails, Exim behaves as if the name lookup failed.
16332 .vindex "&$host_lookup_failed$&"
16333 .vindex "&$sender_host_name$&"
16334 After any kind of failure, the host name (in &$sender_host_name$&) remains
16335 unset, and &$host_lookup_failed$& is set to the string &"1"&. See also
16336 &%dns_again_means_nonexist%&, &%helo_lookup_domains%&, and
16337 &`verify = reverse_host_lookup`& in ACLs.
16340 .option host_lookup_order main "string list" &`bydns:byaddr`&
16341 This option specifies the order of different lookup methods when Exim is trying
16342 to find a host name from an IP address. The default is to do a DNS lookup
16343 first, and then to try a local lookup (using &[gethostbyaddr()]& or equivalent)
16344 if that fails. You can change the order of these lookups, or omit one entirely,
16347 &*Warning*&: The &"byaddr"& method does not always yield aliases when there are
16348 multiple PTR records in the DNS and the IP address is not listed in
16349 &_/etc/hosts_&. Different operating systems give different results in this
16350 case. That is why the default tries a DNS lookup first.
16354 .option host_reject_connection main "host list&!!" unset
16355 .cindex "host" "rejecting connections from"
16356 If this option is set, incoming SMTP calls from the hosts listed are rejected
16357 as soon as the connection is made.
16358 This option is obsolete, and retained only for backward compatibility, because
16359 nowadays the ACL specified by &%acl_smtp_connect%& can also reject incoming
16360 connections immediately.
16362 The ability to give an immediate rejection (either by this option or using an
16363 ACL) is provided for use in unusual cases. Many hosts will just try again,
16364 sometimes without much delay. Normally, it is better to use an ACL to reject
16365 incoming messages at a later stage, such as after RCPT commands. See
16366 chapter &<<CHAPACL>>&.
16369 .option hosts_connection_nolog main "host list&!!" unset
16370 .cindex "host" "not logging connections from"
16371 This option defines a list of hosts for which connection logging does not
16372 happen, even though the &%smtp_connection%& log selector is set. For example,
16373 you might want not to log SMTP connections from local processes, or from
16374 127.0.0.1, or from your local LAN. This option is consulted in the main loop of
16375 the daemon; you should therefore strive to restrict its value to a short inline
16376 list of IP addresses and networks. To disable logging SMTP connections from
16377 local processes, you must create a host list with an empty item. For example:
16379 hosts_connection_nolog = :
16381 If the &%smtp_connection%& log selector is not set, this option has no effect.
16384 .option hosts_require_alpn main "host list&!!" unset
16385 .cindex ALPN "require negotiation in server"
16387 .cindex TLS "Application Layer Protocol Names"
16388 If the TLS library supports ALPN
16389 then a successful negotiation of ALPN will be required for any client
16390 matching the list, for TLS to be used.
16391 See also the &%tls_alpn%& option.
16393 &*Note*&: prevention of fallback to in-clear connection is not
16394 managed by this option, and should be done separately.
16397 .option hosts_proxy main "host list&!!" unset
16398 .cindex proxy "proxy protocol"
16399 This option enables use of Proxy Protocol proxies for incoming
16400 connections. For details see section &<<SECTproxyInbound>>&.
16403 .option hosts_treat_as_local main "domain list&!!" unset
16404 .cindex "local host" "domains treated as"
16405 .cindex "host" "treated as local"
16406 If this option is set, any host names that match the domain list are treated as
16407 if they were the local host when Exim is scanning host lists obtained from MX
16409 or other sources. Note that the value of this option is a domain list, not a
16410 host list, because it is always used to check host names, not IP addresses.
16412 This option also applies when Exim is matching the special items
16413 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`& in a domain list (see
16414 section &<<SECTdomainlist>>&), and when checking the &%hosts%& option in the
16415 &(smtp)& transport for the local host (see the &%allow_localhost%& option in
16416 that transport). See also &%local_interfaces%&, &%extra_local_interfaces%&, and
16417 chapter &<<CHAPinterfaces>>&, which contains a discussion about local network
16418 interfaces and recognizing the local host.
16421 .option ibase_servers main "string list" unset
16422 .cindex "InterBase" "server list"
16423 This option provides a list of InterBase servers and associated connection data,
16424 to be used in conjunction with &(ibase)& lookups (see section &<<SECID72>>&).
16425 The option is available only if Exim has been built with InterBase support.
16429 .option ignore_bounce_errors_after main time 10w
16430 .cindex "bounce message" "discarding"
16431 .cindex "discarding bounce message"
16432 This option affects the processing of bounce messages that cannot be delivered,
16433 that is, those that suffer a permanent delivery failure. (Bounce messages that
16434 suffer temporary delivery failures are of course retried in the usual way.)
16436 After a permanent delivery failure, bounce messages are frozen,
16437 because there is no sender to whom they can be returned. When a frozen bounce
16438 message has been in the queue for more than the given time, it is unfrozen at
16439 the next queue run, and a further delivery is attempted. If delivery fails
16440 again, the bounce message is discarded. This makes it possible to keep failed
16441 bounce messages around for a shorter time than the normal maximum retry time
16442 for frozen messages. For example,
16444 ignore_bounce_errors_after = 12h
16446 retries failed bounce message deliveries after 12 hours, discarding any further
16447 failures. If the value of this option is set to a zero time period, bounce
16448 failures are discarded immediately. Setting a very long time (as in the default
16449 value) has the effect of disabling this option. For ways of automatically
16450 dealing with other kinds of frozen message, see &%auto_thaw%& and
16451 &%timeout_frozen_after%&.
16454 .option ignore_fromline_hosts main "host list&!!" unset
16455 .cindex "&""From""& line"
16456 .cindex "UUCP" "&""From""& line"
16457 Some broken SMTP clients insist on sending a UUCP-like &"From&~"& line before
16458 the headers of a message. By default this is treated as the start of the
16459 message's body, which means that any following headers are not recognized as
16460 such. Exim can be made to ignore it by setting &%ignore_fromline_hosts%& to
16461 match those hosts that insist on sending it. If the sender is actually a local
16462 process rather than a remote host, and is using &%-bs%& to inject the messages,
16463 &%ignore_fromline_local%& must be set to achieve this effect.
16466 .option ignore_fromline_local main boolean false
16467 See &%ignore_fromline_hosts%& above.
16469 .option keep_environment main "string list" unset
16470 .cindex "environment" "values from"
16471 This option contains a string list of environment variables to keep.
16472 You have to trust these variables or you have to be sure that
16473 these variables do not impose any security risk. Keep in mind that
16474 during the startup phase Exim is running with an effective UID 0 in most
16475 installations. As the default value is an empty list, the default
16476 environment for using libraries, running embedded Perl code, or running
16477 external binaries is empty, and does not not even contain PATH or HOME.
16479 Actually the list is interpreted as a list of patterns
16480 (&<<SECTlistexpand>>&), except that it is not expanded first.
16482 WARNING: Macro substitution is still done first, so having a macro
16483 FOO and having FOO_HOME in your &%keep_environment%& option may have
16484 unexpected results. You may work around this using a regular expression
16485 that does not match the macro name: ^[F]OO_HOME$.
16487 Current versions of Exim issue a warning during startup if you do not mention
16488 &%keep_environment%& in your runtime configuration file and if your
16489 current environment is not empty. Future versions may not issue that warning
16492 See the &%add_environment%& main config option for a way to set
16493 environment variables to a fixed value. The environment for &(pipe)&
16494 transports is handled separately, see section &<<SECTpipeenv>>& for
16498 .option keep_malformed main time 4d
16499 This option specifies the length of time to keep messages whose spool files
16500 have been corrupted in some way. This should, of course, never happen. At the
16501 next attempt to deliver such a message, it gets removed. The incident is
16505 .option ldap_ca_cert_dir main string unset
16506 .cindex "LDAP", "TLS CA certificate directory"
16507 .cindex certificate "directory for LDAP"
16508 This option indicates which directory contains CA certificates for verifying
16509 a TLS certificate presented by an LDAP server.
16510 While Exim does not provide a default value, your SSL library may.
16511 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
16512 and constrained to be a directory.
16515 .option ldap_ca_cert_file main string unset
16516 .cindex "LDAP", "TLS CA certificate file"
16517 .cindex certificate "file for LDAP"
16518 This option indicates which file contains CA certificates for verifying
16519 a TLS certificate presented by an LDAP server.
16520 While Exim does not provide a default value, your SSL library may.
16521 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
16522 and constrained to be a file.
16525 .option ldap_cert_file main string unset
16526 .cindex "LDAP" "TLS client certificate file"
16527 .cindex certificate "file for LDAP"
16528 This option indicates which file contains an TLS client certificate which
16529 Exim should present to the LDAP server during TLS negotiation.
16530 Should be used together with &%ldap_cert_key%&.
16533 .option ldap_cert_key main string unset
16534 .cindex "LDAP" "TLS client key file"
16535 .cindex certificate "key for LDAP"
16536 This option indicates which file contains the secret/private key to use
16537 to prove identity to the LDAP server during TLS negotiation.
16538 Should be used together with &%ldap_cert_file%&, which contains the
16539 identity to be proven.
16542 .option ldap_cipher_suite main string unset
16543 .cindex "LDAP" "TLS cipher suite"
16544 This controls the TLS cipher-suite negotiation during TLS negotiation with
16545 the LDAP server. See &<<SECTreqciphssl>>& for more details of the format of
16546 cipher-suite options with OpenSSL (as used by LDAP client libraries).
16549 .option ldap_default_servers main "string list" unset
16550 .cindex "LDAP" "default servers"
16551 This option provides a list of LDAP servers which are tried in turn when an
16552 LDAP query does not contain a server. See section &<<SECTforldaque>>& for
16553 details of LDAP queries. This option is available only when Exim has been built
16557 .option ldap_require_cert main string unset.
16558 .cindex "LDAP" "policy for LDAP server TLS cert presentation"
16559 This should be one of the values "hard", "demand", "allow", "try" or "never".
16560 A value other than one of these is interpreted as "never".
16561 See the entry "TLS_REQCERT" in your system man page for ldap.conf(5).
16562 Although Exim does not set a default, the LDAP library probably defaults
16566 .option ldap_start_tls main boolean false
16567 .cindex "LDAP" "whether or not to negotiate TLS"
16568 If set, Exim will attempt to negotiate TLS with the LDAP server when
16569 connecting on a regular LDAP port. This is the LDAP equivalent of SMTP's
16570 "STARTTLS". This is distinct from using "ldaps", which is the LDAP form
16572 In the event of failure to negotiate TLS, the action taken is controlled
16573 by &%ldap_require_cert%&.
16574 This option is ignored for &`ldapi`& connections.
16577 .option ldap_version main integer unset
16578 .cindex "LDAP" "protocol version, forcing"
16579 This option can be used to force Exim to set a specific protocol version for
16580 LDAP. If it option is unset, it is shown by the &%-bP%& command line option as
16581 -1. When this is the case, the default is 3 if LDAP_VERSION3 is defined in
16582 the LDAP headers; otherwise it is 2. This option is available only when Exim
16583 has been built with LDAP support.
16587 .option local_from_check main boolean true
16588 .cindex "&'Sender:'& header line" "disabling addition of"
16589 .cindex "&'From:'& header line" "disabling checking of"
16590 When a message is submitted locally (that is, not over a TCP/IP connection) by
16591 an untrusted user, Exim removes any existing &'Sender:'& header line, and
16592 checks that the &'From:'& header line matches the login of the calling user and
16593 the domain specified by &%qualify_domain%&.
16595 &*Note*&: An unqualified address (no domain) in the &'From:'& header in a
16596 locally submitted message is automatically qualified by Exim, unless the
16597 &%-bnq%& command line option is used.
16599 You can use &%local_from_prefix%& and &%local_from_suffix%& to permit affixes
16600 on the local part. If the &'From:'& header line does not match, Exim adds a
16601 &'Sender:'& header with an address constructed from the calling user's login
16602 and the default qualify domain.
16604 If &%local_from_check%& is set false, the &'From:'& header check is disabled,
16605 and no &'Sender:'& header is ever added. If, in addition, you want to retain
16606 &'Sender:'& header lines supplied by untrusted users, you must also set
16607 &%local_sender_retain%& to be true.
16609 .cindex "envelope from"
16610 .cindex "envelope sender"
16611 These options affect only the header lines in the message. The envelope sender
16612 is still forced to be the login id at the qualify domain unless
16613 &%untrusted_set_sender%& permits the user to supply an envelope sender.
16615 For messages received over TCP/IP, an ACL can specify &"submission mode"& to
16616 request similar header line checking. See section &<<SECTthesenhea>>&, which
16617 has more details about &'Sender:'& processing.
16622 .option local_from_prefix main string unset
16623 When Exim checks the &'From:'& header line of locally submitted messages for
16624 matching the login id (see &%local_from_check%& above), it can be configured to
16625 ignore certain prefixes and suffixes in the local part of the address. This is
16626 done by setting &%local_from_prefix%& and/or &%local_from_suffix%& to
16627 appropriate lists, in the same form as the &%local_part_prefix%& and
16628 &%local_part_suffix%& router options (see chapter &<<CHAProutergeneric>>&). For
16631 local_from_prefix = *-
16633 is set, a &'From:'& line containing
16635 From: anything-user@your.domain.example
16637 will not cause a &'Sender:'& header to be added if &'user@your.domain.example'&
16638 matches the actual sender address that is constructed from the login name and
16642 .option local_from_suffix main string unset
16643 See &%local_from_prefix%& above.
16646 .option local_interfaces main "string list" "see below"
16647 This option controls which network interfaces are used by the daemon for
16648 listening; they are also used to identify the local host when routing. Chapter
16649 &<<CHAPinterfaces>>& contains a full description of this option and the related
16650 options &%daemon_smtp_ports%&, &%extra_local_interfaces%&,
16651 &%hosts_treat_as_local%&, and &%tls_on_connect_ports%&. The default value for
16652 &%local_interfaces%& is
16654 local_interfaces = 0.0.0.0
16656 when Exim is built without IPv6 support; otherwise it is
16658 local_interfaces = <; ::0 ; 0.0.0.0
16661 .option local_scan_timeout main time 5m
16662 .cindex "timeout" "for &[local_scan()]& function"
16663 .cindex "&[local_scan()]& function" "timeout"
16664 This timeout applies to the &[local_scan()]& function (see chapter
16665 &<<CHAPlocalscan>>&). Zero means &"no timeout"&. If the timeout is exceeded,
16666 the incoming message is rejected with a temporary error if it is an SMTP
16667 message. For a non-SMTP message, the message is dropped and Exim ends with a
16668 non-zero code. The incident is logged on the main and reject logs.
16672 .option local_sender_retain main boolean false
16673 .cindex "&'Sender:'& header line" "retaining from local submission"
16674 When a message is submitted locally (that is, not over a TCP/IP connection) by
16675 an untrusted user, Exim removes any existing &'Sender:'& header line. If you
16676 do not want this to happen, you must set &%local_sender_retain%&, and you must
16677 also set &%local_from_check%& to be false (Exim will complain if you do not).
16678 See also the ACL modifier &`control = suppress_local_fixups`&. Section
16679 &<<SECTthesenhea>>& has more details about &'Sender:'& processing.
16684 .option localhost_number main string&!! unset
16685 .cindex "host" "locally unique number for"
16686 .cindex "message ids" "with multiple hosts"
16687 .vindex "&$localhost_number$&"
16688 Exim's message ids are normally unique only within the local host. If
16689 uniqueness among a set of hosts is required, each host must set a different
16690 value for the &%localhost_number%& option. The string is expanded immediately
16691 after reading the configuration file (so that a number can be computed from the
16692 host name, for example) and the result of the expansion must be a number in the
16693 range 0&--16 (or 0&--10 on operating systems with case-insensitive file
16694 systems). This is available in subsequent string expansions via the variable
16695 &$localhost_number$&. When &%localhost_number is set%&, the final two
16696 characters of the message id, instead of just being a fractional part of the
16697 time, are computed from the time and the local host number as described in
16698 section &<<SECTmessiden>>&.
16702 .option log_file_path main "string list&!!" "set at compile time"
16703 .cindex "log" "file path for"
16704 This option sets the path which is used to determine the names of Exim's log
16705 files, or indicates that logging is to be to syslog, or both. It is expanded
16706 when Exim is entered, so it can, for example, contain a reference to the host
16707 name. If no specific path is set for the log files at compile or runtime,
16708 or if the option is unset at runtime (i.e. &`log_file_path = `&)
16709 they are written in a sub-directory called &_log_& in Exim's spool directory.
16710 A path must start with a slash.
16711 To send to syslog, use the word &"syslog"&.
16712 Chapter &<<CHAPlog>>& contains further details about Exim's logging, and
16713 section &<<SECTwhelogwri>>& describes how the contents of &%log_file_path%& are
16714 used. If this string is fixed at your installation (contains no expansion
16715 variables) it is recommended that you do not set this option in the
16716 configuration file, but instead supply the path using LOG_FILE_PATH in
16717 &_Local/Makefile_& so that it is available to Exim for logging errors detected
16718 early on &-- in particular, failure to read the configuration file.
16721 .option log_selector main string unset
16722 .cindex "log" "selectors"
16723 This option can be used to reduce or increase the number of things that Exim
16724 writes to its log files. Its argument is made up of names preceded by plus or
16725 minus characters. For example:
16727 log_selector = +arguments -retry_defer
16729 A list of possible names and what they control is given in the chapter on
16730 logging, in section &<<SECTlogselector>>&.
16733 .option log_timezone main boolean false
16734 .cindex "log" "timezone for entries"
16735 .vindex "&$tod_log$&"
16736 .vindex "&$tod_zone$&"
16737 By default, the timestamps on log lines are in local time without the
16738 timezone. This means that if your timezone changes twice a year, the timestamps
16739 in log lines are ambiguous for an hour when the clocks go back. One way of
16740 avoiding this problem is to set the timezone to UTC. An alternative is to set
16741 &%log_timezone%& true. This turns on the addition of the timezone offset to
16742 timestamps in log lines. Turning on this option can add quite a lot to the size
16743 of log files because each line is extended by 6 characters. Note that the
16744 &$tod_log$& variable contains the log timestamp without the zone, but there is
16745 another variable called &$tod_zone$& that contains just the timezone offset.
16748 .option lookup_open_max main integer 25
16749 .cindex "too many open files"
16750 .cindex "open files, too many"
16751 .cindex "file" "too many open"
16752 .cindex "lookup" "maximum open files"
16753 .cindex "limit" "open files for lookups"
16754 This option limits the number of simultaneously open files for single-key
16755 lookups that use regular files (that is, &(lsearch)&, &(dbm)&, and &(cdb)&).
16756 Exim normally keeps these files open during routing, because often the same
16757 file is required several times. If the limit is reached, Exim closes the least
16758 recently used file. Note that if you are using the &'ndbm'& library, it
16759 actually opens two files for each logical DBM database, though it still counts
16760 as one for the purposes of &%lookup_open_max%&. If you are getting &"too many
16761 open files"& errors with NDBM, you need to reduce the value of
16762 &%lookup_open_max%&.
16765 .option max_username_length main integer 0
16766 .cindex "length of login name"
16767 .cindex "user name" "maximum length"
16768 .cindex "limit" "user name length"
16769 Some operating systems are broken in that they truncate long arguments to
16770 &[getpwnam()]& to eight characters, instead of returning &"no such user"&. If
16771 this option is set greater than zero, any attempt to call &[getpwnam()]& with
16772 an argument that is longer behaves as if &[getpwnam()]& failed.
16775 .option message_body_newlines main bool false
16776 .cindex "message body" "newlines in variables"
16777 .cindex "newline" "in message body variables"
16778 .vindex "&$message_body$&"
16779 .vindex "&$message_body_end$&"
16780 By default, newlines in the message body are replaced by spaces when setting
16781 the &$message_body$& and &$message_body_end$& expansion variables. If this
16782 option is set true, this no longer happens.
16785 .option message_body_visible main integer 500
16786 .cindex "body of message" "visible size"
16787 .cindex "message body" "visible size"
16788 .vindex "&$message_body$&"
16789 .vindex "&$message_body_end$&"
16790 This option specifies how much of a message's body is to be included in the
16791 &$message_body$& and &$message_body_end$& expansion variables.
16794 .option message_id_header_domain main string&!! unset
16795 .cindex "&'Message-ID:'& header line"
16796 If this option is set, the string is expanded and used as the right hand side
16797 (domain) of the &'Message-ID:'& header that Exim creates if a
16798 locally-originated incoming message does not have one. &"Locally-originated"&
16799 means &"not received over TCP/IP."&
16800 Otherwise, the primary host name is used.
16801 Only letters, digits, dot and hyphen are accepted; any other characters are
16802 replaced by hyphens. If the expansion is forced to fail, or if the result is an
16803 empty string, the option is ignored.
16806 .option message_id_header_text main string&!! unset
16807 If this variable is set, the string is expanded and used to augment the text of
16808 the &'Message-id:'& header that Exim creates if a locally-originated incoming
16809 message does not have one. The text of this header is required by RFC 2822 to
16810 take the form of an address. By default, Exim uses its internal message id as
16811 the local part, and the primary host name as the domain. If this option is set,
16812 it is expanded, and provided the expansion is not forced to fail, and does not
16813 yield an empty string, the result is inserted into the header immediately
16814 before the @, separated from the internal message id by a dot. Any characters
16815 that are illegal in an address are automatically converted into hyphens. This
16816 means that variables such as &$tod_log$& can be used, because the spaces and
16817 colons will become hyphens.
16820 .option message_logs main boolean true
16821 .cindex "message logs" "disabling"
16822 .cindex "log" "message log; disabling"
16823 If this option is turned off, per-message log files are not created in the
16824 &_msglog_& spool sub-directory. This reduces the amount of disk I/O required by
16825 Exim, by reducing the number of files involved in handling a message from a
16826 minimum of four (header spool file, body spool file, delivery journal, and
16827 per-message log) to three. The other major I/O activity is Exim's main log,
16828 which is not affected by this option.
16831 .option message_size_limit main string&!! 50M
16832 .cindex "message" "size limit"
16833 .cindex "limit" "message size"
16834 .cindex "size" "of message, limit"
16835 This option limits the maximum size of message that Exim will process. The
16836 value is expanded for each incoming connection so, for example, it can be made
16837 to depend on the IP address of the remote host for messages arriving via
16838 TCP/IP. After expansion, the value must be a sequence of decimal digits,
16839 optionally followed by K or M.
16841 .cindex "SIZE" "ESMTP extension, advertising"
16842 .cindex "ESMTP extensions" SIZE
16843 If nonzero the value will be advertised as a parameter to the ESMTP SIZE
16844 service extension keyword.
16846 &*Note*&: This limit cannot be made to depend on a message's sender or any
16847 other properties of an individual message, because it has to be advertised in
16848 the server's response to EHLO. String expansion failure causes a temporary
16849 error. A value of zero means no limit, but its use is not recommended. See also
16850 &%bounce_return_size_limit%&.
16852 Incoming SMTP messages are failed with a 552 error if the limit is
16853 exceeded; locally-generated messages either get a stderr message or a delivery
16854 failure message to the sender, depending on the &%-oe%& setting. Rejection of
16855 an oversized message is logged in both the main and the reject logs. See also
16856 the generic transport option &%message_size_limit%&, which limits the size of
16857 message that an individual transport can process.
16859 If you use a virus-scanner and set this option to to a value larger than the
16860 maximum size that your virus-scanner is configured to support, you may get
16861 failures triggered by large mails. The right size to configure for the
16862 virus-scanner depends upon what data is passed and the options in use but it's
16863 probably safest to just set it to a little larger than this value. E.g., with a
16864 default Exim message size of 50M and a default ClamAV StreamMaxLength of 10M,
16865 some problems may result.
16867 A value of 0 will disable size limit checking; Exim will still advertise the
16868 SIZE extension in an EHLO response, but without a limit, so as to permit
16869 SMTP clients to still indicate the message size along with the MAIL verb.
16872 .option move_frozen_messages main boolean false
16873 .cindex "frozen messages" "moving"
16874 This option, which is available only if Exim has been built with the setting
16876 SUPPORT_MOVE_FROZEN_MESSAGES=yes
16878 in &_Local/Makefile_&, causes frozen messages and their message logs to be
16879 moved from the &_input_& and &_msglog_& directories on the spool to &_Finput_&
16880 and &_Fmsglog_&, respectively. There is currently no support in Exim or the
16881 standard utilities for handling such moved messages, and they do not show up in
16882 lists generated by &%-bp%& or by the Exim monitor.
16885 .option mua_wrapper main boolean false
16886 Setting this option true causes Exim to run in a very restrictive mode in which
16887 it passes messages synchronously to a smart host. Chapter &<<CHAPnonqueueing>>&
16888 contains a full description of this facility.
16892 .option mysql_servers main "string list" unset
16893 .cindex "MySQL" "server list"
16894 This option provides a list of MySQL servers and associated connection data, to
16895 be used in conjunction with &(mysql)& lookups (see section &<<SECID72>>&). The
16896 option is available only if Exim has been built with MySQL support.
16899 .option never_users main "string list&!!" unset
16900 This option is expanded just once, at the start of Exim's processing. Local
16901 message deliveries are normally run in processes that are setuid to the
16902 recipient, and remote deliveries are normally run under Exim's own uid and gid.
16903 It is usually desirable to prevent any deliveries from running as root, as a
16906 When Exim is built, an option called FIXED_NEVER_USERS can be set to a
16907 list of users that must not be used for local deliveries. This list is fixed in
16908 the binary and cannot be overridden by the configuration file. By default, it
16909 contains just the single user name &"root"&. The &%never_users%& runtime option
16910 can be used to add more users to the fixed list.
16912 If a message is to be delivered as one of the users on the fixed list or the
16913 &%never_users%& list, an error occurs, and delivery is deferred. A common
16916 never_users = root:daemon:bin
16918 Including root is redundant if it is also on the fixed list, but it does no
16919 harm. This option overrides the &%pipe_as_creator%& option of the &(pipe)&
16923 .option notifier_socket main string "$spool_directory/exim_daemon_notify"
16924 This option gives the name for a unix-domain socket on which the daemon
16925 listens for work and information-requests.
16926 Only installations running multiple daemons sharing a spool directory
16927 should need to modify the default.
16929 The option is expanded before use.
16930 If the platform supports Linux-style abstract socket names, the result
16931 is used with a nul byte prefixed.
16933 it should be a full path name and use a directory accessible
16936 If this option is set as empty,
16937 or the command line &%-oY%& option is used, or
16938 the command line uses a &%-oX%& option and does not use &%-oP%&,
16939 then a notifier socket is not created.
16942 .option openssl_options main "string list" "+no_sslv2 +no_sslv3 +single_dh_use +no_ticket +no_renegotiation"
16943 .cindex "OpenSSL "compatibility options"
16944 This option allows an administrator to adjust the SSL options applied
16945 by OpenSSL to connections. It is given as a space-separated list of items,
16946 each one to be +added or -subtracted from the current value.
16948 This option is only available if Exim is built against OpenSSL. The values
16949 available for this option vary according to the age of your OpenSSL install.
16950 The &"all"& value controls a subset of flags which are available, typically
16951 the bug workaround options. The &'SSL_CTX_set_options'& man page will
16952 list the values known on your system and Exim should support all the
16953 &"bug workaround"& options and many of the &"modifying"& options. The Exim
16954 names lose the leading &"SSL_OP_"& and are lower-cased.
16956 Note that adjusting the options can have severe impact upon the security of
16957 SSL as used by Exim. It is possible to disable safety checks and shoot
16958 yourself in the foot in various unpleasant ways. This option should not be
16959 adjusted lightly. An unrecognised item will be detected at startup, by
16960 invoking Exim with the &%-bV%& flag.
16962 The option affects Exim operating both as a server and as a client.
16964 Historical note: prior to release 4.80, Exim defaulted this value to
16965 "+dont_insert_empty_fragments", which may still be needed for compatibility
16966 with some clients, but which lowers security by increasing exposure to
16967 some now infamous attacks.
16971 # Make both old MS and old Eudora happy:
16972 openssl_options = -all +microsoft_big_sslv3_buffer \
16973 +dont_insert_empty_fragments
16975 # Disable older protocol versions:
16976 openssl_options = +no_sslv2 +no_sslv3
16979 Possible options may include:
16983 &`allow_unsafe_legacy_renegotiation`&
16985 &`cipher_server_preference`&
16987 &`dont_insert_empty_fragments`&
16991 &`legacy_server_connect`&
16993 &`microsoft_big_sslv3_buffer`&
16995 &`microsoft_sess_id_bug`&
16997 &`msie_sslv2_rsa_padding`&
16999 &`netscape_challenge_bug`&
17001 &`netscape_reuse_cipher_change_bug`&
17005 &`no_session_resumption_on_renegotiation`&
17019 &`safari_ecdhe_ecdsa_bug`&
17023 &`single_ecdh_use`&
17025 &`ssleay_080_client_dh_bug`&
17027 &`sslref2_reuse_cert_type_bug`&
17029 &`tls_block_padding_bug`&
17033 &`tls_rollback_bug`&
17036 As an aside, the &`safari_ecdhe_ecdsa_bug`& item is a misnomer and affects
17037 all clients connecting using the MacOS SecureTransport TLS facility prior
17038 to MacOS 10.8.4, including email clients. If you see old MacOS clients failing
17039 to negotiate TLS then this option value might help, provided that your OpenSSL
17040 release is new enough to contain this work-around. This may be a situation
17041 where you have to upgrade OpenSSL to get buggy clients working.
17044 .option oracle_servers main "string list" unset
17045 .cindex "Oracle" "server list"
17046 This option provides a list of Oracle servers and associated connection data,
17047 to be used in conjunction with &(oracle)& lookups (see section &<<SECID72>>&).
17048 The option is available only if Exim has been built with Oracle support.
17051 .option percent_hack_domains main "domain list&!!" unset
17052 .cindex "&""percent hack""&"
17053 .cindex "source routing" "in email address"
17054 .cindex "address" "source-routed"
17055 The &"percent hack"& is the convention whereby a local part containing a
17056 percent sign is re-interpreted as a new email address, with the percent
17057 replaced by @. This is sometimes called &"source routing"&, though that term is
17058 also applied to RFC 2822 addresses that begin with an @ character. If this
17059 option is set, Exim implements the percent facility for those domains listed,
17060 but no others. This happens before an incoming SMTP address is tested against
17063 &*Warning*&: The &"percent hack"& has often been abused by people who are
17064 trying to get round relaying restrictions. For this reason, it is best avoided
17065 if at all possible. Unfortunately, a number of less security-conscious MTAs
17066 implement it unconditionally. If you are running Exim on a gateway host, and
17067 routing mail through to internal MTAs without processing the local parts, it is
17068 a good idea to reject recipient addresses with percent characters in their
17069 local parts. Exim's default configuration does this.
17072 .option perl_at_start main boolean false
17074 This option is available only when Exim is built with an embedded Perl
17075 interpreter. See chapter &<<CHAPperl>>& for details of its use.
17078 .option perl_startup main string unset
17080 This option is available only when Exim is built with an embedded Perl
17081 interpreter. See chapter &<<CHAPperl>>& for details of its use.
17083 .option perl_taintmode main boolean false
17085 This option enables the taint mode of the embedded Perl interpreter.
17088 .option pgsql_servers main "string list" unset
17089 .cindex "PostgreSQL lookup type" "server list"
17090 This option provides a list of PostgreSQL servers and associated connection
17091 data, to be used in conjunction with &(pgsql)& lookups (see section
17092 &<<SECID72>>&). The option is available only if Exim has been built with
17093 PostgreSQL support.
17096 .option pid_file_path main string&!! "set at compile time"
17097 .cindex "daemon" "pid file path"
17098 .cindex "pid file, path for"
17099 This option sets the name of the file to which the Exim daemon writes its
17100 process id. The string is expanded, so it can contain, for example, references
17103 pid_file_path = /var/log/$primary_hostname/exim.pid
17105 If no path is set, the pid is written to the file &_exim-daemon.pid_& in Exim's
17107 The value set by the option can be overridden by the &%-oP%& command line
17108 option. A pid file is not written if a &"non-standard"& daemon is run by means
17109 of the &%-oX%& option, unless a path is explicitly supplied by &%-oP%&.
17112 .option pipelining_advertise_hosts main "host list&!!" *
17113 .cindex "PIPELINING" "suppressing advertising"
17114 .cindex "ESMTP extensions" PIPELINING
17115 This option can be used to suppress the advertisement of the SMTP
17116 PIPELINING extension to specific hosts. See also the &*no_pipelining*&
17117 control in section &<<SECTcontrols>>&. When PIPELINING is not advertised and
17118 &%smtp_enforce_sync%& is true, an Exim server enforces strict synchronization
17119 for each SMTP command and response. When PIPELINING is advertised, Exim assumes
17120 that clients will use it; &"out of order"& commands that are &"expected"& do
17121 not count as protocol errors (see &%smtp_max_synprot_errors%&).
17123 .option pipelining_connect_advertise_hosts main "host list&!!" *
17124 .cindex "pipelining" "early connection"
17125 .cindex "pipelining" PIPE_CONNECT
17126 .cindex "ESMTP extensions" PIPE_CONNECT
17127 If Exim is built with the SUPPORT_PIPE_CONNECT build option
17128 this option controls which hosts the facility is advertised to
17129 and from which pipeline early-connection (before MAIL) SMTP
17130 commands are acceptable.
17131 When used, the pipelining saves on roundtrip times.
17133 See also the &%hosts_pipe_connect%& smtp transport option.
17135 The SMTP service extension keyword advertised is &"PIPE_CONNECT"&.
17138 .option prdr_enable main boolean false
17139 .cindex "PRDR" "enabling on server"
17140 .cindex "ESMTP extensions" PRDR
17141 This option can be used to enable the Per-Recipient Data Response extension
17142 to SMTP, defined by Eric Hall.
17143 If the option is set, PRDR is advertised by Exim when operating as a server.
17144 If the client requests PRDR, and more than one recipient, for a message
17145 an additional ACL is called for each recipient after the message content
17146 is received. See section &<<SECTPRDRACL>>&.
17148 .option preserve_message_logs main boolean false
17149 .cindex "message logs" "preserving"
17150 If this option is set, message log files are not deleted when messages are
17151 completed. Instead, they are moved to a sub-directory of the spool directory
17152 called &_msglog.OLD_&, where they remain available for statistical or debugging
17153 purposes. This is a dangerous option to set on systems with any appreciable
17154 volume of mail. Use with care!
17157 .option primary_hostname main string "see below"
17158 .cindex "name" "of local host"
17159 .cindex "host" "name of local"
17160 .cindex "local host" "name of"
17161 .vindex "&$primary_hostname$&"
17162 This specifies the name of the current host. It is used in the default EHLO or
17163 HELO command for outgoing SMTP messages (changeable via the &%helo_data%&
17164 option in the &(smtp)& transport), and as the default for &%qualify_domain%&.
17165 The value is also used by default in some SMTP response messages from an Exim
17166 server. This can be changed dynamically by setting &%smtp_active_hostname%&.
17168 If &%primary_hostname%& is not set, Exim calls &[uname()]& to find the host
17169 name. If this fails, Exim panics and dies. If the name returned by &[uname()]&
17170 contains only one component, Exim passes it to &[gethostbyname()]& (or
17171 &[getipnodebyname()]& when available) in order to obtain the fully qualified
17172 version. The variable &$primary_hostname$& contains the host name, whether set
17173 explicitly by this option, or defaulted.
17176 .option print_topbitchars main boolean false
17177 .cindex "printing characters"
17178 .cindex "8-bit characters"
17179 By default, Exim considers only those characters whose codes lie in the range
17180 32&--126 to be printing characters. In a number of circumstances (for example,
17181 when writing log entries) non-printing characters are converted into escape
17182 sequences, primarily to avoid messing up the layout. If &%print_topbitchars%&
17183 is set, code values of 128 and above are also considered to be printing
17186 This option also affects the header syntax checks performed by the
17187 &(autoreply)& transport, and whether Exim uses RFC 2047 encoding of
17188 the user's full name when constructing From: and Sender: addresses (as
17189 described in section &<<SECTconstr>>&). Setting this option can cause
17190 Exim to generate eight bit message headers that do not conform to the
17194 .option process_log_path main string unset
17195 .cindex "process log path"
17196 .cindex "log" "process log"
17197 .cindex "&'exiwhat'&"
17198 This option sets the name of the file to which an Exim process writes its
17199 &"process log"& when sent a USR1 signal. This is used by the &'exiwhat'&
17200 utility script. If this option is unset, the file called &_exim-process.info_&
17201 in Exim's spool directory is used. The ability to specify the name explicitly
17202 can be useful in environments where two different Exims are running, using
17203 different spool directories.
17206 .option prod_requires_admin main boolean true
17207 .cindex "restricting access to features"
17211 The &%-M%&, &%-R%&, and &%-q%& command-line options require the caller to be an
17212 admin user unless &%prod_requires_admin%& is set false. See also
17213 &%queue_list_requires_admin%& and &%commandline_checks_require_admin%&.
17216 .option proxy_protocol_timeout main time 3s
17217 .cindex proxy "proxy protocol"
17218 This option sets the timeout for proxy protocol negotiation.
17219 For details see section &<<SECTproxyInbound>>&.
17222 .option qualify_domain main string "see below"
17223 .cindex "domain" "for qualifying addresses"
17224 .cindex "address" "qualification"
17225 This option specifies the domain name that is added to any envelope sender
17226 addresses that do not have a domain qualification. It also applies to
17227 recipient addresses if &%qualify_recipient%& is not set. Unqualified addresses
17228 are accepted by default only for locally-generated messages. Qualification is
17229 also applied to addresses in header lines such as &'From:'& and &'To:'& for
17230 locally-generated messages, unless the &%-bnq%& command line option is used.
17232 Messages from external sources must always contain fully qualified addresses,
17233 unless the sending host matches &%sender_unqualified_hosts%& or
17234 &%recipient_unqualified_hosts%& (as appropriate), in which case incoming
17235 addresses are qualified with &%qualify_domain%& or &%qualify_recipient%& as
17236 necessary. Internally, Exim always works with fully qualified envelope
17237 addresses. If &%qualify_domain%& is not set, it defaults to the
17238 &%primary_hostname%& value.
17241 .option qualify_recipient main string "see below"
17242 This option allows you to specify a different domain for qualifying recipient
17243 addresses to the one that is used for senders. See &%qualify_domain%& above.
17247 .option queue_domains main "domain list&!!" unset
17248 .cindex "domain" "specifying non-immediate delivery"
17249 .cindex "queueing incoming messages"
17250 .cindex "message" "queueing certain domains"
17251 This option lists domains for which immediate delivery is not required.
17252 A delivery process is started whenever a message is received, but only those
17253 domains that do not match are processed. All other deliveries wait until the
17254 next queue run. See also &%hold_domains%& and &%queue_smtp_domains%&.
17257 .option queue_fast_ramp main boolean false
17258 .cindex "queue runner" "two phase"
17259 .cindex "queue" "double scanning"
17260 If set to true, two-phase queue runs, initiated using &%-qq%& on the
17261 command line, may start parallel delivery processes during their first
17262 phase. This will be done when a threshold number of messages have been
17263 routed for a single host.
17266 .option queue_list_requires_admin main boolean true
17267 .cindex "restricting access to features"
17269 The &%-bp%& command-line option, which lists the messages that are on the
17270 queue, requires the caller to be an admin user unless
17271 &%queue_list_requires_admin%& is set false.
17272 See also &%prod_requires_admin%& and &%commandline_checks_require_admin%&.
17275 .option queue_only main boolean false
17276 .cindex "queueing incoming messages"
17277 .cindex "message" "queueing unconditionally"
17278 If &%queue_only%& is set, a delivery process is not automatically started
17279 whenever a message is received. Instead, the message waits in the queue for the
17280 next queue run. Even if &%queue_only%& is false, incoming messages may not get
17281 delivered immediately when certain conditions (such as heavy load) occur.
17283 The &%-odq%& command line has the same effect as &%queue_only%&. The &%-odb%&
17284 and &%-odi%& command line options override &%queue_only%& unless
17285 &%queue_only_override%& is set false. See also &%queue_only_file%&,
17286 &%queue_only_load%&, and &%smtp_accept_queue%&.
17289 .option queue_only_file main string unset
17290 .cindex "queueing incoming messages"
17291 .cindex "message" "queueing by file existence"
17292 This option can be set to a colon-separated list of absolute path names, each
17293 one optionally preceded by &"smtp"&. When Exim is receiving a message,
17294 it tests for the existence of each listed path using a call to &[stat()]&. For
17295 each path that exists, the corresponding queueing option is set.
17296 For paths with no prefix, &%queue_only%& is set; for paths prefixed by
17297 &"smtp"&, &%queue_smtp_domains%& is set to match all domains. So, for example,
17299 queue_only_file = smtp/some/file
17301 causes Exim to behave as if &%queue_smtp_domains%& were set to &"*"& whenever
17302 &_/some/file_& exists.
17305 .option queue_only_load main fixed-point unset
17306 .cindex "load average"
17307 .cindex "queueing incoming messages"
17308 .cindex "message" "queueing by load"
17309 If the system load average is higher than this value, incoming messages from
17310 all sources are queued, and no automatic deliveries are started. If this
17311 happens during local or remote SMTP input, all subsequent messages received on
17312 the same SMTP connection are queued by default, whatever happens to the load in
17313 the meantime, but this can be changed by setting &%queue_only_load_latch%&
17316 Deliveries will subsequently be performed by queue runner processes. This
17317 option has no effect on ancient operating systems on which Exim cannot
17318 determine the load average. See also &%deliver_queue_load_max%& and
17319 &%smtp_load_reserve%&.
17322 .option queue_only_load_latch main boolean true
17323 .cindex "load average" "re-evaluating per message"
17324 When this option is true (the default), once one message has been queued
17325 because the load average is higher than the value set by &%queue_only_load%&,
17326 all subsequent messages received on the same SMTP connection are also queued.
17327 This is a deliberate choice; even though the load average may fall below the
17328 threshold, it doesn't seem right to deliver later messages on the same
17329 connection when not delivering earlier ones. However, there are special
17330 circumstances such as very long-lived connections from scanning appliances
17331 where this is not the best strategy. In such cases, &%queue_only_load_latch%&
17332 should be set false. This causes the value of the load average to be
17333 re-evaluated for each message.
17336 .option queue_only_override main boolean true
17337 .cindex "queueing incoming messages"
17338 When this option is true, the &%-od%&&'x'& command line options override the
17339 setting of &%queue_only%& or &%queue_only_file%& in the configuration file. If
17340 &%queue_only_override%& is set false, the &%-od%&&'x'& options cannot be used
17341 to override; they are accepted, but ignored.
17344 .option queue_run_in_order main boolean false
17345 .cindex "queue runner" "processing messages in order"
17346 If this option is set, queue runs happen in order of message arrival instead of
17347 in an arbitrary order. For this to happen, a complete list of the entire queue
17348 must be set up before the deliveries start. When the queue is all held in a
17349 single directory (the default), a single list is created for both the ordered
17350 and the non-ordered cases. However, if &%split_spool_directory%& is set, a
17351 single list is not created when &%queue_run_in_order%& is false. In this case,
17352 the sub-directories are processed one at a time (in a random order), and this
17353 avoids setting up one huge list for the whole queue. Thus, setting
17354 &%queue_run_in_order%& with &%split_spool_directory%& may degrade performance
17355 when the queue is large, because of the extra work in setting up the single,
17356 large list. In most situations, &%queue_run_in_order%& should not be set.
17360 .option queue_run_max main integer&!! 5
17361 .cindex "queue runner" "maximum number of"
17362 This controls the maximum number of queue runner processes that an Exim daemon
17363 can run simultaneously. This does not mean that it starts them all at once,
17364 but rather that if the maximum number are still running when the time comes to
17365 start another one, it refrains from starting another one. This can happen with
17366 very large queues and/or very sluggish deliveries. This option does not,
17367 however, interlock with other processes, so additional queue runners can be
17368 started by other means, or by killing and restarting the daemon.
17370 Setting this option to zero does not suppress queue runs; rather, it disables
17371 the limit, allowing any number of simultaneous queue runner processes to be
17372 run. If you do not want queue runs to occur, omit the &%-q%&&'xx'& setting on
17373 the daemon's command line.
17375 .cindex queues named
17376 .cindex "named queues" "resource limit"
17377 To set limits for different named queues use
17378 an expansion depending on the &$queue_name$& variable.
17380 .option queue_smtp_domains main "domain list&!!" unset
17381 .cindex "queueing incoming messages"
17382 .cindex "message" "queueing remote deliveries"
17383 .cindex "first pass routing"
17384 When this option is set, a delivery process is started whenever a message is
17385 received, routing is performed, and local deliveries take place.
17386 However, if any SMTP deliveries are required for domains that match
17387 &%queue_smtp_domains%&, they are not immediately delivered, but instead the
17388 message waits in the queue for the next queue run. Since routing of the message
17389 has taken place, Exim knows to which remote hosts it must be delivered, and so
17390 when the queue run happens, multiple messages for the same host are delivered
17391 over a single SMTP connection. The &%-odqs%& command line option causes all
17392 SMTP deliveries to be queued in this way, and is equivalent to setting
17393 &%queue_smtp_domains%& to &"*"&. See also &%hold_domains%& and
17397 .option receive_timeout main time 0s
17398 .cindex "timeout" "for non-SMTP input"
17399 This option sets the timeout for accepting a non-SMTP message, that is, the
17400 maximum time that Exim waits when reading a message on the standard input. If
17401 the value is zero, it will wait forever. This setting is overridden by the
17402 &%-or%& command line option. The timeout for incoming SMTP messages is
17403 controlled by &%smtp_receive_timeout%&.
17405 .option received_header_text main string&!! "see below"
17406 .cindex "customizing" "&'Received:'& header"
17407 .cindex "&'Received:'& header line" "customizing"
17408 This string defines the contents of the &'Received:'& message header that is
17409 added to each message, except for the timestamp, which is automatically added
17410 on at the end (preceded by a semicolon). The string is expanded each time it is
17411 used. If the expansion yields an empty string, no &'Received:'& header line is
17412 added to the message. Otherwise, the string should start with the text
17413 &"Received:"& and conform to the RFC 2822 specification for &'Received:'&
17415 The default setting is:
17418 received_header_text = Received: \
17419 ${if def:sender_rcvhost {from $sender_rcvhost\n\t}\
17420 {${if def:sender_ident \
17421 {from ${quote_local_part:$sender_ident} }}\
17422 ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\
17423 by $primary_hostname \
17424 ${if def:received_protocol {with $received_protocol }}\
17425 ${if def:tls_in_ver { ($tls_in_ver)}}\
17426 ${if def:tls_in_cipher_std { tls $tls_in_cipher_std\n\t}}\
17427 (Exim $version_number)\n\t\
17428 ${if def:sender_address \
17429 {(envelope-from <$sender_address>)\n\t}}\
17430 id $message_exim_id\
17431 ${if def:received_for {\n\tfor $received_for}}
17434 The references to the TLS version and cipher are
17435 omitted when Exim is built without TLS
17436 support. The use of conditional expansions ensures that this works for both
17437 locally generated messages and messages received from remote hosts, giving
17438 header lines such as the following:
17440 Received: from scrooge.carol.example ([192.168.12.25] ident=root)
17441 by marley.carol.example with esmtp (Exim 4.00)
17442 (envelope-from <bob@carol.example>)
17443 id 16IOWa-00019l-00
17444 for chas@dickens.example; Tue, 25 Dec 2001 14:43:44 +0000
17445 Received: by scrooge.carol.example with local (Exim 4.00)
17446 id 16IOWW-000083-00; Tue, 25 Dec 2001 14:43:41 +0000
17448 Until the body of the message has been received, the timestamp is the time when
17449 the message started to be received. Once the body has arrived, and all policy
17450 checks have taken place, the timestamp is updated to the time at which the
17451 message was accepted.
17454 .option received_headers_max main integer 30
17455 .cindex "loop" "prevention"
17456 .cindex "mail loop prevention"
17457 .cindex "&'Received:'& header line" "counting"
17458 When a message is to be delivered, the number of &'Received:'& headers is
17459 counted, and if it is greater than this parameter, a mail loop is assumed to
17460 have occurred, the delivery is abandoned, and an error message is generated.
17461 This applies to both local and remote deliveries.
17464 .option recipient_unqualified_hosts main "host list&!!" unset
17465 .cindex "unqualified addresses"
17466 .cindex "host" "unqualified addresses from"
17467 This option lists those hosts from which Exim is prepared to accept unqualified
17468 recipient addresses in message envelopes. The addresses are made fully
17469 qualified by the addition of the &%qualify_recipient%& value. This option also
17470 affects message header lines. Exim does not reject unqualified recipient
17471 addresses in headers, but it qualifies them only if the message came from a
17472 host that matches &%recipient_unqualified_hosts%&,
17473 or if the message was submitted locally (not using TCP/IP), and the &%-bnq%&
17474 option was not set.
17477 .option recipients_max main integer 50000
17478 .cindex "limit" "number of recipients"
17479 .cindex "recipient" "maximum number"
17480 If this option is set greater than zero, it specifies the maximum number of
17481 original recipients for any message. Additional recipients that are generated
17482 by aliasing or forwarding do not count. SMTP messages get a 452 response for
17483 all recipients over the limit; earlier recipients are delivered as normal.
17484 Non-SMTP messages with too many recipients are failed, and no deliveries are
17487 .cindex "RCPT" "maximum number of incoming"
17488 &*Note*&: The RFCs specify that an SMTP server should accept at least 100
17489 RCPT commands in a single message.
17492 .option recipients_max_reject main boolean false
17493 If this option is set true, Exim rejects SMTP messages containing too many
17494 recipients by giving 552 errors to the surplus RCPT commands, and a 554
17495 error to the eventual DATA command. Otherwise (the default) it gives a 452
17496 error to the surplus RCPT commands and accepts the message on behalf of the
17497 initial set of recipients. The remote server should then re-send the message
17498 for the remaining recipients at a later time.
17501 .option remote_max_parallel main integer 2
17502 .cindex "delivery" "parallelism for remote"
17503 This option controls parallel delivery of one message to a number of remote
17504 hosts. If the value is less than 2, parallel delivery is disabled, and Exim
17505 does all the remote deliveries for a message one by one. Otherwise, if a single
17506 message has to be delivered to more than one remote host, or if several copies
17507 have to be sent to the same remote host, up to &%remote_max_parallel%&
17508 deliveries are done simultaneously. If more than &%remote_max_parallel%&
17509 deliveries are required, the maximum number of processes are started, and as
17510 each one finishes, another is begun. The order of starting processes is the
17511 same as if sequential delivery were being done, and can be controlled by the
17512 &%remote_sort_domains%& option. If parallel delivery takes place while running
17513 with debugging turned on, the debugging output from each delivery process is
17514 tagged with its process id.
17516 This option controls only the maximum number of parallel deliveries for one
17517 message in one Exim delivery process. Because Exim has no central queue
17518 manager, there is no way of controlling the total number of simultaneous
17519 deliveries if the configuration allows a delivery attempt as soon as a message
17522 See also the &%max_parallel%& generic transport option,
17523 and the &%serialize_hosts%& smtp transport option.
17525 .cindex "number of deliveries"
17526 .cindex "delivery" "maximum number of"
17527 If you want to control the total number of deliveries on the system, you
17528 need to set the &%queue_only%& option. This ensures that all incoming messages
17529 are added to the queue without starting a delivery process. Then set up an Exim
17530 daemon to start queue runner processes at appropriate intervals (probably
17531 fairly often, for example, every minute), and limit the total number of queue
17532 runners by setting the &%queue_run_max%& parameter. Because each queue runner
17533 delivers only one message at a time, the maximum number of deliveries that can
17534 then take place at once is &%queue_run_max%& multiplied by
17535 &%remote_max_parallel%&.
17537 If it is purely remote deliveries you want to control, use
17538 &%queue_smtp_domains%& instead of &%queue_only%&. This has the added benefit of
17539 doing the SMTP routing before queueing, so that several messages for the same
17540 host will eventually get delivered down the same connection.
17543 .option remote_sort_domains main "domain list&!!" unset
17544 .cindex "sorting remote deliveries"
17545 .cindex "delivery" "sorting remote"
17546 When there are a number of remote deliveries for a message, they are sorted by
17547 domain into the order given by this list. For example,
17549 remote_sort_domains = *.cam.ac.uk:*.uk
17551 would attempt to deliver to all addresses in the &'cam.ac.uk'& domain first,
17552 then to those in the &%uk%& domain, then to any others.
17555 .option retry_data_expire main time 7d
17556 .cindex "hints database" "data expiry"
17557 This option sets a &"use before"& time on retry information in Exim's hints
17558 database. Any older retry data is ignored. This means that, for example, once a
17559 host has not been tried for 7 days, Exim behaves as if it has no knowledge of
17563 .option retry_interval_max main time 24h
17564 .cindex "retry" "limit on interval"
17565 .cindex "limit" "on retry interval"
17566 Chapter &<<CHAPretry>>& describes Exim's mechanisms for controlling the
17567 intervals between delivery attempts for messages that cannot be delivered
17568 straight away. This option sets an overall limit to the length of time between
17569 retries. It cannot be set greater than 24 hours; any attempt to do so forces
17573 .option return_path_remove main boolean true
17574 .cindex "&'Return-path:'& header line" "removing"
17575 RFC 2821, section 4.4, states that an SMTP server must insert a
17576 &'Return-path:'& header line into a message when it makes a &"final delivery"&.
17577 The &'Return-path:'& header preserves the sender address as received in the
17578 MAIL command. This description implies that this header should not be present
17579 in an incoming message. If &%return_path_remove%& is true, any existing
17580 &'Return-path:'& headers are removed from messages at the time they are
17581 received. Exim's transports have options for adding &'Return-path:'& headers at
17582 the time of delivery. They are normally used only for final local deliveries.
17585 .option return_size_limit main integer 100K
17586 This option is an obsolete synonym for &%bounce_return_size_limit%&.
17589 .option rfc1413_hosts main "host list&!!" @[]
17591 .cindex "host" "for RFC 1413 calls"
17592 RFC 1413 identification calls are made to any client host which matches
17593 an item in the list.
17594 The default value specifies just this host, being any local interface
17597 .option rfc1413_query_timeout main time 0s
17598 .cindex "RFC 1413" "query timeout"
17599 .cindex "timeout" "for RFC 1413 call"
17600 This sets the timeout on RFC 1413 identification calls. If it is set to zero,
17601 no RFC 1413 calls are ever made.
17604 .option sender_unqualified_hosts main "host list&!!" unset
17605 .cindex "unqualified addresses"
17606 .cindex "host" "unqualified addresses from"
17607 This option lists those hosts from which Exim is prepared to accept unqualified
17608 sender addresses. The addresses are made fully qualified by the addition of
17609 &%qualify_domain%&. This option also affects message header lines. Exim does
17610 not reject unqualified addresses in headers that contain sender addresses, but
17611 it qualifies them only if the message came from a host that matches
17612 &%sender_unqualified_hosts%&, or if the message was submitted locally (not
17613 using TCP/IP), and the &%-bnq%& option was not set.
17616 .option slow_lookup_log main integer 0
17617 .cindex "logging" "slow lookups"
17618 .cindex "dns" "logging slow lookups"
17619 This option controls logging of slow lookups.
17620 If the value is nonzero it is taken as a number of milliseconds
17621 and lookups taking longer than this are logged.
17622 Currently this applies only to DNS lookups.
17626 .option smtp_accept_keepalive main boolean true
17627 .cindex "keepalive" "on incoming connection"
17628 This option controls the setting of the SO_KEEPALIVE option on incoming
17629 TCP/IP socket connections. When set, it causes the kernel to probe idle
17630 connections periodically, by sending packets with &"old"& sequence numbers. The
17631 other end of the connection should send an acknowledgment if the connection is
17632 still okay or a reset if the connection has been aborted. The reason for doing
17633 this is that it has the beneficial effect of freeing up certain types of
17634 connection that can get stuck when the remote host is disconnected without
17635 tidying up the TCP/IP call properly. The keepalive mechanism takes several
17636 hours to detect unreachable hosts.
17640 .option smtp_accept_max main integer 20
17641 .cindex "limit" "incoming SMTP connections"
17642 .cindex "SMTP" "incoming connection count"
17644 This option specifies the maximum number of simultaneous incoming SMTP calls
17645 that Exim will accept. It applies only to the listening daemon; there is no
17646 control (in Exim) when incoming SMTP is being handled by &'inetd'&. If the
17647 value is set to zero, no limit is applied. However, it is required to be
17648 non-zero if either &%smtp_accept_max_per_host%& or &%smtp_accept_queue%& is
17649 set. See also &%smtp_accept_reserve%& and &%smtp_load_reserve%&.
17651 A new SMTP connection is immediately rejected if the &%smtp_accept_max%& limit
17652 has been reached. If not, Exim first checks &%smtp_accept_max_per_host%&. If
17653 that limit has not been reached for the client host, &%smtp_accept_reserve%&
17654 and &%smtp_load_reserve%& are then checked before accepting the connection.
17657 .option smtp_accept_max_nonmail main integer 10
17658 .cindex "limit" "non-mail SMTP commands"
17659 .cindex "SMTP" "limiting non-mail commands"
17660 Exim counts the number of &"non-mail"& commands in an SMTP session, and drops
17661 the connection if there are too many. This option defines &"too many"&. The
17662 check catches some denial-of-service attacks, repeated failing AUTHs, or a mad
17663 client looping sending EHLO, for example. The check is applied only if the
17664 client host matches &%smtp_accept_max_nonmail_hosts%&.
17666 When a new message is expected, one occurrence of RSET is not counted. This
17667 allows a client to send one RSET between messages (this is not necessary,
17668 but some clients do it). Exim also allows one uncounted occurrence of HELO
17669 or EHLO, and one occurrence of STARTTLS between messages. After
17670 starting up a TLS session, another EHLO is expected, and so it too is not
17671 counted. The first occurrence of AUTH in a connection, or immediately
17672 following STARTTLS is not counted. Otherwise, all commands other than
17673 MAIL, RCPT, DATA, and QUIT are counted.
17676 .option smtp_accept_max_nonmail_hosts main "host list&!!" *
17677 You can control which hosts are subject to the &%smtp_accept_max_nonmail%&
17678 check by setting this option. The default value makes it apply to all hosts. By
17679 changing the value, you can exclude any badly-behaved hosts that you have to
17683 . Allow this long option name to split; give it unsplit as a fifth argument
17684 . for the automatic .oindex that is generated by .option.
17685 . We insert " &~&~" which is both pretty nasty visually and results in
17686 . non-searchable text. HowItWorks.txt mentions an option for inserting
17687 . zero-width-space, which would be nicer visually and results in (at least)
17688 . html that Firefox will split on when it's forced to reflow (rather than
17689 . inserting a horizontal scrollbar). However, the text is still not
17690 . searchable. NM changed this occurrence for bug 1197 to no longer allow
17691 . the option name to split.
17693 .option "smtp_accept_max_per_connection" main integer&!! 1000 &&&
17694 smtp_accept_max_per_connection
17695 .cindex "SMTP" "limiting incoming message count"
17696 .cindex "limit" "messages per SMTP connection"
17697 The value of this option limits the number of MAIL commands that Exim is
17698 prepared to accept over a single SMTP connection, whether or not each command
17699 results in the transfer of a message. After the limit is reached, a 421
17700 response is given to subsequent MAIL commands. This limit is a safety
17701 precaution against a client that goes mad (incidents of this type have been
17703 The option is expanded after the HELO or EHLO is received
17704 and may depend on values available at that time.
17705 An empty or zero value after expansion removes the limit.
17708 .option smtp_accept_max_per_host main string&!! unset
17709 .cindex "limit" "SMTP connections from one host"
17710 .cindex "host" "limiting SMTP connections from"
17711 This option restricts the number of simultaneous IP connections from a single
17712 host (strictly, from a single IP address) to the Exim daemon. The option is
17713 expanded, to enable different limits to be applied to different hosts by
17714 reference to &$sender_host_address$&. Once the limit is reached, additional
17715 connection attempts from the same host are rejected with error code 421. This
17716 is entirely independent of &%smtp_accept_reserve%&. The option's default value
17717 of zero imposes no limit. If this option is set greater than zero, it is
17718 required that &%smtp_accept_max%& be non-zero.
17720 &*Warning*&: When setting this option you should not use any expansion
17721 constructions that take an appreciable amount of time. The expansion and test
17722 happen in the main daemon loop, in order to reject additional connections
17723 without forking additional processes (otherwise a denial-of-service attack
17724 could cause a vast number or processes to be created). While the daemon is
17725 doing this processing, it cannot accept any other incoming connections.
17729 .option smtp_accept_queue main integer 0
17730 .cindex "SMTP" "incoming connection count"
17731 .cindex "queueing incoming messages"
17732 .cindex "message" "queueing by SMTP connection count"
17733 If the number of simultaneous incoming SMTP connections being handled via the
17734 listening daemon exceeds this value, messages received by SMTP are just placed
17735 in the queue; no delivery processes are started automatically. The count is
17736 fixed at the start of an SMTP connection. It cannot be updated in the
17737 subprocess that receives messages, and so the queueing or not queueing applies
17738 to all messages received in the same connection.
17740 A value of zero implies no limit, and clearly any non-zero value is useful only
17741 if it is less than the &%smtp_accept_max%& value (unless that is zero). See
17742 also &%queue_only%&, &%queue_only_load%&, &%queue_smtp_domains%&, and the
17743 various &%-od%&&'x'& command line options.
17746 . See the comment on smtp_accept_max_per_connection
17748 .option "smtp_accept_queue_per_connection" main integer 10 &&&
17749 smtp_accept_queue_per_connection
17750 .cindex "queueing incoming messages"
17751 .cindex "message" "queueing by message count"
17752 This option limits the number of delivery processes that Exim starts
17753 automatically when receiving messages via SMTP, whether via the daemon or by
17754 the use of &%-bs%& or &%-bS%&. If the value of the option is greater than zero,
17755 and the number of messages received in a single SMTP session exceeds this
17756 number, subsequent messages are placed in the queue, but no delivery processes
17757 are started. This helps to limit the number of Exim processes when a server
17758 restarts after downtime and there is a lot of mail waiting for it on other
17759 systems. On large systems, the default should probably be increased, and on
17760 dial-in client systems it should probably be set to zero (that is, disabled).
17763 .option smtp_accept_reserve main integer 0
17764 .cindex "SMTP" "incoming call count"
17765 .cindex "host" "reserved"
17766 When &%smtp_accept_max%& is set greater than zero, this option specifies a
17767 number of SMTP connections that are reserved for connections from the hosts
17768 that are specified in &%smtp_reserve_hosts%&. The value set in
17769 &%smtp_accept_max%& includes this reserve pool. The specified hosts are not
17770 restricted to this number of connections; the option specifies a minimum number
17771 of connection slots for them, not a maximum. It is a guarantee that this group
17772 of hosts can always get at least &%smtp_accept_reserve%& connections. However,
17773 the limit specified by &%smtp_accept_max_per_host%& is still applied to each
17776 For example, if &%smtp_accept_max%& is set to 50 and &%smtp_accept_reserve%& is
17777 set to 5, once there are 45 active connections (from any hosts), new
17778 connections are accepted only from hosts listed in &%smtp_reserve_hosts%&,
17779 provided the other criteria for acceptance are met.
17782 .option smtp_active_hostname main string&!! unset
17783 .cindex "host" "name in SMTP responses"
17784 .cindex "SMTP" "host name in responses"
17785 .vindex "&$primary_hostname$&"
17786 This option is provided for multi-homed servers that want to masquerade as
17787 several different hosts. At the start of an incoming SMTP connection, its value
17788 is expanded and used instead of the value of &$primary_hostname$& in SMTP
17789 responses. For example, it is used as domain name in the response to an
17790 incoming HELO or EHLO command.
17792 .vindex "&$smtp_active_hostname$&"
17793 The active hostname is placed in the &$smtp_active_hostname$& variable, which
17794 is saved with any messages that are received. It is therefore available for use
17795 in routers and transports when the message is later delivered.
17797 If this option is unset, or if its expansion is forced to fail, or if the
17798 expansion results in an empty string, the value of &$primary_hostname$& is
17799 used. Other expansion failures cause a message to be written to the main and
17800 panic logs, and the SMTP command receives a temporary error. Typically, the
17801 value of &%smtp_active_hostname%& depends on the incoming interface address.
17804 smtp_active_hostname = ${if eq{$received_ip_address}{10.0.0.1}\
17805 {cox.mydomain}{box.mydomain}}
17808 Although &$smtp_active_hostname$& is primarily concerned with incoming
17809 messages, it is also used as the default for HELO commands in callout
17810 verification if there is no remote transport from which to obtain a
17811 &%helo_data%& value.
17813 .option smtp_backlog_monitor main integer 0
17814 .cindex "connection backlog" monitoring
17815 If this option is set to greater than zero, and the backlog of available
17816 TCP connections on a socket listening for SMTP is larger than it, a line
17817 is logged giving the value and the socket address and port.
17818 The value is retrived jsut before an accept call.
17819 This facility is only available on Linux.
17821 .option smtp_banner main string&!! "see below"
17822 .cindex "SMTP" "welcome banner"
17823 .cindex "banner for SMTP"
17824 .cindex "welcome banner for SMTP"
17825 .cindex "customizing" "SMTP banner"
17826 This string, which is expanded every time it is used, is output as the initial
17827 positive response to an SMTP connection. The default setting is:
17829 smtp_banner = $smtp_active_hostname ESMTP Exim \
17830 $version_number $tod_full
17832 Failure to expand the string causes a panic error. If you want to create a
17833 multiline response to the initial SMTP connection, use &"\n"& in the string at
17834 appropriate points, but not at the end. Note that the 220 code is not included
17835 in this string. Exim adds it automatically (several times in the case of a
17836 multiline response).
17839 .option smtp_check_spool_space main boolean true
17840 .cindex "checking disk space"
17841 .cindex "disk space, checking"
17842 .cindex "spool directory" "checking space"
17843 When this option is set, if an incoming SMTP session encounters the SIZE
17844 option on a MAIL command, it checks that there is enough space in the
17845 spool directory's partition to accept a message of that size, while still
17846 leaving free the amount specified by &%check_spool_space%& (even if that value
17847 is zero). If there isn't enough space, a temporary error code is returned.
17850 .option smtp_connect_backlog main integer 20
17851 .cindex "connection backlog" "set maximum"
17852 .cindex "SMTP" "connection backlog"
17853 .cindex "backlog of connections"
17854 This option specifies a maximum number of waiting SMTP connections. Exim passes
17855 this value to the TCP/IP system when it sets up its listener. Once this number
17856 of connections are waiting for the daemon's attention, subsequent connection
17857 attempts are refused at the TCP/IP level. At least, that is what the manuals
17858 say; in some circumstances such connection attempts have been observed to time
17859 out instead. For large systems it is probably a good idea to increase the
17860 value (to 50, say). It also gives some protection against denial-of-service
17861 attacks by SYN flooding.
17864 .option smtp_enforce_sync main boolean true
17865 .cindex "SMTP" "synchronization checking"
17866 .cindex "synchronization checking in SMTP"
17867 The SMTP protocol specification requires the client to wait for a response from
17868 the server at certain points in the dialogue. Without PIPELINING these
17869 synchronization points are after every command; with PIPELINING they are
17870 fewer, but they still exist.
17872 Some spamming sites send out a complete set of SMTP commands without waiting
17873 for any response. Exim protects against this by rejecting a message if the
17874 client has sent further input when it should not have. The error response &"554
17875 SMTP synchronization error"& is sent, and the connection is dropped. Testing
17876 for this error cannot be perfect because of transmission delays (unexpected
17877 input may be on its way but not yet received when Exim checks). However, it
17878 does detect many instances.
17880 The check can be globally disabled by setting &%smtp_enforce_sync%& false.
17881 If you want to disable the check selectively (for example, only for certain
17882 hosts), you can do so by an appropriate use of a &%control%& modifier in an ACL
17883 (see section &<<SECTcontrols>>&). See also &%pipelining_advertise_hosts%&.
17887 .option smtp_etrn_command main string&!! unset
17888 .cindex "ETRN" "command to be run"
17889 .cindex "ESMTP extensions" ETRN
17890 .vindex "&$domain$&"
17891 If this option is set, the given command is run whenever an SMTP ETRN
17892 command is received from a host that is permitted to issue such commands (see
17893 chapter &<<CHAPACL>>&). The string is split up into separate arguments which
17894 are independently expanded. The expansion variable &$domain$& is set to the
17895 argument of the ETRN command, and no syntax checking is done on it. For
17898 smtp_etrn_command = /etc/etrn_command $domain \
17899 $sender_host_address
17901 If the option is not set, the argument for the ETRN command must
17902 be a &'#'& followed by an address string.
17903 In this case an &'exim -R <string>'& command is used;
17904 if the ETRN ACL has set up a named-queue then &'-MCG <queue>'& is appended.
17906 A new process is created to run the command, but Exim does not wait for it to
17907 complete. Consequently, its status cannot be checked. If the command cannot be
17908 run, a line is written to the panic log, but the ETRN caller still receives
17909 a 250 success response. Exim is normally running under its own uid when
17910 receiving SMTP, so it is not possible for it to change the uid before running
17914 .option smtp_etrn_serialize main boolean true
17915 .cindex "ETRN" "serializing"
17916 When this option is set, it prevents the simultaneous execution of more than
17917 one identical command as a result of ETRN in an SMTP connection. See
17918 section &<<SECTETRN>>& for details.
17921 .option smtp_load_reserve main fixed-point unset
17922 .cindex "load average"
17923 If the system load average ever gets higher than this, incoming SMTP calls are
17924 accepted only from those hosts that match an entry in &%smtp_reserve_hosts%&.
17925 If &%smtp_reserve_hosts%& is not set, no incoming SMTP calls are accepted when
17926 the load is over the limit. The option has no effect on ancient operating
17927 systems on which Exim cannot determine the load average. See also
17928 &%deliver_queue_load_max%& and &%queue_only_load%&.
17932 .option smtp_max_synprot_errors main integer 3
17933 .cindex "SMTP" "limiting syntax and protocol errors"
17934 .cindex "limit" "SMTP syntax and protocol errors"
17935 Exim rejects SMTP commands that contain syntax or protocol errors. In
17936 particular, a syntactically invalid email address, as in this command:
17938 RCPT TO:<abc xyz@a.b.c>
17940 causes immediate rejection of the command, before any other tests are done.
17941 (The ACL cannot be run if there is no valid address to set up for it.) An
17942 example of a protocol error is receiving RCPT before MAIL. If there are
17943 too many syntax or protocol errors in one SMTP session, the connection is
17944 dropped. The limit is set by this option.
17946 .cindex "PIPELINING" "expected errors"
17947 When the PIPELINING extension to SMTP is in use, some protocol errors are
17948 &"expected"&, for instance, a RCPT command after a rejected MAIL command.
17949 Exim assumes that PIPELINING will be used if it advertises it (see
17950 &%pipelining_advertise_hosts%&), and in this situation, &"expected"& errors do
17951 not count towards the limit.
17955 .option smtp_max_unknown_commands main integer 3
17956 .cindex "SMTP" "limiting unknown commands"
17957 .cindex "limit" "unknown SMTP commands"
17958 If there are too many unrecognized commands in an incoming SMTP session, an
17959 Exim server drops the connection. This is a defence against some kinds of abuse
17962 into making connections to SMTP ports; in these circumstances, a number of
17963 non-SMTP command lines are sent first.
17967 .option smtp_ratelimit_hosts main "host list&!!" unset
17968 .cindex "SMTP" "rate limiting"
17969 .cindex "limit" "rate of message arrival"
17970 .cindex "RCPT" "rate limiting"
17971 Some sites find it helpful to be able to limit the rate at which certain hosts
17972 can send them messages, and the rate at which an individual message can specify
17975 Exim has two rate-limiting facilities. This section describes the older
17976 facility, which can limit rates within a single connection. The newer
17977 &%ratelimit%& ACL condition can limit rates across all connections. See section
17978 &<<SECTratelimiting>>& for details of the newer facility.
17980 When a host matches &%smtp_ratelimit_hosts%&, the values of
17981 &%smtp_ratelimit_mail%& and &%smtp_ratelimit_rcpt%& are used to control the
17982 rate of acceptance of MAIL and RCPT commands in a single SMTP session,
17983 respectively. Each option, if set, must contain a set of four comma-separated
17987 A threshold, before which there is no rate limiting.
17989 An initial time delay. Unlike other times in Exim, numbers with decimal
17990 fractional parts are allowed here.
17992 A factor by which to increase the delay each time.
17994 A maximum value for the delay. This should normally be less than 5 minutes,
17995 because after that time, the client is liable to timeout the SMTP command.
17998 For example, these settings have been used successfully at the site which
17999 first suggested this feature, for controlling mail from their customers:
18001 smtp_ratelimit_mail = 2,0.5s,1.05,4m
18002 smtp_ratelimit_rcpt = 4,0.25s,1.015,4m
18004 The first setting specifies delays that are applied to MAIL commands after
18005 two have been received over a single connection. The initial delay is 0.5
18006 seconds, increasing by a factor of 1.05 each time. The second setting applies
18007 delays to RCPT commands when more than four occur in a single message.
18010 .option smtp_ratelimit_mail main string unset
18011 See &%smtp_ratelimit_hosts%& above.
18014 .option smtp_ratelimit_rcpt main string unset
18015 See &%smtp_ratelimit_hosts%& above.
18018 .option smtp_receive_timeout main time&!! 5m
18019 .cindex "timeout" "for SMTP input"
18020 .cindex "SMTP" "input timeout"
18021 This sets a timeout value for SMTP reception. It applies to all forms of SMTP
18022 input, including batch SMTP. If a line of input (either an SMTP command or a
18023 data line) is not received within this time, the SMTP connection is dropped and
18024 the message is abandoned.
18025 A line is written to the log containing one of the following messages:
18027 SMTP command timeout on connection from...
18028 SMTP data timeout on connection from...
18030 The former means that Exim was expecting to read an SMTP command; the latter
18031 means that it was in the DATA phase, reading the contents of a message.
18033 If the first character of the option is a &"$"& the option is
18034 expanded before use and may depend on
18035 &$sender_host_name$&, &$sender_host_address$& and &$sender_host_port$&.
18039 The value set by this option can be overridden by the
18040 &%-os%& command-line option. A setting of zero time disables the timeout, but
18041 this should never be used for SMTP over TCP/IP. (It can be useful in some cases
18042 of local input using &%-bs%& or &%-bS%&.) For non-SMTP input, the reception
18043 timeout is controlled by &%receive_timeout%& and &%-or%&.
18046 .option smtp_reserve_hosts main "host list&!!" unset
18047 This option defines hosts for which SMTP connections are reserved; see
18048 &%smtp_accept_reserve%& and &%smtp_load_reserve%& above.
18051 .option smtp_return_error_details main boolean false
18052 .cindex "SMTP" "details policy failures"
18053 .cindex "policy control" "rejection, returning details"
18054 In the default state, Exim uses bland messages such as
18055 &"Administrative prohibition"& when it rejects SMTP commands for policy
18056 reasons. Many sysadmins like this because it gives away little information
18057 to spammers. However, some other sysadmins who are applying strict checking
18058 policies want to give out much fuller information about failures. Setting
18059 &%smtp_return_error_details%& true causes Exim to be more forthcoming. For
18060 example, instead of &"Administrative prohibition"&, it might give:
18062 550-Rejected after DATA: '>' missing at end of address:
18063 550 failing address in "From" header is: <user@dom.ain
18067 .option smtputf8_advertise_hosts main "host list&!!" *
18068 .cindex "SMTPUTF8" "ESMTP extension, advertising"
18069 .cindex "ESMTP extensions" SMTPUTF8
18070 When Exim is built with support for internationalised mail names,
18071 the availability thereof is advertised in
18072 response to EHLO only to those client hosts that match this option. See
18073 chapter &<<CHAPi18n>>& for details of Exim's support for internationalisation.
18076 .option spamd_address main string "127.0.0.1 783"
18077 This option is available when Exim is compiled with the content-scanning
18078 extension. It specifies how Exim connects to SpamAssassin's &%spamd%& daemon.
18079 See section &<<SECTscanspamass>>& for more details.
18083 .option spf_guess main string "v=spf1 a/24 mx/24 ptr ?all"
18084 This option is available when Exim is compiled with SPF support.
18085 See section &<<SECSPF>>& for more details.
18087 .option spf_smtp_comment_template main string&!! "Please%_see%_http://www.open-spf.org/Why"
18088 This option is available when Exim is compiled with SPF support. It
18089 allows the customisation of the SMTP comment that the SPF library
18090 generates. You are strongly encouraged to link to your own explanative
18091 site. The template must not contain spaces. If you need spaces in the
18092 output, use the proper placeholder. If libspf2 can not parse the
18093 template, it uses a built-in default broken link. The following placeholders
18094 (along with Exim variables (but see below)) are allowed in the template:
18098 &*%{L}*&: Envelope sender's local part.
18100 &*%{S}*&: Envelope sender.
18102 &*%{O}*&: Envelope sender's domain.
18104 &*%{D}*&: Current(?) domain.
18106 &*%{I}*&: SMTP client Ip.
18108 &*%{C}*&: SMTP client pretty IP.
18110 &*%{T}*&: Epoch time (UTC).
18112 &*%{P}*&: SMTP client domain name.
18114 &*%{V}*&: IP version.
18116 &*%{H}*&: EHLO/HELO domain.
18118 &*%{R}*&: Receiving domain.
18120 The capitalized placeholders do proper URL encoding, if you use them
18121 lowercased, no encoding takes place. This list was compiled from the
18124 A note on using Exim variables: As
18125 currently the SPF library is initialized before the SMTP EHLO phase,
18126 the variables useful for expansion are quite limited.
18129 .option split_spool_directory main boolean false
18130 .cindex "multiple spool directories"
18131 .cindex "spool directory" "split"
18132 .cindex "directories, multiple"
18133 If this option is set, it causes Exim to split its input directory into 62
18134 subdirectories, each with a single alphanumeric character as its name. The
18135 sixth character of the message id is used to allocate messages to
18136 subdirectories; this is the least significant base-62 digit of the time of
18137 arrival of the message.
18139 Splitting up the spool in this way may provide better performance on systems
18140 where there are long mail queues, by reducing the number of files in any one
18141 directory. The msglog directory is also split up in a similar way to the input
18142 directory; however, if &%preserve_message_logs%& is set, all old msglog files
18143 are still placed in the single directory &_msglog.OLD_&.
18145 It is not necessary to take any special action for existing messages when
18146 changing &%split_spool_directory%&. Exim notices messages that are in the
18147 &"wrong"& place, and continues to process them. If the option is turned off
18148 after a period of being on, the subdirectories will eventually empty and be
18149 automatically deleted.
18151 When &%split_spool_directory%& is set, the behaviour of queue runner processes
18152 changes. Instead of creating a list of all messages in the queue, and then
18153 trying to deliver each one, in turn, it constructs a list of those in one
18154 sub-directory and tries to deliver them, before moving on to the next
18155 sub-directory. The sub-directories are processed in a random order. This
18156 spreads out the scanning of the input directories, and uses less memory. It is
18157 particularly beneficial when there are lots of messages in the queue. However,
18158 if &%queue_run_in_order%& is set, none of this new processing happens. The
18159 entire queue has to be scanned and sorted before any deliveries can start.
18162 .option spool_directory main string&!! "set at compile time"
18163 .cindex "spool directory" "path to"
18164 This defines the directory in which Exim keeps its spool, that is, the messages
18165 it is waiting to deliver. The default value is taken from the compile-time
18166 configuration setting, if there is one. If not, this option must be set. The
18167 string is expanded, so it can contain, for example, a reference to
18168 &$primary_hostname$&.
18170 If the spool directory name is fixed on your installation, it is recommended
18171 that you set it at build time rather than from this option, particularly if the
18172 log files are being written to the spool directory (see &%log_file_path%&).
18173 Otherwise log files cannot be used for errors that are detected early on, such
18174 as failures in the configuration file.
18176 By using this option to override the compiled-in path, it is possible to run
18177 tests of Exim without using the standard spool.
18179 .option spool_wireformat main boolean false
18180 .cindex "spool directory" "file formats"
18181 If this option is set, Exim may for some messages use an alternative format
18182 for data-files in the spool which matches the wire format.
18183 Doing this permits more efficient message reception and transmission.
18184 Currently it is only done for messages received using the ESMTP CHUNKING
18187 The following variables will not have useful values:
18189 $max_received_linelength
18194 Users of the local_scan() API (see &<<CHAPlocalscan>>&),
18195 and any external programs which are passed a reference to a message data file
18196 (except via the &"regex"&, &"malware"& or &"spam"&) ACL conditions)
18197 will need to be aware of the different formats potentially available.
18199 Using any of the ACL conditions noted will negate the reception benefit
18200 (as a Unix-mbox-format file is constructed for them).
18201 The transmission benefit is maintained.
18203 .option sqlite_lock_timeout main time 5s
18204 .cindex "sqlite lookup type" "lock timeout"
18205 This option controls the timeout that the &(sqlite)& lookup uses when trying to
18206 access an SQLite database. See section &<<SECTsqlite>>& for more details.
18208 .option strict_acl_vars main boolean false
18209 .cindex "&ACL;" "variables, handling unset"
18210 This option controls what happens if a syntactically valid but undefined ACL
18211 variable is referenced. If it is false (the default), an empty string
18212 is substituted; if it is true, an error is generated. See section
18213 &<<SECTaclvariables>>& for details of ACL variables.
18215 .option strip_excess_angle_brackets main boolean false
18216 .cindex "angle brackets, excess"
18217 If this option is set, redundant pairs of angle brackets round &"route-addr"&
18218 items in addresses are stripped. For example, &'<<xxx@a.b.c.d>>'& is
18219 treated as &'<xxx@a.b.c.d>'&. If this is in the envelope and the message is
18220 passed on to another MTA, the excess angle brackets are not passed on. If this
18221 option is not set, multiple pairs of angle brackets cause a syntax error.
18224 .option strip_trailing_dot main boolean false
18225 .cindex "trailing dot on domain"
18226 .cindex "dot" "trailing on domain"
18227 If this option is set, a trailing dot at the end of a domain in an address is
18228 ignored. If this is in the envelope and the message is passed on to another
18229 MTA, the dot is not passed on. If this option is not set, a dot at the end of a
18230 domain causes a syntax error.
18231 However, addresses in header lines are checked only when an ACL requests header
18235 .option syslog_duplication main boolean true
18236 .cindex "syslog" "duplicate log lines; suppressing"
18237 When Exim is logging to syslog, it writes the log lines for its three
18238 separate logs at different syslog priorities so that they can in principle
18239 be separated on the logging hosts. Some installations do not require this
18240 separation, and in those cases, the duplication of certain log lines is a
18241 nuisance. If &%syslog_duplication%& is set false, only one copy of any
18242 particular log line is written to syslog. For lines that normally go to
18243 both the main log and the reject log, the reject log version (possibly
18244 containing message header lines) is written, at LOG_NOTICE priority.
18245 Lines that normally go to both the main and the panic log are written at
18246 the LOG_ALERT priority.
18249 .option syslog_facility main string unset
18250 .cindex "syslog" "facility; setting"
18251 This option sets the syslog &"facility"& name, used when Exim is logging to
18252 syslog. The value must be one of the strings &"mail"&, &"user"&, &"news"&,
18253 &"uucp"&, &"daemon"&, or &"local&'x'&"& where &'x'& is a digit between 0 and 7.
18254 If this option is unset, &"mail"& is used. See chapter &<<CHAPlog>>& for
18255 details of Exim's logging.
18258 .option syslog_pid main boolean true
18259 .cindex "syslog" "pid"
18260 If &%syslog_pid%& is set false, the PID on Exim's log lines are
18261 omitted when these lines are sent to syslog. (Syslog normally prefixes
18262 the log lines with the PID of the logging process automatically.) You need
18263 to enable the &`+pid`& log selector item, if you want Exim to write it's PID
18264 into the logs.) See chapter &<<CHAPlog>>& for details of Exim's logging.
18268 .option syslog_processname main string &`exim`&
18269 .cindex "syslog" "process name; setting"
18270 This option sets the syslog &"ident"& name, used when Exim is logging to
18271 syslog. The value must be no longer than 32 characters. See chapter
18272 &<<CHAPlog>>& for details of Exim's logging.
18276 .option syslog_timestamp main boolean true
18277 .cindex "syslog" "timestamps"
18278 .cindex timestamps syslog
18279 If &%syslog_timestamp%& is set false, the timestamps on Exim's log lines are
18280 omitted when these lines are sent to syslog. See chapter &<<CHAPlog>>& for
18281 details of Exim's logging.
18284 .option system_filter main string&!! unset
18285 .cindex "filter" "system filter"
18286 .cindex "system filter" "specifying"
18287 .cindex "Sieve filter" "not available for system filter"
18288 This option specifies an Exim filter file that is applied to all messages at
18289 the start of each delivery attempt, before any routing is done. System filters
18290 must be Exim filters; they cannot be Sieve filters. If the system filter
18291 generates any deliveries to files or pipes, or any new mail messages, the
18292 appropriate &%system_filter_..._transport%& option(s) must be set, to define
18293 which transports are to be used. Details of this facility are given in chapter
18294 &<<CHAPsystemfilter>>&.
18295 A forced expansion failure results in no filter operation.
18298 .option system_filter_directory_transport main string&!! unset
18299 .vindex "&$address_file$&"
18300 This sets the name of the transport driver that is to be used when the
18301 &%save%& command in a system message filter specifies a path ending in &"/"&,
18302 implying delivery of each message into a separate file in some directory.
18303 During the delivery, the variable &$address_file$& contains the path name.
18306 .option system_filter_file_transport main string&!! unset
18307 .cindex "file" "transport for system filter"
18308 This sets the name of the transport driver that is to be used when the &%save%&
18309 command in a system message filter specifies a path not ending in &"/"&. During
18310 the delivery, the variable &$address_file$& contains the path name.
18312 .option system_filter_group main string unset
18313 .cindex "gid (group id)" "system filter"
18314 This option is used only when &%system_filter_user%& is also set. It sets the
18315 gid under which the system filter is run, overriding any gid that is associated
18316 with the user. The value may be numerical or symbolic.
18318 .option system_filter_pipe_transport main string&!! unset
18319 .cindex "&(pipe)& transport" "for system filter"
18320 .vindex "&$address_pipe$&"
18321 This specifies the transport driver that is to be used when a &%pipe%& command
18322 is used in a system filter. During the delivery, the variable &$address_pipe$&
18323 contains the pipe command.
18326 .option system_filter_reply_transport main string&!! unset
18327 .cindex "&(autoreply)& transport" "for system filter"
18328 This specifies the transport driver that is to be used when a &%mail%& command
18329 is used in a system filter.
18332 .option system_filter_user main string unset
18333 .cindex "uid (user id)" "system filter"
18334 If this option is set to root, the system filter is run in the main Exim
18335 delivery process, as root. Otherwise, the system filter runs in a separate
18336 process, as the given user, defaulting to the Exim run-time user.
18337 Unless the string consists entirely of digits, it
18338 is looked up in the password data. Failure to find the named user causes a
18339 configuration error. The gid is either taken from the password data, or
18340 specified by &%system_filter_group%&. When the uid is specified numerically,
18341 &%system_filter_group%& is required to be set.
18343 If the system filter generates any pipe, file, or reply deliveries, the uid
18344 under which the filter is run is used when transporting them, unless a
18345 transport option overrides.
18348 .option tcp_nodelay main boolean true
18349 .cindex "daemon" "TCP_NODELAY on sockets"
18350 .cindex "Nagle algorithm"
18351 .cindex "TCP_NODELAY on listening sockets"
18352 If this option is set false, it stops the Exim daemon setting the
18353 TCP_NODELAY option on its listening sockets. Setting TCP_NODELAY
18354 turns off the &"Nagle algorithm"&, which is a way of improving network
18355 performance in interactive (character-by-character) situations. Turning it off
18356 should improve Exim's performance a bit, so that is what happens by default.
18357 However, it appears that some broken clients cannot cope, and time out. Hence
18358 this option. It affects only those sockets that are set up for listening by the
18359 daemon. Sockets created by the smtp transport for delivering mail always set
18363 .option timeout_frozen_after main time 0s
18364 .cindex "frozen messages" "timing out"
18365 .cindex "timeout" "frozen messages"
18366 If &%timeout_frozen_after%& is set to a time greater than zero, a frozen
18367 message of any kind that has been in the queue for longer than the given time
18368 is automatically cancelled at the next queue run. If the frozen message is a
18369 bounce message, it is just discarded; otherwise, a bounce is sent to the
18370 sender, in a similar manner to cancellation by the &%-Mg%& command line option.
18371 If you want to timeout frozen bounce messages earlier than other kinds of
18372 frozen message, see &%ignore_bounce_errors_after%&.
18374 &*Note:*& the default value of zero means no timeouts; with this setting,
18375 frozen messages remain in the queue forever (except for any frozen bounce
18376 messages that are released by &%ignore_bounce_errors_after%&).
18379 .option timezone main string unset
18380 .cindex "timezone, setting"
18381 .cindex "environment" "values from"
18382 The value of &%timezone%& is used to set the environment variable TZ while
18383 running Exim (if it is different on entry). This ensures that all timestamps
18384 created by Exim are in the required timezone. If you want all your timestamps
18385 to be in UTC (aka GMT) you should set
18389 The default value is taken from TIMEZONE_DEFAULT in &_Local/Makefile_&,
18390 or, if that is not set, from the value of the TZ environment variable when Exim
18391 is built. If &%timezone%& is set to the empty string, either at build or run
18392 time, any existing TZ variable is removed from the environment when Exim
18393 runs. This is appropriate behaviour for obtaining wall-clock time on some, but
18394 unfortunately not all, operating systems.
18397 .option tls_advertise_hosts main "host list&!!" *
18398 .cindex "TLS" "advertising"
18399 .cindex "encryption" "on SMTP connection"
18400 .cindex "SMTP" "encrypted connection"
18401 .cindex "ESMTP extensions" STARTTLS
18402 When Exim is built with support for TLS encrypted connections, the availability
18403 of the STARTTLS command to set up an encrypted session is advertised in
18404 response to EHLO only to those client hosts that match this option. See
18405 chapter &<<CHAPTLS>>& for details of Exim's support for TLS.
18406 Note that the default value requires that a certificate be supplied
18407 using the &%tls_certificate%& option. If TLS support for incoming connections
18408 is not required the &%tls_advertise_hosts%& option should be set empty.
18411 .option tls_alpn main "string list&!!" "smtp : esmtp"
18412 .cindex TLS "Application Layer Protocol Names"
18414 .cindex ALPN "set acceptable names for server"
18415 If this option is set,
18416 the TLS library supports ALPN,
18417 and the client offers either more than
18418 ALPN name or a name which does not match the list,
18419 the TLS connection is declined.
18422 .option tls_certificate main "string list&!!" unset
18423 .cindex "TLS" "server certificate; location of"
18424 .cindex "certificate" "server, location of"
18425 The value of this option is expanded, and must then be a list of absolute paths to
18426 files which contain the server's certificates (in PEM format).
18427 Commonly only one file is needed.
18428 The server's private key is also
18429 assumed to be in this file if &%tls_privatekey%& is unset. See chapter
18430 &<<CHAPTLS>>& for further details.
18432 &*Note*&: The certificates defined by this option are used only when Exim is
18433 receiving incoming messages as a server. If you want to supply certificates for
18434 use when sending messages as a client, you must set the &%tls_certificate%&
18435 option in the relevant &(smtp)& transport.
18437 &*Note*&: If you use filenames based on IP addresses, change the list
18438 separator in the usual way (&<<SECTlistsepchange>>&) to avoid confusion under IPv6.
18440 &*Note*&: Under versions of OpenSSL preceding 1.1.1,
18441 when a list of more than one
18442 file is used, the &$tls_in_ourcert$& variable is unreliable.
18443 The macro "_TLS_BAD_MULTICERT_IN_OURCERT" will be defined for those versions.
18445 .cindex SNI "selecting server certificate based on"
18446 If the option contains &$tls_out_sni$& and Exim is built against OpenSSL, then
18447 if the OpenSSL build supports TLS extensions and the TLS client sends the
18448 Server Name Indication extension, then this option and others documented in
18449 &<<SECTtlssni>>& will be re-expanded.
18451 If this option is unset or empty a self-signed certificate will be
18453 Under Linux this is generated at daemon startup; on other platforms it will be
18454 generated fresh for every connection.
18456 .option tls_crl main string&!! unset
18457 .cindex "TLS" "server certificate revocation list"
18458 .cindex "certificate" "revocation list for server"
18459 This option specifies a certificate revocation list. The expanded value must
18460 be the name of a file that contains CRLs in PEM format.
18462 Under OpenSSL the option can specify a directory with CRL files.
18464 &*Note:*& Under OpenSSL the option must, if given, supply a CRL
18465 for each signing element of the certificate chain (i.e. all but the leaf).
18466 For the file variant this can be multiple PEM blocks in the one file.
18468 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
18471 .option tls_dh_max_bits main integer 2236
18472 .cindex "TLS" "D-H bit count"
18473 The number of bits used for Diffie-Hellman key-exchange may be suggested by
18474 the chosen TLS library. That value might prove to be too high for
18475 interoperability. This option provides a maximum clamp on the value
18476 suggested, trading off security for interoperability.
18478 The value must be at least 1024.
18480 The value 2236 was chosen because, at time of adding the option, it was the
18481 hard-coded maximum value supported by the NSS cryptographic library, as used
18482 by Thunderbird, while GnuTLS was suggesting 2432 bits as normal.
18484 If you prefer more security and are willing to break some clients, raise this
18487 Note that the value passed to GnuTLS for *generating* a new prime may be a
18488 little less than this figure, because GnuTLS is inexact and may produce a
18489 larger prime than requested.
18492 .option tls_dhparam main string&!! unset
18493 .cindex "TLS" "D-H parameters for server"
18494 The value of this option is expanded and indicates the source of DH parameters
18495 to be used by Exim.
18497 &*Note: The Exim Maintainers strongly recommend using a filename with site-generated
18498 local DH parameters*&, which has been supported across all versions of Exim. The
18499 other specific constants available are a fallback so that even when
18500 "unconfigured", Exim can offer Perfect Forward Secrecy in older ciphersuites in TLS.
18502 If &%tls_dhparam%& is a filename starting with a &`/`&,
18503 then it names a file from which DH
18504 parameters should be loaded. If the file exists, it should hold a PEM-encoded
18505 PKCS#3 representation of the DH prime. If the file does not exist, for
18506 OpenSSL it is an error. For GnuTLS, Exim will attempt to create the file and
18507 fill it with a generated DH prime. For OpenSSL, if the DH bit-count from
18508 loading the file is greater than &%tls_dh_max_bits%& then it will be ignored,
18509 and treated as though the &%tls_dhparam%& were set to "none".
18511 If this option expands to the string "none", then no DH parameters will be
18514 If this option expands to the string "historic" and Exim is using GnuTLS, then
18515 Exim will attempt to load a file from inside the spool directory. If the file
18516 does not exist, Exim will attempt to create it.
18517 See section &<<SECTgnutlsparam>>& for further details.
18519 If Exim is using OpenSSL and this option is empty or unset, then Exim will load
18520 a default DH prime; the default is Exim-specific but lacks verifiable provenance.
18522 In older versions of Exim the default was the 2048 bit prime described in section
18523 2.2 of RFC 5114, "2048-bit MODP Group with 224-bit Prime Order Subgroup", which
18524 in IKE is assigned number 23.
18526 Otherwise, the option must expand to the name used by Exim for any of a number
18527 of DH primes specified in RFC 2409, RFC 3526, RFC 5114, RFC 7919, or from other
18528 sources. As names, Exim uses a standard specified name, else "ike" followed by
18529 the number used by IKE, or "default" which corresponds to
18530 &`exim.dev.20160529.3`&.
18532 The available standard primes are:
18533 &`ffdhe2048`&, &`ffdhe3072`&, &`ffdhe4096`&, &`ffdhe6144`&, &`ffdhe8192`&,
18534 &`ike1`&, &`ike2`&, &`ike5`&,
18535 &`ike14`&, &`ike15`&, &`ike16`&, &`ike17`&, &`ike18`&,
18536 &`ike22`&, &`ike23`& and &`ike24`&.
18538 The available additional primes are:
18539 &`exim.dev.20160529.1`&, &`exim.dev.20160529.2`& and &`exim.dev.20160529.3`&.
18541 Some of these will be too small to be accepted by clients.
18542 Some may be too large to be accepted by clients.
18543 The open cryptographic community has suspicions about the integrity of some
18544 of the later IKE values, which led into RFC7919 providing new fixed constants
18545 (the "ffdhe" identifiers).
18547 At this point, all of the "ike" values should be considered obsolete;
18548 they are still in Exim to avoid breaking unusual configurations, but are
18549 candidates for removal the next time we have backwards-incompatible changes.
18551 Two of them in particular (&`ike1`& and &`ike22`&) are called out by RFC 8247
18552 as MUST NOT use for IPSEC, and two more (&`ike23`& and &`ike24`&) as
18554 Because of this, Exim regards them as deprecated; if either of the first pair
18555 are used, warnings will be logged in the paniclog, and if any are used then
18556 warnings will be logged in the mainlog.
18557 All four will be removed in a future Exim release.
18560 The TLS protocol does not negotiate an acceptable size for this; clients tend
18561 to hard-drop connections if what is offered by the server is unacceptable,
18562 whether too large or too small, and there's no provision for the client to
18563 tell the server what these constraints are. Thus, as a server operator, you
18564 need to make an educated guess as to what is most likely to work for your
18567 Some known size constraints suggest that a bit-size in the range 2048 to 2236
18568 is most likely to maximise interoperability. The upper bound comes from
18569 applications using the Mozilla Network Security Services (NSS) library, which
18570 used to set its &`DH_MAX_P_BITS`& upper-bound to 2236. This affects many
18571 mail user agents (MUAs). The lower bound comes from Debian installs of Exim4
18572 prior to the 4.80 release, as Debian used to patch Exim to raise the minimum
18573 acceptable bound from 1024 to 2048.
18576 .option tls_eccurve main string&!! &`auto`&
18577 .cindex TLS "EC cryptography"
18578 This option selects a EC curve for use by Exim when used with OpenSSL.
18579 It has no effect when Exim is used with GnuTLS.
18581 After expansion it must contain a valid EC curve parameter, such as
18582 &`prime256v1`&, &`secp384r1`&, or &`P-512`&. Consult your OpenSSL manual
18583 for valid selections.
18585 For OpenSSL versions before (and not including) 1.0.2, the string
18586 &`auto`& selects &`prime256v1`&. For more recent OpenSSL versions
18587 &`auto`& tells the library to choose.
18589 If the option expands to an empty string, no EC curves will be enabled.
18592 .option tls_ocsp_file main string&!! unset
18593 .cindex TLS "certificate status"
18594 .cindex TLS "OCSP proof file"
18596 must if set expand to the absolute path to a file which contains a current
18597 status proof for the server's certificate, as obtained from the
18598 Certificate Authority.
18600 Usable for GnuTLS 3.4.4 or 3.3.17 or OpenSSL 1.1.0 (or later).
18601 The macro "_HAVE_TLS_OCSP" will be defined for those versions.
18603 For OpenSSL 1.1.0 or later, and
18604 for GnuTLS 3.5.6 or later the expanded value of this option can be a list
18605 of files, to match a list given for the &%tls_certificate%& option.
18606 The ordering of the two lists must match.
18607 The macro "_HAVE_TLS_OCSP_LIST" will be defined for those versions.
18609 The file(s) should be in DER format,
18610 except for GnuTLS 3.6.3 or later
18612 when an optional filetype prefix can be used.
18613 The prefix must be one of "DER" or "PEM", followed by
18614 a single space. If one is used it sets the format for subsequent
18615 files in the list; the initial format is DER.
18616 If multiple proofs are wanted, for multiple chain elements
18617 (this only works under TLS1.3)
18618 they must be coded as a combined OCSP response.
18620 Although GnuTLS will accept PEM files with multiple separate
18621 PEM blobs (ie. separate OCSP responses), it sends them in the
18622 TLS Certificate record interleaved with the certificates of the chain;
18623 although a GnuTLS client is happy with that, an OpenSSL client is not.
18625 .option tls_on_connect_ports main "string list" unset
18628 This option specifies a list of incoming SSMTP (aka SMTPS) ports that should
18629 operate the SSMTP (SMTPS) protocol, where a TLS session is immediately
18630 set up without waiting for the client to issue a STARTTLS command. For
18631 further details, see section &<<SECTsupobssmt>>&.
18635 .option tls_privatekey main "string list&!!" unset
18636 .cindex "TLS" "server private key; location of"
18637 The value of this option is expanded, and must then be a list of absolute paths to
18638 files which contains the server's private keys.
18639 If this option is unset, or if
18640 the expansion is forced to fail, or the result is an empty string, the private
18641 key is assumed to be in the same file as the server's certificates. See chapter
18642 &<<CHAPTLS>>& for further details.
18644 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
18647 .option tls_remember_esmtp main boolean false
18648 .cindex "TLS" "esmtp state; remembering"
18649 .cindex "TLS" "broken clients"
18650 If this option is set true, Exim violates the RFCs by remembering that it is in
18651 &"esmtp"& state after successfully negotiating a TLS session. This provides
18652 support for broken clients that fail to send a new EHLO after starting a
18656 .option tls_require_ciphers main string&!! unset
18657 .cindex "TLS" "requiring specific ciphers"
18658 .cindex "cipher" "requiring specific"
18659 This option controls which ciphers can be used for incoming TLS connections.
18660 The &(smtp)& transport has an option of the same name for controlling outgoing
18661 connections. This option is expanded for each connection, so can be varied for
18662 different clients if required. The value of this option must be a list of
18663 permitted cipher suites. The OpenSSL and GnuTLS libraries handle cipher control
18664 in somewhat different ways. If GnuTLS is being used, the client controls the
18665 preference order of the available ciphers. Details are given in sections
18666 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
18669 .option tls_resumption_hosts main "host list&!!" unset
18670 .cindex TLS resumption
18671 This option controls which connections to offer the TLS resumption feature.
18672 See &<<SECTresumption>>& for details.
18675 .option tls_try_verify_hosts main "host list&!!" unset
18676 .cindex "TLS" "client certificate verification"
18677 .cindex "certificate" "verification of client"
18678 See &%tls_verify_hosts%& below.
18681 .option tls_verify_certificates main string&!! system
18682 .cindex "TLS" "client certificate verification"
18683 .cindex "certificate" "verification of client"
18684 The value of this option is expanded, and must then be either the
18686 or the absolute path to
18687 a file or directory containing permitted certificates for clients that
18688 match &%tls_verify_hosts%& or &%tls_try_verify_hosts%&.
18690 The "system" value for the option will use a
18691 system default location compiled into the SSL library.
18692 This is not available for GnuTLS versions preceding 3.0.20,
18693 and will be taken as empty; an explicit location
18696 The use of a directory for the option value is not available for GnuTLS versions
18697 preceding 3.3.6 and a single file must be used.
18699 With OpenSSL the certificates specified
18701 either by file or directory
18702 are added to those given by the system default location.
18704 These certificates should be for the certificate authorities trusted, rather
18705 than the public cert of individual clients. With both OpenSSL and GnuTLS, if
18706 the value is a file then the certificates are sent by Exim as a server to
18707 connecting clients, defining the list of accepted certificate authorities.
18708 Thus the values defined should be considered public data. To avoid this,
18709 use the explicit directory version. (If your peer is Exim up to 4.85,
18710 using GnuTLS, you may need to send the CAs (thus using the file
18711 variant). Otherwise the peer doesn't send its certificate.)
18713 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
18715 A forced expansion failure or setting to an empty string is equivalent to
18719 .option tls_verify_hosts main "host list&!!" unset
18720 .cindex "TLS" "client certificate verification"
18721 .cindex "certificate" "verification of client"
18722 This option, along with &%tls_try_verify_hosts%&, controls the checking of
18723 certificates from clients. The expected certificates are defined by
18724 &%tls_verify_certificates%&, which must be set. A configuration error occurs if
18725 either &%tls_verify_hosts%& or &%tls_try_verify_hosts%& is set and
18726 &%tls_verify_certificates%& is not set.
18728 Any client that matches &%tls_verify_hosts%& is constrained by
18729 &%tls_verify_certificates%&. When the client initiates a TLS session, it must
18730 present one of the listed certificates. If it does not, the connection is
18732 &*Warning*&: Including a host in &%tls_verify_hosts%& does not require
18733 the host to use TLS. It can still send SMTP commands through unencrypted
18734 connections. Forcing a client to use TLS has to be done separately using an
18735 ACL to reject inappropriate commands when the connection is not encrypted.
18737 A weaker form of checking is provided by &%tls_try_verify_hosts%&. If a client
18738 matches this option (but not &%tls_verify_hosts%&), Exim requests a
18739 certificate and checks it against &%tls_verify_certificates%&, but does not
18740 abort the connection if there is no certificate or if it does not match. This
18741 state can be detected in an ACL, which makes it possible to implement policies
18742 such as &"accept for relay only if a verified certificate has been received,
18743 but accept for local delivery if encrypted, even without a verified
18746 Client hosts that match neither of these lists are not asked to present
18750 .option trusted_groups main "string list&!!" unset
18751 .cindex "trusted groups"
18752 .cindex "groups" "trusted"
18753 This option is expanded just once, at the start of Exim's processing. If this
18754 option is set, any process that is running in one of the listed groups, or
18755 which has one of them as a supplementary group, is trusted. The groups can be
18756 specified numerically or by name. See section &<<SECTtrustedadmin>>& for
18757 details of what trusted callers are permitted to do. If neither
18758 &%trusted_groups%& nor &%trusted_users%& is set, only root and the Exim user
18761 .option trusted_users main "string list&!!" unset
18762 .cindex "trusted users"
18763 .cindex "user" "trusted"
18764 This option is expanded just once, at the start of Exim's processing. If this
18765 option is set, any process that is running as one of the listed users is
18766 trusted. The users can be specified numerically or by name. See section
18767 &<<SECTtrustedadmin>>& for details of what trusted callers are permitted to do.
18768 If neither &%trusted_groups%& nor &%trusted_users%& is set, only root and the
18769 Exim user are trusted.
18771 .option unknown_login main string&!! unset
18772 .cindex "uid (user id)" "unknown caller"
18773 .vindex "&$caller_uid$&"
18774 This is a specialized feature for use in unusual configurations. By default, if
18775 the uid of the caller of Exim cannot be looked up using &[getpwuid()]&, Exim
18776 gives up. The &%unknown_login%& option can be used to set a login name to be
18777 used in this circumstance. It is expanded, so values like &%user$caller_uid%&
18778 can be set. When &%unknown_login%& is used, the value of &%unknown_username%&
18779 is used for the user's real name (gecos field), unless this has been set by the
18782 .option unknown_username main string unset
18783 See &%unknown_login%&.
18785 .option untrusted_set_sender main "address list&!!" unset
18786 .cindex "trusted users"
18787 .cindex "sender" "setting by untrusted user"
18788 .cindex "untrusted user setting sender"
18789 .cindex "user" "untrusted setting sender"
18790 .cindex "envelope from"
18791 .cindex "envelope sender"
18792 When an untrusted user submits a message to Exim using the standard input, Exim
18793 normally creates an envelope sender address from the user's login and the
18794 default qualification domain. Data from the &%-f%& option (for setting envelope
18795 senders on non-SMTP messages) or the SMTP MAIL command (if &%-bs%& or &%-bS%&
18796 is used) is ignored.
18798 However, untrusted users are permitted to set an empty envelope sender address,
18799 to declare that a message should never generate any bounces. For example:
18801 exim -f '<>' user@domain.example
18803 .vindex "&$sender_ident$&"
18804 The &%untrusted_set_sender%& option allows you to permit untrusted users to set
18805 other envelope sender addresses in a controlled way. When it is set, untrusted
18806 users are allowed to set envelope sender addresses that match any of the
18807 patterns in the list. Like all address lists, the string is expanded. The
18808 identity of the user is in &$sender_ident$&, so you can, for example, restrict
18809 users to setting senders that start with their login ids
18810 followed by a hyphen
18811 by a setting like this:
18813 untrusted_set_sender = ^$sender_ident-
18815 If you want to allow untrusted users to set envelope sender addresses without
18816 restriction, you can use
18818 untrusted_set_sender = *
18820 The &%untrusted_set_sender%& option applies to all forms of local input, but
18821 only to the setting of the envelope sender. It does not permit untrusted users
18822 to use the other options which trusted user can use to override message
18823 parameters. Furthermore, it does not stop Exim from removing an existing
18824 &'Sender:'& header in the message, or from adding a &'Sender:'& header if
18825 necessary. See &%local_sender_retain%& and &%local_from_check%& for ways of
18826 overriding these actions. The handling of the &'Sender:'& header is also
18827 described in section &<<SECTthesenhea>>&.
18829 The log line for a message's arrival shows the envelope sender following
18830 &"<="&. For local messages, the user's login always follows, after &"U="&. In
18831 &%-bp%& displays, and in the Exim monitor, if an untrusted user sets an
18832 envelope sender address, the user's login is shown in parentheses after the
18836 .option uucp_from_pattern main string "see below"
18837 .cindex "&""From""& line"
18838 .cindex "UUCP" "&""From""& line"
18839 Some applications that pass messages to an MTA via a command line interface use
18840 an initial line starting with &"From&~"& to pass the envelope sender. In
18841 particular, this is used by UUCP software. Exim recognizes such a line by means
18842 of a regular expression that is set in &%uucp_from_pattern%&. When the pattern
18843 matches, the sender address is constructed by expanding the contents of
18844 &%uucp_from_sender%&, provided that the caller of Exim is a trusted user. The
18845 default pattern recognizes lines in the following two forms:
18847 From ph10 Fri Jan 5 12:35 GMT 1996
18848 From ph10 Fri, 7 Jan 97 14:00:00 GMT
18850 The pattern can be seen by running
18852 exim -bP uucp_from_pattern
18854 It checks only up to the hours and minutes, and allows for a 2-digit or 4-digit
18855 year in the second case. The first word after &"From&~"& is matched in the
18856 regular expression by a parenthesized subpattern. The default value for
18857 &%uucp_from_sender%& is &"$1"&, which therefore just uses this first word
18858 (&"ph10"& in the example above) as the message's sender. See also
18859 &%ignore_fromline_hosts%&.
18862 .option uucp_from_sender main string&!! &`$1`&
18863 See &%uucp_from_pattern%& above.
18866 .option warn_message_file main string&!! unset
18867 .cindex "warning of delay" "customizing the message"
18868 .cindex "customizing" "warning message"
18869 This option defines a template file containing paragraphs of text to be used
18870 for constructing the warning message which is sent by Exim when a message has
18871 been in the queue for a specified amount of time, as specified by
18872 &%delay_warning%&. Details of the file's contents are given in chapter
18873 &<<CHAPemsgcust>>&.
18874 .cindex warn_message_file "tainted data"
18875 The option is expanded to give the file path, which must be
18876 absolute and untainted.
18877 See also &%bounce_message_file%&.
18880 .option write_rejectlog main boolean true
18881 .cindex "reject log" "disabling"
18882 If this option is set false, Exim no longer writes anything to the reject log.
18883 See chapter &<<CHAPlog>>& for details of what Exim writes to its logs.
18884 .ecindex IIDconfima
18885 .ecindex IIDmaiconf
18890 . ////////////////////////////////////////////////////////////////////////////
18891 . ////////////////////////////////////////////////////////////////////////////
18893 .chapter "Generic options for routers" "CHAProutergeneric"
18894 .scindex IIDgenoprou1 "options" "generic; for routers"
18895 .scindex IIDgenoprou2 "generic options" "router"
18896 This chapter describes the generic options that apply to all routers.
18897 Those that are preconditions are marked with ‡ in the &"use"& field.
18899 For a general description of how a router operates, see sections
18900 &<<SECTrunindrou>>& and &<<SECTrouprecon>>&. The latter specifies the order in
18901 which the preconditions are tested. The order of expansion of the options that
18902 provide data for a transport is: &%errors_to%&, &%headers_add%&,
18903 &%headers_remove%&, &%transport%&.
18905 The name of a router is limited to be &drivernamemax; ASCII characters long;
18906 prior to Exim 4.95 names would be silently truncated at this length, but now
18910 .option address_data routers string&!! unset
18911 .cindex "router" "data attached to address"
18912 The string is expanded just before the router is run, that is, after all the
18913 precondition tests have succeeded. If the expansion is forced to fail, the
18914 router declines, the value of &%address_data%& remains unchanged, and the
18915 &%more%& option controls what happens next. Other expansion failures cause
18916 delivery of the address to be deferred.
18918 .vindex "&$address_data$&"
18919 When the expansion succeeds, the value is retained with the address, and can be
18920 accessed using the variable &$address_data$& in the current router, subsequent
18921 routers, and the eventual transport.
18923 &*Warning*&: If the current or any subsequent router is a &(redirect)& router
18924 that runs a user's filter file, the contents of &$address_data$& are accessible
18925 in the filter. This is not normally a problem, because such data is usually
18926 either not confidential or it &"belongs"& to the current user, but if you do
18927 put confidential data into &$address_data$& you need to remember this point.
18929 Even if the router declines or passes, the value of &$address_data$& remains
18930 with the address, though it can be changed by another &%address_data%& setting
18931 on a subsequent router. If a router generates child addresses, the value of
18932 &$address_data$& propagates to them. This also applies to the special kind of
18933 &"child"& that is generated by a router with the &%unseen%& option.
18935 The idea of &%address_data%& is that you can use it to look up a lot of data
18936 for the address once, and then pick out parts of the data later. For example,
18937 you could use a single LDAP lookup to return a string of the form
18939 uid=1234 gid=5678 mailbox=/mail/xyz forward=/home/xyz/.forward
18941 In the transport you could pick out the mailbox by a setting such as
18943 file = ${extract{mailbox}{$address_data}}
18945 This makes the configuration file less messy, and also reduces the number of
18946 lookups (though Exim does cache lookups).
18948 See also the &%set%& option below.
18950 .vindex "&$sender_address_data$&"
18951 .vindex "&$address_data$&"
18952 The &%address_data%& facility is also useful as a means of passing information
18953 from one router to another, and from a router to a transport. In addition, if
18954 &$address_data$& is set by a router when verifying a recipient address from an
18955 ACL, it remains available for use in the rest of the ACL statement. After
18956 verifying a sender, the value is transferred to &$sender_address_data$&.
18960 .option address_test routers&!? boolean true
18962 .cindex "router" "skipping when address testing"
18963 If this option is set false, the router is skipped when routing is being tested
18964 by means of the &%-bt%& command line option. This can be a convenience when
18965 your first router sends messages to an external scanner, because it saves you
18966 having to set the &"already scanned"& indicator when testing real address
18971 .option cannot_route_message routers string&!! unset
18972 .cindex "router" "customizing &""cannot route""& message"
18973 .cindex "customizing" "&""cannot route""& message"
18974 This option specifies a text message that is used when an address cannot be
18975 routed because Exim has run out of routers. The default message is
18976 &"Unrouteable address"&. This option is useful only on routers that have
18977 &%more%& set false, or on the very last router in a configuration, because the
18978 value that is used is taken from the last router that is considered. This
18979 includes a router that is skipped because its preconditions are not met, as
18980 well as a router that declines. For example, using the default configuration,
18983 cannot_route_message = Remote domain not found in DNS
18985 on the first router, which is a &(dnslookup)& router with &%more%& set false,
18988 cannot_route_message = Unknown local user
18990 on the final router that checks for local users. If string expansion fails for
18991 this option, the default message is used. Unless the expansion failure was
18992 explicitly forced, a message about the failure is written to the main and panic
18993 logs, in addition to the normal message about the routing failure.
18996 .option caseful_local_part routers boolean false
18997 .cindex "case of local parts"
18998 .cindex "router" "case of local parts"
18999 By default, routers handle the local parts of addresses in a case-insensitive
19000 manner, though the actual case is preserved for transmission with the message.
19001 If you want the case of letters to be significant in a router, you must set
19002 this option true. For individual router options that contain address or local
19003 part lists (for example, &%local_parts%&), case-sensitive matching can be
19004 turned on by &"+caseful"& as a list item. See section &<<SECTcasletadd>>& for
19007 .vindex "&$local_part$&"
19008 .vindex "&$original_local_part$&"
19009 .vindex "&$parent_local_part$&"
19010 The value of the &$local_part$& variable is forced to lower case while a
19011 router is running unless &%caseful_local_part%& is set. When a router assigns
19012 an address to a transport, the value of &$local_part$& when the transport runs
19013 is the same as it was in the router. Similarly, when a router generates child
19014 addresses by aliasing or forwarding, the values of &$original_local_part$&
19015 and &$parent_local_part$& are those that were used by the redirecting router.
19017 This option applies to the processing of an address by a router. When a
19018 recipient address is being processed in an ACL, there is a separate &%control%&
19019 modifier that can be used to specify case-sensitive processing within the ACL
19020 (see section &<<SECTcontrols>>&).
19024 .option check_local_user routers&!? boolean false
19025 .cindex "local user, checking in router"
19026 .cindex "router" "checking for local user"
19027 .cindex "&_/etc/passwd_&"
19029 When this option is true, Exim checks that the local part of the recipient
19030 address (with affixes removed if relevant) is the name of an account on the
19031 local system. The check is done by calling the &[getpwnam()]& function rather
19032 than trying to read &_/etc/passwd_& directly. This means that other methods of
19033 holding password data (such as NIS) are supported. If the local part is a local
19035 .cindex "tainted data" "de-tainting"
19036 &$local_part_data$& is set to an untainted version of the local part and
19037 &$home$& is set from the password data. The latter can be tested in other
19038 preconditions that are evaluated after this one (the order of evaluation is
19039 given in section &<<SECTrouprecon>>&). However, the value of &$home$& can be
19040 overridden by &%router_home_directory%&. If the local part is not a local user,
19041 the router is skipped.
19043 If you want to check that the local part is either the name of a local user
19044 or matches something else, you cannot combine &%check_local_user%& with a
19045 setting of &%local_parts%&, because that specifies the logical &'and'& of the
19046 two conditions. However, you can use a &(passwd)& lookup in a &%local_parts%&
19047 setting to achieve this. For example:
19049 local_parts = passwd;$local_part : lsearch;/etc/other/users
19051 Note, however, that the side effects of &%check_local_user%& (such as setting
19052 up a home directory) do not occur when a &(passwd)& lookup is used in a
19053 &%local_parts%& (or any other) precondition.
19057 .option condition routers&!? string&!! unset
19058 .cindex "router" "customized precondition"
19059 This option specifies a general precondition test that has to succeed for the
19060 router to be called. The &%condition%& option is the last precondition to be
19061 evaluated (see section &<<SECTrouprecon>>&). The string is expanded, and if the
19062 result is a forced failure, or an empty string, or one of the strings &"0"& or
19063 &"no"& or &"false"& (checked without regard to the case of the letters), the
19064 router is skipped, and the address is offered to the next one.
19066 If the result is any other value, the router is run (as this is the last
19067 precondition to be evaluated, all the other preconditions must be true).
19069 This option is unusual in that multiple &%condition%& options may be present.
19070 All &%condition%& options must succeed.
19072 The &%condition%& option provides a means of applying custom conditions to the
19073 running of routers. Note that in the case of a simple conditional expansion,
19074 the default expansion values are exactly what is wanted. For example:
19076 condition = ${if >{$message_age}{600}}
19078 Because of the default behaviour of the string expansion, this is equivalent to
19080 condition = ${if >{$message_age}{600}{true}{}}
19083 A multiple condition example, which succeeds:
19085 condition = ${if >{$message_age}{600}}
19086 condition = ${if !eq{${lc:$local_part}}{postmaster}}
19090 If the expansion fails (other than forced failure) delivery is deferred. Some
19091 of the other precondition options are common special cases that could in fact
19092 be specified using &%condition%&.
19094 Historical note: We have &%condition%& on ACLs and on Routers. Routers
19095 are far older, and use one set of semantics. ACLs are newer and when
19096 they were created, the ACL &%condition%& process was given far stricter
19097 parse semantics. The &%bool{}%& expansion condition uses the same rules as
19098 ACLs. The &%bool_lax{}%& expansion condition uses the same rules as
19099 Routers. More pointedly, the &%bool_lax{}%& was written to match the existing
19100 Router rules processing behavior.
19102 This is best illustrated in an example:
19104 # If used in an ACL condition will fail with a syntax error, but
19105 # in a router condition any extra characters are treated as a string
19107 $ exim -be '${if eq {${lc:GOOGLE.com}} {google.com}} {yes} {no}}'
19110 $ exim -be '${if eq {${lc:WHOIS.com}} {google.com}} {yes} {no}}'
19113 In each example above, the &%if%& statement actually ends after
19114 &"{google.com}}"&. Since no true or false braces were defined, the
19115 default &%if%& behavior is to return a boolean true or a null answer
19116 (which evaluates to false). The rest of the line is then treated as a
19117 string. So the first example resulted in the boolean answer &"true"&
19118 with the string &" {yes} {no}}"& appended to it. The second example
19119 resulted in the null output (indicating false) with the string
19120 &" {yes} {no}}"& appended to it.
19122 In fact you can put excess forward braces in too. In the router
19123 &%condition%&, Exim's parser only looks for &"{"& symbols when they
19124 mean something, like after a &"$"& or when required as part of a
19125 conditional. But otherwise &"{"& and &"}"& are treated as ordinary
19128 Thus, in a Router, the above expansion strings will both always evaluate
19129 true, as the result of expansion is a non-empty string which doesn't
19130 match an explicit false value. This can be tricky to debug. By
19131 contrast, in an ACL either of those strings will always result in an
19132 expansion error because the result doesn't look sufficiently boolean.
19135 .option debug_print routers string&!! unset
19136 .cindex "testing" "variables in drivers"
19137 If this option is set and debugging is enabled (see the &%-d%& command line
19138 option) or in address-testing mode (see the &%-bt%& command line option),
19139 the string is expanded and included in the debugging output.
19140 If expansion of the string fails, the error message is written to the debugging
19141 output, and Exim carries on processing.
19142 This option is provided to help with checking out the values of variables and
19143 so on when debugging router configurations. For example, if a &%condition%&
19144 option appears not to be working, &%debug_print%& can be used to output the
19145 variables it references. The output happens after checks for &%domains%&,
19146 &%local_parts%&, and &%check_local_user%& but before any other preconditions
19147 are tested. A newline is added to the text if it does not end with one.
19148 The variable &$router_name$& contains the name of the router.
19152 .option disable_logging routers boolean false
19153 If this option is set true, nothing is logged for any routing errors
19154 or for any deliveries caused by this router. You should not set this option
19155 unless you really, really know what you are doing. See also the generic
19156 transport option of the same name.
19158 .option dnssec_request_domains routers "domain list&!!" *
19159 .cindex "MX record" "security"
19160 .cindex "DNSSEC" "MX lookup"
19161 .cindex "security" "MX lookup"
19162 .cindex "DNS" "DNSSEC"
19163 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
19164 the DNSSEC request bit set.
19165 This applies to all of the SRV, MX, AAAA, A lookup sequence.
19167 .option dnssec_require_domains routers "domain list&!!" unset
19168 .cindex "MX record" "security"
19169 .cindex "DNSSEC" "MX lookup"
19170 .cindex "security" "MX lookup"
19171 .cindex "DNS" "DNSSEC"
19172 DNS lookups for domains matching &%dnssec_require_domains%& will be done with
19173 the DNSSEC request bit set. Any returns not having the Authenticated Data bit
19174 (AD bit) set will be ignored and logged as a host-lookup failure.
19175 This applies to all of the SRV, MX, AAAA, A lookup sequence.
19178 .option domains routers&!? "domain list&!!" unset
19179 .cindex "router" "restricting to specific domains"
19180 .vindex "&$domain_data$&"
19181 If this option is set, the router is skipped unless the current domain matches
19182 the list. If the match is achieved by means of a file lookup, the data that the
19183 lookup returned for the domain is placed in &$domain_data$& for use in string
19184 expansions of the driver's private options and in the transport.
19185 See section &<<SECTrouprecon>>& for
19186 a list of the order in which preconditions are evaluated.
19190 .option driver routers string unset
19191 This option must always be set. It specifies which of the available routers is
19195 .option dsn_lasthop routers boolean false
19196 .cindex "DSN" "success"
19197 .cindex "Delivery Status Notification" "success"
19198 If this option is set true, and extended DSN (RFC3461) processing is in effect,
19199 Exim will not pass on DSN requests to downstream DSN-aware hosts but will
19200 instead send a success DSN as if the next hop does not support DSN.
19201 Not effective on redirect routers.
19205 .option errors_to routers string&!! unset
19206 .cindex "envelope from"
19207 .cindex "envelope sender"
19208 .cindex "router" "changing address for errors"
19209 If a router successfully handles an address, it may assign the address to a
19210 transport for delivery or it may generate child addresses. In both cases, if
19211 there is a delivery problem during later processing, the resulting bounce
19212 message is sent to the address that results from expanding this string,
19213 provided that the address verifies successfully. The &%errors_to%& option is
19214 expanded before &%headers_add%&, &%headers_remove%&, and &%transport%&.
19216 The &%errors_to%& setting associated with an address can be overridden if it
19217 subsequently passes through other routers that have their own &%errors_to%&
19218 settings, or if the message is delivered by a transport with a &%return_path%&
19221 If &%errors_to%& is unset, or the expansion is forced to fail, or the result of
19222 the expansion fails to verify, the errors address associated with the incoming
19223 address is used. At top level, this is the envelope sender. A non-forced
19224 expansion failure causes delivery to be deferred.
19226 If an address for which &%errors_to%& has been set ends up being delivered over
19227 SMTP, the envelope sender for that delivery is the &%errors_to%& value, so that
19228 any bounces that are generated by other MTAs on the delivery route are also
19229 sent there. You can set &%errors_to%& to the empty string by either of these
19235 An expansion item that yields an empty string has the same effect. If you do
19236 this, a locally detected delivery error for addresses processed by this router
19237 no longer gives rise to a bounce message; the error is discarded. If the
19238 address is delivered to a remote host, the return path is set to &`<>`&, unless
19239 overridden by the &%return_path%& option on the transport.
19241 .vindex "&$address_data$&"
19242 If for some reason you want to discard local errors, but use a non-empty
19243 MAIL command for remote delivery, you can preserve the original return
19244 path in &$address_data$& in the router, and reinstate it in the transport by
19245 setting &%return_path%&.
19247 The most common use of &%errors_to%& is to direct mailing list bounces to the
19248 manager of the list, as described in section &<<SECTmailinglists>>&, or to
19249 implement VERP (Variable Envelope Return Paths) (see section &<<SECTverp>>&).
19253 .option expn routers&!? boolean true
19254 .cindex "address" "testing"
19255 .cindex "testing" "addresses"
19256 .cindex "EXPN" "router skipping"
19257 .cindex "router" "skipping for EXPN"
19258 If this option is turned off, the router is skipped when testing an address
19259 as a result of processing an SMTP EXPN command. You might, for example,
19260 want to turn it off on a router for users' &_.forward_& files, while leaving it
19261 on for the system alias file.
19262 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19265 The use of the SMTP EXPN command is controlled by an ACL (see chapter
19266 &<<CHAPACL>>&). When Exim is running an EXPN command, it is similar to testing
19267 an address with &%-bt%&. Compare VRFY, whose counterpart is &%-bv%&.
19271 .option fail_verify routers boolean false
19272 .cindex "router" "forcing verification failure"
19273 Setting this option has the effect of setting both &%fail_verify_sender%& and
19274 &%fail_verify_recipient%& to the same value.
19278 .option fail_verify_recipient routers boolean false
19279 If this option is true and an address is accepted by this router when
19280 verifying a recipient, verification fails.
19284 .option fail_verify_sender routers boolean false
19285 If this option is true and an address is accepted by this router when
19286 verifying a sender, verification fails.
19290 .option fallback_hosts routers "string list" unset
19291 .cindex "router" "fallback hosts"
19292 .cindex "fallback" "hosts specified on router"
19293 String expansion is not applied to this option. The argument must be a
19294 colon-separated list of host names or IP addresses. The list separator can be
19295 changed (see section &<<SECTlistsepchange>>&), and a port can be specified with
19296 each name or address. In fact, the format of each item is exactly the same as
19297 defined for the list of hosts in a &(manualroute)& router (see section
19298 &<<SECTformatonehostitem>>&).
19300 If a router queues an address for a remote transport, this host list is
19301 associated with the address, and used instead of the transport's fallback host
19302 list. If &%hosts_randomize%& is set on the transport, the order of the list is
19303 randomized for each use. See the &%fallback_hosts%& option of the &(smtp)&
19304 transport for further details.
19307 .option group routers string&!! "see below"
19308 .cindex "gid (group id)" "local delivery"
19309 .cindex "local transports" "uid and gid"
19310 .cindex "transport" "local"
19311 .cindex "router" "setting group"
19312 When a router queues an address for a transport, and the transport does not
19313 specify a group, the group given here is used when running the delivery
19315 The group may be specified numerically or by name. If expansion fails, the
19316 error is logged and delivery is deferred.
19317 The default is unset, unless &%check_local_user%& is set, when the default
19318 is taken from the password information. See also &%initgroups%& and &%user%&
19319 and the discussion in chapter &<<CHAPenvironment>>&.
19323 .option headers_add routers list&!! unset
19324 .cindex "header lines" "adding"
19325 .cindex "router" "adding header lines"
19326 This option specifies a list of text headers,
19327 newline-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
19328 that is associated with any addresses that are accepted by the router.
19329 Each item is separately expanded, at routing time. However, this
19330 option has no effect when an address is just being verified. The way in which
19331 the text is used to add header lines at transport time is described in section
19332 &<<SECTheadersaddrem>>&. New header lines are not actually added until the
19333 message is in the process of being transported. This means that references to
19334 header lines in string expansions in the transport's configuration do not
19335 &"see"& the added header lines.
19337 The &%headers_add%& option is expanded after &%errors_to%&, but before
19338 &%headers_remove%& and &%transport%&. If an item is empty, or if
19339 an item expansion is forced to fail, the item has no effect. Other expansion
19340 failures are treated as configuration errors.
19342 Unlike most options, &%headers_add%& can be specified multiple times
19343 for a router; all listed headers are added.
19345 &*Warning 1*&: The &%headers_add%& option cannot be used for a &(redirect)&
19346 router that has the &%one_time%& option set.
19348 .cindex "duplicate addresses"
19349 .oindex "&%unseen%&"
19350 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
19351 additions are deleted when the address is passed on to subsequent routers.
19352 For a &%redirect%& router, if a generated address is the same as the incoming
19353 address, this can lead to duplicate addresses with different header
19354 modifications. Exim does not do duplicate deliveries (except, in certain
19355 circumstances, to pipes -- see section &<<SECTdupaddr>>&), but it is undefined
19356 which of the duplicates is discarded, so this ambiguous situation should be
19357 avoided. The &%repeat_use%& option of the &%redirect%& router may be of help.
19361 .option headers_remove routers list&!! unset
19362 .cindex "header lines" "removing"
19363 .cindex "router" "removing header lines"
19364 This option specifies a list of text headers,
19365 colon-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
19366 that is associated with any addresses that are accepted by the router.
19367 However, the option has no effect when an address is just being verified.
19368 Each list item is separately expanded, at transport time.
19369 If an item ends in *, it will match any header with the given prefix.
19371 the text is used to remove header lines at transport time is described in
19372 section &<<SECTheadersaddrem>>&. Header lines are not actually removed until
19373 the message is in the process of being transported. This means that references
19374 to header lines in string expansions in the transport's configuration still
19375 &"see"& the original header lines.
19377 The &%headers_remove%& option is handled after &%errors_to%& and
19378 &%headers_add%&, but before &%transport%&. If an item expansion is forced to fail,
19379 the item has no effect. Other expansion failures are treated as configuration
19382 Unlike most options, &%headers_remove%& can be specified multiple times
19383 for a router; all listed headers are removed.
19385 &*Warning 1*&: The &%headers_remove%& option cannot be used for a &(redirect)&
19386 router that has the &%one_time%& option set.
19388 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
19389 removal requests are deleted when the address is passed on to subsequent
19390 routers, and this can lead to problems with duplicates -- see the similar
19391 warning for &%headers_add%& above.
19393 &*Warning 3*&: Because of the separate expansion of the list items,
19394 items that contain a list separator must have it doubled.
19395 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
19399 .option ignore_target_hosts routers "host list&!!" unset
19400 .cindex "IP address" "discarding"
19401 .cindex "router" "discarding IP addresses"
19402 Although this option is a host list, it should normally contain IP address
19403 entries rather than names. If any host that is looked up by the router has an
19404 IP address that matches an item in this list, Exim behaves as if that IP
19405 address did not exist. This option allows you to cope with rogue DNS entries
19408 remote.domain.example. A 127.0.0.1
19412 ignore_target_hosts = 127.0.0.1
19414 on the relevant router. If all the hosts found by a &(dnslookup)& router are
19415 discarded in this way, the router declines. In a conventional configuration, an
19416 attempt to mail to such a domain would normally provoke the &"unrouteable
19417 domain"& error, and an attempt to verify an address in the domain would fail.
19418 Similarly, if &%ignore_target_hosts%& is set on an &(ipliteral)& router, the
19419 router declines if presented with one of the listed addresses.
19421 You can use this option to disable the use of IPv4 or IPv6 for mail delivery by
19422 means of the first or the second of the following settings, respectively:
19424 ignore_target_hosts = 0.0.0.0/0
19425 ignore_target_hosts = <; 0::0/0
19427 The pattern in the first line matches all IPv4 addresses, whereas the pattern
19428 in the second line matches all IPv6 addresses.
19430 This option may also be useful for ignoring link-local and site-local IPv6
19431 addresses. Because, like all host lists, the value of &%ignore_target_hosts%&
19432 is expanded before use as a list, it is possible to make it dependent on the
19433 domain that is being routed.
19435 .vindex "&$host_address$&"
19436 During its expansion, &$host_address$& is set to the IP address that is being
19439 .option initgroups routers boolean false
19440 .cindex "additional groups"
19441 .cindex "groups" "additional"
19442 .cindex "local transports" "uid and gid"
19443 .cindex "transport" "local"
19444 If the router queues an address for a transport, and this option is true, and
19445 the uid supplied by the router is not overridden by the transport, the
19446 &[initgroups()]& function is called when running the transport to ensure that
19447 any additional groups associated with the uid are set up. See also &%group%&
19448 and &%user%& and the discussion in chapter &<<CHAPenvironment>>&.
19452 .option local_part_prefix routers&!? "string list" unset
19453 .cindex affix "router precondition"
19454 .cindex "router" "prefix for local part"
19455 .cindex "prefix" "for local part, used in router"
19456 If this option is set, the router is skipped unless the local part starts with
19457 one of the given strings, or &%local_part_prefix_optional%& is true. See
19458 section &<<SECTrouprecon>>& for a list of the order in which preconditions are
19461 The list is scanned from left to right, and the first prefix that matches is
19462 used. A limited form of wildcard is available; if the prefix begins with an
19463 asterisk, it matches the longest possible sequence of arbitrary characters at
19464 the start of the local part. An asterisk should therefore always be followed by
19465 some character that does not occur in normal local parts.
19466 .cindex "multiple mailboxes"
19467 .cindex "mailbox" "multiple"
19468 Wildcarding can be used to set up multiple user mailboxes, as described in
19469 section &<<SECTmulbox>>&.
19471 .vindex "&$local_part$&"
19472 .vindex "&$local_part_prefix$&"
19473 During the testing of the &%local_parts%& option, and while the router is
19474 running, the prefix is removed from the local part, and is available in the
19475 expansion variable &$local_part_prefix$&. When a message is being delivered, if
19476 the router accepts the address, this remains true during subsequent delivery by
19477 a transport. In particular, the local part that is transmitted in the RCPT
19478 command for LMTP, SMTP, and BSMTP deliveries has the prefix removed by default.
19479 This behaviour can be overridden by setting &%rcpt_include_affixes%& true on
19480 the relevant transport.
19482 .vindex &$local_part_prefix_v$&
19483 If wildcarding (above) was used then the part of the prefix matching the
19484 wildcard is available in &$local_part_prefix_v$&.
19486 When an address is being verified, &%local_part_prefix%& affects only the
19487 behaviour of the router. If the callout feature of verification is in use, this
19488 means that the full address, including the prefix, will be used during the
19491 The prefix facility is commonly used to handle local parts of the form
19492 &%owner-something%&. Another common use is to support local parts of the form
19493 &%real-username%& to bypass a user's &_.forward_& file &-- helpful when trying
19494 to tell a user their forwarding is broken &-- by placing a router like this one
19495 immediately before the router that handles &_.forward_& files:
19499 local_part_prefix = real-
19501 transport = local_delivery
19503 For security, it would probably be a good idea to restrict the use of this
19504 router to locally-generated messages, using a condition such as this:
19506 condition = ${if match {$sender_host_address}\
19507 {\N^(|127\.0\.0\.1)$\N}}
19510 If both &%local_part_prefix%& and &%local_part_suffix%& are set for a router,
19511 both conditions must be met if not optional. Care must be taken if wildcards
19512 are used in both a prefix and a suffix on the same router. Different
19513 separator characters must be used to avoid ambiguity.
19516 .option local_part_prefix_optional routers boolean false
19517 See &%local_part_prefix%& above.
19521 .option local_part_suffix routers&!? "string list" unset
19522 .cindex "router" "suffix for local part"
19523 .cindex "suffix for local part" "used in router"
19524 This option operates in the same way as &%local_part_prefix%&, except that the
19525 local part must end (rather than start) with the given string, the
19526 &%local_part_suffix_optional%& option determines whether the suffix is
19527 mandatory, and the wildcard * character, if present, must be the last
19528 character of the suffix. This option facility is commonly used to handle local
19529 parts of the form &%something-request%& and multiple user mailboxes of the form
19533 .option local_part_suffix_optional routers boolean false
19534 See &%local_part_suffix%& above.
19538 .option local_parts routers&!? "local part list&!!" unset
19539 .cindex "router" "restricting to specific local parts"
19540 .cindex "local part" "checking in router"
19541 The router is run only if the local part of the address matches the list.
19542 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19544 section &<<SECTlocparlis>>& for a discussion of local part lists. Because the
19545 string is expanded, it is possible to make it depend on the domain, for
19548 local_parts = dbm;/usr/local/specials/$domain_data
19550 .vindex "&$local_part_data$&"
19551 If the match is achieved by a lookup, the data that the lookup returned
19552 for the local part is placed in the variable &$local_part_data$& for use in
19553 expansions of the router's private options or in the transport.
19554 You might use this option, for
19555 example, if you have a large number of local virtual domains, and you want to
19556 send all postmaster mail to the same place without having to set up an alias in
19557 each virtual domain:
19561 local_parts = postmaster
19562 data = postmaster@real.domain.example
19566 .option log_as_local routers boolean "see below"
19567 .cindex "log" "delivery line"
19568 .cindex "delivery" "log line format"
19569 Exim has two logging styles for delivery, the idea being to make local
19570 deliveries stand out more visibly from remote ones. In the &"local"& style, the
19571 recipient address is given just as the local part, without a domain. The use of
19572 this style is controlled by this option. It defaults to true for the &(accept)&
19573 router, and false for all the others. This option applies only when a
19574 router assigns an address to a transport. It has no effect on routers that
19575 redirect addresses.
19579 .option more routers boolean&!! true
19580 The result of string expansion for this option must be a valid boolean value,
19581 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
19582 result causes an error, and delivery is deferred. If the expansion is forced to
19583 fail, the default value for the option (true) is used. Other failures cause
19584 delivery to be deferred.
19586 If this option is set false, and the router declines to handle the address, no
19587 further routers are tried, routing fails, and the address is bounced.
19589 However, if the router explicitly passes an address to the following router by
19590 means of the setting
19594 or otherwise, the setting of &%more%& is ignored. Also, the setting of &%more%&
19595 does not affect the behaviour if one of the precondition tests fails. In that
19596 case, the address is always passed to the next router.
19598 Note that &%address_data%& is not considered to be a precondition. If its
19599 expansion is forced to fail, the router declines, and the value of &%more%&
19600 controls what happens next.
19603 .option pass_on_timeout routers boolean false
19604 .cindex "timeout" "of router"
19605 .cindex "router" "timeout"
19606 If a router times out during a host lookup, it normally causes deferral of the
19607 address. If &%pass_on_timeout%& is set, the address is passed on to the next
19608 router, overriding &%no_more%&. This may be helpful for systems that are
19609 intermittently connected to the Internet, or those that want to pass to a smart
19610 host any messages that cannot immediately be delivered.
19612 There are occasional other temporary errors that can occur while doing DNS
19613 lookups. They are treated in the same way as a timeout, and this option
19614 applies to all of them.
19618 .option pass_router routers string unset
19619 .cindex "router" "go to after &""pass""&"
19620 Routers that recognize the generic &%self%& option (&(dnslookup)&,
19621 &(ipliteral)&, and &(manualroute)&) are able to return &"pass"&, forcing
19622 routing to continue, and overriding a false setting of &%more%&. When one of
19623 these routers returns &"pass"&, the address is normally handed on to the next
19624 router in sequence. This can be changed by setting &%pass_router%& to the name
19625 of another router. However (unlike &%redirect_router%&) the named router must
19626 be below the current router, to avoid loops. Note that this option applies only
19627 to the special case of &"pass"&. It does not apply when a router returns
19628 &"decline"& because it cannot handle an address.
19632 .option redirect_router routers string unset
19633 .cindex "router" "start at after redirection"
19634 Sometimes an administrator knows that it is pointless to reprocess addresses
19635 generated from alias or forward files with the same router again. For
19636 example, if an alias file translates real names into login ids there is no
19637 point searching the alias file a second time, especially if it is a large file.
19639 The &%redirect_router%& option can be set to the name of any router instance.
19640 It causes the routing of any generated addresses to start at the named router
19641 instead of at the first router. This option has no effect if the router in
19642 which it is set does not generate new addresses.
19646 .option require_files routers&!? "string list&!!" unset
19647 .cindex "file" "requiring for router"
19648 .cindex "router" "requiring file existence"
19649 This option provides a general mechanism for predicating the running of a
19650 router on the existence or non-existence of certain files or directories.
19651 Before running a router, as one of its precondition tests, Exim works its way
19652 through the &%require_files%& list, expanding each item separately.
19654 Because the list is split before expansion, any colons in expansion items must
19655 be doubled, or the facility for using a different list separator must be used
19656 (&<<SECTlistsepchange>>&).
19657 If any expansion is forced to fail, the item is ignored. Other expansion
19658 failures cause routing of the address to be deferred.
19660 If any expanded string is empty, it is ignored. Otherwise, except as described
19661 below, each string must be a fully qualified file path, optionally preceded by
19662 &"!"&. The paths are passed to the &[stat()]& function to test for the
19663 existence of the files or directories. The router is skipped if any paths not
19664 preceded by &"!"& do not exist, or if any paths preceded by &"!"& do exist.
19667 If &[stat()]& cannot determine whether a file exists or not, delivery of
19668 the message is deferred. This can happen when NFS-mounted filesystems are
19671 This option is checked after the &%domains%&, &%local_parts%&, and &%senders%&
19672 options, so you cannot use it to check for the existence of a file in which to
19673 look up a domain, local part, or sender. (See section &<<SECTrouprecon>>& for a
19674 full list of the order in which preconditions are evaluated.) However, as
19675 these options are all expanded, you can use the &%exists%& expansion condition
19676 to make such tests. The &%require_files%& option is intended for checking files
19677 that the router may be going to use internally, or which are needed by a
19678 transport (e.g., &_.procmailrc_&).
19680 During delivery, the &[stat()]& function is run as root, but there is a
19681 facility for some checking of the accessibility of a file by another user.
19682 This is not a proper permissions check, but just a &"rough"& check that
19683 operates as follows:
19685 If an item in a &%require_files%& list does not contain any forward slash
19686 characters, it is taken to be the user (and optional group, separated by a
19687 comma) to be checked for subsequent files in the list. If no group is specified
19688 but the user is specified symbolically, the gid associated with the uid is
19691 require_files = mail:/some/file
19692 require_files = $local_part_data:$home/.procmailrc
19694 If a user or group name in a &%require_files%& list does not exist, the
19695 &%require_files%& condition fails.
19697 Exim performs the check by scanning along the components of the file path, and
19698 checking the access for the given uid and gid. It checks for &"x"& access on
19699 directories, and &"r"& access on the final file. Note that this means that file
19700 access control lists, if the operating system has them, are ignored.
19702 &*Warning 1*&: When the router is being run to verify addresses for an
19703 incoming SMTP message, Exim is not running as root, but under its own uid. This
19704 may affect the result of a &%require_files%& check. In particular, &[stat()]&
19705 may yield the error EACCES (&"Permission denied"&). This means that the Exim
19706 user is not permitted to read one of the directories on the file's path.
19708 &*Warning 2*&: Even when Exim is running as root while delivering a message,
19709 &[stat()]& can yield EACCES for a file in an NFS directory that is mounted
19710 without root access. In this case, if a check for access by a particular user
19711 is requested, Exim creates a subprocess that runs as that user, and tries the
19712 check again in that process.
19714 The default action for handling an unresolved EACCES is to consider it to
19715 be caused by a configuration error, and routing is deferred because the
19716 existence or non-existence of the file cannot be determined. However, in some
19717 circumstances it may be desirable to treat this condition as if the file did
19718 not exist. If the filename (or the exclamation mark that precedes the filename
19719 for non-existence) is preceded by a plus sign, the EACCES error is treated
19720 as if the file did not exist. For example:
19722 require_files = +/some/file
19724 If the router is not an essential part of verification (for example, it
19725 handles users' &_.forward_& files), another solution is to set the &%verify%&
19726 option false so that the router is skipped when verifying.
19730 .option retry_use_local_part routers boolean "see below"
19731 .cindex "hints database" "retry keys"
19732 .cindex "local part" "in retry keys"
19733 When a delivery suffers a temporary routing failure, a retry record is created
19734 in Exim's hints database. For addresses whose routing depends only on the
19735 domain, the key for the retry record should not involve the local part, but for
19736 other addresses, both the domain and the local part should be included.
19737 Usually, remote routing is of the former kind, and local routing is of the
19740 This option controls whether the local part is used to form the key for retry
19741 hints for addresses that suffer temporary errors while being handled by this
19742 router. The default value is true for any router that has any of
19743 &%check_local_user%&,
19746 &%local_part_prefix%&,
19747 &%local_part_suffix%&,
19750 set, and false otherwise. Note that this option does not apply to hints keys
19751 for transport delays; they are controlled by a generic transport option of the
19754 Failing to set this option when it is needed
19755 (because a remote router handles only some of the local-parts for a domain)
19756 can result in incorrect error messages being generated.
19758 The setting of &%retry_use_local_part%& applies only to the router on which it
19759 appears. If the router generates child addresses, they are routed
19760 independently; this setting does not become attached to them.
19764 .option router_home_directory routers string&!! unset
19765 .cindex "router" "home directory for"
19766 .cindex "home directory" "for router"
19768 This option sets a home directory for use while the router is running. (Compare
19769 &%transport_home_directory%&, which sets a home directory for later
19770 transporting.) In particular, if used on a &(redirect)& router, this option
19771 sets a value for &$home$& while a filter is running. The value is expanded;
19772 forced expansion failure causes the option to be ignored &-- other failures
19773 cause the router to defer.
19775 Expansion of &%router_home_directory%& happens immediately after the
19776 &%check_local_user%& test (if configured), before any further expansions take
19778 (See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19780 While the router is running, &%router_home_directory%& overrides the value of
19781 &$home$& that came from &%check_local_user%&.
19783 When a router accepts an address and assigns it to a local transport (including
19784 the cases when a &(redirect)& router generates a pipe, file, or autoreply
19785 delivery), the home directory setting for the transport is taken from the first
19786 of these values that is set:
19789 The &%home_directory%& option on the transport;
19791 The &%transport_home_directory%& option on the router;
19793 The password data if &%check_local_user%& is set on the router;
19795 The &%router_home_directory%& option on the router.
19798 In other words, &%router_home_directory%& overrides the password data for the
19799 router, but not for the transport.
19803 .option self routers string freeze
19804 .cindex "MX record" "pointing to local host"
19805 .cindex "local host" "MX pointing to"
19806 This option applies to those routers that use a recipient address to find a
19807 list of remote hosts. Currently, these are the &(dnslookup)&, &(ipliteral)&,
19808 and &(manualroute)& routers.
19809 Certain configurations of the &(queryprogram)& router can also specify a list
19811 Usually such routers are configured to send the message to a remote host via an
19812 &(smtp)& transport. The &%self%& option specifies what happens when the first
19813 host on the list turns out to be the local host.
19814 The way in which Exim checks for the local host is described in section
19815 &<<SECTreclocipadd>>&.
19817 Normally this situation indicates either an error in Exim's configuration (for
19818 example, the router should be configured not to process this domain), or an
19819 error in the DNS (for example, the MX should not point to this host). For this
19820 reason, the default action is to log the incident, defer the address, and
19821 freeze the message. The following alternatives are provided for use in special
19826 Delivery of the message is tried again later, but the message is not frozen.
19828 .vitem "&%reroute%&: <&'domain'&>"
19829 The domain is changed to the given domain, and the address is passed back to
19830 be reprocessed by the routers. No rewriting of headers takes place. This
19831 behaviour is essentially a redirection.
19833 .vitem "&%reroute: rewrite:%& <&'domain'&>"
19834 The domain is changed to the given domain, and the address is passed back to be
19835 reprocessed by the routers. Any headers that contain the original domain are
19840 .vindex "&$self_hostname$&"
19841 The router passes the address to the next router, or to the router named in the
19842 &%pass_router%& option if it is set. This overrides &%no_more%&. During
19843 subsequent routing and delivery, the variable &$self_hostname$& contains the
19844 name of the local host that the router encountered. This can be used to
19845 distinguish between different cases for hosts with multiple names. The
19851 ensures that only those addresses that routed to the local host are passed on.
19852 Without &%no_more%&, addresses that were declined for other reasons would also
19853 be passed to the next router.
19856 Delivery fails and an error report is generated.
19859 .cindex "local host" "sending to"
19860 The anomaly is ignored and the address is queued for the transport. This
19861 setting should be used with extreme caution. For an &(smtp)& transport, it
19862 makes sense only in cases where the program that is listening on the SMTP port
19863 is not this version of Exim. That is, it must be some other MTA, or Exim with a
19864 different configuration file that handles the domain in another way.
19869 .option senders routers&!? "address list&!!" unset
19870 .cindex "router" "checking senders"
19871 If this option is set, the router is skipped unless the message's sender
19872 address matches something on the list.
19873 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19876 There are issues concerning verification when the running of routers is
19877 dependent on the sender. When Exim is verifying the address in an &%errors_to%&
19878 setting, it sets the sender to the null string. When using the &%-bt%& option
19879 to check a configuration file, it is necessary also to use the &%-f%& option to
19880 set an appropriate sender. For incoming mail, the sender is unset when
19881 verifying the sender, but is available when verifying any recipients. If the
19882 SMTP VRFY command is enabled, it must be used after MAIL if the sender address
19886 .option set routers "string list" unset
19887 .cindex router variables
19888 This option may be used multiple times on a router;
19889 because of this the list aspect is mostly irrelevant.
19890 The list separator is a semicolon but can be changed in the
19893 Each list-element given must be of the form &"name = value"&
19894 and the names used must start with the string &"r_"&.
19895 Values containing a list-separator should have them doubled.
19896 When a router runs, the strings are evaluated in order,
19897 to create variables which are added to the set associated with
19899 This is done immediately after all the preconditions, before the
19900 evaluation of the &%address_data%& option.
19901 The variable is set with the expansion of the value.
19902 The variables can be used by the router options
19903 (not including any preconditions)
19904 and by the transport.
19905 Later definitions of a given named variable will override former ones.
19906 Variable use is via the usual &$r_...$& syntax.
19908 This is similar to the &%address_data%& option, except that
19909 many independent variables can be used, with choice of naming.
19912 .option translate_ip_address routers string&!! unset
19913 .cindex "IP address" "translating"
19914 .cindex "packet radio"
19915 .cindex "router" "IP address translation"
19916 There exist some rare networking situations (for example, packet radio) where
19917 it is helpful to be able to translate IP addresses generated by normal routing
19918 mechanisms into other IP addresses, thus performing a kind of manual IP
19919 routing. This should be done only if the normal IP routing of the TCP/IP stack
19920 is inadequate or broken. Because this is an extremely uncommon requirement, the
19921 code to support this option is not included in the Exim binary unless
19922 SUPPORT_TRANSLATE_IP_ADDRESS=yes is set in &_Local/Makefile_&.
19924 .vindex "&$host_address$&"
19925 The &%translate_ip_address%& string is expanded for every IP address generated
19926 by the router, with the generated address set in &$host_address$&. If the
19927 expansion is forced to fail, no action is taken.
19928 For any other expansion error, delivery of the message is deferred.
19929 If the result of the expansion is an IP address, that replaces the original
19930 address; otherwise the result is assumed to be a host name &-- this is looked
19931 up using &[gethostbyname()]& (or &[getipnodebyname()]& when available) to
19932 produce one or more replacement IP addresses. For example, to subvert all IP
19933 addresses in some specific networks, this could be added to a router:
19935 translate_ip_address = \
19936 ${lookup{${mask:$host_address/26}}lsearch{/some/file}\
19939 The file would contain lines like
19941 10.2.3.128/26 some.host
19942 10.8.4.34/26 10.44.8.15
19944 You should not make use of this facility unless you really understand what you
19949 .option transport routers string&!! unset
19950 This option specifies the transport to be used when a router accepts an address
19951 and sets it up for delivery. A transport is never needed if a router is used
19952 only for verification. The value of the option is expanded at routing time,
19953 after the expansion of &%errors_to%&, &%headers_add%&, and &%headers_remove%&,
19954 and result must be the name of one of the configured transports. If it is not,
19955 delivery is deferred.
19957 The &%transport%& option is not used by the &(redirect)& router, but it does
19958 have some private options that set up transports for pipe and file deliveries
19959 (see chapter &<<CHAPredirect>>&).
19963 .option transport_current_directory routers string&!! unset
19964 .cindex "current directory for local transport"
19965 This option associates a current directory with any address that is routed
19966 to a local transport. This can happen either because a transport is
19967 explicitly configured for the router, or because it generates a delivery to a
19968 file or a pipe. During the delivery process (that is, at transport time), this
19969 option string is expanded and is set as the current directory, unless
19970 overridden by a setting on the transport.
19971 If the expansion fails for any reason, including forced failure, an error is
19972 logged, and delivery is deferred.
19973 See chapter &<<CHAPenvironment>>& for details of the local delivery
19979 .option transport_home_directory routers string&!! "see below"
19980 .cindex "home directory" "for local transport"
19981 This option associates a home directory with any address that is routed to a
19982 local transport. This can happen either because a transport is explicitly
19983 configured for the router, or because it generates a delivery to a file or a
19984 pipe. During the delivery process (that is, at transport time), the option
19985 string is expanded and is set as the home directory, unless overridden by a
19986 setting of &%home_directory%& on the transport.
19987 If the expansion fails for any reason, including forced failure, an error is
19988 logged, and delivery is deferred.
19990 If the transport does not specify a home directory, and
19991 &%transport_home_directory%& is not set for the router, the home directory for
19992 the transport is taken from the password data if &%check_local_user%& is set for
19993 the router. Otherwise it is taken from &%router_home_directory%& if that option
19994 is set; if not, no home directory is set for the transport.
19996 See chapter &<<CHAPenvironment>>& for further details of the local delivery
20002 .option unseen routers boolean&!! false
20003 .cindex "router" "carrying on after success"
20004 The result of string expansion for this option must be a valid boolean value,
20005 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
20006 result causes an error, and delivery is deferred. If the expansion is forced to
20007 fail, the default value for the option (false) is used. Other failures cause
20008 delivery to be deferred.
20010 When this option is set true, routing does not cease if the router accepts the
20011 address. Instead, a copy of the incoming address is passed to the next router,
20012 overriding a false setting of &%more%&. There is little point in setting
20013 &%more%& false if &%unseen%& is always true, but it may be useful in cases when
20014 the value of &%unseen%& contains expansion items (and therefore, presumably, is
20015 sometimes true and sometimes false).
20017 .cindex "copy of message (&%unseen%& option)"
20018 Setting the &%unseen%& option has a similar effect to the &%unseen%& command
20019 qualifier in filter files. It can be used to cause copies of messages to be
20020 delivered to some other destination, while also carrying out a normal delivery.
20021 In effect, the current address is made into a &"parent"& that has two children
20022 &-- one that is delivered as specified by this router, and a clone that goes on
20023 to be routed further. For this reason, &%unseen%& may not be combined with the
20024 &%one_time%& option in a &(redirect)& router.
20026 &*Warning*&: Header lines added to the address (or specified for removal) by
20027 this router or by previous routers affect the &"unseen"& copy of the message
20028 only. The clone that continues to be processed by further routers starts with
20029 no added headers and none specified for removal. For a &%redirect%& router, if
20030 a generated address is the same as the incoming address, this can lead to
20031 duplicate addresses with different header modifications. Exim does not do
20032 duplicate deliveries (except, in certain circumstances, to pipes -- see section
20033 &<<SECTdupaddr>>&), but it is undefined which of the duplicates is discarded,
20034 so this ambiguous situation should be avoided. The &%repeat_use%& option of the
20035 &%redirect%& router may be of help.
20037 Unlike the handling of header modifications, any data that was set by the
20038 &%address_data%& option in the current or previous routers &'is'& passed on to
20039 subsequent routers.
20042 .option user routers string&!! "see below"
20043 .cindex "uid (user id)" "local delivery"
20044 .cindex "local transports" "uid and gid"
20045 .cindex "transport" "local"
20046 .cindex "router" "user for filter processing"
20047 .cindex "filter" "user for processing"
20048 When a router queues an address for a transport, and the transport does not
20049 specify a user, the user given here is used when running the delivery process.
20050 The user may be specified numerically or by name. If expansion fails, the
20051 error is logged and delivery is deferred.
20052 This user is also used by the &(redirect)& router when running a filter file.
20053 The default is unset, except when &%check_local_user%& is set. In this case,
20054 the default is taken from the password information. If the user is specified as
20055 a name, and &%group%& is not set, the group associated with the user is used.
20056 See also &%initgroups%& and &%group%& and the discussion in chapter
20057 &<<CHAPenvironment>>&.
20061 .option verify routers&!? boolean true
20062 Setting this option has the effect of setting &%verify_sender%& and
20063 &%verify_recipient%& to the same value.
20066 .option verify_only routers&!? boolean false
20067 .cindex "EXPN" "with &%verify_only%&"
20069 .cindex "router" "used only when verifying"
20070 If this option is set, the router is used only when verifying an address,
20071 delivering in cutthrough mode or
20072 testing with the &%-bv%& option, not when actually doing a delivery, testing
20073 with the &%-bt%& option, or running the SMTP EXPN command. It can be further
20074 restricted to verifying only senders or recipients by means of
20075 &%verify_sender%& and &%verify_recipient%&.
20077 &*Warning*&: When the router is being run to verify addresses for an incoming
20078 SMTP message, Exim is not running as root, but under its own uid. If the router
20079 accesses any files, you need to make sure that they are accessible to the Exim
20083 .option verify_recipient routers&!? boolean true
20084 If this option is false, the router is skipped when verifying recipient
20086 delivering in cutthrough mode
20087 or testing recipient verification using &%-bv%&.
20088 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
20090 See also the &$verify_mode$& variable.
20093 .option verify_sender routers&!? boolean true
20094 If this option is false, the router is skipped when verifying sender addresses
20095 or testing sender verification using &%-bvs%&.
20096 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
20098 See also the &$verify_mode$& variable.
20099 .ecindex IIDgenoprou1
20100 .ecindex IIDgenoprou2
20107 . ////////////////////////////////////////////////////////////////////////////
20108 . ////////////////////////////////////////////////////////////////////////////
20110 .chapter "The accept router" "CHID4"
20111 .cindex "&(accept)& router"
20112 .cindex "routers" "&(accept)&"
20113 The &(accept)& router has no private options of its own. Unless it is being
20114 used purely for verification (see &%verify_only%&) a transport is required to
20115 be defined by the generic &%transport%& option. If the preconditions that are
20116 specified by generic options are met, the router accepts the address and queues
20117 it for the given transport. The most common use of this router is for setting
20118 up deliveries to local mailboxes. For example:
20122 domains = mydomain.example
20124 transport = local_delivery
20126 The &%domains%& condition in this example checks the domain of the address, and
20127 &%check_local_user%& checks that the local part is the login of a local user.
20128 When both preconditions are met, the &(accept)& router runs, and queues the
20129 address for the &(local_delivery)& transport.
20136 . ////////////////////////////////////////////////////////////////////////////
20137 . ////////////////////////////////////////////////////////////////////////////
20139 .chapter "The dnslookup router" "CHAPdnslookup"
20140 .scindex IIDdnsrou1 "&(dnslookup)& router"
20141 .scindex IIDdnsrou2 "routers" "&(dnslookup)&"
20142 The &(dnslookup)& router looks up the hosts that handle mail for the
20143 recipient's domain in the DNS. A transport must always be set for this router,
20144 unless &%verify_only%& is set.
20146 If SRV support is configured (see &%check_srv%& below), Exim first searches for
20147 SRV records. If none are found, or if SRV support is not configured,
20148 MX records are looked up. If no MX records exist, address records are sought.
20149 However, &%mx_domains%& can be set to disable the direct use of address
20152 MX records of equal priority are sorted by Exim into a random order. Exim then
20153 looks for address records for the host names obtained from MX or SRV records.
20154 When a host has more than one IP address, they are sorted into a random order,
20155 except that IPv6 addresses are sorted before IPv4 addresses. If all the
20156 IP addresses found are discarded by a setting of the &%ignore_target_hosts%&
20157 generic option, the router declines.
20159 Unless they have the highest priority (lowest MX value), MX records that point
20160 to the local host, or to any host name that matches &%hosts_treat_as_local%&,
20161 are discarded, together with any other MX records of equal or lower priority.
20163 .cindex "MX record" "pointing to local host"
20164 .cindex "local host" "MX pointing to"
20165 .oindex "&%self%&" "in &(dnslookup)& router"
20166 If the host pointed to by the highest priority MX record, or looked up as an
20167 address record, is the local host, or matches &%hosts_treat_as_local%&, what
20168 happens is controlled by the generic &%self%& option.
20171 .section "Problems with DNS lookups" "SECTprowitdnsloo"
20172 There have been problems with DNS servers when SRV records are looked up.
20173 Some misbehaving servers return a DNS error or timeout when a non-existent
20174 SRV record is sought. Similar problems have in the past been reported for
20175 MX records. The global &%dns_again_means_nonexist%& option can help with this
20176 problem, but it is heavy-handed because it is a global option.
20178 For this reason, there are two options, &%srv_fail_domains%& and
20179 &%mx_fail_domains%&, that control what happens when a DNS lookup in a
20180 &(dnslookup)& router results in a DNS failure or a &"try again"& response. If
20181 an attempt to look up an SRV or MX record causes one of these results, and the
20182 domain matches the relevant list, Exim behaves as if the DNS had responded &"no
20183 such record"&. In the case of an SRV lookup, this means that the router
20184 proceeds to look for MX records; in the case of an MX lookup, it proceeds to
20185 look for A or AAAA records, unless the domain matches &%mx_domains%&, in which
20186 case routing fails.
20189 .section "Declining addresses by dnslookup" "SECTdnslookupdecline"
20190 .cindex "&(dnslookup)& router" "declines"
20191 There are a few cases where a &(dnslookup)& router will decline to accept
20192 an address; if such a router is expected to handle "all remaining non-local
20193 domains", then it is important to set &%no_more%&.
20195 The router will defer rather than decline if the domain
20196 is found in the &%fail_defer_domains%& router option.
20198 Reasons for a &(dnslookup)& router to decline currently include:
20200 The domain does not exist in DNS
20202 The domain exists but the MX record's host part is just "."; this is a common
20203 convention (borrowed from SRV) used to indicate that there is no such service
20204 for this domain and to not fall back to trying A/AAAA records.
20206 Ditto, but for SRV records, when &%check_srv%& is set on this router.
20208 MX record points to a non-existent host.
20210 MX record points to an IP address and the main section option
20211 &%allow_mx_to_ip%& is not set.
20213 MX records exist and point to valid hosts, but all hosts resolve only to
20214 addresses blocked by the &%ignore_target_hosts%& generic option on this router.
20216 The domain is not syntactically valid (see also &%allow_utf8_domains%& and
20217 &%dns_check_names_pattern%& for handling one variant of this)
20219 &%check_secondary_mx%& is set on this router but the local host can
20220 not be found in the MX records (see below)
20226 .section "Private options for dnslookup" "SECID118"
20227 .cindex "options" "&(dnslookup)& router"
20228 The private options for the &(dnslookup)& router are as follows:
20230 .option check_secondary_mx dnslookup boolean false
20231 .cindex "MX record" "checking for secondary"
20232 If this option is set, the router declines unless the local host is found in
20233 (and removed from) the list of hosts obtained by MX lookup. This can be used to
20234 process domains for which the local host is a secondary mail exchanger
20235 differently to other domains. The way in which Exim decides whether a host is
20236 the local host is described in section &<<SECTreclocipadd>>&.
20239 .option check_srv dnslookup string&!! unset
20240 .cindex "SRV record" "enabling use of"
20241 The &(dnslookup)& router supports the use of SRV records (see RFC 2782) in
20242 addition to MX and address records. The support is disabled by default. To
20243 enable SRV support, set the &%check_srv%& option to the name of the service
20244 required. For example,
20248 looks for SRV records that refer to the normal smtp service. The option is
20249 expanded, so the service name can vary from message to message or address
20250 to address. This might be helpful if SRV records are being used for a
20251 submission service. If the expansion is forced to fail, the &%check_srv%&
20252 option is ignored, and the router proceeds to look for MX records in the
20255 When the expansion succeeds, the router searches first for SRV records for
20256 the given service (it assumes TCP protocol). A single SRV record with a
20257 host name that consists of just a single dot indicates &"no such service for
20258 this domain"&; if this is encountered, the router declines. If other kinds of
20259 SRV record are found, they are used to construct a host list for delivery
20260 according to the rules of RFC 2782. MX records are not sought in this case.
20262 When no SRV records are found, MX records (and address records) are sought in
20263 the traditional way. In other words, SRV records take precedence over MX
20264 records, just as MX records take precedence over address records. Note that
20265 this behaviour is not sanctioned by RFC 2782, though a previous draft RFC
20266 defined it. It is apparently believed that MX records are sufficient for email
20267 and that SRV records should not be used for this purpose. However, SRV records
20268 have an additional &"weight"& feature which some people might find useful when
20269 trying to split an SMTP load between hosts of different power.
20271 See section &<<SECTprowitdnsloo>>& above for a discussion of Exim's behaviour
20272 when there is a DNS lookup error.
20277 .option fail_defer_domains dnslookup "domain list&!!" unset
20278 .cindex "MX record" "not found"
20279 DNS lookups for domains matching &%fail_defer_domains%&
20280 which find no matching record will cause the router to defer
20281 rather than the default behaviour of decline.
20282 This maybe be useful for queueing messages for a newly created
20283 domain while the DNS configuration is not ready.
20284 However, it will result in any message with mistyped domains
20288 .option ipv4_only "string&!!" unset
20289 .cindex IPv6 disabling
20290 .cindex DNS "IPv6 disabling"
20291 The string is expanded, and if the result is anything but a forced failure,
20292 or an empty string, or one of the strings “0” or “no” or “false”
20293 (checked without regard to the case of the letters),
20294 only A records are used.
20296 .option ipv4_prefer "string&!!" unset
20297 .cindex IPv4 preference
20298 .cindex DNS "IPv4 preference"
20299 The string is expanded, and if the result is anything but a forced failure,
20300 or an empty string, or one of the strings “0” or “no” or “false”
20301 (checked without regard to the case of the letters),
20302 A records are sorted before AAAA records (inverting the default).
20304 .option mx_domains dnslookup "domain list&!!" unset
20305 .cindex "MX record" "required to exist"
20306 .cindex "SRV record" "required to exist"
20307 A domain that matches &%mx_domains%& is required to have either an MX or an SRV
20308 record in order to be recognized. (The name of this option could be improved.)
20309 For example, if all the mail hosts in &'fict.example'& are known to have MX
20310 records, except for those in &'discworld.fict.example'&, you could use this
20313 mx_domains = ! *.discworld.fict.example : *.fict.example
20315 This specifies that messages addressed to a domain that matches the list but
20316 has no MX record should be bounced immediately instead of being routed using
20317 the address record.
20320 .option mx_fail_domains dnslookup "domain list&!!" unset
20321 If the DNS lookup for MX records for one of the domains in this list causes a
20322 DNS lookup error, Exim behaves as if no MX records were found. See section
20323 &<<SECTprowitdnsloo>>& for more discussion.
20328 .option qualify_single dnslookup boolean true
20329 .cindex "DNS" "resolver options"
20330 .cindex "DNS" "qualifying single-component names"
20331 When this option is true, the resolver option RES_DEFNAMES is set for DNS
20332 lookups. Typically, but not standardly, this causes the resolver to qualify
20333 single-component names with the default domain. For example, on a machine
20334 called &'dictionary.ref.example'&, the domain &'thesaurus'& would be changed to
20335 &'thesaurus.ref.example'& inside the resolver. For details of what your
20336 resolver actually does, consult your man pages for &'resolver'& and
20341 .option rewrite_headers dnslookup boolean true
20342 .cindex "rewriting" "header lines"
20343 .cindex "header lines" "rewriting"
20344 If the domain name in the address that is being processed is not fully
20345 qualified, it may be expanded to its full form by a DNS lookup. For example, if
20346 an address is specified as &'dormouse@teaparty'&, the domain might be
20347 expanded to &'teaparty.wonderland.fict.example'&. Domain expansion can also
20348 occur as a result of setting the &%widen_domains%& option. If
20349 &%rewrite_headers%& is true, all occurrences of the abbreviated domain name in
20350 any &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-to:'&, &'Sender:'&, and &'To:'&
20351 header lines of the message are rewritten with the full domain name.
20353 This option should be turned off only when it is known that no message is
20354 ever going to be sent outside an environment where the abbreviation makes
20357 When an MX record is looked up in the DNS and matches a wildcard record, name
20358 servers normally return a record containing the name that has been looked up,
20359 making it impossible to detect whether a wildcard was present or not. However,
20360 some name servers have recently been seen to return the wildcard entry. If the
20361 name returned by a DNS lookup begins with an asterisk, it is not used for
20365 .option same_domain_copy_routing dnslookup boolean false
20366 .cindex "address" "copying routing"
20367 Addresses with the same domain are normally routed by the &(dnslookup)& router
20368 to the same list of hosts. However, this cannot be presumed, because the router
20369 options and preconditions may refer to the local part of the address. By
20370 default, therefore, Exim routes each address in a message independently. DNS
20371 servers run caches, so repeated DNS lookups are not normally expensive, and in
20372 any case, personal messages rarely have more than a few recipients.
20374 If you are running mailing lists with large numbers of subscribers at the same
20375 domain, and you are using a &(dnslookup)& router which is independent of the
20376 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
20377 lookups for identical domains in one message. In this case, when &(dnslookup)&
20378 routes an address to a remote transport, any other unrouted addresses in the
20379 message that have the same domain are automatically given the same routing
20380 without processing them independently,
20381 provided the following conditions are met:
20384 No router that processed the address specified &%headers_add%& or
20385 &%headers_remove%&.
20387 The router did not change the address in any way, for example, by &"widening"&
20394 .option search_parents dnslookup boolean false
20395 .cindex "DNS" "resolver options"
20396 When this option is true, the resolver option RES_DNSRCH is set for DNS
20397 lookups. This is different from the &%qualify_single%& option in that it
20398 applies to domains containing dots. Typically, but not standardly, it causes
20399 the resolver to search for the name in the current domain and in parent
20400 domains. For example, on a machine in the &'fict.example'& domain, if looking
20401 up &'teaparty.wonderland'& failed, the resolver would try
20402 &'teaparty.wonderland.fict.example'&. For details of what your resolver
20403 actually does, consult your man pages for &'resolver'& and &'resolv.conf'&.
20405 Setting this option true can cause problems in domains that have a wildcard MX
20406 record, because any domain that does not have its own MX record matches the
20411 .option srv_fail_domains dnslookup "domain list&!!" unset
20412 If the DNS lookup for SRV records for one of the domains in this list causes a
20413 DNS lookup error, Exim behaves as if no SRV records were found. See section
20414 &<<SECTprowitdnsloo>>& for more discussion.
20419 .option widen_domains dnslookup "string list" unset
20420 .cindex "domain" "partial; widening"
20421 If a DNS lookup fails and this option is set, each of its strings in turn is
20422 added onto the end of the domain, and the lookup is tried again. For example,
20425 widen_domains = fict.example:ref.example
20427 is set and a lookup of &'klingon.dictionary'& fails,
20428 &'klingon.dictionary.fict.example'& is looked up, and if this fails,
20429 &'klingon.dictionary.ref.example'& is tried. Note that the &%qualify_single%&
20430 and &%search_parents%& options can cause some widening to be undertaken inside
20431 the DNS resolver. &%widen_domains%& is not applied to sender addresses
20432 when verifying, unless &%rewrite_headers%& is false (not the default).
20435 .section "Effect of qualify_single and search_parents" "SECID119"
20436 When a domain from an envelope recipient is changed by the resolver as a result
20437 of the &%qualify_single%& or &%search_parents%& options, Exim rewrites the
20438 corresponding address in the message's header lines unless &%rewrite_headers%&
20439 is set false. Exim then re-routes the address, using the full domain.
20441 These two options affect only the DNS lookup that takes place inside the router
20442 for the domain of the address that is being routed. They do not affect lookups
20443 such as that implied by
20447 that may happen while processing a router precondition before the router is
20448 entered. No widening ever takes place for these lookups.
20449 .ecindex IIDdnsrou1
20450 .ecindex IIDdnsrou2
20460 . ////////////////////////////////////////////////////////////////////////////
20461 . ////////////////////////////////////////////////////////////////////////////
20463 .chapter "The ipliteral router" "CHID5"
20464 .cindex "&(ipliteral)& router"
20465 .cindex "domain literal" "routing"
20466 .cindex "routers" "&(ipliteral)&"
20467 This router has no private options. Unless it is being used purely for
20468 verification (see &%verify_only%&) a transport is required to be defined by the
20469 generic &%transport%& option. The router accepts the address if its domain part
20470 takes the form of an RFC 2822 domain literal. For example, the &(ipliteral)&
20471 router handles the address
20475 by setting up delivery to the host with that IP address. IPv4 domain literals
20476 consist of an IPv4 address enclosed in square brackets. IPv6 domain literals
20477 are similar, but the address is preceded by &`ipv6:`&. For example:
20479 postmaster@[ipv6:fe80::a00:20ff:fe86:a061.5678]
20481 Exim allows &`ipv4:`& before IPv4 addresses, for consistency, and on the
20482 grounds that sooner or later somebody will try it.
20484 .oindex "&%self%&" "in &(ipliteral)& router"
20485 If the IP address matches something in &%ignore_target_hosts%&, the router
20486 declines. If an IP literal turns out to refer to the local host, the generic
20487 &%self%& option determines what happens.
20489 The RFCs require support for domain literals; however, their use is
20490 controversial in today's Internet. If you want to use this router, you must
20491 also set the main configuration option &%allow_domain_literals%&. Otherwise,
20492 Exim will not recognize the domain literal syntax in addresses.
20496 . ////////////////////////////////////////////////////////////////////////////
20497 . ////////////////////////////////////////////////////////////////////////////
20499 .chapter "The iplookup router" "CHID6"
20500 .cindex "&(iplookup)& router"
20501 .cindex "routers" "&(iplookup)&"
20502 The &(iplookup)& router was written to fulfil a specific requirement in
20503 Cambridge University (which in fact no longer exists). For this reason, it is
20504 not included in the binary of Exim by default. If you want to include it, you
20507 ROUTER_IPLOOKUP=yes
20509 in your &_Local/Makefile_& configuration file.
20511 The &(iplookup)& router routes an address by sending it over a TCP or UDP
20512 connection to one or more specific hosts. The host can then return the same or
20513 a different address &-- in effect rewriting the recipient address in the
20514 message's envelope. The new address is then passed on to subsequent routers. If
20515 this process fails, the address can be passed on to other routers, or delivery
20516 can be deferred. Since &(iplookup)& is just a rewriting router, a transport
20517 must not be specified for it.
20519 .cindex "options" "&(iplookup)& router"
20520 .option hosts iplookup string unset
20521 This option must be supplied. Its value is a colon-separated list of host
20522 names. The hosts are looked up using &[gethostbyname()]&
20523 (or &[getipnodebyname()]& when available)
20524 and are tried in order until one responds to the query. If none respond, what
20525 happens is controlled by &%optional%&.
20528 .option optional iplookup boolean false
20529 If &%optional%& is true, if no response is obtained from any host, the address
20530 is passed to the next router, overriding &%no_more%&. If &%optional%& is false,
20531 delivery to the address is deferred.
20534 .option port iplookup integer 0
20535 .cindex "port" "&(iplookup)& router"
20536 This option must be supplied. It specifies the port number for the TCP or UDP
20540 .option protocol iplookup string udp
20541 This option can be set to &"udp"& or &"tcp"& to specify which of the two
20542 protocols is to be used.
20545 .option query iplookup string&!! "see below"
20546 This defines the content of the query that is sent to the remote hosts. The
20549 $local_part@$domain $local_part@$domain
20551 The repetition serves as a way of checking that a response is to the correct
20552 query in the default case (see &%response_pattern%& below).
20555 .option reroute iplookup string&!! unset
20556 If this option is not set, the rerouted address is precisely the byte string
20557 returned by the remote host, up to the first white space, if any. If set, the
20558 string is expanded to form the rerouted address. It can include parts matched
20559 in the response by &%response_pattern%& by means of numeric variables such as
20560 &$1$&, &$2$&, etc. The variable &$0$& refers to the entire input string,
20561 whether or not a pattern is in use. In all cases, the rerouted address must end
20562 up in the form &'local_part@domain'&.
20565 .option response_pattern iplookup string unset
20566 This option can be set to a regular expression that is applied to the string
20567 returned from the remote host. If the pattern does not match the response, the
20568 router declines. If &%response_pattern%& is not set, no checking of the
20569 response is done, unless the query was defaulted, in which case there is a
20570 check that the text returned after the first white space is the original
20571 address. This checks that the answer that has been received is in response to
20572 the correct question. For example, if the response is just a new domain, the
20573 following could be used:
20575 response_pattern = ^([^@]+)$
20576 reroute = $local_part@$1
20579 .option timeout iplookup time 5s
20580 This specifies the amount of time to wait for a response from the remote
20581 machine. The same timeout is used for the &[connect()]& function for a TCP
20582 call. It does not apply to UDP.
20587 . ////////////////////////////////////////////////////////////////////////////
20588 . ////////////////////////////////////////////////////////////////////////////
20590 .chapter "The manualroute router" "CHID7"
20591 .scindex IIDmanrou1 "&(manualroute)& router"
20592 .scindex IIDmanrou2 "routers" "&(manualroute)&"
20593 .cindex "domain" "manually routing"
20594 The &(manualroute)& router is so-called because it provides a way of manually
20595 routing an address according to its domain. It is mainly used when you want to
20596 route addresses to remote hosts according to your own rules, bypassing the
20597 normal DNS routing that looks up MX records. However, &(manualroute)& can also
20598 route to local transports, a facility that may be useful if you want to save
20599 messages for dial-in hosts in local files.
20601 The &(manualroute)& router compares a list of domain patterns with the domain
20602 it is trying to route. If there is no match, the router declines. Each pattern
20603 has associated with it a list of hosts and some other optional data, which may
20604 include a transport. The combination of a pattern and its data is called a
20605 &"routing rule"&. For patterns that do not have an associated transport, the
20606 generic &%transport%& option must specify a transport, unless the router is
20607 being used purely for verification (see &%verify_only%&).
20610 In the case of verification, matching the domain pattern is sufficient for the
20611 router to accept the address. When actually routing an address for delivery,
20612 an address that matches a domain pattern is queued for the associated
20613 transport. If the transport is not a local one, a host list must be associated
20614 with the pattern; IP addresses are looked up for the hosts, and these are
20615 passed to the transport along with the mail address. For local transports, a
20616 host list is optional. If it is present, it is passed in &$host$& as a single
20619 The list of routing rules can be provided as an inline string in
20620 &%route_list%&, or the data can be obtained by looking up the domain in a file
20621 or database by setting &%route_data%&. Only one of these settings may appear in
20622 any one instance of &(manualroute)&. The format of routing rules is described
20623 below, following the list of private options.
20626 .section "Private options for manualroute" "SECTprioptman"
20628 .cindex "options" "&(manualroute)& router"
20629 The private options for the &(manualroute)& router are as follows:
20631 .option host_all_ignored manualroute string defer
20632 See &%host_find_failed%&.
20634 .option host_find_failed manualroute string freeze
20635 This option controls what happens when &(manualroute)& tries to find an IP
20636 address for a host, and the host does not exist. The option can be set to one
20637 of the following values:
20646 The default (&"freeze"&) assumes that this state is a serious configuration
20647 error. The difference between &"pass"& and &"decline"& is that the former
20648 forces the address to be passed to the next router (or the router defined by
20651 overriding &%no_more%&, whereas the latter passes the address to the next
20652 router only if &%more%& is true.
20654 The value &"ignore"& causes Exim to completely ignore a host whose IP address
20655 cannot be found. If all the hosts in the list are ignored, the behaviour is
20656 controlled by the &%host_all_ignored%& option. This takes the same values
20657 as &%host_find_failed%&, except that it cannot be set to &"ignore"&.
20659 The &%host_find_failed%& option applies only to a definite &"does not exist"&
20660 state; if a host lookup gets a temporary error, delivery is deferred unless the
20661 generic &%pass_on_timeout%& option is set.
20664 .option hosts_randomize manualroute boolean false
20665 .cindex "randomized host list"
20666 .cindex "host" "list of; randomized"
20667 If this option is set, the order of the items in a host list in a routing rule
20668 is randomized each time the list is used, unless an option in the routing rule
20669 overrides (see below). Randomizing the order of a host list can be used to do
20670 crude load sharing. However, if more than one mail address is routed by the
20671 same router to the same host list, the host lists are considered to be the same
20672 (even though they may be randomized into different orders) for the purpose of
20673 deciding whether to batch the deliveries into a single SMTP transaction.
20675 When &%hosts_randomize%& is true, a host list may be split
20676 into groups whose order is separately randomized. This makes it possible to
20677 set up MX-like behaviour. The boundaries between groups are indicated by an
20678 item that is just &`+`& in the host list. For example:
20680 route_list = * host1:host2:host3:+:host4:host5
20682 The order of the first three hosts and the order of the last two hosts is
20683 randomized for each use, but the first three always end up before the last two.
20684 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored. If a
20685 randomized host list is passed to an &(smtp)& transport that also has
20686 &%hosts_randomize set%&, the list is not re-randomized.
20689 .option route_data manualroute string&!! unset
20690 If this option is set, it must expand to yield the data part of a routing rule.
20691 Typically, the expansion string includes a lookup based on the domain. For
20694 route_data = ${lookup{$domain}dbm{/etc/routes}}
20696 If the expansion is forced to fail, or the result is an empty string, the
20697 router declines. Other kinds of expansion failure cause delivery to be
20701 .option route_list manualroute "string list" unset
20702 This string is a list of routing rules, in the form defined below. Note that,
20703 unlike most string lists, the items are separated by semicolons. This is so
20704 that they may contain colon-separated host lists.
20707 .option same_domain_copy_routing manualroute boolean false
20708 .cindex "address" "copying routing"
20709 Addresses with the same domain are normally routed by the &(manualroute)&
20710 router to the same list of hosts. However, this cannot be presumed, because the
20711 router options and preconditions may refer to the local part of the address. By
20712 default, therefore, Exim routes each address in a message independently. DNS
20713 servers run caches, so repeated DNS lookups are not normally expensive, and in
20714 any case, personal messages rarely have more than a few recipients.
20716 If you are running mailing lists with large numbers of subscribers at the same
20717 domain, and you are using a &(manualroute)& router which is independent of the
20718 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
20719 lookups for identical domains in one message. In this case, when
20720 &(manualroute)& routes an address to a remote transport, any other unrouted
20721 addresses in the message that have the same domain are automatically given the
20722 same routing without processing them independently. However, this is only done
20723 if &%headers_add%& and &%headers_remove%& are unset.
20728 .section "Routing rules in route_list" "SECID120"
20729 The value of &%route_list%& is a string consisting of a sequence of routing
20730 rules, separated by semicolons. If a semicolon is needed in a rule, it can be
20731 entered as two semicolons. Alternatively, the list separator can be changed as
20732 described (for colon-separated lists) in section &<<SECTlistconstruct>>&.
20733 Empty rules are ignored. The format of each rule is
20735 <&'domain pattern'&> <&'list of hosts'&> <&'options'&>
20737 The following example contains two rules, each with a simple domain pattern and
20741 dict.ref.example mail-1.ref.example:mail-2.ref.example ; \
20742 thes.ref.example mail-3.ref.example:mail-4.ref.example
20744 The three parts of a rule are separated by white space. The pattern and the
20745 list of hosts can be enclosed in quotes if necessary, and if they are, the
20746 usual quoting rules apply. Each rule in a &%route_list%& must start with a
20747 single domain pattern, which is the only mandatory item in the rule. The
20748 pattern is in the same format as one item in a domain list (see section
20749 &<<SECTdomainlist>>&),
20750 except that it may not be the name of an interpolated file.
20751 That is, it may be wildcarded, or a regular expression, or a file or database
20752 lookup (with semicolons doubled, because of the use of semicolon as a separator
20753 in a &%route_list%&).
20755 The rules in &%route_list%& are searched in order until one of the patterns
20756 matches the domain that is being routed. The list of hosts and then options are
20757 then used as described below. If there is no match, the router declines. When
20758 &%route_list%& is set, &%route_data%& must not be set.
20762 .section "Routing rules in route_data" "SECID121"
20763 The use of &%route_list%& is convenient when there are only a small number of
20764 routing rules. For larger numbers, it is easier to use a file or database to
20765 hold the routing information, and use the &%route_data%& option instead.
20766 The value of &%route_data%& is a list of hosts, followed by (optional) options.
20767 Most commonly, &%route_data%& is set as a string that contains an
20768 expansion lookup. For example, suppose we place two routing rules in a file
20771 dict.ref.example: mail-1.ref.example:mail-2.ref.example
20772 thes.ref.example: mail-3.ref.example:mail-4.ref.example
20774 This data can be accessed by setting
20776 route_data = ${lookup{$domain}lsearch{/the/file/name}}
20778 Failure of the lookup results in an empty string, causing the router to
20779 decline. However, you do not have to use a lookup in &%route_data%&. The only
20780 requirement is that the result of expanding the string is a list of hosts,
20781 possibly followed by options, separated by white space. The list of hosts must
20782 be enclosed in quotes if it contains white space.
20787 .section "Format of the list of hosts" "SECID122"
20788 A list of hosts, whether obtained via &%route_data%& or &%route_list%&, is
20789 always separately expanded before use. If the expansion fails, the router
20790 declines. The result of the expansion must be a colon-separated list of names
20791 and/or IP addresses, optionally also including ports.
20792 If the list is written with spaces, it must be protected with quotes.
20793 The format of each item
20794 in the list is described in the next section. The list separator can be changed
20795 as described in section &<<SECTlistsepchange>>&.
20797 If the list of hosts was obtained from a &%route_list%& item, the following
20798 variables are set during its expansion:
20801 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(manualroute)& router"
20802 If the domain was matched against a regular expression, the numeric variables
20803 &$1$&, &$2$&, etc. may be set. For example:
20805 route_list = ^domain(\d+) host-$1.text.example
20808 &$0$& is always set to the entire domain.
20810 &$1$& is also set when partial matching is done in a file lookup.
20813 .vindex "&$value$&"
20814 If the pattern that matched the domain was a lookup item, the data that was
20815 looked up is available in the expansion variable &$value$&. For example:
20817 route_list = lsearch;;/some/file.routes $value
20821 Note the doubling of the semicolon in the pattern that is necessary because
20822 semicolon is the default route list separator.
20826 .section "Format of one host item" "SECTformatonehostitem"
20827 Each item in the list of hosts can be either a host name or an IP address,
20828 optionally with an attached port number, or it can be a single "+"
20829 (see &%hosts_randomize%&).
20830 When no port is given, an IP address
20831 is not enclosed in brackets. When a port is specified, it overrides the port
20832 specification on the transport. The port is separated from the name or address
20833 by a colon. This leads to some complications:
20836 Because colon is the default separator for the list of hosts, either
20837 the colon that specifies a port must be doubled, or the list separator must
20838 be changed. The following two examples have the same effect:
20840 route_list = * "host1.tld::1225 : host2.tld::1226"
20841 route_list = * "<+ host1.tld:1225 + host2.tld:1226"
20844 When IPv6 addresses are involved, it gets worse, because they contain
20845 colons of their own. To make this case easier, it is permitted to
20846 enclose an IP address (either v4 or v6) in square brackets if a port
20847 number follows. For example:
20849 route_list = * "</ [10.1.1.1]:1225 / [::1]:1226"
20853 .section "How the list of hosts is used" "SECThostshowused"
20854 When an address is routed to an &(smtp)& transport by &(manualroute)&, each of
20855 the hosts is tried, in the order specified, when carrying out the SMTP
20856 delivery. However, the order can be changed by setting the &%hosts_randomize%&
20857 option, either on the router (see section &<<SECTprioptman>>& above), or on the
20860 Hosts may be listed by name or by IP address. An unadorned name in the list of
20861 hosts is interpreted as a host name. A name that is followed by &`/MX`& is
20862 interpreted as an indirection to a sublist of hosts obtained by looking up MX
20863 records in the DNS. For example:
20865 route_list = * x.y.z:p.q.r/MX:e.f.g
20867 If this feature is used with a port specifier, the port must come last. For
20870 route_list = * dom1.tld/mx::1225
20872 If the &%hosts_randomize%& option is set, the order of the items in the list is
20873 randomized before any lookups are done. Exim then scans the list; for any name
20874 that is not followed by &`/MX`& it looks up an IP address. If this turns out to
20875 be an interface on the local host and the item is not the first in the list,
20876 Exim discards it and any subsequent items. If it is the first item, what
20877 happens is controlled by the
20878 .oindex "&%self%&" "in &(manualroute)& router"
20879 &%self%& option of the router.
20881 A name on the list that is followed by &`/MX`& is replaced with the list of
20882 hosts obtained by looking up MX records for the name. This is always a DNS
20883 lookup; the &%bydns%& and &%byname%& options (see section &<<SECThowoptused>>&
20884 below) are not relevant here. The order of these hosts is determined by the
20885 preference values in the MX records, according to the usual rules. Because
20886 randomizing happens before the MX lookup, it does not affect the order that is
20887 defined by MX preferences.
20889 If the local host is present in the sublist obtained from MX records, but is
20890 not the most preferred host in that list, it and any equally or less
20891 preferred hosts are removed before the sublist is inserted into the main list.
20893 If the local host is the most preferred host in the MX list, what happens
20894 depends on where in the original list of hosts the &`/MX`& item appears. If it
20895 is not the first item (that is, there are previous hosts in the main list),
20896 Exim discards this name and any subsequent items in the main list.
20898 If the MX item is first in the list of hosts, and the local host is the
20899 most preferred host, what happens is controlled by the &%self%& option of the
20902 DNS failures when lookup up the MX records are treated in the same way as DNS
20903 failures when looking up IP addresses: &%pass_on_timeout%& and
20904 &%host_find_failed%& are used when relevant.
20906 The generic &%ignore_target_hosts%& option applies to all hosts in the list,
20907 whether obtained from an MX lookup or not.
20911 .section "How the options are used" "SECThowoptused"
20912 The options are a sequence of words, space-separated.
20913 One of the words can be the name of a transport; this overrides the
20914 &%transport%& option on the router for this particular routing rule only. The
20915 other words (if present) control randomization of the list of hosts on a
20916 per-rule basis, and how the IP addresses of the hosts are to be found when
20917 routing to a remote transport. These options are as follows:
20920 &%randomize%&: randomize the order of the hosts in this list, overriding the
20921 setting of &%hosts_randomize%& for this routing rule only.
20923 &%no_randomize%&: do not randomize the order of the hosts in this list,
20924 overriding the setting of &%hosts_randomize%& for this routing rule only.
20926 &%byname%&: use &[getipnodebyname()]& (&[gethostbyname()]& on older systems) to
20927 find IP addresses. This function may ultimately cause a DNS lookup, but it may
20928 also look in &_/etc/hosts_& or other sources of information.
20930 &%bydns%&: look up address records for the hosts directly in the DNS; fail if
20931 no address records are found. If there is a temporary DNS error (such as a
20932 timeout), delivery is deferred.
20934 &%ipv4_only%&: in direct DNS lookups, look up only A records.
20936 &%ipv4_prefer%&: in direct DNS lookups, sort A records before AAAA records.
20941 route_list = domain1 host1:host2:host3 randomize bydns;\
20942 domain2 host4:host5
20944 If neither &%byname%& nor &%bydns%& is given, Exim behaves as follows: First, a
20945 DNS lookup is done. If this yields anything other than HOST_NOT_FOUND, that
20946 result is used. Otherwise, Exim goes on to try a call to &[getipnodebyname()]&
20947 or &[gethostbyname()]&, and the result of the lookup is the result of that
20950 &*Warning*&: It has been discovered that on some systems, if a DNS lookup
20951 called via &[getipnodebyname()]& times out, HOST_NOT_FOUND is returned
20952 instead of TRY_AGAIN. That is why the default action is to try a DNS
20953 lookup first. Only if that gives a definite &"no such host"& is the local
20956 &*Compatibility*&: From Exim 4.85 until fixed for 4.90, there was an
20957 inadvertent constraint that a transport name as an option had to be the last
20962 If no IP address for a host can be found, what happens is controlled by the
20963 &%host_find_failed%& option.
20966 When an address is routed to a local transport, IP addresses are not looked up.
20967 The host list is passed to the transport in the &$host$& variable.
20971 .section "Manualroute examples" "SECID123"
20972 In some of the examples that follow, the presence of the &%remote_smtp%&
20973 transport, as defined in the default configuration file, is assumed:
20976 .cindex "smart host" "example router"
20977 The &(manualroute)& router can be used to forward all external mail to a
20978 &'smart host'&. If you have set up, in the main part of the configuration, a
20979 named domain list that contains your local domains, for example:
20981 domainlist local_domains = my.domain.example
20983 You can arrange for all other domains to be routed to a smart host by making
20984 your first router something like this:
20987 driver = manualroute
20988 domains = !+local_domains
20989 transport = remote_smtp
20990 route_list = * smarthost.ref.example
20992 This causes all non-local addresses to be sent to the single host
20993 &'smarthost.ref.example'&. If a colon-separated list of smart hosts is given,
20994 they are tried in order
20995 (but you can use &%hosts_randomize%& to vary the order each time).
20996 Another way of configuring the same thing is this:
20999 driver = manualroute
21000 transport = remote_smtp
21001 route_list = !+local_domains smarthost.ref.example
21003 There is no difference in behaviour between these two routers as they stand.
21004 However, they behave differently if &%no_more%& is added to them. In the first
21005 example, the router is skipped if the domain does not match the &%domains%&
21006 precondition; the following router is always tried. If the router runs, it
21007 always matches the domain and so can never decline. Therefore, &%no_more%&
21008 would have no effect. In the second case, the router is never skipped; it
21009 always runs. However, if it doesn't match the domain, it declines. In this case
21010 &%no_more%& would prevent subsequent routers from running.
21013 .cindex "mail hub example"
21014 A &'mail hub'& is a host which receives mail for a number of domains via MX
21015 records in the DNS and delivers it via its own private routing mechanism. Often
21016 the final destinations are behind a firewall, with the mail hub being the one
21017 machine that can connect to machines both inside and outside the firewall. The
21018 &(manualroute)& router is usually used on a mail hub to route incoming messages
21019 to the correct hosts. For a small number of domains, the routing can be inline,
21020 using the &%route_list%& option, but for a larger number a file or database
21021 lookup is easier to manage.
21023 If the domain names are in fact the names of the machines to which the mail is
21024 to be sent by the mail hub, the configuration can be quite simple. For
21028 driver = manualroute
21029 transport = remote_smtp
21030 route_list = *.rhodes.tvs.example $domain
21032 This configuration routes domains that match &`*.rhodes.tvs.example`& to hosts
21033 whose names are the same as the mail domains. A similar approach can be taken
21034 if the host name can be obtained from the domain name by a string manipulation
21035 that the expansion facilities can handle. Otherwise, a lookup based on the
21036 domain can be used to find the host:
21039 driver = manualroute
21040 transport = remote_smtp
21041 route_data = ${lookup {$domain} cdb {/internal/host/routes}}
21043 The result of the lookup must be the name or IP address of the host (or
21044 hosts) to which the address is to be routed. If the lookup fails, the route
21045 data is empty, causing the router to decline. The address then passes to the
21049 .cindex "batched SMTP output example"
21050 .cindex "SMTP" "batched outgoing; example"
21051 You can use &(manualroute)& to deliver messages to pipes or files in batched
21052 SMTP format for onward transportation by some other means. This is one way of
21053 storing mail for a dial-up host when it is not connected. The route list entry
21054 can be as simple as a single domain name in a configuration like this:
21057 driver = manualroute
21058 transport = batchsmtp_appendfile
21059 route_list = saved.domain.example
21061 though often a pattern is used to pick up more than one domain. If there are
21062 several domains or groups of domains with different transport requirements,
21063 different transports can be listed in the routing information:
21066 driver = manualroute
21068 *.saved.domain1.example $domain batch_appendfile; \
21069 *.saved.domain2.example \
21070 ${lookup{$domain}dbm{/domain2/hosts}{$value}fail} \
21073 .vindex "&$domain$&"
21075 The first of these just passes the domain in the &$host$& variable, which
21076 doesn't achieve much (since it is also in &$domain$&), but the second does a
21077 file lookup to find a value to pass, causing the router to decline to handle
21078 the address if the lookup fails.
21081 .cindex "UUCP" "example of router for"
21082 Routing mail directly to UUCP software is a specific case of the use of
21083 &(manualroute)& in a gateway to another mail environment. This is an example of
21084 one way it can be done:
21090 command = /usr/local/bin/uux -r - \
21091 ${substr_-5:$host}!rmail ${local_part}
21092 return_fail_output = true
21097 driver = manualroute
21099 ${lookup{$domain}lsearch{/usr/local/exim/uucphosts}}
21101 The file &_/usr/local/exim/uucphosts_& contains entries like
21103 darksite.ethereal.example: darksite.UUCP
21105 It can be set up more simply without adding and removing &".UUCP"& but this way
21106 makes clear the distinction between the domain name
21107 &'darksite.ethereal.example'& and the UUCP host name &'darksite'&.
21109 .ecindex IIDmanrou1
21110 .ecindex IIDmanrou2
21119 . ////////////////////////////////////////////////////////////////////////////
21120 . ////////////////////////////////////////////////////////////////////////////
21122 .chapter "The queryprogram router" "CHAPdriverlast"
21123 .scindex IIDquerou1 "&(queryprogram)& router"
21124 .scindex IIDquerou2 "routers" "&(queryprogram)&"
21125 .cindex "routing" "by external program"
21126 The &(queryprogram)& router routes an address by running an external command
21127 and acting on its output. This is an expensive way to route, and is intended
21128 mainly for use in lightly-loaded systems, or for performing experiments.
21129 However, if it is possible to use the precondition options (&%domains%&,
21130 &%local_parts%&, etc) to skip this router for most addresses, it could sensibly
21131 be used in special cases, even on a busy host. There are the following private
21133 .cindex "options" "&(queryprogram)& router"
21135 .option command queryprogram string&!! unset
21136 This option must be set. It specifies the command that is to be run. The
21137 command is split up into a command name and arguments, and then each is
21138 expanded separately (exactly as for a &(pipe)& transport, described in chapter
21139 &<<CHAPpipetransport>>&).
21142 .option command_group queryprogram string unset
21143 .cindex "gid (group id)" "in &(queryprogram)& router"
21144 This option specifies a gid to be set when running the command while routing an
21145 address for deliver. It must be set if &%command_user%& specifies a numerical
21146 uid. If it begins with a digit, it is interpreted as the numerical value of the
21147 gid. Otherwise it is looked up using &[getgrnam()]&.
21150 .option command_user queryprogram string unset
21151 .cindex "uid (user id)" "for &(queryprogram)&"
21152 This option must be set. It specifies the uid which is set when running the
21153 command while routing an address for delivery. If the value begins with a digit,
21154 it is interpreted as the numerical value of the uid. Otherwise, it is looked up
21155 using &[getpwnam()]& to obtain a value for the uid and, if &%command_group%& is
21156 not set, a value for the gid also.
21158 &*Warning:*& Changing uid and gid is possible only when Exim is running as
21159 root, which it does during a normal delivery in a conventional configuration.
21160 However, when an address is being verified during message reception, Exim is
21161 usually running as the Exim user, not as root. If the &(queryprogram)& router
21162 is called from a non-root process, Exim cannot change uid or gid before running
21163 the command. In this circumstance the command runs under the current uid and
21167 .option current_directory queryprogram string /
21168 This option specifies an absolute path which is made the current directory
21169 before running the command.
21172 .option timeout queryprogram time 1h
21173 If the command does not complete within the timeout period, its process group
21174 is killed and the message is frozen. A value of zero time specifies no
21178 The standard output of the command is connected to a pipe, which is read when
21179 the command terminates. It should consist of a single line of output,
21180 containing up to five fields, separated by white space. The maximum length of
21181 the line is 1023 characters. Longer lines are silently truncated. The first
21182 field is one of the following words (case-insensitive):
21185 &'Accept'&: routing succeeded; the remaining fields specify what to do (see
21188 &'Decline'&: the router declines; pass the address to the next router, unless
21189 &%no_more%& is set.
21191 &'Fail'&: routing failed; do not pass the address to any more routers. Any
21192 subsequent text on the line is an error message. If the router is run as part
21193 of address verification during an incoming SMTP message, the message is
21194 included in the SMTP response.
21196 &'Defer'&: routing could not be completed at this time; try again later. Any
21197 subsequent text on the line is an error message which is logged. It is not
21198 included in any SMTP response.
21200 &'Freeze'&: the same as &'defer'&, except that the message is frozen.
21202 &'Pass'&: pass the address to the next router (or the router specified by
21203 &%pass_router%&), overriding &%no_more%&.
21205 &'Redirect'&: the message is redirected. The remainder of the line is a list of
21206 new addresses, which are routed independently, starting with the first router,
21207 or the router specified by &%redirect_router%&, if set.
21210 When the first word is &'accept'&, the remainder of the line consists of a
21211 number of keyed data values, as follows (split into two lines here, to fit on
21214 ACCEPT TRANSPORT=<transport> HOSTS=<list of hosts>
21215 LOOKUP=byname|bydns DATA=<text>
21217 The data items can be given in any order, and all are optional. If no transport
21218 is included, the transport specified by the generic &%transport%& option is
21219 used. The list of hosts and the lookup type are needed only if the transport is
21220 an &(smtp)& transport that does not itself supply a list of hosts.
21222 The format of the list of hosts is the same as for the &(manualroute)& router.
21223 As well as host names and IP addresses with optional port numbers, as described
21224 in section &<<SECTformatonehostitem>>&, it may contain names followed by
21225 &`/MX`& to specify sublists of hosts that are obtained by looking up MX records
21226 (see section &<<SECThostshowused>>&).
21228 If the lookup type is not specified, Exim behaves as follows when trying to
21229 find an IP address for each host: First, a DNS lookup is done. If this yields
21230 anything other than HOST_NOT_FOUND, that result is used. Otherwise, Exim
21231 goes on to try a call to &[getipnodebyname()]& or &[gethostbyname()]&, and the
21232 result of the lookup is the result of that call.
21234 .vindex "&$address_data$&"
21235 If the DATA field is set, its value is placed in the &$address_data$&
21236 variable. For example, this return line
21238 accept hosts=x1.y.example:x2.y.example data="rule1"
21240 routes the address to the default transport, passing a list of two hosts. When
21241 the transport runs, the string &"rule1"& is in &$address_data$&.
21242 .ecindex IIDquerou1
21243 .ecindex IIDquerou2
21248 . ////////////////////////////////////////////////////////////////////////////
21249 . ////////////////////////////////////////////////////////////////////////////
21251 .chapter "The redirect router" "CHAPredirect"
21252 .scindex IIDredrou1 "&(redirect)& router"
21253 .scindex IIDredrou2 "routers" "&(redirect)&"
21254 .cindex "alias file" "in a &(redirect)& router"
21255 .cindex "address redirection" "&(redirect)& router"
21256 The &(redirect)& router handles several kinds of address redirection. Its most
21257 common uses are for resolving local part aliases from a central alias file
21258 (usually called &_/etc/aliases_&) and for handling users' personal &_.forward_&
21259 files, but it has many other potential uses. The incoming address can be
21260 redirected in several different ways:
21263 It can be replaced by one or more new addresses which are themselves routed
21266 It can be routed to be delivered to a given file or directory.
21268 It can be routed to be delivered to a specified pipe command.
21270 It can cause an automatic reply to be generated.
21272 It can be forced to fail, optionally with a custom error message.
21274 It can be temporarily deferred, optionally with a custom message.
21276 It can be discarded.
21279 The generic &%transport%& option must not be set for &(redirect)& routers.
21280 However, there are some private options which define transports for delivery to
21281 files and pipes, and for generating autoreplies. See the &%file_transport%&,
21282 &%pipe_transport%& and &%reply_transport%& descriptions below.
21284 If success DSNs have been requested
21285 .cindex "DSN" "success"
21286 .cindex "Delivery Status Notification" "success"
21287 redirection triggers one and the DSN options are not passed any further.
21291 .section "Redirection data" "SECID124"
21292 The router operates by interpreting a text string which it obtains either by
21293 expanding the contents of the &%data%& option, or by reading the entire
21294 contents of a file whose name is given in the &%file%& option. These two
21295 options are mutually exclusive. The first is commonly used for handling system
21296 aliases, in a configuration like this:
21300 data = ${lookup{$local_part}lsearch{/etc/aliases}}
21302 If the lookup fails, the expanded string in this example is empty. When the
21303 expansion of &%data%& results in an empty string, the router declines. A forced
21304 expansion failure also causes the router to decline; other expansion failures
21305 cause delivery to be deferred.
21307 A configuration using &%file%& is commonly used for handling users'
21308 &_.forward_& files, like this:
21313 file = $home/.forward
21316 If the file does not exist, or causes no action to be taken (for example, it is
21317 empty or consists only of comments), the router declines. &*Warning*&: This
21318 is not the case when the file contains syntactically valid items that happen to
21319 yield empty addresses, for example, items containing only RFC 2822 address
21322 .cindex "tainted data" "in filenames"
21323 .cindex redirect "tainted data"
21324 Tainted data may not be used for a filename.
21326 &*Warning*&: It is unwise to use &$local_part$& or &$domain$&
21327 directly for redirection,
21328 as they are provided by a potential attacker.
21329 In the examples above, &$local_part$& is used for looking up data held locally
21330 on the system, and not used directly (the second example derives &$home$& via
21331 the passsword file or database, using &$local_part$&).
21335 .section "Forward files and address verification" "SECID125"
21336 .cindex "address redirection" "while verifying"
21337 It is usual to set &%no_verify%& on &(redirect)& routers which handle users'
21338 &_.forward_& files, as in the example above. There are two reasons for this:
21341 When Exim is receiving an incoming SMTP message from a remote host, it is
21342 running under the Exim uid, not as root. Exim is unable to change uid to read
21343 the file as the user, and it may not be able to read it as the Exim user. So in
21344 practice the router may not be able to operate.
21346 However, even when the router can operate, the existence of a &_.forward_& file
21347 is unimportant when verifying an address. What should be checked is whether the
21348 local part is a valid user name or not. Cutting out the redirection processing
21349 saves some resources.
21357 .section "Interpreting redirection data" "SECID126"
21358 .cindex "Sieve filter" "specifying in redirection data"
21359 .cindex "filter" "specifying in redirection data"
21360 The contents of the data string, whether obtained from &%data%& or &%file%&,
21361 can be interpreted in two different ways:
21364 If the &%allow_filter%& option is set true, and the data begins with the text
21365 &"#Exim filter"& or &"#Sieve filter"&, it is interpreted as a list of
21366 &'filtering'& instructions in the form of an Exim or Sieve filter file,
21367 respectively. Details of the syntax and semantics of filter files are described
21368 in a separate document entitled &'Exim's interfaces to mail filtering'&; this
21369 document is intended for use by end users.
21371 Otherwise, the data must be a comma-separated list of redirection items, as
21372 described in the next section.
21375 When a message is redirected to a file (a &"mail folder"&), the filename given
21376 in a non-filter redirection list must always be an absolute path. A filter may
21377 generate a relative path &-- how this is handled depends on the transport's
21378 configuration. See section &<<SECTfildiropt>>& for a discussion of this issue
21379 for the &(appendfile)& transport.
21383 .section "Items in a non-filter redirection list" "SECTitenonfilred"
21384 .cindex "address redirection" "non-filter list items"
21385 When the redirection data is not an Exim or Sieve filter, for example, if it
21386 comes from a conventional alias or forward file, it consists of a list of
21387 addresses, filenames, pipe commands, or certain special items (see section
21388 &<<SECTspecitredli>>& below). The special items can be individually enabled or
21389 disabled by means of options whose names begin with &%allow_%& or &%forbid_%&,
21390 depending on their default values. The items in the list are separated by
21391 commas or newlines.
21392 If a comma is required in an item, the entire item must be enclosed in double
21395 Lines starting with a # character are comments, and are ignored, and # may
21396 also appear following a comma, in which case everything between the # and the
21397 next newline character is ignored.
21399 If an item is entirely enclosed in double quotes, these are removed. Otherwise
21400 double quotes are retained because some forms of mail address require their use
21401 (but never to enclose the entire address). In the following description,
21402 &"item"& refers to what remains after any surrounding double quotes have been
21405 .vindex "&$local_part$&"
21406 &*Warning*&: If you use an Exim expansion to construct a redirection address,
21407 and the expansion contains a reference to &$local_part$&, you should make use
21408 of the &%quote_local_part%& expansion operator, in case the local part contains
21409 special characters. For example, to redirect all mail for the domain
21410 &'obsolete.example'&, retaining the existing local part, you could use this
21413 data = ${quote_local_part:$local_part}@newdomain.example
21417 .section "Redirecting to a local mailbox" "SECTredlocmai"
21418 .cindex "routing" "loops in"
21419 .cindex "loop" "while routing, avoidance of"
21420 .cindex "address redirection" "to local mailbox"
21421 A redirection item may safely be the same as the address currently under
21422 consideration. This does not cause a routing loop, because a router is
21423 automatically skipped if any ancestor of the address that is being processed
21424 is the same as the current address and was processed by the current router.
21425 Such an address is therefore passed to the following routers, so it is handled
21426 as if there were no redirection. When making this loop-avoidance test, the
21427 complete local part, including any prefix or suffix, is used.
21429 .cindex "address redirection" "local part without domain"
21430 Specifying the same local part without a domain is a common usage in personal
21431 filter files when the user wants to have messages delivered to the local
21432 mailbox and also forwarded elsewhere. For example, the user whose login is
21433 &'cleo'& might have a &_.forward_& file containing this:
21435 cleo, cleopatra@egypt.example
21437 .cindex "backslash in alias file"
21438 .cindex "alias file" "backslash in"
21439 For compatibility with other MTAs, such unqualified local parts may be
21440 preceded by &"\"&, but this is not a requirement for loop prevention. However,
21441 it does make a difference if more than one domain is being handled
21444 If an item begins with &"\"& and the rest of the item parses as a valid RFC
21445 2822 address that does not include a domain, the item is qualified using the
21446 domain of the incoming address. In the absence of a leading &"\"&, unqualified
21447 addresses are qualified using the value in &%qualify_recipient%&, but you can
21448 force the incoming domain to be used by setting &%qualify_preserve_domain%&.
21450 Care must be taken if there are alias names for local users.
21451 Consider an MTA handling a single local domain where the system alias file
21456 Now suppose that Sam (whose login id is &'spqr'&) wants to save copies of
21457 messages in the local mailbox, and also forward copies elsewhere. He creates
21460 Sam.Reman, spqr@reme.elsewhere.example
21462 With these settings, an incoming message addressed to &'Sam.Reman'& fails. The
21463 &(redirect)& router for system aliases does not process &'Sam.Reman'& the
21464 second time round, because it has previously routed it,
21465 and the following routers presumably cannot handle the alias. The forward file
21466 should really contain
21468 spqr, spqr@reme.elsewhere.example
21470 but because this is such a common error, the &%check_ancestor%& option (see
21471 below) exists to provide a way to get round it. This is normally set on a
21472 &(redirect)& router that is handling users' &_.forward_& files.
21476 .section "Special items in redirection lists" "SECTspecitredli"
21477 In addition to addresses, the following types of item may appear in redirection
21478 lists (that is, in non-filter redirection data):
21481 .cindex "pipe" "in redirection list"
21482 .cindex "address redirection" "to pipe"
21483 An item is treated as a pipe command if it begins with &"|"& and does not parse
21484 as a valid RFC 2822 address that includes a domain. A transport for running the
21485 command must be specified by the &%pipe_transport%& option.
21486 Normally, either the router or the transport specifies a user and a group under
21487 which to run the delivery. The default is to use the Exim user and group.
21489 Single or double quotes can be used for enclosing the individual arguments of
21490 the pipe command; no interpretation of escapes is done for single quotes. If
21491 the command contains a comma character, it is necessary to put the whole item
21492 in double quotes, for example:
21494 "|/some/command ready,steady,go"
21496 since items in redirection lists are terminated by commas. Do not, however,
21497 quote just the command. An item such as
21499 |"/some/command ready,steady,go"
21501 is interpreted as a pipe with a rather strange command name, and no arguments.
21503 Note that the above example assumes that the text comes from a lookup source
21504 of some sort, so that the quotes are part of the data. If composing a
21505 redirect router with a &%data%& option directly specifying this command, the
21506 quotes will be used by the configuration parser to define the extent of one
21507 string, but will not be passed down into the redirect router itself. There
21508 are two main approaches to get around this: escape quotes to be part of the
21509 data itself, or avoid using this mechanism and instead create a custom
21510 transport with the &%command%& option set and reference that transport from
21511 an &%accept%& router.
21514 .cindex "file" "in redirection list"
21515 .cindex "address redirection" "to file"
21516 An item is interpreted as a path name if it begins with &"/"& and does not
21517 parse as a valid RFC 2822 address that includes a domain. For example,
21519 /home/world/minbari
21521 is treated as a filename, but
21523 /s=molari/o=babylon/@x400gate.way
21525 is treated as an address. For a filename, a transport must be specified using
21526 the &%file_transport%& option. However, if the generated path name ends with a
21527 forward slash character, it is interpreted as a directory name rather than a
21528 filename, and &%directory_transport%& is used instead.
21530 Normally, either the router or the transport specifies a user and a group under
21531 which to run the delivery. The default is to use the Exim user and group.
21533 .cindex "&_/dev/null_&"
21534 However, if a redirection item is the path &_/dev/null_&, delivery to it is
21535 bypassed at a high level, and the log entry shows &"**bypassed**"&
21536 instead of a transport name. In this case the user and group are not used.
21539 .cindex "included address list"
21540 .cindex "address redirection" "included external list"
21541 If an item is of the form
21543 :include:<path name>
21545 a list of further items is taken from the given file and included at that
21546 point. &*Note*&: Such a file can not be a filter file; it is just an
21547 out-of-line addition to the list. The items in the included list are separated
21548 by commas or newlines and are not subject to expansion. If this is the first
21549 item in an alias list in an &(lsearch)& file, a colon must be used to terminate
21550 the alias name. This example is incorrect:
21552 list1 :include:/opt/lists/list1
21554 It must be given as
21556 list1: :include:/opt/lists/list1
21558 .cindex "tainted data" "in filenames"
21559 .cindex redirect "tainted data"
21560 Tainted data may not be used for a filename.
21562 .cindex "address redirection" "to black hole"
21563 .cindex "delivery" "discard"
21564 .cindex "delivery" "blackhole"
21565 .cindex "black hole"
21566 .cindex "abandoning mail"
21567 Sometimes you want to throw away mail to a particular local part. Making the
21568 &%data%& option expand to an empty string does not work, because that causes
21569 the router to decline. Instead, the alias item
21573 can be used. It does what its name implies. No delivery is
21574 done, and no error message is generated. This has the same effect as specifying
21575 &_/dev/null_& as a destination, but it can be independently disabled.
21577 &*Warning*&: If &':blackhole:'& appears anywhere in a redirection list, no
21578 delivery is done for the original local part, even if other redirection items
21579 are present. If you are generating a multi-item list (for example, by reading a
21580 database) and need the ability to provide a no-op item, you must use
21584 .cindex "delivery" "forcing failure"
21585 .cindex "delivery" "forcing deferral"
21586 .cindex "failing delivery" "forcing"
21587 .cindex "deferred delivery, forcing"
21588 .cindex "customizing" "failure message"
21589 An attempt to deliver a particular address can be deferred or forced to fail by
21590 redirection items of the form
21595 respectively. When a redirection list contains such an item, it applies
21596 to the entire redirection; any other items in the list are ignored. Any
21597 text following &':fail:'& or &':defer:'& is placed in the error text
21598 associated with the failure. For example, an alias file might contain:
21600 X.Employee: :fail: Gone away, no forwarding address
21602 In the case of an address that is being verified from an ACL or as the subject
21604 .cindex "VRFY" "error text, display of"
21605 VRFY command, the text is included in the SMTP error response by
21607 .cindex "EXPN" "error text, display of"
21608 The text is not included in the response to an EXPN command. In non-SMTP cases
21609 the text is included in the error message that Exim generates.
21611 .cindex "SMTP" "error codes"
21612 By default for verify, Exim sends a 451 SMTP code for a &':defer:'&, and 550 for
21613 &':fail:'&. However, if the message starts with three digits followed by a
21614 space, optionally followed by an extended code of the form &'n.n.n'&, also
21615 followed by a space, and the very first digit is the same as the default error
21616 code, the code from the message is used instead. If the very first digit is
21617 incorrect, a panic error is logged, and the default code is used. You can
21618 suppress the use of the supplied code in a redirect router by setting the
21619 &%forbid_smtp_code%& option true. In this case, any SMTP code is quietly
21622 .vindex "&$acl_verify_message$&"
21623 In an ACL, an explicitly provided message overrides the default, but the
21624 default message is available in the variable &$acl_verify_message$& and can
21625 therefore be included in a custom message if this is desired.
21627 Normally the error text is the rest of the redirection list &-- a comma does
21628 not terminate it &-- but a newline does act as a terminator. Newlines are not
21629 normally present in alias expansions. In &(lsearch)& lookups they are removed
21630 as part of the continuation process, but they may exist in other kinds of
21631 lookup and in &':include:'& files.
21633 During routing for message delivery (as opposed to verification), a redirection
21634 containing &':fail:'& causes an immediate failure of the incoming address,
21635 whereas &':defer:'& causes the message to remain in the queue so that a
21636 subsequent delivery attempt can happen at a later time. If an address is
21637 deferred for too long, it will ultimately fail, because the normal retry
21641 .cindex "alias file" "exception to default"
21642 Sometimes it is useful to use a single-key search type with a default (see
21643 chapter &<<CHAPfdlookup>>&) to look up aliases. However, there may be a need
21644 for exceptions to the default. These can be handled by aliasing them to
21645 &':unknown:'&. This differs from &':fail:'& in that it causes the &(redirect)&
21646 router to decline, whereas &':fail:'& forces routing to fail. A lookup which
21647 results in an empty redirection list has the same effect.
21651 .section "Duplicate addresses" "SECTdupaddr"
21652 .cindex "duplicate addresses"
21653 .cindex "address duplicate, discarding"
21654 .cindex "pipe" "duplicated"
21655 Exim removes duplicate addresses from the list to which it is delivering, so as
21656 to deliver just one copy to each address. This does not apply to deliveries
21657 routed to pipes by different immediate parent addresses, but an indirect
21658 aliasing scheme of the type
21660 pipe: |/some/command $local_part
21664 does not work with a message that is addressed to both local parts, because
21665 when the second is aliased to the intermediate local part &"pipe"& it gets
21666 discarded as being the same as a previously handled address. However, a scheme
21669 localpart1: |/some/command $local_part
21670 localpart2: |/some/command $local_part
21672 does result in two different pipe deliveries, because the immediate parents of
21673 the pipes are distinct.
21677 .section "Repeated redirection expansion" "SECID128"
21678 .cindex "repeated redirection expansion"
21679 .cindex "address redirection" "repeated for each delivery attempt"
21680 When a message cannot be delivered to all of its recipients immediately,
21681 leading to two or more delivery attempts, redirection expansion is carried out
21682 afresh each time for those addresses whose children were not all previously
21683 delivered. If redirection is being used as a mailing list, this can lead to new
21684 members of the list receiving copies of old messages. The &%one_time%& option
21685 can be used to avoid this.
21688 .section "Errors in redirection lists" "SECID129"
21689 .cindex "address redirection" "errors"
21690 If &%skip_syntax_errors%& is set, a malformed address that causes a parsing
21691 error is skipped, and an entry is written to the main log. This may be useful
21692 for mailing lists that are automatically managed. Otherwise, if an error is
21693 detected while generating the list of new addresses, the original address is
21694 deferred. See also &%syntax_errors_to%&.
21698 .section "Private options for the redirect router" "SECID130"
21700 .cindex "options" "&(redirect)& router"
21701 The private options for the &(redirect)& router are as follows:
21704 .option allow_defer redirect boolean false
21705 Setting this option allows the use of &':defer:'& in non-filter redirection
21706 data, or the &%defer%& command in an Exim filter file.
21709 .option allow_fail redirect boolean false
21710 .cindex "failing delivery" "from filter"
21711 If this option is true, the &':fail:'& item can be used in a redirection list,
21712 and the &%fail%& command may be used in an Exim filter file.
21715 .option allow_filter redirect boolean false
21716 .cindex "filter" "enabling use of"
21717 .cindex "Sieve filter" "enabling use of"
21718 Setting this option allows Exim to interpret redirection data that starts with
21719 &"#Exim filter"& or &"#Sieve filter"& as a set of filtering instructions. There
21720 are some features of Exim filter files that some administrators may wish to
21721 lock out; see the &%forbid_filter_%&&'xxx'& options below.
21723 It is also possible to lock out Exim filters or Sieve filters while allowing
21724 the other type; see &%forbid_exim_filter%& and &%forbid_sieve_filter%&.
21727 The filter is run using the uid and gid set by the generic &%user%& and
21728 &%group%& options. These take their defaults from the password data if
21729 &%check_local_user%& is set, so in the normal case of users' personal filter
21730 files, the filter is run as the relevant user. When &%allow_filter%& is set
21731 true, Exim insists that either &%check_local_user%& or &%user%& is set.
21735 .option allow_freeze redirect boolean false
21736 .cindex "freezing messages" "allowing in filter"
21737 Setting this option allows the use of the &%freeze%& command in an Exim filter.
21738 This command is more normally encountered in system filters, and is disabled by
21739 default for redirection filters because it isn't something you usually want to
21740 let ordinary users do.
21744 .option check_ancestor redirect boolean false
21745 This option is concerned with handling generated addresses that are the same
21746 as some address in the list of redirection ancestors of the current address.
21747 Although it is turned off by default in the code, it is set in the default
21748 configuration file for handling users' &_.forward_& files. It is recommended
21749 for this use of the &(redirect)& router.
21751 When &%check_ancestor%& is set, if a generated address (including the domain)
21752 is the same as any ancestor of the current address, it is replaced by a copy of
21753 the current address. This helps in the case where local part A is aliased to B,
21754 and B has a &_.forward_& file pointing back to A. For example, within a single
21755 domain, the local part &"Joe.Bloggs"& is aliased to &"jb"& and
21756 &_&~jb/.forward_& contains:
21758 \Joe.Bloggs, <other item(s)>
21760 Without the &%check_ancestor%& setting, either local part (&"jb"& or
21761 &"joe.bloggs"&) gets processed once by each router and so ends up as it was
21762 originally. If &"jb"& is the real mailbox name, mail to &"jb"& gets delivered
21763 (having been turned into &"joe.bloggs"& by the &_.forward_& file and back to
21764 &"jb"& by the alias), but mail to &"joe.bloggs"& fails. Setting
21765 &%check_ancestor%& on the &(redirect)& router that handles the &_.forward_&
21766 file prevents it from turning &"jb"& back into &"joe.bloggs"& when that was the
21767 original address. See also the &%repeat_use%& option below.
21770 .option check_group redirect boolean "see below"
21771 When the &%file%& option is used, the group owner of the file is checked only
21772 when this option is set. The permitted groups are those listed in the
21773 &%owngroups%& option, together with the user's default group if
21774 &%check_local_user%& is set. If the file has the wrong group, routing is
21775 deferred. The default setting for this option is true if &%check_local_user%&
21776 is set and the &%modemask%& option permits the group write bit, or if the
21777 &%owngroups%& option is set. Otherwise it is false, and no group check occurs.
21781 .option check_owner redirect boolean "see below"
21782 When the &%file%& option is used, the owner of the file is checked only when
21783 this option is set. If &%check_local_user%& is set, the local user is
21784 permitted; otherwise the owner must be one of those listed in the &%owners%&
21785 option. The default value for this option is true if &%check_local_user%& or
21786 &%owners%& is set. Otherwise the default is false, and no owner check occurs.
21789 .option data redirect string&!! unset
21790 This option is mutually exclusive with &%file%&. One or other of them must be
21791 set, but not both. The contents of &%data%& are expanded, and then used as the
21792 list of forwarding items, or as a set of filtering instructions. If the
21793 expansion is forced to fail, or the result is an empty string or a string that
21794 has no effect (consists entirely of comments), the router declines.
21796 When filtering instructions are used, the string must begin with &"#Exim
21797 filter"&, and all comments in the string, including this initial one, must be
21798 terminated with newline characters. For example:
21800 data = #Exim filter\n\
21801 if $h_to: contains Exim then save $home/mail/exim endif
21803 If you are reading the data from a database where newlines cannot be included,
21804 you can use the &${sg}$& expansion item to turn the escape string of your
21805 choice into a newline.
21808 .option directory_transport redirect string&!! unset
21809 A &(redirect)& router sets up a direct delivery to a directory when a path name
21810 ending with a slash is specified as a new &"address"&. The transport used is
21811 specified by this option, which, after expansion, must be the name of a
21812 configured transport. This should normally be an &(appendfile)& transport.
21815 .option file redirect string&!! unset
21816 This option specifies the name of a file that contains the redirection data. It
21817 is mutually exclusive with the &%data%& option. The string is expanded before
21818 use; if the expansion is forced to fail, the router declines. Other expansion
21819 failures cause delivery to be deferred. The result of a successful expansion
21820 must be an absolute path. The entire file is read and used as the redirection
21821 data. If the data is an empty string or a string that has no effect (consists
21822 entirely of comments), the router declines.
21824 .cindex "NFS" "checking for file existence"
21825 If the attempt to open the file fails with a &"does not exist"& error, Exim
21826 runs a check on the containing directory,
21827 unless &%ignore_enotdir%& is true (see below).
21828 If the directory does not appear to exist, delivery is deferred. This can
21829 happen when users' &_.forward_& files are in NFS-mounted directories, and there
21830 is a mount problem. If the containing directory does exist, but the file does
21831 not, the router declines.
21834 .option file_transport redirect string&!! unset
21835 .vindex "&$address_file$&"
21836 A &(redirect)& router sets up a direct delivery to a file when a path name not
21837 ending in a slash is specified as a new &"address"&. The transport used is
21838 specified by this option, which, after expansion, must be the name of a
21839 configured transport. This should normally be an &(appendfile)& transport. When
21840 it is running, the filename is in &$address_file$&.
21843 .option filter_prepend_home redirect boolean true
21844 When this option is true, if a &(save)& command in an Exim filter specifies a
21845 relative path, and &$home$& is defined, it is automatically prepended to the
21846 relative path. If this option is set false, this action does not happen. The
21847 relative path is then passed to the transport unmodified.
21850 .option forbid_blackhole redirect boolean false
21851 .cindex "restricting access to features"
21852 .cindex "filter" "locking out certain features"
21853 If this option is true, the &':blackhole:'& item may not appear in a
21857 .option forbid_exim_filter redirect boolean false
21858 .cindex "restricting access to features"
21859 .cindex "filter" "locking out certain features"
21860 If this option is set true, only Sieve filters are permitted when
21861 &%allow_filter%& is true.
21866 .option forbid_file redirect boolean false
21867 .cindex "restricting access to features"
21868 .cindex "delivery" "to file; forbidding"
21869 .cindex "filter" "locking out certain features"
21870 .cindex "Sieve filter" "forbidding delivery to a file"
21871 .cindex "Sieve filter" "&""keep""& facility; disabling"
21872 If this option is true, this router may not generate a new address that
21873 specifies delivery to a local file or directory, either from a filter or from a
21874 conventional forward file. This option is forced to be true if &%one_time%& is
21875 set. It applies to Sieve filters as well as to Exim filters, but if true, it
21876 locks out the Sieve's &"keep"& facility.
21879 .option forbid_filter_dlfunc redirect boolean false
21880 .cindex "restricting access to features"
21881 .cindex "filter" "locking out certain features"
21882 If this option is true, string expansions in Exim filters are not allowed to
21883 make use of the &%dlfunc%& expansion facility to run dynamically loaded
21886 .option forbid_filter_existstest redirect boolean false
21887 .cindex "restricting access to features"
21888 .cindex "filter" "locking out certain features"
21889 .cindex "expansion" "statting a file"
21890 If this option is true, string expansions in Exim filters are not allowed to
21891 make use of the &%exists%& condition or the &%stat%& expansion item.
21893 .option forbid_filter_logwrite redirect boolean false
21894 .cindex "restricting access to features"
21895 .cindex "filter" "locking out certain features"
21896 If this option is true, use of the logging facility in Exim filters is not
21897 permitted. Logging is in any case available only if the filter is being run
21898 under some unprivileged uid (which is normally the case for ordinary users'
21899 &_.forward_& files).
21902 .option forbid_filter_lookup redirect boolean false
21903 .cindex "restricting access to features"
21904 .cindex "filter" "locking out certain features"
21905 If this option is true, string expansions in Exim filter files are not allowed
21906 to make use of &%lookup%& items.
21909 .option forbid_filter_perl redirect boolean false
21910 .cindex "restricting access to features"
21911 .cindex "filter" "locking out certain features"
21912 This option has an effect only if Exim is built with embedded Perl support. If
21913 it is true, string expansions in Exim filter files are not allowed to make use
21914 of the embedded Perl support.
21917 .option forbid_filter_readfile redirect boolean false
21918 .cindex "restricting access to features"
21919 .cindex "filter" "locking out certain features"
21920 If this option is true, string expansions in Exim filter files are not allowed
21921 to make use of &%readfile%& items.
21924 .option forbid_filter_readsocket redirect boolean false
21925 .cindex "restricting access to features"
21926 .cindex "filter" "locking out certain features"
21927 If this option is true, string expansions in Exim filter files are not allowed
21928 to make use of &%readsocket%& items.
21931 .option forbid_filter_reply redirect boolean false
21932 .cindex "restricting access to features"
21933 .cindex "filter" "locking out certain features"
21934 If this option is true, this router may not generate an automatic reply
21935 message. Automatic replies can be generated only from Exim or Sieve filter
21936 files, not from traditional forward files. This option is forced to be true if
21937 &%one_time%& is set.
21940 .option forbid_filter_run redirect boolean false
21941 .cindex "restricting access to features"
21942 .cindex "filter" "locking out certain features"
21943 If this option is true, string expansions in Exim filter files are not allowed
21944 to make use of &%run%& items.
21947 .option forbid_include redirect boolean false
21948 .cindex "restricting access to features"
21949 .cindex "filter" "locking out certain features"
21950 If this option is true, items of the form
21952 :include:<path name>
21954 are not permitted in non-filter redirection lists.
21957 .option forbid_pipe redirect boolean false
21958 .cindex "restricting access to features"
21959 .cindex "filter" "locking out certain features"
21960 .cindex "delivery" "to pipe; forbidding"
21961 If this option is true, this router may not generate a new address which
21962 specifies delivery to a pipe, either from an Exim filter or from a conventional
21963 forward file. This option is forced to be true if &%one_time%& is set.
21966 .option forbid_sieve_filter redirect boolean false
21967 .cindex "restricting access to features"
21968 .cindex "filter" "locking out certain features"
21969 If this option is set true, only Exim filters are permitted when
21970 &%allow_filter%& is true.
21973 .cindex "SMTP" "error codes"
21974 .option forbid_smtp_code redirect boolean false
21975 If this option is set true, any SMTP error codes that are present at the start
21976 of messages specified for &`:defer:`& or &`:fail:`& are quietly ignored, and
21977 the default codes (451 and 550, respectively) are always used.
21982 .option hide_child_in_errmsg redirect boolean false
21983 .cindex "bounce message" "redirection details; suppressing"
21984 If this option is true, it prevents Exim from quoting a child address if it
21985 generates a bounce or delay message for it. Instead it says &"an address
21986 generated from <&'the top level address'&>"&. Of course, this applies only to
21987 bounces generated locally. If a message is forwarded to another host, &'its'&
21988 bounce may well quote the generated address.
21991 .option ignore_eacces redirect boolean false
21993 If this option is set and an attempt to open a redirection file yields the
21994 EACCES error (permission denied), the &(redirect)& router behaves as if the
21995 file did not exist.
21998 .option ignore_enotdir redirect boolean false
22000 If this option is set and an attempt to open a redirection file yields the
22001 ENOTDIR error (something on the path is not a directory), the &(redirect)&
22002 router behaves as if the file did not exist.
22004 Setting &%ignore_enotdir%& has another effect as well: When a &(redirect)&
22005 router that has the &%file%& option set discovers that the file does not exist
22006 (the ENOENT error), it tries to &[stat()]& the parent directory, as a check
22007 against unmounted NFS directories. If the parent can not be statted, delivery
22008 is deferred. However, it seems wrong to do this check when &%ignore_enotdir%&
22009 is set, because that option tells Exim to ignore &"something on the path is not
22010 a directory"& (the ENOTDIR error). This is a confusing area, because it seems
22011 that some operating systems give ENOENT where others give ENOTDIR.
22015 .option include_directory redirect string unset
22016 If this option is set, the path names of any &':include:'& items in a
22017 redirection list must start with this directory.
22020 .option modemask redirect "octal integer" 022
22021 This specifies mode bits which must not be set for a file specified by the
22022 &%file%& option. If any of the forbidden bits are set, delivery is deferred.
22025 .option one_time redirect boolean false
22026 .cindex "one-time aliasing/forwarding expansion"
22027 .cindex "alias file" "one-time expansion"
22028 .cindex "forward file" "one-time expansion"
22029 .cindex "mailing lists" "one-time expansion"
22030 .cindex "address redirection" "one-time expansion"
22031 Sometimes the fact that Exim re-evaluates aliases and reprocesses redirection
22032 files each time it tries to deliver a message causes a problem when one or more
22033 of the generated addresses fails be delivered at the first attempt. The problem
22034 is not one of duplicate delivery &-- Exim is clever enough to handle that &--
22035 but of what happens when the redirection list changes during the time that the
22036 message is on Exim's queue. This is particularly true in the case of mailing
22037 lists, where new subscribers might receive copies of messages that were posted
22038 before they subscribed.
22040 If &%one_time%& is set and any addresses generated by the router fail to
22041 deliver at the first attempt, the failing addresses are added to the message as
22042 &"top level"& addresses, and the parent address that generated them is marked
22043 &"delivered"&. Thus, redirection does not happen again at the next delivery
22046 &*Warning 1*&: Any header line addition or removal that is specified by this
22047 router would be lost if delivery did not succeed at the first attempt. For this
22048 reason, the &%headers_add%& and &%headers_remove%& generic options are not
22049 permitted when &%one_time%& is set.
22051 &*Warning 2*&: To ensure that the router generates only addresses (as opposed
22052 to pipe or file deliveries or auto-replies) &%forbid_file%&, &%forbid_pipe%&,
22053 and &%forbid_filter_reply%& are forced to be true when &%one_time%& is set.
22055 &*Warning 3*&: The &%unseen%& generic router option may not be set with
22058 The original top-level address is remembered with each of the generated
22059 addresses, and is output in any log messages. However, any intermediate parent
22060 addresses are not recorded. This makes a difference to the log only if
22061 &%all_parents%& log selector is set. It is expected that &%one_time%& will
22062 typically be used for mailing lists, where there is normally just one level of
22066 .option owners redirect "string list" unset
22067 .cindex "ownership" "alias file"
22068 .cindex "ownership" "forward file"
22069 .cindex "alias file" "ownership"
22070 .cindex "forward file" "ownership"
22071 This specifies a list of permitted owners for the file specified by &%file%&.
22072 This list is in addition to the local user when &%check_local_user%& is set.
22073 See &%check_owner%& above.
22076 .option owngroups redirect "string list" unset
22077 This specifies a list of permitted groups for the file specified by &%file%&.
22078 The list is in addition to the local user's primary group when
22079 &%check_local_user%& is set. See &%check_group%& above.
22082 .option pipe_transport redirect string&!! unset
22083 .vindex "&$address_pipe$&"
22084 A &(redirect)& router sets up a direct delivery to a pipe when a string
22085 starting with a vertical bar character is specified as a new &"address"&. The
22086 transport used is specified by this option, which, after expansion, must be the
22087 name of a configured transport. This should normally be a &(pipe)& transport.
22088 When the transport is run, the pipe command is in &$address_pipe$&.
22091 .option qualify_domain redirect string&!! unset
22092 .vindex "&$qualify_recipient$&"
22093 If this option is set, and an unqualified address (one without a domain) is
22094 generated, and that address would normally be qualified by the global setting
22095 in &%qualify_recipient%&, it is instead qualified with the domain specified by
22096 expanding this string. If the expansion fails, the router declines. If you want
22097 to revert to the default, you can have the expansion generate
22098 &$qualify_recipient$&.
22100 This option applies to all unqualified addresses generated by Exim filters,
22101 but for traditional &_.forward_& files, it applies only to addresses that are
22102 not preceded by a backslash. Sieve filters cannot generate unqualified
22105 .option qualify_preserve_domain redirect boolean false
22106 .cindex "domain" "in redirection; preserving"
22107 .cindex "preserving domain in redirection"
22108 .cindex "address redirection" "domain; preserving"
22109 If this option is set, the router's local &%qualify_domain%& option must not be
22110 set (a configuration error occurs if it is). If an unqualified address (one
22111 without a domain) is generated, it is qualified with the domain of the parent
22112 address (the immediately preceding ancestor) instead of the global
22113 &%qualify_recipient%& value. In the case of a traditional &_.forward_& file,
22114 this applies whether or not the address is preceded by a backslash.
22117 .option repeat_use redirect boolean true
22118 If this option is set false, the router is skipped for a child address that has
22119 any ancestor that was routed by this router. This test happens before any of
22120 the other preconditions are tested. Exim's default anti-looping rules skip
22121 only when the ancestor is the same as the current address. See also
22122 &%check_ancestor%& above and the generic &%redirect_router%& option.
22125 .option reply_transport redirect string&!! unset
22126 A &(redirect)& router sets up an automatic reply when a &%mail%& or
22127 &%vacation%& command is used in a filter file. The transport used is specified
22128 by this option, which, after expansion, must be the name of a configured
22129 transport. This should normally be an &(autoreply)& transport. Other transports
22130 are unlikely to do anything sensible or useful.
22133 .option rewrite redirect boolean true
22134 .cindex "address redirection" "disabling rewriting"
22135 If this option is set false, addresses generated by the router are not
22136 subject to address rewriting. Otherwise, they are treated like new addresses
22137 and are rewritten according to the global rewriting rules.
22140 .option sieve_subaddress redirect string&!! unset
22141 The value of this option is passed to a Sieve filter to specify the
22142 :subaddress part of an address.
22144 .option sieve_useraddress redirect string&!! unset
22145 The value of this option is passed to a Sieve filter to specify the :user part
22146 of an address. However, if it is unset, the entire original local part
22147 (including any prefix or suffix) is used for :user.
22150 .option sieve_vacation_directory redirect string&!! unset
22151 .cindex "Sieve filter" "vacation directory"
22152 To enable the &"vacation"& extension for Sieve filters, you must set
22153 &%sieve_vacation_directory%& to the directory where vacation databases are held
22154 (do not put anything else in that directory), and ensure that the
22155 &%reply_transport%& option refers to an &(autoreply)& transport. Each user
22156 needs their own directory; Exim will create it if necessary.
22160 .option skip_syntax_errors redirect boolean false
22161 .cindex "forward file" "broken"
22162 .cindex "address redirection" "broken files"
22163 .cindex "alias file" "broken"
22164 .cindex "broken alias or forward files"
22165 .cindex "ignoring faulty addresses"
22166 .cindex "skipping faulty addresses"
22167 .cindex "error" "skipping bad syntax"
22168 If &%skip_syntax_errors%& is set, syntactically malformed addresses in
22169 non-filter redirection data are skipped, and each failing address is logged. If
22170 &%syntax_errors_to%& is set, a message is sent to the address it defines,
22171 giving details of the failures. If &%syntax_errors_text%& is set, its contents
22172 are expanded and placed at the head of the error message generated by
22173 &%syntax_errors_to%&. Usually it is appropriate to set &%syntax_errors_to%& to
22174 be the same address as the generic &%errors_to%& option. The
22175 &%skip_syntax_errors%& option is often used when handling mailing lists.
22177 If all the addresses in a redirection list are skipped because of syntax
22178 errors, the router declines to handle the original address, and it is passed to
22179 the following routers.
22181 If &%skip_syntax_errors%& is set when an Exim filter is interpreted, any syntax
22182 error in the filter causes filtering to be abandoned without any action being
22183 taken. The incident is logged, and the router declines to handle the address,
22184 so it is passed to the following routers.
22186 .cindex "Sieve filter" "syntax errors in"
22187 Syntax errors in a Sieve filter file cause the &"keep"& action to occur. This
22188 action is specified by RFC 3028. The values of &%skip_syntax_errors%&,
22189 &%syntax_errors_to%&, and &%syntax_errors_text%& are not used.
22191 &%skip_syntax_errors%& can be used to specify that errors in users' forward
22192 lists or filter files should not prevent delivery. The &%syntax_errors_to%&
22193 option, used with an address that does not get redirected, can be used to
22194 notify users of these errors, by means of a router like this:
22200 file = $home/.forward
22201 file_transport = address_file
22202 pipe_transport = address_pipe
22203 reply_transport = address_reply
22206 syntax_errors_to = real-$local_part@$domain
22207 syntax_errors_text = \
22208 This is an automatically generated message. An error has\n\
22209 been found in your .forward file. Details of the error are\n\
22210 reported below. While this error persists, you will receive\n\
22211 a copy of this message for every message that is addressed\n\
22212 to you. If your .forward file is a filter file, or if it is\n\
22213 a non-filter file containing no valid forwarding addresses,\n\
22214 a copy of each incoming message will be put in your normal\n\
22215 mailbox. If a non-filter file contains at least one valid\n\
22216 forwarding address, forwarding to the valid addresses will\n\
22217 happen, and those will be the only deliveries that occur.
22219 You also need a router to ensure that local addresses that are prefixed by
22220 &`real-`& are recognized, but not forwarded or filtered. For example, you could
22221 put this immediately before the &(userforward)& router:
22226 local_part_prefix = real-
22227 transport = local_delivery
22229 For security, it would probably be a good idea to restrict the use of this
22230 router to locally-generated messages, using a condition such as this:
22232 condition = ${if match {$sender_host_address}\
22233 {\N^(|127\.0\.0\.1)$\N}}
22237 .option syntax_errors_text redirect string&!! unset
22238 See &%skip_syntax_errors%& above.
22241 .option syntax_errors_to redirect string unset
22242 See &%skip_syntax_errors%& above.
22243 .ecindex IIDredrou1
22244 .ecindex IIDredrou2
22251 . ////////////////////////////////////////////////////////////////////////////
22252 . ////////////////////////////////////////////////////////////////////////////
22254 .chapter "Environment for running local transports" "CHAPenvironment" &&&
22255 "Environment for local transports"
22256 .scindex IIDenvlotra1 "local transports" "environment for"
22257 .scindex IIDenvlotra2 "environment" "local transports"
22258 .scindex IIDenvlotra3 "transport" "local; environment for"
22259 Local transports handle deliveries to files and pipes. (The &(autoreply)&
22260 transport can be thought of as similar to a pipe.) Exim always runs transports
22261 in subprocesses, under specified uids and gids. Typical deliveries to local
22262 mailboxes run under the uid and gid of the local user.
22264 Exim also sets a specific current directory while running the transport; for
22265 some transports a home directory setting is also relevant. The &(pipe)&
22266 transport is the only one that sets up environment variables; see section
22267 &<<SECTpipeenv>>& for details.
22269 The values used for the uid, gid, and the directories may come from several
22270 different places. In many cases, the router that handles the address associates
22271 settings with that address as a result of its &%check_local_user%&, &%group%&,
22272 or &%user%& options. However, values may also be given in the transport's own
22273 configuration, and these override anything that comes from the router.
22277 .section "Concurrent deliveries" "SECID131"
22278 .cindex "concurrent deliveries"
22279 .cindex "simultaneous deliveries"
22280 If two different messages for the same local recipient arrive more or less
22281 simultaneously, the two delivery processes are likely to run concurrently. When
22282 the &(appendfile)& transport is used to write to a file, Exim applies locking
22283 rules to stop concurrent processes from writing to the same file at the same
22286 However, when you use a &(pipe)& transport, it is up to you to arrange any
22287 locking that is needed. Here is a silly example:
22291 command = /bin/sh -c 'cat >>/some/file'
22293 This is supposed to write the message at the end of the file. However, if two
22294 messages arrive at the same time, the file will be scrambled. You can use the
22295 &%exim_lock%& utility program (see section &<<SECTmailboxmaint>>&) to lock a
22296 file using the same algorithm that Exim itself uses.
22301 .section "Uids and gids" "SECTenvuidgid"
22302 .cindex "local transports" "uid and gid"
22303 .cindex "transport" "local; uid and gid"
22304 All transports have the options &%group%& and &%user%&. If &%group%& is set, it
22305 overrides any group that the router set in the address, even if &%user%& is not
22306 set for the transport. This makes it possible, for example, to run local mail
22307 delivery under the uid of the recipient (set by the router), but in a special
22308 group (set by the transport). For example:
22311 # User/group are set by check_local_user in this router
22315 transport = group_delivery
22318 # This transport overrides the group
22320 driver = appendfile
22321 file = /var/spool/mail/$local_part_data
22324 If &%user%& is set for a transport, its value overrides what is set in the
22325 address by the router. If &%user%& is non-numeric and &%group%& is not set, the
22326 gid associated with the user is used. If &%user%& is numeric, &%group%& must be
22329 .oindex "&%initgroups%&"
22330 When the uid is taken from the transport's configuration, the &[initgroups()]&
22331 function is called for the groups associated with that uid if the
22332 &%initgroups%& option is set for the transport. When the uid is not specified
22333 by the transport, but is associated with the address by a router, the option
22334 for calling &[initgroups()]& is taken from the router configuration.
22336 .cindex "&(pipe)& transport" "uid for"
22337 The &(pipe)& transport contains the special option &%pipe_as_creator%&. If this
22338 is set and &%user%& is not set, the uid of the process that called Exim to
22339 receive the message is used, and if &%group%& is not set, the corresponding
22340 original gid is also used.
22342 This is the detailed preference order for obtaining a gid; the first of the
22343 following that is set is used:
22346 A &%group%& setting of the transport;
22348 A &%group%& setting of the router;
22350 A gid associated with a user setting of the router, either as a result of
22351 &%check_local_user%& or an explicit non-numeric &%user%& setting;
22353 The group associated with a non-numeric &%user%& setting of the transport;
22355 In a &(pipe)& transport, the creator's gid if &%deliver_as_creator%& is set and
22356 the uid is the creator's uid;
22358 The Exim gid if the Exim uid is being used as a default.
22361 If, for example, the user is specified numerically on the router and there are
22362 no group settings, no gid is available. In this situation, an error occurs.
22363 This is different for the uid, for which there always is an ultimate default.
22364 The first of the following that is set is used:
22367 A &%user%& setting of the transport;
22369 In a &(pipe)& transport, the creator's uid if &%deliver_as_creator%& is set;
22371 A &%user%& setting of the router;
22373 A &%check_local_user%& setting of the router;
22378 Of course, an error will still occur if the uid that is chosen is on the
22379 &%never_users%& list.
22385 .section "Current and home directories" "SECID132"
22386 .cindex "current directory for local transport"
22387 .cindex "home directory" "for local transport"
22388 .cindex "transport" "local; home directory for"
22389 .cindex "transport" "local; current directory for"
22390 Routers may set current and home directories for local transports by means of
22391 the &%transport_current_directory%& and &%transport_home_directory%& options.
22392 However, if the transport's &%current_directory%& or &%home_directory%& options
22393 are set, they override the router's values. In detail, the home directory
22394 for a local transport is taken from the first of these values that is set:
22397 The &%home_directory%& option on the transport;
22399 The &%transport_home_directory%& option on the router;
22401 The password data if &%check_local_user%& is set on the router;
22403 The &%router_home_directory%& option on the router.
22406 The current directory is taken from the first of these values that is set:
22409 The &%current_directory%& option on the transport;
22411 The &%transport_current_directory%& option on the router.
22415 If neither the router nor the transport sets a current directory, Exim uses the
22416 value of the home directory, if it is set. Otherwise it sets the current
22417 directory to &_/_& before running a local transport.
22421 .section "Expansion variables derived from the address" "SECID133"
22422 .vindex "&$domain$&"
22423 .vindex "&$local_part$&"
22424 .vindex "&$original_domain$&"
22425 Normally a local delivery is handling a single address, and in that case the
22426 variables such as &$domain$& and &$local_part$& are set during local
22427 deliveries. However, in some circumstances more than one address may be handled
22428 at once (for example, while writing batch SMTP for onward transmission by some
22429 other means). In this case, the variables associated with the local part are
22430 never set, &$domain$& is set only if all the addresses have the same domain,
22431 and &$original_domain$& is never set.
22432 .ecindex IIDenvlotra1
22433 .ecindex IIDenvlotra2
22434 .ecindex IIDenvlotra3
22442 . ////////////////////////////////////////////////////////////////////////////
22443 . ////////////////////////////////////////////////////////////////////////////
22445 .chapter "Generic options for transports" "CHAPtransportgeneric"
22446 .scindex IIDgenoptra1 "generic options" "transport"
22447 .scindex IIDgenoptra2 "options" "generic; for transports"
22448 .scindex IIDgenoptra3 "transport" "generic options for"
22449 The name of a transport is limited to be &drivernamemax; ASCII characters long;
22450 prior to Exim 4.95 names would be silently truncated at this length, but now
22453 The following generic options apply to all transports:
22456 .option body_only transports boolean false
22457 .cindex "transport" "body only"
22458 .cindex "message" "transporting body only"
22459 .cindex "body of message" "transporting"
22460 If this option is set, the message's headers are not transported. It is
22461 mutually exclusive with &%headers_only%&. If it is used with the &(appendfile)&
22462 or &(pipe)& transports, the settings of &%message_prefix%& and
22463 &%message_suffix%& should be checked, because this option does not
22464 automatically suppress them.
22467 .option current_directory transports string&!! unset
22468 .cindex "transport" "current directory for"
22469 This specifies the current directory that is to be set while running the
22470 transport, overriding any value that may have been set by the router.
22471 If the expansion fails for any reason, including forced failure, an error is
22472 logged, and delivery is deferred.
22475 .option disable_logging transports boolean false
22476 If this option is set true, nothing is logged for any
22477 deliveries by the transport or for any
22478 transport errors. You should not set this option unless you really, really know
22479 what you are doing.
22482 .option debug_print transports string&!! unset
22483 .cindex "testing" "variables in drivers"
22484 If this option is set and debugging is enabled (see the &%-d%& command line
22485 option), the string is expanded and included in the debugging output when the
22487 If expansion of the string fails, the error message is written to the debugging
22488 output, and Exim carries on processing.
22489 This facility is provided to help with checking out the values of variables and
22490 so on when debugging driver configurations. For example, if a &%headers_add%&
22491 option is not working properly, &%debug_print%& could be used to output the
22492 variables it references. A newline is added to the text if it does not end with
22494 The variables &$transport_name$& and &$router_name$& contain the name of the
22495 transport and the router that called it.
22497 .option delivery_date_add transports boolean false
22498 .cindex "&'Delivery-date:'& header line"
22499 If this option is true, a &'Delivery-date:'& header is added to the message.
22500 This gives the actual time the delivery was made. As this is not a standard
22501 header, Exim has a configuration option (&%delivery_date_remove%&) which
22502 requests its removal from incoming messages, so that delivered messages can
22503 safely be resent to other recipients.
22506 .option driver transports string unset
22507 This specifies which of the available transport drivers is to be used.
22508 There is no default, and this option must be set for every transport.
22511 .option envelope_to_add transports boolean false
22512 .cindex "&'Envelope-to:'& header line"
22513 If this option is true, an &'Envelope-to:'& header is added to the message.
22514 This gives the original address(es) in the incoming envelope that caused this
22515 delivery to happen. More than one address may be present if the transport is
22516 configured to handle several addresses at once, or if more than one original
22517 address was redirected to the same final address. As this is not a standard
22518 header, Exim has a configuration option (&%envelope_to_remove%&) which requests
22519 its removal from incoming messages, so that delivered messages can safely be
22520 resent to other recipients.
22522 &*Note:*& If used on a transport handling multiple recipients
22523 (the smtp transport unless &%rcpt_max%& is 1, the appendfile, pipe or lmtp
22524 transport if &%batch_max%& is greater than 1)
22525 then information about Bcc recipients will be leaked.
22526 Doing so is generally not advised.
22529 .option event_action transports string&!! unset
22531 This option declares a string to be expanded for Exim's events mechanism.
22532 For details see chapter &<<CHAPevents>>&.
22535 .option group transports string&!! "Exim group"
22536 .cindex "transport" "group; specifying"
22537 This option specifies a gid for running the transport process, overriding any
22538 value that the router supplies, and also overriding any value associated with
22539 &%user%& (see below).
22542 .option headers_add transports list&!! unset
22543 .cindex "header lines" "adding in transport"
22544 .cindex "transport" "header lines; adding"
22545 This option specifies a list of text headers,
22546 newline-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
22547 which are (separately) expanded and added to the header
22548 portion of a message as it is transported, as described in section
22549 &<<SECTheadersaddrem>>&. Additional header lines can also be specified by
22550 routers. If the result of the expansion is an empty string, or if the expansion
22551 is forced to fail, no action is taken. Other expansion failures are treated as
22552 errors and cause the delivery to be deferred.
22554 Unlike most options, &%headers_add%& can be specified multiple times
22555 for a transport; all listed headers are added.
22558 .option headers_only transports boolean false
22559 .cindex "transport" "header lines only"
22560 .cindex "message" "transporting headers only"
22561 .cindex "header lines" "transporting"
22562 If this option is set, the message's body is not transported. It is mutually
22563 exclusive with &%body_only%&. If it is used with the &(appendfile)& or &(pipe)&
22564 transports, the settings of &%message_prefix%& and &%message_suffix%& should be
22565 checked, since this option does not automatically suppress them.
22568 .option headers_remove transports list&!! unset
22569 .cindex "header lines" "removing"
22570 .cindex "transport" "header lines; removing"
22571 This option specifies a list of text headers,
22572 colon-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
22573 to be removed from the message.
22574 However, the option has no effect when an address is just being verified.
22575 Each list item is separately expanded.
22576 If the result of the expansion is an empty string, or if the expansion
22577 is forced to fail, no action is taken. Other expansion failures are treated as
22578 errors and cause the delivery to be deferred.
22579 If an item ends in *, it will match any header with the given prefix.
22581 Matching headers are omitted from the message as it is transported, as described
22582 in section &<<SECTheadersaddrem>>&. Header removal can also be specified by
22585 Unlike most options, &%headers_remove%& can be specified multiple times
22586 for a transport; all listed headers are removed.
22588 &*Warning*&: Because of the separate expansion of the list items,
22589 items that contain a list separator must have it doubled.
22590 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
22594 .option headers_rewrite transports string unset
22595 .cindex "transport" "header lines; rewriting"
22596 .cindex "rewriting" "at transport time"
22597 This option allows addresses in header lines to be rewritten at transport time,
22598 that is, as the message is being copied to its destination. The contents of the
22599 option are a colon-separated list of rewriting rules. Each rule is in exactly
22600 the same form as one of the general rewriting rules that are applied when a
22601 message is received. These are described in chapter &<<CHAPrewrite>>&. For
22604 headers_rewrite = a@b c@d f : \
22607 changes &'a@b'& into &'c@d'& in &'From:'& header lines, and &'x@y'& into
22608 &'w@z'& in all address-bearing header lines. The rules are applied to the
22609 header lines just before they are written out at transport time, so they affect
22610 only those copies of the message that pass through the transport. However, only
22611 the message's original header lines, and any that were added by a system
22612 filter, are rewritten. If a router or transport adds header lines, they are not
22613 affected by this option. These rewriting rules are &'not'& applied to the
22614 envelope. You can change the return path using &%return_path%&, but you cannot
22615 change envelope recipients at this time.
22618 .option home_directory transports string&!! unset
22619 .cindex "transport" "home directory for"
22621 This option specifies a home directory setting for a local transport,
22622 overriding any value that may be set by the router. The home directory is
22623 placed in &$home$& while expanding the transport's private options. It is also
22624 used as the current directory if no current directory is set by the
22625 &%current_directory%& option on the transport or the
22626 &%transport_current_directory%& option on the router. If the expansion fails
22627 for any reason, including forced failure, an error is logged, and delivery is
22631 .option initgroups transports boolean false
22632 .cindex "additional groups"
22633 .cindex "groups" "additional"
22634 .cindex "transport" "group; additional"
22635 If this option is true and the uid for the delivery process is provided by the
22636 transport, the &[initgroups()]& function is called when running the transport
22637 to ensure that any additional groups associated with the uid are set up.
22640 .option max_parallel transports integer&!! unset
22641 .cindex limit "transport parallelism"
22642 .cindex transport "parallel processes"
22643 .cindex transport "concurrency limit"
22644 .cindex "delivery" "parallelism for transport"
22645 If this option is set and expands to an integer greater than zero
22646 it limits the number of concurrent runs of the transport.
22647 The control does not apply to shadow transports.
22649 .cindex "hints database" "transport concurrency control"
22650 Exim implements this control by means of a hints database in which a record is
22651 incremented whenever a transport process is being created. The record
22652 is decremented and possibly removed when the process terminates.
22653 Obviously there is scope for
22654 records to get left lying around if there is a system or program crash. To
22655 guard against this, Exim ignores any records that are more than six hours old.
22657 If you use this option, you should also arrange to delete the
22658 relevant hints database whenever your system reboots. The names of the files
22659 start with &_misc_& and they are kept in the &_spool/db_& directory. There
22660 may be one or two files, depending on the type of DBM in use. The same files
22661 are used for ETRN and smtp transport serialization.
22664 .option message_size_limit transports string&!! 0
22665 .cindex "limit" "message size per transport"
22666 .cindex "size" "of message, limit"
22667 .cindex "transport" "message size; limiting"
22668 This option controls the size of messages passed through the transport. It is
22669 expanded before use; the result of the expansion must be a sequence of decimal
22670 digits, optionally followed by K or M. If the expansion fails for any reason,
22671 including forced failure, or if the result is not of the required form,
22672 delivery is deferred. If the value is greater than zero and the size of a
22673 message exceeds this limit, the address is failed. If there is any chance that
22674 the resulting bounce message could be routed to the same transport, you should
22675 ensure that &%return_size_limit%& is less than the transport's
22676 &%message_size_limit%&, as otherwise the bounce message will fail to get
22681 .option rcpt_include_affixes transports boolean false
22682 .cindex "prefix" "for local part, including in envelope"
22683 .cindex "suffix for local part" "including in envelope"
22684 .cindex "local part" "prefix"
22685 .cindex "local part" "suffix"
22686 When this option is false (the default), and an address that has had any
22687 affixes (prefixes or suffixes) removed from the local part is delivered by any
22688 form of SMTP or LMTP, the affixes are not included. For example, if a router
22691 local_part_prefix = *-
22693 routes the address &'abc-xyz@some.domain'& to an SMTP transport, the envelope
22696 RCPT TO:<xyz@some.domain>
22698 This is also the case when an ACL-time callout is being used to verify a
22699 recipient address. However, if &%rcpt_include_affixes%& is set true, the
22700 whole local part is included in the RCPT command. This option applies to BSMTP
22701 deliveries by the &(appendfile)& and &(pipe)& transports as well as to the
22702 &(lmtp)& and &(smtp)& transports.
22705 .option retry_use_local_part transports boolean "see below"
22706 .cindex "hints database" "retry keys"
22707 When a delivery suffers a temporary failure, a retry record is created
22708 in Exim's hints database. For remote deliveries, the key for the retry record
22709 is based on the name and/or IP address of the failing remote host. For local
22710 deliveries, the key is normally the entire address, including both the local
22711 part and the domain. This is suitable for most common cases of local delivery
22712 temporary failure &-- for example, exceeding a mailbox quota should delay only
22713 deliveries to that mailbox, not to the whole domain.
22715 However, in some special cases you may want to treat a temporary local delivery
22716 as a failure associated with the domain, and not with a particular local part.
22717 (For example, if you are storing all mail for some domain in files.) You can do
22718 this by setting &%retry_use_local_part%& false.
22720 For all the local transports, its default value is true. For remote transports,
22721 the default value is false for tidiness, but changing the value has no effect
22722 on a remote transport in the current implementation.
22725 .option return_path transports string&!! unset
22726 .cindex "envelope sender"
22727 .cindex "envelope from"
22728 .cindex "transport" "return path; changing"
22729 .cindex "return path" "changing in transport"
22730 If this option is set, the string is expanded at transport time and replaces
22731 the existing return path (envelope sender) value in the copy of the message
22732 that is being delivered. An empty return path is permitted. This feature is
22733 designed for remote deliveries, where the value of this option is used in the
22734 SMTP MAIL command. If you set &%return_path%& for a local transport, the
22735 only effect is to change the address that is placed in the &'Return-path:'&
22736 header line, if one is added to the message (see the next option).
22738 &*Note:*& A changed return path is not logged unless you add
22739 &%return_path_on_delivery%& to the log selector.
22741 .vindex "&$return_path$&"
22742 The expansion can refer to the existing value via &$return_path$&. This is
22743 either the message's envelope sender, or an address set by the
22744 &%errors_to%& option on a router. If the expansion is forced to fail, no
22745 replacement occurs; if it fails for another reason, delivery is deferred. This
22746 option can be used to support VERP (Variable Envelope Return Paths) &-- see
22747 section &<<SECTverp>>&.
22749 &*Note*&: If a delivery error is detected locally, including the case when a
22750 remote server rejects a message at SMTP time, the bounce message is not sent to
22751 the value of this option. It is sent to the previously set errors address.
22752 This defaults to the incoming sender address, but can be changed by setting
22753 &%errors_to%& in a router.
22757 .option return_path_add transports boolean false
22758 .chindex Return-path:
22759 If this option is true, a &'Return-path:'& header is added to the message.
22760 Although the return path is normally available in the prefix line of BSD
22761 mailboxes, this is commonly not displayed by MUAs, and so the user does not
22762 have easy access to it.
22764 RFC 2821 states that the &'Return-path:'& header is added to a message &"when
22765 the delivery SMTP server makes the final delivery"&. This implies that this
22766 header should not be present in incoming messages. Exim has a configuration
22767 option, &%return_path_remove%&, which requests removal of this header from
22768 incoming messages, so that delivered messages can safely be resent to other
22772 .option shadow_condition transports string&!! unset
22773 See &%shadow_transport%& below.
22776 .option shadow_transport transports string unset
22777 .cindex "shadow transport"
22778 .cindex "transport" "shadow"
22779 A local transport may set the &%shadow_transport%& option to the name of
22780 another local transport. Shadow remote transports are not supported.
22782 Whenever a delivery to the main transport succeeds, and either
22783 &%shadow_condition%& is unset, or its expansion does not result in the empty
22784 string or one of the strings &"0"& or &"no"& or &"false"&, the message is also
22785 passed to the shadow transport, with the same delivery address or addresses. If
22786 expansion fails, no action is taken except that non-forced expansion failures
22787 cause a log line to be written.
22789 The result of the shadow transport is discarded and does not affect the
22790 subsequent processing of the message. Only a single level of shadowing is
22791 provided; the &%shadow_transport%& option is ignored on any transport when it
22792 is running as a shadow. Options concerned with output from pipes are also
22793 ignored. The log line for the successful delivery has an item added on the end,
22796 ST=<shadow transport name>
22798 If the shadow transport did not succeed, the error message is put in
22799 parentheses afterwards. Shadow transports can be used for a number of different
22800 purposes, including keeping more detailed log information than Exim normally
22801 provides, and implementing automatic acknowledgment policies based on message
22802 headers that some sites insist on.
22805 .option transport_filter transports string&!! unset
22806 .cindex "transport" "filter"
22807 .cindex "filter" "transport filter"
22808 This option sets up a filtering (in the Unix shell sense) process for messages
22809 at transport time. It should not be confused with mail filtering as set up by
22810 individual users or via a system filter.
22811 If unset, or expanding to an empty string, no filtering is done.
22813 When the message is about to be written out, the command specified by
22814 &%transport_filter%& is started up in a separate, parallel process, and
22815 the entire message, including the header lines, is passed to it on its standard
22816 input (this in fact is done from a third process, to avoid deadlock). The
22817 command must be specified as an absolute path.
22819 The lines of the message that are written to the transport filter are
22820 terminated by newline (&"\n"&). The message is passed to the filter before any
22821 SMTP-specific processing, such as turning &"\n"& into &"\r\n"& and escaping
22822 lines beginning with a dot, and also before any processing implied by the
22823 settings of &%check_string%& and &%escape_string%& in the &(appendfile)& or
22824 &(pipe)& transports.
22826 The standard error for the filter process is set to the same destination as its
22827 standard output; this is read and written to the message's ultimate
22828 destination. The process that writes the message to the filter, the
22829 filter itself, and the original process that reads the result and delivers it
22830 are all run in parallel, like a shell pipeline.
22832 The filter can perform any transformations it likes, but of course should take
22833 care not to break RFC 2822 syntax. Exim does not check the result, except to
22834 test for a final newline when SMTP is in use. All messages transmitted over
22835 SMTP must end with a newline, so Exim supplies one if it is missing.
22837 .cindex "content scanning" "per user"
22838 A transport filter can be used to provide content-scanning on a per-user basis
22839 at delivery time if the only required effect of the scan is to modify the
22840 message. For example, a content scan could insert a new header line containing
22841 a spam score. This could be interpreted by a filter in the user's MUA. It is
22842 not possible to discard a message at this stage.
22844 .cindex "SIZE" "ESMTP extension"
22845 A problem might arise if the filter increases the size of a message that is
22846 being sent down an SMTP connection. If the receiving SMTP server has indicated
22847 support for the SIZE parameter, Exim will have sent the size of the message
22848 at the start of the SMTP session. If what is actually sent is substantially
22849 more, the server might reject the message. This can be worked round by setting
22850 the &%size_addition%& option on the &(smtp)& transport, either to allow for
22851 additions to the message, or to disable the use of SIZE altogether.
22853 .vindex "&$pipe_addresses$&"
22854 The value of the &%transport_filter%& option is the command string for starting
22855 the filter, which is run directly from Exim, not under a shell. The string is
22856 parsed by Exim in the same way as a command string for the &(pipe)& transport:
22857 Exim breaks it up into arguments and then expands each argument separately (see
22858 section &<<SECThowcommandrun>>&). Any kind of expansion failure causes delivery
22859 to be deferred. The special argument &$pipe_addresses$& is replaced by a number
22860 of arguments, one for each address that applies to this delivery. (This isn't
22861 an ideal name for this feature here, but as it was already implemented for the
22862 &(pipe)& transport, it seemed sensible not to change it.)
22865 .vindex "&$host_address$&"
22866 The expansion variables &$host$& and &$host_address$& are available when the
22867 transport is a remote one. They contain the name and IP address of the host to
22868 which the message is being sent. For example:
22869 . used to have $sender_address in this cmdline, but it's tainted
22871 transport_filter = /some/directory/transport-filter.pl \
22872 $host $host_address $pipe_addresses
22875 Two problems arise if you want to use more complicated expansion items to
22876 generate transport filter commands, both of which due to the fact that the
22877 command is split up &'before'& expansion.
22879 If an expansion item contains white space, you must quote it, so that it is all
22880 part of the same command item. If the entire option setting is one such
22881 expansion item, you have to take care what kind of quoting you use. For
22884 transport_filter = '/bin/cmd${if eq{$host}{a.b.c}{1}{2}}'
22886 This runs the command &(/bin/cmd1)& if the host name is &'a.b.c'&, and
22887 &(/bin/cmd2)& otherwise. If double quotes had been used, they would have been
22888 stripped by Exim when it read the option's value. When the value is used, if
22889 the single quotes were missing, the line would be split into two items,
22890 &`/bin/cmd${if`& and &`eq{$host}{a.b.c}{1}{2}`&, and an error would occur when
22891 Exim tried to expand the first one.
22893 Except for the special case of &$pipe_addresses$& that is mentioned above, an
22894 expansion cannot generate multiple arguments, or a command name followed by
22895 arguments. Consider this example:
22897 transport_filter = ${lookup{$host}lsearch{/a/file}\
22898 {$value}{/bin/cat}}
22900 The result of the lookup is interpreted as the name of the command, even
22901 if it contains white space. The simplest way round this is to use a shell:
22903 transport_filter = /bin/sh -c ${lookup{$host}lsearch{/a/file}\
22904 {$value}{/bin/cat}}
22908 The filter process is run under the same uid and gid as the normal delivery.
22909 For remote deliveries this is the Exim uid/gid by default. The command should
22910 normally yield a zero return code. Transport filters are not supposed to fail.
22911 A non-zero code is taken to mean that the transport filter encountered some
22912 serious problem. Delivery of the message is deferred; the message remains on
22913 the queue and is tried again later. It is not possible to cause a message to be
22914 bounced from a transport filter.
22916 If a transport filter is set on an autoreply transport, the original message is
22917 passed through the filter as it is being copied into the newly generated
22918 message, which happens if the &%return_message%& option is set.
22921 .option transport_filter_timeout transports time 5m
22922 .cindex "transport" "filter, timeout"
22923 When Exim is reading the output of a transport filter, it applies a timeout
22924 that can be set by this option. Exceeding the timeout is normally treated as a
22925 temporary delivery failure. However, if a transport filter is used with a
22926 &(pipe)& transport, a timeout in the transport filter is treated in the same
22927 way as a timeout in the pipe command itself. By default, a timeout is a hard
22928 error, but if the &(pipe)& transport's &%timeout_defer%& option is set true, it
22929 becomes a temporary error.
22932 .option user transports string&!! "Exim user"
22933 .cindex "uid (user id)" "local delivery"
22934 .cindex "transport" "user, specifying"
22935 This option specifies the user under whose uid the delivery process is to be
22936 run, overriding any uid that may have been set by the router. If the user is
22937 given as a name, the uid is looked up from the password data, and the
22938 associated group is taken as the value of the gid to be used if the &%group%&
22941 For deliveries that use local transports, a user and group are normally
22942 specified explicitly or implicitly (for example, as a result of
22943 &%check_local_user%&) by the router or transport.
22945 .cindex "hints database" "access by remote transport"
22946 For remote transports, you should leave this option unset unless you really are
22947 sure you know what you are doing. When a remote transport is running, it needs
22948 to be able to access Exim's hints databases, because each host may have its own
22950 .ecindex IIDgenoptra1
22951 .ecindex IIDgenoptra2
22952 .ecindex IIDgenoptra3
22959 . ////////////////////////////////////////////////////////////////////////////
22960 . ////////////////////////////////////////////////////////////////////////////
22962 .chapter "Address batching in local transports" "CHAPbatching" &&&
22964 .cindex "transport" "local; address batching in"
22965 The only remote transport (&(smtp)&) is normally configured to handle more than
22966 one address at a time, so that when several addresses are routed to the same
22967 remote host, just one copy of the message is sent. Local transports, however,
22968 normally handle one address at a time. That is, a separate instance of the
22969 transport is run for each address that is routed to the transport. A separate
22970 copy of the message is delivered each time.
22972 .cindex "batched local delivery"
22973 .oindex "&%batch_max%&"
22974 .oindex "&%batch_id%&"
22975 In special cases, it may be desirable to handle several addresses at once in a
22976 local transport, for example:
22979 In an &(appendfile)& transport, when storing messages in files for later
22980 delivery by some other means, a single copy of the message with multiple
22981 recipients saves space.
22983 In an &(lmtp)& transport, when delivering over &"local SMTP"& to some process,
22984 a single copy saves time, and is the normal way LMTP is expected to work.
22986 In a &(pipe)& transport, when passing the message
22987 to a scanner program or
22988 to some other delivery mechanism such as UUCP, multiple recipients may be
22992 These three local transports all have the same options for controlling multiple
22993 (&"batched"&) deliveries, namely &%batch_max%& and &%batch_id%&. To save
22994 repeating the information for each transport, these options are described here.
22996 The &%batch_max%& option specifies the maximum number of addresses that can be
22997 delivered together in a single run of the transport. Its default value is one
22998 (no batching). When more than one address is routed to a transport that has a
22999 &%batch_max%& value greater than one, the addresses are delivered in a batch
23000 (that is, in a single run of the transport with multiple recipients), subject
23001 to certain conditions:
23004 .vindex "&$local_part$&"
23005 If any of the transport's options contain a reference to &$local_part$&, no
23006 batching is possible.
23008 .vindex "&$domain$&"
23009 If any of the transport's options contain a reference to &$domain$&, only
23010 addresses with the same domain are batched.
23012 .cindex "customizing" "batching condition"
23013 If &%batch_id%& is set, it is expanded for each address, and only those
23014 addresses with the same expanded value are batched. This allows you to specify
23015 customized batching conditions. Failure of the expansion for any reason,
23016 including forced failure, disables batching, but it does not stop the delivery
23019 Batched addresses must also have the same errors address (where to send
23020 delivery errors), the same header additions and removals, the same user and
23021 group for the transport, and if a host list is present, the first host must
23025 In the case of the &(appendfile)& and &(pipe)& transports, batching applies
23026 both when the file or pipe command is specified in the transport, and when it
23027 is specified by a &(redirect)& router, but all the batched addresses must of
23028 course be routed to the same file or pipe command. These two transports have an
23029 option called &%use_bsmtp%&, which causes them to deliver the message in
23030 &"batched SMTP"& format, with the envelope represented as SMTP commands. The
23031 &%check_string%& and &%escape_string%& options are forced to the values
23034 escape_string = ".."
23036 when batched SMTP is in use. A full description of the batch SMTP mechanism is
23037 given in section &<<SECTbatchSMTP>>&. The &(lmtp)& transport does not have a
23038 &%use_bsmtp%& option, because it always delivers using the SMTP protocol.
23040 .cindex "&'Envelope-to:'& header line"
23041 If the generic &%envelope_to_add%& option is set for a batching transport, the
23042 &'Envelope-to:'& header that is added to the message contains all the addresses
23043 that are being processed together. If you are using a batching &(appendfile)&
23044 transport without &%use_bsmtp%&, the only way to preserve the recipient
23045 addresses is to set the &%envelope_to_add%& option.
23047 .cindex "&(pipe)& transport" "with multiple addresses"
23048 .vindex "&$pipe_addresses$&"
23049 If you are using a &(pipe)& transport without BSMTP, and setting the
23050 transport's &%command%& option, you can include &$pipe_addresses$& as part of
23051 the command. This is not a true variable; it is a bit of magic that causes each
23052 of the recipient addresses to be inserted into the command as a separate
23053 argument. This provides a way of accessing all the addresses that are being
23054 delivered in the batch. &*Note:*& This is not possible for pipe commands that
23055 are specified by a &(redirect)& router.
23060 . ////////////////////////////////////////////////////////////////////////////
23061 . ////////////////////////////////////////////////////////////////////////////
23063 .chapter "The appendfile transport" "CHAPappendfile"
23064 .scindex IIDapptra1 "&(appendfile)& transport"
23065 .scindex IIDapptra2 "transports" "&(appendfile)&"
23066 .cindex "directory creation"
23067 .cindex "creating directories"
23068 The &(appendfile)& transport delivers a message by appending it to an existing
23069 file, or by creating an entirely new file in a specified directory. Single
23070 files to which messages are appended can be in the traditional Unix mailbox
23071 format, or optionally in the MBX format supported by the Pine MUA and
23072 University of Washington IMAP daemon, &'inter alia'&. When each message is
23073 being delivered as a separate file, &"maildir"& format can optionally be used
23074 to give added protection against failures that happen part-way through the
23075 delivery. A third form of separate-file delivery known as &"mailstore"& is also
23076 supported. For all file formats, Exim attempts to create as many levels of
23077 directory as necessary, provided that &%create_directory%& is set.
23079 The code for the optional formats is not included in the Exim binary by
23080 default. It is necessary to set SUPPORT_MBX, SUPPORT_MAILDIR and/or
23081 SUPPORT_MAILSTORE in &_Local/Makefile_& to have the appropriate code
23084 .cindex "quota" "system"
23085 Exim recognizes system quota errors, and generates an appropriate message. Exim
23086 also supports its own quota control within the transport, for use when the
23087 system facility is unavailable or cannot be used for some reason.
23089 If there is an error while appending to a file (for example, quota exceeded or
23090 partition filled), Exim attempts to reset the file's length and last
23091 modification time back to what they were before. If there is an error while
23092 creating an entirely new file, the new file is removed.
23094 Before appending to a file, a number of security checks are made, and the
23095 file is locked. A detailed description is given below, after the list of
23098 The &(appendfile)& transport is most commonly used for local deliveries to
23099 users' mailboxes. However, it can also be used as a pseudo-remote transport for
23100 putting messages into files for remote delivery by some means other than Exim.
23101 &"Batch SMTP"& format is often used in this case (see the &%use_bsmtp%&
23106 .section "The file and directory options" "SECTfildiropt"
23107 The &%file%& option specifies a single file, to which the message is appended;
23108 the &%directory%& option specifies a directory, in which a new file containing
23109 the message is created. Only one of these two options can be set, and for
23110 normal deliveries to mailboxes, one of them &'must'& be set.
23112 .vindex "&$address_file$&"
23113 .vindex "&$local_part$&"
23114 However, &(appendfile)& is also used for delivering messages to files or
23115 directories whose names (or parts of names) are obtained from alias,
23116 forwarding, or filtering operations (for example, a &%save%& command in a
23117 user's Exim filter). When such a transport is running, &$local_part$& contains
23118 the local part that was aliased or forwarded, and &$address_file$& contains the
23119 name (or partial name) of the file or directory generated by the redirection
23120 operation. There are two cases:
23123 If neither &%file%& nor &%directory%& is set, the redirection operation
23124 must specify an absolute path (one that begins with &`/`&). This is the most
23125 common case when users with local accounts use filtering to sort mail into
23126 different folders. See for example, the &(address_file)& transport in the
23127 default configuration. If the path ends with a slash, it is assumed to be the
23128 name of a directory. A delivery to a directory can also be forced by setting
23129 &%maildir_format%& or &%mailstore_format%&.
23131 If &%file%& or &%directory%& is set for a delivery from a redirection, it is
23132 used to determine the file or directory name for the delivery. Normally, the
23133 contents of &$address_file$& are used in some way in the string expansion.
23135 If the &%create_file%& option is set to a path which
23136 matches (see the option definition below for details)
23137 a file or directory name
23138 for the delivery, that name becomes de-tainted.
23140 .cindex "tainted data" "in filenames"
23141 .cindex appendfile "tainted data"
23142 Tainted data may not be used for a file or directory name.
23143 This means that, for instance, &$local_part$& cannot be used directly
23144 as a component of a path. It can however be used as the key for a lookup
23145 which returns a path (or component).
23148 .cindex "Sieve filter" "configuring &(appendfile)&"
23149 .cindex "Sieve filter" "relative mailbox path handling"
23150 As an example of the second case, consider an environment where users do not
23151 have home directories. They may be permitted to use Exim filter commands of the
23156 or Sieve filter commands of the form:
23158 require "fileinto";
23159 fileinto "folder23";
23161 In this situation, the expansion of &%file%& or &%directory%& in the transport
23162 must transform the relative path into an appropriate absolute filename. In the
23163 case of Sieve filters, the name &'inbox'& must be handled. It is the name that
23164 is used as a result of a &"keep"& action in the filter. This example shows one
23165 way of handling this requirement:
23167 file = ${if eq{$address_file}{inbox} \
23168 {/var/mail/$local_part_data} \
23169 {${if eq{${substr_0_1:$address_file}}{/} \
23171 {$home/mail/$address_file} \
23175 With this setting of &%file%&, &'inbox'& refers to the standard mailbox
23176 location, absolute paths are used without change, and other folders are in the
23177 &_mail_& directory within the home directory.
23179 &*Note 1*&: While processing an Exim filter, a relative path such as
23180 &_folder23_& is turned into an absolute path if a home directory is known to
23181 the router. In particular, this is the case if &%check_local_user%& is set. If
23182 you want to prevent this happening at routing time, you can set
23183 &%router_home_directory%& empty. This forces the router to pass the relative
23184 path to the transport.
23186 &*Note 2*&: An absolute path in &$address_file$& is not treated specially;
23187 the &%file%& or &%directory%& option is still used if it is set.
23192 .section "Private options for appendfile" "SECID134"
23193 .cindex "options" "&(appendfile)& transport"
23197 .option allow_fifo appendfile boolean false
23198 .cindex "fifo (named pipe)"
23199 .cindex "named pipe (fifo)"
23200 .cindex "pipe" "named (fifo)"
23201 Setting this option permits delivery to named pipes (FIFOs) as well as to
23202 regular files. If no process is reading the named pipe at delivery time, the
23203 delivery is deferred.
23206 .option allow_symlink appendfile boolean false
23207 .cindex "symbolic link" "to mailbox"
23208 .cindex "mailbox" "symbolic link"
23209 By default, &(appendfile)& will not deliver if the path name for the file is
23210 that of a symbolic link. Setting this option relaxes that constraint, but there
23211 are security issues involved in the use of symbolic links. Be sure you know
23212 what you are doing if you set this. Details of exactly what this option affects
23213 are included in the discussion which follows this list of options.
23216 .option batch_id appendfile string&!! unset
23217 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
23218 However, batching is automatically disabled for &(appendfile)& deliveries that
23219 happen as a result of forwarding or aliasing or other redirection directly to a
23223 .option batch_max appendfile integer 1
23224 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
23227 .option check_group appendfile boolean false
23228 When this option is set, the group owner of the file defined by the &%file%&
23229 option is checked to see that it is the same as the group under which the
23230 delivery process is running. The default setting is false because the default
23231 file mode is 0600, which means that the group is irrelevant.
23234 .option check_owner appendfile boolean true
23235 When this option is set, the owner of the file defined by the &%file%& option
23236 is checked to ensure that it is the same as the user under which the delivery
23237 process is running.
23240 .option check_string appendfile string "see below"
23241 .cindex "&""From""& line"
23242 As &(appendfile)& writes the message, the start of each line is tested for
23243 matching &%check_string%&, and if it does, the initial matching characters are
23244 replaced by the contents of &%escape_string%&. The value of &%check_string%& is
23245 a literal string, not a regular expression, and the case of any letters it
23246 contains is significant.
23248 If &%use_bsmtp%& is set the values of &%check_string%& and &%escape_string%&
23249 are forced to &"."& and &".."& respectively, and any settings in the
23250 configuration are ignored. Otherwise, they default to &"From&~"& and
23251 &">From&~"& when the &%file%& option is set, and unset when any of the
23252 &%directory%&, &%maildir%&, or &%mailstore%& options are set.
23254 The default settings, along with &%message_prefix%& and &%message_suffix%&, are
23255 suitable for traditional &"BSD"& mailboxes, where a line beginning with
23256 &"From&~"& indicates the start of a new message. All four options need changing
23257 if another format is used. For example, to deliver to mailboxes in MMDF format:
23258 .cindex "MMDF format mailbox"
23259 .cindex "mailbox" "MMDF format"
23261 check_string = "\1\1\1\1\n"
23262 escape_string = "\1\1\1\1 \n"
23263 message_prefix = "\1\1\1\1\n"
23264 message_suffix = "\1\1\1\1\n"
23266 .option create_directory appendfile boolean true
23267 .cindex "directory creation"
23268 When this option is true, Exim attempts to create any missing superior
23269 directories for the file that it is about to write. A created directory's mode
23270 is given by the &%directory_mode%& option.
23272 The group ownership of a newly created directory is highly dependent on the
23273 operating system (and possibly the file system) that is being used. For
23274 example, in Solaris, if the parent directory has the setgid bit set, its group
23275 is propagated to the child; if not, the currently set group is used. However,
23276 in FreeBSD, the parent's group is always used.
23280 .option create_file appendfile string anywhere
23281 This option constrains the location of files and directories that are created
23282 by this transport. It applies to files defined by the &%file%& option and
23283 directories defined by the &%directory%& option. In the case of maildir
23284 delivery, it applies to the top level directory, not the maildir directories
23287 The option must be set to one of the words &"anywhere"&, &"inhome"&, or
23288 &"belowhome"&, or to an absolute path.
23290 In the second and third cases, a home directory must have been
23291 set for the transport, and the file or directory being created must
23293 The "belowhome" checking additionally checks for attempts to use "../"
23294 to evade the testing.
23295 This option is not useful when an explicit filename is
23296 given for normal mailbox deliveries. It is intended for the case when filenames
23297 are generated from users' &_.forward_& files. These are usually handled
23298 by an &(appendfile)& transport called &%address_file%&. See also
23299 &%file_must_exist%&.
23301 In the fourth case,
23302 the value given for this option must be an absolute path for an
23303 existing directory.
23304 The value is used for checking instead of a home directory;
23305 checking is done in "belowhome" mode.
23307 .cindex "tainted data" "de-tainting"
23308 If "belowhome" checking is used, the file or directory path
23309 becomes de-tainted.
23312 .option directory appendfile string&!! unset
23313 This option is mutually exclusive with the &%file%& option, but one of &%file%&
23314 or &%directory%& must be set, unless the delivery is the direct result of a
23315 redirection (see section &<<SECTfildiropt>>&).
23317 When &%directory%& is set, the string is expanded, and the message is delivered
23318 into a new file or files in or below the given directory, instead of being
23319 appended to a single mailbox file. A number of different formats are provided
23320 (see &%maildir_format%& and &%mailstore_format%&), and see section
23321 &<<SECTopdir>>& for further details of this form of delivery.
23323 The result of expansion must not be tainted, unless the &%create_file%& option
23327 .option directory_file appendfile string&!! "see below"
23329 .vindex "&$inode$&"
23330 When &%directory%& is set, but neither &%maildir_format%& nor
23331 &%mailstore_format%& is set, &(appendfile)& delivers each message into a file
23332 whose name is obtained by expanding this string. The default value is:
23334 q${base62:$tod_epoch}-$inode
23336 This generates a unique name from the current time, in base 62 form, and the
23337 inode of the file. The variable &$inode$& is available only when expanding this
23341 .option directory_mode appendfile "octal integer" 0700
23342 If &(appendfile)& creates any directories as a result of the
23343 &%create_directory%& option, their mode is specified by this option.
23346 .option escape_string appendfile string "see description"
23347 See &%check_string%& above.
23350 .option file appendfile string&!! unset
23351 This option is mutually exclusive with the &%directory%& option, but one of
23352 &%file%& or &%directory%& must be set, unless the delivery is the direct result
23353 of a redirection (see section &<<SECTfildiropt>>&). The &%file%& option
23354 specifies a single file, to which the message is appended. One or more of
23355 &%use_fcntl_lock%&, &%use_flock_lock%&, or &%use_lockfile%& must be set with
23358 The result of expansion must not be tainted, unless the &%create_file%& option
23361 .cindex "NFS" "lock file"
23362 .cindex "locking files"
23363 .cindex "lock files"
23364 If you are using more than one host to deliver over NFS into the same
23365 mailboxes, you should always use lock files.
23367 The string value is expanded for each delivery, and must yield an absolute
23368 path. The most common settings of this option are variations on one of these
23371 file = /var/spool/mail/$local_part_data
23372 file = /home/$local_part_data/inbox
23375 .cindex "&""sticky""& bit"
23376 In the first example, all deliveries are done into the same directory. If Exim
23377 is configured to use lock files (see &%use_lockfile%& below) it must be able to
23378 create a file in the directory, so the &"sticky"& bit must be turned on for
23379 deliveries to be possible, or alternatively the &%group%& option can be used to
23380 run the delivery under a group id which has write access to the directory.
23384 .option file_format appendfile string unset
23385 .cindex "file" "mailbox; checking existing format"
23386 This option requests the transport to check the format of an existing file
23387 before adding to it. The check consists of matching a specific string at the
23388 start of the file. The value of the option consists of an even number of
23389 colon-separated strings. The first of each pair is the test string, and the
23390 second is the name of a transport. If the transport associated with a matched
23391 string is not the current transport, control is passed over to the other
23392 transport. For example, suppose the standard &(local_delivery)& transport has
23395 file_format = "From : local_delivery :\
23396 \1\1\1\1\n : local_mmdf_delivery"
23398 Mailboxes that begin with &"From"& are still handled by this transport, but if
23399 a mailbox begins with four binary ones followed by a newline, control is passed
23400 to a transport called &%local_mmdf_delivery%&, which presumably is configured
23401 to do the delivery in MMDF format. If a mailbox does not exist or is empty, it
23402 is assumed to match the current transport. If the start of a mailbox doesn't
23403 match any string, or if the transport named for a given string is not defined,
23404 delivery is deferred.
23407 .option file_must_exist appendfile boolean false
23408 If this option is true, the file specified by the &%file%& option must exist.
23409 A temporary error occurs if it does not, causing delivery to be deferred.
23410 If this option is false, the file is created if it does not exist.
23413 .option lock_fcntl_timeout appendfile time 0s
23414 .cindex "timeout" "mailbox locking"
23415 .cindex "mailbox" "locking, blocking and non-blocking"
23416 .cindex "locking files"
23417 By default, the &(appendfile)& transport uses non-blocking calls to &[fcntl()]&
23418 when locking an open mailbox file. If the call fails, the delivery process
23419 sleeps for &%lock_interval%& and tries again, up to &%lock_retries%& times.
23420 Non-blocking calls are used so that the file is not kept open during the wait
23421 for the lock; the reason for this is to make it as safe as possible for
23422 deliveries over NFS in the case when processes might be accessing an NFS
23423 mailbox without using a lock file. This should not be done, but
23424 misunderstandings and hence misconfigurations are not unknown.
23426 On a busy system, however, the performance of a non-blocking lock approach is
23427 not as good as using a blocking lock with a timeout. In this case, the waiting
23428 is done inside the system call, and Exim's delivery process acquires the lock
23429 and can proceed as soon as the previous lock holder releases it.
23431 If &%lock_fcntl_timeout%& is set to a non-zero time, blocking locks, with that
23432 timeout, are used. There may still be some retrying: the maximum number of
23435 (lock_retries * lock_interval) / lock_fcntl_timeout
23437 rounded up to the next whole number. In other words, the total time during
23438 which &(appendfile)& is trying to get a lock is roughly the same, unless
23439 &%lock_fcntl_timeout%& is set very large.
23441 You should consider setting this option if you are getting a lot of delayed
23442 local deliveries because of errors of the form
23444 failed to lock mailbox /some/file (fcntl)
23447 .option lock_flock_timeout appendfile time 0s
23448 This timeout applies to file locking when using &[flock()]& (see
23449 &%use_flock%&); the timeout operates in a similar manner to
23450 &%lock_fcntl_timeout%&.
23453 .option lock_interval appendfile time 3s
23454 This specifies the time to wait between attempts to lock the file. See below
23455 for details of locking.
23458 .option lock_retries appendfile integer 10
23459 This specifies the maximum number of attempts to lock the file. A value of zero
23460 is treated as 1. See below for details of locking.
23463 .option lockfile_mode appendfile "octal integer" 0600
23464 This specifies the mode of the created lock file, when a lock file is being
23465 used (see &%use_lockfile%& and &%use_mbx_lock%&).
23468 .option lockfile_timeout appendfile time 30m
23469 .cindex "timeout" "mailbox locking"
23470 When a lock file is being used (see &%use_lockfile%&), if a lock file already
23471 exists and is older than this value, it is assumed to have been left behind by
23472 accident, and Exim attempts to remove it.
23475 .option mailbox_filecount appendfile string&!! unset
23476 .cindex "mailbox" "specifying size of"
23477 .cindex "size" "of mailbox"
23478 If this option is set, it is expanded, and the result is taken as the current
23479 number of files in the mailbox. It must be a decimal number, optionally
23480 followed by K or M. This provides a way of obtaining this information from an
23481 external source that maintains the data.
23484 .option mailbox_size appendfile string&!! unset
23485 .cindex "mailbox" "specifying size of"
23486 .cindex "size" "of mailbox"
23487 If this option is set, it is expanded, and the result is taken as the current
23488 size the mailbox. It must be a decimal number, optionally followed by K or M.
23489 This provides a way of obtaining this information from an external source that
23490 maintains the data. This is likely to be helpful for maildir deliveries where
23491 it is computationally expensive to compute the size of a mailbox.
23495 .option maildir_format appendfile boolean false
23496 .cindex "maildir format" "specifying"
23497 If this option is set with the &%directory%& option, the delivery is into a new
23498 file, in the &"maildir"& format that is used by other mail software. When the
23499 transport is activated directly from a &(redirect)& router (for example, the
23500 &(address_file)& transport in the default configuration), setting
23501 &%maildir_format%& causes the path received from the router to be treated as a
23502 directory, whether or not it ends with &`/`&. This option is available only if
23503 SUPPORT_MAILDIR is present in &_Local/Makefile_&. See section
23504 &<<SECTmaildirdelivery>>& below for further details.
23507 .option maildir_quota_directory_regex appendfile string "See below"
23508 .cindex "maildir format" "quota; directories included in"
23509 .cindex "quota" "maildir; directories included in"
23510 This option is relevant only when &%maildir_use_size_file%& is set. It defines
23511 a regular expression for specifying directories, relative to the quota
23512 directory (see &%quota_directory%&), that should be included in the quota
23513 calculation. The default value is:
23515 maildir_quota_directory_regex = ^(?:cur|new|\..*)$
23517 This includes the &_cur_& and &_new_& directories, and any maildir++ folders
23518 (directories whose names begin with a dot). If you want to exclude the
23520 folder from the count (as some sites do), you need to change this setting to
23522 maildir_quota_directory_regex = ^(?:cur|new|\.(?!Trash).*)$
23524 This uses a negative lookahead in the regular expression to exclude the
23525 directory whose name is &_.Trash_&. When a directory is excluded from quota
23526 calculations, quota processing is bypassed for any messages that are delivered
23527 directly into that directory.
23530 .option maildir_retries appendfile integer 10
23531 This option specifies the number of times to retry when writing a file in
23532 &"maildir"& format. See section &<<SECTmaildirdelivery>>& below.
23535 .option maildir_tag appendfile string&!! unset
23536 This option applies only to deliveries in maildir format, and is described in
23537 section &<<SECTmaildirdelivery>>& below.
23540 .option maildir_use_size_file appendfile&!! boolean false
23541 .cindex "maildir format" "&_maildirsize_& file"
23542 The result of string expansion for this option must be a valid boolean value.
23543 If it is true, it enables support for &_maildirsize_& files. Exim
23544 creates a &_maildirsize_& file in a maildir if one does not exist, taking the
23545 quota from the &%quota%& option of the transport. If &%quota%& is unset, the
23546 value is zero. See &%maildir_quota_directory_regex%& above and section
23547 &<<SECTmaildirdelivery>>& below for further details.
23549 .option maildirfolder_create_regex appendfile string unset
23550 .cindex "maildir format" "&_maildirfolder_& file"
23551 .cindex "&_maildirfolder_&, creating"
23552 The value of this option is a regular expression. If it is unset, it has no
23553 effect. Otherwise, before a maildir delivery takes place, the pattern is
23554 matched against the name of the maildir directory, that is, the directory
23555 containing the &_new_& and &_tmp_& subdirectories that will be used for the
23556 delivery. If there is a match, Exim checks for the existence of a file called
23557 &_maildirfolder_& in the directory, and creates it if it does not exist.
23558 See section &<<SECTmaildirdelivery>>& for more details.
23561 .option mailstore_format appendfile boolean false
23562 .cindex "mailstore format" "specifying"
23563 If this option is set with the &%directory%& option, the delivery is into two
23564 new files in &"mailstore"& format. The option is available only if
23565 SUPPORT_MAILSTORE is present in &_Local/Makefile_&. See section &<<SECTopdir>>&
23566 below for further details.
23569 .option mailstore_prefix appendfile string&!! unset
23570 This option applies only to deliveries in mailstore format, and is described in
23571 section &<<SECTopdir>>& below.
23574 .option mailstore_suffix appendfile string&!! unset
23575 This option applies only to deliveries in mailstore format, and is described in
23576 section &<<SECTopdir>>& below.
23579 .option mbx_format appendfile boolean false
23580 .cindex "locking files"
23581 .cindex "file" "locking"
23582 .cindex "file" "MBX format"
23583 .cindex "MBX format, specifying"
23584 This option is available only if Exim has been compiled with SUPPORT_MBX
23585 set in &_Local/Makefile_&. If &%mbx_format%& is set with the &%file%& option,
23586 the message is appended to the mailbox file in MBX format instead of
23587 traditional Unix format. This format is supported by Pine4 and its associated
23588 IMAP and POP daemons, by means of the &'c-client'& library that they all use.
23590 &*Note*&: The &%message_prefix%& and &%message_suffix%& options are not
23591 automatically changed by the use of &%mbx_format%&. They should normally be set
23592 empty when using MBX format, so this option almost always appears in this
23599 If none of the locking options are mentioned in the configuration,
23600 &%use_mbx_lock%& is assumed and the other locking options default to false. It
23601 is possible to specify the other kinds of locking with &%mbx_format%&, but
23602 &%use_fcntl_lock%& and &%use_mbx_lock%& are mutually exclusive. MBX locking
23603 interworks with &'c-client'&, providing for shared access to the mailbox. It
23604 should not be used if any program that does not use this form of locking is
23605 going to access the mailbox, nor should it be used if the mailbox file is NFS
23606 mounted, because it works only when the mailbox is accessed from a single host.
23608 If you set &%use_fcntl_lock%& with an MBX-format mailbox, you cannot use
23609 the standard version of &'c-client'&, because as long as it has a mailbox open
23610 (this means for the whole of a Pine or IMAP session), Exim will not be able to
23611 append messages to it.
23614 .option message_prefix appendfile string&!! "see below"
23615 .cindex "&""From""& line"
23616 The string specified here is expanded and output at the start of every message.
23617 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
23618 in which case it is:
23620 message_prefix = "From ${if def:return_path{$return_path}\
23621 {MAILER-DAEMON}} $tod_bsdinbox\n"
23623 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
23624 &`\n`& to &`\r\n`& in &%message_prefix%&.
23626 .option message_suffix appendfile string&!! "see below"
23627 The string specified here is expanded and output at the end of every message.
23628 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
23629 in which case it is a single newline character. The suffix can be suppressed by
23634 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
23635 &`\n`& to &`\r\n`& in &%message_suffix%&.
23637 .option mode appendfile "octal integer" 0600
23638 If the output file is created, it is given this mode. If it already exists and
23639 has wider permissions, they are reduced to this mode. If it has narrower
23640 permissions, an error occurs unless &%mode_fail_narrower%& is false. However,
23641 if the delivery is the result of a &%save%& command in a filter file specifying
23642 a particular mode, the mode of the output file is always forced to take that
23643 value, and this option is ignored.
23646 .option mode_fail_narrower appendfile boolean true
23647 This option applies in the case when an existing mailbox file has a narrower
23648 mode than that specified by the &%mode%& option. If &%mode_fail_narrower%& is
23649 true, the delivery is deferred (&"mailbox has the wrong mode"&); otherwise Exim
23650 continues with the delivery attempt, using the existing mode of the file.
23653 .option notify_comsat appendfile boolean false
23654 If this option is true, the &'comsat'& daemon is notified after every
23655 successful delivery to a user mailbox. This is the daemon that notifies logged
23656 on users about incoming mail.
23659 .option quota appendfile string&!! unset
23660 .cindex "quota" "imposed by Exim"
23661 This option imposes a limit on the size of the file to which Exim is appending,
23662 or to the total space used in the directory tree when the &%directory%& option
23663 is set. In the latter case, computation of the space used is expensive, because
23664 all the files in the directory (and any sub-directories) have to be
23665 individually inspected and their sizes summed. (See &%quota_size_regex%& and
23666 &%maildir_use_size_file%& for ways to avoid this in environments where users
23667 have no shell access to their mailboxes).
23669 As there is no interlock against two simultaneous deliveries into a
23670 multi-file mailbox, it is possible for the quota to be overrun in this case.
23671 For single-file mailboxes, of course, an interlock is a necessity.
23673 A file's size is taken as its &'used'& value. Because of blocking effects, this
23674 may be a lot less than the actual amount of disk space allocated to the file.
23675 If the sizes of a number of files are being added up, the rounding effect can
23676 become quite noticeable, especially on systems that have large block sizes.
23677 Nevertheless, it seems best to stick to the &'used'& figure, because this is
23678 the obvious value which users understand most easily.
23680 The value of the option is expanded, and must then be a numerical value
23681 (decimal point allowed), optionally followed by one of the letters K, M, or G,
23682 for kilobytes, megabytes, or gigabytes, optionally followed by a slash
23683 and further option modifiers. If Exim is running on a system with
23684 large file support (Linux and FreeBSD have this), mailboxes larger than 2G can
23687 The option modifier &%no_check%& can be used to force delivery even if the over
23688 quota condition is met. The quota gets updated as usual.
23690 &*Note*&: A value of zero is interpreted as &"no quota"&.
23692 The expansion happens while Exim is running as root, before it changes uid for
23693 the delivery. This means that files that are inaccessible to the end user can
23694 be used to hold quota values that are looked up in the expansion. When delivery
23695 fails because this quota is exceeded, the handling of the error is as for
23696 system quota failures.
23698 By default, Exim's quota checking mimics system quotas, and restricts the
23699 mailbox to the specified maximum size, though the value is not accurate to the
23700 last byte, owing to separator lines and additional headers that may get added
23701 during message delivery. When a mailbox is nearly full, large messages may get
23702 refused even though small ones are accepted, because the size of the current
23703 message is added to the quota when the check is made. This behaviour can be
23704 changed by setting &%quota_is_inclusive%& false. When this is done, the check
23705 for exceeding the quota does not include the current message. Thus, deliveries
23706 continue until the quota has been exceeded; thereafter, no further messages are
23707 delivered. See also &%quota_warn_threshold%&.
23710 .option quota_directory appendfile string&!! unset
23711 This option defines the directory to check for quota purposes when delivering
23712 into individual files. The default is the delivery directory, or, if a file
23713 called &_maildirfolder_& exists in a maildir directory, the parent of the
23714 delivery directory.
23717 .option quota_filecount appendfile string&!! 0
23718 This option applies when the &%directory%& option is set. It limits the total
23719 number of files in the directory (compare the inode limit in system quotas). It
23720 can only be used if &%quota%& is also set. The value is expanded; an expansion
23721 failure causes delivery to be deferred. A value of zero is interpreted as
23724 The option modifier &%no_check%& can be used to force delivery even if the over
23725 quota condition is met. The quota gets updated as usual.
23727 .option quota_is_inclusive appendfile boolean true
23728 See &%quota%& above.
23731 .option quota_size_regex appendfile string unset
23732 This option applies when one of the delivery modes that writes a separate file
23733 for each message is being used. When Exim wants to find the size of one of
23734 these files in order to test the quota, it first checks &%quota_size_regex%&.
23735 If this is set to a regular expression that matches the filename, and it
23736 captures one string, that string is interpreted as a representation of the
23737 file's size. The value of &%quota_size_regex%& is not expanded.
23739 This feature is useful only when users have no shell access to their mailboxes
23740 &-- otherwise they could defeat the quota simply by renaming the files. This
23741 facility can be used with maildir deliveries, by setting &%maildir_tag%& to add
23742 the file length to the filename. For example:
23744 maildir_tag = ,S=$message_size
23745 quota_size_regex = ,S=(\d+)
23747 An alternative to &$message_size$& is &$message_linecount$&, which contains the
23748 number of lines in the message.
23750 The regular expression should not assume that the length is at the end of the
23751 filename (even though &%maildir_tag%& puts it there) because maildir MUAs
23752 sometimes add other information onto the ends of message filenames.
23754 Section &<<SECID136>>& contains further information.
23756 This option should not be used when other message-handling software
23757 may duplicate messages by making hardlinks to the files. When that is done Exim
23758 will count the message size once for each filename, in contrast with the actual
23759 disk usage. When the option is not set, calculating total usage requires
23760 a system-call per file to get the size; the number of links is then available also
23761 as is used to adjust the effective size.
23764 .option quota_warn_message appendfile string&!! "see below"
23765 See below for the use of this option. If it is not set when
23766 &%quota_warn_threshold%& is set, it defaults to
23768 quota_warn_message = "\
23769 To: $local_part@$domain\n\
23770 Subject: Your mailbox\n\n\
23771 This message is automatically created \
23772 by mail delivery software.\n\n\
23773 The size of your mailbox has exceeded \
23774 a warning threshold that is\n\
23775 set by the system administrator.\n"
23779 .option quota_warn_threshold appendfile string&!! 0
23780 .cindex "quota" "warning threshold"
23781 .cindex "mailbox" "size warning"
23782 .cindex "size" "of mailbox"
23783 This option is expanded in the same way as &%quota%& (see above). If the
23784 resulting value is greater than zero, and delivery of the message causes the
23785 size of the file or total space in the directory tree to cross the given
23786 threshold, a warning message is sent. If &%quota%& is also set, the threshold
23787 may be specified as a percentage of it by following the value with a percent
23791 quota_warn_threshold = 75%
23793 If &%quota%& is not set, a setting of &%quota_warn_threshold%& that ends with a
23794 percent sign is ignored.
23796 The warning message itself is specified by the &%quota_warn_message%& option,
23797 and it must start with a &'To:'& header line containing the recipient(s) of the
23798 warning message. These do not necessarily have to include the recipient(s) of
23799 the original message. A &'Subject:'& line should also normally be supplied. You
23800 can include any other header lines that you want. If you do not include a
23801 &'From:'& line, the default is:
23803 From: Mail Delivery System <mailer-daemon@$qualify_domain_sender>
23805 .oindex &%errors_reply_to%&
23806 If you supply a &'Reply-To:'& line, it overrides the global &%errors_reply_to%&
23809 The &%quota%& option does not have to be set in order to use this option; they
23810 are independent of one another except when the threshold is specified as a
23814 .option use_bsmtp appendfile boolean false
23815 .cindex "envelope from"
23816 .cindex "envelope sender"
23817 If this option is set true, &(appendfile)& writes messages in &"batch SMTP"&
23818 format, with the envelope sender and recipient(s) included as SMTP commands. If
23819 you want to include a leading HELO command with such messages, you can do
23820 so by setting the &%message_prefix%& option. See section &<<SECTbatchSMTP>>&
23821 for details of batch SMTP.
23824 .option use_crlf appendfile boolean false
23825 .cindex "carriage return"
23827 This option causes lines to be terminated with the two-character CRLF sequence
23828 (carriage return, linefeed) instead of just a linefeed character. In the case
23829 of batched SMTP, the byte sequence written to the file is then an exact image
23830 of what would be sent down a real SMTP connection.
23832 &*Note:*& The contents of the &%message_prefix%& and &%message_suffix%& options
23833 (which are used to supply the traditional &"From&~"& and blank line separators
23834 in Berkeley-style mailboxes) are written verbatim, so must contain their own
23835 carriage return characters if these are needed. In cases where these options
23836 have non-empty defaults, the values end with a single linefeed, so they must be
23837 changed to end with &`\r\n`& if &%use_crlf%& is set.
23840 .option use_fcntl_lock appendfile boolean "see below"
23841 This option controls the use of the &[fcntl()]& function to lock a file for
23842 exclusive use when a message is being appended. It is set by default unless
23843 &%use_flock_lock%& is set. Otherwise, it should be turned off only if you know
23844 that all your MUAs use lock file locking. When both &%use_fcntl_lock%& and
23845 &%use_flock_lock%& are unset, &%use_lockfile%& must be set.
23848 .option use_flock_lock appendfile boolean false
23849 This option is provided to support the use of &[flock()]& for file locking, for
23850 the few situations where it is needed. Most modern operating systems support
23851 &[fcntl()]& and &[lockf()]& locking, and these two functions interwork with
23852 each other. Exim uses &[fcntl()]& locking by default.
23854 This option is required only if you are using an operating system where
23855 &[flock()]& is used by programs that access mailboxes (typically MUAs), and
23856 where &[flock()]& does not correctly interwork with &[fcntl()]&. You can use
23857 both &[fcntl()]& and &[flock()]& locking simultaneously if you want.
23859 .cindex "Solaris" "&[flock()]& support"
23860 Not all operating systems provide &[flock()]&. Some versions of Solaris do not
23861 have it (and some, I think, provide a not quite right version built on top of
23862 &[lockf()]&). If the OS does not have &[flock()]&, Exim will be built without
23863 the ability to use it, and any attempt to do so will cause a configuration
23866 &*Warning*&: &[flock()]& locks do not work on NFS files (unless &[flock()]&
23867 is just being mapped onto &[fcntl()]& by the OS).
23870 .option use_lockfile appendfile boolean "see below"
23871 If this option is turned off, Exim does not attempt to create a lock file when
23872 appending to a mailbox file. In this situation, the only locking is by
23873 &[fcntl()]&. You should only turn &%use_lockfile%& off if you are absolutely
23874 sure that every MUA that is ever going to look at your users' mailboxes uses
23875 &[fcntl()]& rather than a lock file, and even then only when you are not
23876 delivering over NFS from more than one host.
23878 .cindex "NFS" "lock file"
23879 In order to append to an NFS file safely from more than one host, it is
23880 necessary to take out a lock &'before'& opening the file, and the lock file
23881 achieves this. Otherwise, even with &[fcntl()]& locking, there is a risk of
23884 The &%use_lockfile%& option is set by default unless &%use_mbx_lock%& is set.
23885 It is not possible to turn both &%use_lockfile%& and &%use_fcntl_lock%& off,
23886 except when &%mbx_format%& is set.
23889 .option use_mbx_lock appendfile boolean "see below"
23890 This option is available only if Exim has been compiled with SUPPORT_MBX
23891 set in &_Local/Makefile_&. Setting the option specifies that special MBX
23892 locking rules be used. It is set by default if &%mbx_format%& is set and none
23893 of the locking options are mentioned in the configuration. The locking rules
23894 are the same as are used by the &'c-client'& library that underlies Pine and
23895 the IMAP4 and POP daemons that come with it (see the discussion below). The
23896 rules allow for shared access to the mailbox. However, this kind of locking
23897 does not work when the mailbox is NFS mounted.
23899 You can set &%use_mbx_lock%& with either (or both) of &%use_fcntl_lock%& and
23900 &%use_flock_lock%& to control what kind of locking is used in implementing the
23901 MBX locking rules. The default is to use &[fcntl()]& if &%use_mbx_lock%& is set
23902 without &%use_fcntl_lock%& or &%use_flock_lock%&.
23907 .section "Operational details for appending" "SECTopappend"
23908 .cindex "appending to a file"
23909 .cindex "file" "appending"
23910 Before appending to a file, the following preparations are made:
23913 If the name of the file is &_/dev/null_&, no action is taken, and a success
23917 .cindex "directory creation"
23918 If any directories on the file's path are missing, Exim creates them if the
23919 &%create_directory%& option is set. A created directory's mode is given by the
23920 &%directory_mode%& option.
23923 If &%file_format%& is set, the format of an existing file is checked. If this
23924 indicates that a different transport should be used, control is passed to that
23928 .cindex "file" "locking"
23929 .cindex "locking files"
23930 .cindex "NFS" "lock file"
23931 If &%use_lockfile%& is set, a lock file is built in a way that will work
23932 reliably over NFS, as follows:
23935 Create a &"hitching post"& file whose name is that of the lock file with the
23936 current time, primary host name, and process id added, by opening for writing
23937 as a new file. If this fails with an access error, delivery is deferred.
23939 Close the hitching post file, and hard link it to the lock filename.
23941 If the call to &[link()]& succeeds, creation of the lock file has succeeded.
23942 Unlink the hitching post name.
23944 Otherwise, use &[stat()]& to get information about the hitching post file, and
23945 then unlink hitching post name. If the number of links is exactly two, creation
23946 of the lock file succeeded but something (for example, an NFS server crash and
23947 restart) caused this fact not to be communicated to the &[link()]& call.
23949 If creation of the lock file failed, wait for &%lock_interval%& and try again,
23950 up to &%lock_retries%& times. However, since any program that writes to a
23951 mailbox should complete its task very quickly, it is reasonable to time out old
23952 lock files that are normally the result of user agent and system crashes. If an
23953 existing lock file is older than &%lockfile_timeout%& Exim attempts to unlink
23954 it before trying again.
23958 A call is made to &[lstat()]& to discover whether the main file exists, and if
23959 so, what its characteristics are. If &[lstat()]& fails for any reason other
23960 than non-existence, delivery is deferred.
23963 .cindex "symbolic link" "to mailbox"
23964 .cindex "mailbox" "symbolic link"
23965 If the file does exist and is a symbolic link, delivery is deferred, unless the
23966 &%allow_symlink%& option is set, in which case the ownership of the link is
23967 checked, and then &[stat()]& is called to find out about the real file, which
23968 is then subjected to the checks below. The check on the top-level link
23969 ownership prevents one user creating a link for another's mailbox in a sticky
23970 directory, though allowing symbolic links in this case is definitely not a good
23971 idea. If there is a chain of symbolic links, the intermediate ones are not
23975 If the file already exists but is not a regular file, or if the file's owner
23976 and group (if the group is being checked &-- see &%check_group%& above) are
23977 different from the user and group under which the delivery is running,
23978 delivery is deferred.
23981 If the file's permissions are more generous than specified, they are reduced.
23982 If they are insufficient, delivery is deferred, unless &%mode_fail_narrower%&
23983 is set false, in which case the delivery is tried using the existing
23987 The file's inode number is saved, and the file is then opened for appending.
23988 If this fails because the file has vanished, &(appendfile)& behaves as if it
23989 hadn't existed (see below). For any other failures, delivery is deferred.
23992 If the file is opened successfully, check that the inode number hasn't
23993 changed, that it is still a regular file, and that the owner and permissions
23994 have not changed. If anything is wrong, defer delivery and freeze the message.
23997 If the file did not exist originally, defer delivery if the &%file_must_exist%&
23998 option is set. Otherwise, check that the file is being created in a permitted
23999 directory if the &%create_file%& option is set (deferring on failure), and then
24000 open for writing as a new file, with the O_EXCL and O_CREAT options,
24001 except when dealing with a symbolic link (the &%allow_symlink%& option must be
24002 set). In this case, which can happen if the link points to a non-existent file,
24003 the file is opened for writing using O_CREAT but not O_EXCL, because
24004 that prevents link following.
24007 .cindex "loop" "while file testing"
24008 If opening fails because the file exists, obey the tests given above for
24009 existing files. However, to avoid looping in a situation where the file is
24010 being continuously created and destroyed, the exists/not-exists loop is broken
24011 after 10 repetitions, and the message is then frozen.
24014 If opening fails with any other error, defer delivery.
24017 .cindex "file" "locking"
24018 .cindex "locking files"
24019 Once the file is open, unless both &%use_fcntl_lock%& and &%use_flock_lock%&
24020 are false, it is locked using &[fcntl()]& or &[flock()]& or both. If
24021 &%use_mbx_lock%& is false, an exclusive lock is requested in each case.
24022 However, if &%use_mbx_lock%& is true, Exim takes out a shared lock on the open
24023 file, and an exclusive lock on the file whose name is
24025 /tmp/.<device-number>.<inode-number>
24027 using the device and inode numbers of the open mailbox file, in accordance with
24028 the MBX locking rules. This file is created with a mode that is specified by
24029 the &%lockfile_mode%& option.
24031 If Exim fails to lock the file, there are two possible courses of action,
24032 depending on the value of the locking timeout. This is obtained from
24033 &%lock_fcntl_timeout%& or &%lock_flock_timeout%&, as appropriate.
24035 If the timeout value is zero, the file is closed, Exim waits for
24036 &%lock_interval%&, and then goes back and re-opens the file as above and tries
24037 to lock it again. This happens up to &%lock_retries%& times, after which the
24038 delivery is deferred.
24040 If the timeout has a value greater than zero, blocking calls to &[fcntl()]& or
24041 &[flock()]& are used (with the given timeout), so there has already been some
24042 waiting involved by the time locking fails. Nevertheless, Exim does not give up
24043 immediately. It retries up to
24045 (lock_retries * lock_interval) / <timeout>
24047 times (rounded up).
24050 At the end of delivery, Exim closes the file (which releases the &[fcntl()]&
24051 and/or &[flock()]& locks) and then deletes the lock file if one was created.
24054 .section "Operational details for delivery to a new file" "SECTopdir"
24055 .cindex "delivery" "to single file"
24056 .cindex "&""From""& line"
24057 When the &%directory%& option is set instead of &%file%&, each message is
24058 delivered into a newly-created file or set of files. When &(appendfile)& is
24059 activated directly from a &(redirect)& router, neither &%file%& nor
24060 &%directory%& is normally set, because the path for delivery is supplied by the
24061 router. (See for example, the &(address_file)& transport in the default
24062 configuration.) In this case, delivery is to a new file if either the path name
24063 ends in &`/`&, or the &%maildir_format%& or &%mailstore_format%& option is set.
24065 No locking is required while writing the message to a new file, so the various
24066 locking options of the transport are ignored. The &"From"& line that by default
24067 separates messages in a single file is not normally needed, nor is the escaping
24068 of message lines that start with &"From"&, and there is no need to ensure a
24069 newline at the end of each message. Consequently, the default values for
24070 &%check_string%&, &%message_prefix%&, and &%message_suffix%& are all unset when
24071 any of &%directory%&, &%maildir_format%&, or &%mailstore_format%& is set.
24073 If Exim is required to check a &%quota%& setting, it adds up the sizes of all
24074 the files in the delivery directory by default. However, you can specify a
24075 different directory by setting &%quota_directory%&. Also, for maildir
24076 deliveries (see below) the &_maildirfolder_& convention is honoured.
24079 .cindex "maildir format"
24080 .cindex "mailstore format"
24081 There are three different ways in which delivery to individual files can be
24082 done, controlled by the settings of the &%maildir_format%& and
24083 &%mailstore_format%& options. Note that code to support maildir or mailstore
24084 formats is not included in the binary unless SUPPORT_MAILDIR or
24085 SUPPORT_MAILSTORE, respectively, is set in &_Local/Makefile_&.
24087 .cindex "directory creation"
24088 In all three cases an attempt is made to create the directory and any necessary
24089 sub-directories if they do not exist, provided that the &%create_directory%&
24090 option is set (the default). The location of a created directory can be
24091 constrained by setting &%create_file%&. A created directory's mode is given by
24092 the &%directory_mode%& option. If creation fails, or if the
24093 &%create_directory%& option is not set when creation is required, delivery is
24098 .section "Maildir delivery" "SECTmaildirdelivery"
24099 .cindex "maildir format" "description of"
24100 If the &%maildir_format%& option is true, Exim delivers each message by writing
24101 it to a file whose name is &_tmp/<stime>.H<mtime>P<pid>.<host>_& in the
24102 directory that is defined by the &%directory%& option (the &"delivery
24103 directory"&). If the delivery is successful, the file is renamed into the
24104 &_new_& subdirectory.
24106 In the filename, <&'stime'&> is the current time of day in seconds, and
24107 <&'mtime'&> is the microsecond fraction of the time. After a maildir delivery,
24108 Exim checks that the time-of-day clock has moved on by at least one microsecond
24109 before terminating the delivery process. This guarantees uniqueness for the
24110 filename. However, as a precaution, Exim calls &[stat()]& for the file before
24111 opening it. If any response other than ENOENT (does not exist) is given,
24112 Exim waits 2 seconds and tries again, up to &%maildir_retries%& times.
24114 Before Exim carries out a maildir delivery, it ensures that subdirectories
24115 called &_new_&, &_cur_&, and &_tmp_& exist in the delivery directory. If they
24116 do not exist, Exim tries to create them and any superior directories in their
24117 path, subject to the &%create_directory%& and &%create_file%& options. If the
24118 &%maildirfolder_create_regex%& option is set, and the regular expression it
24119 contains matches the delivery directory, Exim also ensures that a file called
24120 &_maildirfolder_& exists in the delivery directory. If a missing directory or
24121 &_maildirfolder_& file cannot be created, delivery is deferred.
24123 These features make it possible to use Exim to create all the necessary files
24124 and directories in a maildir mailbox, including subdirectories for maildir++
24125 folders. Consider this example:
24127 maildir_format = true
24128 directory = /var/mail/$local_part_data\
24129 ${if eq{$local_part_suffix}{}{}\
24130 {/.${substr_1:$local_part_suffix}}}
24131 maildirfolder_create_regex = /\.[^/]+$
24133 If &$local_part_suffix$& is empty (there was no suffix for the local part),
24134 delivery is into a toplevel maildir with a name like &_/var/mail/pimbo_& (for
24135 the user called &'pimbo'&). The pattern in &%maildirfolder_create_regex%& does
24136 not match this name, so Exim will not look for or create the file
24137 &_/var/mail/pimbo/maildirfolder_&, though it will create
24138 &_/var/mail/pimbo/{cur,new,tmp}_& if necessary.
24140 However, if &$local_part_suffix$& contains &`-eximusers`& (for example),
24141 delivery is into the maildir++ folder &_/var/mail/pimbo/.eximusers_&, which
24142 does match &%maildirfolder_create_regex%&. In this case, Exim will create
24143 &_/var/mail/pimbo/.eximusers/maildirfolder_& as well as the three maildir
24144 directories &_/var/mail/pimbo/.eximusers/{cur,new,tmp}_&.
24146 &*Warning:*& Take care when setting &%maildirfolder_create_regex%& that it does
24147 not inadvertently match the toplevel maildir directory, because a
24148 &_maildirfolder_& file at top level would completely break quota calculations.
24150 .cindex "quota" "in maildir delivery"
24151 .cindex "maildir++"
24152 If Exim is required to check a &%quota%& setting before a maildir delivery, and
24153 &%quota_directory%& is not set, it looks for a file called &_maildirfolder_& in
24154 the maildir directory (alongside &_new_&, &_cur_&, &_tmp_&). If this exists,
24155 Exim assumes the directory is a maildir++ folder directory, which is one level
24156 down from the user's top level mailbox directory. This causes it to start at
24157 the parent directory instead of the current directory when calculating the
24158 amount of space used.
24160 One problem with delivering into a multi-file mailbox is that it is
24161 computationally expensive to compute the size of the mailbox for quota
24162 checking. Various approaches have been taken to reduce the amount of work
24163 needed. The next two sections describe two of them. A third alternative is to
24164 use some external process for maintaining the size data, and use the expansion
24165 of the &%mailbox_size%& option as a way of importing it into Exim.
24170 .section "Using tags to record message sizes" "SECID135"
24171 If &%maildir_tag%& is set, the string is expanded for each delivery.
24172 When the maildir file is renamed into the &_new_& sub-directory, the
24173 tag is added to its name. However, if adding the tag takes the length of the
24174 name to the point where the test &[stat()]& call fails with ENAMETOOLONG,
24175 the tag is dropped and the maildir file is created with no tag.
24178 .vindex "&$message_size$&"
24179 Tags can be used to encode the size of files in their names; see
24180 &%quota_size_regex%& above for an example. The expansion of &%maildir_tag%&
24181 happens after the message has been written. The value of the &$message_size$&
24182 variable is set to the number of bytes actually written. If the expansion is
24183 forced to fail, the tag is ignored, but a non-forced failure causes delivery to
24184 be deferred. The expanded tag may contain any printing characters except &"/"&.
24185 Non-printing characters in the string are ignored; if the resulting string is
24186 empty, it is ignored. If it starts with an alphanumeric character, a leading
24187 colon is inserted; this default has not proven to be the path that popular
24188 maildir implementations have chosen (but changing it in Exim would break
24189 backwards compatibility).
24191 For one common implementation, you might set:
24193 maildir_tag = ,S=${message_size}
24195 but you should check the documentation of the other software to be sure.
24197 It is advisable to also set &%quota_size_regex%& when setting &%maildir_tag%&
24198 as this allows Exim to extract the size from your tag, instead of having to
24199 &[stat()]& each message file.
24202 .section "Using a maildirsize file" "SECID136"
24203 .cindex "quota" "in maildir delivery"
24204 .cindex "maildir format" "&_maildirsize_& file"
24205 If &%maildir_use_size_file%& is true, Exim implements the maildir++ rules for
24206 storing quota and message size information in a file called &_maildirsize_&
24207 within the toplevel maildir directory. If this file does not exist, Exim
24208 creates it, setting the quota from the &%quota%& option of the transport. If
24209 the maildir directory itself does not exist, it is created before any attempt
24210 to write a &_maildirsize_& file.
24212 The &_maildirsize_& file is used to hold information about the sizes of
24213 messages in the maildir, thus speeding up quota calculations. The quota value
24214 in the file is just a cache; if the quota is changed in the transport, the new
24215 value overrides the cached value when the next message is delivered. The cache
24216 is maintained for the benefit of other programs that access the maildir and
24217 need to know the quota.
24219 If the &%quota%& option in the transport is unset or zero, the &_maildirsize_&
24220 file is maintained (with a zero quota setting), but no quota is imposed.
24222 A regular expression is available for controlling which directories in the
24223 maildir participate in quota calculations when a &_maildirsizefile_& is in use.
24224 See the description of the &%maildir_quota_directory_regex%& option above for
24228 .section "Mailstore delivery" "SECID137"
24229 .cindex "mailstore format" "description of"
24230 If the &%mailstore_format%& option is true, each message is written as two
24231 files in the given directory. A unique base name is constructed from the
24232 message id and the current delivery process, and the files that are written use
24233 this base name plus the suffixes &_.env_& and &_.msg_&. The &_.env_& file
24234 contains the message's envelope, and the &_.msg_& file contains the message
24235 itself. The base name is placed in the variable &$mailstore_basename$&.
24237 During delivery, the envelope is first written to a file with the suffix
24238 &_.tmp_&. The &_.msg_& file is then written, and when it is complete, the
24239 &_.tmp_& file is renamed as the &_.env_& file. Programs that access messages in
24240 mailstore format should wait for the presence of both a &_.msg_& and a &_.env_&
24241 file before accessing either of them. An alternative approach is to wait for
24242 the absence of a &_.tmp_& file.
24244 The envelope file starts with any text defined by the &%mailstore_prefix%&
24245 option, expanded and terminated by a newline if there isn't one. Then follows
24246 the sender address on one line, then all the recipient addresses, one per line.
24247 There can be more than one recipient only if the &%batch_max%& option is set
24248 greater than one. Finally, &%mailstore_suffix%& is expanded and the result
24249 appended to the file, followed by a newline if it does not end with one.
24251 If expansion of &%mailstore_prefix%& or &%mailstore_suffix%& ends with a forced
24252 failure, it is ignored. Other expansion errors are treated as serious
24253 configuration errors, and delivery is deferred. The variable
24254 &$mailstore_basename$& is available for use during these expansions.
24257 .section "Non-special new file delivery" "SECID138"
24258 If neither &%maildir_format%& nor &%mailstore_format%& is set, a single new
24259 file is created directly in the named directory. For example, when delivering
24260 messages into files in batched SMTP format for later delivery to some host (see
24261 section &<<SECTbatchSMTP>>&), a setting such as
24263 directory = /var/bsmtp/$host
24265 might be used. A message is written to a file with a temporary name, which is
24266 then renamed when the delivery is complete. The final name is obtained by
24267 expanding the contents of the &%directory_file%& option.
24268 .ecindex IIDapptra1
24269 .ecindex IIDapptra2
24276 . ////////////////////////////////////////////////////////////////////////////
24277 . ////////////////////////////////////////////////////////////////////////////
24279 .chapter "The autoreply transport" "CHID8"
24280 .scindex IIDauttra1 "transports" "&(autoreply)&"
24281 .scindex IIDauttra2 "&(autoreply)& transport"
24282 The &(autoreply)& transport is not a true transport in that it does not cause
24283 the message to be transmitted. Instead, it generates a new mail message as an
24284 automatic reply to the incoming message. &'References:'& and
24285 &'Auto-Submitted:'& header lines are included. These are constructed according
24286 to the rules in RFCs 2822 and 3834, respectively.
24288 If the router that passes the message to this transport does not have the
24289 &%unseen%& option set, the original message (for the current recipient) is not
24290 delivered anywhere. However, when the &%unseen%& option is set on the router
24291 that passes the message to this transport, routing of the address continues, so
24292 another router can set up a normal message delivery.
24295 The &(autoreply)& transport is usually run as the result of mail filtering, a
24296 &"vacation"& message being the standard example. However, it can also be run
24297 directly from a router like any other transport. To reduce the possibility of
24298 message cascades, messages created by the &(autoreply)& transport always have
24299 empty envelope sender addresses, like bounce messages.
24301 The parameters of the message to be sent can be specified in the configuration
24302 by options described below. However, these are used only when the address
24303 passed to the transport does not contain its own reply information. When the
24304 transport is run as a consequence of a
24306 or &%vacation%& command in a filter file, the parameters of the message are
24307 supplied by the filter, and passed with the address. The transport's options
24308 that define the message are then ignored (so they are not usually set in this
24309 case). The message is specified entirely by the filter or by the transport; it
24310 is never built from a mixture of options. However, the &%file_optional%&,
24311 &%mode%&, and &%return_message%& options apply in all cases.
24313 &(Autoreply)& is implemented as a local transport. When used as a result of a
24314 command in a user's filter file, &(autoreply)& normally runs under the uid and
24315 gid of the user, and with appropriate current and home directories (see chapter
24316 &<<CHAPenvironment>>&).
24318 There is a subtle difference between routing a message to a &(pipe)& transport
24319 that generates some text to be returned to the sender, and routing it to an
24320 &(autoreply)& transport. This difference is noticeable only if more than one
24321 address from the same message is so handled. In the case of a pipe, the
24322 separate outputs from the different addresses are gathered up and returned to
24323 the sender in a single message, whereas if &(autoreply)& is used, a separate
24324 message is generated for each address that is passed to it.
24326 Non-printing characters are not permitted in the header lines generated for the
24327 message that &(autoreply)& creates, with the exception of newlines that are
24328 immediately followed by white space. If any non-printing characters are found,
24329 the transport defers.
24330 Whether characters with the top bit set count as printing characters or not is
24331 controlled by the &%print_topbitchars%& global option.
24333 If any of the generic options for manipulating headers (for example,
24334 &%headers_add%&) are set on an &(autoreply)& transport, they apply to the copy
24335 of the original message that is included in the generated message when
24336 &%return_message%& is set. They do not apply to the generated message itself.
24338 .vindex "&$sender_address$&"
24339 If the &(autoreply)& transport receives return code 2 from Exim when it submits
24340 the message, indicating that there were no recipients, it does not treat this
24341 as an error. This means that autoreplies sent to &$sender_address$& when this
24342 is empty (because the incoming message is a bounce message) do not cause
24343 problems. They are just discarded.
24347 .section "Private options for autoreply" "SECID139"
24348 .cindex "options" "&(autoreply)& transport"
24350 .option bcc autoreply string&!! unset
24351 This specifies the addresses that are to receive &"blind carbon copies"& of the
24352 message when the message is specified by the transport.
24355 .option cc autoreply string&!! unset
24356 This specifies recipients of the message and the contents of the &'Cc:'& header
24357 when the message is specified by the transport.
24360 .option file autoreply string&!! unset
24361 The contents of the file are sent as the body of the message when the message
24362 is specified by the transport. If both &%file%& and &%text%& are set, the text
24363 string comes first.
24366 .option file_expand autoreply boolean false
24367 If this is set, the contents of the file named by the &%file%& option are
24368 subjected to string expansion as they are added to the message.
24371 .option file_optional autoreply boolean false
24372 If this option is true, no error is generated if the file named by the &%file%&
24373 option or passed with the address does not exist or cannot be read.
24376 .option from autoreply string&!! unset
24377 This specifies the contents of the &'From:'& header when the message is
24378 specified by the transport.
24381 .option headers autoreply string&!! unset
24382 This specifies additional RFC 2822 headers that are to be added to the message
24383 when the message is specified by the transport. Several can be given by using
24384 &"\n"& to separate them. There is no check on the format.
24387 .option log autoreply string&!! unset
24388 This option names a file in which a record of every message sent is logged when
24389 the message is specified by the transport.
24392 .option mode autoreply "octal integer" 0600
24393 If either the log file or the &"once"& file has to be created, this mode is
24397 .option never_mail autoreply "address list&!!" unset
24398 If any run of the transport creates a message with a recipient that matches any
24399 item in the list, that recipient is quietly discarded. If all recipients are
24400 discarded, no message is created. This applies both when the recipients are
24401 generated by a filter and when they are specified in the transport.
24405 .option once autoreply string&!! unset
24406 This option names a file or DBM database in which a record of each &'To:'&
24407 recipient is kept when the message is specified by the transport. &*Note*&:
24408 This does not apply to &'Cc:'& or &'Bcc:'& recipients.
24410 If &%once%& is unset, or is set to an empty string, the message is always sent.
24411 By default, if &%once%& is set to a non-empty filename, the message
24412 is not sent if a potential recipient is already listed in the database.
24413 However, if the &%once_repeat%& option specifies a time greater than zero, the
24414 message is sent if that much time has elapsed since a message was last sent to
24415 this recipient. A setting of zero time for &%once_repeat%& (the default)
24416 prevents a message from being sent a second time &-- in this case, zero means
24419 If &%once_file_size%& is zero, a DBM database is used to remember recipients,
24420 and it is allowed to grow as large as necessary. If &%once_file_size%& is set
24421 greater than zero, it changes the way Exim implements the &%once%& option.
24422 Instead of using a DBM file to record every recipient it sends to, it uses a
24423 regular file, whose size will never get larger than the given value.
24425 In the file, Exim keeps a linear list of recipient addresses and the times at
24426 which they were sent messages. If the file is full when a new address needs to
24427 be added, the oldest address is dropped. If &%once_repeat%& is not set, this
24428 means that a given recipient may receive multiple messages, but at
24429 unpredictable intervals that depend on the rate of turnover of addresses in the
24430 file. If &%once_repeat%& is set, it specifies a maximum time between repeats.
24433 .option once_file_size autoreply integer 0
24434 See &%once%& above.
24437 .option once_repeat autoreply time&!! 0s
24438 See &%once%& above.
24439 After expansion, the value of this option must be a valid time value.
24442 .option reply_to autoreply string&!! unset
24443 This specifies the contents of the &'Reply-To:'& header when the message is
24444 specified by the transport.
24447 .option return_message autoreply boolean false
24448 If this is set, a copy of the original message is returned with the new
24449 message, subject to the maximum size set in the &%return_size_limit%& global
24450 configuration option.
24453 .option subject autoreply string&!! unset
24454 This specifies the contents of the &'Subject:'& header when the message is
24455 specified by the transport. It is tempting to quote the original subject in
24456 automatic responses. For example:
24458 subject = Re: $h_subject:
24460 There is a danger in doing this, however. It may allow a third party to
24461 subscribe your users to an opt-in mailing list, provided that the list accepts
24462 bounce messages as subscription confirmations. Well-managed lists require a
24463 non-bounce message to confirm a subscription, so the danger is relatively
24468 .option text autoreply string&!! unset
24469 This specifies a single string to be used as the body of the message when the
24470 message is specified by the transport. If both &%text%& and &%file%& are set,
24471 the text comes first.
24474 .option to autoreply string&!! unset
24475 This specifies recipients of the message and the contents of the &'To:'& header
24476 when the message is specified by the transport.
24477 .ecindex IIDauttra1
24478 .ecindex IIDauttra2
24483 . ////////////////////////////////////////////////////////////////////////////
24484 . ////////////////////////////////////////////////////////////////////////////
24486 .chapter "The lmtp transport" "CHAPLMTP"
24487 .cindex "transports" "&(lmtp)&"
24488 .cindex "&(lmtp)& transport"
24489 .cindex "LMTP" "over a pipe"
24490 .cindex "LMTP" "over a socket"
24491 The &(lmtp)& transport runs the LMTP protocol (RFC 2033) over a pipe to a
24493 or by interacting with a Unix domain socket.
24494 This transport is something of a cross between the &(pipe)& and &(smtp)&
24495 transports. Exim also has support for using LMTP over TCP/IP; this is
24496 implemented as an option for the &(smtp)& transport. Because LMTP is expected
24497 to be of minority interest, the default build-time configure in &_src/EDITME_&
24498 has it commented out. You need to ensure that
24502 .cindex "options" "&(lmtp)& transport"
24503 is present in your &_Local/Makefile_& in order to have the &(lmtp)& transport
24504 included in the Exim binary. The private options of the &(lmtp)& transport are
24507 .option batch_id lmtp string&!! unset
24508 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
24511 .option batch_max lmtp integer 1
24512 This limits the number of addresses that can be handled in a single delivery.
24513 Most LMTP servers can handle several addresses at once, so it is normally a
24514 good idea to increase this value. See the description of local delivery
24515 batching in chapter &<<CHAPbatching>>&.
24518 .option command lmtp string&!! unset
24519 This option must be set if &%socket%& is not set. The string is a command which
24520 is run in a separate process. It is split up into a command name and list of
24521 arguments, each of which is separately expanded (so expansion cannot change the
24522 number of arguments). The command is run directly, not via a shell. The message
24523 is passed to the new process using the standard input and output to operate the
24526 .option ignore_quota lmtp boolean false
24527 .cindex "LMTP" "ignoring quota errors"
24528 If this option is set true, the string &`IGNOREQUOTA`& is added to RCPT
24529 commands, provided that the LMTP server has advertised support for IGNOREQUOTA
24530 in its response to the LHLO command.
24532 .option socket lmtp string&!! unset
24533 This option must be set if &%command%& is not set. The result of expansion must
24534 be the name of a Unix domain socket. The transport connects to the socket and
24535 delivers the message to it using the LMTP protocol.
24538 .option timeout lmtp time 5m
24539 The transport is aborted if the created process or Unix domain socket does not
24540 respond to LMTP commands or message input within this timeout. Delivery
24541 is deferred, and will be tried again later. Here is an example of a typical
24546 command = /some/local/lmtp/delivery/program
24550 This delivers up to 20 addresses at a time, in a mixture of domains if
24551 necessary, running as the user &'exim'&.
24555 . ////////////////////////////////////////////////////////////////////////////
24556 . ////////////////////////////////////////////////////////////////////////////
24558 .chapter "The pipe transport" "CHAPpipetransport"
24559 .scindex IIDpiptra1 "transports" "&(pipe)&"
24560 .scindex IIDpiptra2 "&(pipe)& transport"
24561 The &(pipe)& transport is used to deliver messages via a pipe to a command
24562 running in another process. One example is the use of &(pipe)& as a
24563 pseudo-remote transport for passing messages to some other delivery mechanism
24564 (such as UUCP). Another is the use by individual users to automatically process
24565 their incoming messages. The &(pipe)& transport can be used in one of the
24569 .vindex "&$local_part$&"
24570 A router routes one address to a transport in the normal way, and the
24571 transport is configured as a &(pipe)& transport. In this case, &$local_part$&
24572 contains the local part of the address (as usual), and the command that is run
24573 is specified by the &%command%& option on the transport.
24575 .vindex "&$pipe_addresses$&"
24576 If the &%batch_max%& option is set greater than 1 (the default is 1), the
24577 transport can handle more than one address in a single run. In this case, when
24578 more than one address is routed to the transport, &$local_part$& is not set
24579 (because it is not unique). However, the pseudo-variable &$pipe_addresses$&
24580 (described in section &<<SECThowcommandrun>>& below) contains all the addresses
24581 that are routed to the transport.
24583 .vindex "&$address_pipe$&"
24584 A router redirects an address directly to a pipe command (for example, from an
24585 alias or forward file). In this case, &$address_pipe$& contains the text of the
24586 pipe command, and the &%command%& option on the transport is ignored unless
24587 &%force_command%& is set. If only one address is being transported
24588 (&%batch_max%& is not greater than one, or only one address was redirected to
24589 this pipe command), &$local_part$& contains the local part that was redirected.
24593 The &(pipe)& transport is a non-interactive delivery method. Exim can also
24594 deliver messages over pipes using the LMTP interactive protocol. This is
24595 implemented by the &(lmtp)& transport.
24597 In the case when &(pipe)& is run as a consequence of an entry in a local user's
24598 &_.forward_& file, the command runs under the uid and gid of that user. In
24599 other cases, the uid and gid have to be specified explicitly, either on the
24600 transport or on the router that handles the address. Current and &"home"&
24601 directories are also controllable. See chapter &<<CHAPenvironment>>& for
24602 details of the local delivery environment and chapter &<<CHAPbatching>>&
24603 for a discussion of local delivery batching.
24605 .cindex "tainted data" "in pipe command"
24606 .cindex pipe "tainted data"
24607 Tainted data may not be used for the command name.
24610 .section "Concurrent delivery" "SECID140"
24611 If two messages arrive at almost the same time, and both are routed to a pipe
24612 delivery, the two pipe transports may be run concurrently. You must ensure that
24613 any pipe commands you set up are robust against this happening. If the commands
24614 write to a file, the &%exim_lock%& utility might be of use.
24615 Alternatively the &%max_parallel%& option could be used with a value
24616 of "1" to enforce serialization.
24621 .section "Returned status and data" "SECID141"
24622 .cindex "&(pipe)& transport" "returned data"
24623 If the command exits with a non-zero return code, the delivery is deemed to
24624 have failed, unless either the &%ignore_status%& option is set (in which case
24625 the return code is treated as zero), or the return code is one of those listed
24626 in the &%temp_errors%& option, which are interpreted as meaning &"try again
24627 later"&. In this case, delivery is deferred. Details of a permanent failure are
24628 logged, but are not included in the bounce message, which merely contains
24629 &"local delivery failed"&.
24631 If the command exits on a signal and the &%freeze_signal%& option is set then
24632 the message will be frozen in the queue. If that option is not set, a bounce
24633 will be sent as normal.
24635 If the return code is greater than 128 and the command being run is a shell
24636 script, it normally means that the script was terminated by a signal whose
24637 value is the return code minus 128. The &%freeze_signal%& option does not
24638 apply in this case.
24640 If Exim is unable to run the command (that is, if &[execve()]& fails), the
24641 return code is set to 127. This is the value that a shell returns if it is
24642 asked to run a non-existent command. The wording for the log line suggests that
24643 a non-existent command may be the problem.
24645 The &%return_output%& option can affect the result of a pipe delivery. If it is
24646 set and the command produces any output on its standard output or standard
24647 error streams, the command is considered to have failed, even if it gave a zero
24648 return code or if &%ignore_status%& is set. The output from the command is
24649 included as part of the bounce message. The &%return_fail_output%& option is
24650 similar, except that output is returned only when the command exits with a
24651 failure return code, that is, a value other than zero or a code that matches
24656 .section "How the command is run" "SECThowcommandrun"
24657 .cindex "&(pipe)& transport" "path for command"
24658 The command line is (by default) broken down into a command name and arguments
24659 by the &(pipe)& transport itself. The &%allow_commands%& and
24660 &%restrict_to_path%& options can be used to restrict the commands that may be
24663 .cindex "quoting" "in pipe command"
24664 Unquoted arguments are delimited by white space. If an argument appears in
24665 double quotes, backslash is interpreted as an escape character in the usual
24666 way. If an argument appears in single quotes, no escaping is done.
24668 String expansion is applied to the command line except when it comes from a
24669 traditional &_.forward_& file (commands from a filter file are expanded). The
24670 expansion is applied to each argument in turn rather than to the whole line.
24671 For this reason, any string expansion item that contains white space must be
24672 quoted so as to be contained within a single argument. A setting such as
24674 command = /some/path ${if eq{$local_part}{postmaster}{xx}{yy}}
24676 will not work, because the expansion item gets split between several
24677 arguments. You have to write
24679 command = /some/path "${if eq{$local_part}{postmaster}{xx}{yy}}"
24681 to ensure that it is all in one argument. The expansion is done in this way,
24682 argument by argument, so that the number of arguments cannot be changed as a
24683 result of expansion, and quotes or backslashes in inserted variables do not
24684 interact with external quoting. However, this leads to problems if you want to
24685 generate multiple arguments (or the command name plus arguments) from a single
24686 expansion. In this situation, the simplest solution is to use a shell. For
24689 command = /bin/sh -c ${lookup{$local_part}lsearch{/some/file}}
24692 .cindex "transport" "filter"
24693 .cindex "filter" "transport filter"
24694 .vindex "&$pipe_addresses$&"
24695 Special handling takes place when an argument consists of precisely the text
24696 &`$pipe_addresses`& (no quotes).
24697 This is not a general expansion variable; the only
24698 place this string is recognized is when it appears as an argument for a pipe or
24699 transport filter command. It causes each address that is being handled to be
24700 inserted in the argument list at that point &'as a separate argument'&. This
24701 avoids any problems with spaces or shell metacharacters, and is of use when a
24702 &(pipe)& transport is handling groups of addresses in a batch.
24704 If &%force_command%& is enabled on the transport, special handling takes place
24705 for an argument that consists of precisely the text &`$address_pipe`&. It
24706 is handled similarly to &$pipe_addresses$& above. It is expanded and each
24707 argument is inserted in the argument list at that point
24708 &'as a separate argument'&. The &`$address_pipe`& item does not need to be
24709 the only item in the argument; in fact, if it were then &%force_command%&
24710 should behave as a no-op. Rather, it should be used to adjust the command
24711 run while preserving the argument vector separation.
24713 After splitting up into arguments and expansion, the resulting command is run
24714 in a subprocess directly from the transport, &'not'& under a shell. The
24715 message that is being delivered is supplied on the standard input, and the
24716 standard output and standard error are both connected to a single pipe that is
24717 read by Exim. The &%max_output%& option controls how much output the command
24718 may produce, and the &%return_output%& and &%return_fail_output%& options
24719 control what is done with it.
24721 Not running the command under a shell (by default) lessens the security risks
24722 in cases when a command from a user's filter file is built out of data that was
24723 taken from an incoming message. If a shell is required, it can of course be
24724 explicitly specified as the command to be run. However, there are circumstances
24725 where existing commands (for example, in &_.forward_& files) expect to be run
24726 under a shell and cannot easily be modified. To allow for these cases, there is
24727 an option called &%use_shell%&, which changes the way the &(pipe)& transport
24728 works. Instead of breaking up the command line as just described, it expands it
24729 as a single string and passes the result to &_/bin/sh_&. The
24730 &%restrict_to_path%& option and the &$pipe_addresses$& facility cannot be used
24731 with &%use_shell%&, and the whole mechanism is inherently less secure.
24735 .section "Environment variables" "SECTpipeenv"
24736 .cindex "&(pipe)& transport" "environment for command"
24737 .cindex "environment" "&(pipe)& transport"
24738 The environment variables listed below are set up when the command is invoked.
24739 This list is a compromise for maximum compatibility with other MTAs. Note that
24740 the &%environment%& option can be used to add additional variables to this
24741 environment. The environment for the &(pipe)& transport is not subject
24742 to the &%add_environment%& and &%keep_environment%& main config options.
24744 &*Note*&: Using enviroment variables loses track of tainted data.
24745 Writers of &(pipe)& transport commands should be wary of data supplied
24746 by potential attackers.
24749 &`DOMAIN `& the domain of the address
24750 &`HOME `& the home directory, if set
24751 &`HOST `& the host name when called from a router (see below)
24752 &`LOCAL_PART `& see below
24753 &`LOCAL_PART_PREFIX `& see below
24754 &`LOCAL_PART_SUFFIX `& see below
24755 &`LOGNAME `& see below
24756 &`MESSAGE_ID `& Exim's local ID for the message
24757 &`PATH `& as specified by the &%path%& option below
24758 &`QUALIFY_DOMAIN `& the sender qualification domain
24759 &`RECIPIENT `& the complete recipient address
24760 &`SENDER `& the sender of the message (empty if a bounce)
24761 &`SHELL `& &`/bin/sh`&
24762 &`TZ `& the value of the &%timezone%& option, if set
24763 &`USER `& see below
24765 When a &(pipe)& transport is called directly from (for example) an &(accept)&
24766 router, LOCAL_PART is set to the local part of the address. When it is
24767 called as a result of a forward or alias expansion, LOCAL_PART is set to
24768 the local part of the address that was expanded. In both cases, any affixes are
24769 removed from the local part, and made available in LOCAL_PART_PREFIX and
24770 LOCAL_PART_SUFFIX, respectively. LOGNAME and USER are set to the
24771 same value as LOCAL_PART for compatibility with other MTAs.
24774 HOST is set only when a &(pipe)& transport is called from a router that
24775 associates hosts with an address, typically when using &(pipe)& as a
24776 pseudo-remote transport. HOST is set to the first host name specified by
24780 If the transport's generic &%home_directory%& option is set, its value is used
24781 for the HOME environment variable. Otherwise, a home directory may be set
24782 by the router's &%transport_home_directory%& option, which defaults to the
24783 user's home directory if &%check_local_user%& is set.
24786 .section "Private options for pipe" "SECID142"
24787 .cindex "options" "&(pipe)& transport"
24791 .option allow_commands pipe "string list&!!" unset
24792 .cindex "&(pipe)& transport" "permitted commands"
24793 The string is expanded, and is then interpreted as a colon-separated list of
24794 permitted commands. If &%restrict_to_path%& is not set, the only commands
24795 permitted are those in the &%allow_commands%& list. They need not be absolute
24796 paths; the &%path%& option is still used for relative paths. If
24797 &%restrict_to_path%& is set with &%allow_commands%&, the command must either be
24798 in the &%allow_commands%& list, or a name without any slashes that is found on
24799 the path. In other words, if neither &%allow_commands%& nor
24800 &%restrict_to_path%& is set, there is no restriction on the command, but
24801 otherwise only commands that are permitted by one or the other are allowed. For
24804 allow_commands = /usr/bin/vacation
24806 and &%restrict_to_path%& is not set, the only permitted command is
24807 &_/usr/bin/vacation_&. The &%allow_commands%& option may not be set if
24808 &%use_shell%& is set.
24811 .option batch_id pipe string&!! unset
24812 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
24815 .option batch_max pipe integer 1
24816 This limits the number of addresses that can be handled in a single delivery.
24817 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
24820 .option check_string pipe string unset
24821 As &(pipe)& writes the message, the start of each line is tested for matching
24822 &%check_string%&, and if it does, the initial matching characters are replaced
24823 by the contents of &%escape_string%&, provided both are set. The value of
24824 &%check_string%& is a literal string, not a regular expression, and the case of
24825 any letters it contains is significant. When &%use_bsmtp%& is set, the contents
24826 of &%check_string%& and &%escape_string%& are forced to values that implement
24827 the SMTP escaping protocol. Any settings made in the configuration file are
24831 .option command pipe string&!! unset
24832 This option need not be set when &(pipe)& is being used to deliver to pipes
24833 obtained directly from address redirections. In other cases, the option must be
24834 set, to provide a command to be run. It need not yield an absolute path (see
24835 the &%path%& option below). The command is split up into separate arguments by
24836 Exim, and each argument is separately expanded, as described in section
24837 &<<SECThowcommandrun>>& above.
24840 .cindex "tainted data"
24841 No part of the resulting command may be tainted.
24845 .option environment pipe string&!! unset
24846 .cindex "&(pipe)& transport" "environment for command"
24847 .cindex "environment" "&(pipe)& transport"
24848 This option is used to add additional variables to the environment in which the
24849 command runs (see section &<<SECTpipeenv>>& for the default list). Its value is
24850 a string which is expanded, and then interpreted as a colon-separated list of
24851 environment settings of the form <&'name'&>=<&'value'&>.
24854 .option escape_string pipe string unset
24855 See &%check_string%& above.
24858 .option freeze_exec_fail pipe boolean false
24859 .cindex "exec failure"
24860 .cindex "failure of exec"
24861 .cindex "&(pipe)& transport" "failure of exec"
24862 Failure to exec the command in a pipe transport is by default treated like
24863 any other failure while running the command. However, if &%freeze_exec_fail%&
24864 is set, failure to exec is treated specially, and causes the message to be
24865 frozen, whatever the setting of &%ignore_status%&.
24868 .option freeze_signal pipe boolean false
24869 .cindex "signal exit"
24870 .cindex "&(pipe)& transport", "signal exit"
24871 Normally if the process run by a command in a pipe transport exits on a signal,
24872 a bounce message is sent. If &%freeze_signal%& is set, the message will be
24873 frozen in Exim's queue instead.
24876 .option force_command pipe boolean false
24877 .cindex "force command"
24878 .cindex "&(pipe)& transport", "force command"
24879 Normally when a router redirects an address directly to a pipe command
24880 the &%command%& option on the transport is ignored. If &%force_command%&
24881 is set, the &%command%& option will used. This is especially
24882 useful for forcing a wrapper or additional argument to be added to the
24883 command. For example:
24885 command = /usr/bin/remote_exec myhost -- $address_pipe
24889 Note that &$address_pipe$& is handled specially in &%command%& when
24890 &%force_command%& is set, expanding out to the original argument vector as
24891 separate items, similarly to a Unix shell &`"$@"`& construct.
24894 .option ignore_status pipe boolean false
24895 If this option is true, the status returned by the subprocess that is set up to
24896 run the command is ignored, and Exim behaves as if zero had been returned.
24897 Otherwise, a non-zero status or termination by signal causes an error return
24898 from the transport unless the status value is one of those listed in
24899 &%temp_errors%&; these cause the delivery to be deferred and tried again later.
24901 &*Note*&: This option does not apply to timeouts, which do not return a status.
24902 See the &%timeout_defer%& option for how timeouts are handled.
24905 .option log_defer_output pipe boolean false
24906 .cindex "&(pipe)& transport" "logging output"
24907 If this option is set, and the status returned by the command is
24908 one of the codes listed in &%temp_errors%& (that is, delivery was deferred),
24909 and any output was produced on stdout or stderr, the first line of it is
24910 written to the main log.
24913 .option log_fail_output pipe boolean false
24914 If this option is set, and the command returns any output on stdout or
24915 stderr, and also ends with a return code that is neither zero nor one of
24916 the return codes listed in &%temp_errors%& (that is, the delivery
24917 failed), the first line of output is written to the main log. This
24918 option and &%log_output%& are mutually exclusive. Only one of them may
24922 .option log_output pipe boolean false
24923 If this option is set and the command returns any output on stdout or
24924 stderr, the first line of output is written to the main log, whatever
24925 the return code. This option and &%log_fail_output%& are mutually
24926 exclusive. Only one of them may be set.
24929 .option max_output pipe integer 20K
24930 This specifies the maximum amount of output that the command may produce on its
24931 standard output and standard error file combined. If the limit is exceeded, the
24932 process running the command is killed. This is intended as a safety measure to
24933 catch runaway processes. The limit is applied independently of the settings of
24934 the options that control what is done with such output (for example,
24935 &%return_output%&). Because of buffering effects, the amount of output may
24936 exceed the limit by a small amount before Exim notices.
24939 .option message_prefix pipe string&!! "see below"
24940 The string specified here is expanded and output at the start of every message.
24941 The default is unset if &%use_bsmtp%& is set. Otherwise it is
24944 From ${if def:return_path{$return_path}{MAILER-DAEMON}}\
24948 .cindex "&%tmail%&"
24949 .cindex "&""From""& line"
24950 This is required by the commonly used &_/usr/bin/vacation_& program.
24951 However, it must &'not'& be present if delivery is to the Cyrus IMAP server,
24952 or to the &%tmail%& local delivery agent. The prefix can be suppressed by
24957 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
24958 &`\n`& to &`\r\n`& in &%message_prefix%&.
24961 .option message_suffix pipe string&!! "see below"
24962 The string specified here is expanded and output at the end of every message.
24963 The default is unset if &%use_bsmtp%& is set. Otherwise it is a single newline.
24964 The suffix can be suppressed by setting
24968 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
24969 &`\n`& to &`\r\n`& in &%message_suffix%&.
24972 .option path pipe string&!! "/bin:/usr/bin"
24973 This option is expanded and
24974 specifies the string that is set up in the PATH environment
24975 variable of the subprocess.
24976 If the &%command%& option does not yield an absolute path name, the command is
24977 sought in the PATH directories, in the usual way. &*Warning*&: This does not
24978 apply to a command specified as a transport filter.
24981 .option permit_coredump pipe boolean false
24982 Normally Exim inhibits core-dumps during delivery. If you have a need to get
24983 a core-dump of a pipe command, enable this command. This enables core-dumps
24984 during delivery and affects both the Exim binary and the pipe command run.
24985 It is recommended that this option remain off unless and until you have a need
24986 for it and that this only be enabled when needed, as the risk of excessive
24987 resource consumption can be quite high. Note also that Exim is typically
24988 installed as a setuid binary and most operating systems will inhibit coredumps
24989 of these by default, so further OS-specific action may be required.
24992 .option pipe_as_creator pipe boolean false
24993 .cindex "uid (user id)" "local delivery"
24994 If the generic &%user%& option is not set and this option is true, the delivery
24995 process is run under the uid that was in force when Exim was originally called
24996 to accept the message. If the group id is not otherwise set (via the generic
24997 &%group%& option), the gid that was in force when Exim was originally called to
24998 accept the message is used.
25001 .option restrict_to_path pipe boolean false
25002 When this option is set, any command name not listed in &%allow_commands%& must
25003 contain no slashes. The command is searched for only in the directories listed
25004 in the &%path%& option. This option is intended for use in the case when a pipe
25005 command has been generated from a user's &_.forward_& file. This is usually
25006 handled by a &(pipe)& transport called &%address_pipe%&.
25009 .option return_fail_output pipe boolean false
25010 If this option is true, and the command produced any output and ended with a
25011 return code other than zero or one of the codes listed in &%temp_errors%& (that
25012 is, the delivery failed), the output is returned in the bounce message.
25013 However, if the message has a null sender (that is, it is itself a bounce
25014 message), output from the command is discarded. This option and
25015 &%return_output%& are mutually exclusive. Only one of them may be set.
25019 .option return_output pipe boolean false
25020 If this option is true, and the command produced any output, the delivery is
25021 deemed to have failed whatever the return code from the command, and the output
25022 is returned in the bounce message. Otherwise, the output is just discarded.
25023 However, if the message has a null sender (that is, it is a bounce message),
25024 output from the command is always discarded, whatever the setting of this
25025 option. This option and &%return_fail_output%& are mutually exclusive. Only one
25026 of them may be set.
25030 .option temp_errors pipe "string list" "see below"
25031 .cindex "&(pipe)& transport" "temporary failure"
25032 This option contains either a colon-separated list of numbers, or a single
25033 asterisk. If &%ignore_status%& is false
25034 and &%return_output%& is not set,
25035 and the command exits with a non-zero return code, the failure is treated as
25036 temporary and the delivery is deferred if the return code matches one of the
25037 numbers, or if the setting is a single asterisk. Otherwise, non-zero return
25038 codes are treated as permanent errors. The default setting contains the codes
25039 defined by EX_TEMPFAIL and EX_CANTCREAT in &_sysexits.h_&. If Exim is
25040 compiled on a system that does not define these macros, it assumes values of 75
25041 and 73, respectively.
25044 .option timeout pipe time 1h
25045 If the command fails to complete within this time, it is killed. This normally
25046 causes the delivery to fail (but see &%timeout_defer%&). A zero time interval
25047 specifies no timeout. In order to ensure that any subprocesses created by the
25048 command are also killed, Exim makes the initial process a process group leader,
25049 and kills the whole process group on a timeout. However, this can be defeated
25050 if one of the processes starts a new process group.
25052 .option timeout_defer pipe boolean false
25053 A timeout in a &(pipe)& transport, either in the command that the transport
25054 runs, or in a transport filter that is associated with it, is by default
25055 treated as a hard error, and the delivery fails. However, if &%timeout_defer%&
25056 is set true, both kinds of timeout become temporary errors, causing the
25057 delivery to be deferred.
25059 .option umask pipe "octal integer" 022
25060 This specifies the umask setting for the subprocess that runs the command.
25063 .option use_bsmtp pipe boolean false
25064 .cindex "envelope sender"
25065 If this option is set true, the &(pipe)& transport writes messages in &"batch
25066 SMTP"& format, with the envelope sender and recipient(s) included as SMTP
25067 commands. If you want to include a leading HELO command with such messages,
25068 you can do so by setting the &%message_prefix%& option. See section
25069 &<<SECTbatchSMTP>>& for details of batch SMTP.
25071 .option use_classresources pipe boolean false
25072 .cindex "class resources (BSD)"
25073 This option is available only when Exim is running on FreeBSD, NetBSD, or
25074 BSD/OS. If it is set true, the &[setclassresources()]& function is used to set
25075 resource limits when a &(pipe)& transport is run to perform a delivery. The
25076 limits for the uid under which the pipe is to run are obtained from the login
25080 .option use_crlf pipe boolean false
25081 .cindex "carriage return"
25083 This option causes lines to be terminated with the two-character CRLF sequence
25084 (carriage return, linefeed) instead of just a linefeed character. In the case
25085 of batched SMTP, the byte sequence written to the pipe is then an exact image
25086 of what would be sent down a real SMTP connection.
25088 The contents of the &%message_prefix%& and &%message_suffix%& options are
25089 written verbatim, so must contain their own carriage return characters if these
25090 are needed. When &%use_bsmtp%& is not set, the default values for both
25091 &%message_prefix%& and &%message_suffix%& end with a single linefeed, so their
25092 values must be changed to end with &`\r\n`& if &%use_crlf%& is set.
25095 .option use_shell pipe boolean false
25096 .vindex "&$pipe_addresses$&"
25097 If this option is set, it causes the command to be passed to &_/bin/sh_&
25098 instead of being run directly from the transport, as described in section
25099 &<<SECThowcommandrun>>&. This is less secure, but is needed in some situations
25100 where the command is expected to be run under a shell and cannot easily be
25101 modified. The &%allow_commands%& and &%restrict_to_path%& options, and the
25102 &`$pipe_addresses`& facility are incompatible with &%use_shell%&. The
25103 command is expanded as a single string, and handed to &_/bin/sh_& as data for
25108 .section "Using an external local delivery agent" "SECID143"
25109 .cindex "local delivery" "using an external agent"
25110 .cindex "&'procmail'&"
25111 .cindex "external local delivery"
25112 .cindex "delivery" "&'procmail'&"
25113 .cindex "delivery" "by external agent"
25114 The &(pipe)& transport can be used to pass all messages that require local
25115 delivery to a separate local delivery agent such as &%procmail%&. When doing
25116 this, care must be taken to ensure that the pipe is run under an appropriate
25117 uid and gid. In some configurations one wants this to be a uid that is trusted
25118 by the delivery agent to supply the correct sender of the message. It may be
25119 necessary to recompile or reconfigure the delivery agent so that it trusts an
25120 appropriate user. The following is an example transport and router
25121 configuration for &%procmail%&:
25126 command = /usr/local/bin/procmail -d $local_part_data
25130 check_string = "From "
25131 escape_string = ">From "
25133 user = $local_part_data
25140 transport = procmail_pipe
25142 In this example, the pipe is run as the local user, but with the group set to
25143 &'mail'&. An alternative is to run the pipe as a specific user such as &'mail'&
25144 or &'exim'&, but in this case you must arrange for &%procmail%& to trust that
25145 user to supply a correct sender address. If you do not specify either a
25146 &%group%& or a &%user%& option, the pipe command is run as the local user. The
25147 home directory is the user's home directory by default.
25149 &*Note*&: The command that the pipe transport runs does &'not'& begin with
25153 as shown in some &%procmail%& documentation, because Exim does not by default
25154 use a shell to run pipe commands.
25157 The next example shows a transport and a router for a system where local
25158 deliveries are handled by the Cyrus IMAP server.
25159 . Used to have R: local_part_suffix = .* + T: -m $local_part_suffix_v
25160 . but that suffix is tainted so cannot be used in a command arg
25161 . Really, you'd want to use a lookup for acceptable suffixes to do real detainting
25164 local_delivery_cyrus:
25166 command = /usr/cyrus/bin/deliver \
25167 -- $local_part_data
25179 transport = local_delivery_cyrus
25181 Note the unsetting of &%message_prefix%& and &%message_suffix%&, and the use of
25182 &%return_output%& to cause any text written by Cyrus to be returned to the
25184 .ecindex IIDpiptra1
25185 .ecindex IIDpiptra2
25188 . ////////////////////////////////////////////////////////////////////////////
25189 . ////////////////////////////////////////////////////////////////////////////
25191 .chapter "The smtp transport" "CHAPsmtptrans"
25192 .scindex IIDsmttra1 "transports" "&(smtp)&"
25193 .scindex IIDsmttra2 "&(smtp)& transport"
25194 The &(smtp)& transport delivers messages over TCP/IP connections using the SMTP
25195 or LMTP protocol. The list of hosts to try can either be taken from the address
25196 that is being processed (having been set up by the router), or specified
25197 explicitly for the transport. Timeout and retry processing (see chapter
25198 &<<CHAPretry>>&) is applied to each IP address independently.
25201 .section "Multiple messages on a single connection" "SECID144"
25202 The sending of multiple messages over a single TCP/IP connection can arise in
25206 If a message contains more than &%max_rcpt%& (see below) addresses that are
25207 routed to the same host, more than one copy of the message has to be sent to
25208 that host. In this situation, multiple copies may be sent in a single run of
25209 the &(smtp)& transport over a single TCP/IP connection. (What Exim actually
25210 does when it has too many addresses to send in one message also depends on the
25211 value of the global &%remote_max_parallel%& option. Details are given in
25212 section &<<SECToutSMTPTCP>>&.)
25214 .cindex "hints database" "remembering routing"
25215 When a message has been successfully delivered over a TCP/IP connection, Exim
25216 looks in its hints database to see if there are any other messages awaiting a
25217 connection to the same host. If there are, a new delivery process is started
25218 for one of them, and the current TCP/IP connection is passed on to it. The new
25219 process may in turn send multiple copies and possibly create yet another
25224 For each copy sent over the same TCP/IP connection, a sequence counter is
25225 incremented, and if it ever gets to the value of &%connection_max_messages%&,
25226 no further messages are sent over that connection.
25230 .section "Use of the $host and $host_address variables" "SECID145"
25232 .vindex "&$host_address$&"
25233 At the start of a run of the &(smtp)& transport, the values of &$host$& and
25234 &$host_address$& are the name and IP address of the first host on the host list
25235 passed by the router. However, when the transport is about to connect to a
25236 specific host, and while it is connected to that host, &$host$& and
25237 &$host_address$& are set to the values for that host. These are the values
25238 that are in force when the &%helo_data%&, &%hosts_try_auth%&, &%interface%&,
25239 &%serialize_hosts%&, and the various TLS options are expanded.
25242 .section "Use of $tls_cipher and $tls_peerdn" "usecippeer"
25243 .vindex &$tls_bits$&
25244 .vindex &$tls_cipher$&
25245 .vindex &$tls_peerdn$&
25246 .vindex &$tls_sni$&
25247 At the start of a run of the &(smtp)& transport, the values of &$tls_bits$&,
25248 &$tls_cipher$&, &$tls_peerdn$& and &$tls_sni$&
25249 are the values that were set when the message was received.
25250 These are the values that are used for options that are expanded before any
25251 SMTP connections are made. Just before each connection is made, these four
25252 variables are emptied. If TLS is subsequently started, they are set to the
25253 appropriate values for the outgoing connection, and these are the values that
25254 are in force when any authenticators are run and when the
25255 &%authenticated_sender%& option is expanded.
25257 These variables are deprecated in favour of &$tls_in_cipher$& et. al.
25258 and will be removed in a future release.
25261 .section "Private options for smtp" "SECID146"
25262 .cindex "options" "&(smtp)& transport"
25263 The private options of the &(smtp)& transport are as follows:
25266 .option address_retry_include_sender smtp boolean true
25267 .cindex "4&'xx'& responses" "retrying after"
25268 When an address is delayed because of a 4&'xx'& response to a RCPT command, it
25269 is the combination of sender and recipient that is delayed in subsequent queue
25270 runs until the retry time is reached. You can delay the recipient without
25271 reference to the sender (which is what earlier versions of Exim did), by
25272 setting &%address_retry_include_sender%& false. However, this can lead to
25273 problems with servers that regularly issue 4&'xx'& responses to RCPT commands.
25275 .option allow_localhost smtp boolean false
25276 .cindex "local host" "sending to"
25277 .cindex "fallback" "hosts specified on transport"
25278 When a host specified in &%hosts%& or &%fallback_hosts%& (see below) turns out
25279 to be the local host, or is listed in &%hosts_treat_as_local%&, delivery is
25280 deferred by default. However, if &%allow_localhost%& is set, Exim goes on to do
25281 the delivery anyway. This should be used only in special cases when the
25282 configuration ensures that no looping will result (for example, a differently
25283 configured Exim is listening on the port to which the message is sent).
25286 .option authenticated_sender smtp string&!! unset
25288 When Exim has authenticated as a client, or if &%authenticated_sender_force%&
25289 is true, this option sets a value for the AUTH= item on outgoing MAIL commands,
25290 overriding any existing authenticated sender value. If the string expansion is
25291 forced to fail, the option is ignored. Other expansion failures cause delivery
25292 to be deferred. If the result of expansion is an empty string, that is also
25295 The expansion happens after the outgoing connection has been made and TLS
25296 started, if required. This means that the &$host$&, &$host_address$&,
25297 &$tls_out_cipher$&, and &$tls_out_peerdn$& variables are set according to the
25298 particular connection.
25300 If the SMTP session is not authenticated, the expansion of
25301 &%authenticated_sender%& still happens (and can cause the delivery to be
25302 deferred if it fails), but no AUTH= item is added to MAIL commands
25303 unless &%authenticated_sender_force%& is true.
25305 This option allows you to use the &(smtp)& transport in LMTP mode to
25306 deliver mail to Cyrus IMAP and provide the proper local part as the
25307 &"authenticated sender"&, via a setting such as:
25309 authenticated_sender = $local_part
25311 This removes the need for IMAP subfolders to be assigned special ACLs to
25312 allow direct delivery to those subfolders.
25314 Because of expected uses such as that just described for Cyrus (when no
25315 domain is involved), there is no checking on the syntax of the provided
25319 .option authenticated_sender_force smtp boolean false
25320 If this option is set true, the &%authenticated_sender%& option's value
25321 is used for the AUTH= item on outgoing MAIL commands, even if Exim has not
25322 authenticated as a client.
25325 .option command_timeout smtp time 5m
25326 .cindex timeout "smtp transport command"
25327 This sets a timeout for receiving a response to an SMTP command that has been
25328 sent out. It is also used when waiting for the initial banner line from the
25329 remote host. Its value must not be zero.
25332 .option connect_timeout smtp time 5m
25333 .cindex timeout "smtp transport connect"
25334 This sets a timeout for the &[connect()]& function, which sets up a TCP/IP call
25335 to a remote host. A setting of zero allows the system timeout (typically
25336 several minutes) to act. To have any effect, the value of this option must be
25337 less than the system timeout. However, it has been observed that on some
25338 systems there is no system timeout, which is why the default value for this
25339 option is 5 minutes, a value recommended by RFC 1123.
25342 .option connection_max_messages smtp integer 500
25343 .cindex "SMTP" "passed connection"
25344 .cindex "SMTP" "multiple deliveries"
25345 .cindex "multiple SMTP deliveries"
25346 This controls the maximum number of separate message deliveries that are sent
25347 over a single TCP/IP connection. If the value is zero, there is no limit.
25348 For testing purposes, this value can be overridden by the &%-oB%& command line
25352 .option dane_require_tls_ciphers smtp string&!! unset
25353 .cindex "TLS" "requiring specific ciphers for DANE"
25354 .cindex "cipher" "requiring specific"
25355 .cindex DANE "TLS ciphers"
25356 This option may be used to override &%tls_require_ciphers%& for connections
25357 where DANE has been determined to be in effect.
25358 If not set, then &%tls_require_ciphers%& will be used.
25359 Normal SMTP delivery is not able to make strong demands of TLS cipher
25360 configuration, because delivery will fall back to plaintext. Once DANE has
25361 been determined to be in effect, there is no plaintext fallback and making the
25362 TLS cipherlist configuration stronger will increase security, rather than
25363 counter-intuitively decreasing it.
25364 If the option expands to be empty or is forced to fail, then it will
25365 be treated as unset and &%tls_require_ciphers%& will be used instead.
25368 .option data_timeout smtp time 5m
25369 .cindex timeout "for transmitted SMTP data blocks"
25370 This sets a timeout for the transmission of each block in the data portion of
25371 the message. As a result, the overall timeout for a message depends on the size
25372 of the message. Its value must not be zero. See also &%final_timeout%&.
25375 .option dkim_canon smtp string&!! unset
25376 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25377 .option dkim_domain smtp "string list&!!" unset
25378 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25379 .option dkim_hash smtp string&!! sha256
25380 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25381 .option dkim_identity smtp string&!! unset
25382 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25383 .option dkim_private_key smtp string&!! unset
25384 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25385 .option dkim_selector smtp string&!! unset
25386 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25387 .option dkim_strict smtp string&!! unset
25388 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25389 .option dkim_sign_headers smtp string&!! "per RFC"
25390 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25391 .option dkim_timestamps smtp string&!! unset
25392 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25395 .option delay_after_cutoff smtp boolean true
25396 .cindex "final cutoff" "retries, controlling"
25397 .cindex retry "final cutoff"
25398 This option controls what happens when all remote IP addresses for a given
25399 domain have been inaccessible for so long that they have passed their retry
25402 In the default state, if the next retry time has not been reached for any of
25403 them, the address is bounced without trying any deliveries. In other words,
25404 Exim delays retrying an IP address after the final cutoff time until a new
25405 retry time is reached, and can therefore bounce an address without ever trying
25406 a delivery, when machines have been down for a long time. Some people are
25407 unhappy at this prospect, so...
25409 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
25410 addresses are past their final cutoff time, Exim tries to deliver to those
25411 IP addresses that have not been tried since the message arrived. If there are
25412 none, of if they all fail, the address is bounced. In other words, it does not
25413 delay when a new message arrives, but immediately tries those expired IP
25414 addresses that haven't been tried since the message arrived. If there is a
25415 continuous stream of messages for the dead hosts, unsetting
25416 &%delay_after_cutoff%& means that there will be many more attempts to deliver
25420 .option dns_qualify_single smtp boolean true
25421 If the &%hosts%& or &%fallback_hosts%& option is being used,
25422 and the &%gethostbyname%& option is false,
25423 the RES_DEFNAMES resolver option is set. See the &%qualify_single%& option
25424 in chapter &<<CHAPdnslookup>>& for more details.
25427 .option dns_search_parents smtp boolean false
25428 If the &%hosts%& or &%fallback_hosts%& option is being used, and the
25429 &%gethostbyname%& option is false, the RES_DNSRCH resolver option is set.
25430 See the &%search_parents%& option in chapter &<<CHAPdnslookup>>& for more
25434 .option dnssec_request_domains smtp "domain list&!!" *
25435 .cindex "MX record" "security"
25436 .cindex "DNSSEC" "MX lookup"
25437 .cindex "security" "MX lookup"
25438 .cindex "DNS" "DNSSEC"
25439 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
25440 the DNSSEC request bit set. Setting this transport option is only useful if the
25441 transport overrides or sets the host names. See the &%dnssec_request_domains%&
25446 .option dnssec_require_domains smtp "domain list&!!" unset
25447 .cindex "MX record" "security"
25448 .cindex "DNSSEC" "MX lookup"
25449 .cindex "security" "MX lookup"
25450 .cindex "DNS" "DNSSEC"
25451 DNS lookups for domains matching &%dnssec_require_domains%& will be done with
25452 the DNSSEC request bit set. Setting this transport option is only
25453 useful if the transport overrides or sets the host names. See the
25454 &%dnssec_require_domains%& router option.
25458 .option dscp smtp string&!! unset
25459 .cindex "DCSP" "outbound"
25460 This option causes the DSCP value associated with a socket to be set to one
25461 of a number of fixed strings or to numeric value.
25462 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
25463 Common values include &`throughput`&, &`mincost`&, and on newer systems
25464 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
25466 The outbound packets from Exim will be marked with this value in the header
25467 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
25468 that these values will have any effect, not be stripped by networking
25469 equipment, or do much of anything without cooperation with your Network
25470 Engineer and those of all network operators between the source and destination.
25473 .option fallback_hosts smtp "string list" unset
25474 .cindex "fallback" "hosts specified on transport"
25475 String expansion is not applied to this option. The argument must be a
25476 colon-separated list of host names or IP addresses, optionally also including
25477 port numbers, though the separator can be changed, as described in section
25478 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
25479 item in a &%route_list%& setting for the &(manualroute)& router, as described
25480 in section &<<SECTformatonehostitem>>&.
25482 Fallback hosts can also be specified on routers, which associate them with the
25483 addresses they process. As for the &%hosts%& option without &%hosts_override%&,
25484 &%fallback_hosts%& specified on the transport is used only if the address does
25485 not have its own associated fallback host list. Unlike &%hosts%&, a setting of
25486 &%fallback_hosts%& on an address is not overridden by &%hosts_override%&.
25487 However, &%hosts_randomize%& does apply to fallback host lists.
25489 If Exim is unable to deliver to any of the hosts for a particular address, and
25490 the errors are not permanent rejections, the address is put on a separate
25491 transport queue with its host list replaced by the fallback hosts, unless the
25492 address was routed via MX records and the current host was in the original MX
25493 list. In that situation, the fallback host list is not used.
25495 Once normal deliveries are complete, the fallback queue is delivered by
25496 re-running the same transports with the new host lists. If several failing
25497 addresses have the same fallback hosts (and &%max_rcpt%& permits it), a single
25498 copy of the message is sent.
25500 The resolution of the host names on the fallback list is controlled by the
25501 &%gethostbyname%& option, as for the &%hosts%& option. Fallback hosts apply
25502 both to cases when the host list comes with the address and when it is taken
25503 from &%hosts%&. This option provides a &"use a smart host only if delivery
25507 .option final_timeout smtp time 10m
25508 .cindex timeout "for transmitted SMTP data accept"
25509 This is the timeout that applies while waiting for the response to the final
25510 line containing just &"."& that terminates a message. Its value must not be
25513 .option gethostbyname smtp boolean false
25514 If this option is true when the &%hosts%& and/or &%fallback_hosts%& options are
25515 being used, names are looked up using &[gethostbyname()]&
25516 (or &[getipnodebyname()]& when available)
25517 instead of using the DNS. Of course, that function may in fact use the DNS, but
25518 it may also consult other sources of information such as &_/etc/hosts_&.
25520 .option gnutls_compat_mode smtp boolean unset
25521 This option controls whether GnuTLS is used in compatibility mode in an Exim
25522 server. This reduces security slightly, but improves interworking with older
25523 implementations of TLS.
25525 .option helo_data smtp string&!! "see below"
25526 .cindex "HELO" "argument, setting"
25527 .cindex "EHLO" "argument, setting"
25528 .cindex "LHLO argument setting"
25529 The value of this option is expanded after a connection to a another host has
25530 been set up. The result is used as the argument for the EHLO, HELO, or LHLO
25531 command that starts the outgoing SMTP or LMTP session. The default value of the
25536 During the expansion, the variables &$host$& and &$host_address$& are set to
25537 the identity of the remote host, and the variables &$sending_ip_address$& and
25538 &$sending_port$& are set to the local IP address and port number that are being
25539 used. These variables can be used to generate different values for different
25540 servers or different local IP addresses. For example, if you want the string
25541 that is used for &%helo_data%& to be obtained by a DNS lookup of the outgoing
25542 interface address, you could use this:
25544 helo_data = ${lookup dnsdb{ptr=$sending_ip_address} \
25545 {${listextract{1}{<\n $value}}} \
25546 {$primary_hostname}}
25548 The use of &%helo_data%& applies both to sending messages and when doing
25552 .option host_name_extract smtp "string list&!!" "see below"
25553 .cindex "load balancer" "hosts behind"
25554 .cindex TLS resumption
25555 Some mail-accepting sites
25556 (notably Microsoft)
25557 operate many servers behind a network load-balancer. When this is done,
25558 with separated TLS session caches, TLS session resuption becomes problematic.
25559 It will only succeed when the same server happens to be selected by the
25560 load-balancer, matching the session stored in the client's cache.
25562 Exim can pull out a server name, if there is one, from the response to the
25563 client's SMTP EHLO command.
25564 The default value of this option:
25566 ${if and { {match {$host} {.outlook.com\$}} \
25567 {match {$item} {\N^250-([\w.]+)\s\N}} \
25570 suffices for one known case.
25571 During the expansion of this option the &$item$& variable will have the
25572 server's EHLO response.
25573 The result of the option expansion is included in the key used to store and
25574 retrieve the TLS session, for session resumption.
25576 Operators of high-load sites may wish to evaluate their logs for indications
25577 of other destination sites operating load-balancers, and develop a suitable
25578 expression for this option.
25579 The smtp:ehlo event and the &$tls_out_resumption$& variable
25580 will be useful for such work.
25583 .option hosts smtp "string list&!!" unset
25584 Hosts are associated with an address by a router such as &(dnslookup)&, which
25585 finds the hosts by looking up the address domain in the DNS, or by
25586 &(manualroute)&, which has lists of hosts in its configuration. However,
25587 email addresses can be passed to the &(smtp)& transport by any router, and not
25588 all of them can provide an associated list of hosts.
25590 The &%hosts%& option specifies a list of hosts to be used if the address being
25591 processed does not have any hosts associated with it. The hosts specified by
25592 &%hosts%& are also used, whether or not the address has its own hosts, if
25593 &%hosts_override%& is set.
25595 The string is first expanded, before being interpreted as a colon-separated
25596 list of host names or IP addresses, possibly including port numbers. The
25597 separator may be changed to something other than colon, as described in section
25598 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
25599 item in a &%route_list%& setting for the &(manualroute)& router, as described
25600 in section &<<SECTformatonehostitem>>&. However, note that the &`/MX`& facility
25601 of the &(manualroute)& router is not available here.
25603 If the expansion fails, delivery is deferred. Unless the failure was caused by
25604 the inability to complete a lookup, the error is logged to the panic log as
25605 well as the main log. Host names are looked up either by searching directly for
25606 address records in the DNS or by calling &[gethostbyname()]& (or
25607 &[getipnodebyname()]& when available), depending on the setting of the
25608 &%gethostbyname%& option. When Exim is compiled with IPv6 support, if a host
25609 that is looked up in the DNS has both IPv4 and IPv6 addresses, both types of
25612 During delivery, the hosts are tried in order, subject to their retry status,
25613 unless &%hosts_randomize%& is set.
25616 .option hosts_avoid_esmtp smtp "host list&!!" unset
25617 .cindex "ESMTP, avoiding use of"
25618 .cindex "HELO" "forcing use of"
25619 .cindex "EHLO" "avoiding use of"
25620 .cindex "PIPELINING" "avoiding the use of"
25621 This option is for use with broken hosts that announce ESMTP facilities (for
25622 example, PIPELINING) and then fail to implement them properly. When a host
25623 matches &%hosts_avoid_esmtp%&, Exim sends HELO rather than EHLO at the
25624 start of the SMTP session. This means that it cannot use any of the ESMTP
25625 facilities such as AUTH, PIPELINING, SIZE, and STARTTLS.
25628 .option hosts_avoid_pipelining smtp "host list&!!" unset
25629 .cindex "PIPELINING" "avoiding the use of"
25630 .cindex "ESMTP extensions" PIPELINING
25631 Exim will not use the ESMTP PIPELINING extension when delivering to any host
25632 that matches this list, even if the server host advertises PIPELINING support.
25634 .option hosts_pipe_connect smtp "host list&!!" unset
25635 .cindex "pipelining" "early connection"
25636 .cindex "pipelining" PIPE_CONNECT
25637 If Exim is built with the SUPPORT_PIPE_CONNECT build option
25638 this option controls which to hosts the facility watched for
25639 and recorded, and used for subsequent connections.
25641 The retry hints database is used for the record,
25642 and records are subject to the &%retry_data_expire%& option.
25643 When used, the pipelining saves on roundtrip times.
25644 It also turns SMTP into a client-first protocol
25645 so combines well with TCP Fast Open.
25647 See also the &%pipelining_connect_advertise_hosts%& main option.
25651 When the facility is used, if the transport &%interface%& option is unset
25652 the &%helo_data%& option
25654 will be expanded before the &$sending_ip_address$& variable
25656 A check is made for the use of that variable, without the
25657 presence of a &"def:"& test on it, but suitably complex coding
25658 can avoid the check and produce unexpected results.
25659 You have been warned.
25662 .option hosts_avoid_tls smtp "host list&!!" unset
25663 .cindex "TLS" "avoiding for certain hosts"
25664 Exim will not try to start a TLS session when delivering to any host that
25665 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
25667 .option hosts_verify_avoid_tls smtp "host list&!!" unset
25668 .cindex "TLS" "avoiding for certain hosts"
25669 Exim will not try to start a TLS session for a verify callout,
25670 or when delivering in cutthrough mode,
25671 to any host that matches this list.
25674 .option hosts_max_try smtp integer 5
25675 .cindex "host" "maximum number to try"
25676 .cindex "limit" "number of hosts tried"
25677 .cindex "limit" "number of MX tried"
25678 .cindex "MX record" "maximum tried"
25679 This option limits the number of IP addresses that are tried for any one
25680 delivery in cases where there are temporary delivery errors. Section
25681 &<<SECTvalhosmax>>& describes in detail how the value of this option is used.
25684 .option hosts_max_try_hardlimit smtp integer 50
25685 This is an additional check on the maximum number of IP addresses that Exim
25686 tries for any one delivery. Section &<<SECTvalhosmax>>& describes its use and
25691 .option hosts_nopass_tls smtp "host list&!!" unset
25692 .cindex "TLS" "passing connection"
25693 .cindex "multiple SMTP deliveries"
25694 .cindex "TLS" "multiple message deliveries"
25695 For any host that matches this list, a connection on which a TLS session has
25696 been started will not be passed to a new delivery process for sending another
25697 message on the same connection. See section &<<SECTmulmessam>>& for an
25698 explanation of when this might be needed.
25700 .option hosts_noproxy_tls smtp "host list&!!" unset
25701 .cindex "TLS" "passing connection"
25702 .cindex "multiple SMTP deliveries"
25703 .cindex "TLS" "multiple message deliveries"
25704 For any host that matches this list, a TLS session which has
25705 been started will not be passed to a new delivery process for sending another
25706 message on the same session.
25708 The traditional implementation closes down TLS and re-starts it in the new
25709 process, on the same open TCP connection, for each successive message
25710 sent. If permitted by this option a pipe to to the new process is set up
25711 instead, and the original process maintains the TLS connection and proxies
25712 the SMTP connection from and to the new process and any subsequents.
25713 The new process has no access to TLS information, so cannot include it in
25718 .option hosts_override smtp boolean false
25719 If this option is set and the &%hosts%& option is also set, any hosts that are
25720 attached to the address are ignored, and instead the hosts specified by the
25721 &%hosts%& option are always used. This option does not apply to
25722 &%fallback_hosts%&.
25725 .option hosts_randomize smtp boolean false
25726 .cindex "randomized host list"
25727 .cindex "host" "list of; randomized"
25728 .cindex "fallback" "randomized hosts"
25729 If this option is set, and either the list of hosts is taken from the
25730 &%hosts%& or the &%fallback_hosts%& option, or the hosts supplied by the router
25731 were not obtained from MX records (this includes fallback hosts from the
25732 router), and were not randomized by the router, the order of trying the hosts
25733 is randomized each time the transport runs. Randomizing the order of a host
25734 list can be used to do crude load sharing.
25736 When &%hosts_randomize%& is true, a host list may be split into groups whose
25737 order is separately randomized. This makes it possible to set up MX-like
25738 behaviour. The boundaries between groups are indicated by an item that is just
25739 &`+`& in the host list. For example:
25741 hosts = host1:host2:host3:+:host4:host5
25743 The order of the first three hosts and the order of the last two hosts is
25744 randomized for each use, but the first three always end up before the last two.
25745 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored.
25747 .option hosts_require_auth smtp "host list&!!" unset
25748 .cindex "authentication" "required by client"
25749 This option provides a list of servers for which authentication must succeed
25750 before Exim will try to transfer a message. If authentication fails for
25751 servers which are not in this list, Exim tries to send unauthenticated. If
25752 authentication fails for one of these servers, delivery is deferred. This
25753 temporary error is detectable in the retry rules, so it can be turned into a
25754 hard failure if required. See also &%hosts_try_auth%&, and chapter
25755 &<<CHAPSMTPAUTH>>& for details of authentication.
25758 .option hosts_request_ocsp smtp "host list&!!" *
25759 .cindex "TLS" "requiring for certain servers"
25760 Exim will request a Certificate Status on a
25761 TLS session for any host that matches this list.
25762 &%tls_verify_certificates%& should also be set for the transport.
25764 .option hosts_require_alpn smtp "host list&!!" unset
25765 .cindex ALPN "require negotiation in client"
25767 .cindex TLS "Application Layer Protocol Names"
25768 If the TLS library supports ALPN
25769 then a successful negotiation of ALPN will be required for any host
25770 matching the list, for TLS to be used.
25771 See also the &%tls_alpn%& option.
25773 &*Note*&: prevention of fallback to in-clear connection is not
25774 managed by this option; see &%hosts_require_tls%&.
25776 .option hosts_require_dane smtp "host list&!!" unset
25777 .cindex DANE "transport options"
25778 .cindex DANE "requiring for certain servers"
25779 If built with DANE support, Exim will require that a DNSSEC-validated
25780 TLSA record is present for any host matching the list,
25781 and that a DANE-verified TLS connection is made.
25782 There will be no fallback to in-clear communication.
25783 See the &%dnssec_request_domains%& router and transport options.
25784 See section &<<SECDANE>>&.
25786 .option hosts_require_helo smtp "host list&!!" *
25787 .cindex "HELO/EHLO" requiring
25788 Exim will require an accepted HELO or EHLO command from a host matching
25789 this list, before accepting a MAIL command.
25791 .option hosts_require_ocsp smtp "host list&!!" unset
25792 .cindex "TLS" "requiring for certain servers"
25793 Exim will request, and check for a valid Certificate Status being given, on a
25794 TLS session for any host that matches this list.
25795 &%tls_verify_certificates%& should also be set for the transport.
25797 .option hosts_require_tls smtp "host list&!!" unset
25798 .cindex "TLS" "requiring for certain servers"
25799 Exim will insist on using a TLS session when delivering to any host that
25800 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
25801 &*Note*&: This option affects outgoing mail only. To insist on TLS for
25802 incoming messages, use an appropriate ACL.
25804 .option hosts_try_auth smtp "host list&!!" unset
25805 .cindex "authentication" "optional in client"
25806 This option provides a list of servers to which, provided they announce
25807 authentication support, Exim will attempt to authenticate as a client when it
25808 connects. If authentication fails
25809 and &%hosts_require_auth%& permits,
25810 Exim will try to transfer the message unauthenticated.
25811 See also chapter &<<CHAPSMTPAUTH>>& for details of authentication.
25813 .option hosts_try_chunking smtp "host list&!!" *
25814 .cindex CHUNKING "enabling, in client"
25815 .cindex BDAT "SMTP command"
25816 .cindex "RFC 3030" "CHUNKING"
25817 This option provides a list of servers to which, provided they announce
25818 CHUNKING support, Exim will attempt to use BDAT commands rather than DATA.
25819 Unless DKIM signing is being done,
25820 BDAT will not be used in conjunction with a transport filter.
25822 .option hosts_try_dane smtp "host list&!!" *
25823 .cindex DANE "transport options"
25824 .cindex DANE "attempting for certain servers"
25825 If built with DANE support, Exim will look up a
25826 TLSA record for any host matching the list,
25827 If one is found and that lookup was DNSSEC-validated,
25828 then Exim requires that a DANE-verified TLS connection is made for that host;
25829 there will be no fallback to in-clear communication.
25830 See the &%dnssec_request_domains%& router and transport options.
25831 See section &<<SECDANE>>&.
25833 .option hosts_try_fastopen smtp "host list&!!" *
25834 .cindex "fast open, TCP" "enabling, in client"
25835 .cindex "TCP Fast Open" "enabling, in client"
25836 .cindex "RFC 7413" "TCP Fast Open"
25837 This option provides a list of servers to which, provided
25838 the facility is supported by this system, Exim will attempt to
25839 perform a TCP Fast Open.
25840 No data is sent on the SYN segment but, if the remote server also
25841 supports the facility, it can send its SMTP banner immediately after
25842 the SYN,ACK segment. This can save up to one round-trip time.
25844 The facility is only active for previously-contacted servers,
25845 as the initiator must present a cookie in the SYN segment.
25847 On (at least some) current Linux distributions the facility must be enabled
25848 in the kernel by the sysadmin before the support is usable.
25849 There is no option for control of the server side; if the system supports
25850 it it is always enabled. Note that lengthy operations in the connect ACL,
25851 such as DNSBL lookups, will still delay the emission of the SMTP banner.
25853 .option hosts_try_prdr smtp "host list&!!" *
25854 .cindex "PRDR" "enabling, optional in client"
25855 .cindex "ESMTP extensions" PRDR
25856 This option provides a list of servers to which, provided they announce
25857 PRDR support, Exim will attempt to negotiate PRDR
25858 for multi-recipient messages.
25859 The option can usually be left as default.
25861 .option interface smtp "string list&!!" unset
25862 .cindex "bind IP address"
25863 .cindex "IP address" "binding"
25865 .vindex "&$host_address$&"
25866 This option specifies which interface to bind to when making an outgoing SMTP
25867 call. The value is an IP address, not an interface name such as
25868 &`eth0`&. Do not confuse this with the interface address that was used when a
25869 message was received, which is in &$received_ip_address$&, formerly known as
25870 &$interface_address$&. The name was changed to minimize confusion with the
25871 outgoing interface address. There is no variable that contains an outgoing
25872 interface address because, unless it is set by this option, its value is
25875 During the expansion of the &%interface%& option the variables &$host$& and
25876 &$host_address$& refer to the host to which a connection is about to be made
25877 during the expansion of the string. Forced expansion failure, or an empty
25878 string result causes the option to be ignored. Otherwise, after expansion, the
25879 string must be a list of IP addresses, colon-separated by default, but the
25880 separator can be changed in the usual way (&<<SECTlistsepchange>>&).
25883 interface = <; 192.168.123.123 ; 3ffe:ffff:836f::fe86:a061
25885 The first interface of the correct type (IPv4 or IPv6) is used for the outgoing
25886 connection. If none of them are the correct type, the option is ignored. If
25887 &%interface%& is not set, or is ignored, the system's IP functions choose which
25888 interface to use if the host has more than one.
25891 .option keepalive smtp boolean true
25892 .cindex "keepalive" "on outgoing connection"
25893 This option controls the setting of SO_KEEPALIVE on outgoing TCP/IP socket
25894 connections. When set, it causes the kernel to probe idle connections
25895 periodically, by sending packets with &"old"& sequence numbers. The other end
25896 of the connection should send a acknowledgment if the connection is still okay
25897 or a reset if the connection has been aborted. The reason for doing this is
25898 that it has the beneficial effect of freeing up certain types of connection
25899 that can get stuck when the remote host is disconnected without tidying up the
25900 TCP/IP call properly. The keepalive mechanism takes several hours to detect
25904 .option lmtp_ignore_quota smtp boolean false
25905 .cindex "LMTP" "ignoring quota errors"
25906 If this option is set true when the &%protocol%& option is set to &"lmtp"&, the
25907 string &`IGNOREQUOTA`& is added to RCPT commands, provided that the LMTP server
25908 has advertised support for IGNOREQUOTA in its response to the LHLO command.
25910 .option max_rcpt smtp integer 100
25911 .cindex "RCPT" "maximum number of outgoing"
25912 This option limits the number of RCPT commands that are sent in a single
25913 SMTP message transaction. Each set of addresses is treated independently, and
25914 so can cause parallel connections to the same host if &%remote_max_parallel%&
25915 permits this. A value setting of zero disables the limit.
25918 .option message_linelength_limit smtp integer 998
25919 .cindex "line length" limit
25920 This option sets the maximum line length, in bytes, that the transport
25921 will send. Any messages with lines exceeding the given value
25922 will fail and a failure-DSN ("bounce") message will if possible be returned
25924 The default value is that defined by the SMTP standards.
25926 It is generally wise to also check in the data ACL so that messages
25927 received via SMTP can be refused without producing a bounce.
25930 .option multi_domain smtp boolean&!! true
25931 .vindex "&$domain$&"
25932 When this option is set, the &(smtp)& transport can handle a number of
25933 addresses containing a mixture of different domains provided they all resolve
25934 to the same list of hosts. Turning the option off restricts the transport to
25935 handling only one domain at a time. This is useful if you want to use
25936 &$domain$& in an expansion for the transport, because it is set only when there
25937 is a single domain involved in a remote delivery.
25939 It is expanded per-address and can depend on any of
25940 &$address_data$&, &$domain_data$&, &$local_part_data$&,
25941 &$host$&, &$host_address$& and &$host_port$&.
25943 If the connection is DANE-enabled then this option is ignored;
25944 only messages having the domain used for the DANE TLSA lookup are
25945 sent on the connection.
25947 .option port smtp string&!! "see below"
25948 .cindex "port" "sending TCP/IP"
25949 .cindex "TCP/IP" "setting outgoing port"
25950 This option specifies the TCP/IP port on the server to which Exim connects.
25951 &*Note:*& Do not confuse this with the port that was used when a message was
25952 received, which is in &$received_port$&, formerly known as &$interface_port$&.
25953 The name was changed to minimize confusion with the outgoing port. There is no
25954 variable that contains an outgoing port.
25956 If the value of this option begins with a digit it is taken as a port number;
25957 otherwise it is looked up using &[getservbyname()]&. The default value is
25959 but if &%protocol%& is set to &"lmtp"& the default is &"lmtp"&
25960 and if &%protocol%& is set to &"smtps"& the default is &"smtps"&.
25961 If the expansion fails, or if a port number cannot be found, delivery
25964 Note that at least one Linux distribution has been seen failing
25965 to put &"smtps"& in its &"/etc/services"& file, resulting is such deferrals.
25969 .option protocol smtp string smtp
25970 .cindex "LMTP" "over TCP/IP"
25971 .cindex "ssmtp protocol" "outbound"
25972 .cindex "TLS" "SSL-on-connect outbound"
25974 If this option is set to &"lmtp"& instead of &"smtp"&, the default value for
25975 the &%port%& option changes to &"lmtp"&, and the transport operates the LMTP
25976 protocol (RFC 2033) instead of SMTP. This protocol is sometimes used for local
25977 deliveries into closed message stores. Exim also has support for running LMTP
25978 over a pipe to a local process &-- see chapter &<<CHAPLMTP>>&.
25980 If this option is set to &"smtps"&, the default value for the &%port%& option
25981 changes to &"smtps"&, and the transport initiates TLS immediately after
25982 connecting, as an outbound SSL-on-connect, instead of using STARTTLS to upgrade.
25983 The Internet standards bodies used to strongly discourage use of this mode,
25984 but as of RFC 8314 it is preferred over STARTTLS for message submission
25985 (as distinct from MTA-MTA communication).
25988 .option retry_include_ip_address smtp boolean&!! true
25989 Exim normally includes both the host name and the IP address in the key it
25990 constructs for indexing retry data after a temporary delivery failure. This
25991 means that when one of several IP addresses for a host is failing, it gets
25992 tried periodically (controlled by the retry rules), but use of the other IP
25993 addresses is not affected.
25995 However, in some dialup environments hosts are assigned a different IP address
25996 each time they connect. In this situation the use of the IP address as part of
25997 the retry key leads to undesirable behaviour. Setting this option false causes
25998 Exim to use only the host name.
25999 Since it is expanded it can be made to depend on the host or domain.
26002 .option serialize_hosts smtp "host list&!!" unset
26003 .cindex "serializing connections"
26004 .cindex "host" "serializing connections"
26005 Because Exim operates in a distributed manner, if several messages for the same
26006 host arrive at around the same time, more than one simultaneous connection to
26007 the remote host can occur. This is not usually a problem except when there is a
26008 slow link between the hosts. In that situation it may be helpful to restrict
26009 Exim to one connection at a time. This can be done by setting
26010 &%serialize_hosts%& to match the relevant hosts.
26012 .cindex "hints database" "serializing deliveries to a host"
26013 Exim implements serialization by means of a hints database in which a record is
26014 written whenever a process connects to one of the restricted hosts. The record
26015 is deleted when the connection is completed. Obviously there is scope for
26016 records to get left lying around if there is a system or program crash. To
26017 guard against this, Exim ignores any records that are more than six hours old.
26019 If you set up this kind of serialization, you should also arrange to delete the
26020 relevant hints database whenever your system reboots. The names of the files
26021 start with &_misc_& and they are kept in the &_spool/db_& directory. There
26022 may be one or two files, depending on the type of DBM in use. The same files
26023 are used for ETRN serialization.
26025 See also the &%max_parallel%& generic transport option.
26028 .option size_addition smtp integer 1024
26029 .cindex "SIZE" "ESMTP extension"
26030 .cindex "message" "size issue for transport filter"
26031 .cindex "size" "of message"
26032 .cindex "transport" "filter"
26033 .cindex "filter" "transport filter"
26034 If a remote SMTP server indicates that it supports the SIZE option of the
26035 MAIL command, Exim uses this to pass over the message size at the start of
26036 an SMTP transaction. It adds the value of &%size_addition%& to the value it
26037 sends, to allow for headers and other text that may be added during delivery by
26038 configuration options or in a transport filter. It may be necessary to increase
26039 this if a lot of text is added to messages.
26041 Alternatively, if the value of &%size_addition%& is set negative, it disables
26042 the use of the SIZE option altogether.
26045 .option socks_proxy smtp string&!! unset
26046 .cindex proxy SOCKS
26047 This option enables use of SOCKS proxies for connections made by the
26048 transport. For details see section &<<SECTproxySOCKS>>&.
26051 .option tls_alpn smtp string&!! unset
26052 .cindex TLS "Application Layer Protocol Names"
26054 .cindex ALPN "set name in client"
26055 If this option is set
26056 and the TLS library supports ALPN,
26057 the value given is used.
26059 As of writing no value has been standardised for email use.
26060 The authors suggest using &"smtp"&.
26064 .option tls_certificate smtp string&!! unset
26065 .cindex "TLS" "client certificate, location of"
26066 .cindex "certificate" "client, location of"
26068 .vindex "&$host_address$&"
26069 The value of this option must be the absolute path to a file which contains the
26070 client's certificate, for possible use when sending a message over an encrypted
26071 connection. The values of &$host$& and &$host_address$& are set to the name and
26072 address of the server during the expansion. See chapter &<<CHAPTLS>>& for
26075 &*Note*&: This option must be set if you want Exim to be able to use a TLS
26076 certificate when sending messages as a client. The global option of the same
26077 name specifies the certificate for Exim as a server; it is not automatically
26078 assumed that the same certificate should be used when Exim is operating as a
26082 .option tls_crl smtp string&!! unset
26083 .cindex "TLS" "client certificate revocation list"
26084 .cindex "certificate" "revocation list for client"
26085 This option specifies a certificate revocation list. The expanded value must
26086 be the name of a file that contains a CRL in PEM format.
26089 .option tls_dh_min_bits smtp integer 1024
26090 .cindex "TLS" "Diffie-Hellman minimum acceptable size"
26091 When establishing a TLS session, if a ciphersuite which uses Diffie-Hellman
26092 key agreement is negotiated, the server will provide a large prime number
26093 for use. This option establishes the minimum acceptable size of that number.
26094 If the parameter offered by the server is too small, then the TLS handshake
26097 Only supported when using GnuTLS.
26100 .option tls_privatekey smtp string&!! unset
26101 .cindex "TLS" "client private key, location of"
26103 .vindex "&$host_address$&"
26104 The value of this option must be the absolute path to a file which contains the
26105 client's private key. This is used when sending a message over an encrypted
26106 connection using a client certificate. The values of &$host$& and
26107 &$host_address$& are set to the name and address of the server during the
26108 expansion. If this option is unset, or the expansion is forced to fail, or the
26109 result is an empty string, the private key is assumed to be in the same file as
26110 the certificate. See chapter &<<CHAPTLS>>& for details of TLS.
26113 .option tls_require_ciphers smtp string&!! unset
26114 .cindex "TLS" "requiring specific ciphers"
26115 .cindex "cipher" "requiring specific"
26117 .vindex "&$host_address$&"
26118 The value of this option must be a list of permitted cipher suites, for use
26119 when setting up an outgoing encrypted connection. (There is a global option of
26120 the same name for controlling incoming connections.) The values of &$host$& and
26121 &$host_address$& are set to the name and address of the server during the
26122 expansion. See chapter &<<CHAPTLS>>& for details of TLS; note that this option
26123 is used in different ways by OpenSSL and GnuTLS (see sections
26124 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&). For GnuTLS, the order of the
26125 ciphers is a preference order.
26128 .option tls_resumption_hosts smtp "host list&!!" unset
26129 .cindex TLS resumption
26130 This option controls which connections to use the TLS resumption feature.
26131 See &<<SECTresumption>>& for details.
26135 .option tls_sni smtp string&!! unset
26136 .cindex "TLS" "Server Name Indication"
26138 .cindex SNI "setting in client"
26139 .vindex "&$tls_sni$&"
26140 If this option is set
26141 and the connection is not DANE-validated
26142 then it sets the $tls_out_sni variable and causes any
26143 TLS session to pass this value as the Server Name Indication extension to
26144 the remote side, which can be used by the remote side to select an appropriate
26145 certificate and private key for the session.
26147 See &<<SECTtlssni>>& for more information.
26149 Note that for OpenSSL, this feature requires a build of OpenSSL that supports
26155 .option tls_tempfail_tryclear smtp boolean true
26156 .cindex "4&'xx'& responses" "to STARTTLS"
26157 When the server host is not in &%hosts_require_tls%&, and there is a problem in
26158 setting up a TLS session, this option determines whether or not Exim should try
26159 to deliver the message unencrypted. If it is set false, delivery to the
26160 current host is deferred; if there are other hosts, they are tried. If this
26161 option is set true, Exim attempts to deliver unencrypted after a 4&'xx'&
26162 response to STARTTLS. Also, if STARTTLS is accepted, but the subsequent
26163 TLS negotiation fails, Exim closes the current connection (because it is in an
26164 unknown state), opens a new one to the same host, and then tries the delivery
26168 .option tls_try_verify_hosts smtp "host list&!!" *
26169 .cindex "TLS" "server certificate verification"
26170 .cindex "certificate" "verification of server"
26171 This option gives a list of hosts for which, on encrypted connections,
26172 certificate verification will be tried but need not succeed.
26173 The &%tls_verify_certificates%& option must also be set.
26174 Note that unless the host is in this list
26175 TLS connections will be denied to hosts using self-signed certificates
26176 when &%tls_verify_certificates%& is matched.
26177 The &$tls_out_certificate_verified$& variable is set when
26178 certificate verification succeeds.
26181 .option tls_verify_cert_hostnames smtp "host list&!!" *
26182 .cindex "TLS" "server certificate hostname verification"
26183 .cindex "certificate" "verification of server"
26184 This option give a list of hosts for which,
26185 while verifying the server certificate,
26186 checks will be included on the host name
26187 (note that this will generally be the result of a DNS MX lookup)
26188 versus Subject and Subject-Alternate-Name fields. Wildcard names are permitted
26189 limited to being the initial component of a 3-or-more component FQDN.
26191 There is no equivalent checking on client certificates.
26194 .option tls_verify_certificates smtp string&!! system
26195 .cindex "TLS" "server certificate verification"
26196 .cindex "certificate" "verification of server"
26198 .vindex "&$host_address$&"
26199 The value of this option must be either the
26201 or the absolute path to
26202 a file or directory containing permitted certificates for servers,
26203 for use when setting up an encrypted connection.
26205 The "system" value for the option will use a location compiled into the SSL library.
26206 This is not available for GnuTLS versions preceding 3.0.20; a value of "system"
26207 is taken as empty and an explicit location
26210 The use of a directory for the option value is not available for GnuTLS versions
26211 preceding 3.3.6 and a single file must be used.
26213 With OpenSSL the certificates specified
26215 either by file or directory
26216 are added to those given by the system default location.
26218 The values of &$host$& and
26219 &$host_address$& are set to the name and address of the server during the
26220 expansion of this option. See chapter &<<CHAPTLS>>& for details of TLS.
26222 For back-compatibility,
26223 if neither tls_verify_hosts nor tls_try_verify_hosts are set
26224 (a single-colon empty list counts as being set)
26225 and certificate verification fails the TLS connection is closed.
26228 .option tls_verify_hosts smtp "host list&!!" unset
26229 .cindex "TLS" "server certificate verification"
26230 .cindex "certificate" "verification of server"
26231 This option gives a list of hosts for which, on encrypted connections,
26232 certificate verification must succeed.
26233 The &%tls_verify_certificates%& option must also be set.
26234 If both this option and &%tls_try_verify_hosts%& are unset
26235 operation is as if this option selected all hosts.
26236 &*Warning*&: Including a host in &%tls_verify_hosts%& does not require
26237 that connections use TLS.
26238 Fallback to in-clear communication will be done unless restricted by
26239 the &%hosts_require_tls%& option.
26241 .option utf8_downconvert smtp integer&!! -1
26242 .cindex utf8 "address downconversion"
26243 .cindex i18n "utf8 address downconversion"
26244 If built with internationalization support,
26245 this option controls conversion of UTF-8 in message envelope addresses
26247 If, after expansion, the value is 1, 0, or -1 then this value overrides
26248 any value previously set for the message. Otherwise, any previously
26249 set value is used. To permit use of a previous value,
26250 set this option to an empty string.
26251 For details on the values see section &<<SECTi18nMTA>>&.
26256 .section "How the limits for the number of hosts to try are used" &&&
26258 .cindex "host" "maximum number to try"
26259 .cindex "limit" "hosts; maximum number tried"
26260 There are two options that are concerned with the number of hosts that are
26261 tried when an SMTP delivery takes place. They are &%hosts_max_try%& and
26262 &%hosts_max_try_hardlimit%&.
26265 The &%hosts_max_try%& option limits the number of hosts that are tried
26266 for a single delivery. However, despite the term &"host"& in its name, the
26267 option actually applies to each IP address independently. In other words, a
26268 multihomed host is treated as several independent hosts, just as it is for
26271 Many of the larger ISPs have multiple MX records which often point to
26272 multihomed hosts. As a result, a list of a dozen or more IP addresses may be
26273 created as a result of routing one of these domains.
26275 Trying every single IP address on such a long list does not seem sensible; if
26276 several at the top of the list fail, it is reasonable to assume there is some
26277 problem that is likely to affect all of them. Roughly speaking, the value of
26278 &%hosts_max_try%& is the maximum number that are tried before deferring the
26279 delivery. However, the logic cannot be quite that simple.
26281 Firstly, IP addresses that are skipped because their retry times have not
26282 arrived do not count, and in addition, addresses that are past their retry
26283 limits are also not counted, even when they are tried. This means that when
26284 some IP addresses are past their retry limits, more than the value of
26285 &%hosts_max_retry%& may be tried. The reason for this behaviour is to ensure
26286 that all IP addresses are considered before timing out an email address (but
26287 see below for an exception).
26289 Secondly, when the &%hosts_max_try%& limit is reached, Exim looks down the host
26290 list to see if there is a subsequent host with a different (higher valued) MX.
26291 If there is, that host is considered next, and the current IP address is used
26292 but not counted. This behaviour helps in the case of a domain with a retry rule
26293 that hardly ever delays any hosts, as is now explained:
26295 Consider the case of a long list of hosts with one MX value, and a few with a
26296 higher MX value. If &%hosts_max_try%& is small (the default is 5) only a few
26297 hosts at the top of the list are tried at first. With the default retry rule,
26298 which specifies increasing retry times, the higher MX hosts are eventually
26299 tried when those at the top of the list are skipped because they have not
26300 reached their retry times.
26302 However, it is common practice to put a fixed short retry time on domains for
26303 large ISPs, on the grounds that their servers are rarely down for very long.
26304 Unfortunately, these are exactly the domains that tend to resolve to long lists
26305 of hosts. The short retry time means that the lowest MX hosts are tried every
26306 time. The attempts may be in a different order because of random sorting, but
26307 without the special MX check, the higher MX hosts would never be tried until
26308 all the lower MX hosts had timed out (which might be several days), because
26309 there are always some lower MX hosts that have reached their retry times. With
26310 the special check, Exim considers at least one IP address from each MX value at
26311 every delivery attempt, even if the &%hosts_max_try%& limit has already been
26314 The above logic means that &%hosts_max_try%& is not a hard limit, and in
26315 particular, Exim normally eventually tries all the IP addresses before timing
26316 out an email address. When &%hosts_max_try%& was implemented, this seemed a
26317 reasonable thing to do. Recently, however, some lunatic DNS configurations have
26318 been set up with hundreds of IP addresses for some domains. It can
26319 take a very long time indeed for an address to time out in these cases.
26321 The &%hosts_max_try_hardlimit%& option was added to help with this problem.
26322 Exim never tries more than this number of IP addresses; if it hits this limit
26323 and they are all timed out, the email address is bounced, even though not all
26324 possible IP addresses have been tried.
26325 .ecindex IIDsmttra1
26326 .ecindex IIDsmttra2
26332 . ////////////////////////////////////////////////////////////////////////////
26333 . ////////////////////////////////////////////////////////////////////////////
26335 .chapter "Address rewriting" "CHAPrewrite"
26336 .scindex IIDaddrew "rewriting" "addresses"
26337 There are some circumstances in which Exim automatically rewrites domains in
26338 addresses. The two most common are when an address is given without a domain
26339 (referred to as an &"unqualified address"&) or when an address contains an
26340 abbreviated domain that is expanded by DNS lookup.
26342 Unqualified envelope addresses are accepted only for locally submitted
26343 messages, or for messages that are received from hosts matching
26344 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
26345 appropriate. Unqualified addresses in header lines are qualified if they are in
26346 locally submitted messages, or messages from hosts that are permitted to send
26347 unqualified envelope addresses. Otherwise, unqualified addresses in header
26348 lines are neither qualified nor rewritten.
26350 One situation in which Exim does &'not'& automatically rewrite a domain is
26351 when it is the name of a CNAME record in the DNS. The older RFCs suggest that
26352 such a domain should be rewritten using the &"canonical"& name, and some MTAs
26353 do this. The new RFCs do not contain this suggestion.
26356 .section "Explicitly configured address rewriting" "SECID147"
26357 This chapter describes the rewriting rules that can be used in the
26358 main rewrite section of the configuration file, and also in the generic
26359 &%headers_rewrite%& option that can be set on any transport.
26361 Some people believe that configured address rewriting is a Mortal Sin.
26362 Others believe that life is not possible without it. Exim provides the
26363 facility; you do not have to use it.
26365 The main rewriting rules that appear in the &"rewrite"& section of the
26366 configuration file are applied to addresses in incoming messages, both envelope
26367 addresses and addresses in header lines. Each rule specifies the types of
26368 address to which it applies.
26370 Whether or not addresses in header lines are rewritten depends on the origin of
26371 the headers and the type of rewriting. Global rewriting, that is, rewriting
26372 rules from the rewrite section of the configuration file, is applied only to
26373 those headers that were received with the message. Header lines that are added
26374 by ACLs or by a system filter or by individual routers or transports (which
26375 are specific to individual recipient addresses) are not rewritten by the global
26378 Rewriting at transport time, by means of the &%headers_rewrite%& option,
26379 applies all headers except those added by routers and transports. That is, as
26380 well as the headers that were received with the message, it also applies to
26381 headers that were added by an ACL or a system filter.
26384 In general, rewriting addresses from your own system or domain has some
26385 legitimacy. Rewriting other addresses should be done only with great care and
26386 in special circumstances. The author of Exim believes that rewriting should be
26387 used sparingly, and mainly for &"regularizing"& addresses in your own domains.
26388 Although it can sometimes be used as a routing tool, this is very strongly
26391 There are two commonly encountered circumstances where rewriting is used, as
26392 illustrated by these examples:
26395 The company whose domain is &'hitch.fict.example'& has a number of hosts that
26396 exchange mail with each other behind a firewall, but there is only a single
26397 gateway to the outer world. The gateway rewrites &'*.hitch.fict.example'& as
26398 &'hitch.fict.example'& when sending mail off-site.
26400 A host rewrites the local parts of its own users so that, for example,
26401 &'fp42@hitch.fict.example'& becomes &'Ford.Prefect@hitch.fict.example'&.
26406 .section "When does rewriting happen?" "SECID148"
26407 .cindex "rewriting" "timing of"
26408 .cindex "&ACL;" "rewriting addresses in"
26409 Configured address rewriting can take place at several different stages of a
26410 message's processing.
26412 .vindex "&$sender_address$&"
26413 At the start of an ACL for MAIL, the sender address may have been rewritten
26414 by a special SMTP-time rewrite rule (see section &<<SECTrewriteS>>&), but no
26415 ordinary rewrite rules have yet been applied. If, however, the sender address
26416 is verified in the ACL, it is rewritten before verification, and remains
26417 rewritten thereafter. The subsequent value of &$sender_address$& is the
26418 rewritten address. This also applies if sender verification happens in a
26419 RCPT ACL. Otherwise, when the sender address is not verified, it is
26420 rewritten as soon as a message's header lines have been received.
26422 .vindex "&$domain$&"
26423 .vindex "&$local_part$&"
26424 Similarly, at the start of an ACL for RCPT, the current recipient's address
26425 may have been rewritten by a special SMTP-time rewrite rule, but no ordinary
26426 rewrite rules have yet been applied to it. However, the behaviour is different
26427 from the sender address when a recipient is verified. The address is rewritten
26428 for the verification, but the rewriting is not remembered at this stage. The
26429 value of &$local_part$& and &$domain$& after verification are always the same
26430 as they were before (that is, they contain the unrewritten &-- except for
26431 SMTP-time rewriting &-- address).
26433 As soon as a message's header lines have been received, all the envelope
26434 recipient addresses are permanently rewritten, and rewriting is also applied to
26435 the addresses in the header lines (if configured). This happens before adding
26436 any header lines that were specified in MAIL or RCPT ACLs, and
26437 .cindex "&[local_scan()]& function" "address rewriting; timing of"
26438 before the DATA ACL and &[local_scan()]& functions are run.
26440 When an address is being routed, either for delivery or for verification,
26441 rewriting is applied immediately to child addresses that are generated by
26442 redirection, unless &%no_rewrite%& is set on the router.
26444 .cindex "envelope from"
26445 .cindex "envelope sender" "rewriting at transport time"
26446 .cindex "rewriting" "at transport time"
26447 .cindex "header lines" "rewriting at transport time"
26448 At transport time, additional rewriting of addresses in header lines can be
26449 specified by setting the generic &%headers_rewrite%& option on a transport.
26450 This option contains rules that are identical in form to those in the rewrite
26451 section of the configuration file. They are applied to the original message
26452 header lines and any that were added by ACLs or a system filter. They are not
26453 applied to header lines that are added by routers or the transport.
26455 The outgoing envelope sender can be rewritten by means of the &%return_path%&
26456 transport option. However, it is not possible to rewrite envelope recipients at
26462 .section "Testing the rewriting rules that apply on input" "SECID149"
26463 .cindex "rewriting" "testing"
26464 .cindex "testing" "rewriting"
26465 Exim's input rewriting configuration appears in a part of the runtime
26466 configuration file headed by &"begin rewrite"&. It can be tested by the
26467 &%-brw%& command line option. This takes an address (which can be a full RFC
26468 2822 address) as its argument. The output is a list of how the address would be
26469 transformed by the rewriting rules for each of the different places it might
26470 appear in an incoming message, that is, for each different header and for the
26471 envelope sender and recipient fields. For example,
26473 exim -brw ph10@exim.workshop.example
26475 might produce the output
26477 sender: Philip.Hazel@exim.workshop.example
26478 from: Philip.Hazel@exim.workshop.example
26479 to: ph10@exim.workshop.example
26480 cc: ph10@exim.workshop.example
26481 bcc: ph10@exim.workshop.example
26482 reply-to: Philip.Hazel@exim.workshop.example
26483 env-from: Philip.Hazel@exim.workshop.example
26484 env-to: ph10@exim.workshop.example
26486 which shows that rewriting has been set up for that address when used in any of
26487 the source fields, but not when it appears as a recipient address. At the
26488 present time, there is no equivalent way of testing rewriting rules that are
26489 set for a particular transport.
26492 .section "Rewriting rules" "SECID150"
26493 .cindex "rewriting" "rules"
26494 The rewrite section of the configuration file consists of lines of rewriting
26497 <&'source pattern'&> <&'replacement'&> <&'flags'&>
26499 Rewriting rules that are specified for the &%headers_rewrite%& generic
26500 transport option are given as a colon-separated list. Each item in the list
26501 takes the same form as a line in the main rewriting configuration (except that
26502 any colons must be doubled, of course).
26504 The formats of source patterns and replacement strings are described below.
26505 Each is terminated by white space, unless enclosed in double quotes, in which
26506 case normal quoting conventions apply inside the quotes. The flags are single
26507 characters which may appear in any order. Spaces and tabs between them are
26510 For each address that could potentially be rewritten, the rules are scanned in
26511 order, and replacements for the address from earlier rules can themselves be
26512 replaced by later rules (but see the &"q"& and &"R"& flags).
26514 The order in which addresses are rewritten is undefined, may change between
26515 releases, and must not be relied on, with one exception: when a message is
26516 received, the envelope sender is always rewritten first, before any header
26517 lines are rewritten. For example, the replacement string for a rewrite of an
26518 address in &'To:'& must not assume that the message's address in &'From:'& has
26519 (or has not) already been rewritten. However, a rewrite of &'From:'& may assume
26520 that the envelope sender has already been rewritten.
26522 .vindex "&$domain$&"
26523 .vindex "&$local_part$&"
26524 The variables &$local_part$& and &$domain$& can be used in the replacement
26525 string to refer to the address that is being rewritten. Note that lookup-driven
26526 rewriting can be done by a rule of the form
26530 where the lookup key uses &$1$& and &$2$& or &$local_part$& and &$domain$& to
26531 refer to the address that is being rewritten.
26534 .section "Rewriting patterns" "SECID151"
26535 .cindex "rewriting" "patterns"
26536 .cindex "address list" "in a rewriting pattern"
26537 The source pattern in a rewriting rule is any item which may appear in an
26538 address list (see section &<<SECTaddresslist>>&). It is in fact processed as a
26539 single-item address list, which means that it is expanded before being tested
26540 against the address. As always, if you use a regular expression as a pattern,
26541 you must take care to escape dollar and backslash characters, or use the &`\N`&
26542 facility to suppress string expansion within the regular expression.
26544 Domains in patterns should be given in lower case. Local parts in patterns are
26545 case-sensitive. If you want to do case-insensitive matching of local parts, you
26546 can use a regular expression that starts with &`^(?i)`&.
26548 .cindex "numerical variables (&$1$& &$2$& etc)" "in rewriting rules"
26549 After matching, the numerical variables &$1$&, &$2$&, etc. may be set,
26550 depending on the type of match which occurred. These can be used in the
26551 replacement string to insert portions of the incoming address. &$0$& always
26552 refers to the complete incoming address. When a regular expression is used, the
26553 numerical variables are set from its capturing subexpressions. For other types
26554 of pattern they are set as follows:
26557 If a local part or domain starts with an asterisk, the numerical variables
26558 refer to the character strings matched by asterisks, with &$1$& associated with
26559 the first asterisk, and &$2$& with the second, if present. For example, if the
26562 *queen@*.fict.example
26564 is matched against the address &'hearts-queen@wonderland.fict.example'& then
26566 $0 = hearts-queen@wonderland.fict.example
26570 Note that if the local part does not start with an asterisk, but the domain
26571 does, it is &$1$& that contains the wild part of the domain.
26574 If the domain part of the pattern is a partial lookup, the wild and fixed parts
26575 of the domain are placed in the next available numerical variables. Suppose,
26576 for example, that the address &'foo@bar.baz.example'& is processed by a
26577 rewriting rule of the form
26579 &`*@partial-dbm;/some/dbm/file`& <&'replacement string'&>
26581 and the key in the file that matches the domain is &`*.baz.example`&. Then
26587 If the address &'foo@baz.example'& is looked up, this matches the same
26588 wildcard file entry, and in this case &$2$& is set to the empty string, but
26589 &$3$& is still set to &'baz.example'&. If a non-wild key is matched in a
26590 partial lookup, &$2$& is again set to the empty string and &$3$& is set to the
26591 whole domain. For non-partial domain lookups, no numerical variables are set.
26595 .section "Rewriting replacements" "SECID152"
26596 .cindex "rewriting" "replacements"
26597 If the replacement string for a rule is a single asterisk, addresses that
26598 match the pattern and the flags are &'not'& rewritten, and no subsequent
26599 rewriting rules are scanned. For example,
26601 hatta@lookingglass.fict.example * f
26603 specifies that &'hatta@lookingglass.fict.example'& is never to be rewritten in
26606 .vindex "&$domain$&"
26607 .vindex "&$local_part$&"
26608 If the replacement string is not a single asterisk, it is expanded, and must
26609 yield a fully qualified address. Within the expansion, the variables
26610 &$local_part$& and &$domain$& refer to the address that is being rewritten.
26611 Any letters they contain retain their original case &-- they are not lower
26612 cased. The numerical variables are set up according to the type of pattern that
26613 matched the address, as described above. If the expansion is forced to fail by
26614 the presence of &"fail"& in a conditional or lookup item, rewriting by the
26615 current rule is abandoned, but subsequent rules may take effect. Any other
26616 expansion failure causes the entire rewriting operation to be abandoned, and an
26617 entry written to the panic log.
26621 .section "Rewriting flags" "SECID153"
26622 There are three different kinds of flag that may appear on rewriting rules:
26625 Flags that specify which headers and envelope addresses to rewrite: E, F, T, b,
26628 A flag that specifies rewriting at SMTP time: S.
26630 Flags that control the rewriting process: Q, q, R, w.
26633 For rules that are part of the &%headers_rewrite%& generic transport option,
26634 E, F, T, and S are not permitted.
26638 .section "Flags specifying which headers and envelope addresses to rewrite" &&&
26640 .cindex "rewriting" "flags"
26641 If none of the following flag letters, nor the &"S"& flag (see section
26642 &<<SECTrewriteS>>&) are present, a main rewriting rule applies to all headers
26643 and to both the sender and recipient fields of the envelope, whereas a
26644 transport-time rewriting rule just applies to all headers. Otherwise, the
26645 rewriting rule is skipped unless the relevant addresses are being processed.
26647 &`E`& rewrite all envelope fields
26648 &`F`& rewrite the envelope From field
26649 &`T`& rewrite the envelope To field
26650 &`b`& rewrite the &'Bcc:'& header
26651 &`c`& rewrite the &'Cc:'& header
26652 &`f`& rewrite the &'From:'& header
26653 &`h`& rewrite all headers
26654 &`r`& rewrite the &'Reply-To:'& header
26655 &`s`& rewrite the &'Sender:'& header
26656 &`t`& rewrite the &'To:'& header
26658 "All headers" means all of the headers listed above that can be selected
26659 individually, plus their &'Resent-'& versions. It does not include
26660 other headers such as &'Subject:'& etc.
26662 You should be particularly careful about rewriting &'Sender:'& headers, and
26663 restrict this to special known cases in your own domains.
26666 .section "The SMTP-time rewriting flag" "SECTrewriteS"
26667 .cindex "SMTP" "rewriting malformed addresses"
26668 .cindex "RCPT" "rewriting argument of"
26669 .cindex "MAIL" "rewriting argument of"
26670 The rewrite flag &"S"& specifies a rewrite of incoming envelope addresses at
26671 SMTP time, as soon as an address is received in a MAIL or RCPT command, and
26672 before any other processing; even before syntax checking. The pattern is
26673 required to be a regular expression, and it is matched against the whole of the
26674 data for the command, including any surrounding angle brackets.
26676 .vindex "&$domain$&"
26677 .vindex "&$local_part$&"
26678 This form of rewrite rule allows for the handling of addresses that are not
26679 compliant with RFCs 2821 and 2822 (for example, &"bang paths"& in batched SMTP
26680 input). Because the input is not required to be a syntactically valid address,
26681 the variables &$local_part$& and &$domain$& are not available during the
26682 expansion of the replacement string. The result of rewriting replaces the
26683 original address in the MAIL or RCPT command.
26686 .section "Flags controlling the rewriting process" "SECID155"
26687 There are four flags which control the way the rewriting process works. These
26688 take effect only when a rule is invoked, that is, when the address is of the
26689 correct type (matches the flags) and matches the pattern:
26692 If the &"Q"& flag is set on a rule, the rewritten address is permitted to be an
26693 unqualified local part. It is qualified with &%qualify_recipient%&. In the
26694 absence of &"Q"& the rewritten address must always include a domain.
26696 If the &"q"& flag is set on a rule, no further rewriting rules are considered,
26697 even if no rewriting actually takes place because of a &"fail"& in the
26698 expansion. The &"q"& flag is not effective if the address is of the wrong type
26699 (does not match the flags) or does not match the pattern.
26701 The &"R"& flag causes a successful rewriting rule to be re-applied to the new
26702 address, up to ten times. It can be combined with the &"q"& flag, to stop
26703 rewriting once it fails to match (after at least one successful rewrite).
26705 .cindex "rewriting" "whole addresses"
26706 When an address in a header is rewritten, the rewriting normally applies only
26707 to the working part of the address, with any comments and RFC 2822 &"phrase"&
26708 left unchanged. For example, rewriting might change
26710 From: Ford Prefect <fp42@restaurant.hitch.fict.example>
26714 From: Ford Prefect <prefectf@hitch.fict.example>
26717 Sometimes there is a need to replace the whole address item, and this can be
26718 done by adding the flag letter &"w"& to a rule. If this is set on a rule that
26719 causes an address in a header line to be rewritten, the entire address is
26720 replaced, not just the working part. The replacement must be a complete RFC
26721 2822 address, including the angle brackets if necessary. If text outside angle
26722 brackets contains a character whose value is greater than 126 or less than 32
26723 (except for tab), the text is encoded according to RFC 2047. The character set
26724 is taken from &%headers_charset%&, which gets its default at build time.
26726 When the &"w"& flag is set on a rule that causes an envelope address to be
26727 rewritten, all but the working part of the replacement address is discarded.
26731 .section "Rewriting examples" "SECID156"
26732 Here is an example of the two common rewriting paradigms:
26734 *@*.hitch.fict.example $1@hitch.fict.example
26735 *@hitch.fict.example ${lookup{$1}dbm{/etc/realnames}\
26736 {$value}fail}@hitch.fict.example bctfrF
26738 Note the use of &"fail"& in the lookup expansion in the second rule, forcing
26739 the string expansion to fail if the lookup does not succeed. In this context it
26740 has the effect of leaving the original address unchanged, but Exim goes on to
26741 consider subsequent rewriting rules, if any, because the &"q"& flag is not
26742 present in that rule. An alternative to &"fail"& would be to supply &$1$&
26743 explicitly, which would cause the rewritten address to be the same as before,
26744 at the cost of a small bit of processing. Not supplying either of these is an
26745 error, since the rewritten address would then contain no local part.
26747 The first example above replaces the domain with a superior, more general
26748 domain. This may not be desirable for certain local parts. If the rule
26750 root@*.hitch.fict.example *
26752 were inserted before the first rule, rewriting would be suppressed for the
26753 local part &'root'& at any domain ending in &'hitch.fict.example'&.
26755 Rewriting can be made conditional on a number of tests, by making use of
26756 &${if$& in the expansion item. For example, to apply a rewriting rule only to
26757 messages that originate outside the local host:
26759 *@*.hitch.fict.example "${if !eq {$sender_host_address}{}\
26760 {$1@hitch.fict.example}fail}"
26762 The replacement string is quoted in this example because it contains white
26765 .cindex "rewriting" "bang paths"
26766 .cindex "bang paths" "rewriting"
26767 Exim does not handle addresses in the form of &"bang paths"&. If it sees such
26768 an address it treats it as an unqualified local part which it qualifies with
26769 the local qualification domain (if the source of the message is local or if the
26770 remote host is permitted to send unqualified addresses). Rewriting can
26771 sometimes be used to handle simple bang paths with a fixed number of
26772 components. For example, the rule
26774 \N^([^!]+)!(.*)@your.domain.example$\N $2@$1
26776 rewrites a two-component bang path &'host.name!user'& as the domain address
26777 &'user@host.name'&. However, there is a security implication in using this as
26778 a global rewriting rule for envelope addresses. It can provide a backdoor
26779 method for using your system as a relay, because the incoming addresses appear
26780 to be local. If the bang path addresses are received via SMTP, it is safer to
26781 use the &"S"& flag to rewrite them as they are received, so that relay checking
26782 can be done on the rewritten addresses.
26789 . ////////////////////////////////////////////////////////////////////////////
26790 . ////////////////////////////////////////////////////////////////////////////
26792 .chapter "Retry configuration" "CHAPretry"
26793 .scindex IIDretconf1 "retry" "configuration, description of"
26794 .scindex IIDregconf2 "configuration file" "retry section"
26795 The &"retry"& section of the runtime configuration file contains a list of
26796 retry rules that control how often Exim tries to deliver messages that cannot
26797 be delivered at the first attempt. If there are no retry rules (the section is
26798 empty or not present), there are no retries. In this situation, temporary
26799 errors are treated as permanent. The default configuration contains a single,
26800 general-purpose retry rule (see section &<<SECID57>>&). The &%-brt%& command
26801 line option can be used to test which retry rule will be used for a given
26802 address, domain and error.
26804 The most common cause of retries is temporary failure to deliver to a remote
26805 host because the host is down, or inaccessible because of a network problem.
26806 Exim's retry processing in this case is applied on a per-host (strictly, per IP
26807 address) basis, not on a per-message basis. Thus, if one message has recently
26808 been delayed, delivery of a new message to the same host is not immediately
26809 tried, but waits for the host's retry time to arrive. If the &%retry_defer%&
26810 log selector is set, the message
26811 .cindex "retry" "time not reached"
26812 &"retry time not reached"& is written to the main log whenever a delivery is
26813 skipped for this reason. Section &<<SECToutSMTPerr>>& contains more details of
26814 the handling of errors during remote deliveries.
26816 Retry processing applies to routing as well as to delivering, except as covered
26817 in the next paragraph. The retry rules do not distinguish between these
26818 actions. It is not possible, for example, to specify different behaviour for
26819 failures to route the domain &'snark.fict.example'& and failures to deliver to
26820 the host &'snark.fict.example'&. I didn't think anyone would ever need this
26821 added complication, so did not implement it. However, although they share the
26822 same retry rule, the actual retry times for routing and transporting a given
26823 domain are maintained independently.
26825 When a delivery is not part of a queue run (typically an immediate delivery on
26826 receipt of a message), the routers are always run, and local deliveries are
26827 always attempted, even if retry times are set for them. This makes for better
26828 behaviour if one particular message is causing problems (for example, causing
26829 quota overflow, or provoking an error in a filter file). If such a delivery
26830 suffers a temporary failure, the retry data is updated as normal, and
26831 subsequent delivery attempts from queue runs occur only when the retry time for
26832 the local address is reached.
26834 .section "Changing retry rules" "SECID157"
26835 If you change the retry rules in your configuration, you should consider
26836 whether or not to delete the retry data that is stored in Exim's spool area in
26837 files with names like &_db/retry_&. Deleting any of Exim's hints files is
26838 always safe; that is why they are called &"hints"&.
26840 The hints retry data contains suggested retry times based on the previous
26841 rules. In the case of a long-running problem with a remote host, it might
26842 record the fact that the host has timed out. If your new rules increase the
26843 timeout time for such a host, you should definitely remove the old retry data
26844 and let Exim recreate it, based on the new rules. Otherwise Exim might bounce
26845 messages that it should now be retaining.
26849 .section "Format of retry rules" "SECID158"
26850 .cindex "retry" "rules"
26851 Each retry rule occupies one line and consists of three or four parts,
26852 separated by white space: a pattern, an error name, an optional list of sender
26853 addresses, and a list of retry parameters. The pattern and sender lists must be
26854 enclosed in double quotes if they contain white space. The rules are searched
26855 in order until one is found where the pattern, error name, and sender list (if
26856 present) match the failing host or address, the error that occurred, and the
26857 message's sender, respectively.
26860 The pattern is any single item that may appear in an address list (see section
26861 &<<SECTaddresslist>>&). It is in fact processed as a one-item address list,
26862 which means that it is expanded before being tested against the address that
26863 has been delayed. A negated address list item is permitted. Address
26864 list processing treats a plain domain name as if it were preceded by &"*@"&,
26865 which makes it possible for many retry rules to start with just a domain. For
26868 lookingglass.fict.example * F,24h,30m;
26870 provides a rule for any address in the &'lookingglass.fict.example'& domain,
26873 alice@lookingglass.fict.example * F,24h,30m;
26875 applies only to temporary failures involving the local part &%alice%&.
26876 In practice, almost all rules start with a domain name pattern without a local
26879 .cindex "regular expressions" "in retry rules"
26880 &*Warning*&: If you use a regular expression in a retry rule pattern, it
26881 must match a complete address, not just a domain, because that is how regular
26882 expressions work in address lists.
26884 &`^\Nxyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Wrong%&
26885 &`^\N[^@]+@xyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Right%&
26889 .section "Choosing which retry rule to use for address errors" "SECID159"
26890 When Exim is looking for a retry rule after a routing attempt has failed (for
26891 example, after a DNS timeout), each line in the retry configuration is tested
26892 against the complete address only if &%retry_use_local_part%& is set for the
26893 router. Otherwise, only the domain is used, except when matching against a
26894 regular expression, when the local part of the address is replaced with &"*"&.
26895 A domain on its own can match a domain pattern, or a pattern that starts with
26896 &"*@"&. By default, &%retry_use_local_part%& is true for routers where
26897 &%check_local_user%& is true, and false for other routers.
26899 Similarly, when Exim is looking for a retry rule after a local delivery has
26900 failed (for example, after a mailbox full error), each line in the retry
26901 configuration is tested against the complete address only if
26902 &%retry_use_local_part%& is set for the transport (it defaults true for all
26905 .cindex "4&'xx'& responses" "retry rules for"
26906 However, when Exim is looking for a retry rule after a remote delivery attempt
26907 suffers an address error (a 4&'xx'& SMTP response for a recipient address), the
26908 whole address is always used as the key when searching the retry rules. The
26909 rule that is found is used to create a retry time for the combination of the
26910 failing address and the message's sender. It is the combination of sender and
26911 recipient that is delayed in subsequent queue runs until its retry time is
26912 reached. You can delay the recipient without regard to the sender by setting
26913 &%address_retry_include_sender%& false in the &(smtp)& transport but this can
26914 lead to problems with servers that regularly issue 4&'xx'& responses to RCPT
26919 .section "Choosing which retry rule to use for host and message errors" &&&
26921 For a temporary error that is not related to an individual address (for
26922 example, a connection timeout), each line in the retry configuration is checked
26923 twice. First, the name of the remote host is used as a domain name (preceded by
26924 &"*@"& when matching a regular expression). If this does not match the line,
26925 the domain from the email address is tried in a similar fashion. For example,
26926 suppose the MX records for &'a.b.c.example'& are
26928 a.b.c.example MX 5 x.y.z.example
26932 and the retry rules are
26934 p.q.r.example * F,24h,30m;
26935 a.b.c.example * F,4d,45m;
26937 and a delivery to the host &'x.y.z.example'& suffers a connection failure. The
26938 first rule matches neither the host nor the domain, so Exim looks at the second
26939 rule. This does not match the host, but it does match the domain, so it is used
26940 to calculate the retry time for the host &'x.y.z.example'&. Meanwhile, Exim
26941 tries to deliver to &'p.q.r.example'&. If this also suffers a host error, the
26942 first retry rule is used, because it matches the host.
26944 In other words, temporary failures to deliver to host &'p.q.r.example'& use the
26945 first rule to determine retry times, but for all the other hosts for the domain
26946 &'a.b.c.example'&, the second rule is used. The second rule is also used if
26947 routing to &'a.b.c.example'& suffers a temporary failure.
26949 &*Note*&: The host name is used when matching the patterns, not its IP address.
26950 However, if a message is routed directly to an IP address without the use of a
26951 host name, for example, if a &(manualroute)& router contains a setting such as:
26953 route_list = *.a.example 192.168.34.23
26955 then the &"host name"& that is used when searching for a retry rule is the
26956 textual form of the IP address.
26958 .section "Retry rules for specific errors" "SECID161"
26959 .cindex "retry" "specific errors; specifying"
26960 The second field in a retry rule is the name of a particular error, or an
26961 asterisk, which matches any error. The errors that can be tested for are:
26964 .vitem &%auth_failed%&
26965 Authentication failed when trying to send to a host in the
26966 &%hosts_require_auth%& list in an &(smtp)& transport.
26968 .vitem &%data_4xx%&
26969 A 4&'xx'& error was received for an outgoing DATA command, either immediately
26970 after the command, or after sending the message's data.
26972 .vitem &%mail_4xx%&
26973 A 4&'xx'& error was received for an outgoing MAIL command.
26975 .vitem &%rcpt_4xx%&
26976 A 4&'xx'& error was received for an outgoing RCPT command.
26979 For the three 4&'xx'& errors, either the first or both of the x's can be given
26980 as specific digits, for example: &`mail_45x`& or &`rcpt_436`&. For example, to
26981 recognize 452 errors given to RCPT commands for addresses in a certain domain,
26982 and have retries every ten minutes with a one-hour timeout, you could set up a
26983 retry rule of this form:
26985 the.domain.name rcpt_452 F,1h,10m
26987 These errors apply to both outgoing SMTP (the &(smtp)& transport) and outgoing
26988 LMTP (either the &(lmtp)& transport, or the &(smtp)& transport in LMTP mode).
26991 .vitem &%lost_connection%&
26992 A server unexpectedly closed the SMTP connection. There may, of course,
26993 legitimate reasons for this (host died, network died), but if it repeats a lot
26994 for the same host, it indicates something odd.
26997 A DNS lookup for a host failed.
26998 Note that a &%dnslookup%& router will need to have matched
26999 its &%fail_defer_domains%& option for this retry type to be usable.
27000 Also note that a &%manualroute%& router will probably need
27001 its &%host_find_failed%& option set to &%defer%&.
27003 .vitem &%refused_MX%&
27004 A connection to a host obtained from an MX record was refused.
27006 .vitem &%refused_A%&
27007 A connection to a host not obtained from an MX record was refused.
27010 A connection was refused.
27012 .vitem &%timeout_connect_MX%&
27013 A connection attempt to a host obtained from an MX record timed out.
27015 .vitem &%timeout_connect_A%&
27016 A connection attempt to a host not obtained from an MX record timed out.
27018 .vitem &%timeout_connect%&
27019 A connection attempt timed out.
27021 .vitem &%timeout_MX%&
27022 There was a timeout while connecting or during an SMTP session with a host
27023 obtained from an MX record.
27025 .vitem &%timeout_A%&
27026 There was a timeout while connecting or during an SMTP session with a host not
27027 obtained from an MX record.
27030 There was a timeout while connecting or during an SMTP session.
27032 .vitem &%tls_required%&
27033 The server was required to use TLS (it matched &%hosts_require_tls%& in the
27034 &(smtp)& transport), but either did not offer TLS, or it responded with 4&'xx'&
27035 to STARTTLS, or there was a problem setting up the TLS connection.
27038 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
27041 .vitem &%quota_%&<&'time'&>
27042 .cindex "quota" "error testing in retry rule"
27043 .cindex "retry" "quota error testing"
27044 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
27045 transport, and the mailbox has not been accessed for <&'time'&>. For example,
27046 &'quota_4d'& applies to a quota error when the mailbox has not been accessed
27050 .cindex "mailbox" "time of last read"
27051 The idea of &%quota_%&<&'time'&> is to make it possible to have shorter
27052 timeouts when the mailbox is full and is not being read by its owner. Ideally,
27053 it should be based on the last time that the user accessed the mailbox.
27054 However, it is not always possible to determine this. Exim uses the following
27058 If the mailbox is a single file, the time of last access (the &"atime"&) is
27059 used. As no new messages are being delivered (because the mailbox is over
27060 quota), Exim does not access the file, so this is the time of last user access.
27062 .cindex "maildir format" "time of last read"
27063 For a maildir delivery, the time of last modification of the &_new_&
27064 subdirectory is used. As the mailbox is over quota, no new files are created in
27065 the &_new_& subdirectory, because no new messages are being delivered. Any
27066 change to the &_new_& subdirectory is therefore assumed to be the result of an
27067 MUA moving a new message to the &_cur_& directory when it is first read. The
27068 time that is used is therefore the last time that the user read a new message.
27070 For other kinds of multi-file mailbox, the time of last access cannot be
27071 obtained, so a retry rule that uses this type of error field is never matched.
27074 The quota errors apply both to system-enforced quotas and to Exim's own quota
27075 mechanism in the &(appendfile)& transport. The &'quota'& error also applies
27076 when a local delivery is deferred because a partition is full (the ENOSPC
27081 .section "Retry rules for specified senders" "SECID162"
27082 .cindex "retry" "rules; sender-specific"
27083 You can specify retry rules that apply only when the failing message has a
27084 specific sender. In particular, this can be used to define retry rules that
27085 apply only to bounce messages. The third item in a retry rule can be of this
27088 &`senders=`&<&'address list'&>
27090 The retry timings themselves are then the fourth item. For example:
27092 * rcpt_4xx senders=: F,1h,30m
27094 matches recipient 4&'xx'& errors for bounce messages sent to any address at any
27095 host. If the address list contains white space, it must be enclosed in quotes.
27098 a.domain rcpt_452 senders="xb.dom : yc.dom" G,8h,10m,1.5
27100 &*Warning*&: This facility can be unhelpful if it is used for host errors
27101 (which do not depend on the recipient). The reason is that the sender is used
27102 only to match the retry rule. Once the rule has been found for a host error,
27103 its contents are used to set a retry time for the host, and this will apply to
27104 all messages, not just those with specific senders.
27106 When testing retry rules using &%-brt%&, you can supply a sender using the
27107 &%-f%& command line option, like this:
27109 exim -f "" -brt user@dom.ain
27111 If you do not set &%-f%& with &%-brt%&, a retry rule that contains a senders
27112 list is never matched.
27118 .section "Retry parameters" "SECID163"
27119 .cindex "retry" "parameters in rules"
27120 The third (or fourth, if a senders list is present) field in a retry rule is a
27121 sequence of retry parameter sets, separated by semicolons. Each set consists of
27123 <&'letter'&>,<&'cutoff time'&>,<&'arguments'&>
27125 The letter identifies the algorithm for computing a new retry time; the cutoff
27126 time is the time beyond which this algorithm no longer applies, and the
27127 arguments vary the algorithm's action. The cutoff time is measured from the
27128 time that the first failure for the domain (combined with the local part if
27129 relevant) was detected, not from the time the message was received.
27131 .cindex "retry" "algorithms"
27132 .cindex "retry" "fixed intervals"
27133 .cindex "retry" "increasing intervals"
27134 .cindex "retry" "random intervals"
27135 The available algorithms are:
27138 &'F'&: retry at fixed intervals. There is a single time parameter specifying
27141 &'G'&: retry at geometrically increasing intervals. The first argument
27142 specifies a starting value for the interval, and the second a multiplier, which
27143 is used to increase the size of the interval at each retry.
27145 &'H'&: retry at randomized intervals. The arguments are as for &'G'&. For each
27146 retry, the previous interval is multiplied by the factor in order to get a
27147 maximum for the next interval. The minimum interval is the first argument of
27148 the parameter, and an actual interval is chosen randomly between them. Such a
27149 rule has been found to be helpful in cluster configurations when all the
27150 members of the cluster restart at once, and may therefore synchronize their
27151 queue processing times.
27154 When computing the next retry time, the algorithm definitions are scanned in
27155 order until one whose cutoff time has not yet passed is reached. This is then
27156 used to compute a new retry time that is later than the current time. In the
27157 case of fixed interval retries, this simply means adding the interval to the
27158 current time. For geometrically increasing intervals, retry intervals are
27159 computed from the rule's parameters until one that is greater than the previous
27160 interval is found. The main configuration variable
27161 .cindex "limit" "retry interval"
27162 .cindex "retry" "interval, maximum"
27163 .oindex "&%retry_interval_max%&"
27164 &%retry_interval_max%& limits the maximum interval between retries. It
27165 cannot be set greater than &`24h`&, which is its default value.
27167 A single remote domain may have a number of hosts associated with it, and each
27168 host may have more than one IP address. Retry algorithms are selected on the
27169 basis of the domain name, but are applied to each IP address independently. If,
27170 for example, a host has two IP addresses and one is unusable, Exim will
27171 generate retry times for it and will not try to use it until its next retry
27172 time comes. Thus the good IP address is likely to be tried first most of the
27175 .cindex "hints database" "use for retrying"
27176 Retry times are hints rather than promises. Exim does not make any attempt to
27177 run deliveries exactly at the computed times. Instead, a queue runner process
27178 starts delivery processes for delayed messages periodically, and these attempt
27179 new deliveries only for those addresses that have passed their next retry time.
27180 If a new message arrives for a deferred address, an immediate delivery attempt
27181 occurs only if the address has passed its retry time. In the absence of new
27182 messages, the minimum time between retries is the interval between queue runner
27183 processes. There is not much point in setting retry times of five minutes if
27184 your queue runners happen only once an hour, unless there are a significant
27185 number of incoming messages (which might be the case on a system that is
27186 sending everything to a smart host, for example).
27188 The data in the retry hints database can be inspected by using the
27189 &'exim_dumpdb'& or &'exim_fixdb'& utility programs (see chapter
27190 &<<CHAPutils>>&). The latter utility can also be used to change the data. The
27191 &'exinext'& utility script can be used to find out what the next retry times
27192 are for the hosts associated with a particular mail domain, and also for local
27193 deliveries that have been deferred.
27196 .section "Retry rule examples" "SECID164"
27197 Here are some example retry rules:
27199 alice@wonderland.fict.example quota_5d F,7d,3h
27200 wonderland.fict.example quota_5d
27201 wonderland.fict.example * F,1h,15m; G,2d,1h,2;
27202 lookingglass.fict.example * F,24h,30m;
27203 * refused_A F,2h,20m;
27204 * * F,2h,15m; G,16h,1h,1.5; F,5d,8h
27206 The first rule sets up special handling for mail to
27207 &'alice@wonderland.fict.example'& when there is an over-quota error and the
27208 mailbox has not been read for at least 5 days. Retries continue every three
27209 hours for 7 days. The second rule handles over-quota errors for all other local
27210 parts at &'wonderland.fict.example'&; the absence of a local part has the same
27211 effect as supplying &"*@"&. As no retry algorithms are supplied, messages that
27212 fail are bounced immediately if the mailbox has not been read for at least 5
27215 The third rule handles all other errors at &'wonderland.fict.example'&; retries
27216 happen every 15 minutes for an hour, then with geometrically increasing
27217 intervals until two days have passed since a delivery first failed. After the
27218 first hour there is a delay of one hour, then two hours, then four hours, and
27219 so on (this is a rather extreme example).
27221 The fourth rule controls retries for the domain &'lookingglass.fict.example'&.
27222 They happen every 30 minutes for 24 hours only. The remaining two rules handle
27223 all other domains, with special action for connection refusal from hosts that
27224 were not obtained from an MX record.
27226 The final rule in a retry configuration should always have asterisks in the
27227 first two fields so as to provide a general catch-all for any addresses that do
27228 not have their own special handling. This example tries every 15 minutes for 2
27229 hours, then with intervals starting at one hour and increasing by a factor of
27230 1.5 up to 16 hours, then every 8 hours up to 5 days.
27234 .section "Timeout of retry data" "SECID165"
27235 .cindex "timeout" "of retry data"
27236 .oindex "&%retry_data_expire%&"
27237 .cindex "hints database" "data expiry"
27238 .cindex "retry" "timeout of data"
27239 Exim timestamps the data that it writes to its retry hints database. When it
27240 consults the data during a delivery it ignores any that is older than the value
27241 set in &%retry_data_expire%& (default 7 days). If, for example, a host hasn't
27242 been tried for 7 days, Exim will try to deliver to it immediately a message
27243 arrives, and if that fails, it will calculate a retry time as if it were
27244 failing for the first time.
27246 This improves the behaviour for messages routed to rarely-used hosts such as MX
27247 backups. If such a host was down at one time, and happens to be down again when
27248 Exim tries a month later, using the old retry data would imply that it had been
27249 down all the time, which is not a justified assumption.
27251 If a host really is permanently dead, this behaviour causes a burst of retries
27252 every now and again, but only if messages routed to it are rare. If there is a
27253 message at least once every 7 days the retry data never expires.
27258 .section "Long-term failures" "SECID166"
27259 .cindex "delivery failure, long-term"
27260 .cindex "retry" "after long-term failure"
27261 Special processing happens when an email address has been failing for so long
27262 that the cutoff time for the last algorithm is reached. For example, using the
27263 default retry rule:
27265 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
27267 the cutoff time is four days. Reaching the retry cutoff is independent of how
27268 long any specific message has been failing; it is the length of continuous
27269 failure for the recipient address that counts.
27271 When the cutoff time is reached for a local delivery, or for all the IP
27272 addresses associated with a remote delivery, a subsequent delivery failure
27273 causes Exim to give up on the address, and a bounce message is generated.
27274 In order to cater for new messages that use the failing address, a next retry
27275 time is still computed from the final algorithm, and is used as follows:
27277 For local deliveries, one delivery attempt is always made for any subsequent
27278 messages. If this delivery fails, the address fails immediately. The
27279 post-cutoff retry time is not used.
27281 .cindex "final cutoff" "retries, controlling"
27282 .cindex retry "final cutoff"
27283 If the delivery is remote, there are two possibilities, controlled by the
27284 .oindex "&%delay_after_cutoff%&"
27285 &%delay_after_cutoff%& option of the &(smtp)& transport. The option is true by
27286 default. Until the post-cutoff retry time for one of the IP addresses,
27287 as set by the &%retry_data_expire%& option, is
27288 reached, the failing email address is bounced immediately, without a delivery
27289 attempt taking place. After that time, one new delivery attempt is made to
27290 those IP addresses that are past their retry times, and if that still fails,
27291 the address is bounced and new retry times are computed.
27293 In other words, when all the hosts for a given email address have been failing
27294 for a long time, Exim bounces rather then defers until one of the hosts' retry
27295 times is reached. Then it tries once, and bounces if that attempt fails. This
27296 behaviour ensures that few resources are wasted in repeatedly trying to deliver
27297 to a broken destination, but if the host does recover, Exim will eventually
27300 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
27301 addresses are past their final cutoff time, Exim tries to deliver to those IP
27302 addresses that have not been tried since the message arrived. If there are
27303 no suitable IP addresses, or if they all fail, the address is bounced. In other
27304 words, it does not delay when a new message arrives, but tries the expired
27305 addresses immediately, unless they have been tried since the message arrived.
27306 If there is a continuous stream of messages for the failing domains, setting
27307 &%delay_after_cutoff%& false means that there will be many more attempts to
27308 deliver to permanently failing IP addresses than when &%delay_after_cutoff%& is
27311 .section "Deliveries that work intermittently" "SECID167"
27312 .cindex "retry" "intermittently working deliveries"
27313 Some additional logic is needed to cope with cases where a host is
27314 intermittently available, or when a message has some attribute that prevents
27315 its delivery when others to the same address get through. In this situation,
27316 because some messages are successfully delivered, the &"retry clock"& for the
27317 host or address keeps getting reset by the successful deliveries, and so
27318 failing messages remain in the queue for ever because the cutoff time is never
27321 Two exceptional actions are applied to prevent this happening. The first
27322 applies to errors that are related to a message rather than a remote host.
27323 Section &<<SECToutSMTPerr>>& has a discussion of the different kinds of error;
27324 examples of message-related errors are 4&'xx'& responses to MAIL or DATA
27325 commands, and quota failures. For this type of error, if a message's arrival
27326 time is earlier than the &"first failed"& time for the error, the earlier time
27327 is used when scanning the retry rules to decide when to try next and when to
27328 time out the address.
27330 The exceptional second action applies in all cases. If a message has been on
27331 the queue for longer than the cutoff time of any applicable retry rule for a
27332 given address, a delivery is attempted for that address, even if it is not yet
27333 time, and if this delivery fails, the address is timed out. A new retry time is
27334 not computed in this case, so that other messages for the same address are
27335 considered immediately.
27336 .ecindex IIDretconf1
27337 .ecindex IIDregconf2
27344 . ////////////////////////////////////////////////////////////////////////////
27345 . ////////////////////////////////////////////////////////////////////////////
27347 .chapter "SMTP authentication" "CHAPSMTPAUTH"
27348 .scindex IIDauthconf1 "SMTP" "authentication configuration"
27349 .scindex IIDauthconf2 "authentication"
27350 The &"authenticators"& section of Exim's runtime configuration is concerned
27351 with SMTP authentication. This facility is an extension to the SMTP protocol,
27352 described in RFC 2554, which allows a client SMTP host to authenticate itself
27353 to a server. This is a common way for a server to recognize clients that are
27354 permitted to use it as a relay. SMTP authentication is not of relevance to the
27355 transfer of mail between servers that have no managerial connection with each
27358 The name of an authenticator is limited to be &drivernamemax; ASCII characters long;
27359 prior to Exim 4.95 names would be silently truncated at this length, but now
27362 .cindex "AUTH" "description of"
27363 .cindex "ESMTP extensions" AUTH
27364 Very briefly, the way SMTP authentication works is as follows:
27367 The server advertises a number of authentication &'mechanisms'& in response to
27368 the client's EHLO command.
27370 The client issues an AUTH command, naming a specific mechanism. The command
27371 may, optionally, contain some authentication data.
27373 The server may issue one or more &'challenges'&, to which the client must send
27374 appropriate responses. In simple authentication mechanisms, the challenges are
27375 just prompts for user names and passwords. The server does not have to issue
27376 any challenges &-- in some mechanisms the relevant data may all be transmitted
27377 with the AUTH command.
27379 The server either accepts or denies authentication.
27381 If authentication succeeds, the client may optionally make use of the AUTH
27382 option on the MAIL command to pass an authenticated sender in subsequent
27383 mail transactions. Authentication lasts for the remainder of the SMTP
27386 If authentication fails, the client may give up, or it may try a different
27387 authentication mechanism, or it may try transferring mail over the
27388 unauthenticated connection.
27391 If you are setting up a client, and want to know which authentication
27392 mechanisms the server supports, you can use Telnet to connect to port 25 (the
27393 SMTP port) on the server, and issue an EHLO command. The response to this
27394 includes the list of supported mechanisms. For example:
27396 &`$ `&&*&`telnet server.example 25`&*&
27397 &`Trying 192.168.34.25...`&
27398 &`Connected to server.example.`&
27399 &`Escape character is '^]'.`&
27400 &`220 server.example ESMTP Exim 4.20 ...`&
27401 &*&`ehlo client.example`&*&
27402 &`250-server.example Hello client.example [10.8.4.5]`&
27403 &`250-SIZE 52428800`&
27408 The second-last line of this example output shows that the server supports
27409 authentication using the PLAIN mechanism. In Exim, the different authentication
27410 mechanisms are configured by specifying &'authenticator'& drivers. Like the
27411 routers and transports, which authenticators are included in the binary is
27412 controlled by build-time definitions. The following are currently available,
27413 included by setting
27416 AUTH_CYRUS_SASL=yes
27420 AUTH_HEIMDAL_GSSAPI=yes
27425 in &_Local/Makefile_&, respectively. The first of these supports the CRAM-MD5
27426 authentication mechanism (RFC 2195), and the second provides an interface to
27427 the Cyrus SASL authentication library.
27428 The third is an interface to Dovecot's authentication system, delegating the
27429 work via a socket interface.
27430 The fourth provides for negotiation of authentication done via non-SMTP means,
27431 as defined by RFC 4422 Appendix A.
27432 The fifth provides an interface to the GNU SASL authentication library, which
27433 provides mechanisms but typically not data sources.
27434 The sixth provides direct access to Heimdal GSSAPI, geared for Kerberos, but
27435 supporting setting a server keytab.
27436 The seventh can be configured to support
27437 the PLAIN authentication mechanism (RFC 2595) or the LOGIN mechanism, which is
27438 not formally documented, but used by several MUAs.
27439 The eighth authenticator
27440 supports Microsoft's &'Secure Password Authentication'& mechanism.
27441 The last is an Exim authenticator but not an SMTP one;
27442 instead it can use information from a TLS negotiation.
27444 The authenticators are configured using the same syntax as other drivers (see
27445 section &<<SECTfordricon>>&). If no authenticators are required, no
27446 authentication section need be present in the configuration file. Each
27447 authenticator can in principle have both server and client functions. When Exim
27448 is receiving SMTP mail, it is acting as a server; when it is sending out
27449 messages over SMTP, it is acting as a client. Authenticator configuration
27450 options are provided for use in both these circumstances.
27452 To make it clear which options apply to which situation, the prefixes
27453 &%server_%& and &%client_%& are used on option names that are specific to
27454 either the server or the client function, respectively. Server and client
27455 functions are disabled if none of their options are set. If an authenticator is
27456 to be used for both server and client functions, a single definition, using
27457 both sets of options, is required. For example:
27461 public_name = CRAM-MD5
27462 server_secret = ${if eq{$auth1}{ph10}{secret1}fail}
27464 client_secret = secret2
27466 The &%server_%& option is used when Exim is acting as a server, and the
27467 &%client_%& options when it is acting as a client.
27469 Descriptions of the individual authenticators are given in subsequent chapters.
27470 The remainder of this chapter covers the generic options for the
27471 authenticators, followed by general discussion of the way authentication works
27474 &*Beware:*& the meaning of &$auth1$&, &$auth2$&, ... varies on a per-driver and
27475 per-mechanism basis. Please read carefully to determine which variables hold
27476 account labels such as usercodes and which hold passwords or other
27477 authenticating data.
27479 Note that some mechanisms support two different identifiers for accounts: the
27480 &'authentication id'& and the &'authorization id'&. The contractions &'authn'&
27481 and &'authz'& are commonly encountered. The American spelling is standard here.
27482 Conceptually, authentication data such as passwords are tied to the identifier
27483 used to authenticate; servers may have rules to permit one user to act as a
27484 second user, so that after login the session is treated as though that second
27485 user had logged in. That second user is the &'authorization id'&. A robust
27486 configuration might confirm that the &'authz'& field is empty or matches the
27487 &'authn'& field. Often this is just ignored. The &'authn'& can be considered
27488 as verified data, the &'authz'& as an unverified request which the server might
27491 A &'realm'& is a text string, typically a domain name, presented by a server
27492 to a client to help it select an account and credentials to use. In some
27493 mechanisms, the client and server provably agree on the realm, but clients
27494 typically can not treat the realm as secure data to be blindly trusted.
27498 .section "Generic options for authenticators" "SECID168"
27499 .cindex "authentication" "generic options"
27500 .cindex "options" "generic; for authenticators"
27502 .option client_condition authenticators string&!! unset
27503 When Exim is authenticating as a client, it skips any authenticator whose
27504 &%client_condition%& expansion yields &"0"&, &"no"&, or &"false"&. This can be
27505 used, for example, to skip plain text authenticators when the connection is not
27506 encrypted by a setting such as:
27508 client_condition = ${if !eq{$tls_out_cipher}{}}
27512 .option client_set_id authenticators string&!! unset
27513 When client authentication succeeds, this condition is expanded; the
27514 result is used in the log lines for outbound messages.
27515 Typically it will be the user name used for authentication.
27518 .option driver authenticators string unset
27519 This option must always be set. It specifies which of the available
27520 authenticators is to be used.
27523 .option public_name authenticators string unset
27524 This option specifies the name of the authentication mechanism that the driver
27525 implements, and by which it is known to the outside world. These names should
27526 contain only upper case letters, digits, underscores, and hyphens (RFC 2222),
27527 but Exim in fact matches them caselessly. If &%public_name%& is not set, it
27528 defaults to the driver's instance name.
27531 .option server_advertise_condition authenticators string&!! unset
27532 When a server is about to advertise an authentication mechanism, the condition
27533 is expanded. If it yields the empty string, &"0"&, &"no"&, or &"false"&, the
27534 mechanism is not advertised.
27535 If the expansion fails, the mechanism is not advertised. If the failure was not
27536 forced, and was not caused by a lookup defer, the incident is logged.
27537 See section &<<SECTauthexiser>>& below for further discussion.
27540 .option server_condition authenticators string&!! unset
27541 This option must be set for a &%plaintext%& server authenticator, where it
27542 is used directly to control authentication. See section &<<SECTplainserver>>&
27545 For the &(gsasl)& authenticator, this option is required for various
27546 mechanisms; see chapter &<<CHAPgsasl>>& for details.
27548 For the other authenticators, &%server_condition%& can be used as an additional
27549 authentication or authorization mechanism that is applied after the other
27550 authenticator conditions succeed. If it is set, it is expanded when the
27551 authenticator would otherwise return a success code. If the expansion is forced
27552 to fail, authentication fails. Any other expansion failure causes a temporary
27553 error code to be returned. If the result of a successful expansion is an empty
27554 string, &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
27555 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds. For any
27556 other result, a temporary error code is returned, with the expanded string as
27560 .option server_debug_print authenticators string&!! unset
27561 If this option is set and authentication debugging is enabled (see the &%-d%&
27562 command line option), the string is expanded and included in the debugging
27563 output when the authenticator is run as a server. This can help with checking
27564 out the values of variables.
27565 If expansion of the string fails, the error message is written to the debugging
27566 output, and Exim carries on processing.
27569 .option server_set_id authenticators string&!! unset
27570 .vindex "&$authenticated_id$&"
27571 .vindex "&$authenticated_fail_id$&"
27572 When an Exim server successfully authenticates a client, this string is
27573 expanded using data from the authentication, and preserved for any incoming
27574 messages in the variable &$authenticated_id$&. It is also included in the log
27575 lines for incoming messages. For example, a user/password authenticator
27576 configuration might preserve the user name that was used to authenticate, and
27577 refer to it subsequently during delivery of the message.
27578 On a failing authentication the expansion result is instead saved in
27579 the &$authenticated_fail_id$& variable.
27580 If expansion fails, the option is ignored.
27583 .option server_mail_auth_condition authenticators string&!! unset
27584 This option allows a server to discard authenticated sender addresses supplied
27585 as part of MAIL commands in SMTP connections that are authenticated by the
27586 driver on which &%server_mail_auth_condition%& is set. The option is not used
27587 as part of the authentication process; instead its (unexpanded) value is
27588 remembered for later use.
27589 How it is used is described in the following section.
27595 .section "The AUTH parameter on MAIL commands" "SECTauthparamail"
27596 .cindex "authentication" "sender; authenticated"
27597 .cindex "AUTH" "on MAIL command"
27598 When a client supplied an AUTH= item on a MAIL command, Exim applies
27599 the following checks before accepting it as the authenticated sender of the
27603 If the connection is not using extended SMTP (that is, HELO was used rather
27604 than EHLO), the use of AUTH= is a syntax error.
27606 If the value of the AUTH= parameter is &"<>"&, it is ignored.
27608 .vindex "&$authenticated_sender$&"
27609 If &%acl_smtp_mailauth%& is defined, the ACL it specifies is run. While it is
27610 running, the value of &$authenticated_sender$& is set to the value obtained
27611 from the AUTH= parameter. If the ACL does not yield &"accept"&, the value of
27612 &$authenticated_sender$& is deleted. The &%acl_smtp_mailauth%& ACL may not
27613 return &"drop"& or &"discard"&. If it defers, a temporary error code (451) is
27614 given for the MAIL command.
27616 If &%acl_smtp_mailauth%& is not defined, the value of the AUTH= parameter
27617 is accepted and placed in &$authenticated_sender$& only if the client has
27620 If the AUTH= value was accepted by either of the two previous rules, and
27621 the client has authenticated, and the authenticator has a setting for the
27622 &%server_mail_auth_condition%&, the condition is checked at this point. The
27623 valued that was saved from the authenticator is expanded. If the expansion
27624 fails, or yields an empty string, &"0"&, &"no"&, or &"false"&, the value of
27625 &$authenticated_sender$& is deleted. If the expansion yields any other value,
27626 the value of &$authenticated_sender$& is retained and passed on with the
27631 When &$authenticated_sender$& is set for a message, it is passed on to other
27632 hosts to which Exim authenticates as a client. Do not confuse this value with
27633 &$authenticated_id$&, which is a string obtained from the authentication
27634 process, and which is not usually a complete email address.
27636 .vindex "&$sender_address$&"
27637 Whenever an AUTH= value is ignored, the incident is logged. The ACL for
27638 MAIL, if defined, is run after AUTH= is accepted or ignored. It can
27639 therefore make use of &$authenticated_sender$&. The converse is not true: the
27640 value of &$sender_address$& is not yet set up when the &%acl_smtp_mailauth%&
27645 .section "Authentication on an Exim server" "SECTauthexiser"
27646 .cindex "authentication" "on an Exim server"
27647 When Exim receives an EHLO command, it advertises the public names of those
27648 authenticators that are configured as servers, subject to the following
27652 The client host must match &%auth_advertise_hosts%& (default *).
27654 If the &%server_advertise_condition%& option is set, its expansion must not
27655 yield the empty string, &"0"&, &"no"&, or &"false"&.
27658 The order in which the authenticators are defined controls the order in which
27659 the mechanisms are advertised.
27661 Some mail clients (for example, some versions of Netscape) require the user to
27662 provide a name and password for authentication whenever AUTH is advertised,
27663 even though authentication may not in fact be needed (for example, Exim may be
27664 set up to allow unconditional relaying from the client by an IP address check).
27665 You can make such clients more friendly by not advertising AUTH to them.
27666 For example, if clients on the 10.9.8.0/24 network are permitted (by the ACL
27667 that runs for RCPT) to relay without authentication, you should set
27669 auth_advertise_hosts = ! 10.9.8.0/24
27671 so that no authentication mechanisms are advertised to them.
27673 The &%server_advertise_condition%& controls the advertisement of individual
27674 authentication mechanisms. For example, it can be used to restrict the
27675 advertisement of a particular mechanism to encrypted connections, by a setting
27678 server_advertise_condition = ${if eq{$tls_in_cipher}{}{no}{yes}}
27680 .vindex "&$tls_in_cipher$&"
27681 If the session is encrypted, &$tls_in_cipher$& is not empty, and so the expansion
27682 yields &"yes"&, which allows the advertisement to happen.
27684 When an Exim server receives an AUTH command from a client, it rejects it
27685 immediately if AUTH was not advertised in response to an earlier EHLO
27686 command. This is the case if
27689 The client host does not match &%auth_advertise_hosts%&; or
27691 No authenticators are configured with server options; or
27693 Expansion of &%server_advertise_condition%& blocked the advertising of all the
27694 server authenticators.
27698 Otherwise, Exim runs the ACL specified by &%acl_smtp_auth%& in order
27699 to decide whether to accept the command. If &%acl_smtp_auth%& is not set,
27700 AUTH is accepted from any client host.
27702 If AUTH is not rejected by the ACL, Exim searches its configuration for a
27703 server authentication mechanism that was advertised in response to EHLO and
27704 that matches the one named in the AUTH command. If it finds one, it runs
27705 the appropriate authentication protocol, and authentication either succeeds or
27706 fails. If there is no matching advertised mechanism, the AUTH command is
27707 rejected with a 504 error.
27709 .vindex "&$received_protocol$&"
27710 .vindex "&$sender_host_authenticated$&"
27711 When a message is received from an authenticated host, the value of
27712 &$received_protocol$& is set to &"esmtpa"& or &"esmtpsa"& instead of &"esmtp"&
27713 or &"esmtps"&, and &$sender_host_authenticated$& contains the name (not the
27714 public name) of the authenticator driver that successfully authenticated the
27715 client from which the message was received. This variable is empty if there was
27716 no successful authentication.
27718 .cindex authentication "expansion item"
27719 Successful authentication sets up information used by the
27720 &%authresults%& expansion item.
27725 .section "Testing server authentication" "SECID169"
27726 .cindex "authentication" "testing a server"
27727 .cindex "AUTH" "testing a server"
27728 .cindex "base64 encoding" "creating authentication test data"
27729 Exim's &%-bh%& option can be useful for testing server authentication
27730 configurations. The data for the AUTH command has to be sent using base64
27731 encoding. A quick way to produce such data for testing is the following Perl
27735 printf ("%s", encode_base64(eval "\"$ARGV[0]\""));
27737 .cindex "binary zero" "in authentication data"
27738 This interprets its argument as a Perl string, and then encodes it. The
27739 interpretation as a Perl string allows binary zeros, which are required for
27740 some kinds of authentication, to be included in the data. For example, a
27741 command line to run this script on such data might be
27743 encode '\0user\0password'
27745 Note the use of single quotes to prevent the shell interpreting the
27746 backslashes, so that they can be interpreted by Perl to specify characters
27747 whose code value is zero.
27749 &*Warning 1*&: If either of the user or password strings starts with an octal
27750 digit, you must use three zeros instead of one after the leading backslash. If
27751 you do not, the octal digit that starts your string will be incorrectly
27752 interpreted as part of the code for the first character.
27754 &*Warning 2*&: If there are characters in the strings that Perl interprets
27755 specially, you must use a Perl escape to prevent them being misinterpreted. For
27756 example, a command such as
27758 encode '\0user@domain.com\0pas$$word'
27760 gives an incorrect answer because of the unescaped &"@"& and &"$"& characters.
27762 If you have the &%mimencode%& command installed, another way to produce
27763 base64-encoded strings is to run the command
27765 echo -e -n `\0user\0password' | mimencode
27767 The &%-e%& option of &%echo%& enables the interpretation of backslash escapes
27768 in the argument, and the &%-n%& option specifies no newline at the end of its
27769 output. However, not all versions of &%echo%& recognize these options, so you
27770 should check your version before relying on this suggestion.
27774 .section "Authentication by an Exim client" "SECID170"
27775 .cindex "authentication" "on an Exim client"
27776 The &(smtp)& transport has two options called &%hosts_require_auth%& and
27777 &%hosts_try_auth%&. When the &(smtp)& transport connects to a server that
27778 announces support for authentication, and the host matches an entry in either
27779 of these options, Exim (as a client) tries to authenticate as follows:
27782 For each authenticator that is configured as a client, in the order in which
27783 they are defined in the configuration, it searches the authentication
27784 mechanisms announced by the server for one whose name matches the public name
27785 of the authenticator.
27788 .vindex "&$host_address$&"
27789 When it finds one that matches, it runs the authenticator's client code. The
27790 variables &$host$& and &$host_address$& are available for any string expansions
27791 that the client might do. They are set to the server's name and IP address. If
27792 any expansion is forced to fail, the authentication attempt is abandoned, and
27793 Exim moves on to the next authenticator. Otherwise an expansion failure causes
27794 delivery to be deferred.
27796 If the result of the authentication attempt is a temporary error or a timeout,
27797 Exim abandons trying to send the message to the host for the moment. It will
27798 try again later. If there are any backup hosts available, they are tried in the
27801 If the response to authentication is a permanent error (5&'xx'& code), Exim
27802 carries on searching the list of authenticators and tries another one if
27803 possible. If all authentication attempts give permanent errors, or if there are
27804 no attempts because no mechanisms match (or option expansions force failure),
27805 what happens depends on whether the host matches &%hosts_require_auth%& or
27806 &%hosts_try_auth%&. In the first case, a temporary error is generated, and
27807 delivery is deferred. The error can be detected in the retry rules, and thereby
27808 turned into a permanent error if you wish. In the second case, Exim tries to
27809 deliver the message unauthenticated.
27812 Note that the hostlist test for whether to do authentication can be
27813 confused if name-IP lookups change between the time the peer is decided
27814 upon and the time that the transport runs. For example, with a manualroute
27815 router given a host name, and with DNS "round-robin" used by that name: if
27816 the local resolver cache times out between the router and the transport
27817 running, the transport may get an IP for the name for its authentication
27818 check which does not match the connection peer IP.
27819 No authentication will then be done, despite the names being identical.
27821 For such cases use a separate transport which always authenticates.
27823 .cindex "AUTH" "on MAIL command"
27824 When Exim has authenticated itself to a remote server, it adds the AUTH
27825 parameter to the MAIL commands it sends, if it has an authenticated sender for
27826 the message. If the message came from a remote host, the authenticated sender
27827 is the one that was receiving on an incoming MAIL command, provided that the
27828 incoming connection was authenticated and the &%server_mail_auth%& condition
27829 allowed the authenticated sender to be retained. If a local process calls Exim
27830 to send a message, the sender address that is built from the login name and
27831 &%qualify_domain%& is treated as authenticated. However, if the
27832 &%authenticated_sender%& option is set on the &(smtp)& transport, it overrides
27833 the authenticated sender that was received with the message.
27834 .ecindex IIDauthconf1
27835 .ecindex IIDauthconf2
27842 . ////////////////////////////////////////////////////////////////////////////
27843 . ////////////////////////////////////////////////////////////////////////////
27845 .chapter "The plaintext authenticator" "CHAPplaintext"
27846 .scindex IIDplaiauth1 "&(plaintext)& authenticator"
27847 .scindex IIDplaiauth2 "authenticators" "&(plaintext)&"
27848 The &(plaintext)& authenticator can be configured to support the PLAIN and
27849 LOGIN authentication mechanisms, both of which transfer authentication data as
27850 plain (unencrypted) text (though base64 encoded). The use of plain text is a
27851 security risk; you are strongly advised to insist on the use of SMTP encryption
27852 (see chapter &<<CHAPTLS>>&) if you use the PLAIN or LOGIN mechanisms. If you do
27853 use unencrypted plain text, you should not use the same passwords for SMTP
27854 connections as you do for login accounts.
27856 .section "Avoiding cleartext use" "SECTplain_TLS"
27857 The following generic option settings will disable &(plaintext)& authenticators when
27858 TLS is not being used:
27860 server_advertise_condition = ${if def:tls_in_cipher }
27861 client_condition = ${if def:tls_out_cipher}
27864 &*Note*&: a plaintext SMTP AUTH done inside TLS is not vulnerable to casual snooping,
27865 but is still vulnerable to a Man In The Middle attack unless certificates
27866 (including their names) have been properly verified.
27868 .section "Plaintext server options" "SECID171"
27869 .cindex "options" "&(plaintext)& authenticator (server)"
27870 When configured as a server, &(plaintext)& uses the following options:
27872 .option server_condition authenticators string&!! unset
27873 This is actually a global authentication option, but it must be set in order to
27874 configure the &(plaintext)& driver as a server. Its use is described below.
27876 .option server_prompts plaintext "string list&!!" unset
27877 The contents of this option, after expansion, must be a colon-separated list of
27878 prompt strings. If expansion fails, a temporary authentication rejection is
27881 .section "Using plaintext in a server" "SECTplainserver"
27882 .cindex "AUTH" "in &(plaintext)& authenticator"
27883 .cindex "binary zero" "in &(plaintext)& authenticator"
27884 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
27885 "in &(plaintext)& authenticator"
27886 .vindex "&$auth1$&, &$auth2$&, etc"
27887 .cindex "base64 encoding" "in &(plaintext)& authenticator"
27889 When running as a server, &(plaintext)& performs the authentication test by
27890 expanding a string. The data sent by the client with the AUTH command, or in
27891 response to subsequent prompts, is base64 encoded, and so may contain any byte
27892 values when decoded. If any data is supplied with the command, it is treated as
27893 a list of strings, separated by NULs (binary zeros), the first three of which
27894 are placed in the expansion variables &$auth1$&, &$auth2$&, and &$auth3$&
27895 (neither LOGIN nor PLAIN uses more than three strings).
27897 For compatibility with previous releases of Exim, the values are also placed in
27898 the expansion variables &$1$&, &$2$&, and &$3$&. However, the use of these
27899 variables for this purpose is now deprecated, as it can lead to confusion in
27900 string expansions that also use them for other things.
27902 If there are more strings in &%server_prompts%& than the number of strings
27903 supplied with the AUTH command, the remaining prompts are used to obtain more
27904 data. Each response from the client may be a list of NUL-separated strings.
27906 .vindex "&$authenticated_id$&"
27907 Once a sufficient number of data strings have been received,
27908 &%server_condition%& is expanded. If the expansion is forced to fail,
27909 authentication fails. Any other expansion failure causes a temporary error code
27910 to be returned. If the result of a successful expansion is an empty string,
27911 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
27912 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
27913 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
27914 For any other result, a temporary error code is returned, with the expanded
27915 string as the error text.
27917 &*Warning*&: If you use a lookup in the expansion to find the user's
27918 password, be sure to make the authentication fail if the user is unknown.
27919 There are good and bad examples at the end of the next section.
27923 .section "The PLAIN authentication mechanism" "SECID172"
27924 .cindex "PLAIN authentication mechanism"
27925 .cindex authentication PLAIN
27926 .cindex "binary zero" "in &(plaintext)& authenticator"
27927 The PLAIN authentication mechanism (RFC 2595) specifies that three strings be
27928 sent as one item of data (that is, one combined string containing two NUL
27929 separators). The data is sent either as part of the AUTH command, or
27930 subsequently in response to an empty prompt from the server.
27932 The second and third strings are a user name and a corresponding password.
27933 Using a single fixed user name and password as an example, this could be
27934 configured as follows:
27938 public_name = PLAIN
27940 server_condition = \
27941 ${if and {{eq{$auth2}{username}}{eq{$auth3}{mysecret}}}}
27942 server_set_id = $auth2
27944 Note that the default result strings from &%if%& (&"true"& or an empty string)
27945 are exactly what we want here, so they need not be specified. Obviously, if the
27946 password contains expansion-significant characters such as dollar, backslash,
27947 or closing brace, they have to be escaped.
27949 The &%server_prompts%& setting specifies a single, empty prompt (empty items at
27950 the end of a string list are ignored). If all the data comes as part of the
27951 AUTH command, as is commonly the case, the prompt is not used. This
27952 authenticator is advertised in the response to EHLO as
27956 and a client host can authenticate itself by sending the command
27958 AUTH PLAIN AHVzZXJuYW1lAG15c2VjcmV0
27960 As this contains three strings (more than the number of prompts), no further
27961 data is required from the client. Alternatively, the client may just send
27965 to initiate authentication, in which case the server replies with an empty
27966 prompt. The client must respond with the combined data string.
27968 The data string is base64 encoded, as required by the RFC. This example,
27969 when decoded, is <&'NUL'&>&`username`&<&'NUL'&>&`mysecret`&, where <&'NUL'&>
27970 represents a zero byte. This is split up into three strings, the first of which
27971 is empty. The &%server_condition%& option in the authenticator checks that the
27972 second two are &`username`& and &`mysecret`& respectively.
27974 Having just one fixed user name and password, as in this example, is not very
27975 realistic, though for a small organization with only a handful of
27976 authenticating clients it could make sense.
27978 A more sophisticated instance of this authenticator could use the user name in
27979 &$auth2$& to look up a password in a file or database, and maybe do an encrypted
27980 comparison (see &%crypteq%& in chapter &<<CHAPexpand>>&). Here is a example of
27981 this approach, where the passwords are looked up in a DBM file. &*Warning*&:
27982 This is an incorrect example:
27984 server_condition = \
27985 ${if eq{$auth3}{${lookup{$auth2}dbm{/etc/authpwd}}}}
27987 The expansion uses the user name (&$auth2$&) as the key to look up a password,
27988 which it then compares to the supplied password (&$auth3$&). Why is this example
27989 incorrect? It works fine for existing users, but consider what happens if a
27990 non-existent user name is given. The lookup fails, but as no success/failure
27991 strings are given for the lookup, it yields an empty string. Thus, to defeat
27992 the authentication, all a client has to do is to supply a non-existent user
27993 name and an empty password. The correct way of writing this test is:
27995 server_condition = ${lookup{$auth2}dbm{/etc/authpwd}\
27996 {${if eq{$value}{$auth3}}} {false}}
27998 In this case, if the lookup succeeds, the result is checked; if the lookup
27999 fails, &"false"& is returned and authentication fails. If &%crypteq%& is being
28000 used instead of &%eq%&, the first example is in fact safe, because &%crypteq%&
28001 always fails if its second argument is empty. However, the second way of
28002 writing the test makes the logic clearer.
28005 .section "The LOGIN authentication mechanism" "SECID173"
28006 .cindex "LOGIN authentication mechanism"
28007 .cindex authentication LOGIN
28008 The LOGIN authentication mechanism is not documented in any RFC, but is in use
28009 in a number of programs. No data is sent with the AUTH command. Instead, a
28010 user name and password are supplied separately, in response to prompts. The
28011 plaintext authenticator can be configured to support this as in this example:
28015 public_name = LOGIN
28016 server_prompts = User Name : Password
28017 server_condition = \
28018 ${if and {{eq{$auth1}{username}}{eq{$auth2}{mysecret}}}}
28019 server_set_id = $auth1
28021 Because of the way plaintext operates, this authenticator accepts data supplied
28022 with the AUTH command (in contravention of the specification of LOGIN), but
28023 if the client does not supply it (as is the case for LOGIN clients), the prompt
28024 strings are used to obtain two data items.
28026 Some clients are very particular about the precise text of the prompts. For
28027 example, Outlook Express is reported to recognize only &"Username:"& and
28028 &"Password:"&. Here is an example of a LOGIN authenticator that uses those
28029 strings. It uses the &%ldapauth%& expansion condition to check the user
28030 name and password by binding to an LDAP server:
28034 public_name = LOGIN
28035 server_prompts = Username:: : Password::
28036 server_condition = ${if and{{ \
28039 user="uid=${quote_ldap_dn:$auth1},ou=people,o=example.org" \
28040 pass=${quote:$auth2} \
28041 ldap://ldap.example.org/} }} }
28042 server_set_id = uid=$auth1,ou=people,o=example.org
28044 We have to check that the username is not empty before using it, because LDAP
28045 does not permit empty DN components. We must also use the &%quote_ldap_dn%&
28046 operator to correctly quote the DN for authentication. However, the basic
28047 &%quote%& operator, rather than any of the LDAP quoting operators, is the
28048 correct one to use for the password, because quoting is needed only to make
28049 the password conform to the Exim syntax. At the LDAP level, the password is an
28050 uninterpreted string.
28053 .section "Support for different kinds of authentication" "SECID174"
28054 A number of string expansion features are provided for the purpose of
28055 interfacing to different ways of user authentication. These include checking
28056 traditionally encrypted passwords from &_/etc/passwd_& (or equivalent), PAM,
28057 Radius, &%ldapauth%&, &'pwcheck'&, and &'saslauthd'&. For details see section
28063 .section "Using plaintext in a client" "SECID175"
28064 .cindex "options" "&(plaintext)& authenticator (client)"
28065 The &(plaintext)& authenticator has two client options:
28067 .option client_ignore_invalid_base64 plaintext boolean false
28068 If the client receives a server prompt that is not a valid base64 string,
28069 authentication is abandoned by default. However, if this option is set true,
28070 the error in the challenge is ignored and the client sends the response as
28073 .option client_send plaintext string&!! unset
28074 The string is a colon-separated list of authentication data strings. Each
28075 string is independently expanded before being sent to the server. The first
28076 string is sent with the AUTH command; any more strings are sent in response
28077 to prompts from the server. Before each string is expanded, the value of the
28078 most recent prompt is placed in the next &$auth$&<&'n'&> variable, starting
28079 with &$auth1$& for the first prompt. Up to three prompts are stored in this
28080 way. Thus, the prompt that is received in response to sending the first string
28081 (with the AUTH command) can be used in the expansion of the second string, and
28082 so on. If an invalid base64 string is received when
28083 &%client_ignore_invalid_base64%& is set, an empty string is put in the
28084 &$auth$&<&'n'&> variable.
28086 &*Note*&: You cannot use expansion to create multiple strings, because
28087 splitting takes priority and happens first.
28089 Because the PLAIN authentication mechanism requires NUL (binary zero) bytes in
28090 the data, further processing is applied to each string before it is sent. If
28091 there are any single circumflex characters in the string, they are converted to
28092 NULs. Should an actual circumflex be required as data, it must be doubled in
28095 This is an example of a client configuration that implements the PLAIN
28096 authentication mechanism with a fixed user name and password:
28100 public_name = PLAIN
28101 client_send = ^username^mysecret
28103 The lack of colons means that the entire text is sent with the AUTH
28104 command, with the circumflex characters converted to NULs.
28105 Note that due to the ambiguity of parsing three consectutive circumflex characters
28106 there is no way to provide a password having a leading circumflex.
28110 that uses the LOGIN mechanism is:
28114 public_name = LOGIN
28115 client_send = : username : mysecret
28117 The initial colon means that the first string is empty, so no data is sent with
28118 the AUTH command itself. The remaining strings are sent in response to
28120 .ecindex IIDplaiauth1
28121 .ecindex IIDplaiauth2
28126 . ////////////////////////////////////////////////////////////////////////////
28127 . ////////////////////////////////////////////////////////////////////////////
28129 .chapter "The cram_md5 authenticator" "CHID9"
28130 .scindex IIDcramauth1 "&(cram_md5)& authenticator"
28131 .scindex IIDcramauth2 "authenticators" "&(cram_md5)&"
28132 .cindex "CRAM-MD5 authentication mechanism"
28133 .cindex authentication CRAM-MD5
28134 The CRAM-MD5 authentication mechanism is described in RFC 2195. The server
28135 sends a challenge string to the client, and the response consists of a user
28136 name and the CRAM-MD5 digest of the challenge string combined with a secret
28137 string (password) which is known to both server and client. Thus, the secret
28138 is not sent over the network as plain text, which makes this authenticator more
28139 secure than &(plaintext)&. However, the downside is that the secret has to be
28140 available in plain text at either end.
28143 .section "Using cram_md5 as a server" "SECID176"
28144 .cindex "options" "&(cram_md5)& authenticator (server)"
28145 This authenticator has one server option, which must be set to configure the
28146 authenticator as a server:
28148 .option server_secret cram_md5 string&!! unset
28149 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(cram_md5)& authenticator"
28150 When the server receives the client's response, the user name is placed in
28151 the expansion variable &$auth1$&, and &%server_secret%& is expanded to
28152 obtain the password for that user. The server then computes the CRAM-MD5 digest
28153 that the client should have sent, and checks that it received the correct
28154 string. If the expansion of &%server_secret%& is forced to fail, authentication
28155 fails. If the expansion fails for some other reason, a temporary error code is
28156 returned to the client.
28158 For compatibility with previous releases of Exim, the user name is also placed
28159 in &$1$&. However, the use of this variables for this purpose is now
28160 deprecated, as it can lead to confusion in string expansions that also use
28161 numeric variables for other things.
28163 For example, the following authenticator checks that the user name given by the
28164 client is &"ph10"&, and if so, uses &"secret"& as the password. For any other
28165 user name, authentication fails.
28169 public_name = CRAM-MD5
28170 server_secret = ${if eq{$auth1}{ph10}{secret}fail}
28171 server_set_id = $auth1
28173 .vindex "&$authenticated_id$&"
28174 If authentication succeeds, the setting of &%server_set_id%& preserves the user
28175 name in &$authenticated_id$&. A more typical configuration might look up the
28176 secret string in a file, using the user name as the key. For example:
28180 public_name = CRAM-MD5
28181 server_secret = ${lookup{$auth1}lsearch{/etc/authpwd}\
28183 server_set_id = $auth1
28185 Note that this expansion explicitly forces failure if the lookup fails
28186 because &$auth1$& contains an unknown user name.
28188 As another example, if you wish to re-use a Cyrus SASL sasldb2 file without
28189 using the relevant libraries, you need to know the realm to specify in the
28190 lookup and then ask for the &"userPassword"& attribute for that user in that
28195 public_name = CRAM-MD5
28196 server_secret = ${lookup{$auth1:mail.example.org:userPassword}\
28197 dbmjz{/etc/sasldb2}{$value}fail}
28198 server_set_id = $auth1
28201 .section "Using cram_md5 as a client" "SECID177"
28202 .cindex "options" "&(cram_md5)& authenticator (client)"
28203 When used as a client, the &(cram_md5)& authenticator has two options:
28207 .option client_name cram_md5 string&!! "the primary host name"
28208 This string is expanded, and the result used as the user name data when
28209 computing the response to the server's challenge.
28212 .option client_secret cram_md5 string&!! unset
28213 This option must be set for the authenticator to work as a client. Its value is
28214 expanded and the result used as the secret string when computing the response.
28218 .vindex "&$host_address$&"
28219 Different user names and secrets can be used for different servers by referring
28220 to &$host$& or &$host_address$& in the options. Forced failure of either
28221 expansion string is treated as an indication that this authenticator is not
28222 prepared to handle this case. Exim moves on to the next configured client
28223 authenticator. Any other expansion failure causes Exim to give up trying to
28224 send the message to the current server.
28226 A simple example configuration of a &(cram_md5)& authenticator, using fixed
28231 public_name = CRAM-MD5
28233 client_secret = secret
28235 .ecindex IIDcramauth1
28236 .ecindex IIDcramauth2
28240 . ////////////////////////////////////////////////////////////////////////////
28241 . ////////////////////////////////////////////////////////////////////////////
28243 .chapter "The cyrus_sasl authenticator" "CHID10"
28244 .scindex IIDcyrauth1 "&(cyrus_sasl)& authenticator"
28245 .scindex IIDcyrauth2 "authenticators" "&(cyrus_sasl)&"
28246 .cindex "Cyrus" "SASL library"
28248 The code for this authenticator was provided by Matthew Byng-Maddick while
28249 at A L Digital Ltd.
28251 The &(cyrus_sasl)& authenticator provides server support for the Cyrus SASL
28252 library implementation of the RFC 2222 (&"Simple Authentication and Security
28253 Layer"&). This library supports a number of authentication mechanisms,
28254 including PLAIN and LOGIN, but also several others that Exim does not support
28255 directly. In particular, there is support for Kerberos authentication.
28257 The &(cyrus_sasl)& authenticator provides a gatewaying mechanism directly to
28258 the Cyrus interface, so if your Cyrus library can do, for example, CRAM-MD5,
28259 then so can the &(cyrus_sasl)& authenticator. By default it uses the public
28260 name of the driver to determine which mechanism to support.
28262 Where access to some kind of secret file is required, for example, in GSSAPI
28263 or CRAM-MD5, it is worth noting that the authenticator runs as the Exim
28264 user, and that the Cyrus SASL library has no way of escalating privileges
28265 by default. You may also find you need to set environment variables,
28266 depending on the driver you are using.
28268 The application name provided by Exim is &"exim"&, so various SASL options may
28269 be set in &_exim.conf_& in your SASL directory. If you are using GSSAPI for
28270 Kerberos, note that because of limitations in the GSSAPI interface,
28271 changing the server keytab might need to be communicated down to the Kerberos
28272 layer independently. The mechanism for doing so is dependent upon the Kerberos
28275 For example, for older releases of Heimdal, the environment variable KRB5_KTNAME
28276 may be set to point to an alternative keytab file. Exim will pass this
28277 variable through from its own inherited environment when started as root or the
28278 Exim user. The keytab file needs to be readable by the Exim user.
28279 With newer releases of Heimdal, a setuid Exim may cause Heimdal to discard the
28280 environment variable. In practice, for those releases, the Cyrus authenticator
28281 is not a suitable interface for GSSAPI (Kerberos) support. Instead, consider
28282 the &(heimdal_gssapi)& authenticator, described in chapter &<<CHAPheimdalgss>>&
28285 .section "Using cyrus_sasl as a server" "SECID178"
28286 The &(cyrus_sasl)& authenticator has four private options. It puts the username
28287 (on a successful authentication) into &$auth1$&. For compatibility with
28288 previous releases of Exim, the username is also placed in &$1$&. However, the
28289 use of this variable for this purpose is now deprecated, as it can lead to
28290 confusion in string expansions that also use numeric variables for other
28294 .option server_hostname cyrus_sasl string&!! "see below"
28295 This option selects the hostname that is used when communicating with the
28296 library. The default value is &`$primary_hostname`&. It is up to the underlying
28297 SASL plug-in what it does with this data.
28300 .option server_mech cyrus_sasl string "see below"
28301 This option selects the authentication mechanism this driver should use. The
28302 default is the value of the generic &%public_name%& option. This option allows
28303 you to use a different underlying mechanism from the advertised name. For
28307 driver = cyrus_sasl
28308 public_name = X-ANYTHING
28309 server_mech = CRAM-MD5
28310 server_set_id = $auth1
28313 .option server_realm cyrus_sasl string&!! unset
28314 This specifies the SASL realm that the server claims to be in.
28317 .option server_service cyrus_sasl string &`smtp`&
28318 This is the SASL service that the server claims to implement.
28321 For straightforward cases, you do not need to set any of the authenticator's
28322 private options. All you need to do is to specify an appropriate mechanism as
28323 the public name. Thus, if you have a SASL library that supports CRAM-MD5 and
28324 PLAIN, you could have two authenticators as follows:
28327 driver = cyrus_sasl
28328 public_name = CRAM-MD5
28329 server_set_id = $auth1
28332 driver = cyrus_sasl
28333 public_name = PLAIN
28334 server_set_id = $auth2
28336 Cyrus SASL does implement the LOGIN authentication method, even though it is
28337 not a standard method. It is disabled by default in the source distribution,
28338 but it is present in many binary distributions.
28339 .ecindex IIDcyrauth1
28340 .ecindex IIDcyrauth2
28345 . ////////////////////////////////////////////////////////////////////////////
28346 . ////////////////////////////////////////////////////////////////////////////
28347 .chapter "The dovecot authenticator" "CHAPdovecot"
28348 .scindex IIDdcotauth1 "&(dovecot)& authenticator"
28349 .scindex IIDdcotauth2 "authenticators" "&(dovecot)&"
28350 This authenticator is an interface to the authentication facility of the
28351 Dovecot 2 POP/IMAP server, which can support a number of authentication methods.
28352 Note that Dovecot must be configured to use auth-client not auth-userdb.
28353 If you are using Dovecot to authenticate POP/IMAP clients, it might be helpful
28354 to use the same mechanisms for SMTP authentication. This is a server
28355 authenticator only. There is only one option:
28357 .option server_socket dovecot string unset
28359 This option must specify the UNIX socket that is the interface to Dovecot
28360 authentication. The &%public_name%& option must specify an authentication
28361 mechanism that Dovecot is configured to support. You can have several
28362 authenticators for different mechanisms. For example:
28366 public_name = PLAIN
28367 server_socket = /var/run/dovecot/auth-client
28368 server_set_id = $auth1
28373 server_socket = /var/run/dovecot/auth-client
28374 server_set_id = $auth1
28376 If the SMTP connection is encrypted, or if &$sender_host_address$& is equal to
28377 &$received_ip_address$& (that is, the connection is local), the &"secured"&
28378 option is passed in the Dovecot authentication command. If, for a TLS
28379 connection, a client certificate has been verified, the &"valid-client-cert"&
28380 option is passed. When authentication succeeds, the identity of the user
28381 who authenticated is placed in &$auth1$&.
28383 The Dovecot configuration to match the above will look
28386 conf.d/10-master.conf :-
28391 unix_listener auth-client {
28398 conf.d/10-auth.conf :-
28400 auth_mechanisms = plain login ntlm
28403 .ecindex IIDdcotauth1
28404 .ecindex IIDdcotauth2
28407 . ////////////////////////////////////////////////////////////////////////////
28408 . ////////////////////////////////////////////////////////////////////////////
28409 .chapter "The gsasl authenticator" "CHAPgsasl"
28410 .scindex IIDgsaslauth1 "&(gsasl)& authenticator"
28411 .scindex IIDgsaslauth2 "authenticators" "&(gsasl)&"
28412 .cindex "authentication" "GNU SASL"
28413 .cindex "authentication" "SASL"
28414 .cindex "authentication" "EXTERNAL"
28415 .cindex "authentication" "ANONYMOUS"
28416 .cindex "authentication" "PLAIN"
28417 .cindex "authentication" "LOGIN"
28418 .cindex "authentication" "DIGEST-MD5"
28419 .cindex "authentication" "CRAM-MD5"
28420 .cindex "authentication" "SCRAM family"
28421 The &(gsasl)& authenticator provides integration for the GNU SASL
28422 library and the mechanisms it provides. This is new as of the 4.80 release
28423 and there are a few areas where the library does not let Exim smoothly
28424 scale to handle future authentication mechanisms, so no guarantee can be
28425 made that any particular new authentication mechanism will be supported
28426 without code changes in Exim.
28428 The library is expected to add support in an upcoming
28429 realease for the SCRAM-SHA-256 method.
28430 The macro _HAVE_AUTH_GSASL_SCRAM_SHA_256 will be defined
28433 To see the list of mechanisms supported by the library run Exim with "auth" debug
28434 enabled and look for a line containing "GNU SASL supports".
28435 Note however that some may not have been tested from Exim.
28438 .option client_authz gsasl string&!! unset
28439 This option can be used to supply an &'authorization id'&
28440 which is different to the &'authentication_id'& provided
28441 by &%client_username%& option.
28442 If unset or (after expansion) empty it is not used,
28443 which is the common case.
28445 .option client_channelbinding gsasl boolean false
28446 See &%server_channelbinding%& below.
28448 .option client_password gsasl string&!! unset
28449 This option is exapanded before use, and should result in
28450 the password to be used, in clear.
28452 .option client_username gsasl string&!! unset
28453 This option is exapanded before use, and should result in
28454 the account name to be used.
28457 .option client_spassword gsasl string&!! unset
28458 This option is only supported for library versions 1.9.1 and greater.
28459 The macro _HAVE_AUTH_GSASL_SCRAM_S_KEY will be defined when this is so.
28461 If a SCRAM mechanism is being used and this option is set
28462 and correctly sized
28463 it is used in preference to &%client_password%&.
28464 The value after expansion should be
28465 a 40 (for SHA-1) or 64 (for SHA-256) character string
28466 with the PBKDF2-prepared password, hex-encoded.
28468 Note that this value will depend on the salt and iteration-count
28469 supplied by the server.
28470 The option is expanded before use.
28471 During the expansion &$auth1$& is set with the client username,
28472 &$auth2$& with the iteration count, and
28473 &$auth3$& with the salt.
28475 The intent of this option
28476 is to support clients that can cache thes salted password
28477 to save on recalculation costs.
28478 The cache lookup should return an unusable value
28479 (eg. an empty string)
28480 if the salt or iteration count has changed
28482 If the authentication succeeds then the above variables are set,
28483 .vindex "&$auth4$&"
28484 plus the calculated salted password value value in &$auth4$&,
28485 during the expansion of the &%client_set_id%& option.
28486 A side-effect of this expansion can be used to prime the cache.
28489 .option server_channelbinding gsasl boolean false
28490 Some authentication mechanisms are able to use external context at both ends
28491 of the session to bind the authentication to that context, and fail the
28492 authentication process if that context differs. Specifically, some TLS
28493 ciphersuites can provide identifying information about the cryptographic
28496 This should have meant that certificate identity and verification becomes a
28497 non-issue, as a man-in-the-middle attack will cause the correct client and
28498 server to see different identifiers and authentication will fail.
28501 only usable by mechanisms which support "channel binding"; at time of
28502 writing, that's the SCRAM family.
28503 When using this feature the "-PLUS" variants of the method names need to be used.
28505 This defaults off to ensure smooth upgrade across Exim releases, in case
28506 this option causes some clients to start failing. Some future release
28507 of Exim might have switched the default to be true.
28509 . However, Channel Binding in TLS has proven to be vulnerable in current versions.
28510 . Do not plan to rely upon this feature for security, ever, without consulting
28511 . with a subject matter expert (a cryptographic engineer).
28513 This option was deprecated in previous releases due to doubts over
28514 the "Triple Handshake" vulnerability.
28515 Exim takes suitable precausions (requiring Extended Master Secret if TLS
28516 Session Resumption was used) for safety.
28519 .option server_hostname gsasl string&!! "see below"
28520 This option selects the hostname that is used when communicating with the
28521 library. The default value is &`$primary_hostname`&.
28522 Some mechanisms will use this data.
28525 .option server_mech gsasl string "see below"
28526 This option selects the authentication mechanism this driver should use. The
28527 default is the value of the generic &%public_name%& option. This option allows
28528 you to use a different underlying mechanism from the advertised name. For
28533 public_name = X-ANYTHING
28534 server_mech = CRAM-MD5
28535 server_set_id = $auth1
28539 .option server_password gsasl string&!! unset
28540 Various mechanisms need access to the cleartext password on the server, so
28541 that proof-of-possession can be demonstrated on the wire, without sending
28542 the password itself.
28544 The data available for lookup varies per mechanism.
28545 In all cases, &$auth1$& is set to the &'authentication id'&.
28546 The &$auth2$& variable will always be the &'authorization id'& (&'authz'&)
28547 if available, else the empty string.
28548 The &$auth3$& variable will always be the &'realm'& if available,
28549 else the empty string.
28551 A forced failure will cause authentication to defer.
28553 If using this option, it may make sense to set the &%server_condition%&
28554 option to be simply "true".
28557 .option server_realm gsasl string&!! unset
28558 This specifies the SASL realm that the server claims to be in.
28559 Some mechanisms will use this data.
28562 .option server_scram_iter gsasl string&!! 4096
28563 This option provides data for the SCRAM family of mechanisms.
28564 The &$auth1$&, &$auth2$& and &$auth3$& variables are available
28565 when this option is expanded.
28567 The result of expansion should be a decimal number,
28568 and represents both a lower-bound on the security, and
28569 a compute cost factor imposed on the client
28570 (if it does not cache results, or the server changes
28571 either the iteration count or the salt).
28572 A minimum value of 4096 is required by the standards
28573 for all current SCRAM mechanism variants.
28575 .option server_scram_salt gsasl string&!! unset
28576 This option provides data for the SCRAM family of mechanisms.
28577 The &$auth1$&, &$auth2$& and &$auth3$& variables are available
28578 when this option is expanded.
28579 The value should be a base64-encoded string,
28580 of random data typically 4-to-16 bytes long.
28581 If unset or empty after expansion the library will provides a value for the
28582 protocol conversation.
28585 .option server_key gsasl string&!! unset
28586 .option server_skey gsasl string&!! unset
28587 These options can be used for the SCRAM family of mechanisms
28588 to provide stored information related to a password,
28589 the storage of which is preferable to plaintext.
28591 &%server_key%& is the value defined in the SCRAM standards as ServerKey;
28592 &%server_skey%& is StoredKey.
28594 They are only available for version 1.9.0 (or later) of the gsasl library.
28595 When this is so, the macros
28596 _OPT_AUTHENTICATOR_GSASL_SERVER_KEY
28597 and _HAVE_AUTH_GSASL_SCRAM_S_KEY
28600 The &$authN$& variables are available when these options are expanded.
28602 If set, the results of expansion should for each
28603 should be a 28 (for SHA-1) or 44 (for SHA-256) character string
28604 of base64-coded data, and will be used in preference to the
28605 &%server_password%& option.
28606 If unset or not of the right length, &%server_password%& will be used.
28608 The libgsasl library release includes a utility &'gsasl'& which can be used
28609 to generate these values.
28612 .option server_service gsasl string &`smtp`&
28613 This is the SASL service that the server claims to implement.
28614 Some mechanisms will use this data.
28617 .section "&(gsasl)& auth variables" "SECTgsaslauthvar"
28618 .vindex "&$auth1$&, &$auth2$&, etc"
28619 These may be set when evaluating specific options, as detailed above.
28620 They will also be set when evaluating &%server_condition%&.
28622 Unless otherwise stated below, the &(gsasl)& integration will use the following
28623 meanings for these variables:
28626 .vindex "&$auth1$&"
28627 &$auth1$&: the &'authentication id'&
28629 .vindex "&$auth2$&"
28630 &$auth2$&: the &'authorization id'&
28632 .vindex "&$auth3$&"
28633 &$auth3$&: the &'realm'&
28636 On a per-mechanism basis:
28639 .cindex "authentication" "EXTERNAL"
28640 EXTERNAL: only &$auth1$& is set, to the possibly empty &'authorization id'&;
28641 the &%server_condition%& option must be present.
28643 .cindex "authentication" "ANONYMOUS"
28644 ANONYMOUS: only &$auth1$& is set, to the possibly empty &'anonymous token'&;
28645 the &%server_condition%& option must be present.
28647 .cindex "authentication" "GSSAPI"
28648 GSSAPI: &$auth1$& will be set to the &'GSSAPI Display Name'&;
28649 &$auth2$& will be set to the &'authorization id'&,
28650 the &%server_condition%& option must be present.
28653 An &'anonymous token'& is something passed along as an unauthenticated
28654 identifier; this is analogous to FTP anonymous authentication passing an
28655 email address, or software-identifier@, as the "password".
28658 An example showing the password having the realm specified in the callback
28659 and demonstrating a Cyrus SASL to GSASL migration approach is:
28661 gsasl_cyrusless_crammd5:
28663 public_name = CRAM-MD5
28664 server_realm = imap.example.org
28665 server_password = ${lookup{$auth1:$auth3:userPassword}\
28666 dbmjz{/etc/sasldb2}{$value}fail}
28667 server_set_id = ${quote:$auth1}
28668 server_condition = yes
28672 . ////////////////////////////////////////////////////////////////////////////
28673 . ////////////////////////////////////////////////////////////////////////////
28675 .chapter "The heimdal_gssapi authenticator" "CHAPheimdalgss"
28676 .scindex IIDheimdalgssauth1 "&(heimdal_gssapi)& authenticator"
28677 .scindex IIDheimdalgssauth2 "authenticators" "&(heimdal_gssapi)&"
28678 .cindex "authentication" "GSSAPI"
28679 .cindex "authentication" "Kerberos"
28680 The &(heimdal_gssapi)& authenticator provides server integration for the
28681 Heimdal GSSAPI/Kerberos library, permitting Exim to set a keytab pathname
28684 .option server_hostname heimdal_gssapi string&!! "see below"
28685 This option selects the hostname that is used, with &%server_service%&,
28686 for constructing the GSS server name, as a &'GSS_C_NT_HOSTBASED_SERVICE'&
28687 identifier. The default value is &`$primary_hostname`&.
28689 .option server_keytab heimdal_gssapi string&!! unset
28690 If set, then Heimdal will not use the system default keytab (typically
28691 &_/etc/krb5.keytab_&) but instead the pathname given in this option.
28692 The value should be a pathname, with no &"file:"& prefix.
28694 .option server_service heimdal_gssapi string&!! "smtp"
28695 This option specifies the service identifier used, in conjunction with
28696 &%server_hostname%&, for building the identifier for finding credentials
28700 .section "&(heimdal_gssapi)& auth variables" "SECTheimdalgssauthvar"
28701 Beware that these variables will typically include a realm, thus will appear
28702 to be roughly like an email address already. The &'authzid'& in &$auth2$& is
28703 not verified, so a malicious client can set it to anything.
28705 The &$auth1$& field should be safely trustable as a value from the Key
28706 Distribution Center. Note that these are not quite email addresses.
28707 Each identifier is for a role, and so the left-hand-side may include a
28708 role suffix. For instance, &"joe/admin@EXAMPLE.ORG"&.
28710 .vindex "&$auth1$&, &$auth2$&, etc"
28712 .vindex "&$auth1$&"
28713 &$auth1$&: the &'authentication id'&, set to the GSS Display Name.
28715 .vindex "&$auth2$&"
28716 &$auth2$&: the &'authorization id'&, sent within SASL encapsulation after
28717 authentication. If that was empty, this will also be set to the
28722 . ////////////////////////////////////////////////////////////////////////////
28723 . ////////////////////////////////////////////////////////////////////////////
28725 .chapter "The spa authenticator" "CHAPspa"
28726 .scindex IIDspaauth1 "&(spa)& authenticator"
28727 .scindex IIDspaauth2 "authenticators" "&(spa)&"
28728 .cindex "authentication" "Microsoft Secure Password"
28729 .cindex "authentication" "NTLM"
28730 .cindex "Microsoft Secure Password Authentication"
28731 .cindex "NTLM authentication"
28732 The &(spa)& authenticator provides client support for Microsoft's &'Secure
28733 Password Authentication'& mechanism,
28734 which is also sometimes known as NTLM (NT LanMan). The code for client side of
28735 this authenticator was contributed by Marc Prud'hommeaux, and much of it is
28736 taken from the Samba project (&url(https://www.samba.org/)). The code for the
28737 server side was subsequently contributed by Tom Kistner. The mechanism works as
28741 After the AUTH command has been accepted, the client sends an SPA
28742 authentication request based on the user name and optional domain.
28744 The server sends back a challenge.
28746 The client builds a challenge response which makes use of the user's password
28747 and sends it to the server, which then accepts or rejects it.
28750 Encryption is used to protect the password in transit.
28754 .section "Using spa as a server" "SECID179"
28755 .cindex "options" "&(spa)& authenticator (server)"
28756 The &(spa)& authenticator has just one server option:
28758 .option server_password spa string&!! unset
28759 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(spa)& authenticator"
28760 This option is expanded, and the result must be the cleartext password for the
28761 authenticating user, whose name is at this point in &$auth1$&. For
28762 compatibility with previous releases of Exim, the user name is also placed in
28763 &$1$&. However, the use of this variable for this purpose is now deprecated, as
28764 it can lead to confusion in string expansions that also use numeric variables
28765 for other things. For example:
28770 server_password = \
28771 ${lookup{$auth1}lsearch{/etc/exim/spa_clearpass}{$value}fail}
28773 If the expansion is forced to fail, authentication fails. Any other expansion
28774 failure causes a temporary error code to be returned.
28780 .section "Using spa as a client" "SECID180"
28781 .cindex "options" "&(spa)& authenticator (client)"
28782 The &(spa)& authenticator has the following client options:
28786 .option client_domain spa string&!! unset
28787 This option specifies an optional domain for the authentication.
28790 .option client_password spa string&!! unset
28791 This option specifies the user's password, and must be set.
28794 .option client_username spa string&!! unset
28795 This option specifies the user name, and must be set. Here is an example of a
28796 configuration of this authenticator for use with the mail servers at
28802 client_username = msn/msn_username
28803 client_password = msn_plaintext_password
28804 client_domain = DOMAIN_OR_UNSET
28806 .ecindex IIDspaauth1
28807 .ecindex IIDspaauth2
28813 . ////////////////////////////////////////////////////////////////////////////
28814 . ////////////////////////////////////////////////////////////////////////////
28816 .chapter "The external authenticator" "CHAPexternauth"
28817 .scindex IIDexternauth1 "&(external)& authenticator"
28818 .scindex IIDexternauth2 "authenticators" "&(external)&"
28819 .cindex "authentication" "Client Certificate"
28820 .cindex "authentication" "X509"
28821 .cindex "Certificate-based authentication"
28822 The &(external)& authenticator provides support for
28823 authentication based on non-SMTP information.
28824 The specification is in RFC 4422 Appendix A
28825 (&url(https://tools.ietf.org/html/rfc4422)).
28826 It is only a transport and negotiation mechanism;
28827 the process of authentication is entirely controlled
28828 by the server configuration.
28830 The client presents an identity in-clear.
28831 It is probably wise for a server to only advertise,
28832 and for clients to only attempt,
28833 this authentication method on a secure (eg. under TLS) connection.
28835 One possible use, compatible with the
28836 K-9 Mail Android client (&url(https://k9mail.github.io/)),
28837 is for using X509 client certificates.
28839 It thus overlaps in function with the TLS authenticator
28840 (see &<<CHAPtlsauth>>&)
28841 but is a full SMTP SASL authenticator
28842 rather than being implicit for TLS-connection carried
28843 client certificates only.
28845 The examples and discussion in this chapter assume that
28846 client-certificate authentication is being done.
28848 The client must present a certificate,
28849 for which it must have been requested via the
28850 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& main options
28851 (see &<<CHAPTLS>>&).
28852 For authentication to be effective the certificate should be
28853 verifiable against a trust-anchor certificate known to the server.
28855 .section "External options" "SECTexternsoptions"
28856 .cindex "options" "&(external)& authenticator (server)"
28857 The &(external)& authenticator has two server options:
28859 .option server_param2 external string&!! unset
28860 .option server_param3 external string&!! unset
28861 .cindex "variables (&$auth1$& &$auth2$& etc)" "in &(external)& authenticator"
28862 These options are expanded before the &%server_condition%& option
28863 and the result are placed in &$auth2$& and &$auth3$& resectively.
28864 If the expansion is forced to fail, authentication fails. Any other expansion
28865 failure causes a temporary error code to be returned.
28867 They can be used to clarify the coding of a complex &%server_condition%&.
28869 .section "Using external in a server" "SECTexternserver"
28870 .cindex "AUTH" "in &(external)& authenticator"
28871 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
28872 "in &(external)& authenticator"
28873 .vindex "&$auth1$&, &$auth2$&, etc"
28874 .cindex "base64 encoding" "in &(external)& authenticator"
28876 When running as a server, &(external)& performs the authentication test by
28877 expanding a string. The data sent by the client with the AUTH command, or in
28878 response to subsequent prompts, is base64 encoded, and so may contain any byte
28879 values when decoded. The decoded value is treated as
28880 an identity for authentication and
28881 placed in the expansion variable &$auth1$&.
28883 For compatibility with previous releases of Exim, the value is also placed in
28884 the expansion variable &$1$&. However, the use of this
28885 variable for this purpose is now deprecated, as it can lead to confusion in
28886 string expansions that also use them for other things.
28888 .vindex "&$authenticated_id$&"
28889 Once an identity has been received,
28890 &%server_condition%& is expanded. If the expansion is forced to fail,
28891 authentication fails. Any other expansion failure causes a temporary error code
28892 to be returned. If the result of a successful expansion is an empty string,
28893 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
28894 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
28895 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
28896 For any other result, a temporary error code is returned, with the expanded
28897 string as the error text.
28901 ext_ccert_san_mail:
28903 public_name = EXTERNAL
28905 server_advertise_condition = $tls_in_certificate_verified
28906 server_param2 = ${certextract {subj_altname,mail,>:} \
28907 {$tls_in_peercert}}
28908 server_condition = ${if forany {$auth2} \
28909 {eq {$item}{$auth1}}}
28910 server_set_id = $auth1
28912 This accepts a client certificate that is verifiable against any
28913 of your configured trust-anchors
28914 (which usually means the full set of public CAs)
28915 and which has a mail-SAN matching the claimed identity sent by the client.
28917 &*Note*&: up to TLS1.2, the client cert is on the wire in-clear, including the SAN.
28918 The account name is therefore guessable by an opponent.
28919 TLS 1.3 protects both server and client certificates, and is not vulnerable
28923 .section "Using external in a client" "SECTexternclient"
28924 .cindex "options" "&(external)& authenticator (client)"
28925 The &(external)& authenticator has one client option:
28927 .option client_send external string&!! unset
28928 This option is expanded and sent with the AUTH command as the
28929 identity being asserted.
28935 public_name = EXTERNAL
28937 client_condition = ${if !eq{$tls_out_cipher}{}}
28938 client_send = myaccount@smarthost.example.net
28942 .ecindex IIDexternauth1
28943 .ecindex IIDexternauth2
28949 . ////////////////////////////////////////////////////////////////////////////
28950 . ////////////////////////////////////////////////////////////////////////////
28952 .chapter "The tls authenticator" "CHAPtlsauth"
28953 .scindex IIDtlsauth1 "&(tls)& authenticator"
28954 .scindex IIDtlsauth2 "authenticators" "&(tls)&"
28955 .cindex "authentication" "Client Certificate"
28956 .cindex "authentication" "X509"
28957 .cindex "Certificate-based authentication"
28958 The &(tls)& authenticator provides server support for
28959 authentication based on client certificates.
28961 It is not an SMTP authentication mechanism and is not
28962 advertised by the server as part of the SMTP EHLO response.
28963 It is an Exim authenticator in the sense that it affects
28964 the protocol element of the log line, can be tested for
28965 by the &%authenticated%& ACL condition, and can set
28966 the &$authenticated_id$& variable.
28968 The client must present a verifiable certificate,
28969 for which it must have been requested via the
28970 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& main options
28971 (see &<<CHAPTLS>>&).
28973 If an authenticator of this type is configured it is
28974 run before any SMTP-level communication is done,
28975 and can authenticate the connection.
28976 If it does, SMTP authentication is not offered.
28978 A maximum of one authenticator of this type may be present.
28981 .cindex "options" "&(tls)& authenticator (server)"
28982 The &(tls)& authenticator has three server options:
28984 .option server_param1 tls string&!! unset
28985 .cindex "variables (&$auth1$& &$auth2$& etc)" "in &(tls)& authenticator"
28986 This option is expanded after the TLS negotiation and
28987 the result is placed in &$auth1$&.
28988 If the expansion is forced to fail, authentication fails. Any other expansion
28989 failure causes a temporary error code to be returned.
28991 .option server_param2 tls string&!! unset
28992 .option server_param3 tls string&!! unset
28993 As above, for &$auth2$& and &$auth3$&.
28995 &%server_param1%& may also be spelled &%server_param%&.
29002 server_param1 = ${certextract {subj_altname,mail,>:} \
29003 {$tls_in_peercert}}
29004 server_condition = ${if and { {eq{$tls_in_certificate_verified}{1}} \
29007 {${lookup ldap{ldap:///\
29008 mailname=${quote_ldap_dn:${lc:$item}},\
29009 ou=users,LDAP_DC?mailid} {$value}{0} \
29011 server_set_id = ${if = {1}{${listcount:$auth1}} {$auth1}{}}
29013 This accepts a client certificate that is verifiable against any
29014 of your configured trust-anchors
29015 (which usually means the full set of public CAs)
29016 and which has a SAN with a good account name.
29018 Note that, up to TLS1.2, the client cert is on the wire in-clear, including the SAN,
29019 The account name is therefore guessable by an opponent.
29020 TLS 1.3 protects both server and client certificates, and is not vulnerable
29022 Likewise, a traditional plaintext SMTP AUTH done inside TLS is not.
29024 . An alternative might use
29026 . server_param1 = ${sha256:$tls_in_peercert}
29028 . to require one of a set of specific certs that define a given account
29029 . (the verification is still required, but mostly irrelevant).
29030 . This would help for per-device use.
29032 . However, for the future we really need support for checking a
29033 . user cert in LDAP - which probably wants a base-64 DER.
29035 .ecindex IIDtlsauth1
29036 .ecindex IIDtlsauth2
29039 Note that because authentication is traditionally an SMTP operation,
29040 the &%authenticated%& ACL condition cannot be used in
29041 a connect- or helo-ACL.
29045 . ////////////////////////////////////////////////////////////////////////////
29046 . ////////////////////////////////////////////////////////////////////////////
29048 .chapter "Encrypted SMTP connections using TLS/SSL" "CHAPTLS" &&&
29049 "Encrypted SMTP connections"
29050 .scindex IIDencsmtp1 "encryption" "on SMTP connection"
29051 .scindex IIDencsmtp2 "SMTP" "encryption"
29052 .cindex "TLS" "on SMTP connection"
29055 Support for TLS (Transport Layer Security), formerly known as SSL (Secure
29056 Sockets Layer), is implemented by making use of the OpenSSL library or the
29057 GnuTLS library (Exim requires GnuTLS release 1.0 or later). There is no
29058 cryptographic code in the Exim distribution itself for implementing TLS. In
29059 order to use this feature you must install OpenSSL or GnuTLS, and then build a
29060 version of Exim that includes TLS support (see section &<<SECTinctlsssl>>&).
29061 You also need to understand the basic concepts of encryption at a managerial
29062 level, and in particular, the way that public keys, private keys, and
29063 certificates are used.
29065 RFC 3207 defines how SMTP connections can make use of encryption. Once a
29066 connection is established, the client issues a STARTTLS command. If the
29067 server accepts this, the client and the server negotiate an encryption
29068 mechanism. If the negotiation succeeds, the data that subsequently passes
29069 between them is encrypted.
29071 Exim's ACLs can detect whether the current SMTP session is encrypted or not,
29072 and if so, what cipher suite is in use, whether the client supplied a
29073 certificate, and whether or not that certificate was verified. This makes it
29074 possible for an Exim server to deny or accept certain commands based on the
29077 &*Warning*&: Certain types of firewall and certain anti-virus products can
29078 disrupt TLS connections. You need to turn off SMTP scanning for these products
29079 in order to get TLS to work.
29083 .section "Support for the &""submissions""& (aka &""ssmtp""& and &""smtps""&) protocol" &&&
29085 .cindex "submissions protocol"
29086 .cindex "ssmtp protocol"
29087 .cindex "smtps protocol"
29088 .cindex "SMTP" "submissions protocol"
29089 .cindex "SMTP" "ssmtp protocol"
29090 .cindex "SMTP" "smtps protocol"
29091 The history of port numbers for TLS in SMTP is a little messy and has been
29092 contentious. As of RFC 8314, the common practice of using the historically
29093 allocated port 465 for "email submission but with TLS immediately upon connect
29094 instead of using STARTTLS" is officially blessed by the IETF, and recommended
29095 by them in preference to STARTTLS.
29097 The name originally assigned to the port was &"ssmtp"& or &"smtps"&, but as
29098 clarity emerged over the dual roles of SMTP, for MX delivery and Email
29099 Submission, nomenclature has shifted. The modern name is now &"submissions"&.
29101 This approach was, for a while, officially abandoned when encrypted SMTP was
29102 standardized, but many clients kept using it, even as the TCP port number was
29103 reassigned for other use.
29104 Thus you may encounter guidance claiming that you shouldn't enable use of
29106 In practice, a number of mail-clients have only ever supported submissions,
29107 not submission with STARTTLS upgrade.
29108 Ideally, offer both submission (587) and submissions (465) service.
29110 Exim supports TLS-on-connect by means of the &%tls_on_connect_ports%&
29111 global option. Its value must be a list of port numbers;
29112 the most common use is expected to be:
29114 tls_on_connect_ports = 465
29116 The port numbers specified by this option apply to all SMTP connections, both
29117 via the daemon and via &'inetd'&. You still need to specify all the ports that
29118 the daemon uses (by setting &%daemon_smtp_ports%& or &%local_interfaces%& or
29119 the &%-oX%& command line option) because &%tls_on_connect_ports%& does not add
29120 an extra port &-- rather, it specifies different behaviour on a port that is
29123 There is also a &%-tls-on-connect%& command line option. This overrides
29124 &%tls_on_connect_ports%&; it forces the TLS-only behaviour for all ports.
29131 .section "OpenSSL vs GnuTLS" "SECTopenvsgnu"
29132 .cindex "TLS" "OpenSSL &'vs'& GnuTLS"
29133 TLS is supported in Exim using either the OpenSSL or GnuTLS library.
29134 To build Exim to use OpenSSL you need to set
29140 To build Exim to use GnuTLS, you need to set
29146 You must also set TLS_LIBS and TLS_INCLUDE appropriately, so that the
29147 include files and libraries for GnuTLS can be found.
29149 There are some differences in usage when using GnuTLS instead of OpenSSL:
29152 The &%tls_verify_certificates%& option
29153 cannot be the path of a directory
29154 for GnuTLS versions before 3.3.6
29155 (for later versions, or OpenSSL, it can be either).
29157 The default value for &%tls_dhparam%& differs for historical reasons.
29159 .vindex "&$tls_in_peerdn$&"
29160 .vindex "&$tls_out_peerdn$&"
29161 Distinguished Name (DN) strings reported by the OpenSSL library use a slash for
29162 separating fields; GnuTLS uses commas, in accordance with RFC 2253. This
29163 affects the value of the &$tls_in_peerdn$& and &$tls_out_peerdn$& variables.
29165 OpenSSL identifies cipher suites using hyphens as separators, for example:
29166 DES-CBC3-SHA. GnuTLS historically used underscores, for example:
29167 RSA_ARCFOUR_SHA. What is more, OpenSSL complains if underscores are present
29168 in a cipher list. To make life simpler, Exim changes underscores to hyphens
29169 for OpenSSL and passes the string unchanged to GnuTLS (expecting the library
29170 to handle its own older variants) when processing lists of cipher suites in the
29171 &%tls_require_ciphers%& options (the global option and the &(smtp)& transport
29174 The &%tls_require_ciphers%& options operate differently, as described in the
29175 sections &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
29177 The &%tls_dh_min_bits%& SMTP transport option is only honoured by GnuTLS.
29178 When using OpenSSL, this option is ignored.
29179 (If an API is found to let OpenSSL be configured in this way,
29180 let the Exim Maintainers know and we'll likely use it).
29182 With GnuTLS, if an explicit list is used for the &%tls_privatekey%& main option
29183 main option, it must be ordered to match the &%tls_certificate%& list.
29185 Some other recently added features may only be available in one or the other.
29186 This should be documented with the feature. If the documentation does not
29187 explicitly state that the feature is infeasible in the other TLS
29188 implementation, then patches are welcome.
29190 The output from "exim -bV" will show which (if any) support was included
29192 Also, the macro "_HAVE_OPENSSL" or "_HAVE_GNUTLS" will be defined.
29196 .section "GnuTLS parameter computation" "SECTgnutlsparam"
29197 This section only applies if &%tls_dhparam%& is set to &`historic`& or to
29198 an explicit path; if the latter, then the text about generation still applies,
29199 but not the chosen filename.
29200 By default, as of Exim 4.80 a hard-coded D-H prime is used.
29201 See the documentation of &%tls_dhparam%& for more information.
29203 GnuTLS uses D-H parameters that may take a substantial amount of time
29204 to compute. It is unreasonable to re-compute them for every TLS session.
29205 Therefore, Exim keeps this data in a file in its spool directory, called
29206 &_gnutls-params-NNNN_& for some value of NNNN, corresponding to the number
29208 The file is owned by the Exim user and is readable only by
29209 its owner. Every Exim process that start up GnuTLS reads the D-H
29210 parameters from this file. If the file does not exist, the first Exim process
29211 that needs it computes the data and writes it to a temporary file which is
29212 renamed once it is complete. It does not matter if several Exim processes do
29213 this simultaneously (apart from wasting a few resources). Once a file is in
29214 place, new Exim processes immediately start using it.
29216 For maximum security, the parameters that are stored in this file should be
29217 recalculated periodically, the frequency depending on your paranoia level.
29218 If you are avoiding using the fixed D-H primes published in RFCs, then you
29219 are concerned about some advanced attacks and will wish to do this; if you do
29220 not regenerate then you might as well stick to the standard primes.
29222 Arranging this is easy in principle; just delete the file when you want new
29223 values to be computed. However, there may be a problem. The calculation of new
29224 parameters needs random numbers, and these are obtained from &_/dev/random_&.
29225 If the system is not very active, &_/dev/random_& may delay returning data
29226 until enough randomness (entropy) is available. This may cause Exim to hang for
29227 a substantial amount of time, causing timeouts on incoming connections.
29229 The solution is to generate the parameters externally to Exim. They are stored
29230 in &_gnutls-params-N_& in PEM format, which means that they can be
29231 generated externally using the &(certtool)& command that is part of GnuTLS.
29233 To replace the parameters with new ones, instead of deleting the file
29234 and letting Exim re-create it, you can generate new parameters using
29235 &(certtool)& and, when this has been done, replace Exim's cache file by
29236 renaming. The relevant commands are something like this:
29239 [ look for file; assume gnutls-params-2236 is the most recent ]
29242 # chown exim:exim new-params
29243 # chmod 0600 new-params
29244 # certtool --generate-dh-params --bits 2236 >>new-params
29245 # openssl dhparam -noout -text -in new-params | head
29246 [ check the first line, make sure it's not more than 2236;
29247 if it is, then go back to the start ("rm") and repeat
29248 until the size generated is at most the size requested ]
29249 # chmod 0400 new-params
29250 # mv new-params gnutls-params-2236
29252 If Exim never has to generate the parameters itself, the possibility of
29253 stalling is removed.
29255 The filename changed in Exim 4.80, to gain the -bits suffix. The value which
29256 Exim will choose depends upon the version of GnuTLS in use. For older GnuTLS,
29257 the value remains hard-coded in Exim as 1024. As of GnuTLS 2.12.x, there is
29258 a way for Exim to ask for the "normal" number of bits for D-H public-key usage,
29259 and Exim does so. This attempt to remove Exim from TLS policy decisions
29260 failed, as GnuTLS 2.12 returns a value higher than the current hard-coded limit
29261 of the NSS library. Thus Exim gains the &%tls_dh_max_bits%& global option,
29262 which applies to all D-H usage, client or server. If the value returned by
29263 GnuTLS is greater than &%tls_dh_max_bits%& then the value will be clamped down
29264 to &%tls_dh_max_bits%&. The default value has been set at the current NSS
29265 limit, which is still much higher than Exim historically used.
29267 The filename and bits used will change as the GnuTLS maintainers change the
29268 value for their parameter &`GNUTLS_SEC_PARAM_NORMAL`&, as clamped by
29269 &%tls_dh_max_bits%&. At the time of writing (mid 2012), GnuTLS 2.12 recommends
29270 2432 bits, while NSS is limited to 2236 bits.
29272 In fact, the requested value will be *lower* than &%tls_dh_max_bits%&, to
29273 increase the chance of the generated prime actually being within acceptable
29274 bounds, as GnuTLS has been observed to overshoot. Note the check step in the
29275 procedure above. There is no sane procedure available to Exim to double-check
29276 the size of the generated prime, so it might still be too large.
29279 .section "Requiring specific ciphers in OpenSSL" "SECTreqciphssl"
29280 .cindex "TLS" "requiring specific ciphers (OpenSSL)"
29281 .oindex "&%tls_require_ciphers%&" "OpenSSL"
29282 There is a function in the OpenSSL library that can be passed a list of cipher
29283 suites before the cipher negotiation takes place. This specifies which ciphers
29284 are acceptable for TLS versions prior to 1.3.
29285 The list is colon separated and may contain names like
29286 DES-CBC3-SHA. Exim passes the expanded value of &%tls_require_ciphers%&
29287 directly to this function call.
29288 Many systems will install the OpenSSL manual-pages, so you may have
29289 &'ciphers(1)'& available to you.
29290 The following quotation from the OpenSSL
29291 documentation specifies what forms of item are allowed in the cipher string:
29294 It can consist of a single cipher suite such as RC4-SHA.
29296 It can represent a list of cipher suites containing a certain algorithm,
29297 or cipher suites of a certain type. For example SHA1 represents all
29298 ciphers suites using the digest algorithm SHA1 and SSLv3 represents all
29301 Lists of cipher suites can be combined in a single cipher string using
29302 the + character. This is used as a logical and operation. For example
29303 SHA1+DES represents all cipher suites containing the SHA1 and the DES
29307 Each cipher string can be optionally preceded by one of the characters &`!`&,
29310 If &`!`& is used, the ciphers are permanently deleted from the list. The
29311 ciphers deleted can never reappear in the list even if they are explicitly
29314 If &`-`& is used, the ciphers are deleted from the list, but some or all
29315 of the ciphers can be added again by later options.
29317 If &`+`& is used, the ciphers are moved to the end of the list. This
29318 option does not add any new ciphers; it just moves matching existing ones.
29321 If none of these characters is present, the string is interpreted as
29322 a list of ciphers to be appended to the current preference list. If the list
29323 includes any ciphers already present they will be ignored: that is, they will
29324 not be moved to the end of the list.
29327 The OpenSSL &'ciphers(1)'& command may be used to test the results of a given
29330 # note single-quotes to get ! past any shell history expansion
29331 $ openssl ciphers 'HIGH:!MD5:!SHA1'
29334 This example will let the library defaults be permitted on the MX port, where
29335 there's probably no identity verification anyway, but ups the ante on the
29336 submission ports where the administrator might have some influence on the
29337 choice of clients used:
29339 # OpenSSL variant; see man ciphers(1)
29340 tls_require_ciphers = ${if =={$received_port}{25}\
29345 This example will prefer ECDSA-authenticated ciphers over RSA ones:
29347 tls_require_ciphers = ECDSA:RSA:!COMPLEMENTOFDEFAULT
29350 For TLS version 1.3 the control available is less fine-grained
29351 and Exim does not provide access to it at present.
29352 The value of the &%tls_require_ciphers%& option is ignored when
29353 TLS version 1.3 is negotiated.
29355 As of writing the library default cipher suite list for TLSv1.3 is
29357 TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256
29361 .section "Requiring specific ciphers or other parameters in GnuTLS" &&&
29363 .cindex "GnuTLS" "specifying parameters for"
29364 .cindex "TLS" "specifying ciphers (GnuTLS)"
29365 .cindex "TLS" "specifying key exchange methods (GnuTLS)"
29366 .cindex "TLS" "specifying MAC algorithms (GnuTLS)"
29367 .cindex "TLS" "specifying protocols (GnuTLS)"
29368 .cindex "TLS" "specifying priority string (GnuTLS)"
29369 .oindex "&%tls_require_ciphers%&" "GnuTLS"
29370 The GnuTLS library allows the caller to provide a "priority string", documented
29371 as part of the &[gnutls_priority_init]& function. This is very similar to the
29372 ciphersuite specification in OpenSSL.
29374 The &%tls_require_ciphers%& option is treated as the GnuTLS priority string
29375 and controls both protocols and ciphers.
29377 The &%tls_require_ciphers%& option is available both as an global option,
29378 controlling how Exim behaves as a server, and also as an option of the
29379 &(smtp)& transport, controlling how Exim behaves as a client. In both cases
29380 the value is string expanded. The resulting string is not an Exim list and
29381 the string is given to the GnuTLS library, so that Exim does not need to be
29382 aware of future feature enhancements of GnuTLS.
29384 Documentation of the strings accepted may be found in the GnuTLS manual, under
29385 "Priority strings". This is online as
29386 &url(https://www.gnutls.org/manual/html_node/Priority-Strings.html),
29387 but beware that this relates to GnuTLS 3, which may be newer than the version
29388 installed on your system. If you are using GnuTLS 3,
29389 then the example code
29390 &url(https://www.gnutls.org/manual/gnutls.html#Listing-the-ciphersuites-in-a-priority-string)
29391 on that site can be used to test a given string.
29395 # Disable older versions of protocols
29396 tls_require_ciphers = NORMAL:%LATEST_RECORD_VERSION:-VERS-SSL3.0
29399 Prior to Exim 4.80, an older API of GnuTLS was used, and Exim supported three
29400 additional options, "&%gnutls_require_kx%&", "&%gnutls_require_mac%&" and
29401 "&%gnutls_require_protocols%&". &%tls_require_ciphers%& was an Exim list.
29403 This example will let the library defaults be permitted on the MX port, where
29404 there's probably no identity verification anyway, and lowers security further
29405 by increasing compatibility; but this ups the ante on the submission ports
29406 where the administrator might have some influence on the choice of clients
29410 tls_require_ciphers = ${if =={$received_port}{25}\
29416 .section "Configuring an Exim server to use TLS" "SECID182"
29417 .cindex "TLS" "configuring an Exim server"
29418 .cindex "ESMTP extensions" STARTTLS
29419 When Exim has been built with TLS support, it advertises the availability of
29420 the STARTTLS command to client hosts that match &%tls_advertise_hosts%&,
29421 but not to any others. The default value of this option is *, which means
29422 that STARTTLS is always advertised. Set it to blank to never advertise;
29423 this is reasonable for systems that want to use TLS only as a client.
29425 If STARTTLS is to be used you
29426 need to set some other options in order to make TLS available.
29428 If a client issues a STARTTLS command and there is some configuration
29429 problem in the server, the command is rejected with a 454 error. If the client
29430 persists in trying to issue SMTP commands, all except QUIT are rejected
29433 554 Security failure
29435 If a STARTTLS command is issued within an existing TLS session, it is
29436 rejected with a 554 error code.
29438 To enable TLS operations on a server, the &%tls_advertise_hosts%& option
29439 must be set to match some hosts. The default is * which matches all hosts.
29441 If this is all you do, TLS encryption will be enabled but not authentication -
29442 meaning that the peer has no assurance it is actually you he is talking to.
29443 You gain protection from a passive sniffer listening on the wire but not
29444 from someone able to intercept the communication.
29446 Further protection requires some further configuration at the server end.
29448 To make TLS work you need to set, in the server,
29450 tls_certificate = /some/file/name
29451 tls_privatekey = /some/file/name
29453 These options are, in fact, expanded strings, so you can make them depend on
29454 the identity of the client that is connected if you wish. The first file
29455 contains the server's X509 certificate, and the second contains the private key
29456 that goes with it. These files need to be
29457 PEM format and readable by the Exim user, and must
29458 always be given as full path names.
29459 The key must not be password-protected.
29460 They can be the same file if both the
29461 certificate and the key are contained within it. If &%tls_privatekey%& is not
29462 set, or if its expansion is forced to fail or results in an empty string, this
29463 is assumed to be the case. The certificate file may also contain intermediate
29464 certificates that need to be sent to the client to enable it to authenticate
29465 the server's certificate.
29467 For dual-stack (eg. RSA and ECDSA) configurations, these options can be
29468 colon-separated lists of file paths. Ciphers using given authentication
29469 algorithms require the presence of a suitable certificate to supply the
29470 public-key. The server selects among the certificates to present to the
29471 client depending on the selected cipher, hence the priority ordering for
29472 ciphers will affect which certificate is used.
29474 If you do not understand about certificates and keys, please try to find a
29475 source of this background information, which is not Exim-specific. (There are a
29476 few comments below in section &<<SECTcerandall>>&.)
29478 &*Note*&: These options do not apply when Exim is operating as a client &--
29479 they apply only in the case of a server. If you need to use a certificate in an
29480 Exim client, you must set the options of the same names in an &(smtp)&
29483 With just these options, an Exim server will be able to use TLS. It does not
29484 require the client to have a certificate (but see below for how to insist on
29485 this). There is one other option that may be needed in other situations. If
29487 tls_dhparam = /some/file/name
29489 is set, the SSL library is initialized for the use of Diffie-Hellman ciphers
29490 with the parameters contained in the file.
29491 Set this to &`none`& to disable use of DH entirely, by making no prime
29496 This may also be set to a string identifying a standard prime to be used for
29497 DH; if it is set to &`default`& or, for OpenSSL, is unset, then the prime
29498 used is &`ike23`&. There are a few standard primes available, see the
29499 documentation for &%tls_dhparam%& for the complete list.
29505 for a way of generating file data.
29507 The strings supplied for these three options are expanded every time a client
29508 host connects. It is therefore possible to use different certificates and keys
29509 for different hosts, if you so wish, by making use of the client's IP address
29510 in &$sender_host_address$& to control the expansion. If a string expansion is
29511 forced to fail, Exim behaves as if the option is not set.
29513 .cindex "cipher" "logging"
29514 .cindex "log" "TLS cipher"
29515 .vindex "&$tls_in_cipher$&"
29516 The variable &$tls_in_cipher$& is set to the cipher suite that was negotiated for
29517 an incoming TLS connection. It is included in the &'Received:'& header of an
29518 incoming message (by default &-- you can, of course, change this), and it is
29519 also included in the log line that records a message's arrival, keyed by
29520 &"X="&, unless the &%tls_cipher%& log selector is turned off. The &%encrypted%&
29521 condition can be used to test for specific cipher suites in ACLs.
29523 Once TLS has been established, the ACLs that run for subsequent SMTP commands
29524 can check the name of the cipher suite and vary their actions accordingly. The
29525 cipher suite names vary, depending on which TLS library is being used. For
29526 example, OpenSSL uses the name DES-CBC3-SHA for the cipher suite which in other
29527 contexts is known as TLS_RSA_WITH_3DES_EDE_CBC_SHA. Check the OpenSSL or GnuTLS
29528 documentation for more details.
29530 For outgoing SMTP deliveries, &$tls_out_cipher$& is used and logged
29531 (again depending on the &%tls_cipher%& log selector).
29534 .section "Requesting and verifying client certificates" "SECID183"
29535 .cindex "certificate" "verification of client"
29536 .cindex "TLS" "client certificate verification"
29537 If you want an Exim server to request a certificate when negotiating a TLS
29538 session with a client, you must set either &%tls_verify_hosts%& or
29539 &%tls_try_verify_hosts%&. You can, of course, set either of them to * to
29540 apply to all TLS connections. For any host that matches one of these options,
29541 Exim requests a certificate as part of the setup of the TLS session. The
29542 contents of the certificate are verified by comparing it with a list of
29543 expected trust-anchors or certificates.
29544 These may be the system default set (depending on library version),
29545 an explicit file or,
29546 depending on library version, a directory, identified by
29547 &%tls_verify_certificates%&.
29549 A file can contain multiple certificates, concatenated end to end. If a
29552 each certificate must be in a separate file, with a name (or a symbolic link)
29553 of the form <&'hash'&>.0, where <&'hash'&> is a hash value constructed from the
29554 certificate. You can compute the relevant hash by running the command
29556 openssl x509 -hash -noout -in /cert/file
29558 where &_/cert/file_& contains a single certificate.
29560 There is no checking of names of the client against the certificate
29561 Subject Name or Subject Alternate Names.
29563 The difference between &%tls_verify_hosts%& and &%tls_try_verify_hosts%& is
29564 what happens if the client does not supply a certificate, or if the certificate
29565 does not match any of the certificates in the collection named by
29566 &%tls_verify_certificates%&. If the client matches &%tls_verify_hosts%&, the
29567 attempt to set up a TLS session is aborted, and the incoming connection is
29568 dropped. If the client matches &%tls_try_verify_hosts%&, the (encrypted) SMTP
29569 session continues. ACLs that run for subsequent SMTP commands can detect the
29570 fact that no certificate was verified, and vary their actions accordingly. For
29571 example, you can insist on a certificate before accepting a message for
29572 relaying, but not when the message is destined for local delivery.
29574 .vindex "&$tls_in_peerdn$&"
29575 When a client supplies a certificate (whether it verifies or not), the value of
29576 the Distinguished Name of the certificate is made available in the variable
29577 &$tls_in_peerdn$& during subsequent processing of the message.
29579 .cindex "log" "distinguished name"
29580 Because it is often a long text string, it is not included in the log line or
29581 &'Received:'& header by default. You can arrange for it to be logged, keyed by
29582 &"DN="&, by setting the &%tls_peerdn%& log selector, and you can use
29583 &%received_header_text%& to change the &'Received:'& header. When no
29584 certificate is supplied, &$tls_in_peerdn$& is empty.
29587 .section "Revoked certificates" "SECID184"
29588 .cindex "TLS" "revoked certificates"
29589 .cindex "revocation list"
29590 .cindex "certificate" "revocation list"
29591 .cindex "OCSP" "stapling"
29592 Certificate issuing authorities issue Certificate Revocation Lists (CRLs) when
29593 certificates are revoked. If you have such a list, you can pass it to an Exim
29594 server using the global option called &%tls_crl%& and to an Exim client using
29595 an identically named option for the &(smtp)& transport. In each case, the value
29596 of the option is expanded and must then be the name of a file that contains a
29598 The downside is that clients have to periodically re-download a potentially huge
29599 file from every certificate authority they know of.
29601 The way with most moving parts at query time is Online Certificate
29602 Status Protocol (OCSP), where the client verifies the certificate
29603 against an OCSP server run by the CA. This lets the CA track all
29604 usage of the certs. It requires running software with access to the
29605 private key of the CA, to sign the responses to the OCSP queries. OCSP
29606 is based on HTTP and can be proxied accordingly.
29608 The only widespread OCSP server implementation (known to this writer)
29609 comes as part of OpenSSL and aborts on an invalid request, such as
29610 connecting to the port and then disconnecting. This requires
29611 re-entering the passphrase each time some random client does this.
29613 The third way is OCSP Stapling; in this, the server using a certificate
29614 issued by the CA periodically requests an OCSP proof of validity from
29615 the OCSP server, then serves it up inline as part of the TLS
29616 negotiation. This approach adds no extra round trips, does not let the
29617 CA track users, scales well with number of certs issued by the CA and is
29618 resilient to temporary OCSP server failures, as long as the server
29619 starts retrying to fetch an OCSP proof some time before its current
29620 proof expires. The downside is that it requires server support.
29622 Unless Exim is built with the support disabled,
29623 or with GnuTLS earlier than version 3.3.16 / 3.4.8
29624 support for OCSP stapling is included.
29626 There is a global option called &%tls_ocsp_file%&.
29627 The file specified therein is expected to be in DER format, and contain
29628 an OCSP proof. Exim will serve it as part of the TLS handshake. This
29629 option will be re-expanded for SNI, if the &%tls_certificate%& option
29630 contains &`tls_in_sni`&, as per other TLS options.
29632 Exim does not at this time implement any support for fetching a new OCSP
29633 proof. The burden is on the administrator to handle this, outside of
29634 Exim. The file specified should be replaced atomically, so that the
29635 contents are always valid. Exim will expand the &%tls_ocsp_file%& option
29636 on each connection, so a new file will be handled transparently on the
29639 When built with OpenSSL Exim will check for a valid next update timestamp
29640 in the OCSP proof; if not present, or if the proof has expired, it will be
29643 For the client to be able to verify the stapled OCSP the server must
29644 also supply, in its stapled information, any intermediate
29645 certificates for the chain leading to the OCSP proof from the signer
29646 of the server certificate. There may be zero or one such. These
29647 intermediate certificates should be added to the server OCSP stapling
29648 file named by &%tls_ocsp_file%&.
29650 Note that the proof only covers the terminal server certificate,
29651 not any of the chain from CA to it.
29653 There is no current way to staple a proof for a client certificate.
29656 A helper script "ocsp_fetch.pl" for fetching a proof from a CA
29657 OCSP server is supplied. The server URL may be included in the
29658 server certificate, if the CA is helpful.
29660 One failure mode seen was the OCSP Signer cert expiring before the end
29661 of validity of the OCSP proof. The checking done by Exim/OpenSSL
29662 noted this as invalid overall, but the re-fetch script did not.
29666 .section "Caching of static server configuration items" "SECTserverTLScache"
29667 .cindex certificate caching
29668 .cindex privatekey caching
29669 .cindex crl caching
29670 .cindex ocsp caching
29671 .cindex ciphers caching
29672 .cindex "CA bundle" caching
29673 .cindex "certificate authorities" caching
29674 .cindex tls_certificate caching
29675 .cindex tls_privatekey caching
29676 .cindex tls_crl caching
29677 .cindex tls_ocsp_file caching
29678 .cindex tls_require_ciphers caching
29679 .cindex tls_verify_certificate caching
29680 .cindex caching certificate
29681 .cindex caching privatekey
29682 .cindex caching crl
29683 .cindex caching ocsp
29684 .cindex caching ciphers
29685 .cindex caching "certificate authorities
29686 If any of the main configuration options &%tls_certificate%&, &%tls_privatekey%&,
29687 &%tls_crl%& and &%tls_ocsp_file%& have values with no
29688 expandable elements,
29689 then the associated information is loaded at daemon startup.
29690 It is made available
29691 to child processes forked for handling received SMTP connections.
29693 This caching is currently only supported under Linux and FreeBSD.
29695 If caching is not possible, for example if an item has to be dependent
29696 on the peer host so contains a &$sender_host_name$& expansion, the load
29697 of the associated information is done at the startup of the TLS connection.
29699 The cache is invalidated and reloaded after any changes to the directories
29700 containing files specified by these options.
29702 The information specified by the main option &%tls_verify_certificates%&
29703 is similarly cached so long as it specifies files explicitly
29704 or (under GnuTLS) is the string &"system,cache"&.
29705 The latter case is not automatically invalidated;
29706 it is the operator's responsibility to arrange for a daemon restart
29707 any time the system certificate authority bundle is updated.
29708 A HUP signal is sufficient for this.
29709 The value &"system"& results in no caching under GnuTLS.
29711 The macro _HAVE_TLS_CA_CACHE will be defined if the suffix for "system"
29712 is acceptable in configurations for the Exim executavble.
29714 Caching of the system Certificate Authorities bundle can
29715 save siginificant time and processing on every TLS connection
29721 .section "Configuring an Exim client to use TLS" "SECTclientTLS"
29722 .cindex "cipher" "logging"
29723 .cindex "log" "TLS cipher"
29724 .cindex "log" "distinguished name"
29725 .cindex "TLS" "configuring an Exim client"
29726 The &%tls_cipher%& and &%tls_peerdn%& log selectors apply to outgoing SMTP
29727 deliveries as well as to incoming, the latter one causing logging of the
29728 server certificate's DN. The remaining client configuration for TLS is all
29729 within the &(smtp)& transport.
29731 .cindex "ESMTP extensions" STARTTLS
29732 It is not necessary to set any options to have TLS work in the &(smtp)&
29733 transport. If Exim is built with TLS support, and TLS is advertised by a
29734 server, the &(smtp)& transport always tries to start a TLS session. However,
29735 this can be prevented by setting &%hosts_avoid_tls%& (an option of the
29736 transport) to a list of server hosts for which TLS should not be used.
29738 If you do not want Exim to attempt to send messages unencrypted when an attempt
29739 to set up an encrypted connection fails in any way, you can set
29740 &%hosts_require_tls%& to a list of hosts for which encryption is mandatory. For
29741 those hosts, delivery is always deferred if an encrypted connection cannot be
29742 set up. If there are any other hosts for the address, they are tried in the
29745 When the server host is not in &%hosts_require_tls%&, Exim may try to deliver
29746 the message unencrypted. It always does this if the response to STARTTLS is
29747 a 5&'xx'& code. For a temporary error code, or for a failure to negotiate a TLS
29748 session after a success response code, what happens is controlled by the
29749 &%tls_tempfail_tryclear%& option of the &(smtp)& transport. If it is false,
29750 delivery to this host is deferred, and other hosts (if available) are tried. If
29751 it is true, Exim attempts to deliver unencrypted after a 4&'xx'& response to
29752 STARTTLS, and if STARTTLS is accepted, but the subsequent TLS
29753 negotiation fails, Exim closes the current connection (because it is in an
29754 unknown state), opens a new one to the same host, and then tries the delivery
29757 The &%tls_certificate%& and &%tls_privatekey%& options of the &(smtp)&
29758 transport provide the client with a certificate, which is passed to the server
29760 This is an optional thing for TLS connections, although either end
29762 If the server is Exim, it will request a certificate only if
29763 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client.
29765 &*Note*&: Do not use a certificate which has the OCSP-must-staple extension,
29766 for client use (they are usable for server use).
29767 As the TLS protocol has no means for the client to staple before TLS 1.3 it will result
29768 in failed connections.
29770 If the &%tls_verify_certificates%& option is set on the &(smtp)& transport, it
29771 specifies a collection of expected server certificates.
29773 the system default set (depending on library version),
29775 or (depending on library version) a directory.
29776 The client verifies the server's certificate
29777 against this collection, taking into account any revoked certificates that are
29778 in the list defined by &%tls_crl%&.
29779 Failure to verify fails the TLS connection unless either of the
29780 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& options are set.
29782 The &%tls_verify_hosts%& and &%tls_try_verify_hosts%& options restrict
29783 certificate verification to the listed servers. Verification either must
29784 or need not succeed respectively.
29786 The &%tls_verify_cert_hostnames%& option lists hosts for which additional
29787 name checks are made on the server certificate.
29788 The match against this list is, as per other Exim usage, the
29789 IP for the host. That is most closely associated with the
29790 name on the DNS A (or AAAA) record for the host.
29791 However, the name that needs to be in the certificate
29792 is the one at the head of any CNAME chain leading to the A record.
29793 The option defaults to always checking.
29795 The &(smtp)& transport has two OCSP-related options:
29796 &%hosts_require_ocsp%&; a host-list for which a Certificate Status
29797 is requested and required for the connection to proceed. The default
29799 &%hosts_request_ocsp%&; a host-list for which (additionally)
29800 a Certificate Status is requested (but not necessarily verified). The default
29801 value is "*" meaning that requests are made unless configured
29804 The host(s) should also be in &%hosts_require_tls%&, and
29805 &%tls_verify_certificates%& configured for the transport,
29806 for OCSP to be relevant.
29809 &%tls_require_ciphers%& is set on the &(smtp)& transport, it must contain a
29810 list of permitted cipher suites. If either of these checks fails, delivery to
29811 the current host is abandoned, and the &(smtp)& transport tries to deliver to
29812 alternative hosts, if any.
29815 These options must be set in the &(smtp)& transport for Exim to use TLS when it
29816 is operating as a client. Exim does not assume that a server certificate (set
29817 by the global options of the same name) should also be used when operating as a
29821 .vindex "&$host_address$&"
29822 All the TLS options in the &(smtp)& transport are expanded before use, with
29823 &$host$& and &$host_address$& containing the name and address of the server to
29824 which the client is connected. Forced failure of an expansion causes Exim to
29825 behave as if the relevant option were unset.
29827 .vindex &$tls_out_bits$&
29828 .vindex &$tls_out_cipher$&
29829 .vindex &$tls_out_peerdn$&
29830 .vindex &$tls_out_sni$&
29831 Before an SMTP connection is established, the
29832 &$tls_out_bits$&, &$tls_out_cipher$&, &$tls_out_peerdn$& and &$tls_out_sni$&
29833 variables are emptied. (Until the first connection, they contain the values
29834 that were set when the message was received.) If STARTTLS is subsequently
29835 successfully obeyed, these variables are set to the relevant values for the
29836 outgoing connection.
29840 .section "Caching of static client configuration items" "SECTclientTLScache"
29841 .cindex certificate caching
29842 .cindex privatekey caching
29843 .cindex crl caching
29844 .cindex ciphers caching
29845 .cindex "CA bundle" caching
29846 .cindex "certificate authorities" caching
29847 .cindex tls_certificate caching
29848 .cindex tls_privatekey caching
29849 .cindex tls_crl caching
29850 .cindex tls_require_ciphers caching
29851 .cindex tls_verify_certificate caching
29852 .cindex caching certificate
29853 .cindex caching privatekey
29854 .cindex caching crl
29855 .cindex caching ciphers
29856 .cindex caching "certificate authorities
29857 If any of the transport configuration options &%tls_certificate%&, &%tls_privatekey%&
29858 and &%tls_crl%& have values with no
29859 expandable elements,
29860 then the associated information is loaded per smtp transport
29861 at daemon startup, at the start of a queue run, or on a
29862 command-line specified message delivery.
29863 It is made available
29864 to child processes forked for handling making SMTP connections.
29866 This caching is currently only supported under Linux.
29868 If caching is not possible, the load
29869 of the associated information is done at the startup of the TLS connection.
29871 The cache is invalidated in the daemon
29872 and reloaded after any changes to the directories
29873 containing files specified by these options.
29875 The information specified by the main option &%tls_verify_certificates%&
29876 is similarly cached so long as it specifies files explicitly
29877 or (under GnuTLS) is the string &"system,cache"&.
29878 The latter case is not automatically invaludated;
29879 it is the operator's responsibility to arrange for a daemon restart
29880 any time the system certificate authority bundle is updated.
29881 A HUP signal is sufficient for this.
29882 The value &"system"& results in no caching under GnuTLS.
29884 The macro _HAVE_TLS_CA_CACHE will be defined if the suffix for "system"
29885 is acceptable in configurations for the Exim executavble.
29887 Caching of the system Certificate Authorities bundle can
29888 save siginificant time and processing on every TLS connection
29894 .section "Use of TLS Server Name Indication" "SECTtlssni"
29895 .cindex "TLS" "Server Name Indication"
29898 .vindex "&$tls_in_sni$&"
29899 .oindex "&%tls_in_sni%&"
29900 With TLS1.0 or above, there is an extension mechanism by which extra
29901 information can be included at various points in the protocol. One of these
29902 extensions, documented in RFC 6066 (and before that RFC 4366) is
29903 &"Server Name Indication"&, commonly &"SNI"&. This extension is sent by the
29904 client in the initial handshake, so that the server can examine the servername
29905 within and possibly choose to use different certificates and keys (and more)
29908 This is analogous to HTTP's &"Host:"& header, and is the main mechanism by
29909 which HTTPS-enabled web-sites can be virtual-hosted, many sites to one IP
29912 With SMTP to MX, there are the same problems here as in choosing the identity
29913 against which to validate a certificate: you can't rely on insecure DNS to
29914 provide the identity which you then cryptographically verify. So this will
29915 be of limited use in that environment.
29917 With SMTP to Submission, there is a well-defined hostname which clients are
29918 connecting to and can validate certificates against. Thus clients &*can*&
29919 choose to include this information in the TLS negotiation. If this becomes
29920 wide-spread, then hosters can choose to present different certificates to
29921 different clients. Or even negotiate different cipher suites.
29923 The &%tls_sni%& option on an SMTP transport is an expanded string; the result,
29924 if not empty, will be sent on a TLS session as part of the handshake. There's
29925 nothing more to it. Choosing a sensible value not derived insecurely is the
29926 only point of caution. The &$tls_out_sni$& variable will be set to this string
29927 for the lifetime of the client connection (including during authentication).
29930 If DANE validated the connection attempt then the value of the &%tls_sni%& option
29931 is forced to the name of the destination host, after any MX- or CNAME-following.
29934 Except during SMTP client sessions, if &$tls_in_sni$& is set then it is a string
29935 received from a client.
29936 It can be logged with the &%log_selector%& item &`+tls_sni`&.
29938 If the string &`tls_in_sni`& appears in the main section's &%tls_certificate%&
29939 option (prior to expansion) then the following options will be re-expanded
29940 during TLS session handshake, to permit alternative values to be chosen:
29943 &%tls_certificate%&
29949 &%tls_verify_certificates%&
29954 Great care should be taken to deal with matters of case, various injection
29955 attacks in the string (&`../`& or SQL), and ensuring that a valid filename
29956 can always be referenced; it is important to remember that &$tls_in_sni$& is
29957 arbitrary unverified data provided prior to authentication.
29958 Further, the initial certificate is loaded before SNI has arrived, so
29959 an expansion for &%tls_certificate%& must have a default which is used
29960 when &$tls_in_sni$& is empty.
29962 The Exim developers are proceeding cautiously and so far no other TLS options
29965 When Exim is built against OpenSSL, OpenSSL must have been built with support
29966 for TLS Extensions. This holds true for OpenSSL 1.0.0+ and 0.9.8+ with
29967 enable-tlsext in EXTRACONFIGURE. If you invoke &(openssl s_client -h)& and
29968 see &`-servername`& in the output, then OpenSSL has support.
29970 When Exim is built against GnuTLS, SNI support is available as of GnuTLS
29971 0.5.10. (Its presence predates the current API which Exim uses, so if Exim
29972 built, then you have SNI support).
29975 .cindex ALPN "general information"
29976 .cindex TLS "Application Layer Protocol Names"
29977 There is a TLS feature related to SNI
29978 called Application Layer Protocol Name (ALPN).
29979 This is intended to declare, or select, what protocol layer will be using a TLS
29981 The client for the connection proposes a set of protocol names, and
29982 the server responds with a selected one.
29983 It is not, as of 2021, commonly used for SMTP connections.
29984 However, to guard against misirected or malicious use of web clients
29985 (which often do use ALPN) against MTA ports, Exim by default check that
29986 there is no incompatible ALPN specified by a client for a TLS connection.
29987 If there is, the connection is rejected.
29989 As a client Exim does not supply ALPN by default.
29990 The behaviour of both client and server can be configured using the options
29991 &%tls_alpn%& and &%hosts_require_alpn%&.
29992 There are no variables providing observability.
29993 Some feature-specific logging may appear on denied connections, but this
29994 depends on the behavious of the peer
29995 (not all peers can send a feature-specific TLS Alert).
29997 This feature is available when Exim is built with
29998 OpenSSL 1.1.0 or later or GnuTLS 3.2.0 or later;
29999 the macro _HAVE_TLS_ALPN will be defined when this is so.
30003 .section "Multiple messages on the same encrypted TCP/IP connection" &&&
30005 .cindex "multiple SMTP deliveries with TLS"
30006 .cindex "TLS" "multiple message deliveries"
30007 Exim sends multiple messages down the same TCP/IP connection by starting up
30008 an entirely new delivery process for each message, passing the socket from
30009 one process to the next. This implementation does not fit well with the use
30010 of TLS, because there is quite a lot of state information associated with a TLS
30011 connection, not just a socket identification. Passing all the state information
30012 to a new process is not feasible. Consequently, for sending using TLS Exim
30013 starts an additional proxy process for handling the encryption, piping the
30014 unencrypted data stream from and to the delivery processes.
30016 An older mode of operation can be enabled on a per-host basis by the
30017 &%hosts_noproxy_tls%& option on the &(smtp)& transport. If the host matches
30018 this list the proxy process described above is not used; instead Exim
30019 shuts down an existing TLS session being run by the delivery process
30020 before passing the socket to a new process. The new process may then
30021 try to start a new TLS session, and if successful, may try to re-authenticate
30022 if AUTH is in use, before sending the next message.
30024 The RFC is not clear as to whether or not an SMTP session continues in clear
30025 after TLS has been shut down, or whether TLS may be restarted again later, as
30026 just described. However, if the server is Exim, this shutdown and
30027 reinitialization works. It is not known which (if any) other servers operate
30028 successfully if the client closes a TLS session and continues with unencrypted
30029 SMTP, but there are certainly some that do not work. For such servers, Exim
30030 should not pass the socket to another process, because the failure of the
30031 subsequent attempt to use it would cause Exim to record a temporary host error,
30032 and delay other deliveries to that host.
30034 To test for this case, Exim sends an EHLO command to the server after
30035 closing down the TLS session. If this fails in any way, the connection is
30036 closed instead of being passed to a new delivery process, but no retry
30037 information is recorded.
30039 There is also a manual override; you can set &%hosts_nopass_tls%& on the
30040 &(smtp)& transport to match those hosts for which Exim should not pass
30041 connections to new processes if TLS has been used.
30046 .section "Certificates and all that" "SECTcerandall"
30047 .cindex "certificate" "references to discussion"
30048 In order to understand fully how TLS works, you need to know about
30049 certificates, certificate signing, and certificate authorities.
30050 This is a large topic and an introductory guide is unsuitable for the Exim
30051 reference manual, so instead we provide pointers to existing documentation.
30053 The Apache web-server was for a long time the canonical guide, so their
30054 documentation is a good place to start; their SSL module's Introduction
30055 document is currently at
30057 &url(https://httpd.apache.org/docs/current/ssl/ssl_intro.html)
30059 and their FAQ is at
30061 &url(https://httpd.apache.org/docs/current/ssl/ssl_faq.html)
30064 Eric Rescorla's book, &'SSL and TLS'&, published by Addison-Wesley (ISBN
30065 0-201-61598-3) in 2001, contains both introductory and more in-depth
30067 More recently Ivan Ristić's book &'Bulletproof SSL and TLS'&,
30068 published by Feisty Duck (ISBN 978-1907117046) in 2013 is good.
30069 Ivan is the author of the popular TLS testing tools at
30070 &url(https://www.ssllabs.com/).
30073 .section "Certificate chains" "SECID186"
30074 A file named by &%tls_certificate%& may contain more than one
30075 certificate. This is useful in the case where the certificate that is being
30076 sent is validated by an intermediate certificate which the other end does
30077 not have. Multiple certificates must be in the correct order in the file.
30078 First the host's certificate itself, then the first intermediate
30079 certificate to validate the issuer of the host certificate, then the next
30080 intermediate certificate to validate the issuer of the first intermediate
30081 certificate, and so on, until finally (optionally) the root certificate.
30082 The root certificate must already be trusted by the recipient for
30083 validation to succeed, of course, but if it's not preinstalled, sending the
30084 root certificate along with the rest makes it available for the user to
30085 install if the receiving end is a client MUA that can interact with a user.
30087 Note that certificates using MD5 are unlikely to work on today's Internet;
30088 even if your libraries allow loading them for use in Exim when acting as a
30089 server, increasingly clients will not accept such certificates. The error
30090 diagnostics in such a case can be frustratingly vague.
30094 .section "Self-signed certificates" "SECID187"
30095 .cindex "certificate" "self-signed"
30096 You can create a self-signed certificate using the &'req'& command provided
30097 with OpenSSL, like this:
30098 . ==== Do not shorten the duration here without reading and considering
30099 . ==== the text below. Please leave it at 9999 days.
30101 openssl req -x509 -newkey rsa:1024 -keyout file1 -out file2 \
30104 &_file1_& and &_file2_& can be the same file; the key and the certificate are
30105 delimited and so can be identified independently. The &%-days%& option
30106 specifies a period for which the certificate is valid. The &%-nodes%& option is
30107 important: if you do not set it, the key is encrypted with a passphrase
30108 that you are prompted for, and any use that is made of the key causes more
30109 prompting for the passphrase. This is not helpful if you are going to use
30110 this certificate and key in an MTA, where prompting is not possible.
30112 . ==== I expect to still be working 26 years from now. The less technical
30113 . ==== debt I create, in terms of storing up trouble for my later years, the
30114 . ==== happier I will be then. We really have reached the point where we
30115 . ==== should start, at the very least, provoking thought and making folks
30116 . ==== pause before proceeding, instead of leaving all the fixes until two
30117 . ==== years before 2^31 seconds after the 1970 Unix epoch.
30119 NB: we are now past the point where 9999 days takes us past the 32-bit Unix
30120 epoch. If your system uses unsigned time_t (most do) and is 32-bit, then
30121 the above command might produce a date in the past. Think carefully about
30122 the lifetime of the systems you're deploying, and either reduce the duration
30123 of the certificate or reconsider your platform deployment. (At time of
30124 writing, reducing the duration is the most likely choice, but the inexorable
30125 progression of time takes us steadily towards an era where this will not
30126 be a sensible resolution).
30128 A self-signed certificate made in this way is sufficient for testing, and
30129 may be adequate for all your requirements if you are mainly interested in
30130 encrypting transfers, and not in secure identification.
30132 However, many clients require that the certificate presented by the server be a
30133 user (also called &"leaf"& or &"site"&) certificate, and not a self-signed
30134 certificate. In this situation, the self-signed certificate described above
30135 must be installed on the client host as a trusted root &'certification
30136 authority'& (CA), and the certificate used by Exim must be a user certificate
30137 signed with that self-signed certificate.
30139 For information on creating self-signed CA certificates and using them to sign
30140 user certificates, see the &'General implementation overview'& chapter of the
30141 Open-source PKI book, available online at
30142 &url(https://sourceforge.net/projects/ospkibook/).
30143 .ecindex IIDencsmtp1
30144 .ecindex IIDencsmtp2
30147 .section "TLS Resumption" "SECTresumption"
30148 .cindex TLS resumption
30149 TLS Session Resumption for TLS 1.2 and TLS 1.3 connections can be used (defined
30150 in RFC 5077 for 1.2). The support for this requires GnuTLS 3.6.3 or OpenSSL 1.1.1
30153 Session resumption (this is the "stateless" variant) involves the server sending
30154 a "session ticket" to the client on one connection, which can be stored by the
30155 client and used for a later session. The ticket contains sufficient state for
30156 the server to reconstruct the TLS session, avoiding some expensive crypto
30157 calculation and (on TLS1.2) one full packet roundtrip time.
30160 Operational cost/benefit:
30162 The extra data being transmitted costs a minor amount, and the client has
30163 extra costs in storing and retrieving the data.
30165 In the Exim/Gnutls implementation the extra cost on an initial connection
30166 which is TLS1.2 over a loopback path is about 6ms on 2017-laptop class hardware.
30167 The saved cost on a subsequent connection is about 4ms; three or more
30168 connections become a net win. On longer network paths, two or more
30169 connections will have an average lower startup time thanks to the one
30170 saved packet roundtrip. TLS1.3 will save the crypto cpu costs but not any
30173 .cindex "hints database" tls
30174 Since a new hints DB is used on the TLS client,
30175 the hints DB maintenance should be updated to additionally handle "tls".
30180 The session ticket is encrypted, but is obviously an additional security
30181 vulnarability surface. An attacker able to decrypt it would have access
30182 all connections using the resumed session.
30183 The session ticket encryption key is not committed to storage by the server
30184 and is rotated regularly (OpenSSL: 1hr, and one previous key is used for
30185 overlap; GnuTLS 6hr but does not specify any overlap).
30186 Tickets have limited lifetime (2hr, and new ones issued after 1hr under
30187 OpenSSL. GnuTLS 2hr, appears to not do overlap).
30189 There is a question-mark over the security of the Diffie-Helman parameters
30190 used for session negotiation.
30195 The &%log_selector%& "tls_resumption" appends an asterisk to the tls_cipher "X="
30198 The variables &$tls_in_resumption$& and &$tls_out_resumption$&
30199 have bits 0-4 indicating respectively
30200 support built, client requested ticket, client offered session,
30201 server issued ticket, resume used. A suitable decode list is provided
30202 in the builtin macro _RESUME_DECODE for in &%listextract%& expansions.
30207 The &%tls_resumption_hosts%& main option specifies a hostlist for which
30208 exim, operating as a server, will offer resumption to clients.
30209 Current best practice is to not offer the feature to MUA connection.
30210 Commonly this can be done like this:
30212 tls_resumption_hosts = ${if inlist {$received_port}{587:465} {:}{*}}
30214 If the peer host matches the list after expansion then resumption
30215 is offered and/or accepted.
30217 The &%tls_resumption_hosts%& smtp transport option performs the
30218 equivalent function for operation as a client.
30219 If the peer host matches the list after expansion then resumption
30220 is attempted (if a stored session is available) or the information
30221 stored (if supplied by the peer).
30227 In a resumed session:
30229 The variables &$tls_{in,out}_cipher$& will have values different
30230 to the original (under GnuTLS).
30232 The variables &$tls_{in,out}_ocsp$& will be "not requested" or "no response",
30233 and the &%hosts_require_ocsp%& smtp trasnport option will fail.
30234 . XXX need to do something with that hosts_require_ocsp
30240 .section DANE "SECDANE"
30242 DNS-based Authentication of Named Entities, as applied to SMTP over TLS, provides assurance to a client that
30243 it is actually talking to the server it wants to rather than some attacker operating a Man In The Middle (MITM)
30244 operation. The latter can terminate the TLS connection you make, and make another one to the server (so both
30245 you and the server still think you have an encrypted connection) and, if one of the "well known" set of
30246 Certificate Authorities has been suborned - something which *has* been seen already (2014), a verifiable
30247 certificate (if you're using normal root CAs, eg. the Mozilla set, as your trust anchors).
30249 What DANE does is replace the CAs with the DNS as the trust anchor. The assurance is limited to a) the possibility
30250 that the DNS has been suborned, b) mistakes made by the admins of the target server. The attack surface presented
30251 by (a) is thought to be smaller than that of the set of root CAs.
30253 It also allows the server to declare (implicitly) that connections to it should use TLS. An MITM could simply
30254 fail to pass on a server's STARTTLS.
30256 DANE scales better than having to maintain (and communicate via side-channel) copies of server certificates
30257 for every possible target server. It also scales (slightly) better than having to maintain on an SMTP
30258 client a copy of the standard CAs bundle. It also means not having to pay a CA for certificates.
30260 DANE requires a server operator to do three things: 1) run DNSSEC. This provides assurance to clients
30261 that DNS lookups they do for the server have not been tampered with. The domain MX record applying
30262 to this server, its A record, its TLSA record and any associated CNAME records must all be covered by
30264 2) add TLSA DNS records. These say what the server certificate for a TLS connection should be.
30265 3) offer a server certificate, or certificate chain, in TLS connections which is is anchored by one of the TLSA records.
30267 There are no changes to Exim specific to server-side operation of DANE.
30268 Support for client-side operation of DANE can be included at compile time by defining SUPPORT_DANE=yes
30269 in &_Local/Makefile_&.
30270 If it has been included, the macro "_HAVE_DANE" will be defined.
30272 A TLSA record consist of 4 fields, the "Certificate Usage", the
30273 "Selector", the "Matching type", and the "Certificate Association Data".
30274 For a detailed description of the TLSA record see
30275 &url(https://tools.ietf.org/html/rfc7671#page-5,RFC 7671).
30277 The TLSA record for the server may have "Certificate Usage" (1st) field of DANE-TA(2) or DANE-EE(3).
30278 These are the "Trust Anchor" and "End Entity" variants.
30279 The latter specifies the End Entity directly, i.e. the certificate involved is that of the server
30280 (and if only DANE-EE is used then it should be the sole one transmitted during the TLS handshake);
30281 this is appropriate for a single system, using a self-signed certificate.
30282 DANE-TA usage is effectively declaring a specific CA to be used; this might be a private CA or a public,
30284 A private CA at simplest is just a self-signed certificate (with certain
30285 attributes) which is used to sign server certificates, but running one securely
30286 does require careful arrangement.
30287 With DANE-TA, as implemented in Exim and commonly in other MTAs,
30288 the server TLS handshake must transmit the entire certificate chain from CA to server-certificate.
30289 DANE-TA is commonly used for several services and/or servers, each having a TLSA query-domain CNAME record,
30290 all of which point to a single TLSA record.
30291 DANE-TA and DANE-EE can both be used together.
30293 Our recommendation is to use DANE with a certificate from a public CA,
30294 because this enables a variety of strategies for remote clients to verify
30296 You can then publish information both via DANE and another technology,
30297 "MTA-STS", described below.
30299 When you use DANE-TA to publish trust anchor information, you ask entities
30300 outside your administrative control to trust the Certificate Authority for
30301 connections to you.
30302 If using a private CA then you should expect others to still apply the
30303 technical criteria they'd use for a public CA to your certificates.
30304 In particular, you should probably try to follow current best practices for CA
30305 operation around hash algorithms and key sizes.
30306 Do not expect other organizations to lower their security expectations just
30307 because a particular profile might be reasonable for your own internal use.
30309 When this text was last updated, this in practice means to avoid use of SHA-1
30310 and MD5; if using RSA to use key sizes of at least 2048 bits (and no larger
30311 than 4096, for interoperability); to use keyUsage fields correctly; to use
30312 random serial numbers.
30313 The list of requirements is subject to change as best practices evolve.
30314 If you're not already using a private CA, or it doesn't meet these
30315 requirements, then we encourage you to avoid all these issues and use a public
30316 CA such as &url(https://letsencrypt.org/,Let's Encrypt) instead.
30318 The TLSA record should have a "Selector" (2nd) field of SPKI(1) and
30319 a "Matching Type" (3rd) field of SHA2-512(2).
30321 For the "Certificate Authority Data" (4th) field, commands like
30324 openssl x509 -pubkey -noout <certificate.pem \
30325 | openssl rsa -outform der -pubin 2>/dev/null \
30330 are workable to create a hash of the certificate's public key.
30332 An example TLSA record for DANE-EE(3), SPKI(1), and SHA-512 (2) looks like
30335 _25._tcp.mail.example.com. TLSA 3 1 2 8BA8A336E...
30338 At the time of writing, &url(https://www.huque.com/bin/gen_tlsa)
30339 is useful for quickly generating TLSA records.
30342 For use with the DANE-TA model, server certificates must have a correct name (SubjectName or SubjectAltName).
30344 The Certificate issued by the CA published in the DANE-TA model should be
30345 issued using a strong hash algorithm.
30346 Exim, and importantly various other MTAs sending to you, will not
30347 re-enable hash algorithms which have been disabled by default in TLS
30349 This means no MD5 and no SHA-1. SHA2-256 is the minimum for reliable
30350 interoperability (and probably the maximum too, in 2018).
30352 The use of OCSP-stapling should be considered, allowing for fast revocation of certificates (which would otherwise
30353 be limited by the DNS TTL on the TLSA records). However, this is likely to only be usable with DANE-TA. NOTE: the
30354 default of requesting OCSP for all hosts is modified iff DANE is in use, to:
30357 hosts_request_ocsp = ${if or { {= {0}{$tls_out_tlsa_usage}} \
30358 {= {4}{$tls_out_tlsa_usage}} } \
30362 The (new) variable &$tls_out_tlsa_usage$& is a bitfield with numbered bits set for TLSA record usage codes.
30363 The zero above means DANE was not in use, the four means that only DANE-TA usage TLSA records were
30364 found. If the definition of &%hosts_request_ocsp%& includes the
30365 string "tls_out_tlsa_usage", they are re-expanded in time to
30366 control the OCSP request.
30368 This modification of hosts_request_ocsp is only done if it has the default value of "*". Admins who change it, and
30369 those who use &%hosts_require_ocsp%&, should consider the interaction with DANE in their OCSP settings.
30372 For client-side DANE there are three new smtp transport options, &%hosts_try_dane%&, &%hosts_require_dane%&
30373 and &%dane_require_tls_ciphers%&.
30374 The &"require"& variant will result in failure if the target host is not
30375 DNSSEC-secured. To get DNSSEC-secured hostname resolution, use
30376 the &%dnssec_request_domains%& router or transport option.
30378 DANE will only be usable if the target host has DNSSEC-secured MX, A and TLSA records.
30380 A TLSA lookup will be done if either of the above options match and the host-lookup succeeded using DNSSEC.
30381 If a TLSA lookup is done and succeeds, a DANE-verified TLS connection
30382 will be required for the host. If it does not, the host will not
30383 be used; there is no fallback to non-DANE or non-TLS.
30385 If DANE is requested and usable, then the TLS cipher list configuration
30386 prefers to use the option &%dane_require_tls_ciphers%& and falls
30387 back to &%tls_require_ciphers%& only if that is unset.
30388 This lets you configure "decent crypto" for DANE and "better than nothing
30389 crypto" as the default. Note though that while GnuTLS lets the string control
30390 which versions of TLS/SSL will be negotiated, OpenSSL does not and you're
30391 limited to ciphersuite constraints.
30393 If DANE is requested and useable (see above) the following transport options are ignored:
30397 tls_try_verify_hosts
30398 tls_verify_certificates
30400 tls_verify_cert_hostnames
30404 If DANE is not usable, whether requested or not, and CA-anchored
30405 verification evaluation is wanted, the above variables should be set appropriately.
30407 The router and transport option &%dnssec_request_domains%& must not be
30408 set to &"never"&, and &%dnssec_require_domains%& is ignored.
30410 If verification was successful using DANE then the "CV" item in the delivery log line will show as "CV=dane".
30412 There is a new variable &$tls_out_dane$& which will have "yes" if
30413 verification succeeded using DANE and "no" otherwise (only useful
30414 in combination with events; see &<<CHAPevents>>&),
30415 and a new variable &$tls_out_tlsa_usage$& (detailed above).
30417 .cindex DANE reporting
30418 An event (see &<<CHAPevents>>&) of type "dane:fail" will be raised on failures
30419 to achieve DANE-verified connection, if one was either requested and offered, or
30420 required. This is intended to support TLS-reporting as defined in
30421 &url(https://tools.ietf.org/html/draft-ietf-uta-smtp-tlsrpt-17).
30422 The &$event_data$& will be one of the Result Types defined in
30423 Section 4.3 of that document.
30425 Under GnuTLS, DANE is only supported from version 3.0.0 onwards.
30427 DANE is specified in published RFCs and decouples certificate authority trust
30428 selection from a "race to the bottom" of "you must trust everything for mail
30429 to get through". There is an alternative technology called MTA-STS, which
30430 instead publishes MX trust anchor information on an HTTPS website. At the
30431 time this text was last updated, MTA-STS was still a draft, not yet an RFC.
30432 Exim has no support for MTA-STS as a client, but Exim mail server operators
30433 can choose to publish information describing their TLS configuration using
30434 MTA-STS to let those clients who do use that protocol derive trust
30437 The MTA-STS design requires a certificate from a public Certificate Authority
30438 which is recognized by clients sending to you.
30439 That selection of which CAs are trusted by others is outside your control.
30441 The most interoperable course of action is probably to use
30442 &url(https://letsencrypt.org/,Let's Encrypt), with automated certificate
30443 renewal; to publish the anchor information in DNSSEC-secured DNS via TLSA
30444 records for DANE clients (such as Exim and Postfix) and to publish anchor
30445 information for MTA-STS as well. This is what is done for the &'exim.org'&
30446 domain itself (with caveats around occasionally broken MTA-STS because of
30447 incompatible specification changes prior to reaching RFC status).
30451 . ////////////////////////////////////////////////////////////////////////////
30452 . ////////////////////////////////////////////////////////////////////////////
30454 .chapter "Access control lists" "CHAPACL"
30455 .scindex IIDacl "&ACL;" "description"
30456 .cindex "control of incoming mail"
30457 .cindex "message" "controlling incoming"
30458 .cindex "policy control" "access control lists"
30459 Access Control Lists (ACLs) are defined in a separate section of the runtime
30460 configuration file, headed by &"begin acl"&. Each ACL definition starts with a
30461 name, terminated by a colon. Here is a complete ACL section that contains just
30462 one very small ACL:
30466 accept hosts = one.host.only
30468 You can have as many lists as you like in the ACL section, and the order in
30469 which they appear does not matter. The lists are self-terminating.
30471 The majority of ACLs are used to control Exim's behaviour when it receives
30472 certain SMTP commands. This applies both to incoming TCP/IP connections, and
30473 when a local process submits a message using SMTP by specifying the &%-bs%&
30474 option. The most common use is for controlling which recipients are accepted
30475 in incoming messages. In addition, you can define an ACL that is used to check
30476 local non-SMTP messages. The default configuration file contains an example of
30477 a realistic ACL for checking RCPT commands. This is discussed in chapter
30478 &<<CHAPdefconfil>>&.
30481 .section "Testing ACLs" "SECID188"
30482 The &%-bh%& command line option provides a way of testing your ACL
30483 configuration locally by running a fake SMTP session with which you interact.
30486 .section "Specifying when ACLs are used" "SECID189"
30487 .cindex "&ACL;" "options for specifying"
30488 In order to cause an ACL to be used, you have to name it in one of the relevant
30489 options in the main part of the configuration. These options are:
30490 .cindex "AUTH" "ACL for"
30491 .cindex "DATA" "ACLs for"
30492 .cindex "ETRN" "ACL for"
30493 .cindex "EXPN" "ACL for"
30494 .cindex "HELO" "ACL for"
30495 .cindex "EHLO" "ACL for"
30496 .cindex "DKIM" "ACL for"
30497 .cindex "MAIL" "ACL for"
30498 .cindex "QUIT, ACL for"
30499 .cindex "RCPT" "ACL for"
30500 .cindex "STARTTLS, ACL for"
30501 .cindex "VRFY" "ACL for"
30502 .cindex "SMTP" "connection, ACL for"
30503 .cindex "non-SMTP messages" "ACLs for"
30504 .cindex "MIME content scanning" "ACL for"
30505 .cindex "PRDR" "ACL for"
30508 .irow &%acl_not_smtp%& "ACL for non-SMTP messages"
30509 .irow &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
30510 .irow &%acl_not_smtp_start%& "ACL at start of non-SMTP message"
30511 .irow &%acl_smtp_auth%& "ACL for AUTH"
30512 .irow &%acl_smtp_connect%& "ACL for start of SMTP connection"
30513 .irow &%acl_smtp_data%& "ACL after DATA is complete"
30514 .irow &%acl_smtp_data_prdr%& "ACL for each recipient, after DATA is complete"
30515 .irow &%acl_smtp_dkim%& "ACL for each DKIM signer"
30516 .irow &%acl_smtp_etrn%& "ACL for ETRN"
30517 .irow &%acl_smtp_expn%& "ACL for EXPN"
30518 .irow &%acl_smtp_helo%& "ACL for HELO or EHLO"
30519 .irow &%acl_smtp_mail%& "ACL for MAIL"
30520 .irow &%acl_smtp_mailauth%& "ACL for the AUTH parameter of MAIL"
30521 .irow &%acl_smtp_mime%& "ACL for content-scanning MIME parts"
30522 .irow &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
30523 .irow &%acl_smtp_predata%& "ACL at start of DATA command"
30524 .irow &%acl_smtp_quit%& "ACL for QUIT"
30525 .irow &%acl_smtp_rcpt%& "ACL for RCPT"
30526 .irow &%acl_smtp_starttls%& "ACL for STARTTLS"
30527 .irow &%acl_smtp_vrfy%& "ACL for VRFY"
30530 For example, if you set
30532 acl_smtp_rcpt = small_acl
30534 the little ACL defined above is used whenever Exim receives a RCPT command
30535 in an SMTP dialogue. The majority of policy tests on incoming messages can be
30536 done when RCPT commands arrive. A rejection of RCPT should cause the
30537 sending MTA to give up on the recipient address contained in the RCPT
30538 command, whereas rejection at other times may cause the client MTA to keep on
30539 trying to deliver the message. It is therefore recommended that you do as much
30540 testing as possible at RCPT time.
30543 .section "The non-SMTP ACLs" "SECID190"
30544 .cindex "non-SMTP messages" "ACLs for"
30545 The non-SMTP ACLs apply to all non-interactive incoming messages, that is, they
30546 apply to batched SMTP as well as to non-SMTP messages. (Batched SMTP is not
30547 really SMTP.) Many of the ACL conditions (for example, host tests, and tests on
30548 the state of the SMTP connection such as encryption and authentication) are not
30549 relevant and are forbidden in these ACLs. However, the sender and recipients
30550 are known, so the &%senders%& and &%sender_domains%& conditions and the
30551 &$sender_address$& and &$recipients$& variables can be used. Variables such as
30552 &$authenticated_sender$& are also available. You can specify added header lines
30553 in any of these ACLs.
30555 The &%acl_not_smtp_start%& ACL is run right at the start of receiving a
30556 non-SMTP message, before any of the message has been read. (This is the
30557 analogue of the &%acl_smtp_predata%& ACL for SMTP input.) In the case of
30558 batched SMTP input, it runs after the DATA command has been reached. The
30559 result of this ACL is ignored; it cannot be used to reject a message. If you
30560 really need to, you could set a value in an ACL variable here and reject based
30561 on that in the &%acl_not_smtp%& ACL. However, this ACL can be used to set
30562 controls, and in particular, it can be used to set
30564 control = suppress_local_fixups
30566 This cannot be used in the other non-SMTP ACLs because by the time they are
30567 run, it is too late.
30569 The &%acl_not_smtp_mime%& ACL is available only when Exim is compiled with the
30570 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
30572 The &%acl_not_smtp%& ACL is run just before the &[local_scan()]& function. Any
30573 kind of rejection is treated as permanent, because there is no way of sending a
30574 temporary error for these kinds of message.
30577 .section "The SMTP connect ACL" "SECID191"
30578 .cindex "SMTP" "connection, ACL for"
30579 .oindex &%smtp_banner%&
30580 The ACL test specified by &%acl_smtp_connect%& happens at the start of an SMTP
30581 session, after the test specified by &%host_reject_connection%& (which is now
30582 an anomaly) and any TCP Wrappers testing (if configured). If the connection is
30583 accepted by an &%accept%& verb that has a &%message%& modifier, the contents of
30584 the message override the banner message that is otherwise specified by the
30585 &%smtp_banner%& option.
30588 For tls-on-connect connections, the ACL is run after the TLS connection
30589 is accepted (however, &%host_reject_connection%& is tested before).
30593 .section "The EHLO/HELO ACL" "SECID192"
30594 .cindex "EHLO" "ACL for"
30595 .cindex "HELO" "ACL for"
30596 The ACL test specified by &%acl_smtp_helo%& happens when the client issues an
30597 EHLO or HELO command, after the tests specified by &%helo_accept_junk_hosts%&,
30598 &%helo_allow_chars%&, &%helo_verify_hosts%&, and &%helo_try_verify_hosts%&.
30599 Note that a client may issue more than one EHLO or HELO command in an SMTP
30600 session, and indeed is required to issue a new EHLO or HELO after successfully
30601 setting up encryption following a STARTTLS command.
30603 Note also that a deny neither forces the client to go away nor means that
30604 mail will be refused on the connection. Consider checking for
30605 &$sender_helo_name$& being defined in a MAIL or RCPT ACL to do that.
30607 If the command is accepted by an &%accept%& verb that has a &%message%&
30608 modifier, the message may not contain more than one line (it will be truncated
30609 at the first newline and a panic logged if it does). Such a message cannot
30610 affect the EHLO options that are listed on the second and subsequent lines of
30614 .section "The DATA ACLs" "SECID193"
30615 .cindex "DATA" "ACLs for"
30616 Two ACLs are associated with the DATA command, because it is two-stage
30617 command, with two responses being sent to the client.
30618 When the DATA command is received, the ACL defined by &%acl_smtp_predata%&
30619 is obeyed. This gives you control after all the RCPT commands, but before
30620 the message itself is received. It offers the opportunity to give a negative
30621 response to the DATA command before the data is transmitted. Header lines
30622 added by MAIL or RCPT ACLs are not visible at this time, but any that
30623 are defined here are visible when the &%acl_smtp_data%& ACL is run.
30625 You cannot test the contents of the message, for example, to verify addresses
30626 in the headers, at RCPT time or when the DATA command is received. Such
30627 tests have to appear in the ACL that is run after the message itself has been
30628 received, before the final response to the DATA command is sent. This is
30629 the ACL specified by &%acl_smtp_data%&, which is the second ACL that is
30630 associated with the DATA command.
30632 .cindex CHUNKING "BDAT command"
30633 .cindex BDAT "SMTP command"
30634 .cindex "RFC 3030" CHUNKING
30635 If CHUNKING was advertised and a BDAT command sequence is received,
30636 the &%acl_smtp_predata%& ACL is not run.
30637 . XXX why not? It should be possible, for the first BDAT.
30638 The &%acl_smtp_data%& is run after the last BDAT command and all of
30639 the data specified is received.
30641 For both of these ACLs, it is not possible to reject individual recipients. An
30642 error response rejects the entire message. Unfortunately, it is known that some
30643 MTAs do not treat hard (5&'xx'&) responses to the DATA command (either
30644 before or after the data) correctly &-- they keep the message on their queues
30645 and try again later, but that is their problem, though it does waste some of
30648 The &%acl_smtp_data%& ACL is run after
30649 the &%acl_smtp_data_prdr%&,
30650 the &%acl_smtp_dkim%&
30651 and the &%acl_smtp_mime%& ACLs.
30653 .section "The SMTP DKIM ACL" "SECTDKIMACL"
30654 The &%acl_smtp_dkim%& ACL is available only when Exim is compiled with DKIM support
30655 enabled (which is the default).
30657 The ACL test specified by &%acl_smtp_dkim%& happens after a message has been
30658 received, and is executed for each DKIM signature found in a message. If not
30659 otherwise specified, the default action is to accept.
30661 This ACL is evaluated before &%acl_smtp_mime%& and &%acl_smtp_data%&.
30663 For details on the operation of DKIM, see section &<<SECDKIM>>&.
30666 .section "The SMTP MIME ACL" "SECID194"
30667 The &%acl_smtp_mime%& option is available only when Exim is compiled with the
30668 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
30670 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
30673 .section "The SMTP PRDR ACL" "SECTPRDRACL"
30674 .cindex "PRDR" "ACL for"
30675 .oindex "&%prdr_enable%&"
30676 The &%acl_smtp_data_prdr%& ACL is available only when Exim is compiled
30677 with PRDR support enabled (which is the default).
30678 It becomes active only when the PRDR feature is negotiated between
30679 client and server for a message, and more than one recipient
30682 The ACL test specified by &%acl_smtp_data_prdr%& happens after a message
30683 has been received, and is executed once for each recipient of the message
30684 with &$local_part$& and &$domain$& valid.
30685 The test may accept, defer or deny for individual recipients.
30686 The &%acl_smtp_data%& will still be called after this ACL and
30687 can reject the message overall, even if this ACL has accepted it
30688 for some or all recipients.
30690 PRDR may be used to support per-user content filtering. Without it
30691 one must defer any recipient after the first that has a different
30692 content-filter configuration. With PRDR, the RCPT-time check
30693 .cindex "PRDR" "variable for"
30694 for this can be disabled when the variable &$prdr_requested$&
30696 Any required difference in behaviour of the main DATA-time
30697 ACL should however depend on the PRDR-time ACL having run, as Exim
30698 will avoid doing so in some situations (e.g. single-recipient mails).
30700 See also the &%prdr_enable%& global option
30701 and the &%hosts_try_prdr%& smtp transport option.
30703 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
30704 If the ACL is not defined, processing completes as if
30705 the feature was not requested by the client.
30707 .section "The QUIT ACL" "SECTQUITACL"
30708 .cindex "QUIT, ACL for"
30709 The ACL for the SMTP QUIT command is anomalous, in that the outcome of the ACL
30710 does not affect the response code to QUIT, which is always 221. Thus, the ACL
30711 does not in fact control any access.
30712 For this reason, it may only accept
30713 or warn as its final result.
30715 This ACL can be used for tasks such as custom logging at the end of an SMTP
30716 session. For example, you can use ACL variables in other ACLs to count
30717 messages, recipients, etc., and log the totals at QUIT time using one or
30718 more &%logwrite%& modifiers on a &%warn%& verb.
30720 &*Warning*&: Only the &$acl_c$&&'x'& variables can be used for this, because
30721 the &$acl_m$&&'x'& variables are reset at the end of each incoming message.
30723 You do not need to have a final &%accept%&, but if you do, you can use a
30724 &%message%& modifier to specify custom text that is sent as part of the 221
30727 This ACL is run only for a &"normal"& QUIT. For certain kinds of disastrous
30728 failure (for example, failure to open a log file, or when Exim is bombing out
30729 because it has detected an unrecoverable error), all SMTP commands from the
30730 client are given temporary error responses until QUIT is received or the
30731 connection is closed. In these special cases, the QUIT ACL does not run.
30734 .section "The not-QUIT ACL" "SECTNOTQUITACL"
30735 .vindex &$acl_smtp_notquit$&
30736 The not-QUIT ACL, specified by &%acl_smtp_notquit%&, is run in most cases when
30737 an SMTP session ends without sending QUIT. However, when Exim itself is in bad
30738 trouble, such as being unable to write to its log files, this ACL is not run,
30739 because it might try to do things (such as write to log files) that make the
30740 situation even worse.
30742 Like the QUIT ACL, this ACL is provided to make it possible to do customized
30743 logging or to gather statistics, and its outcome is ignored. The &%delay%&
30744 modifier is forbidden in this ACL, and the only permitted verbs are &%accept%&
30747 .vindex &$smtp_notquit_reason$&
30748 When the not-QUIT ACL is running, the variable &$smtp_notquit_reason$& is set
30749 to a string that indicates the reason for the termination of the SMTP
30750 connection. The possible values are:
30752 .irow &`acl-drop`& "Another ACL issued a &%drop%& command"
30753 .irow &`bad-commands`& "Too many unknown or non-mail commands"
30754 .irow &`command-timeout`& "Timeout while reading SMTP commands"
30755 .irow &`connection-lost`& "The SMTP connection has been lost"
30756 .irow &`data-timeout`& "Timeout while reading message data"
30757 .irow &`local-scan-error`& "The &[local_scan()]& function crashed"
30758 .irow &`local-scan-timeout`& "The &[local_scan()]& function timed out"
30759 .irow &`signal-exit`& "SIGTERM or SIGINT"
30760 .irow &`synchronization-error`& "SMTP synchronization error"
30761 .irow &`tls-failed`& "TLS failed to start"
30763 In most cases when an SMTP connection is closed without having received QUIT,
30764 Exim sends an SMTP response message before actually closing the connection.
30765 With the exception of the &`acl-drop`& case, the default message can be
30766 overridden by the &%message%& modifier in the not-QUIT ACL. In the case of a
30767 &%drop%& verb in another ACL, it is the message from the other ACL that is
30771 .section "Finding an ACL to use" "SECID195"
30772 .cindex "&ACL;" "finding which to use"
30773 The value of an &%acl_smtp_%&&'xxx'& option is expanded before use, so
30774 you can use different ACLs in different circumstances. For example,
30776 acl_smtp_rcpt = ${if ={25}{$interface_port} \
30777 {acl_check_rcpt} {acl_check_rcpt_submit} }
30779 In the default configuration file there are some example settings for
30780 providing an RFC 4409 message &"submission"& service on port 587 and
30781 an RFC 8314 &"submissions"& service on port 465. You can use a string
30782 expansion like this to choose an ACL for MUAs on these ports which is
30783 more appropriate for this purpose than the default ACL on port 25.
30785 The expanded string does not have to be the name of an ACL in the
30786 configuration file; there are other possibilities. Having expanded the
30787 string, Exim searches for an ACL as follows:
30790 If the string begins with a slash, Exim uses it as a filename, and reads its
30791 contents as an ACL. The lines are processed in the same way as lines in the
30792 Exim configuration file. In particular, continuation lines are supported, blank
30793 lines are ignored, as are lines whose first non-whitespace character is &"#"&.
30794 If the file does not exist or cannot be read, an error occurs (typically
30795 causing a temporary failure of whatever caused the ACL to be run). For example:
30797 acl_smtp_data = /etc/acls/\
30798 ${lookup{$sender_host_address}lsearch\
30799 {/etc/acllist}{$value}{default}}
30801 This looks up an ACL file to use on the basis of the host's IP address, falling
30802 back to a default if the lookup fails. If an ACL is successfully read from a
30803 file, it is retained in memory for the duration of the Exim process, so that it
30804 can be re-used without having to re-read the file.
30806 If the string does not start with a slash, and does not contain any spaces,
30807 Exim searches the ACL section of the configuration for an ACL whose name
30808 matches the string.
30810 If no named ACL is found, or if the string contains spaces, Exim parses
30811 the string as an inline ACL. This can save typing in cases where you just
30812 want to have something like
30814 acl_smtp_vrfy = accept
30816 in order to allow free use of the VRFY command. Such a string may contain
30817 newlines; it is processed in the same way as an ACL that is read from a file.
30823 .section "ACL return codes" "SECID196"
30824 .cindex "&ACL;" "return codes"
30825 Except for the QUIT ACL, which does not affect the SMTP return code (see
30826 section &<<SECTQUITACL>>& above), the result of running an ACL is either
30827 &"accept"& or &"deny"&, or, if some test cannot be completed (for example, if a
30828 database is down), &"defer"&. These results cause 2&'xx'&, 5&'xx'&, and 4&'xx'&
30829 return codes, respectively, to be used in the SMTP dialogue. A fourth return,
30830 &"error"&, occurs when there is an error such as invalid syntax in the ACL.
30831 This also causes a 4&'xx'& return code.
30833 For the non-SMTP ACL, &"defer"& and &"error"& are treated in the same way as
30834 &"deny"&, because there is no mechanism for passing temporary errors to the
30835 submitters of non-SMTP messages.
30838 ACLs that are relevant to message reception may also return &"discard"&. This
30839 has the effect of &"accept"&, but causes either the entire message or an
30840 individual recipient address to be discarded. In other words, it is a
30841 blackholing facility. Use it with care.
30843 If the ACL for MAIL returns &"discard"&, all recipients are discarded, and no
30844 ACL is run for subsequent RCPT commands. The effect of &"discard"& in a
30845 RCPT ACL is to discard just the one recipient address. If there are no
30846 recipients left when the message's data is received, the DATA ACL is not
30847 run. A &"discard"& return from the DATA or the non-SMTP ACL discards all the
30848 remaining recipients. The &"discard"& return is not permitted for the
30849 &%acl_smtp_predata%& ACL.
30851 If the ACL for VRFY returns &"accept"&, a recipient verify (without callout)
30852 is done on the address and the result determines the SMTP response.
30855 .cindex "&[local_scan()]& function" "when all recipients discarded"
30856 The &[local_scan()]& function is always run, even if there are no remaining
30857 recipients; it may create new recipients.
30861 .section "Unset ACL options" "SECID197"
30862 .cindex "&ACL;" "unset options"
30863 The default actions when any of the &%acl_%&&'xxx'& options are unset are not
30864 all the same. &*Note*&: These defaults apply only when the relevant ACL is
30865 not defined at all. For any defined ACL, the default action when control
30866 reaches the end of the ACL statements is &"deny"&.
30868 For &%acl_smtp_quit%& and &%acl_not_smtp_start%& there is no default because
30869 these two are ACLs that are used only for their side effects. They cannot be
30870 used to accept or reject anything.
30872 For &%acl_not_smtp%&, &%acl_smtp_auth%&, &%acl_smtp_connect%&,
30873 &%acl_smtp_data%&, &%acl_smtp_helo%&, &%acl_smtp_mail%&, &%acl_smtp_mailauth%&,
30874 &%acl_smtp_mime%&, &%acl_smtp_predata%&, and &%acl_smtp_starttls%&, the action
30875 when the ACL is not defined is &"accept"&.
30877 For the others (&%acl_smtp_etrn%&, &%acl_smtp_expn%&, &%acl_smtp_rcpt%&, and
30878 &%acl_smtp_vrfy%&), the action when the ACL is not defined is &"deny"&.
30879 This means that &%acl_smtp_rcpt%& must be defined in order to receive any
30880 messages over an SMTP connection. For an example, see the ACL in the default
30881 configuration file.
30886 .section "Data for message ACLs" "SECID198"
30887 .cindex "&ACL;" "data for message ACL"
30889 .vindex &$local_part$&
30890 .vindex &$sender_address$&
30891 .vindex &$sender_host_address$&
30892 .vindex &$smtp_command$&
30893 When a MAIL or RCPT ACL, or either of the DATA ACLs, is running, the variables
30894 that contain information about the host and the message's sender (for example,
30895 &$sender_host_address$& and &$sender_address$&) are set, and can be used in ACL
30896 statements. In the case of RCPT (but not MAIL or DATA), &$domain$& and
30897 &$local_part$& are set from the argument address. The entire SMTP command
30898 is available in &$smtp_command$&.
30900 When an ACL for the AUTH parameter of MAIL is running, the variables that
30901 contain information about the host are set, but &$sender_address$& is not yet
30902 set. Section &<<SECTauthparamail>>& contains a discussion of this parameter and
30905 .vindex "&$message_size$&"
30906 The &$message_size$& variable is set to the value of the SIZE parameter on
30907 the MAIL command at MAIL, RCPT and pre-data time, or to -1 if
30908 that parameter is not given. The value is updated to the true message size by
30909 the time the final DATA ACL is run (after the message data has been
30912 .vindex "&$rcpt_count$&"
30913 .vindex "&$recipients_count$&"
30914 The &$rcpt_count$& variable increases by one for each RCPT command received.
30915 The &$recipients_count$& variable increases by one each time a RCPT command is
30916 accepted, so while an ACL for RCPT is being processed, it contains the number
30917 of previously accepted recipients. At DATA time (for both the DATA ACLs),
30918 &$rcpt_count$& contains the total number of RCPT commands, and
30919 &$recipients_count$& contains the total number of accepted recipients.
30925 .section "Data for non-message ACLs" "SECTdatfornon"
30926 .cindex "&ACL;" "data for non-message ACL"
30927 .vindex &$smtp_command_argument$&
30928 .vindex &$smtp_command$&
30929 When an ACL is being run for AUTH, EHLO, ETRN, EXPN, HELO, STARTTLS, or VRFY,
30930 the remainder of the SMTP command line is placed in &$smtp_command_argument$&,
30931 and the entire SMTP command is available in &$smtp_command$&.
30932 These variables can be tested using a &%condition%& condition. For example,
30933 here is an ACL for use with AUTH, which insists that either the session is
30934 encrypted, or the CRAM-MD5 authentication method is used. In other words, it
30935 does not permit authentication methods that use cleartext passwords on
30936 unencrypted connections.
30939 accept encrypted = *
30940 accept condition = ${if eq{${uc:$smtp_command_argument}}\
30942 deny message = TLS encryption or CRAM-MD5 required
30944 (Another way of applying this restriction is to arrange for the authenticators
30945 that use cleartext passwords not to be advertised when the connection is not
30946 encrypted. You can use the generic &%server_advertise_condition%& authenticator
30947 option to do this.)
30951 .section "Format of an ACL" "SECID199"
30952 .cindex "&ACL;" "format of"
30953 .cindex "&ACL;" "verbs, definition of"
30954 An individual ACL consists of a number of statements. Each statement starts
30955 with a verb, optionally followed by a number of conditions and &"modifiers"&.
30956 Modifiers can change the way the verb operates, define error and log messages,
30957 set variables, insert delays, and vary the processing of accepted messages.
30959 If all the conditions are met, the verb is obeyed. The same condition may be
30960 used (with different arguments) more than once in the same statement. This
30961 provides a means of specifying an &"and"& conjunction between conditions. For
30964 deny dnslists = list1.example
30965 dnslists = list2.example
30967 If there are no conditions, the verb is always obeyed. Exim stops evaluating
30968 the conditions and modifiers when it reaches a condition that fails. What
30969 happens then depends on the verb (and in one case, on a special modifier). Not
30970 all the conditions make sense at every testing point. For example, you cannot
30971 test a sender address in the ACL that is run for a VRFY command.
30974 .section "ACL verbs" "SECID200"
30975 The ACL verbs are as follows:
30978 .cindex "&%accept%& ACL verb"
30979 &%accept%&: If all the conditions are met, the ACL returns &"accept"&. If any
30980 of the conditions are not met, what happens depends on whether &%endpass%&
30981 appears among the conditions (for syntax see below). If the failing condition
30982 is before &%endpass%&, control is passed to the next ACL statement; if it is
30983 after &%endpass%&, the ACL returns &"deny"&. Consider this statement, used to
30984 check a RCPT command:
30986 accept domains = +local_domains
30990 If the recipient domain does not match the &%domains%& condition, control
30991 passes to the next statement. If it does match, the recipient is verified, and
30992 the command is accepted if verification succeeds. However, if verification
30993 fails, the ACL yields &"deny"&, because the failing condition is after
30996 The &%endpass%& feature has turned out to be confusing to many people, so its
30997 use is not recommended nowadays. It is always possible to rewrite an ACL so
30998 that &%endpass%& is not needed, and it is no longer used in the default
31001 .cindex "&%message%& ACL modifier" "with &%accept%&"
31002 If a &%message%& modifier appears on an &%accept%& statement, its action
31003 depends on whether or not &%endpass%& is present. In the absence of &%endpass%&
31004 (when an &%accept%& verb either accepts or passes control to the next
31005 statement), &%message%& can be used to vary the message that is sent when an
31006 SMTP command is accepted. For example, in a RCPT ACL you could have:
31008 &`accept `&<&'some conditions'&>
31009 &` message = OK, I will allow you through today`&
31011 You can specify an SMTP response code, optionally followed by an &"extended
31012 response code"& at the start of the message, but the first digit must be the
31013 same as would be sent by default, which is 2 for an &%accept%& verb.
31015 If &%endpass%& is present in an &%accept%& statement, &%message%& specifies
31016 an error message that is used when access is denied. This behaviour is retained
31017 for backward compatibility, but current &"best practice"& is to avoid the use
31022 .cindex "&%defer%& ACL verb"
31023 &%defer%&: If all the conditions are true, the ACL returns &"defer"& which, in
31024 an SMTP session, causes a 4&'xx'& response to be given. For a non-SMTP ACL,
31025 &%defer%& is the same as &%deny%&, because there is no way of sending a
31026 temporary error. For a RCPT command, &%defer%& is much the same as using a
31027 &(redirect)& router and &`:defer:`& while verifying, but the &%defer%& verb can
31028 be used in any ACL, and even for a recipient it might be a simpler approach.
31032 .cindex "&%deny%& ACL verb"
31033 &%deny%&: If all the conditions are met, the ACL returns &"deny"&. If any of
31034 the conditions are not met, control is passed to the next ACL statement. For
31037 deny dnslists = blackholes.mail-abuse.org
31039 rejects commands from hosts that are on a DNS black list.
31043 .cindex "&%discard%& ACL verb"
31044 &%discard%&: This verb behaves like &%accept%&, except that it returns
31045 &"discard"& from the ACL instead of &"accept"&. It is permitted only on ACLs
31046 that are concerned with receiving messages. When all the conditions are true,
31047 the sending entity receives a &"success"& response. However, &%discard%& causes
31048 recipients to be discarded. If it is used in an ACL for RCPT, just the one
31049 recipient is discarded; if used for MAIL, DATA or in the non-SMTP ACL, all the
31050 message's recipients are discarded. Recipients that are discarded before DATA
31051 do not appear in the log line when the &%received_recipients%& log selector is set.
31053 If the &%log_message%& modifier is set when &%discard%& operates,
31054 its contents are added to the line that is automatically written to the log.
31055 The &%message%& modifier operates exactly as it does for &%accept%&.
31059 .cindex "&%drop%& ACL verb"
31060 &%drop%&: This verb behaves like &%deny%&, except that an SMTP connection is
31061 forcibly closed after the 5&'xx'& error message has been sent. For example:
31063 drop condition = ${if > {$rcpt_count}{20}}
31064 message = I don't take more than 20 RCPTs
31066 There is no difference between &%deny%& and &%drop%& for the connect-time ACL.
31067 The connection is always dropped after sending a 550 response.
31070 .cindex "&%require%& ACL verb"
31071 &%require%&: If all the conditions are met, control is passed to the next ACL
31072 statement. If any of the conditions are not met, the ACL returns &"deny"&. For
31073 example, when checking a RCPT command,
31075 require message = Sender did not verify
31078 passes control to subsequent statements only if the message's sender can be
31079 verified. Otherwise, it rejects the command. Note the positioning of the
31080 &%message%& modifier, before the &%verify%& condition. The reason for this is
31081 discussed in section &<<SECTcondmodproc>>&.
31084 .cindex "&%warn%& ACL verb"
31085 &%warn%&: If all the conditions are true, a line specified by the
31086 &%log_message%& modifier is written to Exim's main log. Control always passes
31087 to the next ACL statement. If any condition is false, the log line is not
31088 written. If an identical log line is requested several times in the same
31089 message, only one copy is actually written to the log. If you want to force
31090 duplicates to be written, use the &%logwrite%& modifier instead.
31092 If &%log_message%& is not present, a &%warn%& verb just checks its conditions
31093 and obeys any &"immediate"& modifiers (such as &%control%&, &%set%&,
31094 &%logwrite%&, &%add_header%&, and &%remove_header%&) that appear before the
31095 first failing condition. There is more about adding header lines in section
31096 &<<SECTaddheadacl>>&.
31098 If any condition on a &%warn%& statement cannot be completed (that is, there is
31099 some sort of defer), the log line specified by &%log_message%& is not written.
31100 This does not include the case of a forced failure from a lookup, which
31101 is considered to be a successful completion. After a defer, no further
31102 conditions or modifiers in the &%warn%& statement are processed. The incident
31103 is logged, and the ACL continues to be processed, from the next statement
31107 .vindex "&$acl_verify_message$&"
31108 When one of the &%warn%& conditions is an address verification that fails, the
31109 text of the verification failure message is in &$acl_verify_message$&. If you
31110 want this logged, you must set it up explicitly. For example:
31112 warn !verify = sender
31113 log_message = sender verify failed: $acl_verify_message
31117 At the end of each ACL there is an implicit unconditional &%deny%&.
31119 As you can see from the examples above, the conditions and modifiers are
31120 written one to a line, with the first one on the same line as the verb, and
31121 subsequent ones on following lines. If you have a very long condition, you can
31122 continue it onto several physical lines by the usual backslash continuation
31123 mechanism. It is conventional to align the conditions vertically.
31127 .section "ACL variables" "SECTaclvariables"
31128 .cindex "&ACL;" "variables"
31129 There are some special variables that can be set during ACL processing. They
31130 can be used to pass information between different ACLs, different invocations
31131 of the same ACL in the same SMTP connection, and between ACLs and the routers,
31132 transports, and filters that are used to deliver a message. The names of these
31133 variables must begin with &$acl_c$& or &$acl_m$&, followed either by a digit or
31134 an underscore, but the remainder of the name can be any sequence of
31135 alphanumeric characters and underscores that you choose. There is no limit on
31136 the number of ACL variables. The two sets act as follows:
31138 The values of those variables whose names begin with &$acl_c$& persist
31139 throughout an SMTP connection. They are never reset. Thus, a value that is set
31140 while receiving one message is still available when receiving the next message
31141 on the same SMTP connection.
31143 The values of those variables whose names begin with &$acl_m$& persist only
31144 while a message is being received. They are reset afterwards. They are also
31145 reset by MAIL, RSET, EHLO, HELO, and after starting up a TLS session.
31148 When a message is accepted, the current values of all the ACL variables are
31149 preserved with the message and are subsequently made available at delivery
31150 time. The ACL variables are set by a modifier called &%set%&. For example:
31152 accept hosts = whatever
31153 set acl_m4 = some value
31154 accept authenticated = *
31155 set acl_c_auth = yes
31157 &*Note*&: A leading dollar sign is not used when naming a variable that is to
31158 be set. If you want to set a variable without taking any action, you can use a
31159 &%warn%& verb without any other modifiers or conditions.
31161 .oindex &%strict_acl_vars%&
31162 What happens if a syntactically valid but undefined ACL variable is
31163 referenced depends on the setting of the &%strict_acl_vars%& option. If it is
31164 false (the default), an empty string is substituted; if it is true, an
31165 error is generated.
31167 Versions of Exim before 4.64 have a limited set of numbered variables, but
31168 their names are compatible, so there is no problem with upgrading.
31171 .section "Condition and modifier processing" "SECTcondmodproc"
31172 .cindex "&ACL;" "conditions; processing"
31173 .cindex "&ACL;" "modifiers; processing"
31174 An exclamation mark preceding a condition negates its result. For example:
31176 deny domains = *.dom.example
31177 !verify = recipient
31179 causes the ACL to return &"deny"& if the recipient domain ends in
31180 &'dom.example'& and the recipient address cannot be verified. Sometimes
31181 negation can be used on the right-hand side of a condition. For example, these
31182 two statements are equivalent:
31184 deny hosts = !192.168.3.4
31185 deny !hosts = 192.168.3.4
31187 However, for many conditions (&%verify%& being a good example), only left-hand
31188 side negation of the whole condition is possible.
31190 The arguments of conditions and modifiers are expanded. A forced failure
31191 of an expansion causes a condition to be ignored, that is, it behaves as if the
31192 condition is true. Consider these two statements:
31194 accept senders = ${lookup{$host_name}lsearch\
31195 {/some/file}{$value}fail}
31196 accept senders = ${lookup{$host_name}lsearch\
31197 {/some/file}{$value}{}}
31199 Each attempts to look up a list of acceptable senders. If the lookup succeeds,
31200 the returned list is searched, but if the lookup fails the behaviour is
31201 different in the two cases. The &%fail%& in the first statement causes the
31202 condition to be ignored, leaving no further conditions. The &%accept%& verb
31203 therefore succeeds. The second statement, however, generates an empty list when
31204 the lookup fails. No sender can match an empty list, so the condition fails,
31205 and therefore the &%accept%& also fails.
31207 ACL modifiers appear mixed in with conditions in ACL statements. Some of them
31208 specify actions that are taken as the conditions for a statement are checked;
31209 others specify text for messages that are used when access is denied or a
31210 warning is generated. The &%control%& modifier affects the way an incoming
31211 message is handled.
31213 The positioning of the modifiers in an ACL statement is important, because the
31214 processing of a verb ceases as soon as its outcome is known. Only those
31215 modifiers that have already been encountered will take effect. For example,
31216 consider this use of the &%message%& modifier:
31218 require message = Can't verify sender
31220 message = Can't verify recipient
31222 message = This message cannot be used
31224 If sender verification fails, Exim knows that the result of the statement is
31225 &"deny"&, so it goes no further. The first &%message%& modifier has been seen,
31226 so its text is used as the error message. If sender verification succeeds, but
31227 recipient verification fails, the second message is used. If recipient
31228 verification succeeds, the third message becomes &"current"&, but is never used
31229 because there are no more conditions to cause failure.
31231 For the &%deny%& verb, on the other hand, it is always the last &%message%&
31232 modifier that is used, because all the conditions must be true for rejection to
31233 happen. Specifying more than one &%message%& modifier does not make sense, and
31234 the message can even be specified after all the conditions. For example:
31237 !senders = *@my.domain.example
31238 message = Invalid sender from client host
31240 The &"deny"& result does not happen until the end of the statement is reached,
31241 by which time Exim has set up the message.
31245 .section "ACL modifiers" "SECTACLmodi"
31246 .cindex "&ACL;" "modifiers; list of"
31247 The ACL modifiers are as follows:
31250 .vitem &*add_header*&&~=&~<&'text'&>
31251 This modifier specifies one or more header lines that are to be added to an
31252 incoming message, assuming, of course, that the message is ultimately
31253 accepted. For details, see section &<<SECTaddheadacl>>&.
31255 .vitem &*continue*&&~=&~<&'text'&>
31256 .cindex "&%continue%& ACL modifier"
31257 .cindex "database" "updating in ACL"
31258 This modifier does nothing of itself, and processing of the ACL always
31259 continues with the next condition or modifier. The value of &%continue%& is in
31260 the side effects of expanding its argument. Typically this could be used to
31261 update a database. It is really just a syntactic tidiness, to avoid having to
31262 write rather ugly lines like this:
31264 &`condition = ${if eq{0}{`&<&'some expansion'&>&`}{true}{true}}`&
31266 Instead, all you need is
31268 &`continue = `&<&'some expansion'&>
31271 .vitem &*control*&&~=&~<&'text'&>
31272 .cindex "&%control%& ACL modifier"
31273 This modifier affects the subsequent processing of the SMTP connection or of an
31274 incoming message that is accepted. The effect of the first type of control
31275 lasts for the duration of the connection, whereas the effect of the second type
31276 lasts only until the current message has been received. The message-specific
31277 controls always apply to the whole message, not to individual recipients,
31278 even if the &%control%& modifier appears in a RCPT ACL.
31280 As there are now quite a few controls that can be applied, they are described
31281 separately in section &<<SECTcontrols>>&. The &%control%& modifier can be used
31282 in several different ways. For example:
31284 . ==== As this is a nested list, any displays it contains must be indented
31285 . ==== as otherwise they are too far to the left. That comment applies only
31286 . ==== when xmlto and fop are used; formatting with sdop gets it right either
31290 It can be at the end of an &%accept%& statement:
31292 accept ...some conditions
31295 In this case, the control is applied when this statement yields &"accept"&, in
31296 other words, when the conditions are all true.
31299 It can be in the middle of an &%accept%& statement:
31301 accept ...some conditions...
31303 ...some more conditions...
31305 If the first set of conditions are true, the control is applied, even if the
31306 statement does not accept because one of the second set of conditions is false.
31307 In this case, some subsequent statement must yield &"accept"& for the control
31311 It can be used with &%warn%& to apply the control, leaving the
31312 decision about accepting or denying to a subsequent verb. For
31315 warn ...some conditions...
31319 This example of &%warn%& does not contain &%message%&, &%log_message%&, or
31320 &%logwrite%&, so it does not add anything to the message and does not write a
31324 If you want to apply a control unconditionally, you can use it with a
31325 &%require%& verb. For example:
31327 require control = no_multiline_responses
31331 .vitem &*delay*&&~=&~<&'time'&>
31332 .cindex "&%delay%& ACL modifier"
31334 This modifier may appear in any ACL except notquit. It causes Exim to wait for
31335 the time interval before proceeding. However, when testing Exim using the
31336 &%-bh%& option, the delay is not actually imposed (an appropriate message is
31337 output instead). The time is given in the usual Exim notation, and the delay
31338 happens as soon as the modifier is processed. In an SMTP session, pending
31339 output is flushed before the delay is imposed.
31341 Like &%control%&, &%delay%& can be used with &%accept%& or &%deny%&, for
31344 deny ...some conditions...
31347 The delay happens if all the conditions are true, before the statement returns
31348 &"deny"&. Compare this with:
31351 ...some conditions...
31353 which waits for 30s before processing the conditions. The &%delay%& modifier
31354 can also be used with &%warn%& and together with &%control%&:
31356 warn ...some conditions...
31362 If &%delay%& is encountered when the SMTP PIPELINING extension is in use,
31363 responses to several commands are no longer buffered and sent in one packet (as
31364 they would normally be) because all output is flushed before imposing the
31365 delay. This optimization is disabled so that a number of small delays do not
31366 appear to the client as one large aggregated delay that might provoke an
31367 unwanted timeout. You can, however, disable output flushing for &%delay%& by
31368 using a &%control%& modifier to set &%no_delay_flush%&.
31372 .cindex "&%endpass%& ACL modifier"
31373 This modifier, which has no argument, is recognized only in &%accept%& and
31374 &%discard%& statements. It marks the boundary between the conditions whose
31375 failure causes control to pass to the next statement, and the conditions whose
31376 failure causes the ACL to return &"deny"&. This concept has proved to be
31377 confusing to some people, so the use of &%endpass%& is no longer recommended as
31378 &"best practice"&. See the description of &%accept%& above for more details.
31381 .vitem &*log_message*&&~=&~<&'text'&>
31382 .cindex "&%log_message%& ACL modifier"
31383 This modifier sets up a message that is used as part of the log message if the
31384 ACL denies access or a &%warn%& statement's conditions are true. For example:
31386 require log_message = wrong cipher suite $tls_in_cipher
31387 encrypted = DES-CBC3-SHA
31389 &%log_message%& is also used when recipients are discarded by &%discard%&. For
31392 &`discard `&<&'some conditions'&>
31393 &` log_message = Discarded $local_part@$domain because...`&
31395 When access is denied, &%log_message%& adds to any underlying error message
31396 that may exist because of a condition failure. For example, while verifying a
31397 recipient address, a &':fail:'& redirection might have already set up a
31400 The message may be defined before the conditions to which it applies, because
31401 the string expansion does not happen until Exim decides that access is to be
31402 denied. This means that any variables that are set by the condition are
31403 available for inclusion in the message. For example, the &$dnslist_$&<&'xxx'&>
31404 variables are set after a DNS black list lookup succeeds. If the expansion of
31405 &%log_message%& fails, or if the result is an empty string, the modifier is
31408 .vindex "&$acl_verify_message$&"
31409 If you want to use a &%warn%& statement to log the result of an address
31410 verification, you can use &$acl_verify_message$& to include the verification
31413 If &%log_message%& is used with a &%warn%& statement, &"Warning:"& is added to
31414 the start of the logged message. If the same warning log message is requested
31415 more than once while receiving a single email message, only one copy is
31416 actually logged. If you want to log multiple copies, use &%logwrite%& instead
31417 of &%log_message%&. In the absence of &%log_message%& and &%logwrite%&, nothing
31418 is logged for a successful &%warn%& statement.
31420 If &%log_message%& is not present and there is no underlying error message (for
31421 example, from the failure of address verification), but &%message%& is present,
31422 the &%message%& text is used for logging rejections. However, if any text for
31423 logging contains newlines, only the first line is logged. In the absence of
31424 both &%log_message%& and &%message%&, a default built-in message is used for
31425 logging rejections.
31428 .vitem "&*log_reject_target*&&~=&~<&'log name list'&>"
31429 .cindex "&%log_reject_target%& ACL modifier"
31430 .cindex "logging in ACL" "specifying which log"
31431 This modifier makes it possible to specify which logs are used for messages
31432 about ACL rejections. Its argument is a colon-separated list of words that can
31433 be &"main"&, &"reject"&, or &"panic"&. The default is &`main:reject`&. The list
31434 may be empty, in which case a rejection is not logged at all. For example, this
31435 ACL fragment writes no logging information when access is denied:
31437 &`deny `&<&'some conditions'&>
31438 &` log_reject_target =`&
31440 This modifier can be used in SMTP and non-SMTP ACLs. It applies to both
31441 permanent and temporary rejections. Its effect lasts for the rest of the
31445 .vitem &*logwrite*&&~=&~<&'text'&>
31446 .cindex "&%logwrite%& ACL modifier"
31447 .cindex "logging in ACL" "immediate"
31448 This modifier writes a message to a log file as soon as it is encountered when
31449 processing an ACL. (Compare &%log_message%&, which, except in the case of
31450 &%warn%& and &%discard%&, is used only if the ACL statement denies
31451 access.) The &%logwrite%& modifier can be used to log special incidents in
31454 &`accept `&<&'some special conditions'&>
31455 &` control = freeze`&
31456 &` logwrite = froze message because ...`&
31458 By default, the message is written to the main log. However, it may begin
31459 with a colon, followed by a comma-separated list of log names, and then
31460 another colon, to specify exactly which logs are to be written. For
31463 logwrite = :main,reject: text for main and reject logs
31464 logwrite = :panic: text for panic log only
31468 .vitem &*message*&&~=&~<&'text'&>
31469 .cindex "&%message%& ACL modifier"
31470 This modifier sets up a text string that is expanded and used as a response
31471 message when an ACL statement terminates the ACL with an &"accept"&, &"deny"&,
31472 or &"defer"& response. (In the case of the &%accept%& and &%discard%& verbs,
31473 there is some complication if &%endpass%& is involved; see the description of
31474 &%accept%& for details.)
31476 The expansion of the message happens at the time Exim decides that the ACL is
31477 to end, not at the time it processes &%message%&. If the expansion fails, or
31478 generates an empty string, the modifier is ignored. Here is an example where
31479 &%message%& must be specified first, because the ACL ends with a rejection if
31480 the &%hosts%& condition fails:
31482 require message = Host not recognized
31485 (Once a condition has failed, no further conditions or modifiers are
31488 .cindex "SMTP" "error codes"
31489 .oindex "&%smtp_banner%&
31490 For ACLs that are triggered by SMTP commands, the message is returned as part
31491 of the SMTP response. The use of &%message%& with &%accept%& (or &%discard%&)
31492 is meaningful only for SMTP, as no message is returned when a non-SMTP message
31493 is accepted. In the case of the connect ACL, accepting with a message modifier
31494 overrides the value of &%smtp_banner%&. For the EHLO/HELO ACL, a customized
31495 accept message may not contain more than one line (otherwise it will be
31496 truncated at the first newline and a panic logged), and it cannot affect the
31499 When SMTP is involved, the message may begin with an overriding response code,
31500 consisting of three digits optionally followed by an &"extended response code"&
31501 of the form &'n.n.n'&, each code being followed by a space. For example:
31503 deny message = 599 1.2.3 Host not welcome
31504 hosts = 192.168.34.0/24
31506 The first digit of the supplied response code must be the same as would be sent
31507 by default. A panic occurs if it is not. Exim uses a 550 code when it denies
31508 access, but for the predata ACL, note that the default success code is 354, not
31511 Notwithstanding the previous paragraph, for the QUIT ACL, unlike the others,
31512 the message modifier cannot override the 221 response code.
31514 The text in a &%message%& modifier is literal; any quotes are taken as
31515 literals, but because the string is expanded, backslash escapes are processed
31516 anyway. If the message contains newlines, this gives rise to a multi-line SMTP
31519 .vindex "&$acl_verify_message$&"
31520 While the text is being expanded, the &$acl_verify_message$& variable
31521 contains any message previously set.
31522 Afterwards, &$acl_verify_message$& is cleared.
31524 If &%message%& is used on a statement that verifies an address, the message
31525 specified overrides any message that is generated by the verification process.
31526 However, the original message is available in the variable
31527 &$acl_verify_message$&, so you can incorporate it into your message if you
31528 wish. In particular, if you want the text from &%:fail:%& items in &(redirect)&
31529 routers to be passed back as part of the SMTP response, you should either not
31530 use a &%message%& modifier, or make use of &$acl_verify_message$&.
31532 For compatibility with previous releases of Exim, a &%message%& modifier that
31533 is used with a &%warn%& verb behaves in a similar way to the &%add_header%&
31534 modifier, but this usage is now deprecated. However, &%message%& acts only when
31535 all the conditions are true, wherever it appears in an ACL command, whereas
31536 &%add_header%& acts as soon as it is encountered. If &%message%& is used with
31537 &%warn%& in an ACL that is not concerned with receiving a message, it has no
31541 .vitem &*queue*&&~=&~<&'text'&>
31542 .cindex "&%queue%& ACL modifier"
31543 .cindex "named queues" "selecting in ACL"
31544 This modifier specifies the use of a named queue for spool files
31546 It can only be used before the message is received (i.e. not in
31548 This could be used, for example, for known high-volume burst sources
31549 of traffic, or for quarantine of messages.
31550 Separate queue-runner processes will be needed for named queues.
31551 If the text after expansion is empty, the default queue is used.
31554 .vitem &*remove_header*&&~=&~<&'text'&>
31555 This modifier specifies one or more header names in a colon-separated list
31556 that are to be removed from an incoming message, assuming, of course, that
31557 the message is ultimately accepted. For details, see section &<<SECTremoveheadacl>>&.
31560 .vitem &*set*&&~<&'acl_name'&>&~=&~<&'value'&>
31561 .cindex "&%set%& ACL modifier"
31562 This modifier puts a value into one of the ACL variables (see section
31563 &<<SECTaclvariables>>&).
31566 .vitem &*udpsend*&&~=&~<&'parameters'&>
31567 .cindex "UDP communications"
31568 This modifier sends a UDP packet, for purposes such as statistics
31569 collection or behaviour monitoring. The parameters are expanded, and
31570 the result of the expansion must be a colon-separated list consisting
31571 of a destination server, port number, and the packet contents. The
31572 server can be specified as a host name or IPv4 or IPv6 address. The
31573 separator can be changed with the usual angle bracket syntax. For
31574 example, you might want to collect information on which hosts connect
31577 udpsend = <; 2001:dB8::dead:beef ; 1234 ;\
31578 $tod_zulu $sender_host_address
31585 .section "Use of the control modifier" "SECTcontrols"
31586 .cindex "&%control%& ACL modifier"
31587 The &%control%& modifier supports the following settings:
31590 .vitem &*control&~=&~allow_auth_unadvertised*&
31591 This modifier allows a client host to use the SMTP AUTH command even when it
31592 has not been advertised in response to EHLO. Furthermore, because there are
31593 apparently some really broken clients that do this, Exim will accept AUTH after
31594 HELO (rather than EHLO) when this control is set. It should be used only if you
31595 really need it, and you should limit its use to those broken clients that do
31596 not work without it. For example:
31598 warn hosts = 192.168.34.25
31599 control = allow_auth_unadvertised
31601 Normally, when an Exim server receives an AUTH command, it checks the name of
31602 the authentication mechanism that is given in the command to ensure that it
31603 matches an advertised mechanism. When this control is set, the check that a
31604 mechanism has been advertised is bypassed. Any configured mechanism can be used
31605 by the client. This control is permitted only in the connection and HELO ACLs.
31608 .vitem &*control&~=&~caseful_local_part*& &&&
31609 &*control&~=&~caselower_local_part*&
31610 .cindex "&ACL;" "case of local part in"
31611 .cindex "case of local parts"
31612 .vindex "&$local_part$&"
31613 These two controls are permitted only in the ACL specified by &%acl_smtp_rcpt%&
31614 (that is, during RCPT processing). By default, the contents of &$local_part$&
31615 are lower cased before ACL processing. If &"caseful_local_part"& is specified,
31616 any uppercase letters in the original local part are restored in &$local_part$&
31617 for the rest of the ACL, or until a control that sets &"caselower_local_part"&
31620 These controls affect only the current recipient. Moreover, they apply only to
31621 local part handling that takes place directly in the ACL (for example, as a key
31622 in lookups). If a test to verify the recipient is obeyed, the case-related
31623 handling of the local part during the verification is controlled by the router
31624 configuration (see the &%caseful_local_part%& generic router option).
31626 This facility could be used, for example, to add a spam score to local parts
31627 containing upper case letters. For example, using &$acl_m4$& to accumulate the
31630 warn control = caseful_local_part
31631 set acl_m4 = ${eval:\
31633 ${if match{$local_part}{[A-Z]}{1}{0}}\
31635 control = caselower_local_part
31637 Notice that we put back the lower cased version afterwards, assuming that
31638 is what is wanted for subsequent tests.
31641 .vitem &*control&~=&~cutthrough_delivery/*&<&'options'&>
31642 .cindex "&ACL;" "cutthrough routing"
31643 .cindex "cutthrough" "requesting"
31644 This option requests delivery be attempted while the item is being received.
31646 The option is usable in the RCPT ACL.
31647 If enabled for a message received via smtp and routed to an smtp transport,
31648 and only one transport, interface, destination host and port combination
31649 is used for all recipients of the message,
31650 then the delivery connection is made while the receiving connection is open
31651 and data is copied from one to the other.
31653 An attempt to set this option for any recipient but the first
31654 for a mail will be quietly ignored.
31655 If a recipient-verify callout
31657 connection is subsequently
31658 requested in the same ACL it is held open and used for
31659 any subsequent recipients and the data,
31660 otherwise one is made after the initial RCPT ACL completes.
31662 Note that routers are used in verify mode,
31663 and cannot depend on content of received headers.
31664 Note also that headers cannot be
31665 modified by any of the post-data ACLs (DATA, MIME and DKIM).
31666 Headers may be modified by routers (subject to the above) and transports.
31667 The &'Received-By:'& header is generated as soon as the body reception starts,
31668 rather than the traditional time after the full message is received;
31669 this will affect the timestamp.
31671 All the usual ACLs are called; if one results in the message being
31672 rejected, all effort spent in delivery (including the costs on
31673 the ultimate destination) will be wasted.
31674 Note that in the case of data-time ACLs this includes the entire
31677 Cutthrough delivery is not supported via transport-filters or when DKIM signing
31678 of outgoing messages is done, because it sends data to the ultimate destination
31679 before the entire message has been received from the source.
31680 It is not supported for messages received with the SMTP PRDR
31684 Should the ultimate destination system positively accept or reject the mail,
31685 a corresponding indication is given to the source system and nothing is queued.
31686 If the item is successfully delivered in cutthrough mode
31687 the delivery log lines are tagged with ">>" rather than "=>" and appear
31688 before the acceptance "<=" line.
31690 If there is a temporary error the item is queued for later delivery in the
31692 This behaviour can be adjusted by appending the option &*defer=*&<&'value'&>
31693 to the control; the default value is &"spool"& and the alternate value
31694 &"pass"& copies an SMTP defer response from the target back to the initiator
31695 and does not queue the message.
31696 Note that this is independent of any recipient verify conditions in the ACL.
31698 Delivery in this mode avoids the generation of a bounce mail to a
31700 sender when the destination system is doing content-scan based rejection.
31703 .vitem &*control&~=&~debug/*&<&'options'&>
31704 .cindex "&ACL;" "enabling debug logging"
31705 .cindex "debugging" "enabling from an ACL"
31706 This control turns on debug logging, almost as though Exim had been invoked
31707 with &`-d`&, with the output going to a new logfile in the usual logs directory,
31708 by default called &'debuglog'&.
31711 Options are a slash-separated list.
31712 If an option takes an argument, the option name and argument are separated by
31713 an equals character.
31714 Several options are supported:
31717 tag=<&'suffix'&> The filename can be adjusted with thise option.
31718 The argument, which may access any variables already defined,
31719 is appended to the default name.
31721 opts=<&'debug&~options'&> The argument specififes what is to be logged,
31722 using the same values as the &`-d`& command-line option.
31724 stop Logging started with this control may be
31725 stopped by using this option.
31727 kill Logging started with this control may be
31728 stopped by using this option.
31729 Additionally the debug file will be removed,
31730 providing one means for speculative debug tracing.
31732 pretrigger=<&'size'&> This option specifies a memory buffuer to be used
31733 for pre-trigger debug capture.
31734 Debug lines are recorded in the buffer until
31735 and if) a trigger occurs; at which time they are
31736 dumped to the debug file. Newer lines displace the
31737 oldest if the buffer is full. After a trigger,
31738 immediate writes to file are done as normal.
31740 trigger=<&'reason'&> This option selects cause for the pretrigger buffer
31741 see above) to be copied to file. A reason of $*now*
31742 take effect immediately; one of &*paniclog*& triggers
31743 on a write to the panic log.
31746 Some examples (which depend on variables that don't exist in all
31750 control = debug/tag=.$sender_host_address
31751 control = debug/opts=+expand+acl
31752 control = debug/tag=.$message_exim_id/opts=+expand
31753 control = debug/kill
31754 control = debug/opts=+all/pretrigger=1024/trigger=paniclog
31755 control = debug/trigger=now
31759 .vitem &*control&~=&~dkim_disable_verify*&
31760 .cindex "disable DKIM verify"
31761 .cindex "DKIM" "disable verify"
31762 This control turns off DKIM verification processing entirely. For details on
31763 the operation and configuration of DKIM, see section &<<SECDKIM>>&.
31766 .vitem &*control&~=&~dmarc_disable_verify*&
31767 .cindex "disable DMARC verify"
31768 .cindex "DMARC" "disable verify"
31769 This control turns off DMARC verification processing entirely. For details on
31770 the operation and configuration of DMARC, see section &<<SECDMARC>>&.
31773 .vitem &*control&~=&~dscp/*&<&'value'&>
31774 .cindex "&ACL;" "setting DSCP value"
31775 .cindex "DSCP" "inbound"
31776 This option causes the DSCP value associated with the socket for the inbound
31777 connection to be adjusted to a given value, given as one of a number of fixed
31778 strings or to numeric value.
31779 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
31780 Common values include &`throughput`&, &`mincost`&, and on newer systems
31781 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
31783 The outbound packets from Exim will be marked with this value in the header
31784 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
31785 that these values will have any effect, not be stripped by networking
31786 equipment, or do much of anything without cooperation with your Network
31787 Engineer and those of all network operators between the source and destination.
31790 .vitem &*control&~=&~enforce_sync*& &&&
31791 &*control&~=&~no_enforce_sync*&
31792 .cindex "SMTP" "synchronization checking"
31793 .cindex "synchronization checking in SMTP"
31794 These controls make it possible to be selective about when SMTP synchronization
31795 is enforced. The global option &%smtp_enforce_sync%& specifies the initial
31796 state of the switch (it is true by default). See the description of this option
31797 in chapter &<<CHAPmainconfig>>& for details of SMTP synchronization checking.
31799 The effect of these two controls lasts for the remainder of the SMTP
31800 connection. They can appear in any ACL except the one for the non-SMTP
31801 messages. The most straightforward place to put them is in the ACL defined by
31802 &%acl_smtp_connect%&, which is run at the start of an incoming SMTP connection,
31803 before the first synchronization check. The expected use is to turn off the
31804 synchronization checks for badly-behaved hosts that you nevertheless need to
31808 .vitem &*control&~=&~fakedefer/*&<&'message'&>
31809 .cindex "fake defer"
31810 .cindex "defer, fake"
31811 This control works in exactly the same way as &%fakereject%& (described below)
31812 except that it causes an SMTP 450 response after the message data instead of a
31813 550 response. You must take care when using &%fakedefer%& because it causes the
31814 messages to be duplicated when the sender retries. Therefore, you should not
31815 use &%fakedefer%& if the message is to be delivered normally.
31817 .vitem &*control&~=&~fakereject/*&<&'message'&>
31818 .cindex "fake rejection"
31819 .cindex "rejection, fake"
31820 This control is permitted only for the MAIL, RCPT, and DATA ACLs, in other
31821 words, only when an SMTP message is being received. If Exim accepts the
31822 message, instead the final 250 response, a 550 rejection message is sent.
31823 However, Exim proceeds to deliver the message as normal. The control applies
31824 only to the current message, not to any subsequent ones that may be received in
31825 the same SMTP connection.
31827 The text for the 550 response is taken from the &%control%& modifier. If no
31828 message is supplied, the following is used:
31830 550-Your message has been rejected but is being
31831 550-kept for evaluation.
31832 550-If it was a legitimate message, it may still be
31833 550 delivered to the target recipient(s).
31835 This facility should be used with extreme caution.
31837 .vitem &*control&~=&~freeze*&
31838 .cindex "frozen messages" "forcing in ACL"
31839 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
31840 other words, only when a message is being received. If the message is accepted,
31841 it is placed on Exim's queue and frozen. The control applies only to the
31842 current message, not to any subsequent ones that may be received in the same
31845 This modifier can optionally be followed by &`/no_tell`&. If the global option
31846 &%freeze_tell%& is set, it is ignored for the current message (that is, nobody
31847 is told about the freezing), provided all the &*control=freeze*& modifiers that
31848 are obeyed for the current message have the &`/no_tell`& option.
31850 .vitem &*control&~=&~no_delay_flush*&
31851 .cindex "SMTP" "output flushing, disabling for delay"
31852 Exim normally flushes SMTP output before implementing a delay in an ACL, to
31853 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
31854 use. This control, as long as it is encountered before the &%delay%& modifier,
31855 disables such output flushing.
31857 .vitem &*control&~=&~no_callout_flush*&
31858 .cindex "SMTP" "output flushing, disabling for callout"
31859 Exim normally flushes SMTP output before performing a callout in an ACL, to
31860 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
31861 use. This control, as long as it is encountered before the &%verify%& condition
31862 that causes the callout, disables such output flushing.
31864 .vitem &*control&~=&~no_mbox_unspool*&
31865 This control is available when Exim is compiled with the content scanning
31866 extension. Content scanning may require a copy of the current message, or parts
31867 of it, to be written in &"mbox format"& to a spool file, for passing to a virus
31868 or spam scanner. Normally, such copies are deleted when they are no longer
31869 needed. If this control is set, the copies are not deleted. The control applies
31870 only to the current message, not to any subsequent ones that may be received in
31871 the same SMTP connection. It is provided for debugging purposes and is unlikely
31872 to be useful in production.
31874 .vitem &*control&~=&~no_multiline_responses*&
31875 .cindex "multiline responses, suppressing"
31876 This control is permitted for any ACL except the one for non-SMTP messages.
31877 It seems that there are broken clients in use that cannot handle multiline
31878 SMTP responses, despite the fact that RFC 821 defined them over 20 years ago.
31880 If this control is set, multiline SMTP responses from ACL rejections are
31881 suppressed. One way of doing this would have been to put out these responses as
31882 one long line. However, RFC 2821 specifies a maximum of 512 bytes per response
31883 (&"use multiline responses for more"& it says &-- ha!), and some of the
31884 responses might get close to that. So this facility, which is after all only a
31885 sop to broken clients, is implemented by doing two very easy things:
31888 Extra information that is normally output as part of a rejection caused by
31889 sender verification failure is omitted. Only the final line (typically &"sender
31890 verification failed"&) is sent.
31892 If a &%message%& modifier supplies a multiline response, only the first
31896 The setting of the switch can, of course, be made conditional on the
31897 calling host. Its effect lasts until the end of the SMTP connection.
31899 .vitem &*control&~=&~no_pipelining*&
31900 .cindex "PIPELINING" "suppressing advertising"
31901 .cindex "ESMTP extensions" PIPELINING
31902 This control turns off the advertising of the PIPELINING extension to SMTP in
31903 the current session. To be useful, it must be obeyed before Exim sends its
31904 response to an EHLO command. Therefore, it should normally appear in an ACL
31905 controlled by &%acl_smtp_connect%& or &%acl_smtp_helo%&. See also
31906 &%pipelining_advertise_hosts%&.
31908 .vitem &*control&~=&~queue/*&<&'options'&>* &&&
31909 &*control&~=&~queue_only*&
31910 .oindex "&%queue%&"
31911 .oindex "&%queue_only%&"
31912 .cindex "queueing incoming messages"
31913 .cindex queueing "forcing in ACL"
31914 .cindex "first pass routing"
31915 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
31916 other words, only when a message is being received. If the message is accepted,
31917 it is placed on Exim's queue and left there for delivery by a subsequent queue
31919 If used with no options set,
31920 no immediate delivery process is started. In other words, it has the
31921 effect as the &%queue_only%& global option or &'-odq'& command-line option.
31923 If the &'first_pass_route'& option is given then
31924 the behaviour is like the command-line &'-oqds'& option;
31925 a delivery process is started which stops short of making
31926 any SMTP delivery. The benefit is that the hints database will be updated for
31927 the message being waiting for a specific host, and a later queue run will be
31928 able to send all such messages on a single connection.
31930 The control only applies to the current message, not to any subsequent ones that
31931 may be received in the same SMTP connection.
31933 .vitem &*control&~=&~submission/*&<&'options'&>
31934 .cindex "message" "submission"
31935 .cindex "submission mode"
31936 This control is permitted only for the MAIL, RCPT, and start of data ACLs (the
31937 latter is the one defined by &%acl_smtp_predata%&). Setting it tells Exim that
31938 the current message is a submission from a local MUA. In this case, Exim
31939 operates in &"submission mode"&, and applies certain fixups to the message if
31940 necessary. For example, it adds a &'Date:'& header line if one is not present.
31941 This control is not permitted in the &%acl_smtp_data%& ACL, because that is too
31942 late (the message has already been created).
31944 Chapter &<<CHAPmsgproc>>& describes the processing that Exim applies to
31945 messages. Section &<<SECTsubmodnon>>& covers the processing that happens in
31946 submission mode; the available options for this control are described there.
31947 The control applies only to the current message, not to any subsequent ones
31948 that may be received in the same SMTP connection.
31950 .vitem &*control&~=&~suppress_local_fixups*&
31951 .cindex "submission fixups, suppressing"
31952 This control applies to locally submitted (non TCP/IP) messages, and is the
31953 complement of &`control = submission`&. It disables the fixups that are
31954 normally applied to locally-submitted messages. Specifically:
31957 Any &'Sender:'& header line is left alone (in this respect, it is a
31958 dynamic version of &%local_sender_retain%&).
31960 No &'Message-ID:'&, &'From:'&, or &'Date:'& header lines are added.
31962 There is no check that &'From:'& corresponds to the actual sender.
31965 This control may be useful when a remotely-originated message is accepted,
31966 passed to some scanning program, and then re-submitted for delivery. It can be
31967 used only in the &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
31968 and &%acl_not_smtp_start%& ACLs, because it has to be set before the message's
31971 &*Note:*& This control applies only to the current message, not to any others
31972 that are being submitted at the same time using &%-bs%& or &%-bS%&.
31974 .vitem &*control&~=&~utf8_downconvert*&
31975 This control enables conversion of UTF-8 in message envelope addresses
31977 For details see section &<<SECTi18nMTA>>&.
31981 .section "Summary of message fixup control" "SECTsummesfix"
31982 All four possibilities for message fixups can be specified:
31985 Locally submitted, fixups applied: the default.
31987 Locally submitted, no fixups applied: use
31988 &`control = suppress_local_fixups`&.
31990 Remotely submitted, no fixups applied: the default.
31992 Remotely submitted, fixups applied: use &`control = submission`&.
31997 .section "Adding header lines in ACLs" "SECTaddheadacl"
31998 .cindex "header lines" "adding in an ACL"
31999 .cindex "header lines" "position of added lines"
32000 .cindex "&%add_header%& ACL modifier"
32001 The &%add_header%& modifier can be used to add one or more extra header lines
32002 to an incoming message, as in this example:
32004 warn dnslists = sbl.spamhaus.org : \
32005 dialup.mail-abuse.org
32006 add_header = X-blacklisted-at: $dnslist_domain
32008 The &%add_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
32009 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
32010 receiving a message). The message must ultimately be accepted for
32011 &%add_header%& to have any significant effect. You can use &%add_header%& with
32012 any ACL verb, including &%deny%& (though this is potentially useful only in a
32015 Headers will not be added to the message if the modifier is used in
32016 DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing.
32018 Leading and trailing newlines are removed from
32019 the data for the &%add_header%& modifier; if it then
32020 contains one or more newlines that
32021 are not followed by a space or a tab, it is assumed to contain multiple header
32022 lines. Each one is checked for valid syntax; &`X-ACL-Warn:`& is added to the
32023 front of any line that is not a valid header line.
32025 Added header lines are accumulated during the MAIL, RCPT, and predata ACLs.
32026 They are added to the message before processing the DATA and MIME ACLs.
32027 However, if an identical header line is requested more than once, only one copy
32028 is actually added to the message. Further header lines may be accumulated
32029 during the DATA and MIME ACLs, after which they are added to the message, again
32030 with duplicates suppressed. Thus, it is possible to add two identical header
32031 lines to an SMTP message, but only if one is added before DATA and one after.
32032 In the case of non-SMTP messages, new headers are accumulated during the
32033 non-SMTP ACLs, and are added to the message after all the ACLs have run. If a
32034 message is rejected after DATA or by the non-SMTP ACL, all added header lines
32035 are included in the entry that is written to the reject log.
32037 .cindex "header lines" "added; visibility of"
32038 Header lines are not visible in string expansions
32040 until they are added to the
32041 message. It follows that header lines defined in the MAIL, RCPT, and predata
32042 ACLs are not visible until the DATA ACL and MIME ACLs are run. Similarly,
32043 header lines that are added by the DATA or MIME ACLs are not visible in those
32044 ACLs. Because of this restriction, you cannot use header lines as a way of
32045 passing data between (for example) the MAIL and RCPT ACLs. If you want to do
32046 this, you can use ACL variables, as described in section
32047 &<<SECTaclvariables>>&.
32049 The list of headers yet to be added is given by the &%$headers_added%& variable.
32051 The &%add_header%& modifier acts immediately as it is encountered during the
32052 processing of an ACL. Notice the difference between these two cases:
32054 &`accept add_header = ADDED: some text`&
32055 &` `&<&'some condition'&>
32057 &`accept `&<&'some condition'&>
32058 &` add_header = ADDED: some text`&
32060 In the first case, the header line is always added, whether or not the
32061 condition is true. In the second case, the header line is added only if the
32062 condition is true. Multiple occurrences of &%add_header%& may occur in the same
32063 ACL statement. All those that are encountered before a condition fails are
32066 .cindex "&%warn%& ACL verb"
32067 For compatibility with previous versions of Exim, a &%message%& modifier for a
32068 &%warn%& verb acts in the same way as &%add_header%&, except that it takes
32069 effect only if all the conditions are true, even if it appears before some of
32070 them. Furthermore, only the last occurrence of &%message%& is honoured. This
32071 usage of &%message%& is now deprecated. If both &%add_header%& and &%message%&
32072 are present on a &%warn%& verb, both are processed according to their
32075 By default, new header lines are added to a message at the end of the existing
32076 header lines. However, you can specify that any particular header line should
32077 be added right at the start (before all the &'Received:'& lines), immediately
32078 after the first block of &'Received:'& lines, or immediately before any line
32079 that is not a &'Received:'& or &'Resent-something:'& header.
32081 This is done by specifying &":at_start:"&, &":after_received:"&, or
32082 &":at_start_rfc:"& (or, for completeness, &":at_end:"&) before the text of the
32083 header line, respectively. (Header text cannot start with a colon, as there has
32084 to be a header name first.) For example:
32086 warn add_header = \
32087 :after_received:X-My-Header: something or other...
32089 If more than one header line is supplied in a single &%add_header%& modifier,
32090 each one is treated independently and can therefore be placed differently. If
32091 you add more than one line at the start, or after the Received: block, they end
32092 up in reverse order.
32094 &*Warning*&: This facility currently applies only to header lines that are
32095 added in an ACL. It does NOT work for header lines that are added in a
32096 system filter or in a router or transport.
32100 .section "Removing header lines in ACLs" "SECTremoveheadacl"
32101 .cindex "header lines" "removing in an ACL"
32102 .cindex "header lines" "position of removed lines"
32103 .cindex "&%remove_header%& ACL modifier"
32104 The &%remove_header%& modifier can be used to remove one or more header lines
32105 from an incoming message, as in this example:
32107 warn message = Remove internal headers
32108 remove_header = x-route-mail1 : x-route-mail2
32110 The &%remove_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
32111 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
32112 receiving a message). The message must ultimately be accepted for
32113 &%remove_header%& to have any significant effect. You can use &%remove_header%&
32114 with any ACL verb, including &%deny%&, though this is really not useful for
32115 any verb that doesn't result in a delivered message.
32117 Headers will not be removed from the message if the modifier is used in
32118 DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing.
32120 More than one header can be removed at the same time by using a colon separated
32121 list of header names. The header matching is case insensitive. Wildcards are
32122 not permitted, nor is list expansion performed, so you cannot use hostlists to
32123 create a list of headers, however both connection and message variable expansion
32124 are performed (&%$acl_c_*%& and &%$acl_m_*%&), illustrated in this example:
32126 warn hosts = +internal_hosts
32127 set acl_c_ihdrs = x-route-mail1 : x-route-mail2
32128 warn message = Remove internal headers
32129 remove_header = $acl_c_ihdrs
32131 Header names for removal are accumulated during the MAIL, RCPT, and predata ACLs.
32132 Matching header lines are removed from the message before processing the DATA and MIME ACLs.
32133 If multiple header lines match, all are removed.
32134 There is no harm in attempting to remove the same header twice nor in removing
32135 a non-existent header. Further header lines to be removed may be accumulated
32136 during the DATA and MIME ACLs, after which they are removed from the message,
32137 if present. In the case of non-SMTP messages, headers to be removed are
32138 accumulated during the non-SMTP ACLs, and are removed from the message after
32139 all the ACLs have run. If a message is rejected after DATA or by the non-SMTP
32140 ACL, there really is no effect because there is no logging of what headers
32141 would have been removed.
32143 .cindex "header lines" "removed; visibility of"
32144 Header lines are not visible in string expansions until the DATA phase when it
32145 is received. Any header lines removed in the MAIL, RCPT, and predata ACLs are
32146 not visible in the DATA ACL and MIME ACLs. Similarly, header lines that are
32147 removed by the DATA or MIME ACLs are still visible in those ACLs. Because of
32148 this restriction, you cannot use header lines as a way of controlling data
32149 passed between (for example) the MAIL and RCPT ACLs. If you want to do this,
32150 you should instead use ACL variables, as described in section
32151 &<<SECTaclvariables>>&.
32153 The &%remove_header%& modifier acts immediately as it is encountered during the
32154 processing of an ACL. Notice the difference between these two cases:
32156 &`accept remove_header = X-Internal`&
32157 &` `&<&'some condition'&>
32159 &`accept `&<&'some condition'&>
32160 &` remove_header = X-Internal`&
32162 In the first case, the header line is always removed, whether or not the
32163 condition is true. In the second case, the header line is removed only if the
32164 condition is true. Multiple occurrences of &%remove_header%& may occur in the
32165 same ACL statement. All those that are encountered before a condition fails
32168 &*Warning*&: This facility currently applies only to header lines that are
32169 present during ACL processing. It does NOT remove header lines that are added
32170 in a system filter or in a router or transport.
32175 .section "ACL conditions" "SECTaclconditions"
32176 .cindex "&ACL;" "conditions; list of"
32177 Some of the conditions listed in this section are available only when Exim is
32178 compiled with the content-scanning extension. They are included here briefly
32179 for completeness. More detailed descriptions can be found in the discussion on
32180 content scanning in chapter &<<CHAPexiscan>>&.
32182 Not all conditions are relevant in all circumstances. For example, testing
32183 senders and recipients does not make sense in an ACL that is being run as the
32184 result of the arrival of an ETRN command, and checks on message headers can be
32185 done only in the ACLs specified by &%acl_smtp_data%& and &%acl_not_smtp%&. You
32186 can use the same condition (with different parameters) more than once in the
32187 same ACL statement. This provides a way of specifying an &"and"& conjunction.
32188 The conditions are as follows:
32192 .vitem &*acl&~=&~*&<&'name&~of&~acl&~or&~ACL&~string&~or&~file&~name&~'&>
32193 .cindex "&ACL;" "nested"
32194 .cindex "&ACL;" "indirect"
32195 .cindex "&ACL;" "arguments"
32196 .cindex "&%acl%& ACL condition"
32197 The possible values of the argument are the same as for the
32198 &%acl_smtp_%&&'xxx'& options. The named or inline ACL is run. If it returns
32199 &"accept"& the condition is true; if it returns &"deny"& the condition is
32200 false. If it returns &"defer"&, the current ACL returns &"defer"& unless the
32201 condition is on a &%warn%& verb. In that case, a &"defer"& return makes the
32202 condition false. This means that further processing of the &%warn%& verb
32203 ceases, but processing of the ACL continues.
32205 If the argument is a named ACL, up to nine space-separated optional values
32206 can be appended; they appear within the called ACL in $acl_arg1 to $acl_arg9,
32207 and $acl_narg is set to the count of values.
32208 Previous values of these variables are restored after the call returns.
32209 The name and values are expanded separately.
32210 Note that spaces in complex expansions which are used as arguments
32211 will act as argument separators.
32213 If the nested &%acl%& returns &"drop"& and the outer condition denies access,
32214 the connection is dropped. If it returns &"discard"&, the verb must be
32215 &%accept%& or &%discard%&, and the action is taken immediately &-- no further
32216 conditions are tested.
32218 ACLs may be nested up to 20 deep; the limit exists purely to catch runaway
32219 loops. This condition allows you to use different ACLs in different
32220 circumstances. For example, different ACLs can be used to handle RCPT commands
32221 for different local users or different local domains.
32223 .vitem &*authenticated&~=&~*&<&'string&~list'&>
32224 .cindex "&%authenticated%& ACL condition"
32225 .cindex "authentication" "ACL checking"
32226 .cindex "&ACL;" "testing for authentication"
32227 If the SMTP connection is not authenticated, the condition is false. Otherwise,
32228 the name of the authenticator is tested against the list. To test for
32229 authentication by any authenticator, you can set
32234 .vitem &*condition&~=&~*&<&'string'&>
32235 .cindex "&%condition%& ACL condition"
32236 .cindex "customizing" "ACL condition"
32237 .cindex "&ACL;" "customized test"
32238 .cindex "&ACL;" "testing, customized"
32239 This feature allows you to make up custom conditions. If the result of
32240 expanding the string is an empty string, the number zero, or one of the strings
32241 &"no"& or &"false"&, the condition is false. If the result is any non-zero
32242 number, or one of the strings &"yes"& or &"true"&, the condition is true. For
32243 any other value, some error is assumed to have occurred, and the ACL returns
32244 &"defer"&. However, if the expansion is forced to fail, the condition is
32245 ignored. The effect is to treat it as true, whether it is positive or
32248 .vitem &*decode&~=&~*&<&'location'&>
32249 .cindex "&%decode%& ACL condition"
32250 This condition is available only when Exim is compiled with the
32251 content-scanning extension, and it is allowed only in the ACL defined by
32252 &%acl_smtp_mime%&. It causes the current MIME part to be decoded into a file.
32253 If all goes well, the condition is true. It is false only if there are
32254 problems such as a syntax error or a memory shortage. For more details, see
32255 chapter &<<CHAPexiscan>>&.
32257 .vitem &*dnslists&~=&~*&<&'list&~of&~domain&~names&~and&~other&~data'&>
32258 .cindex "&%dnslists%& ACL condition"
32259 .cindex "DNS list" "in ACL"
32260 .cindex "black list (DNS)"
32261 .cindex "&ACL;" "testing a DNS list"
32262 This condition checks for entries in DNS black lists. These are also known as
32263 &"RBL lists"&, after the original Realtime Blackhole List, but note that the
32264 use of the lists at &'mail-abuse.org'& now carries a charge. There are too many
32265 different variants of this condition to describe briefly here. See sections
32266 &<<SECTmorednslists>>&&--&<<SECTmorednslistslast>>& for details.
32268 .vitem &*domains&~=&~*&<&'domain&~list'&>
32269 .cindex "&%domains%& ACL condition"
32270 .cindex "domain" "ACL checking"
32271 .cindex "&ACL;" "testing a recipient domain"
32272 .vindex "&$domain_data$&"
32273 This condition is relevant only after a RCPT command. It checks that the domain
32274 of the recipient address is in the domain list. If percent-hack processing is
32275 enabled, it is done before this test is done. If the check succeeds with a
32276 lookup, the result of the lookup is placed in &$domain_data$& until the next
32279 &*Note carefully*& (because many people seem to fall foul of this): you cannot
32280 use &%domains%& in a DATA ACL.
32283 .vitem &*encrypted&~=&~*&<&'string&~list'&>
32284 .cindex "&%encrypted%& ACL condition"
32285 .cindex "encryption" "checking in an ACL"
32286 .cindex "&ACL;" "testing for encryption"
32287 If the SMTP connection is not encrypted, the condition is false. Otherwise, the
32288 name of the cipher suite in use is tested against the list. To test for
32289 encryption without testing for any specific cipher suite(s), set
32295 .vitem &*hosts&~=&~*&<&'host&~list'&>
32296 .cindex "&%hosts%& ACL condition"
32297 .cindex "host" "ACL checking"
32298 .cindex "&ACL;" "testing the client host"
32299 This condition tests that the calling host matches the host list. If you have
32300 name lookups or wildcarded host names and IP addresses in the same host list,
32301 you should normally put the IP addresses first. For example, you could have:
32303 accept hosts = 10.9.8.7 : dbm;/etc/friendly/hosts
32305 The lookup in this example uses the host name for its key. This is implied by
32306 the lookup type &"dbm"&. (For a host address lookup you would use &"net-dbm"&
32307 and it wouldn't matter which way round you had these two items.)
32309 The reason for the problem with host names lies in the left-to-right way that
32310 Exim processes lists. It can test IP addresses without doing any DNS lookups,
32311 but when it reaches an item that requires a host name, it fails if it cannot
32312 find a host name to compare with the pattern. If the above list is given in the
32313 opposite order, the &%accept%& statement fails for a host whose name cannot be
32314 found, even if its IP address is 10.9.8.7.
32316 If you really do want to do the name check first, and still recognize the IP
32317 address even if the name lookup fails, you can rewrite the ACL like this:
32319 accept hosts = dbm;/etc/friendly/hosts
32320 accept hosts = 10.9.8.7
32322 The default action on failing to find the host name is to assume that the host
32323 is not in the list, so the first &%accept%& statement fails. The second
32324 statement can then check the IP address.
32326 .vindex "&$host_data$&"
32327 If a &%hosts%& condition is satisfied by means of a lookup, the result
32328 of the lookup is made available in the &$host_data$& variable. This
32329 allows you, for example, to set up a statement like this:
32331 deny hosts = net-lsearch;/some/file
32332 message = $host_data
32334 which gives a custom error message for each denied host.
32336 .vitem &*local_parts&~=&~*&<&'local&~part&~list'&>
32337 .cindex "&%local_parts%& ACL condition"
32338 .cindex "local part" "ACL checking"
32339 .cindex "&ACL;" "testing a local part"
32340 .vindex "&$local_part_data$&"
32341 This condition is relevant only after a RCPT command. It checks that the local
32342 part of the recipient address is in the list. If percent-hack processing is
32343 enabled, it is done before this test. If the check succeeds with a lookup, the
32344 result of the lookup is placed in &$local_part_data$&, which remains set until
32345 the next &%local_parts%& test.
32347 .vitem &*malware&~=&~*&<&'option'&>
32348 .cindex "&%malware%& ACL condition"
32349 .cindex "&ACL;" "virus scanning"
32350 .cindex "&ACL;" "scanning for viruses"
32351 This condition is available only when Exim is compiled with the
32352 content-scanning extension
32353 and only after a DATA command.
32354 It causes the incoming message to be scanned for
32355 viruses. For details, see chapter &<<CHAPexiscan>>&.
32357 .vitem &*mime_regex&~=&~*&<&'list&~of&~regular&~expressions'&>
32358 .cindex "&%mime_regex%& ACL condition"
32359 .cindex "&ACL;" "testing by regex matching"
32360 This condition is available only when Exim is compiled with the
32361 content-scanning extension, and it is allowed only in the ACL defined by
32362 &%acl_smtp_mime%&. It causes the current MIME part to be scanned for a match
32363 with any of the regular expressions. For details, see chapter
32366 .vitem &*ratelimit&~=&~*&<&'parameters'&>
32367 .cindex "rate limiting"
32368 This condition can be used to limit the rate at which a user or host submits
32369 messages. Details are given in section &<<SECTratelimiting>>&.
32371 .vitem &*recipients&~=&~*&<&'address&~list'&>
32372 .cindex "&%recipients%& ACL condition"
32373 .cindex "recipient" "ACL checking"
32374 .cindex "&ACL;" "testing a recipient"
32375 This condition is relevant only after a RCPT command. It checks the entire
32376 recipient address against a list of recipients.
32378 .vitem &*regex&~=&~*&<&'list&~of&~regular&~expressions'&>
32379 .cindex "&%regex%& ACL condition"
32380 .cindex "&ACL;" "testing by regex matching"
32381 This condition is available only when Exim is compiled with the
32382 content-scanning extension, and is available only in the DATA, MIME, and
32383 non-SMTP ACLs. It causes the incoming message to be scanned for a match with
32384 any of the regular expressions. For details, see chapter &<<CHAPexiscan>>&.
32387 .vitem &*seen&~=&~*&<&'parameters'&>
32388 .cindex "&%sseen%& ACL condition"
32389 This condition can be used to test if a situation has been previously met,
32390 for example for greylisting.
32391 Details are given in section &<<SECTseen>>&.
32394 .vitem &*sender_domains&~=&~*&<&'domain&~list'&>
32395 .cindex "&%sender_domains%& ACL condition"
32396 .cindex "sender" "ACL checking"
32397 .cindex "&ACL;" "testing a sender domain"
32398 .vindex "&$domain$&"
32399 .vindex "&$sender_address_domain$&"
32400 This condition tests the domain of the sender of the message against the given
32401 domain list. &*Note*&: The domain of the sender address is in
32402 &$sender_address_domain$&. It is &'not'& put in &$domain$& during the testing
32403 of this condition. This is an exception to the general rule for testing domain
32404 lists. It is done this way so that, if this condition is used in an ACL for a
32405 RCPT command, the recipient's domain (which is in &$domain$&) can be used to
32406 influence the sender checking.
32408 &*Warning*&: It is a bad idea to use this condition on its own as a control on
32409 relaying, because sender addresses are easily, and commonly, forged.
32411 .vitem &*senders&~=&~*&<&'address&~list'&>
32412 .cindex "&%senders%& ACL condition"
32413 .cindex "sender" "ACL checking"
32414 .cindex "&ACL;" "testing a sender"
32415 This condition tests the sender of the message against the given list. To test
32416 for a bounce message, which has an empty sender, set
32420 &*Warning*&: It is a bad idea to use this condition on its own as a control on
32421 relaying, because sender addresses are easily, and commonly, forged.
32423 .vitem &*spam&~=&~*&<&'username'&>
32424 .cindex "&%spam%& ACL condition"
32425 .cindex "&ACL;" "scanning for spam"
32426 This condition is available only when Exim is compiled with the
32427 content-scanning extension. It causes the incoming message to be scanned by
32428 SpamAssassin. For details, see chapter &<<CHAPexiscan>>&.
32430 .vitem &*verify&~=&~certificate*&
32431 .cindex "&%verify%& ACL condition"
32432 .cindex "TLS" "client certificate verification"
32433 .cindex "certificate" "verification of client"
32434 .cindex "&ACL;" "certificate verification"
32435 .cindex "&ACL;" "testing a TLS certificate"
32436 This condition is true in an SMTP session if the session is encrypted, and a
32437 certificate was received from the client, and the certificate was verified. The
32438 server requests a certificate only if the client matches &%tls_verify_hosts%&
32439 or &%tls_try_verify_hosts%& (see chapter &<<CHAPTLS>>&).
32441 .vitem &*verify&~=&~csa*&
32442 .cindex "CSA verification"
32443 This condition checks whether the sending host (the client) is authorized to
32444 send email. Details of how this works are given in section
32445 &<<SECTverifyCSA>>&.
32447 .vitem &*verify&~=&~header_names_ascii*&
32448 .cindex "&%verify%& ACL condition"
32449 .cindex "&ACL;" "verifying header names only ASCII"
32450 .cindex "header lines" "verifying header names only ASCII"
32451 .cindex "verifying" "header names only ASCII"
32452 This condition is relevant only in an ACL that is run after a message has been
32454 This usually means an ACL specified by &%acl_smtp_data%& or &%acl_not_smtp%&.
32455 It checks all header names (not the content) to make sure
32456 there are no non-ASCII characters, also excluding control characters. The
32457 allowable characters are decimal ASCII values 33 through 126.
32459 Exim itself will handle headers with non-ASCII characters, but it can cause
32460 problems for downstream applications, so this option will allow their
32461 detection and rejection in the DATA ACL's.
32463 .vitem &*verify&~=&~header_sender/*&<&'options'&>
32464 .cindex "&%verify%& ACL condition"
32465 .cindex "&ACL;" "verifying sender in the header"
32466 .cindex "header lines" "verifying the sender in"
32467 .cindex "sender" "verifying in header"
32468 .cindex "verifying" "sender in header"
32469 This condition is relevant only in an ACL that is run after a message has been
32470 received, that is, in an ACL specified by &%acl_smtp_data%& or
32471 &%acl_not_smtp%&. It checks that there is a verifiable address in at least one
32472 of the &'Sender:'&, &'Reply-To:'&, or &'From:'& header lines. Such an address
32473 is loosely thought of as a &"sender"& address (hence the name of the test).
32474 However, an address that appears in one of these headers need not be an address
32475 that accepts bounce messages; only sender addresses in envelopes are required
32476 to accept bounces. Therefore, if you use the callout option on this check, you
32477 might want to arrange for a non-empty address in the MAIL command.
32479 Details of address verification and the options are given later, starting at
32480 section &<<SECTaddressverification>>& (callouts are described in section
32481 &<<SECTcallver>>&). You can combine this condition with the &%senders%&
32482 condition to restrict it to bounce messages only:
32485 !verify = header_sender
32486 message = A valid sender header is required for bounces
32489 .vitem &*verify&~=&~header_syntax*&
32490 .cindex "&%verify%& ACL condition"
32491 .cindex "&ACL;" "verifying header syntax"
32492 .cindex "header lines" "verifying syntax"
32493 .cindex "verifying" "header syntax"
32494 This condition is relevant only in an ACL that is run after a message has been
32495 received, that is, in an ACL specified by &%acl_smtp_data%& or
32496 &%acl_not_smtp%&. It checks the syntax of all header lines that can contain
32497 lists of addresses (&'Sender:'&, &'From:'&, &'Reply-To:'&, &'To:'&, &'Cc:'&,
32498 and &'Bcc:'&), returning true if there are no problems.
32499 Unqualified addresses (local parts without domains) are
32500 permitted only in locally generated messages and from hosts that match
32501 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
32504 Note that this condition is a syntax check only. However, a common spamming
32505 ploy used to be to send syntactically invalid headers such as
32509 and this condition can be used to reject such messages, though they are not as
32510 common as they used to be.
32512 .vitem &*verify&~=&~helo*&
32513 .cindex "&%verify%& ACL condition"
32514 .cindex "&ACL;" "verifying HELO/EHLO"
32515 .cindex "HELO" "verifying"
32516 .cindex "EHLO" "verifying"
32517 .cindex "verifying" "EHLO"
32518 .cindex "verifying" "HELO"
32519 This condition is true if a HELO or EHLO command has been received from the
32520 client host, and its contents have been verified. If there has been no previous
32521 attempt to verify the HELO/EHLO contents, it is carried out when this
32522 condition is encountered. See the description of the &%helo_verify_hosts%& and
32523 &%helo_try_verify_hosts%& options for details of how to request verification
32524 independently of this condition, and for detail of the verification.
32526 For SMTP input that does not come over TCP/IP (the &%-bs%& command line
32527 option), this condition is always true.
32530 .vitem &*verify&~=&~not_blind/*&<&'options'&>
32531 .cindex "verifying" "not blind"
32532 .cindex "bcc recipients, verifying none"
32533 This condition checks that there are no blind (bcc) recipients in the message.
32534 Every envelope recipient must appear either in a &'To:'& header line or in a
32535 &'Cc:'& header line for this condition to be true. Local parts are checked
32536 case-sensitively; domains are checked case-insensitively. If &'Resent-To:'& or
32537 &'Resent-Cc:'& header lines exist, they are also checked. This condition can be
32538 used only in a DATA or non-SMTP ACL.
32540 There is one possible option, &`case_insensitive`&. If this is present then
32541 local parts are checked case-insensitively.
32543 There are, of course, many legitimate messages that make use of blind (bcc)
32544 recipients. This check should not be used on its own for blocking messages.
32547 .vitem &*verify&~=&~recipient/*&<&'options'&>
32548 .cindex "&%verify%& ACL condition"
32549 .cindex "&ACL;" "verifying recipient"
32550 .cindex "recipient" "verifying"
32551 .cindex "verifying" "recipient"
32552 .vindex "&$address_data$&"
32553 This condition is relevant only after a RCPT command. It verifies the current
32554 recipient. Details of address verification are given later, starting at section
32555 &<<SECTaddressverification>>&. After a recipient has been verified, the value
32556 of &$address_data$& is the last value that was set while routing the address.
32557 This applies even if the verification fails. When an address that is being
32558 verified is redirected to a single address, verification continues with the new
32559 address, and in that case, the subsequent value of &$address_data$& is the
32560 value for the child address.
32562 .vitem &*verify&~=&~reverse_host_lookup/*&<&'options'&>
32563 .cindex "&%verify%& ACL condition"
32564 .cindex "&ACL;" "verifying host reverse lookup"
32565 .cindex "host" "verifying reverse lookup"
32566 This condition ensures that a verified host name has been looked up from the IP
32567 address of the client host. (This may have happened already if the host name
32568 was needed for checking a host list, or if the host matched &%host_lookup%&.)
32569 Verification ensures that the host name obtained from a reverse DNS lookup, or
32570 one of its aliases, does, when it is itself looked up in the DNS, yield the
32571 original IP address.
32573 There is one possible option, &`defer_ok`&. If this is present and a
32574 DNS operation returns a temporary error, the verify condition succeeds.
32576 If this condition is used for a locally generated message (that is, when there
32577 is no client host involved), it always succeeds.
32579 .vitem &*verify&~=&~sender/*&<&'options'&>
32580 .cindex "&%verify%& ACL condition"
32581 .cindex "&ACL;" "verifying sender"
32582 .cindex "sender" "verifying"
32583 .cindex "verifying" "sender"
32584 This condition is relevant only after a MAIL or RCPT command, or after a
32585 message has been received (the &%acl_smtp_data%& or &%acl_not_smtp%& ACLs). If
32586 the message's sender is empty (that is, this is a bounce message), the
32587 condition is true. Otherwise, the sender address is verified.
32589 .vindex "&$address_data$&"
32590 .vindex "&$sender_address_data$&"
32591 If there is data in the &$address_data$& variable at the end of routing, its
32592 value is placed in &$sender_address_data$& at the end of verification. This
32593 value can be used in subsequent conditions and modifiers in the same ACL
32594 statement. It does not persist after the end of the current statement. If you
32595 want to preserve the value for longer, you can save it in an ACL variable.
32597 Details of verification are given later, starting at section
32598 &<<SECTaddressverification>>&. Exim caches the result of sender verification,
32599 to avoid doing it more than once per message.
32601 .vitem &*verify&~=&~sender=*&<&'address'&>&*/*&<&'options'&>
32602 .cindex "&%verify%& ACL condition"
32603 This is a variation of the previous option, in which a modified address is
32604 verified as a sender.
32606 Note that '/' is legal in local-parts; if the address may have such
32607 (eg. is generated from the received message)
32608 they must be protected from the options parsing by doubling:
32610 verify = sender=${listquote{/}{${address:$h_sender:}}}
32616 .section "Using DNS lists" "SECTmorednslists"
32617 .cindex "DNS list" "in ACL"
32618 .cindex "black list (DNS)"
32619 .cindex "&ACL;" "testing a DNS list"
32620 In its simplest form, the &%dnslists%& condition tests whether the calling host
32621 is on at least one of a number of DNS lists by looking up the inverted IP
32622 address in one or more DNS domains. (Note that DNS list domains are not mail
32623 domains, so the &`+`& syntax for named lists doesn't work - it is used for
32624 special options instead.) For example, if the calling host's IP
32625 address is 192.168.62.43, and the ACL statement is
32627 deny dnslists = blackholes.mail-abuse.org : \
32628 dialups.mail-abuse.org
32630 the following records are looked up:
32632 43.62.168.192.blackholes.mail-abuse.org
32633 43.62.168.192.dialups.mail-abuse.org
32635 As soon as Exim finds an existing DNS record, processing of the list stops.
32636 Thus, multiple entries on the list provide an &"or"& conjunction. If you want
32637 to test that a host is on more than one list (an &"and"& conjunction), you can
32638 use two separate conditions:
32640 deny dnslists = blackholes.mail-abuse.org
32641 dnslists = dialups.mail-abuse.org
32643 If a DNS lookup times out or otherwise fails to give a decisive answer, Exim
32644 behaves as if the host does not match the list item, that is, as if the DNS
32645 record does not exist. If there are further items in the DNS list, they are
32648 This is usually the required action when &%dnslists%& is used with &%deny%&
32649 (which is the most common usage), because it prevents a DNS failure from
32650 blocking mail. However, you can change this behaviour by putting one of the
32651 following special items in the list:
32653 &`+include_unknown `& behave as if the item is on the list
32654 &`+exclude_unknown `& behave as if the item is not on the list (default)
32655 &`+defer_unknown `& give a temporary error
32657 .cindex "&`+include_unknown`&"
32658 .cindex "&`+exclude_unknown`&"
32659 .cindex "&`+defer_unknown`&"
32660 Each of these applies to any subsequent items on the list. For example:
32662 deny dnslists = +defer_unknown : foo.bar.example
32664 Testing the list of domains stops as soon as a match is found. If you want to
32665 warn for one list and block for another, you can use two different statements:
32667 deny dnslists = blackholes.mail-abuse.org
32668 warn dnslists = dialups.mail-abuse.org
32669 message = X-Warn: sending host is on dialups list
32671 .cindex caching "of dns lookup"
32673 DNS list lookups are cached by Exim for the duration of the SMTP session
32674 (but limited by the DNS return TTL value),
32675 so a lookup based on the IP address is done at most once for any incoming
32676 connection (assuming long-enough TTL).
32677 Exim does not share information between multiple incoming
32678 connections (but your local name server cache should be active).
32680 There are a number of DNS lists to choose from, some commercial, some free,
32681 or free for small deployments. An overview can be found at
32682 &url(https://en.wikipedia.org/wiki/Comparison_of_DNS_blacklists).
32686 .section "Specifying the IP address for a DNS list lookup" "SECID201"
32687 .cindex "DNS list" "keyed by explicit IP address"
32688 By default, the IP address that is used in a DNS list lookup is the IP address
32689 of the calling host. However, you can specify another IP address by listing it
32690 after the domain name, introduced by a slash. For example:
32692 deny dnslists = black.list.tld/192.168.1.2
32694 This feature is not very helpful with explicit IP addresses; it is intended for
32695 use with IP addresses that are looked up, for example, the IP addresses of the
32696 MX hosts or nameservers of an email sender address. For an example, see section
32697 &<<SECTmulkeyfor>>& below.
32702 .section "DNS lists keyed on domain names" "SECID202"
32703 .cindex "DNS list" "keyed by domain name"
32704 There are some lists that are keyed on domain names rather than inverted IP
32705 addresses (see, e.g., the &'domain based zones'& link at
32706 &url(http://www.rfc-ignorant.org/)). No reversing of components is used
32707 with these lists. You can change the name that is looked up in a DNS list by
32708 listing it after the domain name, introduced by a slash. For example,
32710 deny dnslists = dsn.rfc-ignorant.org/$sender_address_domain
32711 message = Sender's domain is listed at $dnslist_domain
32713 This particular example is useful only in ACLs that are obeyed after the
32714 RCPT or DATA commands, when a sender address is available. If (for
32715 example) the message's sender is &'user@tld.example'& the name that is looked
32716 up by this example is
32718 tld.example.dsn.rfc-ignorant.org
32720 A single &%dnslists%& condition can contain entries for both names and IP
32721 addresses. For example:
32723 deny dnslists = sbl.spamhaus.org : \
32724 dsn.rfc-ignorant.org/$sender_address_domain
32726 The first item checks the sending host's IP address; the second checks a domain
32727 name. The whole condition is true if either of the DNS lookups succeeds.
32732 .section "Multiple explicit keys for a DNS list" "SECTmulkeyfor"
32733 .cindex "DNS list" "multiple keys for"
32734 The syntax described above for looking up explicitly-defined values (either
32735 names or IP addresses) in a DNS blacklist is a simplification. After the domain
32736 name for the DNS list, what follows the slash can in fact be a list of items.
32737 As with all lists in Exim, the default separator is a colon. However, because
32738 this is a sublist within the list of DNS blacklist domains, it is necessary
32739 either to double the separators like this:
32741 dnslists = black.list.tld/name.1::name.2
32743 or to change the separator character, like this:
32745 dnslists = black.list.tld/<;name.1;name.2
32747 If an item in the list is an IP address, it is inverted before the DNS
32748 blacklist domain is appended. If it is not an IP address, no inversion
32749 occurs. Consider this condition:
32751 dnslists = black.list.tld/<;192.168.1.2;a.domain
32753 The DNS lookups that occur are:
32755 2.1.168.192.black.list.tld
32756 a.domain.black.list.tld
32758 Once a DNS record has been found (that matches a specific IP return
32759 address, if specified &-- see section &<<SECTaddmatcon>>&), no further lookups
32760 are done. If there is a temporary DNS error, the rest of the sublist of domains
32761 or IP addresses is tried. A temporary error for the whole dnslists item occurs
32762 only if no other DNS lookup in this sublist succeeds. In other words, a
32763 successful lookup for any of the items in the sublist overrides a temporary
32764 error for a previous item.
32766 The ability to supply a list of items after the slash is in some sense just a
32767 syntactic convenience. These two examples have the same effect:
32769 dnslists = black.list.tld/a.domain : black.list.tld/b.domain
32770 dnslists = black.list.tld/a.domain::b.domain
32772 However, when the data for the list is obtained from a lookup, the second form
32773 is usually much more convenient. Consider this example:
32775 deny dnslists = sbl.spamhaus.org/<|${lookup dnsdb {>|a=<|\
32776 ${lookup dnsdb {>|mxh=\
32777 $sender_address_domain} }} }
32778 message = The mail servers for the domain \
32779 $sender_address_domain \
32780 are listed at $dnslist_domain ($dnslist_value); \
32783 Note the use of &`>|`& in the dnsdb lookup to specify the separator for
32784 multiple DNS records. The inner dnsdb lookup produces a list of MX hosts
32785 and the outer dnsdb lookup finds the IP addresses for these hosts. The result
32786 of expanding the condition might be something like this:
32788 dnslists = sbl.spamhaus.org/<|192.168.2.3|192.168.5.6|...
32790 Thus, this example checks whether or not the IP addresses of the sender
32791 domain's mail servers are on the Spamhaus black list.
32793 The key that was used for a successful DNS list lookup is put into the variable
32794 &$dnslist_matched$& (see section &<<SECID204>>&).
32799 .section "Data returned by DNS lists" "SECID203"
32800 .cindex "DNS list" "data returned from"
32801 DNS lists are constructed using address records in the DNS. The original RBL
32802 just used the address 127.0.0.1 on the right hand side of each record, but the
32803 RBL+ list and some other lists use a number of values with different meanings.
32804 The values used on the RBL+ list are:
32808 127.1.0.3 DUL and RBL
32810 127.1.0.5 RSS and RBL
32811 127.1.0.6 RSS and DUL
32812 127.1.0.7 RSS and DUL and RBL
32814 Section &<<SECTaddmatcon>>& below describes how you can distinguish between
32815 different values. Some DNS lists may return more than one address record;
32816 see section &<<SECThanmuldnsrec>>& for details of how they are checked.
32818 Values returned by a properly running DBSBL should be in the 127.0.0.0/8
32819 range. If a DNSBL operator loses control of the domain, lookups on it
32820 may start returning other addresses. Because of this, Exim now ignores
32821 returned values outside the 127/8 region.
32824 .section "Variables set from DNS lists" "SECID204"
32825 .cindex "expansion" "variables, set from DNS list"
32826 .cindex "DNS list" "variables set from"
32827 .vindex "&$dnslist_domain$&"
32828 .vindex "&$dnslist_matched$&"
32829 .vindex "&$dnslist_text$&"
32830 .vindex "&$dnslist_value$&"
32831 When an entry is found in a DNS list, the variable &$dnslist_domain$& contains
32832 the name of the overall domain that matched (for example,
32833 &`spamhaus.example`&), &$dnslist_matched$& contains the key within that domain
32834 (for example, &`192.168.5.3`&), and &$dnslist_value$& contains the data from
32835 the DNS record. When the key is an IP address, it is not reversed in
32836 &$dnslist_matched$& (though it is, of course, in the actual lookup). In simple
32837 cases, for example:
32839 deny dnslists = spamhaus.example
32841 the key is also available in another variable (in this case,
32842 &$sender_host_address$&). In more complicated cases, however, this is not true.
32843 For example, using a data lookup (as described in section &<<SECTmulkeyfor>>&)
32844 might generate a dnslists lookup like this:
32846 deny dnslists = spamhaus.example/<|192.168.1.2|192.168.6.7|...
32848 If this condition succeeds, the value in &$dnslist_matched$& might be
32849 &`192.168.6.7`& (for example).
32851 If more than one address record is returned by the DNS lookup, all the IP
32852 addresses are included in &$dnslist_value$&, separated by commas and spaces.
32853 The variable &$dnslist_text$& contains the contents of any associated TXT
32854 record. For lists such as RBL+ the TXT record for a merged entry is often not
32855 very meaningful. See section &<<SECTmordetinf>>& for a way of obtaining more
32858 You can use the DNS list variables in &%message%& or &%log_message%& modifiers
32859 &-- even if these appear before the condition in the ACL, they are not
32860 expanded until after it has failed. For example:
32862 deny hosts = !+local_networks
32863 message = $sender_host_address is listed \
32865 dnslists = rbl-plus.mail-abuse.example
32870 .section "Additional matching conditions for DNS lists" "SECTaddmatcon"
32871 .cindex "DNS list" "matching specific returned data"
32872 You can add an equals sign and an IP address after a &%dnslists%& domain name
32873 in order to restrict its action to DNS records with a matching right hand side.
32876 deny dnslists = rblplus.mail-abuse.org=127.0.0.2
32878 rejects only those hosts that yield 127.0.0.2. Without this additional data,
32879 any address record is considered to be a match. For the moment, we assume
32880 that the DNS lookup returns just one record. Section &<<SECThanmuldnsrec>>&
32881 describes how multiple records are handled.
32883 More than one IP address may be given for checking, using a comma as a
32884 separator. These are alternatives &-- if any one of them matches, the
32885 &%dnslists%& condition is true. For example:
32887 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
32889 If you want to specify a constraining address list and also specify names or IP
32890 addresses to be looked up, the constraining address list must be specified
32891 first. For example:
32893 deny dnslists = dsn.rfc-ignorant.org\
32894 =127.0.0.2/$sender_address_domain
32897 If the character &`&&`& is used instead of &`=`&, the comparison for each
32898 listed IP address is done by a bitwise &"and"& instead of by an equality test.
32899 In other words, the listed addresses are used as bit masks. The comparison is
32900 true if all the bits in the mask are present in the address that is being
32901 tested. For example:
32903 dnslists = a.b.c&0.0.0.3
32905 matches if the address is &'x.x.x.'&3, &'x.x.x.'&7, &'x.x.x.'&11, etc. If you
32906 want to test whether one bit or another bit is present (as opposed to both
32907 being present), you must use multiple values. For example:
32909 dnslists = a.b.c&0.0.0.1,0.0.0.2
32911 matches if the final component of the address is an odd number or two times
32916 .section "Negated DNS matching conditions" "SECID205"
32917 You can supply a negative list of IP addresses as part of a &%dnslists%&
32920 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
32922 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
32923 IP address yielded by the list is either 127.0.0.2 or 127.0.0.3"&,
32925 deny dnslists = a.b.c!=127.0.0.2,127.0.0.3
32927 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
32928 IP address yielded by the list is not 127.0.0.2 and not 127.0.0.3"&. In other
32929 words, the result of the test is inverted if an exclamation mark appears before
32930 the &`=`& (or the &`&&`&) sign.
32932 &*Note*&: This kind of negation is not the same as negation in a domain,
32933 host, or address list (which is why the syntax is different).
32935 If you are using just one list, the negation syntax does not gain you much. The
32936 previous example is precisely equivalent to
32938 deny dnslists = a.b.c
32939 !dnslists = a.b.c=127.0.0.2,127.0.0.3
32941 However, if you are using multiple lists, the negation syntax is clearer.
32942 Consider this example:
32944 deny dnslists = sbl.spamhaus.org : \
32946 dnsbl.njabl.org!=127.0.0.3 : \
32949 Using only positive lists, this would have to be:
32951 deny dnslists = sbl.spamhaus.org : \
32953 deny dnslists = dnsbl.njabl.org
32954 !dnslists = dnsbl.njabl.org=127.0.0.3
32955 deny dnslists = relays.ordb.org
32957 which is less clear, and harder to maintain.
32959 Negation can also be used with a bitwise-and restriction.
32960 The dnslists condition with only be trus if a result is returned
32961 by the lookup which, anded with the restriction, is all zeroes.
32964 deny dnslists = zen.spamhaus.org!&0.255.255.0
32970 .section "Handling multiple DNS records from a DNS list" "SECThanmuldnsrec"
32971 A DNS lookup for a &%dnslists%& condition may return more than one DNS record,
32972 thereby providing more than one IP address. When an item in a &%dnslists%& list
32973 is followed by &`=`& or &`&&`& and a list of IP addresses, in order to restrict
32974 the match to specific results from the DNS lookup, there are two ways in which
32975 the checking can be handled. For example, consider the condition:
32977 dnslists = a.b.c=127.0.0.1
32979 What happens if the DNS lookup for the incoming IP address yields both
32980 127.0.0.1 and 127.0.0.2 by means of two separate DNS records? Is the
32981 condition true because at least one given value was found, or is it false
32982 because at least one of the found values was not listed? And how does this
32983 affect negated conditions? Both possibilities are provided for with the help of
32984 additional separators &`==`& and &`=&&`&.
32987 If &`=`& or &`&&`& is used, the condition is true if any one of the looked up
32988 IP addresses matches one of the listed addresses. For the example above, the
32989 condition is true because 127.0.0.1 matches.
32991 If &`==`& or &`=&&`& is used, the condition is true only if every one of the
32992 looked up IP addresses matches one of the listed addresses. If the condition is
32995 dnslists = a.b.c==127.0.0.1
32997 and the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
32998 false because 127.0.0.2 is not listed. You would need to have:
33000 dnslists = a.b.c==127.0.0.1,127.0.0.2
33002 for the condition to be true.
33005 When &`!`& is used to negate IP address matching, it inverts the result, giving
33006 the precise opposite of the behaviour above. Thus:
33008 If &`!=`& or &`!&&`& is used, the condition is true if none of the looked up IP
33009 addresses matches one of the listed addresses. Consider:
33011 dnslists = a.b.c!&0.0.0.1
33013 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
33014 false because 127.0.0.1 matches.
33016 If &`!==`& or &`!=&&`& is used, the condition is true if there is at least one
33017 looked up IP address that does not match. Consider:
33019 dnslists = a.b.c!=&0.0.0.1
33021 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
33022 true, because 127.0.0.2 does not match. You would need to have:
33024 dnslists = a.b.c!=&0.0.0.1,0.0.0.2
33026 for the condition to be false.
33028 When the DNS lookup yields only a single IP address, there is no difference
33029 between &`=`& and &`==`& and between &`&&`& and &`=&&`&.
33034 .section "Detailed information from merged DNS lists" "SECTmordetinf"
33035 .cindex "DNS list" "information from merged"
33036 When the facility for restricting the matching IP values in a DNS list is used,
33037 the text from the TXT record that is set in &$dnslist_text$& may not reflect
33038 the true reason for rejection. This happens when lists are merged and the IP
33039 address in the A record is used to distinguish them; unfortunately there is
33040 only one TXT record. One way round this is not to use merged lists, but that
33041 can be inefficient because it requires multiple DNS lookups where one would do
33042 in the vast majority of cases when the host of interest is not on any of the
33045 A less inefficient way of solving this problem is available. If
33046 two domain names, comma-separated, are given, the second is used first to
33047 do an initial check, making use of any IP value restrictions that are set.
33048 If there is a match, the first domain is used, without any IP value
33049 restrictions, to get the TXT record. As a byproduct of this, there is also
33050 a check that the IP being tested is indeed on the first list. The first
33051 domain is the one that is put in &$dnslist_domain$&. For example:
33054 sbl.spamhaus.org,sbl-xbl.spamhaus.org=127.0.0.2 : \
33055 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
33057 rejected because $sender_host_address is blacklisted \
33058 at $dnslist_domain\n$dnslist_text
33060 For the first blacklist item, this starts by doing a lookup in
33061 &'sbl-xbl.spamhaus.org'& and testing for a 127.0.0.2 return. If there is a
33062 match, it then looks in &'sbl.spamhaus.org'&, without checking the return
33063 value, and as long as something is found, it looks for the corresponding TXT
33064 record. If there is no match in &'sbl-xbl.spamhaus.org'&, nothing more is done.
33065 The second blacklist item is processed similarly.
33067 If you are interested in more than one merged list, the same list must be
33068 given several times, but because the results of the DNS lookups are cached,
33069 the DNS calls themselves are not repeated. For example:
33072 http.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.2 : \
33073 socks.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.3 : \
33074 misc.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.4 : \
33075 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
33077 In this case there is one lookup in &'dnsbl.sorbs.net'&, and if none of the IP
33078 values matches (or if no record is found), this is the only lookup that is
33079 done. Only if there is a match is one of the more specific lists consulted.
33083 .section "DNS lists and IPv6" "SECTmorednslistslast"
33084 .cindex "IPv6" "DNS black lists"
33085 .cindex "DNS list" "IPv6 usage"
33086 If Exim is asked to do a dnslist lookup for an IPv6 address, it inverts it
33087 nibble by nibble. For example, if the calling host's IP address is
33088 3ffe:ffff:836f:0a00:000a:0800:200a:c031, Exim might look up
33090 1.3.0.c.a.0.0.2.0.0.8.0.a.0.0.0.0.0.a.0.f.6.3.8.
33091 f.f.f.f.e.f.f.3.blackholes.mail-abuse.org
33093 (split over two lines here to fit on the page). Unfortunately, some of the DNS
33094 lists contain wildcard records, intended for IPv4, that interact badly with
33095 IPv6. For example, the DNS entry
33097 *.3.some.list.example. A 127.0.0.1
33099 is probably intended to put the entire 3.0.0.0/8 IPv4 network on the list.
33100 Unfortunately, it also matches the entire 3::/4 IPv6 network.
33102 You can exclude IPv6 addresses from DNS lookups by making use of a suitable
33103 &%condition%& condition, as in this example:
33105 deny condition = ${if isip4{$sender_host_address}}
33106 dnslists = some.list.example
33109 If an explicit key is being used for a DNS lookup and it may be an IPv6
33110 address you should specify alternate list separators for both the outer
33111 (DNS list name) list and inner (lookup keys) list:
33113 dnslists = <; dnsbl.example.com/<|$acl_m_addrslist
33118 .section "Previously seen user and hosts" "SECTseen"
33119 .cindex "&%sseen%& ACL condition"
33120 .cindex greylisting
33121 The &%seen%& ACL condition can be used to test whether a
33122 situation has been previously met.
33123 It uses a hints database to record a timestamp against a key.
33124 host. The syntax of the condition is:
33126 &`seen =`& <&'optional flag'&><&'time interval'&> &`/`& <&'options'&>
33131 defer seen = -5m / key=${sender_host_address}_$local_part@$domain
33133 in a RCPT ACL will implement simple greylisting.
33135 The parameters for the condition are
33136 a possible minus sign,
33138 then, slash-separated, a list of options.
33139 The interval is taken as an offset before the current time,
33140 and used for the test.
33141 If the interval is preceded by a minus sign then the condition returns
33142 whether a record is found which is before the test time.
33143 Otherwise, the condition returns whether one is found which is since the
33146 Options are read in order with later ones overriding earlier ones.
33148 The default key is &$sender_host_address$&.
33149 An explicit key can be set using a &%key=value%& option.
33151 If a &%readonly%& option is given then
33152 no record create or update is done.
33153 If a &%write%& option is given then
33154 a record create or update is always done.
33155 An update is done if the test is for &"since"&.
33156 If none of those hold and there was no existing record,
33157 a record is created.
33159 Creates and updates are marked with the current time.
33161 Finally, a &"before"& test which succeeds, and for which the record
33162 is old enough, will be refreshed with a timestamp of the test time.
33163 This can prevent tidying of the database from removing the entry.
33164 The interval for this is, by default, 10 days.
33165 An explicit interval can be set using a
33166 &%refresh=value%& option.
33168 Note that &"seen"& should be added to the list of hints databases
33169 for maintenance if this ACL condition is used.
33173 .section "Rate limiting incoming messages" "SECTratelimiting"
33174 .cindex "rate limiting" "client sending"
33175 .cindex "limiting client sending rates"
33176 .oindex "&%smtp_ratelimit_*%&"
33177 The &%ratelimit%& ACL condition can be used to measure and control the rate at
33178 which clients can send email. This is more powerful than the
33179 &%smtp_ratelimit_*%& options, because those options control the rate of
33180 commands in a single SMTP session only, whereas the &%ratelimit%& condition
33181 works across all connections (concurrent and sequential) from the same client
33182 host. The syntax of the &%ratelimit%& condition is:
33184 &`ratelimit =`& <&'m'&> &`/`& <&'p'&> &`/`& <&'options'&> &`/`& <&'key'&>
33186 If the average client sending rate is less than &'m'& messages per time
33187 period &'p'& then the condition is false; otherwise it is true.
33189 As a side-effect, the &%ratelimit%& condition sets the expansion variable
33190 &$sender_rate$& to the client's computed rate, &$sender_rate_limit$& to the
33191 configured value of &'m'&, and &$sender_rate_period$& to the configured value
33194 The parameter &'p'& is the smoothing time constant, in the form of an Exim
33195 time interval, for example, &`8h`& for eight hours. A larger time constant
33196 means that it takes Exim longer to forget a client's past behaviour. The
33197 parameter &'m'& is the maximum number of messages that a client is permitted to
33198 send in each time interval. It also specifies the number of messages permitted
33199 in a fast burst. By increasing both &'m'& and &'p'& but keeping &'m/p'&
33200 constant, you can allow a client to send more messages in a burst without
33201 changing its long-term sending rate limit. Conversely, if &'m'& and &'p'& are
33202 both small, messages must be sent at an even rate.
33204 There is a script in &_util/ratelimit.pl_& which extracts sending rates from
33205 log files, to assist with choosing appropriate settings for &'m'& and &'p'&
33206 when deploying the &%ratelimit%& ACL condition. The script prints usage
33207 instructions when it is run with no arguments.
33209 The key is used to look up the data for calculating the client's average
33210 sending rate. This data is stored in Exim's spool directory, alongside the
33211 retry and other hints databases. The default key is &$sender_host_address$&,
33212 which means Exim computes the sending rate of each client host IP address.
33213 By changing the key you can change how Exim identifies clients for the purpose
33214 of ratelimiting. For example, to limit the sending rate of each authenticated
33215 user, independent of the computer they are sending from, set the key to
33216 &$authenticated_id$&. You must ensure that the lookup key is meaningful; for
33217 example, &$authenticated_id$& is only meaningful if the client has
33218 authenticated (which you can check with the &%authenticated%& ACL condition).
33220 The lookup key does not have to identify clients: If you want to limit the
33221 rate at which a recipient receives messages, you can use the key
33222 &`$local_part@$domain`& with the &%per_rcpt%& option (see below) in a RCPT
33225 Each &%ratelimit%& condition can have up to four options. A &%per_*%& option
33226 specifies what Exim measures the rate of, for example, messages or recipients
33227 or bytes. You can adjust the measurement using the &%unique=%& and/or
33228 &%count=%& options. You can also control when Exim updates the recorded rate
33229 using a &%strict%&, &%leaky%&, or &%readonly%& option. The options are
33230 separated by a slash, like the other parameters. They may appear in any order.
33232 Internally, Exim appends the smoothing constant &'p'& onto the lookup key with
33233 any options that alter the meaning of the stored data. The limit &'m'& is not
33234 stored, so you can alter the configured maximum rate and Exim will still
33235 remember clients' past behaviour. If you change the &%per_*%& mode or add or
33236 remove the &%unique=%& option, the lookup key changes so Exim will forget past
33237 behaviour. The lookup key is not affected by changes to the update mode and
33238 the &%count=%& option.
33241 .section "Ratelimit options for what is being measured" "ratoptmea"
33242 .cindex "rate limiting" "per_* options"
33243 The &%per_conn%& option limits the client's connection rate. It is not
33244 normally used in the &%acl_not_smtp%&, &%acl_not_smtp_mime%&, or
33245 &%acl_not_smtp_start%& ACLs.
33247 The &%per_mail%& option limits the client's rate of sending messages. This is
33248 the default if none of the &%per_*%& options is specified. It can be used in
33249 &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&, &%acl_smtp_mime%&,
33250 &%acl_smtp_data%&, or &%acl_not_smtp%&.
33252 The &%per_byte%& option limits the sender's email bandwidth. It can be used in
33253 the same ACLs as the &%per_mail%& option, though it is best to use this option
33254 in the &%acl_smtp_mime%&, &%acl_smtp_data%& or &%acl_not_smtp%& ACLs; if it is
33255 used in an earlier ACL, Exim relies on the SIZE parameter given by the client
33256 in its MAIL command, which may be inaccurate or completely missing. You can
33257 follow the limit &'m'& in the configuration with K, M, or G to specify limits
33258 in kilobytes, megabytes, or gigabytes, respectively.
33260 The &%per_rcpt%& option causes Exim to limit the rate at which recipients are
33261 accepted. It can be used in the &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
33262 &%acl_smtp_mime%&, or &%acl_smtp_data%& ACLs. In
33263 &%acl_smtp_rcpt%& the rate is updated one recipient at a time; in the other
33264 ACLs the rate is updated with the total (accepted) recipient count in one go. Note that
33265 in either case the rate limiting engine will see a message with many
33266 recipients as a large high-speed burst.
33268 The &%per_addr%& option is like the &%per_rcpt%& option, except it counts the
33269 number of different recipients that the client has sent messages to in the
33270 last time period. That is, if the client repeatedly sends messages to the same
33271 recipient, its measured rate is not increased. This option can only be used in
33274 The &%per_cmd%& option causes Exim to recompute the rate every time the
33275 condition is processed. This can be used to limit the rate of any SMTP
33276 command. If it is used in multiple ACLs it can limit the aggregate rate of
33277 multiple different commands.
33279 The &%count=%& option can be used to alter how much Exim adds to the client's
33280 measured rate. For example, the &%per_byte%& option is equivalent to
33281 &`per_mail/count=$message_size`&. If there is no &%count=%& option, Exim
33282 increases the measured rate by one (except for the &%per_rcpt%& option in ACLs
33283 other than &%acl_smtp_rcpt%&). The count does not have to be an integer.
33285 The &%unique=%& option is described in section &<<ratoptuniq>>& below.
33288 .section "Ratelimit update modes" "ratoptupd"
33289 .cindex "rate limiting" "reading data without updating"
33290 You can specify one of three options with the &%ratelimit%& condition to
33291 control when its database is updated. This section describes the &%readonly%&
33292 mode, and the next section describes the &%strict%& and &%leaky%& modes.
33294 If the &%ratelimit%& condition is used in &%readonly%& mode, Exim looks up a
33295 previously-computed rate to check against the limit.
33297 For example, you can test the client's sending rate and deny it access (when
33298 it is too fast) in the connect ACL. If the client passes this check then it
33299 can go on to send a message, in which case its recorded rate will be updated
33300 in the MAIL ACL. Subsequent connections from the same client will check this
33304 deny ratelimit = 100 / 5m / readonly
33305 log_message = RATE CHECK: $sender_rate/$sender_rate_period \
33306 (max $sender_rate_limit)
33309 warn ratelimit = 100 / 5m / strict
33310 log_message = RATE UPDATE: $sender_rate/$sender_rate_period \
33311 (max $sender_rate_limit)
33314 If Exim encounters multiple &%ratelimit%& conditions with the same key when
33315 processing a message then it may increase the client's measured rate more than
33316 it should. For example, this will happen if you check the &%per_rcpt%& option
33317 in both &%acl_smtp_rcpt%& and &%acl_smtp_data%&. However it's OK to check the
33318 same &%ratelimit%& condition multiple times in the same ACL. You can avoid any
33319 multiple update problems by using the &%readonly%& option on later ratelimit
33322 The &%per_*%& options described above do not make sense in some ACLs. If you
33323 use a &%per_*%& option in an ACL where it is not normally permitted then the
33324 update mode defaults to &%readonly%& and you cannot specify the &%strict%& or
33325 &%leaky%& modes. In other ACLs the default update mode is &%leaky%& (see the
33326 next section) so you must specify the &%readonly%& option explicitly.
33329 .section "Ratelimit options for handling fast clients" "ratoptfast"
33330 .cindex "rate limiting" "strict and leaky modes"
33331 If a client's average rate is greater than the maximum, the rate limiting
33332 engine can react in two possible ways, depending on the presence of the
33333 &%strict%& or &%leaky%& update modes. This is independent of the other
33334 counter-measures (such as rejecting the message) that may be specified by the
33337 The &%leaky%& (default) option means that the client's recorded rate is not
33338 updated if it is above the limit. The effect of this is that Exim measures the
33339 client's average rate of successfully sent email,
33340 up to the given limit.
33341 This is appropriate if the countermeasure when the condition is true
33342 consists of refusing the message, and
33343 is generally the better choice if you have clients that retry automatically.
33344 If the action when true is anything more complex then this option is
33345 likely not what is wanted.
33347 The &%strict%& option means that the client's recorded rate is always
33348 updated. The effect of this is that Exim measures the client's average rate
33349 of attempts to send email, which can be much higher than the maximum it is
33350 actually allowed. If the client is over the limit it may be subjected to
33351 counter-measures by the ACL. It must slow down and allow sufficient time to
33352 pass that its computed rate falls below the maximum before it can send email
33353 again. The time (the number of smoothing periods) it must wait and not
33354 attempt to send mail can be calculated with this formula:
33356 ln(peakrate/maxrate)
33360 .section "Limiting the rate of different events" "ratoptuniq"
33361 .cindex "rate limiting" "counting unique events"
33362 The &%ratelimit%& &%unique=%& option controls a mechanism for counting the
33363 rate of different events. For example, the &%per_addr%& option uses this
33364 mechanism to count the number of different recipients that the client has
33365 sent messages to in the last time period; it is equivalent to
33366 &`per_rcpt/unique=$local_part@$domain`&. You could use this feature to
33367 measure the rate that a client uses different sender addresses with the
33368 options &`per_mail/unique=$sender_address`&.
33370 For each &%ratelimit%& key Exim stores the set of &%unique=%& values that it
33371 has seen for that key. The whole set is thrown away when it is older than the
33372 rate smoothing period &'p'&, so each different event is counted at most once
33373 per period. In the &%leaky%& update mode, an event that causes the client to
33374 go over the limit is not added to the set, in the same way that the client's
33375 recorded rate is not updated in the same situation.
33377 When you combine the &%unique=%& and &%readonly%& options, the specific
33378 &%unique=%& value is ignored, and Exim just retrieves the client's stored
33381 The &%unique=%& mechanism needs more space in the ratelimit database than the
33382 other &%ratelimit%& options in order to store the event set. The number of
33383 unique values is potentially as large as the rate limit, so the extra space
33384 required increases with larger limits.
33386 The uniqueification is not perfect: there is a small probability that Exim
33387 will think a new event has happened before. If the sender's rate is less than
33388 the limit, Exim should be more than 99.9% correct. However in &%strict%& mode
33389 the measured rate can go above the limit, in which case Exim may under-count
33390 events by a significant margin. Fortunately, if the rate is high enough (2.7
33391 times the limit) that the false positive rate goes above 9%, then Exim will
33392 throw away the over-full event set before the measured rate falls below the
33393 limit. Therefore the only harm should be that exceptionally high sending rates
33394 are logged incorrectly; any countermeasures you configure will be as effective
33398 .section "Using rate limiting" "useratlim"
33399 Exim's other ACL facilities are used to define what counter-measures are taken
33400 when the rate limit is exceeded. This might be anything from logging a warning
33401 (for example, while measuring existing sending rates in order to define
33402 policy), through time delays to slow down fast senders, up to rejecting the
33403 message. For example:
33405 # Log all senders' rates
33406 warn ratelimit = 0 / 1h / strict
33407 log_message = Sender rate $sender_rate / $sender_rate_period
33409 # Slow down fast senders; note the need to truncate $sender_rate
33410 # at the decimal point.
33411 warn ratelimit = 100 / 1h / per_rcpt / strict
33412 delay = ${eval: ${sg{$sender_rate}{[.].*}{}} - \
33413 $sender_rate_limit }s
33415 # Keep authenticated users under control
33416 deny authenticated = *
33417 ratelimit = 100 / 1d / strict / $authenticated_id
33419 # System-wide rate limit
33420 defer ratelimit = 10 / 1s / $primary_hostname
33421 message = Sorry, too busy. Try again later.
33423 # Restrict incoming rate from each host, with a default
33424 # set using a macro and special cases looked up in a table.
33425 defer ratelimit = ${lookup {$sender_host_address} \
33426 cdb {DB/ratelimits.cdb} \
33427 {$value} {RATELIMIT} }
33428 message = Sender rate exceeds $sender_rate_limit \
33429 messages per $sender_rate_period
33431 &*Warning*&: If you have a busy server with a lot of &%ratelimit%& tests,
33432 especially with the &%per_rcpt%& option, you may suffer from a performance
33433 bottleneck caused by locking on the ratelimit hints database. Apart from
33434 making your ACLs less complicated, you can reduce the problem by using a
33435 RAM disk for Exim's hints directory (usually &_/var/spool/exim/db/_&). However
33436 this means that Exim will lose its hints data after a reboot (including retry
33437 hints, the callout cache, and ratelimit data).
33441 .section "Address verification" "SECTaddressverification"
33442 .cindex "verifying address" "options for"
33443 .cindex "policy control" "address verification"
33444 Several of the &%verify%& conditions described in section
33445 &<<SECTaclconditions>>& cause addresses to be verified. Section
33446 &<<SECTsenaddver>>& discusses the reporting of sender verification failures.
33447 The verification conditions can be followed by options that modify the
33448 verification process. The options are separated from the keyword and from each
33449 other by slashes, and some of them contain parameters. For example:
33451 verify = sender/callout
33452 verify = recipient/defer_ok/callout=10s,defer_ok
33454 The first stage of address verification, which always happens, is to run the
33455 address through the routers, in &"verify mode"&. Routers can detect the
33456 difference between verification and routing for delivery, and their actions can
33457 be varied by a number of generic options such as &%verify%& and &%verify_only%&
33458 (see chapter &<<CHAProutergeneric>>&). If routing fails, verification fails.
33459 The available options are as follows:
33462 If the &%callout%& option is specified, successful routing to one or more
33463 remote hosts is followed by a &"callout"& to those hosts as an additional
33464 check. Callouts and their sub-options are discussed in the next section.
33466 If there is a defer error while doing verification routing, the ACL
33467 normally returns &"defer"&. However, if you include &%defer_ok%& in the
33468 options, the condition is forced to be true instead. Note that this is a main
33469 verification option as well as a suboption for callouts.
33471 The &%no_details%& option is covered in section &<<SECTsenaddver>>&, which
33472 discusses the reporting of sender address verification failures.
33474 The &%success_on_redirect%& option causes verification always to succeed
33475 immediately after a successful redirection. By default, if a redirection
33476 generates just one address, that address is also verified. See further
33477 discussion in section &<<SECTredirwhilveri>>&.
33479 If the &%quota%& option is specified for recipient verify,
33480 successful routing to an appendfile transport is followed by a call into
33481 the transport to evaluate the quota status for the recipient.
33482 No actual delivery is done, but verification will succeed if the quota
33483 is sufficient for the message (if the sender gave a message size) or
33484 not already exceeded (otherwise).
33487 .cindex "verifying address" "differentiating failures"
33488 .vindex "&$recipient_verify_failure$&"
33489 .vindex "&$sender_verify_failure$&"
33490 .vindex "&$acl_verify_message$&"
33491 After an address verification failure, &$acl_verify_message$& contains the
33492 error message that is associated with the failure. It can be preserved by
33495 warn !verify = sender
33496 set acl_m0 = $acl_verify_message
33498 If you are writing your own custom rejection message or log message when
33499 denying access, you can use this variable to include information about the
33500 verification failure.
33501 This variable is cleared at the end of processing the ACL verb.
33503 In addition, &$sender_verify_failure$& or &$recipient_verify_failure$& (as
33504 appropriate) contains one of the following words:
33507 &%qualify%&: The address was unqualified (no domain), and the message
33508 was neither local nor came from an exempted host.
33510 &%route%&: Routing failed.
33512 &%mail%&: Routing succeeded, and a callout was attempted; rejection
33513 occurred at or before the MAIL command (that is, on initial
33514 connection, HELO, or MAIL).
33516 &%recipient%&: The RCPT command in a callout was rejected.
33518 &%postmaster%&: The postmaster check in a callout was rejected.
33520 &%quota%&: The quota check for a local recipient did non pass.
33523 The main use of these variables is expected to be to distinguish between
33524 rejections of MAIL and rejections of RCPT in callouts.
33526 The above variables may also be set after a &*successful*&
33527 address verification to:
33530 &%random%&: A random local-part callout succeeded
33536 .section "Callout verification" "SECTcallver"
33537 .cindex "verifying address" "by callout"
33538 .cindex "callout" "verification"
33539 .cindex "SMTP" "callout verification"
33540 For non-local addresses, routing verifies the domain, but is unable to do any
33541 checking of the local part. There are situations where some means of verifying
33542 the local part is desirable. One way this can be done is to make an SMTP
33543 &'callback'& to a delivery host for the sender address or a &'callforward'& to
33544 a subsequent host for a recipient address, to see if the host accepts the
33545 address. We use the term &'callout'& to cover both cases. Note that for a
33546 sender address, the callback is not to the client host that is trying to
33547 deliver the message, but to one of the hosts that accepts incoming mail for the
33550 Exim does not do callouts by default. If you want them to happen, you must
33551 request them by setting appropriate options on the &%verify%& condition, as
33552 described below. This facility should be used with care, because it can add a
33553 lot of resource usage to the cost of verifying an address. However, Exim does
33554 cache the results of callouts, which helps to reduce the cost. Details of
33555 caching are in section &<<SECTcallvercache>>&.
33557 Recipient callouts are usually used only between hosts that are controlled by
33558 the same administration. For example, a corporate gateway host could use
33559 callouts to check for valid recipients on an internal mailserver. A successful
33560 callout does not guarantee that a real delivery to the address would succeed;
33561 on the other hand, a failing callout does guarantee that a delivery would fail.
33563 If the &%callout%& option is present on a condition that verifies an address, a
33564 second stage of verification occurs if the address is successfully routed to
33565 one or more remote hosts. The usual case is routing by a &(dnslookup)& or a
33566 &(manualroute)& router, where the router specifies the hosts. However, if a
33567 router that does not set up hosts routes to an &(smtp)& transport with a
33568 &%hosts%& setting, the transport's hosts are used. If an &(smtp)& transport has
33569 &%hosts_override%& set, its hosts are always used, whether or not the router
33570 supplies a host list.
33571 Callouts are only supported on &(smtp)& transports.
33573 The port that is used is taken from the transport, if it is specified and is a
33574 remote transport. (For routers that do verification only, no transport need be
33575 specified.) Otherwise, the default SMTP port is used. If a remote transport
33576 specifies an outgoing interface, this is used; otherwise the interface is not
33577 specified. Likewise, the text that is used for the HELO command is taken from
33578 the transport's &%helo_data%& option; if there is no transport, the value of
33579 &$smtp_active_hostname$& is used.
33581 For a sender callout check, Exim makes SMTP connections to the remote hosts, to
33582 test whether a bounce message could be delivered to the sender address. The
33583 following SMTP commands are sent:
33585 &`HELO `&<&'local host name'&>
33587 &`RCPT TO:`&<&'the address to be tested'&>
33590 LHLO is used instead of HELO if the transport's &%protocol%& option is
33593 The callout may use EHLO, AUTH and/or STARTTLS given appropriate option
33596 A recipient callout check is similar. By default, it also uses an empty address
33597 for the sender. This default is chosen because most hosts do not make use of
33598 the sender address when verifying a recipient. Using the same address means
33599 that a single cache entry can be used for each recipient. Some sites, however,
33600 do make use of the sender address when verifying. These are catered for by the
33601 &%use_sender%& and &%use_postmaster%& options, described in the next section.
33603 If the response to the RCPT command is a 2&'xx'& code, the verification
33604 succeeds. If it is 5&'xx'&, the verification fails. For any other condition,
33605 Exim tries the next host, if any. If there is a problem with all the remote
33606 hosts, the ACL yields &"defer"&, unless the &%defer_ok%& parameter of the
33607 &%callout%& option is given, in which case the condition is forced to succeed.
33609 .cindex "SMTP" "output flushing, disabling for callout"
33610 A callout may take a little time. For this reason, Exim normally flushes SMTP
33611 output before performing a callout in an ACL, to avoid unexpected timeouts in
33612 clients when the SMTP PIPELINING extension is in use. The flushing can be
33613 disabled by using a &%control%& modifier to set &%no_callout_flush%&.
33618 .section "Additional parameters for callouts" "CALLaddparcall"
33619 .cindex "callout" "additional parameters for"
33620 The &%callout%& option can be followed by an equals sign and a number of
33621 optional parameters, separated by commas. For example:
33623 verify = recipient/callout=10s,defer_ok
33625 The old syntax, which had &%callout_defer_ok%& and &%check_postmaster%& as
33626 separate verify options, is retained for backwards compatibility, but is now
33627 deprecated. The additional parameters for &%callout%& are as follows:
33631 .vitem <&'a&~time&~interval'&>
33632 .cindex "callout" "timeout, specifying"
33633 This specifies the timeout that applies for the callout attempt to each host.
33636 verify = sender/callout=5s
33638 The default is 30 seconds. The timeout is used for each response from the
33639 remote host. It is also used for the initial connection, unless overridden by
33640 the &%connect%& parameter.
33643 .vitem &*connect&~=&~*&<&'time&~interval'&>
33644 .cindex "callout" "connection timeout, specifying"
33645 This parameter makes it possible to set a different (usually smaller) timeout
33646 for making the SMTP connection. For example:
33648 verify = sender/callout=5s,connect=1s
33650 If not specified, this timeout defaults to the general timeout value.
33652 .vitem &*defer_ok*&
33653 .cindex "callout" "defer, action on"
33654 When this parameter is present, failure to contact any host, or any other kind
33655 of temporary error, is treated as success by the ACL. However, the cache is not
33656 updated in this circumstance.
33658 .vitem &*fullpostmaster*&
33659 .cindex "callout" "full postmaster check"
33660 This operates like the &%postmaster%& option (see below), but if the check for
33661 &'postmaster@domain'& fails, it tries just &'postmaster'&, without a domain, in
33662 accordance with the specification in RFC 2821. The RFC states that the
33663 unqualified address &'postmaster'& should be accepted.
33666 .vitem &*mailfrom&~=&~*&<&'email&~address'&>
33667 .cindex "callout" "sender when verifying header"
33668 When verifying addresses in header lines using the &%header_sender%&
33669 verification option, Exim behaves by default as if the addresses are envelope
33670 sender addresses from a message. Callout verification therefore tests to see
33671 whether a bounce message could be delivered, by using an empty address in the
33672 MAIL command. However, it is arguable that these addresses might never be used
33673 as envelope senders, and could therefore justifiably reject bounce messages
33674 (empty senders). The &%mailfrom%& callout parameter allows you to specify what
33675 address to use in the MAIL command. For example:
33677 require verify = header_sender/callout=mailfrom=abcd@x.y.z
33679 This parameter is available only for the &%header_sender%& verification option.
33682 .vitem &*maxwait&~=&~*&<&'time&~interval'&>
33683 .cindex "callout" "overall timeout, specifying"
33684 This parameter sets an overall timeout for performing a callout verification.
33687 verify = sender/callout=5s,maxwait=30s
33689 This timeout defaults to four times the callout timeout for individual SMTP
33690 commands. The overall timeout applies when there is more than one host that can
33691 be tried. The timeout is checked before trying the next host. This prevents
33692 very long delays if there are a large number of hosts and all are timing out
33693 (for example, when network connections are timing out).
33696 .vitem &*no_cache*&
33697 .cindex "callout" "cache, suppressing"
33698 .cindex "caching callout, suppressing"
33699 When this parameter is given, the callout cache is neither read nor updated.
33701 .vitem &*postmaster*&
33702 .cindex "callout" "postmaster; checking"
33703 When this parameter is set, a successful callout check is followed by a similar
33704 check for the local part &'postmaster'& at the same domain. If this address is
33705 rejected, the callout fails (but see &%fullpostmaster%& above). The result of
33706 the postmaster check is recorded in a cache record; if it is a failure, this is
33707 used to fail subsequent callouts for the domain without a connection being
33708 made, until the cache record expires.
33710 .vitem &*postmaster_mailfrom&~=&~*&<&'email&~address'&>
33711 The postmaster check uses an empty sender in the MAIL command by default.
33712 You can use this parameter to do a postmaster check using a different address.
33715 require verify = sender/callout=postmaster_mailfrom=abc@x.y.z
33717 If both &%postmaster%& and &%postmaster_mailfrom%& are present, the rightmost
33718 one overrides. The &%postmaster%& parameter is equivalent to this example:
33720 require verify = sender/callout=postmaster_mailfrom=
33722 &*Warning*&: The caching arrangements for postmaster checking do not take
33723 account of the sender address. It is assumed that either the empty address or
33724 a fixed non-empty address will be used. All that Exim remembers is that the
33725 postmaster check for the domain succeeded or failed.
33729 .cindex "callout" "&""random""& check"
33730 When this parameter is set, before doing the normal callout check, Exim does a
33731 check for a &"random"& local part at the same domain. The local part is not
33732 really random &-- it is defined by the expansion of the option
33733 &%callout_random_local_part%&, which defaults to
33735 $primary_hostname-$tod_epoch-testing
33737 The idea here is to try to determine whether the remote host accepts all local
33738 parts without checking. If it does, there is no point in doing callouts for
33739 specific local parts. If the &"random"& check succeeds, the result is saved in
33740 a cache record, and used to force the current and subsequent callout checks to
33741 succeed without a connection being made, until the cache record expires.
33743 .vitem &*use_postmaster*&
33744 .cindex "callout" "sender for recipient check"
33745 This parameter applies to recipient callouts only. For example:
33747 deny !verify = recipient/callout=use_postmaster
33749 .vindex "&$qualify_domain$&"
33750 It causes a non-empty postmaster address to be used in the MAIL command when
33751 performing the callout for the recipient, and also for a &"random"& check if
33752 that is configured. The local part of the address is &`postmaster`& and the
33753 domain is the contents of &$qualify_domain$&.
33755 .vitem &*use_sender*&
33756 This option applies to recipient callouts only. For example:
33758 require verify = recipient/callout=use_sender
33760 It causes the message's actual sender address to be used in the MAIL
33761 command when performing the callout, instead of an empty address. There is no
33762 need to use this option unless you know that the called hosts make use of the
33763 sender when checking recipients. If used indiscriminately, it reduces the
33764 usefulness of callout caching.
33767 This option applies to recipient callouts only. For example:
33769 require verify = recipient/callout=use_sender,hold
33771 It causes the connection to be held open and used for any further recipients
33772 and for eventual delivery (should that be done quickly).
33773 Doing this saves on TCP and SMTP startup costs, and TLS costs also
33774 when that is used for the connections.
33775 The advantage is only gained if there are no callout cache hits
33776 (which could be enforced by the no_cache option),
33777 if the use_sender option is used,
33778 if neither the random nor the use_postmaster option is used,
33779 and if no other callouts intervene.
33782 If you use any of the parameters that set a non-empty sender for the MAIL
33783 command (&%mailfrom%&, &%postmaster_mailfrom%&, &%use_postmaster%&, or
33784 &%use_sender%&), you should think about possible loops. Recipient checking is
33785 usually done between two hosts that are under the same management, and the host
33786 that receives the callouts is not normally configured to do callouts itself.
33787 Therefore, it is normally safe to use &%use_postmaster%& or &%use_sender%& in
33788 these circumstances.
33790 However, if you use a non-empty sender address for a callout to an arbitrary
33791 host, there is the likelihood that the remote host will itself initiate a
33792 callout check back to your host. As it is checking what appears to be a message
33793 sender, it is likely to use an empty address in MAIL, thus avoiding a
33794 callout loop. However, to be on the safe side it would be best to set up your
33795 own ACLs so that they do not do sender verification checks when the recipient
33796 is the address you use for header sender or postmaster callout checking.
33798 Another issue to think about when using non-empty senders for callouts is
33799 caching. When you set &%mailfrom%& or &%use_sender%&, the cache record is keyed
33800 by the sender/recipient combination; thus, for any given recipient, many more
33801 actual callouts are performed than when an empty sender or postmaster is used.
33806 .section "Callout caching" "SECTcallvercache"
33807 .cindex "hints database" "callout cache"
33808 .cindex "callout" "cache, description of"
33809 .cindex "caching" "callout"
33810 Exim caches the results of callouts in order to reduce the amount of resources
33811 used, unless you specify the &%no_cache%& parameter with the &%callout%&
33812 option. A hints database called &"callout"& is used for the cache. Two
33813 different record types are used: one records the result of a callout check for
33814 a specific address, and the other records information that applies to the
33815 entire domain (for example, that it accepts the local part &'postmaster'&).
33817 When an original callout fails, a detailed SMTP error message is given about
33818 the failure. However, for subsequent failures use the cache data, this message
33821 The expiry times for negative and positive address cache records are
33822 independent, and can be set by the global options &%callout_negative_expire%&
33823 (default 2h) and &%callout_positive_expire%& (default 24h), respectively.
33825 If a host gives a negative response to an SMTP connection, or rejects any
33826 commands up to and including
33830 (but not including the MAIL command with a non-empty address),
33831 any callout attempt is bound to fail. Exim remembers such failures in a
33832 domain cache record, which it uses to fail callouts for the domain without
33833 making new connections, until the domain record times out. There are two
33834 separate expiry times for domain cache records:
33835 &%callout_domain_negative_expire%& (default 3h) and
33836 &%callout_domain_positive_expire%& (default 7d).
33838 Domain records expire when the negative expiry time is reached if callouts
33839 cannot be made for the domain, or if the postmaster check failed.
33840 Otherwise, they expire when the positive expiry time is reached. This
33841 ensures that, for example, a host that stops accepting &"random"& local parts
33842 will eventually be noticed.
33844 The callout caching mechanism is based on the domain of the address that is
33845 being tested. If the domain routes to several hosts, it is assumed that their
33846 behaviour will be the same.
33850 .section "Quota caching" "SECTquotacache"
33851 .cindex "hints database" "quota cache"
33852 .cindex "quota" "cache, description of"
33853 .cindex "caching" "quota"
33854 Exim caches the results of quota verification
33855 in order to reduce the amount of resources used.
33856 The &"callout"& hints database is used.
33858 The default cache periods are five minutes for a positive (good) result
33859 and one hour for a negative result.
33860 To change the periods the &%quota%& option can be followed by an equals sign
33861 and a number of optional paramemters, separated by commas.
33864 verify = recipient/quota=cachepos=1h,cacheneg=1d
33866 Possible parameters are:
33868 .vitem &*cachepos&~=&~*&<&'time&~interval'&>
33869 .cindex "quota cache" "positive entry expiry, specifying"
33870 Set the lifetime for a positive cache entry.
33871 A value of zero seconds is legitimate.
33873 .vitem &*cacheneg&~=&~*&<&'time&~interval'&>
33874 .cindex "quota cache" "negative entry expiry, specifying"
33875 As above, for a negative entry.
33877 .vitem &*no_cache*&
33878 Set both positive and negative lifetimes to zero.
33880 .section "Sender address verification reporting" "SECTsenaddver"
33881 .cindex "verifying" "suppressing error details"
33882 See section &<<SECTaddressverification>>& for a general discussion of
33883 verification. When sender verification fails in an ACL, the details of the
33884 failure are given as additional output lines before the 550 response to the
33885 relevant SMTP command (RCPT or DATA). For example, if sender callout is in use,
33888 MAIL FROM:<xyz@abc.example>
33890 RCPT TO:<pqr@def.example>
33891 550-Verification failed for <xyz@abc.example>
33892 550-Called: 192.168.34.43
33893 550-Sent: RCPT TO:<xyz@abc.example>
33894 550-Response: 550 Unknown local part xyz in <xyz@abc.example>
33895 550 Sender verification failed
33897 If more than one RCPT command fails in the same way, the details are given
33898 only for the first of them. However, some administrators do not want to send
33899 out this much information. You can suppress the details by adding
33900 &`/no_details`& to the ACL statement that requests sender verification. For
33903 verify = sender/no_details
33906 .section "Redirection while verifying" "SECTredirwhilveri"
33907 .cindex "verifying" "redirection while"
33908 .cindex "address redirection" "while verifying"
33909 A dilemma arises when a local address is redirected by aliasing or forwarding
33910 during verification: should the generated addresses themselves be verified,
33911 or should the successful expansion of the original address be enough to verify
33912 it? By default, Exim takes the following pragmatic approach:
33915 When an incoming address is redirected to just one child address, verification
33916 continues with the child address, and if that fails to verify, the original
33917 verification also fails.
33919 When an incoming address is redirected to more than one child address,
33920 verification does not continue. A success result is returned.
33923 This seems the most reasonable behaviour for the common use of aliasing as a
33924 way of redirecting different local parts to the same mailbox. It means, for
33925 example, that a pair of alias entries of the form
33928 aw123: :fail: Gone away, no forwarding address
33930 work as expected, with both local parts causing verification failure. When a
33931 redirection generates more than one address, the behaviour is more like a
33932 mailing list, where the existence of the alias itself is sufficient for
33933 verification to succeed.
33935 It is possible, however, to change the default behaviour so that all successful
33936 redirections count as successful verifications, however many new addresses are
33937 generated. This is specified by the &%success_on_redirect%& verification
33938 option. For example:
33940 require verify = recipient/success_on_redirect/callout=10s
33942 In this example, verification succeeds if a router generates a new address, and
33943 the callout does not occur, because no address was routed to a remote host.
33945 When verification is being tested via the &%-bv%& option, the treatment of
33946 redirections is as just described, unless the &%-v%& or any debugging option is
33947 also specified. In that case, full verification is done for every generated
33948 address and a report is output for each of them.
33952 .section "Client SMTP authorization (CSA)" "SECTverifyCSA"
33953 .cindex "CSA" "verifying"
33954 Client SMTP Authorization is a system that allows a site to advertise
33955 which machines are and are not permitted to send email. This is done by placing
33956 special SRV records in the DNS; these are looked up using the client's HELO
33957 domain. At the time of writing, CSA is still an Internet Draft. Client SMTP
33958 Authorization checks in Exim are performed by the ACL condition:
33962 This fails if the client is not authorized. If there is a DNS problem, or if no
33963 valid CSA SRV record is found, or if the client is authorized, the condition
33964 succeeds. These three cases can be distinguished using the expansion variable
33965 &$csa_status$&, which can take one of the values &"fail"&, &"defer"&,
33966 &"unknown"&, or &"ok"&. The condition does not itself defer because that would
33967 be likely to cause problems for legitimate email.
33969 The error messages produced by the CSA code include slightly more
33970 detail. If &$csa_status$& is &"defer"&, this may be because of problems
33971 looking up the CSA SRV record, or problems looking up the CSA target
33972 address record. There are four reasons for &$csa_status$& being &"fail"&:
33975 The client's host name is explicitly not authorized.
33977 The client's IP address does not match any of the CSA target IP addresses.
33979 The client's host name is authorized but it has no valid target IP addresses
33980 (for example, the target's addresses are IPv6 and the client is using IPv4).
33982 The client's host name has no CSA SRV record but a parent domain has asserted
33983 that all subdomains must be explicitly authorized.
33986 The &%csa%& verification condition can take an argument which is the domain to
33987 use for the DNS query. The default is:
33989 verify = csa/$sender_helo_name
33991 This implementation includes an extension to CSA. If the query domain
33992 is an address literal such as [192.0.2.95], or if it is a bare IP
33993 address, Exim searches for CSA SRV records in the reverse DNS as if
33994 the HELO domain was (for example) &'95.2.0.192.in-addr.arpa'&. Therefore it is
33997 verify = csa/$sender_host_address
33999 In fact, this is the check that Exim performs if the client does not say HELO.
34000 This extension can be turned off by setting the main configuration option
34001 &%dns_csa_use_reverse%& to be false.
34003 If a CSA SRV record is not found for the domain itself, a search
34004 is performed through its parent domains for a record which might be
34005 making assertions about subdomains. The maximum depth of this search is limited
34006 using the main configuration option &%dns_csa_search_limit%&, which is 5 by
34007 default. Exim does not look for CSA SRV records in a top level domain, so the
34008 default settings handle HELO domains as long as seven
34009 (&'hostname.five.four.three.two.one.com'&). This encompasses the vast majority
34010 of legitimate HELO domains.
34012 The &'dnsdb'& lookup also has support for CSA. Although &'dnsdb'& also supports
34013 direct SRV lookups, this is not sufficient because of the extra parent domain
34014 search behaviour of CSA, and (as with PTR lookups) &'dnsdb'& also turns IP
34015 addresses into lookups in the reverse DNS space. The result of a successful
34018 ${lookup dnsdb {csa=$sender_helo_name}}
34020 has two space-separated fields: an authorization code and a target host name.
34021 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
34022 authorization required but absent, or &"?"& for unknown.
34027 .section "Bounce address tag validation" "SECTverifyPRVS"
34028 .cindex "BATV, verifying"
34029 Bounce address tag validation (BATV) is a scheme whereby the envelope senders
34030 of outgoing messages have a cryptographic, timestamped &"tag"& added to them.
34031 Genuine incoming bounce messages should therefore always be addressed to
34032 recipients that have a valid tag. This scheme is a way of detecting unwanted
34033 bounce messages caused by sender address forgeries (often called &"collateral
34034 spam"&), because the recipients of such messages do not include valid tags.
34036 There are two expansion items to help with the implementation of the BATV
34037 &"prvs"& (private signature) scheme in an Exim configuration. This scheme signs
34038 the original envelope sender address by using a simple key to add a hash of the
34039 address and some time-based randomizing information. The &%prvs%& expansion
34040 item creates a signed address, and the &%prvscheck%& expansion item checks one.
34041 The syntax of these expansion items is described in section
34042 &<<SECTexpansionitems>>&.
34043 The validity period on signed addresses is seven days.
34045 As an example, suppose the secret per-address keys are stored in an MySQL
34046 database. A query to look up the key for an address could be defined as a macro
34049 PRVSCHECK_SQL = ${lookup mysql{SELECT secret FROM batv_prvs \
34050 WHERE sender='${quote_mysql:$prvscheck_address}'\
34053 Suppose also that the senders who make use of BATV are defined by an address
34054 list called &%batv_senders%&. Then, in the ACL for RCPT commands, you could
34057 # Bounces: drop unsigned addresses for BATV senders
34059 recipients = +batv_senders
34060 message = This address does not send an unsigned reverse path
34062 # Bounces: In case of prvs-signed address, check signature.
34064 condition = ${prvscheck {$local_part@$domain}\
34065 {PRVSCHECK_SQL}{1}}
34066 !condition = $prvscheck_result
34067 message = Invalid reverse path signature.
34069 The first statement rejects recipients for bounce messages that are addressed
34070 to plain BATV sender addresses, because it is known that BATV senders do not
34071 send out messages with plain sender addresses. The second statement rejects
34072 recipients that are prvs-signed, but with invalid signatures (either because
34073 the key is wrong, or the signature has timed out).
34075 A non-prvs-signed address is not rejected by the second statement, because the
34076 &%prvscheck%& expansion yields an empty string if its first argument is not a
34077 prvs-signed address, thus causing the &%condition%& condition to be false. If
34078 the first argument is a syntactically valid prvs-signed address, the yield is
34079 the third string (in this case &"1"&), whether or not the cryptographic and
34080 timeout checks succeed. The &$prvscheck_result$& variable contains the result
34081 of the checks (empty for failure, &"1"& for success).
34083 There is one more issue you must consider when implementing prvs-signing:
34084 you have to ensure that the routers accept prvs-signed addresses and
34085 deliver them correctly. The easiest way to handle this is to use a &(redirect)&
34086 router to remove the signature with a configuration along these lines:
34090 data = ${prvscheck {$local_part@$domain}{PRVSCHECK_SQL}}
34092 This works because, if the third argument of &%prvscheck%& is empty, the result
34093 of the expansion of a prvs-signed address is the decoded value of the original
34094 address. This router should probably be the first of your routers that handles
34097 To create BATV-signed addresses in the first place, a transport of this form
34100 external_smtp_batv:
34102 return_path = ${prvs {$return_path} \
34103 {${lookup mysql{SELECT \
34104 secret FROM batv_prvs WHERE \
34105 sender='${quote_mysql:$sender_address}'} \
34108 If no key can be found for the existing return path, no signing takes place.
34112 .section "Using an ACL to control relaying" "SECTrelaycontrol"
34113 .cindex "&ACL;" "relay control"
34114 .cindex "relaying" "control by ACL"
34115 .cindex "policy control" "relay control"
34116 An MTA is said to &'relay'& a message if it receives it from some host and
34117 delivers it directly to another host as a result of a remote address contained
34118 within it. Redirecting a local address via an alias or forward file and then
34119 passing the message on to another host is not relaying,
34120 .cindex "&""percent hack""&"
34121 but a redirection as a result of the &"percent hack"& is.
34123 Two kinds of relaying exist, which are termed &"incoming"& and &"outgoing"&.
34124 A host which is acting as a gateway or an MX backup is concerned with incoming
34125 relaying from arbitrary hosts to a specific set of domains. On the other hand,
34126 a host which is acting as a smart host for a number of clients is concerned
34127 with outgoing relaying from those clients to the Internet at large. Often the
34128 same host is fulfilling both functions,
34130 . as illustrated in the diagram below,
34132 but in principle these two kinds of relaying are entirely independent. What is
34133 not wanted is the transmission of mail from arbitrary remote hosts through your
34134 system to arbitrary domains.
34137 You can implement relay control by means of suitable statements in the ACL that
34138 runs for each RCPT command. For convenience, it is often easiest to use
34139 Exim's named list facility to define the domains and hosts involved. For
34140 example, suppose you want to do the following:
34143 Deliver a number of domains to mailboxes on the local host (or process them
34144 locally in some other way). Let's say these are &'my.dom1.example'& and
34145 &'my.dom2.example'&.
34147 Relay mail for a number of other domains for which you are the secondary MX.
34148 These might be &'friend1.example'& and &'friend2.example'&.
34150 Relay mail from the hosts on your local LAN, to whatever domains are involved.
34151 Suppose your LAN is 192.168.45.0/24.
34155 In the main part of the configuration, you put the following definitions:
34157 domainlist local_domains = my.dom1.example : my.dom2.example
34158 domainlist relay_to_domains = friend1.example : friend2.example
34159 hostlist relay_from_hosts = 192.168.45.0/24
34161 Now you can use these definitions in the ACL that is run for every RCPT
34165 accept domains = +local_domains : +relay_to_domains
34166 accept hosts = +relay_from_hosts
34168 The first statement accepts any RCPT command that contains an address in
34169 the local or relay domains. For any other domain, control passes to the second
34170 statement, which accepts the command only if it comes from one of the relay
34171 hosts. In practice, you will probably want to make your ACL more sophisticated
34172 than this, for example, by including sender and recipient verification. The
34173 default configuration includes a more comprehensive example, which is described
34174 in chapter &<<CHAPdefconfil>>&.
34178 .section "Checking a relay configuration" "SECTcheralcon"
34179 .cindex "relaying" "checking control of"
34180 You can check the relay characteristics of your configuration in the same way
34181 that you can test any ACL behaviour for an incoming SMTP connection, by using
34182 the &%-bh%& option to run a fake SMTP session with which you interact.
34187 . ////////////////////////////////////////////////////////////////////////////
34188 . ////////////////////////////////////////////////////////////////////////////
34190 .chapter "Content scanning at ACL time" "CHAPexiscan"
34191 .scindex IIDcosca "content scanning" "at ACL time"
34192 The extension of Exim to include content scanning at ACL time, formerly known
34193 as &"exiscan"&, was originally implemented as a patch by Tom Kistner. The code
34194 was integrated into the main source for Exim release 4.50, and Tom continues to
34195 maintain it. Most of the wording of this chapter is taken from Tom's
34198 It is also possible to scan the content of messages at other times. The
34199 &[local_scan()]& function (see chapter &<<CHAPlocalscan>>&) allows for content
34200 scanning after all the ACLs have run. A transport filter can be used to scan
34201 messages at delivery time (see the &%transport_filter%& option, described in
34202 chapter &<<CHAPtransportgeneric>>&).
34204 If you want to include the ACL-time content-scanning features when you compile
34205 Exim, you need to arrange for WITH_CONTENT_SCAN to be defined in your
34206 &_Local/Makefile_&. When you do that, the Exim binary is built with:
34209 Two additional ACLs (&%acl_smtp_mime%& and &%acl_not_smtp_mime%&) that are run
34210 for all MIME parts for SMTP and non-SMTP messages, respectively.
34212 Additional ACL conditions and modifiers: &%decode%&, &%malware%&,
34213 &%mime_regex%&, &%regex%&, and &%spam%&. These can be used in the ACL that is
34214 run at the end of message reception (the &%acl_smtp_data%& ACL).
34216 An additional control feature (&"no_mbox_unspool"&) that saves spooled copies
34217 of messages, or parts of messages, for debugging purposes.
34219 Additional expansion variables that are set in the new ACL and by the new
34222 Two new main configuration options: &%av_scanner%& and &%spamd_address%&.
34225 Content-scanning is continually evolving, and new features are still being
34226 added. While such features are still unstable and liable to incompatible
34227 changes, they are made available in Exim by setting options whose names begin
34228 EXPERIMENTAL_ in &_Local/Makefile_&. Such features are not documented in
34229 this manual. You can find out about them by reading the file called
34230 &_doc/experimental.txt_&.
34232 All the content-scanning facilities work on a MBOX copy of the message that is
34233 temporarily created in a file called:
34235 <&'spool_directory'&>&`/scan/`&<&'message_id'&>/<&'message_id'&>&`.eml`&
34237 The &_.eml_& extension is a friendly hint to virus scanners that they can
34238 expect an MBOX-like structure inside that file. The file is created when the
34239 first content scanning facility is called. Subsequent calls to content
34240 scanning conditions open the same file again. The directory is recursively
34241 removed when the &%acl_smtp_data%& ACL has finished running, unless
34243 control = no_mbox_unspool
34245 has been encountered. When the MIME ACL decodes files, they are put into the
34246 same directory by default.
34250 .section "Scanning for viruses" "SECTscanvirus"
34251 .cindex "virus scanning"
34252 .cindex "content scanning" "for viruses"
34253 .cindex "content scanning" "the &%malware%& condition"
34254 The &%malware%& ACL condition lets you connect virus scanner software to Exim.
34255 It supports a &"generic"& interface to scanners called via the shell, and
34256 specialized interfaces for &"daemon"& type virus scanners, which are resident
34257 in memory and thus are much faster.
34259 Since message data needs to have arrived,
34260 the condition may be only called in ACL defined by
34262 &%acl_smtp_data_prdr%&,
34263 &%acl_smtp_mime%& or
34266 A timeout of 2 minutes is applied to a scanner call (by default);
34267 if it expires then a defer action is taken.
34269 .oindex "&%av_scanner%&"
34270 You can set the &%av_scanner%& option in the main part of the configuration
34271 to specify which scanner to use, together with any additional options that
34272 are needed. The basic syntax is as follows:
34274 &`av_scanner = <`&&'scanner-type'&&`>:<`&&'option1'&&`>:<`&&'option2'&&`>:[...]`&
34276 If you do not set &%av_scanner%&, it defaults to
34278 av_scanner = sophie:/var/run/sophie
34280 If the value of &%av_scanner%& starts with a dollar character, it is expanded
34282 The usual list-parsing of the content (see &<<SECTlistconstruct>>&) applies.
34283 The following scanner types are supported in this release,
34284 though individual ones can be included or not at build time:
34288 .cindex "virus scanners" "avast"
34289 This is the scanner daemon of Avast. It has been tested with Avast Core
34290 Security (currently at version 2.2.0).
34291 You can get a trial version at &url(https://www.avast.com) or for Linux
34292 at &url(https://www.avast.com/linux-server-antivirus).
34293 This scanner type takes one option,
34294 which can be either a full path to a UNIX socket,
34295 or host and port specifiers separated by white space.
34296 The host may be a name or an IP address; the port is either a
34297 single number or a pair of numbers with a dash between.
34298 A list of options may follow. These options are interpreted on the
34299 Exim's side of the malware scanner, or are given on separate lines to
34300 the daemon as options before the main scan command.
34302 .cindex &`pass_unscanned`& "avast"
34303 If &`pass_unscanned`&
34304 is set, any files the Avast scanner can't scan (e.g.
34305 decompression bombs, or invalid archives) are considered clean. Use with
34310 av_scanner = avast:/var/run/avast/scan.sock:FLAGS -fullfiles:SENSITIVITY -pup
34311 av_scanner = avast:/var/run/avast/scan.sock:pass_unscanned:FLAGS -fullfiles:SENSITIVITY -pup
34312 av_scanner = avast:192.168.2.22 5036
34314 If you omit the argument, the default path
34315 &_/var/run/avast/scan.sock_&
34317 If you use a remote host,
34318 you need to make Exim's spool directory available to it,
34319 as the scanner is passed a file path, not file contents.
34320 For information about available commands and their options you may use
34322 $ socat UNIX:/var/run/avast/scan.sock STDIO:
34328 If the scanner returns a temporary failure (e.g. license issues, or
34329 permission problems), the message is deferred and a paniclog entry is
34330 written. The usual &`defer_ok`& option is available.
34332 .vitem &%aveserver%&
34333 .cindex "virus scanners" "Kaspersky"
34334 This is the scanner daemon of Kaspersky Version 5. You can get a trial version
34335 at &url(https://www.kaspersky.com/). This scanner type takes one option,
34336 which is the path to the daemon's UNIX socket. The default is shown in this
34339 av_scanner = aveserver:/var/run/aveserver
34344 .cindex "virus scanners" "clamd"
34345 This daemon-type scanner is GPL and free. You can get it at
34346 &url(https://www.clamav.net/). Some older versions of clamd do not seem to
34347 unpack MIME containers, so it used to be recommended to unpack MIME attachments
34348 in the MIME ACL. This is no longer believed to be necessary.
34350 The options are a list of server specifiers, which may be
34351 a UNIX socket specification,
34352 a TCP socket specification,
34353 or a (global) option.
34355 A socket specification consists of a space-separated list.
34356 For a Unix socket the first element is a full path for the socket,
34357 for a TCP socket the first element is the IP address
34358 and the second a port number,
34359 Any further elements are per-server (non-global) options.
34360 These per-server options are supported:
34362 retry=<timespec> Retry on connect fail
34365 The &`retry`& option specifies a time after which a single retry for
34366 a failed connect is made. The default is to not retry.
34368 If a Unix socket file is specified, only one server is supported.
34372 av_scanner = clamd:/opt/clamd/socket
34373 av_scanner = clamd:192.0.2.3 1234
34374 av_scanner = clamd:192.0.2.3 1234:local
34375 av_scanner = clamd:192.0.2.3 1234 retry=10s
34376 av_scanner = clamd:192.0.2.3 1234 : 192.0.2.4 1234
34378 If the value of av_scanner points to a UNIX socket file or contains the
34380 option, then the ClamAV interface will pass a filename containing the data
34381 to be scanned, which should normally result in less I/O happening and be
34382 more efficient. Normally in the TCP case, the data is streamed to ClamAV as
34383 Exim does not assume that there is a common filesystem with the remote host.
34385 The final example shows that multiple TCP targets can be specified. Exim will
34386 randomly use one for each incoming email (i.e. it load balances them). Note
34387 that only TCP targets may be used if specifying a list of scanners; a UNIX
34388 socket cannot be mixed in with TCP targets. If one of the servers becomes
34389 unavailable, Exim will try the remaining one(s) until it finds one that works.
34390 When a clamd server becomes unreachable, Exim will log a message. Exim does
34391 not keep track of scanner state between multiple messages, and the scanner
34392 selection is random, so the message will get logged in the mainlog for each
34393 email that the down scanner gets chosen first (message wrapped to be readable):
34395 2013-10-09 14:30:39 1VTumd-0000Y8-BQ malware acl condition:
34396 clamd: connection to localhost, port 3310 failed
34397 (Connection refused)
34400 If the option is unset, the default is &_/tmp/clamd_&. Thanks to David Saez for
34401 contributing the code for this scanner.
34404 .cindex "virus scanners" "command line interface"
34405 This is the keyword for the generic command line scanner interface. It can be
34406 used to attach virus scanners that are invoked from the shell. This scanner
34407 type takes 3 mandatory options:
34410 The full path and name of the scanner binary, with all command line options,
34411 and a placeholder (&`%s`&) for the directory to scan.
34414 A regular expression to match against the STDOUT and STDERR output of the
34415 virus scanner. If the expression matches, a virus was found. You must make
34416 absolutely sure that this expression matches on &"virus found"&. This is called
34417 the &"trigger"& expression.
34420 Another regular expression, containing exactly one pair of parentheses, to
34421 match the name of the virus found in the scanners output. This is called the
34422 &"name"& expression.
34425 For example, Sophos Sweep reports a virus on a line like this:
34427 Virus 'W32/Magistr-B' found in file ./those.bat
34429 For the trigger expression, we can match the phrase &"found in file"&. For the
34430 name expression, we want to extract the W32/Magistr-B string, so we can match
34431 for the single quotes left and right of it. Altogether, this makes the
34432 configuration setting:
34434 av_scanner = cmdline:\
34435 /path/to/sweep -ss -all -rec -archive %s:\
34436 found in file:'(.+)'
34439 .cindex "virus scanners" "DrWeb"
34440 The DrWeb daemon scanner (&url(https://www.sald.ru/)) interface
34442 either a full path to a UNIX socket,
34443 or host and port specifiers separated by white space.
34444 The host may be a name or an IP address; the port is either a
34445 single number or a pair of numbers with a dash between.
34448 av_scanner = drweb:/var/run/drwebd.sock
34449 av_scanner = drweb:192.168.2.20 31337
34451 If you omit the argument, the default path &_/usr/local/drweb/run/drwebd.sock_&
34452 is used. Thanks to Alex Miller for contributing the code for this scanner.
34455 .cindex "virus scanners" "f-protd"
34456 The f-protd scanner is accessed via HTTP over TCP.
34457 One argument is taken, being a space-separated hostname and port number
34461 av_scanner = f-protd:localhost 10200-10204
34463 If you omit the argument, the default values shown above are used.
34465 .vitem &%f-prot6d%&
34466 .cindex "virus scanners" "f-prot6d"
34467 The f-prot6d scanner is accessed using the FPSCAND protocol over TCP.
34468 One argument is taken, being a space-separated hostname and port number.
34471 av_scanner = f-prot6d:localhost 10200
34473 If you omit the argument, the default values show above are used.
34476 .cindex "virus scanners" "F-Secure"
34477 The F-Secure daemon scanner (&url(https://www.f-secure.com/)) takes one
34478 argument which is the path to a UNIX socket. For example:
34480 av_scanner = fsecure:/path/to/.fsav
34482 If no argument is given, the default is &_/var/run/.fsav_&. Thanks to Johan
34483 Thelmen for contributing the code for this scanner.
34485 .vitem &%kavdaemon%&
34486 .cindex "virus scanners" "Kaspersky"
34487 This is the scanner daemon of Kaspersky Version 4. This version of the
34488 Kaspersky scanner is outdated. Please upgrade (see &%aveserver%& above). This
34489 scanner type takes one option, which is the path to the daemon's UNIX socket.
34492 av_scanner = kavdaemon:/opt/AVP/AvpCtl
34494 The default path is &_/var/run/AvpCtl_&.
34497 .cindex "virus scanners" "mksd"
34498 This was a daemon type scanner that is aimed mainly at Polish users,
34499 though some documentation was available in English.
34500 The history can be shown at &url(https://en.wikipedia.org/wiki/Mks_vir)
34501 and this appears to be a candidate for removal from Exim, unless
34502 we are informed of other virus scanners which use the same protocol
34504 The only option for this scanner type is
34505 the maximum number of processes used simultaneously to scan the attachments,
34506 provided that mksd has
34507 been run with at least the same number of child processes. For example:
34509 av_scanner = mksd:2
34511 You can safely omit this option (the default value is 1).
34514 .cindex "virus scanners" "simple socket-connected"
34515 This is a general-purpose way of talking to simple scanner daemons
34516 running on the local machine.
34517 There are four options:
34518 an address (which may be an IP address and port, or the path of a Unix socket),
34519 a commandline to send (may include a single %s which will be replaced with
34520 the path to the mail file to be scanned),
34521 an RE to trigger on from the returned data,
34522 and an RE to extract malware_name from the returned data.
34525 av_scanner = sock:127.0.0.1 6001:%s:(SPAM|VIRUS):(.*)$
34527 Note that surrounding whitespace is stripped from each option, meaning
34528 there is no way to specify a trailing newline.
34529 The socket specifier and both regular-expressions are required.
34530 Default for the commandline is &_%s\n_& (note this does have a trailing newline);
34531 specify an empty element to get this.
34534 .cindex "virus scanners" "Sophos and Sophie"
34535 Sophie is a daemon that uses Sophos' &%libsavi%& library to scan for viruses.
34536 You can get Sophie at &url(http://sophie.sourceforge.net/). The only option
34537 for this scanner type is the path to the UNIX socket that Sophie uses for
34538 client communication. For example:
34540 av_scanner = sophie:/tmp/sophie
34542 The default path is &_/var/run/sophie_&, so if you are using this, you can omit
34546 When &%av_scanner%& is correctly set, you can use the &%malware%& condition in
34547 the DATA ACL. &*Note*&: You cannot use the &%malware%& condition in the MIME
34550 The &%av_scanner%& option is expanded each time &%malware%& is called. This
34551 makes it possible to use different scanners. See further below for an example.
34552 The &%malware%& condition caches its results, so when you use it multiple times
34553 for the same message, the actual scanning process is only carried out once.
34554 However, using expandable items in &%av_scanner%& disables this caching, in
34555 which case each use of the &%malware%& condition causes a new scan of the
34558 The &%malware%& condition takes a right-hand argument that is expanded before
34559 use and taken as a list, slash-separated by default.
34560 The first element can then be one of
34563 &"true"&, &"*"&, or &"1"&, in which case the message is scanned for viruses.
34564 The condition succeeds if a virus was found, and fail otherwise. This is the
34567 &"false"& or &"0"& or an empty string, in which case no scanning is done and
34568 the condition fails immediately.
34570 A regular expression, in which case the message is scanned for viruses. The
34571 condition succeeds if a virus is found and its name matches the regular
34572 expression. This allows you to take special actions on certain types of virus.
34573 Note that &"/"& characters in the RE must be doubled due to the list-processing,
34574 unless the separator is changed (in the usual way &<<SECTlistsepchange>>&).
34577 You can append a &`defer_ok`& element to the &%malware%& argument list to accept
34578 messages even if there is a problem with the virus scanner.
34579 Otherwise, such a problem causes the ACL to defer.
34581 You can append a &`tmo=<val>`& element to the &%malware%& argument list to
34582 specify a non-default timeout. The default is two minutes.
34585 malware = * / defer_ok / tmo=10s
34587 A timeout causes the ACL to defer.
34589 .vindex "&$callout_address$&"
34590 When a connection is made to the scanner the expansion variable &$callout_address$&
34591 is set to record the actual address used.
34593 .vindex "&$malware_name$&"
34594 When a virus is found, the condition sets up an expansion variable called
34595 &$malware_name$& that contains the name of the virus. You can use it in a
34596 &%message%& modifier that specifies the error returned to the sender, and/or in
34599 Beware the interaction of Exim's &%message_size_limit%& with any size limits
34600 imposed by your anti-virus scanner.
34602 Here is a very simple scanning example:
34605 message = This message contains malware ($malware_name)
34607 The next example accepts messages when there is a problem with the scanner:
34609 deny malware = */defer_ok
34610 message = This message contains malware ($malware_name)
34612 The next example shows how to use an ACL variable to scan with both sophie and
34613 aveserver. It assumes you have set:
34615 av_scanner = $acl_m0
34617 in the main Exim configuration.
34619 deny set acl_m0 = sophie
34621 message = This message contains malware ($malware_name)
34623 deny set acl_m0 = aveserver
34625 message = This message contains malware ($malware_name)
34629 .section "Scanning with SpamAssassin and Rspamd" "SECTscanspamass"
34630 .cindex "content scanning" "for spam"
34631 .cindex "spam scanning"
34632 .cindex "SpamAssassin"
34634 The &%spam%& ACL condition calls SpamAssassin's &%spamd%& daemon to get a spam
34635 score and a report for the message.
34636 Support is also provided for Rspamd.
34638 For more information about installation and configuration of SpamAssassin or
34639 Rspamd refer to their respective websites at
34640 &url(https://spamassassin.apache.org/) and &url(https://www.rspamd.com/)
34642 SpamAssassin can be installed with CPAN by running:
34644 perl -MCPAN -e 'install Mail::SpamAssassin'
34646 SpamAssassin has its own set of configuration files. Please review its
34647 documentation to see how you can tweak it. The default installation should work
34650 .oindex "&%spamd_address%&"
34651 By default, SpamAssassin listens on 127.0.0.1, TCP port 783 and if you
34652 intend to use an instance running on the local host you do not need to set
34653 &%spamd_address%&. If you intend to use another host or port for SpamAssassin,
34654 you must set the &%spamd_address%& option in the global part of the Exim
34655 configuration as follows (example):
34657 spamd_address = 192.168.99.45 783
34659 The SpamAssassin protocol relies on a TCP half-close from the client.
34660 If your SpamAssassin client side is running a Linux system with an
34661 iptables firewall, consider setting
34662 &%net.netfilter.nf_conntrack_tcp_timeout_close_wait%& to at least the
34663 timeout, Exim uses when waiting for a response from the SpamAssassin
34664 server (currently defaulting to 120s). With a lower value the Linux
34665 connection tracking may consider your half-closed connection as dead too
34669 To use Rspamd (which by default listens on all local addresses
34671 you should add &%variant=rspamd%& after the address/port pair, for example:
34673 spamd_address = 127.0.0.1 11333 variant=rspamd
34676 As of version 2.60, &%SpamAssassin%& also supports communication over UNIX
34677 sockets. If you want to us these, supply &%spamd_address%& with an absolute
34678 filename instead of an address/port pair:
34680 spamd_address = /var/run/spamd_socket
34682 You can have multiple &%spamd%& servers to improve scalability. These can
34683 reside on other hardware reachable over the network. To specify multiple
34684 &%spamd%& servers, put multiple address/port pairs in the &%spamd_address%&
34685 option, separated with colons (the separator can be changed in the usual way &<<SECTlistsepchange>>&):
34687 spamd_address = 192.168.2.10 783 : \
34688 192.168.2.11 783 : \
34691 Up to 32 &%spamd%& servers are supported.
34692 When a server fails to respond to the connection attempt, all other
34693 servers are tried until one succeeds. If no server responds, the &%spam%&
34696 Unix and TCP socket specifications may be mixed in any order.
34697 Each element of the list is a list itself, space-separated by default
34698 and changeable in the usual way (&<<SECTlistsepchange>>&);
34699 take care to not double the separator.
34701 For TCP socket specifications a host name or IP (v4 or v6, but
34702 subject to list-separator quoting rules) address can be used,
34703 and the port can be one or a dash-separated pair.
34704 In the latter case, the range is tried in strict order.
34706 Elements after the first for Unix sockets, or second for TCP socket,
34708 The supported options are:
34710 pri=<priority> Selection priority
34711 weight=<value> Selection bias
34712 time=<start>-<end> Use only between these times of day
34713 retry=<timespec> Retry on connect fail
34714 tmo=<timespec> Connection time limit
34715 variant=rspamd Use Rspamd rather than SpamAssassin protocol
34718 The &`pri`& option specifies a priority for the server within the list,
34719 higher values being tried first.
34720 The default priority is 1.
34722 The &`weight`& option specifies a selection bias.
34723 Within a priority set
34724 servers are queried in a random fashion, weighted by this value.
34725 The default value for selection bias is 1.
34727 Time specifications for the &`time`& option are <hour>.<minute>.<second>
34728 in the local time zone; each element being one or more digits.
34729 Either the seconds or both minutes and seconds, plus the leading &`.`&
34730 characters, may be omitted and will be taken as zero.
34732 Timeout specifications for the &`retry`& and &`tmo`& options
34733 are the usual Exim time interval standard, e.g. &`20s`& or &`1m`&.
34735 The &`tmo`& option specifies an overall timeout for communication.
34736 The default value is two minutes.
34738 The &`retry`& option specifies a time after which a single retry for
34739 a failed connect is made.
34740 The default is to not retry.
34742 The &%spamd_address%& variable is expanded before use if it starts with
34743 a dollar sign. In this case, the expansion may return a string that is
34744 used as the list so that multiple spamd servers can be the result of an
34747 .vindex "&$callout_address$&"
34748 When a connection is made to the server the expansion variable &$callout_address$&
34749 is set to record the actual address used.
34751 .section "Calling SpamAssassin from an Exim ACL" "SECID206"
34752 Here is a simple example of the use of the &%spam%& condition in a DATA ACL:
34755 message = This message was classified as SPAM
34757 The right-hand side of the &%spam%& condition specifies a name. This is
34758 relevant if you have set up multiple SpamAssassin profiles. If you do not want
34759 to scan using a specific profile, but rather use the SpamAssassin system-wide
34760 default profile, you can scan for an unknown name, or simply use &"nobody"&.
34761 Rspamd does not use this setting. However, you must put something on the
34764 The name allows you to use per-domain or per-user antispam profiles in
34765 principle, but this is not straightforward in practice, because a message may
34766 have multiple recipients, not necessarily all in the same domain. Because the
34767 &%spam%& condition has to be called from a DATA-time ACL in order to be able to
34768 read the contents of the message, the variables &$local_part$& and &$domain$&
34770 Careful enforcement of single-recipient messages
34771 (e.g. by responding with defer in the recipient ACL for all recipients
34773 or the use of PRDR,
34774 .cindex "PRDR" "use for per-user SpamAssassin profiles"
34775 are needed to use this feature.
34777 The right-hand side of the &%spam%& condition is expanded before being used, so
34778 you can put lookups or conditions there. When the right-hand side evaluates to
34779 &"0"& or &"false"&, no scanning is done and the condition fails immediately.
34782 Scanning with SpamAssassin uses a lot of resources. If you scan every message,
34783 large ones may cause significant performance degradation. As most spam messages
34784 are quite small, it is recommended that you do not scan the big ones. For
34787 deny condition = ${if < {$message_size}{10K}}
34789 message = This message was classified as SPAM
34792 The &%spam%& condition returns true if the threshold specified in the user's
34793 SpamAssassin profile has been matched or exceeded. If you want to use the
34794 &%spam%& condition for its side effects (see the variables below), you can make
34795 it always return &"true"& by appending &`:true`& to the username.
34797 .cindex "spam scanning" "returned variables"
34798 When the &%spam%& condition is run, it sets up a number of expansion
34800 Except for &$spam_report$&,
34801 these variables are saved with the received message so are
34802 available for use at delivery time.
34805 .vitem &$spam_score$&
34806 The spam score of the message, for example, &"3.4"& or &"30.5"&. This is useful
34807 for inclusion in log or reject messages.
34809 .vitem &$spam_score_int$&
34810 The spam score of the message, multiplied by ten, as an integer value. For
34811 example &"34"& or &"305"&. It may appear to disagree with &$spam_score$&
34812 because &$spam_score$& is rounded and &$spam_score_int$& is truncated.
34813 The integer value is useful for numeric comparisons in conditions.
34815 .vitem &$spam_bar$&
34816 A string consisting of a number of &"+"& or &"-"& characters, representing the
34817 integer part of the spam score value. A spam score of 4.4 would have a
34818 &$spam_bar$& value of &"++++"&. This is useful for inclusion in warning
34819 headers, since MUAs can match on such strings. The maximum length of the
34820 spam bar is 50 characters.
34822 .vitem &$spam_report$&
34823 A multiline text table, containing the full SpamAssassin report for the
34824 message. Useful for inclusion in headers or reject messages.
34825 This variable is only usable in a DATA-time ACL.
34826 Beware that SpamAssassin may return non-ASCII characters, especially
34827 when running in country-specific locales, which are not legal
34828 unencoded in headers.
34830 .vitem &$spam_action$&
34831 For SpamAssassin either 'reject' or 'no action' depending on the
34832 spam score versus threshold.
34833 For Rspamd, the recommended action.
34837 The &%spam%& condition caches its results unless expansion in
34838 spamd_address was used. If you call it again with the same user name, it
34839 does not scan again, but rather returns the same values as before.
34841 The &%spam%& condition returns DEFER if there is any error while running
34842 the message through SpamAssassin or if the expansion of spamd_address
34843 failed. If you want to treat DEFER as FAIL (to pass on to the next ACL
34844 statement block), append &`/defer_ok`& to the right-hand side of the
34845 spam condition, like this:
34847 deny spam = joe/defer_ok
34848 message = This message was classified as SPAM
34850 This causes messages to be accepted even if there is a problem with &%spamd%&.
34852 Here is a longer, commented example of the use of the &%spam%&
34855 # put headers in all messages (no matter if spam or not)
34856 warn spam = nobody:true
34857 add_header = X-Spam-Score: $spam_score ($spam_bar)
34858 add_header = X-Spam-Report: $spam_report
34860 # add second subject line with *SPAM* marker when message
34861 # is over threshold
34863 add_header = Subject: *SPAM* $h_Subject:
34865 # reject spam at high scores (> 12)
34866 deny spam = nobody:true
34867 condition = ${if >{$spam_score_int}{120}{1}{0}}
34868 message = This message scored $spam_score spam points.
34873 .section "Scanning MIME parts" "SECTscanmimepart"
34874 .cindex "content scanning" "MIME parts"
34875 .cindex "MIME content scanning"
34876 .oindex "&%acl_smtp_mime%&"
34877 .oindex "&%acl_not_smtp_mime%&"
34878 The &%acl_smtp_mime%& global option specifies an ACL that is called once for
34879 each MIME part of an SMTP message, including multipart types, in the sequence
34880 of their position in the message. Similarly, the &%acl_not_smtp_mime%& option
34881 specifies an ACL that is used for the MIME parts of non-SMTP messages. These
34882 options may both refer to the same ACL if you want the same processing in both
34885 These ACLs are called (possibly many times) just before the &%acl_smtp_data%&
34886 ACL in the case of an SMTP message, or just before the &%acl_not_smtp%& ACL in
34887 the case of a non-SMTP message. However, a MIME ACL is called only if the
34888 message contains a &'Content-Type:'& header line. When a call to a MIME
34889 ACL does not yield &"accept"&, ACL processing is aborted and the appropriate
34890 result code is sent to the client. In the case of an SMTP message, the
34891 &%acl_smtp_data%& ACL is not called when this happens.
34893 You cannot use the &%malware%& or &%spam%& conditions in a MIME ACL; these can
34894 only be used in the DATA or non-SMTP ACLs. However, you can use the &%regex%&
34895 condition to match against the raw MIME part. You can also use the
34896 &%mime_regex%& condition to match against the decoded MIME part (see section
34897 &<<SECTscanregex>>&).
34899 At the start of a MIME ACL, a number of variables are set from the header
34900 information for the relevant MIME part. These are described below. The contents
34901 of the MIME part are not by default decoded into a disk file except for MIME
34902 parts whose content-type is &"message/rfc822"&. If you want to decode a MIME
34903 part into a disk file, you can use the &%decode%& condition. The general
34906 &`decode = [/`&<&'path'&>&`/]`&<&'filename'&>
34908 The right hand side is expanded before use. After expansion,
34912 &"0"& or &"false"&, in which case no decoding is done.
34914 The string &"default"&. In that case, the file is put in the temporary
34915 &"default"& directory <&'spool_directory'&>&_/scan/_&<&'message_id'&>&_/_& with
34916 a sequential filename consisting of the message id and a sequence number. The
34917 full path and name is available in &$mime_decoded_filename$& after decoding.
34919 A full path name starting with a slash. If the full name is an existing
34920 directory, it is used as a replacement for the default directory. The filename
34921 is then sequentially assigned. If the path does not exist, it is used as
34922 the full path and filename.
34924 If the string does not start with a slash, it is used as the
34925 filename, and the default path is then used.
34927 The &%decode%& condition normally succeeds. It is only false for syntax
34928 errors or unusual circumstances such as memory shortages. You can easily decode
34929 a file with its original, proposed filename using
34931 decode = $mime_filename
34933 However, you should keep in mind that &$mime_filename$& might contain
34934 anything. If you place files outside of the default path, they are not
34935 automatically unlinked.
34937 For RFC822 attachments (these are messages attached to messages, with a
34938 content-type of &"message/rfc822"&), the ACL is called again in the same manner
34939 as for the primary message, only that the &$mime_is_rfc822$& expansion
34940 variable is set (see below). Attached messages are always decoded to disk
34941 before being checked, and the files are unlinked once the check is done.
34943 The MIME ACL supports the &%regex%& and &%mime_regex%& conditions. These can be
34944 used to match regular expressions against raw and decoded MIME parts,
34945 respectively. They are described in section &<<SECTscanregex>>&.
34947 .cindex "MIME content scanning" "returned variables"
34948 The following list describes all expansion variables that are
34949 available in the MIME ACL:
34952 .vitem &$mime_anomaly_level$& &&&
34953 &$mime_anomaly_text$&
34954 .vindex &$mime_anomaly_level$&
34955 .vindex &$mime_anomaly_text$&
34956 If there are problems decoding, these variables contain information on
34957 the detected issue.
34959 .vitem &$mime_boundary$&
34960 .vindex &$mime_boundary$&
34961 If the current part is a multipart (see &$mime_is_multipart$& below), it should
34962 have a boundary string, which is stored in this variable. If the current part
34963 has no boundary parameter in the &'Content-Type:'& header, this variable
34964 contains the empty string.
34966 .vitem &$mime_charset$&
34967 .vindex &$mime_charset$&
34968 This variable contains the character set identifier, if one was found in the
34969 &'Content-Type:'& header. Examples for charset identifiers are:
34975 Please note that this value is not normalized, so you should do matches
34976 case-insensitively.
34978 .vitem &$mime_content_description$&
34979 .vindex &$mime_content_description$&
34980 This variable contains the normalized content of the &'Content-Description:'&
34981 header. It can contain a human-readable description of the parts content. Some
34982 implementations repeat the filename for attachments here, but they are usually
34983 only used for display purposes.
34985 .vitem &$mime_content_disposition$&
34986 .vindex &$mime_content_disposition$&
34987 This variable contains the normalized content of the &'Content-Disposition:'&
34988 header. You can expect strings like &"attachment"& or &"inline"& here.
34990 .vitem &$mime_content_id$&
34991 .vindex &$mime_content_id$&
34992 This variable contains the normalized content of the &'Content-ID:'& header.
34993 This is a unique ID that can be used to reference a part from another part.
34995 .vitem &$mime_content_size$&
34996 .vindex &$mime_content_size$&
34997 This variable is set only after the &%decode%& modifier (see above) has been
34998 successfully run. It contains the size of the decoded part in kilobytes. The
34999 size is always rounded up to full kilobytes, so only a completely empty part
35000 has a &$mime_content_size$& of zero.
35002 .vitem &$mime_content_transfer_encoding$&
35003 .vindex &$mime_content_transfer_encoding$&
35004 This variable contains the normalized content of the
35005 &'Content-transfer-encoding:'& header. This is a symbolic name for an encoding
35006 type. Typical values are &"base64"& and &"quoted-printable"&.
35008 .vitem &$mime_content_type$&
35009 .vindex &$mime_content_type$&
35010 If the MIME part has a &'Content-Type:'& header, this variable contains its
35011 value, lowercased, and without any options (like &"name"& or &"charset"&). Here
35012 are some examples of popular MIME types, as they may appear in this variable:
35016 application/octet-stream
35020 If the MIME part has no &'Content-Type:'& header, this variable contains the
35023 .vitem &$mime_decoded_filename$&
35024 .vindex &$mime_decoded_filename$&
35025 This variable is set only after the &%decode%& modifier (see above) has been
35026 successfully run. It contains the full path and filename of the file
35027 containing the decoded data.
35032 .vitem &$mime_filename$&
35033 .vindex &$mime_filename$&
35034 This is perhaps the most important of the MIME variables. It contains a
35035 proposed filename for an attachment, if one was found in either the
35036 &'Content-Type:'& or &'Content-Disposition:'& headers. The filename will be
35039 decoded, but no additional sanity checks are done.
35041 found, this variable contains the empty string.
35043 .vitem &$mime_is_coverletter$&
35044 .vindex &$mime_is_coverletter$&
35045 This variable attempts to differentiate the &"cover letter"& of an e-mail from
35046 attached data. It can be used to clamp down on flashy or unnecessarily encoded
35047 content in the cover letter, while not restricting attachments at all.
35049 The variable contains 1 (true) for a MIME part believed to be part of the
35050 cover letter, and 0 (false) for an attachment. At present, the algorithm is as
35054 The outermost MIME part of a message is always a cover letter.
35057 If a multipart/alternative or multipart/related MIME part is a cover letter,
35058 so are all MIME subparts within that multipart.
35061 If any other multipart is a cover letter, the first subpart is a cover letter,
35062 and the rest are attachments.
35065 All parts contained within an attachment multipart are attachments.
35068 As an example, the following will ban &"HTML mail"& (including that sent with
35069 alternative plain text), while allowing HTML files to be attached. HTML
35070 coverletter mail attached to non-HTML coverletter mail will also be allowed:
35072 deny !condition = $mime_is_rfc822
35073 condition = $mime_is_coverletter
35074 condition = ${if eq{$mime_content_type}{text/html}{1}{0}}
35075 message = HTML mail is not accepted here
35078 .vitem &$mime_is_multipart$&
35079 .vindex &$mime_is_multipart$&
35080 This variable has the value 1 (true) when the current part has the main type
35081 &"multipart"&, for example, &"multipart/alternative"& or &"multipart/mixed"&.
35082 Since multipart entities only serve as containers for other parts, you may not
35083 want to carry out specific actions on them.
35085 .vitem &$mime_is_rfc822$&
35086 .vindex &$mime_is_rfc822$&
35087 This variable has the value 1 (true) if the current part is not a part of the
35088 checked message itself, but part of an attached message. Attached message
35089 decoding is fully recursive.
35091 .vitem &$mime_part_count$&
35092 .vindex &$mime_part_count$&
35093 This variable is a counter that is raised for each processed MIME part. It
35094 starts at zero for the very first part (which is usually a multipart). The
35095 counter is per-message, so it is reset when processing RFC822 attachments (see
35096 &$mime_is_rfc822$&). The counter stays set after &%acl_smtp_mime%& is
35097 complete, so you can use it in the DATA ACL to determine the number of MIME
35098 parts of a message. For non-MIME messages, this variable contains the value -1.
35103 .section "Scanning with regular expressions" "SECTscanregex"
35104 .cindex "content scanning" "with regular expressions"
35105 .cindex "regular expressions" "content scanning with"
35106 You can specify your own custom regular expression matches on the full body of
35107 the message, or on individual MIME parts.
35109 The &%regex%& condition takes one or more regular expressions as arguments and
35110 matches them against the full message (when called in the DATA ACL) or a raw
35111 MIME part (when called in the MIME ACL). The &%regex%& condition matches
35112 linewise, with a maximum line length of 32K characters. That means you cannot
35113 have multiline matches with the &%regex%& condition.
35115 The &%mime_regex%& condition can be called only in the MIME ACL. It matches up
35116 to 32K of decoded content (the whole content at once, not linewise). If the
35117 part has not been decoded with the &%decode%& modifier earlier in the ACL, it
35118 is decoded automatically when &%mime_regex%& is executed (using default path
35119 and filename values). If the decoded data is larger than 32K, only the first
35120 32K characters are checked.
35122 The regular expressions are passed as a colon-separated list. To include a
35123 literal colon, you must double it. Since the whole right-hand side string is
35124 expanded before being used, you must also escape dollar signs and backslashes
35125 with more backslashes, or use the &`\N`& facility to disable expansion.
35126 Here is a simple example that contains two regular expressions:
35128 deny regex = [Mm]ortgage : URGENT BUSINESS PROPOSAL
35129 message = contains blacklisted regex ($regex_match_string)
35131 The conditions returns true if any one of the regular expressions matches. The
35132 &$regex_match_string$& expansion variable is then set up and contains the
35133 matching regular expression.
35134 The expansion variables &$regex1$& &$regex2$& etc
35135 are set to any substrings captured by the regular expression.
35137 &*Warning*&: With large messages, these conditions can be fairly
35145 . ////////////////////////////////////////////////////////////////////////////
35146 . ////////////////////////////////////////////////////////////////////////////
35148 .chapter "Adding a local scan function to Exim" "CHAPlocalscan" &&&
35149 "Local scan function"
35150 .scindex IIDlosca "&[local_scan()]& function" "description of"
35151 .cindex "customizing" "input scan using C function"
35152 .cindex "policy control" "by local scan function"
35153 In these days of email worms, viruses, and ever-increasing spam, some sites
35154 want to apply a lot of checking to messages before accepting them.
35156 The content scanning extension (chapter &<<CHAPexiscan>>&) has facilities for
35157 passing messages to external virus and spam scanning software. You can also do
35158 a certain amount in Exim itself through string expansions and the &%condition%&
35159 condition in the ACL that runs after the SMTP DATA command or the ACL for
35160 non-SMTP messages (see chapter &<<CHAPACL>>&), but this has its limitations.
35162 To allow for further customization to a site's own requirements, there is the
35163 possibility of linking Exim with a private message scanning function, written
35164 in C. If you want to run code that is written in something other than C, you
35165 can of course use a little C stub to call it.
35167 The local scan function is run once for every incoming message, at the point
35168 when Exim is just about to accept the message.
35169 It can therefore be used to control non-SMTP messages from local processes as
35170 well as messages arriving via SMTP.
35172 Exim applies a timeout to calls of the local scan function, and there is an
35173 option called &%local_scan_timeout%& for setting it. The default is 5 minutes.
35174 Zero means &"no timeout"&.
35175 Exim also sets up signal handlers for SIGSEGV, SIGILL, SIGFPE, and SIGBUS
35176 before calling the local scan function, so that the most common types of crash
35177 are caught. If the timeout is exceeded or one of those signals is caught, the
35178 incoming message is rejected with a temporary error if it is an SMTP message.
35179 For a non-SMTP message, the message is dropped and Exim ends with a non-zero
35180 code. The incident is logged on the main and reject logs.
35184 .section "Building Exim to use a local scan function" "SECID207"
35185 .cindex "&[local_scan()]& function" "building Exim to use"
35186 To make use of the local scan function feature, you must tell Exim where your
35187 function is before building Exim, by setting
35188 both HAVE_LOCAL_SCAN and
35189 LOCAL_SCAN_SOURCE in your
35190 &_Local/Makefile_&. A recommended place to put it is in the &_Local_&
35191 directory, so you might set
35193 HAVE_LOCAL_SCAN=yes
35194 LOCAL_SCAN_SOURCE=Local/local_scan.c
35196 for example. The function must be called &[local_scan()]&;
35197 the source file(s) for it should first #define LOCAL_SCAN
35198 and then #include "local_scan.h".
35200 Exim after it has received a message, when the success return code is about to
35201 be sent. This is after all the ACLs have been run. The return code from your
35202 function controls whether the message is actually accepted or not. There is a
35203 commented template function (that just accepts the message) in the file
35204 _src/local_scan.c_.
35206 If you want to make use of Exim's runtime configuration file to set options
35207 for your &[local_scan()]& function, you must also set
35209 LOCAL_SCAN_HAS_OPTIONS=yes
35211 in &_Local/Makefile_& (see section &<<SECTconoptloc>>& below).
35216 .section "API for local_scan()" "SECTapiforloc"
35217 .cindex "&[local_scan()]& function" "API description"
35218 .cindex &%dlfunc%& "API description"
35219 You must include this line near the start of your code:
35222 #include "local_scan.h"
35224 This header file defines a number of variables and other values, and the
35225 prototype for the function itself. Exim is coded to use unsigned char values
35226 almost exclusively, and one of the things this header defines is a shorthand
35227 for &`unsigned char`& called &`uschar`&.
35228 It also makes available the following macro definitions, to simplify casting character
35229 strings and pointers to character strings:
35231 #define CS (char *)
35232 #define CCS (const char *)
35233 #define CSS (char **)
35234 #define US (unsigned char *)
35235 #define CUS (const unsigned char *)
35236 #define USS (unsigned char **)
35238 The function prototype for &[local_scan()]& is:
35240 extern int local_scan(int fd, uschar **return_text);
35242 The arguments are as follows:
35245 &%fd%& is a file descriptor for the file that contains the body of the message
35246 (the -D file). The file is open for reading and writing, but updating it is not
35247 recommended. &*Warning*&: You must &'not'& close this file descriptor.
35249 The descriptor is positioned at character 19 of the file, which is the first
35250 character of the body itself, because the first 19 characters are the message
35251 id followed by &`-D`& and a newline. If you rewind the file, you should use the
35252 macro SPOOL_DATA_START_OFFSET to reset to the start of the data, just in
35253 case this changes in some future version.
35255 &%return_text%& is an address which you can use to return a pointer to a text
35256 string at the end of the function. The value it points to on entry is NULL.
35259 The function must return an &%int%& value which is one of the following macros:
35262 .vitem &`LOCAL_SCAN_ACCEPT`&
35263 .vindex "&$local_scan_data$&"
35264 The message is accepted. If you pass back a string of text, it is saved with
35265 the message, and made available in the variable &$local_scan_data$&. No
35266 newlines are permitted (if there are any, they are turned into spaces) and the
35267 maximum length of text is 1000 characters.
35269 .vitem &`LOCAL_SCAN_ACCEPT_FREEZE`&
35270 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
35271 queued without immediate delivery, and is frozen.
35273 .vitem &`LOCAL_SCAN_ACCEPT_QUEUE`&
35274 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
35275 queued without immediate delivery.
35277 .vitem &`LOCAL_SCAN_REJECT`&
35278 The message is rejected; the returned text is used as an error message which is
35279 passed back to the sender and which is also logged. Newlines are permitted &--
35280 they cause a multiline response for SMTP rejections, but are converted to
35281 &`\n`& in log lines. If no message is given, &"Administrative prohibition"& is
35284 .vitem &`LOCAL_SCAN_TEMPREJECT`&
35285 The message is temporarily rejected; the returned text is used as an error
35286 message as for LOCAL_SCAN_REJECT. If no message is given, &"Temporary local
35289 .vitem &`LOCAL_SCAN_REJECT_NOLOGHDR`&
35290 This behaves as LOCAL_SCAN_REJECT, except that the header of the rejected
35291 message is not written to the reject log. It has the effect of unsetting the
35292 &%rejected_header%& log selector for just this rejection. If
35293 &%rejected_header%& is already unset (see the discussion of the
35294 &%log_selection%& option in section &<<SECTlogselector>>&), this code is the
35295 same as LOCAL_SCAN_REJECT.
35297 .vitem &`LOCAL_SCAN_TEMPREJECT_NOLOGHDR`&
35298 This code is a variation of LOCAL_SCAN_TEMPREJECT in the same way that
35299 LOCAL_SCAN_REJECT_NOLOGHDR is a variation of LOCAL_SCAN_REJECT.
35302 If the message is not being received by interactive SMTP, rejections are
35303 reported by writing to &%stderr%& or by sending an email, as configured by the
35304 &%-oe%& command line options.
35308 .section "Configuration options for local_scan()" "SECTconoptloc"
35309 .cindex "&[local_scan()]& function" "configuration options"
35310 It is possible to have option settings in the main configuration file
35311 that set values in static variables in the &[local_scan()]& module. If you
35312 want to do this, you must have the line
35314 LOCAL_SCAN_HAS_OPTIONS=yes
35316 in your &_Local/Makefile_& when you build Exim. (This line is in
35317 &_OS/Makefile-Default_&, commented out). Then, in the &[local_scan()]& source
35318 file, you must define static variables to hold the option values, and a table
35321 The table must be a vector called &%local_scan_options%&, of type
35322 &`optionlist`&. Each entry is a triplet, consisting of a name, an option type,
35323 and a pointer to the variable that holds the value. The entries must appear in
35324 alphabetical order. Following &%local_scan_options%& you must also define a
35325 variable called &%local_scan_options_count%& that contains the number of
35326 entries in the table. Here is a short example, showing two kinds of option:
35328 static int my_integer_option = 42;
35329 static uschar *my_string_option = US"a default string";
35331 optionlist local_scan_options[] = {
35332 { "my_integer", opt_int, &my_integer_option },
35333 { "my_string", opt_stringptr, &my_string_option }
35336 int local_scan_options_count =
35337 sizeof(local_scan_options)/sizeof(optionlist);
35339 The values of the variables can now be changed from Exim's runtime
35340 configuration file by including a local scan section as in this example:
35344 my_string = some string of text...
35346 The available types of option data are as follows:
35349 .vitem &*opt_bool*&
35350 This specifies a boolean (true/false) option. The address should point to a
35351 variable of type &`BOOL`&, which will be set to TRUE or FALSE, which are macros
35352 that are defined as &"1"& and &"0"&, respectively. If you want to detect
35353 whether such a variable has been set at all, you can initialize it to
35354 TRUE_UNSET. (BOOL variables are integers underneath, so can hold more than two
35357 .vitem &*opt_fixed*&
35358 This specifies a fixed point number, such as is used for load averages.
35359 The address should point to a variable of type &`int`&. The value is stored
35360 multiplied by 1000, so, for example, 1.4142 is truncated and stored as 1414.
35363 This specifies an integer; the address should point to a variable of type
35364 &`int`&. The value may be specified in any of the integer formats accepted by
35367 .vitem &*opt_mkint*&
35368 This is the same as &%opt_int%&, except that when such a value is output in a
35369 &%-bP%& listing, if it is an exact number of kilobytes or megabytes, it is
35370 printed with the suffix K or M.
35372 .vitem &*opt_octint*&
35373 This also specifies an integer, but the value is always interpreted as an
35374 octal integer, whether or not it starts with the digit zero, and it is
35375 always output in octal.
35377 .vitem &*opt_stringptr*&
35378 This specifies a string value; the address must be a pointer to a
35379 variable that points to a string (for example, of type &`uschar *`&).
35381 .vitem &*opt_time*&
35382 This specifies a time interval value. The address must point to a variable of
35383 type &`int`&. The value that is placed there is a number of seconds.
35386 If the &%-bP%& command line option is followed by &`local_scan`&, Exim prints
35387 out the values of all the &[local_scan()]& options.
35391 .section "Available Exim variables" "SECID208"
35392 .cindex "&[local_scan()]& function" "available Exim variables"
35393 The header &_local_scan.h_& gives you access to a number of C variables. These
35394 are the only ones that are guaranteed to be maintained from release to release.
35395 Note, however, that you can obtain the value of any Exim expansion variable,
35396 including &$recipients$&, by calling &'expand_string()'&. The exported
35397 C variables are as follows:
35400 .vitem &*int&~body_linecount*&
35401 This variable contains the number of lines in the message's body.
35402 It is not valid if the &%spool_wireformat%& option is used.
35404 .vitem &*int&~body_zerocount*&
35405 This variable contains the number of binary zero bytes in the message's body.
35406 It is not valid if the &%spool_wireformat%& option is used.
35408 .vitem &*unsigned&~int&~debug_selector*&
35409 This variable is set to zero when no debugging is taking place. Otherwise, it
35410 is a bitmap of debugging selectors. Two bits are identified for use in
35411 &[local_scan()]&; they are defined as macros:
35414 The &`D_v`& bit is set when &%-v%& was present on the command line. This is a
35415 testing option that is not privileged &-- any caller may set it. All the
35416 other selector bits can be set only by admin users.
35419 The &`D_local_scan`& bit is provided for use by &[local_scan()]&; it is set
35420 by the &`+local_scan`& debug selector. It is not included in the default set
35424 Thus, to write to the debugging output only when &`+local_scan`& has been
35425 selected, you should use code like this:
35427 if ((debug_selector & D_local_scan) != 0)
35428 debug_printf("xxx", ...);
35430 .vitem &*uschar&~*expand_string_message*&
35431 After a failing call to &'expand_string()'& (returned value NULL), the
35432 variable &%expand_string_message%& contains the error message, zero-terminated.
35434 .vitem &*header_line&~*header_list*&
35435 A pointer to a chain of header lines. The &%header_line%& structure is
35438 .vitem &*header_line&~*header_last*&
35439 A pointer to the last of the header lines.
35442 .vitem &*const&~uschar&~*headers_charset*&
35443 The value of the &%headers_charset%& configuration option.
35446 .vitem &*BOOL&~host_checking*&
35447 This variable is TRUE during a host checking session that is initiated by the
35448 &%-bh%& command line option.
35450 .vitem &*uschar&~*interface_address*&
35451 The IP address of the interface that received the message, as a string. This
35452 is NULL for locally submitted messages.
35454 .vitem &*int&~interface_port*&
35455 The port on which this message was received. When testing with the &%-bh%&
35456 command line option, the value of this variable is -1 unless a port has been
35457 specified via the &%-oMi%& option.
35459 .vitem &*uschar&~*message_id*&
35460 This variable contains Exim's message id for the incoming message (the value of
35461 &$message_exim_id$&) as a zero-terminated string.
35463 .vitem &*uschar&~*received_protocol*&
35464 The name of the protocol by which the message was received.
35466 .vitem &*int&~recipients_count*&
35467 The number of accepted recipients.
35469 .vitem &*recipient_item&~*recipients_list*&
35470 .cindex "recipient" "adding in local scan"
35471 .cindex "recipient" "removing in local scan"
35472 The list of accepted recipients, held in a vector of length
35473 &%recipients_count%&. The &%recipient_item%& structure is discussed below. You
35474 can add additional recipients by calling &'receive_add_recipient()'& (see
35475 below). You can delete recipients by removing them from the vector and
35476 adjusting the value in &%recipients_count%&. In particular, by setting
35477 &%recipients_count%& to zero you remove all recipients. If you then return the
35478 value &`LOCAL_SCAN_ACCEPT`&, the message is accepted, but immediately
35479 blackholed. To replace the recipients, you can set &%recipients_count%& to zero
35480 and then call &'receive_add_recipient()'& as often as needed.
35482 .vitem &*uschar&~*sender_address*&
35483 The envelope sender address. For bounce messages this is the empty string.
35485 .vitem &*uschar&~*sender_host_address*&
35486 The IP address of the sending host, as a string. This is NULL for
35487 locally-submitted messages.
35489 .vitem &*uschar&~*sender_host_authenticated*&
35490 The name of the authentication mechanism that was used, or NULL if the message
35491 was not received over an authenticated SMTP connection.
35493 .vitem &*uschar&~*sender_host_name*&
35494 The name of the sending host, if known.
35496 .vitem &*int&~sender_host_port*&
35497 The port on the sending host.
35499 .vitem &*BOOL&~smtp_input*&
35500 This variable is TRUE for all SMTP input, including BSMTP.
35502 .vitem &*BOOL&~smtp_batched_input*&
35503 This variable is TRUE for BSMTP input.
35505 .vitem &*int&~store_pool*&
35506 The contents of this variable control which pool of memory is used for new
35507 requests. See section &<<SECTmemhanloc>>& for details.
35511 .section "Structure of header lines" "SECID209"
35512 The &%header_line%& structure contains the members listed below.
35513 You can add additional header lines by calling the &'header_add()'& function
35514 (see below). You can cause header lines to be ignored (deleted) by setting
35519 .vitem &*struct&~header_line&~*next*&
35520 A pointer to the next header line, or NULL for the last line.
35522 .vitem &*int&~type*&
35523 A code identifying certain headers that Exim recognizes. The codes are printing
35524 characters, and are documented in chapter &<<CHAPspool>>& of this manual.
35525 Notice in particular that any header line whose type is * is not transmitted
35526 with the message. This flagging is used for header lines that have been
35527 rewritten, or are to be removed (for example, &'Envelope-sender:'& header
35528 lines.) Effectively, * means &"deleted"&.
35530 .vitem &*int&~slen*&
35531 The number of characters in the header line, including the terminating and any
35534 .vitem &*uschar&~*text*&
35535 A pointer to the text of the header. It always ends with a newline, followed by
35536 a zero byte. Internal newlines are preserved.
35541 .section "Structure of recipient items" "SECID210"
35542 The &%recipient_item%& structure contains these members:
35545 .vitem &*uschar&~*address*&
35546 This is a pointer to the recipient address as it was received.
35548 .vitem &*int&~pno*&
35549 This is used in later Exim processing when top level addresses are created by
35550 the &%one_time%& option. It is not relevant at the time &[local_scan()]& is run
35551 and must always contain -1 at this stage.
35553 .vitem &*uschar&~*errors_to*&
35554 If this value is not NULL, bounce messages caused by failing to deliver to the
35555 recipient are sent to the address it contains. In other words, it overrides the
35556 envelope sender for this one recipient. (Compare the &%errors_to%& generic
35557 router option.) If a &[local_scan()]& function sets an &%errors_to%& field to
35558 an unqualified address, Exim qualifies it using the domain from
35559 &%qualify_recipient%&. When &[local_scan()]& is called, the &%errors_to%& field
35560 is NULL for all recipients.
35565 .section "Available Exim functions" "SECID211"
35566 .cindex "&[local_scan()]& function" "available Exim functions"
35567 The header &_local_scan.h_& gives you access to a number of Exim functions.
35568 These are the only ones that are guaranteed to be maintained from release to
35572 .vitem "&*pid_t&~child_open(uschar&~**argv,&~uschar&~**envp,&~int&~newumask,&&&
35573 &~int&~*infdptr,&~int&~*outfdptr, &~&~BOOL&~make_leader)*&"
35575 This function creates a child process that runs the command specified by
35576 &%argv%&. The environment for the process is specified by &%envp%&, which can
35577 be NULL if no environment variables are to be passed. A new umask is supplied
35578 for the process in &%newumask%&.
35580 Pipes to the standard input and output of the new process are set up
35581 and returned to the caller via the &%infdptr%& and &%outfdptr%& arguments. The
35582 standard error is cloned to the standard output. If there are any file
35583 descriptors &"in the way"& in the new process, they are closed. If the final
35584 argument is TRUE, the new process is made into a process group leader.
35586 The function returns the pid of the new process, or -1 if things go wrong.
35588 .vitem &*int&~child_close(pid_t&~pid,&~int&~timeout)*&
35589 This function waits for a child process to terminate, or for a timeout (in
35590 seconds) to expire. A timeout value of zero means wait as long as it takes. The
35591 return value is as follows:
35596 The process terminated by a normal exit and the value is the process
35602 The process was terminated by a signal and the value is the negation of the
35608 The process timed out.
35612 The was some other error in wait(); &%errno%& is still set.
35615 .vitem &*pid_t&~child_open_exim(int&~*fd)*&
35616 This function provide you with a means of submitting a new message to
35617 Exim. (Of course, you can also call &_/usr/sbin/sendmail_& yourself if you
35618 want, but this packages it all up for you.) The function creates a pipe,
35619 forks a subprocess that is running
35621 exim -t -oem -oi -f <>
35623 and returns to you (via the &`int *`& argument) a file descriptor for the pipe
35624 that is connected to the standard input. The yield of the function is the PID
35625 of the subprocess. You can then write a message to the file descriptor, with
35626 recipients in &'To:'&, &'Cc:'&, and/or &'Bcc:'& header lines.
35628 When you have finished, call &'child_close()'& to wait for the process to
35629 finish and to collect its ending status. A timeout value of zero is usually
35630 fine in this circumstance. Unless you have made a mistake with the recipient
35631 addresses, you should get a return code of zero.
35634 .vitem &*pid_t&~child_open_exim2(int&~*fd,&~uschar&~*sender,&~uschar&~&&&
35635 *sender_authentication)*&
35636 This function is a more sophisticated version of &'child_open()'&. The command
35639 &`exim -t -oem -oi -f `&&'sender'&&` -oMas `&&'sender_authentication'&
35641 The third argument may be NULL, in which case the &%-oMas%& option is omitted.
35644 .vitem &*void&~debug_printf(char&~*,&~...)*&
35645 This is Exim's debugging function, with arguments as for &'(printf()'&. The
35646 output is written to the standard error stream. If no debugging is selected,
35647 calls to &'debug_printf()'& have no effect. Normally, you should make calls
35648 conditional on the &`local_scan`& debug selector by coding like this:
35650 if ((debug_selector & D_local_scan) != 0)
35651 debug_printf("xxx", ...);
35654 .vitem &*uschar&~*expand_string(uschar&~*string)*&
35655 This is an interface to Exim's string expansion code. The return value is the
35656 expanded string, or NULL if there was an expansion failure.
35657 The C variable &%expand_string_message%& contains an error message after an
35658 expansion failure. If expansion does not change the string, the return value is
35659 the pointer to the input string. Otherwise, the return value points to a new
35660 block of memory that was obtained by a call to &'store_get()'&. See section
35661 &<<SECTmemhanloc>>& below for a discussion of memory handling.
35663 .vitem &*void&~header_add(int&~type,&~char&~*format,&~...)*&
35664 This function allows you to an add additional header line at the end of the
35665 existing ones. The first argument is the type, and should normally be a space
35666 character. The second argument is a format string and any number of
35667 substitution arguments as for &[sprintf()]&. You may include internal newlines
35668 if you want, and you must ensure that the string ends with a newline.
35670 .vitem "&*void&~header_add_at_position(BOOL&~after,&~uschar&~*name,&~&&&
35671 BOOL&~topnot,&~int&~type,&~char&~*format, &~&~...)*&"
35672 This function adds a new header line at a specified point in the header
35673 chain. The header itself is specified as for &'header_add()'&.
35675 If &%name%& is NULL, the new header is added at the end of the chain if
35676 &%after%& is true, or at the start if &%after%& is false. If &%name%& is not
35677 NULL, the header lines are searched for the first non-deleted header that
35678 matches the name. If one is found, the new header is added before it if
35679 &%after%& is false. If &%after%& is true, the new header is added after the
35680 found header and any adjacent subsequent ones with the same name (even if
35681 marked &"deleted"&). If no matching non-deleted header is found, the &%topnot%&
35682 option controls where the header is added. If it is true, addition is at the
35683 top; otherwise at the bottom. Thus, to add a header after all the &'Received:'&
35684 headers, or at the top if there are no &'Received:'& headers, you could use
35686 header_add_at_position(TRUE, US"Received", TRUE,
35687 ' ', "X-xxx: ...");
35689 Normally, there is always at least one non-deleted &'Received:'& header, but
35690 there may not be if &%received_header_text%& expands to an empty string.
35693 .vitem &*void&~header_remove(int&~occurrence,&~uschar&~*name)*&
35694 This function removes header lines. If &%occurrence%& is zero or negative, all
35695 occurrences of the header are removed. If occurrence is greater than zero, that
35696 particular instance of the header is removed. If no header(s) can be found that
35697 match the specification, the function does nothing.
35700 .vitem "&*BOOL&~header_testname(header_line&~*hdr,&~uschar&~*name,&~&&&
35701 int&~length,&~BOOL&~notdel)*&"
35702 This function tests whether the given header has the given name. It is not just
35703 a string comparison, because white space is permitted between the name and the
35704 colon. If the &%notdel%& argument is true, a false return is forced for all
35705 &"deleted"& headers; otherwise they are not treated specially. For example:
35707 if (header_testname(h, US"X-Spam", 6, TRUE)) ...
35709 .vitem &*uschar&~*lss_b64encode(uschar&~*cleartext,&~int&~length)*&
35710 .cindex "base64 encoding" "functions for &[local_scan()]& use"
35711 This function base64-encodes a string, which is passed by address and length.
35712 The text may contain bytes of any value, including zero. The result is passed
35713 back in dynamic memory that is obtained by calling &'store_get()'&. It is
35716 .vitem &*int&~lss_b64decode(uschar&~*codetext,&~uschar&~**cleartext)*&
35717 This function decodes a base64-encoded string. Its arguments are a
35718 zero-terminated base64-encoded string and the address of a variable that is set
35719 to point to the result, which is in dynamic memory. The length of the decoded
35720 string is the yield of the function. If the input is invalid base64 data, the
35721 yield is -1. A zero byte is added to the end of the output string to make it
35722 easy to interpret as a C string (assuming it contains no zeros of its own). The
35723 added zero byte is not included in the returned count.
35725 .vitem &*int&~lss_match_domain(uschar&~*domain,&~uschar&~*list)*&
35726 This function checks for a match in a domain list. Domains are always
35727 matched caselessly. The return value is one of the following:
35729 &`OK `& match succeeded
35730 &`FAIL `& match failed
35731 &`DEFER `& match deferred
35733 DEFER is usually caused by some kind of lookup defer, such as the
35734 inability to contact a database.
35736 .vitem "&*int&~lss_match_local_part(uschar&~*localpart,&~uschar&~*list,&~&&&
35738 This function checks for a match in a local part list. The third argument
35739 controls case-sensitivity. The return values are as for
35740 &'lss_match_domain()'&.
35742 .vitem "&*int&~lss_match_address(uschar&~*address,&~uschar&~*list,&~&&&
35744 This function checks for a match in an address list. The third argument
35745 controls the case-sensitivity of the local part match. The domain is always
35746 matched caselessly. The return values are as for &'lss_match_domain()'&.
35748 .vitem "&*int&~lss_match_host(uschar&~*host_name,&~uschar&~*host_address,&~&&&
35750 This function checks for a match in a host list. The most common usage is
35753 lss_match_host(sender_host_name, sender_host_address, ...)
35755 .vindex "&$sender_host_address$&"
35756 An empty address field matches an empty item in the host list. If the host name
35757 is NULL, the name corresponding to &$sender_host_address$& is automatically
35758 looked up if a host name is required to match an item in the list. The return
35759 values are as for &'lss_match_domain()'&, but in addition, &'lss_match_host()'&
35760 returns ERROR in the case when it had to look up a host name, but the lookup
35763 .vitem "&*void&~log_write(unsigned&~int&~selector,&~int&~which,&~char&~&&&
35765 This function writes to Exim's log files. The first argument should be zero (it
35766 is concerned with &%log_selector%&). The second argument can be &`LOG_MAIN`& or
35767 &`LOG_REJECT`& or &`LOG_PANIC`& or the inclusive &"or"& of any combination of
35768 them. It specifies to which log or logs the message is written. The remaining
35769 arguments are a format and relevant insertion arguments. The string should not
35770 contain any newlines, not even at the end.
35773 .vitem &*void&~receive_add_recipient(uschar&~*address,&~int&~pno)*&
35774 This function adds an additional recipient to the message. The first argument
35775 is the recipient address. If it is unqualified (has no domain), it is qualified
35776 with the &%qualify_recipient%& domain. The second argument must always be -1.
35778 This function does not allow you to specify a private &%errors_to%& address (as
35779 described with the structure of &%recipient_item%& above), because it pre-dates
35780 the addition of that field to the structure. However, it is easy to add such a
35781 value afterwards. For example:
35783 receive_add_recipient(US"monitor@mydom.example", -1);
35784 recipients_list[recipients_count-1].errors_to =
35785 US"postmaster@mydom.example";
35788 .vitem &*BOOL&~receive_remove_recipient(uschar&~*recipient)*&
35789 This is a convenience function to remove a named recipient from the list of
35790 recipients. It returns true if a recipient was removed, and false if no
35791 matching recipient could be found. The argument must be a complete email
35798 .vitem "&*uschar&~rfc2047_decode(uschar&~*string,&~BOOL&~lencheck,&&&
35799 &~uschar&~*target,&~int&~zeroval,&~int&~*lenptr, &~&~uschar&~**error)*&"
35800 This function decodes strings that are encoded according to RFC 2047. Typically
35801 these are the contents of header lines. First, each &"encoded word"& is decoded
35802 from the Q or B encoding into a byte-string. Then, if provided with the name of
35803 a charset encoding, and if the &[iconv()]& function is available, an attempt is
35804 made to translate the result to the named character set. If this fails, the
35805 binary string is returned with an error message.
35807 The first argument is the string to be decoded. If &%lencheck%& is TRUE, the
35808 maximum MIME word length is enforced. The third argument is the target
35809 encoding, or NULL if no translation is wanted.
35811 .cindex "binary zero" "in RFC 2047 decoding"
35812 .cindex "RFC 2047" "binary zero in"
35813 If a binary zero is encountered in the decoded string, it is replaced by the
35814 contents of the &%zeroval%& argument. For use with Exim headers, the value must
35815 not be 0 because header lines are handled as zero-terminated strings.
35817 The function returns the result of processing the string, zero-terminated; if
35818 &%lenptr%& is not NULL, the length of the result is set in the variable to
35819 which it points. When &%zeroval%& is 0, &%lenptr%& should not be NULL.
35821 If an error is encountered, the function returns NULL and uses the &%error%&
35822 argument to return an error message. The variable pointed to by &%error%& is
35823 set to NULL if there is no error; it may be set non-NULL even when the function
35824 returns a non-NULL value if decoding was successful, but there was a problem
35828 .vitem &*int&~smtp_fflush(void)*&
35829 This function is used in conjunction with &'smtp_printf()'&, as described
35832 .vitem &*void&~smtp_printf(char&~*,BOOL,&~...)*&
35833 The arguments of this function are almost like &[printf()]&; it writes to the SMTP
35834 output stream. You should use this function only when there is an SMTP output
35835 stream, that is, when the incoming message is being received via interactive
35836 SMTP. This is the case when &%smtp_input%& is TRUE and &%smtp_batched_input%&
35837 is FALSE. If you want to test for an incoming message from another host (as
35838 opposed to a local process that used the &%-bs%& command line option), you can
35839 test the value of &%sender_host_address%&, which is non-NULL when a remote host
35842 If an SMTP TLS connection is established, &'smtp_printf()'& uses the TLS
35843 output function, so it can be used for all forms of SMTP connection.
35845 The second argument is used to request that the data be buffered
35846 (when TRUE) or flushed (along with any previously buffered, when FALSE).
35847 This is advisory only, but likely to save on system-calls and packets
35848 sent when a sequence of calls to the function are made.
35850 The argument was added in Exim version 4.90 - changing the API/ABI.
35851 Nobody noticed until 4.93 was imminent, at which point the
35852 ABI version number was incremented.
35854 Strings that are written by &'smtp_printf()'& from within &[local_scan()]&
35855 must start with an appropriate response code: 550 if you are going to return
35856 LOCAL_SCAN_REJECT, 451 if you are going to return
35857 LOCAL_SCAN_TEMPREJECT, and 250 otherwise. Because you are writing the
35858 initial lines of a multi-line response, the code must be followed by a hyphen
35859 to indicate that the line is not the final response line. You must also ensure
35860 that the lines you write terminate with CRLF. For example:
35862 smtp_printf("550-this is some extra info\r\n");
35863 return LOCAL_SCAN_REJECT;
35865 Note that you can also create multi-line responses by including newlines in
35866 the data returned via the &%return_text%& argument. The added value of using
35867 &'smtp_printf()'& is that, for instance, you could introduce delays between
35868 multiple output lines.
35870 The &'smtp_printf()'& function does not return any error indication, because it
35872 guarantee a flush of
35873 pending output, and therefore does not test
35874 the state of the stream. (In the main code of Exim, flushing and error
35875 detection is done when Exim is ready for the next SMTP input command.) If
35876 you want to flush the output and check for an error (for example, the
35877 dropping of a TCP/IP connection), you can call &'smtp_fflush()'&, which has no
35878 arguments. It flushes the output stream, and returns a non-zero value if there
35881 .vitem &*void&~*store_get(int,BOOL)*&
35882 This function accesses Exim's internal store (memory) manager. It gets a new
35883 chunk of memory whose size is given by the first argument.
35884 The second argument should be given as TRUE if the memory will be used for
35885 data possibly coming from an attacker (eg. the message content),
35886 FALSE if it is locally-sourced.
35887 Exim bombs out if it ever
35888 runs out of memory. See the next section for a discussion of memory handling.
35890 .vitem &*void&~*store_get_perm(int,BOOL)*&
35891 This function is like &'store_get()'&, but it always gets memory from the
35892 permanent pool. See the next section for a discussion of memory handling.
35894 .vitem &*uschar&~*string_copy(uschar&~*string)*&
35897 .vitem &*uschar&~*string_copyn(uschar&~*string,&~int&~length)*&
35900 .vitem &*uschar&~*string_sprintf(char&~*format,&~...)*&
35901 These three functions create strings using Exim's dynamic memory facilities.
35902 The first makes a copy of an entire string. The second copies up to a maximum
35903 number of characters, indicated by the second argument. The third uses a format
35904 and insertion arguments to create a new string. In each case, the result is a
35905 pointer to a new string in the current memory pool. See the next section for
35911 .section "More about Exim's memory handling" "SECTmemhanloc"
35912 .cindex "&[local_scan()]& function" "memory handling"
35913 No function is provided for freeing memory, because that is never needed.
35914 The dynamic memory that Exim uses when receiving a message is automatically
35915 recycled if another message is received by the same process (this applies only
35916 to incoming SMTP connections &-- other input methods can supply only one
35917 message at a time). After receiving the last message, a reception process
35920 Because it is recycled, the normal dynamic memory cannot be used for holding
35921 data that must be preserved over a number of incoming messages on the same SMTP
35922 connection. However, Exim in fact uses two pools of dynamic memory; the second
35923 one is not recycled, and can be used for this purpose.
35925 If you want to allocate memory that remains available for subsequent messages
35926 in the same SMTP connection, you should set
35928 store_pool = POOL_PERM
35930 before calling the function that does the allocation. There is no need to
35931 restore the value if you do not need to; however, if you do want to revert to
35932 the normal pool, you can either restore the previous value of &%store_pool%& or
35933 set it explicitly to POOL_MAIN.
35935 The pool setting applies to all functions that get dynamic memory, including
35936 &'expand_string()'&, &'store_get()'&, and the &'string_xxx()'& functions.
35937 There is also a convenience function called &'store_get_perm()'& that gets a
35938 block of memory from the permanent pool while preserving the value of
35945 . ////////////////////////////////////////////////////////////////////////////
35946 . ////////////////////////////////////////////////////////////////////////////
35948 .chapter "System-wide message filtering" "CHAPsystemfilter"
35949 .scindex IIDsysfil1 "filter" "system filter"
35950 .scindex IIDsysfil2 "filtering all mail"
35951 .scindex IIDsysfil3 "system filter"
35952 The previous chapters (on ACLs and the local scan function) describe checks
35953 that can be applied to messages before they are accepted by a host. There is
35954 also a mechanism for checking messages once they have been received, but before
35955 they are delivered. This is called the &'system filter'&.
35957 The system filter operates in a similar manner to users' filter files, but it
35958 is run just once per message (however many recipients the message has).
35959 It should not normally be used as a substitute for routing, because &%deliver%&
35960 commands in a system router provide new envelope recipient addresses.
35961 The system filter must be an Exim filter. It cannot be a Sieve filter.
35963 The system filter is run at the start of a delivery attempt, before any routing
35964 is done. If a message fails to be completely delivered at the first attempt,
35965 the system filter is run again at the start of every retry.
35966 If you want your filter to do something only once per message, you can make use
35967 of the &%first_delivery%& condition in an &%if%& command in the filter to
35968 prevent it happening on retries.
35970 .vindex "&$domain$&"
35971 .vindex "&$local_part$&"
35972 &*Warning*&: Because the system filter runs just once, variables that are
35973 specific to individual recipient addresses, such as &$local_part$& and
35974 &$domain$&, are not set, and the &"personal"& condition is not meaningful. If
35975 you want to run a centrally-specified filter for each recipient address
35976 independently, you can do so by setting up a suitable &(redirect)& router, as
35977 described in section &<<SECTperaddfil>>& below.
35980 .section "Specifying a system filter" "SECID212"
35981 .cindex "uid (user id)" "system filter"
35982 .cindex "gid (group id)" "system filter"
35983 The name of the file that contains the system filter must be specified by
35984 setting &%system_filter%&. If you want the filter to run under a uid and gid
35985 other than root, you must also set &%system_filter_user%& and
35986 &%system_filter_group%& as appropriate. For example:
35988 system_filter = /etc/mail/exim.filter
35989 system_filter_user = exim
35991 If a system filter generates any deliveries directly to files or pipes (via the
35992 &%save%& or &%pipe%& commands), transports to handle these deliveries must be
35993 specified by setting &%system_filter_file_transport%& and
35994 &%system_filter_pipe_transport%&, respectively. Similarly,
35995 &%system_filter_reply_transport%& must be set to handle any messages generated
35996 by the &%reply%& command.
35999 .section "Testing a system filter" "SECID213"
36000 You can run simple tests of a system filter in the same way as for a user
36001 filter, but you should use &%-bF%& rather than &%-bf%&, so that features that
36002 are permitted only in system filters are recognized.
36004 If you want to test the combined effect of a system filter and a user filter,
36005 you can use both &%-bF%& and &%-bf%& on the same command line.
36009 .section "Contents of a system filter" "SECID214"
36010 The language used to specify system filters is the same as for users' filter
36011 files. It is described in the separate end-user document &'Exim's interface to
36012 mail filtering'&. However, there are some additional features that are
36013 available only in system filters; these are described in subsequent sections.
36014 If they are encountered in a user's filter file or when testing with &%-bf%&,
36017 .cindex "frozen messages" "manual thaw; testing in filter"
36018 There are two special conditions which, though available in users' filter
36019 files, are designed for use in system filters. The condition &%first_delivery%&
36020 is true only for the first attempt at delivering a message, and
36021 &%manually_thawed%& is true only if the message has been frozen, and
36022 subsequently thawed by an admin user. An explicit forced delivery counts as a
36023 manual thaw, but thawing as a result of the &%auto_thaw%& setting does not.
36025 &*Warning*&: If a system filter uses the &%first_delivery%& condition to
36026 specify an &"unseen"& (non-significant) delivery, and that delivery does not
36027 succeed, it will not be tried again.
36028 If you want Exim to retry an unseen delivery until it succeeds, you should
36029 arrange to set it up every time the filter runs.
36031 When a system filter finishes running, the values of the variables &$n0$& &--
36032 &$n9$& are copied into &$sn0$& &-- &$sn9$& and are thereby made available to
36033 users' filter files. Thus a system filter can, for example, set up &"scores"&
36034 to which users' filter files can refer.
36038 .section "Additional variable for system filters" "SECID215"
36039 .vindex "&$recipients$&"
36040 The expansion variable &$recipients$&, containing a list of all the recipients
36041 of the message (separated by commas and white space), is available in system
36042 filters. It is not available in users' filters for privacy reasons.
36046 .section "Defer, freeze, and fail commands for system filters" "SECID216"
36047 .cindex "freezing messages"
36048 .cindex "message" "freezing"
36049 .cindex "message" "forced failure"
36050 .cindex "&%fail%&" "in system filter"
36051 .cindex "&%freeze%& in system filter"
36052 .cindex "&%defer%& in system filter"
36053 There are three extra commands (&%defer%&, &%freeze%& and &%fail%&) which are
36054 always available in system filters, but are not normally enabled in users'
36055 filters. (See the &%allow_defer%&, &%allow_freeze%& and &%allow_fail%& options
36056 for the &(redirect)& router.) These commands can optionally be followed by the
36057 word &%text%& and a string containing an error message, for example:
36059 fail text "this message looks like spam to me"
36061 The keyword &%text%& is optional if the next character is a double quote.
36063 The &%defer%& command defers delivery of the original recipients of the
36064 message. The &%fail%& command causes all the original recipients to be failed,
36065 and a bounce message to be created. The &%freeze%& command suspends all
36066 delivery attempts for the original recipients. In all cases, any new deliveries
36067 that are specified by the filter are attempted as normal after the filter has
36070 The &%freeze%& command is ignored if the message has been manually unfrozen and
36071 not manually frozen since. This means that automatic freezing by a system
36072 filter can be used as a way of checking out suspicious messages. If a message
36073 is found to be all right, manually unfreezing it allows it to be delivered.
36075 .cindex "log" "&%fail%& command log line"
36076 .cindex "&%fail%&" "log line; reducing"
36077 The text given with a fail command is used as part of the bounce message as
36078 well as being written to the log. If the message is quite long, this can fill
36079 up a lot of log space when such failures are common. To reduce the size of the
36080 log message, Exim interprets the text in a special way if it starts with the
36081 two characters &`<<`& and contains &`>>`& later. The text between these two
36082 strings is written to the log, and the rest of the text is used in the bounce
36083 message. For example:
36085 fail "<<filter test 1>>Your message is rejected \
36086 because it contains attachments that we are \
36087 not prepared to receive."
36090 .cindex "loop" "caused by &%fail%&"
36091 Take great care with the &%fail%& command when basing the decision to fail on
36092 the contents of the message, because the bounce message will of course include
36093 the contents of the original message and will therefore trigger the &%fail%&
36094 command again (causing a mail loop) unless steps are taken to prevent this.
36095 Testing the &%error_message%& condition is one way to prevent this. You could
36098 if $message_body contains "this is spam" and not error_message
36099 then fail text "spam is not wanted here" endif
36101 though of course that might let through unwanted bounce messages. The
36102 alternative is clever checking of the body and/or headers to detect bounces
36103 generated by the filter.
36105 The interpretation of a system filter file ceases after a
36107 &%freeze%&, or &%fail%& command is obeyed. However, any deliveries that were
36108 set up earlier in the filter file are honoured, so you can use a sequence such
36114 to send a specified message when the system filter is freezing (or deferring or
36115 failing) a message. The normal deliveries for the message do not, of course,
36120 .section "Adding and removing headers in a system filter" "SECTaddremheasys"
36121 .cindex "header lines" "adding; in system filter"
36122 .cindex "header lines" "removing; in system filter"
36123 .cindex "filter" "header lines; adding/removing"
36124 Two filter commands that are available only in system filters are:
36126 headers add <string>
36127 headers remove <string>
36129 The argument for the &%headers add%& is a string that is expanded and then
36130 added to the end of the message's headers. It is the responsibility of the
36131 filter maintainer to make sure it conforms to RFC 2822 syntax. Leading white
36132 space is ignored, and if the string is otherwise empty, or if the expansion is
36133 forced to fail, the command has no effect.
36135 You can use &"\n"& within the string, followed by white space, to specify
36136 continued header lines. More than one header may be added in one command by
36137 including &"\n"& within the string without any following white space. For
36140 headers add "X-header-1: ....\n \
36141 continuation of X-header-1 ...\n\
36144 Note that the header line continuation white space after the first newline must
36145 be placed before the backslash that continues the input string, because white
36146 space after input continuations is ignored.
36148 The argument for &%headers remove%& is a colon-separated list of header names.
36149 This command applies only to those headers that are stored with the message;
36150 those that are added at delivery time (such as &'Envelope-To:'& and
36151 &'Return-Path:'&) cannot be removed by this means. If there is more than one
36152 header with the same name, they are all removed.
36154 The &%headers%& command in a system filter makes an immediate change to the set
36155 of header lines that was received with the message (with possible additions
36156 from ACL processing). Subsequent commands in the system filter operate on the
36157 modified set, which also forms the basis for subsequent message delivery.
36158 Unless further modified during routing or transporting, this set of headers is
36159 used for all recipients of the message.
36161 During routing and transporting, the variables that refer to the contents of
36162 header lines refer only to those lines that are in this set. Thus, header lines
36163 that are added by a system filter are visible to users' filter files and to all
36164 routers and transports. This contrasts with the manipulation of header lines by
36165 routers and transports, which is not immediate, but which instead is saved up
36166 until the message is actually being written (see section
36167 &<<SECTheadersaddrem>>&).
36169 If the message is not delivered at the first attempt, header lines that were
36170 added by the system filter are stored with the message, and so are still
36171 present at the next delivery attempt. Header lines that were removed are still
36172 present, but marked &"deleted"& so that they are not transported with the
36173 message. For this reason, it is usual to make the &%headers%& command
36174 conditional on &%first_delivery%& so that the set of header lines is not
36175 modified more than once.
36177 Because header modification in a system filter acts immediately, you have to
36178 use an indirect approach if you want to modify the contents of a header line.
36181 headers add "Old-Subject: $h_subject:"
36182 headers remove "Subject"
36183 headers add "Subject: new subject (was: $h_old-subject:)"
36184 headers remove "Old-Subject"
36189 .section "Setting an errors address in a system filter" "SECID217"
36190 .cindex "envelope from"
36191 .cindex "envelope sender"
36192 In a system filter, if a &%deliver%& command is followed by
36194 errors_to <some address>
36196 in order to change the envelope sender (and hence the error reporting) for that
36197 delivery, any address may be specified. (In a user filter, only the current
36198 user's address can be set.) For example, if some mail is being monitored, you
36201 unseen deliver monitor@spying.example errors_to root@local.example
36203 to take a copy which would not be sent back to the normal error reporting
36204 address if its delivery failed.
36208 .section "Per-address filtering" "SECTperaddfil"
36209 .vindex "&$domain_data$&"
36210 .vindex "&$local_part_data$&"
36211 In contrast to the system filter, which is run just once per message for each
36212 delivery attempt, it is also possible to set up a system-wide filtering
36213 operation that runs once for each recipient address. In this case, variables
36214 such as &$local_part_data$& and &$domain_data$& can be used,
36215 and indeed, the choice of filter file could be made dependent on them.
36216 This is an example of a router which implements such a filter:
36221 domains = +local_domains
36222 file = /central/filters/$local_part_data
36227 The filter is run in a separate process under its own uid. Therefore, either
36228 &%check_local_user%& must be set (as above), in which case the filter is run as
36229 the local user, or the &%user%& option must be used to specify which user to
36230 use. If both are set, &%user%& overrides.
36232 Care should be taken to ensure that none of the commands in the filter file
36233 specify a significant delivery if the message is to go on to be delivered to
36234 its intended recipient. The router will not then claim to have dealt with the
36235 address, so it will be passed on to subsequent routers to be delivered in the
36237 .ecindex IIDsysfil1
36238 .ecindex IIDsysfil2
36239 .ecindex IIDsysfil3
36246 . ////////////////////////////////////////////////////////////////////////////
36247 . ////////////////////////////////////////////////////////////////////////////
36249 .chapter "Message processing" "CHAPmsgproc"
36250 .scindex IIDmesproc "message" "general processing"
36251 Exim performs various transformations on the sender and recipient addresses of
36252 all messages that it handles, and also on the messages' header lines. Some of
36253 these are optional and configurable, while others always take place. All of
36254 this processing, except rewriting as a result of routing, and the addition or
36255 removal of header lines while delivering, happens when a message is received,
36256 before it is placed on Exim's queue.
36258 Some of the automatic processing takes place by default only for
36259 &"locally-originated"& messages. This adjective is used to describe messages
36260 that are not received over TCP/IP, but instead are passed to an Exim process on
36261 its standard input. This includes the interactive &"local SMTP"& case that is
36262 set up by the &%-bs%& command line option.
36264 &*Note*&: Messages received over TCP/IP on the loopback interface (127.0.0.1
36265 or ::1) are not considered to be locally-originated. Exim does not treat the
36266 loopback interface specially in any way.
36268 If you want the loopback interface to be treated specially, you must ensure
36269 that there are appropriate entries in your ACLs.
36274 .section "Submission mode for non-local messages" "SECTsubmodnon"
36275 .cindex "message" "submission"
36276 .cindex "submission mode"
36277 Processing that happens automatically for locally-originated messages (unless
36278 &%suppress_local_fixups%& is set) can also be requested for messages that are
36279 received over TCP/IP. The term &"submission mode"& is used to describe this
36280 state. Submission mode is set by the modifier
36282 control = submission
36284 in a MAIL, RCPT, or pre-data ACL for an incoming message (see sections
36285 &<<SECTACLmodi>>& and &<<SECTcontrols>>&). This makes Exim treat the message as
36286 a local submission, and is normally used when the source of the message is
36287 known to be an MUA running on a client host (as opposed to an MTA). For
36288 example, to set submission mode for messages originating on the IPv4 loopback
36289 interface, you could include the following in the MAIL ACL:
36291 warn hosts = 127.0.0.1
36292 control = submission
36294 .cindex "&%sender_retain%& submission option"
36295 There are some options that can be used when setting submission mode. A slash
36296 is used to separate options. For example:
36298 control = submission/sender_retain
36300 Specifying &%sender_retain%& has the effect of setting &%local_sender_retain%&
36301 true and &%local_from_check%& false for the current incoming message. The first
36302 of these allows an existing &'Sender:'& header in the message to remain, and
36303 the second suppresses the check to ensure that &'From:'& matches the
36304 authenticated sender. With this setting, Exim still fixes up messages by adding
36305 &'Date:'& and &'Message-ID:'& header lines if they are missing, but makes no
36306 attempt to check sender authenticity in header lines.
36308 When &%sender_retain%& is not set, a submission mode setting may specify a
36309 domain to be used when generating a &'From:'& or &'Sender:'& header line. For
36312 control = submission/domain=some.domain
36314 The domain may be empty. How this value is used is described in sections
36315 &<<SECTthefrohea>>& and &<<SECTthesenhea>>&. There is also a &%name%& option
36316 that allows you to specify the user's full name for inclusion in a created
36317 &'Sender:'& or &'From:'& header line. For example:
36319 accept authenticated = *
36320 control = submission/domain=wonderland.example/\
36321 name=${lookup {$authenticated_id} \
36322 lsearch {/etc/exim/namelist}}
36324 Because the name may contain any characters, including slashes, the &%name%&
36325 option must be given last. The remainder of the string is used as the name. For
36326 the example above, if &_/etc/exim/namelist_& contains:
36328 bigegg: Humpty Dumpty
36330 then when the sender has authenticated as &'bigegg'&, the generated &'Sender:'&
36333 Sender: Humpty Dumpty <bigegg@wonderland.example>
36335 .cindex "return path" "in submission mode"
36336 By default, submission mode forces the return path to the same address as is
36337 used to create the &'Sender:'& header. However, if &%sender_retain%& is
36338 specified, the return path is also left unchanged.
36340 &*Note*&: The changes caused by submission mode take effect after the predata
36341 ACL. This means that any sender checks performed before the fix-ups use the
36342 untrusted sender address specified by the user, not the trusted sender address
36343 specified by submission mode. Although this might be slightly unexpected, it
36344 does mean that you can configure ACL checks to spot that a user is trying to
36345 spoof another's address.
36347 .section "Line endings" "SECTlineendings"
36348 .cindex "line endings"
36349 .cindex "carriage return"
36351 RFC 2821 specifies that CRLF (two characters: carriage-return, followed by
36352 linefeed) is the line ending for messages transmitted over the Internet using
36353 SMTP over TCP/IP. However, within individual operating systems, different
36354 conventions are used. For example, Unix-like systems use just LF, but others
36355 use CRLF or just CR.
36357 Exim was designed for Unix-like systems, and internally, it stores messages
36358 using the system's convention of a single LF as a line terminator. When
36359 receiving a message, all line endings are translated to this standard format.
36360 Originally, it was thought that programs that passed messages directly to an
36361 MTA within an operating system would use that system's convention. Experience
36362 has shown that this is not the case; for example, there are Unix applications
36363 that use CRLF in this circumstance. For this reason, and for compatibility with
36364 other MTAs, the way Exim handles line endings for all messages is now as
36368 LF not preceded by CR is treated as a line ending.
36370 CR is treated as a line ending; if it is immediately followed by LF, the LF
36373 The sequence &"CR, dot, CR"& does not terminate an incoming SMTP message,
36374 nor a local message in the state where a line containing only a dot is a
36377 If a bare CR is encountered within a header line, an extra space is added after
36378 the line terminator so as not to end the header line. The reasoning behind this
36379 is that bare CRs in header lines are most likely either to be mistakes, or
36380 people trying to play silly games.
36382 If the first header line received in a message ends with CRLF, a subsequent
36383 bare LF in a header line is treated in the same way as a bare CR in a header
36391 .section "Unqualified addresses" "SECID218"
36392 .cindex "unqualified addresses"
36393 .cindex "address" "qualification"
36394 By default, Exim expects every envelope address it receives from an external
36395 host to be fully qualified. Unqualified addresses cause negative responses to
36396 SMTP commands. However, because SMTP is used as a means of transporting
36397 messages from MUAs running on personal workstations, there is sometimes a
36398 requirement to accept unqualified addresses from specific hosts or IP networks.
36400 Exim has two options that separately control which hosts may send unqualified
36401 sender or recipient addresses in SMTP commands, namely
36402 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&. In both
36403 cases, if an unqualified address is accepted, it is qualified by adding the
36404 value of &%qualify_domain%& or &%qualify_recipient%&, as appropriate.
36406 .oindex "&%qualify_domain%&"
36407 .oindex "&%qualify_recipient%&"
36408 Unqualified addresses in header lines are automatically qualified for messages
36409 that are locally originated, unless the &%-bnq%& option is given on the command
36410 line. For messages received over SMTP, unqualified addresses in header lines
36411 are qualified only if unqualified addresses are permitted in SMTP commands. In
36412 other words, such qualification is also controlled by
36413 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&,
36418 .section "The UUCP From line" "SECID219"
36419 .cindex "&""From""& line"
36420 .cindex "UUCP" "&""From""& line"
36421 .cindex "sender" "address"
36422 .oindex "&%uucp_from_pattern%&"
36423 .oindex "&%uucp_from_sender%&"
36424 .cindex "envelope from"
36425 .cindex "envelope sender"
36426 .cindex "Sendmail compatibility" "&""From""& line"
36427 Messages that have come from UUCP (and some other applications) often begin
36428 with a line containing the envelope sender and a timestamp, following the word
36429 &"From"&. Examples of two common formats are:
36431 From a.oakley@berlin.mus Fri Jan 5 12:35 GMT 1996
36432 From f.butler@berlin.mus Fri, 7 Jan 97 14:00:00 GMT
36434 This line precedes the RFC 2822 header lines. For compatibility with Sendmail,
36435 Exim recognizes such lines at the start of messages that are submitted to it
36436 via the command line (that is, on the standard input). It does not recognize
36437 such lines in incoming SMTP messages, unless the sending host matches
36438 &%ignore_fromline_hosts%& or the &%-bs%& option was used for a local message
36439 and &%ignore_fromline_local%& is set. The recognition is controlled by a
36440 regular expression that is defined by the &%uucp_from_pattern%& option, whose
36441 default value matches the two common cases shown above and puts the address
36442 that follows &"From"& into &$1$&.
36444 .cindex "numerical variables (&$1$& &$2$& etc)" "in &""From ""& line handling"
36445 When the caller of Exim for a non-SMTP message that contains a &"From"& line is
36446 a trusted user, the message's sender address is constructed by expanding the
36447 contents of &%uucp_sender_address%&, whose default value is &"$1"&. This is
36448 then parsed as an RFC 2822 address. If there is no domain, the local part is
36449 qualified with &%qualify_domain%& unless it is the empty string. However, if
36450 the command line &%-f%& option is used, it overrides the &"From"& line.
36452 If the caller of Exim is not trusted, the &"From"& line is recognized, but the
36453 sender address is not changed. This is also the case for incoming SMTP messages
36454 that are permitted to contain &"From"& lines.
36456 Only one &"From"& line is recognized. If there is more than one, the second is
36457 treated as a data line that starts the body of the message, as it is not valid
36458 as a header line. This also happens if a &"From"& line is present in an
36459 incoming SMTP message from a source that is not permitted to send them.
36463 .section "Resent- header lines" "SECID220"
36465 RFC 2822 makes provision for sets of header lines starting with the string
36466 &`Resent-`& to be added to a message when it is resent by the original
36467 recipient to somebody else. These headers are &'Resent-Date:'&,
36468 &'Resent-From:'&, &'Resent-Sender:'&, &'Resent-To:'&, &'Resent-Cc:'&,
36469 &'Resent-Bcc:'& and &'Resent-Message-ID:'&. The RFC says:
36472 &'Resent fields are strictly informational. They MUST NOT be used in the normal
36473 processing of replies or other such automatic actions on messages.'&
36476 This leaves things a bit vague as far as other processing actions such as
36477 address rewriting are concerned. Exim treats &%Resent-%& header lines as
36481 A &'Resent-From:'& line that just contains the login id of the submitting user
36482 is automatically rewritten in the same way as &'From:'& (see below).
36484 If there's a rewriting rule for a particular header line, it is also applied to
36485 &%Resent-%& header lines of the same type. For example, a rule that rewrites
36486 &'From:'& also rewrites &'Resent-From:'&.
36488 For local messages, if &'Sender:'& is removed on input, &'Resent-Sender:'& is
36491 For a locally-submitted message,
36492 if there are any &%Resent-%& header lines but no &'Resent-Date:'&,
36493 &'Resent-From:'&, or &'Resent-Message-Id:'&, they are added as necessary. It is
36494 the contents of &'Resent-Message-Id:'& (rather than &'Message-Id:'&) which are
36495 included in log lines in this case.
36497 The logic for adding &'Sender:'& is duplicated for &'Resent-Sender:'& when any
36498 &%Resent-%& header lines are present.
36504 .section "The Auto-Submitted: header line" "SECID221"
36505 Whenever Exim generates an autoreply, a bounce, or a delay warning message, it
36506 includes the header line:
36508 Auto-Submitted: auto-replied
36511 .section "The Bcc: header line" "SECID222"
36512 .cindex "&'Bcc:'& header line"
36513 If Exim is called with the &%-t%& option, to take recipient addresses from a
36514 message's header, it removes any &'Bcc:'& header line that may exist (after
36515 extracting its addresses). If &%-t%& is not present on the command line, any
36516 existing &'Bcc:'& is not removed.
36519 .section "The Date: header line" "SECID223"
36521 If a locally-generated or submission-mode message has no &'Date:'& header line,
36522 Exim adds one, using the current date and time, unless the
36523 &%suppress_local_fixups%& control has been specified.
36525 .section "The Delivery-date: header line" "SECID224"
36526 .cindex "&'Delivery-date:'& header line"
36527 .oindex "&%delivery_date_remove%&"
36528 &'Delivery-date:'& header lines are not part of the standard RFC 2822 header
36529 set. Exim can be configured to add them to the final delivery of messages. (See
36530 the generic &%delivery_date_add%& transport option.) They should not be present
36531 in messages in transit. If the &%delivery_date_remove%& configuration option is
36532 set (the default), Exim removes &'Delivery-date:'& header lines from incoming
36536 .section "The Envelope-to: header line" "SECID225"
36537 .chindex Envelope-to:
36538 .oindex "&%envelope_to_remove%&"
36539 &'Envelope-to:'& header lines are not part of the standard RFC 2822 header set.
36540 Exim can be configured to add them to the final delivery of messages. (See the
36541 generic &%envelope_to_add%& transport option.) They should not be present in
36542 messages in transit. If the &%envelope_to_remove%& configuration option is set
36543 (the default), Exim removes &'Envelope-to:'& header lines from incoming
36547 .section "The From: header line" "SECTthefrohea"
36549 .cindex "Sendmail compatibility" "&""From""& line"
36550 .cindex "message" "submission"
36551 .cindex "submission mode"
36552 If a submission-mode message does not contain a &'From:'& header line, Exim
36553 adds one if either of the following conditions is true:
36556 The envelope sender address is not empty (that is, this is not a bounce
36557 message). The added header line copies the envelope sender address.
36559 .vindex "&$authenticated_id$&"
36560 The SMTP session is authenticated and &$authenticated_id$& is not empty.
36562 .vindex "&$qualify_domain$&"
36563 If no domain is specified by the submission control, the local part is
36564 &$authenticated_id$& and the domain is &$qualify_domain$&.
36566 If a non-empty domain is specified by the submission control, the local
36567 part is &$authenticated_id$&, and the domain is the specified domain.
36569 If an empty domain is specified by the submission control,
36570 &$authenticated_id$& is assumed to be the complete address.
36574 A non-empty envelope sender takes precedence.
36576 If a locally-generated incoming message does not contain a &'From:'& header
36577 line, and the &%suppress_local_fixups%& control is not set, Exim adds one
36578 containing the sender's address. The calling user's login name and full name
36579 are used to construct the address, as described in section &<<SECTconstr>>&.
36580 They are obtained from the password data by calling &[getpwuid()]& (but see the
36581 &%unknown_login%& configuration option). The address is qualified with
36582 &%qualify_domain%&.
36584 For compatibility with Sendmail, if an incoming, non-SMTP message has a
36585 &'From:'& header line containing just the unqualified login name of the calling
36586 user, this is replaced by an address containing the user's login name and full
36587 name as described in section &<<SECTconstr>>&.
36590 .section "The Message-ID: header line" "SECID226"
36591 .chindex Message-ID:
36592 .cindex "message" "submission"
36593 .oindex "&%message_id_header_text%&"
36594 If a locally-generated or submission-mode incoming message does not contain a
36595 &'Message-ID:'& or &'Resent-Message-ID:'& header line, and the
36596 &%suppress_local_fixups%& control is not set, Exim adds a suitable header line
36597 to the message. If there are any &'Resent-:'& headers in the message, it
36598 creates &'Resent-Message-ID:'&. The id is constructed from Exim's internal
36599 message id, preceded by the letter E to ensure it starts with a letter, and
36600 followed by @ and the primary host name. Additional information can be included
36601 in this header line by setting the &%message_id_header_text%& and/or
36602 &%message_id_header_domain%& options.
36605 .section "The Received: header line" "SECID227"
36607 A &'Received:'& header line is added at the start of every message. The
36608 contents are defined by the &%received_header_text%& configuration option, and
36609 Exim automatically adds a semicolon and a timestamp to the configured string.
36611 The &'Received:'& header is generated as soon as the message's header lines
36612 have been received. At this stage, the timestamp in the &'Received:'& header
36613 line is the time that the message started to be received. This is the value
36614 that is seen by the DATA ACL and by the &[local_scan()]& function.
36616 Once a message is accepted, the timestamp in the &'Received:'& header line is
36617 changed to the time of acceptance, which is (apart from a small delay while the
36618 -H spool file is written) the earliest time at which delivery could start.
36621 .section "The References: header line" "SECID228"
36622 .chindex References:
36623 Messages created by the &(autoreply)& transport include a &'References:'&
36624 header line. This is constructed according to the rules that are described in
36625 section 3.64 of RFC 2822 (which states that replies should contain such a
36626 header line), and section 3.14 of RFC 3834 (which states that automatic
36627 responses are not different in this respect). However, because some mail
36628 processing software does not cope well with very long header lines, no more
36629 than 12 message IDs are copied from the &'References:'& header line in the
36630 incoming message. If there are more than 12, the first one and then the final
36631 11 are copied, before adding the message ID of the incoming message.
36635 .section "The Return-path: header line" "SECID229"
36636 .chindex Return-path:
36637 .oindex "&%return_path_remove%&"
36638 &'Return-path:'& header lines are defined as something an MTA may insert when
36639 it does the final delivery of messages. (See the generic &%return_path_add%&
36640 transport option.) Therefore, they should not be present in messages in
36641 transit. If the &%return_path_remove%& configuration option is set (the
36642 default), Exim removes &'Return-path:'& header lines from incoming messages.
36646 .section "The Sender: header line" "SECTthesenhea"
36647 .cindex "&'Sender:'& header line"
36648 .cindex "message" "submission"
36650 For a locally-originated message from an untrusted user, Exim may remove an
36651 existing &'Sender:'& header line, and it may add a new one. You can modify
36652 these actions by setting the &%local_sender_retain%& option true, the
36653 &%local_from_check%& option false, or by using the &%suppress_local_fixups%&
36656 When a local message is received from an untrusted user and
36657 &%local_from_check%& is true (the default), and the &%suppress_local_fixups%&
36658 control has not been set, a check is made to see if the address given in the
36659 &'From:'& header line is the correct (local) sender of the message. The address
36660 that is expected has the login name as the local part and the value of
36661 &%qualify_domain%& as the domain. Prefixes and suffixes for the local part can
36662 be permitted by setting &%local_from_prefix%& and &%local_from_suffix%&
36663 appropriately. If &'From:'& does not contain the correct sender, a &'Sender:'&
36664 line is added to the message.
36666 If you set &%local_from_check%& false, this checking does not occur. However,
36667 the removal of an existing &'Sender:'& line still happens, unless you also set
36668 &%local_sender_retain%& to be true. It is not possible to set both of these
36669 options true at the same time.
36671 .cindex "submission mode"
36672 By default, no processing of &'Sender:'& header lines is done for messages
36673 received over TCP/IP or for messages submitted by trusted users. However, when
36674 a message is received over TCP/IP in submission mode, and &%sender_retain%& is
36675 not specified on the submission control, the following processing takes place:
36677 .vindex "&$authenticated_id$&"
36678 First, any existing &'Sender:'& lines are removed. Then, if the SMTP session is
36679 authenticated, and &$authenticated_id$& is not empty, a sender address is
36680 created as follows:
36683 .vindex "&$qualify_domain$&"
36684 If no domain is specified by the submission control, the local part is
36685 &$authenticated_id$& and the domain is &$qualify_domain$&.
36687 If a non-empty domain is specified by the submission control, the local part
36688 is &$authenticated_id$&, and the domain is the specified domain.
36690 If an empty domain is specified by the submission control,
36691 &$authenticated_id$& is assumed to be the complete address.
36694 This address is compared with the address in the &'From:'& header line. If they
36695 are different, a &'Sender:'& header line containing the created address is
36696 added. Prefixes and suffixes for the local part in &'From:'& can be permitted
36697 by setting &%local_from_prefix%& and &%local_from_suffix%& appropriately.
36699 .cindex "return path" "created from &'Sender:'&"
36700 &*Note*&: Whenever a &'Sender:'& header line is created, the return path for
36701 the message (the envelope sender address) is changed to be the same address,
36702 except in the case of submission mode when &%sender_retain%& is specified.
36706 .section "Adding and removing header lines in routers and transports" &&&
36707 "SECTheadersaddrem"
36708 .cindex "header lines" "adding; in router or transport"
36709 .cindex "header lines" "removing; in router or transport"
36710 When a message is delivered, the addition and removal of header lines can be
36711 specified in a system filter, or on any of the routers and transports that
36712 process the message. Section &<<SECTaddremheasys>>& contains details about
36713 modifying headers in a system filter. Header lines can also be added in an ACL
36714 as a message is received (see section &<<SECTaddheadacl>>&).
36716 In contrast to what happens in a system filter, header modifications that are
36717 specified on routers and transports apply only to the particular recipient
36718 addresses that are being processed by those routers and transports. These
36719 changes do not actually take place until a copy of the message is being
36720 transported. Therefore, they do not affect the basic set of header lines, and
36721 they do not affect the values of the variables that refer to header lines.
36723 &*Note*&: In particular, this means that any expansions in the configuration of
36724 the transport cannot refer to the modified header lines, because such
36725 expansions all occur before the message is actually transported.
36727 For both routers and transports, the argument of a &%headers_add%&
36728 option must be in the form of one or more RFC 2822 header lines, separated by
36729 newlines (coded as &"\n"&). For example:
36731 headers_add = X-added-header: added by $primary_hostname\n\
36732 X-added-second: another added header line
36734 Exim does not check the syntax of these added header lines.
36736 Multiple &%headers_add%& options for a single router or transport can be
36737 specified; the values will append to a single list of header lines.
36738 Each header-line is separately expanded.
36740 The argument of a &%headers_remove%& option must consist of a colon-separated
36741 list of header names. This is confusing, because header names themselves are
36742 often terminated by colons. In this case, the colons are the list separators,
36743 not part of the names. For example:
36745 headers_remove = return-receipt-to:acknowledge-to
36748 Multiple &%headers_remove%& options for a single router or transport can be
36749 specified; the arguments will append to a single header-names list.
36750 Each item is separately expanded.
36751 Note that colons in complex expansions which are used to
36752 form all or part of a &%headers_remove%& list
36753 will act as list separators.
36755 When &%headers_add%& or &%headers_remove%& is specified on a router,
36756 items are expanded at routing time,
36757 and then associated with all addresses that are
36758 accepted by that router, and also with any new addresses that it generates. If
36759 an address passes through several routers as a result of aliasing or
36760 forwarding, the changes are cumulative.
36762 .oindex "&%unseen%&"
36763 However, this does not apply to multiple routers that result from the use of
36764 the &%unseen%& option. Any header modifications that were specified by the
36765 &"unseen"& router or its predecessors apply only to the &"unseen"& delivery.
36767 Addresses that end up with different &%headers_add%& or &%headers_remove%&
36768 settings cannot be delivered together in a batch, so a transport is always
36769 dealing with a set of addresses that have the same header-processing
36772 The transport starts by writing the original set of header lines that arrived
36773 with the message, possibly modified by the system filter. As it writes out
36774 these lines, it consults the list of header names that were attached to the
36775 recipient address(es) by &%headers_remove%& options in routers, and it also
36776 consults the transport's own &%headers_remove%& option. Header lines whose
36777 names are on either of these lists are not written out. If there are multiple
36778 instances of any listed header, they are all skipped.
36780 After the remaining original header lines have been written, new header
36781 lines that were specified by routers' &%headers_add%& options are written, in
36782 the order in which they were attached to the address. These are followed by any
36783 header lines specified by the transport's &%headers_add%& option.
36785 This way of handling header line modifications in routers and transports has
36786 the following consequences:
36789 The original set of header lines, possibly modified by the system filter,
36790 remains &"visible"&, in the sense that the &$header_$&&'xxx'& variables refer
36791 to it, at all times.
36793 Header lines that are added by a router's
36794 &%headers_add%& option are not accessible by means of the &$header_$&&'xxx'&
36795 expansion syntax in subsequent routers or the transport.
36797 Conversely, header lines that are specified for removal by &%headers_remove%&
36798 in a router remain visible to subsequent routers and the transport.
36800 Headers added to an address by &%headers_add%& in a router cannot be removed by
36801 a later router or by a transport.
36803 An added header can refer to the contents of an original header that is to be
36804 removed, even it has the same name as the added header. For example:
36806 headers_remove = subject
36807 headers_add = Subject: new subject (was: $h_subject:)
36811 &*Warning*&: The &%headers_add%& and &%headers_remove%& options cannot be used
36812 for a &(redirect)& router that has the &%one_time%& option set.
36818 .section "Constructed addresses" "SECTconstr"
36819 .cindex "address" "constructed"
36820 .cindex "constructed address"
36821 When Exim constructs a sender address for a locally-generated message, it uses
36824 <&'user name'&>&~&~<&'login'&&`@`&&'qualify_domain'&>
36828 Zaphod Beeblebrox <zaphod@end.univ.example>
36830 The user name is obtained from the &%-F%& command line option if set, or
36831 otherwise by looking up the calling user by &[getpwuid()]& and extracting the
36832 &"gecos"& field from the password entry. If the &"gecos"& field contains an
36833 ampersand character, this is replaced by the login name with the first letter
36834 upper cased, as is conventional in a number of operating systems. See the
36835 &%gecos_name%& option for a way to tailor the handling of the &"gecos"& field.
36836 The &%unknown_username%& option can be used to specify user names in cases when
36837 there is no password file entry.
36840 In all cases, the user name is made to conform to RFC 2822 by quoting all or
36841 parts of it if necessary. In addition, if it contains any non-printing
36842 characters, it is encoded as described in RFC 2047, which defines a way of
36843 including non-ASCII characters in header lines. The value of the
36844 &%headers_charset%& option specifies the name of the encoding that is used (the
36845 characters are assumed to be in this encoding). The setting of
36846 &%print_topbitchars%& controls whether characters with the top bit set (that
36847 is, with codes greater than 127) count as printing characters or not.
36851 .section "Case of local parts" "SECID230"
36852 .cindex "case of local parts"
36853 .cindex "local part" "case of"
36854 RFC 2822 states that the case of letters in the local parts of addresses cannot
36855 be assumed to be non-significant. Exim preserves the case of local parts of
36856 addresses, but by default it uses a lower-cased form when it is routing,
36857 because on most Unix systems, usernames are in lower case and case-insensitive
36858 routing is required. However, any particular router can be made to use the
36859 original case for local parts by setting the &%caseful_local_part%& generic
36862 .cindex "mixed-case login names"
36863 If you must have mixed-case user names on your system, the best way to proceed,
36864 assuming you want case-independent handling of incoming email, is to set up
36865 your first router to convert incoming local parts in your domains to the
36866 correct case by means of a file lookup. For example:
36870 domains = +local_domains
36871 data = ${lookup{$local_part}cdb\
36872 {/etc/usercased.cdb}{$value}fail}\
36875 For this router, the local part is forced to lower case by the default action
36876 (&%caseful_local_part%& is not set). The lower-cased local part is used to look
36877 up a new local part in the correct case. If you then set &%caseful_local_part%&
36878 on any subsequent routers which process your domains, they will operate on
36879 local parts with the correct case in a case-sensitive manner.
36883 .section "Dots in local parts" "SECID231"
36884 .cindex "dot" "in local part"
36885 .cindex "local part" "dots in"
36886 RFC 2822 forbids empty components in local parts. That is, an unquoted local
36887 part may not begin or end with a dot, nor have two consecutive dots in the
36888 middle. However, it seems that many MTAs do not enforce this, so Exim permits
36889 empty components for compatibility.
36893 .section "Rewriting addresses" "SECID232"
36894 .cindex "rewriting" "addresses"
36895 Rewriting of sender and recipient addresses, and addresses in headers, can
36896 happen automatically, or as the result of configuration options, as described
36897 in chapter &<<CHAPrewrite>>&. The headers that may be affected by this are
36898 &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-To:'&, &'Sender:'&, and &'To:'&.
36900 Automatic rewriting includes qualification, as mentioned above. The other case
36901 in which it can happen is when an incomplete non-local domain is given. The
36902 routing process may cause this to be expanded into the full domain name. For
36903 example, a header such as
36907 might get rewritten as
36909 To: hare@teaparty.wonderland.fict.example
36911 Rewriting as a result of routing is the one kind of message processing that
36912 does not happen at input time, as it cannot be done until the address has
36915 Strictly, one should not do &'any'& deliveries of a message until all its
36916 addresses have been routed, in case any of the headers get changed as a
36917 result of routing. However, doing this in practice would hold up many
36918 deliveries for unreasonable amounts of time, just because one address could not
36919 immediately be routed. Exim therefore does not delay other deliveries when
36920 routing of one or more addresses is deferred.
36921 .ecindex IIDmesproc
36925 . ////////////////////////////////////////////////////////////////////////////
36926 . ////////////////////////////////////////////////////////////////////////////
36928 .chapter "SMTP processing" "CHAPSMTP"
36929 .scindex IIDsmtpproc1 "SMTP" "processing details"
36930 .scindex IIDsmtpproc2 "LMTP" "processing details"
36931 Exim supports a number of different ways of using the SMTP protocol, and its
36932 LMTP variant, which is an interactive protocol for transferring messages into a
36933 closed mail store application. This chapter contains details of how SMTP is
36934 processed. For incoming mail, the following are available:
36937 SMTP over TCP/IP (Exim daemon or &'inetd'&);
36939 SMTP over the standard input and output (the &%-bs%& option);
36941 Batched SMTP on the standard input (the &%-bS%& option).
36944 For mail delivery, the following are available:
36947 SMTP over TCP/IP (the &(smtp)& transport);
36949 LMTP over TCP/IP (the &(smtp)& transport with the &%protocol%& option set to
36952 LMTP over a pipe to a process running in the local host (the &(lmtp)&
36955 Batched SMTP to a file or pipe (the &(appendfile)& and &(pipe)& transports with
36956 the &%use_bsmtp%& option set).
36959 &'Batched SMTP'& is the name for a process in which batches of messages are
36960 stored in or read from files (or pipes), in a format in which SMTP commands are
36961 used to contain the envelope information.
36965 .section "Outgoing SMTP and LMTP over TCP/IP" "SECToutSMTPTCP"
36966 .cindex "SMTP" "outgoing over TCP/IP"
36967 .cindex "outgoing SMTP over TCP/IP"
36968 .cindex "LMTP" "over TCP/IP"
36969 .cindex "outgoing LMTP over TCP/IP"
36972 .cindex "SIZE" "option on MAIL command"
36973 Outgoing SMTP and LMTP over TCP/IP is implemented by the &(smtp)& transport.
36974 The &%protocol%& option selects which protocol is to be used, but the actual
36975 processing is the same in both cases.
36977 .cindex "ESMTP extensions" SIZE
36978 If, in response to its EHLO command, Exim is told that the SIZE
36979 extension is supported, it adds SIZE=<&'n'&> to each subsequent MAIL
36980 command. The value of <&'n'&> is the message size plus the value of the
36981 &%size_addition%& option (default 1024) to allow for additions to the message
36982 such as per-transport header lines, or changes made in a
36983 .cindex "transport" "filter"
36984 .cindex "filter" "transport filter"
36985 transport filter. If &%size_addition%& is set negative, the use of SIZE is
36988 If the remote server advertises support for PIPELINING, Exim uses the
36989 pipelining extension to SMTP (RFC 2197) to reduce the number of TCP/IP packets
36990 required for the transaction.
36992 If the remote server advertises support for the STARTTLS command, and Exim
36993 was built to support TLS encryption, it tries to start a TLS session unless the
36994 server matches &%hosts_avoid_tls%&. See chapter &<<CHAPTLS>>& for more details.
36995 Either a match in that or &%hosts_verify_avoid_tls%& apply when the transport
36996 is called for verification.
36998 If the remote server advertises support for the AUTH command, Exim scans
36999 the authenticators configuration for any suitable client settings, as described
37000 in chapter &<<CHAPSMTPAUTH>>&.
37002 .cindex "carriage return"
37004 Responses from the remote host are supposed to be terminated by CR followed by
37005 LF. However, there are known to be hosts that do not send CR characters, so in
37006 order to be able to interwork with such hosts, Exim treats LF on its own as a
37009 If a message contains a number of different addresses, all those with the same
37010 characteristics (for example, the same envelope sender) that resolve to the
37011 same set of hosts, in the same order, are sent in a single SMTP transaction,
37012 even if they are for different domains, unless there are more than the setting
37013 of the &%max_rcpt%&s option in the &(smtp)& transport allows, in which case
37014 they are split into groups containing no more than &%max_rcpt%&s addresses
37015 each. If &%remote_max_parallel%& is greater than one, such groups may be sent
37016 in parallel sessions. The order of hosts with identical MX values is not
37017 significant when checking whether addresses can be batched in this way.
37019 When the &(smtp)& transport suffers a temporary failure that is not
37020 message-related, Exim updates its transport-specific database, which contains
37021 records indexed by host name that remember which messages are waiting for each
37022 particular host. It also updates the retry database with new retry times.
37024 .cindex "hints database" "retry keys"
37025 Exim's retry hints are based on host name plus IP address, so if one address of
37026 a multi-homed host is broken, it will soon be skipped most of the time.
37027 See the next section for more detail about error handling.
37029 .cindex "SMTP" "passed connection"
37030 .cindex "SMTP" "batching over TCP/IP"
37031 When a message is successfully delivered over a TCP/IP SMTP connection, Exim
37032 looks in the hints database for the transport to see if there are any queued
37033 messages waiting for the host to which it is connected. If it finds one, it
37034 creates a new Exim process using the &%-MC%& option (which can only be used by
37035 a process running as root or the Exim user) and passes the TCP/IP socket to it
37036 so that it can deliver another message using the same socket. The new process
37037 does only those deliveries that are routed to the connected host, and may in
37038 turn pass the socket on to a third process, and so on.
37040 The &%connection_max_messages%& option of the &(smtp)& transport can be used to
37041 limit the number of messages sent down a single TCP/IP connection.
37043 .cindex "asterisk" "after IP address"
37044 The second and subsequent messages delivered down an existing connection are
37045 identified in the main log by the addition of an asterisk after the closing
37046 square bracket of the IP address.
37051 .section "Errors in outgoing SMTP" "SECToutSMTPerr"
37052 .cindex "error" "in outgoing SMTP"
37053 .cindex "SMTP" "errors in outgoing"
37054 .cindex "host" "error"
37055 Three different kinds of error are recognized for outgoing SMTP: host errors,
37056 message errors, and recipient errors.
37059 .vitem "&*Host errors*&"
37060 A host error is not associated with a particular message or with a
37061 particular recipient of a message. The host errors are:
37064 Connection refused or timed out,
37066 Any error response code on connection,
37068 Any error response code to EHLO or HELO,
37070 Loss of connection at any time, except after &"."&,
37072 I/O errors at any time,
37074 Timeouts during the session, other than in response to MAIL, RCPT or
37075 the &"."& at the end of the data.
37078 For a host error, a permanent error response on connection, or in response to
37079 EHLO, causes all addresses routed to the host to be failed. Any other host
37080 error causes all addresses to be deferred, and retry data to be created for the
37081 host. It is not tried again, for any message, until its retry time arrives. If
37082 the current set of addresses are not all delivered in this run (to some
37083 alternative host), the message is added to the list of those waiting for this
37084 host, so if it is still undelivered when a subsequent successful delivery is
37085 made to the host, it will be sent down the same SMTP connection.
37087 .vitem "&*Message errors*&"
37088 .cindex "message" "error"
37089 A message error is associated with a particular message when sent to a
37090 particular host, but not with a particular recipient of the message. The
37091 message errors are:
37094 Any error response code to MAIL, DATA, or the &"."& that terminates
37097 Timeout after MAIL,
37099 Timeout or loss of connection after the &"."& that terminates the data. A
37100 timeout after the DATA command itself is treated as a host error, as is loss of
37101 connection at any other time.
37104 For a message error, a permanent error response (5&'xx'&) causes all addresses
37105 to be failed, and a delivery error report to be returned to the sender. A
37106 temporary error response (4&'xx'&), or one of the timeouts, causes all
37107 addresses to be deferred. Retry data is not created for the host, but instead,
37108 a retry record for the combination of host plus message id is created. The
37109 message is not added to the list of those waiting for this host. This ensures
37110 that the failing message will not be sent to this host again until the retry
37111 time arrives. However, other messages that are routed to the host are not
37112 affected, so if it is some property of the message that is causing the error,
37113 it will not stop the delivery of other mail.
37115 If the remote host specified support for the SIZE parameter in its response
37116 to EHLO, Exim adds SIZE=&'nnn'& to the MAIL command, so an
37117 over-large message will cause a message error because the error arrives as a
37120 .vitem "&*Recipient errors*&"
37121 .cindex "recipient" "error"
37122 A recipient error is associated with a particular recipient of a message. The
37123 recipient errors are:
37126 Any error response to RCPT,
37128 Timeout after RCPT.
37131 For a recipient error, a permanent error response (5&'xx'&) causes the
37132 recipient address to be failed, and a bounce message to be returned to the
37133 sender. A temporary error response (4&'xx'&) or a timeout causes the failing
37134 address to be deferred, and routing retry data to be created for it. This is
37135 used to delay processing of the address in subsequent queue runs, until its
37136 routing retry time arrives. This applies to all messages, but because it
37137 operates only in queue runs, one attempt will be made to deliver a new message
37138 to the failing address before the delay starts to operate. This ensures that,
37139 if the failure is really related to the message rather than the recipient
37140 (&"message too big for this recipient"& is a possible example), other messages
37141 have a chance of getting delivered. If a delivery to the address does succeed,
37142 the retry information gets cleared, so all stuck messages get tried again, and
37143 the retry clock is reset.
37145 The message is not added to the list of those waiting for this host. Use of the
37146 host for other messages is unaffected, and except in the case of a timeout,
37147 other recipients are processed independently, and may be successfully delivered
37148 in the current SMTP session. After a timeout it is of course impossible to
37149 proceed with the session, so all addresses get deferred. However, those other
37150 than the one that failed do not suffer any subsequent retry delays. Therefore,
37151 if one recipient is causing trouble, the others have a chance of getting
37152 through when a subsequent delivery attempt occurs before the failing
37153 recipient's retry time.
37156 In all cases, if there are other hosts (or IP addresses) available for the
37157 current set of addresses (for example, from multiple MX records), they are
37158 tried in this run for any undelivered addresses, subject of course to their
37159 own retry data. In other words, recipient error retry data does not take effect
37160 until the next delivery attempt.
37162 Some hosts have been observed to give temporary error responses to every
37163 MAIL command at certain times (&"insufficient space"& has been seen). It
37164 would be nice if such circumstances could be recognized, and defer data for the
37165 host itself created, but this is not possible within the current Exim design.
37166 What actually happens is that retry data for every (host, message) combination
37169 The reason that timeouts after MAIL and RCPT are treated specially is that
37170 these can sometimes arise as a result of the remote host's verification
37171 procedures. Exim makes this assumption, and treats them as if a temporary error
37172 response had been received. A timeout after &"."& is treated specially because
37173 it is known that some broken implementations fail to recognize the end of the
37174 message if the last character of the last line is a binary zero. Thus, it is
37175 helpful to treat this case as a message error.
37177 Timeouts at other times are treated as host errors, assuming a problem with the
37178 host, or the connection to it. If a timeout after MAIL, RCPT,
37179 or &"."& is really a connection problem, the assumption is that at the next try
37180 the timeout is likely to occur at some other point in the dialogue, causing it
37181 then to be treated as a host error.
37183 There is experimental evidence that some MTAs drop the connection after the
37184 terminating &"."& if they do not like the contents of the message for some
37185 reason, in contravention of the RFC, which indicates that a 5&'xx'& response
37186 should be given. That is why Exim treats this case as a message rather than a
37187 host error, in order not to delay other messages to the same host.
37192 .section "Incoming SMTP messages over TCP/IP" "SECID233"
37193 .cindex "SMTP" "incoming over TCP/IP"
37194 .cindex "incoming SMTP over TCP/IP"
37197 Incoming SMTP messages can be accepted in one of two ways: by running a
37198 listening daemon, or by using &'inetd'&. In the latter case, the entry in
37199 &_/etc/inetd.conf_& should be like this:
37201 smtp stream tcp nowait exim /opt/exim/bin/exim in.exim -bs
37203 Exim distinguishes between this case and the case of a locally running user
37204 agent using the &%-bs%& option by checking whether or not the standard input is
37205 a socket. When it is, either the port must be privileged (less than 1024), or
37206 the caller must be root or the Exim user. If any other user passes a socket
37207 with an unprivileged port number, Exim prints a message on the standard error
37208 stream and exits with an error code.
37210 By default, Exim does not make a log entry when a remote host connects or
37211 disconnects (either via the daemon or &'inetd'&), unless the disconnection is
37212 unexpected. It can be made to write such log entries by setting the
37213 &%smtp_connection%& log selector.
37215 .cindex "carriage return"
37217 Commands from the remote host are supposed to be terminated by CR followed by
37218 LF. However, there are known to be hosts that do not send CR characters. In
37219 order to be able to interwork with such hosts, Exim treats LF on its own as a
37221 Furthermore, because common code is used for receiving messages from all
37222 sources, a CR on its own is also interpreted as a line terminator. However, the
37223 sequence &"CR, dot, CR"& does not terminate incoming SMTP data.
37225 .cindex "EHLO" "invalid data"
37226 .cindex "HELO" "invalid data"
37227 One area that sometimes gives rise to problems concerns the EHLO or
37228 HELO commands. Some clients send syntactically invalid versions of these
37229 commands, which Exim rejects by default. (This is nothing to do with verifying
37230 the data that is sent, so &%helo_verify_hosts%& is not relevant.) You can tell
37231 Exim not to apply a syntax check by setting &%helo_accept_junk_hosts%& to
37232 match the broken hosts that send invalid commands.
37234 .cindex "SIZE option on MAIL command"
37235 .cindex "MAIL" "SIZE option"
37236 The amount of disk space available is checked whenever SIZE is received on
37237 a MAIL command, independently of whether &%message_size_limit%& or
37238 &%check_spool_space%& is configured, unless &%smtp_check_spool_space%& is set
37239 false. A temporary error is given if there is not enough space. If
37240 &%check_spool_space%& is set, the check is for that amount of space plus the
37241 value given with SIZE, that is, it checks that the addition of the incoming
37242 message will not reduce the space below the threshold.
37244 When a message is successfully received, Exim includes the local message id in
37245 its response to the final &"."& that terminates the data. If the remote host
37246 logs this text it can help with tracing what has happened to a message.
37248 The Exim daemon can limit the number of simultaneous incoming connections it is
37249 prepared to handle (see the &%smtp_accept_max%& option). It can also limit the
37250 number of simultaneous incoming connections from a single remote host (see the
37251 &%smtp_accept_max_per_host%& option). Additional connection attempts are
37252 rejected using the SMTP temporary error code 421.
37254 The Exim daemon does not rely on the SIGCHLD signal to detect when a
37255 subprocess has finished, as this can get lost at busy times. Instead, it looks
37256 for completed subprocesses every time it wakes up. Provided there are other
37257 things happening (new incoming calls, starts of queue runs), completed
37258 processes will be noticed and tidied away. On very quiet systems you may
37259 sometimes see a &"defunct"& Exim process hanging about. This is not a problem;
37260 it will be noticed when the daemon next wakes up.
37262 When running as a daemon, Exim can reserve some SMTP slots for specific hosts,
37263 and can also be set up to reject SMTP calls from non-reserved hosts at times of
37264 high system load &-- for details see the &%smtp_accept_reserve%&,
37265 &%smtp_load_reserve%&, and &%smtp_reserve_hosts%& options. The load check
37266 applies in both the daemon and &'inetd'& cases.
37268 Exim normally starts a delivery process for each message received, though this
37269 can be varied by means of the &%-odq%& command line option and the
37270 &%queue_only%&, &%queue_only_file%&, and &%queue_only_load%& options. The
37271 number of simultaneously running delivery processes started in this way from
37272 SMTP input can be limited by the &%smtp_accept_queue%& and
37273 &%smtp_accept_queue_per_connection%& options. When either limit is reached,
37274 subsequently received messages are just put on the input queue without starting
37275 a delivery process.
37277 The controls that involve counts of incoming SMTP calls (&%smtp_accept_max%&,
37278 &%smtp_accept_queue%&, &%smtp_accept_reserve%&) are not available when Exim is
37279 started up from the &'inetd'& daemon, because in that case each connection is
37280 handled by an entirely independent Exim process. Control by load average is,
37281 however, available with &'inetd'&.
37283 Exim can be configured to verify addresses in incoming SMTP commands as they
37284 are received. See chapter &<<CHAPACL>>& for details. It can also be configured
37285 to rewrite addresses at this time &-- before any syntax checking is done. See
37286 section &<<SECTrewriteS>>&.
37288 Exim can also be configured to limit the rate at which a client host submits
37289 MAIL and RCPT commands in a single SMTP session. See the
37290 &%smtp_ratelimit_hosts%& option.
37294 .section "Unrecognized SMTP commands" "SECID234"
37295 .cindex "SMTP" "unrecognized commands"
37296 If Exim receives more than &%smtp_max_unknown_commands%& unrecognized SMTP
37297 commands during a single SMTP connection, it drops the connection after sending
37298 the error response to the last command. The default value for
37299 &%smtp_max_unknown_commands%& is 3. This is a defence against some kinds of
37300 abuse that subvert web servers into making connections to SMTP ports; in these
37301 circumstances, a number of non-SMTP lines are sent first.
37304 .section "Syntax and protocol errors in SMTP commands" "SECID235"
37305 .cindex "SMTP" "syntax errors"
37306 .cindex "SMTP" "protocol errors"
37307 A syntax error is detected if an SMTP command is recognized, but there is
37308 something syntactically wrong with its data, for example, a malformed email
37309 address in a RCPT command. Protocol errors include invalid command
37310 sequencing such as RCPT before MAIL. If Exim receives more than
37311 &%smtp_max_synprot_errors%& such commands during a single SMTP connection, it
37312 drops the connection after sending the error response to the last command. The
37313 default value for &%smtp_max_synprot_errors%& is 3. This is a defence against
37314 broken clients that loop sending bad commands (yes, it has been seen).
37318 .section "Use of non-mail SMTP commands" "SECID236"
37319 .cindex "SMTP" "non-mail commands"
37320 The &"non-mail"& SMTP commands are those other than MAIL, RCPT, and
37321 DATA. Exim counts such commands, and drops the connection if there are too
37322 many of them in a single SMTP session. This action catches some
37323 denial-of-service attempts and things like repeated failing AUTHs, or a mad
37324 client looping sending EHLO. The global option &%smtp_accept_max_nonmail%&
37325 defines what &"too many"& means. Its default value is 10.
37327 When a new message is expected, one occurrence of RSET is not counted. This
37328 allows a client to send one RSET between messages (this is not necessary,
37329 but some clients do it). Exim also allows one uncounted occurrence of HELO
37330 or EHLO, and one occurrence of STARTTLS between messages. After
37331 starting up a TLS session, another EHLO is expected, and so it too is not
37334 The first occurrence of AUTH in a connection, or immediately following
37335 STARTTLS is also not counted. Otherwise, all commands other than MAIL,
37336 RCPT, DATA, and QUIT are counted.
37338 You can control which hosts are subject to the limit set by
37339 &%smtp_accept_max_nonmail%& by setting
37340 &%smtp_accept_max_nonmail_hosts%&. The default value is &`*`&, which makes
37341 the limit apply to all hosts. This option means that you can exclude any
37342 specific badly-behaved hosts that you have to live with.
37347 .section "The VRFY and EXPN commands" "SECID237"
37348 When Exim receives a VRFY or EXPN command on a TCP/IP connection, it
37349 runs the ACL specified by &%acl_smtp_vrfy%& or &%acl_smtp_expn%& (as
37350 appropriate) in order to decide whether the command should be accepted or not.
37352 .cindex "VRFY" "processing"
37353 When no ACL is defined for VRFY, or if it rejects without
37354 setting an explicit response code, the command is accepted
37355 (with a 252 SMTP response code)
37356 in order to support awkward clients that do a VRFY before every RCPT.
37357 When VRFY is accepted, it runs exactly the same code as when Exim is
37358 called with the &%-bv%& option, and returns 250/451/550
37359 SMTP response codes.
37361 .cindex "EXPN" "processing"
37362 If no ACL for EXPN is defined, the command is rejected.
37363 When EXPN is accepted, a single-level expansion of the address is done.
37364 EXPN is treated as an &"address test"& (similar to the &%-bt%& option) rather
37365 than a verification (the &%-bv%& option). If an unqualified local part is given
37366 as the argument to EXPN, it is qualified with &%qualify_domain%&. Rejections
37367 of VRFY and EXPN commands are logged on the main and reject logs, and
37368 VRFY verification failures are logged on the main log for consistency with
37373 .section "The ETRN command" "SECTETRN"
37374 .cindex "ETRN" "processing"
37375 .cindex "ESMTP extensions" ETRN
37376 RFC 1985 describes an ESMTP command called ETRN that is designed to
37377 overcome the security problems of the TURN command (which has fallen into
37378 disuse). When Exim receives an ETRN command on a TCP/IP connection, it runs
37379 the ACL specified by &%acl_smtp_etrn%& in order to decide whether the command
37380 should be accepted or not. If no ACL is defined, the command is rejected.
37382 The ETRN command is concerned with &"releasing"& messages that are awaiting
37383 delivery to certain hosts. As Exim does not organize its message queue by host,
37384 the only form of ETRN that is supported by default is the one where the
37385 text starts with the &"#"& prefix, in which case the remainder of the text is
37386 specific to the SMTP server. A valid ETRN command causes a run of Exim with
37387 the &%-R%& option to happen, with the remainder of the ETRN text as its
37388 argument. For example,
37396 which causes a delivery attempt on all messages with undelivered addresses
37397 containing the text &"brigadoon"&. When &%smtp_etrn_serialize%& is set (the
37398 default), Exim prevents the simultaneous execution of more than one queue run
37399 for the same argument string as a result of an ETRN command. This stops
37400 a misbehaving client from starting more than one queue runner at once.
37402 .cindex "hints database" "ETRN serialization"
37403 Exim implements the serialization by means of a hints database in which a
37404 record is written whenever a process is started by ETRN, and deleted when
37405 the process completes. However, Exim does not keep the SMTP session waiting for
37406 the ETRN process to complete. Once ETRN is accepted, the client is sent
37407 a &"success"& return code. Obviously there is scope for hints records to get
37408 left lying around if there is a system or program crash. To guard against this,
37409 Exim ignores any records that are more than six hours old.
37411 .oindex "&%smtp_etrn_command%&"
37412 For more control over what ETRN does, the &%smtp_etrn_command%& option can
37413 used. This specifies a command that is run whenever ETRN is received,
37414 whatever the form of its argument. For
37417 smtp_etrn_command = /etc/etrn_command $domain \
37418 $sender_host_address
37420 .vindex "&$domain$&"
37421 The string is split up into arguments which are independently expanded. The
37422 expansion variable &$domain$& is set to the argument of the ETRN command,
37423 and no syntax checking is done on the contents of this argument. Exim does not
37424 wait for the command to complete, so its status code is not checked. Exim runs
37425 under its own uid and gid when receiving incoming SMTP, so it is not possible
37426 for it to change them before running the command.
37430 .section "Incoming local SMTP" "SECID238"
37431 .cindex "SMTP" "local incoming"
37432 Some user agents use SMTP to pass messages to their local MTA using the
37433 standard input and output, as opposed to passing the envelope on the command
37434 line and writing the message to the standard input. This is supported by the
37435 &%-bs%& option. This form of SMTP is handled in the same way as incoming
37436 messages over TCP/IP (including the use of ACLs), except that the envelope
37437 sender given in a MAIL command is ignored unless the caller is trusted. In
37438 an ACL you can detect this form of SMTP input by testing for an empty host
37439 identification. It is common to have this as the first line in the ACL that
37440 runs for RCPT commands:
37444 This accepts SMTP messages from local processes without doing any other tests.
37448 .section "Outgoing batched SMTP" "SECTbatchSMTP"
37449 .cindex "SMTP" "batched outgoing"
37450 .cindex "batched SMTP output"
37451 Both the &(appendfile)& and &(pipe)& transports can be used for handling
37452 batched SMTP. Each has an option called &%use_bsmtp%& which causes messages to
37453 be output in BSMTP format. No SMTP responses are possible for this form of
37454 delivery. All it is doing is using SMTP commands as a way of transmitting the
37455 envelope along with the message.
37457 The message is written to the file or pipe preceded by the SMTP commands
37458 MAIL and RCPT, and followed by a line containing a single dot. Lines in
37459 the message that start with a dot have an extra dot added. The SMTP command
37460 HELO is not normally used. If it is required, the &%message_prefix%& option
37461 can be used to specify it.
37463 Because &(appendfile)& and &(pipe)& are both local transports, they accept only
37464 one recipient address at a time by default. However, you can arrange for them
37465 to handle several addresses at once by setting the &%batch_max%& option. When
37466 this is done for BSMTP, messages may contain multiple RCPT commands. See
37467 chapter &<<CHAPbatching>>& for more details.
37470 When one or more addresses are routed to a BSMTP transport by a router that
37471 sets up a host list, the name of the first host on the list is available to the
37472 transport in the variable &$host$&. Here is an example of such a transport and
37477 driver = manualroute
37478 transport = smtp_appendfile
37479 route_list = domain.example batch.host.example
37483 driver = appendfile
37484 directory = /var/bsmtp/$host
37489 This causes messages addressed to &'domain.example'& to be written in BSMTP
37490 format to &_/var/bsmtp/batch.host.example_&, with only a single copy of each
37491 message (unless there are more than 1000 recipients).
37495 .section "Incoming batched SMTP" "SECTincomingbatchedSMTP"
37496 .cindex "SMTP" "batched incoming"
37497 .cindex "batched SMTP input"
37498 The &%-bS%& command line option causes Exim to accept one or more messages by
37499 reading SMTP on the standard input, but to generate no responses. If the caller
37500 is trusted, the senders in the MAIL commands are believed; otherwise the
37501 sender is always the caller of Exim. Unqualified senders and receivers are not
37502 rejected (there seems little point) but instead just get qualified. HELO
37503 and EHLO act as RSET; VRFY, EXPN, ETRN and HELP, act
37504 as NOOP; QUIT quits.
37506 Minimal policy checking is done for BSMTP input. Only the non-SMTP
37507 ACL is run in the same way as for non-SMTP local input.
37509 If an error is detected while reading a message, including a missing &"."& at
37510 the end, Exim gives up immediately. It writes details of the error to the
37511 standard output in a stylized way that the calling program should be able to
37512 make some use of automatically, for example:
37514 554 Unexpected end of file
37515 Transaction started in line 10
37516 Error detected in line 14
37518 It writes a more verbose version, for human consumption, to the standard error
37521 An error was detected while processing a file of BSMTP input.
37522 The error message was:
37524 501 '>' missing at end of address
37526 The SMTP transaction started in line 10.
37527 The error was detected in line 12.
37528 The SMTP command at fault was:
37530 rcpt to:<malformed@in.com.plete
37532 1 previous message was successfully processed.
37533 The rest of the batch was abandoned.
37535 The return code from Exim is zero only if there were no errors. It is 1 if some
37536 messages were accepted before an error was detected, and 2 if no messages were
37538 .ecindex IIDsmtpproc1
37539 .ecindex IIDsmtpproc2
37543 . ////////////////////////////////////////////////////////////////////////////
37544 . ////////////////////////////////////////////////////////////////////////////
37546 .chapter "Customizing bounce and warning messages" "CHAPemsgcust" &&&
37547 "Customizing messages"
37548 When a message fails to be delivered, or remains in the queue for more than a
37549 configured amount of time, Exim sends a message to the original sender, or
37550 to an alternative configured address. The text of these messages is built into
37551 the code of Exim, but it is possible to change it, either by adding a single
37552 string, or by replacing each of the paragraphs by text supplied in a file.
37554 The &'From:'& and &'To:'& header lines are automatically generated; you can
37555 cause a &'Reply-To:'& line to be added by setting the &%errors_reply_to%&
37556 option. Exim also adds the line
37558 Auto-Submitted: auto-generated
37560 to all warning and bounce messages,
37563 .section "Customizing bounce messages" "SECID239"
37564 .cindex "customizing" "bounce message"
37565 .cindex "bounce message" "customizing"
37566 If &%bounce_message_text%& is set, its contents are included in the default
37567 message immediately after &"This message was created automatically by mail
37568 delivery software."& The string is not expanded. It is not used if
37569 &%bounce_message_file%& is set.
37571 When &%bounce_message_file%& is set, it must point to a template file for
37572 constructing error messages. The file consists of a series of text items,
37573 separated by lines consisting of exactly four asterisks. If the file cannot be
37574 opened, default text is used and a message is written to the main and panic
37575 logs. If any text item in the file is empty, default text is used for that
37578 .vindex "&$bounce_recipient$&"
37579 .vindex "&$bounce_return_size_limit$&"
37580 Each item of text that is read from the file is expanded, and there are two
37581 expansion variables which can be of use here: &$bounce_recipient$& is set to
37582 the recipient of an error message while it is being created, and
37583 &$bounce_return_size_limit$& contains the value of the &%return_size_limit%&
37584 option, rounded to a whole number.
37586 The items must appear in the file in the following order:
37589 The first item is included in the headers, and should include at least a
37590 &'Subject:'& header. Exim does not check the syntax of these headers.
37592 The second item forms the start of the error message. After it, Exim lists the
37593 failing addresses with their error messages.
37595 The third item is used to introduce any text from pipe transports that is to be
37596 returned to the sender. It is omitted if there is no such text.
37598 The fourth, fifth and sixth items will be ignored and may be empty.
37599 The fields exist for back-compatibility
37602 The default state (&%bounce_message_file%& unset) is equivalent to the
37603 following file, in which the sixth item is empty. The &'Subject:'& and some
37604 other lines have been split in order to fit them on the page:
37606 Subject: Mail delivery failed
37607 ${if eq{$sender_address}{$bounce_recipient}
37608 {: returning message to sender}}
37610 This message was created automatically by mail delivery software.
37612 A message ${if eq{$sender_address}{$bounce_recipient}
37613 {that you sent }{sent by
37617 }}could not be delivered to all of its recipients.
37618 This is a permanent error. The following address(es) failed:
37620 The following text was generated during the delivery attempt(s):
37622 ------ This is a copy of the message, including all the headers.
37625 ------ The body of the message is $message_size characters long;
37627 ------ $bounce_return_size_limit or so are included here.
37630 .section "Customizing warning messages" "SECTcustwarn"
37631 .cindex "customizing" "warning message"
37632 .cindex "warning of delay" "customizing the message"
37633 The option &%warn_message_file%& can be pointed at a template file for use when
37634 warnings about message delays are created. In this case there are only three
37638 The first item is included in the headers, and should include at least a
37639 &'Subject:'& header. Exim does not check the syntax of these headers.
37641 The second item forms the start of the warning message. After it, Exim lists
37642 the delayed addresses.
37644 The third item then ends the message.
37647 The default state is equivalent to the following file, except that some lines
37648 have been split here, in order to fit them on the page:
37650 Subject: Warning: message $message_exim_id delayed
37651 $warn_message_delay
37653 This message was created automatically by mail delivery software.
37655 A message ${if eq{$sender_address}{$warn_message_recipients}
37656 {that you sent }{sent by
37660 }}has not been delivered to all of its recipients after
37661 more than $warn_message_delay in the queue on $primary_hostname.
37663 The message identifier is: $message_exim_id
37664 The subject of the message is: $h_subject
37665 The date of the message is: $h_date
37667 The following address(es) have not yet been delivered:
37669 No action is required on your part. Delivery attempts will
37670 continue for some time, and this warning may be repeated at
37671 intervals if the message remains undelivered. Eventually the
37672 mail delivery software will give up, and when that happens,
37673 the message will be returned to you.
37675 .vindex "&$warn_message_delay$&"
37676 .vindex "&$warn_message_recipients$&"
37677 However, in the default state the subject and date lines are omitted if no
37678 appropriate headers exist. During the expansion of this file,
37679 &$warn_message_delay$& is set to the delay time in one of the forms &"<&'n'&>
37680 minutes"& or &"<&'n'&> hours"&, and &$warn_message_recipients$& contains a list
37681 of recipients for the warning message. There may be more than one if there are
37682 multiple addresses with different &%errors_to%& settings on the routers that
37688 . ////////////////////////////////////////////////////////////////////////////
37689 . ////////////////////////////////////////////////////////////////////////////
37691 .chapter "Some common configuration settings" "CHAPcomconreq"
37692 This chapter discusses some configuration settings that seem to be fairly
37693 common. More examples and discussion can be found in the Exim book.
37697 .section "Sending mail to a smart host" "SECID240"
37698 .cindex "smart host" "example router"
37699 If you want to send all mail for non-local domains to a &"smart host"&, you
37700 should replace the default &(dnslookup)& router with a router which does the
37701 routing explicitly:
37703 send_to_smart_host:
37704 driver = manualroute
37705 route_list = !+local_domains smart.host.name
37706 transport = remote_smtp
37708 You can use the smart host's IP address instead of the name if you wish.
37709 If you are using Exim only to submit messages to a smart host, and not for
37710 receiving incoming messages, you can arrange for it to do the submission
37711 synchronously by setting the &%mua_wrapper%& option (see chapter
37712 &<<CHAPnonqueueing>>&).
37717 .section "Using Exim to handle mailing lists" "SECTmailinglists"
37718 .cindex "mailing lists"
37719 Exim can be used to run simple mailing lists, but for large and/or complicated
37720 requirements, the use of additional specialized mailing list software such as
37721 Majordomo or Mailman is recommended.
37723 The &(redirect)& router can be used to handle mailing lists where each list
37724 is maintained in a separate file, which can therefore be managed by an
37725 independent manager. The &%domains%& router option can be used to run these
37726 lists in a separate domain from normal mail. For example:
37730 domains = lists.example
37731 file = ${lookup {$local_part} dsearch,ret=full {/usr/lists}}
37734 errors_to = ${quote_local_part:$local_part-request}@lists.example
37737 This router is skipped for domains other than &'lists.example'&. For addresses
37738 in that domain, it looks for a file that matches the local part. If there is no
37739 such file, the router declines, but because &%no_more%& is set, no subsequent
37740 routers are tried, and so the whole delivery fails.
37742 The &%forbid_pipe%& and &%forbid_file%& options prevent a local part from being
37743 expanded into a filename or a pipe delivery, which is usually inappropriate in
37746 .oindex "&%errors_to%&"
37747 The &%errors_to%& option specifies that any delivery errors caused by addresses
37748 taken from a mailing list are to be sent to the given address rather than the
37749 original sender of the message. However, before acting on this, Exim verifies
37750 the error address, and ignores it if verification fails.
37752 For example, using the configuration above, mail sent to
37753 &'dicts@lists.example'& is passed on to those addresses contained in
37754 &_/usr/lists/dicts_&, with error reports directed to
37755 &'dicts-request@lists.example'&, provided that this address can be verified.
37756 There could be a file called &_/usr/lists/dicts-request_& containing
37757 the address(es) of this particular list's manager(s), but other approaches,
37758 such as setting up an earlier router (possibly using the &%local_part_prefix%&
37759 or &%local_part_suffix%& options) to handle addresses of the form
37760 &%owner-%&&'xxx'& or &%xxx-%&&'request'&, are also possible.
37764 .section "Syntax errors in mailing lists" "SECID241"
37765 .cindex "mailing lists" "syntax errors in"
37766 If an entry in redirection data contains a syntax error, Exim normally defers
37767 delivery of the original address. That means that a syntax error in a mailing
37768 list holds up all deliveries to the list. This may not be appropriate when a
37769 list is being maintained automatically from data supplied by users, and the
37770 addresses are not rigorously checked.
37772 If the &%skip_syntax_errors%& option is set, the &(redirect)& router just skips
37773 entries that fail to parse, noting the incident in the log. If in addition
37774 &%syntax_errors_to%& is set to a verifiable address, a message is sent to it
37775 whenever a broken address is skipped. It is usually appropriate to set
37776 &%syntax_errors_to%& to the same address as &%errors_to%&.
37780 .section "Re-expansion of mailing lists" "SECID242"
37781 .cindex "mailing lists" "re-expansion of"
37782 Exim remembers every individual address to which a message has been delivered,
37783 in order to avoid duplication, but it normally stores only the original
37784 recipient addresses with a message. If all the deliveries to a mailing list
37785 cannot be done at the first attempt, the mailing list is re-expanded when the
37786 delivery is next tried. This means that alterations to the list are taken into
37787 account at each delivery attempt, so addresses that have been added to
37788 the list since the message arrived will therefore receive a copy of the
37789 message, even though it pre-dates their subscription.
37791 If this behaviour is felt to be undesirable, the &%one_time%& option can be set
37792 on the &(redirect)& router. If this is done, any addresses generated by the
37793 router that fail to deliver at the first attempt are added to the message as
37794 &"top level"& addresses, and the parent address that generated them is marked
37795 &"delivered"&. Thus, expansion of the mailing list does not happen again at the
37796 subsequent delivery attempts. The disadvantage of this is that if any of the
37797 failing addresses are incorrect, correcting them in the file has no effect on
37798 pre-existing messages.
37800 The original top-level address is remembered with each of the generated
37801 addresses, and is output in any log messages. However, any intermediate parent
37802 addresses are not recorded. This makes a difference to the log only if the
37803 &%all_parents%& selector is set, but for mailing lists there is normally only
37804 one level of expansion anyway.
37808 .section "Closed mailing lists" "SECID243"
37809 .cindex "mailing lists" "closed"
37810 The examples so far have assumed open mailing lists, to which anybody may
37811 send mail. It is also possible to set up closed lists, where mail is accepted
37812 from specified senders only. This is done by making use of the generic
37813 &%senders%& option to restrict the router that handles the list.
37815 The following example uses the same file as a list of recipients and as a list
37816 of permitted senders. It requires three routers:
37820 domains = lists.example
37821 local_part_suffix = -request
37822 local_parts = ${lookup {$local_part} dsearch,filter=file {/usr/lists}}
37823 file = /usr/lists/${local_part_data}-request
37828 domains = lists.example
37829 local_parts = ${lookup {$local_part} dsearch,filter=file,ret=full {/usr/lists}}
37830 senders = ${if exists {$local_part_data} {lsearch;$local_part_data}{*}}
37831 file = ${lookup {$local_part} dsearch,ret=full {/usr/lists}}
37834 errors_to = ${quote_local_part:$local_part-request}@lists.example
37839 domains = lists.example
37841 data = :fail: $local_part@lists.example is a closed mailing list
37843 All three routers have the same &%domains%& setting, so for any other domains,
37844 they are all skipped. The first router runs only if the local part ends in
37845 &%-request%&. It handles messages to the list manager(s) by means of an open
37848 The second router runs only if the &%senders%& precondition is satisfied. It
37849 checks for the existence of a list that corresponds to the local part, and then
37850 checks that the sender is on the list by means of a linear search. It is
37851 necessary to check for the existence of the file before trying to search it,
37852 because otherwise Exim thinks there is a configuration error. If the file does
37853 not exist, the expansion of &%senders%& is *, which matches all senders. This
37854 means that the router runs, but because there is no list, declines, and
37855 &%no_more%& ensures that no further routers are run. The address fails with an
37856 &"unrouteable address"& error.
37858 The third router runs only if the second router is skipped, which happens when
37859 a mailing list exists, but the sender is not on it. This router forcibly fails
37860 the address, giving a suitable error message.
37865 .section "Variable Envelope Return Paths (VERP)" "SECTverp"
37867 .cindex "Variable Envelope Return Paths"
37868 .cindex "envelope from"
37869 .cindex "envelope sender"
37870 Variable Envelope Return Paths &-- see &url(https://cr.yp.to/proto/verp.txt) &--
37871 are a way of helping mailing list administrators discover which subscription
37872 address is the cause of a particular delivery failure. The idea is to encode
37873 the original recipient address in the outgoing envelope sender address, so that
37874 if the message is forwarded by another host and then subsequently bounces, the
37875 original recipient can be extracted from the recipient address of the bounce.
37877 .oindex &%errors_to%&
37878 .oindex &%return_path%&
37879 Envelope sender addresses can be modified by Exim using two different
37880 facilities: the &%errors_to%& option on a router (as shown in previous mailing
37881 list examples), or the &%return_path%& option on a transport. The second of
37882 these is effective only if the message is successfully delivered to another
37883 host; it is not used for errors detected on the local host (see the description
37884 of &%return_path%& in chapter &<<CHAPtransportgeneric>>&). Here is an example
37885 of the use of &%return_path%& to implement VERP on an &(smtp)& transport:
37891 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
37892 {${quote_local_part:$1-request+$local_part=$domain}@your.dom.example}fail}
37894 This has the effect of rewriting the return path (envelope sender) on outgoing
37895 SMTP messages, if the local part of the original return path ends in
37896 &"-request"&, and the domain is &'your.dom.example'&. The rewriting inserts the
37897 local part and domain of the recipient into the return path. Suppose, for
37898 example, that a message whose return path has been set to
37899 &'somelist-request@your.dom.example'& is sent to
37900 &'subscriber@other.dom.example'&. In the transport, the return path is
37903 somelist-request+subscriber=other.dom.example@your.dom.example
37905 .vindex "&$local_part$&"
37906 For this to work, you must tell Exim to send multiple copies of messages that
37907 have more than one recipient, so that each copy has just one recipient. This is
37908 achieved by setting &%max_rcpt%& to 1. Without this, a single copy of a message
37909 might be sent to several different recipients in the same domain, in which case
37910 &$local_part$& is not available in the transport, because it is not unique.
37912 Unless your host is doing nothing but mailing list deliveries, you should
37913 probably use a separate transport for the VERP deliveries, so as not to use
37914 extra resources in making one-per-recipient copies for other deliveries. This
37915 can easily be done by expanding the &%transport%& option in the router:
37919 domains = ! +local_domains
37921 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
37922 {verp_smtp}{remote_smtp}}
37925 If you want to change the return path using &%errors_to%& in a router instead
37926 of using &%return_path%& in the transport, you need to set &%errors_to%& on all
37927 routers that handle mailing list addresses. This will ensure that all delivery
37928 errors, including those detected on the local host, are sent to the VERP
37931 On a host that does no local deliveries and has no manual routing, only the
37932 &(dnslookup)& router needs to be changed. A special transport is not needed for
37933 SMTP deliveries. Every mailing list recipient has its own return path value,
37934 and so Exim must hand them to the transport one at a time. Here is an example
37935 of a &(dnslookup)& router that implements VERP:
37939 domains = ! +local_domains
37940 transport = remote_smtp
37942 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}}
37943 {${quote_local_part:$1-request+$local_part=$domain}@your.dom.example}fail}
37946 Before you start sending out messages with VERPed return paths, you must also
37947 configure Exim to accept the bounce messages that come back to those paths.
37948 Typically this is done by setting a &%local_part_suffix%& option for a
37949 router, and using this to route the messages to wherever you want to handle
37952 The overhead incurred in using VERP depends very much on the size of the
37953 message, the number of recipient addresses that resolve to the same remote
37954 host, and the speed of the connection over which the message is being sent. If
37955 a lot of addresses resolve to the same host and the connection is slow, sending
37956 a separate copy of the message for each address may take substantially longer
37957 than sending a single copy with many recipients (for which VERP cannot be
37965 .section "Virtual domains" "SECTvirtualdomains"
37966 .cindex "virtual domains"
37967 .cindex "domain" "virtual"
37968 The phrase &'virtual domain'& is unfortunately used with two rather different
37972 A domain for which there are no real mailboxes; all valid local parts are
37973 aliases for other email addresses. Common examples are organizational
37974 top-level domains and &"vanity"& domains.
37976 One of a number of independent domains that are all handled by the same host,
37977 with mailboxes on that host, but where the mailbox owners do not necessarily
37978 have login accounts on that host.
37981 The first usage is probably more common, and does seem more &"virtual"& than
37982 the second. This kind of domain can be handled in Exim with a straightforward
37983 aliasing router. One approach is to create a separate alias file for each
37984 virtual domain. Exim can test for the existence of the alias file to determine
37985 whether the domain exists. The &(dsearch)& lookup type is useful here, leading
37986 to a router of this form:
37990 domains = dsearch;/etc/mail/virtual
37991 data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain_data}}
37994 The &%domains%& option specifies that the router is to be skipped, unless there
37995 is a file in the &_/etc/mail/virtual_& directory whose name is the same as the
37996 domain that is being processed.
37997 The &(dsearch)& lookup used results in an untainted version of &$domain$&
37998 being placed into the &$domain_data$& variable.
38000 When the router runs, it looks up the local
38001 part in the file to find a new address (or list of addresses). The &%no_more%&
38002 setting ensures that if the lookup fails (leading to &%data%& being an empty
38003 string), Exim gives up on the address without trying any subsequent routers.
38005 This one router can handle all the virtual domains because the alias filenames
38006 follow a fixed pattern. Permissions can be arranged so that appropriate people
38007 can edit the different alias files. A successful aliasing operation results in
38008 a new envelope recipient address, which is then routed from scratch.
38010 The other kind of &"virtual"& domain can also be handled in a straightforward
38011 way. One approach is to create a file for each domain containing a list of
38012 valid local parts, and use it in a router like this:
38016 domains = dsearch;/etc/mail/domains
38017 local_parts = lsearch;/etc/mail/domains/$domain
38018 transport = my_mailboxes
38020 The address is accepted if there is a file for the domain, and the local part
38021 can be found in the file. The &%domains%& option is used to check for the
38022 file's existence because &%domains%& is tested before the &%local_parts%&
38023 option (see section &<<SECTrouprecon>>&). You cannot use &%require_files%&,
38024 because that option is tested after &%local_parts%&. The transport is as
38028 driver = appendfile
38029 file = /var/mail/$domain_data/$local_part_data
38032 This uses a directory of mailboxes for each domain. The &%user%& setting is
38033 required, to specify which uid is to be used for writing to the mailboxes.
38035 The configuration shown here is just one example of how you might support this
38036 requirement. There are many other ways this kind of configuration can be set
38037 up, for example, by using a database instead of separate files to hold all the
38038 information about the domains.
38042 .section "Multiple user mailboxes" "SECTmulbox"
38043 .cindex "multiple mailboxes"
38044 .cindex "mailbox" "multiple"
38045 .cindex "local part" "prefix"
38046 .cindex "local part" "suffix"
38047 Heavy email users often want to operate with multiple mailboxes, into which
38048 incoming mail is automatically sorted. A popular way of handling this is to
38049 allow users to use multiple sender addresses, so that replies can easily be
38050 identified. Users are permitted to add prefixes or suffixes to their local
38051 parts for this purpose. The wildcard facility of the generic router options
38052 &%local_part_prefix%& and &%local_part_suffix%& can be used for this. For
38053 example, consider this router:
38058 file = $home/.forward
38059 local_part_suffix = -*
38060 local_part_suffix_optional
38063 .vindex "&$local_part_suffix$&"
38064 It runs a user's &_.forward_& file for all local parts of the form
38065 &'username-*'&. Within the filter file the user can distinguish different
38066 cases by testing the variable &$local_part_suffix$&. For example:
38068 if $local_part_suffix contains -special then
38069 save /home/$local_part_data/Mail/special
38072 If the filter file does not exist, or does not deal with such addresses, they
38073 fall through to subsequent routers, and, assuming no subsequent use of the
38074 &%local_part_suffix%& option is made, they presumably fail. Thus, users have
38075 control over which suffixes are valid.
38077 Alternatively, a suffix can be used to trigger the use of a different
38078 &_.forward_& file &-- which is the way a similar facility is implemented in
38084 local_part_suffix = -*
38085 local_part_suffix_optional
38086 file = ${lookup {.forward$local_part_suffix} dsearch,ret=full {$home} {$value}fail}
38089 If there is no suffix, &_.forward_& is used; if the suffix is &'-special'&, for
38090 example, &_.forward-special_& is used. Once again, if the appropriate file
38091 does not exist, or does not deal with the address, it is passed on to
38092 subsequent routers, which could, if required, look for an unqualified
38093 &_.forward_& file to use as a default.
38097 .section "Simplified vacation processing" "SECID244"
38098 .cindex "vacation processing"
38099 The traditional way of running the &'vacation'& program is for a user to set up
38100 a pipe command in a &_.forward_& file
38101 (see section &<<SECTspecitredli>>& for syntax details).
38102 This is prone to error by inexperienced users. There are two features of Exim
38103 that can be used to make this process simpler for users:
38106 A local part prefix such as &"vacation-"& can be specified on a router which
38107 can cause the message to be delivered directly to the &'vacation'& program, or
38108 alternatively can use Exim's &(autoreply)& transport. The contents of a user's
38109 &_.forward_& file are then much simpler. For example:
38111 spqr, vacation-spqr
38114 The &%require_files%& generic router option can be used to trigger a
38115 vacation delivery by checking for the existence of a certain file in the
38116 user's home directory. The &%unseen%& generic option should also be used, to
38117 ensure that the original delivery also proceeds. In this case, all the user has
38118 to do is to create a file called, say, &_.vacation_&, containing a vacation
38122 Another advantage of both these methods is that they both work even when the
38123 use of arbitrary pipes by users is locked out.
38127 .section "Taking copies of mail" "SECID245"
38128 .cindex "message" "copying every"
38129 Some installations have policies that require archive copies of all messages to
38130 be made. A single copy of each message can easily be taken by an appropriate
38131 command in a system filter, which could, for example, use a different file for
38132 each day's messages.
38134 There is also a shadow transport mechanism that can be used to take copies of
38135 messages that are successfully delivered by local transports, one copy per
38136 delivery. This could be used, &'inter alia'&, to implement automatic
38137 notification of delivery by sites that insist on doing such things.
38141 .section "Intermittently connected hosts" "SECID246"
38142 .cindex "intermittently connected hosts"
38143 It has become quite common (because it is cheaper) for hosts to connect to the
38144 Internet periodically rather than remain connected all the time. The normal
38145 arrangement is that mail for such hosts accumulates on a system that is
38146 permanently connected.
38148 Exim was designed for use on permanently connected hosts, and so it is not
38149 particularly well-suited to use in an intermittently connected environment.
38150 Nevertheless there are some features that can be used.
38153 .section "Exim on the upstream server host" "SECID247"
38154 It is tempting to arrange for incoming mail for the intermittently connected
38155 host to remain in Exim's queue until the client connects. However, this
38156 approach does not scale very well. Two different kinds of waiting message are
38157 being mixed up in the same queue &-- those that cannot be delivered because of
38158 some temporary problem, and those that are waiting for their destination host
38159 to connect. This makes it hard to manage the queue, as well as wasting
38160 resources, because each queue runner scans the entire queue.
38162 A better approach is to separate off those messages that are waiting for an
38163 intermittently connected host. This can be done by delivering these messages
38164 into local files in batch SMTP, &"mailstore"&, or other envelope-preserving
38165 format, from where they are transmitted by other software when their
38166 destination connects. This makes it easy to collect all the mail for one host
38167 in a single directory, and to apply local timeout rules on a per-message basis
38170 On a very small scale, leaving the mail on Exim's queue can be made to work. If
38171 you are doing this, you should configure Exim with a long retry period for the
38172 intermittent host. For example:
38174 cheshire.wonderland.fict.example * F,5d,24h
38176 This stops a lot of failed delivery attempts from occurring, but Exim remembers
38177 which messages it has queued up for that host. Once the intermittent host comes
38178 online, forcing delivery of one message (either by using the &%-M%& or &%-R%&
38179 options, or by using the ETRN SMTP command (see section &<<SECTETRN>>&)
38180 causes all the queued up messages to be delivered, often down a single SMTP
38181 connection. While the host remains connected, any new messages get delivered
38184 If the connecting hosts do not have fixed IP addresses, that is, if a host is
38185 issued with a different IP address each time it connects, Exim's retry
38186 mechanisms on the holding host get confused, because the IP address is normally
38187 used as part of the key string for holding retry information. This can be
38188 avoided by unsetting &%retry_include_ip_address%& on the &(smtp)& transport.
38189 Since this has disadvantages for permanently connected hosts, it is best to
38190 arrange a separate transport for the intermittently connected ones.
38194 .section "Exim on the intermittently connected client host" "SECID248"
38195 The value of &%smtp_accept_queue_per_connection%& should probably be
38196 increased, or even set to zero (that is, disabled) on the intermittently
38197 connected host, so that all incoming messages down a single connection get
38198 delivered immediately.
38200 .cindex "SMTP" "passed connection"
38201 .cindex "SMTP" "multiple deliveries"
38202 .cindex "multiple SMTP deliveries"
38203 .cindex "first pass routing"
38204 Mail waiting to be sent from an intermittently connected host will probably
38205 not have been routed, because without a connection DNS lookups are not
38206 possible. This means that if a normal queue run is done at connection time,
38207 each message is likely to be sent in a separate SMTP session. This can be
38208 avoided by starting the queue run with a command line option beginning with
38209 &%-qq%& instead of &%-q%&. In this case, the queue is scanned twice. In the
38210 first pass, routing is done but no deliveries take place. The second pass is a
38211 normal queue run; since all the messages have been previously routed, those
38212 destined for the same host are likely to get sent as multiple deliveries in a
38213 single SMTP connection.
38217 . ////////////////////////////////////////////////////////////////////////////
38218 . ////////////////////////////////////////////////////////////////////////////
38220 .chapter "Using Exim as a non-queueing client" "CHAPnonqueueing" &&&
38221 "Exim as a non-queueing client"
38222 .cindex "client, non-queueing"
38223 .cindex "smart host" "suppressing queueing"
38224 On a personal computer, it is a common requirement for all
38225 email to be sent to a &"smart host"&. There are plenty of MUAs that can be
38226 configured to operate that way, for all the popular operating systems.
38227 However, there are some MUAs for Unix-like systems that cannot be so
38228 configured: they submit messages using the command line interface of
38229 &_/usr/sbin/sendmail_&. Furthermore, utility programs such as &'cron'& submit
38232 If the personal computer runs continuously, there is no problem, because it can
38233 run a conventional MTA that handles delivery to the smart host, and deal with
38234 any delays via its queueing mechanism. However, if the computer does not run
38235 continuously or runs different operating systems at different times, queueing
38236 email is not desirable.
38238 There is therefore a requirement for something that can provide the
38239 &_/usr/sbin/sendmail_& interface but deliver messages to a smart host without
38240 any queueing or retrying facilities. Furthermore, the delivery to the smart
38241 host should be synchronous, so that if it fails, the sending MUA is immediately
38242 informed. In other words, we want something that extends an MUA that submits
38243 to a local MTA via the command line so that it behaves like one that submits
38244 to a remote smart host using TCP/SMTP.
38246 There are a number of applications (for example, there is one called &'ssmtp'&)
38247 that do this job. However, people have found them to be lacking in various
38248 ways. For instance, you might want to allow aliasing and forwarding to be done
38249 before sending a message to the smart host.
38251 Exim already had the necessary infrastructure for doing this job. Just a few
38252 tweaks were needed to make it behave as required, though it is somewhat of an
38253 overkill to use a fully-featured MTA for this purpose.
38255 .oindex "&%mua_wrapper%&"
38256 There is a Boolean global option called &%mua_wrapper%&, defaulting false.
38257 Setting &%mua_wrapper%& true causes Exim to run in a special mode where it
38258 assumes that it is being used to &"wrap"& a command-line MUA in the manner
38259 just described. As well as setting &%mua_wrapper%&, you also need to provide a
38260 compatible router and transport configuration. Typically there will be just one
38261 router and one transport, sending everything to a smart host.
38263 When run in MUA wrapping mode, the behaviour of Exim changes in the
38267 A daemon cannot be run, nor will Exim accept incoming messages from &'inetd'&.
38268 In other words, the only way to submit messages is via the command line.
38270 Each message is synchronously delivered as soon as it is received (&%-odi%& is
38271 assumed). All queueing options (&%queue_only%&, &%queue_smtp_domains%&,
38272 &%control%& in an ACL, etc.) are quietly ignored. The Exim reception process
38273 does not finish until the delivery attempt is complete. If the delivery is
38274 successful, a zero return code is given.
38276 Address redirection is permitted, but the final routing for all addresses must
38277 be to the same remote transport, and to the same list of hosts. Furthermore,
38278 the return address (envelope sender) must be the same for all recipients, as
38279 must any added or deleted header lines. In other words, it must be possible to
38280 deliver the message in a single SMTP transaction, however many recipients there
38283 If these conditions are not met, or if routing any address results in a
38284 failure or defer status, or if Exim is unable to deliver all the recipients
38285 successfully to one of the smart hosts, delivery of the entire message fails.
38287 Because no queueing is allowed, all failures are treated as permanent; there
38288 is no distinction between 4&'xx'& and 5&'xx'& SMTP response codes from the
38289 smart host. Furthermore, because only a single yes/no response can be given to
38290 the caller, it is not possible to deliver to some recipients and not others. If
38291 there is an error (temporary or permanent) for any recipient, all are failed.
38293 If more than one smart host is listed, Exim will try another host after a
38294 connection failure or a timeout, in the normal way. However, if this kind of
38295 failure happens for all the hosts, the delivery fails.
38297 When delivery fails, an error message is written to the standard error stream
38298 (as well as to Exim's log), and Exim exits to the caller with a return code
38299 value 1. The message is expunged from Exim's spool files. No bounce messages
38300 are ever generated.
38302 No retry data is maintained, and any retry rules are ignored.
38304 A number of Exim options are overridden: &%deliver_drop_privilege%& is forced
38305 true, &%max_rcpt%& in the &(smtp)& transport is forced to &"unlimited"&,
38306 &%remote_max_parallel%& is forced to one, and fallback hosts are ignored.
38309 The overall effect is that Exim makes a single synchronous attempt to deliver
38310 the message, failing if there is any kind of problem. Because no local
38311 deliveries are done and no daemon can be run, Exim does not need root
38312 privilege. It should be possible to run it setuid to &'exim'& instead of setuid
38313 to &'root'&. See section &<<SECTrunexiwitpri>>& for a general discussion about
38314 the advantages and disadvantages of running without root privilege.
38319 . ////////////////////////////////////////////////////////////////////////////
38320 . ////////////////////////////////////////////////////////////////////////////
38322 .chapter "Log files" "CHAPlog"
38323 .scindex IIDloggen "log" "general description"
38324 .cindex "log" "types of"
38325 Exim writes three different logs, referred to as the main log, the reject log,
38330 The main log records the arrival of each message and each delivery in a single
38331 line in each case. The format is as compact as possible, in an attempt to keep
38332 down the size of log files. Two-character flag sequences make it easy to pick
38333 out these lines. A number of other events are recorded in the main log. Some of
38334 them are optional, in which case the &%log_selector%& option controls whether
38335 they are included or not. A Perl script called &'eximstats'&, which does simple
38336 analysis of main log files, is provided in the Exim distribution (see section
38337 &<<SECTmailstat>>&).
38339 .cindex "reject log"
38340 The reject log records information from messages that are rejected as a result
38341 of a configuration option (that is, for policy reasons).
38342 The first line of each rejection is a copy of the line that is also written to
38343 the main log. Then, if the message's header has been read at the time the log
38344 is written, its contents are written to this log. Only the original header
38345 lines are available; header lines added by ACLs are not logged. You can use the
38346 reject log to check that your policy controls are working correctly; on a busy
38347 host this may be easier than scanning the main log for rejection messages. You
38348 can suppress the writing of the reject log by setting &%write_rejectlog%&
38351 .cindex "panic log"
38352 .cindex "system log"
38353 When certain serious errors occur, Exim writes entries to its panic log. If the
38354 error is sufficiently disastrous, Exim bombs out afterwards. Panic log entries
38355 are usually written to the main log as well, but can get lost amid the mass of
38356 other entries. The panic log should be empty under normal circumstances. It is
38357 therefore a good idea to check it (or to have a &'cron'& script check it)
38358 regularly, in order to become aware of any problems. When Exim cannot open its
38359 panic log, it tries as a last resort to write to the system log (syslog). This
38360 is opened with LOG_PID+LOG_CONS and the facility code of LOG_MAIL. The
38361 message itself is written at priority LOG_CRIT.
38364 Every log line starts with a timestamp, in the format shown in the following
38365 example. Note that many of the examples shown in this chapter are line-wrapped.
38366 In the log file, this would be all on one line:
38368 2001-09-16 16:09:47 SMTP connection from [127.0.0.1] closed
38371 By default, the timestamps are in the local timezone. There are two
38372 ways of changing this:
38375 You can set the &%timezone%& option to a different time zone; in particular, if
38380 the timestamps will be in UTC (aka GMT).
38382 If you set &%log_timezone%& true, the time zone is added to the timestamp, for
38385 2003-04-25 11:17:07 +0100 Start queue run: pid=12762
38389 .cindex "log" "process ids in"
38390 .cindex "pid (process id)" "in log lines"
38391 Exim does not include its process id in log lines by default, but you can
38392 request that it does so by specifying the &`pid`& log selector (see section
38393 &<<SECTlogselector>>&). When this is set, the process id is output, in square
38394 brackets, immediately after the time and date.
38399 .section "Where the logs are written" "SECTwhelogwri"
38400 .cindex "log" "destination"
38401 .cindex "log" "to file"
38402 .cindex "log" "to syslog"
38404 The logs may be written to local files, or to syslog, or both. However, it
38405 should be noted that many syslog implementations use UDP as a transport, and
38406 are therefore unreliable in the sense that messages are not guaranteed to
38407 arrive at the loghost, nor is the ordering of messages necessarily maintained.
38408 It has also been reported that on large log files (tens of megabytes) you may
38409 need to tweak syslog to prevent it syncing the file with each write &-- on
38410 Linux this has been seen to make syslog take 90% plus of CPU time.
38412 The destination for Exim's logs is configured by setting LOG_FILE_PATH in
38413 &_Local/Makefile_& or by setting &%log_file_path%& in the runtime
38414 configuration. This latter string is expanded, so it can contain, for example,
38415 references to the host name:
38417 log_file_path = /var/log/$primary_hostname/exim_%slog
38419 It is generally advisable, however, to set the string in &_Local/Makefile_&
38420 rather than at runtime, because then the setting is available right from the
38421 start of Exim's execution. Otherwise, if there's something it wants to log
38422 before it has read the configuration file (for example, an error in the
38423 configuration file) it will not use the path you want, and may not be able to
38426 The value of LOG_FILE_PATH or &%log_file_path%& is a colon-separated
38427 list, currently limited to at most two items. This is one option where the
38428 facility for changing a list separator may not be used. The list must always be
38429 colon-separated. If an item in the list is &"syslog"& then syslog is used;
38430 otherwise the item must either be an absolute path, containing &`%s`& at the
38431 point where &"main"&, &"reject"&, or &"panic"& is to be inserted, or be empty,
38432 implying the use of a default path.
38434 When Exim encounters an empty item in the list, it searches the list defined by
38435 LOG_FILE_PATH, and uses the first item it finds that is neither empty nor
38436 &"syslog"&. This means that an empty item in &%log_file_path%& can be used to
38437 mean &"use the path specified at build time"&. If no such item exists, log
38438 files are written in the &_log_& subdirectory of the spool directory. This is
38439 equivalent to the setting:
38441 log_file_path = $spool_directory/log/%slog
38443 If you do not specify anything at build time or runtime,
38444 or if you unset the option at runtime (i.e. &`log_file_path = `&),
38445 that is where the logs are written.
38447 A log file path may also contain &`%D`& or &`%M`& if datestamped log filenames
38448 are in use &-- see section &<<SECTdatlogfil>>& below.
38450 Here are some examples of possible settings:
38452 &`LOG_FILE_PATH=syslog `& syslog only
38453 &`LOG_FILE_PATH=:syslog `& syslog and default path
38454 &`LOG_FILE_PATH=syslog : /usr/log/exim_%s `& syslog and specified path
38455 &`LOG_FILE_PATH=/usr/log/exim_%s `& specified path only
38457 If there are more than two paths in the list, the first is used and a panic
38462 .section "Logging to local files that are periodically &""cycled""&" "SECID285"
38463 .cindex "log" "cycling local files"
38464 .cindex "cycling logs"
38465 .cindex "&'exicyclog'&"
38466 .cindex "log" "local files; writing to"
38467 Some operating systems provide centralized and standardized methods for cycling
38468 log files. For those that do not, a utility script called &'exicyclog'& is
38469 provided (see section &<<SECTcyclogfil>>&). This renames and compresses the
38470 main and reject logs each time it is called. The maximum number of old logs to
38471 keep can be set. It is suggested this script is run as a daily &'cron'& job.
38473 An Exim delivery process opens the main log when it first needs to write to it,
38474 and it keeps the file open in case subsequent entries are required &-- for
38475 example, if a number of different deliveries are being done for the same
38476 message. However, remote SMTP deliveries can take a long time, and this means
38477 that the file may be kept open long after it is renamed if &'exicyclog'& or
38478 something similar is being used to rename log files on a regular basis. To
38479 ensure that a switch of log files is noticed as soon as possible, Exim calls
38480 &[stat()]& on the main log's name before reusing an open file, and if the file
38481 does not exist, or its inode has changed, the old file is closed and Exim
38482 tries to open the main log from scratch. Thus, an old log file may remain open
38483 for quite some time, but no Exim processes should write to it once it has been
38488 .section "Datestamped log files" "SECTdatlogfil"
38489 .cindex "log" "datestamped files"
38490 Instead of cycling the main and reject log files by renaming them
38491 periodically, some sites like to use files whose names contain a datestamp,
38492 for example, &_mainlog-20031225_&. The datestamp is in the form &_yyyymmdd_& or
38493 &_yyyymm_&. Exim has support for this way of working. It is enabled by setting
38494 the &%log_file_path%& option to a path that includes &`%D`& or &`%M`& at the
38495 point where the datestamp is required. For example:
38497 log_file_path = /var/spool/exim/log/%slog-%D
38498 log_file_path = /var/log/exim-%s-%D.log
38499 log_file_path = /var/spool/exim/log/%D-%slog
38500 log_file_path = /var/log/exim/%s.%M
38502 As before, &`%s`& is replaced by &"main"& or &"reject"&; the following are
38503 examples of names generated by the above examples:
38505 /var/spool/exim/log/mainlog-20021225
38506 /var/log/exim-reject-20021225.log
38507 /var/spool/exim/log/20021225-mainlog
38508 /var/log/exim/main.200212
38510 When this form of log file is specified, Exim automatically switches to new
38511 files at midnight. It does not make any attempt to compress old logs; you
38512 will need to write your own script if you require this. You should not
38513 run &'exicyclog'& with this form of logging.
38515 The location of the panic log is also determined by &%log_file_path%&, but it
38516 is not datestamped, because rotation of the panic log does not make sense.
38517 When generating the name of the panic log, &`%D`& or &`%M`& are removed from
38518 the string. In addition, if it immediately follows a slash, a following
38519 non-alphanumeric character is removed; otherwise a preceding non-alphanumeric
38520 character is removed. Thus, the four examples above would give these panic
38523 /var/spool/exim/log/paniclog
38524 /var/log/exim-panic.log
38525 /var/spool/exim/log/paniclog
38526 /var/log/exim/panic
38530 .section "Logging to syslog" "SECID249"
38531 .cindex "log" "syslog; writing to"
38532 The use of syslog does not change what Exim logs or the format of its messages,
38533 except in one respect. If &%syslog_timestamp%& is set false, the timestamps on
38534 Exim's log lines are omitted when these lines are sent to syslog. Apart from
38535 that, the same strings are written to syslog as to log files. The syslog
38536 &"facility"& is set to LOG_MAIL, and the program name to &"exim"&
38537 by default, but you can change these by setting the &%syslog_facility%& and
38538 &%syslog_processname%& options, respectively. If Exim was compiled with
38539 SYSLOG_LOG_PID set in &_Local/Makefile_& (this is the default in
38540 &_src/EDITME_&), then, on systems that permit it (all except ULTRIX), the
38541 LOG_PID flag is set so that the &[syslog()]& call adds the pid as well as
38542 the time and host name to each line.
38543 The three log streams are mapped onto syslog priorities as follows:
38546 &'mainlog'& is mapped to LOG_INFO
38548 &'rejectlog'& is mapped to LOG_NOTICE
38550 &'paniclog'& is mapped to LOG_ALERT
38553 Many log lines are written to both &'mainlog'& and &'rejectlog'&, and some are
38554 written to both &'mainlog'& and &'paniclog'&, so there will be duplicates if
38555 these are routed by syslog to the same place. You can suppress this duplication
38556 by setting &%syslog_duplication%& false.
38558 Exim's log lines can sometimes be very long, and some of its &'rejectlog'&
38559 entries contain multiple lines when headers are included. To cope with both
38560 these cases, entries written to syslog are split into separate &[syslog()]&
38561 calls at each internal newline, and also after a maximum of
38562 870 data characters. (This allows for a total syslog line length of 1024, when
38563 additions such as timestamps are added.) If you are running a syslog
38564 replacement that can handle lines longer than the 1024 characters allowed by
38565 RFC 3164, you should set
38567 SYSLOG_LONG_LINES=yes
38569 in &_Local/Makefile_& before building Exim. That stops Exim from splitting long
38570 lines, but it still splits at internal newlines in &'reject'& log entries.
38572 To make it easy to re-assemble split lines later, each component of a split
38573 entry starts with a string of the form [<&'n'&>/<&'m'&>] or [<&'n'&>\<&'m'&>]
38574 where <&'n'&> is the component number and <&'m'&> is the total number of
38575 components in the entry. The / delimiter is used when the line was split
38576 because it was too long; if it was split because of an internal newline, the \
38577 delimiter is used. For example, supposing the length limit to be 50 instead of
38578 870, the following would be the result of a typical rejection message to
38579 &'mainlog'& (LOG_INFO), each line in addition being preceded by the time, host
38580 name, and pid as added by syslog:
38582 [1/5] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected from
38583 [2/5] [127.0.0.1] (ph10): syntax error in 'From' header
38584 [3/5] when scanning for sender: missing or malformed lo
38585 [4/5] cal part in "<>" (envelope sender is <ph10@cam.exa
38588 The same error might cause the following lines to be written to &"rejectlog"&
38591 [1/18] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected fro
38592 [2/18] m [127.0.0.1] (ph10): syntax error in 'From' head
38593 [3/18] er when scanning for sender: missing or malformed
38594 [4/18] local part in "<>" (envelope sender is <ph10@cam
38596 [6\18] Recipients: ph10@some.domain.cam.example
38597 [7\18] P Received: from [127.0.0.1] (ident=ph10)
38598 [8\18] by xxxxx.cam.example with smtp (Exim 4.00)
38599 [9\18] id 16RdAL-0006pc-00
38600 [10/18] for ph10@cam.example; Mon, 16 Sep 2002 16:
38601 [11\18] 09:43 +0100
38603 [13\18] Subject: this is a test header
38604 [18\18] X-something: this is another header
38605 [15/18] I Message-Id: <E16RdAL-0006pc-00@xxxxx.cam.examp
38608 [18/18] Date: Mon, 16 Sep 2002 16:09:43 +0100
38610 Log lines that are neither too long nor contain newlines are written to syslog
38611 without modification.
38613 If only syslog is being used, the Exim monitor is unable to provide a log tail
38614 display, unless syslog is routing &'mainlog'& to a file on the local host and
38615 the environment variable EXIMON_LOG_FILE_PATH is set to tell the monitor
38620 .section "Log line flags" "SECID250"
38621 One line is written to the main log for each message received, and for each
38622 successful, unsuccessful, and delayed delivery. These lines can readily be
38623 picked out by the distinctive two-character flags that immediately follow the
38624 timestamp. The flags are:
38626 &`<=`& message arrival
38627 &`(=`& message fakereject
38628 &`=>`& normal message delivery
38629 &`->`& additional address in same delivery
38630 &`>>`& cutthrough message delivery
38631 &`*>`& delivery suppressed by &%-N%&
38632 &`**`& delivery failed; address bounced
38633 &`==`& delivery deferred; temporary problem
38637 .section "Logging message reception" "SECID251"
38638 .cindex "log" "reception line"
38639 The format of the single-line entry in the main log that is written for every
38640 message received is shown in the basic example below, which is split over
38641 several lines in order to fit it on the page:
38643 2002-10-31 08:57:53 16ZCW1-0005MB-00 <= kryten@dwarf.fict.example
38644 H=mailer.fict.example [192.168.123.123] U=exim
38645 P=smtp S=5678 id=<incoming message id>
38647 The address immediately following &"<="& is the envelope sender address. A
38648 bounce message is shown with the sender address &"<>"&, and if it is locally
38649 generated, this is followed by an item of the form
38653 which is a reference to the message that caused the bounce to be sent.
38657 For messages from other hosts, the H and U fields identify the remote host and
38658 record the RFC 1413 identity of the user that sent the message, if one was
38659 received. The number given in square brackets is the IP address of the sending
38660 host. If there is a single, unparenthesized host name in the H field, as
38661 above, it has been verified to correspond to the IP address (see the
38662 &%host_lookup%& option). If the name is in parentheses, it was the name quoted
38663 by the remote host in the SMTP HELO or EHLO command, and has not been
38664 verified. If verification yields a different name to that given for HELO or
38665 EHLO, the verified name appears first, followed by the HELO or EHLO
38666 name in parentheses.
38668 Misconfigured hosts (and mail forgers) sometimes put an IP address, with or
38669 without brackets, in the HELO or EHLO command, leading to entries in
38670 the log containing text like these examples:
38672 H=(10.21.32.43) [192.168.8.34]
38673 H=([10.21.32.43]) [192.168.8.34]
38675 This can be confusing. Only the final address in square brackets can be relied
38678 For locally generated messages (that is, messages not received over TCP/IP),
38679 the H field is omitted, and the U field contains the login name of the caller
38682 .cindex "authentication" "logging"
38683 .cindex "AUTH" "logging"
38684 For all messages, the P field specifies the protocol used to receive the
38685 message. This is the value that is stored in &$received_protocol$&. In the case
38686 of incoming SMTP messages, the value indicates whether or not any SMTP
38687 extensions (ESMTP), encryption, or authentication were used. If the SMTP
38688 session was encrypted, there is an additional X field that records the cipher
38689 suite that was used.
38691 .cindex log protocol
38692 The protocol is set to &"esmtpsa"& or &"esmtpa"& for messages received from
38693 hosts that have authenticated themselves using the SMTP AUTH command. The first
38694 value is used when the SMTP connection was encrypted (&"secure"&). In this case
38695 there is an additional item A= followed by the name of the authenticator that
38696 was used. If an authenticated identification was set up by the authenticator's
38697 &%server_set_id%& option, this is logged too, separated by a colon from the
38698 authenticator name.
38700 .cindex "size" "of message"
38701 The id field records the existing message id, if present. The size of the
38702 received message is given by the S field. When the message is delivered,
38703 headers may be removed or added, so that the size of delivered copies of the
38704 message may not correspond with this value (and indeed may be different to each
38707 The &%log_selector%& option can be used to request the logging of additional
38708 data when a message is received. See section &<<SECTlogselector>>& below.
38712 .section "Logging deliveries" "SECID252"
38713 .cindex "log" "delivery line"
38714 The format of the single-line entry in the main log that is written for every
38715 delivery is shown in one of the examples below, for local and remote
38716 deliveries, respectively. Each example has been split into multiple lines in order
38717 to fit it on the page:
38719 2002-10-31 08:59:13 16ZCW1-0005MB-00 => marv
38720 <marv@hitch.fict.example> R=localuser T=local_delivery
38721 2002-10-31 09:00:10 16ZCW1-0005MB-00 =>
38722 monk@holistic.fict.example R=dnslookup T=remote_smtp
38723 H=holistic.fict.example [192.168.234.234]
38725 For ordinary local deliveries, the original address is given in angle brackets
38726 after the final delivery address, which might be a pipe or a file. If
38727 intermediate address(es) exist between the original and the final address, the
38728 last of these is given in parentheses after the final address. The R and T
38729 fields record the router and transport that were used to process the address.
38731 If SMTP AUTH was used for the delivery there is an additional item A=
38732 followed by the name of the authenticator that was used.
38733 If an authenticated identification was set up by the authenticator's &%client_set_id%&
38734 option, this is logged too, as a second colon-separated list item.
38735 Optionally (see the &%smtp_mailauth%& &%log_selector%&) there may be a third list item.
38737 If a shadow transport was run after a successful local delivery, the log line
38738 for the successful delivery has an item added on the end, of the form
38740 &`ST=<`&&'shadow transport name'&&`>`&
38742 If the shadow transport did not succeed, the error message is put in
38743 parentheses afterwards.
38745 .cindex "asterisk" "after IP address"
38746 When more than one address is included in a single delivery (for example, two
38747 SMTP RCPT commands in one transaction) the second and subsequent addresses are
38748 flagged with &`->`& instead of &`=>`&. When two or more messages are delivered
38749 down a single SMTP connection, an asterisk follows the
38750 remote IP address (and port if enabled)
38751 in the log lines for the second and subsequent messages.
38752 When two or more messages are delivered down a single TLS connection, the
38753 DNS and some TLS-related information logged for the first message delivered
38754 will not be present in the log lines for the second and subsequent messages.
38755 TLS cipher information is still available.
38757 .cindex "delivery" "cutthrough; logging"
38758 .cindex "cutthrough" "logging"
38759 When delivery is done in cutthrough mode it is flagged with &`>>`& and the log
38760 line precedes the reception line, since cutthrough waits for a possible
38761 rejection from the destination in case it can reject the sourced item.
38763 The generation of a reply message by a filter file gets logged as a
38764 &"delivery"& to the addressee, preceded by &">"&.
38766 The &%log_selector%& option can be used to request the logging of additional
38767 data when a message is delivered. See section &<<SECTlogselector>>& below.
38770 .section "Discarded deliveries" "SECID253"
38771 .cindex "discarded messages"
38772 .cindex "message" "discarded"
38773 .cindex "delivery" "discarded; logging"
38774 When a message is discarded as a result of the command &"seen finish"& being
38775 obeyed in a filter file which generates no deliveries, a log entry of the form
38777 2002-12-10 00:50:49 16auJc-0001UB-00 => discarded
38778 <low.club@bridge.example> R=userforward
38780 is written, to record why no deliveries are logged. When a message is discarded
38781 because it is aliased to &":blackhole:"& the log line is like this:
38783 1999-03-02 09:44:33 10HmaX-0005vi-00 => :blackhole:
38784 <hole@nowhere.example> R=blackhole_router
38788 .section "Deferred deliveries" "SECID254"
38789 When a delivery is deferred, a line of the following form is logged:
38791 2002-12-19 16:20:23 16aiQz-0002Q5-00 == marvin@endrest.example
38792 R=dnslookup T=smtp defer (146): Connection refused
38794 In the case of remote deliveries, the error is the one that was given for the
38795 last IP address that was tried. Details of individual SMTP failures are also
38796 written to the log, so the above line would be preceded by something like
38798 2002-12-19 16:20:23 16aiQz-0002Q5-00 Failed to connect to
38799 mail1.endrest.example [192.168.239.239]: Connection refused
38801 When a deferred address is skipped because its retry time has not been reached,
38802 a message is written to the log, but this can be suppressed by setting an
38803 appropriate value in &%log_selector%&.
38807 .section "Delivery failures" "SECID255"
38808 .cindex "delivery" "failure; logging"
38809 If a delivery fails because an address cannot be routed, a line of the
38810 following form is logged:
38812 1995-12-19 16:20:23 0tRiQz-0002Q5-00 ** jim@trek99.example
38813 <jim@trek99.example>: unknown mail domain
38815 If a delivery fails at transport time, the router and transport are shown, and
38816 the response from the remote host is included, as in this example:
38818 2002-07-11 07:14:17 17SXDU-000189-00 ** ace400@pb.example
38819 R=dnslookup T=remote_smtp: SMTP error from remote mailer
38820 after pipelined RCPT TO:<ace400@pb.example>: host
38821 pbmail3.py.example [192.168.63.111]: 553 5.3.0
38822 <ace400@pb.example>...Addressee unknown
38824 The word &"pipelined"& indicates that the SMTP PIPELINING extension was being
38825 used. See &%hosts_avoid_esmtp%& in the &(smtp)& transport for a way of
38826 disabling PIPELINING. The log lines for all forms of delivery failure are
38827 flagged with &`**`&.
38831 .section "Fake deliveries" "SECID256"
38832 .cindex "delivery" "fake; logging"
38833 If a delivery does not actually take place because the &%-N%& option has been
38834 used to suppress it, a normal delivery line is written to the log, except that
38835 &"=>"& is replaced by &"*>"&.
38839 .section "Completion" "SECID257"
38842 2002-10-31 09:00:11 16ZCW1-0005MB-00 Completed
38844 is written to the main log when a message is about to be removed from the spool
38845 at the end of its processing.
38850 .section "Summary of Fields in Log Lines" "SECID258"
38851 .cindex "log" "summary of fields"
38852 A summary of the field identifiers that are used in log lines is shown in
38853 the following table:
38855 &`A `& authenticator name (and optional id and sender)
38856 &`C `& SMTP confirmation on delivery
38857 &` `& command list for &"no mail in SMTP session"&
38858 &`CV `& certificate verification status
38859 &`D `& duration of &"no mail in SMTP session"&
38860 &`DKIM`& domain verified in incoming message
38861 &`DN `& distinguished name from peer certificate
38862 &`DS `& DNSSEC secured lookups
38863 &`DT `& on &`=>`&, &'=='& and &'**'& lines: time taken for, or to attempt, a delivery
38864 &`F `& sender address (on delivery lines)
38865 &`H `& host name and IP address
38866 &`I `& local interface used
38867 &`id `& message id (from header) for incoming message
38868 &`K `& CHUNKING extension used
38869 &`L `& on &`<=`& and &`=>`& lines: PIPELINING extension used
38870 &`M8S `& 8BITMIME status for incoming message
38871 &`P `& on &`<=`& lines: protocol used
38872 &` `& on &`=>`& and &`**`& lines: return path
38873 &`PRDR`& PRDR extension used
38874 &`PRX `& on &`<=`& and &`=>`& lines: proxy address
38875 &`Q `& alternate queue name
38876 &`QT `& on &`=>`& lines: time spent on queue so far
38877 &` `& on &"Completed"& lines: time spent on queue
38878 &`R `& on &`<=`& lines: reference for local bounce
38879 &` `& on &`=>`& &`>>`& &`**`& and &`==`& lines: router name
38880 &`RT `& on &`<=`& lines: time taken for reception
38881 &`S `& size of message in bytes
38882 &`SNI `& server name indication from TLS client hello
38883 &`ST `& shadow transport name
38884 &`T `& on &`<=`& lines: message subject (topic)
38885 &`TFO `& connection took advantage of TCP Fast Open
38886 &` `& on &`=>`& &`**`& and &`==`& lines: transport name
38887 &`U `& local user or RFC 1413 identity
38888 &`X `& TLS cipher suite
38892 .section "Other log entries" "SECID259"
38893 Various other types of log entry are written from time to time. Most should be
38894 self-explanatory. Among the more common are:
38897 .cindex "retry" "time not reached"
38898 &'retry time not reached'&&~&~An address previously suffered a temporary error
38899 during routing or local delivery, and the time to retry has not yet arrived.
38900 This message is not written to an individual message log file unless it happens
38901 during the first delivery attempt.
38903 &'retry time not reached for any host'&&~&~An address previously suffered
38904 temporary errors during remote delivery, and the retry time has not yet arrived
38905 for any of the hosts to which it is routed.
38907 .cindex "spool directory" "file locked"
38908 &'spool file locked'&&~&~An attempt to deliver a message cannot proceed because
38909 some other Exim process is already working on the message. This can be quite
38910 common if queue running processes are started at frequent intervals. The
38911 &'exiwhat'& utility script can be used to find out what Exim processes are
38914 .cindex "error" "ignored"
38915 &'error ignored'&&~&~There are several circumstances that give rise to this
38918 Exim failed to deliver a bounce message whose age was greater than
38919 &%ignore_bounce_errors_after%&. The bounce was discarded.
38921 A filter file set up a delivery using the &"noerror"& option, and the delivery
38922 failed. The delivery was discarded.
38924 A delivery set up by a router configured with
38925 . ==== As this is a nested list, any displays it contains must be indented
38926 . ==== as otherwise they are too far to the left.
38930 failed. The delivery was discarded.
38933 .cindex DKIM "log line"
38934 &'DKIM: d='&&~&~Verbose results of a DKIM verification attempt, if enabled for
38935 logging and the message has a DKIM signature header.
38942 .section "Reducing or increasing what is logged" "SECTlogselector"
38943 .cindex "log" "selectors"
38944 By setting the &%log_selector%& global option, you can disable some of Exim's
38945 default logging, or you can request additional logging. The value of
38946 &%log_selector%& is made up of names preceded by plus or minus characters. For
38949 log_selector = +arguments -retry_defer
38951 The list of optional log items is in the following table, with the default
38952 selection marked by asterisks:
38954 &` 8bitmime `& received 8BITMIME status
38955 &`*acl_warn_skipped `& skipped &%warn%& statement in ACL
38956 &` address_rewrite `& address rewriting
38957 &` all_parents `& all parents in => lines
38958 &` arguments `& command line arguments
38959 &`*connection_reject `& connection rejections
38960 &`*delay_delivery `& immediate delivery delayed
38961 &` deliver_time `& time taken to attempt delivery
38962 &` delivery_size `& add &`S=`&&'nnn'& to => lines
38963 &`*dkim `& DKIM verified domain on <= lines
38964 &` dkim_verbose `& separate full DKIM verification result line, per signature
38965 &`*dnslist_defer `& defers of DNS list (aka RBL) lookups
38966 &` dnssec `& DNSSEC secured lookups
38967 &`*etrn `& ETRN commands
38968 &`*host_lookup_failed `& as it says
38969 &` ident_timeout `& timeout for ident connection
38970 &` incoming_interface `& local interface on <= and => lines
38971 &` incoming_port `& remote port on <= lines
38972 &`*lost_incoming_connection `& as it says (includes timeouts)
38973 &` millisec `& millisecond timestamps and RT,QT,DT,D times
38974 &`*msg_id `& on <= lines, Message-ID: header value
38975 &` msg_id_created `& on <= lines, Message-ID: header value when one had to be added
38976 &` outgoing_interface `& local interface on => lines
38977 &` outgoing_port `& add remote port to => lines
38978 &`*queue_run `& start and end queue runs
38979 &` queue_time `& time on queue for one recipient
38980 &`*queue_time_exclusive `& exclude recieve time from QT times
38981 &` queue_time_overall `& time on queue for whole message
38982 &` pid `& Exim process id
38983 &` pipelining `& PIPELINING use, on <= and => lines
38984 &` proxy `& proxy address on <= and => lines
38985 &` receive_time `& time taken to receive message
38986 &` received_recipients `& recipients on <= lines
38987 &` received_sender `& sender on <= lines
38988 &`*rejected_header `& header contents on reject log
38989 &`*retry_defer `& &"retry time not reached"&
38990 &` return_path_on_delivery `& put return path on => and ** lines
38991 &` sender_on_delivery `& add sender to => lines
38992 &`*sender_verify_fail `& sender verification failures
38993 &`*size_reject `& rejection because too big
38994 &`*skip_delivery `& delivery skipped in a queue run
38995 &`*smtp_confirmation `& SMTP confirmation on => lines
38996 &` smtp_connection `& incoming SMTP connections
38997 &` smtp_incomplete_transaction`& incomplete SMTP transactions
38998 &` smtp_mailauth `& AUTH argument to MAIL commands
38999 &` smtp_no_mail `& session with no MAIL commands
39000 &` smtp_protocol_error `& SMTP protocol errors
39001 &` smtp_syntax_error `& SMTP syntax errors
39002 &` subject `& contents of &'Subject:'& on <= lines
39003 &`*tls_certificate_verified `& certificate verification status
39004 &`*tls_cipher `& TLS cipher suite on <= and => lines
39005 &` tls_peerdn `& TLS peer DN on <= and => lines
39006 &` tls_resumption `& append * to cipher field
39007 &` tls_sni `& TLS SNI on <= lines
39008 &` unknown_in_list `& DNS lookup failed in list match
39010 &` all `& all of the above
39012 See also the &%slow_lookup_log%& main configuration option,
39013 section &<<SECID99>>&
39015 More details on each of these items follows:
39019 .cindex "log" "8BITMIME"
39020 &%8bitmime%&: This causes Exim to log any 8BITMIME status of received messages,
39021 which may help in tracking down interoperability issues with ancient MTAs
39022 that are not 8bit clean. This is added to the &"<="& line, tagged with
39023 &`M8S=`& and a value of &`0`&, &`7`& or &`8`&, corresponding to "not given",
39024 &`7BIT`& and &`8BITMIME`& respectively.
39026 .cindex "&%warn%& ACL verb" "log when skipping"
39027 &%acl_warn_skipped%&: When an ACL &%warn%& statement is skipped because one of
39028 its conditions cannot be evaluated, a log line to this effect is written if
39029 this log selector is set.
39031 .cindex "log" "rewriting"
39032 .cindex "rewriting" "logging"
39033 &%address_rewrite%&: This applies both to global rewrites and per-transport
39034 rewrites, but not to rewrites in filters run as an unprivileged user (because
39035 such users cannot access the log).
39037 .cindex "log" "full parentage"
39038 &%all_parents%&: Normally only the original and final addresses are logged on
39039 delivery lines; with this selector, intermediate parents are given in
39040 parentheses between them.
39042 .cindex "log" "Exim arguments"
39043 .cindex "Exim arguments, logging"
39044 &%arguments%&: This causes Exim to write the arguments with which it was called
39045 to the main log, preceded by the current working directory. This is a debugging
39046 feature, added to make it easier to find out how certain MUAs call
39047 &_/usr/sbin/sendmail_&. The logging does not happen if Exim has given up root
39048 privilege because it was called with the &%-C%& or &%-D%& options. Arguments
39049 that are empty or that contain white space are quoted. Non-printing characters
39050 are shown as escape sequences. This facility cannot log unrecognized arguments,
39051 because the arguments are checked before the configuration file is read. The
39052 only way to log such cases is to interpose a script such as &_util/logargs.sh_&
39053 between the caller and Exim.
39055 .cindex "log" "connection rejections"
39056 &%connection_reject%&: A log entry is written whenever an incoming SMTP
39057 connection is rejected, for whatever reason.
39059 .cindex "log" "delayed delivery"
39060 .cindex "delayed delivery, logging"
39061 &%delay_delivery%&: A log entry is written whenever a delivery process is not
39062 started for an incoming message because the load is too high or too many
39063 messages were received on one connection. Logging does not occur if no delivery
39064 process is started because &%queue_only%& is set or &%-odq%& was used.
39066 .cindex "log" "delivery duration"
39067 &%deliver_time%&: For each delivery, the amount of real time it has taken to
39068 perform the actual delivery is logged as DT=<&'time'&>, for example, &`DT=1s`&.
39069 If millisecond logging is enabled, short times will be shown with greater
39070 precision, eg. &`DT=0.304s`&.
39072 .cindex "log" "message size on delivery"
39073 .cindex "size" "of message"
39074 &%delivery_size%&: For each delivery, the size of message delivered is added to
39075 the &"=>"& line, tagged with S=.
39077 .cindex log "DKIM verification"
39078 .cindex DKIM "verification logging"
39079 &%dkim%&: For message acceptance log lines, when an DKIM signature in the header
39080 verifies successfully a tag of DKIM is added, with one of the verified domains.
39082 .cindex log "DKIM verification"
39083 .cindex DKIM "verification logging"
39084 &%dkim_verbose%&: A log entry is written for each attempted DKIM verification.
39086 .cindex "log" "dnslist defer"
39087 .cindex "DNS list" "logging defer"
39088 .cindex "black list (DNS)"
39089 &%dnslist_defer%&: A log entry is written if an attempt to look up a host in a
39090 DNS black list suffers a temporary error.
39093 .cindex dnssec logging
39094 &%dnssec%&: For message acceptance and (attempted) delivery log lines, when
39095 dns lookups gave secure results a tag of DS is added.
39096 For acceptance this covers the reverse and forward lookups for host name verification.
39097 It does not cover helo-name verification.
39098 For delivery this covers the SRV, MX, A and/or AAAA lookups.
39100 .cindex "log" "ETRN commands"
39101 .cindex "ETRN" "logging"
39102 &%etrn%&: Every valid ETRN command that is received is logged, before the ACL
39103 is run to determine whether or not it is actually accepted. An invalid ETRN
39104 command, or one received within a message transaction is not logged by this
39105 selector (see &%smtp_syntax_error%& and &%smtp_protocol_error%&).
39107 .cindex "log" "host lookup failure"
39108 &%host_lookup_failed%&: When a lookup of a host's IP addresses fails to find
39109 any addresses, or when a lookup of an IP address fails to find a host name, a
39110 log line is written. This logging does not apply to direct DNS lookups when
39111 routing email addresses, but it does apply to &"byname"& lookups.
39113 .cindex "log" "ident timeout"
39114 .cindex "RFC 1413" "logging timeout"
39115 &%ident_timeout%&: A log line is written whenever an attempt to connect to a
39116 client's ident port times out.
39118 .cindex "log" "incoming interface"
39119 .cindex "log" "outgoing interface"
39120 .cindex "log" "local interface"
39121 .cindex "log" "local address and port"
39122 .cindex "TCP/IP" "logging local address and port"
39123 .cindex "interface" "logging"
39124 &%incoming_interface%&: The interface on which a message was received is added
39125 to the &"<="& line as an IP address in square brackets, tagged by I= and
39126 followed by a colon and the port number. The local interface and port are also
39127 added to other SMTP log lines, for example, &"SMTP connection from"&, to
39128 rejection lines, and (despite the name) to outgoing
39129 &"=>"&, &"->"&, &"=="& and &"**"& lines.
39130 The latter can be disabled by turning off the &%outgoing_interface%& option.
39132 .cindex log "incoming proxy address"
39133 .cindex proxy "logging proxy address"
39134 .cindex "TCP/IP" "logging proxy address"
39135 &%proxy%&: The internal (closest to the system running Exim) IP address
39136 of the proxy, tagged by PRX=, on the &"<="& line for a message accepted
39137 on a proxied connection
39138 or the &"=>"& line for a message delivered on a proxied connection.
39139 See &<<SECTproxyInbound>>& for more information.
39141 .cindex "log" "incoming remote port"
39142 .cindex "port" "logging remote"
39143 .cindex "TCP/IP" "logging incoming remote port"
39144 .vindex "&$sender_fullhost$&"
39145 .vindex "&$sender_rcvhost$&"
39146 &%incoming_port%&: The remote port number from which a message was received is
39147 added to log entries and &'Received:'& header lines, following the IP address
39148 in square brackets, and separated from it by a colon. This is implemented by
39149 changing the value that is put in the &$sender_fullhost$& and
39150 &$sender_rcvhost$& variables. Recording the remote port number has become more
39151 important with the widening use of NAT (see RFC 2505).
39153 .cindex "log" "dropped connection"
39154 &%lost_incoming_connection%&: A log line is written when an incoming SMTP
39155 connection is unexpectedly dropped.
39157 .cindex "log" "millisecond timestamps"
39158 .cindex millisecond logging
39159 .cindex timestamps "millisecond, in logs"
39160 &%millisec%&: Timestamps have a period and three decimal places of finer granularity
39161 appended to the seconds value.
39163 .cindex "log" "message id"
39164 &%msg_id%&: The value of the Message-ID: header.
39166 &%msg_id_created%&: The value of the Message-ID: header, when one had to be created.
39167 This will be either because the message is a bounce, or was submitted locally
39168 (submission mode) without one.
39169 The field identifier will have an asterix appended: &"id*="&.
39171 .cindex "log" "outgoing interface"
39172 .cindex "log" "local interface"
39173 .cindex "log" "local address and port"
39174 .cindex "TCP/IP" "logging local address and port"
39175 .cindex "interface" "logging"
39176 &%outgoing_interface%&: If &%incoming_interface%& is turned on, then the
39177 interface on which a message was sent is added to delivery lines as an I= tag
39178 followed by IP address in square brackets. You can disable this by turning
39179 off the &%outgoing_interface%& option.
39181 .cindex "log" "outgoing remote port"
39182 .cindex "port" "logging outgoing remote"
39183 .cindex "TCP/IP" "logging outgoing remote port"
39184 &%outgoing_port%&: The remote port number is added to delivery log lines (those
39185 containing => tags) following the IP address.
39186 The local port is also added if &%incoming_interface%& and
39187 &%outgoing_interface%& are both enabled.
39188 This option is not included in the default setting, because for most ordinary
39189 configurations, the remote port number is always 25 (the SMTP port), and the
39190 local port is a random ephemeral port.
39192 .cindex "log" "process ids in"
39193 .cindex "pid (process id)" "in log lines"
39194 &%pid%&: The current process id is added to every log line, in square brackets,
39195 immediately after the time and date.
39197 .cindex log pipelining
39198 .cindex pipelining "logging outgoing"
39199 &%pipelining%&: A field is added to delivery and accept
39200 log lines when the ESMTP PIPELINING extension was used.
39201 The field is a single "L".
39203 On accept lines, where PIPELINING was offered but not used by the client,
39204 the field has a minus appended.
39206 .cindex "pipelining" "early connection"
39207 If Exim is built with the SUPPORT_PIPE_CONNECT build option
39208 accept "L" fields have a period appended if the feature was
39209 offered but not used, or an asterisk appended if used.
39210 Delivery "L" fields have an asterisk appended if used.
39213 .cindex "log" "queue run"
39214 .cindex "queue runner" "logging"
39215 &%queue_run%&: The start and end of every queue run are logged.
39217 .cindex "log" "queue time"
39218 &%queue_time%&: The amount of time the message has been in the queue on the
39219 local host is logged as QT=<&'time'&> on delivery (&`=>`&) lines, for example,
39221 If millisecond logging is enabled, short times will be shown with greater
39222 precision, eg. &`QT=1.578s`&.
39224 &%queue_time_overall%&: The amount of time the message has been in the queue on
39225 the local host is logged as QT=<&'time'&> on &"Completed"& lines, for
39226 example, &`QT=3m45s`&.
39228 .cindex "log" "receive duration"
39229 &%receive_time%&: For each message, the amount of real time it has taken to
39230 perform the reception is logged as RT=<&'time'&>, for example, &`RT=1s`&.
39231 If millisecond logging is enabled, short times will be shown with greater
39232 precision, eg. &`RT=0.204s`&.
39234 .cindex "log" "recipients"
39235 &%received_recipients%&: The recipients of a message are listed in the main log
39236 as soon as the message is received. The list appears at the end of the log line
39237 that is written when a message is received, preceded by the word &"for"&. The
39238 addresses are listed after they have been qualified, but before any rewriting
39240 Recipients that were discarded by an ACL for MAIL or RCPT do not appear
39243 .cindex "log" "sender reception"
39244 &%received_sender%&: The unrewritten original sender of a message is added to
39245 the end of the log line that records the message's arrival, after the word
39246 &"from"& (before the recipients if &%received_recipients%& is also set).
39248 .cindex "log" "header lines for rejection"
39249 &%rejected_header%&: If a message's header has been received at the time a
39250 rejection is written to the reject log, the complete header is added to the
39251 log. Header logging can be turned off individually for messages that are
39252 rejected by the &[local_scan()]& function (see section &<<SECTapiforloc>>&).
39254 .cindex "log" "retry defer"
39255 &%retry_defer%&: A log line is written if a delivery is deferred because a
39256 retry time has not yet been reached. However, this &"retry time not reached"&
39257 message is always omitted from individual message logs after the first delivery
39260 .cindex "log" "return path"
39261 &%return_path_on_delivery%&: The return path that is being transmitted with
39262 the message is included in delivery and bounce lines, using the tag P=.
39263 This is omitted if no delivery actually happens, for example, if routing fails,
39264 or if delivery is to &_/dev/null_& or to &`:blackhole:`&.
39266 .cindex "log" "sender on delivery"
39267 &%sender_on_delivery%&: The message's sender address is added to every delivery
39268 and bounce line, tagged by F= (for &"from"&).
39269 This is the original sender that was received with the message; it is not
39270 necessarily the same as the outgoing return path.
39272 .cindex "log" "sender verify failure"
39273 &%sender_verify_fail%&: If this selector is unset, the separate log line that
39274 gives details of a sender verification failure is not written. Log lines for
39275 the rejection of SMTP commands contain just &"sender verify failed"&, so some
39278 .cindex "log" "size rejection"
39279 &%size_reject%&: A log line is written whenever a message is rejected because
39282 .cindex "log" "frozen messages; skipped"
39283 .cindex "frozen messages" "logging skipping"
39284 &%skip_delivery%&: A log line is written whenever a message is skipped during a
39285 queue run because it another process is already delivering it or because
39287 .cindex "&""spool file is locked""&"
39288 .cindex "&""message is frozen""&"
39289 The message that is written is either &"spool file is locked"& or
39290 &"message is frozen"&.
39292 .cindex "log" "smtp confirmation"
39293 .cindex "SMTP" "logging confirmation"
39294 .cindex "LMTP" "logging confirmation"
39295 &%smtp_confirmation%&: The response to the final &"."& in the SMTP or LMTP dialogue for
39296 outgoing messages is added to delivery log lines in the form &`C=`&<&'text'&>.
39297 A number of MTAs (including Exim) return an identifying string in this
39300 .cindex "log" "SMTP connections"
39301 .cindex "SMTP" "logging connections"
39302 &%smtp_connection%&: A log line is written whenever an incoming SMTP connection is
39303 established or closed, unless the connection is from a host that matches
39304 &%hosts_connection_nolog%&. (In contrast, &%lost_incoming_connection%& applies
39305 only when the closure is unexpected.) This applies to connections from local
39306 processes that use &%-bs%& as well as to TCP/IP connections. If a connection is
39307 dropped in the middle of a message, a log line is always written, whether or
39308 not this selector is set, but otherwise nothing is written at the start and end
39309 of connections unless this selector is enabled.
39311 For TCP/IP connections to an Exim daemon, the current number of connections is
39312 included in the log message for each new connection, but note that the count is
39313 reset if the daemon is restarted.
39314 Also, because connections are closed (and the closure is logged) in
39315 subprocesses, the count may not include connections that have been closed but
39316 whose termination the daemon has not yet noticed. Thus, while it is possible to
39317 match up the opening and closing of connections in the log, the value of the
39318 logged counts may not be entirely accurate.
39320 .cindex "log" "SMTP transaction; incomplete"
39321 .cindex "SMTP" "logging incomplete transactions"
39322 &%smtp_incomplete_transaction%&: When a mail transaction is aborted by
39323 RSET, QUIT, loss of connection, or otherwise, the incident is logged,
39324 and the message sender plus any accepted recipients are included in the log
39325 line. This can provide evidence of dictionary attacks.
39327 .cindex "log" "non-MAIL SMTP sessions"
39328 .cindex "MAIL" "logging session without"
39329 &%smtp_no_mail%&: A line is written to the main log whenever an accepted SMTP
39330 connection terminates without having issued a MAIL command. This includes both
39331 the case when the connection is dropped, and the case when QUIT is used. It
39332 does not include cases where the connection is rejected right at the start (by
39333 an ACL, or because there are too many connections, or whatever). These cases
39334 already have their own log lines.
39336 The log line that is written contains the identity of the client in the usual
39337 way, followed by D= and a time, which records the duration of the connection.
39338 If the connection was authenticated, this fact is logged exactly as it is for
39339 an incoming message, with an A= item. If the connection was encrypted, CV=,
39340 DN=, and X= items may appear as they do for an incoming message, controlled by
39341 the same logging options.
39343 Finally, if any SMTP commands were issued during the connection, a C= item
39344 is added to the line, listing the commands that were used. For example,
39348 shows that the client issued QUIT straight after EHLO. If there were fewer
39349 than 20 commands, they are all listed. If there were more than 20 commands,
39350 the last 20 are listed, preceded by &"..."&. However, with the default
39351 setting of 10 for &%smtp_accept_max_nonmail%&, the connection will in any case
39352 have been aborted before 20 non-mail commands are processed.
39354 &%smtp_mailauth%&: A third subfield with the authenticated sender,
39355 colon-separated, is appended to the A= item for a message arrival or delivery
39356 log line, if an AUTH argument to the SMTP MAIL command (see &<<SECTauthparamail>>&)
39357 was accepted or used.
39359 .cindex "log" "SMTP protocol error"
39360 .cindex "SMTP" "logging protocol error"
39361 &%smtp_protocol_error%&: A log line is written for every SMTP protocol error
39362 encountered. Exim does not have perfect detection of all protocol errors
39363 because of transmission delays and the use of pipelining. If PIPELINING has
39364 been advertised to a client, an Exim server assumes that the client will use
39365 it, and therefore it does not count &"expected"& errors (for example, RCPT
39366 received after rejecting MAIL) as protocol errors.
39368 .cindex "SMTP" "logging syntax errors"
39369 .cindex "SMTP" "syntax errors; logging"
39370 .cindex "SMTP" "unknown command; logging"
39371 .cindex "log" "unknown SMTP command"
39372 .cindex "log" "SMTP syntax error"
39373 &%smtp_syntax_error%&: A log line is written for every SMTP syntax error
39374 encountered. An unrecognized command is treated as a syntax error. For an
39375 external connection, the host identity is given; for an internal connection
39376 using &%-bs%& the sender identification (normally the calling user) is given.
39378 .cindex "log" "subject"
39379 .cindex "subject, logging"
39380 &%subject%&: The subject of the message is added to the arrival log line,
39381 preceded by &"T="& (T for &"topic"&, since S is already used for &"size"&).
39382 Any MIME &"words"& in the subject are decoded. The &%print_topbitchars%& option
39383 specifies whether characters with values greater than 127 should be logged
39384 unchanged, or whether they should be rendered as escape sequences.
39386 .cindex "log" "certificate verification"
39388 .cindex DANE logging
39389 &%tls_certificate_verified%&: An extra item is added to <= and => log lines
39390 when TLS is in use. The item is &`CV=yes`& if the peer's certificate was
39392 using a CA trust anchor,
39393 &`CV=dane`& if using a DNS trust anchor,
39394 and &`CV=no`& if not.
39396 .cindex "log" "TLS cipher"
39397 .cindex "TLS" "logging cipher"
39398 &%tls_cipher%&: When a message is sent or received over an encrypted
39399 connection, the cipher suite used is added to the log line, preceded by X=.
39401 .cindex "log" "TLS peer DN"
39402 .cindex "TLS" "logging peer DN"
39403 &%tls_peerdn%&: When a message is sent or received over an encrypted
39404 connection, and a certificate is supplied by the remote host, the peer DN is
39405 added to the log line, preceded by DN=.
39407 .cindex "log" "TLS resumption"
39408 .cindex "TLS" "logging session resumption"
39409 &%tls_resumption%&: When a message is sent or received over an encrypted
39410 connection and the TLS session resumed one used on a previous TCP connection,
39411 an asterisk is appended to the X= cipher field in the log line.
39413 .cindex "log" "TLS SNI"
39414 .cindex "TLS" "logging SNI"
39415 .cindex SNI logging
39416 &%tls_sni%&: When a message is received over an encrypted connection, and
39417 the remote host provided the Server Name Indication extension, the SNI is
39418 added to the log line, preceded by SNI=.
39420 .cindex "log" "DNS failure in list"
39421 &%unknown_in_list%&: This setting causes a log entry to be written when the
39422 result of a list match is failure because a DNS lookup failed.
39426 .section "Message log" "SECID260"
39427 .cindex "message" "log file for"
39428 .cindex "log" "message log; description of"
39429 .cindex "&_msglog_& directory"
39430 .oindex "&%preserve_message_logs%&"
39431 In addition to the general log files, Exim writes a log file for each message
39432 that it handles. The names of these per-message logs are the message ids, and
39433 they are kept in the &_msglog_& sub-directory of the spool directory. Each
39434 message log contains copies of the log lines that apply to the message. This
39435 makes it easier to inspect the status of an individual message without having
39436 to search the main log. A message log is deleted when processing of the message
39437 is complete, unless &%preserve_message_logs%& is set, but this should be used
39438 only with great care because they can fill up your disk very quickly.
39440 On a heavily loaded system, it may be desirable to disable the use of
39441 per-message logs, in order to reduce disk I/O. This can be done by setting the
39442 &%message_logs%& option false.
39448 . ////////////////////////////////////////////////////////////////////////////
39449 . ////////////////////////////////////////////////////////////////////////////
39451 .chapter "Exim utilities" "CHAPutils"
39452 .scindex IIDutils "utilities"
39453 A number of utility scripts and programs are supplied with Exim and are
39454 described in this chapter. There is also the Exim Monitor, which is covered in
39455 the next chapter. The utilities described here are:
39457 .itable none 0 0 3 7* left 15* left 40* left
39458 .irow &<<SECTfinoutwha>>& &'exiwhat'& &&&
39459 "list what Exim processes are doing"
39460 .irow &<<SECTgreptheque>>& &'exiqgrep'& "grep the queue"
39461 .irow &<<SECTsumtheque>>& &'exiqsumm'& "summarize the queue"
39462 .irow &<<SECTextspeinf>>& &'exigrep'& "search the main log"
39463 .irow &<<SECTexipick>>& &'exipick'& "select messages on &&&
39465 .irow &<<SECTcyclogfil>>& &'exicyclog'& "cycle (rotate) log files"
39466 .irow &<<SECTmailstat>>& &'eximstats'& &&&
39467 "extract statistics from the log"
39468 .irow &<<SECTcheckaccess>>& &'exim_checkaccess'& &&&
39469 "check address acceptance from given IP"
39470 .irow &<<SECTdbmbuild>>& &'exim_dbmbuild'& "build a DBM file"
39471 .irow &<<SECTfinindret>>& &'exinext'& "extract retry information"
39472 .irow &<<SECTdumpdb>>& &'exim_dumpdb'& "dump a hints database"
39473 .irow &<<SECTtidydb>>& &'exim_tidydb'& "clean up a hints database"
39474 .irow &<<SECTfixdb>>& &'exim_fixdb'& "patch a hints database"
39475 .irow &<<SECTmailboxmaint>>& &'exim_lock'& "lock a mailbox file"
39478 Another utility that might be of use to sites with many MTAs is Tom Kistner's
39479 &'exilog'&. It provides log visualizations across multiple Exim servers. See
39480 &url(https://duncanthrax.net/exilog/) for details.
39485 .section "Finding out what Exim processes are doing (exiwhat)" "SECTfinoutwha"
39486 .cindex "&'exiwhat'&"
39487 .cindex "process, querying"
39489 On operating systems that can restart a system call after receiving a signal
39490 (most modern OS), an Exim process responds to the SIGUSR1 signal by writing
39491 a line describing what it is doing to the file &_exim-process.info_& in the
39492 Exim spool directory. The &'exiwhat'& script sends the signal to all Exim
39493 processes it can find, having first emptied the file. It then waits for one
39494 second to allow the Exim processes to react before displaying the results. In
39495 order to run &'exiwhat'& successfully you have to have sufficient privilege to
39496 send the signal to the Exim processes, so it is normally run as root.
39498 &*Warning*&: This is not an efficient process. It is intended for occasional
39499 use by system administrators. It is not sensible, for example, to set up a
39500 script that sends SIGUSR1 signals to Exim processes at short intervals.
39503 Unfortunately, the &'ps'& command that &'exiwhat'& uses to find Exim processes
39504 varies in different operating systems. Not only are different options used,
39505 but the format of the output is different. For this reason, there are some
39506 system configuration options that configure exactly how &'exiwhat'& works. If
39507 it doesn't seem to be working for you, check the following compile-time
39510 &`EXIWHAT_PS_CMD `& the command for running &'ps'&
39511 &`EXIWHAT_PS_ARG `& the argument for &'ps'&
39512 &`EXIWHAT_EGREP_ARG `& the argument for &'egrep'& to select from &'ps'& output
39513 &`EXIWHAT_KILL_ARG `& the argument for the &'kill'& command
39515 An example of typical output from &'exiwhat'& is
39517 164 daemon: -q1h, listening on port 25
39518 10483 running queue: waiting for 0tAycK-0002ij-00 (10492)
39519 10492 delivering 0tAycK-0002ij-00 to mail.ref.example
39520 [10.19.42.42] (editor@ref.example)
39521 10592 handling incoming call from [192.168.243.242]
39522 10628 accepting a local non-SMTP message
39524 The first number in the output line is the process number. The third line has
39525 been split here, in order to fit it on the page.
39529 .section "Selective queue listing (exiqgrep)" "SECTgreptheque"
39530 .cindex "&'exiqgrep'&"
39531 .cindex "queue" "grepping"
39532 This utility is a Perl script contributed by Matt Hubbard. It runs
39536 or (in case &*-a*& switch is specified)
39540 to obtain a queue listing, and then greps the output to select messages
39541 that match given criteria. The following selection options are available:
39544 .vitem &*-f*&&~<&'regex'&>
39545 Match the sender address using a case-insensitive search. The field that is
39546 tested is enclosed in angle brackets, so you can test for bounce messages with
39550 .vitem &*-r*&&~<&'regex'&>
39551 Match a recipient address using a case-insensitive search. The field that is
39552 tested is not enclosed in angle brackets.
39554 .vitem &*-s*&&~<&'regex'&>
39555 Match against the size field.
39557 .vitem &*-y*&&~<&'seconds'&>
39558 Match messages that are younger than the given time.
39560 .vitem &*-o*&&~<&'seconds'&>
39561 Match messages that are older than the given time.
39564 Match only frozen messages.
39567 Match only non-frozen messages.
39569 .vitem &*-G*&&~<&'queuename'&>
39570 Match only messages in the given queue. Without this, the default queue is searched.
39573 The following options control the format of the output:
39577 Display only the count of matching messages.
39580 Long format &-- display the full message information as output by Exim. This is
39584 Display message ids only.
39587 Brief format &-- one line per message.
39590 Display messages in reverse order.
39593 Include delivered recipients in queue listing.
39596 The following options give alternates for configuration:
39599 .vitem &*-C*&&~<&'config&~file'&>
39600 is used to specify an alternate &_exim.conf_& which might
39601 contain alternate exim configuration the queue management might be using.
39603 .vitem &*-E*&&~<&'path'&>
39604 can be used to specify a path for the exim binary,
39605 overriding the built-in one.
39608 There is one more option, &%-h%&, which outputs a list of options.
39610 At least one selection option, or either the &*-c*& or &*-h*& option, must be given.
39615 .section "Summarizing the queue (exiqsumm)" "SECTsumtheque"
39616 .cindex "&'exiqsumm'&"
39617 .cindex "queue" "summary"
39618 The &'exiqsumm'& utility is a Perl script which reads the output of &`exim
39619 -bp`& and produces a summary of the messages in the queue. Thus, you use it by
39620 running a command such as
39622 exim -bp | exiqsumm
39624 The output consists of one line for each domain that has messages waiting for
39625 it, as in the following example:
39627 3 2322 74m 66m msn.com.example
39629 Each line lists the number of pending deliveries for a domain, their total
39630 volume, and the length of time that the oldest and the newest messages have
39631 been waiting. Note that the number of pending deliveries is greater than the
39632 number of messages when messages have more than one recipient.
39634 A summary line is output at the end. By default the output is sorted on the
39635 domain name, but &'exiqsumm'& has the options &%-a%& and &%-c%&, which cause
39636 the output to be sorted by oldest message and by count of messages,
39637 respectively. There are also three options that split the messages for each
39638 domain into two or more subcounts: &%-b%& separates bounce messages, &%-f%&
39639 separates frozen messages, and &%-s%& separates messages according to their
39642 The output of &'exim -bp'& contains the original addresses in the message, so
39643 this also applies to the output from &'exiqsumm'&. No domains from addresses
39644 generated by aliasing or forwarding are included (unless the &%one_time%&
39645 option of the &(redirect)& router has been used to convert them into &"top
39646 level"& addresses).
39651 .section "Extracting specific information from the log (exigrep)" &&&
39653 .cindex "&'exigrep'&"
39654 .cindex "log" "extracts; grepping for"
39655 The &'exigrep'& utility is a Perl script that searches one or more main log
39656 files for entries that match a given pattern. When it finds a match, it
39657 extracts all the log entries for the relevant message, not just those that
39658 match the pattern. Thus, &'exigrep'& can extract complete log entries for a
39659 given message, or all mail for a given user, or for a given host, for example.
39660 The input files can be in Exim log format or syslog format.
39661 If a matching log line is not associated with a specific message, it is
39662 included in &'exigrep'&'s output without any additional lines. The usage is:
39664 &`exigrep [-t<`&&'n'&&`>] [-I] [-l] [-M] [-v] <`&&'pattern'&&`> [<`&&'log file'&&`>] ...`&
39666 If no log filenames are given on the command line, the standard input is read.
39668 The &%-t%& argument specifies a number of seconds. It adds an additional
39669 condition for message selection. Messages that are complete are shown only if
39670 they spent more than <&'n'&> seconds in the queue.
39672 By default, &'exigrep'& does case-insensitive matching. The &%-I%& option
39673 makes it case-sensitive. This may give a performance improvement when searching
39674 large log files. Without &%-I%&, the Perl pattern matches use Perl's &`/i`&
39675 option; with &%-I%& they do not. In both cases it is possible to change the
39676 case sensitivity within the pattern by using &`(?i)`& or &`(?-i)`&.
39678 The &%-l%& option means &"literal"&, that is, treat all characters in the
39679 pattern as standing for themselves. Otherwise the pattern must be a Perl
39680 regular expression.
39682 The &%-v%& option inverts the matching condition. That is, a line is selected
39683 if it does &'not'& match the pattern.
39685 The &%-M%& options means &"related messages"&. &'exigrep'& will show messages
39686 that are generated as a result/response to a message that &'exigrep'& matched
39690 user_a sends a message to user_b, which generates a bounce back to user_b. If
39691 &'exigrep'& is used to search for &"user_a"&, only the first message will be
39692 displayed. But if &'exigrep'& is used to search for &"user_b"&, the first and
39693 the second (bounce) message will be displayed. Using &%-M%& with &'exigrep'&
39694 when searching for &"user_a"& will show both messages since the bounce is
39695 &"related"& to or a &"result"& of the first message that was found by the
39698 If the location of a &'zcat'& command is known from the definition of
39699 ZCAT_COMMAND in &_Local/Makefile_&, &'exigrep'& automatically passes any file
39700 whose name ends in COMPRESS_SUFFIX through &'zcat'& as it searches it.
39701 If the ZCAT_COMMAND is not executable, &'exigrep'& tries to use
39702 autodetection of some well known compression extensions.
39705 .section "Selecting messages by various criteria (exipick)" "SECTexipick"
39706 .cindex "&'exipick'&"
39707 John Jetmore's &'exipick'& utility is included in the Exim distribution. It
39708 lists messages from the queue according to a variety of criteria. For details
39709 of &'exipick'&'s facilities, run &'exipick'& with
39710 the &%--help%& option.
39713 .section "Cycling log files (exicyclog)" "SECTcyclogfil"
39714 .cindex "log" "cycling local files"
39715 .cindex "cycling logs"
39716 .cindex "&'exicyclog'&"
39717 The &'exicyclog'& script can be used to cycle (rotate) &'mainlog'& and
39718 &'rejectlog'& files. This is not necessary if only syslog is being used, or if
39719 you are using log files with datestamps in their names (see section
39720 &<<SECTdatlogfil>>&). Some operating systems have their own standard mechanisms
39721 for log cycling, and these can be used instead of &'exicyclog'& if preferred.
39722 There are two command line options for &'exicyclog'&:
39724 &%-k%& <&'count'&> specifies the number of log files to keep, overriding the
39725 default that is set when Exim is built. The default default is 10.
39727 &%-l%& <&'path'&> specifies the log file path, in the same format as Exim's
39728 &%log_file_path%& option (for example, &`/var/log/exim_%slog`&), again
39729 overriding the script's default, which is to find the setting from Exim's
39733 Each time &'exicyclog'& is run the filenames get &"shuffled down"& by one. If
39734 the main log filename is &_mainlog_& (the default) then when &'exicyclog'& is
39735 run &_mainlog_& becomes &_mainlog.01_&, the previous &_mainlog.01_& becomes
39736 &_mainlog.02_& and so on, up to the limit that is set in the script or by the
39737 &%-k%& option. Log files whose numbers exceed the limit are discarded. Reject
39738 logs are handled similarly.
39740 If the limit is greater than 99, the script uses 3-digit numbers such as
39741 &_mainlog.001_&, &_mainlog.002_&, etc. If you change from a number less than 99
39742 to one that is greater, or &'vice versa'&, you will have to fix the names of
39743 any existing log files.
39745 If no &_mainlog_& file exists, the script does nothing. Files that &"drop off"&
39746 the end are deleted. All files with numbers greater than 01 are compressed,
39747 using a compression command which is configured by the COMPRESS_COMMAND
39748 setting in &_Local/Makefile_&. It is usual to run &'exicyclog'& daily from a
39749 root &%crontab%& entry of the form
39751 1 0 * * * su exim -c /usr/exim/bin/exicyclog
39753 assuming you have used the name &"exim"& for the Exim user. You can run
39754 &'exicyclog'& as root if you wish, but there is no need.
39758 .section "Mail statistics (eximstats)" "SECTmailstat"
39759 .cindex "statistics"
39760 .cindex "&'eximstats'&"
39761 A Perl script called &'eximstats'& is provided for extracting statistical
39762 information from log files. The output is either plain text, or HTML.
39763 . --- 2018-09-07: LogReport's Lire appears to be dead; website is a Yahoo Japan
39764 . --- 404 error and everything else points to that.
39766 The &'eximstats'& script has been hacked about quite a bit over time. The
39767 latest version is the result of some extensive revision by Steve Campbell. A
39768 lot of information is given by default, but there are options for suppressing
39769 various parts of it. Following any options, the arguments to the script are a
39770 list of files, which should be main log files. For example:
39772 eximstats -nr /var/spool/exim/log/mainlog.01
39774 By default, &'eximstats'& extracts information about the number and volume of
39775 messages received from or delivered to various hosts. The information is sorted
39776 both by message count and by volume, and the top fifty hosts in each category
39777 are listed on the standard output. Similar information, based on email
39778 addresses or domains instead of hosts can be requested by means of various
39779 options. For messages delivered and received locally, similar statistics are
39780 also produced per user.
39782 The output also includes total counts and statistics about delivery errors, and
39783 histograms showing the number of messages received and deliveries made in each
39784 hour of the day. A delivery with more than one address in its envelope (for
39785 example, an SMTP transaction with more than one RCPT command) is counted
39786 as a single delivery by &'eximstats'&.
39788 Though normally more deliveries than receipts are reported (as messages may
39789 have multiple recipients), it is possible for &'eximstats'& to report more
39790 messages received than delivered, even though the queue is empty at the start
39791 and end of the period in question. If an incoming message contains no valid
39792 recipients, no deliveries are recorded for it. A bounce message is handled as
39793 an entirely separate message.
39795 &'eximstats'& always outputs a grand total summary giving the volume and number
39796 of messages received and deliveries made, and the number of hosts involved in
39797 each case. It also outputs the number of messages that were delayed (that is,
39798 not completely delivered at the first attempt), and the number that had at
39799 least one address that failed.
39801 The remainder of the output is in sections that can be independently disabled
39802 or modified by various options. It consists of a summary of deliveries by
39803 transport, histograms of messages received and delivered per time interval
39804 (default per hour), information about the time messages spent in the queue,
39805 a list of relayed messages, lists of the top fifty sending hosts, local
39806 senders, destination hosts, and destination local users by count and by volume,
39807 and a list of delivery errors that occurred.
39809 The relay information lists messages that were actually relayed, that is, they
39810 came from a remote host and were directly delivered to some other remote host,
39811 without being processed (for example, for aliasing or forwarding) locally.
39813 There are quite a few options for &'eximstats'& to control exactly what it
39814 outputs. These are documented in the Perl script itself, and can be extracted
39815 by running the command &(perldoc)& on the script. For example:
39817 perldoc /usr/exim/bin/eximstats
39820 .section "Checking access policy (exim_checkaccess)" "SECTcheckaccess"
39821 .cindex "&'exim_checkaccess'&"
39822 .cindex "policy control" "checking access"
39823 .cindex "checking access"
39824 The &%-bh%& command line argument allows you to run a fake SMTP session with
39825 debugging output, in order to check what Exim is doing when it is applying
39826 policy controls to incoming SMTP mail. However, not everybody is sufficiently
39827 familiar with the SMTP protocol to be able to make full use of &%-bh%&, and
39828 sometimes you just want to answer the question &"Does this address have
39829 access?"& without bothering with any further details.
39831 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%&. It takes
39832 two arguments, an IP address and an email address:
39834 exim_checkaccess 10.9.8.7 A.User@a.domain.example
39836 The utility runs a call to Exim with the &%-bh%& option, to test whether the
39837 given email address would be accepted in a RCPT command in a TCP/IP
39838 connection from the host with the given IP address. The output of the utility
39839 is either the word &"accepted"&, or the SMTP error response, for example:
39842 550 Relay not permitted
39844 When running this test, the utility uses &`<>`& as the envelope sender address
39845 for the MAIL command, but you can change this by providing additional
39846 options. These are passed directly to the Exim command. For example, to specify
39847 that the test is to be run with the sender address &'himself@there.example'&
39850 exim_checkaccess 10.9.8.7 A.User@a.domain.example \
39851 -f himself@there.example
39853 Note that these additional Exim command line items must be given after the two
39854 mandatory arguments.
39856 Because the &%exim_checkaccess%& uses &%-bh%&, it does not perform callouts
39857 while running its checks. You can run checks that include callouts by using
39858 &%-bhc%&, but this is not yet available in a &"packaged"& form.
39862 .section "Making DBM files (exim_dbmbuild)" "SECTdbmbuild"
39863 .cindex "DBM" "building dbm files"
39864 .cindex "building DBM files"
39865 .cindex "&'exim_dbmbuild'&"
39866 .cindex "lower casing"
39867 .cindex "binary zero" "in lookup key"
39868 The &'exim_dbmbuild'& program reads an input file containing keys and data in
39869 the format used by the &(lsearch)& lookup (see section
39870 &<<SECTsinglekeylookups>>&). It writes a DBM file using the lower-cased alias
39871 names as keys and the remainder of the information as data. The lower-casing
39872 can be prevented by calling the program with the &%-nolc%& option.
39874 A terminating zero is included as part of the key string. This is expected by
39875 the &(dbm)& lookup type. However, if the option &%-nozero%& is given,
39876 &'exim_dbmbuild'& creates files without terminating zeroes in either the key
39877 strings or the data strings. The &(dbmnz)& lookup type can be used with such
39880 The program requires two arguments: the name of the input file (which can be a
39881 single hyphen to indicate the standard input), and the name of the output file.
39882 It creates the output under a temporary name, and then renames it if all went
39886 If the native DB interface is in use (USE_DB is set in a compile-time
39887 configuration file &-- this is common in free versions of Unix) the two
39888 filenames must be different, because in this mode the Berkeley DB functions
39889 create a single output file using exactly the name given. For example,
39891 exim_dbmbuild /etc/aliases /etc/aliases.db
39893 reads the system alias file and creates a DBM version of it in
39894 &_/etc/aliases.db_&.
39896 In systems that use the &'ndbm'& routines (mostly proprietary versions of
39897 Unix), two files are used, with the suffixes &_.dir_& and &_.pag_&. In this
39898 environment, the suffixes are added to the second argument of
39899 &'exim_dbmbuild'&, so it can be the same as the first. This is also the case
39900 when the Berkeley functions are used in compatibility mode (though this is not
39901 recommended), because in that case it adds a &_.db_& suffix to the filename.
39903 If a duplicate key is encountered, the program outputs a warning, and when it
39904 finishes, its return code is 1 rather than zero, unless the &%-noduperr%&
39905 option is used. By default, only the first of a set of duplicates is used &--
39906 this makes it compatible with &(lsearch)& lookups. There is an option
39907 &%-lastdup%& which causes it to use the data for the last duplicate instead.
39908 There is also an option &%-nowarn%&, which stops it listing duplicate keys to
39909 &%stderr%&. For other errors, where it doesn't actually make a new file, the
39915 .section "Finding individual retry times (exinext)" "SECTfinindret"
39916 .cindex "retry" "times"
39917 .cindex "&'exinext'&"
39918 A utility called &'exinext'& (mostly a Perl script) provides the ability to
39919 fish specific information out of the retry database. Given a mail domain (or a
39920 complete address), it looks up the hosts for that domain, and outputs any retry
39921 information for the hosts or for the domain. At present, the retry information
39922 is obtained by running &'exim_dumpdb'& (see below) and post-processing the
39923 output. For example:
39925 $ exinext piglet@milne.fict.example
39926 kanga.milne.example:192.168.8.1 error 146: Connection refused
39927 first failed: 21-Feb-1996 14:57:34
39928 last tried: 21-Feb-1996 14:57:34
39929 next try at: 21-Feb-1996 15:02:34
39930 roo.milne.example:192.168.8.3 error 146: Connection refused
39931 first failed: 20-Jan-1996 13:12:08
39932 last tried: 21-Feb-1996 11:42:03
39933 next try at: 21-Feb-1996 19:42:03
39934 past final cutoff time
39936 You can also give &'exinext'& a local part, without a domain, and it
39937 will give any retry information for that local part in your default domain.
39938 A message id can be used to obtain retry information pertaining to a specific
39939 message. This exists only when an attempt to deliver a message to a remote host
39940 suffers a message-specific error (see section &<<SECToutSMTPerr>>&).
39941 &'exinext'& is not particularly efficient, but then it is not expected to be
39944 The &'exinext'& utility calls Exim to find out information such as the location
39945 of the spool directory. The utility has &%-C%& and &%-D%& options, which are
39946 passed on to the &'exim'& commands. The first specifies an alternate Exim
39947 configuration file, and the second sets macros for use within the configuration
39948 file. These features are mainly to help in testing, but might also be useful in
39949 environments where more than one configuration file is in use.
39953 .section "Hints database maintenance" "SECThindatmai"
39954 .cindex "hints database" "maintenance"
39955 .cindex "maintaining Exim's hints database"
39956 Three utility programs are provided for maintaining the DBM files that Exim
39957 uses to contain its delivery hint information. Each program requires two
39958 arguments. The first specifies the name of Exim's spool directory, and the
39959 second is the name of the database it is to operate on. These are as follows:
39962 &'retry'&: the database of retry information
39964 &'wait-'&<&'transport name'&>: databases of information about messages waiting
39967 &'callout'&: the callout cache
39969 &'ratelimit'&: the data for implementing the ratelimit ACL condition
39971 &'tls'&: TLS session resumption data
39973 &'misc'&: other hints data
39976 The &'misc'& database is used for
39979 Serializing ETRN runs (when &%smtp_etrn_serialize%& is set)
39981 Serializing delivery to a specific host (when &%serialize_hosts%& is set in an
39982 &(smtp)& transport)
39984 Limiting the concurrency of specific transports (when &%max_parallel%& is set
39990 .section "exim_dumpdb" "SECTdumpdb"
39991 .cindex "&'exim_dumpdb'&"
39992 The entire contents of a database are written to the standard output by the
39993 &'exim_dumpdb'& program,
39995 taking as arguments the spool and database names.
39996 An option &'-z'& may be given to request times in UTC;
39997 otherwise times are in the local timezone.
39998 An option &'-k'& may be given to dump only the record keys.
40000 For example, to dump the retry database:
40002 exim_dumpdb /var/spool/exim retry
40004 For the retry database
40005 two lines of output are produced for each entry:
40007 T:mail.ref.example:192.168.242.242 146 77 Connection refused
40008 31-Oct-1995 12:00:12 02-Nov-1995 12:21:39 02-Nov-1995 20:21:39 *
40010 The first item on the first line is the key of the record. It starts with one
40011 of the letters R, or T, depending on whether it refers to a routing or
40012 transport retry. For a local delivery, the next part is the local address; for
40013 a remote delivery it is the name of the remote host, followed by its failing IP
40014 address (unless &%retry_include_ip_address%& is set false on the &(smtp)&
40015 transport). If the remote port is not the standard one (port 25), it is added
40016 to the IP address. Then there follows an error code, an additional error code,
40017 and a textual description of the error.
40019 The three times on the second line are the time of first failure, the time of
40020 the last delivery attempt, and the computed time for the next attempt. The line
40021 ends with an asterisk if the cutoff time for the last retry rule has been
40024 Each output line from &'exim_dumpdb'& for the &'wait-xxx'& databases
40025 consists of a host name followed by a list of ids for messages that are or were
40026 waiting to be delivered to that host. If there are a very large number for any
40027 one host, continuation records, with a sequence number added to the host name,
40028 may be seen. The data in these records is often out of date, because a message
40029 may be routed to several alternative hosts, and Exim makes no effort to keep
40034 .section "exim_tidydb" "SECTtidydb"
40035 .cindex "&'exim_tidydb'&"
40036 The &'exim_tidydb'& utility program is used to tidy up the contents of a hints
40037 database. If run with no options, it removes all records that are more than 30
40038 days old. The age is calculated from the date and time that the record was last
40039 updated. Note that, in the case of the retry database, it is &'not'& the time
40040 since the first delivery failure. Information about a host that has been down
40041 for more than 30 days will remain in the database, provided that the record is
40042 updated sufficiently often.
40044 The cutoff date can be altered by means of the &%-t%& option, which must be
40045 followed by a time. For example, to remove all records older than a week from
40046 the retry database:
40048 exim_tidydb -t 7d /var/spool/exim retry
40050 Both the &'wait-xxx'& and &'retry'& databases contain items that involve
40051 message ids. In the former these appear as data in records keyed by host &--
40052 they were messages that were waiting for that host &-- and in the latter they
40053 are the keys for retry information for messages that have suffered certain
40054 types of error. When &'exim_tidydb'& is run, a check is made to ensure that
40055 message ids in database records are those of messages that are still on the
40056 queue. Message ids for messages that no longer exist are removed from
40057 &'wait-xxx'& records, and if this leaves any records empty, they are deleted.
40058 For the &'retry'& database, records whose keys are non-existent message ids are
40059 removed. The &'exim_tidydb'& utility outputs comments on the standard output
40060 whenever it removes information from the database.
40062 Certain records are automatically removed by Exim when they are no longer
40063 needed, but others are not. For example, if all the MX hosts for a domain are
40064 down, a retry record is created for each one. If the primary MX host comes back
40065 first, its record is removed when Exim successfully delivers to it, but the
40066 records for the others remain because Exim has not tried to use those hosts.
40068 It is important, therefore, to run &'exim_tidydb'& periodically on all the
40069 hints databases. You should do this at a quiet time of day, because it requires
40070 a database to be locked (and therefore inaccessible to Exim) while it does its
40071 work. Removing records from a DBM file does not normally make the file smaller,
40072 but all the common DBM libraries are able to re-use the space that is released.
40073 After an initial phase of increasing in size, the databases normally reach a
40074 point at which they no longer get any bigger, as long as they are regularly
40077 &*Warning*&: If you never run &'exim_tidydb'&, the space used by the hints
40078 databases is likely to keep on increasing.
40083 .section "exim_fixdb" "SECTfixdb"
40084 .cindex "&'exim_fixdb'&"
40085 The &'exim_fixdb'& program is a utility for interactively modifying databases.
40086 Its main use is for testing Exim, but it might also be occasionally useful for
40087 getting round problems in a live system. Its interface
40088 is somewhat crude. On entry, it prompts for input with a right angle-bracket. A
40089 key of a database record can then be entered, and the data for that record is
40092 If &"d"& is typed at the next prompt, the entire record is deleted. For all
40093 except the &'retry'& database, that is the only operation that can be carried
40094 out. For the &'retry'& database, each field is output preceded by a number, and
40095 data for individual fields can be changed by typing the field number followed
40096 by new data, for example:
40100 resets the time of the next delivery attempt. Time values are given as a
40101 sequence of digit pairs for year, month, day, hour, and minute. Colons can be
40102 used as optional separators.
40105 Both displayed and input times are in the local timezone by default.
40106 If an option &'-z'& is used on the command line, displayed times
40113 .section "Mailbox maintenance (exim_lock)" "SECTmailboxmaint"
40114 .cindex "mailbox" "maintenance"
40115 .cindex "&'exim_lock'&"
40116 .cindex "locking mailboxes"
40117 The &'exim_lock'& utility locks a mailbox file using the same algorithm as
40118 Exim. For a discussion of locking issues, see section &<<SECTopappend>>&.
40119 &'Exim_lock'& can be used to prevent any modification of a mailbox by Exim or
40120 a user agent while investigating a problem. The utility requires the name of
40121 the file as its first argument. If the locking is successful, the second
40122 argument is run as a command (using C's &[system()]& function); if there is no
40123 second argument, the value of the SHELL environment variable is used; if this
40124 is unset or empty, &_/bin/sh_& is run. When the command finishes, the mailbox
40125 is unlocked and the utility ends. The following options are available:
40129 Use &[fcntl()]& locking on the open mailbox.
40132 Use &[flock()]& locking on the open mailbox, provided the operating system
40135 .vitem &%-interval%&
40136 This must be followed by a number, which is a number of seconds; it sets the
40137 interval to sleep between retries (default 3).
40139 .vitem &%-lockfile%&
40140 Create a lock file before opening the mailbox.
40143 Lock the mailbox using MBX rules.
40146 Suppress verification output.
40148 .vitem &%-retries%&
40149 This must be followed by a number; it sets the number of times to try to get
40150 the lock (default 10).
40152 .vitem &%-restore_time%&
40153 This option causes &%exim_lock%& to restore the modified and read times to the
40154 locked file before exiting. This allows you to access a locked mailbox (for
40155 example, to take a backup copy) without disturbing the times that the user
40158 .vitem &%-timeout%&
40159 This must be followed by a number, which is a number of seconds; it sets a
40160 timeout to be used with a blocking &[fcntl()]& lock. If it is not set (the
40161 default), a non-blocking call is used.
40164 Generate verbose output.
40167 If none of &%-fcntl%&, &%-flock%&, &%-lockfile%& or &%-mbx%& are given, the
40168 default is to create a lock file and also to use &[fcntl()]& locking on the
40169 mailbox, which is the same as Exim's default. The use of &%-flock%& or
40170 &%-fcntl%& requires that the file be writeable; the use of &%-lockfile%&
40171 requires that the directory containing the file be writeable. Locking by lock
40172 file does not last forever; Exim assumes that a lock file is expired if it is
40173 more than 30 minutes old.
40175 The &%-mbx%& option can be used with either or both of &%-fcntl%& or
40176 &%-flock%&. It assumes &%-fcntl%& by default. MBX locking causes a shared lock
40177 to be taken out on the open mailbox, and an exclusive lock on the file
40178 &_/tmp/.n.m_& where &'n'& and &'m'& are the device number and inode
40179 number of the mailbox file. When the locking is released, if an exclusive lock
40180 can be obtained for the mailbox, the file in &_/tmp_& is deleted.
40182 The default output contains verification of the locking that takes place. The
40183 &%-v%& option causes some additional information to be given. The &%-q%& option
40184 suppresses all output except error messages.
40188 exim_lock /var/spool/mail/spqr
40190 runs an interactive shell while the file is locked, whereas
40192 &`exim_lock -q /var/spool/mail/spqr <<End`&
40193 <&'some commands'&>
40196 runs a specific non-interactive sequence of commands while the file is locked,
40197 suppressing all verification output. A single command can be run by a command
40200 exim_lock -q /var/spool/mail/spqr \
40201 "cp /var/spool/mail/spqr /some/where"
40203 Note that if a command is supplied, it must be entirely contained within the
40204 second argument &-- hence the quotes.
40208 . ////////////////////////////////////////////////////////////////////////////
40209 . ////////////////////////////////////////////////////////////////////////////
40211 .chapter "The Exim monitor" "CHAPeximon"
40212 .scindex IIDeximon "Exim monitor" "description"
40213 .cindex "X-windows"
40214 .cindex "&'eximon'&"
40215 .cindex "Local/eximon.conf"
40216 .cindex "&_exim_monitor/EDITME_&"
40217 The Exim monitor is an application which displays in an X window information
40218 about the state of Exim's queue and what Exim is doing. An admin user can
40219 perform certain operations on messages from this GUI interface; however all
40220 such facilities are also available from the command line, and indeed, the
40221 monitor itself makes use of the command line to perform any actions requested.
40225 .section "Running the monitor" "SECID264"
40226 The monitor is started by running the script called &'eximon'&. This is a shell
40227 script that sets up a number of environment variables, and then runs the
40228 binary called &_eximon.bin_&. The default appearance of the monitor window can
40229 be changed by editing the &_Local/eximon.conf_& file created by editing
40230 &_exim_monitor/EDITME_&. Comments in that file describe what the various
40231 parameters are for.
40233 The parameters that get built into the &'eximon'& script can be overridden for
40234 a particular invocation by setting up environment variables of the same names,
40235 preceded by &`EXIMON_`&. For example, a shell command such as
40237 EXIMON_LOG_DEPTH=400 eximon
40239 (in a Bourne-compatible shell) runs &'eximon'& with an overriding setting of
40240 the LOG_DEPTH parameter. If EXIMON_LOG_FILE_PATH is set in the environment, it
40241 overrides the Exim log file configuration. This makes it possible to have
40242 &'eximon'& tailing log data that is written to syslog, provided that MAIL.INFO
40243 syslog messages are routed to a file on the local host.
40245 X resources can be used to change the appearance of the window in the normal
40246 way. For example, a resource setting of the form
40248 Eximon*background: gray94
40250 changes the colour of the background to light grey rather than white. The
40251 stripcharts are drawn with both the data lines and the reference lines in
40252 black. This means that the reference lines are not visible when on top of the
40253 data. However, their colour can be changed by setting a resource called
40254 &"highlight"& (an odd name, but that's what the Athena stripchart widget uses).
40255 For example, if your X server is running Unix, you could set up lighter
40256 reference lines in the stripcharts by obeying
40259 Eximon*highlight: gray
40262 .cindex "admin user"
40263 In order to see the contents of messages in the queue, and to operate on them,
40264 &'eximon'& must either be run as root or by an admin user.
40266 The command-line parameters of &'eximon'& are passed to &_eximon.bin_& and may
40267 contain X11 resource parameters interpreted by the X11 library. In addition,
40268 if the first parameter starts with the string "gdb" then it is removed and the
40269 binary is invoked under gdb (the parameter is used as the gdb command-name, so
40270 versioned variants of gdb can be invoked).
40272 The monitor's window is divided into three parts. The first contains one or
40273 more stripcharts and two action buttons, the second contains a &"tail"& of the
40274 main log file, and the third is a display of the queue of messages awaiting
40275 delivery, with two more action buttons. The following sections describe these
40276 different parts of the display.
40281 .section "The stripcharts" "SECID265"
40282 .cindex "stripchart"
40283 The first stripchart is always a count of messages in the queue. Its name can
40284 be configured by setting QUEUE_STRIPCHART_NAME in the
40285 &_Local/eximon.conf_& file. The remaining stripcharts are defined in the
40286 configuration script by regular expression matches on log file entries, making
40287 it possible to display, for example, counts of messages delivered to certain
40288 hosts or using certain transports. The supplied defaults display counts of
40289 received and delivered messages, and of local and SMTP deliveries. The default
40290 period between stripchart updates is one minute; this can be adjusted by a
40291 parameter in the &_Local/eximon.conf_& file.
40293 The stripchart displays rescale themselves automatically as the value they are
40294 displaying changes. There are always 10 horizontal lines in each chart; the
40295 title string indicates the value of each division when it is greater than one.
40296 For example, &"x2"& means that each division represents a value of 2.
40298 It is also possible to have a stripchart which shows the percentage fullness of
40299 a particular disk partition, which is useful when local deliveries are confined
40300 to a single partition.
40302 .cindex "&%statvfs%& function"
40303 This relies on the availability of the &[statvfs()]& function or equivalent in
40304 the operating system. Most, but not all versions of Unix that support Exim have
40305 this. For this particular stripchart, the top of the chart always represents
40306 100%, and the scale is given as &"x10%"&. This chart is configured by setting
40307 SIZE_STRIPCHART and (optionally) SIZE_STRIPCHART_NAME in the
40308 &_Local/eximon.conf_& file.
40313 .section "Main action buttons" "SECID266"
40314 .cindex "size" "of monitor window"
40315 .cindex "Exim monitor" "window size"
40316 .cindex "window size"
40317 Below the stripcharts there is an action button for quitting the monitor. Next
40318 to this is another button marked &"Size"&. They are placed here so that
40319 shrinking the window to its default minimum size leaves just the queue count
40320 stripchart and these two buttons visible. Pressing the &"Size"& button causes
40321 the window to expand to its maximum size, unless it is already at the maximum,
40322 in which case it is reduced to its minimum.
40324 When expanding to the maximum, if the window cannot be fully seen where it
40325 currently is, it is moved back to where it was the last time it was at full
40326 size. When it is expanding from its minimum size, the old position is
40327 remembered, and next time it is reduced to the minimum it is moved back there.
40329 The idea is that you can keep a reduced window just showing one or two
40330 stripcharts at a convenient place on your screen, easily expand it to show
40331 the full window when required, and just as easily put it back to what it was.
40332 The idea is copied from what the &'twm'& window manager does for its
40333 &'f.fullzoom'& action. The minimum size of the window can be changed by setting
40334 the MIN_HEIGHT and MIN_WIDTH values in &_Local/eximon.conf_&.
40336 Normally, the monitor starts up with the window at its full size, but it can be
40337 built so that it starts up with the window at its smallest size, by setting
40338 START_SMALL=yes in &_Local/eximon.conf_&.
40342 .section "The log display" "SECID267"
40343 .cindex "log" "tail of; in monitor"
40344 The second section of the window is an area in which a display of the tail of
40345 the main log is maintained.
40346 To save space on the screen, the timestamp on each log line is shortened by
40347 removing the date and, if &%log_timezone%& is set, the timezone.
40348 The log tail is not available when the only destination for logging data is
40349 syslog, unless the syslog lines are routed to a local file whose name is passed
40350 to &'eximon'& via the EXIMON_LOG_FILE_PATH environment variable.
40352 The log sub-window has a scroll bar at its lefthand side which can be used to
40353 move back to look at earlier text, and the up and down arrow keys also have a
40354 scrolling effect. The amount of log that is kept depends on the setting of
40355 LOG_BUFFER in &_Local/eximon.conf_&, which specifies the amount of memory
40356 to use. When this is full, the earlier 50% of data is discarded &-- this is
40357 much more efficient than throwing it away line by line. The sub-window also has
40358 a horizontal scroll bar for accessing the ends of long log lines. This is the
40359 only means of horizontal scrolling; the right and left arrow keys are not
40360 available. Text can be cut from this part of the window using the mouse in the
40361 normal way. The size of this subwindow is controlled by parameters in the
40362 configuration file &_Local/eximon.conf_&.
40364 Searches of the text in the log window can be carried out by means of the ^R
40365 and ^S keystrokes, which default to a reverse and a forward search,
40366 respectively. The search covers only the text that is displayed in the window.
40367 It cannot go further back up the log.
40369 The point from which the search starts is indicated by a caret marker. This is
40370 normally at the end of the text in the window, but can be positioned explicitly
40371 by pointing and clicking with the left mouse button, and is moved automatically
40372 by a successful search. If new text arrives in the window when it is scrolled
40373 back, the caret remains where it is, but if the window is not scrolled back,
40374 the caret is moved to the end of the new text.
40376 Pressing ^R or ^S pops up a window into which the search text can be typed.
40377 There are buttons for selecting forward or reverse searching, for carrying out
40378 the search, and for cancelling. If the &"Search"& button is pressed, the search
40379 happens and the window remains so that further searches can be done. If the
40380 &"Return"& key is pressed, a single search is done and the window is closed. If
40381 ^C is typed the search is cancelled.
40383 The searching facility is implemented using the facilities of the Athena text
40384 widget. By default this pops up a window containing both &"search"& and
40385 &"replace"& options. In order to suppress the unwanted &"replace"& portion for
40386 eximon, a modified version of the &%TextPop%& widget is distributed with Exim.
40387 However, the linkers in BSDI and HP-UX seem unable to handle an externally
40388 provided version of &%TextPop%& when the remaining parts of the text widget
40389 come from the standard libraries. The compile-time option EXIMON_TEXTPOP can be
40390 unset to cut out the modified &%TextPop%&, making it possible to build Eximon
40391 on these systems, at the expense of having unwanted items in the search popup
40396 .section "The queue display" "SECID268"
40397 .cindex "queue" "display in monitor"
40398 The bottom section of the monitor window contains a list of all messages that
40399 are in the queue, which includes those currently being received or delivered,
40400 as well as those awaiting delivery. The size of this subwindow is controlled by
40401 parameters in the configuration file &_Local/eximon.conf_&, and the frequency
40402 at which it is updated is controlled by another parameter in the same file &--
40403 the default is 5 minutes, since queue scans can be quite expensive. However,
40404 there is an &"Update"& action button just above the display which can be used
40405 to force an update of the queue display at any time.
40407 When a host is down for some time, a lot of pending mail can build up for it,
40408 and this can make it hard to deal with other messages in the queue. To help
40409 with this situation there is a button next to &"Update"& called &"Hide"&. If
40410 pressed, a dialogue box called &"Hide addresses ending with"& is put up. If you
40411 type anything in here and press &"Return"&, the text is added to a chain of
40412 such texts, and if every undelivered address in a message matches at least one
40413 of the texts, the message is not displayed.
40415 If there is an address that does not match any of the texts, all the addresses
40416 are displayed as normal. The matching happens on the ends of addresses so, for
40417 example, &'cam.ac.uk'& specifies all addresses in Cambridge, while
40418 &'xxx@foo.com.example'& specifies just one specific address. When any hiding
40419 has been set up, a button called &"Unhide"& is displayed. If pressed, it
40420 cancels all hiding. Also, to ensure that hidden messages do not get forgotten,
40421 a hide request is automatically cancelled after one hour.
40423 While the dialogue box is displayed, you can't press any buttons or do anything
40424 else to the monitor window. For this reason, if you want to cut text from the
40425 queue display to use in the dialogue box, you have to do the cutting before
40426 pressing the &"Hide"& button.
40428 The queue display contains, for each unhidden queued message, the length of
40429 time it has been in the queue, the size of the message, the message id, the
40430 message sender, and the first undelivered recipient, all on one line. If it is
40431 a bounce message, the sender is shown as &"<>"&. If there is more than one
40432 recipient to which the message has not yet been delivered, subsequent ones are
40433 listed on additional lines, up to a maximum configured number, following which
40434 an ellipsis is displayed. Recipients that have already received the message are
40437 .cindex "frozen messages" "display"
40438 If a message is frozen, an asterisk is displayed at the left-hand side.
40440 The queue display has a vertical scroll bar, and can also be scrolled by means
40441 of the arrow keys. Text can be cut from it using the mouse in the normal way.
40442 The text searching facilities, as described above for the log window, are also
40443 available, but the caret is always moved to the end of the text when the queue
40444 display is updated.
40448 .section "The queue menu" "SECID269"
40449 .cindex "queue" "menu in monitor"
40450 If the &%shift%& key is held down and the left button is clicked when the mouse
40451 pointer is over the text for any message, an action menu pops up, and the first
40452 line of the queue display for the message is highlighted. This does not affect
40455 If you want to use some other event for popping up the menu, you can set the
40456 MENU_EVENT parameter in &_Local/eximon.conf_& to change the default, or
40457 set EXIMON_MENU_EVENT in the environment before starting the monitor. The
40458 value set in this parameter is a standard X event description. For example, to
40459 run eximon using &%ctrl%& rather than &%shift%& you could use
40461 EXIMON_MENU_EVENT='Ctrl<Btn1Down>' eximon
40463 The title of the menu is the message id, and it contains entries which act as
40467 &'message log'&: The contents of the message log for the message are displayed
40468 in a new text window.
40470 &'headers'&: Information from the spool file that contains the envelope
40471 information and headers is displayed in a new text window. See chapter
40472 &<<CHAPspool>>& for a description of the format of spool files.
40474 &'body'&: The contents of the spool file containing the body of the message are
40475 displayed in a new text window. There is a default limit of 20,000 bytes to the
40476 amount of data displayed. This can be changed by setting the BODY_MAX
40477 option at compile time, or the EXIMON_BODY_MAX option at runtime.
40479 &'deliver message'&: A call to Exim is made using the &%-M%& option to request
40480 delivery of the message. This causes an automatic thaw if the message is
40481 frozen. The &%-v%& option is also set, and the output from Exim is displayed in
40482 a new text window. The delivery is run in a separate process, to avoid holding
40483 up the monitor while the delivery proceeds.
40485 &'freeze message'&: A call to Exim is made using the &%-Mf%& option to request
40486 that the message be frozen.
40488 .cindex "thawing messages"
40489 .cindex "unfreezing messages"
40490 .cindex "frozen messages" "thawing"
40491 &'thaw message'&: A call to Exim is made using the &%-Mt%& option to request
40492 that the message be thawed.
40494 .cindex "delivery" "forcing failure"
40495 &'give up on msg'&: A call to Exim is made using the &%-Mg%& option to request
40496 that Exim gives up trying to deliver the message. A bounce message is generated
40497 for any remaining undelivered addresses.
40499 &'remove message'&: A call to Exim is made using the &%-Mrm%& option to request
40500 that the message be deleted from the system without generating a bounce
40503 &'add recipient'&: A dialog box is displayed into which a recipient address can
40504 be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
40505 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
40506 Otherwise it must be entered as a fully qualified address. Pressing RETURN
40507 causes a call to Exim to be made using the &%-Mar%& option to request that an
40508 additional recipient be added to the message, unless the entry box is empty, in
40509 which case no action is taken.
40511 &'mark delivered'&: A dialog box is displayed into which a recipient address
40512 can be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
40513 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
40514 Otherwise it must be entered as a fully qualified address. Pressing RETURN
40515 causes a call to Exim to be made using the &%-Mmd%& option to mark the given
40516 recipient address as already delivered, unless the entry box is empty, in which
40517 case no action is taken.
40519 &'mark all delivered'&: A call to Exim is made using the &%-Mmad%& option to
40520 mark all recipient addresses as already delivered.
40522 &'edit sender'&: A dialog box is displayed initialized with the current
40523 sender's address. Pressing RETURN causes a call to Exim to be made using the
40524 &%-Mes%& option to replace the sender address, unless the entry box is empty,
40525 in which case no action is taken. If you want to set an empty sender (as in
40526 bounce messages), you must specify it as &"<>"&. Otherwise, if the address is
40527 not qualified and the QUALIFY_DOMAIN parameter is set in &_Local/eximon.conf_&,
40528 the address is qualified with that domain.
40531 When a delivery is forced, a window showing the &%-v%& output is displayed. In
40532 other cases when a call to Exim is made, if there is any output from Exim (in
40533 particular, if the command fails) a window containing the command and the
40534 output is displayed. Otherwise, the results of the action are normally apparent
40535 from the log and queue displays. However, if you set ACTION_OUTPUT=yes in
40536 &_Local/eximon.conf_&, a window showing the Exim command is always opened, even
40537 if no output is generated.
40539 The queue display is automatically updated for actions such as freezing and
40540 thawing, unless ACTION_QUEUE_UPDATE=no has been set in
40541 &_Local/eximon.conf_&. In this case the &"Update"& button has to be used to
40542 force an update of the display after one of these actions.
40544 In any text window that is displayed as result of a menu action, the normal
40545 cut-and-paste facility is available, and searching can be carried out using ^R
40546 and ^S, as described above for the log tail window.
40553 . ////////////////////////////////////////////////////////////////////////////
40554 . ////////////////////////////////////////////////////////////////////////////
40556 .chapter "Security considerations" "CHAPsecurity"
40557 .scindex IIDsecurcon "security" "discussion of"
40558 This chapter discusses a number of issues concerned with security, some of
40559 which are also covered in other parts of this manual.
40561 For reasons that this author does not understand, some people have promoted
40562 Exim as a &"particularly secure"& mailer. Perhaps it is because of the
40563 existence of this chapter in the documentation. However, the intent of the
40564 chapter is simply to describe the way Exim works in relation to certain
40565 security concerns, not to make any specific claims about the effectiveness of
40566 its security as compared with other MTAs.
40568 What follows is a description of the way Exim is supposed to be. Best efforts
40569 have been made to try to ensure that the code agrees with the theory, but an
40570 absence of bugs can never be guaranteed. Any that are reported will get fixed
40571 as soon as possible.
40574 .section "Building a more &""hardened""& Exim" "SECID286"
40575 .cindex "security" "build-time features"
40576 There are a number of build-time options that can be set in &_Local/Makefile_&
40577 to create Exim binaries that are &"harder"& to attack, in particular by a rogue
40578 Exim administrator who does not have the root password, or by someone who has
40579 penetrated the Exim (but not the root) account. These options are as follows:
40582 ALT_CONFIG_PREFIX can be set to a string that is required to match the
40583 start of any filenames used with the &%-C%& option. When it is set, these
40584 filenames are also not allowed to contain the sequence &"/../"&. (However, if
40585 the value of the &%-C%& option is identical to the value of CONFIGURE_FILE in
40586 &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as usual.) There is no
40587 default setting for &%ALT_CONFIG_PREFIX%&.
40589 If the permitted configuration files are confined to a directory to
40590 which only root has access, this guards against someone who has broken
40591 into the Exim account from running a privileged Exim with an arbitrary
40592 configuration file, and using it to break into other accounts.
40595 If a non-trusted configuration file (i.e. not the default configuration file
40596 or one which is trusted by virtue of being listed in the TRUSTED_CONFIG_LIST
40597 file) is specified with &%-C%&, or if macros are given with &%-D%& (but see
40598 the next item), then root privilege is retained only if the caller of Exim is
40599 root. This locks out the possibility of testing a configuration using &%-C%&
40600 right through message reception and delivery, even if the caller is root. The
40601 reception works, but by that time, Exim is running as the Exim user, so when
40602 it re-execs to regain privilege for the delivery, the use of &%-C%& causes
40603 privilege to be lost. However, root can test reception and delivery using two
40607 The WHITELIST_D_MACROS build option declares some macros to be safe to override
40608 with &%-D%& if the real uid is one of root, the Exim run-time user or the
40609 CONFIGURE_OWNER, if defined. The potential impact of this option is limited by
40610 requiring the run-time value supplied to &%-D%& to match a regex that errs on
40611 the restrictive side. Requiring build-time selection of safe macros is onerous
40612 but this option is intended solely as a transition mechanism to permit
40613 previously-working configurations to continue to work after release 4.73.
40615 If DISABLE_D_OPTION is defined, the use of the &%-D%& command line option
40618 FIXED_NEVER_USERS can be set to a colon-separated list of users that are
40619 never to be used for any deliveries. This is like the &%never_users%& runtime
40620 option, but it cannot be overridden; the runtime option adds additional users
40621 to the list. The default setting is &"root"&; this prevents a non-root user who
40622 is permitted to modify the runtime file from using Exim as a way to get root.
40627 .section "Root privilege" "SECID270"
40629 .cindex "root privilege"
40630 The Exim binary is normally setuid to root, which means that it gains root
40631 privilege (runs as root) when it starts execution. In some special cases (for
40632 example, when the daemon is not in use and there are no local deliveries), it
40633 may be possible to run Exim setuid to some user other than root. This is
40634 discussed in the next section. However, in most installations, root privilege
40635 is required for two things:
40638 To set up a socket connected to the standard SMTP port (25) when initialising
40639 the listening daemon. If Exim is run from &'inetd'&, this privileged action is
40642 To be able to change uid and gid in order to read users' &_.forward_& files and
40643 perform local deliveries as the receiving user or as specified in the
40647 It is not necessary to be root to do any of the other things Exim does, such as
40648 receiving messages and delivering them externally over SMTP, and it is
40649 obviously more secure if Exim does not run as root except when necessary.
40650 For this reason, a user and group for Exim to use must be defined in
40651 &_Local/Makefile_&. These are known as &"the Exim user"& and &"the Exim
40652 group"&. Their values can be changed by the runtime configuration, though this
40653 is not recommended. Often a user called &'exim'& is used, but some sites use
40654 &'mail'& or another user name altogether.
40656 Exim uses &[setuid()]& whenever it gives up root privilege. This is a permanent
40657 abdication; the process cannot regain root afterwards. Prior to release 4.00,
40658 &[seteuid()]& was used in some circumstances, but this is no longer the case.
40660 After a new Exim process has interpreted its command line options, it changes
40661 uid and gid in the following cases:
40666 If the &%-C%& option is used to specify an alternate configuration file, or if
40667 the &%-D%& option is used to define macro values for the configuration, and the
40668 calling process is not running as root, the uid and gid are changed to those of
40669 the calling process.
40670 However, if DISABLE_D_OPTION is defined in &_Local/Makefile_&, the &%-D%&
40671 option may not be used at all.
40672 If WHITELIST_D_MACROS is defined in &_Local/Makefile_&, then some macro values
40673 can be supplied if the calling process is running as root, the Exim run-time
40674 user or CONFIGURE_OWNER, if defined.
40679 If the expansion test option (&%-be%&) or one of the filter testing options
40680 (&%-bf%& or &%-bF%&) are used, the uid and gid are changed to those of the
40683 If the process is not a daemon process or a queue runner process or a delivery
40684 process or a process for testing address routing (started with &%-bt%&), the
40685 uid and gid are changed to the Exim user and group. This means that Exim always
40686 runs under its own uid and gid when receiving messages. This also applies when
40687 testing address verification
40690 (the &%-bv%& option) and testing incoming message policy controls (the &%-bh%&
40693 For a daemon, queue runner, delivery, or address testing process, the uid
40694 remains as root at this stage, but the gid is changed to the Exim group.
40697 The processes that initially retain root privilege behave as follows:
40700 A daemon process changes the gid to the Exim group and the uid to the Exim
40701 user after setting up one or more listening sockets. The &[initgroups()]&
40702 function is called, so that if the Exim user is in any additional groups, they
40703 will be used during message reception.
40705 A queue runner process retains root privilege throughout its execution. Its
40706 job is to fork a controlled sequence of delivery processes.
40708 A delivery process retains root privilege throughout most of its execution,
40709 but any actual deliveries (that is, the transports themselves) are run in
40710 subprocesses which always change to a non-root uid and gid. For local
40711 deliveries this is typically the uid and gid of the owner of the mailbox; for
40712 remote deliveries, the Exim uid and gid are used. Once all the delivery
40713 subprocesses have been run, a delivery process changes to the Exim uid and gid
40714 while doing post-delivery tidying up such as updating the retry database and
40715 generating bounce and warning messages.
40717 While the recipient addresses in a message are being routed, the delivery
40718 process runs as root. However, if a user's filter file has to be processed,
40719 this is done in a subprocess that runs under the individual user's uid and
40720 gid. A system filter is run as root unless &%system_filter_user%& is set.
40722 A process that is testing addresses (the &%-bt%& option) runs as root so that
40723 the routing is done in the same environment as a message delivery.
40729 .section "Running Exim without privilege" "SECTrunexiwitpri"
40730 .cindex "privilege, running without"
40731 .cindex "unprivileged running"
40732 .cindex "root privilege" "running without"
40733 Some installations like to run Exim in an unprivileged state for more of its
40734 operation, for added security. Support for this mode of operation is provided
40735 by the global option &%deliver_drop_privilege%&. When this is set, the uid and
40736 gid are changed to the Exim user and group at the start of a delivery process
40737 (and also queue runner and address testing processes). This means that address
40738 routing is no longer run as root, and the deliveries themselves cannot change
40742 .cindex "daemon" "restarting"
40743 Leaving the binary setuid to root, but setting &%deliver_drop_privilege%& means
40744 that the daemon can still be started in the usual way, and it can respond
40745 correctly to SIGHUP because the re-invocation regains root privilege.
40747 An alternative approach is to make Exim setuid to the Exim user and also setgid
40748 to the Exim group. If you do this, the daemon must be started from a root
40749 process. (Calling Exim from a root process makes it behave in the way it does
40750 when it is setuid root.) However, the daemon cannot restart itself after a
40751 SIGHUP signal because it cannot regain privilege.
40753 It is still useful to set &%deliver_drop_privilege%& in this case, because it
40754 stops Exim from trying to re-invoke itself to do a delivery after a message has
40755 been received. Such a re-invocation is a waste of resources because it has no
40758 If restarting the daemon is not an issue (for example, if &%mua_wrapper%& is
40759 set, or &'inetd'& is being used instead of a daemon), having the binary setuid
40760 to the Exim user seems a clean approach, but there is one complication:
40762 In this style of operation, Exim is running with the real uid and gid set to
40763 those of the calling process, and the effective uid/gid set to Exim's values.
40764 Ideally, any association with the calling process' uid/gid should be dropped,
40765 that is, the real uid/gid should be reset to the effective values so as to
40766 discard any privileges that the caller may have. While some operating systems
40767 have a function that permits this action for a non-root effective uid, quite a
40768 number of them do not. Because of this lack of standardization, Exim does not
40769 address this problem at this time.
40771 For this reason, the recommended approach for &"mostly unprivileged"& running
40772 is to keep the Exim binary setuid to root, and to set
40773 &%deliver_drop_privilege%&. This also has the advantage of allowing a daemon to
40774 be used in the most straightforward way.
40776 If you configure Exim not to run delivery processes as root, there are a
40777 number of restrictions on what you can do:
40780 You can deliver only as the Exim user/group. You should explicitly use the
40781 &%user%& and &%group%& options to override routers or local transports that
40782 normally deliver as the recipient. This makes sure that configurations that
40783 work in this mode function the same way in normal mode. Any implicit or
40784 explicit specification of another user causes an error.
40786 Use of &_.forward_& files is severely restricted, such that it is usually
40787 not worthwhile to include them in the configuration.
40789 Users who wish to use &_.forward_& would have to make their home directory and
40790 the file itself accessible to the Exim user. Pipe and append-to-file entries,
40791 and their equivalents in Exim filters, cannot be used. While they could be
40792 enabled in the Exim user's name, that would be insecure and not very useful.
40794 Unless the local user mailboxes are all owned by the Exim user (possible in
40795 some POP3 or IMAP-only environments):
40798 They must be owned by the Exim group and be writeable by that group. This
40799 implies you must set &%mode%& in the appendfile configuration, as well as the
40800 mode of the mailbox files themselves.
40802 You must set &%no_check_owner%&, since most or all of the files will not be
40803 owned by the Exim user.
40805 You must set &%file_must_exist%&, because Exim cannot set the owner correctly
40806 on a newly created mailbox when unprivileged. This also implies that new
40807 mailboxes need to be created manually.
40812 These restrictions severely restrict what can be done in local deliveries.
40813 However, there are no restrictions on remote deliveries. If you are running a
40814 gateway host that does no local deliveries, setting &%deliver_drop_privilege%&
40815 gives more security at essentially no cost.
40817 If you are using the &%mua_wrapper%& facility (see chapter
40818 &<<CHAPnonqueueing>>&), &%deliver_drop_privilege%& is forced to be true.
40823 .section "Delivering to local files" "SECID271"
40824 Full details of the checks applied by &(appendfile)& before it writes to a file
40825 are given in chapter &<<CHAPappendfile>>&.
40829 .section "Running local commands" "SECTsecconslocalcmds"
40830 .cindex "security" "local commands"
40831 .cindex "security" "command injection attacks"
40832 There are a number of ways in which an administrator can configure Exim to run
40833 commands based upon received, untrustworthy, data. Further, in some
40834 configurations a user who can control a &_.forward_& file can also arrange to
40835 run commands. Configuration to check includes, but is not limited to:
40838 Use of &%use_shell%& in the pipe transport: various forms of shell command
40839 injection may be possible with this option present. It is dangerous and should
40840 be used only with considerable caution. Consider constraints which whitelist
40841 allowed characters in a variable which is to be used in a pipe transport that
40842 has &%use_shell%& enabled.
40844 A number of options such as &%forbid_filter_run%&, &%forbid_filter_perl%&,
40845 &%forbid_filter_dlfunc%& and so forth which restrict facilities available to
40846 &_.forward_& files in a redirect router. If Exim is running on a central mail
40847 hub to which ordinary users do not have shell access, but home directories are
40848 NFS mounted (for instance) then administrators should review the list of these
40849 forbid options available, and should bear in mind that the options that may
40850 need forbidding can change as new features are added between releases.
40852 The &%${run...}%& expansion item does not use a shell by default, but
40853 administrators can configure use of &_/bin/sh_& as part of the command.
40854 Such invocations should be viewed with prejudicial suspicion.
40856 Administrators who use embedded Perl are advised to explore how Perl's
40857 taint checking might apply to their usage.
40859 Use of &%${expand...}%& is somewhat analogous to shell's eval builtin and
40860 administrators are well advised to view its use with suspicion, in case (for
40861 instance) it allows a local-part to contain embedded Exim directives.
40863 Use of &%${match_local_part...}%& and friends becomes more dangerous if
40864 Exim was built with EXPAND_LISTMATCH_RHS defined: the second string in
40865 each can reference arbitrary lists and files, rather than just being a list
40867 The EXPAND_LISTMATCH_RHS option was added and set false by default because of
40868 real-world security vulnerabilities caused by its use with untrustworthy data
40869 injected in, for SQL injection attacks.
40870 Consider the use of the &%inlisti%& expansion condition instead.
40876 .section "Trust in configuration data" "SECTsecconfdata"
40877 .cindex "security" "data sources"
40878 .cindex "security" "regular expressions"
40879 .cindex "regular expressions" "security"
40880 .cindex "PCRE2" "security"
40881 If configuration data for Exim can come from untrustworthy sources, there
40882 are some issues to be aware of:
40885 Use of &%${expand...}%& may provide a path for shell injection attacks.
40887 Letting untrusted data provide a regular expression is unwise.
40889 Using &%${match...}%& to apply a fixed regular expression against untrusted
40890 data may result in pathological behaviour within PCRE2. Be aware of what
40891 "backtracking" means and consider options for being more strict with a regular
40892 expression. Avenues to explore include limiting what can match (avoiding &`.`&
40893 when &`[a-z0-9]`& or other character class will do), use of atomic grouping and
40894 possessive quantifiers or just not using regular expressions against untrusted
40897 It can be important to correctly use &%${quote:...}%&,
40898 &%${quote_local_part:...}%& and &%${quote_%&<&'lookup-type'&>&%:...}%& expansion
40899 items to ensure that data is correctly constructed.
40901 Some lookups might return multiple results, even though normal usage is only
40902 expected to yield one result.
40908 .section "IPv4 source routing" "SECID272"
40909 .cindex "source routing" "in IP packets"
40910 .cindex "IP source routing"
40911 Many operating systems suppress IP source-routed packets in the kernel, but
40912 some cannot be made to do this, so Exim does its own check. It logs incoming
40913 IPv4 source-routed TCP calls, and then drops them. Things are all different in
40914 IPv6. No special checking is currently done.
40918 .section "The VRFY, EXPN, and ETRN commands in SMTP" "SECID273"
40919 Support for these SMTP commands is disabled by default. If required, they can
40920 be enabled by defining suitable ACLs.
40925 .section "Privileged users" "SECID274"
40926 .cindex "trusted users"
40927 .cindex "admin user"
40928 .cindex "privileged user"
40929 .cindex "user" "trusted"
40930 .cindex "user" "admin"
40931 Exim recognizes two sets of users with special privileges. Trusted users are
40932 able to submit new messages to Exim locally, but supply their own sender
40933 addresses and information about a sending host. For other users submitting
40934 local messages, Exim sets up the sender address from the uid, and doesn't
40935 permit a remote host to be specified.
40938 However, an untrusted user is permitted to use the &%-f%& command line option
40939 in the special form &%-f <>%& to indicate that a delivery failure for the
40940 message should not cause an error report. This affects the message's envelope,
40941 but it does not affect the &'Sender:'& header. Untrusted users may also be
40942 permitted to use specific forms of address with the &%-f%& option by setting
40943 the &%untrusted_set_sender%& option.
40945 Trusted users are used to run processes that receive mail messages from some
40946 other mail domain and pass them on to Exim for delivery either locally, or over
40947 the Internet. Exim trusts a caller that is running as root, as the Exim user,
40948 as any user listed in the &%trusted_users%& configuration option, or under any
40949 group listed in the &%trusted_groups%& option.
40951 Admin users are permitted to do things to the messages on Exim's queue. They
40952 can freeze or thaw messages, cause them to be returned to their senders, remove
40953 them entirely, or modify them in various ways. In addition, admin users can run
40954 the Exim monitor and see all the information it is capable of providing, which
40955 includes the contents of files on the spool.
40959 By default, the use of the &%-M%& and &%-q%& options to cause Exim to attempt
40960 delivery of messages on its queue is restricted to admin users. This
40961 restriction can be relaxed by setting the &%no_prod_requires_admin%& option.
40962 Similarly, the use of &%-bp%& (and its variants) to list the contents of the
40963 queue is also restricted to admin users. This restriction can be relaxed by
40964 setting &%no_queue_list_requires_admin%&.
40966 Exim recognizes an admin user if the calling process is running as root or as
40967 the Exim user or if any of the groups associated with the calling process is
40968 the Exim group. It is not necessary actually to be running under the Exim
40969 group. However, if admin users who are not root or the Exim user are to access
40970 the contents of files on the spool via the Exim monitor (which runs
40971 unprivileged), Exim must be built to allow group read access to its spool
40974 By default, regular users are trusted to perform basic testing and
40975 introspection commands, as themselves. This setting can be tightened by
40976 setting the &%commandline_checks_require_admin%& option.
40977 This affects most of the checking options,
40978 such as &%-be%& and anything else &%-b*%&.
40981 .section "Spool files" "SECID275"
40982 .cindex "spool directory" "files"
40983 Exim's spool directory and everything it contains is owned by the Exim user and
40984 set to the Exim group. The mode for spool files is defined in the
40985 &_Local/Makefile_& configuration file, and defaults to 0640. This means that
40986 any user who is a member of the Exim group can access these files.
40990 .section "Use of argv[0]" "SECID276"
40991 Exim examines the last component of &%argv[0]%&, and if it matches one of a set
40992 of specific strings, Exim assumes certain options. For example, calling Exim
40993 with the last component of &%argv[0]%& set to &"rsmtp"& is exactly equivalent
40994 to calling it with the option &%-bS%&. There are no security implications in
40999 .section "Use of %f formatting" "SECID277"
41000 The only use made of &"%f"& by Exim is in formatting load average values. These
41001 are actually stored in integer variables as 1000 times the load average.
41002 Consequently, their range is limited and so therefore is the length of the
41007 .section "Embedded Exim path" "SECID278"
41008 Exim uses its own path name, which is embedded in the code, only when it needs
41009 to re-exec in order to regain root privilege. Therefore, it is not root when it
41010 does so. If some bug allowed the path to get overwritten, it would lead to an
41011 arbitrary program's being run as exim, not as root.
41015 .section "Dynamic module directory" "SECTdynmoddir"
41016 Any dynamically loadable modules must be installed into the directory
41017 defined in &`LOOKUP_MODULE_DIR`& in &_Local/Makefile_& for Exim to permit
41021 .section "Use of sprintf()" "SECID279"
41022 .cindex "&[sprintf()]&"
41023 A large number of occurrences of &"sprintf"& in the code are actually calls to
41024 &'string_sprintf()'&, a function that returns the result in malloc'd store.
41025 The intermediate formatting is done into a large fixed buffer by a function
41026 that runs through the format string itself, and checks the length of each
41027 conversion before performing it, thus preventing buffer overruns.
41029 The remaining uses of &[sprintf()]& happen in controlled circumstances where
41030 the output buffer is known to be sufficiently long to contain the converted
41035 .section "Use of debug_printf() and log_write()" "SECID280"
41036 Arbitrary strings are passed to both these functions, but they do their
41037 formatting by calling the function &'string_vformat()'&, which runs through
41038 the format string itself, and checks the length of each conversion.
41042 .section "Use of strcat() and strcpy()" "SECID281"
41043 These are used only in cases where the output buffer is known to be large
41044 enough to hold the result.
41045 .ecindex IIDsecurcon
41050 . ////////////////////////////////////////////////////////////////////////////
41051 . ////////////////////////////////////////////////////////////////////////////
41053 .chapter "Format of spool files" "CHAPspool"
41054 .scindex IIDforspo1 "format" "spool files"
41055 .scindex IIDforspo2 "spool directory" "format of files"
41056 .scindex IIDforspo3 "spool files" "format of"
41057 .cindex "spool files" "editing"
41058 A message on Exim's queue consists of two files, whose names are the message id
41059 followed by -D and -H, respectively. The data portion of the message is kept in
41060 the -D file on its own. The message's envelope, status, and headers are all
41061 kept in the -H file, whose format is described in this chapter. Each of these
41062 two files contains the final component of its own name as its first line. This
41063 is insurance against disk crashes where the directory is lost but the files
41064 themselves are recoverable.
41066 The file formats may be changed, or new formats added, at any release.
41067 Spool files are not intended as an interface to other programs
41068 and should not be used as such.
41070 Some people are tempted into editing -D files in order to modify messages. You
41071 need to be extremely careful if you do this; it is not recommended and you are
41072 on your own if you do it. Here are some of the pitfalls:
41075 You must ensure that Exim does not try to deliver the message while you are
41076 fiddling with it. The safest way is to take out a write lock on the -D file,
41077 which is what Exim itself does, using &[fcntl()]&. If you update the file in
41078 place, the lock will be retained. If you write a new file and rename it, the
41079 lock will be lost at the instant of rename.
41081 .vindex "&$body_linecount$&"
41082 If you change the number of lines in the file, the value of
41083 &$body_linecount$&, which is stored in the -H file, will be incorrect and can
41084 cause incomplete transmission of messages or undeliverable messages.
41086 If the message is in MIME format, you must take care not to break it.
41088 If the message is cryptographically signed, any change will invalidate the
41091 All in all, modifying -D files is fraught with danger.
41093 Files whose names end with -J may also be seen in the &_input_& directory (or
41094 its subdirectories when &%split_spool_directory%& is set). These are journal
41095 files, used to record addresses to which the message has been delivered during
41096 the course of a delivery attempt. If there are still undelivered recipients at
41097 the end, the -H file is updated, and the -J file is deleted. If, however, there
41098 is some kind of crash (for example, a power outage) before this happens, the -J
41099 file remains in existence. When Exim next processes the message, it notices the
41100 -J file and uses it to update the -H file before starting the next delivery
41103 Files whose names end with -K or .eml may also be seen in the spool.
41104 These are temporaries used for DKIM or malware processing, when that is used.
41105 They should be tidied up by normal operations; any old ones are probably
41106 relics of crashes and can be removed.
41108 .section "Format of the -H file" "SECID282"
41109 .cindex "uid (user id)" "in spool file"
41110 .cindex "gid (group id)" "in spool file"
41111 The second line of the -H file contains the login name for the uid of the
41112 process that called Exim to read the message, followed by the numerical uid and
41113 gid. For a locally generated message, this is normally the user who sent the
41114 message. For a message received over TCP/IP via the daemon, it is
41115 normally the Exim user.
41117 The third line of the file contains the address of the message's sender as
41118 transmitted in the envelope, contained in angle brackets. The sender address is
41119 empty for bounce messages. For incoming SMTP mail, the sender address is given
41120 in the MAIL command. For locally generated mail, the sender address is
41121 created by Exim from the login name of the current user and the configured
41122 &%qualify_domain%&. However, this can be overridden by the &%-f%& option or a
41123 leading &"From&~"& line if the caller is trusted, or if the supplied address is
41124 &"<>"& or an address that matches &%untrusted_set_senders%&.
41126 The fourth line contains two numbers. The first is the time that the message
41127 was received, in the conventional Unix form &-- the number of seconds since the
41128 start of the epoch. The second number is a count of the number of messages
41129 warning of delayed delivery that have been sent to the sender.
41132 There follow a number of lines starting with a hyphen.
41133 These contain variables, can appear in any
41134 order, and are omitted when not relevant.
41136 If there is a second hyphen after the first,
41137 the corresponding data is tainted.
41138 If there is a value in parentheses, the data is quoted for a lookup.
41140 The following word specifies a variable,
41141 and the remainder of the item depends on the variable.
41145 .vitem "&%-acl%&&~<&'number'&>&~<&'length'&>"
41146 This item is obsolete, and is not generated from Exim release 4.61 onwards;
41147 &%-aclc%& and &%-aclm%& are used instead. However, &%-acl%& is still
41148 recognized, to provide backward compatibility. In the old format, a line of
41149 this form is present for every ACL variable that is not empty. The number
41150 identifies the variable; the &%acl_c%&&*x*& variables are numbered 0&--9 and
41151 the &%acl_m%&&*x*& variables are numbered 10&--19. The length is the length of
41152 the data string for the variable. The string itself starts at the beginning of
41153 the next line, and is followed by a newline character. It may contain internal
41156 .vitem "&%-aclc%&&~<&'rest-of-name'&>&~<&'length'&>"
41157 A line of this form is present for every ACL connection variable that is
41158 defined. Note that there is a space between &%-aclc%& and the rest of the name.
41159 The length is the length of the data string for the variable. The string itself
41160 starts at the beginning of the next line, and is followed by a newline
41161 character. It may contain internal newlines.
41163 .vitem "&%-aclm%&&~<&'rest-of-name'&>&~<&'length'&>"
41164 A line of this form is present for every ACL message variable that is defined.
41165 Note that there is a space between &%-aclm%& and the rest of the name. The
41166 length is the length of the data string for the variable. The string itself
41167 starts at the beginning of the next line, and is followed by a newline
41168 character. It may contain internal newlines.
41170 .vitem "&%-active_hostname%&&~<&'hostname'&>"
41171 This is present if, when the message was received over SMTP, the value of
41172 &$smtp_active_hostname$& was different to the value of &$primary_hostname$&.
41174 .vitem &%-allow_unqualified_recipient%&
41175 This is present if unqualified recipient addresses are permitted in header
41176 lines (to stop such addresses from being qualified if rewriting occurs at
41177 transport time). Local messages that were input using &%-bnq%& and remote
41178 messages from hosts that match &%recipient_unqualified_hosts%& set this flag.
41180 .vitem &%-allow_unqualified_sender%&
41181 This is present if unqualified sender addresses are permitted in header lines
41182 (to stop such addresses from being qualified if rewriting occurs at transport
41183 time). Local messages that were input using &%-bnq%& and remote messages from
41184 hosts that match &%sender_unqualified_hosts%& set this flag.
41186 .vitem "&%-auth_id%&&~<&'text'&>"
41187 The id information for a message received on an authenticated SMTP connection
41188 &-- the value of the &$authenticated_id$& variable.
41190 .vitem "&%-auth_sender%&&~<&'address'&>"
41191 The address of an authenticated sender &-- the value of the
41192 &$authenticated_sender$& variable.
41194 .vitem "&%-body_linecount%&&~<&'number'&>"
41195 This records the number of lines in the body of the message, and is
41196 present unless &%-spool_file_wireformat%& is.
41198 .vitem "&%-body_zerocount%&&~<&'number'&>"
41199 This records the number of binary zero bytes in the body of the message, and is
41200 present if the number is greater than zero.
41202 .vitem &%-deliver_firsttime%&
41203 This is written when a new message is first added to the spool. When the spool
41204 file is updated after a deferral, it is omitted.
41206 .vitem "&%-frozen%&&~<&'time'&>"
41207 .cindex "frozen messages" "spool data"
41208 The message is frozen, and the freezing happened at <&'time'&>.
41210 .vitem "&%-helo_name%&&~<&'text'&>"
41211 This records the host name as specified by a remote host in a HELO or EHLO
41214 .vitem "&%-host_address%&&~<&'address'&>.<&'port'&>"
41215 This records the IP address of the host from which the message was received and
41216 the remote port number that was used. It is omitted for locally generated
41219 .vitem "&%-host_auth%&&~<&'text'&>"
41220 If the message was received on an authenticated SMTP connection, this records
41221 the name of the authenticator &-- the value of the
41222 &$sender_host_authenticated$& variable.
41224 .vitem &%-host_lookup_failed%&
41225 This is present if an attempt to look up the sending host's name from its IP
41226 address failed. It corresponds to the &$host_lookup_failed$& variable.
41228 .vitem "&%-host_name%&&~<&'text'&>"
41229 .cindex "reverse DNS lookup"
41230 .cindex "DNS" "reverse lookup"
41231 This records the name of the remote host from which the message was received,
41232 if the host name was looked up from the IP address when the message was being
41233 received. It is not present if no reverse lookup was done.
41235 .vitem "&%-ident%&&~<&'text'&>"
41236 For locally submitted messages, this records the login of the originating user,
41237 unless it was a trusted user and the &%-oMt%& option was used to specify an
41238 ident value. For messages received over TCP/IP, this records the ident string
41239 supplied by the remote host, if any.
41241 .vitem "&%-interface_address%&&~<&'address'&>.<&'port'&>"
41242 This records the IP address of the local interface and the port number through
41243 which a message was received from a remote host. It is omitted for locally
41244 generated messages.
41247 The message is from a local sender.
41249 .vitem &%-localerror%&
41250 The message is a locally-generated bounce message.
41252 .vitem "&%-local_scan%&&~<&'string'&>"
41253 This records the data string that was returned by the &[local_scan()]& function
41254 when the message was received &-- the value of the &$local_scan_data$&
41255 variable. It is omitted if no data was returned.
41257 .vitem &%-manual_thaw%&
41258 The message was frozen but has been thawed manually, that is, by an explicit
41259 Exim command rather than via the auto-thaw process.
41262 A testing delivery process was started using the &%-N%& option to suppress any
41263 actual deliveries, but delivery was deferred. At any further delivery attempts,
41266 .vitem &%-received_protocol%&
41267 This records the value of the &$received_protocol$& variable, which contains
41268 the name of the protocol by which the message was received.
41270 .vitem &%-sender_set_untrusted%&
41271 The envelope sender of this message was set by an untrusted local caller (used
41272 to ensure that the caller is displayed in queue listings).
41274 .vitem "&%-spam_score_int%&&~<&'number'&>"
41275 If a message was scanned by SpamAssassin, this is present. It records the value
41276 of &$spam_score_int$&.
41278 .vitem &%-spool_file_wireformat%&
41279 The -D file for this message is in wire-format (for ESMTP CHUNKING)
41280 rather than Unix-format.
41281 The line-ending is CRLF rather than newline.
41282 There is still, however, no leading-dot-stuffing.
41284 .vitem &%-tls_certificate_verified%&
41285 A TLS certificate was received from the client that sent this message, and the
41286 certificate was verified by the server.
41288 .vitem "&%-tls_cipher%&&~<&'cipher name'&>"
41289 When the message was received over an encrypted connection, this records the
41290 name of the cipher suite that was used.
41292 .vitem "&%-tls_peerdn%&&~<&'peer DN'&>"
41293 When the message was received over an encrypted connection, and a certificate
41294 was received from the client, this records the Distinguished Name from that
41298 Following the options there is a list of those addresses to which the message
41299 is not to be delivered. This set of addresses is initialized from the command
41300 line when the &%-t%& option is used and &%extract_addresses_remove_arguments%&
41301 is set; otherwise it starts out empty. Whenever a successful delivery is made,
41302 the address is added to this set. The addresses are kept internally as a
41303 balanced binary tree, and it is a representation of that tree which is written
41304 to the spool file. If an address is expanded via an alias or forward file, the
41305 original address is added to the tree when deliveries to all its child
41306 addresses are complete.
41308 If the tree is empty, there is a single line in the spool file containing just
41309 the text &"XX"&. Otherwise, each line consists of two letters, which are either
41310 Y or N, followed by an address. The address is the value for the node of the
41311 tree, and the letters indicate whether the node has a left branch and/or a
41312 right branch attached to it, respectively. If branches exist, they immediately
41313 follow. Here is an example of a three-node tree:
41315 YY darcy@austen.fict.example
41316 NN alice@wonderland.fict.example
41317 NN editor@thesaurus.ref.example
41319 After the non-recipients tree, there is a list of the message's recipients.
41320 This is a simple list, preceded by a count. It includes all the original
41321 recipients of the message, including those to whom the message has already been
41322 delivered. In the simplest case, the list contains one address per line. For
41326 editor@thesaurus.ref.example
41327 darcy@austen.fict.example
41329 alice@wonderland.fict.example
41331 However, when a child address has been added to the top-level addresses as a
41332 result of the use of the &%one_time%& option on a &(redirect)& router, each
41333 line is of the following form:
41335 <&'top-level address'&> <&'errors_to address'&> &&&
41336 <&'length'&>,<&'parent number'&>#<&'flag bits'&>
41338 The 01 flag bit indicates the presence of the three other fields that follow
41339 the top-level address. Other bits may be used in future to support additional
41340 fields. The <&'parent number'&> is the offset in the recipients list of the
41341 original parent of the &"one time"& address. The first two fields are the
41342 envelope sender that is associated with this address and its length. If the
41343 length is zero, there is no special envelope sender (there are then two space
41344 characters in the line). A non-empty field can arise from a &(redirect)& router
41345 that has an &%errors_to%& setting.
41348 A blank line separates the envelope and status information from the headers
41349 which follow. A header may occupy several lines of the file, and to save effort
41350 when reading it in, each header is preceded by a number and an identifying
41351 character. The number is the number of characters in the header, including any
41352 embedded newlines and the terminating newline. The character is one of the
41356 .row <&'blank'&> "header in which Exim has no special interest"
41357 .row &`B`& "&'Bcc:'& header"
41358 .row &`C`& "&'Cc:'& header"
41359 .row &`F`& "&'From:'& header"
41360 .row &`I`& "&'Message-id:'& header"
41361 .row &`P`& "&'Received:'& header &-- P for &""postmark""&"
41362 .row &`R`& "&'Reply-To:'& header"
41363 .row &`S`& "&'Sender:'& header"
41364 .row &`T`& "&'To:'& header"
41365 .row &`*`& "replaced or deleted header"
41368 Deleted or replaced (rewritten) headers remain in the spool file for debugging
41369 purposes. They are not transmitted when the message is delivered. Here is a
41370 typical set of headers:
41372 111P Received: by hobbit.fict.example with local (Exim 4.00)
41373 id 14y9EI-00026G-00; Fri, 11 May 2001 10:28:59 +0100
41374 049 Message-Id: <E14y9EI-00026G-00@hobbit.fict.example>
41375 038* X-rewrote-sender: bb@hobbit.fict.example
41376 042* From: Bilbo Baggins <bb@hobbit.fict.example>
41377 049F From: Bilbo Baggins <B.Baggins@hobbit.fict.example>
41378 099* To: alice@wonderland.fict.example, rdo@foundation,
41379 darcy@austen.fict.example, editor@thesaurus.ref.example
41380 104T To: alice@wonderland.fict.example, rdo@foundation.example,
41381 darcy@austen.fict.example, editor@thesaurus.ref.example
41382 038 Date: Fri, 11 May 2001 10:28:59 +0100
41384 The asterisked headers indicate that the envelope sender, &'From:'& header, and
41385 &'To:'& header have been rewritten, the last one because routing expanded the
41386 unqualified domain &'foundation'&.
41387 .ecindex IIDforspo1
41388 .ecindex IIDforspo2
41389 .ecindex IIDforspo3
41391 .section "Format of the -D file" "SECID282a"
41392 The data file is traditionally in Unix-standard format: lines are ended with
41393 an ASCII newline character.
41394 However, when the &%spool_wireformat%& main option is used some -D files
41395 can have an alternate format.
41396 This is flagged by a &%-spool_file_wireformat%& line in the corresponding -H file.
41397 The -D file lines (not including the first name-component line) are
41398 suitable for direct copying to the wire when transmitting using the
41399 ESMTP CHUNKING option, meaning lower processing overhead.
41400 Lines are terminated with an ASCII CRLF pair.
41401 There is no dot-stuffing (and no dot-termination).
41403 . ////////////////////////////////////////////////////////////////////////////
41404 . ////////////////////////////////////////////////////////////////////////////
41406 .chapter "DKIM, SPF, SRS and DMARC" "CHAPdkim" &&&
41407 "DKIM, SPF, SRS and DMARC Support"
41409 .section "DKIM (DomainKeys Identified Mail)" SECDKIM
41412 DKIM is a mechanism by which messages sent by some entity can be provably
41413 linked to a domain which that entity controls. It permits reputation to
41414 be tracked on a per-domain basis, rather than merely upon source IP address.
41415 DKIM is documented in RFC 6376.
41417 As DKIM relies on the message being unchanged in transit, messages handled
41418 by a mailing-list (which traditionally adds to the message) will not match
41419 any original DKIM signature.
41421 DKIM support is compiled into Exim by default if TLS support is present.
41422 It can be disabled by setting DISABLE_DKIM=yes in &_Local/Makefile_&.
41424 Exim's DKIM implementation allows for
41426 Signing outgoing messages: This function is implemented in the SMTP transport.
41427 It can co-exist with all other Exim features
41428 (including transport filters)
41429 except cutthrough delivery.
41431 Verifying signatures in incoming messages: This is implemented by an additional
41432 ACL (acl_smtp_dkim), which can be called several times per message, with
41433 different signature contexts.
41436 In typical Exim style, the verification implementation does not include any
41437 default "policy". Instead it enables you to build your own policy using
41438 Exim's standard controls.
41440 Please note that verification of DKIM signatures in incoming mail is turned
41441 on by default for logging (in the <= line) purposes.
41443 Additional log detail can be enabled using the &%dkim_verbose%& log_selector.
41444 When set, for each signature in incoming email,
41445 exim will log a line displaying the most important signature details, and the
41446 signature status. Here is an example (with line-breaks added for clarity):
41448 2009-09-09 10:22:28 1MlIRf-0003LU-U3 DKIM:
41449 d=facebookmail.com s=q1-2009b
41450 c=relaxed/relaxed a=rsa-sha1
41451 i=@facebookmail.com t=1252484542 [verification succeeded]
41454 You might want to turn off DKIM verification processing entirely for internal
41455 or relay mail sources. To do that, set the &%dkim_disable_verify%& ACL
41456 control modifier. This should typically be done in the RCPT ACL, at points
41457 where you accept mail from relay sources (internal hosts or authenticated
41461 .section "Signing outgoing messages" "SECDKIMSIGN"
41462 .cindex "DKIM" "signing"
41464 For signing to be usable you must have published a DKIM record in DNS.
41465 Note that RFC 8301 (which does not cover EC keys) says:
41467 rsa-sha1 MUST NOT be used for signing or verifying.
41469 Signers MUST use RSA keys of at least 1024 bits for all keys.
41470 Signers SHOULD use RSA keys of at least 2048 bits.
41473 Note also that the key content (the 'p=' field)
41474 in the DNS record is different between RSA and EC keys;
41475 for the former it is the base64 of the ASN.1 for the RSA public key
41476 (equivalent to the private-key .pem with the header/trailer stripped)
41477 but for EC keys it is the base64 of the pure key; no ASN.1 wrapping.
41479 Signing is enabled by setting private options on the SMTP transport.
41480 These options take (expandable) strings as arguments.
41482 .option dkim_domain smtp "string list&!!" unset
41483 The domain(s) you want to sign with.
41484 After expansion, this can be a list.
41485 Each element in turn,
41487 is put into the &%$dkim_domain%& expansion variable
41488 while expanding the remaining signing options.
41489 If it is empty after expansion, DKIM signing is not done,
41490 and no error will result even if &%dkim_strict%& is set.
41492 .option dkim_selector smtp "string list&!!" unset
41493 This sets the key selector string.
41494 After expansion, which can use &$dkim_domain$&, this can be a list.
41495 Each element in turn is put in the expansion
41496 variable &%$dkim_selector%& which may be used in the &%dkim_private_key%&
41497 option along with &%$dkim_domain%&.
41498 If the option is empty after expansion, DKIM signing is not done for this domain,
41499 and no error will result even if &%dkim_strict%& is set.
41501 To do, for example, dual-signing with RSA and EC keys
41502 this could be be used:
41504 dkim_selector = ec_sel : rsa_sel
41505 dkim_private_key = KEYS_DIR/$dkim_selector
41508 .option dkim_private_key smtp string&!! unset
41509 This sets the private key to use.
41510 You can use the &%$dkim_domain%& and
41511 &%$dkim_selector%& expansion variables to determine the private key to use.
41512 The result can either
41514 be a valid RSA private key in ASCII armor (.pem file), including line breaks
41516 with GnuTLS 3.6.0 or OpenSSL 1.1.1 or later,
41517 be a valid Ed25519 private key (same format as above)
41519 start with a slash, in which case it is treated as a file that contains
41522 be "0", "false" or the empty string, in which case the message will not
41523 be signed. This case will not result in an error, even if &%dkim_strict%&
41527 To generate keys under OpenSSL:
41529 openssl genrsa -out dkim_rsa.private 2048
41530 openssl rsa -in dkim_rsa.private -out /dev/stdout -pubout -outform PEM
41532 The result file from the first command should be retained, and
41533 this option set to use it.
41534 Take the base-64 lines from the output of the second command, concatenated,
41535 for the DNS TXT record.
41536 See section 3.6 of RFC6376 for the record specification.
41540 certtool --generate-privkey --rsa --bits=2048 --password='' -8 --outfile=dkim_rsa.private
41541 certtool --load-privkey=dkim_rsa.private --pubkey-info
41544 Note that RFC 8301 says:
41546 Signers MUST use RSA keys of at least 1024 bits for all keys.
41547 Signers SHOULD use RSA keys of at least 2048 bits.
41550 EC keys for DKIM are defined by RFC 8463.
41551 They are considerably smaller than RSA keys for equivalent protection.
41552 As they are a recent development, users should consider dual-signing
41553 (by setting a list of selectors, and an expansion for this option)
41554 for some transition period.
41555 The "_CRYPTO_SIGN_ED25519" macro will be defined if support is present
41558 OpenSSL 1.1.1 and GnuTLS 3.6.0 can create Ed25519 private keys:
41560 openssl genpkey -algorithm ed25519 -out dkim_ed25519.private
41561 certtool --generate-privkey --key-type=ed25519 --outfile=dkim_ed25519.private
41564 To produce the required public key value for a DNS record:
41566 openssl pkey -outform DER -pubout -in dkim_ed25519.private | tail -c +13 | base64
41567 certtool --load_privkey=dkim_ed25519.private --pubkey_info --outder | tail -c +13 | base64
41570 Exim also supports an alternate format
41571 of Ed25519 keys in DNS which was a candidate during development
41572 of the standard, but not adopted.
41573 A future release will probably drop that support.
41575 .option dkim_hash smtp string&!! sha256
41576 Can be set to any one of the supported hash methods, which are:
41578 &`sha1`& &-- should not be used, is old and insecure
41580 &`sha256`& &-- the default
41582 &`sha512`& &-- possibly more secure but less well supported
41585 Note that RFC 8301 says:
41587 rsa-sha1 MUST NOT be used for signing or verifying.
41590 .option dkim_identity smtp string&!! unset
41591 If set after expansion, the value is used to set an "i=" tag in
41592 the signing header. The DKIM standards restrict the permissible
41593 syntax of this optional tag to a mail address, with possibly-empty
41594 local part, an @, and a domain identical to or subdomain of the "d="
41595 tag value. Note that Exim does not check the value.
41597 .option dkim_canon smtp string&!! unset
41598 This option sets the canonicalization method used when signing a message.
41599 The DKIM RFC currently supports two methods: "simple" and "relaxed".
41600 The option defaults to "relaxed" when unset. Note: the current implementation
41601 only supports signing with the same canonicalization method for both headers and body.
41603 .option dkim_strict smtp string&!! unset
41604 This option defines how Exim behaves when signing a message that
41605 should be signed fails for some reason. When the expansion evaluates to
41606 either &"1"& or &"true"&, Exim will defer. Otherwise Exim will send the message
41607 unsigned. You can use the &%$dkim_domain%& and &%$dkim_selector%& expansion
41610 .option dkim_sign_headers smtp string&!! "see below"
41611 If set, this option must expand to a colon-separated
41612 list of header names.
41613 Headers with these names, or the absence or such a header, will be included
41614 in the message signature.
41615 When unspecified, the header names listed in RFC4871 will be used,
41616 whether or not each header is present in the message.
41617 The default list is available for the expansion in the macro
41618 &"_DKIM_SIGN_HEADERS"&
41619 and an oversigning variant is in &"_DKIM_OVERSIGN_HEADERS"&.
41621 If a name is repeated, multiple headers by that name (or the absence thereof)
41622 will be signed. The textually later headers in the headers part of the
41623 message are signed first, if there are multiples.
41625 A name can be prefixed with either an &"="& or a &"+"& character.
41626 If an &"="& prefix is used, all headers that are present with this name
41628 If a &"+"& prefix if used, all headers that are present with this name
41629 will be signed, and one signature added for a missing header with the
41630 name will be appended.
41632 .option dkim_timestamps smtp integer&!! unset
41633 This option controls the inclusion of timestamp information in the signature.
41634 If not set, no such information will be included.
41635 Otherwise, must be an unsigned number giving an offset in seconds from the current time
41637 (eg. 1209600 for two weeks);
41638 both creation (t=) and expiry (x=) tags will be included.
41640 RFC 6376 lists these tags as RECOMMENDED.
41643 .section "Verifying DKIM signatures in incoming mail" "SECDKIMVFY"
41644 .cindex "DKIM" "verification"
41646 Verification of DKIM signatures in SMTP incoming email is done for all
41647 messages for which an ACL control &%dkim_disable_verify%& has not been set.
41648 .cindex DKIM "selecting signature algorithms"
41649 Individual classes of signature algorithm can be ignored by changing
41650 the main options &%dkim_verify_hashes%& or &%dkim_verify_keytypes%&.
41651 The &%dkim_verify_minimal%& option can be set to cease verification
41652 processing for a message once the first passing signature is found.
41654 .cindex authentication "expansion item"
41655 Performing verification sets up information used by the
41656 &%authresults%& expansion item.
41658 For most purposes the default option settings suffice and the remainder
41659 of this section can be ignored.
41661 The results of verification are made available to the
41662 &%acl_smtp_dkim%& ACL, which can examine and modify them.
41663 A missing ACL definition defaults to accept.
41664 By default, the ACL is called once for each
41665 syntactically(!) correct signature in the incoming message.
41666 If any ACL call does not accept, the message is not accepted.
41667 If a cutthrough delivery was in progress for the message, that is
41668 summarily dropped (having wasted the transmission effort).
41670 To evaluate the verification result in the ACL
41671 a large number of expansion variables
41672 containing the signature status and its details are set up during the
41673 runtime of the ACL.
41675 Calling the ACL only for existing signatures is not sufficient to build
41676 more advanced policies. For that reason, the main option
41677 &%dkim_verify_signers%&, and an expansion variable
41678 &%$dkim_signers%& exist.
41680 The main option &%dkim_verify_signers%& can be set to a colon-separated
41681 list of DKIM domains or identities for which the ACL &%acl_smtp_dkim%& is
41682 called. It is expanded when the message has been received. At this point,
41683 the expansion variable &%$dkim_signers%& already contains a colon-separated
41684 list of signer domains and identities for the message. When
41685 &%dkim_verify_signers%& is not specified in the main configuration,
41688 dkim_verify_signers = $dkim_signers
41690 This leads to the default behaviour of calling &%acl_smtp_dkim%& for each
41691 DKIM signature in the message. Current DKIM verifiers may want to explicitly
41692 call the ACL for known domains or identities. This would be achieved as follows:
41694 dkim_verify_signers = paypal.com:ebay.com:$dkim_signers
41696 This would result in &%acl_smtp_dkim%& always being called for "paypal.com"
41697 and "ebay.com", plus all domains and identities that have signatures in the message.
41698 You can also be more creative in constructing your policy. For example:
41700 dkim_verify_signers = $sender_address_domain:$dkim_signers
41703 If a domain or identity is listed several times in the (expanded) value of
41704 &%dkim_verify_signers%&, the ACL is only called once for that domain or identity.
41706 Note that if the option is set using untrustworthy data
41707 (such as the From: header)
41708 care should be taken to force lowercase for domains
41709 and for the domain part if identities.
41710 The default setting can be regarded as trustworthy in this respect.
41712 If multiple signatures match a domain (or identity), the ACL is called once
41713 for each matching signature.
41716 Inside the DKIM ACL, the following expansion variables are
41717 available (from most to least important):
41721 .vitem &%$dkim_cur_signer%&
41722 The signer that is being evaluated in this ACL run. This can be a domain or
41723 an identity. This is one of the list items from the expanded main option
41724 &%dkim_verify_signers%& (see above).
41726 .vitem &%$dkim_verify_status%&
41727 Within the DKIM ACL,
41728 a string describing the general status of the signature. One of
41730 &%none%&: There is no signature in the message for the current domain or
41731 identity (as reflected by &%$dkim_cur_signer%&).
41733 &%invalid%&: The signature could not be verified due to a processing error.
41734 More detail is available in &%$dkim_verify_reason%&.
41736 &%fail%&: Verification of the signature failed. More detail is
41737 available in &%$dkim_verify_reason%&.
41739 &%pass%&: The signature passed verification. It is valid.
41742 This variable can be overwritten using an ACL 'set' modifier.
41743 This might, for instance, be done to enforce a policy restriction on
41744 hash-method or key-size:
41746 warn condition = ${if eq {$dkim_verify_status}{pass}}
41747 condition = ${if eq {${length_3:$dkim_algo}}{rsa}}
41748 condition = ${if or {{eq {$dkim_algo}{rsa-sha1}} \
41749 {< {$dkim_key_length}{1024}}}}
41750 logwrite = NOTE: forcing DKIM verify fail (was pass)
41751 set dkim_verify_status = fail
41752 set dkim_verify_reason = hash too weak or key too short
41755 So long as a DKIM ACL is defined (it need do no more than accept),
41756 after all the DKIM ACL runs have completed, the value becomes a
41757 colon-separated list of the values after each run.
41758 This is maintained for the mime, prdr and data ACLs.
41760 .vitem &%$dkim_verify_reason%&
41761 A string giving a little bit more detail when &%$dkim_verify_status%& is either
41762 "fail" or "invalid". One of
41764 &%pubkey_unavailable%& (when &%$dkim_verify_status%&="invalid"): The public
41765 key for the domain could not be retrieved. This may be a temporary problem.
41767 &%pubkey_syntax%& (when &%$dkim_verify_status%&="invalid"): The public key
41768 record for the domain is syntactically invalid.
41770 &%bodyhash_mismatch%& (when &%$dkim_verify_status%&="fail"): The calculated
41771 body hash does not match the one specified in the signature header. This
41772 means that the message body was modified in transit.
41774 &%signature_incorrect%& (when &%$dkim_verify_status%&="fail"): The signature
41775 could not be verified. This may mean that headers were modified,
41776 re-written or otherwise changed in a way which is incompatible with
41777 DKIM verification. It may of course also mean that the signature is forged.
41780 This variable can be overwritten, with any value, using an ACL 'set' modifier.
41782 .vitem &%$dkim_domain%&
41783 The signing domain. IMPORTANT: This variable is only populated if there is
41784 an actual signature in the message for the current domain or identity (as
41785 reflected by &%$dkim_cur_signer%&).
41787 .vitem &%$dkim_identity%&
41788 The signing identity, if present. IMPORTANT: This variable is only populated
41789 if there is an actual signature in the message for the current domain or
41790 identity (as reflected by &%$dkim_cur_signer%&).
41792 .vitem &%$dkim_selector%&
41793 The key record selector string.
41795 .vitem &%$dkim_algo%&
41796 The algorithm used. One of 'rsa-sha1' or 'rsa-sha256'.
41797 If running under GnuTLS 3.6.0 or OpenSSL 1.1.1 or later,
41798 may also be 'ed25519-sha256'.
41799 The "_CRYPTO_SIGN_ED25519" macro will be defined if support is present
41802 Note that RFC 8301 says:
41804 rsa-sha1 MUST NOT be used for signing or verifying.
41806 DKIM signatures identified as having been signed with historic
41807 algorithms (currently, rsa-sha1) have permanently failed evaluation
41810 To enforce this you must either have a DKIM ACL which checks this variable
41811 and overwrites the &$dkim_verify_status$& variable as discussed above,
41812 or have set the main option &%dkim_verify_hashes%& to exclude
41813 processing of such signatures.
41815 .vitem &%$dkim_canon_body%&
41816 The body canonicalization method. One of 'relaxed' or 'simple'.
41818 .vitem &%$dkim_canon_headers%&
41819 The header canonicalization method. One of 'relaxed' or 'simple'.
41821 .vitem &%$dkim_copiedheaders%&
41822 A transcript of headers and their values which are included in the signature
41823 (copied from the 'z=' tag of the signature).
41824 Note that RFC6376 requires that verification fail if the From: header is
41825 not included in the signature. Exim does not enforce this; sites wishing
41826 strict enforcement should code the check explicitly.
41828 .vitem &%$dkim_bodylength%&
41829 The number of signed body bytes. If zero ("0"), the body is unsigned. If no
41830 limit was set by the signer, "9999999999999" is returned. This makes sure
41831 that this variable always expands to an integer value.
41832 &*Note:*& The presence of the signature tag specifying a signing body length
41833 is one possible route to spoofing of valid DKIM signatures.
41834 A paranoid implementation might wish to regard signature where this variable
41835 shows less than the "no limit" return as being invalid.
41837 .vitem &%$dkim_created%&
41838 UNIX timestamp reflecting the date and time when the signature was created.
41839 When this was not specified by the signer, "0" is returned.
41841 .vitem &%$dkim_expires%&
41842 UNIX timestamp reflecting the date and time when the signer wants the
41843 signature to be treated as "expired". When this was not specified by the
41844 signer, "9999999999999" is returned. This makes it possible to do useful
41845 integer size comparisons against this value.
41846 Note that Exim does not check this value.
41848 .vitem &%$dkim_headernames%&
41849 A colon-separated list of names of headers included in the signature.
41851 .vitem &%$dkim_key_testing%&
41852 "1" if the key record has the "testing" flag set, "0" if not.
41854 .vitem &%$dkim_key_nosubdomains%&
41855 "1" if the key record forbids subdomaining, "0" otherwise.
41857 .vitem &%$dkim_key_srvtype%&
41858 Service type (tag s=) from the key record. Defaults to "*" if not specified
41861 .vitem &%$dkim_key_granularity%&
41862 Key granularity (tag g=) from the key record. Defaults to "*" if not specified
41865 .vitem &%$dkim_key_notes%&
41866 Notes from the key record (tag n=).
41868 .vitem &%$dkim_key_length%&
41869 Number of bits in the key.
41870 Valid only once the key is loaded, which is at the time the header signature
41871 is verified, which is after the body hash is.
41873 Note that RFC 8301 says:
41875 Verifiers MUST NOT consider signatures using RSA keys of
41876 less than 1024 bits as valid signatures.
41879 This is enforced by the default setting for the &%dkim_verify_min_keysizes%&
41884 In addition, two ACL conditions are provided:
41887 .vitem &%dkim_signers%&
41888 ACL condition that checks a colon-separated list of domains or identities
41889 for a match against the domain or identity that the ACL is currently verifying
41890 (reflected by &%$dkim_cur_signer%&). This is typically used to restrict an ACL
41891 verb to a group of domains or identities. For example:
41894 # Warn when Mail purportedly from GMail has no gmail signature
41895 warn sender_domains = gmail.com
41896 dkim_signers = gmail.com
41898 log_message = GMail sender without gmail.com DKIM signature
41901 Note that the above does not check for a total lack of DKIM signing;
41902 for that check for empty &$h_DKIM-Signature:$& in the data ACL.
41904 .vitem &%dkim_status%&
41905 ACL condition that checks a colon-separated list of possible DKIM verification
41906 results against the actual result of verification. This is typically used
41907 to restrict an ACL verb to a list of verification outcomes, for example:
41910 deny sender_domains = paypal.com:paypal.de
41911 dkim_signers = paypal.com:paypal.de
41912 dkim_status = none:invalid:fail
41913 message = Mail from Paypal with invalid/missing signature
41916 The possible status keywords are: 'none','invalid','fail' and 'pass'. Please
41917 see the documentation of the &%$dkim_verify_status%& expansion variable above
41918 for more information of what they mean.
41924 .section "SPF (Sender Policy Framework)" SECSPF
41925 .cindex SPF verification
41927 SPF is a mechanism whereby a domain may assert which IP addresses may transmit
41928 messages with its domain in the envelope from, documented by RFC 7208.
41929 For more information on SPF see &url(http://www.open-spf.org), a static copy of
41930 the &url(http://openspf.org).
41931 . --- 2019-10-28: still not https, open-spf.org is told to be a
41932 . --- web-archive copy of the now dead openspf.org site
41933 . --- See https://www.mail-archive.com/mailop@mailop.org/msg08019.html for a
41936 Messages sent by a system not authorised will fail checking of such assertions.
41937 This includes retransmissions done by traditional forwarders.
41939 SPF verification support is built into Exim if SUPPORT_SPF=yes is set in
41940 &_Local/Makefile_&. The support uses the &_libspf2_& library
41941 &url(https://www.libspf2.org/).
41942 There is no Exim involvement in the transmission of messages;
41943 publishing certain DNS records is all that is required.
41945 For verification, an ACL condition and an expansion lookup are provided.
41946 .cindex authentication "expansion item"
41947 Performing verification sets up information used by the
41948 &%authresults%& expansion item.
41951 .cindex SPF "ACL condition"
41952 .cindex ACL "spf condition"
41953 The ACL condition "spf" can be used at or after the MAIL ACL.
41954 It takes as an argument a list of strings giving the outcome of the SPF check,
41955 and will succeed for any matching outcome.
41959 The SPF check passed, the sending host is positively verified by SPF.
41962 The SPF check failed, the sending host is NOT allowed to send mail for the
41963 domain in the envelope-from address.
41965 .vitem &%softfail%&
41966 The SPF check failed, but the queried domain can't absolutely confirm that this
41970 The queried domain does not publish SPF records.
41973 The SPF check returned a "neutral" state. This means the queried domain has
41974 published a SPF record, but wants to allow outside servers to send mail under
41975 its domain as well. This should be treated like "none".
41977 .vitem &%permerror%&
41978 This indicates a syntax error in the SPF record of the queried domain.
41979 You may deny messages when this occurs.
41981 .vitem &%temperror%&
41982 This indicates a temporary error during all processing, including Exim's
41983 SPF processing. You may defer messages when this occurs.
41986 There was an error during processing of the SPF lookup
41989 You can prefix each string with an exclamation mark to invert
41990 its meaning, for example "!fail" will match all results but
41991 "fail". The string list is evaluated left-to-right, in a
41992 short-circuit fashion.
41997 message = $sender_host_address is not allowed to send mail from \
41998 ${if def:sender_address_domain \
41999 {$sender_address_domain}{$sender_helo_name}}. \
42000 Please see http://www.open-spf.org/Why;\
42001 identity=${if def:sender_address_domain \
42002 {$sender_address}{$sender_helo_name}};\
42003 ip=$sender_host_address
42006 Note: The above mentioned URL may not be as helpful as expected. You are
42007 encouraged to replace the link with a link to a site with more
42010 When the spf condition has run, it sets up several expansion
42013 .cindex SPF "verification variables"
42015 .vitem &$spf_header_comment$&
42016 .vindex &$spf_header_comment$&
42017 This contains a human-readable string describing the outcome
42018 of the SPF check. You can add it to a custom header or use
42019 it for logging purposes.
42021 .vitem &$spf_received$&
42022 .vindex &$spf_received$&
42023 This contains a complete Received-SPF: header (name and
42024 content) that can be added to the message. Please note that
42025 according to the SPF draft, this header must be added at the
42026 top of the header list, i.e. with
42028 add_header = :at_start:$spf_received
42030 See section &<<SECTaddheadacl>>& for further details.
42032 Note: in case of "Best-guess" (see below), the convention is
42033 to put this string in a header called X-SPF-Guess: instead.
42035 .vitem &$spf_result$&
42036 .vindex &$spf_result$&
42037 This contains the outcome of the SPF check in string form,
42038 currently one of pass, fail, softfail, none, neutral, permerror,
42039 temperror, or &"(invalid)"&.
42041 .vitem &$spf_result_guessed$&
42042 .vindex &$spf_result_guessed$&
42043 This boolean is true only if a best-guess operation was used
42044 and required in order to obtain a result.
42046 .vitem &$spf_smtp_comment$&
42047 .vindex &$spf_smtp_comment$&
42048 .vindex &%spf_smtp_comment_template%&
42049 This contains a string that can be used in a SMTP response
42050 to the calling party. Useful for "fail".
42051 The string is generated by the SPF library from the template configured in the main config
42052 option &%spf_smtp_comment_template%&.
42056 .cindex SPF "ACL condition"
42057 .cindex ACL "spf_guess condition"
42058 .cindex SPF "best guess"
42059 In addition to SPF, you can also perform checks for so-called
42060 "Best-guess". Strictly speaking, "Best-guess" is not standard
42061 SPF, but it is supported by the same framework that enables SPF
42063 Refer to &url(http://www.open-spf.org/FAQ/Best_guess_record)
42064 for a description of what it means.
42065 . --- 2019-10-28: still not https:
42067 To access this feature, simply use the spf_guess condition in place
42068 of the spf one. For example:
42071 deny spf_guess = fail
42072 message = $sender_host_address doesn't look trustworthy to me
42075 In case you decide to reject messages based on this check, you
42076 should note that although it uses the same framework, "Best-guess"
42077 is not SPF, and therefore you should not mention SPF at all in your
42080 When the spf_guess condition has run, it sets up the same expansion
42081 variables as when spf condition is run, described above.
42083 Additionally, since Best-guess is not standardized, you may redefine
42084 what "Best-guess" means to you by redefining the main configuration
42085 &%spf_guess%& option.
42086 For example, the following:
42089 spf_guess = v=spf1 a/16 mx/16 ptr ?all
42092 would relax host matching rules to a broader network range.
42095 .cindex SPF "lookup expansion"
42097 A lookup expansion is also available. It takes an email
42098 address as the key and an IP address
42103 ${lookup {username@domain} spf {ip.ip.ip.ip}}
42106 The lookup will return the same result strings as can appear in
42107 &$spf_result$& (pass,fail,softfail,neutral,none,err_perm,err_temp).
42113 .section "SRS (Sender Rewriting Scheme)" SECTSRS
42114 .cindex SRS "sender rewriting scheme"
42116 SRS can be used to modify sender addresses when forwarding so that
42117 SPF verification does not object to them.
42118 It operates by encoding the original envelope sender in a new
42119 sender local part and using a domain run by the forwarding site
42120 as the new domain for the sender. Any DSN message should be returned
42121 to this new sender at the forwarding site, which can extract the
42122 original sender from the coded local part and forward the DSN to
42125 This is a way of avoiding the breakage that SPF does to forwarding.
42126 The constructed local-part will be longer than the original,
42127 leading to possible problems with very long addresses.
42128 The changing of the sender address also hinders the tracing of mail
42131 Exim can be built to include native SRS support. To do this
42132 SUPPORT_SRS=yes must be defined in &_Local/Makefile_&.
42133 If this has been done, the macros _HAVE_SRS and _HAVE_NATIVE_SRS
42135 The support is limited to SRS0-encoding; SRS1 is not supported.
42137 .cindex SRS excoding
42138 To encode an address use this expansion item:
42140 .vitem &*${srs_encode&~{*&<&'secret'&>&*}{*&<&'return&~path'&>&*}{*&<&'original&~domain'&>&*}}*&
42141 .cindex "&%srs_encode%& expansion item"
42142 .cindex SRS "expansion item"
42143 The first argument should be a secret known and used by all systems
42144 handling the recipient domain for the original message.
42145 There is no need to periodically change this key; a timestamp is also
42147 The second argument should be given as the envelope sender address before this
42148 encoding operation.
42149 The third argument should be the recipient domain of the message when
42150 it arrived at this system.
42153 .cindex SRS decoding
42154 To decode an address use this expansion condition:
42156 .vitem &*inbound_srs&~{*&<&'local&~part'&>&*}{*&<&'secret'&>&*}*&
42157 The first argument should be the recipient local prt as is was received.
42158 The second argument is the site secret.
42160 If the messages is not for an SRS-encoded recipient the condition will
42161 return false. If it is, the condition will return true and the variable
42162 &$srs_recipient$& will be set to the decoded (original) value.
42168 SRS_SECRET = <pick something unique for your site for this. Use on all MXs.>
42174 # if outbound, and forwarding has been done, use an alternate transport
42175 domains = ! +my_domains
42176 transport = ${if eq {$local_part@$domain} \
42177 {$original_local_part@$original_domain} \
42178 {remote_smtp} {remote_forwarded_smtp}}
42183 domains = +my_domains
42184 # detect inbound bounces which are SRS'd, and decode them
42185 condition = ${if inbound_srs {$local_part} {SRS_SECRET}}
42186 data = $srs_recipient
42188 inbound_srs_failure:
42191 domains = +my_domains
42192 # detect inbound bounces which look SRS'd but are invalid
42193 condition = ${if inbound_srs {$local_part} {}}
42195 data = :fail: Invalid SRS recipient address
42197 #... further routers here
42200 # transport; should look like the non-forward outbound
42201 # one, plus the max_rcpt and return_path options
42202 remote_forwarded_smtp:
42204 # modify the envelope from, for mails that we forward
42206 return_path = ${srs_encode {SRS_SECRET} {$return_path} {$original_domain}}
42213 .section DMARC SECDMARC
42214 .cindex DMARC verification
42216 DMARC combines feedback from SPF, DKIM, and header From: in order
42217 to attempt to provide better indicators of the authenticity of an
42218 email. This document does not explain the fundamentals; you
42219 should read and understand how it works by visiting the website at
42220 &url(http://www.dmarc.org/).
42222 If Exim is built with DMARC support,
42223 the libopendmarc library is used.
42225 For building Exim yourself, obtain the library from
42226 &url(http://sourceforge.net/projects/opendmarc/)
42227 to obtain a copy, or find it in your favorite package
42228 repository. You will need to attend to the local/Makefile feature
42229 SUPPORT_DMARC and the associated LDFLAGS addition.
42230 This description assumes
42231 that headers will be in /usr/local/include, and that the libraries
42232 are in /usr/local/lib.
42236 There are three main-configuration options:
42237 .cindex DMARC "configuration options"
42239 The &%dmarc_tld_file%& option
42240 .oindex &%dmarc_tld_file%&
42241 defines the location of a text file of valid
42242 top level domains the opendmarc library uses
42243 during domain parsing. Maintained by Mozilla,
42244 the most current version can be downloaded
42245 from a link at &url(https://publicsuffix.org/list/public_suffix_list.dat).
42246 See also the util/renew-opendmarc-tlds.sh script.
42247 The default for the option is unset.
42248 If not set, DMARC processing is disabled.
42251 The &%dmarc_history_file%& option, if set
42252 .oindex &%dmarc_history_file%&
42253 defines the location of a file to log results
42254 of dmarc verification on inbound emails. The
42255 contents are importable by the opendmarc tools
42256 which will manage the data, send out DMARC
42257 reports, and expire the data. Make sure the
42258 directory of this file is writable by the user
42260 The default is unset.
42262 The &%dmarc_forensic_sender%& option
42263 .oindex &%dmarc_forensic_sender%&
42264 defines an alternate email address to use when sending a
42265 forensic report detailing alignment failures
42266 if a sender domain's dmarc record specifies it
42267 and you have configured Exim to send them.
42268 If set, this is expanded and used for the
42269 From: header line; the address is extracted
42270 from it and used for the envelope from.
42271 If not set (the default), the From: header is expanded from
42272 the dsn_from option, and <> is used for the
42275 . I wish we had subsections...
42277 .cindex DMARC controls
42278 By default, the DMARC processing will run for any remote,
42279 non-authenticated user. It makes sense to only verify DMARC
42280 status of messages coming from remote, untrusted sources. You can
42281 use standard conditions such as hosts, senders, etc, to decide that
42282 DMARC verification should *not* be performed for them and disable
42283 DMARC with an ACL control modifier:
42285 control = dmarc_disable_verify
42287 A DMARC record can also specify a "forensic address", which gives
42288 exim an email address to submit reports about failed alignment.
42289 Exim does not do this by default because in certain conditions it
42290 results in unintended information leakage (what lists a user might
42291 be subscribed to, etc). You must configure exim to submit forensic
42292 reports to the owner of the domain. If the DMARC record contains a
42293 forensic address and you specify the control statement below, then
42294 exim will send these forensic emails. It is also advised that you
42295 configure a &%dmarc_forensic_sender%& because the default sender address
42296 construction might be inadequate.
42298 control = dmarc_enable_forensic
42300 (AGAIN: You can choose not to send these forensic reports by simply
42301 not putting the dmarc_enable_forensic control line at any point in
42302 your exim config. If you don't tell exim to send them, it will not
42305 There are no options to either control. Both must appear before
42310 DMARC checks cam be run on incoming SMTP messages by using the
42311 &"dmarc_status"& ACL condition in the DATA ACL. You are required to
42312 call the &"spf"& condition first in the ACLs, then the &"dmarc_status"&
42313 condition. Putting this condition in the ACLs is required in order
42314 for a DMARC check to actually occur. All of the variables are set
42315 up before the DATA ACL, but there is no actual DMARC check that
42316 occurs until a &"dmarc_status"& condition is encountered in the ACLs.
42318 The &"dmarc_status"& condition takes a list of strings on its
42319 right-hand side. These strings describe recommended action based
42320 on the DMARC check. To understand what the policy recommendations
42321 mean, refer to the DMARC website above. Valid strings are:
42323 &'accept '& The DMARC check passed and the library recommends accepting the email.
42324 &'reject '& The DMARC check failed and the library recommends rejecting the email.
42325 &'quarantine '& The DMARC check failed and the library recommends keeping it for further inspection.
42326 &'none '& The DMARC check passed and the library recommends no specific action, neutral.
42327 &'norecord '& No policy section in the DMARC record for this RFC5322.From field
42328 &'nofrom '& Unable to determine the domain of the sender.
42329 &'temperror '& Library error or dns error.
42330 &'off '& The DMARC check was disabled for this email.
42332 You can prefix each string with an exclamation mark to invert its
42333 meaning, for example "!accept" will match all results but
42334 "accept". The string list is evaluated left-to-right in a
42335 short-circuit fashion. When a string matches the outcome of the
42336 DMARC check, the condition succeeds. If none of the listed
42337 strings matches the outcome of the DMARC check, the condition
42340 Of course, you can also use any other lookup method that Exim
42341 supports, including LDAP, Postgres, MySQL, etc, as long as the
42342 result is a list of colon-separated strings.
42344 Performing the check sets up information used by the
42345 &%authresults%& expansion item.
42347 Several expansion variables are set before the DATA ACL is
42348 processed, and you can use them in this ACL. The following
42349 expansion variables are available:
42352 .vitem &$dmarc_status$&
42353 .vindex &$dmarc_status$&
42354 .cindex DMARC result
42355 A one word status indicating what the DMARC library
42356 thinks of the email. It is a combination of the results of
42357 DMARC record lookup and the SPF/DKIM/DMARC processing results
42358 (if a DMARC record was found). The actual policy declared
42359 in the DMARC record is in a separate expansion variable.
42361 .vitem &$dmarc_status_text$&
42362 .vindex &$dmarc_status_text$&
42363 Slightly longer, human readable status.
42365 .vitem &$dmarc_used_domain$&
42366 .vindex &$dmarc_used_domain$&
42367 The domain which DMARC used to look up the DMARC policy record.
42369 .vitem &$dmarc_domain_policy$&
42370 .vindex &$dmarc_domain_policy$&
42371 The policy declared in the DMARC record. Valid values
42372 are "none", "reject" and "quarantine". It is blank when there
42373 is any error, including no DMARC record.
42378 By default, Exim's DMARC configuration is intended to be
42379 non-intrusive and conservative. To facilitate this, Exim will not
42380 create any type of logging files without explicit configuration by
42381 you, the admin. Nor will Exim send out any emails/reports about
42382 DMARC issues without explicit configuration by you, the admin (other
42383 than typical bounce messages that may come about due to ACL
42384 processing or failure delivery issues).
42386 In order to log statistics suitable to be imported by the opendmarc
42387 tools, you need to:
42389 Configure the global option &%dmarc_history_file%&
42391 Configure cron jobs to call the appropriate opendmarc history
42392 import scripts and truncating the dmarc_history_file
42395 In order to send forensic reports, you need to:
42397 Configure the global option &%dmarc_forensic_sender%&
42399 Configure, somewhere before the DATA ACL, the control option to
42400 enable sending DMARC forensic reports
42408 warn domains = +local_domains
42409 hosts = +local_hosts
42410 control = dmarc_disable_verify
42412 warn !domains = +screwed_up_dmarc_records
42413 control = dmarc_enable_forensic
42415 warn condition = (lookup if destined to mailing list)
42416 set acl_m_mailing_list = 1
42419 warn dmarc_status = accept : none : off
42421 log_message = DMARC DEBUG: $dmarc_status $dmarc_used_domain
42423 warn dmarc_status = !accept
42425 log_message = DMARC DEBUG: '$dmarc_status' for $dmarc_used_domain
42427 warn dmarc_status = quarantine
42429 set $acl_m_quarantine = 1
42430 # Do something in a transport with this flag variable
42432 deny condition = ${if eq{$dmarc_domain_policy}{reject}}
42433 condition = ${if eq{$acl_m_mailing_list}{1}}
42434 message = Messages from $dmarc_used_domain break mailing lists
42436 deny dmarc_status = reject
42438 message = Message from $dmarc_used_domain failed sender's DMARC policy, REJECT
42440 warn add_header = :at_start:${authresults {$primary_hostname}}
42447 . ////////////////////////////////////////////////////////////////////////////
42448 . ////////////////////////////////////////////////////////////////////////////
42450 .chapter "Proxies" "CHAPproxies" &&&
42452 .cindex "proxy support"
42453 .cindex "proxy" "access via"
42455 A proxy is an intermediate system through which communication is passed.
42456 Proxies may provide a security, availability or load-distribution function.
42459 .section "Inbound proxies" SECTproxyInbound
42460 .cindex proxy inbound
42461 .cindex proxy "server side"
42462 .cindex proxy "Proxy protocol"
42463 .cindex "Proxy protocol" proxy
42465 Exim has support for receiving inbound SMTP connections via a proxy
42466 that uses &"Proxy Protocol"& to speak to it.
42467 To include this support, include &"SUPPORT_PROXY=yes"&
42470 It was built on the HAProxy specification, found at
42471 &url(https://www.haproxy.org/download/1.8/doc/proxy-protocol.txt).
42473 The purpose of this facility is so that an application load balancer,
42474 such as HAProxy, can sit in front of several Exim servers
42475 to distribute load.
42476 Exim uses the local protocol communication with the proxy to obtain
42477 the remote SMTP system IP address and port information.
42478 There is no logging if a host passes or
42479 fails Proxy Protocol negotiation, but it can easily be determined and
42480 recorded in an ACL (example is below).
42482 Use of a proxy is enabled by setting the &%hosts_proxy%&
42483 main configuration option to a hostlist; connections from these
42484 hosts will use Proxy Protocol.
42485 Exim supports both version 1 and version 2 of the Proxy Protocol and
42486 automatically determines which version is in use.
42488 The Proxy Protocol header is the first data received on a TCP connection
42489 and is inserted before any TLS-on-connect handshake from the client; Exim
42490 negotiates TLS between Exim-as-server and the remote client, not between
42491 Exim and the proxy server. The Proxy Protocol header must be received
42492 within &%proxy_protocol_timeout%&, which defaults to 3s.
42494 The following expansion variables are usable
42495 (&"internal"& and &"external"& here refer to the interfaces
42498 &'proxy_external_address '& IP of host being proxied or IP of remote interface of proxy
42499 &'proxy_external_port '& Port of host being proxied or Port on remote interface of proxy
42500 &'proxy_local_address '& IP of proxy server inbound or IP of local interface of proxy
42501 &'proxy_local_port '& Port of proxy server inbound or Port on local interface of proxy
42502 &'proxy_session '& boolean: SMTP connection via proxy
42504 If &$proxy_session$& is set but &$proxy_external_address$& is empty
42505 there was a protocol error.
42506 The variables &$sender_host_address$& and &$sender_host_port$&
42507 will have values for the actual client system, not the proxy.
42509 Since the real connections are all coming from the proxy, and the
42510 per host connection tracking is done before Proxy Protocol is
42511 evaluated, &%smtp_accept_max_per_host%& must be set high enough to
42512 handle all of the parallel volume you expect per inbound proxy.
42513 With the option set so high, you lose the ability
42514 to protect your server from many connections from one IP.
42515 In order to prevent your server from overload, you
42516 need to add a per connection ratelimit to your connect ACL.
42517 A possible solution is:
42519 # Set max number of connections per host
42521 # Or do some kind of IP lookup in a flat file or database
42522 # LIMIT = ${lookup{$sender_host_address}iplsearch{/etc/exim/proxy_limits}}
42524 defer ratelimit = LIMIT / 5s / per_conn / strict
42525 message = Too many connections from this IP right now
42530 .section "Outbound proxies" SECTproxySOCKS
42531 .cindex proxy outbound
42532 .cindex proxy "client side"
42533 .cindex proxy SOCKS
42534 .cindex SOCKS proxy
42535 Exim has support for sending outbound SMTP via a proxy
42536 using a protocol called SOCKS5 (defined by RFC1928).
42537 The support can be optionally included by defining SUPPORT_SOCKS=yes in
42540 Use of a proxy is enabled by setting the &%socks_proxy%& option
42541 on an smtp transport.
42542 The option value is expanded and should then be a list
42543 (colon-separated by default) of proxy specifiers.
42544 Each proxy specifier is a list
42545 (space-separated by default) where the initial element
42546 is an IP address and any subsequent elements are options.
42548 Options are a string <name>=<value>.
42549 The list of options is in the following table:
42551 &'auth '& authentication method
42552 &'name '& authentication username
42553 &'pass '& authentication password
42555 &'tmo '& connection timeout
42557 &'weight '& selection bias
42560 More details on each of these options follows:
42563 .cindex authentication "to proxy"
42564 .cindex proxy authentication
42565 &%auth%&: Either &"none"& (default) or &"name"&.
42566 Using &"name"& selects username/password authentication per RFC 1929
42567 for access to the proxy.
42568 Default is &"none"&.
42570 &%name%&: sets the username for the &"name"& authentication method.
42573 &%pass%&: sets the password for the &"name"& authentication method.
42576 &%port%&: the TCP port number to use for the connection to the proxy.
42579 &%tmo%&: sets a connection timeout in seconds for this proxy.
42582 &%pri%&: specifies a priority for the proxy within the list,
42583 higher values being tried first.
42584 The default priority is 1.
42586 &%weight%&: specifies a selection bias.
42587 Within a priority set servers are queried in a random fashion,
42588 weighted by this value.
42589 The default value for selection bias is 1.
42592 Proxies from the list are tried according to their priority
42593 and weight settings until one responds. The timeout for the
42594 overall connection applies to the set of proxied attempts.
42596 .section Logging SECTproxyLog
42597 To log the (local) IP of a proxy in the incoming or delivery logline,
42598 add &"+proxy"& to the &%log_selector%& option.
42599 This will add a component tagged with &"PRX="& to the line.
42601 . ////////////////////////////////////////////////////////////////////////////
42602 . ////////////////////////////////////////////////////////////////////////////
42604 .chapter "Internationalisation" "CHAPi18n" &&&
42605 "Internationalisation""
42606 .cindex internationalisation "email address"
42609 .cindex utf8 "mail name handling"
42611 Exim has support for Internationalised mail names.
42612 To include this it must be built with SUPPORT_I18N and the libidn library.
42613 Standards supported are RFCs 2060, 5890, 6530 and 6533.
42615 If Exim is built with SUPPORT_I18N_2008 (in addition to SUPPORT_I18N, not
42616 instead of it) then IDNA2008 is supported; this adds an extra library
42617 requirement, upon libidn2.
42619 .section "MTA operations" SECTi18nMTA
42620 .cindex SMTPUTF8 "ESMTP option"
42621 .cindex "ESMTP extensions" SMTPUTF8
42622 The main configuration option &%smtputf8_advertise_hosts%& specifies
42623 a host list. If this matches the sending host and
42624 accept_8bitmime is true (the default) then the ESMTP option
42625 SMTPUTF8 will be advertised.
42627 If the sender specifies the SMTPUTF8 option on a MAIL command
42628 international handling for the message is enabled and
42629 the expansion variable &$message_smtputf8$& will have value TRUE.
42631 The option &%allow_utf8_domains%& is set to true for this
42632 message. All DNS lookups are converted to a-label form
42633 whatever the setting of &%allow_utf8_domains%&
42634 when Exim is built with SUPPORT_I18N.
42636 Both localparts and domain are maintained as the original
42637 UTF-8 form internally; any comparison or regular-expression use will
42638 require appropriate care. Filenames created, eg. by
42639 the appendfile transport, will have UTF-8 names.
42641 HELO names sent by the smtp transport will have any UTF-8
42642 components expanded to a-label form,
42643 and any certificate name checks will be done using the a-label
42646 .cindex log protocol
42647 .cindex SMTPUTF8 logging
42648 .cindex i18n logging
42649 Log lines and Received-by: header lines will acquire a "utf8"
42650 prefix on the protocol element, eg. utf8esmtp.
42652 The following expansion operators can be used:
42654 ${utf8_domain_to_alabel:str}
42655 ${utf8_domain_from_alabel:str}
42656 ${utf8_localpart_to_alabel:str}
42657 ${utf8_localpart_from_alabel:str}
42660 .cindex utf8 "address downconversion"
42661 .cindex i18n "utf8 address downconversion"
42663 may use the following modifier:
42665 control = utf8_downconvert
42666 control = utf8_downconvert/<value>
42668 This sets a flag requiring that envelope addresses are converted to
42669 a-label form before smtp delivery.
42670 This is usually for use in a Message Submission Agent context,
42671 but could be used for any message.
42673 If a value is appended it may be:
42675 &`1 `& mandatory downconversion
42676 &`0 `& no downconversion
42677 &`-1 `& if SMTPUTF8 not supported by destination host
42679 If no value is given, 1 is used.
42681 If mua_wrapper is set, the utf8_downconvert control
42682 is initially set to -1.
42684 The smtp transport has an option &%utf8_downconvert%&.
42685 If set it must expand to one of the three values described above,
42686 or an empty string.
42687 If non-empty it overrides value previously set
42688 (due to mua_wrapper or by an ACL control).
42691 There is no explicit support for VRFY and EXPN.
42692 Configurations supporting these should inspect
42693 &$smtp_command_argument$& for an SMTPUTF8 argument.
42695 There is no support for LMTP on Unix sockets.
42696 Using the "lmtp" protocol option on an smtp transport,
42697 for LMTP over TCP, should work as expected.
42699 There is no support for DSN unitext handling,
42700 and no provision for converting logging from or to UTF-8.
42704 .section "MDA operations" SECTi18nMDA
42705 To aid in constructing names suitable for IMAP folders
42706 the following expansion operator can be used:
42708 ${imapfolder {<string>} {<sep>} {<specials>}}
42711 The string is converted from the charset specified by
42712 the "headers charset" command (in a filter file)
42713 or &%headers_charset%& main configuration option (otherwise),
42715 modified UTF-7 encoding specified by RFC 2060,
42716 with the following exception: All occurrences of <sep>
42717 (which has to be a single character)
42718 are replaced with periods ("."), and all periods and slashes that are not
42719 <sep> and are not in the <specials> string are BASE64 encoded.
42721 The third argument can be omitted, defaulting to an empty string.
42722 The second argument can be omitted, defaulting to "/".
42724 This is the encoding used by Courier for Maildir names on disk, and followed
42725 by many other IMAP servers.
42729 &`${imapfolder {Foo/Bar}} `& yields &`Foo.Bar`&
42730 &`${imapfolder {Foo/Bar}{.}{/}} `& yields &`Foo&&AC8-Bar`&
42731 &`${imapfolder {Räksmörgås}} `& yields &`R&&AOQ-ksm&&APY-rg&&AOU-s`&
42734 Note that the source charset setting is vital, and also that characters
42735 must be representable in UTF-16.
42738 . ////////////////////////////////////////////////////////////////////////////
42739 . ////////////////////////////////////////////////////////////////////////////
42741 .chapter "Events" "CHAPevents" &&&
42745 The events mechanism in Exim can be used to intercept processing at a number
42746 of points. It was originally invented to give a way to do customised logging
42747 actions (for example, to a database) but can also be used to modify some
42748 processing actions.
42750 Most installations will never need to use Events.
42751 The support can be left out of a build by defining DISABLE_EVENT=yes
42752 in &_Local/Makefile_&.
42754 There are two major classes of events: main and transport.
42755 The main configuration option &%event_action%& controls reception events;
42756 a transport option &%event_action%& controls delivery events.
42758 Both options are a string which is expanded when the event fires.
42759 An example might look like:
42760 .cindex logging custom
42762 event_action = ${if eq {msg:delivery}{$event_name} \
42763 {${lookup pgsql {SELECT * FROM record_Delivery( \
42764 '${quote_pgsql:$sender_address_domain}',\
42765 '${quote_pgsql:${lc:$sender_address_local_part}}', \
42766 '${quote_pgsql:$domain}', \
42767 '${quote_pgsql:${lc:$local_part}}', \
42768 '${quote_pgsql:$host_address}', \
42769 '${quote_pgsql:${lc:$host}}', \
42770 '${quote_pgsql:$message_exim_id}')}} \
42774 Events have names which correspond to the point in process at which they fire.
42775 The name is placed in the variable &$event_name$& and the event action
42776 expansion must check this, as it will be called for every possible event type.
42779 The current list of events is:
42781 &`dane:fail after transport `& per connection
42782 &`msg:complete after main `& per message
42783 &`msg:defer after transport `& per message per delivery try
42784 &`msg:delivery after transport `& per recipient
42785 &`msg:rcpt:host:defer after transport `& per recipient per host
42786 &`msg:rcpt:defer after transport `& per recipient
42787 &`msg:host:defer after transport `& per host per delivery try; host errors
42788 &`msg:fail:delivery after transport `& per recipient
42789 &`msg:fail:internal after main `& per recipient
42790 &`tcp:connect before transport `& per connection
42791 &`tcp:close after transport `& per connection
42792 &`tls:cert before both `& per certificate in verification chain
42793 &`tls:fail:connect after main `& per connection
42794 &`smtp:connect after transport `& per connection
42795 &`smtp:ehlo after transport `& per connection
42798 New event types may be added in future.
42800 The event name is a colon-separated list, defining the type of
42801 event in a tree of possibilities. It may be used as a list
42802 or just matched on as a whole. There will be no spaces in the name.
42804 The second column in the table above describes whether the event fires
42805 before or after the action is associates with. Those which fire before
42806 can be used to affect that action (more on this below).
42808 The third column in the table above says what section of the configuration
42809 should define the event action.
42811 An additional variable, &$event_data$&, is filled with information varying
42812 with the event type:
42814 &`dane:fail `& failure reason
42815 &`msg:defer `& error string
42816 &`msg:delivery `& smtp confirmation message
42817 &`msg:fail:internal `& failure reason
42818 &`msg:fail:delivery `& smtp error message
42819 &`msg:host:defer `& error string
42820 &`msg:rcpt:host:defer `& error string
42821 &`msg:rcpt:defer `& error string
42822 &`tls:cert `& verification chain depth
42823 &`tls:fail:connect `& error string
42824 &`smtp:connect `& smtp banner
42825 &`smtp:ehlo `& smtp ehlo response
42828 The :defer events populate one extra variable: &$event_defer_errno$&.
42830 For complex operations an ACL expansion can be used in &%event_action%&
42831 however due to the multiple contexts that Exim operates in during
42832 the course of its processing:
42834 variables set in transport events will not be visible outside that
42837 acl_m variables in a server context are lost on a new connection,
42838 and after smtp helo/ehlo/mail/starttls/rset commands
42840 Using an ACL expansion with the logwrite modifier can be
42841 a useful way of writing to the main log.
42843 The expansion of the event_action option should normally
42844 return an empty string. Should it return anything else the
42845 following will be forced:
42847 &`tcp:connect `& do not connect
42848 &`tls:cert `& refuse verification
42849 &`smtp:connect `& close connection
42851 All other message types ignore the result string, and
42852 no other use is made of it.
42854 For a tcp:connect event, if the connection is being made to a proxy
42855 then the address and port variables will be that of the proxy and not
42858 For tls:cert events, if GnuTLS is in use this will trigger only per
42859 chain element received on the connection.
42860 For OpenSSL it will trigger for every chain element including those
42863 . ////////////////////////////////////////////////////////////////////////////
42864 . ////////////////////////////////////////////////////////////////////////////
42866 .chapter "Adding new drivers or lookup types" "CHID13" &&&
42867 "Adding drivers or lookups"
42868 .cindex "adding drivers"
42869 .cindex "new drivers, adding"
42870 .cindex "drivers" "adding new"
42871 The following actions have to be taken in order to add a new router, transport,
42872 authenticator, or lookup type to Exim:
42875 Choose a name for the driver or lookup type that does not conflict with any
42876 existing name; I will use &"newdriver"& in what follows.
42878 Add to &_src/EDITME_& the line:
42880 <&'type'&>&`_NEWDRIVER=yes`&
42882 where <&'type'&> is ROUTER, TRANSPORT, AUTH, or LOOKUP. If the
42883 code is not to be included in the binary by default, comment this line out. You
42884 should also add any relevant comments about the driver or lookup type.
42886 Add to &_src/config.h.defaults_& the line:
42888 #define <type>_NEWDRIVER
42891 Edit &_src/drtables.c_&, adding conditional code to pull in the private header
42892 and create a table entry as is done for all the other drivers and lookup types.
42894 Edit &_scripts/lookups-Makefile_& if this is a new lookup; there is a for-loop
42895 near the bottom, ranging the &`name_mod`& variable over a list of all lookups.
42896 Add your &`NEWDRIVER`& to that list.
42897 As long as the dynamic module would be named &_newdriver.so_&, you can use the
42898 simple form that most lookups have.
42900 Edit &_Makefile_& in the appropriate sub-directory (&_src/routers_&,
42901 &_src/transports_&, &_src/auths_&, or &_src/lookups_&); add a line for the new
42902 driver or lookup type and add it to the definition of OBJ.
42904 Edit &_OS/Makefile-Base_& adding a &_.o_& file for the predefined-macros, to the
42905 definition of OBJ_MACRO. Add a set of line to do the compile also.
42907 Create &_newdriver.h_& and &_newdriver.c_& in the appropriate sub-directory of
42910 Edit &_scripts/MakeLinks_& and add commands to link the &_.h_& and &_.c_& files
42911 as for other drivers and lookups.
42914 Then all you need to do is write the code! A good way to start is to make a
42915 proforma by copying an existing module of the same type, globally changing all
42916 occurrences of the name, and cutting out most of the code. Note that any
42917 options you create must be listed in alphabetical order, because the tables are
42918 searched using a binary chop procedure.
42920 There is a &_README_& file in each of the sub-directories of &_src_& describing
42921 the interface that is expected.
42926 . ////////////////////////////////////////////////////////////////////////////
42927 . ////////////////////////////////////////////////////////////////////////////
42929 . /////////////////////////////////////////////////////////////////////////////
42930 . These lines are processing instructions for the Simple DocBook Processor that
42931 . Philip Hazel has developed as a less cumbersome way of making PostScript and
42932 . PDFs than using xmlto and fop. They will be ignored by all other XML
42934 . /////////////////////////////////////////////////////////////////////////////
42939 foot_right_recto="&chaptertitle;"
42940 foot_right_verso="&chaptertitle;"
42944 .makeindex "Options index" "option"
42945 .makeindex "Variables index" "variable"
42946 .makeindex "Concept index" "concept"
42949 . /////////////////////////////////////////////////////////////////////////////
42950 . /////////////////////////////////////////////////////////////////////////////